1. Inhibition of glucose utilization in homogenates of brains of mice infected with poliomyelitis virus (Lansing strain) is reported. The inhibition occurs with glucose, or fructose-6-phosphate as substrate. No inhibition occurs in the presence of hexosediphosphate.
2. Brain homogenates of mice infected with the Theiler FA strain of mouse encephalomyelitis virus show inhibition ranging between 45 and 85 per cent (average 73 per cent).
3. Purified preparations of the Lansing and the Theiler FA strain invariably inhibit glycolysis when added to homogenates of normal mouse brain. A similar, but much less consistent inhibition is provoked by adding high concentrations of non-neurotropic viruses (influenza A and tobacco mosaic virus) to normal mouse brains.
4. The magnitude of inhibition caused by the purified virus is a function of the virus concentration and depends on temperature and time of incubation of the virus-brain mixture.
5. The inhibition of glycolysis in the brains of mice infected with Theiler FA virus and in normal brain-Theiler FA virus mixtures is prevented by the addition of preparations of DPN and glucose.