THE NERVOUS SYSTEM. 151 



Much progress, surprisingly much, has been made of late in 

 our knowledge of the functions of the nervous system, but great 

 obscurity still hangs over the subject. 



(I) These oscillations are purely hypothetical and indeed im- 

 probable. Were their existence proved, we should know nothing 

 more of the real nature of the cerebral functions, for we should 

 have to learn what were the peculiar properties of the nervous 

 system, which enabled it alone of all substances to produce, when 

 oscillating, the phenomena which it exhibits. We might as well 

 attempt to explain the phenomena of motion or of chemical 

 affinity and galvanism, by vitality and mind, as the phenomena 

 of vitality and mind by mechanics or chemical affinity and gal- 

 vanism. They are altogether distinct principles, although there 

 can be no question that the laws of mechanics and chemical 

 affinity and galvanism, are important and indispensable in every 

 living system, in subservience to life and mind. The mind., for 

 aught we know, may stimulate the voluntary muscles by means 

 of galvanism communicated along the nerves, but then the gal- 

 vanism is not mind, it is merely an instrument employed by 

 the mind.* 



* The voluntary muscles contract for some time after death, when their 

 nerves are galvanised ; the involuntary will not, although for twenty-four hours 

 after death the heart is excited on the contact of a mechanical or chemical 

 irritant, v. c. Wilson, Lectures on the Blood, fyc. p. 139. 



When the stomach has suffered by the division of the par vagum, galvanism 

 is said to enable it to perform digestion, 



