ISTITUTO SIEROTERAPICO MILANESE
“SERAFINO BELFANTI”

ENTE MORALE AGGREGATO ALLA UNIVERSITA DI MILANO

Direttore Scientifico: Prof. Augusto De Barbieri

. : : ep: Via Darwin, 20 - MILANO
Dixo=sone Sctoutitien TELEFONO n. 35.74.44 (5 lince)

Dor, Poy abt
vear + OSM,

Thank you for your letter of nov.25 . My appendix Ll
was only a slignt remodeling of what was in my original draft the
derivation of the formula for expected enrichment ,taking into
account your wish to simplify my original cumbersoma formula. ke
fo this was added an analysis of the consequences of one simpli-
fying assumption introdudea in the caiculation,namely that only
one resistant organism goes into the enrichment tube.Perhaps one
mignt just add a footnote somwhere,saying ;:

in the calculation of the expected enrichment no account has
been taken of tne fact that occasionally more than one resistant
organism may be present in the sample used for enrichment.A calcu-
dation of the correction B tnat/t e gorse on cognizance of tins
fact might ii trodug shows .that/ £18 prac Tealiy insiguficant; e.g.
in the @xse8% givag Ree. here gpPt oee would be highest | m= 2, n=iU) the
expected enrichment should be multiplied by the cor:ection factor
1.055.

ihis could substitute for page 2,appendix 1, out 1 feel that
it may be useful to add \tne fewk lines above,

Stability of chlorampheticol-resistant mutant : atter 25 daily
transfers in broth, with a multiplication factor of Lu.Uuuu x at
every transfer,there was no variation in resistance, For this expe-
riment, the strain was reisoiated from an agar slant;on xRisolation
ama a colony was found which had a slightly decreased resistance,
This latter fact need not,probably,be quoted ; it just gives a hint
however,of how compiex @ reversion pattern may be,

Book; i am working slowly at chapter 5,but am waiting form more
encouragement from the other sidd of the Ailantic,it 1s difticult
to give a definite shape to chapter 5 if 1 do not know how chapters
3 and 4 wili look,at least roughiy.i would prefer to have your skex
sketth of these chapters before going on ;otherwise, dangers of
gaps and repetitions are too high.

Boli.,i.S.iij in the just four or five years,reprints have had
tneir pages numbered ook trthsy. Ceppellini s paper was an unlycky
exception aue to the fact that many people(includiug Ceppellini,
at that time) want their reprints in advan:e of publication,tfor
examinatioyj purposes, forvy {

{will keep W i6U2 in mind. What will you be aoing for .smas?
Ours 18 not likely to be teriibly good. My brothei-in-_aw,who just
married my wife's sister,and who is an extremely charming person,

a psychiatrist,heas just received a diagnosis of adenocarcinoma of
tne intestine (he is about 38 years old).He does not know,nor does
most of the family. + tt 18 aw not operable form.