ORIGIN OF ANIMAL PRINCIPLES. 375 



CHAPTER VIII. 



OF THE FEEDING OF THE ANIMALS BELONGING TO A FARM ; 

 AND OF THE IMMEDIATE PRINCIPLES OF ANIMAL ORIGIN. 



^ 1. ORIGIN OF ANIMAL PRINCIPLES. 



It is now generally admitted that the food of animals must ne- 

 cessarily contain azote ; and this circumstance has led to the infer- 

 ence, that the herbivorous tribes obtain from their food the azote 

 which enters into the constitution of their bodies. 



In a general way, the individual consuming a certain portion of 

 food every day, nevertheless does not increase in his average 

 weight. This is what occurs with animals upon the quantity of 

 food which is known to be sufficient for their keep ; and it has been 

 found that the human subject, living very regularly, returns at a cer- 

 tain hour, or at certain hours of the day, to a certain mean weight. 

 Grooms, farm servants, &c.. are perfectly well aware of the fact, 

 that with a certain allowance of hay and corn, a horse will be kept 

 in the condition necessary to do the work required of him without 

 either gaining or losing in flesh. 



Under such circumstances, the whole of the elementary matter 

 contained in the food consumed, ought to be found in the dejections, 

 the excretions, and the products of the act of respiration. And as- 

 suming that this is so, it might then be maintained that none of the 

 elements is assimilated, assimilation being taken in the sense of an 

 addition of principles introduced with the food to the principles al- 

 ready present in the body. Yet is there unquesti(jnably assimila- 

 tion, in the sense that the alimentary matters of the food become 

 fixed in the system, having there undergone modification or change ; 

 and that they replace, or come instead of other elements of the 

 same kind, which are daily thrown off by tiie vital acts of the 

 economy. 



During the nutrition of a young animal, and also in the process 

 of fattening an adult, things go on differently ; here there is unques- 

 tionably definitive fixation of a portion of the matter contained in the 

 food : there is no longer balance between the waste and the supply ; 

 an animal then increases in weight notably and rapidly. 



Looking at the question of feeding in the most general way, then, 

 I admit that an adult animal, upon the daily allowance, voids a 

 quantity of matter in its various excretions precisely equal to the 

 quantity which it receives in its food :* all the elements, the same 

 in nature and in quantity, which are contained in the food, are also 

 contained in the excrements, vapors, and gases, which pass off from 

 the living body ; carbon and azote, hydrogen and oxygen, phospho. 



* Boussingault, Annates do Chiniie, 2e s^rie, t. Ixxxi, j). 113» 



