FLEXOR BREVIS AND ADDUCTOR HALLUCIS. 271 



metatarsal bone is sometimes present (6 per cent.). The abductor ossis metatarsi quinti is an 

 occasional muscle which arises from the external tubercle of the os calcis, and is inserted into 

 the tuberosity of the fifth metatarsal bone in common with, or beneath the outer margin of 

 the plantar fascia. It may be adherent to the abductor minimi digiti, and it has been seen 

 inserted into the middle or even the anterior part of the metatarsal bone. It occurs in about 

 18 per cent. (G-ruber, Virchow's Archiv, 1886, cvi, 489.) 



The SECOND LAYER OF MUSCLES OF THE SOLE is constituted by the tendons of 

 the flexor longus digitorum and flexor longus hallucis, together with the flexor 

 accessorius and lumbricales, all of which have been described in the_last section 

 (pp. 265266). 



The THIRD LAYER OF MUSCLES comprises the short flexor and the adductors 

 of the great toe, and the short flexor of the little toe. 



The flexor brevis hallucis (fl. brev. pollicis pedis) arises by a flat tendinous 

 process from the inner border of the cuboid bone, and by a second band from the 



Fig. 263. THIRD LAYER OF MUSCLES OP THE SOLE. 



d, tendon of peroneus longus ; e, long plantar ligament ; 6, 

 flexor brevis hallucis ; 7, adductor obliquus hallucis ; 8, adductor 

 transversus hallucis ; 9, flexor brevis minimi digiti ; 10, 10, 

 second and third plantar interosseous muscles ; 11, 11, third and 

 fourth dorsal interosseous muscles. 



offset of the tibialis posticus tendon which passes to 

 the middle and outer cuneiform bones. The muscular 

 part is single and narrow behind, but in front it divides 

 so as to form two bellies or heads which are inserted 

 by tendinous fibres, one into the inner border of the 

 base of the first phalanx in union with the abductor 

 hallucis, the other into the outer border in union with 

 the adductors. A sesamoid bone is developed in each 

 of the heads. 



Relations. This muscle is in great part covered by the 

 abductor hallucis and the short flexor of the toes, while the 

 tendon of the flexor longus hallucis runs in the groove between 

 its heads. 



Varieties. The origin of the flexor brevis hallucis is 

 subject to considerable variation : it often receives fibres 

 from the os calcis or long plantar ligament, and the attach- 

 ment to the cuboid is sometimes wanting. The muscle has 

 been seen sending a slip to the first phalanx of the second toe. 



The adductor obliquus hallucis (add. pollicis 



pedis), a thick fleshy mass occupying the hollow on the outer side of the first 

 metatarsal bone, arises from the tarsal extremities of the third and fourth metatarsal 

 bones, and from the sheath of the peroneus longus muscle ; narrowing as it passes 

 forwards, it is inserted, conjointly with the external head of the flexor brevis hallucis, 

 into the base of the first phalanx of the great toe. 



Relations. At its inner side it is connected with the flexor brevis hallucis ; its deep 

 surface rests upon the second, third and fourth metatarsal bones and the intervening inter- 

 osseous muscles. The deep parts of the external plantar artery and nerve pass inwards 

 beneath its outer border. 



Varieties. A slip has been observed from this muscle also to the base of the first phalanx 

 of the second toe. The opponents hallucis is a muscle occasionally found, coming off as a slip 

 from the adductor, and inserted into the metatarsal bone of the great toe It occurs in some 

 apes. 



