STAPHYLOCOCCUS PYOGENES AUREUS 385 



but varying within the extreme limits of 0.4 to 1.2 miera. Any 

 considerable variation from the average size, however, is rare. The 

 perfectly spherical character may not develop, whenever, as is 

 usually the case, two or more are grouped together, unseparated 

 after cell cleavage. In this case, adjacent cocci are slightly flattened 

 along their contiguous surfaces. 



Examined in smears from cultures or pus, the staphylococci may 

 appear as single individuals, in pairs, or, most frequently, in irregular 

 grape-like clusters, Occasionally, short chains of three or four may 





FIG. 43. STAPHYLOCOCCUS PYOGENES AUREUS. (After Gunther.) 



be seen. In very young cultures in fluid media, the diplococcus form 

 may predominate. 



The staphylococci stain with all the usual basic aqueous anilin 

 dyes, and, less intensely, with some of the acid dyes. Stained by 

 the method of Gram, they retain the amlin-gentian-violet. Gram's 

 method of staining is excellently adapted for demonstration of these 

 cocci in tissue sections. 



Although exhibiting marked Brownian movements in the hang- 

 ing drop, staphylococci are non-motile and possess no flagella. They 

 are non-sporogenous and form no capsules. 



Cultural Characters. Staphylococci grow readily upon the usual 

 laboratory media. The simpler media, made of meat extract, are 

 quite as efficient for their cultivation as are the freshly made meat- 



