DIGESTIVE ACTIVITY OF MESENCHYME. 99 



enormous amounts of introduced material were easily digested 

 within the tadpole tail, the details of this process and especially 

 the structure and origin of those cells which exercised this ac- 

 tivity were determined. When it was found that the region into 

 which the material was introduced and which was promptly in- 

 vaded after the experiment by numberless cells was as promptly 

 abandoned by most of them, an attempt was made to determine 

 their new whereabouts and to identify them. This part of the 

 work has so far been only partly successful. The ultimate dis- 

 tribution of the phagocytes will be studied further in greater detail 

 and the results given in another paper. 



Material and Method Used. 



The transparent tail of the tadpole has been frequently used 

 not only as a convenient object for observing normal processes 

 of growth and differentiation, but also as a medium in which the 

 activity of the various stroma cells, under experimental conditions, 

 could be studied with remarkable ease. Work on the tadpole 

 tail has been done in this country chiefly by Eliot R. Clark and 

 Eleanor Linton Clark. They studied in it the growth of vessels 

 in vivo. They introduced under its epidermis microscopic par- 

 ticles of paraffin, India ink, croton oil and starch granules and 

 studied the reaction called forth in the adjacent tissues by the 

 presence of these foreign materials. Some of the materials used 

 by them (paraffin and India ink) were of such a nature as 

 would lead us to expect only a physical reaction from the adja- 

 cent cells. Among the other material used by them, the croton 

 oil produced upon the adjacent tissue injurious effects such as it 

 would upon any other living tissue. Uncooked starch granules 

 produced no other effect than foreign bodies, while starch gran- 

 ules cooked to the point of gelatinization proved to be a powerful 

 chemotactic agent for leucocytes. Ingestion of such starch 

 granules took place, but digestion of it was not followed. 



The result of this work did not permit of any decisive conclu- 

 sions regarding the digestive activity of the tadpole stroma for 

 the simple reason that most of the substances used are not 

 digestible. If the same material were introduced into our regu- 



