g alone and whose families break up very
rapidly (cats for example) incestuous unions, between parents and
young, for instance, are quite common.

Let us now consider the scientific side of the question. We see
everywhere that sexual union between quite distinct animal species
gives no result. At the most, certain closely allied species, such as
the ass and the horse, the rabbit and the hare, give progeny which are
themselves sterile (mules, etc.). The feebleness and sterility of
hybrids derived from widely separated races or nearly allied different
species proves the deficiency in vital force of the offspring of
fundamentally dissimilar procreators. But, on the other hand, the
dangers of continuous consanguineous reproduction are no less evident.
Perpetual unions between brothers and sisters for several generations,
lead to degeneration of the race. For example, the still-births will
be 25 per cent. instead of 8 per cent., which is the figure in
ordinary crossings. The prejudice against consanguineous unions may,
however, depend on the accumulation of certain pathological defects.

Westermark admits that it is difficult to show clearly that
consanguineous marriages are prejudicial in man. The consanguinity
which causes evil effects in animals concerns long-continued unions
between parents and children or brothers and sisters. But this never
occurs in man. Animals and plants may be perpetuated for many years in
the closest consanguinity without degeneration resulting. Among the
Persians and Egyptians, intimate unions have existed for a long time
without producing degeneration.

On the other hand, breeders of animals tell us that a single drop of
new blood (or rather sperm) is enough to counteract all the evil
effects of consanguinity. In man the most frequent incests are always
interrupted by some other union. The Ptolemies, who nearly always
married their sisters, nieces or cousins, lived long and were far from
being sterile. In Ceylon, the Weddas perpetuate their consanguineous
unions; insanity is rare among them, but they are small, unfruitful
and tend to become extinct.

In Europe, the question of marriages between first cousins has been
much discussed, and it has been constantly attempted to prove that
they are injurious. Nevertheless, when we examine the question
impartially, we always find that the prejudices against them do not
arrive from consanguinity, but from certain pathological defects, such
as insani