H A VERA DANCHAKOFF AND S. M. SEIDLIN. 



of injected edestin disappeared from this region, but the millions 

 of cells which after 2 days of injection invaded it have left it. 

 There is no indication whatever of degenerative processes in the 

 lymphoid phagocytes. Their changes and fate will be discussed 

 in the following paragraph. 



3. Phagocytes after Digestion. A cursory glance and com- 

 parison of a small lymphocyte traversing within the blood current 

 the region of injection (Figs. 4 and 5) with the phagocytes scat- 

 tered through it, is sufficient to establish the difference between 

 these two types of cells, as such. Nevertheless, as seen from the 

 preceding sections, the phagocytes did develop from the small 

 lymphocytes of the blood stream through a series of changes 

 which the emigrated cells exhibited while approaching the in- 

 jected mass. The exercise of digestive activity by the lymphoid 

 phagocytes seems to have further fixed the acquired structural 

 characters and most of the phagocytes are seen to retain their 

 new structure. They now appear in the form of large cells with 

 especially abundant cytoplasm. They are very similar to the usual 

 types of phagocytes encountered in the loose connective tissue and 

 described under many different names (resting or histiotopic 

 wandering cells, clasmatocytes, macrophages, cellules rhagio- 

 crines). Only the loose mesenchyme in the tadpole does not 

 normally contain any wandering cells. The mesenchymal cells 

 though observed to transform occasionally into wandering cells 

 after injection, are extremely scarce. No mononuclear leucocytes 

 are present in the blood current at that time. The only cells 

 capable of further progressive development and differentiation in 

 the tadpole blood are cells which exhibit the structure of small 

 lymphocytes. They are seen indeed to give rise suddenly to 

 numerous generations of phagocytes. These cells after digestion 

 retain their newly acquired structure and are easily recognizable. 

 They exercise their digestive power locally but do not remain in 

 this region indefinitely. They are seen to increase in number 

 while supplies of injected edestin last, but as soon as all of it is 

 consumed, the immigration of new cells stops. The phagocytes 

 remain in this region while they are actively digesting the injected 

 edestin, but then begin to emigrate individually. By far the great- 



