stances which tend to destroy the germs or neutralize their 

 poisons. The degree of this natural vital resistance varies 

 widely. Disease germs, like other enemies, are more likely 

 to attack weak people than strong ones, though some dis- 

 eases, like measles and smallpox, affect all alike. 



Besides this sort of general vital resistance, a person who 

 lias recovered from an attack of some spe- T . 



cific communicable disease enjoys a special . . , ,~ 

 A , .. i • Against Specific 



immunity against the particular germ m _?: 



question as a result of the struggle through 

 which it has passed. In a number of diseases it is now pos- 

 sible to produce at will a state of immunity by the introduc- 

 tion into the body of weakened or killed cultures of the germ 

 which have lost the power to produce active disease, but 

 are still able to stimulate the tissues of the body, so that they 

 can defend themselves against a later attack of living and 

 virulent microbes. 



This principle w r as applied over a century ago in the case 

 of smallpox by Edward Jenner, an English „ .. 



physician. It has been said that this dis- TT . x . 



Vaccination, 

 covery of vaccination by Jenner was the 



greatest single practical benefit ever bestowed by one man 

 upon the human race. As soon as vaccination was generally 

 introduced, the dreaded epidemics of smallpox ceased, and 

 this disease now exists only as far as vaccination is neglected. 

 During the eight years before the American Army entered 

 Havana, there were 3,132 deaths from smallpox in the city; 

 during the next eight years, when vaccination was enforced, 

 there were seven. 



Vaccination has conquered smallpox so successfully that 

 people have almost forgotten what a terrible disease it was, 

 and some of them have grown careless about vaccination. 

 Others object to being vaccinated for fear some infection 

 may get into the wound. All vaccine used in the United 

 States is now tested as to its purity by the National Gov- 

 ernment, and there is no danger from its use, provided that 



39 



