516 SPECIAL PHYSIOLOGY. 



phatics, and nerves, ramify. The mucous coat, unlike that of the 

 small intestine, follows strictly the form of the intestinal canal itself; 

 for it is not thrown into proper folds, like the valvulae conniventes, but 

 only follows the concentric ridges between the sacculi. Moreover, 

 it differs from the mucous membrane of the small intestine, in being 

 somewhat thicker and paler, and in being perfectly smooth and en- 

 tirely destitute of villi. In the caecum and colon it is of a grayish- 

 yellow color, but in the rectum it is darker, thicker, more vascular, 

 and more loosely connected with the muscular coat. Its glands will be 

 presently described. The nerves belong to the sympathetic system ; 

 in the submucous coat, their fine branches present microscopic ganglia, 

 which are also found outside the muscular coat. The movements of 

 the large intestine are not retarded by irritation of the splanchnic 

 nerves. 



At the junction of the lower end of the ileum, Fig. 92, z, with the 

 caecum, c, and colon, co 9 there is found a very perfect valve, the ileo- 

 ccecal valve, or valve of Tulp or Bauhin, composed of two semiluriar 

 segments, having their free edges directed towards the large intestine. 

 The end of the ileum is somewhat flattened on its upper and under as- 

 pects, and is here inserted into the left side of the large intestine. The 

 flattened part of the small intestine carries in, with it, the side of the 

 large intestine, and so forms the segments of the valve, which consist 



Fig. 92. 



Fig. 92. The caecum, and the commencement of the ascending colon, laid open in front, to show the lleo- 

 caecal or ileo-colic valve, at the junction of the small and large intestines, c, the cul-de-sac, named the 

 caecum, or blind intestine, a, vermiform appendix of the caecum, co, part of the ascending colon, i, a 

 piece of the ileum, or small intestine, entering the side of the large intestine, between the caecum and 

 colon, by a horizontal transverse fissure, bounded above and below, by the crescentic segments of the ileo- 

 csecal or ileo colic valve. Much reduced in size. 



therefore of the coats of both intestines, excepting, however, the longi- 

 tudinal muscular fibres and the peritoneal tunic. If the latter be 

 carefully divided where it passes from one intestine to the other, the 

 inserted part of the small intestine may be drawn out from the side 

 of the large intestine, when the two segments of the ileo-caecal valve 

 disappear, and the small intestine seems to open widely into the side 

 of the large intestine. In the natural condition, the segments of this 

 valve are placed one above the other, and leave, between their free 

 edges, a narrow, nearly horizontal slit, leading from the small into the 



