1. The Rosenow antistreptococcic poliomyelitis serum concentrated or unconcentrated does not neutralize the virus of poliomyelitis as tested in monkeys.
2. The Pettit antipoliomyelitis horse serum neutralizes the virus only occasionally.
3. "Immune" sheep sera prepared according to the method of Pettit have not neutralized virus even when the normal sera of the same animal have given neutralization.
4. The reason for such chance neutralizations is obscure and should not be confused with the constant virus-neutralizing action of both human and monkey convalescent sera.
5. Experimental evidence affords no basis for the use of either the Rosenow or the Pettit serum in the therapy of poliomyelitis.