128 



THE LYMPHATIC SYSTEM 



(Fig. 76.) Within each is one or more small arteries, usually eccen- 

 tric; a feature which serves to identify spleens so organized. The 

 red pulp is composed of a reticular network, diffuse lymphoid tissue, 

 and sinusoids filled with blood. 



Fig. 76. — Spleen of the woodehuck, showing the large splenic corpuscles scattered 

 through the diffuse red pulp. The nodules have light germinal centers and arterial 

 branches appear in their peripheral portion as small, open, white areas. 



The microsco]jic structiu-e of a mannnalian spleen is clarified by 

 an understanding of the distribution of blood vessels in it. The 

 main splenic artery and splenic vein enter at the hilum and each 



Splenic 1^\^ 

 sinusoid 



Fig. 77. — Diagram showing scheme of circidation in the spleen. 



vessel dixides into branches which arc su})p(»rtc(l by the branching 

 tra})eculie. As the trabccuhe divide, each supports a l)raiich of an 

 artery and an accom])anying vein. Small arterial branciies lea\'e 

 the trabecular tissue and enter the lymphoid tissue. (Fig. ~~.) 



