ROBERT RUSSELL BENSLEY 45 



As regards the similarity of the glands of Brunner to the pyloric glands of the 

 stomach, it may be said that in nearly all cases examined slight differences in structure 

 could be discerned. I do not, however, regard these differences as of fundamental 

 importance. Certainly they are primitively cells of the same type. An interesting 

 fact is that the greatest differences between the cells of the two sorts of glands were 

 found, in the series of animals studied by the writer, in those animals in which the 

 stomach was highly specialized. This fact can be explained by the assumption that 

 the two groups of glands were primitively similar, and that their great dissimilarity in 

 the case of animals with specialized stomachs is due to the fact that the pyloric glands 

 have also been modified in the course of this specialization. The writer, however, 

 hesitates to generalize in this respect until a much larger series of animals has been 

 studied by the methods employed in this research. 



The question of the phylogeny of the glands of Brunner is an exceedingly difficult 

 one to discuss. Up to the present the only clear-cut theory of their origin advanced 

 is that of Oppel (1897). This author expresses his views as follows: 



Bei zahlreichen niederen Wirbeltieren finden sich Spuren einer Tendenz der Pylorusdriisen, 

 sich iiber den Sphinkter hinaus auszubreiten, so z. B. bei Urodelen, wo eine scharfe Grenze 

 zwischen den letzten Pylorusdrusen und den Darmdriisen iiberhaupt schwer zu ziehen ist. Die 

 letzten Pylorusdrusen zeigen ferner bei manchen Reptilien und Vogeln an ihren unteren Enden 

 die Tendenz, sich starker zu entwickeln, eine Tendenz, die auch noch bei SSugern zum Ausdruck 

 kommt. Verbinden wir beides, so werden wir leicht den Vorgang der Eiitstehung der Brun- 

 nerschen Driisen so deuten konnen, dass die Driisen der Pylorusdrusenzone iiber den Sphinkter 

 hinauswachsend und zu einer excessiven Entwicklung gelangend, die Muscularis mucosae 

 durchbrechen und so zu Brunnerschen Driisen werden. 



The attractiveness of this hypothesis becomes apparent when we examine such a case 

 as that of the opossum, in which the glands all open on circumscribed areas of the 

 intestine, covered by gastric epithelium. The facts in favor of the hypothesis are 

 briefly: the contiguity of the glands of Brunner to the pyloric glands in the less 

 specialized mammals; and the great similarity of the cellular components. As regards 

 the similarity of the cells, however, it must be remembered that the cells of the glands 

 of Brunner resemble just as strongly the mucous cells of many buccal, cesophageal, and 

 trachcal glands. We are thus reduced to the fact of contiguity as an effective argu- 

 ment for the phylogenetic development of the pyloric glands into glands of Brunner. 

 Furthermore, in accepting this hypothesis we must assume that the epithelium of the 

 small intestine is specifically differentiated from that of the stomach, not only in the 

 adult, but in the embryo at the time the glands of Brunner are formed; that is to say 

 that at a time when no structural differences can be discerned between the cells of the 

 gastric and intestinal epithelium the cells actually have a different developmental 

 potential, those of the stomach having lost the power of developing into cells of the 

 intestinal type and those of the intestine that of developing into cells of the gastric 

 type. We must also assume that there is a mingling of this gastric hypoblast and 

 intestinal hypoblast in the region of the formation of the glands of Brunner, because 



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