Chapter IV 

 SUMMARY AND CRITICAL COMMENTS 



I shall now summarize, as I did for decreased pressure, first the 

 physiological symptoms brought on by the use of compressed air 

 and the more or less serious conditions which have often followed 

 it, and finally the theories which the authors have advanced to 

 explain all these phenomena. 



1. Physiological effect of compressed air. 



It appears very clearly from the data given in Chapter I that 

 the phenomena which are to be reported here are divided into two 

 categories very different in their origin, and which we should, for 

 fear of confusion, separate in the exposition, although the distinc- 

 tion has not always been made by the authors. Some, in fact, 

 appear even during the compression, and are the result of the stay 

 in compressed air; others occur only at the time of return to normal 

 pressure; they are the result of the decompression, and their in- 

 tensity is in proportion to the speed of the decompression and 

 the degree of the compression. This differentiation, which was first 

 suggested in a rather vague manner by Pol and Watelle, will 

 govern our summary. 



A. Phenomena Due to Compression. 



Pains in the ears. Pains in the ears have been noted by all 

 observers during the process of compression as well as during the 

 decompression. All have given the exact explanation of them; they 

 have shown that since the Eustachian tube, obstructed for different 

 reasons, does not permit the compressed air to enter the tympanic 

 cavity, the tympanic membrane is pushed back and distended, 

 causing pains which may be unendurable. Sometimes it is even 

 ruptured, as happened to M. Cezanne, at the bridge of Sgedezin. 



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