160 PHYSIOLOGY AND HEALTH. 



every individual in the promiscuous crowd exhalations 

 offensive, to a certain extent, from the most healthy individ- 

 uals ; but when arising from a living mass of skin and lungs, 

 in all stages of evaporation, disease, and putridity, prevented 

 by the walls and ceiling from escaping, they are, when thus 

 concentrated, in the .highest degree deleterious and loath- 

 some." * 



371. When one enters any rooms thus crowded, and 

 inhales the air thus exhausted and corrupted, he perceives, 

 at once, an offensive and oppressive smell, and there comes 

 a feeling of suffocation about his throat and chest, followed 

 by some degree of faintness. But those who live in it, hav- 

 ing by degrees become accustomed to it, do not perceive the 

 smell ; the sensibility of their lungs and nostrils is blunted ; 

 they are not offended with the foul odor of the atmosphere; 

 yet their lungs do not find the oxygen to purify the blood, 

 and cannot perform their work successfully. They are not 

 relieved of the waste of dead atoms of flesh within them. 



372. It is evident that unless there is some way of re- 

 moving the respired and foul air from these rooms, arid of 

 replacing it with new and fresh air from abroad, the work of 

 respiration cannot be carried on as it should be, the blood 

 cannot be purified of its dead particles, and the system can- 

 not be nourished with life and energy ; and then the con- 

 ditions which nature established for our existence cannot 

 be fulfilled. 



373. Ventilation, or the means of supplying fresh air to 

 every inhabited room, every parlor, sleeping chamber, school- 

 house, public hall, church, or shop, in which people live, is, 

 then, as necessary as the supply of food. After the air already 

 in the room is consumed or vitiated, it must be removed, and 

 as much brought in every minute as is used or spoiled. There 

 must, then, be two constant currents ; one outward, carrying 

 off the foul air, and the other inward, bringing in pure air. 

 The outward current may pass upward through the chimney, 



* Bernan, Art and History of Warming and Ventilation, Vol. II. p. 313, 



