THIGH AND BUTTOCK. 



The long (or internal) saphenous (terminal branch of anterior 

 crural) descends from Scarpa's triangle throughout Hunter's 

 canal, crossing over the femoral sheath from without inward; 

 then crossing over the Adductor magnus tendon and running 

 between the Sartorius and Gracilis it becomes cutaneous at the 

 inner side of the knee, descends on the leg with the internal 

 saphenous vein, runs in front of the inner ankle, and ends at the 

 middle of the inner border of the foot. Its branches are : commu- 

 nicating, to the obturator plexus, arising in Hunter's canal and 

 running inward ; patellar, arising at the lower end of Hunter's 

 canal, piercing the Sartorius, and descending below the patella 

 and over the inner tibial tuberosity to the front of the knee 

 and upper part of the leg, as well as the patellar plexus; articu- 

 lar (inconstant) to the knee, arising at its inner side; terminal, 

 to the front and inner side of the leg, and posterior half of the 

 dorsum and inner side of the foot. [646] 



Patellar Plexus. This consists of fine subcutaneous com- 

 munications, in front of the knee, between branches of the in- 

 ternal (patellar branch) saphenous, internal and middle cu- 

 taneous, and (sometimes) external cutaneous. [647] 



SACRAL or SCIATIC PLEXUS. 



This lies at the back of the pelvis upon the Pyriformis, under 

 the parietal fascia, and is formed by the descending part of the 

 fourth lumbar, the fifth lumbar, the upper two sacral, and the 

 upper part of the third sacral nerves. These converge and unite 

 in a triangular band whose apex runs through the great sacro- 

 sciatic foramen, below the Pyriformis, to become the great 

 sciatic nerve. The lumbar and first two sacral nerves each di- 

 vide into anterior and posterior (ventral and dorsal) parts; the 

 third sacral divides into upper and lower parts. The anterior 

 parts of the lumbar nerves unite in a trunk, and the posterior 

 parts in another ; together these trunks form the lumbo-sacral 

 cord. The anterior parts of the lumbar and upper two sacral 

 nerves unite with the upper part of the third sacral to form the 

 tibial nerve and anterior collateral branches; the posterior 



[283] 



