ARTICLE VI.

Sketch of a General Theory of the Intellectual Functions of Man and Animals, given in reply to Drs. Cross and Leach. By Alexander Walker.

(Concluded from p. 34.)

On the subject of the cerebellum, I have only to add, that all the observations which Drs. Gall and Spurzheim have adduced to prove that it is the organ of amativeness, are accountable from the circumstance that the degree of physical love seems to be more or less connected with the degree of voluntary power-the proper function of this organ: and hence it is that the man, the stallion, and the bull, having more voluntary power, have also more amativeness and a larger cerebellum than the eunuch, the gelding, and the ox. With this modification-considering the cerebellum not as the organ, but as a convenient sign, of amativeness, the general theory which I now deliver of the nervous system is in perfect harmony with the more particular doctrine of Gall and Spurzheim as to the cerebral organs.

My former brief paper being entitled, On the Use of the Cerebellum and Spinal Marrow, it was less to the structure of these parts (which I conceived to be sufficiently well known) than to their use that I referred. In particular, I meant to lay no claim to the first observation of the division of the spinal marrow, either on the ground of its having lateral fissures, asserted by Soemmerring, who, however, will no doubt now abandon his opinion, since Dr. Leach

has carefully examined the structure of the spinal mass of nerves,' or on a ground which is, I believe, peculiar to myself, that these columns being laterally separated by cineritious matter, that substance serves the purpose of insulating them from each other, and serves a similar purpose, and no other, throughout the brain. Even on this ground, which I believe to be the best one, however peculiar it may be, it was not my intention to claim the observation; but it was my intention to consider as my own, the observation that the anterior columns (in which end the anterior spinal nerves) terminate in the cerebrum, while the posterior columns (in which begin the posterior spinal nerves) commence in the cerebellum; as well as that the anterior may be termed the ascending columns and nerves, and the posterior the descending-that the former may be called those of sensation or impression, which, to be cognizable to the brain, must ascend from by far the greater part of the surface of the body; and that the posterior may be called those of volition or expression, which, to affect almost all the muscles, must descend from the head. And, to say the least of it, this is rendered highly probable by the circumstances that sensation and volition-an ascending and a descending motion cannot possibly take place in

the same fibrils of the same nerve; that consequently all nerves, having at once sensation and volition, divide into two series of fibrils on joining the spinal marrow, namely, an anterior series and a posterior one; that the anterior series is, in form and structure, totally different from the posterior; and that the spinal marrow, divided as it is by fissures and by cineritious matter, does really form four columns which are joined by these series, viz. the anterior columns, by the anterior fasciculi, and the posterior columns, by the posterior fasciculi.

In reply to my statement, that the anterior columns join the cerebrum, and the posterior the cerebellum, Dr. Leach says, "Gall and Spurzheim have shown that the brain and cerebellum cannot be considered as the continuation of the spinal marrow, any more than the spinal marrow can that of the brain and cerebellum.” This reply the Doctor no doubt thinks decisive; and as I have shown that he has rather too hastily, and without reason, called my anatomical and physiological statement inaccurate, I must now inquire into his. The argument, then, which he here adduces, from whatever source derived, is a bad one, because it proves a great deal too much, as the following observation will show.Various parts, then, of the body, have been generated separately in the uterus or ovaria, as hair, teeth, limbs, &c. Now, in the case of the lower part of the body or the lower extremity being generated alone or detached from the superior parts, the generated parts would contain vessels as well as nerves-namely, an aorta and vena cava, or a femoral artery and vein. But, from the Doctor's argument, it would follow that, because in this case the lower parts of these vessels were produced separately from the upper, therefore, in the natural state, these parts are not continuations of each other! and that the aorta and femoral artery are not descending, and the vena cava and femoral vein ascending! * Such, then, are the precise and accurate arguments employed by Dr. Leach to prove that the anterior columns and their nerves do not join the cerebrum, and the posterior the cerebellum.

In reply to my statement, that the anterior of the nervous fasciculi which join the spinal marrow are not nerves of sensation, nor the posterior nerves of volition, Dr. Leach, instead of proving my inaccuracy, places upon record a most astonishing specimen of his own!-Dr. Leach says, "The two roots of nerves of each half of the spinal marrow, namely, the anterior and posterior, go to different parts of the body:-the muscles and skin of the back receive their nerves from the posterior roots, whilst the muscles and skin of the abdomen receive theirs from the anterior roots, and yet the fore and back parts of the body have sensation and voluntary motion." Now certainly if this were but true, my doctrine would be not

*This argument is not limited to the separate production of one part of the body, as the trunk, or the lower extremity; but obviously applies to any part which may ever have been separately produced, and even to all degrees of mutilation.

merely inaccurate, but altogether false; for this would prove, that both roots were at once nerves of sensation and of volition: but, not being true, the case is certainly somewhat altered. Unluckily for Dr. Leach, it is his own statement which is inaccurate. In his careful examination of the structure of the spinal mass of nerves,' the Doctor has absolutely mistaken the branches for the roots of these nerves! It is from the branches that the nerves he alludes to go off; for, however lucky this may be for humanity, since it prevents our moving with only one half the body, and feeling only with the other, it is certainly unfortunate for the Doctor's argument that neither to skin nor muscles is the slightest twig given from the roots. These roots then combine, communicate, and even cross by twigs, in order to form a trunk; and, that the Doctor may not be put to the trouble of another "careful examination," if he will only cross the fingers of one of his hands between those of the other, he will have a tolerable conception of the trunk so formed, remembering, however, that only about half the fibrils of either root do so cross, while the other half, instead of crossing to the opposite branch, runs onward in the branch of the same side. A rather greater number of fibrils, indeed, pass from the posterior root to the anterior branch than from the anterior root to the posterior branch, because the anterior branch, being destined to supply a greater portion of the body, requires to be larger. I do not find this decussation described in any anatomical book, which I have at hand; but the slightest inspection will demonstrate it. The law of this decussation is maintained even in very inferior animals; for, in those which have no vertebræ and in which the spinal marrow is formed below the oesophagus by the union of the two crura of the cerebellum, though the two fasciculi generally remain distinct throughout the greater part of their length, yet they always unite at different spaces by knots whenever a nerve is given off! Thus each branch is composed from both roots: and it is only from the branches thus composed, and by no means from the roots, that the nerves the Doctor speaks of are distributed: hence it is not wonderful that they give both sensation and voluntary motion. These branches, however, the Doctor calls "the two roots of nerves of each half of the spinal marrow, namely, the anterior and posterior; and asserts, as is seen above, that these identical ROOTS of each half of the spinal marrow " go to different parts of the body!" Every anatomist and every anatomical work declares that from the roots no twig proceeds either to skin or muscles; and if it were not obvious that the Doctor had mistaken the branches for the roots, I should be apt to think that, in his careful examination of the structure of the spinal mass of nerves,' the Doctor had refuted the whole of them.

2

I have now to mention, that even some of those anatomists who

Thus, too, the Doctor after all allows that there are a sternal and dorsal half. of the spinal marrow.

succeeded Willis conjectured that there were cerebral and cerebellic nerves. They indeed only conjectured this; and they, moreover, erred by distinguishing them into vital and animal. The vital nerves, said they, are chiefly derived from the cerebellum, and the animal from the cerebrum. They have believed, says Haller, that several nerves have roots partly from the cerebellum. But Haller objects that the fifth pair arising, as he says, from the cerebellum, is appropriated both to sense and to motion ; "nor would," says he, "Nature have so solicitously blended both species of nervous fibres if their nature had been different," and if, he might have added, they had been destined to supply totally distinct parts of the body. He shows also, that some of those nerves which they believe to have some origin from the cerebellum, have nothing to do with vitality; and he adduces various other objections. Speaking of the possibility of fibrils of different kinds being in the same nerve, Haller also says, "Infinitum ad infinitessimum possis deponere, falli hominem, qui Dei consilia voluerit conjectura expiscari.' Even Haller, however, when speaking of the double series of roots of the spinal nerves, involuntarily allows some connection of that kind; for he says, 66 quarum anterior altera in eodem cum cerebralibus nervis ordine pergit, posterior medullæ propria est, et demum sub fine quarti ventriculi incipit.

In proof, however, that the sensitive and motive nerves are perfectly distinct, I can quote for Dr. Leach a much better authority than that of any old author: first, that of reason, which tells us, that as sensation cannot reach the cerebrum without an ascending motion-a motion towards the brain; as the consequent volition cannot affect the muscles without a descending motion-a motion from the brain; and as it is contrary to all analogy that there should be motion in opposite directions in the same tubes of neurilemafor these reasons, there must be a series of nerves appropriated to each: and, secondly, the authority of anatomy, which shows us that, though nerves supplying parts which are contiguous in position but different in nature often run in one common sheath, yet on arriving at the spinal marrow they split into two roots, as they are termed; that these roots are quite different in form, the anterior being more fibrous, and the posterior more simple and round; that the anterior roots join the anterior columns of the spinal marrow, and the posterior roots the posterior columns; that these columns actually do join the cerebrum and cerebellum respectively; and that even those cerebral nerves which are at once nerves of sensation and volition have two roots, one from the cerebrum, and another from the cerebellum. This may be most easily observed in the seventh pair or facial nerves, the origin of which has hitherto been mistaken by all anatomists. They directly penetrate the medulla oblongata from its lower to its upper surface; and, throughout this very considerable internal passage, each nerve consists of two perfectly distinct, silvery and glistening cords, of which one joins the cerebellum, and the other runs onward to the cerebrum. This may

easily be seen by any anatomist who chooses to look at the subject itself, instead of only making such a "careful examination Dr. Leach last instituted on " the spinal mass of nerves."

as

The views which I have now taken enable me to answer a most important question on this subject, which has twice been put by Soemmerring. After stating the opinion that the use of the ganglia is to place certain parts out of the power of the will, or to change voluntary into spontaneous motions, he asks why the spinal ganglia are formed only on the posterior roots-" Qua causa est," says he, "cur in radice posteriore tantum nervorum spinalium ganglia inveniuntur, minime autem in priore? And again, "Cur radix prior nervorum spinæ medullæ, adeo vicina, ganglia non immiscitur? The obvious answer to these two questions is, that the anterior roots, as stated above, have nothing to do with motion-are those of sensation alone; while the posterior, being those of motion, it is on them alone that ganglia can be necessary to impede the impulse of the will, or to change, in some of their fibrils, voluntary into involuntary motion.

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. Now as in this situation, ganglia impede voluntary motion, so in others do they impede sensation, and prevent the brain being disturbed by all the impressions on the viscera, which would have been incompatible with thought. Such, then, are the ganglia of the viscera, &c.; for wherever the anterior spinal branch communicates with the great sympathetic, there is a ganglion at the place of this union. Thus there are ganglia of sensation as well as ganglia of motion; and these ganglia are always as near as possible to the origins of their respective nerves :-in other words, as these sensitive or ascending nerves originate from the internal surfaces of the body, their ganglia, which prevent sensation reaching the sensorium commune and becoming perception, are placed nearer to their systemthe great sympathetic nerve, and the organs from which they arise; and as the motive or descending nerves originate from the cerebellum, their ganglia, which prevent volition reaching certain muscular parts, are placed nearer to their system the cerebellum, &c. That the ganglia are admirably adapted thus to impede sensation, as I have stated, and volition as conjectured by Johnstone, and confirmed by these remarks, is evident from the observation of Cuvier, that the ganglia of red-blooded animals do not differ much from nervous plexus; that even the simple ganglia, or those formed by a single nerve, are resolved by maceration into several filaments which anastomoze together; and that in the crustacea, insects, and worms, the ganglia are mere homogeneous enJargements of the medullary cord to which they belong. All of these circumstances are well adapted to impede the motion which takes place in them-a motion, however, which is only of this kind, that each globule communicates its impulse to a succeeding one; and, as the last of a series of globules must thus move the instant that the first is impelled, the extreme velocity of nervous action is thus conceivable. It does not follow, however, that all the