INDUCED ELECTRICITY. 23 



the second lielix, which exerts, as we shall see, an elective action 

 on the cutaneous sensibility, may produce an erytliema that will 

 last for many days. 



In the present state of science, no difference has been established 

 physiologically between electricity communicated to organs from 

 the induced current of the first or of the second helix. We shall 

 see facts, however, whicli prove incontestably that each of these 

 currents acts physiologically in an especial manner.^ In the 

 experiments by whicli they are demonstrated, it is necessary first 

 to equalise the power of each helix by holding a moist rheophore 

 in each hand. (It is known that, on thus placing oneself in the 

 circuit of an induced current, each intermission communicates to 

 the upper extremities a shock that extends to the wrists, the 

 elbows, the shoulders, or even the chest, according to the strength 

 of the current). 



A. — The current of the second helix excites the retina more vividly 

 than does that of the first helix, tvhen api)lied to the face or to the 

 eyeball hy means of moist excitors. 



This special property of the current of the second helix, the 

 production of stronger luminous sensations than the current of 

 the first helix, is infinitely more developed in my electro-magnetic 

 apparatus with two spirals^ than in my electro-dynamic apparatus. 

 Thus the current of the second helix of my electro-magnetic 

 apparatus acts powerfully on the retina, applied to any point of 

 the face, even when a very feeble current is employed ; while 

 the current of the second helix of the volta-electric instrument 

 oidy produces luminous sensations when comparatively powerful ; 

 and even then only when the moist rheophores are placed on the 



3 Abria alone has endeavoured to de- gave him more powerful shocks in the 

 termine the comiaarative power of physio- i upper extremities, he infei-ied that its 



logical action possessed by the second, physiological power was greater. This 



third, fourth, iifth, sixth, and seventh was all. In my experiments, as we sliall 



helices; or, in ordinary language, of the see hereafter, I iirst equalised the strength 



current of the first, second, third, fourth, of the currents tliat I wished to compare; 



fifth, and sixth order ; but he has not and then studied their dift'erential action 



studied the diflerential action of the extra upon the sensibility of the skin, of the 



current (current of the first hehx), and of muscles, of the retina, &c. Abria was 



the current of the first order (current of unable to undertake such researches, be- 



the second helix), the only diflerence that cause he did not know how to localize 



it is important to know in practice, since the electric force in certain organs ; a pro- 



the difff rential actions described by Abria ceeding tliat requires before all things, spe- 



are quite insignificant therapeutically, cial anatomical and physiological know- 



I should say also that there is no resem- ledge. 



blance between the re.searclies of Abria * The apparatus with two spirals, or 



and my own. Abria simply took the of double induction, which I was the 



rheophores in his hands to compare the first to construct, will be fully described 



difiereut action of induced currents of in the fourth chapter. 

 difleicnt orders ; and when any current 



