DIGESTIVE ACTIVITY OF MESENCHYME. 



dermal anlage, the intracellular digestive power seems to be lost 

 by a great number of highly differentiated mesodermic structures 

 but is being retained by those mesenchymal elements, which, scat- 

 tered through the whole organism, remain practically undiffer- 

 entiated. 



The conditions are by far more striking in those classes of ani- 

 mals whose eggs, as in the case of the tadpole, are rich in yolk, 

 but segment completely. Though segmentation results in this 

 case in uneven distribution of yolk among the various groups of 

 cells, nevertheless all of them contain nutritive material and 

 gradually digest it. The mesodermal cells are in this case 

 developed in intimate association with the primitive entoderm, at 

 a time part of it. The primitive blood cells are loaded with yolk 

 granules gradually digested and used up. Later, however, the 

 mesenchyme and its derivatives not being in contact with undi- 

 gested protein, digestive capacity is not exercised by these tissues. 

 But phagocytic digestive power remains inherent in them and is 

 revealed every time mesenchyme or its derivatives are in the pres- 

 ence of particulate protein. 



As seen from the preceding section, the injected mass is sur- 

 rounded, six hours after injection, by a great number of wan- 

 dering cells (Fig. i) of different nature. Some of them are 

 actually seen within the injected mass. The polymorphonuclear 

 leucocytes are not only first to appear around the injected edestin, 

 but they also are the first to bore their way into the rather compact 

 mass of edestin. Wherever a group of edestin particles has been 

 carried by the injection deeper into the tissues and found detached 

 from the more compact mass, the granular leucocytes gather 

 around them and often at this early stage edestin particles are 

 found already ingested by them. While actively ingesting large 

 amounts of edestin particles, the granular leucocytes may attain 

 a considerable size. Their cytoplasm is often seen to be reduced 

 to a narrow rim holding a large amount of ingested material. Its 

 granular structure, becoming less distinctive, while the cell is 

 moving toward the injected mass, has now practically disappeared 

 altogether. But the nucleus retains its polymorphous structure 

 and this makes the identification of these cells always easy. It is 

 remarkable that a great number of polymorphonuclear leucocytes, 



