below the head, and in a straight line extending down the femur.
_Insertion._—By a broad tendon along the thickened inner border of the
summit of the tibia.
_Shape._—Thick, long.
_Relations._—Anteriorly, with the bone; surrounded by the other crural
muscles.
_Action._—Extends the leg upon the knee; a powerful assistant of the
extensor femoris.
=Biceps Flexor Cruris= (Fig. 17, No. D, 1). _Location._—Posterior tibial
region.
_Origin._—By a tendinous fascia from the post-acetabular ridge,
extending between the antitrochanter and the anterior point of the
insertion of the semitendinosus.
_Insertion._—To the tuberosity on the external part of the shaft of the
fibula a short distance below the head.
_Shape._—Large, rather cone-shaped with base directed upward.
_Relations._—Anteriorly, with the vastus externus; posteriorly, with the
semitendinosus. The inferior tendinous portion passes through a
tendinous sling or pulley called the biceps band.
_Action._—Flexes the leg upon the thigh.
=Semitendinosus= (Fig. 23, No. 10). _Location._—Posterior femoral
region.
_Origin._—By a tough, strong fascia from the surface of the caudal
muscles and from the posterior third of the post-acetabular ridge.
_Insertion._—The fibers pass downward and forward, and insert to the
tendinous raphe along the posterior margin of the semitendinosus
accessorius; lower down it merges with the median fascia of the inner
head of the gastrocnemius.
_Shape._—Fleshy, broad, flat and long.
_Relations._—Internally, with the semimembranosus and anteriorly, with
the biceps flexor cruris.
_Action._—Flexes the leg.
=Semitendinosus Accessorius.= _Location._—Posterior femoral region.
_Origin._—From an oblique line just above the condyle, on the posterior
of the shaft of the femur.
_Insertion._—Its fibers, passing upward and backward, attach themselves
to the tendinous raphe common to this muscle and the semitendinosus, and
are finally inserted to the inner side of the shaft of the tibia.
_Shape._—Flat, oblong.
_Relations._—Posteriorly to the shaft of the femur, and externally to
the long adductors of the thigh.
_Action._—Aids the preceding in flexing the leg.
=Semimembranosus= (Fig. 24, No. 17). _Location._—Postero-internal to the
semitendinosus.
_Origin._—From the outer surface of the ischium, beginning at the lower
margin of its notch on the posterior pelvic border, extends on a curved
line on the adjacent surface beyond.
_Insertion._—The fibers, passing downward and forward, insert by a
broad, thin tendon to the shaft of the tibia a short distance below the
head and on a line parallel to the long axis of the tibia.
_Shape._—Long, narrow, ribbon-shaped.
_Relations._—Lies adjacent to the semitendinosus and in the same plane.
_Action._—Directly flexes the leg.
=Femoro-caudal= (Fig. 24, No. 8). _Location._—Infero-lateral to the
caudal and post-femoral region.
_Origin._—By a delicate tendon from the base of the pygostyle.
_Insertion._—By a thin, flat tendon upon the outer part of the shaft of
the femur below the trochanter and at about the juncture of the upper
and middle third of the bone.
[Illustration:
FIG. 24.—Second layer of muscles of the thigh of a cock. Outside view.
1, Appendico-costales. 2, Levatores costarum. 3, Sacro-lumbalis. 4,
Longissimus dorsi. 5, Intercostales. 6, Longissimus dorsi. 7,
Latissimus dorsi. 8, Femoro-caudal. 9, Edge of obturator externus.
11, Gluteus medius. 12, Gluteus minimus. 13, Crureus. 14, Vastus
externus. 15, Extensor femoris. 16, Biceps flexor cruris. 17,
Semimembranosus. 18, Adductor magnus. 19, Adductor longus. 20,
External abdominal oblique. 21, Depressor coccygis. 22, Tibialis
anticus. 23, Tibialis posticus. 24, Flexor perforans digitorum
profundus. 25, Flexor perforatus medius secundus pedis. 26, Flexor
longus hallucis.
]
_Shape._—Long, narrow, spindle-shaped, flattened from side to side.
_Relations._—Interiorly to the obturator externus, and along the upper
border of the long adductors of the thigh and the semimembranosus.
_Action._—Pulls the tail down and to one side.
=Obturator Externus= (Fig. 24, No. 9). _Location._—External
posterolateral side of the pelvis.
_Origin._—From the posterior half of the periphery of the ischiatic
foramen and the concavity found on the external surface of the lateral
part of the pelvis.
_Insertion._—The fibers pass across to the femur and are inserted by a
broad, flat tendon to the shaft of the femur just below the trochanter.
_Shape._—Thick, fleshy.
_Relations._—Lies just above the femoro-caudal muscle, the sciatic nerve
and femoral artery pass over and external to its tendon.
_Action._—Pulls the head of the femur backward.
=Obturator Internus= (Fig. 16, No. _E_, 1). _Location._—Occupies the
space between the ischium and the pubis.
_Origin._—From the ventral surface of the ischium, including the
posterior border, from the inner line of the corresponding post-pubis,
and from the membrane covering the space between these two bones.
_Insertion._—Becoming dense, subcylindrical, and strong, it passes
through the obturator foramen and is inserted to the outer part of the
trochanter of the femur, in common with the gemellus and opposite to the
insertion of the gluteus medius.
_Shape._—Subtriangular and flat with a central tendon; bipenniform.
_Relations._—Outside the pelvis the tendon lies upon the gemellus and is
external to it. Fills the obturator foramen and the space between the
ischium and the pubis.
_Action._—Acts as a posterior stay to the head of the femur.
=Gemellus= (Fig. 25, No. 5). _Location._—Posterior to the head of the
femur.
_Origin._—From the fossa between the acetabulum and the obturator
foramen, and on the outer side of the pelvis.
_Insertion._—Its fibers are attached by fascia to the tendon of the
obturator internus, and pass directly to the trochanter of the femur
where they insert in common with that of the obturator internus.
_Shape._—Strong, thick, chunky.
_Relations._—Postero-external to the head of the femur.
_Action._—Like the two preceding, when the head of the femur is fixed,
it pulls the pelvis forward and steadies it on the head of the femur.
=Adductor Longus= (Fig. 24, No. 19). _Location._—In the posterior
femoral region.
_Origin._—From a line on the lateral part of the pelvis.
_Insertion._—The fibers, passing downward and forward, are inserted on a
longitudinal line along the posterior part of the shaft of the femur.
_Shape._—Broad, flat, fleshy.
_Relations._—Posteriorly to the femur, and anteriorly to the adductor
magnus.
_Action._—Adducts the thigh.
=Adductor Magnus= (Fig. 24, No. 18). _Location._—Posterior femoral
region.
_Origin._—From the fine constituting the lower boundary of the ischiatic
fossa on the outer lateral part of the pelvis.
_Insertion._—The fibers pass downward and are inserted to the superior
curve of the internal femoral condyle. The internal head of the
gastrocnemius blends with this muscle just above its attachment.
_Shape._—Long, narrow.
_Relations._—Posteriorly to the adductor magnus and anteriorly to the
semimembranosus.
_Action._—Strongly adducts the thigh.
THE TIBIAL GROUP
Gastrocnemius
Peroneus longus
Extensor longus digitorum
Tibialis posticus
Flexor longus hallucis
Flexor perforatus annularis primus pedis
Flexor perforatus medius secundus pedis
Flexor perforans digitorum profundus
Soleus
Tibialis anticus
Extensor hallucis brevis
Flexor perforatus indicis secundus pedis
Flexor perforatus medius primus pedis
Flexor perforatus indicis primus pedis
Extensor brevis digitorum
Flexor hallucis brevis
Extensor annularis brevis
=Gastrocnemius= (Fig. 23, No. 11). _Location._—Posterior tibial region.
_Origin._—There are three heads: the internal, the external, and the
tibial. The external head extends by a short, flattened, strong tendon
from the postero-external part of the external condyle of the femur; the
internal head extends from the outer surface of the inner condyle of the
femur; and the tibial head extends from the entire inner rim of the
tibial summit and from the free edge of the adjacent crest.
_Insertion._—At the lower fourth of the tibial shaft, terminates in a
broad, flat tendon which passes over the shallow, longitudinal groove of
the tibial cartilage, and, crossing the tibio-tarsal joint, is inserted
to the posterior surface of the hypotarsus of the metatarsal bone, and
finally, below this point, merges into the podothecal sheath confining
the flexor tendons.
_Shape._—Large, fleshy, somewhat cone-shaped with the base upward.
_Relations._—The posterior fleshy muscle of the post-tibial region
located anterior to the soleus.
_Action._—Extends the metatarsus on the tibia.
=Soleus= (Fig. 25, No. _G_, 1). _Location._—The posterior tibial region.
_Origin._—From the posterior part of the head of the tibia.
_Insertion._—By a long slender tendon to the proximal end and toward the
inner angle of the tibial cartilage, some of the fibers passing to the
tendon of the gastrocnemius.
_Shape._—Small, flattened.
_Relations._—Anteriorly, with the flexor perforans digitorum profundus
and posteriorly, with the gastrocnemius.
_Action._—Similar to that of the gastrocnemius.
=Peroneus Longus= (Fig. 23, No. 12). _Location._—Antero-lateral tibial
region.
_Origin._—From the raised crest in front of the head of the tibia, and
from the fascia that covers the outer side of the knee-joint.
_Insertion._—The fibers, passing downward, then downward and outward,
terminate in a small tendon at the lower third of the tibia. This tendon
bifurcates just above the tibial condyles at the outer part of the limb,
the shorter and stronger attaches to the fibrous fascia covering the
tibial cartilage, the other merging with the tendon of the flexor
perforatus medius primus pedis about 1 centimeter below the hypotarsus
of the tarso-metatarsus.
_Relations._—Covers over all the muscles of the anterior tibial region.
_Shape._—A broad muscular sheet.
_Action._—Assists the flexor perforatus medius primus pedis.
=Tibialis Anticus= (Fig. 24, No. 22). _Location._—In the anterior tibial
region.
_Origin._—The muscular belly may be easily divided into two parts. The
inner head extends from the head of the tibia immediately beneath the
peroneus longus. The outer head arises by a strong tendon from a
depression on the antero-inferior ridge of the outer condyle of the
femur.
_Insertion._—The tendon passing through the fibrous ligamentous loop
just above the tibial condyles, inserts to a tubercle on the shaft just
below the head of the tarso-metatarsus.
_Shape._—Large, fusiform.
_Relations._—Beneath the peroneus longus.
_Action._—Flexes the metatarsus upon the tibia.
=Extensor Longus Digitorum= (Fig. 25, No. _G_, 6). _Location._—Anterior
tibial region.
_Origin._—From the inferior portion of the crest and a portion of the
shaft of the fibula.
_Insertion._—It becomes tendinous at the lower third of the bone,
passing under the bony ridge just above the condyle in front, and over
the ankle-joint. It is bound down by firm fascia, and at the trochlea of
the basal toe joints, divides into three small tendinous slips. These
pass over the superior part of the second, the third, and the fourth
toes, bifurcating in their course, and are inserted to the distal ones.
_Shape._—Long, penniform, with a long, slender tendon.
_Relations._—Immediately below the tibialis anticus.
_Action._—Extends the digits as their long extensor.
=Extensor Hallucis Brevis= (Fig. 25, No. _G_, 4). _Location._—The
anterior metatarsal region, along the antero-internal edge.
_Origin._—From just below the summit of the antero-internal part of the
head of the tarso-metatarsus, and from the adjacent shaft below, and
from the tendon of the tibialis anticus.
_Insertion._—Into the process at the superior part of the bone of the
bony claw of the hallux.
_Shape._—Slender, thin in diameter, with a long, slender tendon.
_Relations._—Superiorly, with the antero-internal edge of the metatarsus
and interiorly, its tendon with the top of the hallux.
_Action._—Extends the hallux.
=Extensor Brevis Digitorum.= _Location._—On the anterior surface of the
metatarsus.
[Illustration:
FIG. 25.—Inner layer of muscles of the thigh of a hen. Outside view.
_A._ Pad of fibrocartilage or meniscus of femoro-tibial articulation.
1, Inner semi-lunar fibrocartilage. 2, External semi-lunar
cartilage. 3, Anterior border.
_B._ Tarsal meniscus or pad of fibrocartilage.
_C._ Articular surface of the tarsal joint. 1, Posterior ligamentum
cruciatum genu. 2, Femoral tendinous insertion of tibialis anticus.
3, Ligamentum tibio-fibulare. 4, Ligamentum interosseum. 5,
Ligamentum transversum of the meniscus. 6, Anterior ligamentum
cruciatum genu.
_D._ 1, Tibia. 2, Fibula. 3, Femur. 4, External ligamentum laterale
genu.
_E._ Inferior surface of the tail of a hen. 1, Infracoccygis. 2,
Lateralis coccygis.
_F._ Outside pelvic view. 1, Obturator ligament. 2, Tendon of the
obturator internus. 3, Ligamentum oblongum. 4, Ligamentum capsulare.
5, Gemellus.
_G._ Outside view of leg of a cock. 1, Soleus. 2, Flexor longus
hallucis. 3, Flexor perforans digitorum profundus. 4, Extensor
brevis hallucis. 5, Extensor brevis annularis. 6, Extensor longus
digitorum. 7, Tendon of the tibialis posticus.
_H._ 1, Transversalis abdominalis. 2, Cotyloid cavity.
]
_Origin._—By a small fleshy belly to the anterior part of the proximal
end of the metatarsus.
_Insertion._—It becomes tendinous about the middle third of the
metatarsus. Extending down the anterior face of the metatarsus it is
inserted to the inner tubercle of the base of the first phalanx of the
outer or fourth toe.
_Shape._—Long, slender.
_Relations._—Posteriorly with the metatarsus.
_Action._—Pulls the fourth toe upward and inward.
=Flexor Hallucis Brevis.= _Location._—Postero-internal side of the
metatarsus.
_Origin._—Side and lower margin of the inner aspect of the hypotarsus of
the tarso-metatarsus and from the shaft of this bone immediately below
it.
_Insertion._—Winds round inner side of basal joint of the hallux and is
inserted on its under side.
_Shape._—Small flat muscle gradually tapering into a tendon.
_Relations._—Posteriorly with the metatarsus.
_Action._—To flex the hallux.
=Extensor Annularis Brevis.= _Location._—On postero-external side of
metatarsus.
_Origin._—External aspect of the hypotarsus and the shaft below.
_Insertion._—Supero-external part of the basal phalanx of the fourth
toe.
_Shape._—Small flat muscle.
_Relations._—Posteriorly with the metatarsus.
_Action._—Extensor of the fourth toe.
=Tibialis Posticus= (Fig. 24, No. 23). _Location._—In the posterior
tibial region.
_Origin._—From the whole shaft of the fibula below the insertion of the
biceps flexor cruris, and from the shaft of the tibia a short distance
below this insertion. Also from the interosseous membrane, and the
adjacent surface of the tibial shaft.
_Insertion._—Passing in front of the external malleolus, crossing the
ankle-joint, finally inserted into the outer edge of the summit of the
tarso-metatarsal bone.
_Shape._—Long, subcylindrical.
_Relations._—Medially, with the flexor perforans digitorum pedis;
superiorly, with the postero-external portion of the tibia.
_Action._—Extends the metatarsus upon the tibia.
=Flexor Perforatus Indicis Secundus Pedis= (Fig. 17, No. 5).
_Location._—The posterior tibial region.
_Origin._—From the external surface of the outer condyle of the femur,
just below the head of the gastrocnemius.
_Insertion._—Passing in an oblique manner along posterior to the tibia,
extends through the superficial part of the tibial cartilage to the
outer side of the leg; then crossing the tibio-tarsal joint, it passes
through a special canal of the hypotarsus, down the back of the
tarso-metatarsus, under the annular ligament of the sole of the foot and
a cartilaginous structure below this ligament, over the trochlea, and is
inserted to the middle shaft of the second phalanx of the second toe.
_Shape._—Thin, flat, broadly spindle-shaped.
_Relations._—Posteriorly, with the flexor perforatus medius secundus
pedis, and anteriorly, with the flexor perforatus annularis primus
pedis.
_Action._—Flexes the toes.
=Flexor Longus Hallucis= (Fig. 17, No. 7; Fig. 25, No. 2).
_Location._—The posterior tibial region.
_Origin._—By two tendinous heads: one from the posterior part of the
femur, just below the two condyles; the other from the outer part of the
external condyle of the femur. The deep flexor passes between these two
heads.
_Insertion._—Becoming tendinous at the lower third of the leg, passes
beneath the superficial flexors in a special canal on the outer side of
the tibial cartilage, and extends through the large canal of the
hypotarsus (Fig. 12, No. _F_, 5) next to the shaft, then down to the
apex of the accessory metacarpal bone. It is inserted to the tubercle on
the inferior proximal end of the ungual phalanx.
_Shape._—Large, fusiform.
_Relations._—With the exterior of the deep flexors.
_Action._—Flexes the hallux as its long flexor.
=Flexor Perforatus Annularis Primus Pedis= (Fig. 17, Nos. _D_, 8 and
_C_, 6). _Location._—The posterior tibial region.
_Origin._—From the inner side of the belly of the flexor longus
hallucis.
_Insertion._—Becoming tendinous at the lower third of the tibia, passes
a little to the outer side and through the tibial cartilage, then over
the ankle-joint and through the hypotarsal canal (Fig. 12, No. 5) to the
under side of the outer toe, where it forms a sheath through which the
deep flexors extend. It gives off on either side a tendinous slip which
attaches to the basal phalanx.
_Shape._—Long, slender, compressed laterally.
_Relations._—Internally, with the flexor perforatus indicis secundus
pedis, and externally, with the flexor longus hallucis.
_Action._—Flexes the toes as their long flexor. A second flexor of the
outer toe.
=Flexor Perforatus Medius Secundus Pedis= (Fig. 17, No. 9).
_Location._—The posterior tibial region.
_Origin._—From a strong fascia that merges with the knee-joint, and by a
tendon from the external condyle of the femur in common with the tendon
of the flexor perforatus indicis secundus pedis.
_Insertion._—Continued as a flattened tendon extending from the lower
third of the leg, passing obliquely through the tibial cartilage and
then through the interno-posterior canal of the hypotarsus, (Fig. 12,
No. _F_, 5) inserted to the second joint of the middle toe.
_Shape._—Long, fusiform.
_Relations._—With the shaft of the fibula, which it covers.
_Action._—Flexes the middle toe.
=Flexor Perforatus Medius Primus Pedis= (Fig. 17, No. 2).
_Location._—Posterior tibial region.
_Origin._—From the inner side of the muscular portion of the flexor
perforatus annularis primus pedis.
_Insertion._—Terminating in a flattened tendon, passes through the
tibial cartilage and hypotarsus, and then extends along the shaft of the
basal joint of the third toe, and, dividing into two slips, inserts to
either side of its shaft.
_Shape._—Long, rather small.
_Relations._—With the flexor perforatus annularis primus pedis on the
inner side.
_Action._—Flexes the third toe.
=Flexor Perforatus Indicis Primus Pedis= (Fig. 17, No. 4).
_Location._—The posterior tibial region.
_Origin._—From a thin, broad tendon, on the external condyle of the
femur, in common with the flexor perforatus medius secundus pedis.
_Insertion._—Becoming tendinous, passes through the tibial cartilage and
the hypotarsus of the metatarsus (Fig. 16, _A_) and inserts to the sides
of the basal joint of the second toe.
_Shape._—Long, slender, fusiform; somewhat flattened laterally.
_Relations._—With the flexor perforatus medius secundis pedis,
posteriorly.
_Action._—A flexor of the toes.
=Flexor Perforans Digitorum Profundus= (Fig. 24, No. 24 and Fig. 25, No.
_G_, 3). _Location._—The posterior tibial region.
_Origin._—From the posterior part of the external condyle of the femur,
from the posterior part of the tibia just below the summit, and from a
point near the origin of the soleus.
_Insertion._—Its heavy flattened tendon passes through the tibial
cartilage, this tendon dividing, the branches pass along the under side
of the toes, perforating the outer tendons and become inserted to the
proximal tubercle at the base of the under side of the ungual phalanxes
of the second, third, and fourth toes.
_Shape._—Long, fleshy, with a long tendon.
_Relations._—Closely with the tibial bone; the deepest of all the
flexors.
_Action._—Flexes the digits.
THE MUSCLES OF THE EYE
Orbicularis palpebrarum
Depressor palpebræ inferioris
Pyramidalis nictitans
Obliquus inferior
Rectus inferior
Levator palpebræ superioris
Quadratus nictitans
Obliquus superior
Rectus superior
Rectus externus
Rectus internus
=Orbicularis Palpebrarum= (Fig. 7, No. 30). (Synonym.—Orbicularis
oculi.)
_Location._—Upon the lacrimal and maxillary bones.
_Origin._—From the lacrimal and maxillary bones and the ciliary margin.
_Insertion._—To the lower free edge of the tarsal cartilage.
_Shape._—Thin, delicate layer of fibers.
_Relations._—Externally, with the skin; internally, with the lacrimal
and the maxillary bones.
_Action._—Aids in closing the eye.
=Levator Palpebræ Superioris= (Fig. 7, No. 24). _Location._—Along the
superior roof of the orbit.
_Origin._—Along a longitudinal line found near the middle of the roof of
the orbit.
_Insertion._—To the ciliary margin of the upper lid, near the outer
canthus.
_Shape._—Thin, delicate layer.
_Relations._—Superiorly, with the bony wall, and inferiorly, with the
eyeball.
_Action._—Raises the superior eyelid.
=Depressor Palpebræ Inferioris= (Fig. 7, No. 29). (Synonym.—Malaris.)
_Location._—Along the inferior border of the eye.
_Origin._—From the inferior border of the interorbital foramen.
_Insertion._—To the lower lid.
_Shape._—Thin, flat, delicate.
_Relations._—Superiorly, with the eyeball; inferiorly, with the inferior
orbital wall.
_Action._—Pulls the lower lid down.
=Quadratus Nictitans= (Fig. 26, No. _B_, 7). _Location._—Above the
eyeball along the inferior border of the upper wall of the orbit.
_Origin._—From the sclerotic from the upper part of the ball.
_Insertion._—To the upper part of the sheath of the optic nerve near the
optic foramen.
_Shape._—Broad, thin, quadrate.
_Relations._—Inferiorly, with the eyeball; superiorly, with the orbital
wall, with the superior oblique, and with the superior rectus.
_Action._—Aids in pulling the nictitating membrane obliquely outward and
downward over the forepart of the eyeball.
=Pyramidalis Nictitans= (Fig. 26, No. _B_, 8).
_Location._—Inferoposteriorly to the eyeball.
_Origin._—From the lower nasal side of the eyeball.
_Insertion._—The fibers converge toward the upper part of the optic
nerve, into a tendon which passes through a pulley at the free margin of
the quadratus. Inserts to the lower part of the margin of the third
eyelid, the nictitans.
_Shape._—Pyramidal; of thin layers of fibers.
_Relations._—Internally, with the bony orbital wall; externally, with
the eyeball.
_Action._—Aids the quadratus nictitans.
=Obliquus Superior= (Fig. 26, No. _B_, 5). (Synonym.—Obliquus dorsalis.)
_Location._—Superior to the eyeball.
[Illustration:
FIG. 26.—Structures of the eye and nasal passage.