In our previous articles1 on the transmission of epidemic poliomyelitis to monkeys, we have left undiscussed the nature of the virus responsible for producing the disease. Prom the beginning, our attention has been directed toward the solution of that fundamental question, but the results of our studies were, until recently, wholly of a negative nature. We failed utterly to discover bacteria, either in film preparations or in cultures, that could account for the disease; and, since among our long series of propagations of the virus in monkeys not one animal showed, in the lesions, the cocci described by some previous investigators and we had failed to obtain any such bacteria from the human material studied by us, we felt that they could be excluded from consideration.
We have, up to this time, made a very painstaking study of film preparations and sections prepared from two specimens of human spinal