ABSORPTION 363 



An idea of the average amount of water present is shown 

 in the following table given by Gamgee : — 



Approximate percentage Composition of the Fceces. 



100 100 100 100 



When first passed freces usually float in water owing to 

 the amount of gas contained in them. They are nearly 

 always acid in reaction from the presence of organic acids. 



As in carnivora fseces consist of material derived from 

 two sources — (1) food residues ; and (2) excretions by way of 

 the intestines. 



Food Residues. — These consist of indiscestible material such 

 as lignin and waxes, which pass through the gut unchanged, 

 and also of material that has escaped digestion either because 

 as in the case of cellulose digestion is difiicult, and only part 

 is dealt with, or because it is protected by an envelope that 

 is not dissolved by the digestive juices. This part consists 

 chiefly of the constituents of the crude fibre of the diet. 



Excretions. — These consist of the same material as in the 

 case of carnivora. Inorganic matter, e.g. calcium, magnesium, 

 iron, and phosphates are, however, excreted by the bowel to a 

 much greater extent than in carnivora. 



Meconium is the name given to the first fseces passed 

 by the young after birth. It is greenish-black in colour, 

 and consists of inspissated bile and shed epithelium from 

 the intestine. 



Availability of Food-Stuffs. 

 Only that part of the food which is digested and absorbed 

 is available as a source of either enersry or material to the 

 animal. In carnivora the indigestible residue is very small. 

 In herbivora, however, a very large proportion of the food is 

 not digested. In comparing the value of different food- 

 stuffs, therefore, it is necessary to know what proportion is 

 available. 



