50 VACCINE AND SERUM THERAPY. 



jection of tetanus toxin there is at first a slight diminution in the 

 anti-toxin in the milk of the animals injected while later there 

 is an increase in the amount of anti-toxin. Likewise Solomonson 

 and Madsen found that similar results are produced in the blood 

 when diphtheria toxin is injected. Agglutinins, precipitins, bac- 

 teriolysins, after injection of killed cultures of bacteria, are also 

 at first decreased and later increased. 



Wright and Douglas did not, as has been supposed by many, 

 find that all pathogenic bacteria are sensible to opsonins. They 

 divide the pathogenic bacteria into four groups: 



a. Those bacteria that are sensible to bactericidal, bacter- 

 iolytic and opsonic action of the normal human blood. B. ty- 

 phosus and Spir. cholerae belong to this group. 



b. Those bacteria that are sensible to opsonic and especially 

 bactericidal action of normal blood serum. Examples of this 

 group are to be found in B. coli and B. dysenteriae. 



c. Those bacteria that are definitely sensible to opsonin 

 but not to the bactericidal action of normal blood. B. pestis, 

 Mic. melitensis and Mic. pneumonias belong to this group. 



d. Those bacteria that are insensible to the opsonic and bac- 

 tericidal action of normal human blood serum. Examples of 

 this group are found in the bacillus of diphtheria. 



Practically all of Wright's observations on opsonic immuni- 

 zation were determined in man. In the human, following the 

 injection of killed cultures, the negative phase is usually of short 

 duration, lasting from 24 to 48 hours. The positive phase may 

 not, but usually follows the negative phase and lasts from 3 to 

 4 days to two weeks. In active immunization Wright reasons 

 the curve of protected substances may be affected in different 

 ways. If the dose of vaccine injected is very small, the negative 

 phase may be omitted, while if a very large dose is injected it will 

 be marked and the highest index in the positive phase may not be 

 as high as it was at the time of injection. Usually in active im- 

 munization a number of injections of vaccine must be made. 

 These may produce one of three effects on the opsonic index: 



a. If injections are made after the index has returned to 

 the normal, the index curve may show a series of indices above 

 and below the normal. This is what happens, according to Wright, 



