426 SACRAL NERVES. 



inner condyle, perforating the sartorius, and dividing into a number of 

 filaments which supply the integument over the patella and around the 

 joint, and the integument of the front and outer aspect of the leg as far as 

 the ankle ; lastly, cutaneous filaments below the knee to supply the inner 

 side and front of the leg and foot, and articular branches to the ankle joint. 



The OBTURATOR NERVE is formed by a branch from the third, and an- 

 other from the fourth lumbar nerve. It passes downwards among the 

 fibres of the psoas muscle, through the angle of bifurcation of the common 

 iliac vessels, and along the inner border of the brim of the pelvis, to the 

 obturator foramen, where it joins the obturator artery. Having escaped 

 from the pelvis it gives off two small twigs to the obturator externus muscle 

 and divides into four branches, three anterior, which pass in front of the 

 adductor brevis, supplying that muscle, the pectineus, the adductor longus, 

 and the gracilis ; and a posterior branch which passes downwards behind 

 the adductor brevis, and ramifies in the adductor magnus. 



From the branch which supplies the adductor brevis, a communicating 

 filament passes outwards through the angle of bifurcation of the femoral 

 vessels to unite with the long saphenous nerve. From the branch to the 

 adductor longus a long cutaneous nerve proceeds, which issues from be- 

 neath the inferior border of that muscle, sends filaments of communication 

 to the plexus of the short saphenous nerve, and descends to the inner side 

 of the knee, where it pierces the fascia and communicates with the long 

 saphenous nerve. It is distributed to the integument upon the inner side 

 of the leg. From the posterior branch an articular branch is given off 

 which pierces the adductor magnus muscle, accompanies the popliteal 

 artery, and is distributed to the synovial membrane of the knee joint on 

 its posterior aspect. 



The LUMBO-SACRAL NERVE. The anterior division of the fifth lumbar 

 nerve, conjoined with a branch from the fourth, constitutes the lumbo- 

 sacral nerve, which descends over the base of the sacrum into the pelvis, 

 and assists in forming the sacral plexus. 



SACRAL NERVES. 



There are six pairs of sacral nerves ; the first escape from the vertebral 

 canal through the first sacral foramina, and the two last between the sacrum 

 and coccyx. The posterior sacral nerves are very small, and diminish in 

 size from above dow r nwards ; they communicate with each other immedi- 

 ately after their escape from the posterior sacral foramina, and divide into 

 external and internal branches. The external branches pierce the gluteus 

 maximus, to which they give filaments, and are distributed to the integu- 

 ment of the posterior part of the gluteal region (n. cutanei clunium poste- 

 riores). The internal supply the integument over the sacrum and coccyx. 



The anterior sacral nerves diminish in size from above downwards ; the 

 first is large and unites with the lumbo-sacral nerve ; the second, of equal 

 size, unites with the preceding; the third, \vhich is scarcely one-fourth so 

 iarge as the second, also joins with the preceding nerves in the formation 

 of the sacral plexus. The fourth anterior sacral nerve is about one-third 

 the size of the preceding sacral nerve ; it divides into several branches 

 one of \vhich is sent to the sacral plexus, a second to join the fifth sacral 



