100 PHYSIOLOGY AND TEMPERANCE. 



places, such as chemical works, soap and bone factories, 

 are all harmful, and often spread such diseases as cholera, 

 typhoid fever and diphtheria. " Disease germs " float in the 

 air. and are carried from place to place. 



-^ Ventilation. Of the many sources of impurity we 

 have already given enough to show the necessity for a con- 

 stant and abundant supply of pure, fresh air in dwelling 

 houses, schools, halls, churches, etc. The rapidity with 

 which the oxygen in a room is taken up will depend upon 

 the number of persons occupying the room. We must also 

 take into consideration the amount consumed by fires, gas 

 and lamps. Then, too, it must be remembered that each 

 individual is giving off a quantity of impure material, which 

 will accumulate and become foul. The drowsiness, headache 

 and general feeling of languor and discomfort experienced in 

 a badly-ventilated room are attributable rather to the pres- 

 ence of this noxious matter than to the want of oxygen. 

 No system of ventilation is complete unless, in addition to 

 entrances for fresh air, there are exits for foul air. 



It is estimated that each individual should have for his 

 allowance about eight hundred cubic feet of fresh air, and 

 that this should be renewed at the rate of one cubic foot 

 per minute. To renew this in sufficient quantity, without 

 draught and without lowering the temperature, is the great 

 object to be attained by ventilation. No system is perfect 

 that does not fulfil these requirements. 



In summer, little difficulty is met with where there are 

 plenty of windows and doors. These give lots of space for 

 the entrance and outflow of air. Besides, in warm weather 

 it is not necessary to keep the heat confined in the room, 

 and as the temperature of the room and the outside air are 

 nearly alike, draughts are not very noticeable, and, if felt, 

 are not so severe, the atmosphere being soft and mild. The 

 winter season is the time when proper ventilation is most 



