Determining the functions of the spinal cord roots during the first quarter of the nineteenth century was one of the most significant achievements in physiology. The concept that the anterior (ventral) and posterior (dorsal) roots had different functions was first suggested by a young Scotsman, Alexander Walker, in 1808, first tested by experiment by another young Scot, Charles Bell, in 1811 and, unaware of Bell’s work, by a young Frenchman, François Magendie, in 1822. However, an at times acrimonious dispute soon arose as to who should get the credit for showing that the anterior roots had a motor function and the posterior roots a sensory function. This essay traces the debate which is to some extent still ongoing.
At the dawn of the nineteenth century the gross anatomy of the brain and spinal cord had been well – described. Andreas Vesalius (1514 – 1564) in De Humanis Corporis Fabrica (1555) included 12 drawings of the skull and its contents in the seventh section of his book, while 15 plates drawn by Christopher Wren (1632 – 1723) illustrated Thomas Willis’ (1621 – 1675) Cerebri Anatome: cui accessit Nervorum descriptio et usus of 1664.
However, as far as knowledge of the functions of the brain and nerves was concerned, the best Andrew Marshal (1742 – 1813) could offer at the beginning of the century was: “ The primary functions of the brain and nerves consists in their rendering us conscious of the existence and properties of surrounding objects, and while in this world, of the existence and properties of ourselves “ .
Things were about to be changed by two multi- talented young Scotsmen, Alexander Walker -- more of him later -- and Charles Bell.
Bell was born in Edinburgh on 12 November 1774, the fourth and youngest son of the Reverend William Bell (1704 – 1779) who died when Charles was five years old. He graduated from the medical faculty of Edinburgh University in 1798 and was soon afterwards appointed a surgeon and teacher of anatomy at the Royal Infirmary. In 1804 he moved to London when a squabble involving his brother John and other surgeons precluded him from practising at the Infirmary. In a dilapidated building near Leicester Square he set up a school of anatomy and worked there until October 1812 when he bought The Great Windmill Street School which had been established by William Hunter (1718 – 1783) in 1769.
Having noted the differences in the appearances of the cerebral hemispheres and the cerebellum Bell pondered on their various functions. Eventually he put pen to paper and wrote a 36 - page pamphlet in which he expressed his thoughts and reported on the experiments he had carried out to test them.
IDEA OF A NEW ANATOMY OF THE BRAIN; SUBMITTED FOR THE OBSERVATION OF HIS FRIENDS. BY CHARLES BELL, F.R.S.E.
The pamphlet was undated, but a subsequent enquiry to the printers Strahan and Preston of London revealed that 100 copies were printed towards the end of August 1811. Bell did not publish the pamphlet but circulated it amongst his family and acquaintances; he asked them for comments, but none responded.
Incredibly, this inauspicious - looking pamphlet has acquired the status of the Magna Carta of Neurology .
After a short introduction, in which he explains that he is not in search of the seat of the soul, four of the eight opening paragraphs can be edited to read:
“ The prevailing doctrine of the anatomical school is, that the whole brain is a common sensorium; that the extremities of the nerves are organized, so that each is fitted to receive a peculiar impression; …..
It is imagined that impressions, thus differing in kind, are carried along the nerves to the sensorium, and presented to the mind; and that the mind, by the same nerves which receive sensation, sends out the mandate of the will to the moving parts of the body. …..
In opposition to these opinions, I have to offer reasons for believing, that the cerebrum and cerebellum are different in function as in form; that the parts of the cerebrum have different functions; …..
That the nerves of sense, the nerves of motion, and the vital nerves(those responsible for respiration), are distinct through their whole course, though they seem sometimes united in one bundle; and that they depend for their attributes on the organs of the brain to which they are severally attached “.
After describing the visible differences between the divisions of the cerebrum and cerebellum, he continues:
“ From these facts ….. we are entitled to conclude ….. that the anterior and posterior grand divisions of the brain perform distinct offices.
In thinking of this subject, it is natural to expect that we should be able to put the matter to proof by experiment. But how is this to be accomplished, since any experiment direct upon the brain itself must be difficult, if not impossible ? ---- I took this view of the subject. The medulla spinalis has a central division, and also a distinction into anterior and posterior fasciculi, corresponding with the anterior and posterior portions of the brain. Further we can trace down the crura of the cerebrum into the anterior fasciculus of the spinal marrow, and the crura of the cerebellum into the posterior fasciculus. I thought that here I might have an opportunity of touching the cerebellum, as it were, through the posterior portion of the spinal marrow, and the cerebrum by the anterior portion. To this end I made experiments which, though they were not conclusive, encouraged me in the view I had taken “.
He then, on pages 21 and 22, described in more words the results of experiments which he had carried out and mentioned to his brother George Joseph Bell (1770 – 1843), Professor of Scots Law at Edinburgh University, in a letter written on 12 March 1810:
“ Experiment 1. I opened the spine and pricked and injured the posterior filaments of the nerves – no convulsive movements followed. I then touched the anterior division -- immediately the parts were convulsed.
Experiment 2. I now destroyed the posterior part of the spinal marrow by the point of a needle -- no convulsive movements followed. I injured the anterior part and the animal convulsed “.
From these observations he concluded that the ‘cerebrum and the cerebellum were parts distinct in function‘:
"The cerebrum I consider as the grand organ by which the mind is united to the body. Into it all the nerves from the external organs of the senses enter; and from it all the nerves which are the agents of the will pass out".
In view of the priority dispute that was to erupt a little more than a decade later, Bell nowhere in the pamphlet states that the posterior roots were sensory and the anterior roots motor in function. Indeed the following passage could be interpreted to imply that he thought the roots carried both motor and sensory nerves, but his writing is not as clear as one would have liked:
"The spinal nerves being double, and having their roots in the spinal marrow, of which a portion comes from the cerebrum and a portion from the cerebellum, they convey the attributes of both grand divisions of the brain to every part; and therefore the distribution of such nerve is simple, one nerve supplying its destined part ".
Bell was preoccupied with his conviction that the cerebrum and cerebellum had different functions. The cerebrum, he conceived, was concerned with motion and sensation - higher functions -- and the cerebellum with controlling the viscera and the maintenance of balance. This meant that the fibres to and from the cerebrum had to be located in the anterior columns of the spinal cord and those to and from the cerebellum in the posterior spinal columns. The experiments he did on the spinal cord roots were his attempts to test this hypothesis because the soft consistency of the brain and the lack of available laboratory techniques at his disposal precluded direct experimentation on the brain. Bell was not interested in the functions of the anterior and posterior spinal roots as such. In any case, he could not have tested for sensory responses because he was operating on stunned rabbits .
During the ensuing years Bell busied himself with ‘all the nerves which serve to combine the muscles employed in the act of breathing and speaking ‘. In The Transactions of the Royal Society of London for 1821 it was recorded that on 12 July that year Sir Humphry Davy, Bart. P. R. S. (1778 – 1829) ‘communicated’ to the Fellows a forty - seven page essay written by Charles Bell, Esq.: On the Nerves; giving an account of some experiments on their structure and functions, which lead to a new arrangement of the system. The nerves supplying the face are described in great detail and there is mention of the partial paralysis of one side of the face affecting young people ‘ which the physician knows is not formidable ‘. The communication included an astonishingly beautiful engraving of a human head drawn by Bell, who was a superb artist, showing the distribution of the trigeminal and facial nerves. No mention was made in this communication of the spinal cord or its roots .
Across the channel a young Frenchman, who was oblivious of Bell’s experiments, was about to report on what had happened when he fulfilled a long – held desire to cut the spinal cord roots of an animal.
Magendie, who was born on 15 October 1783 at Bordeaux where his father was surgeon, started his medical studies as a 15 – year old. He was a brilliant student and wanted to be a surgeon but the established surgeons discouraged him. This made him depressed and he considered suicide. After a period of rest and contemplation he decided to become a physician and experimental physiologist; and flourished.
Somebody had given him a litter of puppies. He could cut their as yet poorly - ossified vertebrae without damaging the cords (see note 1). On 22 July 1822, in his own Journal de Physiologic Experimentale  which he had launched in June 1821, he reported that
cutting the posterior lumbar-sacral roots caused loss of sensation in the leg, while cutting the anterior roots caused the leg to be lame, and, when he cut both the anterior and posterior roots, the leg was both lame and numb.
Magendie, who was fascinated by the properties of drugs, on 22 October 1822 reported on more experiments he had carried out:
“ The convulsions of the leg caused by strychnine applied to the cut end of a posterior root was as intense as if the root had not been cut, whereas there was no movement in the leg in which the anterior root had been cut ”.
He mentioned that in the interim he had had a visit from an English surgeon called John Shaw (1792 – 1827) who was a brother - in- law of Charles Bell:
“ He informs me M. Ch. Bell had made this section thirteen years before, and had ascertained that the section of the posterior roots did not prevent the movements from continuing “.
Magendie also commented on his reading of Idea, a copy of which had been sent to him:
“ M. Bell, led by his ingenious ideas regarding the nervous system, was very close to discovering the functions of the spinal roots ….. However, the fact that the anterior roots are motor while the posterior are specifically sensory seems to have escaped him. Because I established this fact in a positive manner, I make my claim “ .
It was left to Johannes Petrus Müller(1801 – 1858) of Bonn -- soon to move to Berlin where he would become a legend as a researcher and teacher  -- to clear up any uncertainty that might still have existed when in 1831 he reported:
“ If in the same frog the three posterior roots of the nerves going to the hinder extremity, be divided on the left side, and the three anterior roots on the right side, the left extremity will be deprived of sensation, the right of motion ” .
And so was born spinal cord localization:
“ Bell’s law, the Bell’sche Lehrsatz of J. Müller(1831), the Lex Belliana of G. Valentin (1839), the Bell’sche Lehre of J. W. Arnold (1844), and the Bell – Magendie Law of Sherrington(1900), is based on the discovery of one – way in the nerves ….. where the ‘ way in ‘ is represented by the dorsal or sensory root and the ‘way out ‘ by the ventral or motor root “ .
“ ….. after Harvey(De Motu Cordis, 1628)), (is) probably the most momentous single discovery in physiology ….. “ .
The ink had hardly dried on Magendie’s 1822 articles before Bell -- who had made no further efforts to define the functions of the spinal cord roots since the experiments he had reported in Idea -- teamed up with brothers – law John and, after John’s death on 19 July 1827, with Alexander(1804 – 1890) to counter Magendie’s claim to have been the first to demonstrate that the anterior spinal roots were motor and the posterior roots sensory in function. To add to Bell’s woes Londoner Herbert Mayo(1796 – 1852), a former pupil of his with whom he had worked on the anatomy and physiology of the Vth and VIIth cranial nerves, had said harsh things in August 1822 about what he perceived were his teacher ‘s mistakes.
Stunned by these developments Bell in 1824 was prompted to republish Idea with amendments “ ….. as if he had always known that the anterior root was motor and the dorsal root sensory “ . He also updated the 1821 communication to the Royal Society to be more in line with the findings of Mayo .
The continuing public debate as to who was first to make the discovery must have upset the hierarchy of The Royal College of Surgeons of England who had elected Bell professor of anatomy and surgery in 1824. In 1839 they decided to appoint a commission of enquiry to look into the matter. By this time Bell had moved up the social and academic ladder: he had been elected a Fellow of the Royal Society in 1826, appointed a Knight of the Royal Guelphic Order of Hanover in 1831, and invited to occupy the chair of surgery in Edinburgh in 1836.
The Royal College of Surgeons report of 1839 was a 172 page book Documents and dates of modern discoveries in the nervous system.  Seventeen documents published between 1751 and 1839 were reviewed, including those of Bell of 1811 and 1821, Magendie’s two articles of 1822 and a Müller article of 1823. Under the title on the front page of the book was printed:
“On every subject of the work, the Editor is desirous of avoiding all expression of his own opinion, when it can be supposed to have the slightest relation to any of the authors of these discoveries “.
However, the editor felt compelled to break his rule after scrutinising the documents of Bell:
“ But as new editions of it have been published ….. while retaining the original date of 1821, new matters have been introduced …... These surreptitious additions ….. by giving a false appearance of anticipation, unjustly tend to deprive Messrs. Magendie and Mayo of their unquestionable priority on some more important points “.
Despite this damning report the President of the Royal Society, Spencer Compton (1790 – 1851) the 2nd Marquis of Northampton, had this to say at the Anniversary Meeting of the society on 30 November 1842  :
“Among the deceased Fellows of the present year, we have to lament the loss of one of the most eminent surgeons and physiologists of our times -- one whose investigations have shed new light on that most intricate part of the human organization – the Nervous System.
He was the first to ascertain ….. that the spinal nerves arising from the lateral and anterior columns of the medulla spinalis convey the power of motion, while the nerves arising from the posterior strands communicate the faculty of sensation to the several parts of the body to which they are distributed.
In fact, the great advancement which has been made of late years in our knowledge of the nature and treatment of the diseases of the nervous system, is mainly attributable to the labours and discoveries of Sir Charles Bell.
In private life this eminent man was distinguished by the suavity and simplicity of his manners, by his elegant tastes, and domestic virtues”.
High praise indeed for Bell who had died on 28 April that year from a heart condition while travelling by train from Edinburgh to London.
The priority debate continued unabated with some of the pro – Bell/ anti – Magendie writers landing below the belt blows; by and large Magendie, who did not like being challenged, kept his cool.
In response to a comment made by Bell during a lecture to the College of Surgeons in 1828:
“ He (Magendie) may even, in short, have employed his fingers, those ‘pickers and stealers ‘, as Shakespeare calls them, without control of his head -- without intention or ideas of any kind -- with a perfect purity which belongs to entire ignorance “.
“Why must this scientist spoil his work and injure himself by not rendering to his rivals the justice due them ? Why must he cling to that barbarous patriotism which rejects everything that does not come from his own country ? Why does he persist in his pretensions to discoveries which he has not made ?” 
The next reviewer of the spinal cord priority contest was an American physiologist who in 1861 had spent a few months in Paris working with Claude Bernard (1813 - 1878) who had succeeded Magendie as full professor at the College de France in 1855, having worked with him since 1841. The reviewer was Austin Flint Jr. (1836 – 1915) who was on the staff of the Bellevue Hospital Medical College.
His review Historical Considerations concerning the properties of the Roots of the Spinal Nerves was published in October 1868 . He noted that:
“ In nearly every treatise on physiology published since 1822, and in almost all works on the nervous system subsequent of that date, the great discovery of the distinct seat of motion and sensation in the spinal nerves is ascribed to Sir Charles Bell. The name of Magendie is seldom mentioned in this connection, even in France; and his discoveries are supposed to relate chiefly to the seat of sensation and motion in the different columns of the spinal cord ”.
Flint compared the original and the reworked texts of Idea of 1811 and Philosophical Transactions of 1821. Of the 1844 version of the 1821 paper Flint wrote:
“ In the reprint of this paper, Bell has not hesitated to so modify his language as to make his remarks correspond with the facts discovered by Magendie in 1822, giving the reader the impression that he held these opinions as early as 1821 “.
The final sentence of his Conclusion was short, sharp and to the point:
“ From the experiments of Magendie dates all of our positive knowledge of the physiological properties of the two roots of the spinal nerves “.
Thereafter the debate continued with the odd salvo and review here and there until 1911, one hundred years after the printing of Idea, when there was a significant spat between two prominent United Kingdom medical men who had both graduated from Aberdeen University Medical School -- Englishman Augustus Waller (1856 – 1922), Fullerian Professor of Physiology in the University of London, in 1878, and Scotsman Arthur Keith (1866 – 1955), Hunterian Professor and Curator of the Hunterian Museum of the Royal College of Surgeons, ten years later.
In An Address on the position of Sir Charles Bell amongst anatomists delivered on 19 January 1911 Keith, after enumerating the turbulences the newly - wed 37 year old Bell endured when he wrote Idea said, under the heading ‘ What Bell Achieved’:
“ To most medical students Charles Bell is simply known as the man who found out that the anterior root of a spinal nerve is motor in function, the posterior root sensory “.
In Keith’s opinion:
“ On whatever standard one proceeds to judge, Charles Bell must be assigned a first place amongst the world’s anatomists. He did for the anatomy of the nervous system what Harvey did for the circulatory system -- brought order out of chaos “.
The address was published in The Lancet soon afterwards. (18) Waller almost immediately retorted by suggesting that Keith had not examined the original text, an accusation which annoyed Keith. In another letter Keith said he translated Bell’s use of ‘cerebral ‘ to mean motor and ‘cerebellar’ to mean sensory. The nit – picking argument continued until November 1912 when the editor called a halt to the correspondence. But by then Waller had been fired up and towards the end of The Lancet Correspondence he published a 29 – page article. He had painstakingly reviewed Bell’s publications on the spinal cord roots and the nerves to the face. The last sentence of his essay reads:
“ There is no escape from the conclusion that Bell’s claims as a discoverer was a carefully fabricated claim and that the discovery of the distinction between motor and sensory nerves belongs entirely to Magendie “. 
The dust would not settle on the dispute. Contributions by people in – the - know kept on appearing at irregular intervals.
Then in 1974 Futura Publishing Company of Mount Kisco, New York, produced a book that is unique -- there is none like it on the History of Medicine bookshelves. Written by Paul Frederic Cranefield (1925 - 2003) of The Rockefeller University, New York, the book of approximately 780 pages (there is no formal paging apart from the introductory pages) consists mainly of facsimile reproductions of nearly all (he missed out on two Danish articles of 1825  ) that had been written on The Bell – Magendie Law up to that point:
“ In compiling the present volume I have leaned towards including anything that seemed either important or interesting. This has made for a long book, but also for one that is sufficiently complete to enable the reader to satisfy himself about the issues and to rely on the primary sources rather than on my evaluation of those sources. For that reason I have not concealed my bias in favor of Magendie. I began this undertaking only mildly prejudiced in favor of Magendie; my present prejudice against Bell is the result of my reading his polemical articles and those of John and Alexander Shaw “.
The reason is to return to Alexander Walker(1779 – 1825) who in the first decade of the nineteenth century started the functions of the roots of the spinal cord debate.
Little is known of him.  Although he enrolled to study medicine at Edinburgh University there is no record that he completed the course. Anatomy was his interest and he continued his studies in London at St. Bartholomew’s Hospital. He had a gift for words and was soon lecturing and writing on anatomy, with an interest in the anatomy and function of the nervous system.
Walker was the author of the damning Royal College of Surgeons report of 1839, having in 1835 published a book the long title of which says what he thought of the preceding studies of Bell and Magendie: The nervous system, anatomical and physiological: in which the functions of the various parts of the brain are for the first time assigned; and in which is prefixed some account of the author’s earliest discoveries, of which the more recent doctrine of Bell, Magendie, etc. is shewn to be at once a plagiarism, an inversion, a blunder associated with useless experiments, which they have neither understood or explained.
Walker, who was against vivisection, had on theoretical grounds decided that the spinal roots had different functions. Cranefield’s assessment is:
“As matters stand, he was certainly the first person in the period under discussion to suggest that the roots had different functions, and he was certainly the first to suggest that the one root was sensory and the other motor “ .
The only problem was that Walker guessed wrong – he thought the anterior roots to be sensory and the posterior roots motor.
Why did Bell, when in 1822 he heard of Magendie’s work, decide to alter the texts of Idea and his 1821 communication to The Royal Society to bring them more in line with Magendie’s findings at the same time omitting to give them new dates of publication ?
A clue might be found in what two of Bell’s biographers had to say about his personality:
“Charles Bell was fond of analysing his feelings in all the vicissitudes of his temperament, alternatively enthusiastic and melancholy “ . (see note 2)
“Sometimes Charles Bell, confessing his love of renown, his ambition of becoming the first man in his profession, in credit as well as in talent, sought to reconcile this desire with a true social instinct “ . (see note 3)
“Bell’s personality and behavior were gradually changing from that of the shy young man who had come to London in 1804. He began to take any disagreements, criticism, or opposition to his views in a more openly personal way, and --- as he gained in professional stature -- any challenges to his professional beliefs and researches became acrimonious. ….. He believed in his own greatness, and he did not hesitate to say so in his letters to George “(his oldest brother) .
Bell, who had helped to treat the wounded of both sides after the Battle of Waterloo (15 June 1815), and did not like the French although he admired the stoicism of their wounded soldiers, was not going to beaten by a Frenchman in the race to be the first to describe the function of the spinal cord roots.
In addition he was still struggling to make himself heard in the London medical environment which at the time was regulated by Fellows of the Royal College of Surgeons of England and Licentiates of the Society of Apothecaries -- members of both institutions were termed ‘general practitioners ‘ -- while the physicians, mostly graduates of Cambridge and Oxford Universities, looked on . (There was no medical school in London until 1826 when the University of London was established. Bell was one of the founding professors and delivered the opening inaugural lecture on 1 October 1828) .
Through these subtle changes to the original texts of Idea and his 1821 presentation to the Royal Society, Bell planned to convince the scientific community that he knew all along that the anterior spinal roots had a motor function and the posterior roots a sensory function, and that the Vth cranial nerve was sensory and the VIIth nerve motor in function; he implied that he had earlier not expressed himself clearly enough.
Bell had to be the winner and once he had amended the texts -- something which he might have done when in a less - than - rational mood -- and published these, there was no turning back without running the risk of harming his professional reputation.
Luckily for him the level of criticism, which started as a murmur in 1825, became loud only after his death.
The Professors of Physiology of modern – day medical students should tell their students something of the lives and times of the three men who early in the nineteenth century had started the studies that proved that the anterior roots of the spinal cord have a motor function and the posterior roots a sensory function, one of the most respected of the fundamental principles in animal and human anatomy and physiology:
Alexander Walker(1779 - 1825): in 1808, and entirely on theoretical grounds, he postulated that the anterior and posterior spinal roots fulfilled different functions, but he guessed wrong when he attributed motor function to the posterior roots;
Charles Bell (1774 - 1842): during the first decade of the nineteenth century he did the first experiments in an attempt to find out which root was responsible for which function. He came to the conclusion the anterior roots had a motor function but, because he worked with stunned or dead rabbits, he could not for certain ascertain how the sensory impulses got from the periphery to the cerebrum – he thought they might also be relayed through the anterior roots; and
François Magendie(1783 - 1855): in 1822 he reported on experiments he carried out on live puppies which revealed that the anterior roots had a motor function and the posterior roots a sensory function.
The students will then realise that the process of acquiring scientific knowledge is not necessarily a straightforward process, but can be associated with the vagaries of human nature.
If the professors were then to start talking of "The Law of Walker, Bell and Magendie". they would give credit where credit is due and help to bring to an end a torrid priority dispute that has plagued the medical stage for nearly two hundred years.
- 1. Magendie was heavily criticised by his contemporaries for his extreme cruelty to laboratory animals. This conduct contributed to the Irish MP Richard Martin (1754 – 1834) forming The Society for the Prevention of Cruelty to Animals in 1822 and persuading the British Parliament to pass The Cruel Treatment of Cattle Act; Martin described Magendie as “ a disgrace to Society “ .
- 2. Idea was written after a protracted period of delirium, possibly related to his reaction to dealing with the casualties of the Battle of Corunna (16 January 1809); depression was his dominant mood.
- 3. It is not clear what he meant by the last part of the sentence.
I am a retired gastro-enterologist with no academic association and paid for the expenses incurred.
The article was recommended for publication by: Professor Michael Aminoff, Department of Neurology, University of California, San Francisco, U.S.A., and Emeritus Professor Robert Porter, Monash University, Melbourne, Australia. Thank you to them and Mary Bock for their help.
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