The titration of vaccinia virus on the chorio-allantoic membrane of the developing chick embryo

A detailed investigation has been made of the pock-counting method for titrating vaccinia virus on embryonated eggs with a view to eliminating the wide scatter of results hitherto inseparable from the technique, and of assessing the precision of which it is capable. A detailed description is given of the technique evolved. Reasons are given for supposing that the distribution of counts should follow the Poisson series, and considerable progress is claimed towards the achievement of such a distribution.