490 Historical 



Similar symptoms, but less severe, accompany decompression. 

 They can be checked by opening the tube, either by the movements 

 of swallowing, or, and this is a more certain method, by making 

 a strong expiration with the nose and mouth closed. 



These repeated procedures result in reestablishing the per- 

 meability of the tube, the obliteration of which is a frequent cause 

 of deafness; hence come, no doubt, the improvement in this in- 

 firmity which is often observed in compressed air, and the effec- 

 tiveness of the treatment originated by Pravaz. But the question 

 is complicated by the direct effect of the compressed air upon the 

 mucous membranes, of which I shall speak presently. 



Voice. The voice is impaired in compressed air: one talks 

 through the nose, Triger says; it rises in pitch, and in this regard 

 Vivenot made an exact observation upon a well-known woman 

 singer who gained a half-tone in the apparatus. The act of whis- 

 tling becomes impossible beginning with 3 atmospheres, as Triger 

 had already noted; it even takes a certain effort to talk, according 

 to Pol and Watelle. All of this is quite evidently due to the in- 

 creased density of the air. 



Respiration. It has been very definitely determined that the 

 maximum respiratory capacity increases considerably during the 

 stay in compressed air. The diaphragm and the base of the lungs 

 drop; respiration therefore goes on in a certain constant state of 

 enlargement of the thorax. No doubt that is one of the causes of 

 the improvement in asthmatic patients, in whom pulmonary expan- 

 sion then takes place more fully. This change, which increases 

 with each of the first treatments, persists for a longer or shorter 

 time after return to open air. 



The frequency of the respiratory movements decreases con- 

 siderably; everyone agrees on that; their amplitude increases in 

 inverse proportion. But after all, a smaller volume of air under 

 pressure passes through the lungs in a given time than of ordinary 

 air. At least that seems to be the conclusion to be drawn from the 

 figures of Vivenot and Panum; but it must be said that no direct 

 experiment has been made, and that these conclusions have been 

 drawn from calculations in which one had to take into account 

 the amplitude of one or several respirations and the number of 

 respiratory movements per minute: complex calculations strewn 

 with causes of errors of a physiological order. 



As to the rhythm itself, Vivenot and Panum contradict each 

 other completely in their statements; however, the point is of little 

 importance. 



