gate of bodies may
possess properties and powers which the separate bodies themselves
possess in no kind or sort of way. It is not a question of degree, but
of kind.

So also, further, if the aggregate is large enough, very much larger
than any planet, as large as a million earths aggregated together, it
acquires the property of conspicuous radio-activity, it becomes a
self-heating and self-luminous body, able to keep the ether violently
agitated in all space round it, and thus to supply the radiation
necessary for protecting the habitable worlds from the cold of space to
which they are exposed, for maintaining them at a temperature
appropriate to organic existence, and likewise for supplying and
generating the energy for their myriad activities. It has become in
fact a central sun, and source of heat, solely because of its enormous
size combined with the fact of the mutual gravitative attraction of its
own constituent particles. No body of moderate size could perform this
function, nor act as a perennial furnace to the rest.

_Application to Protoplasm._

Very well then, return now to our complex molecular aggregate, and ask
what new property, beyond the province of ordinary chemistry and
physics, is to be expected of a compound which contains millions or
billions of atoms attached to each other in no rigid, stable, frigid
manner, but by loose unstable links, enabling them constantly to
re-arrange themselves and to be the theatre of perpetual change,
aggregating and reaggregating in various ways and manifesting ceaseless
activities. Such unstable aggregates of matter may, like the water of a
pond or a heap of organic refuse, serve as the vehicle for influences
wholly novel and unexpected.

Too much agitation--that is, too high a temperature--will split them up
and destroy the new-found potentiality of such aggregates; too little
agitation--that is, too low a temperature--will permit them to begin to
cohere and settle down into frozen rigid masses insusceptible of
manifold activities. But take them just at the right temperature, when
sufficiently complex and sufficiently mobile; take care of them, so to
speak, for the structure may easily be killed; and what shall we find?
We could not infer or guess what would be the result, but we can
observe the result as it is.

The result is that the complexes group themselves into minute masses
visible in the microscope, each mass being called by us a "cell"; that
these c