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.