CIRCULATORY SYSTEM. 



127 



left side, as given above. The histology of the walls 

 of these vessels resembles that of the veins. 



3. Lymph Glands.. These represent adenoid tis- 

 sue, and consist of (i) reticular connective tissue and 

 (2) lymph cells. Lymph glands are found throughout 

 the body in connection with lymph vessels, fat and 

 connective tissue. They serve as filters to the lymph 



Gland. 



Fig. 91. A solitary lymph nodule from the human colon. At 

 a is seen the pronounced concentric arrangement of the lymph cells 

 (Bohm and Davidoff). 



and contribute white corpuscles to the blood. 

 Structurally, these nodes have a connective-tissue 

 capsule, that sends filaments into the node, called 

 trabecula. Within these meshes lymph cells are 

 densely packed around the periphery of secondary 

 nodules, which in turn occupy the cortex of each 

 node. The center of each nodule is known as the 

 germ center or lymph pulp. The periphery of each 

 secondary nodule, being densely packed with white 

 lymph-corpuscles, takes a darker stain than the 



