GALVANISM. 



19 



action ; and that it is not merely the effect 

 of a direct impression of the electric 

 current on the nerves of the tongue. 



(60.) When the current of voltaic 

 electricity is made to pass along a nerve 

 distributed to any of the muscles of 

 voluntary motion, these muscles are 

 thrown into violent contractions of a 

 convulsive kind. It was an observation 

 of this kind that led the way, as we have 

 already seen, to the discovery of the gal- 

 vanic influence. The muscles of a frog 

 are, indeed, peculiarly sensible to this 

 influence, and are therefore the fittest 

 for the exhibition of this phenomenon, 

 with very weak galvanic powers. The 

 susceptibility of some of the animals 

 belonging to the class of vermes, is also 

 very great. If a crown piece be laid 

 upon a plate of zinc of larger size, and 

 a living leech be placed upon the silver 

 coin, it will suffer no inconvenience as 

 long as it remains in contact with the sil- 

 ver only ; but the moment it has stretched 

 out its head so as to touch the zinc, it 

 suddenly recoils, as if it had experienced 

 a painful shock. An earthworm will 

 also exhibit the same kind of sensitive- 

 ness ; and the same effect is still more 

 strikingly exhibited by the nais, which 

 is an aquatic worm. Humboldt found 

 that the lerncca, or water-serpent, and 

 even the tcenia, ascaris, and other spe- 

 cies of intestinal worms, had their move- 

 ments accelerated by the influence of 

 galvanism, which also speedily de- 

 stroyed their life. Powerful shocks from 

 a voltaic battery are no less immediately 

 fatal to animals, than discharges from 

 an ordinary electric battery.* Small 

 animals are easily killed by discharges 

 which would only produce a temporary 

 stunning effect on larger animals. 



(61.) Convulsive movements may be 

 excited by galvanism in the muscles of 

 an animal, after its death, as long as 

 they retain their contractility. These ef- 

 fects become exceedingly striking, when 

 large animals are made the subjects of 

 experiment, and when powerful batte- 

 ries are employed. Thus if two wires, 

 connected with the poles of a battery of 

 a hundred plates, be inserted into the 

 ears of an ox, or sheep, when the head 

 is removed from the body of the animal 

 recently killed, very strong actions will 

 be excited in the muscles of the face 

 every time the circuit is completed. 

 The convulsions are so general, as often 

 to impress the spectator with a belief 



* See Treatise ou Electricity. 5 182. 



that the animal has been restored to the 

 power of sensation, and that he is en- 

 during the most cruel sufferings. The 

 eyes are seen to open and shut sponta- 

 neously, they roll in the sockets as if 

 again endued with vision ; the pupils are 

 at the same time widely dilated. The 

 nostrils vibrate as in the act of smell- 

 ing ; and the movements of mastication 

 are imitated by the jaws. The strug- 

 gles of the limbs of a horse galvanised, 

 soon after it has been killed, are so 

 powerful as to require the strength of 

 several persons to restrain them. 



(62.) It is needless to enter into the 

 details of experiments of a similar kind 

 performed in hospitals on limbs re- 

 moved by amputation ; or on the bodies 

 of criminals soon after their execution. A 

 great number of these are stated to have 

 been made at Turin, on the victims of 

 the guillotine ; and in this country, Al- 

 dini, by operating with a considerable 

 number of plates on the body of a cri- 

 minal executed at Newgate, produced 

 effects very similar to those already de- 

 scribed in the sheep and ox ; but which 

 were necessarily of a more impressive 

 character, from their conveying the 

 more terrific expressions of human pas- 

 sion and of human agony. 



(63.) Muscles whose actions, like 

 those of the heart, are not under the 

 guidance of the will, are less easily af- 

 fected by galvanism than the muscles of 

 voluntary motion. But Fowler, Vassali, 

 Humboldt, Nysten, and others, have 

 sufficiently proved that even these mus- 

 cles may, by the proper application of 

 this power, be made to contract. 



(64.) The most curious and hitherto 

 unexplained of the physiological effects 

 of galvanism, are those on the functions 

 of secretion, especially on that of the 

 gastric juice, a fluid which is essentially 

 subservient to the process of digestion. 

 But these topics appertain more to phy- 

 siology than to the subject of the pre- 

 sent treatise. 



CHAPTER V. 

 Theory of Galvanism. 



(65.) THE various attempts which have 

 at different times been made to explain 

 the phenomena of galvanism, by the 

 application of the laws which are known 

 to govern those of ordinary electricity, 

 have on the whole been attended with 

 very indifferent success ; and the theory 

 c 2 



