Abstract
Yeast autolysate (a filtrate of autolysed fresh yeast) was found to contain the necessary V and X factor for the growth of H. influenzae. All the 19 strains used gave a profuse growth within 24 hours in 10% yeast autolysate brain heart infusion, whereas controls in brain heart infusion produced no growth. In 10% yeast autolysate saline growth was less profuse and took place more slowly.