CRANIAL NERVES. 



275 



branches, the auricular 

 and the main stem. 

 The auricular is a 

 sensory nerve to the 

 skin. The main stem 

 is a mixed nerve which 

 contains the elements 

 of the spinal accessory 

 or 11th nerve of higher 

 types (branch to the m. 

 cucullaris). Its motor 

 fibres supph^ the three 

 posterior slips of the 

 petrohyoid muscle, the 

 laryngeal muscles and 

 one of the shoulder- 

 girdle muscles (inter- 

 scapularis). There are 

 no occipital and spino- 

 occipital nerves (ven- 

 tral vagus roots) in 

 Amphibia. 



In the Anura (Fig. 

 153) there are only ten 

 pairs of spinal nerves 

 and the spinal cord is 

 shorter than the ver- 

 tebral column, ending 

 in the filuin terminale 

 (Fig. 153). In the 

 Urodcla the spinal 

 nerves are more nume- 

 rous and the spinal 

 cord extends along 

 the caudal region. In 

 adult Urodeles * and 

 aglossal Anura the first 

 spinal nerve is without 

 a dorsal root ; in the 

 phaneroglossal Anura 

 it is absent in the 

 adult and the first 

 spinal nerve, which 

 leaves the spinal canal 

 between the first and 

 second vertebrae, is 



really the second. , , , .. -^ , ^ d 



rr^ . J • , Fig. 1.53.— Nervous system o£ the frog (atter Ecker). Bt, 



ihis second spmal bradiial nerve; ■/«, ischial nerve; O, eye; 01, olfactory 



nerve ioins the bra- nerves ; Op, optic nerve ; Spn 1 , first spinal nerve ; Sg. 1-10, 



,. , , u 4. -4- the ten canglia of the sympathetic system ; Fj?, gasserian 



chial plexus but it ganglion ; Kg, ganglion of vagus. 



* This nerve is present with both roots in the embryo, but the dorsal 

 root disappears in development. It resembles in this respect the occipito- 

 spinal nerves of fishes. 



