666 



HUMAN ANATOMY. 



Tendo 



Achillis 



Deep 



flexor 



tendons 



I 



-Protruding 

 lower end 

 of upper 

 fragment 



Tendon of 

 ■tibialis 

 anticus 



ence on either the skin or fascial surface, and although described as a guide to the 

 anterior tibial artery {g.v.), is untrustworthy on account of the difficulty of recog- 

 nizing it (Treves). 



Posteriorly the deep layer of fascia that holds down the deep muscles to the 

 tibia and fibula and runs transversely beneath the soleusand gastrocnemius, is weaker 



above, where it is covered and reinforced by the latter 

 muscles, and stronger below, where it loses their sup- 

 port. It is continued downward and separates the 

 tendo Achillis from the deeper structures. In ap- 

 proaching the vessels behind the malleolus, one finds, 

 therefore, two layers of deep fascia. 



Growths originating in the head of the tibia or 

 occupying the interosseous space are much influenced 

 by the resistance of the deep fascia, which, as is the 

 case with the fascia lata, may for a time determine 

 their shape and direction and alter their surface ap- 

 pearance and their apparent density. 



Cellulitis and abscess are for a while confined 

 beneath the fascia, but, like the coloring matter of 

 the blood after fracture, may soon find their way to 

 the surface by following the vessels that perforate it. 



Some fibres of the gastrocnemius or, more fre- 

 quently, the tendo Achillis at its weakest point, on a 

 level with the internal malleolus, may be ruptured 

 during strong effort, as in raising the body on the 

 toes while bearing a weight. Sometimes, however, 

 this accident follows comparatively trifling exertion. 



2. The Ankle and Foot. — The skin around 

 the ankle and upon the dorsum of the foot is thin 

 and lax. The absence of a fatty or muscular layer 

 between it and the subjacent bones and the distance 

 of the region from the centre of circulation make 

 gangrene from relatively slight contusion, or from the 

 pressure of splints or dressings, more common here 

 than elsewhere. 



Over the sole, especially at those places which 

 normally bear the weight of the body, — the heel, the 

 ball of the great toe, the line of the heads of the metatarsal bones (page 452), and 

 the outer side of the foot, — the skin is much denser. It often contains callosities 

 which cause pain by pressure and are usually the result of friction between the sole 

 and an ill-fitting shoe. Its close connection with the underlying plantar fascia is 

 similar to that between the skin of the palm and the palmar fascia, and between the 

 skin of the scalp and the occipito-frontalis aponeurosis, in all of which regions the 

 integument is exceptionally thick and dense, and in the former two hairless (page 

 491). Under the heel the thick skin and the pad of subcutaneous fascia containing 

 fat are especially valuable in lessening the force of falls upon that part of the foot, 

 where there is no elastic arch composed of a number of bones and joints to take up 

 and distribute the force, as do both the transverse arch and the anterior pillar of 

 the main arch (page 436). This tissue, vertical and scanty in the sole, is loose and 

 abundant on the dorsum and around the tendo Achillis, in which latter region it 

 contains some fat. Its laxity over the dorsum, while it somewhat protects the instep 

 from the effects of direct violence, adds greatly to the ease with which swelling or 

 oedema may occur in cellulitis or, on account of the dependent position of the part 

 and its remoteness from the heart, in anasarca. 



The deep fascia at the ankle is thickened on the dorsum and sides to form the 

 annular ligaments, the chief function of which is to hold in place the tendons that 

 move the foot and toes. Anteriorly this is done by two bands, beneath the upper of 

 which the tendon of the tibialis anticus runs, while the lower covers in the tendon of 

 the same muscle and those of the extensor proprius pollicis and of the extensor com- 



■'\ 



Dissection of fracture of left tibia, 



showing effect of muscular 



action on fragments. 



