perfect skin, for elastic tissue is not produced till long
afterwards.[720] "The activity of the _nisus formativus_," says
Blumenbach, "is in an inverse ratio to the age of the organised body."
To this may be added that its power is greater in animals the lower
they are in the scale of organisation; and animals low in the scale
correspond with the embryos of higher animals belonging to the same
class. Newport's observations[721] afford a good illustration of this
fact, for he found that "myriapods, whose highest development scarcely
carries them beyond the larvae of perfect insects, can regenerate limbs
and antennae up to the time of their last moult;" and so can the larvae
of true insects, but not the mature insect. Salamanders correspond in
development with the tadpoles or larvae of the tailless Batrachians,
and both possess to a large extent the power of regrowth; but not so
the mature tailless Batrachians.

Absorption often plays an important part in the repairs of injuries.
When a bone is broken, and does not unite, the ends are absorbed and
rounded, so that a false joint is formed; or if the ends unite, but
overlap, the projecting parts are removed.[722] But absorption comes
into action, as Virchow remarks, during the normal growth of bones;
parts which are solid during youth become hollowed out for the
medullary tissue as the bone increases in size. In trying to understand
the many well-adapted cases of regrowth when aided by absorption, we
should remember that most parts of the organisation, even whilst
retaining the same form, undergo constant renewal; so that a part which
was not renewed would naturally be liable to complete absorption.

Some cases, usually classed under the so-called _nisus formativus_, at
first appear to come under a distinct head; for not only are old
structures reproduced, but structures which appear new are formed.
Thus, after inflammation "false membranes," furnished with
blood-vessels, lymphatics, and nerves, are developed; or a foetus
escapes from the Fallopian tubes, and falls into the abdomen, "nature
pours out a quantity of plastic lymph, which forms itself into
organised membrane, richly supplied with blood-vessels," and the foetus
is nourished for a time. In certain cases of {295} hydrocephalus the
open and dangerous spaces in the skull are fil