Statistical Analysis of Factors Affecting the Susceptibility of Chick Embryos to Eastern Equine Encephalomyelitis Virus

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Abstract
Summary: By application of Bliss's probit method of analyses it can be shown that: Chick embryos react in a more uniform manner at 39 C than at 35 C to infection with one strain of the virus of Eastern equine encephalomyelitis.With increasing age above eight days the chick embryo becomes more resistant to infection following inoculation via the chorio-allantoic sac route.Conversely, with increasing age up to fifteen days, at least, the embryo becomes more susceptible to infection when inoculated by the yolk sac route.Not only the susceptibility but also the uniformity of response varies with the temperature of incubation, the age of the embryo, and the route of inoculation. The uniformity of response of a population undergoing a change in susceptibility to the virus of equine encephalomyelitis is inversely related to the rate of such change.