1, Exit of olfactory nerve.
Owing to the small size of the olfactory lobes the anterior arms of the latter commissure are wanting.
The olfactory organ is poorly developed, and it is still a question whether birds possess much power of smell; many are certainly devoid of it.
The olfactory perceptive membrane is restricted to the posterior innermost region of the nasal chamber, where it covers a slight bulging-out prominence on the nasal wall.
In cormorants (Phalacrocoracidae), and especially in Sula, where the nasal slits become completely closed up, and the greater portion of the nasal cavity is also abolished, being restricted to the olfactory region with its unusually wide choanae.
These segments are abundantly supplied with elongate tooth-like projections connected with nerve-endings probably olfactory in function.
Nr, Olfactory nerve.
R, Olfactory organ.
Near to each rudimentary ctenidium Spengel has discovered an olfactory patch or osphradium (consisting of modified epithelium) and an olfactory nerve-ganglion (fig.
It will be remembered that, according to Spengel, the osphradium of mollusca is definitely and intimately related to the gill-plume or ctenidium, being always placed near the base of that organ; further, Spengel has shown that the nerve-supply of this olfactory organ is always derived from the visceral loop. Accord ingly, the nerve-supply FIG.
- A, Section in a plane vertical to the surface of the neck of Patella through a, the rudimentary ctenidium (Lankester's organ), and b, the olfactory epithelium (osphradium); c, the olfactory (osphradial) ganglion.
Pericardium, and is therefore a typical o, Olfactory ganglion, nephridium, was not known.
9, 10) of _ the nervous systems of ` Patella and of Haliotis, e as determined by Spengel, show the identity in the origin of the nerves passing from the visceral loop to Spengel's olfactory ganglion of the fig..
Limpet, and that of the g ' nerves which pass from the visceral loop of Haliotis to the olfactory patch or osphradium, which lies in immediate relation on the right and on the left side to the right and left gill-plumes (ctenidia) respectively.
O, o, Right and left olfactory ce.pl, The cerebro-pleural conganglia and osphradia re nective.
Pbr, Parabranchia (= the osphradium or olfactory patch).
Spengel showed that the parabranchia of Gastropods is the typical olfactory organ or osphradium in a highly developed condition.
Dium or olfactory Yet in some Pectinibranchia (Paludina) organ).
The Heteropoda are further remarkable for the high development of their cephalic eyes, and for the typical character of their osphradium (Spengel's olfactory organ).
Beneath the ciliated groove is placed an elongated ganglion (olfactory ganglion) connected by a nerve to the supraintestinal (therefore the primitively dextral) ganglion of the long h, k, m, Stomach.
In front, near the anterior attachment of the gill-plume, is the osphradium (olfactory organ) dis h covered by J.
Spengel, yellowish in colour, in the typical position, and overlying an olfactory ganglion with typical nerve-connexion (see fig.
The osphradium (olfactory organ of Spengel).
43) shows the nerve connecting this abdomino-visceral ganglion with the olfactory ganglion of Spengel.
Sp, Abdominal ganglion which represents also the supra-intestinal ganglion of Streptoneura and gives off the nerve to the osphradium (olfactory organ) o, and another to an unlettered socalled " genital " ganglion.
On account of the shortness of the visceral loop and the proximity of the right visceral ganglion to the oesophageal nerve-ring, the nerve to the osphradium and olfactory ganglion is very long.
Krohn posite to it is the visceral ganglion of in Marsenia =Echino- the right side, which gives off the long spira) there may be a nerve to the olfactory ganglion and break at a later stage, osphradium o.
The nautiloid shell In Planorbis and in Auricula (Pulmonata, formed on the larva allied to Limnaeus) the olfactory organ is being cast, and a new on the left side and receives its nerve from shell of a different form the left visceral:ganglion.
In their simpler condition they are long and many-jointed, the segments bearing numerous olfactory and tactile nerve-endings.
It is said that 13,000 such olfactory organs are present on the feeler of a wasp, and 40,000 on the complex antennae of a male cockchafer.
Nez), the organ of the sense of smell in man and other animals (see Olfactory System).
Left olfactory ganglion (parieto-splanch nic).
C, Olfactory (osphradial) ganglionpair.
A pair of eyes lie dorsally and behind them is a b closed circlet, often pulled out into various shapes, of modified epidermis, to which an olfactory function has been attributed.
In addition to the eyes and the olfactory circle on the head scattered tactile papillae are found on the ectoderm.
138) imagined it merely "to contain an infinity of nerves, disposed like net-work, all of which lead immediately to the nostrils," and add to the olfactory faculty.
One osphradium or branchial olfactory organ is usually present on each side, on either side of the anus on the inner wall of the mantle, near the base of the last gill.
The regions of the cortex, whose conduction paths are early completed, may be arranged in groups by their connexions with sense-organs: eye-region, ear-region, skin and somaesthetic region, olfactory and taste region.
One of the most puzzling features in its structure, and, at the same time, one of the greatest obstacles to the view that it is essentially primitive and not merely a degenerate creature, is the entire absence of the paired organs of special sense, olfactory, optic and auditory, which are so characteristic of the higher vertebrates.
Von Kdlliker's olfactory pit.
Each of the visceral ganglia is connected or combined with an olfactory ganglion underlying an area of specialized epithelium, which constitutes the olfactory organ, the osphradium.
Exumbral) face of the lappet there is frequently a patch of sensory ciliated epithelium regarded as olfactory in function and termed the olfactory pit (fig.
A, Superior or aboral olfactory A, Superior or aboral olfactory ML, Marginal lappets.
A radial vertical plane so as B, Inferior or adoral olfactory to pass through the long axis of_the tentaculocyst.
When specialized as bearers of sensory (olfactory or tactile) organs, the rami are generally elongated, many-jointed and flagelliform.
In the great majority of Crustacea the antennules are purely sensory in function and carry numerous " olfactory " hairs.
These are known as olfactory filaments or aesthetascs.
Its physiological effects are much more persistent and injurious than sulphuretted hydrogen, producing temporary paralysis of the olfactory nerves and inflammation of the mucous membrane.