482 Historical 



Compressed air over open air (0.197% instead of 0.147%, for ex- 

 ample) . 



G. Liebig also takes up the explanation of the changes in the 

 rhythmic phenomena Of respiration. 



In regard to the increase of pulmonary volume, he expresses 

 himself as follows: 



The barometric pressure acts at the same time upon the surface 

 of the body and that of the lungs. As it rises, it opposes more vigor- 

 ously the elasticity of the pulmonary tissue; this elasticity, which is 

 equal to 35 mm. of mercury, corresponds to 1/24 of the pressure 720 

 mm. (average pressure of Reichenhall), but is only 1/34 of 1030 mm. 

 (pressure of the apparatus) ; so that in compressed air the contraction 

 of the inspiratory muscles has less resistance to overcome. The dia- 

 phragm is also assisted in its action by the decrease in volume of the 

 intestinal gases. The inspiration is therefore easier and stronger; for 

 the same reasons the expiration is slightly delayed, so that one cannot 

 breathe as quickly in compressed air as at ordinary pressure. The 

 lungs also collapse less, so that their volume is greater in a state of 

 repose. (P. 16.) 



As for the increased capacity of the chest, which persists after 

 the treatments are over, like G. Lange, he considers that to be the 

 result of the helpful exercise undergone by the inspiratory muscles 

 because of the new position of the thoracic cage in compressed air. 



The authors still left to be mentioned were particularly inter- 

 ested in the symptoms of decompression. 



M. Gavarret, 32 in the article which we have already quoted 

 (page 274), also discusses the symptoms affecting workmen: 



The return to open air often produces buccal and nasal hemor- 

 rhages, which generally are not accompanied by any pain. In our 

 opinion, these discharges of blood are the result of ruptures of capil- 

 laries caused by the tension of the gas with which the blood is super- 

 saturated. 



The changes caused in the cutaneous circulation at the time of the 

 decompression seem to us sufficient to explain these symptoms. The 

 blood, supersaturated with free gases at high tension, flows into the 

 capillaries, distends them, twitches the innumerable nerve net- 

 works which surround them, and causes, depending upon the speed 

 and the intensity of the vascular congestion, sometimes a simple 

 sensation of heat, sometimes real pains. (P. 156.) 



M. Leroy de Mericourt, 33 after describing the paralyses which 

 attack divers using the diving suit, explains them by saying: 



We think that we may state that in these cases a lesion of the 

 spinal cord is produced, and that this lesion must have been a hemor- 

 rhage. According to the seat and the severity of this hemorrhage, death 



