In the legs there are groups of muscles that are opposed to each other in their action, and it is the balancing of these actions upon the foot that enable standing and walking to be performed. In infancy, these muscles not being under control, the movements are undecided, and it is only after long practice that the combination of muscular movement is attained. The muscles in the leg are large and strong, and transmit power to the foot by means of tendons. These tendons do not change in form, i.e. stretch, and when in a state of tension they may be often seen beneath the skin. The muscles in the foot are smaller than those in the leg, and their action is direct, consequently they are graceful in their functions. The muscles of the leg perform the more powerful movements of the foot, while those situated in the foot itself give the more delicate and graceful motions.

Muscles of the Leg.

A. The anterior group (Fig. 15); B. The peroneal group (Figs. 16 and 17); and C. The posterior group (Fig. 18).

A. The Anterior Group.

1. Tibialis anticus.

2. Extensor proprius pollicis.

3. Extensor longus digitorum.

4. Peroneus tertius.

B. The Peroneal Group.

5. Peroneus longus.

6. Peroneus brevis.

C. The Posterior Group.

7. Gastro-cnemius, 2 (inside and outside).

8. Plantaris.

9. Soleus.

10. Tibialis posticus.

11. Flexor longus digitorum.

12. Flexor proprius pollicis.

1. The Tibialis anticus is a flexor muscle. It arises from the outside of the tibia and front of' fibula, and descends inwards, where it is replaced by a tendon which inclines to the inner side, passing beneath the annular ligament, and is inserted in the first cuneiform and first metatarsal. Its action is to draw the upper surface of the foot towards the front of the leg; it also turns the great toe inwards, and raises the inside border. During contraction it is seen externally, marking in front of the ankle a clearly defined cord (Fig. 19).

2. The Extensor proprius pollicis arises from under the Tibialis anticus (1) and descends (passing on the outer side of the tendon of the Tibialis anticus, beneath the annular ligament) along the upper surface of the foot, and is inserted in the base of the second phalanx of the great toe. Its action is to raise the great toe. It has a strong tendon that may be seen when the foot is extended and the toe is forced up (Fig. 20).

3. The Extensor longus digitorum arises from the outside of the tibia, and lies to the outer side of the Tibialis anticus (1). It descends by a tendon that divides but remains together, and passes beneath the annular ligament. After it has passed the annular ligament, the divided tendon separates and spreads out. The four divisions are inserted into the last phalanx of the toes (Fig. 21). Its action, in conjunction with the Tibialis anticus (1), is to flex the foot on the leg, and also to extend the toes on the foot. During action it is visible on the upper surface of the foot.

Fig. 15.

Fig. 15.

Fig. 16.

Fig. 16.

Fig. 17.

Fig. 17.

4. The Peroneus tertius is sometimes classed as the fifth tendon of the Extensor longus digitorum (3), with which tendon it goes beneath the annular ligament to be inserted in the fifth metatarsal. Its action is to raise the outer border of the foot.

5. The Peroneus longus arises from the head of the fibula, arid runs behind the outer ankle along the heel-bone, through the groove in the cuboid bone, across the sole of the foot, and is inserted in the first metatarsal. Its action is similar to that of the Peroneus brevis (6), and also serves as a bow across the arch increasing the hollow. It is brought into play during dancing.

6. The Peroneus brevis arises underneath the previous muscle, and unites its tendon with the Peroneus longus (5). They together pass on the outside ankle along the heel, and the tendons (Peroneus longus and brevis) separate, and are inserted in the base of the fifth metatarsal. The action is to extend the foot and raise the outer border, turning the toe outwards. It is the reverse of the 7 Tibialis anticus (1). These muscles are developed in those who walk, run, and dance, and with others give the largely developed calves that are observable in athletes.

7. The Gastro-cnemius. - There are two muscles bearing this name, one situated on the outside, and the other on the inside of the leg. Their origin is from the femur, and they are connected with the tendon Achilles. The action is to extend the foot on the leg, and by the tendon to raise" the heel of the foot.

8. The Plantaris rises on the outside of the femur. It is a very short muscle united with the outside Gastro-cnemius (7). It is situated between the Gastro-cnemii (7), and gives place to a long thin tendon that sometimes unites with the tendon Achilles and sometimes with the fatty tissue of the os calcis.

Fig. 18.

Fig. 18.

9. The Soleus muscle is placed beneath the Gastrocnemii (7). It arises from the tibia and fibula, and combines with the Gastro-cnemii (7) to form the tendon Achilles, that is the strongest tendon in the body. The tendon is very tough and cord-like, and does not change in bulk.

Fig. 19.

Fig. 19.

Fig.20.

Fig. 20.

It is affixed to the os calcis, and is the means afforded to raise the heel and depress the toes.

10. The Tibialis posticus arises, from the tibia and fibula, and descends, by means of a tendon, behind the inside ankle, and is inserted in the scaphoid. Its action is to bend and turn the foot inwards.

11. The Flexor longus digitorum runs at the back of the inner ankle from the tibia. In the sole it divides into four branches that are inserted in the toes. Its action is to bend the toes and to cause them to grip in walking.

12. The Flexor longus pollicis has origin in the fibula, and passes through the groove at the outer side of the astragalus to the great toe. Its action is to raise the body on the end of the great toe, to press the ball of the toe to the ground, and thereby to raise the outer ankle.

It must be understood that when the muscle is spoken of as passing under the annular ligament, or round the ankle, the tendon which transmits the muscular force is meant. It is thus described for brevity.