CURVK 01 PROTECTIVE SUBSTANCES. 51 



when the individual is allowed to recover completely between 

 injections. The curve is illustrated in Fig. 12A. 



b. The injections may be given at such times that one nega- 

 tive phase is superimposed upon another negative phase and in 

 this way produce a cummulative effect in the duration and degree 

 of the negative phase. This result is obtained according to Wright 

 when active immunization is pushed rapidly or forced. The curve 

 of protective substance is shown in Fig. 12B. 



c. The injection may be made at such times and in such 

 amounts that there is a summation of positive phases. This is 

 the result sought for in immunization. The curve representing 

 the amount of protective substances in this case is represented 

 in Fig. 12C. 



FIG. 12. 



Wright, in his treatment of infections by the injection of vac- 

 cine, tries to inject such doses at such intervals of time as to give 

 him a continuous "high tide phase." It is to be noted, however, 

 that even with the most favorable summation of positive phases 

 Wright has not obtained an index as high as 4 . except in rare in - 

 stances. This, of course, is entirely out of proportion with the amount 

 of other immune bodies produced by active immunization. 



Before the principle and methods as formulated by Wright 

 can be accepted it is necessary to decide (a) that opsonins are of 



