THE STREPTOCOCCI 277 



pyogenes ; now several varieties, if not species, are 

 recognised. 



Morphology. The streptococci are non-motile cocci, 

 which by regular division become arranged in chains 

 (Plate II, 6). They stain well with anilin dyes and are 

 generally Gram-positive. 



The cells average about 1 ju, in diameter, but a cell here 

 and there in the chain is frequently somewhat larger than 

 its fellows. These enlarged individuals have been con- 

 sidered by some to be arthrospores, but they are probably 

 merely involution forms. The length of the chain is 

 very variable and may be modified by cultivation, and 

 branch-chains occasionally form. In pus, etc., the chains 

 are usually not very long (Plate II, a). 



Two varieties of Streptococcus, brevis and longus, were 

 distinguished by Von Lingelsheim, the former a short 

 chain, rendering broth turbid, and non-pathogenic to mice 

 and rabbits, the latter a long chain, leaving the broth clear, 

 and always pathogenic to these animals. 



Gordon divided the streptococci into four varieties, 

 viz. (1) the S. longus, isolated from the mouth, restricted 

 to an organism forming exceptionally long chains ; (2) 8. 

 medius, including the majority of streptococci from pus, 

 sepsis, and erysipelas, and Lingelsheim's longus ; (3) 8. 

 brevis, including Lingelsheim's brevis and the Diplococcus 

 pneumonice ; (4) 8. scarlatince or conglomeratus , isolated 

 from scarlatinal angina. The Diplococcus pneumonice is 

 a short streptococcus ; it and the S. mucosus are described 

 under " Pneumonia." 



Cultural reactions. Most of the streptococci can be 

 cultivated on the ordinary culture media, and usually 

 grow both aerobically and anaerobically. On agar, or 

 better, glycerin agar, minute whitish, semi-transparent, 

 more or less isolated colonies form in twenty-four to forty- 

 eight hours (Plate II, c). Serum agar or blood agar is the 



