CULTIVATION OF ANAEROBES 61 



In order to prepare plate cultures of anaerobic mic7'o- 

 organisms the oxygen can be excluded after Koch's method 

 by laying upon the gelatine or agar before it has fully set 

 a thin sterilised plate of mica or selenite, which adheres 

 closely to the surface of the nutrient mass. The exclusion of 

 oxygen is rendered complete if melted paraffin be run round 

 the border of the mica plate. 



The removal of oxygen is effected by Buchner in a very 

 simple way by means of an alkaline solution of pyrogallol, 

 prepared by dissolving a gram of pyrogallol in 10 c.cm. 

 water, and adding 1 c.cm. concentrated solution of caustic 

 potash. 



Another mode of cultivating anaerobic microbes on 

 plates consists in bringing the plate prepared with the 

 micro-organism under the receiver of an air-pump and 

 expelling the oxygen by pumping. 



Bliicher and Botkin secure the removal of oxygen by 

 displacing the air in the receiver with another gaS, viz. 

 hydrogen, by means of an india-rubber tube, the lower 

 opening of the receiver being closed with paraffin or with 

 glycerine and water. 



Complete removal of the oxygen from a test-tube by pump- 

 ing has been effected by Gruber in the following way : — 

 A test-tube of more than the usual length is drawn out at 

 about 15 cm. from the bottom to a narrow neck. It is, 

 filled with 10 c.cm. of nutrient material by the aid of a 

 funnel, closed with cotton- wool and sterilised. After inocu- 

 lation, the wool plug is pressed down as low as the narrowed 

 part and a tight-fitting rubber cork introduced into the 

 mouth, through a hole in which passes a right-angled tube of 

 glass connected with an air-pump. The air is then pumped 

 out (the culture medium in the rarefied space being 

 meanwhile kept in a water-bath at 30°-40° C), after which 

 the tube is sealed at the constricted part over the flame of 



