Animal Electricity, electricity produced in the bodies of animals. Of this electricity there arc two kinds, the dynamical or galvanic and the statical. I. The production of dynamic electricity. Few discoveries in science have more importance than the almost accidental observation made by Luigi Galvani in 1786. After having examined the influence of the shock produced by a spark of the electrical machine on a frog's leg, Galvani observed a new and very curious phenomenon. He had skinned a frog, taking away its two legs with a part of the spine, and attached the whole to a copper hook which he had hung upon an iron railing near his laboratory. He stood watching to see if the electricity of the atmosphere would produce upon these legs the same effect as an electrical machine. After some time, having observed no sign of electrical influence, he decided to remove the frog's limbs, and while doing so he perceived the very muscular contraction which he had been vainly expecting to see produced by atmospheric electricity. He soon discovered the condition of this contraction, which was the contact of the moist limbs of the frog with the iron rail. Having substituted for the copper hook and iron rail a metallic arc composed of pieces of these two metals, he found that he could produce the contraction at will.

For the production of sudden muscular contraction and of a movement of the limb, it was only necessary to place one end of the arc in contact with a nerve or with the spinal canal, from which the nerves emerge, and with the other end one of the muscles of the leg. Galvani first published these experiments in 1791, in his celebrated work, De Viribus Electricitatis in Motu Musculari Commentarius. According to the theory proposed in this work, the muscles chiefly contain the animal electricity which manifested itself in the above experiments, and which he thought was supplied by the nerves and the blood. When the discoveries of Galvani became known, the whole civilized world was seized with admiration, and the curiosity to witness his experiments became universal. Du Bois-Reymond says: " Wherever frogs were to be found, and where two different kinds of metal could be procured, everybody was anxious to see the mangled limbs of frogs brought to life in this wonderful way. The physiologists believed that at length they should realize their visions of a vital power.

The physicians, whom Galvani had somewhat thoughtlessly led on with attempts to explain all kinds of nervous diseases, as sciatica, tetanus, and epilepsy, began to believe that no cure was impossible."Volta soon opposed the views of Galvani, and maintained that the pretended animal electricity was nothing but the electricity developed by the contact of two different metals. Galvani replied that with one metal only the muscular contraction was produced, although very feebly. Volta answered that the metals employed were not pure, and that as they had no homogeneity they acted like two metals. He showed that even the least physical alteration of a part of an arc of one metal was sufficient to make it act as if it were composed of two metals. Galvani, however, succeeded in producing contractions without the intervention of any metal whatever, by merely applying the nerve of a leg on the muscles or establishing a communication between the muscles and the nerve by a piece of moist animal tissue. Alexander von Humboldt took sides with Galvani against Volta. In employing very irritable frogs he found that there were strong muscular contractions in the following circumstances: 1, when the leg of a frog was bent back against the ischiatic nerve, both parts being still originally connected; 2, when the crural nerve and its muscles were connected by a fragment cut from the same nerve; 3, when a connection was established between two parts of the same nerve by means of some animal tissue.

In 1798 Galvani died, and the next year Volta discovered the pile; and, as it has been said, he then earned the right of exclaiming, with triumphant scorn, "I don't need your frog; give me two metals and a moist rag, and I will produce your animal electricity. Your frog is nothing but a moist conductor, and in this respect it is inferior to my wet rag." For nearly 30 years the supporters of the theory of animal electricity were silenced by the great discovery of Volta. - In 1825 Nobili, having rendered extremely sensitive the galvanometer (instrument for the measuring of galvanic currents), thought that the current which produces muscular contractions in the frog's legs might be detected by his instrument. He failed in \ his first attempt, the contractions taking place ! while the needle of his instrument stood still; but after having improved the instrument Le succeeded in obtaining a notable deflection of the needle. Unfortunately for the progress of science, Nobili admitted that the current funned in muscles was due to a differ-ence of temperature between the nerves and the muscles.

Nevertheless, he left to his suc-cessors some facts of great importance, the most interesting of which is that when the legs of several frogs are disposed in such a way that the nerves of one touch the muscles of another, this kind of pile increases in power with the number of legs. - To Prof. Carlo Matteucci belongs the merit of having positively proved the production of galvanic currents in muscles. His researches, those of Du Bois-Reymond, of Donne, of Baxter, of Brown-Sequard, of Eck-ard, and others, have established beyond doubt that a production of electricity is constantly going on in all the tissues of the living animal economy. The following facts, among others, have been well demonstrated: 1. When the electrodes or conductors of a galvanometer are applied one on one surface, and the other on another surface, of the animal body, a current takes place which moves the needle of the instrument. Thus Donne found a current between the skin and most of the internal membranes; thus Matteucci ascertained that there are different electrical states in the liver and the stomach; and thus also Baxter found a current between the internal surface of an intestinal vein and any part of the mucous membrane of the bowels. 2. There are electrical currents in muscles and nerves, as we will show hereafter. 3. All the organs of the body yield electrical currents when they have been divided, and when their normal surface and the surface of the section are in communication with the electrodes of a galvanometer. - No one has been more successful than Du Bois-Reymond in experimenting upon the production of galvanic or electrical currents in the various parts of the body.