on the relations of man to the lower animals-第7部分

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crosses　the　foot　obliquely　to　be　attached　to　the　base　of　the　great　toe。
No　muscle　in　the　hand　exactly　corresponds　with　this；　which　is　eminently
a　foot　muscle。

To　resumethe　foot　of　man　is　distinguished　from　his　hand　by　the
following　absolute　anatomical　differences：

1。　By　the　arrangement　of　the　tarsal　bones。

2。　By　having　a　short　flexor　and　a　short　extensor　muscle　of　the　digits。

3。　By　possessing　the　muscle　termed　'peronaeus　longus'。

And　if　we　desire　to　ascertain　whether　the　terminal　division　of　a　limb；
in　other　Primates；　is　to　be　called　a　foot　or　a　hand；　it　is　by　the
presence　or　absence　of　these　characters　that　we　must　be　guided；　and　not
by　the　mere　proportions　and　greater　or　lesser　mobility　of　the　great　toe；
which　may　vary　indefinitely　without　any　fundamental　alteration　in　the
structure　of　the　foot。

Keeping　these　considerations　in　mind；　let　us　now　turn　to　the　limbs　of
the　Gorilla。　　The　terminal　division　of　the　fore　limb　presents　no
difficultybone　for　bone　and　muscle　for　muscle；　are　found　to　be
arranged　essentially　as　in　man；　or　with　such　minor　differences　as　are
found　as　varieties　in　man。　　The　Gorilla's　hand　is　clumsier；　heavier；
and　has　a　thumb　somewhat　shorter　in　proportion　than　that　of　man；　but　no
one　has　ever　doubted　its　being　a　true　hand。

FIG　19。Foot　of　Man；　Gorilla；　and　Orang…Utan　of　the　same　absolute
length；　to　show　the　differences　in　proportion　of　each。　　Letters　as　in
Fig。　18。　　Reduced　from　original　drawings　by　Mr。　Waterhouse　Hawkins。

At　first　sight；　the　termination　of　the　hind　limb　of　the　Gorilla　looks
very　hand…like；　and　as　it　is　still　more　so　in　many　of　the　lower　apes；
it　is　not　wonderful　that　the　appellation　〃Quadrumana；〃　or　four…handed
creatures；　adopted　from　the　older　anatomists*　by　Blumenbach；　and
unfortunately　rendered　current　by　Cuvier；　should　have　gained　such　wide
acceptance　as　a　name　for　the　Simian　group。　　But　the　most　cursory
anatomical　investigation　at　once　proves　that　the　resemblance　of　the
so…called　〃hind　hand〃　to　a　true　hand；　is　only　skin　deep；　and　that；　in
all　essential　respects；　the　hind　limb　of　the　Gorilla　is　as　truly
terminated　by　a　foot　as　that　of　man。　The　tarsal　bones；　in　all　important
circumstances　of　number；　disposition；　and　form；　resemble　those　of　man
（Fig。　19）。　The　metatarsals　and　digits；　on　the　other　hand；　are
proportionally　longer　and　more　slender；　while　the　great　toe　is　not　only
proportionally　shorter　and　weaker；　but　its　metatarsal　bone　is　united　by
a　more　moveable　joint　with　the　tarsus。　　At　the　same　time；　the　foot　is
set　more　obliquely　upon　the　leg　than　in　man。

｛Footnote｝　*In　speaking　of　the　foot　of　his　〃Pygmie；〃　Tyson　remarks；　p。
13：　〃But　this　part　in　the　formation　and　in　its　function　too；　being
liker　a　Hand　than　a　Foot：　for　the　distinguishing　this　sort　of　animals
from　others；　I　have　thought　whether　it　might　not　be　reckoned　and　called
rather　Quadru…manus　than　Quadrupes；　'i。e。'　a　four…handed　rather　than　a
four…footed　animal。〃

As　this　passage　was　published　in　1699；　M。　I。　G。　St。　Hilaire　is　clearly
in　error　in　ascribing　the　invention　of　the　term　〃quadrumanous〃　to
Buffon；　though　〃himanous〃　may　belong　to　him。　Tyson　uses　〃Quadrumanus〃
in　several　places；　as　at　p。　91。。。。　　〃Our　'Pygmie'　is　no　Man；　nor　yet
the　'common　Ape'；　but　a　sort　of　'Animal'　between　both；　and　though　a
'Biped'；　yet　of　the　'Quadrumanus'…kind：　though　some　'Men'　too　have　been
observed　to　use　their　'Feet'　like　'Hands'；　as　I　have　seen　several。〃

As　to　the　muscles；　there　is　a　short　flexor；　a　short　extensor；　and　a
'peronaeus　longus'；　while　the　tendons　of　the　long　flexors　of　the　great
toe　and　of　the　other　toes　are　united　together　and　with　an　accessory
fleshy　bundle。

The　hind　limb　of　the　Gorilla；　therefore；　ends　in　a　true　foot；　with　a
very　moveable　great　toe。　　It　is　a　prehensile　foot；　indeed；　but　is　in　no
sense　a　hand：　it　is　a　foot　which　differs　from　that　of　man　not　in　any
fundamental　character；　but　in　mere　proportions；　in　the　degree　of
mobility；　and　in　the　secondary　arrangement　of　its　parts。

It　must　not　be　supposed；　however；　because　I　speak　of　these　differences
as　not　fundamental；　that　I　wish　to　underrate　their　value。　　They　are
important　enough　in　their　way；　the　structure　of　the　foot　being　in
strict　correlation　with　that　of　the　rest　of　the　organism　in　each　case。
Nor　can　it　be　doubted　that　the　greater　division　of　physiological　labour
in　Man；　so　that　the　function　of　support　is　thrown　wholly　on　the　leg　and
foot；　is　an　advance　in　organization　of　very　great　moment　to　him；　but；
after　all；　regarded　anatomically；　the　resemblances　between　the　foot　of
Man　and　the　foot　of　the　Gorilla　are　far　more　striking　and　important　than
the　differences。

I　have　dwelt　upon　this　point　at　length；　because　it　is　one　regarding
which　much　delusion　prevails；　but　I　might　have　passed　it　over　without
detriment　to　my　argument；　which　only　requires　me　to　show　that；　be　the
differences　between　the　hand　and　foot　of　Man　and　those　of　the　Gorilla
what　they　maythe　differences　between　those　of　the　Gorilla；　and　those
of　the　lower　Apes　are　much　greater。

It　is　not　necessary　to　descend　lower　in　the　scale　than　the　Orang　for
conclusive　evidence　on　this　head。

The　thumb　of　the　Orang　differs　more　from　that　of　the　Gorilla　than　the
thumb　of　the　Gorilla　differs　from　that　of　Man；　not　only　by　its
shortness；　but　by　the　absence　of　any　special　long　flexor　muscle。　　The
carpus　of　the　Orang；　like　that　of　most　lower　apes；　contains　nine　bones；
while　in　the　Gorilla；　as　in　Man　and　the　Chimpanzee；　there　are　only
eight。

The　Orang's　foot　（Fig。　19）　is　still　more　aberrant；　its　very　long　toes
and　short　tarsus；　short　great　toe；　short　and　raised　heel；　great
obliquity　of　articulation　in　the　leg；　and　absence　of　a　long　flexor
tendon　to　the　great　toe；　separating　it　far　more　widely　from　the　foot　of
the　Gorilla　than　the　latter　is　separated　from　that　of　Man。

But；　in　some　of　the　lower　apes；　the　hand　and　foot　diverge　still　more
from　those　of　the　Gorilla；　than　they　do　in　the　Orang。　　The　thumb　ceases
to　be　opposable　in　the　American　monkeys；　is　reduced　to　a　mere　rudiment
covered　by　the　skin　in　the　Spider　Monkey；　and　is　directed　forwards　and
armed　with　a　curved　claw　like　the　other　digits；　in　the　Marmosetsso
that；　in　all　these　cases；　there　can　be　no　doubt　but　that　the　hand　is
more　different　from　that　of　the　Gorilla　than　the　Gorilla's　hand　is　from
Man's。

And　as　to　the　foot；　the　great　toe　of　the　Marmoset　is　still　more
insignificant　in　proportion　than　that　of　the　Orangwhile　in　the　Lemurs
it　is　very　large；　and　as　completely　thumb…like　and　opposable　as　in　the
Gorillabut　in　these　animals　the　second　toe　is　often　irregularly
modified；　and　in　some　species　the　two　principal　bones　of　the　tarsus；
the　'astragalus'　and　the　'os　calcis'；　are　so　immensely　elongated　as　to
render　the　foot；　so　far；　totally　unlike　that　of　any　other　mammal。

So　with　regard　to　the　muscles。　　The　short　flexor　of　the　toes　of　the
Gorilla　differs　from　that　of　Man　by　the　circumstance　that　one　slip　of
the　muscle　is　attached；　not　to　the　heel　bone；　but　to　the　tendons　of　the
long　flexors。　　The　lower　Apes　depart　from　the　Gorilla　by　an　exaggeration
of　the　same　character；　two；　three；　or　more；　slips　becoming　fixed　to　the
long　flexor　tendonsor　by　a　multiplication　of　the　slips。Again；　the
Gorilla　differs　slightly　from　Man　in　the　mode　of　interlacing　of　the
long　flexor　tendons：　and　the　lower　apes　differ　from　the　Gorilla　in
exhibiting　yet　other；　sometimes　very　complex；　arrangements　of　the　same
parts；　and　occasionally　in　the　absence　of　the　accessory　fleshy　bundle。

Throughout　all　these　modifications　it　must　be　recollected　that　the　foot
loses　no　one　of　its　essential　characters。　　Every　Monkey　and　Lemur
exhibits　the　characteristic　arrangement　of　tarsal　bones；　possesses　a
short　flexor　and　short　extensor　muscle；　and　a　'peronaeus　longus'。
Varied　as　the　proportions　and　appearance　of　the　organ　may　be；　the
terminal　division　of　the　hind　limb　remains；　in　plan　and　principle　of
construction；　a　foot；　and　never；　in　those　respects；　can　be　confounded
with　a　hand。

Hardly　any　part　of　the　bodily　frame；　then；　could　be　found　better
calculated　to　illustrate　the　truth　that　the　structural　differences
between　Man　and　the　highest　Ape　are　of　less　value　than　those　between
the　highest　and　the　lower　Apes；　than　the　hand　or　the　foot；　and　yet；
perhaps；　there　is　one　organ　the　study　of　which　enforces　the　same
conclusion　in　a　still　more　striking　mannerand　that　is　the　Brain。

But　before　entering　upon　the　precise　question　of　the　amount　of
difference　between　the　Ape's　brain　and　that　of　Man；　it　is　necessary
that　we　should　clearly　understand　what　constitutes　a　great；　and　what　a
small　difference　in　cerebral　structure；　and　we　shall　be　best　enabled　to
do　this　by　a　brief　study　of　the　chief　modifications　which　the　brain
exhibits　in　the　series　of　vertebrate　animals。

The　brain　of　a　fish　is　very　small；　compared　with　the　spinal　cord　into
which　it　is　continued；　and　with　the　nerves　which　come　off　from　it：　of
the　segments　of　which　it　is　composedthe　olfactory　lobes；　the　cerebral
hemisphere；　and　the　succeeding　divisionsno　one　predominates　so　much
over　the　rest　as　to　obscure　or　cover　them；　and　the　so…called　optic　lobes
are；　frequently；　the　largest　masses　of　all。　　In　Reptiles；　the　mass　of
the　brain；　relatively　to　the　spinal　cord；　increases　and　the　cerebral
hemispheres　begin　to　predominate　over　the　other　parts；　while　in　Birds
this　predominance　is　still　more　marked。　　The　brain　of　the　lowest
Mammals；　such　as　the　duck…billed　Platypus　and　the　Opossums　and
Kangaroos；　exhibits　a　still　more　definite　advance　in　the　same
direction。　　The　cerebral　hemispheres　have　now　so　much　increased　in　size
as；　more　or　less；　to　hide　the　representatives　of　the　optic　lobes；　which
remain　comparatively　small；　so　that　the　brain　of　a　Marsupial　is
extremely　different　from　that　of　a　Bird；　Reptile；　or　Fish。　　A　step
higher　in　the　scale；　among　the　placental　Mammals；　the　structure　of　the
brain　acquires　a　vast　modificationnot　that　it　appears　much　altered
externally；　in　a　Rat　or　in　a　Rabbit；　from　what　it　is　in　a
Marsupialnor　that　the　proportions　of　its　parts　are　much　changed；　but
an　apparently　new　structure　is　found　between　the　cerebral　hemispheres；
connecting　them　together；　as　what　is　called　the　'great　c