Physiological Foundations of Behavior

is different from, and on a larger scale than, the patterns of its con- _Stituent parts. If the organism is a physico-chemical, and not, as the _ vitalists maintain, a metaphysical unity and order, its primary physiological pattern is the action system which constitutes the basis of this unity and order. Whatever the nature of this primary physiological pattern, it is evident that it must constitute the physiological basis of the behavior pattern of the organism and the investigation of the origins of behavior cannot stop short of this problem. Organismic pattern represents the first step in the origin of organismic behavior since it is the foundation of the order which appears in all such behavior. To interpret behavior we must know something of the nature and origin of organismic pattern, of the substratum or materials in which it arises and of the patterns of these materials. Such analysis carries us finally to the fundamental conceptions of chemistry and physics. This question of pattern and material has been more fully discussed elsewhere (Child, ’21 a, Chap. I)

On the other hand, every organism as we know it is a product of evolution and bears in itself the records of its past history, if we could read them aright. Its behavior, as well as its structure depends upon this past history. The organismic mechanisms are characteristic and constant to a high degree for each particular species or kind of organism because of this history. Different kinds of organisms arise from different kinds of protoplasm and each such protoplasm must possess a specific constitution handed down from the past, 7. e., hereditary. Whatever the role of environmental factors in determining the characteristics of an individual organism, there

~ ean of course be no doubt that the organismic mechanisms arise on the basis of the hereditary substratum and that this determines - that the organism shall be a certain species or variety of fern, elm, snail, fish, or ape. From this viewpoint the problem of behavior involves the whole problem of evolution as well as that of inheritance. This consideration of the physiological and historical aspects of the organism presents of course nothing new, but is concerned with facts so familiar as to be almost truisms. It serves, however, as a basis for emphasizing the fact that biological problems are fundamentally indissociable. The different fields of biological investi~- gation are merely the different aspects under which life appears and as investigation progresses their interrelation becomes more and more evident. Every biological problem involves finally all of life and the environment of life. The present purpose is the consideration of one aspect of this interrelation, viz., the significance of organismic pattern as a physiological factor in the origin and development of organismic behavior and its mechanisms. This consideration involves the questions of the nature and origin of organismic pattern, of its relations on the one hand, to the specific protoplasmic substratum in which it appears and on the other, to the external world, of the progressive modification and complication of the primary pattern in the course of development, and of the bearing of the data at hand in these various fields upon the problem of behavior. It is evident that the viewpoint in this consideration must be physiological, rather than historical. In other words, we are concerned primarily with factors and conditions in the development, maintenance and relation to environment of the individual organism in a protoplasm of specific hereditary constitution, rather than with the evolution of this specific constitution.

As will appear in the following chapters, the recognition and maintenance of this distinction is important, particularly as regards the conception of organismic pattern to which experimental investigation leads us. We are accustomed to speak of protoplasm as the substratum or seat of life and as if it were fundamentally the same substance in all organisms and all organs. At present this is little more than a manner of speech, but in earlier times, following recognition of the fact that the phenomena of life take place in the more or less fluid gel to which the name protoplasm was given, there was a widespread tendency, at least to speak of protoplasm, as Huxley, for example, does repeatedly, as if it were identical in all organisms. This was perhaps due in part to the fact that most of the earlier investigators of the material substratum of life were morphologists rather than chemists and were devoting their attention to the general physical properties of protoplasms as they appeared under the miscroscope and to the naked eye. As regards these properties, many different protoplasms show a high degree of similarity and it is not difficult to see how the conception of a fundamentally identical molecular ccnstitution arose. But we as have come to learn something of the chemical and colloidal constitution of this material substratum of life, it has become increasingly evident, as Ritter (19, Chap. V) has pointed out, that we have to do, not with a single substance, protoplasm, but with many different protoplasms, and that no protoplasm is a single chemical individual. At present, even though our knowledge of the physico-chemical differences of different protoplasms represents little more than a beginning, no biologist doubts that the protoplasms of different species are different in constitution and that even within the species many differences of constitution must exist. Already these differences are demonstrated by many different lines of investigation.

For example, the differences in metabolism and its products such as cellulose, chitin, bone, starches, sugar, fats, proteins, gland secretions, odoriferous substances, etc., show us clearly enough that the protoplasms of different organisms are doing different things. The remarkable specificities of relation brought to light in serological investigations and in allied fields of work also demonstrate that different protoplasms are physiologieally different. The work of Reichert and Brown (’09) showing that characteristic differences in crystal form of the hemoglobins and certain of their derivatives exist in different species and the later work of Reichert (13) on the differentiation and specificity of starches have brought to light other aspects of specificity of protoplasmic constitution. Again, the experimental work of recent years on nutrition demonstrates that substances which are adequate for the synthesis and maintenance of the protoplasm of certain species are inadequate for other species. In various cases it has been ‘possible to show that a particular chemical substance or group is necessary. What we know of the chemistry of digestion and the chemistry and metabolism of different tissues and organs in different organisms points to the same conclusion. In fact, it is possible that at present we are rather extreme in our belief in specificity and inclined to regard differences in protoplasm and organisms as specific or qualitative until the contrary is demonstrated. The hormones, so called, are usually regarded as specific in their action, though the work of certain investigators suggests that in certain cases the specificity is less marked than usually supposed.t| But whatever the truth concerning this or that detail, differences and specificities of constitution of different protoplasms exist beyond all question, not only in different species but in different parts of the individual organism. Granting this, however, we need not lose sight of the fact that different protoplasms are physico-chemical systems of the same general sort and that certain resemblances or identities are recognizable as well as specific differences between them. Moreover, various factors in the differences of different protoplasms are non-specifically or quantitatively, rather than qualitatively, difforent.

In fact, the distinction between quantitative and qualitative differences in protoplasms presents many difficulties. Differences which are quantitative from one viewpoint are qualitative from another. For example, purely quantitative differences in rate of respiration may be dependent upon qualitative differences in the substances concerned 1For example, more than ten years ago Meisenheimer (712) suggested that the internal secretions of the sex organs are not specific for the organs of a particular sex, but are merely substances necessary for the development and maintenance of the body in general. Investigations of recent years have made it highly probable that secretin and gastrin, which may be regarded as foundation stones of the hormone theory, are not specific substances. For the present status of this question see a recent discussion by Carlson (’23, pp. 18-21) and for further literature, the following papers: Luckhardt, Keeton, Koch and LaMer, ’20;

Keeton, Koch and Luckhardt, ’20; Keeton, Luckhardt and Koch, ’20; Koch, Luckhardt and Keeton, ’20; Luckhardt, Henn and Palmer, Ppp in the metabolic reactions, and again differences in the relative amounts of substances entering reaction may determine qualitatively different products. In its fundamental features the specific constitution of a protoplasm is continuous from generation to generation, 7. e., hereditary, | though we believe that it has undergone change in one way or another in the course of evolution. Each protoplasm apparently represents in a broad sense a dynamic equilibrium, or more properly speaking is always approaching a dynamic equilibrium which is always being disturbed by external factors (see Chap. XIII). Within the usual range of environmental conditions to which they are subjected living protoplasms possess in a high degree the capacity of equilibration. It is probable, however, that a protoplasm after action of an external factor upon it never returns to exactly the condition which existed before such action. In nature protoplasms exist only in organisms and since we make a distinction between protoplasms and organisms it is necessary to consider the basis on which this distinction rests and this involves the problem of organismic pattern and the differences between it and protoplasmic pattern.—

/y As pointed out elsewhere (Child ’21 a, Chap. I), organismic pat- | tern is an order, plan, unity or integration of which a protoplasm constitutes the material substratum. Certain features of this pattern are highly significant in their relations to behavior. In the first place, protoplasms are found in nature only as organisms or parts of organisms. Nevertheless, it is evident that the organism represents a pattern of a higher order of magnitude, on a larger scale, which arises in some way upon the substratum which constitutes protoplasmic pattern. The organismic pattern involves molar regions or masses of living protoplasm, or whole cells or cell masses as its constituent elements, while protoplasmic pattern is colloidal, or perhaps as regards certain features cerystalloidal, molecular and submolecular. Organismic pattern determines in some way what | we call organization in protoplasm, that is, different regions or cells become different in structure, constitution and function. This organization is orderly and definite in character for each organism and functional relations exist between its constituent parts. The organism represents then certain sorts of ordering, differentiation and physiological correlation of activities in different molar regions of

protoplasm or in different protoplasms. As the house represents a pattern and integration on a larger scale than the patterns of any of the materials entering into its construction, so the organism represents a pattern and an integration on a larger scale than protoplasmic patterns. In multicellular organisms the pattern is on a larger scale than that of the single cell and in colonial forms the pattern of the colony is on a larger scale than that of the single zooid or person of the colony. In short, it is evident that in an organism different regions of protoplasm, different cells, or cell masses, or even different individuals are in some way integrated into a definite and orderly whole.

If we say that a protoplasm is a physico-chemical system in which various dynamic changes of certain sorts occur, then an organism is a system of protoplasms. That is to say an organism is an integration of protoplasmic systems differing from each other in some way. If the changes in a protoplasm constitute life, the organism is an idtegration of different rates or kinds of living. It is of course true that we know life and protoplasms only as they occur in organisms, but it is also true that we can distinguish different protoplasms in an organism, that these different protoplasms are alive and that the changes which constitute life in them differ in some way. Even though we cannot define life nor protoplasm exactly, it is perfectly evident that an organism is not merely life nor merely a protoplasm, but an orderly and definite integration of different ways of living and different protoplasms. Second, organismic pattern has _reference at every point to the relations between protoplasms and environment. The organism as a pattern, a mechanism, has no meaning except in relation to environment. It is in fact a pattern which makes it possible first of all for protoplasm to persist in the external world, and second to modify and control its environment to an increasing degree. In whatever aspect we regard the organism, it is obviously in relation to environment at every point. Its mechanisms are all concerned in some way with either the dynamic or the material factors of its environment. The mechanisms and therefore the relations to environment of different organisms are of course different, primarily because their protoplasms are different, but however these mechanisms differ, they are all concerned with reactions 4o environment.

The evolution of the organism has modified organismic pattern chiefly in two directions. First, the adjustment of certain mechanisms to external excitatory impacts has become more and more delicate and exact, and second, mechanisms making possible in one way or another the control and modification of environment have been increasingly effective. The physiological foundations of these modifications are found in the simplest organisms. In the light of our present knowledge it appears that the simplest possible organism consists of a mass of protoplasm with a plasma membrane at its surface. In such an organism the impact of external energy may alter the physico-chemical state of the membrane, inducing what we call excitation and so affecting the interior. Moreover, the semipermeability of the limiting membrane makes possible some degree of selection among material environmental factors.

Turning to axiate organisms, we see that the presence of an axiate pattern provides a basis for a differential axial relation to the external world which may express itself in position or direction of growth, as in plants and sessile animals, or in directed locomotion, as in motile animals (see Chap. VI). And the character of axiate response to environmental factors is still further differentiated by the symmetry relations of the pattern. A bilateral organism behaves differently from a radiate organism. The development of localized sensory, nervous and motor organs contributes to the def- iIniteness and speed of response. Other features of the organism, the alimentary, respiratory, circulatory and excretory systems, are concerned with the materia] exchange between organism and external world, and their development is in the direction of greater efficiency in this relation to environment. The organism may, in fact, be defined as a pattern of relation to environment appearing in protoplasm.

From this viewpoint the life of an organism is actually, as Spencer put it, “the continuous adjustment of internal relations to external relations.”” The organismic pattern, on the one hand, and the specific hereditary constitutions of the protoplasms in which the pattern is expressed, on the other, determine the possibilities, the directions, the range and the complexity of this adjustment. Organismic pattern then appears to ke a behavior pattern in a protoplasm. Different regions and cells come to behave differently instead of alike, and these different behaviors are integrated into an orderly whole. In as far as it is concerned with organismic pattern, the so-called organization of protoplasm originates in, and is the expression of these regional differences in behavior. :

It may appear at first glance that to call the organism a behavior pattern in protoplasm is little more than a fanciful figure of speech, It may be objected, for example, that localization and morphological differentiation of organs in an embryo are processes very different from the use of these organs in behavior of the fully developed animal. Moreover, even if it be granted that such phenomena may in some sense be called behavior, it may be maintained that such behavior is, at least in considerable degree predetermined or inher-

ent in the protoplasmic constitution. If this is true, it is not an adjustment of internal relations to external relations, but is independent of external relations, whether these are relations of one part of the organism to others or of the organism to its environment. So-called mosaic development, for example, in which parts of the organism are able to develop and differentiate up to a certain point independently of each other, has often been regarded as proving such predetermination. All the evidence indicates, however, that mosaic development and self-differentiation are, with certain exceptions, secondary conditions in development (see pp. 146, 244). On the other hand, we find that many developmental processes do stand in direct relation to environmental factors, either intra- or extraorganismic. When we alter these relations, e. g., by isolation of such parts, they respond to the change by altered development. In fact by far the greater part of what biologists call plant behavior consists of exactly such changes in development, growth and differentiation.

Motor reactions, which are not infrequently regarded as essential factors of animal behavior, are, properly. speaking, only one aspect ‘ofthe behavior of living things, viz., excito-motor behavior. They are singled out and emphasized as behavior because of their very direct relation to environmental factors and their value to the or- -ganism as means of adjustment. If Spencer’s definition of life has any real meaning, it is that life is the behavior of protoplasmic systems in relation to an external world. From this viewpoint organisms as individuals must represent behavior patterns of protoplasms, the specific constitution of the protoplasm and the environmental factors determining the behavior in each case. In other words, the individual organism represents certain hereditary potentialities of the particular protoplasm or protoplasms concerned which are realized under certain conditions as individuals. Similarly, behavior in the ordinary sense of the organism as a whole, represents in each particular case a behavior pattern potentially present in the organism, but realized only through the action of an external factor. This conception of the organism as a behavior pattern is really

nothing more than a conception of the organism in dynamic terms. The biologist, particularly the zodlogist, has in the past been inclined to look at life from the morphological side and to attempt to conceive it in morphological terms, but it becomes increasingly evident that morphology must sooner or later be interpreted in dynamic terms, that is to say, in terms, of the behavior of the system in which it appears. That the organism is primarily a behavior pattern in a protoplasm of specific constitution is the principal thesis of this book.

In general the relations of a protoplasm or an organism to its environment are, biologically speaking, of two sorts, the material, and the dynamic or energetic. The material relations include all material exchange between a protoplasm and the external world, that is, all relations which involve the transfer or transportation in mass of substance between the protoplasm and its environment. The intake of nutritive substance and water, the intake of oxygen and of CO, in photosynthesis in plants and, on the other hand, the outgo of water, of food residues, of excretory products of metabolism of all sorts, are all relations of material character. On the import side, relations of this sort provide the material for growth and maintenance as well as that used in the energy liberation involved in functional activity. On the export side, they serve for the removal of by-products and residues of metabolism which have no further part to play in the protoplasmic system. The by-products or the residues, or even the substance itself of one sort of protoplasmic system may represent nutrition for another system or play some other part in its activity. Such relations are the nutritive relations of animals to plants, of the carnivore to its prey, of the parasite to its host and the mutual relations between symbiotic forms.

These material relations are specific so far as the material factors of the external world on the one hand or the protoplasmic constitution on the other are specific. Undoubtedly the specific material relations between protoplasm and environment have been factors in the evolution of the specific constitutions of the different protoplasms. In fact, we must believe that such material relations between different physico-chemical systems or individuals were concerned in the origin of protoplasm.

The dynamic or energetic relations between pretoplasms and environment are concerned, not with the transport in mass of substance, but with the transfer of energy in one form or another. These relations may be grouped under two heads: first, the direct purely mechanical or non-excitatory relations in which the effect is mechanical and proportional to the energy; second, the indirect or excitatory relations in which the energy transfer between the external world and protoplasm serves merely as the initiating factor in bringing about energy changes which themselves depend upon the configuration of the system acted upon.

There may be difficulty, as in the case of most abstractions, in drawing a hard and fast line between these two groups of relations. Practically it may be difficult to determine in a given case whether, or to what extent a particular relation is mechanical or excitatory. As a matter of fact, some degree of excitation or inhibition probably occurs in living protoplasm in connection with most or all dynamic action of external factors upon it. In spite of such difficulties as regards particular cases, the difference between the two sorts of relation is sufficiently clear. In the one the system acted upon behaves as an inert system and the effect produced is brought about solely by the external energy. In the other the external energy merely serves to initiate changes in the energy relations between component parts of the system and energy liberated by such changes may produce effects immeasurably greater than the original external energy.

So far as protoplasms are concerned, the action of external factors in its purely mechanical aspects is in general of less importance than other dynamic relations in determining the condition of the protoplasmic system. It may bring about passive deformation and so be a factor in determining shape in some cases: gravity may determine the positions or distribution of substances of different weight and in this way determine. other changes. Again, extreme mechanical action may produce death and disruption of protoplasm, but such relations are “accidental” rather than an essential feature of life. Of course mechanical factors may act on protoplasm as exciting or inhibiting factors, but in such case their effect is no longer purely mechanical, the mechanical energy of the external action undergoing transformation in the protoplasm. Such effects belong in the excitatory rather than in the purely mechanical group of relations.

Turning to the other aspect of the mechanical relations, it is evident that the mechanical action of protoplasm in the form of organisms upon the external world is a factor of fundamental importance in life. The locomotion of organisms, the taking of food, lung breathing and the propulsion of water over gills all depend very largely upon such action. A large part of the work of man in altering the configuration of his environment is accomplished through mechanical action either directly or with the aid of tools and machines, that is, contrivances for bringing about mechanical action more rapidly or on a larger scale than is possible with the mechanical energy of the human organism alone. Most organisms would cease to exist in a very short time if it were impossible for them to alter their environment by mechanical action upon it. In short, the purely mechanical action of external factors upon protoplasms is of relatively little significance in life, while the mechanical action of protoplasms in the form of organisms upon the external world is essential to the life of organisms.

As already pointed out, the second group of dynamic relations, the excitatory relations, involves the transformation of the energy of the factor acting into other forms in the systems acted upon. Such transformation usually or always determines changes which liberate energy from the system. In any case the course and character of excitation depend primarily on the configuration and state of this system. Here the factor acting merely initiates and the result depends on the system affected as in the relation of the spark to the explosion, or the forest fire.

Whatever the exact nature and relation of the processes concerned in protoplasmic excitation — or inhibition — may prove to be, the process in general is a complex dynamic change, probably involying both physical and chemical factors. Doubtless the component processes differ in different protoplasms and perhaps even with different degrees of excitation in the same protoplasms, but it is evident that excitation is more or less similar in all protoplasms. Even though we regard excitation merely as a more or less complex physico-chemical change, depending rather on the configuration of the system acted upon than upon the energy acting, the general conception of excitation has not lost its usefulness, as some physiologists have suggested.

In excitatory relations it is the action of the external factor upon protoplasms, which is of fundamental importance for life. We believe that irritability or excitability is a fundamental property of all living protoplasms, though it may vary widely in degree. In excitation the action of the external factor is, so far as the excitatory effect is concerned, non-specific, that is, essentially quantitative, though of course the process of excitation may differ in different protoplasms, and while some protoplasms are more readily excited by certain forms of energy, others by other forms, it is probably

s ~ true that all forms of energy within certain limits of amount and intensity are capable of exciting most if not all protoplasms to some degree. While the material relations between protoplasms and the external world are of course absolutely essential for the maintenance of life, since they supply fuel, 7. e., energy to the system and accomplish the removal of residues, the excitatory relations constitute the primary factor in the behavior of living things. The irritability of protoplasm, its sensitiveness to the impact of external energies and the change in state brought about by such impact, are the foundations of all that we call reaction or response in organisms. Many non-living systems are irritable or excitable in one way or another, é. g., dynamite, dry wood, coal, but the excitability of protoplasms constitutes the physiological basis of those characteristics of living things which distinguish them most sharply from the non-living, viz., the ability to react or to respond to the.impact of external energies by changes in state which include a reference to the external factor and therefore serve a purpose, or in the higher animals and man are consciously purposive or intelligent in character. The evolution of intelligent behavior from the relatively simple excitation and its transmission in a primitive protoplasm is of course associated with and dependent upon the development and integration of complex mechanisms of excitation, conduction and effect and involves the whole problem of the evolution of organisms, but it is nevertheless true that the excitability of protoplasms in general is the primary physiological factor concerned in the functioning of all these mechanisms (Herrick, 1924, Chap. XXI). Life as we see it, particularly in the higher animals, and man, is a series of excitations with the resulting equilibration of the organismic mechanisms to the exciting changes.

We cannot conceive what life without excitation would be and it is a question of some importance, though perhaps largely academic, how long life can continue in the total absence of excitation. Many excitations are obviously only indirectly related to an external factor, but we have at present no evidence to indicate that protoplasm is fundamentally capable of self-excitation in the strict sense (see pp. 184-186) and the arguments of the vitalist in favor of such autonomy are in the present state of our knowledge far from conclusive.

It is unquestionably true that the excitability of protoplasm constitutes the primary physiological factor in the behavior of organisms in its broadest sense. At least in motile animals the material relations are determined and ordered to a large extent by the ex- — citatory relations. Even in most of the simpler animals the reaction to food involves excitation and the excitatory factor is undoubtedly concerned in the growth orientation of the roots and of other parts of plants with respect to chemical and photic conditions. In

the case of internal parasites which live in a nutritive medium and in plants which also may be said to live in a nutritive medium the material relations may be to a considerable extent independent of excitation, but even in such forms the intake must depend to some degree upon the rate of transformation in the body and in this excitation is concerned. Even on the basis of this general discussion it is not going too far to say that the excitability of protoplasms has