BUCHNER'S TUBE 



87 



which consists of a strong glass tube of about | inch diameter 

 with a constriction about \\ inch from the sealed end, is placed 

 I gramme of pyrogallic acid. Within this tube is then placed 

 the test-tube containing the cultivation, the top of which should 

 come sufficiently below the mouth of the larger 

 tube to enable the latter to be effectually stop- 

 pered with an india-rubber cork. By means of a 

 thistle funnel 10 cc of a 10 per cent, solution of 

 caustic potash is then delivered into the bulb 

 containing the pyrogallic acid, and the tube is 

 immediately stoppered with the india-rubber cork, 

 which should be previously moistened with ben- 

 zole to make an air-tight joint By gently tilting 

 the tube a complete solution of the acid in the 

 potash solution is then made in the bulb. The 

 absorption of the oxygen takes some time, but 

 if the operation has been performed with care it 

 becomes finally so complete that growths even of 

 the stricter forms of anaerobes will take place in 

 the lesser tube. 



This method of culture is both suitable for 

 cultures in milk, bouillon, or other liquid media, 

 and those upon potato, gelatinised whey, wort 

 gelatine, or ordinary nutrient gelatine or agar. 

 It is well, however, in the case of such media as 

 will not be injured thereby, previously to boil, 

 and cool quickly prior to inoculation, in order to, 

 as far as possible, get rid of the oxygen held in 

 suspension. 



Test-tube cultures {Wrighfs vietJiod). — The 

 tube cultivations are prepared in the ordinary 

 manner, and that portion of the cotton-wool plug 

 which projects above the mouth of the tube is 

 cut off with scissors. The plug is then pushed 

 down into the tube for a distance of about i inch, 

 and about i c.c. of a 10 per cent, aqueous solution 

 of pyrogallic acid is dropped upon the plug, by which it will be 

 at once absorbed. An equal quantity of a 10 per cent, solution 

 of caustic potash is then run in, and the mouth of the tube at 

 once closed with a tightly fitting india-rubber stopper, sterilised 

 by boiling. Incubation can then take place at any desired 

 temperature according to the medium employed. 



Fig. 



20. — Buchners 



tube. 



