RESPIRATION. 159 



afternoon, too plainly shows that they have not sufficient 

 ventilation. 



368. In times of great excitement, the crowds in the 

 churches or halls are more dense even than thes. It is esti- 

 mated by those observant of the matter, that, in the closest 

 crowds, a man standing will not occupy more than two 

 square feet of surface ; and therefore a room can hold half 

 as many as there are square feet of floor. This would give 

 twice as many cubic feet of air as the height of the room 

 above the heads of the people. I have stood in Faneuil 

 Hall when each man had very little more space for air than 

 that which was over his head to the ceiling above. 



369. School-houses seem to be as imperfectly supplied 

 with air as public halls. It is rare that one enters a school- 

 room from the fresh air abroad, after the scholars have been 

 in a few minutes, without perceiving the foulness of the 

 atmosphere within. A room thirty feet square is ordinarily 

 supposed to be large enough for eighty or ninety children ; 

 and, if the room be nine feet high, this will allow eighty or 

 ninety feet of air for every child, which is sufficient for their 

 respiration twelve or thirteen minutes. The air of these 

 rooms becomes loaded with carbonic acid gas, with the foul 

 secretions of the lungs, and the excretions of the skin. It 

 is offensive, so much so as sometimes to produce sickness 

 and faintness in those who enter from the external air. 



370. But " not the least remarkable example of the power 

 of habit is its reconciling us to practices which, but for its 

 influence, would be considered noxious and disgusting. We 

 instinctively shun approach to the dirty, the squalid, and the 

 diseased, and use no garment that may have been worn by 

 another. We open sewers for matters that offend the sight 

 or the smell, and contaminate the air. We carefully remove 

 impurities from what we eat and drink, filter turbid water, 

 and fastidiously avoid drinking from a cup that may have 

 been pressed to the lips of a friend. On the other hand, we 

 resort to places of assembly, and draw into our mouths air 

 loaded with effluvia from the lungs, skin, and clothing of 



