OF GALVANISM. 21 



3. An influence over the organs of secretion. Upon these we 

 will observe in succession. 



And first, with reference to the production of certain sensations. 

 Voltaic Electricity acts in a manner peculiar to itself on all the 

 nerves of sensation. If a slip of zinc applied to the tip of the 

 tongue, and a silver coin placed between the gum and upper lip 

 be brought into contact, an acid taste is experienced, but if the 

 position of the metals be reversed, the taste is then decidedly 

 alkaline. In order to the production of these sensations, the 

 tongue must be covered with some moisture, for, when perfectly 

 dry, no such impressions are perceived. For this reason it has 

 been suggested, and it is quite probable, that such sensation is 

 owing not to any direct action of Galvanism upon the tongue, 

 but to the decomposition of the salts of the saliva, and to the 

 consequent developement of an acid and an alkali at the opposite 

 poles. When this experiment is performed in the dark, a flash 

 of light is perceived, which is observable not only on bringing 

 the metals into contact, but also upon separating them from each 

 other; and it is worthy of remark that the flash is most vivid 

 when the zinc is in contact with the tongue. A more decided 

 effect is produced by attaching to the eye-ball, beneath the eye- 

 lid, a slip of tinfoil, placing a silver spoon in the mouth, and 

 connecting it and the foil. The experiment succeeds also in the 

 light, and whether the eye be open or shut ; and at the instant 

 of contact of the metals, the pupil is observed to diminish in size, 

 just as when the eye from comparative darkness is suddenly ex- 

 posed to the glare of sunshine. By affecting the auditory nerve, 

 in like manner, a peculiar sound is excited. 



Upon the pain produced by Galvanism it is unnecessary to 

 dwell at any length. It is an invariable accompaniment of the 

 sudden transmission through, or withdrawal from, the body, of a 

 strong electric current. During the completion of the circuit 

 also, a disagreeable sensation is experienced, which becomes 

 extremely distressing if the part of the body at which the current 

 enters, or from which it issues, be deprived of its cuticle, or if 

 there be a sore or cut in its line of passage. Pain may even, 

 indeed, be produced by a very feeble current. 



