116 LOCALIZED ELECTRIZATION. 



action of the electricity, without exposing the patients to the 

 startling effects of the Leyden jar, soon superseded the older modes 

 of application, and gave new life to medical electricity. Magendie, 

 by his talent and by the authority of his name, powerfully contri- 

 buted to its popularity. 



§ II. Critical considerations. 



I shall next endeavour to show that electro-puncture is far from 

 the attainment of the end that was proposed by Sarlandiere and 



Mfigendie. 



1. Electro-Juncture does not exactly localize electriciti/ in the organs. 



I hope to afford proof of the foregoing proposition, by analyzing 

 successively the phenomena of electro-cutaneous sensibility, and 

 the phenomena of electro-muscular contractility and sensibility, 

 that are witnessed under the influence of electro-puncture. 



In thin patients, or in those whose subcutaneous cellular tissue 

 is scanty, needles thrust into the skin, in such a manner as not to 

 pass through the dermis, produce, even under the influence of a 

 very feeble current, simnltaneous excitation of the skin and of the 

 muscles and nerves, if the needles are placed over the course of 

 muscles or nerves. In order that the excitation may be confined 

 within the skin, it is necessary that the cellular tissue should be 

 either plentiful or infiltrated with serosity, and that the current 

 should be extremely weak. 



Electro- puncture cannot produce muscular contraction without, 

 at the same time, exciting the sensibility of the skin. In order to 

 prevent this effect, M. Petrequin has covered the needles with a 

 layer of caoutchouc, leaving only their extremities free, for an 

 extent of one or two millimetres, commencing a millimetre from 

 the point. But the covering of caoutchouc, which is not very 

 thick, speedily becomes moistened and softened when the needle 

 is plunged into the tissues. It then permits the passage of the 

 current ; and the skin is excited almost as acutely as if the needle 

 were bare. Patients on whom I have made comparative trials 

 with the insulated and with the common needles, have been 

 unable to discover any difference between tliem as far as regards 

 their action upon the skin. 



The cutaneous sensation produced by electro-puncture masks 

 the muscular sensation produced by the direct excitation of the 

 muscle into which the needle is plunged. It might be supposed 

 that the two sensations are the same, and that they blend to- 

 gether ; but this is not the case, as may be shown by the following 



