EXCHANGE OF MATERIAL. 455 



been fed on large quantities of meat is suddenly fed with a small 

 quantity of meat per day, then the animal gives up its own bodily 

 proteids, the amount decreasing from day to day. The elimination 

 of nitrogen and the metabolism of proteids decrease constantly, and 

 the animal may in this case also pass into nitrogenous equilibrium 

 or nearly into this condition. These conditions are illustrated by 

 the following table (Vorr) : 



TABLE IV. 



Grms. of Flesh in the Food per Day. 



Before the Test. During the Test' 



1 500 1500 



2. . ... 1500 1000 



Grms. of Flesh metabolized in Body per Day. 



'1 2 3 ~4~~ 5 6 T" 



1222 1310 1390 1410 1440 1450 1500 

 1153 1086 1088 1080 1027 



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

 of the actual experiment on feeding with 500 grms. meat was 447 

 grms., and it increased considerably on the first day of the experi- 

 ment, after feeding on 1500 grms. meat. In the second case (2),. 

 in which the animal was previously in nitrogenous equilibrium 

 with 1500 grms. meat, the metabolism of flesh on the first day of 

 the experiment, with only 1000 grms. meat, decreased considerably, 

 and on the fifth day a nearly nitrogenous equilibrium was obtained. 

 During this time the animal gave up daily some of its own proteids. 

 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, car- 

 nivora may be kept in a nitrogenous equilibrium with a varying 

 quantity of proteids in the food. 



The supply of proteids, as well as the condition of the body, 

 affects the extent of the proteid metabolism. A body which has 

 become rich in proteids by a previous abundant meat diet must, to 

 prevent a loss of proteids, take up more proteid with the food than 

 a body poor in proteids. The quantity of fat in the body also has 

 a great influence. As the fat of the body lowers the disintegration 



