38 JOURNAL AND PROCEEDINGS 



2. The Rod or Bacillus — longer than broad — straight or 



slightly bent. Some are motile, e.g:, t3'phoid 

 germs. Others have capsules and form spores, 

 e.g., anthrax. Others are clubbed shaped, e.g., 

 diphtheria. 



3. Spiral Forms or The Spirillum. These occur in 



spirals or segments of a spiral. The most com- 

 mon example is the spirillum, causing cholera. 

 Bacteria live on organic matter, either living or dead. Germs 

 existing on living organic matter are called parasites. Those de- 

 pendent on dead organized matter are calhid saprophytes. 



Saprophytes form the great majority of bacteria. They are 

 harmless to living organisms and are necessary to life, performing 

 many important functions in the economy of nature, e.g:, sewage 

 disposal, putrefaction and fermentation. 



The parasites are harmful invaders. They are the pathogenic 

 or disease-producing bacteria and give rise to infectious diseases. 

 Bacteria reproduce themselves in two ways — 

 a. Fission or simple division is the more common method, 

 requiring 20 to 30 minutes in favorable environment, 

 so that a single bacillus, if left under absolutely favor- 

 able conditions, would in three days multiply to seven 

 tons of matter. 

 6. Spore formation is a special adaptation of certain bacilli 

 to unfavorable environment. Where conditions of 

 growth are unsatisfactory the bacillus develops a 

 spore which is exceedingly tenacious of life and able 

 to resist the destructive effects of the most unfavor- 

 able surroundings. In this condition the life of the 

 bacillus is sustained until more acceptable conditions 

 favor its return to the original form. The spores of 

 anthrax have been known to survive a period of 

 twenty years. 



Like the higher plants bacteria depend for nourishment on 

 O. H. C. N and salts of Na. and K. as food elements. They thrive 



