e are associated with more or
less fatty and amyloid (or starchy and saccharine) substances, and
with very small quantities of certain mineral bodies, of which the
most important appear to be phosphorus, iron, lime, and potash.

Thus there is a substance composed of water + proteids + fat +
amyloids + mineral matters which is found in all animals and plants;
and, when these are alive, this substance is termed protoplasm.

The wheat plant in the field is said to be a living thing; the fowl
running about the farmyard is also said to be a living thing. If the
plant is plucked up, and if the fowl is knocked on the head, they soon
die and become dead things. Both the fowl and the wheat plant, as we
have seen, are composed of the same elements as those which enter into
the composition of mineral matter, though united into compounds which
do not exist in the mineral world. Why, then, do we distinguish this
matter when it takes the shape of a wheat plant or a fowl, as living
matter?

In the spring a wheat-field is covered with small green plants. These
grow taller and taller until they attain many times the size which
they had when they first appeared; and they produce the heads of
flowers which eventually change into ears of corn.

In so far as this is a process of growth, accompanied by the
assumption of a definite form, it might be compared with the growth of
a crystal of salt in brine: but, on closer examination, it turns out
to be something very different. For the crystal of salt grows by
taking to itself the salt contained in the brine, which is added to
its exterior; whereas the plant grows by addition to its interior: and
there is not a trace of the characteristic compounds of the plant's
body, albumin, gluten, starch, or cellulose, or fat, in the soil, or
in the water, or in the air.

Yet the plant creates nothing; and, therefore, the matter of the
proteins and amyloids and fats which it contains must be supplied to
it, and simply manufactured, or combined in new fashions, in the body
of the plant.

It is easy to see, in a general way, what the raw materials are which
the plant works up, for the plant get nothing but the materials
supplied to it by the atmosphere and by the soil. The atmosphere
contains oxygen and nitrogen, a little carbonic acid gas, a minute
quantity of ammoniacal salts, and a variable proportion of water. The
soil contains clay and sand (silica), lime, iron, potash, phosphorus,
sulphur, ammo