v SEPARATION OF CHOLERA VIBRIOS 103 



(2) Examine another microscopically, and if vibrios 

 are found to be present, prepare gelatine plates 

 and work these up as above. 



II. Gruber's method. 



(1) Grow cholera vibrios in tubes, containing broth or 

 peptone solution, for twenty-four hours at 38 '5 C. 



(2) Then sterilise these tubes by heating them from 

 60 C. to 65 C. for ten minutes in a water bath. 



Such tubes should be kept in readiness. 



(3) Inoculate four such tubes with 1 to *5 cc. of the sus- 

 pected water, and place them in the warm incubator for 

 twenty-four hours. 



(4) Then test one tube for " Cholera Ked," and compare 

 the tint with that obtained from a tube not inoculated 

 with the suspected water : the former should be a deeper 

 red ; examine another tube microscopically for vibrios ; 

 from the others make gelatine plates, and work them up in 

 the manner described above. 



It is often possible to give a definite opinion in from 

 eighteen to forty- eight hours. 



III. A gar-agar plates. 



(1) Liquefy three agar-agar tubes and cool them down 

 to 40 C. in a water bath. 



(2) Inoculate one with -25 to -5 cc. of the suspected 

 water. 



(3) From this tube inoculate the second with three 

 platinum loops, and from this second tube the third also 

 with three loops. 



