THE CRANIAL NERVES. 265 



those of the soft palate. The sensory fibers carry impulses of 

 common sensation and of taste from the root of the tongue, the 

 neighboring portions of the pharnyx, the tonsils, the soft palate, 

 and the pillars of the fauces. This nerve does not commonly 

 become the seat of local lesions. 



THE TENTH OR VAGUS NERVE. This is the main cerebrospinal 

 nerve supplying the viscera and it is both motor and sensory 

 in function. We shall see. later that the nerves to the viscera 

 belong to the so-called autonomic system, which is distinguished 

 from the somatic by two main facts, one anatomical and one 

 functional. The anatomical difference is that every nerve fiber 

 becomes connected through synapses with nerve cells located 

 peripherally (i. e., near the end of the nerve), and the axons of 

 the cells continue the impulse on to the structure ; the functional 

 difference is that the autonomic fibers, as their name indicates, 

 control automatically-acting or involuntary functions instead of 

 voluntary movements, as is the case with the ordinary or somatic 

 cerebrospinal nerve fibers. 



The most important of the vagus autonomic fibers run to the 

 heart (see p. 185), the oesophagus (p. 57), the stomach (p. 60) 

 and the intestines (p. 79). The vagus also contains afferent 

 fibers which have their cell stations in ganglia situated in the 

 trunk of the nerve. These fibers carry sensory impulses par- 

 ticularly from the larynx and lungs (p. 219). Further details 

 regarding the functions controlled by the vagus are fully given 

 in the references indicated above. When the vagus nerve, or 

 its center, is the seat of paralysis, swallowing is seriously in- 

 terfered with, and food is liable to pass into the larynx and 

 cause pneumonia. Various forms of paralysis of the vocal cords 

 may also result from paralysis of the vagus. 



THE ELEVENTH OR SPINAL ACCESSORY NERVE. The eleventh 

 or spinal accessory is entirely an efferent nerve, one part of 

 it, the accessory, being derived from the same column of nerve 

 cells as the vagus and being really a part of this nerve; the 

 other arises from the cells of the anterior horn of the spinal 

 cord in the upper cervical region and supplies the trapr/ius and 

 sterno-mastoid muscles. 



