ROBERT RUSSELL BENSLEY 19 



musculnris mucosse to the tunica muscularis. The amount of interlobular connective 

 tissue is relatively small. The zone begins with a number of small scattered elliptical 

 lobules confined to the superficial portion of the tela submucosa, but rapidly increases 

 in width and in number of lobules as the duodenum is descended. The greatest width, 

 0.7 mm., is reached at a distance of about 5.3mm. from the beginning of the zone. 

 From this point onward the layer of glands gradually diminishes in thickness until it 

 disappears, so that the whole mass has a fusiform shape in longitudinal section. 



The lamina muscularis rnucosae is continuous throughout except at the points 

 where the ducts pass through to enter the tunica mucosa. It consists of a thin internal 

 layer of circular fibers and a thicker external layer of smooth muscle fibers. The 

 structure of the mucous membrane covering the Brunner's glands of the mink is 

 unique, inasmuch as the tunica mucosa of the proximal half of this region, although 

 on the duodenal side of the pyloric sphincter, is covered by gastric epithelium and 

 occupied exclusively by glandulse pyloricse identical in structure with those which 

 occur in the stomach itself. These pyloric glands extend into the duodenum a total 

 distance of 8.8mm. (measured from the summit of the sphincter), slightly beyond the 

 point of greatest thickness of the glands of Brunner. Here they are abruptly suc- 

 ceeded by the intestinal epithelium and glands. 



Beyond the point where this change takes place, however, for a distance of 

 0.3mm. one may meet pyloric glands mingled with the glands of Lieberktlhn, opening 

 into typical foveolse gastricse, and may even find patches of gastric epithelium on the 

 surface. There is no lymphatic nodule at the junction of gastric and intestinal 

 mucosse; both of these mucosce in this animal are singularly poor in lymphatic tissue. 



The glands of Brunner of the proximal half of the zone open directly into 

 branches of the pyloric glands by ducts which pierce the lamina muscularis mucosse. 

 Beyond the point where the intestinal glands of Lieberkuhn make their appearance 

 the glands of Brunner open either into the glands of Lieberkuhn or into the pyloric 

 glands with which these are mingled. In the distal parts of the area independent 

 ducts are rare, the glands opening almost exclusively into the bottoms of Lieberkuh- 

 nian glands. A curious fact in these latter instances is that the epithelium of the 

 proximal branches in the lobule may be lined by cylindrical and goblet cells ; in other 

 words, the glands of Lieberkuhn, instead of receiving the ducts of the glands of 

 Brunner in the tunica mucosa internal to the lamina muscularis mucosse, perforate the 

 latter and may subdivide into several branches which retain the typical epithelium 

 before receiving the tubules formed of the epithelium characteristic of the glands of 

 Brunner. We may thus have illustrated in this single animal all the various kinds of 

 ducts between two extremes, one of these being the condition in which independent 

 d"ucts lined by glandular epithelium and opening into gastric foveolse are present ; the 

 other, that in which the branched glands of Lieberkuhn penetrate the tela submucosa 

 and receive the tubules of Brunner's glands. 



The tubules of the glands of Brunner in the mink bear a very close resemblance 



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