62 METHODS OF CULTIVATION OF BACTERIA 



is passed through three wash -bottles, as in Fig. 17. In the first is 

 placed a solution of lead acetate (1 in 10 of water) to remove any traces 

 of sulphuretted hydrogen. In the second is placed a 1 in 10 solution of 

 silver nitrate to remove any arseniuretted 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 (1 : 10) to remove any 

 traces of oxygen. The tube leading 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. 



Commercial hydrogen as sold in cylinders may be used, but this must 

 be purified as above. 



Pyrogallate of Potassium for Anaerobic Cultures. —In arranging for the 



Fig. 17. — Apparatus for supplying hydrogen for anaerobic cultures. 



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

 taining 1-10 solution of lead acetate, c. Wash-bottle containing 1-10 solution 

 of silver nitrate, d. Wash-bottle containing 1-10 solution of pyrogallic acid. 

 (&, c, and d are intentionally drawn to a larger scale than a to show details.) 



absorption of oxygen by this substance the proportions used in Bulloch's 

 separation method (below) may be employed. Here 109 grms. solid caustic 

 potash are dissolved in 145 c. c. water, and to this 2-4 grms. pyrogallol 

 are added. 



Bulloch's Apparatus for ' Anaerobic Culture. — This can 

 be recommended for plating out mixtures containing anaerobes, 

 and for obtaining growths (especially surface growths) of the 

 latter. It consists (Fig. 18) of a glass plate as base on which a 

 bell-jar can be firmly luted down with unguentum resinee. In 

 the upper part of the bell-jar are two apertures furnished with 

 ground stoppers, and through each of the latter passes a glass 

 tube on which is a stop-cock. One tube, bent slightly just after 

 passing through the stopper, extends nearly to the bottom of 



