Full text: Problems in eugenics

Exhibit C 48 — 51. 
organisms which for innumerable generations have not been active, 
or. perhaps, have never functioned in every possible way, and 
that, therefore, if the occasion arises replacements or accommoda­ 
tions of an unprecedented character may occur. In an unprejudiced 
system of race-hygiene these facts must not be overlooked. The 
exhibition in this section gives two specially striking instances; the 
one from animal the other from plant life. 
To begin with Figure C 49 gives a diagrammatic representation C 19 
■of the development of the eye of a vertebrate—after K. Kraepelin 
(taken from “ Experimentelle Biologie II., T. v. Curt Thesing, 
Leipzig, Teubner, 1911 ”)—which shows that the lens is formed out 
of an invagination of the cornea and the retina by an extension of the 
brain. In the lower part of the plate the various phases of the 
reconstruction of the lens out of the iris are shown, after it had been 
removed by a cataract operation from the eye of a Triton larva. 
(This experiment was carried out by Gustav Wolff.)* Thus an 
organ which normally is not concerned with the formation of the 
lens takes charge of its regeneration. 
A large number of tables deal with the influence of the numerical 
position in the progeny, with the number of births and the interval 
between births, on, the health of the children, partly acting alone, 
partly in combination with the influence of the manner of nourish­ 
ment during infancy. 
Numerical position in family and infantile mortality, after Geissler. C 50 
According to the^e statistics, the fifth child of a mother has materially 
less vitality than the first four, the second and third children have 
the most; but this does not agree with other statistics. 
According to Riffel’s investigations—influence of the numerical C 51 
position of the child and the age of the parents at the time of marriage 
on infant mortality, after v. d. Velden, a material difference between the 
mortality of the three earliest born children and the three next born 
is only shown if both parents at the time of marriage have attained a 
certain age (man over 28, woman over 25); only the seventh to ninth 
show under all circumstances a materially greater mortality than the 
earlier children. The children of more aged parents show a materially 
greater mortality than those of younger parents. The number of 
children in a family up to the eleventh has no material influence 
on infant mortahty, only in families with twelve children or more a 
materially greater number of children perish before the fifth year. 
^Studies in the Physiology of Development II. Archiv, für Entwick- 
lungs mechanic der Organismen, XII. Vol., 3 Part, 1901.D

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