616 Professor Joseph Barcroft [June 9, 



must always succumb. We were naturally somewhat interested in 

 the question of whether we could foretell which of our own party 

 would succumb most quickly, and various members of the party 

 worked out systems of prophecy which differed not only in character 

 but in the prophetic order in which the various individuals would 

 prove susceptible to altitude. One of these proved quite successful. 

 It was based on the determination of Bohr's diffusion constant (the 

 ratio of the quantity of oxygen absorbed per minute to the average 

 difference of pressure between the oxygen in the alveolar spaces and 

 alveolar capillaries) for the lung, and was suggested by Prof. Krogh. 

 The members of the expedition could be divided into two distinct 

 groups — those who had a constant for oxygen of more than 40 and 

 those who had a constant less than that figure. One group with 

 the higher diffusion constant suffered from obvious symptoms of 

 mountain sickness, while the other did not. It is true that of the 

 four who suffered the salient feature was different in each case ; in 

 one it was faintness, in another vomiting, in a third high temperature 

 and intense headache, and in the fourth deafness and indistinct 

 vision. Only further research can show whether the coincidence was 

 fortuitous, or whether any causal relation exists between the diffusion 

 constant and the tendency to " seroche." The hint, however, seemed 

 to be worth taking, and in consequence an arrangement has been 

 come to by which persons intending to go to the mining districts in 

 the Andes are being tested in the Rockefeller Institute in New York. 

 I must also make some allusion to the goodwill which was 

 extended to us by everyone with whom we came in contact in Peru, 

 from the President down to the humblest employee of the Cerro de 

 Pasco Copper Corporation. Of the manager and the officials of this 

 company we can only say that their kindness in placing themselves 

 and their resources at our disposal was one of the most potent factors 

 in enabling us to achieve such scientific results as we obtained. No 

 less can be said of the officials of the Pacific Steam Navigation 

 Company. 



The problem of Everest from the point of view of physiology, 

 upon which our work in the Andes throws some light, may be stated 

 thus : — 



Every cubic centimetre of arterial blood which leaves the lung 

 must contain a certain quantity of oxygen, expressed as a percentage 

 of the maximum which the blood can hold, if life is to be maintained 

 at a level consistent with any degree of efficiency. It is not known 

 what this quantity of oxygen may be. The following considerations, 

 however, give some clue to it : — 



(a) Let the maximum quantity of oxygen (shown on the ordinate 

 of the graph in Fig. 1) which the blood can hold be called 100. 



(b) There is a certain relation in the blood for normal persons 

 between the amount of oxygen it can hold and the pressure of oxygen 

 to which it is exposed ; that relation is shown in the graph labelled 



