The different forms of milk-mirrors are represented by the shaded part of figures 29, 30, 31, etc.; but it is necessary to premise that upon the cows themselves they are always partly concealed by the thighs, the udder, and the folds of the skin, which are not shown, and so they are not always so uniform in nature as they appear in the cuts. Their size varies as the skin is more or less folded or stretched, while we have supposed in the figures that the skin is uniform or free from folds, but not stretched out. In order to understand the differences which the milk-mirrors present in respect to size, according to the state of the skin, the milk-mirror is shown in two ways in Figs. 52 and 53. In Fig. 53 the proportions are preserved the same as in the other mirrors represented, but an effort is made to represent the folds of the skin; while in Fig. 52 the mirror is just as it would have been had the folds of the udder been smoothed out, and the skin between the udder and the thighs stretched out; or, in other words, as if the skin, covered with up-growing hair, had been fully extended. This mirror, but little developed, just as shown in Fig. 53, was observed on a very large Norman cow. It is usually very easy to distinguish the milk-mirrors by the upward direction of the hair which forms them. They are sometimes marked by a line of bristly hair growing in the opposite direction, which surrounds them, forming a sort of outline by the upward and downward growing hair. Yet, when the hair is very fine and short, mixed with longer hairs, and the skin much folded, and the udder voluminous and pressed by the thighs, it is necessary, in order to distinguish the part enclosed between the udder and the legs, and examine the full size of the mirrors, to observe them attentively, and to place the legs wide apart, and to smooth out the skin, in order to avoid the folds. The mirrors may also be observed by holding the back of the hand against the perineum, and drawing it from above downwards, when the nails rubbing against the up-growing hair, make the parts covered by it very perceptible. As the hair of the milk-mirror has not the same direction as the hair which surrounds it, it may often be distinguished by a difference in the shade reflected by it. It is then sufficient to place it properly to the light to see the difference in shade, and to make out the part covered by the upward-growing hair. Most frequently, however, the hair of the milk-mirror is thin and fine, and the color of the skin can easily be seen. If we trust alone to the eye, we shall often be deceived. Thus, in Figs. 52 and 53, the shaded part, which extends from the vulva to the mirror E, represents a strip of hair of a brownish tint, which covered the perineum, and which might easily have been taken for a part of the milk-mirror.