Chapter 14

Application of this theory to explain the variations in the cycle or zoic course

1993. From what has been said, it follows that:

1. From the first moment of human existence to the moment of death, there is an uninterrupted flow of actions alternating between life and sensuous instincts. From now on, I shall call this the zoic course;

2. The laws followed by both instincts in their action are always the same and can never be essentially changed;

3. The animal's healthy and unhealthy states, together with its increase or decrease, depend equally on the alternating actions of the two instincts; the unhealthy state and the disease processes are simply a part of the flow of the alternating actions of which we are speaking. They do not interrupt, but continue this flow. Unhealthy phenomena, therefore, do not differ essentially from physiological phenomena.

1994. It follows, despite the immutability and necessity of the laws according to which the two instincts incessantly operate, that the alternating flow of the sense-experiences and movements is so different that it varies in type in every animal of different species. Even in the same species, it is impossible to find two individuals in whom this flow is exactly the same. Indeed, it is never uniform at different moments of life, even in the same individual. The variation in this zoic course in human beings must, therefore, be much greater than variations in their physiognomy. Granted that this flow is disposed in a series of innumerable links of reciprocal actions, the smallest change in one of the links is sufficient to change the entire course and to open a new path, different from the first, in which it continues. For brevity's sake, I shall call any couple of actions, one from the life instinct and one from the sensuous instinct, links in the zoic course.

1995. I have already explained why, if the laws of the two instincts are unchangeable, the zoic course takes so many different directions that it changes path in each human being, in each animal. If we go back to the first causes setting the zoic course in one direction rather than another, or, once the zoic course has been given its direction, making it diverge from that direction, we are necessarily referring to causes extraneous to the animal, and principally to matter.

Sometimes matter submits itself obediently, as term, to the life instinct; sometimes it struggles with the life instinct, forcing it to fight painfully. Sometimes it solaces the life instinct with a suitable stimulus, exciting it to a pleasurable feeling; sometimes it vanishes, overcoming the retentive faculty of the life instinct and withdrawing from its action. These different actions and aptitudes which matter takes in relationship to the life instinct force the instinct to produce different feelings, which determine different zoic courses.

1996. I said that brute matter is the principal, but not the only cause directing the zoic course in one path rather than another. I qualified my statement because intelligence, intimately associated with animality in the human being, is yet another cause extraneous to the concept of animal, and influencing the zoic course.
Consequently, if we consider animality in the human being, the zoic course receives impulses directing it in one way rather than another, or making it divert from the first way, from two causes: from matter, an agent inferior to animality, and from intelligence, an agent superior to animality.

1997. Matter, therefore, and intelligence are the two causes in human animality which determine the direction of the zoic course. They do this in such a way that the flow follows its path necessarily without moving to left or right. Provided that matter and intelligence offer no further irritation, this is prescribed by the laws of the two instincts. But if one of the two causes we have mentioned exercises some new influence on animality, the flow is forced to change direction and follow the new path with equal certainty and necessity.

1998. We need to note, however, that as matter determines the zoic course or moves it to another path by acting in the life instinct in so far as this instinct is passive towards matter, so intelligence determines the zoic course or makes it change path by acting on the life instinct in so far as this instinct is active towards matter itself. Indeed, a sad, depressed feeling can arise from unhappy news only if the intellective soul, saddened by the fatal information, deprives the life instinct and, in part, the sensuous instinct of their strength in such a way that the circulation slows down and other symptoms of weakness and mutual reaction appear. Consequently, the degree of activity of the life instinct is diminished or increased by the direct action of the intelligent soul, and the zoic course is changed.

1999. From what has been said, it is clear that the first steps taken by the sensuous instinct are determined by the first feelings, the effects of the life instinct; there are as many species, forms, degrees of first movements caused in the animal body by the sensuous instinct as there are species, forms, degrees of first feelings produced by the life instinct. Hence the entire zoic course depends on the first feelings which in turn depend on the two causes I have mentioned, matter and intelligence.

2000. Let us list the primal feelings(85) according to their types or full-species(86) to see the special causes on which each depends, and how each initiates its different zoic course.
The fundamental feeling has continuous matter and motion as its terms.

I shall consider it with continuous matter as its term.

The fundamental feeling of continuity must be given some matter which has certain dispositions preceding the action of the life instinct. Such a general proposition cannot, however, be proved because we never find matter and life instinct separated from one another. We first have to suppose, therefore, an animated germ which has matter appropriate for the animating action of the life instinct, and an organisation suitable for the germ's ulterior development. This organisation is called the primal type of the animal. The development takes place through incessant movements caused by the sensuous instinct.

2001. Hence

I. An animal cannot preserve its life unless it receives as nourishment some matter which has certain dispositions prior to the action of animal instinct.
This proposition is obvious when we consider that not all material substances are suitable for animal nourishment.
It is absolutely necessary that nitrogen and oxygen molecules be substituted for those which the animal is constantly losing. Magendie, having fed several dogs with nitrogen substances such as sugar, oil, water, etc., soon killed them.

If oxygen does not nourish the blood, the animal dies through asphyxiation. Nor is it normally sufficient for oxygen to be received through the lungs by means of respiration. Oxygen nourishes and maintains the animal by entering it also through the skin. Magendie himself, having covered the whole body of rabbits and other animals, the face excepted, with a viscous plaster formed by a concentrated solution of rubber, gelatine or terebinth in such a way that the skin no longer absorbed the atmospheric gases, killed the animals from asphyxiation in little less than an hour, although they were able to breathe.(87) On the other hand, Magendie also showed through experiments that the epidermis and in general all membranes are permeable by gas.(88)

2002. II. Besides the quality of matter, which probably depends on its form and composition, matter must also be placed in continuity with the already animated body so that the life instinct instinct can invade it. Although experience does not and cannot demonstrate the necessity of this continuity but only of some proximity, reasoning does, I think, demonstrate it.

2003. III. In the third place, it is also necessary that suitable matter should be elaborated (that is, broken up, recomposed, purged, classified and distributed) by the life instinct through the already living body.

2004. IV. In the fourth place, matter should receive from the soul the ultimate quality that makes it act on the soul itself. I have spoken about this elsewhere.(89)

2005. Granted these conditions, the fundamental feeling of continuity is conceived as placed in being where it maintains itself. The first three conditions form the organisation, and the fourth furnishes organisation with its final act, called 'extrasubjective life'. Through this act the body is in its turn rendered active relative to the soul, a necessary condition for explaining the passivity found in feeling. All these conditions are present in the animated germ in which the animal begins. They can, however, be reduced to three: 1. suitable matter, 2. continuity, 3. animalisation.(90)

2006. The last condition, the final act of extrasubjective life in the body, depends (granted organisation) on the activity of the sensitive principle. Because this activity can be modified by the influence of the intellective principle, there is no doubt that the production of life and its consequent feeling can be modified at every moment according to the disposition of the intellective principle. This occurs to such an extent that the vital effect and the production of the fundamental feeling can be impeded. In this case, there is disorganisation, and death follows very quickly. Nicholls describes an English lady of his time who was found to have committed adultery. She was so deeply upset by pain and shame that she contracted a fever and lay at death's door. She asked forgiveness from her outraged husband and revived through her hope of pleasing him once more. After her recovery, however, her in-laws persuaded the husband that his unfaithful wife had simulated sickness to win his pardon. He then went off to the country and sent a message to her affirming that he had done sufficient in keeping her alive and now wanted a divorce. The unhappy woman, distraught by the message, could only reply that she was now dying. Her pulse gradually slowed, she experienced constriction in the chest, and after a few hours ceased to live.(91) This is one very effective way (but there are a great many others) of showing that the condition of the intellective principle influences the activity of the animal principle which it increases, diminishes, binds and dissolves. The fundamental feeling of continuity differs, therefore, in human beings, above all as a result of the state in which the intellective principle is found.

2007. In the second place, the fundamental feeling differs according to the degree of continuity between living molecules. It seems probable that life does not require as its condition any continuity determined in such a way that it cannot permit any modification. On the contrary, it is probable, I think, that there are two limits to the continuity of molecules, limits within which life is preserved in a perfect state. I am speaking here of the mere life of continuity which seems to require continuity and nothing more. The degree of continuity depends on the form and size of the molecules. Such circumstances bring about spaces of varying quantity and sizes between the molecules.

2008. It seems that the strength and robustness of the life of continuity is proportionate to the compactness of the mixed being and the number of points at which the particles touch. However, over-adherence of molecules impedes their movement and lowers their life of excitation.

2009. Moreover, the excited feeling is much more than the feeling of continuity. Animal instinct, therefore, tends on the one hand to accumulate feeling by drawing together the molecules and adapting them so that they touch one another with the largest possible surfaces. On the other hand, it tends to assist their reciprocal, organic movement and hence to round them off, and to keep them at a distance at the greatest possible number of points without their losing continuity. This is a real problem of extremes which the animal principle resolves factually.

2010. The fundamental feeling of continuity varies, therefore, also according to the varying degree of continuity in the molecules from which the animal results. It varies according to the absolute quantity of matter which is its term, while the extension of the fundamental feeling of continuity varies according to the quantity of matter.

2011. A living body also loses a certain number of molecules. This loss normally has two effects: 1. it diminishes the extension of the fundamental feeling of continuity; 2. it modifies to a varying degree the fundamental feeling of excitation.

The first effect is the loss of certain parts of the feeling of continuity. We need to note the difference between this loss and the modification suffered by the feeling of excitation. This modification supposes molecules which change place without abandoning their continuity. When this change of place is diffused in a given organ communicating with the physical centre of the animal according to certain laws, special sense-experiences arise through a faculty appropriately called special sensitivity or special excitation. The sensitivity proper to the two orders of nerves is of this kind. Other parts of the body, incapable of such great, special, excitatory movements, have only the fundamental feeling of continuity which, by becoming more dense (either by extending itself or admitting new molecules or by relinquishing them) is modified without exciting our attention. In this sense, all parts of the body can be called sensitive, but not in the same way as nerves, whose sensitivity is special and excitable.(92)

2012. Finally, the fundamental feeling of continuity varies in the degree that matter is predisposed to receive the action of the life instinct and with it life itself. Describing and enumerating these predispositions is far beyond my limited knowledge; nor would I be able to indicate, except partially, the true causes which provide matter with the predispositions necessary for life. From what has been said, it simply appears that matter added to a living body to be enlivened with its life must have certain qualities or forms. This explains the attribution to matter of certain names indicating the presence of oxygen, of nitrogen, etc. It also seems that matter must be elaborated, or worked on, by the living body to which it draws near. This elaboration will be perfect to the extent that the living, elaborating machine, and the principle moving the entire machine, are perfect. However, while these may be the causes which provide matter with the preparatory dispositions for life, it is certain that even in these predispositions there are degrees and limits of various kinds within which life takes place.

2013. But knowing whether the predispositions of matter can vary in some way without lessening the perfection of life (so that degrees or different and equivalent forms may be present in the identical perfection) is far more difficult to verify. By perfection of life, I understand the complete triumph of the life instinct over matter in a state where there is no further struggle between the two elements. The life instinct, which dominates with an absolute act, rests in matter. It is certainly not impossible to conceive that the life instinct fully invades matter or that it invades it with different degrees of force. The fact of the influence of the intellective principle on the increase or decrease of forces proper to the animal principle shows that the potency of the animal principle varies in degree. Nothing prevents the life instinct from producing different effects in the animal principle, according to the disposition of matter, by giving some parts life of continuity alone, and other parts life of excitation, etc. But so far no attempt has been made to determine these various effects, these various degrees.

2014. Every variation in the fundamental feeling of continuity is an element of variation for the sensuous instinct which receives from it a different aptitude. But what is the effect of this aptitude?

2015. First, the sensuous instinct tends to maintain feeling. Nevertheless, this effect, in so far as it is opposed to the forces which desire to destroy or diminish feeling, can also be attributed to the life instinct. In fact, this is the point at which the two instincts converge. If the life instinct is that which produces feeling, it must also be that which preserves it. Preserving feeling means continuing to produce it; the act with which it is produced is the act with which it is preserved. On the other hand, if the sensuous instinct is that which works as a result of a feeling in order to continue and increase it, the very activity which desires to continue and increase feeling must tend first of all to preserve it. The truth is that the two instincts are a single activity which I re-unite and call animal instinct.

But because the effects divide into two classes, we have two names for the same activity in so far as we consider it as the cause of one or other class of effects. These classes are so distinguished that the effects pertaining to the second class follow those pertaining to the first class. The activity itself, therefore, does not produce the final effects in its first moment, but in its second. It does not produce them when it begins to act, but when it continues its act. It is the activity itself which, however, has attained a second degree of development. Moreover, because the second effects can begin only where the first finish, there is a point common to both kinds of activity, a point where the first activity ends, and the second begins. Thus preservation of a feeling possesses characteristics belonging to both classes of effects because the duration of a feeling involves both the concept of production on the one hand, and of continuation on the other. It is an effect referred to both instincts, which are radically a single activity.

2016. If, therefore, we consider preservation of a feeling as the effect of the sensuous instinct, this effect will vary 1. in force according to the degree of efficacy of the life instinct; 2. in extension according to the quantity of matter; 3. in consistency according to the continuity or thickness of matter itself; 4. in character or quality according to the way in which matter is organated, and according to the degree of perfection present in the preparatory qualities for life.

2017. Finally, we may suppose that certain particles, not totally lacking predispositions for life, may be at odds with the life instinct and produce a state of pain or disturbance (which also varies according to the nature and degree of the disposition of such particles, of their quality, of their place, etc.). The variation of the forces of the life instinct impress a different stamp on the activity of the sensuous instinct.

2018. Generally speaking, we need to notice that the fundamental feeling of continuity is unsuitable for moving the sensuous instinct to its act; it can only adapt it in one way rather than another, that is, constitute and determine it as a potency. The sensuous instinct always requires excited feelings, transient of their nature, to move towards its act. We need, therefore, to speak about the feeling of excitation to explain how the sensuous instinct rises to its act.

2019. We begin by supposing the existence of a group of living particles in contact with one another.
As soon as any kind of stimulus moves those particles from their reciprocal position without destroying their continuity, we say that the feeling enclosed in that group is modified and excited, and that sense-experiences arise.

2020. These sense-experiences admit infinite variations: speed, frequency of motion, number of particles, reciprocal pressure and force proper to a more or less centred vital principle,(93) are variable elements which must change the character, degree and number of sense-experiences. It pertains to progress in science to determine as far as possible all the sensible differences of which a living being is susceptible.

2021. However, the fundamental feeling of excitation does not mean any kind of complex of sense-experiences, but only that complex of excitation and sense-experiences which through the unity of its harmony is unified in an individual feeling which preserves the same type. This type is the foundation of the animal species itself.

2022. Consequently, we see that even in the fundamental feeling of excitation natural stimuli are supposed. They are reproduced according to a constant law, but manifest variations in various individuals of the same species. These stimuli are foreign to the animal, which is feeling, and pertain to the sensiferous element. Their effect is extrasubjective movement accompanied by the sense-experience, that is, the harmonic complexity of continually reproduced sense-experiences which constitute the fundamental feeling of excitation. These sense-experiences are those which before all others provide a lever to sensuous instinct which thus attains its first act. This act seconds such sense-experiences and assists the movements, which produce the sense-experiences, to continue and repeat themselves.(94)

2023. First, let us examine the concept we should form of stimuli.
A stimulus or stimulating potency is derived from material forces which may be mechanical, physical, chemical, etc. It is derived, that is, from all forces foreign to the vital force of the individual animal.

2024. They act in opposition to this vital force. The opposition is more apparent in a living solid when material forces, or any other kind of foreign force, are applied to produce some movement within it.
Every movement produced in the interior of a living solid can be considered as the effect of a stimulus.

2025. In human beings, these stimuli are divided into two great classes: intellectual forces, in so far as they influence the vital force, and material forces.

2026. We restrict our consideration to variations in material stimuli. These variations can first be distinguished into two great classes:

Class I. Material substances composing the living body itself.
Class II. Material substances not composing the living body.

2027. Material substances composing the living body can be divided into fluids and solids. The former function principally as stimuli; the second as stimulated.

2028. Giovanni Rasori does not consider all fluids of the living body as stimuli. He posits the blood as the supreme stimulating faculty, but thinks of the bile, the gastric and intestinal juices and the marrow principles which penetrate all the viscera and even the smallest fibres as counter-stimulant substances. However, the sense I give to the word 'stimulus' does not allow the existence of material substances which are truly counter-stimulant in a positive sense. They can be granted only in a negative sense, that is, suitable for impeding the application or action of stimuli, or of destroying, through a contrary motion, any motion which produces some stimulus. They are not suitable for directly lowering the vital force, unless they are disorganising factors.

2029. Consequently I think it better to consider as counter-stimuli only 1. that which disorganises the machine; and 2. sense-experiences and affections which by means of the sensuous instinct directly lessen the force of the life instinct. Let us consider those material substances which, applied to the living body, produce a de-acceleration and diminution of vital movements. These are indirect counter-stimulants.

2030. If 'stimulus is everything that produces an internal movement in a living solid, the concept of stimulus is always reduced to a cause of motion in the interior of a living solid'. There is therefore no stimulating action without motion. If we then suppose that the motion is produced by material causes, these can act in a chemical, physical or mechanical way. An identical agent can act on the human machine in all three of these ways. Note, however, that although the agent acts principally in a chemical way on the fluids of a living body, it acts on solids in a much more physical and mechanical way. Air acts chemically on the blood; physically on the whole body, with its weight; mechanically, by its impulse and movement. The impulse given by red blood to the brain and all the nerves is a mechanical mode of action. But it also acts in a way which cannot be called merely chemical, but chemico-vital, by enlivening and nourishing all the tissues. Here its chemical forces are associated with vital forces which produce these final effects.(95)

2031. Although solids are not of themselves stimuli but stimulated, they nevertheless produce stimuli through secretion of fluids and with the movement and direction they give to fluids. Thus, they direct the blood towards a wound by increasing the stimulating action at that point. Moreover, because it is the solids which work on and secrete fluids, the normal or abnormal action of solids alters the nature of fluids for good or bad. If, for example, there is a spasm in the solids, the blood is unnecessarily accelerated and heated. Once inflamed, the fine fibre tends to separate from the serum and coagulate by oozing out of the veins and solidifying. The disposition towards separation from the other two elements acquired by the fine fibre tends in this case to disorganisation; a manifest struggle ensues with the vital principle, which has already lost part of its dominion over the material forces.

2032. Excitation is an animal condition provided that 1. it does not tend to remove the continuity of the parts; 2. it tends to perpetuate itself; 3. it does not tend to remove the animal's unity and individuality. The animal, therefore, must take pleasure in being stimulated; a certain system of stimuli must be continually applied to the animal. In the second place, we see that only a given excitation, not every excitation, is suitable. Only certain stimuli, not all, are appropriate for the animal.

2033. Inappropriate stimuli are therefore:

1. Those which tend to destroy the continuity of the parts.
2. Those which impede the continuation of excitation either by altering the organisation, or disturbing the application and action of appropriate stimuli, or provoking movements contrary to those provoked by appropriate stimuli.
3. Those which tend to destroy the unity and individuality of excitation;

This serves to confirm that it is not the quantity but the inappropriateness of stimuli which makes them dangerous. It is, however, true that a quantity which exceeds certain limits renders stimuli inappropriate.

2034. Matter composing the living body can be considered from the point of view of the agent which stimulates the living body itself, or as reduced to a fluid state, or as moved from its place. In the same way, we can consider from the point of view of a stimulating agent any matter whatsoever which is extraneous to the human body and which, applied to it in any way, produces intestine movement in the solid. In addition, matter extraneous to the human body can, in the power of its chemical forces or even through its mechanical movement, or through the special condition of the part of the body to which it is applied, or as a result of any other circumstance, be made an appropriate or inappropriate stimulus.

2035. Inappropriateness of stimulus, therefore, does not lie in any stimulating matter extraneous to the body, but in matter's producing in the body an action at odds with the action of the vital forces, that is, an action contrary to the three conditions for an animal: continuity of parts, perpetual excitation and individuality.

2036. External matter is solid or fluid.
Any solid matter which does not become fluid normally produces only certain movements in the parts of the human body to which it is mechanically applied. But fluid matter, or matter rendered fluid when applied by contact to the human body, can be drawn into the vortex of life. Sometimes the vital principle attempts to invade it by continuing its own feeling in such matter which can then become nourishment for the body itself. But between such matter in a state altogether extraneous to the body and as assimilated to the body, there is a middle time and state during which nutrition takes place (I take nutrition here in its widest sense).

2037. Even nutrition, therefore, comes about by way of stimuli. The body which must become nourishment stimulates the living body when applied to it. In the power of this stimulation, the living body appropriates this nutritive matter. It divides, distributes and, if it is solid, breaks it up and dissolves it into liquid in order to be able to nourish itself. All these movements are excitations pleasing to the body. But if matter is not disposed as it should be, a struggle arises between the chemical and material forces of this matter and the animal's vital forces which are unable to invade and dominate it. Hence, the pain, disturbance and harmful effects experienced by the living machine.

Moreover, matter destroys the animal, if it exercises on the living body a chemical force so contrary and prevalent to its vital force that it removes the body's organisation and proper adaptation for life, and eliminates the animal's own matter. This is the effect of poisons and powerful solvents such as fire, and so on.

2038. But a stimulus, when applied to a group of living molecules which it moves without expelling them from the sphere of continuity, arouses sense-experiences. At this point, the sensuous instinct begins to act with an effect of its own, no longer shared with the life instinct. The action of the sensuous instinct, which is intended to assist the production of pleasant senseexperiences, seconds the motions (begun by the force of the external stimulus) which augment the degree of pleasure. Seconding them, it leads them much further than the sole force of the stimulus would, and continues them spontaneously even after this stimulus has ceased.

2039. Indeed, if this action were not opposed, and contrary forces did not tire it and continuously reduce its quantity of motion, there would be no reason for believing that movement once begun would ever cease. It could well be said that sensuous instinct, considered in itself and differentiated from all brute forces, is the cause of perpetual motion.

2040. If the motion of the sensuous instinct ceases, therefore, the cause is to be found in the obstacles to its path. These arise principally from the inertia and wear-and-tear of matter, and from instinct's opposite tendency for preserving its continuity and cohesion. Stimuli must be reproduced if the primal, natural movement is to be continued. Nature achieves this partly by preparing new external stimuli, and partly through the incredibly ingenious organisation of the living body. This organisation ensures that the same living parts which are moved by the sensuous instinct to promulgate and increase experience and excitation, themselves become stimulants through their motion. In other words, they generate, impel and direct stimulating fluids which then produce new sense-experiences. These in turn renew the activity of the sensuous instinct, activity weakened by the difficulties I have mentioned.

2041. Living parts of the body become stimuli of other living parts because life does not remove their sensiferous force. But in order to obtain the continuation of movements produced by the sensuous instinct, and through them reproduction of stimuli and consequent sense-experiences, it is necessary to maintain the highest regularity and proportion between the sense-experiences of the first link of the zoic course and those of the second and successive links, and indeed between movements of the first link and others which come later. There must be no jump, and everything should take place in a cycle according to a law of highly regulated succession. To attain this, the organisation of the group of molecules which we called the living body must be brought about in such a way that the stimuli, reproduced by the sensuous instinct and administered by exterior nature, must always be of the same kind and possess constant activity or activity ordered to progression. When this is achieved the group of living particles manifests the phenomenon that I have called the zoic course.

2042. This characteristic phenomenon of the animal becomes (in the system which sees all elements of the body as living) the specific difference between what are normally called 'brute bodies' and animals. This difference enables us to perfect the definition of animal which I have already given as 'a materially sensitive and instinctive individual being'.(96) Now, by adding the difference separating animals from so-called brute bodies, the definition can be expressed as follows: 'A materially sensitive instinctive individual in which the excited sensitivity reproduces, according to a fixed law, an alternating sequence of stimuli, sense-experiences and movements.'

2043. This alternating sequence, as habitual and normal, that is, as required for the healthy state of an animal, contains and reproduces innumerable sense-experiences pertaining to a single sensible principle. These constitute the fundamental feeling of excitation of which human beings normally form only a very obscure awareness.(97) Now the first sense-experiences are, as sense-experiences, effects of the life instinct and of external and internal stimuli applied by nature to the fundamental feeling of continuity. These stimuli and the movements they produce do not pertain to the sensuous instinct, which begins to operate in those first senseexperiences when it endeavours to assist them and prolong the continuation of excitatory motions. The first link of the zoic course, therefore, has to be considered as that composed of 1. the first sense-experiences and 2. movements continued or produced by the sensuous instinct as a consequence of the first semse-experiences.(98)

2044. The movements causing these sense-experiences vary for many reasons which can perhaps be reduced to the three following classes:

1. All the differences which we have noted in the fundamental feeling of continuity influence the movements which produce the fundamental feeling of excitation and produce in it a similar number of corresponding variations.

2. There are many species of organisation suitable for positing a perpetual, fundamental feeling of excitation in such a way that the animal principle perseveres without struggle or pain within the above-mentioned cycle of sense-experiences, movements and stimuli. Such species of organisations and the organically different zoic courses constitute, as I have said, the types of different animals, from zoophytes to human beings.

3. In animals of the same type, even when full health is supposed, the fundamental system of excitatory movements varies according to the quality of the tissues which may be more or less close, developed or individuated etc., above all in human beings, according to the various degrees of force in the life instinct. These accidental variations in the same type constitute the various characters, temperaments, degrees of robustness, various susceptibilities, and so on manifested in a single animal species. Every fundamental system of such movements is the basis of a zoic course which differs in various animal species and in individuals of the same species.

2045. The zoic course is aroused, therefore, by stimuli applied from outside to a body living a life of continuity. I say 'stimuli applied from outside' because we must distinguish extraneous stimuli, received but not produced by the living being, from stimuli produced internally by the being's own action. External stimuli are air, water, heat, cold, food and any foreign body which, when applied to the animated machine, cause in it some healthy or harmful effect. Even the intellective principle is an external stimulus.

2046. Various suppositions have to be made if we are to conceive the immense variation of the stimuli. I mention some of these suppositions here. First supposition. — Foreign stimuli applied to the body from the beginning are not renewed. — In this case, the zoic course, together with the mind, would soon cease.

2047.Second supposition.-Foreign stimuli constantly renew themselves from the point of view of quality and quantity. In other words, the same air, heat, light and nourishment, etc., are reapplied to the body. In this case, the zoic course would provide the body with a succession of better or worse states. The variation towards good or bad would depend on the action of the body's internal forces, determined by the unique way in which stimuli, with their quality and quantity, would be applied to it. It seems evident, however, that under these conditions the zoic course would be unable to continue for long because the animal constitution requires different stimuli, especially in quantity — an adult, for example, needs more food than a baby.

2048.Third supposition.-The application of the same stimuli is either continuous or periodic. In a word, the time in which such stimuli are applied varies, and varies in every possible way. — It is clear that every time-variation in the application of the same stimuli changes and determines a new zoic course.

2049.Fourth supposition.-Renewed external stimuli change in quantity only.
Fifth supposition. — The stimuli change in quantity and in the time they are renewed, continued or removed.
Sixth supposition. — They change in quality only.
Seventh supposition. — They change in quality and time.
Eighth supposition. — They change in quantity and quality.
Ninth supposition. — They change in quantity, quality and time.

All these suppositions include innumerable different determinations of the zoic course. But all these changes of external stimuli are in fact what actually takes place. It follows, therefore, that there are not even two instants of life in which external stimuli applied to the living machine are the same. They change unceasingly in quality, quantity, time and the way in which they are applied to the machine. Consequently, the zoic course deviates from its direction in every instant of life. This occurs as a result of several associated causes, of which one alone is sufficient to make the machine deviate. However, not all the new directions which the course continually takes are necessarily harmful or diseased.

This confirms the presence of innumerable directions and changes, contained within the limits of a healthy state, in the zoic course. Moreover, animal health is not determined by a single line of causes, but has as it were a territory in which to roam. Leaving this territory, however, the animal enters an unhealthy state, or even a state of decline (if indeed we are prepared to distinguish unhealthy from insensible decline).(99)

2050. We can distinguish stimuli in the external and internal productions of the action of a living being. In the same way, we can distinguish the excitative movements of sense-experience produced by primal, external stimuli from those produced by second, internal stimuli. I call primal stimuli those given to the animal and not produced by the animal itself. Second stimuli are those produced by the animal itself as a result of the alternating actions of its course.

2051. Both primal and second movements can be divided into three classes considered in relationship to the changes they produce in the three elements making up the animal, that is: 1. continuity of parts; 2. excitation; 3. individuation of the excitation.
Moreover, these movements can be useful or harmful to each of these elements.(100) The result can be seen in six classes of excitatory movements for each of the two kinds, that is:

It is clear that these six variations can be found both in primal movements produced by external stimuli and in second movements produced by internal stimuli.

2052. Having considered the variation of stimuli and movements, we come to sense-experiences which are also divided into primal and second. Primal sense-experiences are caused by movements produced by primal stimuli and, in so far as they are natural and typical, constitute the fundamental feeling of excitation. Second sense-experiences appertain to all successive links of the same course.

2053. The animal ens has what I would call two corresponding facets: the subjective facet, constituted by feelings, and the extrasubjective, constituted by movements. In the same way, the classification of movements is repeated in sense-experiences. Indeed, the classification of sense-experiences and of movements go hand in hand, and each can serve reciprocally as the foundation of the other. We need to note in general, therefore, even relative to sense-experiences, that these are useful or harmful to the feeling of continuity, to excited feeling and to the individuation of feeling. This classification is present as much in primal sense-experiences as it is in second.

Notes

(85) By primal, I mean those which pertain to the first link of the zoic course.

(86) NE, vol. 2, 646-659.

(87) Note that after an autopsy the little vessels at the periphery of the body were entirely empty, while all the blood was concentrated towards the heart and lungs. This seems to show that the vital movements of the vessels were impeded at their extremities either though lack of external stimulus coming from contact of the skin with the atmosphere, or through the mechanical impediment of the plaster which the animal instinct was unable to overcome. This also seems to confirm the teaching of modern physiologists who maintain that the movement of the blood is due in great part to tonic movements of the vessels. Moreover, a greater flow of blood should be present where the vessels are larger. When such movements cease altogether in one part of the human body, but continue in others, it is highly probable that the blood flows towards the latter, leaving the first part empty. This shows how effectively the circulation depends on the activity of the vital principle, that is, the soul.

(88) A vesica full of blood left suspended in the air soon takes on a reddish tint. This shows that it permits the passage of oxygen. If camphor and ether are put in an enema, the person who receives the treatment soon has breath smelling of these substances. The phenomenon is explained through the attraction of odiferous particles into the vein tissue of the rectum. Having entered the blood, the particles are taken to the lungs and then breathed out through the capillary walls. In other words, the molecules of those fluids enter through one wall of the membranes and are exhaled through another. This shows that membranes are permeable on both their surfaces.

(89) AMS, 380-384.

(90) They are reduced to three because there is still doubt whether primal matter receives all the conditions rendering it suitable for animation, or whether it acquires other conditions from the action of some exterior cause. For example, from chemical actions and re-actions, or from the divine fabricator of the human body.

(91) Nicholls, De anima medica, pp. 15-16.

(92) In other works I said that I was extremely doubtful of the sensitivity which certain physiologists called latent (NE, vol. 2, 695; AMS, 377 ). Now, however, reflecting that latent sensitivity can mean sensitivity of mere continuity without excitation because of the lack of suitable organs, I realise that sensitivity can be admitted with this meaning.

(93) Although the sentient principle is simple, it has nevertheless in itself the whole sensible body (what is extended is present, as I said, in what is simple). Its activity, therefore, is more developed where the fundamental feeling of life is greater. The place where this feeling dominates and where consequently the sensitive activity dominates, is the 'centre'. When this place is one and not greatly extended, the sensitive principle is said to be more centred (relative to its action on the sensible body, not to itself). In more perfect animals, this physical centre of activity is the brain.

(94) The sense-experiences which do not form part of the harmonic whole are not feelings pertaining to the individual. This explains why, when a nerve has been tied, the movement produced by the stimulus does not reach the brain and the animal does not sense the corresponding sense-experience.

(95) There is no doubt that chemical activity, although of a special character, continuously intervenes in vital activity. This renders more probable the opinion that chemical forces are truly vital, annexed to non-organated bodies and moved by other sentient principles forming different individuals which are then based on a greater individual.

(96) AMS, 45.

(97) We cannot easily become aware of these sense-experiences (which are continually reproduced and form habits) unless a part of them ceases or slows down considerably. For example, when the circulation suddenly ceases or slows down, we experience a feeling of weakness and of diminution in all our senses. After syncope, our intellective attention is no longer able to concentrate its thought on what takes place within us. When Jean Baptiste Denys and Emmerez put lamb's blood into a man's veins (1666 A.D.), the individual noticed the course of hot blood to his heart (Journal des Savants., pp. 87-94, 182-185). This shows how the sensibility of the vessels becomes suitable for perception by consciousness simply through a greater degree of heat added by an external cause.

(98) Prior to this first link of the course, there is another couple of phenomena: 1. the fundamental feeling of continuity; 2. the extrasubjective movements, produced, through stimuli applied by nature, in a body living a life of continuity.

(99) This change may be a question solely of the loss of particles, or consolidation (but with lesser activity) of the vessels and parts to a certain extent, within which animal functions are carried out. If so, such change — taking place insensibly but without seriously altering the functions — is not normally called illness, which is characterised by a serious alteration or disorder of the functions.

(100) It is not absurd to conceive even a third kind of indifferent movements, that is, movements which do indeed change the state of an animal, but in such a way that the new state is neither better nor worse than the preceding one. But because this seems a continuation of highly improbable, future balance, I have omitted it in order to simplify an argument already complicated by such a great number of elements. Nevertheless, the reader should be informed of it.