why this riv. brings down a volume of water, which raises | ternal covering termed dura mater, from its being of a it far above the Ganges and Irawaddy, and claims for it the firmer texture than the other two membranes, encloses the first place among the rivers of S. Asia. (Rennell; Francis brain with all its appendages, and lines the whole internal Hamilton; Klaproth's Mémoires; Nefville and Wilcox in surface of the bones of the cranium. It is of a fibrous texAsiatic Researches; Ritter, Asien; Maps of Klaproth, Ber- ture, the component fibres interlacing each other in every ghaus, and Wilcox.) possible direction, and forming by their firmness and density the thickest and strongest membrane of the whole body. By its external surface the dura mater adheres every where to the inner surface of the cranium, just as the periosteum adheres to other bones. When torn from the cranium this surface appears somewhat rough and irregularly spotted with bloody points, which are the lacerated orifices of vessels that pass between the membrane and the surrounding bones. These vessels are much more numerous in the young than in the adult, and are most abundant at the sutures or junctions of the bones that compose the skull. The inner surface of the dura mater, which is shining and smooth, is lubricated and kept in a state of moisture by a fluid secreted by its own vessels. This membrane performs a twofold office; it supplies the place of the periosteum to the inner surface of the bones of the cranium, sustaining their nutrient vessels; and it serves as a defence to the brain, and a support to the different masses into which it is divided. BRAHMEGUPTA. [VIGA GANITA.] BRAIDWOOD, THOMAS, is known as one of the earliest teachers of the deaf and dumb in this island. He began this useful career at Edinburgh in 1760. No authentic record of the methods which he pursued has been made known, unless a work published by the late Dr. Watson, formerly the head master of the London Institution for the Deaf and Dumb, may be so considered. Dr. Watson, as an assistant to Mr. Braidwood, acquired his mode of tuition, and says, speaking of Braidwood, His method was founded upon the same principles; and his indefatigable industry and great success would claim from me respectful notice, even if I could forget the ties of blood and of friendship (Instruction of the Deaf and Dumb, Introduction, p. xxiii. London, 1809). A work entitled Vox Oculis Subjecta, published at London in 1783, the production of an American gentleman, whose son was educated by Braidwood, professes to give a particular account of the academy of Messrs. Braidwood, of Edinburgh,' but it throws no light upon the system of instruction pursued by those gentlemen. It is chiefly valuable for its copious extracts from the writings of Bulwer, Holder, Amman, Wallis, and Lord Monboddo, who had all considered the subject of speech with philosophical attention, and in relation to those persons who are born deaf, or who become so at an early age, and who consequently labour under the deprivation of speech. There was doubtless much merit in the mechanical methods used by Braidwood and his son to produce in their pupils an artificial articulation, and in the persevering application of principles which had been previously ascertained. Braidwood succeeded in attracting the notice of many eminent persons. He is spoken of with praise by Arnot (Hist. of Edinburgh), Dr. Johnson (Tour to the Hebrides), Lord Monboddo (Origin and Progress of Language), Pennant (Tour through Scotland), and John Herries (Elements of Speech). In addition to these, Lord Morton, president of the Royal Society, Lord Hailes, Dr. Robertson, Sir John Pringle, Dr. Franklin, Dr. Hunter, and others attended the public examinations of his pupils, and attested their progress. After having resided some years at Edinburgh, Braidwood removed his establishment to Hackney, near London, where he continued to instruct the deaf and dumb, and to relieve impediments in the speech, till his death in 1806. BRAIN, a soft and pulpy organ, which in man occupies the cavity of the cranium, and forms one of the central masses of the nervous system [NERVOUS SYSTEM]. In man and all the higher animals the nervous system consists of four distinct parts--the white threads called nerves; knots or masses of nervous matter situated along the course of the nerves called ganglions; a long cord of nervous matter filling the cavity of the vertebral or spinal column, called the spinal cord; and a large mass of nervous matter now generally considered as a continuation and expansion of the spinal cord, called the brain. The spinal cord and brain constitute the two central masses of the nervous system, that is, the immediate seat of the functions peculiar to this system. The general mass of nervous matter designated under the common term brain, together with its membranes, vessels, and nerves, completely fills the cavity of the skull. This mass is divided into three parts, the cerebrum or brain proper, which occupies the whole of the superior part of the cavity of the cranium; the cerebellum, much smaller than the cerebrum, whence its name, little brain, which occupies the lower and back part of the cavity of the cranium; and the medulla oblongata, by much the smallest portion of the mass, situated at the basis of the cavity, beneath the cerebrum and cerebellum. The medulla oblongata passes out of the cavity of the cranium into that of the vertebral canal by the foramen magnum of the occipital bone, being continuous with and forming the commencement of the spinal cord. This general nervous mass is closely enveloped in three distinct membranous coverings, two of which have been called matres, from the fanciful notion that they give rise to all the other membranes of the body. The ex The dura mater gives off several elongations or productions called processes, which descend between certain portions of the brain; the most remarkable of which is termed the superior longitudinal process, which extends from the fore to the back part of the skull, between the lateral halves of the cerebrum. Narrow in front, it becomes gradually broader as it passes backwards, bearing, as has been conceived, some resemblance in shape to a sickle or scythe, whence the common name of it, falx cerebri. Where the falx cerebri terminates behind, there proceeds a large lateral expansion of the same membrane, extending across the back part of the skull beneath the posterior parts of the cerebrum, and forming a complete floor or vault over the cerebellum. This membranous expansion is called tentorium, the obvious use of which is to prevent the cerebrum from pressing upon the cerebellum; while from the middle of the tentorium proceeds another membranous expansion, which descends between the lobes of the cerebellum and terminates insensibly at the edge of the foramen magnum, performing for the cerebellum the same office as the falx performs for the cerebrum: hence it is called falx cerebelli. Moreover, the component fibres of the dura mater, in certain parts of its course, separate into layers, which are so disposed as to leave spaces between them, for the most part of a triangular form. These triangular spaces, which are commonly termed sinuses, are lined by a smooth membrane perfectly analogous to that which lines the veins in the other parts of the body, and these sinuses perform the office of veins, returning the blood from all the parts of the brain to the neck. Nothing analogous to this structure occurs in any other part of the venous system. In almost every other part of the body the pressure of surrounding parts is a most important aid to these vessels in enabling them to carry on the circulation of the blood; but in the brain, the venous tubes are guarded from pressure, the dense dura mater being for this purpose stretched so tensely over them that the weight of the surrounding parts is completely taken off them. One of the conditions essential to the performance of the functions of the brain is, that it be free from pressure. The brain is a soft substance, enclosed in a hard unyielding ease. A preternatural accumulation of blood in its vessels would produce pressure upon its substance, because that substance cannot expand with any additional quantity of fluid that may be poured into it; consequently, such additional quantity of fluid would inevitably occasion a disturbance of function, if not organie injury. The smooth surface of the brain which is exposed on the reflection of the dura mater, is formed by its second investing membrane, which is named the tunica arachnoidea, from the extreme tenderness and delicacy of its tissue, which give it a resemblance to a spider's web. This thin colourless and transparent membrane is spread uniformly over the surface of the brain, covering all the eminences termed convolutions (fig. 1. 2, 2), but not insinuating itself between any of the depressions between the convolutiona (fig. 1v. 7). On account of its extreme tenuity and its close adhesion to the membrane beneath it, it cannot be easily separated from the latter; but there are situations at the basis where the arachnoid membrane, as it passes between opposite parts of the brain, can be seen distinct from the subjacent tunic. The third investing membrane, the pia mater, derives its name, like the former, from the tenderness and delicacy of its tissue; but unlike the tunica arachnoidea, in which not a single blood vessel has hitherto been discovered, the pia mater is exceedingly vascular. The blood vessels with which every part of this delicate membrane is covered are the nutrient arteries of the brain; before they penetrate the brain these vessels divide, subdivide, and ramify to an extreme degree of minuteness upon the external surface of this membrane, so that the blood does not enter the tender cerebral substance with too great force. When a portion of the pia mater is gently raised from the brain, these blood vessels appear as exceedingly fine delicate threads, which on account of the elasticity with which they are endowed are capable of elongation as they are drawn out of the cerebral substance. As the pia mater contains and supports the nutrient vessels of the brain, this membrane is not only spread as a general envelop over its entire surface, but it penetrates between all its convolutions and lines every cavity which is formed in it. It has been stated that the large portion of the cerebral mass, termed the cerebrum, occupies the whole of the upper part of the cavity of the cranium. The cerebrum is divided FIG. I. [Upper surface of the brain.] 1, cut edge of the bones of the cranium; 2, superior convex surface of the two hemispheres of the cerebrum with their convolutions; 3, separation between the two hemispheres of the cerebrum occupied by the falx cerebri, into two equal lateral halves termed hemispheres (fig. 1. 2), which have an ovoid figure somewhat resembling an egg cut longitudinally into two equal parts. The hemispheres are separated from each other by the membrane already described, the falx cerebri (fig. 1. 3); and their inner sides, in apposition with the falx, are flattened, while their upper and outer surfaces are convex, being accurately adapted to the concavity formed by the inner surface of the bones of the cranium. Each hemisphere is subdivided into an anterior, a middle, and a posterior lobe, but it is only on the under surface of the brain that these lobes are accurately defined (fig. 11. 1, 2, 3). The anterior and middle lobes are separated from each other by a deep fissure, named the fissura sylvia (fig. 11. 4), which extends obliquely backwards from the basis to a considerable depth between the convolutions; but the middle is distinguished from the posterior lobe, not by a fissure but by a superficial excavation on the under surface of the posterior lobe (fig. 11. 5). The anterior lobes rest upon the orbitar plates of the frontal bone; the middle lobes are lodged in the temporal fosse formed by the sphenoid and temporal bones, while the posterior lobes are supported upon the tentorium. FIG. II. [Base of the brain.] 1, anterior lobes of the cerebrum; 2, middle lobes of the cerebrum; 3, posterior lobes of the cerebrum; 4, fissure separating the anterior from the middle lobes, named the fissura sylvii; 5, situation of the supe ficial excavation forming the boundary between the middle and the posterior lubes; 6. the two hemispheres of the cerebellum composed of flattened lamina or layers; 7, the medulla oblongata, which in this position of the brain rests upon and covers the vermiform process; 8, corpora pyramidalia; 9, corpora olivaria; 10. tuber annulare, or pons varolii; 11, decussation of the corpora pyramidalia; a, b, c, d, cerebral nerves. The whole of the external convex surface of the hemispheres is divided into numerous eminences termed convolutions, which run in different directions, and are of different sizes and lengths, in different parts of the hemisphere (fig. 1. 2). The depressions or fissures between the convolutions termed clefts, or sulci, generally penetrate the consistence of the brain to the depth of about an inch or an inch and a half (fig. 1v. 7). The greater number of these pursue a zigzag course, but some run longitudinally, others obliquely; some communicate with each other, while others terminate separately in the substance of the brain (fig. iv. 7). The nervous matter constituting the cerebrum is composed of two distinct substances, which differ from each other materially both in their colour and consistence (fig. iv. 7). The outer substance is sometimes termed cineritious, from its being of a greyish brown colour; at other times cortical, from its surrounding the inner part of the brain, as the bark the inner parts of the tree; by some it is also called glandulur, and by others secretory, from the supposition that its nature is that of a gland, and that it secretes a peculiar fluid. It is of a softer consistence than the inner part, and leaves by desiccation a smaller quantity of solid residuum. It is composed almost entirely of blood vessels connected and sustained by exceedingly fine cellular membrane. Its structure is uniform throughout, presenting no appearance whatever of a fibrous texture. It gives to the entire surface of the cerebrum an external covering, generally about the tenth of an inch in thickness (fig. IV. 7). The inner substance, termed white or medullary (fig. 1v. 7), is firmer in consistence and larger in quantity than the grey matter; and when an incision is made into it, its surface is spotted with red points, the cut orifices of its vessels, which vary in number and size according as they may be more or less distended with blood. It is now universally agreed that this part of the brain is composed of fibres. When examined in its recent and most perfect state, especially after it has been artificially hardened and condensed by the action of heat or certain chemical substances, if it be carefully scraped with a blunt instrument, these fibres become perfectly distinct and are of considerable magnitude, with furrows between them, which for the most part are placed in such a direction as to converge towards the base of the brain (fig. Iv. 6, 5, 4). The fibres do not merely unite, forming what are called commis sures, but they actually cross each other and pass into the opposite sides of the body. This decussation of the medullary fibres has been demonstrated in the most satisfactory manner by Drs. Gall and Spurzheim. It is now very generally admitted that the medullary substance of the brain is the true and proper nervous matter, or the nervous substance in its most perfect state; that the grey matter is entirely subservient to it, and is indispensable, if not to its generation, at least to its nutriment and support. Drs. Gall and Spurzheim indeed maintain that the sole use of the grey is to form or secrete the medullary matter; and this opinion they ground, first, on the fact, that whenever the medullary matter is obviously to be increased, it is invariably surrounded by a mass of grey matter, which incloses it as in a bed or nucleus; and, secondly, on this further fact, that in the course of the spinal cord, wherever it sends off nerves, masses of grey matter are always accumulated. Professor Tiedemann, who disputes the correctness of the opinion of these physiologists, on the ground that in the foetus the medullary is formed before that grey substance, thinks nevertheless that the use of the grey substance is to convey the arterial blood which may be necessary to support the energy of the perfect nervous matter. It is not intended, in this article, to pursue further the dissection of the cerebrum in the mode usually adopted by anatomists, both because the description could not be followed unless the object were before the eye, while that description, if needed, can be easily obtained in the common anatomical books; and because however convenient such a mode of examining the organ may be for the purpose of ascertaining its healthy or diseased conditions, it affords no insight into its real structure. The cerebellum is situated at the basis of the cerebrum, towards its posterior part (fig. 11. 6, 6). Its form is elliptical, its largest diameter extending transversely from one side to the other (fig. 11. 6). Like the cerebrum, it is divided into two lateral halves or hemispheres (fig. 11. 6), which are separated by the falx cerebelli. In the centre of its upper surface there is a distinct prominence termed the vermiform process (fig. 11. 7), which may be considered as the fundamental part of the organ, because in the lower animals, whatever other parts of the cerebellum are absent, this is invariably present, affording thus the nucleus or rudiment of the organ, from which, by the addition of other parts, as the hemispheres or lateral lobes, &c., the more perfect organ of the higher animal is built up. The external surface of the cerebellum is divided into flattened strata or layers (fig. 11. 6), separated by fissures which correspond to the clefts or sulci between the convolutions. The pia mater, bearing the nutrient arteries of the cerebellum, passes between every one of these fissures; while the arachnoid membrane is simply extended over them. If a vertical section be made through either he FIG. 111. [Vertical section of the brain.] 1, bundles of medullary fibres in the central part of the nervous apparatus; 2, white matter forming the centre of the fundamental part of the cerebel. um; 3. vertical section of the cerebellum, showing the arborescent arrangement of its component lamina, and forming the appearance called arbor vita; 4. situation of the third ventricle; 5, fibres of white matter, forming the septum lucidum, the medullary layer which separates the two lateral ventricles from each other; 6, fibres of white matter, forming the corpus cal losum, immediately beneath which are situated the lateral ventricles; 7, convolutions of the cerebrum. misphere of the cerebellum, a thick mass of white substance is seen in the centre, which, as it divides into the several strata, presents an arborescent appearance commonly denominated the arbor vita (fig. 111. 3). These strata diverge towards the circumference of the cerebellum, and are covered externally by grey substance (fig. 111. 3). In front of the cerebellum is placed a large mass of nervous matter, forming a very considerable eminence, commonly termed the tuber annulare, or the pons varolii (fig. 11. 10). The external surface of this body is convex, and it is divided into two lateral halves by a middle groove (fig. 11. 10). It is joined to the cerebrum by two thick white cords named the crura cerebri, and to the cerebellum by two similar cords named the crura cerebelli. The crura cerebri are continued (from the tuber) outwards and forwards to the under and middle part of each hemisphere of the cerebrum, in which they are lost. In like manner the crura cerebelli are continued outwards and backwards into the hemispheres of the cerebellum, in which they terminate. The medulla oblongata is that portion of the cerebral mass which intervenes between the tuber annulare and the foramen magnum (fig. 11. 7): beyond the foramen magnum it takes the name of spinal cord. On the anterior surface of the medulla oblongata there are four eminences contiguous to each other (fig. 11. 7). The two internal are named corpora pyramidalia, or the pyramids (fig. 11. 8); and the two internal the corpora olivaria (fig. 11. 9), or the olivary bodies. If the membranes which invest the medulla oblongata are carefully removed, and its middle groove be gently drawn asunder, there will be discovered four or five bands of white substance ascending obliquely from one side of the medulla to the other (fig. 11. 11). These bands on each side decussate, some of them passing above and others below those of the other side, so that they are interwoven like plaited straw (fig. 11. 11). These bands are named the decussating bands of the corpora pyramidalia, and their decussation is conceived to explain the phenomenon familiar to the physician and surgeon, that when injury is done to one side of the brain, the consequent disturbance of function is manifested on the opposite side of the body. Taken as a whole, the nervous mass constituting the brain is strictly symmetrical, that is, the different parts of which it is composed are so arranged, that if the organ be supposed to be divided into two lateral halves by a plane passing perpendicularly through its centre, the parts placed on each side of this plane have a perfect correspondence with each other, and form in fact reduplications of each other (fig. 11). The principal parts of the cerebral mass are thus double, but they are all united on the median line with their fellows of the opposite side. This union is effected by medullary bands of various sizes, and figures which pass from one to the other, called commissures. Thus the double parts of the cerebellum are united by means of the large mass of cerebral matter already spoken of under the name of tuber annulare or pons varolii (fig. 11. 10). The hemispheres of the cerebrum are united chiefly by a broad expansion of medullary matter, which extends transversely across from the bottom of one hemisphere to that of the opposite side, called the corpus callosum, or the great commissure of the brain (fig. 111. 6, 6). There are other connecting bands of smaller size, by which minor portions of the cerebral mass are placed in communication, into a description of which it is not necessary to enter here. The cerebral parts are separated from one another at certain places, and the intervals form cavities which are termed ventricles. Of these ventricles there are commonly enumerated four, all of which are in communication with each other. By far the largest of these are the two great cavities called the lateral ventricles, which are situated in the interior of the hemispheres of the cerebrum. Commencing in the fore part of the anterior lobes, these cavities proceed backwards in a direction parallel to each other through the middle into the posterior lobes. Their figure is winding and exceedingly irregular, and they are separated from each other by a tender mass of medullary matter termed the septum lucidum (fig. 111. 5). They are lined throughout by a fine transparent membrane, which secretes a fluid that keeps them moist, gives them a bright polished appearance, and prevents them from uniting. This membrane is the pia mater, which is continued from the exterior surface of the brain into these interior cavities, and some anatomists describe the arachnoid membrane as accompanying the pia mater in all its course through the ventricles. The middle or third ventricle is a vertical fissure between It is not necessary to enter into a more minute description of the several parts of the cerebral mass; but it is indispensable to a clear conception of the organization of the brain that something should be understood of the course of the fibres that constitute the main part of the medullary substance. For a detailed account of the course of these fibres, the reader is referred to the admirable work of Drs. Gall and Spurzheim, entitled Recherches sur le Système Nerveux en général, et sur celui du Cerveau en particulier in which the direction of the cerebral fibres is not only minutely and exactly described, but illustrated by excellent drawings as large as the objects. Some idea the two large convex eminences called the thalami optici | that one-fifth of all the blood sent out of the left ventricle (fig. 111. 4), situated in the middle and back part of the of the heart is carried to the head, yet the weight of the lateral ventricles. The fourth ventricle, called also ventricle brain in the human subject is not more than one-fortieth of of the cerebellum, is a cavity of considerable extent, situated that of the whole body. Even if this estimate, which is between the cerebrum, the tuber annulare, and the medulla generally thought too large, be reduced to one-tenth, accordoblongata. ing to the idea of Monro, it will still leave a very great over-proportion. There is no part of the structure of the brain more curious than the various contrivances connected with the circulation through the head, which have for their object the prevention of this prodigious quantity of blood from producing any injurious effects upon the tender cere bral substance, whether by its pressure, or by its unequal distribution, in consequence of its stagnating in the vessels, or of its being too violently propelled against them. Many conjectures have been formed respecting the object of furnishing this organ with such an extraordinary quantity of blood; but nothing is really known of the use to which it is applied, through it may be admitted to give a degree of plausibility to the opinion that the brain has some analogy to a secreting organ. Without doubt, one use both of the ventricles and the convolutions is to afford a more extended surface by which the blood vessels may enter the cerebral substance at a greater number of points, and consequently in small quantity at any one point, while at the same time they are more firmly supported in their passage by the greater quantity of investing membrane with which they are supplied. FIG. IV. [Course of the fibres of the brain.] 1, entrance of the anterior pyramids into 2, the tuber annulare, or pous varolii; 3, fibres of the pyramids much increased as they issue from the tuber annulare; 4,5, continued increase in the fibres of the pyramids as they advance onwards towards the convolutions; 6. divergence of the fibres of the pyramids; 7, convolutions of the cerebrum, showing their depth, their grey matter, and the sulci between them; 8, cerebellum. may be formed of the course of the fibres from fig. IV., taken from a smaller work by Dr. Spurzheim. Let us follow the course of some of these fibres; those, for example, that compose the pyramids (fig. 11. 8, and fig. iv. 1), and trace them from the medulla oblongata to the convolutions of the cerebrum (fig. 1v. 7). Immediately before their entrance into the tuber annulare, the pyramids are a little contracted (fig. 11. 8). As soon as they enter this mass, the pyramids are divided into innumerable bundles of fibres (fig. IV. 2), which are covered by a thick layer of transverse fibres (fig. IV. 2) that come from the cerebellum (fig. Iv. 8). These fibres of the pyramids, thus increased in number, ascend and receive at every point of their course fresh accessions, until at their exit (from the tuber) forward and outward, they form at least two-thirds of the crura cerebri, as is seen at fig. IV. 3. Followed in their course forwards from fig. 1v. 3, they are manifestly increased at every point by the accession of infinite numbers of fibres (fig. iv. 4). At the point (fig. IV. 5) the fibres, now exceedingly numerous, manifestly assume a diverging course, proceeding in every direction forwards, upwards, laterally, and backwards (fig. 1v. 5, 6, 7). At length the radiating fibres, crossing and interlacing each other in all directions, form an expansion or tissue, which being folded in various ways and covered with grey matter constitute the convolutions (fig. 1v. 5, 6, 7, 7). Thus the pyramids progressively increased and developed form a large portion of the anterior and middle lobes of the cerebrum. If the corpora olivara (fig. 11. 9) were traced in like manner, they would be found to form the posterior lobes of the cerebrum; and the origin and course of the fibres constituting the main bulk of the cerebellum can be demonstrated with the same clearness and exactness. From the preceding account of the structure of the brain, which shows it to be an exceedingly complex organ, it might have been inferred from analogy that it would receive a large supply of blood; but the quantity actually sent to it is far greater than any analogy could have led us to suppose. Haller made a calculation, from which he concluded The cerebral substance, when examined by a powerful microscope, is found to be composed of a pulp containing a number of small particles or rounded globules. The pulp itself appears to consist of flocculi, likewise formed of globules, connected together by fine cellular substance, the ultimate globules being of a tolerably firm consistence and about eight times less than the red particles of the blood. These observations, which were first made by Prochaska, have been confirmed in the essential points by the still more recent and elaborate examination of the Wenzels, who by using higher magnifiers detected more clearly the constitution of the brain as composed of a series of these small globules, which were apparently of a cellular texture, and which constituted the whole solid mass of the organ. Bauer states that the globules are disposed in lines so as to give the brain its fibrous appearance; that the diameter of the globules varies from too of an inch, the general size being; that they are both larger and in greater proportion in the medullary than in the cineritious substance, and that they are connected together by a peculiar gelatinous matter. Chemical analysis shows that the medullary matter consists of a peculiar chemical compound, unlike any other of the constituents of the body. In some respects this compound resembles a saponaceous substance, being miscible with water, and forming with it an emulsion which remains for a long time without being decomposed. Vauquelin has found in it two species of adipose or adiposerous matter, soluble in alcohol; also the peculiar animal principle called osmazome, together with a quantity of albumen, a small quantity of phosphorus, and some saline matter, consisting principally of the phosphates of lime, soda, and ammonia. Such is a brief outline of the nature and relation of the principal parts that enter into the composition of the brain. The functions of this organ will be considered in connexion with those of the spinal cord, and of the nerve. [NERVOUS SYSTEM.] *BRAIN OF ANIMALS, its peculiarities and diseases. The most obvious distinction between the brain of man and that of the other mammalia is its diminished size in most of the latter. The moment the skull-cap is raised, the difference between the full rounded appearance of the former and the compressed flattened shape of the latter cannot fail to be observed. The convexity of the middle lobes is strangely lessened, and the posterior lobe is in a manner lost in quadrupeds. If the brain is now removed from the cranial cavity, the difference in bulk between that of man and the inferior animals is strikingly displayed. The brain of the ox scarcely weighs a pound: the average weight of the brain of the human being is more than 24lbs. In man the brain is supposed to constitute about 1-35th part of the weight of his body. In the dog, averaging the different breeds, it is 1-120th part; in the horse it is only the As the reader may perceive some discrepancies between the two articles on the Brain, it is necessary to remark that these articles contain the re spective views or opinions of two different writers. 450th part, in the sheep the 750th part, and in the ox the 800th part. Does there appear already a connexion between the relative bulk of brain and the quantity of mind? The bulk of the brain has alone been spoken of, but, in point of fact, these animals have just been ranged in the order of their intelligence and docility. The prominences and depressions which mark the surface of the brain in man, and which are supposed by phrenologists to indicate certain peculiarities of mind and disposition, are tame and inexpressive in the quadruped. They are not found in the hare, or the rabbit, or in the rodentia generally. They are not so bold or so deep in the ox as in the horse; nor so much so in the horse as in the dog. The brain is composed of two substances essentially distimet from each other, the medullary deep in the base of the organ, and the cortical or cineritious without the one connected with the animal, and the other with the intellectual principle: the one the medium through which the impression made by surrounding objects is conveyed, and the other the substance to which that impression is referred, and where it is received, registered, and compared: the one the agent by means of which the voluntary motions of the frame are effected, and the other directing and controlling the working of the machine. As an illustration of the greater size and development of the nerves of sense in animals, the olfactory one may be selected. In man, who has other means of judging of the qualities of his food, and of surrounding objects, than by the sense of smell, the olfactory nerve is not one-fourth of the size of that of the horse; in the ox, that is not so much domesticated as the horse, and oftener sent into the field to shift for himself, it is considerably larger; it is larger still in the swine, who has to search for a portion of his food buried in the earth, or deeply immersed in refuse or filth; and it is largest of all in the dog, whose acuteness of scent renders him so useful a servant to man. The different development of the medulla oblongata in different animals may be adduced as another proof of the admirable adaptation of each to the situation which he occupies and the functions which he discharges. The medulla oblongata is the prolongation and condensation of the medullary matter of the brain, and it is the origin of that portion of the spinal cord which is devoted to organic life. In the human being the breadth of it is only a seventh part of that of the brain; in the horse and the ox it is nearly a third; and in the dog it is more than a half. redbreast, it approaches to the proportionate size of that of the human being, it is, as in the smaller quadruped, on account of the quantity of medullary matter required for the origins of the nerves; and the cineritious matter forms only a very small part of the brain. The brain of the bird has no convolutions on its surface; no corpora striata in the ventricles; no pons varolii between the brain and the spinal cord; and the origins of the optic nerves are separate from the brain, and lie behind and below it. In fishes the brain is yet more diminished in proportionate size. In some species it does not constitute a twothousandth part of the bulk of the fish. It scarcely half fills the cranial cavity, but is surrounded by a cellular tissue containing a transparent semifluid mass. It singularly varies in different species. It consists of at least four or more rounded eminences, placed in pairs opposite to each other, and forming two parallel lines; and there is often only a very slight connexion between these lines, or the eminences of which either of them is composed. The two principal hemispheres of the brain and the optic thalami are always present. The olfactory nerves often form a third pair of tubercles anterior to these and the cerebellum, and is always found posteriorly on the mesian line. The optic nerves usually cross each other without any intermingling of medullary matter. The cineritious substance is found in an exceedingly small proportion in the brain of fishes. As for insects and worms, little needs to be said here. In the worm the brain or upper ganglion of the nervous system is placed near to, or may be said to be perforated by, the superior portion of the esophagus, and thence proceed little white threads or cords, which run along the course of the digestive canal. In insects, the upper ganglion usually surrounds the œsophagus, and a ganglionic system of nerves can generally be traced proceeding from it. In the larvæ of insects the brain is inclosed in a horny cavity. The spinal cord proceeding from it, pursues its course through the whole of the abdomen, presenting evident ganglia at different points, from which nerves are distributed: while from the intermediate spaces are given out other nerves without ganglia; presenting a rude but satisfactory sketch of the combined systems of sensitive and motor nerves discovered by modern physiologists. In every part of the brain of the quadruped the medullary portion preponderates, and the cineritious is deficient. In his wild state the brute has no idea beyond his food and the reproduction of his species: in his domesticated state, he is the servant of man. The acuteness of his senses and the preponderance of animal power qualify him for this service; but were proportionate intellectual capacity added, he would speedily burst his bonds. It is, however, only in the pro portions of the two substances that the brain of the biped and of the quadruped differs: the cineritious and the medullary parts are found in each. It was necessary that in the servant of man some degree of intelligence should be added to animal power; that he should possess the faculties of attention, meinory, and judgment, and that to these should be added not only the gerin, but, often, the pleasing development of courage, fidelity, gratitude, disinterested-mania? ness, and a consciousness of right and wrong. In the smaller quadrupeds the comparative size of the brain approaches nearer to that of the human being. In the mouse it is a forty-third part of the weight of the animal. But of what is it composed? Of the medullary matter which is necessary to form the origin of the nerves of pure sensation, and of those of the spinal cord, which are as numerous as in a larger animal. This must necessarily occupy a considerable bulk; but there is little of the cineritious matter, or that which is connected with the mind. For several miner points of difference between the brain of the biped and the quadruped, the reader is referred to Coulson's edition of Blumenbach's Comparative Anatomy,' and to Dr. Grant's 'Outlines of Comparative Anatomy.' A sketch of the diseases of the brain in different animals can, in this place, scarcely extend beyond those that have been domesticated by man. The preponderance of the medullary matter explains the cause of the unfrequency of any affection of the brain that can be called insanity in animals. If there is so small a portion of cineritious matter, if the intellectual principle is so slightly developed, aberration of the mind is scarcely to be expected. In certain states of cerebral excitation, delirium is occasionally observed. It is one of the concomitants and characteristic symptoms of rabies. Pure mental alienation unaccom panied by inflammatory or other disease is however, although very rarely, seen in the quadruped. The eagerness with which the female, the sow, the bitch, the rabbit, or the cat, will search out and pursue their own offspring in order to destroy them, and the evident delight with which they devour them, is not this insanity? The fury which some animals, gentle in every other respect, show at the sight of one object, and one alone, is not this true monoA mare that had not the slightest fear of any other object, was always roused to uncontrollable fury by the sight or rustling of paper; another mare would endea vour to fly upon and tear to pieces every light grey horse that came within her view; and a third would rush furiously against every white object, animate or inanimate ;were not these cases of monomania ? The brain of the quadruped is proportionally much smaller than that of man. Comparing bulk with bulk, the brain of the horse is not a twelfth, and that of the ox is not a twentieth part so large as that of the human being. In a state of health, a much greater quantity of blood is determined to the brain than to any other part, in order to enable it to discharge its important functions. From some sudden disturbance in the circulation, a still greater quanThe brain of the larger birds agrees with that of the tity of blood is sometimes determined to the brain of the humammalia in the smallness of its bulk, compared with the man being. What is the consequence? All the vessels of development of the same organ in the human being. The that organ are overloaded the origins of the nerves are brain of the eagle is not more than a two-hundred-and-pressed upon-no cerebral functions can be dischargedsixtieth part of the weight of the bird. The brain of the goose is not more than a three-hundred-and-sixtieth part. If in some of the lesser birds, as in the chaffinch and the the man is seized with a fit of apoplexy, and unless the cur rent is speedily diverted, and the overcharged vessels to a certain extent drained of their contents, he must inevitably |