SEPARA TION OF ANAEROBES. 65 



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

 In the third is a solution of pyrogallic acid in caustic potash 

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

 ing from the last bottle to the vessel containing the medium 

 ought to be sterilised by passing through a Bunsen flame, 

 and should have a small plug of cotton wool in it to filter 

 the hydrogen germ-free. 



The removal of the air from an apparatus used in 

 anaerobic culture may be accelerated by sucking the air 



FIG. 21. Apparatus for supplying hydrogen for anaerobic cultures. 



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

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

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

 pyrogallic acid. (, c, and d are intentionally drawn to a larger scale 

 than a to show details.) 



out of one end of it as well as supplying hydrogen by the 

 other. The means adopted may be either an ordinary air- 

 pump or a water- exhaust pump. The exhaust tube is 

 connected with the tube by which under ordinary circum- 

 stances the hydrogen escapes (e.g.. Fig. 22, /). The inner 

 end of this tube must of course be above the level of any 

 contained liquid. Such a procedure in actual practice is 

 rarely necessary. 



Separation of Anaerobic Organisms. (a) In glucose 

 gelatine. A i^ inch test-tube has as much gelatine put 



5 



