THE ALIMENTARY TRACT. 



293 



Fig. 193- 



by an abrupt curve at its anterior end. The large intestine is the 

 widest part of the alimentary canal, is thin-walled, and diminishes 

 in width towards its hinder end, where it opens into the cloaca 

 above the opening of the bladder. 



b. [Minute structure. 



(1) The serous coat resembles that of the small intestine, etc. 



(2) The muscular coats resemble those of the small intestine, but 

 are thinner ; the longitudinal layer is, however, proportionally 

 thicker (AViedersheim). 



(3) The submucous coat (Fig. 192) resembles that of the small 

 intestine in its general structure ; the portion lying immediately 

 beneath the mucous membrane (13) is denser in structure. 



This layer has no 3 fit Scutari* mu.cosa. 



(4) The mucous coat (A) is a simple layer of large, columnar, 

 epithelial cells, with large oval nuclei. The cells have a hyaline 

 free border, but this possesses no stri- 



ation. The mucous membrane is usually 

 described as possessing numerous simple 

 follicles (glands of Lieberkiihn) ; in 

 those specimens which I have exa- 

 mined they have been entirely absent 

 (Figs. 192, 193). At six to eight 

 points in a transverse section of a 

 rectum moderately distended the sub- 

 mucous coat is thinner, and so throws the 

 mucous coat into slight, longitudinal 

 grooves; but these do not in the least 

 resemble the glands of Lieberkiihn. 



(5) The epithelium possesses goblet- 

 or chalice-cells (Hoffmann), the number 

 of which probably depends upon 

 the period of the year and the state 

 of digestion. In the rectum, from 

 which the section for the figures 192 

 and 193 were cut, not one goblet-cell 

 was found in a complete series of 

 sections. 



If the rectum be contracted, the mucous membrane is thrown into 

 longitudinal folds. 



Transverse section of large intestine of 

 Kana etculenta ; the mucous mem- 

 brane thrown into longitudinal folds 

 in consequence of the organ being 

 contracted. Arteries injected with 

 carmine. G. H. 



A Large circular vessels within the 



muscular coats. 

 B Fine anastomosis to the mucons 



coat. 



