22 THE STRUCTURE OF THE GLANDS OF BBUNNEB 



In the rabbit, according to Kuczynski (1890), these glands occur in the duodenum 

 OB far as the opening of the ductus paucreaticus, a distance of 30 crn. 



The glands in the rabbit make their appearance in the tela submucosa at the point 

 where the intestinal epithelium begins. For a distance of about three and one-half 

 centimeters they form two groups, one located in the tunica niucosa, the other in the 

 tela submucosa. These groups are incompletely separated from one another by the 

 lamina muscularis mucosse, which is interrupted here and there, to permit of commuui- 

 cati'on between the superficial and the deep glands, and the passage of ducts from the 

 latter to the surface. Throughout the rest of the duodenum the glands are for the 

 most part confined to the tela submucosa, although here and there a duct may give off 

 a small group of branches in the tunica mucosa before reaching the submucous group. 



The ducts of the superficial lobules of the glands open directly into the glands of 

 Lieberkuhn; those belonging to the submucous group preserve their characteristic 

 epithelium for a short distance after passing through the lamina muscularis mucosse, 

 but are in the majority of cases continued to the free surface by a gland of Lieberkiilm. 

 There are, however, a few independent ducts in which the epithelium retains the type 

 characteristic of the glands of Brunner as far as the free surface. 



The glands of Brunner of the rabbit are unique in structure, inasmuch as they 

 contain two kinds of cells. This fact was discovered by Schwalbe (1872) who described 

 the more deeply staining elements as independent glands, having the same structure 

 as the pancreas. _ 'Schwalbe' s observations have been confirmed by Dekhuyzen (1888) 

 and Kuczynski (1890). The latter author showed that the deeply staining elements 

 did not, as Schwalbe thought, form independent glands, but occurred along with the 

 clear cells in the same tubules. Dekhuyzen came to the conclusion that the two kinds 

 of cells represented different functional stages of the same element, and claimed to 

 have seen intermediate types. Castellant (1898) gives an excellent description of the 

 deeply staining cells, in which he observed the small refractive granules of the distal 

 zone and the striation (basal filaments) of the basal zone. He takes exception to the 

 conclusion of Dekhuyzen on the grounds that he could not discover any intermediate 

 stages between the two kinds of cells, and that deeply staining cells are altogether 

 absent in the glands at the beginning of the duodenum. Castellant does not come to 

 any definite conclusion as to the relative specificity of the two kinds of cells, but 

 suggests an interesting comparison between the glands of Brunner of the rabbit and 

 the mixed glands of the trachea. 



My own observations confirm the conclusion of Kuczynski that the deeply staining 

 cells occur in the same tubules as the clear cells. The glands of the rabbit are of the 

 compound acinotubular type, the main tubules and some of the terminal acini being 

 composed of clear cells ; many of the terminal tubules or acini, of deeply staining cells. 

 The deeply staining cells may occur (contra Castellant) in the glands of Brunner at 

 the very beginning of the duodenum. 



The transparent tubules are formed by large, clear cuboidal cells surrounding a 



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