The words “atom” and “atoms” will be often used in the following pages.
Therefore, it is deemed proper to state the nature and properties of an
atom, so far as known. It is defined as: “An extremely minute particle
of matter; a hypothetical particle of matter, so minute as to admit of
no division; an ultimate indivisible particle of matter. (Cent. Dic. 1,
p. 365.) The Encyclopedia Britannica says: “Atom is a body which cannot
be cut in two. The Atomic theory is a theory of the constitution of
bodies, which asserts that they are made up of atoms.” (Encyc. Brit.
3, p. 36.) A molecule is the smallest mass of any substance, which is
capable of existing in a separate form; that is the smallest part, into
which the substance can be divided without destroying its chemical
identity. A molecule of any substance is conceived of as made up of two
or more atoms. (Cent. Dic. 5, p. 3822.)
In biology a cell is defined, first, as the fundamental form-element of
every organized body. Secondly, as a nucleated, capsulated form element
of any structure or tissue; one of the protoplasmic bodies, which build
up an animal fabric; a body consisting of cell-substance, cell-wall and
cell-nucleus, as bone-cell, etc. (Cent. Dic. 1, p. 878.) The body of
every animal and plant is made of cells; and each cell is composed of
many atoms.
For a full discussion of “The Atomic Theory,” see Encyc. Brit. 3, pp.
36-49, (9th ed.); New Int. Encyc. 13, pp. 683-685.