cultivated. But we must rather transfer our
attention to a second aspect of Environment, not perhaps so fascinating
but yet more important.

So much of the modern discussion of Environment revolves round the mere
question of Variation that one is apt to overlook a previous question.
Environment as a factor in life is not exhausted when we have realized
its modifying influence. Its significance is scarcely touched. The great
function of Environment is not to modify but to _sustain_. In sustaining
life, it is true, it modifies. But the latter influence is incidental,
the former essential. Our Environment is that in which we live and move
and have our being. Without it we should neither live or move nor have
any being. In the organism lies the principle of life; in the
Environment are the conditions of life. Without the fulfillment of these
conditions, which are wholly supplied by Environment, there can be no
life. An organism in itself is but a part; Nature is its complement.
Alone, cut off from its surroundings, it is not. Alone, cut off from my
surroundings, I am not--physically I am not. I am, only as I am
sustained. I continue only as I receive. My Environment may modify me,
but it has first to keep me. And all the time its secret transforming
power is indirectly moulding body and mind it is directly active in the
more open task of ministering to my myriad wants and from hour to hour
sustaining life itself.

To understand the sustaining influence of Environment in the animal
world, one has only to recall what the biologist terms the extrinsic or
subsidiary conditions of vitality. Every living thing normally requires
for its development an Environment containing air, light, heat, and
water. In addition to these, if vitality is to be prolonged for any
length of time, and if it is to be accompanied with growth and the
expenditure of energy, there must be a constant supply of food. When we
simply remember how indispensable food is to growth and work, and when
we further bear in mind that the food-supply is solely contributed by
the Environment, we shall realize at once the meaning and the truth of
the proposition that without Environment there can be no life. Seventy
per cent. at least of the human body is made of pure water, the rest of
gases and earth. These have all come from Environment. Through the
secret pores of the skin two pounds of water are exhaled daily from
every healthy adult. The supply is kept up by Envir