ADULTERATION OF MILK LACTOSCOPE. 



milk lie proposes to sell, to stand until the richer portion forms 

 a creamy stratum at its surface, then skims off this stratum 

 which he sells at a high price, as cream. The remainder and 

 impoverished portion of the milk is then undoubtedly heavier 

 than before it was deprived of the cream, and its poverty would 

 be detected by Quevenne's hydrometer : but the crafty milkman, 

 aware of this, has the adroitness, not only to correct the too great 

 weight of the fluid, but to do so to his own increased profit. He 

 knows that the addition of water will diminish the specific 

 gravity of his skimmed milk, and he accordingly mixes with it 

 just so much of that cheap liquid as will reduce its weight to that 

 of milk of the proper richness. 



96. This manoeuvre is attended also with another deceptive 

 effect ; it is found that the mixture of water with milk facilitates 

 the disengagement of cream, and expedites its collection at the 

 surface. Whatever creamy particles, therefore, may remain in 

 the milk thus impoverished and adulterated, will rise quickly to 

 the surface, and collecting there, will deceive the consumer, pro- 

 ducing the impression that the milk on which cream so quickly 

 collects, must necessarily be rich. 



The great importance of discovering such an easy and practi- 

 cable test of the quality of an element so important to the 

 sanitary condition of the people, as milk, ought, one should have 

 supposed, to stimulate scientific men to such an invention. The 

 frauds practised so extensively by the vendors of milk on great 

 public establishments, such as hospitals and schools, are notorious. 

 An eminent medical practitioner says, that in conversing with one 

 of the great milk contractors of the public establishments in 

 Paris, during a season in which forage had risen to a very high 

 price, the milkman observed frankly, and with a smile, "in 

 common seasons, we do put a little water to the milk, but at pre- 

 sent we are obliged to put milk to the water." 



97. Dr. Donne has invented an instrument to ascertain the 

 richness of milk, which he calls a lactoscope, which was presented 

 to the Academy of Sciences, and favourably reported upon by a 

 committee consisting of MM. Thenard, Chevreul, Boussingault, 

 Regnault et Seguier, who experimented with it and verified its 

 results. This instrument is based upon the fact, that while the 

 butter glolbules, which float in milk, are opaque, the liquid which 

 surrounds them is nearly transparent. It follows from this, that 

 the transparency of milk will diminish as its richness increases, 

 and vice versd. 



The lactoscope consists of two plates of glass, set parallel to 

 each other, so as to form a cell in the end of a tube, like an 

 opera-glass, the cell being at the wide end of the tube. A screw- 



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