Under the impression that nervous power is nothing more than a form of electricity, which some physiologists were at one time disposed to believe, it was imagined that the latter agent might be made extremely useful in disease, by supplying the deficiency, or correcting the redundancy of the former. Theoretical notions, founded on this basis, have always had, and continue to have more or less influence upon therapeutics. It has been supposed that nervous action in excess might be controlled by the use of negative, and when deficient might be replaced by that of positive electricity. It has been considered important, through the direction of the electrical current, to imitate the natural presumed nervous currents; for one purpose to send the influence in one direction, for another in another direction; to procure in certain cases its transmission by one set of nerves rather than another; in short, to make use of electricity as if it were really the true nervous fluid, and wield it, as that instrument is wielded under the powers of life, for the maintenance of all the functions in their due action and subordination. It is true that this supposition of the identity of the two agents has been quite abandoned, under the irresistible contradiction of experiment;* but there still remains the undoubted and extraordinary analogy between them, to sustain the conjecture that they might operate under similar laws upon the system, and that consequently electricity might, in many instances, be substituted for the nervous influence, if brought to bear on the system in a similar manner. I fear, however, that it will be necessary to abandon this view of the powers and uses of electricity.

With the facts at present known in relation to its effects on the system, it is best to consider it simply as a universal excitant, capable of stimulating any function or organ upon which it can be brought to bear directly into increased activity, and having this special advantage over every other remedial agent, that, by its peculiar nature, it is capable of being directed to, and in a great degree limited in, any part which it may be desirable to operate upon exclusively. It must be borne in mind that it is not by its accumulation that it is capable of fulfilling any therapeutic purpose, but only by movement; and hence it cannot be brought to exert a direct simultaneous influence upon the whole system; for it is scarcely possible so to direct its current, that it should pass at the same time through all parts of the body. It is, therefore, though a universal stimulant, necessarily more or less local in its therapeutic action at any one time.

With its universal stimulant power, it exercises a special excitant influence upon the properties of sensation and muscular contraction; and upon this influence its most important remedial applications are based.

Through the quick and powerful impression it makes upon the nervous centres, commonly designated as the shock, it is capable, if not carried too far, of arousing the whole system, and thus fulfilling another important indication.

By this same shock, in its more forcible application, it overwhelms, and for a time depresses or suspends function; and by a continued excitant influence, it exhausts excitability, and thus may induce secondary depression. It may consequently be made use of occasionally as a sedative agent. In the depressing influence of the shock, it has, if properly managed, this great advantage, that, as it acts mainly on the nervous system, the reaction which follows is also mainly nervous, and, therefore, not disposed to lead to fever or inflammation.

* This was demonstrated by the experiments of Matteucci and others; but an observation of M. Duchenne shows, in a striking point of view, the distinction of the two actions, the nervous, namely, and electric. According to that author, the muscles may be wholly insensible to electrical influence, and yet capable of acting under the influence of the will. (Electrisation Lucalisee, etc., p. 402).

Again, it may, in certain forms, be made to produce inflammation, and thus act revulsively.

The influences hitherto mentioned have been vital. But it also produces chemical effects, of which we may sometimes avail ourselves therapeutically.

From what has been just stated, the following practical indications for the use of electricity may be deduced: 1. to excite any particular function or organ which may be inactive or torpid, and which may stand in need of stimulation; 2. especially to stimulate parts in which sensation or the normal power of motion may be defective or wanting, as in paralytic conditions of the muscular power or general sensibility, or of the special senses; 3. to awaken the system generally from a state of torpor, as in asphyxia, syncope, and the poisonous effects of the narcotics; 4. to benumb deranged sensation, or suppress excessive muscular contraction, as in neuralgia, some forms of rheumatism, and tetanus; 5. to operate revulsively by inflaming or irritating the skin, as in various internal and subcutaneous affections, including chronic inflammations, rheumatism, etc.; 6. to alter morbid nutrition by stimulating the disintegrating process, and thus promoting the absorption of indolent tumours; and T. through its chemical agency to effect various objects, as the coagulation of the blood in aneurisms, the solution of stone in the bladder, and the extraction of poisonous metals from the system, for all which purposes it has been recommended and employed. It is, I believe, in some one of the above methods, or some combination of them, that it operates as a remedial agent. But to render it practically useful, we must be more precise, and consider severally the various diseases in which it may be used; pointing out in each the particular circumstances which may indicate or contraindicate it, and the particular modes of application most appropriate.