Attempts to Produce Poliomyelitis in Eastern Cotton Rats with Flexner's M. V. Strain. ∗

Forty-five cotton rats were injected with 9 strains of poliomyelitis virus (Flexner M. V., Flexner W. E., Toomey, Philadelphia, Kramer, Harmon, Howitt, Trask, W. E., Australian). The doses injected were the same as those used by Armstrong 1 to produce poliomyelitis, i. e., 0.06 cc intranasally, 0.06 cc intracerebrally and 0.5 cc subcutaneously of a 10% cord brain suspension. After 6 weeks of observation, 11 animals had died—2 after the injection of Harmon's and one each after the injection of the other strains, except Toomey's and Trask's. The cords and brains of those animals that died were made up into 10% suspensions in saline and injected into other animals. None of the latter either died or developed paralysis even after 4 months of observation.

Flexner's M.V. virus strain, which was also our most potent monkey poliomyelitis virus strain and the one most recently passaged by us, was injected into 25 other cotton rats in the same manner as described before. The results were negative.

Previously, it was found that the addition of 10 day colon typhoid paratyphoid (list of organisms used, 2 ) toxic broth filtrate (called “enteric organism filtrate” for convenience) to poliomyelitis virus accelerated the production of the disease when the combination was injected intracerebrally into monkeys. 3 Perhaps such a virus filtrate mixture would produce poliomyelitis in Eastern cotton rats. Ten per cent virus suspensions in enteric organism filtrate were used throughout save where otherwise noted.

Ten animals were injected with the standard dose in enteric organism filtrate in the usual way. Three animals were living after 4 months. The 2 which died of shock on the first day and 2 which died on the sixty-ninth day were discarded.