EXCRETION OF F^CAL MATTER. 313 



Muscarin excites very lively peristalsis of the intestines, which may be set aside 

 by atropin (Schmiecleberg and Koppe). 



Pathological. -When any condition excites an acute inflammation of the intes- 

 tinal 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 in darned part, the peristalsis recurs, and is 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. 



Antiperistalsis i.e., a- movement which sets in and travels in an upward 

 direction towards the stomach, does not occur normally. That such a condition 

 takes place has been inferred from the fact, that in cases where the intestine is 

 occluded (Ileus) faecal matter is vomited. The most recent experiments of 

 Nothnagel throw doubts upon this view, as he failed to observe antiperistalsis 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 Fsocal 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. The contents assume the characters of faeces, and 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 faeces have been expelled, the external 

 sphincter (Fig. 129, S, and Fig. 130) usually contracts vigorously, and 

 remains in this condition for some time. Afterwards it relaxes, when 

 the elasticity of the parts surrounding the anal opening, particularly of 

 the two sphincters, suffices to keep the anus closed. In the interval 

 between two evacuations, there does not seem to be a continued tonic 

 contraction of the sphincters. As long as the faeces lie above the 

 rectum, they do not excite any conscious sensations, but the sensation 

 of requiring to go to stool occurs, when the faeces pass into the rectum. 

 At the same time, the stimulation of the sensory nerves of the rectum 

 causes a reflex excitement of the sphincters. The centre for these 

 movements (Budge's centrum anospinale) lies in the lumbar region of 

 the spinal cord ; in the rabbit, between the sixth and seventh, and in 

 the dog, at the fifth lumbar vertebra (Masius). 



In animals, whose spinal cord is divided above the centre, a slight touch in the 

 region of the anus causes this orifice to contract, but after this lively reflex con- 

 traction, the sphincters relax again, and the anus may remain opeu for a time. 

 This occurs, because the voluntary impulses which proceed from the brain to cause 

 the contraction of the external sphincter are absent. Landois observed, that in 



