176 ORGANISED FLUIDS. 



ADULTERATIONS OF MILK. 



There are but few articles of general consumption more 

 adulterated, and on which more frauds are practised, than 

 the milk. 



The more usual substances employed for the purpose of 

 adulteration are water, flour or starch, chalk, and the brains 

 of sheep ; of these, water is the one which is most frequently 

 had recourse to, and which is the most difficult to detect. 



The effect of water in altering the specific gravity of milk 

 has already been referred to ; and it has been shown that the 

 result of its addition to milk, a portion of the cream of which 

 has been abstracted, is to restore the specific gravity which 

 usually belongs to it. 



Donne has shown that however much the gravity of milk 

 may vary, that the density of the serum of the milk is almost 

 constant. This fact is interesting and important, for by a 

 knowledge of it the deterioration of milk by its admixture 

 with water or with some other substance of the same density 

 with it may be ascertained. The serum is constantly heavier 

 than water : adulteration with it would then cause the serum 

 to exhibit a less specific gravity than that which should 

 properly characterise it ; the conclusion to be deduced from 

 this circumstance being that the milk has been deteriorated, 

 most probably, by the addition of water. 



The adulterations with flour and sheep's brains are readily 

 detected by means of the microscope. The fraud by the former 

 may be recognised by the peculiar form of the flour granules, 

 as well as by the action of iodine upon them (See Plate 

 XV. fig. 6.) ; and that by the latter may be distinguished by 

 the detection, in the fluid, of more or less of cerebral struc- 

 ture, and especially of the nervous tubuli. 



The chalk in the milk is readily revealed by its efferves- 

 cence with hydrochloric acid, as well as by its weight, which 

 causes it to subside at the bottom of the vessel containing the 

 milk. 



