V. 



REQUIREMENTS OF BACTERIA. 



Bacteria, like all living cells, require certain nourish- 

 ing substances. 



Absence of chlorophyll inability to acquire carbon 

 from carbonic acid. Carbon, therefore, derived from pre- 

 formed carbon compounds sugar, proteids, etc. 



Nitrogen derived from organic and inorganic sources 

 --proteids, nitrates, nitrites, ammonia. 



Presence of moisture necessary for growth. 



Suitable reaction of medium neutral or slightly alka- 

 line. 



These conditions solutions of organic nitrogenous 

 substances widely distributed in nature. Hence the 

 occurrence of bacteria almost everywhere on the surface 

 of the ear tli. 



Almost total absence of bacteria at high altitudes, in 

 air of mid ocean, and in deeper layers of the earth. 



Absence of bacteria in organs and circulating fluids 

 of the healthy normal body. 



Theory of spontaneous generation, the outcome of the 

 wide distribution of bacteria and lack of knowledge con- 

 cerning the resistance of bacteria and their spores. Its 

 overthrow. 



Classification of bacteria according to habitat sapro- 

 phytic and parasitic. No sharp line of distinction to be 

 drawn facultative and obligative. 



Temperature requirements. Each organism has its 

 minimum, optimum and maximum temperature for 

 growth. 



In general the minimum temperature is about 

 15 C.; the maximum about 40. 



