1. Of three species of mammals tested by peripheral inoculation (guinea pig, cat, and horse) none showed viremia under conditions which suggested that any of these species would serve as a frequent source of mosquito infection.
2. Of the birds tested (chicken, duck, and dove) all developed viremia and might readily serve as natural sources of mosquito infection. Chickens were shown to be very highly susceptible to infection by minute amounts of virus inoculated subcutaneously.
3. Virus may appear in the blood of chickens within 16 hours after inoculation and it has persisted till at least the 120th hour. No fowl showed any sign of illness as a result of the infection.