94 HOUSEHOLD BACTERIOLOGY 



It seems, then, probable that in the blood serum of 

 immune persons there may be another factor in the 

 vital resistance. That is, the body cells in some way 

 manufacture substances that neutralize the poisons or 

 toxines produced by the germs, thus enabling the body 

 to expel the germs themselves, and recover. These 

 antitoxines or the power of producing them may re- 

 main and the body becomes immune to the disease. 

 These antitoxines are specific in nature, that is, are 

 capable of neutralizing the toxine of only one kind of 

 germ. 



Immunity may also be "acquired" by the injection 

 into the blood, in some cases, of the germs themselves, 

 as in the case of inoculation for small pox as was 

 as was originally done in the case of inoculation for 

 small pox. Formerly some "matter," that is, the in- 

 fectious material, was taken from a person sick with 

 small pox and injected directly into another person by 

 placing it under the skin, where it quickly affected the 

 whole body. 



Jenner a celebrated doctor in England about 1796 

 first modified inoculation by introducing the "mat- 

 ter" into healthy calves or cows. These animals be- 

 ing very susceptible to the disease, contracted it, and 

 then from the pustules of their bodies the "matter" 

 or "vaccine" was drawn and injected into human be- 

 ings. This, in man, was found to produce a milder 

 form of the disease and to leave in the system upon 

 recovery something which gave immunity or protec- 

 tion from small pox. 



