Abstract
The western virus of equine encephalomyelitis has been found capable of infecting man in certain districts of northern and central California and neutralizing substances for this strain have been found in the sera of 32 (37%) out of 86 encephalitic cases diagnosed in 1937 and 1938. 49 (47.5%) out of 103 sera of this group gave positive protection tests for the virus of St. Louis encephalitis.