THE SPLEEN. 



105 



The sustentacular or connective-tissue framework of the 

 spleen consists of a firm fibrous capsule enveloping the organ ; 

 of fibrous trabeculse or septa, continuous with the capsule, 

 traversing the organ in all directions and dividing it into small 

 compartments or lobules ; and of an open reticular tissue 

 filling these compartments. This reticular tissue, which is 

 of similar character to the retiform basis of lymphoid tissue, 

 consists of fibres interlacing to form open communicating 

 spaces or sinuses, w r hich are incompletely lined with stellate 

 flat endothelioid connective-tissue cells. These spaces open 

 directly into the bloodvessels, and, filled with free cells of 

 various kinds, form the splenic pulp. 



Scattered involuntary muscle-cells occur in the capsule and 

 larger trabeculae. 



The ample bloodvessels of the spleen enter at the hilum, 



FIG. 43. 



Portion of spleen, a, capsule ; 6, trabecula ; c, splenic pulp; </, Malpighian 

 corpuscle ; e, portion of artery. 



and the larger branches lie in the trabecular tissue as they 

 ramify through the organ. The terminal arteries and veins, 

 instead of being connected by capillaries, open into the reti- 

 form sinuses making up the splenic parenchyma, so that the 

 blood-current percolates through this spongy tissue in its pas- 



