iii.J SINGLE INDUCTION SHOCKS 45 



as a matter of fact it is due to both factors, the electro-motive 

 force of the response is increased, and the resistance of the eye- 

 ball is diminished. You will recognise both these points on the 

 accompanying record, where the tetanisation has raised the 

 voltage of the response from about TjoVo to nearly T <yVo- 5 y u 

 notice also that the standard deflection by rIT Vcr v lt has been 

 evidently increased indicating increased conductivity, i.e., 

 diminished resistance. 



25. In the experiment just made you have witnessed a 

 marked effect subsequent to tetanisation ; a similar effect is 

 witnessed during tetanisation, but it is rather more troublesome 

 to demonstrate properly, and I have not therefore included it in 

 to-day's list. I will content myself with quoting the results of 

 a former experiment in which the deflections in response to 

 light were : 



Before tetanisation 12 degrees of scale. 

 During tetanisation 36 degrees of scale. 

 After tetanisation 27 degrees of scale. 



| 26. The effects of single shocks. Experiment III. The 

 very strong currents that you have just witnessed as after- 

 effects of strong tetanisation are as I hope to prove to 

 you in a future lecture in chief part of physiological origin, 

 but in minor degree merely the physical effects of ordinary 

 polarisation. Their experimental analysis is a complicated 

 matter that cannot profitably be dealt with before we have 

 become familiar with the less complicated results of excita- 

 tion by single induction shocks and by condenser discharges. 

 And since for the purpose of our third experiment it is indifferent 

 which of these two forms of electrical excitation we may choose 

 to take, I will use the more familiar apparatus, to show the effects 

 and after-effects of a single break induction shock, first in one 

 and then in the other direction. You understand, of course, that 

 the expressions " effect " and " after-effect " are simply used to 

 distinguish between the two experimental cases, where (i) the 

 induction shock and the response are allowed to pass through 

 the galvanometer ; and (2) only the respon.se is allowed to pass,, 



