BLOOD 



505 



back to branches of the splenic vein in the trabeculae. The 

 pulp may thus be compared Avith the blood sinuses of the 

 hffimolymph glands, and the spleen may be considered as 

 being a still further development of the hsemolymph gland 

 from the lymph gland (tig. 205). 



2. Functions — 



A. Blood Formation. — -(1) Lymphocytes are undoubtedly 

 formed in the Malpighian corpuscles. But their formation 

 is probably unimportant. Their number is not greater in 

 the blood of the splenic vein than in that of the artery, and 



LYMPH 



H.EMOLYMPH 



SPLEEN 



Fig. 205. — To show the Relationship of the Spleen to Lymph Glands and 

 Hremolymph Glands. The black indicates lymphoid tissue ; the 

 coarsely spotted part, lymph sinuses, and the finely dotted part, 

 blood sinuses. (Lewis.) 



removal of the spleen causes no change in the number in 

 the blood. 



(2) Erythrocytes. — That the spleen is not a seat of the 

 formation of erythrocytes in normal extra-uterine life is 

 indicated — (i) by there being no greater number in the 

 blood of the splenic vein than in that of the splenic artery ; 

 (ii) by the fact that removal of the spleen causes no 

 decrease in the total number of erythrocytes ; and (iii) by 

 the equally rapid regeneration of erythrocytes in animals 

 from which the spleen has been removed and in normal 

 animals. 



B. Blood Destruction. — 1. That it takes no active part in 



