no WHITNEY: 



pheres. On the work of the Brooklyn Bridge, the pressure 

 exceeded -\- 36 pounds to the inch, and on much of the sub- 

 aqueous tunnel system of New York it has ranged from three 

 to four atmospheres. The time during which men can be 

 safely subjected to such pressure is very limited. 

 Air being a gas composed as follows : 



Nitrogen Oxygen Argon 



By Weight, 75.5 percent. 23.2 per cent. 1.3 percent. 

 By Volume, 78.06 " 21.0 " .94 " 



and the rate of respiration being little if at all changed in 

 compressed air, it is evident that the lungs take in three to 

 four times the normal amount of nitrogen, oxygen and argon, 

 and we have as a result a peculiar and little understood dis- 

 ease, known as "caisson disease," or more commonly, "the 

 bends." Many men are subjected daily to compressed air 

 and enjoy entire immunity for months, or years ; others expe- 

 rience it whenever subjected to pressure for any length of 

 time, while the majority of workers have it slightly at consid- 

 erable intervals of time. 



It is caused largely by emerging too rapidly from com- 

 pressed into normal air. The attack usually begins a few 

 hours after coming out, though there are many cases in which 

 it comes on almost at the moment when all pressure is removed. 



The symptoms are confined almost entirely to the ner\'ous 

 system, beginning with neuralgic pains in the knees and arms 

 in mild cases, and in the trunk in severe ones. In the latter 

 case, paralysis of the motor nerves is likely to follow if the 

 patient is not promptly treated. The most efficacious method 

 of relief is to at once put the subject in air of about the same 

 pressure as that from which he has emerged, and then with- 

 draw the pressure at the rate of about one atmosphere per 

 hour. For this treatment an iron room is provided, furnished 

 with sofas, electric light, clock and pressure gauges. The 

 door closes upon a rubber gasket, and a thick bull's eye of 

 glass serves as a window. This room is connected with the 



