yeast-第1章

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Yeast


by　Thomas　H。　Huxley






I　HAVE　selected　to…night　the　particular　subject　of　Yeast　for　two
reasonsor；　rather；　I　should　say　for　three。　　In　the　first　place；
because　it　is　one　of　the　simplest　and　the　most　familiar　objects　with
which　we　are　acquainted。　　In　the　second　place；　because　the　facts　and
phenomena　which　I　have　to　describe　are　so　simple　that　it　is　possible　to
put　them　before　you　without　the　help　of　any　of　those　pictures　or
diagrams　which　are　needed　when　matters　are　more　complicated；　and　which；
if　I　had　to　refer　to　them　here；　would　involve　the　necessity　of　my
turning　away　from　you　now　and　then；　and　thereby　increasing　very　largely
my　difficulty　（already　sufficiently　great）　in　making　myself　heard。　　And
thirdly；　I　have　chosen　this　subject　because　I　know　of　no　familiar
substance　forming　part　of　our　every…day　knowledge　and　experience；　the
examination　of　which；　with　a　little　care；　tends　to　open　up　such　very
considerable　issues　as　does　this　substanceyeast。

In　the　first　place；　I　should　like　to　call　your　attention　to　a　fact　with
which　the　whole　of　you　are；　to　begin　with；　perfectly　acquainted；　I　mean
the　fact　that　any　liquid　containing　sugar；　any　liquid　which　is　formed
by　pressing　out　the　succulent　parts　of　the　fruits　of　plants；　or　a
mixture　of　honey　and　water；　if　left　to　itself　for　a　short　time；　begins
to　undergo　a　peculiar　change。　　No　matter　how　clear　it　might　be　at
starting；　yet　after　a　few　hours；　or　at　most　a　few　days；　if　the
temperature　is　high；　this　liquid　begins　to　be　turbid；　and　by…and…by
bubbles　make　their　appearance　in　it；　and　a　sort　of　dirty…looking
yellowish　foam　or　scum　collects　at　the　surface；　while　at　the　same　time；
by　degrees；　a　similar　kind　of　matter；　which　we　call　the　〃lees；〃　sinks
to　the　bottom。

The　quantity　of　this　dirty…looking　stuff；　that　we　call　the　scum　and　the
lees；　goes　on　increasing　until　it　reaches　a　certain　amount；　and　then　it
stops；　and　by　the　time　it　stops；　you　find　the　liquid　in　which　this
matter　has　been　formed　has　become　altered　in　its　quality。　　To　begin
with　it　was　a　mere　sweetish　substance；　having　the　flavour　of　whatever
might　be　the　plant　from　which　it　was　expressed；　or　having　merely　the
taste　and　the　absence　of　smell　of　a　solution　of　sugar；　but　by　the　time
that　this　change　that　I　have　been　briefly　describing　to　you　is
accomplished　the　liquid　has　become　completely　altered；　it　has　acquired　a
peculiar　smell；　and；　what　is　still　more　remarkable；　it　has　gained　the
property　of　intoxicating　the　person　who　drinks　it。　　Nothing　can　be　more
innocent　than　a　solution　of　sugar；　nothing　can　be　less　innocent；　if
taken　in　excess；　as　you　all　know；　than　those　fermented　matters　which　are
produced　from　sugar。　　Well；　again；　if　you　notice　that　bubbling；　or；　as
it　were；　seething　of　the　liquid；　which　has　accompanied　the　whole　of
this　process；　you　will　find　that　it　is　produced　by　the　evolution　of
little　bubbles　of　air…like　substance　out　of　the　liquid；　and　I　dare　say
you　all　know　this　air…like　substance　is　not　like　common　air；　it　is　not
a　substance　which　a　man　can　breathe　with　impunity。　You　often　hear　of
accidents　which　take　place　in　brewers'　vats　when　men　go　in　carelessly；
and　get　suffocated　there　without　knowing　that　there　was　anything　evil
awaiting　them。　　And　if　you　tried　the　experiment　with　this　liquid　I　am
telling　of　while　it　was　fermenting；　you　would　find　that　any　small
animal　let　down　into　the　vessel　would　be　similarly　stifled；　and　you
would　discover　that　a　light　lowered　down　into　it　would　go　out。　　Well；
then；　lastly；　if　after　this　liquid　has　been　thus　altered　you　expose　it
to　that　process　which　is　called　distillation；　that　is　to　say；　if　you
put　it　into　a　still；　and　collect　the　matters　which　are　sent　over；　you
obtain；　when　you　first　heat　it；　a　clear　transparent　liquid；　which；
however；　is　something　totally　different　from　water；　it　is　much　lighter；
it　has　a　strong　smell；　and　it　has　an　acrid　taste；　and　it　possesses　the
same　intoxicating　power　as　the　original　liquid；　but　in　a　much　more
intense　degree。　　If　you　put　a　light　to　it；　it　burns　with　a　bright
flame；　and　it　is　that　substance　which　we　know　as　spirits　of　wine。

Now　these　facts　which　I　have　just　put　before　youall　but　the　lasthave
been　known　from　extremely　remote　antiquity。　　It　is；　I　hope　one　of　the
best　evidences　of　the　antiquity　of　the　human　race；　that　among　the
earliest　records　of　all　kinds　of　men；　you　find　a　time　recorded　when
they　got　drunk。　　We　may　hope　that　that　must　have　been　a　very　late　period
in　their　history。　　Not　only　have　we　the　record　of　what　happened　to
Noah；　but　if　we　turn　to　the　traditions　of　a　different　people；　those
forefathers　of　ours　who　lived　in　the　high　lands　of　Northern　India；　we
find　that　they　were　not　less　addicted　to　intoxicating　liquids；　and　I
have　no　doubt　that　the　knowledge　of　this　process　extends　far　beyond　the
limits　of　historically　recorded　time。　　And　it　is　a　very　curious　thing
to　observe　that　all　the　names　we　have　of　this　process；　and　all　that
belongs　to　it；　are　names　that　have　their　roots　not　in　our　present
language；　but　in　those　older　languages　which　go　back　to　the　times　at
which　this　country　was　peopled。　　That　word　〃fermentation〃　for　example；
which　is　the　title　we　apply　to　the　whole　process；　is　a　Latin　term；　and　a
term　which　is　evidently　based　upon　the　fact　of　the　effervescence　of　the
liquid。　　Then　the　French；　who　are　very　fond　of　calling　themselves　a
Latin　race；　have　a　particular　word　for　ferment；　which　is　'levure'。　And；
in　the　same　way；　we　have　the　word　〃leaven；〃　those　two　words　having
reference　to　the　heaving　up；　or　to　the　raising　of　the　substance　which
is　fermented。　　Now　those　are　words　which　we　get　from　what　I　may　call
the　Latin　side　of　our　parentage；　but　if　we　turn　to　the　Saxon　side；
there　are　a　number　of　names　connected　with　this　process　of　fermentation。
For　example；　the　Germans　call　fermentationand　the　old　Germans　did
so〃gahren；〃　and　they　call　anything　which　is　used　as　a　ferment　by　such
names；　such　as　〃gheist〃　and　〃geest；〃　and　finally　in　low　German；
〃yest〃；〃　and　that　word　you　know　is　the　word　our　Saxon　forefathers　used；
and　is　almost　the　same　as　the　word　which　is　commonly　employed　in　this
country　to　denote　the　common　ferment　of　which　I　have　been　speaking。　　So
they　have　another　name；　the　word　〃hefe；〃　which　is　derived　from　their
verb　〃heben；〃　which　signifies　to　raise　up；　and　they　have　yet　a　third
name；　which　is　also　one　common　in　this　country　（I　do　not　know　whether　it
is　common　in　Lancashire；　but　it　is　certainly　very　common　in　the　Midland
countries）；　the　word　〃barm；〃　which　is　derived　from　a　root　which
signifies　to　raise　or　to　bear　up。　　Barm　is　a　something　borne　up；　and
thus　there　is　much　more　real　relation　than　is　commonly　supposed　by　those
who　make　puns；　between　the　beer　which　a　man　takes　down　his　throat　and
the　bier　upon　which　that　process；　if　carried　to　excess；　generally　lands
him；　for　they　are　both　derived　from　the　root　signifying　bearing　up；　the
one　thing　is　borne　upon　men's　shoulders；　and　the　other　is　the　fermented
liquid　which　was　borne　up　by　the　fermentation　taking　place　in　itself。

Again；　I　spoke　of　the　produce　of　fermentation　as　〃spirit　of　wine。〃　　Now
what　a　very　curious　phrase　that　is；　if　you　come　to　think　of　it。　　The
old　alchemists　talked　of　the　finest　essence　of　anything　as　if　it　had
the　same　sort　of　relation　to　the　thing　itself　as　a　man's　spirit　is
supposed　to　have　to　his　body；　and　so　they　spoke　of　this　fine　essence　of
the　fermented　liquid　as　being　the　spirit　of　the　liquid。　　Thus　came
about　that　extraordinary　ambiguity　of　language；　in　virtue　of　which　you
apply　precisely　the　same　substantive　name　to　the　soul　of　man　and　to　a
glass　of　gin！　And　then　there　is　still　yet　one　other　most　curious　piece
of　nomenclature　connected　with　this　matter；　and　that　is　the　word
〃alcohol〃　itself；　which　is　now　so　familiar　to　everybody。　　Alcohol
originally　meant　a　very　fine　powder。　　The　women　of　the　Arabs　and　other
Eastern　people　are　in　the　habit　of　tinging　their　eyelashes　with　a　very
fine　black　powder　which　is　made　of　antimony；　and　they　call　that
〃kohol；〃　and　the　〃al〃　is　simply　the　article　put　in　front　of　it；　so　as　to
say　〃the　kohol。〃　　And　up　to　the　17th　century　in　this　country　the　word
alcohol　wa