
BACTERIA 
Bacteria are minute single-celled 
plants. Most of them are harmless; 
some are necessary to the life and indus- 
trial pursuits of man; a few cause disease. 
When properly stainedand viewedthrough 
a microscope, they are seen to occur in 
three shapes: 
Different bacteria vary greatly in pro- 
portions and appearance. Some species 
have long, thread-like processes (flagella), 
which enable them to swim about, while 
others are surrounded with slime. A great 
many contain resistant spores and others 
contain granules, which give them a 
barred or spotted appearance. 
Bacteria may be made to live and 
multiply by planting them on a specially 
prepared jelly. 
increase that a colony of millions of 
Soon their numbers so 
microbes becomes visible at each point 
where asingle germ was planted originally. 
BACTERIA=INSECT-BORNE DISEASES 
Transparencies in WINDOW CASE 
1 are photographs of bacteria as they 
appear under a microscope. 
WINDOW CASE 2 contains en- 
larged glass models of each type: for 
example: 
Staphylococci (2d panel). 
Bacillus of tuberculosis (1st panel). 
Spirochete of relapsing fever 
(bottom panel). 
See bacilli in two central panels. 
See acetic acid bacilli just above. 
See one of the center panels. 
Bacillus of diphtheria (top row). 
Preserved colonies are shown at both 
sides of WINDOW CASE 1. 
INSECT-BORNE DISEASES 
An insect may carry disease from one man, or from one animal, to 
another in two ways: 
1. By acquiring and dispersing the parasites during the act of biting. 
A few of the most important diseases carried in this way are: 
Bubonic Plague -— carried by the flea. 
Malaria — carried by Anopheles mosquitoes. 
Yellow Fever — carried by the 4édes mosquito. 
‘Typhus Fever — carried by the body louse. 
Sleeping Sickness —— carried by the Tsetse fly. 
Tick Fevers — carried by ticks. 
With the exception of Bubonic Plague, these diseases can be 
contracted only through the agency of insects and in the 
way described above. 
2. By spreading germs lodged on its body and feet. 
Typhoid fever organisms and germ of infant diarrhoea are 
sometimes carried in this way by the fly. 
6 

