14 Cincinnati Society of Natural History. 



There are modifications of this, which have more or less rela- 

 tion to personal comfort or health. Altitude modifies it in 

 some regularity of proportion to ascent above sea-level. The 

 effect of sudden change from low to high levels has often been 

 experienced and described b}- those who have made balloon 

 ascents. These voyages, wdien undertaken for scientific 

 purposes, have been to such extreme heights as to afford no 

 basis proper for experiences that would be applicable to the 

 residents of low levels, or even the ordinarj^ high ones. The 

 time consumed in the change is the very important condition 

 of such experiments. As a consetjuence, there is no vigor of 

 constitution or elasticity of adjustment of the organs of cir- 

 culation and respiration that will prevent asphyxia or heart 

 failure when the change is very rapid, or to very high levels. 

 The late Paul Bert, an eminent member of the French 

 Academy, has given us the most scientific treatise on barome- 

 tric pressure, has investigated experimentally the results on 

 animals and vegetables. He proved, by many experiments, 

 that seeds and plants germinated and grew more slowly under 

 diminished pressures, and endeavored to determine to what 

 this was due, the rarified air as a ph^^sical condition or the 

 diminished oxygen as a vital one. His conclusion is that the 

 diminished amount of oxygen is the true cause. He says : 

 "I am entirely authorized to draw, from all of the facts, the 

 conclusion that, at low barometric pressures, an animal con- 

 sumes, in a given time, a notabh- less (quantity of oxygen and 

 produces a notably less quantity of car])onic acid than at 

 normal pressure," and farther, " that it remains proved that 

 at low pressures the diminished activity of chemical phe- 

 nomena bears not only upon those which result in the produc- 

 tion of carbonic acid, l)Ut that the whole series of intra- 

 organic oxidations is diminished when the air is sufficiently 

 expanded." 



Where change of altitude is made slowly and with as little 

 fatigue as possible, tolerance becomes established without 

 danger, and the acclimatizing process is facilitated. It is the 

 uniform advice of physicians to patients going to high alti- 

 tudes, not to go abruptly, but by easy stages. 



The exjieriments of Paul l^ert furnish the scientific justifi- 

 cation of such advice. It often ha])pens that in our weather 



