358 ELECTRO-PHYSIOLOGY CHAP. 



Eedi's predictive designation of the electrical organs of 

 Torpedo as " muscles " led, in the first instance, to a purely 

 mechanical theory of their action, which was most clearly set 

 forth by Borelli (1685). He assumed that the organs contracted 

 rapidly several times in succession, thus giving to the limbs in 

 contact with them a series of vigorous shocks, which produced a 

 cramp similar to that due to a blow on the elbow. This theory 

 was universally accepted, the most famous scientists, Reaumur, 

 Linnaeus, Haller, sanctioned it, and it may be said by 1750 to 

 have reigned supreme as the sole possible, and at the same time 

 adequate, explanation. Soon after the discovery of the Leyden 

 jar (1*745), a French botanist, Michael Adansoii (1751), travelling 

 on the Senegal, became acquainted with the far more energetic 

 action of Malapterurus, the shocks from which at once impressed 

 him (as previously noted by Gravesaiide ; du Bois-Eeymond, 

 4 e, p. 127) by their similarity to discharges from a Leyden 

 jar, more especially as it was found possible to lead them off 

 by long wires. The same was reported by Dutch explorers from 

 Surinam, of Gymnotus, the first account of which reached Europe 

 in 1672. It was found that the shock would pass through a 

 circuit of several persons, and, like the electric current, could 

 only be conveyed by conductors, and not by insulators (William- 

 son, 1773). Walsh had discovered the same in the previous 

 year at La Eochelle for Torpedo, and thus for the first time 

 established the electrical nature of the discharge (du Bois- 

 Eeymond, 4 c, p. 418). He showed at the same time that the 

 back and belly of the fish give a different electrical reaction at 

 the moment of the shock, and therefore held the " sickle-shaped 

 muscles " of Eedi to be an electrical apparatus, which the animal 

 could throw into voluntary activity. In a gymnotus sent in 

 1775 from Guiana to London, Walsh saw sparks leaping over a 

 gap in the discharging circuit, and was able to show the experi- 

 ment ten or twelve times consecutively to the Fellows of the 

 Eoyal Society (3, p. 158). From this time the attention of ex- 

 plorers in this department was mainly directed to establishing 

 the complete identity of the discharge from the fish with the 

 electrical current. Cavendish (1776) whose investigations on 

 Torpedo were so extensive that (as du Bois-Eeymond pointed out) 

 Faraday was the first to recover the same standpoint attempted 

 to imitate the action of the shock by ordinary electricity. On a 



