War Department, Surgeon General’s Office, Army Medical Museum and Library, Washington, May 23, 1901. MY DEAR GORGAS: I had only just penned you a short note, inquiring into the yellow-fever situation, when here comes your most welcome and interesting letter of May 15th. I was so much interested in Guiteras’ results. One positive case in nine inoculations is better than we had at first. We only succeeded with our _tenth_ individual. Of course, you were biting often with non-contaminated mosquitoes, as your fever cases were doubtful. Cases 3 and 6 should have failed. I expect better results from your May-infected mosquitoes. I see that Finlay and Guiteras continue to harp on the harmlessness of a _single_ mosquito’s bite, drawing the conclusion that ordinarily y. f. is due to _multiple_ bites. After some poor devil dies, they may change their minds. Carroll’s severe illness was due to a _single_ insect and poor Lazear died from a _single_ bite. Why are not malarial fevers generally double or multiple infections? We know that the opposite—single infections, as shown by one group of parasites—is the rule.... What’s the need for us to return, if you have no y. f.? Havana should get a more accommodating Chief Sanitary Officer! Hurry up your new infections. Again thanking you for your letter and the copy of G.’s report, and with best regards to your wife, believe me, Sincerely yours, W. REED. (4) War Department, Surgeon General’s Office, Army Medical Museum and Library, Washington, June 5, 1901. MY DEAR GORGAS: