Staphylococci Pyogenes Aureus et Albus 255 



houses and hospitals, especially in the surgical wards if 

 proper precautions are not exercised. They are common 

 upon the skin, in the nose, mouth, eyes, and ears of man; 

 they are nearly always present beneath the finger-nails, 

 and they sometimes occur in the feces, especially of chil- 

 dren. 



Morphology. The cocci are small, measuring about 

 o. 7 fJ. in diameter. When properly stained, the organisms are 

 found to consist of hemispheres separated from one another 

 by a narrow interval, the approximated surfaces being flat- 

 tened. As observed in hastily stained preparations, they 

 are spheric. There is no definite grouping in either liquid' 

 or solid cultures. It is only in pus or in the organs or tissues 

 of diseased animals that one can say that a true staphylo- 

 coccus grouping occurs. 



The organisms are not motile and have no flagella. 



Staining. The organisms stain easily and brilliantly 

 with aqueous solutions of the anilin dyes and by Gram's 

 method. 



Isolation. Staphylococcus aureus is an easy organism to 

 isolate, and can be secured by plating out a drop of pus in 

 gelatin or in agar-agar. Such preparations, however, gen- 

 erally do not contain Staphylococcus aureus by itself, but in 

 association with Staphylococcus albus. 



As the colonies of Staphylococcus aureus differ considerably 

 in color, some being much paler than others, I have often 

 doubted whether Staphylococcus albus was a different spe- 

 cies, or simply a non-chromogenic form of pus coccus. It is 

 possible to secure nearly every intermediate tint from white 

 to golden yellow by a little manipulation. Should this be 

 the case, it would reduce the pus cocci to a single species, 

 Staphylococcus pyogenes. 



Cultivation. The staphylococci grow well upon all the 

 standard culture media either in the presence or in the ab- 

 sence of oxygen at temperatures above 18 C., the most rapid 

 development being at about 37 C. 



Colonies. Upon the surface of gelatin plates the colonies 

 appear as small whitish points after from twenty-four to 

 forty-eight hours (Fig. 74), rapidly extending to the sur- 

 face and causing extensive liquefaction of the medium. 

 The formation of the orange pigment can be best observed 

 near the center of the colonies. Under the microscope the 

 colonies appear as round disks with circumscribed, smooth 



