54 PHYSIOLOGY. 



the stomach of an executed criminal, and found it to consist of 

 Oxygen, 11-03, Carbonic acid, 14-00, Hydrogen, 3-55, Nitrogen. 

 71-45. 



Action of the small intestine. — The passage of the chyme through 

 the pyloric orifice is at first slow ; but when the digestive process is 

 nearly completed, it is transmitted in larger quantities. The move- 

 ments by which this passage is effected are of a peristaltic charac- 

 ter, each one being preceded by a series of slighter movements in 

 the opposite direction. The chyme is mingled in the duodenum 

 with the biliary and pancreatic secretions, which effect an immediate 

 alteration in its sensible and chemical properties. When mingled 

 out of the body, as was done by Dr. Beaumont, the chyme is sepa- 

 rated into three parts ; a reddish-brown sediment, — a whey-coloured 

 fluid in the centre, — and a creamy pellicle on the top. The central 

 portion, and the creamy pellicle, seem to constitute the materials 

 from which the chyle is elaborated ; the creamy matter consisting of 

 the oleaginous particles, and the whey-like fluid containing proteine 

 compounds, saccharine, and saline matters in solution ; while the 

 sediment, consisting of the insoluble matter of the food and of biliary 

 matter, is probably excrementitious. 



The contents of the alimentary canal become more consistent, 

 and obtain more of the fsecal character as they pass down the intes- 

 tinal tube; during which time there is also mixed with them, the 

 secretions of the various follicles ; of Brunner, in the duodenum ; 

 Lieberkuhn, in the whole route ; and Peyer, at the termination of the 

 ilium. The last have no excretory orifice, but discharge their secre- 

 tion by cell agency. In the neighbourhood of these glands the faecal 

 matter obtains its characteristic odour, probably from their secretion, 

 which is depuratory. 



The movements of the intestinal canal are dependent upon the 

 contraction of its muscular coat, and are directly excited by the con- 

 tact, either of the fsecal matter, or of the secretions poured into it. 

 This movement is called the peristaltic action of the bowels. It is 

 not dependent on nervous influence, as is seen from the fact, that it 

 will continue after all nervous communication has been cut off. The 

 influence of the emotions upon this movement is probably due to the 

 sympathetic nerve which is distributed to the whole intestinal tract. 



Defecation. — The large intestines act as a reservoir and excretory 

 canal for the foeces. And as the passage through them is not so 

 rapid as in the small intestine, the fsecal matter accumulates until 

 the desire to expel it arises. The contractions of the muscular coat of 

 the large intestines are wholly without the domain of the will ; but 

 the involuntary escape of the faeces is prevented by the action of the 

 sphincter ani muscle, which is partly under the influence of the reflex 

 system of nerves. The concurrence of the voluntary muscles with 

 the action of the intestines, is necessary to overcome the contraction 



