A History of Nerve Functions: From Animal Spirits to Molecular Mechanisms

by Sidney Ochs

Overview

Sidney Ochs begins his survey with a chronological look at the history of nerves from the fifth century B.C. to the early eighteenth century to demonstrate the development of our knowledge of the molecular mechanisms of neuronal function. Ochs then adopts a thematic approach, considering key topics from the eighteenth century to the present. The volume will serve as an invaluable resource for historians of neuroscience and medicine, philosophers of science and medicine, and neuroscientists.

Product Details

ISBN-13:	9780521247429
Publisher:	Cambridge University Press
Publication date:	04/19/2004
Pages:	450
Product dimensions:	6.30(w) x 9.29(h) x 0.98(d)

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Cambridge University Press
052124742X - A History of Nerve Functions - From Animal Spirits to Molecular Mechanisms - by Sidney Ochs
Excerpt

1

INTRODUCTION: GREEK SCIENCE AND THE
RECOGNITION OF NERVE AS A CHANNEL

Before the dawn of civilization, primitive man believed, as does primitive man today, in animism, magic, and supernatural forces to account for events in the world he experienced.¹ The powers of nature are seen when, after the death of vegetation in winter, its rebirth occurs in spring. Storms with their lightning and thunder, wild animals, and the unpredictable and often turbulent behavior of man in relation to man were powers anthropomorphized through the action of spirits who were either beneficent or malevolent. The emotions felt within himself, man projected to other men, to other living beings, and even to inanimate objects moved by unseen forces.

With the rise of Greek philosophy and science, another view of nature and man arose: the belief that the cosmos and man are ruled by impersonal laws, that the gods do not take a providential interest in the affairs of man. As scientific knowledge evolved and the structures and functions of the various body organs became recognized, the nerves were singled out as having an integral relation to sensation and body movements. In some of the earliest accounts of nerve, they were thought of as channels carrying a spiritual influence to the brain in which consciousness and willed motor control over the body was located.

THE EARLY CONCEPTION OF NERVE CONFOUNDED WITH TENDONS
The artifacts and cave drawings left by prehistoric man attest to his powers of observation. In the course of hunting or warfare, he would have seen muscles become lax and limbs made useless by the severing of large tendons. But the tendon was not clearly identified. It could be muscle tendons (such as those of the hamstrings) or a major nerve (such as the sciatic). In the archaic Greek civilization represented in Homer's epic The Iliad,² the word neuron was applied both to tendons and nerves, and analogized to a bowstring taut with tension applied to it or lax when severed. The standard dictionary definitions in use to this day attest to the order of its ancient derivation. Under the dictionary heading of "nerve," we find the first meanings given are "sinew" and "tendon," with the idea of putting forward the utmost exertion, as to "strain every tendon."³ The later meaning given is that it is "cord-like or filamentous tissue connecting parts of the nervous system and organs of the body." It was defined in 1606 as, "A fibre or bundle of fibres arising from the brain, spinal cord, or other ganglionic organ, capable of stimulation by various means, and serving to convey impulses (especially of sensation and motion) between the brain, etc., and some other part of the body."⁴ A number of other meanings given for its modern use relate to its original meaning as a tendon, namely as subserving vitality, force, physical strength, fortitude, vigor, endurance, and also curiously its inverse, oversensitiveness and nervous weakness.⁵

In the Old Testament, reference is made to "the sinew present in the thigh" with some confusion with blood vessels, as in the translation "the principal vein of the leg which is in the thigh, commonly the sciatic nerve" and, to the "sinew of the thigh-vein or thigh-nerve." That the nerve was implicated is indicated when, in the struggle of Jacob with a strange man (Angel or God?), Jacob was "touched on the hollow of his thigh, which lamed him."⁶ This is why it is said that, "the Israelites to this day do not eat the sinew of the nerve that runs in the hollow of the thigh." From the era of the Patriarchs, eating the flesh of that part of the leg (the rump) containing this nerve (the sciatic) was forbidden, and this proscription was maintained as part of Kosher law. However, the flesh may be eaten if the nerve is first removed in the process known as porging.⁷ The custom of porging appears to have been carried out in an old, isolated Jewish enclave in China by the Jews who lived in Kaifeng (K'ai-feng), the old Capital city of the province of Honan,⁸ where the Chinese referred to them as the T'iao-chin chiao, the people who "pick out the tendons."⁹

An analogy to the biblical injunction against eating the rump because of the sciatic nerve within it was the practice carried out among some North American Indian tribes of regularly cutting out and throwing away the thigh muscles containing the nerve.¹⁰ The reason given by the Cherokee Indians was that the "tendon," when cut, retracts, with the muscles becoming lax; and they did not wish to expose themselves to the danger of also becoming weakened if they were to eat it. The notion is clearly based on sympathetic magic.¹¹ The struggle of Jacob in Genesis may very well also have had a similar origin in sympathetic magic that was later given a mythic interpretation.

PRIMITIVE ANIMISTIC BELIEF IN SPIRITS ANIMATING THINGS, AS
WELL AS LIVING BEINGS
An insight into the thought of the ancient man was given by the studies of aboriginal peoples in Polynesia and elsewhere in remote corners of the world by explorers, evangelizers, and anthropologists. An extraordinary opportunity to directly study the thinking of a primitive man came about when in 1911 an Indian, Ishi, emerged from the foothills of a remote mountain in northern California. He was the last of an isolated Stone Age tribe that had completely died out but for him.¹² Ishi was patient, cheerful, good-natured, with the capacity to learn equal to that of modern man. He lived at ease with the supernatural and the mystical, which for him were so pervasive in all aspects of his life, feeling no need to differentiate mystical truth from directly observed evidential or "material" truth, the supernatural from the natural.

Anthropologists have described the primitive's belief that the world is ruled by spirits, with the power to do him harm or good.¹³ To the primitive mind, there are no accidents. Everything has a cause. A falling rock or a swaying tree was directed by some hidden force.¹⁴ Misfortunes and diseases are attributed to malevolent agencies.¹⁵ These include taboo violation, disease-object intrusion, spirit intrusion by sorcery, and soul loss. When human ghosts feel lonesome or if disrespect has been shown to its body after death, they can cause disease. The power of the wind was of importance, and the meaning given to it by American Navajo Indians gives some insight into what prehistoric man may likely have understood of the world. The chants of the singers transmitted the traditional sacred lore in which the term Niłch'i, meant Wind, Air, or Atmosphere, which was conceived by the Navajo to be endowed with powers.¹⁶ Suffusing all of nature, Holy Wind gives life, thought, speech, and the power of motion to all living things, and serves as the means of communication among all elements in the living world. By the winds of the East, West, North and South, man is given direction to life, to movement, thinking, and action to carry out his plans; these external winds are the same as "the wind standing within us."¹⁷ The great force of the wind is shown by its power to knock down large trees. The wind was also thought by the ancients to have procreative power. Mares were reported to become impregnated by facing their hind quarters into the wind; and, at a relatively later time, the Roman writer Varro (116-127 B.C.) affirmed it as certain truth "that about Lisbon some mares conceived by the wind, at a certain season, as hens conceive what is called a 'wind egg.'"¹⁸

The belief in powers that control the world and man was the basis of magical practices. If followed in exact accordance with the laws of those powers, a desired end - such as the cure of a disease - could be brought about. An important distinction was made by Fraser between the practice of magic and religion.¹⁹ The magician acts to bring about the desired end by following his belief in the immutable laws of nature as he understood them. In this sense, his thought process is analogous to that of the scientist - the difference being that, for the scientist, those laws and the understanding of them can evolve and be replaced by others. Religion, on the other hand, is the belief that superhuman agencies, the gods, take a personal interest in man. The function of the priest is to intervene to bring about a desired end by placating the gods or to make them turn from their foreordained detrimental purposes. In the course of the development of man's thought, the offices of magician and priest were combined. The priest could, as in ancient Egypt, not only placate, but also compel the highest of gods to do his bidding.

To primitive man, the dramatic transformation of a living man or animal, warm and moving, into a cold immobile form when dead, appeared to be due to the loss of an internal "spirit" or "soul" essential for life. The very term spirit is related to breath, which confers life. The ancient Egyptians describe how Isis, by breathing on the dismembered body of Osiris, brought him back to life. In the Old Testament, the Hebrew word for spirit, neshuma, encompasses the concept of breath and wind. It is written in Genesis 2:7 that man formed from clay (or dust) was inert until "God breathed into his nostrils the breath of life and he became a living soul." In the book Ezekiel 36:2-11, the prophet was put down in a plain full of bones. Prophesy to these dry bones he was told and hear the word of the Lord:

I will put breath into you and you shall live. There was a rustling sound and the bones fitted themselves together. Sinews appeared, flesh appeared and skin covered them but there was no life. Prophesy to the wind to come from every quarter that they might come to life. Breath came into them. They came to life, and rose to their feet a mighty host.

In the Egyptian Coptic rite, the priest immediately after baptism breathes on the face of the infant saying, "Receive the Holy Ghost"; and their priests are ordained by the reigning bishop breathing on the new prelate's face. And, by inhaling a dying breath capture its power.

Pneuma, the ancient Greek term cognate with the Latin spirit, was thought to suffuse the cosmos, with wind being the expression of its presence and power. To the Vedic Indians, the cognate term prana was used to indicate the presence of breath-giving life:

The cosmic wind that blows in the atmosphere motivates and regulates the normal course of things or the cosmic order in the same way that the breath in living beings motivates life. Thus, wind is the breath of the cosmic person and the dead person's spirit (atman) goes to the wind.

This pneumatological belief is widespread. It is the basis of the practice of Yoga in India²⁰ and in Chinese and Japanese medicine where the term qi is cognate with the Greek term pneuma and its Latin equivalent spirit (spiritus).²¹

The word soul used in the New Testament is the translation of the Hebrew word for spirit that embraces a complex of ideas extending the idea of spirit. The soul can have appetites, hunger, and thirst. It is the seat of emotions, desires, and can experience sorrow or joy. It can show volition and think; it is the self-conscious manifestation of life. The Homeric Greeks pictured the soul as thin and impalpable, a shadow haunting a ghostly realm, a replica of the human body that resembles its former self.²² According to Tylor, "nothing but dreams and visions could have ever put into men's minds such an idea as that of souls being ethereal images of bodies."²³ To the primitive mind, the dream is no less real than the waking state, and the dreamer may accuse another of a crime he saw committed in a dream.²⁴

ANCIENT BELIEF IN POWERS RESIDING IN THE HEAD
INDICATED BY TREPANATION
The association of important spiritual powers residing in the brain is seen by practices such as those of the head hunting cannibals of Dutch New Guinea and adjacent islands who took their enemies' heads to gain the powers felt to reside within them. In the 27 skulls found by Lord Moyne in an abandoned village on the Bloemen River region in Dutch New Guinea, enlargements were made around foramen magnum at the bottom of the skulls "that shows the effect of a deliberate and successful removal of a large part of its base to facilitate the extraction of the contained brain, for use either for food or for ritual purposes."²⁵ Cave quotes Frazier who gives examples of the eating of the brain of a vanquished warrior to "acquire thereby his virtues and qualities."²⁶ Among primitives in the Celebes, it was to acquire the victim's bravery, among those in the Philippines it was to obtain courage, and among those in the New Guinea territory it was to procure strength. In Southern Guinea, "the decayed brain of a wise man is consumed in the belief that his wisdom passes to the consumer. . . ."²⁷ Some additional ritualistic reasons for the practice of taking the brains other than that of vanquished warriors is indicated by the presence among Lord Moyne's collection of the skulls of children 4-8 years of age that had similarly been broken into at the base. In recent years, transmission of the disease called kuru, a form of Creutzfeldt-Jakob disease affecting the brain, was traced to the practice of eating brains.²⁸

The loss of consciousness and prostration or death following a blow to the head and convulsions must not have been an uncommon observation made by prehistoric and primitive man. This could well have suggested the idea that the head plays an especially powerful role in controlling conscious life, as well as controlling the lively vigor of the body leading to the ancient practice of trepanation, the opening of holes in the skull of a living subject.²⁹ The first example of trepanned skulls that had been made in ancient times was discovered in France in 1834. Subsequently, such skulls were found elsewhere in Europe, North Africa, parts of Asia, and America, with greatest frequency in the highlands of Peru and Bolivia.³⁰ That these openings had incurred in life was shown by the healed edges of the holes. Also testifying to the subjects outliving the operation are skulls found with two, three, or more holes in them (Figure 1.1). Perhaps epileptic attacks, chorea, insanity, or some other aberrant behavior could have led to the thought that an indwelling evil spirit was responsible and had to be let out. That the basis for the operation was magical is indicated by the portion of bone removed from the trepanated skull, the rondel, being used as an amulet. With the dawn of the science of medicine, Hippocrates describes trepanation as a surgical procedure in the treatment of head injuries. It is of interest that trepanation, outside of its use in surgical interventions, was still carried out in various remote places in Europe and the Americas on into the nineteenth century and exists today as a bizarre cult practice performed in supposedly normal people.³¹

1.1 Examples of trepanation. Different types of openings made into the skulls with signs of healing seen at their edges. The skull on the right reveals five round holes. An example of a square hole is shown at the bottom left. From (Guiard, 1930), Plates 1 and 8, Figures 1 and 2.

The rise of Greek philosophy and science
It was the genius of the ancient Greek thinkers of the sixth and fifth centuries B.C. that replaced animistic belief in spiritual powers, magic, and the supernatural anthropomorphic religion expressed by Homer and Hesiod (c. ninth and eighth centuries B.C.) with philosophy and science.³² The gods were no longer thinly veiled anthropomorphic powers controlling human events. They were replaced by physical forces and entities operating by inexorable laws. The impetus was the search for the arche, the principle underlying things and the basic "stuff" of which all things are made. In the Platonic dialogue Timaeus, at the onset all was chaos out of which the Demiurge (a lesser god) made the world. This was presented as a fable, what we may call a hypothesis, one that could undergo modification. In contrast, in the religious account given in Genesis, God created the world from nothing, ex nihil (by divine fiat),³³ and continues to intervene in the affairs of men - a providential God. In the Greek philosophical accounts, the whole of physis (nature) of the Cosmos that encompasses all - the earth, sea, and sky with its heavenly bodies of the sun, moon, and stars and the earth and its living creatures - is ruled by impersonal fixed law.³⁴ Some of the earliest of these thinkers, the physiologists,³⁵ appeared in the important commercial Greek city of Miletus at the western shore of Anatolia, now Turkey, facing the Aegean Sea.³⁶

Among them was Thales of Miletus (c. 640-546 B.C.), who taught that water was the fundamental substance, the concept likely inspired by its necessity for life. For Anaximenes (fl. 546 B.C.), the fundamental substance was aer (air), which includes pneuma (breath or spirit), the term later extended to include the psyche (soul) present in animate beings.³⁷ In us the soul enables life: "Just as our soul being air, holds us together, so do breath and air encompass the whole world."³⁸ The term then further extended to include the concept of the mind. Philosophers appeared in other city states of the Greek world. Pythagoras of Samos (c. 580-489 B.C.) founded a mystical philosophical brotherhood at Croton, a Greek colony located at the foot of Italy. He taught that the world could be understood on rational principles, on mathematical laws, and considered the world to be made of four elements: earth, water, air, and fire. His pupil Empedocles (490-430 B.C.) advanced the concept that, under the opposing forces of "love" and "strife," the four fundamental elements of earth, air, fire, and water become transformed into one thing or another.³⁹ Anaxagoras (500-428 B.C.) viewed the cosmos as being formed by nous (mind or reason) from an infinite number of different elements. These come together on the basis of "like coming together with like," just as "fluid" merging with other "fluid" forms the oceans, the various parts of the body are formed the same way with bone formed from elementary bone, flesh from elementary flesh, and so on. As Greek thought developed, the special role played by air, the term originally given as spirit, was extended to soul as the animating principle responsible for life and then extended to encompass the mind by nous, the cognitive (noetic) function, whereby things, their number, harmony, and their relations to one another could be understood.⁴⁰ Nous was not only deemed a property of the mind of man, but it was also revealed by the cosmos with the regularity of the movement of the stars, sun, and moon in the heavens expressing by the regularity of their progression in the skies harmony and order, the presence of intelligence. This was the anima mundi, the immortal animated world, the cosmos that included the air, the sky, and the heavens; the macrocosm that is related to man, the microcosm. The divine air of the cosmos, from which all things take their origin and are held together by its invisible organizing principle, is taken in by respiration to animate the body, hold it together, and regulate changes within it.⁴¹

The concept that inspired air carried in the carotids confers consciousness and thought in the brain was taught by Diogenes of Apollonia (412?-323 B.C.). He took air to be the source of all things, identifying the warm air within the body (apparently carried by the arteries) to mix within the brain where the soul is located. Perception arises there with the psyche acting as the mediator between sensation and cognition.⁴² This relationship of the intelligence of the cosmos brought in by air to man, the microcosm, was clearly expressed when he wrote:

And it seems to me that that which has Intelligence is that which is called Air by mankind; and further, that by this, all creatures are guided, and that it rules everything; for this in itself seems to me to be God and to reach everywhere and to arrange everything and to be in everything. And there is nothing which has no share of it; but the share of each thing is not the same as that of any other, but on the contrary there are many forms both of the Air itself and of other Intelligence; for it is manifold in form: hotter and colder and dryer and wetter and more stationary or having a swifter motion; and there are many other differences inherent in it and infinite (forms) of savor and color. Also in all animals the Soul is the same thing, (namely) Air, warmer than that outside in which we are, but much colder than that near the sun.⁴³

CONCEPTION OF NERVES AS CHANNELS FOR SENSATION
AND MOTION

With Alcmaeon of Croton (fl. fifth century B.C.), a pupil of Pythagorus, the differentiation of science from philosophy was widened. He is credited with carrying out animal dissections, which led to his proposing that special channels in the body exist for sensory reception.⁴⁴ His idea of sensory channels appears to have risen from his observation of the empty blood vessel seen in sections of the optic nerves. By extension, he thought channels invisible to the naked eye were also present in other nerves to convey auditory, olfactory, gustatory, and somatic sensory impressions from the ears, nose, tongue, and skin to the brain to there give rise to the perceptions of objects. An argument he gave to support the specificity of the various sensory channels was that damage of the optic nerve causes blindness without involving the other senses, similarly damage to the ear results in deafness alone, and so on. Furthermore, such specific sensory deficits can occur without a perturbation of general sensibility and intellect, or of motor powers.⁴⁵

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© Cambridge University Press

Table of Contents

1. Introduction: Greek science and the recognition of nerves' function; 2. Galen's physiology of the nervous system; 3. Nerve, brain, and soul in the Middle Ages; 4. Renaissance and the New Physiology; 5. New physical and chemical models of nerve in the Enlightenment; 6. New systematizations of nerve function in the Enlightenment; 7. Electricity as the Agent of Nerve Action; 8. Nerve fiber form and transformation; 9. Wallerian degeneration: early and late phases; 10. Nerve regeneration; 11. Characterization of axoplasmic transport; 12. Molecular models of transport; 13. Actions of neurotoxins and neuropathic changes related to transport; 14. Purposeful reflexes and instinctive behavior; 15. Neural events related to learning and memory; 16. Epilogue; Bibliography.

Editorial Reviews

"Sidney Ochs is that rare and modern scientist whose lifelong passion for studying the history of science is combined with broad scholarly knowledge of contemporary paths in neuroscience research. The resulting story of how we have reached our understanding of how nerves function is presented with the profound insights that can only derive from thorough scholarly research plus several decades of engagement at the "cutting edge" of bench science. It would be difficult to identify any book in recent years that could provide as much excitement and profound insight into this field in the context of its broad history."
Journal of the History of the Neurosciences: Basic and Clinical Perspectives

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