THE MICROBES THAT MAKE US SICK 67 
Many disease germs enter the body through 
the mouth and nose. Some, such as typhoid 
fever and diphtheria, get inside along with the 
food or drink that we swallow. Others we 
breathe in through the nose. The most im¬ 
portant of these is tuberculosis; but diphtheria, 
whooping cough, pneumonia, and influenza 
may get into the body in the same way. 
As most disease-germs can grow and multiply How long do 
only in the bodies of animals and human they lwe? 
beings, they can live only a short time in the 
outside world. Some live longer than others, 
but few of them can multiply, except under 
special conditions, as when the typhoid or 
diphtheria germs get into milk. 
Healthy persons, therefore, are likely to 
contract a disease only when they come in direct 
contact with a person suffering from it, or with 
matter containing the germs, which has recently 
been thrown off from the body of such a person. 
Most germs leave the body of a sick person by 
way of the mouth, nose, through the bowels; or 
as in smallpox or chicken-pox, by scaled-off skin. 
