224 RALPH DOUGALL LILLIE 



becomes evident, the chromatin at the same time increasing in 

 amount and in coarseness of karyosomes and the nucleolus los- 

 ing its metachromasia and blending with the nuclear chromatin, 

 and the cytoplasm becomes less and less strongly basophil as the 

 nucleus assumes its final polymorphous form and the granules 

 increase in number and come to be purely oxyphil. 



Since phagocytosis of erythrocytes is absent in this extravas- 

 cular tissue, it seems very improbable that these eosinophil 

 granules arise as fragmentation derivatives of ingested hemo- 

 globin containing cells, as maintained by Weidenreich ('11). 



The interpretation of the eosinophil endothelium cell described 

 above is a matter of difficulty, but it seems possible that this 

 may be just another manifestation of the close relationship of 

 the endothelium cell and the blood-cell. Danchakoff ('16 d) has 

 used differentiation into similar end types as a proof of identity 

 of stem cells in regard to the small cortical cells of the chick 

 thymus and their mother cells. So it seems here that the dif- 

 ferentiation of an endothelium cell into an eosinophil granu- 

 locyte would tend to show the identity of the endothelium cell 

 with the large lymphocyte, which is the mother cell of the eosin- 

 ophil granulocyte. According to the view of exogenous origin 

 of eosinophil granules, it would merely be a proof of phagocytic 

 activity on the part of the endothelium cell. Ordinarily phag- 

 ocytosis is followed by intracellular digestion, and not by the 

 preservation of the fragments of the ingested cell as an integral 

 part of the phagocyte, even when autogenous erythrocytes are 

 ingested by the endothelial phagocytes of the liver and spleen 

 (Kyes, '15). The hemosiderin granules which are formed as a 

 result of the intracellular digestion of red cells have no resem- 

 blance to true eosinophil granules. 



Mast cells. This type of cell is first seen extravascularly in 

 the 16-mm. stage. Maximow ('10) finds them in Rana only 

 after the metamorphosis. Mietens ('10) does not find any mast 

 cells at all, which is probably due to mast granules being soluble 

 in such acid fixatives as he used. In Bufo halophilus these gran- 

 ules resist the action of water after fixation with Zenker formol. 



