378 INFECTION AND IMMUNITY. 



amboceptors ; agglutinins and precipitins are 

 formed incidentally. The amboceptors naturally 

 depend on the complement of the body for their 

 activation. If the disease is one of unknown etiol- 

 ogy the nature of the antibodies is not easily de- 

 termined. We should keep in mind the possibil- 

 ity that vaccination may cause an increase of the 

 opsonins and that the potential phagocytosis may 

 thereby become greater. 



In case the incubation period of the vaccination 

 is shorter than that of the disease (smallpox,, hy- 

 drophobia) vaccination usually is successful even if 

 practiced within a limited time after exposure to 

 infection. 



Vaccination in individual diseases is considered 

 in Part II. 



Mixed Active Theoretically it would be possible to immunize 

 m an against diphtheria and tetanus by inoculating 

 with small amounts of the corresponding toxins. 

 Such a procedure, for obvious reasons, would be 

 unnecessary and unjustifiable. 



It is not unlikely that mixed active and passive 

 immunization will be of great service in some in- 

 fections. A successful campaign against rinder- 

 pest has been carried on in the Philippines by this 

 method. The blood of infected cattle contains the 

 virus, which as yet has not been cultivated artifi- 

 cially. The serum of cattle which have recovered 

 from the disease, or which have been immunized 

 cautiously with infected blood, contains the speci- 

 fic antibodies. Both the immune serum and viru- 

 lent blood are used for the inoculations. The same 

 principle has been found effective in experimental 

 work with cholera, typhoid and plague. Immedi- 

 ate immunity is established by the serum, which 



