THE SPINAL XERV: '-. 191 



the coccygeal nen-e immediately beyond the Canal i* coccygeus, 

 perforates the 31. Hio-coccygeu*, and runs on its dorsal surface 

 obliquely over the lymph-heart, without supplying it ; the nerve 

 then pierces the fascia to supply the skin of the back and thigh. 



(e) The Ramn* abdominals also arises from the coccygeal nerve ; 

 it is larger than the E. dor*ali*, and arises at the same point ; the 

 nerve runs on the ventral surface of the 31. ilio-coccygeu* towards the 

 Ivmph-heart, and inosculates with the sympathetic. It is from this 

 nen-e that the branch to the sciatic plexus is usually given off ; it 

 further supplies a varying number of branches, which with branches 

 derived directly or indirectly from the sciatic nerve, form a plexus 

 (Plexus coccygeitsi) ; the two plexuses may together be regarded as a 

 Plexus ixcliio-coccygeiis or a Plexus sacro-coccygev*. 



(/) In addition to the Kami rommii.nicante* given off by the spinal 

 nerves near the vertebral column, the sciatic plexus supplies a few 

 t\vifs, usually two (Fig. 127). 



(g) Other small twigs pass from the sympathetic system for- 

 wards and outwards to join the sciatic plexus or the sciatic nerve. 

 A i ' ording to Waldeyer two of these are very constant. 



(h] Branches to the oviduct (Fig. 127 b). 



(i) Branches to the rectum (Fig. 127 ). 



(k) Branches to the bladder (Fig. 127 d). 



(I) Branches to the 31. lecator ani (Fig. 1 27 a'). 



(m) A branch to the Ivmph-heart, which runs along the anterior 

 border of the 31. /e>\ ani, on to its dorsal surface, and then direct to 

 the lymph -heart. 



Variations in the sciatic plexus. The arrangement of the 

 nerves in the sciatic plexus is subject to many variations ; ac- 

 cording to \Viedersheim most of these variations belong to two 

 chief classes : either the N. cocci/geii* inosculates directly with the 

 ninth spinal nerve by one or several branches, or it joins the ninth 

 nen-e indirectly by uniting with its branches. A case of the 

 latter arrangement is seen in Fig. 127, and is thus described by 

 Wiedersheim : 



' After cutting through the pelvic symphysis and drawing to one 

 side the contained viscera, namely, the hinder end of the oviduct, 

 the rectum, and the bladder, one sees a row of small twigs (a, 6. 

 re. iJ, and e) arising from the inner, hinder, and anterior surfaces of 

 the ninth spinal nerve : the first (a) runs backwards parallel with 



