EXAMINATION OF WATER. 431 



Dunham's solution the vibrio grows rapidly, and on account 

 of its extreme aerobic tendency it accumulates or gathers 

 on the surface of the liquid forming- a broken pellicle. Dun- 

 ham's solution is water to which 1 per cent, pepton and 0.5 

 per cent, salt has been added (p. 344). A modification by 

 Metchnikoff contains 1 per cent, each of pepton and salt, 

 and 2 per cent, of gelatin. 



About 100 c.c. of the liquid are placed in each of several 

 Erlenmeyer flasks. These are then inoculated and set aside 

 at 37. In from 10-20 hours the surface growth is examined. 

 A loopful can be used for staining- and for hanging-drop ex- 

 amination. At the same time gelatin and agar plates 

 should be made from this surface pellicle. 



The gelatin plates should be developed at as high a 

 temperature (22-24) as possible, without melting the gela- 

 tin. This can be done very satisfactorily by keeping the 

 plates in the water-cooler (Pig. 33, p. 179). The agar plates 

 are not prepared in the ordinary way. Koch's procedure 

 consists of pouring the agar into Petri dishes where it is 

 allowed to solidify and remain for several days. This is to 

 allow the water of condensation to evaporate. The surface 

 of the agar plates, thus prepared, is repeatedly streaked 

 with a platinum wire. The organisms are thus planted on 

 the surface and hence good isolated colonies can be obtained. 

 The agar plates are placed at 37 and in urgent cases they 

 can be examined in about 8 or 10 hours. 



The characteristic colonies on gelatin or on agar are 

 transplanted to Dunham's solution in tubes^ and to agar and 

 gelatin tubes. The first two media are then placed at 37. 

 In about 10 hours the indol reaction may be applied to the 

 culture in Dunham's solution. A loopful of the growth 

 (2 mg.) on inclined agar can be removed at the end of about 

 20 hours, suspended in 1 c.c. of bouillon and this then injec- 

 ted into the peritoneal cavity of a guinea-pig. The tem- 

 perature and the weight of the animal should be taken be- 

 fore the injection. The former should again be taken every 



