The days on which the butter-fat analysis were made are quite accurately indicated by the dots on the butter-fat curve. Figures for the milk production each week are given to hundredths of a pound in the appropriate column above, and the butter-fat analysis is given to one one-hundredth of one per cent for each date on which the analysis was made. The grand total milk production for the year of the test is given at the foot of the column. Note the diagonal arrangement of the two headings, "Pounds" and "Per cent Butter Fat". This diagonal arrangement is a convenient one as it is easy to read and refers to each of two columns of figures, one column vertical and the other horizontal.
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Fig. 214. Milk Production of a Cow by Months for Five Years
Since a card 12 inches long is necessary in order to show figures for fifty-two weeks in one year, we can also use a card 12 inches long for five years bys
months. Having five years on one card saves handling so many separate cards, but there is a disadvantage in that curve cycles for different years
cannot be so easily and accurately compared as with the vertical arrangement of yearly cards seen in Fig. 207
A card for each cow as indicated above is worth while in a modern dairy. Individual records are fundamentally necessary to efficient operation. There is such a wide variation in cows that unless they are care-
