COMPOSITION OF F^CES. 447 



with about 4.6 kilos of solids ; dogs, when fed on a purely meat diet, 

 only every two to four days, and only a few grammes in amount. The 

 consistency, as mentioned before, depends upon the amount of water con- 

 tained in them, and is naturally governed by the activity of secretion, of 

 absorption,. and the amount of water drunk. Thus, in man they contain, 

 on an average, 31 per cent, of water ; in the hog, 75 per cent. ; in the sheep, 

 5t> per cent. ; in the horse, 77 per cent, and in the ox, 70 to 80 per cent. 



The reaction of the faeces may be either alkaline, neutral, or acid, 

 depending upon the character of the fermentations occurring in the con- 

 tents of the large intestine. Thus, when alkaline, as is usually the case 

 in abundant albuminous diet, the reaction is due to ammoniacal fermen- 

 tation, while an acid reaction is usually due to the fermentation occurring 

 in the carbohydrate constituents of the food. 



The faeces are composed of excrementitious substances no longer of 

 use to the economy and which must be eliminated. They contain indi- 

 gestible matters, such as chlorophyll granules, gums, resin, wax, animal 

 and vegetable elastic tissue, cellulose, hulls of seeds, and epithelial cells. 

 Lactic acid, butyric acid, and various gases, such as hydrogen, oxygen, 

 carbonic acid, and carburetted hydrogen, are present, while in addition 

 various salts are found in large amounts, of which the ammonio-phosphate 

 of magnesium is usually in excess. As putrefactive products, leucin, 

 ty rosin, indol, and finally skatol and the volatile aromatic acids, such as 

 valerianic and caproic acids, are met with, while cholesterin and the 

 bile coloring-matters and glycochol are also found, taurocholic acid being 

 again absorbed. 



The contents of the large intestine are alwa3*s in a more or less 

 marked degree of putrefaction, which, however, though hindered, is not 

 entirely prevented by the bile. 



In carnivora fed on bones, the faeces are dense and gray from the 

 presence of lime salts. Silicious salts constitute a large percentage 

 of the excrement of the lower animals ; thus, in the horse and ox they 

 amount to from 2J to 3 per cent.; in the sheep, to 6 per cent.; while in 

 the hog as much as 8 per cent, of silicious salts are present. These 

 salts are products derived from the matters taken into the alimentary 

 canal of inorganic nature, and from the inorganic matter of the hulls of 

 the cereals. A small amount of soluble salts are present. 



The following table gives the percentage of salts found in the faeces 

 of different animals. The percentage will, of course, vary according to 

 the nature of the food. It may, as a rule, be said that in the faeces of the 

 dog about 20 per cent, of inorganic matter is present when on a pure meat 

 diet, and 24 per cent, on a mixed diet ; in that of the herbivora 58 per 

 cent, is inorganic, though the faeces of the sucking calf will contain only 

 2.6 per cent, of the inorganic matter contained in the food. According 



