116 ANNUAL OF SCIENTIFIC DISCOVERY. 



electricity, which passed along the nerves to the electric organ, and 

 was there condensed and held in reserve. In a memoir recently 



E resented to the Academy of Sciences, M. Moreau brings forward 

 icts which conclusively settle this point. Having divided all the 

 nerves which supplied the electric organ on one side of the fish, thus 

 entirely removing all communication between the brain and the organ, 

 he excited the cut ends of these nerves, and produced electric dis- 

 charges. This is precisely analogous to the experiment of producing 

 contraction in a muscle removed from all connection with the brain 

 (or indeed in an amputated limb), by exciting its nerve. If the 

 experiment stopped there it would prove nothing. We might say 

 that the electric organ had a certain amount of electricity condensed 

 in it, and this was discharged when the nerves were irritated; such 

 has been the objection raised in the case of the stimulated muscle. 

 But in neither case does the experiment stop there. Electric fishes, it 

 is notorious, exhaust their electric power after a few shocks, and some 

 repose is necessary before their organ recovers its power. When, 

 therefore, the discharges had ceased, M. Moreau returned his mutilated 

 fish to the water ; allowed it a certain time for repose ; removed it 

 from the water, and on again irritating the cut ends of the nerves, 

 again produced powerful and reiterated discharges ; and these dis- 

 charges were not appreciably less intense than those produced from 

 the uninjured side ! " These experiments," says the report of the com- 

 mission, " conduct to the rigorous conclusion that the brain is only 

 an excitor, a point where the nerves receive a stimulus. The electric 

 organ is related to the brain as the muscles are related to the brain." 

 Precisely analogous is the case with the muscle when separated from 

 its nerve-centre ; repeated irritations of the nerve exhaust its neu- 

 rility so that it will no longer cause the muscle to contract ; but after 

 a period of repose, under proper conditions, the nerve will again, on 

 being stimulated, cause the muscle to contract. And that this is owing 

 to the nerve's having recovered its neurility, may be proved by this : 

 at a time when a stimulus applied to the nerve causes no contrac- 

 tion in the muscle, certain stimuli applied directly to the muscle cause 

 it to contract. Nay, more, at a time when a stimulus applied to a 

 point of a nerve at the distance of one inch from the muscle pro- 

 duces no contraction, this stimulus applied to a point at only half an 

 inch is followed by contraction. 



M. Moreau's observations are thus not only valuable as regards the 

 source of the electricity in fishes, and the part played by the brain 

 in the electrical phenomena, but also as confirming the existence of a 

 special force (neurility) in the nerves themselves, a force developed 

 out of the molecular changes of the nerve tissue, and not derived 

 from the brain. The nerves are agents, not passive conductors. 

 That nerves are not simply conductors, but are endowed with a spe- 

 cial force of their own, is strikingly seen in Pfliiger's empirical law, 

 Which is thus stated : " One and the same irritant which is applied 

 successively to two different points of a nerve does not irritate the 

 muscle in the same degree, but the irritation which is applied at the 

 greater distance from the muscle acts the more powerfully." Pfliiger 

 thinks that " the excitation increases in an avalanche-like manner, 

 and this is the more considerable the greater the portion of nerve 

 over which it travels." 





