34 
HEMOLYMPH NODES OF THE SHEEP 
The Microscopic Structure 
Under low-power magnification a hemal node in section may show 
nothing but a thin capsule containing a solid mass of lymphoid tissue 
with few or no follicles or trabeculae, and with but a sprinkling of barely 
noticeable erythrocytes. Or, on the other hand, it may look like a sac 
filled with blood in which the coarser framework of the node is revealed 
here and there, but with only a few small masses of lymphoid tissue with 
or without lacunae containing some blood cells and granular detritus. 
In short, then, the appearance of a hemal node on section may be similar 
to that of a section of sheep's spleen without Malphighian corpuscles and 
few erythrocytes and but few and small trabeculae, on the one hand; or 
that of a sack of blood containing a few small islands, or merely scat- 
tered lymphocytes or groups of them lying near small connective tissue 
trabeculae, on the other. Rarely, too, one finds a practically empty node 
containing but little lymphatic tissue surrounded by scattered erythrocytes 
and enclosing wide-open spaces ; the venous lacunae of Weidenreich, con- 
taining some granular detritus and degenerated blood corpuscles. Be- 
tween these extremes literally every conceivable gradation is found. The 
cross-section, for example, may be crowded with follicles (figs. 6 and 14) 
which encroach on each other, on the blood islands, and even on the per- 
ipheral (sinus) blood space; or, perchance, they may be absent alto- 
gether (fig. 15). A classification of follicles into definite types, as reported 
by Vincent and Harrison [28] , was never possible ; and such differences 
as were observed were structurally of a very minor character. A like 
inconstancy is found in case of the empty venous lacunae found in the par- 
enchyma, which are frequently very conspicuous in nodes containing much 
blood but little lymphatic tissue. (See figs. 16 and 17.) It is these 
spaces, I take it, which have probably been mistaken for lymph spaces. 
Equally great variations exist in all the constituents of hemal nodes, 
save perhaps the capsule and the artery. These are the least subject to 
variations ; although it is evident that in a node which practically repre- 
sents a sac of blood the original distribution and disposition of the artery 
must also have been modified very profoundly. It follows, to be sure, 
from these considerations that a node having neither blood islands nor 
blood spaces, not even a peripheral (sinus) blood space or evident venous 
lacunae, may yet be a true hemal node. And, on the contrary, it also 
follows that a node containing a mere remnant of lymphatic tissue in a 
mass of blood may also be a true hemal node (figs. 18 and 19). This 
being the case, it is highly probable that these facts account in some meas- 
ure at least for the confusion regarding the occurrence of mixed nodes, . 
