No evidence was found to support the idea that vaccine virus placed in the cisterna magna is capable of producing an acute disseminated encephalomyelitis with perivascular demyelination either in normal or in partially immune monkeys. A testicular extract (Reynals' factor) did not induce vaccine virus to cause an acute disseminated encephalomyelitis in monkeys. Repeated intramuscular injections of brain extracts and brain emulsions into eight monkeys were followed in two instances by an inflammatory reaction, accompanied by demyelination, in the central nervous system. The exact relation of the injections to the disease of the nervous system is not clear. The combined action of vaccine virus and an emulsion of fresh rabbit brain did not lead to the production of an acute disseminated encephalomyelitis in monkeys that had received repeated intramuscular injections of emulsions and alcohol-ether extracts of normal rabbit brains.

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The repeated intramuscular injections of aqueous emulsions and alcohol-ether extracts of sterile normal rabbit brains in some manner produced pathological changes accompanied by myelin destruction in the brains of 7 of 8 monkeys (Macacus rhesus). Eight, control monkeys remained well. Cultures from the involved brains remained sterile, and no transmissible agent was demonstrated by means of intracerebral inoculations of emulsions of bits of the brains into monkeys, rabbits, guinea pigs, and white mice.

In the preceding paper (1) we described the clinical picture presented by two patients who were suffering from a nonbacterial lymphocytic meningitis, and the method b y which a virus-like agent was isolated from each patient's spinal fluid. Then we showed t h a t the two agents were immunologically identical and t h a t they were etiologically related to the disease process in the individuals from whom they were obtained. In the present communication we shall describe experiments in support of the viral nature of the agent, state details concerning the range of susceptible hosts and the clinical and pathological picture developed in each, compare our active agent with known viruses t h a t spontaneously affect the central nervous system of man or lower animals or t h a t might have contaminated our materials because of their proximity in the laboratory, and, finally, discuss the relative importance of our agent as a cause of disease in human beings. Viral Nature of the Transmissible AgentInvisibility.--Numerous sections of organs from animals dead of infection with the active agent have been stained according to Giemsa's method and studied by means of the microscope. In no instance has it been possible to demonstrate the presence of ordinary bacteria, protozoa, or fungi. Failure of Cultivation.--Infectious material was seeded in meat infusionbroth and on blood agar. The cultures were then incubated either aerobically or anaerobically at 37°C. for 2 weeks. With the exception of a few obvious contaminants no organism of etiological significance was encountered.Filterability.--Both strains of the active agent were tested by means of Seitz filters and graded collodion membranes. Inasmuch as the findings with the 2 strains were the same and since only the W. E. strain was tested with Berkefeld 415 on

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