FLEXOR B RE VIS DIG ITORUM— ABDUCTOR MINIMI DIGITI 379 



by the inner head. The tendon to which these llesliy tibres converge appears first 

 upon the inner and lower aspect of tlie muscle, and receives lleshy fil)res nearly to 

 its insertion, which is closely blended with that of the inner portion of the flexor 

 brevis hallucis. The deep surface of the muscle arises from a fil)rous arch attached 

 on the one side to the septum between it and the flexor l)revis digitorum; on the 

 other side to the tibialis i)osticus tendon and the fil)rous tissue; covering the under 

 surface of the tarsal bones along the inner border of the foot. Through this arch 

 pass the plantar vessels and nerves. 



Nerve-supply. — The internal plantar division of the posterior tiltial nerve, by 

 filaments wliicli t'uter the deep surface of the middle of the muscle. 



Action. — (1) To flex the first phalanx upon the metatarsal bone; (2) to abduct 

 from tlie middle line of the foot the first phalanx of the great toe. 



Relations. — Superficially, the internal division of the plantar fascia; upon its 

 outer border, tlie flexor Invvis digitorum; deeply, the tendons of the tibialis anti- 

 cus, tibialis posticus, flexor longus digitorum, flexor longus hallucis, the plantar 

 vessels and nerves. 



Variations. — A tliirtl liead is occasionallj' tlerived from the deep surface of the skin upon 

 the inner border of the foot, or from the long plantar ligament. The muscle may give a slip to 

 the second toe. 



2. FLEXOR BREVIS DIGITORUM PEDIS 



The flexor brevis digitorum pedis, or flexor perforatus — named from its 

 being the shorter of the flexors of the four outer toes — is a triangular sheet, divided 

 in front into four processes corresponding to the tendons of the toes. 



Origin. — (1 ) The outer part of the front of the lower surface of the great tubercle 

 of tlie calcaneum; (2) the deep surface of the back part of the central portion of 

 the plantar fascia; (3) the back part of the intermuscular septa on either side. 



Insertion. — The sides of the middle phalanx of each of the four outer toes 

 ujjon its plantar aspect. 



Structure. — Arising tendinous by a pointed process from the under surface of 

 the great tubercle, the fleshy filjres extend in a fan-shaped sheet, which, about half- 

 way between the origin and the heads of the metatarsal bones, divides into four 

 fleshy processes which soon become tendinous. The tendons are arranged in a 

 similar manner to those of the flexor sublimis digitorum in the hand. After split- 

 ting beneath the first phalanx of the toe, the two halves of each tendon pass round 

 the sides of the flexor longus digitorum tendon, and aliout the level of the base of 

 the second phalanx they unite l)y their adjacent margins, and again diverge to be 

 attached to the sides of the plantar surface of the second i)halanx. 



Nerve-supply. — From the internal plantar division of the posterior tibial, by 

 branches which enter the back of the deep aspect of the muscle near its inner 

 border. 



Action. — This muscle, which is comparatively feeble, will flex the second pha- 

 langes of the toes, and in combination with the flexor longus digitorum it will 

 assist in walking, by pressing the under surface of the phalanges of the toes against 

 the ground. After it has flexed the second phalanges, it will act in a similar man- 

 ner upon the metatarso-phalangeal and medio-tarsal joints. 



Relations. — Superficially, the plantar fascia; on either side, the other muscles 

 of the first layer of the sole; deeply, the tendons of the flexor longus digitorum and 

 the lumbricales, the accessorius muscle, and the external plantar vessels and nerve. 



Variations. — The part of the muscle which belongs to the little toe is often absent (see fig. 

 I2".t4), and its place may be supplied by a small perforated slip from the tendon of the flexor 

 longus digitorum. 



3. ABDUCTOR MINIMI DIGITI PEDIS 



Tlie abductor mininii digiti (pedis) — named from its action upon the fifth and 

 smallest toe — is a thick triangular slieet, jiartly muscular and partly aponeurotic. 

 Origin. — (1) The outer side and tlie under surface of the front of the lesser 



