OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
515 
largest, and therefore the most easily appreciated, vital electromotive change which 
has up to this time been examined by the rheotome method. The extraordinary 
prolongation of the delay by cold, although apparently connected with the condition 
of the nerve endings, may, however, be at least partially accounted for by the 
increased time of transmission down the nerve branches contained in the organ itself. 
It is hoped that an early opportunity will afford means for ascertaining to what 
extent this is the case. 
Experiments upon the Character and Duration of the Response. 
For information on these points the experiments had to be of such a character that 
the results should indicate the extent of the electromotive change as appreciated by 
the galvanometer at successive periods after excitation, and it was found that the most 
practicable plan consisted in massing together all the changes which occurred during 
a period of y^o^- The galvanometer circuit was closed for •01" at periods of '01", 
'02", '03", &c., after excitation of the nerve. 
The results of such observations show that when the temperature of the organ is 
not below 10° C. the electromotive change develops with such rapidity that it reaches 
its maximum in less than one-hundredth of a second from the time art which it first 
becomes appreciable. If the change is expressed by a curve, the curve must thus 
be represented as rising very steeply from start to summit. The effect is always 
declining in the second and third hundredth of a second, and declines more slowly 
than it rose ; but the rate of decline varies in different preparations, and thus the 
duration of the appreciable effect must vary. There is so marked a difference in this 
respect that, whereas in some cases no further change conld be appreciated in the 
fourth hundredth of a second, in others a change was still perceived thirty seconds 
after the commencement of the response. This prolonged decline was, however, of 
such a character that it could be distinguished from the main decline of the organ 
response, and may be termed an “ after-effect.” Temperature, strength of response, 
and vigour and size of animal influence the above features of the response. 
The influence of temperature is shown by the following experiment upon a nerve- 
organ preparation from a large Torpedo, 42 cm. X 31 cm., the response of which did 
not show the prolonged “after-effect.” It was placed upon the apparatus previously 
described; the total response to excitation with Galv. yfo was + 7'0 scale. 
The quickening of the response as the temperature rose rendered it necessary to 
shorten the time of closure of the galvanometer circuit, which was thus fixed 
at '005". 
3 u 2 
