The Structure of the Mammalian (Esophagus. 23 
In the upper part of the duct a third layer is added and the surface 
layer becomes flattened. The ducts enter the epithelium between the 
ridges of the lamina propria. 
The duets run perpendicular to the surface and have no ampulla- 
like enlargements. No lymphatic nodules nor accumulations of 
lymphocytes occur in relation to the ducts. 
The tunica muscularis is composed of striated muscle throughout 
nearly its whole extent. In the stratum circulare smooth muscles 
make their appearance a short distance above the cardia and expand 
at the cardia into a lower sphincter. 
Merpuitis Mepurrica. 
In Mephitis the epithelium is extremely uneven in thickness owing 
to the fact that from the deep surface epithelial processes descend 
into the lamina propria mucose. The connective tissue separating 
these processes represents, somewhat more highly developed, the 
longitudinal and transverse ridges of the esophagus of the raccoon. 
The thickness varies from 122 micra to 294 micra, the difference 
between these measurements indicating the height of the epithelial 
processes. The epithelium shows very little evidence of cornifica- 
tion, although the superficial layers of cells are much flattened and 
stain more readily in eosin than the deeper ones. . 
The lamina muscularis mucosz begins at the upper end of the 
esophagus as scattered bundles, but rapidly becomes a complete 
layer 47 to 118 micra in thickness, according to the degree of 
extension of the mucous membrane. : 
The only glands present in the esophagus are found just at the 
cardiac orifice of the stomach. They are located in the submucosa 
and are similar in structure to the glands of the esophagus of Pro- 
‘eyon. The demilunes are particularly abundant and have the char- 
acteristic form and structure. The ducts begin in the lobules with 
a lining of cubical cells beneath which is an imperfect second layer 
of cells. This second layer quickly becomes complete on going up 
the duct and additional layers are added as the surface is approached, 
as in esophageal glands elsewhere. These glands are therefore in 
