I'OXTROL DURIXr; DELIVERY. 243 



which have been found to hold sufl&cient milk for analysis, while 

 not being too large to be easily carried. A case holding a dozen 

 bottles should be provided for this purpose. 



The testing of these samples may be performed largely with a 

 lactometer ; in fact, it is in this work that the usefulness of the 

 lactometer is most appreciated.. 



The specific gravity of the samples of series (2) and (3) should 

 be carefully compared with those of series (1), which will form a 

 standard by which the others may be judged. In all cases the 

 specific gravities must be corrected to 60° F. Three cases may 

 occur. 



1. The specific gravity of a sample of series (2) or (3) is equal 

 to the specific gravity of the corresponding samples of series (1). 

 In l)v far the greater number of cases this indicates that the 

 composition of the samples is identical. It is possible, however, 

 that the milk may have been skimmed, which would raise the 

 specific gravity, and then slightly watered, which would bring 

 the .specific gravity back to the original degree. It i.s, however, 

 excessively unlikely that a milk carrier could perform this feat 

 with such accuracy as would be required, and an experienced 

 observer would have his suspicions aroused by the thin appear- 

 ance of the milk. It is also patent that a man adulterating milk 

 for the sake of profit, or with malice, would not confine himself 

 to one isolated occasion, but would do so liabitually ; and only 

 a skilled .scientist could habitually remove cream from milk, 

 and reduce its specific gravity to the original degree by watering. 

 For all practical purposes it may be taken that when the specific 

 gravities agree the milk has not been tampered with. 



"2. The specific gravity of the sample of series (2) or (3) is 

 higher than the specific gravity of the corresponding sample 

 of series (1). This indicates that it contains less cream than 

 the original. 



3. The specific gravity of the sample of series (2) or (3) is 

 lower than the specific gravity of the corresponding sample 

 of series (1). This may be due to two causes — either the milk 

 contains more cream than the original, or it has been watered. 

 In some instances both causes may be responsible for the lowness 

 of the specific gravity. 



If the second or third cases have occurred, a further examina- 

 tion of the milk should be proceeded with. Either the fat 

 or total solids should be estimated, and the soUds not fat 

 calculated ; the corresponding sample of series (1) should be 

 simultaneously examined. It is advisable that the samples — 

 or a selected number of them — should be examined if it has 

 been found that the specific gravities agree, as it affords a means 

 of checking the accuracy of the specific gravity determinations, 



