1. _Natural immunity_ = constitutional protection produced by _alexines_. 2. _Acquired immunity_ { _Acquired naturally_ (involuntarily) produced by antitoxins formed { byan attack of the disease. { { _Acquired artificially_ (voluntary)= { { (_a_) _Active_ immunity, produced by direct inoculation of the { weakened bacteria or weakened toxins of the disease, = { _e. g._, vaccination, or Pasteur's treatment of rabies, { or Haffkine's inoculation for cholera. { { (_b_) _Passive_ immunity, produced by inoculation, not of the { disease or of its toxins, but of the _antitoxins_ { produced in the body of an animal suffering from the { specific disease. It is hoped that previous remarks will have explained the meaning of the terms used in the above table, with the exception of the last two phrases of active and passive immunity. We propose now to consider in some detail the four illustrations quoted under these two headings, viz., vaccination, Pasteur's treatment of rabies, anti-cholera inoculation, and antitoxin inoculation. From all accounts, it is to be feared that these four phases of artificial immunity are hopelessly confused in the educated public mind. Nor is this to be wondered at when we reflect upon the rapid growth of the whole science of immunity, and upon the ever-varying forms of nomenclature through which it has passed. _Vaccination for Small-pox._ In 1717 Lady Mary Wortley Montagu[82] described the inoculation of small-pox as she had seen it practised in Constantinople. So greatly was she impressed with the efficacy of this process that she had her own son inoculated there, and in 1721 Mr. Maitland, a surgeon, inoculated her daughter in London. This was the first time inoculation was openly practised in England.[83] For one hundred and twenty years small-pox inoculation (or _variolation_, as it is more correctly termed) was practised in England, until by Act of Parliament in 1840 it was prohibited.