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

INTRODUCTION

vehemently asserted arguments of the vitalists—until, in 1828, Wéhler synthesized urea in the laboratory. Since that time our knowledge of the chemistry and physics of the systems that are found in living tissues has developed rapidly. It has been found possible to imitate a number of the properties of living things by means of artificial models. It is at least possible that the distinctive properties of living things depend simply upon the complexity of their molecular organization—in which case, spontaneous generation, under suitable circumstances, is at least credible. But one fact remains, that all the life we know is one continuing sort of life, that all the life which exists at this moment derives, so far as human knowledge goes, in unbroken succession from life in past time, and that the unindividualized non-living world is separated from it by a definite gap. We will return to the questions of its origin and of its separation from nonliving matter at a later stage, after a fuller account of its chemical and physical processes has been given.

§ 3 The Limitation of Life in Space

So far as our certain knowledge goes, life is wholly confined to the surface of the planet Earth and to the few miles above and below its surface. Before we reach the summits of the highest earthly mountains life has practically ceased, and the bottom of the sea is the downward limit of the vital process. Within the earth is lifeless matter, and never in all human experience and observation has there come the slightest intimation of any life beyond our atmosphere. So far as we know, the immensities of space, the other planets, the suns and stars and nebule know nothing of this thing we are studying, this something of which we are a part, that feels and moves of itself and reproduces its kind. It is a unique being, it appears, new and strange ; it is an aggressive continuing being that does as yet but begin in the limitless universe of matter.

There is reason to believe—we shall give some of the considerations later—that life appeared upon this planet thousands of millions of years ago, and that it was confined to warmish saline water. Since then it has extended its range very greatly, in height, in depth, and into cold, dry, and desolate regions. And it still extends its range. It still presses against its limitations.

Within the last few years men have thrust 6

themselves in aeroplanes far above the level of Mount Everest, and that great mountain itself, more than six miles above the sea, was perhaps conquered by G. L. Mallory and A. C. Irvine in 1924. They started from a camp pitched at a height of 26,800 feet on June 6th and never returned. From this camp they were watched high up on the mountain slopes still struggling onward, and then they were hidden by driving mists and never seen again. Dr. Somerville and Lieut-Col. Norton, with infinite pain and suffering, had previously got to 28,200 feet. Somerville suffered horribly from the parching of his throat in the intensely cold and dry air, and Norton, after his return to camp, was stricken with snow-blindness. It is probable, but not certain, that Coxwell and Glaisher exceeded these limits in a balloon in 1862, and attained something over 30,000 feet. They were conscious above 29,000 feet. After Glaisher became insensible, Coxwell, by a last effort, pulled the valve cord with his teeth, his hands being too frost-bitten to use. Until recently, the height record for any living thing was the balloon record of Berson and a companion, made in July, 1901. They certainly reached 34,500 feet, but then they became unconscious in spite of their inhalation of oxygen. In November, 1927, this was exceeded by Captain Gray, of the United States Army Aviation Service, who reached 42,470 feet. He lost his life through his oxygen running out as he descended. No other living creature, so far as our knowledge goes, has ever transcended these limits. The condor of the Andes is credited with 23,000 feet by Humboldt. At the higher levels these great birds use the passes, flying low and close over the heads of travellers.

Forty-two thousand feet, a trifle over eight miles, not a tenth of what a fast automobile can do in an hour on the level, but so far it is practically the limit of the upward range of life. Even to win that much demands elaborate preparation and frightful exertion.

Three main wants restrict the living body to the lower levels—deficiency of oxygen to breathe, deficiency of pressure upon the exterior of the body, and intense cold. The Everest expeditions of 1922 and 1924 met the former need by taking up large supplies of compressed oxygen, and the same thing is done in the attempts of aviators to break the height record. Within limits the body of the mountain climber can be gradually educated to the diminished pressure, but the aviator runs great danger of suffering from an extreme form of mountain sickness.