BACTERIA AND THEIR RELATION TO DAIRYING. 



Steam Sterilizer. When this method is followed, the milk 

 is, however, often brown colored 



14 



15 16 



FIGS. 14-17. 



The 



FIG. 14. Test-tube closed with a cotton plug and filled with gelatine, 

 inner surface of the tube, the cotton plug, and the gelatine are sterilized. 



FIG. 15. Culture of a bacterium in a test-tube. The bacterium has formed 

 a large colony on the surface of the gelatine, and a weak bacterial growth is 

 shown in the inoculation-needle track " stick. 1 ' 



FIG. 16. Shows a culture which peptonizes (liquefies) the gelatine. A colony 

 is also in this case first formed on the surface of the substratum, but as the 

 bacteria liquefied this it gradually sank into the liquid formed. At the stage 

 shown in the cut the bacteria appear as a small precipitate, c, at the bottom of 

 the funnel-shaped, liquefied gelatine. 



FIG. 1?. Shows a culture of bacteria which also liquefied the gelatine, but to 

 a smaller extent than the one last mentioned. Before the liquefaction, short 

 filaments grow out into the solid gelatine from the " stick." 



The sterilization of some substrata may be accomplished 

 by nitration through clay, gypsum, porcelain, asbestos 



