Alexander M. Kellas and the Physiological Challenge of Mt. Everest

Abstract

Alexander M. Kellas (1868–1921) was a British physiologist who made pioneering contributions to the exploration of Everest and to the early physiology of extreme altitudes, but his physiological contributions have been almost completely overlooked. Although he had a full-time faculty position at the Middlesex Hospital Medical School in London, he was able to make eight expeditions to the Himalayas in the first two decades of the century, and by 1919 when the first official expedition to Everest was being planned, he probably knew more about the approaches than anybody else. But his most interesting contributions were made in an unpublished manuscript written in 1920 and entitled “A consideration of the possibility of ascending Mount Everest.” In this he discussed the physiology of acclimatization and most of the important variables including the summit altitude and barometric pressure, and the alveolar Po₂, arterial oxygen saturation, maximal oxygen consumption, and maximal ascent rate near the summit. On the basis of this extensive analysis, he concluded that “Mount Everest could be ascended by a man of excellent physical and mental constitution in first-rate training, without adventitious aids [supplementary oxygen] if the physical difficulties of the mountain are not too great.” Kellas was one of the first physiologists to study extreme altitude, and he deserves to be better known.

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At the beginning of this century it was customary for explorers and geographers to cite three unattained goals: reaching the North and South Poles and ascending Mt. Everest. The first two were readily accomplished within the first decade, but the last took more than half the century.

When the Royal Geographical Society met in London on May 18, 1916, Alexander M. Kellas, Lecturer in Chemistry at the Middlesex Hospital Medical School, delivered a paper entitled “A consideration of the possibility of ascending the loftier Himalaya.” The President of the Society, Sir Thomas Holdich, introduced Kellas with the following words: “The poles having been reached, it is obvious that the next object of importance on the earth’s surface to be attacked by adventurers is the highest mountain in the world. There are, perhaps I should say not unfortunately, a good many difficulties in the way of reaching it. In the first place, you have to deal with a Government which has up to the present time forbidden you to approach within 100 miles of the mountain’s base. In the next place, the mountain itself is probably—though of this we have no sufficient evidence—of considerable difficulty; and there is thirdly the main obstacle, the effect of the rarity of the air at great heights on the human frame” [15].

Kellas had been invited by A. R. Hinks, Secretary of the Royal Geographical Society, to prepare this lecture. Hinks wrote to him on April 14,1916, as follows¹: “If you could give us a paper with some general title like ‘The possibilities of climbing above 25,000 ft’ it would be the subject of first-rate interest,” and he went on, “especially since no-one perhaps in the world combines your enterprise as a mountaineer and your knowledge of physiology.” Hinks was remarkably perceptive. Indeed, Kellas was unique in his knowledge of the physical problems of approaching Mt. Everest and the physiological challenge presented by its enormous altitude.

The story of the ten major expeditions to Mt. Everest beginning with the reconnaissance in 1921 and culminating with the first successful ascent in 1953 is one of the sagas of the twentieth century. Most historians have, not surprisingly, concentrated on the problems of finding the best route and the technical difficulties of reaching the summit. However, of equal importance was the gradual understanding of the physiological factors that made it possible for humans to reach these great heights.

It is remarkable that one man, Alexander M. Kellas, made major contributions both to the geography of the approaches to Mt. Everest and to the physiology of human performance at extreme altitude. In fact, when the first official reconnaissance was being planned in 1919, Kellas probably knew more about ways of getting to the mountain than anybody else. But in addition, Kellas had given more thought to the physiological problems of reaching the summit and had climbed more often to altitudes above 20,000 ft (6100 m) than anyone. His paper “A consideration of the possibility of ascending the loftier Himalaya” [15] and particularly his unpublished manuscript “A consideration of the possibility of ascending Mount Everest” were landmarks in the early physiology of extreme altitude. Despite this, his name is almost unknown in high-altitude physiology or indeed in physiology at all.

Alexander Mitchell Kellas (Fig. 17.1) was born in Aberdeen, Scotland, on June 21, 1868. His father, James Fowler Kellas, was Secretary and Superintendent of the Mercantile Marine Company in Aberdeen and married Mary Boyd Mitchell. They had nine children (six sons and three daughters) of whom Alexander was the second oldest. One of Alexander’s brothers, Henry, was an advocate (attorney) in Aberdeen and looked after Alexander’s affairs when he was abroad. His letters are a valuable source of information about Alexander.¹ Alexander never married, but Henry had four children, three of whom are still alive. Interestingly, one became British Ambassador to Nepal; another became a Doctor of Science and lectured in histology; and the third is a retired general practitioner in Swindon, Wiltshire, UK.²

Fig. 17.1

Alexander M. Kellas (1868–1921). Archives of the Royal Geographical Society, by permission

Alexander Kellas was educated at Aberdeen Grammar School and in 1889 went to Edinburgh to study for two years at the University and the Heriot-Watt College there. He then moved to University College, London, where he obtained his BSc in 1892. He already had a stepbrother in London, James N. F. Kellas; Alexander used to visit the family on Sunday evenings and later brought them small presents from Tibet and India.³

For a time Alexander Kellas was a Research Assistant at University College, London, with Sir William Ramsey, who worked on the chemistry of the noble gases. In 1895 Kellas went to Heidelberg University in Germany to study for his DPhil degree, which he received in 1897. He was appointed Lecturer in Chemistry at the Middlesex Hospital Medical School in London in 1900 and held that appointment until 1919. The University of London awarded him the degree of DSc in 1918.

Kellas developed an early love for hill walking. His brother Henry wrote to the Secretary of the Royal Geographical Society after Alexander’s death as follows⁴: “As a boy, the hills seemed to have a fascination for him, and he was ardently devoted to walking and climbing, first among the Grampians, and later on in Wales and on the continent. When he was only 14, he and a younger companion slept under the shelter stone in the Cairngorms, ascending Ben Macdhui and other mountains.” His first expedition to the Himalayas was in 1907, when he spent the months from August to October exploring mountains in Kashmir and Sikkim, the region of India north of Darjeeling and east of Mt. Everest. This was followed by further visits in the summers of 1909, 1911, 1912, 1913, 1914, and 1920 and the early spring of 1921.

It was impossible for Kellas to visit India between 1914 and 1918 because of the First World War. However, we know that he had planned expeditions to Sikkim to take place in both 1915 and 1916 because a typewritten proposal for these still exists. The proposal sets out an ambitious plan including making a large-scale map of the north and west approaches to Everest and obtaining a series of photographs showing the best prospects for climbing the mountain.

Kellas particularly explored the mountains of north Sikkim and thus became familiar with the approaches to the Everest region from the east and north [7]. He also spent some time in southern Tibet especially near the village of Kampa Dzong. Kellas was not a prolific writer but accounts of some of these expeditions were published in the Alpine Journal and the Geographical Journal [11–14, 16, 18, 19].

These explorations to extremely remote regions were carried out during the summer vacations, and it is remarkable that Kellas was able to find the time. The expeditions themselves lasted 3 or 4 months and at that time it would take some 3 weeks to sail from London to India and an additional 3 weeks to return. In spite of this, Kellas was described as a conscientious faculty member who was commended for his teaching [26]. However, there are indications in one of his letters of tensions between the medical school administration and himself over the amount of extra leave he requested for these expeditions.⁵

On most of these expeditions, Kellas went alone accompanied only by some native porters. Occasionally he had an English companion; for example, Henry Morshead accompanied him on his expedition to Kamet in 1920. Kellas was apparently the first Himalayan explorer to recognize the immense value of the Sherpas, the people of Tibetan origin who live near Mt. Everest, to exploration in these regions [27]. Since his early contact with the Sherpas, they have played critical roles in expeditions to Everest and other Himalayan mountains.

From a physical point of view, Kellas must have been remarkably tough to withstand the rigors of these small expeditions to remote areas at great altitudes. It is believed that he probably made more ascents over 20,000 ft than anyone else [26]. However, his appearance belied his athletic abilities. The well-known British climber, George Leigh Mallory, described him in a letter to his wife during the early stages of the 1921 Everest reconnaissance expedition thus: “Kellas I love already. He is beyond description Scotch and uncouth in his speech—altogether uncouth. He arrived at the great dinner party 10 min after we had sat down, and very dishevelled, having walked in from Grom, a little place four miles away. His appearance would form an admirable model to the stage for a farcical representation of an alchemist. He is very slight in build, short, thin, stooping, and narrow-chested; his head… made grotesque by veritable gig-lamps of spectacles and a long-pointed moustache. He is an absolutely devoted and disinterested person” [30].

The first two decades of this century were an exciting time in the physiology of extreme altitude. In the late 1900’s many people were of the opinion that ~ 21,500 ft (6,500 m) represented the maximum height attainable by humans. Kellas quotes the President of the Alpine Club, T. W. Hinchliff, who wrote in 1876 after visiting Santiago, Chile, as follows⁶ “I could not repress a strange feeling as I looked at Tupungato (21,550 ft) and Aconcagua (23,080 ft) and reflected that endless successions of men must in all probability be forever debarred from their lofty crests…. Those who, like Major Godwin-Austen, have had all the advantages of experience and acclimatization to aid them in attacks upon the higher Himalaya agree that 21,500 ft is near the limit at which man ceases to be capable of the slightest further exertion” [9].

However in 1909 the Duke of the Abruzzi led an expedition to the Karakorum that was designed “to contribute to the solution of the problem as to the greatest height to which man may attain in mountain climbing,” as the Duke’s biographer put it [4]. His party reached 7500 m (24,600 ft) without supplementary oxygen, far higher than anyone had been before. This feat astonished climbers and physiologists alike. The English physiologists Douglas, Haldane, and their co-workers [5] estimated from the reported barometric pressure of 312 Torr that the alveolar P_O2 was only 30 Torr, and they concluded that adequate oxygenation of the blood would be impossible under these conditions without active secretion in the lung. However, this conclusion was disputed by Marie Krogh [22], who had recently developed a technique for measuring the diffusion characteristics of the lung using carbon monoxide. She argued that Douglas and his colleagues had markedly underestimated the pulmonary diffusing capacity. This was just one of the exchanges between the two camps arguing for and against active secretion of oxygen by the lung in a controversy that lasted into the mid-1930’s.

Kellas had trained in chemistry, and he taught this subject to medical students at Middlesex Hospital Medical School for some 18 years. At this time, many students would have received relatively little chemistry before coming to medical school, and Kellas lectured in both inorganic and organic chemistry. His obituary in the Mddlesex Hospital Journal [25] refers to his great interest in teaching, especially to the weaker students, and he wrote three short textbooks to assist with his laboratory classes in chemistry.

Kellas’ early research was on various aspects of organic and inorganic chemistry. His DPhil thesis was devoted to the esterification of benzoic acids, and after his period with Sir William Ramsey, he studied the distribution of argon in human expired gas and in various vegetable and animal substances. He also carried out an extensive investigation on “The molecular complexity of liquid sulphur,” which was published in 1891.

Kellas gradually became increasingly interested in the physiology of high altitude, which was not surprising given his scientific background and his immense personal experience at extreme altitude. He became an authority on acute mountain sickness and contributed two short articles on this subject [20]. At one stage he even began studying to take a medical degree at the Middlesex Hospital Medical School⁷. In 1918 he collaborated with J. S. Haldane, one of the most eminent British physiologists of the day, on a study of acclimatization obtained by repeated exposures to low pressure in a chamber at the Lister Institute in London. A description of this work was published in the Journal of Physiology (London) and is referred to again below [8].

Although Kellas’ early Himalayan expeditions were primarily exploratory in nature, he became progressively more interested in using them to study the physiological problems of extreme altitude. At one stage he wrote a tentative proposal for a medical scientific expedition to remain for a period of several months at an altitude of 20,000 ft to study the physiology of acclimatization. In a letter to Hinks dated October 9, 1917¹, he suggested possible locations for a long-term camp, for example, the summit of Kanchenjhau (22,700 ft), and added “it might even be possible to drag up in small parts the framework of a small wooden hut.” He planned to carry out the types of experiments that Haldane and his colleagues had made on Pikes Peak. It is remarkable that such an expedition was not organized until over 40 years later, and even then the altitude was a more modest 19,000 ft. [28].

The major published contribution in the area of physiology by Kellas was his paper entitled “A consideration of the possibility of ascending the loftier Himalaya,” which was read at the meeting of the Royal Geographical Society on May 18, 1916, and subsequently published in the Geographical Journal [15]. The fact that the article was published in a geographical rather than physiological journal might indicate that Kellas thought of himself more as an explorer than a physiologist, although another factor may well have been that he received some financial support for his Himalayan expeditions from the Royal Geographical Society and presumably wanted to report his findings directly to them. The paper contains many features of interest that throw light on the state of high-altitude physiology at the time. For example, Kellas correctly predicts the barometric pressure on the summit of Mt. Everest to be 251 Torr (for a mean air temperature of 0 °C) based on the work of FitzGerald [6]. This correct value contrasts with later estimates made in the 1940’s, when the pressure was thought to be much lower based on the inappropriate use of the standard atmosphere.

The article in the Geographical Journal created a great deal of interest, particularly among climbers, and it was extensively reviewed in a subsequent issue of the Alpine Journal [15]. However, it is probable that Kellas’ choice of the Geographical Journal resulted in relatively few physiologists seeing the article, and this no doubt contributed to the fact that Kellas’ work is not well known.

Kellas’ most interesting study was entitled “A consideration of the possibility of ascending Mount Everest”. Although two complete manuscripts survive, one in the archives of the Royal Geographical Society and the other in the archives of the Alpine Club library,⁸ the paper was never published. One manuscript was sent to A. R. Hinks on April 24, 1920, at a time when Kellas was very busy preparing for what were to be his last two Himalayan expeditions. It is not clear why the manuscript was never published, although it may simply be that because he died abroad and never returned to England, no one pressed for publication. A French translation of the manuscript was published in a very obscure place, the proceedings of the Congres de l’Alpinisme held in Monaco in 1920 [17]. Kellas apparently presented the paper at this meeting when he was en route to India.⁹

Kellas begins by stating his main question: “Is it possible for man to reach the summit of Mount Everest without adventitious aids [by which he meant supple-mentary oxygen], and if not, does an ascent with oxygen appear to be feasible?” He divides the problems to be overcome into two groups: “I. Physical difficulties” and “II. Physiological difficulties,” and he considers each of these in considerable detail.

The introduction to the paper is interesting because he cites the altitude of Everest as 29,141 ft (8882 m). The official altitude at that time was 29,002 ft, having been determined by Sir Andrew Waugh, Surveyor-General of India, in 1852. Waugh succeeded Sir George Everest, the Surveyor-General after whom the mountain was named; this was when Everest was first identified as the highest mountain in the world. However, in 1909 Sir Sidney Burrard, a later Surveyor-General, recomputed the altitude from the original sightings but using different values for the refractive errors caused by the bending of light in the lower atmosphere, and he came up with the figure of 29,141 ft. It is not clear why Kellas preferred the higher altitude when most people accepted the official lower value. It was not until the 1950’s that D. L. Gulatee used new sightings to establish the now-accepted altitude of 29,028 ft (8848 m).

The first physical difficulty discussed by Kellas is that of access to the mountain. He points out that “The mountain has so far never been visited by white men, and it is unlikely that any mortal has reached an altitude of even 20,000 ft (6096 m) upon it.” However, with his unrivaled experience of the geography of the region, Kellas was able to suggest three possible routes from Darjeeling depending on whether the authorities of Tibet or Nepal gave permission. He believed the former to be more likely, which indeed proved to be true. Kellas’ knowledge of the area was supplemented by explorations made by Captain J. B. Noel, who at one stage disguised himself as a Tibetan to reconnoiter the Himalayan range east of Everest [24].

Kellas then goes on to discuss the best time of the year for an ascent. He correctly reasoned that the monsoon period would be impossible because of the heavy snowfall and recommended the months immediately preceding or succeeding the summer monsoon. These have proved to be the most suitable periods up to the present time. Kellas also considered possible routes on Everest itself. Here he was at a very considerable disadvantage because no climber had been anywhere near the mountain and available photographs were taken from many miles away. The two routes to the summit selected by Kellas were the east face and the northeast ridge. The latter was a good choice and was the route attempted by all the early expeditions from the north side, but the former proved to be exceptionally difficult and indeed was not climbed until 1983.¹⁰ Kellas also made the point that the climbing on Mt. Everest above an altitude of 26,500 ft looked easier than on some other Himalayan peaks such as Kanchenjunga, K2, and Nanga Parbat. In this he was correct.

Kellas’ most interesting studies from our point of view are in the section headed “Physiological difficulties.” He divided this section into four parts: (1) information from balloon ascents, (2) studies in low pressure chambers, (3) observations up to altitudes of 20,000 ft, and (4) the physiology of acclimatization to high altitude.

Under balloon ascents, Kellas briefly describes the experiences of the Englishmen Glaisher and Coxwell and the three Frenchmen led by Tissandier, who both ascended to altitudes near the summit of Mt. Everest. All five men lost consciousness, and in the ill-fated French ascent only Tissandier survived, the other two men dying from acute hypoxia. However, Kellas was quite clear that these dramatic consequences would not be expected during a climb up Mt. Everest because of the advantages coming from acclimatization. He also noted that even higher ascents in more recent times had been made safe by the balloonists inhaling oxygen.

The air chamber experiments fall into two categories. The acute exposure experiments gave results similar to those found in ballooning in that they also showed that humans could not survive the low barometric pressure on Mt. Everest without losing consciousness. Kellas quoted E. H. Starling’s influential textbook [31] which stated that “the lowest limit at which life is possible corresponds to an oxygen tension in the alveoli of 27–30 mm, which is distinctly above that calculated for Mt. Everest.” Parenthetically, recent work shows that these estimates are too low [34].

Kellas then briefly describes a very interesting set of experiments in which two subjects (J. S. Haldane and himself) spent 4 consecutive days in a low-pressure chamber at altitudes equivalent to 11,600, 16,000, 21,000, and 25,000 ft. This was the study referred to earlier [8] that was carried out at the Lister Institute in London and was apparently the only time that Kellas had an opportunity to collaborate with J. S. Haldane, one of the leading British high-altitude physiologists. Both subjects spent several hours in the chamber on each of the 4 days, and many interesting physiological observations were made. On the 4th day, when the pressure was only 312 Torr (corresponding to an altitude of 25,000 ft), Haldane’s alveolar P_CO2 was 19.8 and P_O2 30.1 Torr. Nevertheless he was able to cycle on the ergometer and do 3300 foot-pounds of work for 4 min but stopped because “he was exhausted and vision was becoming blurred.” This work rate corresponds to 456 kg.m.min⁻¹ which is not a great deal less than the 600 kg.m.min⁻¹ measured as the maximal work rate for subjects at an equivalent altitude after several weeks of acclimatization [33]. Administering oxygen at a low flow rate resulted in a dramatic improvement. Haldane stated: “The light seemed to increase and there was a short apnea. At the same time the lips and face became bright red.”

This remarkable series of experiments showed that as little as 3 days of acclimatization apparently increased tolerance to an altitude of 25,000 ft. The full description published in the Journal of Physiology (London) makes good reading and contains a number of vignettes disdained by modern-day editors. For example, on the last day in the chamber, which was the climax of the experiment (simulated altitude 25,000 ft), Haldane apparently cut the experiment short and “come out about 4 PM, as it was necessary to catch a train.” Presumably this was the last train to Oxford. J. S. Haldane’s son J. B. S. Haldane, who later became an eminent biologist, also took part in some of the acute experiments. On one occasion when the pressure was 330 Torr, outside observers noted that he could not stand properly and looked very blue and shaky. The paper records: “The emergency tap was therefore opened so as to raise the pressure. There is a correspondingly indignant and just legible note ‘some bastard has turned tap,’ after which the notes become quite legible again as the pressure rose.”

An interesting sidelight on these experiments is that Kellas apparently tolerated the very low pressures much better than J. S. Haldane. In connection with this the paper states: “In the experience of one of us (A. M. K.) ordinary mountain sickness has never been experienced, either in himself or among the native carriers accompanying him, at heights up to 23,180 ft in the Himalayas.” However, paradoxically, Kellas showed more cyanosis than Haldane. The article states: “A further point which appeared quite definitely was that the symptoms of anoxaemia did not coincide in the different subjects with the degree of blueness of the face. The contrast in this respect between A. M. K. and J. S. H. was very marked. The former was always much bluer than the latter, but was otherwise much less affected, and retained his faculties when the latter was helpless.” This is surprising. The more intense cyanosis of Kellas suggests that he did not increase his ventilation as much as Haldane, and one would therefore have expected less tolerance to low pressure. Unfortunately, the data given in the paper on alveolar P_CO2 are rather sparse; they do not show obvious differences between the two subjects.

The next section of Kellas’ manuscript is devoted to observations on physiologists and mountaineers up to altitudes of 20,000 ft Some 14 foolscap pages of manuscript are devoted to mountain sickness, including the symptoms and signs, variability between subjects, and etiology. This section shows that Kellas had a very good understanding of this condition, and most of what he wrote remains true today. He rightly attributes the condition to hypoxia, as first shown by Paul Bert in 1878, although he wonders whether respiratory alkalosis may also play a role. Kellas clearly recognized that adequate acclimatization was the key to tolerating the extreme oxygen lack on the summit of Mt. Everest.

The last section of the manuscript under the heading “The process of acclimatization to altitude” is of great interest. Here Kellas considers in turn the various features of physiological adaptation to extreme altitude. Although there are many factual errors because he had almost no data on which to base his work, Kellas’ insight in asking all the right questions was outstanding.

The central issue as Kellas saw it was: Can sufficient physiological adaptation occur to allow a climber to ascend from a camp at ~ 25,500 ft to the summit (29,141 ft) in 1 day? He starts by reviewing the oxygen dissociation curve including the striking difference between hemoglobin solution and blood and the effects of carbon dioxide and lactic acid on the position of the curve. This part of the manuscript has some overlap with his earlier study that was read to the Royal Geographical Society in 1916 (several of the figures are the same). Note that this was not long after the factors affecting the position of the oxygen dissociation curve were first described; the influence of lactic acid was first understood in 1910 [2].

Kellas then goes on to ask a crucial question: What is the alveolar P_O2 on the summit of Mt. Everest? He correctly argues that the hyperventilation caused by hypoxia will reduce the alveolar P_CO2 and correspondingly increase the alveolar P_O2. He concluded that for an altitude of 29,141 ft (8,882 m) the P_O2 would be 23.6 Torr (Table 17.1). The details of this calculation are not given, but it is clear that Kellas was strongly influenced by the measurements of Mabel P. FitzGerald, who made an extensive survey of the alveolar P_CO2 at various altitudes in the Rocky Mountains during the Anglo-American Expedition to Pikes Peak in 1911 [6]. From her measurements (made at much lower altitudes) she made a linear extrapolation that gave an alveolar P_CO2 of 19 Torr at the altitude of the summit of Mt. Everest. She also assumed a respiratory exchange ratio (R) of 0.83 at rest. It appears that Kellas used the same equation as FitzGerald

$$\text{P}_{\text{A}_{{\rm o}_{2}}}= 0.2093 (\text{P}_\text{B}-47)-\text{P}_{\text{A}_{{\rm o}_{2}}}/\text{R}$$

Table 17.1 Comparisons of Kellas’ values and prediction with currently accepted values on physiology at extreme altitudes on Mt. Everest

where Pa _O2 and Pa _CO2 are alveolar P_O2 and P_CO2, respectively, and Pb is barometric pressure. Kellas apparently assumed a P_CO2, of 18.6 and R of 0.83. For a barometric pressure of 267, which is the value for an assumed air temperature of 15 °C (see later), this would give his alveolar P_O2 of 23.6 mmHg.

Parenthetically, we now know that this value of P_CO2 is much too high and therefore the calculated P_O2 is much too low. Actual measurements of the alveolar P_CO2 and P_O2 on the Everest summit gave values of ~ 7.5 and 35 Torr respectively [34].

Kellas pointed out that the fall in P_CO2 at high altitude would displace the oxygen dissociation curve to the left and increase the oxygen saturation of the blood, which would be advantageous. However, he also recognized a disadvantage of this leftward shift in a footnote, namely that the dissociation of oxygen from hemoglobin in peripheral tissues would be impaired. Having said this, he argued from Barcroft’s measurements on the peak of Tenerife that the position of the oxygen dissociation curve is normal at high alkalinity of the blood [1]. He therefore calculated an arterial oxygen saturation of 42 %. We now know that this is far too low because of the marked respiratory alkalosis that occurs near the Everest summit [34].

Kellas then discusses the increase in erythrocytes at high altitude. Curiously, some studies he quoted had not shown this to occur, but he concluded that there would be a substantial increase, perhaps up to 8 × 10⁶/mm³, a 60 % rise over the normal value of 5 × 10⁶. This is actually considerably higher than is seen in acclimatized climbers.

There is a brief section on the possible secretion of oxygen by the alveolar epithelium at high altitude. Here Kellas was on difficult ground. His recent eminent collaborator, J. S. Haldane, staunchly promoted oxygen secretion, whereas other physiologists such as Krogh and Barcroft equally strongly argued for passive diffusion. Kellas tactfully concluded that the issue was not settled.

There is a short section on evidence for the more rapid circulation of blood at high altitudes during moderate exercise. Kellas points out that the pulse rate during moderate exercise is always increased at high altitude (compared with sea level), though it may be nearly normal at rest. He concludes that the higher cardiac output would enhance oxygen delivery to the tissues. Current evidence is that, after acclimatization, cardiac output returns to the sea-level values for a given work level [29].

Kellas then deals with the relationships between barometric pressure and altitude. He tabulates and plots the pressure against altitude for two values of the “mean temperature of the air column,” namely 15 and 0 °C. These give barometric pressures on the Everest summit of 267 and 251 Torr, respectively. Again the details of these calculations are not given, but he probably used the Zuntz et al. formula [35] as had been done by FitzGerald [6]. Incidentally the value of 251 is very close to that of 248 Torr quoted by Paul Bert in his book La pression barométrique published in 1878 [3].

The next section is entitled “Limits of permanent acclimatization to high altitudes.” Kellas writes that “the experiences of most mountaineers, who have climbed above 20,000 ft seemed to indicate that there is a distinct depreciation of strength above that altitude….” He therefore chose this altitude as the limit of permanent acclimatization, although he recognized that there were differences of opinion and indeed many present-day physiologists would choose a lower altitude. For example, Keys and his colleagues on the 1935 International High Altitude Expedition described a group of miners who lived at an altitude of 17,500 ft and who preferred to climb every day to the mine at 19,000 ft rather than live there [21]. Largely based on this observation, it has often been said that 17,500 ft is the highest altitude for permanent habitation.

Interestingly enough, very recent reports indicate that a small group of men now live indefinitely at an altitude of 19,500 ft [32]. They are caretakers of the Aucanquilcha mine in north Chile, and the longest period of residence has been ~ 2 year. These remarkable men apparently vindicate Kellas’ value.

The next section of the manuscript deals with the key issues of the maximum rate of climbing and the maximum oxygen consumption at extreme altitudes. Again, the importance of this discussion is not so much that Kellas obtained nearly the right answers; this was partly by chance, since he had so few data. But Kellas recognized that the questions were crucial, and he approached them in two ways.

First, he assumed that maximum climbing rate is proportional to the oxygen concentration of the arterial blood. He stated that experience shows a maximum rate of ascent of ~ 1,000 ft/h at an altitude of 16,000 ft, where he calculated the arterial oxygen saturation to be 80 %. He also had evidence for a rate of ascent of ~ 600 ft/h at an altitude of 23,000 ft, where he believed the saturation to be 60 %. Since the 20 % fall in oxygen saturation resulted in a 40 % loss of climbing rate, he calculated that the climbing rate near the Everest summit, where he believed the saturation to be ~ 40 %, would be 300–350 ft/h. This value of 5–6 ft/min of vertical ascent is remarkably close to present-day estimates of the maximum climbing rate near the summit. For example, Rheinhold Messner, the first man (with Peter Habeler) to reach the Everest summit without supplementary oxygen reported that “the last 100 m took us more than an hour to climb” [23]. Kellas also made the calculation a different way using the relationship between alveolar P_O2 and altitude. Again the results were similar.

Consistent with these predictions of maximum climbing rates, Kellas also calculated maximum oxygen uptakes at various altitudes partly based on measurements made by Haldane and his colleagues on Pikes Peak [5]. He concluded that near the summit of Mt. Everest maximum oxygen uptake would be ~ 970 ml/min, a value remarkably close to that of 1070 ml/min measured on well-acclimatized subjects with the same inspired P_O2 as the Everest summit [33]. He also pointed out that some 400 ml/min of that oxygen uptake would be required for “vital processes,” that is, metabolism not related to climbing.

Kellas noted in the final section of the manuscript that this calculated maximum climbing rate would require the highest camp to be at an altitude of at least 25,500 ft and that a very early morning start would be necessary. Subsequent history bore out this prediction too. When Rheinhold Messner and Peter Habeler made their historic first ascent of Everest without supplementary oxygen in 1978 they started their final climb from the South Col at an altitude of 26,200 ft (7986 m) at 5:30 a.m.¹¹

The last few lines of the manuscript are under the heading “General conclusion”: “Mt. Everest could be ascended by a man of excellent physical and mental constitution in first rate training, without adventitious aids if the physical difficulties of the mountain are not too great, and with the use of oxygen even if the mountain can be classed as difficult from the climbing point of view.” It took 58 years for this assertion to be proved true!

Six days after Kellas mailed a copy of this manuscript to the secretary of the Royal Geographical Society, he left for India for another Himalayan expedition and never returned to England. The circumstances of his death are worthy of a Greek tragedy.

Kellas was apparently under a great deal of strain during his last years as a lecturer at the Middlesex Hospital Medical School. There are several references in his letters to the very demanding work that he was required to do during the years of World War I, 1914–1918, when the Medical School was understaffed, and he made the decision to resign from the faculty of the School in 1919. In a letter dated October 21, 1919, addressed to A. R. Hinks¹ he referred to a “peculiar and continuous annoyance… a disturbance which medical men tell me is due to overwork and which takes the form of malevolent aural communications, including threats of murder.” There is no other reference in his correspondence to this bizarre condition that suggests an incipient paranoid psychosis.

Nevertheless Kellas apparently worked hard to prepare for the forthcoming expedition to Kamet, on which he was proposing to study the effects of breathing oxygen at extreme altitudes. His list of projects including measuring the alveolar P_O2 and P_CO2 using the gas analysis techniques described by Haldane, determining changes in hemoglobin concentration and erythrocyte count, and assessing the beneficial effects of breathing oxygen. This work was supported by the Oxygen Research Committee of the British Admiralty in association with the Royal Geographical Society. Kellas had earlier proposed the use of the chemical sodium peroxide in a breathing circuit to prepare oxygen at high altitude, but on this occasion he planned to test the value of oxygen from compressed gas cylinders.

The expedition to Kamet was not completely successful. In a letter from Darjeeling dated November 17, 1920, to Hinks,¹ Kellas wrote that the “lateness of arrival of scientific apparatus and oxygen cylinders caused a retreat from Kamet after reaching only about 23,600 ft…. Although I managed to get all the essential experiments carried out, I am so dissatisfied with certain factors that I intend to arrange a small expedition for next year, and complete the ascent.”

During the winter, Kellas remained in India at Darjeeling because he wanted to obtain additional information about the best approaches to Everest. While he was there he received an invitation to take part in the first official reconnaissance expedition to take place in the spring of 1921. After many years of unsuccessful attempts, permission had finally been obtained from the Dalai Lama to approach Everest through Tibet. Naturally Kellas was enormously elated, since much of the previous 15 years of his life had been a preparation for this event.

However, in early 1921 he was back in the Himalayan ranges climbing alone with a few Sherpas. In a letter to Hinks of May 18, 1921 he wrote¹: “my main object in ascending Kabru (besides training coolies for the Mt. Everest expedition) was to obtain for your use a photograph of Mt. Everest and all the peaks to the N.W…. part of the [Everest reconnaissance] expedition starts today, and Raeburn and I get off tomorrow… after return from Mt. Everest I intend to try Kabru again.” Kellas took his photographic equipment up to ~ 21,000 ft on Kabru to obtain the best possible photographs. He returned to Darjeeling from Kabru on May 10, which meant that he had only 9 days of rest before starting on the momentous Everest reconnaissance expedition.

The trek from Darjeeling followed the route that Kellas had earlier recommended and knew well. They went north through the humid jungle of Sikkim and crossed into Tibet over the Jelep La pass. Several members of the expedition suffered from diarrhea, a very common condition in lowland treks because of the poor hygiene. Kellas, who was almost 53 years old, was badly affected. He grew so weak that he had to be carried on an improvised stretcher. Mallory, who was one of the expedition members, wrote: “Can you imagine anything less like a mountaineering party? It was an arrangement which made me very unhappy and which appalls me now in the light of what has happened… and yet it was a difficult position. The old gentleman (such he seemed) was obliged to retire a number of times en route and could not bear to be seen in his distress and so insisted that everyone should be in front of him” [30].

Tragically, Kellas died as the expedition was approaching the Tibetan village of Kampa Dzong. It was here that the expedition members had their first view of Everest. Mallory described it thus: “It was a perfect morning as we plodded up the barren slopes above our camp … we had mounted perhaps a thousand feet when we stayed and turned, and saw what we came to see. There was no mistaking the two great peaks in the west: that to the left must be Makalu, gray, severe, and yet distinctly graceful, and the other away to the right—who could doubt its identity? It was a prodigious white fang excrescent from the jaw of the world” [10].

Kellas was buried on a hillside south of the village, in a place which looks out across the arid Tibetan plain to the distant snows of the Himalayas where there rose the three peaks of Pauhunri, Kangchenjhau, and Chomiomo, which Kellas alone had climbed. Mallory described the scene: “It was an extraordinarily affecting little ceremony, burying Kellas on a stony hillside—a place on the edge of a great plain and looking across it to the three great snow peaks of his conquest. I shan’t easily forget the four boys, his own trained mountain men, children of nature, seated in wonder on a great stone near the grave while Bury read out the passage from I Corinthians” [30].

Kellas’ death was ascribed to heart failure, but that means little, since it was a catchall for various conditions in those days. Perhaps he developed high-altitude pulmonary edema; the expedition had just come over a 17,500 ft pass, although, of course, Kellas had been much higher many times before. Or perhaps the combined effects of severe diarrhea with the tremendously demanding climbing program that he had completed over the last 6 month was too much for him.

So Kellas, who had spent much of the last 15 year of his life studying the physical and physiological problems of climbing Mt. Everest and who probably knew more about these subjects than anyone else alive, died just as the first official reconnaissance expedition had its first view of the mountain they came to climb. It would be difficult to imagine a more dramatic end to the life of this remarkable man.