But, as all diseases are merely the result of two conditions—namely, the injurious influence acting, and the body acted on—it matters not whether the injurious influence be sudden, violent, slow, moderate, chemical, mechanical, or what not; so the foregoing positions affect the whole practice of medicine, and must not be held as affecting any one part of it, but as influencing equally both medicine and surgery. We do trust that these few propositions will induce some to think; for, as Abernethy used to say, lectures will never make surgeons: and we feel equally confident that no books, no individual efforts, however costly or sincere, will really benefit or inform any portion of the public or the profession, except such of them as may be induced to _think_ for themselves. They have only to recollect that, in carrying out such principles, they must not measure their influence by their previously conceived notions; they must encourage labour when they see the profession willing, and not thwart them by showing that it will be labour in vain. There will soon be science, if it is encouraged: "Sint Mæcenates, non deerunt Flacci." If they are disposed to think investigation too minute to be practical, or precision too unpleasant to be necessary, let them remember the story of Professor Owen's beautiful application of minute relation, and that the distinction between a huge common quadruped and an unknown wingless bird could alone be discovered by particulars far more minute than they will be called on once in a hundred times to observe or to follow. The obligation we have already noticed has in some sense revolutionized the practice of medicine and surgery, and is no doubt the capital debt we owe to Abernethy; but there are many others. His application and adjustment of the operation of the trephine was a beautiful and discriminating achievement, and would alone have been sufficient to have raised an ordinary reputation. His first extension of John Hunter's operation for aneurism, shows how ready he was—when he could do so with advantage—to enlarge the application of that branch of our duties which he least valued—namely, operative surgery.