the circulation of the blood-第3章

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Galen's　next　point　was　to　inquire　into　the　mode　of　communication
between　the　arteries　and　veins。　　It　was　known　before　his　time　that　both
arteries　and　veins　branched　out。　　Galen　maintained；　though　he　could　not
prove　the　fact；　that　the　ultimate　branches　of　the　arteries　and　veins
communicated　together　somehow　or　other；　by　what　he　called
'anastomoses'；　and　that　these　'anastomoses'　existed　not　only　in　the　body
in　general　but　also　in　the　lungs。　　In　the　next　place；　Galen　maintained
that　all　the　veins　of　the　body　arise　from　the　liver；　that　they　draw　the
blood　thence　and　distribute　it　over　the　body。　　People　laugh　at　that
notion　now…a…days；　but　if　anybody　will　look　at　the　facts　he　will　see
that　it　is　a　very　probable　supposition。　　There　is　a　great　vein　（hepatic
veinFig。　1）　which　rises　out　of　the　liver；　and　that　vein　goes　straight
into　the　'vena　cava'　（Fig。　1）　which　passes　to　the　heart；　being　there
joined　by　the　other　veins　of　the　body。　　The　liver　itself　is　fed　by　a
very　large　vein　（portal　veinFig。　1）；　which　comes　from　the　alimentary
canal。　　The　way　the　ancients　looked　at　this　matter　was；　that　the　food；
after　being　received　into　the　alimentary　canal；　was　then　taken　up　by　the
branches　of　this　great　vein；　which　are　called　the　'vena　portae'；　just
as　the　roots　of　a　plant　suck　up　nourishment　from　the　soil　in　which　it
lives；　that　then　it　was　carried　to　the　liver；　there　to　be　what　was
called　〃concocted；〃　which　was　their　phrase　for　its　conversion　into
substances　more　fitted　for　nutrition　than　previously　existed　in　it。
They　then　supposed　that　the　next　thing　to　be　done　was　to　distribute
this　fluid　through　the　body；　and　Galen　like　his　predecessors；　imagined
that　the　〃concocted〃　blood；　having　entered　the　great　'vena　cava'；　was
distributed　by　its　ramifications　all　over　the　body。　　So　that；　in　his
view　（Fig。　2）；　the　course　of　the　blood　was　from　the　intestine　to　the
liver；　and　from　the　liver　into　the　great　'vena　cava'；　including　what　we
now　call　the　right　auricle　of　the　heart；　whence　it　was　distributed　by
the　branches　of　the　veins。　　But　the　whole　of　the　blood　was　not　thus
disposed　of。　　Part　of　the　blood；　it　was　supposed；　went　through　what　we
now　call　the　pulmonary　arteries　（Fig。　1）；　and；　branching　out　there；　gave
exit　to　certain　〃fuliginous〃　products；　and　at　the　same　time　took　in
from　the　air　a　something　which　Galen　calls　the　'pneuma'。　　He　does　not
know　anything　about　what　we　call　oxygen；　but　it　is　astonishing　how　very
easy　it　would　be　to　turn　his　language　into　the　equivalent　of　modern
chemical　theory。　　The　old　philosopher　had　so　just　a　suspicion　of　the
real　state　of　affairs　that　you　could　make　use　of　his　language　in　many
cases；　if　you　substituted　the　word　〃oxygen；〃　which　we　now…a…days　use；
for　the　word　'pneuma'。　　Then　he　imagined　that　the　blood；　further
concocted　or　altered　by　contact　with　the　'pneuma'；　passed　to　a　certain
extent　to　the　left　side　of　the　heart。　　So　that　Galen　believed　that
there　was　such　a　thing　as　what　is　now　called　the　pulmonary
circulation。　　He　believed；　as　much　as　we　do；　that　the　blood　passed
through　the　right　side　of　the　heart；　through　the　artery　which　goes　to
the　lungs；　through　the　lungs　themselves；　and　back　by　what　we　call　the
pulmonary　veins　to　the　left　side　of　the　heart。　　But　he　thought　it　was
only　a　very　small　portion　of　the　blood　which　passes　to　the　right　side　of
the　heart　in　this　way；　the　rest　of　the　blood；　he　thought；　passed
through　the　partition　which　separates　the　two　ventricles　of　the　heart。
He　describes　a　number　of　small　pits；　which　really　exist　there；　as
holes；　and　he　supposed　that　the　greater　part　of　the　blood　passed
through　these　holes　from　the　right　to　the　left　ventricle　（Fig　2）。

It　is　of　great　importance　you　should　clearly　understand　these　teachings
of　Galen；　because；　as　I　said　just　now；　they　sum　up　all　that　anybody
knew　until　the　revival　of　learning；　and　they　come　to　thisthat　the
blood　having　passed　from　the　stomach　and　intestines　through　the　liver；
and　having　entered　the　great　veins；　was　by　them　distributed　to　every
part　of　the　body；　that　part　of　the　blood；　thus　distributed；　entered　the
arterial　system　by　the　'anastomoses'；　as　Galen　called　them；　in　the
lungs；　that　a　very　small　portion　of　it　entered　the　arteries　by　the
'anastomoses'　in　the　body　generally；　but　that　the　greater　part　of　it
passed　through　the　septum　of　the　heart；　and　so　entered　the　left　side
and　mingled　with　the　pneumatised　blood；　which　had　been　subjected　to　the
air　in　the　lungs；　and　was　then　distributed　by　the　arteries；　and
eventually　mixed　with　the　currents　of　blood；　coming　the　other　way；
through　the　veins。

Yet　one　other　point　about　the　views　of　Galen。　　He　thought　that　both　the
contractions　and　dilatations　of　the　heartwhat　we　call　the　'systole'
or　contraction　of　the　heart；　and　the　'diastole'　or　dilatationGalen
thought　that　these　were　both　active　movements；　that　the　heart　actively
dilated；　so　that　it　had　a　sort　of　sucking　power　upon　the　fluids　which
had　access　to　it。　　And　again；　with　respect　to　the　movements　of　the
pulse；　which　anybody　can　feel　at　the　wrist　and　elsewhere；　Galen　was　of
opinion　that　the　walls　of　the　arteries　partook　of　that　which　he
supposed　to　be　the　nature　of　the　walls　of　the　heart；　and　that　they　had
the　power　of　alternately　actively　contracting　and　actively　dilating；　so
that　he　is　careful　to　say　that　the　nature　of　the　pulse　is　comparable；
not　to　the　movement　of　a　bag；　which　we　fill　by　blowing　into　it；　and
which　we　empty　by　drawing　the　air　out　of　it；　but　to　the　action　of　a
bellows；　which　is　actively　dilated　and　actively　compressed。

Fig　3。The　course　of　the　blood　from　the　right　to　the　left　side　of　the
heart　（Realdus　Columbus；　1559）。

After　Galen's　time　came　the　collapse　of　the　Roman　Empire；　the　extinction
of　physical　knowledge；　and　the　repression　of　every　kind　of　scientific
inquiry；　by　its　powerful　and　consistent　enemy；　the　Church；　and　that
state　of　things　lasted　until　the　latter　part　of　the　Middle　Ages　saw　the
revival　of　learning。　　That　revival　of　learning；　so　far　as　anatomy　and
physiology　are　concerned；　is　due　to　the　renewed　influence　of　the
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　sur