“The earliest statement which we possess of the mortality of our hospitals is in Sir William Petty’s work on Political Arithmetic, from which it appears, that in the year 1685 the proportion of the deaths to the cures in St. Bartholomew’s and St. Thomas’s hospitals was about 1 to 7. The annual printed report of St. Thomas’s hospital for 1689 is still preserved: the mortality was then about 1 in 10. During the ten years from 1773 to 1783, the mortality at St Thomas’s became still smaller, it was 1 in 14. About the year 1783, some improvements were made with respect to cleanliness and ventilation, and during the ten subsequent years the annual deaths were accordingly still fewer than before, less than 1 in 15. During the ten years intervening between 1803 and 1813 the improvement continued, and the proportion fell to only 1 in 16. The average during the 50 years from 1764 to 1813 was remarkably small, only 1 in 15.” _Parent Du Chátelet_ notices in the following terms the diminution in the mortality of the Hôtel Dieu from better ventilation:— “The mortality has diminished in the Hôtel Dieu in remarkable proportions. Without saying anything of the enlargement of the windows, of the warm clothing, of a better system of heating the apartments, are we to count for nothing the destruction of all the high houses which surrounded the Hôtel Dieu on every side? In our opinion the pure and dry air which circulates now in every part, the sun which penetrates there, the stoves which have been erected, have as much contributed to its healthiness as the suppression of the amphitheatres of anatomy which were in its neighbourhood.” The reports of other hospitals present similar and generally corroborative experience. In the space of four years, ending in 1784, in a badly-ventilated house, the Lying-in Hospital in Dublin, there died 2,944 children out of 7,650; but after freer ventilation, the deaths in the same period of time, and in a like number of children, amounted only to 279.