DIGESTIVE ACTIVITY OF MESENCHYME 467 



experimental conditions, and can also be awakened anew in the 

 adult splenic mesenchyme by transferring this into the embryonic 

 allantois. The agencies which change the splenic mesenchyme 

 and endow the adult tissue with a capacity of surrounding a 

 living tumor cell and digesting it are not definitely known. 

 Possibly the radical alterations in nutrition which take place 

 after birth are factors in the development of a more vigor- 

 ous digestive capacity of the adult mesenchyme, but this sug- 

 gestion at present is no more than a working hypothesis. 

 W. Bullock has found a general change in the organism of the 

 rat which takes place about two weeks after birth, resulting in 

 the development of a resistance against heterogeneous grafting. 

 A few data which have been obtained in regard to the chick allow 

 us to surmise that changes in the mesenchyme of the chick spleen 

 take place at about the same period, for the phagocytic and 

 digestive capacity against heterogeneous cells is not manifested by 

 the grafted splenic mesenchymal cells of animals until two weeks 

 after hatching. It is difficult at present to decide whether the 

 phagocytic and digestive capacity toward heterogeneous living 

 cells is a property which the adult splenic mesenchymal cell 

 develops only within the allantois or whether it may be manifested 

 also in other localities. There exists even less evidence for specu- 

 lation about the nature of the factors within the allantois which 

 may be especially favorable for the exercise of such an activity. 

 It is not possible at present to determine with any degree of 

 certainty whether the phagocytic digestive property toward a 

 heterogeneous living cell belongs to a mesenchymal cell of the 

 spleen only, or whether it is a general attribute of any adult mesen- 

 chymal cell. In mixed grafts of tumor and other organs, the tumor 

 grows unhampered, though a certain amount of adult mesenchyme 

 from the stroma of those organs which are mixed with the tumor 

 tissue is certainly present in these grafts. But if we consider 

 that the stroma cells in organs like the kidney, liver, and muscles 

 are sparse in comparison with the parenchyma of the organ, it 

 becomes obvious that the immediate contact of a tumor cell and 

 mesenchyme will be seldom effected in such grafts, and mesenchy- 

 mal cells are not in sufficient numbers to encircle and destroy 



