In the course of the three experiments detailed here, the serum of eleven persons who are reported to have had yellow fever in Mexico, Brazil, and Peru was employed. These attacks occurred from 1919 to 1927. A variety of nationalities are represented. Four of these eleven specimens protected M. rhesus against lethal doses of yellow fever virus of West African origin. The protecting sera were from Peru and Brazil.
In the same experiments, all sera tested from six African natives and a pooled serum from several natives who had had yellow fever in four epidemics in 1926 to 1928 in the Gold Coast and Belgian Congo, West Africa, protected against the same virus as used with the Western Hemisphere sera.
The amount of serum employed in each case varied from 2.0 to 0.1 cc., depending in part on the amount of serum at hand. Two monkeys were used to test each specimen, except in one instance when only one monkey was injected, 0.5 cc. serum being available.
In the first experiment, the serum was injected subcutaneously at the same time as the virus. In the two latter experiments, the serum, diluted, was administered intraperitoneally one hour before the subcutaneous inoculation of virus. In no instance, was there any evidence of peritonitis in fatal cases.
The virus was in the form of infected monkey blood (citrated) of the Asibi strain. The dosage was 0.25, 0.2, and 0.25 cc., in experiments 1, 2 and 3, respectively.
In the unprotected animals, the course of the disease, and the pathology at necropsy were not apparently altered by the presence of the serum. Death occurred in these monkeys at intervals found to obtain in this experimental disease, averaging 5.7 days.
Of the twenty-two protected monkeys, seven seem to have recovered from mild attacks of yellow fever, as evidenced by short periods of fever a few days after inoculation.