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On The Generation Of Animals   


diverted to growth. But since the period of gestation in such
animals is a year, the mule must not only conceive, if she is to be
fertile, but must also nourish the embryo till birth, and this is
impossible if there are no catamenia. But there are none in the
mule; the useless part of the nutriment is discharged with the
excretion from the bladder- this is why male mules do not smell to the
pudenda of the females, as do the other solid-hoofed ungulates, but
only to the evacuation itself- and the rest of the nutriment is used
up to increase the size of the body. Hence it is sometimes possible
for the female to conceive, as has been known to happen before now,
but it is impossible for her to complete the process of nourishing the
embryo and bringing it to birth.

The male, again, may sometimes generate, both because the male sex
is naturally hotter than the female and because it does not contribute
any material substance to the mixture. The result in such cases is a
'ginnus', that is to say, a dwarf mule; for 'ginni' are produced
also from the crossing of horse and ass when the embryo is diseased in
the uterus. The ginnus is in fact like the so-called 'metachoera' in
swine, for a 'metachoerum' also is a pig injured in the uterus; this
may happen to any pig. The origin of human dwarfs is similar, for
these also have their parts and their whole development injured during
gestation, and resemble ginni and metachoera.

Book III

1

WE have now spoken about the sterility of mules, and about those
animals which are viviparous both externally and within themselves.
The generation of the oviparous sanguinea is to a certain extent
similar to that of the animals that walk, and all may be embraced in
the same general statement; but in other respects there are
differences in them both as compared with each other and with those
that walk. All alike are generated from sexual union, the male
emitting semen into the female. But among the ovipara (1) birds
produce a perfect hard-shelled egg, unless it be injured by disease,
and the eggs of birds are all two-coloured. (2) The cartilaginous
fishes, as has been often said already, are oviparous internally but
produce the young alive, the egg changing previously from one part
of the uterus to another; and their egg is soft-shelled and of one
colour. One of this class alone does not produce the young from the
egg within itself, the so-called 'frog'; the reason of which must be
stated later. (3) All other oviparous fishes produce an egg of one
colour, but this is imperfect, for its growth is completed outside the
mother's body by the same cause as are those eggs which are
perfected within.

Concerning the uterus of these classes of animals, what
differences there are among them and for what reasons, has been stated
previously. For in some of the viviparous creatures it is high up near
the hypozoma, in others low down by the pudenda; the former in the
cartilaginous fishes, the latter in animals both internally and
externally viviparous, such as man and horse and the rest; in the
ovipara it is sometimes low, as in the oviparous fish, and sometimes
high, as in birds.

Some embryos are formed in birds spontaneously, which are called
wind-eggs and 'zephyria' by some; these occur in birds which are not
given to flight nor rapine but which produce many young, for these
birds have much residual matter, whereas in the birds of prey all such
secretion is diverted to the wings and wing-feathers, while the body
is small and dry and hot. (The secretion corresponding in hen-birds
to catamenia, and the semen of the cock, are residues.) Since then

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