The profession as a whole has been committed before now to erroneous doctrines and injurious practices, which have been upheld by its solid authority for generations. Lesages satire upon blood-letting, in Gil Blas, which appeared in 1715, ought of itself to have made that practice ludicrous in the eyes of the world; but blood-letting survived a hundred years after that in all countries. . . It is difficult to conceive what will be the excuse made for a century of cowpoxing; but it cannot be doubted that the practice will appear in as absurd a light to the common sense of the twentieth century as blood-letting now does to us. Vaccination differs, however, from all previous errors of the faculty, in being maintained as the law of the land on the warrant of medical authority. That is the reason why the blow to professional credit can hardly help being severe, and why the efforts to ward if off have been, and will continue to be so ingenious.