lying connective tissue. It contains small vessels for the nourishment of the epithelium, and is pierced by minute canaliculi. Beneath this again is a layer of adenoid tissue, often well, often slightly marked. This tissue is greatly increased in catarrhal affections, but is probably a normal structure. The round cells are chiefly seen around the glands, but may be collected into lymphoid follicles. Below the adenoid layer are large masses of glands and venous spaces forming the bulk of the mucous membrane. The glands are racemose and mucus-secreting, and are most numerous in the posterior part of the nasal fossa. Around and below the glands are numerous large vascular spaces, forming a cavernous plexus. These venous sinuses have thick walls containing much muscular tissue. They receive their blood supply in a somewhat peculiar manner. The arterioles of the mucous membrane run up vertically towards the surface and branch extensively in the above-mentioned adenoid layer. From this the blood is again collected into small veins, which open into the large cavernous spaces. Thus the blood does not pass directly from the arteries into the sinuses, but goes through a previous capillary circulation. The mucous membrane is traversed by numerous bundles of elastic fibres, which come off from the superficial layer of the periosteum, and end in the adenoid layer of the mucous membrane. Subdividing and reuniting they form an elastic network between the glands and the cavernous sinuses. Bundles of plain muscular fibres are also found around the veins and the acini of the glands, as well as running independently through the mucous membrane. These structures have led some authors to describe the nasal mucous membrane as being "largely composed of erectile tissue," but the designation is hardly accurate. The abundance and size of the venous sinuses and the large amount of muscular and elastic fibres in the mucous membrane allow of rapid and great variations in its thickness in response to the varying needs of the respiratory function. The mucous membrane over the greater part of the ethmoidal region of the nose is intimately blended with the periosteum, while in the inferior meatus it is separated from it by the thick vascular and glandular layer above described. The mucous membrane around the ostia of the cavities in the infundibular region is very loosely attached, and tends to form folds which easily and rapidly become oedematous. The olfactory region is very small it is limited to the median side of the superior turbinate and the corresponding area of the septum, but is somewhat irregular. The mucous membrane is brownish grey, and covered by columnar non-ciliated epithelium. It contains little connective tissue, but many lymphoid cells, some of which are pigmented. It also contains many serous glands which are less branched than those in the lower region of the nose; the acini are lined, or almost filled, with small columnar cubical cells. These are the tubular glands of Bowman. The accessory sinuses are lined by a thin, pale mucous membrane covered throughout with ciliated columnar epithelium. The epithelial layer is usually two or three cells in thickness, and beneath it is a loose areolar tissue containing a few small racemose glands and blood-vessels. The deeper part of this layer is dense in structure and continuous with the periosteum covering the bone. This is my own experience and I believe that of most other observers. Wingrave, however, states that the mucous membrane is covered by a single layer of columnar epithelium which is cilitated only near the ostia of the sinuses: also that in the antrum the glands are found only on the inner wall. FUNCTIONS OF THE NOSE. The path of the air stream through the nose has been studied by Paulsen, Zwaardemaker, Scheff and Kayser, Franke and Schäffer, on models and on the dead body, and by Parker and others on the living. The results of these experiments practically agree, and show that the air in 6 5 FIG. 21.-A DIAGRAMMATIC FIGURE SHOWING THE PATH OF THE AIR STREAM THROUGH THE NOSE. 1, Frontal sinus; 2, sphenoidal sinus; 3, superior turbinate; 4, middle turbinate; 5, entrance to the middle meatus; 6, inferior turbinate. The path of the air stream is indicated by the dotted lines. A, B, C represent three whorls or eddies. inspiration does not take a straight course along the inferior meatus, but ascends in a curved direction from the anterior nares through the vestibule and atrium meatus medii into the middle and superior meatus, and then gradually descends towards the choanae. Parker in a series of cases noted the result of breathing air impregnated with the fine white dust of lycopodium. A broad band of deposited dust was seen along the septum and the outer wall of the nose ascending towards the anterior end of the middle turbinate and passing along its free edge and the corresponding part of the septum. By posterior rhinoscopy the posterior and upper border of the middle and superior turbinates and the roof of the postnasal space were seen covered with dust. The path of the expired air was observed by making the patient, while under observation, exhale ordinary tobacco smoke through the nose. The smoke was seen to pass along the inferior meatus, and in a less degree along the lower part of the middle meatus. This last observation differs from the results obtained by experiments on the dead body, in which the path of the expired air was shown to be similar to that of the inspiration, but to extend less high into the nose. Parker's experiment is probably correct, for if a small piece of wool be placed in the middle meatus, there is great difficulty in expelling it by blowing the nose, but it can quite easily be blown out if placed in the inferior meatus. The same holds true of the nasal secretion which naturally tends to accumulate in the inferior meatus. The experiments on models show that in addition to the main stream of air, one or more whorls are formed, chiefly in the lower part of the nose (Fig. 21). The best model to demonstrate the air currents is obtained by splitting a skull, removing the nasal septum, and replacing it by a glass plate. The nasal passages are blackened, and tobacco smoke is passed through the nose by the aid of an ordinary air pump. The smoke shows up well against the blackened surface. Experiments have been carried out to test the air pressure in the nose in normal respiration. Franke showed that the negative pressure of inspiration was about six millimetres, and the positive pressure of expiration about four millimetres in quiet breathing. The experiments of Goodale1 and of Scanes Spicer2 practically agree with this. Owing to the very slight variations in pressure it is advisable to use a water instead of a mercury manometer. Olfactory Functions. The olfactory sense includes not only smell, but the greater part of what is popularly known as taste. This function is of much greater importance to the organism than is perhaps generally recognised. It not only lends much to the pleasures of life, to the appetite for, and enjoyment of, food, but acts as a sentinel placed at the very entrance of the respiratory and alimentary channels to give immediate warning of the approach of unhealthy foods and atmospheres. For the proper fulfilment of the function it is necessary that the special nerve cells and centres should be intact, that the mucous membrane of the nose should be slightly moist, and that the inspired air should have free access to the olfactory region. The Respiratory Functions of the nasal mucous membrane are extremely important. 1 Boston Medical and Surgical Journal, 1896, cxxxv. pp. 457 and 487. 2 Proceedings of the Laryngological Society of London, 1902, x. pp. 7 and 30. 1. The inspired air is warmed, being raised approximately to the body temperature. It is obvious that the large extent and the arrangement of the venus plexuses of the mucous membrane are peculiarly adapted to the fulfilment of this function. The importance and action of these plexuses may be best studied clinically. On examining the normal nose the inferior turbinate appears large, round and plump, but if a little cocaine or other astringent be applied, it soon presents a sharp thin edge, and the mucous membrane becomes pale and wrinkled. In health the turbinated bodies vary in size according to the atmospheric conditions. Thus they swell when cold air is breathed so as to provide a larger blood supply to warm it, and they diminish in size when warmer air is inspired. 2. The air is saturated with moisture. The fluid is probably secreted by the glands of the nose and, to a less extent, by those of the accessory cavities and by the superficial beaker cells in the mucous membrane. It may also be partly due to exudation through the small canaliculi in the basement membrane. These two functions, for which the convoluted surfaces render the nose specially adapted, save the other respiratory organs a great amount of work. When the functions of the nose are in abeyance there is a great tendency to a dry condition of the pharnyx, larynx, and trachea, and a liability to catarrh of these regions, and probably also to pulmonary diseases. 3. The air is purified from dust and micro-organisms. This function has been studied by Heymann, Kayser, Bloch, Aschenbrand, StClair Thomson, Hewlett, and others. Most observers agree that the interior of the nose and the mucus covering the nasal mucous membrane proper are usually sterile. Thus Thomson and Hewlett found the nasal mucosa sterile in 80 per cent. of their examinations, and only a few organisms were obtained in the remainder. What becomes of the organisms in the inspired air still remains doubtful. It is probable that some of them are arrested by the vibrissae, upon which numerous bacteria are always found, and that those which reach the interior of the nose are entangled in the thin layer of sticky mucus which everywhere covers the nasal mucous membrane, and, thus held, are swept away by the movements of the cilia of the epithelium. It is possible that the nasal mucus, or the serous exudation which exudes from the canaliculi of the basement membrane, possesses a certain amount of bactericidal action as Lermoyez suggested. At any rate, when living cultures of non-pathogenic organisms are introduced into the nose, they are found to disappear rapidly. The importance of the ciliated epithelium to the well-being of the nose and to the general health can hardly be over-estimated. The action of a single cilium is extremely slight, but the aggregate effect of the myriads 1 See also Piaget, Annales des Mal. de l'Oreille, etc., 1897, xxiii. p. 117. This observer finds nasal mucus bactericidal to some organisms. of cilia within the nose must be enormous. The whole of the nasal secretion with the dust, organisms, etc., which gain entrance to it, is ceaselessly swept back towards the naso-pharynx, and the secretion of the accessory cavities is also removed entirely by this agency. Ciliated epithelium is a highly specialised cell. Its functions are easily impaired by catarrh, etc., and if it is destroyed, as by severe purulent catarrhs, by extensive operations or traumatism, its place will be taken by a lower form of epithelium, either simple cubical or squamous cells. This is an important factor in the causation of that grave disorder known as atrophic rhinitis. The large vascular sinuses which form a peculiar feature of the nasal mucous membrane, together with the bulk of the secreting glands are collected in the inferior turbinate. These structures play the chief part in cleansing, warming and moistening the inspired air. When dust or any other irritating particles gain entrance into the nose, the vascular sinuses dilate, the secretion of the glands is increased, and abundant fluid is poured out to wash the irritant away. Similar physiological responses are constantly made to meet variations in the temperature or dryness of the air. It is most important, therefore, to respect the integrity of the inferior turbinates. Parts of them may often be removed without harm resulting, but as a rule, it is worse than useless to restore nasal breathing by removing the structure upon which the value of nasal respiration mainly depends. The upper air passages will suffer less from respiration through the healthy mouth than from breathing through a nose when the inferior turbinates have been removed. The following works may be consulted: On Anatomy of the nose generally. ZUCKERKANDL. Normal u. path. Anat. der Nasenhöhle u. ihrer pneumatischen Anhänge. Wien, 1893. QUAIN'S ANATOMY. Arts. by Thane, vol. ii. part i. 1890, and Schäffer, vol. iii. part iii. 1894. Edinb. 1901. LOGAN TURNER. The Accessory Sinuses of the Nose. MIHALKOVICS. Heymann's Handbuch der Laryngol. u. Rhinol., Bd. iii., p. 1-86. Wien, 1899. HAJEK. Path. u. Therap. der entzündl. Erkrank. der Nebenhöhlen der Nase. Leipzig u. Wien, 1899. BRAUNE AND CLASEN. Zeitschrift für Anat. u. Entwicklung, 1877, ii. p. 1. GRÜNWALD. Die Lehre von den Naseneiterungen, 2te Aufl., München, 1896. ONODI. The Anatomy of the Nasal Cavity (Trans. by StC. Thomson). London, 1895. CRYER. The Dental Cosmos, 1903, xlv. p. 841. COFFIN. (Development of the Sinuses) Amer. Journ. of Med. Science, 1905, cxxix. p. 297, and Journal of Laryngol., 1904, xix. p. 593. Antrum. DMOCHOWSKI. Archiv für Laryngol., 1895, iii. p. 255. |