236 



THE LYMPHATIC SYSTEM 



Afferent LynphV<** e *> 



An afferent lymph vessel, pursuing its course within the capsule, 

 enters the lymph node by a number of subdivisions which penetrate the 

 deeper layers of the capsule and open into a peripheral lacunar space, 

 the lymph sinus, which separates the inner surface of the capsule from 

 the adjacent lymphoid tissue, but which is bridged across at frequent 

 intervals by the fine strands of lymph reticulum. 



The lymphoid tissue, which forms the substance of the node, consists 



of a dense peripheral 



portion, the C T te X , 



formed by closely 

 packed lymph nodules, 

 and a looser medulla in 

 which are columnar ac- 

 cumulations of dense 

 lymphoid tissue, the 

 lymph cords. 



Cortex. The nod- 

 ules of the cortex are 

 partially separated 

 from each other by sep- 

 tum - like trabeculae 



which extend inward 

 from th 



FIG. 242.-DIAGRAMMATIC ILLUSTRATION OF A LYMPH Sule > EIld &l U S 



NODE. the peripheral lymph 



sinuses are continued 



into the substance of the node to partially surround its lymph nodules. 



Each lymph nodule is thus surrounded, except at its central pole, by 

 a peripheral lymph sinus, into which the afferent lymphatic vessels pour 

 their contents. The lymph on entering the gland is thus permitted to 

 enter the spaces of the reticulum and percolate through the lymph 

 nodules of the cortex before it can reach the looser portions of the 

 medulla. Each of the nodules of the cortex contains a germinal center 

 in which lymphocytes are actively formed by mitosis, and from which 

 the lymphocytes readily escape along the lymph channels of the reticu- 

 lum into the more open meshes of the medulla. 



Medulla. The medulla occupies the center of the gland, and at 

 one point, the hilum, it reaches the surface. At this point a considerable 

 mass of fibrous trabeculae enters the medulla, carrying with it the larger 

 blood-vessels to be distributed to all portions of the gland. The finer 



