THE GENUS DIPLOCOCCUS 119 



saccharides, polysaccharides, and inulin. It produces 

 acid and a greenish coloration in serum-media, but does 

 not exert hemolytic action ; and it reacts to more or less 

 specific group agglutinins. The Str. pyogenes type 

 differs in all of these respects. Between the two extremes, 

 organisms are found which exhibit almost every grade of 

 intermediate character, in morphology, cultural features, 

 fermentative power, and serum reactions. These are 

 evidently transitional forms between the commoner and 

 more stable types; and it seems hardly wise to give definite 

 names to the variety of D. pneumonia without capsules 

 or the Str. pyogenes that ferments inulin. 



The type species of the genus Diplococcus is clearly 

 D. pneumonia (Weichselbaum). This organism was first 

 described by Friedlander (1883), and named a few 

 years later by Weichselbaum (1886). Synonyms are 

 B. salivarius-septicus, D. lanceolatus-capsulatus-pneumoni- 

 cus and Str. lanceolatus. It occurs in the exudate and in 

 the lungs in many cases of pneumonia and is probably 

 the most frequent cause of that disease. The organism 

 is round or elliptical in shape, often with pointed or 

 lanceolate ends; it occurs most commonly in pairs, and 

 in the body is generally surrounded by a capsule. 



On artificial media chains are frequently observed. 

 The organism is typically Gram-positive. In cultures 

 D. pneumonia grows at temperatures over 25 degrees, 

 tho not vigorously, and develops best away from the 

 air. Heyrovsky (1905) found that the rapid death of 



