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 534 THE AMERICAN JOURNAL OF SOCIOLOGY

rule, by use, disuse, or injury. For example, a man's hand is inborn. It comes to him by nature; it arises because the germ- plasm in the germ-cell whence he sprang was so constituted that it caused that germ-cell, under fit conditions of shelter and nutri- tion, to multiply into a being having a man's hand. In brief, a man's hand is a germinal character; but the thickening of the skin in the palm of the hand which results from use, or a scar which results from injury, is not an inborn character, but an acquirement.

The principal mass of both inborn and acquired characters are ancient possessions of the race. Thus the hand and the thickened skin of the palm have been possessed by innumerable generations of men. But in some characters offspring differ from their parents. When these new characters are inborn, they are tech- nically termed variations. Thus, if the child of normal parents were "blind" "by nature," his peculiarity would be a variation; but if he became blind by injury, it would be an acquirement. The great importance of distinguishing between inborn and acquired characters lies in the fact that the former, including variations, tend to be inherited by offspring, whereas most stu- dents of heredity deny that the latter are ever inherited. It should be noted that some acquirements are of great magnitude. Thus, in the human being, the limbs develop beyond the infantile stand- ard mainly under the influence of use, a paralyzed infant limb growing little, if at all. Almost all growth, therefore, that occurs in the limbs after birth is an acquirement.

Offspring tend to reproduce the main mass of the parental inborn characters, but always with variations with innumer- able inborn differences which, as a rule, are minute as com- pared with the likenesses. Thus the child of a human being is always another human being, but "by nature" he is invariably somewhat different from his parent a little taller or shorter, stronger or weaker, fairer or darker, and so forth. The chief problem of heredity, both theoretical and practical, is the question as to what causes offspring to differ from their parents in this inborn way. The importance of the problem at once becomes evident when we remember that all racial change, all evolution,