According to this view the skin and other tissues are supposed to be made from dead protoplasm which living protoplasm turns to account as the British Museum authorities are believed to stuff their new specimens with the skins of old ones; the matter used by the living protoplasm for this purpose is held to be entirely foreign to protoplasm itself, and no more capable of acting in concert with it than bricks can understand and act in concert with the bricklayer. As the bricklayer is held to be living and the bricks non-living, so the bones and skin which protoplasm is supposed to construct are held non-living and the protoplasm alone living. Protoplasm, it is said, goes about masked behind the clothes or habits which it has fashioned. It has habited itself as animals and plants, and we have mistaken the garment for the wearer—as our dogs and cats doubtless think with Giordano Bruno that our boots live when we are wearing them, and that we keep spare paws in our bedrooms which lie by the wall and go to sleep when we have not got them on. If, in answer to the assertion that the osseous parts of bone are non-living, it is said that they must be living, for they heal if broken, which no dead matter can do, it is answered that the broken pieces of bone do not grow together; they are mended by the protoplasm which permeates the Haversian canals; the bones themselves are no more living merely because they are tenanted by something which really does live, than a house lives because men and women inhabit it; and if a bone is repaired, it no more repairs itself than a house can be said to have repaired itself because its owner has sent for the bricklayer and seen that what was wanted was done.