544 THE MUSCLES AND FASCIA 



from the adjacent sides of the metatarsal bones, between which they are placed; 

 their tendons are inserted into the bases of the first phalanges, and into the apon- 

 eurosis of the corresponding slip of the common Extensor tendon. In the angular 

 interval left between the heads of each muscle at its posterior extremity the per- 

 forating arteries pass to the dorsum of the foot, except in the First interosseous 

 muscle, where the interval allows the passage of the communicating branch of the 

 dorsalis pedis artery. The First dorsal interosseous muscle is inserted into the 

 inner side of the second toe; the other three are inserted into the outer sides of 

 the second, third, and fourth toes. 



The Plantar Interossei (m. interossei platitares), three in number, lie beneath, 

 rather than between, the metatarsal bones. They are single muscles, and each 

 arises from but one metatarsal bone. They arise from the base and inner sides 

 of the shaft of the third, fourth, and fifth metatarsal bones, and are inserted into 

 the inner sides of the bases of the first phalanges of the same toes, and into the 

 aponeurosis of the corresponding slip of the common Extensor tendon. 



Nerves. The Flexor brevis digitorum, the Flexor brevis and Abductor hallucis, and the 

 innermost Lumbrical are supplied by the medial plantar nerve. All the other muscles in the 

 sole of the foot by the lateral plantar. The First dorsal interosseous muscle frequently receives 

 an extra filament from the internal branch of the anterior tibial nerve on the dorsum of the foot, 

 and the Second dorsal interosseous a twig from the external branch of the same nerve. 



Actions. All the muscles of the foot act upon the toes, and for purposes of description as 

 regard their action may be grouped as Abductors, Adductors, Flexors, or Extensors. The Abduc- 

 tors are the Dorsal interossei, the Abductor hallucis, and the Abductor minimi digiti. The Dorsal 

 interossei are Abductors from an imaginary line passing through the axis of the second toe, so that 

 the first muscle draws the second toe inward, toward the great toe; the second muscle draws the 

 same toe outward; the third draws the third toe, and the fourth draws the fourth toe, in the same 

 direction. Like the Interossei in the hand, they also help to flex the proximal phalanges and to 

 extend the two terminal phalanges. The Abductor hallucis abducts the great toe from the others, 

 and also flexes the proximal phalanx of this toe. And in the same way the action of the Abductor 

 minimi digiti is twofold as an Abductor of this toe from the others, and also as a Flexor of the prox- 

 imal phalanx. The Adductors are the Plantar interossei, the Adductor obliquus hallucis, and the 

 Adductor transversus hallucis. The Plantar interosseous muscles adduct the third, fourth, and 

 fifth toes toward the imaginary line passing through the second toe, and by means of their inser- 

 tion into the aponeurosis of the Extensor tendon they, with the Dorsal interossei, flex the prox- 

 imal phalanges and extend the two terminal phalanges. The Adductor obliquus hallucis is 

 chiefly concerned in adducting the great toe toward the second one, but also assists in flexing 

 this toe. The Adductor transversus hallucis approximates all the toes, and thus increases the 

 curve of the transverse arch of the metatarsus. The Flexors are the Flexor brevis digitorum, the 

 Flexor accessorius, the Flexor brevis hallucis, the Flexor brevis minimi digiti, and the Lum- 

 bricales. The Flexor brevis digitorum flexes the second phalanges upon the first, and, con- 

 tinuing its action, may flex the first phalanges also and bring the toes together. The Flexor 

 accessorius assists the long Flexor of the toes, and converts the oblique pull of the tendons of 

 that muscle into a direct backward pull upon the toes. The Flexor brevis hallucis flexes and 

 slightly adducts the first phalanx of the great toe. The Flexor brevis minimi digiti flexes the 

 little toe and draws its metatarsal bone downward and inward. The Lumbricales, like the 

 corresponding muscles in the hand, assist in flexing the proximal prialanx, and by their insertion 

 into the long Extensor tendon aid in straightening the two terminal phalanges. The only muscle 

 in the Extensor group is the Extensor brevis digitorum. It extends the first phalanx of the great 

 toe, and assists the long Extensor in extending the next three toes, and at the same time gives to 

 the toes an outward direction when they are extended. 



SURFACE FORM OF THE LOWER EXTREMITY. 



Of the muscles of the thigh, those of the iliac region have no influence on surface form, while 

 those of the anterior femoral region, being to a great extent superficial, largely contribute to the 

 surface form of this part of the body. The Tensor fasciae femoris produces a broad elevation 

 immediately below the anterior portion of the crest of the ilium and behind the anterior supe- 

 rior spinous process. From its lower border a longitudinal groove, corresponding to the ilio- 

 tibial band, may be seen running down the outer side of the thigh to the outer side of the knee- 

 joint. The Sartorius muscle, when it is brought into action by flexing the leg on the thigh 



