PRACTICAL CONSIDERATIONS : THE LEG. 665 



metatarsal and passes distally along the outer side or the fourth plantar interosseus 

 to be inserted by a tendon into the outer surface of the base of the first phalanx of 

 the fifth toe and also into the distal portion of the fiftn metatarsal. 



Nerve -Supply. — From the external plantar nerve from the second sacral 

 nerve. 



Action. — To flex the fifth toe and draw it lateralward. 



Variations. — The portion of the flexor brevis minimi digiti which passes to the fifth meta- 

 tarsal is frequently more or less distinct from the rest of the muscle, and has then been termed 

 the oppoiiens quinti digiti. 



{b) THE POST-AXIAL MUSCLES. 

 I. Extensor Brevis Digitorum (Fig. 624). 



Attachments. — The short extensor of the toes (m. extensor digitorum brevis) 

 arises from the lateral and superior surfaces of the calcaneum. It passes distally 

 beneath the tendons of the extensor longus digitorum and divides into four portions, 

 the outer three of which soon become tendinous and are inserted by fusing with the 

 tendons of the extensor longus to the second, third, and fourth toes over the first 

 phalanges of those toes; the innermost tendon is inserted into the base of the first 

 phalanx of the great toe. 



Nerve-Supply. — By the anterior tibial nerve from the fourth and fifth lumbar 

 and first sacral nerves. 



Action. — To extend and draw laterally the first, second, third, and fourth toes. 



Variations. — Occasionally one or other of the tendons of the extensor brevis may be 

 doubled, this condition being most frequent in the tendon to the second toe ; sometimes a fifth 

 tendon passes to the little toe. 



The innermost tendon is nearly always much stronger than the others ; the fibres which 

 insert into it are occasionally separate from the remainder of the muscle, then forming the 

 extensor brevis hallucis. 



PRACTICAL CONSIDERATIONS: MUSCLES AND FASCIA 

 OF THE LEG, ANKLE, AND FOOT. 



I. The Leg. — The skin over the leg is everywhere more adherent to the un- 

 derlying fascia than it is in the thigh. Its inability at certain places, as over the spine 

 and antero-internal surface of the tibia, to glide away when force is applied partly 

 accounts for the frequency with which bruising or laceration, superficial ulceration, 

 or even periostitis or caries follows injuries to the ' ' shin. 



The deep fascia blends with the periosteum at the head and inner and anterior 

 borders of the tibia, at the head of the fibula, and at the two malleoli. It is thicker 

 and denser above and anteriorly than below and posteriorly. The two septa (Figs. 

 627, 623) that run inward from it on the outer side of the leg and are attached to the 

 anterior and external borders of the fibula constitute an osseo-aponeurotic space that 

 contains the peroneal muscles and that may, for a time, limit the spread of infection 

 or of suppuration. The peronei, in their compartment, and, farther in, the bones and 

 interosseous membrane, separate the anterior group of muscles — the tibialis anticus, 

 extensor communis, etc. — from the posterior group. The fascia over the anterior 

 group embraces them so closely, that when it is wounded or torn the muscle-fibres 

 protrude and approximation of the edges of the fascial wound may be difificult. In 

 the anterior compartment the muscles are intimately adherent to its fibrous walls, as 

 is the case in the forearm, but not in the arm or thigh (Tillaux). In the posterior 

 compartment, on the contrary, a loose layer of connective tissue intervenes between 

 the gastrocnemius and the deep fascia, and permits the greater degree of motion 

 between the muscle and the aponeurosis necessitated by the greater range of motion 

 in plantar, as compared with dorsal, flexion of the foot. 



The difference will be noted in dealing with wounds involving these regions, or 

 in some operations, as amputation of the leg. 



The septum, anteriorly, at the upper third of the leg, between the tibialis anticus 

 and extensor longus digitorum, is of variable density, gives no indication of its pres- 



