PATHOGENIC SPIRILLA. 223 



gelatine on the surface becomes liquefiedj and directly 

 that this liquefaction has reached the sides of the 

 test-tube, it begins to extend downwards. The whit- 

 ish mass of the colonies now sinks to the bottom of 

 the fluid gelatine, and as the liquefaction proceeds 

 the colonies sink lower and lower, without the rem- 

 nant of the whitish thread being altered in appearance. 

 On agar-agar the comma bacillus forms whitish aggre- 

 gations, which, however, are not characteristic. If 

 sulphuric or hydrochloric acid be added to a cholera 

 bacillus culture, a slight red coloration is produced. 

 This, however, as has been recently discovered, is not 

 peculiar to the cholera bacillus, but also occurs with 

 the cultures of a large number of other bacteria, especi- 

 ally with those of some allied spirilla. 



There are not a few organisms which are very 

 similar to the cholera bacillus, both morphologically 

 and in their development in cultures, and which have 

 been frequently mistaken for it. Although they are 

 not pathogenic in man, on account of this resemblance, 

 a short description is here given of them. 



Firstly, the Spirillum Finchleri presents morpho- 

 logically an appearance not essentially different from 

 that of the comma bacillus of Asiatic cholera. It 

 may be a little thicker and plumper, but no distinc- 

 tinction can be based on this. On this account at 

 first they were confused with each other, and later the 

 Spirillum Finchleri was considered to be the exciting 



