SOURCES OF POLLUTION 183 



Probably the commonest source of contamination is in the use of 

 11 ten ail_a_ an d milk-cans. Any unnecessary delay in transit 



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affords increased opportunity for multiplication ; particularly is this 

 the case in the summer months, for at such times all the conditions 

 are favourable to an enormous increase of any extraneous germs 

 which may have gained admittance at the time of milking. Thus 

 we have (1) the milk itself affording an excellent medium and 

 supplying ideal pabulum for bacteria ; (2) a more or less lengthened 

 railway journey or period of transit giving ample time for multi- 

 plication ; (3) the favourable temperature of summer heat. We shall 

 refer again to the rate of multiplication of germs in milk. It has 

 been shown that milk brought into large cities, such as London, 

 Paris, or New York, has been travelling often for as long as two to 

 ten hours, often under conditions favourable to pollution or at least 

 under conditions of temperature favourable to the multiplication of 

 bacteria. 



Pollution at the MilJcshqp. Many are the advantages given to 

 bacteria when milk has reached its commercial destination. In milk- 

 shops there are not a few risks to be added to the already imposing 

 category. Water is occasionally, if not frequently, added to milk to 

 increase its volume, either at the farm or the milkshop. Such water of 

 itself will make its own contribution to the flora of the milk, unless 

 indeed, which is unlikely, the water has been recently and thoroughly 

 boiled before addition to the milk. Again, it is impossible to suppose . 

 that in small milkshops, perhaps of a general nature where the 

 milk stands for several hours, pollution is avoidable. From a hundred 

 different sources such milk runs the risk of being polluted. The 

 dust of the shop and the street gain access to the pan of milk on 

 the counter, which, commonly, is uncovered. The " differ " and the 

 vendoisMiands and clothes contribute bacteria. Flies also increase 

 the pollution. 



Pollution in the Home. Lastly, there is pollution from dust and 

 dirt, inorganic and organic, in the home. More than a million of 

 the population of London live in tenements of two rooms or less. 

 Cooking, eating, sleeping, cleaning, and sometimes even trade employ- 

 ments in the form of " home-work," are all conducted under conditions 

 of overcrowding and lack of space. Often there is no pantry or 

 larder, and consequently the days' supply of milk stands in a dirty 

 uncovered vessel in the midst of dirty surroundings. It is evident 

 that this is but one more opportunity for pollution. 



Fore-Milk. Before proceeding, a word must be said respecting 

 the first milk which flows from the udder in the process of milking, 

 and which is known as the fQTp,-vn,illf.. This portioi^ of ffift millr i 

 ahvu^.s rich in bacterial life, on account of the fact that it lias 

 remained in iho milk-ducts sinco the last milking. However thorough 



