i 9 2 THE POPULAR SCIENCE MONTHLY. 



cubic feet, of air expired by each sleeper during the night of eight 

 hours. This expired air contains 4 per cent, of carbonic acid. 

 ..100: 7 7. 7 7 :: 4 = 3.11 cubic feet of carbonic acid exhaled by each sleeper 

 during the night. Suppose the number of sleepers occupying the bed- 

 room to be four, this will give 3.11 x 4 = 12.44 cubic feet as the quan- 

 tity of carbonic acid which is exhaled by the four sleepers during the 

 eight hours of night. The room itself contains 960 cubic feet of air, 

 and through this 12.44 cubic feet of carbonic acid would have been 

 diffused by the termination of the night. It therefore follows that, if 

 no fresh air entered the room, and if in consequence the carbonic acid 

 had no means of escape, the air of the apartment would, at the end of 

 the eight hours of night, contain 1.29 per cent, of this gas: a quantity 

 sufficient to produce serious results. 



This statement, however, does not represent all the facts of the 

 case. It must be remembered that the oxygen contained in the air of 

 the room would be constantly undergoing reduction by respiration 

 during the night. If the quantity thus consumed were determined 

 from the quantity of carbonic acid exhaled, allowing for the fact that 

 15 per cent, more oxygen is taken into the blood than is contained in 

 the carbonic acid of the air expired, it will be found that from one- 

 third to one-half of the oxygen originally contained in the air of tbe 

 room would have been consumed by the end of the night. This re- 

 duction in the quantity of oxygen, and the great increase of carbonic 

 acid, would affect the body in two ways : firstly, by a deficiency of 

 oxygen ; and, secondly, by an excess of carbonic acid, in the air re- 

 spired. Hence the reduction of the one and the increase of the other 

 would render the air far more injurious than if only one of these 

 changes in its constitution had taken place. 



The actual result is not, however, in strict accordance with this 

 calculation, because fresh air, although in limited quantity, does find 

 its way into the room, and carbonic acid does, to a limited extent, find 

 its way out. These, therefore, would modify the constitution of the 

 air of the room at the close of night ; but they would still leave it 

 with an excess of carbonic acid injurious to life. 



It is found that when air moderately impregnated with carbonic 

 acid is inspired it greatly impedes the exhalation of more from the 

 lungs ; and that the greatest quantity of carbonic acid which exists in 

 prebreathed air never exceeds 10 per cent. It is much to be feared 

 that to this degree of vitiation the air of the bedrooms of the poor 

 and of others not unfrequently rises by the too prevalent system of 

 excluding fresh air, and by the frequent absence of provision for the 

 escape of that which has already passed through the lungs. 



Can it then be a matter of surprise that death from diseased heart 

 should so often occur during the night ? 



In thousands of instances of cardiac disease life is thus sacrificed, 

 where, had but proper ventilation of the bedrooms been observed, the 



