246 ELECTRIC CURRENT. L.ECT. XII. XIII. 



nerves are due rather to a difference of structure than to a 

 different state of the nervous fluid. 



Effects on the Nerves of Sensation. Let us now pass to 

 the nerves of sensation. Magendie caused the current to 

 pass through the optic nerve of a living animal without 

 obtaining contractions or symptoms of pain. In operating 

 on himself, by touching with the extremities of a pile, 

 formed by a single element, the ear and the eye, or the ear 

 and the tongue, or the eye and the tongue, he obtained 

 sensations of sound, flashes of light and a peculiar taste. 

 These effects could only depend on an action exercised by 

 the current on the sensorial nerves of these organs, and not 

 on the contractions excited in the muscles dependent on 

 them. In fact, a very feeble current, insufficient to excite 

 the slightest muscular movement, is capable of acting upon 

 the senses. The peculiar taste cannot be attributed to the 

 impression exercised upon the tongue by substances pro- 

 duced by the decomposition of the salts of the saliva effected 

 by the pile; for a very feeble current, and one that is unable 

 to cause this decomposition, is yet sufficiently strong to give 

 rise to the electric sensation upon the tongue. 



Effects on the Ganglionic Nerves. A few words, in the 

 last place, on the action of the current on the nerves of the 

 ganglionic system. For the little that we know on this 

 subject we are indebted to the celebrated Humboldt. 



When we transmit a current through the heart of a 

 recently killed animal, a few instances after pulsations have 

 ceased, we observe that this organ recovers its usual move- 

 ments some time after the passage of the electric current ; 

 and that these movements are preserved for a certain time 

 after the organ has been withdrawn from the action of the 

 current. 



If, instead of waiting until the natural movements of the 

 heart have entirely ceased, we transmit the current when 



