Albino rats raised on a synthetic basal diet containing 2% desiccated yeast as the sole source of vitamin B showed normal growth and reproduction, but lost 72.9% of their 233 young before the end of the nursing period. One-half the deaths occurred in the 1st week, with subcutaneous, visceral, and intracranial hemorrhages predominating; remaining deaths occurred in the 3rd week, with clinical picture of marked paralysis, profuse watery stools, and subnormal temp. Paralytic rats strong enough to eat directly from the experimental ration recovered completely. Those dying showed at autopsy myelin degeneration of the sciatics, vagi, and other myelinated nerves, and numerous macroscopic and microscopic visceral and intracranial hemorrhages. Addition of lemon juice had no visible effect on hemorrhagic condition or paralysis. Increase of yeast to 7% in the mother''s diet decreased the mortality in the 96 offspring to 9.3%, practically eliminated paralysis, and greatly lessened the hemorrhagic condition.