The Air We Breathe 263 



contracted this fever, the notion arose that it was the foul-smelhng 

 air in the sewers that caused the malady. It was not until 1880 

 that Laveran revealed the mosquito transmission of malaria, but 

 the old misnomer, malaria, has persisted through the years. 



The sense of smell varies widely between individuals. Odors 

 can be perceived more readily in a moist air than they can be de- 

 tected in a dry atmosphere. Many poisonous gases, including 

 carbon monoxide, are practically without odor. It should be re- 

 membered that the foul smell of exhaust fumes from a motor 

 vehicle is not due to the lethal carbon monoxide; other products 

 of combustion overshadow the barely detectable monoxide fumes. 



Rosenau has stated that science has demonstrated that our sense 

 of smell is a poor sanitary guide. While disagreeable odors may 

 not be harmful, they should be eliminated for esthetic and psy- 

 chological reasons, as well as for decency and cleanliness. 



The more recent fundamental investigations of Winslow and 

 his colleagues relative to the effect of odors on health have added 

 a great deal of knowledge to this phase of science. Odors, for 

 instance, affect the appetite, just as clean and pleasant surround- 

 ings are conducive to better appetites. Winslow summarizes the 

 information by stating that we may conclude that while air does 

 not as a rule bear the microorganisms causing disease and does not 

 carry with it mysterious and specific organic poisons, an atmos- 

 phere laden with offensive odors is not only objectionable on 

 esthetic and economic grounds, but may under certain circum- 

 stances constitute a real menace to public health. 



There are differences of opinion about such scientific matters, 

 and that is what makes research such a challenge. 



RAISING MICROBE-FREE ANIMALS 



The tremendous number of bacteria found in the intestines of 

 M^arm-blooded animals, particularly in the colon, raised a number 

 of questions within the minds of early investigators. One of these 

 questions concerned the ability of rearing animals in the complete 

 absence of living microbes. Some workers expressed the opinion 

 that proper digestion of food might not take place in the absence 



