20 LABORATORY EQUIPMENT. 



about 2 mg. of bacterial substance. It is prepared as explained in Fig. 2. 

 If smaller amounts of bacteria are used, dilutions must be made. 



For instance, 1/4 of a loopful of bacteria is desired; i loopful is suspended in i c.c. 

 of saline and 3 c.c. of saline added. As a result, i c.c. of this emulsion contains 1/4 

 of a loopful of bacteria. If 1/16 of a loopful is necessary i c.c. of the above dilution is 

 added to 3 c.c. of saline, thus making i c.c. of this mixture contain 1/16 of a loopful of 

 bacteria. 



