= UNIVERSITY OF LONDON

es Department of

Bacteriology,

POSTGRADUATE MEDICAL SCHOOL
OF LONDON

Telegrams

POSGRADMED CHISK LONDON DUCANE ROAD

Telephone
SHEpherds Bush 1260 (4 lines) LONDON, W.12
8th. October,1950.

Dear Dr.Cavalli,

I wrote to you yesterday
asking if you would be kind enough to let me
have some threonine until I can get some of
my own. On looking over the details of my
proposed experiment I now find that I also
require biotin which I had been hoping to be
able to manage without. I am sorry to trouble
you again,but could you let me have a
milligram or so of biotin? If you cannot
manage this,would you let me know from whom
I can obtain some or who manufactures it
commercially? I require enough to supply
the requirements of the K12 mutant 58-161
' for a dozen or so plates. I gather that the

requirement of this vitamin is minute.

Yours sincerely,

*
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| Midlivn

(Dr.William Hayes)