77 2 THE POPULAR SCIENCE MONTHLY. 



You know that, if we should put a horse under a bell weighing sixty 

 thousand kilogrammes, it could not make its cover move at all. That 

 is because the animal can not insinuate itself under the eclsre of the 

 bell, and is not formed to raise weights with its head. But fix a lever 

 under the edge so that the horse can work conveniently at its longer 

 arm, and require him to raise the weight, not to a proportionate, but 

 to an equal height with that to which the insect raised his board in 

 the same time, and he would not fail to achieve the task. 



The interest of the problem before us does not lie singly in learn- 

 ing why insects are capable of efforts which appear enormous as com- 

 pared with their size. The important thing is to discover whether 

 Nature, as has been said, has regarded them more favorably than it 

 has the vertebrates and man, and has endued them prodigally with 

 muscular force, while it has been parsimonious to the other animals. 

 We need not believe anything of this kind. The prodigies of force 

 that astonish us are due to a very simple cause, and can be accounted 

 for under the common law that, of two muscles having the same mass 

 and the same energy, the shorter one is capable of raising the more 

 considerable weight. We may figure muscular fiber as a spiral spring, 

 habitually relaxed, which, under nervous action, flies back upon itself. 

 Suppose this fiber to be a decimetre long and capable of contracting to 

 half its length, and that it has attached to it a weight, say, of a centi- 

 gramme. Under the nervous action, it will raise this weight half its 

 length, or five centimetres. Now, if we replace this single fiber, a 

 decimetre long, by a muscular bundle weighing just as much but 

 composed of ten fibers a centimetre long, we can attach a centigramme 

 weight to each of these fibers, or ten centigrammes to the whole bundle ; 

 but the weight will be raised, under the contraction of the muscle, only 

 five millimetres instead of five centimetres. What we have gained in 

 power we have lost in extent of motion. That is the rule. We have 

 hence a right to conclude, that short muscles have the peculiarity, as 

 compared with long muscles of the same volume, that they act more 

 slowly but can move more considerable masses. Consequently, small 

 animals perform, absolutely, slower motions, but, in compensation they 

 can move proportionately heavier masses. We can thus comjDrehend 

 how our insect can move masses a hundred times heavier than itself, 

 without having to infer that it is a hundred times stronger than a 

 horse. Introducing its head and corselet under the obstacle it desires 

 to remove, it stretches its six legs, raises its body, and develops an 

 apparently surprising force. Really, it has lifted the obstacle only in 

 the slightest degree, but enough to allow it to escape. Its strength 

 has been furnished by the short and thick muscles of its six legs and 

 its neck. These considerations furnish the key to all the Herculean 

 labors performed by small animals. The smaller the animal, the more 

 capable it is of great efforts ; only it loses in speed what it develops in 

 force. Hence the strongest insects are generally the slowest. 



