VII.] 



DIRECT EFFECTS 



117 



In surgical practice it is a very common proceeding to 

 accelerate the recovering of a raw surface by "skin-grafting." 

 It is essential that such grafts should include cells of the 

 malpighian layer. 



All these things point to an exceptional vitality of cutan- 

 eous or rather subcutaneous malpighian elements. 



I find that in the skin of persons dying suddenly in other- 

 wise good health, .the cutaneous blaze-currents persist for several 

 days, whereas the skin taken from ordinary post-mortem room 

 subjects, having died gradually and completely, exhibits little 

 or none of this sign of life twenty-four and forty-eight hours 

 post mortem. 



Let me remind you of the nature of this sign, for the 

 questions to which it may serve as an indicator are by no means 

 exhausted. A piece of living skin set up between electrodes, 

 and tested in the usual way by induction currents of both 

 directions, responds by blaze-current in one the outgoing 

 direction. A piece of dead skin does nothing of the kind, but 

 gives, if anything, small polarisation counter-currents. And 

 since living skin responds in one direction to both directions 

 of excitation, you may (observing due reservation and pre- 

 caution) obtain outgoing blaze-currents after tetanisation by 

 alternating currents in both pairs of directions. Here are 

 galvanometric records of the electrical responses of surviving 

 human skin, and of the same skin, killed by heat. 



0-0010, 



voit. 





Time 



TTTTTTT 



Dead. 



Living: 



FlG. 49 (4201). Skin of breast 8 hours after amputation. Living. Two + 

 responses to single break induction shocks in + and -- directions. 8 L. 10,000. 

 Dead. Several - and + effects to + and - shocks, i.e., polarisation. Resistance 

 diminished. 



