THE PASTEURIZATION OF MILK 



near the bottom of each compartment in turn 

 till all are emptied. Since these plugs are re- 

 moved by hand, it is necessary to place the hand 

 and arm into the empty compartment at each 

 operation. The danger of contamination is thus 

 evident. 



When the partitions are low it has been found 

 that the milk flows over the tops of all of them, 

 and there is thus but little holding time possible, 

 since the milk flows almost directly from the inlet 

 to the outlet pipe. Even with the best of con- 

 struction, tests have shown that the percentage of 

 holding time to the filling time is small, sometimes 

 being as low as 10 per cent, to 15 per cent. 



The third form of continuous flow type holder 

 now used quite extensively is shown in Fig. 27. It 

 consists of a series of large-size tubes arranged in 

 a box- like structure. These tubes are connected 

 one with another at the ends by suitable hinged 

 heads, so that the milk which enters the top tube 

 of the series flows forward and backward through 

 all of them and is discharged from the lower tube. 

 The discharge pipe is carried upward in the form 

 of an inverted U tube in a similar manner to that 

 shown in Fig. 24. This gives assurance that no 

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