662 HUMAN ANATOMY. 



Abductor Minimi Digiti (Fig. 627), 



Attachments. — -The abductor of the little toe (m. abductor digiti quinti) is 

 situated along the outer border of the foot. It arises from the under surface of the 

 calcaneum and from the plantar aponeurosis, and extends distally and laterally to be 

 i?iserted partly into the tuberosity of the fifth metatarsal bone and partly into the 

 lateral side of the base of the first phalanx of the little toe. 



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

 sacral nerves. 



Action. — To abduct and flex the little toe. 



Variations.— A portion of the abductor digiti quinti frequently separates from the rest of 

 the muscle to form a fusiform belly which has been termed the abductor ossis tneiatarsi quinti. 

 It arises from the lateral part of the inferior surface of the os calcis and is inserted, either inde- 

 pendently or in common with the abductor, into the tuberosity of the fifth metatarsal. 



{bb) The Muscles of the Second Layer. 



I. LUMBRICALES (Fig. 628). 



Attachments. — The lumbricales are four spindle-shaped muscles which arise 

 from the adjatent borders of the tendons of the flexor longus digitorum and from the 

 inner border of its first tendon. They pass distally to the inner surfaces of the first 

 phalanges of the second, third, fourth, and fifth" digits, where they are inserted into the 

 membranous expansions of the tendons of the extensor longus digitorum. 



Nerve-Supply. — The first or first and second muscles, counting from the tibial 

 side, are supplied by the internal plantar nerve ; the remaining three or two are sup- 

 plied from the external plantar from the fourth and fifth lumbar and first sacral nerves. 



Action. — To flex and draw medially the second, third, fourth, and fifth toes. 



Variations. — Absence of one or other of the lumbricales has been noted, the fourth and third 

 being those most frequently lacking ; these same muscles are frequently bifid at their insertions. 

 Small bursje may intervene between the tendons and the first phalanges. 



The signiiicance of the lumbricales is similar to that of the corresponding muscles of the 

 hand. They arise primarily from the deeper layers of the plantar aponeurosis, and when these 

 differentiate into the tendons of the flexor longus digitorum they come to arise from those 

 structures. 



(^r) The Muscles of the Third Layer. 

 I. Adductor Hallucis (Fig. 629). 



Attachments. — The adductor hallucis consists of two portions, often described 

 as two distinct muscles, united only at their insertions. The oblique po7-tion (caput 

 obliquum), or adductor obliquiis, arises from the bases of the second, third, and 

 fourth metatarsals and from the long plantar ligament and passes distally and inward 

 along the interval between the first and second metatarsals, its fibres converging to a 

 strong tendon which unites with that of the tra?isve7'se portio7i (caput transversum), or 

 adductor tra?isversus. This extends almost transversely, under cover of the three 

 medial tendons of the long and short fiexors and the lumbricales, over the heads of 

 the fourth, third, and second metatarsals. It arises from the capsules of the four 

 lateral metatarso-phalangeal joints and passes medially to join the tendon of the 

 oblique portion. The common tendon so formed unites with the tendon of the first 

 plantar interosseous and is iyiserted into the sesamoid bone of that tendon and into the 

 lateral surface of the base of the first phalanx of the great toe. 



Nerve-Supply. — By the deep branch of the external plantar nerve from the 

 fifth lumbar and first and second sacral nerves. 



Action. — To flex and adduct the hallux. 



Variations. — Some variation occurs' in the extent of the origin of both portions of the 

 adductor hallucis. The oblique portion may be limited to the long plantar ligament, or may 

 receive an accessory slip from the shaft of the second metatarsal, while the origin of the trans- 

 verse portion from the fifth metatarso-phalangeal joint may be lacking. 



It is to be noted that in the fnetus the two portions of the adductor are not separated by a 

 wide interval as in the adult, but lie in contact with each other. 



