38 THE STRUCTURE OP THE GLANDS OF BKUNNEB 



the writer confirm the description given by Castellant (1898), except with respect to 

 their downward extent. In this case the glands extend only within about 3.5 cm. of 

 the duodenojejunal flexure; in Castellant 1 s case isolated lobules were found in the 

 upper part of the jejunum. 



From the beginning of the pars descendens duodeni downward the glands are 

 progressively reduced in bulk and tend, as Castellant observed, to become located in 

 the plicae circulares (Kerkringi), although not wholly confined to the latter. In the 

 lower part of the duodenum they are reduced to scattered small lobules. Throughout, 

 however, there are tubules in the tunica mucosa as well as in the submucosa, although 

 the latter predominate. Castellant remarks concerning these tubules of the mucous 

 membrane: "Elles cessent mfime presque comple"tement an niveau de 1' union de la 

 premiere portion du duodenum avec la seconde ; on n' en retrouve plus qu' accidentelle- 

 ment au deli" indicating that he observed them in the lower portion of the duode- 

 num, but in smaller numbers than in the material described above. 



In each of the lobules of the submucous group may be distinguished a central 

 tubule which is the duct of the lobule. From this duct, which may be extremely 

 tortuous in its course, come off numerous side branches of various lengths and com- 

 plexity of secondary branching. After passing through one lobule, a duct may enter 

 a second and a third, branching in each in a similar way ; or some of the side branches 

 may pass out and form the central duct of accessory lobules. Often the central duct 

 of a lobule may be locally enlarged, as may be seen in some parts of Fig. 15. 



The ducts pass through openings in the muscularis mucosae sometimes singly, 

 more often in groups, and empty into the bottoms, sides, or branches of the glands of 

 Lieberkuhn. In the submucous as in the mucous group, the terminal branches of the 

 secreting tubules are short tubules of the same size as the main branches, or elongated, 

 pear-shaped acini. In both cases they are formed of cells similar to those forming the 

 ducts and their various branches. 



All the tubules of the glands of Brunner of man are provided with a delicate 

 basement membrane composed of reticulum. The ducts and tubules are formed of 

 somewhat rectangular epithelial cells, 15 /* to 21 p in height, uniform in type through- 

 out the gland, but with some differences of structural details in different parts. In the 

 terminal tubules in the material from the young subject, the cells are of the type repre- 

 sented in Plate XXII, Figs. 11 and 12. The nucleus is crescentic or flattened in form, 

 and is located in the outer end of the cell. The body of the cell contains a network com- 

 posed of extremely fine cytoplasmic fibrils forming large meshes in which the secretion 

 of the cell is contained. In the center of the cell the cytoplasm forms a network of 

 smaller meshes and coarser trabeculse corresponding to the band of cytoplasm 

 separating the two masses of secretion in the cells of the opossum, cat, mink, etc. 



As may be seen from Figs. 14 and 15, which are half-tone reproductions of 

 photomicrographs of specimens stained in strong muchffimatein, the glands of 

 Brunner stain even more intensely in this solution than the goblet cells of the 



314 



