Page:Popular Science Monthly Volume 78.djvu/21

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will apply his intelligence to the bettering of his condition" (p. 26). "Why are men and women so apathetic over the prevalence of disease? Why do they not devote their energies to stamping it out? For no other reason than their disbelief in the teachings of science, coupled with a lingering superstition that, after all, it is fate, not will power, which rules the destinies of mankind' (p. 28). "There is no greater evil than the congestion of streets and buildings" (p, 48).

In apparent contrast to the euthenics view of the importance of conditions is the eugenics view of the importance of blood. Taking an extreme case, a child is born an imbecile and neither the best of nutrition, the most scrupulous cleanliness, the purest air and sunshine, nor the best of physical and mental training will make anything else out of him. Imbecility can not be cured; in most of its forms it is a necessary result of the nature of the parental mating. It is a defect due to a patent or latent defect in both of the paternal germ plasms. The imbecile is an imbecile for the same reason that a blue-eyed person is blue-eyed.

Lest you have not heard where a blue-eyed child gets its eye color, let me recount the story. Brown eyes are due to a brown pigment laid down in the iris; blue eyes are due to a lack of such pigment. When both parents are brown-eyed the children get the tendency to form iris pigment from both sides of the house, and the condition of the pigment is said to be duplex. If the children get the tendency from one parent only, they still have brown eyes, but the condition is said to be simplex. If both of the parents lack brown eye-pigment, that is proof that the power of producing it is absent from their germ cells. Now, what is absent from the germ cells can not be transmitted, consequently, two parents lacking brown in the iris (blue-eyed) will never have children with brown eyes, but only with blue eyes. If both parents have brown eyes simplex, then one in four of the children will have blue eyes. If one parent has simplex brown eyes and the other has blue eyes, one half of the children will have blue eyes. But, if in both or either one of the parents the brown iris pigmentation is duplex all of the offspring will have brown eyes.[1]

Table of Matings and Offspring—Eye Color

One Parent Other Parent Offspring
PP PP PP, PP. All with pigmented iris (brown-eyed).
PP Pp PP, Pp. All pigmented, but half simplex.
PP pp Pp, Pp. All pigmented and all simplex.
Pp Pp PP, PP, pP, pp. ¼ duplex pigmented; ½ simplex; ¼ un-pigmented (blue-eyed).
Pp pp Pp, PP. ½ simplex; ½ unpigmented (blue-eyed).
pp pp pp, pp. All unpigmented (blue-eyed).
  1. These different cases of inheritance fall into six groups as in the following table, in which PP stands for duplex pigmentation, Pp for simplex pigmentation and pp for lack of pigmentation.