CHAP. XI.] MATTEUCCI'S PHYSIOLOGICAL RESEARCHES. 377 



this effect is due to an electric current developed by the muscle, because it is 

 necessary that the nerve should touch the muscle at two points ; and because, 

 if the nerve be brought into similar contact with two points of any other body, 

 no such effect will follow. To guard against the fallacy that might arise from 

 contact with the blood, Matteucci shews, that if a nerve be brought into con- 

 tact with a layer of blood at two different points, no evidence of an electric 

 current will appear. In this, and all experiments with the galvanoscopic frog, 

 it is to be remembered, that the frog's leg must be held in the glass tube to 

 insure perfect insulation. The experiment is always followed by the same 

 results, whatever be the muscle of the animal touched, or even if muscles 

 separated from the animal be operated on. The indications of the electric 

 current remain longest in those animals in which muscular contractility lasts 

 longest ; in cold-blooded animals, such as fish and reptiles, Matteucci has seen 

 the phenomena last for many hours. The current is sufficient to excite the 

 nerve of a warm-blooded animal. The thighs of a rabbit having been removed, 

 a long portion of the crural nerve was dissected out, and the muscles exposed. 

 With a glass tube the nerve was raised and brought to touch the muscles at 

 two points, when the whole limb was thrown into contraction. 



So far distinct evidence was afforded by the animal galvanometer (so to 

 speak) of the existence of a muscular current. When the frog's leg becomes a 

 little weak, it indicates the direction of the current to be from the interior to 

 the surface of the muscle. 



In order to demonstrate the influence of this current on the galvanometer, 

 a particular arrangement is necessary. 



Several small cup-like cavities are scooped out in a piece of wood, twelve 

 inches square, and an inch and a half thick. The wood and its little cavities 

 are coated over with a layer of varnish, or small capsules sunk into the wood 

 may be employed. Five or six frogs are prepared by flaying the posterior ex- 

 tremities, and the legs are separated by disarticulating them at the knee ; 

 which must be done with care, in order not to wound the mass of crural 

 muscles. Next, each thigh is divided at its middle, and thus a certain number 

 of conical masses (the lower halves of the thighs) are obtained. These must 

 be arranged on the board in a chain. One half-thigh is placed at the edge of 

 one of the cavities, with its apex to the cavity, and the cut surface outwards ; 

 and the chain is completed by arranging the others in a semicircle, so that the 

 apex of one freely touches the cut surface of the other, and the piece which 

 forms the opposite extreme of the series ought to touch the edge of another of 

 the cavities by its cut surface. Thus a pile is formed, of which one of the ex- 

 tremities is the interior of the muscle, and the other its external surface. The 

 board, with the muscular pile arranged upon it in this way, is now brought to 

 the galvanometer, the platinum poles of which, if it be a very sensitive one, 

 have been some time placed in distilled water ; or, if not very sensitive, in a 

 saline solution. The next step of the experiment is with a pipette, to pour 

 into the cavities with which the extremes of the pile are connected, either 

 water or some of the saline solution, according as the plates of the galvano- 

 meter have been immersed in either of those fluids. 



The platinum poles of the galvanometer are now withdrawn from the fluid 

 in which they had been immersed, and introduced into the fluid of either of 

 the cavities ; if no deviation of the needle follow this, they are at the same 

 time plunged into the two extreme cavities of the pile, so as to close the 



