nutritive functions are particularly active in supporting the individual, the reproductive system is undeveloped, and vice versa."
Let, therefore, on this principle, any class of organs or any parts of the body be unduly or very much exercised, it requires the more nutrition to support them, thereby withdrawing what should go to other organs. In accordance with this physiological law, if any class of organs become predominant in their development, it conflicts with this great law of increase. In other words, if the organization is carried by successive generations to an extreme, that is, to a high nervous temperament—a predominance of the brain and nervous system—or, on the other hand, to a lymphatic temperament—a predominance of the mere animal nature—it operates unfavorably upon the increase of progeny. Accordingly, in the highest states of refinement, culture, and civilization of a people, the tendency has always been to run out in offspring; while, on the other hand, all tribes and races sunk in the lowest stages of barbarism, and controlled principally by their animal nature, do not abound in offspring, and in the course of time they tend also to run out. The truth of both these statements is confirmed by history. The same general fact has been observed among all the abnormal classes, such as idiots, cretins, the insane, the blind, the deaf and dumb, and to some extent, with extreme or abnormal organizations, such as are excessively corpulent or spare, as well as of unnatural size, either very large or diminutively small.
It would seem that Nature herself is bound to put an end to organizations that are monstrous, that are defective, and abnormal or unnatural or imperfect in any respect. All history, we believe, proves that such organizations are not prolific in offspring, and the number of this class born into the world, reaching an advanced age, is comparatively not large. Such facts would indicate that there must be a general law of propagation that aims at a higher or more perfect standard.
If this principle is applied to distinct classes in society, some striking illustrations may be obtained. Take the families belonging to the nobility, the aristocracy, or the most select circles, where by inheritance, refinement, and culture the nervous temperament has become very predominant, it is found that such families do not increase from generation to generation in offspring, and not unfrequently, in time, they become extinct.
A similar result has also followed the intermarriage of relations, from the fact that the same weaknesses or predispositions are intensified by this alliance. On the other hand, in case these relations have healthy, well-balanced organizations—it may be that they are cousins—they will abound with healthy offspring, and the stock may improve, and not deteriorate, from the mere fact of relationship.
Again, if we take those families and races which for several generations have steadily increased most, we shall find that, as a whole,