24 
HEMOLYMPH NODES OF THE SHEEP 
these injections; and that they were not extravasations is shown by the 
entire absence of points of rupture, and by the identical character of the 
injection masses in nodes injected indirectly from an adjacent one, under 
conditions of free outflow to the vena cava through the vein common to 
several nodes. For under such conditions serious structural derange- 
ment is avoided, or at least made improbable, because excessive pressures 
cannot be produced if the entrance of the injection mass is a very grad- 
ual and gentle one. The irregularity in form of the injection mass is 
further accounted for by the fact that the venous lacunae or true sinuses 
are encroached upon to a varying extent by the surrounding parenchyma, 
thus offering different amounts of obstruction to the onward flow of the 
injection masses or fluids; and by the fact that a partial injection of such 
wide, irregular channels must of necessity vary greatly in calibre. 
The partial character of the injections in hemal nodes injected from 
the arterial side can be accounted for by the fact that the path of least 
resistance is undoubtedly in the direction of intra-vitam flow. Hence 
the injection mass can easily enter some empty venous lacuna or sinus, 
and pass directly into the vein or the larger venous radicles^ rather than 
flow from one lacuna to another, until all or almost all are filled. Conse- 
quently it happens that only a sufficient number of venous lacunae may 
be injected to conduct the injection mass away as fast as it enters through 
the artery. Since both the arterioles and capillaries, and to a less extent 
also the venous lacunae, are usually in a state of partial or total collapse 
and more or less encroached upon by the parenchyma, they naturally offer 
varying resistances to the injection mass. Consequently limitation of it 
to certain lacunae is further promoted. The injection of the venous 
lacunae which lie at the periphery of the node in the lymphatic tissue, 
directly internal to the peripheral or subcapsular blood space, to the ex- 
clusion of those more centrally located, can be explained by the fact that 
the vein is often in more direct connection with them, as shown in fig. 8 ; 
and that as it leaves the node it rarely receives a number of tributaries 
which encircle the node, pierce the capsule, enter the lymphatic tissue, 
and open directly into these lacunae near the periphery. The presence of 
accessory or accessory tributary veins also can explain why only a very 
small portion of a section of a node may contain injection mass, and why 
the injected fluid, in case of puncture injections, can rarely be seen to 
leave the punctured node in several directions. 
In those instances of venous injections in which some of the central 
or internal and the peripheral blood spaces contain injection mass, the 
path taken by the latter can usually be found easily in numerous places. 
