MODERN DISCOVERIES IN THE NERVOUS SYSTEM.

THE two volumes which treat of this subject—Mr. SHAW'S Nar.■1 retire of the Discoveries (f Sir CharleS'Bell;.and Dates and Doenbs mitts of Modern Discoreries in 'the Nerrons Systrin—relate to questions as important in a scientific as they are obscure in a popu- lar sense. In endeavouring to present the case, and the principal evidence necessary to determine it, succinctly to our readers, it will be difficult perhaps to avoid omitting points which are neces- sary to a full exposition of the subject, but totally impossible to avoid omitting what the parties interested may consider very im- portant evidence. Let it therefore be understood, that we are not about to exhaust the minutiae of the dispute, and that any one who feels sufficient interest in the subject to desire further investi- gation, must be at the trouble of investigating for himself. One of the greatest anatomical discoveries of modern times, is that which assigns different functions to nerves enveloped in the same sheath, but PROCEEDING FROM DIFFERENT ROOTS, and Con- joined after their origin. Various difficulties prevent an extensive practical application of this principle ; but a moment's reflection will show its importance. If in a nervous affection, tic douloureux for example, a nerve be cut after the conjunction of the roots, sensation and motion would both be destroyed ; but if it be pos- sible to operate upon the root of the nerve of sensation, the patient might be cured and the use of the part remain. So likewise there are many other cases, in which an action upon the roots of the nerves might be beneficial, either in a curative or palliative sense. It is needless to observe, that not only medical but mental science may receive great accessions from following up an inquiry which investigates feeling, volition, and almost thought, upon the same demonstrative principles as optics.

Unless it be held that the late experiments of Dr. MAttsam. HALL and Meetca throw a doubt upon the whole question, its present position may be stated thus. The brain consists of two main divisions,—the cerebrum, the chief portion of the brain, occu- pying the whole upper cavity of the skull; the cerebellum, or little brain, forming the postero-inferior part. Each of these communi-

cates with the spinal marrow by crura or roots, (though perhaps they might as well be called elongations or tails,) the cerebrum

being connected with the anterior fasciculus of the spinal mar- row, the cerebellum with the posterior. Each of these divisions gives out roots of nerves ; and if a spinal root of the anterior be cut, motion is destroyed—if the posterior, sensation. Hence we have An inference, that the cerebrum is the seat of motion, the cere- bellum of sensation : A fact, that the anterior spinal roots are destined to motion, the posterior to sensation. Who discovered this fact? is the point at issue. We proceed to notice the claimants chronologically ; and first of WALKER. 1808-9.

In these years, Mr. ALEXANDER WALKER published several works (,,,r priers. Their character acid object was physiological, but treated

distinctly of the nerves and intellectual organs. were distin-

guished by considerable ingenuity, but were sPecul::uve and hypotheti- cal, if not sometimes fanciful ; and, to ine best, they rested upon reasoning rather than ext2tIlments. Of late years, the author has Charged BELL and MAGENDIE with stealing his system, and "inverting," without understanding it. Though this accusation may be dis- missed, it is possible that Sir CHARLES BELL may have derived some hints from Mr. WALKERS speculations; and it is clear that WALKER was on the verge of a discovery. Though he had a not very explicable theory, that " motion " was the animating cause of the nervous system—though he pronounced a "division of nerves into those of motion and those of sensation i absurd' "—yet he had got a clear idea of two distinct nerves being contained in one sheath, which he held to consist of "nerves. of sen- sation and nerves of volition." The following passage contains the clearest exposition of this opinion-

" Now, as in some cases, sensation exists without volition, and as almost all nerves arise by distinct filaments, I am of opinion, that wherever a part, having both sensation and motion, is supplied from one nervous trunk, that trunk envelops both a nerve of sensation and one of volition."

He also all but forestalled the future discovery, in expounding his theory of a double action; but reversed the conclusion to which later experiments have led, attributing motion to the posterior, sensation to the anterior. It may be doubted, however, whether he understood the force of these expressions—" Several nerves of mere sensation join the anterior masses; hence they must be ascending : one nerve of mere locomotion proceeds from the posterior masses ; hence they must be the ascending." The following passages are also curious, if nothing more— "Thus, then, it is proved to us, that medullary action commences in the organs of sense ; passes, in a general manner, to the spinal marrow by the an- terior fasciculi of the spinal nerves, which are, therefore, nerves of sensation, and the connexions of which with the spinal marrow or brain must be termed their spinal or cerebral terminations." " From the cerebellum, it descends through the posterior columns of the spinal marrow, which arc, therefore, its descending columns ; and expands through the posterior fiisciculi of all the nerves, which are, therefore, the nerves of volition, and the connexions of which with the spinal marrow or brain must be termed their spinal or cerebellic origins."

BELL. 1811.

Previous to this date, Sir CHARLES (then Mr.) BELL appears to have put forward sonic new views of the nervous system, or the brain, in his lectures, which exposed him to misconception ; some of his friends asserting that he was " in search of the seat of the soul." In 1811, he privately printed an essay under the title of Idea of a New Anatomy of the Brain, to remove these " misconceptions," by stating what his views and his objects were. This tract, compressible into little more than twenty octavo pages, is a production of great ability, animated by a spirit of deep devotion. The rather takes a large and enlightened view of creation; he points out, wi0 distinctness, the differences between the two grand divisions of thel brain ; and he thence proceeds to infer that they are distinct in function. He emphatically laid it down as his opinion, " that the nerves, which we trace in the body, are not single nerves possessing various powers, but bundles of different nerves, whose filaments are united for the convenience of distribution, but which

are distinct in office as they are in origin from the brain." • This was speculation, based indeed On anatomical knowledge, and prompted by a philosophical intellect, but still speculation. The question was, how to ascertain the truth, since direct experiment could be made upon the brain. The plan adopted was one of great ingenuity; " I took this view of the subject. The medulla spinalis (spinal marrow) has a central division, and also a distinction into anterior and posterior faseiculit corresponding with the anterior and posterior portions of the brain. Further i

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. 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.

"I found that injury done to the anterior portion of the spinal marrow convulsed the animal more certainly than injury done to the posterior portion; but I found it difficult to make the experiment without injuring both portions. "Next, considering that the spinal nerves have a double root, and being of opinion that the properties of the nerves are derived from their connexions with the parts of the brain, I thought that I had an opportunity of putting may opinion to the test of experiment, and of proving at the same time that nerves of different endowments were in the same cord, and held together by the same sheath.

" On laying bare the roots of the spinal nerves, I found that I could cut across the posterior fuscieulus of 71erVCS, which took its origin from the posterior portion of the spinal marrow, without convulsing the muscles of the back; but that on touching the anterior :fasciculus with the point of a knife, the muscles of the back were immediately convulsed. Such were my reasons for concluding that the cerebrum and the cerebellum were parts distinct in function, and that every nerve possessing a double function obtained that by having a double root."

From these experiments, CHARLES BELL advanced to other facto, and deduced further opinions ; sometimes approaching rather closely to the notions of WALKER, sometimes following out the views we have already indicated, and sometimes entering into anatomical points con- nected with the nerves, especially of sensation. Into these points we do not propose to enter ; but we may say that lie distinctly assigned different functions to different nerves • of the brain ; asserting that " from the crura cerebri, or its prolongation in the anterior fascieuli of the spinal marrow, go off the nerves of motion ;" and considering (con- trary to the inference or conjecture from MAGENDIE'S experiments) "the cerebrum 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 agents of the will pass out."

[In 1815, Mr. WALKER put forth some further views and explanations, in reply to remarks upon his system by Doctors Cnoss and LEACH ; and CHARLES BELL published a paper on the Nerves, in the Philoso- phical Transactions. To go into them would only be uselessly swelling the case, as they have no direct bearing upon the issue. BELL, how- ever, in his paper, clearly marked as the result of an experiment, that some nerves convey sensation, whilst others do not.

JOHN SHAw. 1821-2.

The late Mr. JOHN SHAw was a pupil and assistant of Sir CHARLES :i: viii was to show the practical uses of BELL'S discoveries, and further to unfold oeneve his relative. 111 izepiemoer 182i, he hed a Manual of Anatomy, and in April 1822 a paper on Partial Paralysis. So far as they relate to the point before us, their object them. He reiterates his master's previous views respecting the double functions and double origin of the nerves : referring to their own ex- periments on the spinal nerves, he states, that "it was easily shown, that if only the posterior set was destroyed, the voluntary power over the muscles continued unimpaired; but the pain necessarily attendant upon the per- formance of the experiment, prevented us from judging of the degree of sensibility remaining in the part ; " and lie thus speaks of the results of experiments on nerves of the brain-- " It is not too much to suppose, that either of these origins may be affected while the other remains entire. To prove tlds by ocular demonstration will perhaps be impossible; and therefore the question will probably remain unde- cided. But we have already seen examples of the consequences of injury to a nerve that has a single root, viz. the portio dura; for if we cut it, there will be only one set of actions paralyzed ; while by dividing a nerve which has double origin, viz. the fifth, we shall destroy two powers, namely, voluntary motion and sensibility."

MAGENDIE. 1822.

In the August and September of this year, MAGENDIE published the results of his experiments upon "the functions of the roots of the spinal nerves." Having been several times foiled by the difficulty of the attempt, he at last succeeded on some puppies, first euttingithe pos- terior roots.

"I was ignorant what might be the result of this attempt; I reunited the wound by a suture, and then observed the animal. 1 at first thought the member corresponding to the cut nerves was entirely paralyzed : it was in- sensible to the strongest prickings and pressures, it seemed to me also incapable of moving ; but soon, to my great surprise, I saw it move in a manner very apparent, although sensibility was entirely extinct. A second and third ex- periment gave me exactly the same result : I began to think it probable that the posterior roots of the spinal nerves might have different functions from the anterior roots, and that they were more particularly destined fur sensation."

He next attempted the anterior roots, and with equal success.

"As in the preceding experiments, I made the section on one side only, in order to have a point of comparison. It may be conceived with what curi- osity I observed the effects of this section : they were not doubtful—the member was completely immovable and flaccid, at the same time preserving. an unequi- vocal sensibility. Finally, that nothing might be neglected, I cut theanterior and posterior roots at the same time : there ensued absolute loss both of sen- sibility and of motion."

MAYO. 1823.

Taking the statements as we find them in Mr. ALEXANDER SHAW'S Narrative, Mr. MAYO has no pretensions to a share in the merit of these discoveries. He had been a house pupil and sort of assistant to BELL; but in August 1822, he wrote simultaneously with MAGENDIE upon the Nerves, disregarding or canvassing the views of his master. In July 1823, he again wrote upon the subject, adopting the disco- veries of MAGENDIE, and representing himself to have been engaged in similar experiments at the same time, though his contemporary publication flatly contradicts his assertion. Since that period, he has sunk the date of his first paper, substituting that of the second, so as to snake it appear that he was a contemporaneous discoverer with MAGENDIE, whereas he was then writing in opposition to the principle on which the discoveries were based.

In offering an opinion upon the evidence we have adduced upon this subject, we think that the chief honour should be assigned to Sir CHARLES BELL. He first considered the brain under a new and rational point of view : if he is not entitled to the merit of first conceiving the separate functions of the nerves, he at least pursued the hint of WALKER, with the logic and the knowledge of a scien- tific philosopher ; he experimented, extensively, if not always con- clusively, upon the nervous system ; and by his lectures, &c. stimu- lated a general attention to the subject, pointing out the means of rational investigation. But we think MAGENDIE first fully esta- blished the true nature of the spinal roots, if truth it be. Of the two works which have occasioned this narrative, whilst they have supplied us with the means of making it, Mr. SHAW'S is strictly controversial. His object is to advocate the claims of Sir CHARLES BELL, and to denounce those of MAGENDIE and Mayo.

Though possessing the zeal, he is somewhat deficient in the art of

an advocate ; for he overlays his subject with unnecessary matter, frequently repeats his case, and consequently does not present it with the desirable distinctness. But he leaves nothing undone ; seizing his points with avidity, and tenaciously sticking to them. He has clearly shown that MacEsnxE was well acquainted with several of the foregoing papers on the nerves, for he republished them in his journal ; and that it is more than probable he knew of the paper on Partial Paralysis, (in which mention is made of the experiments on the spinal nerves,) for he suppressed its republica- tion. Our author also hunts Mr. MAYO through his various edi- tions, with dogged pertinacity. Dates and Documents is simply a collection of the papers that have been published on the subject, in the order of their respective dates. They arc printed verbatim from the original editions, any

subsequent changes made by the authors being noticed ; they are introduced by a preface, stating the views of the ancients upon

the nervous system ; and they are accompanied by occasional notes upon matters of fact, the editor avoiding, as much as possible, all expression of opinion,—though he seems to consider the question yet unsettled, and that, from the nature of nervous power, and the difficulties of experimenting upon living subjects, experiment cannot decide it. His leaning, if he has a leaning, seems in favour of ME. WALKER ; but. this is a conjecture of ours, not an opinion. The authors he reprints are WALKER, BELL, MAGENDIE, and of late date MARSHALL HALL and MULLER. Ile also refers to Some of the older anatomical writers. SHAW he omits, and only briefly notices

3Isro. The volume is essential to any one who wishes to inves- tigate the subject, or who is curious in medical lore.

We cannot help remarking, that the review of the evidence connected with this discovery, does not impress us with the highest notion of the candour of medical philosophers. We

see Sir CHARLES BELL tacitly countenancing for a long time the mistake or misstatement of SHAW and others, by which the appearance of his essay on the Brain was carried back from 1811 to 1809—the period of WALKER'S publications; and a paper pub- lished before MAGENDIE'S experiments, has been silently altered since. In the opening of his article, MAGEN WE speaks of his long wish to make experiments on the spinal nerves, as if it were an in- spiration suggested to him at a remote period ; though there seems little doubt that he took the hint from Suaw.* And Mayo ap- pears to have resorted to arts the reverse of candid, to bolster up a

reputation for discovery, to which he had little or no pretensions. So it is "grand anatomiste, grand voleur

* When the circumstance was brought before him, MAGENDIE, howAver made the encode explicitly and well, limiting his own claim to what lie WKS' entitled to.