COMPARISON OF STRENGTH OF LARGE AND SMALL ANIMALS. 515 
much less than that of a horse as its body is smaller, it would take two steps per 
second, and be caught at once." Would not Nature have done better for the 
mouse had she suppressed the cat? Is it not a fact that small animals often owe 
their escape to their want of swiftness, which enables them to change their direc- 
tion readily. A man can easily overtake a mouse in a straight run, but the ready 
change of direction baffles him. 
M. Plateau has experimented on the strength of insects, and the facts are 
unassailable. He has harnessed carabi, necrophori, June-beetles (Melolontha) 
and other insects in such a way that, with a delicate balance, he can measure 
their powers of draught. He announces the result that the smallest insects are 
the strongest proportioned to their size, but that all are enormously strong when 
compared, bulk for bulk, with vertebrates. A horse can scarcely lift two-thirds 
of its own weight, while one small species of June-beetle can lift sixty-six times 
its weight: forty thousand such June-beetles could lift as much as a draught-horse. 
Were our strength in proportion to this we could play with weights equal to ten 
times that of a horse, while an elephant could move mountains. 
This seems, again, great kindness in Nature to the smaller animal. But all 
these calculations leave out the elementary mechanical law: "What is gained 
in power is lost in time." The elevation of a ton to a given height represents 
an expenditure of an equal amount of force, whether the labor is performed by 
flea, man or horse. Time supplies lack of strength. We can move as much as 
a horse by taking more time, and can choose two methods — either to divide the 
load or use a lever or a pulley. If a horse moves half its own weight three feet 
in a second, while a June-beetle needs a hundred seconds to convey fifty times 
its weight an equal distance, the two animals perform equal work proportioned 
to their weights. True, the cockchafer can hold fourteen times its weight in 
equilibrium (one small June-beetle sixty-six times), while a horse cannot balance 
nearly his own weight. But this does not measure the amount of oscillatory 
motion induced by the respective pulls. For this both should operate against a 
spring. 
A small beetle can escape from under a piece of cardboard a hundred times 
its weight. Pushing its head under the edge and using it as a lever, it straight- 
ens itself on its legs and moves the board just a little, but enough to escape. 
Of course, we know a horse would be powerless to escape from a load a hundred 
times its own weight. His head cannot be made into a lever. Give him a lever 
that will make the time he takes equal to that taken by the insect, and he will 
throw off the load at a touch. The fact is that in small creatures the lack of 
muscular energy is replaced by time. 
Of two muscles equal in bulk and in energy the shortest moves most weight. 
If a muscular fiber ten inches in length can move a given weight five inches, ten 
fibers one inch long will move ten times that weight a distance of half an inch. 
Thus smaller muscles have an absolutely slower motion, but move a greater 
proportional weight than larger. The experimenter before mentioned was sur- 
prised to find that two grasshoppers, one of which was three times the bulk of 
