Chap, xxi.] THE POPLITEAL SPACE. 431 



tibia backwards, and produce in some cases a partial 

 luxation. 



The hamstring tendons may be ruptured by 

 violence, the tendon most frequently torn being that 

 of the biceps. The muscles are greatly stretched when 

 the trunk is bent forcibly forwards at the hip joint, 

 the knee remaining extended. Extreme movement in 

 this position has ruptured some of the fibres of this 

 muscle. The difficulty experienced in touching the 

 toes with the fingers while the knees are kept stiff 

 depends upon the resistance offered by the stretched 

 hamstrings. In tenotomy of the biceps tendon the 

 peroneal nerve is in great risk of being wounded. It 

 may be noted that contraction of the muscle tends to 

 increase the distance between the tendon and the 

 nerve, and to render the former more superficial. The 

 peroneal nerve is in still greater risk of being wounded 

 in resecting the head of the fibula, an operation, how- 

 ever, that is seldom performed. 



The vessels of the ham. The popliteal vessels 

 are, from their depth, but seldom wounded. It must 

 be borne in mind that the lower part of the artery may 

 be reached from the anterior aspect of the leg by an 

 instrument passing between the tibia and fibula. 

 Thus Spence reports the case of a farmer who received 

 a wound in front of the leg, just below the knee, from 

 the slipping of his knife while cutting a stick. It was 

 discovered subsequently that the knife had entered the 

 interosseous space and had wounded the popliteal 

 artery at its bifurcation. It had indeed nearly severed 

 the anterior tibial artery from the main trunk. 



The popliteal artery has been ruptured by external 

 violence, as when a wheel has passed over the region 

 of the vessel. Mr. Harrison Cripps (Lancet, 1876) 

 believes that the rupture is, as a rule, the result of a 

 force acting in an oblique direction from below upwards 

 upon the lower expanded end of the femur. This 



