CHAPTER VII 



THE QUESTION OF IMMUNITY AND ANTI- 

 TOXINS 



THE term natural immunity is used to denote natural 

 resistance to some particular specific disease. It may 

 refer to race, or age, or individual idiosyncrasies. We not 

 infrequently meet with examples of this freedom from dis- 

 ease. Certain races of men do not, as a rule, take certain 

 diseases. For example, plague and leprosy, though en- 

 demic in some countries, fail to get a footing in England. 

 This, of course, is due in great measure to the sanitary 

 organisation and cleanly customs of the English people. 

 Still, it is also due to the fact that the English appear in 

 some degree to be immune. Some authorities hold that the 

 immunity against leprosy is due to the fact that the disease 

 has exhausted itself in the English race. However that may 

 be, we know that immunity, entire or partial, exists. Child- 

 ren, again, are susceptible to certain diseases and insuscept- 

 ible to certain others to which older people are susceptible. 

 We know, too, that some individuals have a marked pro- 

 tection against some diseases. Some people coming into 

 the way of infection at once fall victims to the disease, whilst 

 others appear to be proof against it. It is only in recent 

 times that any very intelligent explanations have been 

 offered to account for this phenomenon. The most recent 

 of these, and that which appears to have most to substanti- 

 ate it, is known as immunity due to antitoxins, 



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