Essay on the Interpretation of Milk Records. 159 



Constants of variation, 2,665 lactations, normal and abnormal. 



Totals in gallons ; remainder in quarts. 

 [Compiled from everv complete available record (free from illness) of "Whitelnnds," 

 "Taylors," and "Hatfield Wick" herds from 1888—1910.] 



On comparing these constants with those obtained from 

 "normal" lactations only, it is found, as might have been 

 expected, that a very great increase in the variability of the 

 totals has occurred. The modal coefficient shows that only 

 about one in six cows now conform to the dominant yield- 

 type, when judged by this method. Both standard deviation 

 and skewness have increased, and the coeiEcient of variability 

 has risen from 25*72 to 31*G9, an advance of 5*97, or 23 per 

 cent, of its previous value. 



According to these data, the least variable function of a, 

 coiv's milk-production is the maximuyn day yield, ivhich gives 

 a coefficient of 26-OS, falling to 24*68 when restricted to normal 

 lactations. 



It is of some interest to compare this figure with those 

 obtained for other physiological characters. A few connected 

 with the primary sexual organs are given in the following 

 table.' 



* From Raymond Pearl. Study of Egg Production. U.S. Bureau Animal 

 Industry. Bull. 110. 



" Raymond Pearl. American Naturalist. XL. page 756. 1906. 

 ' Rommel. U.S. Bureau Animal Industry. Circular No, 95. 



* K. Pearson. Biometrika. Vol. I. page 289. 1902. 

 » Powys. do. Vol. V. page 251. 1905. 



* When measured by maximum day yiekl. Present paper. 



