226 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 311. — The middle layer of plantar muscles. 

 The flexor digitorum brevis, the abductor hallucis, and the abductor digiti quinti have been removed; the tendon 

 sheaths of the digits and of the perona^us longus have been opened. 



Fig. 312. — The deep layer of plantar muscles. 

 The tendons of the flexor digitorum longus, the flexor hallucis longus, and the quadratus plantae have been removed. 



THE MUSCLES OF THE BALL OF THE GREAT TOE. 



The muscles of the ball of the great toe differ from those of the thenar eminence not only 

 in their number but also in the fact that one of them arises from the posterior extremity of the 

 calcaneus and the other two from the anterior portion of the tarsus. The ball of the great toe 

 consequently contains one long and two short muscles, while all four muscles of the thenar 

 eminence are practically of the same length, on account of the shortness of the carpus. 



The abductor hallucis (Fig. 310) is a long, triangular, penniform muscle which occupies 

 the entire inner margin of the foot and whose origin is situated immediately alongside of that 

 of the flexor digitorum. It forms the internal plantar eminence (Fig. 309) and arises from 

 the inner tubercle of the calcaneus from the adjacent portion of the inner surface of that bone, 

 from the laciniate ligament, and also from the plantar aponeurosis, which covers the muscle 

 completely by the radiations of its middle portion. Soon after its origin, a flat strong tendon 

 develops in the middle of the muscle, which is inserted by means of the internal sesamoid bone 

 into the first phalanx of the great toe and into its dorsal aponeurosis. The flexor hallucis brevis 

 is situated between the tendons of the abductor hallucis and flexor hallucis longus. 



The muscle is supplied by the internal plantar nerve. Its chief function is the abduction of the great toe.* 



The flexor hallucis brevis (Figs. 311 and 312) is much shorter than the abductor. It 

 arises partly from the plantar surfaces of the middle and external cuneiform bones and partly 

 from the tendinous prolongations of the long plantar ligament which form the sheath of the 

 peronaeus longus. Like the flexor pollicis brevis, the insertion of the muscle divides into two 

 slips, between which passes the tendon of the flexor hallucis longus. The inner slip, together 

 with the adductor hallucis, passes into the tendon of the internal sesamoid bone; the outer slip, 

 together with the adductor hallucis, passes to the external sesamoid bone. The outer margin 

 of the muscle is in relation with the abductor, the inner with the adductor hallucis. 



The muscle flexes the great toe and is supplied partly by the internal plantar nerve and partly by the external plantar 

 nerve. 



The adductor hallucis (Fig. 312) is a distinctly bicipital muscle and the two heads do 

 not unite until they almost reach the insertion. The oblique head is a round, strong, elongated 

 muscle arising from the plantar surface of the external cuneiform bone, in common with and 

 partly adherent to the flexor hallucis, from the bases of the second and third metatarsal bones, 



*The marked development of most of the muscles of the great and little toes, in spite of the limited 

 range of motion of these digits within the usual coverings of the foot, allows of the conclusion that these muscles not 

 only move the toes, but that they play an important role in supporting the arch of the foot, especially since the abductor 

 digiti V does not extend to the toe at all, but is inserted into the practically immovable fifth metatarsal bone. 



