THE SPLEEN. 



^785 



FIG. 1507. 



Germ-centre 



and supported by the mesh-work. The pulp-cells include a variety of elements, the 

 most constant of which are : (a) small mononuclear lymphocytes ; ($) leucocytes of 

 the mononuclear and polymorphonuclear types ; (c) red blood-cells ; (</ ) nucleated 

 red blood-cells ; (e) large 

 phagocytic cells containing 

 disintegrating red blood-cells, 

 or pigment particles derived 

 from the destruction of the 

 same; (_/") giant-cells with 

 large composite nuclei, chiefly 

 in young animals. In addi- 

 tion a variable amount of free 

 pigment is present, probably 

 from the broken-down red 

 blood-cells. During embry- 

 onic life and later, in response 

 to unusual demands for addi- 

 tional red blood-cells, as after cord" 

 severe hemorrhage, the spleen 

 may be the birthplace of red 

 corpuscles ; these are at first 

 nucleated, but soon lose their 

 nuclei. 



Peritoneal Relations. The spleen is developed in the posterior mesogas- 

 trium, and usually retains all, or nearly all, of its original serous covering, which is 

 reflected at the hilum over the vessels. The splenic artery reaches the spleen 

 through the peritoneal duplicature known as the lieno-renal or lieno-phrenic fold, 

 which leaves the abdominal wall at the tail of the pancreas. The vessels for the 

 stomach leave the artery before it enters the spleen by the fold known as the gastro- 



Puip 



Venous space 



Transverse section of Malpighian body, showing its relations to sur- 



rounding pulp-tissue, x 120. 



FIG. 1508. 



Arteriole 



Pulp-cords 



Venous space 



Arteriole 



Cell containing 

 pigment 



Section of spleen, showing: details of pulp-tissue. ;<>o. 



splenic omentum, which extends forward to the greater curvature and above to the 

 back of the fundus of the stomach. These two folds, stretching respectively back- 

 ward and forward from the hilum, bound a part of the lesser cavity of the peritoneum. 



