yeast-第4部分

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last　thirty　years；　will　bear　me　out　in　saying　that　the　first　germ　of
them；　to　a　very　great　extent；　was　made　to　grow　and　fructify　by　the　study
of　the　yeast　plant；　which　presents　us　with　living　matter　in　almost　its
simplest　condition。

Then　there　is　yet　one　last　and　most　important　bearing　of　this　yeast
question。　　There　is　one　direction　probably　in　which　the　effects　of　the
careful　study　of　the　nature　of　fermentation　will　yield　results　more
practically　valuable　to　mankind　than　any　other。　　Let　me　recall　to　your
minds　the　fact　which　I　stated　at　the　beginning　of　this　lecture。　Suppose
that　I　had　here　a　solution　of　pure　sugar　with　a　little　mineral　matter
in　it；　and　suppose　it　were　possible　for　me　to　take　upon　the　point　of　a
needle　one　single；　solitary　yeast　cell；　measuring　no　more　perhaps　than
the　three…thousandth　of　an　inch　in　diameternot　bigger　than　one　of
those　little　coloured　specks　of　matter　in　my　own　blood　at　this　moment；
the　weight　of　which　it　would　be　difficult　to　express　in　the　fraction　of
a　grainand　put　it　into　this　solution。　　From　that　single　one；　if　the
solution　were　kept　at　a　fair　temperature　in　a　warm　summer's　day；　there
would　be　generated；　in　the　course　of　a　week；　enough　torulae　to　form　a
scum　at　the　top　and　to　form　lees　at　the　bottom；　and　to　change　the
perfectly　tasteless　and　entirely　harmless　fluid；　syrup；　into　a　solution
impregnated　with　the　poisonous　gas　carbonic　acid；　impregnated　with　the
poisonous　substance　alcohol；　and　that；　in　virtue　of　the　changes　worked
upon　the　sugar　by　the　vital　activity　of　these　infinitesimally　small
plants。　　Now　you　see　that　this　is　a　case　of　infection。　　And　from　the
time　that　the　phenomenon　of　fermentation　were　first　carefully　studied；
it　has　constantly　been　suggested　to　the　minds　of　thoughtful　physicians
that　there　was　a　something　astoundingly　similar　between　this　phenomena
of　the　propagation　of　fermentation　by　infection　and　contagion；　and　the
phenomena　of　the　propagation　of　diseases　by　infection　and　contagion。
Out　of　this　suggestion　has　grown　that　remarkable　theory　of　many
diseases　which　has　been　called　the　〃germ　theory　of　disease；〃　the　idea；
in　fact；　that　we　owe　a　great　many　diseases　to　particles　having　a
certain　life　of　their　own；　and　which　are　capable　of　being　transmitted
from　one　living　being　to　another；　exactly　as　the　yeast　plant　is　capable
of　being　transmitted　from　one　tumbler　of　saccharine　substance　to
another。　　And　that　is　a　perfectly　tenable　hypothesis；　one　which　in　the
present　state　of　medicine　ought　to　be　absolutely　exhausted　and　shown　not
to　be　true；　until　we　take　to　others　which　have　less　analogy　in　their
favour。　　And　there　are　some　diseases　most　assuredly　in　which　it　turns
out　to　be　perfectly　correct。　　There　are　some　forms　of　what　are　called
malignant　carbuncle　which　have　been　shown　to　be　actually　effected　by　a
sort　of　fermentation；　if　I　may　use　the　phrase；　by　a　sort　of　disturbance
and　destruction　of　the　fluids　of　the　animal　body；　set　up　by　minute
organisms　which　are　the　cause　of　this　destruction　and　of　this
disturbance；　and　only　recently　the　study　of　the　phenomena　which
accompany　vaccination　has　thrown　an　immense　light　in　this　direction；
tending　to　show　by　experiments　of　the　same　general　character　as　that　to
which　I　referred　as　performed　by　Helmholz；　that　there　is　a　most
astonishing　analogy　between　the　contagion　of　that　healing　disease　and
the　contagion　of　destructive　diseases。　　For　it　has　been　made　out　quite
clearly；　by　investigations　carried　on　in　France　and　in　this　country；
that　the　only　part　of　the　vaccine　matter　which　is　contagious；　which　is
capable　of　carrying　on　its　influence　in　the　organism　of　the　child　who　is
vaccinated；　is　the　solid　particles　and　not　the　fluid。　　By　experiments
of　the　most　ingenious　kind；　the　solid　parts　have　been　separated　from
the　fluid　parts；　and　it　has　then　been　discovered　that　you　may　vaccinate
a　child　as　much　as　you　like　with　the　fluid　parts；　but　no　effect　takes
place；　though　an　excessively　small　portion　of　the　solid　particles；　the
most　minute　that　can　be　separated；　is　amply　sufficient　to　give　rise　to
all　the　phenomena　of　the　cow　pock；　by　a　process　which　we　can　compare　to
nothing　but　the　transmission　of　fermentation　from　one　vessel　into
another；　by　the　transport　to　the　one　of　the　torula　particles　which
exist　in　the　other。　　And　it　has　been　shown　to　be　true　of　some　of　the
most　destructive　diseases　which　infect　animals；　such　diseases　as　the
sheep　pox；　such　diseases　as　that　most　terrible　and　destructive　disorder
of　horses；　glanders；　that　in　these；　also；　the　active　power　is　the
living　solid　particle；　and　that　the　inert　part　is　the　fluid。　However；
do　not　suppose　that　I　am　pushing　the　analogy　too　far。　　I　do　not　mean　to
say　that　the　active；　solid　parts　in　these　diseased　matters　are　of　the
same　nature　as　living　yeast　plants；　but；　so　far　as　it　goes；　there　is　a
most　surprising　analogy　between　the　two；　and　the　value　of　the　analogy
is　this；　that　by　following　it　out　we　may　some　time　or　other　come　to
understand　how　these　diseases　are　propagated；　just　as　we　understand；
now；　about　fermentation；　and　that；　in　this　way；　some　of　the　greatest
scourges　which　afflict　the　human　race　may　be；　if　not　prevented；　at
least　largely　alleviated。

This　is　the　conclusion　of　the　statements　which　I　wished　to　put　before
you。　　You　see　we　have　not　been　able　to　have　any　accessories。　　If　you
will　come　in　such　numbers　to　hear　a　lecture　of　this　kind；　all　I　can　say
is；　that　diagrams　cannot　be　made　big　enough　for　you；　and　that　it　is　not
possible　to　show　any　experiments　illustrative　of　a　lecture　on　such　a
subject　as　I　have　to　deal　with。　　Of　course　my　friends　the　chemists　and
physicists　are　very　much　better　off；　because　they　can　not　only　show　you
experiments；　but　you　can　smell　them　and　hear　them！　　But　in　my　case　such
aids　are　not　attainable；　and　therefore　I　have　taken　a　simple　subject　and
have　dealt　with　it　in　such　a　way　that　I　hope　you　all　understand　it；　at
least　so　far　as　I　have　been　able　to　put　it　before　you　in　words；　and
having　once　apprehended　such　of　the　ideas　and　simple　facts　of　the　case
as　it　was　possible　to　put　before　you；　you　can　see　for　yourselves　the
great　and　wonderful　issues　of　such　an　apparently　homely　subject。







End