THE ANIMAL AS A PRIME MOVER. 329 



in which the galvanometer is made to reveal a current passing from an 

 uuflexed arm to the other side and into the arm, which, contracting its 

 muscles strongly, grasps an object forcibly, especially interests the 

 student of the vital machine as indicating, in correspondence with 

 the fundamental laws of energetics in this case of electric action, as in 

 thermodynamic operations, the reduction of the energy supply by con- 

 version into mechanical work. 1 



The experiments of the Italian physicists and of Dr. Ure on cadav- 

 ers are familiar proofs of the substitutive value of the electric fluid and 

 the vital fluid, if, indeed, they are not evidence of their identity; and 

 the still more familiar experiences of all who have had to work with 

 electricity in any form at moderate or high tensions may be accepted 

 as more convincing testimony of the relationship of the one form of 

 energy to the other. The discovery by Pouillet and the later inves- 

 tigations of Donne, Becquerel, and others relative to the now well- 

 recognized form of vegetable electricity constitute an interesting if 

 superfluous confirmation of the idea that nature employs the electric 

 current in her work much more generally than is popularly supposed. 



The identity of animal electricity with the familiar forms of that 

 energy is perhaps best shown by the fact that where, as in the gym- 

 notus and torpedo, the best known among some fifty such creatures, 

 the fluid is made the means of attack and defense, thus necessarily 

 being given considerable volume and tension, it responds to every test 

 customarily employed to identify and measure the voltaic current. 



The assumption, which perhaps may now be fairly taken as possess- 

 ing a basis of probability, that electrical or some related or in many 

 ways similar form of energy may prove to be an intermediary between 

 the chemical energy known to be a necessary initial action in the 

 reduction to the active form of potential energy supplied to the vital 

 system, and those ultimate energy products — mechanical power, heat, 

 sometimes light, and always physiological manifestations — is strongly 

 corroborated by the facts developed by research in those organisms 

 which most extensively and strikingly exhibit that kinetic energy. It is 

 known not only that about fifty creatures are capable of applying the 

 electric fluid to their own purposes, in defense and in pursuit of their 

 prey, but that all species of the ray family have at least rudimentary 

 electric organs, a fact first stated explicitly probably by Robin. Five 

 species are known to be capable of producing a sensible, often pow- 

 erful, electric discharge. Muscheubroeck, Walsh, Davy, Becquerel, 

 Breschet, Linari, Matteucci, Moreau, and others, some of whom have 

 been elsewhere mentioned, have shown this fact and have revealed dis- 

 tinctly the identity of this energy of these fishes and other creatures 

 with the electricity now familiar to us in a thousand daily operations. 

 Marey has shown that the discharge is effected by transmission of the 



1 Recherches d'61ectricit6 auimale. Aunales do Chemie de Physique, 3e sevie, T. 

 XXX, page 119. 



