MOVEMENTS OF THE INTESTINE. 333 



rid of on exciting vomiting by the subcutaneous injection of apomorphin. As the diaphragm 

 contracts vigorously during vomiting, it compresses the liver, and thus bile is expelled into the 

 duodenum, or the passage of a small calculus along the bile-duct may be aided. They also are 

 useful in removing mucus or false membranes from the respiratory passages.] 



[Anti-Emetics. Vomiting may be allayed by local anti-emetics such as ice, and many chemical 

 substances such as bismuth, hydrocyanic acid, opium, and morphia, as well as by general 

 remedies which act on the vomiting centre. Some of the foregoing drugs perhaps act both 

 locally and generally.] 



Vomiting is analogous to the process of rumination in animals that chew the cud ( 187). 

 Some persons can empty their stomach in this way. 



159. MOVEMENTS OF THE INTESTINE. Peristalsis. The best example 

 of peristaltic movements is afforded by the small intestine ; the progressive 

 narrowing of the tube proceeds from above downwards, thus propelling the 

 contents before it. Frequently after death, or when air acts freely upon the gut, 

 the peristalsis develops at various parts of the intestine simultaneously, whereby 

 the loops of intestine present the appearance of a heap of worms creeping amongst 

 each other. The advance of new intestinal contents again increases the movement. 

 In the large intestine, the movements are more sluggish and less extensive. The 

 peristaltic movements may be seen and felt when the abdominal walls are very 

 thin, and also in hernial sacs. They are more lively in vegetable feeders than in 

 carnivora. The peristalsis is perhaps conducted directly through the muscular 

 substance itself, as in the heart and ureter. The movements of the stomach and 

 intestine cease during sleep (Busch). 



[Rate of Motion. In a Thiry-Velly fistula ( 183, IT.) Fubini estimated the rate of motion of 

 a smooth sphere of sealing-wax. It took 55 sec. to travel 1 ctm. [f in.] ; an induction-current 

 greatly increases the motion, to 1 ctm. in 10 seconds ; NaCl does not affect it, but excites 

 secretion ; laudanum paralyses it.] 



Method of Observation. Open the abdomen of an animal under a *6 per cent, saline solution 

 to prevent the exposure of the gut to air (Sanders and Braam-Houckgeest). 



The ileo-colic valve, as a rule, prevents the contents of the large intestine from 

 passing backwards into the small intestine. 



When fluid is slowly introduced into the rectum through a tube, it passes upwards into the 

 intestine, and even goes through the ileo-colic valve into the small intestine. Muscarin excites 

 very lively peristalsis of the intestines, which may be set aside by atropin (Schmiedeberg and 

 Koppe). 



Pathological. "When any condition excites an acute inflammation of the intestinal mucous 

 membrane, catarrh is rapidly produced, and very strong contractions of the inflamed parts filled 

 with food take place. When these parts of the gut become empty, the movements are not 

 stronger than normal. If new material passes into the inflamed part, the peristalsis recurs, 

 becomes more lively than normal, and the result is diarrhoea (Nothnagel). Sometimes a greatly 

 contracted part of the small intestine is pushed into the piece of gut directly continuous with it, 

 giving rise to invagination or intussusception. 



Anti-peristalsis, i.e., a movement which travels in an upward direction towards the stomach, 

 does not occur normally. This has been inferred from the fact, that in cases where the intestine 

 is occluded, called ileus, faecal matter is vomited. Nothnagel's experiments throw doubts upon 

 this view, as he failed to observe anti-peristalsis in cases where the intestine was occluded 

 artificially. The ftecal odour of the ejecta may result from the prolonged retention of the 

 material within the small intestine. 



160. EXCRETION OF YMCAL MATTER. The contents of the small 

 intestine remain in it about three hours, and about twelve hours in the large 

 intestine, where they become less watery, and they assume the characters of 

 faeces, become " formed " in the lower part of the great intestine. The faeces are 

 gradually carried along by the peristaltic movement, until they reach a point a 

 little above that part of the rectum which is surrounded by both sphincters, the 

 internal sphincter consisting of non-striped, and the external of striped muscle. 



Immediately after the expulsion of the faeces the external sphincter (fig. 172, S, 

 and fig. 173) usually contracts vigorously, and remains so for some time. After- 

 wards it relaxes, when the elasticity of the parts surrounding the anal opening, 



