The Structure of the Mammalian Csophagus. 3 
demilunes occur in the cesophageal glands of the dog. Renaut (97) 
describing the cesophageal glands of the dog and of man makes the 
statement that they may be seen in preparations stained with his 
elycerine-hematoxylin-eosin mixture, without specifying whether 
he found them in one or both species. Schaffer (97) denies their 
presence in the human. esophageal glands and Rubeli (90) failed to 
find them in a number of domestic mammals. Stohr (87) appears 
to have seen demilunes in his preparations, but to have interpreted 
them in accord with his well-known phase-theory as inactive mucous 
cells. More recently Helm (67) has described typical demilunes 
in the dog and pig and has demonstrated in them, by means of the 
iron-hematoxylin method, the intercellular secretion canaliculi. — 
Assuming that the function of the secretion of these glands is in 
part at least that of mechanically aiding deglutition, one would expect 
that in those cases where the character of the food and the nature 
of mastication suggest the need of these structures, but where, not- 
withstanding, no cesophageal glands are present, a compensatory 
development of other structures will be found, as, for example, a 
thickening of the stratified epithelium or an increased development 
of the muscularis mucose or of the external muscular coat. In 
other words, it is to be expected that a correlation of some sort will 
be found between the relative development of these structures and 
that of the cesophageal glands. 
Accordingly, it seemed desirable to extend the investigation of 
the structure of the esophagus to a much larger series of animals 
than has been considered hitherto by any single investigator, and to 
determine, as accurately as may be, the specializations which have 
arisen as a result of the response to the differences in the nature of 
the food on which these animals subsist. Among these, it might 
reasonably be expected that animals which live on coarse vegetable 
food would develop either a thickened epithelium, or a more com- 
pletely cornified epithelium, or a layer of glands furnishing a lubricant 
secretion. It is, however, not by any means easy to estimate the 
degree of cornification of an epithelium except in those cases where 
a true stratum corneum composed of cells which have lost their 
nuclei is present. The thickness of the epithelium too is variable 
