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The metanephros of the bird Clayton, Blanche-P. 1949

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THE METANEPHROS OP THE BIRD Blanche-P. C l a y t o n A T h e s i s Submitted i n P a r t i a l F u l f i l m e n t o f the Requirements f o r the Degree o f Master o f A r t s i n the Department of Zoology The U n i v e r s i t y of B r i t i s h Columbia x A p r i l , 1949. A b s t r a c t C e r t a i n i n v e s t i g a t i o n s were undertaken on the kidneys of v a r i o u s b i r d s using t h a t of the domestic fowl, as a type; and, where p o s s i b l e , comparing the r e s u l t s w i t h those r e p o r t e d f o r other c l a s s e s of animals. The v a s c u l a r system was co n s i d e r e d , to e s t a b l i s h the statement of Spanner ( 1 9 2 * 0 , t h a t the b i r d kidney pos-sesses a r e n a l p o r t a l system. E m b r y o l o g i c a l , h i s t o l o g i c a l , and anatomical evidence, were brought forward i n f a v o u r of t h i s venous arrangement. The h i s t o l o g y was examined w i t h d i f f e r e n t techniques. In t h i s c o n n e c t i o n , a comparative examination of f i x a t i o n f l u i d s was undertaken, as d i f f i c u l t y was experienced i n the h i s t o l o g i c a l examination of b i r d kidney t i s s u e . The h i s t o l o g i c a l r e s u l t s i n d i c a t e d some degree of glomerular d e g e n e r a t i o n and an Increase i n p r o x i m a l tubule development as compared to that of the mammal. C y t o l o g i c a l s t u d i e s were c a r r i e d out on mitochon-d r i a and the G-olgl apparatus. The mitochondria o f the domestic fowl, and the pigeon, showed great c o n c e n t r a t i o n i n the c e l l s of the proximal t u b u l e . The G-olgi apparatus was i n v e s t i g a t e d i n the f o x v - 1 ; and showed a development i n the c e l l s of the proximal seg-ment of the nephron, i n excess of t h a t m n the mammal. The c o n c l u s i o n deduced from both these c y t o l o g i c a l s t u d i e s , I n d i c a t e d an i n c r e a s e i n a c t i v i t y of the proximal segment i n the b i r d , over t h a t p f the mammal., A h l s t o c h e m i c a l t e s t was performed," to deci d e f\ /' whether the r e p o r t e d g l o m e r u l a r degeneration In the b i r d i s such that glucose e l i m i n a t i o n i s reduced o r absent. A l k a l i n e phosphatase i s an e n z y m e ^ s t a t e d to a s s i s t i n the reabsorp-t i o n of glucose e l i m i n a t e d by glomerular f i l t r a t i o n . The r e s u l t s were compared w i t h those of the c l a s s e s p o s s e s s i n g good glomerular development. I t was noted t h a t the avian kidney shows c o n s i d e r a b l e evidence of a l k a l i n e phosphatase a c t i v i t y . Two c o n c l u s i o n s are reached: (1) That the b i r d kidney shoxtfs d e f i n i t e evidence of t u b u l a r a c t i v i t y . ( 2 ) That i n s p i t e of apparent s i g n s of dege n e r a t i o n , the glomerulus i n the avian kidney f u n c t i o n s comparably to that of the mammal. Table of Contents Page 1. I n t r o d u c t i o n 1 2. Acknowledgments • 4 3. H i s t o r i c a l Review ....» 5 I The m i c r o s c o p i c u n i t s o f the a v i a n metanephros ........ •.. •. 6 Ma l p i g h i a n c o r p u s c l e Convoluted or u r i n i f e r o u s t u b u l e s Proximal segment Henle*s loop Descending segment Ascending segment D i s t a l segment C o l l e c t i n g t u b u l e s I I V a s c u l a r Supply 1 2 E x t r i n s i c I n t r i n s i c I I I C ytology 1 3 M i t o c h o n d r i a 4. M a t e r i a l s and Methods 15 V a s c u l a r system 13 H i s t o l o g y 1 4 Cytology 20 Mi t o c h o n d r i a 20 G o l g i Body • 23 Page H i s t o c h e m i s t r y 24 5. Observations • • • 28 I Avian Metanephros: macroscopic f e a t u r e s I I The V a s c u l a r System •' 29 Venous Tympanic v a l v e A r t e r i a l I I I The H i s t o l o g y • 3 6 IV The Cytology • 4 4 M i t o c h o n d r i a 4 4 G o l g i apparatus ...... 52 V The H i s t o c h e m i s t r y • 58 A l k a l i n e phosphatase 6. Summary • 65 7. L i t e r a t u r e c i t e d 6 6 THE AVIAN METANEPHROS 1. Introduction It was Bowman (1842), the f i r s t investigator of the function of the Malpighian corpuscle, who remarked in his c lass ica l monograph on this structure that much knowledge might be gained by comparing the various parts of the kidney in different species of animals* The comparative approach stressed so long ago by Bowman, i s often essential for a correct understanding of the physiological mechanisms of a part icular group* This fact i s again emphasized at the opening of this thesis, because i t i s f e l t that only by means of th is method some l ight might be shed on the confused statements^ concerning the avian kidney in i t s various aspects^ which meet the Investigator at every turn* Orig inal ly , this thesis was intended to be a study of the normal and pathological histology of the kidney of the domestic fowl, Gallus domesticus, in relat ion to the disease under such names as "Blue Comb" or "Pullets" disease, but owing to the confusion met with i n the l i tera ture the writer 2 . decided to col lect the existing isolated facts concerning the b i rd kidney i n embryology, blood c i rcu la t ion , morphology, (nervous system) histology and physiology, with these facts, and with fresh work in certain of the above f i e ld s , i t was hoped to be able to sort out the contradictions, and to cor-relate the whole Into a homogeneous presentation* JL Moreover, i t was f e l t that homogenity could not be i achieved unless comparison was made with those forms of animals which are closest i n the phylogenetic scale* This fact i s stated, because i t i s f e l t that certain theories, such as Cushny's (19170 and Richard 1s (1932), of f i l t r a t i o n reabsorp-t ion theory, are inclined to dominate the f i e l d of kidney function to the exclusion of another theory which may be va l i d for other groups of animals. Owing to the natural interest of man i n his own body In health and disease the greater part of work on kidney function has been concerned with that of the mammal. Further-more, because i t i s an animal easi ly obtained and experimented with, the kidney of the frog has been much worked on. Now, i t i s only f a i r to point out that these two classes of animals belong to the ureotelic type, that i s to say animals in which the end-product of nitrogen metabolism i s predominantly urea. The kidneys of these two classes w i l l therefore to a great extent function somewhat s imi la r ly . Now i t has been stated by Needham (1929) that the end product of nitrogen metabolism 3. depends on the e m b r y o l o g i c a l environment. Thus, an animal w i t h an a q u a t i c environment w i l l , i f i t i s small enough, e x c r e t e ammonia which, though h i g h l y t o x i c , d i f f u s e s out r e a d i l y , o r urea whose removal depends on a good water supply. With the assumption o f a t e r r e s t i a l l i f e , as i n the b i r d and r e p t i l e , i t was necessary t o conserve water and y e t f i n d some end-product which would be n e i t h e r t o x i c , nor upset the osmotic g r a d i e n t i n a c l e i d o l c egg, i . e . , an "egg p r o v i d e d w i t h water when l a i d and p r o t e c t e d a g a i n s t i t s l o s s by b e i n g surrounded w i t h a more or l e s s impermeable s h e l l or membranes". (Baldwin, 1940, p.38) U r i c a c i d f u l f i l s these requirements i n most o f the r e p t i l e s and i n b i r d s ; i t i s n o n - t o x i c and s u f f i c i e n t l y i n s o l u b l e t o be p r e c i p i t a t e d out and so e x e r t s no harmful osmotic e f f e c t s . However, these animals a l r e a d y possessed a M a l p i g h i a n body, a r e l i c from a remote an c e s t o r whose osmotic body g r a d i e n t was h i g h e r than t h a t o f the e x t e r n a l medium. Because of t h i s c o n d i t i o n water moved i n t o the animal's body and was removed by f i l t r a t i o n through the glomerular t u f t . Thus the r e p t i l e and the b i r d , u r i c o t e l i c t e r r e s t i a l animals p o s s e s s i n g an a n c e s t r a l organ whose f u n c t i o n i s l a r g e l y v e s t i g i a l , except i n some r e p t i l e s , must have made a d a p t a t i o n s t o conserve water w i t h an apparatus designed to e l i m i n a t e i t . A d a p t a t i o n s , t h e r e f o r e , have been d i r e c t e d towards mo d i f y i n g the glomerulus ( M a r s h a l l and Smith, 1930) and i n d i c a t i o n s are shown o f a r e t u r n to a much more p r i m i t i v e mode o f n i t r o g e n e x c r e t i o n , namely t u b u l a r s e c r e t i o n . In a d d i t i o n the s i t u a t i o n i s f u r t h e r complicated In the b i r d by the f a c t t h a t I t i s a warm-blooded animal and, t h e r e f o r e , w i l l have a h i g h e r r a t e o f metabolism w i t h a c o r r e s p o n d i n g l y h i g h e r water i n t a k e and g r e a t e r need f o r i t s c o n s e r v a t i o n . I t w i l l , t h e r e f o r e , be the purpose o f t h i s t h e s i s , by v a r i o u s means to show t o some smal l e x t e n t how the a v i a n kidney i s c o n s t r u c t e d ; and to c o r r e l a t e the f a c t s w i t h the known p h y s i o l o g y , and to produce some c o n c l u s i o n s which may i n the f u t u r e be used i n the study o f b i r d kidney d i s e a s e . 2. Acknowledgments The w r i t e r i s indebted to Dr. W.A. Clemens f o r h i s k i n d l y suggestions and I n t e r e s t at a l l times. She wishes to express her thanks to P r o f e s s o r G.J. Spencer under whom t h i s work was commenced, Dr. I . MoT. Cowan, Dr. W.S. Hoar, Dr. J.R. Adams, a l l o f the Department o f Zoology, P r o f e s s o r J . B i e l y o f the Department of P o u l t r y Husbandry, Dr. B. E a g l e s o f the Department o f D a i r y i n g , and my f e l l o w students and,in p a r t i c u l a r , Miss A. L a z a r e f f , and Miss L. Cowie f o r much k i n d l y h e l p , c r i t i c i s m , p r o c u r i n g o f s p e c i -mens, l o a n o f equipment, and g i f t o f m a t e r i a l s . 5 . She a l s o wishes to thank Miss A. Smith o f the L i b r a r y f o r o b t a i n i n g many i n t e r l l b r a r y i o a n s . The w r i t e r takes p l e a s u r e i n acknowledging the suggestions and c r i t i c i s m stemming from the profound knowledge of Dr. J.A.C. N i c o l under whose s t i m u l a t i n g d i r e c t i o n t h i s study was f i n a l l y c a r r i e d to completion. 3. H i s t o r i c a l Review In order to adequately p r e s e n t an h i s t o r i c a l review of the l i t e r a t u r e c o n cerning the a v i a n metanephros, i t i s n e c e s s a r y to g i v e a b r i e f summary o f the s u b j e c t s which w i l l be d e a l t w i t h i n t h i s s e c t i o n . Furthermore, to c l a r i f y the s i t u a t i o n , a schematic r e p r e s e n t a t i o n (PLATE I.(p. ) of the a v i a n r e n a l u n i t adapted from M a r s h a l l (1934) i s g i v e n , accompanied by e x p l a n a t o r y n o t e s . I f PLATE I i s examined,it w i l l be seen t h a t the a v a i n r e n a l u n i t i s made up o f f i v e m o r p h o l o g i c a l l y d i s t i n c t segments: 1, the r e n a l or M a l p i g h i a n c o r p u s c l e ; 2, the p r o x i -mal c o n v o l u t e d t u b u l e ; 3, the loop o f Henle, which Huber (1917) by means o f maceration and i s o l a t i o n , showed to v a r y from the r e p t i l i a n type (PLATE I, f i g . 1) w i t h a s h o r t i n t e r m e d i a t e p o r t i o n , t o t h a t of the mammal (PLATE I, f i g . 2) w i t h w e l l developed descending and ascending r e g i o n s . The r e p t i l i a n form i s found at the p e r i p h e r y o f the l o b u l e , and the mammalian at the c e n t e r . The d i s t a l t u b u l e 4 , extends from the r e g i o n where the ascending loop o f Henle approaches the glomerular r o o t , to the i n i t i a l c o l l e c t i n g t u b u l e , 5 , (1) M i c r o s c o p i c u n i t s of the a v i a n metanephros. Lobule, components: Ma l p i g h i a n body convoluted or u r i n i f e r o u s t u b u l e s proximal segment Henle's loop descending segment ascending segment d i s t a l t u b u l e c o l l e c t i n g t u b u l e stroma (no r e f e r e n c e s to aves) (2) L o b u l a r o r g a n i z a t i o n (3) V a s c u l a r supply ( 4 ) Cytology M i t o c h o n d r i a G o l g i body (no r e f e r e n c e s to aves) ( 5 ) H i s t o c h e m i s t r y (no r e f e r e n c e s to aves) (1) M i c r o s c o p i c u n i t s of the a v i a n metanephros  L o b u l a r components  Mal p i g h i a n body In comparison w i t h the kidney o f amphibians and mammals t h a t o f the b i r d has been s u b j e c t e d to ve r y l i t t l e s ystematic work. No review o f the s u b j e c t has as y e t been w r i t t e n and i n many cases, p a r t i c u l a r l y In t e x t books, the data are c o n t r a d i c t o r y . Bowman (1842) p r o c e e d i n g by the comparative method, noted t h a t i n b i r d s and r e p t i l e s the e f f e r e n t g lomerular a r t e r y "seldom d i v i d e s , but d i l a t e s , i n s t e a d , i n t o a pouch-l i k e c a v i t y which a f t e r t a k i n g two or thr e e c o i l s c o n t r a c t s again and becomes the e f f e r e n t v e s s e l . " L a t e r Bowman d e s c r i b e d A the glomerular v e s s e l In the b i r d "as a c o i l e d ampula." He a l s o compared the s i z e o f the Malpi g h i a n b o d i e s o f v a r i o u s c l a s s e s (and s p e c i e s ) and gave the s i z e o f the p a r r o t ' s as 1/430 o f an i n c h (59 m i c r a ) , i n c i d e n t a l l y the s m a l l e s t he re c o r d e d . Bowman g i v e s the diameter o f the t u b u l e s as 1/600 -tn tc ifo.x. 1/700 (42 - 36 ) o f an i n c h and a l s o mentions t h a t the A " p o r t a l system o f the kidney i n the lower t r i b e s , has a two-f o l d o r i g i n , one extraneous, the other In the organ i t s e l f . In both cases the extraneous source i s the p r i n c i p a l one, and the a r t e r y f u r n i s h i n g the I n t e r n a l source i s ve r y s m a l l . n Huber (1917) showed t h a t the conv o l u t e d t u b u l e s o f b i r d s are of two types: (a) Mammalian, i . e . , w i t h a f a i r l y w e l l - d e v e l o p e d Henle»s l o o p . (b) r e p t i l i a n , i . e . , v e r y s h o r t , w i t h i n t e g r a t i n g forms between the two. Huber a l s o g i v e s the l e n g t h s o f the d i f f e r e n t segments. 8 L i Koue Tchang (1923, c i t e d from M a r s h a l l and Smith, 1930) worked on the h i s t o l o g y o f the b i r d k idney. In t h i s c o n n e c t i o n , M a r s h a l l and Smith (1930) b e l i e v e d t h a t t h e y were the f i r s t to d e s c r i b e the " c e n t r a l core o f dense s y n c i t -i a l - l i k e t i s s u e " i n the a v i a n glomerulus, but i t was f i r s t n o t i c e d by Tchang^ to whom they gave the c r e d i t i n a f o o t n o t e . Tchang (1924) s t u d i e d the br u s h border i n the prox i m a l t u b u l e o f the kidney o f the s p e c i e s o f e x o t i c sparrow u s u a l l y known as i g n i c o l o r e (Buplectes f r a n c i s c a n u s ) . He noted t h a t the bru s h border i s the same as t h a t i n the mammal w i t h t h i s d i f -f e r e n c e , t h a t i t i s mich more h i g h l y developed i n the b i r d I.e., one qua r t e r of the he i g h t o f the c e l l . He a l s o s t a t e d t h a t the s t r i a t e d appearance i s i n the b i r d a post-mortem a r t e f a c t due to m a l - f i x a t i o n and t h a t o r d i n a r i l y i t i s a homogeneous s t r u c t u r e . Warner (1927) examined the a v i a n kidney f o r v e s t i g i a l and p r o v i s i o n a l u r i n i f e r o u s t u b u l e s which had been r e p o r t e d by Kampmeier t o occur c o n s t a n t l y i n human f e t u s e s , and which he a l l e g e d were a s i g n t h a t not o n l y the pronephros and meso-nephros are r e t r o g r e s s i v e organs, but t h a t the metanephros a l s o Is i n some p a r t v e s t i g i a l . Warner showed t h a t n e i t h e r the f i r s t formed t u b u l e s no* the e a r l y g l o m e r u l i degenerate i n the b i r d . He compared the r e l a t i v e diameters o f M a l p i g h i a n b o d i e s o f the c e n t r a l and p e r i p h e r a l areas o f the metanephros, and found no marked d i s p a r i t y between the c e n t r a l and most p e r i p h e r a l b o d i e s . The l a r g e s t b o d i e s were p r e s e n t In the 9 . newly hatched c h i c k , there b e i n g a g r a d u a l i n c r e a s e i n the s i z e o f the M a l p i g h i a n c o r p u s c l e from the t h i r t e e n t h day on. von M o l l e n d o r f (1929) measured glomerular diameters i n the pigeon and the r i n g sparrow and found t h a t they were 55 x 55 m i c r a i n the pigeon,and 42 x 37 micra i n the sparrow. M a r s h a l l and Smith (1930) s t u d i e d the glomerular development of the v e r t e b r a t e k i d n e y In r e l a t i o n t o h a b i t a t . They gave the average diameters o f the g l o m e r u l i of the pigeon as 48 m i c r a , 38 m i c r a f o r the ring-sparrow, 28 m i c r a f o r the house sparrow and 24 m i c r a f o r the f i n c h . They a l s o determined the "average diameter o f the M a l p i g h i a n body o f the c h i c k e n and pigeon, and found i t to be 70 m i c r a i n the former and 50 m i c r a i n the l a t t e r . They noted s y n c y t l a l - l i k e t i s s u e In the c e n t r a l p a r t of the glomerular t u f t mentioned p r e v i o u s -l y . M a r s h a l l and Smith concluded t h e i r remarks on the b i r d kidney^ by s a y i n g t h a t i t i s obvious t h a t i t shows g l o m e r u l a r degeneration I s i n d i c a t e d by the v e r y . s m a l l s i z e and poor v a s c u l a r i z a t i o n o f the g l o m e r u l i , and by the replacement o f the c e n t r a l p a r t of the t u f t by s y n c y t i a l t i s s u e . They a l s o s a i d t h a t i t i s improbable t h a t i n c r e a s e d number o f g l o m e r u l i can o f f s e t t h i s r e d u c t i o n i n f i l t e r i n g s u r f a c e . M a r s h a l l (1934) found t h a t the t o t a l numbers o f g l o m e r u l i i n the kidneys o f two chickens o f about 2,500 grams body weight were 840,000 and 848,000. Edwards and S c h n i t t e r (1933) s t u d i e d the r e n a l u n i t i n the kidney of v e r t e b r a t e s . They s t a t e d t h a t the p r o x i m a l 10 region of the nephron i s the most differentiated In the kidneys of a l l the vertebrates studied. This convolution i n the kidney of the mammal, b i r d , rep t i le and frog i s cytologic-a l l y uniform throughout i t s length. They also noted that the d i s t a l convolution and duct portion i s present and cytologic-a l l y comparable In the tubule of the kidney i n a l l of the vertebrates studied. They mentioned also that the glomerulus varies i n size and degree of vascularity i n various verteb-rates. The least developed i s present In the avian kidney and the most developed in that of the frog and mammal. V i l t e r (1935) examined the morphology and develop-ment of the pigeon metanephros to confirm Bowman's or ig ina l assertion that the glomerular vessel of the b i rd was a "coiled ampula". Using a reconstruction method he found that the afferent glomerular blood vessel enters the corpuscle and divides dichotomously, and that either or both of the resul t -ant branches may show further subdivision, which can be quite extensive. V i l t e r also noted that the glomerulus of the pigeon shows a central avascular core. Lobular organization Spanner (1924) gave a clear account of the lobular organization In the bird kidney. He noted that each lobule, whose actual shape has not yet been worked out, consists of a r ing of Malpighian corpuscles, at the periphery. The proximal tubules from Bowman's capsule take several turns, then descend towards the centre of the lobule, either s t i l l as proximal 11. tubule or as the descending limb of Henle (this depends on the position of the Malpighian corpuscle in the lobule) . At the center of each lobule l i e s the efferent or intralobular ve in . This vessel col lects the blood brought to the proximal tubules by the afferent, or renal portal system. The efferent vein also receives the blood supplied to the glomeruli by the in t ra -lobular arteries which accompany this ve in . The blood i s f i n a l l y discharged into the posterior vena cava by the efferent vein. The tubule now ascends back towards the glomerular pole to which It i s always attached (as shown by Huber, 1917). I t f i n a l l y merges into the col lect ing tubule which i s interlobular and runs with the afferent or interlobular (renal portal) vein . This renal portal vein runs, as stated above, between the lobules, giving off regular branches which supply the proximal tubules. The blood i s collected up again by the central effer-ent vein and carried out of the kidney to the posterior vena cava. The small intralobular artery, that accompanies the efferent vein, gives off regular branches which supply the glomerular tufts , and these then run into the efferent blood capi l la r ies which themselves run into the Intralobular vein (see PLATE I I ) . Spanner remarks here on the very small diameter of the intralobular artery and says that i t s diameter and that of the afferent renal portal vein just approximate that of the efferent vein. 12. The V a s c u l a r Supply E x t r i n s i c and I n t r i n s i c The problem of the b l o o d supply to the avian k idney i s a c o n t r o v e r s i a l one. Jacobsen e a r l y i n the l a s t c e n t u r y , and a f t e r him G r a t i o l e t and J o u r d a i n , maintained t h a t the b i r d metanephros i s s u p p l i e d not":only by an a r t e r i a l v a s c u l a r system but a l s o by a small r e n a l p o r t a l system. T h i s o p i n i o n was very soon opposed by many workers i n c l u d i n g H y r t l . Spanner (1924) made3 a s e r i e s o f c a r e f u l examinations of 178 b i r d s o f d i f f e r e n t s p e c i e s . He found t h a t the b i r d possesses a r e n a l p o r t a l system but that J a c o b s e n 1 s o r i g i n a l a s s e r t i o n was i n -ln tHa-^ b l o o d c l o d Vuoy ^vot*t.- Hie Ki'«in.t~f -Ta^cKf-dLi We-V. a c c u r a t e ^ Spanner based h i s assumptions on the f a c t t h a t a "tympanic" v a l v e e x i s t s between the a f f e r e n t or r e n a l p o r t a l system and the e f f e r e n t v e i n . He a l s o showed t h a t the diamet-er s o f the a f f e r e n t v e i n and I n t e r l o b u l a r a r t e r y are t o g e t h e r about equal to t h a t o f the e f f e r e n t v e i n . Spanner's c o n c l u -s i o n s were accepted by von M o l l e n d o r f (1929) and l a t e r by P i t t s (1933). Das (1924, 1931) on the b a s i s of p e r f u s i o n e x p e r i -ments denied t h a t the r e n a l p o r t a l v e i n g i v e s o f f an a f f e r e n t supply to the kidney; he was unaware however o f . t h e o e x i s t e n c e of the v a l v e d e s c r i b e d by Spanner, w i t h whose work he was not acquainted, and he d i d not r e a l i z e t h at the flow of b l o o d i n the r e n a l - p o r t a l v e i n i s i n c r e a s e d i n volume by b l o o d coming i n from the coccygo-mesenteric v e i n . Das, however, d i s s e c t e d a number o f specimens of s p e c i e s of Indian b i r d s , and showed 13. t h a t (at l e a s t i n the s p e c i e s examined) there are three main types o f r e n a l venous c i r c u l a t i o n s , which he d e s i g n a t e d as "pigeon", "duck", and " p a r r o t " . In the kidney o f the Grey H o r n b i l l (Ocyceros g r i s e u s ) , of which s p e c i e s he examined e i g h t specimens, he found t h a t the kidney c o n s i s t e d o f two l o b e s o n l y , the a n t e r i o r and the p o s t e r i o r , the middle l o b e b e i n g absent. The two remaining l o b e s were completely separated from each o t h e r , b e i n g about 11 mm, apart and o n l y j o i n e d by the a f f e r e n t and e f f e r e n t r e n a l v e i n s . Das a l s o s a i d , among other o b s e r v a t i o n s , t h a t e s s e n t i a l l y a l l b i r d s are endowed w i t h a s i m i l a r type of venous o r g a n i z a t i o n such as t h a t demon-s t r a t e d i n the pigeon, i n which animal the b l o o d from the a f f e r e n t r e n a l has a d i r e c t communication w i t h the p o s t e r i o r vena cava. He mentioned the f a c t t h a t the a f f e r e n t r e n a l v e i n j o i n s the p o s t - c a v a l v e i n "with undiminished c a l i b r e , and does not break up i n t o s i n u s o i d s or c a p i l l a r i e s i n the substance o f the k i d n e y " . Cytology Cowdry (1918) mentioned t h a t m i t o c h o n d r i a are found i n the metanephric proximal t u b u l e s o f b i r d s , 4. M a t e r i a l s and Methods The V a s c u l a r Supply A r t e r i a l Venous Tympanic v a l v e 14. M a t e r i a l . 5 G a l l u s domestlcus Domestic Fowl and 1 Gavla a r C t l c a p a c i f i c a (Lawrence). P a c i f i c Loon, 1 U r l a aalge c a l l f o r n i c a (Bryant) C a l i f o r n i a Murre, 1 Lunda c l r r h a t a ( P a l l a s ) . T u f t e d P u f f i n 1. P u f f i n u s g r i s e u s (Gmelln). Sooty Shearwater 1 Columba l l v l a l l v i a (Gmelln) Rock Dove, Methods. These specimens c o n s i s t e d o f whole c a r c a s s e s i n some cases, i n o t h e r s the kidneys as removed from the specimen. A l l were pr e s e r v e d i n : Commercial f o r m a l i n 10 c c . 0.9 per cent Sodium C h l o r i d e ......... 90 c c . D i s s e c t i o n s were c a r r i e d out under a b i n o c u l a r microscope i n a l l c a s e s . H i s t o l o g y M a t e r i a l . 10 G a l l u s domestlcus Domestic Fowl 2 Columba l i v l a l i v l a (Gmelin). Rock Dove 1 Diomedea n l g r i p e s (Audubon). B l a c k - f o o t e d A l b a t r o s s 1 M e l o s p l z a melodla morphna ( O b e r h o l s e r ) • Rusty Song Sparrow K i l l i n g . The specimens used were k i l l e d by s h o o t i n g , anaes-t h e s i a , by e t h e r , and by having t h e i r necks wrung. Methods. F i x a t i o n f l u i d s . Such d i f f i c u l t y was encountered i n f i x a t i o n o f b i r d k idney, t h a t a comparative t e s t was made on the m e r i t s o f the f o l l o w i n g f l u i d s , which are l i s t e d below, w i t h remarks as to t h e i r e f f e c t i v e n e s s , i n the hope t h a t they may prove of use to workers on b i r d k idney. (1) A l l e n ' s B-15 method (Guyer, 1947). T h i s f l u i d should be avoided as i t g i v e s most unsat-i s f a c t o r y r e s u l t s I.e., t y p i c a l " B o u i n " p i c t u r e o f kidney t i s s u e , (see Bouin's f l u i d ) . (2) Bouin's f l u i d (Guyer, 1947). T h i s f i x should not be used f o r b i r d kidney as I t causes cloudy s w e l l i n g and d i s i n t e g r a t i o n o f the c e l l s , e s p e c i a l l y , those of the p r o x i m a l convoluted t u b u l e . Peacock (1945), s t a t e s t h a t Bouin's f l u i d i s a bad f i x a t i v e f o r mammalian kidney, and a l s o f o r m i t o c h o n d r i a . As the a v i a n 16. proximal tubule c e l l s are packed w i t h these c e l l u l a r c o n s t i t u -e nts, t h e i r d e s t r u c t i o n may be a c o n t r i b u t i n g cause t o mal-f i x a t i o n i n t h i s t i s s u e . (3) Carnoy's f l u i d (Lee, 1946). Although Lee quotes t h i s as the b e s t f i x a t i v e f o r r e n a l e p i t h e l i u m (presumably mammalian), i t was found i n b i r d k idney t h a t i t caused d i s i n t e g r a t i o n o f the e p i t h e l i u m of the proximal t u b u l e . However, s t a i n i n g w i t h Heidenhain's azan a f t e r t h i s , f l u i d , gave q u i t e good r e s u l t s i n d e l i n e a t i o n o f the connective t i s s u e i n the Ma l p i g h i a n c o r p u s c l e . (4) F o r m o l - s a l i n e . A 10 per cent s o l u t i o n o f n e u t r a l f o r m a l i n (4 per cent formaldehyde) i n b i r d p h y s i o l o g i c a l s a l t s o l u t i o n (0.9 per cent sodium c h l o r i d e ) . T h i s f l u i d proved f a i r l y s a t i s -f a c t o r y as a p r e s e r v a t i v e o f the c e l l s o f the p r o x i m a l t u b u l e ; i t has a l s o the advantage t h a t t i s s u e may be l e f t i n i t l o n g e r than any o f the other f i x e s used f o r b i r d k i d n e y . S t a i n s are f a i r l y b r i l l i a n t a f t e r t h i s f i x . (5) H e l l y ' s f l u i d (Baker, 1945). T h i s f i x a t i v e proved very d i s a p p o i n t i n g ; i t hardened the t i s s u e extremely; c a u s i n g f l a t t e n i n g on the s i d e almost i m p o s s i b l e ; however i t p r e s e r v e d the t i s s u e f a i r l y w e l l , except m i t o c h o n d r i a , which were not f i x e d a t a l l . (6) Regaud's f l u i d (Baker, 1945). T h i s s o l u t i o n , w h i l e very v a r i a b l e i n i t s r e s u l t s , gave the most b r i l l i a n t s t a i n i n g o f c e l l d e t a i l . 17 (?) Zenker's f l u i d (Guyer, 1947). As a g e n e r a l f i x a t i v e f o r kidney, t h i s mixture proved the most u s e f u l . For t h i s t i s s u e , i t i s a d v i s e d t h a t mercury be removed w i t h i o d i z e d a l c o h o l on the s l i d e , and not i n bulK, or s t a i n i n g , which i s u s u a l l y b r i l l i a n t a f t e r t h i s f l u i d , w i l l be g r e a t l y Impaired. (8) 80 per c e n t , a l c o h o l . The use of t h i s f l u i d f o r 2 - 4 hours, f o l l o w e d by r a p i d changes o f 95 per c e n t . , 100 per cent, a l c o h o l , t o l u e n e , 3 changes of p a r a f f i n f o r one h a l f hour to one hour each, gave, wi t h s m a l l k i d n e y s , m a t e r i a l which c o u l d be r e a d i l y s e c t i o n e d and e a s i l y f l a t t e n e d . B i r d kidney i s , i f mammalian h i s t o l o g i c a l methods are f o l l o w e d , v e r y e a s i l y hardened, t h e r e f o r e , f l a t t e n e d w i t h d i f f i c u l t y on the s l i d e . These f a c t s prevent s e r i a l work, as some s e c t i o n s are u s u a l l y l o s t , b u t , w i t h 80 per c e n t , a l c o h o l , s a t i s f a c t o r y work can be done. H i s t o l o g i c a l d e t a i l w i l l not be very good, but the g e n e r a l o r g a n i z a t i o n of the t i s s u e can be e a s i l y examined. General remarks on f i x a t i v e s . No f i x a t i o n f l u i d proved p e r f e c t . T h i s c o n c l u s i o n i s i n accordance w i t h the remarks on t h i s phase o f the h i s t o l o g y , made by Regaud and P o l i c a r d (1903-04), i n t h e i r work on the snake kidney. B i r d s have a h i g h e r r a t e of metabolism than snakes, and i t i s t h e r e f o r e p o s s i b l e that a u t o l y s i s i s v e r y r a p i d i n - t h e i r kidney t i s s u e . In t h i s c o n n e c t i o n , the author has n o t i c e d t h a t the kidneys of f i s h and amphibians are much 18. more e a s i l y f i x e d , c u t , f l a t t e n e d and s t a i n e d . These f a c t s would seem to support the remarks made above concerning a u t o l y s i s . Washing. T h i s process was c a r r i e d out a c c o r d i n g to the method adv i s e d f o r the p a r t i c u l a r f i x a t i v e employed. Dehydration. T h i s p r o c e s s was e f f e c t e d by means o f : (1) dioxan f o r the u s u a l p e r i o d s o f time; (2) a l c o h o l as u s u a l l y employed; however i t was found advantageous to shor t e n c o n s i d e r a b l y the l e n g t h o f time i n the s o l u t i o n s . B efore t r a n s f e r e n c e to wax, i t was found p r e f e r a b l e to p l a c e the t i s s u e i n toluene f o r 15-30 minutes, r a t h e r than i n cedar, or wintergreen o i l . These two o i l s were almost im-p o s s i b l e to remove from kidney t i s s u e , even a f t e r soaking i n to l u e n e , and caused crumbling o f the t i s s u e when i t was s e c t -i o n e d . Embedding. Three changes of p a r a f f i n wax of m e l t i n g p o i n t o f 54-56 C. were used. I t was found necessary to shorten c o n s i d -e r a b l y the time i n the wax, u s i n g p e r i o d s averaging one h a l f to one hour f o r each. S e c t i o n i n g . In order t o see h i s t o l o g i c a l d e t a i l w i t h c l a r i t y , s e c t i o n i n g was c a r r i e d out at 5 - 8 m i c r a . 19. • F l a t t e n i n g and A f f i x i n g S e c t i o n s . D i s t i l l e d water and Mayer's albumin were used f o r f l a t t e n i n g and a f f i x i n g s e c t i o n s on to the s l i d e s . Great d i f f i c u l t y was encountered i n s u c c e s s f u l l y f l a t t e n i n g the t i s s u e which, p r o b a b l y , owing to i t s t u b u l a r n a t u r e , s u f f e r e d b a d l y from compression under the m i c r o t o n i c b l a d e . Descending S o l u t i o n s P r i o r to S t a i n i n g . Owing to the reasons s t a t e d above, i n c o n n e c t i o n w i t h f l a t t e n i n g and a f f i x i n g , t h i s t i s s u e was very i n c l i n e d t o wash o f f the s l i d e when descending through the f l u i d s p r i o r to s t a i n i n g , e s p e c i a l l y i n a l c o h o l s lower than 95 per c e n t . In order to overcome t h i s d i f f i c u l t y ^ a l l s l i d e s , a f t e r immersion i n a b s o l u t e a l c o h o l , were soaked i n a mixture of approximately one per cent, c e l l o i d e n i n e t h e r - a l c o h o l ; they were then d r a i n -ed one minute, and hardened f o r 1-5 minutes i n 80 per c e n t , a l c o h o l . A f t e r t h i s treatment, even w i t h v e r y b a s i c s o l u t i o n s , no l o s s of- s e c t i o n s was encountered. S t a i n i n g . 1. The g e n e r a l s t a i n s . H a r r i s and E h r l i c h ' s haematoxylin*s c o u n t e r s t a i n e d w i t h e o s l n , congo-red, or Van G l e s e n . These s t a i n s proved the most s a t i s f a c t o r y f o r g e n e r a l h i s t o l o g i c a l examination o f kidney t i s s u e . ( C o n g o - r o d empha-s i z e d the hemopolotlo noduloo s a t l s f a c t o r i l y j ) Van Glesen showed up the f i b r o b l a s t s forming the core o f the glomerulus. 2. Heidenhain's azan s t a i n ( P a n t i n , 1946) A m o d i f i c a t i o n was made i n t h i s method, a c c o r d i n g t o that suggested by McGregor (1929), who used t h i s s t a i n f o r the examination of the- normal h i s t o l o g y of the mammalian glomerulus. M o d i f i c a t i o n . I n stead of employing a 0.1 per cent, s o l u t i o n o f azocarmine G, the c o n c e n t r a t i o n was i n c r e a s e d t o 1 per ce n t . Otiierwise the s t a i n was used as P a n t i n suggests. 3. Foot's short method f o r s i l v e r impregnation of r e t i c u l u m (Bensley and Bensley, 1938). T h i s method was used a c c o r d i n g to the d i r e c t i o n s g i v e n by Bensley and Be n s l e y . I t was found very s a t i s f a c t o r y w i t h s l i d e s coated w i t h c e l l o i d i n . No c o u n t e r s t a i n was used, as the f i n e f i b r e s showed up more c l e a r l y without i t . Ascending S o l u t i o n s a f t e r S t a i n i n g . The u s u a l procedures were f o l l o w e d as f a r as 70 per cent a l c o h o l ; a f t e r t h i s step, c e l l o i d i n was removed, and deh y d r a t i o n e f f e c t e d , by means of at l e a s t two changes o f c h e m i c a l l y pure acetone. The s l i d e s were then immersed i n two changes of t o l u e n e , and f i n a l l y mounted i n t h i n balsam. C y t o l o g y M i t o c h o n d r i a . M a t e r i a l 2 G a l l u s domesticus 21. Domestic Fowl 1, Columba l i v i a l i v i a (Gmelin) Rock Dove (Common Pigeon) Method. Small p i e c e s were taken from the animal as soon a f t e r death as p o s s i b l e . Pigeon. F i x a t i o n . Regaud's f l u i d . Postchroming was c a r r i e d out i n t h r e e per cent, potassium dichrornate f o r 6-7 days. S e c t i o n i n g . Tlssvies were c u t a t 5 m i c r a . S t a i n : Altmann's a c i d - f u c h s i n e , a c c o r d i n g to L i l l i e (1948) w i t h the f o l l o w i n g m o d i f i c a t i o n s : Altmann's a n i l i n e a c i d f u c h s i n e 2-3 minutes o n l y from the commencement of h e a t i n g . T o l u i d i n e b l u e : 1 minute. Dehydration: i n two changes of acetone C o u n t e r s t a i n : Methyl green L i g h t green T o l u i d i n e b l u e Domestic Fowl F i x a t i o n : Regaud's f l u i d , as above H e l l e y ' s f l u i d post-ohr-omioal 48 h r s . a t 37 C. Washed: i n water, run through the a l c o h o l s , t o l u e n e , 3 changes of wax. Se c t i o n e d : at 5 m i c r a . S t a i n s : Altmann's a c i d - f u c h s i n e C o u n t e r s t a i n s : T o l u i d i n e b l u e Comments on Methods. H e l l y ' s f l u i d : b r i t t l e , hard to c u t , hard to f l a t t e n washed o f f s l i d e m i t o c h o n d r i a p o o r l y p r e s e r v e d s t a i n e d p o o r l y Regaud's f l u i d : v a r i a b l e i . e . , some s e c t i o n s on s l i d e e x c e l l e n t : b e a u t i f u l h i s t o l o g i c a l d e t a i l , s t a i n i n g b r i l l i a n t m i t o c h o n d r i a w e l l p r e s e r v e d ; other s e c t i o n s : t u b u l a r c e l l s much swollen, s t a i n i n g d u l l . S t a i n s : Altmann's a c i d f u c h s i n e ; b r i l l i a n t a f t e r good Regaud's f i x a t i o n . C o u n t e r s t a i n s : T o l u i d i n e b l u e - the b e s t Methyl green) L i g h t green) would not s t a i n . Orrii t" (Rana o a t e s b l a n l a : mpisonephros Method: adapted from Lee (1946) L i l l i e , R.D. (1948) 23 S t a i n : Janus green B 1 per cent, aqueous s a l t Janus green B ... 1 c c . 0.9 per cent. Sodium C h l o r i d e 99 c c . Kidney was removed from f r e s h l y k i l l e d male b u l l f r o g , cut i n t o s m a l l p i e c e s i n 0.9 per cent sodium c h l o r i d e i n s m a l l p e t r l e -d i s h ; s a l i n e poured o f f ; 1:10,000 Janus green B added; incubated i n 38 C oven 10-20 minutes. Small p i e c e s were then crushed between two s l i d e s , c o v e r - s l i p was added. Examination made by means of g l y c e r i n e and o i l - i m m e r s i o n l e n s , w i t h x l 5 o c u l a r . R e s u l t s . The cytoplasm of the c e l l was c l e a r , crowded w i t h p a l e green s p h e r i c a l granules ( m i t o c h o n d r i a ) . Nucleus p l a i n l y seen w i t h n u c l e o l u s ; dark shadow i n p o s i t i o n o f G o l g i body.^) G o l g i Body M a t e r i a l . Song Sparrow, No. 1. Chicken No. X 2 Method. Small p i e c e s o f kidney t i s s u e were taken and prepared a c c o r d i n g to Aoyama's method f o r the G o l g i body, as g i v e n by Baker (1945). The p e r i o d s of time allowed f o r s i l v e r i n g were 13, 15, and 17 hours r e s p e c t i v e l y , as reccommended. Dehydration: 50, 70, 95 per cent a l c o h o l s C l e a r i n g : Toluene Embedding: 3 changes of wax S e c t i o n i n g : at 8 micra C o u n t e r s t a i n i n g s : t h i o n i n e 24. H i s t o c h e m i s t r y  A l k a l i n e Phosphatase M a t e r i a l . Small p i e c e s were taken of Pigeon - kidney and small i n t e s t i n e Song Sparrow - kidney Chickens (3) kidney White r a t kidney B u l l f r o g Kidney Method. K i l l i n g . Pigeon necks wrung Chickens ne^ w v u n j Song Sparrow shot White r a t a n e s t h e t i z e d w i t h sodium p e n t o t h a l B u l l f r o g p i t h e d F i x a t i o n , Dehydration, C l e a r i n g , Embedding Chicken;#1 D a n i e l l i (1946) F i x a t i o n : 80 per cent a l c o h o l f o r 2 hours i n the r e f r i g e r a t o r D ehydration: a b s o l u t e a l c o h o l , 2-3 changes. C l e a r i n g : cedar o i l 2-3 changes Embedding: wax 2-3 changes (1 hour each) b l o c k s were t h e r e a f t e r kept i n the r e f r i g e r a t o r u n t i l needed ( i n t h i s case, one y e a r , see D a n i e l l i (1946), who says they may be sp s t o r e d and s t i l l show unimpaired phosphatase a c t i v i t y ) • 25 Chicken #2,3 L i l l i e (1948) F i x a t i o n : (1) acetone 24 hours i n the r e f r i g -e r a t o r . Dehydration: a b s o l u t e a l c o h o l 2 changes 24 hours C l e a r i n g : cedar o i l 6 hours Embedding: wax, 3 changes 1 hour each (2) 95 per cent, a l c o h o l 24 hours t h e r e a f t e r as above. White r a t F i x a t i o n : acetone 24 hours t h e r e a f t e r as above Pigeon Song Sparrow B u l l f r o g F i x a t i o n : 80 per cent a l c o h o l f o r 4 hours i n the r e f r i g e r a t o r . Dehydration: 4-5 changes o f a b s o l u t e a l c o h o l f o r 1 hour i n a l l . C l e a r i n g : 3 changes of toluene o f 15 minutes each. Embedding: 3 changes o f wax f o r one h a l f hour each S e c t i o n e d : a l l b l o c k s were s e c t i o n e d at 8 m i c r a . In a l l cases the b l o c k s were s e c t i o n e d a t 8 micra mounted w i t h d i s t i l l e d water and Meyer's albumin, d r i e d a t 37 C. o v e r n i g h t (or f o r 3-4 hours o n l y ) , and t e s t e d f o r a l k a l i n e phosphatase a c t i v i t y a c c o r d i n g t o the f o l l o w i n g 26. methods of L i l l i e (1948) and D a n i e l l i (1946). I t should be e x p l a i n e d t h a t these two methods were combined owing to the f a c t t h a t the s u b s t r a t e needed by D a n i e l l i ' s method was Sodium glycerophosphate. However, the o n l y m a t e r i a l i n s t o c k at the time i n the Departmental s t o r e s was marked merely, "Sodium glycerophosphate". I t was assumed t h a t t h i s was a mixture o f alpha and b e t a , and, as L i l l i e g i v e s a procedure u s i n g Eastman sodium glycerophosphate which i s 52 per cent a l p h a , i t was thought worth w h i l e to f o l l o w h i s method as f o l l o w s : (1) S e r i a l s e c t i o n s were c u t , mounted on c o n s e c u t i v e l y numbered separate s l i d e s . Adjacent s l i d e s were used f o r phos-phatase method and c a l c i u m c o n t r o l . (2) P a r a f f i n was removed w i t h two changes of t o l u e n e , 2 changes of 95 per cent a l c o h o l 100 per cent a l c o h o l , s l i d e s were soaked i n 0.5 - 1.0 per cent e t h e r a l c o h o l s o l u t i o n o f c o l l o d i o n f o r one minute, d r a i n e d f o r one minute, hardened f o r one minute i n 80 per cent a l c o h o l , and t r a n s f e r r e d t o d i s t i l l e d water. (3) Calcium c o n t r o l s l i d e s were incubated i n 0.1 per cent Calcium n i t r a t e at 37 C. f o r 12-14 hours, the phosphatase s l i d e s f o r 14 hours a t 37 C. i n : 3.2 per cent aqueous s o l u t i o n of sodium glyc e r o p h o s -phate (S.G. c r y s t a l s , C i t y Chemical Corp.,N.Y.) 6 c c . 27. 2 per cent aqueous c a l c i u m n i t r a t e , Ca(N0 3)2 - 4 HgO, c r y s t a l l i n e 9 c c . 10 per cent aqueous sodium b a r b i t a l 6 c c . 2.465 per cent magnesium s u l f a t e MgS04 . 7H20 (0.1M) 6 c c . D i s t i l l e d water 33 c c . The f i n a l s o l u t i o n measured 60 c c , and had a pH o f 9.0j t h i s was checked with a pH meter. T h e r e a f t e r , D a n i e l l i ' s method was f o l l o w e d : (4) A f t e r I ncubation b o t h the c o n t r o l CaCNOsJg s l i d e s and the phosphatase s l i d e s were r i n s e d i n 2 per cent Ca(N03)g s o l u t i o n , immersed i n 2 per cent c o b a l t n i t r a t e f o r 2 minutes. The Co(N03)2 converts the c a l c i u m phosphate to c o b a l t phos-phate. (5) Washed i n d i s t i l l e d water (1 minute, 2 changes) (6) Tested w i t h d i l u t e ammonium s u l p h i d e • (a few drops to a c o p l i n j a r o f water) f o r 1-2 minutes. Here the s i t e of enzyme a c t i v i t y i s made v i s i b l e by c o n v e r t i n g the c a l c i u m phosphate t o b l a c k c o b a l t s u l p h i d e . N.B. (uaej wax coated f o r c e p s v^e»-e u.sa4. (7) Washed f o r f i v e minutes In tap water. (8) At t h i s p o i n t , some of b o t h the c o n t r o l s l i d e s and the phosphatase s l i d e s were s t a i n e d i n : 28. 0.1 per cent s a f r a n i n 0. t h i o n i n t o l u i d i n e b l u e E h r l i c h ' s haematoxylin and e o s i n (9) The r e s t o f the c o n t r o l and phosphatase s l i d e s were taken to 70 per cent ( and with the s t a i n e d s l i d e s ) , dehydrated w i t h two changes o f acetone, which a l s o removed the c e l l o d i o n , 2 changes o f toluene and mounted i n balsam. Notes. D a n i e l l i ' s p r e c a u t i o n s were observed concerning the enzyme p r e s e r v a t i o n by a v o i d i n g prolonged soaking i n : (1) d i s t i l l e d water (2) a l c o h o l s (3) toluene A l l u t e n s i l s used were c h e m i c a l l y pure. A l l s o l u t i o n s of sodium glycerophosphate, sodium b a r b i t a l e t c . , (should be) made up f r e s h l y as they are very q u i c k l y s p o i l t by growth of moulds. 5. Observations I The Avian Metanephros: macroscopic f e a t u r e s . The kidneys of the. bird are metanephrol. Each one i s a somewhat f l a t t e n e d , u s u a l l y t r i - l o b e d , organ, l y i n g on the v e n t r a l s i d e o f the d o r s a l body w a l l beneath the 29. synsacrum, and e x t e r n a l to the peritoneum. Amongst the b i r d s examined i n c o n n e c t i o n w i t h macro-s c o p i c f e a t u r e s , i t was noted t h a t there was c o n s i d e r a b l e v a r i a t i o n i n the shape and extent of the l o b e s i n d i f f e r e n t s p e c i e s . In the pigeon, b o t h a n t e r i o r and p o s t e r i o r l o b e s , are about equal In s i z e , whereas the middle lobe i s somewhat reduced i n e x t e n t . The s i t u a t i o n i n the domestic f o w l c l o s e l y approximates t h a t i n the p i g e o n . The P a c i f i c , l o o n shows no sharp d i v i s i o n between the middle and p o s t e r i o r l o b e s , the l a t t e r b e i n g v e r y much extended. The a n t e r i o r l o b e i s the most developed i n the C a l i f o r n i a murre. D i s c u s s i o n . Prom the few o b s e r v a t i o n s r e c o r d e d above, i t can be seen t h a t there i s c o n s i d e r a b l e l o b u l a r v a r i a t i o n i n the b i r d kidney. Das (1924) r e p o r t s t h a t the Indian pond heron shows two separated l o b e s , the a n t e r i o r and p o s t e r i o r , which are j o i n e d only by the a f f e r e n t and e f f e r e n t venous systems. T h i s s i t u a t i o n , Das n o t e s , i s normal i n t h i s b i r d . The V a s c u l a r System Venous Tympanic Valve A r t e r i a l I n t r o d u c t i o n . As a foreword to t h i s s e c t i o n on the v a s c u l a r system o f the a v i a n kidney, I t should be s t a t e d t h a t the l i t e r a t u r e 30 . g e n e r a l l y , and i n p a r t i c u l a r , that s e c t i o n which comprises the v a r i o u s text-hooks, i s i n a very confused s t a t e . T h i s d i s o r d e r i s e s p e c i a l l y n o t i c e a b l e when the venous system i s examined. There i s ap p a r e n t l y no agreement as to whether a (a?) r e n a l p o r t a l system e x i s t s or n o t . S i m i l a r l y , the nomencla-ture o f the v e s s e l s themselves needs c l a r i f y i n g . I t i s beyond the scope of t h i s work, to g i v e the v a r i o u s statements and t h e i r c o n t r a d i c t i o n s , which have appeared from time to time. Instead, w i t h the a i d o f p e r s o n a l o b s e r v a t i o n s gained from anatomical and h i s t o l o g i c a l s t u d i e s , combined w i t h p e r t i n e n t m a t e r i a l from the l i t e r a t u r e o f the avi a n kidney, an attempt w i l l be made to g i v e as u n i f i e d a p i c t u r e as p o s s i b l e of t h i s very c o n t r o v e r s i a l s u b j e c t . M i c r o d i s s e c t i o n of the venous system, of the kidney coupled, with a h i s t o l o g i c a l examination o f the v e s s e l w a l l s , brought the c o n c l u s i o n t h a t there were two separate venous systems i n t h i s organ. One system, which can be s a i d to be a f f e r e n t , has a well-developed venous w a l l ; the other system which can be termed e f f e r e n t , has a t h i n v a s c u l a r c o a t , c o n s i s t i n g o f an e n d o t h e l i a l l i n i n g , one c e l l t h i c k , r e s t i n g on a smal l amount o f con n e c t i v e t i s s u e . These o b s e r v a t i o n s were f u r t h e r confirmed by Spanner's (1924) study o f the r e n a l - p o r t a l system i n the b i r d kidney, wherein he g i v e s much evidence i n support of t h i s v a s c u l a r p l a n . At t h i s p o i n t , a b r i e f d e s c r i p t i o n of the venous and a r t e r i a l systems w i l l be g i v e n , u s i n g Spanner's 31. d i a g r a m a t i c r e p r e s e n t a t i o n of the v a s c u l a r supply as an out-l i n e (PLATE UL" ). The nomenclature which, i t has a l r e a d y been s t a t e d i s not uniform, w i l l be t h a t used by Hyman (1947), w i t h a d d i t i o n s where necessa r y . Venous System S t a r t i n g caudad to each kidney w i l l be found the a f f e r e n t , or r e n a l p o r t a l v e i n . T h i s v e i n i s formed by the e m b r y o l o g i c a l union ( M i l l e r , 1903) o f the two caudal p a r t s o f the p o s t e r i o r c a r d i n a l s . Into t h i s anastomosis, on each s i d e , run the i n t e r n a l i l i a c v e i n s ( h y p o g a s t r i c ) from the p e l v i c r e g i o n , and a s m a l l single!?)caudal v e i n . At about the c e n t r e o f the union, the f a i r l y l a r g e coccgeomesenteric ( I n -f e r i o r mesenteric or Jacobsen's v e i n ) e n t e r s from the gut. The l a t t e r v e i n i s s a i d to connect the two p o r t a l systems i . e . , r e n a l p o r t a l and h e p a t i c p o r t a l (Hyman, 1947; Jungherr and L e v i n e , 1941), and i s p r o b a b l y homologous to the v e n t r a l ab-dominal v e i n s of r e p t i l e s (Hyman). Each r e n a l p o r t a l v e i n e n t e r s the p o s t e r i o r lobe o f the kidney and g i v e s o f f branches i n t o the substance of the organ. These branches run p e r p e n d i c -u l a r l y between the l o b u l e s as f a r as the s u r f a c e o f the kidney, where they t u r n at r i g h t a n g l e s , and send out s m a l l e r venules In a r o s e t t e f o r m a t i o n (Spanner, 1924). T h i s r o s e t t e f o r m a t i o n i s r e a d i l y d i s c e r n i b l e upon examining the s u r f a c e of the kidney under a b i n o c u l a r microscope. The r e n a l p o r t a l v e i n passes on through the p o s t e r i o r and median l o b e s as f a r as the e x t e r n a l I l i a c , i n t o which i t f l o w s . Prom the e x t e r n a l 32 i l i a c , an a f f e r e n t branch passes to the a n t e r i o r l o b e . The behaviour of:"this branch i s s i m i l a r to that s u p p l y i n g the other two l o b e s . I t should be mentioned t h a t the a f f e r e n t system i s i n t e r l o b u l a r , and runs w i t h the c o l l e c t i n g t u b u l e s which course i n a s i m i l a r manner. Branches of the a f f e r e n t system, as c a p i l l a r i e s , supply the pr o x i m a l convoluted t u b u l e s . The behaviour o f the e f f e r e n t system, as Spanner has p o i n t e d out i s r a d i c a l l y d i f f e r e n t . The i n i t i a l branches are I n t r a l o b u -l a r . Under the microscope, c r o s s - s e c t i o n s o f these v e i n s can be seen as l a r g e l a c u n a - l i k e spaces, w i t h t h i n w a l l s , l y i n g at the ce n t r e o f the l o b u l e s . The c a p i l l a r i e s from the a f f e r e n t system, t h a t supply the prox i m a l t u b u l e s , f i n a l l y merge w i t h those running i n t o the i n t e r l o b u l a r v e i n . T h i s b l o o d v e s s e l communicates w i t h the l a r g e e f f e r -ent r e n a l v e i n (vena r e n a l e s magna, gre a t r e n a l v e i n ) , which can be seen emerging as a t h i n w a l l e d v e s s e l on the v e n t r a l s u r f a c e o f the p o s t e r i o r l o b e . The e f f e r e n t r e n a l v e i n then runs forward and j o i n s the s o - c a l l e d common i l i a c , a t the p o i n t where the e x t e r n a l i l i a c l i k e w i s e e n t e r s . The two common i l i a c s t o g e t h e r u n i t e t o form the p o s t e r i o r vena cava. The a n t e r i o r lobe a l s o has an a f f e r e n t branch, c a l l e d by Spanner the "super-f i c i a l e f f e r e n t v e i n " . T h i s v e s s e l d r a i n s the lob e and j o i n s the common i l i a c . At the anastomosis o f the a f f e r e n t and e f f e r e n t systems, Spanner (1924) made a v e r y s i g n i f i c a n t d i s c o v e r y , upon which he l a r g e l y bases h i s theory f o r the e x i s t e n c e o f a 3 3 . r e n a l p o r t a l c i r c u l a t i o n i n the b i r d . At t h i s j u n c t i o n , he found a v a l v e , s h u t t i n g o f f the opening o f the anastomosis i n t o the e f f e r e n t r e n a l v e i n . He c a l l e d i t the "tympanic v a l v e " , and confirmed i t s presence i n a l l the s p e c i e s he examined. T h i s s t r u c t u r e i s d e s c r i b e d by Spanner as f o l l o w s : " T h i s p e r f o r a t e d tympanic membrane, p i e r c e d o n l y by a f i n e communicating aperture i n a d i r e c t i o n towards the e f f e r e n t r e n a l v e i n , i s comparable to an e f f i c i e n t v a l v e . The opening u s u a l l y l i e s e c c e n t r i c a l l y , and i s f r e q u e n t l y surround-ed by a t h i c k - l i p p e d r i n g . Larger openings o f t e n show i n a d d i -t i o n a f i n e , f l o a t i n g membrane ( s e g e l ) . " (Spanner, p.24, 1929) In one sp e c i e s Spanner noted an almost completely c l o s e d - o f f v a l v e . He suggests, that t h i s tympanic v a l v e serves as a h i g h l y e f f i c i e n t dam to the flow o f b l o o d , from the e x t e r n a l i l i a c i n t o the common i l i a c j and t h e r e f o r e , f o r c e s the b l o o d to enter the a f f e r e n t or r e n a l p o r t a l system o f the a n t e r i o r l o b e . A r t e r i a l System. Even a c u r s o r y examination of the a r t e r i a l supply to the kidney, w i l l show t h a t , as compared t o the venous system, i t i s s m a l l . S t a r t i n g cephalad t o the kidney, I t w i l l be apparent t h a t the d o r s a l a o r t a g i v e s o f f a very s m a l l reno-lumbar a r t e r y , which s u p p l i e s the a n t e r i o r l o b e . The reno-femoral ( e x t e r n a l i l i a c or c r u r a l ) i s the next a r t e r y a r i s i n g from the d o r s a l a o r t a ; i t passes d o r s a l to the kidney, sup-p l y i n g some branches to the middle l o b e ; i t then proceeds t o 34 the l a t e r a l body w a l l . The t h i r d a r t e r y t o e n t e r the kidney by means of s m a l l branches, i s the l a r g e s c i a t i c ( i s c h i a d i c ) , which courses v e n t r a l l y over the kidney, and then runs out i n t o the l e g . Spanner has shown t h a t the a r t e r i a l branches which e n t e r the kidney accompany the e f f e r e n t system i . e . , they are i n t r a l o b u l a r . In the l o b u l e they c i r c l e the e f f e r e n t v e i n sending o f f r e g u l a r branches l i k e the spokes o f a wheel. These r a d i a t i n g a r t e r i o l e s ascend to the M a l p i g h i a n c o r p u s c l e s which they supply, e n t e r i n g and forming the glomerular t u f t o f c a p i l l a r i e s . The b l o o d from the g l o m e r u l i Is f i n a l l y t r a n s -p o r t e d to the c a p i l l a r y network between the a f f e r e n t and e f f e r e n t systems (see PLATE H ), from thence i t runs i n t o the i n t r a l o b u l a r , or e f f e r e n t v e i n , which c a r r i e s i t to the p o s t -e r i o r vena cava. D i s c u s s i o n . M a r s h a l l (1934) has suggested t h a t a t u b u l a r s e c r e t -i n g kidney depends more on a venous, than an a r t e r i a l b l o o d supply. There i s evidence i n the b i r d k i d n e y o f a l a r g e , a f f e r e n t venous system, which would i n d i c a t e , i f M a r s h a l l ' s statement i s borne i n mind, t h a t the organ i n t h i s c l a s s , f u n c t i o n s to a g r e a t e r or l e s s degree by t u b u l a r s e c r e t i o n . In t h i s c o n n e c t i o n , i t i s s i g n i f i c a n t to note, t h a t the median lobe of the b i r d k i dney i s o f t e n the s m a l l e s t . Das (1924) r e p o r t e d a kidney which c o n s i s t e d of two separate l o b e s , the median one b e i n g m i s s i n g . T h i s lobe i s the most p o o r l y f u r n -i s h e d by an a f f e r e n t system. I t would appear t h a t , i n t h i s 35. animal, there i s a d i r e c t r e l a t i o n s h i p , between the amount o f venous b l o o d e n t e r i n g the kidney, and i t s development. U r i c o t e l i c r e p t i l e s possess a r e n a l p o r t a l system, however, t h i s has o f t e n been denied i n the b i r d . M i l l e r (1903) s t a t e s t h a t t h i s system i s destroyed, d u r i n g embryonic development i n the b i r d , by the union o f the e f f e r e n t r e n a l v e i n ( g r e a t r e n a l v e i n ) w i t h the p o s t e r i o r c a r d i n a l s ; these l a t t e r v e i n s c o n s t i t u t i n g p a r t of the r e n a l p o r t a l system i n r e p t i l e s . However, M i l l e r d i d not r e a l i z e t h a t a new r e n a l p o r t a l system must s u r e l y a r i s e when the anastomosis, p r e v i o u s l y mentioned, takes p l a c e . Prom a study of M i l l e r ' s i l l u s t r a t i o n s , the c o n c l u s i o n can be drawn, that i t i s at t h i s j u n c t i o n t h a t Spanner's tympanic v a l v e i s formed. However, there i s a p o s s i b i l i t y t h a t there may be v a r i a t i o n s , from the schematic r e p r e s e n t a t i o n o f the venous b l o o d system d e s c r i b e d above. Das (1924), working on Indian b i r d s , r e p o r t e d the e x i s t e n c e o f three main types of venous c i r c u l a t i o n . The author, d u r i n g a n . i n v e s t i g a t i o n o f Spanner's v a l v e i n f i v e s p e c i e s o f b i r d s , found f o u r d i f f e r e n t p a t t e r n s and I t s complete absence i n one s p e c i e s (although i t must be admitted that o n l y one specimen was examined i n t h i s c a s e ) . The author suggests, t h a t more work should be undertaken on the c h i e f end product of n i t r o g e n metabolism i n the d i f f e r e n t s p e c i e s of b i r d s . Although i t has been r e p o r t e d t h a t u r i c a c i d accounts f o r the b u l k of the t o t a l u r i n a r y n i t r o g e n i n the c h i c k e n , (Davis, 1927; Coulson and Hughes, 1930), t h i s animal, because o f i t s economic importance,, appears to be the only-b i r d to have been i n v e s t i g a t e d i n any d e t a i l . Moreover, the chicken's venous p a t t e r n corresponds to t h a t d e s c r i b e d above, In which t h e r e i s a w e l l - d e v e l o p e d r e n a l p o r t a l supply and an e f f i c i e n t tympanic v a l v e . Perhaps, i n other s p e c i e s , i n whiclj the venous scheme d i f f e r s , and i n which the tympanic v a l v e i s l e s s developed, or l a c k i n g , there may be a d i f f e r e n c e i n the c h i e f end product of n i t r o g e n metabolism. H i s t o l o g y The kidney o f the b i r d s enumerated under " M a t e r i a l s and Methods" were examined h i s t o l o g i c a l l y . While minor d i f f e r -ences were noted, t h a t of the c h i c k e n w i l l be g i v e n as a type o f the h i s t o l o g i c a l components l i s t e d below: Ma l p i g h i a n c o r p u s c l e Bowman's capsule e p i t h e l i u m p a r i e t a l v i s c e r a l Glomerulus Blo o d v e s s e l s basement membrane a v a s c u l a r core of f i b r o b l a s t s Proximal t u b u l e Henle's loop 37. limbs descending ascending D i s t a l t u b u l e C o l l e c t i n g t u b u l e Malpighian c o r p u s c l e The M a l p i g h i a n c o r p u s c l e o r r e n a l u n i t c o n s i s t s o f Bowman's ca p s u l e , and the glomerulus o r Ma l p i g h i a n t u f t . . Bowman's capusle i s i n the g l o b u l a r d i l a t i o n which forms the beg i n n i n g o f an u r l n l f e r o u s t u b u l e . I t c o n s i s t s o f an outer, or p a r i e t a l l a y e r , which i s r e f l e c t e d onto the s u r f a c e o f the glomerular t u f t as the v i s c e r a l l a y e r . The glomerulus i s a c o i l o f b l o o d v e s s e l s p r o j e c t i n g i n t o Bowman's c a p s u l e . Bowman's capsule P a r i e t a l l a y e r T h i s l a y e r i n the b i r d kidney i s t y p i c a l o f t h a t i n other animals, i . e . , i t c o n s i s t s o f a squamous e p i t h e l i u m . The c e l l s c o n t a i n scanty cytoplasm, the elongated, o v a l nuc-l e u s causes a b u l g i n g o f the c e n t r a l p a r t o f the c e l l body i n t o the subcapsular space. T h i s e p i t h e l i u m r e s t s on a base-ment membrane o f f i n e r e t i c u l a r f i b r e s which are continuous w i t h the stroma o f the r e s t o f the l i d n e y . V i s c e r a l l a y e r T h i s r e f l e c t e d l a y e r i s composed of c e l l s which are u n l i k e those seen i n the mammal. They are c u b o i d a l i n s t e a d o f squamous. The c e l l o u t l i n e s can o c c a s i o n a l l y be seen,and there 38. Is a c o n s i d e r a b l e amount o f cytoplasm. The n u c l e u s I s round or o v a l , and c o n t a i n s one to two w e l l marked n u c l e o l i . T h i s v i s c e r a l l a y e r r e s t s on a basement membrane, which Is c o n t i n u -ous w i t h t h a t upon which the endothelium o f the-glomerular c a p i l l a r i e s i s l i k e w i s e based. Glomerulus At the c e n t r e of the glomerulus i s the mass o f f i b r o b l a s t s r e c o g n i z e d as such by V i l t e r (1935). These c e l l s do not show any d i s t i n g u i s h a b l e o u t l i n e s , possess a somewhat o v a l n u c l e u s , c o n t a i n i n g chromatin, and one or more prominent n u c l e o l i . An e x t e n s i v e f i b r i l l a r network separates the c e l l s . These f i b r i l s s t a i n b l u e w i t h Heidenhain's azan carmine s t a i n (PLATE 12") and can a l s o be demonstrated w i t h s i l v e r impregna-t i o n methods used f o r r e t i c u l a r f i b r e s (PLATE YL ) . A The glomerular c a p i l l a r y l o o p s are p e r i p h e r a l l y p l a c e d and vary from two or t h r e e , i n the r e n a l u n i t s a t the edge of the kidney to a number of branches, i n those l a r g e r , c e n t r a l l y p l a c e d u n i t s . The endothelium l i n i n g the glomerular c a p i l l a r i e s , appears to c o n s i s t of squamous c e l l s not v e r y i n d i s t i n g u i s h a b l e from f i b r o b l a s t s , but w i t h a r a t h e r d a r k e r n u c l e u s , and very scanty cytoplasm. The a f f e r e n t and e f f e r e n t glomerular v e s s e l s are very s m a l l i n the b i r d and are much l e s s o f t e n seen than those i n the mammal. They c o n s i s t appar-e n t l y of an e n d o t h e l i e a l l a y e r , but whether smooth muscle c e l l s are p r e s e n t such as e x i s t i n the mammalian kidney, the author i s not prepared to s t a t e . 39. Proximal t u b u l e T h i s p a r t o f the nephron which l i e s at the p e r i p h e r y of the l o b u l e (PLATE ) has a l e n g t h and diameter g i v e n by M a r s h a l l (1934) as 0.075 x 0.065 mm., and 0.110 x 0.100 mm. I t extends from Bowman's capsule t o the descending limb o f Henle. The opening from Bowman's subcapsular space to the proximal tubule i s seldom seen except i n co n n e c t i o n w i t h the l a r g e r r e n a l -unite i n the v i c i n i t y o f the small medullary a r e a . In the more p e r i p h e r a l c o r p u s c l e s i t i s o n l y seen when the t i s s u e i s sQOtional a t 5 mic r a e r l e s s . In c r o s s s e c t i o n the proximal tubule has a c h a r a c t e r -i s t i c , somewhat I r r e g u l a r o u t l i n e on the lumen s i d e o f the c e l l such as t h a t seen In the mammal. The c e l l s themselves, pass a b r u p t l y from the squamous type o f e p i t h e l i u m o f the p a r i e t a l l a y e r of Bowman's c a p s u l e , to a low columnar type somewhat i r r e g u l a r i n h e i g h t . In c o n t r a d i c t i o n to the tubule i n the mammal, i n which the n u c l e i are r e p o r t e d as b e i n g r e l a t i v e l y i n f r e q u e n t i . e . , w i t h o n l y three t o f o u r n u c l e i In one t r a n -s e c t i o n o f a t u b u l e , they appear i n every c e l l . In shape the n u c l e i are round, s i t u a t e d s l i g h t l y b a s a l l y . They c o n t a i n a d u s t - l i k e chromatin and from one to s e v e r a l n u c l e o l i . The cytoplasm i s abundant and o f t e n appears g r a n u l a r . I t i s not pre s e r v e d w e l l by r o u t i n e h i s t o l o g i c a l f i x e s . C e l l o u t l i n e s are seen o c c a s i o n a l l y . B a s a l s t r i a t i o n s such as have been d e s c r i b e d f o r the kidney o f high e r v e r t e b r a t e s do not appear. The b r u s h border which c h a r a c t e r i z e s t h i s p a r t o f the nephron 40. p r e s e n t s a very v a r i a b l e appearance i n accordance w i t h the v a r i o u s f i x a t i o n methods used. With Aoyama's cadmium c h l o r i d e f l u i d (Baker, 1945)^ w i t h which i t i s w e l l p r e s e r v e d , the b r u s h border has a h e i g h t of about one t h i r d t h a t o f the c e l l . ( L i Koue Tchang, year not g i v e n ) . W i t h t h i s f l u i d i t has a homogen-eous, r a t h e r than the s t r i a t e d appearance r e p o r t e d i n the mammal. H e n l e f s loop The extent o f the development of t h i s segment dep-ends on the p o s i t i o n o f the nephron i n the l o b u l e . I f the mammalian type i s approached, i t has a t y p i c a l l y descending and ascending l i m b s . Descending limb T h i s segment possesses a low c u b o i d a l to squamous e p i t h e l i u m . The c e l l s c o n t a i n an elongated to round n u c l e u s . Ascending limb That p o r t i o n o f the nephron opposed to the glomeru-l a r r o o t , w i l l be d e s c r i b e d here. T h i s p a r t i s v a r i o u s l y s t a t e d to be the ascending limb, or the d i s t a l t u b u l e , In t e x t histology books o f mammalian anatomy and the s i t u a t i o n l i k e w i s e In the b i r d needs c l a r i f y i n g . T h i s segment shows i n c r o s s s e c t i o n , a low c u b o i d a l e p i t h e l i u m , a round to o v a l n u c l e u s , and s l i g h t l y more c y t o -plasm than i n the descending limb. C o l l e c t i n g tubule These t u b u l e s which run almost s t r a i g h t out from the 41 medullary r e g i o n t o the p e r i p h e r y o f the kidney (PLATE:J£ ) are e a s i l y observed owing t o t h i s c h a r a c t e r i s t i c . Moreover, they take a b a s o p h i l i c s t a i n as compared t o the r e s t o f the t u b u l e s . The c e l l s are q u i t e d i f f e r e n t t o those i n the oth e r p o r t i o n s o f the nephron. They are h i g h c u b o i d a l c e l l s and the o u t l i n e s are v e r y d i s t i n c t . The d a r k l y s t a i n i n g nucleus I s round. The cytoplasm i s c l e a r around the nucleus but g r a n u l a r at the supranuclear zone. Stroma With s i l v e r methods, the stroma o f the a v i a n k i d n e y i s seen t o c o n s i s t o f a w e l l d e f i n e d network o f r e t i c u l a r o r a r g y r o p h i l f i b r e s , which form a framework around the t u b u l e s , r e n a l u n i t s and bloo d v e s s e l s (PLATE3ZE )• A f i n e network o f these f i b r e s a l s o appears at the c e n t r e o f the a v a s c u l a r core p'\7 of the glomerulus (PLATEYL ). D i s c u s s i o n : The c h i e f p o i n t s worthy of note, i n co n n e c t i o n w i t h the h i s t o l o g y of the b i r d kidney would appear to be the f o l l o w i n g : M a l p i g h i a n c o r p u s c l e Bowman's c a p s u l e : The s m a l l s i z e o f the subcapsular space as c o n t r a s -ted, w i t h t h a t o f the mammalian kidney; and the narrow diameter of the e x i t o f the proximal t u b u l e from the same r e g i o n . The c u b o i d a l e p i t h e l i u m of the v i s c e r a l l a y e r o f the c a p s u l e . T h i s e p i t h e l i u m i s In c o n t r a s t to t h a t found i n the mammal 42 i n which i t i s squamous, except i n the e a r l y p o s t n a t a l l i f e , when i t c o n s i s t s o f h i g h columnar e p i t h e l i u m (G-ruenwald and Popper, 1940). T h i s e p i t h e l i u m , i t i s suggested, i m p a i r s f i l -t r a t i o n i n the embryonic kidney o f the mammal (Gruenwald and Popper)• Glomerulus The l o o k o f l o b n t i o n and v a o o u l a r l s a t l o n o f tho glomerulus; and the a v a s c u l a r core o f f i b r o b l a s t s . In connec-A t i o n w i t h the l a t t e r s t r u c t u r e , t h e r e i s a c o u n t e r p a r t i n the c e n t r a l mass o f dense conn e c t i v e t i s s u e r e p o r t e d i n the snake kidney (Regaud and P o l i c a r d , 1903-1904; M a r s h a l l and Smith, 1930). Proximal t u b u l e s In c o n t r a s t to the r e n a l c o r p u s c l e , the pr o x i m a l tubule shows g r e a t e r development than t h a t o f the mammal. M a r s h a l l and Smith (1934) g i v e the l e n g t h s and diameter o f the proximal tubule o f the r a b b i t and domestic f o w l , as b e i n g 6.90 x 0»036 mm. f o r the former, and 7.00 x 0.063 mm. f o r the l a t t e r . An examination o f the f i g u r e s w i l l show t h a t the d i a -meter o f the tu b u l e o f the b i r d i s almost double t h a t o f the mammal. To t h i s f a c t should be added t h a t h i s t o l o g i c a l e v i d -ence of an i n c r e a s e i n h e i g h t of the br u s h b o r d e r o f the c e l l s o f t h i s a r e a . In summarizing one can say t h a t , t h e r e I s h i s t o l o g i -c a l evidence o f a decrease i n development of the glomerulus i n the b i r d , as compared to the mammal; and a c o r r e s p o n d i n g i n c r e a s e i n the development o f the proximal t u b u l e . 44. The Cytology-M i t o c h o n d r i a R e s u l t s B e f o r e commenting on the r e s u l t s o b t a i n e d f o r mito-c h o n d r i a , the same g e n e r a l remarks can be made which are app a r e n t l y t o be expected In the f i x a t i o n o f a v i a n k i d n e y d u r i n g the course o f t h i s work, i . e . , the f i x a t i o n shows d i s -a p p o i n t i n g r e s u l t s , e s p e c i a l l y i n H e l l y ' s f l u i d . On t h i s p o i n t o f f i x a t i o n o f kidney Baker (1945, p.45) says, "Some kin d s of c e l l s are ve r y r e s i s t a n t t o rough treatment, o t h e r s are d e l i c a t e . For i n s t a n c e , the i n t e s t i n a l o f the newt i s reasonably w e l l f i x e d by almost any f i x a t i v e , w h i l e the kidney and t e s t i s o f mammals are wretchedly p r e s e r -ved by many well-known mixtures. The reason f o r t h i s has not been e x p l a i n e d . " On examination of t h i s s t a t e m e n t , i t w i l l be seen t h a t i t i s the t i s s u e of a p o i k i l o i t h e r m i c organism which i s e a s i l y p r e s e r v e d whereas t h a t o f the mammal, a homoithermic animal i s p o o r l y so. I t c o u l d , t h e r e f o r e , seem as i f those o f the b i r d might be even l e s s w e l l f i x e d as i n the case of these the body temperature i s even h i g h e r than t h a t o f the mammal, and would on t h a t account undergo auto-l y t i c changes even more r a p i d l y . Again, the f a c t t h a t k idney always f i x e s even more p o o r l y than other t i s s u e s may be f u r t h e r a s c r i b e d t o the reason t h a t I t i s an i n t e n s e l y a c t i v e organ. 45 Probably some method of f i x a t i o n a long the l i n e s o f Baker's (1944) f o r the G o l g i body, u s i n g a f o r m o l - c a l c i u m f i x w i t h g e l a t i n e embedding, might be advantageous though time consuming. The Chicken H e l l y ' s f l u i d . The r e s u l t s were u n i f o r m a l l y poor: the m i t o c h o n d r i a were not p r o p e r l y p r e s e r v e d and the g e n e r a l f i x a t i o n i t s e l f inadequate. S t a i n i n g by Altmann's method was, owing to the r e s u l t of m i t o c h o n d r i a l f i x a t i o n , almost u s e l e s s . Regaud's f l u i d . Here the r e s u l t s were b e t t e r than w i t h the method above, but not as good as c o u l d be d e s i r e d . Proximal convoluted t u b u l e . I t can be seen under medium power t h a t the contents of t h i s segment s t a i n almost e n t i r e l y r e d w i t h f u c h s i n e , which on i n s p e c t i o n by o i l immersion, are found to c o n s i s t o f a s o l i d mass of mostly s p h e r i c a l r e d granules which are too c l o s e l y packed to i n d i c a t e whether any p o l a r i t y e x i s t s . The brush border i s f r e e o f g r a n u l e s . D i s t a l c onvoluted t u b u l e . The c e l l s o f t h i s area c o n t a i n the same gran u l e s but to a l e s s e r degree so t h a t the appearance i s not a s o l i d mass of r e d s t a i n at h i g h power. Henle's l o o p . T h i s p a r t of the nephron found i n c l o s e p r o x i m i t y 46. to the e f f e r e n t i n t r a l o b u l a r v e i n , l i k e w i s e I n c l u d e s the same granules i n much the same d e n s i t y as the c o n d i t i o n found i n the d i s t a l t u b u l e . C o l l e c t i n g t u b u l e . T h i s segment i s o r d i n a r i l y s t a i n e d b l u e w i t h meta-chromatic t o l u i d i n e b l u e ; however, i t was not v e r y apparent is here except on the s i d e b o r d e r i n g the lumen w h i c k L so c o l o r e d . Most of the c e l l s s t a i n somewhat d i f f u s e l y w i t h no p a r t i c u l a r g r a n u l a t i o n ; however, i n each c r o s s s e c t i o n one or two c e l l s are f i l l e d w i t h l a r g e r e d - s t a i n i n g g r a n u l e s . The s i d e of these c e l l s b o r d e r i n g on the lumen p r o j e c t s beyond the l i m i t s of the other c e l l s . T h i s c o n d i t i o n would seem t o i n d i c a t e a d i f -f e r e n c e i n f u n c t i o n of the c e l l s In t h i s area i n which the c e l l s s t a i n u n i f o r m a l l y w i t h metachromatic s t a i n s i n p r e p a r a -t i o n s not f i x e d f o r m itochondria; or r a t h e r perhaps a d i f f e r -ence i n s e c r e t o r y a c t i v i t y . M a l p i g h i a n C o r p u s c l e . T h i s s t r u c t u r e i s not very w e l l p r e s e r v e d i n t h i s specimen. As f a r as can be a s c e r t a i n e d , the c e n t r a l a v a s c u l a r core o f f i b r o b l a s t s c o n t a i n some small s p h e r i c a l m i t o c h o n d r i a . The c e l l s o f the v i s c e r a l l a y e r s do not show any v i s i b l e evidence of g r a n u l a t i o n . Pigeon Kidney.. T h i s t i s s u e gave b e t t e r r e s u l t s than t h a t o f the c h i c k e n , however, even here the r e s u l t s were very v a r i a b l e . In p l a c e s on the s l i d e almost p e r f e c t f i x a t i o n was shown w i t h 47. very exact c e l l u l a r d e t a i l , many mi t o c h o n d r i a , and most b r i l -l i a n t s t a i n i n g o f f e a t u r e s . Other p l a c e s showing much s w e l l i n g of c e l l s i n the t u b u l e s , l e s s e a s i l y d i s t i n g u i s h e d mitochond-r i a and d u l l e r s t a i n i n g . , Concerning t h i s v a r i a b i l i t y a f t e r Regaud's f l u i d , M i Baker (1945^) says of t h i s s o l u t i o n t h a t i t i s ^ " l e s s s t a b l e than H e l l y ' s , f i x e s some t i s s u e s b a d l y (e.g., mammalian t e s t i s ) i t i s poor f o r n u c l e i , and does not g i v e such b r i l l i a n t s t a i n -i n g . " Bensley and Bensley (1935) say i n r e f e r e n c e t o the same subject, " f o r m i t o c h o n d r i a good g e n e r a l f i x a t i o n , e s p e c i a l l y f o r the kidney." Proximal convoluted t u b u l e . (PLATET2H , fig.9 , /c$ As b e f o r e the c e l l s o f t h i s segment are under medium power of the microscope, s t a i n e d a uniform r e d . Under o i l im-m e r s i o n ^ i t can be seen t h a t a dense mass of s p h e r i c a l g r a n u l e s f i l l s the c e l l s so t h a t no r e a l p o l a r i t y can be a s s i g n e d . The br u s h border appears to be u s u a l l y f r e e o f granules^except i n some tubule8^ i n which an e r u p t i o n o f granules takes p l a c e from the c e l l i n t o the lumen. D i s t a l c onvoluted t u b u l e . T h i s t u b u l a r area a l s o c o n t a i n s g r a n u l e s , though to a much l e s s e r degree than does the proximal segment; moreover, i n g e n e r a l the gran u l e s appear to be l a r g e r . H e n l e 1 s l o o p . Both descending and ascending p o r t i o n s c o n t a i n r e d granules i n l e s s e r degree than i n the prox i m a l and d i s t a l 48. segments. As t h i s t i s s u e was i n a b e t t e r s t a t e o f p r e s e r v a t i o n than t h a t of the c h i c k e n , an examination was made f o r the macula densa (McManus, 1945) i n c o n n e c t i o n w i t h the ascending p o r t i o n of H e n l e f s l o o p . T h i s s t r u c t u r e c o n s i s t s o f t h a t p a r t of the ascending loop which i s adjacent t o the glomerular p o l e , i n p a r t i c u l a r to the vas a f f e r e n s . Here the c e l l s con-s i s t , a c c o r d i n g to Maximov and Bloom (1944) "of an e l l i p t i c a l d i s c of t a l l t h i n c e l l s measuring 40 m i c r a by 70 m i c r a i n man." Best and T a y l o r (1945) suggest t h a t t h i s s t r u c t u r e probably should be c o n s i d e r e d f u n c t i o n a l l y as an i n t e g r a l p a r t of the j u x t a - g l o m e r u l a r apparatus, i . e . , t h a t c u f f o f m y o - e p i t h e l i a l c e l l s which l i e s on the w a l l s of the glomeru-l a r a r t e r i o l e s . Maximov and Bloom (1944) say t h a t t h i s appar-atus i s r e p o r t e d as absent from the lower v e r t e b r a t e s . That s i d e of the ascending loop of Henle a g a i n s t the glomerular p o l e i n the pige6n does not possess s i g n i f i c a n t l y h i g h e r c e l l s than does the other s i d e , nor do they show any d i f f e r e n c e i n m i t o c h o n d r i a l arrangement. The a f f e r e n t a r t e r i o l e s are v e r y s m a l l i n the b i r d and do not appear to possess m y o - e p i t h e l i a l c e l l s . C o l l e c t i n g t u b u l e s . These tubules s t a i n a c l e a r b l u e and are easy to p i c k out. The b l u e s t a i n marks a few red g r a n u l e s . Malpighian c o r p u s c l e . No m i t o c h o n d r i a appear i n the a v a s c u l a r core or i n 49. the v i s c e r a l and p a r i e t a l e p e t h e l i a . D i s c u s s i o n * M i t o c h o n d r i a were f i r s t d e s c r i b e d by Flemming (1882), Altmann (1890) and by Benda (1897) at the end of the 19th century. Lazarow (1943) says that they are m i c r o s c o p i c s t r u c -t u r e s , v a r y i n g i n s i z e and shape and found i n p r a c t i c a l l y a l l l i v i n g c e l l s where they can be s t a i n e d i n t r a v i t a l l y w i t h Janus green. They may be as l a r g e as s e v e r a l m i c r a i n s i z e . They are m o r p h o l o g i c a l e n t i t i e s which can be seen d i s p e r s i n g i n t o the surrounding medium upon c r u s h i n g a c e l l under a cover s l i p . Then the m i t o c h o n d r i a sometimes r e t a i n t h e i r exact s i z e and shape and can be compared w i t h those w i t h i n the c e l l , B ensley and Hoerr f i r s t separated m i t o c h o n d r i a i n 1934, making accurate chemical a n a l y s i s p o s s i b l e . These g r a n u l e s c o n t a i n c h o l e s t e r o l , g i v e a p o s i t i v e t e s t f o r pentose and have a p u r i n e base, and t h e r e f o r e c o n t a i n n u c l e o p r o t e i n . They a l s o g i v e a p o s i t i v e t e s t f o r cytochrome onidase w i t h the Wadi reagent, they are a l s o able to o x i d i z e glutamic a c i d . The n a t u r a l y e l l o w c o l o r i s due to r i b o f l a v i n . Lazarow notes t h a t t h e r e i s a c o n f u s i o n as to term-i n o l o g y , which f a c t can w e l l be noted by r e f e r r i n g to Cowdry's (1918) e a r l y exhaustive work i n which he l i s t s the nomencla-tu r e used up to t h a t date. T h i s c o n f u s i o n makes c l a r i f i c a t i o n o f the s u b j e c t somewhat d i f f i c u l t because i t i s not always c l e a r as to what m i c r o s c o p i c s t r u c t u r e s are under d i s c u s s i o n . 50. Cowdry (1928) on t h i s p o i n t i n r e f e r e n c e t o r e n a l s e c r e t i o n and m i t o c h o n d r i a says t h a t there are other g r a n u l a r c o n s t i t u -ents present i n the c e l l s o f the proximal convoluted tubule•> These c o n s t i t u e n t s both resemble and d i f f e r from m i t o c h o n d r i a i n some r e s p e c t s and a c c o r d i n g l y complicate the q u e s t i o n , Maximov and Bloom (1944) s t a t e t h a t a l t h o u g h m i t o c h o n d r i a may take p a r t i n d i r e c t l y i n s e c r e t o r y p r o c e s s e s , they p r o b a b l y are not transformed i n t o s e c r e t i o n g r a n u l e s . Cowdry says t h a t the l a r g e granules which Claude separated from l i v e r c e l l s and which he (Claude) c a l l e d s e c r e t i o n g r a n u l e s are without doubt m i t o c h o n d r i a . Cowdry (1928) says t h a t m i t o c h o n d r i a have been seen d i s t r i b u t e d i n the protoplasm of the c e l l s o f the p r o x i m a l convoluted segment i n the metanephric t u b u l e o f r e p t i l e s , b i r d s , and mammals, but, concerning b i r d s he g i v e s no s p e c i f i c r e f e r e n c e , nor does he d e s c r i b e t h e i r form i n t h i s c l a s s o f animal. (_The w r i t e r was ab l e to s t a i n m i t o c h o n d r i a i n r e n a l c e l l s w i t h Janus green i n Rana c a t e s b i a n a and found them to be s p h e r i c a l s t r u c t u r e s . ) Regaud and P o l i c a r d (1903-04) d i d e x t e n s i v e s t u d i e s on snake kidneys and r e p o r t t h a t the c e l l s o f the prox i m a l convoluted t u b u l e are r i d d l e d w i t h many vacuo l e s o f ve r y d i v e r s e shape and form; they a l s o note t h a t i n t r a c e l l u l a r i n c l u s i o n s (enclaves i n t r a c e l l u l a i r e s ) o f a l i p o i d a l n a t u r e are found i n the e p i t h e l i u m here. The l i p o i d a l i n c l u s i o n s 51. are sometimes found i n Henle's l o o p . Cowdry (1918) g i v e s an i l l u s t r a t i o n o f m i t o c h o n d r i a i n the c e l l s o f the kidney of the white mouse but does not s t a t e from which p a r t of the nephron they were taken. Prom h i s I l l u s t r a t i o n , these m i t o c h o n d r i a appear t o be d i s p o s e d p r i n c i p a l l y i n an i n f r a n u c l e a r p o s i t i o n w i t h a few i n the supranuclear zone. The shape seems p r i n c i p -a l l y r o d - l i k e . Covel (1927) s t u d i e d m i t o c h o n d r i a - c y t o p l a s m i c r a t i o of the r e n a l t u b u l e s o f a l b i n o r a t s . In h i s i l l u s t r a t i o n s (drawings) the m i t o c h o n d r i a i n a l l t u b u l e s are r o d - l i k e . He found t h a t the m i t o c h o n d r i a - c y t o p l a s m i c r a t i o was h i g h e s t i n the c e l l s o f the p r o x i m a l convoluted t u b u l e s . B a i l e y (1936) g i v e s an i l l u s t r a t i o n ( c o l o u r e d draw-ing) of m i t o c h o n d r i a i n the p r o x i m a l and d i s t a l t u b u l e s o f the kidney of a mouse a f t e r Regaud's f l u i d f i x a t i o n and Altmann's a c i d f u c h s i n e . The g r a n u l e s are r o d shaped i n b o t h t u b u l e s and prominently arranged i n p a r a l l e l l i n e s , p a r t i c u -l a r l y i n the proximal segment. The m i t o c h o n d r i a are e s p e c i a l l y dense i n the l a t t e r t u b u l e , and there appear to be s e c r e t i o n g r a n u l e s l e a v i n g the apex o f the c e l l and e n t e r i n g the lumen which a l s o s t a i n p i n k as do the m i t o c h o n d r i a . The d e n s i t y o f the m i t o c h o n d r i a and the s e c r e t i o n g r a n u l e s compare f a v o u r a b l y w i t h those seen i n the b i r d k i d n e y . That the c o n d i t i o n c o n c e r n i n g m i t o c h o n d r i a l forma-t i o n and c o n c e n t r a t i o n i n the a v i a n kidney should most approach t h a t o f the r e p t i l e might be expected when i t i s r e a l i z e d 52. t h a t both p h y l o g e n e t i c a l l y and p h y s i o l o g i c a l l y i n r e n a l func-t i o n the b i r d i s c l o s e r t o t h i s c l a s s than to the mammal. Although Regaud and P o l i c a r d do not c a l l e i t h e r t h e i r v a c u o l e s or t h e i r l i p o i d a l i n c l u s i o n s m i t o c h o n d r i a , i t may be taken from t h e i r p o s i t i o n and a l s o from the f a c t o f a s i m i l a r pos-i t i o n i n oth e r c l a s s e s o f animals, t h a t these s t r u c t u r e s , at l e a s t the l i p o i d a l " I n t r a c e l l u l a r i n c l u s i o n s " do so r e p r e -sent them. No mi t o c h o n d r i a - c y t o p l a s m i c r a t i o was worked out on the a v i a n kidney; moreover, i t would be here, e n t i r e l y unneces-sary and even im p o s s i b l e to f o l l o w Cowdry and Covel's method. Even under medium power of the microscope i t can be seen i n the c e l l s o f the proximal convoluted tubule t h a t t h e i r r a t i o i s q u a l i t a t i v e l y v ery h i g h . T h i s c o n d i t i o n f a r surpasses t h a t i n the mammalian kidney which i s a predominantly glomerular f i l t r a t i o n organ i n u r i n e f o r m a t i o n . Cowdry and Covel suggest on account o f ' t h i s ; h i g h r a t i o t h a t there i s f a i r reason to b e l i e v e t h a t the p a r t p l a y e d by t h i s segment i n u r i n a r y s e c r e t i o n d i f f e r s r a d i c a l l y from t h a t of the other segments. I f t h i s statement i s made of the mammal, how much more should i t be made of the b i r d i n which animal the s e c r e t i o n of u r i c a c i d has shown to be i n -dependent o f b l o o d flow (Gibbs, 1929). G o l g i Body I n t r o d u c t i o n . Baker (1944) In h i s study of the s t r u c t u r e and 53 chemical composition of the G o l g i body says t h a t i n i t s f u l l y developed c o n d i t i o n , t h i s apparatus of d i v e r s e c e l l s c o n s i s t s of f o u r p a r t s : (1) t h e " n e u t r a l - r e d vacuoles"; (2) the dense l i p o i d - c o n t a i n i n g substance, g e n e r a l l y i n c l o s e r e l a t i o n to the vacuoles i n the form of strands, "lepidosomes", caps, c r e s c e n t s , r i n g s or complete Investments; (3) the d i f f u s e l i p o i d - c o n t a i n i n g substance, which f i l l s a l l the space i n the G o l g i element not occupied by the other c o n s t i t u e n t s ; (4) the G o l g i - p r o d u c t , which a r i s e s i n the vacu-o l e s and i s the r e s u l t of the s y n t h e s i s achieved by the appar-a t u s . Baker s t a t e s that a review of the l i t e r a t u r e r e v e a l s t h a t there had been no r e l i a b l e evidence of the chemical com-p o s i t i o n of the esmophil substance of the G o l g i element, apart from the f a c t t h a t i t c o n t a i n s l i p o i d ( i n the widest s e n s e ) . T h e r e f o r e , i n order to t e s t the G o l g i apparatus f o r i t s chemical composition, Baker used the lepidosomes ( G o l g i b a t o n e t t e s ) of the spermatocytes and young spermatids of the common s n a i l , H e l i x aspera. T h i s m a t e r i a l was chosen as i t i s v i s i b l e without s t a i n i n g i n l i v i n g c e l l s and there i s t h e r e f o r e no p o s s i b i l i t y t h a t the i n v e s t i g a t o r i s examining an a r t e f a c t . Baker, u s i n g the S m i t h - D i e t r i c h t e s t says t h a t the 54. r e s u l t s s t r o n g l y suggest t h a t the lepidosomes c o n t a i n " l e c i t h i n , c e p h a l i n , or sphingomyelin. A f t e r f u r t h e r chemical t e s t s he concluded t h a t the lepidosomes of the m a t e r i a l i n v e s t i g a t e d c o n s i s t o f , or c o n t a i n l e c i t h i n or c e p h a l i n or b o t h . As w e l l as t h i s method used by Baker, the G o l g i element can be blackened e i t h e r by osmiura t e t r o x i d e or by one of the s i l v e r methods. An Important r o l e i n v a r i o u s c e l l u l a r p r ocesses has been assig n e d to the G o l g i body by many i n v e s t i g a t o r s , p a r t i c -u l a r l y In those d e a l i n g w i t h s e c r e t i o n . Maximov and Bloom (1944) say t h a t i t i s q u i t e improbable t h a t t h i s s t r u c t u r e i s transformed d i r e c t l y i n t o s e c r e t o r y v a c u o l e s , t h e r e f o r e a l l t h a t can be s a i d at p r e s e n t of the G o l g i element i s t h a t i t i s a c e n t e r of c e l l u l a r a c t i v i t y . R e s u l t s . The o n l y m a t e r i a l i n which the G o l g i element showed i n a c h a r a c t e r i s t i c f a s h i o n was i n t h a t of the c h i c k e n . Unfor-t u n a t e l y t h a t of the song-sparrow o n l y showed t h i s s t r u c t u r e i n the d i s t a l and c o l l e c t i n g t u b u l e s . T h i s was perhaps owing to a l a p s e of time between k i l l i n g the animal and f i x a t i o n , as i t i s known th a t the c e l l s of the proximal t u b u l e v e r y r a p i d l y undergo a u t o l y s i s . Chicken k i d n e y . The f i x a t i o n of t h i s m a t e r i a l by Aoyama's cadmium c h l o r i d e formaldehyde f l u i d was q u i t e f a i r i n r e f e r e n c e to the h i s t o l o g i c a l p i c t u r e and, i n p a r t i c u l a r , to the brush b o r d e r 55. which p r e s e n t s the homogeneous appearance spoken of by L i Koue Tchang (year not g i v e n ) . Malpighian C o r p u s c l e . The c e n t r a l a v a s c u l a r core of f i b r o b l a s t s shows o n l y an o c c a s i o n a l s i g n o f the G o l g i apparatus on deep impregnation. In the l a r g e r c o r p u s c l e s , i n which the v i s c e r a l l a y e r is" c u b o i d a l ? a n d not of the squamous type, G o l g i b o d i e s can be demonstrated. These s t r u c t u r e s c o n s i s t o f a v e r y dark, c a p - l i k e shape c l o s e l y a p p l i e d to the n u c l e u s . Proximal Tubule. The p i c t u r e o f the G o l g i apparatus i n the c e l l s o f t h i s tubule (PLATE f i g . 11) appears to vary somewhat, perhaps, concomitant w i t h the a c t i v i t y o f the p a r t i c u l a r seg-ment at the moment of death, or owing to the degree of impreg-n a t i o n which i s v a r i a b l e (Baker, 1945). However, i n g e n e r a l , i t may be s a i d t h a t the supra-nuclear zone darkens somewhat, and t h a t from one to s e v e r a l b l a c k f i l a m e n t o u s p r o j e c t i o n s (PLATEWI f i g . 1 2 ) extend outwards towards the b r u s h b o r d e r . The dark f i l a m e n t s are probably the "lepidosomes" v Pr-: "bato-n e t t e s " d e s c r i b e d by Baker (1944). H e n l e 1 s Loop. The shape of the- G o l g i element i n t h i s segment i s somewhat d i f f i c u l t to estimate, as d i f f u s e impregnation o f the whole c e l l takes p l a o e . However, i t a p p a r e n t l y has the appear-ance of a dense, dark "cap1} c l o s e l y a p p l i e d to the nucleu s towards the lumen s i d e of the c e l l . 56. D i s t a l Tubule. At the p o i n t o f a p p l i c a t i o n at the d i s t a l t u b u l e to the glomerular p o l e (Haximov, 1944), w i l l be found a good area f o r o b s e r v i n g the G o l g i apparatus i n t h i s segment. The whole c e l l d i f f u s e l y reduces the s i l v e r . Here the G o l g i element has a very s i m i l a r s t r u c t u r e to t h a t i n Henle»s l o o p . A g a i n s t the glomerular p o l e , t h a t s i d e of the t u b u l e which would be d e s i g -nated the macula densa i n the mammal, there i s u s u a l l y such a dense impregnation t h a t the G o l g i body cannot u s u a l l y be spec-i f i c a l l y l o c a t e d . However, r e v e r s a l of p o l a r i t y i s not seen, such as t h a t r e p o r t e d by McManus (1942-43 )• C o l l e c t i n g Tubules. In the c o l l e c t i n g t u b u l e s some c e l l s show no element; i n others, the G o l g i body appears as a b l a c k s t r u c t u r e c l o s e l y a p p l i e d t o the lumen s i d e of the n u c l e u s . Sometimes, l e p i d o -somes are demonstrated which c l o s e l y approximate those i n the proximal t u b u l e , although they are not as prominent. In most o f the t u b u l e s , from one to s e v e r a l c e l l s take up the s i l v e r so t h a t the cytoplasm i s completely blackened. T h i s s i t u a t i o n , i t would appear, can be c o r r e l a t e d w i t h t h a t shown d u r i n g the study of m i t o c h o n d r i a i n the same t u b u l e . In the l a t t e r case some c e l l s were n o t i c e d to be f i l l e d w i t h l a r g e r g r a n u l e s than i n the other c e l l s , and p r o j e c t e d Into the lumen beyond the border of the adjacent c e l l s . These f a c t s suggest a v a r i a t i o n o f t h e G o l g i body w i t h r e s p e c t to s e c r e t o r y a c t i v i t y , which can be f u r t h e r confirmed by showing t h a t the c e l l s of t h i s 57. area can be s t a i n e d s p e c i f i c a l l y f o r mucin w i t h metachromatic dyes. These c e l l s are known to v a r y i n a c t i v i t y . D i s c u s s i o n . There ar e , as f a r as the w r i t e r i s aware, no s p e c i f i c r e f e r e n c e s to the G o l g i element i n the a v i a n k i d n e y . There-f o r e , comparison must be made w i t h the somewhat scanty l i t e r a -t u r e which i s t o be found c o n c e r n i n g t h i s s t r u c t u r e i n the am-p h i b i a n and mammalian c l a s s e s . McManus (1944) says t h a t Emmel (1938) g i v e s a review of the G o l g i element i n the k i d n e y . T h i s statement i s somewhat erroneous as most of Emmel 1s r e f e r e n c e s are concerned w i t h the G o l g i body i n t i s s u e c u l t u r e . Emmel does, however, g i v e a good A d e s c r i p t i o n o f the s i t u a t i o n i n the f r o g kidney, and shows t h a t the G o l g i body c l o s e l y approximates t h a t seen i n the b i r d , although i n the proximal c e l l s o f t h i s animal, the lepidosomes have a more d i s t a l p o s i t i o n i n r e f e r e n c e to the n u c l e u s . In the c e l l s of the d i s t a l t u b u l e , the G o l g i apparatus l i e s i n a more a p i c a l p o s i t i o n . McManus (1944) g i v e s some i l l u s t r a t i o n s o f the element i n the mammalian nephron taken from Ramon-C a j a l (1933), i n which aga i n the t y p i c a l appearances of the G o l g i body i s repeated, v a r y i n g from a s m a l l f i l a m e n t o u s s t r a n d i n the i n i t i a l p a r t of the proximal t u b u l e , to a g r e a t l y ex-tended p r o j e c t i o n i n the a c t i v e c e l l s o f t h i s a r e a . McManus (1943, 44) l i k e w i s e d e s c r i b e s the G o l g i element i n the r a b b i t , c a t , and human proximal and d i s t a l c e l l s , w i t h s p e c i a l r e f e r -ence to those c e l l s of the macula densa wherein the p o s i t i o n 5 8 . o f the element i s r e v e r s e d , i . e . , the p o l a r i t y i s I n f r a - i n s t e i n s t e a d of su p r a - n u c l e a r . In r e t r o s p e c t i t may be s a i d t h a t the G o l g i element i n the one s p e c i e s o f b i r d examined, shows i n the c e l l s p a r t i c -u l a r l y o f the proximal t u b u l e , a great s i m i l a r i t y i n form and p o s i t i o n to t h a t seen i n the amphibian and mammal. While i t i s s t i l l a h i g h l y c o n t r o v e r s i a l s u b j e c t as to whether or not the G o l g i body p a r t i c i p a t e s i n s e c r e t i o n , the degree o f i t s development demonstrated i n the kidney p r o x i m a l t u b u l e c e l l s i n the c h i c k e n , taken i n c o n j u n c t i o n w i t h the h i g h c o n c e n t r a -t i o n o f mi t o c h o n d r i a lrR&wiVe*. :.n i n the c e l l s o f t h i s area, would I n d i c a t e some s p e c i a l a c t i v i t y i n t h i s p a r t o f the nephron. The H i s t o c h e m i s t r y A l k a l i n e Phosphatase I n t r o d u c t i o n . The e x i s t e n c e o f the enzyme " a l k a l i n e phosphatase" has been demonstrated i n many organs and t i s s u e s o f the mammal-ia n body. T h i s enzyme i s capable o f h y d r o l y z i n g v a r i o u s phos-p h o r i c e s t e r s , e.g., hexomonophosphate, glycerophosphate, ete. Among oth e r t i s s u e s showing phosphatase a c t i v i t y the kidney has a f a i r l y h i g h p l a c e (Best and T a y l o r , 1945). Taking the a r b i t r a r y f i g u r e o f 100 to i n d i c a t e the enzyme a c t i v i t y i n the jejenum of an a d u l t man, the kidney i s g i v e n as 35, a d u l t cat jejenum 100, kidney 38. In the kidney t h i s enzyme i s 59 found i n the "brush border" o f the c e l l s o f the p r o x i m a l tub-u l e and the s i t e o f i t s a c t i v i t y can be shown h i s t o c h e m i c a l l y by the method o f Gomori (1939) and o t h e r s . The glucose f i l t e r -ed out o f the glomerular c a p i l l a r i e s i s reabsorbed i n t h i s r e g i o n of the proximal tubule as can be shown by p o i s o n i n g the t u b u l a r c e l l s w i t h p h l o r i z i n , i n which case the sugar i s passed out i n the u r i n e . In i t s t r a n s f e r a c r o s s the t u b u l a r membrane, p h o s p h o r y l a t i o n o f the g l u c o s e molecule appears to be a neces-sary s t e p . T h i s change i s brought about by a s c i e n t i f i c enzyme, kidney phosphorylase. The f u n c t i o n of a l k a l i n e phosphatase appears to be at t h i s p o i n t a d e p h o s p h o r y l a t i o n o f the hexose phosphate p r e v i o u s l y formed. The p r i n c i p l e s u n d e r l y i n g the method f o r the h i s t o -chemical d e t e c t i o n of the s i t e o f the a c t i v i t y of a l k a l i n e phosphatase are as f o l l o w s ( D a n i e l l i , 1946): the s e c t i o n s are Incubated a t 37 C. i n a s o l u t i o n c o n t a i n i n g glycerophosphate and c a l c i u m a t a pH o f approxim-a t e l y 9. Calcium phosphate i s d e p o s i t e d i n the s e c t i o n s as a r e s u l t of the enzymatic s p l i t t i n g o f glycerophosphate. The s e c t i o n s are t r e a t e d w i t h c o b a l t n i t r a t e , washed w i t h d i s t i l -l e d water, t r e a t e d w i t h ammonium s u l p h i d e , washed i n tap water, and mounted i n balsam. Cobalt phosphate i s l e s s s o l u b l e than c a l c i u m phosphate, consequently the treatment o f a sec-t i o n w i t h c o b a l t s o l u t i o n changes any c a l c i u m phosphate p r e -sent to c o b a l t phosphate. A l s o , c o b a l t s u l p h i d e i s l e s s soluble than c o b a l t s u l p h a t e , t h e r e f o r e the a p p l i c a t i o n to a s e c t i o n 6 0 of ammonium s u l p h i d e converts the c o b a l t phosphate i n t o c o b a l t s u l p h i d e . T h i s l a t t e r substance forms a b l a c k p r e c i p i t a t e which appears i n the t i s s u e s e c t i o n s i n the p o s i t i o n s where i n i t i a l l y c a l c i u m phosphate had been p r e c i p i t a t e d f o l l o w i n g enzymatic h y d r o l y s i s of glycerophosphate. I t has been suggested by M a r s h a l l and Smith (1930) th a t the glomerulus o f the b i r d shows deg e n e r a t i o n as i n d i c a t e d by the v e r y small s i z e and poor v a s c u l a r i z a t i o n o f the glomer-u l i , and by the replacement o f the c e n t r a l p o r t i o n of the t u f t by a dense mass o f f i b r o b l a s t s . There are a l s o other i n -d i c a t i o n s g i v e n by Spanner (1924), such as the smal l s i z e o f the a r t e r i a l b l o o d supply t o the t u f t , the double venous sup-p l y to t u b u l e s , and p e r s o n a l o b s e r v a t i o n s gleaned from an ex-amination of the h i s t o l o g y of the b i r d k i d n e y . These l a t t e r i n c l u d e d i m i n i s h i n g s i z e o f M a l p i g h i a n c o r p u s c l e s as they approach the p e r i p h e r y o f the l i d n e y , v e r y p o o r l y developed subcapsular space, c u b o i d a l e p i t h e l i u m i n the v i s c e r a l l a y e r o v e r l y i n g the glomerulus i n s t e a d o f the squamous l a y e r found i n the mammal, and the smal l diameter of the p r o x i m a l t u b u l e at i t s j u n c t i o n w i t h Bowman's c a p s u l e . G r a f f l i n (1933), i n h i s study o f glomerular degeneration i n the kidney o f the daddy s c u l p i n (gjyoxcephalus s c o r p l u s ) l i s t s the f o l l o w i n g i n d i c a t i o n s (among othe r s ) o f t h i s c o n d i t i o n : (1) a l o s s o f v a s c u l a r i t y (2) i n c r e a s e i n c e l l u l a r make up (3) marked c o n s t r i c t i o n o f t u b u l a r o u t l e t . TABLE SHOWING RESULTS OF ALKALINE PHOSPHATASE EXPERIMENTATION CLASS TIME IN EXTENT TO WHTCH ALKALINE FIXATION FIXATION PHOSPHATASE ACTIVITY SHOWN FLUID FLUID IN TISSUE SECTION DEGREE OF LOCATION OF ACTIVITY ENZYME ACTIVITY (ARBITRARY FIGURE ONLY) CONTROL (i.e. INCUBATED WITHOUT SUBSTRATE) REMARKS Amphibian Bullfrog 80$ Alcohol 4 hrs. Throughout tissue seotion except in central area (which oontains collecting tubules only, which would therefore, not show activity) Brush border of proximal tubule cells, also in supra-*iuolear zone. Distal tubule, supra—nuclear Tissue quite well preserved Aves About half -nay through Proximal tubule: brush border of Pigeon 80$ Alcohol 12 hrs. the tissue section. cells and in 4 0 Tissue poorly supranuclear zone Henle's loop descending seg-ment, supra-nuclear zone (of some segments only) preserved Chicken No. 1 80$ Aloohol 2 hrs. At edge only of tissue section No. 2 Acetone 24 hrs. No sign of aotivity No. 3 95$ Alcohol 24 hrs. No sign of activity Proximal tubules brush border 0 0 0 6 Tissue f a i r l y well preserved (This tissue was one year old, but see Danielli (1946) Song Sparrow 80$ Alcohol 4 hrs, Throughout Tissue Section Proximal tubule: confined to brush border i.e. not in suptra-^iuclear zone Tissue well preserved i.e. o e l l de-t a i l good, Suoleus stains well. Mammalia White Rat Aoetone Edges of tissue section 24 hrs. on^y Proximal tubule: brush border Tissue f a i r l y well preserved 61. M a r s h a l l (1954) says t h a t one o f the f u n c t i o n a l d i f f e r e n c e s between the glomerular and the aglomerular t u b u l e s i s the i n -a b i l i t y o f the l a t t e r to e l i m i n a t e glucose or other sugars which i n the mammal pass by f i l t r a t i o n from the glomerular c a p i l l a r i e s through the squamous v i s c e r a l l a y e r s . Glucose i s reabsorbed by means o f kidney phosphorylase and a l k a l i n e phos-phatase i n the proximal tubule as d e s c r i b e d p r e v i o u s l y . In view of these f a c t s some t e s t s were c a r r i e d out to determine the degree o f a l k a l i n e phosphatase a c t i v i t y i n the a v i a n kidney u s i n g , as s t a t e d tinder " M a t e r i a l s and Method" a combin-a t i o n o f D a n i e l l i ' s (1946) and L i l l i e ' s (1948) methods. R e s u l t s . The r e s u l t s of the h i s t o c h e m i c a l d e t e c t i o n o f a l k a -l i n e phosphatase are l i s t e d under Table i An examination of Table £ would seem t o i n d i c a t e t h a t there i s a f a i r l y d i r e c t r e l a t i o n s h i p between degree o f enzyme a c t i v i t y and the l e n g t h of time i n f i x a t i o n f l u i d . The most i n t e n s e , and,general b l a c k p r e c i p i t a t i o n was ob t a i n e d u s i n g as a f i x a t i o n f l u i d , i c e - c o l d 80 per cent a l c o h o l f o r f o u r hours. The mesonephros o f the f r o g and the kidney o f the mammal were i n c l u d e d as c o n t r o l s on the s u b s t r a t e , as the author was not c e r t a i n as to the i d e n t i t y of the mi x t u r e . The extent to which a l k a l i n e phosphatase a c t i v i t y was shown i n the t i s s u e of the c l a s s e s examined i s b r i e f l y 62. summarized below: Amphibia. B u l l f r o g (PLATBK , f i g . 13andlJf): the a c t i v i t y was noted throughout the t i s s u e s e c t i o n except i n the c e n t r a l r e g i o n which c o n t a i n s c o l l e c t i n g t u b u l e s o n l y , which would t h e r e f o r e , not show any such f u n c t i o n . In the d o r s a l r e g i o n the proximal t u b u l e s are most abundant, while the v e n t r a l r e g i o n o f the mesonephros c o n t a i n s the d i s t a l t u b u l e s ( C o l e , 1941). The p r e c i p i t a t i o n o f c o b a l t s u l p h i d e was e q u a l l y d i s -t r i b u t e d between these areas, and was e v i d e n t i n the brush borders o f the c e l l s o f the p r o x i m a l tubule and a l s o i n the supra-nuclear zone. In the d i s t a l tubule, the p r e c i p i t a t e l i k e -# wise showed e& t h i s zone. : .Aves, Pigeon (PLATEX , f i g . / 5 ) : l o c a t i o n of enzymatic a c t i o n was evident about half-way through the m a t e r i a l . T h i s r e s u l t was probably due to the use of o v e r - l a r g e b l o c k s of t i s s u e , and a l s o l e a v i n g i t too l o n g a p e r i o d i n the f i x a t i o n f l u i d , w i t h subsequent d e s t r u c t i o n of the enzyme. The prox-imal t u b u l e s demonstrated a l k a l i n e phosphatase a c t i v i t y i n b o t h the b r u s h border andl the supra-nuclear zone. Henle*s descending segment showed o c c a s i o n a l l y a f a i r l y s t r o n g r e a c t i o n . Chicken: o n l y one l o t of t i s s u e - s e c t i o n s manifested enzyme a c t i v i t y In the b r u s h border at the very edge o f the kidney. A'glance a t the l e n g t h of times i n the f i x a t i o n f l u i d s would i n d i c a t e t h a t they were, i n the case o f c h i c k e n nos. 2 63. and 3, unduly prolonged. The t i s s u e from c h i c k e n no. 1 was one year o l d ; a f a c t which may e x p l a i n the l a c k of r e s u l t s ; though D a n i e l l i (1946) s t a t e s that t i s s u e may he kept i n r e f r i g e r a -t i o n f o r a year and s t i l l show enzymic a c t i v i t y . U n f o r t u n a t e l y , l a c k o f time and m a t e r i a l p r e c l u d e d f u r t h e r e x perimentation w i t h t h i s s p e c i e s . Song-Sparrow (PLATE2E , f i g . l ^ a n d i ^ ) : the m a t e r i a l obtained from t h i s s p e c i e s was comparable to t h a t o b t a i n e d from the b u l l f r o g i n i n t e n s i t y . The p r e c i p i t a t i o n o c c u r r e d throughout the t i s s u e and was very w e l l shown i n the b r u s h border to which i t was c o n f i n e d . Mammalian. White r a t : the r e a c t i o n was e v i d e n t o n l y at the edges o f the kidney where i t was l o c a t e d i n the b r u s h b o r d e r . D i s c u s s i o n . There i s , as f a r as the author i s aware, o n l y one r e f e r e n c e to phosphatase a c t i v i t y i n the b i r d and, i n p a r t i c u -l a r , to the metanephros. Moog (1943) worked on the l o c a l i z a -t i o n o f a l k a l i n e and a c i d phosphatases i n the e a r l y c h i c k embryo. She recorded the changes i n phosphatase d i s t r i b u t i o n i n the p r i n c i p a l s o f t organs, i n c l u d i n g the metanephros, up to the e i g h t h day. Thus the r e l a t i v e enzymatic a c t i v i t y i n the metanephric tubules at 4, 6, and 8 days o f i n c u b a t i o n shows th a t a l k a l i n e phosphatase a c t i v i t y i s 10 , 14 , 14 at 4,6, and 8 days r e s p e c t i v e l y i n the b r u s h border of the mesonephric t u b u l e s . I n c i d e n t a l l y , the mesonephros reaches i t s peak 64. f u n c t i o n a l l y ( i n the p r o d u c t i o n of urea) about the e i g h t h day (Needham, 1929), and t h e r e a f t e r degenerates, g i v i n g p l a c e t o the metanephros which s t a r t s t o f u n c t i o n a t about e l e v e n days w i t h the p r o d u c t i o n o f u r i c a c i d . The a l k a l i n e phosphatase a c t i v i t y i n the metanephric t u b u l e s a t 6, and 8 days, i s g i v e n as 4 , 4 • I t would be i n v i t i n g t o attempt to c o r r e l a t e the decrease i n a l k a l i n e phosphatase a c t i v i t y i n the metaneph-r o s w i t h an Increase i n glomerular degeneration In t h a t organ* I.e., a decrease i n f i l t r a t i o n powers. However, as no d a t a are g i v e n beyond e i g h t days, i t cannot be seen whether t h e r e i s s t i l l f u r t h e r decrease i n t h i s s p e c i e s . Moreover, Moog suggests t h a t the phosphatase a c t i v i t y shown here i s , con-cerned w i t h d i f f e r e n t i a t i o n of t i s s u e s . As f a r as the b i r d kidney i s concerned, a t l e a s t i n the two s p e c i e s i n which the r e s u l t s were p o s i t i v e , the f i n d -i n g s o f t h i s h i s t o c h e m i c a l e x p e r i m e n t a t i o n , would seem to i n d i c a t e t h a t , i n s p i t e of apparent h i s t o l o g i c a l m a n i f e s t a -t i o n s o f glomerular d e g e n e r a t i o n , the organ i n t h i s c l a s s f u n c t i o n s comparably to those of the amphibian and mammal. In these c l a s s e s , w e l l developed g l o m e r u l i e x i s t , and they have been shown to Reabsorb g l u c o s e by means o f the p r o x i m a l convoluted t u b u l e s . (Wearn and R i c h a r d s , 1924; Best and T a y l o r , 1945). 65. Summary The v a s c u l a r supply has been c o n s i d e r e d ; the h i s t o l -ogy* c e r t a i n c y t o l o g y , and a h i s t o c h e m i c a l t e s t o f the a v i a n metanephros have been c a r r i e d out i n as Imperative a manner as p o s s i b l e . Emphasis i s p l a c e d on the f o l l o w i n g p o i n t s : (1) The v a s c u l a r supply shows a d e f i n i t e r e n a l p o r -t a l system. There may be a v a r i a t i o n In venous p a t t e r n here which should be f u r t h e r i n v e s t i g a t e d . (2) The h i s t o l o g y shows s i g n s o f dege n e r a t i o n i n the r e n a l u n i t , w i t h an Increase i n pr o x i m a l t u b u l e development. (3) The c y t o l o g i c a l study, which c o n s i s t s o f the examination o f the mitoc h o n d r i a and the G o l g i apparatus, i n d i c a t e s an i n c r e a s e i n a c t i v i t y o f the prox i m a l t u b u l e a r e a as compared to t h a t i n the mammal. (4) The h i s t o c h e m i c a l work r e v e a l s s i g n s o f a l k a l i n e phosphatase a c t i v i t y i n the b i r d , i n s p i t e o f h i s t o l o g i c a l evidence concerning g l o m e r u l a r - d e g e n e r a t i o n . C o n c l u s i o n s : The a v i a n proximal t u b u l e shows s i g n s o f i n c r e a s e d a c t i v i t y over t h a t In the mammal. The glomerulus I s able to f u n c t i o n comparably t o th a t i n the mammal i n s p i t e o f h i s t o l o g i c a l evidence to the c o n t r a r y . 66. L i t e r a t u r e C i t e d Baldwin, E . An I n t r o d u c t i o n to Comparative B i o c h e m i s t r y . The U n i v e r s i t y P r e s s , Cambridge, 1940. Baker, J.R. The s t r u c t u r e and chemical composition o f the G o l g i element. Quart. J . M i c r . S c i . , 85: 1, 1944. Baker, J.R. C y t o l o g i c a l Technique. 2nd ed., Methuen and Co. L t d . , London, 1945. Bensley, R.R.,and S.H. Be n s l e y Handbook o f H i s t o l o g i c a l and C y t o l o g i c a l Technique. U n i v e r s i t y o f Chicago P r e s s , Chicago, 1938. Bes t , C.H.,and N.B. T a y l o r The P h y s i o l o g i c a l B a s i s o f Medi c a l P r a c t i c e . 4 th ed., W i l l i a m s and W i l k i n s Co., 1945. Bowman, W. On the s t r u c t u r e and use o f the Ma l p i g h i a n b o d i e s of the kidney, with o b s e r v a t i o n s on the c i r c u l a t i o n through t h a t g l a n d . P h i l . Trans. Roy. S o c , 152 : 57, 1842. Cole, E.C. Textbook o f Comparative H i s t o l o g y . B l a k i s t o n Co., P h i l a d e l p h i a , 1941. Cowdry, E.V. S p e c i a l Cytology. Paul B. Hoeber, Inc., New York, 1928. 1 Coulson, E . J . , and J.S. Hughes. C o l l e c t i o n and a n a l y s i s o f chi c k e n u r i n e . P o u l t r y S c i . , 10: 53, 1930. Cowdry, E.V. The m i t o c h o n d r i a l c o n s t i t u e n t s o f protoplasm. C o n t r i b . Embryol., 7^8: 39, 1918. ^ Cowdry, E.V., and W.P. C o v e l l . Q u a n t i t a t i v e c y t o l o g i c a l \ s t u d i e s on the r e n a l t u b u l e s . I I . M i t o c h o n d r i a -cytoplasmic r a t i o . Anat. R e c , 36: 349, 1927. Cushny, A.R. The S e c r e t i o n o f U r i n e . Longmans, Green and Co. London, 1926. D a n i e l l i , J.P. A c r i t i c a l study o f techniques f o r d e t e r m i n i n g the c y t o l o g i c a l p o s i t i o n o f a l k a l i n e phosphatase. J . Exp. B i o l . , 22:110, 1946. Das, B.K. On the i n t r a - r e n a l course o f the s o - c a l l e d " r e n a l -p o r t a l " v e i n s i n some common b i r d s . P r o c . Z o o l . S o c , London, p t . I I : 757, 1924. 6 7 . Das, B.K. Observations on the " r e n a l - p o r t a l " p e r f u s i o n i n e t h e r i s e d b i r d s . J . Morph., 51: 309, 1931. Davi s , R.A. The ni t r o g e n o u s c o n s t i t u e n t s of hens 1 u r i n e . J . B i o l . Chem., 74: 507, 1927. Edwards, J.G., and C. S c h n i t t e r The r e n a l u n i t i n the kidn e y . Amer. J . Anat., 53: 55, 1933. Emmel, V.M. The G o l g i apparatus i n the proximal and d i s t a l t ubule c e l l s o f the p e r f u s e d f r o g ' s k i d n e y . Anat. R e c , 70: 371, 1938. Gibbs, O.S. The r e n a l b l o o d - f l o w o f the b i r d . J . Pharm. and Exp. Therap., 34: 277, 1928. Gomori, G. M i c r o t e c h n i c a l demonstration o f phosphatase i n t i s s u e s e c t i o n s . P r o c . Soc. Exper. B i o l , and Med., 42: 23, 1939. G r a f f l i n , A.L. Glomerular degeneration i n the kidney o f the daddy s c u l p i n (Myoxcephalus s c o r p i u s ) Anat. R e c , 57-58: 59, 1933. Gruenwald, P., and H. Popper The h i s t o g e n e s i s and p h y s i o l o g y o f the r e n a l glomerulus i n e a r l y p o s t n a t a l l i f e : h i s t o l o g i c a l examinations. J . U r o l . , 43: 452, 1940. Guyer, M.P. Animal M i c r o l o g y . 4 t h ed., The U n i v e r s i t y o f Chicago P r e s s , Chicago, 1947. Huber, G.C. On the morphology o f the r e n a l t u b u l e s o f the v e r t e b r a t e s . Anat. R e c , 13 s 305, 1917. Hyman, H.L. Comparative V e r t e b r a t e Anatomy. 8 t h ed., U n l v d r s i t y o f Chicago P r e s s , Chicago, 1947. Jungherr, E., and J.M. Levine The pathology o f s o - c a l l e d p u l l e t d i s e a s e . Amer. J . Vet. Res., 2: 261, 1941. J o u r d a i n , S. Recherches sur l a ve i n e p o r t e r e n a l e . Ann. des Sciences n a t . Z o o l . , 4 me s e r . , 12: 134, 1859. C i t e d from Spanner (1924). K o r r , I.M. The osmotic f u n c t i o n s o f the c h i c k e n Bidney. J . C e l l . Comp. P h y s i o l . , 13(2): 175, 1939. Lazarow, A. The chemical s t r u c t u r e o f cytoplasm as i n v e s t i -gated In P r o f e s s o r Bensley's l a b o r a t o r y d u r i n g the pa s t t e n y e a r s . B i o l . Symposia, 10: 9, 1943. L i Koue Tchang. Recherches h i s t o l o g i q u e s sur l a s t r u c t u r e des T v e i n s des o i seaux. These medicale. Lyon, 1923. C i t e d from M a r s h a l l (1934). L i Koue Tchang. Sur l a c u t i c u l e des c e l l u l e s chez l e s oiseaux C R . B i o l . , P a r i s , 88t 520 (No y e a r given) L i l l i e , R.D. H i s t o p a t h o l o g i c T e c h n i c . B l a k i s t o n Co., P h i l a d e l p h i a , 1948. McGregor, L. The h i s t o l o g y o f the: normal glomerulus. Am. J . Path., 5: 545, 1929. McManus, J.F.A. Apparent r e v e r s a l o f the p o s i t i o n of the G o l g i element i n the r e n a l t u b u l e . Nature, 152: 417, 1943. McManus, J.F.A. The G o l g i element i n the c e l l s o f the f i r s t and second convoluted t u b u l e s o f the c a t kidney. Quart. J . M i c r . S c i . , 85: 97, 1944. McManus, J.F.A. F u r t h e r o b s e r v a t i o n s on the glomerular r o o t o f the v e r t e b r a t e k i d n e y . Quart. J . M i c r o . S c i . , 85: 39, 1947. M a r s h a l l , E.K. J r . The comparative p h y s i o l o g y o f the k idney i n r e l a t i o n t o t h e o r i e s o f r e n a l s e c r e t i o n . P h y s i o l . Rev., 14: 133, 1934. M a r s h a l l , E.K. J r . , and H.W. Smith The glomerular development of the v e r t e b r a t e k idney i n r e l a t i o n t o h a b i t a t . B i o l . B u l l . , 59: 135, 1930. Maxlmov, A.A., and W. Bloom. A Textbook o f H i s t o l o g y . 4 t h ed» W.B. Saunders Co., 1944. M i l l e r , A.M. The development of the p o s t c a v a l v e i n s i n b i r d s . Amer. J . Anat., 2: 283, 1903. M o l l e n d o r f , W., von. Handbuch der Normalen und P a t h o l o g i s c h e n P h y s l o l o g i e , 4. B e r l i n , J u l i u s S p r i n g e r , 1927. Moog, F. L o c a l i z a t i o n o f a l k a l i n e and a c i d phosphatases i n the e a r l y embryogenesis of the c h i c k . B i o l . B u l l . , 86: 51, 1943. Needham, J . P r o t e i n metabolism and o r g a n i c e v o l u t i o n . S c i . Prog., 23: 633, 1929. P a n t i n , C.F.A. Notes on M i c r o s c o p i c a l Technique f o r Zoolo-g i s t s . U n i v e r s i t y P r e s s , Cambridge, 1946. 69 Peacock, H.A. Elementary M i c r o t e c h n i q u e . 2nd ed., E . A r n o l d and Co., London, 1945. P i t t s , R.F. T h e . e x c r e t i o n o f phenol r e d by the c h i c k e n . J . C e l l . Comp. P h y s i o l . , 11: 99, 1938. Smith, P.E., ed. B a i l e y ' s Text-Book o f H i s t o l o g y , 9 t h ed., W i l l i a m Wood and Co., 1936. Spanner, R. Der P f o r t a d e r k r e i s l a u f i n der V o g e l n l e r e . Verhandl. der Anat. G e s e l l s . , 33: 23, 1924. Ramon-Cajal, S. H i s t o l o g y , W i l l i a m Wood and Co., B a l t i m o r e , 1933. C i t e d from McManus (1944);. Regaud, C. and A. P o l i c a r d . Recherches sur l a s t r u c t u r e du r e i n de quelques O r p h l d i e n s . Arch, d'anat. m i c r . , 6: 191, 1903-04. R i c h a r d s , A.N. Methods and R e s u l t s o f D i r e c t I n v e s t i g a t i o n s o f the F u n c t i o n o f the Kidney. W i l l i a m s and W i l k i n s Co., B a l t i m o r e , 1929. C i t e d from M a r s h a l l (1934). V i l t e r , R.W. The morphology and development o f the metaneph-r i c glomerulus o f the pigeon. Anat. R e c , 63: 371, 1935. Warner, F . J . V e s t i g i a l and p r o v i s i o n a l u r i n i f e r o u s t u b u l e s absent i n the metanephros of the b i r d s . Anat. R e c , 36: 271, 1927. Wearn, J.T.,and A.N. R i c h a r d s . Observations on the composi-t i o n of glom e r u l a r u r i n e , w i t h p a r t i c u l a r r e f e r e n c e to the problem of r e a b s o r b t i o n i n the r e n a l t u b u l e s . Am. J . P h y s i o l . , 71: 209, 1924. C i t e d from Best and T a y l o r (1945). PLATE I Schematic r e p r e s e n t a t i o n of the two types of a v i a n nephron (adapted from Spanner, -192^). F i g . 1 R e p t i l i a n type F i g . 2 Mammalian type 7£e Tvo rHf>es of A Wast /V&phnron mm McUptyht'an. Cor-.ou.scJe/ P-t-oxtmuJ Con voluJ&d. In f& ym e. d/aj&; m. p i AZepft/(\ an Typ^ Hcnle's Loop, Thin. 3ccfme.rit~ QlsfciJ Con i/&/uJe.cJ Xn'/ffo-A eoU&cfTrtq \ (Adapted from f(*-r3/t<*ttt/?3+) Ffy z fla-mmo>-lt'cut Type* PLATE I I L o b u l a r O r g a n i z a t i o n F i g . 3 Schematic r e p r e s e n t a t i o n of l o b u l a r o r g a n i z a t i o n of the a v i a n kidney (adapted from Spanner, 19240 . /^ox//7?co/ Convo/ut&d | TubaJe* Ju. lnfra./c PLATE II G/ome>-r~u/u3 ...Efferent Vcsse,/ Ir £'4.3-i-OO/t, Co//e,ol7n<j X Tubule-oj. Lobular Orcf a.n'/z.ajtion In fhe^ Avian Kj'oinesLj (Adapted f PLATE I I I V a s c u l a r system F i g . k Diagramatic r e p r e s e n t a t i o n of the v a s c u l a r system of the a v i a n kidney (adapted from Spanner, 1924) . Plate, ZEL Afferent V. C o ommon Tlla a) Co/on AnasTom os/s £:xfe,Y-na/ T//'ac V. Efj-e-Tt-cnT {/. R&nat) CocGyyr2,o,-n e.s&n7& vie. XrrtL-r-na.1 1/ta.c K Common Co&cyejects v. Lively" Post. Cax/af V. .Efferent I / o Ant. OUJO/'//CL -y-le-s l/a/i/e-Afferent Vein •To Ant. Lob&> _ . -R&nai Portal)/. ' Dor-sa/ Aorta Of- l/asoula.-y- Syite-m ap A^ian. Kl'dne-Lf C Adaptec/ -from. PLATE IV H i s t o l o g y F i g . 5 S e c t i o n of kidney of Domestic fow l Heidenhain's azan s t a i n x IZLk M a l p i g h i a n body, on r e n a l u n i t , showing g l o m e r u l a r a v a s c u l a r core ( f i b r o b l a s t s ) and basement membrane. PLATE V H i s t o l o g y F i g . 6 S e c t i o n of kidney of Song sparrow Aoyama's method (no counter s t a i n ) . x 70 Proximal t u b u l e s are shox^n a t p e r i p h e r y of l o b u l e . PLATE VI H i s t o l o g y F i g . 7 S e c t i o n of kidney of Domestic fowl Foot's s h o r t method f o r s i l v e r im-pr e g n a t i o n o f r e t i c u l u m . x 450 M a l p i g h i a n body, showing r e t i c u l a r f i b r e s at the centre of .the glomer-u l u s , Flgw 8 S e c t i o n of kidney of Domestic fowl Foot's s h o r t method x 450 Stroma of a r g y r o p h i l o r r e t i c u l a r f i b r e s . PLATE V I I Cytology M i t o c h o n d r i a F i g . 9 S e c t i o n of kidney of Pigeon Altmann's a c M f u c h s l n e s t a i n , c o u n t e r s t a l n t o l u i d i n e b l u e . x 900 (a) Proximal tubule showing c e l l s f i l l e d w i t h m i t o c h o n d r i a . (b) D i s t a l t u b u l e showing c e l l s w ith fewer m i t o c h o n d r i a . Fig.10 C e l l from pr o x i m a l tubule showing mitochondria (drawn to s c a l e ) . PLATE VIII Cytology. - • G o l g i body F i g . 11 S e c t i o n of kidney of Song sparrow Aoyama's G-olgi method (no counter s t a i n ) . x l 4 l 6 (a) Proximal convoluted tubules showing G o l g i b o d i e s i n the s u p r a - n u c l e a r zone of the c e l l s (b) C o l l e c t i n g t u b u l e s , showing deeply impregnated mucin p r o -ducing c e l l s . F i g . 12 High power of a c e l l from the proximal tubule showing t y p i c a l - lepidosomes i n the supra-nuclear r e g i o n (not drax^n to s c a l e ) . PLATE IX H i s t o c h e m i s t r y A l k a l i n e phosphatase F i g . 13 S e c t i o n of kidney of B u l l f r o g L i l l i e ' s and D a n i e H i ' s methods (combined) x 900 Enzyme a l k a l i n e phosphatase a c t i v i t y showing i n b r u s h border and s u p r a - n u c l e a r zone. F i g . 14 S e c t i o n of kidney of B u l l f r o g prepared by L i l l i e ' s and D a n i e l l i ' s methods (combined) w i t h the omi s s i o n of s u b s t r a t e . x 90° No enzyme a c t i v i t y shown PLATE X H i s t o c h e m i s t r y A l k a l i n e phosphatase F i g . 15 S e c t i o n of kidney of Pigeon L i l l l e ' s and D a n i e l l l ' s methods (combined) x 900 Enzyme a c t i v i t y i n b r u s h border and s u p r a - n u c l e a r zone. PLATE XI H i s t o c h e m i s t r y A l k a l i n e pho s phatas e F i g . 16 S e c t i o n of kidney of Song sparrow L i l l i e ' s and D a n i e l l i ' s methods (combined) x 900 Enzyme a c t i v i t y showing i n brush b o r d e r . F i g . 1? S e c t i o n of kidney of Song sparrow c o n t r o l , no enzyme a c t i v i t y shown. 

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