Summary and Conclusions
The addition of subneutralizing doses of immune serum to suspensions of equine encephalomyelitis virus caused a definite decrease in the titer of the virus, indicating a 90 to 99 per cent neutralization. This occurred over a wide range of serum-virus ratios.
In the narrow zone of serum-virus ratios in which neutralization was complete there was a direct relationship between the number of infective doses of virus present and the serum required for neutralization.
It is believed that two phenomena were being measured, namely, aggregation and neutralization, and it is suggested that the phenomenon of percentage neutralization with the virus in question, as well as with phage, is probably due to aggregation of virus, or phage, particles.