scar on the surface with a vertical keel of scar tissue descending
from it. If the lips cannot be drawn together and there be no surgical
skill at hand to assist them with stitches or bandages, then the gap
will be filled up by the fibrous transformation of this granulation
tissue and a thick, heavy scar result. Meanwhile, the skin-cells of the
surface have not been idle, but are budding out on either side of the
healing wound, pushing a little line of colonists forward across the raw
surface. In longer or shorter time, according to the width of the gap,
these two lines meet, and the site of our wound or the scar that it has
left is perfectly coated over with a layer of healthy skin. This drama
has occurred so many score of times in every one of us that custom has
blinded our eyes to its ingenious perfection, but it took a million
years to bring it to its present finish.

It may be a healthy corrective to our overweening conceit to remind
ourselves that, remarkable and valuable as it is, it is a mere infant
in arms compared to the superb powers of replacement and repair
possessed by our more remote ancestors. Most invertebrates and many of
the lowest two classes of backboned animals, the fishes and the
amphibians, cannot merely stop up a rent, but renew an entire limb,
fin,--yes, even eye or head. Cut an earthworm in two and the rear half
will grow a new head and the front half a new tail. It may even be cut
in four or five segments, each of which will proceed to form a head at
one end and a tail at the other. The lobster can regrow a complete gill
and any number of claws or an eye. A salamander will reproduce a foot
and part of a limb. Take out the crystalline lens in the eye of a
salamander and the edge of the iris, or colored part of the eye, will
grow another lens. Take out both the lens and the iris and the choroid
coat of the eye will reproduce both.

We are in the A, B, C class in powers of repair by comparison with the
angleworm, the lobster, or the salamander. Yet we are not without
gruesome echoes of this lost power of regeneration in that our whole
brood of tumors, including the deadly cancer and sarcoma, are due to a
strange resumption, on the part of some little knot of our body-cells,
of the power of reproducing themselves or the organ in which they are
situated, without any regard to the welfare of the rest of the body.
Cancer is, in one sense, a throwing off of the allegiance to the
body-state and a re