Excerpt from Michael Heidelberger's laboratory notebook

In this entry in his laboratory notebook Heidelberger recorded the results of some early chemical studies of complement, isolated from the immune serum of rabbits infected with type-II and type-III pneumococcus bacteria. Heidelberger was one of the founders of the study of complement. In the 1930s, he showed that it consisted of a complex group of protein, today known to number over twenty, which play an essential enzymatic role in host defense mechanisms against invading organisms.

Raymond Dochez, whose name appears on the first page, in 1923, collaborated with Oswald Avery on isolating the soluble specific substance of pneumococcus, which they realized to be the capsular material that made each type of the bacteria immunologically-specific and determined its virulence. Heidelberger later discovered with Avery that the soluble specific substance consisted of polysaccharides--carbohydrates--not protein, as had widely been assumed.