FUNCTIONS OF THE SYMPATHETIC. 305 



reflex acts, or acts of unconscious volition, which itself, viewed as a 

 cerebral process, is a reflex act of the highest order. 



In passing from the functions of the cerebro-spinal nervous system, 

 to a consideration of those of the sympathetic nervous system, we 

 shall find that this system also acts in a reflex manner, possibly solely 

 and entirely in that manner, and tjiat the reflex acts governed by it 

 are quite involuntary, and, at least in health, independent of sensation. 



Functions of the Sympathetic G-anglia and Nerves. 



The structure of the sympathetic nerves, and their anatomical con- 

 nections with the cerebro-spinal system, afford reasonable ground for 

 the opinion, that this remarkably complicated part of the nervous 

 system is, neither physiologically nor anatomically, to be considered 

 as a mere portion of the cerebro-spinal nervous system, nor yet as a 

 system independent of it ; but that it is physiologically possessed of 

 certain special functions, at the same time that it is, in many points, 

 functionally associated with the cerebro-spinal system. 



The nerve-fibres, whether white or ganglionic, and the substance of 

 the ganglia themselves, are, like the nerves and gray centres of the 

 cerebro-spinal system, conductors of the effects of impressions made 

 upon them. 



Doubtless, also, the nerves consist of both afferent and efferent 

 fibres, some of the afferent fibres probably terminating in the sympa- 

 thetic ganglia; whilst some undoubtedly proceed through the ganglia 

 on to the cerebro-spinal centres, and some also perhaps pass from the 

 gray matter of the sympathetic ganglia to the gray matter of the 

 cerebro-spinal centres. The connections of the efferent fibres are cer- 

 tainly with the ganglionic gray substance of the sympathetic ganglia 

 themselves; and most probably also, they have indirect or direct 

 connections with the cerebro-spinal nervous centres. There is reason 

 to believe further, that the gray matter of the sympathetic ganglia, 

 can not only conduct the effects of impressions, but may also trans- 

 fer and radiate them. This gray matter of the various .sympathetic 

 ganglia, is also considered by some to be the seat or centre of origin 

 of special nerve force, and the whole sympathetic system to be, so 

 far, independent. Lastly, the power of the sympathetic nervous 

 system, perhaps the force originating in its ganglia, may be inhibited 

 or interfered with by the superior force of the cerebro-spinal nervous 

 centres. 



The sympathetic nervous system, considered generally, has for its 

 function the office of presiding over the viscera of the body, as its 

 distribution implies. It has been named the vegetative, or nutritive 

 nervous system, and sometimes, from its distribution, the visceral ner- 

 vous system. From the fact, that its branches reach their ultimate 

 destination, supported upon the large and small arteries, and since 

 they may be traced likewise on to the arteries of the trunk of the 

 body and of the limbs, it is probable that the greater part of the in- 

 fluence which they exert upon the viscera, and on other parts of the 

 body, is exercised through a certain control over the muscular sub- 



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