EXTENSOR PROPRIUS POLLICIS. 235 



lar ligament. By its posterior surface with the interosseous .mem- 

 brane, tibia, ankle-joint, and bones of the tarsus with their articula- 

 tions. By its internal surface with the tibia. By the external sur- 

 face with the extensor longus digitorum, extensor proprius pollicis, 

 and with the anterior tibial vessels and nerve. 



The Extensor longus digitorum arises from the head of the tibia, 

 from the upper three-fourths of the fibula, from the interosseous 

 membrane, and from the deep fascia. Below, it divides into four 

 tendons, which pass beneath the annular ligament, to be inserted 

 into the second and third phalanges of the four lesser toes. The 

 mode of insertion of the extensor tendons, both in the hand and in 

 the foot, is remarkable ; each tendon spreads into a broad aponeu- 

 rosis over the first phalanx ; this aponeurosis divides into three slips, 

 the middle one is inserted into the base of the second phalanx, and 

 the two lateral slips are continued onwards, to be inserted into the 

 base of the third. 



Relations. By its anterior surface with the deep fascia of the leg 

 and foot, and with the anterior annular ligament. By its posterior 

 surface with the interosseous membrane, fibula, ankle-joint, extensor 

 brevis digitorum, which separates its tendons from the tarsus, and 

 with the metatarsus and phalanges. By its inner surface with the 

 tibialis anticus, extensor proprius pollicis, and anterior tibial vessels. 

 By its outer border with the peroneus longus and brevis. 



The Peroneus tertius (flexor tarsi fibularis) arises from the lower 

 fourth of the fibula, and is inserted into the base of the metatarsal 

 bone of the little toe. Although apparently but a mere division or 

 continuation of the extensor longus digitorum, this muscle may be 

 looked upon as analogous to the flexor carpi ulnaris of the fore-arm. 

 Sometimes it is altogether wanting. 



The Extensor proprius pollicis lies between the tibialis anticus 

 and extensor longus digitorum. It arises from the lower two-thirds 

 of the fibula and interosseous membrane. Its tendon passes through 

 a distinct sheath in the annular ligament, and is inserted into the 

 base of the last phalanx of the great toe. 



Relations. By its anterior surface with the deep fascia of the leg 

 and foot, and with the anterior annular ligament. By its posterior 

 surface with the interosseous membrane, the fibula, the tibia, the 

 ankle-joint, the extensor brevis digitorum, and the bones and articu- 

 lations of the great toe. It is crossed upon this aspect by the ante- 

 rior tibial vessels and nerve. By its outer side with the extensor 

 longus digitorum, and in the foot with the dorsalis pedis artery and 

 veins ; the outer side of its tendon upon the dorsum of the foot being 

 the guide to these vessels. By its inner side with the tibialis anti- 

 cus, and with the anterior tibial vessels. 



Actions. The tibialis anticus and peroneus tertius are direct flexors 

 of the tarsus upon the leg; acting in conjunction with the tibialis 

 posticus they direct the foot inwards, and with the peroneus longus 

 and brevis outwards. They assist also in preserving the flatness of 

 the foot during progression. The extensor longus digitorum and 



