GENERAL CHEMISTRY OF MILK 



113 



An instructive series of tests, comparing the composition of 

 fore-milk and strippings, not only in regard to fat but also as to 

 other constituents, was published by Eckles and Shaw in the fol- 

 lowing complete table : 



Breed. 



Jersey . 



Holstein.. 



Shorthorn 



Ayrshire. 



ANALYSIS OF FORE-MILK AND STRIPPINGS 



Specific Per Per Per Per Per 



grav- cent. cent. cent. cent. cent. 



Kind of milk. ity. water. soUds. ash. protein. fat. 



Fore-milk 1.0349 89.54 10.46 0.71 3.45 1.59 



Strippings 1.0314 85.44 14.56 0.69 3.25 5 92 



Fore-milk 1.0358 89.94 10.06 0.75 3.32 137 



Strippings 1.0274 84.85 15.16 0.70 3.13 6.92 



Fore-milk 1.0323 90.57 9.43 0.73 3.00 142 



Strippings 1.0265 86.43 13.57 0.69 2.81 5 82 



Fore-milk 1.0333 90.76 9.24 0.77 3.00 0.88 



Strippings 1.0284 87.14 12.06 0.72 2.87 4.80 



Fore-milk 1.0343 90.16 9.84 0.74 3.19 1.31 



Strippings 1.0283 85.62 14 38 0.63 3.06 6.23 



Fore-milk 1.0350 89.66 10.34 0.77 3.25 1.35 



Strippings 1.0298 85.68 14.32 0.69 3.19 5.54 



Fore-milk 1.0340 89.86 10.14 0.70 3.70 1.09 



Strippings 1.0244 81.85 18.35 0.64 3.45 10.00 



Fore-milk 1.0384 88.50 11.50 0.79 4.15 1.64 



Strippings 1.0283 82.83 17.17 0.73 3.76 7.88 



While sometimes the difference in the fat content of fore-milk 

 and strippings is from less than 1 to 10 per cent., it should be re- 

 membered that these figures are more relative than they appear 

 on the surface. That is to say, the smaller the quantity of fore- 

 milk and strippings examined, the greater will be the difference. 

 The fat increases gradually from the first to the last streams, and 

 it is known that the fat accumulates in the ducts by adhesion and 

 perhaps by gravity, so that the last streams become the richest. 

 The large globules remain tenaciously in the strippings until 

 they are washed down by the last streams of milk, which require 

 more energetic milking than the fore-milk. 



The figures of Eckles and Shaw show that in fore-milk and 

 strippings there is no appreciable difference in the plasma solids, 

 protein, sugar, and ash. The only marked variation is in the fat 

 content. While it is true that there is some variation in the 

 specific gravity, this is in accord with the higher fat content. 



The Reichert-Meissl, saponification, and iodin numbers are 

 lower in the strippings than in the fore-milk, while the melting- 

 point of the fat and the yellow color seem to be the same. 



The marked difference in size of the fat globules is clearly in- 

 dicated in the relative figures given in the last column. 



A variation in composition of milk from the same cow has 

 sometimes been observed to follow different calving periods, al- 

 though this variation is probably not consistent and not marked. 

 White and Judkins observed a decrease in fat from first calving to 

 the mature condition, but state that the age factor was so small 

 that other factors easily offset it. The same authors found that 



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