1352 



HUMAN ANATOMY. 

 The Coccygeal Plexus. 



6. The sacro-coccygeal nerves (nn. anococcygei) are derived from a small 

 nerve inosculation called the coccygeal plexus (plexus coccygeus), a structure formed 

 by the fifth sacral and the coccygeal nerve, with a contribution from the fourth sacral 

 which descends over or through the great sacro-sciatic ligament. The fifth sacral, 

 having been joined by this twig from the fourth, descends along the margin of the 

 coccyx and is joined by the coccygeal nerve, the resulting nerve-bundle constituting 

 the coccygeal plexus. From it arise minute filaments which pierce the great sacro- 

 sciatic ligament and are distributed to the integument in the immediate neighbor- 

 hood of the coccyx (Fig. 1084). 



Practical Considerations. — Of the branches of the sacral plexus, the ^^reat 

 sciatic nerve is the most important, owing to its size, its extensive distribution and 

 its exposed position. The greater part of the sacral plexus is continued into the 



Fig. 1 1 28. 



Bulbo-cavernosiis 



Iscliio- cavern osjs 



Inferior pudendal nerve 



Posterior superficial 

 perineal nerve 



Anterior superficial 

 perineal nervs 



Transversus perinei 

 superficialis 



Perineal division of 

 pudic nerve 



Inferior hemorrhoidal 

 nerve 



Sphincter ani 

 Anal fascia 



Deep fascia of !>uttock 



Glans clitoridis 



Deep layer of 

 triangular ligament 



Dorsal nerve of clitoris 



Superficial perineal 

 nerves 



Dorsal nerve 

 of clitoris 



Perineal division 

 of pudic nerve 



Levator ani 



Great scacro-siatic 

 ligament 



Fudic nerve 



Inferior 

 hemorrhoidal nerve 



Perforating 

 cutaneous nerve 



Gluteus maximus 



Coccyx From IV. sacral nerve Coccjgeus 



Dissection of female perineum, showing nerves; anal fascia in position on right side of body, removed on 

 left ; Colles' fascia removed on right side, exposing superficial perineal interspace ; superior layer of triangular 

 ligament, denuded of muscular tissue, seen on left side. 



nerve. Except in complete lesions of the spinal cord this nerve is rarely paralyzed 

 in all its branches. The paralysis may result from fractures of the lumbar vertebrae, 

 of the sacrum or of the innominate bone, from pressure of tumors in the pelvis or of 

 the child's head in labor or from the use of forceps. It is the structure in greatest 

 danger in dislocation of the hip, since the head of the femur in the most frequent 

 varieties sweeps backward against this nerve. In the reduction of these posterior 

 dislocations the nerve has been hooked up by the head and made to pass across the 

 front of the neck of the bone. F"rom its close relation to the head and neck, it 

 may be injured in violent movements of the hip joint without dislocation. 



It passes out of the pelvis through the greater sacro-sciatic foramen, below the 

 pyriformis muscle, and after curving outward and downward under the gluteus maxi- 

 mus muscle it continues its course, approximately, in a line from a point midway 



