PLANTS WHIG a CSCSE DECAY 387 



water by putting ice around the vessel containing it 

 rather than in it. 



In the case of eggs, bacteria often gain entrance 

 before they are laid ; if this is not the case they can be 

 preserved by keeping the bacteria out. For this purpose 

 the pores of the shell are filled by dipping them into 

 water-glass (vaseline and other substances have been 

 used; they are also packed in brine, etc). 



Prominent among the bacteria of fermentation ant, 

 in addition to the lactic -acid bacteria of milk, the 

 vinegar- making bacteria. In order to study these bac- 

 teria it is only necessary to take a little "mother" 

 (which is a gelatinous mass containing the bacteria) 

 from vinegar and place it in a little hard cider or a 

 weak solution of alcohol (containing not more than 6 

 or 7 per cent alcohol) neutralize with lime-water, add 

 enough liquid litmus to give a good blue color and allow 

 it to stand in a warm placi- (light should be excluded). 

 If the liquid be poured over a mass of excelsior or 

 shavings, the vinegar is formed with great I'apidity, as 

 shown by the color of the litmus. ^ The reason is that 

 in this case the bacteria are abundantly supplied with 

 air, which is essential to their activity. This experi- 

 ment may be conveniently carried out in a covered 

 wooden pail or tub filled with excelsior (or shavings). 



In recent years the use of silage has become very 

 extensivp. Silage is made by filling a pit or other 



1 Ordinary litmus paper may be used in place of liquid litmus. 



