The virus of vesicular stomatitis is not readily killed by formalin. This chemical is one of a group which coagulates the proteins of the medium in which the virus is usually contained. It has already been found7 that other reagents of the protein-coagulating group are not actively virucidal) and the effect of formalin in this instance is therefore characteristic of the group.
The so called formalinized vaccines which give rise to immunity can be shown to have done so because of the presence of living virus. A single injection of such so called "vaccine," or of other material containing living virus, is capable of inducing immunity in guinea pigs. No protection, however, follows a single injection of dead virus. Furthermore, repeated inoculations of virus killed by formalin likewise fail to induce resistance against subsequent injections of the living virus.
It is concluded, with respect to the virus of vesicular stomatitis, that the use of formalin has failed to solve the problem of active immunization with dead virus.