852 THE VAKIABILITY OF COWS' MILK,!., 



are also less than the mean values, the former to the extent of 

 about 7%, the latter to the extent of about 6%. The mode of 

 the percentage of total solids is also less than the mean value, as 

 a consequence of the behaviour of the values of the percentage 

 of fat. The three forms of mean of the percentage of solids not 

 fat, however, are practically identical. 



Relations between Constituents and Properties. 



Although no general relations, between the percentages of the 

 various constituents of the milk and the values of the various pro- 

 perties, are at once apparent from an examination of the figures 

 for the individual samples, such relations do exist. So definite is 

 the relation between the density, the percentage of fat, and the 

 percentage of solids not fat, or total solids, for example, that 

 Fleischmann (1885), and Helmer and Droop Richmond (1888) 

 have devised formulae by which the value of one of these three 

 quantities may be calculated from the values of the other two. 



From the figures for the mean values of the composition and 

 properties of the milk collected on the same days, however, it 

 may be seen more readily whether any relations exist between 

 the different quantities. To display graphically any such rela- 

 tion, the mean values of the quantities for the several days have 

 been plotted as ordinates in the following diagram (Text-fig. 4). 

 The different ordinates on which the values are measured are 

 spaced equally along the abscissa, and represent the different 

 days on which the samples were collected. The points represent- 

 ing the different mean values of the same quantity have been 

 joined by straight lines. It is to be borne in mind, that the 

 lines obtained in this way are not graphs in the ordinary sense 

 of the word. They do not represent the values of the ordinates 

 corresponding to given values of the abscissae. The points on 

 the abscissa have no "values," they simply represent different 

 groups of samples; and the ordinates for the different values of 

 each quantity have been joined by lines merely to connect them 

 together, and to facilitate their comparison with the correspond- 

 ing points for the values of other quantities. 



