OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
505 
as far as the gills. The organ was left untouched, and the animal fixed on a perforated 
vertical boa.rd. Through the perforation the ventral surface of the organ was led off 
by one non-polarisable electrode, the other being placed upon a corresponding point on 
the dorsal skin covering the organ. A pair of fine platinum electrodes were placed 
under the second nerve. 
There was a slight electromotive difference between the dorsal and ventral contacts, 
amounting to + •002. The nerve was now excited by the break of the current of two 
Grove cells placed in the primary circuit of the induction apparatus. It was noticed 
that a considerable strength of induction current had to be used before an organ 
response could be obtained. This point has been observed and commented upon by 
du Bois-Reymond (26). With the secondary coil at 5 cm. the galvanometric effect 
obtained by excitation was = -f- 750 scale G. xq ; the sign 4- signifying that a current 
passed through the galvanometer directed from the dorsal to the ventral leading-off 
electrode. 
A preliminary rheotome experiment was now made, the short-circuiting key K, 
being fixed at •01" after the exciting key K 1? whilst K 3 was moved so as to lengthen 
the duration of the galvanometer closure. 
O 
Time of closure of galvanometer, the 1 
moment of excitation being zero J 
0l"-014" 
•01"—015" 
•oi"—oie" 
| 
•01 ,, --0165 // •01 // --0225 ,/ 
■01"—0275" 
Deflections observed in gal¬ 
vanometer. (Where more 
than one reading is given, it 
indicates another experi¬ 
ment under same condi¬ 
tions.) 
0 
0 
0 
+ 65 
+ 72 
+ 65 
+ 240 
+ 550 + 500 
G. 
+ 650 
G. 4j- 
This showed that in this preparation the electromotive response, as indicated by 
the galvanometer, commenced at Tool) /, after excitation of the nerve, and was fully 
developed by toou" after excitation. 
The rapid development of the response is also shown in the next experiment, in 
which the organ of the other side of the same animal was led off, and all the electrical 
nerve trunks excited. Here, with a galvanometric closure of from '01—'014, no 
effect occurred after excitation; with ’Ol-’OISS, an effect of -f- 195 scale; with 
'01-’0165 a large effect shot the needle off the scale (-]- oo ). 
On examining this same preparation half-an-hour or so later, the time relations of 
the effect were found to have changed thus :— 
Galvanometer closure . 
■01"--012" 
•01V0125" 
•or-014" 
•01"--015" 
Deflections. 
0 
0 
+ 55 
+ 165 
+ to 
3 T 
MDCCCLXXXVII.-B. 
