THE NERVOUS SYSTEM. 



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a, a, Anterior corpora py- 

 ramidalia of the chorda 

 oblongata. 6, b, Corpora oli- 

 varia. c, c, Corpora restifor- 

 mia. d, Glosso-pharyn- 

 geal nerve. e, Pneumono- 

 gastric. f, Hypo-glossal, g, 

 Accessory nerve, h, Poste- 

 rior root of the first cervical 

 pair, i, Anterior root. The 

 posterior root in this, as in 

 many subjects, gives a twig, 

 k, to the accessory, and 

 crosses before it to reach the 

 anterior root. In this in- 

 stance, not only is there a 

 communication between the 

 accessory and the posterior 

 root of the first pair, but 

 the accessory actually be- 

 gins from a twig uniting the 

 posterior roots together. I, 

 First root of the accessory, 

 ra, 1, The first cervical pair, 

 formed of its anterior and 

 posterior root. m, 2, to 

 ra, 8, are the successive cer- 

 vical nerves, with their two 

 roots. n, 1, to n, 12, The 

 successive dorsal ditto, o, 1, 

 to o, 5, The successive lum- 

 bar, p, 1, to p y 6, The suc- 

 cessive sacral. q, q, q, q y 

 The cervical plexus, formed 

 by the eight cervical and 

 first dorsal nerves ; and fur- 

 nishing, among other nerves, 

 r, The phrenic. s y s, s, s, 

 The lumbo-sacral plexus, 

 consisting of nerves fur- 

 nished by the lumbar and 

 sacral nerves, t, The cer- 

 vical enlargement of the 

 spinal chord, u, The lum- 

 bar enlargement. v, Its 

 termination, where it splits 

 into many nerves, called 

 altogether, w, w, The cauda 

 equina. x. The last nerve 

 of the lumbro-sacral plexus, 

 or sciatic. (Dr. Manec.) 



