56 



ESSENTIALS OF BACTERIOLOGY. 



made liquid by heating in water bath, and then inoculated with 

 the material as follows . A looped platinum needle is dipped 

 into the material and then shaken in the tube of liquid media, 

 (gelatine, agar, etc.). 



This first tube is called original. From this three drops (taken 

 with the looped platinum rod) are placed in a second tube, the 

 rod being shaken somewhat in the gelatine or agar ; this is 

 labeled first dilution (a colored pencil is useful for such markings). 



FIG. 28. 



Manner of holding tubes for inoculation : a, tube with material ; b, tube to be 

 inoculated ; c, cotton plugs. (After Woodhead and Hare.) 



From the first dilution three drops are taken into a third tube, 

 which becomes the second dilution. Fig. 28. 



The plugs of cotton must be replaced aRer each inoculation, 

 and during the same must be carefully protected from contami- 

 nation. 



