98 CONTEMPORARY SCIENCE 



mountain sickness from the conditions resulting from 

 work in compressed air so-called caisson disease. It is 

 clear that it is from the former, and not at all from the 

 latter, that aviators suffer; but, as the two disorders are 

 sometimes confused, a few words regarding the latter 

 are in place here. 



Caisson disease known also as the "bends," "diver's 

 palsy," and by other names depends upon the fact that, 

 under the high pressure necessary for diving, tunneling, 

 and other work below water, the nitrogen of the air dis- 

 solves in the blood and in the other fluids and tissues of 

 the body in amounts proportional to the pressure. This 

 in itself does no harm, and has in fact no effect upon the 

 body, until the subject comes out of the pressure lock 

 or caisson, or rises from the depth of the sea where he has 

 been working. Then the nitrogen which has been dis- 

 solved begins to diffuse out of the body. This also does 

 no harm and has no effect unless the pressure under 

 which the man has been working is so high, and the low- 

 ering of the external pressure is so rapid, that the dis- 

 solved nitrogen separates in the form of bubbles. Such 

 bubbles may form in the blood, in the synovial fluid of 

 the joints, and even in the brain. They induce intense 

 pain, and even paralysis and death. In order that bub- 

 bles may be formed it is essential, however, that the 

 pressure with which the tissues are in equilibrium should 

 have been lowered considerably more than half its abso- 

 lute amount in a few seconds. 



In the present state of the art of flying it is scarcely 

 possible for an aviator to rise to a height of more than 

 20,000 feet, where the barometer would be less than half 

 of that at sea level, in a period sufficiently short to allow 

 bubbles of nitrogen to form in this way. The disorders 

 from which aviators suffer are, therefore, of a different 

 class from those to which workers in compressed air are 

 exposed. 



When the study of the effects of lowered barometric 



