366 PRACTICAL ANATOMY. 



The small sciatic nerve supplies the skin covering the flexor muscles of the 

 leg. It may be regarded as the dismembered branch of the great sciatic nerve. 

 The long pudendal branch of this nerve crosses the tuber ischii and is distributed 

 to the scrotum of the male and its homologue, the labia majora of the female. 



The long saphenons nerve is a branch of the anterior crural, but to carry out 

 the law governing cutaneous distribution, it extends to the inner side of the 

 ankle, to supply the skin over the fullest insertion (periosteal) of the sartorius. 



If you will now clean off all the fat, you will see a rather dense fascia cover- 

 ing the muscles. This is the deep fascia. That part of this fascia that covers 

 the popliteal space is called the popliteal fascia. Now remove the deep fascia 

 and make your muscles look like figure 256, taking pains not to destroy vessels 

 and nerves. 



You have now exposed to view the gluteus mediu's and maximus, biceps, 

 semitendinosus, semi-membranosus, gracilis, sartorius, plantaris, gastrocnemius, 

 and tendo Achillis. 



THE POPLITEAL SPACE 



is a surgical area occupying the lower posterior one-third of the thigh and the 

 upper posterior one-sixth of the tibia. It is diamond in shape. Its floor is 

 formed by the femur, ligament of Winslow, and popliteus muscle. Its roof is 

 formed by the skin, superficial fascia, and deep popliteal fascia. (See above.) The 

 space is bounded (Fig. 256), above the joint, externally by the biceps muscle, 

 internally by the semitendinosus, semi-membranosus, gracilis, and sartorius ; 

 below the joint, externally by the outer head of the gastrocnemius and plantaris 

 muscle, internally by the inner head of the gastrocnemius. The space contains, 

 in a variable amount of fat and connective tissue : 



1. The terminus of the short saphenous vein in the popliteal. 



2. The descending branch of the small sciatic nerve. (Fig. 260.) 



3. The communicating branches to the short saphenous nerve. 



4. The internal popliteal nerve in the centre of the popliteal space. (Fig. 266.) 



5. The external popliteal nerve with the biceps tendon. 



6. The articular branch of the obturator nerve to the knee. 



7. The popliteal artery and vein and their branches. 



In figure 255 note in particular the formation of the short or external 

 saphenous nerve, by the union of two communicating branches, from the inter- 

 nal and external popliteal nerves. There is no constant level at which this union 

 takes place between the communicans tibialis and the communicans fibularis. 



Locate tlie popliteal space. 



It occupies the lower posterior one-third of the thigh and the upper poste- 

 rior one-sixth of the leg ; it extends from the aperture in the adductor magnuj 

 muscle to the lower border of the popliteus muscle. 



dire tlic relation, in tlic centre' of tlie space, of the internal popliteal ncri-c, and 

 tlie popliteal vein an<l artery. (Fig. 261.) 



The nerve is above, the vein in the middle, and the artery below. (Fig. 269.) 



Remember, when we dissect the popliteal space, the subject is face downward, 

 hence the order referred t<> is as follows : having cut through the skin, super- 

 ficial fascia, and deep fascia, called in this region popliteal fascia, the most super- 

 ficial structure seen in the space under the deep fascia is the internal popliteal 

 nerve; the next deep structure immediately under the nerve is the popliteal 

 vein ; the third deep structure is the popliteal artery. This relation of the vein 

 to its artery is in harmony with the rule governing the relation of arteries 

 their veins, above and below the diaphragm. 



