THE SOLUBLE SPECIFIC SUBSTANCE OF PNEUMOCOCCUS : THIRD PAPER.

1. Refinements in the methods for the isolation of the soluble specific substances of Types II and III pneumococcus are described. These improvements have resulted in the isolation of the end-products in a form free from nitrogen and of enhanced activity with immune serum. 2. The soluble specific substance of Type I pneumococcus is described and shown to differ sharply from the corresponding substances of the other two types, each of which, in turn, differs from the other. 3. Progress is reported on the identification of the sugar units from which the polysaccharides are built up. 4. The evidence so far accumulated is believed to favor strongly the view that the polysaccharides isolated are the actual specific substances of Pneumococcus.