CONTROL OF THE MILK SUPPLY 233 



headings. There are, first, those in which a sheet of milk is allowed 

 to flow over a surface heated by steam or hot water. This may be a 

 flat, corrugated surface or a revolving cylinder. The milk is then 

 passed into coolers. Secondly, milk is pasteurised by being placed 

 in reservoirs surrounded by an external shell containing hot water or 

 steam. Dr H. L. Eussell * has described one apparatus consisting of 

 a pasteuriser, a water cooler, and an ice cooler. The pasteuriser is 

 heated by hot water in the outside casement. To equalise rapidly 

 the temperature of the water and milk, a series of agitators must be 

 used. These are suspended on movable rods, and hang vertically in 

 the milk and water chambers. By this ingenious arrangement, the 

 heat is diffused rapidly throughout the whole mass, and as the 

 temperature of the milk reaches the proper point, the steam is shut 

 off and the heat of the whole body of water and milk will remain 

 constant for the proper length of time. The somewhat difficult 

 problem of drawing off the pasteurised milk from the vat without 

 reinfecting it by contact with the air is solved by placing a valve 

 inside the chamber, and by means of a pipe leading the pasteurised 

 milk directly and rapidly into the coolers. These are of two kinds, 

 which may be used separately or conjointly. In one set of cylinders 

 there is cold circulating water, in the other finely-crushed ice. 



In England, many methods (including a number of patents) are 

 in common use where milk is pasteurised. For instance, at the 

 Hospital for Sick Children in Great Ormond Street, which is in 

 advance of other London hospitals in this respect, milk is received 

 from a well-known metropolitan dairy company in quantities of 200 

 quarts daily, some being delivered in the morning, and a smaller 

 quantity in the evening. The milk is derived from healthy cows, 

 and sanitary cowsheds, the farms being placed under strict super- 

 vision. On receipt, the milk is filtered through muslin, by downward 

 and upward filtration, and passed directly into a bottle-filling 

 machine. Clean, stoppered bottles are kept in readiness. When 

 filled, the bottles are placed in circles in the cage at the bottom of 

 the pasteuriser. Into the centre of the apparatus is placed the 

 thermometer. The lid is closed down and clamped, and the steam is 

 admitted from below. The temperatures used are 160 F. (or 71 C.) 

 for twenty minutes in winter, and 180 F. (or 82 C.) for twenty 

 minutes in summer. After the elapse of this period, the lid is 

 removed, the stoppers of the bottles are fixed down, and hot water 

 is admitted into the floor of the apparatus. To this hot water is 

 slowly added cold water, and in about forty minutes the pasteurised 

 milk has been cooled down, and is ready for use in the wards. The 

 apparatus is readily cleansed after use, and the various parts, includ- 

 ing the bottles, stoppers, etc., are cleaned daily. A somewhat 



* Report from Wisconsin Agricultural Experiment Station, 1896. 



