DEPARTMENT OF GENETICS
FACULTY OF MEDICINE, OSAKA UNIVERSITY

Joanchs-33, Kitaku, Osaka, Japan.

February 16, 1957

Prof. J. Lederberg

Department of Genetics,

The University of Wisconsin,
College of Agriculture,
Agricultural Hall,

Madison 6, Wisconsin, U. S. A.

Dear Professor Lederberg: =~

I thank you very mich for your kindness in giving
us the facility that Mr. Hirota of my laboratory will be able
to take an opportunity to study abroad. According to the
indication of Dr. Ryan, I am sending you letters of recommen-~
dation written by Prof. Inoki and myself respectively. The
remaining one will be sent from Dr. Ryan directly. We shall
be very glad if you would accept these letters and give the
facility to Mr. Hirota.

Now, Hirota states me that F factor is easily
eliminated from F+ cell by the treatment of acriflavin.
But he says that the concentration of acriflavin shown in
my previous letter is incorrect. The correct concentration
is 20 ag per ml of broth, instead of 200A1¢. Mr. II jima
and Mr. Ikoma who are engaged in the same work in my
laboratory have obtained the same result, and they have
testified that Mr. Hirota's experiment is right. We shall
be very glad if you would try this method:in your laboratory.

Very sincerely yours,

NK heoure

H. Kikkawa