QUESTIONS. 173 



Diagnosis. For this purpose the rate of the growth on 

 gelatin plates and the rapidity of the indol-formation in 

 Dunham's solution are made use of. The experiments are 

 carried on as follows : 



The small flocculent masses found in the discharges of 

 choleraic patients are taken and mixed with a large quantity 

 of diluted peptone-bouillon, or preferably with Dunham's 

 solution of peptone, and put into the incubator for three or 

 four hours. At the end of that time a few drops from the 

 surface of the liquid are taken and inoculated on gelatin 

 plates, when characteristic colonies are developed in a few 

 hours. Cover-glass preparations are also made, and if rods 

 with a morphological appearance of cholera bacteria are found, 

 agar plates are also made in this way. Melted agar is poured 

 into Petri dishes, and these put into the incubator for a few 

 hours in order to allow the evaporation water to collect on the 

 surface of the agar ; this water is poured off and the dishes 

 inoculated by streaking the surface with the suspected material. 

 In a very short time characteristic colonies develop along the 

 line of the streak. 



The cholera bacteria are of very rapid growth, but possess 

 little or no resisting power, being destroyed by the physical 

 measures just mentioned, and also in a very short time by 

 the use of weak disinfectants. 



Vaccinations against cholera have been performed on an ex- 

 tensive scale in cholera-infected countries. Haffkine's method 

 of injecting attenuated or small doses of virulent cultures of 

 the cholera spirillum as a means of protection against an 

 attack of cholera seems to have rendered considerable service 

 in protecting persons exposed to the disease ; and experiments 

 made by Ferran, in Spain, with attenuated cultures seem to 

 have given encouraging results at the time of the cholera 

 visitation. 



QUESTIONS. 



When and by whom was the Spirillum choleras Asiaticse (comma bacillus) 

 discovered ? 



Describe the spirillum. 



What is the peculiar arrangement of the bacteria in cultures and secre- 

 tions? 



