THE GENUS DIPLOCOCCUS 1 15 



divided them into five groups as follows: (1) typical 

 pneumococci (including forms which produce acid in 

 inulin but in insufficient amount to coagulate serum); 



(2) Sir. mucosus (distinguished from the first class 

 by abundant moist growth and chain formation); 



(3) inulin-fermenting diplococci without capsules; (4) 

 streptococci, with no capsule, but fermenting inulin; (5) 

 typical streptococci (no capsule, no fermentation of inu- 

 lin). The relative proportion of the various types is 

 significant; typical pneumococci were isolated twenty-one 

 times and typical streptococci twenty-four times, while 

 only three cultures fell in group 2, seven in group 3, 

 and eight in group 4. 



Duval and Lewis (1905), working in Boston, studied 

 the inulin reaction with special detail, and found marked 

 variations among organisms which they considered as 

 undoubted pneumococci. They distinguished high acid 

 producers (also fermenting mannite), medium acid pro- 

 ducers, low acid producers, and forms which failed entirely 

 to ferment inulin altho showing the typical morphology. 



Buerger's (1905) results were essentially similar to 

 those of Park and Williams. Of some fifty cultures of 

 pneumococci, most showed the typical morphology, all 

 fermented lactose and inulin, and most were virulent. 

 A few showed cells smaller than the average, a few, rounded 

 cells, and a few, cells more elongated and rod-like than the 

 normal. Two cultures exhibited the wide capsule and 

 large slimy colonies of Str. mucosus; and several minor 



