166 TECHNOLOGY OF BACTERIA. 



minous fluid which has been utilized, especially by 

 the earlier investigators, as a culture-medium. The 

 method of operation has commonly been to place 

 a drop of this fluid, obtained from the eye through 

 a sterilized canula, upon a perfectly clean cover- 

 glass, and to invert this over a shallow glass cell 

 the margin of which has been wet with olive oil, 

 or with a liquid cement of some kind. This 

 serves to attach the cover and to exclude atmos- 

 pheric organisms. The drop of fluid is inoculated 

 by means of a needle, the point of which has been 

 dipped into the stock-solution containing the par- 

 ticular organism which it is proposed to culti- 

 vate. 



This method is especially useful when the de- 

 velopment of an organism is to be studied by 

 continuous observation ; for the slide supporting a 

 culture-cell made in this way may be placed upon 

 the stage of the microscope, and bacteria in the 

 drop of fluid may be observed with high powers 

 through the thin glass cover. This method does 

 not, however, offer as perfect security as regards 

 the exclusion of extraneous organisms as is desira- 

 ble, and it has generally been abandoned for the 

 methods to be described later, in which a consid- 

 erable quantity of fluid, enclosed in a germ-proof 

 receptacle, is used. In this case a microscopical 

 examination of .the contained organisms requires 

 that a small portion of the culture-fluid be with- 

 drawn from the culture-flask, and continuous ob- 

 servation would be impracticable. 



