1902.] 



On Skin Currents. 



381 



my own conclusion with regard to the endurance of human skin. On 

 a healthy skin I have obtained what I take to be signs of life as long 

 as 10 days after excision, and this did not appear to be a longest 

 possible period. I was fully alive to possibilities of fallacy, and 

 expended much care and time upon their experimental exclusion. 

 Whether I have succeeded or not is matter for future investigation. 

 Pathological observations on the human skin in relation to its surgical 

 transplantation to some extent bear out the view that it may survive 

 excision for an extraordinary length of time, especially in a semi- 

 desiccated state and under antiseptic protection. Wentscher* found, 

 e.g., that skin grafts, preserved for 7 to 14 (and in one instance for 21) 

 days, recovered vitality in 3 or 4 days, as indicated particularly by the 

 reappearance of karyokinetic figures. 



As regards skin taken from the post-mortem room, Schede (quoted 

 by Wentscher) made successful transplantation of skin 12 hours post- 

 mortem, but was unsuccessful with 24 hours' old material. 



The conductivity of human skin, more especially of fresh human 

 skin, is greatly augmented in consequence of electrical excitation. It 

 is further increased by boiling, and the change occurring gradually 

 in kept skin is of itself sufficient to greatly reduce the original 

 resistance. 



Thus, e.g., in skin No. IT, examined when I had not yet realised the 

 great influence of previous electrical excitation, and did not therefore 

 measure the resistance of the perfectly fresh skin, the conductivity is 

 increased threefold in consequence of tetanisation, and tenfold in con- 

 sequence of subsequent boiling. 



In a later experiment directed specially to this point, the resistance 

 measured by Wheatstone bridge was originally above 230,000 ohms, 

 falling to below 100,000 ohms in consequence of strong tetanisation. 



In my first observations, hardly anticipating any such considerable 

 alterations of resistance, I contented myself with recording a standard 

 deflection of 0*01 volt through the skin ( + electrodes + galvanometer) 

 to see whether or no the resistance was appreciably altered during 

 observation. But I also frequently recorded, for the sake of compari- 

 son, the standard deflection of 0*01 volt through a megohm (+ gal- 

 vanometer) and was therefore able to utilise for the study of altera- 

 tions of conductivity a considerable body of data directed to other 

 questions. The alterations were indeed so considerable that it was 

 possible without gross error to calculate absolute values of resistance 

 (or conductivity) from the standard deflections recorded at beginning 

 and end of observation. The comparison of such data with data 

 obtained by direct measurement showed that the calculation was per- 

 missible. Of course the calculated data are valid only in the case of 



* Ziegler's 'Beitrage zur Pathologisclien Anatomie und zur Allgemeinen Patho- 

 logie,' toI. 24, p. 101, 1898. 



2 D 2 



