The founder and the smith repair it, supply it, so to speak, with 'plastic food,' the food that becomes embodied with the whole and forms part of it.

But, though it have just come from the engine-shop, it is still inert.

To acquire the power of movement it must receive from the stoker a supply of 'energy-producing food'; in other words, he lights a few shovelfuls of coal in its inside.

This heat will produce mechanical work.
Even so with the beast.

As nothing is made from nothing, the egg supplies first the materials of the new-born animal; then the plastic food, the smith of living creatures, increases the body, up to a certain limit, and renews it as it wears away.