1.Neurotropic yellow fever virus contained in Berkefeld N filtrates of infectious brain material was transferred by direct brain to brain inoculation through four passages in Saimiri sciureus, producing in each animal a well marked encephalitis characterized by a uniform clinical course and definite pathological lesions. The virus recovered from the brain of the last monkey in the series could be positively identified as yellow fever virus by passive immunity tests in mice.
2.A clinically and pathologically characteristic encephalitis was produced in Ateleus monkeys by the intracerebral inoculation of neurotropic yellow fever virus. The virus could be recovered from the brain or sciatic nerve at the death of the monkey and, when injected intracerebrally into a rhesus monkey or into mice, produced typical yellow fever virus encephalitis.
3.Neurotropic yellow fever virus contained in Berkefeld N filtrates of infectious cerebral tissues was carried by intracerebral inoculation through two passages in Cebus frontatus, causing in each animal an encephalitis which ran a typical clinical course and produced characteristic lesions. The virus could be isolated from the brain and adrenal gland at the time of the death of the monkey.
4.Neurotropic yellow fever virus, contained in Berkefeld N filtrates of infectious brain substance, was transferred by intracerebral inoculation through three passages in Callithrix monkeys, with the production of a uniformly fatal encephalitis.
5.The intracerebral inoculation of Leontocebus ursulus with neurotropic yellow fever virus was followed by a febrile reaction and in some instances by neurological symptoms and death, with the presence of small perivascular infiltrations in the brain. No success was attained in a limited attempt to transfer the virus in series in L. ursulus.