ATMOSPHERIC PRESSURE AND LIFE. 319 



must result insufficient respiration, or, more accurately sjjeaking, in- 

 sufficient absorption of oxygen." " The quickening of the respiration, 

 which tends to offset the evil, is insufficient," says Martins, " for it 

 would have to be twice as frequent, and have double amplitude, in 

 order to compensate the diminution in the quantity of air inspired." 

 Finally, Dr. Jourdanet adds that, " the pressure being reduced, tlie 

 oxygen must be dissolved in the blood in a less proportion : " hence a 

 pathological state analogous to anjemia, and which he calls anoxy- 

 hoemia. 



These ideas have been met with many objections. In reply to De 

 Saussure it was said that the atmosphere, even at half-pressure, con- 

 tains a great deal more oxygen than is needed for respiration ; and in 

 reply to Jourdanet that, according to the researches of Fernet, oxy- 

 gen in the blood being in the state of combination, and not of solu- 

 tion, its quantity does not depend on barometric pressure. 



My own experiments show that De Saussure and Jourdanet are 

 right. They further prove the sagacity of Jourdanet in recognizing 

 in the inhabitants of the Anahuac plateau the injurious influence of 

 low pressure which, thougli not perceptible in the state of health, re- 

 veals itself on the slightest attack of disease. I need not detail here 

 the long series of experiments which have led me to conclude that 

 the symptoms following diminished pressure, whether slowly or rapid- 

 ly applied, are simply the result of a diminution of the oxygen in the 

 blood ; in a word, that they are nothing but a sort of asphyxia in the 

 midst of the " pure and invigorating mountain-air." 



Still I may repeat here an experiment which can be performed 

 wherever we have a pneumatic apparatus; this experiment clearly 

 proves that the lessening of the barometric pressure is of no account, 

 mechanically, in the production of the phenomena. These are the re- 

 sult rather of chemico-physical action, the blood not being sufficiently 

 charged with oxygen. 



We place a sparrow in the pneumatic bell-glass A (Fig. 1), which 

 communicates with the manometric tube C E, The pressure is gradu.- 

 ally lessened by means of the tube B. WJien the manometer shows 

 only 30 centimetres' pressure in the bell-glass, the bird gives pretty 

 serious evidence of suflfering ; at 20 centimetres it totters, reels, and 

 falls upon its side ; at 18 centimetres it struggles violently, and would 

 die in a few seconds, were I to leave it in this situation. So I quickly 

 place at a an indicator, to show the height attained by the mercurial 

 column, and, opening the cock Z>, I introduce into the bell-glass not 

 air, but oxygen from the India-rubber bag 0. At once the bird be- 

 comes himself again. I let it breathe a little while, and again I 

 diminish the pressure as before. But now we reach 30 centimetres, 

 25 centimetres, without difficulty ; not till we reach 20 centimetres 

 does the bird appear to show some little signs of discomfort; Ave 

 reach 13 centimetres, a', a pressure much less than before, and yet the 



