“…Jungeblut There are discrepancies between these two sets of data in regard to the neutralization tests in the early stages, but it seems clear that the neutralizing agent appears in the serum of monkeys in response to the infection, even though its appearance is delayed. Uninoculated rhesus monkeys were found to remain seronegative regardless of age (32,33), in contrast to the serologic pattern found in the general human population.…”