STRUCTURE OF THE LARGE INTESTINE. 



373 



The mucous membrane differs fi'om that of the small intestine in 

 being quite smooth and destitute of villi. Viewed with a lens, its 



Fig. 268. 





Fig. 268. — DiAGRAiiMATic View (jMagnifiep) op a Sjiall Portion op the Mucous 

 Membrane op the Colon (Allen Thomson). 

 A small portion of the mucous membrane cut perpendicularly at the edges is sho'mi in. 

 perspective ; on the surface are seen the orifices of the crypts of Lieberkiihn or tubular 

 glands, the most of them lined by their columnar epithelium, a few divested of it and 

 thus ajipearing larger ; along the sides the tubular glands are seen more or less equally 

 divided by the section ; these are resting on a wider portion of the submucous tissue, 

 from which the blood-vessels are represented as passing into the spaces between the 

 glands. 



Fig. 269. 



surface is seen to be marked all over by the orifices of numerous tubular 



glands (cri/pfs of Lieherkuhn) (fig. 268), 



resembling those of the small intestine, 



but longer and more numerous, and 



placed more closely together and at more 



regular intervals. 



Besides these, there are scattered over 

 the whole large intestine hjmjihohl fol- 

 licles, similar to the solitary glands of 

 the small intestine, but less prominent. 

 They are most numerous in the cajcum. 

 and in its vermiform appendix ; being 

 placed closely all over the latter. 



The epithelium, which covers the 

 general surface of the mucous membrane, 

 and lines the tubular glands, is of the 

 columnar kind, and in every respect 

 similar to that of the small intestine. 

 As in the stomach the mucous mem- 

 brane consists of areolar connective 

 tissue with a certain amount of retiform 

 tissue, and is bounded next the submu- 

 cous coat by a layer of plain muscular 

 fibres {muscularis miicosce), which sends 

 prolongations up between the glands to 

 be attached to the basement membrane 

 near the surface, in the same way as in 

 the villi of the small intestine. 



Fig. 269. — Blood- Vessels op 

 Large Intestine as seen in 

 Vertical Section (KoUiker). 

 a, artery i)assing up from sub- 

 mucosa ; c, vein arising from capil- 

 lary plexus, b, around the mouths 

 of the glands. 



