THE RABBIT. 305 



203. The length of the intestine as a whole : it is usually 

 about 15 or 16 times that of the animal to which it belongs. 

 The lengths of its five divisions, duodenum, ileum, caecum, 

 colon, and rectum. 



204. The sacculations of the colon occur in three longitudinal rows, 

 separated by three muscular bands, or taeniae coli, which pass, at 

 equal distances from one another, along the whole length of the colon. 



205. The Peyer's patches, masses of lymphoid tissue occurring in the 

 form of thickened areas on the walls of the intestine : those on the ileuir> 

 are oval and about half an inch long : on the \vide portion of the colon, 

 close to the sacculus rotundus is a larger patch about three-quarters 

 of an inch in diameter : the sacculus rotundus itself and the appendix 

 vermiformis are in reality large Peyer's patches. 



XXII. Cut open the stomach, and parts of the small intestine, 

 colon, rectum, caecum, and appendix vermiformis : in another 

 specimen remove the caecum with a small portion of the ileum 

 and colon, clear out its contents by directing a stream of water 

 through it, and either distend with air and dry, or, better, 

 distend with a 0*5 per cent solution of chromic acid and place 

 in a vessel of the same fluid until hardened : in either case cut 

 apertures in various parts so as to see the interior. Note the 

 following points in the internal structure of the alimentary 

 canal : 



206. The three coats of the stomach : the outer peritoneal invest- 

 ment, the middle muscular layer, and the inner layer of mucous 

 membrane : the great thickness of the muscular layer in the antrum 

 pylori : the slightly different character of the mucous membrane in the 

 cardiac and pyloric regions : the irregularly longitudinal rugse into which 

 the mucous membrane is raised. 



207. The thick projecting rim, or pyloric valve between the stomach 

 and duodenum. 



208. The prominent aperture of the bile-duct in the duodenum 

 just beyond the pylorus. 



209. The three coats of the intestines : much thinner, for the most 

 part, than those of the stomach. 



2.10. The irregular transverse ridges orvalvulae conniventes of the 

 mucous membrane of the small intestine : the minute conical projections 

 or villi which beset these : the latter can only be seen to advantage by 

 examining underwater. 



X 



