APPARATUS, MATERIAL, AND REAGENTS. 21 



opening a gas regulator can be fixed. Test-tubes, 

 flasks, funnels, cotton wool, etc., may be sterilised 

 by exposure to a temperature of 150 C. for an 

 hour or more. 



(G) APPARATUS AND MATERIAL FOR PREPARING 

 AND STORING GELATINE-, AND AGAR-AGAR- 

 PEPTONE-BROTH. 



Water-bath. A water- bath on tripod stand 

 is required for boiling the ingredients of nutrient 

 jellies and for general purposes. The lid may 

 be conveniently composed of a series of con- 

 centric rings, so that the mouth of the vessel 

 may be graduated to any size required. 



Test-tube Water-bath. This consists of 

 a circular rack for test-tubes within a water- 

 bath. It is sometimes employed instead of the 

 steam cylinder for sterilising nutrient jelly in 

 tubes by boiling for an hour, for three successive 

 days. 



Hot-water Filter. A copper funnel with 

 double walls, the interspace between which is 

 filled with hot water. A glass funnel fits inside 

 the copper cone, the stem of the glass funnel 

 passing through and being tightly gripped by a 

 perforated caoutchouc plug, which fits in the 

 opening at the apex of the cone. The water in 

 the cone is heated by applying the flame of a 



