302 BIOLOGY OF PNEUMOCOCCUS 



composts of corn-cob, rye straw, sphagnum, oak leaves, farm ma- 

 nure, and soils rich in organic matter, such as peat soils and soils 

 heavily manured, and finally came to examine a sample of soil from 

 a cranberry bog. It seemed a far cry from a pneumococcus grow- 

 ing in the lung of man and, among its other vital activities, build- 

 ing up a complex carbohydrate, to a lowly saprophytic bacillus 

 capable of decomposing the specific capsular polysaccharide 

 formed by Pneumococcus. Such, nevertheless, was the case. 



In 1930, Avery and Dubos announced that a mixed bacterial 

 suspension made from bog soil was able to split the specific capsu- 

 lar polysaccharide of Type III Pneumococcus, and from the mot- 

 ley crowd of bacteria in this peat, they succeeded in isolating a 

 pleomorphic, motile, spore-bearing bacillus that was responsible 

 for the breaking down of the Type III polysaccharide. 



In their next communication, Avery and Dubos 43 gave fuller de- 

 tails of the isolation, cultivation, vital characters, and enzymatic 

 action of this curious bacillus. The authors mentioned the earlier 

 observation of Toenniessen, 1413 who had found that when Bacillus 

 vulgatus was seeded together with encapsulated Friedlander ba- 

 cilli, the latter organisms grew deprived of their capsule, and then 

 went on to describe the isolation of the new organism. The mineral 

 medium used was based on one previously described by Dubos 329 

 for the isolation of cellulose-decomposing bacteria, with the addi- 

 tion of the capsular polysaccharide of Type III Pneumococcus in 

 final concentrations varying from 0.001 to 0.2 per cent. The pneu- 

 mococcal polysaccharide was the only source of organic carbon in 

 the medium. 



This mineral medium was selected because it contained no nu- 

 trient substances that would act as readily available sources of 

 energy, so that the bacillus, when deprived of any other food, 

 would attack the specific pneumococcal polysaccharide — an exam- 

 ple of the so-called "starvation" phenomenon. By repeated trans- 

 plantation and dilution, and by heating the inoculum at 70°, Dubos 



