156 SECTIONAL ADDRESSES* 



headaches continued at intervals for some time, and lasted certainly for some 

 months after the accident; indeed, I cannot say that they have disappeared 

 altogether. 



To sum up, then, what may be said of the permanent damage caused 

 by acute anoxaemia, it seems to me to be as follows : No degree of 

 anoxaemia which produces a less effect than that of complete uncon- 

 sciousness leaves anything more than the most transient effects ; if the 

 anoxaemia be pushed to the point at which the subject is within a 

 measurable distance of death, the results may take days or weeks to get 

 over, but only in the case of elderly or unsound persons is the machine 

 wrecked beyond repair. 



Chronic AnoxcBViia. 



And now to pass to the consideration of what I may call chronic 

 anoxaemia; that is to say, oxygen want which perhaps is not very great 

 in amount — and I shall have to say something later about the measure- 

 ment of anoxaemia in units — 'but which is continued over a long time : 

 weeks, months, or perhaps years. We have to ask ourselves, how far 

 does chronic anoxaemia stop the machinery ; how far does it wreck the 

 machine? Here we are faced with a much more difficult problem, for 

 the distinction between stopping the machinery and wrecking the 

 machine tends to disappear. In fact so indistinct does it become that 

 you may ask yom'self, with some degree of justice, does chronic 

 anoxaemia stop tlie machine in any other way than by wrecking it ? 



The most obvious instances of men subject to chronic anoxaemia 

 are the dwellers at high altitudes. Now, it is quite clear that in many 

 instances of mountain-dwellers the anoxaemia does not wreck the 

 machine. On what I may call the average healthy man anoxaemia 

 begins to tell at about 18,000 feet. At lower altitudes no doubt he 

 will have some passing trouble, but it seems to me from my own 

 experience that this altitude is a very critical one. Yet there are mining 

 camps at such heights in South America at which the work of life 

 is carried on. Under such circumstances the machine is kept going 

 by a process of compensation. This is in part carried out by a modifi- 

 cation in the chemical properties of the blood. It would appear that 

 both the carbonic acid in the blood and the alkali diminish. The 

 result, according to my interpretation of my own observations on the 

 Peak of Teneriffe, which appeared to be confirmed by the experi- 

 ments in a chamber in Copenhagen'' from which the air was partially 

 exhausted, was this : The hydrogen ion concentration of the blood 

 increased slightly, the respiratory centre worked more actively, and the 

 lung became better ventilated with oxygen, with the natural result that 

 the blood became more oxygenated than it would otherwise have been. 



The difference which this degree of accUmatisation made was very 

 great. Take as an example one of my colleagues, Dr. Roberts. On 

 Monte Eosa in his case, as in that of the rest of the party, 15 mm. of 

 oxygen pressure were gained in the lungs. To put the matter another 

 way, the atnount of oxygen in our lungs at the summit was what it 

 would otherwise have been 5,000 or 6,000 feet lower down. No actual 

 analyses of the oxygen in Roberts' arterial blood were made, but from 

 what we now know it seems probable that his blood was about 82 per 



