Abstract
While clinical experience since the days of Jenner has conclusively proven that successful vaccination with cowpox virus or with the virus of smallpox itself results in establishing a high degree of active immunity against smallpox our knowledge of these protective antibodies is quite limited. Likewise clinical experience indicates quite conclusively that the antibody produced by inoculation with cowpox virus must be identical with or almost so with the antibody produced by smallpox virus, but the establishment of this relation between the two antibodies by means of immunological reactions has been less satisfactory, due probably to our ignorance of the specific micro-organisms of those diseases, our imperfect knowledge of the nature of the antibodies and the present limitations of immunological technic.
Attempts toward inducing passive immunization of animals against cowpox and smallpox by means of the injection of blood from vaccinated animals have been occasionally successful and frequently unsuccessful; likewise in a few experiments the virus of cowpox has been successfully inactivated or destroyed in vitro through contact with the blood serum of vaccinated animals.
