_Habit_ has a decided influence toward producing variations. We find in domestic animals that use--or the demand created by habit--is met by a development or change in the organization adapted to the requirement. For instance, with cows in a state of nature, or where required only to suckle their young, the supply of milk is barely fitted to the requirement. If more is desired, and the milk is drawn completely and regularly, the yield is increased and continued longer. By keeping up the demand there is induced, in the next generation, a greater development of the secreting organs, and more milk is given. By continuing the practice, by furnishing the needful conditions of suitable food and the like, and by selecting in each generation those animals showing the greatest tendency toward milk, a breed specially adapted for the dairy may be established. It is just by this mode that the Ayrshires have, within the past century, been brought to be what they are--a breed giving more good milk upon a certain amount of food than any other. [Illustration: READY FOR ACTION.] It is a fact too well established to be controverted, that the first male produces impressions upon subsequent progeny by other males. To what extent this principle holds, it is impossible to say. Although the instances in which it is known to be of a very marked and obvious character may be comparatively few, yet there is ample reason to believe that, although in a majority of cases the effect may be less noticeable, it is not less real; and it therefore demands the special attention of breeders. The knowledge of this law furnishes a clue to the cause of many of the disappointments of which practical breeders often complain, and of many variations otherwise unaccountable, and it suggests particular caution as to the first male employed in the coupling of animals--a matter which has often been deemed of little consequence in regard to cattle, inasmuch as fewer heifers' first calves are reared, than those are which are borne subsequently. The phenomenon--or law, as it is sometimes called--of atavism, or _ancestral influence_, is one of considerable practical importance, and well deserves the careful attention of the breeder of farm stock.