OPSONIC INDEX AND VACCINE THERAPY 345 



that tuberculin therapy has come into carefully controlled use in 

 recent years only, although it was introduced early in the history 

 of specific therapy by Koch. The misuse and failure of this treat- 

 ment during the years following its introduction are easily explained 

 by the defective knowledge of antibody reactions and the general 

 principles of immunity a condition which was removed only by 

 the subsequent assiduous work of numerous investigators. At the 

 present time the value of this method of treatment is being acknowl- 

 edged, though its limitations and possible dangers are properly 

 recognized. The Wright method of vaccine treatment is also an 

 unquestionably powerful therapeutic weapon, and yet, owing to com- 

 mercialization, unskilful application, and, more especially, because 

 of extensive attempts to apply it in unsuitable cases, it may easily, 

 like tuberculin therapy, enter into a period of neglect and disrepute. 

 It is very necessary to accentuate at the present time that the active 

 immunization of human beings with any form of bacterial product 

 is a serious procedure which requires painstaking and skilled control, 

 and should not be undertaken without the same degree of preliminary 

 experience and study which is considered prerequisite in any other 

 branch of specialized medicine. 



Any opinion expressed regarding the ultimate value of a method 

 of treatment which is still undergoing active clinical investigation 

 must of course be purely tentative. Moreover, there are so many 

 differences of judgment that we wish to emphasize the purely per- 

 sonal character of the views expressed. 



In passing judgment upon the value of active immunization in 

 man we must distinguish sharply between active immunization which 

 is prophylactic and that which is carried out after the disease has 

 gained a definite foothold in the body. In the former case we are 

 dealing with a new method and with one upon which the very foun- 

 dations of our knowledge of immunity have been built. It is the 

 method of Jenner in small-pox. It is that of Pasteur in chicken 

 cholera, in anthrax, and in many other infections. It has been used 

 as a routine in animal experimentation in laboratories since the first 

 days of the systematic study of infections. There is no question 

 about its being a rational and logical procedure. The immunity 

 which can be easily conferred upon a healthy individual in this 

 way need not be extensively above the normal in order to protect 

 from invasion by the small numbers of pathogenic germs which 

 may gain entrance under conditions of accidental, spontaneous in- 

 fection. 



The possibilities of the method were recognized by Ferran, a 

 pupil of Pasteur, who applied it to cholera, and, since his time, it has 

 been extensively attempted in many of the infectious diseases which 

 occur epidemically, and therefore justify attempts in this direction. 



