August 22, 1951.

Dr. 0. E. Bolduan,

PB Divieion, Chemical Corps,
Camp Detrick,

Frederick, Maryland.

Dear Dr. Bolduan:

I mist apologize for having been so tardy in returning the assembly
for the molecular filtere. However, I did not return myself to Madison
until a month after I saw you, and we have been delayed by varicus dislo-~
cations until now. The assembly has been mailed to you under separate cover.

Our conclusions are somewhat indefinite, and I hope we will have an
Opportunity to verffy them when the filters become more readily available.
In general, the filter proved to be roughly equivalent to the l4j-lb. test
Mandler in retention of bacterla, except, of course, in spedd of filtraticn.
fe found it impractical to sterilize with with facilities immediately

Ey:
available, and resorted to immersing the assembled filter in boiling water.
This worked reasonably well, except that re-use of 2 filter was impractical.

Ordinary cultures of Salmonella typhimurium and Serratia marcescens
were retained. In our cleanest experiment, the molecular filter retained
a phage-treated culture of Salmonella, which max permeated our Jandler filter.
In another experimant, the molecular filter also passed a few cells (or "L-forms?")
of phage-treated Salmonella. Until this question is cleared up, I think that
some reservation should be entertained about the absolute bacterial sterility
of ‘molecular filtrates", but under# most conditions, complete retention is
very likely, and at worst, only a fery fmoumicwocex small proportion of cells
is likely to pass, even from cultures expressly treated to encourage their
filtrability.

if the filters do appear on the market, I hope it will be possible to
arrange to have them sterilized at the plant. I would avpreciate any recent
information on their commercial xix availability, and barring that, a copy
of the working drawings for the assembly.

_ Yours sincerely,
- Joshua Lederberg,

Technical Representative
DA-18-064~-C 1-401