Abstract
A method for the cultivation of tubercle bacilli in a liquid medium is described. Cord formation is so marked that it permits differentiation of the growth patterns of the highly virulent, attenuated, and avirulent strains. Normal blood serum or plasma favor cord formation by virulent strains in a liquid Tween-albumin medium. This effect is seen with less than 1% serum. In this medium there was a correlation between degree of cord formation and virulence. Although all cord-formers are not necessarily virulent, all virulent strains are cord-formers.