CONTACT ELECTRICITY. 13 



diminishing the number of pairs of elements, the phenomena above 

 described diminish ; and, when there are only fifteen or twenty- 

 couples, they become at last inappreciable. 



Is the continuous current really an hyposthenisant of nervous 

 force ? If we may apply to mankind the results obtained by vivi- 

 section, the reply should be in the affirmative. We know, in fact, 

 that a continuous current, passed for a certain time through the 

 nerves or the limbs of an animal, not only diminishes the motor 

 power, but even produces paralysis. I shall shew in the sequel, by 

 the results of experiments, that this kind of hyposthenisant action 

 is not ajapreciable in man. (See Chap. III.) With regard to the 

 action of the continuous current upon sensation, although after a 

 certain time it produces numbness of the limb through which it 

 passes, I do not believe that it can be considered as an hypos- 

 thenisant of the nervous system, or, in other words, as an 

 ansesthetic. 



The sensibility of the skin appears to me to be more acutely 

 excited by a galvanic current of rapid intermission than by a 

 continuous curi'ent; although the opposite holds good for their 

 organic action. Thus the continuous current produces a more 

 rapid erythema, vesication, or destruction of the skin. The erection 

 of the nervous papillae, and the disorganization of the tissues, 

 should be ascribed to the action of the continuous current ; and 

 are effects to which the periods of completion and of interruption 

 contribute but very feebly. It is for this reason, doubtless, that 

 the rapidly intermittent current disorganizes the skin much less 

 than the continuous current. But, inasmuch as it is impossible 

 to avoid the continuous action that takes place between the com- 

 mencement and conclusion of each intermittence, so it is impossible 

 to excite the skin galvanically without the production of more 

 or less organic change. The calorific action of the negative (zinc) 

 pole is greater than that of the positive (copper or carbon pole).''' 



Of all the varieties of electricity, it is the galvanic that acts most 

 powerfully upon the retina, when applied to the face by means of 

 moist rheophores. A galvanic current directed upon the nerves 

 of the fifth pair, or even upon their ultimate ramifications, exerts 

 a special action upon the retina ; producing three luminous sensa- 



in the skin of the back of the hands or | importance of this point.) Lastly the sen- 

 feet respectively. These sensations pro- sibility was always most strongly excited 

 gressively increased, and were soon re- in the part or limb that was placed in 

 placed by one analogous to that produced connection with the negative pole, 

 by the action of a strong sinapism. There i ' It has long been known that the 

 was, however, no vesication, even although , other chemical (electrolytic) and phy- 

 the current was continued for half an hour. , siological phenomena are more pronounced 

 (I shall refer hereafter to the practical at the zinc pole. 



M 



