Of the famous Baron Boyer, author of a nine-volumed book on surgery, Doctor Holmes says, "I never saw him do more than look as if he wanted to cut a good collop out of a patient he was examining." Baron Larrey, the favorite surgeon of Napoleon, he describes as a short, square, substantial man, with iron-gray hair, red face, and white apron. To go round the Hotel des Invalides with Larrey was to live over the campaign of Napoleon, to look on the sun of Austerlitz, to hear the cannon of Marengo, to struggle through the icy waters of the Beresina, to shiver in the snows of the Russian retreat, and to gaze through the battle smoke upon the last charge of the red lancers on the redder field of Waterloo. Then there was Baron Dupuytren, "_ce grand homme de lautre côté de la rivièrè_,--with his high, full-doomed head and oracular utterances; Lisfrance, the great drawer of blood and hewer of members; Velpeau, who, coming to Paris in wooden shoes, and starving, almost, at first, raised himself to great eminence as surgeon and author; Broussais, the knotty-featured, savage old man who reminded one of a volcano, which had well-nigh used up its fire and brimstone, and Gabriel Audral, the rapid, fluent, fervid and imaginative speaker. "The object of our reverence, however, I might almost say idolatry," adds Doctor Holmes, "was Pierre Charles Alexandre Louis, a tall, rather spare, dignified personage, of serene and grave aspect, but with a pleasant smile and kindly voice for the student with whom he came into personal relations. "If I summed up the lessons of Louis in two expressions, they would be these: First, always make sure that you form a distinct and clear idea of the matter you are considering. Second, always avoid vague approximations where exact estimates are possible....