ANATOMY OF POPLITEAL SPACE. 593 



Fascia lata. Where this fascia covers the popliteal space it is strength- 

 ened by transverse fibres, particularly on the outer side ; and it is connected 

 laterally with the tendons bounding that interval. The short saphenous 

 vein perforates it sometimes opposite the knee, but usually at a spot lower 

 down. 



Dissection (fig. 202). The fascia over the ham is now to be removed 

 without injuring the small sciatic nerve and artery, and the short saphe- 

 nous vein, which are close beneath it. A large quantity of fat may be 

 next taken out of the space, but without injury to the several small vessels 

 and nerves in it. 



In cleaning the space the student will come upon the large internal 

 popliteal nerve in the middle line ; and nearer the outer side, on the ex- 

 ternal popliteal. Both nerves give branches ; and the numerous offsets of 

 the inner will be recognized more certainly by tracing them from above 

 down along the trunk of the nerve, than by proceeding in the opposite 

 direction ; in fat bodies the two small nerves from the inner popliteal trunk 

 to the knee joint are difficult to find. Under cover of the outer boundary, 

 and deep in the space, is an articular nerve from the external popliteal, 

 which sometimes arises from the great sciatic. 



In the bottom of the space are the popliteal vessels, the vein being more 

 superficial than the artery. The student is to seek an articular branch 

 (superior), on each side, close above the condyle of the femur; and to 

 clean numerous other branches of the vessels to the muscles around, espe- 

 cially to those of the leg. On the upper part of the artery, the branch of 

 nerve from the obturator to the knee joint is to be found : and on the sides 

 of the artery are three or four lymphatic glands in the fat. 



After the ham has been cleaned, the sartorius and the gracilis are to be 

 replaced in their natural position on the inner side. 



The POPLITEAL SPACE, or the ham (fig. 202), is the hollow behind the 

 knee : it allows of the free flexion of the joint, and contains the large ves- 

 sels of the limb. When dissected, this interval has the form of a lozenge, 

 and extends upwards along one-third of the femur, and downwards along 

 one-sixth of the tibia ; but in the natural condition of the parts the sides 

 are approximated by the fascia of the limb, and the space is limited, ap- 

 parently, almost to the region of the joint. 



This hollow is situate between the muscles on the back of the limb ; and 

 the lateral boundaries are therefore formed by the muscles of the thigh 

 (hamstrings), and leg. Thus, on the outer side, is the biceps muscle ( 6 ) as 

 far as the joint ; and the plantaris and the external head of the gastrocne- 

 mius ( 8 ) beyond that spot. On the inner side, as low as the articulation, 

 are the semimembranosus (*) and semitendinosus ( 5 ) muscles, with the gra- 

 cilis and sartorius between them and the femur ; and beyond the joint is 

 the inner head of the gastrocnemius ( 7 ). The upper point of the ham is 

 limited by the apposition of the inner and outer hamstrings ; and at the 

 lower point the heads of the gastrocnemius touch each other. 



Stretched acrross the cavity are the fascia lata and teguments. Forming 

 the deep boundary, or the floor, are the following parts the posterior sur- 

 face of the femur included between the lines to the condyles, the posterior 

 ligament of the knee-joint, and part of the popliteus muscle with the upper 

 end of the tibia. 



The popliteal space is widest opposite the femoral condyles, where the 

 muscles are most drawn to the sides ; and is deepest above the articular 

 38 



