178 



DISSECTION OF THE LEG. 



Anterior 

 annular 

 ligament : 



upper, 



horizontal 



band, 



lower, 

 Y-shaped 

 band ; 



sheaths 

 differ in 

 each. 



External 



annular 



ligament. 



Muscles on 

 the front of 

 the leg 



and foot. 



Tibialis 

 anticus : 

 origin ; 



insertion ; 



are then to be cleaned as high as the knee, as they lie deeply 

 between the muscles. 



The ANTERIOR ANNULAR LIGAMENT (fig. 67 and fig. 70, p. 183) 



consists of two pieces, upper and lower, which confine the 

 muscles in their position, the former serving to bind the fleshy 

 bellies to the bones of the leg, and the latter to keep down the 

 tendons on the dorsum of the foot. 



The upper part (horizontal band) is above the level of the ankle- 

 joint and is attached laterally to the bones of the leg ; it possesses 

 one sheath with synovial membrane for the tibialis anticus. 



The lower part is situate in front of the tarsal bones. It is 

 attached externally by a narrow piece into the upper surface of the 

 os calcis, in front of the interosseous ligament ; and internally it is 

 thin and widened, having a variously defined thickening at its 

 upper part where it passes to the internal malleolus, and another 

 below where it blends with the fascia on the inner side of the foot ; 

 the latter in this place being deep to the tibialis anticus tendon. 

 In view of its single stem externally and the two diverging thicken- 

 ings internally, this portion of the anterior annular ligament is 

 often called the Y-shaped band. Beneath this part of the liga- 

 ment there are the three sheaths : an inner one for the tibialis 

 anticus ; an outer for the extensor longus digitorum and peroneus 

 tertius ; and an intermediate one for the extensor hallucis. Separate 

 synovial membranes line the sheaths. 



The EXTERNAL ANNULAR LIGAMENT is placed below the fibula, 

 and is attached on the one side to the outer malleolus, and on the 

 other to the os calcis. Its lower edge is connected by fibrous tissue 

 to the sheaths of the peronei muscles on the outer side of the os 

 calcis. It contains the two lateral peronei muscles in one com- 

 partment ; and this is lined by a synovial membrane, which sends 

 two offsets below into the separate sheaths of the tendons. 



The MUSCLES ON THE FRONT OF THE LEG (fig. 67 and fig. 69, 

 p. 181) are four in number. The large muscle next the tibia is 

 the tibialis anticus ; that next the fibula, the extensor longus 

 digitorum ; while a small muscle, apparently the lower end of the 

 last with a separate tendon to the fifth metatarsal bone, is the 

 peroneus tertius. The muscle between the tibialis and extensor digi- 

 torum, in the lower part of the leg, is the extensor proprius hallucis. 



On the dorsum of the foot only one other muscle appears, the 

 extensor brevis digitorum. 



The TIBIALIS ANTICUS reaches the tarsus : it is thick and fleshy 

 in the upper, but tendinous in the lower part of the leg. It arises 

 from the outer tuberosity, and the upper half of the external surface 

 of the tibia (fig. 68) ; from the contiguous part of the interosseous 

 membrane ; and from the fascia of the leg, and the intermuscular 

 septum between it and the extensor longus digitorum. Its tendon 

 begins below the middle of the leg, and passes beneath both pieces 

 of the annular ligament, where it is surrounded by a synovial 

 sheath, to be inserted into the internal cuneiform bone, and the 

 metatarsal bone of the great toe. 



