LABORATORY RESEARCH, ETC. 



265 



The stage of the microscope is maintained at the 

 requisite temperature. 



In order to make cultures in large quantities, other 

 kinds of apparatus are in use. The liquid supposed to 

 contain microbes is introduced into sterilized nutritive 

 liquids by means of a platinum wire, which has been 

 heated red hot and then allowed to cool; its end is 



Fig. 104. Gas stove for the heating and 

 sterilizing of flasks. 



Fig. 105. Pasteur's 

 culture tubes. 



dipped into the liquid, and then instantly transferred 

 to the culture, while it is exposed to the heat of a 

 spirit-lamp. The flask is then sealed with a wad of 

 cotton wool. 



The culture liquids employed by Pasteur are the 

 extract of beer-yeast, an infusion of hay, boiled and 

 neutralized urine, and the broth of various kinds of 



