BACTERIOLOGY. 167 



ers are used in the following manner : in using the Ar- 

 nold and the Koch Sterilisers, put the media in the 

 steriliser at the same time you put in the water, and 

 that will insure the media getting the same amount of 

 heat that the water gets. Boil the whole fifteen min- 

 utes for three successive days. This is Tyndall's in- 

 termittent method. Each of these will be demonstrated 

 in the class. 



Sterilisation by steam at high pressure is a quick 

 method but is not adapted to media work. It is car- 

 ried on by means of the autoclave. Sterilisation by 

 low pressure is adapted to one kind of media that is, 

 blood-serum, on Tyndall's principle. 



Plating of Bacteria. Take a sterilised platinum 

 wire ; let it cool slightly ; then introduce it into the col- 

 ony of bacteria and then into tube No. I ; shake 

 well; then sterilise again; take a loop full from 

 tube No. i and inoculate tube No. 2 with the same; 

 sterilise; take a loop from tube No. 2 and inoculate 

 tube No. 3 ; pour the contents into the same number of 

 Petri dishes and number them according as the tubes 

 were numbered; set aside until next day and note the 

 change if any. This will be explained as we go along 

 in our work. Always sterilise your needle before and 

 after use. (The media must be melted.) 



Hanging-Drop Culture. This is made by simply 

 taking the drop of media containing the growth and 



