May 19, 1953
Dear Norton:

Thanks for the verification on LT-~1. Your pedigree agrees with the results on
sensitivity to X-phage (only #84 sens.) SW-202 is, however, pure prototroph now;
203 was of course not saved. We are gradually clearing up the pedigree details
on all stocks actually available, and I hope will not have to bother you very
many times more. The following still are not clear:
1. S. TM copenhagen. #11 or 12: what then do we have in lyophil?
2. SW~-234: from "LT-19 (30)" what's 307 [Aco. Lilleengen, type 15; we probably never

had it.]
3. SW-375-6: from ? Tho
4. SW-376-9: from ? S. paratyphi B.

3. Quite a few SW's state origin from LT-.. without giving specific qusber. Can I
definitely assume that these correspond entirely to the numbers in the "used"

column om p/58 of your theshe? (I.E. that LT-l was the sole exception?) It may take
you a bit of time to check your notes thoroughly on this, but I think it would be
worthwhile to settle it once and for all. As soon as these details are in hand, we'll

send you the summary and pedigrees of all cultures actually available, which should
be quite useful for furture exper imantal designs. Sincerely,