322 TEXT-BOOK OF BACTERIOLOGY. 



on the other hand, that, under natural conditions, suppuration in 

 man is always regarded as a special reaction of the tissue to the 

 presence and activity of micro-organisms, and that, as a rule, 

 certain bacteria act in this manner as specific exciters of infection, 

 and are found in all cases of suppuration, no matter whether we 

 have an extensive and severe phlegmon or a slight paronychia, 

 metastatic pysemic abscesses or a simple furuncle. 



XX. STAPHYLOCOCCUS PYOGENES AUREUS. 



Ogston, Rosenbach, Passet, Liibbert, etc., have given us accu- 

 rate information regarding the properties of these pus bacteria. 

 A species of micrococcus, called by Rosenbach Staphylococcus pyo- 

 genes aureus, appears to be the most common. They are roundish, 

 minute cells and smaller than the erysipelas cocci. They too are 

 apt to form groups, though never in the shape of chains. They 

 are arranged rather in dense irregular heaps, the appearance of 

 which, especially in the tissue, remind one sometimes of a close 

 cluster of grapes, hence their name {arafuX-q, grape). 



Sporulation has not yet been observed in the staphylococcus 

 (nor m any micrococcus), but it exhibits a very remarkable power 

 of resistance. Drying on the cover-glass for ten days does not de- 

 stroy its capacity' of development^ chemical agents kill it only 

 when rather concentrated, and boiling water needs several minutes 

 to destroy it. In gelatin cultures it keeps fresh and capable of re- 

 production for nearly a year. 



The Staphylococcus aureus thrives at ordinary room-tempera- 

 ture, although better and more luxuriantly at a higher point (30° 

 to 37° C). Its need of oxygen is not very urgent and it even 

 thrives under a restricted access of air. It readily takes up the com- 

 mon anihn stains and is exceedingly well adapted for treatment by 

 Gram's method. 



On gelatin plates, on the second day, small, white dots appear 

 deep in the culture medium; they advance rather rapidly to the 

 surface and begin to liquefy the surrounding gelatin. An orange- 

 yellow color, especially apparent in the centre of the colony, is pro- 

 duced at the same time. The liquefaction of the gelatin is 

 usually rather extensive, and the single colonies but rarely exceed 

 a certain size. Under the microscope they appear as roundish 

 discs with sharp, smooth edges of a dark-brown or yellow color, 

 markedly granulated. 



The formation of the pigment is still more distinct on agar 

 plates. The superficial colonies, being in constant contact with 



