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

Fig. 4. cidedly prefer the plate machine, and the plate should not measure less than twenty inches. The room for operating should be a dry one. a^ ^ 9Jik When the air is moist it must be dried and warmed' by furnace heat, or other means, and the glass plate, as well as the insulat- ing supporters of the prime conductor, of the axle of the glass and of the rubber, should be rubbed with a hot, dry cloth, not only to free the machine of moisture, but also from dust, which is as hurtful as moisture to the preservation of electricity on in- sulated conductors. Hence, the apparatus, together with all the appliances about it, must be kept scrupulously neat and dry. I have found that in humid weather, or when the atmosphere is negative as from an approaching storm, that if the glass plate is moistened with a very trifle of sweet oil, it is of advantage; also, that the surface of the rubbers must be from time to time re- newed with an amalgam powder of zinc, or deuto-sulphuret of tin, which can be had of any philosophical instrument maker. Another arrangement or provision is also necessary ; and that is, a good contact conductor with the actual moist earth, or a large body of metal. This should be some way adjustable near the machine, so as to be readily put in contact with the rubber, or negative pole, while we are charging the prime conductor posi- tively, as also for drawing sparks from the patient, or for char- ging the Leyden jars; also, so that at another time it can be re- moved to the prime conductor while we are employing negative electricity from the rubber end of the machine, for the rubber is always the negative, and the prime conductor is positive. And here comes in the laiv, that the one is never evolved without the other; therefore, if we wish to use or accumulate the one, the