In the summer of 1866, the author of this little book, moved by the repeated and earnest solicitation of his Medical Classes, prepared and printed a small pamphlet entitled Practical Principles of Medical Electricity, designed more particularly, as the present work also is, as a Hand-Book to assist the memory of those who have taken a regular course of Lectures from himself, or from some other competent instructor in the same general system of Practice. The edition of that work was exhausted somewhat more than a year ago. Still, the book has continued to be frequently called for. The author has, therefore, prepared, and now offers to the Profession, the present volume, comprising the substance of the previous work—corrected, improved in arrangement and form, and about doubled in size by the introduction of new matter. While he has reason for gratitude that the former manual, referred to above, has met with so favorable a reception, he can not but hope that the present work will be found even more acceptable and valuable to both practitioners and their patients.

It is but justice to say that the most essential principles of practice here presented did not originate with the present author, but with Prof. C. H. Bolles, of Philadelphia, their discoverer, from whom the writer received his first introduction to them. Yet, the explanations here given of the Law of Polarization, as respects the electric current in the circuit of the artificial machine, as well as respecting the natural magnets and magnetic currents of the human organism; the introduction of the long cord, with the explanation of its advantages; and also nearly everything of the philosophic theories here brought to view, the author alone is responsible for.

This work, like its little predecessor from the same pen, has been adapted exclusively to the use of Dr. Jerome Kidder's Electro-Magnetic Machine, manufactured and sold, at present, at No. 544 Broadway, New York; because the author, having used in his own practice a considerable variety of the most popular machines intended for therapeutic purposes, and having examined several others, believes this to be incomparably the best in use. Dr. Kidder has, with most laudable zeal, pressed on his researches and improvements in the manufacture of these instruments, until there seems to be scarcely anything more in them to be desired. They are certainly not equalled by any others in America, and probably not surpassed, if equalled, by any in the world.

D. C.

Plainfield, Ill., June, 1869.