CHAPTER XIII. 



THE STREPTOCOCCUS-PNEUMOCOCCUS GROUP. 



THE STREPTOCOCCUS GROUP. 

 Streptococcus Pyogenes. 



Streptococcus Einheit or Vielheit. 

 THE PNEUMOCOCCUS. 



THE STREPTOCOCCUS GROUP. 



THE Streptococcus Group comprises those spherical bacteria in 

 which as multiplication proceeds the successive planes of division are 

 parallel and the individual cells remain adherent in longer or shorter 

 chains. The limits of the group are poorly defined, both morphologi- 

 cally and pathogenically. It includes organisms which occur habitually 

 in chains, both in culture and in the animal body, and its limits have 

 been extended to enclose types which exhibit chain formation only 

 in fluid media. The latter, of which Micrococcus ovalis and the 

 pneumococcus are examples, occur in the animal body as diplococci, 

 and grow thus on solid media; in fluid media they grow habitually 

 in chains of greater or lesser length, in which, however, the typical 

 diplococcal arrangement persists. The term streptococcus, there- 

 fore, is a purely morphological one ; it includes organisms which excite 

 various types of inflammation in man and in animals, together with 

 those which are ordinarily saprophytic. 



The most important members of the group exist on the skin, and 

 particularly on the mucous membranes of man, as habitual parasites 

 or "opportunists." Streptococcus pyogenes and its variants are the 

 most common of these and the most versatile in their pathogenesis. 



Streptococcus Pyogenes. Synonyms. Streptococcus erysipelatos ; 

 Streptococcus scarlatinosus ; Streptococcus septicus. 



Historical. Streptococci were seen in unstained pus by Klebs in 

 1872. Several years later Koch 1 demonstrated them in stained sec- 

 tions and in inflammatory exudates. Pasteur 2 appears to have been 

 the first to cultivate streptococci from cases of puerperal fever and to 

 differentiate them from staphylococci, both morphologically and by 



1 Untersuchungen iiber Wundinfektion, 1878. 



2 Compt. rend. Acad. sci., 1880, xc, 1035. 



