Stowei.1., Nerves hi the Domestic Cat. 299 



of the internal iliac artery. Terminal ramuli like a leash 

 supply the M. adductor longus and the M. obturator externus. 



SACRAL NERVES. 



General Description. — The sacral vertebrae are three, and 

 the nerves are corresponding three pairs. These nerves are 

 characterized by the length of the ectal roots and by the dis- 

 tance through which they are traced in the neural arch and 

 in the groove from the arch to the intervertebral foramina.. 

 At their respective foramina of exit they separate into two 

 unequal divisions, the dorsal and the ventral; the dorsal 

 division passes directly dorsad and divides into cephalic and 

 caudal rami, each of which anastomoses with the terminal 

 filaments of the adjacent nerves, and each sends a considerable 

 branch to the open plexus of cutaneous nerves; the ventral 

 division passes directly ventrad and laterad to join in the 

 formation of the sacral plexus, from which nerves are distri- 

 buted to the caudal extremity. Each ventral nerve receives 

 an anastomotic nerve from the adjacent sympathic ganglia 

 (Fig. S.). 



THE FIRST SACRAL NERVE. 



Special Description. — The first sacral nerve is the largest 

 of the spinal nerves, and has its ectal origin in the neural 

 arch of the sixth lumbar vertebra, at the caudal border of 

 which may be found its dorsal root ganglion; it traverses the 

 long groove (10 mm.) in the seventh lumbar vertebra, and 

 finds its exit through the foramen mesad of the crista ilii and 

 ventro-mesad of the broad diapophysis of the first sacral 

 vertebra. Immediately peripherad of the foramen of exit it 

 is joined by the lumbo-sacral cord (Fig. L.-S. C.) — which in 

 a medium-sized cat is 2 mm. in section — and has its course 

 mesad and ventrad of the diapophysis and the crista ilii, by 

 which it is concealed, and which renders its exposure some- 

 what diflficult. The nerve trunk at this point (its central 

 10 mm.) is about 4 mm. in section. 



