All animals possess a certain flexibility or pliancy of organization, which renders them capable of change to a greater or less extent. When in a state of nature, variations are comparatively slow and infrequent; but when in a state of domestication they occur much oftener and to a much greater extent. The greater variability in the latter case is doubtless owing, in some measure, to our domestic productions' being reared under conditions of life not so uniform as, and different from, those to which the parent species was exposed in a state of nature. Among what are usually reckoned the more active causes of variation may be named _climate_, _food_, and _habit_. Animals in a cold climate are provided with a thicker covering of hair than in warmer ones. Indeed, it is said that in some of the tropical provinces of South America, there are cattle which have an extremely rare and fine fur, in place of the ordinary pile of hair. The supply of food, whether abundant or scanty, is one of the most efficient causes of variation known to be within the control of man. A due consideration of the natural effects of climate and food is a point worthy the careful attention of the stock-husbandman. If the breeds employed be well adapted to the situation, and the capacity of the soil be such as to feed them fully, profit may be safely anticipated. Animals are to be regarded as machines for converting herbage into money. The bestowal of food sufficient, both in amount and quality, to enable animals to develop all the excellencies inherent in them, and yield all the profit of which they are capable, is something quite distinct from undue forcing of pampering. The latter process may produce wonderful animals to look at, but neither useful nor profitable ones, and there is danger of thus producing a most undesirable variation, since in animals the process may be carried far enough to produce barrenness. Instances are not wanting, particularly among the more recent improved short-horns, of impotency among the males and of barrenness among the females; and in some cases where the latter have borne calves, they have failed to secrete sufficient milk for their nourishment. Impotency in bulls of various breeds has, in many instances, occurred from too high feeding, especially when connected with a lack of sufficient exercise. A working bull, though perhaps not so pleasing to the eye as a fat one, is a surer stock-getter; and his progeny is more likely to inherit full health and vigor.