292 VERA DANCHAKOFF 



they never accumulate in the tissue. The conditions develop 

 quite differently after stimulation, and lead to an excessive 

 granulocytspoiesis (figs. 20 and 21). In this case two factors 

 work together in one direction — fii'st: the granular leucocytes 

 are formed in excessive numbers and secondly vessels develop 

 defectively. Considerable accumulations of granular leucocytes 

 remain therefore in the spleen tissue. They may densely 

 infiltrate the mesenchyme, if there is mesenchyme tissue left 

 (fig. 21). 



On the other hand, they may form enormous agglomerations 

 in the form of spherical masses of semi liquid tissue and finally 

 perish (fig. 22, Grc.'"). Centers of necrotic tissue appear in the 

 spleen as a result of the excessive production and stagnation of 

 granular leucocytes. The development of large accumulations 

 of granular leucocytes are interesting in so far as it seems to 

 indicate that in the particular case cells cannot stop in their 

 development. The reactions displayed by these living cells nec- 

 essarilj' lead the cell to the last stage of its differentiation. 



The universal and imperative conversion of the spleen mesen- 

 chyme into granuloblastic tissue also offers an example of tissue 

 reaction, which being a response to the stimulation, seems to 

 lack the character of purposefulness. The stimulation breaks 

 up the reciprocal normal proportions of the development proc- 

 esses in the spleen. The exclusive development of granu- 

 lopoiesis in the spleen-anlage leads to formation of considerable 

 centers of completely differentiated cells which finally succumb 

 in large masses. The embryos, in which such wide spread 

 changes are observed, do not hatch, and usually die after 16 to 

 19 days of incubation. 



Around the necrotic centers, if they are not too considerable 

 in size and numbers, a characteristic reaction of mesenchymal 

 tissue may be observed. The mesenchj^mal cells proliferate and 

 form plasmodial masses in the form of giant cells around the 

 necrotic center (fig. 22, Gtx). The specific appearance of the 

 nuclei accumulations may suggest here also the idea of occurrence 

 of amitosis (fig. 22, Y). These giant cells are perfectly similar 

 to those encountered around the foreign bodies. Though their 



