DIGESTION 213 



resembling in appearance, through its precipitated albumin, 

 nasal mucus suspended in fluid. The proportion of mucin must 

 be considerable, judging from its ropiness when poured from one 

 vessel to another, and this mucus is probably largely derived from 

 the stomach. Throughout the small intestines the character of 

 the chyme is as follows — viz., a yellow, frothy, precipitated, slimy 

 fluid, the material from the anterior part of the intestinal canal 

 having a peculiar mawkish smell, while that from the region of 

 the ileum is of a distinctly faecal odour ; the latter is due to indol 

 and skatol formed put ref actively during pancreatic digestion. 

 In the ileum the proportion of fluid material is considerably 

 reduced in amount, and the character of the ingesta may now be 

 recognised, which was previously almost impossible. 



Function of the Ileum. — As the flow of material into the small 

 intestines is controlled by a sphincter, so is the flow out of them. 

 The ileum is a remarkably thick and powerful bowel ; it is always 

 found contracted and containing material which is dry compared 

 with that found in the anterior portion of the intestine. One of 

 the functions of the ileum is to control the passage of material 

 into the caecum. Colin describes the chyme in the horse as circu- 

 lating between the pylorus and ileum — viz., that it is poured 

 backwards and forwards in order to expose it sufficiently to the 

 absorbent surface ; this necessitates a reversed peristaltic action. 

 He says that were it not for this the material could not be acted 

 upon and absorbed, as the passage of fluid through the small 

 intestines is very rapid. It would have been impossible to reason 

 out that the fluid material of the small intestines was passed to 

 and fro between the stomach and the ileum, exposed, as Colin 

 expresses it, twenty times over to the absorbent surface of the 

 bowels. This observation must have been made as the result of 

 his examination of the living animal, and there can be no doubt 

 of its correctness. 



Experiment shows that water will pass from the stomach to 

 the caecum in from five to fifteen minutes. By applying the ear 

 over the duodenum, as it passes under the last rib on the right 

 side, the water which a horse at that moment is drinking may be 

 heard rushing through the intestines on its way to the caecum. 

 One is always struck by the fact that the small intestines are 

 never seen full — in fact, are often practically empty — from which 

 we judge either that material passes very rapidly through them, 

 or that only small amounts of chyme are propelled into them at 

 a time. The contents are always in a liquid condition excepting 

 at the ileum, the fluid being derived from the secretions poured 

 into and those originating in the bowel. That active absorption 

 goes on in the intestines is proved by the difference in the physical 

 characters of the contents in their several parts. The rate at 



