PHRENIC NERVE. 507 



The inferior brandies, the first three of which assist in the 

 formation of the lumbo-sacral plexus, converge at the side of the 

 pelvic cavity. The fourth constitutes the internal pudic nerve, 

 which, at its origin, sends a communicating branch to the origin 

 of the fifth. It is distributed to the penis, where it terminates, 

 b}^ numerous branches, in the glans. Before leaving the pelvic 

 cavity, it sends filaments to the muscles and skin of the perineo- 

 aual region. In the female, this nerve is distributed to the 

 parts analogous to those of the male. 



The fifth forms the anal or hcvmorrhoidal nerve, distributed 

 to the sjjhincter ani, and the skin covering it. 



Small filaments which form the pelvic or hypogastric plexus 

 are given off from near the origins of all the sacral nerves. 



COCCYGEAL NERVES (6 or 7 pairs). 



The coccygeal nerves differ from the other spinal nerves in 

 having no immediate communication with the sympathetic. 

 They diminish in size from the first to the last. The superior 

 branches unite to form one large nerve, which passes under the 

 curvator coccygis muscle, and extends to the tip of the tail, 

 giving off muscular and cutaneous filaments in its course ; the 

 inferior branches likewise coalesce and extend in a similar 

 manner under the depressor muscle. 



The inferior branch of the first coccygeal receives a branch 

 from the last sacral, and sends a filament down towards the anus 

 and perina^um. 



NERVES FORMED BY THE INFERIOR BRANCHES OF THE 

 SPINAL NERVES. 



These nerves form three groups, as follows : — The Phrenic 

 nerve, the Brachial plexus, the Lumbo-sacral plexus. 



PHRENIC NERVE. 



The phrenic or diaphragmatic, the motor nerve of the dia- 

 phragm, is formed by three principal branches ; one from the 

 brachial plexus, one from each of the sixth and seventh cervical 

 nerves, with a filament, not constant, from the fifth.. It enters 



