106 BACTERIOLOGICAL ANALYSIS LESSON 



II. QUALITATIVE EXAMINATION. 

 Five samples of milk are supplied. 



Sample A contains Typhoid bacilli. 



B Bacterium coli commune. 

 ,, C ., Streptococcus pyogenes. 

 D Bacillus diphtherias. 

 ,, E Tubercle bacilli. 



(a) Samples A and B : Bacillus of typhoid fever and the 

 Bacterium coli commune. 



Examine for typhoid bacilli and the Bacterium coli 

 commune, in exactly the same manner as was done in 

 the case of water (vide p. 98). It is advisable, however, to 

 dilute the milk with an equal volume of sterile distilled 

 water, so as to facilitate filtration. 



(b) Samples C and D : Streptococcus pyogenes and the 

 Bacillus diphtherice. 



(1) Use three sloped agar-agar tubes. 



(2) Stir up the milk, so as to distribute the suspended 

 organisms uniformly. 



(3) Dip a stout, straight platinum needle into the milk. 



(4) Now make three parallel streaks on the surface of 

 the first agar-agar tube. 



(5) Without dipping the needle again into the milk, 

 make three parallel streaks on the surface of the second 

 agar-agar tube, and also of the third. 



(6) Place the three agar - agar tubes in the warm 

 incubator. 



