534 SPINAL NERYES. 



external cutaneous nerves, forming a plexiform network, the plexus patellae. 

 This nerve is occasionally small, and terminates by joining the internal cutaneous, 

 which supplies its place in front of the knee. 



Below the knee, the branches of the long saphenous nerve are distributed to 

 the integument of the front and inner side of the leg, communicating with the 

 cutaneous branches from the internal cutaneous, or obturator nerve. 



The deep group of branches of the anterior crural nerve are muscular and 

 articular. 



The muscular branches supply the Pectineus, and all the muscles on the front 

 of the thigh, except the Tensor vaginas fernoris, which is supplied from the 

 gluteal nerve, and the Sartorius, which is supplied by filaments from the middle 

 or internal cutaneous nerves. 



The branches to the Pectineus, usually two in number, pass inwards behind the 

 femoral vessels, and enter the muscle on its anterior surface. 



The branch to the Rectus muscle enters its under surface high up. 



The branch to the Vastus externus, of large size, follows the course of the 

 descending branch of the external circumflex artery, to the lower part of the 

 muscle. It gives off an articular filament. 



The branches to the Vastus internus and Crureus enter the middle of those 

 muscles. 



The articular branches, two in number, supply the knee-joint. One, a long, 

 slender filament, is derived from the nerve to the Yastus externus ; it penetrates 

 the capsular ligament of the joint on its anterior aspect. The other is derived 

 from the nerve to the Yastus internus; it descends along the internal inter- 

 muscular septum, accompanying the deep branch of the anastomotica magna, 

 pierces the capsular ligament of the joint on its inner side, and supplies the 

 synovial membrane. 



THE SACEAL AND COCCYGEAL NERVES. 



The sacral nerves are five in number on each side. The four upper ones pass 

 from the sacral canal, through the sacral foramina ; the fifth escaping through the 

 foramen between the sacrum and coccyx. 



The roots of origin of the upper sacral (and lumbar) nerves are the largest of all 

 the spinal nerves ; whilst those of the lowest sacral and coccygeal nerves are the 

 smallest. 



The length of the roots of these nerves is very considerable, being longer than 

 those of any of the other spinal nerves, on account of the spinal cord not extending 

 beyond the first lumbar vertebra. From their great length, and the appearance 

 they present in connection with the spinal cord, the roots of origin of these nerves 

 are called collectively the cauda equina. Each sacral and coccygeal nerve divides 

 into two branches, anterior and posterior. 



The posterior sacral nerves are small, diminish in size from above downwards, 

 and emerge, except the last, from the sacral canal by the posterior sacral foramina. 



The three upper ones are covered, at their exit from the sacral canal, by the 

 Multifidus spinas, and divide into external and internal branches. 



The internal branches are small, and supply the Multifidus spinee. 



The external branches communicate with one another, and with the last lumbar 

 and fourth sacral nerves, by means of anastomosing loops. These branches pass 

 outwards, to the outer surface of the great sacro-sciatic ligament, where they 

 form a second series of loops beneath the Glutens maximus. Cutaneous branches 

 from these second series of loops, usually three in number, pierce this muscle, 

 one near the posterior inferior spine of the ilium ; another opposite the end of the 

 sacrum ; and the third, midway between these two. They supply the integument 

 over the posterior part of the gluteal region. 



The two lower posterior sacral nerves are situated below the Multifidus spinse. 

 They are of small size, and join with each other, and with the coccygeal nerve, 



