CRANIAL NERVES. 



539 



unite with the anterior branch of the first sacral, forming the lumbo-sacral 

 nerve, and enter into the sacral plexus. The upper three anterior sa- 

 cral nerves, with a branch from the fourth, form the sacral plexus. The 

 greatest portion of 

 the fourth anterior 

 sacral is distributed 

 to the pelvic viscera 

 and the muscles of 

 the anus. The fifth 

 anterior sacral and 

 the coccygeal are 

 distributed to parts 

 about the coccyx. 



The posterior 

 branches of the spi- 

 nal nerves are very 

 simple in their dis- 

 tribution. With 

 one or two excep- 

 tions, which have 

 no great physiolog- 

 ical importance, 

 these nerves pass 

 backward from the 

 main trunk, divide 

 into two branches, 

 external and inter- 

 nal, and their fila- 

 ments of distribu- 

 tion go to the mus- 

 cles and to integu- 

 ment behind the 

 spinal column. 



It is farther im- 

 portant to note, that ' all of the cerebro-spinal nerves anastomose with the 

 sympathetic. 



CRANIAL NERVES. 



Many of the cranial nerves are peculiar, either as regards their general 

 properties or in their distribution to parts concerned in special functions. 

 In some of these nerves, the most important facts concerning their distribu- 

 tion have been ascertained only by physiological experimentation, and their 

 anatomy is inseparably connected with their physiology. It would be desira- 

 ble, if it were possible, to classify these nerves with reference strictly to their 

 properties and uses ; but this can be done only to a certain extent. The 

 classification of the cranial nejves adopted by most anatomists is the arrange- 



FIG. 190. Cervical por- 

 tion of the spinal cord 

 (Hirschfeld). 



FIR. 191. Dorsal por- 

 tion of the spinal 

 cord (Hirschfeld). 



FIG. 192. Inferior por- 

 tion of the spinal cord, 

 and cauda equina 

 (Hirschfeld). 



1, antero-inferior wall of the fourth ventricle ; 2, superior peduncle of the 

 cerebellum ; 3, middle peduncle of the cerebellum ; 4, inferior peduncle 

 of the cerebellum ; 5, inferior portion of the posterior median columns 

 of the cord ; 6, glosso-pharyngeal nerve ; 7, pneumogastric ; 8, spinal 

 accessory nerve ; 9, 9, 9, 9, dentated ligament ; 10, 10, 10, 10, posterior 

 roots of the spinal nerves ; 11, 11, 11, 11, posterior lateral groove ; 12, 12, 

 12, 12, ganglia of the posterior roots of the nerves ; 13, 13, anterior roots 

 of the nerves ; 14, division of the nerves into two branches ; 15, lower ex- 

 tremity of the cord : 16, 16, coccygeal ligament ; 17, 17, cauda equina ; 

 I- VIII, cervical nerves ; I, II, III, IV-XII, dorsal nerves ; I, II-V, lumbar 

 nerves ; I-V, sacral nerves. 



