When the Eighteenth Century gave birth to the Nineteenth, its great natal gift in medicine was vaccination. Jenner in 1798 for the first time announced his discovery of this great boon to the human race. In 1799 Dr. Benjamin Waterhouse, in Boston, obtained virus from Jenner and vaccinated four of his children, and in 1801 Dr. Valentine Seaman obtained virus from Dr. Waterhouse and performed the first vaccination in New York. During the Seventeenth and Eighteenth Centuries the annual death rate from smallpox in London ranged from 2 to 4 per 1,000 of population. In 1892 it was only 0.073 per 1,000. It is also stated on good authority that the mortality from smallpox in England alone, was 20,000 a year less after the introduction of vaccination than it was in the preceding century, and that its benefits to the world at large have been so great that the lancet of Jenner has saved more lives than were sacrificed by the sword of Napoleon. Each century in modern history has been marked by some important discovery in the field of medicine. The Seventeenth Century was notable for the discovery of the circulation of the blood by Harvey; the Eighteenth Century brought with it vaccination by Jenner. The Nineteenth Century’s greatest gift in this field has been anæsthesia, or insensibility to pain. Nature has wisely endowed man with nerves of sensation as danger signals for the conservation of life. Accident and disease, however, are the inseparable concomitants of human existence, and suffering and pain the ineffaceable legacies of mortality. Sometimes these nerves of sensation are no longer useful as monitors, and in the unavoidable emergency of accident, surgical operations, child birth, and certain diseases, suffering can do no good, and then pain--that Prince of Terrors--thrusting his presence upon the hapless victim, racks body and limb, calling forth groans, and shrieks and writhings, till the poor sufferer, possessed with a dominating agony which displaces all thought of life, memory of friends, and love of God, breaks down in unutterable distress, and prays for death and oblivion. To this poor sufferer insensibility is next to heaven. For the past half century all the formidable operations of the surgeon have been performed with the aid of anæsthetics and without suffering to the patient, producing happy recoveries, and greatly contributing to the success of the result by relieving the surgeon of the distraction of the patient’s pain, and the interference of his involuntary movements. Quite a number of anæsthetics are known and used to-day. Those more generally employed are--naming them in the order of their first application--nitrous oxide gas, ether, and chloroform. Nitrous oxide gas is chiefly used for the extraction of teeth. Sir Humphrey Davy, in 1800, was the first to observe the peculiar quality of nitrous oxide gas, which gave it the name of “laughing gas,” from the fact that it caused those inhaling it to act in a manner