CLASSIFICATION OF STREPTOCOCCI 409 



or human blood. Meat infusion agar is more favorable than meat 

 extract agar. The most favorable acidity is in the neighborhood of 

 1 per cent acid to phenolphthalein. The presence of dextrose in 

 the medium produces a marked effect, and acid hemolysis may result 

 in some of the so-called Gamma types. Very small amounts of 

 dextrose in blood agar, however, may lead to partial or complete 

 inhibition of hemolysis by the hemolytic Beta types. The reason 

 that the Alpha types do not produce green zones in sugar-free media 

 is explained by Smith and Brown as depending upon their scant 

 growth in such media. Under anaerobic conditions Alpha strepto- 

 cocci and pneumococci simulate Beta type zones. 



This broad classification into the hemolyticus ana viridans is the 

 practical basis on which bacteriologists at the present time deal 

 with the classification of pathogenic streptococci. Since, however, 

 bacteria, morphologically and often culturally indistinguishable 

 from those responsible for disease processes, can be found present 

 on mucous membranes of the mouth, intestines, etc., in many normal 

 persons without apparently doing the slightest harm, a great deal 

 of effort has been spent in attempts to discover whether cultural 

 characteristics could in any way be related to pathogenic properties. 

 This has led to a great many investigations on the classification of 

 various streptococci by carbohydrate fermentation. Such studies 

 have been made by Gordon, 20 Houston, 21 Andrewes and Horder, 22 

 Broadhurst, 23 Winslow and Palmer, 24 Hopkins and Lang, 25 and 

 Holman. 26 



Gordon found ten different fermentation reactions among twenty 

 pyogenic streptococci examined, and forty-eight different fermenta- 

 tion reactions among two hundred streptococci isolated from saliva. 

 Other work by Andrewes and Horder and by Buerger 27 confirms the 

 irregularity of the fermentation reactions within this group. 



20 Gordon, Kep. Med. Off. to Local Gov't Bd., Great Britain, 1902-3, 32 p. 421; 

 ibid; 1903-4, 33, p. 388. 



21 Houston, Eep. Med. Off. to Local Gov't Bd., 1903-4, 33, p. 472. 

 "Andrewes and Horder, Lancet, 2, 1906, 708. 



23 Broadhurst, Jour. Infoc. Dis., 1912, 10, 272. 



24 Winslow and Palmer, Jour. Infec. Dis., 7, 1910, 1. 

 ** Hopkins and Lang, Jour. Infec. Dis., 15, 1914, 63. 

 26 Holman, Jour. Med. Res., 34, 1916, 377. 



"''Andrewes and Horder, Lancet, 1906; Buerger, Jour. Exp. Med., ix, 1907. 



