Electricity and Galvanism. 131 



believed to be always in an electric condition, the interior being nega- 

 tive, the exterior positive. He also noticed the curious fact, that in 

 experiments on frogs, the nerves lose their irritability to the stimu- 

 lus of electricity at their origin first, retaining it longest at their 

 extremities ; and on this hazarded an opinion that probably the dis- 

 tal extremities are really the origin of these structures. Both these 

 statements are of deep interest ; the former from its bearing on the 

 late researches of Prof. Matteucci, the latter from its curious con- 

 nection with some views of Dr. M. Hall, regarding the centripetal 

 origin of incident nerves. 



It may now be asked, what proof do we possess that the action on 

 muscular fibre to which I have alluded, is really produced by electric 

 currents ? It is true that this is generally taken for granted, but 

 still it is important to review our proofs. One great evidence in 

 favour of this opinion is at once found in the fact, that contractions 

 produced in frogs can only be excited when connection is made be- 

 tween a nerve and muscle by a conductor of electricity, all other 

 bodies interfering with the production of this phenomenon. The 

 only thing amounting to positive proof before the researches of Mat- 

 teucci is an experiment of Valli, in which he formed a sort of bottle 

 of fourteen prepared frogs, and by the electricity thus accumulated 

 succeeded in producing the phenomena of divergence in a delicate 

 electrometer. It is to be regretted that no accurate account of this 

 experiment has been left on record ; for if true, it must be regarded 

 as most satisfactory in proving the identity of the electricity of the 

 frog with that obtained from other sources. 



The recent researches of Prof. Matteucci, of Pisa, have, however, 

 completely set this matter at rest. He has incontestably proved 

 that currents of electricity are always circulating in the animal frame, 

 and not limited merely to cold-blooded reptiles, but are common to 

 fishes, birds, and mammalia. From the researches of this philoso- 

 pher it appears that a current of positive electricity is always 

 circulating from the interior to the exterior of a muscle ; and that 

 although the quantity developed is exceedingly small, yet that by 

 arranging a series of muscles having their exterior and interior surfaces 

 alternately connected, he developed sufficient electricity to produce 

 energetic effects. By thus arranging a series of half thighs of frogs, 



