CHEMICAL CONSTITUENTS 243 



nological reactions to the protein and carbohydrate fractions of 

 Avery and Heidelberger. 



FIRST DESCRIPTION OF THE PNEUMOCOCCAL CARBOHYDRATE 



It was, however, Heidelberger and Avery who first gave definite 

 and detailed descriptions of the carbohydrate fraction, or soluble 

 specific substance of pneumococci. No microorganism, except per- 

 haps the tubercle bacillus, has since that time been subjected to 

 such thorough chemical investigation as Pneumococcus. The stud- 

 ies of Heidelberger and Avery and their colleagues and those com- 

 ing from other laboratories have supplied a rationale for the va- 

 ried immunological and pathological behavior of pneumococci and 

 established a chemical basis for understanding many of the diverse 

 phenomena of immunity. 



In their first communication, Heidelberger and Avery (1923) 606 

 described the isolation of the soluble specific substance of Type II 

 Pneumococcus, which they concluded consisted mainly of a carbo- 

 hydrate, which appeared to be a polysaccharide built up of glu- 

 cose molecules and which, in a dilution as high as 1 to 3,000,000, 

 gave a specific precipitin reaction with homologous immune serum. 

 The method of its preparation was simple. It consisted in the con- 

 centration of an eight-day autolyzed broth culture of Type II 

 Pneumococcus, precipitation with alcohol, repeated resolution and 

 precipitation, then a careful series of fractional precipitations 

 with alcohol or acetone after acidification with acetic acid and, 

 finally, repeated fractional precipitation with ammonium sulfate 

 and dialysis of aqueous solutions of the active fractions. The prod- 

 uct gave no biuret reaction and no precipitate with phosphotung- 

 stic acid. It contained a trace of phosphorus but no sulfur and, be- 

 cause 1.2 per cent of nitrogen was found to be present, the authors 

 forebore to make any claim for the purity of the preparation. 



During the next few years there came from the laboratories of 

 the Hospital of the Rockefeller Institute a series of papers under 

 the authorship of Avery and Heidelberger and their associates, 



