414 ELECTRO-PHYSIOLOGY CHAP. 



was put on" (4 d, ii. 618). Of Torpedo, too, we know that "it 

 keeps up a series of discharges at more than seconds speed, for 

 over a minute." Schonlein states that the living organ, with 

 intact circulation, cannot give more than 1000 shocks, either 

 when the discharges follow spontaneously upon strong protracted 

 stimulation of the animal, or when they are artificially discharged 

 from preparations of the organ. In the first case the animal 

 requires a longer recovery (at least a quarter of an hour) for 

 the restoration of its power of discharge. The excited organ, on 

 the other hand (unlike muscle), shows no recovery after con- 

 tinuous excitation of only 10 sec. with tetanising induction 

 currents. Sachs' gymnotus was electrically non-fatiguable. 

 200300 shocks could be elicited from it without perceptible 

 diminution ; an animal which had presumably discharged 150 

 times in an hour could still send a powerful shock through a 

 chain of eight persons, if those at the ends were in contact with 

 its head and tail (du Bois-Eeymond, 4 e, p. 256). 



We have seen that Cavendish (1776) arrived, by means of a 

 submerged model of Torpedo, connected with a Ley den jar, at a 

 substantially correct idea of the distribution of potential on the 

 surface, and in the surrounding water as shown by the 

 accompanying schema, Fig. 269. The improvement in physical 

 technique, more particularly the introduction of the galvano- 

 meter, enabled Colladon, and still more du Bois-Eeymond, to 

 confirm and enlarge the results of Cavendish in all essential 

 points (4 g, h, p. 193). Colladon formulated the three following 

 propositions in 1831 re distribution of potential upon the surface 

 of a torpedo in air, during discharge : 



1. "All points of the back are positive towards any point of 

 the ventral surface. Intensity of current diminishes in pro- 

 portion to the distance of these points from the organ ; at the tail 

 it is almost at zero. 



2. " Two asymmetrical points of the back, or two similar 

 points of the belly, almost always give current through the 

 galvanometer ; the point proximal to the organ is positive on 

 the dorsal, negative on the ventral surface. 



3. " There is no deflection in the galvanometer from two 

 symmetrical points of the back or belly." 



Since the columns, of which the E.M.F. increases with the 

 number of plates, diminish about 0'6 mm. in height from the 



