Jan. 20, 1919 Variations and Mode of Secretion of Milk Solids 



83 



material available where any number of animals are tested for their total 

 solids and percentage of fat. The belief is held that even with these 

 discrepancies the table will give a fair comparative \'iew of the average 

 composition of the milk of the various breeds included. Taken at their 

 face value, the data show that the butter fat percentage in the different 

 breeds varies between 3.05 and 5.12 per cent. Similarly, the total solids 

 are shown to vary between 1 1.54 and 14.39 and the solids-not-fat between 

 8.04 and 9.79. This would make the average composition of the Hol- 

 stein-Friesian breed rather lower than most of the other breeds, both in 

 the percentage of butter fat and in the total solids. If we consider now 

 the ratio of the solids-not-fat to the butter fat when the milk is constant, 

 the values of the ratios run between 1.8 and 2.81. This means that the 

 breed considered in the data has a high proportion of solids-not-fat. 

 There appears to be an association between the percentage of fat charac- 

 teristic of the breed and the content of the solids-not-fat carried in the 

 milk — that is, the Jerseys, with their high fat percentage, also have an 

 increased amount of the solids-not-fat over the other breeds, and the 

 Holland, one of the lowest breeds, also has the lowest amount of solids- 

 not-fat. This increase does not go up in direct proportion to the amount 

 of fat present in the milk, as a glance at the proportion of the two will 

 show. It will remain for a later section to show how these constituents 

 vary within the Holstein-Friesian race. 



Data have been tabulated to show the differences in the milk of different 

 species of animals (Table III). 



Table III. — Mean milk constituents of different species of animals '^ 



Species. 



Sow 



Goat 



Ewe 



Indian buffalo . . 



Bitch 



Ass 



Mare 



Man 



Cow 



Colostrum of cow 

 Colostrum of man 



Ratio of 

 solids-not- 

 fat to 

 butter fat. 



1. 8 : I 



2. 3 : I 

 I. 6 : I 

 I. 4 : I 



1. 8 : I 

 9. 8 : I 

 9. o ; I 



2. 6 : I 

 2. 5 : I 

 8. 9 : I 

 4. o : I 



» The references to the data named in this table will be found in the following numbers of the "I,itera- 

 ture cited." s. 6, 8, 9, 18, 22, 25, 26, 29, 32, 33, 38. 



The data given above are open to the same criticism as that in Table II, 

 and are to be taken with the same limitations. 



The milk of the different species varies considerably both in its butter- 

 fat content and in its solids-not-fat. The lowest percentage of fat pro- 

 duced is 0.90 per cent, found in the milk of the ass. The milk of the mare 

 corresponds closely to this, 0.99 per cent. The highest percentage of 



