DIGESTIVE ACTIVITY OF MESENCHYME. 113 



The digestive power is being exercised by the lymphoid phago- 

 cytes in a most conspicuous way. It is questionable, however, 

 whether or not polymorphonuclear leucocytes actually digest the 

 edestin particles found rather numerous in their cytoplasm at ear- 

 lier stages. Mention was made above regarding degenerative 

 changes frequently observed in the leucocytes within the injected 

 mass. But even those leucocytes which persist at a stage when a 

 great part of the edestin has been digested do not seem to prosper. 

 They are now frequently seen ingested by the lymphoid phagocytes 

 and undergoing a digestion within them. In Fig. 4 three lymphoid 

 phagocytes are seen to contain polymorphonuclear leucocytes in 

 their cytoplasm ; the latter, themselves, had acted as phagocytes, 

 for numerous edestin granules are still present in their cytoplasm. 

 They succumb, however, now to the phagocytic activity of lym- 

 phoid phagocytes. 



The structure of the lymphoid phagocytes is so characteristic 

 as to permit an unmistakable judgment regarding their past ac- 

 tivity and origin. And the new phase of their digestive activity 

 which now is directed against the polymorphonuclear leucocytes 

 is of great interest. Both lymphoid phagocytes and polymorpho- 

 nuclear leucocytes develop in the same hemopoietic center and 

 from the same stem cells. Both were brought in by the blood 

 current to the region of the injection; they both moved into the 

 injected mass and began their active ingestion of the edestin 

 particles. But while ingestion by lymphoid phagocytes is fol- 

 lowed by an intensive digestive activity, the polymorphonuclear 

 leucocytes, though containing ingested edestin,, seem to remain 

 inert. The exercise of digestive activity by the lymphoid phago- 

 cytes seem to have stimulated and sharpened their digestive power 

 and they begin to display it against cells of their own kind, the 

 granular leucocytes. 



The digestion of the injected mass of edestin is completed in 

 about 6 or 7 days. There is no more trace of edestin granules 

 in the tadpole tail at this time and the whole region, in which the 

 edestin appeared as a compact strand of a 0.3-0.5 mm. in thick- 

 ness, has been reduced to a line hardly perceptible to the naked 

 eye and no more than 100,0, thick. Not only has the whole mass 



