108 The Cardiae Glands of Mammals 
ing cells, and that, for example, one cell may store its mucin in a more 
elaborated form than another eell which is its morphological equivalent. 
It is unreasonable to expect that the different mucins and different 
stage of elaboration of mucin would present always the same staining 
properties. 
The importance of this point of view is clearly recognized by Mayer, 
97, in his recent paper “ Ueber Schleimfarbung” in which he points 
out that, in relation to his muchaematein solution, it is possible to con- 
struct a graded series beginning with mucins which stain only with diffi- 
culty and passing by imperceptible gradations to mucins which stain 
rapidly and deeply. He was also able to obtain in the cells of the sub- 
maxillary gland of the hedgehog, the secretion of which, according to 
Krause, does not contain mucin, a typical mucin reaction. 
It may be pointed out, also, that the obtaining of mucin reactions in 
secretory cells is to a certain extent dependent on the technique of the 
individual investigator. The writer, for example, as will be indicated 
in the more special portion of this paper, has had little difficulty in 
staining the cells of the cardiac glands in every instance with mucicar- 
mine and muchematein, and, in some cases, with other mucin stains 
such as indulin and methyl blue. 
It is clear from the foregoing that negative results with mucin stains 
are absolutely without value as evidence of the serous nature of secret- 
ing cells, and that positive results are only of value in so far as they 
are confirmatory to evidence derived from other sources. Some caution 
is even necessary in drawing conclusions from the structure of the cell. 
The submaxillary gland of Erinaczeus is a case in point, where the cells 
have both the structure and staining properties of mucous cells, although 
no mucin is secreted by the gland. Another case is that of the pyloric 
gland which was for many years interpreted as a serous gland, simply 
because the nucleus is often spherical instead of crescentic, and because 
the cells may contain considerable residual protoplasm. 
Edelmann’s theory of the function of the cardiac glands would be a 
simple and sufficient explanation of the occurrence of these glands in 
herbivorous mammals, but for the extraordinary fact that they are ab- 
sent or feebly developed in the most highly specialized of herbivors, 
the ruminants. The occurrence of large areas of cardiac glands in all 
Perissodactyls and in the pigs, camels and llamas among the Artio- 
dactyls, precludes the possibility of supposing that they were absent from 
the stomachs of the herbivorous ancestral types, in which their original 
occurrence is rendered more probable by the discovery by Zimmermann 
and Sal, 94, of what may prove to be remnants of cardiac glands along 
