Page:Popular Science Monthly Volume 29.djvu/660

642 feel that it is a duty they owe, not only to themselves, but also to their country, to propagate a pure race. It is repugnant, at first thought, to speak of "breeding" men and women, but this very repugnance to handling a subject surrounded by so much delicate reserve has been largely conducive to the race-degeneration. We know that the race should be improved; every year, as has been shown, pours its rapidly increasing mass of impure blood into the general current. A man with one or more hereditary diseases on his side, and a woman with a like number among her ancestry, make it almost impossible for their offspring to escape.

We know that the race can be improved, as is shown by analogies among the lower animals. How paradoxical it seems that a man who would scout the idea of breeding his stock to diseased animals should yet without a word of opposition see his children marry into families where the hereditary taint is marked. Yet such is undoubtedly the fact. Ignorance must be the prime cause of much of this misery; for the certainty with which some diseases reproduce themselves in succeeding generations is a fact which can be proved, and not a mere set of coincidences as many suppose.

The theory that healthy blood on one side of the house is sufficient to counteract the diseased of the other is, unfortunately, fallacious. The predisposition to hereditary disease will often survive many influxes of pure blood, and the currents may, like the clear and sparkling Rhone emerging from Lake Geneva, and the dirty-gray Arve from the glaciers, run side by side for a while, separate and distinct, but at last they mingle, forming one turbid stream.



HE disciple of Darwin labors under one disadvantage. The periods necessary for maturing the changes which he investigates being so immeasurably superior to those relating to ordinary mundane affairs, he can not verify the sequence of the events by the independent testimony of contemporary history. It would be interesting to apply the theories of development and natural selection to some department of knowledge in which we could have that aid.

Human society is so largely subject to the influence of emotions which appear to have little or nothing in common with the orderly operation of natural laws, and its course is so checkered with action and reaction, that it is often difficult to follow any particular line of progress for a length of time. Examples of regular development are, however, not wanting, and one of the most striking is to be found in the history of architecture. To a person ignorant of such history 