A propos of Distempers, I am going to tell you a thing that I am sure will make you wish your selfe here. The Small Pox so fatal and so general amongst us is here entirely harmless by the invention of engrafting (which is the term they give it). There is a set of old Women who make it their business to perform the Operation.

I am patriot enough to take pains to bring this usefull invention [smallpox inoculation] into fashion in England, and I should not fail to write to some of our Doctors very particularly about it, if I knew anyone of 'em that I thought had Virtue enough to destroy such a considerable branch of Revenue for the good of Mankind, but that Distemper is too beneficial to them not to expose to all their Resentment the hardy wight that should undertake to put an end to it.

I attained a triumph so complete that it is now rare to meet an American with marks of small pox on his face... Benefits are valuable according to their duration and extent, like the showers from heaven, but the benign remedy Vaccination saves millions of lives every century, like the blessing of the sun, universal and everlasting.
(Remark made near the end of his life.)

Nature, in the first compoundiug and forming of us, hath laid into the Substance and Constitution of each something equivalent to Ovula, of various distinct Kinds, productive of all the contagious, venomous Fevers, we can possibly have as long as we live.

The physical signs of measles are nearly the same as those of smallpox, but nausea and inflammation is more severe, though the pains in the back are less.