THE WESTERN PENNSYLVANIA HOSPITAL

INSTITUTE OF PATHOLOGY
PITTSBURGH, PENN’A

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Lecember 15, 1942

Dr. Joshua Lederberg
Assistant Frofessor of Genetics
he University of “isconsin
College of Agriculture
idadison 6, Wisconsin

Dear Dr, Lederberg:

Your letter of December 11 has just. come in this morning, and
perhaps our manuseript ought to have been a little more precise
en the point that you raise. Actually, the technique in this
respect was to dilute the culture out to a 10-3, and then plat-
tng showed two colonies per cc. » this is not absol-
utely accurate, and we should probably have made sone qyualify-
ing statement to that effect; but when one considers the over-
whelsing muanber of the muccids that were used, it did not seen
co matter a great deal whether it was two organisus, or four,

Lo ae

Of course

‘ - om 4 3 at
or half a dozen. But the fact that it actually calculated out
to two brought the report fron Vises McTircy to me in tat way.

Thanking you Kindly, I an

Kebple Yillpen.

Te rr
RR rbp Raiph R. Mellon, 2. D.