328 Granule Cells of Paneth in Intestinal Glands of Mammals 
affinity for basic dyes, such as toluidene blue, sometimes as a diffused 
substance in the base of the cell, generally in the form of basal filaments. 
The failure of previous observers to find this substance is probably to be 
explained by the fact that the study of these cells has generally been 
undertaken in herbivorous animals which like the guinea pig show the 
effects of an almost continuous secretory activity. Furthermore, this 
basal substance, whether diffused in the basal cytoplasm or in the form of 
the so-called basal filaments, gives when treated by Macallum’s method 
a decided reaction for iron. For these reasons it seems certain that we 
have to do here with a substance exactly comparable to the prozymogen 
of other zymogenic cells. 
In the opossum the cells of Paneth are found not only in the glands 
of Lieberkiihn, but also on the surface of the mucous membrane. In- 
deed, when the small size of the cells in the glands, their large size on 
the villi, and the generally rudimentary character of the glands in this 
animal are taken into consideration, it seems probable that the cells are 
formed in the glands, but only reach physiological maturity after mi- 
grating to the surface in the way described by Bizzozero. ‘This is of 
course only true, as far as we know at present, of the opossum, although 
it is possible that the examination of other polyprotodont marsupials 
might reveal similar conditions in them. In placentals the cells of 
Paneth appear to be confined to the bottoms of the glands of Lieberkiihn, 
which thus function as true glands as maintained by Oppel. 
Whether the condition found in the opossum is the primitive condi- 
tion for mammals or not it is impossible to say, although this view pre- 
sents many interesting possibilities. Nicolas’ observation that they oc- 
cur as a part of the general intestinal epithelium in a lizard points in 
this direction. The observations bearing on the occurrence of Paneth 
cells in lower vertebrates are, however, as yet, too few to enable any 
opinion to be offered as to their phylogenetic source. 
The distribution of the cells of Paneth in the opossum absolutely ex- 
cludes the possibility of the cells of Paneth being young mucous cells, 
and equally opposed to this view are the facts brought out by Nicolas, 
Moller, and the writer, as to the indications of active secretion in the 
structure of the cells and as to their response to physiological stimulation. 
The cells of Paneth of the guinea pig respond to physiological stimulus 
of food by secretion as indicated by changes in the form of the cell and 
reduction in the number and size of the granules. 
The crescent-shaped granules of Nicolas and others are due to im-— 
perfect fixation and have no previous existence in the cell. 
