Bell-Magendie law
Encyclopedia
In anatomy
and neurophysiology
, this is the finding that the anterior spinal nerve
roots contain only motor fibers and posterior roots only sensory fibers and that nerve impulses are conducted in only one direction in each case. The nature and the physiology of the phenomena were described independently by the British
anatomical scientist Sir Charles Bell
and the French
physiologist François Magendie
, later confirmed by the German
physiologist Johannes Peter Müller
.
and Francois Magendie – a pathophysiology
and physiology
professor
. Their independent observations were 11 years apart. Another definitive experimental proof was given nine years after Magendie's experiments by Johannes Peter Müller during a vivisection
of a frog
in 1831.
Charles Bell referred to the motor functions of nerve fibers exiting the ventral root
s of the spinal cord
but did not mention about the sensory functions of the dorsal root
s. That was in part because his studies were dissection
ist and not vivisection
ist. Pain is elicited and detected best in a conscious animal. A dead, or rendered unconscious, animal would not produce the desired effect when posterior horn fibers, responsible for sensation and transfer of noxious signals, are stimulated.
Bell's nephew, John Shaw
travelled in 1812 to Paris
where he presented Bell's system to the French anatomists. Reportedly Shaw staged a demonstration on the facial nerve
s of a donkey
without the intended effect.
exit from the anterior root and the sensory neuron fibers
from the dorsal root: "(trans)section of the dorsal root abolishes sensation, (trans)section of ventral roots abolishes motor activity, and (trans)section of both roots abolishes both sensation and motor activity."
Magendie gave the first complete description of the experimental proof of the Bell-Magendie law. His experiments were often carried in public and were in the presence of medical students and curious citizens. That particular experiment was performed out by severing the anterior and posterior roots of spinal nerves in different combinations of several dogs in a litter of puppies. Stimulation of the posterior roots caused pain, and stimulation of the anterior – movement. That was an experiment scrutinized for its cruelty by the Paris and London Humane societies.
Detailed description of the experiment was published in the same magazine for physiology and pathology.
; he carried out neuroanatomical and physiological experiments on rabbit
s for quite some time and without success
.
Then he decided to simplify his experiments, and thus analysis by reducing the object of the study to a less complex nervous system
– that of a frog
. He conducted his experiments assisted by a then only a student and later famous German physiologist and anatomist Theodor Schwann
. Because the frog spinal cord is relatively simpler and easier to remove, and the relationships between the nerve roots are more apparent, that shift simplified Müller's design and allowed for better reproducibility
of the experiment as well. His experiment was involving the innervations of the hind legs of the frog. One procedure was carried out by first severing posterior roots of the spinal nerve leading to the leg. It revealed that the leg became insensible but not paralyzed. Likewise, the second part of his experiment was cutting the anterior roots, and that paralyzed the limb without causing loss of sensation. The Müller's frog experiment became a physiology professor's favorite – it was an easily reproducible experiment, and it has been used widely since then in teaching neurophysiology.
approach. The dispute between the two happened in an era of a more secular approach to scientific discovery; positivism
had become popular in many sciences. This is at about the same time as the works and theories of Auguste Comte
were published.
On the other hand, Magendie was considering himself in his own words "a mere scavenger of science trying to do science by collecting bits and pieces of nature's truths"; he was not after the grand scheme but after the "inventory of the nuts and bolts of the system". The French were also proud with Magendie's many discoveries and the extension of human knowledge in the areas of pathology, physiology and pharmacology
and stood firmly behind his claim on the matter. Nevertheless, many Frenchmen (and most of our contemporaries) would have agreed with the English that the vivisections were not for the faint of heart. Until his death in 1842, Bell would write against the methods of Magendie and in his letters and books he would disapprove of the "protracted cruelty of the dissection experiments"
.
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
and neurophysiology
Neurophysiology
Neurophysiology is a part of physiology. Neurophysiology is the study of nervous system function...
, this is the finding that the anterior spinal nerve
Spinal nerve
The term spinal nerve generally refers to a mixed spinal nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body...
roots contain only motor fibers and posterior roots only sensory fibers and that nerve impulses are conducted in only one direction in each case. The nature and the physiology of the phenomena were described independently by the British
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
anatomical scientist Sir Charles Bell
Charles Bell
Sir Charles Bell was a Scottish surgeon, anatomist, neurologist and philosophical theologian.His three older brothers included John Bell , also a noted surgeon and writer; and the advocate George Joseph Bell .-Life:...
and the French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
physiologist François Magendie
François Magendie
François Magendie was a French physiologist, considered a pioneer of experimental physiology. He is known for describing the foramen of Magendie. There is also a Magendie sign, a downward and inward rotation of the eye due to a lesion in the cerebellum...
, later confirmed by the German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
physiologist Johannes Peter Müller
Johannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
.
History
The findings were described independently by two professors working in different medical paradigms: by Sir Charles Bell an anatomistAnatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
and Francois Magendie – a pathophysiology
Pathophysiology
Pathophysiology is the study of the changes of normal mechanical, physical, and biochemical functions, either caused by a disease, or resulting from an abnormal syndrome...
and physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
professor
. Their independent observations were 11 years apart. Another definitive experimental proof was given nine years after Magendie's experiments by Johannes Peter Müller during a vivisection
Vivisection
Vivisection is defined as surgery conducted for experimental purposes on a living organism, typically animals with a central nervous system, to view living internal structure...
of a frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
in 1831.
Bell's discovery
In 1811 in a self-sponsored and published pamphletCharles Bell referred to the motor functions of nerve fibers exiting the ventral root
Ventral root
In anatomy and neurology, the ventral root is the efferent motor root of a spinal nerve.At its distal end, the ventral root joins with the dorsal root to form a mixed spinal nerve....
s of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
but did not mention about the sensory functions of the dorsal root
Dorsal root
In anatomy and neurology, the dorsal root is the afferentsensory root of a spinal nerve.At the distal end of the dorsal root is the dorsal root ganglion, which contains the neuron cell bodies of the nerve fibres conveyed by the root.If the dorsal root of a spinal nerve were severed it would lead...
s. That was in part because his studies were dissection
Dissection
Dissection is usually the process of disassembling and observing something to determine its internal structure and as an aid to discerning the functions and relationships of its components....
ist and not vivisection
Vivisection
Vivisection is defined as surgery conducted for experimental purposes on a living organism, typically animals with a central nervous system, to view living internal structure...
ist. Pain is elicited and detected best in a conscious animal. A dead, or rendered unconscious, animal would not produce the desired effect when posterior horn fibers, responsible for sensation and transfer of noxious signals, are stimulated.
Bell's nephew, John Shaw
John Shaw
John Shaw was a Captain in the early years of the United States Navy.-Biography:He was born at Mountmellick, County Laois, Ireland, in 1773, and moved to the United States in 1790, where he settled in Philadelphia, and entered the merchant marine.Appointed Lieutenant in the United States Navy on 3...
travelled in 1812 to Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
where he presented Bell's system to the French anatomists. Reportedly Shaw staged a demonstration on the facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
s of a donkey
Donkey
The donkey or ass, Equus africanus asinus, is a domesticated member of the Equidae or horse family. The wild ancestor of the donkey is the African Wild Ass, E...
without the intended effect.
Magendie's puppies experiment
Eleven years later, Magendie announced in the magazine Journal de physiologie expérimentale et de pathologie his discovery that the motor neuron fibersMotor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
exit from the anterior root and the sensory neuron fibers
Sensory neuron
Sensory neurons are typically classified as the neurons responsible for converting external stimuli from the environment into internal stimuli. They are activated by sensory input , and send projections into the central nervous system that convey sensory information to the brain or spinal cord...
from the dorsal root: "(trans)section of the dorsal root abolishes sensation, (trans)section of ventral roots abolishes motor activity, and (trans)section of both roots abolishes both sensation and motor activity."
Magendie gave the first complete description of the experimental proof of the Bell-Magendie law. His experiments were often carried in public and were in the presence of medical students and curious citizens. That particular experiment was performed out by severing the anterior and posterior roots of spinal nerves in different combinations of several dogs in a litter of puppies. Stimulation of the posterior roots caused pain, and stimulation of the anterior – movement. That was an experiment scrutinized for its cruelty by the Paris and London Humane societies.
Detailed description of the experiment was published in the same magazine for physiology and pathology.
Müller's frog experiment
The third scientist, not credited in the name of the law, was the German physician and physiologist Johannes Peter MüllerJohannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
; he carried out neuroanatomical and physiological experiments on rabbit
Rabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
s for quite some time and without success
.
Then he decided to simplify his experiments, and thus analysis by reducing the object of the study to a less complex nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
– that of a frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
. He conducted his experiments assisted by a then only a student and later famous German physiologist and anatomist Theodor Schwann
Theodor Schwann
Theodor Schwann was a German physiologist. His many contributions to biology include the development of cell theory, the discovery of Schwann cells in the peripheral nervous system, the discovery and study of pepsin, the discovery of the organic nature of yeast, and the invention of the term...
. Because the frog spinal cord is relatively simpler and easier to remove, and the relationships between the nerve roots are more apparent, that shift simplified Müller's design and allowed for better reproducibility
Reproducibility
Reproducibility is the ability of an experiment or study to be accurately reproduced, or replicated, by someone else working independently...
of the experiment as well. His experiment was involving the innervations of the hind legs of the frog. One procedure was carried out by first severing posterior roots of the spinal nerve leading to the leg. It revealed that the leg became insensible but not paralyzed. Likewise, the second part of his experiment was cutting the anterior roots, and that paralyzed the limb without causing loss of sensation. The Müller's frog experiment became a physiology professor's favorite – it was an easily reproducible experiment, and it has been used widely since then in teaching neurophysiology.
The naming controversy
The dispute of the findings, and subsequently the naming of the discovery, started with the publication of Magendie's paper in the Journal de physiologie expérimentale et de pathologie. The conflict lasted until Bell's death in 1842. Some science historians have better resolved to name it after both physicians, giving Bell the honorary first mention, although others have claimed that these are essentially two overlapping discoveries. Because of the independent findings of boths scientist (Bell's claim over the motor function and Magendie's over the sensory function) and the exisitng conflict between England and France on the political arena of the 19th century (and prior to that), the debate on the Bell–Magendie law became a matter of national pride. The English medicine professors, especially Bell, and even English politicians rebuked the "crude methods" of the French vivisectionist. English medical staff and faculty were more tuned into seeking anatomical and structural explanations through disections – taking a sort of medical functionalistStructural functionalism
Structural functionalism is a broad perspective in sociology and anthropology which sets out to interpret society as a structure with interrelated parts. Functionalism addresses society as a whole in terms of the function of its constituent elements; namely norms, customs, traditions and institutions...
approach. The dispute between the two happened in an era of a more secular approach to scientific discovery; positivism
Positivism
Positivism is a a view of scientific methods and a philosophical approach, theory, or system based on the view that, in the social as well as natural sciences, sensory experiences and their logical and mathematical treatment are together the exclusive source of all worthwhile information....
had become popular in many sciences. This is at about the same time as the works and theories of Auguste Comte
Auguste Comte
Isidore Auguste Marie François Xavier Comte , better known as Auguste Comte , was a French philosopher, a founder of the discipline of sociology and of the doctrine of positivism...
were published.
On the other hand, Magendie was considering himself in his own words "a mere scavenger of science trying to do science by collecting bits and pieces of nature's truths"; he was not after the grand scheme but after the "inventory of the nuts and bolts of the system". The French were also proud with Magendie's many discoveries and the extension of human knowledge in the areas of pathology, physiology and pharmacology
Pharmacology
Pharmacology is the branch of medicine and biology concerned with the study of drug action. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function...
and stood firmly behind his claim on the matter. Nevertheless, many Frenchmen (and most of our contemporaries) would have agreed with the English that the vivisections were not for the faint of heart. Until his death in 1842, Bell would write against the methods of Magendie and in his letters and books he would disapprove of the "protracted cruelty of the dissection experiments"
.