Sydenham adopted the epidemic constitutions from Hippocrates, as he did much else in his method and practice. In the first and third books of the ‘Epidemics,’ Hippocrates describes three successive seasons and their reigning diseases in the island of Thasos, as well as a fourth plague-constitution which agrees exactly with the facts of the plague of Athens as described by Thucydides. The Greek term translated “constitution” is κατάστασις, which means literally a settling, appointing; ordaining, and in the epidemiological sense means the type of reigning disease as settled by the season. The method of Hippocrates is first to give an account of the weather--the winds, the rains, the temperature and the like,--and then to describe the diseases of the seasons[17]. Sydenham followed his model with remarkable closeness. The great plague of London has almost the same place in his series of years that the plague-constitution, the fourth in order, has in that of Hippocrates. It looks, indeed, as if Sydenham had begun with the year 1661, more for the purpose of having several constitutions preceding that of the plague than because he had any full observations of his own to record previous to 1665. He is also much influenced by the example of Hippocrates in giving prominence to the intermittent type of fevers. It was remarked by one of our best 18th century epidemiologists, Rogers of Cork, and with special reference to Sydenham’s “intermittent constitutions,” that fevers proper to the climate of Thasos were not likely to be identified in or near London excepted by a forced construction. _Sydenham’s Constitutions._