MYOLOGY. 73 
great or internal cunciform bone, as also into the base of the great toe. 
Use: to flex the ankle, to adduct the foot, to turn the toes inwards, and to 
support the leg when standing. 
Extensor digitorum longus arises from the external part of the head of the 
tibia, and from the upper part of the fibula, and is inserted by four tendons 
into the back of the last phalanx of each toe (except the great toe). Use: 
to extend the toes and flex the ankle. 
Extensor pollicis proprius arises from the inner edge of the middle third 
of the fibula, and is inserted by two tendinous fasciculi, one into the base of 
the first phalanx, and the other into the base of the second or last phalanx 
of the great toe. Use: to extend the great toe and flex the ankle. 
Peroneus tertius or anticus arises from the anterior surface of the lower 
half of the fibula, and is inserted into the base of the fifth metatarsal bone. 
Use: to extend the little toe, to flex the ankle, and to raise the outer edge 
of the foot. 
Peroneeus longus arises from the head of the fibula and from the adjacent 
surface of the tibia; it is inserted into the outer side of the metatarsal bone 
of the great toe and into the adjacant sesamoid bone. Use: to extend the 
ankle joint, to press the great toe against the ground as in walking, and to 
turn the foot outwards, ~ 
 Peronceus brevis arises from the lower half of the fibula, and is inserted 
into the base of the metatarsal bone of the little toe and into the os cuboi- 
des. It is similar to the last in its uses. or 
5. MUSCLES OF THE BACK PART OF THE Lec. These are seven in num- 
ber, arranged in a superficial and a deep layer; the former consists of the 
gastrocnemius, sozlus, and plantaris; the latter, of the tibialis posticus, 
flexor pollicis longus, flexor digitorum communis, and popliteeus. 
Gastrocnenius arises by two heads, one from a digital depression on the 
upper and back part of the internal condyle of the femur, the other from 
above the external condyle. The two fleshy bellies form the calf of the 
leg, these ending in a broad flat tendon about the middle of the limb, which 
with the tendon of the subjacent soleeus is inserted into the lower and back 
part of the os calcis, as the tendo achillis. Use: to extend the ankle joint, 
and to throw the whole weight of the body forward on the, toes, as in pro- 
gression. 
Plantaris arises from the back part of the femur, above the external con- 
dyle and from the posterior ligament of the knee; it is inserted into the os 
calcis a little anterior to the tendo achillis. Use: to extend the foot and 
turn it inwards; also to flex the knee. 
Soleus arises from the back part of the tibia and fibula by two slightly 
developed heads, and is inserted into the. os calcis by the tendo achillis, 
common to it and the gastrocnemius. It assists in extending the ankle, but 
can exert no influence on the knee joint. 
Popliteus arises from a depression on the external surface of the outer 
condyle, and is inserted into a flat triangular surface which occupies the 
superior fifth of the posterior surface of the tibia. Use: to bend the knee, 
and when bent to twist the foot inwards. 
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