DIGESTION. 



257 



Glands of the Small Intestine. The glands are of three princi- 

 pal kinds: viz., those of (1) Lieberkuhn, (2) Brunner, and (3) Peyer. 



(1.) The glands or crypts of Lieberkuhn are simple tubular depressions 

 of the intestinal mucous membrane, thickly distributed over the whole sur- 

 face both of the large and small intestines. In the small intestine they 

 are visible only with the aid of a lens; and their orifices appear as minute 

 dots scattered between the villi. They are larger in the large intestine, 

 and increase in size the nearer J:hey approach the anal end of the intes- 

 tinal tube; and in the rectum their orifices may be visible to the naked 

 eye. In length they vary from -^ to -fa of a line. Each tubule (Fig. 

 186) is constructed of the same essential parts as the intestinal mucous 

 membrane, viz., a. fine membrana propria, or basement membrane, a 



FIG. 185. 



FIG. 186. 



FIG. 185. Transverse section through four crypts of Lieberkuhn from the large intestine of the 



pig. They are lined by columnar epithelial cells, the nuclei being placed in the outer part of the 

 cells. The divisions between the cells are seen as lines radiating 

 epithelial cells, which have become transformed into goblet cells, 



FIG. 186. A gland of Lieberkuhn in longitudinal section. 



from L, the lumen of the crypt; G, 

 x 350. (Klein and Noble Smith.) 

 (Brinton.) 



layer of cylindrical epithelium lining it, and capillary blood-vessels cover- 

 ing its exterior, the free surface of the columnar cells presenting an 

 appearance precisely similar to the "striated basilar border" which covers 

 the villi. Their contents appear to vary, even in health; the varieties 

 being dependent, probably, on the period of time in relation to digestion 

 at which they are examined. 



Among the columnar cells of Lieberkuhn's follicles, goblet-cells fre- 

 quently occur (Fig. 185). 



(2.) Brunner' s glands (Fig. 188) are confined to the duodenum; they 

 are most abundant and thickly set at the commencement of this portion 

 of the intestine, diminishing gradually as the duodenum advances. They 

 are situated beneath the mucous membrane, and imbedded in the submu- 

 cous tissue, each gland is a branched and convoluted tube, lined with 

 columnar epithelium. As before said, in structure they are very similar 

 to the pyloric glands of the stomach, and their epithelium undergoes a 

 VOL. I. 17. 



