344 Historical 



have been cut away. According to M. Jourdanet, the pressure 

 thus exerted would be equivalent to about 23 kilograms. We have 

 seen how this author proved, by calculations based on the surface 

 of the cotyloid cavity, that at the time when the weariness of the 

 lower limb appears, the atmospheric pressure is still capable of 

 supporting a weight double that of this member (page 257) . 



Dr. Faraboeuf, at my request, consented to make precise meas- 

 urements upon a human cadaver. Here are the results which he 

 gave me: 



Man of forty-eight years, weighing 52.5 kilograms; height 1.65 



meters, 0.85 meters in the lower limb; well proportioned, thin, but 



still apparently muscular. 



Diameter of the cotyloid cavity 51.5 mm. 



Surface 20.8 sq. cm. 



Weight of the atmosphere on this surface 21.4 k. 



Weight of the lower limb disarticulated 



in the fold of the buttock and the groin 6.3 k. 



Weight of the lower limb deprived of the muscles 



which are inserted into the pelvis 5. k. 



So the atmospheric pressure is capable by itself of supporting 

 a weight four times greater than that of the lower limb deprived 

 of the muscles which support themselves by their connection to 

 the pelvis. We should therefore have to go to a fourth of an at- 

 mosphere, that is, a pressure of 19 cm. to cancel the support fur- 

 nished by the weight of the air. Evidently then the cause sug- 

 gested by von Humboldt has no connection with the fatigue which 

 appears on Mont Blanc at a pressure of 41 cm., at which point the 

 atmosphere still represents 11.5 kilograms. 



Very certainly the effect of the pressure upon the firmness of 

 the articulations has been exaggerated; setting aside this exaggera- 

 tion, von Humboldt has not drawn the really logical conclusion 

 from the principle which he thought correct. It is not a greater 

 muscular fatigue which should occur, and it should not be limited 

 to the muscles of the thigh; the danger for the traveller in regions 

 where the atmospheric pressure is lessened is dislocations, and in 

 all the articulations; but in spite of the unusual exertions which 

 ascents entail, no such symptom has ever been noted. 



Other mechanical effects of decreased pressure. Borelli at- 

 tributed the fatigue to the presence in the thorax of expanded air 

 which "no longer aids," he says, "the effort of the muscles, com- 

 pressing by its elasticity the air and blood vessels." It is not easy 

 to see clearly what the learned physician-mathematician meant. 

 But there is some truth in what we may suppose to have been his 

 thought. If, in the phenomenon of effort, the chest walls, as M. J. 



