180 



DISSECTION OF THE LEG. 



toe; 

 on tibia. 



Extensor 

 longus 

 digitorum : 



arises from 

 tibia and 

 fibula ; 



inserted 

 into four 

 outer toes ; 

 arrange- 

 ment of the 

 tendons on 

 the toes ; 



origin from surface of the fibula (fig. 68), and from the interosseous membrane 

 for the same distance. At the ankle it ends in a tendon, which 

 comes to the surface through a sheath in the lower piece of the 



insertion to annular ligament, and continues over the tarsus to be inserted into 



great toe ; ^ bage of tne lagt p} ia ] anx o f t } ie great toe> 



it crosses The anterior tibial vessels lie on the inner side of the muscle at 



the vessels; ^ s origin, but afterwards on the outer side of its tendon, so that 



they are crossed by it in the lower third of the leg. 



use on great Action. It straightens the great toe by extending the phalangeal 

 joints, and afterwards bends the ankle. 



When the foot is fixed on the ground and the tibia slants back- 

 wards, the muscle can draw forwards that bone. 



The EXTENSOR LONGUS DIGITORUM is fleshy in the leg, and tendi- 

 nous on the foot, like the other muscles. Its origin is from the 

 head, and iipper three-fourths of the anterior surface of the 

 fibula, from the external tuberosity of the tibia (fig. 68), from 

 about an inch of the upper part of the interosseous membrane, 

 and from the fascia of the leg and the intermuscular septum on 

 each side of it. The tendon enters its sheath in the annular 

 ligament with the peroneus tertius, and divides into four pieces. 

 Below the ligament these slips are continued to the four outer 

 toes, and are inserted into the middle and ungual phalanges in 

 the following manner. On the first phalanx the tendons of the 

 long and short extensor join with prolongations from the inter- 

 ossei and lumbricales to form an aponeurosis ; but there is no 

 tendon from the short extensor to the expansion on the little toe. 

 At the distal end of the first phalanx the aponeurosis is divided 

 into three parts a central and two lateral ; the central piece is 

 inserted into the base of the middle phalanx, and the lateral parts 

 unite at the front of the middle, and are fixed into the last phalanx. 

 In the leg the muscle is placed between the peronei on the one 

 side, and the tibialis anticus and extensor proprius hallucis on the 

 other. It lies on the fibula, the lower end of the tibia, and the 

 ankle-joint. In the foot the tendons rest on the extensor brevis 

 digitorum ; and the vessels and nerve are internal to them. 



Action. The muscle extends the four outer toes, acting mainly 

 on the metatarso-phalangeal joints ; it can also bend the ankle-joint. 

 If the tibia is inclined back, as when the foot reaches the ground 

 in walking, it will be moved forwards by this and the other muscles 

 on the front of the leg. 



The PERONEUS TERTIUS is situate below the extensor longus digi- 

 torum, with. which it is united. It arises from the lower fourth 

 of the anterior surface of the fibula (fig. 68), from the lower end 

 of the interosseous membrane, and from the intermuscular septum 

 between it and the peroneus brevis muscle ; it is inserted into the 

 base of the metatarsal bone of the little toe on the upper surface 

 near its inner border. 



This muscle has the same relations in the leg as the lower part 

 of the long extensor, and is contained in the same space in the 

 annular ligament. 



relations of 

 the muscle : 



use on toes 

 and ankle ; 



on tibia. 



Peroneus 

 tertius : 



origin ; 



insertion 



