On the Movement of Animals, Part One

-usely discuss the conspicuous motions of Animals, namely the flexions and extensions of external parts and limbs, and finally gait, flight, swimming, and their annexes.

In the second [part], we shall discuss the causes of the movement of the muscles and the internal motions, namely of the humors, which occur through the vessels and viscera of Animals. And as regards the first part, we shall proceed not according to the order of things, but according to the demands of clearer doctrine, by inquiring into the structure of the muscles and demonstrating with what motive force the parts of an Animal are agitated, and by what mechanical organs. Afterwards, we shall explain the manner of a muscle's operation. Next, concerning the motive force diffused through the nerves, by which the muscles are agitated. Then, we shall deal with internal motions that do not depend on the command of the will: the pulsation of the heart and the circulation of the blood; the use of respiration, its modes, and the organs by which it is exercised; the spirits, or nervous juices, which provide motion and sensation and serve for nutrition; their motion and motive action; the necessity of eating and the causes of the cooking and digestion of foods; the purification of the chyle and the manner by which nutrition is effected; and the way in which excrements are cast off through pores, glands, and kidneys; the circulation of bile in the abdomen; the partial circulation of the genital seed; sleep and wakefulness; and finally, certain internal, perturbed, and morbid motions, namely, convulsion, lassitude, and febrile motions.

Meanwhile, learned reader, I would have you know that I have very often used the terms "will," "command," and the like in a broad sense, insofar as they are attributed to brute animals by analogy and a certain similarity in the usage of speech. PARS