As the sieve plate grows these non-cellulose regions swell and gradually become converted into the same kind of mucous substance as that contained in the tube; the two cells are thus placed in open communication.
Forms and in terrestrial genera such as Cyclostoma; (2) the anterior pedal gland opening into the anterior groove of the foot, generally present in aquatic species; (3) dorsal posterior mucous glands in certain Cyclostomatidae.
In the same way, the reflex act of coughing is useful in removing either foreign bodies or excessive secretion from the air passages; but when the mucous membrane of the respiratory tract is irritated and inflamed, it produces a feeling of tickling and a desire to cough sometimes very violently; yet the coughing simply tends to exhaust the patient, because there is really little or nothing to bring up. The same is the case in inflammation of the lung substance itself.
The treatment of inflammation of mucous membrane is based upon the same principles as inflammation of the skin, and there too we usually associate means (I) for removing microbes, (2) for destroying them, (3) for lessening the irritation they produce, and (4) for repairing any mischief they have done.
For inflammation of the mouth a similar combination is used as a mouth wash, in the throat as a gargle, and in the nose as a wash and sometimes as an ointment or spray, the ointment possessing the advantage of protecting the delicate nasal mucous membrane from irritation by stopping the entrance of irritant dust into the nasal cavities.