Werner to have subsided, and to have formed separate basins or seas. The subsequent deposits must have varied according to local circumstances. Therefore some variety in the succession of floetz rocks rather confirms than invalidates the Wernerian theory of the earth. I have the honour to be, Sir, College Green, Bristol, With great respect, 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.* In the 26th number of your Annals of Philosophy, was announced a discovery of the use of the cerebellum and spinal marrow by Dr. Cross-in the 27th number, Dr. Leach stated that the same facts, or facts that lead to similar conclusions, were published in Lettres de Hufeland à Portal, 1807, and Anatomie du Systême Nerveux, &c. par Gall et Spurzheim;-in the 28th number, I, conceiving that Dr. Leach meant to ascribe these discoveries to Gall and Spurzheim, denied that they were contained in the work referred to; +-and in the 29th number, Dr. Leach says, "Permit me, Sir, to assure you that the letter from Hufeland to Portal contains precisely the same opinion respecting the use of the cerebellum as that given by Mr. Alexander Walker and Dr. Cross; but he there adds, that he had quoted Gall and Spurzheim's work only as stating these opinions to be erroneous; and, while he asserts that my anatomical and physiological statements are" inaccurate, suppositious, and at variance with nature," he gives the results of his own recent examinations"-the conclusions which he draws after having "carefully examined the structure of the spinal mass of nerves." § 66 * Though this communication is rather too long for the Annals of Philosophy, we have given it a place, that every one of the Gentlemen concerned in this dispute may be upon a footing; but as the object of the Annals of Philosophy is not controversy, the Editor trusts that they will see the propriety of letting this subject rest where it is.-T. Certainly when a Gentleman has said "that facts which lead to similar conclusions were published" in a particular work, meaning thereby to give them priority over another statement, it is most natural to suppose that such was the original source of these facts; and, at all events, the conclusion is unavoidable hat they are there considered as facts-the term which Dr. Leach employs. Annals of Philosophy, vol. v. p. 346, Ibid. p. 345. Now, Sir, however unimportant it may seem to Dr. Leach to investigate the origin of these statements, it seems otherwise to me, who imagine myself to have rather a deeper interest in them; and (though, in reply to this Gentleman, I shall not imitate him in the littleness of perpetually repeating his list of Christian names, as he has done my one; nor, ignorant though I am of him, shall I, like Dr. Cross, designate him as one Dr. Leach; for these are tendencies to personality, which is the bane of rational discussion ;) yet I shall blend the question of the discovery of these facts with that of their absolute truth. The question of the discovery of the circulation of the blood has not been deemed unimportant: I cannot reckon that which regards the circulation of nervous action less so; and into that question the use of the cerebellum enters. This, Dr. Leach will perhaps say is a comparison of very little men with great ones: be it so; but it is not a comparison of very little things with great ones; and to things alone do I wish to attend. No one will venture to say, that the general functions of the brain and cerebellum are less important than that of the heart. With regard, then, Sir, to the cerebellum, as Dr. Leach, though he begs to be "permitted to assure you that Hufeland thinks it the organ of volition," has not quoted that writer's expressions, or, what is of more importance his reasons for such a conclusion, I cannot comment on them. If, however, I may judge of the accuracy of this ascription to Hufeland, by the additional assertion which Dr. Leach now makes as to Willis also having thought so, the conclusion will be most unfavourable to the Doctor's accuracy. Dr. Leach, then, adds that "Willis considered the cerebellum as the source of voluntary power." Now, Sir, it is an absolute fact, that Willis asserts the very opposite of this: he says it is the organ of involuntary power. "The office of the cerebel," says he, seems to be for the animal spirits to supply some nerves, by which involuntary actions, which are made after a constant manner unknown to us, or whether we will or no, are performed."* And now, Sir, I hope you will permit me also to assure you, that I am not a little surprised that any Gentleman, after accusing another of inaccuracy, and referring with such confidence to his own "recent examinations," should have made so untrue a statement, in order to ascribe to an old author new observations. After this, I should be glad, indeed, to see Hufeland's statement, and his reasons for the conclusion alluded to; and, should that writer advance any proofs that the cerebellum is the organ of volition, or rather of those impulses which cause all muscular action, I shall of course readily resign to him the honour or disgrace of the opinion, and shall only regret that my reading has not been as extensive and as accurate as that of Dr. Leach. 66 I am willing, however, to grant something in favour of Willis : On the Brain, chap. xv. he was right in assigning to the cerebellum the involuntary motions; but erred in excluding the voluntary ones; for the cerebellum is the source of all motion, voluntary and involuntary, as I shall show in the sequel while it is the source of every impulse on the muscular system, voluntarity is changed into involuntarity only by ganglia on the cerebellic nerves. I must, however, remark, that even if Willis had stated that which is accurately true, and grounded his statements, as he has done, only on conjecture, or on proofs which do not deserve the name, I should not have thought of yielding to him the merit of observing this truth; for even then he would equally have proved that "the dura mater administers heat for the distillation of the spirits," "that the pia mater does by chemical artifice instil the animal spirits into the brain and cerebel," and innumerable other absurdities-all of which, as well as this one, he supports by ridiculous conjecture, and not by argument. Even truth, however, if struck out only by wild conjecture, and unsupported by proof, would not constitute discovery: the mental effort of rational conjecture, and the personal one of " careful examination" would still remain to be performed by some one who, if successful, would certainly deserve the honour as well as the labour. And now, Sir, I can furnish Dr. Leach with a quotation from the great work of Baron Haller-a more recent and a better writer than Willis, which will be just as much to his purpose as his own "accurate reference to Willis; but which I nevertheless deem it necessary to state, in order that the history of this important question may be completely before the reader. "Convulsiones artuum," says he, "constanter vidimus in animalibus supervenisse, quorum cerebellum vulneraveramus.-Et de convulsionibus dictum est, quæ sunt musculorum voluntariorum. Ex cerebello etiam, si ullus, quintus sensui destinatus et voluntario motui nervus prodit. Quare collectis omnibus, videtur cerebellum et a cerebro hactenus parum differe, et graves in utrovis læsiones mortem inferre, leviores in utroque tolerari. Deinde cerebrum ad vitalia organa et sentientem vim et moventem mittere, et ad partes mentis arbitrio subjectas cerebellum." Here, then, it appears that Haller, after proceeding upon an "it is said " as to the convulsion of the voluntary muscles; observing that the fifth pair coming from the cerebellum is, however, destined both to sense and motion; and thinking that, upon the whole, the cerebellum in so far differs little from the cerebrum, -at last concludes that the cerebrum seems to send both feeling and moving power to the vital organs; while the cerebellum sends both feeling and moving power to the parts which are subject to the will. Now, from this, I differ by asserting, that the cerebrum sends. neither sensation nor motion to any part, but merely receives sensation from the organs of sense; while the cerebellum has not only nothing to do with sensation, as Haller erroneously asserts, but sends motion both to the voluntary and to the involuntary partsor, in other words, both to the mechanical or locomotive, and to the vital or nutritive system, which Haller inaccurately excludes from its influence. The motions of the vital, are, however, not less important than those of the locomotive, system. The term volition, however, may be still applied to the function of this organ, whether voluntary or involuntary action be its result, because the impulse of the cerebellum on which they both depend is one and the same, and the involuntarity is a modification of that impulse or of its effects produced only by ganglia on 'certain fibrils of the cerebellic nerves. This extended meaning of the word volition is perfectly analogous to that of the term sensation; for though sensation does not exist separately, except in those animals which have no sensorium commune,-though, in man, it is inseparable from perception, yet still is the simple term sensation employed. An improved nomenclature, however, or an extension of the very admirable one of Dr. Barclay, would perhaps give us new terms in both cases. 66 I have now said, in opposition to the statement of Haller, that the cerebrum sends neither sensation nor motion to any part external to the encephalic cavity; and, as Dr. Leach says, I have" neglected to take any notice of the cerebrum," and seems to demand what use I assign to it, I may assure him" that there still remain very important uses for it to serve; and as the Doctor, not having submitted them to any "recent examination," is perhaps less familiar with these particular functions, I may hint to him, that they areobservation, reflection, and judgment. I shall now, Sir, state some of my reasons for asserting, that the organs of sense being those of sensation, and the cerebrum that of mental operation, the cerebellum is the organ of volition, or rather of all the motions of animals, voluntary and involuntary. 1. There are three distinct intellectual organs or classes of intellectual organs, namely, the organs of sense, the cerebrum, and the cerebellum.-That the cerebellum, though separated from the cerebrum only by membranes in man, is not on that account less distinct from it than are the organs of sense separated by bony plates, is rendered evident by the consideration, that membranes form, in the one case, as effectual a separation as bony plates do in the other; that many animals have a bony tentorium between the cerebrum and cerebellum, as they have bony plates between the cerebrum and face; and that others (birds) have membranes between the cerebrum and face, as they have a membranous tentorium between the cerebrum and cerebellum. 2. There are three distinct intellectual functions or classes of intellectual functions, namely, sensation, mental operation, † and volition. 3. Of the organs, those of the senses are the first, the cerebrum * Viz. most species of the cat and bear kind, the martin (mustela martes), the coaita (cercopithecus paniscus), and others. + Including observation, reflection, and judgment, and the subordinate faculties analyzed by Gall and Spurzheim, intermediate, and the cerebellum the last.-For, although the face, containing the organs of sense, and the cerebellum, are, in different animals, very differently placed with regard to the cerebrum, yet there is a peculiar relation between the situation of one of these and that of the other with regard to it. In other words, although the face is sometimes in one situation and sometimes in another with relation to the cerebrum, yet to each given variation of its situation with regard to that body there is a corresponding and uniformly accompanying variation in the situation of the cerebellum. Thus as, in man, the face is placed below the anterior part of the cerebrum, so is the cerebellum placed below its posterior part; and precisely as, in the inferior animals, the face advances, precisely so does the cerebellum recede, till, in those animals in which the face is placed exactly before the cerebrum, the cerebellum is placed exactly behind it.* : 4. Of the functions, sensation is the first, mental operation intermediate, and volition the last.-That sensation precedes and excites, if it do not generate, mental operation, few will deny that mental operation, however rapid or evanescent, precedes and excites volition, or that the motive to an action must precede the action, none will refuse and that, of any one series of intellectual action, volition is the last stage, all must admit. 5. As, then, the cerebellum is the last of the intellectual organs, and volition the last of the intellectual functions, and as, at the same time, there is no organ without function, or function without organ, it follows, that the cerebellum must be the organ of volition. 6. In perfect conformity with this truth, the inferior animals, however defective in intellect, possess motion; and, in almost all of them which have any visible nervous system, a cerebellum, the organ of that motion, exists.-This leads me to an observation which seems to me to possess considerable interest and beauty. As we descend among animals, one of the three portions of the nervous system and one of its three general functions gradually disappear. Now it is not the first and the last portions of the nervous system— it is not the organs of sense and the cerebellum, neither is it their respective functions, sensation and volition, which are thus lost. It is the cerebrum and mental operation which are. This organ is, among men, most conspicuous in the Caucasian race; and we accordingly find that that race alone has cultivated the sciences. It is less even in the Mongal and Ethiop, who have ever disregarded them. It gradually disappears and ultimately evanishes as we descend among quadrupeds, birds, reptiles, fishes, &c. and with it gradually disappear and ultimately evanish the powers of thought. But organs of sense and a cerebellum,-sensation and volition, yet remain to characterize myriads of animals below these. The cerebellic cavity, moreover, seems uniformly to commence on the inside of the base of the cranium exactly opposite to the place where the face, or the lower jaw, terminates on the outside. |