LY.MrHATIC ORGANS 



187 



centre (see page 173)- In the adult human spleen germ centres are 

 rarely seen. The blood-vessels of the spleen have a very character- 

 istic arrangement, which must be described before considering further 

 the minute structure of the organ. 



The arteries enter the spleen at the hilum and divide, the branches 

 following the connective-tissue septa. The arteries are at first ac- 

 companied by branches of the splenic veins. Soon, however, the 

 arteries leave the veins and the septa, and pursue an entirely separate 



Spleen sinus 



Sheath artery 



Pulp artery- 



Pulp vein 



Beginning of in- 

 terlobular vein 



Capillary net- 

 work of nodule 



Central arterv 



Interlobular vein 



Interlobular 

 artery 



Trabeculae 



Penicillus 



Lobule 



Hilus Reticulum Spleen nodule Capsule 



Fig. hi. — Scheme of Human Spleen, x, Opening of arterial capillaries into spleen 

 sinus; xx, interruption of closed blood course at ends of arterial capillaries, at margin of 

 nodule, xxx. For sake of clearness, sinus is placed too far from margin of nodule. 

 (Stohr.) 



course through the splenic pulp. Here the adventitia of the smaller 

 arteries assumes the character of reticular tissue and becomes in- 

 filtrated with lymphoid cells. In certain animals, as e.g., the guinea- 

 pig, this infiltration is continuous, forming long cord-hke masses of 

 compact lymphoid tissue. In man, the adventitia is infiltrated only 

 at points along the course of an artery. This may take the form 

 of elongated collections of lymphoid cells — the so-called spindles — 

 or of distinct lymph nodules, the already mentioned splenic corpuscles. 

 Although usually eccentrically situated with reference to the nodules, 



