468 VERA DANCHAKOFF 



tumor cells. This capacity may well be a property of the 

 mesenchyme in general, but manifested only by the splenic 

 mesenchyme owing to its greater concentration in the spleen. 



The phagocytic and digestive capacity of the adult mesen- 

 chyme has long been recognized. Evans' macrophages and 

 Kiyono's histiocytes are isolated mesenchymal or endothelial 

 cells. In many of my own papers illustrations will be found of 

 phagocytic and digestive activity, exercised partly by isolated 

 mesenchymal cells and partly by mesenchyme, the cells of which 

 still retain their syncytial connections. 



The mode of ingesting the tumor cells differs to a certain 

 degree from that by which an isolated mesenchymal cell ingests 

 blood corpuscles or any other small fragments of dead material. 

 Adult splenic mesenchymal cells encircle the tumor cell and 

 form a capsule around it, and the tumor cell is finally found 

 situated in an intracytoplasmic vacuole of the Plasmodium. 

 The formation of such plasmodia, well known under the name 

 of foreign body giant cells, has long been observed around various 

 kinds of materials. The difference between the phagocytic 

 activity of an isolated mesenchymal cell and that exercised by 

 mesenchymal plasmodia may depend upon the size of the ob- 

 ject to be ingested. There must exist, however, a certain posi- 

 tive tropism of the adult splenic mesenchymal cell to the tumor 

 cell, for it has been proved that not every foreign material will 

 exercise such a tactic action upon the mesenchymal and wander- 

 ing cell. Nor will a definite material like the cells of the 

 Ehrlich sarcoma produce the same tactic effect upon the splenic 

 mesenchyme of different developmental stages. 



The results of the present work do not support the recent 

 hypotheses developed by Da Fano, Ribbert, Murphy, and others 

 concerning the immunitive role of the small lymphocyte. Murphy 

 states that a bit of adult splenic tissue grafted on the chick 

 allantois together with a tumor, adjacent to it or even at a dis- 

 tance, inhibits the take of the tumor, or, if grafted after the tumor 

 has taken, causes it to recede. He believes the small lymphocyte 

 to be responsible for the 'induced immunity,' though the mechan- 

 ism by which it effects this immunity remains obscure. The 



