94 



BACTERIOLOGICAL ANALYSIS 



cotton- wool (b). The tube and pipette should then 

 be placed in the hot-air steriliser (vide Fig. 2). 

 Before using the pipette, fix a thin india-rubber tube 

 to it, without removing the cotton- wool plug. 



(3) To other three gelatine tubes add severally -1 cc. of 

 the water. 



FIG. 2. 



FIG. 3. 



(4) Gently shake the gelatine tubes, and prepare plates 

 in the usual manner (vide p. 29). 



(5) Keep these in the cool incubator at 22 C. 



If the water to be tested be suspected of containing 

 large numbers of bacilli, smaller quantities, less 

 than -1 cc., should be added to the gelatine. 1 



1 The pipette of a Thoma-Zeiss hsemacytometer is well adapted for 

 measuring minute quantities. 



