348 MUSCLES AND FASCIAE. 



The Peroneus Brevis lies beneath the Peroneus longus, and is shorter and 

 smaller than it. It arises from the middle third of the external surface of the 

 shaft of the fibula, internal to the Peroneus longus ; from the anterior and posterior 

 borders of the bone ; and from the intermuscular septa separating it from the 

 adjacent muscles on the front and back part of the leg. The fibres pass vertically 

 downwards, and terminate in a tendon, which runs through the same groove as 

 the preceding muscle, behind the external malleolus, being contained in the same 

 fibrous sheath, and lubricated by the same synovial membrane; it then passes 

 through a separate sheath on the outer side of the os calcis, above that for the 

 tendon of the Peroneus longus, and is finally inserted into the base of the meta- 

 tarsal bone of the little toe, on its dorsal surface. 



Relations. By its superficial surface, with the Peroneus longus and the fascia 

 of the leg and foot. By its deep surface, with the fibula and outer side of the 

 os calcis. 



Nerves. The Peroneus longus and Peroneus brevis are supplied by the musculo- 

 cutaneous branch of the external popliteal nerve. 



Actions. The Peroneus longus and Peroneus brevis extend the foot upon the leg, 

 in conjunction with the Tibialis posticus, antagonizing the Tibialis anticus and Pero- 

 neus tertius, which are flexors of the foot. The Peroneus longus also everts the sole 

 of the foot ; hence the extreme e version observed in fracture of the lower end of 

 the fibula, where that bone offers no resistance to the action of this muscle. 

 Taking their fixed point below, they serve to steady the leg upon the foot. This 

 is especially the case in standing upon one leg, when the tendency of the superin- 

 cumbent weight is to throw the leg inwards ; and the Peroneus longus overcomes 

 this by drawing on the outer side of the leg, and thus maintains the perpendicular 

 direction of the limb. 



Surgical Anatomy. The student should now consider the position of the tendons of the various 

 muscles of the leg, their relation with the ankle-joint and surrounding bloodvessels, and especially 

 their action upon the foot, as their rigidity and contraction give rise to one or the other forms 

 of deformity known as club-foot. The most simple and common deformity, and one that is rarely 

 if ever congenital, is the talipes equinus, the heel being raised by rigidity and contraction of the 

 Gastrocnemius muscle, and the patient walking upon the ball of the foot. In the talipes varus, 

 which is the more common congenital form, the heel is raised by the tendo Achillis, the inner 

 border of the foot drawn upwards by the Tibialis anticus, and the anterior two-thirds of the foot 

 twisted inwards by the Tibialis posticus and Flexor longus digitorum, the patient walking upon 

 Jhe outer edge of the foot, and in severe cases upon the dorsum and outer ankle. In the talipes 

 valgus, the outer edge of the foot is raised by the Peronei muscles, and the patient walks on the 

 inner ankle. In the talipes calcaneus, the toes are raised by the Extensor muscles, the heel is 

 depressed, and the patient walks upon it. Other varieties of deformity are met with, as the 

 talipes equino-varus, equino-valgus, and calcaneo-valgus, whose names sufficiently indicate their 

 nature. Each of these deformities may be successfully relieved (after other remedies fail) by 

 division of the opposing tendons and fascia ; by this means, the foot regains its proper position, 

 and the tendons heal by the organization of lymph thrown out between the divided ends. The 

 operation is easily performed by putting the contracted tendon upon the stretch, and dividing it 

 by means of a narrow sharp-pointed knife inserted between it and the skin. 



MUSCLES AND FASCIA OF THE FOOT. 



The fibrous bands which bind down the tendons in front of and behind the ankle in their passage 

 to the foot, should now be examined ; they are termed the annular ligaments, and are three in 

 number, the anterior, internal, and external. 



The Anterior Annular Ligament consists of a superior or vertical portion, 

 which binds down the Extensor tendons as they descend on the front of the tibia 

 and fibula, and an inferior or horizontal portion, which retains them in connection 

 with the tarsus, the two portions being connected by a thin intervening layer of 

 fascia. The vertical portion is attached externally to the lower end of the fibula, 

 internally to the tibia, and above is continuous with the fascia of the leg ; it 

 contains two separate sheaths, one internally for the tendon of the Tibialis anti- 



