Il8 RELATIONSHIPS OF THE COCCACE^ 



relations were marked, the less virulent organisms being 

 best adapted to artificial media. Several cultures coagu- 

 lated milk and one liquefied gelatin. The pathogenicity 

 varied markedly, the cultures from pneumonic sputum 

 being most virulent and those from pus generally non- 

 virulent. Agglutination reactions varied with the race. 



Eyre, Leathern, and Washbourn (1906) claim that two 

 distinct types of pneumococci may be distinguished by 

 the local lesions they produce in the tissue of the rabbit. 

 One form arouses a fibrous, and the other a cellular, 

 exudate in the subcutaneum. Among the fourteen 

 organisms studied by them were three which failed to 

 ferment mannite and four which failed to ferment inulin. 

 The authors were able to transform pneumococci of high 

 virulence and poor vitality on media into forms of low 

 virulence and vigorous saprophytic growth, by artificial 

 cultivation, and to restore their original characters by 

 animal inoculation. 



On the whole this mass of investigation has made it 

 clear that the conception of numerous varieties, clustered 

 about certain well-marked centers, exactly fits the case of 

 the cocci of the nose and throat. Two such type centers 

 stand out with remarkable clearness and justify the reten- 

 tion of the two distinct genera, Diplococcus and Strepto- 

 coccus. The first, exemplified in D. pneumonia, is a 

 lance-shaped coccus, occurring in pairs and surrounded 

 by a capsule. It grows feebly on ordinary culture media, 

 but exhibits active fermentative powers, splitting mono- 



