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

stands in contradistinction to Galvanic electricity, for tins latter term I confine strictly to primary battery currents. The Electro-magnetic Machine gives us one of the most im- portant forms of induction currents with which we have to do in all electro-therapeutics. Under this head, then, we must consider the construction and action of such apparatus, which are important, inasmuch as they have been, and still are, the more frequently resorted to for medical purposes. But these ma- chines are found distributed already in great numbers through the various ranks of the medical profession in cities, towns, and counties over our continent, and also in very many private fam- ilies, but which are constructed in a great variety of ways, or rather forms, and therefore require particular investigation ; for it seems but reasonable that a medical man should well under- stand the instrument with which he proposes to operate. To be the better understood, we will set out with the primary law of physics, namely, that we can only derive force from some prior change of matter, which change ultimately resolves itself into some new form. If we find we have a certain amount of action in a single galvanic battery, it is given us as the effect of relative quantity. When the action takes place in a scries of elements, i. e., in more than one pair, then, in proportion to the number used, do we get the relative effects of intensity. More- over all the kinds of electro-magnetic machines yield us a cur- rent of peculiar intensity, although from a single galvanic pair whose simple characteristic is quantity. This excellent result is obtained by the power electricity possesses when passing through a parallel and approximat- ing wire, particularly when these wires are wound into coils of given lengths ; and still more is the greatness of this result enhanced by the magnetic power that is ^MJSJMI icia iJMBiw^9/ also developed and exer- _ „ _ . ,. „,. .„ -., , _ ciscd simultaneously in the Fig. 18. Electro-magnetic Hens, with \ ibrating Elec- ^ trotonie, but without its Battery. SaiUO direction.