188 AIR AND LIFE. 



of pressure, a purely mechanical element comes into play, one sees 

 that gradual variations operate, not physically nor mechanically, but 

 in a purely chemical manner, by putting the organism under the influ- 

 ence of an atmosphere too rich or too poor in oxygen. 



It must be added that in this case, as well as in many others, adapt- 

 ive phenomena occur. The Indians and animals of the South American 

 Cordilleras are unaffected by mountain sickness which attacks the 

 unaccustomed traveler, and animals of the abysses of the sea live and 

 thrive under pressures which no terrestrial or shore animal could endure. 



This fact of adaptation to altitude, which is confirmed by the other 

 fact that there are villages or cities permanently inhabited by man at 

 3,000 and 4,000 meters above sea level, has long been well known. 

 It has especially attracted the attention of a French physiologist, Dr. 

 Jourdanet, who discovered most of the facts which Paul Bert investi- 

 gated later, but the mechanism of the phenomena has been only 

 recently explained. Jourdanet supposed that the inhabitants of low 

 levels, when transferred to high levels, meeting with low pressure and 

 consequently a small proportion of oxygen, became affected by anoxy- 

 hsemia, a state characterized by the inability of the red blood cor- 

 puscles to absorb a sufficient proportion of oxygen — in brief, incipient 

 asphyxia. 



In that he was right; he also thought that adaptation is effected in 

 the following manner : If the evil is not unbearable, the system begins 

 to produce a larger supply of blood corpuscles ; these can absorb only 

 a small proportion of oxygen to be sure, but then they are more nuiner 

 ous and by this means the balance is restored, and the system may 

 absorb a sufficient quantity of oxygen. Here, again, he was right, but 

 he did not succeed in establishing his hypothesis on a firm basis. The 

 latter task was achieved by Paul Bert, who examined specimens of 

 the blood of Peruvian llamas and vicunas, and proved that the blood of 

 such of these animals, as live on the highlands contains a larger pro- 

 portion of hemoglobin and of oxygen than that of those of the same 

 species living on the plains at lower levels. For instance, 100 cubic 

 centimeters of blood of llamas or vicunas living on the highlands con- 

 tain between 19 and 21 cubic centimeters of oxygen, while the same 

 amount of blood in animals of the same species living on the lowlands 

 contains only 12 to 15 cubic centimeters. 



These results have been very" positively confirmed by the investiga- 

 tions of MM. Viault, Muntz, and Kegnard. M. Muntz has shown that 

 in common domestic rabbits allowed to go wild upon the heights of 

 the Pic du Midi, in France, the blood, after ten months' sojourn in the 

 mountain, contains much more hemoglobin than that of rabbits belong- 

 ing to the same breeds released for the same length of time in the plains 

 at Bagneres de Bigorre. But it may be objected that this experiment 

 is not as conclusive as it seems to be, owing to the fact that the rab- 

 bits of the Pic du Midi may have been surrounded there by different 



