Abstract
Statistical analysis of assays of Rous sarcoma virus (RSV) on the chorioallantoic membrane (CAM) of Brown Leghorn (Edinburgh strain) embryos yielded results similar in some respects to those reported previously with White Leghorn embryos. There was a linear relationship between virus dose and pock count, and the variance of pock counts within dose groups exceeded the mean by factors of 3–15. The distribution of individual pock counts was neither normal nor log-normal. In contrast to other reports, the incidence of nonreactors to RSV on the CAM was very low (2 out of 800 embryos). Comparative assays of standard frozen stocks of RSV were done in eggs and tissue cultures from Brown Leghorn and two strains of White Leghorn chickens. The Brown Leghorns were 10–50 times more sensitive than White Leghorns on the CAM and about 10 times more sensitive by the focus method in tissue culture. A modification of the technique for counting RSV foci in tissue cultures is described.
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