132 THE SIGNS OF LIFE [LECT. 



direction of the break current. Therefore, if to both pairs of 

 directions of tetanisation the after-effect is in one (positive or 

 outgoing) direction, we have proof that the skin is alive ; if to 

 both pairs of directions it is in the direction of the break, we 

 have proof that it is dead. 



I found it at first not a little confusing that a deflection in 

 the direction of the break current which in V. Fleischl's 

 experiment on nerve is generally considered as a sign of life 

 should on skin (and on other killed tissues) be a sign of death. 

 But evidently the deflection in question is, by reason of the 

 physical factor mentioned above, a balance of ordinary polari- 

 sation in the direction of break. Here is the analysis of this 

 physical resultant for the two pairs of tetanisation directions : 



/. Mcike current > 



a.lCs poLcs.ri3a.Cion < > 



3. Bre<a.k current * >- 



the resultant in each case being due to the summated effects, 

 No. 2 being greater than the summated effects No. 4.* You 

 ask, perhaps if you have followed the argument so far why 

 it should be preferable to observe an after-effect of tetanisation 

 rather than an effect during tetanisation. Ought not a positive 

 outgoing effect to manifest itself during as well as after tetani- 

 sation ? So it does, with a lively skin, that will respond to 

 strengths of tetanisation that can be passed through the 

 galvanometer ; such a skin will, however, also respond to the 

 simpler question of single induction shocks ; a skin so little 



* This result maybe observed ; with strong tetanisation the resultant may 

 be in the direction of make, the after-effect of the summated effects No. 4 being 

 greater than that of the summated effects No. i. Yet even in this case the 

 effect during tetanisation is in the direction of the break. I am not certain 

 whether the after-deflection in the direction of the make is physiological or 

 purely physical. I place no reliance whatever upon the deflections obtained 

 during strong tetanisation. They can happen by alterations of the gal- 

 vanometer magnets by the opposed long and short currents, or by reason 

 of asymmetry of the magnetic field in the absence of any electrolyte at all 

 in circuit, or by reason of irreciprocal resistance. 



