488 



MYOLOGY 



Actions. The Peronsoi longus and brevis extend the foot upon Che leg, in conjunction with 

 the Tibialis posterior, antagonizing the Tibialis anterior and Peronseus tertius, which are flexors 

 of the foot. The Peronseus longus also everts the sole of the foot, and from the oblique direction 

 of the tendon across the sole of the foot is an important agent in the maintenance of the trans- 

 verse arch. Taking their fixed points below, the Peroncei 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 medialward; the Peronseus longus overcomes this tendency by drawing 

 on the lateral side of the leg. 





THE FASCIA AROUND THE ANKLE. 



Fibrous bands, or thickened portions of the fascia, bind down the tendons 

 front of and behind the ankle in their passage to the foot. They comprise three 

 ligaments, viz., the transverse crural, the cruciate crural and the laciniate; and the 

 superior and inferior peroneal retinacula. 



Tibialis anterior 



Extensor dig. longus 





Ext. hall. long. 



Ext. dig. brevis 



Tendo calcaneus 



Peronaeua longus 



Peronoeus brevis Peronaeus tertius 



Fia. 441. The mucous sheaths of the tendons around the ankle. Lateral aspect. 



Transverse Crural Ligament (ligamentum, transversum cruris; upper part of anterior 

 annular ligament) (Fig. 441). The transverse crural ligament binds down the 

 tendons of Extensor digitorum longus, Extensor hallucis longus, Peronaeus tertius, 

 and Tibialis anterior as they descend on the front of the tibia and fibula; under 

 it are found also the anterior tibial vessels and deep peroneal nerve. It is attached 

 laterally to the lower end of the fibula, and medially to the tibia; above it is con- 

 tinuous with the fascia of the leg. 



Cruciate Crural Ligament (ligamentum cruciatum cruris; lower part of anterior 

 annular ligament) (Figs. 441, 442). The cruciate crural ligament is a Y-shaped 

 band placed in front of the ankle-joint, the stem of the Y being attached laterally 

 to the upper surface of the calcaneus, in front of the depression for the interosseous 

 talocalcanean ligament; it is directed medialward as a double layer, one lamina 

 passing in front of, and the other behind, the tendons of the Peronaeus tertius 

 and Extensor digitorum longus. At the medial border of the latter tendon these 

 two layers join together, forming a compartment in which the tendons are 

 enclosed. From the medial extremity of this sheath the two limbs of the Y diverge : 

 one is directed upward and medialward, to be attached to the tibial malleolus, 

 passing over the Extensor hallucis longus and the vessels and nerves, but enclosing 



