448 WILLIAM H. F. ADDISON 



SUMMARY 



The cycle of changes associated with the phagocytic activity 

 of the splenocytes of the rabbit has here been followed. 



When washed pigeon corpuscles are injected intravenously, 

 they are rapidly hemolyzed. The hemolysis of the pigeon blood 

 results in the liberation of great numbers of bone-marrow cells, 

 mature and immature. These are caught within the spleen, and 

 quickly begin to be ingested by the splenocytes. The spleno- 

 cytes grow with their increased contents, until at the sixteen-hour 

 stage they reach a very large size. As many as twenty cells are 

 visible in a 4 n section of a splenocyte, measuring 55 X 23.4 n. 

 As digestion proceeds, the splenocytes become smaller, and at 

 the forty-eight-hour stage they are much reduced in size, some 

 not much larger than normal. 



Of the products of hemolysis of the pigeon blood after a single 

 injection, little remains within the organs of the body and most 

 is excreted through the kidneys within sixteen hours. In the 

 spleen, the splenocytes have an increased amount of iron-con- 

 taining substances, while the endothelial cells show, for the most 

 part, very little. The comparatively small results seen within 

 the phagocytic cells follow from the rapid reduction of the foreign 

 blood corpuscles to particles of a very small size, and from the 

 short time in which these fragments remain within the blood 

 stream. 



In this special experimental procedure, where cells and cell 

 fragments are the stimulus to phagocytosis, the splenocytes are 

 the first to act, and they continue to act as the main phagocytic 

 agents. 



