852 PHYSIOLOGY 



and its products of decomposition, dyslysin, and coprosterin, a 

 body allied to cholesterin, and a certain amount of purine bases 

 consisting of guanine, adenine, xanthine, and hypoxanthine. On 

 the average the faeces contain about 0-11 grm. of purine bases per 

 diem, about seven times as much as is contained in the urine passed 

 in the same time. The material basis of the faeces seems to be largely 

 desquamated epithelial cells from the intestinal wall, and bacteria, 

 of which countless numbers, chiefly dead, are present. It has been 

 reckoned that as much as 50 per cent, of the faeces may consist of 

 the dead bodies of bacteria. 



Very different is the composition of faeces if the food contains 

 a large amount of cellulose. Not only does the ingested cellulose 

 pass unchanged into the faeces, but large quantities of other substances 

 enclosed in the cellulose walls may also escape digestion and absorp- 

 tion. Moreover the increased bulk of the undigested residue stimu- 

 lates peristalsis, and thus quickens the passage of the food through 

 the gut to such an extent that the digestive ferments have not time 

 to exert their full action on the digestible constituents of the food. 

 The influence of the character of the food is well illustrated by a 

 comparison of the amount and composition of the faeces on different 

 kinds of bread (Rubner) : 



The following Table is also instructive. In this Table Rubner 

 calculates the amount of faeces which a man would pass in twenty- 

 four hours if he satisfied his energy requirements at the expense 

 of one only of the different kinds of food enumerated. The numbers 

 refer to the amount of organic material which would be excreted 

 in the faeces : 



Meat . 

 Eggs . 

 Macaroni 

 Wheaten bread 

 Milk 



26 grm. Rice . ... 50 grm. 



26 Maize . . .51 



27 Turnips . . .101 

 36 Potatoes . . . 133 

 42 Coarse brown bread 146 



The indigestible cellulose in the food is not without value. It 

 has been shown previously that the peristaltic contractions of the 

 intestine are roused primarily by the mechanical stimulus of dis- 

 tension. If the food is capable of entire digestion and absorption 



