Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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circuit, exterior to the series of pairs, i. e., placed between the poles, is a general law, and applies therefore equally well to what takes place in the interior of the battery, as through the route of the conductors, and the body embraced between the poles. The galvanic circuit of a series, when closed, is indeed but a circle composed in parts and by bits of conductors, united end to end in the series of the battery through which the cur- rent circulates, in a manner perfectly uniform and identical. In this there is brought about a change, by a succession of polariza- tions and recompositions of the contrary electricities of the con- secutive molecules, in such a way that if the current encounters resistance heat is evolved; if the molecules are compound, and the current is persistent, then there is chemical decomposition. All these effects are capable of being equal in all parts of the same cir- cuit or circle, (for such it is,) including the contents of the cups themselves, on the one side, and no less so the matter included between the electrodes that is to be operated upon, on the other. It is then understood that there is a marked difference be- tween the quantity of electricity produced, and the quantity that actually travels the circuit, or, in other words, that jjene- trates and passes through the object of work that is between the poles. This is always more or less retarded, or facilitated, aside from the power or kind of battery, according to the resist- ance or poor conducting property of the given object that is acted upon. The result is necessarily different. There cannot be a current, as we have shown, without some degree of both quantity and intensity ; but we now refer to these two relative properties. A single pair of almost any battery gives a quan- tity current, i. e., more of the character of quantity than of in- tensity. The former has the property for chemical decomposi- tion, the latter for overcoming the resistance of an indifferent or bad conductor. Generally, we can increase the quantity by the larger extent of metal surface in the one battery cup; also by the kind of metals that constitute the pair, or by the increase of acids or salts in the liquid of the battery; in a word, by extensive and rapid oxidation or chemical action in the liquids or metals in a given time. But the intensity is increased, as we