Flesh in the Age of Reason (10 page)

A parallel bid to read the body in terms of the new science came from iatrochemistry. Whereas iatrophysics perceived the human frame through mechanics, iatrochemistry thought that chemistry held the secrets. Equally repudiating the humours as vacuous verbiage, its supporters hailed the chemical theories of the Swiss iconoclast Paracelsus (Philippus Aureolus Theophrastus Bombastus von Hohenheim, 1493–1541), who, while widely dismissed as a quackish ignoramus, was respected by others as a towering reformer. Paracelsus had praised the simplicity of Hippocrates, learned from folk medicine, and touted the power of nature and the mind to heal the body. Above all, as his operative principles he replaced the equivocal humours with the three chemical principles of salt, sulphur and mercury.

Devotees of iatrochemistry also revered his Netherlandish follower, Joannes Baptista van Helmont. Modifying Paracelsus’s notion of a single ‘archeus’ (that is, in-dwelling spirit), van Helmont held that each organ possessed its own specific spirit (
blas
) which regulated it. ‘Spirit’ for him was not mystical or occult but chemical. Indeed, he held all vital processes to be chemical, each being due to the action of a particular ferment or gas. There was, thus, a ferment for converting food into living flesh and blood. Similar transformative
processes occurred throughout the body, but particularly in the stomach, liver and heart. Bodily heat was a by-product of chemical fermentations, and the whole system was governed by a ‘soul’ situated in the pit of the stomach. Chemistry, broadly understood, was thus the key to life. Views like these were unsettling: Gui Patin, leader of Paris’s reactionary medical faculty, denounced van Helmont as a ‘mad Flemish scoundrel’.

By the close of the seventeenth century, advances in anatomy and physiology had created the promise of a scientific understanding of the body, matching what high-prestige mathematical astrophysics and mechanics had done for the inanimate world. Beliefs about the body were in flux, but one thing was clear: all the new models joined in denouncing Aristotelianism and Galenism as empty and barren – if often in reality recycling their ideas under a different guise, pouring old wine into new bottles.

The new mechanical models elicited pride in the body: what a marvellous machine it was! The Cambridge botanist John Ray extolled ‘the admirable Art and Wisdom that discovers itself in the make and constitution, the order and disposition, the ends and uses of all the parts and members of this stately fabrick of Heaven and Earth’, praising the body because there was ‘nothing in it deficient, nothing superfluous, nothing but hath its End and Use’. A school of physico-theology pointed to the contrivances of the body as the finest proofs of God.

Such mechanical models also called for a rethinking of the nature of life itself. Did it reside in the Christian supernatural soul (
anima
) that was attached to the organism since ‘quickening’ and animating it? This was essentially the theory of Georg Stahl, Professor of Medicine at Halle (Prussia) in the early eighteenth century. Or was it an external impulse which God had imparted to the bodily machine, like winding up a clock or striking a billiard ball? – the view of the Leiden medical professor, Hermann Boerhaave. Or was life a property inherent in the organism thanks to its high degree of organization? – an interpretation that gained ground in the eighteenth century, especially among materialists and unbelievers. In
addition, was
human
life qualitatively different from that of a mushroom, a mouse or a monkey?

The mechanization of the world-picture further required rethinking of the interaction between mind and matter. How did reason govern the body? Did the flesh have a reciprocal capacity to sway the mind? If so, was that – or
should
it be – only in the heat of passion (hot blood), or in sickness, physical or mental?

The crucial catalyst for such speculations was René Descartes. Descartes was a dualist who decried dogmatic materialism; but his writings threw down a challenge to investigators of all convictions to locate where and how consciousness acted within the organism, indeed within the brain. Might such thinking be the slippery slope to reducing the soul to the brain or body altogether? His rationalist philosophy will be discussed in detail in the next chapter, but to see how far the ‘new philosophy’ had changed expert opinion about the workings of the human animal by the last decades of the seventeenth century, it will be instructive to examine the works of Thomas Willis (1622–75).

Oxford-trained, Anglican by faith and royalist by politics, an associate of Robert Boyle and Robert Hooke, a fellow of the Royal Society and a fashionable London physician besides, Willis represents the cutting edge of respectable scientific thinking. He is remembered for coining ‘neurologie’, a term for the new discourse of the ‘nerves’ and ‘nervousness’ which became so favoured in the eighteenth century, and for his description of the ‘Circle of Willis’, the arterial circle at the base of the brain. Though a ‘modern’, his theories of neurological activity continued to draw on much of the baggage of traditional biomedicine, including animal spirits, the intermediaries between body and mind distributed through the nervous system. He too, like Harvey, is thus a fascinating intermediary between old and new.

Harvey’s discovery of the circulation of the blood, Willis recognized, called for a rethinking of physiology at large. Building on painstaking anatomical investigations, especially of the nerves, vivisection experiments and clinical experience, his
Cerebri Anatome
…
(Anatomy of the Brain: 1664) put ‘neurologie’ on the map; his
De Anima Brutorum
(On the Soul of Brutes: 1672) explained the workings of living creatures, while a further study, the
Pathologiae Cerebri et Nervosi Generis Specimen
(Pathology of the Brain, and Specimen of the Nature of the Nerves: 1667), proposed the neurological origins of epilepsy and other convulsive disorders.

Impressed by the mechanical philosophy, Willis rejected not just scholasticism’s ‘substantial forms’ but Paracelsus’s ‘archeus’ doctrine as well. Determining what was unique about living beings, he postulated the ‘corporeity’ of a soul (
anima
or animating principle), common to beast and man alike. This ‘animal soul’ depended altogether on the body, being born and dying with it. No medium was needed between the body and this corporeal soul: the various members of the body were all ‘organs’ of this vivifying principle. It had distinct and extended parts, enabling it to activate the different limbs. This animal soul could be divided, and could continue to exercise its functions of sense and motion even if so divided – as with worms and eels when cut into pieces. Willis’s
anima
was roughly what was soon to be called ‘irritability’ by the Swiss investigator Albrecht von Haller – an organism’s capacity to receive and react to stimuli. Responsiveness thus stemmed from the animal soul.

Of what was this ‘soul of brutes’ (the phrase used by John Pordage, Willis’s contemporary translator) composed? Willis likened it to fire, extremely subtle and mobile. As with flame itself, the soul required a twofold food – a sulphurous and a nitrous substance. The animal soul likewise had a double location: in the blood (vital fluid) circulating, as Harvey had shown, through the heart and vessels; and in the ‘animal liquor’, or nervous fluid, present in the brain and flowing through the nerves, envisaged by Willis as tubes. The aspect of the soul inherent in the blood was comparable to a flame; that within the nerves was like the light rays issuing from such a flame. The soul was not actually constituted of blood and nerve juices but (in Pordage’s charmingly flowery and anthropomorphic phraseology) ‘inhabits and graces with its presence both these provinces’.

Being corporeal, the animal soul arose ‘with the body, out of
matter rightly disposed’, though, as it was imperceptible to the senses, it could be known only by its effects. Upon the body’s decease, the particles of the animal soul were dispersed, without trace, leaving the body subject to rapid corruption. The corporeal soul performed various functions, above all activating the blood (metabolic activity) and the nerve juices (nervous activity). In addition, there was a third aspect, an outgrowth of the ‘vital flame’, involved in sexual activity and reproduction.

The most subtle agents involved in the operations of the animal soul were the ‘animal spirits’ which, Willis taught, were vaporized into the brain and cerebellum. They then entered the cortex, flowed down the medulla and spinal marrow and, via the nerve fibres, pervaded the entire body.

Addressing the structure and functioning of the nervous system, Willis distinguished sensory from motor functions. The sensory components, which consisted of images, were transmitted, via the nerve tubes, to the brain where they were represented as on a white sheet – evidently he had in mind a camera obscura. From there they proceeded to the cortex, where they constituted memory. The motor aspects of the nervous system operated through a sequence involving imagination, memory and appetites, with the animal spirits as the vehicle and the nerve ducts as the pathway.

What was the origin of the corporeal soul? Willis held that a ‘heap’ of subtle atoms or animal spirits – a ‘little animal soul, not yet kindled’ – lay in the seminal fluid. When, through sexual intercourse, this ‘heap’ found a suitable berth, a soul was kindled, just as one flame was ignited by another. The animal soul then fashioned the body according to the ‘forms’ (original types ordained by divine providence). Thereafter, the animal soul served to preserve the body from putrefaction, while the body supported the soul by nourishing it.

Crucial to Willis’s thinking was that this
animal
or
corporeal
soul was quite distinct from the
rational
soul of humans, and subordinate to it. Common to mankind and the animal kingdom, the animal soul was material, unlike the superior rational soul (unique to humans), which was immaterial and immortal. The office of the rational soul was the
exercise of reason, judgement and will. It presided over the lower soul. Man was thus a bi-souled biped.

Although the brute creation did not possess a rational or immortal soul, animals nevertheless, Willis held, challenging Descartes, enjoyed some measure of inferior reason. To clarify the difference between the minds of animals and of man, he called to mind a pipe organ. The wind makes a rough noise when it passes into a pipe; the fingers of a musician, by contrast, produce wonderfully harmonious and inventive music. A mechanical device, run by water power, may, however, produce tunes on such a pipe organ vaguely comparable to those performed by human fingers. Governing and directing the animal spirits, the rational soul of man is comparable to the musician, playing a pipe; rather, as with a water-powered organ, animals can produce behaviour somewhat comparable to the human.

Animals, Willis happily conceded, exhibit instincts which may dictate operations of great complexity. Brutes also had a certain capacity to learn by experience, example and imitation, thanks to the senses, memory and imagination. They were thus not, as for Descartes, mere automata. Nevertheless, the distinction between the animal and the rational soul was crucial to Willis, biologically, metaphysically and religiously: the corporeal soul of brutes was limited in scope to the objects of the senses, to the material here-and-now, whereas the rational soul had the capacity to embrace abstractions – the immaterial – and also possessed powers of comprehension and discourse.

The ‘knowing faculty’ (imagination or fantasy) of the corporeal soul was located, Willis held, in mid-brain, where it received sense impressions. Since appearances could obscure or distort the true nature of things, the imagination was prone to being deceived. In man and man alone, however, the intellect presided over the imagination, picking up and correcting its errors. Fed by such sense impressions, it also generated abstract concepts and formulated universals – God, infinity and eternity, and many other ideas far removed from sense and imagination.

Animals were capable of a modicum of reasoning; in man, by
contrast, the intellectual powers were immense. Human reason could make inferences which far transcended mere sense perception; it could formulate axioms, unearth causes, handle mathematics, cultivate the arts, sciences and the ‘laws of political society’, and build wonderful machines. Above all, the rational mind could grasp the ineffable infinitude of God, and the reality of angels, heaven and hell. The reasoning power of brutes, by contrast, ‘will hardly seem greater than the drop of a bucket to the sea’.

The distinction between the animal and the rational soul was thus not just one of degree but of kind – it was qualitative. The animal soul was material, the rational soul immaterial and immortal, divinely implanted. How then – a version of Descartes’s dilemma – did Willis envisage the links between the two kinds of soul in man? He endorsed the traditional Christian view of man’s tripartite nature: he possessed a body, an animal life shared with the brutes and, lastly, ‘spirit, by which is signified the rational soul, at first created by God, which being also immaterial, returns to God’. Man was thus midway between angels and brutes on the Chain of Being.

The relationship between the two souls was complex. The animal soul pervaded the entire body, while the rational soul pertained exclusively to the head, dwelling within the brain as on a throne, just like a king in his palace. Like a monarch, the intellect did not need to attend personally to those functions served by the dutiful corporeal soul.

The rational soul was nevertheless not aloof but plugged into the bodily economy. For its operation, it depended on the imagination, which was itself the end-point of the chain whereby sense impressions were carried to the nerves. Intellects in any case differed – was not one person cleverer than another? This was because of differences in their respective corporeal endowments and brain power. The intellect was thus in certain crucial ways contingent on the brain and hence the body.