In these days science no longer needs justification as a subject worthy of man’s earnest devotion. The gain in exact knowledge of the forces and materials of the universe is recognized on all sides as bringing with it promise of incalculable benefit to humanity. The full importance of this new light, in its bearing upon the amelioration of the human lot, is only just beginning to be realized.

In keeping with the increasing appreciation of the value of scientific research to humanity, there exists to-day among scientific men the effort to relate each particular science to every other, and to associate all together in a coherent whole, without losing sight of the need of accuracy in each part. The existence of such composite branches of study as physical chemistry, biochemistry, physiological botany, and so forth, are one indication of the broader outlook; and some of the greatest modern scientific advances are being made along the border lines between the different sciences. Nature is, after all, a unit, and our classifications of her closely related phenomena into special topics are partly arbitrary.

This effort to relate the various sciences to one another is not only helpful to science as a whole, it is likewise beneficial to the individual worker. A man’s mental outlook must be broadened by an attempt to trace the relation of his special task to the manifold over activities and needs of humanity.

The particular branch of science called chemistry has many relations to human life, as well as to other sciences. It forms an essential part of any philosophy of nature; it serves as an admirable means of intellectual discipline; it guides the manufacturer and the merchant toward efficiency in production and purity of product; but, perhaps most important of all, it holds the key which alone can unlock the gate to really fundamental knowledge of the hidden causes of health and disease. This is one of the most precious and vital ways in which any branch of science can serve humanity in the years to come.

Ten centuries ago, in the time of the alchemists, chemistry was called “the handmaid of medicine;” to-day this relationship is not weaker, but rather much stronger. The object of the present article is to call attention very briefly to some of the ways in which modern chemistry may be able to help the theory and practice of medicine.

That a close relationship between chemistry and medicine exists is clear to every one. Our bodies are wholly built up of chemical substances, and all the manifold functions of the living organism depend, at least in part, upon chemical reactions. Chemical processes enable us to digest our food, keep us warm, supply us with muscular energy. It is highly probable that even the impressions of our senses, and the thoughts of our brains, as well as the mode of conveying these through the nerves, are all concerned more or less intimately with chemical reactions. In short, the human body is a wonderfully intricate chemical machine; and its health and illness, its life and death, are essentially connected with the coordination of a variety of complex chemical changes.

This intricacy of the living body demands clear sight and profound knowledge for its full understanding; and the chemistry of former days was much too simple and superficial to be a very useful guide in the puzzling labyrinth of many converging and crossing paths. Now, circumstances have wholly changed. Chemistry is fast approaching physics in accuracy, and is expanding beyond physics in scope. As chemical understanding has increased, the gap between the simpler phenomena of the chemical laboratory and the more complicated changes underlying organic life has become smaller and smaller. The intelligent physician is perceiving this, and welcomes the help which the rapidly advancing science of chemistry can give him. An eminent pathologist recently said that in the study of the cell and its growth, normal as well as abnormal, the investigating medical scientist has come to the place where he must fall back upon chemical knowledge, because he perceives that the action of the cell depends upon the nature and quantity of the various chemical substances of which it is made. As the cell is the basis of all life, and as our bodies consist simply of aggregations of a great variety of cells, each of which is governed by chemical laws, it is clear that chemistry must underlie all the vital functions.

Chemistry may be of use to medicine in at least three quite different ways. One of these is concerned with discovering the components of things. This kind of chemistry is called analytical chemistry. Another way in which chemistry can help medicine depends upon the ability of the modern chemist, not only to find out what the things are made of, but also to discover how the parts are put together. This branch of chemistry is called structural chemistry, because it has to do not only with the materials, but also with the way in which these materials are arranged. Yet another method of helpfulness comes from a still more recent development of chemistry, commonly called physical chemistry, which deals with the phenomena lying on the border line between physics and chemistry—especially that part of the border line concerning the relation of energy to material. The physical chemist must know, not only what things are made of and how these elements are put together, but also what energy is concerned in putting them together, and what energy is set free when they are decomposed.

Each of these three kinds of chemistry can greatly aid the science and art of medicine—and no philosopher is needed to proclaim how much more effective their assistance may be than the old method of observing merely the outward appearance of fluid and tissue.

Let us now briefly glance in detail at the various aspects of these three modes of helpfulness, taking them in the order in which they have just been mentioned. First comes the field of the analytical chemist. As has been said, the human body is a chemical machine. It is composed entirely of chemicals, and is actuated exclusively by chemical energy. The analytical chemist is able to tell us the composition of each one of the manifold substances that compose this intricate machine. He is able not only to discover the various elements which are present, but also to estimate with considerable precision their exact amounts. He can analyze food, as well as the various parts and secretions of the body, and can determine the relation between the composition of the food which is eaten and the resulting bodily substance. This is all obviously of great value, for it shows us at once in a general way what elements ought to enter into the food; and moreover, in cases of disease it gives us excellent clues to the manner in which the various functions of the body depart from the normal, and thus confers important aid in diagnosis and the suggestion of suitable treatment. But this is an old and obvious story, hence I will not dwell further upon the analytical side of the application of chemistry to medicine, important as it is.

Let us now turn to the second aspect of the subject: namely, the relation of structural chemistry to medicine. So recent is the development of the subject that the very idea of structural chemistry is not yet a part of the average liberally educated man’s equipment.

Structural chemistry had its origin in the discovery that two substances might be made up of exactly the same percentage amount of exactly the same elements, and yet be entirely different from each other. This fact, that two things may be exactly alike as to their constituents, but very different in their properties, implies that there must be difference of arrangement of some kind or other. We can obtain the clearest conception of this idea with the help of the atomic hypothesis. If the smallest particles of any given compound substances are built up of still smaller atoms of the various elements concerned, it is clear that we can conceive of different arrangements of these atoms, and it is reasonable to suppose that the particular arrangements might make considerable difference in the nature of the resulting compounds. Everywhere in life arrangement is significant. In the case of numbers the combination 191 is very different from 911, although each contains the same individual signs. Why may not arrangement be significant in the case of atoms?

I tis not possible in this brief review to explain exactly how chemists obtain a notion of the arrangement of atoms which build up the particles (or molecules) of each substance. We depend upon two methods of working: one, the splitting-up of the compound and finding into what groups it decomposes; the other, the attempt to build up from these or similar groups the original compound. Just as among the fragments of a collapsed building you will find bits enough to show whether it was a dwelling, a stable, or a machine-shop, so among the fragments of a broken-down substance you will find bits of its structure still remaining together, enough to indicate something of the original grouping. Each different chemical structure will leave a different kind of chemical débris. If from similar fragments the original substance can be constructed by suitable means, the evidence is strong that some knowledge of the structure has been gained.

As regards the usefulness of structural chemistry to medicine, we cannot but see at once its vast importance. If the binding together of infinitesimal atoms in different ways modifies the properties of the resulting substances differently, it is obvious that the particular mode of binding together every one of the complicated compounds constituting our bodies is of vital importance to us. Moreover, in the case of our food, the arrangement alone of the atoms may make all the difference between nourishment and poison.

It is easy to see why these different structures should have different effect in the body. Living, in the case of animals, is a continual process of breaking down more complicated structures into simpler ones; and it is clear that this breaking down will happen in different ways with different groupings, and thus produce different results.

The knowledge of the atomic arrangement of the various substances composing the body is not only bound to furnish an invaluable guide in the study of physiology, pathology, and hygiene, but has already led to the logical discovery of entirely new medicines, built up artificially in the laboratory to fit the especial needs of particular ailments, and to the rational use of foods. In the years to come, these gains are bound to multiply.

Thus in the future the physician may do his work, not with a serum or virus of doubtful composition and value, but rather with pure substances built up in the chemical laboratory, — substances with their groups of atoms so arranged by subtle science as to accomplish the reconstruction of worn-out organs or the destruction of malignant germs without working harm of any kind. We may thus dream of the attainment of an artificial immunity from smallpox, for example, as much superior to vaccination as this is superior to the old inoculation.

Beneficent substances of this kind will not often be discovered by accident; the number of possible arrangements is far too great. In order to know all there is to be known about the matter, the structure of each intricate substance existing in the body must be found, and the arrangement of the atoms in each particle of our complex organism. Until this shall be done, we cannot be in a position to predict with any reasonable certainty what is going to happen to these substances in the round of their daily functions, or how they are likely to be influenced by disease. This is a problem so vitally important that it would be hard to exaggerate its significance to posterity.

As I have said, modern knowledge now demands of the chemist that he should know, not only the elements composing all things and how these elements are put together, but also how great an output of energy is involved in every change to which they may be subjected.

Now, there is no doubt that energy is the immediate cause of every action in the known universe. Without any kind of energy, the whole universe would be quiescent, dark, piercingly cold, asleep. A world imbued with physical energies, but without chemical energy, might revolve and have light and warmth; but it could possess no organic life, for life is based upon the action of chemical energy. Thus the study of chemical energy is another very important human problem.

Physical chemistry has to do with the relation of each of the various kinds of energy to chemical change. It deals with the acting, driving forces which make life possible, and in each of its many aspects it brings new intelligence to bear upon the working of the living mechanism.

Physical chemistry treats among other topics the chemical relations of the changes from solid to liquid, and from liquid to gas, and discusses the nature of solutions and mixtures of all kinds. As the living body is composed of solids and liquids, and depends upon the gases of the atmosphere for promotion of the chemical changes animating it, and as solutions and mixtures are present in every cell, the laws and theories of physical chemistry are intertwined with every fact of physiology.

Again, physical chemistry deals with the relation of heat to chemical change. The output of energy in the form of heat in every chemical reaction is worthy of study, but especially ought man to investigate the steps by which is evolved all animal heat—and this is exclusively due to chemical reaction. Moreover, physical chemistry studies the effect of changing temperature upon the speed and tendency of chemical action, — a matter of importance in the study of fevers and other abnormal conditions, as well as in the tracing of the marvelous hidden mechanism by which the body is kept at almost constant temperature.

This dynamic chemistry of the future does not stop here, however. Within its province lie also the recently found relations of chemistry and electricity, bearing perhaps upon some of the mysteries of nervous action, and furnishing much intelligence concerning the nature of solutions in general. More important, perhaps, than all this is the branch of the subject called photochemistry, the chemistry of light, which promises to give great assistance in the interpretation of the changes occurring in the leaves of plants under the influence of sunlight. Through the agency of light alone, nature is able to build up the intricate compounds needed to provide all animals with food; and, until we understand the growth of the vegetable, we cannot hope to understand that of the animal.

A moment’s thought will show that this chemistry of substances in action—that is, the chemistry of energy—brings with it a promise of helpfulness to future generations, which perhaps exceeds that of any other science. For the study of the inert substance from which life has departed, no matter how accurate this study may be, cannot give us a true knowledge of its real office, any more than we can predict from the appearance of a stuffed bird in a museum its complete habit of life. In order to understand the process of living, one must see the substances in action and study their behavior under the influence of the manifold forces which play around them; and this is the aim of physical chemistry.

I have outlined very briefly a few of the ways in which science holds out great promise of help to suffering humanity in the future. To some the point of view may have seemed materialistic; we must remember, however, that science does not attempt to fathom he ultimate mystery, but deals with the facts of nature only. The greatest mysteries of life seem almost as far form solution as ever. Just what relations exist, for example, between chemical change and thought, what permanent alterations of chemical structure cause memory, we know not. Life we have never been able to produce from dead material alone. Personality and heredity defy the chemist, as they do the physiologist and the psychologist. But let us not be impatient. Though it is impossible to predict how far we shall be enabled by means of our limited minds to penetrate into the mysteries of a universe immeasurably vast and wonderful, we may nevertheless comfort ourselves with the thought that each step gained brings new blessing to humanity and new inspiration to greater endeavor.

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