INFLUENCE OF ATMOSPHERIC PRESSURE 235 



equally applied to every part of the outer surface of the body and 

 in the lungs, and that the fluids of the body transmit the pressure 

 equally and instantly to all parts, so that the mechanical effect 

 is nil. How little protoplasm is affected by fluid pressure is 

 shown by the existence of abundant life in the abysm of the 

 ocean, where at a depth of 2000 metres the pressure of the water 

 equals 200 atmospheres. 



The neglect of a simple physical law is the less excusable 

 seeing that Poisseuille in 1835 observed the capillary circulation 



7 



FIG. 11. Air Bubbles set free in Vessels of Heart after rapid 

 Decompression (v . Schrotter). 



in frogs enclosed in a strong glass chamber and submitted to 

 3-9 atm. pressure. The compression had no influence on the 

 circulation. The body of a workman exposed to compressed air 

 supports at +1 atm. an additional 15,000 to 20,000 kilograms. 

 If it were not for the incompressibility of fluids, and the equal 

 and instant distribution of the pressure to all parts of the body, 

 life would be impossible under any variations of atmospheric 

 pressure. 



The only mechanical compressions which can occur on ex- 

 posure to compressed air are the compression of the air in the 

 middle ear, producing tension of the membrana tympani, noises in 

 the ear and pain, if the Eustachian tube is blocked up by a cold, 



