318 BACTERIOLOGY. 



scalloped. (See b and c, Fig. 62.) After forty-eight 

 hours (and frequently sooner), liquefaction of the gelatin 

 has taken place to such an extent that the appearance 

 of the colony is entirely altered. Under the magnify- 

 ing glass the colony proper is now seen to be torn and 

 ragged about its edges, while here and there shreds of 

 the colony can be detected scattered through the liquid 

 into which it is sinking. These shreds evidently repre- 

 sent portions of the colony that have become detached 

 from its margin as it gradually sank into the liquefied 

 area. 



At d, in Fig. 62, will be seen a representation of the 

 several appearances afforded by the colonies at this 

 stage. At the end of the second, or during the early 

 part of the third day the sinking of the colonies into 

 the liquefied pits, resulting from their growth, is about 

 complete, and under a low lens they now appear as 

 dense, granular masses, surrounded by an area of lique- 

 faction through which can be seen granular prolonga- 

 tions of the colony, usually extending irregularly between 

 the periphery and the central mass. (See e. Fig. 62.) If 

 the periphery be examined, it will be seen to be fringed 

 with delicate, cilia-like lines that radiate from it in 

 much the same way that cilia radiate from the ends of 

 certain columnar epithelial cells. 



These are the more marked phases through which 

 he colonies of this organism pass in their development 

 on gelatin plates. With some cultures the various ap- 

 pearances here given appear more quickly, while in 

 cultures from other sources they may be somewhat 

 retarded. 



On plates of nutrient agar-agar the appearance of the 

 colonies is not characteristic. They appear as round or 



