244 BACTERIOLOGICAL EXAMINATION OF WATER. 



Peptone and Salt Solution. Indol and nitrites are produced, 

 so that a red coloui is obtained on adding a few drops of pure 

 sulphuric acid. 



Milk. Becomes acid, and the casein is coagulated about the 

 eighth day. 



Microscopical Appearances. As a rule, it appears nearly iden- 

 tical with Koch's spirillum ; sometimes, however, larger and 

 thicker forms are seen. It is very motile, and has one flagellum. 



Pigeons are readily killed by sub-cutaneous injection of very 

 small quantities of this organism ; inoculation of the same 

 quantity of Koch's organism produces practically no effect. 

 This test at once enables a diagnosis to be made between the 

 two organisms. 



Spirillum of Deneke. 



This spirillum was isolated by Deneke from old cheese ; it is 

 also known as the Spirillum tyrogenum. In morphology it is 

 closely allied to Koch's spirillum. 



Gelatine Plates. The colonies, to the naked eye, have a 

 yellowish colour, and they liquefy gelatine more rapidly than 

 Koch's microbe. Under a low power the margins of the young- 

 colonies are seen to be smooth and regular. Later, there is 

 often a very close resemblance to the colonies of the cholera 

 spirillum ; but, as a rule, the yellow colour and the more 

 marked liquefaction enable a diagnosis to be made. 



Gelatine-stab. Closely resembles the appearances produced by 

 Koch's vibrio. Liquefaction however is more rapid. 



Potato. It produces a thin yellowish layer. 



Peptone and Salt. It produces indol, but only traces of 

 nitrites, so that the " cholera-red " reaction is produced very 

 feebly and irregularly on the addition of pure sulphuric acid. 



Vibrio Aquatilis. 



This vibrio was first isolated by Giinther from the water of 

 the river Spree at Stralaw. It was also found by Kiessling in 

 the washings of the sand used in the water-works of Altona. 



Gelatine Plates. The colonies at first are circular, with a 

 perfectly smooth rim. They are brown in colour, and have 

 granular contents. Liquefaction takes place very slowly, and 

 the colony eventually sinks in a basin of liquefied gelatine. 



