THE SIZE OF LIVING THINGS
thousand million. Echinodcrms have only a range of a million
times, rotifers even less. As proof of how soon the size of insects and
of flying birds is cut short, we find they have ranges of only a million
and ten thousand, respectively.
Man is a very large organism. During his individual existence he
multiplies his original weight a thousand million, and comes to con-
tain about a hundred million million cells. He is a little more than
halfway up the size-scale of mammals, and nearly two-thirds up that
of the vertebrates.
Then we look at the range of life as a whole, and compare it with
the size-ranges of not-living objects above and below the limits of
living things; here too there arc surprises. The sun is almost pre-
cisely as much heavier than a big tree as the big tree is heavier than
the filter-passer; but the range from the filter-passer downward to
the ultimate and smallest unit of world-stuff, the electron, is only half
this—only as much as from the big tree to such an easily visible
creature as the flea. It takes more tubercle bacilli to weigh one man
than there are electrons in a tubercle bacillus.
It is possible to calculate, on the Einstein hypothesis, a minimum
weight for the whole universe, a minimum figure for the totality of
matter. This is nearly io24 times as much as the sun—in other words,
the sun is halfway between the big tree and the whole universe of size.
Although the molecules of living matter are, for molecules, enor-
mous, yet the smallest living organisms are far down on the world's
size-scale. Once started, however, life has achieved a size-range
which is two-fifths of that from electron to star, and probably well
pver a quarter of the whole range of size within the universe. Man is
almost halfway between atom and star; he is nearly two-fifths up the
cosmic scale from electron to the all-embracing weight of the universe.
But so vast is that scale that to be halfway up he would have to be as
big as a million big trees rolled into one. Even if we were to take the
thousand million people who now inhabit the globe as constituting
but one single organism, this would still be more than ten times too
small. The individual man is all but halfway between atom and
star; humanity entire stands in the same position between electron