THE SYMPATHETIC KERVE. 573 



pathetic nerves. There are no means of deciding this ; but 

 if it be admitted that the conduction is effected through 

 the cerebro-spiual nerve-fibres, then, whether or not they 

 pass uninterruptedly between the brain or spinal cord and 

 the part affected, it must be assumed that their mode of 

 conduction is modified by the ganglia. For, if such cere- 

 bro-spinal fibres are conducted in the ordinary manner, 

 the parts should be always sensible and liable to the in- 

 fluence of the will, and impressions should be conveyed to 

 and fro instantaneously. But this is not the case ; on the 

 contrary, through the branches of the S3^mpathetic nerve 

 and its ganglia, none but intense impressions, or impres- 

 sions exaggerated by the morbid excitability of the nerves 

 or ganglia, can be conveyed. 



Respecting the general action of the ganglia of the 

 sympathetic nerve, little need be said here, since they may 

 be taken as examples by which to illustrate the common 

 modes of action of all nerve-centres (see p. 483). Indeed, 

 complex as the sympathetic system, taken as a whole, is, 

 it presents in each of its parts a simplicity not to be found 

 in the cerebio- spinal system : for each ganglion with 

 afferent and efferent nerves forms a simple nervous system, 

 and might serve for the illustration of all the nervous 

 actions with which the mind is unconnected. But it will 

 be more convenient to consider the ganglia now in connec- 

 tion with the functions that they may be supposed to con- 

 trol, in the several organs supplied by the sympathetic 

 system alone, or in conjunction with the cerebro-spinal. 



The general processes which the sympathetic appears to 

 influence, are those of involuntary motion, secretion, and 

 nutrition. 



Many movements take place involuntarily in parts sup- 

 plied with cerebro-spinal nerves, as the respiratory and 

 other spinal reflex motions; but the parts principally 

 supplied with sympathetic nerves are usually capable of 



