ACAPNIA 605 



this view (as the contribution by B. Aggazzotti of observa- 

 tions upon the pathological phenomena in an orang-outang 

 produced by rarefaction of the air and ameliorated by ad- 

 ministration of carbonic acid) is warmly contested, how- 

 ever, by others. 



For the rest, certain experiments conducted in Kron- 

 ecker's laboratory show how difficult it is to come to a cor- 

 rect interpretation of matters of this sort. It was proved 

 in the first place that rats and rabbits in atmospheres of 

 pure oxygen, if the pressure be distinctly diminished, be- 

 come dyspnceic even though the partial oxygen pressure be 

 relatively high. In the second place it would appear that 

 the air hunger of animals in rarefied air disappear quite 

 as well when the normal pressure conditions are produced 

 by addition of nitrogen (instead of oxygen). From which 

 it may be logically concluded that the dyspnoea occurring in 

 places where the air is rarefied is not primarily due so 

 much to oxygen deficiency as to a mechanical disturbance 

 of the pulmonary circulation. 58 



A lowering of atmospheric density corresponding to an 

 elevation of about 6000 metres (356 millimetres of mer- 

 cury) must in fact be regarded as critical, as Boycott and 

 Haldane in personal experiments observed at this grade 

 the appearance of cyanosis, dyspnoea and loss of conscious- 

 ness. 59 At this degree of atmospheric rarefaction scarcely 

 more than half the existing haemoglobin is saturated with 

 oxygen according to N. Zuntz and A. Lowy. This agrees 

 with observations made in Graham Lusk's laboratory upon 

 dogs which were rendered unconscious by half saturating 

 their blood with carbon monoxide. 60 Similar experiments 

 were performed even earlier in Zuntz 's Institute by Frankel, 

 Geppert and Lowy. Aggazotti's orang-outang became 

 apathetic at an atmospheric pressure of about 340 milli- 



68 R. Frumina, A. Rosendahl (Physiol. Instit., Berne), Zeitschr. f. Biol., 

 52, 1, 16, 1909. 



69 A. E. Boycott and J. S. Haldane, Jour, of Physiol., 37, 355, 190& 

 eo Graham Lusk, Ernahrung und Stoffwechsel, 2nd Ed., p. 239, 1910. 



