Nose And Throat Anatomy Of The Upper Air-Passages, Including Histology And Embryology

By HARRISON ALLEN, M. D., LL.D., AND ARTHUR A. BLISS, A. M., M. D.,
OF PHILADELPHIA.
EMBRYOLOGY OF THE NOSE, PHARYNX, LARYNX, AND TRACHEA.
By DR. ARTHUR AMES BLISS.

The Nose. The development of the nose begins about the fourth week of fetal life.

On either side of the fore brain the epiblast becomes thickened, and in the center of the olfactory area thus formed a depression appears, the olfactory depression. This assumes a pyriform shape, the larger opening external, the smaller extending backward as a groove toward the buccal invagination, where, very early, appear the rudiments of Jacobson's organ.

The rudimentary base of the nose, the fronto nasal process, appears in the median line at the lower margin of the fore brain (Fig. 529). A depression exists in the center of this process, and on either side of the depression are the mesial nasal processes, their bases being united to the fronto nasal process, while their free margins terminate in tubercles the globular processes. These eventually approach one another until they unite in the median line and form the intermaxillary process and middle portion of the upper lip. A depressed surface is left between them, and from this is formed the lower part of the nasal septum. During this development the globular processes extend backward, also bordering the space which will become eventually the roof of the mouth (Fig. 530). This backward extension constitutes the nasal laminae, by the development of which the nasal septum is completed. Two processes, the lateral nasal processes, with bases attached to the forebrain on either side, external to the fronto nasal process, grow forward around the olfactory depressions, unite in the median line, and form the ale nasi. In their development they meet the maxillary processes, also growing forward to the median line, and between the maxillary processes and the lateral nasal processes is found a groove on either side of the bead, extending from the eye to the nose the lacrymal groove. The maxillary processes as they approach one another come in contact and unite with the free ends of the globular processes, a junction which, together with the intermaxillary proms, forms the lip and upper jaw, thus making the division between the anterior part of the nasal passage and the buccal cavity (Fig. 531). Posterior to this now closed anterior part, the olfactory depressions still open into the mouth; but from the outer sides of these depressions processes are thrown out (Fig. 531) which develop into the turbinal bodies, while gradually the developing palatine processes of the superior maxilla, outgrowths from the embryonic maxillary processes, approach the lower part of the nasal septum, and unite with it and with one another to form the roof of the mouth and floor of the nose. The Hares and buccal cavity are thus 'separated from one another (Fig. 532), except in the extreme pos¬terior part of the nasal passages, where, in the naso pharynx, is found the free opening from the nares to the oro pharynx.

The Mouth, Pharynx, Larynx, and Trachea. In the process of evolution of the embryo from the blastoderm the three embryonic layers gradually enfold three distinct cavities, called the fore gut, the hind gut, and, between them, a space which long remains in free communication with the yolk sack. The cephalic portion of the embryo is bent at a right angle around the anterior part of the fore gut. Below, the latter is bounded by the heart. A thin epithelial membrane separates the fore gut from the involution of the epiblast which forms the buccal cavity, or stomodaum. This deepens, projecting upward into the angle between the fore and mid brains, where the pituitary body is formed; the epithelial septum between the buccal cavity and the fore gut disappears; and the process of development already described in treating of the growth of the Dose completes the formation of the face and mouth. The anterior part of the fore gut, the area of the pharynx, enlarges, and the hypoblastic layer throws out four projections on either side in order from above downward. Opposite these outgrowths the epiblastic layer projects inward, and four clefts in the pharyngeal wall are thus formed, the cephalic visceral clefts. About them the pharyngeal wall thickens into five curved ridges, the cephalic visceral arches. A forked elevation termed the furcula separates the second and third visceral arches (Fig. 533). A groove passes through its center, and immediately in front of this, in the receding angle between the two arms of the second arch, a tubercle projects, and the tubercle impar (see Fig. 533). The second and third arches coalesce at their receding angles to form one mass with four projecting arms. The latter grow forward into a V shaped projection, enclosing the tubercle impar and uniting into one mass to form the tongue. The epiglottis is developed from the furcula, and from it also develops the ary epiglottic folds and arytenoid cartilages. The groove seen in its center extends to the entrance of the larynx.

Of the visceral clefts the first, called the hyomandibular cleft, is an important element in the formation of the Eustachian tube and middle ear. The median base of the branebial rudiments gradually separates from the esophagus, serving as a partition wall between the latter and the larynx .and trachea. ANATOMY or THE NASO PHARYNX, PHARYNX, LARYNX, AND TRACHEA.

The Pharynx. The pharynx is the common entrance to the respiratory and digestive tracts. For purposes of description and, also, clinically, it may be divided into three distinct areas the naso or rhino pharynx, the oro pharynx, and the laryngo pharynx (Fig. 536).

The rhino pharynx lies immediately posterior to the nasal chambers or posterior nares. It is slightly quadrilateral in shape, its transverse diameter measuring about one and three eighths inches, while its antero posterior and vertical diameters are about three quarters of an inch.

In front it is bounded by the two oval openings of the posterior nares, with the rear margin of the vomer in the median line (see Figs. 535 and 562). This margin is thin below, but widens into two lateral arms or wings above, where the vomer is attached to the body of the sphenoid bone. The upper surface of the naso pharynx or vault is formed by the basilar process of the occipital bone and a portion of the body of the sphenoid bone (see Fig. 434). On either side it is flanked by the pharyngeal openings of the Eustachian tubes (see Figs. 451, 562). Its floor is formed by the soft palate and by the opening into the oro pharynx.

The months of the Eustachian tubes _present prominent projections on either side of the naso pharynx, formed mainly from the cartilage of the tube. The orifice of each tube lies about on a plane with the posterior margin of the vomer. Its exact position varies in different subjects. A well defined ridge of cartilage roofs the tube and forms its posterior lip. The ridge is less prominent in front than above and behind the Eustachian opening. It is not seen below the orifice. The mucous membrane of the naso pharynx forms a distinct fold where it is reflected over the posterior lip of the tube and passes thence to the pharynx. Luschka terms this fold the plica salpingo pharynqea. A similar fold, less marked however, extends from the anterior lip of the tube to the soft palate, termed by Luschka the plica salpingo palatina. A crescent shaped depression is seen immediately behind the posterior lip of the Eustachian opening the fossa of Rosenmuller. It is of considerable clinical importance, as it is a valuable guide in the introduction of a catheter into the Eustachian opening. The Eustachian openings, closed during a state of rest, are opened by the contractions of the tensor and levator palati muscles. The tensor muscle, termed also the spheno salpingo staphylinus, or dilator muscle, arises from the scaphoid fossa and base of the internal pterygoid plate of the sphenoid bone, and from the front of the entire cartilaginous portion of the Eustachian tube. Its fibers pass downward, winding around the hamular process of the sphenoid bone, and are inserted in the soft palate. Its contraction dilates the tube by drawing the anterior margin of its cartilage and the membranous front wall downward and forward (see Fig. 450). The levator palati muscle arises from the petrous portion of the temporal bone and from the cartilaginous part of the Eustachian tube. Its fibers are inserted by a broad tendon into the median line of the soft palate (Fig. 535). Its function is to lift the lower wall of the Eustachian tube, which tends to separate the lateral walls and open the tube. The palato pharyngeus muscle, described later, is also partially attached to the cartilaginous part of the Eustachian tube. It acts as an aid to the levator palati muscle.

The covering of the naso pharynx consists of mucous membrane richly supplied with mucous glands and having a covering of columnar ciliated epithelium. Beneath the mucous membrane lies a dense fibrous aponeurosis, which is the upper part of the general pharyngeal aponeurosis. It is firmly attached to the basilar process of the occipital bone and to the petrous portion of the temporal bone.

In certain subjects suffering from sclerotic or atrophic rhinitis, a welldefined ridge is seen to project from the posterior and lateral walls of the naso pharynx about at the level of the free margin of the soft palate. Acting with the palate, when the latter is raised, this ridge becomes very prominent, “Passavant's cushion,” and helps to close the opening from the nasoto the oro pharynx, as strings pucker up and close the month of a purse.

Its existence often interferes with the escape of secretions downward from the naso pharynx, and thus causes their retention and crust formation at this point. This ridge is caused by the prominence of the contracting upper fibers of the superior constrictor muscle of the pharynx as they pass downward and backward along the free superior margin of the muscle from its wide attachment above to the median line of the pharyngeal aponeurosis.

The lymphoid structure in the naso pharynx is of great clinical importance. This tissue is a part of “the lymphoid ring “of the pharynx. It is located in the center of the superior and posterior walls of the naso¬ pharynx, and spreads laterally on either side to the recesses above the lips of the Eustachian openings and even into the fossa of Rosenmuller. Normally, it is about one fourth of an inch in thickness, and should not cause occlusion of the naso pharyngeal space or pressure upon the Eustachian opening. In structure it is a collection of lymph follicles, or adenoid tissue, held together in a loose fibrous network of connective tissue and covered with mucous membrane having columnar ciliated epithelium. In rather rare instances an opening is observed leading to a closed sac in the center of the mass, termed the bursa pharyngea. Its very existence as a normal structure has been questioned by many writers. When present it is doubtless an abnormal phase of development (see page 949).

The blood supply of the naso pharynx comes through the ascending pharyngeal artery, a branch of the external carotid; through the ascending palatine, a branch of the facial; and through the spheno palatine, a branch of the internal maxillary (see Fig. 549).

The veins pass into the internal jugular vein.

The nerve supply comes from the superior maxillary nerve (second branch of the fifth nerve) and from the pneumogastric and glosso pharyngeal nerves.

The Oro pharynx and Laryngo pharynx. The oro pharynx may be said to extend downward from the projection on the posterior wall of the pharynx caused by the tubercle on the anterior arch of the first cervical vertebra. An imaginary line from this point to the base of the uvula serves as a dividing line between the naso and oro pharynx (Fig. 534). We shall refer to the oro and laryngo pharynx as the pharynx proper. It is quadrilateral in shape, its antero posterior diameter being much more narrow than its transverse. Its anterior wall extends from the base of the uvula and the free margin of the soft palate downward across the oral cavity to the posterior extremity of the greater horn of the hyoid bone. Its posterior wall extends from the tuberosity on the anterior arch of the first cervical vertebra to the orifice of the esophagus. Its lateral walls are in relation with the common and internal carotid arteries, the internal jugular vein, the sympathetic nerve, and the eighth and ninth cranial nerves.

In general structure the pharynx is a musculo membranous sac consisting of three layers, an inner mucous membrane, a middle fibrous layer, and an outer layer of muscular tissue.

The mucous membrane of the pharynx is thin, and in the naso and oropharynx adheres closely to the fibrous layer beneath it. Like the mucous covering of the alimentary tract in general its epithelial layer consists of squamous cells. As the pharyngeal vault is approached the epithelium changes more and more to the type found in the respiratory tract, and, in the purely respiratory tract of the naso pharynx, it becomes columnar and ciliated. Two varieties of glands are found in' the pharyngeal mucous membrane. One, the ordinary muciparous gland, exists in greatest number in the oro pharynx and upon the soft palate. The glands of the second variety lie deeper in the mucous membrane and belong to the lymphoid type. These ductless follicles are scattered irregularly throughout the mucous membrane, but exist in greatest number along the lateral surfaces of the pharyngeal wall, lying closely behind the so called posterior faucial pillars.

The fibrous layer of the pharynx, or pharyngeal aponeurosis, external to the mucous membrane is, in the upper pharyngeal region, very dense in structure; but in the laryngo pharynx it becomes thinner, until it is scarcely to be traced at the entrance of the esophagus. In"tbe naso pharynx it adheres closely to the basilar process of the occipital (Fig. 536).

The muscular coat of the pharynx, its third and deepest layer, consists of three flat constrictor muscles, so arranged as to form a sheath around the posterior and lateral walls.

The superior constrictor muscle arises from the lower portion of the margin of the internal pterygoid plate and from its hamular process, from the portion of the palate bone adjacent and from the reflected tendon of the tensor palati muscle, from the pterygo maxillary ligament, from the alveolar process of the superior maxilla above the posterior extremity of the mylo hyoid ridge, and from the sides of the tongue, where a few fibers of the superior constrictor are in connection with the genio hyoglossus muscle. From this very widely distributed attachment the fibers of the main body of the muscle curve backward to be attached to the raphe in the median line of the pharyngeal aponeurosis. The superior fibers curve backward and upward, blending with the fibrous aponeurosis which covers the pharyngeal vault, and is attached to the pharyngeal spine of the occipital bone. The projecting ledge caused by the free tipper margin of this muscle, already mentioned, assists in closing the naso from the oro pharynx, and is of clinical importance in some cases of atrophic rhinitis. The superior constrictor is quadrilateral in form, and its fibers are thinner than are those of the middle and inferior constrictors. Its inferior fibers are partially overlapped by the upper fibers of the middle constrictor.

The middle constrictor, arising from the greater and lesser horns of the hyoid bone and from the stylo hyoid ligament, is a fan shaped muscle, its fibers passing up, back, and down to the median raphe.

The inferior constrictor, the largest of the three, arises from the thyroid and cricoid cartilages, its attachment to the thyroid being at the inferior cornua and along the oblique lines on the sides of the ale and on the surfaces immediately behind these lines, almost as far as the posterior borders. From the cricoid cartilage it arises in the interval between the crico thyroid muscles in front and the facet for the crico thyroid articulation behind. The fibers pass backward and slightly upward, and are attached to the raphe in the median line of the pharyngeal aponeurosis, the ascending fibers overlapping the lower fibers of the middle constrictor, while the lower fibers blend with the circular muscular fibers of the esophagus. Beneath the constrictor muscles are found the longus colli and the rectus capitis anticus muscles, with the cervical vertebrae beyond.

The three constrictor muscles are the chief elements in the formation of the muscular layer of the pharynx. Certain other muscles, however, contribute to the formation of this muscular coat, and are classified among the muscles of the pharynx. These are the stylo pharyngeus, the palato glossus, the palato pharyngeus, and the stylo hyoid.

The stylo pharyngeus (see Figs. 535, 53 6) is a long, narrow, muscular band, round and cord like above, where it arises from the inner side and base of the styloid process, but flattened and widened as it descends by the side of the pharynx, passing between the superior and middle constrictors. Most of its fibers terminate beneath the mucous membrane of the pharyngeal wall, some merging with fibers of the constrictor muscles. Other fibers descend farther and are inserted into the thyroid cartilage on its posterior border.

The palato pharyngeus muscle (see Figs. 534, 535) is a broad thin band, widening as it descends, apparently from the base of the uvula, and passes down and back, to be lost in the lateral pharyngeal walls. It forms with the covering mucosa the “posterior pillar of the fauces." Its superior origin is by two fasciculi in the soft palate, joining their fellows of the opposite side in the median line. It is inserted with the stylo pharyngeus into the posterior border of the thyroid cartilage. A few of its fibers spread along the sides of the pharynx and cross the latter to join, in the median line, those from the opposite side.

The palato glossus muscle (see Figs. 534, 535) forms the so called “anterior pillar of the fauces." It is a narrow fibrous band, narrower and thinner than the palato pharyngeus muscle, or “posterior pillar." Its upper attachment is the anterior surface of the soft palate. It passes in front of the tonsil downward, forward, and outward, and is inserted into the sides and back of the tongue.

Blood supply of the Pharynx. Arteries. The ascending pharyngeal arteries, branches of the external carotid, supply the constrictor muscles and the mucous membrane. They may be of abnormal size, not rarely so large as to cause a distinct pulsation on one or both sides of the pharynx, just behind the posterior faucial pillars.

The Vidian and descending palatine arteries, branches from the internal maxillary artery also supply the pharyngeal tissues, as do branches from the facial, the tonsillar, and ascending palatine arteries.

Veins. A thick network of veins is found in the fibrous layer of the pharynx, forming the pharyngeal plexus in the posterior and lateral walls. From these the blood is led by the pharyngeal vein into the internal jugular.

Lymphatics. The lymph vessels follow the course of the pharyngeal plexus and veins and enter the chain of lymphatic glands along the sheath of the carotid, terminating on the right side in the right ductus lymphaticus; on the left in the thoracic duct. Nerves. The sensory nerves of the pharynx come from the glosso pharyngeal. The motor nerves are derived from the glosso pharyngeal and pneumogastric. These, with the sympathetic, unite to form the pharyngeal plexus.

Lymphoid Structure of the Pharynx. Reference has been made already to the ductless follicles in the pharyngeal mucous membrane and to their special seats of location on the lateral and postero lateral walls of the pharynx.

At certain points in the pharynx are found conglomerate masses of lymphoid tissue, forming a continuous “lymphoid ring “around the entrance to the alimentary and respiratory tracts.

The upper segment of this ring is formed by the adenoid tissue of the naso pharynx, or “pharyngeal tonsil," already described; the lateral segments are formed by the “faucial tonsils," and the lower segment by the lymphoid tissue found at the base of the tongue, "the lingual tonsil." The faucial tonsils are small oval or almond shaped masses of lymphoid tissue, placed within the somewhat triangular space between the palato pharyngeal and the palato glossal muscles. In the normal condition they are about three quarters, of an inch in vertical length by one third of an inch in breadth. Even within normal limits, however, there is great variation in size. The free Surface of each faucial tonsil is marked by numerous round or slit like openings, arranged in two or more parallel columns, or more irregularly, which lead down into invaginations of the surface called crypts. This peculiar structure is claimed by Retterer to be the result of an ingrowing of the epiblastic membrane into the hypoblast. The epithelial elements are thus forced into a lymphoid mass, and the latter grows around the invaginations or into their walls, breaking up their outline into small, lateral pockets. The diverticula , as Harrison Allen terms the lymph follicles, are thus in the faucial tonsils arranged in groups which occasionally sink below the general surface of the mass, thus forming the crypts.

The lingual tonsil occupies the base of the tongue, being placed between this and the epiglottis. It is a smooth, soft, even mass of lymph follicles, the diverticula of which, as Allen states, are single and not in groups.

The covering of both the faucial and lingual tonsils consists of the pharyngeal mucous membrane. In many instances, however, this is underlaid by bands of fibrous tissue which more or less fully encapsulate the lymphoid masses.

The faucial tonsil is in rather close relation with the internal and external carotid arteries, the internal jugular vein, and the pneumogastric nerve. These structures, however, pass through the posterior portion of the pharyngomaxillary interspace, while the faucial tonsil occupies the anterior part of this space: thus they are safely beyond the reach of any cutting instruments which are used with skill and care in operations upon the tonsils.

The blood supply of the faucial tonsil comes from the facial artery by the tonsillar and ascending palatine; from the lingual artery by the dorsalis lingue from the external carotid by the ascending pharyngeal; and from the internal maxillary by the descending palatine branch. The most important artery is the tonsillar, springing from the facial artery. It is a small vessel in children, but in adults is of more important size. It is not apt to be wounded during cutting operations upon the tonsils, unless such procedures involve the base of these masses. The veins center into a plexus, named the tonsillar plexus. The nerves are from the fifth nerve and the glosso pharyngeal nerve.

The Larynx. The larynx forms the entrance to the respiratory tract and is, at the same time, the organ for the formation of the voice. Its function of voice production depends largely upon the vocal cords, and the general structure of the larynx is designed to protect these and to give attachment to the muscles controlling their movements.

The Cartilages. The framework of the larynx (Fig. 537) consists of the thyroid, the cricoid, and the two arytenoid cartilages, composed of true cartilage; and of the two cornicule laryngis (cartilages of Santorini), the two cuneiform cartilages (cartilages of Wrisberg), and the epiglottis, all fibro cartilaginous in structure. Above the larynx, and at the base of the tongue, which is attached to it, lies the hyoid bone (Figs. 537, 538). The hyoid bone (from the Greek u shaped), besides its important relation to the tongue and its function in serving to stretch the pharynx in its lateral diameter, serves also to give a point of fixation above to the larynx. It consists of a central body with two greater and two lesser cornua. The body is quadrilateral in form, convex on its anterior surface, concave posteriorly. It supports the two lesser cornua which project upward and backward from its superior and lateral margins. From these lateral margins beneath the lesser cornua extend backward the greater cornua, completing the half circle. From the hyoid bone muscles and ligaments pass to the epiglottis and to the thyroid cartilages, uniting it with these structures.

The thyroid cartilage (Fig. 537) (from the Greek, a shield) consists of two curved quadrilateral plates, converging anteriorly to meet in the median line, and forming a projecting angle somewhat like the prow of a ship. This angle is a prominent feature in the neck (see Fig. 534), especially in the adult male (the " Adam's apple "), standing boldly outward beneath the integument, from which occasionally it is separated by a bursa. The tipper margin of each side, or ala, of the thyroid curves downward at this point of junction, forming the thyroid notch, resembling the spout of a pitcher; and backward each descends slightly to rise abruptly at the posterior limit into a long process, pointing upward, called the superior cornu (Fig. 538). The prominent anterior angle of the thyroid is slightly concave below the thyroid notch. The lower border of each ala curves backward and generally downward and forms the lesser cornu. The posterior, free borders of the thyroid, which are rounded and thick, thus terminate, above in the greater, below in the lesser, cornua. An oblique ridge passes downward and forward across the outer surface of each ala of the thyroid, starting from a tubercle near the base of the superior cornu, and gives attachment to the sterno thyroid and thyrohvoid muscles. Back of this ridge, and including the surface to the posterior margin of each ala, is the long narrow area of attachment Of the inferior constrictor muscle of the pharynx, while to the center of the posterior margin is attached the stylo pharyngeus muscle.

The inner surface of each ala is concave, and covered in the upper and posterior portions with mucous membrane. In the receding angle anteriorly, where the two aloe unite immediately below the thyroid notch, the thyroepiglottic ligament forms the attachment of the epiglottis, and just below this, on either side, are the anterior points of attachment for the ventricular bands, or false vocal cords (Fig. 539). The true vocal cords, together with the thyro arytenoid muscles, have their anterior points of attachment immediately beneath these in the lower third of this receding angle. The lower margins of the thyroid cartilage, in their anterior and lateral aspects, give attachment to the crico thyroid membrane and to the crico thyroid muscle.

The cricoid cartilage (from the Greek, a ring) lies immediately below the thyroid (Figs. 537, 538, 540). Its anterior half is small, narrow, rounded, and convex in shape. Its superior margin rises as it extends backward, causing the cartilage to broaden toward its posterior portion, which is almost thrice as broad, in a vertical direction, as is the anterior; while it is at the same time greatly increased in thickness. On the outer lateral surface of this posterior " seal " portion of the ring are facets, one on either side, for articulation with the lesser cornua of the thyroid cartilage. On its upper surface in this posterior half are two facets, their long diameters transverse, for articulation with the arytenoid cartilages. In the median line of the broad posterior border of the cricoid is a vertical ridge for the attachment of the esophagus, with broad points of attachment on either side for the posterior crico arytenoid muscles. The outer surface of the cricoid anteriorly gives attachment to the crico thyroid ligament and to the crico thyroid muscle and to the lateral crico arytenoid muscle.

The cricoid forms the back of the larynx, as well as its lower portion, and is the base upon which the other cartilages of the larynx rest.

The arytenoid cartilages (o a pitcher) (Fig. 539) are two pyramidal cartilages which articulate with the upper margin of the thick posterior portion of the cricoid. They might be called the cartilages of the vocal cords, as the vocal cords, together with all the muscles controlling their movements (with the exception of the crico thyroid), are attached to the arytenoids. They present three surfaces, a base, and an apex for study. The inner surface of each cartilage, covered with mucous membrane, is smooth, flat, and somewhat triangular in shape, for apposition to the corresponding side of its fellow. The anterior surface is convex and gives attachment to the ventricular bands and the thyro arytenoid muscle. The posterior surface is concave and triangular in shape and gives attachment to part of the arytenoid muscle. The base is concave for articulation with the corresponding convex facet on the cricoid, and is marked by two projections or processes terminating its external and anterior angles. The longer of these is the anterior; called the vocal process, as to it the vocal cord is attached. The rounded external process is named the muscular process, and upon it are inserted the posterior and the lateral crico arytenoid muscles. The apices of the arytenoids are pointed and curve backward and inward. Each apex is crowned by a small nodule of cartilage, serving to lengthen it slightly, called the cornicula laryngis, or cartilage of Santorini. To these modules are attached the aryteno epiglottidean folds, in which, close to the outer side of each cartilage, are embedded the two small cartilages of Wrisberg, the cuneiform cartilages. They are sesamoid in character and vary greatly in size in different individuals. Two sets of sesamoid cartilages are also found occasionally, the posterior and anterior sesamoid cartilages. When present, the posterior sesamoids lie between the apices of the arytenoids and the cartilages of Santorini; the anterior are found in the extreme anterior end of the vocal cords, being attached to the receding angle of the thyroid cartilage.

The epiglottis (see Figs. 538 and 539), named from its position above the glottis, is the cover of the larynx. It is an oblong, leaf shaped plate of fibrocartilage, its upper border rounded, its lower somewhat pointed and attached by a long thyro epiglottic ligament to the receding angle of the thyroid cartilage immediately below the thyroid notch. The mucous membrane covering the anterior surface toward the base of the tongue is reflected to the sides and base of the cartilage. in two folds, the glosso epiglottic ligaments. The anterior surface curves forward slightly toward the tongue, but the position varies greatly in different subjects. The posterior surface, transversely concave but vertically rather convex, faces somewhat downward over the laryngeal entrance and is covered with mucous membrane, which at its base is thickened by the presence of adenoid tissue into a smooth, slightly prominent elevation termed the cushion of the epiglottis. Its free margin is rounded, or, especially in children, is narrowed into a curve, with the concavity downward, rendering, when in this form, a view of the interior of the larynx somewhat difficult, as the epiglottis is apt then to be more depressed than when this upper margin is broad and flattened. The epiglottis is also connected with the body of the hyoid bone on the posterior surface of the latter by a ligamentous or elastic band, the hyo epiglottic ligament. The aryteno epiglottic folds are attached to the sides of the epiglottis. Numerous pits, or depressions, are found in the body of the cartilage of the epiglottis, in which lie small mucous glands. The epiglottis being freely movable varies in position during respiration and deglutition. During respiration it maintains a somewhat vertical direction, its free margin being curved toward the base of the tongue. In the act of deglutition, however, as the larynx rises, the epiglottis is carried upward against the base of the tongue and its free margin is greatly depressed, so as to serve as a cover to the entrance of the larynx.

Ligaments of the Larynx. The thyroid cartilage is bound to the hyoid bone by three ligaments, the two lateral thyro hyoid ligaments, narrow, rounded bands of fibro elastic tissue, attached to the extremities of the superior cornua of the thyroid cartilage and extending upward to the greater cornua of the hyoid bone; also, the thyro hyoid membrane, a broad, fibroelastic membrane, attached below to the upper border of the thyroid cartilage, and above to the posterior face of the body of the hyoid bone. The superior laryngeal nerve and vessels pass through the median line of this membrane.

The thyroid and cricoid cartilages are bound together by three ligaments, the crico thyroid membrane and two capsular ligaments (see Fig. 537). The crico thyroid membrane, triangular in shape, passes from the superior margin of the cricoid cartilage in the median line and from both sides anteriorly, and is inserted in the lower border of the anterior part of the thyroid cartilage. Thick in the center, it becomes thinner on either side, and these lateral portions are joined at their insertion with the insertion of the true vocal cords. In the median line the crico thyroid membrane lies directly beneath the skin, and thus offers a ready means for effecting an artificial opening into the larynx. At this point the membrane is crossed by an anastomosis of the two small cricothyroid arteries. It is covered on its inner surface with mucous membrane. The lateral portions of the crico thyroid membrane are covered by the cricothyroid muscle and the lateral crico arytenoid muscles.

The capsular ligaments between the cricoid and thyroid cartilages bind the inferior or short processes of the thyroid to the cricoid cartilage at their points of articulation.

The arytenoid cartilages are held to the cricoid cartilage by loose capsular ligaments, also posteriorly by the small posterior crico arytenoid ligaments.

The epiglottis is bound to the hyoid bone by two ligamentous bands which extend from the sides of the cartilage, near its apex, the hyo epiqlottic ligaments, and to the thyroid cartilage by the thyro epiglottic ligament already described.

The median glosso epiglottic folds of mucous membrane unite the epiglottis to the base of the tongue.

Interior of the Larynx (Fig. 541). The general shape of the laryngeal opening is triangular with the base posterior. Looking from above into the larynx the free margin of the epiglottis is first seen, a curving surface which varies in the degree of its curvature in different subjects. Beneath, and posterior to the inner face of the epiglottis, appear the apices of the arytenoid cartilages, the small cartilages of Santorini at the apex of each, the smooth rounded swelling on the outer side of both arytenoids, paler than the red of the general mucous covering, showing the location of the cartilages of Wrisberg. These are seen to lie each in the body of a broad prominent fold, which passes in a half circle framing the sides of the laryngeal opening, one on each side, from the arytenoid cartilages upward to the side of the epiglottis. These are the aryteno epiglottic folds. Below the level of the apices of the arytenoid cartilages, two bands, covered, like the tissue already named, with mucous membrane, pass from the arytenoids forward to the receding angle of the thyroid cartilage, terminating there beneath the attachment of the epiglottis. These are the ventricular bands, or false vocal cords. They are also named the superior thyro arytenoid ligaments.

Beneath these ventricular bands, and appearing to edge their free border, although in reality below them, are seen two white bands which pass forward from the anterior angles, or vocal processes, of the arytenoid cartilages to the receding angle of the thyroid cartilage. These are the true vocal cords. Between the free margins of the vocal cords is an open space of triangular shape with the base posterior, which varies in width as the cords approach or recede from each other. This is the glottis, or rima glottidis, and through this space can be seen the anterior surface of the trachea ridged by its rings perhaps down to the bifurcation into the bronchi. Between the arytenoids, at about the level of the vocal cords, is a point of considerable clinical importance, the space between the arytenoids, or the interarytenoid space.

A free space exists between the ventricular bands and the vocal cords. This space is found to follow the under surface of the ventricular bands, extending laterally and upward between the ventricular bands and the aloe of the thyroid cartilage on either side, and to terminate anteriorly in a blind pouch. The space is called the ventricle of the larynx, and the pouch named the sacculus laryngis (Fig. 542). This entire area is lined with mucous membrane richly supplied with mucous glands.

The chink of the glottis varies in extent according to age and sex. In the adult male its length is about seven eighths of an inch. In the female it is smaller. When fully dilated this triangular shaped opening at its base posteriorly is about one half of an inch in width. At the posterior attachment of the vocal cords will be seen usually a slight indentation of a whiter color than that of the main body of the cords. This point is the extremity of the vocal process of the arytenoids. It is of some clinical interest, as these points have at times been mistaken for ulcerations or cicatrices on this portion of the vocal cords.

The free margins of the vocal cords mark the most narrow portion of the larynx. Below these the subglottic space widens, assuming the general form of the circle formed by the cricoid cartilage, at first somewhat oval in the lateral diameter, soon changing to circular as the trachea is approached. Thus a section of the entire larynx would roughly resemble an hour glass form, widening above and below, with a constriction in the center at the location of the vocal cords (see Fig. 548).

Muscles of the Larynx. The muscles of the larynx are the posterior crico arytenoid s, the lateral crico arytenoid s, the interarytenoid or arytenoid, which act as the abducting and adducting muscles of the vocal cords; the thyro arytenoids and crico thyroid, whose function it is to regulate the tension of the vocal cords ; the thyro epiglottic, aryteno epiglottic, superior and inferior, supplying some power of movement to the epiglottis; the thyro hyoid and sterno hyoid, which serve as muscles of fixation for the larynx.

The posterior crico arytenoid arises from the posterior surface of the cricoid cartilage, on either side of the median line (Fig. 539). Its fibers pass upward and outward and are attached to the muscular process of the arytenoid cartilage (Fig. 540, 5). With point of fixation on the cricoid, this muscle, by contracting, rotates the arytenoid cartilage outward by drawing its muscular process backward. The two vocal processes of the arytenoid cartilages are thus drawn away from the median line outward and the vocal cords are separated (see Fig. 665.

The lateral crico arytenoid muscles (see Fig. 540) arise, one on either side, from the tipper margin of the lateral part of the cricoid cartilage. The fibers of each muscle pass upward and backward and are inserted in the muscular processes of the arytenoid cartilages at a point just anterior to the insertion of the posterior crico arytenoid muscles. The action of the lateral crico-arytenoid muscles, being fixed at their cricoid attachments, is to adduct the vocal cords by drawing forward the muscular processes of the arytenoid cartilages, thus approximating the vocal processes of these cartilages (Fig. 665.

The arytenoid muscle is a single, square shaped muscle with two sets of fibers, the transverse and oblique. The transverse fibers, which are the deeper, are attached to the posterior surface and outer margin of one arytenoid muscle and pass transversely across to be inserted into the corresponding part of the other arytenoid cartilage (see Fig. 540, 15). The more superficial oblique fibers consist of two thin muscular slips which pass from the base of one arytenoid cartilage to the apex of the other. In some instances fibers from the oblique bands pass around the outer sides of the two cartilages and blend with the fibers of the thyro arytenoid or the aryteno epiglottic muscles. The action of the arytenoid muscle is to bring the bases of the arytenoid cartilages together, thus completing the closure of the chink of the glottis. Contraction of the lateral crico arytenoids alone leaves a small triangular opening between the cords at the interarytenoid space. This opening is closed by the contraction of the arytenoid muscle (Figs. 540 and 541). The thyro arytenoid muscles lie parallel to and slightly below the vocal cords along either side of the larynx (Fig. 540). The muscles arise, one from either side of the receding angle of the thyroid cartilage, to the outer side of the insertions of the vocal cords. Passing outward and backward the fibers ate inserted into the bases and anterior surfaces of the arytenoid cartilages and into the external surfaces of the vocal processes (see Fig. 542). Each thyro arytenoid muscle is divided into two quite distinct portions, internal and external. The internal portion follows the vocal cord closely, some of its fibers, indeed, appearing to pass into the structure of the cord. The external portion passes backward along the outer side of the sacculus laryngis, and has a broad attachment to the external surface and outer side of the arytenoid cartilage. With point of fixation at the receding angle of the thyroid cartilage, the thyro arytenoid muscles draw the arytenoid cartilages forward. The vocal cords are thus shortened and relaxed. The internal portion of this muscle, however, has an apparently contradictory action, for, by its attachment to the vocal cords, its contractions approximate the free margins of the cords and regulate their tension. This function is of importance in the production of the high notes in the singing voice. The external portion of the muscle, besides its action in shortening the cords, has also the power of compressing the sacculus laryngis. A superior thyro arytenoid muscle is sometimes described (Santorini, Luschka, Schrotter), which is viewed by some authorities as a distinct muscle. Its origin is from the receding angle of the thyroid cartilage, immediately above the origin of the thyro-arytenoid muscle. It is attached to the muscular process of the arytenoid cartilage, some fibers passing downward to the cricoid cartilage or to the crico thyroid membrane. It is quite probable that these muscular fibers, instead of forming a distinct muscle, constitute a series of oblique fibers which are, in reality, a part, of the complex thyro arytenoid muscle.

The crico thyroid muscle arises from the anterior and lateral portions of the cricoid cartilages (see Fig. 540, 9). The fibers divide into two bundles, the more anterior pass directly upward and slightly backward and are inserted into the inner portion of the lower margin of the thyroid cartilage. The more posterior fibers pass upward and backward and are attached to the thyroid cartilage at the base of the inferior cornu. The action of this muscle is to render the vocal cords tense by increasing their length, either by drawing the thyroid cartilage downward toward the cricoid, thus stretching the vocal cords and increasing their tension, or, with the thyroid cartilage as the fixed point, to draw the cricoid cartilage upward and backward, which movement, it is claimed by the advocates of this method, will elongate and increase the tension of the vocal cords. The action of this muscle is a question which is still in dispute, and we feel that it has not yet been definitely decided.

Blood supply of the Larynx. The arterial supply of the larynx comes by the superior and inferior thyroid arteries.

The superior thyroid is a branch of the external carotid. It divides before entering the larynx into two branches, the superior laryngeal and the inferior laryngeal; the latter called also the crico thyroid artery.

The inferior thyroid artery, one of the branches of the thyroid axis, supplies the muscles and mucous membrane of the posterior part of the larynx by means of its laryngeal branch, or posterior laryngeal artery.

Veins. The laryngeal veins correspond in their courses to those of the arteries. They unite into three veins, the superior, middle, and inferior thyroid veins, which in turn enter the internal jugular vein.

Lymphatics. The lymphatic vessels of the larynx collect from a thick network of vessels in the laryngeal mucous membrane into two trunks, one above the ventricle of the larynx and one below the cricoid cartilage. These trunks empty into the deep cervical lymphatic glands.

Nerves of the Larynx. The larynx derive its nerve supply from the pneumogastric nerve. The superior laryngeal branch of this nerve is the general nerve of sensation for the mucous membrane of the larynx, and is the motor nerve for the crico thyroid muscle and for the arytenoid muscle, the latter being supplied also by the recurrent laryngeal nerve.

The recurrent laryngeal nerve is the general motor nerve of the larynx.

The superior laryngeal nerve arises in the inferior ganglion of the pneumogastric. It passes downward along the sides of the pharynx to the superior margin of the thyroid cartilage. Here it divides into an external and an internal branch. The external branch of the superior laryngeal nerve passes downward beneath the sterno cleido mastoid muscle to supply the crico thyroid muscle. The internal branch pierces the thyro hyoid membrane and supplies all the mucous membrane of the interior of the larynx, as well as the base of the tongue, with sensory filaments. It sends filaments to the arytenoid muscle, and anastomoses with the recurrent laryngeal nerve.

The recurrent laryngeal nerve, sometimes named the inferior laryngeal nerve, is also a branch of the pneumogastric. On the right side of the body this nerve leaves the pneumogastric at about the level and in front of the right subelavian artery. Passing around this artery from before backward it ascends to the side of the trachea, posterior to the common carotid and inferior thyroid arteries. In winding about the subclavian artery the recurrent laryngeal nerve on the right side comes in very near relation to the apex of the right lung.

On the left side of the body the recurrent laryngeal nerve leaves the pneumogastric in front of the arch of the aorta. It passes around the aortic arch from before backward at the side of the ductus arteriosus, and passes upward to the side of the trachea. Both right and left recurrent laryngeal nerves pass upward in the groove between the trachea and esophagus. They pass beneath the lower border of the inferior constrictor muscles of the pharynx, gaining entrance to the larynx just posterior to the articulation between the inferior cornua of the thyroid cartilage and the cricoid cartilage.

They supply all the muscles of' the larynx with motor filaments, with the exception of the crico thyroid muscle. There is anastomosis between the recurrent laryngeal and superior laryngeal nerves.

The relations of the recurrent laryngeal nerve on the right side with the apex of the lung and with the subclavian artery; on the left side with the arch of the aorta are of great clinical importance, as paralyses of the laryngeal muscles may result from pressure against the recurrent laryngeal nerve by aneurysm of the vessels named, at the point of passage of the nerve around them, or, oil the right side, by irritation from the inflammatory conditions in the apex of the right lung. The motor fibers of the recurrent laryngeal nerve are supposed to be derived from the spinal accessory nerve. Russell of London has investigated the nerve supply of the abducting and adducting muscle of the larynx and feels warranted in "the conclusion that the muscles closing and opening the glottis are respectively supplied by different bundles of nerve fibers, preserving an independent course from center to periphery, the abductors being situated on the tracheal side and the adductors on the external side of the nerve." This theory still requires more general observation, as does also that of Onodi, quoted by Bosworth, that the laryngeal muscles receive a supply of motor fibers from the spinal cord, by way of the spinal ganglia of the sympathetic system, extending as low as the lower cervical and first dorsal spinal ganglia, the course of the fibers being direct from the spinal cord to the first thoracic ganglion ; then through the communicating branch between this ganglion and the last cervical ganglion ; and from this latter directly to the recurrent laryngeal nerve. The advantage of having a double motor nerve supply for the muscles of' the larynx is quite obvious.

The Mucous Membrane of the Larynx. The laryngeal mucous membrane is continuous with the lining membrane of the pharynx and trachea. Its epithelial covering is generally of the squamous variety. Over the lower or posterior surface of the epiglottis it is columnar and ciliated. This is also true of the mucous membrane extending below the ventricular bands, which is continuous with and corresponds to that of the trachea. The vocal cords, however, are covered with squamous epithelium. The mucous membrane is rather loosely attached to the submucosa over the anterior surface of the epiglottis, on the posterior surface of the arytenoids, on the aryteno epiglottic folds, and in the ventricle of the larynx. This fact accounts for the rapid development of edema of these parts in very severe inflammatory processes.

The larynx contains an abundant amount of lymphoid tissue, especially at the border of the epiglottis and in the aryteno epiglottic folds, the arytenoids, the interarytenoid space, and the ventricles of the larynx.

The Trachea. The trachea extends from the lower margin of the cri¬coid cartilage to the bronchial tubes, a distance in the adult of about four and one half inches. It is a cylindrical tube flattened posteriorly where it lies in contact with the esophagus. It is a membranous tube partially sur¬rounded by incomplete rings of cartilage. It extends from the fifth cervical to the third dorsal vertebra, where it divides into the two bronchi. Its trans¬verse diameter varies from three fourths of an inch to an inch. Internally it is lined with mucous membrane covered with columnar ciliated epithelium and richly supplied with lymphoid tissue and mucous glands.

The trachea is surrounded and partly covered by important structures. The common carotid and inferior thyroid arteries lie on either side of it, together with the recurrent laryngeal nerve. Crossing it on a level with the second and third tracheal rings lies the isthmus of the thyroid gland in a sheath formed by two layers of the deep cervical fascia. The lobes of the thyroid gland lie on either side of the trachea and larynx from the isthmus to the thyroid cartilage. Below the isthmus and immediately over the trachea is a network of veins, the intrathyroid plexus.

On either side of the trachea, in the superficial fascia of the neck, lie the two anterior jugular veins, at about two fifths of an inch from the median line. These veins communicate by a transverse trunk which crosses in front of the trachea immediately above the sternum. Of' the arteries, the cricothyroid must be recalled crossing the crico thyroid membrane. An anomalous vessel, the arteria thyroidea ima, is found in rather rare instances running up the front of the trachea from the arch of the aorta. The innominate artery, crossing the trachea at the level of the episternal notch, sometimes crosses higher up within the field of a low operation for tracheotomy. In very rare instances both common carotids spring from the innominate artery. In such cases the left common carotid crosses in front of the trachea to reach the left side of the neck. In all operations for tracheotomy the relation of the trachea to these important structures lying about it, and this possible anomalies, must be borne in mind.

THE CLINICAL ANATOMY OF THE NASAL CHAMBERS.'
BY HARRISON ALLEN, M. D.

Correct impressions of the localities in which morbid processes occur in the nasal chambers, as well as the means resorted to for their relief, demand, to a degree perhaps greater than in other parts of the economy, an intimate acquaintance with the structure and relations of the component parts.

The peripheral olfactory apparatus must be conceived as a special membrane covering the nasal aspects of the lateral masses (Figs. 543, 545), these uniting with the cribriform plate and the perpendicular plate to form the ethmoid bone. Each lateral mass is comparable to the eyeball or to the petrous portion of the temporal bone, in the meaning of the term that it is devised to protect an organ of special sense. The conditions under which the act of smelling is efficient demand the act of breathing to be also efficient: hence, each lateral mass is a part of a system of bones which is in free communication with the outer air. The bones are named as follows: the vomer, the ethmoid bone, the sphenoid bone, the nasal bones, the superior maxilla, the palatal, the inferior turbinated, and the lacrymal bones.

The ethmoid bone, the vomer, and the sphenoid bone belong to the brain case, since they are developed with those structures which enter into the composition of the base of the skull. The nasal bones and the incisorial intermaxillary portions of the superior maxilla are developed in pairs from the fronto nasal process of the embryo. The remaining parts also arise in pairs, but at the sides of the skull, and (excepting the lacrymal) extend inward to join the median structures. All of these, with the exception of the ethmoid and inferior turbinated bones, have relations distinct from those pertaining to the nasal chamber. The communication of the nasal chamber with the ethmoid cells, the frontal, the maxillary, and the sphenoid sinuses add greatly to the intricacy of the region. The os planum is often perforated at more than one point in advanced disease of the ethmoid cells, as is the floor of the orbit in disease of the maxillary sinuses. While both of these systems are accessory to the nasal chambers (Fig. 548), their clinical relations therewith are important.

The nasal chamber is conveniently divided into three parts by planes, the initial lines of which are started at the transverse sutures of the floor.

The anterior part lies in front of the maxillo premaxillary suture: the vertical transverse section defining it will answer to the interior (vestibule) of the external nose (nearly).

The middle part lies between the maxillo premaxillary suture and the maxillo palatal suture: the plane defining it, beginning in front at the ductus ad nasum, will embrace the lateral mass of the ethmoid bone (nearly).

The third part lies back of the maxillo palatal suture and includes the vertical plate of the palatal bone with the end of the middle turbinal: the plane defining it is sharply limited by the anterior border of the vertical plate of the palatal bone. The third part is continuous with the internal pterygoid plate in the meso pterygoid fossa.

It may be observed that the inferior turbinated bone has no morphological value and is ignored in the definitions of the planes. The variations in the nasal chamber are numerous, and it is not assumed here that the regions above named are uniform. They are available, however, since they are based on function and are true in the great majority of examples of crania. Among the exceptions to some statements may be mentioned the following : the floor of the Dose in advance Of the maxillo premaxillary suture is sometimes so shortened as to yield a plane which would not contain all or nearly all the interior of the external nose. The middle turbinated bone sometimes projects forward beyond the line of the ductus ad nasum into the anterior third.

The anterior third is in reality a canal of entrance to the olfactory surfaces, and the posterior third is in a less exact sense a canal like passage of exit. The part last named is the same at different periods of life and in all animals; while that of the anterior passage is exceedingly variable, both in ages of the individual and in groups of animals.

Each nasal chamber is bounded by the roof, the floor, the outer, and the inner, or septal, walls.

The Roof. The roof of the misal chamber is confined to the undersurfaces of the nasal bones in advance of the frontal, a small, unimportant, and variable surface of the bone last named; the cribriform plate of the ethmoid bone; and, at the extreme posterior part, a portion of the body of the sphenoid bone. The cribriform plate is an exceedingly vulnerable part of the roof. Many examples are on record of wounds penetrating it; and its position at the top of the cleft, between the septum and the middle turbinated bone, as the parts are seen when inspected by the anterior rhinoscopy, must be borne in mind in all intranasal procedures.

The Floor. The floor of the nasal chamber on either side of the incisor crest is elevated in proportion as the crest itself is developed (Fig. 546); when the crest is absent, or of moderate proportion, the floor of the vestibule is on the same level as that of the horizontal plate of the maxilla. On the whole, it is disposed to incline downward slightly from before backward. An abrupt fall or “break” in the inclination is sometimes demonstrated at the point where the incisorial portion of the floor ends and the maxillary portion begins (Fig. 546). It is of importance to detect the change of level, for secretions may accumulate in the angle and by undergoing decomposition resist efforts to correct the causes of fetor. The mucous membrane in the recess may be ulcerated and the lesion escape observation. Straight plugs, tubes, or cannule cannot be carried conveniently to the floor of the passage at a level below that of the incisorial portion.

The Outer Wall. The outer wall of the nasal chamber embraces the superior, middle, and inferior turbinated bones and the uncinate process. On the lateral mass of the ethmoid bone is defined the superior meatus; between the middle and the inferior turbinated bone is the middle meatus ; and between the inferior turbinated bone and the floor of the nose the inferior meatus.

The Middle Turbinated Bone. The middle turbinated bone, while understood to be but a process of the ethmoid bone, is clinically defined as though it were a separate element. It presents many variations, and their study becomes a matter of the first importance. The bone, as seen foreshortened in the living subject, relates less to the outer wall of the nose than is described in the manuals of anatomy. It might be compared to a stalactite hanging near the roof of an irregular cavern. It may be laminar, without increased width of the free lower border, which is variously deflected; it may have a moderate amount of inflation and appear in sections pyriform in outline, thus constituting perhaps the average condition; or, as is often found in females, it may be enormously inflated so as to exhibit in sections a veritable globose contour (Fig. 545). Infrequently the inflation is not confined to the pendant portion, but extends into the anterior portion of the pedicle as well, where it may even involve the adjoining ascending process of the maxilla.

The size of the middle turbinate varies, quite apart from its shape. As a rule, the bone answers to the lower limit of the perpendicular plate of the ethmoid bone where it joins the vomer; while it rarely extends below this line, it often falls short of it. One of the most interesting variations in the ethmoid bone arises from the arrest of development after an attack of scarlet fever. The lateral mass remains stunted and is lodged high up in the chamber. When ostitis persists, as is often the case, the proximity of these masses to the cribriform plate should lead the practitioner to conduct all local treatment with due care. It is quite true that small ethmoid bones are sometimes examples of arrest of development from fundamental causes, and probably in some degree correlated with defects in the normal rate of evolution of the brain. For we must not overlook the harmony known to exist between the size of the olfactory surfaces, at least of the ethmoid bone, and the functions they subserve in extending the distribution of the special nerves over a peripheral organ.

The middle turbinate is composed of a straight or globose anterior part and a deeply concave posterior part, the concavity being directed outward. The concave part (conch) can be explored from in front and subjected to treatment, for it is often the seat of retained secretion and granulation tissue. The median and anterior surfaces of the bone are less coarsely marked than is the inferior turbinate, although it may be provided anteriorly with numbers of small spicules. In the infant the anterior end is always thin, compressed, and parallel to the perpendicular plate, although the free lower end is deflected either inward or outward, more commonly in the direction first named. In all ages the bone inclines downward and backward to a degree greater than is seen in the inferior turbinate (see Fig. 546).

The Inferior Turbinated Bone. The inferior turbinated bone is attached to the maxilla and palate bone so as to form a bond of union between these structures. It extends the length of the nasal chamber the extreme front border just back of the anterior nasal aperture being in some examples free. The bone is marked by numerous coarse depressions, grooves, and rugosities. It is concave on its outer surface and convex or straight on its inner. Seen in the living subject the anterior end presents a rounded, almost cherryshaped mass, often with scarcely a suggestion of the Position of the inferior meatus, although this region can be carefully outlined by the aid of the probe; the inner (median) surface of this part of the inferior turbinated bone is, as a rule, sharply convex and, indeed, is the most rounded of any part of the surface. Not infrequently it or its covering forms in diseased states septal apposition, if not actually false union or synechia. In my opinion the disturbing factor in the formation of this union is not septal but turbinal, and the reduction of the turbinal is of greater use than the disturbance of the septum. Directly back of the point of septal apposition the convexity of the bone in great part disappears. The inferior turbinate is often of considerable height a variation never seen in like degree in cabinet crania. In cleft palate the free inferior border tends to grow down to a deeper plane than is normal.

The Middle Meatus and the Uncinate Process. Above the middle turbinated bone lies the middle meatus, sharply defined both from in front and behind. The most conspicuous structure seen in the skull in this region is the uncinate process of the ethmoid bone. Usually this process lies parallel to the anterior part of the lateral mass, but it often projects at right angles to the plane of these cells, from which in the living subject it is often difficult to separate it. The process may be mistaken for the middle turbinate. In text books the usual account of the process is to state that it narrows the opening from the maxillary sinus into the middle meatus. This it certainly does; but its more important clinical connection is to the cells with which indeed it is in true morphological relation. In some instances the process is deeply concave on its anterior surface, and its median border is turned sharply forward. When the lateral masses are moderately developed the process makes no impression upon the eye in the living subject, and is imperfectly discerned even in the skull; but when the process is at right angles to the outer wall the anterior ethmoid cells Fig. 547) are always large, and as a rule, constitute a single, rounded, cherry like mass (bulla ethmoidalis). Thus, when the right angled position of the process is detected, the observer may conclude that the enlarged cells lie directly behind it. It is the relation existing between the uncinate process and the anterior ethmoidal cells and the ascending process of the maxilla that makes this part of the nasal chamber of importance in studying the relations existing between lacrymal and nasal disease. Directly within the middle meatus is sometimes seen the opening into the maxillary sinus, and within the inferior meatus that of the lachrymal canal.

The Inner or Septal Wall. The word “septum” implies that the two chambers are being studied together and that the septum is a partition. In this essay the septum is assumed in the main to yield the inner wall of each chamber (Fig. 544). The septum is composed of a bony and a cartilaginous part. The anterior third (about) of the bony septum is notched; the upper border of the notch is defined by the perpendicular plate of the ethmoid bone, the lower border of the vomer and incisor crest of the maxilla. The notch is occupied by the triangular cartilage, which appears to be unfortunately named according to the studies of Freeman; it is of a quadrilateral figure. The bony inner wall of the nasal chamber is composed of the perpendicular plate of the ethmoid bone, the vomer in front of its ale, the incisor crest, the anterior nasal: Spine, and that much of the horizontal plate of the superior maxilla which ascends to form a crest. The incisor crest, the spine, and the process last named differ from the perpendicular plate and the vomer in being composed of symmetrical parts, and, in common with all such structures, present variations according to the manner in which the right and left constituents unite. This statement is particularly applicable to the incisor crest and the nasal spine, which present innumerable variations no two specimens being alike. The nasal spine is developed before the crest, and is not simply the anterior end of this elevation, as is usually stated. The crest is always rudimental in young subjects, and, indeed, is often absent, although the spine may be prominent. Although divided into right and left parts in adults, not infrequently the crest remains in its juvenile condition throughout life. As :a rule, it is well developed and has a disposition not to extend backward beyond the incisive foramen. The vomer, passing forward as a single straight plate deeply grooved for the accommodation of the triangular cartilage, will have its relation to the crest undisturbed so long as the structure last named is of moderate development; but if it be more than usually high the union is not harmonious. Hence arises the thickening of the septum at this place and the disposition to deflection either to the right or left in most cases the latter. The height of the incisor crest is often so great as to cause the septum to be unyielding in the region answering to the height of the inferior turbinated bone. If a high crest is also carried well to the outer wall of the nose it creates an exceedingly narrow passage within the vestibule.

The perpendicular plate of the ethmoid bone may project forward beyond the maxilla and downward so far as greatly to narrow the size of the septal notch. It may constitute, when malplaced, an important factor in nasal obstruction. The prognosis should always be guarded when the plate is so disposed.

Sharply defined projections from the septum are called “spurs." As a rule, they are ledges of varying degrees of development. The most common of, the “spurs “is on the upper vomerine border, either where it forms the lower boundary of the triangular notch, or where it is joined by the perpendicular plate of the ethmoid bone. But a spur is often found high up and back on the septum, and may occupy in great part the middle meatus.

Asymmetry of the nasal chambers is generally acquired and is often the result of injury. Errors in growth and development may arise, however, in the nasal chambers as elsewhere in the economy. Asymmetries of the group last named are in great measure products of civilization. Ethnological cabinets furnish material for study less valuable than that obtained from the dissecting room or observed in our patients. Inflammatory or other obstructive conditions, even when temporary in character, may cause narrowing of the passages. Whatever may be the etiology of these confessedly obscure variations, the fact remains that one chamber, commonly the left, is the smaller, and that the septum inclines away more or less from the median line. A summary of the above statement is here given : Deviation of the septum from a straight line is associated with a high incisor crest; and when this is well established, the vomer tending to grow forward when there is no space in front to permit it so to do, it is deflected from the straight line; or if it enters into the compass of the triangular notch, it is itself abruptly turned to the left.

Far back in the nasal chamber, at a place answering to the union between the perpendicular plate of the ethmoid and the vomer, an irregular ridge can often be felt in making digital examinations. The ridge is more common on the left than on the right side, and is of varying degrees of hardness. Often it can be pressed away by the finger; but more commonly it will not yield unless sawed or drilled.

The degree of consistence of the septum and turbinated bones is subject to variation. The former may be thin and porous or thick and eburnated. No sign is accepted by which the state of the bone can be determined by inspection. Large bones projecting well into the chambers may yield to slight interference, while small bones may be exceedingly resistant. The application of these facts to practice is of importance. A thin, yielding Septum may be the cause of failure in attempting to arrest hemorrhage by plugging the chambers. A marked deviation can sometimes be corrected by the finger to almost the degree desired; while if the parts are thick and firm nothing will yield until they are attacked vigorously by the aid of instruments.

The Nasal Apertures. The apertures of each nasal chamber are two in number, the anterior and the posterior. The anterior is the nostril and the posterior is the choana. The nasal chamber is examined by reflected light thrown through the nostril, or by a mirror carried into the naso pharynx, which reflects the view as seen at the choane. When the skull is examined, the anterior nasal aperture takes the place of both the nostrils; and the midregion of the base of the skull, of the naso pharynx. If it is accepted that the nostril is an aperture, the term cannot be used as a synonym for “nasal chamber ' A' as is sometimes done by clinical writers. The term “naris " is discarded.

The anterior nasal aperture is defined by the maxil la and the nasal bones, and is exceedingly variable when a series of all races of men is examined. But in clinical studies excluding those conducted on the negro the opening is pyriform, with the base of the figure downward, and presents two trenchant asymmetrical borders which are raised above the level of the floor of the nose. The entire figure has been compared to the heart on the playing card. Welcker happily likens it to the figure of the European elm (Ulmus montanus), from the fact that the lower border of one of the chambers (commonly the left) is below the level of the other. The conjoined incisor crests of the maxilla often appear at the aperture. The perpendicular plate of the ethmoid bone, infrequently here seen, may even project beyond its plane, thus in reality converting the anterior nasal aperture into two apertures.

The choana, or posterior nasal aperture, is bounded inferiorly by the posterior margin Of the palatal bone. The lateral margin answers to the anterior border of the internal pterygoid plate. It would be difficult to define the tipper margin were it not for the presence of a group of minute bone spicules which receive no name in anatomy, so far as I am aware, which, nevertheless, are exceedingly useful in defining the plane of' each choana. The inner margin is the septum, but this is not a reliable guide to the base of the choana, since the posterior margin of the vomer often lies well forward on the crest between the palate bones. I have called this phase of the nasal septum “recedent," to distinguish it from that form where the base comes sharply up to the base of the posterior nasal spine. In subjects that exhibit the recedent form, the vomer will allow the posterior ends of the inferior turbinals to approach, although they do not touch the mucous membrane over both bones remaining normal. Care should be taken in such conditions not to confound these masses with hypertrophy of the posterior ends of the turbinal bodies.

The region of the choana, after all is said, is not of importance. In practice the choane in reality include the meso pterygoid fossa, or, a I have ventured to call it, the posterula, or back porch to the nasal chamber. This is a single region into which the choane debauch. It contains the ale of the vomer and all of the inner surface of the internal pterygoid plates. The finger introduced into the naso pharynx is received into the posterula, and the pterygoid surfaces are clearly defined at the sides. In rare instances these may be thickened, retaining the infantile form, and may aid other conditions in tending to reduce beyond normal limits the posterior apertures of the chambers.

The Nasal Mucous Membrane and its Blood vessels. The mucous membrane lining the nasal chambers is of three kinds: first, the olfactory membrane, which is limited (nearly) to the ethmoid bone on the inner aspect of each lateral mass and the opposed surfaces of the perpendicular plate; second, the highly vascular and partially erectile structures (turbinal bodies) covering the inferior turbinated bones; third, the generalized membranes which line the other bones and the walls of the accessory sinuses.

The property of cocain in constricting small blood vessels is used with advantage in studying the anatomy of the nasal chambers in the living subject. The contrast in the shapes of the inferior turbinal body before and after an application of a 10 per cent. solution of cocain is such as to give the observer an accurate impression of the extent of the erectile mucous membrane covering it. The cushion surfaces of the bodies with contour convex before the cocain is applied disappear, and in their places are noted a membrane bound down to the bone, to whose irregularity it conforms. We speak of a turbinated bone and a turbinal body the, latter phrase to express the fact that the body is an erectile membrane which has a shape in a measure distinct from the skeletal surfaces with which it is closely incorporated.

As a rule, incisions into the turbinal body are followed by moderate bleeding, which ceases spontaneously. Occasionally wounds over the middle turbinal bleed more freely, which in order to stanch require interference by pressure or use of astringents. The mucous membrane on the outer wall and in the sinuses is uniformly indisposed to bleed so as to demand interference. It is far different with the septum. Here the cartilaginous portion, where it joins the incisor crest, is exceptionally vascular. A caruncular swelling is often found at this point, which should be carefully avoided in making incisions for minor surgical procedures. A second point from which hemorrhage is apt to occur is over the triangular cartilage itself. This is never from an incision, but is commonly from abrasions, and is therefore the region from which blood often springs in non surgical epistaxis. The seat of hemorrhage is found at a point just beyond the tip of the triangular notch. Hemorrhage occurring from wound; reaching the submucous tissues is far different from the foregoing. Two distinct locations are here noted namely, the septum along the line of the vomer at any part, which answers to the positions of the deep septal blood vessels; and the posterior third of the outer wall, where it receives the arteries and veins which pass through the spheno palatine foramen (Fig. 549).

The bones of the nasal chamber are remarkable for being in whole or in part covered with mucous membrane, and are supplied largely with its blood vessels. The muco periosteum is a valuable term in describing such a membrane, for it fixes the mind upon the analogy between such a membrane and the periosteum. If the comparison between the two membranes is precise, then the study of the nasal chambers as part of the great skeletal group of bones, being as exact in pathology as in anatomy, relegates many of the morbid conditions of the chamber to phases of periostitis and osteitis.

The Nerves, the nerves that must be recalled in surgical treatment of the nasal chamber are unimportant. The operations on the nasal septum will sometimes cause numbness of the incisor and canine teeth to be complained of for a few days after operation.

Asymmetry and Narrowing of the Nasal Chambers. It has been stated on page 831 that the nasal chambers are often asymmetrical the asymmetry being caused by deviation of the nasal septum, usually to the left side, and that such deviation is acquired either as a direct result of traumatism or of disease. The chambers, however, may be unequal in size, even when the septum remains straight. Such a relation is due to fundamental causes, and will be found, like all these conditions, to correlate with other peculiarities in the economy. An important element in prognosis is here to be considered, for a congenitally narrowed or occluded chamber can never be made entirely efficient. Sometimes the posterior portion only of the chamber exhibits asymmetry. This is due to a defect in the development of the sphenoid bone, the body of which does not normally expand ; thus the pterygoid processes are kept too close together, the palatal bones, as well, remain in an infantile condition, and in time the choana are even inadequate for the accommodation of the posterior ends of the turbinals. If an operation be proposed for deviation of the septum or other causes of obstruction in the anterior portion of a chamber of a subject where the posterior portion remains undeveloped, a statement of the results to be expected should be guarded, since the narrowing at the choana and posterula may in itself maintain obstruction. In these cases the choana are always small and oval; the internal pterygoid processes are convex, and the turbinals are thick and pressed together against the septum. Cases have been observed characterized by retention of all these parts in an embryonic condition, with resultant atresia. Even when the choanal plane is normal, narrowing may occur at the posterior third of the chamber; thus converting each posterior portion into a passage, which might be compared to a funnel laid on its side and with its neck directed forward.

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