328 ANIMAL BIOLOGY 



Another method of securing immunity to disease is by 

 the introduction of the germs of a milder form of the 

 malady. This is the procedure followed in vaccination 

 to prevent smallpox. In 1796 the English physician, 

 Edward Jenner, found that virus taken from cattle 

 with the so-called cow pox would, when inoculated into 

 the human body, prevent the individual from taking 

 smallpox. A properly vaccinated person, if exposed to 

 smallpox, may contract a much milder malady called 

 varioloid, but vaccination decreases his chances of doing 

 even this. Since vaccination has become prevalent 

 smallpox has very greatly decreased. In the i8th century 

 it is estimated that 18,000,000 died of smallpox. In 

 Russia alone from 1893-1897 there were 275,502 deaths 

 from this disease, while in Germany which had compulsory 

 vaccination there were no epidemics. The German army 

 has had but two deaths from smallpox since 1874. Before 

 vaccination was introduced into Sweden the death rate 

 from smallpox was 165 per 100,000, but since vaccination 

 was made compulsory it fell to 18 per 100,000. Formerly 

 undesirable after effects were sometimes produced by 

 vaccination, but with improved methods of securing 

 pure virus the dangers are now very slight. A form of 

 vaccination is now used with remarkable success in typhoid 

 fever. Small amounts of the toxin obtained from dead 

 typhoid bacilli are introduced at different times and the 

 person so treated is rendered comparatively immune 

 from typhoid for a considerable period. In the United 

 States army since vaccination against typhoid was required 

 the death rate from typhoid has been less than one-fiftieth 

 of what it was before. The death rate from typhoid 

 during the Mexican war and the civil war was appalling. 

 In the Spanish war "5000 men in the United States army 



