THE

MEDICO-CHIRURGICAL

REVIEW.

OCTOBER 1847.

THE HUMAN BRAIN; ITS STRUCTURE, PHYSIOLOGY, AND DISEASES. With a Description of the Typical Forms of Brain in the Animal Kingdom. By Samuel Solly, F.R.S., Senior Assistant-Surgeon to St. Thomas's Hospital, and Lecturer on Clinical Surgery, &c. &c. Second Edition, with numerous Wood Engravings. 8vo. pp. 684. London: Longman, Brown, Green, and Longmans, 1847.

We had occasion, at no very distant period, to call the attention of our readers to the existing state of knowledge in reference to the Nervous System (see Med.-Chir. Review, July 1845). The several publications which were then noticed, valuable as they undoubtedly are, have by no means precluded the necessity for further and more varied cultivation of this deeply interesting branch of science; a consideration which causes us to hail with much satisfaction the re-appearance of a well-known and successful labourer in the field of neurological research. It is now some years since the first edition of Mr. Solly's work was published; and it is but just to this gentleman to state, that his treatise on the Brain was the first which, in this country, combined all the elements requisite for a scientific investigation; that is to say, in which comparative anatomy, embryology, experiment and pathology were brought to bear upon the anatomy and physiology of the human cerebrum. This enlightened mode of procedure is deserving of all commendation; and cannot fail, when generally applied, in stamping a philosophic character on Medical literature. In the present edition, the author has pursued the same course, and, by omitting some details of structure, in themselves of no great moment, he has been enabled without objectionally enlarging the work, to present the medical public with the most complete account of the anatomy, physiology, and pathology of the brain that has hitherto appeared. Mr. Solly has enriched the descriptive portion of the volume with a large number of wood-engravings, many of them the product of his own pencil; and which, being intercalated with the text, give an increased interest and clearness to the details they so admirably illustrate.

It is satisfactory to us to perceive that a writer so well qualified to pronounce an opinion as the author of this work, has fully recognised and NEW SERIES, NO. XII.—VI.

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ably supported those principles which, although they have been occasionally lost sight of or even directly opposed, we have ever regarded as the clue by which alone the complex organization and intricate actions of the nervous system can be successfully studied and interpreted. Two of the most fundamental of these principles are thus stated :

:

"The revelations of the microscope regarding the ultimate texture of these different kinds of neurine are most deeply interesting, and quite determine the correctness of the view advocated in the first edition of this work, of their relative function. This view of the subject is now almost universally admitted, but in the year 1836 it was by no means an established point in physiology. The view to which I refer is this: that the cineritious neurine is the source of power, and the medullary neurine merely the conductor of it. The importance of establishing this position will be best understood when we come to the dissection of the human brain and spinal cord, and endeavour to discover the office of their component parts. Until this point was established, (and even now it is not considered to be so by all,) the study of the anatomy of the brain was barren and fruitless." P. 2.

A third fact, equally essential, is the strict independence, structurally and functionally, of the primitive nervous fibrilla-"nerve-tubes never branch like blood-vessels and never inosculate with one another;" and, consequently, a "nerve-tube always performs one and the same office; it always conducts in the same direction, and the same kind of nervous power; not at one time carrying impressions which, on reaching the brain, become sensations, and at another time conveying orders to a muscle to contract." (P. 12.) The power of the primitive fibrillæ being thus limited, the varied actions of the nervous system necessitate the provision of distinct classes of conductors, which the author thus, correctly as we conceive, sets forth :

“We find tubular neurine performing various offices :

"1st. As a conductor of an impression from the surface of the body to the brain, a nerve of sensation.

"2ndly. As a conductor of an order to act, from the brain to the voluntary muscles-nerve of volition.

3rdly and 4thly. As a conductor of an impression from the surface of the body to the spinal cord, which is reflected thence down another set of conductors to the muscles whereby they are called into action, independently of volition; -the excito-motory nerves of Dr. M. Hall.

5thly. As a conducting medium between the centres of power-the commissures." P. 7.

Mr. Solly assumes, as the basis of all inquiries into the nervous centres of man, the facts revealed by comparative anatomy. In the Preface we find these judicious remarks: "The only philosophical method of simplifying and giving a character of general interest to the anatomy of the human brain, is by commencing with the structure and functions of a nervous system in the lowest and simplest forms of animal existence, rising by degrees to the highest, carefully observing each addition of parts, and the relationship borne by these to an addition of function. By pursuing this course we shall be rewarded by finding that the encephalon, this apparently most complicated organ in the human being, is but a gradual development from an extremely simple fundamental type on one uniform and harmonious plan, and that the seeming complexity of the cerebro-spinal

1847]

Comparative Anatomy of the Encephalon.

287

axis in man really arises from the great concentration, as opposed to the extreme diffusion of its component parts in the lower order of animals; for in no particular are the higher orders more strikingly distinguished from the lower than in the concentration of function within circumscribed spaces." (Preface, p. x.) In interpreting the evidence derivable from this source, the author applies as a realised and fertile principle this fact—that one of the most important functions of a nervous system, as regards the vital existence of an animal, is to receive impressions, and to re-act on such impressions, independent of the consciousness or the will of the individual: this fact will be found universal in its application." In other words, the author unreservedly adopts the views of Marshall Hall on the physiology of the nervous system; and those of Grainger, Carpenter, and Newport on its anatomy.

We must pass by, though reluctantly, the details connected with the invertebrate animals, and proceed briefly to notice the interesting facts illustrative of the conformation of the brain among the vertebrata. In order to seize upon the fundamental organs, in the midst of the intricacies of apparent confusion of the cerebral parts, the author assumes three leading facts:-1, that every nerve of sense, whether it be of the sense of smell, sight, hearing, taste, tact, or of simple sensation, has, at its central extremity, a collection of cineritious neurine, or a ganglion; 2, that there is an organ for directing and controlling the actions of locomotion, corresponding to the cerebellum; 3, that there are parts, analogous to the hemispheres of the human brain, which constitute the instrument of the mental operations. We have no doubt that, so far as the anatomy is concerned, this is the true principle in accordance with which the encephalon must be studied—that it is the only mode of escaping from that obscurity, in which, as Mr. Solly justly observes, writers on comparative anatomy have involved this deeply interesting subject. As it is quite clear that the brain of fishes must serve as the basis for the comparison of the higher vertebrata and man, it becomes a point of primary importance to fix upon the signification of the curious series of ganglia which are seen on exposing the cranial cavity in some of the simplest animals of this class. There is one point connected with this inquiry, which, if not truly determined, throws the whole subject into inextricable confusion-we refer to the just appreciation of the olfactory ganglia. These bodies, whether placed close to the hemispherical ganglia, as in the eel, or removed from them to a considerable distance, as in the whiting, constitute invariably the most anterior pair of the encephalic masses. To the author belongs the merit of having given the true homology of these ganglia more than ten years ago, when the most eminent authorities, among whom we may adduce Serres, had evidently no clear idea of their signification. Placed next in order behind the olfactory ganglia or lobes, are the two hemispherical ganglia, as Mr. Solly proposes to call the hemispheres; then follow the two optic ganglia; and, lastly, the cerebellum. There are several other subordinate masses, for an account of which we must refer our readers to the work before us, and to the Hunterian Lectures of Professor Owen. Thus, among fishes, are to be recognised the typical elements of the human brain, the vast distance between them being filled up by the

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multitudinous forms displayed in the ascending animal scale, and by the no less exact evidences of developmental anatomy.

We regret that our limits will not permit us to follow the author through his clear and comprehensive account of the successive perfectioning of the cerebral organization; and especially of the laws in obedience to which the convolutions are developed. The whole of this part of the work, illustrated as it is with a great number of admirably executed woodcuts, is deserving of careful perusal, and will, we feel assured, receive general commendation. Before quitting this subject of the comparative anatomy, it may, however, be desirable to extract the following passage, in which several errors are corrected respecting the existence of that interesting structure, the rete mirabile, a rich network of vessels into which the carotid artery divides after it has penetrated into the skull, and lies beneath the dura mater by the side of the sella turcica.

"Rapp found this plexus in the stag, roe, the fallow-deer, chamois, the goat, sheep, and calf, and oxen. He considers that the arrangement of the foramina in the base of the skull in the camel indicates its existence in this animal, but he has not had the opportunity of seeing the parts in a recent state. It exists also in swine, but it does not occur in other Mammalia besides the Ruminantia and swine. Cuvier's statement certainly differs from this: he says that this vascular arrangement appears to occur in most of the Carnivora, but is absent in the elephant and beaver. According to Carus it is present in most Mammalia, and Willis says it exists in the dog, the fox, cat, &c.; but this is a mistake, for it does not occur in the dog, fox, badger, weazel, otter, or hedgehog, or in the domestic cat. But it has been found by Mr. Quekett in the leopard. Neither is it found in man, the apes, horse, elephant, or the Rodentia.” P. 137.

It is curious that in that remarkable ruminant the Giraffe, notwithstanding it feeds on the tops of trees and with the head therefore elevated, there is a well-developed rete mirabile, a fact which has been lately ascertained in opposition to the commonly-received opinion, by Mr. Quekett; and which proves, what is shown by so many other instances, that unity of structure is a more predominating law in the animal kingdom, than that of final causes or design.

In the Section on the Spinal Cord, Mr. Solly expresses his conviction of the accuracy of Mr. Grainger's account of the origin of the nerves; and he has given a most interesting figure of a minute dissection, made with the assistance of that gentleman, in which the fibres of the anterior root are represented as becoming partly continuous with the longitudinal fibres of the spinal marrow, and partly as running into the gray matter of the cord and there terminating. These results correspond with those obtained by Dr. Budge, noticed already in this Journal (Med.-Chir. Rev., 1845, p. 14); and, as both examinations appear to have been made with much care by the aid of the microscope, they may be received as correct.

The author has given a most minute and detailed account of the composition of the medulla oblongata; of the signification of the various nuclei of gray matter there observed; and especially of the distribution and physiological endowments of the several fasciculi or strands of white fibres connected with this vital segment of the nervous centres. Although gome of our readers may suppose that these anatomical intricacies concern rather the student than the practitioner, they will, on well considering