RESPIRATORY INTERCHANGE UNDER DIFFERENT CONDITIONS 521 



quickly induces a lack of oxygen in the system, commonly called 

 anoxemia. This view has found experimental proof in the work of 

 Zuntz and others, who have shown that the oxygen tension in the alveoli 

 is diminished at high altitudes. Upon Monte Rosa, for example, the 

 different members of his party showed tensions of only 37-57 mm. Hg 

 and all suffered from mountain sickness. In this connection attention 

 should briefly be called to the fact that the number of the erythrocytes 

 increases at high altitudes, but clearly , Wen this change must eventually 

 fail in its purpose for the reason that the tension of this gas finally 

 reaches so low a level that it cannot enter in sufficiently large quan- 

 tities. The hemoglobin remains below its point of saturation. As a 

 result of this scarcity of oxygen, the heart muscle weakens and even- 

 tually fails to sustain the circulation. The nervous tissue is then 

 unable to effect a proper, coordination of the muscular movements. 

 Provided, however, that a certain limit has not been exceeded, these 

 symptoms disappear in the course of time and the individual finally 

 acquires a muscular force as great as that previously shown by him 

 upon the plains. This adaptation is dependent upon the production 

 of acid substances, especially lactic acid and carbon dioxid, which 

 exert a stimulating action upon the respiratory center and augment 

 the ventilation in the lungs. 



Mosso^ has submitted a somewhat different explanation which is 

 based upon a diminution in the carbon dioxid tension of the blood, 

 constituting the condition of acapnia. The claim is made that 

 mountain sickness is associated with an excessive loss of carbon dioxid 

 in consequence of which the tissues themselves are impoverished. We 

 know, however, that acapnia may be present in individuals without 

 that the disorders just mentioned develop, and besides, this condition 

 may be absent during the most acute stage of mountain sickness. 

 It also happens at times that these symptoms appear sometime after 

 the individual has again reached the plains. These facts tend to show 

 that the real difficulty is more deeply seated and must be sought for 

 in a disorder of the tissue oxidations. 



Higher barometric pressures are encountered in submarine work, 

 such as is required during the building of tunnels and caissons. It has 

 previously been mentioned that pressures of 5 to 6 atmospheres cannot 

 be endured for any length of time without serious consequences and 

 that a pressure of 15 atmospheres brings on convulsions and. death. 

 But, since a depth of 10 m. corresponds to an increase in pressure of 

 only 1 atmosphere, the human body will rarely be called upon to endure 

 a pressure of more than 2 or 3 atmospheres. In descending to this 

 depth it is imperative to proceed slowly, and to permit the system to 

 become adapted first to intermediate degrees of pressure before the 

 chamber of greatest pressure is entered. Quite similarly, it is abso- 

 lutely necessary to proceed slowly with the decompression, because 

 any abrupt cessation of the pressure is prone to produce a complex of 

 ^ Der Mensch auf den Hochalpen, Leipzig, 1899. 



