Portable batteries should be furnished with a milliampèremeter. A type of a compact dry cell direct current apparatus is shown in [Fig. 510b]. In the end the best apparatus proves the most economical.
Fig. 510b.—Direct Current Dry Cell Apparatus with Rheostat and Interrupted Current Attachment.
Electrodes.—Having the circuit or current under control, it now becomes necessary to attach electrodes to the free poles to be able to properly apply it to the patient. These electrodes vary considerably according to their use. The author will refer to only those that are of service in electrolysis.
Sponge Electrode.—The one electrode held by the patient is usually made of a metal disk covered with felt or sponge attached to a wooden handle and is shown in [Fig. 511].
Fig. 511.—Sponge Electrode.
This electrode represents the positive; the negative pole is held by the operator. When used, the felt or sponge is moistened with warm water to which a little salt has been added and is placed into the palm of the hand, sponge inward.
The author prefers to use a plain metal disk with the sponge and places a piece of absorbent cotton or gauze over it when in use for hygienic reason.
When the operator prefers he may resort to arm or wrist electrodes which can be clamped upon the limb and be held in position and shown in [Fig. 512].