426 Note 31 : measures of sensation 



y, was interrupted, I took the secondary discharge through my body directly, 

 but when the larger current, y', was interrupted, I made the secondary dis- 

 charge pass through a capillary tube filled with salt solution as well as my body. 



The resistance between rny hands when both were immersed in salt water 

 was 1245 Ohms, making with the secondary coil a resistance of 3955 m the 

 secondary circuit, so that the time-modulus of the discharge was T = 1-3 x io~ 3 

 seconds. 



The resistance of the first capillary tube was 370,000, so that when it was 

 introduced T 1-4 x io~ 5 . 



By a rough estimate of the comparative intensity of the shocks I supposed 

 them to be of equal intensity when y' = 8-^y, and therefore if we suppose that 

 two shocks remain of equal intensity when C varies as T P , p = 0-468. 



By another experiment in which a tube was used whose resistance was 

 450,000, p = 0-534. 



When the shocks at breaking contact were nearly equal, that at making 

 contact was very much more intense with the small primary current and small 

 secondary resistance than with the large primary current and large secondary 

 resistance. 



I then compared the discharges from two condensers of i and o-i micro- 

 farads capacity respectively, charging them with a battery of 25 Leclanche 

 cells, the electromotive force of which was about 36 Ohms. 



The resistance of the discharging circuit for the microfarad was 11,200 Ohms, 

 including my body, so that 



r = 1-12 x io~ 2 seconds. 



The resistance of the discharging circuit of the tenth of a microfarad was 

 3600, so that T' = 3-6 x IQ-*. 



The values of C were inversely as the resistances, so that if the two shocks 

 were, as I estimated them, nearly equal, the value of p would be 0-670. 



This experiment was much more satisfactory and more easily managed than 

 that with the induction coil, and I thought it desirable to apply the same method 

 to the comparison of the contractions of a muscle when its nerve was acted on 

 by the discharge. I therefore availed myself of the kindness of Mr Dew-Smith, 

 who prepared for me the sciatic nerve and gastrocnemius muscle of a frog, and 

 attached the preparation to his myograph. The discharge was conducted through 

 about 0-4 cm. of the nerve by means of Du Bois Reymond's unpolarizable 

 electrodes, the resistance of the electrodes and nerve being 35,000 Ohms. When 

 the electrodes were in contact their resistance was 23,000, leaving about 12,000 

 as the resistance of the nerve itself. 



I used two condensers, one o-i microfarad, and the other an air-condenser 

 of 270 centimetres capacity in electrostatic measure, or about 3 x io~ 4 micro- 

 farads. 



The first was charged by one cell and the second by 25. The resistances 

 were arranged so that the contractions produced in the muscle we,re much less 



