THE STOMACH AND INTESTINE. 2/7 



thelium covering the villi. If, therefore, any cells be destroyed on 

 the surface of the villi, it must be assumed that the loss is replaced 

 by new elements pushed up from the glands below (Bizzozero, 89, 

 92, I). 



In the fundus of the crypts of Lieberkiihn of the small intes- 

 tine are also found a variety of cells first described by Paneth, and 

 known as the cells of Paneth. These cells contain granules which 

 stain readily in eosin and in iron-lac-hematoxylin, and are no 

 doubt cells which contain zymogen granules, cells which elaborate 

 an enzyme. In the opossum the cells of Paneth are found not 

 only in the crypts but also in epithelium of the villi intermixed 

 with the columnar cells and goblet cells (Sidney Klein). 



The entire duodenum, as well as that part of the pylorus in the 

 immediate vicinity of the pyloric valve, is characterized by the 

 presence of glands of a second type. In the duodenum these are 

 seen intermingled with the glands of Lieberkiihn, and in the pylorus 

 with the pyloric glands. These glands, Brunner's glands, have a 

 diameter of from 0.5 to I mm., and are branched tubulo-alveolar 

 glands, with tubules provided with alveoli, especially along their 

 lower portions. The bodies of the glands are situated principally 

 in the submucosa, although a part may be in the mucosa. In the 

 stomach they open into the gastric crypts, in the intestine either in- 

 dependently between the villi, or into the glands of Lieberkiihn. 

 Here the glandular cells are in general similar to those of the 

 pyloric glands, although, as a rule, somewhat smaller than the 

 latter. The secretion of these glands is mucus (Bensley). Just 

 as the duodenal glands extend into the stomach, so also the pyloric 

 glands of the latter are found in the upper portion of the duodenum. 

 Besides short villi, there are also present in the duodenum depres- 

 sions of the mucous membrane analogous to the gastric crypts. The 

 glands of Lieberkiihn begin at a certain distance from the pylorus ; 

 at first they are short, and do not attain their customary length until 

 a point is reached at which the pyloric glands extending into the 

 duodenum finally disappear (vid. Fig. 218). It is therefore obvious 

 that a transition zone exists between pylorus and duodenum, and 

 that a distinct boundary line can not be drawn between the two, at 

 least so far as the mucous membrane is concerned. The duodenal 

 glands, as their name would indicate, are present only in the duod- 

 enum. Between the jejunum and ileum there is no distinct boundary, 

 not even when microscopically examined. The differences are mostly 

 of a quantitative nature ; in the jejunum the valvulae conniventes are 

 more numerous than in the ileum, and the villi more slender and 

 closer together. The glands of Lieberkiihn also appear to be more 

 numerous in the jejunum. 



The mucosa of the small, intestine consists of reticular adenoid 

 tissue containing mononuclear lymphocytes, polymorphonuclear 

 leucocytes, and leucocytes with granular protoplasm. It sup- 

 ports the glands and extends into the villi whose axes it 



