All the interruptions in the surface of the mirror indicate a diminution of the quantity of milk, with the exception, however, of small oval or elliptical plates which are found in the mirror, on the back part of the udders of the best cows, as in Figs. 29, 30, 32, 34, 35, 36, and 40. These ovals have a peculiar tint, which is occasioned by the downward direction of the hair which forms them. In the best cows these ovals exist with the lower mirrors very well developed, as in Figs. 29, 30, and 32. In fine, we should state that in order to determine the extent and significance of a mirror it is necessary to consider the state of the perineum as to fat, and of the fulness of the udder. In a fat cow, with an inflated udder, the mirror would appear larger than it really is; whilst in a lean cow, with a loose and wrinkled udder, it appears smaller. Fat will cover faults, a fact to be kept in mind in selecting a cow. In bulls, Fig. 51, the mirrors present the same peculiarities as in cows; but they are less varied in their form, and especially much less in size. This will easily be understood from the explanation of mirrors given on a preceding page. [Illustration: Fig. 38.] [Illustration: Fig. 39.] [Illustration: Fig. 40.] [Illustration: Fig. 41.] [Illustration: Fig. 42.] In calves the mirrors show the shapes they are afterwards to have, only they are more contracted, because the parts which they cover are but slightly developed. They are easily seen after birth; but the hair which then covers them is long, coarse, and stiff; and when this hair falls off, the calf’s mirror will resemble that of the cow, but be of less size. With calves, however, it should be stated, in addition to what has already been said, that the milk-mirrors are more distinctly recognized on those from cows that are well kept, and that they will generally be fully developed at two years old. Some changes take place in the course of years, but the outlines of the mirror appear prominent at the time of advanced pregnancy, or, in the case of cows giving milk, at the times when the udder is more distended with milk than at others. The classification adopted by Magne appears still further to simplify the whole method, and to bring it within the easy reach and comprehension of every one who will examine the figures and the explanations connected with them. He divides cows, according to the quantity they give, into four classes: First, the very good; second, the good; third, the medium; and fourth, the bad. In the first class he places cows both parts of whose milk-mirror, the mammary and the perinean, are large, continuous, uniform, covering at least a great part of the perineum, the udder, the inner surface of the thighs, and extending more or less out upon the legs, as in Figs. 29 to 33, with no interruptions, or, if any, small ones, oval in form, and situated on the posterior face of the udder, Figs. 29, 30, and 32. [Illustration: Fig. 43.] [Illustration: Fig. 44.]