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chapter is an elaborate statement of the subject as well as the object of the inquiry. The term, here rendered "Vital Principle," has several significations, as was observed in the preface, in the course of this and the other physiological treatises: in one passage, it implies the life of an animal; in another, the nutritive function ; in another, a vital part; in another, a motor force; and in another, the visual power ; some writers, besides, derived the term from  or , coolness or cold, because respiration was held to be a cooling process, and as such essential to life. The object of Aristotle, then, in this treatise, was to learn the nature of that essence or principle which, under whatever denomination, is the innate source of motion, and, consequently, of vital actions in all bodies capable of being animated; for although, in the more complicated forms of being, it is involved in