74 SCIENCE AND PRACTICE OF DAIRYING. 



must not be assumed that milk which differs in composition from 

 the above-stated figures is consequently adulterated, but merely 

 that milk, in which this is the case, possesses unusual properties, 

 which warrant suspicion, and justify further testing for its purity. 

 It can also hardly be contended that the occasional variation of 

 milk from any one of the above figures points to adulteration. 

 Adulteration on a small scale is, as a rule, impossible to detect in 

 milk. 



The opinion of anyone with regard to the genuineness of a 

 sample of milk, who has not taken the precaution, during a year at 

 least, of making himself familiar with the conditions of treatment 

 and the properties of milk, in the districts where the milk-tests are 

 carried out, and who has not performed a very large number of 

 milk analyses, is not worthy of regard. The same may be said 

 also of anyone who neglects to take into consideration a proper 

 study of the action of all the influences which affect the secretion 

 of milk. 



We have already considered the nature and properties of cows' milk, 

 and of the influence which interrupted milking of the cows, or incomplete 

 milking (not milking dry), or of milking at irregular intervals, exercises 

 on the composition of milk. The variations which the composition of milk 

 from day to day and from milking-time to milking-time exhibits, in short, 

 all the influences which affect the secretion of milk, and which have to be 

 taken into careful consideration in the testing of milk, have already been 

 treated in Chapter I. 



32. The Supervision of the Milk-trade in Towns. This has to 

 do, in the first place, with the discovery of the sellers of suspected 

 samples of milk, and, in the second place, with the discovery of how 

 and in what manner the milk has been adulterated. The police 

 supervision of the milk-trade in towns is consequently of a double 

 character, viz. the preliminary testing at the place of sale, and the 

 formation of a final judgment by an experienced and skilled analyst. 

 Careful observations should be constantly if possible daily insti- 

 tuted at the places of sale, and the appearance, smell, flavour, and 

 reaction of the milk should be tested. The specific gravity should 

 be taken with a correct hydrometer, and an observation of the tem- 

 perature of the milk also made. A determination of the percentage 

 of fat, by means of a lactoscope, should perhaps also be made. It 

 should also be noted whether the capacities of the milk-vessels are 



