To render the circumstances of the statement of deaths that has been given perfectly equal, it will be necessary to add, that the measles prevailed in the city, in the year 1802, as generally as they did in 1771. From the history that has been given, of the effects of the late improvements and discoveries in medicine upon human life, in Philadelphia, we are led to appreciate its importance and usefulness. It has been said, by its enemies, to move; but its motions have been asserted to be only in a circle. The facts that have been stated clearly prove, that it has moved, and rapidly too, within the last thirty years, in a straight line. To encourage and regulate application and enterprize in medicine hereafter, let us inquire to what causes we are indebted for the late discoveries and improvements in our science, and for their happy effects in reducing the number of deaths so far below their former proportion to the inhabitants of Philadelphia. The first cause I shall mention is the great physical changes which have taken place in the manners of our citizens in favour of health and life. A second cause, is the assistance which has been afforded to the practice of physic, by the numerous and important discoveries that have lately been made in anatomy, natural history, and chemistry, all of which have been conveyed, from time to time, to the physicians of the city, by means of the Philadelphia and hospital libraries, and by the lectures upon those branches of science which are annually delivered in the university of Pennsylvania. 3. The application of reasoning to our science has contributed greatly to extend its success in the cure of diseases. Simply to observe and to remember, are the humblest operations of the human mind. Brutes do both. But to _theorize_, that is, to _think_, or, in other language, to compare facts, to reject counterfeits, to dissolve the seeming affinity of such as are not true, to combine those that are related, though found in remote situations from each other, and, finally, to deduce practical and useful inferences from them, are the high prerogatives and interest of man, in all his intellectual pursuits, and in none more, than in the profession of medicine. 4. The accommodation of remedies to the changes which are induced in diseases by the late revolutions in our climate, seasons, and manners, has had a sensible influence in improving the practice of medicine in our city. The same diseases, like the descendants of the same families, lose their resemblance to each other by the lapse of time; and the almanacks of 1803 might as well be consulted to inform us of the monthly phases of the moon of the present year, as the experience of former years, or the books of foreign countries, be relied upon to regulate the practice of physic at the present time, in any of the cities of the United States.