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IV.

CONCERNING PROTOPLASM.

THE nature of that curious collocation of actions we commonly denominate "life," and the connection which exists between life and the bodies it invests and whose interests it directs, have ever formed subjects of extreme speculative interest to cultured mankind. In the classic ages such speculation was rife, and modern biology but repeats the procedure of the ancient world, when, with additional sources of knowledge and wealth of research, it proceeds to discuss anew the great question of the origin and nature of life. Each year brings its own quota of detail and argument concerning this important and fundamental matter of modern life-science, and in more than one aspect it may be said to be the pivot around which the research of to-day turns. The subject of the origin of species, itself a burning question of biology, leads directly backwards to the origin of those powers and properties in virtue of which the species retains its hold on the world, and which lie at the root and foundation of the universe of animals and plants. Investigate the development of a living being, and you are led directly backwards to the germ from which it springs, and to the consideration of the power in virtue of which the shapeless evolves the formed, and the general grows to become the special. Study the differences and distinctions or the likenesses and resemblances that biology brings to view between animals and plants, and you will inevitably touch upon the subject of the nature of the common life which invests both regions of living beings, and which even in its most varied aspects appears to present features of strange and confusing identity between the animal kingdom on the one hand, and the plant creation on the other. Pass to consider "the records of the rocks" themselves, and in due course the question of the first beginnings of life on our planet-the when, whence, and whither of vitality-will crop up like some unperceived, but felt, presence, which hovers around the biological arcanum. The subject of life and its nature thus awaits us at the beginning of existence, as it faces us at its close. We cannot therefore feel surprise that of all questions of philosophy the nature of life should be deemed the most important, and that those who sit in high places in temples biological should so often dwell upon its varied aspects as a fit and proper theme for philosophic consideration by both gentle and simple, learned and unlearned, in scientific ways.

The investigation of life from any point of view leads us to seek in the lower confines of the living worlds, the subjects which are most likely to present us with the simplest and most elementary manifestations of living force. The life-history of the higher animal and plant appears before us as the acme of intricate operations, and as a complex collection of manufactories and organisations, the working of which may well puzzle and perplex us even in its plainest details. The mere study of a single function in the higher organism is beset with difficulties of greater or less kind. The circulation of the blood, the elaboration of sap-not to speak of the problems involved in considering animal and plant sensibility and the functions of nerves-are illustrations of points in the history of the high animal or plant which involve problems of well-nigh inexplicable nature in their study. Hence the prevailing tendency in research of the kind before us has been indicated by the selection of the lowest fields of life as the ground best adapted to yield promising results to the scientific inquirer. The lower animal or plant, as we shall presently see, makes its appearance before us as a body apparently of extremely simple structure and nature. Presenting us at the most with the appearance of a single "cell "(Fig. 19), the lower organism might be thought to yield to scientific scrutiny some clear knowledge of the nature of the powers which rule its destinies. And such a supposition might likewise be presumed to gather strength in the hopefulness of the idea that, as the higher animal or plant is but an aggregation of units, each representing the single "cell" of lower life, the study of the low organism should reveal to us, as by deputy, the secrets of the higher organisation. But the problem is hardly resolvable into conditions such as have just been indicated. The living being in higher life is not a mere collection of units, the disposition of which can be mathematically calculated and mechanically analysed. The conditions which might well enough bound the discovery of the mechanical contrivances of mankind, are not those which environ the puzzle of life. The problem which faces us as we gaze at the complex organism with its multifarious functions, is just as recondite as when, by aid of the microscope, we can look through and through the speck of protoplasm which seems hardly to warrant the term "animalcule " bestowed upon it. Thus the mere environments of the problem of living and being, constitute a difficulty of no ordinary kind, and hedge the nature of the life which is in the animal or plant with a mystery that appears to loom darkly enough, even before the shining lights of these latter days.

Although the solution of the problem concerning the nature of life may be said in some respects, therefore, to have gained but little aid from researches into the lower worlds of life that people the stagnant drop-beings which find a home in dimensions that

would hardly have contained even the convenient Angels of the Schoolmen, whose ability to accommodate themselves within the limits of the minute is matter of common knowledge-still the extension of biological knowledge concerning lower organisms has been fraught with importance in certain easily discernible ways. If we have not been enabled to shout out "Eureka" to the waiting races of to-day, we have nevertheless gained some useful ideas regarding the true directions in which our difficulties must be attacked. Through the comprehension of what the lowest animals and plants are, we have been led to form certain reasonable ideas concerning what life may be. The knowledge of the conditions required to perpetuate the normal existence of living beings, has led us to recognise, in some measure, the true nature and extent of the problem that awaits the fuller knowledge of coming years for its solution. Let us, therefore, in the first place, endeavour briefly to gain some adequate ideas concerning the conditions or environments demanded. for the exhibition of life in its lowest grades; since, haply, we may find in such a study a clue which may lead us towards the understanding, in theory at least, of the nature of the forces which make and control the living organism. One of the first decided steps towards the simplification of a theory of life was taken when the living contents of vegetable cells were discovered to present a striking similarity to the substance representing the essentially living part of the cells of animals. Mulder thus recognised the vegetable protoplasm, as he termed the soft, gelatinous matter of the vegetable cell; and Remak in turn described the animal "protoplasm." Needless to remark that this substance, described as locked up within the cells or units composing the tissues of the higher organism-animal or plant-and as constituting the active or vital parts of every living being, was identical with the matter, closely resembling white of egg in appearance, which Dujardin had named "sarcode," and of which the bodies of the lowest animals are entirely composed. Max Schultze had indeed shown that the protoplasm of animals was chemically and microscopically indistinguishable from that of plants; and that beneath the variations of form, and the diversities of life, there thus remained a curious uniformity of substance in living organisms. The life and growth of the animal was seen to depend on a substance which was apparently identical with that constituting the living basis of the plant. A curious community of substance was thus proved to underlie wide and apparently irreconcilable differences of life and habit; and out of this primary fact grew new and bolder conceptions of the nature of life than had before been ventilated by biologists at large.

To appreciate clearly and fully what is implied by the statement that the substance now widely known as "protoplasm " is a sine quâ

non for the manifestation of life and vital action, let us examine a few of the aspects in which this substance makes its appearance as the medium for the exhibition of living actions. It is by no means unusual to find that familiarity with a name in the abstract implies a total inability to appreciate the concrete aspects of the substance which the name describes. Despite the wide acceptation of the name "protoplasm," it is matter of common observation that the nature of the substance itself, as well as its qualities and traits, are frequently unknown by those to whom the term is as a "household word." As a preliminary study, then, the discussion of protoplasm itself, and its varied phases, will not be without its value in the determination of its importance as "the physical basis of life." What protoplasm is, chemically and physically, may be very briefly and readily described. Chemically, it stands as the type of a class of compounds to which Mulder gave the name of "proteine" substances. Of such substances, common albumen seen in white of egg is a familiar example; and white of egg, indeed, hardly differs, save in minute chemical particulars, from protoplasm itself. The latter substance is resolvable by chemical analysis into the elements carbon, hydrogen, oxygen, and nitrogen, along with mere traces of sulphur and phosphorus. Physically, protoplasm presents itself as a clear, viscid, and semi-fluid substance, often highly granular from the presence within its substance of fatty or other particles. By immersion in a carmine solution, dead protoplasm may be stained deeply, whilst living protoplasm resists all such contact with colour; and when we have added that protoplasm can be made to contract under electrical stimulus, and that it coagulates at from 40° to 50° Cent., we shall have completed our examination of its readily observed properties.

Let us now turn to consider some of its living aspects and characters. The low-life deeps which it is the province of the microscope to explore, present us with a suitable starting-point for our

FIG. 20.-AMBA.

b

inquiries; and the stagnant pool, or decomposing infusion, may be made to render from their unsavoury depths the means for scientific sweetness and light. Wandering, in its own erratic fashion, ever in search of

fields and pastures new, stumbling over the fragments of weed that lie in its miniature path, and presenting us with a substance which may be paradoxically described as exhibiting every con

ceivable form, or as possessing no definite shape at all, we see the animalcule known as the Amaba (Fig. 20)—a form which has had the honourable distinction of providing a most typical illustration of lower life for all stages of biological teaching and instruction. The name Amaba signifies change. Of old, the being in question, drawn from the stagnant drop, and placed under the object-glass of our microscope, was named the "Proteus animalcule; and its more modern cognomen testifies to the same characteristics of alteration and change described by the Protean simile of former days. A mere microscopic speck is the being before us, its size being measurable only in the hundredths of an inch. It will require some diligent looking ere its transparent body be clearly discerned. For it seems now and then to merge into the water amid which it lives and moves, and appears frequently to fade away into physical nothingness, just as in the sense of its vitality it may be said to hover on the verge of existence itself. When the eye lights upon the Amoeba, and becomes accustomed to the dim outlines it exhibits, we are enabled likewise to note the prevailing characteristic of the animalcule in the continual tendency to well-marked physical change and contraction which its body exhibits. At no one period can it be described as exactly resem. bling its look or appearance at any previous stage of existence. Each moment brings new changes of shape (Fig. 20, b) and transmutations of outline. Now it has launched forth its soft body in one direction until it appears in a long-drawn-out line; now it has drawn this same body forwards, and has protruded its soft substance on each side into so many processes, that it resembles some solitary island with capes, headlands, and promontories jutting out in a sea of its own.

We note an animalcule, of, it may be, higher organisation than itself, to approach the Amoeba. There is a momentary contact of the foreign body with the soft protoplasm of the Amoeba, and instantly the latter extends its frame outwards so as to encompass the living particle, which is shortly engulfed within the contractile mass. Protoplasm is thus seen to live on protoplasm-a procedure which, by the way, in higher animal life is exactly repeated and imitated in its essential details. By this process of surrounding and enclosing its food-particles within its body, our Amoeba obtains its nutriment; and one may well imagine the horror which the appearance of this gelatinous monster, engulfing, like some formless octopus, all that came in its way, would excite in lower life, were the processes of thought and thinking extant among the animalcular worlds. Thus, also, we see how the Amoeba, like so many of its near neighbours, nourishes itself in the absence of a mouth and digestive system; feels, whilst it wants even the first beginnings of nerves; and moves, despite the fact that no organs of motion are developed. Watch the food-particle that has just been enclosed within the soft frame, and in due time you

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