The present editor, a former assistant of Dr. Hering, under took, at his desire, the task of superintending the publication of the work. Some additions to the text have been made, a few remedies introduced, and, at times, slight alterations in the ar rangement effected, but the well-known views of the author have been respected in whatever has been done, but for unavoidable reasons, the issue of the present edition has been delayed until this time.