Is not this the way that infective diseases have appeared on the earth from age to age?
It was no new thing to say, or to guess, that phthisis was or might be infective.
As with typhoid, so with Malta fever, cholera, and some other infective diseases.
But morbus pauperum is not the only principle of infective disease.
Nor does the blood imbibed by the flea cease to be infective ...