RESPIRATION. 155 



quantity would be sufficient ; but, as the corrupted air min- 

 gles with the pure, this is partially corrupted ; therefore we 

 need a larger supply to support respiration. The best au- 

 thorities on the subject of ventilation consider seven feet as 

 the least that should be supplied to each person; and Dr. 

 Reid allows ten feet. Taking the lowest estimate, seven feet 

 will be considered as necessary for the maintenance of the 

 healthy respiration of each person in each minute of life. 



356. If we always dwelt in the fields, we should have 

 fresh air enough, without any effort on our part. But when 

 we live in closed houses, it becomes a question whether we 

 are thus supplied, and the wants of nature are satisfied ; and, 

 if our rooms are made air-tight, then it is necessary to deter- 

 mine whether they contain air sufficient for the consumption 

 of all that inhabit them, as long as they sfay there. If this 

 be not the case, then it is necessary to find some means to 

 carry off the foul air as fast as it is rendered so by respira- 

 tion, and to bring in a new supply from abroad to take its 

 place. 



357. A continued supply of fresh air for all inhabited 

 rooms is as necessary as a continued supply of heat in cold 

 weather. And yet provision is not usually and intentionally 

 made to meet this necessity in the arrangements of our dwell- 

 ings and our public rooms. The architect and the builder 

 provide carefully for warmth, but they generally make little 

 or no provision for respiration. Fortunately, the imperfec- 

 tion of the builder's work obviates, in some small degree, 

 and generally prevents, the immediately destructive conse- 

 quence of the defects of the architect's plans. It is difficult 

 almost impossible to make a room so tight that no air 

 can force itself into it, when the internal atmosphere is 

 heated, or vitiated by respiration. 



358. A room sixteen feet square, and nine feet high, will 

 contain 2304 cubic feet. This will be sufficient for four 

 persons less than an hour and a half for ordinary day pur- 

 poses. This room, though not so large as some that are 

 inhabited by day or by night, is yet as large as most, and 



