Resting on the upper surface of the thalamus 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.
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.
It dips into the fissures between the convolutions, and a wide prolongation, named velum interpositum, lies in the interior of the cerebrum.
If the velum interpositum be now carefully raised from before backward, the optic thalami, third ventricle, pineal body and corpora quadrigemina are exposed.
The velum interpositum is an expanded fold of pia mater, which passes into the anterior of the hemispheres through the great transverse fissure.
A deeper dissection of the Lateral Ventricle, and of the Velum Interpositum.
To those morphologists who regard the hemisphere region or telencephalon as a primitively unpaired structure the velum is an important landmark indicating the posterior limit of the telencephalon.
In Petromyzon and Chimaera the velum is not developed.
The velum transversum is a transverse, inwardly-projecting fold of the roof of the primitive fore-brain in front of the dorsal sac.
Physiologically the velumis frequently important from the plexus of blood-vessels which passes with it into the III.
In boisterous weather, as we learn from Martial and other authors, these difficulties were so great that the velum could not be spread.
The difficulty of the undertaking has given rise to considerable discussion as to the means by which the Romans contrived to extend the velum at such a height over so great a surface, and to manage it at pleasure.
The swimming is effected by contractions of the muscular velum (the band around the inner margin of the umbrella) instead of wholly by the bell.
The lophophore bears about 20-25 tentacles, which are very slender and of moderate length; the velum at their base is narrow; as a rule the lophophore is accurately circular.
The polypide has normally about 60 tentacles, the velumat the base of which is narrow and by no means strongly festooned.
There are about 90 tentacles, which are long and slender, thevelum at their base being narrow and almost straight.
Both the velum and the tentacular sheath bear numerous minute tubercles on the external surface.
There are about 40 tentacles, the velum at the base of which extends upwards for a considerable distance without being festooned.
When the embryo is nearly ripe there appears immediately ventral to and behind the velum a shallow pit on each side of the middle line, and the two pits appear to be connected by a median transverse bridge.
The free edge of the velum is provided with long motor cilia, and its lower border with small cilia which bring the food to the mouth.
In Tergipes lacinulatus, observed by Schultze, the velum atrophies before the shell and operculum are thrown off.
At the aboral pole the epiblast becomes thickened and invaginated to form the shell-gland, and shortly afterwards the velum and foot are formed in the normal way, and a stomodaeum appears close to the ventral edge of the velum (fig.
A very rudimentaryvelum would appear, according to Leydig (No.
The velumis enormously developed in many Heteropods.
The velum next becomes reduced, and two small processes, which give rise to the lip tentacles and a second pair of gills, sprout out.
The cilia on the velum cause a rotation of the larva within the egg-capsule.
A trochosphere stage with a velum but without a shell is succeeded by a veliger stage with a still more developed velum, a dorsal shell, and a ventral foot.
In conjunction with a gradual elongation of the larva it travels to the ventral side, and is prolonged forwards to the velum as a groove.
Fresh tentacles arise, the velum and cavity of the umbrella become established, but these changes do not involve any points of very special interest.
The annulus, or remnant of velum partiale, v, Remains of volva or velum universale.
The tissue forming the line of insertion of the velum appears to me to represent the mandibular arch.
Anteriorly the cerebellum is connected with the roof of the mid-brain by a delicate membrane, the velum medullae anterius, or valve of Vieussens (fig.
It has the form of an open pit; and a series of such organs are situated along the attached edge of the velum with their apertures directed downwards.
The letter tv pointing to the base of the velum is where Scott believes the hyomandibular cleft to be situated.
Sometimes the margin of the velum is fringed and bears numerous small dependent filaments of silica, comparable to the marginal tentacles of many Medusae (Pl.
This similarity is the greater, as usually the four feet are elegantly curved and the entrance in the shell-cavity partly closed by a marginal diaphragm, comparable to the velum of the Craspedotae or Hydromedusae.
Shell campanulate, subspherical, thorny, with a prominent annular velum on the peristome.
Shell campanulate, covered with numerous curved ascending bristles, with a prominent annular velum on the peristome, similar to that of Medusetta craspedota.
Peristome prolonged into a short funnel-shaped proboscis, twice as long as the similarvelum of the latter.
In many species the peristome is broadened and its margin developed in the form of a horizontal diaphragm, which constricts the entrance into the shell-cavity, and is comparable to the velum of the Hydromedusae (Pl.
In this case the velum surrounds the ovate aperture through which the two lobes of the central capsule (dorsal and ventral) enter into the cavity of both valves.
Shell hemispherical, thorny, with a broad, alveolate velum which bears irregular hollow thorns on the inside and on the free margin (fig.
Shell campanulate, smooth, about as long as broad, and three times as broad as the constricted mouth, which is surrounded by a horizontal broad ring, like the velum of a Hydromedusa.
The hard palate, U, which forms the roof of the mouth, is extended further backwards by the soft palate, V, which hangs as the loose velum of the throat between the nasal fossae above and the fauces below.
The third exhibits the pineal body (soma konoeides) or conarium, concealed by a membrane with numerous veins, meaning that part of the plexus which is now known by the name of velum interpositum, and a complete view of the ventricles.
The velum is also provided with a circlet of twelve tantacles (in some species sixteen) which hang backwards into the pharynx; these are the velar tentacles.
In fact, Langerhans supposed that this portion of the velum acted in a manner closely resembling the action of the gnatho-bases of the prosomatic appendages in Limulus or the Eurypteridae.
The study of Ammocoetes indicates that the velum and lower lip correspond to the metastoma of the Eurypterid, i.
Conversely, the presence of these {300}hyoid tubular muscles in the velumgives evidence that the opercular segment takes part in the formation of the septum, as already suggested.
This chamber is bounded by the lower lip ventrally, the upper lip and trabecular region dorsally, and the remains of the septum orvelum laterally and posteriorly.
B) is plainly visible in the velum and at the base of the tentacles, in the very position where in the more advanced Ammocoetes muco-cartilage exists.
These segmental tubular muscles are found also in the velar folds--the remains of the septum or velum which originally separated the oral from the respiratory chamber.
At the base of the tongue is the prominent transverse fold, noted in connection with figure 7, that meets above the velum palitinum, not shown here but shown in figure 7.
Head broad, surrounded by a funnel-shaped velum or hood; no radula; dorsal appendages foliaceous.
There is a veliger stage in development, but the velum is reduced.
Ulceration of the posterior surface of the velum is marked by dark redness, and swelling of the anterior.
Sometimes it happens, that by deepening of the ulcers, the velum is perforated at one or more points, and the edge of the opening healing, a permanent deficiency remains.
The structure and office of the 'velum palati', or veil of the palate, is in the horse a perfect interposed section between the cavity of the mouth and the nose, and cutting off all communication between them.
When 'coryza' in the dog runs on to catarrh, and the membrane of the pharynx partakes of the inflammation, the velum palati becomes inflamed and thickened, but will not act as a perfect communication between the mouth and the nose.
A plate is given of a whitish membrane loosened from the velum by means of hydrochloric acid on a silver probe; it was not a slough, but a strong tenacious membrane which would bear handling and stretching without breaking.
The palate is long and narrow; its mucous surface has seventeen pairs of not very sharply defined oblique ridges, extending as far back as the last molar tooth, beyond which the velum palati extends for about 3 in.
Under ordinary circumstances the horse breathes entirely by the nasal passages, the communication between the larynx and the mouth being closed by the velum palati.
Still watching your mouth, inhale through the nose and exhale through the mouth; see how the velum moves as you do this.
In French there are four =nasal vowels= (occurring in un bon vin blanc) in which the velum hangs loose, and breath passes through nose and mouth.
It is, however, maintained by some teachers of voice production that the best vowel sounds are produced when the velum does not quite prevent the passage of air through the nose.
