x Contents 



CHAPTER IV 



Pages 



THE FOOD REQUIREMENTS OF BACTERIA 30-35 



The sources of carbon The compounds of carbon in 

 bacteria The source of nitrogen Enzymes Pigments 

 Phosphorescence. 



CHAPTER V 



CONDITIONS AFFECTING THE GROWTH OF BACTERIA .... 36-44 

 Temperature Thermophile bacteria Effect of cold 

 Attenuated cultures Moisture content of the culture 

 medium Relation to oxygen Action of sunlight 

 Electric light Influence of electric currents Influence 

 of the concentration of the culture medium The re- 

 action of the culture medium Importance of reaction 

 of the soil. 



PART II 

 BACTERIA IN AIR AND WATER 45-103 



CHAPTER VI 



BACTERIA IN THE ATMOSPHERE 45-55 



Bacteria on dust particles Determination of the bac- 

 teria in the air Pasteur's method of determination 

 Value of Pasteur's method Quantitative methods. 

 Influence of locality Bacteria in city air Bacteria in 

 the air of the country. Influence of season climate, 

 and altitude Bacteria in the air at different seasons of 

 the year The influence of climate The influence of 

 altitude Bacteria and respiration. 



CHAPTER VII 



THE RELATION OF WATER TO HEALTH AND DISEASE . . . 56-60 

 Ancient .water-supplies Relation of drinking-water and 

 disease discovered Epidemics of cholera and typhoid 

 fever Other sources of typhoid infection Other dis- 

 eases arising from use of impure water, 



