74 
HOUSEHOLD BACTERIOLOGY 
Liquuefying 
Bacteria 
caught in the twenty minutes’ exposure shows the con¬ 
dition in which uncovered jellies, puddings, sauces, 
etc., are likely to be when placed in such places to cool; 
therefore, it is not surprising that lemon jelly, jellied 
meat, etc., are sometimes found in a liquid condition in 
such a place. 
As we have said, some of the bacteria are capable 
of liquefying gelatine. If the right species of bacteria 
had happened to be present in the dust which settled 
in this place, nothing could have prevented the gelatine 
being liquefied, because the presence of the liquefying 
bacterium would have been unknown until its work 
had been done. A slight liquefaction is shown at the 
largest spot in Fig. 46. 
The teacher who followed a lesson on the dangers 
of dust by one on lemon jelly which she placed uncov¬ 
ered in the open window to cool, did not apply the 
scientific knowledge which she had. If she had done 
as well as she knew, the contents of her mold would 
have remained jelly and not become lemonade. 
