DIGESTIVE ACTIVITY OF MESENCHYME 451 



tion of metachromatic glassy substance is found as the last 

 vestige of the tumor cell, A quite regular change, and one 

 of the first, is vacuolization of the peripheral zone of the cyto- 

 plasm, which loses its normal staining capacity and appears of a 

 purplish and greenish color in Zenker-formol, eosin-azur prep- 

 arations. A metachromatic purplish staining of the nucleus 

 and of its chromatin is also a frequent occurrence (fig. 15). 



When reporting these findings before the New York Patholog- 

 ical Society, I expressed the belief in the destructive power of the 

 adult splenic mesenchyme over the living cell of the Ehrlich 

 sarcoma. Since then further evidence for this has been accu- 

 mulated. It is not the damaged and weakened tumor cells 

 alone that are surrounded by the splenic mesenchyme, for, as 

 illustrated by figures 5, 9, 12, and 13, cells in all phases of mitosis 

 are encircled in the same way. For some time after being 

 surrounded they seem still capable of maintaining themselves, 

 but they finally succumb within the intraplasmodial cavity. 



This destruction of tumor cells by splenic mesenchymal cells 

 checks the further expansion of the tumor graft in the direction 

 of the spleen graft. There is no evidence for a rapid active 

 growth of the splenic mesenchyme within the tumor graft. The 

 reaction described is a necessary sequence of the encounter of two 

 tissues of different specific physicochemical constitution, and 

 although a factor contributing toward the recession of the tumor 

 graft within the allantois of the embryonic organism, it is acci- 

 dental to the process. The part of the tumor free from contact 

 with the splenic tissue continues to expand for a certain time, 

 and may do so up to the stage at which the prehatching changes 

 occur in the allantois. Its growth may, however, be markedly 

 inhibited at an earlier moment, if the myeloid metaplasia of the 

 allantois called forth by the adult splenic graft is sufficiently 

 pronounced. 



The growth contact, and consequently the reaction, between 

 spleen and tumor grafts usually develops at the sixth day, 

 though at times it may be observed on the fourth day, while in 

 other cases it is only slightly indicated even at the eighth day of 

 growth. At this late time the injurious effects of the other 



