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Studies of the basal metabolism of albino rats Cooper, William Dewar 1942

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Studies o f the Basal Metabolism of Albino Rats by Wil l i a m Dewar Cooper A Thesis submitted i n P a r t i a l F u l f i l m e n t of The Requinaments f o r the Degree of MASTER OF ARTS i n the Department of f '• CHEMISTRY The U n i v e r s i t y of B r i t i s h Columbia October, 1942. ACZNQWEBDGMENTS I would l i k e to express my sincere thanks, To Dr. J . A l l a r d y c e , under whose guidance t h i s research was c a r r i e d out. To Drv R. H. Clark, and Dr. A. H. Hutchinson, f o r the i n t e r e s t they showed i n t h i s work. To Miss J. M. P r a t t , f o r the work she d i d i n feeding the r a t s and cleaning the cages. To Mr. E. J . Sutherland, f o r the assistance he gave i n preparing the d i e t s f o r the r a t s . TABLE OF CONTENTS Page I . INTRODUCTION 1 I I . SURVEY 3 . A. How to Measure the B.M.R. 3 B. Factors governing the B.M.R. 5. a. D i u r n a l 5. b. Age and Sex 6, c. Surface Area 7. d. A c t i v i t y 8. e. Disease 8. f. F a s t i n g 9. g. Temperature 9. h. Season 10. C. Feeding high percentages of Carbohydrate f a t and p r o t e i n r e s p e c t i v e l y 10. D. R a d i a t i o n 13, E. Desiccated Thyroid and Thyroxin 14. F. Anaesthesia 16. Page EXPERIMENTAL 17 A. The Rats Used 17 B» Environment 17 G* Care o f the Rats 18 a 0 Unbalanced Diets 18 b. R a d i a t i o n 22 c. Controls 24 d» Desiccated Thyro i d 24 e. Anaesthesia 25 D. The Apparatus 25 a. D e t a i l e d D e s c r i p t i o n of the Apparatus 27 b. Operation 50 E. Methods Employed with the Rat 33 RESULTS 34 i . Measurement of' the B.M.S. 34 a» Graphs 35 b. Sample. C a l c u l a t i o n " 35 B. Values of the B.M.R. (Tables) 36-48 i n c l . Page V. DISCUSSION 49 A. Health off' the Rats 49 «B. Method Employed 49 0. Control of V a r i a b l e s 50 D. Controls 51 E. Unbalanced Diets 53 F. R a d i a t i o n 56 a. Desiccated Thyroid 61 H. Anaesthesia 63 VI. SUMMARY 65 A. Suggestions f o r f u r t h e r work 66 STUDIES OF THE BASAL METABOLISM OF ALBINO RATS Determinations of the basal metabolic rate have become more common and s i g n i f i c a n t during the past f i f t y years. E a r l y i n the h i s t o r y of the science of n u t r i t i o n i t was r e a l i z e d that the r a t i o of carbon dioxide production and oxygen consumption * the r e s p i r a t o r y quotient - i n an animal body was profoundly a f f e c t e d by the character of the m a t e r i a l metabolized whether carbohydrate, f a t or p r o t e i n . More r e c e n t l y the discovery of new endocrine f a c t o r s and drugs has increased the i n t e r e s t shown i n basal metabolism s t u d i e s . The b a s a l metabolic r a t e represents the energy required to carry on the e s s e n t i a l functions of' the body. I t i s an index of how the body i s f u n c t i o n i n g . Basal metabolism e x i s t s when heat production i s at a minimum. Certain authors have r e f e r r e d to t h i s c o n d i t i o n as mainten-ance metabolism, post-absorptive metabolism, f a s t i n g metabolism and standard metabolism. ~ The basal metabolic r a t e has been determined i n d i f f e r e n t animals-with many types of apparatuses. Both d i r e c t and i n d i r e c t c a l o r i m e t r i c methods have been used. The d i r e c t method involves the determination of the heat output i t s e l f . The i n d i r e c t method u t i l i z e s the measurement of the gaseous exchange of oxygen and carbon d i o x i d e . In determining the rat e o f energy metabolism by the i n d i r e c t method, i t i s only necessary to measure oxygen consumption. For general laboratory determinations o f the B.M.R. most workers have shown a preference f o r the i n d i r e c t type of apparatus since i t requires comparatively simple equipment and furnishes determinations of s a t i s f a c t o r y accuracy. During the past few years, the white r a t has come to be the most widely used lab o r a t o r y animal since i t o f f e r s the advantages of low cost, s m a l l space requirements, large l i t t e r s , short time span of generations, s t a n d a r d i z a t i o n and ease of comparing r e s u l t s with other workers. The basal metabolic rate has been shown to be dependent upon many f a c t o r s , the c o n t r o l of which i n an animal body i s very important. These are discussed l a t e r . In view of the r e l a t i o n of the basal metabolic r a t e to the subject's d i e t , environment and u t i l i z a t i o n of drugs, a study was begun to show the e f f e c t s o f some f a c t o r s -upon the B.M.R. of r a t s using an apparatus of the i n d i r e c t type. Four f a c t o r s were considered: ( i ) the e f f e c t of unbalancing the d i e t , i . e . feeding high percentages of carbohydrate, f a t , or p r o t e i n , ( i i ) the e f f e c t of v i s i b l e , r a d i a t i o n , i . e . using segregated parts of the v i s i b l e spectrum. ( i i i ) the e f f e c t of a single dose of desiccated t h y r o i d gland. (iv*) ' the e f f e c t of anaesthesia. At the same time, studies- Were'-carried- on concern-ing growth, a c t i v i t y and reproduction, using the d i e t and r a d i a t i o n groups of the same set o f r a t s . Results of the d i e t experiment have been presented i n a t h e s i s by E. J . Sutherland (Dept. of Chemistry, U n i v e r s i t y of B r i t i s h Columbia, 1942), and o f the r a d i a t i o n experiment i n a t h e s i s by J.G. Aldous (Dept. of Biology and Botany, U n i v e r s i t y of B r i t i s h Columbia, 1941). . •SURVEY-How to Measure the B.M.R. " The method u s u a l l y employed i n studies of the v bas a l metabolism of the r a t has been the o p e n - c i r c u i t method of Haldahe, (26). M o d i f i c a t i o n s of Haldane's apparatus have been used by many workers i n c l u d i n g Lee (36) also Krantz and Carr (34). In more recent times workers l i k e Foster and Sundstroem (24), Benedict and MacLeod (7), Horst, Mendel and Benedict (29), Lewis and Luck (37) and Schwabe and G r i f f i t h (45), have shown preference f o r a closed type apparatus. A more complete l i s t of methods has been given by the author (16) and also, by Benedict and MacLeod (7) and Benedict (6). '4. Most methods have.determined both carbon dioxide production and oxygen consumption i n order that a value f o r the r e s p i r a t o r y quotient might be obtained. Richardson (42)-has discussed the s i g n i f i c a n c e of the r e s p i r a t o r y quotient. Poulton (41) has shown that carbon dioxide production by an animal body i s a measure of standard metabolism. Trugg (51) reported methods f o r the determination of carbon d i o x i d e . Benedict (6) stated that i t may be assumed that the r e s p i -r a t o r y quotient of a r a t which has been 24 hours without food i s close to .72. On t h i s assumption, he has shown that l i t t l e error' is introduced, i f oxygen consumption alone i s determined and heat production c a l c u l a t e d from t h i s . When carbon dioxide production i s not measured q u a n t i t a t i v e l y theapparatus may. be s i m p l i f i e s , metabolism determinations are- f a c i l i t a t e d , but the a p p l i c a b i l i t y of the apparatus i s l i m i t e d to the determination of b a s a l metabolism alone. Although carbon dioxide can be measured more e a s i l y and ac c u r a t e l y than oxygen, ba s a l metabolism c a l c u l a t i o n s from carbon dioxide are more l i a b l e to error, than those from oxygen, since with a given change i n the R.Q., the c a l o r i f i c value of a l i t r e , o f carbon d i o x i d e , changes about four times as much as the c a l o r i f i c value of a- l i t r e of oxygen. More-over, because of the nature o f chemical combinations i n which carbon dioxide e x i s t s i n the body, i t s e l i m i n a t i o n can be influenced by changes i n the acid-base e q u i l i b r i u m of the organism and by r e s p i r a t o r y disturbances unrelated to metabolism. Some of the apparatuses have been so constructed as to permit a recording o f the a c t i v i t y o f the animal. Benedict and MacLeod (7) placed beneath the animal chamber a b a l l o o n connected by a hose to a tambour wi t h p o i n t e r . Movements i n the animal chamber changed the pressure, on the b a l l o o n causing a change of p o s i t i o n of the pointer on the -kymograph. In the apparatus of Lewis and Luck (37), the rate of oxygen consumption was measured e l e c t r i c a l l y by the r a t e at which water must be admitted to maintain a constant pressure i n the system; the rate of carbon dioxide produc-t i o n vras determined e l e c t r i c a l l y by the change in,con-d u c t i v i t y , a u t o m a t i c a l l y recorded, of an absorbing s o l u t i o n of barium hydroxide. Schwabe and G r i f f i t h (45) determined a c t i v i t y from a graphic record of the oxygen consumption. Factors Governing the B.M.R. Di u r n a l . Horst et a l (30) have shown the metabolism of the r a t to be subject to d i u r n a l v a r i a t i o n . The oxygen uptake i s , high i n the morning and high i n the l a t e afternoon, the values sometimes ranging from 13 - 50% greater than during the middle of the day. They suggested that f o r comparative purposes the b a s a l metabolism of r a t s should be measured between 10 a*m. and 4 p.m., since during t h i s time a c t i v i t y i s l e s s . Changing from d a y l i g h t to complete darkness causes no changes i n the metabolism between the above hours. Age and Sex. •. Ashworth, Brody and Hogan (3) stated that the meta-bolism per u n i t weight of normally' fed r a t s from b i r t h to one • . year of age declines e x p o n e n t i a l l y with i n c r e a s i n g weight. Davis (18) and Davis and Hastings (19) found that the oxygen consumption per kilogram body weight of r a t s f a l l s ' . r a p i d l y during the f i r s t four months and more slow l y t h e r e a f t e r . Davis and Hastings found no d i f f e r e n c e i n the oxygen consumption of males and females. Sherwood (47) determined the b a s a l metabolism of a number.of r a t s of various s i z e s under standard conditions of d i e t and temperature. He found that heat production i s . higher i n young r a t s and more v a r i a b l e i n males than i n females. Kestner (32) and Blank (10) be l i e v e d that the higher metabolic r a t e per u n i t of weight observed i n small animals cannot be a t t r i b u t e d to the r e l a t i v e l y large surface area but t& the greater proportion of a c t i v e metabolic t i s s u e . Horst et. a l (31) found that the b a s a l metabolism of both male and female r a t s remains at p r a c t i c a l l y a constant l e v e l during the second and t h i r d years of l i f e . They found that male r a t s i n the second and t h i r d years of l i f e have a higher metabolism than female r a t s of the same age. Benedict and MacLeod (8) showed that male r a t s have a d e f i n i t e l y higher heat production than female r a t s up to 14 months of age. Lee. (36) 7. stated that the heat production per square metre of body-surface per day i n the case o f the female r a t shows constant v a r i a t i o n s ^from the general mean only toward the end of stage dioestrum and at the beginning of the stage pro-oestrum. At that time an average increase of 12% i s noted. During none of the other stages of the cycle -is there any s i g n i f i c a n t v a r i a t i o n "in heat production. Sandiford, Wheeler and Boothby (44) reported an increase of 25% i n b a s a l metabolism during-pregnancy which i s adequately accounted f o r by the added metabolism of the f e t u s , placenta and accessory s t r u c -tures . Surface Area* The o r i g i n a l Meeh formula for the surface area of the r a t showed that the area i n square centimetres was equal to a constant times the weight i n grams to the two-third power. Ashworth and Cow g i l l (4) ha^ve shown that the heat production is- p r o p o r t i o n a l to the two-third power of the weight. Heat production can be c a l c u l a t e d either, on the basis-of area or of weight. Many.formulas f o r surface area have been set f o r t h . The most favored of these are those of Rubner (43) and Daick (17) w h i c h ' d i f f e r only i n the constant used. A more complete l i s t of formulas has been given by the author (16). Sherwood (47) b e l i e v e d that the weight technic i s s l i g h t l y more r e l i a b l e than the surface area technic when measured by. the Daick formula. M i t c h e l l (40) 8. discussed the s i g n i f i c a n c e of surface area determinations. He stated that, the surface area i s not a d e f i n i t e measure-ment, but depends to a considerable extent upon the shape of the body as determined by the p o s i t i o n of the body trunk, and i t s appendages. He believed that while the surface area may s t i l l be a h i g h l y u s e f u l measurement f o r comparative purposes, that i n formulas of the Meeh-Bubner type the par-t i c u l a r value of the constant becomes a matter of i n d i f f e r -ence and that of the exponent of body weight becomes of f i r s t importance. A c t i v i t y . • A c t i v i t y increases metabolism. A b a s a l c o n d i t i o n does not e x i s t i n an a c t i v e animal. : In determining the basal metabolic r a t e o f an animal, workers use some method, : e i t h e r v i s u a l or mechanical, to check on the animal's a c t i v i t y sx) as to be able to get a basa l determination. Disease. In r e l a t i o n to diseases In human beings,_ Bodansky (11) stated that metabolism i s increased i n some diseases while i n others i t i s decreased. In cases of hyperthyroidism metabolism i s increased, while In hypothyroid-ism i t i s decreased^ I t i s high i n h y p e r p i t u i t a r i s m and low i n h y p o p i t u i t a r i s m . An increase of one degree centigrade i n the body temperature causes a r i s e i n metabolism of about 13%. 9. Fa s t i n g . Horst, Mendel and Benedict (29) also Benedict and MacLeod (7) have shown values i n d i c a t i n g a decrease i n the basal metabolic r a t e as the time a f t e r eating increases.. With month o l d r a t s Benedict and MacLeod (7) obtained approximately a 10% decrease i n the f i r s t 24 hours a f t e r eating. With younger r a t s they obtained a greater decrease. In general most workers have measured basal metabolism of r a t s about 18 hours a f t e r e a t i n g . Heat production i s i n -creased just a f t e r eating owing to the s p e c i f i c dynamic a c t i o n of the food. P r o t e i n has a much greater e f f e c t than carbohydrate which in, turn has a s l i g h t l y greater e f f e c t than f a t . This e f f e c t i s not permanent and decreases towards basal as the time a f t e r ' e a t i n g increases. Both Rubner (43) : and Graham Lusk have done much work on the s p e c i f i c dynamic . a c t i o n . : . <* Temperature. Horst, Mendel and Benedict (29) have shown that the basal metabolic r a t e increases as the environmental temperature i s decreased. Benedict and MacLeod (8) observed that f o r r a t s the c r i t i c a l t e m p e r a t u r e ^ f o r b a s a l (1) The c r i t i c a l temperature has been defined as that tem-perature below which chemical r e g u l a t i o n i s brought into p l a y to increase o x i d a t i o n o f food or body nu t r i e n t s i n order to maintain the normal body temperature. 10. metabolism i s 28°c. S w i f t and Forbes (49) have reported the c r i t i c a l temperature to be 30°c. Herrington (28) has reported that thermal n e u t r a l i t y f o r the ra.t occurs between 28°c. and 29°c. Schwabe, Emery and G r i f f i t h (46) have reported that exposure to a low temperature 7-12°c. fo r the major p o r t i o n of each day f o r f i f t e e n days increases the B.M.R. of r a t s measured at thermal n e u t r a l i t y by 11-16%. Season. Benedict and MacLeod.(8) observed that the heat production i s 10% lower i n summer than i n winter. Sherwood (47) has obtained values 26% l e s s i n summer than i n winter. Feeding high percentages of Carbohydrate, f a t and p r o t e i n res p'eortlve.ly:.1 .  > Many workers have dealt with, the problem of whether d i f f e r e n t d i e t s caused d i f f e r e n c e s i n body compo-s i t i o n that were r e f l e c t e d i n the metabolism. Considerable work has been done showing the e f f e c t of a high p r o t e i n d i e t on the basal metabolic r a t e . Atkinson, Rapport and Lusk (5) noted that the ba s a l metabolism of a dog on a mixed d i e t increased 23% a f t e r eight days o f meat feed-ing and that a f t e r a r e t u r n to a mixed d i e t the higher B.M.R. pe r s i s t e d f o r two and one half: weeks. Loss of deposited p r o t e i n was associated with the reduction i n ba s a l metabolism. Deuel, Sandiford, Saudiford and Boothby (20) observed a r a p i d 11. f a l l i n the basal heat production of man during the f i r s t eight days of pr o t e i n - f r e e feeding, coincident with a ra p i d f a l l i n e l i m i n a t i o n of nitrogen by the kidneys. Thereafter when, the nitrogen e x c r e t i o n f e l l to lower l e v e l s , the B.M.R. remained p r a c t i c a l l y constant. Subsequently when the subject was put upon a high p r o t e i n d i e t and was r e p l e n i s h -ing h i s stores of body p r o t e i n the B.M.R. was d e f i n i t e l y elevated even above the previous l e v e l . Wang, Hawks, .Huddleston. Wood and Smith (52) studied the e f f e c t of the p r o t e i n l e v e l on basal metabolism on s i x normal adult women. The same number of c a l o r i e s were Ingested d a i l y f o r eleven weeks. For the f i r s t f i v e weeks p r o t e i n percentage was high. In the next four weeks p r o t e i n percentage was low. Then a r e s t period of four weeks was allowed. For the next two weeks a normal diet.was used. No di f f e r e n c e was found i n the B.M.R. of the subjects during the three periods. Black -(9) gave r e s u l t s f o r two groups of r a t s fed d i f f e r e n t d i e t s -eggs and mil k r e s p e c t i v e l y . He observed that basal metabol-' ism was lowest, on the average, on a low p r o t e i n ~ d i e t , some-what higher on a high p r o t e i n d i e t and highest on the high p r o t e i n d i e t supplemented with e x e r c i s e . Talues with m i l k were s l i g h t l y higher- than those. f o r the egg d i e t . Forbes, S w i f t , Black and Kahlenberg (23) reported that an increase i n the p r o t e i n of e q u i c a l o r l e d i e t s tending to improve the n u t r i t i v e balance made no change i n the basa l heat production 12. .per u n i t of computed surface area. They used casein as t h e i r source of p r o t e i n . Horst et a l (31) measured the B.M.R. of r.ats fed at three d i f f e r e n t l e v e l s of pr o t e i n , intake. They have shown the composition of the d i e t s used to be as follows:--Components High P r o t e i n Medium P r o t e i n . Low P r o t e i n Casein 60% 30% 6.0% Cornstarch 12 ,42 65.7 B u t t e r f a t 9 9.0 Lard 15 15 15.0 S a l t Mixture. . 4 . 4 4.0 ; " Cystine 0 0 0.3 Rats were fed the t e s t d i e t s a f t e r the age of 90 days. B a s a l metabolism was determined when the r a t s were between 116 and 145 days o l d . There was p r a c t i c a l l y no d i f f e r e n c e i n the basal metabolism of r a t s fed d i e t s of hig h - p r o t e i n and medium-pro t e i n content, but r a t s on a low-protein d i e t Had a- lower metabolic r a t e . Average values f o r the B.M.R. of the r a t s on the three t e s t d i e t s are as f o l l o w s : P r o t e i n Level 1 ' Heat production per square .- ' ; a _ metre per 24 hours • High 7 2 4 Medium i^gg 13. In the case of f a t s , Asher and Tateyoshi (2) reported that, the b a s a l metabolism of r a t s fed on l a r d was lower than that o f animals fed on a mixed d i e t . Bowen, G r i f f i t h and S l y (13) stated that the basa l metabolism of men a f t e r eating a f a t meal was w i t h i n the average accepted as normal. : " . Fujimoto (25) fed high percentages of carbohydrate and p r o t e i n ,respectively to two groups- of white r a t s . For the carbohydrate he used cooked unpolished r i c e and macaroni; f o r the p r o t e i n he used lean beef. Determinations of the B.M.R. were made during the' f i r s t f i v e weeks and. a f t e r 120 days. In the beef group he found a^ tendency f o r an i n i t i a l r i s e of the B.M.R. U l t i m a t e l y there was a f a l l i n the r e s p i r a t o r y exchange f o r both groups. A l l r a t s died prematurely. . .R'a:dia'tion." No references have been obtained i n the l i t e r a t u r e to show i f the component parts of the v i s i b l e spectrum have any e f f e c t upon the B.M.R. Some work has been- done concern-ing the v i s i b l e region as a whole and also the more remote parts of the spectrum. Lippmann and Yolker (38) reported an increase of 10 - 18% i n b a s a l metabolism during i r r a d i a t i o n w ith u l t r a v i o l e t which returned r a p i d l y to normal a f t e r i r r a d i a t i o n was discontinued. . H a r r i s (27) reported that u l t r a v i o l e t r a d i a t i o n s exerted a stimulant a c t i o n on the gaseous metabolism of small animals. The stimulant a c t i o n of 14. u l t r a ' v i o l e t r a d i a t i o n s was completely annulled by the presence of v i s i b l e r a d i a t i o n s . . Kestner et a l (55) found that the basal metabolism of four subjects during exposure to the sun, wind being excluded, was d e f i n i t e l y higher than i n the shade. Determinations v^ere made on subjects with an empty stomach f o l l o w i n g a high p r o t e i n meal. Eichelberger (22). stated, that i r r a d i a t i o n by s u n l i g h t had no immediate e f f e c t upon basal metabolism. 1 Desiccated Thyroid and Thyroxin. Boothoy and Sandiford (12) stated that to study the e f f e c t of t h y r o i d s e c r e t i o n on the r a t e of heat produc-t i o n the completely myxedematous or t h y r o i d l e s s subject i s preferred because i t i s t h e o r e t i c a l l y probable that with a normal or hyperfunctioning t h y r o i d the q u a n t i t y of the t h y r o i d s e c r e t i o n produced by the gland might vary i n v e r s e l y e i t h e r completely or i n part with- the amount of t h y r o x i n introduced a r t i f i c i a l l y ' whether or not t h i s p o s s i b i l i t y i s true the evidence i s much more e a s i l y i n t e r p r e t e d i f t h i s v a r i a b l e i s e l i m i n a t e d . Meyer and Wertz (39) fed t h y r o i d m a t e r i a l by a stomach tube to r a t s f o r three consecutive days. .75^ were given f o r each ten grams body weight. An increase i n metabolism occurred on the f i f t h day. They found thyroidectomized r a t s to be 25-30 times more s e n s i t i v e than the normal and gave a 25-30% increase i n oxygen consumption. Sos (48) reported t h a t . i n i t i a l l y t h y r o x i n increased the • 15. m o t i l i t y of r a t s to more than double while the B.M.R. was unaltered. The f i r s t c e n t r a l s t i m u l a t i o n passed a f t e r f i v e hours. A f t e r 24 hours the basal metabolism began to r i s e and reached a maximum i n 48 hours. Along with the increase o f metabolism a second c e n t r a l s t i m u l a t i o n occurred but p r a c t i c a l l y disappeared the next day, although the B.M.R. , was the same or higher. Kunde (35) working with dogs found no s i g n i f i c a n t change occ u r r i n g i n the B.M.R. f o r 7-12 hours a f t e r a s i n g l e dose of Kendall's t h y r o x i n intravenously or desiccated t h y r o i d o r a l l y . Following t h i s an appreciable increase i n heat production occurred most marked on the second day, He also found that a f t e r d a i l y repeated doses of e i t h e r t h y r o i d o r t h y r o x i n the B.M.R. p r o g r e s s i v e l y i n c r e -ased reaching a maximum i n three weeks or more. He st a t e d a q u a n t i t a t i v e . r e l a t i o n s h i p between the t h y r o i d ingested and the B.M.R. does not e x i s t . Thompson, et a l (50) found that only intravenous i n j e c t i o n of a l k a l i n e s o l u t i o n of t h y r o x i n caused an appreciable increase i n the B.M.R. when given i n a sin g l e dose. Boyer (14) studied the e f f e c t s of the ortho and meta isomers of t h y r o x i n on the B.M.R. of r a t s . He found that the "meta" compound had l i t t l e i f any e f f e c t i n q u a n t i -t i e s up to 500 milligrams per kilogram body weight and that the "ortho" compound had from. 1/25 to 1/50 the a c t i v i t y of th y r o x i n . Deuel, Sandiford, Sandiford and Boothby (21) reported that a reduction of body p r o t e i n equivalent to 149 16. grams of nitrogen by a pr e l i m i n a r y period of 30 days on a non-protein d i e t did not i n any way a l t e r the c h a r a c t e r i s t i c e f f e c t of thyrox i n on nitrogen or r e s p i r a t o r y metabolism. Anaesthesia. Anderson, Chen and Leake (1) using the recommended therapeutic doses by mouth i n humans, found that b a r b i t a l , i p r a l , neonal and phanodoin tended to reduce oxygen consump-t i o n and t a c t i l e d i s c r i m i n a t i o n but increased the r e s p i r a t o r y r a t e . 17. EXPERIMENTAL The Rats'Used. The r a t s used i n t h i s study o f basal metabolism consisted of male and female Wistar albino r a t s , descendents from a colony supplied by the Dominion F i s h e r i e s Experimental S t a t i o n at Prince Rupert. Environment. . Rats were kept i n a room approximately 8x6x6 f e e t . . The'walls, and c e i l i n g were painted white.. The f l o o r was cemented, The temperature o f the room was t h e r m o s t a t i c a l l y c o n t r o l l e d to 70°F, V e n t i l a t i o n was obtained by drawing a i r from the outside with a f a n . The l i g h t i n g system c o n s i s t i n g of two 100 watt bulbs was a u t o m a t i c a l l y c o n t r o l l e d to give ten hours i l l u m i n a t i o n d a i l y . Each cage was constructed of galvanized metal and had a wire f r o n t , top ; and bottom and s o l i d sides and back and rested on a pan of sawdust... Cages measured 10:inches wide s 8 inches deep and 12 inches long. Inverted 500 c.e. erlenmeyer f l a s k s w i t h a one holed rubber stopper and glass o u t l e t tube were attached to the face of the cage to provide water. Cages were cleaned once a week and then were sprayed with l y s o l . 18. Care of the Rats. For a l l r a t s - water was supplied ad l i b i t u m ; .feeding was done once a day for six- days each week, no f e e d -ing was done on Sunday, double the amount being supplied on Saturday. (a) Unbalanced D i e t s . In March 1941, twelve cages of r a t s approximately ,21 days i n age were placed on t e s t d i e t s . Three of these cages were ; used f o r controls., three f o r excess carbohydrates, three f o r excess f a t s and three f o r excess p r o t e i n s . Rats i n each cage of carbohydrate, f a t and p r o t e i n were fed a d i f f e r e n t substance, namely: for- the carbohydrates - cane sugar, potato s t a r c h and corn s t a r c h ; f o r the f a t s - o l i v e o i l , beef f a t and pork f a t ; f o r the p r o t e i n - casein, beef p r o t e i n and pork protein,. In so f a r as p o s s i b l e , two males and two females were placed i n each cage. The choice of the food substances used was l a r g e l y governed by the desire to use those most l i k e l y to be u t i l -i z ed i n the ordinary d i e t . One from each d i e t was to be a r e l a t i v e l y pure substance, namely cane sugar, o l i v e o i l and casein. Substances chosen are r e a d i l y obtainable and prepared f o r the t e s t animal's use. The carbohydrates s e l e c t e d required no f u r t h e r preparation, neither d i d the o l i v e o i l and casein.' Beef and pork f a t were prepared by s t r i p p i n g the f a t from a side of 19. beef and pork f a t r e s p e c t i v e l y , c u t t i n g the f a t t y m a t e r i a l into small s t r i p s and rendering i t i n a large open v e s s e l over a steady flame f o r f i v e hours. The f a t so prepared was poured through a cheesecloth while s t i l l hot and the remaining mass was pressed to obtain the remaining f a t . This was all-owed to cool -and "solidify :-and was ~' •-'•:>" •  '-: -kept i n a r e f r i g e r a t o r at 5 Gc. u n t i l ready f o r use. Beef and pork pro t e i n w.er'e prepared by c u t t i n g away rrema i n i n g pieces 1 of f a t from a f r e s h cut of lean beef and pork. The lean m a t e r i a l was then cut into small pieces and dehydrated f o r three days at 90°c. The d r i e d product was f i n e l y ground f o r use. The normal d i e t used f o r the c o n t r o l r a t s was i n the form of checkers supplied by the Purina Company under the trade name of "Purina Fox Chow". The Purina Company st a t e d t h e i r checkers contain f l a v i n concentrate,•carotene, wheat germ, dr i e d skim milk, l i v e r meal, brewer's d r i e d yeast, barley malt, f i s h meal, dried meat, a l f a l f a meal, corn g r i t s , soybean meal, molasses, d r i e d beet pulp, cod l i v e r o i l , !%• steamed bone meal and 1% i o d i z e d - s a l t . Each checker weighs approximately 5.5 grams and has a c a l o r i f i c value of 22.5 c a l o r i e s , -Test d i e t s were prepared so t h a t 50% of the t o t a l c a l o r i e s was produced by the powdered checkers and the other 50% by the t e s t substance. The c a l o r i g e n i c values used are: 20 1 gram c o n t r o l = 4.1 c a l o r i e s 1 " carbohydrate a 4.1 " 1 ". f a t = 9.3 " 1 " p r o t e i n » 4.1 " The proportions by weight used in mixing the c o n t r o l and test substances are as f o l l o w s : Carbohydrate: 1 gram of cane sugar and 1 gram of powdered checkers - • \. -1 gram of potato s t a r c h and 1 gram o f poT/dered checkers 1 gram of corn s t a r c h - and 1 gram of powdered checkers Fat: • 480 grams of o l i v e o i l and 1100 grams o f powdered checkers 480 grams of beef f a t ' and 1100 grams of powdered checkers 480.grams of pork f a t and 1100 grams o f powdered checkers P r o t e i n : . . 1 gram of casein and 1 gram of powdered checkers 1 gram of beef p r o t e i n '.- and .1 gram of powdered checkers' 1 gram of pork p r o t e i n -' and 1 gram of powdered checkers To be i n a more s u i t a b l e form f o r feeding the f a t t e s t d i e t s were made into b i s c u i t s by compressing into s o l i d lengths' approximately 4 inches long and 3/4 inch i n diameter. The carbohydrate and p r o t e i n t e s t d i e t s were fed i n powdered form. 21. The Purina Company has given an-analysis of t h e i r product'. By combining t h e i r a n a l y s i s with the proportions shown above f o r the t e s t d i e t s , an a n a l y s i s was obtained f o r the unbalanced diets../ The a n a l y s i s f o r the c o n t r o l and un-balanced d i e t s i s as f o l l o w s : • - High ' High High Percentage Carbohydrate Fat P r o t e i n Content Control Diet Diet Diet Carbohydrate ' 55,34= 77.92 38.88 27.92 P r o t e i n 21.47 10.73 14.94 60.73 Fat 5.14 2.57 33.96 2.57 Fi b r e 4.11 2.05 2.86 2.05 Ash 6.37 3.18 4.43 3.18 Moisture 7.07 3.53 4.91 3.53 The amount of r a t i o n fed to the r a t s was g r a d u a l l y increased as the r a t s grew older to a f i n a l adult r a t i o n of 16.5 grams per r a t per day i n the case of the c o n t r o l s , carbohydrate and protein-and 11.85 grams per r a t per day i n the case of the f a t t e s t r a t s . A l l r a t s were being fed the , same number of c a l o r i e s . These r a t s were maintained on t h i s d i e t f o r a period of one year with the exception of a t h i r t y -day period f o l l o w i n g seven months of d i e t feeding, when a l l r a t s were placed on the normal d i e t . The basal metabolic r a t e s of these r a t s were deter-mined when they were between the ages of 303 days and 358 days*. Five sets of determinations were made on twenty-two r a t s - f i v e controls,, two f o r each of the d i e t s except beef. 22 • p r o t e i n , where only one was present. The remainder o f the r a t s which were present o r i g i n a l l y had been used for post-mortem studies on f a t . d e p o s i t i o n , (b) Radiat ion. " In March 1941 the f i r s t l i t t e r s of the FQ generation of r a t s under constant r a d i a t i o n were set up as t h e . F i generation. This F i generation was used to produee information concerning growth, reproduction, a c t i v i t y and the basal metabolic r a t e . The F Q generation consisted of eight cages of r a t s with one male and two females i n each cage. In f r o n t of each cage was placed a s i n g l e thickness of cellophane of d i f f e r e n t c o l o r s , r e s p e c t i v e l y , red, orange, yellow, b l u e , green, v i o l e t , c l e a r and bla c k . Behind the sheet of black cellophane was placed a sheet o f cardboard to t o t a l l y obscure the l i g h t . Cages were placed on a s h e l f d i r e c t l y f a c i n g two 100 watt l i g h t bulbs and at a, distance of seven f e e t away. L i t t e r s were produced i n a l l cages except that behind the blue f i l t e r . Two females and one male at the. age of days were taken from each of the cages and set up as the F^ generation i n another set of cages behind t h e i r r e s p e c t i v e color f i l t e r s . Due to the apparent s t e r i l i t y o f the r a t s behind the blue f i l t e r , two males and two females were taken at the age of 2 l days from a subsequent l i t t e r produced by a female behind a v i o l e t f i l t e r and set up i n a cage behind a blue f i l t e r with the F]_ generation,, 23. Subsequently l i t t e r s were produced by t h i s F]_ generation i n a l l cages except that behind the blue. From t h i s set of l i t t e r s only two males and two females of the f i r s t l i t t e r from the cage behind the b l a c k f i l t e r were kept and set up as the Fg generation behind a black f i l t e r at the age of 21 days. These nine cages were kept behind t h e i r r e s p e c t i v e color f i l t e r s f o r 180 days, a f t e r which time a l l colors i n -cluding c l e a r , were replaced by a black f i l t e r backed by a sheet of cardboard,, and the two black f i l t e r s were replaced by s i n g l e sheets of blue cellophane. The r a t s were main-tained under t h i s environment f o r 210 days and then were replaced behind t h e i r o r i g i n a l f i l t e r s to be kept under t h i s c ondition f o r 22 days. These r a t s were fed three checkers per day per r a t o f the standardized d i e t prepared by, the Puriha Company, the same normal d i e t as was fed the controls i n the d i e t experiment. The experiment may be divided into three phases: f i r s t , - colors and black, second - colors changed to black and black changed to blue, t h i r d - col o r s and black. The ba s a l metabolic rates^were determined i n the second and t h i r d phases only. Three sets o f determinations were made f o r each phase. 24. (c) Controls. i . In February 1942 t h i r t e e n r a t s , - seven females and s i x males, obtained from l i t t e r s produced under colors,. were set up i n four cages at the age of 21 days as c o n t r o l s . Males and females were kept separate. These r a t s were, fed g r a d u a l l y i n c r e a s i n g amounts of the standardized d i e t of the Purina Company u n t i l they could u t i l i z e three checkers per day each - the adult r a t i o n . _.The b a s a l metabolic rates of these r a t s were determined when they were between the ages of 118 and 133 days. Four sets of determinations were made. i i . In A p r i l 1942, three male r a t s obtained from a l i t t e r produced behind a yellow f i l t e r were set up as controls at the age of 21 days. Feeding was the same as f o r the previous set of c o n t r o l s . The.basal metabolic rates were • determined at two d i f f e r e n t ages, 71 - 78 days and 108 - 110 days. Two sets of determinations were made i n each age group, (d) Desiccated Thyroid. S i n g l e doses of •Burroughs Welcome. Co. 'desiccated thyroid gland s ' were fed to ten r a t s from the group ( i j used as c o n t r o l s . These' r a t s were not fed t h e i r normal r a t i o n s f o r the 24 hours p r i o r to the time of g i v i n g the drug. Four r a t s c o n s i s t i n g of two males and two females were fed 1/10 (1) The Burroughs Welcome Co. states that each 1/10 g r a i n of fresh, healthy gland substance i s equivalent to 1/33 g r a i n o f dry t h y r o i d B..P. 25. g r a i n (.0065 grams) of t h y r o i d . Another group of four - two males and two females, wss- fed 2/10 g r a i n t h y r o i d . A t h i r d group - one male and one female, was fed 5/10 g r a i n of t h y r o i d . The basal metabolic rates were determined p r i o r to feeding the desiccated t h y r o i d and then afterwards every hour f o r s i x hours and then every day f o r one week and then every other day f o r two weeks. During the course, of these deter-minations c o n t r o l r a t i o n s were fed immediately a f t e r the d a i l y t e s t s . (e) Anaesthesia. Four r a t s , two males and two females from c o n t r o l group ( i ) , a f t e r having been starved f o r 24 hours, s e p a r a t e l y received an i n t r a p e r i t o n e a l i n j e c t i o n of 2/5 cc. of a 2§-% s o l u t i o n of Sodium Pen to t h a i (Abbot) (Sodium e t h y l .1 methyl b u t y l t h l o b a r b i t u r a t e ) to produce anaesthesia. The b a s a l metabolic, rates were determined p r i o r to the i n j e c t i o n and also while under the anaesthetic. The Apparatus. „ , , The apparatus .used to determine the, basal meta-b o l i c rate was l a r g e l y designed by E.L.Schwabe and F.R. G r i f f i t h , J r . at the U n i v e r s i t y of B u f f a l o (45). C e r t a i n m o d i f i c a t i o n s have been made which give more r e l i a b l e deter-minations and f a c i l i t a t e operation. Improvements concern the manner of removal of carbon dioxide and the means of 26. r e g i s t e r i n g oxygen consumption. By r a i s i n g and lowering a "vessel with respect to a connected v e s s e l , containing a standardized s o l u t i o n of barium hyroxide (both vessels were connected separately to the animal chamber), Schwabe and G r i f f i t h caused the a i r i n the animal chamber to be brought into contact with the s o l u -t i o n f o r removal of carbon dioxide and to be returned to the chamber without d i s t u r b i n g e q u i l i b r i u m . Oxygen passed into the chamber through an o i l trap to take the place of the absorbed carbon dioxide... In t h i s l a b o r a t o r y the carbon dioxide and water vapour :were removed by soda lime i n the animal chamber. The base of t h i s chamber consisted of a varnished copper pla te 15" x 15" into whiffih was impressed a c i r c u l a r trough 3/8". deep,, i " wide at a distance of from the centre of the p l a t e . A c l e a r glass v e s s e l 9-3/8" i n • diameter and 3^" deep was inverted to f i t into the trough. Mercury was placed i n the trough as a /seal f o r the chamber. . A small d r a i n with tap was i n s t a l l e d to remove the mercury. Inside, t h i s chamber was placed the absorption unit-* This took the form of a c i r c u l a r piece o f wood, 8§" i n diameter and J " t h i c k , a c t i n g as base on to which were n a i l e d small . posts 2^" long and 3/8" wide and t h i c k i n an upright p o s i t i o n which supported two lengths of copper gauze i n t u r n cemented on to the base of wood, forming a w a l l 2^" high and f H wide 27. around the base. 400 grams of soda lime were placed w i t h i n the w a l l . An i n l e t tube f o r oxygen passed through the copper and wood1 en bases and extended upwards to the height of the w a l l w i t h i n the absorption unit from the w a l l . E n c i r c l e d by the w a l l of soda lime was an open space 7|" In diameter, ample space i n which to place the r a t . The soda lime gave e f f i c i e n t usage f o r about two weeks. . A water displacement method was used to get a graphic record o f the, oxygen consumption. Schwabe and G r i f f i t h used a water manometer i n one side of which was placed a p a r a f f i n e d cork f l o a t supporting a bamboo rod and w r i t i n g t i p . ' As water was displaced bubbles of oxygen rose to the surface and b u r s t , i n c r e a s i n g the pressure on the water supporting the f l o a t . F l u c t u a t i o n s i n the graphs obtained are a t t r i b u t e d to over sensitiveness of the l i g h t f l o a t employed. When t h i s f l o a t was replaced by a glass f l o a t seven inches long supporting a '"bamboo, rod with c e l l u -l o i d writing; t i p r i g i d l y sealed into the glass f l o a t with De Kotisky's cement and j u s t f i t t i n g into one side o f the manometer c o n s i s t i n g of glass tubing 16" long and 7/16" i n diameter, s e n s i t i v i t y was not decreased i n that the animal's a c t i v i t y was recorded- but f l u c t u a t i o n s were ' elimina ted. Detai l e d d e s c r i p t i o n of the apparatus (See Diagram). M]_ i s a water manometer system, c o n s i s t i n g of. two parts m^  and mg joined by rubber tu b i n g . 4 i contains the , 28. f l o a t and i s long enough to permit the f l o a t to r i s e the t o t a l height of the kymograph K. The c e l l u l o i d w r i t i n g t i p on the f l o a t , i s held i n place j u s t touching the kymograph by a piece .of glass tubing placed p a r a l l e l to the face of the kymograph. The kymograph i s 6" i n diameter and 8" high. I t i s turned at the r a t e of approximately one r e v o l u t i o n i n 30 minutes by a clock L which has a wheel set i n the place of the. face hands. m2 i s made of glass tubing the same bore as mi but a l i t t l e longer-and i s connected to the r e s t of the apparatus by rubber tubing. A rubber f o o t b a l l bladder 0, used as a r e s e r v o i r at atmospheric pressure, receives oxygen from a commercial c y l i n d e r . C i s a glass Cylinder 8" long and 1-3/8" i n d i a -meter containing 175 c.c. of water when-full.. I t i s provided at the upper,end with a two-holed and at the lower end with a one-holed rubber stopper. R i s a on<l l i t r e s u c t i o n f l a s k containing about 175 c.c. of water and provided with a three-holed' rubber stopper through.which pass a thermometer and the tubes y and z. Through the two-holed rubber stopper i n C. pass two pieces of glass tubing - x, connected with the oxygen supply, extends 4^" down into the water i n 0, and w connected with the oxygen recording manometer and r e s e t t i n g system, j u s t enters; C and remains above the water l e v e l . A s i n g l e tube containing water emerges from G. at the bottom and '29. ••enters R at the top by two arms - z extends below the surface of the water i n R 3 and y passes down into R. and forms a bent t i p at the same l e v e l re g r a v i t y as the open end of x i n C, thus c r e a t i n g equal pressure (atmospheric) at the openings of x and y. x i s used to convey water from C to R, z i s used f o r the reverse. R i s connected with V, a 150 c.c. v/ide , mouth f l a s k containing f l u s h i n g o i l , by a tube extending to .just under the surface of the o i l . V. acts as a M u l l e r valve to prevent back d i f f u s i o n and escape from absorption of the carbon, d i o x i d e . , A manometer Mg containing f l u s h i n g o i l measures the pressure i n R. A .by-pass of the water system connects the oxygen source d i r e c t l y w i t h V. Leading out of Y i s a glass tube connecting d i r e c t l y with the absorption chamber D, p r e v i o u s l y described. •Mg i s a manometer containing f l u s h i n g o i l which measures the pressure i n the chamber. S and Sj_ are l e v e l l i n g bulbs containing water used i n r e s e t t i n g the apparatus. The water remains i n the apparatus and contains copper s u l f a t e to prevent mould growth. The water becomes saturated with oxygen-so very l i t t l e e rror i s introduced due to i t s : absorption of oxygen. The gas contained i n the apparatus i s oxygen at atmospheric.pressure. .:. The s i z e of the apparatus w i l l depend upon the 30. s i z e of the animal. The dimensions used here are f o r use with a r a t . This apparatus has been constructed i n a quiet V room on the shady side of the b u i l d i n g . Temperature remains nearly constant, around 22°c. Operation (See diagram). Carbon dioxide and water vapour are removed i n the animal chamber by the soda lime. . To compensate the de-crease 1 i n pressure produced, oxygen enters the chamber through the M u l l e r valve from H, the by-pass being closed.' To main-t a i n : atmospheric pressure i n R, water flows from C through 4 to...y. I n C, x i s at atmospheric pressure and the surface of the water i s at a pressure l e s s than atmospheric by an amount equal to the height of the water above x* As water flows over to R, the l e v e l i n G drops and oxygen bubbles i n at x and the pressure at the surface of the water i n C must increase towards atmospheric. This increase i n pressure above the water i n C i s transmitted to Mj and the f l o a t i n mi r i s e s , marking the kymograph. When no record of the oxygen consump-t i o n i s r e q u i r e d , the by-pass of the water system i s used to supply oxygen. The volume of oxygen used by the r a t i s the same as the amount of water that passes ; from C into R through y„. ' I t i s rather awkward to measure t h i s volume d i r e c t l y so the apparatus i s c a l i b r a t e d to give a r e l a t i o n between the number ' ' 31. of cubic -centimetres of water removed from G and the corres-ponding r i s e of the f l o a t .in m-i- marking-the kymograph.Schwabe ; and G r i f f i t h c a l l t h i s c a l i b r a t i o n - the determination o f the 'X vo 1 umetrie equivalent of the manometer. Another c a l i b r a t i o n i s required i n determining the number of centimetres traversed ; by the kymograph drum i n a period of one minute. At the s t a r t ^of a run C i s f u l l of water and the manometer M]_ measures the d i f f e r e n c e i n l e v e l between the ; opening of x and the surface of the water i n C. The c e l l u -l o i d marking point of the f l o a t r e s t s d e l i c a t e l y ' a g a i n s t the smoked paper on the kymograph. The kymograph i s turned r through one r e v o l u t i o n to get a basal l i n e f o r graphic com-parison. .' . The r a t i s placed i n the chamber. A f t e r stop :cocks 1, 3', 4,-5, .6.,. 7, 10 and 11 are closed and 8 and 9 are opened:; the apparatus i s flushed with oxygen. When the pressure returns to atmospheric determined by opening stop-• : cock 10 or 11, stopcock 9 i s closed. The r a t i s then obt a i n i n g oxygen d i r e c t l y from the rubber supply bag. To .measure the amount o f oxygen consumed by the r a t , stopcocks 1,: 3 and 4 are opened, a l l the r e s t are closed. At the same /time the clock d r i v i n g mechanism o f the kymograph i s s t a r t e d . No: f u r t h e r manual operation i s required u n t i l the termination of a run. I t i s adMlsahle t o check o c c a s i o n a l l y on the / a c t i v i t y of the r a t and the p o s i t i o n of the f l o a t which some-32. times may s t i c k due to uneven pressure on the drum. ' Time f o r a run can be determined from the oxygen consuming tendency .and a c t i v i t y of the r a t . A basal determination without - a c t i v i t y i s required.. A c t i v i t y i s recorded g r a p h i c a l l y and may be eliminated from c a l c u l a t i o n s , so i t i s not necessary ^to'have-a completely ba s a l run. A part,of the run must be .bas a l . ' Duration of the run found most s a t i s f a c t o r y averaged 20 minutes-. Jlhen the run i s terminated the clock i s stopped, stopcocks 1,,5 and 4 are closed and 8 i s opened. This ensures the: rat, a supply of oxygen without removing i t from or opening the apparatus. The g r a p h i c a l record o f oxygen consumption and a c t i v i t y i s removed from the kymograph, dipped i n varn i s h to preserve i t , and hung up to dry. To reset the water system, 8 remains open, 6 i s opened^ then 5. As S i s lower than S]_, water flows from E into 0. 5 i s closed when G i s at i t s s t a r t i n g p o s i t i o n . To r e t u r n the manometer to. i t s o r i g i n a l p o s i t i o n 1 i s opened and the water. i s drawn into mg from m]_. 6 i s then closed. By opening 3 the l e v e l s of the water i n mg and m]_ set them-selves so as to record the d i f f e r e n c e i n pressure between the opening of x and the surface of the water i n C. To conserve oxygen. 7 i s opened and-S i s placed higher than S^. This r e -sets S-^  i n r e l a t i o n to S. Then 7 i s closed. A new sheet i s placed on the kymograph and smoked. This same procedure i s followed i n f u r t h e r deter-minations . . 33. This apparatus was not used to measure the R.Q. of the r a t although i t might e a s i l y be used f o r t h i s purpose. Methods Employed with the Rat. P r i o r to the determination o f the b a s a l metabolic r a t e , r a t s have been f a s t i n g f o r at l e a s t 16 hours but have not been deprived of water. Rats were weighed before measuring the B.M.R. The animal's a c t i v i t y i s unoontrolable. When possible t h i s must be minimized. I t was found that i n q u i s i -tiveness was decreased by covering the c l e a r glass chamber. 34. R E S U L T S Measurement off the B.M.R. The values f o r the b a s a l metabolic r a t e were based on oxygen consumption, determined by measurement o f the graphs obtained. A set of p a r a l l e l r u l e r s was placed on the graph, a b a s a l p o r t i o n was s e l e c t e d , one of the r u l e r s was moved .to cross the base l i n e , a distance corresponding to 10 minutes was measured from the point where the r u l e r crossed the base l i n e along the base l i n e to a new point from which the distance perpendicular from the base l i n e to the r u l e r was measured. By m u l t i p l y i n g the v e r t i c a l r i s e by the c a l i b r a t e d volumetric equivalent of the manometer the volume of oxygen consumed by the r a t i n 10 minutes at the temperature of deter-mination was obtained. To convert t h i s volume to c a l o r i e s , i t was assumed that a r a t has a constant R.Q. of .72 - 1 l i t r e of oxygen at S.T.P. i s equal to 4.702 c a l o r i e s (15). The surface area o f the r a t was c a l c u l a t e d from Rubner's formula (43). S.A. = 9.1 x W2/3, where S.A. i s the surface area i n square centimetres and W i s the weight i n ;grams. In t h i s work the b a s a l metabolic rate i s ex-pressed i n c a l o r i e s per square metre per hour. Note: C a l i b r a t i o n data: 1 cm. r i s e r 23.47 c.c. 1 cm. h o r i z o n t a l = ,63 min. 35. Graphs«. The form of the graphs obtained, i s shown i n a copy of the o r i g i n a l graph obtained f o r the female (£) whose. B.M.R. i s given i n Table 5. In the "pre-anaesthesia"-deter-mination the l a t t e r part of the curve may. be treated as basal while i n the "under-anaesthesia" determination the whole curve -may 'be considered as b a s a l . Sample C a l c u l a t i o n . The f o l l o w i n g shows the c a l c u l a t ion of, the "pre-anaesthesia'* determination of the B.M.R. for the case of 1 the £ Table 5<, V e r t i c a l r i s e o f a ba s a l p o r t i o n of the graph corresponding to a time of 10 minutes - 1.96 cms. „ Volume of oxygen at temperature of determin-. a t i o n (25°c) used by the r a t i n 10 minutes -1.96 x 23.47 c.c. Basal heat production of the rat, i n , 10 minutes - t .. ' ' 1.96. x 23.47 x 273 z 4 . 7 0 2 o a i s . 1000 • 298 Surface area of the r a t - 9.1 x 1982/3>' sq. ems,. Basal metabolic rate of the r a t i n c a l o r i e s per square metre per hour -1.96 x 25.47^275^ ^  ^ 1 x 60 1000 298 9,1 x 198 ~ f i / g 1 0 10,000 - s 38.5 • " 56. Values of the B.M.R. In the f o l l o w i n g tables age is given i n days, weight i n grams, temperature i n degrees centigrade and the basal metabolic rate i n c a l o r i e s per square metre per hour. 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Rats i n both d i e t and r a d i a t i o n experiments showed : symptoms of pseudo t u b e r c u l o s i s . This disease f i r s t became ..noticeable i n November 1941 when the r a t s were approximately nine, months o l d . Post-mortem studies revealed a c e r t a i n .amount of pus, contained i n nodules on the lungs. No other defects showed up i n t h i s work. I t was rather unfortunate that t h i s c o n d i tion e x i s t e d when basal metabolic r a t e -determinations were made. •" The disease did not appear worse i n anyone p a r t i c u l a r group o f i a n i m a l s . B.M.R. values of the r a t s were averaged f o r each group. The values o f the B.M.R. fo r the various groups maybe considered as r e l a t i v e . Rats used as controls and l a t e r f o r t h y r o i d gland feeding and anaesthesia work were under 160 days o l d and showed no signs of the disease. Thews'e r a t s were o f f s p r i n g of the Infected r a t s and i f l e f t t i l l nine months old probably would have developed symptoms of the disease. Method Employed,, The graphic method employed here i n the determina-t i o n of the b a s a l metabolic r a t e has proved s a t i s f a c t o r y i n operation and very u s e f u l In that periods of a c t i v i t y were elim i n a t e d , l e a v i n g o n l y a basa l portion., A l l graphs, ob-ta i n e d d i d not f u r n i s h a basal p e r i o d ~ some had the slope Changing continuously to form a curve, others which ha;d: a 50. c6.ns'tant slope were a completely a c t i v e run. The f i r s t type were ••disregarded as were also the second type which were differentia.ted from a basal, type by comparing with another , group of determinations. The number of unusable graphs was quite small considering the number of determinations made. -A , small e r r o r was introduced i n measuring the slope of the l i n e ! amounting to about 2$. This e r r o r was more than o f f s e t i n • that a more basal determination was obtained by us ing the ;, graphic method. Control of V a r i a b l e s . The b a s a l metabolic r a t e has been shown to vary Under "o r d i n a r y circumstances".with such properties as age, sex, a c t i v i t y * disease, and fasting,and also w i t h such external f a c t o r s as temperature and season. To consider the e f f e c t of some one p a r t i c u l a r substance or environment a l l v a r i a b l e s , should be reduced to a minimum. In. t h i s work a l l animals i n a p a r t i c u l a r group were of approximately the same age. A number o f determinations have been made so as to average d a i l y v a r i a t i o n s . Results f o r females were obtained on d i f f e r e n t days and did not correspond n e c e s s a r i l y to the same p o s i t i o n i n the sex c y c l e . A l l r a t s have, received the same amount of f a s t i n g before determinations of the B.M.R.. A c t i v i t y has been eliminated i n c a l c u l a t i o n s . Determinations were made i n the ••••winter and. s p r i n g . Temperature has not been regulated to .that reported f o r thermal n e u t r a l i t y o f the r a t . In this. 51.. work determinations were made at room temperature varying ' . s l i g h t l y about 22 o. Values of the B.M.R. obtained at t h i s temperature w i l l be higher than those obtained at the c r i t i -c a l temperature which i s 6 - 8 degrees higher. Controls. Table-3a shows, the i n d i v i d u a l values of the B.M.R. obtained f o r seven males and s i x females. The f i r s t set o f determinations shows higher, values on the average than the •other three s e t s . This may be a t t r i b u t e d to i n q u i s i t i v e n e s s and probably f e a r . A f t e r these sensations have been overcome, they grow accustomed to the apparatus and give more constant values. By averaging the l a s t three s e t s , r epresentative values f o r male and female r a t s may be obtained. -This i s given i n Table 6a. Table 6a S ex ,._4ge . We ight - B.M.R. 130. .. 200.,:; 45.9 9 130 o - 169, 46.8 We may get a fu r t h e r i n d i c a t i o n of the e f f e c t of sex upon the b a s a l metabolic r a t e by averaging the values-obtained for- older male and female r a t s from Table l a . This : i s given i n Table 6b. ;Sex Age Weight B.M.R. cf ' 222 .' 40.4 9 319 170 : 43.2 52. The values shown i n Table 6b can not-be considered conclusive :The number of r a t s -employed'was not. great. The h e a l t h of these animals, used as con t r o l s i n the d i e t experiment, was " f a i r . These, f i g u r e s i n d i c a t e a s l i g h t l y higher b a s a l heat production i n the. female than i n the male. By averaging the values obtained for male r a t s i n Tables l a , 3a and 3b, an i n d i c a t i o n o f the e f f e c t of age upon the b a s a l metabolic r a t e may be obtained. This i s given i n Table 7. . Table 7. Age Weight B.M.R. . 75'7 47.3 109 2.26. >^ 4:0 0 1 130, SOQ 45.9 . 333 222 40.4 These values show a decrease with age. The f o l l o w i n g are some r e s u l t s of ba s a l heat production obtained at the c r i t i c a l temperature, by other workers i n the case of a normal r a t . i . Daick (17) (a) using Daick constant of 7.47 i n surface area formula 36.5 cals/sq.m./hr. (b) using Lee constant of 9,00 i n surface area formula 30.2 ' cals/sq.m./hr., • (c) using Carman, M i t c h e l l con-• stant of 11.36 i n surface area formula 24.0 cals/sq.m./hr. 53. i i . Schwabe., Emery and G r i f f i t h (46) using Daick's surface area formula male 975 cals ./sq_.m./S4 h r s . female 888 cals./sq_.m./24 hrs. i i i . Erantz and Carr (34) using Daick's surface area formula male 1040 cals./sq..m./24 h r s . i v . Sherwood (47) using Daick's surface area formula . • male 34 - 35 cals./sq.m./hr. v.. Lewis and Luck (37) using Lee's surface area formula male 744 cals ,/sq_.m./24 hrs. v i . Benedict and MacLeod! (7) " ' : . using Rubner's surface area formula male 929 cals./sq_..iiu/24 hr. v i l . Horst "Mendel and Benedict (29) using Rubner's surface area formula female 600 - 700 cals./sq.m./24 hr. From these r e s u l t s i t may be seen that the formula f o r surface area plays an important part i n i n t e r p r e t i n g data. There, i s no means of c a l c u l a t i o n common to a l l /workers. This increases t h e d i f f i c u l t y i n comparing r e s u l t s . The values reported here are w i t h i n the range reported by other workers but In general are a l i t t l e higher owing to the lower tempera-ture at which determinations were made. Unbalanced D i e t s • Although each r a t was given the same number o f c a l o r i e s i n the d i e t , the number of c a l o r i e s used by the r a t s on the d i f f e r e n t d i e t s was d i f f e r e n t . Rats on corn starch and 54. potato sta r c h ate t h e i r whole r a t i o n . Rats on o l i v e o i l , beef f a t and pork f a t consumed only about 60% of t h e i r d a i l y r a t i o n . The other r a t s r e c e i v i n g c o n t r o l , casein, beef pro-t e i n and pork p r o t e i n u t i l i z e d about 90% of t h e i r d i e t , while those feeding on sugar used about 75%. I t i s apparent that some of these d i e t s must be short i n some d i e t a r y f a c t o r , thus causing the r a t s to eat t h e i r e n t i r e d i e t i n an e f f o r t to keep up to t h e i r requirement. Rats r e c e i v i n g high f a t d i e t s received a l a r g e r percentage of c o n t r o l r a t i o n i n the di e t than any otherrat except the controls themselves. Tables l a and l b show values f o r the B.M.R. of r a t s on the d i e t experiment. A previous set of determina-t i o n s g i v i n g higher values was not recorded. In averaging these r e s u l t s i t was found best t o disregard values quite d i f f e r e n t from a general mean-and' use only those having small v a r i a t i o n . In most cases high values, were discarded but i n the case of pork p r o t e i n i t was the "low value which seemed to disagree. - This method i s j u s t i f i a b l e - take values of clo s e s t check. As there were not both males and females on every d i e t , values were not averaged separately for each. Average values are given i n Table 8a. 55. : Table 8a Diet Rfit W p . i o - h t T\Tn . V : .. ' . used Pork Protein. 216 4 Casein * } 230 6 Control 189 8 Pork Fat 189 5 Beef P r o t e i n 125 2 Potato Starch 202 6 Sugar _ • • 207 5 Corn Starch 196 5 Beef" Fat 181 • 5 • Oliv e O i l 199 5 ,R< Discarded 2 44c 6 0 43.. 0 0 42.2 2 40.5 0 40.1 0 38.5 1 36.5 2 35.4 1 35.3 0 33.9 With two exceptions that of beef -protein and .pork'. ." f a t j the b a s a l metabolic r a t e appears highest i n the case of p r o t e i n , second f o r the c o n t r o l s , t h i r d f o r the carbohydrates and f o u r t h f o r the f a t s . . In the case of beef protein,, only one female was a v a i l a b l e f o r B.M.R. determinations. , This r a t was small and appeared sick-and died before completion of the experiment. I t appears quite probable that under better c i r -cumstances the value obtained f o r beef p r o t e i n would be higher corresponding w i t h t h a t f o r the other p r o t e i n s . I t i s d i f f i c u l t to see why pork f a t should produce a higher basal metabolic r a t e than the other f a t s . Pork f a t i s intermediary between o l i v e o i l and beef f a t i n the degree of unsaturation. The male (P.F.) has a lox^er metabolic rate than the female ,(P.F.) s t i l l much higher than the average f o r the f a t s . Table 8b gives the average values f o r the types of d i e t carbohydrate, f a t and p r o t e i n . • ' •56.. Table 8b D i e T : —- : - B.M.R", P r o t e i n ' 42,6 Control 43.2 Carbohydrate 36.8 .Fa.*-. 36.6 The f i g u r e s shown i n t h i s t a b l e i n d i c a t e that a high p r o t e i n diet- does hot influence basal metabolism, while a low p r o t e i n -d i e t (high carbohydrate or high f a t ) reduces b a s a l metabolism of the r a t . I f the value f o r the beef p r o t e i n shown i n , Table 8a was disregarded, the average value f o r the B.M.R. of ra t s feeding on a high p r o t e i n d i e t would be 43.8 cals,/sq.m./ hr.,. 3.8% above the value f o r the c o n t r o l s . The average value f o r the B.M.R. of r a t s feeding on a low p r o t e i n d i e t i s 10.7% below the value f o r the c o n t r o l s . Radlat i o n . I t i s r a t h e r -unfortunate that the B.M.R. of the r a t s could not be measured during the f i r s t of the three . phases of the experiment. The experiment was i n the.second phase before the apparatusy necessary f o r B.M.R. determina-t i o n s , was a v a i l a b l e f o r use. Table 2a shows values f o r the B.M.R. of the r a t s , during the second phase of the experiment where colored f i l t e r s have been replaced by black and black f i l t e r s have been changed to blue. In averaging these results' no d i s -t i n c t i o n was made between males and females as both were not • 5 7 . always present i n each cage behind d i f f e r e n t color f i l t e r s . A total-average of the i n d i v i d u a l values was used. Average values f o r the second phase of the experiment are given i n Table 9a. Table 9a - Second Phase No. of Color Weight Determinations. B.M.R. Yellow' 225 . 8 52.9 Red 286 9 44.8 Black (Fg) 202 6 44.5 V i o l e t 224 9 43.4 Bla ck 250 8 43.0 Orange 197 6 43.0 Blue* .205 12 41.2 Clear 239 6 40.1 Green 176 6 40.0 Values f o r the B.M.R. of r a t s shown i n Table 2b fo r the t h i r d phase of the experiment where the o r i g i n a l f i l t e r s were used, were averaged l i k e i n the previous table These average values are given i n Table 9b. Table 9b - Third Phase No • of Color Weight Determinations B.M.R. Yellow 223 9 41.4 Blue# 179 9 39.5 Black (Fg) 191 6 39.2 Black . 230 9 38.3 V i o l e t 183 6 37.1 Red 265 9 36.4 Orange 177 6 35.8 Clear 215 6 Green 159 6 30.6 From these two tables i t may be seen that the 58. average values of the B.M.R. of the r a t s behind t h e i r respective c o l o r f i l t e r s have maintained t h e i r r e l a t i v e p o s i t i o n s , with the most noticeable exception i n the case of the r a t s behind red and blue f i l t e r s whose B.M.R. values have approximately interchanged. The most obvious different: in^the* two tables i s :the •apparent decrease i n B7M.R.' brought about by the change of co l o r f i l t e r . These decreases are shown i n Table 9c. Table 9c. Black Original Color Blue Black (F2) Violet Oram ;e Clear Bed Green Yellow Decrease in BMR. 1.7 4.7. 5.3 6.3 7.2 7.9 8.4 9.4 11.5 Control animals f o r t h i s experiment are those behind the black f i l t e r due t o the f a c t that the r a t i s n a t u r a l l y a nocturnal animal. From the r e s u l t s i n Table 9a, i t appears evident that the c o l o r s imposed upon the r a t s i n the f i r s t phase of the experiment must have had some l a s t i n g e f f e c t upon t h e i r B.M.R. I f t h i s e f f e c t were not permanent, average values f o r t h e B.M.R. of the r a t s ( o r i g i n a l l y behind yellow, red, v i o l e t , orange, blue, c l e a r and green f l i t e r s ) should have been cl o s e r together i n the second phase as a l l those r a t s were then "behind black f i l t e r s . I t i s i n t e r e s t i n g t o note that i n the second phase the value of the B.M.R. f o r the r a t s o r i g i n a l l y behind black f i l t e r s then behind blue f i l t e r s , i s approximately the average of the B.M.R.*s f o r the other c o l o r s . I t i s d i f f i c u l t to show any r e l a t i o n s h i p between the change of colors i n the three phases due to the lack of information regarding values of the B.M.R. during the f i r s t phase. A decrease i n the B.M.R. has been shown i n changing f i l t e r s from black to the c o l o r s and from blue to black between the second and t h i r d phases. What would have been the e f f e c t upon the B.M.R. of r a t s of the opposite procedure as was the case between the f i r s t and second phase? This i n -formation appears important t o a s o l u t i o n of t h i s problem. One would not be j u s t i f i e d i n assuming the B.M.R. to be the same and f o l l o w the same order f o r the colors i n the f i r s t phase of the experiment as on .the t h i r d phase of the experiment. I t appears most probable that a yellow color has an e l e v a t i n g e f f e c t upon the B.M.R. of rats,, while c l e a r and green c o l o r s have a depressing e f f e c t . Nothing d e f i n i t e may be s a i d regarding the other c o l o r s . I t i s i n t e r e s t i n g t o note i n Table 9b that the value f o r the B.M.R. of r a t s behind a blue f i l t e r i s j u s t s l i g h t l y above that f o r those behind black f i l t e r s . Compare t h i s r a t i o of black to blue values w i t h the r a t i o of average black to blue values of Table 9a. \ 60. Very l i t t l e information may be obtained concerning the e f f e c t o f l i g h t passing through colored cellophane on the B.M.R. of r a t s from the p h y s i c a l properties of the various sheets of cellophane. The cellophane used i n t h i s experiment was manufactured by Canadian Industries Limited, l a c h sheet produces p o l a r i z a t i o n to a small degree. Through the co-operation of Thomas C o l l i n s of the Physics Department, transmission curves f o r a s i n g l e thickness of the various sheets of cellophane were obtained on a medium s i z e d Adam H i l g e r spectrograph. The curves obtained are shown on the accompanying' graph. The graphic method o f determining the B.M.R. of ra t s gives a p i c t o r i a l representation of a c t i v i t y . Using these graphs, an approximate order of the degree of a c t i v i t y may be made. This i s as follows:, yellov/, red and black . (Fg) - a c t i v e ; v i o l e t , c l e a r and black - intermediary; orange, blue and green - f a i r l y i n a c t i v e . From the switch of c o l o r s between the second and t h i r d phases and r e f e r r i n g only to the blue to black and black to blue changes, blue appears to i n h i b i t a c t i v i t y , while the black seems to stimu-l a t e a c t i v i t y s l i g h t l y . For the other c o l o r s , a c t i v i t y appears to be much the same before and a f t e r the change of c o l o r s . For colors other than blue, i t would appear that a c t i v i t y follows the same general order as basal metabolism f o r the c o l o r s . Transmits ion Curves of Cellophane Filters 61. Desiccated Thyroid. In order to show values representing increased basal metabolism i n rats,- s i n g l e doses of Burroughs Welcome Co. desiccated t h y r o i d gland were fed to rats supposedly to increase the B.M.R. When i t became apparent that t h i s product was not i n c r e a s i n g the B.M.R. but was i n i t i a l l y decreasing i t , work was s t a r t e d to show the e f f e c t of the s i z e of dose. Determinations were made to show when the animal's B.M.R. returned to normal. Results are shown i n Tables 4a, 4b and 4c. The e f f e c t of the B.W.-desiccated thyroid gland on the B.M.R. .of r a t s i s seen from the accompanying graphs. Average curves are shown f o r males or females r e c e i v i n g the same amount of desiccated t h y r o i d . Males and females are treated separately. The f i r s t set of graphs shows the i n i t i a l depression of the B.M.R. r e s u l t i n g i n the f i r s t s i x hours a f t e r feeding the desiccated 'thyroid. The second set of graphs shows the va r i a t i o n s ^ i n the B.M.R. f o r three weeks a f t e r feeding the desiccated t h y r o i d . The second set of graphs does not i l l u s t r a t e the i n i t i a l e f f e c t shown i n the f i r s t set o f graphs. For doses of 1/10 and 1/5 g r a i n , the rate of depression o f the B8M*R. shown i n the f i r s t set. of graphs i s greater In the case of the male than the female. As the doses are increased the rate of depression of the B.M.R. 62 . decreases and the amount of depression also decreases. This suggests that a dose of desiccated t h y r o i d l a r g e r than those employed here might increase i n i t i a l l y the B.M.R. of r a t s . Percentages of the maximum amount of decrease i n the B.M.R. i n the f i r s t s i x hours are shown i n Table 10. Table 10 •ggff 3 e x Max. Deoreaii At time i n hours 1/10 a" 51 40 1/5 cf 35 ? 40 4 5 3* 1 / 2 t 17 ( P l U S ) 3, (plus) 3J-The second set o f graphs shows considerable v a r i a -t i o n i n the B.M.R. of r a t s f o r the three weeks a f t e r feeding the desiccated t h y r o i d . S i n g l e doses of 1/10 gr a i n and 1/5 gr a i n did not increase the B.M.R. of male r a t s . F l u c t u a t i o n s below ba s a l occurred. For female r a t s these doses produced instances of increased metabolism. For the 1/10 gr a i n metabolism was increased 2.7% on the t h i r d day and 7.7% on the f i f t h day. F o r the 1/5 g r a i n metabolism was increased between the t h i r d and seventh days, a maximum increase o f 21% occurred on the f i f t h day. A dose of 1/2 g r a i n increased metabolism i n both the male and female. For the male, a maximum increase of 19.9% occurred at the end of the f i r s t day 63. a f t e r which time the B.M.R. varied s l i g h t l y above and below b a s a l . For the female, metabolism decreased during the f i r s t day and then increased to maximum, 10,8% above basal on the t h i r d and f i f t h days. No previous work has shown an i n i t i a l decrease of the B.M.R. on feeding desiccated thy r o i d gland. I t has been suggested that a t i s s u e e f f e c t causes the decrease i n the B.M.R.^' As yet i t i s not c l e a r what causes t h i s decrease. In the f l u c t u a t i o n s observed i n the B.M.R. of rat s as time increases a f t e r feeding the B.W. desiccated t h y r o i d • gland, some other f a c t o r , probably i n the product used, must be i n v o l v e d . Anaesthesia. In order to show values representing decreased bas a l metabolism i n r a t s , sodium pentothal was given to r a t s i n t r a p e r i t o n e a l l y to produce anaesthesia. Table 5 shows values f o r -the B.M.R. of r a t s before the anaesthetic and under the anaesthetic. For both males and females anaesthesia decreased the b a s a l metabolism. The percentage decreases i n the B.M.R. caused by the anaesthetic are shown i n Table 11. iiLl? ' 5\?^ n t2 r G f t h e D e P t - ^ Biochemistry at the Uni- ' v e r s i t y o f A l b e r t a r e f e r r e d to that i n a pri v a t e conversation He has found that the Burroughs Welcome Co. I e s l c c a ? l d thyroSd 4. Table 11 R a t Percentage decrease i n B.M.R. • — . due to Ana est hp t i n °" 46.1 39.7 •9 39.2 41.9 Les, The percentage decrease i n the B.M.R. of rats caused by-anaesthesia was p r a c t i c a l l y the same.for males and female The r e s u l t s shown here are as would be expected. While under an anaesthetic an animal does hot expend energy i n m aintaining i t s senses. The u t i l i z a t i o n of energy i s s u f f i c i e n t only to maintain l i f e . This condition i s sub-b a s a l . 65. S U M M A R Y The b a s a l metabolic rate of white r a t s has been determined by a grap h i c a l method, using a modified form of -an apparatus o r i g i n a l l y designed Dy E.L.Schwabe and F.R. G r i f f i t h , J r . , at the U n i v e r s i t y of B u f f a l o . Four f a c t o r s have been considered as a f f e c t i n g the ba s a l metabolic rate of white r a t s : i . the e f f e c t of unbalancing the d i e t , i . e . feeding high percentages of carbohydrate, f a t or p r o t e i n ; i i . the e f f e c t of v i s i b l e r a d i a t i o n , i«e. using segregated parts of the v i s i b l e spectrum; i i i . the e f f e c t of a s i n g l e dose of desiccated t h y r o i d gland; i v . the e f f e c t of anaesthesia. The basal metabolic rate was found to be s l i g h t l y higher on a high p r o t e i n d i e t than on the c o n t r o l d i e t , but lower on a high carbohydrate diet and on a high f a t d i e t . Values of the B.M.R. have been shown f o r three d i f f e r e n t p r o t e i n s , carbohydrates and f a t s . Colors were found t o a f f e c t the b a s a l metabolic r a t e . Values of the B.M.R. were greatest f o r yellow and lowest f o r green; values f o r yellow were about 33% higher than those f o r green. Values of the B.M.R. fo r the other c o l o r s , t o t a l r a d i a t i o n and no r a d i a t i o n , were between those found f o r y e l l o w and green. Single doses of Burroughs: Welcome Co. desiccated 66. t h y r o i d gland i n i t i a l l y decreased the basal metabolic rate of r a t s . Small doses of 1/10 and 1/5 g r a i n produced l a r g e r depressions than did doses of 1/2 g r a i n . For the smaller doses the rate of depression of the B.M.R. was greater f o r the male than f o r the female. For three weeks f o l l o w i n g the feeding of the desiccated t h y r o i d the B.M.R. of the r a t s was found t o f l u c t u a t e . An i n t r a p e r i t o n e a l i n j e c t i o n of sodium pentothal to produce anaesthesia decreased the basal metabolism of male and female r a t s about 40%. Suggestions f o r f u r t h e r work, (a) R a d i a t i o n . The basal metabolic rate of white r a t s should be determined under the o r i g i n a l influence of c o l o r s . I f s i g -n i f i c a n t d i f f e r e n c e s i n the B.M.R. are found, as might be expected, i t would be w e l l to subjec,t t h i s group of r a t s to co l o r changes as was done i n the present work. Work should be done to show complete values of the B.M.R. of white r a t s behind blue and black f i l t e r s , when these f i l t e r s are interchanged and then when the f i l t e r s are returned to t h e i r o r i g i n a l p o s i t i o n . A c t i v i t y and reproduc-t i o n of the r a t s should be noted through these changes, (b) Desiccated Thyroid and Thyroxin. The e f f e c t of s i n g l e doses, larger than those used i n t h i s work, of Burroughs Welcome Co. desiccated t h y r o i d on 6,7. the B.M.R. of white r a t s should be determined. P a r t i c u l a r a t t e n t i o n should be pa i d to i n i t i a l values, determinations should be continued f o r three weeks. Single graded doses of desiccated t h y r o i d , pre-pared by another company, such as Parke Davis, and of pure th y r o x i n also should be used to show t h e i r e f f e c t on the B.M.R. of r a t s . The same procedures should be followed with these products as was used with the product of the Burroughs Welcome Co. The values of the B.M.R. obtained with these products should be compared w i t h the values ob-tain e d by using the product of the Burroughs Welcome Co. 1. B I B L I O G R A P H Y (1) Anderson, H.H., Chen, M.Y. , and Leake, C.D.^ The e f f e c t of b a r b i t u r i c a c i d hypnotics on basal metabolism i n humans. Jour.Pharmacol, and Exp. Therap. 40(2), 215, 1930. (2) Asher, L. and Tateyoshi, H.^ BeitrMge zur Physiologie der Drusen. Nr.105. Die Wirkung von F l e i s c h auf den r e s p i r a t o r i s c h e n Umsatz der mit F e t t g e f u t t e r t e n Ratten. E i n Be i t r a g zur Physiologie der Leber. Bi o . Chem. Z e i t s c h r . 185, 173, 1927. (3) Ashworth, U.S., Brody, S. and Hogan, A.G.# R e l a t i o n between b a s a l metabolism and body weights i n the growing r a t . Univ. M i s s o u r i , C o l l . A g r i c . A g r i c . Exp. S t a t . Res. B u l l . #166, 177, 1932. (4) Ashworth, UoS. and C o w g i l l , G.R. Body composition as a fac t o r governing the basal heat production and endogenous nitrogen e x c r e t i o n . J . nut. 15, 73, 1938. (5) Atkinson, H.V., Rapport, D. and Lusk, G. Animal Calort-metry. ' J . B i o l . Chem. 53, 155, 1922. (6) Benedict, F.G. A multi-chamber apparatus for r a t s and other small animals. J . Nut. 5, 161, 1930. (7) Benedict, F.Ge and MacLeod, G. The heat production of the albino r a t . I.Technique, A c t i v i t y C o n t r o l , and the influence of f a s t i n g . J. Nut. 1, 343, 1929. 2. (8) Benedict, F. G. and MacLeod, G. The heat production of the albino r a t . 2. I n f l u -ence of enviornmental temperature, age and sex; comparison with the basal metabolism of man. J . Nut, 1, 367, 1929-. (9) Black, A. E f f e c t of p r o t e i n and exercise at d i f f e r e n t ages on the basal metabolism. J . Nut.. 17, 361, 1939. (.10) Blank, H.# Tiergrosse und Stoffwechsel. P f l u g e r s Arch. 234, 310, 1934. (11) Bodansky, M. i n t r o d u c t i o n to P h y s i o l o g i c a l Chemistry. New York: John Wiley & Sons. 1938. (12) Boothby, W.M. and Sandiford, I . Basal metabolism. P h y s i o l . Rev. 4, 69, 1924. (13) Bowen, B.D., G r i f f i t h , F.R. J r . and S l y , T.E. E f f e c t of a high f a t meal on the R.Q. and heat production of normal and obese i n d i v i d u a l s . J . Nut. 8, 421, 1934. (14) Boyer s P.D., Jensen, C.W. and P h i l l i p s , P.H.$ A c t i v i t y of c e r t a i n isomers of t h y r o x i n . Proc. Soc. Exp. B i o l , and Med. 49(2), 171, 1942. (15) Carpenter, T.M. Tables, Factors and Formulas f o r computing respir a -tory exchange and b i o l o g i c a l transformations of energy, Washington, D.C., Carnegie I n s t . 1939. (16) Cooper, W.D. Construction of a b a s a l metabolism apparatus f o r r a t s . Dept, of Chemistry, U n i v e r s i t y of B r i t i s h Columbia. Unpublished t h e s i s , 1941. (17) Daick, S.L. The body surface of the r a t . J . Nut. 5, 289, 1930. (18) Davis, J.E. The e f f e c t of advancing age on the oxygen con-sumption of r a t s . Amer. Jour. P h y s i o l . 119, 28, 1937. (19) Davis, J.E. and Hastings, A.R. The measurement of t h e oxygen consumption of immature r a t s . Amer. Jour. P h y s i o l , 109, 683, 1934. (20) Deuel, H.J., Sandiford, I., Sandiford, K. and Boothby, W.M. A study of nitrogen minimum. J . B i o l . Chem. 76, 391, 1928. (21) Deuel, H.J., Sandiford, I . , Sandiford, K. and Boothby, E f f e c t of t h y r o x i n on the r e s p i r a t o r y and nitrogen metabolism of a normal subject f o l l o w i n g prolonged nitrogen f r e e d i e t . J . B i o l . Chem. 76, 407, 1928. (22) E i c h e l b e r g e r , M. The e f f e c t of l i g h t on cr e a t i n i n e and creatine e x c r e t i o n and b a s a l metabolism. J . B i o l . Chem. 69, 17, 1926. (23) Forbes E.B. S w i f t , R.W. , Black, A. and Kohlenberg,O.J. ihe u t i l i z a t i o n of energy producing nutriment and pro t e i n as a f f e c t e d by i n d i v i d u a l nutriment d e f i c -i e n c i e s . J . Nut. 10, 461, 1935. (24) Poster, G.L. and Sundstroem E< A r e s p i r a t i o n apparatus f o r small animals. J . B i o l . Chem. 65, 565, 1926. 4. (25) Fujimoto, K.# Uber den S i n f l u s s der Nahrung auf den Grundumsatz der weissen Ratten. 1. Fleischnahrung und Kohle-hydratnahrung. M i t t e i l . med. Akad. K i s t o . 9, 997, 1933. (26) Haldane, J.B.S.# A new form of apparatus for measuring r e s p i r a t o r y exchange of animals. J. P h y s i o l . 13, 419, 1892. (27) H a r r i s , D.T. Studies on the b i o l o g i c a l a c t i o n of l i g h t . Proc. Roy. Soc. London. Ser. B, 98, 171, 1925. (28) Herrington, L.P. The heat r e g u l a t i o n of small laboratory animals at v a rious environmental temperatures* Amer. Jour. P h y s i o l , 129, 129, 1940. (29) Horst, K., Mendel, L.B. and Benedict, F.G. The metabolism of the Albino Rat during prolonged f a s t i n g at two d i f f e r e n t environmental temperatures J. Nut. 3, 177, 1930. (30) Horst, K., Mendel, L.B. and Benedict, F.G. The e f f e c t s of some e x t e r n a l f a c t o r s upon the ba s a l metabolism of the r a t . J . Nut. 7, 277, 1934. (31) Horst, K., Mendel, L.B. and Benedict, F.G. The i n f l u e n c e of previous d i e t , growth and age upon the metabolism of the r a t . J . Nut. 8, 139, 1934. (32) Kestner, 0.# Uber die Oberfl a c h e n r e g i l des Stoffwechsels. P f l u g e r s Arch. 234, 290, 1934. (33) Kestner, 0., Johnson, C.E. and Laubmann, W.# Stoffwechsel und Sonnenstrahlung. Strahlentherapie 41 (1), 174, 1931. (34) Krantz, J . c . J r . , and Carr, C.J". A s t a t i s t i c a l study of the metabolism of the f a s t i n g albino r a t . J . Nut. 9, 363, 1933. (35) Kunde, M.M. Studies on metabolism. Amer. Jour. P h y s i o l . 82, 195, 1927. (36) Lee, M.O. Basal metabolism i n the r a t during the oestrous c y c l e . Amer. Jour. P h y s i o l . 81, 492, 1927. (37) Lewis, H.G. and Luck, J.M. An apparatus f o r automatically measuring the r e s p i r a t o r y exchange of small animals. J. B i o l . Chem. 103, 209, 1933. (38) Lippmann, A. and Volker, . Beitrfige zur Frage der Stoffwechselbeeinflussung durch U l t r a v i o l e t t b e s t r a h l u n g . K l i n . Wochenschr. 7 (5), 213, 1928. (39) Meyer. A.E. and Werts, A.# The c a l o r i g e n i e e f f i c i e n c y of t h y r o i d m a t e r i a l i n r e l a t i o n to t h y r o x i n and iodine content. Endocrinology. 24, 683, 1939. (40) M i t c h e l l , E.H. The s i g n i f i c a n c e of surface area determinations. J . Nut. 2, 437, 1930. (41) Poulton, E.P.# Carbon dioxide as a measure of standard metabolism. Acta, med, scand. 96, suppl. 90, 323, 1938. (42) Richardson, H.B. The r e s p i r a t o r y quotient. P h y s i o l . Rev. 9, 61, 1929. 6. (43) Rubner, M.# Die gesetze des energieverbrauchs bei der ernahrune. L e i p z i g und Wien. F. Deuticke, 1902. (44) Sandlford, I . , Wheeler, T., and Boothby, W.M. Metabolic studies during pregnancy and menstruation. Amer. Jour. P h y s i o l . 96, 191, 1932. (45) Schwabe, E.L. and G r i f f i t h , F.R. J r . An e a s i l y constructed r a t metabolism apparatus which automatically records oxygen consumption and animal a c t i v i t y . J . Nut. 15, 187, 1938. (46) Schwabe, E.L., Emery, F.E. and G r i f f i t h , F.R. J r . The e f f e c t of prolonged exposure to low tempera-ture on the basal metabolism of the r a t . J . Nut. 15, 199, 1938. (47) Sherwood, T.C. The r e l a t i o n of season, sex and weight to the basal metabolism of the alb i n o r a t . J. Nut. 12, 223, 1936. (48) Sos , J.# „ Trennung der zentralnervosen und der peripheren Thyroxinwirkungen. Arch. Exp. Path. u. Pharmakol. 192 (1), 179, 1939. (49) S w i f t , R.W. and Forbes, R.M. The heat production of the f a s t i n g r a t i n r e l a t i o n to the environmental temperature. J. Nut. 18, 307, 1939. (50) Thompson, W.O., Thompson, P.g., Taylor, S.G. , Olper, J.M. and D i c k i e , L.F.N.# The e f f e c t s of various compounds of thy r o x i n on bas a l metabolism. Endocrinology. 18, 238, 1934. (51) Trugg, J . Methods f o r determination of carbon dioxide and a new form of absorptive tower adapted to the t i t r o m e t r i c method. J. Ind. and Eng. Chem. 7, 1045, 1915. (52) Wang, C.C, Hawks, J.E. , Huddleston, B. , Wood, A.A. and Smith, E.A. The influence of high and low p r o t e i n d i e t on the bas a l metabolism and chemistry of blood and urine i n normal women. J . Nut. 3, 79, 1930. NOTE: ? ^ ^ C e \ m ! r k e d w i t h a n "#n were obtained irom the abstracts. 

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