VACCINATION 



275 



■In army 

 -In civil Off 



1910 io'i^of troops vaccinated 

 1911 ao'''' of troops vaccinated 

 1912 m'^of troops vaccinated 



Cmllife 



it is transferred to man. The great French bacteriologist, Louis 

 Pasteur, discovered a method of treating this disease which is 

 a success if begun soon after the time of the entry of the germ 

 into the body. Here again the treatment is based upon the 

 inoculation of the patient with a weakened organism which causes 

 the body cells to set up a resistance and produce immunity. 



Vaccination against Typhoid. — In recent years typhoid fever 

 has received a new check from a treatment commonly called 

 '' vaccination " which 

 has been introduced into 

 our army and is being 

 used with good effect by 

 some physicians and by 

 the health departments 

 of several large cities. 



The figure shows the 

 effect of vaccination 

 against typhoid, intro- 

 duced in 1910. During 

 the Spanish-American 

 War in the army of 

 107,000 men more than 

 20,000 were disabled with typhoid. Since 1914 the disease has 

 been almost stamped out in the army. 



The principle underlying vaccination against typhoid is that of 

 working up an active immunity by means of the introduction into 

 the body of large numbers of dead typhoid germs. These organ- 

 isms, with their toxins and split protein poisons, cause a disturbance 

 in the body with the result that antibodies are manufactured and 

 immunity secured. 



The Widal test, by means of which it is possible to determine 

 at once whether a person has typhoid, has been described on page 

 165. 



Active immunity is thus brought about in a number of different 

 ways : by the introduction of living organisms, by the introduc- 

 tion of weakened or attenuated organisms, by the introduction of 

 dead organisms, and by the introduction of extracts containing 

 the products of bacteria. All of these substances may be called 



01 02 03 04 05 06 



10 II 12 li I* IS 16 17 IS 19 20 II 



Annual number of deaths from typhoid fever per 

 100,000 ; solid line, in the army ; dashed line, 

 above shaded area, in civil population. 



