THE BACTERIOLOGY OF BEE DISEASES. 11 
These plants, then, constitute an invisible flora, which we can see only 
by the use of a microscope of very high magnifying power. The 
morphology, or the structure, including form and size, is principally 
of two types, rod-shaped or cylindrical and round or spherical. The 
size of bacteria varies. Those which are rod-shaped usually measure 
from 1 to 3-6 microns in length and from one-half to 1 micron in 
diameter. A micron is the unit of measure for very small objects 
and is equivalent to g5}55 of an inch. For example, if a single bac- 
terium of the rod form measures 2 microns, it would take 12,500 
placed end to end to measure | inch in Jength. The spherical bacteria 
or cocci have about the same diameter as the rod-shaped ones. 
Bacteria grow or multiply after a manner called fission; that 1s, 
after increasing in size they become constricted in the middle, which 
constriction finally severs the rod completely, and we then have two 
bacteria where there was but one before. Undgr favorable conditions 
for growth, each bacterium divides by fission every twenty minutes, 
or, in other words, gives rise to three generations in one hour. Such 
being their marvelous rate of increase, a little calculation will demon- 
strate that countless millions may be formed in a short time under 
favorable conditions, which are proper temperature, moisture, food 
in correct proportions, and the absence of much light. The tempera- 
ture most favorable for the growth of a species of bacteria which is 
able to produce a diseased condition in animals is approximately the 
temperature of the animal which is affected by such species. Mois- 
ture is universally necessary. The food must not be too concentrated. 
Light inhibits the growth of bacteria. Direct sunlight is bacteri- 
eidal; that is, it kills bacteria. 
Many species produce spores when the conditions are not favorable 
for the multipheation of bacteria. These are small bodies formed in 
the bacteria (probably never more than one in a single bacterium) 
which are somewhat comparable to the grain in wheat and corn. 
These spores constitute a resting stage and usually also a very resist- 
ant stage, for high temperature and strong disinfectant solutions are 
necessary to kill them. It is these spores which probably make the 
control of the bee diseases more difficult. When the spores again gain 
access to a suitable “soil,” for example, the body of an animal, they 
germinate and a new growth takes place as before. 
Many species of bacteria have the power to move when they are in 
a liquid medium, while others do not. This ability to move is due to 
long, slender processes, which we call flagella, extending from the 
body of the bacterium. 
THE DISTRIBUTION OF BACTERIA. 
Bacteria are very widely distributed. Everyone is familiar with 
the very wide distribution of the higher members of the plant king- 
