on the relations of man to the lower animals-第6部分

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Hence　it　is　obvious　that；　greatly　as　the　dentition　of　the　highest　Ape
differs　from　that　of　Man；　it　differs　far　more　widely　from　that　of　the
lower　and　lowest　Apes。

Whatever　part　of　the　animal　fabricwhatever　series　of　muscles；　whatever
viscera　might　be　selected　for　comparisonthe　result　would　be　the
samethe　lower　Apes　and　the　Gorilla　would　differ　more　than　the　Gorilla
and　the　Man。　　I　cannot　attempt　in　this　place　to　follow　out　all　these
comparisons　in　detail；　and　indeed　it　is　unnecessary　I　should　do　so。　　But
certain　real；　or　supposed；　structural　distinctions　between　man　and　the
apes　remain；　upon　which　so　much　stress　has　been　laid；　that　they　require
careful　consideration；　in　order　that　the　true　value　may　be　assigned　to
those　which　are　real；　and　the　emptiness　of　those　which　are　fictitious
may　be　exposed。　I　refer　to　the　characters　of　the　hand；　the　foot；　and
the　brain。

Man　has　been　defined　as　the　only　animal　possessed　of　two　hands
terminating　his　fore　limbs；　and　of　two　feet　ending　his　hind　limbs；
while　it　has　been　said　that　all　the　apes　possess　four　hands；　and　he　has
been　affirmed　to　differ　fundamentally　from　all　the　apes　in　the
characters　of　his　brain；　which　alone；　it　has　been　strangely　asserted
and　re…asserted；　exhibits　the　structures　known　to　anatomists　as　the
posterior　lobe；　the　posterior　cornu　of　the　lateral　ventricle；　and　the
hippocampus　minor。

That　the　former　proposition　should　have　gained　general　acceptance　is　not
surprisingindeed；　at　first　sight；　appearances　are　much　in　its　favour：
but；　as　for　the　second；　one　can　only　admire　the　surpassing　courage　of
its　enunciator；　seeing　that　it　is　an　innovation　which　is　not　only
opposed　to　generally　and　justly　accepted　doctrines；　but　which　is
directly　negatived　by　the　testimony　of　all　original　inquirers；　who　have
specially　investigated　the　matter：　and　that　it　neither　has　been；　nor
can　be；　supported　by　a　single　anatomical　preparation。　　It　would；　in
fact；　be　unworthy　of　serious　refutation；　except　for　the　general　and
natural　belief　that　deliberate　and　reiterated　assertions　must　have　some
foundation。

Before　we　can　discuss　the　first　point　with　advantage　we　must　consider
with　some　attention；　and　compare　together；　the　structure　of　the　human
hand　and　that　of　the　human　foot；　so　that　we　may　have　distinct　and　clear
ideas　of　what　constitutes　a　hand　and　what　a　foot。

The　external　form　of　the　human　hand　is　familiar　enough　to　every　one。　　It
consists　of　a　stout　wrist　followed　by　a　broad　palm；　formed　of　flesh；
and　tendons；　and　skin；　binding　together　four　bones；　and　dividing　into
four　long　and　flexible　digits；　or　fingers；　each　of　which　bears　on　the
back　of　its　last　joint　a　broad　and　flattened　nail。　　The　longest　cleft
between　any　two　digits　is　rather　less　than　half　as　long　as　the　hand。
From　the　outer　side　of　the　base　of　the　palm　a　stout　digit　goes　off；
having　only　two　joints　instead　of　three；　so　short；　that　it　only　reaches
to　a　little　beyond　the　middle　of　the　first　joint　of　the　finger　next　it；
and　further　remarkable　by　its　great　mobility；　in　consequence　of　which
it　can　be　directed　outwards；　almost　at　a　right　angle　to　the　rest。　　This
digit　is　called　the　'pollex；'　or　thumb；　and；　like　the　others；　it　bears　a
flat　nail　upon　the　back　of　its　terminal　joint。　　In　consequence　of　the
proportions　and　mobility　of　the　thumb；　it　is　what　is　termed
〃opposable〃；　in　other　words；　its　extremity　can；　with　the　greatest　ease；
be　brought　into　contact　with　the　extremities　of　any　of　the　fingers；　a
property　upon　which　the　possibility　of　our　carrying　into　effect　the
conceptions　of　the　mind　so　largely　depends。

The　external　form　of　the　foot　differs　widely　from　that　of　the　hand；　and
yet；　when　closely　compared；　the　two　present　some　singular
resemblances。　　Thus　the　ankle　corresponds　in　a　manner　with　the　wrist；
the　sole　with　the　palm；　the　toes　with　the　fingers；　the　great　toe　with
the　thumb。　　But　the　toes；　or　digits　of　the　foot；　are　far　shorter　in
proportion　than　the　digits　of　the　hand；　and　are　less　moveable；　the　want
of　mobility　being　most　striking　in　the　great　toewhich；　again；　is　very
much　larger　in　proportion　to　the　other　toes　than　the　thumb　to　the
fingers。　　In　considering　this　point；　however；　it　must　not　be　forgotten
that　the　civilized　great　toe；　confined　and　cramped　from　childhood
upwards；　is　seen　to　a　great　disadvantage；　and　that　in　uncivilized　and
barefooted　people　it　retains　a　great　amount　of　mobility；　and　even　some
sort　of　opposability。　　The　Chinese　boatmen　are　said　to　be　able　to　pull
an　oar；　the　artisans　of　Bengal　to　weave；　and　the　Carajas　to　steal
fishhooks；　by　its　help；　though；　after　all；　it　must　be　recollected　that
the　structure　of　its　joints　and　the　arrangement　of　its　bones；
necessarily　render　its　prehensile　action　far　less　perfect　than　that　of
the　thumb。

But　to　gain　a　precise　conception　of　the　resemblances　and　differences　of
the　hand　and　foot；　and　of　the　distinctive　characters　of　each；　we　must
look　below　the　skin；　and　compare　the　bony　framework　and　its　motor
apparatus　in　each　（Fig。　18）。

FIG。　18…。…The　skeleton　of　the　Hand　and　Foot　of　Man　reduced　from　Dr。
Carter's　drawings　in　Gray's　'Anatomy。'　　The　hand　is　drawn　to　a　larger
scale　than　the　foot。　　The　line　'a　a'　in　the　hand　indicates　the　boundary
between　the　carpus　and　the　metacarpus；　'b　b'　that　between　the　latter
and　the　proximal　phalanges；　'c　c'　marks　the　ends　of　the　distal
phalanges。　　The　line　〃a'　a'〃　in　the　foot　indicates　the　boundary　between
the　tarsus　and　metatarsus；　〃b'　b'〃　marks　that　between　the　metatarsus
and　the　proximal　phalanges；　and　〃c'　c'〃　bounds　the　ends　of　the　distal
phalanges；　'ca'；　the　calcaneum；　'as'；　the　astragalus；　'sc'；　the
scaphoid　bone　in　the　tarsus。

The　skeleton　of　the　hand　exhibits；　in　the　region　which　we　term　the
wrist；　and　which　is　technically　called　the　'carpus'two　rows　of
closely　fitted　polygonal　bones；　four　in　each　row；　which　are　tolerably
equal　in　size。　　The　bones　of　the　first　row　with　the　bones　of　the
forearm；　form　the　wrist　joint；　and　are　arranged　side　by　side；　no　one
greatly　exceeding　or　overlapping　the　rest。

The　four　bones　of　the　second　row　of　the　carpus　bear　the　four　long　bones
which　support　the　palm　of　the　hand。　　The　fifth　bone　of　the　same
character　is　articulated　in　a　much　more　free　and　moveable　manner　than
the　others；　with　its　carpal　bone；　and　forms　the　base　of　the　thumb。
These　are　called　'metacarpal'　bones；　and　they　carry　the　'phalanges'；　or
bones　of　the　digits；　of　which　there　are　two　in　the　thumb；　and　three　in
each　of　the　fingers。

The　skeleton　of　the　foot　is　very　like　that　of　the　hand　in　some　respects。
Thus　there　are　three　phalanges　in　each　of　the　lesser　toes；　and　only　two
in　the　great　toe；　which　answers　to　the　thumb。　　There　is　a　long　bone；
termed　'metatarsal'；　answering　to　the　metacarpal；　for　each　digit；　and
the　'tarsus'；　which　corresponds　with　the　carpus；　presents　four　short
polygonal　bones　in　a　row；　which　correspond　very　closely　with　the　four
carpal　bones　of　the　second　row　of　the　hand。　In　other　respects　the　foot
differs　very　widely　from　the　hand。　　Thus　the　great　toe　is　the　longest
digit　but　one；　and　its　metatarsal　is　far　less　moveably　articulated　with
the　tarsus；　than　the　metacarpal　of　the　thumb　with　the　carpus。　　But　a
far　more　important　distinction　lies　in　the　fact　that；　instead　of　four
more　tarsal　bones　there　are　only　three；　and；　that　these　three　are　not
arranged　side　by　side；　or　in　one　row。　　One　of　them；　the　'os　calcis'　or
heel　bone　（'ca'）；　lies　externally；　and　sends　back　the　large　projecting
heel；　another；　the　'astragalus'　（'as'）；　rests　on　this　by　one　face；　and
by　another；　forms；　with　the　bones　of　the　leg；　the　ankle　joint；　while　a
third　face；　directed　forwards；　is　separated　from　the　three　inner　tarsal
bones　of　the　row　next　the　metatarsus　by　a　bone　called　the　'scaphoid'
（'sc'）。

Thus　there　is　a　fundamental　difference　in　the　structure　of　the　foot　and
the　hand；　observable　when　the　carpus　and　the　tarsus　are　contrasted；　and
there　are　differences　of　degree　noticeable　when　the　proportions　and　the
mobility　of　the　metacarpals　and　metatarsals；　with　their　respective
digits；　are　compared　together。

The　same　two　classes　of　differences　become　obvious　when　the　muscles　of
the　hand　are　compared　with　those　of　the　foot。

Three　principal　sets　of　muscles；　called　〃flexors；〃　bend　the　fingers　and
thumb；　as　in　clenching　the　fist；　and　three　setsthe　extensorsextend
them；　as　in　straightening　the　fingers。　　These　muscles　are　all　〃long
muscles〃；　that　is　to　say；　the　fleshy　part　of　each；　lying　in　and　being
fixed　to　the　bones　of　the　arm；　is；　at　the　other　end；　continued　into
tendons；　or　rounded　cords；　which　pass　into　the　hand；　and　are　ultimately
fixed　to　the　bones　which　are　to　be　moved。　　Thus；　when　the　fingers　are
bent；　the　fleshy　parts　of　the　flexors　of　the　fingers；　placed　in　the　arm；
contract；　in　virtue　of　their　peculiar　endowment　as　muscles；　and　pulling
the　tendinous　cords；　connected　with　their　ends；　cause　them　to　pull　down
the　bones　of　the　fingers　towards　the　palm。

Not　only　are　the　principal　flexors　of　the　fingers　and　of　the　thumb　long
muscles；　but　they　remain　quite　distinct　from　one　another　through　their
whole　length。

In　the　foot；　there　are　also　three　principal　flexor　muscles　of　the　digits
or　toes；　and　three　principal　extensors；　but　one　extensor　and　one　flexor
are　short　muscles；　that　is　to　say；　their　fleshy　parts　are　not　situated
in　the　leg　（which　corresponds　with　the　arm）；　but　in　the　back　and　in　the
sole　of　the　footregions　which　correspond　with　the　back　and　the　palm　of
the　hand。

Again；　the　tendons　of　the　long　flexor　of　the　toes；　and　of　the　long
flexor　of　the　great　toe；　when　they　reach　the　sole　of　the　foot；　do　not
remain　distinct　from　one　another；　as　the　flexors　in　the　palm　of　the
hand　do；　but　they　become　united　and　commingled　in　a　very　curious
mannerwhile　their　united　tendons　receive　an　accessory　muscle
connected　with　the　heel…bone。

But　perhaps　the　most　absolutely　distinctive　character　about　the　muscles
of　the　foot　is　the　existence　of　what　is　termed　the　'peronaeus　longus'；
a　long　muscle　fixed　to　the　outer　bone　of　the　leg；　and　sending　its
tendon　to　the　outer　ankle；　behind　and　below　which　it　passes；　and　then
crosses　the　foot　obliquely　to　be　attached　to　the　base　of　the　great　toe。
No　muscle　in　t