The type-specific substance from Pneumococcus type 11A(43).

1. The type-specific substance from Pneumococcus type 11A(43) is a polymer containing d-glucose, d-galactose, glycerol, phosphate and O-acetyl in the approximate molecular proportions 2:2:1:1:2. 2. Removal of the O-acetyl groups with ammonia gave a compound no longer active towards type 11A antiserum. 3. Treatment of S.11A with sodium borohydride, followed by hydrolysis with alkali yielded a phosphorus-free polysaccharide, whose structure was studied by methylation and by degradation with periodate. 4. Examination of S.11A and its de-O-acetyl derivative by periodate oxidation led to the partial structure (XI) for the type-specific substance, which thus has several features in common with S.18.