234 BACTERIA IN MILK AND MILK PRODUCTS 



similar apparatus is in use by a Health Association at York,* which 

 has recently started (1903) the York Infants' Milk Depot, after the 

 manner of the Liverpool and Battersea system. The apparatus pro- 

 vided for this work is one of the latest construction. It consists of 

 an ordinary oval cylinder disinfecting chamber, having doors at both 

 ends. The apparatus is lagged, and with outside steel casing, pro- 

 vided with a steam distributor inside, steam gauge, safety valve, 

 thermometers, ready for steam supply from boiler. In connection 

 with this apparatus there is also provided a convenient size trolley, 

 upon three wheels, together with a steel frame holding three separate 

 platforms, which can be taken apart to suit bottles lor vessels of 

 larger sizes. This frame is mounted also upon wheels running in 

 grooves, and channels are fitted inside steriliser to correspond. The 

 steam rises around the bottles from the bottom of the cylinder. The 

 trolley is fitted for both ends, and when duplicated, a " charge " can 

 be taken from one end of the apparatus, and a fresh one inserted at 

 the other. This apparatus can be used as a steriliser or a pasteuriser. 



Domestic pasteurisation can be accomplished readily by heating 

 the milk in vessels in a water-bath raised to the required tempera- 

 ture for half an hour, or Aymard's milk sterilisers may be used. 



Without entering into a long discussion upon the various 

 pasteurising methods adopted, we may summarise the chief essential 

 conditions. It need scarcely be said that the operation must be 

 efficiently conducted, and in such a way as to maintain absolute con- 

 trol over the time and temperature. The apparatus should be simple 

 enough to be easily cleaned and sterilised, and economical in use. 

 Arrangements must always be made to protect the milk from rein- 

 fection during and after the process. The entire preparation of 

 pasteurised milk for market may be summed up in four items : 



1. Pasteurisation in heat reservoir. 



2. Rapid cooling in water or ice coolers. 



3. All cans, pails, bottles, and other utensils to be thoroughly 

 sterilised in steam before use. 



4. The prepared milk to be placed in sterilised bottles, and 

 sealed up. 



The quality of the milk to be pasteurised is an important point. 

 All milks are not equally suited for this purpose, and those contain- 

 ing a large quantity of contamination, especially of spores, are 

 distinctly unsuitable. Such milks, to be purified, must be sterilised. 

 Dr Eussell has laid down a standard test for the degree of contamina- 

 tion which may be corrected by pasteurisation by estimating the 

 degree of acidity, a low acidity (e.g. 0'2 per cent.) usually indicating 



* The York Health and Housing Reform Association, established 1901. 

 Secretary, Miss Hutchinson, 63 Gillygate, York. Apparatus by Wyttenbach : a 

 central depot in Gillygate, and branch depots elsewhere in the city. 



