12 THE POPULAR SCIENCE MONTHLY 



cooked foods which have been improperly handled in the kitchen, 

 rather than to original infection of the meat before it enters the house- 

 hold. 



Of the food materials which are eaten raw and might therefore be 

 expected to play an important part in the wholesale transmission of 

 disease, some, like certain fruits, are rendered safe by the fact that they 

 are peeled before being eaten so that the edible portion has never been 

 exposed to infection. Others are protected by the fact that long storage 

 usually intervenes between exposure to pollution and ultimate consump- 

 tion. Thus ice, though often cut on polluted streams, is one of the 

 safest foods, as shown by careful bacteriological and epidemiological 

 studies. Ninety per cent, of the bacteria in the water are thrown out 

 in the physical process of freezing ; and in a few weeks ninety-nine per 

 cent, of any disease germs remaining will have perished. 



Water and milk and raw shellfish are the three foods which in the 

 highest degree fulfill all the requirements of a dangerous disease 

 medium. If water is taken from streams or ponds or wells into which 

 sewage enters, and is used for drinking without adequate storage or 

 purification, the best possible opportunity is offered for a transfer of 

 infection on a gigantic scale. The great epidemics of typhoid fever 

 and cholera which used to sweep through European cities and more 

 recently have continued to ravage American communities, bear eloquent 

 testimony to this fact. With the cheap and effective methods of puri- 

 fying water, by storage, filtration or disinfection, now at our disposal, 

 there is no excuse for the delivery of a public water supply which is not 

 absolutely safe. In uncivilized communities, which persist in using 

 polluted supplies, and in the country where a local well is under sus- 

 picion, the householder may always, however, protect himself by using 

 a Berkefeld or Pasteur filter, either of which types is efficient if prop- 

 erly cared for, or by boiling the water to be used for drinking. 



Milk is second only to water as an agent in the transmission of dis- 

 ease. It is frequently infected with tubercle germs and sometimes with 

 other pathogenic organisms from the cow. It is contaminated by dirt in 

 the stable, and it is polluted at a dozen different points by the numerous 

 individuals who handle it on its way through the dairy to the consumer. 

 Furthermore, of all foods milk is the one which in some cases apparently 

 permits an actual multiplication of disease germs and an increase in- 

 stead of a diminution of virulence in transit. Epidemics of typhoid 

 fever, diphtheria, scarlet fever and tonsilitis without number have been 

 traced to milk, and to young children even the ordinary germs of decay 

 in milk, aside from infection with specific diseases, are often fatal, as 

 evidenced by the terrible toll of summer diarrhoea among infants, which 

 is almost exclusively confined to those fed on cow's milk. Carefully 

 protected milk, such as is certified by our medical societies, is of course 

 much freer from danger than the ordinary product, but the history of 



