566 BACTERIOLOGY. 



theii belief in the fundamental soundness of the idea. 

 Metschnikoff himself never swerved. Without entering 

 into a discussion of the many instructive investigations 

 upon the questions of phagocytosis it will suffice for our 

 purposes to state briefly their culmination. We now 

 know, through the studies notably of Bail and of Kikuchi 

 that on the one hand phagocytosis may be inhibited, and 

 by the demonstrations of Wright and Douglass, in par- 

 ticular, that, on the other, it may be accentuated. Bail, 

 believing the real defenses of the body to be cellular, at- 

 tributes the failure of the cells to protect from infection 

 to an inhibition of their defensive powers by a sub- 

 stance, " aggressin," elaborated by the invading bacteria. 

 While Kikuchi, accepting the aggressin doctrine^ re- 

 stricts the action of " aggressin " to the leucocytes 

 and interprets it as in the nature of a negative chemo- 

 tactic phenomenon, whereby the leucocytes are so 

 repelled that they cannot approach and take up the 

 bacteria. 



The efforts of Wright and Douglass have been in the 

 way of accentuating phagocytic activity and their results 

 have shed a flood of most important light upon the subject. 

 In 1903 and 1904, in papers presented to the Royal 

 Society of London, they express the opinion that leuco- 

 cytes alone are incapable of taking up bacteria, and that 

 in order for them to exhibit this function the bacteria 

 must first be acted upon by a something contained in the 

 normal blood, a state of affairs strikingly analogous to 

 that observed by Pfeiffer. They conceived this prepara- 

 tion of bacteria for ingestion by leucocytes to be in the 

 mature of the preparation of food for consumption. They 

 employ the term "Opsonin," (meaning to cater for; to 



