Outlines of evolutionary biology / by Arthur Dendy.

  • Arthur Dendy
Date:
[1912]
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of evolutionary biology / by Arthur Dendy. Source: Wellcome Collection.

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    that living matter differs fundamentally from not-living matter in chemical or physical characters. On the contrary we recog¬ nize in it exactly the same chemical elements—or rather some of them—^as we find in other constituents of the earth, and these elements appear to obey precisely the same chemical and physical “laws” in both cases, but in the living body they are associated and combined with one another in such a manner as to give rise to substances much more complex than any found outside the animal and vegetable kingdoms, and possessed of peculiar properties which raise them to an altogether higher plane of existence. The complex substances in question con¬ stitute protoplasm, which is the one essential constituent of every living thing, upon the peculiar properties of which the life of the organism depends. We may begin our investigations into the nature of this life by examining the well-worn but none the less valuable analogy of the flame of a candle. Chemists and physicists have taught us that flame consists of incandescent matter, raised to a high temperature by the process of combustion, or chemical union with the oxygen of the atmosphere, and that the flame can exist only so long as the combustion goes on and a sufficiently high temperature is thereby maintained to render the burning matter luminous, or in other words to produce those vibrations of the invisible and intangible ether which we recognize as light. The flame, then, is the outward and visible sign of certain chemical and physical processes, of the action and reaction between the material which is being burnt and the atmosphere which surrounds it. Similarly biologists have learnt to recognize life as the expres¬ sion of the constant interaction which goes on between the living organism and its environment, or, in the words of Herbert Spencer, “ the continuous adjustment of internal relations to external relations.” So far as we have yet been able to analyze it, this interaction also consists of chemical and physical pro¬ cesses, amongst which combustion plays a large part; but the whole business is vastly more complex than the processes involved in the production of a flame, and so far many of its details have defied analysis. We may vary our analogy by looking upon the body of a living organism, whether plant or animal, as an extremely elaborate engine or machine, whose existence depends upon a perfect
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