THIRD LAYER OF MUSCLES. 621 



strong tendinous process which, joined by bands of the accessorius, is con- 

 tinued into the pieces of that tendon belonging to the second and third 

 toes (Turner). 



Between the calcaneum and the internal malleolus this tendon lies in a 

 groove in the astragalus ; and in the foot it occupies a hollow below the 

 inner projection (sustentaculum tali) of the os calcis, being enveloped by 

 a synovia! membrane. 



Action. For the action of this muscle on the .great toe, see page 610. 

 Through the slip that it gives to the tendons of the flexor longus going to 

 the s"econd and third toes, it may bend those digits with the great toe. 



Dissection (fig. 212). For the dissection of the third layer of muscles, 

 the accessorius and the tendons of the long flexor are to be cut through 

 near the calcaneum, and turned towards the toes. Whilst raising the 

 tendons the external plantar nerve and artery are not to be interfered 

 with ; and two small nerves and vessels to the outer two lumbricales are 

 to be looked for. Afterwards the areolar tissue is to be taken from the 

 muscles now brought into view. 



THIRD LAYER OF MUSCLES (fig. 212). Only the short muscle of the 

 great and little toes enter into this layer. On the metatarsal bone of the 

 great toe the flexor brevis pollicis lies, and external to it is the adductor 

 pollicis ; on the metatarsal bone of the little toe is placed the flexor brevis 

 minimi digiti. Crossing the heads of the metatarsal bones is the trans- 

 versalis pedis muscle. 



The fleshy mass between the adductor pollicis and the short flexor of 

 the little toe consists of the interossei muscles of the next layer. 



The FLEXOR BREVIS POLLICIS muscle (fig. 212, A ) is tendinous and 

 pointed posteriorly, but bifurcated in front. It is attached behind to the 

 inner part of the under surface of the cuboid bcne, and to a prolongation 

 from the tendon of the tibialis posticus. Near the front of the metatarsal 

 bone of the great toe it divides into two heads, which are inserted into the 

 sides of the base of the metatarsal phalanx. 



Resting on the muscle at one part, and in the interval between the 

 heads at another, is the tendon of the flexor longus pollicis. The inner 

 head joins the abductor, and the outer is united with the adductor pollicis. 

 A sesamoid bone is developed in the tendon connected with each head. 



Action. By its attachment to the first phalanx it flexes the metatarso- 

 phalangeal joint of the great toe. 



The ADDUCTOR POLLICIS (fig. 212, B ), which is larger than the pre- 

 ceding muscle and external to it, arises from the sheath of the tendon of 

 the peroneus longus, and from the bases of the second, third, and fourth 

 metatarsal bones. Anteriorly the muscle is united with the outer head of 

 the short flexor, and is inserted with it into the base of the metatarsal 

 phalanx of the great toe. 



To the inner side is the flexor brevis ; and beneath the outer the exter- 

 nal plantar vessels and nerve are directed inwards. 



Action. Its first action will be to adduct the great toe to the others, and 

 it will help afterwards in bending the matatarso-phalangeal joint of the toe. 



The TRANSVERSALIS PEDIS (fig. 212, D ) is placed transversely over the 

 heads of the metatarsal bones. Its origin is by fleshy bundles from the 

 capsule of the metatarso-phalangeal articulations of the four outer toes 

 (frequently not from the little toe), and from the fascia covering the inter- 

 ossei muscles. Its insertion into the great toe is united with that of the 

 adductor pollicis. 



