264 TEXT-BOOK OF BACTERIOLOGY. 



At this period of development (on about the fifth or sixth day) 

 the culture presents an extremely significant and remarkable pic- 

 ture. Its equal is met with in no other kind of bacterium, and 

 a similar one only in a few micro-organisms now known, such 

 as the violet-water bacillus, Deneke's cheese bacillus, and Metsch- 

 nikoff's vibrio. The former is distinct enough by its color; it pos- 

 sesses also a quality in common with the two latter, that of a 

 much more rapid growth and a quicker liquefaction of the gelatin. 



As the culture of the cholera bacillus grows older, the gelatin is 

 more and more peptonized. It gets softened after a few weeks in 

 the upper half of the inoculating puncture, and changed into a tur- 

 bid yellowish solution. The bacteria settle on the bottom, where the 

 solid layer lies in dense heaps. A whitish film, a kind of mouldy 

 skin, has spread over the surface and consists of thin, brittle little 

 pieces. This is a rich mine for very odd involution forms of the 

 comma bacilli. They are here on the verge of dissolution, and an- 

 ticipate this event by all sorts of deformities and crippled forma- 

 tions, hardly presenting a similarity with the former figure. Large 

 and small balls, thick lumps, mulberry-shaped berries, most minute 

 debris of cells, and things looking like nails with disproportionately 

 large heads, are found in a motley heap. 



The gelatin culture is usually completely liquefied and no longer 

 transmissible after about eight weeks. 



The comma bacilli are sustained longer on agar-agar; they have 

 been found still alive on it after almost nine months. They develop 

 on the oblique surface of this medium as a moist film of white 

 lustre along the entire inoculating line. Blood-serum is gradually 

 liquefied. 



While (as we have stated) the gelatin, agar, etc., on which the 

 cholera bacilli are expected to prosper must be of marked alka- 

 line reaction, the comma bacilli possess a notable capacity of 

 accommodating themselves also to acid media, provided the acid 

 is of vegetable origin. 



The surface of boiled potatoes frequently has a feeble but dis- 

 tinctly acid reaction, and yet the cholera bacilli develop on it, only, 

 of course, by the aid of incubation temperature. Their manner of 

 growth on them is very peculiar. In the vicinity of the inoculating 

 spot there extends a grayish-brown, thin, and somewhat trans- 

 parent layer reminding one of the appearance of the glanders cul- 

 tures on the same medium, but they are usually brighter and less 

 tough. 



The cholera bacilli thrive rapidly and luxuriantly in the com- 

 mon nutrient bouillon. There is formed on the surface, especially at 



