RESPIRATION. THE GASEOUS INTERCHANGES 415 



room, proper openings at the opposite side, by which the old air 

 may pass off to make room for the fresh. An open fire in a room 

 will always keep up a current of air through it, and is the healthiest, 

 though not the most economical, method of warming an apart- 

 ment. 



In severe weather, when there is a tendency to keep rooms rather 

 tightly closed, a good plan is to open widely all doors and windows 

 for a few minutes each day, allowing fresh air to penetrate to 

 every corner, sweeping out the old air before it. This daily re- 

 newing, helped out by such ventilation as is afforded by ill-fitting 

 doors and windows, usually keeps the air of rooms in respirable 

 condition when not occupied by too many persons. The modern 

 habit of sleeping summer and winter in rooms with open windows 

 is to be highly commended, and should be even more generally 

 adopted. In fact the more outdoor air one can have, and at 

 the same time keep warm, the better for the bodily well-being. 

 The beneficial effects of fresh air and sunshine, especially in pul- 

 monary tuberculosis, cannot be too strongly emphasized. 



Reference was made above to the fact that discomfort in illy 

 ventilated rooms is more a matter of the amount of water vapor 

 present than of excess carbon dioxid or other poisons, or of de- 

 ficient oxygen. Recent careful studies have emphasized this 

 fact so clearly as to bring about marked changes in the practice 

 of ventilation experts, particularly in their treatment of the prob- 

 lem of ventilating auditoriums, and other places where large num- 

 bers of people gather temporarily. To secure highest bodily com- 

 fort there should be a certain degree of humidity in association 

 with a certain temperature. If the temperature changes the 

 amount of water vapor in the air should change to correspond. 

 Too low humidity is to be avoided as well as too high. An or- 

 dinary fault in ventilation is that the air is allowed to become too 

 dry. This is particularly true during the winter months when 

 artificial heat is used. To maintain the desired humidity in dwell- 

 ing houses of ordinary size during cold weather from lJ/ to 2 

 gallons of water should be evaporated in the house daily. Where 

 large numbers of house plants are kept the evaporation from their 

 leaves will contribute materially toward this amount. 



While comfort depends on proper relationship of temperature 

 and moisture, we must not lose sight of the fact that ultimate 



