THE ANTERIOR TIBIO-FIBULAR REGION. 521 



vidual muscles in each region ; at the same time a broad transverse intermuscular 

 septum, called the deep transverse fascia of the leg, intervenes between the super- 

 ficial and deep muscles in the posterior tibio-fibular region. 



Xovr remove the fascia by dividing it in the same direction as the integument, excepting 

 opposite the ankle, where it should be left entire. Commence the removal of the fascia from 

 below, opposite the tendons, and detach it in the line of direction of the muscular fibres. 



Muscles of the Leg. These may be subdivided into three groups : those on the 

 anterior, those on the posterior, and those on the outer side. 



Anterior Tibio-fibular Region. 



Tibialis anticus. Extensor longus digitorum. 



Extensor proprius hallucis. Peroneus tertius. 



The Tibialis anticus is situated on the outer side of the tibia ; it is thick and 

 fleshy at its upper part, tendinous below. It arises from the outer tuberosity and 

 upper two-thirds of the external surface of the shaft of the tibia ; from the adjoin- 

 ing part of the interosseous membrane ; from the deep surface of the fascia ; and 

 from the intermuscular septum between it and the Extensor longus digitorum : 

 the fibres pass vertically downward, and terminate in a tendon which is apparent 

 on the anterior surface of the muscle at the lower third of the leg. After passing 

 through the innermost compartment of the anterior annular ligament, it is inserted 

 into the inner and under surface of the internal cuneiform bone and base of the 

 metatarsal bone of the great toe. 



Relations. By its anterior surface, with the fascia and with the annular liga- 

 ment : by its posterior surface, with the interosseous membrane, tibia, ankle-joint, 

 and inner side of the tarsus: this surface also overlaps the anterior tibial vessels 

 and nerve in the upper part of the leg. By its inner surface, with the tibia; by 

 its outer surface, with the Extensor longus digitorum and Extensor proprius hal- 

 lucis, and the anterior tibial vessels and nerve. 



The Extensor proprius hallucis is a thin, elongated, and flattened muscle situ- 

 ated between the Tibialis anticus and Extensor longus digitorum. It arises from 

 the anterior surface of the fibula for about the middle two-fourths of its extent, its 

 origin being internal to that of the Extensor longus digitorum ; it also arises from 

 the interosseous membrane to a similar extent. The fibres pass downward, and 

 terminate in a tendon which occupies the anterior border of the muscle, passes 

 through a distinct compartment in the horizontal portion of the annular ligament, 

 crosses the anterior tibial vessels near the bend of the ankle, and is inserted into 

 the base of the last phalanx of the great toe. Opposite the metatarso-phalangeal 

 articulation the tendon gives off a thin prolongation on each side, which covers 

 the surface of the joint. It usually sends an expansion from the inner side of the 

 tendon, to be inserted into the base of the first phalanx. 



Eelations. By its anterior surface, with the fascia and the anterior annular 

 ligament: by its posterior surface, with the interosseous membrane, fibula, tibia, 

 ankle-joint, and Extensor brevis digitorum ; by its outer side, with the Extensor 

 longus digitorum above, the dorsalis pedis vessels and anterior tibial nerve below ; 

 by its inner *''</. with the Tibialis anticus and the anterior tibial vessels above. 



The Extensor longus digitorum is an elongated, flattened, semipennifonn 

 muscle situated the most externally of all the muscles on the fore part of the leg. 

 It arises from the outer tuberosity of the tibia ; from the upper three-fourths of 

 the anterior surface of the shaft of the fibula ; from the interosseous membrane ; 

 from the deep surface of the fascia ; and from the intermuscular septa between it 

 and the Tibialis anticus on the inner and the Peronei on the outer side. The tendon 

 enters a canal in the annular ligament with the Peroneus tertius, and divides into 

 four slips, which run across the dorsum of the foot and are inserted into the second 

 and third phalanges of the four lesser toes. The mode in which the tendons 

 are inserted is the following : The three inner tendons opposite the metatarso- 

 phalangeal articulation are joined, on their outer side, by a tendon of the Extensor 



