128 THE SIGNS OF LIFE [LECT. vn. 



75. A supplementary experiment. Let us take advantage, 

 of the altered area of skin of our KMnO 4 experiment to make 

 a further trial. Its sweat-ducts are choked with MnO 4 i.e., with 

 a non-living electrolyte that may serve us as a conductor to 

 the inner aspect of the skin. I should like to take this altered 

 area of skin and an unaltered area of intact skin into circuit 

 with an induction coil and a galvanometer, to be tested in the 

 usual way. This is now done by tubes of zinc sulphate, and the 

 first point you notice is that there is a considerable current 

 directed in the body from the irritated to the intact spot, or 

 ingoing through the former and outgoing through the latter. 

 This current being compensated and the galvanometer plugged 

 out, I apply excitation in the usual way by induction shocks and 

 by tetanisation, and look for the after-currents that may be 

 aroused. In accordance with your expectation, they are in 

 every case opposed to the current of injury i.e., ingoing at the 

 intact skin and outgoing at the manganised skin. This result, 

 as far as it goes, agrees with the conclusion that the normal 

 irritated skin of man is the seat of an ingoing current ; but I 

 should be sorry to lay much stress on the result of an isolated 

 experiment, the point deserves further investigation. 



REFERENCES 



Du BoiS-REYMOND. " Willkiirversuch," Untersuchungen iieber thierische 



Elektricitaf, vol. ii., p. 289, 1849. 

 HERMANN. "Ueber den Actionsstrom der Muskeln im lebenden Men- 



schen," Pfliiger's Archiv, xvi., p. 410, 1878. 

 TARCHANOFF. " Ueber die Galvanischen Erscheinungen in der Haut des 



Menschen," u.s.w., Pfliiger's Archiv, xlvi., p. 46, 1890. 

 LEDUC. "Action des Courants Continus sur 1'Organisme Vivant," Annales 



d'Electrobiologie, 1901, p. 261. 

 WALLER. "On Skin-currents. Part III. The Human Skin," Proc. 



Roy. Soc., vol. 70, p. 374, 1902. 



