ADVANCED DEMONSTRATIONS 



401 



objective. The pressure is increased to 20-50 atmospheres. The cir- 

 culation continues unaffected, for the pressure is equally transmitted 

 throughout the fluids of the body. After ten minutes the chamber is 

 decompressed. Emboli, formed of gas bubbles, soon appear in the 

 capillaries, and the circulation ceases. Such gas emboli are the cause 

 of the symptoms (paralysis, etc.) observed in caisson workers and divers. 



FIG. 260. Receiver used with Geryk 

 pump in demonstrating the influence of 

 lowering the atmospheric pressure on 

 animals. The apparatus may also be 

 used as a drying chamber. 



FIG. 261. Hill's apparatus for studying effects of in- 

 creased atmospheric pressure. Thick glass discs, provided 

 with leather washers, close the ends of the chamber. 



The workers are affected on or after decompression. Four atmo- 

 spheres is the limit of safety. Every 10 metres in depth of water 

 roughly equals one atmosphere. Re-compression and slow decom- 

 pression is the rational cure for the symptoms when they appear. 

 Compressed oxygen is also per se a poison. It lowers metabolism, 

 diminishing the output of C0 2 and the body temperature. This can be 

 observed in mice placed in a high-pressure chamber. The oxygen is 

 allowed to leak from the chamber through the Haldane-Pembrey absorp- 

 tion tubes. A mouse is affected with dyspnoaa in 10 atmospheres of 

 2 , and soon dies. In 50 atmospheres it is instantly killed. 



2c 



