MICRO-ORGANISMS IN WATER 



CHAPTEK I 



STERILISATION AND THE PREPARATION OF 

 CULTURE MEDIA 



As the whole success of bacteriological experiments 

 depends primarily upon the absolute sterility of both 

 apparatus and materials employed in their cultivation, 

 it is appropriate in the first instance to briefly describe 

 the methods of effectually removing all organisms from 

 the objects solid, liquid, and gaseous which are 

 used in bacteriological investigations. This sterilisa- 

 tion, as it is called, may be accomplished in various 

 ways: (1) by moist heat; (2) by dry heat; (3) by 

 chemical means ; whilst liquid and gaseous substances 

 may in addition be sterilised by (4) filtration. 



(1) Steam or moist-heat sterilisation. This is most 

 conveniently effected by means of the ' steam steriliser/ 

 devised originally by Koch, Gaffky, and Loffler, and 

 which has the exceedingly simple form represented 

 in the figure below. The cylinder is covered with felt 

 or asbestos, to prevent loss of heat, and the bottom is 

 constructed of copper, under which are placed one or 

 more bunsen or other smokeless burners, according to 

 the size. The heat applied must be sufficient to keep 

 the water in such vigorous ebullition that steam issues 



