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It is the view that each living being, in addition to possessing those properties of which the senses inform us, also possesses, or rather is, a unifying principle, “a principle of individuation" which altogether escapes the cognizance of our senses, though reflective reason agrees with common sense in assuring us that it is by it that an animal concentrates into one mental centre the multitude of impressions made simultaneously and successively upon its various organs of sense.
This view, at once popular and philosophic, has of late years received a remarkable adhesion from one who has been amongst the foremost advocates of a mechanical conception of nature. We refer to the German philosopher, Hermann Lotze, a man free altogether from theological or other prejudices or prepossessions. Moved alone by a profound and patient exercise of his reason, he has come to enunciate in the most uncompromising way that view (so long ago maintained by Aristotle), the existence in each living being of a “ Psyche”-a term most difficult to render into our own tongue because of the misleading connotation of the word "soul," which is its nearest English equivalent.
The existence of such an internal principle in ourselves, is the most certain object of all knowledge. It is conceivable that we may doubt as to the existence of our body, but it is absolutely impossible to doubt the existence of a something which is actually thinking and feeling, and which recollects more or less of its own past. This knowedge, as to our own nature, enables us to conceive the existence of a principle of individuation in other living beings, though we can never imagine such a thing, which, as Lotze says, is as impossible as to know how things look in the dark.
The recognition of the existence of this principle, however, is a matter of philosophy, or pure science, and not of mere physical science, which must ignore it, since it cannot rise to its recognition without going beyond its own province, which is nature, as cognizable to us in and by our senses.
Nevertheless, physical science may serve to confirm the teaching of philosophy, inasmuch as the whole tendency of modern researches is to show that living creatures do not arise except from antecedent living creatures and refutes the notion of “spontaneous generation.” We have no disinclination to believe in spontaneous generation; we confess, it has been with reluctance that we have found ourselves forced by experimental evidence—especially by the evidence adduced by M. Pasteur, to whom we are all so greatly indebted—to reject all belief in it.
According to our present knowledge, then, a great gulf yawns between the living world and the world devoid of life—a gulf which nothing we can imagine seems capable of bridging over. It is true
that certain physicists think that though spontaneous generation cannot take place now, it must have taken place a long while ago; but if asked why they think this, they have no reply but that they cannot otherwise imagine how living creatures could have ever come to be! But we have had no experience of creatures “coming to be.” No wonder, then, if we cannot imagine it; for we can imagine nothing of which we have not had sensuous experience. The wisest course, I venture to think, is at present to say that physical science affords us no ground for affirming anything one way or another about the mode in which living things came to be, though it affirms the fact that all our experience is against the spontaneous origin of living things.
If this conception, that the essential, intimate nature of living things is something beyond the reach of the senses, commends itself, on reflection, to the reader's reason, he will then see how pregnant with true philosophy, and how essentially sufficient, is the popular, common-sense reply to the question, “What are animals and plants?" namely, the answer that “they are living things,” in so far as it implies that each has its own principle of individuation and of spontaneous internal activity.
Apart, however, from the acceptance of this view, we have seen that the totality of animals and plants form together a single immense group of creatures, possessing the ten characteristics which we have hereinbefore briefly enumerated, namely, that they are more or less rounded, aqueous, protoplasmic bodies, of very uniform chemical composition-breathing, feeding, secreting, and growing by intussusception, according to definite laws, reproducing their kind by a series of cyclical changes, and more or less able to form habits through their internal spontaneity.
Such is our answer to the first question: "What are animals and plants, as contrasted with substances which are neither the one nor the other ?” It remains to say a few words as to the second question—that concerning the relations of animals and plants, one to the other.
At first sight nothing could seem more obvious than the distinctness of animals from plants; but a very little science soon shows that to draw a distinction is not so easy a matter. Elaborate and recondite distinctions have been, one after another, drawn out, but these have, one after another, broken down, until there remains no one character which can be at the same time affirmed of all animals and denied of all plants (or vice versa), while these two great groups remain such as they are generally taken to be, the creatures known as Protozoa being reckoned as animals; that is, the lowest so-called animals, the bodies of which are not constituted of “ tissues.''
Let us look at these distinctions, beginning with the most obvious:
1. The first of these relates to external form. The predominant branching vegetal form is denoted by the word "arborescent," but many species of the animals (allied to the Corals) are arborescent also, while multitudes of the lowest plants are more or less spheroidal, and some are worm-like in figure.
2. Secondly, locomotion is common to almost all animals, but some are permanently fixed, like plants, while certain lower plants, especially in the earlier stages of their existence, are actively locomotive.
3. Animals generally live on more or less solid food, which they take into an internal digestive cavity. All animals, however, do not do this, notably the Entozoa, while certain plants are said to more or less nourish themselves on captured prey, as is the case with Venus's fly-trap and Dionæa (the sun-dew), while others, as the Pitcher plants, can receive them into a cavity, which is, to a certain extent, comparable with the animal alimentary cavity, since that is, morphologically, but an involution of the external surface.
4. Plants generally contain a greater amount of non-nitrogenous material in their composition than do animals generally, but this distinction is of little avail as regards the lowest forms of life of both groups.
5. Plants generally have a less evident power of forming habits or of responding to stimuli by increased activity ; but this again does not serve as a distinction as regards the lower plants and animals.
6. Until quite recently it could be said that no animals possess that power of liberating carbonic acid and fixing carbon which is possessed by plants; but now it is known that certain worms also exercise this power. Nevertheless, we may still say that plants generally possess the power of feeding directly on the inorganic world and building up organic matter from it, while the animal kingdom has it not; and this difference constitutes what is sometimes spoken of as “the circulation of the elements."
Until the other day it could have been said that with the exception of a lowly species called myxomycetes, all plants were organisms composed of one, few, or many small masses of protoplasm, separated from each other by partitions of a non-nitrogenous substance called " cellulose," while in animals the protoplasmic particles were not so separated. Quite recently, however, it has been found that in some, and probably in very many if not in all plants, protoplasm is continuous, passing by minute filaments from cell to cell, through such cellulose partitions.
With the failure of this differential character, the very last distinction between the two kingdoms, as ordinarily understood, falls
to the ground. We must profess ourselves utterly unable to frame any definition which shall at the same time include all kinds of one of these two groups, while excluding all kinds of the other group.
Nevertheless, it is obvious that there is an immense difference between animals and plants generally—a difference well expressed by that common-sense assertion we quoted at starting, that “animals are creatures which get their living by the help of their senses, while plants are senseless.” Now, this common-sense view accords with the distinction drawn so many centuries ago by Aristotle, that animals feel, while plants do not.
In biology, however, groups are characterized by structure rather than by function, and we know, moreover, that every difference in “function” has some difference in “structure" as its accompaniment. But what is the structure which is related to the function of "feeling"? It is the nervous system. “Nervous tissue" is the "organ of feeling,” and modifications of it, with accessory accompaniments, constitute every organ of special sense, i.e., of sight, hearing, smell, taste, and touch.
Now, no plant is yet known to possess anything like nervous tissue, and the same may be affirmed of the lowest organisms commonly recognized as animals. We know at present no way of defining a plant save the negative one of saying “a plant is an organism which is not an animal,” while the essence of animal life seems to us to be the power of “feeling,” together with its necessary correlation, the “possession of a nervous system.” If, then, we must draw a hard and fast line between the two kingdoms, we see no way left for us but that of transferring to the vegetal kingdom those lower organisms generally reckoned as animals, which possess no nervous systems. To botanists they will perhaps be an unwelcome present, but they can hardly be refused on any valid scientific grounds. The activity and irritability of many of them are, no doubt, very suggestive of animal life, but so are the activities of some of the lowest organisms always recognized as plants-many of the Algæ, especially in their younger stages and reproductive parts, together with such curious plants of prey as Venus's fly-trap and its allies—lately referred to.
We do not, indeed, yet positively advocate, though we regard with favor, such a mode of dividing the two component groups which together constitute animated nature; but we confess that we see no possible manner in which these two predominantly diverse groups of organisms can be divided, if the whole mass of living creatures, which we have seen to be so sharply and distinctly separated off from the non-living world, are to be completely, sharply, and distinctly separated, one from the other.
Thus, we venture to think, may at present best be answered the
two questions with which we set out: (1) What animals and plants are, as contrasted with substances which are neither the one nor the other; and, (2) How animals and plants stand towards each other; the answers to which constitute the only reply we know of to the fundamental question we have taken as the title of this paper: “What are Animals and Plants?”
THE ENCYCLICAL “IMMORTALE DEI."
HERE never, perhaps, was a time when clearness of ideas
was more demanded among Christian nations than at the present day. Protestantism, which, as its name imports, is a rebellion against God's Church, and, as His Eminence Cardinal Newman has observed, can maintain its position only by asserting that the Church of Rome has gone astray, set up its tribunal of private judgment. That tribunal has called before it every question, religious or moral, with the result of a confusion such that the most ordinary and obvious truths are misapplied, distorted, or rejected, while the most pernicious theories of religion and morality are working havoc among our poor misguided fellow-men. It is no wonder this has occurred. At best, as the sacred writer has said: “The thoughts of mortals are timid, and our foresight uncertain" (Wisdom ix., 14). When men deliberately stray away from the fount of living waters, and from the source of truth, they must expect the natural result. Reason, always of its nature liable to err, will then find itself irresistibly driven to conclusions the folly of which will be shown by the practical results. In the midst of the upheaval of society at this epoch, when the masses rise up against legitimate authority, class is arrayed against class, the most sacred duties are disavowed, and the most tender and delicate ties are sundered and the family made desolate, what a blessing to have speak to the world one whose thoughts are not timid, and who, like his Divine Master, gives forth his utterances “as one having authority!” The Encyclical “Immortale Dei,” dated All Saints' Day, of the year 1885, is a boon to the world. Not since the Vatican Council has a more important document issued from the pen of the Sovereign Pontiff. Non-Catholics as well as Catholics recognize its truth, its wisdom, its opportuneness, and its eminently practical utility. The liberal press of Vienna was, we