322 THE SPINAL NERVES. 



interlacement formed beneath the sartorius by this nerve and branches of the 

 obturator and internal cutaneous nerves. 



The pateUar branch perforates the sartorius muscle and the fascia lata, and 

 spreads out over the front of the knee, where it forms, by uniting with branches of 

 the internal and middle (sometimes also the external) cutaneous nerves, a plexus 

 named i\\e patellar plexus. 



Numerous branches are given off from the nerve to the skin of the leg, and the 

 larger of these turn forwards over the anterior border of the tibia. Its terminal 

 offsets on the inner side of the loot communicate with branches of the musculo- 

 cutaneous nerve. 



Varieties. In the high form of plexus the anterior crural may receive fibres from the 

 last dorsal nerve, in the low form from the fifth lumbar, the root at the opposite end of the 

 plexus being: correspondingly reduced. The nerve has been seen entering- the thigh between 

 the femoral artery and vein (Dubrueil). The several branches of the middle, or of the 

 internal, cutaneous nerve frequently arise independently from the anterior crural. The middle 

 or internal cutaneous nerve sometimes leaves the trunk of the anterior crural at a higher level 

 than usual, within the abdomen. The posterior branch of the internal cutaneous is sometimes 

 very small or absent, its place being supplied by the obturator or the internal saphenous nerve. 

 The anterior crural occasionally gives off the external cutaneous nerve of the thigh. The 

 internal saphenous nerve has been seen ending at the knee, its place in the leg being taken by 

 a branch of the internal popliteal nerve (Gr. H. Meyer). The patellar branch has been 

 observed arising from the nerve to the vastus internus (Guy's Hosp. Reports, 3rd ser.. xvi. 161). 

 The internal saphenous rarely furnishes the internal dorsal digital nerve of the great toe. 

 Branches of the anterior crural nerve to the tensor vaginae femoris and adductor longus are 

 described by several anatomists. Arthur Thomson found a branch passing behind the femoral 

 vessels to join the accessory obturator nerve and supply in part the latter muscle ( Journ. Anat.. 

 xix, 331). 



SUMMARY. The anterior crural nerve is distributed to the skin upon the fore 

 part and inner side of the thigh, commencing below the termination of the ilio- 

 inguinal and genito-crural nerves. It furnishes also a cutaneous nerve to the inner 

 side of the leg and foot. All the muscles on the front of the thigh receive their 

 nerves from the anterior crural^ and the iliacus and pectineus are also supplied by 

 this nerve. Lastly, branches are given from the anterior crural nerve to the femoral 

 artery, to the thigh-bone, and to the hip and knee-joints. 



FIFTH LUMBAR, NERVE. 



The anterior branch of the fifth lumbar nerve, having received a fasciculus from 

 the nerve next above it, descends to join the first sacral nerve, and forms part of the 

 sacral plexus. The trunk resulting from the union of the fifth with a part of the 

 fourth nerve is named the lumbo-sacral cord, and gives origin to the greater part of 

 the superior gluteal nerve. 



SACRAL AND COCCYGEAL NERVES. 



The anterior divisions of the first four sacral nerves emerge from the spinal canal 

 by the anterior sacral foramina, and the fifth passes forwards between the sacrum and 

 coccyx. 



The first two sacral nerves are large, and of nearly equal size ; the others diminish 

 rapidly, and the fifth is exceedingly slender. Like the anterior divisions of the 

 other spinal nerves, those of the sacral nerves communicate with the sympathetic : 

 the communicating cords are very short, as the sympathetic ganglia are close to the 

 inner margin of the foramina of the sacrum. 



The first three nerves and part of the fourth contribute to form the sacral plexus. 

 The fifth has no share in the plexus, it ends on the back of the coccyx. As the 

 description of the fourth and fifth sacral nerves and of the coccygeal will occupy 



