BACTERIA . 
19 
The excretions of the bacteria in milk, fish, etc,, 
may produce changes which, very apparently, ren¬ 
der them unfit for food, or the changes may not be 
apparent. If food containing these excretions be 
eaten, or if the bacteria grow in the body itself, the 
excretions may bring about abnormal conditions more 
or less severe, but all may be called disease. 
Like the mag¬ 
gots in cheese or 
the clothes moth 
larva, the bacteria 
live surrounded by 
their food supply 
and they have only 
to take, digest, and 
absorb it as need¬ 
ed. Like these animal forms, they feed upon com¬ 
plex organized food which has been previously pre¬ 
pared by other plants or animals. In this they differ 
from most plants which must manufacture their food 
out of the mineral and other inorganic substances in 
air, water, or soil. However, some species can do 
this although they have not the green coloring mat¬ 
ter or chlorophyll cells which in the higher plants are 
the food factories. 
Because of this power of living on inorganic sub¬ 
stances, which no known animal possesses, the sci¬ 
entists have decided that these micro-organisms must 
be called plants rather than animals. 
Bacteria have no leaves, roots, stems, or any or- 
A BACILLUS DIVIDING INTO 
TWO GENERATIONS. 
Bacteria 
are Plants 
