BACTERIOLYSINS AND H&MOLYS1NS IO5 



cidal sera has disclosed many difficulties to be 

 overcome before we can hope for much in a practi- 

 cal way. Thus we have as yet found no method of 

 increasing the complements, and these are apparently 

 highly important in destroying the invading bacteria. 

 Nor have we any way to determine the proper 

 dose so as to avoid the phenomenon termed " deflec- 

 tion of complement." Furthermore, we now know 

 that the defence of the animal body against bacterial 

 invasion is not solely a matter of bactericidal and 

 antitoxic substances. The brilliant studies of Ehr- 

 lich, Bordet, and others on the humoral side of 

 immunity has until recently caused the cellular 

 side advocated by Metchnikoff to be much neglected. 

 Perhaps the recent work begun by A. E. Wright on 

 opsonins may lead us in the right direction. The 

 therapeutic results thus far achieved by the use of 

 bactericidal immune sera certainly show that much 

 remains to be done in the study of immunity. 



