THE COMMONWEALTH
OF CELLS
Some Popular Essays on Human Physiology
BY
H. G. F. SPURRELL, B.A. Oxon.
LONDON
BAILLIÈRE, TINDALL AND COX
8, HENRIETTA STREET, STRAND
1901
[All rights reserved]
To
MY ESTEEMED FRIEND AND TUTOR,
GUSTAV MANN, M.D., Etc.
PREFACE
Ever since the very beginning of my student days, when my contemporaries took to plying me with embarrassing demands for information upon all matters medical, I have been constantly impressed by the interest which the unscientific public take in the workings of their bodies and the material basis of their minds. It is this general display of interest among my friends that has emboldened me to add yet another book to the many already dealing with the subject. In using the word ‘unscientific’ I imply, of course, no reproach. I mean simply to denote those people who have specialized in some branch of knowledge other than those collectively known as Natural Science.
I usually find, when discussing physiology with such people, that they take more interest in general principles than in details, which they frequently find repellent, and that they frame their questions in an appallingly comprehensive manner.
My object throughout this little work has therefore been to present the fundamental principles of physiology in a brief, consecutive and readable form, for those who do not care to study the text-books. There is no lack of excellent books already, books illustrated by careful drawings quite gruesome in their accuracy, but they are almost all intended for “students,” and the casual reader, finding the organs divided up for exhaustive treatment, fails to form a conception of the body as an organic whole, and misses the very principles he is in search of, in the heap of details under which they are buried.
It may cause some surprise that, though in my efforts to be up-to-date I have in places outstripped the text-books, I quote no authorities. But a moment’s consideration will show that it would defeat the very object of a sketch like this to burden the text with an account of how my views were formed, while, on the other hand, the pioneers of science will forgive me. Their papers will be quoted in more durable works, and their names honoured long after this little book has been forgotten.
H. G. F. S.
Oxford, March, 1901.
CONTENTS
| PAGE | |
| Introduction | [ix] |
| ESSAY I. | |
| Living Matter | [1] |
| ESSAY II. | |
| The Chemistry of the Body | [8] |
| ESSAY III. | |
| The Mechanics and Physics of the Body | [31] |
| ESSAY IV. | |
| The Nervous System | [58] |
| ESSAY V. | |
| The Body | [94] |
| Conclusion | [107] |
| Index | [113] |
INTRODUCTION
The unscientific public is extremely prone, and not altogether without reason, to take medicine as a starting-point, and arrange all biological science around it. As it is, moreover, apt to gauge the interest and utility of every branch of this science from a practical point of view, and bestows most attention upon that which it imagines is of the greatest service to the doctor, I think a series of popular essays on physiology could not commence with more advantage, at any rate to physiology, than by briefly discussing, not with what it deals, for that is pretty generally known, but what is its relation to medicine. Further, as the doctor is more easily discussed than medicine, the physiologist will be more manageable for our immediate purpose than physiology in the abstract, so we will devote the first few pages to the question of how his labours benefit the patient.
Everyone knows the doctor, and everyone knows that physiology deals with the ‘functions of different organs of the body’; but the public rarely meet the physiologist, except in the fanciful caricatures of his enemies, which though frequently personal are rarely accurate. These rancorous libels, if anyone heeded them, would tend to raise doubts as to whether the physiologist was a good companion for the doctor, and if it were not as well for them to see as little of each other as possible.
The doctor, however, cannot move a step without the physiologist. His business is to correct the revolt of any organ from its allotted task, and repair the damage done by its deviation from the normal path. This he cannot possibly do if he does not know what that organ’s normal conditions are, and what they are it is the physiologist’s duty to tell him. A doctor, therefore, should be an enlightened physiologist, knowing how the body ought to work, and referring diseases to their real cause, such as the poisons formed by an invasion of bacteria or otherwise, or wrong feeding—that is to say, deficiency or excess of fuel for one of the body’s many engines. Medicine is still to a large extent rule of thumb. We don’t know to what many diseases are due, or why certain things relieve them, if any remedy is known; and until these questions are satisfactorily settled, it is vain to hope that disease as a whole can be successfully combated. It is no use knowing what will stop certain unpleasant symptoms if we do not know how to remove their real cause, and for this end the whole body and every individual component organ is being studied, that the process of life may be accurately understood; and the man who is doing this for his friend the doctor is the physiologist.
The physiologist has many enemies, a motley array of cranks held together by such noble bonds as general hatred of science and prejudiced ignorance masquerading as scepticism; but he can afford to ignore them, for the very good reason that people cannot get on without him. It is only on account of this that they are mentioned. People say, ‘The doctor is the person who requires a knowledge of physiology; he is the man who is most likely to study it successfully’—presumably by his mistakes—‘and not waste more time on it than is necessary,’ a point about which they are most solicitous. The doctor, however, prefers to trust the physiologist. If he did not, he would have very little time to do anything else. You might as well expect a tailor to make his own cloth before he makes a coat. He will doubtless be able to make better coats if the quality of the cloth supplied him is improved; but if in order to improve the finished article he lays down his scissors and applies his fingers to weaving, his business will be sure to suffer.
That physiology is a thing which can take up a man’s whole energies will, I think, be admitted by anyone who realizes how wide is its scope. The physiologist himself must specialize, for the subject is too vast for one man to undertake the whole. The body is composed of the same elements as the rest of the world, and their arrangement is very important, so he must be a proficient chemist. It is composed of solids, liquids and gases, and diffusion, filtration, leverage, are frequent processes, and every motion is accompanied by an electric manifestation, so that mechanics and physics must have been part of his training. He can scarcely study organs if he does not know their shape, so he should know some anatomy. And, lastly, as his business is to study life and all its attendant phenomena—and the basis of life is the cell—he must be a histologist. To be all these things is a great deal to require of one man; but though he may specialize for the advancement of a particular branch of his science, he must be au fait with the rest, as no vital function is dependent upon one alone of the factors enumerated. Hard work is required of him, though some people say he has done but little. What he has discovered is briefly, very briefly, set forth in the ensuing essays, with a hint or two at the knots he would like and is trying now to unravel.
THE
COMMONWEALTH OF CELLS.
Some Popular Essays on Human Physiology.
ESSAY I.
LIVING MATTER.
Physiology is the study of life, and the thing of all others which the physiologist would like to discover is what life really is. If this were fully known, all physiological processes could probably be deduced from it, and disease, which is an interference with one or other of them, could be scientifically treated. So far he has not got beyond describing the consequences of life, and his deductions carry him no further than this: life is a property of a substance, protoplasm, and protoplasm can only continue to exist in the form of a cell.
This definition may seem a little cryptic to some people, and very shocking to others. ‘Life,’ many people are accustomed to say, ‘means the presence of a soul, and is supernatural; and as to its being a question of chemical composition, that is absurd. My being made of cells, too, will not account for my thinking.’ But when people dogmatize thus about what they have not considered, they usually find themselves landed in difficulties. They go so fast: the most spiritual of men is so dependent upon matter and its properties that his soul will speedily quit his body if he is prevented from breathing. And the reason of this is, that if he cannot get air, the chemistry of the cells of which his body is made becomes altered; he no longer consists of protoplasm, therefore he no longer lives. Life, that it may exist in a material world, must have a material basis, and if that is interfered with it becomes extinct or quits the material plane; in any case, ceases to interest the physiologist as a physiologist. I do not think anyone need be shocked at this being recognised.
It is, of course, the ambition of the physiologist to make protoplasm, but so far he has got no further than making some of the complicated bodies into which protoplasm breaks up when it dies. A little while ago this bare possibility was loudly derided, but the advance in organic chemistry has been so great of late years, and so many complicated substances which once seemed as unobtainable as protoplasm itself have been made in the laboratory, that we now have hope of a precise knowledge of the chemistry of life some day, though that day may be yet very distant.
To give an account of life is to describe as far as we are able the nature of the living substance, protoplasm; and as protoplasm is a ‘structure of compounds,’ a word or two about chemical compounds may clear the ground for discussing it. If you were to take a compound, say a lump of sugar, and start breaking it up, you could hammer for a very long time and it would be still sugar; but if a tiny fairy with a minute hammer and chisel were to go on breaking up the grains, he would ultimately have molecules of sugar before him. Each molecule would consist of exactly the same number of atoms of carbon, hydrogen and oxygen, and if he divided it further by the removal of a single atom, it would no longer be sugar. He could hammer away at the atoms as hard as he liked, for they are incapable of further division.
There are seventy odd different kinds of atoms. When the molecules of a substance are composed of only one kind, it is said to be simple; when of several kinds, compound. Now, the difference between the various substances we see around us consists not only in what different kinds of atoms their molecules are composed of and their number, but in their arrangement. This arrangement may be in chains or rings, and the relative position which the different atoms occupy in the structure of a molecule makes all the difference in the world.
This difference of composition gives the difference of properties to compounds; so a compound must consist only of molecules which are all alike. If a substance is made up of molecules of different kinds, ununited by chemical bonds, and therefore capable of being mixed in any proportions, it is called, not a compound, but a mixture of compounds.
But just as atoms combine to form molecules, so the smaller molecules sometimes enter into combinations with one another to form new compounds having larger and more complex molecules. Such a compound is said to be composed of radicles, or groups of atoms, and on being decomposed can be broken up, first into simpler compounds, which can afterwards be further divided into their constituent elements.
Now, of all substances, protoplasm seems to consist of the largest number of components, and to have them arranged in the most complicated way known; though ‘known’ is really not the right word to use in this connection. The reason why we do not know what life is, is that we cannot find out in what way the constituent compounds in the protoplasmic structure are combined. Directly we try to analyze protoplasm, it dies; that is, it splits up into a number of simpler bodies and is altered beyond reconstruction.
These compounds into which protoplasm breaks up when it dies are themselves extremely complex; but though much careful study has been bestowed upon them, we cannot as yet say how they are put together to form the living substance. Protoplasm is too variable a body to be considered a single compound, while, on the other hand, the chemical relationships of its components must be too close to admit of its being called a mixture. Its chemical position is therefore unique, and we can only speak of it as a substance of unknown composition.
What, then, is it that makes protoplasm unmistakable and different to all other substances? The complexity of its structure is, after all, merely a matter of degree. The difference is not easily defined, but it roughly amounts to this: Protoplasm is always changing, yet always remains the same. Life is the change in the molecules.
If our definition of life seemed obscure, this sounds like a paradox; but perhaps the following fact may help to explain it: Under certain conditions some of the simpler compounds behave in a somewhat similar way. For instance, there is one which is so greedy of oxygen that it grabs it from whatever will readily give it up, and in order to do so is obliged to relinquish that which it has already got in its molecule to make room for that freshly acquired. Protoplasm is always behaving in this sort of way as long as it is protected from extremes of heat and cold, and from active chemicals which split up its molecules to form fresh compounds. Then it dies, or ceases to be protoplasm.
But the importance of this constant change lies in the fact that by continually breaking down its own molecules protoplasm obtains the energy to rebuild them out of non-living compounds of high potential energy, to modify its environment, and, in fact, to do the work of life.
It was said above that protoplasm only continued to exist in the form of a cell; therefore, what is a cell, and why its necessity?
We have seen that protoplasm has a very complicated structure, and that its normal condition is one of change. This being so, it obviously cannot exist in large masses, for if it did the change would be sure to be uneven in different parts from its very complexity; and the centre of the lump would either be starved or poisoned by the products of its own life. To avoid this, the mass is divided up into a vast number of small units each complete in itself, in communication more or less direct with its neighbours, and all equally accessible to fluids which both feed and cleanse them.
But there is another and still more important reason for such a division. The protoplasm is constantly discharging decomposition products, and needs to be repairing its waste by building in fresh compounds. The raw material around it requires dressing before it can be of use, and the building in is a difficult business. In each cell there is, therefore, a place set apart, where the protoplasm has peculiar capabilities, and it is here that this elaboration is carried out. This spot is called the nucleus. Thus it will be seen that the formation of an animal’s body by the aggregation of cells is a necessary and ingenious way of avoiding a difficulty.
To say, however, that an animal’s body consists of cells is to take an entirely wrong starting-point. A cell is complete in itself, and can live if properly fed, even though separated from its neighbours. Many whole animals consist of only one cell. A cell is, moreover, capable of growing and dividing, thus giving rise to two cells with two nuclei, and it is only because cells find that it pays better not to separate, but to form masses and specialize at different kinds of work, that we have large animals composed of millions of cells like ourselves.
Given a cell, it is necessary to keep that cell under favourable conditions. Otherwise the unstable protoplasm breaks up. It must have the elements necessary to keep up its cycle of changes in the proper form, which we may now call food, and many cells have to go and find this requisite. It must keep away from injurious influences, and it must race other cells for localities favourable to its growth and multiplication; in fact, the cell must work.
That a cell can, in virtue of its chemical affinities alone, move about, seeking favourable conditions, showing discrimination and doing work, seems incomprehensible. In the first place, how can it move? There is only one way: it must effect a redistribution of its substance, and contrive that those parts of the cell whose activity is applied to this end shall be so situated as to produce definite changes in its shape according to the cause which evokes them. Of the way in which different cells move we shall have a good deal more to say later.
Why protoplasm should be influenced to move still requires explanation. Yet the gap between protoplasm and other substances is really not so great, after all. Heat and magnetism cause movement in inanimate matter, and the response of protoplasm as exemplified by some of the minute unicellular animals is almost as mechanical. Some kinds which swim in water move to the positive pole of a galvanic battery, others to the negative, if the wires are dipped into the vessel containing them. Some move towards light, others away from it, with unvarying regularity. Temperature and chemical substances also cause a definite effect upon these micro-organisms. And all these movements are wholly involuntary, absolutely invariable, and, in fact, reactions evoked by fixed causes.
Nevertheless, it will be seen that protoplasm can only continue to exist in the form of a cell, since, unless thus organized, it can neither keep itself among favourable surroundings nor prepare fresh ingredients to make good its waste. If a cell be cut up into several pieces, these detached bits of protoplasm will live for a time; but death overtakes them as soon as they have used up their reserve material. When this is gone, they have to consume their own substance, a process which quickly proves fatal. Should a fragment contain a small part of the nucleus cut away with it, it will live a little longer; but it is only the piece which contains the nucleus more or less intact—in other words, the cell, damaged though it be—which can survive and recover from such mutilation.
The specialization of protoplasm to form a cell is perhaps its most remarkable peculiarity. Not only is protoplasm differentiated to form different structures, but it devotes the energy evolved in its ceaseless change to different purposes. The protoplasm of the motor organs of the cell expends itself wholly in producing the physical movements necessary to approach and capture food. When this has been passed into the cell, protoplasm of another variety works to refine and dissolve it, and then passes it on to the nucleus. The protoplasm of the nucleus, again, has different work to do. It devotes its energy to producing chemical changes in the raw material, and converting it into new compounds which the various parts of the cell can assimilate. Some of these it retains for its own needs; the rest it dispenses to the motor and other organs to repair their waste, and supply them with energy to obtain more food.
Thus do the different varieties of protoplasm which compose a cell supply one another’s needs, and enable one another to live; and thus does a cycle of chemical changes form the foundation upon which the whole fabric of life rests. But into details we cannot yet go, for our investigations of the material basis of life have not yet carried us beyond these general conclusions.
At present we know nothing definite about the first causes of life, and, though we have hopes, perhaps we never shall. Meanwhile we are observing, analyzing, and classifying the phenomena in which life is manifested, in the hope that at last light may break through upon our researches, and we may be able, if not to synthesise protoplasm in a test-tube, at least to demonstrate its workings in equations.
In the meantime, our actual knowledge of living matter can still be compressed into the words in which Professor Huxley summed it up years ago:
‘Carbon, hydrogen, oxygen, and nitrogen are all lifeless bodies. Of these, carbon and oxygen unite, in certain proportions and under certain conditions, to give rise to carbonic acid; hydrogen and oxygen produce water; nitrogen and hydrogen give rise to ammonia. These new compounds, like the elementary bodies of which they are composed, are lifeless. But when they are brought together under certain conditions they give rise to the still more complex body, protoplasm, and this protoplasm exhibits the phenomena of life.’
Until we have further knowledge of the changes which constitute these phenomena, physiology must remain descriptive rather than explanatory.