CHAPTER XV. 



COCCACEAE. 



GENUS STREPTOCOCCUS AND ITS SPECIES PATHOGENIC 

 FOR ANIMALS. 



General discussion of the genus Streptococcus. The 



genus streptococcus is based according to Migula on its 

 method of reproduction or division. Streptococci are chains of 

 spherical bacteria that divide in one plane perpendicular to 

 the long axis of the chain. The segments do not separate but 

 are held together presumably within a capsule in short or 

 longer chains, although the divisions seem to be complete. 

 According to older and more commonly encountered classifi- 

 cations, a streptococcus is simply a number of micrococci 

 (spherical bacteria) united in the form of a chain. In some 

 of the supposedly different species the segments are oblong and 

 vary in size. Frequently, however, the segments vary in size 

 and form in the same chain. 



History. The streptococci were among the first bacteria 

 that were carefully studied. In 1874, Billroth * published a 

 monograph on septic coccabacteria in which this genus was 

 described. The fundamental studies on wound infections by 

 Koch 2 were followed, in 1881, by the work of Ogston 3 who 

 was the first to differentiate between the irregularly grouped 

 staphylococci and the chain-cocci. 



Pure cultures of streptococci were first obtained by 

 Fehleisen 4 in 1883 and by Rosenbach 5 in 1884. The thorough 

 and systematic researches of the last-named authors, together 



1 Billroth. Untersuchungen iiber die Vegetationsformen der 

 Coccabacteria septica. Berlin, 1874. 



2 Koch. Untersuchungen iiber Wundinfektion, u. s. w. 1878. 



3 Ogston. Brit. Med. Jour., 1881. 



4 Fehleisen. Aetiol. d. Erysipelas. Berlin, 1883. 



5 Rosenbach. Mikroor^. bei Wundinfektion, u. s. w. Wiesbaden, 

 1884. 



