FLEXORS OF THE ANKLE-JOINT. 629 



The EXTENSOR PROPRIUS POLLicis (fig. 215) is deeply placed at its 

 origin between the former muscle and the extensor longus digitorum, but 

 its tendon becoms superficial on the dorsurn of the foot. The muscle 

 arises from the middle three-fifths of the narrow anterior part on the inner 

 surface of the fibula, and from the interosseous ligament for the same dis- 

 tance. At the ankle it ends in a tendon, which comes to the surface 

 through a sheath in the lower piece of the annular ligament, and continues 

 over the inner part of the tarsus to be inserted into the base of the last 

 phalanx of the great toe. 



The anterior tibial vessels lie on the inner side of the muscle as low as 

 the sheath in the ligament, but afterwards on the outer side of its tendon, 

 so that they are crossed by it beneath the ligament. 



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 backwards, 

 the muscle can draw forwards that bone. 



The EXTENSOR LONGUS DIGITORUM (fig. 215, 2 ) is fleshy in the leg, 

 and tendinous on the foot, like the tibial muscle. Its origin is from the 

 head and three-fourths of the narrow part of the inner surface of the fibula; 

 from the external tuberosity of the tibia, and about an inch (above) of the 

 interosseous membrane ; and from the fascia of the leg and the intermus- 

 cular septum on each side. 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 in- 

 serted into the middle and ungual phalanges : 



On the metatarsal phalanx the tendons of the long and short extensor 

 join with prolongations from the interossei and lumbricales to form an 

 aponeurosis ; but a tendon from the short extensor is not united to the 

 expansion on the little toe. At the further end of this phalanx the apo- 

 neurosis is divided into three parts a central and two lateral ; the central 

 piece is inserted into the base of the middle phalanx, while the lateral 

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



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

 and the tibialis anticus and extensor proprius pollicis on the other. It 

 lies on the fibula, the lower end of the tibia, and the ankle-joint. On the 

 foot the tendons rest on the extensor brevis digitorum ; and the vessels 

 and nerve are internal to them. 



Action. The muscle extends the joints of the four outer toes from root 

 to tip, as in the fingers ; and still acting, bends 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 digitorum, 

 from which it is seldom separate. It arises from the lower fourth of the 

 narrow part of the inner surface of the fibula, from the lower end of the 

 interosseous ligament, and from the intermuscular septum between it and 

 the peroneous brevis muscle. And it is inserted into the tarsal end (up- 

 per surface) of the metatarsal bone of the little toe. 



This muscle has the same connections in the leg as the lower part of 

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

 ligament. 



Action. The muscle assists the tibialis in bending the ankle, and in 



