THE LOWER LIMB 595 



vein exposed, its varying relation to the more deeply-placed popliteal artery 

 being noted. The tributaries of the popliteal vein, when dissected, should 

 be cut. These correspond with the branches of the pophteal artery, the 

 short saphenous vein being a special tributary'. The vein should next be 

 hooked to one side, which will prepare the popUteal artery for dissection. In 

 order to expose the vessel fully to its termination, the inner head of the 

 gastrocnemius may be di\nded. In cleaning the artery, the geniculate branch 

 of the obturator ner\e should be looked for. If present, it \^-ill be found piercing 

 the adductor magnus close above the femoral opening, after which it usually 

 descends at first upon the inner side of the artery and then in front of it, 

 until it comes into contact with the central or cizygos branch, which it 

 accompanies through the posterior Ugament of the knee-joint to the interior 

 of the articulation. During this dissection the popliteal lymphatic glands 

 may come into view in the interval between the femoral condyles, one gland 

 being superficial to the artery, one beneath it, and one on either side. The 

 branches of the artery are to be carefully cleaned, as follows: (i) muscular, to 

 the hamstring and sural muscles ; (2) cutaneous, to the upper part of the 

 back of the leg ; and (3) the following five articular arteries : (a) two 

 superior, external and internal, above the knee-joint, usually close above 

 the femoral condyles and lying very deeply ; (6) central or azygos, at the 

 back of the joint, and coming either from the front (deep) surface of the 

 main vessel, or in many cases from the superior external articular ; and (c) two 

 inferior, external and internal, below the level of the joint. The floor of the 

 popUteal space should next be cleaned and examined, as follows: (i) the 

 popliteal surface or trigone of the femur ; (2) the posterior ligament of the 

 knee-joint, wth the Hgamentum posticum Winslowii ; eind (3) the popliteal 

 fascia covering the popliteus muscle. 



Back of the Thigh. — The landmarks having been studied, the skin is to be 

 removed by making a single vertical incision in the middle line. In the 

 superficial fascia the femoral cutaneous branches of the small sciatic nerve 

 are to be looked for, along the inner and outer aspects. At the upper and 

 inner part of the back of the thigh twigs may be met with from the long 

 pudendal branch of the small sciatic nerve. 



The superficial fascia having been removed, the deep fascia or fascia lata 

 should be studied. The deep fascia having been removed, the small sciatic 

 nerve should be shown, and the hamstring muscles, namely, the biceps 

 femoris, semitendinosus, and semimembranosus, should be cleaned and 

 studied. The relation of the long head of the biceps to the great sacro- 

 sciatic ligament should be noted. 



The great sciatic nerve is also to be cleaned to its division into external 

 and internal popUteal nerves, which latter nerves sometimes take the place 

 of the great sciatic. The muscular branches of the great sciatic should be 

 dissected, and it should be noted that, with one exception, they are derived 

 from the internal popUteal part of the nerve. The exception is the branch 

 to the femoral head of the biceps, which is derived from the external popUteed 

 part of the nerve. It should cdso be noted that the nerve to the semimembra- 

 nosus gives a branch to that part of the adductor magnus which extends frona 

 the tuber ischii to the adductor tubercle of the femur. The whole course 

 and relations of the great sciatic nerve should be thoroughly mastered. 

 The posterior surface of the adductor magnus should next be cleaned, showing 

 the four arches with the four perforating arteries passing bactwards under 

 them, and the femoral opening where the femoral artery becomes the popUteal. 

 The distribution and anastomoses of the perforating arteries on the back of 

 the thigh should be carefuUy studied, and it should be noted that they com- 

 municate above with the sciatic and gluteal, and below \v-ith the popUteal. It 

 should further be noted that the perforating arteries do not terminate on 

 the back of the thigh, and for this purpose an effort should be mads to show 

 aU four passing outwards preparatory to their \s-inding round the outer side 

 of the femur to the outer side of the thigh, in which situation they end. The 

 relation of muscles at the gluteal ridge of the femur should be studied, as 

 weU as the relation of muscles along the linea asppra. 



