Like these Protozoa, the lowest Metazoa do things which are quite incomprehensible. Here is a sponge formed of classes of monads having among them no internuncial appliances by which in higher types cooperation is carried on – flagellate cells that produce the permeating currents of water, flattened cells forming protective membranes, and amœboid cells lying free in the gelatinous mesoderm. These, without apparent concert, build up not only the horny network constituting the chief mass of their habitation, but also embodied spicules, having remarkable symmetrical forms. By what combined influences the needful processes are effected, it is impossible to imagine.
If we turn to higher types of Metazoa in which, by the agency of a nervous system, many cooperations of parts are achieved in ways that are superficially comprehensible, we still meet with various actions of which the causation cannot be represented in thought. Lacking other calcareous matter, a hen picks up and swallows bits of broken egg-shells; and, occasionally, a cow in calf may be seen mumbling a bone she has found – evidently scraping off with her teeth some of its mass. These proceedings have reference to constitutional needs; but how are they prompted? What generates in the cow a desire to bite a substance so unlike in character to her ordinary food? If it be replied that the blood has become poor in certain calcareous salts and that hence arises the appetite for things containing them, there remains the question – How does this deficiency so act on the nervous system as to generate this vague desire and cause the movements which satisfy it? By no effort can we figure to ourselves the implied causal processes.
In brief, then, we are obliged to confess that Life in its essence cannot be conceived in physico-chemical terms. The required principle of activity, which we found cannot be represented as an independent vital principle, we now find cannot be represented as a principle inherent in living matter. If, by assuming its inherence, we think the facts are accounted for, we do but cheat ourselves with pseud-ideas.
§ 36e. What then are we to say – what are we to think? Simply that in this direction, as in all other directions, our explanations finally bring us face to face with the inexplicable. The Ultimate Reality behind this manifestation, as behind all other manifestations, transcends conception. It needs but to observe how even simple forms of existence are in their ultimate natures incomprehensible, to see that this most complex form of existence is in a sense doubly incomprehensible.
For the actions of that which the ignorant contemptuously call brute matter, cannot in the last resort be understood in their genesis. Were it not that familiarity blinds us, the fall of a stone would afford matter for wonder. Neither Newton nor anyone since his day has been able to conceive how the molecules of matter in the stone are affected not only by the molecules of matter in the adjacent part of the Earth but by those forming parts of its mass 8,000 miles off which severally exercise their influence without impediment from intervening molecules; and still less has there been any conceivable interpretation of the mode in which every molecule of matter in the Sun, 92 millions of miles away, has a share in controlling the movements of the Earth. What goes on in the space between a magnet and the piece of iron drawn towards it, or how on repeatedly passing a magnet along a steel needle this, by some change of molecular state as we must suppose, becomes itself a magnet and when balanced places its poles in fixed directions, we do not know. And still less can we fathom the physical process by which an ordered series of electric pulses sent through a telegraph wire may be made to excite a corresponding series of pulses in a parallel wire many miles off.
Turn to another class of cases. Consider the action of a surface of glass struck by a cathode current and which thereupon generates an order of rays able to pass through solid matters impermeable to light. Or contemplate the power possessed by uranium and other metals of emitting rays imperceptible by our eyes as light but which yet, in what appears to us absolute darkness, will, if passed through a camera, produce photographs. Even the actions of one kind of matter on another are sufficiently remarkable. Here is a mass of gold which, after the addition of 1-500th part of bismuth, has only 1-28th of the tensile strength it previously had; and here is a mass of brass, ordinarily ductile and malleable, but which, on the addition of 1-10,000th part of antimony, loses its character. More remarkable still are the influences of certain medicines. One-hundredth of a grain of nitro-glycerine is a sufficient dose. Taking an average man's weight as 150 pounds, it results that his body is appreciably affected in its state by the 115-millionth part of its weight of this nitrogenous compound.
In presence of such powers displayed by matter of simple kinds we shall see how impossible it is even to imagine those processes going on in organic matter out of which emerges the dynamic element in Life. As no separate form of proteid possesses vitality, we seem obliged to assume that the molecule of protoplasm contains many molecules of proteids, probably in various isomeric states, all capable of ready change and therefore producing great instability of the aggregate they form. As before pointed out (§ 4), a proteid-molecule includes more than 220 equivalents of several so-called elements. Each of these undecomposed substances is now recognized by chemists as almost certainly consisting of several kinds of components. Hence the implication is that a proteid-molecule contains thousands of units, of which the different classes have their respective rates of inconceivably rapid oscillation, while each unit, receiving and emitting ethereal undulations, affects others of its kind in its own and adjacent molecules: an immensely complex structure having immensely complex activities. And this complexity, material and dynamic, in the proteid-molecule we must regard as raised to a far higher degree in the unit of protoplasm. Here as elsewhere alternative impossibilities of thought present themselves. We find it impossible to think of Life as imported into the unit of protoplasm from without; and yet we find it impossible to conceive it as emerging from the cooperation of the components.
§ 36f. But now, having confessed that Life as a principle of activity is unknown and unknowable – that while its phenomena are accessible to thought the implied noumenon is inaccessible – that only the manifestations come within the range of our intelligence while that which is manifested lies beyond it; we may resume the conclusions reached in the preceding chapters. Our surface knowledge continues to be a knowledge valid of its kind, after recognizing the truth that it is only a surface knowledge.
For the conclusions we lately reached and the definition emerging from them, concern the order existing among the actions which living things exhibit; and this order remains the same whether we know or do not know the nature of that from which the actions originate. We found a distinguishing trait of Life to be that its changes display a correspondence with co-existences and sequences in the environment; and this remains a distinguishing trait, though the thing which changes remains inscrutable. The statement that the continuous adjustment of internal relations to external relations constitutes Life as cognizable by us, is not invalidated by the admission that the reality in which these relations inhere is incognizable.
Hence, then, after duly recognizing the fact that, as pointed out above, Life, even phenomenally considered, is not entirely covered by the definition, since there are various abnormal manifestations of life which it does not include, we may safely accept it as covering the normal manifestations – those manifestations which here concern us. Carrying with us the definition, therefore we may hereafter use it for guidance through all those regions of inquiry upon which we now enter.
CHAPTER VII.
THE SCOPE OF BIOLOGY
§ 37. As ordinarily conceived, the science of Biology falls into two great divisions, the one dealing with animal life, called Zoology, and the other dealing with vegetal life, called Botany, or more properly to be called Phytology. But convenient as is this division, it is not that which arises if we follow the scientific method of including in one group all the phenomena of fundamentally the same order and putting separately in another group all the phenomena of a fundamentally different order. For animals and plants are alike in having structures; and animals and plants are alike in having functions performed by these structures; and the distinction between structures and functions transcends the difference between any one structure and any other or between any one function and any other – is, indeed, an absolute distinction, like that between Matter