In several experiments it was shown that a deficiency of vitamin B1 in the diet increased the resistance of mice to the Lansing strain of poliomyelitis. The source of the virus was a suspension of infected mouse brain in saline, which was injected intracerebrally. Both the mortality rate and the incidence of paralysis were lower in the deficient animals than in the normally fed controls. The protection was more pronounced with respect to paralysis than with respect to the number of deaths. Some deaths in the deficient groups were undoubtedly due to the vitamin deficiency, as indicated by numerous deaths among groups of animals which were given the deficient diet but injected with a suspension of normal brain. An attempt was made to maintain a state of chronic vitamin deficiency by giving small amounts of the vitamin. The results also seem to indicate that the effect of the deficiency was more in delaying the action of the virus than in preventing it. The greatest difference between normally fed and deficient animals receiving the virus came at about the 12th day after inoculation.
Comparable results were obtained by restricting the intake of the complete diet to 1 gm. per mouse per day, which is about 40 per cent of the intake of the normally fed mice. Restriction of the caloric intake alone gave similar results. Restriction of food intake was effective in experiments in which extra vitamin B1 was given in the diet and also when a diluted saline solution was given by stomach tube to assure a sufficient intake of fluid.
Other data are necessary before an explanation can be given for the manner in which these deficiencies increase the resistance of the mice to the virus of poliomyelitis.