The disheartening aphorism, in which Hippocrates summed up the experience of his life—“Art is long and life is short, the occasion is fleeting, experiment is dangerous, and judgment is difficult”—is more true of the study of insanity than of any other department of medicine. Were any proof needed of this, it would be sufficient to point to the classification of mental diseases, the symptomatological plan adopted until recently corresponding to the earliest nosology of ordinary medicine, while the schemes which task the ingenuity of a Skae or a Bucknill have a great likeness to the “Phthisiologia” of Morton, or to the nosologies of Sauvages and Cullen.