196 MILK AND THE PUBLIC HEALTH chap. 



the outlet of the cylindrical sedimentation apparatus, and the 

 stopcock of the latter turned sharply on and off several times 

 until all the deposit has been swept into the centrifugal tube. 

 Distilled water (+0-1 per cent No.^COj) is added to the 

 centrifugal tube up to the 10 c.c. mark. After centrifugalisa- 



CCM 



Natural Size 



/^ Natural Size 



Fig. 10. — A, Gla.ss tube holding a litre of milk ; C, Tube for measuring sediment ; B, Rubber 

 tubing connecting A and C. At the side is represented a brass rod, with rubber stopper 

 attached, for plugging the lower end of tube A, when C is tal<en off. Tube C is showu by 

 the side g natural size. It is graduated in Troths and xAnths of a c.c. 



tion for 2 minutes the volume of sediment is read off on the 

 scale. This Houston calls the " secondary reading.'' 



3. Orr's Method} — This method is a modification of that 

 used by Houston. The apparatus used is shown in Fig. 10. 

 The top of the centrifugal tube fits outside the lower part of 

 the large glass cylinder, the two being connected by rubber 



^ Report on an Investigation as to the Contamination of Milk, 1908. 



