526 
MR. F. GOTCH ON THE ELECTROMOTIVE PROPERTIES 
The after-effect of the passage of induction shocJcs. —In order to carry out the 
experiment, the previous method was modified as follows :—The spring myograph was 
substituted for the paraffin switch. The key K x of the instrument was placed in the 
primary circuit of the induction apparatus. The galvanometer circuit was arranged 
as in fig. 4, the secondary coil being directly in the circuit, the induction shock being 
Fig. 4. 
short-circuited by the key Iv. 3 so as to prevent any disturbance of the instrument; to 
render this effectual, a resistance of 10,000 ohms was introduced between the key 
and. the galvanometer. It was ascertained that with K 2 placed so as to be opened 
•003" after K x no appreciable effect was observed by the passage of a strong induction 
shock through the electrodes. By this method an induction shock could be led 
through the tissue, and the galvanometer would respond to all electromotive changes 
which followed that at an interval of *003". The same electrodes must obviously be 
used both for leading in and leading off. It was ascertained by experiment that any 
after-effect due to polarisation in these was extremely small. 
From the organ of a medium-sized fish a strip was cut measuring 16 mm. in 
length, 7 mm. in width, and 2 mm. in thickness. The induction apparatus was used 
with 3 Groves in the primary coil; the secondary coil stood at 5 cm., organ-current 
+ -006 K. 
After-effect. 
Direction of induction stock through tissue (—) Galv. m + 150 
>) 3 ) )> >) ( + ) >) + 650 
)> 3 ) 33 33 ( —) 33 + 180 
3 3 3 3 33 3 3 ( + ) 3 3 + ^50 
This ( + ) after-effect thus occurred with both ( + ) and ( —) currents, but the former 
were far the most effectual for its production. Since the polarisation phenomena are 
by this method reduced to a minimum, the after-effects here observed are due to the 
particular change which the tissue shows apart from those. This change was noticed 
