RESPIRATION 343 



completely realized the conditions. Slow and uniform decompres- 

 sion was, and still is, also enjoined by various government regu- 

 lationSj etc., in different countries, but with only very moderate 

 success; and deaths or paralyses from caisson disease remained 

 common if the extra pressure used was above about 1.5 atmos- 

 pheres. Workers in compressed air had soon discovered that the 

 pain of ''bends" can be relieved at once by returning into the com- 

 pressed air; and this became quite intelligible from Paul Bert's 

 experiment. He made some experiments on the curative effects 

 of recompression, but here again he was not very successful, as 

 he applied the remedy only in extreme cases. Medical recompres- 

 sion chambers for the treatment of compressed air illness were 

 first introduced by Sir Ernest Moir in connection with the con- 

 struction of the first East River tunnel at New York, and the 

 Blackwall Tunnel under the Thames, about 1890. They proved 

 strikingly successful when applied to the cases which occurred 

 with the comparatively slow decompression in the air lock. Pa- 

 ralyses and "bends" were relieved at once, even when they had 

 occurred a considerable time after leaving the tunnel. The pro- 

 vision of medical recompression chambers has now become a 

 necessary adjunct of all considerable engineering undertakings 

 at pressures of over about 1.5 atmospheres, and in extensive deep 

 diving operations. Figures 84 and 85 show one of the recompres- 

 sion chambers used in the British Navy. The trouble, however, 

 about the use of recompression chambers is that it is often very 

 difficult to get the patient out without the symptoms recurring. 

 The decompression may require many hours, or even days in bad 

 cases. 



Paul Bert also tried another method of treatment — that of 

 administering pure oxygen to his animals. This must hasten the 

 diffusion outwards of nitrogen, while the oxygen itself is ab- 

 sorbed by the tissues. At first sight it might seem as if this plan 

 ought to be very successful, either in treatment or in the pre- 

 vention of bubble formation during decompression. The results, 

 however, were disappointing and from causes which will be made 

 evident below. There seems, however, to be some scope for oxy- 

 gen administration where there is great difficulty in getting a 

 patient out of a medical air lock, and where there is no fear of 

 oxygen poisoning — a condition which will be discussed presently. 



When the Admiralty Committee had dealt with the troubles 

 traced to CO2, it was faced by the dangers of caisson disease, 

 which of course became much more important after it had been 



