Summary and Discussion 495 



Almost all the authors, I repeat, even the shrewdest and the 

 best qualified, even Pravaz, Bucquoy, Vivenot, etc., believe in the 

 direct and mechanical effect of the pressure. What could draw 

 such keen intellects into such an error? A very accurate observa- 

 tion, made by all observers: the pallor of the skin and the mucous 

 membranes in workmen or experimenters, and especially in 

 patients, when the mucous membrane was inflamed. In rarified 

 air, we have seen, the veins and the superficial capillaries are filled, 

 as if the blood was forced to the periphery; in compressed air, 

 these vessels are emptied, as if the blood was forced back into the 

 interior. Thence came, in the first case, the theory of the general 

 cupping-glass; in the second, that of the crushing weight; "the 

 compressed air," says M. Foley again, who frequently returns to 

 this idea with singular energy, "everywhere flattens the mucous 

 membrane which is exposed to the air" (page 375). 



The other authors are generally more prudent; they feel em- 

 barrassed by physics, which protests against their theory. Nothing 

 is more curious than the attempts of M. Bucquoy to escape from 

 this contradiction; but his theory of pressure decreasing pro- 

 gressively from the skin to the deep tissues is not tenable (page 

 459) . I also call attention to the ideas of M. Junod, G. Lange, and 

 M. Leroy de Mericourt about the supposed forcing of the blood into 

 the brain, due to the fact that since it is protected by the cranial 

 case, the brain cannot be compressed directly like the rest of the 

 body; these authors have forgotten that the pressure is applied 

 instantaneously to the spinal cord and the brain by other paths 

 than the blood vessels, so that there is equality of pressure in this 

 organ as there is elsewhere, and the circulation of the blood in it 

 cannot be changed at all. 



But even if we can understand that the complexity of the con- 

 ditions presented by the human body, considered as a whole, has 

 drawn distinguished intellects into such astonishing physical errors, 

 we can hardly explain why, when the question was reduced to its 

 simplest terms, they did not immediately recognize what a mistake 

 they were making. And yet we have seen Vivenot, with the aim 

 of explaining the changes which a stay in compressed air causes 

 in the form of the pulse, carry out the strange experiment reported 

 above (page 474), and maintain that a pressure of a third of an 

 atmosphere is enough to change the volume and the elastic reaction 

 of a rubber ball filled with water. 



I was curious enough to repeat this experiment, not to enlighten 

 myself in regard to it, but to learn what could have given Vivenot 



