Systems of nosology, theories of medicine, and classifications of natural objects and phenomena, agree in this one respect, that they are all eagerly embraced, strenuously defended, fall into disuse, and become subjects of ridicule. Such must be the fate of the Linnaean system of botany, as it has been of the other fancies of its author; and such must be the fate of every system not founded on organic structure and its modifications, or upon external form as connected with internal disposition. In 1766, he published a small work extending to only twenty-nine pages, entitled Clavis Medicinae duplex, Exterior et Interior, which may be considered as a syllabus of his lectures. It contains a view of his theory of medicine, and an arrangement of drugs in thirty orders, according to their sensible qualities. The last book which he produced was a continuation of his Mantissa, containing new species and genera, with a variety of emendations. Such of his writings as have not been already mentioned, will be noticed in a subsequent section; and in the mean time we resume our narrative, remarking, that few individuals had a longer scientific career than he; forty-four years having elapsed between the appearance of his first tract, the Hortus Uplandicus (in 1731) and the Mantissa (in 1771). It would appear that Linnaeus possessed a good constitution, although we have seen him suffering under attacks of rheumatism, nephritis, and gout. In 1764, as already mentioned, he had a violent attack of pleurisy; after which he passed the period of his convalescence at his villa of Hammarby, where, on the 9th July, he celebrated the 25th anniversary of his marriage. The same year he had the pleasure of marrying his eldest daughter to Lieutenant Bergencrantz.