The infectivity of poliomyelitis virus by the intracutaneous route occurs in certain strains but is not a constant character. The inconsistency of skin infectivity tests indicates that there is some property yet unknown which influences this characteristic.
Strains of poliomyelitis virus vary in the degree of immunity produced in experimental monkeys injected with active virus by the intracutaneous route and subsequently tested for resistance by intranasal injections. The variation has no relation to the virulence of the strain. Further investigation on the intranasal route of injection should be carried on so that this method may be used with greater assurance in immunity tests, and also in other procedures of poliomyelitis experimentation.