The most obvious differences between different animals are differences of
size, but for some reason the zoologists have paid singularly little attention
to them. In a large textbook of zoology before me I find no indication that
the eagle is larger than the sparrow, or the hippopotamus bigger than the
hare, though some grudging admissions are made in the case of the mouse
and the whale. But yet it is easy to show that a hare could not be as large as
a hippopotamus or a whale as small as a herring. For every type of animal
there is a most convenient size, and a large change in size inevitably carries
with it a change of form.
Let us take the most obvious of possible cases, and consider a giant man
sixty feet high - about the height of Giant Pope and Giant Pagan in the
illustrated Pilgrim’s Progress of my childhood. These monsters were not
only ten times as high as Christian, but ten times as wide and ten times as
thick, so that their total weight was a thousand times his, or about eighty
to ninety tons. Unfortunately the cross sections of their bones were only a
hundred times those of Christian, so that every square inch of giant bone
had to support ten times the weight borne by a square inch of human bone.
As the human thigh-bone breaks under about ten times the human weight,
Pope and Pagan would have broken their thighs every time they took a step.
This was doubtless why they were sitting down in the picture I remember.
But it lessens ones respect for Christian and Jack the Giant Killer.
To turn to zoology, suppose that a gazelle, a graceful little creature with
long thin legs, is to become large, it will break its bones unless it does one of
two things. It may make its legs short and thick, like the rhinoceros, so that
every pound of weight has still about the same area of bone to support it. Or
it can compress its body and stretch out its legs obliquely to gain stability,
like the giraffe. I mention these two beasts because they happen to belong
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to the same order as the gazelle, and both are quite successful mechanically,
being remarkably fast runners.
HOPE YOU UNDERSTAND WHAT I WROTE, THANKS.
