De Motu Animalium

In the second [part], [we will discuss] the causes of the movement of the Muscles, and internal motions: namely, the humors which occur through the vessels and viscera of Animals; and as regards the first, we will proceed not according to the order of things, but according to the requirement of clearer doctrine, 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; afterward, we will explain the muscle's mode of operating; next, concerning the motive force diffused through the nerves, by which the muscles are agitated. Then we will treat the 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; concerning the spirits, or nervous juices, which minister to movement and sensation and serve for nutrition; concerning their motion and motive action, the necessity of eating, and the causes of the cooking and digestion of food, concerning the purification of chyle, and the mode by which nutrition is effected, and excrements are rejected through the pores, glands, and kidneys; concerning the circulation of bile in the abdomen; concerning the sort of circuit of the genital seed; concerning sleep and wakefulness; and finally, concerning some internal, perturbed, and morbid motions, namely, concerning convulsions, fatigue, and febrile motions.*

Meanwhile, learned Reader, I wish you to know that I have very often used the words "will," "command," and similar terms in a broad sense, insofar as they are attributed to brutes by analogy and a certain similarity of speech.