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LYMPHATIC AND VASCULAR RELATIONS 2J 
The artery branches frequently, as it penetrates deeper into the node, 
the smallest branches usually being found easiest near the periphery. 
Although the arteries can only rarely be seen opening directly into 
venous lacunae, they can frequently be seen in the lymphatic tissue near 
them. Since the smallest arteries, arterioles, and the capillaries are prac- 
tically always empty and collapsed, identification of the capillaries is 
necessarily difficult. Rarely an artery can be seen to traverse a small 
node, branching as it does so, and leaving the node approximately oppo- 
site to the point at which it entered, with apparently the same calibre. 
(Fig. ii.) It is evident that such variations of the vascular system of 
the node as these can also easily account for a number of anomalous re- 
sults obtained in the course of injections. 
Immediately after piercing the capsule the veins, on the other hand, 
often communicate by means of very wide openings directly with the ex- 
tensive venous lacunae which lie parallel to the peripheral (sinus) blood 
space, when present, near the outer border of the lymphatic tissue; but 
they can only rarely be seen to communicate with the subcapsular or 
central or internal blood spaces of the parenchyma. (Figs. 8 and 10.) 
Less frequently they can also be seen to communicate directly with the 
deeper-seated lacunae, and with large blood spaces in depleted nodes. 
Accessory veins, which were clearly tributary to the peripheral (sinus) 
or subcapsular blood space, and hence affluent veins, were occasionally 
found, however. (Fig. 12.) In some nodes, on the contrary, it was 
impossible to detect the presence of a single vein or venule within the 
node itself, although serial sections were made. This was found to be 
the case even when numerous sections of arteries and arterioles could be 
found. This fact, and the entire absence of injected veins within some 
nodes, can be accounted for by the fact that in some*cases the veins ap- 
parently come into relation with the peripheral venous lacunae only. 
Consequently, in the absence of the peripheral (sinus) blood space they 
can be seen only where they pierce the capsule. Moreover, in some cases 
the trunk of the vein does not pierce the capsule at all, but merely comes 
into contact with it in such a way that communication with the intra- 
nodal circulation is effected by means of an opening in the adjacent wall 
of the vein, the node appearing to be sessile upon the vessel. Since no 
separate vascular trunk exists between the node and the tangent vein 
in these instances, the near wall of the latter might be thought of as be- 
ing continued through the capsule, and forming its venous circulation. 
As in case of the artery, however, so the vein in rare instances may run 
nearly through the center of the node, communicating directly with the 
