146 The Cardiae Glands of Mammals 
no recent rodent presents the intermediate stage between the simple 
stomachs of the squirrels, rabbits and porcupines and the complex stom- 
ach of the Myomorpha, such a comparison as that of Toepfer shows 
clearly that the stomach of Arvicola arvalis has been produced from 
such a stomach as that of Mus by a continual encroachment of the 
stratified epithelium on the glandular region proceeding particularly 
in the sides and lesser curvature, but ultimately including the pyloric 
gland region. It is furthermore clear from such a series that the lines 
of least resistance to the encroachment have been afforded by the 
cardiac glands and the pyloric glands. 
It is inconceivable that such an important process should take place 
without leaving some traces of the stages in the suppression of the 
glands. In the writer’s opinion this intermediate stage is represented 
by the cardiac glands. It has already been pointed out that in certain 
mammals, more particularly Bradypus, Dicotyles, Camelus, and Au- 
chenia, large areas of cardiac glands occur completely isolated from the 
other gastric glands and surrounded on all sides by stratified non- 
glandular epithelium. The supporters of the theory of cesophageal 
origin would doubtless regard these as cesophageal glands which have 
been included in the cesophageal hernia by which the sae was formed, 
but it must be borne in mind that in no case are they covered by 
cesophageal epithelium, but, on the contrary, have a simple epithelial 
covering. It is true that Schaffer has described such a condition in his 
so-called superior cardiac glands of the human esophagus, but there is 
no evidence that these isolated structures which have been found in no 
other mammal, are primitive. The theory of cesophageal origin is in- 
adequate to explain the persistence of these groups of glands. 
On the other hand, the theory suggested by Oppel that the cardiac 
glands form the intermediate stage in the process of complete oblitera- 
tion of the gastric glands in portions of the stomach affords a simple 
explanation of the occurrence of these isolated groups of cardiac glands, 
and is in accord with the results of histological investigation. Some 
suggestion of this kind apparently occurred to Edelmann, but he was 
turned aside from the full consideration of it by his failure to find une 
cardiac glands in the higher ruminants. 
The facts in favor of this view are briefly as follows: 
1. A layer of cardiac glands is always interposed between the gland- 
less zone with stratified epithelium and the gland-bearing zone. In 
the further advance of the stratified epithelium into the stomach, the 
first structures to suffer suppression would be these cardiac glands. As 
it is unlikely that new glands of a different origin would be produced at 
