38 THE CIRCULATORY SYSTEM. 
What is the relation of the lymphatic vessels to the lymph nodes ? 
The afferent vessels split up into branches as they enter the node 
through the capsule. There they communicate with the spaces 
between the lymph cords and nodules called lymph sinuses. The 
efferent vessels continuous with these sinuses leave the nodule in a 
divided manner usually at the hilum. These branches soon unite. 
THE SPLEEN. 
In studying the spleen what are the points to consider ? 
Capsule, trabeculz, Malpighian bodies or nodules, the spleen pulp 
and the bloodvessels. 
Of what is the capsule and trabecule composed ? 
The capsule consists of a dense layer of connective tissue fibres 
intermixed with a few smooth muscle cells. It enters the hilum with 
the bloodvessels, acting as their support. It unites with a complicated 
system of septa and trabeculz which are produced by processes dipping 
in from the capsule. The nodules and spleen pulp lie in these spaces 
between the septa and trabeculae. 
Describe the Malpighian bodies or nodules. 
They are rounded masses of lymphoid tissue scattered through the 
spleen substance. 
How are they formed ? 
By the infiltration of the walls of the smaller vessels with lymphoid 
cells. The adventitia and connective-tissue sheath which surrounds 
the artery becomes very loose in texture and becomes infiltrated with 
lymphoid cells. At certain points the infiltration is very extensive, and 
nodules of these cells are formed. By this it will be seen that each 
nodule is traversed by a small artery. 
Of what is the spleen pulp composed ? 
Of multitudes of irregular anastomosing cords called pulp cords. 
Between these cords lie a series of branching channels called cavernous 
veins. 
Describe the pulp cords. 
They are made up of a delicate reticular tissue, in the spaces of which 
lie various kinds of cells, viz.: Lymphoid ceils, large colorless cells, 
with one or more nuclei, red bloodcells, whole and broken, large and 
small pigmented colorless cells. Also nucleated cells of the same color 
as the red bloodcells. These are supposed by some to eventually 
