THE SPLEEN. 



203 



The organ has a very typical blood supply. Its arteries enter, 

 at the hilum, or indented surface, and its veins pass out at the same 

 place. On the penetration of the vessels through the capsule, the 

 latter forms sheaths around them (trabeculae), but as soon as the 

 arteries and veins separate, the trabeculae envelop the veins alone. 

 The arteries break up into smaller branches, which in turn divide 

 into a large number of tuft-like groups of arterioles. Soon after their 

 separation from the veins, the adventitia (outer fibrous tissue coat) of 



-z'r 



Fig. 163. Portion of section of human spleen ; X '5- The figure gives a general 

 view of the structure of the spleen : a, Arteries with lymphoid sheaths ; cf, fibrous capsule ; 

 Mk, Malpighian corpuscle ; //, spleen pulp ; tr, trabeculae ; v, vein in trabecula ("Atlas 

 and Epitome of Human Histology," Sobotta). 



the arteries begins to assume a lymphoid character. This lymphoid 

 tissue increases here and there to form true lymphoid nodules, pos- 

 sessing all the characteristics already mentioned reticular tissue, 

 germ centers, etc. These are the Malpighian bodies, or corpuscles ; 

 they are not very plentifully represented in man. The Malpighian 

 bodies with their" germ centers are formative centers for the lympho- 

 cytes. The newly formed cells pass into the pulp and mix with its 

 elements, which are then bathed by the blood emptying from the 



