Thus the cattle now coming forward are thinner and larger than they were a year ago, and this means that they are older and have fattened more slowly. In effect they have been stored longer, a process which necessarily decreases the efficiency with which the animals' food is converted into its own body substance. J. L. Lush (ref: "Food and Life", p.468) has proposed an equation whereby the quantity of fat in a beef animal can be calculated from the killing out per- centage. His method gives results which appear reasonable and I have used it here.