SEPARATION OF ANAEROBES. 



59 



The Principles of the Culture of Anaerobic Organisms. 



All ordinary media, after preparation, may contain traces of 

 free oxygen, and will absorb more from the air on standing. 

 For the growth of anaerobes this oxygen may be gotten rid of 

 in two ways, (i) By the prolonged passing of an inert gas, 

 such as hydrogen, through the medium (liquefied if necessary), 

 and further, the medium must be kept in an atmosphere of the 

 same gas, while growth is going on. (2) By absorption through 

 the use of pyrogallic acid in an alkaline solution as described by 

 Buchner. Media for anaerobes may be kept in contact with 

 the air, if they contain a reducing agent which does not inter- 

 fere with bacterial growth. Such an agent takes up any oxy- 

 gen which may already be in the medium, and prevents further 

 absorption. The reducing body used is generally glucose, though 

 formate of sodium may be similarly employed. The preparation 

 of such media has already been described (pp. 38, 40). In this 

 case the medium ought to be of considerable thickness. 



The Supply of Hydrogen for Aimerobic Cultures. — The gas is 

 generated in a large Kipp's apparatus from pure sulphuric acid 

 and pure zinc. 

 It is passed 

 through three 

 wash-bottles, 

 as in Fig. 23. 

 In the first is 

 placed a solu- 

 tion of lead ace- 

 tate (i in 10 

 of water) to 

 remove any 

 traces of sul- 

 phuretted hy- 

 drogen. In the 

 second is 

 placed a I in 



10 solution of silver nitrate to remove any arsenietted hydrogen 

 which may be present if the zinc is not quite pure. In the 

 third is a 10 per cent solution of pyrogallic acid in caustic potash 

 solution (i : 10) to remove any traces of oxygen. The tube lead- 



i i 



Fig. 23. — Apparatus for supplying hydrogen for anaerobic cultures. 



a. Kipp's apparatus for manufacture of hydrogen. b. Wash-bottle 

 containing i-to solution of lead acetate, c. Wash-bottle containing i-io 

 solution of silver nitrate, d. Wash-bottle containing i-io solution of 

 pyrogallic acid. (3, r, and d are intentionally drawn to a larger scale than 

 a to show details.) 



