214 INTBODUCTION 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." Jts 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, 

 or 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 3,000,000,000 tubercle bacilli 

 in twenty-four hours." l 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. O., General Bacteriology, 1911. 



