SUPPORTS RESPIRATION. 67 



The carbon of the carbonic acid given off, with 

 that of the urine ; the nitrogen of the urine, and the 

 hydrogen 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 ex- 

 actly 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 in- 

 creases from day to day by an appreciable quantity. 



This fact presupposes, that the assimilative pro- 

 cess in the young animal is more energetic, more 

 intense, than the process of transformation in the 

 existing tissues. Tf both processes were equally ac- 

 tive, 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 res- 

 pirations are more frequent; and, for equal bulks, the 

 consumption of oxygen must be greater rather than 

 smaller in the young than in the adult animal. 

 But, since the metamorphosis of organised parts 

 goes on more slowly, there would ensue a deficiency 

 of those substances, the carbon and hydrogen of 

 which are adapted for combination with Oxygen ; 

 because, in the carnivora it is the new compounds, 

 F 2 



