Abstract
This factor was obtained from the chloroform extracts of live and heat-killed cultures of virulent tubercle bacilli. It is present in the acetone-soluble part of the "purified wax." Chromatographic methods were used for purification. The molecular wt. of this component is in the same range as that of mycolic acid, and it contains 1% N. Reduction and hydrolysis of this factor results in the loss of toxicity.