1829.] 
consequent to Exertion at great Elevations. 
331 
of a plant, (the monks-liood,) which grows at the height of about 12 000 feet, and 
perhaps somewhat higher ; but so far from its being found at the height I ascended 
to, nothing of the vegetable kingdom was to be seen, not even a blade of grass or 
patch of moss; which I remarked to them. Even the natives are said to suffer somuch, 
as sometimes to fall down in a state of insensibility ; and this I believe would have 
occurred to me, had I exerted myself, so as to have caused my pulse to rise above 
160. The height to which this may be raised, will, of course, vary w ith the consti- 
tution and habits of the individual, as I tried the pulsc of a sepoy (an inhabitant of 
the lower mountains,) which rose to 172 — mine never exceeded 160 on level 
ground. In descending, however elevated, I never experienced any difficulty in 
breathing, however far I walked. 
I am not aware that any one save myself, evertried the state of his pulse in similar 
situations ; my trials have been frequent, and made with a watch with second hand. 
But although I have proved the extraordinary increase of the pulse to be conneetedwith 
the feeling, this circumstance in itself cannot be considered asa satisfactory elucidation 
of the matter ; much yet remains for discussion, regardingthe cause of this inereaseof 
the circulation. That the rarefied state of the air at great elevations, being insufficient 
forthe due supply of the lungs, will be pronounced to be the sole cause by many of your 
readers, is probable enough;as it may be said, that the lungs require a certain quan- 
tity of air to keep them in proper action, and that in proportion as it is rarefied, so 
much oftener must the person breathe, and consequently so much more must the 
pulse increase. But if this were the true solution, how happens it that the breath- 
ing is not affected, or the pulse accelerated, when a person is stationary and under- 
going no fatigue at the same elevation, which I have proved to be the case ; or even 
when he is walking along level ground, or in descending ? This last was proved by 
my companiou and myself, descending in about 20 minutes, running when the 
ground admitted, a distance which had taken us a full hour to ascend ; without experi- 
encing any inconvenience in breathing, beyond what we should have felt in lower 
situations. That the rarefaction of the air is one cause of this debilitating feeling 
cannot he doubted, and the difficulty lies in explaining the fact of no inconvenience in 
breathing being felt at the heiglitof 17 800 feet whilst in a state of rest, with that of 
every particle of strength being completely prostrated in taking six paces oti my 
ascent to this great elevation- It would be a natural supposition that the inspirations 
roust be in proportion to the density of the atmosphere, and that the state of a person's 
pulse might be told on knowing the height of the column of mercury which was 
supported by the air we breathed, forthe pulse and the breathing will, I imagine, al- 
ways bear a certain proportion to each other ; but this supposition I have proved to be 
erroneous, and that, however elevated the place, the usual number of inspirations are 
in a stale of rest just sufficient for the due supply of the lungs and support of the 
circulation, as the air is at the level of the sea. If then, notwithstanding its rarity, 
the air proves to be an equivalent to that at the level of the sea in a state of rest, 
how is the circumstance, to he accounted for, that X could not take six steps, 
which was also the case with my companion, without being completely exhausted, 
and that my pulse rose from 64 ‘to 16(1. The breathing 1 conceive may act on the 
pulse or vice versa, as I presume the latter is the case with a person labouring under 
the effectof violent fever; and the increased circulation may require a proportional sup- 
ply of fresh air; but the feelings which 1 experienced, did they derive their source 
from the immediate increase of the circulation of the blood, or from the want of a 
due supply of air to the lungs, as the air, notwithstanding its tenuity, was sufficient in 
a state of rest ? We must suppose they were occasioned by the former. Supposing the 
inference 1 have drawn from the facts, which 1 have related, should be correct, the 
next question is, Wlmt is the cause of this rapid circulation? As at thelevel of thesea, 
so at this elevation, we must suppose it to have its origin from violent exertion. But 
when six paces taken at the rate of 60 or 70 in the minute, produce a more power- 
ful effect on the system than perhaps some hundreds taken at the utmost speed in 
the former situation; and as this effect is not produced in walking on level ground ; 
must it not arise from the weight of the body which a person has to raise? Remove 
this, a measure I have frequently had recourse to by fastening a rope round my 
body, and causing a couple of men to assist in pulling me up, and the fatigue is 
comparatively trilling. 
Having traced the subject so far, to the best of my ability, 1 shall not further tres- 
pass on your pages with any crude attempts to bring to light the ultimate cause of 
the feeling, but leave its further elucidation to some abler pen, should the facts 
which I have related draw the attention of such to the subject. 
J. M. 
