268 BACTERIA, YEASTS, AND MOLDS 



brought about by the bite of an insect. Carriage from one 

 individual to another may take place through other animals, 

 especially insects, through water, ice, milk, uncooked vege- 

 tables, or sometimes by direct contact of one person with 

 another. Sometimes diseases are also spread through 

 "carriers," healthy individuals who harbor the germs and 

 can transmit them to others without being sick themselves. 

 Some diseases are spread by one of these means, others by 

 different ones ; and in the case of an epidemic it is important 

 to know the exact facts, so that one may be on his guard 

 against the true channel of infection and not be afraid of 

 others. Invasion of a new host may occur through a broken 

 skin (rarely through an uninjured skin), through the mouth, 

 or through the respiratory tract. Here again each disease 

 has its own method of entrance, and in the fight against it 

 its peculiarities should be taken into account. With an in- 

 telligent understanding of these factors a housewife can do 

 much toward keeping her family in good health. 



