SPLEEN 



213 



The splenic pulp consists of a reticular tissue framework (Fig. 50, 

 p. 61). It supports the terminal arteries and 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 determine which cells are inside and which are outside of the vessels 

 (Fig. 201). The nodules are not sharply separated from the pulp, so 

 that lymphocytes are abundant in their vicinity. These lymphocytes 

 enter the terminal veins and thus are removed from the spleen. In the 

 splenic vein the proportion of lymphocytes to red corpuscles is said to be 

 seventy times as great as in the splenic artery. One for every four red 



Pulp. 



Spindle-shaped 

 nodule. 



Sheathed artery. 



Capsule. 



Trabeculae. 



Central arteries in 

 splenic nodules. 



FIG. 20 1. PART OF A SECTION OF THE SPLEEN FROM AN ADULT MAN. X 15. 



corpuscles has been reported by two investigators, but later estimates are 

 lower. It seems evident that lymphocyte production is an important 

 function of the spleen. Another is the filtration of the blood passing 

 through the pulp. As in haemolymph glands, granular debris is found, 

 and there are phagocytic, pigmented, and eosinophilic cells. The phago- 

 cytes are cells with large round nuclei and considerable protoplasm. They 

 vary in size, but the small forms are most numerous; these are called splenic 

 cells. Some are described as multinucleate. Erythroblasts are not found 

 in the normal adult human spleen; they occur, however, in certain blood 

 diseases, and are normal' in some adult mammals, as in the skunk. They 

 are abundant in the spleens of human embryos. Giant cells are numerous 

 in the spleens of young animals but are seldom found in the human adult. 



