1890.] MICROSCOPICAL JOURNAL. 175 



Continuous Current. — Tabic No. 3. — Dry hands, 14,47^ ohms ; moist 

 hands, 9,750 ohms. 



Alternating^ current. — Dry hands, 1,740; moist hands, 1,437 ohms. 



One feature is prominent in these results, viz., that the resistance ob- 

 tained by the alternating current is very much less than that obtained 

 with the continuous current. 



Mr. Thos. A. Edison instituted a series of experiments to ascertain 

 the resistance of the human body to the passage of the electric force ; 

 259 male persons of all ages from 6S to 192 pounds, measured between 

 the hands immersed to the wrists in caustic potash, acjueous solution of 

 density i.i, gave the mean of all resistances 9S6 ohms. 



The detluctions drawn from this extended series of measurements were 

 as follows : The resistance of a man's body, taken between the hands, 

 varies with the solution employed for immersion, and the area of skin 

 immersed, together with the superficial condition of the epidermis. 

 That with a fixed solution, innnersion, and area, the resistance tloes not 

 vary to any appreciable extent with the battery power used in the 

 measurement, when the efiects of polarization are eliminated. That 

 with the KI 10 solution used as given above, the resistance at about 

 30 seconds innnersion, is about 1,000 ohms. Why the resistance with 

 the alternating current was not used is not stated. These experiments 

 were brought about through the controversy on electro-execution, and 

 from the great dilference in resistance demonstrated by the English 

 gentlemen referred to previously, between the continuous and alternat- 

 ing current, it would have been of great interest to have compared the 

 results in so extended a series of measurements. Few who use elec- 

 tricity in medical practice will question the following statements of Dr. 

 A. D. Rockwell, taken from " Kennnler enquiry," that the resistance 

 falls more rajndly when a low potential is used and that the fall of the 

 resistance-taking men ordinarily would range between i,300and400 

 ohms, and that this fall of resistance would be almost instantaneous. 

 That after the current has once overcome the resistance, the resistance 

 is gradually lessened until about the minimum resistance is reached, 

 when it remains nearly stationary under a constant potentiality. 



THE INFLUENCE OF ELECTRICITY ON SENSATION. 



Any physician practically using galvanism in his medical work will 

 find that 30 milliamperes will generally be painful to his patients. In 

 fact frequently a less powerful current will be objected to. It depends 

 to a great extent upon the portion of the body operated upon. If a 

 mucous membrane, even 5 to 10 milliamperes may prove very painful. 

 As to the comparison between the painful efiects of the continuous and 

 alternating currents, a paper read before the Institution of Electrical 

 Engineers, London, England, March 27, 1S90, throws some light (see 

 Electrical Worlds May zG^ 1890). The writers adopt 10 milliamperes 

 as the maximum continuous current which may be passed through the 

 body without producing unpleasant sensations. With alternating cur- 

 rents they found a great dificrence, inasmuch that before a single mill 

 iampere was registered their patients complained that the current was 

 too strong and practically unbearable. In the course of their investi- 

 gations they found but few persons who could bear with comfort one 

 milliampere of alternating current. From their experiments upon ten 

 persons they found that one and seven-tenths milliamperes of alternating 



