DIGESTIVE ACTIVITY OF MESENCHYME 443 



assumes a spherical form. The allantoic mesenchyme with 

 vessels is found to be abundant in the outer zone of the tumor 

 and scanty in the more central part of it. Both kinds of tissue, 

 mammalian tumor cells and chick mesenchyme, present a 

 healthy appearance and show no signs of interaction. 



Besides the changes brought about by the exercise of its 

 intracellular digestive capacity, the tumor cell grown on the 

 allantois shows other alterations, probably due to the effects of 

 the culture medium. From about the fourth or fifth day after 

 grafting, inclusions appear in the cytoplasm of the tumor cells 

 which resemble crystalline forms. In Zenker-formol fixation 

 and eosin-azur these inclusions appear as clear separate linear 

 or fusiform spaces of various sizes. They may be curved in 

 adaptation to the curvature of the nucleus or to that of the 

 cell periphery. These uniform spaces were probably occupied 

 during cell life by a formed substance somewhat flexible in its 

 consistence. The number of the inclusions in one cell may 

 greatly vary, and they are present during both the resting stage 

 of the cell and mitosis. Sometimes they may be seen between 

 the chromosomes of the equatorial plate keeping them apart, 

 but are never found within the nucleus so long as the nuclear 

 membrane is intact. The inclusions must be interpreted as 

 due to a change in the metabolism of the tumor cells grown upon 

 the allantois, since those cells in their original host in the mouse 

 do not present such inclusions. Great differences in size and 

 modified nuclear-cytoplasmic proportions are further charac- 

 teristics of tumor cells growing on the allantois. There is an 

 interesting correlation between the size of the tumor cells and 

 the basophilia of their cytoplasm, the smaller cells being much 

 more basophilic during the resting stage. This seems to corre- 

 spond with the conception of the cytoplasm as at least a partial 

 center of synthesis of chromatic material for the further build- 

 ing up of the chromosome complex. The highly chromatic 

 nucleolus is also very characteristic of the tumor cell in its 

 resting stage. During the spireme stage of mitosis numerous 

 chromosomes seem to be firmly attached to the nucleolus, which 

 gradually loses ,its basophilic character as the chromosomes 



