246 BACTERIOLOGY. 



ularly grouped together. They are in every way of 

 the same appearance as those seen upon the original 

 cover-slip preparations. 



Prepare from one of these colonies a pure stab-culture 

 in gelatin. After thirty-six to forty-eight hours lique- 

 faction of the gelatin along the track of the needle, 

 most conspicuous at its upper end, will be observed. 

 As growth continues the liquefaction becomes more or 

 less of a stocking-shape, and gradually widens out at its 

 upper end into an irregular funnel. This will continue 

 until the whole of the gelatin in the tube eventually 

 becomes fluid. There can always be noticed at the 

 bottom of the liquefying portion an orange-colored or 

 yellow mass composed of a number of the organisms 

 which have sunk to the bottom of the fluid. 



On potato the growth is quite luxuriant, appearing as 

 a brilliant, orange-colored layer, somewhat lobulated 

 and a little less moist than when growing upon agar- 

 agar. It does not produce fermentation with gas-pro- 

 duction. It belongs to the group of facultative aerobes. 



In milk it rapidly brings about coagulation with acid 

 reaction. 



It is not motile, and being of the family of micro- 

 cocci does not form endogenous spores. It possesses, 

 however, a marked resistance toward detrimental agen- 

 cies. 



In bouillon it causes a diffuse clouding, and after a 

 time presents a yellow sedimentation. 



This organism is the commonest of the pathogenic 

 bacteria with which we shall meet. It is the staphyh- 

 cooous pyogenes aureus, and is the organism most fre- 

 quently concerned in the production of acute, circum- 

 scribed, suppurative inflammations. It is almost every- 



