OF THE FOOT. 443 



terior tibial vessels and nerve, which run through a broad space beneath the liga- 

 ment ; lastly, in a canal formed partly by the astragalus, the tendon of the 

 Flexor longus hallucis. The canals for the tendons are lined by a separate synovial 

 membrane. 



The External Annular Ligament extends from the extremity of the outer mal- 

 leolus to the outer surface of the os calcis : it binds down the tendons of the Pero- 

 neus longus and brevis muscles in their passage beneath the outer ankle. The two 

 tendons are enclosed in one synovial sac. 



Dissection of the Sole of the Foot. The foot should be placed on a high block witli the 

 sole uppermost, and firmly secured in that position. Carry an incision round the heel and along 

 the inner and outer borders of the foot to the great and little toes. This incision should divide 

 the integument and thick layer of granular fat beneath until the fascia is visible ; the skin and 

 fat should then be removed from the fascia in a direction from behind forward, as seen in Fig. 

 255. 



The Plantar Fascia, the densest of all the fibrous membranes, is of great strength, 

 and consists of pearly-white glistening fibres, disposed, for the most part, longi- 

 tudinally : it is divided into a central and two lateral portions. 



The central portion, the thickest, is narrow behind and attached to the inner 

 tubercle of the os calcis, posterior to the origin of the Flexor brevis digitorum, and, 

 becoming broader and thinner in front, divides near the heads of the metatarsal 

 bones into five processes, one for each of the toes. Each of these processes divides 

 opposite the metatarso-phalangeal articulation into two strata, superficial and deep. 

 The superficial stratum is inserted into the skin of the transverse sulcus which 

 divides the toes from the sole. The deeper stratum divides into two slips which 

 embrace the sides of the flexor tendons of the toes, and blend with the sheaths of 

 the tendons, and laterally with the transverse metatarsal ligament, thus forming a 

 series of arches through which the tendons of the short and long flexors pass to 

 the toes. The intervals left between the five processes allow the digital vessels and 

 nerves and the tendons of the Lumbricales muscles to become superficial. . At the 

 point of division of the fascia into processes and slips numerous transverse fibres 

 are superadded, which serve to increase the strength of the fascia at this part by 

 binding the processes together and connecting them with the integument. The 

 central portion of the plantar fascia is continuous with the lateral portions at each 

 side, and sends upward into the foot, at their point of junction, two strong vertical 

 intermuscular septa, broader in front than behind, which separate the middle from 

 the external and internal plantar group of muscles ; from these, again, thinner 

 transverse septa are derived, which separate the various layers of muscles in this 

 region. The upper surface of this fascia gives attachment behind to the Flexor 

 brevis digitorum muscle. 



The lateral portions of the plantar fascia are thinner than the central piece, and 

 cover the sides of the foot. 



The outer portion covers the under surface of the Abductor minimi digiti ; it is 

 thick behind, thin in front, and extends from the os calcis, forward, to the base of 

 the fifth metatarsal bone, into the outer side of which it is attached ; it is con- 

 tinuous internally with the middle portion of the plantar fascia, and externally 

 with the dorsal fascia. 



The inner portion is very thin, and covers the Abductor hallucis muscle ; it is 

 attached behind to the internal annular ligament, and is continuous around the 

 side of the foot with the dorsal fascia, and externally with the middle portion of 

 the plantar fascia. 



8. Dorsal Region. 



Extensor brevis digitorum. 



The Fascia on the dorsum of the foot is a thin membranous layer continuous 

 above with the anterior margin of the annular ligament ; it becomes gradually 

 lost opposite the heads of the metatarsal bones, and on each side blends with the 



