In 1910, Flexner1 reported an attempt to produce an immune horse serum against poliomyelitis as follows:
It has, for instance, been found that the horse does not readily respond even to large injections of filtrates carrying the active virus with the development of immunity principles within the blood. It is true that our experiments are restricted to a single horse for the present, the blood serum of which, after many months of treatment, had no restraining effect on the virus either in vitro or within the body.
It is a known fact that not every horse responds readily with the production of immunity substances alike to every kind of antigen, so that several horses must be tried. This one experiment, therefore, did not discourage me. Then, again, another method might lead to success when this failed.
With this view in mind I enlisted the cooperation of Dr. Banzhaf, one
NEUSTAEDTER M. ANTIPOLIOMYELITIS HORSE SERUMITS PREPARATION AND USE. JAMA. 1931;96(12):933–935. doi:10.1001/jama.1931.02720380021006