102 BACTERIOLOGICAL ANALYSIS LESSON 



If there be a pellicle on the surface of the culture 

 medium in these flasks, examine it for vibrios. 



If vibrios are present 



(a) Prepare gelatine plates in the usual manner, keep 

 them at 22 C., and examine them from day to day. 



Any suspicious colony should be used for subcultiva- 

 tion : 



(1) Under a dissecting microscope fish out the colony 

 with a thin platinum needle, and make gelatine 

 stab cultures and agar-agar streak cultures. 



Keep the former at 22 C. and the latter at 38-5 C. 



Examine from day to day, and prepare cover-glass 

 specimens, which should be stained with carbol 

 fuchsine or aniline gentian-violet (vide p. 40). 



(2) From the suspicious colonies start also subcul- 

 tures in peptone tubes. 



Place them in the warm incubator for eighteen to 

 twenty-four hours. At the expiration of this time 

 examine microscopically for vibrios. 



Apply also the test for " Cholera Red " to one of the 

 tubes, by adding a few drops of pure concentrated 

 sulphuric acid. 



The peptone solution should acquire a markedly red 

 tint. 



(5) Inoculate also a series of peptone tubes from the 

 peptone flasks, and keep them at 38*5 C. for twenty-four 

 hours. 



(1) Then test one of these tubes for "Cholera Red." 



