302 THE NERVOUS SYSTEM 



one part of the brain and not in another, or in different degrees 

 in different parts of the nervous centers. "In the former case 

 [dreams] the cerebrum is still partially active; but the mind 

 products of its action are no longer corrected by the reception, 

 on the part of the* sleeping sensorium, of impressions of objects 

 belonging to the outer world; neither can the cerebrum, in this 

 half-awake condition, act on the centers of reflex action of the 

 voluntary muscles, so as to cause the latter to contract a fact 

 within the painful experience of all who have suffered from night- 

 mare. In somnambulism the cerebrum is capable of exciting 

 that train of reflex nervous action which is necessary for pro- 

 gression, while the nerve center of muscular sense (in the cere- 

 bellum?) is presumably fully awake; but the sensorium is still 

 asleep, and impressions made on it are not sufficiently felt to 

 rouse the cerebrum to a comparison of the difference between 

 mere ideas or memories and sensations derived from external 

 objects" (Kirkes). 



Relation Between the Cerebro-spinal and Sympathetic 

 Systems. A brief resume may help to clarify the association 

 between the two systems. 



i. Anatomically. The two are developed from the same em- 

 bryological tissue ; the vaso-motor sympathetic fibers obey centers 

 in the medulla and cord, and must, therefore, be connected with 

 those centers either directly or indirectly; characteristic small 

 medullated fibers pass at intervals from the cord through the 

 roots into the sympathetic ganglia; they send fibers each to the 

 trunks of the other to be distributed directly, or to form plexuses 

 and then be distributed together; their fibers are found together 

 in all organs which receive cerebro-spinal nerves (unless they 

 be non-vascular) ; in some of these organs just named the sym- 

 pathetic fibers are there only as vaso-motor nerves, while in others, 

 as glandular structures like the liver and salivary glands, sym- 

 pathetic fibers are distributed to the gland cells themselves, 

 and both have a definite but associated influence on secretion. 



