35 



points here in detail, but intend to confine myself to a short discus- 

 sion on those quahties of milk which affect its commercial value, 

 and to describe a few of the methods for testing it. The constitu- 

 ents of a normal milk have been found to vary, usually, within the 

 following figures : 



Water, 86.0 88.5 



Butter, 3.0 4.9 



Casein, 3.0 4.9 



Sugar, 3.4 5.2 



Sahne compounds, .0.6 0.8 



100 100 



Its solid matter has been noticed to vary in extreme cases, even 

 from 11.0 to 16.8 per cent., and its specific gravity from 1.026 to 1.034 

 at 60° F., taking water of that temperature equal to 1.0. As the 

 presence of butter has a tendency to lower the specific gravity, and 

 the presence of casein, sugar and sahne matter reacts in the oppo- 

 site direction, and as all these various constituents are liable to vary 

 in percentage, it is plain that no rehable deduction can be drawn in 

 regard to the total amount of solid matter in milk, from a mere 

 test of its specific gravity. Skimmed milk of a high specific 

 gravity — 1.0338 to 1.0347 — contains ordinarily but from 10 to 11.1 

 per cent, of solid matter, while a milk unusually rich in cream of a 

 specific gravity equal to 1.026, has been shown to contain not less 

 than 16.8 per cent, of sohd matter. A common, good, unadulter- 

 ated milk has a specific gravity from 1.029 to 1.033, and contains 

 fi'om 11 to 14 per cent, of sohd matter. These facts in regard to 

 the composition of milk render it certain that the common practice 

 of deciding the question, "xvJiat is genuine milk, and ivliat is luatered 

 milk ?" is open to serious objection, unless supported by a supple- 

 mentary test, since it is hable to awaken an unjust suspicion of 

 fraudulent j^ractices on the part of the dealer, while it does not 

 efficiently protect the consumer against serious imposition. To pro- 

 tect the dealer against unjust accusations of dishonesty, the scale 

 of specific gravity had to be lowered to a degi'ec (1.026) Avhich 

 would leave it possible for him to add at least one-fourth of water 

 to an ordinary good milk, without i-endering himself oj)eu to the 

 suspicion of fraud. There is httle reason with ixs to fear the adul- 

 teration of milk with chalk, flour, starch, sheej^'s brains, and other 

 auxiharies and abominations, of which our books tell us, as long as 

 ■vrater will answer all practical purposes ; since it is abundant, and 



