Art. 3.-SOME RECENT STUDIES IN THE PROBLEM OF CANCER.

1. The Scientific Reports of the Imperial Cancer Research Fund. London: Taylor and Francis, 1904, etc. 2. The Reports from the Cancer Research Laboratories of the Middlesex Hospital. London: Macmillan, 1902, etc. 3. Le Problème du Cancer. By A. Borrel. In Bulletin de l'Institut Pasteur. Vol. v. Paris: Masson, 1907.

4. The Natural History of Cancer. By W. Roger Williams. London: Heinemann, 1908.

5. The Geographical Distribution of Disease in England By Alfred Haviland. Second edition. London: Sonnenschein, 1892.

6. Cancer. By P. Menetrier. (Vol. XIII in Brouardel, Gilbert and Thoinot's Traité de Médicine.') Paris: Baillière et fils, 1908.

7. Lectures on the Pathology of Cancer. By C. P. White, M.D. Manchester: University Press, 1908.

IN the study of cancer, as in most other sciences, the results obtained are already of such complexity that they can only be understood, and their importance grasped, by the specialist in the subject. The problem has been attacked from all sides, histologists, cytologists, chemists, embryologists, bacteriologists, protozoologists, and statisticians having each and all attempted to solve it in different ways. The result has been the acquisition of an enormous mass of information, if not of knowledge; but we are bound to confess, with regret, but without shame and without despair for the future, that the solution of the mystery is still to seek, and that the work accomplished so far is merely a solid foundation for a building the first brick of which has yet to be laid, and the nature and form of which no man can prophesy. The study of cancer is in a state which may be compared with that of tuberculosis in the days just before the discovery of the tubercle bacillus by Koch.* The disease had been studied both on a large and a small scale with the greatest care, results of much value had been obtained, and had been

* The comparison is employed by Borrel ('Bulletin de l'Institut Pasteur v. 497).

pondered by some of the ablest men of the age. The result had been the production of a crop of theories, some demonstrably false, some improvable, some mere verbiage and a darkening of counsel, and some mere platitudes. Then came Koch's masterly paper, making the whole nature of tubercle clear at a glance, and converting the great mass of undigested facts into a scientific system: it was like the effect of dropping a crystal into a saturated solution, causing each molecule to fit instantly into its appointed place. In cancer research the pioneer studies have been made, all the false issues (and these in great numbers) that have presented themselves have been exposed, and the time seems ripe for the discovery of the road that leads straight to the heart of the maze. In this essay we propose to give a brief account of some of the more important points that are being investigated at the present time, dealing more especially with the questions which appeal to the layman as well as to the medical man or pathologist.

Let us first explain briefly what a cancer is. Plants and animals are built up mainly of cells, which are to be regarded as the units of life, and which build up living beings as atoms build up chemical substances. These cells are highly complex bodies. The painstaking researches of the cytologists, especially those engaged in the subject in connexion with the study of heredity, discover almost daily new complexities in the structure of even the simplest cell; and when we consider that the ovum or egg-cell, from which all living beings develope, contains within itself such endless potentialities, such manifold and various hereditary characters for good and evil, this high degree of organisation need not surprise us. In the normal healthy adult the cells that make up the body are engaged in various functions, differing in each tissue and organ, and have almost ceased to grow. Growth and subdivision of the cells does indeed take place, especially amongst certain cells, but it is a comparatively subordinate process, occurring in an orderly manner and only when the needs of the body demand it. For example, the cells which make up the outer layer of the skin have for their function the defence of the more delicate tissues of the body. They are constantly being rubbed or washed off, and any non-living tissue would

soon be worn away if exposed to the wear and tear to which, for instance, the skin of the hand of a workman is exposed. To make up for this constant loss, the cells in the lower layer divide, each into two, which gradually grow to the full size and go to form the normal thickness of the skin. This takes place in an orderly and regular manner, resulting in a layer of perfectly formed cells which form a beautiful mosaic, and which gradually become hard, horny, and exquisitely adapted for their duties, as they are traced towards the surface. In most other tissues cell-division takes place to a much less extent, but here also it is orderly and regular and takes place only in response to a need for fresh cells in the region.

In cancer a similar cell-division takes place, but in a wild, capricious, and unnecessary manner, and the cells thus formed do not organise themselves into those which make up the normal structure of the organ in which they develope, though they may imitate it to a certain extent. The resulting mass of cells discharges no useful function in the body, on which it lives just like a parasite; indeed, the physiological analogy between a parasite and a tumour is extraordinarily close, only it must be a parasite which increases in size continuously and relentlessly and burrows deeper and deeper into the tissues of its host. An illustration may make this clearer. Imagine a house the walls of which are built of living bricks, which grow in such a way as to repair the weathering and erosion of the surface, so that as each brick is dissolved or removed from the outside it is replaced by one newly formed from below. This is exactly what occurs in the healthy skin. Now suppose one or more of the bricks to cast off all restraint and to start growing and dividing rapidly and in an entirely purposeless fashion; imagine the bricks thus produced to be badly formed, variable in size and shape, and useless in every way; and imagine them growing inwards instead of outwards, invading the house, occupying it with a constantly increasing mass of irregular brickwork which slowly but surely fills up the interior and renders life within impossible. This is what takes place in cancer; and the problem of its nature is to find out what causes this anarchy in the naturally well-ordered hierarchy of cells, and why a cell which had for years discharged its

duty in an orderly fashion should suddenly abandon all restraint and begin dividing and subdividing in so useless a manner. The cancer-cell is one that has lost all-or almost all-its functions save that of growth and subdivision, and modern studies seem to show that its growth can continue-given suitable circumstances-to an unlimited extent. The problem of the nature of cancer resolves itself into the question why a cell, or perhaps a group of cells, suddenly takes on the power of incessant and purposeless growth.

And there are no indications that this problem will be solved in the near future. Suggestion after suggestion, some wild and futile, and some based on a clear knowledge of all the known facts and elaborated with great skill, have been brought forward, but each and all have failed to stand the test of further investigation or to satisfy the profession generally. Even the main question, as to whether cancer is or is not a parasitic disease, and due to a living organism, is not yet settled, and respectable authorities maintain each view. The feeling on the subject, which is not perhaps always expressed, appears to alternate at intervals of a few years, and at present the non-parasitic theory is generally accepted by pathologists. There is, however, no definite and conclusive proof against the microbic theory, and signs are not wanting that it may come into favour again. In the past very many organisms, bacteria, yeasts, and protozoan parasites have been thought to be the true cause, and in some cases on what appeared to be very strong evidence. All these have now been definitely exculpated, and there is now no doubt that, if cancer is due to a living organism, it is either one that requires very special methods of staining to make it visible, or --and this is more probable-that it is one of the microbes, the existence of which is now proved, that are smaller than the smallest objects that can be demonstrated with the highest powers of the microscope available at present. A very minute bacterium, capable only of living (in the body at least) in the substance of a cell of the patient, and stimulating this cell to continued growth, is a possible conception, and if it occurred it would appear to account for most if not all of the facts known about cancer whether of man or of the lower animals.

The other scientific theories of cancer, those which attribute it to developmental defects, or to chemical changes in the blood or tissues, need not be discussed. In most cases the former are founded on analogies, more or less fanciful, with what takes place during the development of the embryo, a period in which the whole of the energies of the body are directed to the one function of growth, just as in the case with the tumour-cell. Even if we admitted their truth, they would only remove the problem a step back, and the actual exciting cause of the disease would be still to seek. The majority of pathologists at the present day, whilst inclining away from a microbic view, and condemning all theories at present advanced as untenable, join with Newton in saying, 'Hypotheses non fingo,' and concentrate their attention on the discovery of new facts.

With the suggestions which attribute cancer to eating meat, tomatoes, or other vegetables, too much or too little salt; to the presence of sulphurous compounds in the air; to the increasing stress of modern life; to vaccination; to the presence of decomposing animal or vegetable matter, and to a thousand and one other supposed causes-it is not necessary to deal. In all cases the theories are readily disprovable by an examination of the distribution of the disease amongst mankind in different countries and conditions. We are not prepared, however, to deny absolutely that meat-eating in excess may have some effect in increasing the liability to the disease, though its occurrence in vegetarians and herbivorous animals demonstrates that it is not an invariable and necessary cause. One of the most thoughtful and philosophical attempts to find an etiological factor for the disease, i.e. a cause which, acting on a large scale, increases its prevalence, as opposed to the vera causa which stimulates the cell to start its anarchistic career, is that of Roger Williams. According to him cancer is pre-eminently a disease due to increased civilisation, accompanied, as is usually the case, with an increased influx of the rural population to the towns, increased material prosperity, and consequent excessive feeding. Williams accepts the figures which appear to show that cancer is actually increasing rapidly, and attempts to show that this increase is due to the sudden change in