THE ANTERIOR TIBIOFIBULAR REGION 



529 



The Extensor proprius hallucis (m. extensor hallu- 

 cis longus) is a thin, elongated, and flattened muscle 

 situated 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 Exten- 

 sor longus digitorum; it also arises from the inter- 

 osseous 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 lower 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. Op- 

 posite the metatarsophalangeal articulation the tendon 

 gives off a thin prolongation on each side, which covers 

 the surface of the joint. It usually sends an expan- 

 sion from the inner side of the tendon, to be inserted 

 into the base of the first phalanx. 



The Extensor longus digitorum (m. extensor digi- 

 torum longus} is an elongated, flattened, penniform 

 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 pha- 

 langes of the four lesser toes. The mode in which 

 the tendons are inserted is the following: Each of the 

 three inner tendons opposite the metatarsophalangeal 

 articulation is joined, on its outer side, by a tendon 

 from the Extensor brevis digitorum. The outer ten- 

 don does not receive such a tendinous slip. They all 

 receive a fibrous expansion from the Interossei and 

 Lumbricales, and then spread out into a broad aponeu- 

 rosis, which covers the dorsal surface of the first pha- 

 lanx; this aponeurosis, at the articulation of the first 

 with the second phalanx, divides into three slips 

 a middle one, which is inserted into the base of the 

 second phalanx, and two lateral slips, which, after 

 uniting on the dorsal surface of the second phalanx, 

 are continued onward, to be inserted into the base 

 of the third. 



The Peroneus tertius (m. peronaeus tertius} is a 

 part of the Extensor longus digitorum, and might be 

 described as its fifth tendon. The fibres belonging 

 to this tendon arise from the lower fourth of the 

 anterior surface of the fibula, from the lower part of 

 the interosseous membrane, and from an intermus- 



34 



\J'ii 



FIG. 393. Muscles of the front of 

 the leg. 



