174 APPLIED BACTERIOLOGY 



to the nature of the disease on the immediate microscopic 

 examinatio'n of one of these flakes, whether from the con- 

 tents of the ileum or in a living patient from the stool, 

 a minute fragment of one of the flakes being suspended 

 in salt -and -water, and examined by the hanging -drop 

 culture, when practice will enable the trained observer to 

 recognise the spirillum of Koch by its characteristic screw- 

 like movement. Again, if a portion of a flake be crushed 

 carefully between two cover-glasses, which are then drawn 

 apart and stained, it will be found that in cases of cholera 

 the organisms present what is known as the ' fish-in-stream ' 

 appearance; and when this is seen, the case may be re- 

 ported as true cholera without awaiting the result of 

 cultural experiments, which of necessity involves some 

 delay, which in the face of a possible epidemic it is of the 

 utmost importance to reduce as far as possible. 



Such characteristic appearances are, however, only to be 

 found in a minority of cases, and it is generally necessary 

 to perform the following cultural experiments : Two or 

 three gelatine tubes are melted, cooled to 35° C, and then 

 inoculated and poured into plates, while at the same time 

 some tubes containing sterilised Dunham solution are 

 inoculated. (This solution consists of peptone 1 per cent., 

 salt 5 per cent., in distilled water.) The gelatine plates 

 are examined after forty-eight hours at 22° C, and the 

 colonies produced by true cholera are distinguishable by 

 the appearance of small funnel-shaped depressions in the 

 gelatine, having yellowish points at their apex, while the 

 gelatine begins to liquefy. Fragments of colonies having 

 these characters are picked out with a platinum needle for 

 microscopic examination, both in the hanging-drop culture 

 and in cover-glass specimens. The Dunham solution 

 tubes are incubated for twelve hours only, and are then 

 probably cloudy from the rapid growth of the organisms, 



