Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

pair was first pointed out by Faraday. M. Matteucci next gave the equivalents for a pile or series of batteries, by using as a good electrolite a solution of the sulphate of copper. If the battery, for example, is composed of ten cups and pairs, then ten equivalents of zinc must be consumed to decompose one equiva- lent of water — thirty where there are thirty cups, and so on. It would seem, then, to be much better to employ only one or two cups and pairs, since to produce the same effects, where no great resistance is to be overcome, we can save some ten to thirty parts of zinc. But we find that the decomposition is less free, and also the electrolite requires a current possessing a certain degree of intensity, or, what amounts to the same thing, having an electro-motive force of a certain power, which can best be given it by multiplying the number of cups. So, also, as regards great resistances that are to be surmounted; M. De la Rive says, " When a current is called upon to trav- erse a long telegraph wire, it is necessary for it to be accom- plished to use a numerous succession of cups, for if it tfere attempted to be produced by only one or two cups and pairs, no matter how great their size and power, it would not have sufficient intensity to overcome the resistance of the long wire." Wc must also be reminded, that the size of surface of the gal- vanic pair or pairs is able to influence only the quantity of chemi- cal action exerted in a given time ; but that it can in no way modify the electro-motive force of the pair or pairs, nor will there be the capability of the produced electricity for surmount- ing a given resistance; for where this resistance exceeds a certain bound, itself limits the quantity of efficacious chemical, or catalytical action, by the very deficient quantity of electricity that can be transmitted in a given time, and hence renders use- less the increased surface of the plates beyond a certain size, which is in relation to that of the resistance and kind of work to be done. The quantity of the current is in proportion to the size of the pair; the intensity of a given current is in pro- portion to the number of pairs. On the whole, then, we see that the law of electro-chemical action, as far as it concerns the electrolysis placed in the given