444 WILLIAM H. F. ADDISON 



splenocytes also contain small yellowish or light brown inclusions 

 derived from the original pigeon blood. Occasionally a spleno- 

 cyte is seen containing one single larger rounded mass of hemo- 

 siderin. While polymorphonuclears are still scattered about, no 

 distinct myelocytes were found. 



Forty-eight hours. The splenocytes are again easily detecta- 

 ble in the microscopic field, because of the deep staining of the 

 remains of the cells which they had ingested. These cellular 

 inclusions, for the most part, no longer resemble the original 

 cells. The nuclei show as shrunken round little masses, which 

 stain intensely with the hematoxylin, and no remains of their 

 cytoplasmic granules are seen. The size of the splenocytes has 

 much diminished, and has returned nearly to the size seen at 

 the early stages. A characteristic one, with a dozen little dark- 

 stained dots within it, measured 18 X 15 /x. Others, in which 

 the digestion of the cells has not advanced so far, are of larger 

 size. In some cells, in addition to the shrunken remains of the 

 nucleated cells, are seen yellowish granules, derived from the red 

 blood corpuscles of the pigeon. The polymorphonuclears are 

 few in number, and no myelocytes remain. 



DISCUSSION OF OBSERVATIONS 



In considering the results of these experiments there are several 

 variables, which have to be taken into account. First, in the 

 washing out of the spleen, the perfusion is more successful in 

 removing the contents of the vascular channels in some cases 

 than in others. However, as mentioned before, the result is 

 never complete washing-out, and by studying various areas in 

 the sections one can reach definite conclusions as to the relative 

 number of the different types of cells present. A second and 

 even more important point is the difference in amount of reaction 

 which the bone-marrow gives. In some animals apparently 

 great numbers of cells are released and in others relatively few. 

 This may depend upon the age of the rabbit, but many other 

 factors must be considered before a solution can be arrived at. 



