357 



as possible; we lean back, on the contrary, ill descending a flight of stairs, 

 or a rapid slope, in order to slacken the motion, by which the body, 

 yielding to its own weight, falls on the leg that is carried forward, 



At the moment when the centre of gravity is no longer within the base 

 of sustentation, all the powers unite in action, that it may fall, as little as 

 possible, from a vertical . direction. The glutsei steady the pelvis, and 

 straighten the thigh, the lumbar muscles extend the trunk on the pelvis ; 

 hence, in going down a slope, the loins get so much fatigued. We are 

 less fatigued in going down hill, when the slope is moderate, than in going 

 up hill | us the force of gravitation, or the weight of the body* assists con- 

 siderably the descending vertical motion* The motion of walking, when 

 we take very long steps, resembles that of going up hill, as the body being 

 lowered, every time the legs are much apart, requires to be elevated, at 

 each step, towards the foremost leg. 



At every step we take, the articulation of the leg with the foot is the 

 principal seat of an effort, to which physiologists have not paid any at- 

 tention. The whole weight of the body is supported by the action of the 

 levatormusclesof the heel, and the astralagus supports this weight, which 

 varies according to the corpulence of the person, and the burthen with 

 which he is loaded. The weight of an adult, of common stature and of 

 moderate size, may be estimated at about one hundred and fifty pounds $ 

 but which sometimes, in corpulent people, amounts to between four and 

 five hundred pounds. If, then, to the weight of the body, there be added 

 that of the burthens which it may support, it will be conceived how im- 

 mense the efforts must be, which are, as it was unconsciously, carried on, 

 in the articulation of the foot with the leg. But how numerous the re- 

 sources which nature has provided to overcome this great resistance; 

 how many the circumstances she has happily combined to accomplish 

 this without fatigue ! In the first place, the foot in this action, repre- 

 sents a lever of the second class, and this lever, it is well known, is the 

 most advantageous, the resistance being always nearer to the fulcrum 

 than the power, and the arm, by which the latter acts, consisting of the 

 whole length of the lever. If you attend to the mechanism of the differ- 

 ent parts of the skeleton, you will no where find so powerful a lever ap- 

 plied in so favourable a manner. The os calcis, by carrying the foot be- 

 yond its articulation with the leg, adds likewise to the length of the lever 

 by which the power acts. Its length has considerable influence on our 

 strength, on our power of talking, without fatigue, long walks, orengaging 

 in exertions requiring considerable muscular force in the lower extremi- 

 ties. The negroes, who excel in running, in dancing, and in all gymnas- 

 tic exercises, have a longer and more projecting heel than Europeans. 

 They dance best, whose tendo Achillis is most detached, that is to say, 

 projecting, and at the greatest distance from the axis of the leg; which 

 implies, that its lower attachment is carried back, by the prolongation of 

 the os calcis. 



Those who have a short heel, have a long and flat foot : this conforma- 

 tion, which, when marked, is faulty, is not only unfavourable to beauty 

 of form, but is, besides, remarkably injurious to the strength of the limb, 

 as well as to freedom of motion. Men with flat feet, are always bad 

 walkers, hence, this flattened form, when very considerable, is considered 

 as unfitting a man for military service. Lastly, the term denoting this 

 physical imperfection (fiieds filats,} is accounted insulting in the French 

 language, as well as in several others. But let us go on with our in* 



