BY H. S. HALCKO WARDLAW. 845 



The above table shows the differences of closeness of grouping 

 about the median of the values of the diiferent quantities 

 measured. The general shape of the table shows almost graphi- 

 cally the different ranges of variation which have been discussed 

 above. 



If a range of, say, 10% from the median be considered, the 

 grouping of the results in the immediate vicinity of the central 

 value may be compared. The results within this range indicate 

 that the quantities measured may be divided into three main 

 groups as regards their relative variability: — 



(1) The total amounts of substances produced by the cows in 

 the period which had elapsed since last milking, about 8 hours. 

 These quantities are the most variable. 



(2) The concentrations in which these substances appear in the 

 milk. The variations of the concentrations are less, and in some 

 eases very considerably less, than the variations of amount. 



(3) The values of certain physical properties. These are the 

 least variable of all the quantities measured. 



The quantity of the milk secreted by a cow in a given time is 

 the most variable quantity observed. As the above Table shows, 

 only 22% of the results fall within a range of 10% from the 

 median value. 



The quantity of fat produced by the cow in the same time is 

 rather less variable, as 33% of the results occur within 10% of 

 the median value. This method of examining the figures, there- 

 fore, shows that there is some tendency of the amount of fat pro- 

 duced to be more "constant" than the total quantity of milk. 



The variations of the quantities of the remaining constituents 

 of the milk must be between that of the amount of milk, and that 

 of the amount of fat, since, as will be seen below, the amounts of 

 these substances produced are more dependent on the amount of 

 milk than is the amount of fat. Their concentrations are more 

 constant. 



As regards the concentrations of the components of the milk, 

 the substances present in milk may be divided into two classes: 

 those wiiich exist in suspension, and those which are in true solu- 



