THE AIR AND VENTILATION 22 5 



390. Malaria. Malaria, chills and fever, fever and 

 ague, or intermittent fever, as the disease is variously 

 called, is caused by germs that grow within the bodies 

 of certain kinds of mosquitoes, and are left beneath the 

 skin when the insects bite a person. In order to rid a 

 place of malaria, the malarial mosquito must be extermi- 

 nated. All mosquitoes spend the first part of their lives 

 in stagnant water as wigglers, and may be destroyed by 

 draining the marshes and stocking the pools with fish 

 which eat the wigglers. 



391. Night air. There is a popular belief that during the night 

 the air contains some harmful substance which disappear^ during the 

 day. But the air of the early evening, which is supposed to be the 

 worst air of the day, has been purified by hours of sunshine, while 

 the air of early morning, which is supposed to be the best of the day, 

 has been exposed to hours of the noxious influences of darkness. So 

 the belief is a contradiction in itself. 



392. Contamination of air by fire and light. In addi- 

 tion to the impurities produced by breathing, the air of 

 inhabited rooms is further rendered impure by fires and 

 lamps. A tallow candle will consume half as much oxy- 

 gen in a given time as a man. A lamp burning a pint of 

 oil in an evening uses as much oxygen, and gives off as 

 much carbonic acid, as a man gives off during a whole 

 day. A stove uses an immense amount of oxygen, but the 

 gases pass up the chimney. Candles and lamps often 

 pour bad-smelling gases into the air. 



393. Coal gas. When coal is heated, it gives off a gas called 

 carbonic oxide. Carbonic oxide is the main part of illuminating gas, 

 and in a stove, burns with a blue flame. It is extremely poisonous 

 when breathed. It unites with the hemoglobin of the red blood cells 

 and destroys their power of carrying oxygen. Gas from a smoking 



ov. PHYSIOL. 15 



