ABSTRACT
People know very little as yet about this natural or inherited immunity. A thousand years hence it perhaps is the task of medicine to confer it upon all future humanity against all possible diseases. When people are not as lucky as to be born immune to a disease one can acquire the immunity in two ways. People can get a mild dose of it or some equivalent malady, or one can take advantage of the acquired immunity of some other man or animal. The former is one of three diseases each of which confers immunity against the others— namely, cow-pox, alastrim, and small-pox. Alastrim is the disease which is now spreading among the unvaccinated in Northern England. Although in its early stages indistinguishable from small-pox, it is not much more dangerous than measles. Acquired immunity to these diseases is, of course, not absolute, but fades away in the course of time, though never completely.
