comparatively larger than the maxillary. At birth the ethmoidal region is double the height of the maxillary region, this difference gradually diminishing until, at the seventh year, the two portions become of about equal height as in adult life. In childhood also the longitudinal section of the nose is relatively smaller, as compared to the transverse section, than in adults. At about the sixth year, as the alveolar border, which is to contain the three molar teeth, develops, the upper jaw becomes pushed forward to make room for it, and the nose at the same time increases in length, attaining its full development about the twentieth to twenty-fifth year, corresponding to the eruption of the wisdom teeth. In infancy the inferior meatus is low and narrow, and the lower border of the inferior turbinate is in contact with the floor of the nose, so that the middle meatus alone is free for respiration. At the third year, after the first dentition, the inferior meatus begins to develop, but remains very narrow until after the seventh year. This late development of the inferior meatus and upper jaw helps to explain the serious results which may follow nasal catarrh and obstruction in the early years of life.

THE ACCESSORY SINUSES.

The accessory sinuses and air cells of the nose are divided into two sets according to the position of their openings: the cavities opening into the middle meatus of the nose, viz. the maxillary antrum, the anterior

FIG. 10.-SHOWING THE RELATIONS OF THE ACCESSORY SINUSES TO THE SURFACE. The anterior walls of the frontal sinuses, part of the roof and outer wall of the orbit, and the outer walls of some of the ethmoidal cells and of the maxillary antrum have been removed. a. The maxillary antrum; b. nasal fossae; c. middle ethmoidal cells; d. frontal sinus.

ethmoidal cells, and the frontal sinus, are known as the anterior set; and the cavities opening above the attachment of the middle turbinate, viz. the posterior ethmoidal cells and the sphenoidal sinus, as the posterior set.

The maxillary antrum, the largest of the accessory sinuses of the nose, is situated in the body of the superior maxilla. It is irregularly pyramidal in shape, the apex being formed by the malar process and the base by the outer wall of the nose.

The inner wall separates the antrum from the inferior meatus of the nose below and from the middle meatus of the nose above, being traversed on its nasal aspect by the attachment of the inferior turbinate. It is slightly convex towards the antrum from above downwards, and very markedly so from before backwards. It consists of thick and dense bone where it joins the nasal floor, and the anterior angle formed by the junction of the inner and anterior walls is a specially strong buttress of bone, but it rapidly diminishes in thickness as it passes upwards and backwards, and the greater part of the inner wall is very thin. Near the maxillary ostium the bone is often defective in places, the openings being filled merely by membrane. At the extreme upper part of the inner wall the antrum communicates with the nose through the posterior end of the hiatus semilunaris by a small rounded or oval opening. In the skeleton this opening is large and irregular, but in the natural state it is partially closed by membrane, and varies in size from 6-10 mm. long and 2–6 mm. in vertical breadth. Occasionally it takes the form of a long narrow slit. The position of the opening concealed by the uncinate process renders catheterization of the sinus through the anterior nares exceedingly difficult, and generally impossible.

Below the posterior end of the uncinate process and between it and the upper edge of the inferior turbinate may be seen in some 10 per cent. of cases one, or occasionally two, accessory openings leading directly into the antrum. These openings are usually circular and larger than the normal ostium. In the upper and anterior part of the inner wall runs the nasal duct, forming a rounded projection in the antral cavity.

The floor of the antrum is formed by the alveolar border of the superior maxilla and comes into close relationship with the teeth, especially with the molars. The roots of the first molar, and occasionally also of the adjacent teeth, may protrude into the antrum as small conical projections on its floor, and are separated from the cavity merely by a very thin plate of bone or, occasionally, by membrane only. As the antrum extends forward it comes into relation with the bicuspid teeth, the roots of which however are generally separated from the cavity by a considerable thickness of bone. Rarely the antrum may extend as far forwards as the canine tooth. The level of the floor of the antrum as compared with the floor of the nose varies. It is said to be generally on the same level in men, and lower in women, but this difference is extremely doubtful. Its posterior part is usually on a higher level than the floor of the nose.

The anterior or outer wall of the antrum corresponds externally to the canine fossa, a depression extending from the ridge formed by the socket

of the canine tooth in front to the malar bone behind. The bone forming it is usually thin, but may be 2 millimetres thick. It is never so thin as that forming the inner wall, and is therefore not so easy to puncture with a trochar. When the canine fossa is deeper than normal, it is probable that the antrum will be proportionately smaller and not extend so far forward.

The roof of the antrum, which separates it from the orbit, is a thin plate of bone. In it runs the canal for the infra-orbital vessels and nerve, and near the ethmoidal border it may contain part of an ethmoidal cell. (Logan Turner.) The posterior wall which separates the antrum from the zygomatic fossa is very thin and of no surgical importance. Both these walls may show congenital perforations. The apex of the antrum, where the malar bone articulates with the maxilla, is very thick and strong.

FIG. 11.-A SEMI-DIAGRAMMATIC FIGURE SHOWING ASYMMETRY OF THE ANTRAL CAVITIES. a. Normal antrum; b. extremely small antrum which it would be impossible to puncture from the alveolar process and extremely difficult to do so from the inferior meatus.

The cavity of the antrum varies much in size. On an average the largest diameters are about 35 millimetres vertical, 25 transverse and 32 antero-posterior. In my experience these cavities are generally symmetrical, a small antrum on one side corresponding to a small one on the other. Ziem and Zuckerkandl state that the antrum may be limited to a mere slit, or to a rounded cavity lying opposite the middle meatus of the nose, its lower part, corresponding to the inferior meatus, being entirely undeveloped. Some clue to this rare state of affairs may usually be gained by external examination. In the slighter cases there may only be an unusually deep canine fossa; in the more marked I have found in addition to a deep canine fossa an extremely high-arched palate and a narrow, high alveolar border (see Fig. 11). If this ill development be limited to one side the face will probably be asymmetrical. These small sinuses may give rise to great difficulties both in the diagnosis and treatment of antral disease. They are dark to transillumination owing to

the density of the bone, and it may be impossible to reach them either by drilling through the alveolar margin or by puncture through the inferior meatus of the nose.

In my clinical experience these small cavities have only been met with in association with a thin narrow face. Macdonald states that the antrum is often small in cases of atrophic rhinitis, and certainly in these cases the outer wall of the inferior meatus of the nose may seem to curve more outwards, but the loss of width thus produced is more than compensated for by increased width of the face.

The interior of the antrum is often more or less divided up by bony septa and membranous folds. Zuckerkandl states that it may be divided into two separate cavities, but this is extremely rare. I have one specimen showing such a condition, and Logan Turner has once met with an almost complete septum. Grüber has found five complete divisions in two hundred specimens. Cryer regards these second cavities. as ethmoidal cells. Frequently the septa are so large that their removal is required to obtain free drainage in cases of suppuration. The antral cavity may also be irregularly enlarged by a local bulging out of its walls in almost any direction. The ridge of bone carrying the infraorbital vessels and nerve almost constantly cuts off a part of the antrum in its upper and inner part, thus forming the infraorbital cell (Cryer).

Development of the Antrum. The antrum is present as a very small slit-like cavity at birth, being 1-3 mm. in height by 7 mm. in anteroposterior diameter. It gradually increases in size as the eruption of the milk teeth proceeds. At six years it forms a more or less round cavity lying opposite the middle meatus of the nose, measuring 5-8 mm. in diameter, and extending outwards beneath the orbit as far as the infraorbital canal. It is separated from the hard palate and alveolar process by a mass of cancellous bone in which lie the germs of the permanent teeth (see Fig. 9). This general arrangement continues until the eruption of the permanent teeth, that is until about the seventh year, when the cavity commences to extend downwards towards the hard palate and alveolar process, gradually attaining its pyramidal shape and adult dimensions with the complete development of the upper jaw.

The structure of the upper jaw at the seventh year, consisting mainly of a large mass of cancellous bone, is well shown in Fig. 9. The development of the antrum has an important surgical significance, especially in reference to certain conditions which have been described as empyemata of the maxillary antrum occurring at early ages. These are really cases of osteomyelitis of the upper jaw, the true pathology of which has been completely misunderstood (see Chap. XVIII). It is also necessary to bear in mind the development of the upper jaw in order to understand the irregularities in its formation produced by obstruction to nasal respiration (see Chap. IV).

Frontal Sinus. The frontal sinus is formed by the separation of the inner and outer tables of the frontal bone in the supra-orbital region, and consists of a vertical portion extending upwards on to the forehead, and a horizontal portion extending backwards over the orbit. It is an irregular, pyramidal cavity, with its apex at its highest point in the frontal bone, its base formed by the roof of the orbit, and with three walls, an anterior, a posterior, and an internal. The last-named wall separates the two frontal sinuses, and is consequently often termed the sinus septum (see Fig. 10).

The anterior wall is convex outwards, both from above downwards and from side to side. Its thickness varies considerably in different skulls, ranging from 2–6 mm. It is often stated, and the statement is emphasized, that this wall contains no diploë, or that traces at most are present; but repeated observations have convinced me that diploic tissue is constantly present, although often in small amount (see Fig. 14).

The posterior wall is usually very thin, -1 mm. in thickness, and is composed of dense brittle bone with no cancelli. It is convex towards the sinus. Its posterior surface is indented by the convolutions of the frontal lobe of the brain.

The internal wall, or sinus septum, is very thin, but almost always complete. In one hundred and four skulls Tilley found it complete in all. Lothrop saw it perforated only twice in one hundred and eighty specimens. Turner found it always complete, and Bosworth is evidently in error when he states that the sinuses frequently communicate. In cases of suppuration, however, the septum may become perforated, and this is probably not very rare. I have three times seen this; and Luc, Tilley, and others have recorded a similar condition. The lower part of the septum is usually in the middle line: as it extends upwards it may be very deflected, or become almost horizontal. If in a skull such as that shown in Fig. 12, an attempt had been made to perforate the right frontal sinus above the supraorbital margin, although the opening was made well to the right of the median line, it would have been quite possible to have opened the left frontal sinus. In rarer cases the septum is twisted so that one cavity may partially overlap the other.

The inferior wall consists of a large outer or orbital portion forming the roof of the orbit, and a small inner or nasal portion forming the roofs of some of the anterior ethmoidal cells. The orbital portion is very thin, is convex towards the sinus, and internally bends abruptly downwards to join the lamina papyracea of the ethmoid. It is perforated by a small vein. near its inner end. The nasal portion of the floor is a small irregular surface composed of very thin bone separating the sinus from a variable number of anterior ethmoidal cells. The inferior wall of the frontal sinus is the thinnest, and is consequently the commonest seat of perforation or bulging, which often occurs in the neighbourhood of the small vein above mentioned. It is here also that tenderness on pressure should be sought