DAIRY FARMING — DAIRYING. 369 



There was found to be a positive correlation between tlie percentage fat 

 composition of tlie milk and the numl^er of fat globules of different sizes, the 

 coefficient being 0.19. In the millc testing 2.8 per cent fat, GO per cent of the 

 number of globules were in the first division, 28 per cent in the second, and 6 

 per cent in the third; in tlie 7.2 per cent milk, 47 per cent in the first division, 

 40 per cent in the second, and 16 per cent in the third. 



In a study of inheritsmce of fat production, as shown by the relation of the 

 l)roduction of dams to that of their offspring, 3,700 pairs of variates were taken 

 from the 1910-11 Official Yearbook of the Advanced Registry of the Ilolsteiu- 

 Friesiau Association. " The mean fat production of the offspring was 16.952± 

 0.039, while that of the dams was 15.971±0.034. The standard deviation and 

 coefficient of variability of the offspring were also greater than those of the 

 dams, showing the tendency of the individuals of the Fi generation to reach the 

 extremes of the parental generations. The correlation coefficient of 0.29 would, 

 according to the statistical method of study of biparental inheritance, show 

 evidence of prepotency on the part of the dams as opposed to the sires. This 

 fact may indicate a sex-linkage of the factors controlling inheritance of fat 

 production. 



"A rearrangement of the data, used in the work just discussed, in classes 

 representing three generations, shows the following coefficients of variability — • 

 parental generation, 21.686, Fi generation 18.737, and Fz generation 21.824." It 

 is stated that this is typically JNIendelian. 



In an attempt to distinguish the unit of inheritance In fat production, a divid- 

 ing point that separated into two classes was readily recognized. The breeding 

 records of the granddams, classified into different groups with the pound as the 

 unit, were tabulated and compared. It was found that " the granddams having 

 records above 21 lbs. produced F2 descendants, as follows : Fifty-four above 21 

 lbs. and GO below. The granddams below 21 lbs. produced 764 below 21 lbs. 

 and 104 above. The latter appears to be a 7 : 1 ratio, indicating a linkage of 

 two factors — one a pure dominant, the other probably sex-linked acting in a 

 simple 3 : 1 ratio." 



The composition of milk as shown by analyses of samples of known purity 

 made by the Massachusetts State Board of Health, H. C. Lythgoe {Jour. 

 Indus. mi4 Engin. Cheni., 6 (1914), No. 11, pp. 899-908, figs. 7).— A large number 

 of samples of milk of known purity were examined in the laboratory of the 

 food and drug inspection of the Massachusetts State Board of Health for total 

 solids, ash, fat, protein, lactose, and milk serum. 



Excluding some of the abnormally high figures the percentages of variation 

 were as follows: Solids from 31 per cent above to 19 per cent below the 

 average; fat from 66 above to 41 below; proteins from 38 above to 27 below; 

 sugar from 15 above to 10 below. The variations calculated from the analyses 

 of the herd milk are much less than those obtained from the milk of individual 

 cows. Variations in the composition of milk are due primarily to the breed, 

 and to a less extent the season of the year and the period of lactation. 



A study of the seasonal variation showed that " milk obtained in the winter 

 is the best, that obtained in the simimer is the worst, while milk obtained in 

 the spring and fall is a mean of the summer and winter samples. . . . The 

 period of lactation appears to have no influence upon the variation by 

 season. . . . All the results are affected by the seasonal variation, and all but 

 the sugar and serum figures are affected by the period of lactation. The protein- 

 fat ratio and the percentage of fat in the solids of these samples were not 

 materially affected either by the season or by the period of lactation." 



The percentage of fat in the solids decreases with the solids, being 38 per 

 cent in Jersey milk and 27 per cent in Holstein milk. The amount of proteins 



