36 



DAIRY BACTERIOLOGY 



of Bact. lactis longi 1 , and the latter by Weigmann 2 ; this organism 

 was to be found in the ropy whey formerly used in the manufacture 

 of Dutch (Edam) cheese. Sc. mastitidis (Sc. agalactice), which 

 produces notable quantities of lactic acid in milk, is the cause of 

 mastitis or inflammation of the udder in cows. It may be recog- 

 nised by the orange colouring matter which it produces after some 

 time in agar or broth with casein peptone and soluble starch. 

 Unlike Sc. cremoris, it ferments saccharose, maltose and dextrin. Sc. 

 pyogenes is a general term for a number of pathogenic streptococci 

 which do not coagulate milk ; they cause boils and many other 

 similar diseases in animals and human beings. 



Belonging to this group are also the common bacteria of sour 

 milk, Sc. lactis (Bact. lactis acidi, Leichmann), which always obtain 



FIG. 38. Streptococcus 

 No. 18). > 



rmioris (Starch's 

 1,000. 



FIG. 39. Streptococcus thermophilus. 



predominance in milk which is kept at ordinary room temperature, 

 appearing mostly as diplococci in milk. It ferments dextrin, but 

 not saccharose. Sc. fcecium is also a typical diplococaus form, 

 which grows even at 50 C., and is very common in the manure of 

 mammals. Other related organisms appear both as diplococci, 

 and as longer chains in the same culture. They are distinguished 

 according to their power to ferment a number of different sub- 

 stances such as glycerine, sorbitol, maltose, dextrin and salicin. 

 and generally also pentoses and saccharose ; their maximum 

 temperature is about 45 C. As an example may be mentioned Sc. 

 liquefaciens 3 , which liquefies gelatine and produces a bitter taste 

 in cheese. 



1 "Zeitschr. fiir Hyg. und Infectionskrankheiten," 1899, Bd. XXXII., 

 p. 361. 



2 " Milchzeitung," 1899, Bd. XVIII., p. 18. 



3 Freudenreich originally named this organism Micrococcus casei amari 

 ("Landwirt. Jahrbuch der Schweiz," 1894, p. 136). 



