Page:Popular Science Monthly Volume 77.djvu/29

Rh would be eminently fitted to become useful members of society, could they be saved. Those who die of bacterial diseases may be unfitted to cope with those diseases, but this does not imply all other forms of unfitness. This has been recognized from time immemorial, in the phrase, "those whom the gods love die young."

In the second place, it should be pointed out that while much of the elimination now occurring is desirable, it is no doubt preposterously haphazard, and those who so keenly recognize the need for elimination, should be the first to advocate a rational method of bringing it about. This rational method consists, not in the destruction, but in the prevention of the unfit.

At this point it will be useful to leave mankind for a while, and consider some of the recent results of the study of heredity; results obtained mainly from investigations on plants and lower animals. Without going into detail, it may be said that through the researches of Mendel, Bateson, de Vries, Davenport and many others, we have come to a very clear recognition of unit-characters in inheritance. That is to say, particular characters, such as hairiness, eye-color or susceptibility to some disease, are inherited separately, passing from one generation to another much as atoms pass without change from one to another chemical compound. These unit characters may be lost, and sometimes the loss is real and final, sometimes it is illusory, due merely to non-potency. In very simple cases, it is found that the inheritance of these units follows easily recognized laws, the distribution being in accordance with the laws of chance. In others, this is not evident, and in man especially, the results are often perplexing. Thus the mulatto is virtually a blend between the white and black races, and at first sight it is not at all apparent that the racial characters are inherited as separate units. Nevertheless, we have indications of this in the remarkable differences sometimes observed within a single family of mulattoes, and it may well be inferred that further investigation will yield results in accordance with recognizable laws, and in so far predicable in advance.

The absolute distinction which at first seems to exist between characters which are inherited as separate units and those which blend may not be real. When the units are obviously separate, but are fairly numerous, they will produce every sort of mosaic, in the most confusing, and at first sight wholly disorderly manner. Let them be somewhat more numerous still and it becomes practically impossible, by mere inspection, to disentangle the result. It is just as black and white balls, if of large size, will appear as separate things when mixed, but if sufficiently small will give an apparent blend, of uniform gray. Because