BIO-CHEMICAL REACTIONS 601 



[In glucose, fructose, mannose, galactose, maltose and dextrin all the ten 

 streptococci tested gave an acid reaction. 



[No acid was formed by any of the streptococci in starch, glycogen, arabin, 

 convolvulin, hesperidin, jalapin, methyl glucoside, saponin, glycol, erythrite 

 or dulcite. 



[In the presence of the following substances some gave an acid reaction. 

 Rhamnose (iso-dulcite), saccharose, lactose, raffinose, inulin, amygdalin, 

 arbutin, coniferin, digitalin, helicin, populin, salicin, syringin, glycerin, sorbite, 

 and mannite. 



[With a view to classifying streptococci according to their bio-chemical 

 characters, Gordon selected from among these last-named substances the 

 following : saccharose, lactose, raffinose, inulin, salicin, coniferin and mannite. 

 He took into account also the reactions in neutral red broth and litmus milk. 

 The reactions with these nine media constitute Gordon's "metabolic" tests 

 for the streptococci. 



[Over 1200 strains of streptococci have now been submitted to Gordon's 

 tests. 300 from normal saliva (Gordon), 300 from normal human stools 

 (Houston), 200 from air (Gordon), 172 from milk (Houston), over 200 from 

 disease processes (Andrewes and Horder) as well as a number from air, 

 sewage, milk and the intestines of carnivorous and herbivorous animals 

 (Andrewes). 



[Andrewes and Horder have summarized the results obtained and conclude 

 that while in themselves the chemical tests are too arbitrary to form a 

 basis for a systematic classification yet taken in conjunction with other 

 characters " they afford a clue to the nature of any given streptococcus 

 which is invaluable." And as a result of their investigations these 

 observers consider it possible to roughly classify all streptococci into seven 

 groups : 



[A. Streptococcus equinus. A saprophytic group apparently derived from the 

 herbivorous intestine. It is chiefly found in air, dust and horse dung : on rare 

 occasions also in human saliva, human stools and urine. So far as is known it is 

 totally devoid of pathogenic properties for man. 



[B. Streptococcus mitis. Essentially saprophytic and occurring chiefly in human 

 saliva and faeces but occasionally associated with disease. It is non-pathogenic and 

 is never associated with suppuration. 



[C. Streptococcus pyogenes. This group has as its type the classical organism 

 first described by Fehleisen as streptococcus erysipelatos. It is pathogenic for man 

 and is typically associated with suppurative processes. It is only occasionally 

 found as a saprophyte. 



[D. Streptococcus salivarius. Characteristically found in saliva though it is 

 common in the intestine. This is the type which many authors describe as the 

 streptococcus brevis of the mouth. In many ways it is related to the pneumococcus 

 but is certainly not identical with it being usually non-pathogenic. According to 

 Rosenau S. salivarius is a modified pneumococcus. 



[E. Streptococcus anginosus. A pathogenic form of S. salivarius " and seems to 

 have a special connexion with inflammation of the fauces and with scarlet fever." 

 It occurs in other forms of sore- throat and in the alimentary canal, and also but 

 less commonly in other diseased conditions. 



[F. Streptococcus faecalis. This is the typical intestinal streptococcus of man 

 and, according to Gordon, is not found in normal saliva. It is sometimes found in 

 disease processes notably in cystitis. 



[G. The Pneumococci. The distinguishing feature of this group is the presence 

 of a capsule when growing in the animal body and on certain special media. The 

 cocci frequently form chains and for this reason, and because the capsule is not 

 formed on ordinary media, Andrewes and Horder are of opinion that " there 

 seems no justification for removing the pneumococci from the genus strepto- 



