158 
A different point of view is presented to 
us by D’Orbigny (1826) in an account of the 
sensations he experienced while crossing 
the highest pass of the Cordillera in Bolivia, 
which is 4,500 meters (about 15,600 ft.) 
high, on his way from the coast of Peru to 
La Paz. For several days before reaching 
the highest part respiration was difficult. 
His driver, the mule he was riding and his 
dog suffered so much that they were com- 
pelled to halt every 20 or 80 meters to re- 
gain their breath. While crossing the 
crest of the ridge he suffered intensely from 
pains in the temples, vertigo, and extreme 
difficulty in breathing. Hvery movement of 
the body produced palpitation of the heart, 
followed hy a feeling of general debility, 
until bleeding of the nose finally relieved 
him. During this attack of ‘mountain- 
sickness’ he saw two natives, who had over- 
taken him, hurry on their way, climbing 
the rocks with the greatest ease. 
It is evident that D’Orbigny did not be- 
long to an Alpine club, and did not have 
the necessary training, or else he would not 
have suffered so intensely at an altitude 
which has no effect upon those who now 
ascend Mount Blane. 
A man who has had no practice in moun- 
tain climbing is apt to experience sensations 
similar to those which D’Orbigny described, 
while yet under the ordinary atmospheric 
pressure. For instance, in hurrying up a 
steep incline, say in the winter, when you 
sink into the snow with every step, you 
will very likely become short of breath, 
since the rapid climb prevents the full ex- 
pansion of the lungs. This disturbs the 
circulation of the blood, which, being no 
longer freely admitted into the contracted 
lungs, collects in the veins. They swell 
up, the face becomes purple, the pulse-beats 
are accelerated, and palpitation of the heart 
sets in. In case the exertion is continued, 
an attack of nausea is imminent, together 
with a feeling of faintness in the lower 
SCIENCE. 
LN. S. Vou. VI. No. 135. 
limbs, as the overworked muscles are de- 
prived of their requisite supply of oxygen. 
A few long drawn breaths usually suffice to 
remedy the disorder. By gradually becom- 
ing accustomed to walking and breathing 
slowly and regularly a further attack is 
prevented. 
These symptoms, as they manifest them- 
selves in the rarefied air of high altitudes, 
constitute what is known as mountain- 
sickness, aud persons unaccustomed to 
mouutain-climbing are frequently affected 
by it even while resting or when not exert- 
ing themselves. Here, again, the cause of 
the disorder is the insufficient expansion of 
the lungs, caused by the diminished atmos- 
pheric pressure which renders respiration 
difficult. 
But, it may be objected that the energy 
with which we inhale the air is the same at 
high altitudes as below, and the rarefied air 
ought to penetrate into the lungs more 
easily. This is perhaps true, but, although 
we expand the chest during inhalation, the 
expansion of the lungs is only accomplished 
by means of the atmospheric pressure. The 
lungs are not attached to the inner surfaces 
of the thorax and can move freely. A 
wound in the thorax which admits the pas- 
sage of air causes the lungs to contract, and 
all the exertions of the breathing apparatus 
will be powerless toward relieving this con- 
traction. 
As long, however, as the cavity of the 
chest remains closed and contains no air, 
the pressure of the air in the lungs acts 
from within outwardly and by expanding 
the lungs will cause them to remain in con- 
tact with the sides of the chest as it expands 
during the process of inhalation. The ease 
with which the lungs are expanded depends 
upon the amount of atmospheric pressure 
which is brought to bear upon their elastic 
power of resistance, and this action conse- 
quently becomes more difficult as the lighter 
pressure of higher altitudesis reached. Let 
