COMPARATIVE. HISTORICAL. 675 



scribed. The earliest statement that Landois could find is made by Cardanus 

 (1553), who makes mention of the appearance of sparks from the hair of the 

 scalp. According to Hosford (1837) a nervous woman of Oxford exhibited sparks 

 more than 4 cm. long at the fingers while standing on insulated carpet. Sparks, 

 on combing the hair or on stroking cats, horses, etc., are often observed when 

 the air is dry. 



Of the various constituents of the body, recently voided urine has been found 

 to be electrically negative; likewise the freshly drawn threads of spiders' webs; 

 while the blood has been found to be positive. Also feathers and hairs become 

 charged with electricity if rubbed. 



COMPARATIVE. HISTORICAL. 



Among the most interesting phenomena in the domain of animal electricity 

 are exhibited by the electrical fish, of which about fifty varieties are known. The 

 electrical eel, gymnotus electricus, is found in the fresn waters of the Orinoco dis- 

 trict, and attains a length of 2.5 meters. The electrical rays include torpedo mar- 

 morata, from 30 to 70 cm. long; torpedo ocellata; nascinae, found in the Mediter- 

 ranean Sea; and a number of related species. The electrical catfish, malapterurus 

 electricus, is found in the Nile. Finally there is mormyrus, or Nile-pike. By 

 means of a special electrical organ these animals are able, in part voluntarily 

 (eel, catfish), in part on reflex stimulation (ray), to give severe electrical shocks. 

 The electrical organ consists of variously formed compartments bounded by con- 

 nective tissue and filled with a mucoid, gelatinous substance designated torpedo- 

 mucin by Weyl, to one surface of which the nerves pass and form a plexus. The 

 latter gives rise finally to a cellular plate representing the terminations of the 

 telodendrites and designated the electrical plate. By stimulation of the afferent 

 electrical nerves the shock-like discharge of the organ takes place. 



In the gymnoti the organ, which is comparable to a Voltaic pile arranged 

 longitudinally in a series of rows, extends on each side of the vertebral column 

 downward to the tail beneath the skin and receives from the anterior aspect 

 several branches from the intercostal nerves. In addition to the larger organ, 

 there is situated above the anal fins on each side a smaller one. The plates 

 in this situation are vertical, and the direction of the electrical ' current is, in the 

 fish, an ascending one, and in the conducting arc of closure, therefore, in the sur- 

 rounding water, a descending one. 



In the electrical catfish the organ, which surrounds the body of the fish like 

 a mantle, is similarly situated, and contains a single nerve-fiber whose axis-cylinder 

 arises in the vicinity of the medulla oblongata from a huge giant-cell, and is con- 

 stituted of dendritic processes. The plates in this animal also are vertical and 

 receive the nerves from the posterior aspect. The direction of the current when 

 the shock is given is descending in the fish. 



In the ray the organ is situated just beneath the skin to one side of the head, 

 extending to the thoracic fins. It receives several nerves, which arise from the 

 special portion of the brain, the electrical lobe, situated between the quadrigeminate 

 bodies and the medulla oblongata. The plates, which do not increase in number 

 with the growth of the animal, occupy a horizontal position. The nerve-filaments 

 pass from these plates from the ventral aspect. The current passes in the fish 

 from the ventral to the dorsal aspect. Torpedo occidentalis, of the eastern coast 

 of America, may attain a length of 1.5 meters and is capable of throwing down 

 a robust man by its discharge. 



It is believed that the electrical organs are modified muscles, in which histo- 

 logically the nerve-endings are highly developed, while the contractile substance 

 has disappeared, and in whose physiological activity the chemical potential is 

 transformed into electricity. In favor of this view is the circumstance that in 

 the process of development the organs are preformed in a manner analogous to 

 the muscles; further, that the organs in the resting state are neutral and in the 

 active or degenerated state are acid in reaction; finally, that they contain an 

 albuminous substance related to myosin, and that both after death exhibit signs 

 of rigidity. Stimulated organs, as well as muscles, exhibit an increase in phos- 

 phoric acid, resulting from decomposition of lecithin or nuclein. Both further 

 become exhausted, and moreover in both a period of latent irritation, lasting 

 o.o 1 6 second, follows actual irritation of the nerve, while a shock of the organ, 

 which thus resembles the current in an active muscle, lasts 0.07 second. About 

 25 such shocks together constitute a discharge, which lasts about 0.23 second. 



