1 784 



HI MAN ANATOMY. 



pigments, when injected into the arteries, pass into the veins. The walls of the 

 ampulla- arc verv thin and, towards the junction with the venous radicles, imper- 

 fect bring here' composed of the reticulum of the surrounding pulp-tissue I he 

 channSTbowever, are sufficiently definite to prevent the escape of the blood-cells 

 undrr m>nnal conditions, although the plasma constantly passes into the intercellular 



,-s of the pulp . Mall ). The walls of the venous spaces are even more pervious 

 than those of tin- ampulla, and, like the latter, possess only an incomplete endothehal 

 lining, supported externally by a mesh of circularly disposed elastic fibres. The endo- 

 thclium o.n^ts of narrow, elongated spindle-cells instead of the usual plate-like ele- 

 ments whu h line the larger splenic blood-vessels. The round or oval nuclei project 

 int. the lumen of the venous space beyond the level of the protoplasm of the cell, which 

 otten presents a distinct striation. . 



The \vnous spaces between the pulp-cords are the beginnings of more definite 

 channels, the intralobular veins, which pass from the primary compartments towards 



FIG. i 506. 



Capsule 



Primary compartment 



Interlobular trabecula 



Intralobular trabecula 



Interlobular vein 



Malpighian body 



Splenic artery 



Diagram showing architecture of splenic unit ; splenic pulp is represented in only one compartment. (After Mall.) 



tin trabeculae between the lobules to become tributaries of the larger interlobular 



U occupying the periphery of the lobules within the boundary septa. These veins 



follow tin larger trabeculae until, finally, they emerge at the hilum to form the splenic 



vein. 



In their journey through the lobule, shortly after leaving the trabeculae, the 

 brandies <>f the splenic artery present marked local accumulations of lymphoid tissue 

 within their adventitia. These aggregations constitute the Malpighian bodies, or 

 splenic nodules. When seen in transverse section, they appear as conspicuous oval 

 ieiiselvmph tissue surrounding the artery, which usually occupies a somewhat 

 eccentric position. I .ong it udinallv sectioned, the splenic nodules appear as cylinders. 

 They correspond in structure with true lymph-nodes, possessing germ -centres. Sur- 

 rounding the Malpighian Ixxlies, the spleen-tissue presents the usual arrangement of 



the pulp-cords. 



The splenic pulp contsta of a delicate supporting reticulum, continuous with 

 the terminal ramifications d the intralobular trabecuhe, and the cells contained within 



