Medicine, Mind, and the Double Brain

A Study in Nineteenth-Century Thought

Anne Harrington

• Publisher: Princeton University Press
• Year: 2021
• Print ISBN: 9780691024226, 9780691084657
• eBook ISBN: 9780691228174
• Topic: History
• Subtopic: Science History
• Index: History

The description for this book, Medicine, Mind, and the Double Brain: A Study in Nineteenth-Century Thought, will be forthcoming.

CHAPTER ONE

The Pre-1860 Legacy

The reason which persuades me . . . is that I reflect that the other parts of our brain are all of them double . . .

—René Descartes, “Passions of the Soul,” 1649

1-1. The Search for the Seat of the Soul

THE DOUBLE BRAIN began its history, not so much as a scientific or a medical problem but as a theological one. The earliest physiologists, searching for the “seat of the soul,” had naturally tended to look for centrally located, unitary organs in the body that could be supposed to correspond to the indivisible unity of the ruling conscious self. As the view gradually gained ground, in the seventeenth and eighteenth centuries, that the workings of the soul were intimately related to the workings of the nervous system, the latter’s almost perfect bilateral symmetry had naturally caused some consternation (cf. McDougall 1911, 286; Wilks 1872, 161). It is well known, for example, that the philosopher René Descartes (1596-1650) believed that the brain’s pineal gland served as the site of the soul’s interaction with the body, though not the site of its physical locale, the soul being nonextended and immaterial. Precisely why Descartes had decided to honor an unassuming organ with such an important office is probably less well understood. In his 1649 “Passions of the Soul,” Descartes explained

The reason which persuades me ... is that I reflect that the other parts of our brain are all of them double, just as we have two eyes, two hands, two ears, and finally all the organs of our outside senses are double; and inasmuch as we have but one solitary and simple thought of one particular thing at one and the same moment, it must necessarily be the case that there must somewhere be a place where the two images which come to us by the two eyes, [and] where the two other impressions which proceed from a single object by means of the double organs of the other senses, can unite before arriving at the soul, in order that they may not represent to it two objects instead of one. And . . . there is no other place in the body where they can be thus united unless they are so in this gland. (Translated in Vesey 1964, 47)

Descartes’ second reason for choosing the pineal gland as the seat of the soul was his belief that it was not found in the brains of animals. Since only man was endowed with an immortal soul, it seemed logical to assume that the site of this soul’s operations would be a uniquely human endowment as well. In fact, the pineal gland not only exists in a well-developed form in many animals but actually was first discovered in animal brains. Descartes’ critics were quick to point out this fact. In 1699, the Danish theologian and physician Nicholaus Steno also criticized Descartes’ choice of organ on the grounds that the pineal gland lacked the complex mechanisms that the Cartesian doctrine of psycho-physical interaction seemed to require (Jaynes 1970). This double-pronged deprecation of the French philosopher’s pioneering localization work may have contributed to a tendency among a number of later Cartesian writers to deny the pineal gland any special association with the soul and to turn instead to the handful of other more or less unitary structures in the brain—the corpus callosum, the pons varolii, the septum lucidum, the central ventricle—in their no less earnest search for some central and unitary meeting ground between mind and matter. There was a tradition in Western neurological thinking, going back to the cell doctrine of the early Church Fathers, that there had to be some place in the brain where all sensory messages from the outside world could come together and coalesce into a coherent unity, the so-called sensorium commune. Otherwise, the seamless unity of the soul’s consciousness was inexplicable. The search for some sensorium commune was to remain one of the chief themes of eighteenth-century neurology. Just because they were not prepared to accept Descartes’ solution does not mean that later generations of neurologists failed to appreciate the seriousness of the problem to which he had called attention.

Unfortunately, little by little, it became clear that the various unitary organs favored by these men had little or no immediate connection with consciousness. Early in the nineteenth century, the phrenologists, led by the Austrian anatomist Franz Joseph Gall (1758-1826), were among the first to take the growing body of evidence as they found it and map out the human soul boldly upon the convolutions of the cerebral hemispheres. Phrenology operated on the basis of three fundamental principles: (1) the brain (above all, the cortex) is the organ of the mind; (2) the brain is a composite of parts, each of which serves a distinct, task-specific “faculty”;¹ and (3) the size of the different parts of the brain, as assessed chiefly through examination of the cranium, is an index of the relative strength of the different faculties being served.

Young has stressed the way in which Gall sought to confirm his theory through a systematic gathering of corroborative cases; to his mind, Gall was making use of a naturalistic method not unlike that of Charles Darwin (Young 1970, 48). Something is slightly misleading about this comparison, however, because Darwin did not first conceive of natural selection, then sail to the Galapagos to confirm his idea. In contrast, the fundamental guiding principle of Gall’s system, that the cortex is a plurality of organs serving different faculties, was developed at the end of the eighteenth century, before he had dissected a single brain or analyzed the bumps on a single skull. While the details of his localization scheme may have come later through, as Young argues, “naturalistic” means, his original conception of mental faculties and how they related to the brain should be seen, first and foremost, not as a scientific (or even pseudo-scientific) theory but as a philosophical solution to a problem in epistemology. The French sensationalists— Condillac, Bonnet, Cabanis—had argued that sensation alone was sufficient to explain knowledge. If they were right, however, it was difficult to see why the mind was not a mere “heap of impressions,” as Hume had put it. What was the means by which knowledge was organized? Gall’s reply was that there must exist an innate material base for the organization of sensations in the mind, just as there was a material base for the process of sensation itself (Bentley 1916).

Gall had been impressed by Charles Bonnet’s emphasis upon the functional relationship between organic and psychic activity in the brain and later recalled Bonnet’s remark that anyone who thoroughly understood the structure of the brain would be able to read all the thoughts passing through it “as in a book.” Bonnet, though, had not gone so far as to localize definite psychic predispositions in discrete parts of the brain but rather had envisioned the brain’s presumed different organs as vehicles that the immortal soul employed at will. This version of Cartesian interactive dualism was unsatisfactory for Gall, and his scheme the overruling soul—the immaterial homunculus expertly manipulating bits of cortex like a pianist at the keyboard— was abandoned (Lesky 1970). In its place was a brain-dwelling mind that resembled, as the German philosopher F. A. Lange would later put it, “a parliament of little men together, of whom, as also happens in real parliaments, each possesses only one single idea which he is ceaselessly trying to assert. . . . Instead of one soul, phrenology gives us nearly forty” (Lange 1881, 124).

The French physiologist Jean-Pierre-Marie Flourens (1794-1867) admired Gall’s anatomical work—Gall, for example, was the first to distinguish clearly between the gray and white matter of the brain— and he agreed with the phrenologists that perception and intelligence “belong exclusively to the cerebral lobes.” Experimenting on pigeons and fowl, Flourens had found that when he removed the whole of the cerebrum, the birds continued to live but apparently lost all sense of perception, instinct, intelligence, and volition. They moved away if touched or otherwise irritated, flew if thrown in the air, but when left alone, they remained motionless in a state of stupor resembling deep sleep (Lewes 1877, 469).

Nevertheless, the theological implications of Gall’s “parliament of little men” were far from lost on Flourens, and he was determined to refute the materialistic heresies he saw in Gall’s approach to the mind-body relationship.² In his critique of phrenology (Flourens 1846), Gall and his followers were declared guilty of undermining the unity of the soul, human immortality, free will, and the very existence of God. There should be no question as to why Flourens would choose to dedicate such a treatise to Descartes (cf. on this point Engelhardt 1976).

Flourens conducted his refutation of Gall on both rational and empirical grounds. On the one hand, he pointed to the testimony of “inner sense”: this assured him of the indivisible unity and moral freedom of his soul, while the conceptual distinctness of mind from body led logically to a belief in its literal distinctness within each individual. Flourens did not stop there, however, but bolstered his case with what seemed at the time to be an impressive body of experimental evidence as well. Again relying mostly on birds (with the odd rodent and rabbit), he performed a series of studies that involved slicing systematically through the brain and noting resulting deficits. And, he concluded,

1. One can excise, either in front, in back, on top, or on the side, a fairly extended portion of the cerebral lobes, without their functions being lost. A rather limited portion of these lobes suffices therefore for the exercise of their functions;

2. In proportion as this excision takes place, all the functions become weaker and gradually fade; and past certain limits, they are wholly extinguished. The cerebral lobes cooperate therefore as a total unity in the full and entire exercise of their functions. (Flourens 1824, cited in Hécaen & Lanteri-Laura 1977, 63)

As Young has pointed out (1970, 60-61), methodology helps shape results, and Flourens’ experiments did not support localization theory, at least in part because he chose to cut indiscriminately through the brain, disregarding structural variations in the cortex that could conceivably be correlated with functional differences. His overreadiness to generalize results obtained from pigeons into a transspecies theory of brain function is also fair target for criticism. Nevertheless, Flourens’ influence on orthodox physiology was to be profound: partly because the crude experimental techniques available in the early nineteenth century meant that a limited amount of counterevidence was available; and, doubtless, partly as well because a unitary conception of mind and brain was as theologically congenial to most of Flourens’ colleagues as to Flourens himself (cf. Tizard 1959). The popularization of phrenology under such men as Spurzheim, its transformation into a social crusade with left-wing, radical tendencies, its growing association with other suspect ideas such as mesmerism, also all indirectly worked to enhance the stolid, respectable appeal of Flourens’ rival views on brain functioning, at least within the conservative, ingrown circles of academic physiology (cf. Cooter 1984).

Through Flourens, then, the Cartesian soul found a new seat within the cerebral hemispheres, even as it was for the moment rescued from the threat of materialization and disintegration at the hands of Gall. No longer cramped inside the tiny pineal gland, it could now be envisioned “sitting enthroned upon the cerebrum,” as the English physiologist Marshall Hall would put it in 1841, “receiving the ambassadors, as it were, from without, along the sentient nerves, deliberating and willing, and sending forth its emissaries and plenipotentiaries, which convey its sovereign mandates, along the voluntary nerves, to muscles subdued to volition” (cited in Riese 1949, 123).

Yet, even if, by the close of the 1820s or so, Flourens had won the battle for antilocalization within official physiology, the outcome of the war remained undetermined. As will be seen in the next chapter, Gall’s candle would be kept burning into the 1860s by Jean-Baptiste Bouillaud, when the whole question of cerebral localization would be again thrown wide open. At this time, a new generation of neurologists would partition itself on one or the other side of the battlelines drawn early in the nineteenth century, and underneath the rumble of scientific rhetoric, many of the same uneasy questions about the destiny of the soul and man’s place in the scheme of things again would be very much a concern.

1-2. Brain-Duality and the “Laws of Symmetry”

In his crusade against phrenology, Flourens had not focused particular attention on Gall’s views on the double brain, doubtless because the immediate dangers raised by the concept of localizing pieces of the soul in different parts of the brain had swamped all other considerations. Nevertheless, there is no question that the role of the double brain within the phrenological system raised a distinct set of theological problems—problems to which Flourens could hardly have been insensitive. From the beginning, Gall had taught that each of the mental faculties existed in perfect symmetrical duplicate, with each pair localized in corresponding regions of the two hemispheres, so that in the end each half of the brain could serve as a complete and independent organ of the mind.³ For someone like Flourens, such a doctrine could be construed to mean that each hemisphere at least was potentially capable of generating a “soul” of its own, capable of independent will and consciousness. Gall, it must be said, had been careful to put the matter in more neutral, biological language:

We have two optic nerves and two nerves of hearing, just as we have two eyes and two ears; and the brain is in like manner double, and all its integrant parts are in pairs. Now, just as when one of the optic nerves, or one of the eyes is destroyed, we continue to see with the other eye; so when one of the hemispheres of the brain, or one of the brains, has become incapable of exercising its functions, the other hemisphere, or the other brain, may continue to perform without obstruction ... ; in other words, the functions may be disturbed or suspended on one side, and remain perfect on the other. (Gall 1822, cited in “Dr. Wigan on the Duality of Mind” 1845)⁴

Although theologically pernicious, it is important to realize that the phrenological view (seen in Figure 1) of the double brain as physically and functionally symmetrical also had very strong heuristic appeal, as even the Cartesians had to admit. If the cortex were ever to stand a chance of becoming an object of scientific investigation, it was essential to show that its convolutions were logically and lawfully constructed according to one specieswide blueprint. Now, prior to the period in which the phrenologists began to make their influence felt, it had been widely believed that the convolutions between the two sides of the human brain were organized according to no particular pattern and varied so greatly from individual to individual as to defy all attempts at classification. The French anatomist Vicq d’Azyr had even gone so far as to make these alleged convolutional irregularities a sign of the superiority of the human species, perhaps because in some way the uniqueness and freedom of each individual soul was thereby affirmed. “In the apes,” d’Azyr had declared in 1805, “as in all the quadrupeds in general, the cerebral convolutions are few in number, symmetrical on the two sides, and similar in individuals of the same genus. In man, on the contrary, they are neither symmetrical on the two sides, nor similar in [any] two subjects” (cited in Hécaen & Lanteri-Laura 1977, 42). In a similar way, one reads in John Gordon’s 1815 anatomy text, written before the new phrenological ideas had been carried to Edinburgh by Spurzheim, how the convolutions in the human brain were “seldom precisely alike, either in shape or size, in any two corresponding points of the opposite Hemispheres. In different Brains,” Gordon confessed, “I do not know that any two corresponding points, in either Hemisphere, have ever been observed” (cited in Shapin 1979b, 153).

Figure 1. The phrenological model of the brain showing duplication of the mental faculties in symmetrical regions of the two hemispheres. (Source: Spurzheim 1833, frontispiece. Reprinted with the permission of the Bodleian Library, Oxford University.)

Certainly, it would be foolish to affirm that each and every early proponent of the emerging symmetry principle in cerebral anatomy was directly indebted to Gall. The manner in which new heuristic concepts arise and achieve acceptance within a scientific community is imprecisely understood, but it seems pretty certain that very few pivotal ideas are ever wholly original with one individual. What is more interesting is how a change in belief at this time was apparently able to bring about a change in what the cerebral anatomists actually saw. Presumably, there was no great difference between the brains that John Gordon studied and those examined by Sir Charles Bell. Yet, in his 1811 “Idea of a New Anatomy of the Brain,” the latter made a point of registering his admiration for the way in which “whatever we observe on one side [of the brain] has a corresponding part on the other; and an exact resemblance and symmetry is preserved in all the lateral divisions of the brain” (Bell 1811, 118).

Now, for Gall, the two halves of the brain existed in symmetrical duplicate in order to provide a buffer against injury. Whether such was the original intention, this idea would prove extremely useful to his followers. Increasingly, phrenologists would be forced to defend themselves against critics armed with medical records that showed how virtually every individual part of the brain mapped out by Gall in its turn had been damaged, without injury to the faculty that was meant to correspond to it. One possible retort to this sort of charge was that there had been a failure to take into account the duality of the brain. As Alexander Combe would write in 1824, the critics in question, “by what rules of logic I know not, appear to think injury of one organ sufficient to destroy the function of both.” He concluded triumphantly

It will be seen, from an attentive perusal of the cases quoted [by critics], that not a single instance is to be found, in which . . . destruction of both organs has occurred, while the alleged manifestations [of the faculty in question] existed. In almost all cases, the injury or disease is expressly said to be on one side only; and where it is on both, the parts affected are different. (Combe 1824, 191-92; cf. on this same point Bouillaud 1825, 263-64; Holland 1840, 183; Davey 1844, 377; Buchanan in “Duality and decussation” 1850, 513-14; and the critical views of Lange 1881...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Dedication
• Contents
• List of Figures and Tables
• Acknowledgments
• A Note on References and Style
• Introduction
• Chapter One: The Pre-1860 Legacy
• Chapter Two: Language Localization and the Problem of Asymmetry
• Chapter Three: Left-Right Polarities of Mind and Brain
• Chapter Four: The Post-Broca Case for “Duality of Mind”: Basic Issues and Themes
• Chapter Five: Left-Brain versus Right-Brain Selves and the Problem of the Corpus Callosum
• Chapter Six: The “Experimental Evidence”: Metalloscopy and Hemi-Hypnosis
• Chapter Seven: The Hughlings Jackson Perspective
• Chapter Eight: Freud and Jackson’s Double Brain: The Case for a Psychoanalytic Debt
• Chapter Nine: The Fate of the Double Brain
• Appendix: Guide to the Major Structures of the Human Brain Discussed in This Study
• Addenda
• References
• Index