METHODS OF STUDY 



19 



obtained. Meanwhile, investigators found that to 

 secure pure cultures, all utensils, media, or anything 

 coming in contact with them must be freed of bacte- 

 ria; i.e. the bacteria must be destroyed, or, as we 

 now say, these articles must be " sterilized," or the 

 cultures would not be pure, but a mixture of many 

 species. 



It was found that cotton used as a cork for flasks 

 and culture tubes would allow the passage of air 

 which was nec- 

 essary for the 

 growth of the 

 aerobic bacteria, 

 but would ex- 

 clude the en- 

 trance of bacteria 

 in the air. 



Later Weigert fig. 4. -culture tube, 



suggested the use ■*. ordinary upright tube. i. Sloped tube. c. "Deep" 



tube for cultures of anaerobes. 



of ajjiline,_d^^ 



for staining bacteria, which were found to take the 

 dyes each in its characteristic way, thus enabling 

 the observer to identify certain species, and from 

 these simple beginnings the elaborate minutiae of 

 the technique of bacteriology has grown — practi- 

 cally all within thirty-five years. 



h 

 Tubes of media. 



