L^'^IPTTATTC ORGANS 



189 



shaped cells with bulging nuclei. These come from the walls of the 

 cavernous veins. 



Two views have been held regarding the vascular channels of the pulp. 

 According to one, these channels have complete walls, the blood-vessel system 

 of the splenic pulp being a closed system as in other organs. According to the 

 other, the cavernous veins or spleen sinuses into which the arterial capillaries 

 open, have fenestrated w<i\\?,—open system. These fenestra are of sufficient size 



w 



Fig. 113. — Section of Monkey's Spleen. Two pulp sinuses are shown and between 

 them some of the reticular tissue of the pulp. The sinus in the upper right corner is cut 

 transversely so that the longitudinal fibres of its wall are cut across and appear as a row 

 of dots. The prominent dark nuclei belong to the endothelium. _ The other sinus is cut 

 obUquely and a branch from it is seen partly in longitudinal section. It shows well the 

 disposition of both longitudinal and circular fibres. (ISIoUier.) 



to allow fluid and formed elements of the blood to pass out freely into the pulp 

 cords and elements of the pulp cords to pass freely into the vessels. From these 

 open-walled sinuses the veins proper take origin. The smaller veins, even those 

 within the trabeculae, have only endothelial walls. These uniting, form veins 

 which enter the septa and ultimately converge to form the splenic veins which 

 leave the organ at the hilum. 



Mollier^ describes the walls of the spleen pulp sinuses as having the following 



^ Arch. f. mikr. Anat., Bd. Ixxvi, 1910-11. 



