77 o THE POPULAR SCIENCE MONTHLY. 



only a single lifting of his body, it has to lift its own perhaps a thou- 

 sand times. The sum of all these little lifts would probably give us a 

 considerable one. 



The conclusion we have just reached, that man is relatively forty 

 times stronger than the ant, deserves, then, a closer examination ; and 

 it may be that the just interpretation of our facts will cause us to be- 

 lieve that the energetic capacity of muscular fibers is nearly uniform 

 in all animals. 



There is another illusion in these matters, which we might call psy- 

 chological. The agility of some animals surprises us. The monad in 

 a drop of water moves so nimbly that we can hardly follow it ; and 

 we naturally make a comparison between the distance which an animal 

 can cover in a certain time and its dimensions. The reasoning of this 

 comparison presents a problem somewhat difficult of solution. It is 

 enough to know that we can not draw from the illusion the conse- 

 quences which we like to see in it. 



If I were to attempt an explanation of this agility, which gives 

 small animals so great facility in escaping their enemies, I should look 

 for it in the small momentum of their mass when in flight, by reason 

 of which only a slight effort is required to enable them to change their 

 direction. Incontestably, we can run much faster than mice ; never- 

 theless, it is not easy to catch a mouse in a closed room. Our own 

 mass is an impediment to our agility. By the time we have made a 

 spring in one direction, the mouse has changed his, and we put our 

 hand, too late, where he was. It is very hard even to lay hold of a 

 bird in a narrow cage. 



The part of our question that remains to be treated is no less ardu- 

 ous or obscure than that which we have gone over. I will try to throw 

 what light is possible upon it, but I can not flatter myself that I shall 

 fully succeed. M. Plateau some seventeen years ago measured, with 

 the aid of ingenious harnessings and other devices, the muscular force of 

 insects. He deduced from his experiments that, aside from the power 

 of flight, insects have, as compared with vertebrates, an enormous 

 strength in proportion to their weight ; and that in the same group of 

 insects the strength varies, as between different species, inversely as 

 the weight, or, in other words, that the smallest insects are the strong- 

 est. 



Some of his single results were really surprising. While a horse 

 weighing six hundred kilogrammes can hardly support four hundred 

 kilogrammes, or two thirds of his weight, he found May-bugs, weigh- 

 ing a sixth of a gramme, able to support sixty-six times their own 

 weight, or more than ten grammes. Here, then, was a humble and stu, 

 pid beetle a hundred times as strong in proportion as the proud and 

 sturdy horse. Another little insect, weighing half a decigramme- 

 could move a hundred times its w r eight. By this standard we men 

 ought to be able to struggle with weights of six thousand kilogrammes 



