October 7. 1959

Dr. J. Lein
Bristol Laboratortes
Syracuse, New York

Dear Joe:

Thanks Joe for the Invitation. 1! don't think | can make the trip.
Lots of luck In any case. I'm sorry we won't be seeing you.

Have you started anything golng In Japan on substitutional chemo-
therapy?

! thought we had a K-12 54 but the closest we have Is a mutant
derivative that requires threonine, leucine and thlamine. It should
be lysogenic. We are sending this. If this Is unsatIisfectory let
us know if any other kinds of background markers would be acceptable,
and If you need quite comparable S$” and S* stratns.

Yours