EXCLUSIVE PROTEIN FEEDING. 849 



nitrogeneous equilibrium was obtained. During this time the animal 

 gave up daily some of its own proteins. Between that point below 

 which the animal loses from its own weight and the maximum, which 

 seems to be dependent upon the digestive and assimilative capacity of 

 the intestinal canal, a carnivore may be kept in nitrogeneous equilibrium 

 with varying quantities of proteins in the food. 



The supply of proteins, as well as the protein condition of the body, 

 affects the extent of the protein metabolism. A body which has become 

 rich in proteins by a previous abundant meat diet must, to prevent a loss 

 of proteins, take up more protein with the food than a body poor in pro- 

 teins. 



In regard to the rapidity with which the protein catabolism takes 

 place FALTA 1 found in man but not, or at least not to the same extent, 

 in dogs, that quite great differences exist between the different proteins. 

 Thus on feeding pure proteins the chief amount of the nitrogen is more 

 quickly eliminated after feeding casein than after genuine ovalbumin. 

 This latter is more easily demolished after a previous modification by 

 coagulation than in the native state, which indicates that an unequal 

 resistance of the different proteins toward the digestive juices plays a 

 part. HAMALAINEX and HELME 2 have also obtained similar results. 

 Even on feeding with easily decomposable proteins it always takes several 

 days before the total nitrogen corresponding thereto is eliminated, which 

 depends, according to FALTA, upon a progressive demolition of the protein. 

 From the unequal .rate at which the different proteins are decom- 

 posed it follows chat in the passage from a diet poor in protein to one 

 rich in protein the time within which nitrogenous equilibrium occurs 

 depends chiefly upon the kind of protein contained in the food. 



PETTENKOFER and VOIT have made investigations on the metabolism 

 of fat with an exclusively protein diet. These investigations have shown 

 that by increasing the quantity of proteins in the food the daily metab- 

 olism of fat decreases, and they have drawn the conclusion from these 

 experiments, as detailed in Chapter X, that there may even take place a 

 formation of fat under these circumstances. The objections presented by 

 PFLUGER to these experiments, as well as the proofs of the formation of 

 fat from proteins, are also given in the above-mentioned chapter. 



According to PFLUGER'S doctrine, the protein can influence the forma- 

 tion of fat only in an indirect way, namely, in that it is consumed instead 

 -of the non-nitrogeneous bodies and hence the fat and fat-forming carbo- 

 hydrates are spared. If sufficient protein is introduced with the food 

 to satisfy the total nutritive requirements, then the decomposition of 

 fat stops; and if non-nitrogenous food is taken at the same time, this is 



1 Deutsch. Arch. f. kiln. Med., 86. ' Skand. Arch. f. Physiol., 19. 



