162 



HISTOLOGY. 



The terminal veins begin as dilated structures (sometimes unfortu- 

 nately called 'splenic sinuses,' or 'ampullae,' the latter term being applied 

 also to the terminal arteries) . Their endothelial cells are so long and slen- 

 der as to suggest smooth muscle fibers, and like certain other endothelial 

 cells they are contractile. Their edges are not closely approximated, so 

 that corpuscles may pass between them freely as shown in Fig. 182. Around 

 them are encircling reticular tissue fibers, and a continuous basement mem- 

 brane-like structure has been described stretching across the intervals be- 

 tween the endothelial cells. The existence of such a membrane has re- 

 cently been denied. A peculiar feature of the endothelial cells is their 



Capsule. 



Pulp 



Spindle-shapet 

 nodule. 



Sheathed artery. 



Trabeculae. 



Central arteries 

 in splenic nodules. 



FIG. 183. PART OF A SECTION OF THE SPLEEN FROM AN ADULT MAN. X 15. 



projection into the lumen of the vessel, their nuclei being at the summits 

 of these elevations as shown in Fig. 182. Several terminal veins unite to 

 form a pulp vein which enters a trabecula in which it passes toward the 

 hilus. The trabecular veins join to form the splenic vein. 



The splenic pulp consists of a reticular tissue framework such as has 

 been described on p. 39. It supports the terminal arteries and the term- 

 inal and pulp veins, and in its meshes are the white and red corpuscles 

 passing between them. 



The pulp appears as a diffuse mass of cells infiltrated with red cor- 

 puscles, and since the vessels within it are thin walled and hard to follow, 

 likewise containing corpuscles, it is often impossible in ordinary sections to 



