Lab notes from Michael Heidelberger and Oswald Avery's experiments on pneumococcus bacteria and polysaccharides (3 of 4)

The laboratory notes document Heidelberger's and Oswald Avery's seminal experiments, conducted between 1923 and 1925, through which they found that powerful antigens of type-specific pneumococcus bacteria were polysaccharides--carbohydrates--not proteins, as scientists had assumed. Heidelberger and Avery showed that it was what Avery had called the "soluble specific substance" (soluble because it could be dissolved in saline solution), the polysaccharides, contained in the capsules of the various types of pneumococcus bacteria, which determined the virulence of each type. Their discovery was a crucial advance in the application of chemistry to immunology. For the rest of his long scientific career, Heidelberger explored the many implications of this discovery both for experimental science and for medicine.