INFLUENCE OF VARIOUS CONDITIONS ON RESPIRATION, 705 



ments to show that there is a diminution in the carbon dioxid 

 contents of the blood (a condition of acapnia), and it is to this, 

 rather than to the anoxemia, that he would attribute the physio- 

 logical results of low barometric pressures. The balance of evi- 

 dence, however, indicates that the chief factor in the production 

 of mountain sickness is deficiency in oxygen, particularly when 

 the oxygen need of the body is increased, as, for example, in mus- 

 cular exercise. The means by which the body seeks to adjust itself 

 to this deficiency in oxygen have been referred to in previous 

 paragraphs (p. 703). The important reactions are an increase in 

 heart-rate, an increase in the depth of respirations, and an increase 

 in the number of red corpuscles and the amount of hemoglobin. 

 At very high altitudes the supply of oxygen for the body exhibits 

 only a small margin of safety, and we may suppose that relatively 

 little muscular exercise, with its attendant increase in oxygen 

 consumption, will suffice to deplete the supply to such an extent 

 as to affect the brain centers. The historical incident of the death 

 of Sivel and Croce-Spinelli at an altitude of 8600 meters (baro- 

 metric pressure, 262 mms.; oxygen pressure, 52.4 mms.) gives an 

 impressive instance of the physiological effects of very high altitudes. 



The incidents connected with the ascent in the balloon Zenith of Sivel, 

 Croce-SpineUi, and Tissandier, April 15, 1875, are described in detail by the 

 last named in "La Nature," 1875, p. 337, also in Bert's "La pression baro- 

 metrique," p. 1061. Only Tissandier survived. The balloonists were pro- 

 vided with bags containing oxygen (72 percent.), but they were unable to 

 make satisfactory use of them since shortly after passing 7500 meters they be- 

 came so weak that the effort to raise the arm to seize the oxygen tube was 

 impossible. Tissandier's graphic description relates that at 8000 meters 

 it was impossible for him to speak, and that shortly afterward he became 

 entirely imconscious. None of the three seems to have shown any signs of 

 violent dyspnea. It is noteworthy, however, that the heart-beats were very 

 rapid, and that they experienced at first great depression of muscular strength 

 without loss of consciousness. The onset of complete unconsciousness was 

 sudden, but was preceded by feelings of sleepiness, which, however, were not 

 associated with any distress. 



The Respiratory Quotient and its Variations.^ — In studying 

 the gaseous exchanges of respiration one may determine the varia- 

 tions in the oxygen absorbed under different conditions or in the 

 carbon dioxid eliminated, or finally in the ratio of one to the other, 

 -~, which is known as the respiratory quotient. In short-lasting 



experiments the respiratory quotient is not a very reliable indicator 

 of the extent or character of the physiological oxidations in the body, 

 since any alteration in the depth or rapidity of the respiratory 

 movements may, by changing the ventilation of the alveoU, make 

 a difference in the output of COj, — a difference, however, which 

 would have no significance in regard to the nutritive changes of the 

 body. In longer experiments and in those during w^hich the respira- 

 tory movements aie not altered the determination of this ratio 



45 



