CRANIAL NERVES. 839 



remains unconscious during the normal physiological state, when it 

 does not seem to be any greater than that of the sympathetic. Dur- 

 ing pathological conditions, however, it acquires a high degree of 

 intensity. Thus, in simple wounds of the stomach, without hemor- 

 rhage or peritonitis, the impression carried to the medullary center 

 may be of such a nature as to cause rapid death. 



The great frequency of gastralgia is due to an affection of the 

 terminal branches of the tenth pair. At its cranial end this same 

 nerve is found to be in direct relation with the trigeminus through 

 the intervention of the gray tubercle of Eolando. This fact un- 

 doubtedly furnishes the key to the headache which so often accom- 

 panies gastralgia. 



The vagus is the chief sensory carrier of the reflex movements 

 of circulation and respiration. Thus, irritation of the renal and 

 hepatic plexuses can produce vomiting. 



Angina pectoris has its seat in the cardiac plexus. The sensa- 

 tion experienced is like that seen in the renal and hepatic plexuses 

 after renal and hepatic colic. 



ELEVENTH PAIR, OR SPINAL ACCESSORY NERVE. 



The eleventh pair of cranial nerves, the spinal accessory, is com- 

 posed of two distinct parts: a spinal portion and an accessory por- 

 tion. A group of cells in the anterior horns of the spinal cord and 

 extending downward to the sixth cervical segment is called the 

 accessory nucleus. There is another group of cells at the exit of 

 the first cervical nerve which extends into the medulla oblongata 

 and is the origin of the hypoglossal nerve. The medulla-oblongata 

 root arises from the nucleus ambiguus, which is connected with the 

 vagus nucleus in the medulla. 



The superficial origin of the accessory portion is from the groove 

 between the inferior olive and the restiform body. Near the jugular 

 foramen both portions come together, but do not exchange fibers. 

 Very soon both roots separate from one another to form the two 

 distinct branches. 



The accessory portion of the nerve passes entirely into the plexus 

 gangliformis of the vagus. This branch supplies the vagus with the 

 major portion of its motor fibers. 



The spinal portion enters the cavity of the cranium by passing 

 through the foramen magnum. The two portions of the spinal 

 accessory leave the cranium together by passing through the middle 

 compartment of the jugular foramen. The spinal portion then 



