METABOLISM WITH FOOD RICH IN PROTEINS. 907 



In the first case (1) the metabolism of meat before the beginning of 

 the actual experiment on feeding with 500 grams of meat was 447 grams, 

 and it increased considerably on the first day of the experiment, after 

 feeding with 1500 grams of meat. In the second case (2), in which the 

 animal was previously in nitrogenous equilibrium with 1500 grams of 

 meat, the metabolism of flesh on the first day of the experiment, with 

 only 1000 grams meat, decreased considerably, and on the fifth day an 

 almost nitrogenous 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 nitrogenous 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 l 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. HAMALAINEN 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 pro- 

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

 posed it follows that 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, that there may even take place a formation of fat under 

 these circumstances. The objections presented by PFLUGER to these 



1 Deutsch. Arch. f. klin. Med., 86. 



2 Skand. Arch. f. Physiol., 19. 



