190 ELECTRIC FISHES. L.ECT. X. 



LECTURE X. 



ELECTRIC FISHES. PROPER CURRENT OF THE FROG. 



ARGUMENT. Electrical phenomena peculiar to certain animals. 

 Electric Fishes. Number of them known. The torpedo has been most 



frequently studied. 

 Torpedo ; the shock produced by it ; electrical phenomena of the discharge . 



Electric organs ; direction of the current; physiological function of the 



discharge ; influence of electricity, mechanical injury, heat, and chemi- 



cal agents on the electric organ. Nervous system of the torpedo ; the 



electric lobe of the brain. Analogies between muscular contractions 



and the discharge of the torpedo. 

 Gymnotus ; Humboldt's description of the mode of catching electric eels ; 



Faraday's experiments on the gymnotus ; direction of the current. 

 General structure and composition of the electric organs of fishes ; hypo- 



thesis of their action and of the influence of the nerves on them. 

 Silurus ; position of its poles. 

 Proper current of the frog; discovered by Galvani; is a phenomenon be- 



longing to all animals; its direction; has a common origin with the 



muscular current. 



IN the preceding lecture I have shown you that elec- 

 tricity is developed in the living muscular fibre, by the 

 chemical actions going on there ; and that by properly con- 

 ducted experiments it may be rendered manifest. The 

 muscular current is a general property of the living or* 

 ganism. To-day I proceed to bring under your consi- 

 deration the development of electricity peculiar to certain 

 animals. 



Electric Fishes. We are acquainted with five different 

 fishes which are endowed with this property: the Raia 



