General Physiology: An Outline of the Science of Life

If the physical world is only my own sensation, or, better, since it involves a complexity of sensations, my own idea, I must assume that a reason for this idea exists. Hence the question arises, What is the thing outside of my mind that produces in me through the senses this idea ? In other words, what is the external world ? This question contains an error. As is well known, natural science has shown that every phenomenon in the physical world has as its cause another physical phenomenon. This is only an expression of the law of cause and effect, 'i.e., the law of causality. Hence the cause of my sensation of the physical is another sensation or idea, which is located not outside of but within my mind. This is nothing but a paraphrase for the fact that our conception of causality has arisen out of a combination of separate experiences, which our mind has obtained by observation of the regular sequence of its own elements, its sensations and ideas. In other words, causality itself, like all other sensations, ideas, conceptions, or whatever we may term it, exists only in our own mind. If, therefore, the cause of my idea of the physical is located within, the supposition of a reality without is wholly unjustified.

Various philosophers have, in fact, endeavoured to base the reality of an external world upon the causality of phenomena. But both rest upon the same error, and the argument presents the rare spectacle of an attempted proof of something by means of that which is to be proved. It is not to be denied that to every one who follows this line of thought for the first time the above result must appear paradoxical, and he will immediately raise the objection that besides himself many other men exist, possessing minds and capable of making •exactly the same assertions concerning themselves and their own minds. But here the delusion is again evident. To me, other men are bodies, I perceive in them nothing else. Hence they are only my idea. And when they tell me that they have a mind like myself, that they likewise feel and think, it is true ; but what they say to me, their speech, their movements, are only physical phenomena and, therefore, only my own ideas According to our scientific mode of expression, their mind has its seat in their brain, but if, by a surgical operation upon a living man, I am ever •enabled to examine the brain, I learn that nothing is to be found there but physical elements. I am thus forced to the conclusion that what I regard as the mind of another is also only my own idea. In short, whatever path I take, I come constantly to the conclusion that all that seems to be outside of me, whether it be a lifeless body, a living man or a human mind, is in reality only my own mind. Beyond my own mind I cannot go. My own individuality, indeed, is only an idea of my mind, and, therefore, I cannot finally say, the world is my idea, but I must say the world is an idea, or a sum of ideas, and what appears to me as my

individuality is only a part of this complex of ideas, just as is the individuality of other men and the whole physical world. Although this reasoning will appear to every one at first sight strange and unusual, it is by no means new. More than two hundred years ago Descartes made the fundamental fact, that the whole physical world is only an idea, the starting-point of his philosophy. Later, Berkeley and, still later, Fichte and Schopenhauer employed it as the basis of their systems, which were widely different in other respects. More recently among men of science Mach ('86) has adopted a similar view as the nucleus of his views regarding the theory of knowledge. It is to be hoped that this monistic conception will gain ground more and more in science ; it alone holds strictly to experience, it is not hypothetical, and it necessarily sets aside the ancient doctrine of the dualism of the body and the mind, a doctrine that reached its highest development in the Egyptian theory of the wandering of the soul and has continued through the whole history of philosophy.

When the history of the problems that have kept the human intellect busy during the long course of its evolution is studied, it is found that many problems that perplexed the ancients have continued unchanged and unsolved down to the present day ; others have been solved ; while still others that have been prominent even for centuries have afterwards disappeared without finding a solution. The ancient question of the squaring of the circle, over which many a brain has puzzled in vain, that of perpetual motion, which since early times has been prominent in physics, and many others, have quite disappeared, although no one has ever squared the circle and no one has constructed a machine for perpetual motion. If it be asked how it happens that this is so, the answer is, because it is recognised that the basis of these supposed problems is false, and they are, therefore, insoluble. If the attempt be made to divide all the numbers of a series by 2 without a remainder, it is found impossible to do it. So it is with the above problems, which for centuries have harassed one generation of thinkers after another.

So it is also with the attempted explanation of psychical by physical events. It still engages unremittingly the attention of those who are not pleased with having limitations to their conception of the world, yet no one, however earnest his thought, comes nearer a solution. Only gradually will the conviction force its way, that this problem, like those above mentioned, will always resist solution because the question is falsely put. That the attempted explanation is wrong is at once clear from

the preceding considerations. It was found that the sole reality that we are able to discover in the world is mind. The idea of the physical world is only a product of the mind, and with the alteration of an old sentence of the sensualists, it can be said : Nihil est in universe, quod non antea fuerit in intellectu. But this idea is not the whole of mind, for we have many mental constituents, such as the simple sensations of pain and of pleasure, that are not ideas of bodies. The task of psychology, i.e., the investigation of mind, consists in the analysis of all mental constituents. By investigating the contents of mind, by decomposing the higher psychical phenomena, the more complex groups and series of ideas, into their simple constituents, psychology arrives, finally, at the most primitive psychical phenomena, the psychical elements, and in the same degree discovers the laws of the arrangement of these elements into the higher groups and series of ideas. Just as in mathematics the endless variety of numbers is formed according to laws out of the numerical unit, so psychology reduces the endless variety of psychical phenomena to their formation, according to laws, out of the psychical elements. But the idea of matter, or, better, of an atom, is not a psychical element, it is a great complex of highly developed ideas. An atom is nothing but a thing possessing all the properties of a body, such as hardness, impenetrability, form, and extension, all of which presuppose very complex psychical processes. The endeavour of natural science to reduce the phenomena of the physical world to the mechanics of atoms is justifiable ; it is an endeavour to derive the phenomena of large bodies from the properties of their material parts.

But the attempt to reduce to the motions of atoms all psychical phenomena, not only ideas of the physical world but others, such as simple sensations, is precisely as absurd as the endeavour to reduce all numbers in the numerical series to 2 instead of to the numerical unit, for the complex notion of the atom is not a unit, not a psychical element. Herein lies the fallacy of the problem, and hence, as the history of human thought has shown so strikingly, all attempts to explain the psychical by the physical must fail.

The actual problem is precisely the reverse. It consists not in explaining psychical ~by physical phenomena, but rather in reducing to its psychical elements physical, like all other psychical, phenomena. In natural science the view is frequently met with, that knowledge of the world falls into two sharply separated categories, namely, metaphysics and science. Metaphysics is left to philosophy, and science is limited to the investigation of the physical world. But the fact is often overlooked or intentionally neglected, that every process of knowledge, including scientific knowledge, is merely a psychical event, that science also deals with " metaphysics," as in accordance with an ancient and unfortunate manner of expression it is customary to term it, and even

that science cannot exist without metaphysics. This fact cannot be banished by the well-known method of the ostrich. It thtfs appears to be a contradiction to contrast nature (0u<m) with something " beyond " nature (fiera rrjv fyvcriv}. There is but one world, whether this be termed nature, mind, reality, or anything else. It follows also that there is but one kind of knowledge, and not two. As soon, therefore, as the question arises of principles and bases of knowledge, all artificial boundaries disappear. We should not be deceived. The goal toward which the human mind is striving in its theoretical investigations is not simply a knowledge of the lifeless physical world or of living bodies, or of this or that psychical phenomenon, but it is a knowledge of the world. A division of labour among investigators, however, should not only not be deprecated, but, because of the excessive multitude of phenomena, should be encouraged ; nevertheless, the purely supplementary purpose of such a division must be kept in mind, and the artificial boundaries between the various fields of labour must not be confounded with the natural boundaries. A severe blow will be inflicted upon the coming centuries, if the gulf between philosophy and science widens constantly from both sides ; if, upon the one side, confused speculation, and, upon the other, narrow specialisation constantly prevail and prevent a mutual approach toward a beneficent common labouring-ground. Science cannot make salutary advances without a philosophical workingplan, and we see in the history of science that great discoveries have been made, not by restricted specialisation, but by investigators working philosophically, i.e., systematically, methodically, and cognisant of their aim. But philosophy can obtain really important results just as little by a purely speculative method, by not keeping close to established facts and not submitting its speculations to the severe criticism of experience.

The history of science proves that true advance comes only by thoughtful investigation. The above theoretical considerations regarding knowledge ought to give us a basis for investigation such as every thinking investigator sooner or later must make for himself, and upon which he must build broadly and freely in order that his labours may be fruitful. The most important result afforded by the above considerations is the monistic standpoint, in accordance with which the world appears as unitary, and the dualism of the physical world and mind as an illusion. The fact, which appears so remarkable from other standpoints, is, therefore, not surprising, that the laws that control the physical world and those that control mental phenomena are completely identical. This appears necessarily so when we find that the phenomena of the physical world are arranged according to space, time and causality, and when we recognise therein the logical principles of our own thought ; the

laws of the physical world are the laws according to which our own psychical phenomena occur, because the physical world is only our own idea. All science, therefore, is in this sense psychology. We will now summarise our considerations regarding investigation. We started out with the question, whether there are impassable limits to a knowledge of the world. If we understand by knowledge the reduction of phenomena to the motions or the mechanics of atoms, limits do, indeed, exist. For not only is the atom, and hence matter, yet to be explained, but, as du Bois- Reymond's clever undertaking has shown very clearly, it is impossible to reduce psychical phenomena to the mechanics of atoms. If, however, we conceive knowledge in a more general and the only justified sense, namely, the reduction of phenomena to the elements of reality, we find that no limits exist, for the sole reality is our mind and all phenomena are only its contents ; explanation, therefore, consists simply in the reduction of all psychical phenomena to their elements. In this sense, all science, and in ^ general all knowledge, is in the end psychology. We thus comey to the only consistent standpoint, namely, monism, the unitary view of the world, which seeks to derive all phenomena from a single cause. From this standpoint we see why we meet with limits when we define knowledge to be the reduction of phenomena to the mechanics of atoms. An atom is not an element of reality but a complex idea, hence all phenomena are not reducible to atoms ; just as in a series of numbers the element of which is the unit 1, all are reducible to the common unit but not to a number more complicated than 1, e.g., 2. It is thus evident that a limit can no more exist to the investigation of physical, than to that of psychical phenomena ; for, since bodies, in other words, atoms or matter, are only ideas, in other words, psychical phenomena, they may be reduced to the same psychical elements as ideas.

We will now turn again to the consideration of vital phenomena. The above reflections have shown the possibility of reducing all phenomena, physical, as well as psychical, to a common cause. The question that led to those reflections, whether vital phenomena are based upon the same causes as those of non-living nature, would be answered affirmatively if we were to go back to final causes — and it has been found that no insurmountable boundaries limit research. If, however, we confine ourselves to the special field of physiology, the investigation of the physical phenomena of life, we know that natural science has shown that the phenomena

of lifeless bodies may be derived from the properties of the smallest material elements, atoms endowed with energy, and the question then takes the form : May the phenomena of living bodies also be reduced to the same factors ? Vitalism says, no ; a special force, vital force, prevails in organisms and induces vital phenomena. Vital force is limited to the world of living matter and is not identical with the chemicophysical forces of lifeless nature.

These words contain the essence of vitalism. It is interesting to inquire upon what the hypothesis of vitalism rests, and what justification it has. In the above review of the history of physiological research, the history of the doctrine of vital force was outlined. It was there seen that the conception arose in connection with the phenomena of irritability, and that it has always been vague and has served chiefly for convenience. This indistinctness regarding it is the chief difficulty in the way of its critical elucidation. If the conception could be sharply defined, it could be treated more easily.

The claim for a vital force rests solely upon the fact that thus far it has not been possible to reduce certain vital phenomena to chemico-physical principles. Indeed, when the achievements of physiological research were summarised above, the discouraging fact became apparent that the vital phenomena that have been explained are only the gross physical and chemical activities of the body, and that whenever the attempt has been made to show their deeper causes, unsolved problems have always opposed it. Bunge ('94) even asserts : " The more we strive to investigate vital phenomena exhaustively, in many directions, and fundamentally, the more we come to perceive that events which we believed we could explain physically and chemically are excessively intricate and for the present mock at all mechanical explanation."

Although the fact is to be little doubted, that thus far, many, especially the elementary and general vital phenomena have defied all chemico-physical explanation, the assertion is not, therefore, logically justified, that these phenomena do not follow chemico-physical laws at all, but that a special vital force exists and causes them. Moreover, there are facts that speak against the existence of such a force. In spite of all endeavours thus far, the vitalists have not succeeded in establishing the existence of any special force in organisms, i.e., they have not been able to characterise such a force from its effects, as physics and chemistry have done for the forces of inorganic nature. With regard to none of the actions of the body supposed to be due to a vital force, have they been able to contradict the assertion that such actions are only the expression of complex chemico-physical relations. E.g., it was long believed

that certain substances found exclusively in the living organism cannot be produced chemico-physically, but arise only through the working of the vital force. But, as has been seen (p. 23), in the year 1828, Wohler weakened this once so powerful support for the vitalistic creed by manufacturing synthetically in his laboratory urea, a body which ordinarily is produced only in the metabolism of the living organism. He obtained this from ammonium cyanate, (NH4)CNO, which is isomeric with urea (NH2)2CO, i.e., possesses the same number of the same atoms in a different arrangement. But ammonium cyanate is manufactured out of purely inorganic materials. This synthesis of urea has been followed by others of equal importance, all of which go to show that characteristic substances belonging to the organism may be compounded artificially. The assumption of a special vital force for their production in the organism is thus rendered superfluous. Of course it has not yet been possible to manufacture a great number of substances belonging to the animal and the plant body. Indeed, the most important of these substances, proteids, have thus far resisted artificial production in the laboratory, but the reasons for this are evident. The exact chemical composition of proteids is not yet known ; we know what atoms are contained in them, but we have no idea how these atoms are joined together. Accordingly it is evident that success in the attempt to manufacture proteids artificially ought not yet to be expected. A second reason is that thus far we have no correct idea of the chemico-physical conditions under which these substances arise in the organism ; and chemistry has recently shown very clearly that the inauguration of a chemical process depends not only upon the presence of the necessary substances, but also upon the fulfilment of certain other conditions.

Thus, it has been found that many chemical transformations that do not take place in a large space, occur very easily in capillary spaces under otherwise like conditions, and vice versa. An example long known is the union of oxygen and hydrogen in the spongy-platinum of Dobereiner's lamp. It is known that hydrogen streaming out of a tube into the air does not spontaneously unite with the oxygen of the air ; but, if it pass into the fine pores of platinum-sponge, the union takes place at once, and the hydrogen burns with a luminous fiame to form water. Such processes are termed condensations. It is known also that many chemical processes take place only when the substances involved are present in large quantity — a phenomenon which as mass-effect plays an important role not only in the laboratory but also, as already demonstrated, in the animal body. Recently, Preyer and Wendt ('91) have suggested the presence of condensation -processes and the absence of mass-effect in capillary spaces as a reason why in the organism, where capillary spaces exist in the cells and their

contents, certain chemical transformations take place differently from their customary manner in mass. Another consideration, which renders the assumption of a special vital force still more untenable, is the following. The calorimetric researches of the present time show that in the adult animal which is in complete metabolic equilibrium, i.e., which gives off from its body as excretions exactly as many atoms as it takes in as food, complete dynamic equilibrium also exists, i.e., exactly the same quantity of energy that enters the body with the food as chemical tension leaves the body during the vital activity of the animal. Hence all the energy that is transformed by the body in the performance of its work must be derived solely from the energy that comes in with the food. If this were not so, we would be led to absurd conclusions ; for, if the activities of the body were supplied from a fund of special energy, a " vital force," we would be obliged to assume, not only that the latter is continually constructed in the body out of nothing in order continually to maintain the work of the body, but also that the potential of the food being superfluous is continually disappearing in the body. At the present day no true man of science can agree with such an idea. Johannes Mliller was a vitalist, and, although the law of the conservation of energy was unknown to him, he felt and endeavoured to avoid this difficulty by assuming that vital force works according to chemico-physical laws. By such an assumption a specific force, different from chemico-physical forces, is in principle laid aside, for vital force is then only a collective term for the complicated chemico-physical relations upon which vital phenomena depend. In fact, many scientists conceive the term in this sense only, and, if Mtiller had been acquainted with the law of the conservation of energy, he would surely have avoided the expression " vital force."

Since the middle of the present century the old conception ot vital force has disappeared completely from physiology. Hence it appears strange to hear at the present time here and there the catch-words of that doctrine. A careful examination of this reappearance shows, however, that the old words are now employed in a very unfortunate connection, that their sense has been completely changed, and that, when " vitalism " and " neovitalism " are now spoken of, something wholly different from the old doctrine of vital force is meant. In general, among the phenomena of the newer vitalism two groups may be distinguished, which may be termed mechanical and psychical vitalism.1

Mechanical vitalism is the view that vital phenomena depend at bottom upon the agency of physical and chemical forces ; but that in living organisms these forces are linked together into such a peculiar and thus far unexplored complex that for the present it must be contrasted with all the forces of inorganic nature as a specific vital force, characterising the actions of living organisms only. In other words, by vital force is meant simply the special aspect of chemico-physical forces that lies at the basis of vital phenomena. It is evident that no objection can be brought against the facts upon which this idea is based. But it is another question whether the terms "vital force" and " vitalism" are. justified in this case. The new idea has nothing to do with the old vitalism, which assumed a "force, hypermfahanique " as the cause of vital phenomena. A return to the ill-reputed word, which arouses a well-defined prejudice, is simply to give up the advantage afforded by the hard-earned conviction of the unity of cause in all nature.

Psychical vitalism, as defended by Bunge ('94), and essentially, although more poetically than exactly, by Rindfleisch ('95), is something wholly different. It is properly not a physiological but rather a philosophical doctrine, which springs from a correct appreciation of the inadequacy of materialism, and it is to be regretted that it employs the extremely unsuitable names. " vitalism " and " neovitalism." We will consider somewhat more fully the vitalistic standpoint of Bunge. Bunge expresses the vitalistic creed unambiguously in the statement : " If the opponents of vitalism maintain that absolutely no other factors are present in living nature than simply and solely the forces and substances of inanimate nature, I must take issue with their doctrine." Nevertheless, from his further deductions it appears equally evident that his vitalism is na vitalism at all. Bunge's vitalism in reality is essentially a philosophical idealism arising from considerations similar to those expressed above regarding the theory of knowledge. Bunge is guilty of the one inconsistency, however, that he ascribes mind to organic, but not to inorganic, nature ; and it is this inconsistency that leads him to profess vitalism, for to him mind is the element that distinguishes the phenomena of the living physical world from those of the lifeless. It is a cause of personal satisfaction that one of our most prominent physiologists has energetically defended views similar to those to which my own general considerations have led, and, therefore, I venture to present herewith the passage in question from the introduction of Bunge's book ; it contains more profound reasoning than is usually realised. Relative to Johannes Miiller's law of the specific energy of the special senses, Bunge says : " I mean the simple law that one and the same stimulus, one and the same event in the external world, one and the same thing-in-itself, acting upon the different sense-nerves always causes (" discharges ") different sensations, and that different stimuli acting upon the same sensenerve always cause the same sensation; in other words, that events in the external world have nothing in common with our

sensations and ideas, that the external world is for us a book with seven seals, and that the only things immediately accessible to our observation and knowledge are the conditions and events of our own consciousness. " This simple truth is the greatest and deepest that the human mind has ever conceived. And it leads us also to a complete understanding of that which constitutes the essence of vitalism. The essence of vitalism does not consist in our being satisfied with a word and foregoing the thought. It consists in our taking the only right path of knowledge, proceeding from the known, the inner world, to explain the unknown, the outer world. Mechanism, which is nothing but materialism, takes the reverse and wrong path, it proceeds from the unknown, the outer world, to explain the known, the inner world."

We have seen that if we would explain the phenomena of the world in their entirety we must go back to elements that are very different from atoms ; that, however, when we confine ourselves to physical phenomena, we find no difference between the factors that work in lifeless and those that work in living bodies. Logic demands that every body, whether living or lifeless, must be subject to the general laws of bodies, which physics and chemistry reveal. It is evident that these two sciences are not yet completed, and that in the future many of their essential views will undergo profound changes. But so much is certain : an explanatory principle can never hold good in physiology with reference to the physical phenomena of life that is not also applicable in chemistry and physics to lifeless nature. The assumption of a specific vital force in every form is not only wholly superfluous, but inadmissible.

How does it happen that after the ill-reputed idea of the existence of a vital force has been regarded for decades as definitely set aside, modern science turns again to this outlawed word as a motto, in spite of the great variety of its significations ? Why have such words as " vital force " and " vitalism " been able to exert in recent times an influence upon investigators such as Hanstein ('80), Kerner ('87), Bunge ('94), Rindfleisch ('88, '95), and others ? It is not difficult to discover the reason. It is the same that in Haller's time gave birth to the idea of vital force, namely, the inability to explain vital phenomena mechanically, i.e., to reduce them to chemico-physical principles. This condition has existed during recent decades also, but it was largely neglected so long as the attention was occupied more with the epoch-making physiological discoveries of Ludwig, du Bois- Reymond, Helmholtz and others. We are becoming more con-

scious of it now, when the brilliant discoveries of the great physiologists of the present century have been followed to their ultimate consequences, when the mechanics of the grosser actions of the body are essentially known, when research is engaged in extending into their details the results obtained in the old direction, and when by the old methods nothing essentially new and pre-eminent is being discovered. There is also another favouring circumstance. The science of to-day is in great part still under the ban of that potent spell with which du Bois-Reymond benumbed and discouraged ambitious minds, when by proclaiming his " ignorabimus " he placed research in an attitude ot eternal renunciation, the necessity of which is acknowledged the more willingly since it was urged by such an authority and in so convincing a form. This renunciation, combined with the fact that great difficulties stand in the way of solving certain problems of life by the methods hitherto in use, is sufficient to explain psychologically an inclination toward coquetting with vitalism, whether the latter appears in its ancient or in its modern attire.

Nevertheless, eternal renunciation falls heavily upon the human mind, and even du Bois-Reymond did not accept it easily. From this natural aversion to such a conclusion we may suppose that the standpoint of renunciation toward vital problems is not inherent in the human mind and is not justified. The above considerations vindicate this supposition, and, moreover, the standpoint is denied in practice by most investigators. If, therefore, it is not the correct one, and if, nevertheless, the physical phenomena of life are based upon mechanical processes, it only remains to adopt another course.

We have arrived at a turning-point in physiology, a turningpoint that was never more apparent. The appearance of neovitalism is a sign of it. The old spirit of vital force is reappearing to many men of science to-day, just as in history, previous to great changes, significant spirits have appeared to clairvoyants. It is not difficult to see what characterises this turning-point. When we inquire what we have attained in physiology, we find that we have become acquainted chiefly with the gross chemical and physical phenomena of the body — thanks to the ingenious methods of investigation and the weighty discoveries of the investigators of our time, which are often characterised by an exactness such as is found elsewhere only in the discoveries of physics. We know the laws of the activity of the heart, the movement of the blood, the exchange of air in the lungs, the contraction of muscle, the conduction of nerves ; we know the actions of the sense-organs, how the digestive juices act upon the food, and the special anatomical basis of many psychical phenomena. But all these are only the mass-effects of large parts of the body,

they are not the end-results of vital activity. All that we are now accomplishing by means of the special methods that were created by the great masters of physiology for this purpose, is essentially only an extension of our present knowledge into finer details, and its application to analogous conditions. Every glance into physiological literature proves this. Every new number of the journals shows it. At present there is no dominating tendency in physiology, such as was the physical tendency a short time ago. A new great discovery is made along the present path only rarely, in spite of a frequently marvellous employment of ingenuity and knowledge, and yet the real riddles of life are not yet solved. We would not go so far as Bunge goes, and maintain that all phenomena which thus far have been explained mechanically are not vital phenomena at all ; but there can be no doubt that thus far we have not been able to explain the general, the elementary, vital phenomena. This impotence of the physiology of to-day in the presence of the simplest vital processes points plainly to the fact that the methods that have explained the mechanics of gross and special physiological activities, however ingeniously they were devised for that purpose, fail for other purposes, for the investigation of the elementary and general activities.

In order to solve the elementary general problem we must take a wholly different path. There is only one such path, and it was clearly indicated when the facts in the history of physiological research were summarised. Consideration of the individual functions of the body urges us constantly toward the cell. The problem of the motion of the heart and of muscle-contraction resides in the muscle-cell : that of secretion in the gland-cell ; that of food-reception and resorption in the epithelium-cell and the white blood-cell ; that of the regulation of all bodily activities in the ganglion-cell. The cell-theory has long shown that the cell is the structural element of the living body, the elementary organism in which the vital processes have their seat. Anatomy, embryology, zoology, and botany have long recognised the significance of this fact, and the great achievements of these sciences are a brilliant proof of the fruitfulness of the cell-method of investigation. But only very recently has the simple and plainly logical consequence begun to be recognised that, if physiology considers its task to be the investigation of vital phenomena, it must investigate them in the place where they have their seat, i.e., in the cell. If it is not to be content with extending still farther the present knowledge of the gross activities of the human body, but would really explain elementary and general vital phenomena, it must assume the character of cell-physiology.