56 THE NORMAL COMPOSITION OF MILK 



stances or by the abstraction of the natural constituents, gen- 

 erally by human agency, is usually conveyed by the term mUk 

 adulteration, and this, strictly speaking, has no reference to 

 any standard that may be adopted. 



For the detection of adulteration, a complete determination 

 of the various constituents of the sample should be made and the 

 amounts of fat, lactose, proteid, and ash so foimd compared 

 with the percentages as calculated from the formulae of Van 



Slyke, Olsen, and Richmond. The „ , — and — —:-; ratios 



tat proteid 



should also be calculated. The addition of water does not 



give proteid values which are materially different from those 



calculated by the Olsen formula but are invariably less than 



those calculated by the Van Slyke formula, the difference being 



proportional to the amount of water added. The PVS (proteid 



calculated by the Van Slyke method) in this case, is greater 



than the P. 0. (proteid calculated by the Olsen method). The 



, ,.^. J. . 1 ,1 proteid , lactose 



addition of water leaves the ^—x— — and — — n ratios un- 



lat proteid 



changed. 



The amount of proteid found by direct estimation in the 



case of abstraction of fat would be greater than either of the 



calculated values, and in this case P.O. would be greater than 



PVS. This is due to the Van Slyke formula being based on the 



constituent which has been abstracted. The --rr ratio 



proteid 



would be normal and the . — ratio abnormally high. In 



To pf^fJQA 



both of these instances the — r-; ratio is unaltered and this 



proteid 



is valuable in distinguishing between naturally abnormal milks 



and those rendered abnormal by external agencies. High 



lactose ,. ^1 L J. 1 1 



:-; ratios are extremely rare but low ones may be pro- 



proteid 



duced by the various causes previously mentioned. 



The refractive power of the serum should also be considered 



