Elementary biology : descriptive and experimental / by John Thornton.

  • Thornton, John
Date:
1907
Catalogue details

Licence: In copyright

Credit: Elementary biology : descriptive and experimental / by John Thornton. Source: Wellcome Collection.

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    are at least five distinctive co-existing marks that distinguish the objects of the living world from the objects of the non- living or mineral world; that living, in fact, consists of per- forming the processes called feeding, breathing, feeling, and multiplying; and that living matter is a highly complex, assimilating, respiring, moving, sensitive, and reproducing substance. A body showing the phenomena of life and attended by structural changes as a result of its living processes is often spoken of as an organism and as consisting of organized matter. Organism as thus used is equal to living being. The science that treats of organized or living things is called Biology (Gk. bios, “ life,” and logos, a “ discourse ”). The branch of Biology that treats of plants is called Botany (Gk. botane, “ a plant ”), and the branch that treats of animals Zoology (Gk. zooti, “an animal”). 3. A Simple Living Creature.—If we examine under the microscope a drop of water taken from the surface of the mud at the bottom of a stagnant pool, we may often notice one or more specks of a jelly-like substance. These specks are slowly but frequently changing their shape. Each speck, in fact, is of irregular shape, and moves with a kind of flowing motion ; the locomotion being caused by the streaming forward of the substance into projections or processes at some points, and the withdrawal of processes at other points. The tiny object we see is a living creature called an amoeba. Careful scrutiny under a high power of the microscope will show that the jelly- like mass forming the amoeba shows a clear outside and a rather granular interior. There is also seen with a high power a denser central body called the nucleus, and usually a clear space called from its action the pulsatory vacuole. The jelly-like mass of which the amoeba consists is present in all living matter, and is called protoplasm. Such a minute mass of nucleated protoplasm is the unit mass of living matter, and is known as a cell. An amoeba is therefore a living creature consisting of a single cell. Chemically considered, protoplasm
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