parts of water by weighing it in a hydrostatic balance. Much mischief has been done by nosological arrangements of diseases. They erect imaginary boundaries between things which are of a homogeneous nature. They degrade the human understanding, by substituting simple perceptions to its more dignified operations in judgment and reasoning. They gratify indolence in a physician, by fixing his attention upon the name of a disease, and thereby leading him to neglect the varying state of the system. They moreover lay a foundation for disputes among physicians, by diverting their attention from the simple, predisposing, and proximate, to the numerous, remote, and exciting causes of diseases, or to their more numerous and complicated effects. The whole materia medica is infected with the baneful consequences of the nomenclature of diseases, for every article in it is pointed only against their names, and hence the origin of the numerous contradictions among authors who describe the virtues and doses of the same medicines. By the rejection of the artificial arrangement of diseases, a revolution must follow in medicine. Observation and judgment will take the place of reading and memory, and prescriptions will be conformed to existing circumstances. The road to knowledge in medicine by this means will likewise be shortened; so that a young man will be able to qualify himself to practise physic at as much less expence of time and labour than formerly, as a child would learn to read and write by the help of the Roman alphabet, instead of Chinese characters. In thus rejecting the nosologies of the schools, I do not wish to see them banished from the libraries of physicians. When consulted as histories of the effects of diseases only, they may still be useful. I use the term diseases, in conformity to custom, for, properly speaking, disease is much a unit as fever. It consists simply of morbid action or excitement in some part of the body. Its different seats and degrees should no more be multiplied into different diseases, than the numerous and different effects of heat and light upon our globe should be multiplied into a plurality of suns. The advocates for Dr. Cullen's system of medicine will not, I hope, be offended by these observations. His immense stock of reputation will enable him to sustain the loss of his nosology without being impoverished by it. In my attempts to introduce a new arrangement of fevers, I shall only give a new direction to his efforts to improve the healing art.