TOXINS AND ANTITOXINS. 11 



1890) with the familiar result of the production 

 of the specific antitoxins. Other investigations in 

 this direction soon showed the independence of 

 the antibacterial and the antitoxic properties of 

 serums. , 



With these facts in hand, the vigor with which 

 investigations have been pushed may be readily 

 imagined. The hope naturally prevailed that phy- 

 sicians might become the masters of all infectious 

 diseases, through the possession of specific anti- 

 bacterial and antitoxic serums. But failures, with 

 which we are only too familiar, met the attempts 

 to produce adequate antiserums for many diseases. 

 Nevertheless these failures, through stimulation 

 to closer study, have resulted in the accumulation 

 of much additional knowledge concerning the 

 pathogenic properties of different bacteria, the 

 nature of the immune serums and the various pro- 

 tective factors of the body. Ehrlich has evolved 

 a new theory 0f immunity from facts which were 

 discovered in his laboratory, the "side-chain" 

 theory, which it is the purpose to utilize in the 

 interpretation of many reactions which will come 

 up for consideration. 



Wright in England, Neufeld in Germany, and 

 Hektoen in America more recently have led in a 

 revival of interest in phagocytosis as a factor in 

 natural and acquired immunity, with the 'result 

 that there can no longer exist any doubt that pha- 

 gocytosis plays an important role in protection 

 against and in recovery from many infections. 

 Thus the opsonins of Wright, and the bacterio- 

 tropic substances of Neufeld, have served to bridge 

 any chasm never a real chasm which seemed to 

 exist between the so-called humoral and cellular 



