682 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



while a part of the carbon remains behind to be stored up as fat. Con- 

 sequently, the body may be kept stationary as regards its store of albumen 

 and fat through the administration of meat alone, but then a large 

 quantity is required. An increase in tissue-fat and albumen may also, 

 to a slight degree, take place from the administration of albumen alone, 

 but only in illy-nourished individuals. 



If peptone is given as food it is entirely destroyed, and the destruc- 

 tion of the tissue-albumen is completely prevented ; but there is no 

 increase in the body albumen, thus showing that peptone is earlier 

 destroyed than albumen and can onl}' partially replace the albumen of 

 the food. 



If gelatin and gelatinous tissue (bones, tendons, etc.) are given 

 exclusively the destruction of albumen does not cease, thus showing 

 that gelatin cannot replace albumen. But if gelatin and albumen are 

 given together the destruction of albumen is greatly reduced. 



(b) Feeding with Fat. — The influence of fat on the destruction of 

 albumen is seen in the fact that in fasting animals the destruction of 

 albumen is less in fat than in thin animals ; this action is also seen in the 

 administration of proteid foods alone, where the destruction of albumen 

 is less in fat than in thin animals. Indeed, we have seen that in an 

 abundant albuminous diet, whereby the excretion of urea is increased, in 

 fat animals there may even be an increase in the body fat. 



If fat is given alone as food to a carnivorous animal the destruction 

 of albumen is reduced but not prevented ; when large amounts of fat are 

 given the fat of the bod} - may even increase and yet the animals pass 

 into a- state of starvation, for the tissue-albumen is gradually being 

 reduced. 



If enough albumen is given to cause a nitrogenous balance and then 

 fat is added to the food, the nitrogenous elimination is reduced and all 

 the carbon of the fat does not appear in the C0 2 ; carbon is, therefore, 

 kept back in the body and stored up in the form of fat, while a certain 

 amount of nitrogen also being retained indicates an increase of the 

 body albumen. So, the addition of fat to the food leads to both an 

 increase of tissue-fat and albumen, though this only occurs when a large 

 amount of fat is added to a moderately small amount of albumen. 



If the amount of albumen is increased the elimination of urea also 

 increases, and, as a consequence of the great destruction of albumen, a 

 certain amount of the fat is spared and is stored up in the body. But 

 if the amount of albumen is reduced more fat is used up, and fat may 

 even* be taken away from the bod}'. 



The amount of fat in the body in feeding with albumen and fat is 

 also of influence on the metabolism of the body ; a body poor in fat, 

 which needs and destroys more albumen, more readily stores up fat; 



