C^MWO^ Columbia ^ntbtr)s:ttp(^o^y ( iA^Uxma ©brarg THE INTKRNAL ANATOMY OF THE PACK BY M. H. CRYER, M.D., D.D.S. PROFESSOR OF ORAL SURGERY, UNIVERSITY OF PEN'NSYLVANIA ; ORAL SURGEON TO THE PHILADELPHIA GENERAL HOSPITAL SECOND EDITION, REVISED AND ENLARGED ILLUSTRATED WITH 377 ENGRAVINGS LEA & FEBIGER PHILADELPHIA AND NEW YORK I g I 6 Entered accordii^ to the Act of Congress, in the year 1916, by LEA & FEBIGER. in the Office of the Librarian of Coi^ress. All'rights reserved. r\' THIS BOOK IS AFFECTIONATELY DEDICATED TO MY WIFE MARTHA GATES CRYER 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 themsehes 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 \'ariant. 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 bon\- structures of the head and face will be found associated with equal variations of the other structures. It further shows that the text-l)ook 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 stud\- 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 i8o 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 H. General Considerations Development of the Face 20 21 CHAPTER HI. The Mandible or Lower Jaw Inflammatory Changes Necrosis and Regeneration . Fractures of the Mandible Neuralgia Secondary Deposits IVIandibular Triangle The Mandibular Articulation 23 48 49 59 64 64 67 68 CHAPTER IV. The Maxilla 76 Studies of Certain External Surfaces of the Skull 81 General Comparisons between the Width of the Upper Dental Arch, the Floor of THE Nasal Fossa, and the Size of the Maxillary Sinus 94 CHAPTER V. The Mouth 100 The Teeth 101 ICruption of Teeth 118 Various L.lustrations of Jaws and Teeth 120 The Vascular Supply of the Teeth 134 The Sensory Nerve Supply of the Teeth and Face 139 Sympathetic Ganglia Connected with the Trigeminal Nerve 154 Local Anesthesia of the Teeth, Surrounding Tissue, and Parts of the Face Pre- sided over by the Trigeminal Nerve 163 viii COX TEXTS CHAPTER VI. Teeth Influenced by Irregular Eruption 166 Retarded Eruption or Impacted Teeth 166 Supernumerary Teeth 173 CHAPTER VII. The Xasal Cavity and its Accessory Cells and Sinuses .... 196 Pathological Condition of the Nasal Cavity 208 CHAPTER VIII. The Maxillary Sinus 217 CHAPTER IX. The Frontal Sinus 248 CHAPTER X. The Ethmoid.\l and other Cells which have Their Final Outlet in the Nasal Cavity 259 The Orbit.\l Processes 260 The Sphenoid.\l Sinuses 260 Cell of the Crista Galli 262 CHAPTER XI. Variations in the Anatomical Structures of the Face .... 263 CHAPTER XII. The Relation between the Mouth, Tongue, Pharynx, and Nasal Chamber . 285 CHAPTER XIII. MODIFIC.VTION OF THE NORMAL ShAPE OF THE BONE THROUGH ABNORMAL FoRCES . 304 Supernu.merary 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 THE IXTHRXAL ANATOMY 01- Till- FACR. 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 the>' 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. — Xo 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 l)e laid down, but the more closely the subject is studied the more variations as to details IS INTRODUCTORY 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 many 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 DIAGSOSTIC IMPORTAXCK 19 influences of personal habit upon the course of anat(^mical 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 usualh' found to differ fnjm the other. In the homonymous bones, as the maxilla?, 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 accordini;ly. 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 many 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 in\olving 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 sla\ish 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 face 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 Ijone varies in thickness and compactness according DEVEWPMEXT OF THE FACE 21 to the (IcMisit)', the i)()siti()n, and the functions of tlu' bone. '1 he arrangement of the trabecuUe is an interlacing network. T(; 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 bon\- canals or tubes, the more distant parts. The bones of the head contain man\' canals and foramina for this last-named i^urjDose, 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 uj^on 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 wxll 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 i)r{)- 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 ]:)rocess 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 22 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 frontonasal; 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 w'hich 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 IT I. thp: mandible or lower jaw. Thk niaiuliblc dcxelops Ironi the first pair of the \iscc-ral or branchial folds called the mandibular plates, which in early embryonic life advance from the sides of the base of the cranium and meet al 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 r-v c D Fig. 1. — Four mandibles ranging from birth to eighteen months: .4, 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. Eigs. 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. i) the angle is very obtuse, but as the teeth develop and erupt, it becomes 24 THE MAXDIBLE 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 MAXDIRLE OR LOWER JAW l^o As the tc'C'lh l)t'(()nu' abraded, or when they are extracted, the alveolar process is resorbed, the horizontal i)lanes of the jaws api)roach each other more closeK', and the an^le ai^ain becomes obtuse (see Fig'. 3). The teeth and their alveolar i)rocesses are placed on the ui)i)er portion of the l)()d>- of the bone. The third molar is partially posterior to the anterior margin of the ramus, and a line can l)e drawn between the first and second premolars to the mental foramen. Fig. 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 lal)ial 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 20 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, 1 06 degrees, the distance from the condyloid process, which acts MANDIBLES Of DIFFERENT RACES 27 as the fulcrum, to the coronoid i)rocx^ss, the place of attachment of the temporal muscle, is 50 nun., which i^ives i^reat jiower to the mandible. 50 MM 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 28 THE MAXDIBLE 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 downw^ard 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 manclible 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- MAXDIBLES OF DIFFERENT RACES 29 nent as in Fig. 2, due in part lo the carrying f(jr\varcl (jt the teetli 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 103° on the right side and 100° on the left. Fig. 9 is made from a mandible of a ])eculiar 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 139°. 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 ha\ ing a \ery flat face (see Fig. 82). There is a slight anterior occlusion. The angle of the jaw is obtuse — viz., 133 degrees. 30 THE MANDIBLE OR LOWER JAW Fig. II is made from the mandible of a Chinese skull (see Fig. 8i). 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 io8°, 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: MANDiniJ'S OF nil- F EKES T RACES 'M 124* ANGLE 75MM Fio. 12.— Mandible, Fig. 2. M ENTAL FORAMEN 136' 77 MM Fig. 14. — Mandible, Fig. 7. I39« 66 MM Fig. 16.— Mandible, Fig. 9. 118' 71 MM Fig. 13. — Mandible, Fig. 6. MENTAL FORAMEN ,03« 89 MM Fig. 15.— Mandible, Fig. 8. MENTAL FORAMEN 135° 73 MM Fig. 17.— Mandible, Fig. 10. I'U;. 18.— Mandible, Fig. 11. The following diagrams illustrate the triangles of mandibles in skulls of various ages from eight months to old age: ISO* 42 n M Fig. 19. — Age eight months. ^lT 48 MM Fig. 20. — Age fifteen months 32 THE MANDIBLE OR LOWER JAW Fig. 21. — Age eighteen months. 51) MM Fig. 23. — Age four years. 120' 65 MM Fig. 25. — Age seven to eight years. so MM Fig. 22. — Age two years. IIS" 55 "^M Fig. 24. — Age five years. 116" 62 MM Fig. 26. — Age eight to nine years. MS" 70MM Fig. 27. — Age thirteen years. 106° 7t> n M Fig. 28.— Age eighteen years. 77 r-iM Fig. 29.— Adult. Fig. .^0.— Old age. Fi(;s. 19 to 30. — Diagrams of mandible, reduced one-half. THE BODY OF THE J AW 33 The Body of the Jaw. — The body of the- jaw in Iransxcrsc section, shows a r-sliai)C'(l cortical or dense l)()n\- strnctnrc, tlic amis of the U terminating in the pkUes of the alveoku- process — outer and inner — which are composed of a mocHhed cortical bone with no dehnite line of demarkation between them and the body of the bone proper; the Fig. M. — 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 projXT is covered with a true periosteum, the alveolar process with mucoperiosteum. the latter being thick and dense and containing many mucous glands. It is commonh- known as gum 3 34 THE MANDIBLE OR LOWER JAW tissue. The space between the arms of the U is filled with fine trabe- culae 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,Mvhich approaches the cortical bone in density, but is cribriform (sieve-like) in character (see Figs. 31, 32 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. — Mandiljle wilh 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 downward and forward from the man- ' A. Hopewcll-Smith, Dental Cosmos, August, 1913, p. 769. CRIBRIFORM TUBE 35 dibular furanien, at first along the inner cortieal 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 I -shaped space. As it ai)proaches the mental foramen, its course is near the outer cortical 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 T,2t 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 36 THE MANDIBLE OR LOWER JAW the growth of the bone, that the tube-Uke formation is almost lost, as is well shown in Fig. 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 occasionally 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 CROW Til 37 a\va\', and in llu- latlcr. a narrow piece of i)a])( r has lieen ])asse(l llir(ni;' be received in this region, (^r if an> inflammatory condition be produced, cither traumatically or by infection from diseased teeth, the nerve is liable to become inii)inged 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. their connection w4th 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. 40 THE MAX BIBLE 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 b^^ 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 alveolodental 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 CROW'TII for which il scr\c's as a conduit. (For further (k'scrii)tion oi tliis ilkis- tration, sec Fig. 196, i)age 220.) Fig. 38 is a view of the anterior portion of the lower jaw shown in ^^^8- 37- Tl"^<-' roots of the second premolar, it will be seen, are nearly 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 nearly to the mandibular nerve, while the bone at this point is usually ver^^ compact, the difficulty occasionally met with, in extracting these teeth without breaking them, is readily accounted for. Surgical 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 comparatively 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 Fig. 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 i^hutograph of three secjuestra produced b>- 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 trabeculse 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 producerl 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 212° F., and a metal of low fusil)ility 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 j^laced in a 10 i)er 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 divisifjn of a mandible, exposing the cancellated tissues in the body of the iaw and between the sockets of the teeth. bone, the nerves, bloodvessels, and their membranes. In Fig. 42, which pictures the outer surface, the dense sj^ot near the border beneath the second i)renKjlar 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. 46 THE MAXDIBLE 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 First premolar Second premolar Third molar Second molar First molar Second premolar First premolar 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 aUeolar i)rs, the lit lie pieces of hoiie hidden in the marrow heconie \isii)le, because ahiiosl all the eells had in\ aded the i)lasniatic niediuin. Around the tissue, there were radiating spindle cells and nian\- red Mood cor- puscles. Leukocytes with active ameboid motion and lari^e cells with granular cytoi)lasm and long pseudopcxlia 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 \aluable work' that the growth and repair of bone does not depend upon the periosteum. One of his concluding remarks is, "W'liile 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 o( 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 wull 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 tinds 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 ' The Cirowth of Bone. 52 THE MAXDIBLE 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.^ 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 ' Journal de Medecine tie Chirurgic ct de Pliarniacie, Paris, 1791. NECROSIS AM) RKGENERATIOX 53 ramus and upwartl t(j\\ard the nuiiulibular iKUch. On opening ihc tissue so that the outer surface of the bone may be examined, the bone will be found lo be somewhat darkened in color, there being numerous small soft tiixjts 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. (A'-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 MAXDIBLE 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 ankvlosis. Fig. 48. — A'-ray picture of phosf)horus necrosis, showing new bone formation on the lower border of mandible. {X-ray by Dr. Pancoast.) Fig. 47 is taken from an .x-ray picture, vshowing 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 sinUvSes. The history of the case gave a diseased premolar tooth XKCROS/S AM) l^ marked, especially in a double fracture. 60 THE MAXDIBLE 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 s\stem. 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 arc 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 c(jndyloid region and malocclusion of the teeth, the molar teeth of the broken side striking together before the others. X-ray i)ictures should be made in both lateral and antero- posterior directions. The latter pictures should show the head of the FRACTURES OF THE M.WDIBLE 01 coikKIl' carric'tl inward aiul forward as scc-n in Figs. 55, 56, 57 and 5mus 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 onh- 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 tenijioral bones are but slightly concave. This arrange- ment allows great latitude of motion, and the gingh mo-arthrodial nattire of the joint is somewhat greater than it is in man.' The mandibular articulation of the rodents is quite different. ' 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 Hving. 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; l)ut 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 fiat at birth, and there is but THE M:\.\I)IBL LM< AKTICLLATIOX 73 little change until the child begins to masticate, it then deepens rapidly until about i)ubert>-. 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 al the tiiue oi birth. The mandible articulates in its fossa, the conch loid 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 l)irth. 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 o\er 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 MAXDIBLE OR LOWER JAW The condyloid 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 MAXDIIULAR ARTICULATION 75 branous mealu>. iluis iiUe'rferin^ with hearing. Otologists treating such cases often request the i)alient U) open the nioulli wide, this usually draws the condyle forward, giving a clear \ iew U) the tympanic nuMiibrane. 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 MAXILLA. 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 ALVKOLAR PROCESS 77 is necessary to delacli the ui)i)c'r jaw from the craniiini, lli<>u;^li it will withstand a blow of i>reat force received from below tlirouLili the lower jaw or from in front, or even from the side. Pathological Relations.— The upper jaw i^ives sup[)orL t' extending outward to the external ])()rtion of the niaxilhe. Fig. 105. — -Shows small niaxillarv sinus. Fig. 106. — Shows nasal cavity extending over the alveolar process. Fig. 106 is from a skull in which the nasal cavity extends outward over the alveolar process until the palatal roots of the first and second molars appear in the floor of the nasal cavity. CHAPTER V. THE MOUTH. The mouth commands attention by its great importance when we consider its many functions. Under normal conditions it is the gate- way through which all food enters for the nourishment of the body. It is the seat of the organs of taste and the workshop wherein are carried on the functions of mastication, insalivation, and the prepara- tion of food for the digestive apparatus. It is also the portal through which more or less of the air received into the lungs passes.^ The mouth, or buccal cavit3^ occupies the space between the upper and lower jaws (see Fig. 37). It is divided into two portions — the vestibule and the mouth proper. The vestibule (see Fig. 37) is a narrow, curved space having two walls, an outer and inner. The outer wall consists of the lips and cheeks, which are lined by mucous membrane containing the labial and buccal glands; the duct of the parotid gland has its opening in this membrane about opposite the second maxillary molar. The inner wall is composed of the teeth, alveolar process, and portion of the upper and lower jaws. The bone is covered by a mucoperiostium con- taining small mucous glands; the upper portion of the alveolar process is covered by gum tissue. The mouth proper can be divided into roof, sides, floor, and outlet. The roof is composed of hard and soft palate; the hard palate has for its base three pairs of bones: two premaxillary, two palatal processes of the maxillse, and the horizontal portions of the palatal bones; the union of these bones forms seven sutures, for description of which see page 78. The soft palate is composed of several muscles, see general anatomy for description. ' Taken from an article by the author in Musser and Kelly's Hand-book of Practical Treatment, vol. iii, p. 286. rilR TRETII 101 The liard and s(jft palates are covered by a continuous niuccnis membrane extending from the vestibule, ])assing between the teeth, to the free edge of the soft pahite. The portion c(jvering the bone is in close relation to the j:)eriosteum, and is called the mucoperiosteum of the hard palate. It is a strong fibrous co\ering and contains a large number of palatal mucous glands, the secretion of which aides in deglutition. The sides of the mouth proper are composed of teeth, maxillary and mandibular, the gum tissue, the alveolar processes of both jaws, and all that portion of the mandible above the attachment of the mylohyoideus. The alveolar process and the true bone are covered by mucoperiosteum. The floor of the mouth contains the tongue and is composed principally of the mylohyoid muscle. The outlet of the mouth is the oropharyngeal opening, for anatomical description see general anatomy. Besides the general mucous glands of the lining of the mouth, the ducts of the submaxillary and the sublingual glands have their open- ing near the frenulum linguae. THE TEETH. In studying the anatomy of the teeth, one finds quite as many variations occurring, as exist in all of the other structures of the body. Adami makes the statements that "there is no absolute standard of either structure or function in any one species," "every individual varies in every particular from evers' other individual." It was also stated by the author in 1901, in the preface to the first edition of this book that "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, the composite of the entire number would properly be accepted as figuring the typal temporal;" in the same way, if photographs could be made of a thousand molars, the composite picture should give the type of a molar tooth which could be taken as. standard in studying that particular tooth; it follows of course that this "type" can only be used as a basis for the practical stud>' of the 102 THE MOUTH variations as to size, shape, color of enamel, etc., which are presented by every individual. The teeth are situated in the mouth at the commencement of the alimentary canal. In man they are equally divided into maxillary and mandibular teeth. They are of dermoid origin and commence development in earh' embryonic life. The principal functions are cutting, masticating and preparing food for digestion. They also assist in articulate speech. Man has two sets of teeth, deciduous and permanent. The decid- uous set is composed of twenty teeth of the following formula. DECIDUOUS SET. ^ . r Maxillary 4 „. (2 ... (^ r^ ■> r,r^ IncisorsJ -, ... ' , Canines <^ „ Molars < . Total, 20 \ Mandibular 4 \ 2 14 THE PERMANENT SET. - . /Maxillary 4 „ . /2 „ , /4 ,, , /6 ^ , ^ .^ Incisors < , , ... , , Canines^ -, rremolars ^ . Molars s , lotal, 32 I Mandibular 4 \1 1 4 I 6 The eight incisor teeth are situated in pairs on either side of the median line of the mouth, the upper ones are in the incisive or inter- maxillary bone, the lower ones in the mandible, these teeth are known as first and second maxillary and mandibular incisors respectively.^ The maxillary canine teeth are situated in the anterior portion of the alveolar process of the true maxillae. The mandibular canines are next to the second incisors in the mandible. The deciduous molars, first and second, are posterior to the canine teeth. The eight premolars, permanent set, are situated in pairs anterior to the molars, on either side, both in the maxillae and mandible. The perminent molars, first, second and third are the last teeth on either side in the maxillae and the mandible and have no deciduous teeth preceeding them. In a general way the anatomy of a tooth consists of four parts, the crown, neck, roots, and pulp. ^ The writer prefers the nomenclature used by general scientists and comparatiye anatomists, and will speak of first and second incisors rather than "central" and "lateral," "canine" rather than "cuspid" and "premolar," rather than "bicuspid," "anterior" and "posterior" faces or cusps instead of "mesial" and "distal." TIIK TKKTII 103 The crown, in normal condition, is that portion extending through the gum tissue and is the tirst i)art of the tooth formed. Its (juter portion is covered with enamel, the IxxK un similar, bein^ convex on the ui)i)er portion of the face and slii;htly concave near the neck, these faces slope inward on i)assini; toward the neck, making the crown much narrower at this point, and helping to make an inverted \'-shaped space between the premolar and the adjoining teeth. The morsal face consists of two cusps with two connecting ridges, anterior and posterior; betw^een the labial and palatal edges of the cusps, there is a sulcus somewhat in the f(jrm of a letter H. This for- mation makes a weak place in the enamel of the crown, which gives a predisposing cause of caries. The neck is a compressed oval somewhat wider on the buccal face. The first premolar usually has two roots. The root of the second premolar nvdy be bifurcated, but it is usually single, with two i)ulp canals; sometimes there is a bifurcation near the apex. The pulp chamber and its pulp canals, under ordinary circum- stances, is a miniature of the premolar tooth. The Second Maxillary Premolar. — The description of the first ])remolar will answer for the second, except that the second is usually smaller, with but one root, but it must be remembered in the treatment of this tooth that occasionally it may have two roots and also that the first i)remolar may have but one root. Molar Teeth.— The molar teeth are twelve in number, six in the maxilla and six in the mandible. These teeth have no i)redecessors as have the other twenty permanent teeth. They are situated on each side of both jaws, and with more or less variation, erupt at different periods. The first molars about the sixth vear, the second from the twelfth to thirteenth year, and the third from the seventeenth to the twenty-third vear or even later. The first molar takes its position in the posterior portion of the alveolar process; as the jaws develop they usually make room for the other two molars. At times the jaws do not seem to grow sufticientl}' to allow proper eruption to take place; in these cases, the third molar is sometimes impacted or misplaced. It also occasionally happens that the third molar does not develop at 108 THE MOUTH all; again, there may be a rudimentary fourth molar sometimes called a supernumerary third molar. When these teeth are in topical occlusion, the six mandibular molars articulate with the maxillary molars and the posterior half of the maxillary second premolars. As they are situated near the fulcrum of the mandibular articulation, and are in close proximity to the attach- ment of the powerful muscles of mastication, they are in position to receive the full force of these muscles for crushing: and grinding the food. The maxillary molar teeth are situated in the alveolar process immediately below the maxillary sinus. In the Caucasian race the alveolar process is shallow, the roots of the molar teeth are spread apart and pass into the outer and inner walls of the sinus (see Figs. 37 and 97). The molar teeth in this position are liable to produce patho- logical conditions in the sinus. In the lower type of man the alveolar processes are much deeper, and the molar roots do not enter the walls of the sinus (see Fig. 200). The crowns are somewhat cuboidal in shape, with five faces, the buccal, palatal, anterior, posterior, and morsal. The buccal face is nearly twice the size of that of the second pre- molar, its general appearance is that of two fused premolar teeth hav- ing the cusps very marked. The anterior buccal cusp was called by Harrison Allen the "canine cusp." In his "Facial Region" he also stated that "Since the cusps exist before the roots, the latter may be said to be conformed to the cusps. So that to every cusp there is a tendency to form a distinct root. It is best, therefore, to study the teeth by their cusps." ^ Following this plan, the cusps indicate the general character of the tooth, whether it be a single, double or multi- cusped tooth. First Maxillary Molar. — As said before, the buccal face has the appearance of two premolars fused together. The centre of this face is convex, sloping as it approaches the neck of the tooth. From just below the centre, a perpendicular groove commences, deepening as it passes toward the morsal edge, thus making an anterior and pos- ' J. B. Lippincott Co. Press, p. IH. THE TEETH 109 terior buccal surface of the cusj), the cdi^cs of wliich iiiccl the anterior and posterior surfaces in a ciirxed manner. The i)ahital face is conxex. ha\ ini; a small fissure about one-third from the posterior edge, i)assini; downward to the occluding surface of the tooth, which joins the posterior fissure of the morsal face. The anterior and posterior faces are generally convex in both directions, sloping downward to the masticating edge in a rounded manner and curx ing upward toward the neck of the tooth. The morsal face is divided into four cusps. The anterior buccal, or canine cusp, is ver\- much the shape of a canine tooth, hence the name; the posterior buccal, or molar cusp, is usually about the same size, though not quite so pointed. The anterior palatal, or premolar cusp, is very much larger and more rounded than the canine cusp. The posterior palatal cusp, the cingule, is small and forms a rather prominent corner or pillar to the tooth. Between the three main cusps there is an irregular surface ; between the two palatal cusps is a deep sulcus which forms a predisposing place for caries. The neck in transverse section is rhomboidal in shape, with rounded corners; the buccal face is wider than the palatal as it forms the base for the two roots. The palatal face of the neck is more rounded than the buccal and forms the base for the large palatal root, which is usually single. The roots are three in number, two buccal and one palatal, they are usually well separated at their upper ends. The anterior buccal root is rather flattened and may have two pulp canals within it. The posterior buccal root is rounded, usually' having but one pulp canal. The palatal root is larger and rounded, having but one pulp canal, which is usually straight and large as compared with the others, and therefore of easy access. The second maxillary molar is usualK' similar to the first, when differences exist, it is in the shape of the crown and the diver- gence of the roots. The crown is somewhat smaller than the first molar and is often triangular in outline. The cingulum is generally much smaller and consequently the premolar (anterior palatal) cusp is larger, which gives a large, smooth surface to the palatal face. The 110 ■ THE MOUTH fissure between the cingulum and the premolar cusps is not so deep, and consequently not so prone to decay. The anterior and posterior faces differ from each other; the anterior face is usually more flat while the posterior face is quite oval, especially when the third molar is small or missing', in the latter case it is liable to be quite rounded as a "finishing tooth." The neck is similar to the neck of the first molar, varying only in proportion to the various shapes of the crowns. The roots are generally the same in number though varying in size, they are also generally close together, due to the fact that the pos- terior root of the first molar is occupying more or less of the space which the anterior root of the second molar might have taken. The size of the maxillary sinus may influence the position and shape of the roots of the molar teeth (see Fig. 199). The third maxillary molar is more varied in its shape than any of the other maxillary teeth; it may be large or small, may have a small cingulum cusp with a single root (called a peg tooth), or it may have many cusps with a corresponding number of roots, which may be straight or curved. If the pulp becomes diseased it is most difficult to treat, and for this reason the maxillary third molar has been classed by some as the pathological tooth of the mouth. Mandibular Teeth. — The mandibular teeth are the active organs of mastication, in as much as they are fixed in the mandible which is acted upon by the temporalis, masseter, pterygoideus, externus and internus muscles (see Fig. 300) . These muscles give the lower jaw power of protru- sion, retrusion, and side-to-side movement (see Mandibular Articulation, page 68). which in turn together with the depressor muscles of the mandible, enable the teeth to cut, tear, and grind food. The loAver anterior teeth come in contact with the upper fixed teeth, striking the cutting edge, then coming against the under concave surface of the upper anterior teeth in a general motion similar to that of a pair of shears, provided the upper blade of the shears were fixed. The posterior mandibular teeth meet the upper posterior teeth in both grinding and crushing motions. THE TRETH HI The two lirst rii;hl and k-ft incisors are situated on either side ot the sxniplnsis. 'lMie\- are the smallest teeth in tlie nicuth. Tlie first nia\illar\ incisors are much wider, as the>' not only cover the first mandii)ular incisors, but extend over one-half the second mandibular incisors, thus " breaking the joint." This breaking of the joint is carried on between the maxillar\- and mandibular teeth throughout the balance of the jaws until the third molars are reached. The third ma\illar\ molar occludes only with the third mandibular molar. The crown of each first mandibular incisor has four faces and a cutting edge. The labial face is slighth' conxex in both directions. It is broadest at the top or cutting e(\'ge, w hich is straight. The face becomes narrow toward the cer\ical portion, whicdi is con\ex. The lingual face is slightly convex from side to side and concave perpendicularly. The lateral faces are concave and wedge-shaped with the point of the wedges at the top or cutting edge and the base at the neck of the tooth. The neck is small, and in a transverse section, is a slightly com- pressed oval. The root is not so long as the second incisor root, and is usually straight and somewhat flattened with but one pulp canal. The iHilp chamber and its canal is of the same shape as the tooth, onh- \er>- much smaller. The second mandibular incisors are similar to the first only somewhat longer and larger. The cutting edge is much wider, and the posterior face tapers into the neck of the tooth. The root is of the same general outline as the first incisor, only larger and longer. The mandibular canine, right and left, is similar to the maxillary canine, the architectural plan is on the same general lines with the strongest point at the neck (see transverse section. Fig. 114). This tooth is the least prone to decay of all the teeth. The crown has four faces. The labial face is convex both horizon- tally and vertically; it is broader at the cutting edge, which is divided 112 THE MOUTH into two portions like a spear point, the posterior portion being the longest; occasionally there are two slight grooves passing vertically from the cutting edge to the base of the crown which is convex. The lingual face is in a general way concave from the cutting point to the neck; there is a slight central ridge curving to a groove on each side of the tooth. The anterior face (mesial) is broader than the posterior. The pos- terior face is wedge-shaped with the base at the neck. Commencing at the cutting edge the face slopes toward the neck, which is narrow, leaving a considerable space between the canine and the first premolar. The neck (see Fig. 114) is much larger than that of any of the teeth except the molar; it is wider at the labial surface than at the lingual. The root is the longest of any of the lower teeth, sometimes extend- ing below the general line of the mandibular canal (see Fig. 161). Occasionally this tooth has two roots and at times in the single root there may be two pulp canals. Mandibular Premolars. — The first mandibular premolars are situated just posterior to the canines, they are usually smaller than the second premolars. The crown of each tooth has five faces; the buccal face is similar to that ot the canine and is named by Harrison Allen, the canine cusp; it has a slight ridge passing from the spear point down to the base, which is convex and there are two slight grooves on each side of the ridge which might be said to divide the face into three lobes. The lingual face is convex horizontally and nearly straight perpen- dicularly, sloping to a narrow, convex base. The lateral faces are also convex horizontally, they slope inward toward the centre of the tooth, making the neck narrow, with inverted Y-shaped spaces between it and the canine and the second premolar. The morsal face varies in different teeth. There are usually two marked cusps: the canine cusp on the buccal side, and the premolar on the lingual side; running from the outer and inner faces of the cusps are ridges of enamel, somewhat elevated in the centre, forming smaller cusps; between these four cusps are two pits or sulci which make predisposing points for caries. rilK TEETH 113 The iK'ck is a c()nij)rcssc(l ()\al, smaller im the iin.uuai cdi^c, tlian on the buccal. The root, iisualh- sinj^lc. is lon^, flattcnerl and comparatively straight, but at times, as the number of cusps indicates, the root may be composed of two or more divisions. The i)ulp chaml)er, and its canals, in earl\- life, is generall>' a minia- ture of the tooth, the number of pulj) canals corresponding to the number of cusps. The second mandibular premolars arc situated between the first premolars and the first molar teetii. In a general way the description of the first premolar will answer for the second except that it is usualK' larger. The morsal face of the crown differs somewhat in the arrangements of the cusps, in some cases it might be called tricusped. The neck of the tooth is a little larger than that of the first premolar. The root is usually single, but occasionally it is flattened and di\ided. In rare cases there are three roots (see Fig. 122). The pulp chamber is practically the same except that there may be several pulp canals. Mandibular Molar Teeth. — The mandibular molar teeth are sit- uated in the posterior portion of the body of the mandible immediateh' over the canal which contains the mandibular nerve and vessels; any disturbance, pathological or mechanical, in this region, is liable to cause serious conditions, such as impacted teeth, neuralgia, reflex nervous disturbances, sometimes only local, but often reaching into the general nervous system. These teeth have no predecessors and erupt one after another as the body of the bone grows sufificienth- to make room for them. When this room is not adequate, the third molar or e\en the second molar is liable to become impacted or misplaced, causing more or less serious complications. The first mandibular molar is situated posterior to the second pre- molar. In correct occlusion, it articulates with the posterior portion of the morsal face of the second maxillary premolar and the anterior portion of the morsal face of the first maxillarA- molar. 8 114 THE MOUTH The crown is of an irregular ciiboidal form, with a greater width anteroposteriorally than buccohngually. It has five faces: buccal, palatal, anterior, posterior, and morsal. The buccal face is usually convex in all directions; it is divided into three columns by two rather deep grooves, the buccal and posterior. The buccal groove occasionally passes down through the face, but usually terminates midway in a pit, which acts as an inducement for decay, the morsal edge is divided into three points, which help to form three buccal cusps. The lingual face is rounded and smooth. There are seldom any fissures on this surface which make it quite free from caries. The morsal edge terminates in two points, which assist in forming two lingual cusps, the fissures between these two elevations is somewhat prone to decay. The anterior and posterior faces are flattened perpendicularly, the upper border is convex and as the face passes downward toward the neck it becomes flattened. These faces are inclined inward, making an inverted V-shaped space between this molar and the premolar, also between the first and second molar. The morsal face is the largest face of any of the teeth and is divided into five cusps, two buccal, two lingual and a posterior cusp. The anterior buccal cusp is very much the shape of the canine crown, and is the largest and most prominent cusp. The median buccal cusp (the molar cusp) is usually somewhat smaller than the canine cusp. The two inner or lingual cusps are nearly the same size. The fifth cusp, which is in the posterior portion of the crown, is small and sometimes spoken of as the cingulum of the tooth. The fissures pass in various directions and at the confluence or sulci, the enamel is not usually perfect which makes the crown prone to decay at these points. The neck is square in outline, much depresvsed on the buccal and labial side, near the place where the root divides. The anterior margin of the neck is slightly concave, where the root begins to flatten on its surface. The posterior margin of the neck is usually convex, matching the posterior face of the root which seldom bifurcates. THE TKETII 115 The roots arc two in iuinil)er, usuall>' well se[jaratcd near their points. The anterior root is quite flattened and concave transversely, it is more inclined to bifurcate than the posterior nKjt; the i)uli) of the bifurcated root sei)arates into two di\isions, one in each root canal, niakini; this root difficult to treat. Ihic mandibular second molar is situated between the first and third molar; it articulates with the posterior i)orlion of the morsal face of the lirsl nuixillary molar and the anterior pt^rtion of the morsal face of the second maxillary molar. The crown is nearer a cube than the hrst and third molars, i. e., is nearly of the same length and breadth and has five faces: buccal, palatal, anterior, posterior, and morsal. The buccal face is usually convex in both directions. On its upper morsal edge it is divided into two portions, helping to form the anterior, canine, and posterior, molar cusps. Sometimes at the base of this division a fissure commences and passes down the centre of this face to a pit, this induces decay of this part. The upper half of this face inclines inward, allowing the buccal cusps of the first and second maxillary molars to overlap the crown. The lingual face is rounded or convex in all directions. On its morsal edge it is divided into two lingual faces, the anterior and pos- terior cusps; on its lower margin it is concave near the commencement of bifurcation of the two roots. The anterior and posterior faces are similar to those of the first molar, the anterior being somewhat convex in the upper portion and concave in the lower; the posterior face is more convex than the anterior. The morsal face is usually divided into four cusps; occasionally there is a cingulum giving it five cusps. At the base or confluence of these cusps there are irregular fissures or sulci, the enamel not being well formed or joined together at these points makes them prone to decay. The neck in cross-section is a square in outline with concave depres- sions on the sides. 116 THE MOUTH The roots are two in number, flattened anteriorally and posterior- ally with a strong inclination to bifurcate. The pulp chamber and pulp canal is a miniature of the crown and roots; there are usualh^ two pulp canals in the anterior root and one in the posterior, though in many cases there are two. The number of pulp divisions being governed by the number of bifurcations of the roots. The third mandibular molar is usually of the same general char- acter as the first or second molar, though like the third maxillary molar it is subject to great variations, as to the number of cusps, roots, and pulp canals. The crown has five faces as in the first molar, and usually the same number of cusps. The posterior face differs from that of the first and second molar in being more convex or rounded in order to make a "finishing tooth." The morsal face is similar to that of the first molar, though it is more liable to vary from the typical. The neck of the tooth is about the same as the first molar, subject to great variations as to the number of roots and their positions, they may be compressed together, spread apart, or curved abruptly back- ward. The roots vary in number, sometimes there is apparently- only one root, but a cross-section w411 show several roots compressed together, each with its separate pulp canal; occasionally two roots are found well separated near the neck, allowing an isthmus of bone to pass Ijetween them, with the roots finally uniting farther down (see Figs. 123 and 124). This condition makes the tooth very diflicult to extract. Occasionally the crown and roots form the segment of a circle (see Fig. 123). The roots of the third molar sometimes grow down and backward, passing beyond the mandibular canal (see Fig. 338). The following interesting observation is given by Dr. Hermann Prinz: "Certain anatomical malformations of the roots of the lower third molars may, on rare occasions, be the cause of very profuse hemor- rilE TEETH 117 rhage, and other serious damaiic as a result ol their extraction. Tliere are, as far as the authoi- knows, li\e cases on record in which the developing tooth inclosed in the body of its roots the contents of the mandibular canal — their artery, vein, and nerve (sec F'igs. 123 and 124). The extraction of a tooth j^ossessing such malformations means tearing of the \essels and the ner\ e, causing extreme henKjrrhage, excruciating pain, and linalh' i)ermanent insensibilit\- of one-half of the lip. These are the s>-mi)toms as recorded fnjm cases which occurred in the practices of Roese, of Munich, in 11X98, and of X'orslund-Kjaer, of Copenhagen, in 1908." Deciduous Teeth. — The twenty deciduous teeth are much smaller than the permanent ones. In infancy they fill the jaws, otten over- lai)ping each other, until the last one is in i)lace. As the jaws grow and exi)and continuoush' from their first de\eloi)ment, the deciduous teeth, b\- the time the child is five years of age, instead of overlai:)ping are often quite separated from each other, as the>' do not increase in size after they are once formed. The twelve anterior deciduous teeth are similar in character to the l)ermanent ones, though very much smaller. The eight deciduous molars are similar to the permanent molars, though very much smaller, their roots diverge much more in order to give room for the development and growth of the premolar teeth. In examination of .v-rays (Fig. 120) the relative position of the pre- molars to the deciduous molars is well illustrated. The roots of the deciduous teeth become resorbed and the i)ermanent teeth advance into their normal positions. The position of the i)remolar should be remembered when extracting a deciduous molar; the forceps must not be placed too far upon the tooth as there is danger of displacing the premolar. Should the roots of the deciduous tooth break during extraction it will do no harm, as they are quickly resorbed. Fig. 107 is taken from the skull of a child of alx)ut six >ears, show- ing all the deciduous teeth in position and the developing permanent teeth, except the third mandibular molar and the second and third maxillar\- molars, which at this period of life are of very immature devel()])ment. The outer i)lates of the aheolar jirocess and the 118 THE MOUTH cancellated tissue ha^'e been removed, in order that the positions and relations of the dental organs at this period of life may be more clearly seen. Fig. 107. — Skull of a child, aged about six years, showing all the deciduous teeth in position and the developing permanent ones. ERUPTION OF TEETH. The deciduous teeth usually commence eruption, according to C. S. Tomes, as follows: Mandibular first incisors, from six to nine months. Maxilla or upper first incisors, from eight to ten months. Mandibular second incisors and first molars, from fifteen to twenty- one months. Canines, from sixteen to twenty months. Second molars, from twenty to twenty-four months. By close observation it will be found that the above table is liable to considerable variation. ERi'PTIOX or TEETH 119 According to Holt :' At the age of one \ear a cliild should ha\e six teeth. At the age of one and a half \ears a child should have twelve teeth. At the age of two years a child should have sixteen teeth. At two and a half years a child should ha\e twent>- teeth. X'arious authorities give eruption of the permanent teeth as follows: The mandibular teeth precede those of the maxilla by short intervals. First molars, sixth year. First central incisors, seventh \ear. Two second lateral incisors, eighth \ear. First premolars, ninth \ear. Second premolars, tenth year. Canines, eleventh to twelfth >ear. Second molars, twelfth to thirteenth year. Third molars, se\enteenth to twenty-fifth year.= The deciduous teeth commence to be shed about the age of six, beginning usually with the mandibular first incisors, soon followed by the first maxillary incisors. The permanent first incisors soon taking their places. These teeth will often overlap each other. Then the second incisors are shed and the permanent ones fill their places. In many children's mouths these teeth do not erupt into their typical positions, sometimes from lack of room, but more often because the deciduous teeth are either not shed at the proper time, or they are lost too early, either b>- deca\-, accident or injudicious extraction. The time of shedding the canine teeth is less definite than that of the other deciduous teeth. If they can be held in position until the premolars have erupted there will be a better space reserved for the permanent canines to erupt. The deciduous first molars are usualh' shed the eighth year and the second molars at nine years of age. These deciduous molar teeth are not replaced by molar teeth, but b\- the premolars. 1 Gray's Anatomy, eighteenth edition, p. 1125. - The foregoing table is from Gray's .Anatomy, eighteenth edition, p. 1125. 120 THE MOUTH From about the age of five or six years, before any of the deciduous teeth are shed, there are more fully developed teeth and those in pro- cess of growth in the mouth than at any other period of life, at least forty-eight teeth are in various stages of transition. The roots of the deciduous teeth, twenty in number, are becoming resorbed and pre- paring to be shed, while the roots of many of the permanent teeth are developing, also the roots and crowns of later permanent teeth are growing and changing their positions in the jaws. This great activity goes on from day to day without any pathological disturbance in nor- mally developed, healthy children, but any disturbance which would cut off the nourishment or interfere with the circulation of the jaws proper, as w^ell as of the teeth, might bring about pathological condi- tions that would not only affect the parts locally but by reflex action, cause systemic troubles such as chronic migraine, indigestion, disturb- ances of the brain centres inducing corea, epilepsy, neurasthenia, and other diseases of this character. This matter w^ill be further spoken of under Impacted Teeth (see page i66). An abnormal deposit of salts of calcium may occur in the bone, which may prevent the teeth from erupting into their normal positions, or might even cause the can- cellated tissue of the alveolar process to become fixed, producing a narrow, dental arch, which, in turn, forces the tongue back into the pharynx, carrying the soft palate upward and plugging the posterior nares, thus interfering with respiration through the nasal passage and blocking the proper drainage of the nasal cavity and its accessory sinuses. One has only to look at Figs. 113 and 114 to see the mass of tooth organs and to realize the mischief which could be produced by injudicious mechanical interference at this time, as well as by pathological disturbances. VARIOUS ILLUSTRATIONS OF JAWS AND TEETH. Fig. 108. The anterior portion of the base of a typical skull, show- ing the bones forming the roof of the mouth, the sutures, and the various foramina. The occluding surfaces of the sixteen maxillary ERLiTiox or ri-.ivni 121 teeth ha\ o an outward inclination, while the nianclil)ular teeth are inchned inward. 1 his allows the outer cusjjs of the U])i)er teeth to "bite" over the (juter iusi)s ol the lower teeth (see Fig. iii). The zyp:oniatic arches extend from the zxiioma at the side of the upper jaw Fig. 108. — .interior portion of the base of a typical skull. to the temporal bone, thus giving the support of a flying buttress to the maxillae. The i^osterior nares can be seen separated b>' the \'omer, which also assists in supporting the upper jaw. Fig. 109. Upper portion of the body of a topical mandible, show- ing the occluding surfaces of the sixteen mandibular teeth, which are 122 THE MOUTH ill good alignment ; the outer faces of the buccal cusps have an inward inclination which allows the buccal cusps of the maxillary teeth to occlude o\'er them. Fig. 1 10^ gives an anterolateral view of an almost ideal occlusion of the permanent teeth. The illustration shows the relation of the bones forming the external structures of the jaws. The outer surfaces of the lateral and anterior walls of the maxillary sinus are shown, the Fig. 109. — Upper part of the body of a typical mandible. teeth having been denuded of the external plate of the alveolar process. It will be seen that in removing the external plate the maxillary sinus has been opened into immediately over the roots of the molars, showing how thin, in this case, is the bone between the roots of the teeth and the external wall of the sinus. It is also very thin over the roots of the canine and first and second premolars. Figs. 43, 44 and no demonstrate the arrangement of the cancel- ' Fig. 110 is a duplication of Fig. 31. KRLPT/OX OF TEETH 123 lated tissue Iji'twccn the icclh, also iK'twccn llu- tct-lh and llu- cortical l)()iu', where il acts as an clastic cushion to lessen shock fnjni blows upon the mandible or from concussi(;n in mastication, it is this arrange- ment which jjermits the movement of the teeth in \arious directions diu'ing eruption or in correcting irregularities of the teeth. Fig. 110. — Anterolateral view of the maxilla and mandible with the external plates of the alveolar process and some of the cancellated tissue removed, exposing the roots of the teeth, the cribriform tubes, and mandibular canal. Fig. III. The right side of the lower portion of the face, showing the relation of the mandible with the base of the skull. It also shows a typical occlusion of the teeth, each tooth occluding with two other teeth, excei^t the third maxillary molar and the first mandibular incisor. 124 THE MOUTH Fig. 112. A'-ra>- of the lower portion of the right maxilla and the mandible, showing the internal structures, such as the cancellated tissue, the shapes of the roots, and their relation w^ith surrounding tissue. The mandibular canal, the maxillary sinus and a portion of the mastoid cells are outlined. The occlusion of the teeth is good. A rudimentary maxillar^' fourth molar is also shown. Fig. 111. — The right side of the lower portion of face. Fig. 113, an .v-ray from a living subject, showing maxillary and mandibular teeth. The first mandibular molar has been diseased, treated, and filled. The anterior root is flattened and not of easy access, consequently the canal has not been properly filled, the pos- terior root is larger and nearer straight, so treatment is not difificult, shown by the better filled root. The roots of the second mandibular molar are compressed, probably owing to lack of room at the time of formation, the si)ace being small between the first molar and the morsal face of the third imi)acted molar. The third molar is of the ERirriox Oh' ruETii 12.") usual (>!)(.' of iuipaclion al\va\s diHicult (o extract, its uiorsal lace is not ()iil\ interlocked with the second molar tooth, hut its j)eculiar- shaped roots are imbedded uixler hard, c(trlical l)one. As soon as such impaction is discoxered, one \v(mld be justified in extracting the second molar, allowin.u the third to remain for future development. Vie. 112. — A'-ray of dried skull. (A'-ray 1)\- Dr. Pancoast.) The first, second and third maxillary molars arc all abnormal; their roots are compressed; the third molar is impacted against the lX)sterior ]:)()rtion of the second molar. In this case also the second molar should be extracted first as there would be great lial)ilit>' of damaging the tissue surrounding the third molar. A portion of the 120 THE MOUTH root is above the floor of the maxillary sinus. The second molar with its compressed roots often gives serious trouble through the pulp becoming diseased. Fk,. U.S. — A'-ray of living sul)ject. (A'-ray by Dr. Pancoast.j Fig. 114. Horizontal section made at the necks of fourteen man- dibular teeth, showing the shape of the teeth in cross-section at this ERUPTION OF TEETH 127 point, also the shape and size of the pulj) chambers in a matured skull. In a younger skull llu' pulj) chamber would be relati\el\- larger. Fig. 114. — Horizontal section made at the necks of fourteen mandibular teeth. Fig. 115. — Horizontal section made at the necks of sixteen mandibular teeth. Fig. 115. Horizontal section made at the necks of sixteen mandib- ular teeth, showing the shape and relation of the teeth at this point. 128 THE MOUTH It also shows the investing membranes of the teeth and the hning of the sockets. The periodontal membrane has various functions, it acts as a cushion between the tooth and the bone, and assists in hold- /, \ r Fig. 116. — Anteroposterior section through the maxillary sinus, alveolar process and the teeth. Fig. 117. — •A'-ray picture of the left half of the lower portion of an upper jaw. (JV-ray by Dr. Pancoast.) K/urriox OF ri:i:rii 12! > ini; the tooth in the alveohis, Rixini; njoni for the- passage of nutrient vessels and ncrx'es. Fiu,. I If). Anter()i)()sterior section through llic maxillary sinus, aheolar process and the teeth, showing the relation of the teeth to each Fig. 118. — ,Y-ray picture of the right half of the lower portion of an upper jaw. (A'-ray by Dr. Pancoast.) Fig. 119. — X-ray of the right half of the body of the mandible. (X-ray by Dr. Pancoast.) other and to the maxillary sinus, which, in this particular skull, are normal though not typical. The shapes of the pulp cavities are also indicated. Figs. 117 and 118. Two .v-ray i)ictures of the right and left halves of the lower portion of an upper jaw. This skull is nearer typical 9 130 THE MOUTH Fig. 120 Fig. 121 Figs. 120 and 121. — Z-ray pictures of the left half of the maxilla and mandible of a child, about five years of age, showing ten deciduous and twelve permanent teeth; the latter are in the process of formation. (X-rays by Dr. Pancoast.J ERLJ'TIOX OF TEETH 131 than that in Fig. ii6. Tlic hnvcr (juthncs of the niaxiUar)- sinuses are shown, also the alveolar i)rocesses, the pulp cavities, and their canals. The api)arent relations of the roots of the teeth to the maxillar>- sinuses # // \f^ - f K -V NOP Fig. 122. — Si.xteen teeth taken from one skull; nearly all of the roots have some peculiarity (Through courtesy of Dr. Ottolengui.) 132 THE MOUTH f*u*. ( .-• L* v . / E |»^- \ V. M ^ ^ A^ D H ^ 9 QB Q R ST Fig. 123. — A collection of twenty abnormal teeth; among them are fusions, odontomes, and irregularities, etc. ERUPTIOX OF TEETH 133 are clecei)ti\c' to one not familiar willi .v-ra\ i)i(tiires. Tlie lower out- lines of the sinuses are l)elo\v the jxiints ot the roots (;1 tlie teeth, which p q r F"lG. 12-4. — ^A group of nineteen abnormal teeth. might indicate that the ends of the roots had penetrated the sinus, instead of this they are in the walls of the sinus (see Fig. 97). The 134 ' THE MOUTH white lines running downward and forward from the posterior wall of the sinuses are the grooves or canals for the passage of the maxillary nerves and vessels; branches may be seen going to roots of the various teeth. Fig. 119. X-ray of the right half of the body of the mandible, show- ing the cancellated tissue of the bone, a typical view of the teeth, and outlines of the pulp chambers and canals. Figs. 120 and 121. X-ray picture of the left half of the maxilla and mandible of a child, about five years of age, showing ten deciduous and twelve permanent teeth; the latter are in the process of formation. Fig. 122. Sixteen teeth taken from one skull. It will be noticed that nearly all of the roots have some peculiarity. A, right mandibular third molar, four roots; the anterior and posterior are flattened with two apical foramen in each root. A buccal root is well shown, and there is also a small lingual root not shown, making six apical foramina; C and D, right first and second maxillary premolars, two roots each; £, left maxillary third molar, five roots; F, left mandibular second molar, the anterior and posterior roots both bifurcated; G, left man- dibular second premolar, three roots; H, left mandibular first premolar, two roots; K, right maxillary second premolar, three roots; L, left maxillary first premolar, two roots; M, left mandibular third molar, three roots; 0, left mandibular second premolar, three roots; P, right mandibular first premolar, three roots compressed together. THE VASCULAR SUPPLY OF THE TEETH. The teeth receive their supply from the internal maxillary artery, which also supplies all the deep portions of the face, including part of the floor of the mouth, the palate, the nasal cavities, the maxillary sinus, the greater portion of the ethmoid cells, part of the pharynx, and part of the dura mater of the brain. The supply to the maxillary teeth comes from the internal maxil- lary, through the alveolar artery. It passes through the foramen, just along the tuberosity of the maxilla into the sinus, passing forward THE VASCULAR SIPPLV OF THE TEETH 135 on the outer wall of the sinus and entering the anterior wall where it anastomoses freelx' with the iiifraorhital and other arteries. During its course it gives ofY branches t(j the roots of the nia\illar\- teeth, their investing meml^rane. the alve(jlar process, and the mucous memljrane of the maxillar\- sinus. In a general way it accomi)anies the superior alveolar ner\e. The hrst or maxillar\' division of the internal maxillary arter>' extends from the external carotid to the sphenomandibular ligament, and gives off fi\e branches, which ])ass into or through osse(jus fora- mina. These branches are the deej) auricular, anterior tympanic, middle and small meningeal, and the inferior alveolar. The second or pter}goid division extends from the sphenoman- dibular ligament to the point at which the artery passes through the space between the two heads of the pterygoideus externus (external pter>'goid muscle). This portion has six branches which supph' the masticatory and buccinator muscle. They are named, according to their distribution, the two deep temporal, two pterygoid, the masse- teric, and the buccinator. The third or pterygopalatine division extends from the inner surface of the internal pterygoid muscle to the termination of the artery in the pterygopalatine fossa. It gives off six branches, each passing into or through the osseous foramina. They are likewise named according to the parts supplied by them, the alveolar already described, infra- orbital, descending palatine, artery of the pterygoid canal, pharyngeal, and sphenopalatine. The inferior alveolar artery arises from the under part of the internal maxillar\-. It passes downward and forward between the sphenoman- dibular ligament and the neck of the mandible to the mandibular foramen, through which it passes into the canal, accompanied by the alveolar nerve, it then terminates anterior to the mental foramen, where it separates into two divisions, known as the incisor and mental branches. The m\ loh\oid branch is given off from the inferior alveolar arter>' immediately before entering the foramen. It descends into the mylb- h\-oid groove with the nerve and \'essels of the same name, and is 136 THE MOUTH distributed to the under surface of the mylohyoid muscle. The por- tion of the alveolar artery within the canal gives off numerous small branches to supply the teeth and their surroundings. The incisor branch is a continuation and passes forward within the cancellated structure of the bone to supply the region of the chin and the anterior teeth. The mental branch passes through the mental foramen, accom- panied by the nerve of the same name, and supplies the soft parts in the region of the chin. In this manner the mandible is richly supplied with blood. As the inferior alveolar artery enters the bone at the mandibular foramen, it passes downward and forward through the body of the bone to the symphysis, and anastomoses with the artery from the opposite side. At a point near the incisor teeth a great portion of the artery curves upon itself and passes out through the mental foramen, anastomosing with the submental, inferior and superior labial or coronary branches of the external maxillary or facial artery. In this manner two complete collateral circulations are formed on the two sides. The mandible is also well supplied through the periosteum of the body of true bone and the mucoperiosteum of the alveolar pro- cess. The vessels from these sources pass into the bone and have free anastomotic relations with the internal supply of blood. Fig. 125 is from an .x-ray picture of the left half of a mandible of a mature dog, which was injected through the inferior alveolar artery. The illustration shows that the mercury passed through the artery to all portions of the bone, the alveolar process, and the teeth, and demonstrates the complete anastomotic relations which the arteries have to each other. A stereoscopic picture would show that branches are given off from the artery as it passes along its canal or tube, to the roots of the teeth and the intervening tissue. It proves that any portion of the artery can be removed without destroying the vitality of any tissue of the jaw, provided that the artery be not destroyed between the structures and the nearest branch of the collateral circu- lation, and also shows that in order to destroy the vitality of a tooth pulp the blood supply would have to be cut off immediately at the apical foramen. THE VASCLLAR SIPPLV OF THE TEETH 137 It tloc's not follow that a tooth that docs not "respond" to tliciinal changes, or vwn to the electric cnrrent, is necessarily a (le\itali/A'd tooth, in operations for neiirali;ia the surgeon often removes a great portion of the mandibular vessels and nerve, or he may remove the semilunar ganglion, hut in so doing he does not destroy the vitality of the tissue supi)lied. He destroys the function of communication with the sensoriuni. When the trigeminal nerve is crii)pled by resection or b>' the remoxal of the semilimar ganglion, the wise surgeon protects Fig. 125. — From an jc-ray picture of the mandible of a dog. The arteries had been injected with mercury. (X-ray by Dr. I^ancoast.) the parts from injury. A tooth under similar conditions should also be protected and not subjected to "test." In time it will regain its sensation, provided meddlesome surgery has not destroyed the pulp. In the application of a spray of ethyl chlorid to the gums to produce an anesthetic condition for lancing an abscess, great care should be taken to protect any vital tooth, for there may be danger of pro- ducing its devitalization by the sudden and extreme lowering of its temperature. 138 THE MOUTH Incifor hranch Fig. 126.— The internal maxillary artery. (Gray.) pharyngeal SjjhenojJcdatine raqrbital Post. SU2). alveolar I Mylohyoid Fig. 127. — Plan of branches of internal maxillary artery. (Gray.) SEXSORV XEKVE SUPPLY OF TEETH AM) FACE i:',!) THE SENSORY NERVE SUPPLY OF THE TEETH AND FACE. The Trigeminal Nerve. — The sensory ner\e siii)j)ly ol the teeth and associated i)arts is governed by the trigeminal (trifacial or fifth ner\e), w liich is the largest of all the cranial ner\es. Through its wide distribution within the face and head, its close relation to other nerves and to the ])lexuses and ganglia of the sympathetic s>stem (Fig. 128), it becomes inxohed in nearly all the diseases of the external portion of the head as well as the superficial and deep j)arts of the face. "The intimate relations which the nerve bears with the points of origin of the sixth, seventh, eighth, ninth, tenth, ele\enth, and twelfth cranial ner\es in the floor of the fourth ventricle jiossibly explain many of those phenomena which are considered as reflex in character, and whose starting-point seems to depend upon some irritation of the fifth nerve by means of various branches" (Ranney). It resembles a spinal nerve, in that it arises by two roots, anterior and posterior. The posterior root is sensor}' in character, and has a ganglion upon it, while the anterior root has no ganglion and is motor in character. The large, sensor\', or posterior root emerges from a point in close proximity to the centre of the lateral surface of the i)ons \'arolii, but nearer its superior than its inferior border. The small, motor, or anterior root is made up of six or eight rounded filaments (Vulpian), and emerges from the jjons a little above the larger posterior root, being separated from it b\- a few transverse fibers of white substance. It is entirely distinct and separate from the larger sensory root until it passes out of the cranial cavit>- through the foramen ovale, when it becomes closeh' united with the third or mandibular division. The deep origin of these two roots is widely' separated from their superficial origin. Following them backward from the anterior surface of the pons Varolii, they pass directly through the pons to the medulla oblongata, without an>- connection whatever with its fibers. On reach- ing the medulla the\' form three main dixisions, one anterior and two posterior. 140 THE MOUTH J Facial nerve Communicates between facial and , . tympanic nerves . Nervus intermedius {of Wrisberg) ^ -Genicular ganglion _ , Greater superficial petrosal nerve Commu7iicates between great superficial petrosal and tympanic nerves - - Small superficial petrosal nerve Internal carotid plexus J . Deep petrosal nerve Nerve of pterygoid canal ■<"^.- Trigeminal nerve, sensory root /•k"^^- Trigeminal nerve, \ motor root Mandibular nerve ■A'-T Ophthalmic nerve " Maxillary nerve ' Optic nerve ^ Infra-orbital nerve with zygo- maticotemporal nerve Branch of infra-orbital nerve Zygomaticotemporal nerve SENSORY NERVE SiPPLV OF TEETH AM) FACE 141 The anterior or motor division arises from the motor luirlcus (A the trigeminal ner\e. which is comijosed of hirge, ramihed, and i)ig- mented cells situated below the lateral angle of the fourth ventricle, anterior to the inferior facial nucleus, and on the proximal side of the large sensory nucleus of this nerve. It also arises from the gray matter at the anterior portion of the iter beneath the corpora quadrigemina. 77/c two posterior or sensory divisions gi\e general sensibilit\- to the face and head, extending as far back as its vertex. From their sui:)erficial origin these two divisions extend obliqueh' upward and forward across the summit of the petrous pcjrtion of the temporal bone, and pass through an o\al opening in the dura mater into the middle fossa of the brain-case. The larger posterior sensory root terminates in the semilunar, which is situated in a depression on the superior part of the anterior surface near the apex of the petrous portion of the temporal bone. This ganglion is broad, flattened, and somewhat crescent-shaped. Its convexity is directed forward and slightly upward. The cells of this ganglion are unipolar in shape. Its surfaces are striated, and it receives on its inner side filaments of com- munication from the carotid plexus of the sympathetic nervous system. From the anterior or concave margin of the ganglion the three large {li\isions of the trigeminal nerve commence. It is from this that the nerve receives its name. The ophthalmic, or first division of the trigeminal nerve, is the smallest of the three cords, being but about an inch in length. Its function is to impart sensation to the eyeball, the lacrimal gland, the mucous lining of the eye, and a portion of the nose, the eyebrow and forehead. It commences from the upper, inner, and anterior portion of the margin of the semilunar ganglion. It is a flattened cord, and passes forward along the outer wall of the cavernous sinus, and termi- nates before or just as it is about to pass through the supraorbital fissure by dividing into three main branches, the frontal, lacrimal, and nasal, which are distributed as their names indicate. Branches of the Ophthalmic Xerve. — Those within the ca\ernous sinus, Lacrimal, Frontal, Nasociliar\'. 142 THE MOUTH The frontal nerve is the largest of the branches given off by the ophthalmic, and is in reality its axial continuation. It enters the orbit through the most superior portion of the supraorbital fissure, and passes forward in the median line above the muscles and below the periosteum. It terminates midway between the apex and base of the orbital cavity, above the levator palpebrae superioris, by dividing into two branches of unequal size, the supratrochlear and the supraorbital. The supratrochlear nerve is much the smaller of the two terminal branches of the frontal. It extends obliquely inward and forward over the trochlear muscle, passing out of the orbit, and curving around the supraorbital arch between the supraorbital foramen and the troch- lear fossa. It then extends beneath the corrugator and frontalis muscles, and divides into two terminal branches. These branches pierce the orbicularis and frontalis muscles, supplying them as well as the integument; also the lower and median portion of the forehead, interlacing with the corresponding nerve of the opposite side. This nerve also gives off two distributing branches, one extending from the nerve near the trochlear muscle, which passes downw^ard and joins the infratrochlear branch of the nasociliary nerve, and the other near its exit from the orbit, which passes to the eyelid and bridge of the nose. The supraorbital nerve is really a continuation of the frontal. It passes forward, and emerges from the orbit through the supraorbital notch or foramen. It then curves upward on the forehead, and divides into a median and a lateral branch, which pierce the muscles and become the cutaneous nerves. Its branches of distribution are several small cords which descend to the structures of the upper eyelid, and one which passes outward under the orbicularis oculi, interlacing with the facial nerve. The muvscular branches are distributed to the cor- rugator, frontalis, and orbicularis oculi. The cutaneous branches are two in number, median and lateral. These extend posteriorly as far as the occiput. The deep or pericranial branches are distributed to the frontal and parietal bones. This nerve also sends a filament which supplies the mucous membrane of the frontal sinus. Occasion- ally the division of the supraorbital nerve takes place within the orbit, the larger branch passing through the supraorbital foramen, SEASORV XJMV/-: SirPLV OF TEETH AM) TACE 143 while the smaller hr.iiich extends iiilenialK- aroiiiid the supraorbital arch or throu.uh tlu' froiilal uolch, which is occasionalK- present. The hicrinud nerve is the smallest of the three branches of the oi)hthalmir. It passes alon,u the outer side of the frontal nerve into the orbit through the anterior foramen lacerum, encased in an indi- vidual sheath derived from the dura mater. It passes forward and outward near the ])eriosteum of the orbit abo\ e the Rectus lateralis to the lacrimal fossa of the frontal bone, accompanied b>- the lacrimal arter>\ It then penetrates the external tendo oculi and terminates in the upper eyelid. Branches of Distributio)!. — On approaching; the lacrimal fossa the lacrimal nerve sends a communicating cord to the zygomaticotemporal branch of the maxillary nerve. This branch occasionally passes back- ward through a canal in the outer wall of the orbit, its divisions form- ing an arch from which branches are distributed to the lacrimal gland and the conjunctiva. Within the lacrimal fossa it sends branches to the lacrimal gland and the conjunctiva. The nasociliary nerve is intermediate in size between the other two branches of the ophthalmic nerve. It commences from the under surface of the ophthalmic nerve, and passes through the widest portion of the foramen lacerum into the orbit between the two heads of the Rectus lateralis, accompanied by the fourth nerve. On either side of it are the two branches of the third nerve. From the foramen it passes obliquely inward and forward over the optic nerve below the Rectus superior and Obliquus superior to the anterior ethmoidal foramen on the inner wall of the orbital cavity. It here di\ides into the internal nasal and infratrochlear nerves. Branches of the Xasociliary Xerve. — Branch to the dura mater. Long ciliary, Communicating branches to Sphenoethmoidal, sympathetic nerve, Internal nasal, Ganglionic, Infratrochlear. The branch to the dura mater is a small filament which turns back- ward and is distributed to the dura mater of the anterior cerebral fossa. 144 THE MOUTH The cotiumiuicatiug branches to the sympathetic are a few distinct lilaments which communicate with the sympathetic network about the ophthahiiic artery (Allen). The ganglionic branch is quite slender and about half an inch in length. It usually commences from the nasociliary as it extends between the two heads. It passes along the outer side of the optic nerve, and terminates at the posterior portion of the ciliary ganglion, constituting its long or sensory root. The long ciliary nerves are two or three in number, and com- mence from the nasociliary as it extends across the optic nerve. They pass along the inner margin of this nerve, and unite with some of the short ciliary nerves from the ciliary ganglion. They then pierce the sclera of the eye, pass forward between it and the choroid, and are distributed to the ciliary muscles, the cornea, and the iris. The spheno-ethmoidal (Luschka) or posterior ethmoidal (Krause) nerve passes from the nasociliary to the posterior ethmoidal foramen (posterior internal orbital canal), and is distributed to the mucous membrane of the sphenoidal sinus and the posterior ethmoidal cells in front of the body of the sphenoid bone. The internal nasal or ethmoidal nerve is in the line of continuation of, and generally described as, the nasociliary nerve. It passes through the anterior ethmoidal foramen, situated between the frontal and ethmoidal bones, into the brain-case, just external to the cribriform plate. It then extends in a shallow groove along the outer wall of the plate to the cerebronasal slit near the crista galli, passes through this slit, enters the nasal cavity, and divides into three branches — the internal or septal branch, the lateral, and the anterior superficial branch. The internal or septal branch of the internal nasal nerve passes downward and forward, and supplies the anterior portion of the septum of the nose. The lateral branches of the internal nerve usually comprise two or three filaments which are distributed to the anterior portions of the lat- eral walls of the nasal cavity, including the extremities of the middle and inferior concha bones. SENSORY NERVE SUPPLY OP TEETH AND FACE 14.") 'f/ic (Ulterior or siiprrjicidl hnnich j)asses downward in a loiii^ilu- dinal i^rooxc or ranal on llu- internal surfacx' of the nasal bone until it reaches the lateral cartilage of the nose. Here it extends between the bone and the cartilacic, runs beneath the nasalis, and becomes sui)erlicial, terniinaling in the spine, the wing, and the tij) of the nose. The infratrochlear nerve is one of the terminal branches of the naso- ciliar>', it being given off near the anterior ethmoidal foramen. It passes forward along the inferior border of the ol)liquus superi(jr, and parallel to the supratrochlear nerve, and receives a communicating branch from it. As it approaches the trochlea it passes to the inner angle of the eye and divides into two sets of branches. Those of the sui:)eri(jr set are distributed to the superficial structures of the superior eyelid; while those of the inferior set are distributed to the superficial structures at the root and side of the nose, the superficial portion of the inferior eye- lid, the caruncle, conjunctiva, the Uicrimal sac, and the lacrimal duct. Variations. — "The nasociliary nerve occasionally (frequently, Krause) gives filaments to the superior and internal recti. A branch to the levator palpebrae superioris has been met with (Fasebeck) ; offshoots from the nerve as it traverses the anterior internal orbital canal to the frontal sinus and ethmoidal cells are described by Meckel and Langenbeck." Maxillary Nerve. — The maxillary or second division of the trigeminal nerve is the second in size of its three great divisions. It is composed entirely of sensory fibers, and gives sensation to nearly all the struc- tures of and around the superior maxillary bone. It commences in the centre of the convex or anterior margin of the semilunar ganglion by a flattened and plexiform band, passes horizontally and directly forward, and leaves the cranium through the foramen rotundum in the great wing of the sphenoid bone. It then enters the pter>'gopaIa- tine fossa, and becomes more rounded and firmer in texture. It passes across this fossa surrounded by adii:)ose tissue, and enters the infraorbital groove, and receives the name of infraorbital nerve. It then passes through this canal, and emerges upon the face through the infraorbital foramen. The branches of this nerve can be divided into four groups, according to the locality of their origin. 10 146 THE MOUTH The Zygomatic branch is a small nerve which arises from the upper portion of the maxillar}' nerve just after it emerges from the foramen rotundum. It passes forward into the orbital cavity through the pterygopalatine fissure, and immediately divides into two branches, temporal and zygomatic. The zygomaticotemporal branch passes forward in a groove on the outer wall of the orbit until it reaches the temporal canal in the zygo- matic bone. It passes through this canal into the anterior portion of the temporal fossa, ascends between the bone and the temporal muscle a short distance, pierces the muscle and its aponeurosis about an inch above the zygoma, and terminates in filaments which supply the cutaneous structures of the temporal region and the side of the forehead. It interlaces with the facial and occasionally with the third division of the fifth nerve. That portion of the nerve within the orbit sends one or two filaments of communication to the lacrimal nerve, a branch of the ophthalmic division of the trigeminal. The zygomaticofacial {malar) branch at its commencement passes through the loose adipose tissue at the lower angle of the orbit to the z^-gomatic bone, through which it extends and emerges upon the face usually by two branches. It is distributed to the cutaneous tissues in the region of the cheek, and interlaces with the facial nerve. The sphe7io palatine branches are usually two in number, and are given ofif from the middle of the lower surface of the pterygomaxillary portion of the second division of the trigeminal nerve. They pass downward to the sphenopalatine or Meckel's ganglion. The Superior Alveolar Nerve. — The superior alveolar nerve branches from the maxillary' in the pterygopalatal fossa before it enters the infraorbital groove, and just after two branches go to the spheno- palatal ganglion. The nerve passes downward along the zygomatic surface of the maxilla. A little above the tuberosity its branches enter one or more foramina and pass into the maxillary sinus, part of the nerves supplying the walls and mucous membrane. The main portion enters a groove in the outer wall and passes into a canal as it enters the anterior wall of the sinus. The superior alveolar nerve gives off branches to the three maxillary molars, two premolars SENSORY NERVE SLPPLV OF TEETH AM) FACE 147 and caiiiiu', and w illi its hraiiclK-s supplies not only the maxillary lecth hut also ihc aKeolar pnjccss, the gum tissue, the investing membrane of the roots of the teeth and sockets, the mucous membrane and bone of the floor of the sinus. The incisor teeth are more than hkeh' supplied b> the arteries and nerves belonging to the original incisive bud. The arteries anastomose with one another no matter what their origin be, but the ner\es do not, though they interlace with each other. The Infraorbital Nerve. — After the maxillary nerve enters the infraorbital groove it passes along the floor of the orbit, and through the infraorbital canal terminating at the infraorbital foramen, where it divides into three sets of branches. The inferior palpebral branch is generally made up of two nerves. They ascend in a groove or canal, pass through the upi)er portion of the elevator muscle of the upper lip, and are distributed to the orbic- ularis oculi, the skin, the conjunctiva of the lower eyelid, and interlace at the outer angle of the orbit with the zygomaticofacial and facial nerves. A branch also passes inward and interlaces with the external nasal nerve, a division of the ophthalmic. The nasal or internal branches, two or three in number, are dis- tributed to the skin of the nose and the lining membrane of the nostril, and interlace with the nasociliary nerve. The superior labial or descending branches are more numerous than the branches of the other sets from the infraorbital nerve. They pass downward beneath the Quadratus labii superioris muscle, and are distributed to the upper lip, its skin, mucous (labial) glands, and mucous membrane. They also extend to the anterior portion of the gums. The infraorbital plexus of ner\-es is situated below the orbit, and is composed of branches from the infraorbital and facial nerves. The Mandibular Nerve. — The mandibular nerve is the largest of the three di\isions of the trigeminal nerve. It differs from the other two in the fact that its function is mixed, being both sensory- and motor; it also probably supplies in a measure the special sense of taste. This nerve is distributed to the lower portion of the face, the mandible, and mandibular teeth, a portion of the tongue, and the muscles of mastication. 148 THE MOUTH The sensory (or larger) portion arises from the inferior lateral and anterior part of the margin of the semilunar ganglion. It passes down- ward through the foramen ovale in the sphenoid bone, accompanied by the smaller anterior or motor root. Immediately after its exit from this foramen the two portions unite, their fibers interlacing, to form one nerve, the mixed function of the nerve being thus accounted for. It then descends vertically to the pterygoideus externus, and divides into two sets of branches, anterior and posterior. The anterior motor branch or trunk of the maxillary nerve is the smaller of the two, and is composed almost entirely of motor fila- ments, which are distributed to the muscles of mastication. It is divided into four branches: Deep temporal, External pterygoid, Masseteric, Buccinator. The deep temporal branches are usually two in number, though occasionally there are three — anterior, middle, and posterior. The anterior branch before piercing the pterygoideus externus is joined by a communicating filament from the buccal nerve. It ascends across the pterygoid ridge of the sphenoid bone, passes to the anterior portion of the temporal fossa, and supplies that part of the temporalis situated in this region. The deep temporal branch passes outward above the pterygoideus externus, then curves upward, running close to the temporal bone, and is distributed to the deep and internal portions of the tem- poralis. The posterior temporal branch is made up entirely of motor fila- ments. During the first portion of its course it is often associated with the masseteric nerve. It passes in a tortuous manner upward and out- ward, then upward through the proximal surface of the temporalis; it passes out of this muscle and through its fascia from a half to three-quarters of an inch above the zygoma, and then turns upward beneath the skin and interlaces with the auriculotemporal and facial nerves. The masseteric nerve is larger than the deep temporal, and arises in close proximity to it. Occasionally these two nerves arise as a common SENSORY NERVE SUPPLY OF TEETII AND FACE 149 Iriiiik from the' third (h\ isioii of tlic fiftli ncr\'c. It i)asses backward and outward between thi' ui)iH'r j)()rtion of the z>'j;(>matic fossa and the superior border of the i3terygoideus externus, curves slightl>' d(j\vn- ward and outward, and passes throuj^h the mandibular notch in the nunuHbuhu' bone. It then extends downward between the ramus of the l)(>ne and the masseter muscle, to which muscle it is mainly dis- tributed. Its other branches of distribution are, first, a small com- municating; filament which interlaces with the deep temjjoral, and an articulating; branch which passes to the mandibular articu- lation. The iiiter/Kil ptiry<^oid nerve is the shortest branch of the third division of the trigeminal nerve. It is given off from its anterior and proximal side on a level with the otic ganglion. It passes backward between the ganglion and the lingual nerve, occasionally extending through the ganglion to the inner side of the pterygoideus internus, to which it is mainly distributed. Its other branches of communication are, first, a motor root to the otic ganglion; second, a filament to the tensor palati; third, a branch to the tensor tympani. The external pterygoid nerve is not constant in its origin; it seldom arises from the main trunk of the inferior maxillary, but generally in conjunction with the buccal branch or from the internal pterygoid nerve. It is distributed to the pterygoideus externus muscle. The buccinator nerve, though described under the head of the motor branches of the mandibular nerve, is almost entirely composed of sen- sory fibers. It arises from the lateral margin of the main trunk of the mandibular nerve by from one to three bundles, and is usually joined at its origin by the anterior deep temj^oral and the external ptenygoid nerves. It passes outward, either between the two heads of the ptery- goideus externus or between the two pterygoid muscles; extends down- ward to the inner surface of the coronoid process of the mandible, thence forward between this process and the tuberosity' of the maxilla, occasionally passing between the fibers of the temporal muscle close to its insertion. Midway between the lobe of the ear and the angle of the mouth it becomes superficial, and terminates b}- di\iding into superior and inferior branches. 150 THE MOUTH Branches of distribution are — (a) Two or three external pterygoids, which are given off as the nerve passes through the pterygoideus externus. {b) An anterior deep temporal bra^tch, which usually joins the deep temporal ner\'e. It passes upward to the thick portion of the temporalis. {c) A descending branch, which passes to the insertion of the temporalis. {d) Superior terminal branches, which supply the upper portion of the buccinator muscle, the skin of the zygomatic and buccal region. These branches interlace with the facial nerve near the parotid duct. (e) I?iferior terminal branches, which pass forward to the angle of the mouth, and are distributed to the skin, the lower portion of the buc- cinator muscle and the buccal mucous membrane and glands. These branches, together with buccal branches of the facial nerve, form a plexus around the facial vein. The posterior or sensory branches of the third division of the fifth nerve are — Auriculotemporal, Mandibular. Lingual, The auriculotemporal nerve usually arises by two roots, of unequal size, situated close to the foramen ovale. At first they pass backward and outward, one on either side of the middle meningeal artery. They then unite and form a flattened trunk, which passes back beneath the pterygoideus externus to the inner side of the neck of the condyle. It cur\^es around the condyle in company with the superficial temporal artery, passes upward between the ear and the mandibular articula- tion, thence over the zygoma and beneath the superficial temporal artery, terminating in several filaments which are distributed to the skin over the greater portion of the temporal region, extending to its superior extremity. They interlace anteriorly with the facial nerve. Branches of the auriculotemporal nerve are — Communicating, Parotid, Articular, Anterior auricular. Branches to external acoustic meatus, SENSORY NERVE SUP PLY OF TEK'ni AM) FACE 151 The coHiiiiiiiiicdliiii^ hrdiir/ics arc sIcikUt lilanu-nls wliich i)as.s between tlie otic ganglion and tlu- third dixision of ihv iilth ner\e near its origin. One or two branches which are given off near the neck of the condyle of the Unver jaw pass forward beneath the facial nerve, unite with it near the posterior border of the niasseter muscle, and form one of the principal communicating branches between the facial and trifacial nerves. llie articular branches are one or two fine filaments which ])ass to the mandibular articulation. 7V/(' branches to the external acoustic meatus are two in number, superior and inferior. They pass between the bone and the cartilage to enter the meatus, and are distributed to the lining of the ear. The superior branch gives off a filament to the tympanic membrane. The parotid brandies supply the parotid gland. They are frequently connected with the facial nerve. The anterior auricular branches are usuall>' two in number. They pass between the tragus and helix, and are distributed to the concave surface of the auricle. The Lingual Nerve. — The lingual nerve is second in size, and is an important l)ranch of the third division of the trigeminal. From its origin it passes down on the internal surface of the pterygoideus ex- ternus, anterior and a little to the inner side of the mandibular nerve. These two nerves have been observed arising from a common trunk and bifurcating near the mandibular foramen. As the lingual ner\'e reaches the lower border of the muscle it curves forward between the ptery- goideus internus and the ramus of the lower jaw, and inclines inward over the superior constrictor of the pharynx, under the styloglossus muscle and above the deep jxjrtion of the submaxillary mucosali\ary gland, it then extends forward, crosses the submaxillary duct, ])asses below the mucous membrane of the alv^eolar lingual groo\e, and ter- minates at the apex of the tongue. Branches of Communication. — Near the origin of the lingual nerve a communicating branch passes over the internal maxillary artery to the mandibular nerve. There is also a small branch which passes to the hypoglossal nerve. This nerve also forms a plexus, from which 152 THE MOUTH branches are distributed to the walls of the internal jugular vein, a portion of the sinuses and the cancelli of the occipital bone, and inter- lace with branches which pass through the anterior condyloid foramen. The chorda tympani branch, which is a small nerve, arises from the facial, and descends from the proximal extremity of the petrot^^mpanic suture to the acute angle of the lingual nerve as it passes forward close to the lower border of the pterygoideus externus. At first there is only mechanical union between these two nerves, but subsequently they are intimately associated. Branches pass directly to the submaxillary ganglion where it is in close relation wdth the submaxillary mucosali- vary gland. Anterior to the last branch, one or two communicating filaments descend over the first portion of the hypoglossal muscle to interlace with filaments from the hypoglossal nerve. The branches of distribution of the lingual nerve are — A small branch to the palatoglossal fold (anterior palatine arch) and the tonsils. A sublingual branch, which is distributed to the mucous membrane of the floor of the mouth, the gum tissue on the inner surface of the mandible, and the sublingual mucous gland. The lingual or tenninal branches, which pass upward between the fibers of the tongue, divide into finer filaments, which are distributed to the mucous membrane of the anterior two-thirds of the tongue and terminate in the conical and fungiform papillae. A few ftexiform filaments, which pass beneath the tongue, some terminating on the under surface of the tip and in the glands of Niihn. The Inferior Alveolar Nerve. — The inferior alveolar nerve is the largest of the branches of the third or mandibular division of the trigeminal nerve (Fig. 130). From its origin it passes downward, accompanied by the inferior alveolar artery, on the external surface of the pterygoideus externus, posterior and a little to the side of the lingual nerve. After reaching the lower border of the muscle, it passes between the .spheno- mandibular ligament and the ramus of the mandible, and enters the mandibular canal or tube (see page 11) from which there are small lateral tubes which serve as nerve and vessel conduits to the roots of all the mandibular teeth and surrounding tissue. In the region of the SENSORY NERVE SUPPLY OF TEETH AM) PACE 153 canine toolli tlic ner\e (li\ ide-s into incisor and nicnlai branches, the former going to the incisor teeth. Tlie latter turns l^ack ujxjn itself, passes along the mental canal and out b\- the mental foramen. The branches of the inferior alveolar nerve are — .1 comiiiiiuicatiug branch, which passes over the internal maxil- lar\- arter\- to the lingual nerve. Termi ruit ion of nasopdlaiine nerve Fig. 129. — The sphenopalatine ganglion and its branches. (Gray.) A mylohyoid branch, which is generally described with the inferior alveolar, which is a sensory nerve, while the former is in reality motor in character. Its fibers can be traced from its point of distribu- tion backward to the anterior or motor root of the trigeminal It is given off from the inferior alveolar nerve just as it is about passing into the mandibular foramen, and passes downward and forward, accom- panied by the mylohyoid artery in the mylohyoid groove of the mandible. It is distributed to the inferior surface of the mylohyoid and the anterior belh' of the digastric, also the tensor palati and tensor 154 THE MOUTH tympani muscles. A few filaments from this branch pass through the myloh^'oid muscle and interlace with the lingual nerve. Branches are also described as passing to the triangularis (depressor anguli oris) and platysma muscles (Henle), to the integument below the chin (Krause and Schwalbe), and to the submaxillary gland (Meckel, Henle, Curnow). The ififerior alveolar branches are numerous, and fine filaments pass through the apical foramina in the roots of the teeth of the lower jaw to supply the pulp and tooth w^ith sensation. There are also filaments which pass upward and supply the alveolodental membranes and gum tissue. The incisor branch is the continuation of the main trunk of the inferior ah^eolar ner\-e. The mental or labial nerve is the larger of the two terminal divis- ions of the inferior alveolar nerve. It passes outward from the mental canal through the mental foramen, and immediately breaks up into three branches beneath the triangularis muscle. The inferior branch descends, and is distributed to the chin. The two superior branches ascend to supply the lip, its mucous membrane, and the labial glands. These three branches freely interlace with the maxillary branch of the facial nerve. SYMPATHETIC GANGLIA CONNECTED WITH THE TRIGEMINAL NERVE. The sympathetic ganglia found in connection with the trigeminal nerve belong to the general sympathetic system found throughout the body. This sympathetic system is composed of a large number of ganglia, cords, and plexuses. The ganglia are separate centres for the conveyance and distribu- tion of various cords and filaments, consisting of motor, sensory, and sympathetic fibers. They contain nerve cells very similar to those found in the encephalon and spinal cord. These ganglia are arranged in two chains situated on each side of the body near the central line. They commence with the ciliary ganglion in the orbit, and extend SYMPATHETIC GAM.UA COWJXTKJ) 11777/ Th'/CKM /.\A L \KRVE 155 dowmvartl akjiii; each side ot the xerlcbral foluiiui, and lerniinale below in the gaiighon inii)ar in tlie ((K^^ygeal region. The ganglionic or symi)allu'lic s\stcni is indciK-ndcnl and separate from the general nervous system, but is intimately connected with it by communicating branches which pass fnim the motor and sensory roots of the cerel)rosi)inal nerves, as well as by direct filaments which extend between it and the cerebrospinal centres. The sympathetic nervous system is distributed to the mucous membranes, the viscera, the coats of bloodvessels, and to the non-striated or involuntary muscular fibers. The nerves of this system form ])lexuses in vari(jus jjarts of the body, especially around the arteries. They are not found in connection with striated xoluntary muscular fiber. The cardiac muscle being partially striated, yet involuntary, is an exception. Numerous ganglionic cells are found situated at the terminal ends of sympathetic nerve fibers. The four pairs of ganglia associated with the trigeminal nerve are as follows: Ciliary, Otic, Sphenopalatine, Submaxillary. The ciliary ophthalmic or lenticular ganglion is situated in the posterior portion of the orbital cavity, between the Rectus lateralis and the optic nerve, in close apposition to the ophthalmic artery. It is a small, flattened, and reddish body, surrounded by adipose tissue, its flattened surfaces being the proximal and the distal. It measures about 2 mm. in length anteroposteriorly. Its branches or roots of communication are — 1. The sensory or long root, which is a slender filament arising within the cavernous sinus from the nasociliary nerve. It enters the posterior superior angle of the ganglion. Occasionalh' a filament is found which extends from the lacrimal nerve to the ganglion. 2. The motor or short root, which is shorter and thicker than the sensory root, and occasionally divides into two branches. It is derived from the inferior oblique branch of the motor oculi or third ner\"e, and joins the ganglion at its posterior inferior angle. 3. The sympathetic or middle root, which is derived from the s>'stem to which the ganglion belongs. This root is smaller than either of the 156 THE MOUTH Others, and originates in the cavernous sinus, being derived from the carotid plexus. Through this plexus it communicates with the cervi- cal ganglion. As it extends forward to the posterior border of the ganglion, it occasionally unites with the long or sensory root, forming a common trunk. Variations in the Roots. — The ciliary ganglion may receive acces- sory roots from the superior division of the motor oculi, the lacrimal, abducens, or sphenopalatine ganglion (Henle, Tiedemann). "According to Reichart, the ciliary ganglion does not receive its sympathetic fibers by a single root, but by several fine filaments, the majority of which accompany the motor oculi. "It appears from the mode of development and arrangement in many of the lower vertebrates that the ophthalmic ganglion is mor- phologically associated more intimately with the motor oculi, having, in fact, the significance of a spinal ganglion of that nerve (M. Marshall, Schwalbe)."^ Its branches of distribution are to the iris and ciliary muscles. The short ciliar}^ nerves, ten to fifteen in number, arise in two sets, superior and inferior. The superior set arises from the anterior superior angle, and passes forward, in a wave-like manner, between the optic nerve and the superior rectus muscle to the posterior part of the eyeball. The inferior set is more numerous than the superior, and arises from the anterior inferior angle of the ganglion. It passes in a wave- like manner below the optic nerve and above the inferior rectus muscle to the posterior part of the eyeball. It is accompanied by the long cili- ary nerves w^hich are derived from the nasal branch of the ophthalmic division of the trigeminal. One or more of its fibers join the short ciliary nerves. . Both the superior and the inferior sets pass forward through the sclera of the eye in delicate grooves on its inner surface, next to the choroid, and are distributed to the ciliaris muscle, the iris, and the cornea. A small filament penetrates the optic nerve to the arteria centralis retinae (Tiedemann). ' Quain's Anatomy. SYMPATHETIC GAMIIJA CONNECTED 117 77/ TKICJiMINAL NERVE 157 Sphenopalatine Ganglion. Ihe sphen()i)alaliiie ganglion (gan- glion of Meckel) (F'ig. 129) isthelargestof theganglia associated with the trigeminal nerve. It is situated in the pterygopalatine fossa in front of the anterior opening (jf the pterygoid canal, close to the sphenopalatine fora- men. It is triangular in form, with its apex pointing backward in the A uriculotcmporah Deep temporal Masseteric Sphe ruyrna nd ih idar ligament Inferior alveolar Mylohyoid Lingual Rarrms of man- dible {cut) Fig. 130. — The pterygoidcus cxternus and the branches of the nianchbular nerve in relation to it. (Gray.) direction of the pterygoid canal, and is surrounded by adipose tissue. Its outer surface is convex, and averages about 8 mm. in diameter. It is reddish-gra>' in color, except at its broadest part, where it is com- posed entirely of gray matter. The branches or roots of communication of the sphenopalatine ganglion are — 158 THE MOUTH 1. The sensory roots, two in number, which arise from the maxil- lary nerve as it passes through the pterygopalatine fossa. They enter the ganglion separately, one at the anterior and the other at the posterior corner of the upper surface. Many of the fibers of these roots pass through the ganglion without becoming incorporated with it, and receive no influence from it. These fibers form the palatine nerves. 2. The motor root, w^hich is quite long, and arises from the facial nerve or the greater superficial petrosal nerve at the genicular ganglion within the prominence of the facial canal. From this point it passes forward through the hiatus on the anterior surface of the petrous portion of the temporal bone, then inward beneath the semilunar ganglion, being separated from it by a thin layer of dura mater. It then pierces the fibrocartilage occupying the foramen lacerum and passes to the outer side of the internal carotid artery. At this point it is joined by the sympathetic root or the large deep petrosal nerve of the spheno- palatine ganglion, and the two conjointly are called the nerve of the pterygoid canal (Vidian nerve). They pass into the pterygoid canal in the sphenoid bone, extend through this canal, and at the exit enter the posterior or apical extremity of the ganglion. The gray matter of the ganglion extends along the nerve as far as the origin of the sympa- thetic at the carotid plexus. 3. The sympathetic root, or the large deep petrosal nerve, commences from the carotid plexus which surrounds the internal carotid artery. These filaments unite and form a short branch of reddish color and soft texture, which passes forward and joins the motor root of the ganglion to form the nerve of the pterygoid canal above described. Occasionally these two roots remain separate throughout their course, and enter the ganglion ununited. The branches of distribution of the sphenopalatine ganglion are — • I. Orbital branches, consisting of three or four fine filaments which pass into the orbit through the inferior orbital fissure, and are distributed to the periosteum and mucous membrane of the posterior ethmoidal and sphenoidal sinuses by passing between the sphenoid and ethmoid bones. SYMPATIII'JIC cam; LI A CONNECTED 117/7/ T RKih.M I \ A I. M.RVE 159 Some of llu' hraiulu's wliich i)ass upward arc distribiik-d U) llie lU'iirik'iniiia of tlic optic iicrve (Arnold and Longct). A branch from (he .uant^lion ascends to the sixth nerve (Bock and Valentin). Also a branch to the ciliary gani^lion (Tiedemann). Two or three branches, sphenoethmoidal, ascend to the superior portion of the internal orl)ital wall, pass through the i)osterior ethmoidal foramen, and enter the brain-case (Luschka). 2. The descending or palatine branches, three in number anterior posterior, and external. These three branches pass from the maxillary nerve through that portion of the ganglion in which there is little ganglionic or gray matter. They thus pass to their distribution with out becoming involved or influenced by the ganglion, excejit it be to a very slight extent. The anterior or large palatine nerve passes downward in the pterygopalatine canal, and enters the oral cavity at the great palatine foramen. It then passes forward in a groove on the side of the hard palate to its anterior portion, where it joins the nasopalatine nerve. It is distributed to the gums, mucous glands, and membrane of the hard palate. This nerve gives ofT a separate branch (middle palatine), which passes downward to the soft palate in a separate canal. It also gives ofif branches (inferior nasal) while in the canal, which are distributed to the middle and inferior conchse. The posterior or middle palatine nerve pa3ses downward, accom- panied by a small artery in the small palatine canal, to the soft palate, and divides into two sets of branches. One set is distributed to the levator palati and musculus uvulae, and may be composed entireK' of motor filaments coming from the great superficial petrosal branch of the motor and facial nerves, and the nerve of the pterygoid canal. The other set, which is sensory, is distributed to the mucous membrane of the superior surface of the soft palate, the glands of the soft palate, and to the tonsils. The external palatine nerve is the smallest of the three descending branches, and is not always constant in its existence. It jjasses cknvn- ward through the external palatine canal, which is situated between IGO THE MOUTH the tuberosit>- of the maxilla and palate bones, and is distributed to the tonsils, uvula, and outer portion of the soft palate. The iutoiiaJ or nasal branches consist of two divisions, upper nasal and nasopalatine. The upper nasal branches, four or five in number, are small, and pass horizontalh' inward through the sphenopalatine foramen into the posterior superior portion of the nasal chamber. They are distributed to the posterior superior portion of the nasal septum, to the mucous membrane covering the superior and middle conchae and to the posterior ethmoidal cells. The nasopalatine branch is larger than the upper nasal branches, and is an important division of the nasal nerves. It is long and slender, and arises from the proximal surface of the sphenopalatine ganglion. It passes through the sphenopalatine foramen across the roof of the nasal cavity to the septum, where it turns downward and forward, and extends in a groove or canal on the vomer to the foramina of Scarpa or nasopalatine foramina. These are two in number, anterior and posterior, and are situated in the intermaxillary suture. The nerve of the right side usually passes through the posterior foramen, while the nerve of the left side passes through the anterior. These two nerves (right and left nasopalatine), meeting in the incisor fora- men, form a fine plexus, from which minute filaments are distributed to the palate posterior to the incisor teeth and interlace with the anterior or great palatine nerve. "In the course along the septum small fila- ments are furnished from the nasopalatine to the pituitary membrane."^ The posterior branches generally assume the name of the nerve of the pterygoid canal (already described) and the pharyngeal nerve. The pharyngeal or pterygopalatine nerve consists of several fine filaments which frequently arise from the nerve of the pterygoid canal, instead of from the posterior portion of the ganglion. It passes down- ward through the pterygopalatine canal, accompanied by an artery of the same name, and is distributed to the mucous membrane of the upper portion of the pharynx and neighborhood of the auditory tube. ' Quain's Anatomy. SYMPATHETIC GAXCIJA CO.WIXTK!) WITH TRICE.M I .\ AL .\KR\K Kil Otic Ganglion. Tlu' otic ganglion (Fig. 131) is a refl(lish-gra\ l)(j(ly situated just below tlic foramen ovale, and in (lose a])j)osition to the Fig. 131. — The otic ganglion and its branches. (Gray.) 11 Fig. 132. — Diagram showing cutaneous areas of face and scalp. (Gray.) 162 THE MOUTH proximal surface of the mandibular nerve at the point of union of its motor root with the third sensory division arising from the semilunar ganglion, with the cartilaginous portion of the auditory tube to its inner surface, while the middle meningeal artery passes up into the brain- case just posterior to it. It is a flattened oval body, its widest diameter, which is about one-sixth of an inch, being anteroposterior. Its branches or roots of communication are — 1. The lo?ig or sensory root of Arnold which is composed of the lesser superficial petrosal nerve, a continuation of the tympanic branch of the glossopharyngeal, and a branch from the geniculate ganglion of the seventh. The ganglion also receives an important sensory branch from the auriculotemporal nerve of the trigeminal. 2. The motor or short root of Arnold which is derived from the internal pterygoid branch of the inferior maxillary division of the trigeminal. It also receives motor filaments through the lesser super- ficial petrosal derived from the genicular ganglion of the seventh nerve. 3. The sympathetic root, which is derived from the plexus around the middle meningeal artery. The branches of distribution of the otic ganglion supply in part the parotid gland, the chorda tympani, tensor tympani, tensor veli pala- tini muscles, and the mucous membrane of the middle ear. The Submaxillary Ganglion. — The submaxillary or lingual gan- glion is situated above the deep portion of the submaxillary muco- salivary gland, close to the outer portion of the hyoglossus muscle. It varies in shape and size, usually being triangular, but occasionally it is fusiform or plexiform, or absent altogether. Its branches or roots of communication are — 1. The sensory root, which arises from the lingual branch of the mandibular nerve and enters the posterior portion of the ganglion. 2. The motor or long root, which is formed from the motor fila- ments of the lingual nerve received from the chorda tympani branch (A the facial. 3. The sympathetic root, which arises from the sympathetic plexus around the facial artery. LOCAL ANESTHESIA UV^ The l)raiuhcs of (lislril>Liti(jii of the subnuixiUary ^anj^hon are i^rin- cipally those that siii)ply the suhmaxiUan' nuico-sahvar>' ghincl and its duct. ()(lui- branches pass upward, and interlace witii the hn.uual ner\ e, forming a ])lexus on the side of the tongue, from which hlaments are given ofif which supj:)K' the mucous membrane of the mouth. Bald- win and other anatcjmists describe a sublingual gangli(jn which is situated on the branch of the submaxillary ganglion which passes to the lingual nerve. Occasionally one or two small branches are found which communicate with the hyjxjglossal nerve (Meckel and Bose). None of the branches of the submaxillary ganglion are distributed to muscles, which is in marked contrast with the branches from the otic ganglion. LOCAL ANESTHESIA OF THE TEETH, SURROUNDING TISSUE, AND PARTS OF THE FACE PRESIDED OVER BY THE TRIGEMINAL NERVE. Local anesthesia may be obtained by several methods: by direct application of the drug to parts such as the mucous membrane of the mouth or nasal cavities, by hypodermic injection of moderate force, by forcing the anesthetic into the bone under high pressure causing infiltration through the bone cells, and by the conductive or blocking process. It should be borne in mind that no injection should ever be made in an infected area. The ordinary hypodermic may be used, but where a deeper anes- thesia is required it is necessary to inject with a stronger and larger syringe into the nerve at a place easy of access, between the point of operation and the sensorium; if for instance it was desired to anesthetize the lower lip "blocking" could be done at the mental foramen on each side. From examination of various mandibles in typical skulls it will be found that at puberty the foramen is in the centre of the body of the bone at a perpendicular line between the two premolar teeth (see Fig. 2) ; by studying this and other illustrations as well as specimens, one can judge the best point for injection within the vestibule of the mouth for this particular location. Though the mental foramen, its 164 THE MOUTH canal and nerves are rather constant as to position and relation, (see Fig. 3) in very old age, if the mouth be edentulous, the mental foramen is often found nearer the top of the body of the mandible (see Fig. 4) ; there may be also modifying pathological conditions mak- ing it necessary to take into consideration, not only age but the many variations that are discussed in the general text. As all the man- dibular teeth, gum tissue and most of the mandible are presided over b}' the mandibular nerve, the anesthetizing centre for this region would be the mandibular foramen which is one of the most constant features in anatomy. The mandibular foramen is in the median surface of the ramus generally in the centre and placed obliquely, it is oval in shape with a sharp border of bone extending upward from the lower margin known as the lingula to which is attached the sphenomandibular ligament. Above the foramen is a depression known as the mandibular sulcus, along which the inferior alveolar nerves and vessels pass into it. In front and medial to these is the lingual nerve (see Fig. 130). It is in the region of the sulcus that the point of injection should be carried for anesthetizing most of the lower jaw. The blocking of the nervous system is more complicated in the maxillary region than in the mandibular as the courses of distribution are more intricate, for this reason the minute knowledge of the varia- tions in the anatomy of this region should be acquired before one can intelligently and accurately anesthetize the middle portions of the face. The reflexes of the various ganglions and interlacing of the nerves either complicate or assist in proportion to the operator's knowledge of the distribution of this nervous system. If the maxillary nerve, as it passes through the pterygoid palatal fossse, be blocked before it branches to the sphenopalatine ganglion, all the structures in front of this region would be deprived of sensation, this might not be desirable. For local operation upon the middle face the ordinary points of injection are the infraorbital foramen, the inci- sive foramen, the greater and lesser palatine foramina, and the alveolar foramina. The infraorbital foramen is not constant in position as it may be found just under the middle of the infraorbital ridge or it may SVM PATHETIC GAXaiJ. I CO.WKCTTI) WITH TRKHiM I \ AL XKRVK Km be lateral to this and niiieh lower down, the location ol i)oint of injec- tion ran usualK he detected 1)>' careful dii;ital examination in the ves- tibule of the mouth going upward over the jDremolar teeth. The incisive foramen, a funnel-shaped opening, is situated imme- diateh' back of the two first incisors. It is in the interj^remaxillary suture just anterior to the ])alatal process of the maxillary bones, four canals usually lead into it from the nasal cavities, two incisive canals or canals of Stenson, for the accommodation of the descending palatine arteries, and two canals of Scarpa, anterior and posterior, for the accom- modation of the nasopalatine nerves. This foramen is the most easy of access. The greater and lesser palatine foramina are situated near the lateral and posterior edge of the hard palate, to the inside of the third molar. The greater palatine foramen is the outlet to the pterygopalatal canal and conve^'s the anterior palatine nerve which passes forward in a groo\c in the hard palate to the incisive foramen, interlacing with the terminal filament of the nasopalatine nerve. The two lesser palatine foramina are for the passage of the middle and posterior palatine nerves. The alveolar foramina are much more difficult to reach as they are not constant in either number or position, it is for this reason that the same result is not always obtainable in anesthetizing. They are situated in the infratemporal surface of the maxilla and transmit the suj^erior alveolar nerves and vessels. The best point for injection is back of the tuberosity along the posterior wall of the maxillan' sinus; all branches of these nerves should l^e blocked as they preside o\'er the maxillary molars, premolars, and canine teeth. To reach the maxil- lary incisors the injection should generally be made in the infraorbital foramen. CHAPTER VI. TEETH INFLUENCED BY IRREGULAR ERUPTION. RETARDED ERUPTION OR IMPACTED TEETH. Deformed, impacted and misplaced teeth should be studied not only as showing evidences of diseased conditions in themselves, but they must be regarded as symptoms of some precedent pathological disturbance which has manifested itself, among other ways, in these anomalies. One must know the history of the development and growth of the face, as well as of each individual tooth, in order to trace the period of the early pathological condition which caused the deformity. It frequently happens that at the same time other facial disturbances may be produced, which could in this way be indicated and traced by recognizing the relationship between the causative pathological lesion and its various manifestations. Precise diagnosis of the many obscure diseases associated with the face is impossible without accurate knowledge of the anatomy of the head — even to each individual tooth. This knowledge must include the various characteristics exhibited by the anatomy at dif- ferent periods of life, and the effect of early pathological conditions on the anatomy of the teeth, jaws and face generally. Among the general pathological disturbances which bring about deformity or retarded eruptions of the teeth may be mentioned syphilis, the acute exanthemata such as scarlet fever, etc., and disorders of nutri- tion. Among local causes are inflammations of the jaw bones set up by carious teeth or other disturbances, deformed arches, etc. The growth of the jaws and the movement of the teeth is in a forward direction, consequently anything which interferes with this forward movement will cause anomalous eruption and impaction of the teeth and deformity of their roots. Chronic conditions resulting from any of RETARDED ERUPTIOX OR IMPACTED TEETH lt)7 the acute exanthemata nia>' interfere w itli the ])roi)er development by causing an excessive deposit of salts of calcium, inducing a hyperplasia, which may either he general or localized within the cancellated bone. The roots of misplaced teeth are often cur\ed in abnormal shapes, or, in the case of molar teeth, compressed together. They are not acti\'el\' bent into these positions, but are built or formed thus in the process of growth. The>' are often held in the place of development, or pushed in the direction of the leeist resistance, until resorption of the bone tissue occurs, when they usually' make their appearance in an abnormal position. The increase of density of the bone not only prevents the teeth from taking their normal positions, but compresses the vessels and nerves, producing local malnutrition and general discomfort, not always severe enough to be called neuralgia, although, on the other hand, this disturbance is sometimes so severe as to incapacitate the individual from doing any kind of mental work. Local increase in the density (sclerosis) of the bone may also be brought about by inflammation of the periodental membrane, extend- ing into the alveolar process. Thus the cancellated tissue, instead of being spongy, and elastic, becomes hard and solid (see Fig. 45). This condition, following caries of the first permanent molar soon after its eruption, is sometimes a cause of impaction of the third molar. The severe traumatism to the jaw may cause a deposit of salts of calcium in the cancellated tissue, and thus bring about impaction. A heavy blow on the chin in childhood has produced ankylosis of the man- dibular joint, resulting in arrest of growth of the jaw, and leaving insufficient space for eruption of all the teeth. Premature extraction of the deciduous teeth, or the neglect to extract them at the proper time, may cause malposition of the permanent teeth, this leading in turn to impaction of unerupted teeth. Failure to freely lance the gums in retarded eruption of the deciduous teeth is also a frequent cause of an abnormal density in the cancellated tissue of the jaw. Impacted teeth may be present without giving rise to an\' local symptoms whatever, but as a usual thing they are a cause of many serious local and often far-reaching general disturbances. 168 TEETH IXFLUEXCED BY IRREGULAR ERUPTION ]\Iagitot^ reports man},' cases of deformed supernumerary, misplaced, transposed and impacted teeth in man, monkey, horse, and other animals. These are fully described and illustrated in the pages of his valuable and important work, to which the interested reader is referred. Figs. 133 and 134 give the under surface of a monkey's skull,- with the occluding surface of the mandible showing two impacted pre- molars in the roof of the mouth near the intermaxillary^ suture. Fig. 133 Fig. 134 Figs. 133 and 134. — Monkey's skull, showing two impacted maxillary premolars. Figs. 135 and 136 are from an x-ray picture of the same skull, show- ing the impacted teeth and their roots, also the developing canines in the upper jaw. ' Traite des Anomalies du Systeme Dentaire, Paris, 1877. 2 F"rom Dr. Kirk's collection. RETAIer of bone is perforated 12 178 TEETH IXFLUENCED BY IRREGULAR ERUPTION by three small openings. This malposition caused the loss of the left first and second premolars, also of the right first premolar. («s^«^*-^-^^'-^*^|k^ ( Fig. 1-1:7. — Showing two inverted canine teeth. -Root of canine tooth Crown of canine tooth Fig. 148. — An impacted canine tooth, the crown in the roof of the mouth, the greater portion of the root in the maxillary sinus. Fig. 1471 shows two inverted canine teeth in the inner and lower border of the orbital margin. This class of impaction would interfere with the function of the nasolacrimal duct. 1 This picture was presented by Dr. John Gravers' University of Utrecht, Holland. SUPERX L MKK. \I from (HsUirl)eince (;f the left e>e for a long time. Considerable improvement t(jok place in the eye soon after the extrac- tion of the inverted tooth. » -V- '^^' Fig. 151. — An impacted first incisor, with the crown partly in the incisive foramen. Fig. 152. — An impacted supernumerary tooth. Fig. 153. — An impacted maxillary third molar. A similar condition is found on the opposite side of the skull. Fig. 151 illustrates an impacted left first incisor, which lies diagon- ally across the alveolar process, with the apex of the root near the 182 TEETH IXFLUEXCED 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 transversely. Fig. 154. — From a Philippine skull, showing an impacted maxillar}^ 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. SUPERXUMER. \Ry TEE III 183 Fig. 154. — Matlc from ihc right side of a Philippine skull in Dr. Ketcham's collection. It shows a similar condition of inii)action of the maxillary third molar (o that in the Caucasian skull, Fig. 153. Fio. 155. — Is from the left side of the same skull as shown in Fig. 154. 1 i^ \ 1 rfi«»sas^;. # / Fr;. 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 184 TEETH IXFLUEXCED 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 common 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.) 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 jDortion. 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 jxjsition as discovered when the cap of bone was removed; in F'ig. 162 the tooth is removed from its socket, showing its inner surface. Its crypt is aKso seen. The second molar is a pulpless S UPERN UMER. [RV 7 KE 1 II ISo Fig. 158. — A common form of impacted lower third molars. Fig. 159 Fig. 160 186 TEETH IXFLUEXCED 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. Uppsr 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 by friction against the second molar. The roots of the SUPERNUMEK. \I• pressure. The terminations of I lie roots Fu;. 163. — A'-ray picture, showing an impacted second mandibular premolar tooth. (.Y-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. 188 TEETH IXFLUEXCED BY IRREGULAR ERUPTION Fig. 163, from an .v-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. SiPERX L MRR. [RV TEETH 189 molar and lias caused resoriitioii of llie ends ot the roots as shown in the extracted tooth (Fii;. 164). Figs. 165 and 166 represent another imjiacted third molar, situated on the inner side of the jaw and i)ointing slightly downward. The posterior root of the second molar is slightly resorhed. rp(^n uncover- ing the tooth and taking it from its cr\i)t, it was foimd to be incased in a thin shell of bone, as though the dental capsule had (jssihed sejia- rateh- around the tooth. The inner portion of the shell is still in i)osi- tion. the nerve and its accomiKuning 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 ha\e 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 190 TEETH IXFLUENCED 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 iiucrlcfl lower third molar erupting into the right submaxillary fossa. (Ur. Whitney.) SUPERNUMER. I A' J' TEETH 191 Fig. 169 gives an illustration where the mandibular third molar has become inverted and is erui)ling into the submaxillar>' fossa. Fig. 170' is from an .v-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 A'-ray picture of a patient of Dr. A. R. Cook, of Syracuse, X. V., it shows impacted second and third mandibular molars. Extraction. — It would ha\'e 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 awa>' with chisel ' From a patient of Dr. .A. R. Cook, Syracuse, X. V. 192 TEETH IXFLUEXCED 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 ma}^ even claim that the teeth which cannot be seen have been extracted. Impacted incisors are 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 i)rotruding 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 SUPERX I MEK. 1 A' 1 ■ //■./•. Til 1 03 \va\-, willi relict iiiul su1)sl'(iik'1iI cure. V\\v (.rtnvns were in normal shape and (luite hcalth\-, the roots more or less clefertive. The i)ul|)s were alixc. and il is |)i()l)al»le thai the nerxes were impini^ed njxin at the points of the roots, thus causing the pain. The writer has seen several cases where a greater ]X)rtion of the root of a single tr)oth was foimd within the antrum, hut he beliexcs this to be the oiiK case where three such teeth have been reported. In the lower jaw imi)acled leeth ai-e liable to impinge upon the mandibular ner\e, thus becoming a hidden cause of neuralgia in this region, which ma\- have its s>'mp- toms exhibited almost anywhere along the distribution of the nerves, eventualh' producing neuritis that may pass back along the nerve e\en into the brain. Cysts. — Teeth prevented from i:)assing in their normal course may, through the resorption of the bone, ad\ance in almost any direction and be erupted through the -bone even upon its cervical aspect. Impacted or supernumerary teeth may also i)roduce 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 cx'stic 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 .v-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 comj^lete removal of 13 194 TEETH IXFLUEXCED BY IRREGULAR ERUPTION the c^st wall, which, as already noted, partially or entirely 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 possibl}' the development of a malignant growth. The great majority of dental and dentigerous cysts can be removed through the mouth, Fig. 171. — A'-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- SUPERXUMERARY TEETH 195 ini^ of the left side of the knver jaw for about two \ears, which grad- ualK increased in size, causing consideral)le deformity. Examination showed a smooth swelling about the size oi a hen's egg, witli thill, i)archment-lik:e walls, covered only b\- 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 une\'entful 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, (i) premolar and (2) temporar\- 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 tilled 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 DKSCRII'I IVI-: ASAIOMV 1<)7 nu'iiihraiu' ot which sccrL'tcs iluids. Tht-sc fluids j)ass over the shcd- likc projt'clions ol the concha Ikjhcs into the nose, supplying the neceSvSar\' moisture. Fiiis. 196 and 197 are good examples of the nasal cavities showing bilateral symnietr\'. For descriptive convenience it may be divided into roof, Hoor, 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 ui)ward to the ethmoid bone, at an angle of about forty- live degrees. The middle portion is narrow, nearly horizontal in direction, and is comix)sed 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 oi)enings 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 i)terygoid plate. It is composed of the bod>- of the sphenoid bone and the alcC of the vomer. The floor of the nasal cavity extends from the external oi)ening anteriorly to the pharyngeal space posteriorly . It is smooth, and concave from side to side. The bon\- structure is composed, anteriorly of the intermaxilla, medialh- 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). 198 NASAL CAVITY AXD ITS ACCESSORY CELLS AXD SIXUSES 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 cavit3^ 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 difhcult 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 XASAL MEAT I 199 inferior, tlic niiddli'. and tlu- suixrior. Ziukcrkandl. however, says thai al)()Ul 6,"„ per ceiil. of ihe skulls examined 1)\- liini have had four meali. 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 live, and in one skull six were found. Sella turcica Auditory — orifice Right frontal sinus Left frontal Superior nasal concha "^■iperior catus iiddle nasal concha Middle meatus Inferior nasal concha Inferior meatus Hard palate — Alveolar process Flc. 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 upi)er portion, or all of that which belongs to the ethmoid bone, is associated with olfaction. The ends of the nerves, usualh' called the terminals, have their origin over this region; they also are distributed o\er the upper portion of 200 XASAL CAVITY AXD ITS ACCESSORY CELLS AND SINUSES the ;:^L'ptuni 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. A B Fig. 173. — Lateral walls of the nasal cavities, each showing four nieatl. M^"^^ #Tl ? A B Fig. 174. — Lateral walls of right and left nasal cavities, with large sphenoidal sinuses, B, ha\'ing 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 2i(S it will be observed that the large sphenoidal sinus extends y.lSOLAi R/.\f.\I. CAXALS 201 well forward toward ihc frontal hone and backward toward tlic basilar process of the occipital bone. Inferior Meatus. — Tht' inferior meatus is situated between the inferior nasal concha and the floor of the nose. It is much lon!Li:er than the others. Frontal sinus — -Middle nasal concha Ostium maxillare -Middle meatus Posterior half of naso- lacrimal duct -Inferior nasal concha "Inferior meatus Zygoma Alveolar Internal wall of process maxillary sinus Fig. 175. — Anterior view of a vertical transverse section of the right side of face. Nasolacrimal Canals. — The nasolacrimal canals, which are tor 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 ui:)per portion of the inferior meatus of the nose (see Figs. 175, 176. 177, 178 and 179). The direction of their descent varies considerabh in diflferent subjects, and even in the same subject. They usually pass backward, 202 X-15.1I CAVITY AXD 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 cavit}' 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 -j^miipAnterior half of nasolac- -BBM-Zygomatic bone "■^ Anterior wall of maxillary sinus Hard palate Alveolar process P'iG. 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 A^^ SOLA CKIMAL CA NA LS 203 is the frontal sinus. To the Icfl of this is the (jrbit. in tiie 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 Af -,1 ' ^si^BB^^H^^^^^^ic^ ^^P?'v^^Jl Middle nasal concha Maxillary smus m^S^^^^^^^K^[^^'~ ^V ' Nasal 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. 204 .Y.15.1Z. CAVirV AXD 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 wdth the middle of the orbits. Two sounds passed down into the nasolacrimal ducts indicate that Fig. 178. — 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 .V.I.VO/..ICA7.1/.I/. C.I.V.IA.V 2(i: roofs of the antra. Atlaclud l(j llic vooi of llu- ri;j,lu maxillary sinus arc two abnormal hoiu j^rowths gencTall>' known as osl('0])h\'tc'S, The middle meatus is situated Ix-twcen the lower jjorlion of the concha of the ethmoid hone and the inferior concha, and forms two-thirds of the posterior i)()rti(jn of the outer wall of the nasal ca\it\-. This is the most important meatus, as it is the princii)le nasal Osteophytes Superior Middle concha meatus Fig. 179. — Horizontal section, showing the under surfaces of the inferior concha and the outlet of the nasolacrimal duct. passap:cway of respiration, and is subject to more variations in its anatom>', ph>siology, and patholog\- 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. 206 XASAL CAVITY AXD ITS ACCESSORY CELLS AND SINUSES Fig. 1 80 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 Section turned tip Posterior ethmoidal cells Sella turcica Auditory orifice Right frontal sinus Left frontal sinus Infundibulum Anterior eth- moidal cells Hiatus semilunaris Unciform process - Middle meatus Inferior concha Probe passing into lacrimal duct Inferior meatus Hard palate Alveolar process 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 lower portion of the left frontal sinus is funnel-shaped. This opens into a passage leading into the ///. I ri 'S SEMILLSA RIS 207 middle nicatus, tlu' luiincl-sliaijcd i)()rti()n and the passage being commonly called the infiindii)iilum. 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 directh' 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 o])ening between the maxillary sinus and the nasal cavity (ostium maxillarc). 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 208 XASAL CAVITY AXD ITS ACCESSORY CELLS AND SINUSES meatus. If there are five mcati the sphenoidal sinus usually 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 b}' 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 hulla 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 w^hich 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. i8i. 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 cnlargcmcMit of llic bulla cUnvnward near the unciform process. We have here illustrated an example showing how enlargement of this structure ma\ 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 i)iclure, the anterior (jne is normal, the posterior is pathological. This abnormal opening and the loss of Fig. 181 P'ig. 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 cavit\-, seen near the centre of the picture, was probably the result of the closure of the 14 210 XASAL CAVITY AXD ITS ACCESSORY CELLS AND SINUSES hiatus semilunaris, shown in Fig. 183. 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 r "^ ^JMWWW*"^^ : Fig. 183 Fig. 184 Figs. 183 and 184. — 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 Pigs. 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 i86 show two anteroposterior sections from another skull in which the Ijulla ethmoidalis has become enlarged. Fig. i86 PM llOHKilCAL L().\/)/J/(}.\ Ol- .\.\SAL CAVITY 211 has the outer wall of (lie nuixiUarx' sinus removed, showini; the inner wall with two outlets al its upi)er niaruin. 'Hie anterior opening is the normal ostium maxillare. The j)osterior one is pathological and similar to those shown in I'igs. icSi, 1S2, 183 and 1S4, hut in this case the Ojicning is nearer the roof of the sinus. Fig. i .S5 is cut frt^ii the inner side of Fig 186. Figs. 187 and 188 illustrate the same sections as Figs. 185 and 186 with Fig. 188 tiu'ued roimd to the left side of the other. The illustration affords a \iew of the nasal ca\'it>' di\ided through the hiatus semilimaris, the bulla ethnioidalis, and the posterior ethnKjidal 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 ttirough tlie frontal sinus, the hiatus semilunaris, the bulla ethnioidalis, and the posterior ethmoidal cells. portion of the concha? 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, w'hich 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 AXD ITS ACCESSORY CELLS AND SINUSES least resistance — in this case at the abnormal opening shown in Fig. 1 86. 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 B Fig. 189. — A 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 Fi^. 189,0110 inch l)c-l()\\ B. Il (.•xhibils ihe (!(n\ iiw aid (.'xca\ a- tion which has occurred in the occUulcd sinus. In the lower surface, A, is shown the excavation exlenchn;^ in the (Hrection of the nasal s])ine. There are marked irretiularities 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 1)\- the thread passing through it. It is reasonable to suppose that the retained fluids have burnnved through the cribriform plate, causing ^. li Fig. 190. — Horizontal sections in same subject as Fig. 189, sliowing 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 w^as unable to obtain antemortem or clear postmortem notes of these two cases. It might be supposed, however, that the patients presented cerebral symptoms. In conhrmation of this idea, there was evidence in the condition of the skulls that there had been a postmortem examination of them. 214 XASAL CAVITY AXD 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. 192. — From same suljject as I'ig. 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 si}ecimen show clearly the iwriioixKiicAL cosniriox of .v.i.v.ia cavity 215 hrokcii-dow 11 coiidilion ijiodiicid in llu- track ol ihe disease. The ahiiornial arraniic'iiu'iu of the c-ells lu'conies especially apparent when C()nii)are(l witii tlie iNpical arran.ncnient shown in Fii;s. 257 and 25H. 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 aiu' portion, or at the inlets, by bony or other growths, it is 21() XASAL CAVITY AXD 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. (MIA rTi: R \' I I !. THK MAXILL.\R\ SINUS. The maxillarx sinus {inilnini of Ilighmore) is situated in the body of the maxilla?, 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 j^resence 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 bemg toward the zyomatic bone — into which it may extend (see Fig. 271) — and the base toward the nasal cavitw Its size and form \av\ in different 21S THE MAXILLARY SINUS subjects, and e\en in the two sides of the same subject (see Figs. 263, 264, 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 \"iew 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. Anterior fossa of brain-case Crista galli — Orbit Medial wall of nasal cavity Ostium maxillare Maxillary sinus Zygoma Maxilla Dental germs Mandible 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.^ 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 From the collection of i'rofessor Thomas C. Stellwagen. DIAELOPMEST 21'.) arc llu' niiddk' and inl\ rior concha. In llic middle meatus may be seen the unciform process i)assin,u ui)\vard and a little inward Irom the base of the inferior concha. Al tlu- 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 jwrtion 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. i\s 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). Fven 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 ver\- thin in this case, will 220 THE MAXILLARY SINUS be found the infraorbital canal as commonly described, and below, the nearh- pyramidal cavity of the maxillary sinus, with a partial septum crossing transversely from the inner to the outer wall. Crvstalline 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 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 u\) in the inner wall of the sinus. IJIAKLOPMJ.XT 221 The rcntriil i)()rli()ns afford cxcclk-nl \icws of transverse sec- tions of the nasal ea\il\'. The septum in the centre is unusualh- straight. Abow llic septum is the crista galh, to which the falx ctrcl)ri is attached antiriorly. On each side of the sej)tum, at the upper attachment, is the roof of the nasal cavity, below at a little distance are the middle conchie, and, on the outer wall, are the inferior concha. The superior conchae cannot be seen in a section cut in this region, as the\' are situated farther back in tlic 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 999 THE MAXILLARY SINUS standpoint. The extraction of teeth having roots in such positions, if not carefully done, might carry away parts of the floor of 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. F"iG. 198. — X-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 DEVELOVMEM' 223 downward tlirous^li llir osliuni frontalis into the hiatus scniikmaris, and then into thi.' nia\illar>' sinus, l)y the ostium maxillarc. The infra-orbital sinus and the inferior and middle conchseare seen, also two large cells between tlu- i)Iates 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 positicjn, 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 .v-ray picture of a large maxillary sinus, showing that it has ai)parentK- 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 .v-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- worth>-. 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 224 THE MAXILLARY SINUS teeth. These elevations are found over the roots of the molars, some- times over those of the premolars, and less frequently over those of 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 anteroposteriorly (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 usually THE ANTERIOR WALL 225 snio(jLh. The (loor is coiu'axc from side to side and slii;hlly .s(j in the anteroposterior direc^lion, as illiistraled in Tiiis. 175, 200, 236 and 237, having lluis a basin-like form, and hein.u iisualK' below the lexcl of the nasal ea\ity (see Fii^s. 295 and 297). The Anterior Wall. — The anterior wall is almost a square with rounded eorners. ll is sm(K)th, with a slight depression, whieh varies aeeordin.u to the position of the i)assage of the infra-orbital eanal or tube, as shown in Figs. 223 and 230. OccasionalK- the ro(;ls of the Fig. 200. — Anterior \'ie\v of a \ertical 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 15 220 THE MAXILLARY SINUS closes around them, lea\ing 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 orljital 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 Till: MAXILLARY SISUS 227 passes int(j the- infra-(>rl)ital canal. The ridtic ixttrds downward and forward to meet the anterior wall of the sinus. The dii)ping down of the ridi;e \ aries grcalK in extinl, bein.ii scarcely noticeable in s(jme specimens, whili- in others it extends so far that the canal becomes distincth' tubular in character, passing diagonally through the sinus, carrying the infra-orbital ner\c s and vessels acnjss the anterior jjortion, with an open space above the tube. Ihc- ojjen sj)ace above the sinus extends outward into the lower rim of the orbit, forming an infra-orl)ital sinus or pocket, a variation which the writer has mA seen mentioned in any work on anatomy. The tube-like canal has a thin lamina ot 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 (nal-shaped foramen, which affords communication between the sinus and the nasal cavity through the hiatus semilunaris, is usually found on the upjxT 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 maxillars- sinus and the nasal cavity (see Figs. 183, 184 and 186. Septa of the Maxillary Sinus. — The shape and size of the maxil- lars- sinus and the character of its partial septa vary so much that it is almost imj^ossible to say what is its typical shajx^ 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 \arious directions, but the writer has been 228 THE MAXILLARY SIX US unable to find complete septa of the maxillar}' 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 bon)- septum arising from the floor and passing transversely across forms two deep pockets. / ?ij^ i' ■■ vy 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 SLMS 229 Fig. 204. — Anteroposterior division through the maxillary sinus. ^ .tfT*— ^^, 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. 230 THE MAXILLARY SINUS 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 ma^^ 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 very small. SEPTA OF rill: MAXILLARY SIMS 231 Figs. 211 and 212 art' takiii Iroiii ihc Icll sick- iA aiKJlhcr ncgn/s skull. The section is niadc in ihc same region as the last, showing a 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. Fk;. 209 Fui. 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, peculiarh' shai)ed sinus, and a crescent-shaped cell which opens into the superior meatus. 232 THE MAXILLARY SINUS Figs. 213 and 2 14 are from the right side of the same skull as Figs. 211 and 212, showing apparently 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 correspond ingty 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 .S7!:/^7'.l OF Till-: MAX/LL.IRV SIX US 233 sinus is cxtrcnicK' small, ll may be ihal on account of this the cell was abnormalh' enlari>i'(l lo increase the air space of this region, or that the palatal process has encroached upon tln' space usually occupied 1)\ the maxillary bone. The bony septum of this specimen might ver>' 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. 216 Figs. 215 and 216. — Anteroposterior division through the centre of the orbit, maxillary sinus, and molar teeth, showing a large ma.xillary 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 234 THE MAXILLARY SIX US 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 extremel}' 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 only a very thin plate of bone between 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. i)i:.\r. 1 /. Ki:i.. 1 1 loxs/i/ps 235 In iIk' usual pliN sioloiiical dcscriplion of llic sinus, ihe lluids are spoken of as passiiiL; oul of it. It is a c|U('stion if this l)e the case under normal conditions. It is more than hkclx that the law ot supi)h- and demand is so balanced that t/ic parls of the uuixillnry sinus are kept moist only, the openings being so arranged at the top as to pre\ent undue loss of the fluids while the subject is l>ing on the back or is standing. The openings in the other air cells or sinuses are so arranged as to make almost comj^Iete drainage through their most dependent parts. Dental Relationships. — Because of the close anatomical relation of the nia.\illar\' sinus with the tooth-germs and the roots of the jier- manent teeth, it is evident that the sinus must l)e more or less influenced by them. As the teeth develop and descend into their normal i)laces, 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 j)alate 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 primarih diseased, causing infection of the sinus and associated cells. In Fig. 197 it 236 THE MAXILLARY SINUS 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. DENT. 1 /, REI.A TIOXSIIIPS 237 class of cases where diseased leelh may cause inteclion (A tlie max- illary sinus. If the i)uli) of a tootli so related to the sinus sh(juld become devitalized and iufecled. ihe i)arts around the apical foramen might also become infected and abscesses occur. PVom the close prox- imity of the points of the roots to the sinus, it might be supposed that these abscesses would l)reak 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 238 THE MAXILLARY SIX US 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, DENTAL RELAT ION SHIPS 239 exposing: the cmuI of tlu- root in the inl\(lc(l ntiioii, tlu- coiulilicjii being somcwhal similar to those siiow n in I''ii;s. 22^ and 225. Infra-orbital sinus_j'"" ■ \ Infra-orbital forainoii — ■, Sound passing through infra-orbital canal and foramen Maxillary sinus Opening caused by apica abscess Fig. 223 — Infra-orbital sinus -— Opening into zygomatic bone Fii;. 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. 227 and 228 was made from the left maxilla of the same skull from which Figs. 223 and 224 were taken. The pulj) of the first molar was devitalized. In 228 an enlargement of the infected root is seen. 240 THE MAXILLARY SINUS Floor of the nasal cavity 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 axillary 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. DENT A L RELA TION SHIPS 241 An exaniiiialion of the hard i)alatL' shows that the discharge of the abscess was made into the moulh, which the writer beheves is the Fig. 227 Fig. 228 /•■ 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 Fig. 229. — Alveolar process. usual outlet for apical abscesses in the upper jaw — of course recognizing that they occasionalh- oj^en into the sinus. IG 242 THE MAXILLARY SIX US 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 only 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- Groove for alveolar nerve and vessels Sound passed through infra-orbital canal and foramen 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 SURGICA L REL. 1 TIONS 243 roots of I he (ccth, as seen in Fi^. 199, if undue f(jrce slioukl be exerted, not onK the looth grasi)ed by the forceps, but also a great portion of the lloor with other teeth attaclied is hable to be carried away. M\anij)les of tlie results of sueh accidents are shown in Figs. 231, 232 and 2^^^. Figs. 231 and 232 are from specMmens 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 placnng 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 ■y/ / 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 jDcriodontal 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. 244 THE MAXILLARY SIXUS The maxillar}- 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 walls 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: (i) 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 maxillar}^ 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 arc covered with epithelium, is immune to infection to a great extent, PAT no LOGICAL LUMJJTIU.WS 245 but repealed or cH)nslant e\i)()sure lo infected mailer will finalK' result in a diseased eondilicju, prcKlucinj; a discharge of the l>'pe of the par- lirular miero()rji:anisms introduced. Therefore anylhinji: that affects the mucosa of the nose will ha\'e its influence 1)\' direct action upon all the associated i)neuniatic splices. 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 vSO 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 ujnvard to the natural outlet. (4) Infection through the l)lo(jd supply. The blood sui)i)h' 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 ha\ ing 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 ])athological condition. They are usually discovered in cases where the sinus has been previously diseased and treated. 246 THE MAXILLARY SINUS (6) Cysts, pol^'pi, impacted or misplaced teeth, odontomata, osteophytes, mahgnant and benign tumors are strong predisposing factors toward pathological conditions of the sinus, and should be carcfulh" 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. TREATMEXTOr PATHOLOGICAL COX D/TKKXS OL MAXILLARY SIXCS 2A1 If Figs. 276 and 277 hv cxaniiiu'd {\\vy will give illustrations of pockets and anatomical conditions of the maxillary sinus that would make it most diHicuIl to treat esjx'cialK if it should be required lo curette the parts. An infra-orbital sinus ma\' 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 difticult to reach through the nasal cavity. In Fig. 287 there are two deej) pockets that would be difficult to reach through the nasal ca\it\', while through the alveolar i^rocess 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 l)elow the level of that of the nasal cavity. An ordinary opening into the maxillary sinus through the mouth heals u]) \ery (juickly, especialh' 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 var^' 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, l^ut 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 arc 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 f)ass (jver the orbit might be called supra-orbital DEVELOPMENT 249 sinuses, cspccialK' if i1k'>- have complete partiticjns and outlets (jther than the one which occupies the ascendinj^ portion of the bone. Figs, 234 and 235 show a large left frontal sinus, wJiich 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. Fr;. 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 runninQ- 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 sinu.ses and nasal cavities, showing the frontal sinus extending below the level of the middle of the orbit. DEVELOPMEXT 251 OccasionalK- llu- fnjiUal sinus extends into the crista ijalli form- ing a cell in that i)rocess (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 th:? 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 only a right frontal 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. 242. — Anterior view of skull with bone removed, exposing only one frontal sinus. 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. DEVELOPMKXT 253 Fii^. 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 yww, showing three frontal sinus Fig. 245.— Anterior view, showing four frontal Fig. 246.— Anterior view, showing five frontal 254 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 Fig. 247. — Posterior views, showing two large maxillary sinuses. The right one forming a common cavity with ethmoid cell and maxil- lary sinuses. Fig. 248. — Anterior view, showing two frontal sinuses, the right one very large ex- 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 niAl'.LOl'MENT 255 iiifra-()rl)ilal loranien, willuHil a scplimi. The ri^lit Ironlal siiuis, meas- urinii 40 iiini., has several small inccjmplete, nearly horizontal septa, making a numhiM- of horizontal jKJckets. Fig. 250 is made from a transverse section of the face with a l)ortion 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 ver\' large frontal sinuses which extend backward over the orbits, where they are divided b\- several incomplete sejDta. 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. 256 THE FROXTAL SIX US 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 smuses. 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 orl)it, showing in the anterior portion a lateral view of DEVELOPMENT 257 tlic frontal sinus cli\ itlcd inUj li\c pockets, all (-»! which haxe one com- mon outlet. The sixth or posterior cell communicates with the upper meatus of the nose. The Uj)per 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 nearh' to the optic ner\e which is seen in position in the optic foramen. The skull i)ictured 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, si)henoid, and maxillary sinuses. The right 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 hone 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 17 258 THE FRONTAL SINUS upward, forward and inward over the orbits (see point marked 7, Fig. 255). 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 tw^o 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 w^hich allows the two compartments to communicate w4th one common outlet into the nasal cavity. CHAPTER X. THE ETHMOIDAL AND OTHER CELLS WHICH HAVE THEIR EIXAL OUTLET IX THE NASAL CAXITV. The ethmoidal cells are situated j^rincipalK between the two orbits. Fig. 257 is an upper \ie\v of a horizontal section cut through the centre of the orbits and the ujjper part of the nasal cavities, Xasal cavity Hiatus semilunaris Lacrimal due: Xasal septum Anterior ethmoidal cells Floor of orbi: Middle ethmoidal cells Posterior ethmoidal cells Sphenoidal sinuses Fig. 257. — Ipper surface of a horizontal section cut through the orbits and upper part of nasal cavity. showing clearh- 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 260 ETHMOIDAL AXD 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 sri/i:\()fi).\r sfxrsEs 261 lined willi mucous membrane, which is continuous with the lining of the ui)iH'r and jK^sterior portion of the nasal cavities. The greater jjortion of the anteri(jr surface of the lj(jdy of the sphenoid bone is open, these openings are covered to a great extent Fig. 258. — Horizontal section through the orbits, ctlinioid 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 sj^henoid bone to which it becomes attached. The anterior surface is convex and is associated with the ethmoid in 262 ETHMOIDAL AXD OTHER 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 conchae 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 slightly 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. CHAi'ri:R XI. VARIATIONS IN THK ANATOAIK AL STRlCTrRES OF THK PACK. The variations exhibited in tlie internal anatom>' of the face are so common that it is sometimes difficult to differentiate the normal from abnormal anatomy. Some of the most imi)ortant 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 264 VARIATIOXS IX AX ATOMIC AL STRUCTURES OF FACE of the mouth. The greater portion of the teeth have been lost in early life. The canine fossa of the right side is lacking, the face being %T.^ 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 r.lA7.l770.V.S I.\ AXATOMICAL STRLCTL RJ:.S UI- J' ACE 2()o of this character tlic inlcrnal structures will usually- be clecicleclly unsyninietrical. One nii^ht supjxjse thai a lari;e sinus would be found under the fulness of the canine fossa, but in this jjarticular 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 d(nvnwar(l between the orbits lower than usual. «* Fig. 261. Auicrior 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. 202. — Posterior \ iew of a vertical trans- \erse 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 occasionally 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 266 VARIATIOXS IX AX ATOMIC AL 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, 264 and 265 are from the same subject as Fig. 262. An instrument passed through the axis of the alveolar process, shown in Fig. 263. — Anterior view of a vertical trans- verse section of the skull shown in Fig. 262, showing an asymmetrical condition of the two sides. Fig. 265. — Anterior view of vertical trans- verse section cut from the posterior part of the nasal cavity and maxillary sinus. It is from the same skull as Figs. 262, 263 and 264. Fig. 264. — Posterior view of section shown in Fisr. 263. Fig. 266. — Anterior view of a vertical trans- verse section, showing lack of uniformity in the two maxillary sinuses. 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; VARf.iriOXS l.\ AXATOMfCAL STRl'CTLRES OF FACE 20^ the ma\illar\' sinuses \ar\', howewr, thnnighcnit the depth of the skull. On the rii;ht side the sinus wcnild not he reached In- drilling through the alveolar process, while on the left side the sinus is just above the i)rocess, 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 maxillar\- sinuses. The lateral wall of the nasal cavit>- of the right side is also the outer plate of the maxilla, the floor of the sinus being on a much higher ])lane. In the floor of the left nasal Fig. 267. — Anterior view of a vertical transverse section, near the first premolar, showing variation in the niaxillar\- 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 maxillar}' 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 maxillar\- 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 sci')tum. the 268 VARIATIOXS IX AX ATOMIC AL 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. Fig. 269. — Two vertical transverse sections. The surfaces shown arc divided from each other. Variations are shown in the maxillary sinuses and nasal cavity. A cell is also shown within the crista gain, which opens into the frontal sinus. WlRIAIfOXS /.V ANATOMICAL STKiCTL'RliS Oh' FACK 2(i9 dental arch is narrow and the nui.\inar>- sinuses small, the>- do n(;t extend downward in the direction of the teeth and alveolar i)rocess. 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 s>'mmetrical. The crista galli has been cut trans\ersely, showing within its walls a cell of considerable size, opening into the frontal sinus. Fig. 270 is made from the skull (jf an aged ])erson, in which the bones have become much resorl^ed. It is comparatively s>m metrical, with the floor of the sinus much higher than usual, and the nasal ca\it\- 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. 270 VARIATIOXS IX ANATOMICAL STRUCTURES OF FACE Fig. 2"/^,. — A sagittal section of a greyhound's skull, showing the nasal cavity extending to the outer wall of the maxilla, no true maxil- lar\- sinus is found, though the inferior concha helps to partly shut off a space which might be named the conchomaxillary sinus. Fig. 271. — Section through the maxillozygomatic articula- tion, showing that occasionally the maxillary sinus passes into the zygoma. Fig. 272. — Interior view of the external wall of the nasal cavity, showing portions of the palatal roots of the first and second molar teeth in the floor of the nose. 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. 272, which illustrates that the resorption of the alveolar process from VARIAT/O.XS I.\ A.XATOMICAL STRUCTURES OF FACE 271 over the buccal roots o*" the teeth may progress while that portion of the bone alon.u the free mariiin of the process is left intact. Figs. 276 and 277 show a \ ertical transverse section of the upper jaw. In Fig. 277 the roof of the niaxillar\- sinus is almost horizontal, which is a \er\ unusual condition. The illustrati(jns show what is Fig. 274. — Sagittal section of a badger's skull. Fig. 275. — E.xternal 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 ot 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 272 VARIATIOXS IX ANATOMICAL STRUCTURES OF FACE Infra-orbital nerve — !^ Muscles of face — ;' -/"y^-AP Middle ethmoidal cells Middle concha Unciform process —Inferior concha Inferior meatus Fig. 276. Middle ethmoidal cells Hiatus semilunaris Unciform process Ma.xillary sinus — -» Inferior concha—^-'/ Inferior meatu Infra-orbital nerve - Muscles of face Fig. 277. — Vertical transverse division of the upper jaw. VAR/AT/OXS IN ANATOMICAL STRiCTURES OF FACE 273 a tube (jr canal coiucxin^ the inlra-(jrl>ital nerves and vessels. Above this, and at the junction of the septum with the floor of the or])it is an adjunct infra-orbital canal and ner\e. At the ui)j)er inner corner of Fig. 277 is the normal opening of the maxillary sinus, the ostium maxillare. communicating with the hiatus semilunaris. This section beautifulK' illustrates how the hiatus semilunaris is bounded on the inner side l)y the unciform process, on the outer side by the wall of the sinus, and above 1)\ 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 Ihruugh ihe orbits, maxillary sinuses, posterior ethmoidal cells, and the third molar teeth. fluids could not pass directh' into the middle meatus but would be thrown into the maxillar^,^ 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 j^robe {ilaced in 18 274 VARIATIOXS IX AX ATOMIC AL STRUCTURES OF FACE Ostium maxillare opening in roof . ■ -, — Sphenoidal 'f>i.' sinus Fig. 279 Sphenoidal sinus Middle concha Middle meatus Maxillary sinus Inferior concha 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. VARJATIOAS l.\ AXATDMJCAL STKUCTLRES Ul- FACE 27.") the left ostium maxillarc indicates its position. Immediately to the left of the i)robe is a section of the nasolacrimal duct. On the opposite side, the lower wall of the rii^ht ostium has been removed. That the ij,reat \arialioiis found in the nasal ca\ities and maxil- lary sinuses may be fully appreciated, skulls of wideh different types have been selected and phototirai:)hed together. Figs. 281 and 2H2 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, F'ig. 282. In Fig. 281 the septum has a spur extending outward until it comes in contact w^ith 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 2S2, 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 inw^ard 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. 276 VARIATIOXS IX ANATOMICAL STRUCTURES 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 Fi(i. 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. VARlATfO.XS l.\ AXATOMICAL STRL'CTLRKS OF I'ACK 277 moidal cells into the maxillan- sinus. Of the two probes passed throui^h the ostium niaxillare. one uoes directK' throui^h the jxjsterior i)ortion Fig. 283 Fig. 284 Figs. 2SS and ISA. — 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 Figs. 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. 278 VARIATIOXS IX 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. VARIAT/OXS IX AN ATOM KM. STRUCTURES OF FACE 279 Fig. 289 is a posterior view of the same section as Fig. 2S8. The course of the i)rol)c can he traced as it passes downward along the hiatus semikniaris, through tlie ostium maxillare, and into the sinus without obstruction. There is a hick 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 l)ackward from the frontal sinus into the middle meatus, a V\o. 288. — Anterior view of a vertical trans- verse section of a negro skull between the second premolar and the first molar tooth, showing probe passing down into the maxillary sinus, through the frontal sinus, the hiatus semilunaris, and ostium maxillare. r^ Fig. 289. — Posterior view of section shown in Fig. 288. 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 awa^^ 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 VARIATIOXS IX AX ATOMIC AL 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 of the nasal cavity with part of the bone cut away to show the hiatus semilunaris and the middle ethmoidal cells. Fig. 291. — Section showing two hiatuses, both leading directly into the maxillary sinus. The posterior hiatus has a probe passing through it, 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. VARIATJOAS J.\ A.XAJOMICAL STRLCnRKS OF I'ACK 2S1 frontal sinuses extend down l)el()\v the middle of the orbit. Between them there is an interfrontal cell extending backward into the crista ^^alli 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 posteriorh' to the first molar teeth. The frontal sinuses extend in an outward direction o\er the orbits. The wire shown in F'ig. 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 trans^•erse 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 282 VARIATIOXS I\ AXATOMICAL STRUCTURES OF FACE hiatus semilunaris without a true hne 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. 223, 224, 229, 230, 276 and 277. The numerous pockets in the anterior portion of the maxillary sinus would render it difficult 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 -ae****'- 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 w^hich extends forward into the frontal sinus. This last formation is also shown in Figs. 269, 2S1, 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 down below the floor of the nasal cavities VAIUATIUSS IN ANATOMICAL STRUCTLRES 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. 284 VARLiriOXS IX AX ATOMIC AL STRUCTURES 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 o^•er 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-orl)ital sinus. CHAPTER XII. THE RELATION BETWEEN THE MOITH, TONGUE, PHARYNX, AND NASAL CHAMBER. Frozen Sections. — The sections of the head which ha\'e 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 ha\'e 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 15° 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 2SG 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 / The mandible cut a little above the / J mylohyoid ridge / ^- / /Sublingual glands /Raphe of the tongue Facial artery Facial vein Facial vein — Facial artery '■ * ",^ -Alasseter muscle The ramus |fc — 1 Pterygoideus internus -Point of uvula [muscle "> \Y^ Sternocleido mastoid r Internal carotid . 'M^ Pneumogastric nerve Internal juglar -— Splenius capitis Vertebral artery Spinal cord Spinous process of the second cervical vertebra 1"1G. 299 RELATION BETWEEN MOUTH, TONGUE AND PHARYNX 287 Fig. 300 is nuide from a horizontal section at the junction (jt the upper lip and nose, showing a longitudinal section of the septum (jf Nose Nostril. Maxilla. Septum of nose. Xasal cavity liilurior cuncha. Maxillary sinus. Upper portion of inferior meatus. Zygomatic process. )f coronoid process, sseter muscle, ppcr head of the pteryguideus cxtenius. iiwer half of the pterygoideus exlernus. terygoid process. Head of condyloid process. Longus capitis. Rectus capitis anterior. Upper portion parotid gland. Internal carotid artery. Internal jugular vein. Jugular process of occipital bone. -Mastoid cells. Spinal cord. Under portion of cerebellum. Uone surrounding foramen magnum. Fig. 300 the nose, the lower borders of the inferior concha, and the ma.\illar>- sinus. Within the outer wall of the nasal cavity the longitudinal 288 RELATIOX BETWEEX MOUTH, TOXGUE AXD PHARYNX section of the auditory tube may be seen, and a little posterior, the phar^'ngeal 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 nearh' 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 postphary^ngeal 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, when 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 RKLATIO.X BETWKES MOLTll, TOMiUK AM) I'lIAKVXX 291 the sinus directh' downward through the infun(lil)iiluni (ostium fron- talus), the hiatus scMiiihuiaris, and the ostium maxillare into the maxil- lary sinus. Below, and a little outward fnjm the frcjntal 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 ])rocesses, the hiatus semilunaris, the middle concha, and the sei)tuni of the nose, which passes downward to the floor of the ncjse over the intermaxillary suture. There is a slight spur on the right side of the sei)tum. 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 j^ass downward to the mandible, passing thnnigh 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 Donders^ 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 Ije 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 lol)es of the brain ' Arch, of ges. Physio!., Bonn, 1875, Bd. x, S. 91. 292 RELATIOX 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 palpebrs 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. RELATIOX BETWEEN MOT Til, TONGUE AM) PHARYNX 29:i Below iIk'sc sinuses are the eross-sections of the orljits and e\es, the xarious recti nuiscles of the eye, the optic nerve and the ojjluhahiiic arteries and \eins. Between tiie ()rl)its are the middle ethmoidal cells. Within the nasal caxil)' are cross-sections of the median wall and the middle and infericjr concha. On each side of the Icnver portion of the nasal c^ivity 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 l)een forced out (jf shaj^e 1a' the i)ressure of the walls, showing that it had not sufficient power to f(jrce the ah'eolar j^rocess outward. Fig. 304 is made from a transxerse secticjn of a frozen head. It ex- hibits a face narrowed and comi)ressed, the maxillary sinus of the right side is lacking, and the other only rudimentar\'. It will be ncjticed that while the internal structures of the face are \ery much c(jm])ressed, 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 xery much compressed and out of shape and is forced backxvard \nU) the phaiynx, thus interfering xvith respiration, especially xvhen the mouth is closed. These anatomical structures are so modified and deformed that all the physiological functions are greatly interfered xvith. Normally the dorsum of the tongue lies against the hard palate, but, according to Donders,^ at the back part it is separated from the soft palate by a small space. Oxving to the xveight of the jaxv, there is a negative pressure in this space of 2 to 4 mm. . . . The jaxv is main- tained in position, not by muscular eft'ort, but by the pressure of the air; so that, if a tube from a manometer be passed betxx'een the tongue and the palate, the manometer shoxvs a slight negative pressure cor- responding to the weight of the jaxv.- Fig. 305 is from a vertical transverse section of the same skull used in Fig. 304, also shoxving a very compressed condition of the structures surrounding the oropharynx. The uvula is txvisted, 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. 294 RELATIOX BETWEEN MOUTH, TONGUE AND PHARYNX Fig. 304. — Vertical transverse section of a frozen head. RKLATIO.X BETWEES MOUTH, TUXGLE AXD PILIRVXX 2\)o Fig. 305. — X'ertical transverse frozen section. 296 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 w^ould 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 accessory 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 w^as 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 uvula 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. Pcerj-goideus internus Masseter muscle. Palatophar>Tigeus Palatoglossus Mandible. Frontal lobe. Mylo-hyoid Tissue in portion of orbit. Sphenoid bone. Xasal septum. Temporal muscle. N'asal fossa. Soft palate. Masseter muscle. Oro-pharyngeal space. Inferior alveolar nerve and vessels. Tongue Larynx. Fig. 306 298 RELATIOX BETWEEN MOUTH, TONGUE AND PHARYNX Fig. 307. — 'IVansverss frozen section of synimclric.il skull. RELATION BETWEEN MOUTH, TONGUE AND PHARYNX 299 Fig. 308. — Vertical transverse section of narrow skull. 300 RELATIOX BETWEEX MOUTH, TONGUE AND PHARYNX 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. 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, ilasseter muscle. Mandible. Pterygoideus internus. Tongue. Submaxillary gland. Fig. 309.— Anterior view of Fig. 308. RELATION BETWKES MOLTII, TONGUE AND rilARVNN 301 Levator veli palutini (Levator paiati>. Naso-pharynx Internal carotid artery. Post-pharyngeal walL Epiglottis. Supciior longitudinal sinus Inferior longitudinal sinus, l-'alx cerebri. Frontal lobe. Temporo-sphenoidal lobe. Posterior part of orbit. Temporalis. Temporal aponeurosis. Zygoma. Fterygoideus e.xternus. Ramus of trandible. Soft palate. Heep portion of masseter Superior portion of masseter. I'terygoideus externus. Tonsil. Palatnpharyngeus. PalatoKliissHS. Hyoid bone. Thyro-hyoid muscle. Thyroid-cartilage. Omohyoid. Sterno-cleido-mastoid. Cricoid cartilage. Fig. 310. — Frozen transverse vertical section. 302 RELATIOX BETWEEN MOUTH, TOXGUE AND PHARYNX Nose. Nasal bone. Xasal Septum. of the orbit. Occipital bone. Straight sinus. firm's Fig. 3il. — Horizontal frozen section. RELATIOS BETWEEN MOUTH, TOXGUE AM) PIIARVXX MO:^ Fig. 308 is a vertical transverse section (jf a narnnv skull, showing a compressed nasal cavity, a deHected septum, lack of development of the ethmoidal cells, small ma\illar\- sinuses and narrow aKeolar arches. The tongue is compressed, i)art of it jiassing out between the jaws until it meets the cheek. When such conditions are found it usually indicates that the posterior nares are more or less obstructed, either with an osseous deposit or enlarged adenoid tissue. Fig. 309, made from the same skull as Fig. 308, is an anterior view of a vertical transverse section cut just behind the posterior nares. Beneath the dome of the skull, the lateral ventricles may be seen under the parietal lobes of the brain, which are separated by the falx cerebri, extending downward to the corpus collosum. The temporosphenoidal lobes are also seen with the body of the sphenoid bone between them. The most important feature of this vsection in regard to respiration :s that the nasopharyngeal space has become almost closed by the enlarge- ment of the adenoid tissue. Fig. 310 is a similar section to Fig. 309. In the centre of the oro- pharyngeal space, the uvula may be seen, below which is the post- pharyngeal wall, at the bottom of this space, the convex surface of the epiglottis is depicted and in the upper and outer corners the ton- sils. To the inner side of the tonsils, portions of the palatophar^-ngeal muscles are shown, while to the outer side, and slightly covering the tonsils anteriorally are the palatoglossus muscles. Fig. 311 is from a horizontal section cut through the centre of the orbits, the optical foramen and the optic nerves, then backward through various tissues including the brain. This section also exposes part of the ethmoidal cells connected with the upper part of the nose. X'arious convolutions of the brain and cross-section of the mesen- cephalon are shown, also section of the cerebellum, the edges of the tentorium cerebelli, the straight sinus, the falx cerebri, and the longi- tudinal sinus. CHAPTER XIII. MODIFICATION OF THE NORMAL SHAPE OF THE BONE THROUGH ABNORMAL FORCES. The illustrations and descriptions already given demonstrate that there are very marked variations in the character of the bones of the face, and of the sinuses and air spaces situated in and between them. It is evident that there must be some general principles underlying these changes. Causes of Variations in Shape. — ^At the beginning of the growth of the embryo, and continuing throughout life, there are two forces constantly acting upon the body which may be described as the intrinsic and extrinsic; the former giving size and bulk to the tissues, but con- trolled and modified by the latter, which, acting from without, tends to limit the growth and give form to the tissues. If these two forces be normal — that is, properly balanced — in potential strength and application throughout life, the result will be a normally developed organism; but if these forces be interfered with in any way, by lack of nourishment or undue external pressure, the individual may fail to develop a normal physique. Deposit of Salts of Calcium. — If for some reason there is an insuffi- cient quantity of salts of calcium assimilated into the bony tissue, the bones will be soft and fail to give proper shape to the body. The brain-case in such instances is apt to enlarge when the intrinsic growth of the brain forces out the soft yielding structures, while on the other hand an overamount of salts of calcium will harden the bone, and cause it to resist the intrinsic force and prevent proper development. In early life the undue deposit of salts of calcium will solidify the sutures of the brain-case and prevent the expansion of the brain. Microcephalic skulls are sometimes caused in this way. By the use of the surgical engine, artificial fissures have been made in the skull, DEPOSIT OF SALTS OT CALCIUM 305 which alKjwed tiic l)rain-case to expand, and thus enabled the brain itself to enlari;e. The slopes and forms of the heads of the various races are influenced not only by the growth of the brain but also by artificial means such as are practised by the Flathead Indians of North America (see Figs. 312 and 313) and by the prehistoric Indians of the Mesa Verde' (see Figs. 314-319). F"iG. 312. — Side view of a skull of Flathead North American Indian. Prof. Retzius gives a very interesting short description of ten pre- historic skulls, found b\' M. Gustaf Xordenskiold in the cliff dwellings of the Mesa \'crde, in which he observes that an artificial deformation of the crania "has been caused in earh' infanc>- by the application of pressure to the superior parieto-occipital region, this jiart ha\ing been depressed with some flat object. - ' A good collection of these skulls may be found in the Wister Institute, University of Pennsyl- vania. - The Cliff Dwellers of the Mesa X'erde, Southwestern Colorado, Stockholm, 1893. 20 306 MODIFICATIOX OF NORMAL SHAPE OF BONE Fig. 313. — Front view of same skull shown in Fig. 312. Fig. 314. — Side view of a prehistoric Indian of the Mesa Verde. I'RI.lIlsrORIC SKVI.LS :m)', Fig. 315. — Posterior view of same skull as shown in Fig. 314 Fig. 316. — Anterior view of the s.ime skull as shown in Fig. 314. 308 MODIFICATION OF NORMAL SHAPE OF BONE Fig. 317. — View of base of skull shown in Fig. 314. I"iG. 318. — Side view of prehistoric skull from a colktliuii in Colorado Springs I'KIJIIsroKIC SKULLS 3(J'J In Au.uiist, 191 5, while \isitinj^ in Denver, the writer throui^h the courtesy of Dr. A. II. Kelcliani obtained permissicjn to examine si.xty skulls, some of which had recent l\ been exca\ated fn^m the ancient clilT (Kxelliniis of the Mesa Verde, and was fortunate in being able to secure i)hotoi;raj)hs and measurements (jf sexeral of these artificially flattened brach>cephalic skulls. Figs. 314-319, except Fig. 318, are photograjihs (jrrhea alveolaris. The arches are of ^ood width. Fig. 327 is made from a mode-rn manchble (see skull V'lg. 80), show- ing alxnit as powerful a lower jaw as that shown in Fig. 326 and the teeth are good, without dera\-, and no evidence of p>'orrhea alveolaris. Figs. 328 and 329 are made from .r-ray pictures of a boy' 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 njots 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 acti(jn. I '. A X Fig. 327. — Side view of a modern heavy mandible. Fig. 330 gives an .v-ray picture of the ui)i)er 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 permement teeth. Fig. 331 is an .v-ray picture, showing teeth of the right side ot the same jaws as Fig. 330, the third molar is de\eloping 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. 316 MODIFICATIOX OF XORMAL SHAPE OF BONE Fig. i29 Figs. 328 anr] 329. — -Y-ray pictures, showing riglit and left impacted second molars. RiniMEXTARV OR sr I'/'RESSED MOLARS 'M7 Fi^. 332 is an .v-ra\' picture of a lixinj; i)atienl about t\\X'nt\ >ears of age, sliowing a deciduous mandibular second molar, in jiosition, there is no second i^remoiar (leveloi)in;^ to take its i)lace; it will be noticed that the roots of the deciduous tooth ha\e been resorbed to a great extent. Fig. 330. — J^-ray of upper and lower jaw. There is no evidence of ttie development of the leli third molar or of the second premolars. Fig. 333 is an .v-ray i)icture of an ancient Egyptian mandible,' show- ing the retention of a second deciduous molar and the absence ot the developing second ])rem()lar similar to the missing premolars in Fig. ;'-^;^2. 1 Belonging to the collection of Dr. \\. (". Kirk". 318 MODIFICATIOX OF XORMAL SHAPE OF BONE Figs. 334 and 335 are .v-ra>' 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. — A'-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 show^ing tw^o impacted third molars; the left one is nearly horizontal, while the right one is badly "locked" under the posterior portion of the second molar. RU DIMES r. I A' 1 ■ OK SL P PRESS KI) MOL. 1 A'.V ■M\) Fig. 33' picture of llie same niandil)le as shown in Figs. 336 and 337. In this way the position of the roots is Fig. 332. — A'-ray of modern jaws showiiij; deciduous molar. (A'-ra\- !)>• Dr. Pancoast.) Fig. 333. — -Y-ray picture of an ancient Egyptian mandible. (A'-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 .v-ray picture, showing a developing lower rudimen- tary fourth molar in a modern mandible.^ 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, ^ 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. ^ X-ray picture loaned In- Dr. Blum of New York. IWDIMEXTARV OK Sir PRESS ED MOLARS 321 Figs. 336 and 337. — Two halves of the same iiiaiuhblc, showing two impacted third molars. oi ^^^'' ^^^' — '^''^^y picture showing two impacted third mandibuhir molars. 322 MODIFICATION OF NORMAL SHAPE OF BONE Fig. 339. — A'-ray picture showing impacted lower rudimentary fourth molar. Fic. 340. — Photograph showing five maxillary incisors. Fig. 341. — Z-ray showing five deciduous and five permanent incisors. .S L TERX LMERA R \ ' FREM OL. 1 A' J KJ: J U 323 SUPERNUMERARY PREOMLAR TEETH. It is not iiiuisual to lind t'Xtra prcniolar teclh in ihc maxilla or mandible. Dr. Robert II. Iv\- has reported a case of si.\ mandibular prenKjlars, et closely resembling them."- FlG. 342. — Plaster cast, showing six premolars lecth. Dr. Hopewell-Smith mentions a case of a negro having a super- numerary premolar on each side of the mandible.^ 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 j)r()cess of eruption. ' Dental Cosmos, June, 1915, p. 670. - Dental Pathology and Therapeutics, fifth edition, p. 282. ' Dental Anatomy and Phys oiogy, 1913, p. 215. 324 MODIFICATIOX OF XORMAL SHAPE OF EOXE The four incisors and two canine teeth were well developed and in normal positions. Fig. 343 is an .v-ra}.' 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. (A^-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 sec(^nd molar indicates that the first molar had .s77v:a'.\7 .i//:a'.i AT i'in with well-formed crowns and an inii)aeted tooth ma>' be seen between the llrst and second premolar to which no better name can be given than extra premolar, making eight premolars in the mandible. Fig. 344. — A'-ray showing four premolars. (A'-ray hy Dr. Pancoast.) Fig. 345 is made from a j^laster 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 fairh- good crowns, while a sixth premolar on the right side is deformed. It will be noticed in this illustration that there are two elevations 526 MODIFICATION OF NORMAL SHAPE OF BONE on the inside of the jaw, above the sublingual fossae, 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 vshows the under surface of the upper jaw seen in Fig. 325 with a rudimentary fourth molar on each side of the arch. Si TERM M ERA RV I'RKMOLAR TEETH 327 Figs. 347 and 348 show the uiukT surfare of two upper jaws, the occkiding surface of the teeth, and their rehitive size. Fig. 348 is about the nornuil size, while V\g. 347 is very much larger. In Fig. 347 there Supernumerary tooth Supernumerary toolh Fig. 348 P^iGS. 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 \iew of the palatal surface of an upper jaw, showing the occluding surfaces of the teeth, with two supernumerar\- teeth situated on the l)uccal sides of the second molars. 328 MODIFICATION OF XORMAL SHAPE OF BOXE Supernumerary tooth Supernumerary tooth Fig. 349. — \'ie\v 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. SL I'KRX L MER. \RV RRLMOL. 1 A' TEETH 329 Comparison of Mandibles of a Caucasian and an African Negro. — Figs. 350 and 351 affords a coiiiiKirison hetwcL-n the niandihlcs of the Caucasian and of the Fan tribe negro (West Africa). Thex' were photographed ii|)()ii the same phite, showing their rehitixe size and shape. The teeth and alveolar process in Fig. 350 ha\e 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 posteri(jr 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 hrst 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 A SKY LOS IS 331 writer l)elieves tlial this i)iclurc', and others to folhnv, sliow thai this is a typical face beloniiing to those who ha\e or who have had ank\ - losis of the jaw. cither true or false. This i)atient has suffered from a false a!ik\ losis since about nine \ears of age. Fig. 353 is taken from the right side of the same face, showing a scar extending ui)ward and backward from the angle of the mouth to the region of the external acoustic meatus. The scar was i)roduced b\- a F"iG. 352. — Characteristic appearance in the region of the lower jaw in long-standing ankylosis. Fig. 353. — Opposite side of face of Fig. i52, showing scar caused by a gunshot wound, the 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 IXFLUEXCE OF MUSCULAR ACTION forcing the jaws asunder, as shown in Fig. 354. The main object in using the apphance was to stretch the temporal and masseter muscles of both sides. In a few weeks the patient could open the jaw^s without the appliance, as shown in Fig. 355. There was at this time sufficient impro\ement 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- mandiljular raphe, myositis ossificans affecting the masseters, pterygoid or buccinatfjr muscles. Typical Ankylosed Mandible. — In cases of true ankylosis of the jaw, especially those of long duration, certain changes in the form of TYriCAL .WKVLOSIJ) M.WDIIiLE 333 the nian(lil)l(' arc not ici-ahli', not only on the affVclcd side* wlicii the ank> losis is unilateral, but also on the o|)i)osite side. The eharaeter of these chaniies is well shown in I^^i.^s. 356 and ,^57. I'"i^. 356 is a view of the unankylosed side of a Ixpical case of true unilateral ankylosed jaw. The condxloid ])rocess is shortened and its articulating; surface is chani^ed. Instead ol heinu rounded at the top it has more of the ¥iv,. 355. — Results of trcatnu'iit for false ankylosis. shape of a (lOthic arch. ThrouL;h this shortening of the conch loid, the coronoid process is apparently elongated. The angle of the man- dible is also elongated so that it forms a projecting point, and tin- base of the bone under the mental foramen is considerabh- thickened. The mental i)rocess is much diminished in size. There is no loss of >o4 IXFLUEXCE 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 vertically 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 TRUK AX KY IDS IS 335 out, and is sharjil)' serrated on the articulating^ surface. The articu- lating surface of the nian(Hl)uhir fossa is also changed to correspond to that of tlie condxle with which it was interlocked. The angle of the jaw on ihis 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 ])rocess, is fuller anrl 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 unank\losed side. Fig. 359 shows the ankylosed side. The lower jaw closely resembles that shown in Fig. 357, in the descending angle, the receding chin, 386 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. e., 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 CIIAMiKS L\ THE MAMJIHL LM< A RJTCL LATIU.X ■.va: muscles. It illustrates the \ari()us nuiscles under si)asni(Klic acti{Jii, inclicalini; how their frecjuent use under such conditions ma\' 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, throu.i>h the necessity of masticating on the opposite side of the mouth, and the consequent use oi the jaws in an abnormal manner. In this way i^reat alterations can be made in the mandibular articulation, and in one or both man(lil)ular fossa*. Fig. 360. — The action of the tlcprcssor muscles of the iiiaTulil)le in ank>losis. The articular tubercle may be entirely lost by resorption. The places of attachment for the muscles of mastication, as the coronoid i:)rocess, the outer surface of the ramus, the angle of the jeiw, 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 gi\en to show the changes brought about by the loss of teeth and changed position of occlusion. 22 338 IXFLUEXCE OF MUSCULAR ACTION Fig. 361 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 left 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 CHAXCKS T\ Till'] .\f.\.\/)f/U/..\R ARTICULATION 339 Fig. 362. — The ri.i>;ht mandibular articulation from skull shown in the i^recedinK photograph, where the condyloid process has not been carried forward. Fig. 363.— Right side of a skull. See mandible, Fig. 9. 840 IXFLUEXCE OF MUSCULAR ACTION mastication was performed, the muscles were thus overworked, and the places of attachment and of their origin and insertion are strongly- marked in consequence. Fig. 363 gives a view^ of the right side of a skull. It w411 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 partl>' on the great wing of the s])henoid. There seem to be two ways in which this deformity could occur. One is by the lack of growth in CI/.WCFS /.\ /■///■: M.WDf/ilLAR .1 A'/VCTAJ 77r>.V :'>41 the raimis aiid hods of boiu'; the otluT theory is that the bone- urew to its normal size (as there is evidence of its having articulated in the niandil)iihir fossa), when an atrophied condition may have occurred wiiich reduced the size of the ramus and part oi the body; in order to Fig. 365. — Under view of the articulation ol ihc niaiidilile as shown in Fig. 364. See base of skull, ¥\g. 93. keej) up occlusion of the teeth, the condyloid process mo\ed forward, first articulating on the articular tubercle, and as the atrophy progressed, moving still forward to keep the occlusicjn. until the condxloid i)rocess 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 Februar}^ 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 of a lad suffering from hypertrophy of the gums and alveolar process. Fig. 367. — Tissue removed from upper jaw of patient shown in Fig. 366. 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 writer has seen recorded. The case was operated upon by the late Professor Garretson and the writer, February 17 and March 11, 1893.^ ' A full description of the operation will he found in the Dental Cosmos, June, 1893. IIVPKRTROP/IV OF aCMS AM) A/AKOLAR PROCESS 343 Fig. 366 is froiu a photograph of the lad taken before the operation. Similarh' to the first picture shown in the ankylosis series, this boy a|)i)ears to ha\e an\thin,i^ l)iit an intellii;ent 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 carr>- the incision around to the alae of the nose. By the aid of the surgical engine and other instruments, the portion 344 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 imi)r(n'ement in his appearance, and it seems to be conclusively demonstrated that Professor Garretson was right in his judgment. CHAi'ri:k XVI. Till-: RKLATIOX OV TllK TWO JAWS. The Relation of the Upper and Lower Jaws Varies Throughout Life. — There is also a difference in tlieir relative time of (le\eloi)nient. The lower jaw is developed slii'htl>' in advance of the uj^per one and is formed trom two processes or buds, the upper jaw bein^ formed from four processes or buds — two from the sides and two from ab(ne. 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 i:)alate 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, perhai)s, 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 /;/ iitero is such that the weight of the entire fetal body could be thrown upon the vertex, the l^ressure 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 ui)per alveolar ridge is immediately over 346 RELATION OF THE TWO JAWS the alveolar 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 alveolar ridge is in vertical line within that of the lower jaw, as is w^ell illustrated in Figs. 196 and 372 and in Figs. 375 and 376. Congenital cleft palate has also been attributed to the effects of s^^philis 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. The}' 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.^ 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. Fig. 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. ' Vor surgical procedure and further description of cleft palate, see Brophy's Oral Surgery, p. 563. ' For description of other features shown in this illustration, see Fig. 195. MOLD L J'(>.\ WHICH THE MAXILLA IS LoKMED :\A\ Fig. 372 is taken from an adult jaw. If lini's he drawn through the longitudinal axes of the upper and the lower teeth, it will be found that those through the former, as the}' extend toward the coronal surfaces, pass a little outward, while those passing up through the lower teeth incline inward. This is e\ idence 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 aKeolar j)rocess has extended out- Anterior fossa of brain-case Crista galli Orbit Medial wall of nasal ca\nty Ostium ma.xillare Maxillary sinus Zygoma ^i axilla ■ Dental germs Mandible Fig. 371. — Vertical tran.sversc 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. FiS- 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. 348 RELATION OF THE TWO JAWS The Resorption of the Alveolar Process. — As the alveolar 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. P'lG. 373. — Anleri(jr 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 bIo(xl 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 KI-.LATIOXS I\ EXT RUM li OLD ACE 349 persists for a coiisidt'iaMN loiiiici- period. thoii;' formerly occupied. The Relations in Extreme Old Age. — As a result, there is i)roduced a twofold effect upon the relation of the jaws. As the resorption (jf the alveolar process goes on, the vertical distance between the body i){ the lower jaw and that of the upi)er is lessened, while the natural difference in their width is increased. The area of the upjKT 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 imder 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 l)romi)tly 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 alxjut the same shape and size. Fig. 374 is from an adult of about twenty-fi\e 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. Fi^s. 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 ])rocess resorbed after middle life, the upper and lower jaws cannot be again brought into occlusion through their aKeolar borders. 350 RELATION 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 3'ears 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 F"igs. 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 MAU'ORM Alios OF TIIF JAWS W'A prevents the normal occlusion of the jaws, during either rest, speech, or mastication, will bring al)out malformation of these i)arts. Among the causes which prevent the normal bringing t(jgether 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 sh(juld be corrected, whether it is caused by bony obstruction, in hypertrophy of the mucous membrane, or by adenoid growths in or about the naso- phanngeal space or by narrow dental arches. While the jaws are! kept apart the muscles in connection with the orbicularis oris are some-l 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 (.A 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 ain- 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. I NDEX. Abscesses, 238-24 1, 209 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, 3^2, 333 of mandible, changes in, 333 typical, 332 unilateral, 334 true, 335 Antrum of Highmore, 217 Arter\-, 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, 27 1 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 Calcum, deposit of salts of, 120, 167, 304 Cancellated tissue, arrangement of, in jaws, 20, 33, 123 Canine teeth, impacted, 176, 177, 178, 179, 1^0 mandibular, 111 crown of. 111 anterior face of, 112 cutting edge of, 112 labial face of, 1 1 1 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, ii, 34 Crista galli, cell of, 251, 262, 275, 276 variations of, 264-284 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, 264-284 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, in 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 sizG 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 IXDKX 355 H Hard palate, 100 Hare-lip, caiisi- of, 345, 346 Head, analumical variations of, 17 frozen sections of, 2.S5-303 directions for niaicin^, 285 Heavy nKui(lil)le, 2.S, 315 skull, SO 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 c^sts in, 193 diagnosis of, 170, 192 value of .Y-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, HI crown of, 111 cutting edge. 111 labial face, 1 1 1 lateral faces, 1 1 1 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, 3i structure of, 33 lower, 23 upper, 81 intermaxillary suture of, 81 interpalatal suture of, 81 interpremaxillary suture of, 81 maxillnpremaxillary suture of, 81 palatomaxillary suture of, 81 premaxillae of, 81 Jaws, malformation of, causes of, 350, 351 modern, .v-ray pictures of, 318, 319 relations of, 345 in old age, 349 variations of, 345 x-ray picture of. 125, 126. 128, 129, 130 356 INDEX Lacrimal nerve, 143 Lamina dura, 77 Lingual nerve, 151 branches of, 151, 152 Long ciliary nerves, 144 M Malformation of jaws, causes of, 350 Mandible, 23 abnormal position of condyle of, 62 abnormalities in density of, 65 alveolar process of, 25 anatomical arrangement of, pathological sig- nificance of, 38, 40 surgical significance of, 38, 42 angles of, 30 ankyloid, typical, 332 ankvlosis of, action of depressor muscles in, 337 articulation of, 68 anatomy of, 68 at birth, 73 in carnivora, 71 changes in, 72 in man, 71 mechanism of, 70 cancellated structure of, 43, 44 cast of, 45 Caucasian, 328 Chinese, 30 cribriform tube of, 34 cross-sections of, 41, 42, 46, 47, 49, 65 dental branches of, 37 development of, records of, 39 diseased, sequestrum of, 59 Egyptian, 317, 319 of Fan tribe. West Africa, 328 of flat-faced person, 30 fractures of, 59 growth of, 23, 37 heavy, 28, 315 hydrogen peroxide necrosis of, 53 of Indian, 27 inflammatory changes in, 48 longitudinal section of, 44 measurements of, 30 in various ages, 31, 32 various types of, 31 mental process of, 25 method of, growth of, 37 necrosis of, 49, 55 phosphorous, 54 prehistoric, 318, 320 prognathous, 28 regeneration of, 49 of bone in, 57, 58 relation of, to base of skull, 124 Mandible, .relation of condyloid process of, to mandibular fossa, 69 of rodents, 72 secondary deposits of, 64 shape of, 23 in aged persons, 24 at maturity, 24 of South African negro, 27 surgical pathology of, 38, 42 of inflammatory changes in, 49 triangle of, 67 variations in, 67 tubercular necrosis of, 52 typical, upper part of, body of, 122 U-shaped, vascular supply of, 136 vascular supply of, 136 of vertebrates, 72 Mandibles of different races, 26 comparison of, 26, 329 Mandibular articulation, 68, 70, 73, 74, 324 changes in, 337 through loss of teeth, 338-341 canal, ii canine teeth, 111 condyle, neck of, fracture of, 60 correction of, 75 fossa, relation of, to condyloid process of mandible, 69, 71, 72 incisor teeth, 110 molar teeth, 113 nerve, 147 premolar teeth, 112 teeth, definition of, 110, 111 neck of, horizontal section of, 126, 127 Masseteric nerve, 148 Maxilla;, 76 alveolar process of, 77 external plate of, 77 internal plate of, 77 architectural features of, 76 definition of, 76 mold for formation of, 346 pathological relations of, 77 vascular supply of, 135 Maxillary alveolar nerve, distribution of, 140 canine teeth, 105 incisors, 103 five, 322 molar teeth, 107 nerve, 145 branches of, 146 premolar teeth, 106 sinus, 94, 128, 129, 217 anterior wall of, 225 anteroposterior section through, 128 dental relationships of, 235 descriptive anatomy of, 217 development of, 219 floor of, 223 impacted tooth in, 178 infection from teeth, 236-242 I.XDKX Maxillary sinus. larj;e, 98, 22.^ nas