72 THE BACTERIA IN ASIATIC CHOLERA. [CH. 



and just at the margin marked by a whitish line that looks, 

 on magnification, granular. The central opaque spot en- 

 larges, and is granular, and gradually shades off, as it were, 

 into the clear areola. In some plate-cultivations the outline 

 of such colonies is not smooth, but more or less serrated. 

 (Mr. Watson Cheyne incorrectly describes the irregular out- 

 line of the colonies as of constant character.) It is not 

 correct to say that the colonies have always a serrated 

 or irregular outline, nor that they have always a smooth out- 

 line. Nor is it correct to say that the colonies at their first 

 appearance have already a central white spot a precipitate 

 of comma-bacilli in the centre for I have seen in the same 

 plates colonies which were of the size of a pea, but did not 

 show the central spot, while others that were smaller 

 possessed it. If the number of colonies that make their 

 appearance in a given plate-cultivation is large, the contigu- 

 ous colonies soon become confluent, and then we obtain an 

 appearance something like that in Fig. 23, when the outlines 

 of the original circular or oval colonies with their central 

 spot and clear areola are still easily distinguishable. If the 

 colonies were originally of irregular outline, by their con- 

 fluence a correspondingly altered appearance is produced. 

 But the general character of the colonies is their central 

 depression and granulation and their peripheral more or less 

 translucent areola of liquefied gelatine. When the growth 

 has proceeded far enough and the original number of colo- 

 nies is sufficiently great, the whole plate cultivation will be 

 found liquefied in four or five days. There is in such 

 liquefied plates a sediment of greyish powder, and here and 

 there an attempt at something like a loose filmy pellicle ; 

 this latter does not, however, extend over the whole surface 

 of the plate, but is only present here and there in the form 

 of greyish scales. On examining under the microscope a 



