h in Physiology" Mr. Paget considers to be "the
development of ova through multiplication and division of their cells."
I would state it more broadly as the agency of the cell in all living
processes. It seems at present necessary to abandon the original idea of
Schwann, that we can observe the building up of a cell from the simple
granules of a blastema, or formative fluid. The evidence points rather
towards the axiom, Omnis cellula a cellula; that is, the germ of a new
cell is always derived from a preexisting cell. The doctrine of Schwann,
as I remarked long ago (1844), runs parallel with the nebular theory in
astronomy, and they may yet stand or fall together.

As we have seen Nature anticipating the plasterer in fibro-cartilage,
so we see her beforehand with the glassblower in her dealings with the
cell. The artisan blows his vitreous bubbles, large or small, to be used
afterwards as may be wanted. So Nature shapes her hyaline vesicles and
modifies them to serve the needs of the part where they are found. The
artisan whirls his rod, and his glass bubble becomes a flattened disk,
with its bull's-eye for a nucleus. These lips of ours are all glazed
with microscopic tiles formed of flattened cells, each one of them with
its nucleus still as plain and relatively as prominent, to the eye of
the microscopist, as the bull's-eye in the old-fashioned windowpane.
Everywhere we find cells, modified or unchanged. They roll in
inconceivable multitudes (five millions and more to the cubic
millimetre, according to Vierordt) as blood-disks through our vessels.
A close-fitting mail of flattened cells coats our surface with a panoply
of imbricated scales (more than twelve thousand millions), as Harting
has computed, as true a defence against our enemies as the buckler of
the armadillo or the carapace of the tortoise against theirs. The same
little protecting organs pave all the great highways of the interior
system. Cells, again, preside over the chemical processes which
elaborate the living fluids; they change their form to become the agents
of voluntary and involuntary motion; the soul itself sits on a throne
of nucleated cells, and flashes its mandates through skeins of glassy
filaments which once were simple chains of vesicles. And, as if to
reduce the problem of living force to its simplest expression, we see
the yolk of a transparent egg dividing itself in whole or in part, and
again dividing and subdividing, until it becomes a