ANAEROBIC CULTURE IN PETRI DISH 



Fig. 22. — Vacuum desiccator for 

 Petri dish cultivations. 



which must be placed on a cold slab to ensure rapid solidification. 

 It is then transferred to a vacuum desiccator of the form shown. 

 The desiccator is connected up with the 

 hydrogen apparatus, a vacuum formed, 

 and after repeated washings in hydrogen 

 the cultivation is either left in an atmo- 

 sphere of that gas, or in vacuo as thought 

 desirable. 



Cultures in glucose agar — 

 For cultures on agar similar tech- 

 nique is employed, care being taken, 

 however, that the medium, before inocu- 

 lation, is not allowed to cool down to a 



temperature approaching too nearly the solidifying point. The 

 operations must be performed quickly, or solidification, which 

 occurs at about 40°, will take place before the medium is evenly 

 distributed in the Petri dish. 



Another method in the case of agar media is that of stroke 

 :ultivation. The media after being allowed to boil for some minutes 

 is quickly poured out into a Petri dish 

 placed on a cold slab in the usual way. 

 When solid, a platinum needle charged 

 with a trace of the culture or material 

 under examination is drawn lightly across 

 the medium in parallel lines extending 

 across the dish. The dishes are then 

 placed in the desiccator and treated as 

 above. Growth can be allowed to take 

 place either at room temperature or at 37° 

 as desired. {^See also Klein's metJwd of isola- 

 tion described above.) 



5. Test-tube cultures in vacuo op 

 hydrogen— 



When it is desired to place ordinary 

 test-tube cultures under anaerobic condi- 

 tions, a vacuum desiccator of the form 

 shown on Fig. 23 will be found of great 

 service for daily use. The tubes are 

 placed upright in the nickel support as 

 shown, the lid replaced, and an air-tight joint made with resin 

 ointment. The air is then exhausted, replaced by hydrogen, 



Fig. 23. — Vacuum desic- 

 cator for test-tube cul- 

 tures. 



