192 UNCONSCIOUS NERVOUS OPERATIONS 



or from openings too near a cesspool or sewer pipe. 

 Houses warmed by the circulation of steam or hot water 

 must have independent arrangements for ventilation by 

 means of open fireplaces or chimney flues, and adequate 

 openings for admitting pure air. The same may be said 

 of houses heated by ordinary air-tight stoves, or by oil 

 and gas stoves. The latter, while making no provision for 

 ventilation, increase the need of it by their combustion. 



When adequate provision for ventilation is not made in 

 the construction of a building, fresh air may be admitted, 

 without causing a direct draught, by fitting a board six 

 or eight inches wide under a raised window sash, so that 

 the exchange between internal and external air may take 

 place between the sashes. Such an arrangement is useful 

 in schoolrooms and other places of assembly. Care should 

 be taken to avoid a draught of cold air, which is some- 

 times more immediately dangerous than to breathe viti- 

 ated air for a little while. At the same time it should 

 not be forgotten that the worst effects of breathing im- 

 pure air do not appear at once. While it is a direct cause 

 of pulmonary consumption (the greatest scourge of the 

 human race) and other ills, it may be a long time before 

 disease appears. The vitality of the system is gradually 

 lowered, strength and vigor are undermined, so that some 

 slight overexertion or exposure to cold or to specific 

 germs of disease may result in serious or fatal conse- 

 quences. When the whole system is kept by correct 

 habits of life at a high level of health, when all the parts 

 work vigorously, easily, and in harmony, one is able to 

 endure unharmed exposure even to active germs of malig- 

 nant diseases. 



273. Correct Breathing. One can breathe properly only 

 when the clothing is loose enough to allow entirely free 



