NERVOUS SYSTEM. 319 



and some of the salivary glands; they are vaso-motory and 

 excito-secretory in function. The auditory are the nerves of 

 hearing ; they spring from the medulla by two roots. The 

 ninth pair go to the tongue and take part in the sense of taste. 

 The vagus is the most important ; it has both sensory and motor 

 roots, and supplies the stomach and respiratory organs. The 

 eleventh arises with the vagus and supplies the intercostal 

 muscles. The last, the hypoglossals, again, supply the tongue, 

 acting on the lingual muscles. 



The spinal nei-ves. The spinal nerves leave the vertebral 

 canal by the intervertebral foramina and proceed to the various 

 organs. There are forty-two or forty-three pairs, as foUows : 

 eight cervical pairs, seventeen dorsal pairs, six lumbar, and five 

 sacral ; the coccygeal vary from six to seven pairs. The spinal 

 nerves difier from the cranial in that they all resemble one an- 

 other at their origin. There are always two roots, one being 

 motor, the other sensory, in function. The two roots unite into 

 a thick trunk in passing through the foramina of the vertebrae, 

 and then divide again into two branches, the superior branch 

 going to the spinal muscles and integuments covering them, the 

 inferior branch passing to the lateral and lower parts of the 

 trunk or to the limbs. All send from their inferior branch one 

 or more nerves to form the great sympathetic system. On the 

 face of the sensory root is found a ganglion. The superior 

 branches of the cervicals go to the oblique muscles of the 

 head, the cervical muscles, and here they anastomose, forming 

 a kind of network, the cervical plexus. The inferior branches 

 cover the anterior lateral parts of the neck and muscles of the 

 breast, and form another plexus, the superficial cervical plexus. 

 The last two mix with those of the dorsal region, and form 

 the brachial plexus. The dorsal nerves send their superior 

 branches to the muscles and skin of the dorsal lumbar region, 

 their inferior branches to the pleurae and intercostal muscles. 

 The lumbar send the superior branches to the spiual muscles 

 and the integument of the loins and croup ; the inferior 



