11-20

http://rgm22.nig.ac.jp/mediawiki-ogareport/index.php/For_Gray_anatomy_normalization
 * The pineal body (corpus pineale; epiphysis) is a small, conical, reddish-gray body which lies in the depression between the superior colliculi. It is placed beneath the splenium of the corpus callosum, but is separated from this by the tela chorioidea of the third ventricle, the lower layer of which envelops it. It measures about 8 mm. in length, and its base, directed forward, is attached by a stalk or peduncle of white substance. The stalk of the pineal body divides anteriorly into two laminæ, a dorsal and a ventral, separated from one another by the pineal recess of the third ventricle. The ventral lamina is continuous with the posterior commissure; the dorsal lamina is continuous with the habenular commissure and divides into two strands the medullary striæ, which run forward, one on either side, along the junction of the medial and upper surfaces of the thalamus to blend in front with the columns of the fornix.	  20
 * The posterior commissure is a rounded band of white fibers crossing the middle line on the dorsal aspect of the upper end of the cerebral aqueduct. Its fibers acquire their medullary sheaths early, but their connections have not been definitely determined. Most of them have their origin in a nucleus, the nucleus of the posterior commissure (nucleus of Darkschewitsch), which lies in the central gray substance of the upper end of the cerebral aqueduct, in front of the nucleus of the oculomotor nerve. Some are probably derived from the posterior part of the thalamus and from the superior colliculus, while others are believed to be continued downward into the medial longitudinal fasciculus.	  21
 * The Hypothalamus (Fig. 720) includes the subthalamic tegmental region and the structures forming the greater part of the floor of the third ventricle, viz., the corpora mammillaria, tuber cinereum, infundibulum, hypophysis, and optic chiasma.	  22
 * The subthalamic tegmental region consists of the upward continuation of the tegmentum; it lies on the ventro-lateral aspect of the thalamus and separates it from the fibers of the internal capsule. The red nucleus and the substantia nigra are prolonged into its lower part; in front it is continuous with the substantia innominata of Meynert, medially with the gray substance of the floor of the third ventricle.	  23
 * It consists from above downward of three strata: (1) stratum dorsale, directly applied to the under surface of the thalamus and consisting of fine longitudinal fibers; (2) zona incerta, a continuation forward of the formatio reticularis of the tegmentum; and (3) the corpus subthalamicum (nucleus of Luys), a brownish mass presenting a lenticular shape on transverse section, and situated on the dorsal aspect of the fibers of the base of the cerebral peduncle; it is encapsuled by a lamina of nerve fibers and contains numerous medium-sized nerve cells, the connections of which are as yet not fully determined.	  24
 * The corpora mammillaria (corpus albicantia) are two round white masses, each about the size of a small pea, placed side by side below the gray substance of the floor of the third ventricle in front of the posterior perforated substance. They consist of white substance externally and of gray substance internally, the cells of the latter forming two nuclei, a medial of smaller and a lateral of larger cells. The white substance is mainly formed by the fibers of the columns of the fornix, which descend to the base of the brain and end partly in the corpora mammillaria. From the cells of the gray substance of each mammillary body two fasciculi arise: one, the thalamomammillary fasciculus (bundle of Vicq d’Azyr), passes upward into the anterior nucleus of the thalamus; the other is directed downward into the tegmentum. Afferent fibers are believed to reach the corpus mammillare from the medial lemniscus and from the tegmentum.
 * The tuber cinereum is a hollow eminence of gray substance situated between the corpora mammillaria behind, and the optic chiasma in front. Laterally it is continuous with the anterior perforated substances and anteriorly with a thin lamina, the lamina terminalis. From the under surface of the tuber cinereum a hollow conical process, the infundibulum, projects downward and forward and is attached to the posterior lobe of the hypophysis.	  26
 * In the lateral part of the tuber cinereum is a nucleus of nerve cells, the basal optic nucleus of Meynert, while close to the cavity of the third ventricle are three additional nuclei. Between the tuber cinereum and the corpora mammillaria a small elevation, with a corresponding depression in the third ventricle, is sometimes seen. Retzius has named it the eminentia saccularis, and regards it as a representative of the saccus vasculosus found in this situation in some of the lower vertebrates.	  27
 * The hypophysis (pituitary body) (Fig. 721) is a reddish-gray, somewhat oval mass, measuring about 12.5 mm. in its transverse, and about 8 mm. in its antero-posterior diameter. It is attached to the end of the infundibulum, and is situated in the fossa hypophyseos of the sphenoidal bone, where it is retained by a circular fold of dura mater, the diaphragma sella; this fold almost completely roofs in the fossa, leaving only a small central aperture through which the infundibulum passes.
 * Optic Chiasma (chiasma opticum; optic commissure).—The optic chiasma is a flattened, somewhat quadrilateral band of fibers, situated at the junction of the floor and anterior wall of the third ventricle. Most of its fibers have their origins in the retina, and reach the chiasma through the optic nerves, which are continuous with its antero-lateral angles. In the chiasma, they undergo a partial decussation (Fig. 722); the fibers from the nasal half of the retina decussate and enter the optic tract of the opposite side, while the fibers from the temporal half of the retina do not undergo decussation, but pass back into the optic tract of the same side. Occupying the posterior part of the commissure, however, is a strand of fibers, the commissure of Gudden, which is not derived from the optic nerves; it forms a connecting link between the medial geniculate bodies.	  29
 * Optic Tracts.—The optic tracts are continued backward and lateralward from the postero-lateral angles of the optic chiasma. Each passes between the anterior perforated substance and the tuber cinereum, and, winding around the ventrolateral aspect of the cerebral peduncle, divides into a medial and a lateral root. The former comprises the fibers of Gudden’s commissure. The lateral root consists mainly of afferent fibers which arise in the retina and undergo partial decussation in the optic chiasma, as described; but it also contains a few fine efferent fibers which have their origins in the brain and their terminations in the retina. When traced backward, the afferent fibers of the lateral root are found to end in the lateral geniculate body and pulvinar of the thalamus, and in the superior colliculus; and these three structures constitute the lower visual centers. Fibers arise from the nerve cells in these centers and pass through the occipital part of the internal capsule, under the name of the optic radiations, to the cortex of the occipital lobe of the cerebrum, where the higher or cortical visual center is situated. Some of the fibers of the optic radiations take an opposite course, arising from the cells of the occipital cortex and passing to the lower visual centers. Some fibers are detached from the optic tract, and pass through the cerebral peduncle to the nucleus of the oculomotor nerve. These may be regarded as the afferent branches for the Sphincter pupillæ and Ciliaris muscles. Other fibers have been described as reaching the cerebellum through the superior peduncle; while others, again, are lost in the pons.	  30
 * The Third Ventricle (ventriculus tertius) (Figs. 716, 720).—The third ventricle is a median cleft between the two thalami. Behind, it communicates with the fourth ventricle through the cerebral aqueduct, and in front with the lateral ventricles through the interventricular foramen. Somewhat triangular in shape, with the apex directed backward, it has a roof, a floor, an anterior and a posterior boundary and a pair of lateral walls.
 * The roof (Fig. 723) is formed by a layer of epithelium, which stretches between the upper edges of the lateral walls of the cavity and is continuous with the epithelial lining of the ventricle. It is covered by and adherent to a fold of pia mater, named the tela chorioidea of the third ventricle, from the under surface of which a pair of vascular fringed processes, the choroid plexuses of the third ventricle, project downward, one on either side of the middle line, and invaginate the epithelial roof into the ventricular cavity.	  32
 * The floor slopes downward and forward and is formed mainly by the structures which constitute the hypothalamus: from before backward these are: the optic chiasma, the tuber cinereum and infundibulum, and the corpora mammillaria. Behind the last, the floor is formed by the interpeduncular fossa and the tegmenta of the cerebral peduncles. The ventricle is prolonged downward as a funnel-shaped recess, the recessus infundibuli, into the infundibulum, and to the apex of the latter the hypophysis is attached.	  33
 * The anterior boundary is constituted below by the lamina terminalis, a thin layer of gray substance stretching from the upper surface of the optic chiasma to the rostrum of the corpus callosum; above by the columns of the fornix and the anterior commissure. At the junction of the floor and anterior wall, immediately above the optic chiasma, the ventricle presents a small angular recess or diverticulum, the optic recess. Between the columns of the fornix, and above the anterior commissure, is a second recess termed the vulva. At the junction of the roof and anterior wall of the ventricle, and situated between the thalami behind and the columns of the fornix in front, is the interventricular foramen (foramen of Monro) through which the third communicates with the lateral ventricles.
 * The posterior boundary is constituted by the pineal body, the posterior commissure and the cerebral aqueduct. A small recess, the recessus pinealis, projects into the stalk of the pineal body, while in front of and above the pineal body is a second recess, the recessus suprapinealis, consisting of a diverticulum of the epithelium which forms the ventricular roof.	  35
 * Each lateral wall consists of an upper portion formed by the medial surface of the anterior two-thirds of the thalamus, and a lower consisting of an upward continuation of the gray substance of the ventricular floor. These two parts correspond to the alar and basal laminæ respectively of the lateral wall of the fore-brain vesicle and are separated from each other by a furrow, the sulcus of Monro, which extends from the interventricular foramen to the cerebral aqueduct (pages 741 and 742). The lateral wall is limited above by the tænia thalami. The columns of the fornix curve downward in front of the interventricular foramen, and then run in the lateral walls of the ventricle, where, at first, they form distinct prominences, but subsequently are lost to sight. The lateral walls are joined to each other across the cavity of the ventricle by a band of gray matter, the massa intermedia (page 809).	  36
 * Interpeduncular Fossa (Fig. 724).—This is a somewhat lozenge-shaped area of the base of the brain, limited in front by the optic chiasma, behind by the antero-superior surface of the pons, antero-laterally by the converging optic tracts, and postero-laterally by the diverging cerebral peduncles. The structures contained in it have already been described; from behind forward, they are the posterior perforated substance, corpora mamillaria, tuber cinereum, infundibulum, and hypophysis.
 * The Telencephalon.—The telencephalon includes: (1) the cerebral hemispheres with their cavities, the lateral ventricles; and (2) the pars optica hypothalami and the anterior portion of the third ventricle (already described under the diencephalon). As previously stated (see page 744), each cerebral hemisphere may be divided into three fundamental parts, viz., the rhinencephalon, the corpus striatum, and the neopallium. The rhinencephalon, associated with the sense of smell, is the oldest part of the telencephalon, and forms almost the whole of the hemisphere in some of the lower animals, e. g., fishes, amphibians, and reptiles. In man it is rudimentary, whereas the neopallium undergoes great development and forms the chief part of the hemisphere.	  38
 * The Cerebral Hemispheres.—The cerebral hemispheres constitute the largest part of the brain, and, when viewed together from above, assume the form of an ovoid mass broader behind than in front, the greatest transverse diameter corresponding with a line connecting the two parietal eminences. The hemispheres are separated medially by a deep cleft, named the longitudinal cerebral fissure, and each possesses a central cavity, the lateral ventricle.	  39
 * The Longitudinal Cerebral Fissure (fissura cerebri longitudinalis; great longitudinal fissure) contains a sickle-shaped process of dura mater, the falx cerebri. It front and behind, the fissure extends from the upper to the under surfaces of the hemispheres and completely separates them, but its middle portion separates them for only about one-half of their vertical extent; for at this part they are connected across the middle line by a great central white commissure, the corpus callosum.	  40

after
The {pineal body [FMA62033:Pineal body]} ({corpus pineale [FMA62033:Pineal body]}; {epiphysis [FMA24012:Epiphysis]}) is a small, conical, reddish-gray body which lies in the depression between the {superior colliculi [FMA62403:Superior colliculus]}. It is placed beneath the {splenium of the corpus callosum [FMA61948:Splenium of corpus callosum]}, but is separated from this by the {tela chorioidea of the third ventricle [FMA78463:Tela choroidea of third ventricle]}, the lower layer of which envelops it. It measures about 8 mm. in length, and its base, directed forward, is attached by a stalk or peduncle of {white substance [FMA83929:White matter of neuraxis]}. The stalk of the {pineal body [FMA62033:Pineal body]} divides anteriorly into two laminæ, a dorsal and a ventral, separated from one another by the {pineal recess of the third ventricle [FMA78458:Pineal recess of third ventricle]}. The ventral {lamina is [FMA242259:Plexiform layer of cerebral cortex]} continuous with the {posterior commissure [FMA62072:Posterior commissure]}; the dorsal {lamina is [FMA242259:Plexiform layer of cerebral cortex]} continuous with the {habenular commissure [FMA62048:Habenular commissure]} and divides into two strands the medullary striæ, which run forward, one on either side, along the junction of the medial and upper surfaces of the {thalamus [FMA62007:Thalamus]} to blend in front with the {columns of the fornix [FMA61968:Body of fornix of forebrain]}. 20   The {posterior commissure [FMA62072:Posterior commissure]} is a rounded band of white fibers crossing the middle line on the dorsal aspect of the upper end of the {cerebral aqueduct [FMA78467:Cerebral aqueduct]}. Its fibers acquire their {medullary sheaths [FMA62983:Myelin sheath]} early, but their connections have not been definitely determined. Most of them have their origin in a nucleus, the {nucleus of the posterior commissure [FMA68463:Nucleus of posterior commissure]} ({nucleus of Darkschewitsch [FMA68464:Ventral nucleus of posterior commissure]}), which lies in the {central gray substance [FMA83134:Central gray substance]} of the upper end of the {cerebral aqueduct [FMA78467:Cerebral aqueduct]}, in front of the {nucleus of the oculomotor nerve [FMA54510:Oculomotor nuclear complex]}. Some are probably derived from the posterior part of the {thalamus [FMA62007:Thalamus]} and from the {superior colliculus [FMA62403:Superior colliculus]}, while others are believed to be continued downward into the {medial longitudinal fasciculus [FMA83846:Medial longitudinal fasciculus]}. 21   The {Hypothalamus [FMA62008:Hypothalamus]} (Fig. 720) includes the {subthalamic tegmental region [FMA62010:Subthalamus]} and the structures forming the greater part of the floor of the {third ventricle [FMA78454:Third ventricle]}, viz., the {corpora mammillaria [FMA74877:Mammillary body]}, {tuber cinereum [FMA62327:Tuber cinereum]}, {infundibulum [FMA74635:Infundibulum of neurohypophysis]}, {hypophysis [FMA13889:Pituitary gland]}, and {optic chiasma [FMA62045:Optic chiasm]}. 22   The {subthalamic tegmental region [FMA62010:Subthalamus]} consists of the upward continuation of the tegmentum; it lies on the {ventro [FMA9719:Muscle belly]}-lateral aspect of the {thalamus [FMA62007:Thalamus]} and separates it from the fibers of the {internal capsule [FMA61950:Internal capsule]}. The {red nucleus [FMA62407:Red nucleus]} and the {substantia nigra [FMA62907:Substantia nigra pars compacta; FMA62908:Substantia nigra pars reticulata; FMA67947:Substantia nigra]} are prolonged into its lower part; in front it is continuous with the {substantia innominata of Meynert [FMA61885:Substantia innominata]}, medially with the {gray substance [FMA67242:Gray matter of neuraxis]} of the floor of the {third ventricle [FMA78454:Third ventricle]}. 23   It consists from above downward of three strata: (1) stratum dorsale, directly applied to the under surface of the {thalamus [FMA62007:Thalamus]} and consisting of fine longitudinal fibers; (2) {zona incerta [FMA62038:Zona incerta]}, a continuation forward of the {formatio reticularis [FMA77719:Reticular formation]} of the tegmentum; and (3) the {corpus subthalamicum [FMA62035:Subthalamic nucleus]} ({nucleus of Luys [FMA62035:Subthalamic nucleus]}), a brownish mass presenting a lenticular shape on transverse section, and situated on the dorsal aspect of the fibers of the {base of the cerebral peduncle [FMA242166:Base of midbrain peduncle]}; it is encapsuled by a lamina of {nerve fibers [FMA5914:Nerve fiber]} and contains numerous medium-sized {nerve cells [FMA54527:Neuron]}, the connections of which are as yet not fully determined. 24   The {corpora mammillaria [FMA74877:Mammillary body]} ({corpus albicantia [FMA74877:Mammillary body]}) are two round white masses, each about the size of a small pea, placed side by side below the {gray substance [FMA67242:Gray matter of neuraxis]} of the floor of the {third ventricle [FMA78454:Third ventricle]} in front of the {posterior perforated substance [FMA77523:Posterior perforated substance]}. They consist of {white substance [FMA83929:White matter of neuraxis]} externally and of {gray substance [FMA67242:Gray matter of neuraxis]} internally, the cells of the latter forming two nuclei, a medial of smaller and a lateral of larger cells. The {white substance [FMA83929:White matter of neuraxis]} is mainly formed by the fibers of the {columns of the fornix [FMA61968:Body of fornix of forebrain]}, which descend to the {base of the brain [FMA77700:Basal forebrain]} and end partly in the {corpora mammillaria [FMA74877:Mammillary body]}. From the cells of the {gray substance [FMA67242:Gray matter of neuraxis]} of each {mammillary body [FMA74877:Mammillary body]} two fasciculi arise: one, the {thalamomammillary fasciculus [FMA83849:Mammillothalamic tract]} ({bundle of Vicq d’Azyr [FMA83849:Mammillothalamic tract]}), passes upward into the {anterior nucleus of the thalamus [FMA62019:Anterior nuclear group of thalamus]}; the other is directed downward into the tegmentum. {Afferent fibers [FMA76570:Set of afferent nerve fibers]} are believed to reach the {corpus mammillare [FMA74877:Mammillary body]} from the {medial lemniscus [FMA83675:Medial lemniscus]} and from the tegmentum. The {tuber cinereum [FMA62327:Tuber cinereum]} is a hollow eminence of {gray substance [FMA67242:Gray matter of neuraxis]} situated between the {corpora mammillaria [FMA74877:Mammillary body]} behind, and the {optic chiasma [FMA62045:Optic chiasm]} in front. Laterally it is continuous with the {anterior perforated substances [FMA61891:Anterior perforated substance]} and anteriorly with a thin lamina, the {lamina terminalis [FMA61975:Lamina terminalis]}. From the under surface of the {tuber cinereum [FMA62327:Tuber cinereum]} a hollow conical process, the {infundibulum [FMA74635:Infundibulum of neurohypophysis]}, projects downward and forward and is attached to the posterior lobe of the {hypophysis [FMA13889:Pituitary gland]}. 26   In the lateral part of the {tuber cinereum [FMA62327:Tuber cinereum]} is a nucleus of {nerve cells [FMA54527:Neuron]}, the basal optic nucleus of Meynert, while close to the {cavity of the third ventricle [FMA242751:Cavity of third ventricle]} are three additional nuclei. Between the {tuber cinereum [FMA62327:Tuber cinereum]} and the {corpora mammillaria [FMA74877:Mammillary body]} a small elevation, with a corresponding depression in the {third ventricle [FMA78454:Third ventricle]}, is sometimes seen. Retzius has named it the {eminentia [FMA75432:Eminence]} saccularis, and regards it as a representative of the saccus vasculosus found in this situation in some of the lower vertebrates. 27   The {hypophysis [FMA13889:Pituitary gland]} ({pituitary body [FMA13889:Pituitary gland]}) (Fig. 721) is a reddish-gray, somewhat oval mass, measuring about 12.5 mm. in its transverse, and about 8 mm. in its antero-posterior diameter. It is attached to the end of the {infundibulum [FMA74635:Infundibulum of neurohypophysis]}, and is situated in the {fossa hypophyseos [FMA54721:Hypophysial fossa]} of the {sphenoidal bone [FMA52736:Sphenoid bone]}, where it is retained by a circular fold of {dura mater [FMA9592:Dura mater]}, the {diaphragma sella [FMA78540:Diaphragma sellae]}; this fold almost completely roofs in the fossa, leaving only a small central aperture through which the {infundibulum [FMA74635:Infundibulum of neurohypophysis]} passes. {Optic Chiasma [FMA62045:Optic chiasm]} ({chiasma opticum [FMA62045:Optic chiasm]}; {optic commissure [FMA62045:Optic chiasm]}).—The {optic chiasma [FMA62045:Optic chiasm]} is a flattened, somewhat quadrilateral band of fibers, situated at the junction of the floor and anterior {wall of the third ventricle [FMA242776:Wall of third ventricle]}. Most of its fibers have their origins in the {retina [FMA58301:Retina]}, and reach the {chiasma [FMA62045:Optic chiasm]} through the {optic nerves [FMA50863:Optic nerve]}, which are continuous with its antero-lateral angles. In the {chiasma [FMA62045:Optic chiasm]}, they undergo a partial decussation (Fig. 722); the fibers from the nasal half of the {retina [FMA58301:Retina]} decussate and enter the {optic tract [FMA62046:Optic tract]} of the opposite side, while the fibers from the temporal half of the {retina [FMA58301:Retina]} do not undergo decussation, but pass {back [FMA24205:Surface of back]} into the {optic tract [FMA62046:Optic tract]} of the same side. Occupying the posterior part of the commissure, however, is a strand of fibers, the {commissure of Gudden [FMA62052:Ventral supraoptic decussation]}, which is not derived from the {optic nerves [FMA50863:Optic nerve]}; it forms a connecting link between the {medial geniculate bodies [FMA62211:Medial geniculate body]}. 29   {Optic Tracts [FMA62046:Optic tract]}.—The {optic tracts [FMA62046:Optic tract]} are continued backward and lateralward from the postero-lateral angles of the {optic chiasma [FMA62045:Optic chiasm]}. Each passes between the {anterior perforated substance [FMA61891:Anterior perforated substance]} and the {tuber cinereum [FMA62327:Tuber cinereum]}, and, winding around the ventrolateral aspect of the {cerebral peduncle [FMA62394:Peduncle of midbrain; FMA72464:Cerebral crus]}, divides into a medial and a lateral root. The former comprises the fibers of {Gudden’s commissure [FMA62052:Ventral supraoptic decussation]}. The lateral root consists mainly of {afferent fibers [FMA76570:Set of afferent nerve fibers]} which arise in the {retina [FMA58301:Retina]} and undergo partial decussation in the {optic chiasma [FMA62045:Optic chiasm]}, as described; but it also contains a few fine efferent fibers which have their origins in the {brain [FMA50801:Brain]} and their terminations in the {retina [FMA58301:Retina]}. When traced backward, the {afferent fibers [FMA76570:Set of afferent nerve fibers]} of the lateral root are found to end in the {lateral geniculate body [FMA62209:Lateral geniculate body]} and {pulvinar [FMA62178:Pulvinar]} of the {thalamus [FMA62007:Thalamus]}, and in the {superior colliculus [FMA62403:Superior colliculus]}; and these three structures constitute the lower visual centers. Fibers arise from the {nerve cells [FMA54527:Neuron]} in these centers and pass through {the occipital part of the internal capsule [FMA61954:Posterior limb of internal capsule]}, under the name of the {optic radiations [FMA61941:Optic radiation]}, to the {cortex of the occipital lobe [FMA242205:Cortex of occipital lobe]} of the {cerebrum [FMA62000:Telencephalon]}, where the higher or cortical visual center is situated. Some of the fibers of the {optic radiations [FMA61941:Optic radiation]} take an opposite course, arising from the cells of the {occipital cortex [FMA67325:Occipital lobe]} and passing to the lower visual centers. Some fibers are detached from the {optic tract [FMA62046:Optic tract]}, and pass through the {cerebral peduncle [FMA62394:Peduncle of midbrain; FMA72464:Cerebral crus]} to the {nucleus of the oculomotor nerve [FMA54510:Oculomotor nuclear complex]}. These may be regarded as the afferent branches for the Sphincter pupillæ and {Ciliaris muscles [FMA49151:Ciliary muscle]}. Other fibers have been described as reaching the {cerebellum [FMA67944:Cerebellum]} through the {superior peduncle [FMA62075:Superior thalamic peduncle]}; while others, again, are lost in the {pons [FMA67943:Pons]}. 30   The {Third Ventricle [FMA78454:Third ventricle]} ({ventriculus tertius [FMA78454:Third ventricle]}) (Figs. 716, 720).—The {third ventricle [FMA78454:Third ventricle]} is a median cleft between the two {thalami [FMA62007:Thalamus]}. Behind, it communicates with the {fourth ventricle [FMA78469:Fourth ventricle]} through the {cerebral aqueduct [FMA78467:Cerebral aqueduct]}, and in front with the {lateral ventricles [FMA78448:Lateral ventricle]} through the {interventricular foramen [FMA75351:Interventricular foramen]}. Somewhat triangular in shape, with the apex directed backward, it has a roof, a floor, an anterior and a posterior boundary and a pair of lateral walls. The roof (Fig. 723) is formed by a layer of {epithelium [FMA9639:Portion of epithelium]}, which stretches between the upper edges of the lateral walls of the cavity and is continuous with the epithelial lining of the ventricle. It is covered by and adherent to a fold of {pia mater [FMA9590:Pia mater]}, named the {tela chorioidea of the third ventricle [FMA78463:Tela choroidea of third ventricle]}, from the under surface of which a pair of vascular fringed processes, the {choroid plexuses of the third ventricle [FMA78462:Choroid plexus of third ventricle]}, project downward, one on either side of the middle line, and invaginate the epithelial roof into the {ventricular cavity [FMA13238:Cavity of ventricle]}. 32   The floor slopes downward and forward and is formed mainly by the structures which constitute the {hypothalamus [FMA62008:Hypothalamus]}: from before backward these are: the {optic chiasma [FMA62045:Optic chiasm]}, the {tuber cinereum [FMA62327:Tuber cinereum]} and {infundibulum [FMA74635:Infundibulum of neurohypophysis]}, and the {corpora mammillaria [FMA74877:Mammillary body]}. Behind the last, the floor is formed by the {interpeduncular fossa [FMA83740:Interpeduncular fossa]} and the tegmenta of the {cerebral peduncles [FMA62394:Peduncle of midbrain; FMA72464:Cerebral crus]}. The ventricle is prolonged downward as a funnel-shaped recess, the {recessus infundibuli [FMA78456:Infundibular recess of third ventricle]}, into the {infundibulum [FMA74635:Infundibulum of neurohypophysis]}, and to the apex of the latter the {hypophysis [FMA13889:Pituitary gland]} is attached. 33   The anterior boundary is constituted below by the {lamina terminalis [FMA61975:Lamina terminalis]}, a thin layer of {gray substance [FMA67242:Gray matter of neuraxis]} stretching from the upper surface of the {optic chiasma [FMA62045:Optic chiasm]} to the {rostrum of the corpus callosum [FMA61945:Rostrum of corpus callosum; FMA61946:Genu of corpus callosum]}; above by the {columns of the fornix [FMA61968:Body of fornix of forebrain]} and the {anterior commissure [FMA61961:Anterior commissure]}. At the junction of the floor and anterior wall, immediately above the {optic chiasma [FMA62045:Optic chiasm]}, the ventricle presents a small angular recess or diverticulum, the {optic recess [FMA78455:Optic recess of third ventricle]}. Between the {columns of the fornix [FMA61968:Body of fornix of forebrain]}, and above the {anterior commissure [FMA61961:Anterior commissure]}, is a second recess termed the {vulva [FMA20462:Vulva]}. At the junction of the roof and anterior {wall of the ventricle [FMA13884:Wall of ventricle]}, and situated between the {thalami [FMA62007:Thalamus]} behind and the {columns of the fornix [FMA61968:Body of fornix of forebrain]} in front, is the {interventricular foramen [FMA75351:Interventricular foramen]} ({foramen of Monro [FMA75351:Interventricular foramen]}) through which the third communicates with the {lateral ventricles [FMA78448:Lateral ventricle]}. The posterior boundary is constituted by the {pineal body [FMA62033:Pineal body]}, the {posterior commissure [FMA62072:Posterior commissure]} and the {cerebral aqueduct [FMA78467:Cerebral aqueduct]}. A small recess, the {recessus pinealis [FMA78458:Pineal recess of third ventricle]}, projects into the stalk of the {pineal body [FMA62033:Pineal body]}, while in front of and above the {pineal body [FMA62033:Pineal body]} is a second recess, the {recessus suprapinealis [FMA78457:Suprapineal recess of third ventricle]}, consisting of a diverticulum of the {epithelium [FMA9639:Portion of epithelium]} which forms the ventricular roof. 35   Each lateral wall consists of an upper portion formed by the medial surface of the anterior two-thirds of the {thalamus [FMA62007:Thalamus]}, and a lower consisting of an upward continuation of the {gray substance [FMA67242:Gray matter of neuraxis]} of the ventricular floor. These two parts correspond to the {alar [FMA264759:Alare]} and basal laminæ respectively of the lateral wall of the {fore-brain [FMA61992:Forebrain]} vesicle and are separated from each other by a furrow, the {sulcus [:]} of Monro, which extends from the {interventricular foramen [FMA75351:Interventricular foramen]} to the {cerebral aqueduct [FMA78467:Cerebral aqueduct]} (pages 741 and 742). The lateral wall is limited above by the {tænia thalami [FMA78461:Tenia of thalamus]}. The {columns of the fornix [FMA61968:Body of fornix of forebrain]} curve downward in front of the {interventricular foramen [FMA75351:Interventricular foramen]}, and then run in the lateral {walls of the ventricle [FMA13884:Wall of ventricle]}, where, at first, they form distinct prominences, but subsequently are lost to sight. The lateral walls are joined to each other across the {cavity of the ventricle [FMA13238:Cavity of ventricle]} by {a band [FMA67918:Anisotropic band]} of {gray matter [FMA67242:Gray matter of neuraxis]}, the {massa intermedia [FMA74869:Interthalamic adhesion]} (page 809). 36   {Interpeduncular Fossa [FMA83740:Interpeduncular fossa]} (Fig. 724).—This is a somewhat lozenge-shaped area of the {base of the brain [FMA77700:Basal forebrain]}, limited in front by the {optic chiasma [FMA62045:Optic chiasm]}, behind by the antero-superior surface of the {pons [FMA67943:Pons]}, antero-laterally by the converging {optic tracts [FMA62046:Optic tract]}, and postero-laterally by the diverging {cerebral peduncles [FMA62394:Peduncle of midbrain; FMA72464:Cerebral crus]}. The structures contained in it have already been described; from behind forward, they are the {posterior perforated substance [FMA77523:Posterior perforated substance]}, {corpora mamillaria [FMA74877:Mammillary body]}, {tuber cinereum [FMA62327:Tuber cinereum]}, {infundibulum [FMA74635:Infundibulum of neurohypophysis]}, and {hypophysis [FMA13889:Pituitary gland]}. The {Telencephalon [FMA62000:Telencephalon]}.—The {telencephalon [FMA62000:Telencephalon]} includes: (1) the {cerebral hemispheres [FMA61817:Cerebral hemisphere]} with their {cavities [:]}, the {lateral ventricles [FMA78448:Lateral ventricle]}; and (2) the {pars optica hypothalami [FMA62027:Anterior hypothalamic region]} and the anterior portion of the {third ventricle [FMA78454:Third ventricle]} (already described under the {diencephalon [FMA62001:Diencephalon]}). As previously stated (see page 744), each {cerebral hemisphere [FMA61817:Cerebral hemisphere]} may be divided into three fundamental parts, viz., the {rhinencephalon [FMA62430:Paleocortex]}, the {corpus striatum [FMA77616:Corpus striatum]}, and the {neopallium [FMA62429:Neocortex]}. The {rhinencephalon [FMA62430:Paleocortex]}, associated with the sense of smell, is the oldest part of the {telencephalon [FMA62000:Telencephalon]}, and forms almost the whole of the hemisphere in some of the lower animals, e. g., fishes, amphibians, and reptiles. In man it is rudimentary, whereas the {neopallium [FMA62429:Neocortex]} undergoes great development and forms the chief part of the hemisphere. 38   The {Cerebral Hemispheres [FMA61817:Cerebral hemisphere]}.—The {cerebral hemispheres [FMA61817:Cerebral hemisphere]} constitute the largest part of the {brain [FMA50801:Brain]}, and, when viewed together from above, assume the form of an ovoid mass broader behind than in front, the greatest transverse diameter corresponding with a line connecting the two {parietal eminences [FMA57080:Parietal tuber]}. The hemispheres are separated medially by a deep cleft, named the {longitudinal cerebral fissure [FMA83727:Longitudinal fissure]}, and each possesses a central cavity, the {lateral ventricle [FMA78448:Lateral ventricle]}. 39   The {Longitudinal Cerebral Fissure [FMA83727:Longitudinal fissure]} ({fissura cerebri longitudinalis [FMA9712:Hand]}; {great longitudinal fissure [FMA9712:Hand]}) contains a sickle-shaped process of {dura mater [FMA9592:Dura mater]}, the {falx cerebri [FMA83967:Falx cerebri]}. It front and behind, the fissure extends from the upper to the under surfaces of the hemispheres and completely separates them, but its middle portion separates them for only about one-half of their vertical extent; for at this part they are connected across the middle line by a great central white commissure, the {corpus callosum [FMA61946:Genu of corpus callosum; FMA61947:Body of corpus callosum; FMA86464:Corpus callosum]}. 40