THE LEG AND ANKLE. 55 



on the inner side, the tendons of the tibialis anticus, the 

 extensor longus pollicis, the extensor longus digitorum, and 

 the peroneus tertius. They start up like cords when the foot 

 is raised, and are kept in their proper relative position by 

 strong pulleys formed by the anterior annular ligament. Of 

 these pulleys the strongest is that of the extensor communis 

 digitorum. When the ankle is sprained, the pain and swelling 

 arise from a stretching of these pulleys and effusion into their 

 synovial sheaths. A laceration of one of the pulleys and 

 escape of the tendon is extremely rare. 



The place for the division of the tendon of the tibialis 

 anticus, so as to divide it below its synovial sheath, is about 

 one inch before its insertion into the cuneiform bone. The 

 knife should be introduced on the outer side, so as to avoid 

 the dorsal artery of the foot. 



Now trace the lines of the arteries, and the landmarks 

 near which they divide. 



1 20. Popliteal artery. About one inch and a quarter 

 below the head of the fibula, or say one inch below the 

 tubercle of the tibia, the popliteal artery divides into the 

 anterior and posterior tibial. The peroneal comes off from the 

 posterior tibia! about three inches below the head of the fibula. 



Consequently we may lay down, as a general rule, that, 

 in amputations one inch below the head of the fibula, only 

 one main artery, the popliteal, is divided. In amputations 

 two inches below the head of the fibula, two main arteries, 

 the anterior and posterior tibial, are divided. In amputations 

 three inches below the head, three main arteries, the two 

 tibials and the peroneal, are divided. 



121. Anterior tibial artery. The anterior tibial artery- 

 comes in front of the interosseous membrane, one inch and a 

 quarter below the head of the fibula, and here lies close to 

 this bone. Its subsequent course is defined by a line drawn 

 from the front of the head of the fibula to the middle of the 

 front of the ankle. This line corresponds pretty nearly with 

 the outer border of the tibialis anticus all the way down. If 

 this muscle be put in action, its outer border (the inter- 

 muscular line) is plainly seen, and the incision for the ligature 



