It gives me pleasure to find this unpopular opinion of the non-contagion of the plague is not a new one. It was held by the Faculty of Medicine in Paris, in the beginning of the eighteenth century, and it has since been defended by Dr. Stoll, of Vienna, Dr. Samoilowitz, of Russia, and several other eminent physicians. Dr. Herberden has lately called in question the truth of all the stories that are upon record of the plague having been imported into England in the last century, and the researches of Sir Robert Wilson of the British army, and of Assellini, and several other French physicians, have produced the most satisfactory proofs of its not being a contagious disease in its native country. A discovery more pregnant with blessings to mankind has seldom been made. Pyramids of error, the works of successive ages and nations, must fall before it, and rivers of tears must be dried up by it. It is impossible fully to appreciate the immense benefits which await this mighty achievement of our science upon the affairs of the globe. Large cities shall no longer be the hot-beds of disease and death. Marshy grounds, teeming with pestilential exhalations, shall become the healthy abodes of men. A powerful source of repulsion between nations shall be removed, and commerce shall shake off the fetters which have been imposed upon it by expensive and vexatious quarantines. A red or a yellow eye shall no longer be the signal to desert a friend or a brother to perish alone in a garret or a barn, nor to expel the stranger from our houses, to seek an asylum in a public hospital, to avoid dying in the street. The number of diseases shall be lessened, and the most mortal of them shall be struck out of the list of human evils. To accelerate these events, it is incumbent upon the physicians of the United States to second the discoveries of their European brethren. It becomes them constantly to recollect, that we are the centinels of the health and lives of our fellow-citizens, and that there is a grade of benevolence in our profession much higher than that which arises from the cure of diseases. It consists in exterminating their causes. A DEFENCE OF _BLOOD-LETTING_, AS A REMEDY FOR CERTAIN DISEASES. Blood-letting, as a remedy for fevers, and certain other diseases, having lately been the subject of much discussion, and many objections having been made to it, which appear to be founded in error and fear, I have considered that a defence of it, by removing those objections, might render it more generally useful, in every part of the United States. I shall begin this subject by remarking, that blood-letting is indicated, in fevers of great morbid excitement, 1. By the sudden suppression or diminution of the natural discharges by the pores, bowels, and kidneys, whereby a plethora is induced in the system.