57 



The results for the successive samples from near the ceiling were 

 14.5, 10.0, IS.O, and 21.0 parts of carbon dioxide in 10,000 parts of air by 

 volume ; near the floor the figure obtained was 14.5 in 3 successive samples. 

 Moisture readings with the hygrometer showed an increase from 52 to 5S 

 per cent, of saturation during the experiment near the ceiling, and from 

 55 to 58 below the table— a greater increase near the ceiling. These re- 

 sults show that the respiration products, carbon dioxide and moisture, 

 move upwards under these conditions. 



The influence of the temperature and moistness of the air of the room 

 on the upward movement of expired air will be shown in what follows. 



The temperature of the exhaled air is necessarily body temperature, 

 ;>T^ C. (D8.G° F.) ; that of the surrounding air of the room can be con- 

 trolled in an artificially heated building, and since cold air is denser than 

 warm air the lower the room temperature tlie greater will be the differ- 

 ence in density between it and the exhaled air, and the greater the tend- 

 ency of the latter to rise and be automatically removed from the respira- 

 tion level. Failure to take advantage of this [principle probably accounts 

 in part at least for the enervating and depressing effects of overheated 

 rooms in our homes, schools, offices, public buildings, and, worst of all, our 

 hotels. The usual temperature aimed at in this part of the country is 

 well up in the seventies — a very mistaken form of luxury ; it should be at 

 least ten degrees lower, and sensible habits in clothing, esiiecially on the 

 part of fashionable women, would soon remove the apparent hardship. 

 The accepted temperature for school rooms in England is said to be 58' 

 r., and the standard temperature of the room generally accepted in Euro- 

 pean scientific work is 15° or 15.5° C. (59° or 60° F.). 



The moisture factor is similar to the temi>erature factor in its effect 

 and to a less degree in its control. The exhaled air is always saturated 

 with moisture, the air of the room if at a higher temperature than out of 

 doors is not saturated unless moisture is added to it after entering the 

 building, and in frosty weather is commonly not over one-fifth saturated. 

 Since, as already stated, water vapor is lighter than air, and since it dis- 

 places an equal volume of air, tlie less moisture there is in the air of the 

 room the greater will be the tendency of the expired air to rise. There 

 may be other reasons against having very dry air in buildings, such as 

 irritation of the nose and throat, though this objection is at present de- 

 batable and not in agreement with the generally recognized benefits of 



