426 MUSCLES AND FASCIAE. 



pass vertically downwards, and terminate in a tendon, which runs in front of 

 that of the preceding muscle through the same groove, 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 metatarsal bone of the little toe, on its dorsal 

 gurtace. 



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 Peroneus Tertius, which are flexors of the foot. The Peroneus 

 Longus also everts the sole of the foot ; hence the extreme eversion occasionally 

 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, the 

 Peroni serve to steady the leg upon the foot. This is especially the case in 

 standing upon one leg, when the tendency of the superincumbent weight is to 

 throw the leg inwards : the Peroneus Longus overcomes this tendency, 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 dub-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 con- 

 traction 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 Digitornm, the patient 

 walking upon the 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 calcancus, 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, eqnino-valgus, and calcanco-valfius, 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 the proper posi- 

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

 The operation is easily performed by putting 1 the contracted tendon upon the stretch, and 

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



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 lie examined : they are termed the annular ligaments, and are 

 three in number, anterior, internal, and external. 



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

 whidi 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 inter- 

 vening 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 Anticus; one externally, for the tendons of the Extensor Longus 

 Digitorum and Peroneus Tertius, the tendon of the Extensor Proprius Pollicis, 

 and the anterior tibial vessels and nerve pass beneath it, but without any dis- 

 tinct sheath. The horizontal portion is attached externally to the upper surface 

 of the os calcis, in front of the depression for the interosseous ligament, and 

 internally to the inner malleolus and plantar fascia: it contains three sheaths; 



