THE SPLEEN 



249 



Differentiation of Spleen from Lymph Node. The spleen in sec- 

 tion can be readily differentiated from a lymph node : it lacks a_dennite 

 subdivision into cortex and medulla characteristic of the lymph node, its 

 pulp contains a preponderating number of red blood corpuscles, and its 

 capsule is relatively very robust and contains a greater amount of smooth 

 muscle. The spleen may be thought of as a congested lymph node, con- 

 sisting wholly of medulla, throughout which are scattered lymph nodulea, 

 the splenic nodules. It might quite properly be described as a huge hemo- 

 lymph node. 



Splenic Cells. Besides erythroplastids and occasional erythrocytes, 

 the pulp contains also the 

 several varieties of leuko- /f 



cytes: lymphocytes, granu- 

 locytes, a few megakaryo- 

 cytes, and blood-platelets. 

 The leukocytes of the spleen 

 are largely of the large 

 mononuclear type. These 

 are notably phagocytic, fre- 

 quently containing erythro- 

 plastids, fragments of cells, 

 pigment and other granular 

 debris. They are in a sense 

 specific for the spleen, hence 

 called splenic cells. Mega- 

 karyocytes are abundant in 

 the fetal spleen during its 

 period of erythropoietic 

 function, but rare in the 

 adult spleen. 



Lymph Supply. The 

 lymph supply of the spleen 



is relatively scanty. The capsular is independent of the parenchymal 

 system, which latter consists . chiefly of perivascular lymph spaces and 

 vessels draining toward the hilum. 



Nerve Supply. The innervation includes both medullated and non- 

 medullated fibers. The latter predominate, and are distributed to the 

 smooth muscle of the capsule, trabeculae, and blood-vessels. 



Functions. The spleen functions as a leukopoietic organ and as a 

 blood filter. This is indicated both by the direct evidence of lymphocyte 



FIG. 253. TYPES OF CELLS FROM A SMEAR PREP- 

 ARATION OF THE PULP OF THE HUMAN SPLEEN. 



o, lymphocytes; b, polymorphonuclear neutro- 

 phil leukocytes whose granules are not stained 

 by the method used; c, large mononuclear leuko- 

 cyte; d, eosinophil cells; e, basophil cell; /, red 

 blood corpuscles. Hematein and eosin. X 1200. 



