534 THE CONTROL OF THE MILK SUPPLY 



next heating before sporulation. Thus eventually the milk would 

 be sterilised. But the method in practice is tedious and unreliable. 

 The term pasteurisation, therefore, is now used to designate a 

 process of heating at any temperature between 60° C. and 90° C. for 

 a short period (not exceeding twenty minutes). In practice, a 

 temperature of between 75° and 85° is generally adopted. There 

 is no fixed standard for the temperature of pasteurisation, except 

 that it must be above the thermal death - point of pathogenic 

 bacteria, and yet below the boiling point. As a matter of fact 70° 

 to 80° C. will kill lactic bacteria as well as most disease-producing 

 bacteria found in milk. If therefore the milk has been kept at that 

 temperature for ten to fifteen minutes, it is said to have been 

 " pasteurised." It is now held that agitation of the milk is neces- 

 sary to efficient pasteurisation. B. tuberculosis in milk has been 

 destroyed by a temperature of 60° C. in ten minutes, the milk being 

 agitated (Russell), but as a rule it is considered that pasteurisation 

 is not to be relied upon as invariably bactericidal to the tubercle 

 bacillus, and probably never destroys spores. 



The methods of pasteurisation are continually being modified 

 and improved, especially in America, Denmark, and Germany, 

 and it will be unnecessary to burden these pages with the large 

 body of facts and experiments we have collected during several 

 years' study of the matter. 



It will be sufficient to refer to three common methods now 

 in vogue, and the first to be considered may well be that practised 

 in Denmark. The milk is here commonly pasteurised in small 

 bottles (1-7 pint) for twenty minutes at 75° C, (167° R), at which 

 temperature it is left for half an hour, and then, in order to destroy 

 any "cooked" flavour, it is rapidly cooled down to about 10° C. 

 In some places the milk is not pasteurised in bottles but in vats 

 holding 500 litres, and the temperature is 85° or 90° C, instead of 

 75° C, and it is kept at such temperature for three or five minutes. 

 This method is in vogue in various countries. In England 

 modifications of it are in common use where milk is pasteurised. 

 For instance, it is adopted 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 2CXD quarts daily, most 

 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 supervision. On 

 receipt the milk is filtered through muslin, by downward and 



