THE LARGE INTESTINE 103 



most foods goes to waste. The principal indigestible com- 

 ponent is the cellulose of vegetable tissues. When it is 

 abundant, as in a diet containing coarse, woody matter, 

 such as is eaten by the rabbit, the feces are given an im- 

 mense bulk. The same result is secured in a measure 

 when man adopts a ration in which fruits and vegetables 

 enter freely. Much cellulose is an impediment to com- 

 plete digestion and absorption of the proteins and carbo- 

 hydrates which it envelops, but the foods in which it 

 occurs are cheap and the waste involved does not open 

 an economic question of moment. Some bacterial decom- 

 position of cellulose is said to take place in the colon and 

 may be of slight advantage to us, not that we profit by the 

 products of such fermentation, but that a freer exposure 

 of proteins and starch may be insured. 



Most writers have held that a moderate amount of in- 

 digestible material is a desirable feature of the diet. This 

 teaching was emphasized by the celebrated Sylvester 

 Graham early in the last century. Lowell has referred to 

 him as an "apostle of bran." Later authorities have not 

 recommended such wholesale loading of the tract with 

 husks and fibers, but an admixture of such elements has 

 been generally advocated. The favorable effects include 

 the well-recognized stimulation of peristalsis and probably 

 a better distribution of food along the canal. The indi- 

 gestible fraction of the food has been spoken of as ballast 

 and also by the expressive name of "roughage." 



Under abnormal circumstances the loss of valuable food 

 through the stools may become extensive. This will be 

 the case when absorption is interfered with either by an 

 acceleration of peristalsis or in other ways. Different 

 cathartics bring this about in a varying manner, some by 

 hastening the rate of propulsion, and others, especially the 

 salines, giving the intestinal contents a concentration and 

 a chemical character which forbids absorption. A mild 

 disturbance of this nature is more apt to result in a waste 

 of fats and fatty acids than of other forms of food. 



Rectal Feeding. While the large intestine of man is not 



