456 



BIOLOGICAL AND SANITARY MATTERS. 



they may be changed during the straining of the milk, and they 

 should be thoroughly washed and sterilised before use. 



The importance of cleanliness in milking is strikingly shown by 

 the comparisons below of London milk, no system of ensuring 

 that really clean milk shall be delivered being employed, and 

 which fairly represents the condition in large towns similarly 

 placed, of New York milk, taken when a system of clean milk 

 supply was talked about, but not strictly enforced, and of milk 

 where the clean milk system is in force. 



The same thing is shown by the rates of infant mortality for 

 the average of five years before and five years after the intro- 

 duction of clean milk systems. 



Before, 

 After, 



Mortality of Infants per 1000. 

 New York. Cincinnati. 



. 135-8 139-2 



100-0 93-4 



All water used for cleansing dairy utensils should be previously 

 boiled, to destroy disease germs if accidentally present ; and, if 

 possible, the vessels themselves should be steamed. 



If the only available water supply be not above suspicion, an 

 immunity from the consequences of its use may be attained by 

 filtration through a Pasteur-Chamberland filter. This consists 

 of one or more tubes of unglazed porcelain of a special quality, 

 through which water will pass, but which keeps back micro- 

 organisms. It has been found that in course of time that certain 

 micro-organisms will grow through the filter, but it appears to 

 be firmly established that pathogenic germs are not among 

 these. To secure efficient working, these filters should be fre- 

 quently cleaned, and it is advisable to sterilise them by steaming 

 from time to time. They have the advantage of being easily 

 tested, as when efficient they will not, when wet, allow air under 

 a pressure of 10 Ibs. per square inch to pass ; while, if defective, 

 a passage is afforded at any place which will allow micro-organisms 

 to traverse the filter. 



Milk as a Food and a Medicine. In considering the food value 

 of milk, two points must be borne in mind ; first, its value in 



