March 29th, 1948
Dear Gajdusek:
I am very sorry I missed you on your recent visit, and sorry, too, to have been so slow in answering your first letter.  I thought it would be more effective for Dr. Fischel to answer it, and the process consumed much time.  However, he was much interested in what you wrote, and will gladly run the sera you were kind enough to bring, as he has written you.  The results ought to be very interesting.
I do not like the plastic tubes for very long periods of storage.  Most of those I've had in the ordinary refridgerator concentrated the sera in them down to a gel in the course of a few years.  I suppose most of the water evaporates through inequalities in the tube where the top screws on.
With hearty congratulations on your Fellowship and all good wishes,
Sincerely,
Michael Heidelberger