2U MUSCLES OF THE LO^ER LUIB. 



covering the head, the spine and the posterior maro-in of the tiliia, the 

 head of the fibula, and the outer and inner malleoli ; and it invests 

 the leg completely except at the inner surftice of the tibia. From its 

 deep surfoce intermuscular septa are prolonged inwards between the 

 muscles ou the anterior and outer aspects of the leg, and afford attach- 

 ment along with the upper part of the fascia itself to some of their fibres. 

 Beneath the gastrocnemius and soleus muscles on the back of the 

 leg, a deep layer of fascia is stretched from side to side, binding down 

 the deeper muscles firmly in the hollow between the tibia and fibula. 

 Where covered by the soleus and gastrocnemius, this fascia is weak, 

 but it becomes stronger as it escapes from under cover of those muscles 

 and approaches the malleoli. 



Below the ankle the deep fascia of the leg becomes continuous with 

 that of the foot. In front, and on the sides of that joint, it is 

 strengthened by broad bands of fibres, which are called annular liga- 

 ments. These serve as retinacula, confining the tendons in their 

 natural positions. 



The anterior annular ligament includes two structures, one placed 

 on the lower part of the leg, the other opposite the bend of the ankle. 

 The vpjjcr laud, ligamcntum iransvcrsmi cruris (Henle), of considerable 

 breadth, stretches from the lower end of the fibula to the lower end of 

 the tibia, and binds down the vertical portion of the extensor tendons 

 as they turn forwards to the foot : the sheath for the tendon of the 

 tibialis anticus is distinct from the others. The lower hand, ligament iirro 

 cruciatum cruris (Henle), presents superficially the appearance of the 

 letter kJ placed thus upon its side, being single in its outer half, and 

 usually divided into two branches internally. The outer portion consists 

 of a strong loop of fibres arising from the fore part of the os calcis, com- 

 pletely surrounding the peroneus tertius and extensor longus digitorum 

 muscles, and inserted into the fore part of the os calcis, deep in the 

 hollow between that bone and the astragalus. Less regular is the 

 arrangement of the bands which pass from the extremity of the loop to 

 the inside of the foot : the strongest and most constant band passes 

 superficial to the extensor pollicis and on the deep surface of the tibialis 

 anticus muscle, only a few fibres passing superficial to the latter ; while 

 another baud, lower down, after crossing both those tendons, is inserted 

 into the lower side of the foot in front of the ankle. 



The internal annular ligament crosses the space between the 

 inner ankle and tlie heel through which the tendons of the flexor 

 muscles run. Its upper border, continuous with the fascia of the leg 

 (more especially the intermuscular layer), is very imperfectly defined ; 

 and its lower border, giving origin to many fibres of the abductor 

 pollicis, is but little more distinct. Its anterior extremity is attached 

 to the inner malleolus, and its posterior is inserted into the inner 

 surface of the calcaneum ; but between these two points it arches over 

 several osseous grooves so as to form canals for the passage of tendons. 

 The first canal (next to the malleolus) contains the tendon of the 

 tibialis posticus, and the second that of the flexor longus digitorum, 

 each being provided with a synovial lining. Then follows a wider 

 space for the passage of the posterior tibial vessels and nerve. Lastly, 

 a fourth canal upon the astragalus, lined like the first two by a synovial 

 bursa, transmits the tendon of the flexor longus pollicis. 



The external annular ligament extends from the point of the 



