LYMPHATIC AND VASCULAR RELATIONS 
2T 
Before giving a statement of the results obtained by these injections, 
a rough sketch of the microscopic structure of the more usual hemal 
nodes seems advisable. In the majority of these nodes, a view of a sec- 
tion made in any plane presents the following well-known appearances. 
Externally there is a fibrous capsule varying considerably in thickness 
in the same and in different species, beneath which there usually is found 
a continuous or, oftener, a discontinuous so-called peripheral sinus, of 
inconstant width, which generally contains more or less blood and lym- 
phocytes. As a rule, by far the larger area of the node is composed of 
lymphatic tissue, containing the well-known blood sinuses, or better, 
blood islands or spaces.* 
A definite cortical and medullary portion, or an arrangement of the 
lymphatic tissue into medullary cords, was never seen. The arteries are 
inconspicuous as a rule, and the veins frequently still more so. In addi- 
tion to the inconstant, large central venous spaces in direct connection 
with veins more or less evident partially collapsed or open spaces, the 
so-called venous lacunae of Weidenreich may also be present through- 
out the parenchyma. When evident they are usually best seen near the 
periphery of the parenchyma, and frequently contain a small number of 
erythrocytes and lymphocytes, the former often being found in varying 
states of degeneration. The blood islands and spaces other than the 
peripheral or subcapsular blood space, and the main arteries, often have 
a more central position, however; but the veins generally branch soon 
after entering the node and traverse the peripheral sinus, or better the 
marginal or subcapsular blood space. Although rarely noticeable 
throughout the node, the trabeculae are few and small, as a rule. The 
coarser reticulum is plainly visible under low-power magnification, and is 
more evident in the partially filled blood spaces, especially in the marginal 
one. Since this sketch is to serve merely as a basis for a statement of 
results obtained by injection, a more detailed and accurate statement of 
structural variations and relations is deferred. 
Injections made from the vena cava, and by puncture from a node, 
always gave a very characteristic and uniform result. No matter how 
little of the injected fluid gained access to the node, it almost always lay 
as an exceedingly irregular mass, often of minute breadth, which zig- 
*Since the blood islands are usually masses of erythrocytes contained in the 
lymphatic tissue, rather than empty spaces temporarily devoid of blood, although 
such undoubtedly occur, the term blood space might preferably be restricted to the 
empty areas, which once contained blood islands ; and since neither of these nor the 
peripheral sinus are really such, the term sinus had better be restricted to the dilated 
venous radicles in direct connection with the circulation. 
