200 MILK HYGIENE 



" As in the case of the lactometer, the purity of a milk sample 

 cannot be positively established by the laetoscope alone. For instance, 

 a watered milk abnormally high in fat would often be found to read 

 within the limits of pure milk, when as a matter of fact its solids 

 would be below standard. By a careful comparison of the readings 

 of both the laetoscope and the lactometer, however, it is rare that a 

 skimmed or watered sample could escape detection. 



" Thus, if the specific gravity by the lactometer is well within 

 the limits of pure milk, and the fat, as shown by the laetoscope, is 

 above 3i per cent., the sample may be safely passed as pure, or 

 as conforming to the standard. 



" A normal lactometer reading in connection with an abnormally 

 low laetoscope reading shows both watering and skimming, and 

 with an abnormally high laetoscope reading shows a milk high in 

 fat, or a cream. With the laetoscope reading below three, and a 

 low lactometer reading, watering is indicated. A lactometer reading 

 above thirty-three, and a low laetoscope reading, indicate skim- 

 ming." L. P.] 



IV. METHODS OF EXAMINATION 



In order to determine whether adulteration has taken 

 place or not, the examination should cover the follow- 

 ing: The specific gravity of the milk and of the whey, 

 the fat content of the milk, the amount of milk solids, 

 the amount of solids not fat, the specific gravity of the 

 solids, the quantity of fat [and the percentage of 

 ash]. Sometimes, the examination is extended to 

 include the taking of a herd sample under special 

 conditions in order to make a comparison between 

 the sample officially collected and the milk offered for 

 sale. Finally, foreign ingredients are tested for, as ni- 

 trates, starch, [preservatives, artificial color, " viseo- 

 gen," gelatin, etc.]. 



a. Taking samples for laboratory examination must be 

 conducted with great care. Upon standing, the cream 

 quickly rises to the top, so that the upper part of the 

 milk contains more fat, even though no definite layer of 

 cream has yet been formed. Therefore, before the test 



