But, however careful we may be to select good milkers, and to breed from them with the hope of improvement, it is by no means easy to select such as are capable of transmitting their qualities to their offspring. This is rendered still more difficult by the fact that there is no known mark to indicate it, and we are left to use our own judgment; for, in the case of bulls, we are often obliged to give them up before their progeny have arrived at an age to show their qualities by actual trial. We are thrown back, therefore, upon their external marks. But, as M. Magne, a very sensible French writer, justly observes in his admirable little work (_Choix des Vaches Latières_, p. 86, Paris, 1857), the fixed characteristics which have existed in races for several generations will be transmitted with most certainty. Hence the importance, he says, of selecting milch cows from good breeds and good families, and especially, in breeding stock, of selecting carefully both male and female. The male designed to get dairy stock ought to possess the structure which, in the cow, indicates the greatest activity of the mammary glands, as fineness of form, mellowness of skin, large hind quarters, large and well-developed veins and escutcheon. A cow of a race or family not noted as milkers may chance to be an excellent milker, and this is enough, if we do not desire to breed from her; but she would not transmit her exceptional qualities like a cow of which these qualities were the fixed characteristics, constant and transmissible in the breed. These considerations apply also, as already said, in the choice of a bull. The attention of practical men has been so much directed to the best points of good cows, of late years, that it becomes necessary to study to propagate these, if the breeder desires to find buyers for his stock. The buyer judges more from external signs than from the intrinsic qualities of the cow, with which he may not be acquainted. To explain the variations in the transmission of milking qualities, we should bear in mind that these qualities are not found in wild cows, and that they are developed only when man can, by a particular course of treatment, as by the act of milking, the separation of the sexes, etc., cause certain natural powers to act with greater strength than others; that they incline to disappear as soon as these powers, the nature of the soil, the peculiarities of climate, the properties of plants, and the temperament of the cows, are permitted to act according to the original plan of creation; so that the variations which we consider as sports of nature are incontestible proofs of the uniformity of her works.