THE PLANTAR REGION 541 



and are attached on each side to the margins of the phalanges. Opposite the middle of the 

 proximal and second phalanges the sheath is very strong, and the fibres pass transversely, hut 

 opposite the joints it is much thinner, and the fibros pass obliquely. Each sheath is lined by 

 a synovial membrane which is reflected upon the contained tendon. 



The Abductor minimi digiti (m. abductor dig Hi quinti) lies along the outer 

 border of the foot, and is in relation by its inner margin with the external plantar 

 vessels and nerves. It arises, by a very broad origin, from the outer tubercle of 

 the os calcis, from the under surface of the os calcis between the two tubercles, 

 from the fore part of the inner tubercle, from the plantar fascia and the intermuscular 

 septum, between it and the Flexor brevis digitorum. Its tendon, after gliding 

 over a smooth facet on the under surface of the base of the fifth metatarsal bone, 

 is inserted with the short Flexor of the little toe into the outer side of the base of the 

 first phalanx of this toe. 



Dissection. The muscles of the superficial layer should be divided at their origin by insert- 

 ing the knife beneath each, and cutting obliquely backward, so as to detach them from the 

 bone; they should then be drawn forward, in order to expose the second layer, but not cut away 

 at their insertion. The two layers are separated by a thin membrane, the deep plantar faxc/a, 

 on the removal of which is seen the tendon of the Flexor longus digitorum, the Flexor accessorius, 

 the tendon of the Flexor longus hallucis, and the Lumbricales. The long Flexor tendons diverge 

 from each other at an acute angle; the Flexor longus hallucis runs along the inner side of the 

 foot, on a plane superior to that of the Flexor longus digitorum, the direction of the latter being 

 obliquely outward. 



The Second Layer. 

 Flexor accessorius. Lumbricales. 



The Flexor accessorius (m. quadratus plantae) is separated from the muscles 

 of the first layer by the external plantar vessels and nerves. It arises by two heads, 

 which are separated from each other by the long plantar ligament; the inner or 

 larger head, which is muscular, arises from the inner concave surface of the os 

 calcis below the groove which lodges the tendon of the Flexor longus digitorum; 

 the outer head, flat and tendinous, arises from the outer surface of the os calcis, in 

 front of its lesser tubercle, and from the long plantar ligament; the two portions 

 join at an acute angle, and are inserted into the outer margin and upper and 

 under surfaces of the tendon of the Flexor longus digitorum, forming a kind of 

 groove in which the tendon is lodged. 1 



The Lumbricales (m. lumbricales} are four small muscles accessory to the 

 tendons of the Flexor longus digitorum; they arise from the tendons of the long 

 Flexor, as far back as their angle of division, each arising from two tendons, except 

 the internal one. Each muscle terminates in a tendon, which passes forward 

 on the inner side of the four lesser toes and is inserted into the expansion of the long 

 Extensor tendon on the dorsum of the first phalanx of the corresponding toe. 



Dissection.The Flexor tendons should be divided at the back part of the foot, and the 

 Flexor accessorius at its origin, and drawn forward, in order to expose the third layer. 



The Third Layer. 



Flexor brevis hallucis. Flexor brevis minimi digiti. 



Adductor obliquus hallucis. Adductor transversus hallucis. 



The Flexor brevis hallucis (m. flexor hallucis brevis} arises, by a pointed 

 tendinous process, from the inner part of the under surface of the cuboid bone, 



1 According to Turner, the fibres of the Flexor accessorius end in aponeurotic bands, which contribute slips 

 to the second, third, and fourth digits. 





