Science from an easy chair / by Sir Ray Lankester.

  • Lankester, E. Ray (Edwin Ray), Sir, 1847-1929.
Date:
1916
Catalogue details

Licence: In copyright

Credit: Science from an easy chair / by Sir Ray Lankester. Source: Wellcome Collection.

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    similarly portrayed, for there is a range and variety of expression in those who sleep, not perhaps as extensive, but as beautiful as that to be found in those who are awake. All things on the earth may be said (if we use the term in a wide sense) to sleep, for all are affected by the stimulation to activity caused by sunlight and by its cessation during night. It is only of late years that we have come to know of fishes, crabs, worms, and star-fishes (many of them without eyes) which live in the depths of the ocean, where no light penetrates and it is always night. The ultimate source of their food is in the upper sunlit layers of water, to which they never penetrate, and from which particles of dead but nutritious matter (the bodies of those who have lived up there) rain down upon them incessantly, like manna on the Israelites. All things accessible to the sun’s rays are not equally, nor even similarly, affected by the alternation of day and night, and some not directly at all, but only by the sleeping and waking of other things. The food of all living things comes ultimately from plants which, in the presence of sunlight, and only in that presence, and in virtue of its action upon their green leaves, manufacture starch and sugar from the carbonic acid which exists in the air and water around them, whilst they are also thus enabled to take up nitrogen, and so to form their living substance or protoplasm. At night those particles or cells of the living protoplasm of plants which are furnished with transparent green granules, so as to entangle the sun¬ light, and by its aid feed on carbonic acid, cease this work. They necessarily repose from their labour because the light has gone. This is the simplest example of the sleep of living things. And that here, too, as in higher creatures, sleep is not a merely negative thing-— a mere cessation—is shown by the fact that it is at night that other changes go on in the plant. The manufactured food takes effect on the cells or particles nourished by it; in the night the well-fed, enlarged “ cells ” in the growing parts of many plants slowly divide each one into two, and each of these again into two, and so on, so as to increase their total number