AIE 



43 



nitrate, and decolourizes potassium permanganate. If 

 water through which expired air has been drawn be dis- 

 tilled, free and albuminoid ammonia are obtained. 



The smell of organic matter in inhabited places is peculiar 

 and penetrating, it adheres to walls, and even after free 

 perflation of air the removal of smell is difficult, showing 

 that the substance is not readily oxidized. 



It was believed at one" time that toxic effects could be 

 produced by inoculation with organic matter in the form of 

 a condensed liquid, but recent researches have not corrobor- 

 ated these observations. 



The organic matter consists of particles of epithelium 

 from the skin, hairs, fatty matters from the surface of the 

 body, organic vapours the result of the decomposition of 

 sweat and sebum, urine and faeces, but the nature of the 

 substance resulting from these is quite unknown excepting, 

 as just pointed out, it is very penetrating, nitrogenous, and 

 putrefiable. 



The feeling amongst hygienists at the present day is not 

 to lay too much stress on the organic matter of badly 

 ventilated rooms, as the chief cause of discomfort experi- 

 enced by breathing air vitiated by respiration ; but rather 

 to attribute the symptoms of oppression, headache and sick- 

 ness, experienced in hot and crowded rooms, to the de- 

 ficiency of oxygen, and excess of carbonic acid, heat, and 

 moisture, the latter being particularly harmful by checking 

 the loss of heat from the skin. 



The number of microbes present in vitiated air bears no 

 relation to the amount of carbonic acid present ; there are 

 no microbes given off during expiration, and many of 

 those contained in inspired air appear to be arrested very 

 early in the respiratory tract, and do not reach the alveoli 

 of the lungs. 



In some extensive chemical and biological examinations 

 of the air of buildings made at Dundee* the observers in 

 their biological work attached importance to the proportion 



* Carnelley, Haldane, and Anderson. 



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