is notched for the passage of the peroneal nerve. The dorsal slips of
insertion show variations similiar to those given above for _T.
pallidicinctus_. In four legs, a tiny vinculum extends from the lateral
edge of the branch of the tendon on digit IV to the lateral edge of the
underlying medial branch of the tendon of M. flexor perforatus digiti IV
at the level of the second phalanx.
=_M. Popliteus_=, Fig. 19B
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Extremely short but relatively broad
and thick; on posterior surface of proximal end of tibiotarsus;
extending distomedially from proximal part of fibula; deep to M. flexor
hallucis longus; lateral end overlapped by, and fused to, posterior head
of M. flexor digitorum longus; medial end often slightly overlapped by,
and fused to, M. plantaris; medial end (insertion) much wider than
lateral end (origin).
ORIGIN.--The origin is fleshy and tendinous (superficial surface) from
the medial surface of the fibula near the proximal end.
INSERTION.--The attachment is fleshy to the posterior surface of the
proximal end of the tibiotarsus adjacent (lateral) to the origin of M.
plantaris.
INNERVATION.--A branch of the medial division of the tibial nerve
penetrates the posterior surface.
INDIVIDUAL VARIATION.--None of significance in any of the three species
studied.
=_M. Peroneus Longus_=, Figs. 12, 13
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Large; on anterolateral surface of
shank; bounded medially by M. gastrocnemius pars interna and
posterolaterally by Mm. flexor perforans et perforatus digiti III and
flexor perforans et perforatus digiti II; proximal three fourths of
posteromedial part (covered by M. gastrocnemius pars interna)
aponeurotic and tightly fused to medial surfaces of underlying Mm.
tibialis anticus and extensor digitorum longus; proximal part of fleshy
belly somewhat fused to anterior surface of underlying M. tibialis
anticus; posterolateral surface strongly fused to aponeurotic medial
head of M. flexor perforans et perforatus digiti II and slightly fused
to anterolateral edge of M. flexor perforans et perforatus digiti III.
ORIGIN.--The muscle arises by fleshy and tendinous fibers from the edges
of the inner and outer cnemial crests; the extreme proximal end arises
either fleshily or aponeurotically from the rotular crest between the
cnemial crests; the posteromedial edge (aponeurotic except distal one
fourth fleshy) arises from the anteromedial intermuscular line.
INSERTION.--The narrow ossified tendon on the superficial surface of the
distal part of the fleshy belly extends several mm. beyond the belly
where it becomes flexible and divides into two branches. The short,
broad posterior branch attaches broadly to the proximolateral corner of
the tibial cartilage. The narrow anterior branch passes along the
lateral surface of the tibiotarsus, through a strong retinaculum
immediately proximal to the external condyle, and crosses the lateral
surface of the joint, where it is covered by connective tissue nearly as
tough as, and continuous with, the retinaculum; the tendon attaches
broadly to the lateral edge of the ossified tendon of M. flexor
perforatus digiti III a short distance below the hypotarsus.
INNERVATION.--The peroneal nerve sends twigs to the deep surface.
INDIVIDUAL VARIATION.--In both legs of two specimens, the extreme
proximal end extends proximal to the rotular crest and attaches fleshily
to the superficial surface of the distal end of the patellar tendon.
_T. cupido_
INDIVIDUAL VARIATION.--None of significance.
_P. p. jamesi_
INDIVIDUAL VARIATION.--One leg shows the variation described above for
_T. pallidicinctus_.
=_M. Tibialis Anticus_=, Figs. 14, 15, 16, 19E, 20N
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Thick; on anterior aspect of thigh
deep to M. peroneus longus; bounded posteriorly by M. extensor digitorum
longus and posterolaterally by Mm. flexor digitorum longus and peroneus
brevis; divided into two heads--tibial and femoral; small femoral head
adjacent to posterolateral surface of much larger tibial head; two heads
joined near midpoint of fleshy part of muscle, forming bipinnate belly
(pinnate structure most evident on deep surface); proximal part of
femoral head situated between outer cnemial crest and head of fibula;
proximal part of anterior surface of tibial head somewhat fused to
overlying M. peroneus longus; medial surface fused to aponeurosis of
latter.
ORIGIN.--_Tibial head_: This arises by fleshy and tendinous fibers from
the edge of the inner cnemial crest, from the rotular crest between the
inner and outer cnemial crests, and from the anterior surface, distal
edge, and posterior surface of the outer cnemial crest; the attachment
may or may not extend onto the superficial surface of the distal part of
the patellar tendon; the attachment is adjacent to the origin of the
underlying M. extensor digitorum longus. _Femoral head_: This arises by
a slender tendon from the notch in the distal end of the external
condyle of the femur.
INSERTION.--The slender ossified tendon extends along the anterior
surface of the distal end of the tibiotarsus and passes through a large,
strong, oblique retinaculum (superficial to the supratendinal bridge);
the lateral end of the retinaculum attaches to the lateral end of the
supratendinal bridge; the medial end attaches immediately proximal to
the medial end of the bridge. The tendon widens and becomes flexible as
it passes across the anterior surface of the intratarsal joint, then
narrows and attaches to the tubercle on the anterior surface of the
proximal part of the tarsometatarsus between Mm. extensor hallucis
longus and extensor brevis digiti IV. The distalmost bundle of
tendinous fibers does not attach to the tubercle, but extends distally
along the anterior surface of the tarsometatarsus and attaches to the
latter a few mm. distal to the tubercle, forming an accessory insertion.
A part of the peroneal nerve passes between the main and accessory
insertions.
INNERVATION.--A variable number of branches of the peroneal nerve
penetrate the lateral surface of the femoral head; a variable number of
branches of the same division pass deep to the femoral head and enter
the posterior edge of the tibial head.
INDIVIDUAL VARIATION.--- In one leg, the accessory insertion is absent.
_T. cupido_
INDIVIDUAL VARIATION.--None of significance.
_P. p. jamesi_
DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The origin of the tibial
head does not extend onto the patellar tendon.
INDIVIDUAL VARIATION.--The accessory insertion is absent in one leg.
=_M. Extensor Digitorum Longus_=, Figs. 15, 17
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Bipinnate; on anterior surface of
tibiotarsus deep to M. tibialis anticus; bounded laterally by M.
peroneus brevis; lateral edge usually slightly fused to proximal half of
latter; medial surface fused to aponeurosis of M. peroneus longus.
ORIGIN.--The muscle arises fleshily from the lateral surface of the
inner cnemial crest, from the rotular crest between the cnemial crests
(deep to the attachment of M. tibialis anticus), from the basal (medial)
half of the anterior surface of the outer cnemial crest, and from the
anterior surface of the tibiotarsus (except the distal part) between the
anteromedial and anterolateral intermuscular lines; proximal to the
anterolateral intermuscular line, the origin usually extends almost to
the lateral edge of the tibiotarsus.
INSERTION.--The ossified tendon extends along the mid-anterior surface
of the distal part of the tibiotarsus deep to the tendon of M. tibialis
anticus and passes under the supratendinal bridge, becoming flexible and
widening slightly as it crosses the anterior surface of the intratarsal
joint; the tendon narrows again and passes through a small but strong
retinaculum on the anterior surface (medial to midline) of the proximal
part of the tarsometatarsus; the retinaculum is immediately proximal and
medial to the insertion of M. tibialis anticus. The tendon ossifies
again as it passes down the anterior surface of the tarsometatarsus and
bifurcates near the midpoint of the latter; the lateral branch soon
bifurcates again; of these three branches, which are ossified for some
distance, the lateral one passes onto the dorsal surface of digit IV,
the middle one passes onto the dorsolateral surface of digit III, and
the medial one subdivides (at the level of the trochleae) into three
branches--one passing onto the dorsal surface of digit III and two
passing onto the dorsal surface of digit II. At the level of the
metatarsophalangeal joints, all of these tendons are interconnected by
strong sheets of connective tissue and it is often difficult exactly to
delimit the tendons at this level. On the digits, tough connective
tissue binds the tendons to the phalanges; this is most pronounced at
the interphalangeal joints. The tendons are distinct on the first
phalanx of each digit, but are often poorly defined farther distally. On
_digit IV_ the tendon subdivides into branches that attach to the
proximal ends of the ungual, fourth, third, and (usually) second
phalanges. On _digit III_ the lateralmost tendon bifurcates, with one
branch attaching to the ungual phalanx and the other to the proximal end
of the third phalanx; the medial tendon attaches to the proximal end of
the second phalanx. On _digit II_ the originally medial tendon passes
underneath and then lateral to the other tendon and attaches to the
ungual phalanx; the other tendon attaches to the proximal end of the
second phalanx.
INNERVATION.--One or more branches of the peroneal nerve enter the
lateral edge.
INDIVIDUAL VARIATION.--In four legs, the lateral branch of the
trifurcated tendon is not ossified at all.
_T. cupido_
INDIVIDUAL VARIATION.--In a few cases, the muscle does not come in
contact with M. peroneus brevis.
_P. p. jamesi_
DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The belly is shorter. The
lateral branch of the tendon on the tarsometatarsus is not ossified
(true also of some legs of _Tympanuchus_).
INDIVIDUAL VARIATION.--In several legs, the muscle also arises from the
distal part of the posterior surface of the outer cnemial crest.
=_M. Peroneus Brevis_=, Figs. 14, 16, 17, 18, 19A
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Small; on lateral surface of distal
part of tibiotarsus; mainly anterior to fibula; bounded posteriorly and
laterally by M. flexor digitorum longus (fused with latter), anteriorly
by M. tibialis anticus, and anteromedially by M. extensor digitorum
longus (usually slightly fused to latter).
ORIGIN.--The muscle arises by fleshy and tendinous fibers from the
medial and anterior surfaces of the fibula beginning a short distance
below the distal end of the fibular crest and from the anterolateral
surface of the tibiotarsus anterior to the fibula; the anteromedial edge
attaches to the anterolateral intermuscular line.
INSERTION.--The short, slender, ossified tendon passes along the
anterolateral surface of the tibiotarsus and through a retinaculum
immediately proximal and anteromedial to the retinaculum for the
anterior branch of the tendon of M. peroneus longus; the tendon becomes
flexible and widens as it passes across the lateral surface of the
intratarsal joint deep to the tendon of M. peroneus longus, turning
posteriorly and attaching to the proximolateral corner of the
hypotarsus.
INNERVATION.--The superficial peroneal branch of the peroneal nerve
gives one or two twigs to the anterior surface of the proximal part.
INDIVIDUAL VARIATION.--None of significance.
_T. cupido_
INDIVIDUAL VARIATION.--In a few legs, the muscle does not come in
contact with M. extensor digitorum longus.
_P. p. jamesi_
INDIVIDUAL VARIATION.--None of significance.
=_M. Extensor Hallucis Longus_=, Figs. 19E, 20N
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Slender and elongate; proximal part
on anterior surface of tarsometatarsus medial to anterior metatarsal
groove; near midlength of tarsometatarsus, muscle twisted onto medial
surface of latter; divisible into two heads--proximal and distal; belly
of proximal head (largest) ending at level of twisting onto medial
surface of bone; short distal head beginning at this point deep to
tendon of proximal head and soon joining latter tendon.
ORIGIN.--_Proximal head_: This arises fleshily from the anterior surface
of approximately the proximal half of the tarsometatarsus medial to the
anterior metatarsal groove; the proximal end is partly medial to and
partly deep to the retinaculum for M. extensor digitorum longus; some
fibers arise from the extreme distal edge of the main insertion of M.
tibialis anticus; the distal end of the belly is unattached. _Distal
head_: This arises fleshily from the medial surface of the
tarsometatarsus proximal to the first metatarsal and deep to the tendon
of the proximal head.
INSERTION.--The slender tendon of the proximal head, which begins along
the medial edge of the distal part of the belly, soon fuses with the
superficial surface of the distal head (ossified here); the common
tendon (unossified) passes onto the dorsal (proximal) surface of the
first metatarsal, where it passes through a retinaculum, then passes
along the dorsal surface of the hallux (bound by strong connective
tissue to the metatarsophalangeal joint), attaching to the dorsal
surface of the ungual phalanx.
INNERVATION.--The branch of the deep peroneal nerve that passes medial
to the main insertion of M. tibialis anticus gives one or two twigs into
the proximal part of the proximal head. No supply to the distal head was
found, but see below.
INDIVIDUAL VARIATION.--In one leg, the proximal end of the distal head
is fused to the distal end of the belly of the proximal head, whereas in
three legs, a distinct gap separates the fleshy parts of the two heads.
The following variations, each found in one leg, pertain to the
relationship of the origin of the proximal head to the retinaculum for
M. extensor digitorum longus: the origin does not extend proximally
medial to the retinaculum; the origin does not extend proximally deep to
this retinaculum; a part of the proximal end extends proximally lateral
to this retinaculum (in this instance there is an unusually wide gap
between the retinaculum and the insertion of M. tibialis anticus). In
one leg, the distalmost fibers of the distal head do not join the common
tendon but insert independently on the articular capsule of the
metatarsophalangeal joint (deep to the common tendon).
_T. cupido_
INDIVIDUAL VARIATION.--The relationship between the two heads varies as
follows: the proximal end of the distal head may be fused to the distal
end of the belly of the proximal head; the proximal end of the distal
head may begin anterior (adjacent) to the distal end of the belly of the
proximal head; there may be a distinct gap between the fleshy parts of
the two heads. In two legs, there is no origin from the insertion of M.
tibialis anticus. In one leg, a small accessory bundle of fleshy fibers
arises from the proximal end of the first metatarsal (widely separated
from the origin of the distal head), passes through the retinaculum deep
to the common tendon and attaches to the dorsal surface of the articular
capsule of the metatarsophalangeal joint; thus this bundle is completely
separate from the remainder of the muscle. In two legs, the same nerve
branch that gives twigs into the proximal head also gives off (much
farther distally) a twig that enters the distal head.
_P. p. jamesi_
INDIVIDUAL VARIATION.--The proximal end of the distal head may begin
anterior (adjacent) to the distal end of the belly of the proximal head.
In four legs, the origin of the proximal head does not extend proximally
medial to the retinaculum for M. extensor digitorum longus; in one of
these legs, a part of the proximal end extends proximally lateral to
this retinaculum. The distalmost fibers of the distal head do not join
the common tendon but insert independently on the dorsal surface of the
articular capsule of the metatarsophalangeal joint in four legs; in
another leg, the entire distal head has the latter insertion
(consequently the two heads are completely separate).
=_M. Abductor Digiti II_= Figs. 19E, 20N
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Short; on medial surface of distal
part of tarsometatarsus; proximal end adjacent (anterior) to distal head
of M. extensor hallucis longus.
ORIGIN.--The origin is fleshy from the medial surface of the distal part
of the tarsometatarsus anterior (adjacent) to the first metatarsal and
from the anteromedial surface of the basal half of the first metatarsal.
INSERTION.--The flat tendon passes over the medial surface of the
trochlea for digit II and attaches to the medial surface of the proximal
end of the first phalanx of digit II; the tendon is fused with the
articular capsule.
INNERVATION.--The compound nerve formed by the fusion of a branch of the
superficial peroneal nerve with a branch of the deep peroneal nerve
gives a twig to the anterolateral edge of the muscle.
INDIVIDUAL VARIATION.--In some cases, the twig arises from the deep
peroneal branch alone (which is not joined by the superficial peroneal
nerve).
_T. cupido_
INDIVIDUAL VARIATION.--In one leg, some of the fleshy fibers arising
from the first metatarsal insert independently on the medial surface of
the trochlea for digit II (deep to the main part of the muscle).
_P. p. jamesi_
INDIVIDUAL VARIATION.--None of significance.
=_M. Extensor Brevis Digiti III_= (M. extensor proprius digiti III),
Figs. 19E, 20N
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Short and relatively broad (narrow
proximally); on mid-anterior surface of distal part of tarsometatarsus;
tendon of insertion fused with articular capsule.
ORIGIN.--The origin is fleshy from the mid-anterior surface of the
distal part of the tarsometatarsus ending a short distance proximal to
the trochlea for digit III.
INSERTION.--The flat tendon passes over the trochlea for digit III and
attaches to the dorsal surface of the proximal end of the first phalanx
of digit III.
INNERVATION.--The compound nerve formed by the fusion of a branch of the
superficial peroneal nerve with a branch of the deep peroneal nerve
gives a twig to the proximal end of the muscle.
INDIVIDUAL VARIATION.--In some cases, the twig arises from the deep
peroneal branch alone (which is not joined by the superficial peroneal
nerve). The individual variation is insignificant in _T. cupido_ and _P.
p. jamesi_.
=_M. Extensor Proprius Digiti III_= (Not found by Hudson, _et al._),
Fig. 20N
_T. pallidicinctus_ and _T. cupido_
Absent in both species.
_P. p. jamesi_
This atypical muscle was found in only two legs (P.p. 1L and 4L). The
following description applies to P.p. 4L (Fig. 20N).
GENERAL DESCRIPTION AND RELATIONS.--Small but well developed; fleshy
part 1-1/2 × 13 mm.; proximal end narrower; on mid-anterior surface of
tarsometatarsus between Mm. extensor brevis digiti IV and extensor
hallucis longus and mostly proximal to M. extensor brevis digiti III;
tendinous distal part superficial to latter; fleshy belly ending
immediately distal to proximal end of latter.
ORIGIN.--The origin is fleshy from a narrow elongate area on the
mid-anterior surface of the tarsometatarsus between Mm. extensor brevis
digiti IV and extensor hallucis longus, beginning at the distal end
(bony) of the elongate accessory insertion of M. tibialis anticus. The
distal part of the belly is free.
INSERTION.--The attachment is by a thin, wide (relative to belly) tendon
to the superficial surface of M. extensor brevis digiti III.
INNERVATION.--Not found.
INDIVIDUAL VARIATION.--In P.p. 1L, the muscle is less well developed.
The fleshy belly is 1 × 5 mm. It arises from the lateral edge of M.
extensor hallucis longus. The extremely slender insertional tendon
attaches as above.
=_M. Extensor Brevis Digiti IV_=, Figs. 19E, 20N
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Slender and tapering; on lateral
part of anterior surface of tarsometatarsus; length of belly variable;
middle of medial edge in contact with M. extensor hallucis longus.
ORIGIN.--The origin is fleshy from the lateral part of the anterior
surface of the tarsometatarsus, including the anterior metatarsal
groove.
INSERTION.--The long slender tendon enters the anterior aperture of the
distal foramen, passes through the intertrochlear canal, emerges from
the terminal foramen, and attaches to the medial surface of the proximal
end of the first phalanx of digit IV.
INNERVATION.--The superficial peroneal branch of the peroneal nerve
sends a twig into the proximal part of the muscle.
INDIVIDUAL VARIATION.--None of significance in any of the three species
studied.
=_M. Lumbricalis_=, Fig. 19F
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Small, thin, and strap-shaped; on
mid-posterior surface of distal end of tarsometatarsus deep to tendon of
M. flexor digitorum longus; belly partly fleshy and partly elastic
connective tissue.
ORIGIN.--The muscle arises from the deep (anterior) surface of the
tendon of M. flexor digitorum longus a short distance proximal to the
trifurcation of the latter.
INSERTION.--The muscle attaches to the proximal end of the subarticular
cartilage ventral to the trochlea for digit III.
INNERVATION.--A long but extremely small twig arises from the
paraperoneal branch of the tibial nerve a short distance distal to the
hypotarsus and extends distally along the mid-posterior surface of the
tarsometatarsus (parallel to a larger nonmuscular branch) and enters the
deep surface distal to the middle. It was possible to follow this twig
in only two legs; it was presumably destroyed in the course of
dissection in the others.
INDIVIDUAL VARIATION.--In some cases, the "muscle" appears grossly to be
entirely connective tissue, although a distinct entity.
_T. cupido_
INDIVIDUAL VARIATION.--In some cases, the "muscle" appears grossly to be
entirely connective tissue. The innervation was found in only one leg,
in which the twig arises more distally than in _T. pallidicinctus_.
_P. p. jamesi_
The innervation was not found.
=_M. Abductor Digiti IV_=, Fig. 19F
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Slender and elongate; on posterior
surface of tarsometatarsus lateral to midline; in contact with M. flexor
hallucis brevis in midline.
ORIGIN.--The origin is fleshy from the posterior surface of the
tarsometatarsus lateral to the midline beginning near the proximal end
(lateral to the hypotarsus) and ending at the level of the first
metatarsal.
INSERTION.--The slender tendon, which begins along the lateral edge of
the distal part of the belly, passes through a retinaculum on the
posterolateral surface of the tarsometatarsus immediately above the
outer trochlea and attaches to the lateral surface of the proximal end
of the first phalanx of digit IV.
INNERVATION.--The paraperoneal branch of the tibial nerve gives one or
two twigs to the proximal part of the muscle.
INDIVIDUAL VARIATION.--None of significance in any of the three species
studied.
=_M. Flexor Hallucis Brevis_=, Fig. 19F
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Slender and elongate; on posterior
surface of tarsometatarsus medial to midline; belly (except proximal
end) adjacent (lateral) to posterior metatarsal crest; proximal end
passing under latter (immediately distal to hypotarsus) and lying
anteromedial to hypotarsus.