388 MILK AND THE PUBLIC HEALTH chap. 



when ingested in small doses by the healthy adult, yet they 

 are actually, or likely to be, hurtful to invalids and young 

 children in the doses in which they have been frequently 

 found in milk, particularly if administered over a long period. 



The available data is a mixture of negative evidence of 

 ill-effects and a smaller but still not inconsiderable volume of 

 evidence of harmful results from their ingestion. In such 

 cases positive evidence is of much greater value than negative, 

 and from the whole it is justifiable to conclude that the 

 addition of preservatives to milk, the food of infants and 

 invalids, is totally unjustifiable. 



It must always be kept in mind that the amounts found 

 have frequently been far in excess of any possible requirements. 

 The milk may be dosed by the farmer, the middleman, and 

 the actual purveyor. The persons who handle milk are, for 

 the most part, unscientific and incapable of adding precise and 

 accurate quantities of preservatives, and in general add much 

 more than is required. 



(2) The action of preservatives upon bacteria is not a 

 simple, general one, but is selective. It is possible to add 

 preservative to milk in quantity sufficient to check lactic acid 

 formation by inhibiting the lactic acid bacteria, while, at the 

 same time, certain other bacteria, some possibly pathogenic, 

 are not inhibited. This aspect of the subject has not been 

 sufficiently investigated, but it is obviously theoretically possible 

 for such milk to be exceedingly dangerous. The lactic acid 

 bacilli are not themselves harmful, but visibly alter the milk. 

 Eemove the warning signal of their presence without inhibiting 

 the other bacteria, and it is possible for a milk to be not 

 visibly altered yet very stale, and containing very numerous 

 bacilli and their toxins. 



(3) Their addition is totally unnecessary, and is a direct 

 incentive to dirty methods of milking and handling milk. 

 There is abundant evidence that cleanly collected milk, pro- 

 perly cooled, requires no addition of preservative to enable it 

 to keep in good condition all the time necessary for its 

 transmission, sale, and use in the consumer's house. Eich- 

 mond,-^ for example, remarks : " It has been found by the 

 experience of the Aylesbury Dairy Company that by cooling 



^ Departmental Committee Rejmrt, 1901, p. 387. 



