MILK 



449 



Case of sterile pipettes, i c.c. (in tenths of a cubic centimetre). 



Sterile teat pipettes. 



Flask of sterile normal saline solution. 



METHOD. 



i. Fill 50 c.c. of the milk sample into each of four 

 tubes, and replace the cotton-wool plugs by solid rubber 

 stoppers (sterilised by boiling) , and fit the tubes in the 

 centrifugal machine. 



NOTE. One or two cubic centimetres of paraffinum liquidum in- 

 troduced into the buckets of the centrifuge before the glass tubes 

 are inserted will obviate any risk of breakage to the latter. 



=r-==i2=_F-r 



-===- 



FIG. 213. Milk sediment- 

 ing tubes. 



> ' 



FIG. 214. Milk in centrifuge 

 tube. 



2. Centrifugalise the milk sample for thirty minutes 

 at a speed of 2500 revolutions per minute. 



3. Remove the motive power and allow the machine 

 to slow down gradually. 



4. Remove the tubes of milk from the centrifuge. 

 Each tube will now show (Fig. 214): 



(a) A superficial layer of cream (varying in thickness 

 with different samples) condensed into a semi-solid 

 29 



