Theories and Experiments 271 



Let us add that farther on M. Foley declares that nausea, 

 cramps, etc., are the sign of "insufficient hematosis". 



In his opinion, it is the presence of the air sacs which saves 

 the bird from the symptoms of decompression; the shocks* with 

 which he would be threatened on his return as workmen are when 

 they leave the caissons (see later, Title II, Chapter III) are spared 

 him because of the elastic tension of the gases contained in the 

 sacs. For that, the bird that is mounting needs only to close 

 its beak and its nostrils; but perhaps we may be permitted to 

 ask how it can breathe then. 



A distinguished veterinarian, M. Liguistin, 110 who was in com- 

 mand of this service during the Mexican expedition, found himself 

 confronted with the same problems as the military physicians. He 

 seems not to have known of the heated discussion the principal 

 points of which we have just summarized: 



"In his opinion, moreover, the effect of the decrease in the density 

 of the air is very well known." (Vol. Ill, p. 583.) 



As to symptoms observed in animals, he states that the respira- 

 tory disturbances noted by doctors seem not to have attacked 

 beasts of burden: 



Would the large solipeds bear more easily than men the effect of 

 an air with low oxygen content? Would the lymphatic temperament 

 with which they are endowed explain sufficiently the less urgent need 

 of a denser air? However we know very well, and have already said 

 so, that the atmospheric pressure most favorable to animals Is also 

 that found at sea level and in places of moderate elevation, where 

 the mercury column registers about 76 centimeters on the barometer; 

 that, if we place a living animal in a vacuum, the air within it, no 

 longer meeting any resistance, expands, the animal is distended and 

 dies; that it is the air pressure which keeps the fluids in the vessels 

 of animals and prevents them from escaping. Therefore, when the 

 barometer drops a few degrees, the blood must evidently flow towards 

 the periphery; then we observe difficulty and acceleration of respira- 

 tion, slackening of the circulation, weariness, prostration, and lack 

 of interest. If in this situation our animals were endowed with the 

 power of speech, they would probably tell us, as men do, that the 

 weather is heavy, thus taking the effect for the cause, for we know 

 that the rarer the air is, the lighter it is. It is unnecessary to explain 

 why the respiration is more hasty. We know well enough that, since 

 the air necessary for life is extremely rare, the respiratory acts must 

 be more frequent to produce the same result. It is still more unnec- 

 essary to add that when the air becomes rarer, one might die of 

 asphyxia. In a rarified air, thoracic inflammations and hemorrhages 

 must necessarily prevail. And yet we have not observed this, and 

 that is why we think that we are authorized to assert that the reduced 

 atmospheric pressure on the lofty plateaux of Mexico does not have 



