Chapter Xlll 



Therefore, of the two methods I have the greater reliance on the 

 spectroscopic one. So I am forced at present to think that during 

 the exercise taken by Hartridge, with or without partial CO-poisoning, 

 there was no secretion. But perhaps I may take the reader into my 

 confidence so far as to say that I wish it were otherwise. 



But while it seems to me fairly certain that there was no secretion 

 in Hartridge's case, there is one possible line along which Hartridge's 

 results might perhaps be brought into harmony with those of Haldane 

 and Douglas. It has been shown that the call for oxygen follows 

 upon the activity. The exercise taken by Hartridge was of a violent 

 but spasmodic type, that of Haldaue and Douglas was less violent and 

 more sustained. It is not an impossible supposition that the secre- 

 tion might show some lag after the exercise, and therefore be most 

 evident in the case of sustained work. 



Lastly, apart from questions of the detail of individual experi- 

 ments there are certain general questions that cannot be overlooked 

 by the holder of the diffusion theory. Before this theory can be 

 regarded as proved on the positive side it must be tested under the 

 circumstances which are likely to strain it most. Two questions it 

 must answer. The first is, can it account for the passage of 3500 c.c. of 

 oxygen per minute through the pulmonary epithelium ? Perhaps it will 

 be able to do so one day, at present it cannot. At the end of the last 

 chapter I spoke of the diffusion coefficient, here I will only say that 

 the more recent determinations of the diffusion coefficient must be 

 materially changed before they will admit of 3500 c.c. of oxygen 

 traversing the lung along a pressure gradient dropping from 100 mm. 

 of mercury in the lung to 50 mm. in the blood. But if the test 

 of exercise is exacting that of exercise at high altitudes is more 

 exacting. I have granted a 50 mm. gradient and incidentally assumed 

 that the blood in the pulmonary artery is 80 / saturated with 

 oxygen. But what if the whole alveolar pressure is but 30 mm. 

 (approximately that which must have obtained in the case of the 

 Duke of Abruzzi 18 ' and his party at 24,000 feet altitude). The 

 work of recent observers on the dissociation curve shows that if the 

 blood were in equilibrium with such a gas it would only be 50 / 

 saturated* with oxygen. What then are we to allow for a gradient? 



* The fact that the dissociation curve of man at rest scarcely changes at high 

 altitudes is treated in Chapter XVII. During activity it becomes meionectic, and 

 that this renders the position even more difficult on the diffusion theory is shown in 

 Chapter XVIII. When Roberts and I arrived at the Capanna Margherita our bloods 

 would have been about 30 / saturated at 25 mm. O 2 pressure. 



