which flow forth from the left cavity of the heart and tend towards the
brain), the weaker and less agitated parts must necessarily be driven
aside from that point by the stronger which alone in this way reach it I
had expounded all these matters with sufficient minuteness in the treatise
which I formerly thought of publishing. And after these, I had shown what
must be the fabric of the nerves and muscles of the human body to give the
animal spirits contained in it the power to move the members, as when we
see heads shortly after they have been struck off still move and bite the
earth, although no longer animated; what changes must take place in the
brain to produce waking, sleep, and dreams; how light, sounds, odors,
tastes, heat, and all the other qualities of external objects impress it
with different ideas by means of the senses; how hunger, thirst, and the
other internal affections can likewise impress upon it divers ideas; what
must be understood by the common sense (sensus communis) in which these
ideas are received, by the memory which retains them, by the fantasy which
can change them in various ways, and out of them compose new ideas, and
which, by the same means, distributing the animal spirits through the
muscles, can cause the members of such a body to move in as many different
ways, and in a manner as suited, whether to the objects that are presented
to its senses or to its internal affections, as can take place in our own
case apart from the guidance of the will. Nor will this appear at all
strange to those who are acquainted with the variety of movements
performed by the different automata, or moving machines fabricated by
human industry, and that with help of but few pieces compared with the
great multitude of bones, muscles, nerves, arteries, veins, and other
parts that are found in the body of each animal. Such persons will look
upon this body as a machine made by the hands of God, which is
incomparably better arranged, and adequate to movements more admirable
than is any machine of human invention. And here I specially stayed to
show that, were there such machines exactly resembling organs and outward