bo 
Or 
The Structure of the Mammalian (Césophagus. 
although the complexes are smaller in size, more compressed, and 
more easily overlooked than in other animals. These demilunes are 
provided with intercellular secretion-canaliculhi. 
In all the ungulates examined, as might be expected, the epithe- 
lum shows a marked thickening, and an unusual degree of cornifica- 
tion. The condition in the sheep as shown in Fig. 14 is typical 
of that found in the sheep, ox and horse. The epithelium is thick 
and presents on its deep surface an irregular outline owing to the 
presence of longitudinal ridges of the lamina propria mucose. In 
addition, both on the summits of these ridges and between them 
there are extraordinarily long papille, for the most part simple, 
which penetrate the epithelium as far as the stratum corneum and 
even penetrate that layer for a short distance. A thick stratum 
corneum forms the outer portion of the epithelium, forming from 
one-third to one-fourth of the entire thickness of the epithelium, 
the thicker portions being found in the lower regions of the cesoph- 
agus. In this stratum corneum two secondary strata may be made 
out which may be compared in general with the strata lucidum and 
corneum of the plantar skin, although there are important differences 
in structure. Both layers are very homogeneous and transparent in 
the fresh condition, and in unstained alcohol-fixed sections. The deeper 
layer is composed of fusiform flattened cells, but with flattened nuclei. 
The superficial layer shows the wrinkled cell borders seen in section 
of the stratum corneum of the skin. No true stratum granulosum 
is present, but the superficial portion of the stratum germinatum 
shows indications of a change preparatory to cornification, in that 
the cell protoplasm of this layer stains more readily in fuchsin than 
the deeper layers. Nuclei are present in the cells of the most 
superficial layers of the stratum corneum, although they are much 
degenerated. Thus while a deep stratum corneum is present the 
changes do not involve the nuclei of the cells to the extent that they 
do in the guinea pig. 
In the pig, also, the epithelium is thick, but the degree of cornifica- 
tion is much less than in the sheep, the contrast between the stratum 
germinativum and the stratum corneum less striking, and the tran- 
sition less abrupt from the one layer to the other. We do not see 
