The science of life : fully illustrated in tone and line and including many diagrams

Airmen who have attempted heightrecords describe themselves as feeling swelled, puffed out, and deformed, with a painful buzzing in the ears. The heart beats too vigorously in the attempt to send sufficient oxygen round the body. There may be bleeding in ears, nose, and lungs, and even from the eyes and gums. The mountaineer at high altitude has to exert himself, whereas his flying compeer sits still ; he moves with a general feebleness, and is in a continual state of fatigue.

Major Hingston, the medical officer of the Mount Everest expedition of 1924, says that “the very slightest exertion, such as the tying of a bootlace, the opening of a rationbox, or the getting into a sleeping-bag, was associated with marked respiratory distress.” At 27,000 feet Dr. Somerville had to take eight or ten deep respirations for every step forward. Lieut-.Col. Norton at his highest ascended 80 feet in an hour of extreme exertion.

Tissandier, who made a balloon ascent to 27,950 feet from Paris in 1875, fainted at 26,500 feet and when he recovered consciousness the balloon was descending and both his companions were dead. A curious apathy comes on the explorer at such elevations. He no longer sees, hears, or acts so rapidly, and there is great loss of muscular and mental power. Glaisher stared at his instruments, but could not read them. “ There is no suffering,’ wrote Tissandier. “Only an inward joy.”

The cold at these heights sinks to levels as low as thirty degrees below zero centigrade and it is extremely difficult to retain the heat of the body. The aviators can wrap themselves amply in wool, paper, and other nonconductors, but the mountaineer must not be too heavily encumbered. Two members of the last Everest expedition died of cold, and seven of the preceding one were killed by an avalanche. The supreme mountain heights are subjected to icy winds and violent snowstorms and to snow and rock avalanches, inconveniences the aviator escapes. But the aviator has to anticipate great stresses upon his machine due to the cooling and consequent contraction of the metal. The task of the engine to sustain the weight of the machine increases with the attenuation of the air. Long before the aviator has struggled to the five-mile limit all other living things have left him. Insects have long since fallen insensible from his planes. No bird can emulate him, though the condor might have kept with him as high as five miles.

Downwards life is also restricted, but

INTRODUCTION

downwards it is increasing pressure and, in the solid earth, increasing temperature, against which life has to fight. The forms of life familiar to us do not extend down into the sea for very many fathoms; they are replaced by other species more adapted to cold and darkness and high pressure. The barriers set to air-breathing life are soon reached. A diver in a diving-dress, with skilful management and under good conditions, can go to about 300 feet below sealevel, can stay there for twenty minutes, and return to the surface by stages in about an hour and a half, provided he is constitutionally adapted to the work. A naked diver may get to something like thirty feet and stay at most about a couple of minutes. A submarine is under similar restrictions in its range of submergence.

The limiting factor to men going upward and downward under water is the increasing solubility of the atmospheric gases in the blood with pressure. The respiratory and circulatory system of a creature adapted to ordinary surface conditions works with increasing difficulty under high pressure, and a rapid return to normality produces an effervescence of the gases absorbed. “Caisson disease’ is a disease due to this release of bubbles of gas in the blood, and its characteristic victims are divers and workers in the submerged caissons used in bridge and breakwater construction. Its symptoms are various, depending upon the part of the body in which the bubbles happen to be released, and include fainting, vomiting, deafness, inability to breathe, paralysis, pain of the joints and muscles, and sometimes sudden death. At the St. Louis Bridge, under a pressure of four and a half atmospheres, one hundred workmen suffered seriously and fourteen died out ofa total of six hundred men employed.

Because of this relationship of living things to limiting pressures, there is a very considerable restriction in the movements of all life in the sea. We are too apt to think of whales, and so forth, plunging into the abyss and rushing up to the surface without inconvenience. Such familiar creatures, however, soon descend to definite limits ; they do not go down to the lowest depths. Whales live deep—astonishingly deep, when the pressures upon them are considered. They have peculiar reticulations of their plood-vessels which may serve to ease off the bubbling of gas as they rush up to the surface again after a prolonged submergence. The Greenland whale, says R. W. Gray, can get down to 800 fathoms, the best part

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