158 RELATIONSHIPS OF THE COCCACE^E 



one trisaccharide, raffinose; one polysaccharide, inulin; 

 two glucosides, salicin and coniferin; and one alcohol, 

 mannite. To these seven reactions, the clotting of milk 

 and the anaerobic reduction of neutral red were added, 

 forming what have since been known as " Gordon's tests. " 

 Applying these nine tests to three hundred different 

 strains of streptococci from normal saliva, forty-eight 

 different combinations of reactions were distinguished. 

 All the streptococci from saliva were alike in forming acid 

 in saccharose, and in failing to produce any in mannite. 

 Two types occurred with marked frequency; in both, 

 positive reactions were obtained with saccharose and 

 lactose, milk was clotted and neutral red reduced, while 

 no acid was formed in inulin, salicin, coniferin, or man- 

 nite. One type fermented rafhnose and the other did not. 

 Short chains were generally found. Twenty streptococci 

 from pathological conditions gave somewhat similar 

 reactions, but in three cases mannite was fermented. 

 Twelve cultures from dust, air, and other sources showed 

 only one positive reaction to raffinose, four negative reac- 

 tions to saccharose, and six positive reactions to mannite. 

 Houston(i905, a)applied Gordon's tests to three hundred 

 strains of streptococci from faeces, and found forty different 

 combinations of characters. A large proportion of his 

 strains fermented the disaccharides, saccharose and 

 lactose, and the glucoside, salicin. Only a third, however, 

 attacked the trisaccharide, raffinose, and a quarter the 

 alcohol, mannite, while less than 5 per cent fermented 



