2. In a state of health, different persons will have different degrees of sensibility to the electric current, depending on their varied nervous susceptibility. Again, the same person will be much less sensitive to the current when directed to the spine, particularly the lower part of it, and to the stomach, than when directed to most other parts. Also, where bones lie near the surface, the periosteum--the membrane immediately investing the bone--is apt to feel more sensibly under the electrodes than the muscular parts. But these variations soon become so familiar to the practitioner that he finds no difficulty in making the proper allowances for them. In making an electrical examination, the two following questions present themselves to be answered: First, whether anywhere, and, if so, where is there a morbid electrical state in the body of this patient? Second, what is the electrical condition of that unhealthy part? Is it _positive_ or _negative_? These questions being answered, according to the tests just given, the well-instructed practitioner is prepared to go on and treat the patient judiciously, and with success, if success be attainable by any form of medication. Let me next say, It is best, as a general rule, to make examinations with the _negative pole_. The reason of this is that, since the current is always more energetic under the negative than under the positive pole, it makes itself more sensibly _felt_ there than under the positive pole. Indeed, it will commonly be felt even to _painfulness_ there, if the part were overcharged and inflamed before. Thus, under the negative electrode, the current readily detects any active disease. But, if we be making the examination with the _positive pole_, as we come upon any point more or less inflamed, the current, quick as lightning, rushes away from such inflamed part to the part under the stationary negative pole, carrying with it, for the time being, more or less of that excess of electro-vital fluid which was in force at the inflamed point; so that _no pain_, perhaps, is experienced there; and thus the disease escapes detection.