Naturalist. Comparison of Strength of Large and Small Animals.

Waikato Times, Volume XXIII, Issue 1914, 11 October 1884, Page 2 (Supplement)

Naturalist. Comparison of Strength of Large and Small Animals.

\ W. N. LoCIUKGTON. ; M. Di-,lbeuf, in a paper read before the Acr.demie Boyale de Belgique, and publiahe.l i in the ltevue Scientique, reviews the attempts of various n&tmaiista to make comparisons between tho strength of large auhnals and tbat of small ones, especially insects, and fchows that ignorance or forgetfulneas of physical laws vitiates all (heir conclusions. A't°r p, pies, for the idea, without which the i fact is barren, M. Diilbeuf repeats certain statements with which readers of. modern zoological science are tolerably familiar, such as the following : — A flea can jump two , hundred times its length ; therefore, a horse, i wejeii'3 strength proportioned to its weight, could leap the Eocky Mountains, and a whale could spring t'^o hundred leagues in height. An Amazon ant walks about eight feet per raiimte, but if the pi ogress o f a human Amazon were proportioned to her larger size, bho conic! str'de over eight leagues an hour ; and if proportioned to her weight, sha would mako the circuit of the globe in about twelve minute*. Thh seems greatly to tho advantage of the insect. What weak creatures vertebrates must be is the impression conveyed. Bat tho work incieases as the weight. Id springing, walking, swimming, or any other activity, the force employed has first to overcome the weight of the body. A man can easily bound a height of two feet, and he wcigh's as much as a hundied thousand grasshoppers, while a hundred thousand grasshoppers could leap no higher than one—say a foot. This shows that the vertebrate has the advantage. A man represents the volume of fifteen millions of ants, yet can easily move more than three hundred feet a minute, a roffijv.iison which gives him forty times r.ioie power, bulk foy bulk, than the ant po-se^scJ. Yei were all the conditions compared, something like equality wouid probably bo the result. Much of the force of a moving man 11 lost from tho inequalities of ihe way. His body, auppci ted on two points only when at lest, oscillates like a pendulum flora one to the oiher as he moves. Tvs ant crawls eloso to t^e ground, and has only a small part of tho body unsupported at once. This economises ioi.ee at each step, but on the other hand multiplies the number of .stcia sogieatly since the smallest inegolarity ol the suiface is a hill to a crawling creature, that the total loss of force ia perhaps, greater, isince it has to slightly laise icy body a thousand times or so to clear a spac° spanned by a man's one's step. By what peculiarity of our mincta do we seem to expect the speed of an animal to be in proportion to iU eize. We do not expeefc a caravan to move faster thau a single horseman, nor an eight hundred pound shot to move twelve thousand eight bundled times farther than an ounce ball. Devout v/riters speuk of a wise provision of Nature. "If," sr.y they, " the rj peed of a mouse were as much less tluu that of a horse as its body ia tmarev, it would take two steps per second, and be caught at once. ' Would iint Nature have done belter for the mouse had she supposed the cat ? 3s it not a fact that small animals often owe their escape to their waat of swiftness, which enable;! them to change their direction readily ? A man can easily overtake a mouse in a straight run, but the ready change of direction bafllcs him. M. Platpau hvs experimented on the strength of. insects, and the facfn are unassailable. He has harnessed carabi, nee ophoii, June-beetles (Melolontha), and othci imects 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 &tionge&t proportioned to their size, but tlrttt all are enormously strong when compared bulk for bulk with vertebrates. A horse can ocarcsly lift two-thirds of its own weight, while one small species of June -beetle can lift pixty-&ix times its weight ; forty thousand &uoh June- beetles could lift as much as a diaughfc-hoise. Wei e our strength in proportion to this, we could play with weights equal to ten times that of a horse. This seems, again, great kindness in Nature to the smaller animal. But all these calculations leave out the eiomentai-y mechanical lav/ : " What is gained in power ia lost in time.' The elevation of a ton to a given height represents an expenditure of an pqual amount oi force, whether the labor ia performed by flea, man, or horse. Time supplier lack of strength. We can move as much ac a horse by taking moie time, and can choo&e two methods — either to divide the load or use a lever or a pulley. If a horse moves lalf its own weight ib'ee feet in a second, while a June-beetle needs a hundred seconds to coivey fifty times ite weight an equal distance, the two animals pe.cf.oim equal work proportioned to their weights. True, the cockchafer can hold fourteen times ifcd weight in equilibrium (one email June-beetle sixty-six times), while a hoiso cannot balance nearly bis own weight. But this does not measure the amount of o?cillatoiy motion induced by the respective pulls. For this, both should operate against a spring. A small beetle can escape from under a piece cf cardboard a hundred times iis weight. Pushing iis head under ihe edge and using it a3 a lever, it straightens 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 o£ muscular energy is .replaced bytime. Of two muscles equal in bulk and energy tbc shortest moves most weight. If a muscular fibre ten inches in length can move a given weight five inches, ten fibres 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 surprised to find that two grasshoppers, one of which was three times the bulk ox the other, leaped an equal height. This was what might be expected of two animals similarly constructed. The spring was proportioned to the bulk. In experiments on the insects with poweiful wings, such as bees, flies, dragon-flies, &c, it was found that the weight they could bear without being forced to descend was in most cases equal to their own. In some cases it was more, but the inequality of rate of flight, had it been taken into the reckoning, would have accounted for this. Take two creatures of different bulk, but built upon exactly the same plan and proportions, say a Brobdignagian and a Lilliputian, and let both show their powers in the arena. Suppose the first to weigh a million times more than the second. If the giant could raise to hia shoulder, some thirty-five feet from the ground, a weight twenty thousand pounds, the dwarf can raise to his shoulder, not, as might be thought, a fiftieth of a pound, but two full pounds. The distance raised would be a hundred times less. In a race the Lilliputian, with a hundred skips a second, will travel an equal distance with the giant, who would take but a skip in a second. The leg of the latter weighs a million times the most, but has only ten thousand times as

many muscle fibres, eaoh a hundred timea longer tban those of the dwarf , who thus takes one hundred skips while the giant takes one. The same physical laws apply to all muscles, so that, when all the factors are considered, muscles of the same quality have equal power. — Am. Field.