454 Mr. M. Donovan on the supposed Identity of the Agent 



the evidence in favour of the alleged identity derived from quan- 

 tity is of no force. The adherents of the doctrine of identity may 

 profess that their explanations of phenomena are independent of 

 all hypothetical notious of two fluids, of one, or of none, or of 

 vibrations. They may declare that they only use the language 

 of these suppositions for convenience of communication. Let 

 these persons, however, in conceiving the phsenomena which they 

 describe as resulting from an enormous quantity of electricity 

 generated in the voltaic series, abstract from all notion of an 

 elastic fluid, or two such, circulating in rapid currents, and then 

 try if their minds be impressed with any real ideas when the 

 words representing these ideas are thus deprived of the meaning 

 which gave them currency in their reasonings. 



In the early discussions which took place, relative to the identity 

 of the electric fluid and the galvanic influence, the circumstance of 

 a shock being communicated by both agents was deemed a strong 

 corroboration on the affirmative side of the question ; yet there 

 is little force in the argument, as will appear from the following 

 considerations. The word shock being used to express both sen- 

 sations, the identity of the two agents is the more easily accre- 

 dited. Let no one contumeliously deny the influence of language 

 on his mind, for it is all-powerful. To judge by the sensation, 

 it appears to me that the two shocks are totally different, although 

 words will scarcely express the difference : sensations depend 

 more on the nature of the organ in which they are induced than 

 on the inducing cause. A blow on the orbital process gives the 

 sensation of a flash of light ; so does the electric or voltaic agent 

 applied in the same quarter. A blow over the ulnar nerve at 

 the elbow gives the same vibratory painful sensation as continued 

 and rapid shocks from a very weak voltaic battery. Puncturing 

 the lacrymal twig of the fifth nerve will produce a flow of tears, 

 as will also emotions of the mind or pain. A voltaic current passed 

 through the ear will affect the auditory nerve with the impression 

 of loud noises. The semiparalytic state of a limb, when it is said 

 to be asleep, resembles the vibration caused by a feeble electro- 

 magnetic apparatus applied to the part. Volta produced an acid 

 taste in the mouth by two small plates of different metals. A 

 person who swallows vinegar affirms that it is sweet, if he have 

 previously chewed the fruit of the shrub called Assaban. The 

 peristaltic motion of the intestinal canal may be urged to dejec- 

 tions of its contents either by a voltaic current or by cathartics. 

 He who unwittingly takes hold of a lump of frozen mercury, 

 drops it, and declares he is burnt, and a blister will shortly 

 appear on his fingers. Cantharides at length affect the skin 

 like boiling water. The iris is dilated by the pressure of excess- 

 ive blood in the head; so also is it by belladonna, by ardent 



