QUALITATIVE BACTERIOLOGICAL ANALYSIS. 247 



the peritoneal cavity of guinea-pigs which had been infected 

 intra-peritoneally by the microbes. The phosphorescence is not 

 an absolutely constant phenomenon ; it may disappear when the 

 microbes are cultivated for a long time on nutritive media. 

 Dunbar found that the phosphorescent vibrios failed to give 

 Pfeiffer's reaction. He tested a large number of these organisms 

 and found that a pathogenic action was exerted both on the 

 control guinea-pigs and on the guinea-pigs which had received 

 the vibrios plus cholera serum ; the vibrios when withdrawn 

 from the peritoneal cavity were found to be still highly motile. 

 RumpePs statement that the true cholera vibrio can be changed 

 into the phosphorescent variety requires confirmation. 



The characteristics of Dunbar^s vibrios will be seen from the 

 following short description of some of these organisms: 



Vibrio No. 17a was a rather plump, curved bacillus, with 

 rounded ends. It was highly motile and stained unevenly. On 

 agar there was a greyish-white, moist layer. In peptone-water 

 at 37 C. a marked growth appeared after fourteen hours ; a 

 thin membrane formed on the surface, which later became very 

 thick and villous ; a typical " cholera-red " reaction was ob- 

 tained. In gelatine-stab after four days there appeared a clear 

 air bubble, below which the gelatine was liquefied in a capillary 

 form along the stab. In gelatine plates there was no lique- 

 faction apparent to the naked eye, the colonies appeared as 

 white points. Under a low power a thin, colourless, finely 

 granular surface growth was seen ; the deep colonies were also 

 colourless and finely granular, and rather sharply outlined. 

 Phosphorescence was always observed. 



Vibrio No. 29 in appearance exactly resembled No. I?A. On 

 agar a greyish-white slimy growth was seen. In peptone- water 

 there was a marked growth, with formation of a thick pellicle cm 

 the surface ; a typical " cholera-red " reaction was obtained, in 

 gelatine-stab after six days the gelatine was completely liquefied 

 to the depth of 1 c.m. ; below this the gelatine was liquefied in 

 a capillary form. The appearance of the colonies in gelatine 

 plates exactly resembled No. 17A. Phosphorescence was always 

 seen. 



Vibrio No. 30 was plump, highly motile, and possessed a long 

 flagellum at one end. On agar there was a greyish slimy 



