Dear Professor Browning:

It wae .most thoughtful ard gracious of you to forward
a copy of the Wml Ehrlich Centennial" SyiqOSiUr;i. I wae
actively reading the university library's copy when yours
arrived, and I am delighted to have it for my own library.

I ~uopos~ ycju had in mind particularly the design of
       A
ezqertimnts on selective recombination, which are the m&n
preoccupation of this laboratory, and which ycu had anticdpated
in your early trypanoao.me expertients.

         Since l'$XX there have been ;r number of not very credible
reports; ix .7WCU&i.t,gr iR trypGanz30me;. It occurs tc me that the time might be
ripe to reopen th3 rquesticn Rith a more comprehensive application of the sa-me
design. 1t would be zp;>ropriate to try to z*crossll a lrger variety of strains
and speciea, to use various laifferent drug-resistance ruarkers, and so forth.
P8rhaps this has been done on a larger scale than was indicated in 1908. If
not, I would earnestly ask that you constier the matter further: there would
hardly be anyohe more a'-~qriztely quali.fied.
                         f'k'

   Under separate cover I am sending '&other offprint that may interest
you, this tLxa of a talk at the dedication of &ksman's research Institute
of @z&&w 'Mxrobiology, held last June. 1 wish I could also send you Dr.
van Niel's ,article, but the book is now in print. I must express my whole-
hearted agreement with van Niel'a closing paragpaph, but &so my discourage-
ment at his hope, which is the contrast of Ehrlich's Institute and the present
one.

Yours sincerely,

Joshua Lederberg
Professor of Genetics