The Everest Expedition of 1922 had no preconceived programme of scientific investigation, and was first and foremost an attempt to get up the mountain; though, as I had been connected with physiological research for some years, I was naturally anxious to make observations on the effect of altitude on the human frame. These observations were rather subjective, and were unaccompanied by any accurate data—in other words, the reader will be relieved to hear that there are no tables of figures to be reproduced. Barcroft and others were in the course of their Expedition to the Andes, and I knew full well their results would supply more accurate information on the exact process of acclimatisation at high altitudes than anything we could do with our simpler apparatus. We left it to this other Expedition, therefore, to supply the figures, while our observations were exclusively on the practical side; that is to say, we observed the rapidity and effect of acclimatisation, while not investigating exactly how it is brought about.

The first effect of altitude, in such moderate degree as we encountered it on the plains of Tibet, was almost entirely a mere breathlessness, which limited our rate of walking, and increased the popularity of our uncomfortable Tibetan saddles when travelling uphill. A few of us had severe headaches from time to time; at the modest height of 17,000 feet I noticed Cheyne-Stokes respiration at night when lying down, though never when sitting or standing; and I remember being distinctly amused at the fact that one was unable to control it.^[7] A few of the party had a single attack of vomiting, but no permanent effect was noticed, and by the time we had lived on the Tibetan Plateau for a few weeks we had lost all ill effects save only breathlessness, which, of course, persisted to some extent until we reached comparatively low elevations. Further effect at these heights was not noticed save in the case of some of the older members of the party, who suffered from a considerable loss of appetite while at the Base Camp at 16,000 feet; this effect on appetite did not improve as time went on.

It was when we began the more serious work on the mountain that we made the most interesting observations on acclimatisation, and proved both its rapidity (which was known before) and its persistence to great heights. Scientists of various schools had, before the start of the Expedition, predicted that acclimatisation would be impossible above the height of 20,000 feet. Why they had done so will always remain a mystery to me; but possibly they were misled by the fact that so many climbing expeditions in the past have failed somewhere in the region of 23,000 feet above sea-level. We were enabled, however, to prove conclusively that acclimatisation does go on to greater heights; in fact, I do not see a theoretical limit to it at any elevation below the top of Mount Everest. Our observations were largely subjective, but for that reason they are perhaps all the more to be appreciated by the general reader; and in view of their subjective nature I may perhaps be pardoned in substituting “feelings” for figures and putting information in the form of a personal experience.

When Mallory and I arrived at Camp III and established it on the site chosen by the reconnaissance party, our first concern was the preparation of another camp at the North Col. I shall never forget our first ascent up that accursed slope of snow and ice, each step a hardship, every foot a fight; until at last we lay almost exhausted on the top. After a day or two at Camp III below, we went up again to the col, this time with Strutt and Morshead, and I think Norton. The ascent of the col this time was hard work, but not more than that; and after the col had been reached Morshead and I were sufficiently cheerful to explore the way leading up to Everest. A day or two later we again ascended the North Col, and never really noticed more discomfort than was occasioned by breathlessness. Though not possessing the scientific data which explained this change in our condition, yet in those few days of life at 21,000 feet we had become acclimatised to our altitude to a very remarkable degree; what had previously been a hard struggle had now become a comparatively easy job. By this rapid change in our constitution we had not only proved the predictions of scientists to be wrong, but had gained the physical power which took us without artificial oxygen supply to 27,000 feet, and we had determined that acclimatisation is not only possible but is also quite rapid at these high altitudes.

Thus, by sojourn and exercise for a week above 20,000 feet, we obtained the physiological equipment necessary for an attempt on the mountain, and at this point some personal experiences may be of interest, though possibly of no great importance. We found that, as we ascended, we fell into an automatic rate of breathing; Mallory preferred to breathe slowly and deeply, while rapid and shallower respirations appealed to me; but we all walked upwards at almost exactly the same rate at any given height. Below the North Col, I took three breaths to a step, while at 26,000 feet I was taking five complete respirations; but as long as I was walking slowly enough I experienced no distress or discomfort. If one hurried for a short distance, one was forced to rest for a few seconds—a rest was imperative, and one felt it were impossible to do without it; but as long as an even pace was kept up, one had no desire to stop, nor to make one’s admiration of the landscape an excuse for delaying one’s comrades. At the height of 26,000 feet, I took my pulse (which was 180) and my respirations (which were 50 to 55 to the minute); but withal one felt perfectly comfortable even though these abnormal physiological conditions were present. No doubt the heart must be young to stand this rate of beating for many hours; yet not too young, or it will easily become enlarged and permanently damaged.

In view of our experiences it seems justifiable to predict that acclimatisation at 23,000 feet will be sufficient for the attainment of the summit of Mount Everest, if indeed a sojourn at 21,000 feet is insufficient—which is to my mind more than doubtful. The other important practical observation we made is less encouraging: namely, that we all varied in our rate of acclimatisation, and in fact some of our number (especially the older ones among us) actually seemed to deteriorate in condition while staying at a great height. But I think we proved that it is possible to climb to the summit of Everest without the use of oxygen, though the selection of men who are able to do so is very difficult until those heights are actually reached at which acclimatisation becomes established. Personally I felt perfectly well at 27,000 feet, and my condition seemed no different at that height from what it had been at 25,000 feet, or even lower; and I have no doubt there are many people, if only they can be found, who can get to the top of Everest unaided save by their own physiological reaction to a life at 21,000 feet for a few days. If a number of such people were allowed to live at a height corresponding to our Camp III for a fortnight or so, making perhaps a few minor excursions to 23,000 or 24,000 feet, then I have no doubt from the physiological point of view that they will be able to climb Mount Everest, provided the weather is fine and the wind not too violent. Without allowing time for acclimatisation to take place, it is probable that nobody—that is, unless some lusus naturÆ exists—will reach the summit; if artificially supplied oxygen be used, the acclimatisation may not be necessary; but the danger of an attempt by non-acclimatised men with oxygen apparatus is that a breakdown of the apparatus might lead to serious consequences, while a fully acclimatised man is probably just as capable of standing a height of 29,000 feet, unaided, as you or I would be able to stand the height of Mount Blanc to-morrow. When the Expedition of 1922 started I was personally of opinion that nobody could exist at a height about 25,000 or 26,000 feet without oxygen; but since we have proved that this can be done, it seems that the chances of climbing the mountain are probably greater if oxygen be not used. For the apparatus, and the spare cylinders required, necessitate the use of a large number of coolies; while in an attempt without oxygen only three or four coolies are required for the camping equipment and the food at the highest camp. Therefore it seems that the best chance of getting to the top of Mount Everest lies in the sending out of some nine or ten climbers, who can remain at a high camp, become thoroughly acclimatised, and then make a series of expeditions up the mountain, three or so at a time, as continuously as weather conditions will allow. By adopting these tactics the number of possible attempts up the mountain can be increased; and it seems to me that the chances of climbing to the summit lie in the multiplicity of possible attempts rather than in any other direction. It were better to prepare for a number of attempts each by a small but acclimatised party, rather than to stake all on one or two highly organised endeavours, in which oxygen, and a large number of coolies, are used. It is only a small proportion of coolies who can get up to the heights of 25,000 or 27,000 feet, and they should be used for any one attempt as sparingly as possible. During the war we all had our ideas of how it should be run, and they were generally wrong; the above plan is the writer’s idea of how to climb Mount Everest, and may or may not be right, but is enunciated for what it is worth.

Among subsidiary effects of extreme altitudes, were those upon appetite, temper, and mental condition generally. Most of us will admit a good deal of peevishness and irritability while at a level of 22,000 feet and more; for the altitude undoubtedly makes one lose to some extent one’s mental balance, and the first way in which this appears on the surface is by a ruffling of the temper. In addition, one has a certain lack of determination, and when at a height approaching 27,000 feet I remember distinctly that I cared very little whether we reached the top of Everest or not. A good instance of this altered attitude of mind is provided by the fact that Finch and Bruce took a camera with them on their ascent, and forgot to take any photographs of their last day’s climbing.

I have mentioned the deleterious effect of altitude on the appetite of some of our older members; but the same was to some extent true of us all. I have the most vivid recollection of distaste for food during our first few days at Camp III, and especially of the way one had almost to push a prune down one’s throat on the way up to the North Col; but with the majority of us this distaste for food (especially for meat and the slowly-digested foods) diminished during our sojourn at great heights, though our appetites never became quite normal until we reached one of the lower camps. Those who had oxygen reported that they had large appetites above the North Col; and there is no doubt that it is the rarefaction of the air that causes this alteration of the appetite. One may perhaps be justified in assuming that the secretion of gastric juice is diminished while air that is poor in oxygen is inhaled, though it is rather hard to understand how this is brought about.

Although acclimatisation is not entirely connected with the actual increase in the number of blood corpuscles (as has been proved by Barcroft in 1922), yet this is still recognised as one of the important factors in its production. But this increase in the concentration of the blood must be associated with a great increase in its viscosity, and when that is combined with intense cold with its accompanying constriction of all the smaller blood-vessels, there are present all the conditions necessary for the production of frostbite. Therefore acclimatisation with all its benefits probably increases the risk of frostbite; hence one who is acclimatised must be especially careful of feet and hands and their coverings. It is hard to put on too many clothes at a great altitude, and very easy to put on too few.

The chief point still remaining to be mentioned concerns the after-effects of the climbing of Everest; but these varied so much that they give us little or no scientific information. Some of us were tired for twenty-four hours only, some for many days; some were reported to have enlarged hearts, while in some the heart was normal; some were incapacitated by frostbite, though their general physical condition was very probably good. One therefore cannot generalise about after-effects, but as a medical man I felt strongly (by observation on myself and my companions on the Expedition) that if one is to “live to fight another day” and to require the minimum recuperation period after an attempt on the mountain, it is essential during the attempt to keep oneself well within one’s powers. One is tempted to go too hard, and to exert one’s strength to its limits; but it is just the last few ounces of strength which call forth the greatest effort and make the maximum demands on one’s resources; and if these resources are to be used to their full extent they should be continuously conserved by an avoidance of definite hurry. Personally I am of opinion that exercise before the climbing begins is of great value. Mallory and I were the only ones whom Longstaff allowed to make two attempts on Everest; and we were probably rendered fit in this way by the subsidiary expeditions we had made on the way to Mount Everest and by our preliminary work in getting the camp ready on the North Col. It is, however, hard to generalise on a point like this, but each man knows the idiosyncrasies of his own constitution, and it should be left to individuals to a great extent to see that their condition on arrival at the foot of the mountain is the best that is possible.