DOMESTIC MAMMAL ADAPTATIONS 



much energy with the bulky diet as with the other. This is in line 

 with Jean Mayer's* idea of the regulation of the food intake, which 

 is a hemostatic principle. It may have been slightly premature to 

 suggest in my scheme of 1926** that these two regulators of food 

 intake, namely the hemostatic principle (which is affected by con- 

 centrations of material in the blood stream) and the thermostatic 

 principle, proposed by Brobeck according to which food intake is 

 affected by the possibility of getting rid of heat.*** 



EAGAN; Limitation in oxidative capacity is not the only factor, 

 for in rabbits which are moved to a cold (5 C) environment, food 

 intake will oftenbeless than normal for the first week or so, where- 

 as a 50% to 100% increase would be required if body weight were to 

 be maintained. It can hardly be thought that oxidative capacity is 

 reduced when the animal is moved into the cold. An explanation 

 must be sought for its change in behavior — a failure to eat suffi- 

 ciently even though food is continuously available. This must repre- 

 sent an effect of cold stress upon the organism as a whole. 



HANNON: I think this is possible in some animals, anyway. I 

 do not think it appears in rats. 



VAUGHAN: Rats will increase their food intake within a couple 

 of days after you put them in the cold — the delay is probably par- 

 tially due to the shock of putting them into the cold environment, 

 but it is also probably due to just moving them into different sur- 

 roundings. If they are accustomed to a certain diet, we have found, 

 especially with synthetic diets, that they will increase their food 

 intake very rapidly in the cold within a few days, e. g., up to 50% 

 over their normal rate of intake. 



*Mayer, J. 1953. Genetic traumatic and environmental factors in the etiology 

 of obesity. Physiol. Rev. 33:472-508. 



**Kleiber, M. 1926. Problems involved in breeding for efficiency of food utiliza- 

 tion. Amer. Soc. Animal Prod. Proceed, pp 249. 



***Kleiber, M. 1961. The Fire of Life. An Introduction to Animal Energetics. New 

 York, Wiley and Sons, Inc. pp 282 ff. 



***Brobeck, J. R. 1946. Regulation of Energy Exchange. Howell's Textbook of 

 Physiology. (J. F. Fulton, ed.) Philadelphia, Saunders. 



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