the circulation of the blood-第3章

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philosophers　of　ancient　Greece；　and　indeed；　of　Galen。　　Arabic
commentators　had　translated　Galen；　and　portions　of　his　works　had　got
into　the　language　of　the　learned　in　the　Middle　Ages；　in　that　way；　but；
by　the　study　of　the　classical　languages；　the　original　text　became
accessible　to　the　men　who　were　then　endeavouring　to　learn　for
themselves　something　about　the　facts　of　nature。　　It　was　a　century　or
more　before　these　men；　finding　themselves　in　the　presence　of　a
masterfinding　that　all　their　lives　were　occupied　in　attempting　to
ascertain　for　themselves　that　which　was　familiar　to　himI　say　it　took
the　best　part　of　a　hundred　years　before　they　could　fairly　see　that　their
business　was　not　to　follow　him；　but　to　follow　his　examplenamely；　to
look　into　the　facts　of　nature　for　themselves；　and　to　carry　on；　in　his
spirit；　the　work　he　had　begun。　　That　was　first　done　by　Vesalius；　one　of
the　greatest　anatomists　who　ever　lived；　but　his　work　does　not　specially
bear　upon　the　question　we　are　now　concerned　with。　　So　far　as　regards
the　motions　of　the　heart　and　the　course　of　the　blood；　the　first　man　in
the　Middle　Ages；　and　indeed　the　only　man　who　did　anything　which　was　of
real　importance；　was　one　Realdus　Columbus；　who　was　professor　at　Padua
in　the　year　1559；　and　published　a　great　anatomical　treatise。　　What
Realdus　Columbus　did　was　this；　once　more　resorting　to　the　method　of
Galen；　turning　to　the　living　animal；　experimenting；　he　came　upon　new
facts；　and　one　of　these　new　facts　was　that　there　was　not　merely　a
subordinate　communication　between　the　blood　of　the　right　side　of　the
heart　and　that　of　the　left　side　of　the　heart；　through　the　lungs；　but
that　there　was　a　constant　steady　current　of　blood；　setting　through　the
pulmonary　artery　on　the　right　side；　through　the　lungs；　and　back　by　the
pulmonary　veins　to　the　left　side　of　the　heart　（Fig。3）。　　Such　was　the
capital　discovery　and　demonstration　of　Realdus　Columbus。　　He　is　the　man
who　discovered　what　is　loosely　called　the　'pulmonary　circulation'；　and
it　really　is　quite　absurd；　in　the　face　of　the　fact；　that　twenty　years
afterwards　we　find　Ambrose　Pare；　the　great　French　surgeon；　ascribing
this　discovery　to　him　as　a　matter　of　common　notoriety；　to　find　that
attempts　are　made　to　give　the　credit　of　it　to　other　people。　　So　far　as
I　know；　this　discovery　of　the　course　of　the　blood　through　the　lungs；
which　is　called　the　pulmonary　circulation；　is　the　one　step　in　real
advance　that　was　made　between　the　time　of　Galen　and　the　time　of
Harvey。　　And　I　would　beg　you　to　note　that　the　word　〃circulation〃　is
improperly　employed　when　it　is　applied　to　the　course　of　the　blood
through　the　lungs。　　The　blood　from　the　right　side　of　the　heart；　in
getting　to　the　left　side　of　the　heart；　only　performs　a　half…circleit
does　not　perform　a　whole　circleit　does　not　return　to　the　place　from
whence　it　started；　and　hence　the　discovery　of　the　so…called　〃pulmonary
circulation〃　has　nothing　whatever　to　do　with　that　greater　discovery
which　I　shall　point　out　to　you　by…and…by　was　made　by　Harvey；　and　which
is　alone　really　entitled　to　the　name　of　the　circulation　of　the　blood。

If　anybody　wants　to　understand　what　Harvey's　great　desert　really　was；　I
would　suggest　to　him　that　he　devote　himself　to　a　course　of　reading；
which　I　cannot　promise　shall　be　very　entertaining；　but　which；　in　this
respect　at　any　rate；　will　be　highly　instructivenamely；　the　works　of
the　anatomists　of　the　latter　part　of　the　16th　century　and　the　beginning
of　the　17th　century。　　If　anybody　will　take　the　trouble　to　do　that　which
I　have　thought　it　my　business　to　do；　he　will　find　that　the　doctrines
respecting　the　action　of　the　heart　and　the　motion　of　the　blood　which
were　taught　in　every　university　in　Europe；　whether　in　Padua　or　in　Paris；
were　essentially　those　put　forward　by　Galen；　'plus'　the　discovery　of
the　pulmonary　course　of　the　blood　which　had　been　made　by　Realdus
Columbus。　　In　every　chair　of　anatomy　and　physiology　（which　studies　were
not　then　separated）　in　Europe；　it　was　taught　that　the　blood　brought　to
the　liver　by　the　portal　vein；　and　carried　out　of　the　liver　to　the　'vena
cava'　by　the　hepatic　vein；　is　distributed　from　the　right　side　of　the
heart；　through　the　other　veins；　to　all　parts　of　the　body；　that　the
blood　of　the　arteries　takes　a　like　course　from　the　heart　towards　the
periphery；　and　that　it　is　there；　by　means　of　the　'anastomoses'；　more　or
less　mixed　up　with　the　venous　blood。　　It　so　happens；　by　a　curious
chance；　that　up　to　the　year　1625　there　was　at　Padua；　which　was　Harvey's
own　university；　a　very　distinguished　professor；　Spigelius；　whose　work
is　extant；　and　who　teaches　exactly　what　I　am　now　telling　you。　　It　is
perfectly　true　that；　some　time　before；　Harvey's　master；　Fabricius；　had
not　only　re…discovered；　but　had　drawn　much　attention　to　certain
pouch…like　structures；　which　are　called　the　valves　of　the　veins；　found
in　the　muscular　parts　of　the　body；　all　of　which　are　directed　towards
the　heart；　and　consequently　impede　the　flow　of　the　blood　in　the
opposite　direction。　　And　you　will　find　it　stated　by　people　who　have　not
thought　much　about　the　matter；　that　it　was　this　discovery　of　the　valves
of　the　veins　which　led　Harvey　to　imagine　the　course　of　the　circulation
of　the　blood。　　Now　it　did　not　lead　Harvey　to　imagine　anything　of　the
kind。　　He　had　heard　all　about　it　from　his　master；　Fabricius；　who　made　a
great　point　of　these　valves　in　the　veins；　and　he　had　heard　the　theories
which　Fabricius　entertained　upon　the　subject；　whose　impression　as　to
the　use　of　the　valves　was　simply　thisthat　they　tended　to　take　off　any
excess　of　pressure　of　the　blood　in　passing　from　the　heart　to　the
extremities；　for　Fabricius　believed；　with　the　rest　of　the　world；　that
the　blood　in　the　veins　flowed　from　the　heart　towards　the　extremities。
This；　under　the　circumstances；　was　as　good　a　theory　as　any　other；
because　the　action　of　the　valves　depends　altogether　upon　the　form　and
nature　of　the　walls　of　the　structures　in　which　they　are　attached；　and
without　accurate　experiment；　it　was　impossible　to　say　whether　the
theory　of　Fabricius　was　right　or　wrong。　　But　we　not　only　have　the
evidence　of　the　facts　themselves　that　these　could　tell　Harvey　nothing
about　the　circulation；　but　we　have　his　own　distinct　declaration　as　to
the　considerations　which　led　him　to　the　true　theory　of　the　circulation
of　the　blood；　and　amongst　these　the　valves　of　the　veins　are　not
mentioned。

Fig。　4。The　circulation　of　the　blood　as　demonstrated　by　Harvey　（A。D。
1628）。

Now　then　we　may　come　to　Harvey　himself。　　When　you　read　Harvey's
treatise；　which　is　one　of　the　most　remarkable　scientific　monographs
with　which　I　am　acquaintedit　occupies　between　50　and　60　pages　of　a
small　quarto　in　Latin；　and　is　as　terse　and　concise　as　it　possibly　can
bewhen　you　come　to　look　at　Harvey's　work；　you　will　find　that　he　had
long　struggled　with　the　difficulties　of　the　accepted　doctrine　of　the
circulation。　　He　had　received　from　Fabricius；　and　from　all　the　great
authorities　of　the　day；　the　current　view　of　the　circulation　of　the
blood。　　But　he　was　a　man　with　that　rarest　of　all
qualitiesintellectual　honesty；　and　by　dint　of　cultivating　that　great
faculty；　which　is　more　moral　than　intellectual；　it　had　become　impossible
for　him　to　say　he　believed　anything　which　he　did　not　clearly　believe。
This　is　a　most　uncomfortable　peculiarityfor　it　gets　you　into　all
sorts　of　difficulties　with　all　sorts　of　peoplebut；　for　scientific
purposes；　it　is　absolutely　invaluable。　　Harvey　possessed　this
peculiarity　in　the　highest　degree；　and　so　it　was　impossible　for　him　to
accept　what　all　the　authorities　told　him；　and　he　looked　into　the　matter
for　himself。　　But　he　was　not　hasty。　　He　worked　at　his　new　views；　and　he
lectured　about　them　at　the　College　of　Physicians　for　nine　years；　he　did
not　print　them　until　he　was　a　man　of　fifty　years　of　age；　and　when　he
did　print　them　he　accompanied　them　with　a　demonstration　which　has　never
been　shaken；　and　which　will　stand　till　the　end　of　time。　　What　Harvey
proved；　in　short；　was　this　（see　Fig。　4）that　everybody　had　made　a
mistake；　for　want　of　sufficiently　accurate　experimentation　as　to　the
actual　existence　of　the　fact　which　everybody　assumed。　　To　anybody　who
looks　at　the　blood…vessels　with　an　unprejudiced　eye　it　seems　so　natural
that　the　blood　should　all　come　out　of　the　liver；　and　be　distributed　by
the　veins　to　the　different　parts　of　the　body；　that　nothing　can　seem
simpler　or　more　plain；　and　consequently　no　one　could　make　up　his　mind
to　dispute　this　apparently　obvious　assumption。　　But　Harvey　did　dispute
it；　and　when　he　came　to　investigate　the　matter　he　discovered　that　it　was
a　profound　mistake；　and　that；　all　this　time；　the　blood　had　been　moving
in　just　the　opposite　direction；　namely；　from　the　small　ramifications　of
the　veins　towards　the　right　side　of　the　heart。　　Harvey　further　found
that；　in　the　arteries；　the　blood；　as　had　previously　been　known；　was
travelling　from　the　greater　trunks　towards　the　ramifications。　Moreover；
referring　to　the　ideas　of　Columbus　and　of　Galen　（for　he　was　a　great
student　of　literature；　and　did　justice　to　all　his　predecessors）；　Harvey
accepts　and　strengthens　their　view　of　the　course　of　the　blood　through
the　lungs；　and　he　shows　how　it　fitted　into　his　general　scheme。　　If　you
will　follow　the　course　of　the　arrows　in　Fig。　4　you　will　see　at　once
thatin　accordance　with　the　views　of　Columbusthe　blood　passes　from
the　right　side　of　the　heart；　through　the　lungs；　to　the　left　side。　　Then；
adds　Harvey；　with　abundant　proof；　it　passes　through　the　arteries　to　all
parts　of　the　body；　and　then；　at　the　extremities　of　their　branches　in
the　different　parts　of　the　body；　it　passes　（in　what　way　he　could　not
tell；　for　his　means　of　investigation　did　not　allow　him　to　say）　into　the
roots　of　the　ventsthen　from　the　roots　of　the　veins　it　goes　into　the
trunk　and　veinsthen　to　the　right　side　of　the　heartand　then　to　the
lungs；　and　so　on。

That；　you　will　observe；　makes　a　complete　circuit；　and　it　was　precisely
here　that　the　originality　of　Harvey　lay。　　There　never　yet　has　been
produced；　and　I　do　not　believe　there　can　be　produced；　a　tittle　of
evidence　to　show　that；　before　his　time；　any　one　had　the　slightest
suspicion　that　a　single　drop　of　blood；　starting　in　the　left　ventricle
of　the　heart；　passes　through　the　whole　arterial　system；　comes　back
through　the　venous　system；　goes　through　the　lungs；　and　comes　back　to
the　place　whence　it　started。　　But　that　is　the　circulation　of　the　blood；
and　it　was　exactly　this　which　Harvey　was　the　first　man　to　suspect；　to
discover；　and　to　demonstrate。

But　this　was　by　no　means　the　only　thing　Harvey　did。　　He　was　the　first
who　discovered　and　who　demonstrated　the　true　mechanism　of　the　heart's
action。　　No　one；　before　his　time；　conceived　that　the　movement　of　the
blood　was　entirely　due　to　the　mechanical　action　of　the　heart　as　a
pump。　　There　were　all　sorts　of　speculations　about　the　matter；　but　nobody
had　formed　this　conception；　and　nobody　understood　that　the　so…called
systole　of　the　heart　is　a　state　of　active　contraction；　and　the
so…called　diastole　is　a　mere　passive　dilatation。　　Even　within　our　own
age　that　matter　had　been　discussed。　　Harvey　is　as　clear　as　possible
about　it。　　He　says　the　movement　of　the　blood　is　entirely　due　to　the
contractions　of　the　wa