IN VITRO TRANSFORMATION OF PNEUMOCOCCAL TYPES : II. THE NATURE OF THE FACTOR RESPONSIBLE FOR THE TRANSFORMATION OF PNEUMOCOCCAL TYPES.

1. Further observations on the conditions under which transformation of pneumococcal types may be induced by in vitro procedures are presented. 2. R cultures possessing only slight degrees of R stability are most suitable for transformation purposes by in vitro procedures. 3. Vaccines prepared from cultures subjected to the action of bacterial enzymes liberated (a) in old broth cultures, (b) during mechanical disruption of young bacterial cells, are not effective in inducing transformation of type. 4. The property of an S vaccine responsible for transformation of type is not related to the specific soluble substance of pneumococcus. 5. Attempts to effect transformation of type by the use of cell-free extracts of pneumococcus have so far proved unsuccessful.