246 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou. VIII. 
substance, thus adding further weight to the contention that the striae 
have free ends. 
Within the parenchyma of the villus is to be found a variable amount 
of smooth muscle fibre together with connective tissue strands. These 
latter branch in various directions between the basement membranes of 
the epithelial layer and the wall of the lacteal, leaving anastomosing spaces 
of irregular size and shape between. Within these spaces and also in the 
connective tissue are to be seen four main types of cells,—the ordinary 
polymorphonuclear leucocyte, the lymphocyte, the ‘‘mastzell,”’ which, 
however, does not stain with the ordinary dyes, but can be easily demon- 
strated with methylene blue and, lastly, cells, which I have termed large 
lymphoid cells, varying insize from about ten to twenty micronsin diameter, 
and from a spherical to a more or less elliptical outline. Their nuclei are, 
as a rule, eccentrically placed, and are usually vesicular. The outline of 
these cells is generally clearly defined, and the protoplasm takes the eosin 
stain, appearing as finely granulated. As far at least as the guinea pig 
is concerned, I have never seen these large lymphoid cells within or between 
the epithelium covering the villus nor in the lacteal, in this respect differing 
from the other leucocytes. They are, however, actually phagocytic as 
will be shown later on. They are precisely similar to the cells described by 
Macallum as containing iron when salts of that element are being ab- 
sorbed from the intestinal cavity.* 
The number of leucocytes in the villus is subject to great variation. 
The majority, however, during fat absorption, at least, are of the large 
lymphoid character and are especially numerous at the tip of the villus, a 
point of considerable importance when one remembers that most of the 
fat enters at that place. 
It is noteworthy too that in the guinea pig very few leucocytes of any 
description are found either within or between the epithelium covering 
the villus, and this is true whether active fat absorption is going on or not, 
a fact of very great moment in relation to one of the older theories of fat 
absorption. In the same animal, too, one very seldom sees a leucocyte 
in the lacteal vessel. 
The occurrence of lymphatics, with well defined walls within the 
parenchyma of the villus is still in doubt. I have on several occasions 
tried to inject such, using soluble Prussian Blue dissolved in gelatin, but 
failed to demonstrate them. The difficulties, however, are great owing 
to the valve at the base of the villus. I am convinced, nevertheless, that 
*On the Absorption of Iron in the Animal Body, Journal of Physiology, Vol. 16, p. 268 
1893. 
