110 The Cardiac Glands of Mammals 
cells in the cardiac glands of man, suggests the possibility that these 
structures may have been derived from the fundus glands by the gradual 
disappearance of the parietal cells and that this change may be the 
initial phase of the process by which the glands are replaced by strati- 
fied epithelium. 
It will be observed that, with the exception just noted, the only 
attempts which have been made to explain the occurrence of cardiac 
glands in mammals have been based on the a priori assumption that 
they have a useful function to perform in digestion. The alternative 
hypothesis that they constitute a stage in an advancing process, and 
that their production and subsequent disappearance in some forms is 
the result of the continued and consistent action of the same causes, 
has scarcely been discussed at all. 
The basis for comparison adopted in this paper is the structure of the 
chief cells as described by the writer and confirmed by Zimmermann, 
98, Cade, o1, and others. In 1896, in a preliminary note, 96, and sub- 
sequently in a more extended paper, 98, I pointed out that the chief 
cells of the body of the fundus glands in common with certain other 
serous glands possess structural and microchemical characters which 
enable one to distinguish with ease between them and all other glandu- 
lar elements of the stomach. These are briefly as follows: The cell 
is divisible into a proximal and distal zone. The distal zone next the 
lumen contains granules of zymogen inclosed in protoplasmic trabe- 
cule. The proximal zone, of variable extent at the attached end of 
the cell, exhibits an indistinct radial striation (basal filaments of Sol- 
ger), and stains strongly in nuclear dyes, owing to the presence in it 
of a kind of chromatin, prozymogen, which, like the chromatin of the 
nucleus can be shown by Macallum’s microchemical methods to contain 
iron in a masked form as an organic compound. MacCallum, 98, has 
since shown that this substance as well as the zymogen granules con- 
tains phosphorus. I found that the chief cells of the neck of the gland 
were the homologues of the large clear cells of the corresponding portion 
of the fundus gland of lower vertebrates and of the cells of the pyloric 
glands, all of which differ in fundamental points from the ferment- 
forming chief cells of the body of the gland. They contain neither 
basal filaments nor granules of zymogen and their protoplasm gives only 
a faint microchemical reaction for iron. These neck chief cells and 
pyloric gland cells I found to pass into the surface epithelium by a 
eradual transition, the mean of which is reached at the deep end of the 
gastric pits or foveole where actively dividing cells are found which 
are probably engaged in replacing, in- accordance with the “ wander” 
