Читать книгу The Science of Life; or, Animal and Vegetable Biology - J. H. Wythe - Страница 5

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WHAT IS LIFE?

Am I but what I seem—mere flesh and blood?

A branching channel, and a mazy flood?

The purple stream that through my vessels glides,

Dull and unconscious flows, like common tides.

The pipes, through which the circling juices stray,

Are not that thinking I, no more than they.

This frame, comparted with transcendent skill,

Of moving joints, obedient to my will,

Nursed from the fruitful glebe, like yonder tree,

Waxes and wastes: I call it mine, not me.

New matter still the moldering mass sustains,

The mansion changed, the tenant still remains;

And from the fleeting stream, repaired by food,

Distinct, as is the swimmer from the flood.

—Arbuthnot.

1. The term Biology, (from the Greek, bios, life, and logos, a discourse, or doctrine,) signifies the Science of Life. It includes the study of all the phenomena of living beings, both animal and vegetable, in order to discover the general principles which underlie their origin, formation, varieties, and functions. The special study of structure is termed Morphology, or Anatomy. The study of functions is Physiology. The origin, development, and arrangement of the varieties of the vegetable world make up the study of Botany. Zoology considers the various kinds of animals. All these sciences, and many others, combine in Biology.

To the Christian student Biology affords a multitude of evidences of intelligent design, proving the universe to be the product of Supreme Will. It also contains proof of the reality of spiritual existences, in addition to physical atoms and physical forces.

2. The cause of difference between the living and the non-living is the most fundamental question of Biology, and the answers given to this question by modern writers depend upon the schools of philosophy to which they are attached.

Much learning and industry have been employed within the past few years to teach the system of Monism, or the theory that all being can be resolved into a single principle. Among those who entertain this view, some hold to materialism, or the development of all forms from primitive atoms. Others are idealists, conceiving matter to be identical with force. Others again are pantheists, holding that mind is the only substance, and that the universe is an emanation of the universal mind.

The doctrine of rational Dualism, which asserts two real principles of existence, mind and matter, with their special endowments and forces, stands in opposition to all forms of Monism whatever.

Since the dawn of history these speculations have divided philosophers, and learning of all kinds has been used to maintain the views of either side. Leucippus and Democritus, the masters of Epicurus, taught the doctrine of invisible and indestructible atoms, with spontaneous motion, as the cause of all things. Anaxagoras and Plato argued for a regulating intelligence, producing order, so that “the world’s activities are reflections of God’s thoughts.” The Hebrew and Christian Scriptures, as well as all other writings which exhibit the religious beliefs of mankind, Koran or Shaster, King or Avesta, (the sacred books of Mohammedans and Hindus, Chinese and Persians,) teach the doctrine of Dualism, or the distinction between mind and matter.

3. The revival of Monistic philosophy in the last century has awakened much discussion, and each of the sciences in turn has been made the arena of conflict. In Biology, Darwin, Spencer, and Hæckel are arrayed against Agassiz, Lionel Beale, and M’Cosh, and the contest of mind has brought to notice a wonderful accumulation of facts, sufficient, we think, to settle the central question of philosophy concerning life.

In the present work the facts of Biology are regarded as confirmatory of the principles of rational Dualism. In the judgment of the writer there is no conflict between science and revealed truth, but such complete agreement that the facts of science can be best understood and explained in consistency with that philosophy which religion has made prevalent in the minds of the majority of men. Yet the learning and apparent candor of many Monistic writers entitle them to respect, even if we fail to agree with them, and truth, which should be the object of all study, is not aided by epithets or personal acrimony.

4. Some scientists ignore the question of the cause of life, and confine themselves to the physical and chemical phenomena associated with living things; but this is quite unsatisfactory. That there are differences between the living and the non-living will only be denied by the most thorough partisans of Monism. These differences depend on something in the living which is absent from the non-living. In common parlance we call it life, or life-force. Such a life-force is as necessary to Biology as gravitation is to Physics, or light to Optics.

Writers who avoid Dualism, or who acknowledge antagonism to it, have not been able to give a clear definition of life.

Bichat defines life as “the sum of the functions by which death is resisted.” This is but saying that life and death are opposite states.

Dr. W. B. Carpenter, although believing in the difference between mind and matter, speaks of life as “the condition of a being which exhibits vital actions;” which is but another mode of stating that life is a condition or state of living.

Coleridge considered life as synonymous with “individuation.” This is equivalent to separate existence, and includes metals, and stones, and all non-living things.

Herbert Spencer defines life as “the continuous adjustment of internal relations to external relations.” This definition will apply to a boiling tea-kettle, a steam-engine, or a burning candle, as well as to a living thing.

Haeckel declares “that all natural bodies which are known to us are equally animated, and that the distinction which has been made between animate and inanimate bodies does not exist.” This exceedingly bold and strange statement is rendered necessary by the logical demands of the Monistic philosophy. In a subsequent place we shall examine particularly the differences between animate and inanimate bodies. (See Chap. II.)

All such definitions and statements evade the real question: that is, What makes the difference between a living body and the same body a moment after death?

5. The cause of life is a mystery only to the materialist. To the Christian philosopher it is as plainly revealed as any other fact of nature. The Bible asserts that life results from the union of a spiritual nature with the material body. In other words, life is the influence resulting from the union of matter and spirit; and this dualistic theory is the only one which suffices to explain the phenomena of living things.

Moses declares of man that God “breathed into his nostrils the breath of life; and man became a living soul.” In accordance with this view death is everywhere referred to in Scripture as a departure of the spirit. The medical evangelist, St. Luke, when describing the resuscitation of Jairus’ daughter, says, “Her spirit came again, and she arose straightway.” St. Paul describes the body as a tent, or house, in which the spirit may be present or absent. It is also remarkable that the same Hebrew word which describes man as a “living soul” is applied to animals in the same history of creation. Gen. i, 20, 30. They also are living souls.

This view of the cause of life was also held by ancient Grecian philosophy. Aristotle attributed organization and vital actions to a series of animating principles, (psychai,) different in each organized body, and acting by power derived from the supreme animating principle, (physis.)

Müller, the father of modern physiology, substituted the term “organic force” for that of “animating principle,” and Dr. Prout used the term “organic agent.” The precise term employed is of but secondary importance compared with the dualistic conception, which is quite satisfactory to the large majority of thinkers.

6. We shall be able to appreciate this subject better if we consider the life-history of some simple animal.

It is well known that infusions of vegetable or animal substances contain many living forms of extreme simplicity of structure, called Infusoria. Many such are found in ponds, or running water, or in the sea. A very beautiful kind of Infusoria, common among half-decayed leaves, has received the name of Vorticella, or bell-shaped animalcule. There are several species, the most common being known as Vorticella nebulifera. Take up from a pond a little twig, covered with mold or mucus-like substance, and place it under the microscope. In all probability you will see a colony of Vorticellæ, (Fig. 1.)

Each animalcule has a glassy, transparent bell, with a thick lip or rim, fringed with cilia or hair-like projections. These cilia are sometimes withdrawn, but when active vibrate rapidly, so as to make a sort of whirlpool in the water, in the vortex of which smaller animals or vegetables may be conveyed as food to the interior of the Vorticella. A number of pellucid spots may be seen in the body of each animalcule, which were formerly regarded as stomachs. Professor Ehrenberg, who elaborately investigated this class of animal life, gave the name Polygastrica (many stomachs) to those animalcules which presented this appearance. By feeding with coloring matter, as carmine or indigo, these stomachs have been found to be merely excavations in the bioplasm, or living matter, which constitutes the body of the animal. Some of these excavations are extemporaneous, but one cavity is persistent, and pulsates in a peculiar manner, so that it has received the name of contractile vesicle. Each glassy bell is attached to the twig by a slender thread, and usually swings to and fro in the water with the thread or footstalk fully stretched, and the cilia moving rapidly. Frequently, however, and especially on some unusual jar, or other cause of alarm, the thread contracts in the form of a spiral, and the cilia are withdrawn into the substance of the bell.

Fig. 1.—a. Colony of Vorticella. b. b. b. Stages of fission, or self-division. c. A separate individual. d. Encysted state. e. Ruptured cyst emitting gemmules in a mass of gelatine or gum. f. Acineta parasites.

These Infusoria usually increase by self-division. The globular bell becomes first flattened, then notched, and lastly divided. As soon as division takes place there are distinct motions in the separate individuals. In one of them the cilia are absorbed, and new cilia appear on the side next to the footstalk. The motions of the new cilia form a current sufficient to detach the newly-formed bell, which becomes isolated, swims away, and develops a new stalk, after fixing itself in a new place.

Another mode of increase sometimes occurs, in which the animalcule seems to pass through a sort of chrysalis state. It becomes encysted, like the primitive forms of vegetables. It is first rounded, then a sort of gelatinous secretion hardens into a case, protecting the interior from antagonizing cold, etc.; then the encysted body breaks up into nuclei, or separate spots, and afterward into numerous gemmules, or small germs, which are set free by the bursting of the envelope, and swim away to grow into new individuals.

During the encysting process the Vorticella often appears like a globular pincushion with pins sticking in it. This is now known to be caused by a parasite, the Acineta, which sends forth a projecting arm into the body of its host to absorb its fluid nutriment.

7. I have selected the Vorticella for a first lesson on Biology because it is quite common, and simple enough for study. What can we learn here of life-force? Is there such a thing as life-force? Is there a difference between the living Vorticella and the dead twig it rests upon? Some philosophers, as we have seen, declare that there is no difference. The old astrologers used to say that all things were living, and the teachers of ancient magic and heathen philosophy taught a universal world-spirit, which is the life of all things. To this pantheistic theory the adherents of the dogma of the mechanical origin of the universe naturally gravitate. It is more consistent with common sense and true philosophy, as well as with the facts of science, to maintain an essential difference between the animate and the inanimate. Can the dead twig move spontaneously, like the living animalcule? Does it assimilate food and reproduce itself like the Vorticella? Or can a dead animal respond to natural stimuli like the living? Not a single fact has been brought forward to prove the identity of the living and the non-living. It is at best only a theory. “On the other hand,” says Dr. Beale, “thanks to the steady progress of minute investigation, unnoticed by popular writers, and perhaps unknown to them, the conclusion that life of every kind is distinct from ordinary forces is at this time more strongly supported by facts, and more firmly established than it ever was.”^[1]

8. In order to defend the Monistic philosophy, and the identity of animate and inanimate objects, some argue that matter has no existence as such, but that each atom is only a center of force. They thus repudiate the charge of materialism, since they teach that every thing is spirit. This is a most subtle and ingenious method of defense, yet is just as baseless as the grosser Monism, which considers all to be material. Newton’s law, of gravity being in direct ratio to the mass of matter, that is, to the number of atoms in the mass, proves atoms to be real physical existences. All chemical science is based on the doctrine that atoms and molecules have weight, definite proportions or relations, and hence definite form. The law of Avogadro and Ampere, as it is called, that “equal volumes of all substances when in the state of gas, and under like conditions, contain the same number of molecules,” is confirmed by all chemical experiments, and necessarily implies the reality of atoms and molecules. Our own consciousness of matter, also, the sense of otherness which pertains to our knowledge of the objects of sense, is as reliable as any other knowledge. We know the otherness, as well as the weight and inertia of matter by the same faculties by which we know that two and two make four, and not five. The obvious distinctions between the living and the not living are all proofs of Dualism.

9. As to the theory that atoms have a physical and a spiritual side, by which opposite qualities are exhibited, it carries its own refutation, since it is plainly impossible for a healthy mind to believe that contrary properties can inhere in any thing at the same time. Mr. Joseph Cook has pertinently said: “If matter is a double-faced unity, having a spiritual and a physical side, there must co-inhere in one and the same substratum extension and the absence of extension, inertia and the absence of inertia, color and the absence of color, form and the absence of form. To assert that these fundamentally antagonistic qualities of matter and mind not only inhere, but co-inhere, in one and the same substratum, is to assert that a thing can be and not be at the same time and in the same sense. This limitless self-contradiction wrecks in this age, as it has wrecked in every age, the pretense that there is but one substance in the universe.^[2]

10. The continuance of life in an organism composed of new atoms, after the old atoms have been cast off, proves that the cause of life does not spring from the atoms themselves. An atom of oxygen or hydrogen, endowed with life to-day, as part of an organized molecule of a Vorticella, or as part of our own bodies, may be to-morrow released from its vital connections, and be transported, as water or air, to remote parts of the globe. It may form part of the gigantic Sequoias of the Sierras, the Cinchona-trees of the Andes, or the Rhododendrons of the Himalayas. Before the death of the original organism, or the tree it next served, that atom of oxygen or hydrogen may be again discarded, and pass into the germ-cell of an animal, or become part of one of the tissues of a man in a distant part of the world. It is evident that that atom did not produce the life with which it was first associated. What may happen to one atom may happen to all the atoms of an organism. In active living beings this actually does happen, so that all the atoms of a living body become disconnected, and return to the inorganic world, or go to serve other organisms, while other atoms take their places, yet the organized body lives on. Its life depends not on the new atoms, for the body was animate before these atoms came; nor does it depend on the old atoms, for it continues after they have gone. It must, therefore, depend upon something different from the material atoms. As matter and spirit are the only objects of thought possible to us, and as life does not depend on matter, it must depend on spirit. If existence and activity continue after the removal of the original matter, as we have seen, they may also continue after all matter is removed. Continued spiritual existence is certainly conceivable, and in view of the endowment of new atoms by the vitalizing force, we must admit it to be probable, even after the material of the organism is all destroyed.

The cause of life is more than matter and physical force. It uses both matter and force for its own ends and after its own laws. “Its power of control over matter and physical laws proves its superiority over, and its distinction from, matter. Life is matter’s master, not its slave. Life is a workman, a builder, a chemist; and each organized being has its own appropriate life, the result of the union of the spiritual and the material in itself.”^[3]

11. The view we have taken of the difference between the animate and the inanimate objects of creation is one which is growing in favor with the principal workers in biological science. Dr. Beale’s discoveries and generalizations in Histology have done much to arrest the skeptical tendencies of scientists, and in one of Mr. Huxley’s latest utterances he acknowledges that “the properties of living matter distinguish it absolutely from all other kinds of things,” and that “the present state of knowledge furnishes us with no link between the living and the not-living.”^[4] The last-named anatomist names the distinctive properties of living matter as follows: 1. Its chemical composition; 2. Its universal disintegration and waste by oxidation, and its concomitant reintegration by the intussusception of new matter; 3. Its tendency to undergo cyclical changes.

Dr. Beale shows that “no relation can be established between the chemical or other material properties of different kinds of living matter that will in any way account for the different results as regards development and formation. The different powers or properties of the particles cannot be due to difference of chemical composition. All living particles consist of comparatively few elements, and no differences in the proportions of these would enable us to explain the different results of the act of living.

“This wonderful stuff, which is the first state of every thing that has life, splits up when it is destroyed into a few chemical compounds, from the study of which, however, chemists have hitherto failed to arrive at any conclusion as regards the atomic relations of the component elements of the matter during life. Neither, as far as has been ascertained, is there any constant relation between the volume, or kind, or aggregation of the matter which is the seat of the manifestation of the vital power and the form of living being that is to be evolved from it. Man’s matter is no more elaborate, no more complex, no more beautiful, than dog’s matter or sheep’s matter; but it is in the power, not in the matter, that we must look for the cause of the remarkable difference of the results. Insignificantly in matter, but transcendently in power, does the man-germ differ from the dog-germ. Wonderfully different power may be transmitted by particles of matter that resemble one another in every particular that can be ascertained.” Again: “It is by the transmission of power to matter, rather than by the bodily transference of millions of particles of matter having particular properties and detached from matter having similar properties, that inheritable peculiarities are handed down from parent to offspring. And it must be borne in mind that structure-forming capacity, which is not even rendered evident until forty or fifty years shall have passed since the original germ-speck originated in the parent, may affect pounds weight of matter, not one grain of which will be acquired until long after every atom of that primitive speck shall have ceased to live and have been removed from the organism. Matter, with its forces, continually comes and goes, while power only remains unimpaired and preserves its identity. Power has been handed down—has been transferred from old particles to new particles of matter; but the original matter—nay, in the case of some of the largest animals, hundreds weight of matter—must have come and gone, while the original power remained.” “Vital power works according to predetermined order, and the results of its working are seen in different consequences, at different periods of its action.” “Vital power prepares for far-off events, and acts as if phenomena, not to occur until after the lapse of a considerable time, had been from the first foreseen. Vital power suspends the action of chemical affinity, and piles material particle above particle, the force of gravity notwithstanding.”^[5]

12. Sometimes life remains dormant from lack of appropriate stimuli, or conditions, or from some unexplained peculiarity. This proves those philosophers to be in error who imagine that molecular change is essential to life. The seed which has been held in the hand of an Egyptian mummy perhaps for thousands of years, retains the vital power, and may sprout under favorable conditions. The wheel animalcule (Rotatoria) has been dried and resuscitated many times in succession, and Messrs. Drysdale and Dollinger have proved that the germs of Infusoria cannot be destroyed by the heat of boiling water, but live when the thermometer shows a heat of 300° F. These resisting germs, floating in the air, will soon revive on the accession of moisture.

13. Death occurs when the cause of life is removed. Life is not synonymous with spirit, but is peculiar spiritual influence on matter; the result of the union of created spirits and elemental matter. When the spiritual essence ceases to act upon the matter of the organism we say the body is dead, and then disintegration and chemical decomposition succeed. There is a two-fold death—the death of the organism as a whole, called somatic, or bodily death, and molecular death, or the loss of vital activity in the molecules of the body. Life begins in a single molecule of bioplasm, and is propagated as a force more or less modified from molecule to molecule, or from cell to cell, as flame proceeds from one combustible substance to another, or as magnetism is disseminated by the action of a single magnet through one bar of steel after another.

Molecular death is a continual phenomenon of life during its activity. It is arrested in dormant life, and is far from being so constant an attendant upon all the actions of the body as some have taught, yet it goes on with great rapidity and uniformity. The bioplasts, or living particles, of each tissue in the body are changed into formed material, and then pass into decay, while other bioplasts take their places and keep up the active dance of life. When the spiritual cause, or origin, of vital phenomena is removed, the molecular activities of the body do not all cease at once, but gradually. Hair will continue to grow on a corpse, and the secretion of rattle-snake poison, or of other glands, continues for a short time after death. Indeed, the circulation of blood has been witnessed in a section of mouse’s kidney some time after it had been removed from the body. Yet, uninfluenced by the energizing spirit, the vital activities gradually cease, and decomposition ensues.

14. To return to our example from the Infusoria, the life-history of the Vorticella demonstrates both the spiritual origin of life and the work of a Supreme Intelligence. The evidence of design in its construction is quite apparent. The extensile threads and vibsatile cilia have, plainly enough, an object. They subserve prehension of food and the preservation of existence. Even the contractile vesicle, whose exact purpose we do not know, impresses our minds with the fact that it serves some purpose. This design is connected with something different from the material atoms of the organism, but which controls those atoms, since there is foresight of future changes, and provision for future changes in the life-history which will occur after the removal of all the present material. The self-division of the Vorticella, the formation of new cilia, the preparation for increase by the encysted form, the division into nuclei and gemmules, are all examples of this, analogous to the formation of new structures in the higher animals. The power to produce these changes is not material but spiritual.

15. Thus our first lesson in Biology brings us to the confines of a spiritual world. We look across the gulf which philosophy and science cannot bridge over except by revealed truth, but the telescope of faith can see realities on the other side as numerous, as diversified, and as true as the objects of sense which can be weighed and measured by our physical instruments. We see also the care and providence of a Supreme Creator. Astronomy adds emphasis to the Psalmist’s declaration, “The heavens declare the glory of God; and the firmament showeth his handy-work.” And Biology indorses the sentiments of his eloquent utterances respecting living creatures: “O Lord, how manifold are thy works! in wisdom hast thou made them all: the earth is full of thy riches. So is this great and wide sea, wherein are things creeping innumerable, both small and great beasts. There go the ships: there is that leviathan, whom thou hast made to play therein. These all wait upon thee; that thou mayest give them their meat in due season. That thou givest them they gather: thou openest thine hand, they are filled with good. Thou hidest thy face, they are troubled: thou takest away their breath, they die, and return to their dust. Thou sendest forth thy spirit, they are created: and thou renewest the face of the earth. The glory of the Lord shall endure forever: the Lord shall rejoice in his works.”