THEORIES OF IMMUNITY. 



cells, and this taken along with such facts as 

 the proliferation in certain infections of the non- 

 phagocytic eosinophilic leucocytes raises anew 

 the question of the possible secretion of chemical 

 substances into the serum which may be con- 

 cerned in the complicated process by which bac- 

 teria are destroyed in the animal body. It may 

 also be noted here that Muir has observed an 

 increase in the size and distinctness of the gran- 

 ules in the young polymorphs which occur in the 

 marrow during a severe infection. This might 

 indicate the preparation of material to be secreted. 

 So that from what has just been said it is thus 

 possible that on the fixed cells of the body and 

 the fixed precursors of the wandering cells are 

 impressed qualities which perpetuate immunity 

 in an animal which has survived an infection." 

 (Ritchie, I. c, p. 283.) 



Such a conclusion as that just drawn is at 

 least in part in direct accord with Metchnikoff's 

 assertion that there is an inheritance of a ten- 

 dency towards phagocytosis by the descendants 

 of cells upon which the property has been 

 impressed. 



92 



