52 VARIATIONS IX FERMENTING POWER [CH. v 



knee joint, which did not ferment glucose, levulose, maltose 

 or saccharose. 



Gordon (quoted Martin, 1911) when testing the "sugar 

 reactions" of 25 strains of micrococcus catarrhaUs, discovered 

 3 strains which fermented glucose, maltose, galactose and 

 saccharose none of which sugars are normally fermented by 

 this organism. 



Strains of B. diphtheriae are very variable in their action 

 on lactose and saccharose (Graham Smith, 1906). 



Klotz (1906) describes a coliform organism, quickly ag- 

 glutinated by high dilutions of typhoid serum, which differed 

 from B. typkosus in being able to ferment glucose, lactose 

 and saccharose. 



Many other examples might be given of differences in 

 fermentation properties displayed by different strains of the 

 same organism. 



II. The same strain may vary spontaneously during 

 cultivation. 



Arkwright (1909) mentions a strain of the meningococcus 

 which when first tested fermented no sugars : subsequently, 

 throughout a period of many months, it fermented maltose 

 only ; finally, after 10 months artificial culture, it fermented 

 both maltose and glucose. Another of his strains, on the 

 other hand, at first fermented both maltose and glucose but 

 later fermented neither. 



Rosenow (1914) obtained a strain of haemolysing strepto- 

 cocci from the throat in a case of Scarlet fever. A culture 

 on blood agar yielded two distinct kinds of colonies, (a) 

 colonies of a haemolysing organism which fermented mannite 

 but failed to ferment maltose and saccharose, (b) green 

 producing colonies of a non-haemolysing organism which 

 would not ferment mannite but fermented maltose and 

 saccharose. The two strains differed also in their patho- 

 genicity. 



Andrewes and Gordon (1905-6) found that i% an undoubtedly 

 pure" strain of staphylococcus pyogenes aureus, which yielded 

 a brilliantly pigmented culture, produced on subculture 



