250 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vo.. VIII. 
the parenchymatous fat? The answer to this question involves a deter- 
mination of the part played by the leucocytes in the absorption of fat from 
the intestinal contents. 
If the leucocytes are wholly or to a large extent responsible for the 
transfer of fat one would expect to see a vast increase in their number when 
a guinea pig has been fed pure olive oil. Such an increase is not found. 
When a guinea pig, ordinarily fed, is killed, the sections show about the 
same number of leucocytes, at least their increase is not at all proportionate 
if they are so necessary for the transference. It is true that the majority 
of the leucocytes present are of the large lymphoid variety, but the same 
is true when iron is being absorbed. Then when the adenoid tissue is laden 
with fat one would expect to see every leucocyte in the central portions 
of the parenchyma, at least, more or less filled with fat, while those leu- 
cocytes near the basement membrane, and the lacteal wall should show 
many variations according as they were laden or uncharged with fat. 
On the contrary no such variation can be demonstrated, and the centrally 
placed cells contain no more fat than those near the chyle vessel or the 
basement membrane, (Fig. 12). Moreover, when so much fat is to be 
transferred one would expect to see these leucocytes discharging it near 
or against the lacteal wall, but I have never been able to demonstrate 
such a condition. Furthermore, if the leucocytes are so active in carrying 
fat one would expect them to be laden with their burden in some direct 
ratio to the abundance of fatty material. No such ratio exists. In some 
sections these cells are surrounded with fat, yet the lymphoid cells con- 
tain none (Fig. 8). Finally fat streams can be traced from the basement 
membrane to the wall of the lacteal with no leucocytes intervening (Fig. 
11). As already remarked there are four kinds of leucocytes in the villus, 
but one only is concerned in this, namely the epithelioid cell, for in the 
guinea pig fat does not occur in the lymphocyte or the polymorphonuclear 
cells (Figs. 2). 
In the demonstration of the presence of fat one must not rely wholly 
on the result given with osmic acid, for as Heidenhain has well said: 
‘‘Everything that stains black with osmic acid is not fat.’’ In preparation 
from guinea pigs fed on the ordinary diet, fixed with Flemming Fluid, and 
stained with iron alum and eosin, dark granules are found in these large 
lymphoid cells, which have the appearance of fat and for some time I con- 
sidered them as such. Later I noticed that in similar specimens fixed with 
absolute alcohol, and stained with hemalum and eosin, these granules were 
present and had the same dark or black appearance. Evidently then such 
granules could not have been fat since the alcohol agent would dissolve 
all the fat out of the sections. These granules were evidently particles 
