Foreshadowing of the Germ Theory
Dr. Samuel Johnson, in a letter to Mrs. Thrale, under date of November 12, 1781, in the course of a sympathetic reference to a friend of theirs who was suffering from dysentery, expressed the opinion that the specific cause of that disease, one of the oldest of which we have any record, was an amœba or animalcule. He says, “If Mr. B—— will drink a great deal of water, the acrimony that corrodes his bowels will be diluted, if the cause be only acrimony; but I suspect dysenteries to be produced by animalculæ which I know not how to kill.” Long before Johnson’s time, Morgagni’s investigations had shown the character of the inflammation of the lower intestines, but that a century before the revelation of pathogenic micro-organisms Johnson should have suspected causal relations between amœboid cells and an infectious disease is very curious. Even the term he employed is used in classification, as of the two forms of dysentery which are recognized, one is known as amœbic, and the other as bacillary.