Fig. 191.' 



SACRAL PLEXUS. 427 



nerve, a third to the viscera of the pelvis commu- 

 nicating with the hypogastric plexus, and a fourth 

 to the coccygeus muscle, and to the integument 

 around the anus. The fifth anterior sacral nerve 

 presents about half the size of the fourth ; it di- 

 vides into two branches, one of which communi- 

 cates with the fourth, the other with the sixth. 

 The sixth sacral nerve (coccygeal) is exceedingly 

 small ; it gives off an ascending filament which is 

 continuous with the communicating branch of the 

 fifth; and a descending filament which passes 

 downwards by the side of the coccyx and traverses 

 the fibres of the great sacro-ischiatic ligament to 

 be distributed to the gluteus maximus and to the 

 integument. All the anterior sacral nerves receive 

 branches from the sacral ganglia of the sympathetic 

 at their emergence from the sacral foramina. 



SACRAL PLEXUS. 



The Sacral plexus is formed by the lumbo-sacral 

 and by the anterior branches of the four upper 

 sacral nerves. The plexus is triangular in form, 

 the base corresponding with the whole length of the sacrum, and the apex 

 with the lower part of the great ischiatic foramen. It is in relation behind 

 with the pyriformis muscle, and in front with the pelvic fascia, which latter 

 separates it from the branches of the internal iliac artery, and from the 

 viscera of the pelvis. 



The Branches of the sacral plexus are divisible into the internal and the 

 external ; they may be thus arranged : 



Internal. External. 



Visceral, 

 Muscular. 



Muscular, 

 Gluteal, 

 Internal pudic, 

 Lesser ischiatic, 

 Greater ischiatic, 



The Visceral nerves are three or four large branches which are derived 

 from the fourth and fifth sacral nerves : they ascend upon the side of the 

 rectum and bladder ; in the female upon the side of the rectum, the va- 

 gina and the bladder ; and interlace with the branches of the hypogastric 

 plexus, sending in their course numerous filaments to those viscera. 



The Muscular branches given off within the pelvis are one or two twigs 

 to the levator ani ; an obturator branch ; which curves around the spine 

 of the ischium to reach the internal surface of the obturator internus mus- 

 cle ; a coccygeal branch ; and an haemorrhoidal nerve which passes 

 through the two ischiatic openings and descends to the termination of the 

 rectum to supply the sphincter arid the integument. 



* A view of the branches of the ischiatic plexus to the hip and back of the thigh. 1, 

 1. Posterior sacral nerves. 2. Nervi glutei. 3. The internal pudic nerve (nervus puden- 

 dalis longus superior). 4. The lesser ischiatic nerve, giving off the perineal cutaneous 

 (pudendalis longus inferior), and 5. The ramus femoralis cutaneus posterior. The re- 

 ference to the great ischiatic has been omitted. It is seen to the right of 3. 



