i86 



Adaptations of Fishes 



mead that leprosy may be so carried. It is further suggested 

 tliat the custom of eating the flesh of fishes raw almost uni- 

 versal in Japan, Hawaii, and other regions may be responsible 

 for the spread of certain contagious diseases, in which the fish 

 acts as an intemiediate host, much as certain mosquitoes spread 

 the germs of malaria and yellow fever. 



Electric Fishes. — Several species of fishes possess the power 

 to inflict electric shocks not unlike those of the Leyden jar. 

 This is useful in stunning their prey and especially in confound- 

 ing their enemies. In most cases these electric organs are 

 evidently developed from muscular substance. Their action, 

 which is largely voluntary, is in its nature like muscular action. 

 The power is soon exhausted and must be restored by rest and 

 food. The eft'ects of artificial stimulation and of poisons are 

 parallel with the effect of similar agents on muscles. 



In the electric rays or torpedos (Narcobatidcr) the electric 

 organs are large honeycomb-like structures, "vertical hexag- 



FiG. 140. — Electric Catfish, Torpedo rlecfriais (Gmelin). Congo River. 

 (After Boulenger.) 



onal jirisms," upwards of 400 of them, at the base of the pec- 

 toral fins. Each prism is filled "with a clear trembhng jeUy-like 

 substance." These fishes give a shock which is communicable 

 through a metallic conductor, as an iron spear or the handle of 

 a knife. It produces a peculiar and disagreeable sensation not 

 at all dangerous. It is said that this living battery shows all 

 the known qualities of magnetism, rendering the needle mag- 

 netic, decomposing chemical compounds, etc. In the Nile is 

 an electric catfish {Tor pain dcctriciis) having similar powers. 

 Its electric organ extends over the whole body, being thickest 

 Ijclow. It consists of rhomboidal cells of a firm gelatinous 

 substance. 



The electric eel {Electro pJiorns dcctriciis), the most powerful 



