the bones are like the wooden levers in the automaton, and the iron;

the tendons are like the strings, for when these are tightened or

leased movement begins. However, in the automata and the toy wagon

there is no change of quality, though if the inner wheels became

smaller and greater by turns there would be the same circular movement

set up. In an animal the same part has the power of becoming now

larger and now smaller, and changing its form, as the parts increase

by warmth and again contract by cold and change their quality. This

change of quality is caused by imaginations and sensations and by

ideas. Sensations are obviously a form of change of quality, and

imagination and conception have the same effect as the objects so

imagined and conceived For in a measure the form conceived be it of

hot or cold or pleasant or fearful is like what the actual objects

would be, and so we shudder and are frightened at a mere idea. Now all

these affections involve changes of quality, and with those changes

some parts of the body enlarge, others grow smaller. And it is not

hard to see that a small change occurring at the centre makes great

and numerous changes at the circumference, just as by shifting the

rudder a hair's breadth you get a wide deviation at the prow. And

further, when by reason of heat or cold or some kindred affection a

change is set up in the region of the heart, even in an

imperceptibly small part of the heart, it produces a vast difference

in the periphery of the body,- blushing, let us say, or turning white,

goose-skin and shivers and their opposites.

8



But to return, the object we pursue or avoid in the field of

action is, as has been explained, the original of movement, and upon

the conception and imagination of this there necessarily follows a

change in the temperature of the body. For what is painful we avoid,

what is pleasing we pursue. We are, however, unconscious of what

happens in the minute parts; still anything painful or pleasing is