150 



THE LYMPHATIC SYSTEM 



phatic vessels pour their contents. The lymph on entering the 

 gland is thus permitted to enter the spaces of the reticulum and 

 percolate through the lymphatic follicles of the cortex before it 

 can reach the looser portions of the medulla. Each of the follicles 

 of the cortex contains a germinal center in which lymphatic cor- 

 puscles are actively formed by mitosis, and from which the leuco- 

 cytes readily escape along the lymphatic channels of the reticulum 

 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 trabecula6 enters the medulla, carry- 

 ing with it the larger blood vessels to be distributed to all portions 

 of the gland. The finer ramifications of these medullary trabeculae 

 are continuous with those of the cortex. 



The lymphoid tissue of the medulla is divisible into the denser 

 branching lymphatic cords, in which the leucocytes are closely 



FIG. 148. TKANSECTION OF A MESENTERIC LYMPHATIC NODE or MAN. 

 Hematein and eosin. Photo, x 38. 



packed, and the intervening pulp spaces, in which leucocytes are 

 less numerous, and the reticulum of which is continuous with that 

 of the cortical follicles. 



The pulp spaces are broad channels, which are occupied by a 

 reticulum whose meshes are partially filled with lymphatic cor- 



