236 BACTERIOLOGY. 



located in the depths of the medium they are commonly 

 seen to be lozenge or whetstone in shape, while often 

 they appear as irregular stars with blunt points, and 

 again as irregularly lobulated dense masses. In struc- 

 ture they are conspicuous for their density. Under the 

 low objective they appear, when on the surface, as 

 coarsely granular, irregularly round patches, with more 

 or less ragged borders and a dark irregular central 

 mass, which has somewhat the appearance of masses of 

 coarser clumps of the same material as that composing 

 the rest of the colony. Microscopically, these colonies 

 are composed of small round cells, irregularly grouped 

 together. They are in every way of the same appear- 

 ance as those seen upon the original cover-slip prepara- 

 tions. 



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 up- 

 per 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 

 aerobes. 



