Chapter 10

Application of the theory to explain the phenomenon of sympathy
between different parts of the living body

1884. I begin, therefore, with a cause whose existence has been proved, and which is sufficient to produce motion. In other words, I begin from a sensitive principle. I want to apply this cause to the explanation of the harmonic complex of animal phenomena. If it seems to provide sufficient explanation for this complex, there will be no point in imagining some other, hidden cause, especially if this hidden cause is unsuitable for explaining the phenomena while the certain, obvious cause is completely suitable. Let us begin, therefore, from the phenomenon of sympathy, and first of all determine the meaning which, I think, we have to give to this word.

1885. When there is a known link between two organs, modern physiologists deny that sympathy is an affection aroused in one part of the human body as a result of irritation or affection in some other organ. Roux, a disciple of Bichat, maintains that a phenomenon is sympathetic only when it can be explained through one of the three excitatories of the vital properties: the brain, which transmits excitation through the nerves, the action of external bodies, and the liquid substances proper to the animal body. But such a restricted definition of sympathy presents two difficulties:

1. It is founded more on ignorance than on the nature of things. Consequently, what we now acknowledge as sympathy would cease to be such as soon as scientific progress showed the presence of previously unknown communication between sympathetic organs.

2. It also rests on an erroneous supposition about material communications (between organs) which, it is presumed, are sufficient of themselves to explain affections communicated even in the order of feeling. But no material communication, no continuity or contiguity of parts, no movement of fibres, no branching out of vessels, can produce sensible effects. They cause only movements, nothing more, unless some preceding feeling and sensitive principle is supposed. These, however, are very different from the extended, corporeal element. Moreover, in the order itself of movements, material communication alone of organs does not offer any explanation of certain movements which exceed the quantity of material forces and are not subject to the laws of ongoing motion. Consequently, it is necessary, whether we like it or not, to recur to a principle of motion different from that of the principle of these material forces. The principle of motion is either the activity itself of feeling, as I believe, or an ens gratuitously presupposed by fantasy which although it fleshes out an abstraction, as our adversaries want, always remains alien to material communication between the parts of the human machine.(43)

1886. For these reasons, I prefer to take the word 'sympathy' in its widest meaning to indicate 'the vital consent between different parts of a living body'. It is to sympathy taken in this broadest meaning that I now want to apply the theory of the sensitive principle as the cause of motion, the theory I have already explained. In other words, I want to show that with this cause alone the phenomena of sympathy which are neither mechanical, physical nor chemical but properly speaking vital and animal, can be explained. This is truly the case, although these phenomena do indeed presuppose and require a mechanism, an organisation, communication of filaments, continuities and contiguities, tissues, vessels, etc. as their preparatory condition if they are to be manifested and exist.

1887. Besides the sensitive principle, there is in the human being an intellective principle which influences the sensitive principle by dominating it, moving it to action, and restraining and dominating it, without, however, changing its nature or destroying the laws of animal feeling. The intellective principle, then, does nothing in the human body except by means of the sensitive principle (cf. EHS, 306-390). I wish to speak only about the sensitive principle, leaving aside intellectual activity altogether.

1888. First, I note that it is erroneous, methodologically speaking, to reason about animal operations by supposing that the sensitive principle works with a known end. We have to recognise the abuse to which animists have subjected final causes by their claim that the operating principle proper to animal phenomena knows the end for which it is working. This is a consequence of the other error which confused the intellective with the sensitive principle. It also includes a third error. The activity even of the intellective principle in the human being does not always work for an end known and distinct from the activity itself. Often the intellective principle itself works as an instinct through the law of nature presiding over the dynamic connection between the intellective principle and the body. I have already pointed out that sudden, sad news causes discomfort in animality. The intellective principle which receives the information does not in any way want this discomfort, nor does any end move the principle to produce the discomfort.

Nevertheless, it is involuntarily produced through natural necessity. The intellective principle, therefore, influences the body relative to an end only when the movement it produces is the desired object of its attention. In this case, the end does not necessarily look to the well-being of the body; frequently it does exactly the opposite, as in the case of suicide or in people who mortify the body to make it obey the more elevated intentions of moral power. The principle of animal activity is even less able to work with an end which it knows (although its operations are ordered, and attain an end intended by the Creator). It operates under spontaneous, necessary, non-free laws, all of which depend on the following formula: 'Feeling tends to preserve and increase itself, that is, dispose itself for and place itself in whatever way is more pleasing to it. This is its more natural state because its nature consists in the act of feeling, and avoids that mode which is painful to it, that is, contrary to its natural act.'

1889. Having placed the essence of animal in feeling,(44) we cannot recognise any other certain, proper characteristic of animal motion except the following: 'There must be some proof that motion is accompanied by feeling.'

No organism, that is, an ingeniously assembled machine, nor organic movements, is sufficient to allow for the existence of life or of the vital principle, unless the organic movements are such that they presuppose the existence of feeling. When material agents are applied to an animal body, the movement they produce begins to be animal action only when sensation begins. Before that, only stimuli and movements are present. These, however, do not pertain to the animal until it begins to use its own activity, the activity of feeling. The principle of all truly animal movements resides in feeling alone. The two following propositions will help us to illustrate this principle.

1890. I. Sometimes the feeling which serves as the origin of animal action or passion is an external sensation. - If you strike or hit a beast, it runs away. The activity which it develops in its motion obviously begins from its sensation of pain. This sensation, associated by the imagination with a state free from pain and with movements leading to such a state, are the three elements that the unitive force joins in one. They determine the action of the animal's motion. Evasion is an act of the sensuous instinct(45) and pertains to adverse mobility.

1891. Note that every time the action or animal function is not determined by a single sensation, but by the association of several sensations, images, etc., the instinct simulates the will. Consequent movements, not exactly proportioned to the individual sensations but to the total impression, seem rather to have an element of free will about them. This is not in fact the case.

1892. The sensation of pain determines the animal not only to great movements, such as those described, but also to minimal movements, such as those which determine secretions. - Pains experienced by teething children cause lassitude in the body, vomiting, coughing and so on. The animal principle in its pain obviously produces those small intestine motions which give rise to this kind of phenomena.

1893. II. Sometimes, the feeling from which animal action or passion begins is a sensation proper to the internal walls of the animal body. - Tickling the throat induces vomiting. This sensation is not associated with imagination but upsets the stomach as the movement begun in the sensation continues through animal spontaneity. In these kinds of instinctive movement, it is more obvious, as I have shown, that movement is excited by sensation alone, which begins a motion that spontaneously continues and develops. - The same can be said about a tickling in the nose. This causes sneezing, an even more complicated movement. - The same can be said about the feeling of nausea by which emetics move the nerves and muscles of the stomach. - The same can be said about any dregs and purgatives which irritate the intestines and provoke evacuation. - In all these cases, it is clear that the uncomfortable feeling manifested on the interior walls of the body is the beginning of animal activity, which is aroused and acts strongly because it experiences some discomfort.

The sensitive principle rebels against the discomfort it experiences, and to free itself from the discomfort calls into action the great organs. Sensuous instinct also acts here with its adverse mobility by withdrawing and making itself as independent as possible from this painful sensation. Its efforts to achieve this result in an effect, that is, the expulsion of the foreign body or the stimulus which causes such disturbance, which is certainly due to the extremely wise fashioning of the animal machine made by the Creator. Note carefully that the sensitive principle tends solely to free itself from the disturbance it experiences. Its action, and the term of its action, does not go beyond the confines of the subjective order to which the relative movements of the animate body conform. The expulsion of the extraneous body now follows as a physical consequence of these efforts. Strictly speaking, the sensitive principle does not intend the expulsion.(46) This is a very important observation, as we shall see in the explanation of other phenomena.

1894. III. Sometimes the feeling with which the animal function begins pertains to the imagination. - The presence of some appetising food provokes an abundant secretion of saliva. The taste image moves this instinctive activity because the animal concurs with its activity in all sensations.(47) This fact shows that the sensitive principle determined by the imagination, an internal sense, works on the ganglionic system, which rules excretory, respiratory and inflammatory phenomena. This is the work of the sensuous instinct through its concupiscent mobility.

The secretion of saliva consequent on the sight of appetising food is a very clear example of minimal movements produced by the sensitive principle through concupiscent mobility. Innumerable similar examples prove the power possessed by feeling over minimal movements of the body. I gladly use Stahl's vocabulary here and call these movements tonic movements. A disgusting sight provokes vomiting in delicate persons, such as women at certain moments, and ruins their appetite.
It is a fact that the sight alone of some harmful medicine, already taken several times, suddenly produces stomach pains and powerful evacuations, as though the sick person had already taken the medicine.(48) In this case, it is the imagination which sympathetically moves the bowel and the intestines (retentive, sympathetic mobility).

1895. The same principle, the same sensuous instinct, working principally through concupiscent mobility, moves a hungry animal to carry out movements necessary to obtain food and, in general, to satisfy all the needs felt in animality, including that of propagation. This kind of action is always an adaptation, a self-movement consequent on feeling, relative to discomfort or incipient pleasure which demands perfection. This is true whether the sensuous instinct searches with external movements for means to attain such an aim (concupiscent mobility) or whether, having found the source itself of pleasure through its own activity, the instinct perfects the pleasure in which it immerses itself until it feels completely satisfied (voluptuous mobility).

1896. The tiny, excretory and tonic movements show the power of the sensitive principle over the nervous, ganglionic system. In the same way, great movements indicate the power of the sensitive principle which operates on the cerebral-spinal nervous system. Nevertheless, we need to note that the action of the cerebral-spinal system is never entirely absent even when the sensitive principle works by moving the ganglionic system.

1897. IV. So far we have viewed the motor power of the sensitive principle by supposing that this power acts as a consequence of shaped feelings such as external sensations and images. We also saw, in part, how this motor power acts as a consequence of feelings which possess little or no shape, such as sensations provoked on the surfaces of the internal walls of the body, or as a consequence of images associated with external feelings. Non-shaped feelings, devoid of precise order and apparent relative locality, easily escape observation and consciousness. When the sensitive principle, aroused by these feelings, moves, its movement appears extraneous to feeling. This, however, is not the case, as careful observation shows. Let us carry on, therefore, noting other facts which allow our attention to be focused on the activity present in feeling and bringing in its wake small and great movements, and consequently extremely different modifications in the animal body.

1898. Sometimes the feeling through which movements and functions of the body begin consists in certain sense-experiences of internal discomfort which are then diffused over a great part or the whole of the animal body. Once the sense-experiences have been diffused, the animal attempts through its sensitive activity, to substitute equally diffused but pleasurable sense-experiences through its movements and functions. - The animal breathes as a consequence of the discomfort it would experience by not breathing, and of the pleasure it experiences in respiration. This extremely important function of animal life has a very effective influence in maintaining continuous excitation of the fundamental feeling. Here the life instinct with its excitatory function is obviously the first cause of movements of the lungs, the heart and all the great and small organs which contribute to the cyclic process.
Childbirth is the effect of the discomfort that the mature foetus feels within the confines of the maternal womb, and of the discomfort the mother herself experiences from the efforts of the foetus to bring birth about.(49)

1899. All vital functions are determined by pain and pleasure, that is, by the need to carry out those operations to avoid the discomfort that nature would feel by not doing them, and to obtain the pleasure it feels in life by doing them. For example, what induces an animal to eat except the discomfort of hunger which it wants to remove, and the pleasure it experiences in eating? This pleasure is not restricted to taste alone, but is also satisfying to the alimentary sense.(50)
The same must be said about the generative function, and about every other function of the human body. It is necessary, therefore, to recur to sense, and consequently to the sensitive principle to explain animal functions.

1900. Note carefully that every function of the animal body supposes a sensitive principle which 1. moves and directs the functions, 2. is simple. It is a very common illusion to believe that several complicated actions, when seen to take place in the animal (all converging to produce something useful for the animal), are sufficiently explained by calling them a 'function'. A word more or a word less is not sufficient for science. If, therefore, we consider any animal function whatsoever without prejudice, we shall see in it an extremely obvious proof of the unity and simplicity of the sensitive principle, its cause and regulator.

1901. Indeed, all animal functions are reduced to two classes:
1. Those which have the fundamental feeling as their aim and effect. These pertain to life instinct.
2. Those which have actual sense-experience as their aim and effect. These pertain to sensuous instinct.

1902. The fundamental feeling is a result of two elements, the felt continuum and perpetual, cyclic excitation. Hence the functions of the life instinct can be divided as follows:

1903. Listing the classes of function of sensuous instinct according to their proximate effects and aims would take too long. We would have to classify all kinds of special senseexperiences to which feeling is susceptible, and describe the instinctive actions which follow them. These instinctive actions would have to be given four or more aims: 1. to keep the sense-experience alive; 2. to increase it; 3. to struggle against forces disturbing excitation; 4. to lessen pain resulting from this struggle; 5. to struggle against the difficulties opposed to these aims (through irate aversion). After this, we would have to add the function which tends to harmonise sense-experiences by producing a satisfactory and tranquil state from them, and removing the unsatisfactory, restless state.

1904. This observation, however, seems to me sufficient to show that every function has as its aim some feeling which has to be preserved or bettered. The cause of every function, therefore, can only be some sensitive activity.

1905. The nature of each of these functions requires simplicity in its cause. Each function is composed of several simultaneous and successive movements, all of which converge to obtain a single aim. If the cause producing them all were not single and perfectly simple, they could not be brought to the unity to which without exception they are always directed. Note, too, that the function, although multiple in the parts of the body that are used, and multiple in the different movements of each part at the moments it carries them out, is nevertheless completed in such a way that one single act is felt in it. As far as feeling is concerned, the animal aims at doing one thing only, and at producing one action. It feels itself operating with a single activity and needs only a single command to carry it out. Our human awareness offers witness to this. Language also expresses it by using a single word to denote nutrition, breathing and generation. Lengthy reflection, and reflection proper to science alone, is needed to succeed in breaking up and analysing these functions by distinguishing their parts and the individual acts which come to form them. Most people do not know these functions except as a whole, in the unity they appear in consciousness. Only as a result of considerable work and determined observation and meditation does the human being know the functions in those parts, which are parts solely because he distinguishes and thus creates them. They do not exist separately in nature, nor in feeling and instinctive activity. Every animal function, therefore, is a consummate demonstration of the simplicity of the sensitive soul.

1906. If we go on to reflect that the animal never operates except by way of functions, that is, by such groups of acts and movements which tend to a single aim,(51) we have to conclude rightly that everything done by the animal without exception proves the simplicity of its principle.

1907. It is a fact that feeling contains an instinctive, locomotive activity. The explanation of phenomena must begin from similar, well-ascertained facts. It is equally certain that this motor activity hidden in feeling is capable of explaining all animal movements, all functions of the human body. It is, therefore, superfluous and arbitrary to introduce another cause. Moreover, this cause could never be more than something unknown. Such procedure is contrary to the most solemn logical and cosmological principles, such as those of sufficient reason and of parsimony in nature.

1908. Human beings, it will be objected, are not always conscious that a feeling is the principle of every action of their animality. I offer two replies to this difficulty.
First, in the animal body itself, several partial, sensitive feelings and consequently several sensitive principles can be present which are only weakly connected with the supreme sensitive principle constituting the animal. Because these partial principles are not closely connected with the supreme principle and are only poorly dominated and governed by it, all the sense-experiences which immediately pertain to them are only slightly sensible to the animal. On this basis, it seems that even the different systems and principal organs of the human body enjoy their own special life which, however, is not so special that it is entirely separate from the all-pervading life and feeling. The less such sense-experiences are subordinated to the sensitive principle constituting the individual animal, the more they are withdrawn from intellective consciousness.

1909. Second, the objection is based in great part on a false supposition. In fact, many people confuse awareness with feeling, and regard the former as an element of the latter. Such people need considerable thought to convince themselves that consciousness and feeling are very different; consciousness pertains to the intellective order, feeling to the animal order.

The person capable of separating the intellective element, the source of consciousness, from animal feeling is soon persuaded that feelings can be present in us without our being conscious of them. Indeed, there are innumerable unconscious feelings within us. They include all those on which we do not reflect and by which our intellective attention is not attracted. This person will also notice various degrees of difficulty in becoming conscious of feelings. We can become conscious of some without difficulty; others we find in ourselves with great difficulty and only after long, profound meditation in the deepest quiet.

But consciousness has to be formed, even of those feelings of which we are conscious, although it does seem that consciousness is habitually present in us as a result of the readiness with which we form it. Moreover, it could not be formed without our being moved by some reason. For example, if I am engaged in conversation and interrupt the exchange to ask the other person suddenly if he is conscious of the insect on his hand, he will say 'Yes', not because he realised its presence during the conversation before I asked him but because as soon as he heard the question, he turned his attention to the tiny animal on his hand. It was sufficient for me to draw his attention to the fact, sufficient that he should want that, for consciousness to be present. The person concerned does not reflect on the beginning of consciousness; he thinks he has always had it, not that he has just formed it.

1910. It is easy to acquire consciousness of lively, actual, new feelings; it is difficult to acquire consciousness of old, habitual, tenuous feelings. Nevertheless even the smallest, most numerous and diffusive feelings have the power to put our biggest muscles into action. Tedium for example, is only a fusion of many tiny feelings of which we are for the most part unconscious. Such tedium causes yawning, for example, a function where many muscles, especially the diaphragm, are drawn into motion. Tickling also is a function of the minutest feelings, as many as the minutest nerve filaments, almost infinite in number, which terminate in the skin. We have no consciousness of each of these feelings and cannot, therefore, distinguish one from another. Tickling, however, produces tremendous effects. Its resultant irritation induces the stomach-muscles to vomit, acts on the brain and causes convulsive movements, reaches and paralyses the heart; this can produce syncope and even death. Very often we are unconscious of the relaxed, open state of our skin and remain unconscious even of the impression made by air cooling and congealing it. But a general disturbance of the economy of the body follows, leaving particular effects in the mucous membranes with consequent inflammation of the pleura or the lungs or the stomach or the intestines or the vesica. Those first skin sensations escaped consciousness because they were so small; although numerous and extended, they were given no attention. Nevertheless, they are the source of consequent illness.(52)

1911. It is normally accepted that no painful sensations are present in diseases which do not manifest acute pain; the phrase 'painful sensations' is restricted to local, lively sensations. The sick person, if asked, says that he feels no pain. But the truth is that no illness of any kind is present unless the sick person experiences some discomfort in his feelings, whether he is conscious of this or not. A sick person whose feelings were all perfectly equal to those of a healthy person, would not be ill. But discomfort, lassitude, lack of appetite, muscular weakness, heat, cold and an infinite number of other general, diffused sensations, resulting from an infinite number of even smaller sensations prove that some disturbance of sensitivity is never lacking in any illness. Consequently, if we consider sensitive activity as the cause of pathological sympathy, we are appealing to a cause whose existence has been demonstrated, not to a mere supposition of the imagination, such as the vitality proposed by certain writers which, although itself not feeling, is taken as the cause of feeling and movement.

1912. All the phenomena proper to sympathetic illnesses confirm that these diseases must be attributed to the sensitive principle as their true cause. Broussais, and his disciples Caignon and Guémont, who have published a partial account of their work on inflammation, have established the following:

1. Sympathetic diseases are found to have greater force and promptness in sensitive than in apathetic individuals. This shows immediately that persons endowed with deep sensitivity are more easily subject to hypochondria;

2. Animal functions alter much more if affected organs are endowed with a greater number of nerves and are thus more sensitive;

3. If irritation or inflammation becomes painful, sympathy acquires greater activity.

All this proves that sympathetic, diseased alterations take place in a certain relationship to the affection proper to the sensitive principle, which therefore is their true cause.

1913. Although doctors have not yet succeeded in absorbing this teaching, they nevertheless draw nearer to it every day. Barthez considers sympathy as the effect of the vital principle in different organs of the living body. He deduces this because he sees sympathy manifested even in distant organs without any possibility of its being explained through some non-existent mechanical communication between these organs. Moreover sympathy, directed by fixed laws, cannot be attributed to chance. Barthez, therefore, was only one step away from the truth. He simply needed to discover that the vital principle is of its nature essentially sensitive, and that its motor energy, because it does not differ from sensitivity, is simply a continuation of feeling energy.

1914. More modern doctors have almost reached agreement in considering the nervous system as the general instrument of all physiological and pathological sympathy, natural or artificial, manifested in the living body. Brachet, in his admirable work, Sulle funzioni del sistema nervoso ganglionare (which won a prize in 1826) replied as follows to authors wishing to attribute sympathy to the cellular system because this system is dispersed throughout the whole body:

Consequently he divides sympathy into cerebral, ganglionic and mixed sympathy.

1915. I think, though, that it is erroneous to believe that the ganglionic system is altogether devoid of feeling. Properly speaking, this system is the organ of passions. We have already distinguished feelings into shaped and non-shaped feelings. These two classes correspond to the two nervous systems. The cerebral system is the organ of shaped feelings; the ganglionic system is that of non-shaped feelings. Feeling is never lacking.

Moreover, the ganglionic system communicates with the spinal-cerebral system. The two series of ganglia on either side of the vertebrae often communicate directly with the cerebral and rachis nerves. The central ganglia make contact with a pair of cerebral nerves, that is, with the pneumo-gastric nerve, and are then in continuous communication with the lateral ganglia through which they communicate once more with the cerebral system. Hence the cerebral-spinal system can never be considered entirely immune to impressions received from the ganglionic system. Thus, it is perhaps possible that a merely ganglionic sensitivity is non-existent. Brachet's classification of sympathy should therefore be restricted in all probability to two members only, that is, to cerebral and mixed sympathy. The second class should then be sub-divided.(54)

1916. The opinion of Barbier and other physiologists on the way remedies work will help to confirm these observations on the intervention of the cerebral system in all kinds of sympathy. These authors maintain that the secret of the transmission of healing power possessed by certain substances should always be sought in the cerebral apparatus. This is especially the case when they refer to medicines which, operating without the intervention of the circulation, more readily manifest sympathy by acting immediately on the gastric organ.(55)

1917. Granted that feeling is the first phenomenon and the cause of all other phenomena in the series of animal phenomena which succeed one another sympathetically, many facts are explained with great propriety. This itself proves our proposition.

1918. I begin from the sympathy noted between the organs symmetrically located in the two vertical halves of the human body - the eyes, ears, nostrils, hands, kidneys, and so on. It is well-known that diseases in one of these organs are communicated to the other. For example, if one of the optic nerves is diseased, the other often contracts the same disease. The history of amaurosis and other kinds of blindness prove this. The observation I want to make is as follows:

Although each of the organs of the symmetrical senses gives a sensation to the soul when stimulated separately, the soul allows only one sensation when both organs are stimulated contemporaneously. I used this fact to prove the simplicity of the soul,(56) and its distinction from every bodily organ, so that the multiplicity of organs collocated in different places in space does not produce multiplicity in the soul, which is immune from space. In other words, the diversity of sensations in the soul is not founded on the diversity of space occupied by the sensory organs, but only on sensile differences, that is, differences pertaining to the essence of sensations, which have no relationship at all to differences of space.

Now if it is true that animal motor activity is inherent in feeling, as I maintain, there must be a single motor activity where there is a single sensation. This is precisely what occurs in our case. The two eyes normally give a single sight-sensation to the soul. In the same way, the soul, acting on both these organs with a single act, produces the same effects. As a result, the movements of the eyes are naturally associated. We can call this 'physiological sympathy'. This also explains how disease in one eye is often experienced in the other. This can be called 'pathological sympathy'. The same argument can be applied to all double and symmetrical parts of the human body,(57) each of which thus becomes a proof of the simplicity of the sensitive principle.

1919. It may be objected that sympathetic disease between symmetrical organs of the human body would always occur if this were the case. Nevertheless, it does not always occur.
The force of this objection will be lessened as soon as we consider that symmetrical organs do not always or necessarily give a single sensation to the soul. This happens only when the sensible actions of the symmetrical organs are so perfectly equal that they differ simply as a result of the different space in which these organs are located. As a result of these different spaces the actions are two in number, although identical in form. Only in this case is a single feeling experienced by the soul because only the space proper to the single sensation is carried back to the soul, not the different spaces occupied by the sensories. This unicity of the sensation is founded in the nature of the sensible principle, not in some habit acquired by the principle.

1920. But is it always true that the sensible action of the two organs is identical in form and differs only in number? No, but it does occur, and the frequency with which it occurs depends for the most part on the soul's tendency to have a single feeling from two organs because two feelings would confuse its operation (it acts under the guidance of feelings). As a result, the soul moves the eyes in perfect harmony. If it moved one eye to one side, and the other eye to the other so that it saw double objects, there would be an uncomfortable contradiction and a struggle between sensations of touch, which offers simple objects. The soul would not know which sense to believe nor how to move its members in relationship to the external objects it requires.

We see, therefore, that the uniformity of double sensations which operate to produce a single sensation is of extreme assistance to the soul in the needs of life. Consequently, the soul, through its own spontaneity directs these sensories with this in view. Its activity, which moves these sensories, acquires a habit of using them in such a way that their uniform action seems natural rather than habitual. In fact, human beings can capriciously do exactly the opposite. They can, if they wish, conquer this habit and even succeed in making the pupils diverge. This never happens in beasts because the sensitive principle does not permit tricks of this nature; it always acts suitably.

1921. The simultaneous, uniform action of symmetrical organs is due to habit; the arousal in the soul of a single feeling, granted this simultaneous, symmetrical action, is due to nature. Sympathy between the symmetrical organs must, therefore, be referred to the habit, contracted by the sensitive principle, of directing its sensitivity and consequent action in this way. Exceptions, therefore, to this action are not surprising. This is better understood if we reflect that habit itself does not act except under certain conditions and given certain opportunities. Habit is normally a faculty of operation so precise and determined that the least difference in circumstances blocks its operation. An example is the habit of memory which helps a person deliver a speech. A single mistaken or misplaced word is sufficient to make him lose the thread.

1922. The law of sympathy between symmetrical organs as a result of the singularity of the feeling which they produce, and the singularity of the sensitive activity which results from that feeling, is extended to many other classes of sympathy which are easily explained by this law.

First, the sympathy between organs with a similar structure is explained. In fact, two most important laws follow from one I have already indicated, that is, 'If the sensible affection of two organs is perfectly equal in form, the feeling corresponding to this affection is single because the difference of space and locality proper to the organs themselves is not carried back into the feeling. Consequently, the affections proper to equal organs intermingle and unite in this feeling.'
These laws are:

1. Because the fundamental feeling is always prior to sensation, whenever two or more sensible organs perfectly equal in structure are present, the fundamental feeling corresponding to them will never be double or multiple but single, as if only a single sensible organ existed. But positing a single fundamental feeling is equivalent to positing a single fundamental instinct or activity.

2. If two or more organs of equal structure are excited and affected differently, the number of sense-experiences or modifications of the fundamental feeling will correspond to the number of the excitations. If, on the contrary, organs of equal structure are affected in the same way, a single corresponding sense-experience, a single modification of the fundamental feeling, will take place.

1923. This equality in the way organs are sensibly affected is often verified in organs of uniform structure. Physiologists and pathologists have noticed that sympathy between uniform organs is manifest only on condition that they are first affected equally. Expounding Barthez' teachings, Montfalcon says:

As a proof, he points to Lieberkünn's cure for the lungs of a person suffering from dropsy. Lieberkünn, by means of foot-baths, forced the waters which had infiltrated the cells of the lungs to be brought to the lower extremities, and then cured the swelling of the legs by using fortifying remedies.

1924. Let us examine the explanation of other phenomena. If a tissue is perfectly uniform, a single fundamental feeling must correspond to it, and a single animal action to a single feeling. As a result, the act of life instinct which operates in the entire extension of a uniform tissue will be the same. There will necessarily be manifestations of sympathy between uniform tissues of the human body because the way a part of such a tissue is affected modifies the single activity giving life to the entire tissue, whether this embraces a single place in the human body or is repeated in many places. This explains the pathological law which was thought to be one of Broussais' most beautiful discoveries: 'When an irritation lasts for a long time in an organ, the tissues analogous to that diseased organ are gradually prepared to contract the same diseases.' Thus chronic inflammations of the pleura are easily propagated to the peritoneum, and those of the mucous membrane and intestines to the membrane covering the internal part of the pulmonary-apparatus; a part of the fibrous system is affected in rheumatism and gout by the inflammation of all the other parts; the inflammation of the lymphatic ganglia of one part of the body is often communicated to their whole system.

1925. We need to consider here the difference between two equal tissues and two equal organs which, like the two eyes, are composed of different parts and tissues. These complicated and ingeniously contrived organs allow for various differences in the way they are affected. Equal tissues allow less variation than equal organs. Of their nature, therefore, two tissues are more easily found in unison than two organs. But because every different sensible affection arouses some different activity in the sensitive principle, the fundamental feeling of two equal organs, which receives various modifications, acts in a more varied way than the fundamental feeling of equal tissues. Again, the presence of sympathy between two organs requires equality in the primal way they are affected. This condition is more easily found in the tissues. They have fewer causes to render unequal the way in which they are initially affected, from which every activity emanates. In a word, if the fundamental feeling common to two equal organs or tissues is modified in those parts in respect of which it is single, sympathy is immediately manifested.

1926. Let us apply this teaching to the functions. A single feeling moves the animal to exercise a function in which simultaneously or successively many organs and their many different movements concur. The unity of the function, arising from the unity of feeling, brings several organs into play harmoniously in such a way that their movements co-operate in producing what the animal feeling is looking for, that is, its preservation and perfection. For example, it is certain that the feeling of discomfort and panic aroused by lack of breath, and the pleasure connected with the act of respiration, makes the animal breathe. This effect is obtained with supreme harmony and suitable measure by the movement of the brain and the heart, as well as the pulmonary apparatus.

Again, it is the uncomfortable feeling of hunger and the pleasing feeling of nourishment which impels the animal to move all the parts of its digestive apparatus along with the vessels serving nutrition [App., no. 2]. In all the more complicated functions of the human body, unicity of purpose directs multiple movements of the multiple parts which concur to carry out these functions. This single purpose, however, is wholly a matter of feeling. It is always an acting feeling which does everything. But where a single feeling is present, a single action is also present, although it is manifested in various parts. We must not be surprised, therefore, if physiological as well as pathological sympathy is noted between these different parts. If the single action is modified and affected, its effects must be seen in all the parts to which it expands, even though these different parts receive the action in different ways. This occurs either because the action is impressed upon them in different ways as the harmony of their operations requires, or because they are constructed and disposed differently.

1927. This last observation is important because it leads us to establish that different results, possible in different organs, merit the title 'sympathy' precisely because they proceed from the same action of the sensitive principle.

1928. But beyond these types of sympathy which are presented to observation in various organs concurring in the same function, there are other types between several equal functions, that is, between organs destined for functions that are numerically different but of the same nature.

Thus Barthez observes that organs furnished with a faculty for secreting analogous fluids demonstrate a special sympathy amongst themselves. Examples would be the womb, the mammalian glands, the larynx, and so on. It is certain, for example, that communication between blood vessels cannot explain how inflammation in one organ may be succeeded by inflammation in a distant organ while the intermediate parts remain unharmed. In this case, the inflammation ought to be propagated without interruption along the length of the vessels. We have to have recourse, therefore, to the laws of the single vital-sensitive principle which directs the whole economy. Here the law of which we were speaking, 'Where the function of two organs is similar and corresponds to a single feeling in the soul, the activity of the soul is equally manifest in two or more places' is very opportune. We have to consider with extreme accuracy that every function is exercised through an activity of the soul placed in a single feeling of discomfort or pleasure. If, then, the two functions which appear in different parts are equal in nature and differ only through the different space in which they are exercised, the feeling which is their source will have to be single. Observation shows that the differences of mere space possessed by organs, functions and affections are not found in animal feeling; the only differences we find are those which render functions and affections different in nature.

Notes

(43) Barthez' definition of sympathy partly avoids this difficulty: 'An organ is in sympathy with another when a certain impression perceived by the cause of VITAL INDIVIDUALITY in one of these organs determines this cause to produce in the other organ an unusual affection of sensation, of motion, or of any other kind.' But why restrict the definition to an unusual affection? Surely an unusual affection could have essentially the same nature as a normal affection? In other words, the unusual affection could be reduced to and explained by the normal affection. Would it not be better if the definition were concerned with the nature itself of the thing defined, rather than with an accident, such as the manifestation of a phenomenon in a usual or unusual form? Moreover, Barthez distinguishes synergy from sympathy in so far as the organ which is affected in consequence of the affection of another organ receives a passion (sympathy) or greater activity (synergy).
This, I think, is a subtle, but not very useful distinction in a treatise such as ours where we are looking for the cause of the animal co-feeling shown in the different parts of a living body, whether this co-feeling is manifested because 1. the passion proper to an organ communicates a similar or different passion to another organ; 2. the passion of one organ arouses a given action in another; 3. the increased action of an organ communicates a given passion to another organ; 4. the increased action of an organ communicates a similar or different action to another organ. It is true that four names could be given to these classes of phenomena, but this would scarcely help; medical vocabulary is already overloaded. On the other hand, there is no action in the animal body without some passion joined to it, nor is there any passion devoid of action. In a word, it would be impossible to draw an accurate line between passion and action. I have done sufficient, therefore, in drawing attention to these differences even if I do not use them.

(44) AMS, 45, 53-55.

(45) I assume that the reader is aware of the way in which animals instinctively operate. Cf. AMS, 367-494.

(46) For example, the disturbance felt by tickling the throat determines the force needed to stop it. This happens as follows. The sensitive principle, wanting to free itself from this troublesome sensation, sets the pneumogastric nerves in motion. The result is contraction of the muscular plane of the stomach. The movement communicated to these nerves by the sensitive principle begins, I think, in the brain where these nerves originate. Brechet believes that if the irritation produced in the throat to excite vomiting affects the pharyngo-glottal nerves, it can immediately pass on the motion from these nerves to the eighth pair which propagates it to the stomach without its passing through the brain. But because it is certain that the sensiferous movement is transmitted to the brain (otherwise there would be no sensation), it seems altogether probable to me that the animal movement with which we are dealing should also proceed in this way.

(47) AMS, 358, 367-369.

(48) Although this is very well known, examples of it can be seen in Olao Borch (in Act. Medic. Hafniensibus, tom. 5, obser. 49).

(49) There is a very beautiful description of birth as the simultaneous work of the sensitive soul of the foetus and of the mother in Francis Nicholls' work De Anima Medica, London 1775, pp. 22 ss.

(50) AMS, 408-411.

(51) Even the animal's simplest actions, if considered carefully, are true functions. There is never any question of a single movement or single element, but of several movements and elements drawn into motion. In fact, there are innumerable elements or parts put into motion even in the fact of a single, external sensation. Such a sensation is never brought about without the activity of the whole nervous system, especially the brain.

(52) Bichat reflects that these deleterious effects must not be attributed to repressed perspiration, as though the re-entering sweat acts mechanically, but to alteration in the vital forces of the skin. Otherwise, every cessation of sweat would be an equal source of harm, although momentary interruption of perspiration is not harmful to people suffering from tuberculosis (Anatomie gnrale, systme dermode). Cold certainly does contribute mechanically to tightening the tissue of the skin, but this would not cause harm to bodily health if it were the only effect. Everything would be terminated in the skin itself which can be healthy whether tensed or relaxed. The animal phenomenon begins after this mechanical action. Cold is only the external stimulus which first produces the sensation of cold, then modifies the sensitive principle by prompting its activity. This in turn draws the nervous system into movement and hence all the phenomena which follow on the first tension in the skin. Once the external pores are closed, the internal inhalants, the pleura for example, are enlarged and receive blood itself rather than blood serum. The result is inflammation. - It is very obvious that cold on the skin does not produce inflammation mechanically when we realise that over-heating could produce the same effect. As far as I can see, too great a stimulus of heat or cold leads the animal principle to withdraw and close the extreme nerve-endings to the troublesome sensation. This part determines the movement of the fluids towards the opposite part and allows the blood to expand, especially in the mucous membranes. Cf. AMS, 355.

(53) Chap. 8. - I make no mention here of the usual misuse of the word 'will'.

(54) Broussais, whose work threw a great deal of light on the functions of the ganglionic system, never excluded the cerebral system. He says: 'The work of the transplanchic nerve is never restricted to simple modification of sensations coming from brain to bowels, or returned from bowels to brain. This correspondence between the two nervous systems has been established to determine certain indirect movements through the reciprocal influence of the two orders of nerves' (Rflxions sur les fonctions du systme nerveux en gnral, sur celles du grand sympathique en particulier et sur quelques autres points de physiologie, two articles in the Journal universel des sciences mdicales, November 1818).

(55) Trait de matire mdicale, tom. 1.

(56) AMS, 104-126.

(57) For example, the inflammation of one kidney easily passes to the other. Disease in one kidney often causes total inability to pass water.