PHAGOCYTOSIS. 



59 



to germ-growth differs according to the kind of germs, as the germs 

 by the production of noxious substances affect the envelopes of cells, 

 and most of the pathogenic microbes assimilate nutritive material 

 from adjacent tissues more readily than ordinary mould. 



Microbes which diffuse themselves rapidly and which do not 

 form colonies cannot become encapsulated by leucocytes. By count- 

 ing the blood-corpuscles, it was found that after injections of small 

 doses of aspergillus fluorescens ten times more leucocytes were 

 found than in normal blood. Ehrlich's method of staining proved 

 that the leucocytes which surrounded the spores as well as the new 

 corpuscles in the blood were poly nuclear and represented the pye- 

 logenous leucocytes. In animals which recovered after infection 

 reinoculation was followed by more prompt encapsulation of the 

 spores by the leucocytes. 



FIG. 1. 



Leucocytes of frog with anthrax bacilli. (METSCHNIKOFF ) 



Metschuikoff (" Ueber den Kampf der Zellen gegen Erysipel 

 Kokken," Virchow's Archiv, B. 101, p. 209), who was the first to 

 describe the struggle of the cells of the organism against invading 

 microbes, gives the name of phagocytes to the cells which possess 

 the property of absorbing and digesting microbes (Fig. 1). He 

 made his researches on the daphnia, which are found invaded by a 

 parasite of the higher animals. The spores of this parasite peue 

 trate with the food into the intestine, from which they escape into 

 the cavity of the body of the daphnia. As soon as they have done 

 so, a struggle commences between them and the white corpuscles, 

 which, isolated or in groups, absorb the spore and destroy and trans - 

 form it into shapeless granules. The daphnia is thus saved. When 

 the victory is not accomplished the spores are not arrested and 

 destroyed by the leucocytes, and they invade the tissues of the 

 animal and 'kill it. Metschnikoff affirms that the same struggle 

 takes place in the higher vertebrates and in man between the 

 microbes and the cell-elements, but in these the process is more 



