I. The human body is composed of a number of individual parts, of diverse nature, each one of which is in itself extremely complex.

II. Of the individual parts composing the human body some are fluid, some soft, some hard.

III. The individual parts composing the human body, and consequently the human body itself, are affected in a variety of ways by external bodies.

IV. The human body stands in need for its preservation of a number of other bodies, by which it is continually, so to speak, regenerated.

V. When the fluid part of the human body is determined by an external body to impinge often on another soft part, it changes the surface of the latter, and, as it were, leaves the impression thereupon of the external body which impels it.

VI. The human body can move external bodies, and arrange them in a variety of ways.