CHAPTER XVI. 



COCCACEAE. 



-GENUS MICROCOCCUS AND ITS SPECIES PATHOGENIC FOR 



ANIMALS. 



General discussion of the genus micrococcus. The genus 

 micrococcus includes the spherical bacteria that divide in two 

 planes. It includes those forms described by the earlier writers 

 as micrococci, that is, single spherical organisms; diplococci, 

 where they are united in pairs ; tetracocci, where they appear 

 in fours ; and staphylococci, where they appear in clumps or 

 masses. This genus contains a large number of species, more 

 than 200 having been described. They are largely saprophytes. 

 There are but few species known to be important in the pro- 

 duction of disease in animals. Several of the infectious dis- 

 eases of man, however, are due to organisms belonging to this 

 genus. In animals, the micrococci of most importance are 

 those associated with wound infection and which are com- 

 monly called pyogenic micrococci. 



History. Historically, micrococci were first described by 

 Billroth, Koch, Eosenbach, 1 Pasteur, 2 Ogston, and others who 

 were engaged in studying wound infection bacteria. The 

 group of micrococci that grow in clumps were found to be 

 the most common cause of wound infection and consequently 

 those forms described in older classifications as staphylococci 

 (so called from their growth in irregular grape-like clusters) 

 were found to be the most common and apparently the most 

 important of the micrococci. Two varieties of these were rec- 

 ognized, namely, Micrococcus pyogenes, varieties albus and 

 citreus, referring to the color of the growth of the colonies on 

 solid media. 



The Botryococcus ascoformans Bellinger or M. botryo- 

 genes Rabe appears to be identified w r ith M. pyogenes. 



1 Loc. cit. 



2 Pasteur. Comp. Rend, de 1'Acad. des Sci., Vol. CX (1880) p. 1033. 



