SUPPORTS RESPIRATION. 65 



containing much carbon and no nitrogen in the food of 

 the young of the carnivora, and in that of the gramini- 

 vora, is resolved in a strikingly simple manner. 



XII. It cannot be disputed, that in an adult carnivor- 

 ous animal, which neither gains nor loses weight, per- 

 ceptibly, from day to day, its nourishment, the waste of 

 organized tissue, and its consumption of oxygen, stand 

 to each other in a well-defined and fixed relation. 



The carbon of the carbonic acid given off, with that 

 of the urine ; the nitrogen of the urine, and the hydro- 

 gen given off as ammonia and water ; these elements, 

 taken together, must be exactly equal in weight to the 

 carbon, nitrogen, and hydrogen of the metamorphosed 

 tissues, and since these last are exactly replaced by the 

 food, to the carbon, nitrogen, and hydrogen of the food. 

 Were this not the case, the weight of the animal could 

 not possibly remain unchanged. 



But, in the young of the carnivora, the weight does 

 not remain unchanged ; on the contrary, it increases 

 from day to day by an appreciable quantity. 



This fact presupposes, that the assimilative process 

 in the young animal is more energetic, more intense, 

 than the process of transformation in the existing tissues. 

 If both processes were equally active, the weight of 

 the. body could not increase ; and were the waste by 

 transformation greater, the weight of the body would 

 decrease. 



Now, the circulation in the young animal is not 

 weaker, but, on the contrary, more rapid ; the respira- 

 6* 



