THE SACRAL NERVES. 



401 



the viscera may be drawn from the side of the pelvis. If the 

 bladder is still distended, let the air escape from it. 



By means of the foregoing dissection the sacral nerves may be 

 found as they issue from the sacral foramina. The dissector should 

 follow the first four into 

 the sacral plexus, and some 

 branches from the third 

 and fourth to the viscera. 

 The last sacral and the 

 coccygeal nerve are of 

 small size, and will be 

 detected coming through 

 the coccygeus muscle, close 

 to the coccyx : these are 

 to be dissected with care ; 

 and the student will suc- 

 ceed best by tracing the 

 connecting filaments which 

 pass from one to another, 

 beginning above with the 

 offset from the fourth 

 nerve. 



Opposite the lower part 

 of the rectum, bladder, 

 and vagina is a large plexus 

 of t the sympathetic (pelvic 

 plexus), which sends 

 branches to the viscera 

 along the arteries. This 

 plexus is generally de- 

 stroyed in the previous 

 dissection ; but if any of 

 it remains, the student 

 may trace the offsets dis- 

 tributed from it, and its 

 communicating branches 

 with the spinal nerves. 



SACRAL SPINAL NERVES 

 (figs. 149; 150, p. 403). 

 The anterior primary 

 branches of the sacral 

 nerves are five in number, 

 and decrease rapidly in 

 size from above down- 

 wards. Issuing by the 

 apertures on the front of the sacrum (the fifth nerve excepted), 

 they receive short filaments of communication from the gangliated 

 cord of the sympathetic. The first three nerves and part of the 

 fourth enter the sacral plexus, but the fifth ends on the back of 

 the coccyx. 



first four 

 sacral, 



last and 

 coccygeal, 



FIG. 149. THE SACRAL NERVES AND 

 PLEXUS (ALTERED FROM HENLE). 



a. Urinary bladder. 

 6. Rectum. 



c. Levator aui. 



d. Coccygeus. 



Nerves : 



4 1 and 5 1. Fourth and fifth lumbar 

 nerves, giving rise to the lumbo-sacral cord. 

 1 S to 5 S. Five sacral nerves. 

 1 c. Coccygeal nerve. 



1. Upper gluteal nerve. 



2. Branch to levator ani. 



3. Branch to the bladder. 



4. Branch to coccygeus. 



5. Branch to the perineum. 



6. Common branch of 4 S, 5 S, and 1 c, 

 for the back of the coccyx. 



The sympathetic chain lies on the front of 

 the sacrum, just outside the plane of section. 



Sacral 

 nerves are 

 five: 



most enter 

 plexus. 



D.A. 



DD 



