YALE UNIVERSITY

DEPARTMENT OF MICROBIOLOGY 310 CEDAR STREET
NEW HAVEN 11, CONNECTICUT

February 2, 1953

Doctor Joshua Lederberg
Vepartment of Genetics

The University of Wisconsin
College of Agriculture
Madison 6, Wisconsin

Dear Dr, Lederberg:

Your comments were by no means confusing, and I think that
your idea that genetic transduction can take place in tumors is
a brilliant thought and a puzzling possibility which certainly
has to be kept in mind.

However, the tumor viruses so far known do not lose their
carcinogenic power regardless of the living media in which they
are grown,For, if it is true, as we have shown in the past, that
chicken sarcoma viruses behave as ordinary destroying viruses
when grown in the embryo, they retain their cancer inducing prop-
erties as shown by the induction of tumors at the end of several
passages through embryonic hosts,

On the other hand, the fowl pox virus.activated by methyl-
cholanthrene applied to the skin of chickens does not seem to have
acquired any new property and, to judge by the experience so far
available, the virus recovered from tumors injected into normal
chickens induces in these hosts the lesions usually caused by
the virus. However, more careful studies will perhaps change this
view.

Under separate cover I am sending you a reprint concerned
with the growth of the Rous sarcoma in the chicken,

Sincerely yours,

F, Duran-Reynals, M.D.
FDR/3