22 
HOUSEHOLD BACTERIOLOGY. 
Rapidity 
of Growth 
The spiral forms also may remain in one colony or 
break up into single cells after division. 
Sometimes they 
unite their bodies 
by a gelatinous 
film to form a 
slime over the sur¬ 
face of whatever 
they are growing 
upon, as seen on 
the walls of the waste pipe of the refrigerator or on 
the surface of the water in the pan. This is known 
as a zoogloea form. Fig. 13. 
The rapidity with which they reproduce depends 
largely upon the food supply, the warmth and moist¬ 
ure—that is, whether the conditions of life and 
growth are favorable. 
In this prolific reproduction lies their great power 
for harm or benefit to the world. 
In some species, under favorable conditions, a new 
generation is born oftener than every half hour. If 
this rate were continued for a day, one bacterium 
might become ancestor of over sixteen million de¬ 
scendants. Some interested observer has calculated 
that in two days the billions thus born would fill a 
pint measure and weigh a pound, while in another 
twenty-four hours their weight would equal eight 
thousand tons. 
These numbers, however, are of no practical im- 
FIG. 13. ZOOGLOEA OR THE 
FILM-FORMING BACTERIA. 
