ASIATIC CHOLERA. 183 



(71.6 F.) a temperature at which the gelatin still retains its 

 solid consistence. After from twenty-four to thirty hours the 

 colonies appear, on microscopic examination, as small, whitish- 

 yellow dots, with an irregular, rough margin. Their contents 

 are coarsely granular. After a time the granules become glis- 

 tening, so that the colonies appear as if they had been strewn 

 with small bits of glass. With the further development of the cul- 

 ture the gelatin undergoes liquefaction, and this occurs the more 

 rapidly the more favorable the temperature and the more nearly 

 the degree of alkalinity approximates its optimum. At the be- 

 ginning liquefaction progresses quite slowly; small, funnel-shaped 

 depressions constitute the first peculiarity visible to the naked eye. 

 Viewed with oblique light, the plate appears as if it has been 

 punctured superficially with a fine needle. This beginning lique- 

 faction is characterized by a bright boundary surrounding the in- 

 dividual colonies, as viewed with low powers of the microscope. 

 The colonies have now become somewhat darker and opaque, 

 and their irregular margin is not rarely marked by fine, pointed 

 processes. Later the liquefaction becomes more active, the 

 funnel-shaped depressions become larger, and the colonies sink 

 to the bottom of the depressions. The border surrounding the 

 colony (area of liquefaction) is no longer bright, but filled with 

 small, grayish masses. These consist of groups of bacteria that 

 have become detached from the colony and admixed with 

 the liquefied gelatin. The colony itself, a brown, irregular 

 mass, lies at the bottom of the funnel. In order to bring it 

 clearly into view, the tube of the microscope must be pushed 

 downward. In employing gelatin prepared according to the 

 method of Forster (p. 8 1 ) the plates may be exposed to a tem- 

 perature of 25 C. (77 F.) or 26 C. (78.8 F.). Under 

 these circumstances growth takes place much more actively, 

 and the peculiarities of the colonies described appear much more 

 quickly. 



Gelatin Stab -culture. Growth takes place along the entire 

 line of inoculation in the form of a white thread that grows 

 thinner downward. After from twenty-four to forty-eight hours 

 liquefaction slowly sets in in the upper portions, and here also 

 leads to the formation of a funnel. This is naturally more ex- 

 tensive than the funnel of liquefaction of the individual colonies 

 in plates. Liquefaction takes place so slowly that at first the 

 fluid formed has time to undergo evaporation. The upper por- 

 tion of the liquefaction-funnel is, therefore, empty, and an ap- 

 pearance is created as if the puncture of inoculation contained 

 an air-bubble. The line of inoculation itself appears in slight 

 degree liquefied, and, in consequence, somewhat enlarged. Its 

 lower portion contains the bacterial masses that have gravi- 

 tated thither, and which here assume the form of a spirally 



