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

heating and chemical by using a large and active battery with strong solution. Of course, it can be regulated or reversed in this respect, even to the lowest degree, by lifting the metal pair partly out of the fluid, or by diluting the fluid, or both. The intensity of the current, as regards tension, can be graduated to the greatest nicety by adjusting the soft iron or the bundle of wires that can be more or less pulled out of the end of the helix, which reduces the current, while pushing them in increases the current. So great is this range of difference that it is ab- solutely necessary to graduate the current in this way, invaria- bly before applying the moist electrodes to the patient. Another important point is to have the machine attached to the battery invariably but one way; and it is better to have the strongest pole always come to the right hand as we face the machine. We then can keep in view the whole, for this is the negative electrode, and the point where the current always leaves the patient. Of course, the other must be the positive pole, and where the current always enters the body or limb of the patient. By thus accustoming one's self to operate only in one way, it is more easy to keep the whole story of " current direction " clear, while the mind is more intent on the anatomical and physiologi- cal phenomena of the case. It is easy to determine which is the strongest, and hence negative electrode, by simply pressing the moist wash-leather or sponge of each electrode into the palm of each hand, and particularly if so as to cover the inner edge of the adductors of the thumbs, which will respond by contrac- tion most strongly to the negative electrode. The current should be strong, and the moist electrodes should be exchanged from hand to hand, back and forth, several times, until this is fairly demonstrated to our satisfaction. But we must always bear in mind that there is no absolutely positive or negative pole to any of these electro-magnetic apparatus. Only the more slight decompositions can be effected by any of these medical apparatus ; but this is shown at both poles simultaneously, and simply more at one than at the other.