Читать книгу The Science of Life; or, Animal and Vegetable Biology - J. H. Wythe - Страница 6

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LIVING MATTER.

You may bury me as you choose, if you can only catch me. But you will not understand me when I tell you that I, Socrates, who am now speaking, shall not remain with you after having drunk the poison, but shall depart to some of the enjoyments of the blest. You must not talk about burying or burning Socrates, as if I were suffering some terrible operation. Such language is inauspicious and depressing to our minds. Keep up your courage, and talk only of burying the body of Socrates; conduct the burial as you think best and most decent.—Plato’s Phædo.

1. The only unexceptionable characteristic of living bodies is the possession of living tissue, or bioplasm. This may be present alone, as in the simple animal and vegetable forms, or it may exist in association with structure which has been formed by it, and hence called formed material. The bioplasm is nourished by pabulum which is generally furnished in fluid form.

Fig. 2.—Amœba princeps × 150. In various shapes.

2. The old division of bodies into organized and unorganized—the former having organs, or distinct parts, with definite structure, and of special use—is no longer applicable, since there are some living things which have no organs. The Amœba princeps, Fig. 2, one of the most elementary animal forms, is composed of a jelly-like homogeneous bioplasm, capable of indefinite extensibility and of indefinite use. It is so constantly altering its outline that it does not retain the same shape for two successive minutes. It obtains its food by flowing around it, and digests by direct absorption.

3. Of such simplicity of structure are all the primitive forms of vegetable and of animal life, while in bone, cartilage, flesh, skin, or any other structure of the higher animals, we find such simple, jelly-like, living matter, or bioplasm, similar in appearance to the Amœba, scattered in minute particles all through the tissue, and careful observation will show how this living matter is transformed into the formed material of the several tissues.

4. All animals and vegetables have originated from minute particles of such bioplasm. Every dog, horse, man, whale, jelly-fish, oak, cedar, grass, sea-weed, etc., began its existence as a particle of bioplasm. And every tissue and organ, no matter what its form or function, was built up by similar living matter.

5. In the lowest type of animal life (the Rhizopods) the vital operations are carried on without any special organs, as we have seen in the Amœba; a little particle of jelly-like bioplasm, changing itself into a variety of forms, laying hold of food without members, swallowing it without a mouth, digesting it without a stomach, moving without muscles, while the mere separation of a fragment of this jelly, however small, is sufficient to originate another and independent living creature, retaining, or rather repeating, all the characteristic endowments of the original mass. In the higher animals, although the first bioplasmic particle subdivides itself into an aggregation of similar particles or cells, yet there soon appears a structural differentiation of organs for special uses, which is more elaborate and heterogeneous as the type approaches the human structure. A single cell or living particle, however, in any structure is, to all intents and purposes, a living thing, and possesses powers of assimilation, growth, and reproduction, altogether different from the mineral or non-living body.

6. Living matter, or bioplasm, may be considered physically as a peculiar compound of the chemical elements—carbon, oxygen, nitrogen, and hydrogen, called by Mulder Proteine, and by Mr. Huxley and the German histologists Protoplasm, or the physical basis of life. It is nearly identical with Albumen. So far as is known, this combination of elements is always the product of pre-existing, living matter. It has never been produced in the laboratory, and if it were possible for a chemist to manufacture albuminoid matter, or protoplasm, it would be dead protoplasm, and not bioplasm, and would be destitute of vital properties. Other conditions are necessary to vital phenomena besides combination of material elements. Light, heat, electricity, and moisture are all necessary conditions; nor these alone, for with all these existing and active, the protoplasm may not live. Some other factor is essential to life besides matter and physical force, as we said in the last chapter. The term bioplasm is well applied to express matter in its living state, while protoplasm should be restricted to the material itself.

7. The essential phenomena of living matter next claim our attention; or, What can a living thing do which the non-living cannot?

1.) All living things have spontaneous motion. The non-living are passive, and only move by the compelling agency of some external force, but the force which moves living matter is a force which is inherent, and cannot be explained by physical laws. Living matter has primary energy, and can overcome inertia, but the non-living are unable to originate motion. The spontaneous motions of bioplasm, or living matter, are molecular, amœboid, or wandering.

a. Molecular movement. This must not be confounded with what has been called Brunonian motion, from Dr. Robert Brown, who first described it in 1827. The latter is a sort of vibration in small particles suspended in fluid, and is supposed to be caused by currents formed by heat or evaporation. In the molecular movements of bioplasm each particle of the mass seems to be independent of the rest. As the passengers in a crowded street may go the full length of the street, or turn back, or stop and double as many times as they wish, so do the particles move in the mass of bioplasm. Up, down, across, backward, and in all directions—even through each other—do these molecules move, each impelled by its own inherent energy.^[6]

b. Amœboid movement receives this name from its resemblance to the notions of the Amœba, described in the present chapter, Sec. 2. The shape is continually changing, by a portion of the body being projected from the mass, or retracted, or altered in form.

c. Wandering movement is a modification of the latter form. A portion of the bioplasm is projected forward, and along this temporary arm, or bridge, the semi-fluid molecules flow along, and accumulate at the farthest end. In this manner the white cells of blood, which are particles of bioplasm, wander out of the vessels, perhaps by means of stomata, or holes, in the sides of the vessels, into those tissues of the body where they are needed, Fig. 3. These motions are wholly unlike any which occur in lifeless material.

Fig. 3.—Clot of Frog’s Blood, with Migrating White Blood-cells.

2.) Another essential property of bioplasm is growth. The term growth does not mean accretion or addition of material, nor increase of size. A piece of chalk, or a bank of mud, or any non-living thing, may increase in size by additions to its material. Growth in a living thing is different. It is enlargement by nutrition, and depends on inherent motion. In Chap. I, Sec. 13, it was stated that hair would grow on a corpse, but the term grow was used in a popular, and not scientific, sense. Hair is not a living part of the body. Hair or nails may be cut or destroyed without sensation or impairment of the body. They consist of scales of formed material, pushed forward by the growth of bioplasm behind them. If you pull out a hair or nail, you reach the quick—that is, the living or sensitive part. We thus see that some parts of our body are alive, and others in a non-living state. The formed portions never grow, but the bioplasm, or living matter, grows. The growth of living matter is by appropriation and transformation. Bioplasm “alone, of all matter in the world, moves toward lifeless matter, incorporates it with itself, and communicates to it, in some way we do not in the least understand, its own transcendentally wonderful properties.” This motion and incorporation and endowment constitute growth.

“The rootlets of the plant extend themselves into the soil because the living matter at their extremities moves onward from the point already reached. The tree grows upward against gravity by virtue of the same living power of bioplasm. In every bud portions of this living matter tend to move away from the spot where they were produced, and stretch upward and onward in advance. No tissue of any living animal could be formed unless the portions of bioplasm moved away from one another.”^[7]

3.) Living matter has also the power of nutrition, or assimilation by selection. As this is connected with growth, we might have considered it under that head, but since writers of the mechanical or materialistic school attempt to account for it on physical or chemical principles, we deem it best to examine it separately.

The non-living always enlarges by accretion from similar material; the living tissue takes into its interior material which it transforms out of pabulum, which is foreign to its own structure, while at the same time it discards such molecules or atoms as are unfit for further use.

The chemical composition of the various tissues of the body cannot be found in the blood, or pabulum, which nourishes the tissues, but results from metamorphosis, or transformation, by means of the bioplasts. Endosmose, or the physical property by which fluids pass through membranes, or gummy matters, will not account for it, since in the latter there is no change of material, while in nutrition there is rearrangement of the atoms in the tissue-molecules.

Nutrition has sometimes been compared with crystallization, but crystallization is a deposit of material from a solution of similar substance, and is altogether different from nutrition by transformation and selection.

Nutrition has also been compared with a chemical phenomenon called catalysis. In this, chemical change takes place because of the presence of a substance which remains itself unaffected, as when spongy platinum induces the combination of oxygen and hydrogen gases. In catalysis the third substance neither gives nor takes from the excited body, but in nutrition the living matter itself selects appropriate chemical elements from its pabulum, dissolving their former affinities, and recombining them in a manner which no non-living substance can do. There is no third substance present which is known to us, and all the phenomena are peculiar to living matter, or bioplasm.

4.) Bioplasm can also transmit vital power to its progeny. This property will be considered more in detail in the next chapter, on Parentage.

8. The peculiar relations and changes of the chemical elements in bioplasm prove it to possess some power different from not-living matter, whose actions or results no chemistry can predict. We have said that bioplasm consists chemically of oxygen, hydrogen, carbon, and nitrogen. Other unessential elements may also be present in some cases. But we cannot tell how these elements are combined, if, indeed, they are combined at all in the proper sense of that word. As all bioplasm presents the same appearance, although differently formed material results from its transformation—different in physical properties and in chemical composition—as muscle, nerve, bone, etc., it is probable that the elements do not combine at all as in inorganic matter, but that the ordinary affinities are suspended or modified by vitality.

Bioplasm is a semi-fluid substance, yet it will not freeze at 32° F., as water does, showing that in this respect it is different from water.

Bioplasm is in a state of constant molecular change, or unstable equilibrium, since it is constantly receiving pabulum and transforming itself into formed material, so that it is doubtful if chemical combination is possible during life, the atomic activities being too transitory for combination.

When change takes place from bioplasm into formed material combination occurs, but the formed material is not living tissue, or bioplasm. The life is gone. It is dead, as if it had never formed part of an organism, although it may have acquired special properties, as the elasticity of muscle, or the conducting power of nerve tissue.

If the change referred to occurs suddenly, that is, if the life of bioplasm is suddenly destroyed, the result is water, albumen, fat, and sometimes fibrin, and certain salts, as chloride of sodium, etc.

In slower transformations, which are equivalent to slow molecular death, different materials result, as fat, sugar, milk, biliary acids, etc. Free oxygen is sometimes absorbed, and very complex compounds result, often baffling analysis.

Physiological Chemistry has traced many of the results of changes in formed material, but the composition and physical surroundings of germinal or living matter will not indicate the nature of its transformations nor its function. No one can tell whether a particular bioplast belongs to a vegetable or an animal, whether it will form an eye or a finger, a nerve or a piece of bone, nor whether its function shall be secretive, excretive, elastic, or conductive. Nothing but observation can tell its future life-history.

9. Although all bioplasm has powers or endowments which transcend all physics and chemistry, and which can only be accounted for by that dualistic philosophy which acknowledges the reality of both matter and spirit, yet “all flesh is not the same flesh.” There is an original and essential distinction between bioplasts. The bioplasm of a fungus never produces a fish, nor that of a butterfly a man. This will be fully discussed in the chapter on Parentage. Yet it is no easy task to discriminate between living forms, especially in what are called the lower orders. It is difficult to distinguish in all cases between animals and plants. In the simpler kinds the characters touch and dissolve into each other, so that no exclusive definition is possible. Some naturalists think that there are organisms which at one period of life are vegetable, and at another animal.

10. If we consider their origin, both animals and plants begin life as a small particle of bioplasm. In plants this forms an ovule, with wall of cellulose, and in animals it becomes an ovum, or egg, with wall of albuminous matter.

Fig. 4.—Sertularia Operculata.

11. As to form, we have no means of separating animals and plants. The zoospores of Algæ are like Infusoria. Sea-mat (Flustra) and Sea-moss (Fig. 4) (Polyzoa) are like Sea-weeds, (Algæ,) Corals and Actiniæ are like flowers.

12. In chemical composition, as a rule, plants are destitute of, and animals are largely supplied with nitrogen. Yet there are some animal structures without nitrogen, and some vegetable structures with it. Cellulose, (woody fiber,) generally found in vegetables, is wanting in the Fungi, and is found in the covering of Ascidians, (Sea-squirts.) Starch, under the name of Glycogen, is found in the liver and in the brain. Chlorophyll, which makes the leaves of vegetables green, is found among animals, as in Stentor, (the trumpet-shaped animalcule,) and in Hydra viridis, (the green hydra.)

13. As to locomotive power, bioplasm is essentially active, as I have described, both in plants and animals. The zoospores of Algæ are covered with cilia, and move in water like animalcules. Motion is common among Diatoms, Desmids, Oscillatoria, and other classes of plants, while Sponges, Corals, Oysters, and Barnacles are largely destitute of locomotive power.

14. With respect to food, plants live generally on mineral or inorganic matter, chiefly water, carbonic acid, and ammonia, while animals require ready-made organic compounds to support life. Thus plants manufacture and animals consume organic pabulum. Yet Fungi, which are generally classed with vegetables, feed as animals on organic matters, and insectivorous plants, as Darwin has shown, feed on animals.

15. Animals generally possess sensation, consciousness, and volition, yet there is a kind of sensation in the sensitive plant, Venus’ fly-trap, etc., and something like volition in zoospores, or they would often collide in the active dance they keep up. Plants need rest as well as animals. Both have their epidemics, poisons, and remedies.

16. If we admit a dualism, or spiritual cause of life, in vegetables, as well as in animals, it does not prove them immortal. Immateriality does not imply immortality. Existence, spiritual or material, depends on the will of the Creator, and we can only know the future as he has revealed it.

“Heaven from all creatures hides the book of Fate,

All save the page revealed—the present state.”

17. Our study thus far impresses us not only with the truth that all living things manifest a dualism, but also that all living are intimately related. Not that all come from a single germ, or from a few germs, but that animals and plants form, after some sort, a common family. From the great Father and Fountain of life all living things proceed, and their existence and endowments are according to his will. Immaterial, or spiritual existences weave for themselves a beautiful garment from the inorganic world. The plant bioplasm appropriates mineral matter, with carbonic acid, water, and ammonia, and by a wonderful vital chemistry transforms it into organic compounds, as starch, sugar, gum, albumen, etc. These compounds afford pabulum to animal bioplasm, and are transformed to blood, muscle, nerve, and other complex animal substances. After these transformed products have served the purposes of animal life they are discarded, and return again to the mineral world. Thus the wonderful wheel of life revolves from age to age under the watchful care of divine Providence.

18. The intimate relations of living things may find a mathematical illustration in the logarithmic spiral, such as is described by a ship sailing N. E. at an angle of 60° from the pole. It is the spira mirabilis of Jas. Bernouilli, who desired one to be engraved on his tomb, with the motto: “Eadem mutata resurgo”—”I rise the same, though changed.” It is a spiral which has the same character in all its parts, and which may continually decrease in the size of its windings without coming to a point, or increase the number of its convolutions to infinity. Such a spiral may illustrate the continuity, yet varying amplitude, of creation. We may trace the progressive windings of creative power from the motions of inorganic bodies in space to the motions of bioplasm in the vegetable world and to the higher nerve-structures of animal life. In all organic matter we see the workmanship of the same Great Artist:

“Lo! on each seed within its slender rind

Life’s golden threads in endless circles wind;

Maze within maze the lucid webs are rolled,

And, as they burst, the living flame unfold.”

In exact truth, however, each widening circle of creation exhibits some new and higher form of creative power and skill. The circle widens, and is also in another plane. Something has pushed forward the center. Every spiral requires a progressive force, as well as a centripetal and centrifugal one. Each specialization—either elevation of type or specific difference—involves new force-expenditure. Certain factors have been successively added. First, we find inorganic matter, of many kinds, or of a single kind. Next, the physical forces, so-called, but really the activity of a personal Creator on the matter he has formed. Then we find life, or the activities in matter of created spirits in most wonderful gradation. Rising to another plane we find added to this life mind-force, or intelligence. Still higher we find spirit, properly so-called, possessed with moral properties, giving dignity to men and angels. Yet the spiral is not broken, it is but expanded, and the analogies and relations have a distinctive similarity, since they are equally the work of one God and Creator of all. As the physical forces, by attraction and vibration, and conservation, arrange the cosmos, or physical universe, so the various bioplasts weave the living tissues for the living creature—the microcosmos—and so the conscious acts of our spirits weave the character of our future life.