THE SPLEEN 



247 



smaller arteries part company with the veins when they leave the tra- 

 becula? and pass into the apices of the lobules. At the point of entrance 

 into the lobule the adventitia of the intralobular artery becomes in- 

 filtrated with lymphocytes, forming thus a spherical or fusiform 

 iymphoid mass, 

 the splenic nodule 

 (Malpighian cor 

 puscle) character- 

 istic of the spleen. 

 This arterial ves- 

 sel gives off nu- 

 merous branches 

 to the splenic 

 nodule, some of 

 which pass beyond 

 the confines of the 

 nodule into the 

 splenic pulp. 

 Some of these 

 nodules contain 

 germ centers. In 

 infancy all of the 

 nodules are said 

 to contain germ 

 centers. 



The artery 

 usually passes 

 excentri cally 

 through the nod- 

 ule. The nod- 

 ules are fre- 

 quently situated 



at the point where the artery branches and in consequence contain two 

 arterial vessels. Beyond the splenic nodules, the intralobular artery 

 breaks into a number of twigs, one for each lobular compartment. Within 

 each compartment, the arteriole divides into a brush of delicate precapil- 

 lary arterioles, the penicilli of Euysch. On these appear an ellipsoidal 

 condensation of reticular tissue forming the so-called splenic ellipsoids. 

 These arterioles (six to ten microns in diameter) are known as sheathed 

 arteries. The splenic pulp of the lobules can be divided into somewhat 



FIG. 251. DIAGRAM OP A LOBULE OF THE SPLEEN. 



A, artery lying in the center of the lobule; Am, a terminal 

 ampulla of the artery; C, intralobular vein; L, a splenic cor- 

 puscle; P, venous plexus within the pulp of the spleen; Tr, 

 fibromuscular trabecula within the lobule; V, interlobular 

 vein, lying in a large trabecula. (After Mall.) 



