64 METHODS OF CULTIVATION OF BACTERIA 



Fig. 21. The ends of the tubes are partly drawn out as shown, 

 and covered with plugs of cotton wool. Three such test-tubes 

 are prepared, and they are sterilised in the steam steriliser (p. 28). 

 After sterilisation the gelatin is melted and one tube inoculated 

 with the mixture containing the anaerobes ; the second is inocu- 

 lated from the first, and the third from the second, as in making 

 ordinary gelatin plates. After inoculation the gelatin is kept 

 liquid by the lower ends of the tubes being placed in water at 



FIG. 20. 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. 

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



about 30 C., and hydrogen is passed in through tube x for 

 twenty minutes. The gas-supply tubes are then completely 

 sealed off at x and i, and each test-tube is rolled as in Esmarch's 

 method till the gelatin solidifies as a thin layer on the internal 

 surface. A little hard paraffin may be run between the rim of the 

 test-tube and the stopper and round the perforations for the gas- 

 supply tubes, to ensure that the apparatus is airtight. The 

 gelatin is thus in an atmosphere of hydrogen in which the 

 colonies may develop. The latter may be examined and isolated 

 in a way which will be presently described. The method is 

 admirably suited for all anaerobes which grow at the ordinary 

 temperature. 



(b) 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. 22) of a glass plate as base on which a 



