Muscle and Electric Organs 617 



There was some question regarding the presence of arginine in cephalo- 

 pods and another nitrogenous base, octopine, was isolated from muscle of 

 squid and scallop. Octopine, however, is a breakdown product formed from 

 arginine post mortem. 



ELECTRIC ORGANS 



The first bioelectric potentials observed by man were the discharges from 

 electric fish; recently the end-plate potential, the homologue of the electric 

 organ discharge, has been discovered. An interesting historical account of 

 electric organs is given by Cox.*^' The electric catfish, Malopter^is, was 

 known to the ancient Egyptians, and the Romans named the "torpedo" which 

 is an elasmobranch or ray. "Electric therapy" with electric fish was recom- 

 mended by Galen; it was used by Indians of Guiana and by eighteenth cen- 

 tury Europeans. The shock from electric fish was experienced for centuries, 

 but what it was remained a mystery. Toward the end of the eighteenth 

 century several observers suggested that the shock from certain fish was simi- 

 lar to lightning or to the electrostatic discharge from a Leyden jar. In 1773 

 John Walsh related that the shock from a Torpedo is conducted through 

 metals but not through glass or air; two years later Williamson made similar 

 observations on electric eels (Electrophorus, formerly called Gymnotus) 

 brought to North America from the Amazon region. The Cambridge physi- 

 cist Cavendish built a model of a Torpedo, from which he deduced the dis- 

 tinction between potential difference and quantity of electricity. Faraday^® 

 made crucial tests with a galvanometer and spark gap on Electrophorus, 

 thus demonstrating the electrical nature of the shock. He prophetically re- 

 marked in his diary: "Oersted showed how we were to convert electric into 

 magnetic forces and I had the delight of adding the other member of the 

 full relation, by reacting back again and converting magnetic into electric 

 forces. So perhaps in these organs where nature has provided the apparatus 

 by means of which the animal can exert and convert nervous into electric 

 force, we may be able, possessing in that point of view a power far beyond 

 that of the fish itself, to reconvert the electric into the nervous force." 



All electric fish are sluggish and depend on their electric discharge to 

 stun both their prey and their predators. The low sensitivity of electric fish 

 to their own shocks is unexplained; in an aquarium with numerous other 

 species of fish, electric fish, although obviously stimulated by each other's 

 shocks, may be unharmed while the other aquatic animals are killed.®^ 

 Stimuli of 220 volts did, however, damage the electric eel. 



An electric organ consists of columns of plates, electroplaxes, which run 

 dorsoventrally in the electric rays and longitudinally in the eel. In Torpedo 

 marmorata each organ has about 450 columns of 400 plates per column. Elec- 

 tric tissue comprises one sixth of the body weight in Torpedo and about 

 one half in Electrophorus. The electroplaxes or plates in each column are 

 in series electrically, the various columns in parallel. The long rows of many 

 plates in series in the eel tend to match the external resistance of the fresh- 

 water medium and the short rows in the Torpedo tend to match that in 

 sea water, each being well suited for power development in its own me- 

 dium. ^^ Each electric organ is entirely undex nervous control; in Torpedo 



