Fróðskaparrit - 01.01.1965, Page 84

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True Hermaphroditism
spond to the external genitalia, which may be of a completely
normal appearance.
In ancient literature a true hermaphrodite is described as
an individual with both male and female gonads — testes and
ovaries — and fully developed male and female external
genitalia, which are able to reproduce the individual both as
a man and as a woman and, from a theoretical point of view,
capable of auto-fertilization. However, no such individual has
ever existed, although strange cases are to be found even in
more recent literature1.
Sexual development.
Sexual differentiation and sexual development are deter-
mined genetically. The genital anlage appears in the embryo
during the fourth week after conception, and this anlage is
identical in male and female embryos till the seventh week
of intrauterine life. This genital anlage may potentially deve-
lop into either a male gonad — a testis — or a female gonad
— an ovary. The differentiation is determined by the genes
of the sex chromosomes. The X-chromosome contains the
feminizing genes and the Y-chromosome the masculinizing
genes.
The genital primordium consists of a cortex and a medulla.
Under the influence of the normal female composition of the
sex chromosomes with two X-chromosomes (XX-), the cortex
will develop into the ovary, whereas the medulla degenerates
in such cases. If the sex chromosomes are composed by one
X-chromosome and one Y-chromosome (XY-), as in normal
males, the testes develop from the medulla, whereas the cortex
degenerates. Hence, the gonadal differentiation and develop-
ment are determined by a balance between the cortex and the
medulla in the genital primordium, depending on the genetic
sex of the individual. It is supposed that this balance is deter-
mined by hormonal cortico-medullary substances, which are
antagonistic, and which are different from the adult sex hor-
mones. It was suggested that these substances should be desig-