THE LVMFII NUDES 



125 



lymph nodules, varying in sliajx', tli()iiti|;li usually coiiiposed of oval 

 or ])yriforni masses of lym])h()i(l cells. Kxteudini; from the coarser 

 connective-tissue framework is a finer network of reticular cells and 

 fibers in whose meshes the lymi)h()id cells are held. The reticulum 

 extends between the nodules and trabecnhe and capsule, forming 

 cortical sinuses. x\fferent lym])h vessels entering; the capsules break 

 into capillaries connecting with these sinuses through which the 

 infiowing lymph passes into the interior. The lymphocytes pro- 

 duced in the nodules move through the reticulum into the cortical 

 lymph sinuses through which lym])h is slowly ])assing toward the 

 medulla. The size of the germinal centers varies with the degree of 

 mitotic activity in them, the active nodules having more marked 



■Afferent lymph vessel 

 apsiile 



Traheeula 



Reticular tissue 

 network 



Efferent lipnph vessel 



Fig. 74. — Diagram of a connective tissue and reticular tissue skeleton of a lymph 



node. 



germinal centers. Cells of the sinus walls become macrophages 

 and remove foreign elements from the hinph as it filters tlu'ough 

 (Fig. 75.) 



Medulla.— The internal ends of the connective-tissue trabeculge 

 form a network of coarse fibers between which extends the 

 reticulum of argyrophil fibers and reticular cells. Clustered 

 along the coarser connective-tissue network are rod-like masses of 

 lym])hoid cells known as medullary cords. Between them are inter- 

 connecting spaces, the medullary sinuses, with which the cortical 

 sinuses are continuous. The walls of the sinuses in the cortex and 

 medulla are formed by reticular and endothelial cells which, in case 

 of invasion by foreign substances, such as bacteria, become active 

 phagocytic cells, or macrophages. There is a slow distribution or 

 circulation of lymph from the lymph vessels at the cortex through 



