THE SYMPATHETIC SYSTEM 303 



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 experi- 

 ence of all who have suffered from nightmare. In somnam- 

 bulism the cerebrum is capable of exciting that train of re- 

 flex nervous action which is necessary for progression, while 

 the nerve center of muscular sense (in the cerebellum?) 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 exter- 

 nal objects" (Kirkes). 



Relation Between the Cerebro-spinal and Sympathetic 

 Systems. A brief resume may help to clarify the association 

 between the two systems. 



1. Anatomically. The two are developed from the same 

 embryological tissue ; the vaso-motor sympathetic fibers obey 

 centers in the medulla and cord, and must, therefore, be con- 

 nected with those centers either directly or indirectly ; char- 

 acteristic 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 to- 

 gether; 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 sympathetic 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. 



2. Physiologically. The physiological relation is best indi- 

 cated by examples. A great many, if not all, the sympathetic 

 ganglia seem to receive their power to generate nerve force 

 from the cerebro-spinal system ; there can be no proper nu- 

 trition of the parts animated by cerebro-spinal fibers with- 

 out the associated aqtion of vaso-motor sympathetic fibers 



