Mechanics as the science of motion (kinematics and phoronomism)--Chemistry of vital movement--Active and passive movements--Undulatory movement--Mechanism of imbibition--Autonomous and reflex movements--Will and willing--Mixed movements--Movements of growth--Direction of the vital movement--Direction of the crystallizing force--Direction of cosmic motion--Movements of protists--Amœboid, myophenous, hydrostatic, secretory, vibratory movements: cilia and lashes--Movements of histona, metaphyta, and metazoa--Locomotion of tissue animals: ciliary motion and muscular movements--Muscles of the skin--Active and passive organs of movement--Radiata, articulata, vertebrata, mammalia--Human movements. All things in the world are in perpetual motion. The universe is a _perpetuum mobile_. There is no real rest anywhere; it is always only apparent or relative. Heat itself, which constantly changes, is merely motion. In the eternal play of cosmic bodies countless suns and planets rush hither and thither in infinite space. In every chemical composition and decomposition the atoms, or smallest particles of matter, are in motion, and so are the molecules they compose. The incessant metabolism of the living substance is associated with a constant movement of its particles, with the building up and decay of plasma-molecules. But here we must disregard all these elementary kinds of movement, and be content with a brief consideration of those forms of motion which are peculiar to organic life, and a comparison of them with the corresponding motions of inorganic bodies. The science of motion, or mechanics, is now taken in very different senses: (1) in the widest sense as a philosophy of life [generally called mechanism or mechanicism in England], equivalent to either monism or materialism; (2) in the stricter sense as the physical science of motion, or of the laws of equilibrium and movement in the whole of nature (organic and inorganic); (3) in the narrowest sense as part of physics, or dynamics, the science of moving forces (in opposition to statics, the science of equilibrium); (4) in the purely mathematical sense as a part of geometry, for the mathematical definition of magnitudes of movement; and (5) in the biological sense as phoronomy, the science of the movements of organisms in space. However, these definitions are not yet universally adopted, and there is a good deal of confusion. It would be best to follow the lead of Johannes Müller, as we are going to do here, and restrict the name phoronomy to the science of the vital movements which are peculiar to organisms, in contrast to kinematics, the exact science of the inorganic movements of all bodies. The real material object of phoronomy is the plasm, the living matter that forms the material substratum of all active vital movements.