THE MUSCLES OF THE FRONT OF THE LEG. 259 



ANTERIOR REGION. 



Between the tibia and fibula, and on the front of the leg, are placed four muscles 

 the tibialis anticus, extensor proprius hallucis, extensor longus digitorum, and 

 peroneus tertius. 



The tibialis anticus arises from the lower part of the external tuberosity of the 

 tibia, and from the upper half of the outer surface of that bone, from the adjoining 

 portion of the interosseous membrane, from the strong fascia of the leg,-and from the 

 intermuscular septum between it and the extensor longus digitorum. The tendon 

 glides in a synovial sheath beneath the anterior annular ligament, and is inserted into 

 an oval mark on the inner and lower part of the internal cuneiform and into the 

 contiguous extremity of the first metatarsal bone, dividing slightly into two slips as 

 it descends. 



Relations. This muscle lies immediately under the aponeurosis of the leg. It rests upon 

 the tibia and the interosseous membrane. Its outer surface is in contact with the extensor 

 longus digitorum, the extensor proprius hallucis, and the anterior tibial vessels and nerve. 

 Its tendon passes over the lower end of the tibia, the ankle-joint, and the inner surface of the 

 tarsus. A small bursa is frequently placed under it close to its insertion. 



Varieties. In a few cases a deep portion of this muscle has been found inserted into the 

 astragalus. The tendon has also been seen sending a slip to the head of the first metatarsal 

 bone or the base of the first phalanx of the great toe. The tibio-fascialis anticus is a small 

 muscle arising from the lower part of the tibia, and inserted into the annular ligament and 

 deep fascia. It may also exist as a tendinous slip from the tibialis anticus. 



The extensor longus s. proprius hallucis muscle (ext. prop, pollicis pedis), 

 placed between the tibialis anticus and the extensor longus digitorum, arises from the 

 middle two-fourths of the narrow anterior surface of the fibula, and from the con- 

 tiguous portion of the interosseous membrane. Its tendon passes through a distinct 

 compartment in the lower portion of the annular ligament and along the dorsum 

 of the foot, to be inserted into the base of the terminal phalanx of the great toe. An 

 expansion given off from the tendon on each side spreads over the metatarso-phalan- 

 geal articulation ; and in a majority of cases there is a distinct slip from the inner 

 edge of the tendon inserted into the base of the first phalanx. 



Relations. This muscle is partly concealed by those between which it is placed. It lies 

 external to the anterior tibial artery at its origin, but crosses in front of that vessel in the 

 lower third of the leg, and is internal to it on the foot. 



Varieties. The extensor proprius hallucis is occasionally united at its origin with the 

 extensor longus digitorum. A partial insertion into the second toe has been observed in a 

 negress (Chudzinski, Rev. d'Anthrop., 1882, 620). 



The extensor ossis metatarsi hallucis is a small muscle, sometimes found as a slip from the 

 extensor proprius, or from the tibialis anticus, or from the extensor longus digitorum ; or 

 it may be a distinct muscle arising close to the extensor proprius, and traversing the same 

 compartment of the annular ligament with that muscle. 



The extensor longus primi internodii hallucis is rare as a separate muscle, but is commonly 

 represented by the offshoot from the tendon of the extensor proprius hallucis, occasionally by 

 a slip from the tibialis anticus, or by a fibrous band springing from the annular ligament and 

 fascia. 



The extensor longus digitorum pedis arises from the external tuberosity of 

 the tibia, from the head and the anterior surface of the fibula for about two-thirds of 

 its length in front of the extensor hallucis, and from a small part of the interosseous 

 membrane at its upper part ; also from the aponeurotic septa intervening between it 

 and the muscles on each side, and from the fascia of the leg. The tendon begins 

 on the anterior border of the muscle and becomes divided below into four slips, which 

 descend through the lower part of the annular ligament, in the same sheath as the pero- 

 neus tertius, and on the dorsum of the foot pass respectively to the four outer toes. 



VOL. II. 8 





