air sinuses are first found extending from the olfactory cavities into the skull-ljones. The birds' arrangement is very like that of the reptiles; olfactory and respiratory chambers are present, and into the latter projects the true turbinal, though there is a pseudo-turbinal in the upper or olfactory chamber. In mammals the olfactory chamber of the nose is variously developed; most of them are "macrosmatic," and have a large area of olfactory mucous membrane; some, like the seals, whalebone whales, monkeys and man are "microsmatic," while the toothed whales have the olfactory region practically suppressed in the adult, and are said to be "anosmatic." There are generally five turbinal bones in macrosmatic marnmals, so that man has a reduced number. The lowest of the series or "maxillo-turbinal" is the equivalent of the single true turbinal bone of birds and reptiles, and in most mammals is a double scroll, one
From A. H. Young and A. Robinson, in Cunningham's Text-Book of Anatomy.
Fig. 3.
I. Side view of the head of human embryo about 27 days old, showing the olfactory pit and the visceral arches and clefts (from His).
II. Transverse section through the head of an embryo, showing the relation of the olfactory pits to the fore brain and to the roof of the stomatodaeal space.
III. Head of human embryo about 29 days old, showing the division of the lower part of the mesial frontal process into the two globular processes, the intervention of the olfactory pits between the mesial and lateral nasal processes, and the approximation of the maxillary and lateral nasal processes, which, however are separated by the oculo-nasal sulcus (from His).
IV. Transverse section of head of embryo, showing the deepening of the olfactory pits and their relation to the hemisphere vesicles of the fore-brain.
leaf turning upward and the other down. Jacobson's organ first appears in amphibians, where it is found as an anteroposterior gutter in the floor of the nasal cavity, sometimes being close to the septum, at other times far away, though the former position is the more primitive. In reptiles the roof of the gutter closes in on each side, and a tube is formed lying below and internal to the nasal cavity, opening anteriorly into the mouth and ending by a blind extremity, posteriorly to which branches of the olfactory and trigeminal nerves are distributed. In the higher reptiles (crocodiles and chelonians) the organ is suppressed in the adult, and the same applies to birds; but in the lower mammals, especially the monotremes, it is very well developed, and is enclosed in a cartilaginous sheath, from which a turbinal process projects into its interior. In other mammals, with the exception of the Primates and perhaps the Chiroptera, the organ is quite distinct, though even in man, as has been shown, its presence can be demonstrated in the embryo. The special opening through which it communicates with the mouth is the foramen of Stensen in the anterior palatine canal.
See J. Symington on the organ of Jacobson in the Ornithorynchus, P. Zool. Soc. (1891), and in the kangaroo, J. Anat. and Phys., vol. 26 (1891); also G. Eliot Smith on Jacobson's organ, Anatom. Anzeiger, xi. Band No. 6 (1895). For general literature on the comparative anatomy of the olfactory system up to 1906, see R. Wiedersheim's Comparative Anatomy of Vertebrates, translated and adapted by W. N. Parker (London, 1907). (F. G. P.)
Diseases of Olfactory System
External Affections and Injuries of the Nose.—Acne rosacea is one of the most frequent nasal skin affections. In an early stage it consists of dilatation or congestion of the capillaries, and later of a hypertrophy of the sebaceous follicles. This may be accompanied by the formation of pustules. In an exaggerated stage the sebaceous glands become overgrown, forming large protuberant nodular masses over which the dilated capillaries are plainly visible. This condition is termed lipoma nasi (rhinophynia or hammer nose), though there is no increase in fatty tissue. Nasal acne occurs mainly in dyspeptics and tea drinkers, and the more advanced condition, lipoma nasi, chiefly in elderly men addicted to alcoholism. The treatment of acne is the removal of the dyspepsia with the local application of sulphur ointment or of a lotion of per chloride of mercury. Unsightly capillaries may be destroyed by an application of the galvano-cautery or by electrolysis. Free dissection of the redundant tissue from around the nasal cartilages is necessary in lipoma nasi, skin being grafted on to the raw surface.
The nasal bones are frequently fractured as the result of direct violence, as by a blow from a cricket ball or stick. The fracture is usually transverse, and may be communicated, leading to much deformity if left untreated. The treatment is the immediate reposition of the bony fragments. The old-standing cases where there is considerable depression wiring the fragments may be resorted to. In numerous cases the subcutaneous injection of paraffin may improve the shape of the organ. Deflection of the septum may also result from similar injuries, and lateral displacement may cause subsequent nasal obstruction and require the straightening of the septum. Lesions involving considerable loss of substance due to injury or to syphilitic or tuberculous disease have led to many methods being devised to supply the missing part. In the Indian method of rhinoplasty a flap is cut from the forehead, to which it is left attached by a pedicle; the flap is then turned downwards to cover the missing portion of the nose; when the parts have united, the pedicle is cut through. In the Italian operation devised by Tagliacotius (Taglia cozzi), a flap was taken from the patient's arm, the arm being kept fixed to the head until the flap has united.
Diseases of the Interior of the Nose.— Epistaxis or bleeding of the nose may arise from many conditions. It is particularly common in young girls at the time of puberty, being a form of vicarious menstruation. It also occurs in cerebral congestion, heart disease, scurvy, haemophylia, or as a sign of local disease. The treatment will depend upon the cause. In patients with high arterial tension epistaxis may be of direct benefit. In other cases rest on the back may be tried, with the local application of tanno-gallic acid or hazelin or adrenalin, either in a spray or on absorbent cotton. If these should not stop the hemorrhage the nose must be plugged. In cases which arise from specific forms of ulceration, such as tuberculosis and syphilis, the area should be rendered anaesthetic by cocaine, the bleeding points found, and the vessels obliterated by the electrocautery. Polypi in the nasal passages are also a frequent cause of epistaxis.
Rhinitis, or inflammation of the mucous membrane of the nose, occurs both in acute and chronic forms. Of the acute the simple catarrhal form termed "coryza" forms the widely known "cold in the head." The tendency of acute coryza to affect entire families, and to be communicable from one person to another, points to its infectious nature, though probably some predisposing condition of health is necessary for its development. It is considered proved that the symptoms are due to the presence and development of
