April 26, 1955

Dr. H. Haardick
Zoologisch Institut
Bonn, Germany

Dear Dr. Haardick:

To your recent reqiests for reprints I have responded with pleasure,
and they are mailed by separate post.

May I ask a retum favor? I am interestdd in resuming my earlier
studies on ths formazan-granule, but only to use it as a cell-marker in
cell lineage studies. (You may have overlooked tha rather casual notice
included in the eccumpanying reprint, which may have been the first obser-
vation of the granule— no matter— es macht nichts. }

At any rate, I would greatly appreciate having roprinta of the papers
by your colleagues (Biolig,Kausche) and yourself on the tetrazclium reaction
of bacterial cells.

Yours sincerely,
f

fw

Joshua Lederberg 8 8
Professor cf Genetics *