i:$&: fW&EW&$S££*i £& ^ ^ S§o:: ';•■:•>:• IJSij Blll^ &Sl5>>: :•.««>!-:•: •:•*: K<-k >:■*&£•: ■'^'•''.''■C.'K.' fc:<^ ^ft^:' K88fi^-{>^fflnnJ8wHHDw?'' <& JPj*Bftfl^V*J^4 8^mi:^^Wft---' >• mmmmmmmi •■-&. :^J<- ::%># *>-;•-• K-:^ S*&:& <* ^f. f'/ucJz^ NATIONAL LIBRARY OF MEDICINE Bethesda, Maryland Gift of Edward B. Schlesinger, M.D. I W8 ^*r > a^** N y^ *. x :^- % j- ■•& 3k w ***» *><*■ "i, A Typical Skull. THE INTERNAL ANATOMY OF THE FACE BY M. H. CRYER, M.D., D.D.S. PROFESSOR OF ORAL SURGERY, UNIVERSITY OF PENNSYLVANIA; ORAL SURGEON TO THE PHILADELPHIA GENERAL HOSPITAL SECOND EDITION, REVISED AND ENLARGED ILLUSTRATED WITH 377 ENGRAVINGS LEA & FEBIGER PHILADELPHIA AND NEW YORK Entered according to the Act of Congress, in the year 1916, by LEA & FEBIGER, in the Office of the Librarian of Congress. All rights reserved. ^jjlm) -P THIS BOOK IS AFFECTIONATELY DEDICATED TO MY WIFE MARTHA GATES CRYER ■H ^ 4-. PREFACE TO THE SECOND EDITION. Many years ago the author began to investigate the variations from the standard typical anatomy of the text-books which constantly presented themselves in his surgical practice. During the past twenty years hundreds of skulls have been sectionized and studied. This investigation completely overturned the author's conception of what was meant by the term typical. There is, doubtless, a typical or typal form for each bone, but it is not often found in nature. If we were to photograph a thousand temporal bones, for example, and make a composite of the entire number, the composite would properly be accepted as figuring the typal temporal. It is possible, though doubtful, that of the thousand bones, two or three could be found which would exactly correspond with the typal bone so pictured. This, in the writer's view, is strong testimony that the typal bone is ideal; that the actual is a variant. It is with these variants that the surgeon and dentist have practically to deal. The author's investigations of the anatomy of the head have convinced him of the need for similar systematic study of the ana- tomical structure of the other parts of the body. For it can scarcely be doubted that the departures from the normal noted in the bony structures of the head and face will be found associated with equal variations of the other structures. It further shows that the text-book by itself is insufficient for the thorough study of anatomy; that the only authentic book of anatomy is the body itself; that, therefore, the use of text-books must be supplemented by the intimate study of the body. In the preparation of this edition the text has been thoroughly and carefully revised to meet the requirements of those making special studies upon, or operating in, the region of which it treats. New VI PREFACE TO THE SECOND EDITION matter has been added to the extent of about 1S0 pages, including chapters on the teeth with their nerve and blood supply; on the dis- tribution of the trigeminal nerve; on the uses of frozen sections; on the inter-relations between the nasal cavity and its accessory sinuses and cells. Wide and narrow dental arches have been further considered, and an extended chapter has been added in which impacted teeth, modern, ancient and prehistoric skulls and teeth have been compared and noted. With certain modifications the Basle nomenclature has been generally adopted. The writer desires to acknowledge the encouragement and assist- ance received from Dr. Thomas C. Stellwagen, Dr. Edward C. Kirk, Dr. Arthur Hopewell-Smith, Dr. Herman Prinz, Dr. Rodrigues Ottolengin, Dr. Truman W. Brophy, Dr. Robert H. Ivy, Dr. A. H. Ketcham, Dr. James D. McCoy, and many others who have kindly furnished specimens or other material which have aided so materially in the preparation of this volume. Matthew H. Cryer. Philadelphia, 1916. CONTENTS. CHAPTER I. Introductory 17 CHAPTER II. General Considerations Development of the Face 20 21 CHAPTER III. The Mandible or Lower Jaw Inflammatory Changes Necrosis and Regeneration . Fractures of the Mandible Neuralgia...... Secondary Deposits Mandibular Triangle The Mandibular Articulation 23 48 49 59 64 64 67 68 CHAPTER IV. The Maxillae........... Studies of Certain External Surfaces of the Skull ... ...... General Comparisons between the Width of the Upper Dental Arch, the Floor of the Nasal Fossa, and the Size of the Maxillary Sinus........ 76 81 94 CHAPTER V. The Mouth The Teeth............. Eruption of Teeth.......... Various Illustrations of Jaws and Teeth The Vascular Supply of the Teeth..... The Sensory Nerve Supply of the Teeth and Face Sympathetic Ganglia Connected with the Trigeminal Nerve Local Anesthesia of the Teeth, Surrounding Tissue, and Parts of the Face Pre sided over by the Trigeminal Nerve.............. 100 101 118 120 134 139 154 163 viii CONTEXTS CHAPTER VI. Teeth Influenced by Irregular Eruption Retarded Eruption or Impacted Teeth......... Supernumerary Teeth .............. CHAPTER VII. The Nasal Cavity and its Accessory Cells and Sinuses Pathological Condition of the Nasal Cavity ........ CHAPTER VIII. The Maxillary Sinus.........217 CHAPTER IX. The Frontal Sinus..........248 CHAPTER X. The Ethmoidal and other Cells which have Their Final Outlet in the Nasal Cavity 259 The Orbital Processes....................260 The Sphenoidal Sinuses..... ..... ..... 260 Cell of the Crista Galli . ..............262 CHAPTER XL Variations in the Anatomical Structures of the Face .... 263 CHAPTER XII. The Relation between the Mouth, Tongue, Pharynx, and Nasal Chamber . -285 CHAPTER XIII. Modification of the Normal Shape of the Bone through Abnormal Forces . 304 Supernumerary Premolar Teeth ................. 323 CHAPTER XIV. The Influence of Muscular Action . . 330 CHAPTER XV. Hypertrophy of the Gums and Alveolar Process 342 CHAPTER XVI. The Relation of the Two Jaws . 345 166 166 173 196 208 THE INTERNAL ANATOMY OF THE FACE. CHAPTER I. INTRODUCTORY. Carefully conducted studies of numerous dissections prove con- clusively that many of the stereotyped descriptions of the internal anatomy of the face are not justified by the facts; and that, therefore, the hard and fast rules for surgical procedures founded on these descriptions do not adequately cover the ground. In pursuance of these studies, hundreds of sections of the facial region have been cut and examined. The lesson they teach is that the accepted descrip- tions are to be received as only general truths, and that they cannot be depended upon or followed literally as a guide for the surgeon or dentist. The results of these investigations afford a basis for the explanation of the failure of many operations conducted on the lines of the accepted anatomical descriptions; such failures have been regarded as merely the natural percentage of unsuccessful treatment; whereas, they have probably been due to variations in the parts clearly within the limits of normality. This will be demonstrated in the following pages by many illustrations. Anatomical Variations.—No man who spends any considerable portion of his time in the study of anatomy—that is, in actual dis- sections—can fail to note how great is the number of anatomical variations which he meets. So common are these that it cannot be said with exactness what are typical and what are atypical conditions. In other words, anatomy as a study is not to be classed among the exact sciences. It is not meant by this that there is not such a basis of anatomical science that general rules cannot be laid down, but the more closely the subject is studied the more variations as to details 2 is IXTRODICTOR] are recorded. From the mandible of an animal, a femur, or even a tarsal bone, the nature of the associated bones, their sizes, positions, and forms can be satisfactorily deduced. Admitting this, however, there are still as main- variations in the internal anatomy as there are differences in the external appearances. Especially is this true of the anatomy of the human head, as it is modified by climate, race, age, disease, occupation, and many other conditions. Climate.—Climate and environment have a great influence in modi- fying the development of the bones of the head, as is demonstrated in the differing formations of the skulls of the great races of the world; and more markedly in branches of the same race living under diverse climatic and social conditions. Age.—The changes produced by age are very marked. The skull consists of bones of both cartilaginous and membranous origin. In the fetus and infant these bones are soft and yielding; they receive deposits of certain salts of calcium, becoming harder and harder as age advances until the degeneration of senility sets in. In the jaws, constant changes are caused by the development, eruption, and loss of teeth and the consequent alterations of the alveolar process. Disease.—Disease causes profound changes in the bony structures as well as in the other tissues of the body (see Fig. 45). In the pres- ence of some disorders of the nutritive system—such for example, as rickets, either the bones may fail to become infiltrated with a sufficient quantity of lime salts, which would have the effect of leaving them soft and yielding; or, on the other hand, an undue proportion of calcareous material may be incorporated into the bones, with the opposite effect of making them hard and unyielding, thus modifying the physiological functions with which they are concerned. Occupation, Diet, etc.—Occupation will modify the shape and character of the face and head, especially in youth. Those persons who are studious, and pass an indoor life, are likely to have a more delicate development of the face, with a larger brain-case than those who are brought up to a laborious outdoor life. The comminution of coarser foods will develop the muscles of mastication and their bony attachments. Numerous other facts might be cited to show the DIAGNOSTIC IMPORTANCE I!) influences of personal habit upon the course of anatomical develop- ment. Asymmetry.—There are also variations in the same individual in the shape, size, and markings of the two sides of the face. In the bilateral bones such as the frontal, sphenoid, vomer, ethmoid, and mandible, one side is usually found to differ from the other. In the homonymous bones, as the maxillae, the malar, the lachrymal, the turbinate, and the palate bones, the same variations are observed. This being the case, it will be readily understood that the internal openings and spaces, viz., the mouth, the nasal chambers, the orbits, the maxillary, frontal, and sphenoidal sinuses, the ethmoidal and other cells, will differ accordingly. Diagnostic Importance.—It is clear that variations of the nature referred to must have a direct bearing on the diagnosis of morbid con- ditions for which there is no evident explanation, and even more so on the performance of operations for their relief. A knowledge of these variations will point the way to an understanding of main- otherwise obscure and doubtful lesions. It will also show why, for example, following stereotyped ideas, the surgeon seeking to open into the antrum will occasionally enter the nasal cavity instead. It would seem that to the surgeon, and more especially to the dentist, such information is a necessity. The main object of this volume is to present a digest of these revealed facts relating to the internal anatomy of the face—facts which have an important bearing on all surgical operations involving this region, and especially on the work of the dentist and the rhinologist. With this in view, the aim will be to call attention to misconceptions of the actual conditions; to correct errors which, having found cur- rency, have been commonly accepted and more especially to enforce the idea that a slavish following of typical descriptions is likely to lead to disaster. CHAPTER II. GENERAL CONSIDERATIONS. Anatomical Structures.—The anatomical bony structures of the facial region include the framework, superficially, of the external lace and, more deeply, the walls of the various cavities and air spaces of the internal face. As with other bones, they consist of a cortical outer wall inclosing cancellated tissue, the latter being extremely fine and delicate in many cases, in some instances becoming so attenuated as to be almost lost. The exterior cortical parts are covered with a true periosteum, while the interior surfaces, those looking toward the inter- nal cavities, as the mouth, nasal cavity, the frontal, maxillary, and sphenoidal sinuses, and the ethmoidal cells, are covered by a muco- periosteum. From these characteristics, the former are known as non-mucous, and the latter as mucous or mucoid surfaces. It is important to consider the difference in these surfaces in the treatment of some of the diseases of the bones. The dense exterior or non-mucous surface is roughened at various points by the actions of the attached muscles. The exterior cortical portion varies in thickness according to the amount of work to which it is subjected or the protection it has to afford. The greatest thick- ness is found in the mandible, the active bone of mastication, which occupies a position in the face where it is peculiarly exposed to the effects of external forces, such as blows, etc. The inner or mucous surfaces, while dense and compact, are thinner, smoother, and more delicate. They are marked by depressions for the lodgment of the mucous glands, by grooves for the lodgment of the nerves and vessels, and also by elevations due to the attachment of the muscles. Cancellated Structure.—The cancellated tissue found between the plates of cortical bone varies in thickness and compactness according DEVELOPMENT OF THE FACE 21 to the density, the position, and the functions of the bone. The arrangement of the trabeculae is an interlacing network. To give bulk to the bone where required, and to diffuse shock, constitute the functions of the cancellated tissue. Through it pass the nerves and vessels to supply local structures and, by means of bony canals or tubes, the more distant parts. The bones of the head contain many canals and foramina for this last-named purpose, thus differing mate- rially from the other bones of the body. This is a fact of surgical importance. For when these bones have become altered either by the breaking down of the tissue or by abnormal growths encroaching upon the foramina or canals, the functions of the nerves and vessels are interfered with, thus affecting not only adjacent tissues, but parts of the face and body remote from the seat of the lesion, causing abnor- malities in the area of distribution, as atrophy, neuralgia, etc. DEVELOPMENT OF THE FACE. The bones of the brain case are in an advanced stage of develop- ment before the facial bones commence to be built. To such an extent is this so that the dermoid structures are nearly in contact with all of that portion of the head below and anterior to the notochord. At this time there is no opening into the alimentary canal. The facial bones arise from the under surface of the brain case, from certain processes that push outward and downward, leaving a layer of dermoid tissue on their inner as well as their outer surfaces. This dermoid tissue becomes the mucous or epidermal lining of the mouth, the nasal cavities, and all internal surfaces of the face. It is also from this dermoid tissue that the teeth and alveolar pro- cesses take their origin, and not from the developing buds or processes that form the remainder of the bones of the face; so that when the teeth are lost and there is no function for the alveolar process to per- form, it is also lost. It is for this reason, also, that when the dermoid tissues are attacked by systemic diseases such as syphilis, scarlet fever, etc., the teeth and alveolar processes are involved simultaneously with the skin, as are also the bones of the face, which were covered -- GENERAL CONSIDERATIONS originally with dermoid tissue. It is quite possible that pyorrhea alveolaris may also be a manifestation of a dermoid disease. When the dermoid appendages are entirely lacking at birth, and do not develop later on, the alveolar process will also be lacking. The processes in front which pass down and forward are called the Irontonasal; those on the side, the maxillary and mandibular; those situated deeply within the face are known as the spheno-ethmoid pro- longations. The general tendency of these buds, forming the upper and lower jaws is to send processes toward the median line which form a union with their fellows of the opposite side. The bonds of these unions vary accordingly to circumstances depending upon their posi- tion, function and the age of the individual. CHAPTER III. THE MANDIBLE OR LOWER JAW. The mandible develops from the first pair of the visceral or branchial folds called the mandibular plates, which in early embryonic life advance from the sides of the base of the cranium and meet at the median line, forming the symphysis menti. The mandible is symmetrical in its general shape, although one side may and usually does differ from the other. It presents for study c d Fig. 1.—Four mandibles ranging from birth to eighteen months: A, at birth; B, at three months; C, at six months; D, at eighteen months. a body which is horizontal in direction, with two rami extending upward to the articulation in the anterior portion of the mandibular fossa of the temporal bones. The angle (gonion) formed by the union of the lower border of the jaw and the posterior border of the ramus, varies considerably at different periods of life. Figs. I, 2, 3 and 4 are views of the external cortical surfaces of the normal lower jaw at various ages, showing progressive changes in the angle between the rami and the body of the bone as life progresses. At birth (A, Fig. 1) the angle is very obtuse, but as the teeth develop and erupt, it becomes 24 THE MANDIBLE OR LOWER JAW less and less obtuse until about the time the last of the permanent teeth are erupted it is almost a right angle, as shown in Fig. 2. Fig. 2.—Side view of a typical mandible at maturity. As the muscles grow and increase in strength, that portion of bone to which they are attached also increases in size, giving the ramus a square appearance, especially in strong muscular persons (see Fig. 8). After full maturity, as time passes, the muscular action becomes less and less, and the tuberosities, etc., throughout the body become Fig. 3.—Mandible of aged person, showing a great change from that of adult life. smaller. The same condition takes place at the angle of the jaw-, and it becomes more obtuse as age advances. When the jaws can be kept apart with good teeth and normal, complete mastication, there is not so much change in the angles. THE MANDIBLE OR LOWER JAW 25 As the teeth become abraded, or when they are extracted, the alveolar process is resorbed, the horizontal planes of the jaws approach each other more closely, and the angle again becomes obtuse (see Fig. 3). The teeth and their alveolar processes are placed on the upper portion of the body of the bone. The third molar is partially posterior to the anterior margin of the ramus, and a line can be drawn between the first and second premolars to the mental foramen. FlG. 4.—Mandible of an aged person showing the mental foramina in the top of the body of the jaw. The incisor teeth should have neither lingual nor labial inclina- tion. Fig. 2 shows a fairly typical mandible: as is also shown in the skull marked Fig. 77. The mental process gives prominence to the chin and lower part of the face. It belongs to man only, and is always associated with the genial tubercles. In the monkey there is a depression instead of the tubercles. The space between the halves of the body of the -•'» THE MANDIBLE OR LOWER JAW mandible in the region of the premolar teeth is much wider in man than in the other mammalia, thus giving more freedom for the action of the tongue. The mental process, the genial tubercles, and the freedom of the tongue are severally and collectively concerned in the produc- tion of articulate speech. The writer also considered that the presence of a well-developed mental process contributes to a greater command of articulate speech than can be attained by individuals in whom it is small or underdeveloped; and as it extends outward beyond the line of the teeth, it—the mental process—gives the origin for the muscles that control the action of the lower lip, and when properly developed holds the latter in position to conform with the upper lip, thus perfecting the labial sounds. In considering the manner in which deaf people can communicate orally by observing the action of the lips, and the fact that the deaf and blind can read what is being said, merely by gently placing the fingers upon the lips, one is inclined to the opinion that the lips are an important factor in the communication of thought as well as in the production of articulate speech. The orbicularis oris muscle and its associates must have great free- dom and power of action in order to produce the numberless varieties of motion necessary to this end. The facial nerve thus becomes one of the nerves of speech, as it not only controls the lips, but also the cheeks and some of the muscles of the soft palate. In order that these oral muscles shall have a free and balanced action, the lower portion of the orbicularis and its associated inferior muscles must be carried forward to a line equal to that of the upper portion, thus as before mentioned, the mental process also becomes an important factor in articulate speech. Mandibles of Different Races.—In comparing mandibles of different races and also of the same race great variations in general characteristic shape and size are found. The following figures illustrate a few of these variations: Fig. 5 is a side view of an Indian mandible found in one of the buttes in western Kansas. It is a very powerful jaw, the angle is almost acute, 106 degrees, the distance from the condyloid process, which acts MANDIBLES OF DIFFERENT RACES 27 as the fulcrum, to the coronoid process, the place of attachment of the temporal muscle, is 50 mm., which gives great power to the mandible. Fig. 5.—A powerful mandible of an Indian found in buttes of western Kansas. (Loaned by Dr. Ketcham.) Fig. 6.—A mandible of a South African negro, a member of the Fan tribe. Fig. 6 is from a mandible«of a South African negro a member of the Fan tribe (see Fig. 78). The body is fairly typical, except that the angle is nearly a right angle. The characteristic features of this 2S THE MANDIBLE OR LOWER JAW mandible are caused by the position of the teeth and their alveolar processes, which are set forward on the body of the jaw. It will be Fig. 7.—A mandible from a skull, showing prognathous jaws. (See Fig. 79.) noticed that the third molar is in advance of the ramus about the width of a molar, and that a line drawn downward between the pre- molar teeth would pass across the body of the jaw a full width of a molar tooth in advance of the mental foramen. The canine and Fig. 8.—A mandible of a heavy skull. (See Fig. 80.) incisor teeth are placed in front of the jaw proper, with considerable labial inclination of the incisors. The mental process is not so promi- MANDIBLES OF DIFFERENT RACES 29 nent as in Fig. 2, due in part to the carrying forward of the teeth and alveolar process. Fig. 7 is made from a skull (see Fig. 79) showing prognathous jaws. In Fig. 6 the prognathism is evidently caused by the malposition of the teeth and their alveolar processes upon the body of the bone. In Fig. 7 the principal cause of prognathism is in the relation of the ramus to the body, which carries the body of the jaw so far forward that the mental process is much more prominent than in Fig. 6 and the anterior teeth have lingual inclination. Fig. 8 is made from the mandible of a very heavy skull with massive teeth in excellent alignment (see Fig. 80) and when articulated Fig. 9.—A mandible of a peculiar skull. (See Figs. 363, 364 and 365.) with its skull there is fairly good occlusion. The marked feature of this mandible is the relation of the ramus to the body of the bone; its external angle is nearly a right angle, being 1030 on the right side and ioo° on the left. Fig. 9 is made from a mandible of a peculiar skull (see Figs. 93, 363, 364 and 365). It is a great contrast to the mandible shown in Fig. 8. The angle of the ramus with the body of the bone is 1390. Age should be taken into consideration in this comparison, as the angle usually increases as age advances. Fig. 10 is made from the mandible of a skull having a very flat face (see Fig. 82). There is a slight anterior occlusion. The angle of the jaw is obtuse—viz., 133 degrees. M THE MANDIBLE OR LOWER JAW Fig. n is made from the mandible of a (hinese skull (see Pig. Si). The rami are rather square and unite with the body of the bone at an Fig. 10.—A mandible from a skull of a flat-faced person. (See Fig. 82.) angle of 1080, which makes the mandible short. On the left side of the mandible there is an impacted lower third molar. " Fig. 11.—A mandible of a skull of a Chinese. (See Fig. 81.) The following diagrams, each reduced one-half, give the measure- ments and angles of the mandibles in Figs. 2, 6, 7, 8, 9, 10 and 11: MANDIBLES OF DIFFERENT RACES 31 P24° ANGLE 75 MM Fig. 12.—Mandible, Fig. 2. MENTAL FORAMEN 136" 77 MM Fig. 14.—Mandible, Fig. 7. 139° 66 MM Fig. 16.—Mandible, Fig. 9. MENTAL FORAMEN 118" 71 MM Fig. 13.—Mandible, Fig. 6. MENTAL FORAMEN 103" 89 MM Fig. 15.—Mandible, Fig. 8. 135° 73 MM Fig. 17.—Mandible, Fig. 10. 108" 78 MM Fig. 18.—Mandible, Fig. 11. The following diagrams illustrate the triangles of mandibles in skulls of various ages from eight months to old age: Fig. 19.—Age eight months. 127° 48 MM Fig. 20.—Age fifteen months. THE MANDIBLE OR LOWER JAW Fig. 21.—Age eighteen months. 125" 55 MM Fig. 23.—Age four years. 120° 65 MM Fig. 25.—Age seven to eight years. m7- so mm Fig. 22.—Age two years. US- 55 MM Fig. 24.—Age five years. 116" 6Z MM Fig. 26.—Age eight to nine years. 119° 70MM Fig. 27.—Age thirteen years. 106* 76 n M Fig. 28.—-Age eighteen years. 77 MM Fig. 29.—Adult. Fig. 30.—Old age. Figs. 19 to 30.—Diagrams of mandible, reduced one-half. THE BODY OF THE JAW 33 The Body of the Jaw.—The body of the jaw in transverse section, shows a U-shaped cortical or dense bony structure, the arms of the U terminating in the plates of the alveolar process—outer and inner— which are composed of a modified cortical bone with no definite line of demarkation between them and the body of the bone proper; the Fig. 31.—Anterior lateral view of upper and lower jaws, with the external cortical portion of bone covering the roots of the teeth removed, exposing the cancellated tissue, the roots, and the cribriform tube. (Mandibular canal.) function of the body, however, is quite different from that of the alveolar process. The bone proper is covered with a true periosteum, the alveolar process with mucoperiosteum, the latter being thick and dense and containing many mucous glands. It is commonly known as gum 3 34 THE MANDIBLE OR LOWER JAW tissue. The space between the arms of the I* is filled with hue trabe- cular forming the cancellated structure. The roots of the teeth are imbedded within this cancellated structure, each root being sur- rounded by thin, compact bony tissue, Lamina dura,1 which approaches the cortical bone in density, but is cribriform (sieve-like) in character ^see Figs. 31, ^2 and 34). Fig. 34 is an upper view of the mandible with the teeth removed, showing single sockets for the ten anterior teeth and double sockets for the six molars. The shapes of the sockets as shown correspond Fig. 32.—Mandible with the cortical portion of bone removed from the body. with the transverse section of the various teeth at the level of the margins. The septa between the sockets are cribriform in character. Cribriform Tube.—Through the cancellated tissue passes the man- dibular canal, which is, however, more accurately described by the term, "cribriform tube of the mandible." The function of this tube is to afford a protective passage for the mandibular nerve and the blood- vessels. The cribriform tube passes dowmward and forward from the man- 1 A. Hopewell-Smith, Dental Cosmos, August, 1913, p. 769. CRIBRIFORM TUBE dibular foramen, at first along the inner cortical portion, then, after it leaves the ramus, gradually crossing over through the cancellated tissue toward the outer cortical portion and downward toward the border of the U-shaped space. As it approaches the mental foramen, its course is near the outer cdrtical portion and along the lower border of the cancellated tissue, passing beneath the foramen to its termina- tion near the roots of the incisor teeth. This tube can be removed from a normal jaw or isolated as shown in Fig. 33, taken from a specimen in which the cortical and cancellated tissues have been cut away, Fig. 33.—Cribriform tube (mandibular canal) of the lower jaw isolated. exposing the cribriform tube. Figs. 31, 32 and 33 show that the crib- riform tube is an independent structure, not merely a canal through the bone. In Fig. 31 it will be noticed that a portion of the outer wall of the tube has been removed, while in Fig. 32 the wall is left intact, showing its tubular form. The outer wall of the tube in the region of the second and third molars is extremely well shown in Fig. 31. As the tube passes along the jaw its cribriform character becomes more and more marked until, beneath the first molar tooth, it becomes so opened, probably by a sort of stretching process coincident with 3d THE MANDIBLE OR LOWER JAW the growth of the bone, that the tube-like formation is almost lost, as is well shown in Pig. 31. Further forward it again resumes its original character. This main cribriform tube gives off lesser branch tubes which afford passage for the nerves and vessels to the substance of the bone; also, in more or less curved course to the roots of each tooth. The branch tube for the accommodation of the nerves and vessels Fig. 34.—View from above of mandible from which all the teeth have been removed, showing the cribriform character of the septa of the sockets of the teeth. to the mental foramen, is usually given off slightly anterior to the foramen, passing backward from the main tube to the foramen. This is almost invariably the rule—namely, that the tube to the mental foramen is in the form of a return or recurrent canal, mental canal, though occasionalh' it passes from the main tube as it approaches the foramen. The recurrent tube is well shown in Figs. 31 and 32. In the former, the anterior wall of the mental foramen has been cut METHOD OF GROWTH 37 away, and in the latter, a narrow piece of paper has been passed through the foramen into the recurrent tube, showing its direction. The Dental Branches.—The small lateral tubes which serve as nerve and vessel conduits to the roots of the teeth posterior to the mental foramen are given off from the main tube and pass upward and forward in a more or less curved direction, the degree of curva- ture varying according to the position of the teeth. Those going to the third molar are nearly vertical in direction. In those going to the second molar the forward direction is greater; in those to the first molar this forward direction is increased still more, while those to the second premolar have the longest curve of all. Sometimes the tube passing to the second premolar, instead of beginning at the main tube, is found as an offshoot of that going to the anterior root of the first molar. The small tubes going to the first premolar and the canine are branches of the recurrent tube of the mental foramen, and are curved slightly backward as they pass upward to the roots. In the unusual cases, where the branch from the mental foramen is not recur- rent, but given off as the main tube approaches the foramen, the latter branches for these two teeth pass directly from the main tube, and with a slight forward curvature. The tubes for the supply of the inci- sors are also branches of the main tube, and curve slightly forward as they pass upward to the roots. Method of Growth.—The cortical U-shaped portion of the bone is the framework of the jaw; its supporting structure. It grows by an interstitial process, each half having three fixed points between which the growth occurs—viz., the ramus, the mental foramen, and the sym- physis menti. There is no doubt that the distance between these points increases, though the growth between the symphysis and the foramen does not occur at the same time as that between the foramen and the ramus. The periods of growth in these regions seem to corre- spond with the time of development and eruption of the teeth of the localities concerned. Thus, the increase between the mental foramen and the symphysis menti occurs during the time the incisor, canine, and premolar teeth are developing. After these teeth are erupted, there is little further increase in the length of this portion of the jaw. :;s THE MANDIBLE OR LOWER JAW From the mental foramen to the ramus the increase is inconsiderable until the time draws near for the eruption of the second and third molars, the greatest growth occurring during the development of these teeth, and generally ceasing after the eruption of the last named. The contents of the U-shaped portion grow forward as the cortical structure increases in length, the teeth immediately posterior to the mental foramen—which are first developed in this region—being pushed forward successively by each developing and erupting tooth. It is this forward movement which gives the curvature to the various small tubes to the roots of the teeth, etc., and accounts for the stretching of the main tube until its distinctive character is nearh' lost under the first molar. It also affords a rational explanation of the recurrent feature of the tube to the mental foramen; the end of this tube being attached to the wall of the foramen, when in the process of growth the mass of cancellated tissue is pushed forward, the tube itself is carried along with it, forming a loop. The reason why the small tubes going to the first premolar and the canine curve backward is, that their points of origin have been carried forward with the return tube from which they spring. The small tubes going to the incisors curve slightly forward, as they arise from the continuation of the main tube near the point where it curves backward to the foramen. Surgical Significance.—This anatomical arrangement has an impor- tant surgical significance in certain phases of the operation of resecting the mandibular nerve, for if the general teaching of anatomy be fol- lowed the surgeon is liable to be misled. If the operator cuts down to the mental foramen, then seizes the mental nerve and uses it as a guide while cutting the bone away with the surgical bur from the posterior wall of the foramen, he will find that the nerve cannot be followed as a rule, as the nerve and the canal do not pass backward. But if the anterior wall be cut away, the nerve can be followed down to the mandibular nerve, which may then be uncovered to any distance deemed necessary. Pathological Significance.—The pathological significance of this bending backward of the nerve and its bony covering is that if any METHOD OF GROWTH 39 injury be received in this region, or if any inflammatory condition be produced, either traumatically or by infection from diseased teeth, the nerve is liable to become impinged upon or compressed, thus causing pain or inflammation of the nerve itself. The writer has found neuromata more common in this region than at any other portion of the mandibular nerve, probably mainly due to the anatomical condition under consideration. Records of Development.—Thus it will be seen that the anatomical structures, the relation of the various teeth considered with regard to the order of their development, and more especially the direction which the lateral branches of the main cribriform tube take to form Fig. 35.—View of mandible (left side), with the cortical portion of bone removed together with the cancellated tissue, exposing the nerves and vessels within the cribriform tubes as they pass to the roots of the teeth. N their connection with the roots of the several teeth, supply us with permanent records of the methods of growth of the mandible during the period between childhood and adult life. In the boiled and cleaned specimen, naturally all the contents of the tubes—the soft tissues—have disappeared; but the illustrations, Figs. 31 and 32, show clearly that the main tube and the smaller ones passing to the various teeth, and the finer tubes going to the inter- spaces and general cancellated tissue, have the same general direction and curvature as those going to the roots in their immediate vicinity. Fig. 35 shows a specimen from which the soft tissues have not been removed. It shows the smaller tubes passing to the roots of the teeth, Id THE MANDIBLE OR LOWER JAW with their contents, proving that these tubes do act as conduits for the nerves and bloodvessels. Fig. 36 is from a specimen which was prepared by grinding away the labial and lingual surfaces of the bone and teeth until the pulp chambers and apical foramina were exposed on both sides of the teeth, leaving the tissues extending out of the foramina and through a por- tion of the bony cribriform tube below. In one tooth, at A, the lateral wall has been broken away, leaving the tissues uncovered by hard structures on the three sides. It will be seen that the nerve has been pushed slightly away from the wall. In this dissection and in many others it will be observed that the tissues passing into the teeth give Fig. 36.—Ground section of the six anterior teeth and two left premolars. off small branches from the nerves and vessels just below the apical foramen. So clear does this appear that the writer is of the opinion that the lower portion of the aheolodental periosteum is supplied from the same branches of the nerves and vessels which supply the pulp. Pathological Significance.—The pathological significance of this condition is found in the reciprocal relation of pulp hyperemia and congestion with the same conditions affecting the apical portion of the peridental membrane so frequently observed in clinical practice. Fig. 37 is a vertical transverse section through the jaws and tongue at the location of the first molars, affording a good idea of the cortical portion of the bone heretofore referred to, of its relation with the roots of the teeth, and of the position of the cribriform tube with the nerve METHOD OF GROWTH 41 for which it serves as a conduit. (For further description of this illus- tration, see Fig. 196, page 220.) Fig. 38 is a view of the anterior portion of the lower jaw shown in Fig. 37- The roots of the second premolar, it will be seen, are nearly Middle Hiatus ethmoidal semilunaris cells Crystalline lens Unciform process Middle concha Middle meatus Maxillary sinus Inferior meatus Inferior nasal concha Vestibule of the mouth First molar Posterior root of first molar Mandibular nerve Fig. 37.—Anterior view of vertical transverse bilateral section of the head, showing the relations of the jaws and the U-shaped cortical bone of the mandible. in a line transversely with the anterior roots of the first molar, a con- dition which is not at all uncommon. As the premolar roots are long and comparatively slender, extending below the roots of the molar, 42 THE MANDIBLE OR LOWER JAW often nearh to the mandibular nerve, while the bone at this point is usually very compact, the difficulty occasionally met with, in extracting these teeth without breaking them, is readily accounted for. Surreal Pathology.—The relation of these roots to the cancellated tissue of the jaw has a pathological significance. If their pulps become diseased and infected, the infectious matter may pass out through the comparativelv open tissue and burrow in various directions, setting up an osteomyelitis and affecting the other teeth, eventually causing an abscess, the discharge of which may pass either through the mental foramen or through the alveolar wall into the mouth, or even through the main portion of the U-shaped cortical bone into the neck. The Anterior root of first molar Root of second premolar Mandibular nerve U-shaped cortical bone pIG 38,__a posterior view of an anterior transverse section of the mandible made through the anterior root of the first molar, showing the U-shaped cortical bone. necrotic process thus extended may include in its destructive area the apical regions of several adjacent teeth, causing devitalization of their pulps. It is the habit of some practitioners to inject hydrogen peroxide through the diseased teeth into abscesses of this character even before an external opening has been formed. The decomposition of the hydrogen peroxide in contact with the pus, generates gas with great force, if the gas has not a perfectly free outlet, it will burrow through the tissue in various directions of the least resistance and carry infection to any part of the mandible. The writer has seen cases in which the use of this drug, continued after extraction of the teeth has resulted in the loss of a large portion of the jaw (see Fig. 39). METHOD OF GROWTH 43 Fig. 39 is from a photograph of three sequestra produced by injecting hydrogen peroxide into a diseased mandible, the bone in each of these cases regenerated. Fig. 40 represents the left side of a lower jaw cut lengthwise nearly through its centre, exposing the cancellated tissue, the sockets of the teeth, and the cribriform tube or mandibular canal, with its branches to the alveoli. As the tissue is very frail, a considerable quantity of the trabecular was lost in the cutting. The outer section shows the direction of the recurrent tube for the accommodation of the mental nerve and vessels. Figs. 41 and 42 represent two sides of a metal cast showing the can- cellated structure within the U-shaped portion of the bone. It was made Fig. 39.—Sequestra from a mandible produced by the use of hydrogen peroxide. in the following manner, from a perfect and thoroughly cleaned jaw with all the teeth extracted. After covering the openings of the sockets of the teeth with paper, the end of a slender tube about eighteen inches long was inserted in the mandibular foramen. The bone and tube were then invested in plaster of Paris mixed with a little asbestos. After the investment was thoroughly set and dried, it was heated to about 2120 F., and a metal of low fusibility was poured into the tube. This metal passed into the cribriform tube and along its course, finding its way out through the many openings into the cancellated tissue and into the sockets of the removed teeth. After the plaster investment was removed, the body of the bone and the lower portion of the ramus were placed in a 10 per cent, solution of hydrochloric acid, which 44 THE MANDIBLE OR LOWER JAW dissolved the lime salts away, except where particles of the cancellated tissue are seen as white spots appearing through the metal. A trans- verse section of this preparation would show fine threads of bony tissue through the body of metal. Fig. 41 shows the inner surface, in which the cast of the canal or tube may be seen also the space occupied by the red marrow of the Fig. 40.—Longitudinal division of a mandible, exposing the cancellated tissues in the body of the jaw and between the sockets of the teeth. bone, the nerves, bloodvessels, and their membranes. In Fig. 42, which pictures the outer surface, the dense spot near the border beneath the second premolar indicates where the nerves and vessels passed out of the mental foramen. Fig. 43 is from a horizontal section of the upper and lower jaws, a little beyond the free margins of the alveolar processes. It shows the METHOD OF GROWTH 45 Fig. 41 Fig. 42 Figs. 41 and 42.—Two views of the sides of a metal cast of the open spaces in the body of the mandible. 4f> THE MANDIBLE OR LOWER JAW shape and position of the various roots on that plane, and their rela- tion to the process and to one another. The conditions here shown are so common as to warrant their classification as the normal type. First Second incisor incisor Canine Fig. 43.—Horizontal sections of the maxilla and mandible cut a little beyond the free margin of the alveolar process, showing the forms and positions of the roots of the various teeth. Particular attention is drawn to the slight distance between the roots and the plates of the alveolar process. It would be manifestly impos- sible in the operation of extraction, to force the beaks of forceps between METHOD OF GROWTH 47 the roots and the alveolar process in such cases without breaking the latter on one or both sides. The not infrequent splitting off of a section of the alveolar process in extraction is thus readily accounted for. The lines in the cut represent the strongest axes in the teeth, those along which the greatest force is exerted in extracting operations, and which are usually at the same time the lines of least resistance of the sur- rounding tissues. Root of canine Root of left second incisor Fig. 44.—Horizontal section of the mandible cut in the region of the points of the roots of the teeth. The roots of the teeth extend to various depths in the lower jaw, as is seen in Fig. 44, which represents a section cut horizontally, from the same subject as Fig. 43, though nearer to the ends of the roots. The ends of the roots of the second and third molars are plainly seen, also the tip of one of the roots of the first molar, and the roots of the first and second premolars. A little of the second incisors will be noticed, but the roots of the first incisors do not extend down so far. The can- cellated portion, with the soft tissue filling the spaces, is well shown 4S THE MANDIBLE OR LOWER JAW in the posterior portion of this picture. The nerve is seen passing into its tube. If all mandibles with their teeth were like those just described, surgery of the lower jaw would be comparatively simple. In fact, there would be little to do except in cases of traumatism; but unfor- tunately this is not the case, as will be demonstrated. INFLAMMATORY CHANGES. Inflammation within the lower jaw caused by diseased teeth, or by constitutional disturbances, may completely change the character of both the cancellated and cortical portions, by stimulating the bone- building cells of these tissues to undue activity. Under such circum- stances, the cancellated tissue may be filled up or converted into a substance so nearly resembling the cortical bone that the line of demar- cation is obliterated; while the cortical portion may be solidified— made more dense, ivory-like—and thickened, presenting conditions which very much complicate the situation and make the performance of operations difficult, and sometimes impracticable by the usual methods. Fig. 45 is taken from a section made transversely through the lower jaw at the mental foramen of each side. On the left side the cortical U-shaped portion and the cancellated tissues are about normal and in condition similar to those in Figs. 31 and 32, while on the right side the cortical portion has thickened and become dense, and the cancellated tissue has become filled with a deposit of secondary bone. The only apparent reason for this difference is that all the teeth on the left side were in good condition, while on the right side the first molar had been much diseased, causing the inflammation of that side of the jaw; vascular changes induced activity of the functions of the osteoblasts, which caused the deposit of secondary bone. Inflamed conditions in the jaws of children, occasioned either by abscessed teeth or by constitutional disturbances, will cause the deposit of secondary bone within the cancellated tissue, binding it to the U-shaped cortical portion. In such cases, when the time for the erup- NECROSIS AND REGENERATION 49 tion of the molars arrives, especially of the second and third, it is impossible for the cancellated tissue and the erupting teeth to glide forward as shown in Fig. 32. Many cases of impaction of the third molar are doubtless due to the existence of such conditions. Surgical Pathology.—The normal and pathological anatomy of the two sides of the jaw shown in Fig. 45 would require different modes of surgical procedure. The teeth on the right side, being placed in an unyielding bone, would fracture in an attempted extraction, and the roots would remain in the jaw. The cutting of the bone down to the Fig. 45.—Transverse division of a mandible at the mental foramina. The left side is in an almost normal condition, while on the right side the cortical bone has thickened and become dense, and the cancellated tissue has become filled with secondary bone. mandibular canal and nerve on the left side in a case of this character would also be quite a different operation from a similar operation on the right side. The first would be done with ease, the other with diffi- culty, and when the cutting was done it would be difficult to find and remove the nerve. Correction of irregularities of the teeth in the consolidated area would be almost impossible. NECROSIS AND REGENERATION. The formation of new bone to repair fractures throughout the human body is known to and observed by all surgeons, but the reproduction 4 :>n THE MANDIBLE OR LOWER JAW of large portions of the mandible has not received the attention it deserves. Before going into the details of this reproduction in the mandible it might be well to speak of the general growth of bone, about which there seems to be a difference of opinion. Many of the text-books on general anatomy and even some of the modern works on surgery, teach that the growth of bone depends to a great extent on the presence of the periosteum. Keen's Surgery,1 states, "In the long bones the vitality of the bone depends upon its relation to the periosteum and marrow. These two structures should be respected. In young persons the periosteum will regenerate new bone, and this property often may be used to the great advantage of the patient." "The periosteum is the most active osteogenic agent, but the medulla is also very active—Osteophytes may develop during the healing of a fracture. They are most apt to spring from points of tendinous inser- tion or from misplaced pieces of the periosteal tissue."'2 On the other hand, Dr. Clarence A. McWilliams, of New York, on "The Periosteum in Bone Transmission," says,3 "The theory that contact with living bone is necessary for the subsequent life of grafts must be given up. Living bone-grafts have life inherent in them- selves and are capable of permanent growth even when transplanted into the soft parts—48 per cent, of my bone grafts without periosteum were successful whether contact with living bone was made or not— periosteum transplanted into the soft parts will produce new bone in a certain proportion of cases." Dr. Alexis Carrell and Montrose T. Burrows, of the Rockefeller Institute, New York, have reported in their article "Cultivation of Adult Tissues and Organs Outside of the Body."4 "During the first hours of the cultivation of fragments of bone marrow and bone, the anatomic elements began to wander away from the tissue. After three or 1 Keen's Surgery, vol. v, p. 732. 2 Park's Surgery, third edition, p. 576. 3 Journal of the American Medical Association, January 31, 1914, p. 351. * Ibid., October 15, 1910, p. 1380. NECROSIS AND REGENERATION 51 four days, the little pieces of bone hidden in the marrow become visible, because almost all the cells had invaded the plasmatic medium. Around the tissue, there were radiating spindle cells and many red blood cor- puscles. Leukocytes with active ameboid motion and large cells with granular cytoplasm and long pseudopodia had reached the remotest part of the medium. A few large spindle cells were seen crawling along the edges of the fragments of bone." Sir William Macewen of Glasgow, has reported his experiments in his most valuable work1 that the growth and repair of bone does not depend upon the periosteum. One of his concluding remarks is, "While not underestimating the periosteum as a limiting and protecting mem- brane of great use in physiological and pathological conditions, there is no data to indicate that it can of itself secrete or reproduce bone. It has no osteogenic function." The process of normal growth of the mandible in length is quite different from that of the long bones, as there are no epiphyseal ends with the growth-producing intervening cartilage. As before stated, the growth of the mandible depends on an interstitial process which varies in different portions of the bone at different periods of life. This variation is to accommodate the development, growth and erup- tion of the teeth into their normal positions. If there be no living bone left on either side of that portion lost by pathological condi- tions or traumatism, there will be no regeneration of new bone, as this process for the repair of fractures and to furnish new bone is procured through the working of the osteogenic system in the bone remaining. In looking up literature of regeneration of the mandible the writer finds very little as compared with that written upon the regeneration of other bones. The most modern works on surgery with a few excep- tions scarcely mention it. The following is taken from Park's Surgery, third edition, page 550, under the head of phosphorus necrosis: "In aggravated cases, such as are rarely if ever seen today since legislation has been brought to 1 The Growth of Bone. :>-j THE MANDIBLE OR LOWER JAW bear upon the subject, practically complete necrosis of the lower jaw, either en masse or in portions, was far from unknown, and the possi- bilities of regeneration of the bone was for a long time discredited, until the late James R. Wood of New York exhibited a specimen, both at home and abroad, which proved its possibility. Since then we have learned that it is possible for bone thus to regenerate, the cause of the disturbance having been removed." One of the most interesting papers upon the subject of regenera- tion of the mandible was written by Dr. Percy, of Paris, in 1791, reporting five cases of regeneration of half or more of the lower jaw which had been destroyed by caries.1 Fig. 46.—Sequestra from tubercular necrosis. Cases of necrotic conditions of the mandible are of frequent occur- rence; some are of slight extent only, caused by infected teeth, which by proper treatment recovered in a short time. There are many others, however, where the whole mandible is more or less involved, the gums and the soft tissues along the lower portion of the bone become very much swollen, the teeth loosen, and, though at first there may be no sign of pus, in a few days it will exude from around the necks of the teeth and may also begin to point in one or more places. Free incisions should be made both in the mouth and along the under surface of the bone, it sometimes being necessary to drill through the cortical portion of the bone to obtain as free drainage as possible. On passing a probe, denuded bone will be found, which condition may extend all along the outer and under surfaces of the bone from the symphysis menti to the 1 Journal de Medecine de Chirurgie et de Pharmacie, Paris, 1791. NECROSIS AND REGENERATION 53 ramus and upward toward the mandibular notch. On opening the tissue so that the outer surface of the bone may be examined, the bone will be found to be somewhat darkened in color, there being numerous small soft spots indicating patches of caries, and in many cases the periosteum is absent having been lost by suppuration. Fig. 47.—X-ray picture of hydrogen peroxide necrosis. (AT-ray by Dr. Pancoast.) Fig. 46 is made from a necrotic sequestra and four teeth, which had been removed from a tubercular patient. The bone around the roots of the teeth was so fragile that it crumbled in pieces, leaving only a little band of soft connective tissue holding the teeth together, the condyloid and coronoid processes were left in position. On removing the sequestra new bone could be felt at the bottom of the space which 54 THE MANDIBLE OR LOWER JAW eventually became entirely filled with osseous tissue. The patient was of course edentulous, but had a new half of a mandible well covered with gum tissue and in good union with the other half. There was no ankylosis. Fig. 48.—X-ray picture of phosphorus necrosis, showing new bone formation on the lower border of mandible. (AT-ray by Dr. Pancoast.) Fig. 47 is taken from an x-ray picture, showing not only the spots on the surface but those in the internal structure of the bone. The body of the jaw appears to be in an advanced stage of necrosis, pus exuding through the tissue into the mouth at several points and through two external sinuses. The history of the case gave a diseased premolar tooth NECROSIS AND REGENERATION 55 which had been treated by hydrogen peroxide, then extracted, but the use of the drug was continued in the treatment of the socket and injected into the bone. Such cases are constantly occurring from the Fig. 49.—X-ray showing necrotic condition of mandible. (X-ray by Dr. Pancoast.) use of hydrogen peroxide upon diseased jaws. This treatment should be discontinued at once and the parts kept thoroughly cleansed by saline solutions. 5(i THE MANDIBLE OR LOWER JAW Fig. 4S is made from an .v-ray picture of the necrosed mandible ot a man who worked in a match factory. It shows a diseased condition of the entire mandible due to phosphorus necrosis, but at the same time a rim of new bone forming along its base. The following interesting case disclosed on examination complete pathological separation of the mandible on the left side in the region of the mental foramen. The bone and apparenth- the periosteum had been lost in the region of the second premolar, the bone around the first premolar was in a necrotic condition and the ends of the mandible on either side of the necrotic area were quite separated. Mastication was impossible and speech very much interfered with. The mandibular nerve had been divided, causing complete numbness of all that part supplied by it anterior to the lesion. This numbness continued for over a year after successful treatment and regeneration of the bone. It would be interesting to know just how the reestablishment of sensation occurs in such cases. It is a simple matter to understand the regeneration of a nerve where it does not pass through a long bony canal as in the mandible. When the body of the mandible or any portion of it involving the canal has been lost by necrosis it is a ques- tion whether regeneration of the bone is accompanied by reformation of the canal and nerve, there seems to be no affirmative evidence of this on record. In the opinion of the author, reestablishment of sen- sation in parts normally supplied by the mental nerve is due to trans- ference of this function to branches of the cervical plexis, and other branches of the fifth nerve, and not to regeneration of the mandibular nerve in the body of the bone. Figs. 49, 50, 51 and 52 are made from x-ray pictures of a patient of Dr. R. Hamil D. Swing's. The patient, a boy, aged seven years, had a badly swollen face with pus discharging in the mouth and through a sinus in the neck. In October, 1912, an x-ray picture was made (see Fig. 49) which shows the necrotic condition of the body of the mandible, with two developing teeth. It also shows a portion of new bone forming apparently from the old bone. The new bone has a process extending backward in the direction of the condyle, NECROSIS AND REGENERATION 01 although a short portion of the old bone was completely denuded. It was thought best to avoid the removal of the dead bone so that it might act as a splint to the new bone. Fig. 50.—X-ray showing regeneration of bone. (X-ray by Dr. Pancoast.) Fig. 50 is an x-ray picture taken November 29, 1913, showing two thin pieces of lead wire passing around the remains of the original bone which is much reduced in thickness. The portion between the rings of wire is quite denuded, and can be plainly seen within the mouth. 5s THE MANDIBLE OR LOWER JAW Under the dead bone that is surrounded by the wires, the new bone may be seen to be forming, showing the new angle very plainh'. The old angle can also be seen. Fig. 51.—X-ray showing regeneration of bone of right half of mandible. (X-ray by Dr. Pancoast.) Fig. 51 is from an x-ray picture taken June 6, 1914. It shows a further increase in the size of the new bone and a deterioration of the old bone. A"-ray pictures were taken from time to time to watch the process of regeneration. In February, 1915, the anterior end of the old bone near the canine tooth became loosened, the posterior end being still attached. On May 18, 1915, Dr. SwTing removed the necrosed jaw (see Fig. 52). Had FRACTURES OF THE MANDIBLE 50 this dead bone been removed as soon as diagnosed, the anterior portion of the mandible would have moved backward and to the side, but by keeping the old bone in place, in the nature of a splint, it gave time for a new half mandible to be regenerated. In all such cases the patient must be carefully watched as to general health, the mouth must be kept as clean as possible to avoid general septic troubles. Had there been any indication of disturbance it would have been necessary tc remove the dead bone, fortunately the child remained healthy through- out the degeneration of the old bone, and practical experience has demonstrated that when a patient is in good healthy condition, with no constitutional disease, it is possible to await developments despite the necrosed condition of the jaw. Fig. 52.—Sequestrum from diseased mandible. Fig. 52 is a sequestrum taken from diseased mandible, as shown in Figs. 49, 50 and 51. FRACTURES OF THE MANDIBLE. Owing to the exposed position of the mandible, fractures may occur at the symphisis at the mental foramen, at the angle, at the neck of the condyloid process or any intermediate portion of the bone. Fractures of the mandible are similar in character to those of the other bones, though compound fractures are most common; the dis- placement of the parts is caused by the action of the various muscles attached to the bone. The displacement is sometimes very marked, especially in a double fracture. Ill) THE MANDIBLE OR LOWER JAW Fractures associated with the mouth are very apt to become a source of infection, not only to the surrounding tissue but to the general system. In treatment, teeth and any fragments of bone found in connection with the break should be removed, and everything possible be done to avoid sepsis. Wiring of the teeth or the screwing of metal plates across the fracture should be avoided. Cases of simple fracture with but little displacement, can be treated by the use of Barton bandage, reinforced when necessary by crinolin and plaster of Paris. If a bandage of this character becomes stretched, it should be cut in four places, the "slack" taken out and the places reunited by adhesive strips. <* \____ Fig. 53.—An interdental splint on a fractured mandible. The best splints are of two characters: First, a swaged metal interdental splint as shown in Fig. 53; second, a swaged and soldered metal maxillomandibular splint as shown in x-ray picture (Fig. 54). When splints of this character are properly made and cemented into place the bandage can be discarded. Fracture of the neck of the condyle is difficult to diagnose. The principal symptoms are pain in the condyloid region and malocclusion of the teeth, the molar teeth of the broken side striking together before the others. X-ray pictures should be made in both lateral and antero- posterior directions. The latter pictures should show the head of the FRACTURES OF THE MANDIBLE 61 condyle carried inward and forward as seen in Figs. 55, 56, 57 and 58. In these fractures the continued actions of the temporalis, the masse- ter and pterygoideus internus pull the ramus upward and backward until the broken end of the ramus strikes the condyloid fossa, the Fig. 54.—X-ray showing a maxillomandibular splint in position. (X-ray by Dr. Pancoast.) muscular action of the pterygoideus externus carries the head of the condyle forward and inward, and it unites by ossification in this position. The best operation, so far suggested for treatment soon after the accident, is to get all teeth in normal occlusion, if possible, and hold (VI THE MANDIBLE OR LOWER JAW them there by a maxillomandibular splint. By inaction, the muscles of mastication will relax, which will allow the head of the condyle to take a fairly normal position. Fig. 55.—A mandible, showing the left condyle in an abnormal position. If, as is the usual way, the head of the condyle is allowed to unite in the position shown in the illustrations, the best treatment is to have a dentist correct the occlusion as far as possible by mechanical means. Fig. 56.—Showing a reunited fracture of the neck of the condyle in an abnormal position. Fig. 55 is taken from a mandible showing the right condyle in normal position, while the left is fairly typical of a fractured neck of the condyle. The action of the pterygoideus externus carried the FRACTURES OF THE MANDIBLE 63 Fig. 57.—Side view of a skull showing fractured neck of the condyle. Fig. 58.—Anterior view of a skull, showing the position of the condyle process after the fracture of its neck. l>4 THE MANDIBLE OR LOWER JAW head of the condyle forward and inward in which position the osseus union of the parts occured. The relations between the head of the condyle and the mandibular foramen would more than likely interfere with the mandibular nerve and vessels. This illustration also shows that there had been another fracture extending from between the second incisor and canine teeth downward through the body of the bone. Fig. 56 is from a similar specimen, showing similar condition of the head of the condyle. Fig. 57 is a side view of a skull showing fracture of the neck of the condyle, the head of the condyle is bent inward and forward until it nearly forms a right angle with the ramus. Fig. 58 is an anterior view of a skull, showing the mandible (Fig. 55) in position. The right side is normal, the left side shows the con- dyle carried forward and inward until it rests in the sphenomaxillary space. X-ray pictures of the living subjects will show similar condi- tions. NEURALGIA. Secondary bone deposit in the cortical and cancellated tissue of the face is an important factor in producing facial neuralgia, as branches of the trigeminal nerve pass through not only to the bone itself, but also to the region beyond in various directions. In the left side of Fig. 45 the spaces are comparatively open, while the right side of the same jaw is nearly solid; nerves passing through this half would be impinged upon, and neuralgia, the cause of which would be difficult to determine, would result. In neuralgia from this cause, the obvious treatment would be the burring away of the greater part of the abnormally solidi- fied bone, using the surgical engine, a much better agent for its removal than the ordinary mallet and chisel. SECONDARY DEPOSITS. The cancellated portion of the mandible usually increases in com- pactness as persons advance in years. Along with the progressive increase in density of the tissues due to advancing years, other factors, SECONDARY DEPOSITS (V) pathological in character, by which the teeth become diseased, set up an inflammatory condition which causes secondary deposits. Fig. 59 shows several sections from a lower jaw, which was not quite normal, there being evidence of past inflammation having changed the structure of the bone. Several teeth had been extracted before death. In some of the sections only one canal is seen, while in others several appear, necessitating close observation to decide into which the main nerves and vessels have passed. ABC D e F G H I J Fig. 59.—Sections made at different points from a mandible which was not quite normal in its density. In the resection or removal of the entire nerve from the bone, a surgeon not anticipating this condition might easily clean out a portion of a canal without touching the main nerve. This mistake might not occur in the dry bone, but in the living, where the parts are vascular, the error could easily be made. In section D (Fig. 59) it will be seen that the anterior root of the second molar penetrates the true mandib- ular nerve canal. In case of abscess of this root, the discharge would 5 Ill) THE MANDIBLE OR LOWER JAW flow into the nerve canal, thence backward or forward along the nerve, causing great pain by compression. Fig. 60 represents a specimen in which the roots of the third molar passed out through the inner wall of the lower jaw, at a considerable distance below the mylohyoid ridge. A putrescent pulp in this tooth would have discharged its infective matter at once into the submaxillary triangle. The writer believes that there are many serious unrecognized cases where devitalized teeth of this character cause infection of the Fig. 60.—Part of a mandible, showing the roots of the third molar tooth passing through the inner wall into the submaxillary fossa. tissues of the neck, and even of the thoracic cavity. Therefore, if diseased teeth in this region do not respond to treatment at once, they should be extracted, as not only ill health, but death itself may occur from their presence. The writer has seen large triangular swellings just under the jaw, which indicated that there was a focus of disease within the submaxillary triangle, a symptom of an enlarged submaxillary gland. L^pon examination of the teeth a diseased molar was found, and after this tooth was removed the swelling subsided. MANDIBULAR TRIANGLE 67 MANDIBULAR TRIANGLE. A marked variation of the lower jaw is found in the relative dis- tances between the centres of the two condyles and between these and the first incisors. These measurements have been commonly accepted as describing an equilateral triangle. The measurements of the jaws which have passed through the writer's hands do not bear out this hypothesis. In fact, the variations are as great as in any other feature of the face. In only one case was an exact equilateral triangle found. Some approached that figure, but in the great majority the sides of the triangle, taking the distance between the centres of the two con- Fig. 61 Fig. 62 Figs. 61 and 62.—Two mandibles showing variations in distance between the two condyles and from the condyles to the incisor teeth. dyles as the base, considerably exceeded the length of the base. In rare instances the base exceeded the length of the sides. The varia- tions here noted would seem to indicate that while the equilateral triangle may be assumed as a general basic principle in the architecture of the krwer jaw, the variations are the anatomical facts with which we are practically concerned so long as the hypothetical form remains unproved. Figs. 61 and 62 are made from photographs of two jaws in which rather extreme conditions were found. In Fig. 61 the base of the triangle is nearly one-third shorter than either of the sides. In Fig. 62 the base exceeds either side. Between these extremes (and probably to lis THE MANDIBLE OR LOWER JAW some extent beyond them on either side) every variation in the rela- tion of the sides to the base of the triangle may be found in normal jaws. In this description of the lower jaw or mandible, the intention has been to emphasize the necessity for the surgeon to promptly recognize departures from the accepted diagrammatic form of the normal jaw, and the results of pathological changes in its structures. The attempt has been to illustrate this necessity by typical cases which should serve to entorce principles, rather than enter into details. THE MANDIBULAR ARTICULATION. The mandibular articulation is formed by the condyloid process of the mandible and the anterior portion of the mandibular fossa of Fig. 63.—Lateral section showing the relation between the condyle and the acoustic meatus. the temporal bone with the articulating disk between. The petro- tympanic fissure is immediately behind the condyle with the articular tubercle in front. This articulation brings the mandible into close relation with one of the most important bones of the cranium—the temporal. This bone forms a portion of the base of the brain case, it contains the THE MANDIBULAR ARTICULATION OU canal through which the carotid artery passes to supply the greater part of the brain and the eye, in the posterior portion is the great groove for the lateral sinus, the nerve of facial expression passes through a tortuous canal in the bone, and the organ of the special sense of hearing is located in the petrous portion, in close juxtaposition to the condyloid process of the mandible. Fig. 64.—Vertical section showing meatus, acoustic tube, middle ear, etc. Fig. 63 is made from a specimen, showing the relation between the condyloid process of the mandible and the mandibular fossa, the exter- nal acoustic meatus and the parotid gland. Fig. 64 is a vertical section made through the left ear, giving a posterior view of the external acoustic meatus, the tympanic membrane and cavity, the auditory tube, and a section of the condyle. A most important point is the relation of the condyle to the temporal bone and 70 THE MANDIBLE OR LOWER JAW its surrounding tissue; the attachment of the pterygoideus externus is well shown. In case of fracture of the neck of the condyle, the mus- cular fibers would pull the head of the process inward and forward as described under the fracture of the neck of the condyle. The movements permitted by the mandibular articulation arc more varied and of a greater number than those of any joint in the body. The jaw has the power of extension and retraction, on one or both sides, it can be depressed and elevated, moved from side to side, and combines all the movements intermediate between these, thus allowing the gliding motion necessary to mastication. The articular disk (interarticular fibrocartilage) probably assists in these varied movements and acts as a multiplier of them. If the mechanism of the articulation of the mandible be carefully examined it will be found that the sphenomandibular, temporo- mandibular, and stylomandibular ligaments act as suspensories to the jaw and have a tendency to fix the angle when it is carried slightly downward and forward', as when the mouth is partially opened. The muscular fibers of the pterygoideus internus and the external portion of the masseter muscles have the same tendency. The condyloid pro- cess of the mandible acts as the fulcrum or pivotal point of the bone. The point, or fulcrum, mainly through the action of the pterygoideus externus, moves forward with its cushion, the articular disk. While the jaw is being carried forward the mouth can be opened slightly, still retaining the fulcrum, or pivotal point at the end of the condyle, but as the mouth is opened wider, the fulcrum is gradually changed from the condyle toward the more central portion of the ramus and then toward the angle, probably eventually becoming the fulcral point through the partial fixation of the ligaments and muscles before referred to. By the action of the pterygoideus externus, the condyle is drawn forward, and the mouth is thrown wide open, with the con- dyle under or slightly in advance of the articular tubercle, as shown in radiograms taken when the mouth is wide open. It is thus that the pterygoideus externus becomes an opener of the mouth. The reason for the change of fulcrum, or pivotal point, may be found in the con- dition which is obtained in the pharyngeal region. If in opening the THE MANDIBULAR ARTICULATION 71 mouth wide the head of the condyle acted within the mandibular fossa as the only pivotal point, the lower portion of the ramus with the body of the bone, the hyoid bone, the base of the tongue, and other asso- ciated tissues would be carried backward until the soft tissue coming against the postpharyngeal wall would interfere with the functions of that region. By the transfer of the point, this interference is avoided. In man the mandibular articulation presents the combination of an arthrodial and a ginglymus or hinge joint. In the carnivora, this joint has no gliding movement as the condyle is a half cylinder working Fig. 65.—Side view of a skull of a Hydrocherus capybara. Fig. 66.—Under view of a skull of a Hydrocherus capybara. in a deep mandibular fossa of corresponding form, which only allows an up and down or hinge movement. In some of the herbivora the condyles of the mandible are only slightly convex and the mandibular fossa of the temporal bones are but slightly concave. This arrange- ment allows great latitude of motion, and the ginglymo-arthrodial nature of the joint is somewhat greater than it is in man.1 The mandibular articulation of the rodents is quite different. 1 For full anatomical description of this joint see general text-book on anatomy. 72 THE MANDIBLE OR LOWER JAW Figs. 65, 66 and 67 are three views of the Hydrocherus capybara, the largest rodent now living. Fig. 65 shows the grinding teeth in occlusion. It will be noticed that the lower incisors are considerably posterior to the upper. Fig. 66. It will be noticed that the mandibular fossa (groove) is quite long anteroposteriorly, which allows great latitude in carrying the lower jaw forward and permits the upper and lower incisors to come into contact for gnawing purposes while the posterior teeth do not occlude. The structure of these teeth consist of enamel plates somewhat like those of the elephant though the cement substance only binds the centres of the plates, leaving knife-like edges on the lingual and buccal surfaces, and partially on the occluding surface. Fig. 67.—Side view of a mandible of a Hydrocherus capybara. Fig. 67 gives a lateral view of the mandible of Fig. 65, showing that the condyloid process, the occluding surfaces of the grinding teeth and the incisors are nearly in a straight line and that the angle of the jaw extends backward beyond the vertical line of the condyles. If the mandibular articulation of a vertebrate be shown to one familiar with the anatomy and occlusion of the teeth in relation to this joint, he could readily classify the animal and give the character of the mandibular articulation also of the maxillary sinus and the alimentary canal. At birth the mandibular articulation of the vertebrates is very similar; but as life advances the similarity disappears, conditions change in proportion to the environment and character of the food. In man the mandibular fossa is quite flat at birth, and there is but THE MANDIBULAR ARTICULATION 73 little change until the child begins to masticate, it then deepens rapidly until about puberty. As age advances the articulation again changes and the mandibular fossa becomes more flattened like that of child- hood. Fig. 68 is made from a side view of a human skull at the time of birth. The mandible articulates in its fossa, the condyloid process is in close juxtaposition to the acoustic process. The fossa is flat and shallow, the condyles are short and rounded. Posterior to the fossa, Fig. 68.—Side view of skull at birth. is the acoustic ring upon which the tympanic membrane is suspended, and also upon which the greater portion of the wall of the external acoustic meatus is built, there is but little change until sometime after birth, it will be noticed how slight is the protection over the organ of hearing and the articulation. An inflammatory condition of this region from any cause, could produce various kinds of mal- occlusion of the teeth and serious acoustic troubles. Fig. 69 is made from the under surface of a human skull at birth. It will be observed that the lower jaw occludes within the upper. 74 THE MANDIBLE OR LOWER JAW The conchloid process is close to the wall of the external acoustic meatus. Part of the tympanic membrane and the auditory ossicles have been preserved, but there is no bony protection to these delicate structures at this period, consequently they are often injured at the time of birth by the use of forceps. Fig. 70 is made from a side view of a skull, showing a slight forward occlusion of the mandibular teeth. It will be noticed that the man- dibular articulation is quite like that of the carnivora, the fossa being Fig. 69.—View of base of skull at birth. deep and narrow, allowing but little play in the joint. The anterior wall of the external acoustic meatus is defective, its resorption may have been caused by the pressure of the condyle, or the wall may never have been formed. There are many cases where the anterior osseous wall of the acoustic meatus is lacking and where the condyle presses against the mem- THE MANDIBULAR ARTICULATION to branous meatus, thus interfering with hearing. Otologists treating such cases often request the patient to open the mouth wide, this usually draws the condyle forward, giving a clear view to the tympanic membrane. Fig. 70.—Side view of skull, showing forward occlusion of mandibular teeth. From the relation shown in the structure of the mandibular articula- tion, it is very evident that in changing the position of this articulation, a forward placement of the jaw could be accomplished with less risk than a backward placement. These pathological points should be taken into consideration when applying pressure on the lower jaw for correction of malocclusion. CHAPTER IV. THE MAXILL/E. The upper jaw, from a surgical point of view, includes the right and left maxilla?, part of the ethmoid and sphenoid bones of the cra- nium, and in addition all the other facial bones except the mandible. The surgical operation of removing the right or left maxilla does not usually involve the removal of the entire bone, for the frontal process, the floor of the orbit, and the zygomatic surface may be left. In its removal, however, the inferior concha, portions of the lacrimal, the palatal, the zygoma, and the ethmoid bones will probably be removed with it. Especially is this true in the general method of operating, but if the resections are made with the assistance of the surgical engine, the greater portion of the associated bones may be left undisturbed. Architectural Features.—The maxillae are situated beneath the walls of the anterior fossae of the brain-case and rather loosely attached by what may be termed buttresses and flying buttresses. In the centre, near the nasion, the frontal processes rest firmly against a buttress in the median line, the maxillary processes of the frontal bone. Below is a flying buttress, the nasal septum, especially that portion formed by the vomer, which passes upward and backward from the interarticulating ridge of the maxillae and palate bones to the buttress- like body of the sphenoid bone, where it is firmly held or braced in place by the vaginal processes. Laterally the upper jaw is supported through the zygomatic bones by the zygomatic processes of the frontal bone and the flying buttresses of the zygomatic arches to the temporal bones at the sides of the skull; posteriorly by the pterygoid process of the sphenoid, with a portion of the palate bone interposed. The buttresses, situated and distributed as they are, not only afford support against forces acting externally, but also dissipate and diffuse shocks which would otherwise be transmitted to the cranium. As a consequence of its construction, but little force in a forward direction THE ALVEOLAR PROCESS t ( is necessary to detach the upper jaw from the cranium, though it will withstand a blow of great force received from below7 through the lower jaw or from in front, or even from the side. Pathological Relations.—The upper jaw gives support to one-half of the teeth and like the mandible is subject to defects of development and to various pathological changes, chief among which may be men- tioned cleft palate congenital or acquired, necrosis, caries, sarcoma, odontoma, odontocele, impacted and supernumerary teeth. It may also be affected by alveolar and dento-alveolar abscesses, diseases of the mucous-lined sinuses and air spaces, which last may also give rise to such symptoms as impaired respiration and the discharge of offen- sive matter. Tumors or abscesses of the maxillary sinus often grow- to such a size as to elevate the floor of the orbit, depress the roof of the mouth, and force outward the walls of the cavity, distorting the con- tour of the face in the region of the canine fossae. Neuralgia in the teeth may be symptomatic of disease of the bones of the jaw, and neuralgia in many regions of the head is traceable to the teeth. The under surface of the upper jaw is bounded by the alveolar process and the roof of the mouth or the palatal processes, both of which are covered by periosteum and mucous membrane (mucoperi- osteum). That portion of the mucous membrane over the alveolar process is thick and dense, and is known as gum tissue; it contains but few mucous glands, while the portion covering the roof of the mouth is not so dense, and is well supplied with racemose mucous glands. The Alveolar Process.—The alveolar process is made up of two plates, an external and an internal, consisting of dense, compact, cor- tical bone. The outer plate extends upward and merges, without a line of demarkation, into the outer surface of the true maxilla. The inner plate extends upward and inward and is continuous with the palatal process of the palate bone and maxilla proper. The space between the plates is occupied by the sockets of the teeth, the alveoli, which are surrounded by a very thin cribriform plate of bone (the lamina dura1) by cancellated tissue, nerves, vessels, etc. The alveolar 1 A. Hopewell-Smith, Dental Cosmos, August, 1913. 7S THE MANILL.K process belongs to the teeth and is developed with them for the pur- pose of holding them in position. It disappears in various degrees after the teeth are lost, sometimes before, more especially when there is pyorrhea alveolaris, and also as an indication of advancing age. Should the alveolar process be the primary seat of disease, sound teeth will loosen and may fall out. The outer alveolar plate is resorbed after the loss of the teeth to a greater extent than the inner one, which is of advantage to the dentist in fitting artificial teeth to the gums; con- sequently, in extracting teeth this fact should be remembered, so that injury to the internal plate may be avoided. At the same time, no particular harm results from the removal of a small portion of the outer plate, though the loss of any gum tissue should be avoided if possible. In the alveolar process, each tooth has its own individual process; as the tooth develops and pushes into its position the process grows around it. These processes are bound together by connective tissue, which vary in number and strength of union in different parts of the circumference, becoming less strong in the upper jaw in the processes between the canine and second incisor teeth, while between the two first incisors there are no bonds of union; consequently when a force is applied for the purpose of spreading the dental arch, the circum- ference increases by the stretching of the connective-tissue fibers of the alveolar processes, and as the interpremaxillary suture is the weakest point, it naturally opens when sufficient force is used. The interpremaxillary suture must not, however, be confused with the intermaxillary which does not open (see Fig. 74). Sutures of the Roof of the Mouth are seven in number (see Figs. 71, 72, 73 and 74). The median palatal suture begins at the centre of the free margin of the hard palate or posterior nasal spine, passes forward between the palatal bone, then between the true maxillae to the incisive foramen, then forward between the premaxillae, terminating at the anterior nasal spine. It is divided into three sections, namely, the interpalatal, the intermaxillary, and the interpremaxillary sutures. There are four transverse sutures, two situated between the palatal bone and the SUTURES OF THE ROOF OF THE MOUTH Fig. 71.—View of under surface of a skull of about five and a half years of age, showing the roof of the mouth with the deciduous teeth in position and the various sutures. Fig. 72.—Anterior view of the same skull as Fig. 71, showing non-union of the two premaxillae in the median line. so THE MANILL.E palatal processes of the maxillae and two pass outward Irom the inci- sive foramen between the maxillae and premaxillary bones, they also pass between the canine teeth and the second incisors. When there is a lack of union in the first two portions of the median palatine sutures and one passing between the canine tooth and the second incisor, there is a single complete congenital cleft palate. If the two sutures passing Fig. 73.—Under view of a child's skull with sutures radiating from the media suture toward the interspace between the teeth. between the canine teeth and the second incisors are not united, there is a double complete congenital cleft palate. Fig. 73 is from a child's skull, showing more than the usual seven sutures, radiating from the median suture out toward the interspaces between the teeth. Prof. Paul Olbrecht1 has also recognized similar conditions. 1 Transactions of the American Society of Orthodontists for 1908. STUDIES OF CERTAIN EXTERNAL SURFACES OF THE SKULL Si Fig. 74 gives a fair idea of the alveoli of the upper jaw, and indi- cates the position of the seven sutures of the roof of the mouth. It will be observed that there are two sockets for the roots of the second premolar teeth. This is not usual, though it occurs occasionally. On the right side there are spaces for five roots for the third molar, which also is not common. Fig. 74.—View of the palatal surface of the upper jaw, showing the alveoli of the various teeth, and the seven sutures of the roof of the mouth. STUDIES OF CERTAIN EXTERNAL SURFACES OF THE SKULL. In order to thoroughly appreciate the differences in the bony anatomy of the face, it is necessary to study skulls and bones considered to be typical at various periods of life. Front View of Skull.—Fig. 75 represents a front view of a skull, it is nearly symmetrical, presenting the typical anatomy of the exter- nal bony structures of the face. There is but the slightest variation in the two sides. It will be noticed that the upper right first molar 6 S'J THE MANILL.E stands out slightly more than the left. The septum of the nose is seen to be deflected in the same direction, and upon examination of the Fig. 75.—Anterior view of the typical skull. internal structures of the nose it is found that the bulla ethmoidalis is enlarged on the left side, projecting toward the concavity in the STUDIES OF CERTAIN EXTERNAL SURFACES OF THE SKULL 83 septum. This is an example of what might be taken as quite a constant anatomical law, that when the mouth, palate, and dental arches are Fig. 76.—Anterolateral view of a typical skull. bilaterally symmetrical, the outer cranial structures exhibit a like condition. M THE MANILL.E Fig. 76 is an anterolateral view of a skull giving a good idea of the occlusion of the incisor, canine, and premolar teeth. It also gives a good view of the facial bones and those associated with them. The inner wall of the orbit is well illustrated. Side View of Skulls.—The following illustrations are taken from various side views of skulls. Fig. 77.—Side view of typical skull. According to the present nomenclature the bone marked malar should be zygoma and that zygoma should be zygomatic arch. Fig. 77 shows a side view of a typical Caucasian skull (see mandible in Fig. 2, and base of skull in Fig. 90) which has been taken as the foun- dation for nearly all studies of the face. The teeth are in typical alignment, shape, and occlusion. Fig. 78 (see Mandible in Fig. 66, base of skull in Fig. 91) is of a dif- ferent character. It is taken from the skull of one of the West African tribes. The skull would be classified by nearly all as prognathous. If, however, this man had lived until all of his teeth and their alveolar processes had been lost, it is doubtful if the jaws, especially the lower one, would be considered prognathous. STUDIES OF CERTAIN EXTERNAL SURFACES OF THE SKULL So Fig. 78.—Side view of a West African skull. Fig. 79.—Side view of a skull belonging to a person of mixed races Mi THE MANILL.E Fig. 79 (see Mandible in Fig. 7, base of skull in Fig. 92) is made from a rather peculiar specimen. In this instance the two jaws are abnormally forward of the typical position. The cranial portion in itself is not of a prognathous character, although the basilar process of the occipital bone is longer than in typical skulls. Fig. 80 (see Mandible in Fig. 8, base of skull in Fig. 94) is made from a heavy skull, with unusually large, strong jaws and heavy teeth, which are in fairly good occlusion, except that the left second incisors Fig. 80.—Side view of a heavy skull. (See mandible, Fig. 8; base of skull, Fig. 94.) are a little out of place. The extraordinary size of the jaws and teeth produces a general appearance of prognathism, but the position of the teeth and their processes does not carry out the idea. Fig. TEETH INFLUENCED BY IRREGULAR ERUPTION outer side of the left anterior nares. The crown passes across the incisive foramen. Impaction of this kind would more than likely interfere with the true function of the nerves and vessels passing through this foramen. Fig. 152 illustrates a supernumerary second incisor impacted imme- diately below the floor of the nose. There was no enlargement of the external plates of the incisive fossa, the floor of the nose, or the roof of the mouth. The tooth was accidentally discovered when cutting the bone transverselv. Fig. 154.—From a Philippine skull, showing an impacted maxillary third molar. Fig. 153 exhibits an impacted and misplaced third molar. The occluding surface of the molar was even with the external plate of the alveolar process, the roots being compressed and somewhat shorter than normal. A complete thin layer of bone made a conical-shaped partition between the tooth sockets and the sinus. A similar condi- tion existed on the opposite side of the jaw. SUPERNUMERARY TEETH is:.! Fig- 154-—Made from the right side of a Philippine skull in Dr. Ketcham's collection. It shows a similar condition of impaction of the maxillary third molar to that in the Caucasian skull, Fig. 153. Fig. 155.—Is from the left side of the same skull as shown in Fig. 154. Fig. 156.—An impacted mandibular third molar. Fig. 156 exhibits an impacted mandibular third molar in the ramus of the jaw just below the anterior portion of the mandilular notch, the tooth being inverted. In this case the capsule of the germ of the tooth 1st TEETH INFLUENCED BY IRREGULAR ERUPTION became adherent to the walls of the jaw, and lost its position within the forming cancellated tissue, when the body of the jaw grew down- ward and forward. Fig. 157 shows a molar tooth in the ramus of the mandible. There is a light area around the greater portion of the crown. Teeth in this position in the living subject often give considerable trouble and their existence is very difficult to diagnose without the use of x-rays. Fig. 158 illustrates the most ccmmon kind of impacted lower third molar teeth. They often give great trouble by irritating the inferior alveolar nerve. They may also cause an inflammatory condition in Fig. 157.—A'-ray showing misplaced mandibular third molar. (Kirk.J this region, and the cellulitis may extend to the mandibular articulation and the base of the tongue. Figs. 159 and 160 represent a similar impaction. In Fig. 160 the external portion of the bone covering the tooth has been removed, and in Fig. 159 the internal portion. In both cases it will be observed that the mandibular canal is encroached upon. It is often necessary to cut away a portion of the bone with the surgical engine before a tooth so situated can be removed. Figs. 161 and 162 give two views of an impacted third molar. In Fig. 161 the tooth is in position as discovered when the cap of bone was removed; in Fig. 162 the tooth is removed from its socket, showing its inner surface. Its crypt is also seen. The second molar is a pulpless 5 UPERN UMERA RY TEETH IS.") Fig. 158.—A common form of impacted lower third molars. Fig. 159 Fig. 160 1st. TEETH INFLUENCED BY IRREGULAR ERUPTION tooth, the posterior root of which shows where the impacted tooth has pressed against it, causing resorption of a portion of the root until the Fig. 161 Fig. 162 Figs. 161 and 162.—Two views of an impacted lower third molar. Uppjr figure shows tooth in position; in lower figure the tooth is removed from its pocket. Part of the posterior root of the second molar has been resorbed, exposing the root-canal, more than likely causing the devitaliz- ation of the tooth and thus producing neuralgia, induced by the pressure from the impacted tooth. pulp-canal was fully exposed. The enamel of the impacted tooth is somewhat lost bv friction against the second molar. The roots of the SUPERNUMERARY TEETH 187 impacted teeth have a slight curve inward at their points; the con- cavity fits immediately over the alveolar or mandibular nerve, and has probably caused pain by pressure. The terminations of the roots Fig. 163.—X-ray picture, showing an impacted second mandibular premolar tooth. (X-ray by Dr. Pfahler.) Fig. 164.—Showing the resorption of the roots of the first mandibular molar (Fig. 163), where the crown of the second premolar had pressed against the roots. are not fully formed, the apical openings being large; it will also be noticed that the roots of the teeth in the jaw are longer than usual, that of the canine, for example, passing below the alveolar or man- dibuar nerve. 1.S.S TEETH INFLUENCED BY IRREGULAR ERUPTION Fig. 163, from an x-ray picture, showing an impacted second right mandibular premolar, its crown is resting against the roots of the first Fig. 165 Fig. 166 Figs. 165 and 166.—Two views of an impacted mandibular third molar. In Fig. 165 it is in its abnormal position; in Fig. 166 it is taken from its crypt. SUPERNUMERARY TEETH ISO molar and has caused resorption of the ends of the roots as shown in the extracted tooth (Fig. 164). Figs. 165 and 166 represent another impacted third molar, situated on the inner side of the jaw and pointing slightly dowmvard. The posterior root of the second molar is slightly resorbed. Upon uncover- ing the tooth and taking it from its crypt, it was found to be incased in a thin shell of bone, as though the dental capsule had ossified sepa- rately around the tooth. The inner portion of the shell is still in posi- tion, the nerve and its accompanying tissues are seen passing into Fig. 167.—An impacted mandibular third molar, and a mandibular third molar with curved and thickened root, both belonging to the same jaw. The bone is much more compacted than normal bone. the mandibular foramen and immediately under or against the shell. Here, again, must have been an obscure cause of neuralgia. Figs. 167 and 168 illustrate the right and left halves of the lower jaw, Fig. 167 showing the internal surface of the right half, while Fig. 168 shows the external surface of the left half. In the former we find the roots of the third molar curved backward at almost a right angle, and enlarged by an abnormal deposit of cementum until the independent character of the roots is lost, the two being fused together. Fig. 168 shows an impacted tooth pushing directly against the 1!»0 TEETH INFLUENCED BY IRREGULAR ERUPTION tooth in front of it. The roots of this tooth have also become much enlarged by deposit of cementum, while the surrounding bone has thickened and grown more compact. Fig. 168.—An impacted mandibular third molar, and a mandibular third molar with curved and thickened root, both belonging to the same jaw. The bone is much more compact than normal bone. Fig. 169.—A mandible showing an inverted lower third molar erupting into the right submaxillary fossa. (Dr. Whitney.) S UPERN UMERA RI' TEETH 191 Fig. 169 gives an illustration where the mandibular third molar has become inverted and is erupting into the submaxillary fossa. Fig. 1701 is from an x-ray picture showing impaction of the second and third right mandibular molars, it is possible that the third is between the first and second molars. Fig. 170.—An X-ray picture of a patient of Dr. A. R. Cook, of Syracuse, N. Y., it shows impacted second and third mandibular molars. Extraction.—It would have been almost impossible to extract either of the two last-named third molars without fracturing the jaw, unless the solid bone over the roots of the teeth had been removed first. In a case of this kind, it is much better to use the surgical engine bur than to cut or break the parts away with chisel 1 From a patient of Dr. A. R. Cook, Syracuse, N. Y. 11)2 TEETH INFLUENCED BY IRREGULAR ERUPTION or forceps. A fracture at this point will cause serious results; the mylohyoid artery is liable to be lacerated or even severed, and the hemorrhage is difficult to control. It is not easy to keep the region clean or aseptic, and the consequent inflammation will often interfere with free movement of the jaws in deglutition, speech, etc. The glottis even may become closed. Diagnosis.—Impacted teeth are frequently the obscure or hidden cause of various diseases about the mouth and jaws. There is often no external evidence of their impaction; patients may even claim that the teeth which cannot be seen have been extracted. Impacted incisors arc liable to induce diseases of the nose or to produce neuralgia by the tooth pressing the sphenopalatine nerve as it passes through the incisive foramen. Occasionally they cause a par- tial separation between the septum and the nasal floor. Impacted teeth may become either partly lodged in the inferior meatus, some- times causing the closure of the lower portion of the nasolacrimal duct, or they may lie horizontally across the roots of the incisors, espe- cially of the second, or the roots of the premolars, causing the devi- talization of these teeth. Impacted upper third molars are liable to interfere with the nerves and vessels in the floor of the maxillary sinus, near where they pass through the superior alveolar foramina into the sinus. They may also cause an enlargement of the tuberosity outwardly until it interferes with the ramus of the lower jaw, and produces a cellulitis which may extend to the mandibular articulation, causing false ankylosis. Neuralgia.—The three impacted teeth shown in Fig. 143 caused a baffling case of facial neuralgia until they were found and removed. The patient was past middle life and had suffered from neuralgia. He had no teeth in the alveolar process of the right maxilla, the region of pain, almost all of them having been extracted in the hope of giving relief. The sinus was opened by the late Professor Garretson and the writer in search of the cause. It was somewhat surprising to see three crowns protruding into the sinus, the roots being imbedded in the inner anterior angle of the wall of the maxillary sinus. After the teeth were extracted by small forceps the parts were treated in the usual SUPERNUMERARY TEETH 193 way, with relief and subsequent cure. The crowms were in normal shape and quite healthy, the roots more or less defective. The pulps were alive, and it is probable that the nerves were impinged upon at the points of the roots, thus causing the pain. The writer has seen several cases where a greater portion of the root of a single tooth was found within the antrum; but he believes this to be the only case where three such teeth have been reported. In the lower jaw impacted teeth are liable to impinge upon the mandibular nerve, thus becoming a hidden cause of neuralgia in this region, which may have its symp- toms exhibited almost anywhere along the distribution of the nerves, eventually producing neuritis that may pass back along the nerve even into the brain. Cysts.—Teeth prevented from passing in their normal course may, through the resorption of the bone, advance in almost any direction and be erupted through the bone even upon its cervical aspect. Impacted or supernumerary teeth may also produce dentigerous cysts of various sizes and forms, some of which may cause the cortical portion of the bone to be pushed outward until large disfiguring tumors are formed. These have sometimes been mistaken for malignant growths, and the entire body of the jaw has been removed on account of this enlarge- ment and mistaken diagnosis. There is considerable confusion in the nomenclature of tumors arising from the dental follicle. A dental cyst is understood by the writer to be one originating from remains of the embryonic epithelial elements of the peridental membrane. These epithelial "rests," as a result of septic infection of the tissue, rapidly proliferate, the central portions degenerate, and ultimately liquefy, thus giving origin to the cystic fluid. A dental cyst is lined with cortical epithelium, which in some instances may become ciliated. A dentigerous cyst is under- stood to be a growth brought about by tissue changes occurring in the dental capsule during developmental periods; as the name implies, it contains one or more teeth. The x-rays are the most valuable means of diagnosis. In both cases the principles of treatment are the same. This consists of evacuation of the fluid and solid contents of the cyst, and complete removal of 13 I'M TEETH INFLUENCED BY IRREGULAR ERUPTION the cyst wall, which, as alreach' noted, partialh or entireh' is lined with epithelial cells. If the cyst wall be not completely removed, these epithelial cells will continue to secrete fluid, and may proliferate with possibly the development of a malignant growth. The great majority of dental and dentigerous cysts can be removed through the mouth, Fig. 171.—X-ray picture from a child aged nine years, showing a retained deciduous second molar surrounded by an ovoid clear area which probably partook the nature of a follicular odontome. without operations on the face, and without destroying the continuity of the jaw bone, in case of involvement of the mandible. Fig. 171 is an x-ray photograph from the jaw of a child aged nine years. It shows a retained deciduous second molar at the bottom of the jaw, surrounded by an ovoid clear area. This patient had a swell- SUPERNUMERARY TEETH 195 ing of the left side of the lower jaw for about two years, which grad- ually increased in size, causing considerable deformity. Examination showed a smooth swelling about the size of a hen's egg, with thin, parchment-like walls, covered only by the mucous membrane. A diagnosis of dentigerous cyst was made. At operation through the mouth the thin shell of bone was found to contain no fluid, but a resilient mass of pinkish-white tissue surrounded by a sac of darker color. The contents including the soft tissue, the dental sac,.and the tooth shown in the picture were removed and the cavity lightly packed with gauze. The patient made an uneventful recovery. Pathological Report.—Characteristics of Tumor.—Size 3x3x3 cur. Macroscopic.—Pinkish-white mass of resilient tissue with villous or papillary surface, enclosed in sac of denser material, (1) premolar and (2) temporary molar embedded in wall. Microscopic.—Fibrocellular stroma, which in places shows small spaces lined with columnar epithelial cells. These cells are much elon- gated in places, and the nuclei appear to be situated away from the connective-tissue stroma, as in the ameloblasts. Here and there, instead of a cavity lined by the epithelial cells, the space appears to be filled with stellate reticulum. CHAPTER VII. THE NASAL CAVITY AND ITS ACCESSORY CELLS AND SINUSES. Descriptive Anatomy.—The nasal cavities—the internal nose—con- sist of two chambers situated on each side of the median line of the face, extending downward from the under surface of the anterior portion of the brain-case superiorly, to the upper surface of the bones forming the hard palate inferiorly, and from the facial border of the external aperture of the nose anteriorly to the free border of the external ptery- goid plate posteriorly. They are lined with mucoperiosteum, covered with ciliated epithelium; and the membrane is continuous with the lining of the several sinuses, cells, and passageways of this region. On the upper, lateral, and posterior borders of the nasal cavity there are various mucosa-lined sinuses, cells, and canals, all communicating with the cavity, the excess of fluids secreted by them passing into the nose. The nasolacrimal ducts conveying the excess of fluids from the anterior surface of the eyes, the auditory tubes communicating with the middle ear, and the maxillary sinus, the frontal sinus, the sphenoidal sinus, the ethmoidal cells, ethmosphenoidal cells, and the cells belong- ing to the orbital process of the palate bone, have their outlets in the nasal cavity. The cavities are separated by a thin partition of bone and cartilage, the nasal septum; it opens on the anterior surface by the anterior nares. The two principal functions of the nose of man are concerned with respiration and with the special sense of olfaction. The middle meatus of the nasal cavity forms the principle nasal passageway for the air into the respiratory tract, also for the expired air leaving the lungs. The upper portion of that part of the cavity formed by the ethmoid bone contains the beginning of the olfactory organs. As it is necessary to their function that these parts be kept moist, there are numerous pockets in and about them, the lining DESCRIPTII 'E A NA TOM I 197 membrane of which secretes fluids. These fluids pass over the shed- like projections of the concha bones into the nose, supplying the necessary moisture. Figs. 196 and 197 are good examples of the nasal cavities showing bilateral symmetry. For descriptive convenience it may be divided into roof, floor, and outer and inner walls, the last named being formed by the medial wall or nasal septum. The roof of the nasal cavity is long, narrow, and irregular in form. It is divided into anterior, middle, and posterior sections. The anterior portion is formed by the under surface of the nasal bones and the nasal spine of the frontal bone. It is concave from side to side, and extends inward and upward to the ethmoid bone, at an angle of about forty-five degrees. The middle portion is narrow, nearly horizontal in direction, and is composed of the under surface of the cribriform plate of the ethmoid bone, through the openings of which the filaments of the olfactory nerves pass between the nasal cavities and the brain. Beside the numerous openings there are slit-like foramina, which give passage to the nasal nerves and vessels. The cribriform plate, on account of its thinness, its sieve-like construction, and the presence of the slit-like openings, affords but a slight partition between the nasal cavity and the anterior portion of the brain-case. The posterior portion of the roof of the nose is the longest of the three parts, and extends from the posterior extremity of the cribriform plate obliquely downward and backward to the free margin of the internal pterygoid plate. It is composed of the body of the sphenoid bone and the alae of the vomer. The floor of the nasal cavity extends from the external opening anteriorly to the pharyngeal space posteriorly. It is smooth, and concave from side to side. The bony structure is composed, anteriorly of the intermaxilla, medially of the palate processes of the maxillae, and posteriorly of the horizontal plate of the palate bone. The naris are made up of cartilage lined with mucous membrane, and form the vestibule of the nose. In the normal nose, the floor joins this on the same plane and gradually slopes downward and backward (see Fig. 301). 19S NASAL CAVITY AND ITS ACCESSORY CELLS AND SINUSES Occasionally there is a depression immediately back of the union of the bone and cartilage. The floor often varies in its relative position to the other structures. It is seldom on the same level as the floor of the maxillary sinus; it may be on either a higher or a lower plane. Examples of these variations are seen in the sections shown in Figs. 261, 262, 263 and 264. The nasal septum (medial wall) forms the inner walls of the nasal cavities. It consists of six bony structures, named in the order of their importance—viz., the vertical plate of the ethmoid, the vomer, the crests of the maxillae and palate bones, the rostrum of the sphenoid, and the nasal spine of the frontal bone. These bones do not form the septum completely, but leave a triangular notch in the anterior portion, which is filled up with cartilage. Septal Spurs.—In Figs. 195, 196 and 197 it will be seen that the nasal septum is nearly vertical, without a bend or a nodular process or "spur" upon it. It is commonly thought by rhinologists that a straight septum is unusual. This would seem to be an error, probably due to the fact that the great majority of the noses which they examine are abnormal. It is quite true that in many cases the septum is more or less deflected to one side or the other, assuming a central position only as it passes downward and nears its connection with the floor of the cavity. On the convex side of the curve in these cases a ridge or pro- cess is often found which is called a "spur," and which may extend quite over and come in contact with the external wall or the inferior concha (see Figs. 262, 263, 281, 292 and 293). Nasal Meati.—The lateral wall is the most extended, irregular, and complicated portion of the nasal fossa. It varies, perhaps, more in its general formation than any other portion of the body of like size, and is correspondingly difficult to treat surgically. Several bones enter into its formation on each side—viz., the nasal, maxillary, lacrimal, ethmoid, inferior nasal concha and palate bones, the ptery- goid process, and the body of the sphenoid bone. By the projection of the inferior nasal concha and processes of the ethmoid bone, the wall is divided into several almost horizontal compartments known as meati. The anatomical works generally name three meati__the NASAL MEATI 199 inferior, the middle, and the superior. Zuckerkandl, however, says that about 6ttf per cent, of the skulls examined by him have had four meati. The writer has found about 60 per cent., with four meati in the skulls of which he has made sections (see Figs. 173 and 285). In many cases there are five, and in one skull six were found. Fig. 172.—Lateral wall of a left nasal cavity. Figs. 172 and 173 give a general idea of the arrangement of the outer walls of the nasal cavity. The upper portion, or all of that which belongs to the ethmoid bone, is associated with olfaction. The ends of the nerves, usually called the terminals, have their origin over this region; they also are distributed over the upper portion of 200 NASAL CAVITY AND ITS ACCESSORY CELLS AND SINUSES the septum and the roof of the nose. The fibers converge as they pass upward to form the filaments, and then through the various fora- mina in the cribriform plate of the ethmoid bone enter the olfactory bulb. The various meati have communications with the maxillary sinus and other air spaces which are formed in the bones of this region. Fig. 173.—Lateral walls of the nasal cavities, each showing four meati. A B Fig. 174.—Lateral walls of right and left nasal cavities, with large sphenoidal sinuses, B, having four meati. Fig. 174 gives a view of the lateral walls of the nasal cavity of the same skull as Figs. 215 and 216. The sphenoidal sinus extends later- ally until it forms the cavity posterior to the maxillary sinus. In Figs. 217 and 218 it will be observed that the large sphenoidal sinus extends NASOLACRIMAL CANALS 201 well forward toward the frontal bone and backward toward the basilar process of the occipital bone. Inferior Meatus.—The inferior meatus is situated between the inferior nasal concha and the floor of the nose. It is much longer than the others. Frontal sinus Middle nasal concha Ostium maxillare Middle meatus Posterior half of naso- lacrimal duct Inferior nasal concha Inferior meatus Fig. 175. Zygoma Alveolar process -Anterior view of a vertical transverse section of the right side of face. Internal wall of maxillary sinus Nasolacrimal Canals.—The nasolacrimal canals, which are for the accommodation of the nasolacrimal ducts, have their origin in the inner anterior lower angle of the orbits. The superior orifices commence between the nasal processes of the maxillae and the lachrimal bone. From this point the canals extend down and terminate in the upper portion of the inferior meatus of the nose (see Figs. 175, 176, 177, 178 and 179). The direction of their descent varies considerably in different subjects, and even in the same subject. They usually pass backward, 202 NASAL CAVITY AND ITS ACCESSORY CELLS AND SINUSES and when the maxillary sinus is large and the nasal cavity narrow, the direction may be inward; where the maxillary sinus is small and the nasal cavity wide, the direction is likely to be outward. In exceptional cases it is slightly curved. The duct may have a valve composed of mucous membrane at its lower extremity. Frontal sinus Nasal cavity Medial wall or nasal septum Inferior nasal concha Inferior meatus rimal duct Anterior half of nasolac- Zygomatic bone Anterior wall of maxillary sinus Hard palate Alveolar process Fig. 176.—Posterior view of a vertical section cut from the front of Fig. 175. Fig. 175 affords an anterior view of a section cut vertically or longitudinally through the nasolacrimal duct, showing its posterior portion as it passes from the orbit downward within the wall, separating the nasal cavity from the maxillary sinus, the duct terminating in the upper portion of the inferior meatus. On the upper right corner NASOLACRIMAL CANALS 203 is the frontal sinus. To the left of this is the orbit. In the centre of the wall between the orbit and the maxillary sinus will be seen the infra-orbital canal, and below it the maxillary sinus, which in this case is very large. In the upper portion of the nasal cavity is seen the middle nasal concha, below which a cord has been passed from the middle meatus through the ostium maxillare into the maxillary sinus. Posterior ethmoidal cells Orbit Middle meatus — Middle nasal concha Maxillary sinus1 Xasal septum Inferior nasal concha Inferior meatus Alveolar process Fig. 177.—Anterior view of vertical section cut posterior to that shown in Fig. 176. Fig. 176 is from a vertical section, cut transversely just within the infra-orbital ridge. In the upper portion is the anterior wall of the frontal sinus, on the left side is the middle wall, and to the right of this is the nasal cavity. The anterior half of the nasolacrimal duct, shown in the previous illustration, will be seen to commence at the inner angle of the orbit and terminate at the inferior meatus. !()■! .V.l.S'.lL CAVITY AND ITS ACCESSORY CELLS AND SINUSES Fig. 177 is from a section near the posterior wall of the maxillary sinus and the orbits, from the same subject as Figs. 175 and 176. It will be noticed that the wall of the maxillary sinus is very thin. At the upper right corner are seen the posterior ethmoidal cells, below which is the nasal cavity. Fig. 178 is from a section showing the greater portion of the upper jaw. The upper boundary is on a level with the middle of the orbits. Two sounds passed dowm into the nasolacrimal ducts indicate that Fig. 17S.—Section showing the greater portion of the upper jaw. S, S, sounds passed down the nasolacrimal ducts, showing that they do not pass at the same angle. The illustration also shows an impacted canine tooth. (For description see page 177.) the ducts pass outwardly as they descend into the upper part of the inferior meatus. It will be observed that the right duct has a greater outward deflection than the left. The horizontal line above the roots of the teeth and below the zygoma makes a division of the section just above the floor of the nasal cavity. The under surface of the upper portion is shown in Fig. 179, which affords a view of the surface of the inferior concha from below, with the lower orifices of the nasolacrimal duct. It also shows the lower edges of the middle and superior concha, and the N. 1 SOL. 1CRIMAL C1NALS 205 roofs of the antra. Attached to the roof of the right maxillary sinus are two abnormal bony growths generally known as osteophytes. The middle meatus is situated between the lower portion of the concha of the ethmoid bone and the inferior concha, and forms two-thirds of the posterior portion of the outer wall of the nasal cavity. This is the most important meatus, as it is the principle nasal Superior Middle concha meatus Fig. 179.—Horizontal section, showing the under surfaces of the inferior concha and the outlet of the nasolacrimal duct. passageway of respiration, and is subject to more variations in its anatomy, physiology, and pathology than are all the others. It has anatomical communications with the frontal and maxillary sinuses, and with the anterior and middle ethmoidal cells. In order to study this meatus and its relations, it is necessary to make a number of sections of the parts with all the tissues in place. By removing the middle concha, the structure of the parts is brought into view. 200 V.LS'.IL CAVITY AND ITS ACCESSORY CELLS AND SINUSES Fig. 180 shows the outer wall of the nasal cavity with the internal wall of the middle concha of the ethmoid bone cut loose and turned up, affording a good idea of the normal anatomy of this region. The frontal sinuses are exposed. In the illustration the right frontal sinus Fig. 180.—An anteroposterior section within the nasal cavity, with the middle concha and portion of the cell walls turned up. extends over the left side of the medial line. The open space imme- diately below this is the left frontal sinus. The partition between these sinuses in some places is thin. The lowrer portion of the left frontal sinus is funnel-shaped. This opens into a passage leading into the HIATUS SEMILUNARIS middle meatus, the funnel-shaped portion and the passage being commonly called the infundibulum. This illustration also gives a good idea of the nasal surface of the partition between the maxillary sinus and the great extent of the mucous-lined sinuses and cells that are so directly related with it. When these pneumatic spaces become diseased, it is almost impossible to keep the sinuses in hygienic condi- tion, and when the infection reaches them, they are much more diffi- cult to treat and drain than when the disturbance comes from the teeth or alveolar process. Hiatus Semilunaris.—The infundibulum is often included in the part which has been named by Zuckerkandl the hiatus semilunaris, and which extends from the frontal sinus to and through the middle meatus in the form of a semicircular groove or cleft along the outer wall of the meatus. It extends downward and backward in a curved direction, being horizontal in its posterior portion, and terminates a little behind the centre of the nasal cavity. At its commencement it is narrow, but it widens as it passes downward and backward, its widest part being at the bottom and near the opening between the maxillary sinus and the nasal cavity (ostium maxillare). Besides the opening of the frontal sinus into the hiatus semilunaris, there are openings from the anterior and middle ethmoidal cells, and from the maxillary sinus. Its inner boundary is falciform in shape, and is composed of the uncinate process of the ethmoid bone with mem- branous tissue, forming a shield or guard to the opening of the maxil- lary sinus, to prevent foreign substance from passing into it. A "sound" cannot be passed from the nasal cavity through the ostium maxillare into the maxillary sinus in a normal living person. The superior meatus is shallow, and is shorter than the inferior or middle meatus. It is situated between the superior and inferior concha masses of the ethmoid bone, and in the articulated skull between the superior and middle concha. The cell situated in the orbital pro- cess of the palate bone, the posterior ethmoidal cells, and the sphenoi- dal sinus all have their openings into this meatus when there are but three meati, but when there are four, the posterior ethmoidal cells and the sphenoidal sinus have their openings into the fourth or superior 2(>s NASAL CAVITY AND ITS ACCESSORY CELLS AND SINUSES meatus. If there are five meati the sphenoidal sinus usualh' opens into the fifth. In other words, this sinus has a tendency to open into the highest meatus. The fourth or superior meatus of Zuckerkandl is formed by an infolding of a portion of the concha similar to that of the third or superior meatus, though smaller in extent. When the fourth meatus exists, the fluids of the posterior ethmoidal cells and those from the sphenoidal sinus pass through it to reach the nasal cavity. The occasional fifth meatus is formed similarly to the third and fourth meati by an infolding of the upper portion of the ethmoid mass. In such cases the fluids from the sphenoidal sinus pass through it instead of into the fourth. PATHOLOGICAL CONDITION OF THE NASAL CAVITY. Pathological Conditions of the Bulla Ethmoidalis.—Through patho- logical increase in the size of the bulla ethmoidalis, disturbances may be caused in the anterior and superior portion of the nasal cavity, in the frontal sinus, and maxillary sinus, for by its enlargement toward the median line it presses toward and against the septum of the nose, closing the space of the nasal cavity. If this enlargement is downward it presses more upon the unciform process and into the hiatus semi- lunaris, closing it and preventing the passage of fluids from the frontal sinuses and the anterior ethmoidal cells into the posterior portion of the middle meatus, and forcing them to enter the maxillary sinus. Through general inflammation of the parts there may result an excess of fluids which cannot find exit. This would interfere with the vitality of the teeth through pressure upon the nerves and vessels passing through the maxillary sinus. It would cause a feeling of fulness of all the anterior cells, as well as the frontal sinus, and might even set up disturbance in the anterior portion of the brain-case. A view of the nasal septum as seen from the left nasal cavity is shown in Fig. 181. An opening in the septum exposes to view the bulla ethmoidalis and the ethmoidal cells. This opening resulted from resorption caused by pressure due to the deflection of the septum and PATHOLOGICAL CONDITION OF NASAL CAVITY 209 the enlargement of the bulla downward near the unciform process. We have here illustrated an example showing how enlargement of this structure may be an important factor in causing various diseases of this region, including those of the maxillary and frontal sinuses. Fig. 182 gives a view of the same subject as Fig. 181, from the same direction, but with the septum removed, exposing the inner surface of the outer wall of the right nasal cavity. Of the two openings into the maxillary sinus as seen in this picture, the anterior one is normal, the posterior is pathological. This abnormal opening and the loss of Fig. 181 • Fig. 182 Fig. 181.—The left side of the medial wall, showing a pathological opening opposite the bulla ethmoidalis. Fig. 182.—Same specimen with the septum removed, showing abnormal opening into the maxillary sinus. the greater portion of the middle concha were caused by resorption due to the pressure of the bulla ethmoidalis before referred to. The effect of blocking up the hiatus semilunaris, causing the secondary or associated openings between the sinus and the nasal cavities, is also shown in Fig. 185. Figs. 183 and 184 show two pictures from the left side of the same skull shown in Figs. 181 and 182. In Fig. 184 the middle concha is in position. The abnormal opening into the nasal cavity, seen near the centre of the picture, was probably the result of the closure of the 14 210 NASAL CAVITY AND ITS ACCESSORY CELLS AND SINL'SES hiatus semilunaris, shown in Fig. 1S3. In this the middle and a portion of the superior concha are cut loose and turned upward, to expose the bulla ethmoidalis extending downward and closing the hiatus. This Fig. 183 Fig. 184 Figs. 183 and 1S4.—Two pictures of the left nasal cavity from the same subject as Figs. 181 and 182, showing a pathological opening into the maxillary sinus in Fig. 184. Fig. 183, the same specimen as Fig. 184 with a portion of the middle and superior conchas cut loose and turned up. Fig. 185 Fig. 186 Figs. 185 and 186.—Anteroposterior sections, Fig. 185 through the nasal cavity, Fig. 186 through the maxillary sinus. The former shows a divided bulla ethmoidalis, the latter shows two ostia maxillaria, one being pathological. closure would compel the fluids from the frontal sinus and the anterior and middle ethmoidal cells to pass into the maxillary sinus. Figs. 185 and 186 show two anteroposterior sections from another skull in which the bulla ethmoidalis has become enlarged. Fig. 186 PATHOLOGICAL CONDITION OF NASAL CAVITY 211 has the outer wall of the maxillary sinus removed, showing the inner wall with two outlets at its upper margin. The anterior opening is the normal ostium maxillare. The posterior one is pathological and similar to those shown in Figs. 181, 182, 183 and 184, but in this case the opening is nearer the roof of the sinus. Fig. 185 is cut from the inner side of Fig 186. Figs. 187 and 188 illustrate the same sections as Figs. 185 and 186 with Fig. 188 turned round to the left side of the other. The illustration affords a view of the nasal cavity divided through the hiatus semilunaris, the bulla ethmoidalis, and the posterior ethmoidal cells. Fig. 188 shows the lateral wall of the nasal cavity with a greater Fig. 187 Fig. 188 Figs. 187 and 188.—Anteroposterior sections, cut apart through the frontal sinus, the hiatus semilunaris, the bulla ethmoidalis, and the posterior ethmoidal cells. portion of the conchae removed. Fig. 187 shows the septum of the nose. The two together give a very clear idea of the character of the hiatus semilunaris and the bulla ethmoidalis. In this case the bulla is very large and extends downward and forward, closing the hiatus. The illustration is taken from a dried specimen, showing an incomplete closure, which in the recent state must have been complete. This would have caused the fluids from the frontal sinus and the eth- moidal cells anterior to the closure to be directed into the maxillary sinus, as the ostium maxillare is also anterior to the bulla ethmoidalis. The maxillary sinus would become engorged with these fluids, which would naturally make their way through the walls in the direction of the 212 NASAL CAVITY AND ITS ACCESSORY CELLS AND SINUSES least resistance—in this case at the abnormal opening shown in Fig. 186. These sections also illustrate a condition sometimes met with, when the hard palate is unusually flat. In such cases the floor of the nose, instead of being horizontal, is depressed about the middle, giving a concavity which affords a lodgment for inspissated mucus. The same condition may also occur in the floor of the nose, when the inferior meatus is occluded, as shown in Fig. 262, and is also found in other spaces in and about the nasal cavity. Collections Fig. 189.—.1 shows the roof of the nasal cavity and the maxillary sinus, B shows the floor of the anterior fossa of the brain-case and part of the frontal sinuses, to one of which there is no foramen of exit. of this character often produce irritation of the mucous membrane interfering with the nourishment of the bone beneath, and at times causing a necrotic condition. Occlusion of the Outlets of the Frontal Sinus.—In Fig. 189, B shows a horizontal section through the anterior fossae of the brain-case and through the frontal sinuses, from one of which there has been no fora- men of exit, an example of unilateral occlusion. A view of the roofs of the maxillary sinuses and of the nasal cavity is given in A. The section shown in Fig. 190 is made from the same subject PATHOLOGICAL CONDITION OF NASAL CAVITY 213 as Fig. 189, one inch below B. It exhibits the downward excava- tion which has occurred in the occluded sinus. In the lower surface, A, is shown the excavation extending in the direction of the nasal spine. There are marked irregularities in the ethmoidal cells of the two sides. Fig. 191 also illustrates unilateral occlusion. This section displays the floor of the brain-case, showing a perforation at the point indicated by the thread passing through it. It is reasonable to suppose that the retained fluids have burrowed through the cribriform plate, causing B Fig. 190.—Horizontal sections in same subject as Fig. 189, showing surfaces cut through the middle of the orbits and the upper part of the nasal cavity. the perforation. The crista galli in the specimen, although not clearly shown in the picture, is bent downward until almost flat by what has evidently been a cyst or tumor within the brain-case in this region. Unfortunately, the writer was unable to obtain antemortem or clear postmortem notes of these two cases. It might be supposed, however, that the patients presented cerebral symptoms. In confirmation of this idea, there was evidence in the condition of the skulls that there had been a postmortem examination of them. 211 NASAL CAVITY AND ITS ACCESSORY CELLS AND SINUSES Fig. 192 is from the same specimen as Fig. 191. It shows the effects of the encroachment of the inflammatory and necrotic condition upon the internal wall of the orbit. Fig. 191.—Horizontal section, showing the floor of the anterior fossa of the brain-case and part of the frontal sinuses. The right sinus had no outlet into the hiatus semilunaris, but had an outlet into the anterior fossa of the brain-case. Fig. V)2.—From same subject as Fig. 191. View showing diseased condition of the inner wall of the orbit. Fig. 193, from the same specimen, shows a horizontal section made through the ethmoidal cells, the nasal fossae, etc., along the line indi- cated in Fig. 192. The two faces of the specimen show clearly the PATHOLOGICAL CONDITION OF NASAL CAVITY 215 broken-down condition produced in the track of the disease. The abnormal arrangement of the cells becomes especially apparent when compared with the typical arrangement shown in Figs. 257 and 258. Fig. 193.—From the same subject as Figs. 191 and 192. Horizontal division through the orbits and ethmoidal cells, showing the diseased condition of these cells. Obstruction of Fluids.—There is a fundamental law of surgery that, wherever an obstruction of any of the passages within the body exists, it should be removed, and if possible the course of fluids be reestablished in their normal channels or conduits. If the hiatus semi- lunaris, which is the outlet of the fluids of the frontal sinus, becomes closed in any portion, or at the inlets, by bony or other growths, it is 210 NASAL CAVITY AND ITS ACCESSORY CELLS AND SINUSES good and proper surgery to remove this obstruction. If the fluids from the various sinuses and cells are allowed to accumulate in the maxillary sinus without an opportunity to escape back into the nasal cavity, through a pathological or surgical opening, the teeth and their alveolar processes are liable to become involved. The mouth should by all means be kept free from foul discharge, and such proper surgical procedure instituted as will restore the natural outlets without infecting the oral cavity, as by the action of mastica- tion, septic fluids become mixed with the food and are thus distributed through the alimentary canal to infect the entire system. CHAPTER VIII. THE MAXILLARY SINUS. The maxillary sinus {antrum of High more) is situated in the body of the maxillae, and is the largest air space associated with the nasal cavity. It varies in shape, size, and in the thickness of its walls, accord- ing to age, race, and the presence or absence of teeth and tooth-germs Fig. 194.—A horizontal section of face cut just above the floor of the nasal cavity. within the jaw. It is lined with mucoperiosteum surmounted by ciliated epithelium. The typical sinus is pyramidal in shape, the apex being toward the zyomatic bone—into which it may extend (see Fig. 271)— and the base toward the nasal cavity. Its size and form vary in different 21s the MAXILLARY SINUS subjects, and even in the two sides of the same subject (see Figs. 2(>3, 2O4, 265 and 266). In rare cases, it is lacking on one or both sides (see Fig. 194). Fig. 194 shows two horizontal sections. The lower one giving a good view of a very wide floor of the nasal cavity. The upper one showing the walls of the nasal cavity, the concha bones and the septum. Fig. 195.—Skull of a fully developed embryo cut vertically through the first deciduous premolars. On the right side there is no maxillary sinus and on the left the sinus is very small, thus accounting for a wide nasal cavity. Fig. 195 is a view of the skull of a fully developed embryo.1 It is a transverse section cut vertically just within the floor of the orbit. In the upper portion are seen two openings into the brain-case with the crista galli and falx cerebri between them, below which is the nasal cavity with its septum. Projecting from the outer wall of the cavity 1 From the collection of Professor Thomas C. Stellwagen. DEVELOPMENT 219 are the middle and inferior concha. In the middle meatus may be seen the unciform process passing upward and a little inward from the base of the inferior concha. At the outer side of this is the passageway known as the hiatus semilunaris, into which the ostium maxillare passes from the maxillary sinus, which is very small at this period of embryonic life. Development.—The development of the sinus begins about the fourth month of intra-uterine life by an invagination of the lining membrane of the nose from the hiatus semilunaris into the body of the maxilla. From the time of the invagination until the eruption of the permanent teeth, the greater portion of the maxilla is occupied by the dental organs (see Fig. 137). As the invagination progresses, the cancellated portion of the bone undergoes resorption. This resorption of the internal portion of the maxilla is continued in a variable degree throughout life, until in old age the walls usually become exceedingly thin, as shown in Fig. 205. In some cases the decalcification and resorption are carried to such an extent that the entire bone is thinned, and an ordinary lancet blade can be easily passed through the wall into the sinus, or the entire substance of the bone may be resorbed in places, leaving nothing but the mucoperiosteum at these points. As this process goes on, the roots of the premolars and molars within the walls are approached, until in many places the points of the roots are covered only by a thin lamina of bone (see Figs. 202 and 203). Even this, in rare cases, may be lost, leaving only the mucoperiosteum as a root-covering. At first the sinus has a spheroidal shape, but it eventually ap- proaches the pyramidal form. Its walls are five in number, the inferior or floor, the anterior or facial, the posterior or zygomatic, the superior or roof, and the proximal or nasal. Fig. 196 is an excellent illustration of a transverse bilateral section cut vertically through the anterior portion of the orbit, the maxillary sinus, and the first molar of each jaw, dividing the eye just in front of the crystalline lens. In the upper portions of the nasal cavities are seen the middle ethmoid cells. At about the centre of the floor of the orbit and the roof of the sinus, which is very thin in this case, will 220 THE MAXILLARY SINUS be found the infraorbital canal as commonly described, and below, the nearly pyramidal cavity of the maxillary sinus, with a partial septum crossing transversely from the inner to the outer wall. — Crystalline lens Unciform process Middle concha Middle meatus __ .. —— — Maxillary sinus I ml tw— Inferior meatus J*."-*:.!"^ — - Inferior nasal concha Vestibule of the mouth First molar Posterior root of first molar Inferior alveolar nerve Fig. 196.—Anterior view of a vertical transverse section of the head, showing the relations of the jaws, and indicating the positions of the conchae, antra, etc. In the lower angle of the left sinus can be seen the anterior buccal root of the second molar, while on the inner wall is a portion of the palatal root of the first molar. The palatal root of the right first molar is easily seen passing well up in the inner wall of the sinus. DEVELOPMENT 221 The central portions afford excellent views of transverse sec- tions of the nasal cavity. The septum in the centre is unusually straight. Above the septum is the crista galli, to which the falx cerebri is attached anteriorly. On each side of the septum, at the upper attachment, is the roof of the nasal cavity, below at a little distance are the middle conchae, and, on the outer wall, are the inferior concha. The superior conchae cannot be seen in a section cut in this region, as they are situated farther back in the skull. First molar First molar Fig. 197.—Posterior view of vertical transverse section of the head from the same skull as Fig. 196, showing the ostium maxillare, which is indicated on each side by a cord passed through it. Fig. 197 represents the anterior portion of the same skull shown in Fig. 196. At the anterior superior angle of the maxillary sinus is a cord marking the passage (ostium maxillare) from the sinus into the hiatus semilunaris. In the floor of the maxillary sinus will be seen the septum referred to in the description of Fig. 196. On the left side will be observed the palatal and anterior buccal roots of the first molar in the outer and inner walls of the sinus. The positions of these roots, as shown here and in Fig. 196, are very interesting from a dental THE MAXILLARY SIXES standpoint. The extraction of teeth having roots in such positions, if not carefully done, might cany away parts of the floor ot the sinus (see Figs. 231, 232 and 233), or in case of breakage in extracting, the roots could easily be forced into the sinus by injudicious use of the forceps. Also, by using too much force in placing artificial crowns, the floor might be fractured. Fig. 198.—A"-ray of a dried skull. In the majority of the skulls belonging to the white races, roots of the molar teeth pass up into the walls of the maxillary sinus, being covered at the point where they approach the surface by a thin conical portion of bone. Fig. 198 is from a radiograph of the anterior portion of the face, showing two large frontal sinuses. Two wires may be seen passing DEVELOPMEXT 223 downward through the ostium frontalis into the hiatus semilunaris, and then into the maxillary sinus, by the ostium maxillare. The infra-orbital sinus and the inferior and middle conchae are seen, also two large cells between the plates of the latter. When the maxillary sinus is large early in life, and extends down- ward into the region of the roots of the teeth, it prevents their normal development in shape and position, the roots grow curved and in the case of molars, are compressed (see Figs. 202 and 203). After early middle life, as the dentine forms, the pulp canals become more or less narrowed until the nerves are impinged upon, causing pain (neuralgia). Fig. 199 is an x-ray picture of a large maxillary sinus, showing that it has apparently extended downward between the roots of the second premolar and the first molar; from the shape and position of the roots, especially of the first and second molar teeth, it is evident that the sinus was over size before these teeth were developed. In this par- ticular case the patient suffered from severe neuralgia of the upper jaw. The .x-ray showed the condition, and after removal of the first molar the pain subsided. Fig. 200 shows a section similar in character to Figs. 196 and 197, but from a negro skull. The greater thickness of the floor of the maxillary sinus, and the position of the roots of the teeth are note- worthy. In the negro race the walls and the floor are much thicker than in the white; therefore, as a rule, the roots of the teeth do not pass up into the wall, or even near the floor of the sinus. Fig. 201 is an illustration of a tooth which has been perforated by a drill while in the mouth, the operator supposing his drill was passing up the palatal root, instead of which it passed through the pulp chamber, the base of the crown, the alveolar process, and into the maxillary sinus. It will be observed that in extracting it, a portion of the floor of the sinus has been brought away with the tooth. At the time of extraction the patient was suffering from empyema of the maxillary sinus. The Floor.—The floor of the maxillary sinus is somewhat triangular in its general outline, and is usually uneven, owing to the presence of partial septa and conical elevations over the roots of the various 221 THE MAXILLARY SIXES teeth. These elevations are found over the roots of the molars, some- times over those of the premolars, and less frequently over those ot the canine teeth. As age advances and the teeth underlying the sinus are lost, the floor becomes comparatively smooth. Septa may extend to various heights transversely from side to side or anteroposterior!)- ^see Figs. 205 and 206), forming deep pockets between them. The Fig. 199.—Showing where a maxillary sinus has been large at the time of the developing of the roots of second premolar and first and second molar teeth. (X-ray by Dr. Pfahler.) floor of the sinus may descend between the roots of the molar teeth, as shown in Figs. 196 and 197. • It may also descend between the teeth (see Fig. 199), a condition much more common among the white races than among negroes. In the negro's skull these elevations over the roots of the teeth are seldom found because of the greater thick- ness of the bone, so that the floor of the sinus in the negro is usualh THE ANTERIOR WALL 99; smooth. The floor is concave from side to side and slightly so in the anteroposterior direction, as illustrated in Figs. 175, 200, 236 and 237, having thus a basin-like form, and being usually below the level of the nasal cavity (see Figs. 295 and 297). The Anterior Wall.—The anterior wall is almost a square with rounded corners. It is smooth, with a slight depression, which varies according to the position of the passage of the infra-orbital canal or tube, as shown in Figs. 223 and 230. Occasionally the roots of the Fig. 200.—Anterior view of a vertical trans- verse bilateral section of a negro skull, showing a deep alveolar process. Fig. 201.—Tooth which has been incorrectly drilled through while in the mouth. canine and premolar teeth are found in this wall. In infancy it con- tains the follicles of the anterior teeth (see Fig. 107). The anterior dental canal, for the accommodation of the superior alveolar nerves and vessels, passes from the sinus into the wall to reach the anterior teeth except the incisors (see Figs. 229 and 230). The reason this canal is so high up in the bone is that the apices of the roots of the teeth, espe- cially the canines, before eruption or during development and growth, are situated high in the bone. As the teeth descend to their positions in the arch, the nerves and vessels are extended, and the bony tissue 15 THE MAXILLARY SIXES closes around them, leaving for their accommodation a canal along the track traveled by the teeth. The Outer Wall.—The outer wall of the sinus is more or less triangular and concave on its inner surface; the concavity may extend into the zygomatic bone (see Fig. 271). The wall also extends upward and outward in a slightly curved manner. The surface may be broken up over the buccal roots of the teeth, as shown Fig. 203. The plate of bone forming the outer wall varies in thickness and density and undergoes changes in this particular at different periods of life. In childhood the dental organs of the upper jaw, before eruption, are located in the outer or anterior wall or in the floor of the sinus. Fig. 195 demonstrates the relation of the deciduous teeth to the floor of the sinus at the location of the molars. A little later, as the develop- ment of the permanent teeth proceeds, and they are pushed forward preparatory to taking their places in the arch, the outer and lower portion of the maxillary bone appears to be crowded with teeth, as shown in Fig. 107. The Posterior or Zygomatic Wall.—The posterior or zygomatic wall extends from a line vertical to the centre of the zygomatic arch backward and inward to the proximal or nasal wall. It is concave in a transverse direction and nearly straight in its vertical direction. In youth it is thick, but, like the outer wall of the sinus, it becomes thinner as age advances, until it may be no thicker than a sheet of note-paper. The Superior Wall or Roof.—The superior wall or roof of the sinus is usually triangular in shape, the base of the triangle being at the inner or nasal wall. It is convex in a transverse direction with the inner edges varying in height. Its junction with the inner wall varies in different subjects. Sometimes it is found on the level of the centre of the floor of the orbit (see Fig. 277). At other times it is higher and near the centre of the inner orbital wall (see Figs. 268 and 298). Its surface is usually marked by a ridge of bone which contains the groove for the passage of the infra-orbital vessels and nerves. This groove commences at the posterior border of the floor of the orbit; continuing forward, it is lost about the middle of the floor, where it SEPTA OF THE MAXILLARY SIXES 227 passes into the infra-orbital canal. The ridge extends downward and forward to meet the anterior wall of the sinus. The dipping down of the ridge varies greatly in extent, being scarcely noticeable in some specimens, while in others it extends so far that the canal becomes distinctly tubular in character, passing diagonally through the sintis, carrying the infra-orbital nerves and vessels across the anterior portion, with an open space above the tube. The open space above the sinus extends outward into the lower rim of the orbit, forming an infra-orbital sinus or pocket, a variation which the writer has not seen mentioned in any work on anatomy. The tube-like canal has a thin lamina of bone extending from it to the side of the true sinus. For the above charac- teristics see Figs. 223, 230, 276, 277 and 361. The Proximal or Nasal Wall.—The proximal or nasal wall of the sinus is quadrangular in shape, with the inferior angles slightly rounded (see Figs. 204 and 287). In a typical skull this wall is vertical and slightly convex. The lower edge almost always turns slightly outward to join the floor of the sinus, but occasionally it is found dipping in under the floor of the nasal cavity toward the median line, and meeting the floor of the sinus over the palatine process (see Figs. 261, 284 and 297). The Ostium Maxillare.—The ostium maxillare, an oval-shaped foramen, which affords communication between the sinus and the nasal cavity through the hiatus semilunaris, is usually found on the upper edge of the proximal wall near its anterior portion. It occa- sionally commences in the roof of the sinus, then passes in a slightly curved direction, terminating in the hiatus semilunaris, as shown in Figs. 279 and 280. In pathological conditions or in extreme old age, there may be two or even more openings between the maxillary sinus and the nasal cavity (see Figs. 183, 184 and 186. Septa of the Maxillary Sinus.—The shape and size of the maxil- lary sinus and the character of its partial septa vary so much that it is almost impossible to say what is its typical shape and what are its typical septa. From whatever direction sections are made, variations in shape and size will be found. Partial bony or membranous septa are found passing partly across in various directions, but the writer has been 22s THE MAXILLARY SIX US unable to find complete septa of the maxillary sinus, though it is said by some investigators that they exist. Fig. 204 represents an anteroposterior section near the inner wall of the orbit, showing a maxillary sinus of about the average size for the age of the subject. A portion of the lumina papyracea or os planum is cut away to show the continuation of the outlet of the sinus. A partial bony septum arising from the floor and passing transversely across forms two deep pockets. Fig. 202 Fig. 203 Figs. 202 and 203.—Two anteroposterior sections made by dividing the orbit and maxillary sinus vertically, showing conical elevations over the roots of the various teeth. The root of the second premolar curves forward. It more commonly curves backward. Fig. 205 is an anterior view from the skull of an old person. It shows vertical membranous septa of different sizes on the two sides, dividing the lower portion of the cavity into semi-chambers. The septum on the left side is small; that on the right extends nearly to the roof. Resorption has reduced the thickness of the walls of the sinus. Fig. 206 is from an anteroposterior section through the frontal sinus, the middle of the orbit, and the maxillary sinus, showing an SEPTA OF THE MAXILLARY SIXES 229 Hiatus semilunaris Ostium maxillare Fig. 204.—Anteroposterior division through the maxillary sinus Fig. 205.—Anterior view of a vertical transverse section from a skull of an old person, showing the thinness of the walls of the maxillary sinus, also membranous septa of the sinus. 2'M) THE MAXILLARY SIXES incomplete vertical anteroposterior membranous septum with a fora- men connecting the external and internal compartments of the sinus. Situated on the membrane are a number of small osteophytes. Fig. 207 and 208 shows what at first sight might be considered to be a bony division of the maxillary sinus; but close investigation reveals that the crescent-shaped cavity situated on the upper posterior corner of the sinus is the cell of the orbital process of the palate bone cut in Osteophytes on the septum Foramen between exter- nal and internal chambers of sinus. Membranous septum of sinus Fig. 206.—A vertical anteroposterior division through the frontal sinus, orbit, and maxillary sinus, showing a partial anteroposterior membranous septum of the sinus. two. A probe passed through the opening in Fig. 208 would enter the superior meatus of the nose. Figs. 209 and 210 show two sections of a negro's face through the molar teeth and the middle of the orbit. A sinus may be seen at the upper posterior corner of the maxillary sinus. This opens into the superior meatus of the nose and belongs to the palate bone. The sinus is verv small. SEPTA OF THE MAXILLARY SIX US 231 Figs. 211 and 212 are taken from the left side of another negro's skull. The section is made in the same region as the last, showing a Fig. 207 Fig. 208 Figs. 207 and 208.—Anteroposterior division through the centre of the orbit, maxillary sinus, and molar teeth, showing a crescent-shaped cell at the upper posterior corner of the maxillary sinus. Fig. 209 Fig. 210 Figs. 209 and 210.—Anteroposterior division through the centre of the orbit, maxillary sinus, and molar teeth, showing a triangular cell at the upper posterior corner of the maxillary sinus. very small, peculiarly shaped sinus, and a crescent-shaped cell which opens into the superior meatus. 2)52 THE MAXILLARY SIX US Figs. 213 and 214 are from the right side of the same skull as Figs. 211 and 212, showing apparenth' two maxillary sinuses. The posterior one Fig. 211 Fig. 212 Figs. 211 and 212.—Anteroposterior division through the centre of the orbit, maxillary sinus, and molar teeth, showing a peculiarly shaped sinus. Fig. 213 Fig. 214 Figs. 213 and 214.—Anteroposterior division through the centre of the orbit, maxillary sinus, and teeth, showing an enlarged cell of the orbital process of the palate bone, and a correspondingly small maxillary sinus. passes around the posterior border of the external surface of the anterior or true sinus. The apparent second sinus is undoubtedly an enlarged cell of the orbital process of the palate bone. The true maxillary SEPTA OF THE MAXILLARY SIXES 233 sinus is extremely small. It may be that on account of this the cell was abnormally enlarged to increase the air space of this region, or that the palatal process has encroached upon the space usually occupied by the maxillary bone. The bony septum of this specimen might very easily be mistaken as dividing the sinus into two; but the writer would not thus classify it, as this posterior sinus opens into the superior meatus, as do the other palatal cells just described. It is a well-established fact that the maxillary sinus is developed by an invagination of the mucous membrane of the middle meatus into the body of the maxilla. If there should be two of these invaginations, it could then be easily accepted that these cells are a divided maxillary Fig. 215 Fig. 216 Figs. 215 and 216.—Anteroposterior division through the centre of the orbit, maxillary sinus, and molar teeth, showing a large maxillary sinus and a large sphenoidal sinus. sinus; but as the outlet of the posterior one is into the superior meatus, into which the cells of the orbital process of the palate bone open, it seems evident that this is an enlarged palatal sinus or cell, and not a divided maxillary sinus. Figs. 215 and 216 are from another section made through the molar teeth and the centre of the orbit. Posterior to the maxillary sinus we find another sinus of a different character, which, from superficial examination, might be thought to be related to it or to be an enlarged cell belonging to the palate bone, a probe passed into it leads to the supreme or fourth meatus of the nose, indicating that it may be related to or connected with the sphenoidal sinus. In fact, it is a very THE MAXILLARY SIXES large sphenoidal sinus extending out laterally in a line almost to the outer part of the maxillary bone. Figs. 217 and 218 are an outer and inner view of a section showing an extremely large sphenoidal sinus. The cut is made through the pre- molar teeth, and a little to the inner side of the middle of the orbit, exposing the inner wall of the maxillary sinus, the cell of the palate bone, and the sphenoidal sinus, over which is seen the sella turcica. The irregular opening in the anterior clinoid process in Fig. 217 leads to and is a part of the sphenoidal sinus. In Fig. 218 the external wall of the nose will be observed. In the region of the body of the sphenoid Fig. 217 Fig. 218 Figs. 217 and 218.—Two views of an anteroposterior section. Fig. 217 shows the inner wall of the orbit, maxillary sinus, and openings leading into the sphenoidal sinus. Fig. 218 shows the lateral wall of the nose and a large sphenoidal sinus. bone is a very large sinus, at the bottom of which will be noticed a space under the sella turcica shown in Fig. 217. This is the largest sphenoidal sinus which has come under the observation of the writer. It extends forward to the cribriform plate of the ethmoid bone; backward to near the basilar process of the occipital bone; laterally on a line with the molar teeth; and superiorly into the anterior clinoid process, with onh' a very thin plate of bone betwreen it and the floor of the anterior fossa of the brain-case. In such cases the partition between the sphe- noidal sinus and the maxillary sinus is so thin and sieve-like that infected fluids will readily find their way from the former to the latter. DEN TA L RELA TION SHI PS 235 In the usual physiological description of the sinus, the fluids are spoken of as passing out of it. It is a question if this be the case under normal conditions. It is more than likely that the law of supply and demand is so balanced that the parts of the maxillary sinus are kept moist only, the openings being so arranged at the top as to prevent undue loss of the fluids while the subject is lying on the back or is standing. The openings in the other air cells or sinuses are so arranged as to make almost complete drainage through their most dependent parts. Dental Relationships.—Because of the close anatomical relation of the maxillary sinus with the tooth-germs and the roots of the per- manent teeth, it is evident that the sinus must be more or less influenced by them. As the teeth develop and descend into their normal places, the sinus increases in size. If a tooth situated near the sinus be retarded in its eruption, the development of the sinus is interfered with at that particular point. If the root of a tooth be left in the jaw in old age, resorption immediately over that root will not progress as in the parts from which the roots have been removed (see Fig. 287). It has been shown how closely the apical portions of the roots of the teeth are often associated with the sinus (see Figs. 196, 197, 199, 202, and 203). This close proximity gives the impression that the maxillary sinus is more often infected from diseased teeth than from any other source, some authorities claiming that three-fifths of the diseases of the sinus are brought about in that way. The writer thinks this a mistake. Though recognizing that diseases of the sinus do arise from the teeth, he believes that, aside from constitutional diseases and malformations, it is more often through the common communica- tion between the nasal cavity, the frontal sinuses, and the ethmoid cells, that infection is conveyed to the maxillary sinus from diseased cells and sinuses above it. He recognizes, at the same time, that the posterior ethmoidal and sphenoidal cells and the cells of the orbital process of the palate bone can also infect the sinus by resorption of the partition between these cavities. It is the writer's observation that there are more cases in which teeth are lost through diseases of the sinus than cases in which the teeth are primarily diseased, causing infection of the sinus and associated cells. In Fig. 197 it 230 THE MAXILLARY SIXES will be observed that the anterior buccal and palatal roots of the first molar tooth pass up into the walls of the sinus. This is the Fig. 219 Fig. 220 Figs. 219 and 220.—Anteroposterior division through the orbit, frontal and maxillary sinuses, and molar teeth, showing an undeveloped molar which was causing irritation in the floor of the sinus. DEX TA L RELA TIONSHIPS 237 class of cases where diseased teeth may cause infection of the max- illary sinus. If the pulp of a tooth so related to the sinus should become devitalized and infected, the parts around the apical foramen might also become infected and abscesses occur. From the close prox- imity of the points of the roots to the sinus, it might be supposed that these abscesses would break into it, as they occasionally do. Other examples of infection through diseased teeth in no way militate against the idea that the teeth are not first in importance as factors in causing disease of the sinuses. It is, however, clear that pus or infected matter will pass in the direction of the least resistance. When the investing tissues of a tooth become so infected, the osteogenetic function of this region is to stimu- late renewed activity, with the result that a new layer of bone is pro- duced which covers these parts and protects this cavity, so that abscesses, with but few exceptions, point and break into the mouth. Careless operation by the dentist sometimes causes infection of the sinus, as drilling through the tooth and the floor of the sinus, or forcing the root of a tooth into the sinus, through fracture of the wall in an unskilful effort to extract, or carelessness in driving artificial crowns or bridges upon the teeth or roots. Figs. 219 and 220 are views of an undeveloped and unerupted third molar which was causing irritation in the floor of the sinus. Figs. 221 and 222 are from the opposite side of the same skull, showing a similar condition and with an abscess which has burrowed under the mucous membrane near the roots of the first molar tooth. Figs. 223 and 224 are views of an anteroposterior section of the upper jaw with the first molar decayed and the pulp-chamber of the tooth open. The root-canal has been infected and the infection has been carried into the sinus. In this case there is evidence of a productive periostitis upon the floor of the sinus, which has caused a thickening of bone over the apex of the root. At a later period suppurative inflam- mation has occurred and perforated the floor. Fig. 225 is a view of the floor of the sinus and the nasal cavity. In the middle of the sinus there is a conical elevation with an opening in the centre exposing the apex of a tooth. In this case new bone has 23S THE MAXILLARY SINUS been formed over the diseased root, but at some subsequent time the bone has been broken down and the sinus has become infected. Fig. 221 Fig. 222 Figs. 221 and 222.—Anteroposterior division through the orbit, frontal sinus, maxillary sinus, and molar teeth, showing a similar condition as in Figs. 219 and 220. An abscess has burrowed under the mucous membrane near the roots of the first molar tooth. Fig. 226 is a vertical transverse section of the sinuses and nasal cavity. In the floor of the right sinus the conical portion of the bone, covering the infected tooth, has been cut through its centre, DEN TA L RELA TION SHI PS 239 exposing the end of the root in the infected region, the condition bein^ somewhat similar to those shown in Figs. 223 and 225. Infra-orbital sinus— Infra-orbital foramen Sound passing through infra-orbital canal and foramen , Maxillary sinus Opening caused by apica abscess Fig. 223 —Infra-orbital sinus Opening into zygomatic bone Fig. 224 Figs. 223 and 224.—Anteroposterior division of the maxilla, showing opening of a dental abscess within the maxillary sinus and an infra-orbital sinus. Figs. 22J and 228 was made from the left maxilla of the same skull from which Figs. 223 and 224 were taken. The pulp of the first molar was devitalized. In 228 an enlargement of the infected root is seen. 210 THE MANILLARY SINES Floor of the nasal cavitv Apical foramen of tooth Floor of maxillary sinus Fig. 225.—Horizontal section above the right floor of the nasal cavity and maxillary sinus, showing the opening of a dental abscess in the floor. Portion of eye Cell in the middle concha Orbit Middle concha Middle meatus Maxillary sinus Fig. 226.—Anterior view of a vertical transverse section in the region of the crista galli, middle of orbit, and molar teeth, showing effect of dental abscess in floor of maxillary sinus. DENTAL RELATIONSHIPS 241 An examination of the hard palate shows that the discharge of the abscess was made into the mouth, which the writer believes is the *r.v .*« Fig. 227 F M S Fig. 228 > F M S Figs. 227 and 228.—Horizontal sections through the maxillary sinus. F M S, floor of the max- illary sinus. In Fig. 228 there is an exostosis over the position of an infected root of the first molar tooth. In Fig. 227 the cap of bone covering the root has been removed, exposing the end of the root and a fistula extending downward, opening into the roof of the mouth. Incisive canal l^P Fig. 229.—Alveolar process. usual outlet for apical abscesses in the upper jaw—of course recognizing that they occasionally open into the sinus. 1G 242 THE MAXILLARY SIXES The vessels of nourishment to the maxillary teeth do not pass through and along a canal in the cancellated tissue as they do in the mandible, but in a groove on the outer wall of the maxillary sinus (as shown in Fig. 230), from which are given off branches to the apices of the roots of the teeth, many of the latter being covered with onh- a thin plate of bone. It is through the vessels of this region that infec- tion can be conveyed from the teeth and alveolar process to the maxillary sinuses or vice versa. It has been shown by these examples how numerous are the varia- tions of the maxillary sinus in shape, size, and position, and in its rela- __ Sound passed through infra-orbital canal and foramen Groove for alveolar nerve and vessels Fig. 230.—Anteroposterior division through the maxillary sinus and the teeth, showing an infra-orbital sinus above the canal. tion to the mouth and teeth, the nasal cavity, the frontal sinus, the ethmoidal cells, the cell of the orbital process of the palate bone, and the sphenoidal sinus. The variations are most important to the dentist and rhinologist. In the field of oral surgery, so many complications often arise in the extraction and treatment of teeth that a thoroughly scientific knowledge of the results of all recent research in this region is absolutely necessary. Surgical Relations.—In the extraction of the upper molar teeth great care should be exercised, because, as has been shown, where the sinus is large, extending downward and inward between the SURGICAL RELATIOXS 243 roots of the teeth, as seen in Fig. 199, if undue force should be exerted, not only the tooth grasped by the forceps, but also a great portion of the floor with other teeth attached is liable to be carried away. Examples of the results of such accidents are shown in Figs. 231, 232 and 233. Figs. 231 and 232 are from specimens broken away with the ordinary forceps, and Fig. 233 is from a specimen of the work of the old-fashioned turnkey. When using much force in placing artificial bridges or crowns upon the teeth immediately beneath the sinus, there is danger of breaking the floor in subjects where the walls are thin. When the pulps of the teeth have become diseased and infected, the infection may pass out of the apical foramen Fig. 231 Fig. 232 Fig. 233 Figs. 231, 232 and 233.—Three pieces of bone with molar teeth that have been accidentally broken away with part of the floor of the maxillary sinus in extraction; Figs. 231 and 232 with ordinary forceps, Fig. 233 with an old-fashioned turnkey. into the tissues immediately surrounding the root, and thence into the sinus, as has before been mentioned. In cleansing the root- canal there is some danger of passing the instrument through the apical foramen directly into the sinus. Certain diseases of the teeth caused by inflammation of the periodontal membrane with abscesses threaten- ing to open into the mouth, sometimes disappear suddenly, although no fistulous opening into the mouth has formed. When this occurs an abscess has frequently found an opening into the sinus. Diseases of the maxillary sinus are liable to produce disturbances in the teeth, as their blood supply passes along the floor of the sinus and through the wall. Branches of the trigeminal nerve accompany the vessels, and these also are liable to become deranged functionally. 211 THE MAXILLARY SIX US The maxillary sinus is on a lower plane than any of the other sinuses and cells associated with the nasal cavity, and has its outlet in the upper anterior portion; when the hiatus semilunaris is blocked below or posterior to the opening of the sinus, it becomes engorged with the fluids which have no other normal exit, thus producing pres- sure upon its wralls and upon the nerves and vessels passing through it. It is in such cases that additional openings are found leading from the maxillary sinus (see Figs. 183, 184, 185, 186, 187 and 188). Pathological Conditions.—Pathological conditions of the maxil- lary sinus vary in almost every aspect, and arise from a great diversity of causes, of which, may be mentioned: (1) Pathological conditions of the parents of the child at time of conception. If either parent should have any constitutional disease which could be transmitted to the offspring, or if a parent should have an abnormally-shaped face such as compressed dental arches, narrow nasal cavities, irregularities of the pneumatic spaces, etc., the child would begin its existence with a strong predisposing cause for patho- logical conditions which might continue throughout life. (2) Constitutional disturbances during the growth and develop- ment of the child. Among the general constitutional disturbances that predispose to pathological conditions of the sinus are syphilis, the acute exan- themata, as scarlet fever and measles, and disorders of nutrition, as rickets, etc.; also local disturbances, as infected or enlarged tonsils, adenoids, nasal polypi, or anything else that tends to obstruct or close the nasal passages, thus shutting off proper breathing spaces, drainage, and ventilation. These conditions should all be taken into considera- tion when studying the pathology and treatment of the maxillary sinus. (3) Infection by continuity from the nasal mucosa. This is one of the most frequent sources by which a pathological condition of the maxillary sinus is brought about, the severity of the condition depending upon the character and quality of the infected matter transmitted. The maxillary sinus, like all open cavities which are covered with epithelium, is immune to infection to a great extent, PA THOLOGJC. 1L CONDITIONS 245 but repeated or constant exposure to infected matter will finally result in a diseased condition, producing a discharge of the type of the par- ticular microorganisms introduced. Therefore anything that affects the mucosa of the nose will have its influence by direct action upon all the associated pneumatic spaces. The effect of an ordinary cold may not reach the sinus, but if the patient suffers from repeated coryza continued for long periods, it will be affected finally and remain so even after the membrane of the nose has recovered; because when the ciliated epithelium of the sinus becomes diseased, it has not the power to convey the infection and broken-down tissue upward to the natural outlet. (4) Infection through the blood supply. The blood supply of the greater portion of the sinus comes from the same source as that of the teeth, namely, the superior alveolar artery, which gives off small branches to the teeth, the alveolar process and the greater portion of the mucous membrane of the sinus. The veins which commence in the alveolar process, the teeth and the mucous membrane of the sinus, anastomose quite freely with one another. A similar arrangement of the bloodvessels exists in the region of the outlet of the sinus into the nose. Consequently it will be seen that infection from one region will easily be carried throughout all the area having the same blood supply. If the frontal sinuses or ethmoidal cells become diseased, fluids may be diverted into the maxillary sinus, which will in turn become infected. Again, if the sinus should become infected through the blood supply to the mucous membrane which receives its nourishment through various vessels, or if the mucous membrane should become infected through diseased teeth or osteo- myelitis or any other sourse, the infection produced would pass from the maxillary sinus to the frontal sinus, the ethmoidal cells and tissues in close relation to those parts. There are but few cases of osteomyelitis on record arising from the walls of the maxillary sinus per se. (5) Foreign bodies are occasionally found in the sinus which pro- duce a pathological condition. They are usually discovered in cases where the sinus has been previously diseased and treated. 210 THE MAXILLARY SIXES (6) Cysts, polypi, impacted or misplaced teeth, odontomata, osteophytes, malignant and benign tumors are strong predisposing factors toward pathological conditions of the sinus, and should be carefully considered in all diagnoses of sinus troubles, especially as cysts and tumors of this region are more or less obscure in their incipi- ency. Impacted or deflected teeth are also often difficult to diagnose, if one be not thoroughly familiar with the variations in the anatomy of the parts, or if a thorough radiographic inspection be omitted. Treatment of Pathological Conditions of the Maxillary Sinus.—As the causes of pathological conditions of the maxillary sinus are so various, it is evident that etiology, diagnosis and treatment must cover a wide range. The principal thing is to make a correct diagnosis and study of the etiology, and when such is obtained, on general principles, the treatment should be to remove the cause, whether it be from constitutional disturbances, diseased teeth, necrosis of the bone, impacted teeth, odontomata, dental or other cysts, polypi, new growths, malignant or benign, foreign bodies, diseases communicated through the circulation, from adjacent parts that are pathological, direct infections from other pneumatic spaces, or from any diseases associated with the nasal cavity. All diseases of the maxillary sinus that are caused by the teeth, or any diseases of its walls, except the nasal, should be treated through the mouth, this usually avoids the contamination of the nasal cavity and its associated parts. On general principles, all diseases of the maxillary sinus caused by diseases of the nasal side of its walls should be treated from the nasal standpoint. Occasionally where a pathological condition originates in the nasal region and is treated and cured, the sinus may become infected and remain diseased, in such cases treatment through the mouth is more appropriate than through the nose. When the maxillary sinuses have complicated septa creating pockets inaccessable through the nasal cavity (see Fig. 295), or in cases where the maxillary sinuses extend downward far below the level of the nasal floor (Figs. 284 and 297), treatment may have to be undertaken through the mouth. TREATMEXT OF PATHOLOGICAL CONDITIONS OF MANILLARY SINUS 247 If Figs. 276 and 277 be examined they will give illustrations of pockets and anatomical conditions of the maxillary sinus that would make it most difficult to treat especially if it should be required to curette the parts. An infra-orbital sinus may be seen under the outer and'anterior portion of the floor of the orbit; in case of disease of this sinus it would be most difficult to reach through the nasal cavity. In Fig. 287 there are two deep pockets that would be difficult to reach through the nasal cavity, while through the alveolar process it would be comparatively easy and would avoid the interfering with the nose. Figs. 284 and 297 show cases where the floors of the maxillary sinuses are far below the level of that of the nasal cavity. An ordinary opening into the maxillary sinus through the mouth heals up very quickfy, especially if the disease of the sinus becomes cured, which is usually accomplished if the trouble has been caused by diseased teeth. CHAPTER IX. THE FRONTAL SINUS. The frontal sinuses are usually two irregular-shaped cavities sit- uated in the lower part of the facial portion of the frontal bone and in the process forming the roofs of the orbits, with a thin lamina of bone between them. They vary considerably in size, shape, position, and number. Development.—They appear about the second year after birth and are formed by an invagination from the upper anterior portion of the hiatus semilunaris and by a dissolution of the tissue between the outer and inner plates of the frontal bone, the excavations for the formation of these sinuses as well as for the various other cells and sinuses being carried on through the agency of the osteoclasts. The sinuses continue to increase in size as age advances. They are lined with mucous membrane and communicate with the nasal cavities through the infundibulum and the hiatus semilunaris. There are skulls in which frontal sinuses do not exist; there are other skulls in which there is but one sinus that may be very small, or it may extend from one of the external angular processes beyond the medial line of the frontal bone and upward to a point above the level of the frontal eminences or posteriorly over the orbit almost to the optic foramen. It sometimes spreads outward and backward terminating in the great wing of the sphenoid bone; it may be found not only in the ascending portion of the bone, but extending downward and backward may become one common cavity with the anterior ethmoid cells and the max- illary sinus (see Figs. 247 and 296). There are usually two frontal sinuses, each having an independent outlet into the nasal cavities, but specimens exist in which three or more sinuses are present, all in the ascending portion of the bone and each having its independent outlet. The portions which pass over the orbit might be called supra-orbital DEVELOPMENT 249 sinuses, especially if they have complete partitions and outlets other than the one which occupies the ascending portion of the bone. Figs. 234 and 235 show a large left frontal sinus, which passes over to the right of the medial line, leaving but little room for the right sinus in its normal position, as is seen in Fig. 235. Often, in such cases, the opposite side will extend its air space in some other direction to make up for the loss caused by the invasion. Fig. 234 Fig. 235 Figs. 234 and 235.—Lateral walls of the nasal cavity, showing the left frontal sinus extended over to the right of the medial line. Figs. 236 and 237 are made from Fig. 235, cut through the centre of the orbit, showing that the frontal sinus has extended back over the orbit to the region of the optic foramen. It has also extended outward under the zygomatic process of the frontal bone. Figs. 238 and 239 are made from a skull where the frontal sinus has extended upward under the region of the frontal eminence and downward to the middle of the orbit or almost on a level with the upper portion of the maxillary sinus. Fig. 240 is an illustration of two large frontal sinuses, extending from one zygomatic process of the frontal bone to the other, with but a thin complete septum between. This septum is not in the centre, but is carried over the left side. The sinuses pass backward over the greater portion of the orbits, and upward toward the frontal 250 THE FRONTAL SINUS eminence. There is quite a depression over the frontal crest, which is very large in this specimen. There are also several partial septa running in various directions in the two sinuses. Fig. 236 Fig. 237 Figs. 236 and 237.—Two anteroposterior sections (made from Fig. 170) through the frontal sinus, centre of orbit, maxillary sinus, and cell of the orbital process of the palate bone, showing the frontal sinus extending backward over the orbit to the region of the optic foramen. It also extends under the zygomatic process of the frontal bone. Fig. 238 Fig. 239 Figs. 238 and 239.—Two vertical transverse sections through the frontal sinuses and nasal cavities showing the frontal sinus extending below the level of the middle of the orbit. DEVELOPMENT 251 Occasionally the frontal sinus extends into the crista galli form- ing a cell in that process (see Figs. 269, 281, 282, 292, 293, 294, 295 and 296), Fig. 240.—Large frontal sinuses extending from one zygomatic process of the frontal bone to the other. Fig. 241.—Two sections of the supra-orbital region, showing no frontal sinus. Fig. 241 is made from two sections taken from the supra-orbital region of the skull. The upper figure shows that the anterior portion of the frontal bone has been removed from the region of the super- ciliary ridges, exhibiting no indication of the sinus in the ascending 252 THE FRONTAL SINUS portion of the frontal bone. The lower picture shows no evidence of the sinuses passing into the horizontal portion or over the orbits. Fig. 242 is made from a specimen having onh' a right Irontal sinus, which extends unbroken far over to the left. This sinus passes partly over the orbit and has but one outlet. Fig. 243 shows two rather typical frontal sinuses with two outlets and a complete septum near the medial line. There is also one par- tial septum near the medial line, and one partial septum in each sinus forming two pockets near the zygomatic process. The right sinus measures horizontally 35 mm., the left 30 mm.; the depth of the right sinus is 42 mm. and the left 35 mm. Fig. 243.—Anterior view, showing two frontal sinuses. Fig. 244 shows three complete frontal sinuses with three individual outlets and two complete septa. The two lateral sinuses pass back- ward well over the orbits. Fig. 245 is made from a skull that has four frontal sinuses, with four independent outlets and three complete septa. Some writers would class the two middle sinuses as anterior ethmoidal cells which had invaded the frontal bone. If these cells should exist without the two larger sinuses they would then be called frontal sinuses by these same writers. DEVELOPMENT 253 Fig. 246 is made from a specimen containing five frontal sinuses and having four complete septa. Four of the sinuses extend well upward to about the same height. Fig. 244.—Anterior view, showing three frontal sinuses. *T" Fig. 245.—Anterior view, showing four frontal Fig. 246.—Anterior view, showing five frontal sinuses. sinuses. 251 THE FRONTAL SINUS Fig. 247 is a posterior view made from a specimen having two large frontal sinuses with a complete septum. The right sinus extends back over the orbit and down through the region of the anterior ethmoidal cell, continuing into the maxillary sinus and making one common cavity of the frontal sinus, the anterior ethmoidal cells and the maxil- lary sinus. Fig. 248 is made from a skull having two large frontal sinuses. There appear to be three sinuses in the picture, but the septum on large maxillary sinuses. The right one forming Fig. 248.—Anterior view, showing two a common cavity with ethmoid cell and maxil- frontal sinuses, the right one very large ex- lary sinuses. tending well over to the left side. the right is incomplete, making but one sinus on that side, which is very large, extending from the right zygomatic process trans- versely well over to the left side, and measuring 65 mm. Its depth from the top to the outlet is 45 mm., and it extends well back over the orbit 40 mm.; the left sinus passes outward and backward to about one-half the distance of that on the right side. Fig. 249, from a horizontal section above the orbit, shows a trans- verse section of a large left frontal sinus, measuring 67 mm. from the left zygomatic process to a position over the centre of the right DEVELOP MEN! 255 infra-orbital foramen, without a septum. The right frontal sinus, meas- uring 40 mm., has several small incomplete, nearly horizontal septa, making a number of horizontal pockets. Fig. 250 is made from a transverse section of the face with a portion of the bone removed to expose the frontal sinuses. The right sinus is extremely large, extending from the right zygomatic process over toward the left and measuring 67 mm., leaving but a slight space for the left frontal sinus, which measures 15 mm. The Fig. 249.—Horizontal section above the orbit. Fig. 250.—Anterior view, showing a large right frontal sinus, the left sinus is very small. septum between these sinuses has an inclination of about 45 degrees. The right sinus also extends well back over the orbit and into the crista galli. Fig. 251 is made from a transverse section of the face with a por- tion of the bone removed, showing two very large frontal sinuses which extend backward over the orbits, where they are divided by- several incomplete septa. They also extend downward and communi- cate directly with the maxillary sinuses. The right and left sinuses measure horizontally 50 mm. and their depth is 40 mm. 250 THE FRONTAL SINES Fig. 252 is a posterior view of the frontal sinuses, showing two incomplete septa. The incompleteness of the latter is more than likely due to pathological conditions. Fig. 251.—Anterior view, showing two very large frontal sinuses extending upward and well back over the orbits. Fig. 252.—Posterior view, showing two incom- plete septa. Fig. 253.—Two lateral views of two specimens, showing large frontal sinuses. Fig. 253 is made from two specimens, showing lateral views of the frontal sinuses. The lower picture is a sagittal section cut near the centre of the orbit, showing in the anterior portion a lateral view of DEVELOPMENT -'»< the frontal sinus divided into five pockets, all of which have one com- mon outlet. The sixth or posterior cell communicates with the upper meatus of the nose. The upper picture is also a sagittal section cut to the median line of the os planum of the ethmoid bone. It shows a frontal sinus extending backward nearly to the optic nerve which is seen in position in the optic foramen. The skull pictured in Figs. 254, 255 and 256 has the largest pneu- matic spaces of any head I have examined, not only of the frontal sinus, but of the supra-orbital, sphenoid, and maxillary sinuses. Theright frontal sinus commences in the right temporal fossae at a point near the articulation of the frontal bone with the great wing of the sphenoid Fig 254 —An anterior view of a skull with frontal sinuses extending from within the great wing of the sphenoid bone forward to the frontal bone then backward to the left sphenoid bone. (see point marked 8, Fig. 255). It extends forward and across the skull to the opposite side, then a little backward, terminating near the left great wing of the sphenoid (see point marked 4, Fig. 256). The frontal portion of this great space is divided into four compart- ments, three of which have a separate outlet, while the fourth is con- nected to one of the others by a small foramen which is placed low down in the sinus. As already stated the right frontal sinus commences at a point marked 8, in Fig. 256, in the temporal fossae and extends upward, forward and inward almost to the nasion, measuring 55 mm. The right supra-orbital sinus commences in the zygomatic fossa (see point marked 9, Fig. 255) or in the right wing of the sphenoid bone; it passes 17 25S THE FRONTAL SINES upward, forward and inward over the orbits (see point marked 7, Fig. 2^). Its outlet is in the anterior and lower portion of the right frontal sinus. It measures in length 55 mm. There are also several other sinuses or cells over the anterior portion of the orbits with inde- pendent outlets. Fig. 255.—Right lateral view of skull shown in Figs. 254 and 256. Fig. 256.—Left lateral view of skull shown in Figs. 254 and 255. The left frontal sinus commences in the temporal fossa at a point marked 4, in Fig. 256. It then passes upward, forward, and to the right, to the wall forming an intermediate frontal sinus. It measures 48 mm. The sinus is divided into two compartments by a septum lying at an angle of 35 degrees from the horizontal. At the lower and median end of this septum there is a small foramen which allows the two compartments to communicate with one common outlet into the nasal cavitv. CHAPTER X. THE ETHMOIDAL AND OTHER CELLS WHICH HAVE THEIR FINAL OUTLET IN THE NASAL CAVITY. The ethmoidal cells are situated principally between the two orbits. Fig. 257 is an upper view of a horizontal section cut through the centre of the orbits and the upper part of the nasal cavities, Fig. 257.—Upper surface of a horizontal section cut through the orbits and upper part of nasal cavity. showing clearly the position of many of the cells, as does also Fig. 258. Many of these ethmoidal cells are formed by the union of the orbital plates of the frontal bone and the ethmoid bone and between the ethmoid bone and the maxilla; others are within the ethmoid alone. They are divided into three groups—anterior, middle, and posterior. The anterior ethmoidal cells are the smallest of the three divisions. They open by several small orifices into the anterior portion of the 200 ETHMOIDAL AND OTHER CELLS IN THE NASAL CAVITY hiatus semilunaris. Occasionally a chain of cells is found opening one into another and finally into the hiatus. The middle ethmoidal cells vary more in size than either the anterior or the posterior. The inner covering or wall of the cells is spheroidal in form and is known as the bulla ethmoidalis. It is situated in the upper portion of the lateral wall of the hiatus semilunaris, and extends downward and inward toward the unciform process. The openings of the cells are in the outer portion of the bulla ethmoidalis and they discharge into the hiatus semilunaris. The posterior ethmoidal cells are usually two or three in number. They are found on about the same plane as the anterior and middle ethmoidal cells, are irregular in shape, and usually have their general outlet into the superior meatus. THE ORBITAL PROCESSES. The cells of the orbital processes of the palate bones are two in number, one on each side. Each cell is small and situated below the posterior part of the floor of the orbit. It is, like many other air cells, irregular in shape and size. It opens into the third or superior meatus. It occasionally extends backward near to the sphenoidal sinus or outward around the posterior wall of the maxillary sinus, from which it is separated by a thin plate of bone (see Figs. 213 and 214). THE SPHENOIDAL SINUSES. The sphenoidal sinuses are two, one on each side, irregular in shape and size, situated in the body of the sphenoid bone (see Figs. 257, 258 and 280). The septum between them is generally deflected to one side or the other (see Figs. 257, 279 and 280). Incomplete septa may also be found at the posterior portion of these cavities, which divide them into several incomplete compartments (see Figs. 279 and 280.) Sometimes these sinuses may extend backward to the basilar process of the occipital bone, or forward to the cribriform plate of the ethmoid bone, or laterally into the base of the great wings of the sphenoidal bone, or into the clinoid process (see Figs. 217 and 218). They are THE SPHENOIDAL SINUSES 201 lined with mucous membrane, which is continuous with the lining of the upper and posterior portion of the nasal cavities. The greater portion of the anterior surface of the body of the sphenoid bone is open, these openings are covered to a great extent Fig. 258.—Horizontal section through the orbits, ethmoid cells and sphenoidal sinuses. by the sphenoid conchas (sphenoidal turbinate processes) which are two thin triangular-shaped plates. The posterior surface is concave and faces the body of the sphenoid bone to which it becomes attached. The anterior surface is convex and is associated with the ethmoid in 202 ETHMOIDAL AND OILIER CELLS IN THE NASAL CAVITY front, forming a portion of the roof of the nasal cavity, through each of these plates is an ostium that gives passageway from the sphenoidal sinus to the highest meatus of the nose. Pathological conditions arising through abnormal irregularity of these concha? are difficult to diagnose and treat. Fig. 258 is from a horizontal section cut through the centre of the orbits, ethmoid cells and sphenoidal sinuses. The sphenoidal sinuses are large with a slighth' curved septum between them. Cross sec- tions of the carotid canal may be seen posterior to the sinuses. CELL OF THE CRISTA GALLI. Sometimes a cell is found within the crista galli (see Figs. 269, 281, 282, 292, 293, 294, 295 and 296). In such a case the opening is in front and communicates with one of the frontal sinuses. It might be termed an extension of the frontal sinus into the crista galli. CHAPTER XI. VARIATIONS IN THE ANATOMICAL STRUCTURES OF THE FACE. The variations exhibited in the internal anatomy of the face are so common that it is sometimes difficult to differentiate the normal from abnormal anatomy. Some of the most important and common Fig. 259.—Front view of asymmetrical skull, showing the right side more fully developed than the left side. variations found in the writer's dissections are described in the following pages. Fig. 259 is a front view of a skull which has an asymmetrical arch 204 VARIATIONS IN ANATOMICAL STRUCTURES OF FACE of the mouth. The greater portion of the teeth have been lost in earh' life. The canine fossa of the right side is lacking, the face being Fig. 260.—Vertical transverse division of Fig. 259, showing a larger maxillary sinus on the left side than on the right. very prominent at that point. The teeth have not been in normal position. The septum is deflected toward the left side. In a skull VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 20.' of this character the internal structures will usually be decidedly unsymmetrical. One might suppose that a large sinus would be found under the fulness of the canine fossa, but in this particular case it is rather small. Fig. 260 represents a vertical transverse section of the skull shown in Fig. 259. It will be seen that the right sinus is smaller than the left, the fulness of the region in the infra-orbital foramen and the canine fossa being due to the thickness of the bone. The frontal sinus of this specimen is large and extends downward between the orbits lower than usual. Fig. 261.—Anterior view of a vertical trans- verse section of skull through the centre of the orbits, nasal cavity, and maxillary sinus, the lower inner corners of the maxillary sinuses passing partly under the nasal cavity. Fig. 262.—Posterior view of a vertical trans- verse section of skull in region of second pre- molar, showing lack of symmetry in nasal cavity and maxillary sinuses, with the septum and "spur" passing over the inferior concha. Fig. 261 exhibits a condition occasionalh' met with, the floor of the sinus dipping downward and passing partly under the floor of the nose. The same condition will be found in Figs. 284 and 297. Resorption has taken place between the plates forming the floor of the nose and the roof of the mouth. Sinuses like these could be drained directly by an opening through the palatal surface of the mouth. In skulls of this character the vault of the mouth is high. Fig. 262 exhibits an entire lack of symmetry between the nasal cavity and the sinuses of the right and left sides, the inferior meatus of VARIATIONS IN ANATOMICAL STRUCTURES OF FACE one side being closed anteriorly by the deflected nasal septum and the "spur" upon it. In such cases as this, inspissated mucus often collects and the outlet of the nasolacrimal duct may be interfered with. Figs. 263, 204 and 205 are from the same subject as Fig. 2O2. An instrument passed through the axis of the alveolar process, shown in Fig. 263.—Anterior view of a vertical trans- Fig. 264.—Posterior view of section shown verse section of the skull shown in Fig. 262, in Fig. 263. showing an asymmetrical condition of the two sides. the right side of Fig. 264 or the left side of Fig. 263 or Fig. 265, would perforate the nasal cavity, instead of the floor of the maxillary sinus. Fig. 266, which is taken from a different skull, shows an almost straight septum, with bilateral symmetry as regards the nasal cavity; VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 207 the maxillary sinuses vary, however, throughout the depth of the skull. On the right side the sinus would not be reached by drilling through the alveolar process, while on the left side the sinus is just above the process, and the floor is below the level of the floor of the nasal cavity. Fig. 267 is from a vertical transverse section in the region of the first premolar. The septum is almost straight, but there is a great variation in the maxillary sinuses. The lateral wall of the nasal cavity of the right side is also the outer plate of the maxilla, the floor of the sinus being on a much higher plane. In the floor of the left nasal Fig. 267.—Anterior view of a vertical transverse section, near the first premolar, showing variation in the maxillary sinuses and the nasal cavities. cavity is an elevation which covers a tooth root, probably that of a supernumerary tooth. In Figs. 263 and 267 the nasal walls of the right inferior meatus pass outward under the maxillary sinus to the facial portion of the maxillary bone. In Figs. 270 and 283, the same condition will be observed on both sides. In the event of attempting to drill into the maxillary sinus from the canine fossa in such cases as are represented in these figures, as is sometimes advised, the opening would be made into the nasal cavity instead of into the sinus. Fig. 268 is a vertical transverse section made in the region of the second molar, the nasal cavities are large with a straight septum, the 20S VARIATIONS IN ANATOMICAL STRUCTURES OF FACE Fig. 268.—Posterior view of a vertical section made in the region of the molar teeth, showing small sinuses and large nasal cavity and narrow dental arch. Cell in crista galli Fig. 269.—Two vertical transverse sections. The surfaces shown are divided from each other. Variations are shown in the maxillary sinuses and nasal cavity. A cell is also">ho\vn within the crista galli, which opens into the frontal sinus. VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 209 dental arch is narrow and the maxillary sinuses small, they do not extend downward in the direction of the teeth and alveolar process. Fig. 269 shows two sections from the same skull as Fig. 268, cut more anteriorly, in the region of the premolars. The parts are almost symmetrical. The crista galli has been cut transversely, showing within its walls a cell of considerable size, opening into the frontal sinus. Fig. 270 is made from the skull of an aged person, in which the bones have become much resorbed. It is comparatively symmetrical, with the floor of the sinus much higher than usual, and the nasal cavity extending outward to the external portion of the maxillary bone. Fig. 270.—Anterior view of a vertical transverse section from the skull of an aged person, showing large nasal cavities with small maxillary sinuses. Occasionally in surgical practice abscesses are found opening on the face in the region of the zygomatic bone. These are usually looked upon as of superficial origin, but sometimes when carefully examined they are found to be associated with the maxillary sinus. Fig. 271 will partly explain why, in some cases, abscesses of the maxillary sinus open at this point. The section is made at the region of the maxillo- zygomatic articulation. The maxillary sinus passes far into the zygo- matic bone, extending backward into the temporal process. Fig. 272 is from a skull in which the nasal cavity extends outward over the alveolar process until it reaches the outer wall of the maxilla. The points of the palatal roots of the first and second molars appear in the floor of the nasal cavity. The floor of the maxillary sinus is well up on the side of the bone. VARIATIONS IN ANATOMICAL STRICTURES OF FACE Fig. 273. A sagittal section of a greyhound's skull, showing the nasal cavity extending to the outer wall of the maxilla, no true maxil- lary sinus is found, though the inferior concha helps to partly shut off a space which might be named the conchomaxillary sinus. Fig. 273.—Sagittal section of a greyhound's skull. Fig. 274.—A sagittal section of a badger, showing conditions similar to that of the greyhound, Fig. 273. The root of a tooth is seen in the floor of the nasal cavity similar to the roots shown in the human nasal cavity, Fig. 272. Fig. 275 is a picture from the external or facial surface of Fig. 2J2, which illustrates that the resorption of the alveolar process from VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 271 over the buccal roots o: the teeth may progress while that portion of the bone along the free margin of the process is left intact. Figs. 276 and 277 show a vertical transverse section of the upper jaw. In Fig. 277 the roof of the maxillary sinus is almost horizontal, which is a very unusual condition. The illustrations show what is Fig. 274.—Sagittal section of a badger's skull. Fig. 275.—External view of facial surface of Fig. 272, showing the resorption of the outer part of the alveolar process, leaving a line of bone near the free margin of the process. apparently a division of the sinus into two, the smaller or outer division forming an infra-orbital sinus. This condition is caused by a bony septum passing down from the centre of the floor of the orbit, cutting off a por- tion of the sinus, and forming an extra chamber, which of course is con- tinuous with the true sinus. In the centre of the septum-like wall is VARIATIONS IN ANATOMICAL STRUCTURES OF FACE Infra-orbital nerve Muscles of face Middle ethmoidal cells Hiatus semilunaris Unciform process Middle ethmoidal cells Middle concha Unciform process i—Inferior concha Inferior meatus Maxillary sinus Inferior concha Inferior meatus —Infra-orbital nerve Muscles of face Fig. 277.—Vertical transverse division of the upper jaw. VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 27.'} a tube or canal conveying the infra-orbital nerves and vessels. Above this, and at the junction of the septum with the floor of the orbit is an adjunct infra-orbital canal and nerve. At the upper inner corner of Fig. 277 is the normal opening of the maxillary sinus, the ostium maxillare, communicating with the hiatus semilunaris. This section beautifully illustrates how the hiatus semilunaris is bounded on the inner side by the unciform process, on the outer side by the wall of the sinus, and above by the bulla ethmoidalis, containing the middle ethmoidal cells. Should the bulla become enlarged, or the mucous membrane of this region be swollen, the hiatus would be closed and Fig. 278.—Posterior view of vertical section through the orbits, maxillary sinuses, posterior ethmoidal cells, and the third molar teeth. fluids could not pass directly into the middle meatus but would be thrown into the maxillary sinus. Fig. 278 illustrates a vertical transverse section of the face. It gives a good sectional view of the posterior ethmoidal cells. The white line is on a level with the floor of the orbit in the anterior portion of the section. It will be noticed, as is often the case, that the roof of the maxillary sinus runs up as it passes backward until it is far above the level of the floor of the orbit at its anterior margin. Figs. 279 and 280 show two sections made by a horizontal trans- verse section a little below the roof of the sinus. In this case the commencement of the ostium maxillare is within the roof. It passes backward and inward to the hiatus semilunaris. A probe placed in is 274 VARIATIONS IN ANATOMICAL STRUCTURES OF FACE Ostium maxillare opening in roof Roof of maxil- lary sinus Middle concha Hiatus semilunaris Middle meatus Superior meatus Sphenoidal sinus Fig. 279 Sphenoidal sinus Middle concha Middle meatus /' , Maxillary ■ t sinus Inferior concha y---Zygomatic ^;_____bone Nasolacrimal duct Nasal septum Fig. 280 Figs. 279 and 280.—Two illustrations. Fig. 279 shows the roof of the maxillary sinus and upper por- tion of the nasal cavity; Fig. 280 shows the maxillary sinus and nasal cavity. VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 27.1 the left ostium maxillare indicates its position. Immediately to the left of the probe is a section of the nasolacrimal duct. On the opposite side, the lower wall of the right ostium has been removed. That the great variations found in the nasal cavities and maxil- lary sinuses may be fully appreciated, skulls of widely different types have been selected and photographed together. Figs. 281 and 282 give a posterior view of two sections made from different skulls. They show great variations in the depth of the face, and the size, shape, and position of the maxillary sinus. In Fig. 281 the sinuses are much smaller than in the shorter-faced picture, Fig. 282. In Fig. 281 the septum has a spur extending outward until it comes in contact with the inferior concha, the frontal sinuses pass well down below the level of the centre of the orbits. In both illus- trations there are distinct cells in the crista galli, which open anteriorly into the frontal sinuses. Figs. 283 and 284 were made in the same manner as Figs. 281 and 282, and show two sections cut in about the same position from two different skulls. There is again a great difference in the depth of the faces. The maxillary sinuses in Fig. 283 are small and placed high up, allowing the lower portion of the nasal cavity to extend outward over the alveolar process. In Fig. 284 the maxillary sinuses are large, their floors extending down below the floor of the nasal cavity, and passing inward over the roof of the mouth, so that only a small space is left between the sinuses. The enlarged sinuses allow but little room for the nasal cavities. Figs. 285 and 286, also made from two different skulls, show variations in the depth of the nasal cavities. A good illustration of the fourth meatus and a part of a fifth is shown in Fig. 285. Figs. 281, 282, 283, 284, 285 and 286 serve to show several varia- tions in the sinuses and nasal cavities. Similar comparisons between the sphenoidal and frontal sinuses, and the ethmoidal and other cells, would show as marked differences. Bilateral variations almost equally extensive are found in the individual skull, except as to the depth of the face. The diagnosis and surgery of such cases must follow in accordance with the variations existing in the anatomical structures. 270 VARIATIONS IN ANATOMICAL STRIX TERES OF FACE In Fig. 287 is shown an anteroposterior section illustrating the close relation between the frontal and maxillary sinuses. It also shows that in this instance fluids could pass from the frontal sinus and eth- Cell within crista galli Fig. 281 Fig. 282 Figs. 281 and 282.—Posterior views of two vertical transverse sections made from different skulls in about the same anatomical region, showing great variations as to the depth of face, and size and shape of the maxillary sinuses and nasal cavities. VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 2 7/ moidal cells into the maxillary sinus. Of the two probes passed through the ostium maxillare, one goes directly through the posterior portion Fig. 283 Fig. 284 Figs. 283 and 284.—Posterior views of two vertical transverse sections made from different skulls in about the same anatomical region, showing great variations as to the depth of face, and size and shape of nasal cavities and maxillary sinuses. Fig. 285 Fig. 286 Fu.s. 285 and 286.—Two illustrations from different subjects, showing great variations as to depth and size in the external wall of the nasal cavities. Fig. 285 shows four meatuses. 27s VARIATIONS IN ANATOMICAL STRUCTURES OF FACE of the hiatus semilunaris into the middle meatus, while the other (the vertical one) passes into the hiatus semilunaris, then upward and a little forward into the frontal sinus. Fig. 288 is an anterior view of a transverse vertical section, showing the lower portion of the frontal sinuses on both sides, with a probe Fig. 287.—Antero-posterior section showing inner wall of the orbit, and the maxillary sinus with two probes through the ostium maxillare. The conical elevation in the floor of the sinus is where a root of a tooth has been left, retarding resorption in this part of the floor, in the remainder of which the process has been active. passed from the right sinus downward and slightly outward along the hiatus semilunaris, and then through the ostium maxillare into the maxillary sinus. It will be noticed that there is quite a difference in the anatomical characteristics of the anterior ethmoidal cells. VARIATIONS IN ANATOMICAL STRUCTURES OF FACE Fig. 289 is a posterior view of the same section as Fig. 288. The course of the probe can be traced as it passes downward along the hiatus semilunaris, through the ostium maxillare, and into the sinus without obstruction. There is a lack of bilateral symmetry in the unciform process and bulla ethmoidalis. As this is a section of a negro skull, the great thickness of the floor of the maxillary sinus is accounted for. Fig. 290 gives another view of the hiatus semilunaris leading down- ward and backward from the frontal sinus into the middle meatus, a Fig. 288.—Anterior view of a vertical trans- Fig. 289.—Posterior view of section shown verse section of a negro skull between the second in Fig. 288. premolar and the first molar tooth, showing probe passing down into the maxillary sinus, through the frontal sinus, the hiatus semilunaris, and ostium maxillare. portion of the walls (bulla ethmoidalis) covering the middle ethmoidal cells having been cut away. Fig. 291 shows two hiatuses, or infundibula, leading directly into maxillary sinus. Through the posterior hiatus a probe has been passed, the outer wall of the anterior one having been cut away in order that a better view could be obtained. Figs. 292 and 293 illustrate a vertical transverse section, show- ing more direct communication between the frontal and maxillary sinuses than Figs. 288 and 289. They give posterior and ante- rior views of the same section, Fig. 292 having that portion 2S0 VARIATIONS IN ANATOMICAL STRUCTURES OF FACE of the face removed which extends back to the premolar teeth below, and exposes the frontal sinuses above. The septum of the nose is deflected and a "spur" reaches over to the right concha. The Fig. 290.—Interior view of the lateral wall Fig. 2°1.—Section showing two hiatuses, both of the nasal cavity with part of the bone cut leading directly into the maxillary sinus. The away to show the hiatus semilunaris and the posterior hiatus has a probe passing through it, middle ethmoidal cells. the anterior one has the external wall cut away in order that a better view may be obtained. Fig. 292 Fig. 293 Figs. 292 and 293.—Anterior and posterior views of a vertical transverse section. VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 2S1 frontal sinuses extend down below the middle of the orbit. Between them there is an interfrontal cell extending backward into the crista galli as is shown in Fig. 293. A wire passed downward from the right frontal sinus is again seen in the maxillary sinus. Fig. 293 shows the section cut posteriorly to the first molar teeth. The frontal sinuses extend in an outward direction over the orbits. The wire shown in Fig. 292 is seen passing downward from the right frontal sinus through the infundibulum and hiatus semilunaris and entering the maxillary sinus through the ostium maxillare. Fig. 294.—Anterior view of vertical transverse section in the region of the first molar teeth, showing anterior ethmoidal cells, and a cell in the crista galli. The frontal sinus extends downward, becoming common with the ethmoidal cells and maxillary sinus. Fig. 294 shows an anterior view of a vertical transverse section in the region of the premolar teeth. Between the orbits are seen the anterior ethmoidal cells, and also a sinus in the crista galli. In this case both sinuses extend upward and become common with the ethmoidal cells and frontal sinuses. Fig. 295 gives a posterior view of a vertical transverse section cut in the region of the first molar teeth and through the crista galli. The septum is deflected toward the left side; the right maxillary sinus extends upward and inward, terminating in a large opening into the 2V VARIATIONS IN ANATOMICAL STRUCTURES OF FACE hiatus semilunaris without a true line of demarcation. The left maxil- lary sinus extends forward into the infra-orbital ridge, forming an infra-orbital sinus somewhat similar to those shown in Figs. 22y^, 224, 229, 230, 276 and 277. The numerous pockets in the anterior portion of the maxillary sinus would render it difticult to treat should it become diseased. Fig. 296 shows a posterior view of a vertical transverse section from the skull of an aged person. The floor of the maxillary sinus, the nasal Infra-orbital sinus Infra-orbital canal Hiatus semilunaris Fig. 295.—Posterior view of a vertical transverse section through the first molar teeth. The right hiatus semilunaris in this subject communicates with the maxillary sinus without a true ostium maxillare. and the lower border of the alveolar process are almost on a horizontal line. The left maxillary sinus extends upward until it passes into the frontal sinus, without any line of demarcation between sinuses or cells. In the crista galli is seen a small sinus or cell which extends forward into the frontal sinus. This last formation is also shown in Figs. 269, 281, 282, 292, 293 and 294. Fig. 297 shows a posterior view of a vertical transverse section cut behind the first molar teeth. The maxillary sinuses are almost cuboidal in shape and extend dowrn below the floor of the nasal cavities VARIATIONS IN ANATOMICAL STRUCTURES OF FACE 283 Fig. 296.—Posterior view of a vertical transverse section in the region of the ostium maxillare. From the skull of an aged person. The floor of the nasal cavity, the alveolar process, and the floor of the sinus are nearly on the same level. The left maxillary sinus extends upward through the region of the anterior ethmoidal cell into the frontal sinus without a line of demarcation between them. Fig. 297.—Posterior view of a vertical transverse section near the first molar teeth, showing maxillary sinuses which are nearly cuboidal in shape and which extend downward below the floor of the nasal cavity. The nasal cavity is narrow and the walls dividing it from the sinuses are concavo- convex in their vertical direction. 2sl VARIATIONS IN ANATOMICAL STRICTURES OF FACE inward and toward the medial line, outward into the zygomatic bones, and upward into the ethmoidal cells. The inner walls are not straight, as in Figs. 196 and 197. Starting at the floor of the sinus, almost over the centre of the dome of the mouth, the inner wall, as it extends upward, curves outwardly, then inwardly to the point at which the inferior concha projects into the nasal cavity. This formation leaves a very narrow or contracted nasal cavity, a deformity also shown in Fig. 284. \ / Fig. 298.—Posterior view of a vertical transverse section in the region of the second premolar. showing wires passing from the frontal sinuses into the maxillary sinuses. Fig. 298 is a posterior view of a section made back of the premolar teeth. On either side a wire has been passed from the two frontal sinuses down through the ostium frontalis into the hiatus semilunaris and thence into the maxillary sinus; the wire on the left side can be seen at various points as it passes downward. This condition indicates direct communication between the frontal and maxillary sinuses. There are also two large cells between the plates of the middle concha. In the upper median corner of the maxillary sinus, especially in the left one, is a septum forming an infra-orbital sinus. CHAPTER XII. THE RELATION BETWEEN THE MOUTH, TONGUE, PHARYNX, AND NASAL CHAMBER. Frozen Sections.—The sections of the head which have hitherto been described were cut from partly dried specimens which answer the purpose very well, especially in and about the nose and its asso- ciated sinuses and cells, but they have one serious fault—the soft tissues have so shrunken that they are far from showing what they were in a fresh condition. Many of the modern applied anatomists have adopted the following plan for the study of the relative values of these parts. The bodies secured for this work should be those that have not lost their true anatomical form through disease. They should be pre- pared as soon as possible after death, first by injecting a solution of formalin to harden the soft tissues, followed by injection of a magma of colored plaster of Paris, after which the body should be covered with a coating of vaselin and wrapped in cloths to prevent evaporation, and placed in a refrigerator at a temperature of about 150 F. When thoroughly frozen it is ready for sectionizing. The saw for making the sections should have a thin, broad blade, with fine, chisel-shaped teeth; in this way the finest bone can be cut without fracture, and even the soft tissue of the brain without displacement. The following illustrations are made from frozen sections: Fig. 299 is an illustration made from a section cut horizontally, just above the mylohyoid muscle looking upward to the base of the tongue. The various structures shown are indicated on the margin. It will be noticed that the tongue rests very close to the inner surface of the mandible and the pterygoideus internus muscle, the cross section of the pharynx is shown with the point of the uvula in view. Should the mandible be compressed and a narrow dental arch exist, the tongue 2S0 RELATION BETWEEN MOUTH, TONGUE AND PHARYNX would be forced backward into the pharyngeal space, interfering with nasal respiration and other functions of the nasal cavity. Lower lip / Muscles and tissues of lower lip J The mandible cut a little above the / J mylohyoid ridge 'Sublingual glands 'Raphe of the tongue Facial artery Facial vein- Facial vein Facial artery Masseter muscle The ramus Pterygoideus internus Point of uvula [muscle Sternocleido mastoid Internal carotid Pneumogastric nerve Internal juglar Splenius capitis Vertebral artery Spinal cord Spinous process of the second cervical vertebra Fig. 299 RELATIOX BETWEEN MOUTH, TONGUE AND PHARYNX 287 Fig. 300 is made from a horizontal section at the junction of the upper lip and nose, showing a longitudinal section of the septum of Nose Nostril. Maxilla. Septum of nose. Nasal cavity Inferior concha. Maxillary sinus. Upper portion of inferior meatus. * Zygomatic process. Tip of coronoid process. Masseter muscle. — Upper head of the pterygoideus externus. Lower half of the pterygoideus externus. Pterygoid process. Head of condyloid process. Longus capitis. Rectus capitis anterior. i' Upper portion parotid gland. Internal carotid artery. Internal jugular vein. Jugular process of occipital bone. Mastoid cells. Spinal cord. Under portion of cerebellum. Bone surrounding foramen magnum. Fig. 300 the nose, the lower borders of the inferior concha, and the maxillary sinus. Within the outer wall of the nasal cavity the longitudinal 2ss RELATION BETWEEN MOUTH, TONGUE AND PHARYNX section of the auditory tube may be seen, and a little posterior, the pharyngeal recess. Fig. 301 is from a sagittal section of a frozen skull, showing the various structures of the brain. It also gives a true idea of the lateral portion of the nasal cavity, the hard and soft "palates, the pharynx, the mouth, the tongue and the epiglottis, and their relations to each other. The first incisor teeth are in good occlusion. The mouth is nearly filled by the tongue, leaving but little space under the arch of the palate. The tongue also extends well back into the oropharynx, coming in contact with the soft palate, which is carried backward against the postpharyngeal wall. The epiglottis at the base of the tongue rests slightly against the back of the pharynx, leaving but little space for respiration which, however, is sufficient when the individual is at rest. But during exertion, wdien more breathing space is required, the mouth is opened and the space in the pharyngeal region is increased. In this section the floor of the nasal cavity extends from the anterior nares backward and slightly downward almost to the postpharyngeal wall without a line of demarcation. The general shape of the roof of the mouth at the median line is well displayed, and may be described as extending from the anterior teeth backward and slightly downward in a concave line nearly to the postpharyngeal wall. In the normal living subject when the mouth is closed, the soft palate, the posterior border of the tongue, and the epiglottis are all in close proximity to the postpharyngeal wall. The soft palate, on its nasal surface is higher along the center line than at the edges, a shape which causes the fluids from the nose and its accessory sinuses and cells to be directed toward the outer wall of the pharynx and on to the esophagus. The dorsum of the tongue also acts in a similar manner for the oral cavity. The epiglottis is so shaped as to throw the fluids to the side of the pharynx past the opening of the pharynx. It does not, as described by some, shut down like a trap-door over the glottis to prevent fluids from passing into it. Fig. 302 is from a vertical transverse section of a negro head, cut in the region of the molar teeth. The section exposes the frontal Longitudinal sinus. Corpus callosum. Ant. commissure. Rostrum. Genu. Frontal lobe Sphenoidal sinus. Lamina cinerea. Septum lucidum. Foramen of Monroe. Middle commissure. Optic thalamus. Crura cerebri. Optic com Frontal sinus Pons varolii Superior concha. Superior meatus. Middle concha. Middle meatus. Inferior concha. Inferior meatus. — Hard palate. Air space above the tongue. Upper incisor. Lower incisor. Frxnum linguae Mandible. Genial tubercles. (lenio-hyo-glossus Genio-hyoid. Epiglottis. Splenium of pad. Scalp. Posterior Commissure Parietal bone. Aqueduct of Sylvius. Longitudinal sinus. Occipital lobe. Occipital bone. Straight sinus. Tentorium cerebelli Torcular herophili. Fourth ventricle. Cerebellum. Odontoid process of second cervical vertebrae. Section of atlas. Hyoid bone. Soft palate. Naso pharynx. Thyroid cartilage. Oro pharynx. ■ Body of vertebrae. Spinal cord. Steno-thyroid. (Esophagus. Trachea Fig. 301.—Frozen section. 290 RELATIOX BETWEEX MOUTH, TOXGUE AXD PHARYXX sinuses, which are larger than common, and extend remarkably deep between the eyes. The septum deflects slightly to the left side of the median line. From the right side a piece of wire has been passed from Fig. 302.—Vertical transverse section of negro head, cut in region of the molar teeth. RELATIOX BETWEEN MOUTH, TONGUE AND PHARYNX 291 the sinus directly downward through the infundibulum (ostium fron- talus), the hiatus semilunaris, and the ostium maxillare into the maxil- lary sinus. Below, and a little outward from the frontal sinuses are the transverse sections of the orbits with the tissues of the eye in position, in which may be seen cross-sections of some of the recti muscles. The dark inner membrane is the choroid. Between the orbits are the anterior ethmoidal cells, the unciform processes, the hiatus semilunaris, the middle concha, and the septum of the nose, which passes downward to the floor of the nose over the intermaxillary suture. There is a slight spur on the right side of the septum. In the lower portion of the nasal cavity are cross-sections of the inferior concha. Below the orbits are two almost typical maxillary sinuses. External to the walls of the sinuses are the muscles of mastication which pass downward to the mandible, passing through these muscular tissues are arteries, veins, and nerves. The upper teeth, the alveolar process and the roof of the mouth are nearly typical in their formation. The space between the tongue and the roof of the mouth is similar to that shown in Fig. 301. Professor Donders1 has spoken of this space as acting somewhat on the same principle as the vacuum chamber in an upper artificial denture. In the cross-section of the tongue will be noticed the raphe and the blood- vessels, etc., the longitudinal section of the mylohyoid muscles is also shown, with a portion of the submaxillary glands and the integuments below them. This section was cut with the mouth closed, so the lines of the fibers of the mylohyoid muscles are nearly horizontal while in Fig. 306, where the mouth was opened when frozen and sectionized, the fibers descend downward and inward. Fig. 303 is a similar section to Fig. 302, giving an anterior view. Immediately below the dome of the skull are the meninges. It will be seen that the membranes in the centre pass downward to form the falx cerebri, the lower edge of which is attached to the posterior portion of the crista galli. At the top of the falx cerebri is a V-shaped cross-section of the longitudinal sinus. The frontal lobes of the brain 1 Arch, of ges. Physiol., Bonn, 1875, Bd. x, S. 91. 292 RELATION BETWEEN MOUTH, TONGUE AND PHARYNX show various convolutions, and it will be noticed that they are not symmetrical. Immediately below the brain are the inner walls of the frontal sinuses, passing well backward and outward over the orbits. Superior longitudinal sinus, Inferior longitudinal sinus. Falx cerebri Frontal lobe. Frontal bone. - Frontal sinus extending back over the orbit. Levator palpebral sup. Rectus lateralis. Optic nerve. Rectus medialis. Anterior ethmoidal cells. Inferior rectus. — Zygoma. Temporal muscle. Middle concha. Middle meatus. Inferior concha. Anterior wall maxillary sinus. ---Inferior meatus Air space between the tongue and roof of the mouth. Maxillary first molar tooth. Tongue. Mandible. Mylo-hyoid muscle. Fig. 303.—Frozen section. RELATION BETWEEN MOUTH, TONGUE AND PHARYNX 293 Below these sinuses are the cross-sections of the orbits and eyes, the various recti muscles of the eye, the optic nerve and the ophthalmic arteries and veins. Between the orbits are the middle ethmoidal cells. Within the nasal cavity are cross-sections of the median wall and the middle and inferior concha. On each side of the lower portion of the nasal cavity are the maxillary sinuses, showing their posterior walls. The entire face is more or less compressed, especially the upper and lower jaws. The tongue has been forced out of shape by the pressure of the walls, showing that it had not sufficient power to force the alveolar process outward. Fig. 304 is made from a transverse section of a frozen head. It ex- hibits a face narrowed and compressed, the maxillary sinus of the right side is lacking, and the other only rudimentary. It will be noticed that while the internal structures of the face are very much compressed, the floor of the nose is of fairly good width. The septum is crooked. The arch of the mouth is very narrow in proportion to the floor of the nose. The mandible is also narrowed, consequently the tongue is very much compressed and out of shape and is forced backward into the pharynx, thus interfering with respiration, especially when the mouth is closed. These anatomical structures are so modified and deformed that all the physiological functions are greatly interfered with. Normally the dorsum of the tongue lies against the hard palate, but, according to Donders,1 at the back part it is separated from the soft palate by a small space. Owing to the weight of the jaw, there is a negative pressure in this space of 2 to 4 mm. . . . The jaw is main- tained in position, not by muscular effort, but by the pressure of the air; so that, if a tube from a manometer be passed between the tongue and the palate, the manometer shows a slight negative pressure cor- responding to the weight of the jaw.2 Fig. 305 is from a vertical transverse section of the same skull used in Fig. 304, also showing a very compressed condition of the structures surrounding the oropharynx. The uvula is twisted, the tonsils, the epiglottis and the larynx are out of shape from pressure 1 Loc. cit. 2 Schafer's Text-book of Physiology, 1900, ii, 314. >4 RELATIOX BETWEEX MOUTH, TONGUE AND PHARYNX Fig. 304.—Vertical transverse section of a frozen head. RELATIOX BETWEEN MOUTH, TONGUE AND PHARYNX 295 Fig. 305.—Vertical transverse frozen section. 29(1 RELATION BETWEEN MOUTH, TONGUE AND PHARYNX of the tongue, produced, not by a narrow floor of the nose, but by a narrow dental arch. In this case it would be difficult to carry on free respiration, and impossible to perform the deep breathing required by great exertion. This morbid condition brings a further congestion and thickening of the mucous membrane of the nose and its accessor} sinuses. Fig. 306 is made from a vertical transverse section of a frozen head cut in the region of the rami of the mandible and the posterior portion of the hard palate. The subject died with the mouth open, and it was not closed before the section was made. Near the anterior portion of the pharynx it will be noticed that the fibres of the mylohyoid mus- .cles pass backward and outward to the internal oblique lines of the mandible. If those muscles are kept in a state of tension, the angles of the mandible will be drawn toward each other and thus tend to contract the lower portion of the face. Comparison of this illustration with Fig. 302 will show great differences in regard to these muscles. In this specimen the palatoglossus and the palatopharyngeus muscles are placed on tension, narrowing the distance between the right and left tonsillar spaces. This action of the muscles naturally influences the narrowing of the face, as also does the lack of percussive force of the lower teeth against the upper. When the mouth is thrown open, the tongue leaves the roof of the mouth, thus giving passage for air; the hyoid bone and all attached to it is drawn downward. This also puts the tongue, the hyoid bone, the pharynx and other structures that are closely associated with them on a tension. The muscles of mastication are also stretched. Fig. 307 is a transverse section of a skull that is almost symmetrical, showing the nasopharyngeal space free from adenoids. The soft palate, the inula and the posterior portion of the tongue are in good position, the tongue and soft palate being close together. Below the tongue and a little to one side, a cross-section of the hyoid bone will be observed and below this the hyoid and cricoid cartilages, showing the inlet of the larynx and trachea. If the posterior portion of the tongue be removed, the tonsillar space will be brought in view as shown in Fig. 260. The section is also made through the brain case, the RELATIOX BETWEEN MOUTH, TONGUE AND PHARYNX 297 Falx cerebri. Optic nerve. Pterygoideus internus Masseter muscle. Palatopharyngeus. Palatoglossus Mandible. Frontal lobe. Tissue in portion of orbit. Sphenoid bone. Nasal septum. Temporal muscle. Nasal fossa. Soft palate. Masseter muscle. Oro-pharyngeal space. Inferior alveolar nerve and vessels. Tongue. Mylo-hyoid Larynx. Fig. 306 29S RELATIOX BETWEEX MOUTH, TOXGUE AXD PHARYXX Fig. 307.—Transverse frozen section of symmetrical skull. RELATIOX BETWEEX MOUTH, TOXGUE AXD PHARYXX 299 Fig. 308.—Vertical transverse section of narrow skull. :•><>() RELATIOX BETWEEX MOUTH, TOXGUE AXD PHARYXX temporal muscles, the external and internal pterygoid muscles and processes, the internal maxillary arteries, the rami of the mandible, and the submaxillary gland. Sup. longitudinal sinus. Falx cerebri. Scalp. Corpus callosum. Lateral ventricle. Septum lucidum. Optic thalamus. Lateral cerebral fissure (fissure of Sylvius). Temporo sphenoidal lobe. Optic tract. Internal carotid artery, Temporalis (temporal muscle). Sphenoid bone. Zygomatic arch. Pterygoideus internus. Adenoid tissue. Soft palate. Masseter muscle. Mandible. Pterygoideus internus. Tongue. Submaxillary gland. Fig. 309.—Anterior view of Fig. 308. RELATIOX BETWEEX MOUTH, TOXGUE AXD PHARYXX 301 Superior longitudinal sinus longitudinal sinus. : cerebri. Frontal lobe. Levator veli palatini (Levator palati). Sphenoidal Naso-pharynx Internal carotid artery. Post-pharyngeal wall. Temporo-sphenoidal lobe. Posterior part of orbit. Temporalis. Temporal aponeurosis. Zygoma. Pterygoideus externus. Ramus of mandible. Soft palate. Deep portion of masseter Superior portion of masseter. Epiglottis. Pterygoideus externus. Tonsil. Palatopharyngeus. Palatoglossus. Hyoid bone. Thyro-hyoid muscle. Thyroid-cartilage. Omohyoid. Sterno-cleido-mastoid. Cricoid cartilage. Fig. 310.—Frozen transverse vertical section. :; ,s made from the upper and lower jaws of a native Australian,1 showing powerful jaws and teeth. There seems to have Fig. 325.—Side view of a prognathous skull of a negro with eighteen teeth in the upper jaw. The roof of the mouth is shown in Fig. 346. Fig. 326.—Side view of an upper and lower jaw of a native Australian. 1 Belonging to the collection of Dr. E. C. Kirk. RUDIMENTARY OR SUPPRESSED MOLARS 315 been no caries in the teeth, but there is strong evidence of pyorrhea alveolaris. The arches are of good width. Fig. 327 is made from a modern mandible (see skull Fig. 80), show- ing about as powerful a lower jaw as that shown in Fig. 326 and the teeth are good, without decay, and no evidence of pyorrhea alveolaris. Figs. 328 and 329 are made from .v-ray pictures of a boy1 sixteen years of age, showing a right and a left impacted mandibular second molar. Apparently the anterior occluding surfaces have caused the resorption of the posterior roots of the first molars; there seems to be no development of the third molars, also no evidence that the lower second premolars have developed. The roots of the deciduous teeth show evidence of resorption, although there are no permanent teeth inciting this action. 4 ■ Fig. 327.—Side view of a modern heavy mandible. Fig- 33° gives an v-ray picture of the upper and lower jaws. There is no evidence of the development of the left third molars or of the second premolars, but as in the case of Figs. 328 and 329, the resorp- tion of the roots of the deciduous teeth had taken place without the action of the permanent teeth. Fig. 331 is an .v-ray picture, showing teeth of' the right side of the same jaws as Fig. 330, the third molar is developing while the second maxillary deciduous molar has been shed without the premolar to take its place. It will also be noticed that there is no development of the maxillary third molar. 1 Taken from a patient of Dr. T. G. Barnes, Springfield, Mass. 310 MODIFICATION OF NORMAL SHARE OF BONE Fig. 329 Figs. 328 and 329.—A'-ray pictures, showing right and left impacted second molars. RUDIMENTARY OR SUPPRESSED MOLARS 317 Fig. 332 is an x-ray picture of a living patient about twenty years of age, showing a deciduous mandibular second molar, in position, there is no second premolar developing to take its place; it will be noticed that the roots of the deciduous tooth have been resorbed to a great extent. Fig. 330.—X-ray of upper and lower jaw. There is no evidence of the development of the left third molar or of the second premolars. Fig. 333 is an .v-ray picture of an ancient Egyptian mandible,1 show- ing the retention of a second deciduous molar and the absence of the developing second premolar similar to the missing premolars in Fig. 332. . 1 Belonging to the collection of Dr. E. C. Kirk. 31 s MODIFICATION OF NORMAL SHAPE OF BONE Figs. 334 and 335 are .v-ray pictures showing two impacted man- dibular third molars in prehistoric mandibles. These two bones were found near Tuckerton, N. J., and are supposed to have belonged to a race of people inhabiting this region before the North American Indians. Fig. 331.—AT-ray picture of a modern jaws. Figs. 336 and 337 are illustrations made from the left outer side and the right inner side of a mandible of a modern skull showing two impacted third molars; the left one is nearly horizontal, while the right one is badly "locked" under the posterior portion of the second molar. RUDIMENTARY OR SUPPRESSED MOLARS 319 Fig. 338 is made from an x-ray picture of the same mandible as shown in Figs. 336 and 337. In this way the position of the roots is Fig. 332.—X-ray of modern jaws showing deciduous molar. (AT-ray by Dr. Pancoast.) Fig. 333.—AT-ray picture of an ancient Egyptian mandible. (X-ray by Dr. Pancoast.) 320 MODIFICATION OF NORMAL SHAPE OF BONE illustrated, shewing considerable thickening of the tissue around the roots. Fig. 339 is an x-ray picture, showing a developing lower rudimen- tary fourth molar in a modern mandible.1 There is strong evidence that a pathological condition existed in the tissue surrounding the first, second and third molar teeth, especially the second and third. Figs. 334 and 335.—X-ray picture of two prehistoric mandibles, showing impacted mandibular third molars. (X-ray by Dr. Pancoast.) Fig. 340 is from a photograph of a living subject, showing five maxillary incisors. Fig. 341 is from an x-ray picture,2 showing five erupted deciduous and five unerupted permanent incisors in the mandible of a living person. 1 Belonging to the collection of Dr. Kirk's. 2 X-ray picture loaned by Dr. Blum of New York. RUDIMENTARY OR SUPPRESSED MOLARS 321 1 I / Figs. 336 and 337.—Two halves of the same mandible, showing two impacted third molars. Fig. 338.—X-ray picture showing two impacted third mandibular molars. MODIFICATION OF NORMAL SHAPE OF BONE Fig. 339.—X-ray picture showing impacted lower rudimentary fourth molar. Fig. 340.—Photograph showing five maxillary incisors. Fig. 341.—X-ray showing five deciduous and five permanent incisors. SUPERNUMERARY PREMOLAR TEETH 323 SUPERNUMERARY PREOMLAR TEETH. It is not unusual to find extra premolar teeth in the maxilla or mandible. Dr. Robert H. Ivy has reported a case of six mandibular premolars, one of which was impacted.1 Dr. Inglis reports a "case of seven lower bicuspids, two supernumeraries in place and one erupting.' The patient has also two supernumerary upper central incisors dis- placing the centrals proper, yet closely resembling them."2 Fig. 342.—Plaster cast, showing six premolars teeth. Dr. Hopewell-Smith mentions a case of a negro having a super- numerary premolar on each side of the mandible.3 Dr. A. H. Ketcham, of Denver, very kindly loaned the cast of a patient's mouth from which Fig. 342 was made, showing three pre- molars on each side of the maxilla. Fig. 343, 344 and 345 were made from a clinical patient about twenty-four years of age, at the Evans Dental Institute. Examina- tion showed that the mandibular first molars had been extracted on both sides to give room for other teeth that were in process of eruption. 1 Dental Cosmos, June, 1915, p. 670. 2 Dental Pathology and Therapeutics, fifth edition, p. 282. 3 Dental Anatomy and Physiology, 1913, p. 215. 321 MODIFICATION OF NORMAL SHAPE OF TONE The tour incisors and two canine teeth were well developed and in normal positions. Fig. 343 is an x-ray of the right side of the upper and lower jaws. Three premolars in fairly good position may be seen in the mandible, also a fourth impacted premolar. The lingual cusp of Fig. 343.—X-ray showing four premolars. (X-ray by Dr. Pancoast.) the second premolar is not well formed (see Fig. 345), the other two, however, have well-shaped crowns. Fig. 344 is made from the left side of the face, the space between the last premolar and the second molar indicates that the first molar had SUPERNUMERARY PREMOLAR TEETH 325 been extracted. There are three premolars in position with well-formed crowns and an impacted tooth may be seen between the first and second premolar to which no better name can be given than extra premolar, making eight premolars in the mandible. Fig. 344.—X-ray showing four premolars. (X-ray by Dr. Pancoast.) Fig. 345 is made from a plaster cast of the occluding surface of the mandibular teeth, showing that the incisors and canines are quite normal in position and shape, five premolars show fairly good crowns, while a sixth premolar on the right side is deformed. It will be noticed in this illustration that there are two elevations 326 MODIFICATION OF XORMAL SHAPE OF FOXE on the inside of the jaw, above the sublingual fossa1, indicating the position of the impacted premolars as shown in the two x-ray pictures. Fig. 345.—Plaster cast of lower jaw from the same as shown in X-ray, Figs. 343 and 344. Fig. 346.—Palatal aspect of the maxillary teeth and bone, from same skull shown in Fig. 325 Fig. 346 shows the under surface of the upper jaw seen in Fig. 325 with a rudimentary fourth molar on each side of the arch. SUPERXUMERARY PREMOLAR TEETH 32; Figs. 347 and 348 show the under surface of two upper jaws, the occluding surface of the teeth, and their relative size. Fig. 348 is about the normal size, while Fig. 347 is very much larger. In Fig. 347 there Supernumerary tooth Fig. 347 Supernumerary tooth Fig. 348 Figs. 347 and 348.—View of two upper jaws. The occluding surfaces of the teeth and roofs of the mouths, and the great difference in relative size, are well shown. Fig. 347 has two rudimentary fourth molars. are two fourth rudimentary molars, one in the line of the arch and one on the buccal side of the second molar. Fig. 349 is a view of the palatal surface of an upper jaw, showing the occluding surfaces of the teeth, with two supernumerary teeth situated on the buccal sides of the second molars. 32s MODIFICATION OF NORMAL SHAPE OF BONE Supernumerary tooth -Supernumerary tooth Fig. 349.—View of the roof of the mouth and occluding surfaces of the teeth from an ordinary sized upper jaw, showing two rudimentary fourth molars. Fig. 351 Figs. 350 and 351.—Two mandibles, Fig. 350 from the Fan tribe, West Africa, Fig. 351 from a Caucasian, showing the difference in the position of the teeth in relation to the ramus, the mental foramen, and the symphysis. SUPERNUMERARY PREMOLAR TEETH 320 Comparison of Mandibles of a Caucasian and an African Negro.— Figs. 350 and 351 affords a comparison between the mandibles of the Caucasian and of the Fan tribe negro (West Africa). They were photographed upon the same plate, showing their relative size and shape. The teeth and alveolar process in Fig. 350 have been carried much further forward than those in Fig. 351. In Fig. 350 the third molar is in advance of the ramus, while in Fig. 351 the third molar, to a great extent, is posterior to the anterior margin of the ramus, the difference being about the width of a molar tooth. In Fig. 350 the mental foramen is beneath the first molar, while in Fig. 351 it is beneath the interspace between the two premolars, again a difference of about the width of a molar tooth. CHAPTER XIV. THE INFLUENCE OF MUSCULAR ACTION. After the birth of the child, muscular action and various forces have direct influence over changes in the shape of the bones, according to the following rules: The normal application of the forces affecting developing bone results in normal development of the form of the bone. Their abnormal application under the same circumstances results in the development of abnormally formed bone. Abnormal application of forces to the bone in adult life will also change and modify the shape and character of the bone tissue. The changes which may be caused by the applica- tion of abnormal forces to the developing individual are well illustrated by the disfigurements resulting from the tight bandages put upon the feet of Chinese girls of the higher class, the use of corsets to contract the waists of the European women of the analogous class, and the flattening of the skulls of certain Indians of North America by binding boards upon the heads of the children. Fig. 312 gives a side view of one of these Indians. Fig. 313 gives a front view, showing that by the compression of the frontal region downward the skull has been extended laterally. The modification of the bones by abnormal muscular action is well illustrated by the changes found in persons suffering from true or false ankylosis of the temporomandibular articulation. The illus- trations which follow are taken from a patient and from the bones of two skulls. False Ankylosis.—Fig. 352 is from the photograph of a patient who has been suffering from false ankylosis. Judging from the general outline of the face, with its protruding lips and receding chin, one might be inclined to classify the individual as a degenerate, but the FALSE ANKYLOSIS 331 writer believes that this picture, and others to follow, show that this is a typical face belonging to those who have or who have had anky- losis of the jaw, either true or false. This patient has suffered from a false ankylosis since about nine years of age. Fig. 353 is taken from the right side of the same face, showing a scar extending upward and backward from the angle of the mouth to the region of the external acoustic meatus. The scar was produced by a Fig. 352.—Characteristic appearance in Fig. 353.—Opposite side of face of Fig. 352, the region of the lower jaw in long-standing showing scar caused by a gunshot wound, the ankylosis. effects of which produced false ankylosis. gunshot wound. The shot in passing severed the masseter muscle as well as a portion of the buccinator. In the healing of the parts false bands of cicatricial tissue were formed, extending from the lower jaw to the zygoma and the zygomatic arch. The pterygomandibular ligament was also shortened, thus preventing the jaws from being opened. The treatment for the false ankylosis consisted in cutting the false bands and using the mouth-gag with a screw to break up the false ligaments. The operator was afterward assisted by the patient in 332 INFLUENCE OF MUSCULAR ACTION forcing the jaws asunder, as shown in Fig. 354. The main object in using the appliance was to stretch the temporal and masseter muscles of both sides. In a few weeks the patient could open the jaws without the appliance, as shown in Fig. 355. There was at this time sufficient improvement to permit of the mastication of food and the proper care of the teeth. The condition has since been further improved. Fig. 354.—Application of jack-screw for forcing the mouth open in false ankylosis. Other causes of false ankylosis are: Ossification of the pterygo- mandibular raphe, myositis ossificans affecting the masseters, pterygoid or buccinator muscles. Typical Ankylosed Mandible.—In cases of true ankylosis of the jaw, especialh those of long duration, certain changes in the form of TYPICAL ANKYLOSED MANDIBLE 333 the mandible are noticeable, not onh' on the affected side when the ankylosis is unilateral, but also on the opposite side. The character of these changes is well shown in Figs. 356 and 357. Fig. 356 is a view of the unankylosed side of a typical case of true unilateral ankylosed jaw. The condyloid process is shortened and its articulating surface is changed. Instead of being rounded at the top it has more of the Fig. 355.—Results of treatment for false ankylosis. shape of a Gothic arch. Through this shortening of the condyloid, the coronoid process is apparently elongated. The angle of the man- dible is also elongated so that it forms a projecting point, and the base of the bone under the mental foramen is considerably thickened. The mental process is much diminished in size. There is no loss of 334 INFLUENCE OF MUSCULAR ACTION bone, but, by the operation of causes to be referred to, a metamorphosis has been induced whereby the base of the bone has been thickened at the expense of the mental process. Owing to the same causes, the base of the bone, between the angle and a point verticalh' underneath Fig. 356 —Unankylosed side of a jaw having a true unilateral ankylosed mandibular articulation. Fig. 357.—The ankylosed side of Fig. 356. the canine teeth, is deeply concave in outline instead of being nearly straight, as in the normal jaw. Fig. 357 is taken from the opposite side of the face in Fig. 356, showing the condyloid process completely changed; it is broadened TRUE ANKYLOSIS 335 out, and is sharply serrated on the articulating surface. The articu- lating surface of the mandibular fossa is also changed to correspond to that of the condyle with which it was interlocked. The angle of the jaw on this side is much more changed than on the opposite side, causing a deep depression in the region of the facial notch. The lower jaw, beneath the mental process, is fuller and more roughened Fig. 358.—A skull with a true ankylosis of the mandibular articulation on the opposite side. and the mental process more concave than on the opposite side. The concavity of the base of the jaw and the elongated angle are readily seen in the picture of the living subject (Fig. 360). True Ankylosis.—Fig. 358 is from a skull with a complete or true unilateral ankylosis of the jaw, taken from the unankylosed side. Fig. 359 shows the ankylosed side. The lower jaw closely resembles that shown in Fig. 357, in the descending angle, the receding chin, 3,30 INFLUENCE OF MUSCULAR ACTION etc. In all cases of prolonged ankylosis it becomes evident that there is cause for the changes observed in the form of the bones. The muscles of mastication, i. c., those which elevate the lower jaw—are inactive, while those which assist in depressing the mandible become more and more active in their work, in an endeavor to overcome the fixation of the mandibular articulation. By their action the lower jaw, from the symphysis to the angle, becomes modified in proportion to the Fig. 359.—View of the ankylosed side of Fig. 358. contraction of the depressing muscles of the jaw. Anteriorly there are the two genioglossus, the sternothyroid, the sternohyoid, the digastricus, the omohyoideus, and the platysma, all of which are abnormally active. Their action, without the normal compensating factor of the mandibular motion, brings about in time the changes noted. Fig. 360 is a picture of the patient shown in Figs. 352 and 353, showing an endeavor to open the mouth by the assisted action of the CHANGES IN THE MANDIBULAR ARTICULATION 337 muscles. It illustrates the various muscles under spasmodic action, indicating how their frequent use under such conditions may cause alterations in the form of the bone. Changes in the Mandibular Articulation other than by Ankylosis.— Teeth becoming diseased or lost on one side of the jaw cause changes in the forms of the various bones, through the necessity of masticating on the opposite side of the mouth, and the consequent use of the jaws in an abnormal manner. In this way great alterations can be made in the mandibular articulation, and in one or both mandibular fossae. Fig. 360.—The action of the depressor muscles of the mandible in ankylosis. The articular tubercle may be entirely lost by resorption. The places of attachment for the muscles of mastication, as the coronoid process, the outer surface of the ramus, the angle of the jaw, etc., become roughened and enlarged on the side in use, and smooth and lessened on the unused side. The spaces where the muscles have their origin, such as the external plate of the pterygoid process, the under surface of the zygomatic arch, and the temporal ridge of the skull, will also become enlarged on one side and lessened on the other. Several illustrations are here given to show the changes brought about by the loss of teeth and changed position of occlusion. 22 3: is INFLUENCE OF MUSCULAR ACTION Fig. 301 is a view of the articulation of the left side of the skull of an aged person who had lost all the teeth except three in the upper jaw and three in the lower jaw. They were not opposite to one another in normal occlusion. In order that the cutting or grinding surfaces of these teeth could come into occlusion, the lett side of the jaw had to be carried forward, bringing the condyloid process of that side upon the articulating tubercle, while the right side remained in Fig. 361.—Modification of the left mandibular articulation through the jaw being forced forward in mastication in order to bring the remaining teeth in occlusion. a nearly normal position, as shown in Fig. 362. Upon close examina- tion of the condyle of the left side, it is found to be flattened out, probably because of coming in contact with the articular tubercle, thus moving the point of articulation forward, or "jumping the bite." The tubercle or eminence is flattened also. The forces of mastication of the left side were but little used, and accordingly the places of origin and insertion of the muscles of that side are much less marked than the normal; while on the right side, upon which alone the function of CHANGES IN THE MANDIBULAR ARTICULATION 339 V,/ Fig. 362.—The right mandibular articulation from skull shown in the preceding photograph, where the condyloid process has not been carried forward. Fig. 363.—Right side of a skull. See mandible, Fig. 9. 310 INFLUENCE OF MUSCULAR ACTION mastication was performed, the muscles were thus overworked, and the places of attachment and of their origin and insertion are strough marked in consequence. Fig. 3^3 gives a view of the right side of a skull. It will be seen that the three molars and one premolar of the maxilla are missing. In^the mandible, all the teeth except the first and second incisors have been lost. Fig. 364.—Left side view of the same skull as Fig. 363, showing the condyloid process, articulating on the squamous portion of the temporal bone and partly on the great wing of the sphenoid instead of the mandibular fossa. Fig. 364 gives a view of the left side of the same skull, showing a few upper and lower teeth in occlusion. The remarkable characteristic is the abnormally small ramus, and portion of the body of the bone. The condyloid process, instead of articulating in the mandibular fossa, articulated partly on the squamous portion of the temporal bone, and partly on the great wing of the sphenoid. There seem to be two ways in which this deformity could occur. One is by the lack of growth in CHANGES IN THE MANDIBULAR ARTICULATION 341 the ramus and body of bone; the other theory is that the bone grew to its normal size (as there is evidence of its having articulated in the mandibular fossa), when an atrophied condition may have occurred which reduced the size of the ramus and part of the body; in order to Fig. 365.—Under view of the articulation of the mandible as shown in Fig. 364. See base of skull, Fig. 93. keep up occlusion of the teeth, the condyloid process moved forward, first articulating on the articular tubercle, and as the atrophy progressed, moving still forward to keep the occlusion, until the condyloid process reached the position shown in the illustration. CHAPTER XV. HYPERTROPHY OF THE GUMS AND ALVEOLAR PROCESS. Abnormal growth of the bone may produce almost the same effect, so far as appearances go, as the modification caused by abnormal muscular action. In February, 1893, Dr. J. W. Hisey, of Cleveland, brought to the Hospital of Oral Surgery- a boy of fifteen years. The Fig. 366.—From the photograph Fig. 367.—Tissue removed from upper jaw of of a lad suffering from hypertrophy patient shown in Fig. 366. of the gums and alveolar process. boy was well developed, bright, intelligent, and well educated. He was afflicted with the most remarkable case of hypertrophy of the gums and alveolar process that the wrriter has seen recorded. The case was operated upon by the late Professor Garretson and the writer, February 17 and March 11, 1893.1 1 A full description of the operation will be found in the Dental Cosmos, June, 1893. HYPERTROPHY OF GUMS AND ALVEOLAR PROCESS 343 Fig. 366 is from a photograph of the lad taken before the operation. Similarly to the first picture shown in the ankylosis series, this boy appears to have anything but an intelligent face. On February 17, Fig. 368.—Tissue removed from the lower jaw of patient shown in Fig. 366. Fig. 369.—From a photograph taken three weeks after the removal of the tissue in Figs. 367 and 368 Professor Garretson decided that it was best to open the upper lip at the median line and carry the incision around to the alse of the nose. By the aid of the surgical engine and other instruments, the portion 311 HYPERTROPHY OF GUMS AND ALVEOLAR PROCESS shown in Fig. 367 was removed from the upper jaw. It was thought best not to remove the abnormal tissue from the lower jaw at this operation, so it was delayed until March 11, when the mass of tissue shown in Fig. 368 was removed from the lower jaw. This last was accomplished without cutting the lip. Fig. 369 is from a photograph taken about April 28, seven weeks after the second operation; the parts were thoroughly healed and the general health of the patient was good. He experienced less difficulty Fig. 370.—From a photograph six years after the operation upon the person represented in Fig. 330. in articulating than previous to the operation, and the improvement in his speech and general appearance was very marked. Artificial dentures were supplied in due time. Fig. 370 is made from a photograph taken six years after the operation. To judge from this, the young man certainly does not look like a degenerate. The operation has evidently made a tremendous improvement in his appearance, and it seems to be conclusively demonstrated that Professor Garretson was right in his judgment. CHAPTER XVI. THE RELATION OF THE TWO JAWS. The Relation of the Upper and Lower Jaws Varies Throughout Life.—There is also a difference in their relative time of development. The lower jaw is developed slightly in advance of the upper one and is formed from two processes or buds, the upper jaw being formed from four processes or buds—two from the sides and two from above. Occasionally these four processes fail to completely unite. This lack of union varies from a slight cleft palate or hare-lip to a double cleft palate and double hare-lip. In a few very exceptional cases there has been an entire lack of union of these parts, leaving the mouth, nasal cavity, and orbits as one common cavity. Various theories have been advanced for this lack of union, the most prominent, perhaps, being that of malnutrition of the parts during the time when the union should take place. While agreeing that malnutrition is probably largely responsible, the writer offers as a plausible explanation of the manner of its operation the idea that as the lower jaw is formed in advance of the upper one, when undue pressure is exerted upon it, it is forced in between the four processes forming the upper jaw, thus mechanically preventing them from coming together. The normal position of the fetus in utero is such that the weight of the entire fetal body could be thrown upon the vertex, the pressure thus exerted would tend to force the mandible into contact with the sternal region and compress the forming jaws together. The relatively advanced development of the mandible, as compared with that of the forming maxilla, would under the circumstances referred to, and especially in cases of low nutritional standard, interfere with the normal closure of the brachial arches and tend to produce a per- manent coloboma. If an examination be made of a young child with a complete cleft, it will be noticed that the upper alveolar ridge is immediately over 34(i RELATION OF THE TWO JAWS the aheolar ridge of the lower jaw, or it may be external to it; in the normal child or in the person of advanced age the upper aheolar ridge is in vertical line within that of the lower jaw, as is well illustrated in Figs. 196 and 372 and in Figs. 375 and 376. Congenital cleft palate has also been attributed to the effects of syphilis during intra-uterine life. (Hopewell-Smith.) Manner of Drinking.—Individuals having cleft palate, especially those with double cleft, have not the power to drink when the anterior portion of the mouth is on a lower level than the posterior portion. They are compelled to raise the head, thus throwing the fluid back into the pharynx, similar to the manner in which a chicken drinks. This mode of drinking is normal with the chicken, as it has naturally a cleft palate, and has not the power of suction as performed in man by the glossopalatinus muscle. A child with a complete cleft has no power of suction with the lips, but if an artificial nipple be long and large, the child may seize it with the palatal muscles, which will give the power of sucking or of drawing the fluid through the nipple.1 Mold upon which the Maxilla is Formed.—It is generally accepted that the lower jaw acts as a matrix or mold upon which the upper jaw is formed. To an extent it certainly becomes the mold upon which the inferior border of the upper jaw is formed, as the latter comes in contact with its inner edges. This action also influences the general contour and shape of the superior alveolar ridge and roof of the mouth. Pig. 371 is a picture taken from the skull of a fully developed fetus. The skull has been cut vertically and transversely in the region of the developing deciduous teeth of both jaws, showing the jaws in trans- verse section. The skull is quite symmetrical. It is plainly to be seen that the width of the upper jaw is much less than that of the lower.2 As a further evidence of this fact, if vertical lines are drawn through the centres of the tooth-germs and the alveolar process of each jaw, it will be found that the lines of the upper jaw are on the inner side of those of the lower jaw, the extent of the difference being about one-half of the thickness of the lower jaw. 1 For surgical procedure and further description of cleft palate, see Brophy's Oral Surgery, p. 563. 8 For description of other features shown in this illustration, see Fig. 195. MOLD UPON WHICH THE MAXILLA IS FORMED 347 * Fig. 372 is taken from an adult jaw. If lines be drawn through the longitudinal axes of the upper and the lower teeth, it will be found that those through the former, as they extend toward the coronal surfaces, pass a little outward, while those passing up through the lower teeth incline inward. This is evidence that the relation found in the fetus has been continued, and that all through the period of growth of the lower jaw and development of its alveolar process, the latter has been directed inward, while the upper alveolar process has extended out- FiG. 371.—Vertical transverse section through the orbits, the nasal cavity, and the premolar teeth. wardly, so that the cusps of the upper permanent teeth, when fully developed normally, bite over the outer cusps of the lower teeth occlud- ing with them. If the teeth and alveolar process be excluded, it will be observed, as in the fetal skull, that the upper jaw is much smaller than the lower. Fig. 373 is from the anterior section of Fig. 372. It illustrates the occlusion of the anterior teeth, also shows the cortical and the cancel- lated tissue of the mandible. 34s RELATIOX OF THE TWO JAWS The Resorption of the Alveolar Process. As the aheolar process belongs to the teeth and is developed with them, and its function is that of holding them in position, it disappears to a greater or less extent after the teeth are lost. Hopewell-Smith has shown that this resorption Fig. 372.—Anterior view of a vertical transverse section through the lower jaw and the lower portion of the upper jaw. Fig. 373.—Anterior section of Fig. 372. of bone may begin at a very early age—on account of the fact that, histologically, the structure of the osseous tissue differs considerably from that found elsewhere, and its blood supply is very inadequate. The manner of its resorption differs in the two jaws. In the upper the external plate disappears more rapidly than the internal, which RELATION'S IX EXTREME OLD AGE 349 persists for a considerably longer period, though in extreme old age the entire process is lost, leaving a very narrow jaw and a small roof to the mouth (see Figs. 375 and 377). In the lower jaw the resorption of the two plates takes place more evenly. Usually they are resorbed in such a manner that a slight ridge is left between the places which they formerly occupied. The Relations in Extreme Old Age.—As a result, there is produced a twofold effect upon the relation of the jaws. As the resorption of the alveolar process goes on, the vertical distance between the body of the lower jaw and that of the upper is lessened, while the natural difference in their width is increased. The area of the upper jaw becomes smaller in proportion to that of the lower, the axes of the mandible extending further outward. In the endeavor to close the jaws under these circumstances, the lower is projected further forward as it rises to meet the upper, until, in extreme cases, it may pass abso- lutely outside of the upper. This is a frequent characteristic of the edentulous jaw in old age. If properly fitting artificial dentures are placed in the mouth promptly after the loss of the natural teeth, the resorption of the alveolar process, and particularly the change in the angle of the jaw, will be retarded. Thus, if these teeth are replaced from time to time by dentures adjusted to the conditions as the processes recede, this characteristic change of old age will be overcome to a very large extent. Figs- 374 and 375 are taken from two skulls of about the same shape and size. Fig. 374 is from an adult of about twenty-five years, having a full series of normally occluded teeth. The direction of the upper and lower teeth can be observed as described. Fig. 375 is from a person of seventy-five years or more, where all the teeth were lost and the alveolar process resorbed, showing the upper and lower jaws in their normal shape and relations. Figs. 376 and 377 are a side view of the same skulls shown in Figs. 374 and 375. It seems evident from these skulls, which are typical and not exceptional, that if the teeth be lost and the alveolar process resorbed after middle life, the upper and lower jaws cannot be again brought into occlusion through their alveolar borders. 350 RELATIOX OF THE TWO JAWS Causes of Malformation of the Jaws.—The normal action and reaction between the two jaws has been spoken of as producing irregu- Fig. 374 Fig. 375 Figs. 374 and 375.—Two adult skulls viewed from below: Fig. 374 from a subject about twenty years old; Fig. 375 from one well advanced in years. Fig. 376 Fig. 377 Figs. 376 and 377.—Side view of the two skulls shown in Figs. 374 and 375. larities in the shape of the arches, of the roof of the mouth, and in the position of the teeth. In general, it may be said that any cause which CAUSES OF MALFORMATION OF THE JAWS 351 prevents the normal occlusion of the jaws, during either rest, speech, or mastication, will bring about malformation of these parts. Among the causes which prevent the normal bringing together of the jaws may be mentioned abnormal mouth-breathing, inflammation of the bone, of its periosteum or of the pericementum, or conditions causing pain when the teeth come in contact. Abnormal mouth-breathing should be corrected, whether it is caused by bony obstruction, in hypertrophy of the mucous membrane, or by adenoid growths in or about the naso- pharyngeal space or by narrow dental arches. While the jaws are kept apart the muscles in connection with the orbicularis oris are some- what tightened, and a pressure which has a tendency to force the teeth inward is brought to bear upon the non-occluding teeth, causing mal- occlusion. While this feature has received very general acceptance, it is, in the opinion of the writer, merely an incidental factor, and of far less etiological significance than the loss of the developing and molding influence which directly results from the percussive force of occlusion exerted by the mandible upon the maxillary arch. The presence of adenoid growths in the nasopharynx, or in fact any cause which interferes with the normal closing of the mouth, at once interferes with occlusion, which, in view of more recent studies, the writer regards as the most potent factor in the normal development of the relation of the upper to the lower dentures. It is, of course, to be understood that the factor behind these anatomical variations, leading to asymmetrical development, is neces- sarily that of nutrition. Some interference with local nutrition has brought about functional disturbance of a part, and this, in turn, a corresponding modification of anatomical form. The writer in conclusion suggests that the data which are embodied in this work will not be regarded as exhaustive of the subject, but rather as an indication of the magnitude of the field to be studied, and more particularly as suggestive of the rational method by which the subject should be investigated. INDEX. Abscesses, 238-241, 269 Acoustic meatus, 73 Alignment of teeth, 120, 121 Alveolar process, anteroposterior section through, 128 hypertrophy of, 342 of mandible, 25, 77 resorption of, 271, 348 Anatomical structures, 20 variations in, 263-284 Anatomy, 263 Anesthesia, local, of parts of face controlled by the trigeminal nerve, 163-165 of teeth, 163-165 Ankylosis, action of depressor muscles of man- dible, 337 false, 330 treatment of, 331, 332, 333 of mandible, changes in, 333 typical, 332 unilateral, 334 true, 335 Antrum of Highmore, 217 Artery, inferior alveolar, 135 internal maxillary, 135, 138 superior alveolar, 134 Articular tubercle, loss of, 337 Articulation of mandible, 70 changes in, 337, 338, 339, 340 Auditory tubes, 196, 206 Auriculotemporal nerve, 150 branches of, 150, 151 Australian, skull of, 314 B Badger, sagittal section of skull of, 271 Barton's bandage in fractures of the mandible, 60 Base of skulls, measurement of, 88 Body of mandible, description of, 23 Bone, effect of hydrogen peroxide on, 55 growth of, 50 necrosis of, 52 phosphorous, 56 regeneration of, 52, 57, 58 tubercular, 52 23 Buccal cavity, 100 Buccinator nerve, 149 branches of, 150 Bulla ethmoidalis, pathological condition of, 208, 210, 260 Calcium, deposit of salts of, 120, 167, 304 Cancellated tissue, arrangement of, in jaws, 20, 33 123 Canine teeth, impacted, 176, 177, 178, 179, 180 mandibular, 111 crown of, 111 anterior face of, 112 cutting edge of, 112 labial face of, 111 lingual face of, 112 posterior face of, 112 definition of, 111 neck of, 112 root of, 112 maxillary, 105 crown of, 105 anterior face of, 106 cutting edge of, 106 labial face of, 105 palatal face of, 105 posterior face of, 106 definition of, 105 neck of, 106 pulp of, 106 root of, 106 Caucasian mandible, 328 skull, 84, 310 Cell of orbital process, 207, 232, 233, 235 Child's head, transverse section of, 95 Chinese mandible, 30 skull, 87 measurement of, 88, 92 Ciliary ganglion, 155 branches of, 155, 156 Cleft palate, 80, 345, 346 Concha, middle inferior, 291 superior, 204, 224 sphenoid, 262 Condyloid process, 69 Cribriform tube, dental branches of, 37 354 INDEX Cribriform tube of mandible, 33, 34 Crista galli, cell of, 251, 262, 275, 276 variations of, 264-2S4 Crown of first mandibular molar teeth, 114 maxillary molar teeth, 108 of mandibular canine teeth, 111 incisors, 111 premolar teeth, 112 of maxillary canine teeth, 105 incisors, 104 premolar teeth, 106 of second mandibular molar teeth, 115 maxillary molar teeth, 109 of third mandibular molar teeth, 116 maxillary molar teeth, 109 tooth, definition of, 103 Cysts, dental, 193, 213 pathology of, 193 x-rays in diagnosis of, 193, 195 dentigerous, 193 in impacted teeth, 193 Deciduous teeth, 102, 103, 117, 171, 172 pathological effects, 120 relations with permanent teeth, 172 Deep temporal nerve, 148 Dental arch, 94 narrow, 94, 96, 97, 120, 269, 296 variations of, 264-2S4 wide, 96, 97 cysts, 193 diagnosis of, x-rays in, 193 pathology of, 193 Dentition, prehensile type of, 312 Deposit of salts of calcium, 304 in early life, 304 insufficient, 304 undue, 304 Depressor muscles of mandible, action of, ankylosis, 337 Development of face, 20 Diagrams of angles of mandible, 31 Egyptian mandible, 317, 319 Engine, surgical, 76 Epiglottis, 288 Eruption of teeth, 118, 119, 171, 172 irregular, influence on teeth, 166 retarded, 166 Ethmoidal cells, 204, 205, 207, 235, 259, 291 anterior, 259 definition of, 259 middle, 260 posterior, 260 nerve, 144 External pterygoid nerve, 149 Extraction, 191 of impacted teeth, 192 of teeth, 42, 46, 49, 224 Face, anatomical structures of, 20 variations in, 263 cancellated structures of, 20 development of, 21 internal anatomy of, 17 neuralgia of, 64 sections of bony structures of, 263-284 sensory nerve supply of, 139 False ankylosis, 330 Fan tribe, West Africa, mandible of, 328 skull of, 310 Fifth nasal meatus, 208 First mandibular incisors, 111 molar teeth, 113 premolar teeth, 112 maxillary incisors, 104 molar teeth, 108 premolar teeth, 106 Five maxillary incisors, 322 Flathead Indian, skull of, 305 Floor of nose, narrow, 96 wide, 94, 96 Foramen, incisive, 182 Fourth meatus of Zuckerkandl, 208 molar teeth, impacted, 322 Fracture of mandible, 50, 59 treatment of, 60, 61 Barton's bandage in, 60 interdental splints in, 60 of neck of mandibular condyle, 60, 62, 63, 70 Frontal nerve, 142 sinus, 203, 206, 212, 248 development of, 248 numerous, 253 obstruction of fluids in, 215 occlusion of outlets of, 212 septa of, 249-256 size of, 254 variations of, 248-258, 276 Frozen sections, 285-303 Ganglion, ciliary, 155 otic, 161 sphenopalatine, 157 submaxillary, 162 sympathetic, 154 Greyhound, sagittal section of skull of, 270 Growth of bone, 50, 51 Gums, hypertrophy of, 342 treatment of, 343 INDEX 355 H Hard palate, 100 Hare-lip, cause of, 345, 346 Head, anatomical variations of, 17 frozen sections of, 285-303 directions for making, 285 Heavy mandible, 28, 315 skull, 86 measurement of, 88, 92 Heidelberg skull, 313 Hiatus semilunaris, 207, 210, 291 variations of, 264-284 Highmore, antrum of, 217 Hydrocherus capybara, 71, 72 Hydrogen peroxide necrosis of mandible, 53 Hypertrophy of alveolar process, 342 of gums, 342-344 Impacted teeth, 166, 174, 176, 177, 178, 179 canine, causes of, 167, 173 cysts in, 193 diagnosis of, 170, 192 value of x-rays in, 170 first mandibular molar, absorption of roots of, 187 fourth molar teeth, 322 general effects of, 170 incisors, 174, 175, 181 local effects of, 169, 178 molar, 180, 181, 182 neuralgia in, 192 second mandibular molar, 187 molar teeth, 316 in skull of monkey, 168, 169 supernumerary tooth, 173, 174, 181 systemic effects of, 172 third, mandibular molar, 171, 183-186, 188, 189, 190, 191 extraction of, 191 maxillary molar, 182, 183 Incisors, impacted, 174, 175, 181 due to disease in nasal cavity, 192 mandibular, 111 crown of, 111 cutting edge, 111 labial face, 111 lateral faces, 111 lingual face, 111 definition of, 111 first, 111 neck of, 111 pulp of, 111 root of, 111 second,111 maxillary, 103 crowns of, 103 Incisors, maxillary, crowns of, anterior face of, 104 cervical margins of, 104 cutting edge of, 104 labial face of, 103 palatal face of, 104 posterior face of, 104 proximal face of, 104 definition of, 103 first, 104 neck of, 104 pulp of, 105 root of, 104 second,104 Indian, mandible of, 27 Inferior alveolar artery, 135 course of, 136 mental branch of, 136 mylohyoid branch of, 135 nerve, 152 branches of, 153 nasal meatus, 201 Inflammatory changes in mandible, 48 of children, 48 surgical pathology of, 49 Infraorbital nerve, 147 branches of, 147 sinus, 228, 272 Infratrochlear nerve, 145 Infundibulum, 291 Interdental splints, 60 Internal maxillary artery, 135, 138 course of, 135 maxillary division of, 135 pterygoid division of, 135 pterygopalatine division of, 135 nasal nerve, 144 pterygoid nerve, 149 Introduction, 17 Irregular eruption, influence on teeth, 166 Jaw, body of, 33 structure of, 33 lower, 23 upper, 81 intermaxillary suture of, 81 interpalatal suture of, 81 interpremaxillary suture of, 81 maxillopremaxillary suture of, 81 palatomaxillary suture of, 81 premaxillse of, 81 Jaws, malformation of, causes of, 350, 351 modern, x-ray pictures of, 318, 319 relations of, 345 in old age, 349 variations of, 345 x-ray picture of. 125, 126, 128, 129, 130 3.-);