240 THE BIOLOGY OF DISEASE 



diseases are unnecessary, and it should be considered a 

 disgrace to a community if some of them appear. Proper 

 hygienic measures will do much towards eliminating 

 most of the communicable diseases, but until the intelli- 

 gence of communities can be aroused enough so that such 

 measures shall be insisted upon, we must depend upon 

 proper food, rest, fresh air, and exercise to keep ourselves 

 fit, and thus avoid the conditions which help disease to 



Figure 242. — A Model Reservoir. 



gain a foothold. Tuberculosis, for example, is more likely 

 to occur in persons who are underfed and overworked, 

 and a cold often follows an attack of indigestion. 



Care of Food. — The care of food is extremely neces- 

 sary in preserving our bodily well-being, for the same 

 germs live and grow in food which cause disease when 

 taken into our bodies. One method of keeping the bac- 

 teria on food from growing is by proper refrigeration. 

 The temperature of a well-cooled refrigerator does not 

 destroy the germs, but makes them incapable of growth 

 until heat is supplied them. So if food is taken from the 

 refrigerator and allowed to stand for a time, the bacteria 

 will at once begin to grow and cause the food to spoil. 



