86 HOUSEHOLD BACTERIOLOGY 



it is put into a refrigerator or in any way used for the 

 storage of food. Safety may be assured if ice is never 

 allowed to touch the food. Its effects can be obtained 

 without actual contact and contact may mean con- 

 tamination. 



The tub of lemonade standing open on the picnic 

 ground or the street corner has sufficient chance of 

 germ infection without a block of doubtful ice in its 

 midst. 



THE RESISTANCE OF THE BODY TO DISEASE GERMS 



sources of We have seen that many diseases which afflict hu- 

 man beings have been definitely traced to these or- 

 ganic forms ; to these micro-organisms found in in- 

 haled dust, in polluted water, in food and on articles 

 which may puncture the skin. 



If the avenues of infection are so common, the ques- 

 tion naturally arises, how can any human being escape ? 

 We know that many do, that there are hundreds of 

 persons who never have had typhoid fever, diphtheria, 

 or other infectious disease ; that two persons may, so 

 far as we know, eat of the same food, drink from the 

 same water supply or live under exactly similar con- 

 ditions one has some infectious disease, the other re- 

 mains well. 



It is too a matter of common knowledge that a der 

 gree of safety from a second attack is often assured to 

 the person after recovery from the first illness. He 

 seems to have some power of resistance which he did 

 not have before and which is absent in his neighbor. 



