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
