RESPIRATION 295 



It has long been known that compressed air has its 

 dangers. Only slight disturbances are experienced on 

 being introduced into it, but serious or even fatal effects 

 may follow emergence from it. The symptoms range 

 all the way from dizziness and muscular pain to apo- 

 plectic death. Experience has shown that the workmen 

 must spend some time in atmospheres of intermediate 

 pressures when coming out of deep workings. Technic- 

 ally speaking, they must be decompressed by stages. 

 The various troubles manifested in cases of too rapid 

 decompression are spoken of collectively as caisson- 

 sickness, divers' palsy, or compressed-air illness. 



The earlier theories advanced to account for these 

 difficulties were elaborate and confusing. The actual 

 basis of caisson-sickness has been found to be exceedingly 

 simple. What happens in the tissues of a man who 

 comes too hastily into the open after a stay in compressed 

 air is just what happens when a bottle of charged water 

 is uncorked; there is a formation of bubbles, an efferves- 

 cence. During the previous period both oxygen and 

 nitrogen have been absorbed in unusual amounts, first 

 by the blood and secondarily by the tissues. It is the 

 nitrogen in this case which threatens damage by separat- 

 ing itself in the form of minute bubbles when the pressure 

 that held it in solution is removed. One can under- 

 stand how the most varied effects may follow the 

 development of bubbles in one place or another. 



Nitrogen bubbles forming in the nervous system 

 may so disorganize its structure as to work a mortal 

 injury, perhaps by playing havoc with the respiratory 

 center. Their presence in muscles and joints may result 

 in nothing more serious than pain and stiffness. The 

 conditions will be slow to pass off for the cells of the 

 body have little affinity for nitrogen and, in fact, it is 

 hard to account for its final disappearance. A certain 

 rigidity of the joints is so often experienced that it has 

 given to caisson-sickness the colloquial name of "the 

 bends" commonly applied to it by workmen. 



