Title II 

 INCREASED PRESSURE 



Nature offers no conditions where man and air-breathing living 

 beings are subjected to the effect of a pressure greater than that 

 exerted by the atmosphere at sea level. 1 Only aquatic animals and 

 plants endure pressures which may, in the depths of the ocean, 

 be reckoned in hundreds of atmospheres. 



The quest for minerals, especially coal, has compelled many 

 laborers to live at depths where the normal pressure of 760 mm. 

 is increased by several centimeters of mercury. But the effect of 

 this slight modification has never attracted the attention of 

 observers, lost as it is, admitting that it is of some importance, in 

 thd host of peculiar and unfavorable conditions under which 

 miners live (dampness, darkness, confinement, deleterious gases, 

 dusts, etc.) 



But since the sixteenth century, the progress of industry has 

 caused men to work under pressures beyond four atmospheres. 

 Diving bells, diving suits, and the caissons with compressed air 

 invented by M. Triger have placed thousands of workmen in this 

 modified medium. Serious symptoms have appeared, the number 

 of which has terrified engineers and physicians. 



However, the latter, struck by the strange and often favorable 

 changes which a stay in compressed air causes in certain patho- 

 logical conditions, had the idea of regulating the use of this new 

 therapeutic agent. Apparatuses have been installed, which have 

 been of service in making interesting physiological observations 

 and useful medical applications. 



In the following chapters, I shall report the data observed 

 under the circumstances which I have just mentioned. A consider- 

 able difference will be noted among them, if they are considered 

 as a whole. Divers and laborers in caissons are subjected to 



353 



