“Of the elements known to chemists,” says Professor Martin, “only
sixteen have been found to take part in the formation of the human
body. These are (1) calcium, (2) carbon, (3) chlorine, (4) fluorine,
(5) hydrogen, (6) iron, (7) lithium, (8) magnesium, (9) manganese, (10)
nitrogen, (11) oxygen, (12) phosphorus, (13) potassium, (14) silicon,
(15) sodium, and (16) sulphur. Copper and lead have sometimes been
found in small quantities, but are probably accidental and occasional.”
(Martin, Human Body, p. 7.)
It is clear that neither the nature nor the properties of these
elementary substances, are changed by the fact that such substance has
become a part of the body. For example, iron is iron whether in or out
of the body.
It is probable that the chemical composition of the human body is
substantially the same as that of the body of every other mammal.