282 MICRO-ORGANISMS IN WATER 



indol-reaction may have been caused through other 

 bacteria having furnished either the indol or the nitrous 

 acid, or both. The reaction being more pronounced 

 and more uniform in cultures in pep tone- solution (1 per 

 cent, peptone, '5 per cent, sodium chloride) than in 

 peptone-broth, only the former medium should be em- 

 ployed for the purpose. 



Another spirillum which gives the cholera-red- 

 reaction is the Vibrio Metschnikovi (not hitherto found 

 in water), which also in many other respects closely re- 

 sembles the cholera bacillus of Koch ; it is, however, 

 sharply distinguishable from the latter by its powerfully 

 pathogenic properties (producing a virulent septicaemia) 

 when subcutaneously inoculated even in the smallest 

 quantities into guinea-pigs, and more especially pigeons. 1 



Neisser 2 found a vibrio (Vibrio Berolinensis, see 

 p. 400) in Berlin tap-water which in every important 

 particular resembles Koch's cholera bacillus, the only 

 difference which could be detected being slight vari- 

 ations in the appearance of the colonies on gelatine- 

 plates. 



The confirmation of cholera bacilli by animal experi- 

 ment is best effected, according to Pfeiffer, 3 by taking a 

 full needle-loop (about '0015 grm.) of the surface-growth 

 on an agar-agar culture, distributing this in 1 c.c. of 

 sterile broth, and then injecting the latter into the 

 peritoneal cavity of a guinea-pig. The above quantity 

 of material should be a fatal dose for an animal of 



1 For further particulars see Gimther's Bakteriologie, Leipzig^ 

 1893. 



a ' Ueber einen neuen Wasser-Vibrio, der die Nitrosoiiidol Reaction 

 liefert,' Archiv fur Hygiene, 1893, p. 194. 



3 Zeitsch.f. Hygiene, vols. xi. and xiv. See also Sabolotny's paper in 

 the Centralblatt f. Bakteriologie, vol. xv. 1894, p. 150, in which he shows 

 that the marmot can be infected by small quantities of broth-cultures 

 subcutaneously introduced. For further particulars see Remarks in 

 Comma- Spirillum Table, p. 399. 



