FOOD AND DIGESTION 375 



fat and the earthy soaps of the fatty acids, and, when a 

 vegetable diet is taken, the cellulose of the vegetable cells, 

 and frequently starch. The cellulose, by stimulating the 

 intestine, is a valuable natural purgative. 



The odour is due to the presence of aromatic bodies such 

 as indol and skatol. 



Meeonium is the name given to the first faeces passed by the 

 child after birth. It is greenish-black in colour, and consists 

 of inspissated bile and shed epithelium from the intestine. 



Movements of the Intestine 



These are of two kinds myogenie and peristaltic. The 

 myogenic movements are slight rhythmic contractions which 

 pass rapidly along the intestine, and are insufficient to drive 

 on the contents, but are probably of use in churning and 

 mixing them. By feeding with food mixed with bismuth, and 

 employing X-rays, Cannon finds that the contents of the 

 small intestine get broken up into small segments. This is 

 possibly due to these myogenic movements (fig. 157, p. 356). 

 These movements occur when all the nerves have been divided, 

 and when the ganglia in the intestinal walls have been poisoned 

 with nicotine, and they are therefore due to the muscle fibres 

 alone. 



The peristaltic movements are much more complex and 

 powerful. They consist of a constriction of the muscles, which 

 seems to be excited by the passage of the food, and may be 

 caused by inserting a bolus of cotton-wool covered with 

 vaseline. Starting at the upper end of the intestine, they 

 pass slowly downwards. In front of the contraction the 

 muscular fibres are relaxed, and thus the contracting part 

 drives its contents into the relaxed part below. These 

 peristaltic movements go on after the nerves to the gut are 

 cut, but they are stopped when the ganglia in the wall of the 

 intestine are poisoned with nicotine. It has therefore been 

 concluded that the nerve ganglia in the intestinal wall form 

 a local reflex mechanism, which is stimulated by the presence 

 of foreign matter in the intestine, and which brings about 

 the co-ordinated contraction and relaxation, which together 

 constitute a true peristalsis. 



