Od's Fish
I
THE creatures of the ocean, whether they live in the sunlit waters near the surface or dwell miles deep in the black abysses and move about in light of their own creation, are all dependent for their breath upon oxygen that comes to them from the air above the surface. The water in which a fish swims consists of oxygen to the extent of one third of its volume, but this oxygen is of no use to the fish. The reason is that water is a compound, being made of oxygen and hydrogen in chemical union. Air, on the other hand, is only a mixture, the oxygen in it being uncombined and free, and therefore available for breathing. In order to support life, water must have in it a proportion of oxygen from the air. Which is to say, a fish in pure water would smother to death.
Oxygen penetrates the water at the surface and slowly diffuses through it; and the greater the surface presented by the water, the more rapidly the oxygen is taken up. Thus a fountain throwing up spray in the midst of an aquarium, and exposing its little globules of water on all sides to the action of the atmosphere, rapidly takes up oxygen and replaces that which has been used by the fish. What is done here is simply to give the water larger surface in proportion to its bulk, and to carry the air down where it is needed. So also any upheaval of body of water, such as the ripples on a pond or the billows at sea, presents a larger area, agitates the particles, and facilitates absorption. The vast surface of the ocean, in storm and in calm, is continually taking in oxygen and passing it on to the depths. Thus the ocean is like a universal mother, her great breast heaving and taking breath for all her inward children. And the high-flung surges that come dashing and thundering along the shore, finding rhythm in the winds and answering to the periods of the moon, are heartbeats bringing new life to the helpless creatures that lie gasping on the sands.
But this diffusion of the life-giving gas is very slow, especially in view of the great depths to be reached. It has been calculated that it would take centuries for the oxygen absorbed at the surface of the ocean to penetrate to the depths by mere diffusion. The distribution and mixing are accelerated by the sinking of the highly oxygenated surface water and the rising of that below, owing to differences in density and temperature. In small lakes such as we have in New York, Wisconsin, and Minnesota, this sinking of the chilled surface and the continual rise of the lower water to take its place are such that there is a complete overturning of the water in spring and fall. At these times every drop of water becomes in turn a part of the surface, and may be said to have done its own breathing. In the ocean there is an interchange by means of vertical currents, and the oxygen-bearing water of the surface is thus enabled to deliver its burden to the depths. The ancients, in regarding the earth as a large animal with all the living functions, were making broad use of their imagination; but when we consider that in lake and ocean there is something that corresponds to respiration and circulation, we may say that scientific fact does much to help out the analogy.
The strange lantern-bearing creatures of the depths thus have their breath brought down to them. Not so directly, however, do they get their daily meat. Being carnivorous, they are, of course, quite willing to eat each other, and do; but it is evident that no community can be self-supporting on such a basis. Every animal that dies and goes into dissolution subtracts just so much from the sum total of animal life; and it cannot be replaced except through the medium of vegetation. The growing plant must use the sunlight to transform inorganic matter into life-supporting sugar, and the herbivorous animal must eat the plant and turn it into meat before the carnivorous creature can find a means of support. As these fish live in the cold black depths where no plant can grow, and as they are not fitted to live in the upper world, they would seem to be in a desperate, a really impossible, situation.
Fortunately for the deep-sea dwellers, the fish nearer the surface have a habit of making a daily descent to a point of semidarkness. Like the herds and flocks of the land, they do not like the noonday sun, so they strike downward and find congenial surroundings in the twilight regions of the sea; at the same time the voracious fish that live upon the next lower level come up to eat them; and these in turn become prey for others. Thus the chain of life reaches to the bottom, or at least a distance of three and a half miles, from which depth a live fish has been brought up. This level at which the surface fish meet those from below is the haunt of the giant squid and other strange creatures unfamiliar to upper waters. It is a rich and populous plane amid the levels of sea society.
II
The ultimate basis of life in the ocean is vegetation; but in saying this we need take little account of plants that are rooted to the bottom and are visible along the shore. Plants in a parlor aquarium may be so much a part of the whole as to furnish sufficient oxygen for the water; but in the ocean this sort of plant life is a mere marginal affair. The great pastures of the ocean consist of unattached plants so small that they are utterly invisible. They float and grow in the water as deep as the sunlight penetrates. More than six million of these microscopic plants have been counted in a quart of sea water. They are too small to be seen or felt except as they may change the color of the water and give it a slippery feel. This vegetation is fed upon by crustaceans that are also microscopically small, and these in turn become food for creatures of larger size.
In clear waters of the tropics the sunlight penetrates effectively to a depth of about six hundred and fifty feet, but the distance varies in different localities; and throughout this varying depth the invisible vegetation flourishes. The rich and ample pastures of the land are measured by their breadth, but in the ocean they must be measured also by their thickness. In fresh waters, too, this microscopic vegetation is of first importance in the support of life. In Lake Mendota, at Madison, Wisconsin, on the shore of which I made my home for a while, there have been counted 37,500,000 diatoms to the quart of water. Considering the impalpable fineness of this nourishing material, it is hardly to be wondered at that biologists refer to the fertile water as forming a life-supporting ‘soup.’ To say that three quarters of the surface of the globe consists of vegetable soup might seem like a large order; but the statement is closely engaged with facts.
This view of the nourishing element in sea water brings us to a consideration of its saltness, and then to the saltness of the blood and body fluids in man. The liquid part of the human blood, together with the lymph or intracellular body fluids in general, contains the same inorganic salts as are to be found in sea water, and there is a striking similarity in the proportions. The total concentration of these salts in the animal body is not that of the ocean to-day, but corresponds rather to what the ocean was at a certain stage in its history. The ocean has received its salts from the land. For ages the rivers have been coming down to the sea bearing chemicals in solution and returning to the land again in the form of mist and cloud; and the operation of this giant still has caused the ocean to grow more and more salty. It has been calculated that the total density of salts in man and his kindred animals (down to and including the fresh-water fishes) is the same as that of the sea in Cambrian times; and this is taken as evidence that the ancestors of these animal forms emerged from the sea at that stage of world history. As the body cells had become habituated to that particular fluid medium, the same chemical make-up and total density have been maintained.
A one-celled animal living its free and independent life in the ocean is used to a fluid medium containing three things — bodily nourishment, a proportion of oxygen for burning the fuel, and a combination of salts for carrying on the chemical transformations. Each cell in the body of a man lives under like conditions. It is constantly bathed in such a body fluid. And if this view of his personal construction seems to any man to be a little far-fetched, he will become sufficiently familiar with it in case he has an accident resulting in a considerable loss of blood and is taken to a hospital. In that case the surgeon in the hospital will fill his depleted veins and arteries with ‘normal salt solution.’ It will serve him quite well in the place of blood until nature has had time to make it richer.
And so, from whatever angle we begin the study of animal life, we seem always to be brought around to this theory of evolution. And, whatever attitude one may take toward the theory, the facts remain the same.
Every living cell in the world, whether in the ocean or in a man, can perform its vital functions only in a fluid medium. The fluid must provide oxygen and nutriment, and must contain the salts of the ocean in certain proportions. While man has been living for thousands of years on dry land and drinking fresh water and taking his food as he finds it, his system automatically manufactures this sustenance into a cell-bathing fluid which has the chemical constituents of sea water. The amniotic fluid in which we float before we are born would seem by its saltness to mark us as creatures of ocean ancestry. The very tears we shed, and the sweat of our too-hard labor, are salt with the saltness of the ancient sea.
III
From this it will be seen that every man is a little ocean in himself. His sea water consists of the straw-colored serum or fluid part of the blood, together with the lymph in the body spaces and between the cells, all of it an interchanging body of salt fluid in which the cells must be constantly bathed. He is a container of ocean the size of a small parlor aquarium; and this amount of fluid, hardly sufficient to support a goldfish unless it were artificially aerated, has got to absorb oxygen fast enough to keep his great myriad of cells going. How does nature contrive to keep alive a creature the size of a man in this little, two-legged aquarium?
It is a problem of increasing the surface of the fluid. Because the ocean is of such vast extent, the slow absorption of oxygen at its surface is more than enough to support the living creatures in its depths; but if a fish or a one-celled creature is confined to water with very small air surface, it will soon exhaust the oxygen and die.
In the case of the parlor fishpond, we have seen that a spray of water thrown up into the air and falling back into the main body will serve to keep the fish alive, the finely comminuted particles exposing themselves on all sides and thereby increasing the surface. But this is not the only mechanism that would serve the purpose. If a portion of the water in this little parlor aquarium were spread out in a wide, shallow sheet, and kept flowing back and forth in a constant interchange with the main body of water, the same effect would be achieved. It is upon this latter principle that a man is built. By means of a delicate membrane whose total area is equal to the ceiling of a fair-sized room, the fluid is conducted through fine capillaries so near the surface that every part of it can take up oxygen direct from the air. The effect is that of a large, shallow sheet of fluid serving to oxygenate the main body of salt water. But in order that this large area of membrane shall not take up an inconvenient and impracticable amount of space, it is all gathered together and shaped like thousands of little rubber balloons clustered close together; and yet it is just as continuous a passage for the blood as if it were a flat sheet. These little rubber balloons of the lungs form what are called alveolar spaces, and into each the air finds entrance as we breathe. The lungs are simply the vaster ocean surface for the fluid that bathes the body cells. It is an ingenious means of having a little sea with a great absorbing capacity.
But this mechanism alone is hardly sufficient to serve an active animal; and so there are special red cells in the fluid carrying iron in a form which rapidly takes up and parts with oxygen. This oxygen, together with the nutriment in the blood, reaches its final destination by passing right through the walls of the fine veins or capillaries and mixing with the lymph that bathes the cells. From this fluid the cells take their supply of oxygen simply by their own power of absorption. And so the act of breathing — the mere filling of the lungs — is only the first step in the intricate process of respiration.
As an infant has no need of lungs before it is born, these important organs are packed tightly together, all the little walls of the air passages being in such close contact that the lungs are solid — so solid, in fact, that the lungs of an unborn infant will sink in water. At the time of birth a sudden movement of the chest muscles inflates the lungs, a most powerful and spasmodic effort being necessary to open all the little balloons, whose walls are packed together like a parachute. Once man has become an airbreathing animal, he never has a supply of oxygen more than enough to last him for a minute or two. His little inward sea is always on the point of being exhausted. Hence it is a most venturous moment when the infant kicks loose of its natural support, and inflates its lungs with a mighty effort as it takes off into the world of air. If the automatic mechanism does not work, and the little balloons do not open up, the jump is fatal.
The ocean is able to support all its internal life by mere surface absorption, not because it is so large merely, but because it is so sparsely populated in comparison with the surface. If the water were as close-packed with fish as the body fluid is with cells, it could not be done. This is an important point to keep in mind, because it has to do with some of nature’s most interesting departures in the designing of animal mechanism. A fishworm, for instance, is very like a man in the regard that it has red blood cells to carry the oxygen to the intracellular fluid, and this red is due to the same iron medium that serves in the case of man. But the fishworm has no lungs. Rather the surface of the body gives all the exposure necessary to provide oxygen for so small a creature.
It is an important physical fact that, the smaller the body, the greater its surface is in proportion to its bulk. An orange cut in two has the same bulk as before, but there is much more surface; and these pieces cut in two give still more air exposure in proportion to the total substance. There is a point in the smallness of the animal body at which the outer surface has become so large in comparison with the bulk of body fluid that additional air surface is not necessary. At this point nature may do away with lungs. The heart still needs to beat and the blood to circulate in order to carry the oxygen inward and distribute the nutriment. The pump is retained, but the bellows is no longer needed.
IV
It has been a theory with biologists and physicians that an infant, for some time after birth, respires to a considerable extent through the skin, the blood being so near the surface in the delicate membrane that the red cells absorb oxygen there. If this is true, man lives at first after the manner of a worm. But, whether it is true or not, it is a fact that if man were small enough he would need no lungs. As in a worm, a damp skin could be made to serve.
That the whole vital and active part of man consists of little jellylike cells bathed in a fluid medium like a singlecelled animal in the sea is hard to admit in view of this ‘too, too solid’ body of flesh and bone. But the true conception comes easily enough when we consider how much of a man is alive and how much dead. The hair and nails are quite lifeless. As with feathers and horns, the scales of fishes and the rattles of rattlesnakes, their chemical basis is keratin, containing nitrogen and sulphur. Bone, too, is not life, but mineral matter. It is largely lime and phosphorus. Scattered through it are live cells connected by fine canals; but these cells are the creatures that built the bone, and which are able to repair it if it breaks. Bone is no more alive than is a coral reef, also made of lime, or the hard, calcareous teeth.
Blood, and the body fluid in general, are not alive. A large part of man is that circulating stream of water carrying dissolved food for the cells, together with their supply of oxygen and the necessary assortment of salts — chlorides of sodium, potassium, and calcium, and many others in smaller quantity. It has been said of the ductless glands that they ration out chemicals in the proportion necessary to make the cells think they are still living in the sea. Iodine, sulphur, phosphorus, iron, magnesia, — enough elements and compounds to start a drug store, — all must come floating along in some small quantity in the blood stream. But they are no more alive in the lymph or in the ductless glands than when they are dispersed at large in the sea or standing in bottles on the chemist’s shelf. Neither is fat alive — it is just so much fuel oil and grease stored up for the flay of need; and as for saliva, mucus, tears, and sweat, they are simply products of the laboratory. Life and its mysterious processes are to be found only in those little builders, the cells. One germ cell started out with the original plans for the structure, and its multitude of children built the whole machine, which, in turn, furnishes them with the material of life and work. But this is far from saying that life is a machine. While the body is a machine, the cell is a process. And in or behind this process is the mystery called life.
This sponge which we use to wash the auto is ramified with holes; it has passages for the sea water, in current and excurrent. Impelled by fine hairs which line the passages and work like little oars, the water comes in at this side and goes out at that, and the cells take their nutriment and oxygen from it as it passes. While the sponge needs circulation, it needs no lungs to renovate the inner fluid, for it draws endlessly upon the sea and vents endlessly into it. It is not like us, who must use our little ocean over and over, exhausting its oxygen one minute and renewing it the next. So also with the sea anemone and the jellyfish; their inner passages circulate a life fluid which is nothing more or less than the sea water itself. For animals whose structure is open to it, the sea water is all that is necessary. It is the primitive blood.
When we take the next step in machine design and the animal is shut off from the surrounding medium by a skin that is impervious to water, it is evident that it has got to carry its little ocean in itself. As its oxygenrenewing properties must be quick and efficient, the fluid stream is helped out and made more active by means of metal, either iron or copper. The lobster, the clam, the octopus, and their kindred, use copper. And when we find that the fish in the ocean has a circulating fluid only half as salt as the water in which it moves, and the fish in fresh water is fully as salt as a man and the other vertebrates, it gives us food for thought. Biologists are of the opinion that the difference in saltness marks the time when these animals or their ancestors became shut off from the sea water or moved out of it and began to live on land. From whatever standpoint we study life, — even the most mechanical, — we find ourselves inevitably led around again to the idea of evolution.
V
The long, dry, hot spell of last summer seemed favorable to the spread of certain diseases, especially infantile paralysis; and as I was curious about the operation of a new artificial respirator to be used in the most desperate cases I spent a little time in a hospital observing its workings. The machine consists essentially of an air-tight box large enough to receive the entire body of the patient with the exception of the head, which remains outside by means of a close-fitting rubber collar. A rotary air pump, driven by an electric motor, brings a powerful suction to bear upon the air inside the box, whereupon the patient’s chest dilates in the partial vacuum and causes him to breathe. The pump exercises this pull at set periods, and in the intervals the chest drops back to its inert position while the air is being expelled from the lungs. And so, by grace of a machine age, a man who has been rushed to the hospital from a great distance, and reaches it in a state of collapse, may find himself suddenly at ease while his breath comes and goes in time with the turning of cogs and wheels and valves and switches. It seems to me that man’s highest development as a tool-using animal has been reached when he uses a machine to breathe by. An apparatus of his own creation serves to build an addition to his body and perform his most vital functions!
The patient who has begun to feel accustomed to a body that is operating in connection with the city power plant suddenly finds that a new experience has been awaiting him. If he wishes to carry on a conversation with his friends or the doctor, he has got to talk in time with the machine. If he happens to be in the middle of a sentence when an expiration ends and an inspiration begins, his voice is shut off. He has got to hold his thoughts in abeyance until a reversal comes and his voice is turned on again. His breath is being meted out to fit his physical needs, not his intellectual requirements. This machine is concerned with life and death; it has no regard for the machinery of the sentence, or such intellectual tools as the period, the comma, or the semicolon.
Habitually we do our talking upon the outgo of the breath, and never upon the intake; and we control the expulsion of breath to fit the needs of the statement we have in mind. As for our more vital needs, we let them wait, or else we minister to the physical machine by a quick breath between times. This machine works on the contrary principle; it tends to the physical needs at a regular tempo and lets the intellectual go hang. If the patient tries to get the best of the situation by talking on the intake of breath, — a thing that is not at all impossible, — he will find himself producing eerie whispers and ghostly squeaks such as he would rather not listen to; but if he will content himself with such opportunities for talk as are offered, he will be able to converse about half the time. His output of words will be cut up into portions of uniform length, regardless of sense; and as for the louder and softer tones that enter into the spirit of speech, shaping and modulating the meaning, he has got to accept his motor-driven volume of voice just as it comes from the machine.
Pondering this state of affairs, I could not help having a few ideas in regard to the bodily machine. When we consider the three principal functions of the human mouth, the nutritional, the respiratory, and the intellectual, — food, breath, and words, — it is evident that the intellectual function is only incidentally and carelessly provided for. We do our talking only upon the stream of carbon dioxide that is emitted from the human engine. All our flowery speech and highflung hopes are modeled out of that. It has been well said that we speak only with our poison breath. We talk between times, as it were. If we wish to draw out a sentence to its logical conclusion we must postpone breathing, thus cheating our body of its rights, or take a quick and niggardly gasp of breath in order to gain time.
I hold it to be evident to all men that this is not an ideal way in which to build an intellectual animal. When you consider how much of the cultural and intellectual, of song and oratory and all-important argument, depends upon that mouth, it would seem that the voice ought to have behind it a column of air that is free and unhampered. Nature might easily take a hint from the Scotchman, who, for the fuller expression of his musical and martial nature, has provided himself with an extra lung which he carries under his arm. Indeed, I will venture to say that a man might have been so constructed if the course of evolution had only been different — and if the gift of words, the last step of all, had not been superimposed upon an apparatus that was first nutritional and circulatory, as in a sponge.
I have allowed myself to make these revolutionary remarks in order to pave the way for the most modern point of view of the biologist, which is that nothing in nature can properly be called abnormal. The white crow, the two-legged cat, the lightning calculator, while they might seem to be the products of nature’s most errant fancy, are really her most typical work, which is that of constantly experimenting. In other words, nature has been free to invent; and out of the millions of variations have resulted such living creatures as we have. It has been customary for scientists to say that man is a monstrosity, the greatest in nature; and this is true in the sense that every production of nature has been a monstrosity just to the extent that it was new and different. But I think those naturalists know how to express the thing best who say that nothing in nature is abnormal. And as for any man’s proposal to improve upon nature — that is nothing when we consider that nature has always been improving upon herself.
VI
Another effect of the long dry spell of last summer, together with the hard times, was that here in Wisconsin it became difficult for a man to get bait. While the dry weather sent the fishworms down to depths undiggable, the market for minnows went up; and then the needy and the unsportsmanlike seined the small brooks so thoroughly that there were no minnows left. The dace, the shiners, the sticklebacks, and all the bright little fish that dart in and out of the quiet pools beneath the willows, or shoot like arrows up the sunlit rapids, were to be seen no more. They had been penned up in submerged live boxes by resort keepers and other predacious publicans while the people suffered from a minnow monopoly.
All of which is fundamentally wrong. It is one of the God-given rights of fishermen to catch their own bait. To have to buy it, paying tribute to money changers who sit on hotel porches, is nature’s deepest insult. It is like buying a ticket to enjoy the sun and air.
In this state of affairs I was called upon by my friend Ur, a man whose natural independence may have something to do with the fact that he is eighth in descent from the Salem Amadown. He is a fisherman of such skill that he virtually carries the key to the waters hereabout; and he said he had come to invite me to bear him company on an auto trip. We would go off to deep woods and secret waters entirely out of the ken of these shameless minnow-mongers; and we would bring back with us a supply of minnows sufficient for several days of fishing.
With a capacious milk can in the back part, of the car, we seemed to be accompanied by success both going and coming. But when we got back home and took the lid off the can we found that the minnows were dead. The supply of oxygen in that amount of water had not been enough to keep them going for so long a trip; and one and all had turned their bellies upward. The venture was a failure, except from the standpoint of my thomas-cat, who arrived promptly on the scene and sat down to the banquet that had been spread for him on the grass.
At this point I invited Ur down into my cellar to search for an ancient bicycle pump; and while we turned things over I explained to him all the scientific facts pertaining to oxygen and its use by gill-breathing animals. And I told him how, by merely fastening the bicycle pump to the outside of the can and dropping the end of the air hose inside, we should be able at any time to inject a new supply of oxygen into the water.
He took strongly to the idea, so strongly, in fact, that he got a tin pump of even larger calibre than mine; and when this had been soldered firmly into place we tried it out by making a second trip. This second trip was a complete success. All Ur had to do was to throw his arm occasionally over the back of the seat and give a few strokes to the pump. The thing was a pleasure to work. It gave us complete power over the life and death of fishes. And thus another joy — and another complication, too — had been added to the art of fishing.
A milk can, with its round body dwindling to a thickish neck and widening out like a hat brim with a rounded top, is not unlike a man. I laid my hat on top of this one for a moment while pulling off a tightish sweater; and then, as I was about to pick it up, I could not help giving a little thought to the general resemblance as the can stood there with its fedora on at a rakish angle and its tin lung by its side.
‘Od’s fish,’ said I, ‘if this is not my old friend Mr. Homo! I knew him well, Horatio; we are such stuff as dreams are made on, and our little life is rounded with a sleep. A man may fish with a worm that hath eat of a king, and dine on the fish that hath fed of that worm. Here’s fine revolution, an’ we had the trick to see it.’
‘What in the world are you talking about?’ said my wife, turning away from a group on the lawn.
‘I was just quoting Shakespeare, my dear,’ I answered. ‘You know I have got to have ideas.’
‘If you have an idea,’ she said, ‘you ought to go in the house and write it down. You know you are always forgetting them.’
‘Madam,’ I said, ‘you are always right. I shall write an article. The world shall be edified. Every modern Hamlet will find in it matter to his liking. And every Horatio will have a chance to remark, “ ’T were to consider too curiously, to consider so.”’