342 Historical 



liquids and solids. If there is decreased pressure on the surface 

 of the skin, on the outer wall of the blood vessels, the decrease is 

 absolutely equal on their inner wall, and there is no change in 

 the state of equilibrium. 



It is really strange that anyone could have thought seriously 

 that by going to Cauterets he would be relieved of 2744 kilograms 

 (page 276), and that Gay-Lussac should have felt 10,000 kilograms 

 removed from his shoulders in a few minutes. If the liquids of 

 the organism were really thus held by the outer pressure, a few 

 centimeters decrease in pressure would produce the most terrible 

 disturbances. It is the comparison with the cupping-glass which 

 has caused the error: they forgot that in the cupping-glass it is 

 the effect of the pressure on the rest of the body which causes 

 the swelling, the congestion, and the local hemorrhages. 



Escape of the gases of the blood. The physicists, most of whom 

 escaped the erroneous hypothesis which we have just discussed, 

 were better inspired when they gave an important role to the 

 escape of the gases of the blood, as an effect of the diminished 

 pressure. Robert Boyle had been the first (page 201) to see that 

 all the liquids of the body, blood, urine, bile, humors of the eye, 

 release bubbles of gas, when they are placed in the vacuum. From 

 it he drew the conclusion that in animals which die under these 

 conditions, death may be, "besides the failure of respiration," the 

 result of the formation of these bubbles, which "check or disturb 

 the circulation in a thousand ways." He even thought that, at 

 the time of slight variations of the barometer, it is "the spirituous 

 or airy particles which, held in abundance in the blood as a whole, 

 naturally expand the liquid, thus being able to distend the large 

 vessels and change considerably the speed of the circulation of 

 the blood in the capillaries and the veins." 



Borelli had the same idea and attributed to a sort of effer- 

 vescence of the blood the symptoms which he had experienced on 

 Mount Etna (page 207) ; but he soon gave up this idea (page 208) , 

 to which, however, there rallied Musschenbroeck (page 198), 

 author of a dissertation De aeris existentia in omnibus animalium 

 humoribus, Veratti (page 204), Rostan (page 225), F. Hoppe, who 

 made experiments upon animals to verify it (page 248), Guilbert 

 (page 254) , and finally Gavarret (page 279) . 



The escape or the tendency to escape of the gases of the blood 

 has been used especially to explain the circulatory acceleration 

 and the hemorrhages. "When the outer pressure diminishes," says 

 M. Gavarret, "these gases tend to escape from the blood, force the 

 walls of the vessels from within outward and distend the pul- 



