INTESTINAL NUTRITION IN THE OPOSSUM 353 



individuals of the same age. Near the pylorus there are a few 

 shallow folds in the mucosa, indicating a very early stage in the 

 development of pyloric glands, and at the opening of the esopha- 

 gus, less definitely marked folds are found where the cardiac 

 glands will later develop. The epithelial lining of the stomach, 

 however, is made up of low columnar cells, which are at this 

 stage undifferentiated in all parts of the organ. 



After birth the distention of the stomach with milk results in 

 the disappearance of the rugae which were present in the embryo. 

 In the living animal the position and large size of the stomach 

 are very evident on account of the milk which can be seen through 

 the transparent body-wall. The greatest enlargement has oc- 

 curred in the portion of the corpus along the greater curvature 

 and in the upper part of the pyloric region. The fundus ends 

 bluntly and is not prominent as in the embryo. 



Bensley ('02), in his comprehensive paper, described the 

 stomach of the adult opossum as a simple structure, resembling 

 closely in shape and arrangement of parts those of insectivores 

 and carnivores. He showed in a diagram (fig. 10 A) that the 

 fundic gland zone occupied the greater portion of the mucous 

 surface, with the remainder covered by pyloric glands, and stated 

 also that the cardiac gland zone occupied an extremely narrow 

 zone at the termination of the esophagus. Except that the 

 glands have not yet developed, the arrangement of parts in the 

 early pouch-young is similar to that described for the adult. 

 However, the epithelial cells are yet of a simple type, and al- 

 though certain cells in the pyloric region are slightly more darkly 

 stained and more closely packed together, there is no differ- 

 entiation among them. A few slight plaited folds occur near the 

 pylorus and also around the entrance of the esophagus. Glands, 

 however, are nowhere present nor can any of the elements be 

 regarded as cells associated with the formation of acid as found 

 in the functioning stomach of higher mammals. 

 . The coils of small intestine in the late embryo are placed 

 medially in the abdominal cavity, lying between the liver and 

 the wolffian bodies. The first loops extend toward the right 

 side, partially surrounding the remaining smaller coils. Mall 



