108 THE SIGNS OF LIFE [LECT. 



to verify the following formula, which previous experiments have 

 shown to be that of the responses of a cat's paw twenty-four 

 hours after death : 



B C A 



Excitation from B to A (B is anodic) 



Response outgoing at B 

 Excitation from A to B (B is kathodic) 



Response outgoing at B 

 Excitation from B to A (A is kathodic) 



Response outgoing at A 

 Excitation from A to B (A is anodic) 



Response outgoing at A 



And now, if I have succeeded in making clear to you that the 

 deflections seen on the scale indicate current in the object 

 towards B (i.e., out at B), or towards A (out at A), or from B (in 

 at B), or from A (in at A) the results of the experiment will be 

 clear to you as it progresses. 



I intend to examine B ; I therefore compensate the points 

 B C with the switch in the position II . Then I plug the 

 galvanometer at the keyboard, move the switch to the first 

 position, and send a break induction shock through the paw 

 from B to A. I turn back the switch to the old position, II B , 

 and unplug the galvanometer. The deflection is to your left 

 as figured, signifying that there is now current from C to B (the 

 previous anode), which is outgoing at B. It is what in Bieder- 

 mann's terminology is called a negative anodic current i.e., 

 " negative " to the original current. 



I repeat a second trial in precisely the same way, but with a 

 reversed direction of excitation, so that B is now its kathode. 

 The deflection is again to your left, outgoing at B ; it is a posi- 

 tive, kathodic current i.e., " positive " to the original current. 



And in precisely the same way, as a confirmatory pair of 

 trials, I repeat on the A C side ; only, perhaps, especially if the 

 previous trials have been made with strong currents, it may 

 be prudent to shift the electrode A to a fresh pad. Both the 

 trials give deflection to your right, outgoing at A, positive 

 kathodic after excitation from B to A, negative anodic after 

 excitation from A to B. So that the formula previously 

 sketched has been precisely fulfilled ; all the responses have 

 been outgoing. 



