66 THE HUMAN BODY. 



Amoros was twenty-five miles in two hours and forty-five 

 minutes, that is, about nine miles an hour. 



Leaping is, properly speaking, nothing but a step of run- 

 ning taken singly. A man can jump with his feet joined, 

 that is to say, the two feet quit the ground at the same in- 

 stant, and the body is thrown vertically upward and forward, 

 or backward. The jump may be preceded by running seve- 

 ral steps in order to get under way, as it is termed. In this 

 case the speed acquired during the first steps is added to the 

 impulse given to the body by the last one. By exercise 

 men have succeeded in jumping vertically a height of two 

 metres, and horizontally over a space of five or six metres. 

 Amoros speaks of an Englishman who jumped across a ditch 

 ten metres in width. 



Swimming. Man can sustain himself upon the water, and 

 traverse it for a considerable space by swimming; but this is 

 not an instinctive method of locomotion for him he must 

 learn to swim, while walking and the other modes of pro- 

 gression are natural to him, and are not acquired by study. 

 Man walks, runs, and jumps just as an amphibious animal 

 swims without having learned to do so; but to swim he must 

 study the attitudes and the movements which neutralize the 

 effect of his specific gravity, which prevent him from sinking 

 into the water, and permit him to gain a resting-point in 

 order to displace it. 



The quadruped swims as if walking in the water, that is, 

 by making just the same movements as in walking on the 

 ground. Man can, it is true, swim as animals walk, striking 

 the water with his four members ; but he is soon overcome 

 by fatigue, and to swim for any length of time he must exe- 

 cute other movements considerably complicated in their 

 combinations. It is from that modest amphibian, the frog, 

 from which he borrows in this case the method of progres- 

 sion, and this loan is certainly the most inoffensive of all 

 those which he makes from the animals. Although he seems 

 to turn his members quite away from their normal functions, 

 he soon attains the power of prolonging this exercise, which 

 is eminently healthful and very precious, since he finds in it a 

 means of saving his own life and the lives of his fellowmen. 



