LECTURE IV 



Skin-currents (of the Frog) The Normal Current is " Ingoing "--The Re- 

 sponse to Indirect Excitation is Outgoing, Mixed, or Ingoing The Latent 

 Period is Two Seconds Fatigue Atropine Mercuric Chloride The 

 Response to Direct Excitation is Outgoing Summation Effects of 

 Tetanisation Localisation of the Response by the ABC Method- 

 Terminology. 



36. From the preliminary observations alluded to in my 

 last lecture ( 33), I formulated the following working rule for 

 the experimental distinction between the living and the dead 

 states of matter : 



" If the object of examination exhibits blaze in one or in 

 both directions, it is living." * 



One of the earliest objects of examination upon which I 

 tested this rule was the human body, living and dead. I thought 

 that it might be possible to place, e.g., a finger between a pair of 

 electrodes, and to learn from the presence or absence of blaze 

 reaction whether the finger was living or dead. But by reason 

 of the fact that a finger is covered by skin, and that it is im- 

 possible to send current by unpolarisable electrodes into the 

 intact human body otherwise than through skin (or mucous 

 membrane), the question has proved to be much less simple than 

 it appeared. It has involved me in an investigation of skin- 

 currents that has taken the best part of two years, and the 

 results, instructive though they are as regards the original 

 question, are, I think, of still greater interest from another point 

 of view. It will be well, therefore, to consider ourselves as 

 entering upon a fresh field, albeit an already much trodden field, 

 in undertaking an exploration of " Skin-Currents." 



* I do not commit myself to the obverse, that if an object exhibits no 



blaze it is not alive. Vide infra, 82, 

 59 



