LIQUID PARTS OF ANIMALS. 



CHAPTER XXIV. 



OF FECES. 



THE excrementitious matter of animals, evacuated per anum, 

 consists of all that part of the food which cannot be employed for 

 the purposes of nutrition, considerably altered, at least in part, 

 and mixed or united with various bodies employed during diges- 

 tion to separate the useless parts of the food from the nutritious. 

 An accurate examination of these matters has long been wished 

 for by physiologists, as likely to throw much new light on the 

 process of digestion. For if we knew accurately the substances 

 which were taken into the body as food, and all the new substan- 

 ces which were formed by digestion ; that is to say, the compo- 

 nent parts of chyle and of excrement, and the variation which 

 different kinds of food produce in the excrement, it would be a 

 very considerable step towards ascertaining precisely the changes 

 produced on food by digestion. 



Some of the older chemists had turned their attention to the 

 excrements of animals ;* but no discovery of importance reward- 

 ed them for their disagreeable labour. Vauquelin has ascertain- 

 ed some curious facts respecting the excrementitious matter of 

 fowls. In the summer of 1806, a laborious set of experiments 

 on human feces was published by Berzelius, undertaken, as he 

 informs us, chiefly with a view to elucidate the function of diges- 

 tion.f About two years before, Thaer and Einhof had publish- 

 ed a similar set of experiments on the excrements of cattle ; made 

 chiefly to discover, if possible, how they act so powerfully as ma- 

 nure.:): I shall in this chapter give a view of the results obtained 

 by these different chemists. 



I. The appearance of human feces requires no particular de- 

 tail. Their colour is supposed to depend upon the bile mixed 

 with the food^in the alimentary canal. When too light, it is 

 supposed to denote a deficiency of bile ; when too dark, there is 

 supposed to be a redundancy of that secretion. The smell is 

 fetid and peculiar, which after some time gradually changes in- 



* Van Helmont's Gustos Errans, Sect. vi. Opera Helmont, p. 14" Neu- 

 mann's Works, p. 585. 



t Gehlen's Jour. vi. 509. J Ibid. iii. 276. 



