Handbook of bacteriology for nurses / [Harry Wardwell Carey].

  • Carey, Harry Wardwell, 1875-1935.
Date:
1930
Catalogue details

Licence: In copyright

Credit: Handbook of bacteriology for nurses / [Harry Wardwell Carey]. Source: Wellcome Collection.

    79/294 (page 75)
    tion of the living bacteria in very small amount. This method of immunization has no wide application. Vaccines.—The introduction of dead bacteria or vac- cines in increasing doses is often used to develop im- munity against those bacteria whose poisons are intra- cellular. This method has been practised a great deal these last few years, and has been attended with con- siderable success in some infections. Its most success- ful application has been in the preventive inoculation against typhoid fever in the army. Finally, active im- munity may be produced by using the toxins of living bacteria. These toxins are extracellular and develop in the fluid culture medium used. The living micro-organ- isms may be removed by passing the fluid through a Berkefeld porcelain filter, leaving the fluid containing the toxin free from bacteria. If slowly increasing doses of this toxin are given to animals they will slowly develop an immunity. Immunization by this method is used against diphtheria and tetanus (lock-jaw) in animals. Active immunity developed by these methods is used largely in the prevention of infection. Because of the time required for the immunity to develop it is not ap- plicable to the cure of infection after it has begun, ex- cept in a few infections, or when the incubation period is long, as in rabies. Passive Immunity.—There is another type of im- munity that can be conferred without the body tissues taking any active part in the process. For this reason it is called passive immunity. In 1890 von Behring dis- covered that the blood-serum of animals that had been immunized to the poisons of diphtheria and tetanus, if injected into other animals, would protect them also.