10 THE STRUCTURE OF THE GLANDS OF BRUNNEB 



distal portions by incomplete bands of cytoplasm, stretching across it, parallel with the 

 free border of the cell. The meaning of these facts will be discussed later. In the 

 meantime it is merely intended to point out that the theca of the epithelial cells under 

 discussion contains a larger proportion of cytoplasmic elements, as distinct from stored- 

 up secretion, than that of the epithelium of the stomach. A further point of differ- 

 ence is to be seen in the size of the theca, which presents a remarkable uniformity in 

 the gastric epithelium, but is very variable in the epithelium of the defects. 



Toward the bottom of the gastric foveolae, however, cells are found which agree 

 very closely in structure with the cells of the defects, and these, as has been frequently 

 pointed out, by Bizzozero (1893) and others, are connected with the cells of the sur- 

 face by a gradual transition. A similar transition may be seen at the gastro-duodenal 

 junction, where the epithelium of one of the defects happens to be continuous with the 

 gastric epithelium. We may therefore conclude that the epithelium of the defects is 

 gastric epithelium not so highly differentiated as that of the surface of the stomach. 



The ducts which open on the defects are lined for a greater or less portion of 

 their course by epithelium of the type described above, except that the cells are as a 

 rule shorter and wider than on the free surface. At variable distances from the open- 

 ing of the duct, there is transition, sometimes abrupt, sometimes gradual, to the glan- 

 dular epithelium which lines all the numerous side and terminal branches of the gland. 



The two animals from which the material was obtained exhibited different physio- 

 logical phases of the gland ; in one the cells were completely filled with secretion, in 

 the other only partly so. A transverse section of two tubules from the latter animal 

 is represented in Plate XX, Fig. 2. Each tubule is composed of somewhat rec- 

 tangular cells, very similar in general characters, but with some differences of detail, 

 surrounding a central cavity. The lumen varies in width from 4/i to 16/4, the largest 

 diameter being usually found in the main branches of the duct and in those terminal 

 tubules (acini) which lie at the margin of a lobule. In each glandular cell a number of 

 distinct zones may be made out. Beginning at the outside of the tubule and. proceed- 

 ing toward the lumen, there may be distinguished, first, a narrow zone of cytoplasm, of 

 a delicate reticular structure, stretching across the base of the cell and containing the 

 somewhat irregular nucleus. On the distal side of the nucleus a clear zone with coarse 

 reticular structure may be observed, then a narrow band of finely reticular cytoplasm, 

 and finally a second coarsely reticular clear zone, bordering the lumen. The meshes 

 of the two clear zones obviously contain the stored-up secretion of the cells, which is 

 divided into a proximal and a distal mass by the transverse bridge of cytoplasm. This 

 reciprocal arrangement of the cytoplasm and its product is deserving of some emphasis 

 because of the fact that it occurs with surprising constancy in corresponding phases of 

 secretion in mucous cells from the most varied sources, e. g., salivary, palatine, ceso- 

 phageal, and tracheal glands, the cardiac and pyloric gland cells of the stomach, and 

 the neck chief cells of the fundus glands. Zimmermann (1898) observed this struc- 

 ture in the cells of the human glands of Brunner, but did not attempt an interpreta- 



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