How Bacteria Are Studied 3 1 



and so will the drama of life and death be 

 enacted anew for long periods. 



In such a confusing mixture as this the stu- 

 dent finds it no easy task to make out much 

 except differences in form and movement, 

 in the jumble of tiny plants. What he needs 

 to do is to get each species by itself, so that 

 he can cultivate it alone, and find out what it 

 is and does under more simple conditions. 



For this purpose it is best to use some solid 

 substance on which bacteria will grow. 



Boiled potatoes, which have been carefully 

 cleansed and sterilized that is, free from any 

 bacteria from the soil or air by steaming, will 

 do very well for some bacteria. These are 

 cut in halves, with knives sterilized by heat, 

 being held in the fingers which have been 

 freed from living germs by washing with 

 corrosive sublimate, and placed under steril- 

 ized bell- jars or in tubes, so that they may 

 not be contaminated by the accidental falling 

 upon them of bacteria from the air. Now, by 

 means of a platinum wire set in a glass handle, 

 which has been sterilized by heating to red- 

 ness, a tiny bit of the bacteria-containing 



