178 THE POPULAR SCIENCE MONTHLY. 



In temperate climates the principal object of ventilation is the re- 

 placement of vitiated air with fresh. Artificial ventilation is produced 

 either by inducing a movement of air by means of draught-chimneys, 

 or by forcing in air through the agency of mechanical ventilators. A 

 trial has been made at the Lariboisiere Hospital of a system of venti- 

 lation in which the air is drawn from the roof and forced into flues 

 that ramify into the several halls to be ventilated. At the moment of 

 entering the halls the air is heated by being brought in contact with 

 steam-pipes, so that a uniform temperature of 78° is maintained in the 

 wards, with an atmosphere free from odor. Notwithstanding purity 

 of air is secured, the mortality in this institution is not inferior to that 

 in non-ventilated hospitals. This is attributed by M. Bouchardat to 

 the mischievous influence of the high temperature which they endeavor 

 to maintain. He favors heating and ventilation by open fire-places. 

 This method is preferred in London, where fires are kept up in summer 

 as well as in winter, at least in the principal office of the institution, 

 and the windows are opened at all times when it is possible, while me- 

 chanical ventilating apparatus is used only exceptionally. The air, 

 sucked in by the strong draught of the chimneys, enters by the joints 

 of the doors and windows. The patients enjoy the sight of the fire and 

 the pleasant feeling of direct radiation, while they collect around the 

 hearths and breathe an air that has not been changed by contact with 

 a heated surface. Possibly the English go too far in this direction. 

 " The importance of pure air," says M. Proust, " has perhaps been 

 exaggerated in some cases by the English physicians, whose example 

 the Americans have followed. It is advisable, according to them, to 

 leave the larger openings, no matter what the weather may be, the 

 windows of dormitories and bedrooms, open during the night. These 

 principles, almost universally observed in the countries of which we 

 speak, entail, in our opinion, great inconveniences." There is really 

 some danger in exposing one's self to cold during sleep. 



The study of the questions of heating and ventilation has made 

 considerable progress in France during the last fifteen or twenty years. 

 The construction of numerous school-houses has especially been the 

 occasion of many praiseworthy improvements, but much still remains 

 to be done. Dr. Larget, in an interesting work on rural habitations, 

 has pointed out an apparent relation between the number of openings 

 indicated in the tax-list of doors and windows and the mortality. The 

 general average, for France, of the number of openings per inhabitant, 

 is one and a half. In one hundred departments, in which the number 

 is less than the mean, fifty-five show a higher mortality, and forty- 

 five a mortality equal to the average ; while, in a hundred departments 

 in which the number is greater than the mean, sixty show a lower rate 

 of mortality than the average, and only twenty-five a higher rate. 



Another point which is too easily forgotten is that, like the walls, 

 floors are permeable to the air. The atmosphere is not bounded by 



