14 MILK-ANALYSIS. 



Very curious tliiiigs, too, are done in this country by reason 

 of trust in the lactometer. There is a prison not far from 

 London, and the prison authorities are specially particular 

 about their supply of milk. They allow no milk to enter the 

 prison unless it comes up to the M. mark on a certain lac- 

 tometer. The M. mark is pitched very high, and the milk 

 purveyor reaches the M. mark by skimming the milk. 



A very littlo consideration will suffice to make intelligible 

 the obliquity of the indications of the lactometer, and to show 

 how untrustworthy it must be. The lactometer, as of course 

 •will be understood, is simply the hydrometer applied to milk ; 

 and readings of the instrument are neither more nor less 

 than specific gravities. The more milk-sugar and caseine 

 and mineral matter there is in a given specimen of milk, the 

 greater (other things being equal) wUl be its density or 

 specific gravity, and the higher the lactometer reading. 



If, however, fat globules (as happens in the instance of 

 milk) be diffused through the fiuid, then, because fat is 

 lighter than water, the effect of the other milk solids on the 

 gravity of the liquid will be more or less neutralized. The 

 density of milk-fat is about 0.9, water being 1.0. Now, if a 

 solution of caseine and milk-sugar, of specific gravity 1.030, 

 be sufficiently charged with fat globules, its specific gravity 

 may be sent down even below the gravity of water. How 

 much would be required to bring about such a result is a 

 matter of simple calculation. 



This being understood, it wiU be obvious, that if the speci- 

 mens of milk differ in specific gravity, there must be two 

 distinct and equally valid ways of accounting for the differ- 

 ence. The milk with the lower gravity may be railk let 

 down with water, or let down with fat, i. e., milk let down 

 by being enriched. 



By way of example, I would just refer to the specific 

 gravity of the so-called strippings, which are the last portions 



