ACTION OF THE LAKGE INTESTINE. 615 



tion from the intestinal glandulae. The agency of the bile was sup- 

 posed to be through its free soda, or the carbonate or tribasic phosphate 

 of soda. The bile, however, as shown elsewhere, is neutral; and accord- 

 ingly it has been suggested as more probable, that the chyme is made 

 alkaline by the ammonia, which is one of the products of the spontaneous 

 decomposition of bile in the intestines. 1 The pancreatic juice is cer- 

 tainly also alkaline. 



During the formation of chyle, gases are almost always present in 

 the small intestine. They were first examined by Jurine; but chemical 

 analysis was by no means as advanced at that day as it is now ; MM. 

 Magendie 2 and Chevreul have more recently analyzed those, which they 

 found in the small intestines of three criminals ; all young and vigorous. 

 The results of this analysis have been given already (p. 599). The 

 gases might originate in various ways. They might pass, for example, 

 from the stomach with the chyme. There is this objection, however, to 

 the view; that the air in the stomach contains oxygen and very little 

 hydrogen; whilst a considerable quantity of the latter gas is almost 

 always found in the small intestine, and never oxygen. Again, they 

 might be secreted by the mucous membrane of the intestine. So far 

 as we know, however, carbonic acid and nitrogen are alone exhaled 

 from the tissues. We would still have to account for the hydrogen. 

 Lastly, they might arise from the reaction of the elements of the chyme 

 upon each other, and this has been considered the most probable origin. 

 M. Magendie 3 has frequently seen bubbles of gas escaping from the 

 chymous mass, between the mouth of the ductus communis choledochus 

 and the ileum; but never from that of the ileum, the upper part of the 

 duodenum, or stomach; and he affirms, that Chevreul, in prosecuting 

 some experiments, found that when the mass obtained from the small 

 intestine was suffered to ferment for some time in a stove, at the tem- 

 perature of the body, the same gases were obtained as those met with 

 in the small intestine. 



When the food has attained the lower part of the ileum, the process 

 of chylification has been accomplished, and the residuary matter is 

 transmitted, by the peristaltic action, into the large intestine. The 

 movement, however, recurs irregularly and at long intervals. In the 

 living animal it can rarely be perceived ; but may be noticed in one 

 recently killed, and appears to have no coincidence with that of the 

 pylorus. 



g. Action of the Large Intestine. 



The large intestine acts as a reservoir and excretory canal for the 

 faeces. The residue of the alimentary matter is sent on through the 

 valve of Bauhin by the peristaltic action of the ileum. This valve, we 

 have seen, is so situate at the point of union between the ileum and 

 caecum as to permit a free passage from the former to the latter, but 

 to prevent return. The chymous mass is sufficiently soft to pass rea- 

 dily ; and the quantity of mucus poured out from the lining membrane, 



1 Valentin, Lehrbuch der Physiologie des Menschen, i. 338, Braunschweig, 1844. 



2 Precis, ii. 115. 3 Ibid. 



117. 



