“…Many attempts to classify haemolytic streptococci into definite serological groups by means of agglutination tests have met with such difficulties as spontaneous clumping of organisms, cross agglutination with different types of immune sera, and partial absorption of agglutinins. To avoid spontaneous agglutination, Dochez, Avery and Lancefield (1919), Bliss (1922), Durand and S6dallian (1925) and Rosner (1928) grew antigens in a salt-free medium containing phosphate buffer; Tunnicliff (1922) usedascitic broth plus glucose; Gordon (1921) used trypagar plus ascitic fluid; Shibley (1924) allowed the organisms to grow at room temperature; Smith (1926) suspended washed organism in 0.001 N/1 NaOH and diluted the immune serum with M/320 NaCl solution; James (1926) grew organisms first in salt-free meat infusion broth, then transplanted them to tryptic digest broth; Noble (1927) used serum and antigen in a more concentrated form than is usual, reading the results after the mixture was shaken for 2 minutes; Stevens and Dochez (1926), Spicer (1930) and Williams and Gurley (1932) added strips of sterile potato to phosphatebuffered broth; McLachan and Mackie (1928) used phosphate-HELEN PLUMMER buffered broth plus glucose; Gunn and Griffith (1928) and Allison (1931) used a slide agglutination test observed microscopically; Mueller and Klise (1932) diluted immune serum with physiological saline containing 2 per cent normal horse serum. To avoid cross agglutination, agglutinin-absorption tests have been chiefly used.…”