THE FEMORAL AND POPLITEAL ARTERIES. 493 



outwards, its point being kept close to the artery. A considerable branch of the saphenous 

 vein may be divided in making the first incision, and if so will require a ligature. 



To reach the artery in Hunter's canal a longer incision is necessary, in consequence of the 

 greater depth of the vessel, and it should be made a finger's breadth internal to the line of 

 the artery, care being taken to avoid the internal saphenous vein. The superficial structures 

 and the fascia lata having been cut through, the sartorius muscle is exposed and is recognized 

 by its fibres running parallel to the line of the incision. The outer border of this muscle is 

 then freed and drawn inwards, when the aponeurosis covering the femoral vessels is laid 

 bare, and is to be carefully divided. The sheath of the artery is now opened, avoiding the 

 internal saphenous nerve which lies on the surface of the vessel, and the needle is to be 

 passed from without inwards, as the vein is placed behind and slightly to the outer side of 

 the artery. 



Collateral circulation. When the common femoral artery has been tied, the circulation in 

 the lower limb is carried on by means of the anastomoses of the internal pudic artery with 

 the pudic branches of the femoral, of the obturator with the internal circumflex, of the 

 circumflex iliac and gluteal with the external circumflex, and of the sciatic with the internal 

 circumflex and upper perforating branches of the profunda. After ligature of the superficial 

 femoral artery, blood reaches the distal portion of the limb through the anastomoses of the 

 descending branch of the external circumflex artery with the articular arteries of the knee, 

 and through the communications along the back of the thigh, between the sciatic artery, the 

 terminal branches of the internal circumflex, the perforating arteries and the branches of the 

 popliteal. In several instances in which the condition of the vessels has been examined after 

 ligature of the femoral (or external iliac) artery, the comes nervi ischiadici has been found 

 much enlarged, forming, with anastomotic branches from the perforating arteries, a vessel 

 which accompanies the great sciatic nerve, and ends below in the popliteal artery or one of 

 its branches. 



POPLITEAL ARTERY (I-II). 



The popliteal artery, continuous with the femoral, is placed at the back of the 

 knee, and extends along the lower fourth of the thigh and the upper sixth of the 

 leg. It reaches from the opening in the adductor magnus to the lower border of 

 the popliteus muscle, where it divides into the anterior and posterior tibial arteries. 

 Its termination is on a level with the lower part of the tubercle of the tibia. 



In the first part of its course the popliteal artery inclines slightly from within 

 outwards, over the inner portion of the popliteal surface of the femur, to reach a 

 point behind the middle of the knee-joint, whence it descends vertically to its lower 

 end. Being deeply situated in its whole extent, it is covered at its upper end by 

 the semimembranosus muscle ; for a short distance above the knee it is placed in 

 the popliteal space ; below this it is covered by the gastrocnemius muscle and is 

 also crossed by the plantaris ; and its termination is beneath the upper margin of 

 the soleus muscle. 



At its commencement the artery lies close to the inner side of the femur, but in 

 descending it is separated by an interval from the somewhat hollowed popliteal sur- 

 face of the bone ; it then rests on the posterior ligament of the knee-joint, and lastly 

 on the popliteus muscle. 



Relation to veins. The popliteal vein lies close to the artery throughout. At the 

 upper end it is placed to the outer side and somewhat behind ; it then gradually 

 crosses over the artery, and below gains the inner side. The vein is frequently 

 double along the lower part of the artery, and more rarely also at the upper part. 

 The short saphenous vein, ascending to join the popliteal, is also placed over the 

 artery in the lower part of the popliteal space. 



Relation to the nerve. The internal popliteal nerve lies at first to the outer side 

 of, but much nearer to the surface than, the artery ; it afterwards crosses gradually 

 over the vessels, and is placed behind and to the inner side of them below the joint. 

 The nerve is separated from the artery throughout its course by the vein. 



BRANCHES. The branches of the popliteal artery may be arranged in two sets, 

 viz., the muscular and the articular. 



