BLOOD AND LYMPH 



221 



these, the vessels open into a series of complex sinuses lined 

 by endothelial cells of large size, from which the blood is 

 collected into channels, the venous sinuses, which carry it 

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

 pulp is thus comparable with the blood sinuses of the 

 haemolymph glands, and thd spleen may be considered as 

 being a still further development of the haemolymph gland 

 (fig. 106). 



So far no decrease in the number of erythrocytes in the 

 blood leaving the spleen has been recorded. In the cells of 

 the spleen pulp and chiefly in the endothelial cells yellow 

 pigment and simple iron compounds are frequently found, 



LYMPH 



H.EMOLYMPH 



SPLEEN- 



FIG. 106. To show the relationship of the Spleen to Lymph Glands and 

 Hfemolymph Glands. The black indicates lymphoid tissue ; the coarsely 

 spotted part, lymph sinuses, and the finely dotted part, blood sinuses. 

 (LEWIS.) 



indicating that haemoglobin is being broken down. But the 

 idea that the spleen plays an important part in the actual 

 destruction of erythrocytes seems to be negatived by the 

 fact that, when blood is injected, the cells are broken down 

 no faster in an animal with the spleen intact than in an 

 animal from which the spleen has been removed. While 

 the spleen appears to have no action in killing and destroy- 

 ing erythrocytes, its cells, like those of the sinuses of the 

 Lymph Glands and Haemolymph Glands, have the power of 

 taking up dead and disintegrating erythrocytes and storing 

 the iron for future use in the body. These organs may, in fact, 

 be regarded as the graves of the dead erythrocytes. 



