268 BACTERIOLOGY. 



the same appearance as those seen upon the original 

 cover-slip preparation. 



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 liquefied portion becomes more 

 or less of a stocking-shape, and gradually widens 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-production. 



It belongs to the group of facultative anaerobes. 



In milk it rapidly brings about coagulation with acid 

 reaction. 



It is not motile, and being of the family of micrococci 

 does not form endogenous spores. It possesses, how- 

 ever, a degree of resistance to detrimental agencies that 

 is somewhat greater than that common to non-spore- 

 bearing bacteria. 



In bouillon it causes a diifuse clouding, and after a 

 time a yellow or orange-colored sedimentation. 



This organism is the commonest of the pathogenic 

 bacteria with which we shall meet. It is micrococcus 

 aureus, and is the organism most frequently concerned 

 in the production of acute, circumscribed, suppurative 



