At the same time that he entered the building two other non-immunes entered the other compartment where they slept for eighteen nights separated from the mosquitoes by the wire screen. They showed no signs of taking the fever.
In another mosquito-proof house two soldiers and a surgeon, all non-immunes, lived for twenty-one days. From time to time they were supplied with soiled articles of bedding, clothing, etc., direct from the yellow fever hospital in the city. These articles had been soiled by the urine, fecal matter and black vomit obtained from fatal and other cases of yellow fever. These articles were handled and shaken daily, but no disease developed among the men and at the end of the twenty-one days, two other non-immunes relieved them and handled a new supply of clothing in the same way, sleeping between the same sheets that had been used by a patient dying of yellow fever and exposing themselves in every possible way to the soiled clothing. But no disease developed. That these men were susceptible was shown later by inoculating some of them, when they developed the disease.
In another experiment certain men in a camp allowed themselves to be bitten by mosquitoes that had passed through the proper period of incubation and every one of them and no others contracted the disease. It was also shown that a mosquito was capable of communicating the disease as long as fifty-seven days after it had bitten a yellow fever patient. Another set of experiments showed that a subcutaneous injection into a non-immune of a very small quantity of blood from the veins of a yellow fever patient in the first two or three days of the disease would produce the fever.
Since that time much other work has been done by independent workers as well as by French and English Commissions both working at Rio de Janeiro. The results of their investigation are practically the same and may be summed up as follows:
1. The virus of the yellow fever is in the blood-plasma, not in the corpuscles, for these may be removed and the plasma still be infective.
2. The virus is conveyed from one patient to another by the yellow fever mosquito, _Stegomyia calopus_, and in no other way except by experimental injections.