'////; CRANIAL M-.in'ES 957 



and to the transvcrsus perinei. bulbocavernosus, and ischiocavernosus. It also 

 .-ends some filaments to supply the murou.- membrane of (lie urethra. The auper- 

 jlcnil liniin-h almost at once divides into external and internal branches, the posterior 

 xi-Hilul (luliiiih nerve-. IJotli branches pass through the wall of Alcock's canal into 

 the anterior part of the ischio-rectal fossa, then they pierce the base of the iiro-gcniial 

 triirone, and enter the superficial pouoa of the urethral triangle. The external 

 branch usually passes below the transversus perinei, and the internal branch above 

 the muscle or through its libres. The external branch communicates with the long 

 pudendal nerve, and with the inferior htemorrhoidal nerve, and both branches end 

 in terminal filaments which anastomose and which are distributed to the skin of the 

 scrotum and the anterior part of the perineum in the male, and to the labium majus 

 in the female. 



The dorsal nerve of the penis runs forwards in Alcock's canal above the internal 

 pudic artery. It pierces the base of the uro-genital trigone, continues forwards be- 

 tween the layers of the trigone, embedded in the fibres of the constrictor urethra, and 

 it gradually passes to the outer side of the internal pudic artery. A short distance 

 below the pudic arch it pierces the anterior layer of the uro-genital trigone, gives a 

 branch to the corpus cavernosum penis, passes forwards between that structure and 

 the bone, and turns downwards on the dorsum of the penis, passing between the 

 layers of the fundiform (suspensory) ligament and along the outer side of the dorsal 

 artery of the penis. It supplies the skin of the dorsum of the penis, and, having 

 given branches to the prepuce, it breaks up into terminal filaments which are dis- 

 tributed to the glans penis. 



The dorsal nerve of the clitoris is much smaller than the dorsal nerve of the 

 penis to which it corresponds. It is distributed to the clitoris. 



THE COCCYGEAL PLEXUS 



This plexus is frequently, and with some reason, considered as a subdivision of 

 the pudendal plexus, and sometimes it is described with the coccygeal nerves. It is 

 formed chiefly by the anterior division of the fifth sacral nerve and the coccygeal 

 nerve, but it receives a small filament from the anterior division of the fourth sacral 

 nerve (figs. 688, 692, 693). These constituents unite to form plexiform cords 

 lying on either side of the coccyx. From these cords arise the ano-coccygeal 

 nerves, which pierce the sacro-tuberous (great sacro-sciatic) ligament and supply 

 the skin in the neighbourhood of the coccyx. 



THE CRANIAL NERVES 







Twelve pairs of cranial nerves are usually recognised, though there is reason for 

 considering the nerves of the seventh and eighth pairs as composed each of two 

 nerves, and the nerves of the eleventh pair as being merely parts of the tenth pair. 

 The twelve are numbered from in front backwards. Their numbers, corresponding 

 names, and functional nature are given in the following table: 



NrunERS. NAMES. NATURE. 



I st ............................ Olfactory sensory 



II nd ............................ Optic sensory 



III rd ............................ Oculomotor motor 



IV th ............................ Trochlear or patheticus motor 



V th ............................ Trigeminal or trifacial mixed 



VI th ............................ Abducens motor 



VII th ............................ Facial (Facial and Intermedius) mixed 



Cochle- 



VIII th ............................ Auditory ( Acusticus) < tu... sensory 



. laris 



IX th ............................ Glosso-pharyngeal mixed 



Xth ............................ Vagus or pneumogastric mixed 



Xlth ............................ Spinal accessory motor 



XII th ............................ Hypoglossal motor 



