THE SYMPATHETIC NERVE. 445 



PHYSIOLOGY OF THE SYMPATHETIC NERVE. 



The sympathetic nerve, or sympathetic system of nerves, 

 obtained its name from the opinion that it is the means 

 through which are effected the several sympathies in morbid 

 action which distant organs manifest. It has also been called 

 the nervous system of organic life, upon the supposition, now 

 proved erroneous, that it alone, as a nervous system, influences 

 the organic processes. Both terms are defective ; but, since 

 the title sympathetic nerve has the advantage of long and most 

 general custom in its favor, and is not more inaccurate than 

 the other, it will be here employed. 



The general differences between the fibres of the cerebro- 

 spinal and sympathetic nerves have been already stated (p. 

 371) ; and it has been said, that although such general differ- 

 ences exist, and are sufficiently discernible in selected filaments 

 of each system of nerves, yet they are neither so constant, nor 

 of such a kind, as to warrant the supposition, that the different 

 modes of action of the two systems can be referred to the dif- 

 ferent structures of their fibres. Kather, it is probable, that 

 the laws of conduction by the fibres are in both systems the 

 same, and that the differences manifest in the modes of action 

 of the systems are due to the multiplication and separation of 

 the nervous centres of the sympathetic : ganglia, or nerve- 

 centres, being placed in connection with the fibres of the sym- 

 pathetic in nearly all parts of their course. 



According to the most general view, the sympathetic system 

 may be described as arranged in two principal divisions, each 

 of which consists of ganglia and connecting fibres. The first 

 division may include those ganglia which are seated on and 

 involve the main trunks or branches of cerebral and spinal 

 nerves. This division will include the large Gasserian gan- 

 glion on the sensitive trunk of the fifth cerebral nerve (Fig. 

 152), the ganglia on the glosso-pharyngeal and pneumogastric 

 nerves, and the ganglia on the posterior or sensitive branches 

 of the spinal nerves (Fig. 141). 



To the second division belong the double chain of praeverte- 

 bral ganglia (24, 30, Fig. 151) and their branches, extend- 

 ing from the interior and base of the skull to the coccyx ; the 

 various sympathetic visceral plexuses and their ganglia, as the 

 cardiac, the solar, the renal and hypogastric plexuses ; and in 

 the same division may be included the ganglia in the neigh- 

 borhood of the head and neck, namely, the ophthalmic or len- 

 ticular, the spheno-palatine, the otic, and the submaxillary 

 ganglia (Fig. 152). 



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