LYMPHATIC GLANDS OR LYMPH NODES. 387 
ner and is thrown up into folds or flaps, one on each side of the vein. 
These form the valves of veins and are placed at varying intervals along 
the course of the vessel. 
LYMPHATIC VESSELS. 
What is the structure of lymphatic vessels ? 
Their structure is similar to that of the veins. Tracing them from 
the larger to the smaller vessels toward the peripheral distribution they 
pass into irregular branching and pouching chambers or channels, the 
walls of which are made up of a single layer of endothelial cells. 
These channels are called lymph capillaries. 
LYMPHATIC GLANDS OR LYMPH NODES. 
What are lymphatic glands or lymph nodes? 
They are round or oval-shaped bodies of varying size scattered along 
the course of lymphatic vessels, and through which the contents of 
these vessels pass. The depressed portion at which the blood and 
lymphatic vessels enter is called the hilum. 
What are the parts to be considered microscopically ? 
Capsule, trabeculz, cortical and medullary portions, lymph follicles 
or nodules, and lymph cords. 
Of what is the substance of a lymph node composed ? 
Of lymphoid tissue. 
Describe the capsule and trabecule. 
The capsule is the firm investing coat of the lymph node and is com- 
posed of dense connective tissue. Running down from the capsule 
there are a number of fibrous partitions or branches which act as a 
support to the substance of the node. These branches are called 
trabecule. 
Describe the cortical or outer portion of a lymph node. 
It is composed of lymphoid tissue more dense than in the medullary 
portions of the node, and scattered through it are the lymph nodules. 
These are round masses in which the lymphoid cells are arranged in a 
more dense manner than in adjacent portions. 
Describe the medullary portion. 
It is the inner portion of the nodule immediately adjacent to the 
hilum. In it the lymphoid tissue is disposed in cords called lymph 
cords, These cords are suspended from trabecule by reticular tissue. 
