Experiment regarding the Thigh-bone, ^5 



mospherical air, and which has heen pointed out by my bro- 

 ther and myself, in our work " On the Mechanics of the 

 Organs of the Human Body*" ( Mechamk der Menschlichen 

 Gehwerkzeuge, eine anatomisch-pUysiologischc Untersuchung 

 vwi den Briidern Wilhelm Weber, Professor in Gottingen, und 

 Edzvard Weber, Prosector in Leipzig, Mit 17 Tqfeln. Got- 

 tingen, 1836. J 



We have, in the above-mentioned work, proved by direct 

 experiments, that the weight of the bone, when attached to the 

 trunk, and which amounts to about twenty pounds, neither 

 hangs on the muscles or h'gaments, nor even rests on the 

 edge of the socket, but is supported by the pressure of the 

 air, which squeezes the two surfaces of the joint together. 

 By means of this equilibration of its weight, the bone acquires 

 as perfect a power of turning in its socket as is necessary for 

 the performance of such active movements as walking and 

 running. If, then, the pressure of the air becomes diminished, 

 a point must be reached, when that pressure can no longer 

 preserve the equilibrium of the weight of the bone. Another 

 power, such for example as that of the muscles, must now take 

 its place and support the bone ; as, otherwise, the two sur- 

 faces of the joint would remove from each other. It is how- 

 ever to be expected, that, when the bone is supported in this 

 less advantageous manner, which not only causes an expendi- 

 ture of strength, but also obstructs the movements of the bone, 

 owing to the stiffness that is induced in the muscles called in- 

 to action, derangements and inconveniences should take place 

 in walking, which would not occur if the bone were kept in 

 equilibrium by the pressure of the air. 



In very elevated regions, where the pressure of the air is reduced 

 almost a half, such inconveniences really occur, viz., so great a 

 degree of fatigue of the bones is perceived, as would lead us 

 to suppose a derangement of the mechanism employed in walk- 

 ing, and which is only felt so long as we walk, is removed by 

 sitting down, but again produced by walking onwards ; and 

 on this account Humboldt requested us to make an experiment 

 with the air-pump, by which the sinking down of the head of 

 the thigh-bone under such circumstances might be made appa- 

 rent, and which might at the same time decide if the amount 



s£ 



