214 INTRODUCTION TO BOTANY 
199. Benefits from use of diphtheria antitoxin. Great bene- 
fits have come to the human race through the discovery of 
diphtheria antitoxin. It was generally introduced in 1894. 
A study of the table on page 213, containing data for ten years 
before and ten years after the introduction of this remedy, will 
give an idea of the value of this scientific discovery. 
200. Tuberculosis: the great white plague. The disease 
commonly known as tuberculosis is so generally distributed 
and so destructive that it has been called “the great white 
plague.” Its universal importance demands that a separate 
section be given to a brief statement concerning it. It is the 
most destructive disease that affects the human race, and in 
the United States it causes about one ninth of all deaths. 
The lungs are the organs most frequently attacked, though 
the bones and joints, the intestines, the throat, the skin, and 
other organs are often infected. The growth of tubercle bacilli 
in the body is usually very slow, and months or years may pass 
before conspicuous consequences follow infection. Further- 
more, the bacilli may live upon a handkerchief, in the floor of 
a house, in a public building, in public-transportation vehicles, 
ov in the dirt of the street, for a very long time, and then 
grow when they are introduced into the human body. Some 
of the lower animals (cattle, hogs, and poultry) are subject to 
tuberculosis and may infect human beings. 
Infection is usually through the organs of breathing, though 
the germs may be introduced into the digestive system in milk 
and other food. Persons who have tuberculosis may “expec- 
torate from 500,000,000 to 38,000,000,000 tubercle bacilli 
in twenty-four hours.” + Also, such persons, while coughing, 
may inject into the air very small droplets which contain 
many bacteria, and these may float in the air for a short time. 
Since the dried or partially dried tubercle bacilli may be 
transported by the air, it is evident that every precaution 
should be taken to keep the air from becoming contaminated. 
Furthermore, it is known that when tubercle bacilli are moist, 
1 Jordan, E, ©,, General Bacteriology, 1911. 
