INTESTINAL DIGESTION 211 



be relaxed and the rectum emptied by its own contrac- 

 tions reinforced by the voluntary application of pressure 

 to the abdomen. When this is in progress there may 

 be a transference of more fecal matter from the region 

 of the spleen through the sigmoid to the rectum and this 

 second portion may be evacuated after the original mass. 



The Feces. The waste in the lower bowel is often 

 thought of as a residue from the diet. It may be so in 

 part but when the health is good and the food digestible 

 it consists more largely of secretions. The absorption 

 of food is usually very nearly as good as it can possibly 

 be. Not more than 10 per cent. often not more than 

 5 per cent. of the ration, so far as it has theoretic value, 

 is allowed to escape. It is otherwise, of course, when 

 there is diarrhea. 



Anything which is entirely indigestible must naturally 

 be included in the feces. The most important substance 

 which has this character is cellulose, the material which 

 is found in the walls of plant cells. Fruits and coarse 

 vegetables furnish it in large amounts. The digestive 

 juices do not appear to attack it; the bacteria of the 

 intestine may decompose it to some extent. Its possible 

 solution is probably of no moment to us so far as the 

 cellulose itself is concerned, but it may be indirectly 

 important since the removal of the envelopes from plant 

 cells may expose the proteins and starch to the action 

 of the juices. 



Cellulose is a type of what some writers have called 

 " roughage." It is taught by most authorities that a 

 moderate amount of indigestible matter in the diet is 

 wholesome. It is supposed to stimulate the lining of 

 the canal by its contact and to promote peristalsis. 

 It may be considered to act like the sawdust which the 

 janitor throws upon the floor before sweeping. As the 

 roughage is pushed along the tube it gathers up and 

 takes with it the less bulky but more deleterious wastes. 

 The action might be described as a scouring. 



The feces contain enormous numbers of bacteria, 



