HO USE- V EN TIL A TION. 5 99 



as it becomes tainted, can insure perfect salubrity. Dr. Dalton esti- 

 mated the average respiration of a man to be 24 cubic inches, and the 

 average number per minute to be 20 : consequently, 400 cubic feet 

 pass through the lungs of an ordinary man in twenty-four hours ; while 

 the fallacy to which we have alluded assumes that a supply of 400 

 cubic feet in the room, in twenty-four hours, insures sufficient ventila- 

 tion. Certainly, if any one would draw breath out of one bag, and 

 discliarge the tainted air from his lungs into anothei', he would always 

 breathe good air. But it is calculated that a man will taint and ren- 

 der unwholesome by mixture 17,500 cubic feet of air in the twenty- 

 four hours ; for every respiration not only robs the imbibed 24 cubic 

 inches of a certain portion of its oxygen, but it has mixed with it a 

 quantity of carbonic-acid gas and some vapor; and theoretically, at 

 least, the second respiration, drawn from a room in which the air is 

 stagnant, begins the process of blood-poisoning. 



The first rule, therefore, to be laid down in reference to perfect 

 ventilation, prescribes the entire removal of the whole stratum of air 

 tainted in a room by each respiration ; for by no less a movement do 

 we conceive it possible to take away the polluted air. This removal 

 must be effected no less than twenty times per minute. Part of the 

 expired air being rarefied by the heat of the lungs will rise, and part 

 the carbonic-acid gas will fall. Twenty-four cubic inches, thus spread, 

 may be assumed to taint a stratum, at or about a mouth of an occupant, 

 of 18 inclies. Any lateral movement would, in the case of several oc- 

 cupants, simply sweep the air breathed by one person close by the 

 lips of some other; and hence we hold, as a corollary to this rule, that 

 the prescribed movement should be either up or down, not lateral. 



But the preceding calculation is based upon the minimum con- 

 sumption of each person during quiescence. When talking, laughing, 

 singing, walking, or dancing, the average respirations are, relatively, 

 quickened, the consumption of air increased, and the necessity for a 

 rapid change of atmosphere further enhanced. The amount of air in- 

 spired has been found to be as follows : 



When lying down (say) 1-00 



" sitting 1-18 



" standing 1-33 



" singing - - 1-26 



" walking 1 mile per hour 1.90 



" " 2 miles " 2.'76 



u u 3 (i " ^ 3.22 



(1 11 S " " 



" " and carrying 34 pounds 



" " 4 miles per hour 5.00 



n " 6 " " 7.00 



" riding (trotting) 4.05 



" swimming 4.33 



I 3.50 



The above-ascertained accelerations of the respiratory organs suffi- 

 ciently indicate the effect produced by all kinds of in-door exertion, 



