The same is true of Europe, Asia and Africa. If Memphis, in Egypt, had been an endemic center of yellow fever in the dim dawn of man’s civilization, the disease would be endemic there at present. While the native of Memphis who labored on the pyramids of Cheops would have been immune to yellow fever, enough fresh material from up the Nile would have continued coming into Memphis to have kept the disease going. And the hundred thousand men whom old Cheops kept at work on his pyramids for twenty years would have died in such numbers that he would either have had to give up this work, or would have exhausted the population of his kingdom; but the interior of Egypt would never have become immune any more than has the interior of Cuba, or Panama, or Brazil in our own time. Had Athens been subject to yellow fever in the time of Alcibiades, yellow fever would certainly be there to-day. All the citizens of the city of Athens would have become immune, but a sufficient number of Greeks would have been constantly coming into the city from the interior to have kept the disease endemic, exactly as has occurred in our own time at Havana. I think, then, that we can throw aside Europe and Asia as the original source of yellow fever. Another theory of the origin of yellow fever is that it originated in Africa and was carried to America in connection with the slave trade. Next to that of the origin in America, this is the most generally accepted explanation. But the arguments against this belief are unanswerable. According to Lind, the first yellow fever that appeared in Africa was in Senegal, in 1759. If yellow fever had existed along the coast, it would certainly have spread in the two hundred and fifty years during which this coast had been occupied by Europeans since its settlement by the Portuguese in the year 1415. As a matter of fact, it was recognized many times in America before it appeared in Africa. The American origin of yellow fever impresses me as being the most reasonable and the one most in accord with the recorded facts. But it seems to me that the bulk of evidence points toward its having originated in America at some period prior to its discovery by Columbus.