2 7 8 



MILK AND ITS HYGIENIC RELATIONS 



After milking, the milk should be at once cooled. The most 

 usual apparatus is shown in some detail in the figure on p. 277, and 

 on a smaller scale in plate facing p. 280. 



The milk is usually conducted straight from the filter to the 

 trough on the top of the cooler. It then passes through the small 

 holes on to the outer aspect of the cooler, passing down in a thin 

 stream over the corrugated surface to the lower trough, whence it is 



203" 



Section of churn illustrating experi- 

 ments on p. 279. The position of 

 the four thermometers is seen in 

 the diagram. 



conveyed to bottles, churns, or a pasteurising plant, as desired. 

 The corrugated surface is formed by the outside of pipes, which 

 contain water, the entering and exit pipes for which are shown in 

 the figure. Except in the summer-time it is usually sufficient to 

 employ a full stream of ordinary water, but in hot weather artificial 

 cooling of the water by ice or the use of carbon dioxide or ammonia 

 may be necessary. 



In some dairies the cooler is covered during use so as to avoid 

 aerial contamination during the process. When the cooling is 

 carried out in a clean room it is probable that there is very little 

 contamination from this source. When, however, such cooling is 



