ROBERT RUSSELL BENSLEY 



they occur for the first time in mammals, the fact that they have been found without 

 exception in all mammals belonging to the three main subclasses in which they have 

 been sought, indicates that they must have appeared very early in the history of the 

 Mammalia. The fact that the pyloric glands and the Brunner's glands have been 

 subject throughout this long phylogenetic history to conditions which are not identical 

 would alone be sufficient to explain slight differences in the nature of their cells, even 

 if, as some suspect, the two sets of glands have had a common origin. Furthermore, 

 in many groups of animals, owing to a change of food habits, the stomach has under- 

 gone important secondary adaptive modifications, resulting in the suppression of 

 extensive areas of gastric glands, the replacement of the cylindrical epithelium by a 

 stratified squamous epithelium, and the modification in type of the remaining glands. 

 It is reasonable to expect that, under these extraordinary conditions, the pyloric glands 

 would be modified, and the differences between them and Brunner's glands intensified. 

 Clearly, it would be unfair to assume that, because the pyloric-gland cells differ from 

 those of Brunner's glands in an animal with such a specialized stomach, they are 

 primitively different. In other words, in discussing the question of the difference or 

 similarity of the two sets of glands, both the long phylogenetic history of the glands 

 and the relative visceral specialization of the animal under discussion must be given 

 due weight. 



The present memoir embodies the results of an investigation undertaken with a 

 view of applying to the solution of the problems presented by the glands of Brunner 

 the microchemical and staining methods employed by the writer in the stiidy of the 

 glandular elements of the stomach, and the more recent conception of the structure 

 of these and other cells. With this end in view, the glands of Brunner of one mar- 

 siipial and of nineteen placental species representing six orders of mammals have 

 been submitted to a careful anatomical and histological examination. The results 

 from a phylogenetic standpoint are somewhat disappointing, but it is hoped that 

 they will bring us nearer to a proper conception of the morphology of the glands in 

 question. 



The material for study included the pyloric glands and glands of Brunner of the 

 opossum, dog, cat, mink (Lutreola), raccoon (Procyon), hedgehog (Erinaceus), por- 

 cupine (Erethizon), guinea pig, ground hog (Arctomys monax), squirrel, rabbit, 

 dormouse (Muscardinus avellanarius), muskrat (Fiber zibethicus), mouse, rat, deer 

 mouse (Peromysciis), sheep, pig, and man. 



The glands of Brunner of the opossum have been selected for the preliminary 

 description, because the shape and structure of the stomach in this form correspond 

 so closely to those which we have reason to believe were primitive in mammals that 

 we may expect to find primitive conditions in the glands, and because the peculiar 

 characteristics of the glands of Brunner in the opossum furnish, it is thought, the 

 strongest argument which could be brought forward in favor of the theory that they are 

 produced directly from the pyloric glands. 



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