110 BACTERIOLOGY 



-which are much used than in locaHties but Httle frequented 

 by human beings. Ullmann also found them very widely 

 diffused elsewhere in nature, not only in the air but in 

 river-water and rain-water, though not in spring- water ; 

 also in ice, in the earth, and on walls. 



They are small globular immotile cells, always tend- 

 ing to form closely-packed clusters, particularly in the 



interior of tissue (fig. 35). Those 

 Ik «"s^ ^ cells, however, which are not in- 



cluded in the clusters possess the 

 power of moving with tolerable 

 activity. The individual cells take 

 up all the different aniline dyes, 

 Fie. 36.— staphyloooc grow even at ordinary tempera- 



PYOGENES AUItEUS. 



tures, though more energetically at 

 degrees of heat approaching that of the human body, and, 

 if added to sterilised milk, precipitate the casein e. 



The Staphylococcus pyogenes aureus grows very quickly 

 on the gelatine plate at the temperature of an ordinary 



Smallest islets 



- An older 

 islet, lique- 

 fying in the 

 centre 



Fie. 36. Fig. 37. 



Islets of Staphylococcus ptogekes auheus on a Gelatdje Plate. 



room, so that even as early as the second day small puncti- 

 form colonies are to be seen, which are round and possess 

 a sharply-defined circumference, and these soon approach 

 the surface and liquefy. The liquefaction extends out at 

 the periphery, and soon shows a yellowish colour in the 

 centre (figs. 36 and 37). In the thrust-culture the gelatine 

 begins to undergo liquefaction on the second or third day. 



