GALVANIC ELECTRICITY. 45 



A tact so new, illustrated with so many experiments and much 

 ingenious reasoning, which professor Galvani soon published, could 

 not fail to attract the attention of physiologists all over Europe; 

 and the result of a vast number of experiments, equally cruel and 

 surprising, has been from time to time laid before the public by 

 Valli, Fowler, Monro, Volta, Hmnbolt, and others. 



Frogs, unhappily for themselves, have been found the most con. 

 venient subjects for these experiments, as they retain their muscular 

 irritability and susceptibility of the galvanic influence very long. 

 Many hours after they have been decapitated, or have had their 

 brain and spinal marrow destroyed, strong convulsions can be pro. 

 duced in them by the application of the metals. A leg separated 

 from the body will often continue capable of excitement for several 

 days. Nay, very distinct movements have been produced in frogs 

 pretty far advanced in the process of putrefaction. Ditfcrent kinds 

 of fishes, and many other animals, both of cold and warm blood, 

 have been subjected to similar experiments, and have exhibited the 

 same phenomena ; but the warm blooded animals lose their sus. 

 ceptibility of galvanism, as of every other stimulus, very soon afler 

 death. 



/ Almost any two metals will produce the movements; but, it is 



j believed, the most powerful are the fbllowing, in the order which 



^ they are here placed: 1. Zinc; 2. Tin; 3. Lead; in conjunction 



with 1. Gold: 2. Silver; 3. Molybdena; 4. Steel; 5. Copper. 



\Upon this point, however, authors are not perfectly agreed. 



The process by which these singular phenomena are produced 

 consists in effecting, by the use of the exciting apparatus, a mutual 

 communication between any two points of contact, more or less dis. 

 tant from one another, in a system of nervous and muscular organs. 

 The sphere of this mutual communication may be regarded as a 

 complete circle, divided into two parts. That part of it which con- 

 sists of the organs of the animal under the experiment has been 

 called the animal arc ; that which is formed by the galvanic instru- 

 ments has been called the excitatory arc. The latter usually con- 

 sists of more pieces than one ; of which some are named stays, 

 braces, &c. others communicators, from their respective uses. 



Besides the effects thus produced on the muscles, the impressions 

 made on the organs of sense are equally remarkable. And as the 

 experiments illustrating them may be easily repeated, we shall spe- 

 cify some of the most interesting. For instance, if a thiu plate of 



