Man: the double animal

Are Hierarchies Necessary?, BBC Radio 3, 3 July 1972¹³⁹

I want to describe an experiment which has acquired a classical status in the history of neurology. In 1903, Sir Henry Head and his colleague W. H. R. Rivers, the psychiatrist and anthropologist, agreed to undertake an experiment on the sensory nerves to the skin, and Head, a practising consultant neurologist at the London Hospital, offered himself as the guinea pig. At the London Hospital, with the help of a surgeon, the nerve supplying the forearm was severed under surgical anaesthesia. The cut ends of this nerve were then joined together with silk sutures. In other words, the nerve was put back again in physical continuity. The fibres, however, had been interrupted. Living nerve fibres will grow together again after they have been severed, providing anatomical continuity is maintained. After the acute phase of the injury had passed off, Sir Henry Head then subjected himself to a series of psychological experiments on the area of anaesthesia which was produced.

He would travel up once a week to St John’s College, Cambridge, and in the quiet of Rivers’ rooms there he would submit himself to a series of minutely detailed investigations on the recovering sensation in his own arm. This involved a series of graduated assaults on his skin. Rivers would test the temperature sensation in Head’s arm by using warmer or colder water in a test-tube. He would use a series of bristles of various thicknesses to detect the touch sensibility, or a wisp of cotton wool. Or he would use pins. A whole battery of these tests was done and recorded. Areas on Head’s arm were inked and photographed week after week. These results are now contained in five or six leather-bound volumes in the Cambridge Psychological Laboratory.140

One might have thought that the recovery of sensation would have proceeded by a slow encroachment from the edge of the lake of anaesthesia towards the centre – rather in the way in which a puddle dries up in the sun: the puddle of anaesthesia would get smaller and smaller until it returned to normal. However, Head and Rivers claimed to have discovered a different course of recovery altogether: instead of this simple advance, the encroachment proceeded in two phases. Sensation began to appear as the nerve recovered in the form of a sensation which seemed abnormal and unusual and, in Head’s words, extreme. There was a much higher threshold, for a start. In other words, it needed a much stronger stimulus applied to the skin before any sensation was reported, and when that sensation was reported, it was extreme, painful, very poorly localized, and had a capacity to radiate beyond the actual location of the stimulus itself. The first phase of recovery, which proceeded concentrically towards the centre, resulted in a state of sensation which was totally different from that of a normal skin.

Once this phase had been completed, a second phase started to occur, encroaching over the surface of this first phase like a varnish spread over a picture. It began to appear within the course of a few months, and as it took place the skin gradually returned to its full complement of normal sensation. It was now possible to evoke a sensation by using the light wisp of cotton wool or the bristles, and the subjective feeling evoked by these stimuli was now normal. It was well-localized, it was moderate, it was graduated; with each increment of stimulus there was an increment of response by comparison with the previous state of recovery, in which there was either an extreme response or none at all. Eventually there was a more or less complete return to normal sensation in the skin.

Head and Rivers described these two forms of sensation as protopathic – the crude early stage of recovery – and epicritic. Epicritic meant the final varnishing of the recovered area of skin with normal, precise, accurate, graduated sensation. From this observation they went on to elaborate a theory of the central nervous system which they used as an explanation. The theory which they relied on was in one sense an evolutionary theory. What they claimed they had done was – to use a metaphor which Head himself did not use – to open a sort of manhole cover into the central nervous system and thereby observe a previous stage in the evolutionary development of the nervous system before it arrived at the human condition. In the protopathic stage of recovery we were having a glance at the more primitive stage of the nervous system, and in the subsequent stage of recovery we were returning to the fully-evolved condition of the human that we know.

Subsequent investigators, notably Wilfred Trotter, a neurosurgeon working at University College who had also shown a great interest in sociology, repeated the experiment of Head and Rivers, severing a skin nerve, but did not find the results proceeding in this strictly biphasic form.141 I’m not saying, nor was Trotter saying, that Head was dishonest. The comparison shows, however, the risk of using oneself as a subject of sensory investigations.

The general theory which had helped to shape both Head’s and Rivers’ preconception was, of course, the theory of evolution; not necessarily that which was inherited directly from Darwin, but the one which was inherited through those who had been influenced by Darwin – notably the English clinician John Hughlings Jackson, a practising consultant neurologist working at the National Hospital for Nervous Diseases in Queen’s Square. Jackson is hailed by neurologists today as the father of modern clinical neurology, and he’s justly celebrated for a particular evolutionary notion of the effects of disease upon the nervous system. Jackson was studying the clinical appearance of epilepsy following injury or tumour or thrombosis in the brain. And he observed that, broadly speaking, the symptoms could be divided into two groups. On the one hand, you had the negative symptoms: the symptoms of loss. But in addition there were what he called ‘positive symptoms’: symptoms of release, symptoms which were due, or so Jackson thought, to the release of a more ancient part of the nervous system which had been held and suppressed and subdued by subsequent stages of refined higher evolution.142 In certain movements in the epileptic fit, in certain regressions which the patient exhibited – particularly when language was lost – he noticed that the patients tended to retain swear words and violent emotional expressions, which indicated to him that here was an older, more emotional, more incoherent level of the nervous system being revealed now by the loss of the restraining higher levels.

Jackson derived this theory not so much from Darwin as from Herbert Spencer, who prior to Darwin had developed a fairly elaborate evolutionary notion of the nervous system, in which he saw, as it were, a double animal in each living creature. There was the higher, well-integrated, organized animal at the summit of its own evolutionary branch, and within it an older, more incoherent animal which represented its ancient, incapable ancestry.¹⁴³ Jackson then put this general theory of Spencer’s into combination with his specific clinical observations to say that through disease we obtain a brief and incomplete snapshot of our ancestry – not, of course, a complete one, because the entire nervous system is not damaged. The old animal was coming up because of the absence of the restraints of the newer animal. It has to be remembered that Jackson was working nearly 40 years before the work of Head and Rivers. The great papers in which Jackson expressed this fundamental idea of evolution and dissolution in the nervous system appeared between 1850 and 1870.¹⁴⁴ But clinical neurology as it is taught today in medical schools is still framed by Jackson’s notions of evolution in the nervous system, with the results of damage to the nervous system seen as a gradual climbing down the evolutionary tree to the level just below the disease.

While he derived a large part of his theory from Spencer, Jackson also referred to the work of a physician who is generally not mentioned in the history of medicine – a practising physician working almost at the same time at the Westminster Hospital, a pharmacologist called Anstie who was interested in the effects of narcotics (morphine and alcohol) on the nervous system. Anstie explained some of the effects of drugs upon the nervous system in terms of this notion of a duplex animal, although he never expressed it as explicitly and as vividly as Jackson was later to do.¹⁴⁵ He thought that some of the extreme sensations which were produced when a finger was inflamed were due not so much to a positive irritant of the poison in the injured part as to the fact that the poison removed an inhibiting higher function and had consequently released a lower form of function.

It’s possible to attribute all these ideas to specifically biological theories of nervous function, and of animal function in general. But I believe there are other sources of inspiration for this notion of the double animal. The notion that the human being is in some respects double forms a part of the fundamental theory of Romantic poetry. In a letter to Miss Millbank, Byron says that poetry ‘is the lava of the imagination, whose eruption prevents an earth-quake.’146 Behind that proposal is the notion that there is something split about the nature of the human being, that there is a crust of higher or more familiar function beneath which are fluid, incandescent levels of activity held in by this crust. There are two ways of interpreting this duplicity. You could simply propose that all individuals are fundamentally and inexplicably duplex. This makes no reference either to our ancestry or to our individual development in the womb: it simply asserts that human nature is ranked in some way, that there is a familiar surface of highly organized, public, rather decorous function, and that underneath there is some other level. It may be conceived as a rather dangerous, violent level, or it may be conceived rather more favourably – as the Romantics conceived it – as the source of some higher, inspirational level of organization. In neither case is any reference made to the source of this duplicity.

This notion of ranking, of organization based on levels, is very old indeed. It goes back to Aristotle and perhaps even before. The great historian of ideas, Arthur Lovejoy, wrote a whole book devoted to it – The Great Chain of Being (1933) – in which he refers to the history of the notion that life was arranged in a scale of organization from the least complex to the most elaborate, from the lowly to the most exalted. This notion has undergone successive transformations in the history of European thought. It does not, however, until we get to Darwin, make specific reference to the genetic origin of this ranking: it’s simply an architectural statement about the way the universe is put together, the universe at large, the universe of man himself and also the great zoological and biological scale of being. It makes no assertions as to the origin of this scale and certainly no reference to there being an ancestral or genetic relationship between the successive rungs of the ladder. It is this which brings the theory into very effective line with Jackson’s notions, because once we get to Darwin the assertion is made, not just that nature is ranked in a series of scales of being, but that life itself has passed through these scales of being and has proceeded from one to the other.147 By making this proposal, you open up the possibility of asserting that one of two things might take place. On the one hand, the creature might go on making his ascent, pulling up the ladder after it, showing no trace of its previous condition. Looking at these creatures, therefore, we could detect nothing about their ancestry. But of course one only has to open and look at animals to see that they do show affinity with their previous condition. And this is the second theory: that in proceeding upwards on the scale of being – in passing from one stage to another in evolution – the animal successively conceals fragments or residues of its older self, these being successively covered up by the more recent stage of evolution. One can now suggest a whole series of methods whereby one can recover some image of or insight into that previous condition by looking at a contemporary animal. For example, one can, by opening it, detect vestigial organs; this is a morphological recovery of the previous state. We look at the appendix of man and see in it a dwindled residue of what was once a more elaborate, functioning piece of tissue.

When looking at function, you can also recover some residues of the previous condition, but you have to do so by subjecting the animal to certain assaults or experiences, of which the most obvious is disease or injury. If you were to injure an animal about whom you have proposed that it has moved from one stage to another, it might be possible that in injuring him you would knock off the top levels and allow an older level to come up and express itself. But in order to make this a viable proposal, it’s necessary not just to suggest that, like a series of Chinese boxes, these older functions are there passively awaiting this act of retrieval. You also have to suggest that they exist in an active but concealed condition, bound down and restrained by all that has developed subsequently. And once you propose this, once you propose that there is a dynamic condition of existence of this previous version, then you have to suggest on top of that that the higher function exerts two activities of its own: first, there are its movements towards the outside world, all the behaviours through which it negotiates with the outside world; but then, in addition, by the back door or through its own basement, there’s an inhibiting function which helps it to sit on and suppress this jack-in-the-box of previous evolutionary condition. And this raises the notion of inhibition in the nervous system as an essential feature of nervous function. The nervous system is now conceived in terms of two sorts of neurological function. On the one hand there is the excitatory action of the nervous system, through which it responds to stimuli from the outside world and negotiates with them more or less successfully, and behind it there’s a level of concealed inhibition – active neurological inhibition – which is keeping down the dynamic, springy, antique version of the animal which is concealed under this evolutionary heap of subsequent development.

I can now return to the work of John Hughlings Jackson and to the influence that Jackson wielded later upon Head and Rivers. We can see that both Jackson’s and Head’s and Rivers’ results flow from the basic idea of a restraining higher level holding down some older animal. They were in fact proposing that the epicritic level – that refined, delicate, well-located, graduated function of the intact nerve – was exerting two functions within the nervous system. One was its positive function of providing accurate information about the outside world, and the other was a domestic, internal affair of suppressing the older protopathic animal that was crouched like a monster – like a dog beneath the skin, like something older which had had to be suppressed – which the injury had released and which for the moment was running rampant.

Wilfred Trotter and, later, a clinical neurologist, Sir Francis Walshe, criticized the theoretical basis of Head’s and Rivers’ conclusion on the grounds that, by claiming that the protopathic stage of recovery was a picture of an earlier stage of evolution, they were claiming something about the biological style of that older stage of evolution.148 And what were they claiming? They were claiming that the older animal was incoherent, ungraduated in its response, gross, unlocalized, rather savage and also vague. Now, in claiming this they were making errors on two levels. First, it was a piece of conjectural biology: they had no grounds for saying that this was the previous stage. Secondly, it was an unjustified and unsophisticated biological assumption, since it proposed a sort of animal which would seem to have very little chance of ordinary biological success. What sort of animal could survive with such gross, incoherent and vague responses to the outside world? If we look at the insects, or if we look at the lower invertebrates, their behaviour is as graduated, as well-geared, as well-localized and as discriminating as their life requires. There is no such thing as a protopathic animal. A protopathic animal is a damaged and injured animal, so that, simply on the grounds of ordinary biological ecology, this seems to be a fruitless notion. Head and Rivers were sophisticated investigators – why should they have committed themselves to a theory which even a moderate amount of thought would have shown to be bankrupt?

It’s profitable to look at some of the sources of inspiration which are not declared overtly in Head’s and Rivers’ work, or indeed in Jackson’s. It’s important to remember that at the time when Jackson was writing his theory of evolution in the nervous system, England had passed through a series of social upheavals in which riot and public disorder had alarmed a large number of middle-class intellectuals. It was, moreover, less than a hundred years since the French Revolution had produced a sense of enormous anxiety about the incoherent, violent, ungraduated energies of the mob. It’s interesting to note in this respect that when Jackson came to use a metaphor for describing the double symptoms of the central nervous system, he actually made reference to a social model: ‘If the governing body of this country were destroyed suddenly, we should have two causes for lamentation: 1. the loss of services of eminent men; and 2. the anarchy of the now uncontrolled people.’149 And this paper was written within a few years of the Hyde Park Riots in 1866.

The sociologist Bagehot also uses an evolutionary theory to describe the structure of society. He was the first, incidentally, actually to use the word ‘atavism.’ In his Physics and Politics (1872) he wrote:

Lastly, we now understand why order and civilisation are so unstable even in progressive communities. We see frequently in states that physiologists call ‘Atavism’ – the return, in part, to the unstable nature of their barbarous ancestors. Such scenes of cruelty and horror as happened in the great French Revolution, and as happen, more or less, in every great riot, have always been said to bring out a secret and suppressed side of human nature, and we now see that they were the outbreak of inherited passions long repressed by fixed custom, but starting into life as soon as that repression was catastrophically removed.¹⁵⁰

If you were simply to remove the social words from that particular paragraph, it would almost be a paraphrase of Jackson’s description of evolution and dissolution in the nervous system. In injury we have the catastrophic removal of the services of eminent men, and if we think of eminent men as the summit of the nervous system, offering their positive services to the community at large but also repressing the incoherent energies of the mob whom they rule, we see a perfect mirror image of this model of the nervous system.

I don’t want to suggest that Head and Rivers were using their theory as a Trojan horse for the expression of a series of anxieties about the state of society. Nevertheless, it’s important to note that Rivers himself, in addition to being a clinical neurologist and a psychiatrist, was also a social anthropologist. He was one of the most important members of the epoch-making anthropological excursion made in 1898 to the Torres Straits and headed by A. C. Haddon the zoologist – Haddon the headhunter, with McDougall the social psychologist – to investigate the condition of primitive society, and with Rivers to examine the sensory endowments of primitive peoples. The social preoccupations of anthropologists with an allegiance to evolutionary theory, and a concealed allegiance to certain fears which they shared as middle-class intellectuals, can be seen to have a bearing on a purely physiological experiment.

Head passed on to other experiments and to other interests in the functioning of the nervous system, but Rivers continued his psychiatric work and his sociological work. He later wrote a book called Instinct and the Unconscious (1920) in which he continued the vocabulary which Head and Rivers had together formulated. He believed that we could look at certain phenomena in society as being exhibitions of the protopathic man. The behaviour of the rioting mob is an exhibition of the protopathic state of society in just the same way as the removal of the epicritic levels of sensation reveals the protopathic individual:

I have now to suggest that hysteria is the result of the abrogation of the modifying principle based on intelligence, leaving in full power the other and more or less opposed principle of suggestibility.151 […] The mimetic nature of hysteria provides another characteristic indication of regression. The mimesis of hysteria may be regarded as a throw-back, partly to the dramatic character of the activity of early life, partly to the mimetic aspect of the activity of the gregarious instinct.152

We have here a picture of the mob which embodies a theory about the condition of primitive society. This is conjectural anthropology, in which Rivers is making an assumption about some sort of primal herd which exhibits a protopathic form of mental life analogous to the protopathic form of sensation that he and Head had revealed when they cut the nerve in Head’s arm.

This theory continues to be expressed. McDougall, who had been a colleague of Rivers on the Torres Straits expedition of 1898 but had not taken part in the experiments, wrote a book called The Group Mind (1920):

We may sum up the psychological characters of the unorganised or simple crowd by saying that it is excessively emotional, impulsive, violent, fickle, inconsistent, irresolute and extreme in action, displaying only the coarser emotions and the less refined sentiments; extremely suggestible, careless in deliberation, hasty in judgment, incapable of any but the simpler and imperfect forms of reasoning. […] Hence its behaviour is like that of an unruly child or an untutored passionate savage.¹⁵³

In that single paragraph of McDougall’s you have a whole series of conjectures about primitive society, about the state of the child, and, behind it all, the phantom image of the nervous system as it was reflected, first of all, in Jackson’s notion of the double animal, and later in Head’s and Rivers’ distinction between protopathic and epicritic levels of sensation. What we can see here is not a simple chain of cause and effect in the history of ideas, but what Lovejoy describes as a series of elective affinities between ideas which have some common origin – some common, general model both of society and of the individual. This model was based on evolutionary theory as inherited from Darwin and Spencer, but also on certain ideas about society as a structure dominated from the top by a refined elite, holding in restraint an incoherent, raucous mob of savages.

It’s now nearly 70 years since the formulation of Head’s and Rivers’ great notion of the protopathic and epicritic nervous system, and the idea has undergone a great deal of modification in that time. However, it still exerts a considerable influence. In the teaching of anaesthesia, the levels of anaesthesia – as the patient gradually goes under with the gas – are often explained in terms of the successive peeling-off of evolutionary layers, until, as the patient lies on the table, we are witnessing a parody or a caricature of what he was before he became a man. It’s almost as if the surgeon is going to work on a hairless monkey.

Competing with this notion is a theory of nervous function which is beginning to replace it. No one wishes to repudiate the notion that we have in fact climbed up an evolutionary ladder and have arrived at our excellent current condition through previous states. But what I think we would quarrel with now is the idea that evolution consists of a concentric series of restraints upon these older conditions, and that you can reveal these older conditions by injury or assault or by special procedures of one sort or another. It’s quite possible that this vertical model of nervous organization is no longer useful for examining the nervous system that we now know. It’s certainly the case that when the nervous system is injured, very dramatic symptoms are produced. What we have to ask ourselves, however, is this: is it profitable to view these symptoms in a simple evolutionary light, as the mere release of an older stage? Is it profitable to look at these symptoms with a purely vertical model in mind, a purely hierarchical model, in which we view the nervous system as something which is dominated from the top?