Controlled clinical and experimental studies have shown that convalescent serum is inefficacious in the treatment of preparalytic poliomyelitis. 1 The reason for this can be seen from the pathogenesis of the disease, which indicates that poliomyelitis is an infection of the central nervous system exclusively. Evidence has been brought forth to show that the virus of poliomyelitis travels by way of the nerve tracts 2 and becomes fixed to the anterior horn cells of the spinal cord. 3 With this fact in mind, and knowing that the central nervous system is a well insulated and closed system, we believe it unlikely that serum could reach the affected cells, and, if it did, it is even more unlikely that it could dislodge the virus. 4 With the consideration that convalescent serum is of little or no value and that isolation to prevent contact infection is impracticable because of the probable high