94 



CLINICAL BACTERIOLOGY AND JLEMATOLOGY 



the second, and Paratyphoid B in the back row. The final dilutions 

 will then be : 



O 



10 drops of normal saline 



o ,, diluted serum (i-io) 



15 culture of Paratyphoid B 



O 



O 



10 . drops of normal saline 



o ,, diluted serum (i-io) 



15 ,, culture of Paratyphoid A 



O O O O O 



drops of normal saline 



,, diluted serum (i-io) 



culture of typhoid bacilli 



Mix each tube in succession by covering it with the tip of the finger 

 and shaking gently. You will now have three series of dilutions, 



r 



FIG. 21. METHOD OF MAKING THE DILUTIONS (Dreyer's) x . 



The pipette is best held a little above the mouth of the tube, so that the- 

 fluid drops clear. 



