676 COMPARATIVE. HISTORICAL. 



The discharge is thus, like tetanus, a discontinuous process. However, isolated 

 individual discharges also take place, in the torpedo 0.006 second in duration, which 

 thus would correspond to single muscular contractions. Veratrin causes marked 

 discharges, comparable to the veratrin muscular tracings (p. 263). Mechanical, 

 thermal, chemical, and tetanic-electrical stimuli give rise to discharge-shocks. 

 During the occurrence of the electrical shock in the fish, a number of currents pass 

 also through the muscles of the animal. In the ray the muscles are thrown into 

 contraction, while in the eel and the catfish they remain at rest. An electrical 

 ray may give fifty shocks in a minute; it then becomes fatigued and must re- 

 cuperate; it is capable also of discharging the organ but partially. The activity 

 of the organ is enfeebled by cooling and increased by heating it to about 22 . 

 The organ is thrown into a state of tetanus by strychnin and it is paralyzed by 

 curare. Irritation of the electrical lobe of the ray causes discharge; cold retards 

 the discharge. Division of the electrical nerve paralyzes the organ. The electrical 

 fish are themselves only slightly sensitive to strong faradic currents passed into 

 the water surrounding them. 



The substance of the electrical organ is simply refracting; excised portions 

 exhibit a resting current that has the same direction as the shock and is increased 

 by heat. Tetanus of the organ enfeebles the current. Mormyrus, raja, and gym- 

 narchus are among the "feebly electrical fish," whose discharge is incomparably 

 feebler, but which possess an organ, formerly improperly designated "pseudo- 

 electrical," analogous in construction to that of the "strongly electrical fish" 

 previously mentioned. 



Historical. The ancients were familiar with the shocks of the electrical fish 

 -of the Mediterranean Sea. Richer (1672) made the first reports upon the elec- 

 trical eel. Walsh (1772) investigated experimentally the discharge and the power 

 of the rays to give shocks. J. Davy was able to magnetize bits of steel by means 

 of the shocks, to deflect the magnetic needle, and to induce electrolysis. In addi- 

 tion to the investigators named, Becquerel, Brechet, and Matteucci studied the 

 direction of the discharging current, from which the last named and Linari ob- 

 tained from 8 to 10 sparks. Al. v. Humboldt described the mode of life and the 

 action of the gymnoti ("trembladores") of South America, which are able to 

 throw down even horses by their shock. 



Hausen (1743) and de Sauvages (1744) assumed the active force in the nerves 

 to be electricity. ' The actual investigations into animal electricity begin after 

 Caldini (1756) had first observed that the muscles of the frog move on applying 

 an electrical current with Luigi Galvani (1789-92), who observed contractions 

 in the frog's thigh as a result of the return stroke on discharge of the electrical 

 machine and likewise when the muscle was placed in contact with two different 

 metals. He believed that the nerves and the muscles possess the power of gen- 

 erating electricity independently. Alessandro Volta, on the other hand, attributed 

 the contraction in the second experiment to an electrical current, whose source 

 is situated outside of the frog-preparation at the point of contact of the hetero- 

 geneous metals. The contraction without metals of Galvani and Aldini (1794) 

 appeared at first to contradict this view. Then, the latter showed that the animal 

 parts themselves must contain sources of electricity. Pfaff (1793) was the first 

 to observe the influence of the direction of the current upon the contraction of 

 the frog's leg stimulated from the nerve. Bunzen prepared an effective pile from 

 muscles of the frog. The subject entered upon a new phase as a result of the 

 discovery of the galvanometer and of the classical methods introduced by du Bois- 

 Reymond in 1843. 



