The first of the Essays following appeared in "Scribner's Monthly," in July, 1880; and immediately became honored by the attention of the Medical Press throughout the country. The aggressive title of the paper, justified, in great measure, perhaps, the vigor of the criticism bestowed. Again and again the point was raised by reviewers that the problem presented by the title, was not solved or answered by the article itself. At this day, it perhaps may be mentioned that the question-"Does Vivisection Pay?" was never raised by the writer, who selected as his title the single word "Vivisection." The more taking headline was affixed by the editor of the magazine as more apt to arrest attention and arouse professional pugnacity. That in this latter respect it was eminently successful, the author had the best reason to remember. With this explanation-which is made simply to prevent future criticism on the same point-the old title is retained. If the present reader continues the inquiry here presented, he will learn wherein the writer believes in the utility of vivisection, and on the other hand, in what respects and under what conditions he very seriously questions whether any gains can possibly compensate the infinitely great cost.