THE LEG 1453 



of about 2.5 cm. (1 in.), the vessel is comparatively superficial after division of the fasciae. The 

 nerve is generally seen first, and, with the vein, must be drawn laterally. The needle should be 

 passed from the' vein. (B) From the front, at the medial side. The thigh being flexed, ab- 

 ducted, and rotated laterally, a free incision is made parallel and just behind the adductor 

 magnus tendon, commencing at the junction of the middle and lower third of the thigh. The 

 sartorius and the hamstrings are drawn backward, and the adductor magnus forward. Care 

 must be taken of the genu suprema (fig. 1168). The space between the hamstrings and the 

 adductor magnus being carefulh' opened up, the artei-y wiU be found in fatty areolar tissue. 

 The vein and tibial nerve are on the lateral side of the vessel. The needle is passed in latero- 

 medially. The collateral circulation (fig. 1156) depends chiefly on the genu suprema. 



The small saphenous vein perforates the roof of the popUteal space in its lower part. As 

 a rule, it is not visible, unless enlarged. 



The popliteal nodes are not to be felt unless enlarged. 



Bursae in the popliteal space. — These have been already spoken of (p. 1449). 



THE LEG 



The skin. — The proneness of the skin to dermatitis in the lower third of the 

 medial and front aspect of the leg as a result of varicose veins is well kno\sTi. The 

 close contiguity of the periosteum to the skin here accounts for the difficulty in 

 healing chronic ulcers whose callous base has become fixed to the periosteum, and 

 the frequency with which the upper fragment of a fractured tibia perforates the 

 skin. 



Bony landmarks. — From the tuberosity (tubercle) of the tibia descends the 

 anterior border or 'shin. ' This soon becomes sharp, and continues so for its upper 

 two-thirds; in the lower third it disappears, to be overlaid by the extensor tendons. 

 It is curved somewhat laterally above and medially below. The medial border can 

 also be felt from the medial condyle to the medial malleolus. Between these two 

 borders lies the medial surface, subcutaneous save above, where it is covered by 

 the three tendons of insertion of the gracilis and semi-tendinosus, and, overlying 

 them, that of the sartorius. The tibia is narrowest and weakest at the junction of 

 the middle and lower thirds, the most common site of fracture. Behind the 

 medial malleolus, part of the groove for and the tendon of the tibialis posterior can 

 be felt. 



The head of the fibula can be felt distinctly, but the shaft soon becomes buried 

 amongst muscles till about 7.5 cm. (3 in.) above the lateral malleolus, where the 

 bone expands into a large triangular subcutaneous surface. 



This lies between the peroneus tertius and the other two peronei. The peroneus longus 

 overlaps the brevis, especially in the upper two-thirds of the leg. In the lower third the brevis 

 tends to become anterior (fig. 1173). Behind the lateral malleolus these tendons descend to the 

 foot in a groove on its posterior border. The shaft of the fibula is placed on a plane posterior 

 to that of the tibia, and curves backward in a dkection reverse to that of the tibia. 



Muscular compartments and prominences. — When the muscles of the leg are 

 thrown into action by dorsi-flexion and plantar flexion of the foot or by standing 

 on the toes, several groups of muscles stand out on the surface, owing to certain 

 compartments, and the origin of certain muscles from, and their separation by, the 

 deep fascia, which knits the surface into corresponding elevations and depressions. 

 The bones and the two peroneal septa divide the leg into four compartments. 



These are, medio-laterally: — (1) A medial, corresponding to the medial surface of the tibia. 

 (2) An anterior, between the crest of the tibia and the anterior peroneal septum, attached 

 to the antero-lateral border of the fibula, and separating the extensors from the peronei. Its 

 sm-face-marking would be a line from the front of the head of the fibula to the front of the 

 lateral malleolus. In this anterior compartment lie the extensor muscles and origin of the 

 peroneus tertius, and the anterior tibial vessels and nerves. (3) A lateral or peroneal com- 

 partment, Ij'ing between the anterior and posterior peroneal septum, the latter being attached 

 to the postero-lateral border of the fibula, and separating the peronei from the calf and deep 

 flexors. This peroneal compartment, a narrow one, contains the two chief peronei and the 

 peroneal (external popUteal) nerve and its three divisions. (4) Much the largest, this, the 

 posterior, lies between the posterior peroneal septum and the medial border of the tibia, and 

 contains the caK and deep flexor muscles, the posterior tibial vessels and nerves, and the 

 peroneal artery and its posterior branch. 



The space between the tibia and fibula in front is mainly occupied by the flesh}' belly of the 

 tibiaUs anterior; lateral to this, and much less prominent, is the narrower extensor digitorum 

 longus; lateral to this, again, are the peronei longus and brevis. Lower down, in an 

 interval between the tibialis and the extensor of the toes, the extensor haUucis, here almost 

 entirely tendinous, comes to the surface. Behind, the prominence of the calf is mainly formed 

 by the gastrocnemius. On the patient's rising on tip-toe, the tendo Achillis starts into relief 



