See also:

• BRAIN (A.S. braegen)

Superior See also:

• LONGITUDINAL

Ophthalmic vein, from 15, 7. Inferior longitudinal sinus. the eyeball. 8. See also:

• VEINS

A large band See also:

• ARCHES, COURT OF

Between the dura mater and the subjacent arachnoid membrane is a See also:

• FINE

Sometimes the Pacchionian bodies greatly See also:

• HYPERTROPHY (Gr. inrEp, over, and rpo(A, nourishment)

It is a bilateral See also:

• ORGAN

peduncles which meet just before the inferior quadri- FIG. 4,-Transverse Section through the Human geminal bodies are reached. Stretching across between Lower Olivary Region. them is the superior medullary velum or See also:

• VALVE (Lat. valva, a leaf of a double or folding door, allied to volvere, to roll, as of a door on its hinges)

4). The up from the anterior basis bundle of the cord. External to and behind the pyramid is the crenated section of the olivary See also:

• NUCLEUS (Lat. for the kernal of a nut, nux, the stone of fruit)

In the human brain the trapezium is concealed by the lower transverse fibres of the pons, but when sections are made through it, as L. See also:

• CLARKE, ADAM (1762?—1832)
• CLARKE, CHARLES COWDEN (1787-1877)
• CLARKE, EDWARD DANIEL (1769–1822)
• CLARKE, JAMES FREEMAN (1810–1888)
• CLARKE, JOHN SLEEPER (1833–1899)
• CLARKE, MARCUS ANDREW HISLOP (1846–1881)
• CLARKE, MARY ANNE (c.1776–1852)
• CLARKE, SAMUEL (1675–1729)
• CLARKE, SIR ANDREW (1824-1902)
• CLARKE, SIR EDWARD GEORGE (1841– )
• CLARKE, THOMAS SHIELDS (1866- )
• CLARKE, WILLIAM BRANWHITE (1798-1878)

The Cerebellum.lobes, of which the most important are the amygdala or tonsil, which forms the lateral boundary of the anterior part of the vallecula, and the flocculus, which is situated immediately behind the middle peduncle of the cerebellum. The inferior vermiform See also:

• PROCESS

The white matter is more abundant in the hemispheres than in the median lobe, and is for the most part directly continuous with the fibres of the pe- duncles of the cerebellum. Thus the restiform or inferior peduncles pass from below upward through the white core, to end in the grey matter of the tentorial surface of the cerebellum, more especially in that of the central lobe; on their way they are connected with the Middle peduncle of cerebellum From Cunningham, Text-book of Anatomy. The Cerebellum, LITTLE BRAIN, Or AFTER BRAIN occupies the inferior pair of occipital fossae, and lies below the plane of the tentorium cerebelli. It consists of two hemispheres or lateral lobes, and of a median or central lobe, which in human anatomy is called the vermis. It is connected below with the medulla oblongata by the two callosum restiform bodies which form its inferior peduncles, and above with the corpora quadrigemina of the cerebrum by two bands, which form its superior peduncles; whilst the two hemispheres are connected together by the trans-verse fibres of the pons, which form the middle peduncles of the cerebellum. On the superior or tentorial surface of the cerebellum the median or vermiform lobe is a See also:

• MERE
• MERE, ADALBERT (1838-1909)

in the grey matter of the foliated cortex of the hemispheres. It has been noticed that those fibres which are lowest in the pons go to the upper surface of the cerebellum and See also:

• VICE

The branchings of this dendron From Cunningham, Text-book of Anatomy. See also:

• KOLLIKER, RUDOLPH ALBERT VON (1817-1905)

Purkinje. GL. Neuroglial cell. M. Small cell of the molecular N. Axon of an association GR. Granule cell. [layer. cell. are also highly characteristic in that they are approximately restricted to a single plane like an See also:

• ESPALIER (a French word, derived from the Ital. spalliera, something to rest the spalla or shoulder against; the word is ultimately the same as epauliere, a shoulder-piece)

In its course, this gives off numerous collaterals which run downward to the bodies of Purkinje's cells. Their terminal branchings together with similar terminals of other collaterals form the basket-work around the bodies of these cells. The granular layer is sometimes termed the See also:

• RUST (O.E. rust, a word which appears in -many Teutonic languages, cf. Du. roest, Ger. rost); in origin it is allied with " ruddy " and " red," the reddish-brown powdery substance which forms on the surface of iron or steel exposed to atmospheric corrosio

The position of the cells of these latter fibres is not known. The fibres give rise to an abundant plexus of fibrils in the granular layer, and many reaching into the molecular layer ramify there, especially in the immediate neighbourhood of the dendrites of Purkinje's cells. From the appearance of their plexus of fibrils these are sometimes called moss fibres. The Fourth Ventricle is the'dilated upper end of the central canal of the medulla oblongata. Its shape is like an heraldic See also:

• LOZENGE (from the Fr. losenge, or losange; the word also appears in Span. losanje, and Ital. losanga; perhaps derived from a word meaning a stone slab laid on a grave, which appears in forms such as Provencal lousa, Span. losa, the ultimate origin of whic

The Cerebrum. The Cerebrum or GREAT BRAIN lies above the plane of the tentorium, and forms much the largest division of the encephalon. It is customary in human anatomy to include under the name of cerebrum, not only the convolutions, the corpora striata, and the optic thalami, developed in the anterior cerebral vesicle, but also the corpora quadrigemina and crura cerebri developed in the mesencephalon or middle cerebral vesicle. The cerebrum is ovoid in shape, and presents superiorly, anteriorly and posteriorly a deep median longitudinal fissure, which subdivides it into two hemispheres. Inferiorly there is a continuity of structure between the two hemispheres across the mesial plane, and if the two hemispheres be See also:

• DRAWN

If a transverse section is made at right angles to the surface of the crura cerebri it will pass right through the mesencephalon and come out on the dorsal side through the corpora quadrigemina (see fig. 8). The ventral part of each crus forms the crusta, which is the continuation forward of the anterior pyramidal fibres of the medulla and pons, and is the great motor path from the brain to the cord. Dorsal to this is a layer of pigmented grey matter, called the substantia See also:

• NIGRA, COSTANTINO, COUNT (1828-1907)

The inferior pair of quadrigeminal bodies are more closely in See also:

• TOUCH (derived through Fr. toucher from a common Teutonic and Indo-Germanic root, cf. " tug," " tuck," O. H. Ger. zucchen, to twitch or draw)

The frontal lobe body is separated from the parietal by the fissure of Rolando (fig. 9, r) which extends on the outer face of the hemisphere from the Sylvian grey matter longitudinal fissure obliquely downward and forward towards the Sylvian fissure. About 2 in. from the hinder end of the hemisphere is the parieto-occipital fissure, which, commencing at the longitudinal fissure, passes down the inner surface of the hemisphere, and transversely outwards for Nucleus of third nerve a short distance on the outer surface of the hemisphere; it separates the parietal and occipital lobes from each other. The Temporo-Sphenoidal Lobe presents on the outer surface of the hemisphere three convolutions, arranged in parallel tiers from above downward, and named superior, middle and inferior temporal gyri. The fissure which separates the superior and Fibres of superior middle of these convolutions is called the parallel fissure (fig. 9, tf). The Occipital Lobe also consists from above downwards of three parallel gyri, named superior, middle and inferior occipital. The Frontal Lobe is more complex; immediately in front of the fissure of Rolando, and forming indeed its anterior boundary, is a convolution named ascending frontal or pre-central, which ascends obliquely backward and upward from the Sylvian to the longitudinal fissure. Springing from the front of this gyrus, and passing forward to the anterior end of the cerebrum, are three gyri, arranged in parallel tiers from above downwards, and named superior, middle and inferior frontal gyri, which are also prolonged on to the orbital face of the frontal lobe. The Parietal Lobe is also complex; its most anterior gyrus, named ascending parietal or See also:

• POST

Po<E From Cunningham, Text-book of Anatomy. ff, Sulcus frontalis superior. See also:

• F2(X2+Y2)

r, Fissure of Rolando. g.s, Superior genu. g.i, Inferior genu. d, Sulcus diagonalis. ti, Superior temporal sulcus (parallel t2, Inferior temporal sulcus. [sulcus). pf, Inferior postcentral sulcus. p2, Superior postcentral sulcus. p3, See also:

• RAMUS, PETRUS, or PIERRE DE LA RAMEE (1515-1572)

upper boundary of the hinder part of the Sylvian fissure; as this part in front of the junction is called the pre-calcarine, and that behind gyrus occupies the hollow in the parietal bone, which corresponds the post-calcarine fissure. The internal parieto-occipital and cal-to the See also:

• EMINENCE (Lat. eminentia)

Sylvian fissure, the oper- cula forming the margin of Interior of the Cerebrum. which, conceal it. It con- If a horizontal slice be removed from the upper part of each sists of four or five short hemisphere (see fig. 12), the peripheral grey matter of the gyri will gyri, which radiate from be seen to follow their various windings, whilst the core of each gyrus the locus perforatus anticus, consists of white matter continuous with a mass of white matter situated at the inner end of in the interior of the hemisphere. If a deeper slice be now made the fissure. This lobe is down to the plane of the corpus callosum, the white matter of that almost entirely surrounded structure will be seen to be continuous with the white centre of by a deep sulcus called each hemisphere known as the centrum ovale. The corpus callosum longitudinal fissure. articulates with the parietal brain which has been hardened in spirit, the corpus callosum is seen 0. Olfactory fissure, over which the and squamous-temporal. to consist almost entirely of bundles of nerve fibres, passing trans- olfactory peduncle and lobe are In front of the central versely across the mesial plane between the two hemispheres; these situated. lobe, on the base of the fibres may be traced into the white cores and grey matter of the TR. Orbital sulcus. [surface. brain, are the orbital gyri, gyri, and connect the gyri, though by no means always corresponding i" 1". Convolutions on the orbital which are separated from ones, in the opposite hemispheres. Hence the corpus callosum is a con-e, I, I, i.

Under surface of infero- one another by the orbital necting or commissural structure, which brings the gyri of the two frontal convolution. sulcus. This is usually hemispheres into anatomical and physiological relation with each 4. Under surface of ascending frontal; H-shaped, and the gyri other. On the surface of the corpus callosum a few fibres, the striae and 5, of ascending parietal con- are therefore anterior, longitudinales, run in the antero-posterior or longitudinal direction volutions. posterior, external and in- (see fig. 12, b). Their morphological interest is referred to in the C. Central lobe or insula. ternal. Bisecting the in- section below on See also:

• COMPARATIVE

This is the calloso-marginal sulcus, so called because it separates the callosal gyros, which lies between it and the corpus callosum, from the marginal gyri nearer the margin of the brain. When the sulcus reaches a point vertically above the hind end of the corpus callosum it turns sharply upward and so forms the hinder limit of the marginal gyri, the posterior See also:

• INCH (O. Eng. ynce from Lat. uncia, a twelfthpart; cf. " ounce," and see As)

Resting on the upper surface of the thalamus Corpus Callosum. a, Transverse fibres, and g, Taenia semicircularis. b, Longitudinal fibres of corpus h, Optic thalamus. callosum. k, Choroid plexus. c, Anterior, and [ventricle. 1, Taenia hippocampi. d, Posterior cornua of lateral m, Hippocampus major. e, Septum lucidum. n, Hippocampus minor. f, Corpus striatum. o, Eminentia collateralis. is the vascular fringe of the velum interpositum, named choroid plexus, and immediately internal to this fringe is the free edge of the white posterior pillar of the fornix. The anterior cornu has the anterior end of the corpus striatum projecting into it. The posterior cornu has an elevation on its floor, the hippocampus minor (fig. 12, n), and between this cornu and the descending cornu is the elevation called eminentia collateralis, formed by the collateral fissure (fig.

12, o). Extending down the descending cornu and following its curvature is the hippocampus major, which terminates below in a nodular end, the pes hippocampi; on its inner border is the white taenia hippocampi, continuous above with the posterior pillar of the fornix. If the taenia be drawn to one side the hippocampal fissure is exposed, at the bottom of which the grey matter of the gyrus hippocampi may be seen to form a well-defined dentated border (the so-called fascia dentata). The choroid plexus of the pia mater turns round the gyrus hippocampi, and enters the descending cornu through the lateral part of the great transverse fissure between the taenia hippocampi and optic thalamus. The lateral ventricle is lined by a ciliated epithelium called the ependyma. This lining is continuous through the foramen of Monro with that of the third ventricle, which again is continuous with the lining of the fourth ventricle through the aqueduct of Sylvius. A little fluid is contained in the cerebral ventricles, which, under some pathological conditions, may increase greatly in quantity, so as to occasion considerable See also:

• DILATATION (from Lat. dis-, distributive, and lotus, wide)

13, e), and this space does not communicate with the other ventricles nor is it lined with ependyma. If the septum be now removed, the anterior part of the fornix is brought into view. The fornix is an See also:

• ARCH
• ARCH, JOSEPH (1826– )

If the body of the fornix be now divided by a transverse incision, its anterior part thrown forward, and its posterior part backward, the great transverse fissure of the cerebrum is opened into, and the velum interpositum lying in that fissure is exposed. The velum inter positum is an See also:

• EXPANDED

fornix, turned back. k, Choroid plexus. c, c, Anterior pillars of the fornix. 1, Taenia hippocampi. d, Velum interpositum and m, Hippocampus major in de-veins of Galen. scending cornu. e, Fifth ventricle. n, Hippocampus minor. f, f, Corpus striatum. o, Eminentia collateralis. The optic thalamus is a large, somewhat ovoid body situated behind the corpus striatum, and above the crus cerebri. Its upper surface is partly seen in the floor of the body of the lateral ventricle, but is for the most part covered by the fornix and velum interpositum. Its postero-inferior surface forms the roof of the descending cornu and posteriorly at the splenium, but the body is above the plane of section. Behind the genu the fifth ventricle is cut, and behind that the two pillars of the fornix which here form the anterior boundary of the third ventricle. At the posterior end of this is the pineal body, which the section has just escaped. To the outer side of the fornix is seen the foramen of See also:

• MUNRO, HUGH ANDREW JOHNSTONE (1819-1885)
• MUNRO, MUNRO
• MUNRO, SIR HECTOR (1726-1805)
• MUNRO, SIR THOMAS (1761-1827)

It will be seen that the lateral boundary of this horn is the cut caudate nucleus of the corpus striatum, while the lateral boundary of the third ventricle is the cut optic thalamus, both of which bodies have been already described, but external to these is a third triangular grey mass, with its apex directed inward, which cannot be seen except in a section. This is the lenticular nucleus of the corpus striatum, the inner or apical half of which is of a See also:

• LIGHT

optic See also:

• WEIGHT

The results, however, have not been conclusive. Further details of the brain, abundantly illustrated, will be found in the later See also:

• EDITIONS

Thus, in vertical section, the following layers may be made out of the ventricle, whilst its inner surface forms the side See also:

• WALL (O. Eng. weal, weall, Mid. Eng. wal, wane, adapted from Lat. vallum, rampart; the original O. Eng. word for a wall was wag or tenth)
• WALL, RICHARD (1694-1778)

From its broad anterior end two white bands, the peduncles of the pineal body, pass forward, one on the inner side of each optic thalamus. Each peduncle joins, along with the taenia semicircularis, the anterior pillar of the fornix of its own side. In its structure this body consists of tubular gland tissue containing gritty calcareous particles, constituting the brain See also:

• SAND
• SAND, GEORGE (1804-1876)

The Layer of small Pyramidal Cells.—The typical cells of this layer are pyramid-shaped, the apices of the pyramids being directed towards the surface. The apex terminates in a dendron which reaches into the molecular layer, giving off several collateral horizontal branches in its course. The final branches in the molecular layer take a direction parallel to the surface. Smaller dendrites arise from the lateral and basal surfaces of these cells, but do not extend far from the body of the cell. .The neuraxon always arises from the base of the cell and passes towards the central white From Cunningham, Text-book of Anatomy. A. E. Small pyramidal cell. B Neuroglia cells. F. Large pyramidal cell. C.

Cell with short axon (N) which breaks G. Cell of Martinotti. up in a free arborization. H. Polymorphic cell. D. Spindle-shaped cell in stratum zonale. K. Corticipetal fibres. matter, thus forming one of the nerve-fibres of that substance. In its path it gives off a number of collaterals at right angles, which are distributed to the adjacent grey matter. 3.

The Layer of large Pyramidal Cells.—This is characterized by the presence of numbers of cells of the same type as those of the preceding layer, but of larger size. The nerve-fibre process becomes a medullated fibre of the white matter. 4. The Layer of Polymorphous Cells.—The cells of this layer are irregular in outline, and give off several dendrites branching into the surrounding grey matter. The neuraxon gives off a number of collaterals, and then becomes a nerve-fibre of the central white matter. Scattered through these three layers there are also a number of cells (cells of Golgi) whose neuraxon divides at once, the divisions terminating within the immediate vicinity of the cell-body. Some cells are also found in which the neuraxon, instead of running into[ANATOMY the white matter of the brain, passes toward the surface; these are called cells of Martinotti. The medullated nerve-fibres of the white matter when traced into the cortex are seen to enter in bundles set vertically to the surface. These bundles taper and are resolved into isolated fibres in the upper parts of the pyramidal layers. The fibres constituting the bundles form two sets. (a) The centrifugal fibres consist as above described of the fibre processes of the pyramidal and polymorphous cells. (b) The centripetal fibres ascend through the cortex to terminate within the molecular layer by horizontally running branches.

As they pass through they give off a number of collaterals. The position of the cells from which these fibres arise is not known. In addition to the radially arranged bundles of fibres, networks are formed by the interlacement with them of large numbers of fine medullated fibres running tangentially to the surface. These are derived chiefly from the collaterals of the pyramidal cells and of the centripetal fibres. They form two specially marked bundles, one within the layer of the polymorphous cells known as the inner band of Baillarger, and another in the layer of large pyramidal cells called the outer band of Baillarger. This latter is very thick in the calcarine region, and forms the white stria of Gennin, while the inner band is best seen in the precentral gyrus. As both these strands See also:

• CROSS

R. See also:

• SOC

This fossa is roofed over by the epithelium lining the cavity of the ventricle, by pia mater and blood-vessels constituting a choroid plexus (fig. 16, B). The fourth ventricle communicates with the parts in front by means of a passage known as the aqueduct of Sylvius. The mesencephalon or mid-brain, when looked at from the dorsal surface, shows a pair of large hollow swellings, the optic lobes or corpora bigemina. Their cavities open out from the aqueduct of B. Sylvius, and from the nervous tissue in their walls the optic nerves derive their fibres. From the front of the prosencephalon or anterior vesicle the olfactory nerves come off, and at the base of each of these are two hollow swellings; the larger and more anterior is the olfactory bulb, the smaller and more posterior the cerebral hemisphere. Both these swellings must be regarded as lateral outgrowths from the See also:

• BLIND, MATHILDE (1841—1896)

The anterior closed end of the nerve-See also:

• TUBE (Lat. tuba)

The infundibulum dilates into two rounded bodies, the lobi inferiores, while the pituitary body or hypophysis cerebri has two lateral diverticula known as sacci vasculosi. Ganglia geniculata are found for the first See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

Bd. lviii., 1901, p. 661, " Cerebellum "). The Teleostean Fish are chiefly remarkable for the great development of the optic lobes and suppression of the olfactory apparatus. The pallium is non-nervous, and the optic tracts merely cross one another instead of forming a commissure. A process of the cerebellum called valvula cerebelli projects into the cavity of each optic lobe (Rabl. Ruckhard, Arch. Anat. it. Phys., 1898, p. 345 [Pallium]; See also:

• HALLER, ALBRECHT VON (1708–1777)
• HALLER, BERTHOLD (1492–1536)

The brain of the Dipnoi, or mud fish, shows no very important developments, except that the 40I anterior pineal organ or paraphysis is large (Saunders, See also:

• ANN

Between these two a narrow area of ganglionic matter runs forward from the side of the lamina lerminalis and is known as the paraterminal or precommissural area (Elliot Smith, Journ. Anat. and Phys. vol. xxxii. p. 411). To the upper lateral part of the hemisphere Elliot Smith has given the name of neopallium, while the lower lateral part, imperfectly separated from it, is called the pyriform lobe. In the Lacertilia the pineal eye, if it be an eye, is better developed than in any existing vertebrate, though even in them there is no See also:

• EVIDENCE (Lat. evidentia, evideri, to appear clearly)

252). Among the birds there is great unity of type, the cerebellum is large and, by its forward See also:

• PROJECTION

534; See also:

• BOYCE, WILLIAM (1710-1779)

(y) A right and left epiphysis, one of which may be wholly or partially suppressed. These may See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)