THE PLANTAR REGION 237 



The Central Group. 1. M. Flexor Brevis Digitorum (per- 

 foratus). Origin, inner tubercle of the os calcis, plantar fascia, 

 septa, and calcaneocuboid ligaments. Terminates in four 

 slender tendons inserted into the sides of the mesial phalanges 

 of the four outer toes; each divides and gives passage to the 

 long flexor, as does the flexor sublimis of the hand. 



2. Flexor Accessorius (m. quadra tus plan tee, p. n.). Henle 

 calls it the "plantar head of the flexor longus digitorum." 

 Flat quadrilateral muscle. Origin, two heads internal and 

 larger from the inner surface of the os calcis; external, narrow 

 and tendinous, from the under surface of the os calcis just 

 in front of the outer tuberosity and from the long plantar 

 ligament; insertion, external border and upper surface of the 

 flexor longus digitorum tendon. 



3. Mm. Lumbricalcs. Four in number. Origin, at points 

 of division of the flexor longus digitorum tendon, each attached 

 to two tendons, except the most internal one; they pass to 

 the inner side of the four outer toes; inserted into the bases 

 of the proximal phalanges (Henle). 



The Internal Group. 1. M. Abductor Hallucis. Origin, inner 

 tubercle of the os calcis, internal annular ligament, septum, 

 plantar fascia; insertion, inner border of the base of the proximal 

 phalanx of the great toe, inner sesamoid bone, and tendon of 

 the extensor longus hallucis. Slip to the proximal phalanx 

 of the second toe. May have a second head from the scaphoid. 



2. M. Flexor Brevis Hallucis. Origin, flat process from the 

 cuboid inner border, from the slip of the tibialis posticus tendon 

 to the two outer cuneiform bones, from the sheath of the flexor 

 longus digitorum; inserted by two heads into the inner and 

 outer borders of the base of the proximal phalanx, in connec- 

 tion with the abductor hallucis and adductors. Sesamoid 

 bone in each head. 



Origin from the os calcis or long plantar ligament. Sends 

 slip to the second toe, first phalanx. Inner head regarded by 

 some as belonging to the abductor. 



3. M. adductor hallucis has two heads, as in hand, an oblique 

 and transverse, only more separated. 



Caput Obliquum, p. n. Origin, tarsal extremities of the 

 third and fourth metatarsals, sheath of the peroneus longus, 

 calcaneocuboid ligament, and third cuneiform; insertion, 



