664 



HUMAN ANATOMY. 



hallucis, from the inner cuneiform bones and the adjacent ligamentous structures. 

 It extends distally along the lateral surface of the first metatarsal bone and passes 

 v^ver into a strong tendon, which contains a sesamoid bone, and is iiiserted into the 

 outer surface of the base of the first phalanx of the great toe, along with the 

 adductor hallucis. 



The remaining three muscles are much smaller and arise in succession from the 

 medial surfaces of the third, fourth, and fifth metatarsals, and, passing distally, are 



inserted by slender ten- 

 FiG. 630. dons into the membranous 



expansions of the long ex- 

 tensor tendonsof the third, 

 fourth, and fifth toes, on 

 the medial sides of their 

 first phalanges. 



Nerve-Supply. — By 

 the external plantar nerve 

 from the first and second 

 sacral nerves. 



Action. — To flex the 

 first, third, fourth, and fifth 

 toes and to draw the last 

 three medially. 



Flexor 

 accessorius 



Tibialis 



posticus 



tendon 



Insertion of 

 peroneus longus 



Insertion of 

 tibialis amicus 



Adductor 

 obliquus hallucis 



Dorsal 

 interossei 



Long plantar ligament 



Peroneous brevis 

 tendon 



Peroneus longus 

 tendon 



Superficial fibres 

 of long plantar lig. 

 Tubercle of fifth 

 metatarsus 



Flexor brevis 

 minimi digiti, 

 stump 



Variations. — As above 

 stated, the first plantar inter- 

 osseus is usually described as 

 a second head of the flexor 

 brevis hallucis. It is some- 

 times more or less insepara- 

 ble from the oblique portion 

 of the adductor hallucis. 



Plantar 

 interos- 

 seous 

 muscles 



2. Interossei Dorsales 

 (Figs. 623, 630). 



Attachments. — The 



dorsal interossei are also 

 four in number. They 

 arise from the adjacent 

 sides of each pair of met- 

 atarsals and pass distally 

 in the interspaces between 

 these bones. The fibres 

 of each muscle converge 

 to a narrow tendon which 

 is inserted into the mem- 

 branous expansions of the 

 extensor tendons over the 

 first phalanges of the sec- 

 ond, third, and fourth toes. 

 The first and second mus- 

 cles insert into the opposite sides of the second toe and the third and fourth into the 

 lateral sides of the third and fourth toes. 



Nerve-Supply. — By the external plantar nerve from the first and second sacral 

 nerves. 



Action. — To flex the second, third, and fourth toes ; the first also draws the 

 second toe medially and the rest the second, third, and fourth toes laterally. 



3. Flexor Brevis Minimi Digiti (Fig. 629). 



Attachments. — The short flexor of the little toe (m. flexor digiti quinti brevis), 

 which really represents a fifth plantar interosseus, arises from the base of the fifth 



Tendonsof flex-, 

 or brevis hallucis 

 and first plantar 

 i nterosseus re- 

 flected, with ab- 

 ductor and ad- 

 ductor tendons, 

 jhowing the two 

 sesamoid bones 



Deep dissection of sole of right foot, showing interosseous muscles. 



