fm m V '*'*" ■ , - -*,^ •^ ^ vs? ^ V ^ '^ BOUGHT WITH THE INCOME' - ,'• * .-. FROM THE ■*',,.•'- ?^- S'AGE ENDOWMENT FUND ' ■' THE GIFT OF :, ■--, ,., XS91 A..^.H.jj±x. )j:hM&j Date Due . - - xfy'-^ ? % ' % QM 531.M115 ""'"™"* '-'""^ V.I "*fti™im?iHiiB,,.',!f relation to medi 3 1924 024 791 737 531 v.l ^^ K ^^ Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924024791737 Regional Anatomy m ITS EBLATION TO Medicine and Surgery. BY GEOEGE McCLELLAN, M.D., LECTURBR ON DESCRIPTIVE AND REGIONAL ANATOMY AT THE PENNSYLVANIA SCHOOL OP ANATOMY, PROFESSOR OP ANATOMY AT THE PENNSYLVANIA ACADEMY OP THE FINE ARTS, MEMBER OF THE ASSOCIATION OP AMERICAN ANATOMISTS, ACADEMY OP NATURAL SCIENCES, ACADEMY OP SURGERY, COLLEGE OF PHYSICIANS, ETC., OF PHILADELPHIA. ILLUSTRATED FROM PHOTOGRAPHS TAKEN BY THE AUTHOR OP HIS OWIsr DISSECTIONS, EXPRESSLY DESIGNED AND PREPARED FOR THIS WORK, AND COLORED BY HIM AFTER NATURE. *' L'anatomic n'est pas telle qu'on Venseigne dans les 6coles." — Bichat, IN TWO VOLUMES. VOL. I. PHILADELPHIA: J. B. LIPPINCOTT COMPANY. 1891. Copyright, 1890, by Gborqb McClkllan, M.D. TO THE MEMORY OP MY TATHEK, JOHN H. B. McCLELLAN, M.D., AND OF MY GEANDFATHER, GEOEGE McCLELLAN, M.D. PREFACE. There has been a great deal said of the importance of anatomical knowledge, which is nniversally conceded to be the foundation of the study of medicine. As a teacher of anatomy, I have used all my influence to impress this on the minds of students, assuring them that the best book on anatomy is, and always will be, the body itself. In the curricula of the colleges and universities this is emphasized by a compulsory course in the dissecting-room, and each candidate for a degree is obliged to dissect three parts — the head, and the extremities, with contiguous portions of the trunk — at least once. From the knowledge gained by these dissections, and from lectures and text- books, a student is supposed to acquire the information necessary to enable him to work intelligently and beneficially in his profession. He is expected to learn anatomy from his three parts. Considering the facts that the first part is generally wasted in acquiring the methods of using the instruments ; that all the parts are seldom carefully injected with proper preservative ; that the student rarely has the opportunity of seeing the viscera of the cranium, thorax, and abdomen in situ, much less of examining them and noting their size or structure and their relative positions to one another and to the cavities which contain them ; and that often the value of the opportunity is not estimated until it is lost, it cannot be a matter of wonder that students look upon anatomy as one of their chief difficulties, and that only a few continue its study after graduation. There are many practical obstacles in the way of obtaining better and more abundant material for such research ; but, after some years' experience, I am forced to acknowledge that, even if these obstacles were overcome, the distaste for the actual labor of dissecting, which, besides being exacting, is associated with much that is revolting, and even haz- ardous to health, would deter many students from gaining that practical knowledge from personal observation which would enable them to recognize the different tissues by the sense of touch as well as by the sense of sight. In a crowded lecture-room only those who are very near can see the demonstrations so as really to profit by them. Extempore drawings are of great value in awakening and retaining the interest of students, whose memories are often overtasked, and have an advantage over the most carefully prepared diagrams, models, or preparations; but there VI PREFACE. cannot be any means of illustration equal to the real thing in teaching, and the best substitute is that which aims at producing the most realistic impressions. Such illus- trations have been attempted in the plates for the present work. Regional Anatomy, or the anatomy of the diiferent regions of the body individ- ually considered, in the relations of their parts to one another, as they are naturally found, is really the most direct method of studying the subject. It is also the most useful form of anatomical research, and, although it may at first sight seem more difficult because it presents a complex in the place of a simple object, such as was demonstrated in the old method of considering the bones, the ligaments, the muscles, the vessels, and the nerves as so many distinct structures, the greater interest soon growing from the evidence of its practical usefulness fully compensates for the effort required. The interest which my classes have shown in this treatment of anatomy has led me to undertake this work. It is largely the result of information acquired by dissecting, and of clinical observations in hospital and private practice. In its preparation I have consulted such ancient and modern books on anatomy as I could obtain, and have gleaned from them much information which suggested many of the dissections showing relations of structures. No quotation from or direct refer- ence to these works, however, is introduced in the text, which has also, for the sake of clearness, been kept free from notes. Assuming some previous knowledge of the bones on the part of the reader, I have exercised the privilege of adopting such modifications in the nomenclature as may render certain parts more easily comprehended, but have retained such names and tei-ms as have an historic association, believing that they add to the interest and fasten themselves on the memory, rather than detract from the mastery of so difficult a study. It is to be regretted that anatomy loses much in consequence of the want of a definite nomenclature. The suggestions of modern writers as to technical terms, if accompanied by a corresponding clearness of description, might be of benefit to the student; but, while not underrating the importance of scientific exactness of expression, I am of the opinion that the ordinary student's attention soon wearies of technicality, whether written or spoken, and I have therefore made use of such terms in my text as experience has shown to be most easily understood and remembered. Anatomy, to be of use, must be made a practical and not a theoretical study. It is difficult enough pro re naia, and, if hard, need not be dry. Should the present book fulfil its mission, it will be by presenting the matter in a new form, which it is hoped will prove interesting and useful, alike to the practitioner and to the student who intends to pi'actise. The plates are expressly prepared to illustrate and verify the descriptions, and are as faithful representations of the dissections as they could be made. It should be borne in mind, however, that no true picture of the actual subject will have the distinct demarcation and clearness of a diagram, any more than the representation of a natural landscape indicates mountains, rivers, and boundary lines with the exactness of a map. Diagrams will therefore always be useful to the student in showing him what he ought to see, but such illustrations as are here attempted PREFACE. Vii should be valuable in enabling him to recognize things as they actually are. These representations are intended to meet the need both of the beginner in dissecting, who is appalled by the want of correspondence between that which he actually sees and that which he lias been led to expect by diagrams or description, and of those whose time is too gravely occupied by the pressure of professional duties to warrant their dissecting for themselves. Accuracy has been the chief object, and I have relied upon the unfailing precision of the camera to present the true relations of the parts, which were in each case left in situ, only the adipose and connective tissues being removed, to give distinct impressions. Much thought, time, and expense have been given to tlie photograj^hic details, such as the arrangement of the light to modify the shadows, the exposure and development of the negatives, and the subsequent printing and toning of the pictures to get the desired effect for the application of the water-colors. The coloring of the originals from which the plates were made on stone, under my personal supervision, was a study from nature, with j)erhaps some excess of tint or shade, as might be expected where the paints were mixed and applied with more enthusiasm than artistic skill. The dissections, in all about three hundred, were invariably the work of my own scalpel, and were all done upon subjects selected as best showing the normal relations of the parts, without pathological change, while such facts as seem valuable regarding the conditibn or modes of preparation are mentioned in the description of every plate. Each figure is also accompanied by a separate and complete explanatory table, — every number being placed in regular order, so that any object may be readily found. To Messrs. Lippincott Company, the publishers, my thanks are due for the warmth with which they have entered into my undertaking, for the strong sympathy and in- terest they have shown in my work, and for the care which they have taken to present the text to the reader in a clear and attractive form. To Messrs. Armstrong & Co., of Boston, I am indebted for their painstaking fac-simile reproductions of my systematized views of dissections, which preserve the photographic accuracy and the realistic effect of tiie coloring of the originals, and whicli not only ought to render this an acceptable text-book, but should also awaken a keener interest in tlie study of Regional Anatomy. GEORGE McCLELLAN. Philadelphia, October, 1890. CONTENTS OF VOLUME I. THE REGION OF THE HEAD pages 1-60 Surface-Form and Landmarks of the Skull. — Bones of the Head. — Sutures. — Tables of the Skull. — Diploic Structures. — Fontanelles.— Foramina.— Scalp. — Scalp Hair. — Arteries of the Scalp. — Veins of the Scalp.— Lymphatic Vessels of the Scalp. — Nerves of the Scalp. — Occipito-Fron talis Muscle. — Aponeurosis of the Scalp. — Epicranium. — Peri- cranium. — Temporal Fascia.— Thickness of the Skull-Cap .—Dura Mater.— Pacchi- onian Bodies. — Tentorium. — Falx Cerebri. — Falx Cerebelli. — Arteries of the Dura Mater. — Arachnoid. — Cerebro-Spinal Fluid. — Pia Mater. — Arteries of the Brain. — The Brain. — Lobes of the Cerebrum. — Primary Fissures of the Hemispheres. — Secondary Fissures of the Hemispheres. — Fissure of Rolando. — Sylvian Fissure. — Parieto-Occip- ital Fissure. — Hippocampal Fissure. — Transverse Fissure. — Interparietal Fissure. — Convolutions of the Brain. — Cranio-Cerebral Topography. — Base of the Cerebrum. — Cranial Nerves. — Medulla Oblongata. — Pons Varolii.— Cerebellum. — Fourth Ven- tricle. — Aqueduct of Sylvius. — Third Ventricle. — Foramen of Monro. — Lateral Ven- tricles. — Fornix. — Septum Lucidum. — Fifth Ventricle. — Corpus Striatum. — Optic Thalamus. — Corpus Callosum. — Diverging Fibres of the Medullary Structure. THE REGION OP THE EAR pages 60-79 Pinna, or Auricle. — Cartilages of the Auricle. — Ligaments and Muscles of the Auricle. — Arteries, Veins, and Nerves of the Auricle. — Auditory Meatus. — Membrana Tym- pani. — Tympanum, or Middle Ear. — Ossicles. — Facial Nerve within the Temporal Bone. — Internal Ear, or Labyrinth.— Organ of Corti. — Auditory Nerve. — Auditory Artery and Auditory Vein. THE ORBITAL REGION AND THE EYE pages 79-107 Walls of the Orbits. — Eyebrows. — Eyelids. — Muscles of the Eyelids. — Lachrymal Gland. —Conjunctiva. — Cornea. — Sclerotic Coat. — Muscles of the Eyeball. —Capsule of Tenon. — Sensory Nerves of the Orbit. — Ophthalmic or Ciliary Ganglion. — Ophthalmic Ar- tery. — Optic Nerve. — Choroid Coat. — Ciliary Muscles. — Iris. — Pupil. — AqueousHumor. — Crystalline Lens. — Vitreous Body. — Retina. — Porus Opticus. THE REGION OF THE NOSE AND THE NASAL CAVITIES . pages 107-116 Nasal Bones. — Cartilaginous Framework of the Nose. — Muscles in connection with the Nose. — Arteries, Veins, and Lymphatics of the Nose. — Nerves of the Nose.— Nasal Fossae or Cavities. — Infundibulum. — Nasal Meatuses. — Nasal Duct. — Schneiderian Mucous Membrane and Olfactory Cells. — Anterior and Posterior Nares.— Vessels of the Nasal Cavities. — Olfactory Nerves. X CONTEXTS. THE REGION OF THE PACE pages 116-130 Landmarks of the Face. — Skin of the Face. — Muscles of the Face. — Arteries of the Face. — Sensory Nerves of tlie Face. — Branches of the Trifacial Nerve of the Face. — Motor Nerves of the Face. THE REGION OP THE PAROTID GLAND pages 130-136 Parotid Fascia. — Duct of Stenson. — Extra- and Intra-Parotid Lymphatic Glands. — Branches of the External Carotid Artery in relation to the Parotid Gland. — Lobes of the Parotid Gland. — Branches of the Facial Nerve (Pes Anserinus) in relation to the Parotid Gland. — Removal of the Parotid Gland. THE DEEP STRUCTURES OP THE PACE pages 136-148 Landmarks. — Temporo-Maxillary Joint. — Pterygoid Muscles. — Branches of the Internal Maxillary Artery and Vein.— Spheno-Palatine or Meckel's Ganglion. — Branches of the Inferior Maxillary Nerve. — Otic Ganglion. — Superior Maxillary Bones. — Antra of Highmore. — Palatine Canals and Foramina.— The Incisive Bone in relation to Cleft Palate. THE REGION OP THE MOUTH pages 148-175 Lips. — Coronary Arteries. — Buccal Glands. — Gums and Teeth. — Cavity of the Mouth. — Hard Palate. — Soft Palate. — Pillars of the Palate.— Muscles of the Palate. — Vessels and Nerves of the Palate. — Tongue. — Papillae. — Muscles of the Tongue. — Sublingual Salivary Gland. — Submaxillary Salivary Gland. — Hyoid Bone. — Lingual Artery. — Exposure of the Lingual Artery for Ligation. — Motor Nerve (Hypoglossal) to the Tongue.— Sensory Nerves (Lingual and Glosso-Pharyngeal) to the Tongue. — Submaxillary Ganglion. — Lymphatic Vessels to the Tongue. — Fauces. — Tonsils. — Pharynx. — Muscles of the Pharynx. — Eustachian Tube, THE REGION OP THE LARYNX pages 175-187 Cartilages of the Larynx.— Thyroid, Cricoid, and Arytenoid.— Epiglottis.— Vocal Cords. — Glottis.— Intrinsic Muscles of the Larynx. — Extrinsic Muscles of the Larynx. — Nerves and Vessels of the Larynx. THE REGION OP THE NECK pages 187-240 Landmarks. — Skin on the Neck.- Platysma Myoides Muscle. — Cutaneous Nerves and Vessels of the Neck.— Deep Fascia and its Reflections.— Sterno-Cleido-Mastoid Mus- cle. — Triangles of the Neck. — Digastric Muscle.— Omo-Hyoid Muscle. — Common Carotid Artery and Jugular Vein.— Inter-Carotic Body.— Pneumogastric Nerve in the Neck.— Glosso-Pharyngeal.— Descendens Hypoglossi.— Deep Cervical Plexus of Nerves.— Deep Muscles at the Side of the Neck.— Trapezius Muscle.— Deep Mus- cles at the Back of the Neck. — Cervical Spinal Nerves. — Vertebral Arteries. Cervical Vertebrae and their Ligaments. — Cervical Portion of the Sympathetic Nerve and Ganglia.— Scalene Muscles. — Structures collected at the Root of the Neck.— Deep Cervical Lymphatic Glands.— Subclavian Arteries.— Subclavian Veins. —Ligation of the Subclavian Arteries.— Thyroid Body.— Trachea. —Operation of Tracheotomy. CONTENTS. xi THE REGION OP THE THORAX pages 240-320 Skeleton of the Thorax.— Ribs and their Articulations.— Sternum.— Intercostal Spaces.— Dorsal or Thoracic Vertebrss.— Skin on the Anterior Surface of the Thorax.— Mam- mary Glands. — ^Vessels and Nerves of the Mammary Glands. — Operation for Removal of the Breast. — Deep Fascia of the Anterior Surface of the Thorax. — Pectoralis Major and Minor Muscles. — Costo-Coracoid Membrane.— Intercostal Muscles. — Tri- angularis Sterni Muscle. — Internal Mammary Artery.— Anterior, Middle, and Poste- rior Mediastina. — Thymus Gland. — Pleurae. — Pleural Sinuses. — The Lungs. — Relation of the Lungs in Expiration and luspiration. — Fissures of the Lungs. — Lobes of the Lungs. — Roots of the Lungs. — Ligamenta Lata Pulmoualia. — Bronchi. — Lobules. — Structure of the Lungs. — Bronchial Glands. — Pulmonary Vessels and Nerves. — Peri- cardium. — The Heart. — Relative Position of the Heart to the Walls of the Thorax. — Exterior of the Heart. — Coronary Arteries.— Shape of the Heart. — Auricles and Ventricles of the Heart.— Openings and Valves of the Heart. — Structure of the Heart. — Nerves and Lymphatic Vessels of the Heart. — Superior Vena Cava. — Relations of the Different Parts of the Aorta. — Anomalous Distribution of the Great Vessels from the Aorta, and Condition of the Heart. — Common Pulmonary Artery.— Pulmonary Veins.— Systemic Arteries, and their Variations in Different Localities. — Anastomosis of Arteries. — Structure of the Walls of the Arteries. — Systemic Veins, and their Variations in Different Localities. — Superficial and. Deep Veins. — Vense Comites.— Structure of the Walls of the Veins.^Capillaries. — Vaso-Motor Nerves. — The Blood. — Developmental Changes in the Heart and Vascular System. — Ductus Venosus.— Ductus Arteriosus.— Hypogastric Arteries. — Umbilical Arteries.— The Fcetal Heart, and the Circulation of the Blood before Birth. — Heart-Sounds. — Arterial Pulse.— Topographical Survey of the Chest for Clinical Study of tlie Relative Positions of the Heart and Lungs. — Descending Thoracic Aorta and its Branches. — (Esophagus. — Operation of (Esophagotomy. — Pneumogas- tric Nerves in the Thorax. — Thoracic Duct.— Azygos Veins.— Splanchnic Nerves. THE DIAPHRAGM pages 320-323 Ligamenta Arcuata.— Openings in the Diaphragm.— Vessels and Nerves of the Diaphragm. THE REGION OF THE SHOULDER pages 323-337 Shoulder-Girdle.— Clavicle. — Scapula. — Muscles of the Scapula.— Upper End of the Humerus. — Shoulder-Joint.— Capsular Ligament.— Tendons of the Muscles in rela- tion to the Shoulder-Joint. — Bursae in relation to the Shoulder-Joint.— The Deltoid Muscle and its Insertion.- Grouping of the Muscles in effecting the Various Move- ments of the Shoulder.— Dislocations of the Shoulder.— Fractures at the Shoulder.— Relations of the Parts in Amputation at the Shoulder. THE REGION OF THE AXILLA pages 337-348 Axillary Folds.— Axillary Fascia.— Cervico-Axillary Passage.— Relations of the Cuta- neous Branches of the Intercostal Nerves to the Axilla.— Axillary Artery and its Branches.— Axillary Veins.— Brachial or Axillary Plexus of Nerves.— Lymphatic Glands of the Axilla. xii CONTENTS. THE REGION OP THE ARM pages 348-362 Lower Portion of the Humerus.— Epicondyles and Supra-Condyloid Ridges.— Surface- Marking. — Skin.- Bicipital Depressions. — Deep Fascia of the Arm. — Hiatus Semilu- naris. — Biceps Muscle. — Brachialis Anticus Muscle.— Triceps Muscle. — Brachial Ar- tery and its Branches.— Operation for Ligating the Brachial Artery. — Vense Comites of the Brachial Artery. — Branches of the Brachial Plexus in the Arm. — Median Nerve. — Musculo-Cutaneous Nerve. — Ulnar Nerve. — Internal Cutaneous Nerve, and Musculo-Spiral Nerve.— Fractures of the Shaft of the Humerus. — Relations of the Parts in Amputation through the Middle of the Arm.— Ossification of the Humerus. THE REGION OP THE ELBOW pages 362-372 Upper Ends of the Ulna and Radius. — Elbow-Joint. — Superior Radio-Ulnar Joint. — Skin over the Front of the Elbow. — Superficial Veins at the Bend of the Elbow. — Bursee about the Elbow. — Dislocation at the Elbow. — Fractures at the Elbow. — Relations of the Parts in Amputation at the Elbow. — Resection of the Elbow. THE REGION OP THE POREARM pages 372-396 Shafts and Lower Ends of the Radius and Ulna. — Inferior Radio-Ulnar Joint. — Inter- osseous Ligament. — Humero-Ulnar Shaft. — The Skin over the Forearm. — Superficial Radial Vein. — Cutaneous Nerves of the Forearm. — Deep Fascia of the Forearm. — Muscles of the Forearm. — Radial Artery and its Branches. — Ulnar Artery and its Branches. — Median Nerve in the Forearm. — Branches of the Musculo-Spiral Nerve in the Forearm. — Fractures of the Bones in the Forearm. — Development of the Radius and Ulna. — Relations of the Parts in Amputation through the Middle of the Forearm. THE REGION OP THE WRIST AND THE HAND . . . pages 396-418 Carpal Bones.— Radio-Carpal or Wrist Joint.— Triangular Fibro-Cartilage. — Synovial Membrane. — Ligaments of the Wrist. — Movements at the Wrist-Joint. — Metacarpal Bones.— Phalanges. — Metacarpo-Phalangeal Joint. — Interosseous Muscles. — Dorsal Aponeurosis of the Fingers. — Joint of the Thumb with the Trapezium. — Muscles of the Ball of the Tliumb.— Muscles of the Ball of the Little Finger.— Surface-Markings of the Wrist and Hand.— Skin over the Wrist. — Superficial Veins and Nerves. — Pos- terior Annular Ligament.— Skin over the Back of the Hand.— Superficial Veins of the Hand.— Branches of the Radial Nerve.— Radial Artery passing between the First and Second Metacarpal Bones to enter the Palm. — Branches of the Ulnar Nerve.— Palm of the Hand.— Thenar Eminence.— Hypothenar Eminence.— Linea Vitalis.— Linea Cephalica.— Linea Mensalis.— Linea Hepatica.— Plica In terdigi talis. — Subcutaneous Tissije of the Palm.— Palmar Fascia. — Anterior Annular Ligament. —Superficial Arterial Palmar Arch.— Deep Arterial Palmar Arch.— Wounds of the Palm.— Distribution on the Fingers of the Ulnar Nerve.— Distribution of the Median Nerve on the Fingers.— Superficial Lymphatic Vessels of the Palmar and Dorsal Surfaces of the Hand.— Nails.— Growth of the Nails.— Relation of the Parts in Amputations of the Fingers.— Development of the Bones of the Wrist and Hand. LIST OF ILLUSTRATIONS TO VOLUME I. PLATE 1. The landmarks of the skeleton of the regions of the head, face, and neck, on the right side, with their relations to the surface coverings. PLATE 2. Figure 1. Skull showing a topographical survey of the relations of the sutures and eminences to the principal fissures of the brain, and the approximate lower level line of the cerebrum. Figure 2. The left side of a skull, with the parietal bone removed, showing the subjacent convolutions of the left cerebral hemisjihere (stripped of their membranes), with a topographical survey of the motor area of the opercular region thus exposed. PLATE 3. Figure 1. The base of the skull seen from within, showing the exits of the cranial nerves. The dura mater lining the fossse of the skull is retained, surrounding and forming sheaths for all the nerves which are left in situ after the removal of the brain. (From a female head aged twenty-one years.) Figure 2. The distribution of the branches of the trifacial (or fifth cranial) nerve, and their relation to the branches of the internal maxillary artery. Figure 3. The posterior view of an adult European skull (the norma occipitalis). Showing remarkable Wormian bones (or ossa triquetra). Nos. 4 and 13. Figure 4. The right side of a skull of an adult male, with the outer table rasped away, to show the diploic veins. Figure 5. Oblique section through the left temporal bone, to show the tympanic cavity and mastoid cells on one side, and on the other the membrana tympani, the ossicles, and the Eusta- chian tube. xiii XIV LIST OF ILLUSTRATIONS TO VOLUME L PLATE 4. Figure 1. The right hemisphere of the cerebrum removed, to show the falx cerebri and tentorium of the dura mater, and the relations of tlie great sinuses and their tributaries. (From same head as in Plates 9 and 10.) FigTire 2. The posterior third of the skull and its scalp removed, to show the posterior view of the dura mater, and the confluence of the lateral and occipital sinuses with the superior longitudi- nal sinus. Also the posterior segments of the cervical vertebrse are removed, to show the continuation of the dura mater of the brain with that of the spinal cord, the ganglions on the posterior roots of the cervical nerves, and the course of the vertebral arteries through the vertebral foramina. PLATE 5. Figure 1. The pia mater, with its vessels ramifying over the convolutions on the upper surface of the hemispheres. The longitudinal sinus in position, with clusters of the Pacchionian granules within it and upon either side. Figure 2. The base of the skull, with the cerebellum retained in the occipital fossse. Portions of the orbital roofs are removed, to show the nerves and muscles passing to the eyeballs. Figure 3. The base of the brain, showing the anastomosis of the arteries called the circle of Willis. (From an adult male.) PLATE 6. Figure 1. The upper surface of the brain of a white man about forty-five years of age, in sound con- dition and normal in general conformation, size, and weight. The right hemisphere is larger than the left, the longitudinal fissure not being in the middle of the cerebral mass. The pia mater has been removed, to demonstrate the surface-markings. Figure 2. The under surface of the same brain as in Figure 1, showing the superficial origins of the cranial nerves. The pia mater is removed from the cerebrum, although retained over the cerebellum. PLATE 7. Figure 1. The convolutions and fissures on the external surface of the riffht hemisphere. (From same brain as in Plate 6.) Figure 2. The convolutions and fissures on the external surface of the left hemisphere. (From same brain as in Plate 6.) PLATE S. Figure 1. The convolutions and fissures of the inner surface of the left hemisphere of the cerebrum, and median section through the base of the brain, cerebellum, pons Varolii, and medulla oblongata. (From same brain as in Plates 6 and 7.) LIST OF ILLUSTRATIONS TO VOLUME L xv Figure 2. The convolutions and fissures of the inner surface of the right hemisphere of the cere- brum, and median section through the base of tlie brain, cerebellum, pons Varolii, and medulla oblongata. (Prom same brain as in Plates 6 and 7.) N.B. — All the figures representing the brain are from recent healthy specimens in a per- fectly natural state, •wh'ch were prepared and photographed sliortly after death, the tissues being unaltered by chemical reagents. PLATE 9. Figure 1. The right side of the head, with the scalp removed, to show the topographical survey of the skull in its relations to the brain. The temporal muscle and its fascia have also been removed, to show their ridges. Figure 2. The right side of the head, with the skull removed, showing the dura mater and the main branches of the great meningeal artery. This also illustrates the contiguous relations of the tissues of the scalp to the tables of the skull in their surgical application, and especially to the operation of trephining. PLATE lO. Figure 1. The dura mater removed, to show the vessels of the pia mater over the cortical surface of the right hemisphere. (From same head as in Plate 9.) Figure 2. The pia mater removed from the right hemisphere to show the surface-markings of the fissures and convolutions, and a topographical survey of the subdivisions of tlie motor area of the opercular region according to tlie most recent investigations of tlie centres of function of the cortical surface of the cerebrum. (From same head as in Figure 1.) N.B. — The figures on Plates 9 and 10 were taken in succession from the head of an adult male in remarkable physical health, and represent the structures in their normal condition and position. Comparison of the series will demonstrate the perplexities attending the study of cerebral localization, and the parts to be encountered in cerebral surgery. PLATE 11. Figure 1. Transverse (coronal) section through the head just in front of the ears, passing through the basilar part of the occipital bone below and the bregma above, showing the section of the brain, in situ, at the middle of the lateral ventricles. (The figure represents the parts as seen from before.) Figure 2. Horizontal section of the head, with the brain in position, showing the lateral ventricles and adjacent parts. Figure 3. Antero-posterior section of the head, with the brain in position, through the middle of the right hemisphere. The orbital muscles are seen in relation to the eyeball. PLATE 12. Median antero-posterior vertical section through the head, face, and neck of a powerfully- built man, thirty years of age. xvi LIST OF ILLUSTRATIONS TO VOLUME L PLATE 13. Figure 1. The relations of the great vessels and nerves at the base of the skull to the posterior wall of the pharynx. Figure 2. The face laid open on the left side, to show the relations of the salivary glands and the vessels and nerves to the tongue. Figure 3. The posterior wall of the pharynx opened, to show the larynx and the relations of the palate and tonsils from behind. Figure 4. The lower jaw removed, to show the palate, the tonsils, the fauces, and the tongue extended. FLATE 14. Figure 1. Transverse section of the neck of a negro (male), aged thirty years, from the fifth cervical vertebra behind to the cricoid cartilage in front. Figure 2. Transverse section at the root of the neck (same as Figure 1) on a level with the first dorsal vertebra. « N.B. — These sections were made on a recent well-developed cadaver, placed in the horizontal position, without any freezing or hardening agent, and the plates represent the relations of the parts absolutely as they were. PLATE 15. Anterior view of the muscles of the face of a well-developed man, aged thirty-five years, showing the delicate interlacing of the fibres about the corners of the eyelids and mouth. This dissection was made with especial care to demonstrate the anatomy of expression in its application to the facial markings now considered characteristic of disorders pertaining to mental, nervous, digestive, and respiratory functions. N.B. — The platysma muscles have been removed from their attachment at the outer corners of the mouth, where they form the laughing muscles of Santorini. The vessels and nerves have also been removed, as they are shown in other plates, in order to give a clearer idea of the interdependence of the facial muscles. PLATE 16. Dissection of the superficial muscles of the right side of the head, face, neck, thorax, and arm. (From a well-developed male, aged thirty-five years.) Tlie superficial lymphatic glands and vessels of the face and neck are drawn on the photograph (after notes of many dissections), to show their arrangement and position. PLATE 17. The skin removed on the left side of the neck, to show the platysma myoides muscle and the usual position of the great external jugular vein. PLATE 18. The superficial fascia removed from the left side of the face, together with the platysma myoides muscle from the neck, to show the superficial vessels and nerves in these regions, and especially the superficial relations of the parotid gland. LIST OF ILLUSTRATIONS TO VOLUME L xvii PLATE 19. The parotid gland removed from the left side of the face, to show the branches of the facial nerve, and the fascia removed from the posterior cervical triangle, to show more clearly the superficial cervical plexus of nerves. PLATE 20. Dissection of the vessels and nerves of the scalp and face on tlie left side, and the steruo- mastoid muscle removed from its sternal and clavicular attachments, to display the deep cervical plexus of nerves. Tlie fascial slip to the centre of the omo-hyoid muscle is also removed, to show the relations of the common carotid artery and the internal jugular vein. PLATE 21. Deep dissection of the head and neck on the right side, to show the temporal muscle un- covered by its fascia, and the relative positions of the deep cervical and the brachial plexuses of nerves. PLATE 22. Figure 1. Dissection of the back of the neck, to show the superficial muscles and the nerves and arteries in the occipital triangles. „. „ ^ ^ Figure 2. The deep parotid region. The malar bone and ramus of the lower maxillary bone have been removed, to show the parts beneath, involving the internal maxillary artery (or deep facial artery). PLATE 23. Figure 1. The skin removed from the anterior region of the neck, to show the platysma myoides muscle and the superficial cervical veins. _,. _ The anterior cervical muscles in relation to the veins, arteries, and nerves. The median raph6 has been cut through, and the anterior thyroid muscles separated, to display the vessels over the larynx and trachea. PLATE 2-4, Figure 1. The anterior region of the neck. The sterno-thyroid and sterno-hyoid muscles are removed, to show the thyroid body in position. (Same as Plate 23.) Figure 2. The anterior region of the neck. The isthmus of the thyroid body is divided, and the two lobes drawn to either side, to expose the depth of the trachea at the root of the neck, and its relation to the deep transverse thyroid veins. (Same as Plate 23.) N.B.— The dissections represented in Plates 23 and 24 were made upon a thick, short-necked, well-developed male subject, aged thirty-five years, to demonstrate the parts especially concerned in the operations of laryngotomy and tracheotomy. PLATE 25. Figure 1. Deep dissection of the root of the neck. The thyroid body and omo-hyoid muscle are hooked aside, to show the vessels and nerves, and the clavicle is detached from the sternum. Figure 2. Deep dissection of the root of the neck. (Same as Figure 1, the veins being removed.) xviii LIST OF ILLUSTRATIONS TO VOLUME I. PLATE 26. Figure 1. The sternum and costal cartilages removed to show the anterior mediastinum, and par- ticularly the relations of tlie pleurae to the pericardium. Figure 2. Dissection of the vascular system of the foetus (at five months and a half). N.B.— The injection was introduced by tlie umbilical vein, and the photograph represents the actual size. Figure 3. Dissection of a child, three weeks after birth, showing especially the relations of the thymus gland and the supra-renal capsules. Figure 4. Photograph of a preparation (in the author's cabinet), showing a remarkable disposition of the heart and independent origins of all the great vessels from the root of the aorta. N.B. — This specimen was removed from the body of a young man, aged twenty-seveu years, who died from phthisis. There is no arch to the aorta, and the position of the heart, wlien discovered, was vertical within the thorax, as sliown in the figure. There is only one auricle and one ventricle. No other abnormality of the arteries was found in the body. PLATE 27. Topographical survey of the front of the body of a well-developed adult male, with especial reference to the accuracy of the relations of the thoracic and abdominal viscera to the external surface coverings. PLATE 28. Front view of a natural (ligamentous) sl^eleton of a European male, aged thirty-eight years, showing the landmarks with their relations to the surface covering. PLATE 29. The anterior wall of the thorax and upper part of the abdomen removed, to show the relations of the heart, lungs, diaphragm, liver, stomach, aud spleen to the ribs and their sternal cartilages. The lungs are inflated (as in full inspiration), to indicate the so-called area of the heart's dulness. (From, a male subject, about forty years old, with normal condition of the organs.) N.B. — The subject upon which this dissection was made presented tlie rare anomaly of a distinct eighth true rib on either side. This is well shown in the plate. PLATE 30. The lungs inflated, so as to demonstrate the approximation of their edges over the heart, as in full inspiration. N.B. — This and the succeeding plates (31, 32, and 33) were taken from a male subject, about thirty-two years of age, who died from choking. The lungs were absolutely healthy. The pleurse were removed in the dissection. PLATE 31. The relations of the lungs, in moderate distention, to the pericardium, as in ordinary breathing. Also the great vessels and nerves at the root of the neck. The sternum and costal cartilages are removed. LIST OF ILLUSTRATIONS TO VOLUME I. xix PLATE 32. The relations of the kings, partially distended (as in tranquil respiration), to the pericardium. Also the vessels and nerves at the root of the neck. PLATE; 33. The relations of the lungs, when completely collapsed, to the heart. Also the deeper relations of the vessels and nerves at the root of the neck. The pericardium is removed, and the ribs sawn through at their middle, to give a better view into the cavity of the thorax. The clavicles also are removed. ELATE 34. Preparation to show the relations of the heart witliin the pericardium. N.B. — The ribs are cut away, so as to give an unrestricted view. ELATE 35. Preparation to show the relations of the heart and the great vessels at the root of the neck. The pericardium is opened and held aside. PLATE 36. Dissection of the pneumogastric nerve on the left side, and its relations to the phrenic and sympathetic nerves. (From a female, aged thirty-seven years.) PLATE 3?". The posterior mediastinum, exposed on the right side by removing the ribs near their angles and drawing forward the heart and lungs, to demonstrate the entrance of the vena azygos major into the superior vena cava, and the distribution of the right pneumogastric and phrenic nerves. PLATE 38. The posterior mediastinum and its contents, as seen on removal of the dorsal vertebrse (from the second to the ninth) with portions of their contiguous ribs. The lungs are expanded, so as to show their proper relations posteriorly. PLATE 39. View of the thoracic organs from behind, the dorsal vertebrse (from the second to the tenth) with portions of their contiguous ribs removed. The lungs are displaced, to show the relations of the heart. PLATE 40. The normal position and I'elations of the thoracic aorta, seen from behind, the lungs being removed, to show their roots. PLATE -41. Figure 1. The thorax of a young female, with the second, third, fourth, fifth, and sixth ribs removed on the left side, and the left lung drawn aside, to show the relations of the root of the lung and the apex of the heart to the diaphragm. Figure 2. Transverse section through the thorax of an adult male, on a level with the lower borders of the third ribs anteriorly and through the body of the eighth dorsal vertebra posteriorly, seen from below. XX LTST OF ILLUSTRATIONS TO VOLUME L RLATE 42. Dissection of the vascular system in a child eight months old, showing the principal arteries and veins in their proper relations and positions. PLATE 43. Figure 1. The front view of the heart removed from the body, with the roots of the great vessels arising from the aorta. Figure 2. Section of the right auricle and ventricle, to show the interior of their cavities. Figure 3. The posterior view of tlie heart in relation to the thoracic aorta. Figure 4. The posterior walls of the left auricle and ventricle removed, to show the inteiior of their cavities. PLATE 44. Figure 1. Dissection of the anterior thoracic region, showing the superficial fascia and mammary glands on the left side and the great pectoral muscle on the right. The arms are drawn upward and outward, to bring the axillary borders into prominence and expose their relations to the vessels and lymphatic glands ; of importance in operations upon the breast. (From a female, aged twenty-four years.) Figure 2. Dissection of the muscles of the shoulder and axilla on the right side. The lymphatic glands and vessels are superposed upon the photograph (from notes of many observations), to show their proper relations. PLATE 45. Figure 1. Dissection of the right axillary space and inner side of the arm, to show the relations of the vessels and nerves. Figure 2. Deep dissection of the right axilla and inner side of the arm. The deltoid and pectoralis major and minor muscles are detached and reflected, to show the intricate relations of the brachial plexus of nerves to the artery and veins. « PLATE 46. Figure 1. The anterior view of the right elbow and forearm of an adult male, with the superficial fascia carefully removed, to show the relations of the superficial veins and nerves. Figure 2. Deeper dissection of same arm as Figure 1. The bicipital fascia and the superficial flexor muscles are removed, while most of the superficial veins are retained, to preserve their relations. PLATE 47. Figure 1, The radial border of the forearm and elbow, showing the relations of the superficial veins— the superficial fascia being carefully removed— to the muscles and tendons. LIST OF ILLUSTRATIONS TO VOLUME L xxi Figure 2. The anterior view of the left elbow, to show particularly the bicipital fascia in relation to the superficial veins and the deep vessels and nerves. Figure 3. Dissection of the veins on the bade of the hand and forearm, with their relations to tlie underlying tendons and nerves. PLATE 48. Figure 1. Dissection of the palm of the right hand, showing the superficial layer of the palmar fascia. Figure 2. Dissection of the palm of the right hand. The superiicial layer of the palmar fascia is hooked aside, to show tlie deep layer of the fascia and the superficial palmar arterial arch. Figure 3. Dissection of the palm of the right hand, showing the position of the superficial arterial arch and the relations of its digital branches to the nerves and flexor tendons. Figure 4. Dissection of the palm of the right hand. The tendons are cut away, to show the deep palmar arterial arch and its relations, etc. PLATE 49. Figure 1. Dissection of the muscles of the right forearm and hand in pronation, to show the relations of the extensor tendons of the thumb to the radial artery. Figure 2. Dissection of the muscles and tendons of the back of the right forearm and hand in extension. Figure 3. Dissection of the tendons of tlie back of the left hand, showing tlie relations of the nerves and arteries. PLATE 50. Figure 1. The relations of the structures involved in the operation of trephining the skull, as in a case of cortical epilepsy. The disk of bone has been removed and the pia mater partially detached, to expose the convolutions on the right hemisphere, supposed to include the centre of the movements of the hand, and especially of the thumb. Figure 2. Amputation at the left shoulder-joint by the oval-flap method (of Larrey), showing tlie rela- tions of the parts exactly as they appear after the completion of the operation. PLATE 51. Figure 1. Amputation through the middle of the left arm by the antero-posterior oval-flap method, showing the proper relations of the vessels and nerves to the humerus, in a well-developed man, aged forty-eight years. xxii LIST OF ILLUSTRATIONS TO VOLUME L Figure 2. Amputation at the left elbow-joint by the antero-posterior flap method (of Dupuytren), showing tlie relations of the severed structures immediately after the completion of the operation. The olecranon process of the ulna is retained, to preserve the function of extension of the triceps muscle. Figure 3. Amputation through the middle of the left forearm by the antero-posterior oval-flap method, showing the relations of the severed structures on completion of the operation. PLATE; 52. Figure 1. The second phalangeal joint of the middle finger of the left hand laid open by an oval in- cision, as for the anterior flap of an amputation at this joint, to show the relations of the bone surfaces and the adjacent vessels. Figure 2. The metacarpo-phalangeal joint of the middle finger of the left hand opened, as in the first stage of an amputation (by the lateral-flap method) of the finger, to show the appearance of the ends of the bones at this joint. The position of the joint, on the dorsal surface, before the incisions were made, can be judged by comparison witli the adjacent fingers. Figure 3. Amputation at the carpo-metacarpal joint of the thumb of the left hand (by the flap method), showing the relative positions of the structures severed in the operation. Figure 4. The wrist-joint of the right hand laid open by an oval incision, as for the dorsal flap in ampu- tation at this joint, showing especially the appearance of the articulation between the lower end of the radius and the semilunar and scaphoid bones. Figure 5. Vertical section through the articulations at the wrist-joint of the right hand, to show the synovial membranes and the cancellous structure and arrangement of the carpal bones. Figure 6. The left elbow-joint laid open posteriorly, as in the process of resection or excision of this articulation, to show the relations of the opposing bones and the adjacent structures. PLATE 53. Figure 1. Topographical survey of the right side of the head, face, and neck, with especial adaptation to cranio-cerebral study, the localization of the areas of distribution of the sensory nerves, and spots where electrical stimulation produces reflex contractions of some of the muscles in these regions. Also the landmarlis for the operations of tracheotomy and of laryngotomy. Figure 2. The left hand in the position of pronation, showing a topographical survey of the areas of distribution of the sensory nerves on the back of the hand and fingers, and spots where elictrical stimulation produces reflex contraction of some of the muscles. Figure 3. The right hand in the position of supination, showing a topographical survey of the areas of distribution of the sensory nerves on the palm of the hand and anterior surface of the fingers, and spots where some of the muscles may be caused to contract by electrical stimu- lation. Also the surface-markings on the palm of the hand in relation to the arterial arches. REGIONAL ANATOMY. REGIONAL ANATOMY IN ITS RELATION TO MEDICINE AND SURGERY. THE REGION OE THE HEAD. The surface-form of the head is always pronounced, because the prominences and depressions, or landmarks (Plate 1), of the skull are slightly masked by the overlying soft structures. The thickness of the skull-cap varies greatly, and can only be con- jectured from external appearances. The average thickness is five milli- metres, or one-fifth of an inch ; the thickest parts are in the basilar portions, which are originally developed in cartilage, whereas the bones composing the vault are formed in membrane. In no other part of the skeleton is the combination of strength and lightness so beautifully adapted to its purposes as in the cranium. The contour of the head itself tends to avert the effect of external violence received at any point, and the natural eminences and processes occur where protection to the brain is most needed, while in those parts where it is less needed the bones are thin and light, so as to serve as a covering with but little extra weight. The hollows or sinuses of the cranial bones are rudimentary at birth, and remain of small size up to about the ninth year, after which they gradually increase until puberty, when they undergo great enlargement. 2 THE REGION OF THE HEAD. The bones of the head are the frontal, two parietal, occipital, two temporal, sphenoid, and ethmoid. They are immovably connected in the adult at their edges by the sutures, which vary in character according to their position and adaptation. The frontal bone is originally developed in two portions, which become joined by the frontal suture shortly after birth. This suture usually closes rapidly, so that it is obliterated between the second and sixth years, but occasionally it may persist to the end of a long life. Continued backward approximately in the middle line from the root of the nose and along the course of the frontal suture to the occipital bone is the interparietal or sagittal suture, by which the two parietal bones are dovetailed together. The parietal bones are connected with the frontal bone by the coronal suture, and with the occipital by the lambdoid suture. The coronal suture is more deeply indented laterally than above, and the lambdoid is remarkable for the tortuous course of its deep dentations. The junc- tion of the coronal and sagittal sutures, the bregma, may be ascertained on the living head by drawing upward from the external auditory openings two lines, which will meet over this point on the top of the head when it is held in the erect position. The point of junction of the lambdoid and sagittal sutures, the lambda, is in the middle line, one-third of the distance from the external occipital protuberance to the bregma. The lambdoid suture may be represented by a line drawn from the lambda to the apex of the mastoid process on each side. The coronal suture corresponds to a line drawn from the bregma to the middle of the zygomatic ai'ch. The point where the anterior inferior angle of the parietal bone is joined to the great wing of the sphenoid bone is the pterion, and is three centimetres, or about an inch and a quarter, behind the external angular process of the orbit. At the sides, the arches of the skull are maintained by the thin scaly margins of the temporal bones overlapping the bevelled lower edges of the parietal bones, forming the squamous sutures. The top of each squamous suture is five centimetres, or about two inches, above the zygoma in the adult head. The dentate sutures are formed by serrations mainly from the outer THE REGION OF THE HEAD. 3 table of the bones of the vertex interlocking. They gradually dis- appear after the fortieth year, the cranial bones becoming fused together in old age (synosteosis), when they, like the rest of the skeleton, become more porous and brittle and are in consequence more readily fractured. The closure of the cranial sutures usually begins on the inside of the vault, but there is great variability as to the time and order in which it takes place. The age of an individual cannot be determined from the state of the cranial sutures. They sometimes disappear at an early age. The author has several specimens where not a sign of the coronal, sagittal, or lambdoid sutures remains at the ages of thirty-three and thirty-seven years. At birth all the tabular bones are soft and yielding and capable of overlapping one another, thereby facilitating the delivery of the head of the child. In the subsequent growth of the bones the compact layers are produced, forming the outer and inner tables, with an intervening cancellated structure, the diploe. In old persons the diploe is often absorbed, so that the skull in some places becomes very thin, and it should be borne in mind that the plane of the inner table is not always equidistant from that of the outer, a matter of no little moment in applying the trephine. The limiting membranes of the vertex bones are united at the lines of the sutures, and until ossification is completed there are interspaces at the angles of the parietal bones, known as the fontanelles. These usually close in shortly after birth, with the exception of the anterior fontanelle, which occupies the bregma and does not disappear until the end of the second year. Until this is completely closed by ossific matter, there is a depression in this locality, through which there is a regular pulsation perceptible, due to the action of the arteries of the brain. Persistence of the anterior fontanelle is generally indicative of hydrocephalus. Occasionally congenital fissures occur before the normal approxima- tion of the skull bones is completed. They most commonly occupy the occipital region, and when they persist in the position of the lambdoid PLATE 1. The landmarks of the skeleton of the regions of the head, face, and neck, on the right side, with their relations to the surface coverings. 1. The point of junction of the coronal and sagittal su- tures ((fte bregma). 2. The temporal ridge, for the temporal fascia. 3. The parietal foramen {the obclion). 4. The parietal eminence. 5. The squamous suture. 6. The point of junction of the lambdoid and sagittal su- tures {the lambda). 7. The great wing of the sphenoid bone {the pterion). 8. The external auditory meatus. 9. The mastoid foramen {Ike asterion), 10. The external occipital protuberance (the inion). 11. The mastoid process of the temporal bone. 12. The spine of the second cervical vertebra. 13. The spine of the fifth cervical vertebra. 14. The transverse process of the sixth cervical vertebra, with first foramen for the vertebral artery. 15. The spine of the seventh cervical vertebra {the vertebra prominena), 16. The first rib. 17. The spine of the second dorsal vertebra. 18. The frontal eminence. . 19. The anterior inferior angle of the parietal bono. 20. The supra-orbital foramen. 21. The superciliary ridge {the ophryon). 22. The glabella. 23. The external angular process. 24. The junction of the frontal and nasal bones {the nasion). 25. The zygomatic arch. 26. The infra-orbital foramen. 27. The second upper molar tooth. 28. The angle of the lower jaw {the gonion), 29. The mental foramen. 30. The top of the hyold bone. 81. The top of the thyroid cartilage. 82. The cricoid cartilage. 83. The second ring of the trachea. 84. The acromial end of the clavicle. 85. The acromion process of the scapula. 30. The top of the sternum {the manubrium), 37. The coracoid process (if the scapula. 88. The glenoid fossa of the scapula. N. B.— This plate was taken from the skeleton of a well-developed European male, aged about thirty-seven years. Plate I Vol I -rcted, Ph'-.tceraph^c at-d Colqrec from '■iaiure r>y (7/ro9a£ Mc. Ci.f.li.an, M 0_ Copyn^^ht, 1831 . by GroRGE Mc Clellan.. M D. A,F.i.',i'on5(>:o liih Sjsi THE REGION OF THE HEAD. 6 sutures they may be mistaken for fractures. In this locality also are frequently found isolated triangular bony pieces {Wormian bones), originating from accessory centres of ossification (Plate 3, Fig. 3, ISTos. 4 and 13). Supernumerary bones are also often found in hydrocephalic skulls. The superciliary ridges are the prominences which support the eye- brows. They indicate in a measure the size of the frontal sinuses within the bone, which are first formed by absorption of the spongy substance (diploe) at the inner angular processes of the orbits, and gradually spread upward and outward. The dimensions of the frontal sinuses (Plate 12, No. 25) cannot always be foretold by the external conformation of the ridges ; and they often appear to be formed by a retrocession of the inner table, especially in elderly people. They reach a greater degree of development in the male than in the female. They are usually unsymmetrical, the larger being on the side from which the nasal septum is bent. The frontal sinuses connect with the anterior ethmoidal cells and the middle meatus of the nose by a curved canal called the infundibulum (page 113). The intervening point between the two superciliary ridges is called the ophryon. Above the ridges are the frontal eminences (Plate 2, No. 4, and Plate 28, No. 35), indicating the centres of primary ossi- fication of the original two halves of the frontal bone of infancy, and corresponding in a measure to the development of the anterior lobes of the cerebral hemispheres. The glabella is the smooth area between the superciliary ridges above the nose. Just below it is the point of junction of the nasal bones with the frontal spine, — the nasion. The external angular processes of the orbits are the outer limits of the superciliary ridges. The glabella and the angular processes are subcutaneous, the ridges being covered by the superciliary muscles and integument (Plate 1). The supraorbital foramen or notch is on the border of the orbital arch, just below the superciliary ridge, two and a half centimetres, or about an inch, from the external angular process. The temporal ridge, for the attachment of the temporal fascia, starts from the external angular process and arches backward, usually mid- 6 THE REGION OF THE HEAD. way between the squamous and sagittal sutures. The temporal muscle is attached one centimetre, or about half an inch, below the attachment of the temporal fascia, and sometimes a second distinct ridge is noticeable on the cranium. The point of intersection of the upper temporal ridge with the coronal suture is the stephanion. The parietal foramina are approximately midway between the bregma and the external occipital protuberance. They are very near the middle line, and the area of the brain-case in their locality is often flattened. This area is called the obelion. Tlie parietal eminences are the points where ossification first began in the parietal bones. They are very noticeable, and correspond to the development of the lateral lobes of the cerebrum. The external occipital protuberance, the inion, is on a line drawn horizontally backward from the sockets of the incisor teeth of the upper jaw. This process is the thickest part of the cranium, but is not always so prominent that it can be detected through the scalp. From it on each side the superior curved line arches outward toward the mastoid process. The mastoid processes are hardly noticeable during childhood. There is a continuous formation of new bone from the periosteum on the surface between infancy and puberty, and during this period the process consists of cancellous tissue which can be readily penetrated by the knife in mastoid disease. At puberty this cancellous tissue becomes hollowed by absorption into air-cells, and a larger cavity, the mastoid antrum, all of which communicate with one another and are connected with the tympanum. The antrum is separated from the cranial cavity by only a thin roof of bone (Plate 3, Fig. 5, No. 1). The cells vary in size in different bodies, and on the two sides of the same head. The proximity of the lateral sinus renders it liable to become involved by extension of inflammation in suppurative disease of the mastoid cells, esjjecially in the adult. The mastoid foramen is situated near the junction of the mastoid portion of the temporal bone and the occipital. It is the largest of several foramina in this locality, and transmits a vein to the lateral sinus, and sometimes a small artery to the dura mater. THE REGION OF THE HEAD. 7 The petrous portions of the temporal bones are hard and dense upon their surfaces, but, as they are hollowed within for the lodgement of the structures composing the middle and the internal ear, they are liable to fracture. The skull is not inherently strong at its base, and although undoubtedly fractures do occur in this region by transmitted force from blows upon the vertex, yet fracture by contre-coup is not now admitted to be so probable as it was formerly thought to be. The discharge of cerebro-spinal fluid from the ear, which is one of the diagnostic signs of fracture at the base of the skull, indicates that the internal auditory meatus must have been fractured and that a commu- nication has been established between the tympanum and the internal ear. Sometimes a serous discharge from the ear follows injury to the head, where fracture has not taken place : this is due to escape of fluid from the mastoid cells through a rupture in the tympanic membrane. Injuries involving the base of the skull must of necessity be serious, as in this region the cavity of the skull is in relation with the nasal cavity, the orbit, the frontal sinuses, the sphenoidal sinus, the tympanic cavity, the upper part of the pharynx, and the spinal cord. Besides these there are the foramina which give exit to the cranial nerves (Plate 3, Figs. 1 and 5 ; Plate 4, Fig. 2 ; Plate 5, Fig. 2 ; Plate 11, Figs. 1 and 3; Plate 12; and Plate 13). The skin covering the head, which constitutes the scalp, is peculiarly constructed for the growth of the hair and for protection to the vault of the cranium. It is thicker than in any other part of the body, and is closely connected by means of the subcutaneous tissue with the aponeu- roses of the occipito-frontales muscles, so that it moves freely with their contraction. This mobility is very noticeable in infancy. The readiness with which the whole thickness of the scalp gives way in contused wounds is due to the intimate connection between the skin and the subjacent textures. The subcutaneous tissue here consists of a dense fibrous structure enclosing fat lobules (Plates 9 and 12), and resembles that of the palm of the hand. This continues with the superficial fascia over the muscles at the back of the neck, and at the sides passes over the temporal fascia. 8 THE REGION OF THE HEAD. The vessels, nerves, hair-bulbs, and sebaceous glands are contained within the meshes of this subcutaneous tissue. The scalp hairs mostly diverge from the obelion. They vary in character according to their color, length, and diameter, and the manner in which the hair-follicles are set in the skin, being straight, wavy, curly, or woolly, according to the straight or the curved axis of each follicle. Fair hairs are finer and more delicate than dark hairs, and are usually more closely set in the scalp. The arteries of the scalp are the terminal branches of the tem- poral, supra-orbital, frontal, posterior auricular, and occipital. They pass toward the vertex of the head, running in a tortuous course from their origins. The temporal artery is the continuation of the external carotid artery after it has tunnelled through the upper part of the parotid gland (Plate 18, No. 37). It is six millimetres, or a quarter of an inch, in front of the ear, and is accompanied by the temporal vein and the auriculo-temporal nerve. It divides into the anterior and middle tem- poral branches, which run immediately under the skin (Plate 17, No. 1), and may serve to indicate the pulse to the physician. Tlie supra- orbital artery ascends with the supra-orbital nerve (Plate 18, No. 1) from the supra-orbital notch, or foramen, which is situated two and a half centimetres, or about an inch, from the outer orbital angle, toward the nose on the border of the orbital arch. The frontal artery and supra- trochlear nerve (Plate 19, No. 1) pass upward between the supra-orbital notch and the root of the nose. The supra-orbital and fi-ontal arteries come from the ophthalmic artery within the orbit. The posterior auricular artery and the occipital (Plate 20, Nos. 45 and 50) are branches of the external carotid artery. The former passes with the posterior auricular nerve in a groove behind the mastoid process of the temporal bone, and the occipital artery, accompanied by the great occipital nerve, reaches the scalp at a point midway between the external occipital protuberance and the mastoid process. The anterior branch of the temporal artery often becomes very tortuous in the aged, and sometimes undergoes calcareous degeneration. Owing to the toughness of the scalp in which the arteries ramify, they THE BEGION OF THE HEAD. 9 cannot be drawn out, and do not retract when divided, as they do else- where, and hence incised wounds in this region are frequently attended with troublesome hemorrhage. The veins of the scalp are quite large, and in a measure accom- pany the arteries, receiving similar names in their different localities, but their course is more direct and they freely anastomose. There are two frontal veins, which generally run parallel at the middle of the fore- head, sometimes being very prominent in life, and are united at the root of the nose by a transverse trunk called the nasal arch. Thence they branch into the angular veins of the face, being joined by the supra- orbital veins. At this point they receive branches from the superior ophthalmic veins and establish direct communication with the cavernous sinuses at the base of the brain. Sometimes there is only one temporal vein. The temporal veins commence by anastomosing plexuses on the top of the head which form into anterior and posterior branches, and unite into main trunks in close relation to the temporal arteries at the zygoma, where they receive the blood from the middle temporal veins coming from the substance of the temporal muscles. The posterior auricular veins descend behind the ear, receiving the stylo-mastoid veins, and empty into the temporo-m axillary veins. The occipital veins follow the course of the occipital arteries, passing beneath the deep muscles at the back of the neck and terminating usually in the internal jugular veins. At the mastoid portion of the temporal bone the mastoid vein enters the occipital or the posterior auricular, thus communicating with the lateral sinus. This is the largest and most constant of the so-called emissary veins, which connect the extra- and the intra-venous circulation. Besides the intercommunication by the ophthalmic and angular veins and the mas- toid and occipital veins, there are many others which are less constant, but of equal importance when they do occur. The parietal foramina are at the vertex in the vicinity of the median line, where the interlocking of the serrated edges of the parietal bones forms the sagittal suture, and transmit veins from the scalp to the longitudinal sinus. There is generally a vein connecting the lateral sinus with the deep veins at the 2 10 THE BEGION OF THE HEAD. back of the neck through the posterior condyloid foramen, on one side or the other ; and there are many apertures at the base of the skull through which veins pass connecting the cavernous sinuses with the venous' plex- uses of the pharynx and the internal jugular veins. A similar connection exists more often than is supposed between the veins of the nasal fossae and the front part of the longitudinal sinus through the foramen ccecum, which in such cases is not closed. There are also minute veins which connect the diploic veins (Plate 3, Fig. 4) within the tabular bones of the skull with the veins of the scalp. The emissary veins are well worthy the attention of the physician or surgeon, for through their various channels inflammation often spreads from the surface to the interior of the head, or the reverse ; as is witnessed where erysipelas of the scalp induces meningitis, or in external abscess following injury to a sinus by a fracture or the application of the trephine. The lymphatic vessels of the scalp are in relation to the prin- cipal veins. The frontal lymphatics descend from the forehead and eyebrows, some going to the lymphatics of the face and ending in the submaxillary lymphatic glands, while the greater number converge toward the front of the ear, where they enter the lymphatic glands of the parotid region (Plate 16, No. 15). The parietal lymphatics pass to the mastoid glands, are four or five in number, and lie about the insertion of the steruo-mastoid muscle. The occipital lymphatics go partly to the sub-occipital glands in front of the occipital attachment of the trapezius muscle, and partly to the deep cervical glands beneath the sterno-mastoid muscle at the middle of the neck. The frontal, parietal, and occipital lymphatic vessels all communicate with one another. The nerves of the scalp have been considered in their relations with the arteries. It will be noticed that they also pass toward the vertex of the head. In front are the supra-orbital and supra-trochlear branches of the ophthalmic division of the fifth cranial nerve, — the trifacial (Plate 3, Fig. 2). They give sensation to the integument over the top of the head and forehead (Plate 53, Fig. 1, Nos. 1 and 13). The supra-orbital nerve is often the seat of frontal neuralgia, which THE REGION OF THE HEAD. 11 probably depends much upon whether the nerve issues from a distinct bony foramen or only from a notch. In the temporal region are the filaments from the orbital branch of the superior maxillary division, and the auriculo-temporal nerve from the inferior maxillary division, of the fifth nerve (Plate 19, No. 20). All of these supply sensation. The motor nerves are derived from the temporal branches of the facial nerve, which pass upward from among the lobules of the parotid gland to the anterior portion of the occipito-frontalis, corrugator, supra-auricular, and anterior auricular muscles. Behind are the posterior auricular branch of the facial nerve, giving motion to the posterior portion of the occipito- frontalis and posterior auricular muscles, and the small and great occipital nerves (Plate 22, Fig. 1, Nos. 3 and 8), the former a branch of the an- terior division and the latter a branch of the posterior division of the second cervical nerve. These last are the sensory nerves to the skin over the back of the head. The auricular branch of the pneumogastric nerve (Arnold's) emerges from the auricular fissure just behind the concha of the ear, which it supplies. The nerves of the scalp communicate fre- quently with one another. The cutaneous muscle of the scalp, the occipito-frontalis, con- sists of two fleshy portions, the frontal and the occipital, united by a broad aponeurosis, which is continuous with the aponeurosis of the opposite muscle across the vertex and forms the galea capitis (Plate 15, No. 1). In bald persons the frontal muscles often plainly show in out- line on the sides of the forehead. The frontal portion is a thin layer of pale fleshy fibres extending upward five centimetres, or about two inches, on the side of the forehead, where it joins the aponeurosis. In the middle line, at the nasion, the fibres blend with those of the fellow muscle, sending a slip downward to intersect with the pyramidal nasal muscle. The middle and outer fibres commingle with those of tbe orbicular and corrugator muscles at the eyebrows. Some of the innermost fibres are attached to the nasal bones, some of the outer to the external angular process of the orbit (Plate 15, No. 3). The occipital portion is of a darker color than the frontal. It takes origin by a tendinous insertion on the outer part of PLATE 2. Figure 1. Skull showing topographical survey of the relations of the sutures and eminences to the principal fissures of the brain, and the approximate lower level line of the cerebrum. 1. The hregma, the junction of the coronal and sagittal sutures. 2. Tlie superior frontal sulcus. 3. Tlie posterior frontal or vertical sulcus. 4. Tlie frontal eminence. 5. Tlie superior slepltanion, or intersection of the ridge for the temporal fascia with the coronal suture, in its relation to the inferior frontal sulcus. 6. The line indicating the anterior limit of the corpus stri- atum. 7. The glabella (or opinion). 8. The pterion, the junction of the great wing of the sphenoid bone with the frontal, parietal, and temporal bones, indicating the position of the ascending branch of the fissure of Sylvius in its relation to the coronal suture. 9. The nasion, the junction of the nasal and frontal bones. 10. The external angular process of the orbit. 11. The fissure of Rolando. 12. The inter-pai-ietal sulcus. 13. The parietal eminence. 14. The squamo-parietal suture In relation to the horizontal branch of the fissure of Sylvius. 15. The line indicating the posterior limit of the optic thalamus. 16. The upper temporo- sphenoidal sulcus. 17. The external parieto-occipital fissure. 18. The lambda, the junction of the lambdoid and sagittal sutures. 19. The tower temporo-sphenoidal sulcus. 20. The inion, the external occipital protuberance. Figure 2. The left side of skull with the parietal bone removed, showing the subjacent convolutions of the left cerebral hemi- sphere (stripped of their membranes), with topographical survey of the motor area of the opercular region thus exposed. 1. The centre for the movements of the face (the expres- sions). 2. The centre for the movements of the lips, tongue, throat, and larynx. 3. The speech centre. 4. The pre-central, or posterior, frontal sulcus. 5. The ascending frontal convolution. 6. The ascending branch of the fissure of Sylvius. 7. The centre for the movements of the fingers. 8. The centre for the movements of the thumb. 9. The centre for the movements of the wrist. 10. The centre for the movements of the shoulder and elbow. 11. The centre for the movements of the hip, knee, and leg. 12. Tlie centre for the movements of the foot and toes. 13. The fissure of Rolando. 14. The ascending parietal convolution. 15. The horizontal branch of the fissure of Sylvius. 16. The external parieto-occipital fissure. 17. The cerebellum. Plate; Vol I Photographed a/id Coiorpa from f/atu/t^ oy GEOf>G€ Mc. Clellan, M D. Copyn^^hi, 1831 , by- Geo»6E Mc Clellan, M. D ArrvVTrron^iCo Lpth B-jji THE BEGIOJSr OF THE HEAD. 13 the upper curved line of the occipital bone and the mastoid portion of the temporal bone, and, immediately becoming muscular, its parallel fibres extend upward three centimetres, or about an inch, and then join the aponeurosis. The aponeurosis of the scalp is continuous across the top of the head, and is more characteristic behind, where there is a median area chiefly composed of longitudinal fibres which are attached to the external occipital protuberance and adjoining portions of the upper curved line. It is thinner in front, and at the sides, in the temporal region, it is not so closely associated with the scalp, being continued over the subjacent temporal fascia as far as the zygoma. Between the aponeurosis (epicranmm) and the delicate membrane overlying the skull bones {pericranium) there is a layer of loose "connective tissue, upon which the mobility of the scalp depends. This mobility is readily seen in the raising of the brows by contraction of the frontal muscles, in many of the ordinary facial expressions, and the laxity of the connective tissue is demonstrated in extensive scalp wounds, where a large flap may be peeled off" from the skull. Incised wounds gape most when they occur across the direction of the fibres of the muscle. The attachments of the occipito-frontales muscles, above described, constitute a limited area of surgical significance in case of wounds and inflammatory affec- tions attended with suppuration in this region. This area is roughly indicated by a line drawn round the head from the superciliary ridges above the zygoma to the occipital protuberance. The pericranium is very thin in the adult, and exercises only a protective influence over the skull bones, playing no part in their nourishment. It is unlike the periosteum elsewhere, being destitute of its bone-producing properties, the bones of the cranium receiving their nutrition from the vessels of the dura mater. The pericranium may be regarded as the remains of the outer layer of the developing membrane which surrounded the bones in early life. It is very slightly attached, except at the sutures, where, in the young, it blends with the membrane between the soft and growing bones. In the latter instance sometimes extravasations occur, due generally to pressure on the head at birth, which are limited to one bone, commonly 14 THE MEGION OF THE HEAD. the parietal. In tlie temporal region the perici-anium is more adherent to the bone than anywhere else. The temporal region corresponds with the temporal muscle, which occupies the temporal fossa. The skin here is somewhat different from the scalp proper, having a variable quantity of fat in its subcutaneous tissue, besides the rudimentary auricular muscles. The temporal fascia is a bluish-white shining aponeurosis, underlying the above, of a very unyielding nature, which firmly binds down the temporal muscle, and sends radiating tendinous slips among the outer bundles of fibres of the muscle which greatly augment its power. Above it is attached to the upper temporal ridge on the frontal and parietal bones, and below it is separated into two leaflets which are inserted into the outer and inner borders of the zygomatic arch. There is usually a pad of fat between the muscle and its ajaoneurosis at the zygoma, the wasting of which in emaciation and in old age occasions conspicuous hollows at the temples. When the temporal muscle is stripped of its fascia, it presents a fan- shaped appearance (Plate 21, No. 2), with its fibres converging into a strong tendon, which is inserted into the coronoid process of the lower jaw at its apex and anterior border. The temporal muscle arises from the side of the skull one centimetre, or a half-inch, below the attach- ment of the fascia. Its deeper surface is in relation to the deep tem- poral arteries and nerves and to the internal maxillary vessels. Its motor nerves are derived from the inferior maxillary nerve. The func- tion of the temporal muscle is to raise the lower jaw forcibly against the upper. With the masseter (page 122) and pterygoid muscles it is con- cerned in the mastication of food. The inequality of the thickness of the skull-cap has already been mentioned. It depends upon the amount of the diploe between the outer and inner tables of compact bone. This structure varies consider- ably, and its amount cannot be determined before a section of the bone is made. The diploe contains a number of large veins, which occupy channels in its structure and freely anastomose (Plate 3, Fig. 4) and at points have extra- and intra-communications with the veins of the scalp THE REGION OF THE HEAD. 15 and the sinuses of the dura mater. When the diploe is reached by the teeth of a trephine saw, the blood from the diploic veins wells up in a peculiar and distinctive manner. The inner table of compact bone is thinner and more brittle than the outer, and is in consequence called the vitreous table. Thus its fracture is accounted for in those cases where it has been broken with- out the outer table being implicated ; and in nearly all cases of com- plete fracture of the skull bones it is the internal table which is most broken. The egg-shaped form of the skull has undoubtedly much to do with the diversion of the effects of violence from the brain, and explains the possibility of the occurrence of fracture at the base of the skull from contre-coup. When the skull-cap is removed its inner surface is found to be grooved for the branches of the meningeal arteries at the sides, and along the median line about the attachment of the walls of the superior longitudinal sinus of the dura mater are depressions for the reception of the so-called Pacchionian bodies. The dura mater is the white, dense, fibrous membrane which lines the interior of the skull, serving the double purpose of being the true (nutritive) periosteum of the cranial bones and of affording a tough pro- tective envelope and support to the brain. It is closely adherent over the whole of the base of the skull, where it is prolonged through the foramina, becoming continuous with the pericranium and blending with the fibrous sheaths of the nerves and vessels which pass out of and into the cranium. Over the vault its attachments are chiefly in the position of the sutures, where its outer fibrous layer separates to form the venous sinuses. Elsewhere it is comparatively loose, so that extravasations from rupture of the meningeal vessels or purulent accumulations may collect between the dura mater and the bone and cause compression of the brain. When compression occurs immediately on the receipt of an injury to the head, it is generally due to a depressed fragment of bone ; but if it follows after an interval it is probably caused by an extravasation of this sort. It is worthy of note in this connection that rupture of a vessel of the dura is usually followed by symptoms of compression more pronounced 16 THE BEGION OF THE HEAD. than when one of the cerebral vessels is involved, owing to the softer and more yielding nature of the brain-substance. On the other hand, when a cerebral vessel is ruptured there is little impediment to the escape of the blood, and often clots of great size are found in the locality of one of the cerebral vessels. Even in the lines of the sutures the dura mater can be severed from its bony attachment by taking pains in the removal of the skull-cap (Plate 4, Fig. 2), and there is little danger of wounding any of the sinuses with the trephine if the button of bone, when it has been cut through by that instrument, is seized with the forceps and extracted by a gentle rotatory motion. During the growth of the skull bones in childhood the dura mater is very adherent, and does not allow extravasations to collect between it and the inner wall of the cranium. The Pacchionian bodies, depressions for which are often noticed on the inner table of the skull-cap, are clusters of whitish granulations of variable size (Plate 5, Fig. 1). They first appear about the seventh year, and increase in number as age advances. The localities in which they are liable to be found are the neighborhood of the great longitudinal sinus, on the outer surface of the dura, and sometimes within the walls of the sinus itself. They are also, but rarely, met with in the fissure of Sylvius and on the margins of the hemispheres. They have been demonstrated to be hypertrophied villi of the arachnoid membrane, which perforate the dura mater by pressing outward, and cause the formation of the pits in the bone by absorption. The dura mater sends vertical processes between the hemispheres of the cerebrum and those of the cerebellum, and a transverse arching partition between the posterior lobes of the cerebrum and the cerebellum (Plate 4, Fig. 1). The latter is called the tentorium, and serves to prevent the posterior lobes of the cerebrum from pressing upon the cerebellum. It is attached to the transverse ridges upon the inner sur- face of the occipital bone, and extends laterally to the superior borders of the petrous portion of the temporal bones, and forward to the clinoid processes of the sphenoid bone. The vertical processes are known respectively as the falx cerebri and the falx cerebelli. The falx cerebri THE REGION OF THE HEAD. 17 is received into the longitudinal fissure between the two cerebral hemi- spheres. It is attached in front to the crista galli of the ethmoid bone by a sharp point, and gradually becomes broader as it arches backward, assuming the characteristic shape of the blade of a sickle. At its back part it is connected with the upper surface of the tentorium. The falx cerebelli is projected into the notch between the hemispheres of the cere- bellum and extends to the sides of the foramen magnum. The arteries of the dura mater are very numerous, but the one of chief importance is the great or middle meningeal artery (Plate 9, Fig. 2) . This vessel is a branch of the internal maxillary artery, and enters the skull at the foramen spinosum in the margin of the great wing of the sphenoid bone where it joins the anterior inferior angle of the parietal bone, at the middle fossa of the skull. It passes upward over the side of the dura mater in close connection with its two veins, and divides into anterior and posterior branches, which are received by grooves or channels in the inner table of the parietal bone. Very often these channels become in places distinct bony tunnels, so that removal of a section of the bone so constructed necessitates the rupture of the embedded artery. At the lower anterior angle of the parietal bone fracture is very liable to occur, because the bone is peculiarly thin and weak, and, although the dura mater is adherent here, in such an injury the vessel can hardly escape laceration. In almost every case of fracture of the vault of the skull, attended with extravasation of blood, it is one or other of the branches of the middle meningeal artery which gives way, and this may even occur without fracture, owing to the loose attachment of the dura mater within the vault being separated by the vibration produced by a blow. The other arteries which supply the dura mater and the various regions of the skull are, in the temporal region, the lesser meningeal, which enters at the foramen ovale coming from the internal maxillary (Plate 22, Fig. 2), and a small twig from the ascending pharyngeal artery, which comes through the middle lacerated foramen at the base of the skull. Anteriorly there are meningeal arteries from the ethmoid and internal carotid arteries, and posteriorly branches from the occipital, ascending pharyngeal, and 3 18 THE BEGION OF THE HEAD. vertebral arteries. The first two enter by the jugular foramen, and the latter by the foramen magnum. All the veins of the dura mater, with the exception of the two which accompany the middle meningeal artery on either side, terminate in the great sinuses. They freely anastomose with the diploic veins. The dura mater not only affords support to the divisions of the brain-mass, but in certain places separates into two layers, so as to form canals, or sinuses, by which the venous blood from the brain and its membranes is conveyed without interference to the internal jugular veins. There are as many as fifteen of these sinuses, but the most important (from a surgical point of view) are the superior longitudinal and the lateral (Plate 4, Figs. 1 and 2). The lateral sinuses are the main channels to which all the other sinuses converge. They often differ in size upon the two sides of the head. They commence at the internal occipital protuberance and curve outward and downward and inward to the jugular foramina, being received in the grooves of the occipital and temporal bones and included in folds of the tentorium. In their course they receive veins from the cerebellum and from the occipital diploic veins, and are joined by the petrosal sinuses. They also communicate with the veins of the scalp by emissary veins through the mastoid foramina, and sometimes by the posterior condyloid foramina. It is owing to this intercommu- nication that many cerebral affections are relieved by counter-irritation, or the application of leeches, in this region. The superior longitudinal sinus (Plates 4 and 12) is formed by a separation of the layers of the falx cerebri in the line of the sagittal suture. It commences at the fora- men caecum in front of the crista galli of the ethmoid bone, and passes backward, gradually becoming larger, until it reaches the internal occipital protuberance. At this point the sinus deviates, usually to the right side. It becomes dilated and terminates in the corresponding lateral sinus. The dilatation has long been known as the torcular Herophili, or confluence of the sinuses (Plate 4, Fig. 1, JSTo. 12). A transverse section of the superior longitudinal sinus is found to be triangular, with the base of the triangle upward against the skull (Plate 11, Fig. 1, No. 1). Its lower angle is bridged across at intervals by THE REGION OF THE HEAD. 19 slender fibrous cords, called chordae WilUsii. This sinus receives blood from numerous veins from the adjacent cancellous structure of the skull- cap, from several large veins from each hemisphere of the cerebrum, and through a venous link by means of the parietal foramen from the veins of the scalp. These veins usually enter the walls of the sinus obliquely, passing from behind forward (Plate 4, Fig. 1) in a direction contrary to that of the blood-current in the sinus, probably to prevent regurgitation of blood into the cerebral veins. Very frequently there is a communica- tion between the veins of the nasal fossae and the apex of the sinus, and in some cases of severe epistaxis the sinus has been supposed to be tapped through such a connection. The superior longitudinal sinus, from its position, is often subjected to wounds in fracture of the skull, and less frequently in trephining. The hemorrhage resulting is by no means so serious as to warrant great alarm, for there are many recorded cases where such hemorrhage has been easily controlled by gentle pressure. Observation has led to the supposition that the blood circulates more slowly in the sinuses than in the ordinary veins ; and their construction seems to be especially for venous receptacles into which a reflux of blood can take place without exercising compression upon the brain-substance. The cavernous sinuses are the only other sinuses of importance, and that because of their intimate relations with the internal carotid arteries. Owing to these relations, arterio- venous aneurism some- times follows injury to the base of the brain. The cavernous sinuses are truly venous plexuses situated at the sides of the body of the sphenoid bone, surrounding the carotid arteries. They receive blood from the anterior inferior cerebral veins, and through the ophthalmic veins from the orbits. This latter communication may lead to thrombosis of the sinuses by extension of inflammation from disease within the orbits along the ophthalmic veins. The cavernous sinuses empty their blood by means of the upper and lower petrosal sinuses into the lateral sinuses. The nerves of the dura mater are the recurrent branches of the fourth and some filaments from the fifth of the cranial nerves. Besides these there have been demonstrated upon the dura filaments from the ophthalmic and hypoglossal nerves, as well as some from the sympathetic nerve. PLATE 3. Figure 1. The base of the skull seen from within, showing the exits of the cranial nerves. The dura mater lining the fossae of the skull is retained, surrounding and forming sheaths for all the nerves which are left in situ after the removal of the brain. (From a female head, aged twenty-one years.) 1. The left olfactory bulb (or Jirst cranial nerve). 2. The left optic nerve (or second cranial nerve). 3. The left internal carotid artery. 4. The optic chiasm. 5. The motor oculi nerve (or third cranial nerve). 6. The trochlearis nerve (or fourth cranial nerve). 7. The trifacial nerve (or fifth cranial nerve). 8. The abducent nerve (or sixth cra- nial nerve). 9. The facial nerve (or seventh cra- nial nerve); and the auditory nerve (or eighth cranial nerve). 10. The hypoglossal nerve (or twelfth cranial nerve). U. The glosso-pharyngeal nerve (or ninth cranial nerve). 12. The pneumogastric nerve (or the tenth cranial nerve). 13. The spinal accessory nerve (or eleventh cranial nerve). 14. The crista galli of the ethmoid bone. 15. The right frontal fossa, 16. The olivary process of the sphe- noid bone. 17. The right internal carotid artery. 18. The temporal fossa. 19. The basilar portion of the occipital bone, joining that of the sphe- noid. 20. The right occipital fossa. 21. The internal occipital crest. 22. The internal occipital protuber- ance. Figure 2. The distribution of the branches of the trifacial (or fifth cranial nerve), and their relation to the arteries of the face. 1. The supra-orbital nerve. 2. The supra-trochlear nerve. 3. The infra-trochlear nerve. 4. The terminal branches of the lachrymal nerve. 5. The infra-orbital branch of the superior maxillary nerve. 6. The spheno-palatine (sympathetic) ganglion (or Meckel's ganglion). 7. The descending palatine nerves. 8. The infra-orbital nerve and artery. 9. The anterior and posterior dental nerves and arteries. 10. The superior buccal nerve. 11. The inferior buccal nerve. 12. The inferior dental nerve and artery. 13. The mental nerves and artery. 14. The optic nerve. 15. A nasal branch from the infra- orbital nerve. 16. The position of the Vidian nerve. 17. The branches of the inferior max- illary nerve to the muscles of mastication. 18. The ophtlialmic nerve (or first di- vision of the trifacial nerve). 19. The anterior branch of the tem- poral artery. 20. The auriculo-temporal nerve. 21. The posterior branch of the tem-. poral artery. 22. The temporal artery. 23. The middle meningeal artery. 24. The chorda-tympani nerve. 25. The internal maxillary artery. 26. The occipital artery. 27. The posterior auricular artery. 28. The facial nerve. 29. The lingual nerve (or gustatory nerve). 30. The chorda tympani nerve, where it joins witli the lingual nerve. 31. The infra-maxillary branch of the facial nerve. 32. The external carotid artery. 33. Tlie internal carotid artery. 34. Tlie common carotid artery. 35. The facial artery. Figure 3. The posterior view of a European skull (the norma occipitalis). Showing remarkable Wormian bones (or ossa triquetra). Nos. 4 and 13. 7. The external occipital protuber- ance (t/ieinion). 8. Tlie left mastoid process. 9. The digastric groove. 10. The obelion. 11. The right parietal eminence. 1. The sagittal suture. 2. The left parietal foramen. 3. The left parietal eminence. 4. Tlie left side of the upper portion of tire occipital Ijone (Wormian). 6. The lambdoid suture. 6. The left asterion. 12. The lambda. 13. The right side of the upper portion of the occipital bone (Wormian). 14. The right asterion. 15. Tlie right mastoid process. 16. The occipital crest. Figure 4. The right side of a skull of an adult male, with the outer table rasped away to show the diploic veins. 1. The fronto-parietal veins, which communicate with the superior petrosal sinus. 2. The external parietal veins, which terminate usually in the mastoid vein, 3. The parieto-occipital veins empty- ing into the lateral sinus. 4. The frontal veins, which communi- cate with tlie supra-orbital veins. 5. The fronto-sphenoidal veins, which connect with the deep temporal veins. Figure 5. Oblique .section through the left temporal bone, to show the tympanic cavity and the other tlie membrana tympani, the ossicles, and the Eustachian tube. 1. The position of the squamo-petrosal 6. ITie pyramid for the stapedius 13. muscle. 14. 7. The stapes resting on the fenestra ovalis. 15. 8. The fenestra rotunda. 9. The aqueduct of Fallopius. 16. 10. Section through the mastoid cells. 17. 11. The squamous portion of the tem- 18. poral bone. 19. 12. The position of the canal of Hu- guier. suture. 2. The eminence over the semicircu- lar canals. 3. The depression for the Gasserian ganglion of the fifth cranial nerve on the apex of the petrous bone. 4. The internal carotid artery entering its canal. 5. The tympanic cavity. mastoid cells on one side, and on The tensor tympani muscle. The end of the manubrium of the malleus. The osseous portion of the Eusta- chian tube. The incus. Tlie membrana tympani. Tlie styloid process. The mastoid process. Plate 3 Vol I Fi? I Fl£; 3 ■^ xr^ — . — rw^^%„. Fig 4- ^>2S2tiiii Fig 5 ^m. Dissected, Plmtojrjphed H'lJ Colored from Niwrn by Geokss Mc. Clell^x, MB. Copyright, ISSI , by SnoitaE Mc Clullun, M D ArrfisIrongSCo Lilh Scsl THE REGION OF THE HEAD. 21 The cerebral surface of the dura mater is lined by the delicate arachnoid membrane (Plate 5, Fig. 1), which in the normal state facilitates the pulsations of the underlying convolutions, owing to its property of secreting a serous fluid. The amount of fluid between the dura and the arachnoid tissue is inconsiderable. It is contained within the sub-dural space, so called in contradistinction to the sub- arachnoid space, which is between the arachnoid membrane and the sub- jacent vascular tissue, — the pia mater. The arachnoid membrane is color- less and extremely thin over the upper surface of the hemispheres, but it becomes thicker at the base of the brain in front and behind the pons Varolii, where it is opaque. At these localities there is always a quantity of serous fluid which serves to support the overlying brain. The arach- noid fluid passes into the interior ventricular cavities of the brain by means of the opening into the fourth ventricle for the choroid tela (Magendie's foramen), and thus serves to exert a sustaining pressure both within and without, thereby preventing the ill efiects of concussion, and enabling one hemisphere to support the weight of the other when the head rests upon the side. The arachnoid membrane does not unite with the dura except where the cerebral veins pass to the sinuses or around the corpora Pacchioni, and it does not accompany the pia mater into the sulci between the convolutions. The arachnoid or cerebrospinal fluid is a limpid liquid with a salty taste and a slightly alkaline re- action. In cases of fracture of the base of the skull, involving the petrous portion of the temporal bone, the escape of the cerebro-spinal fluid through the ear is a diagnostic feature, as previously stated. The pia mater is a delicate net-work of connective tissue in immediate relation to the surface of the brain, containing within its meshes the rami- fications of the cerebral vessels. It closely follows the infolding of the brain-surface, which constitutes the convolutions, and lines the great fissures which characterize the development of the organ, and by some of them is continued into the ventricular cavities. After removal of the dura mater many large superficial veins will be noted passing between the layers of the pia mater to empty their blood into the sinuses (Plate 5, Fig. 1, and Plate 10, Fig. 1). They do not regularly accompany the 22 THE BEGION OF THE HEAD. arteries, and on the surface of the hemispheres they freely communicate with one another. At the base of the brain the pia mater becomes more dense and fibrous, investing the cerebral crura, the pons, and the medulla oblongata. Here the contained arteries divide into groups of long vessels Vfhich penetrate the brain-substance and give rise to the anterior and posterior perforated spaces. The arteries of the brain are derived from the two internal carotid arteries, which enter the base of the skull through the carotid canals in the temporal bones, and from the two vertebral arteries, which, after ascending through the foramen magnum, unite to form the basilar artery on the surface of the pons. These main sources which furnish the blood to the brain pursue a tortuous course (Plate 3, Fig. 5, and Plate 4, Fig. 2) before they gain entrance into the calvarium, and immediately after- ward are disjjosed in a remarkable inosculation (the circle of Willis) (Plate 5, Fig. 3), for the purpose of equalizing and moderating the flow of the blood in the several parts of the brain. The internal carotid artery is surrounded by the cavernous plexus of veins by the side of the body of the sphenoid bone, and branches into the ophthalmic, anterior, and middle cerebral, posterior communicating, and anterior choroid arteries. The anterior and middle cerebral arteries arise from the internal carotid at the inner end of the fissure of Sylvius. The former passes to the longi- tudinal fissure, where it is joined to its fellow from the opposite side by the anterior communicating artery ; thence the two anterior cerebral arteries run side by side, supplying the adjacent frontal lobes and corpus callosum. The middle cerebral is the largest branch of the internal carotid (Plate 5, Fig. 3, No. 18). After giving off numerous small branches to the anterior perforated space to go to the corpus striatum, it penetrates deej)ly into the fissure of Sylvius, furnishing the anterior and middle lobes of the hemisphere. The anterior choroid branch of the internal carotid passes, by means of the slit (the hippocampal fissure) in the middle horn of the lateral ventricle, to the choroid plexus. The posterior communicating artery is often of unequal size (Plate 5, Fig. 3) on the two sides, and passes backward to join the posterior cerebral artery from the basilar, thus completing the arterial chain at the base of the brain. THE REGION OF THE HEAD. 23 The branches from the posterior cerebral arteries communicate with those from the anterior and middle cerebral. Before the vertebral arteries join to form the basilar they give off small branches in the neighborhood of the medulla oblongata to the contiguous parts, meningeal and spinal branches, and the posterior cerebellar artery on each side. Tlie other cerebellar arteries arise from the basilar. The basilar artery also gives off transverse twigs (Plate 5, Fig. 3) as it lies in the median groove on the pons, the auditory artery, accompanying the auditory nerve, being one of them. The vessels which penetrate into the brain are accomjDanied by delicate sheaths from the pia mater, which serve as lymphatic channels communicating with the sub-arachnoid and sub-dural spaces, the great cerebral lymph-spaces. The chief routes by which the pia mater conveys its capillary meshes into the brain-cavities are by the transverse fissure, as the choroid tela, into the lateral and third ventricles, and along the roof of the fourth ventricle, forming the velum interpositum and choroid plexus. The free intercommunication from side to side of the arteries at the base of the brain is most important, as there is no anastomosis between the peripheral arteries to the cortical surface and the ganglionic masses. Softening of the brain probably ensues upon inadequate collateral cir- culation of these vessels, whether due to a pathological or to a traumatic condition. Recently it has been shown that there are special systems of nutrient arteries derived from the circle of Willis, the central or gan- glionic and the cortical arteries. These systems are independent of each other, and their terminal arteries {of Cohnheim) do not anastomose. The most. noteworthy group of vessels of the ganglionic system are the branches from the middle cerebral artery which penetrate the anterior perforated space to supply the corpus striatum and optic thalamus on each side. A particular branch, the lenticulo-striate artery, so called because of its distribution to the lenticular and caudate nuclei, is often the source of cerebral hemorrhage. The cortical arteries are peculiar in their mode of origin, being adapted to the immediate supply of blood to the brain- tissue. They arise directly from the larger arteries in minute branches, which take a vertical or an oblique course, according to their destination. 24 THE REGION OF THE HEAD. those on the upper border of a convohition being vertical, and those on the sides passing obliquely. Those which penetrate the layers of cortical gray matter to the centrum ovale are the medullary capillaries, and vary from three to five centimetres, or from one to two inches, in length. These are the terminal arteries proper. In consequence of the independence of these cerebral capillary systems, many localized lesions, arising from emboli obstructing the blood-current, can be recognized and explained during life. Such a lesion may be limited to an area involving a special function, especially in the region supplied by the branches of the middle cerebral artery, — i.e., the motor centres and the faculty of speech. As elsewhere in the body, the principal vessels are supplied with sympathetic nerves, and these form in the head intricate plexuses mainly around the internal carotid arteries at the base of the brain. After removal of the pia mater, the brain-mass, with its furrows and convolutions, is exposed directly to view (Plate 10, Fig. 2). If the organ is retained within the skull, the proper relations which the surface- markings of the brain bear to the overlying structures can be profitably studied; and, as the subject of cranio-cerebral topography has now attained great importance, owing to the recent development of intra- cranial surgery, it will receive especial attention. In order that a clearer comprehension of this difficult and complex region may be obtained, a succinct description of the surface anatomy of the brain removed from the head will be given before explaining its application. The brain (encephalon) is that portion of the central nervous sys- tem which is contained within the cranium, and consists of the cerebrum, cerebellum, pons, and medulla oblongata. The cerebrum overlies the other portions of the brain, occupying the whole of the upper part of the cranial cavity. Its base rests on the anterior and middle fossae of the skull, and posteriorly it is separated from the cerebellum by the tentorium, the arching transverse fold of the dura mater. The cerebellum occupies the occipital fossae. The pons (Varolii) rests upon the basilar process and body of the sphenoid bone, and is connected with the cerebrum by the crura cerebri, and with the cerebellum by the crura cerebelli. The THE REGION OF THE HEAD. 25 medulla oblongata is the portion below the pons, and rests upon the basi- lar process of the occipital bone. It is continuous with the spinal cord. The brain conforms in size and shape with the interior of the skull, or brain-case. Its mass is to some extent related to the size of the body, and it is modified by the degree of mental development of the individual to whom it belongs, the intelligence probably depending upon the quality rather than upon the quantity of the organ. During intra-uterine life the development of the brain is very active, and at birth it is relatively of large size, of a soft pulpy consistence, presenting an approximation in form and relations to the adult brain. It grows rapidly up to the seventh year, becoming gradually firmer, and from that period until about the age of forty it increases very slowly. Its full growth is considered to have been attained between forty-five and fifty years of age. The average weight of the brain in males is forty-nine ounces; in females, forty-four ounces. In old age it decreases in a measure commensurate with the waning of the faculties. The brain consists of gray and white neural tissue variously disposed, the gray matter, composed mainly of nerve-cells, being arranged on the cortical surface, and in the ganglionic masses at the base of the organ ; the white matter, made up of nerve-fibres, being within, and serving to connect the gray portions and to bring them into relation with the spinal cord through the pons and medulla. The gray matter on the cortical surface is arranged in several layers of various forms of cells, which are intimately surrounded with numberless capillary vessels from the adjacent pia mater. These cells are connected through their pro- longations with the nerve-fibres of the white substance. The minute structure of the nerve-cells and nerve-fibres is described with the anatomy of the spinal cord in Vol. II. The whole brain is partially divided into symmetrical halves by a median fissure extending from before backward. The area of the surface of the brain is greatly extended by the cortical gray matter being irregularly raised in tortuous convolutions {gyri) or involuted into furrows {sulci), so that, with great economy of space, its actual surface is nearly six times what it would be were it merely a smooth envelope. The number of convolutions and the depth of the furrows between them 4 26 THE REGION OF THE HEAD. vary in diflfereut brains, and consequently the extent of the gray surface- matter upon which the intellectual capacity dejoends is variable. All physical and moral actions have their perceptive centres some- where in the cortical substance of the cerebrum. An animal may live after removal of its cerebral hemispheres, but it will be insensible to peripheral disturbance and incapable of exercising volition. The anterior portions of the hemispheres are without sensibility, as is manifest in cases of wounds in which they have been injured. The cerebrum consists chiefly of two lateral masses, called, from their shape, hemispheres, which are partially separated by the falx cerebri of the dura mater being received into the great longitudinal fissure between them. At the bottom of this fissure a band of Avhite transverse nerve- tissue connects the two hemispheres : this band, owing to the decussation of its component fibres, is known as the commissure of the cerehrum, or the corpus callosum (Plate 11, Fig. 1, No. 8). The hemispheres are not always of equal size, as the longitudinal fissure is not always placed exactly in the middle line (Plate 6, Fig. 1). The left hemisphere has generally been found to be larger than the right, and this has been attributed to the more direct l)lood-supply to the brain on that side, the left vertebral and carotid arteries having indepen- dent origins from the arch of the aorta. The right hemisphere is often, however, larger than the left (Plate 6, Fig. . 1) in a brain otherwise normally developed. Each hemisphere consists of an anterior {frontal), a middle [temporo-sphenoidal) , and a posterior [occipital) lobe, which are best seen on the under surface, and correspond to their respective posi- tions in the fossae of the cranium. Besides these there are the parietal lobe, placed between the frontal and the occipital lobe, on the lateral and upper surface, and the central lobe, situated within the fissure of Sylvius, at the base of the brain. The disposition of the convolutions and furrows on the surfaces of the two hemispheres is not identical, owing to the varying development of the several localities. It is, therefore, improbable that any definite area will always possess the same group of nerve-cells, for they may be on the surface of a convolution in one brain, and in an adjacent furrow THE REGION OF THE HEAD. 27 in another, depending upon tlie relative growth, of the locality. The primary fissures of the cerebral hemispheres — viz., the Sylvian, hippo- campal, parieto-occipital, and calcarine — appear during the third month of foetal life. The secondary fissures, the most important being the fissure of Rolando, appear between the fifth and sixth months. The further de- velopment of the fissures, and consequently of the convolutions, occujoies the last two months of foetal life and the first five or six weeks after birth, at which time the cerebral surface can be clearly mapped out. The largest and most complicated convolutions characteristic of the human brain are upon the upper surface of the hemispheres, frequently branch- ing toward the longitudinal fissure in their course like the letter Y. They do not exactly correspond upon the two sides. The most important of the convolutions on the external surface of the hemispheres are the central, or parietal, convolutions, which are always the most perfectly developed in all animals whose brains are convoluted. They occupy approximately the same relative position on each side of the brain, and are separated by the deep fissure of Rolando or central fissure (Plates 6 and 7). The area surrounding this fissure has been satisfactorily proved by physiological research and pathological facts to involve the principal motor functions of the body (Plate 2, Fig. 2, and Plate 10, Fig. 2). The fissure of Rolando (Plate 6, Fig. 1, Nos. 3 and 13, and Plate 7, Figs. 1 and 2, No. 1) usually begins close to the longitudinal fissure, about its middle, on the upper surface, and runs obliquely over the outer convex surface of the hemisphere downward and forward, until within a short distance of the fork of the Sylvian fissure. The lesser wing of the sphenoid bone is lodged within the fissure of Sylvius. This fissure begins (Plate 6, Fig. 2, No. 6) in a depression called the vallecula, at the anterior perforated space at the base of the cerebrum, and passes outward as a deep cleft (Plate 7, Fig. 1, No. 22), which divides into an ascending or vertical branch two centimetres, or a little less than an inch, in length, and a horizontal branch, which passes backward and curves slightly upward. It usually terminates in the parietal lobe in a bifid extremity. At the point where these branches originate, a third branch passes trans- versely, and is hidden within the substance of the brain. The branches PLATE 4. Figure 1. The right hemisphere of the cerebrum removed to show the falx cerebri and tentorium of the dura mater, and the relations of the great sinuses and their tributaries. (From the same head as in Plates 9 and 10.) 1. The cut tissues of the scalp. 2. The outer table of the skull-cap. 3. The diploic structure. 4. The inner table of the skull-cap. 5. The superior longitudinal sinus. 6. The inferior longitudinal sinus. 7. The falx cerebri. 8. One of the posterior tributary Telna. 9. The vense Galeni. 10. The straight sinus. 11. The tentorium cerebelli. 12. The position of the torcular Herophlli. 13. One of the anterior tributary veins. 14. The convolution of the corpus callosum of the left hemisphere. 15. The apex of the longitudinal sinus passing to the fora- men caicum. 16. The artery of the corpus callosura. 17. The crista galli of the ethmoid bone. 18. The corpus callosum. Figure 2, The posterior third of the skull and its scalp removed to show the posterior view of the dura mater, and the conflu- ence of the lateral and occipital sinuses with the superior longitudinal sinus. Also the posterior segments of the cervical vertebraj are removed to show the continuation of the dura mater of the brain with that of the spinal cord, the ganglions on the posterior roots of the cervical nerves, and the course of the vertebral arteries through the vertebral foramina. 10. The cut tissues of the scalp. The section of the parietal bones at the sagittal su- ture. The dura mater over the posterior lobe of the left hemisphere of the cerebrum. The great, or superior, longitudinal sinus. The posterior branches of the left middle meningeal artery. The left lateral sinus. The left occipital sinus. The left sub-oecipital (or first cervical nerve). The left vertebral artery curving upon itself before entering the foramen magnum. The ganglion on the posterior root of the second cer- vical nerve. The left transverse process of the atlas vertebra. The descending branch of the posterior division of the second cervical nerve, passing to the third. The ganglion on the posterior root of the third cervical nerve. The left internal jugular vein. The left common carotid artery. The ganglion on the posterior root of the fourth cervical nerve. 17. The left sterno-cleido mastoid muscle. 18. The ganglion on the posterior root of the fifth cervical nerve. 19. The left brachial plexus of nerves. 20. The posterior branches of the right middle meningeal artery. 21. The right lateral sinus. 22. The right occipital sinus. 23. The right posterior meningeal artery. 24. The right suboccipital (or first cervical nerve). 25. The right vertebral artery at its curvature. 26. The occipitalis major nerve (or internal branch of the posterior division of the second cervical nerve). 27. The right spinal accessory nerve. 28. The descending branch of the second cervical nerve. 29. The right common carotid artery. 30. The ganglion on the posterior root of the third cervical nerve. 31. The right internal jugular vein. 32. The right vertebral artery. 33. The dura mater of the spinal cord. 34. The right fourth cervical nerve. 35. The right fifth cervical nerve. 36. The right brachial plexus. Vol I Fif) 2 Copyright, 1831, ty fronSE Mc Cleuan, M D Dissects. PhotoinpM and Colored from Nature by GEomc Mc Clsllah. MB. ArmstrongtCo Litti. Boston, THE REGION OF THE HEAD. 29 of the fissure of Sylvius originate from the development of the hemi- sphere around the central lobe (or insula), which is usually covered in (Plate 7, Fig. 1), but is occasionally visible (Plate 7, Fig. 2, No. 7). The portion of the hemisphere overlapping the central lobe is called the operculum, from its lid-like character. The fissure of Sylvius is the most conspicuous of the cerebral fissures, and is easily recognizable. The parieto-occipital fissure is seen on the median surface (Plate 8, Fig. 1, No. 5, and Fig. 2, No. 20). It begins at the calcarine fissure near the corpus callosum, and ascends vertically, ending on the external surface, about an inch beyond the longitudinal fissure. It partially defines the parietal and occipital lobes, and occasionally blends with the horizontal branch of the Sylvian fissure. The calcarine fissure (Plate 8, Fig. 1, No. 7, and Fig. 2, No. 23) begins. near the posterior border of the hemi- sphere and passes forward, receiving the parieto-occipital fissure midway, and ends under the corpus callosum, penetrating into the posterior horn of the lateral ventricle, dividing the hippocampal convolution. The hippocampal fissure extends from the gyrus fornicatus to the hip- pocampal hook. The fascia dentata projects inwardly through this fissure, over which the pia mater passes to join with the choroid plexus of the lateral ventricle. The transverse fissure {of Bichat) is the breach between the cerebrum and the cerebellum (Plate 7, Fig. 1, No. 12). This fissure is due to the cerebral hemispheres being folded backward over the thalamic region, and it admits the pia mater into the interior of the brain as the velum interpositum. The interparietal fissure (Plate 7, Fig. 1, No. 5, and Fig. 2, No. 20) is the most important of the secondary furrows on the parietal portion of the hemisphere. It is very variable in form and position, sometimes being connected with the parieto-occipital and sometimes with the horizontal branch of the Sylvian fissure. Generally it begins between the latter and the Rolandian fissure, and curves backward somewhat parallel with the superior border of the cerebrum. It will be noticed that the character of nearly all the great fissures which separate the cortical surface into lobes is variable. This is even 30 THE REaiON OF THE HEAD. more so with regard to the smaller [intra-lohular) fissures between the convolutions in the difierent lobes of the hemispheres. The changes in the position of these furrows probably depend upon the variability of the development of their localities in difierent brains. The frontal lobe (Plate 6, Fig. 1, No. 2) consists of the cerebral surface situated in front of the fissure of Rolando and over the fissure of Sylvius. This lobe is divided by furrows (the frontal sulci) into four principal convolutions (the frontal gyri), which are subdivided into sec- ondary convolutions by modifications of their arrangement and connections. The frontal convolutions are the superior, middle, and inferior, and the anterior central (Plate 7, Fig. 2, Nos. 2, 3, 4, and 5). The superior frontal convolution (Plate 7, Fig. 1, No. 15) is in relation to the longitudinal fissure, borders on the anterior part of the corpus callosum internally, and extends to the under surface, where it is known as the olfactory convolu- tion, from its reception of the olfactory bulb in a depression (Plate 6, Fig. 2, No. 2). The adjacent middle frontal convolution (Plate 7, Fig. 1, No. 17) also extends to the under surface, and is there called the orbital convolution. The inferior frontal convolution (Plate 7, Fig. 1, No. 19) is below the preceding and in relation to the Sylvian fissure. It is now often called Broca's convolution, or the speech centre, from the localization of the movements of the lips and tongue, in articulation, in its posterior portion. The anterior central or ascending frontal convolution (Plate 7, Fig. 1, No. 14) is separated from the three frontal convolutions by the posterior frontal (or vertical) furrow (Plate 7, Fig. 1, No. 16), and it usually blends with the upper and lower frontal convolutions, and with the posterior central convolution, curving round the ends of the central fissure of Rolando. The parietal lobe occupies the upper and lateral portions of the hemisphere between the fissure of Rolando and the external part of the parieto-occipital fissure, and is over the horizontal branch of the fissure of Sylvius. There are three principal convolutions on the outer surface of this lobe, — the posterior central and the superior and inferior parietal convolutions. THE BEGION OF THE HEAD. 31 The posterior central or ascending parietal convolution is, as before stated, ordinarily continuous with the anterior central or ascending frontal. The two convolutions thus completely surround the fissure of Eolando (on the cortical surface), and the area thus formed is called the opercular lobe (Plates 6 and 7). The connecting portion above the fissure of Rolando is the para-central lobule, and that below it is the infra-central lobule. The latter region is considered to be correlated with the movements of the head and face, while those of the arm and hand are referred to the middle por- tions of the anterior and posterior central convolutions, and those of the leg and foot to the para-central region. The superior and inferior parietal convolutions are separated by the inter-parietal fissure (Plate 7, Fig. 2, No. 20), and are usually continuous with the convolutions of the occipital lobe by bridges of gray matter called the annectent convolutions. Both of the parietal convolutions are variously subdivided. The inferior is very tortuous, and commonly consists of two chief portions, the superior marginal and the angular convolution. The former usually blends with the lower part of the posterior central convolution and arches over the end of the horizontal branch of the Sylvian fissure to join the superior temporal convolution. The angular convolution (Plate 7, Fig. 1, !No. 7) is behind the suj)ra-marginal and parallel with the Sylvian fissure. It usually joins the middle temporal convolution by means of the two lower annectent convolutions. Upon the median surface the superior parietal convolution joins with the upper extremity of the posterior central con- volution to form the prcBcuneus, or quadrate lobule (Plate 8, Fig. 2, No. 18), which is continuous with the convolution of the corpus callosum. The occipital lobe, also variously subdivided, presents three principal convolutions, superior, middle, and inferior, which are subdivided by the occipital fissures and continuous with the convolutions of the parietal and temporal lobes. Upon the median surface the superior occipital convolu- tion, somewhat triangular in shape, forms the cuneus lobule, placed between the parieto-occipital fissure and the calcarine fissure. The surface of the occipital lobe which rests upon the tentorium is composed chiefly of two convolutions, the inner one of which blends with 32 THE BEGION OF THE HEAD. the hippocampal convolution and the outer one] is the occipital part of the occipito-temporal convolution. They are both continuous with the con- volutions on the under surface of the temporal lobe. The temporal lobe [temporo-sphenoidal) presents on its outer surface generally three defined convolutions, superior, middle, and inferior, separated by variously arranged temporal fissures, and connected, as above stated, with the parietal and occipital convolutions. The hippoeampal convolution is separated from the occipito-temporal convolution, on the under surface, by the collateral fissure. It forms the floor of the middle horn of the lateral ventricle, terminating in the hippoeampal hook {processus unciformis). The calcarine fissure divides the hippoeampal convolution at the back part of the corpus callosum. The central lobe, island of Reil, or insula, as it is variously known, is situated within the fork of the Sylvian fissure, where it is occasion- ally partially visible on the external surface (Plate 7, Fig. 2, No. 7), and is overlapped by the operculum. It consists of from four to six small convolutions (the gyri operti), arranged side by side upon a trian- gular mass, and appearing, when exjDOsed, very much like the fingers of the hand when closed upon the palm. These convolutions are the first to appear in the foetus and among animals, and are gradually enclosed by the other principal convolutions developing around them. Behind the central lobe there are usually several small convolutions, known as the temporo-parietal or retro-insular convolutions. They bridge over the temporal and parietal lobes. The fornicate convolution, or con- volution of the corpics callosum, which is to be seen on the median surface (Plate 8, Fig. 1, No. 16), extends round the upper surface of the corpus callosum, beginning at the anterior perforated space, and blending behind with the uncinate convolution below the quadrate lobule. Cranio-Cerebral Topography. — In the description of the landmarks of the head the relations which the external parts of the cranium bear to the surface-coverings are stated in detail. The topographical survey of the skull is here considered in its relation to the brain (Plate 9, Fig. 1). The points on the outer surface of the calvarium which bear upon THE REGION OF THE HEAD. 33 the position of the principal fissures of the brain cannot always be defi- nitely determined through the scalp, even though the head be shaved; and the most careful observation, or calculation based on statistics of measurements, cannot insure accuracy, for no two heads are precisely alike in their conformation and the arrangement of their contents. Only approximative results can be obtained by deducing from the landmarks of any skull the relative positions of the parts of the brain which it contains. A line drawn across the forehead above the eye- brows in front, and along the side of the head, two centimetres, or a finger's breadth, above the external angular process of the orbit, to the root of the zygomatic process and thence to the external occipital protube- rance, corresponds in a measure to the lower level of the cerebrum (Plate 2, Fig. 1) ; the cerebellum occupies the space below the latter portion of this line, but its lower level cannot be defined externally, as it depends upon the extent to which the lower occipital fossae project at the nape of the neck. The frontal and parietal eminences seem to indicate the propor- tionate development of the frontal and parietal lobes of the cerebrum. The parietal eminence corresponds to the supra-marginal convolution, and the frontal eminence to the superior frontal convolution. The pterion is the junction of the great wing of the sphenoid bone with the frontal, parietal, and temporal bones. Here the fissure of Sylvius commences. Its short ascending branch is just behind and parallel with the coronal suture, and its long horizontal branch extends upward and backward across the upper margin of the squamo-parietal suture on a line drawn on the side of the head from the nasion to the lambda (Plate 2, Fig. 2, No. 6, and Plate 53, Fig. 1, No. 18). The coronal suture passes from the bregma, the junction of the coronal and sagittal sutures, at the top of the head, to the middle of the zygomatic arch. The lambda is the junction of the sagittal and lambdoid sutures. The external portion of the parieto-occipital fissure is a little in front of the lambda. The inion is the external occipital protuberance. The upper end of the fissure of Rolando (Plate 2, Fig. 2, No. 13) begins at or near the middle line five centimetres, or about two inches, behind the coronal suture, or at a point one centimetre, or about half an inch, back from the middle of 5 PLATE 5. Figure I. The pia mater, with its vessels ramifying over the convolutions on the upper surface of the hemispheres, tudinal sinus in position, with clusters of the Paceliionian granules within it and upon either side. The longi- 1. The frontal sinus of the skull. 2. The forepart of the longitudinal sinus passing towards the foramen caecum. 3. The Pacchionian granules in relation to the left side of the longitudinal sinus. 4. The longitudinal sinus of the dura mater. 5. The vessels of the pia mater over the left hemisphere. 6. The longitudinal sinus passing backward to the tor- cular Herophili. 7. The Pacchionian granules in relation to the right side of the longitudinal sinus. 8. The vessels of the pia mater over the right hemisphere. Figure 2. The base of the skull with the cerebellum retained in the occipital fossae, to show the nerves and muscles passing to the eyeballs. Portions of the orbital roofs are removed 1. The frontal branch of the left ophthalmic nerve. 2. The left supra-trochlear nerve. 3. The left eyeball. 4. The left superior rectus muscle. 6. The nasal branch of the left ophthalmic nerve. 6. The fatty capsule of Tenon. 7. The left external rectus muscle. 8. The left optic nerve, passing Into the optic fora- men. 9. The left internal carotid artery. 10. The optic commissure. 11. The nerve to the left superior oblique muscle (or fourth cranial nerve). 12. The Gasserian ganglion of the left fifth cranial nerve. 13. The cut end of the left abducent nerve to the external rectus muscle. 14. The left lobe of the cerebellum, showing the superior cerebellar veins. 15. The right eyeball. 16. The right external rectus muscle. 17. The frontal branch of the right ophthalmic nerve. 18. The right superior rectus muscle. 19. The nasal branch of the right ophthalmic nerve. 20. The capsule of Tenon. 21. The right optic nerve. 22. The right internal carotid artery. 23. The pituitary fossa. 24. The nerve to the right superior oblique muscle (or fourth cranial nerve). 25. The Gasserian ganglion of the right fifth cranial nerve. 26. Section through the pons Varolii. 27. The right lobe of the cerebellum. Figure 3. The base of the brain, showing the anastomosis of the arteries, called the circle of Willis. (From an adult male.) The arteries of the corpus callosum within the longi- tudinal fissure. The arteries to the right frontal convolutions. The right anterior cerebral artery. The right fissure of Sylvius. The anterior communicating artery. The optic commissure. The cut end of the right internal carotid artery. The right posterior communicating artery. The right posterior cerebral artery. The basilar artery, resting on the median groove of the pons Varolii. The right superior cerebellar artery. The right inferior cerebellar artery. The right vertebral artery. The anterior spinal artery. The posterior inferior cerebellar artery. 16. The arteries to the left frontal lobe. 17. The left anterior cerebral artery. 18. The middle cerebral artery, within the fissure of Syl- vius, which is displayed by separation of the frontal and parietal lobes. 19. The cut end of the left internal carotid artery. 20. The pituitary body (in this case unusually large). 21. The left corpus albicans. 22. The left posterior communicating artery. 23. The left posterior cerebral artery. 24. The left auditory artery. 25. The left posterior cerebellar artery. 26. The left vertebral artery. 27. The medulla oblongata. 28. The external branches of the left posterior cerebellar artery. Plate 5 Vol I Fig Fiis 2 rvi ^ 1^ « an f X, n c />asecrt^, Phominphed md Colored from Nature by SEoirei- Mc a^LLM, M B. Copyright, m , by GccmE Mc Clellai,, M. D Atmsrro^SiCD Lith Bos THE REGION OF THE HEAD. 35 the distance from the ophryon, or glabella, to the inion. This fissure passes obliquely downward toward the horizontal branch of the fissure of Sylvius, and its lower end is two and one-half centimetres, or about one inch, behind the coronal suture where it joins the other bones to form the pterion. The posterior frontal sulcus (or furrow) is just behind and parallel with the coronal suture (Plate 2, Fig. 2, No. 4). It is some- times called the vertical sulcus. The ascending frontal convolution is between the posterior frontal sulcus and the fissure of Rolando. The upper end of the posterior frontal sulcus reaches to about the middle of the fissure of Rolando. The inferior frontal sulcus branches off from it about on a level with the superior stephanion, which is the point of intersection of the coronal suture and the ridge for the temporal fascia (Plate 2, Fig. 1, No. 5). The superior frontal sulcus begins in the upper part of the ascending frontal convolution, over the posterior frontal sulcus, and passes forward and parallel with the inferior. The lower end of the inferior frontal sulcus is separated from the fissure of Sylvius by the opei^- culum. The inter-parietal sulcus is behind the fissure of Rolando and parallel with the great longitudinal fissure between the hemispheres. It is midway between the latter and the parietal eminence (Plate 2, Fig. 1, No. 12). The basion is the middle of the anterior border of the foramen magnum at the base of the skull. The convolutions in the various regions are designated according to their positions, and their relations are mapped out when the positions of the fissures and sulci are determined. In seeking to ascertain the function of any locality on the cerebrum, it has been discovered, by means of gentle electrical stimulation, that the so-called motor cells are only in the gray matter on the surface, and that faradism of the sides and bottom of the fissures produces no motor reaction. The area of the opercular lobe, which includes the central fissure of Rolando, has been demonstrated to be the controlling centre of the move- ments of the limbs (Plate 2, Fig. 2, and Plate 10, Fig. 2). This area consists of the following convolutions : the anterior central (or ascending frontal) convolution, in front of the central fissure ; the posterior central 36 THE REGION OF THE HEAD. (or ascending parietal) convolution, behind the central fissure ; the para- central convolution, which surmounts the central fissure and extends on the median surface of the hemisphere to the calloso-marginal fissure (Plate 8, Fig. 2, No. 17) ; and the infra-central convolution, which separates the central fissure from the horizontal branch of the fissure of Sylvius. The infra-central convolution is correlated with the movements of the face (mouth, lips, tongue, throat, and larynx). Movements of the fingers are produced by stimulation of the cortical surface in the lower portion of the anterior central convolution, and movements of the thumb by stimulation of the corresponding portion of the posterior central convolution. The centre for the wrist is just above the latter, at about the middle of the central fissure, and that for the elbow and shoulder a little higher. Observation has shown that the centres for the upper extremity embrace the adjacent portions of the convolutions on both sides of the central fissure (Plate 10, Fig. 2). The movements of the hip, knee, leg, foot, and toes are presided over by the para-central convolution and the contiguous parts of the anterior and posterior central convolutions. The inter-parietal fissure is probably the posterior limit of the motor area. The frontal lobe of the brain anterior to the motor region seems to be related to the highest processes of the mind. Lesions in this locality are generally followed by proportionate mental deterioration. The sensorial area has not been conclusively determined, but it is believed to include the general surface of the cerebrum posterior to the inter-parietal fissure, limited externally by the parieto-occipital fissure (Plate 7 and Plate 10, Fig. 2) and internally by the calloso-marginal fissure (Plate 8). The centre for the movements of the eyes and eyelids involves the angular gyrus ; while the centre for vision extends from the angular gyrus over the occipital lobe and adjoining portions of the temporal and parietal lobes. The centre for hearing seems to be localized in the first and second temporo-sphenoidal convolutions. The centre for smell is supposed to be established in the hook of the hippocampal convolution, and the centre for taste just below it. The speech-centre has already been mentioned THE REGION OF THE HEAD. 37 in the description of the inferior frontal convolution (page 30). It is posterior to the fork of the fissure of Sylvius. The function of the island of Reil, or central lobe, is not determined, but, from its development, its position, and its relation to the other lobes of the brain as well as the basal ganglia, it probably plays an important role in the association of their related functions. During life the vessels of the pia mater are engorged with blood, especially if the patient has been under the influence of alcohol or an anaesthetic, and the subjacent cerebral fissures and sulci are indistinguish- able through an opening in the skull. All that is possible, therefore, is to conjecture or infer what portion of the cortical surface of the brain is at the bottom of a hole made by the trephine (Plate 50, Fig. 1). That the results of operative interference with the brain-structure should so often verify diagnosis is cause for wonder, when one considers the uncertain features of the anatomy of localization (Plates 9 and 10). Repeated examinations of the relations of the fissures to carefully mapped- out points after removal of a disk of bone on the heads of many cadavers have shown the author the fallacy of depending solely upon measurements, and the importance of making the artificial opening in the skull large enough to enable the operator to see the parts exposed. The base of the cerebrum is subdivided, as already described, into anterior, middle, and posterior lobes for each hemisphere. The posterior lobes are separated from the cerebellum by the tentorium of the dura mater. When the entire brain is removed from the calvarium and its under surface (Plate 6, Fig. 2) examined, the arrangement of the objects brought to view can be best studied by commencing in front. The longi- tudinal fissure, approximately in the middle line, separates the frontal lobes. Within the longitudinal fissure is the transverse commissure, or corpus callosum, from which white bands pass backward on each side to the fissure of Sylvius. They are called the peduncles of the corpus cal- losum. The lamina cinerea is a thiu layer of gray tissue extending from the corpus callosum to the optic commissure. The fissure of Sylvius, between the frontal and middle lobes, lodges the middle cerebral artery, 38 THE BEGION OF THE HEAD. and the fissure begins in the vallecula, which is also known as the anterior perforated space, because it is perforated by the vessels which supply the corpus striatum. This anterior perforated space is the apparent origin of the three roots of the first cranial nerves (or olfactory bulbs) (Plate 6, Fig. 2), on each side. Each olfactory bulb is received into a straight furrow on the orbital surface of the frontal lobe and lies on the cribriform plate of the ethmoid bone (Plate 3, Fig. 1, No. 1). The outer white root of the olfactory bulb originates in a nucleus of gray matter in the anterior part of the middle lobe of the hemisphere, and from the fissure of Sylvius passes along the outer side of the anterior perforated space. The middle gray root takes origin from the anterior perforated space and the furrow in which it rests on the frontal lobe. The inner white root arises from the gyrus fornicatus on the median surface of the hemisphere. The olfac- tory bulbs are in reality the prolongations of the frontal portions of the cerebral substance. On their under surface, as they rest on the cribri- form plate of the ethmoid bone, they give off about twenty nerves, which are distributed to the nasal mucous membrane (page 116), Behind the lamina cinerea is the optic commissure, formed by the union of the optic tracts, which arise from the anterior lobes {nates) of the corpora quadri- gemina, the corpora geniculata, and the posterior portions of the optic thalami, winding round the crura cerebri. In the skull the optic commissure rests upon the olivary process of the sphenoid bone, and from it the second cranial nerves (or optic), surrounded by prolongations of the dura mater, pass into the orbits through the optic foramina and enter the back of the eyeballs (Plate 5, Fig. 2, Nos. 8 and 21), eventually expanding into the retinse. The ophthalmic arteries accompany the optic nerves through the optic foramina. The commissure consists of lateral fibres which pass from one optic tract to the optic nerve of the same side, anterior fibres which pass from one optic nerve to the other optic nerve, posterior fibres which pass from one optic tract to the other optic tract, and middle decussating fibres which cross from the optic nerve of one side to the optic tract of the other side. The tuber cinereum is the gray prominence behind the optic commis- sure. This prominence is the floor of the third ventricle of the brain. THE REGION OF THE HEAD. 39 and from it is projected a red-colored conical tube, the infundibulum, to which is attached the pituitary body (Plate 5, Fig. 3, No. 20). The pituitary body is lodged in the sella turcica of the sphenoid bone (Plate 12, No. 27), and is difficult to retain in removing the brain from the skull. It consists of two lobes, the posterior one being originally a pro- longation downward of the cavity of the third ventricle through the infundibulum. Usually in later life the cavity in the posterior lobe of the pituitary body is obliterated. Behind the tuber cinereum are the corpora albicantia (Plate 6, Fig. 2, No. 34), which are formed by the bulbs of the fornix, the fibres of which pass downward, and then, after twisting in a figure-of-eight manner, pass upward to end in the optic thalami (Plate 8, Fig. 2, No. 11). Posterior to the corpora albicantia is a gray depression perforated by vessels which supply the optic thalami : it is called the posterior perforated space. It is placed between the diverging crura cerebri and in front of the pons Varolii. The crura cerebri consist of longitudinal fibres from the pons Varolii and upper part of the medulla oblongata, which pass forward and outward to the middle lobes of the hemispheres (Plate 6, Fig. 2). Division of one of the crura will exhibit in its middle some dark-colored tissue, called the locus niger, which separates the crus into two layers of fibres. The lower layer (the crusta) consists of coarse fibres arising from the anterior portion of the medulla and the pons. The upper layer (the tegmentum) is composed of fine fibres from the lateral portions of the medulla oblongata and also from the corresponding crus of the cerebellum. The lower fibres of each crus cerebri pass chiefly through the corpora striata, and the upper fibres through the optic thalami. In their passage through the ganglionic masses the fibres are greatly augmented, and, branching out, are dis- tributed to the cortical substance on the surface of the hemispheres. The third cranial nerves (or oculo-motor) appear just in front of the pons Varolii, issuing from among the fibres on the inner sides of the crura cerebri (Plate 6, Fig. 2, No. 11). These nerves originate from yellow nuclei beneath the passage-way between the third and fourth ven- tricles {aqueduct of Sylvius) (Plate 8, Fig. 1, No. 9), whence they pass forward through the locus niger and tegmentum in each of the crura, and, 40 THE REGION OF THE HEAD. after passing through the plexus of veins called the cavernous sinus, in close relation to the internal carotid arteries, enter the orbits by means of the sphenoidal fissures, to be distributed to the muscles of the eye- balls, with the exception of the external recti and the superior oblique. The fourth cranial nerves (or trochlear) (Plate 6, Fig. 2, No. 13) wind round the outer sides of the crura cerebri, having each originated from a gray nucleus in the floor of the aqueduct of Sylvius, very near the yellow nuclei of the third nerves. Their fibres decussate in the roof of the aque- duct, called the valve of Vieussens, about the middle line. They enter the orbit by the sphenoidal fissure and supply the superior oblique muscles (Plate 5, Fig. 2, No. 11). The fifth cranial nerves (or trifacial) appear at the base of the brain, each issuing in two separate bundles of fibres from the sides of the pons Varolii near its anterior border (Plate 8, Fig. 2, Nos. 15 and 16). These nerves are the largest of the cranial nerves, and, owing to their complex character and important associations, are of the greatest interest. Each nerve has two distinct roots, and therefore resembles a spinal nerve ; the anterior root is the smaller, consisting of three or four bundles of fibres, and having motor function, and the posterior the larger, com- posed of from seventy to one hundred bundles of fibres, and possessed of sensory function. The motor influences are chiefly confined to the muscles of mastication, while the sensory branches are distributed throughout the head and face (Plate 53, Fig. 1, No. 19). The two roots of this nerve commence in the upper portion of the medulla oblongata, the sensory root originating in the gray tubercle of Rolando, and the motor root from a nucleus of large cells closely connected with the posterior cornu of the medulla wherein the tubercle is situated. On its way forward the motor root receives some fibres from the floor of the fourth ventricle and also from the sides of the aqueduct of Sylvius. As the two roots issue from the pons Varolii they are separated from each other by a few of the transverse fibres of this body. They proceed forward on the apex of the petrous portion of the temporal bone, where there is a depression (Plate 3, Fig. 5, No. 3) for a semilunar ganglionic enlargement which occurs here upon the sensory root. This is the Gas- THE REGION OF THE HEAD. 41 serian ganglion (Plate 5, Fig. 2, No. 25), and it furnishes additional resem- blance to a spinal nerve, being somewhat similar to the ganglia on their posterior roots (Plate 4, Fig. 2). The motor root passes beneath the ganglion, and has no connection with it, — proceeding independently with the inferior maxillary branch of the sensory root through the foramen ovale, and after its exit at this foramen blending its fibres with those of that nerve. From the anterior border of the Gasserian ganglion three great nerve-trunks are given off, — viz., the ophthalmdc nerve, which passes through the sphenoidal fissure with the third, fourth, and sixth nerves and the ophthalmic vein, the superior maxillary nerve, which passes through the foramen rotundum, and the inferior maxillary nerve, which passes through the foramen ovale, by which the lesser meningeal artery (Plate 3, Fig. 2) also enters the skull. The sixth cranial nerves (or abducent) emerge between the pons and the anterior pyramids of the medulla oblongata (Plate 6, Fig. 2, No. 17), being connected with both of them. Their deep origins are in the fasciculi teretes in the floor of the fourth ventricle. They leave the skull by the sphenoidal fissures, passing between and supplying the two portions of the external recti muscles of the eyeballs (Plate 5, Fig. 2, No. 13). The seventh cranial nerves (or facial) have their deep origins in the floor of the fourth ventricle, whence they pass more superficially than the sixth nerves, and, bending abruptly upon themselves, emerge between the pons and the restiform tract of the medulla oblongata. They enter the internal auditory openings in the temporal bones, and, after passing through the aqueduct of Fallopius (Plate 3, Fig. 5, No. 9) and giving off" petrosal branches in their course, pass out by the stylo-mastoid foramina, to be distributed to the facial muscles. The eighth cranial nerves (or auditory) also arise from the floor of the fourth ventricle, and are in close relation with the seventh nerves, a con- necting link of nerve-tissue (the pars intermedia of Wrisberg) being interposed between both of them on each side. On account of this intimate relation, the facial and auditory nerves were formerly classified as two separate portions of the seventh cranial nerve, and because of their difference in character the former was called the portio dura and 6 PLATE 6. Flgfure 1. The upper surface of the brain of a white man about forty-five years of age, in sound condition and normal in general conformation, size, and weight. The right hemisphere is larger than the left, the longitudinal fissure not being in the middle of the cerebral mass. The pia mater has been removed to demonstrate the surface marlsings. 1. The longitudinal fissure. 2. The left frontal lobe. 3. The left fissure of Rolando. 4. The left parietal lobe. 5. Tiie left calloso-marginal fissure. 6. The left supra-marginal convolution. 7. The left angular convolution {gyrus), 8. The left occipital lobe. 9. The right superior frontal convolution. 10. The right middle frontal convolution. 11. The right inferior frontal convolution. 12. The right ascending frontal convolution. 13. The right fissure of Rolando. 14. The right ascending parietal convolution. 15. The end of the horizontal branch of the right fissure of Sylvius. 16. The right parieto-occipital fissure. 17. The right inferior occipital convolution. 18. The right middle occipital convolution. 19. The right superior occipital convolution. Figure 2- The under surface of the same brain as in Figure 1, showing the superficial origins of the cranial nerves. The pia mater is removed from the cerebrum, although retained over the cerebellum. 1. The longitudinal fissure. 2. The right olfactory convolution. 3. The right orbital convolution, 4. The right frontal lobe. 5. The right olfactory bulb (or first cranial nerve). 6. The right fissure of Sylvius. 7. The lamina cinerea. 8. The right optic nerve {or second cranial nerve). 9. The right temporo-sphenoldal lobe. 10. The right middle temporo-sphenoidal convolution. 11. The right oculo-motor nerve (or third cranial nerve). 12. The right inferior temporo-sphenoidal convolution. 13. The right trochlear nerve (or fourth cranial nerve). 14. The lobulus fusiformis. 15. The motor root of the right trifacial nerve (or fifth cranial nerve). 16. The sensory root of the trifacial nerve. 17. The right abducent nerve (or sixth cranial nerve). 18. The right facial nerve (or seventh cranial nerve). 19. The right auditory nerve (or eighth cranial nerve). 20. The right glosso-pharyngeal nerve (or ninth cranial nerve). 21. The right pneumogastric nerve (or tenth cranial nerve.) 22. The right hypoglossal nerve (or twelfth cranial nerve). 23. The right spinal accessory nerve (or eleventh cranial nerve). 24. The gray substance of the medulla oblongata. 25. The right lobe of the cerebellum. 26. The left first frontal convolution (gyrus rectus). 27. The left middle frontal convolution. 28. The left third frontal convolution. 29. The left olfactory bulb (or first cranial nerve). 30. The left fissure of Sylvius. 31. The anterior perforated space. 32. The optic commissure. 33. The pituitary body. 34. The corpora alblcantia. 35. The left oculo-motor nerve (or third cranial nerve). 36. The posterior perforated space. 37. The left trochlear nerve (or fourth cranial nerve). 38. The left trifacial nerve (or fifth cranial nerve). 39. The pons Varolii. 40. The left abducent nerve (or sixth cranial nerve). 41. The left facial nerve (or seventh cranial nerve). 42. The left auditory nerve (or eighth cranial nerve). 43. The left glosso-pharyngeal nerve (or ninth cranial nerve). 44. The left pneumogastric nerve (or tenth cranial nerve). 45. The left olivary body. 46. The left hypoglossal nerve (or twelfth cranial nerve). 47. The left spinal accessory nerve (or eleventh cranial nerve). 48. The left occipital lobe of the cerebrum. 49. The left lobe of the cerebellum. 01 -F- IX). THE REGION OF THE HEAD. 43 the latter tlie portio mollis. The auditory nerves commence by fibres which originate in the outer and inner auditory nuclei beneath the acoustic tubercles on each side of the floor of the fourth ventricle, and, after receiving some fibres from the transverse striae in this situation, unite into individual trunks which enter the internal auditory openings of the temporal bones in company with the facial nerves. Within the auditory openings these nerves subdivide into cochlear and vestibular branches, which are distributed to the internal ears (page 78). The nmth cranial nerves (or glosso-pharyngeal) appear on the surface of the restiform bodies, below the auditory nerves (Plate 6, Fig. 2, No. 20). The deep origins of these nerves are very close to those of the auditory nerves in the floor of the fourth ventricle. They make their exits from the cranium by means of the middle compartments of the jugular foramina, and are distributed to the mucous membrane of the pharynx and back of the tongue (Plate 13, Fig. 2, No. 16). The tenth cranial nei'ves (or pneumogastric) also appear on the restiform bodies, in close proximity to the ]Dreceding nerves (Plate 6, Fig. 2, No. 21). Their fibres of origin arise from special nuclei in the inferior part of the fourth ventricle, and soon blend together, forming single nerve-trunks which pass through the jugular foramina and are distributed to the pharynx, larynx, heart, lungs, oesophagus, and stomach (Plate 36, No. 61, and Plate 37, No. 32). The pneumogastric nerve is of extreme interest and importance, and is often called the vagus nerve, from its wandering course. The eleventh cranial nerves (or spinal accessory) are each composed of two separate parts, an upper or accessory part, which arises from the medulla below the pneumogastric, and a lower part, which arises from the spinal cord (Plate 6, Fig. 2, No. 23). The deep origin of the upper part commences in a special nucleus about the calamus scriptorius in the fourth ventricle. The spinal part of this nerve is composed of fibres which originate as low down on the cord as the fifth cervical vertebra, and it enters the skull at the foramen magnum to join the accessory part. The combined nerve then passes out of the jugular foramen with the pneumogastric and glosso-pharyngeal nerves, the acces- 44 THE REGION OF THE HEAD. sory portion blending with the pneumogastrie, while the spinal portion (Plate 13, Fig. 1, No. 8, and Plate 21, No. 13) supplies the sterno- mastoid and trapezius muscles. The twelfth cranial nerves (or hypoglossal) appear on the surface of the medulla oblongata, in the grooves between the olivary bodies and the anterior pyramids (Plate 6, Fig. 2, No. 46). The special nuclei from which the fibres of these nerves originate are to be found on the floor of the fourth ventricle in front of and nearer the middle line than the nuclei for the pneumogastrie nerves. The fibres are formed into two bundles which pierce the dura mater through separate openings and afterward combine within the anterior condyloid foramina, their final distribution being to the muscles of the tongue (Plate 13, Fig. 2, No. 19) and the depressor muscles of the hyoid bone and larynx. It will be noticed that most of the cranial nerves originate in the neighborhood of the fourth ventricle (or ventricle of the cerebellum) and the top of the medulla oblongata. These portions of the brain are there- fore of the greatest importance. The pons Varolii and the medulla oblon- gata, which rest upon the basilar portions of the occipital and sphenoid bones, have in the natural state interposed between them and the bone, as well as between them and the superposed cerebrum and cerebellum, a quantity of cerebro-spinal fluid which collects in the anterior and posterior sub-arachnoidean spaces. This fluid serves to equalize pressure and affords resistance to shock, especially from the effects of injury by contre-coup. The sub-arachnoid space communicates with the ventricular cavities of the brain by the foramen of Magendie, which is an aperture in the pia mater closing in the fourth ventricle. The aqueduct of Sylvius connects the fourth ventricle with the third ventricle at the base of the brain, and the latter is connected in front with the lateral ventricles by the foramen of Monro. The medulla oblongata (Plate 6, Fig. 9, No. 24) is the upper expanded extremity of the spinal cord on a level with the lower border of the foramen magnum. It is a white, pyramidal body, two and one-half centimetres, or about an inch, in length, and is partially divided anteri- orly and posteriorly by median fissures. The anterior median fissure ends THE REGION OF THE HEAD. 45 in the foramen ccecum just below the pons Varolii. The posterior median fissure expands into the floor of the fourth ventricle. Each half of the medulla oblongata consists of four longitudinal masses, — viz., the anterior pyramids, the lateral tracts and olivary bodies, the restiform bodies, and the posterior pyramids. The anterior pyramids increase in breadth as they approach the pons Varolii, through which their fibres pass to reach the crura cerebri. They are continuous with the anterior columns of the spinal cord, and consist of motor fibres. When the anterior pyramids are separated at their commencement, their inner nerve-fibres, below the surface, are readily seen decussating at the bottom of the anterior fissure. The outer fibres do not decussate, and ascend directly upward. An injury received upon one side of the brain is followed by loss of motion on the opposite side of the body {cross-paralysis), which effect is explained by the decussation of the inner fibres of the medulla which are continuous with the fibres of the lateral tracts of the opposite sides. The lateral tracts are situated on the outer side of the anterior pyra- mids. The olivary bodies project from the upper part of the lateral tracts, being separated by a depression from the pons. They are embraced by the ascending fibres of the lateral tracts as they diverge on their way to the pons and restiform bodies. These ascending fibres from the lateral tracts are more or less obscured by the arciform fibres, which loop across the surface and connect the anterior pyramids with the restiform bodies. The roots of the hypoglossal, glosso-pharyngeal, pneumogastric, and spinal accessory nerves emerge from the medulla in the immediate vicinity of the olivary bodies. The olivary nucleus is a layer of gray tissue within the olivary body upon each side, which presents on section a jagged toothed appearance, in consequence of which it is also called the corpus dentatum. The restiform bodies are the continuation upward of the posterior columns of the spinal cord. They diverge toward the cerebellum, constituting its inferior peduncles, and with the posterior pyramids assist in forming the lateral boundaries of the fourth ventricle. Gray matter is found in the interior of the restiform bodies. The posterior pyramids {funiculi graciles) are the two slender bundles on each side of the posterior median fissure, which diverge at the apex 46 THE REGION OF THE HEAD. of the fourth ventricle. The enlargement upon each of the posterior pyramids at this locality is called the clava, and it contains within it some gray matter, the nucleus gracilis. From the clava the posterior pyramid on each side gradually dwindles, its fibres passing to the cere- brum alono; the floor of the fourth ventricle and constitutins; with the fibres for the adjacent restiform body, which take the same course, the fasciculi teretes. The transverse strice on the fioor of the fourth ventricle, which form the roots of the auditory nerves, are derived from the arci- form fibres above described. They are chiefly composed of the fibres which do not enter the olivary body, but wind round beneath it and over the restiform body. The decussation of the fibres of the lateral tracts and the divergence of the restiform bodies and posterior pyramids cause a change in the arrangement of the gray matter in the upper part of the medulla oblongata, from the characteristic disposition of the gray matter in the spinal cord. The anterior cornua of the cord become separated from the mass of gray matter, owing to the decussation of the fibres from the lateral tracts, and behind the olivary bodies form the lateral nuclei. The rest of the gray matter of the anterior cornua in this locality is broken up into an interlacement of fibres, the formatio reticularis, by the longitudinal fibres from the lateral tracts being inter- sected by the deejjer set of arciform fibres. The pons Varolii (Plate 6, Fig. 2, No. 39) is situated just above the medulla oblongata, and in the skull rests upon the body of the sphenoid bone. It serves to connect the fibres of the medulla below with the cerebellum behind it by means of the crura cerebelli, as well as with the cerebrum above by means of the crura cerebri. The pons is defined above and below by very prominent margins, the upper margin arching over the crura cerebri, and the lower one, much less curved, distin- guishing it from the medulla. A shallow groove in the middle of its anterior surface accommodates the basilar artery (Plate 11, Fig. 1, No. 15). A section of the pons will show that the anterior portion is mainly composed of white transverse fibres crossed by white longitudinal fibres. The longitudinal fibres ascend from the medulla to pass to the cerebrum, and occasion the prominences on each side of the anterior surface of the THE REGION OF THE HEAD. 47 pons. The transverse fibres connect the hemispheres of the cerebellum. These fibres are arranged in layers having gray matter variously disposed among them, especially in the locality of the fourth ventricle, where most of the cranial nerves have their origin. The cerebellum in the skull (Plate 5, Fig. 2, Nos. 14 and 27) occupies the inferior occipital fossae, being protected by the tentorium of the dura mater from the weight of the overlying posterior lobes of the cerebrum. It consists of two lateral lobes or hemispheres separated pos- teriorly by the falx cerebelli of the dura mater and joined anteriorly by the vermiform process, or central lobe. The cortical surface, which is darker than that of the cerebrum, is arranged in parallel curved folds, with intervening fissures which vary in depth from the centre and subdivide the surface into lobules. There are four lobules on each hemisphere, the marginal lohde, the lobulus gracilis, the cuneiform or digastric lobule, and the amygdala or tonsil lobule. The horizontal fissure separates the upper and lower surfaces of each hemisphere of the cerebellum. The space between the two hemispheres below is called the valley. The upper surface consists of the expanded middle lobe, which is here designated the superior vermis. In front there is a notch into which the optic lobes are received, the surface overlapping the superior peduncles of the cerebellum and the valve of Vieussens. Behind them is another notch, into which the internal occipital protuberance projects. The superior vermis is subdivided into four parts. The central lobule stands out prominently in front; beneath this and over the valve of Vieussens is the lingula, a flattened transverse lamella, with small ridges extending into it from the crura cerebelli, the frcenula. Behind the central lobule is the monticulus cerebelli, and posteriorly is the smaller portion called the commissura simplex. The lamellae constituting the monticulus continue into the quadrilateral lobules on each side, and those which form the commissura pass to the posterior or crescentic lobules. The inferior vermis can best be seen after removing the amygdalae. It consists of three portions, — the pyramid, the uvula, and the nodulus. At the anterior part of the under surface is the sub-peduncular lobule, or flocculus. Passing from the nodulus to the floe- PLATE 7. The convolutions and fissures on the external surface of the right hemisphere. (Of same brain as In Plate 6.) The fissure of Rolando. The ascending parietal convolution. The superior parietal convolution. The calloso-marginal fissure. The inter-parietal fissure. The inferior parietal convolution. The angular convolution. The occipito-parietal fissure. The superior occipital convolution. The middle occipital convolution. The inferior occipital convolution. The transverse fissure (of Bichat). The right lobe of the cerebellum. Figu re 1. surface of the righ 14. The 15. The 16. The 17. The 18. The 19. The 20, The 21. The 22. The 23. The 24. The 25. The 26. The ascending frontal convolution. superior frontal convolution. posterior frontal fissure. middle frontal convolution. horizontal branch of the fissure of Sylvius. inferior frontal convolution. ascending branch of the fissure of Sylvius. superior temporal convolution. fissure of Sylvius. middle temporal convolution. inferior temporal convolution. pons Varolii. medulla oblongata. Figrure 2. The convolutions and fissures on the external surface of the left hemisphere. (Of same brain as In Plate 6.) 1. The fissure of Rolando. 2. The ascending frontal convolution. 3. The superior frontal convolution. 4. The posterior frontal fissure. 5. The middle frontal convolution. 6. The horizontal branch of the fissure of Sylvius. 7. The central lobe, seen on this side externally, in the fork of the fissure of Sylvius. 8. The ascending branch of the fissure of Sylvius. 9. The inferior frontal convolution. 10. The superior temporal convolution. 11. The middle temporal convolution. 12. The fissure of Sylvius, 13. The optic nerve. 14. The inferior temporal convolution. 15. The pons Varolii. 16. The medulla oblongata. 17. The calloso-marginal fissure. 18. The ascending parietal convolution. 19. Annectant convolutions. 20. The inter- parietal fissure. 21. The occipito-parietal fissure. 22. The angular convolution. 23. The superior occipital convolution. 24. The middle occipital convolution. 25. The inferior occipital convolution. 26. The transverse fissure. 27. The left lobe of the cerebellum. 2 m fD --J ' \ :^ >-\vl^.. THE REGION OF THE HEAD. 49 cuius is a thin valve-like fold of white matter, which is called the posterior medullary velum. This velum as it passes from the cerebellum becomes a very delicate layer of tissue covered with pia mater, and closes in the fourth ventricle. A longitudinal section of one of the hemispheres (Plate 11, Fig. 3, and Plate 12) will disclose a mass of white substance with radiating branches upon which the gray cortical substance is infolded. This is the arbor vitoe of the cerebellum (Plate 8, Fig. 1, No. 12). The white sub- stance of each hemisphere contains in its centre a nucleus of gray matter, the corpus dentatum. The function of the cerebellum has been concluded from physiological observations to be the co-ordination of muscular movements. As above described, the cerebellum is connected with the medulla oblongata by the fibres which ascend from the restiform tracts and constitute the inferior peduncles, or inferior crura. The lateral parts of the pons Varolii are the middle peduncles, or middle crura, of the cerebellum ; and its superior peduncles, or superior crura, are the fibres which connect it with the cere- brum. The innermost fibres of the superior peduncles decussate beneath the corpora quadrigemina, so that some fibres from one half of the cerebrum are continued into the opposite half of the cerebellum. Many of these fibres have been traced into the corpora deutata. Each of the superior peduncles {processus e cerebello ad testes) forms the upper part of the lateral boundary of the fourth ventricle, and is connected with its opposite fellow by means of the valve of Vieussens, or superior medullary velum. The valve is a thin layer of gray matter which forms the upper wall or roof of the important fourth ventricle (Plate 8, Fig. 2, No, 25). The fourth ventricle is the space between the cerebellum and the posterior surfaces of the medulla oblongata and the pons Varolii. Upon vertical section (Plate 8, Fig. 1, No. 10) it appears triangular in shape. This subdivision of the general ventricular cavity is the first part of the primordial central canal formed in the foetus. As just stated, the fourth ventricle is roofed over by the valve of Vieussens, bounded on each side by the superior peduncles of the cerebellum, and behind by the diverging posterior pyramids and restiform bodies. Inferiorly the arachnoid membrane is continued on to the posterior 7 50 THE REGION OF THE HEAD. surface of the spinal cord, an aperture usually existing here, called the foramen of Magendie, by which the ventricle communicates with the sub- arachnoidean space. A median furrow exists in the floor of this ventricle, which begins below in a pit (the ventricle of Arantius) and ends in the aqueduct of Sylvius. The divergence of the inferior cerebellar peduncles from this median furrow constitutes a resemblance to the point of a quill pen, and forms the calamus scriptorius of the old anatomists. The obex is an arching fold of tissue hanging over the apex of the calamus scriptorius. On each side of the median furrow are longitudinal eminences, the fasciculi teretes, which are crossed by the transverse strice (or strice acousticce) toward the posterior part of the ventricle. Externally to the fasciculus teres on each side is a shallow groove which terminates below in a depression, the fovea posterior, within which is the cinereous eminence. The fovea anterior is another depression in this groove, opposite the widest part of the ventricle. The auditory eminences are on each side between the foveas. These are crossed by the above-mentioned strice acousticce. The locus cceruleus is the name given to a variable bluish-gray nucleus in the upper angle of the ventricle. Besides these objects on the floor of the fourth venti'icle there are the nuclei of the cranial nerves which originate here. The pia mater {velum interpositum) , lining the fourth ventricle, is con- tinued into the third ventricle by the aqueduct of Sylvius (or iter a tertio ad quartum ventriculum) . The aqueduct is about half an inch long, and contains in its walls a large amount of gray matter, in which are the nuclei for the third, fourth, and upper part of the fifth cranial nerves. In front of and above the aqueduct of Sylvius are two pairs of bodies, — the corpora quadrigemina (Plate 8, Fig. 2, No. 24), or more properly the optic lobes, as they give origin to the optic nerves. They are relatively smaller in man, although their size in most animals bears relation to the power of sight. In birds there is only one pair of optic lobes; in the early stage of the human embryo there is only one pair also, but about the seventh month of foetal life this pair is sub- divided into two by a transverse groove. The posterior pair are the smallest, and are called the testes; the anterior pair, the nates, are larger and of a darker color. Immediately in front of the nates is situ- THE REGION OF THE HEAD. 51 ated a very vascular cone-shaped body, — the conarium, or pineal gland. It is about the size of a cherry-stone, and consists of many small follicles containing cells. These cells have a gritty substance within them {acervu- lus cerebri) consisting of carbonate of calcium and phosphate of calcium and of magnesium. This curious little body is larger in the child and in the adult female than in the adult male. Its function is unknown, but in birds is supposed to be associated with their homing instinct. The pineal gland is connected with the cerebrum by two white bands or crura (the peduncles of the pineal gland) which extend forward upon the inner sides of the optic thalami in the lateral walls of the third ventricle. The third ventricle is the narrow oblong fissure into which the aque- duct of Sylvius, which passes beneath the corpora quadrigemina, opens anteriorly. Its floor is formed by the parts within the inter-peduncular space at the base of the brain, — viz., the posterior perforated space, the corpora albicantia, the tuber cinereum, the infundibulum, and the lamina cinerea (Plates 6 and 8). The velum interpositum is stretched across above, and with the fornix, the arching layer of white matter beneath the corpus callosum, forms the roof of the third ventricle. The cavity of this ventricle is crossed by three commissural bands. ThQ posterior commissure is just in front of the pineal gland, and is com- posed of white fibres which serve to connect the optic thalami. The 7niddle or soft commissure is about half an inch broad, composed of gray matter, and also serves to connect the optic thalami. It is not always found even upon careful examination. The anterior commissure is a round white cord in the fore part of the cavity of the ventricle, the fibres of which pass through the adjacent corpora striata and extend into the temporo- sphenoidal lobes of the cerebrum. Just behind the anterior commissure is the foramen of Monro, an aperture leading into a short passage which soon branches after the manner of the letter Y> thus affording a com- munication between the third ventricle and the two lateral ventricles, by which the choroid plexuses of opposite sides are joined. The velum in- terpositum is a duplicature of the pia mater which is projected into the ventricular cavity of the cerebrum through the breach between its posterior lobes and the cerebellum (the transverse fissure of Bichat, Plate 8, Fig. 52 THE REGION OF THE HEAD. 2, No. 22). Its shape corresponds to that of the fornix, its projecting borders being the convoluted fringes called the choroid plexuses (Plate 11, Fig. 2, Nos. 8 and 19). These plexuses consist of minute arteries and veins in connective tissue. In the centre of the velum are two large veins (the venoR Galeni) which convey the blood from the great cerebral ganglia into the straight sinus (Plate 4, Fig. 1, No. 9). The ganglionic masses at the base of the brain consist of two pairs. The anterior are called, from their internal arrangement of alternate white and gray layers, the corpora striata. The posterior are the optic thalami, which are oval, elevated masses placed on each side of the third ventricle, and, embracing the crura cerebri, project portions of their upper surfaces in the floors of the lateral ventricles. They are exposed by removing the choroid plexuses. They are comj^osed of gray substance covered with a superficial thin layer of white tissue. The upper surface of each thalamus is subdivided by an oblique groove into an anterior tubercle and a posterior tubercle, or pulvinar. Beneath and behind the optic thalami on each side are two small gray eminences, known as the corpora geniculata, intermim and externum according to their position. They are in relation to the roots of the optic tract (the brachia), and are connected posteriorly by white bands with the corresponding corpora quadrigemina. The inner margins of the optic thalami are covered by the choroid plexuses, which separate them from the fornix, which is the layer of white matter arching over the inter-thalaraic region and enclosing the third ventricle. The fornix consists of a triangular central portion, the body, the broadest part of which is posterior to and closely connected with the corpus callosum, and anterior and posterior prolongations, known as the pillars or crura of the fornix. The posterior pillars descend from the outer angles of the body into the middle cornua of the lateral ventricles, constituting the hippocampi majores and terminating in the pes hippocampi. In their course they are in contact with the pulvinar of the optic thalamus on each side. The anterior pillars curve downward from the front of the body of the fornix, leaving the corpus callosum about the position of the foramen of Monro in the floor of the third ventricle, and, receiving THE REGION OF THE HEAD. 53 the peduncles of the pineal gland and fibres from the taenia and septum lucidum, pass to the base of the brain, their component fibres twisting in a figure-of-eight manner and returning upward and backward into the fore portions of the optic thalami. The curve which the fibres of each anterior pillar take at the base of the brain forms the corpus albicans of that side, as has been previously stated in the view of that region. On the portion of the under surface of the fornix which rests on the velum interpositum there are some transverse fibres which pass from the corpus callosum and form the lyra. The septum lucidum (Plate 8, Fig. 2, No. 6) is a delicate, almost trans- lucent, vertical partition extending from the front of the fornix, where it bends downward, and attached above and below to the under surface of the corpus callosum. It consists of two layers, gray on the inside and white without, and the space between them is called the fifth ventricle. This septum serves to divide the upper ventricular space within the hemi- spheres of the cerebrum into the right and left lateral ventricles. In cases of serous effusion within the general ventricular cavity of the brain the septum is often ruptured and free communication exists from side to side. The lateral ventricles (Plate 11) are semilunar in shape, and consist of a central part, or body, and anterior, middle, and posterior cornua, which extend respectively into the frontal, temporo-sphenoidal, and occipital lobes. The floor of the central portion of either of the lateral ventricles presents many objects of interest, which have the following relative positions. Posteriorly the margin of the posterior pillar of the fornix (the corpus fimbriatum) appears as a white cord accompanying the hippocampus major and sometimes called on this account the tainia hippocampi. In front of this is the choroid plexus, which usually extends so far forward into the cavity that very little of the subjacent optic thalamus is seen unless it is purposely uncovered. Beyond the thalamus, and separating it from the caudate portion of the corpus striatum, or anterior ganglionic mass, is the white band called from its course the tcenia semicircularis. The taenia descends anteriorly in connection with the anterior pillar of the fornix, and blends with the fibres composing the corpus albicans, as previously 54 THE REGION OF THE HEAD. described. Posteriorly it passes into the middle cornii of the lateral ventricle, apparently losing itself in the white substance in that cavity, but eventually terminating in the gray mass, the nucleus amygdalae. Owing to the upper surface of the taenia being somewhat harder than its deeper part, it was called by Tarinus the horny band. In the fore part of the centre of the lateral ventricle is seen the intra- ventricular portion of the corpus striatum (Plate 11, Fig. 2, No. 15). This ganglionic centre is best understood by making a horizontal section through it from the tsenia semicircularis outward, where it appears to consist of five ]Darts. The intra-ventricular portion, or the caudate nucleus, of the corpus striatum, above mentioned, is a gray, pear-shaped mass, the broad part of which is directed forward into the lateral ventricle, and its narrow end, the tail or surcingle, is continued into the middle cornu as far as the nucleus amygdalae. The surface of the caudate nucleus in the recent state is covered with a plexus of veins which empty into the vente Galeni. The extra-ventricular portion or lenticular nucleus (Plate 11, Fig. 1, No. 6) of the corpus striatum is the largest, and is lodged within the white substance of the hemisphere, being separated from the caudate nucleus by a layer of white matter, the internal capsule (Plate 11, Fig. 1, No. 12). On the external surface of the lenticular nucleus is another layer of white tissue, the external capsule (Plate 11, Fig. 1, No. 30), which again separates this portion from a thin layer of gray matter, the claustrum. External to the latter is the white matter which is subjacent to the central lobe, or island of Reil, the claustrum being formed by a portion of the under surface of the convolutions of the latter turned inward. A vertical transverse section of the lenticular nucleus demonstrates that it is composed of three smaller nuclei, the inner one gray, the middle dark yellow, and the outer of a reddish color. These parts are separated by layers of fibres which originate in the convolutions of the operculum. The nucleus amygdalee underlies the corpus striatum, and is in relation with the tail of the caudate nucleus, being continuous with the deep-seated cortex of the temporal lobe. The caudate and lenticular nuclei are united by many gray striae, which cross the internal capsule and give to the mass the peculiar striation to which it owes its name. TEE REGION OF THE HEAD. 55 The internal capsule consists of white fibres passing between the caudate nucleus and the thalamus opticus and the lenticular nucleus. Its anterior portion, or caudo-lenticular limb, is composed of fibres from the frontal lobe, and its posterior portion, or thalamo-lenticular limb, consists of motor fibres from the operculum on their way through the crusta of the crus cerebri to the anterior pyramid of the medulla oblongata. Fibres from the temporal and occipital lobes also compose the extreme end of the thalamo-lenticular limb, passing through the crus cerebri and pons to the cerebellum. There are also fibres passing from the cortex to the thalamus and to the gray matter in the pons. These fibres diverge above the caudate nucleus and intermingle with the fibres of the corpus callosum. The external capsule is thinner than the internal, with which it is con- tinuous behind. It consists of white fibres in connection with the claus- trum derived from the crus cerebri and the anterior commissure of the third ventricle. The posterior cornua (or digital cavities) of the lateral ventricles are not always equally developed in both hemispheres, and they are sometimes absent. They usually curve backward into the substance of the occipital lobes. In the floor of each posterior cornu is a claw-shaped eminence, the hippocampus minor, which is also known as the calcar, because it is produced by the infolding of the contiguous convolutions of the calcarine fissure. Between the posterior and middle cornua there is a smooth mass of variable size, the eminentia collateralis (or the pes acces- sorius), formed by the inward protrusion of the collateral fissure. The middle or descending cornua are the largest of the prolongations of the cavity of the lateral ventricles. They pass downward into the temporo- sphenoidal lobes toward the base of the brain, making remarkable curves backward, outward, and downward round the backs of the optic thalami, and forward and inward round the crura cerebri, resembling somewhat the horns of a ram, and hence are also known as the cornua Am- monis. They terminate in close proximity to the fissures of Sylvius. Continuous with the hippocampus minor, from the posterior cornu on each side, is a long, white, rounded eminence which follows the curve of the middle cornu and occupies the principal part of its cavity, the PLATE 8. Figrure 1. The convolutions and fissures of the inner surface of the left hemisphere of the cerebrum, and median section through the base of the brain, cerebellum, pons Varolii, and medulla oblongata. (From same brain as in Plates 6 and 7.) The ascending frontal convolution. The fissure of Rolando. The ascending parietal convolution. The prsecuneus, or quadrate lobe. The parieto-occipital fissure. The cuneus, or cuneate lobe. Theealcarine fissure. The corpora quadrigemina. The aquecluct of Sylvius, leading from the third to the fourth ventricle. The fourth ventricle. Tlie transverse fissure. The arbor vitse of the cerebellum. The left lobe of the cerebellum. The superior frontal convolution. 15. The calloso -marginal fissure. 16. The fornicate convolution. 17. The corpus callosum. 18. The anterior bend of the calloso-marginal fissure. 19. The septum lucidum. 20. The fornix. 21. The thalamus opticus. 22. The inferior frontal convolution. 23. The corpus albicans. 24. The optic nerve. 25. The fissure of Sylvius. 26. The motor oculi nerve. 27. Tlie pons Varolii. 28. The temporo-sphenoidal lobe. 29. The medulla oblongata. Figure 2. The convolutions and fissures of the inner surface of the right hemisphere of the cerebrum, and median section through the base of the brain, cerebellum, pons Varolii, and medulla oblongata. (From same braiu as in Plates 6 and 7.) The superior frontal convolution. The calloso-marginal fissure. The middle frontal convolution. The fornicate convolution. The corpus callosum. The septum lucidum. The fornix. The anterior pillar of the fornix. The optic thalamus. The inferior frontal convolution. The corpus albicans. The optic nerve. The motor oculi nerve. The pons Varolii. The medulla oblongata. 16. The fissure of Rolando. 17. The calloso-marginal fissure. 18. The quadrate lobe. 19. The corpus callosum. 20. The parieto-oeclpital fissure. 21. The cuneate lobe. 22. The velum interpositum. 23. The calcarine fissure. 24. The corpora quadrigemina. 25. The valve of Vieussens. 26. The great transverse fissure. 27. The fourth ventricle. 28. The arbor vitee of the cerebellum. 29. The right lobe of the cerebellum. ' T#;-fc) ^1 Y" THE REGION OF THE HEAD. 67 hippocampus major. This body is formed by the reduplication of the hippocampal convolution. Extending along its upper margin is the tcenia hippocampi, or white band continuous with the posterior pillar of the fornix, as previously described. At the lower extremity of the hippo- campus major there are four or five small elevations with intervening depressions, producing a fancied likeness to the paw of an animal, and hence called the pes hippocampi. Along the inner border of the hippo- campus major about the hippocampal fissure (which is really the lateral part of the transverse fissure) there is an edge composed of white fibres from the fornix {corpus fimbriatum) passing to the uncinate gyrus. Here there is a notched ridge of gray matter, the fascia dentata, which derives its name from the arrangement of the choroid arteries as they pass through the dentate fissure into the middle cornu. The anterior cornua of the lateral ventricles curve outward from each other into the substance of the frontal lobes round the caudate nucleus of the corpus striatum. The general roof of the lateral ventricles is formed by the corpus callosum, which, owing to its being formed of white transverse fibres extending between the hemispheres, is called the great transverse commis- sure of the cerebrum. The corpus callosum (Plate 8, Fig. 2, No. 5) is thicker and broader at its back part, the splenium, which is in relation with the transverse fissure where the pia mater enters the ventricles. It arches forward over the ventricular cavity, ten centimetres, or about four inches, in length, and anteriorly bends downward and backward, forming the genu. The lowest part of the bend is called the rostrum (or beak), and terminates in the two peduncles of the corpus callosum, they severally disappearing in the fissures of Sylvius. Upon the upper surface of the corpus callosum there is a middle groove, or raphe, and, in the recent state, on each side of this groove are readily distinguished two white longitudi7ial strice, called the nerves of Lancisi. Parallel and external to these are other fibres, the lateral strice. The anterior cerebral arteries proceed from before backward on the upper surface, and are here called the arteries of the corpus callosum (Plate 4, Fig. 1, No. 16). On its external borders the corpus callosum is overlapped on each side by the gyri fornicati (Plate 8). The borders themselves are known as the labia 68 THE REGION OF THE HEAD. cerebri, and the spaces between them and the commissure are the ven- tricles of the corpus callosum. If a section through the brain is made, either vertically or horizontally, the white matter is spotted with dots (the puncta vasculosa), due to the escape of blood from the severed ves- sels of the medullary substance (Plate 11, Fig. 2, No. 13). The medullary substance of the cerebrum consists of fine white fibres, which may be described as longitudinal, transverse, and diverging fibres. The longitudinal fibres compose the fornix, the striae longitudinales, the taeniae semicirculares, the gyri fornicati, the gyri uncinati, and the peduncles of the pineal gland. The transverse fibres connect the two hemispheres, and are found in the corpus callosum and the anterior and posterior commissures. The diverging (or peduncular) fibres are derived partly from the crusta and partly from the tegmenta of the crura cerebri, having originated in the cord and medulla oblongata. Those from the crusta are derived mainly from the anterior pyramids of the medulla, receiving en route through the crusta fibres from the gray walls of the aqueduct of Sylvius and the locus niger, and pass forward and outward to the internal caj)sule between the caudate and lenticular nuclei on each side. They distribute fibres to the nuclei of the corpora striata and receive others from them, and after issuing from the capsule radiate in all directions toward the cortical surface of the cerebrum, forming the corona radiata. Many of the fibres of the crusta liave been traced directly through the internal capsule to the cortex. The so-called pyramidal tract is composed of such fibres passing to the gray surface-matter of the ascending frontal and parietal convolutions in the neighborhood of the fissure of Rolando. Some bundles of the fibres on the outer portion of the crusta have been traced into the occipital convolutions of the hemi- spheres, and are known as the direct sensory tracts. The fibres from the tegmenta are derived from the reticular formation of the medulla oblon- gata, and are joined by fibres from the superior and middle peduncles of the cerebellum, and by fibres from the corpora quadrigemina, terminating apparently in the sub-thalamic region and the optic thalami. Many fibres from the external portions of the optic thalami have been traced radiating into the temporo-sphenoidal and occipital lobes. They constitute THE REGION OF THE HEAD. 69 the radiatio thalami. Besides these there are arcuate or association fibres, which bring adjacent convokitions into communication. Much patient and critical study has been given to the unravelling of the fibres of the medullary structure of the cerebro-spinal system by anatomists. Briefly stated, the conclusions drawn from their observations establish that there are three sets of nerve-centres, and three sets of nerve- fibres through which impressions are transmitted to and from the periphery and to and from the gray cortical surface of the hemispheres. The nerve- centres are the gray matter of the cord and medulla oblongata, the optic thalami and corpora striata, and the cortical surface of the convolutions. The nerve-fibres are those which connect the periphery with the gray matter of the cord and medulla, those which connect the gray matter of the cord and medulla with the basal ganglionic centres, the optic thalami, and the corpora striata, and those which bring these centres into relation with the cortical surface of the convolutions. The precise function of the basal ganglionic centres is unknown, but from their relations as above described it may be inferred that the corpora striata are connected with motion, and that the optic thalami are connected with sensation. In both there is crossed action; and the above inference is further empha- sized by clinical and pathological data, as well as by physiological ex- periments. Apoplexy attended by hemorrhage of one of the lenticulo-striate arteries into the substance of either of the corpora striata is followed by paralysis of motion of the opposite side of the body, without loss of sensa- tion; and similar involvement of either of the optic thalami is followed by loss of sensation in the opposite side, without diminution of power of motion. The approximate topographical relation of the anterior limit of the corpora striata to the external surface of the head may be indicated by drawing a line on each side from the stephanion to the pterion (Plate 2, Fig. 1). The same relative bearing which the optic thalami, within the head, probably hold may be mapped out by an anterior vertical line drawn from the bregma to the external auditory opening on each side, and a posterior vertical line drawn from the parietal eminence to the 60 THE REGION OF THE EAR. asterion (Plate 2, Fig. 1). A line drawn from the ophryon backward on the side of the head to the occiput, through the asterion, will indicate the position of the lateral ventricle, its anterior limitation corresponding to a line from the stephanion to the pterion, and its posterior limitation to a line from the parietal eminence to the asterion, as above described. The operation of trephining for tapping the ventricles for intra-cranial hemorrhage is very hazardous, and requires careful consideration of the position of the corpus striatum and optic thalamus and their relations to the highly vascular region of the Sylvian fossa and island of Reil, where the cortical vessels are large and near their origin from the middle cerebral and internal carotid arteries. If the procedure is attempted, in order to avoid this important area the best position for the application of the trephine Avill be on a line drawn from the ophryon to the lambda, and midway between the external auditory opening and the asterion. This will expose the temporo-sphenoidal lobe about the junction of the middle and inferior temporo-sphenoidal convolutions. A fine trocar passed in a direction forward and obliquely downward will (in the adult) reach the corresponding lateral ventricle. If the ventricle be distended with blood its walls will be reached two and half centimetres, or about an inch, from the surface. In two instances within the author's experience where ex- ploratory tapping was practised, although no benefit was derived from the operation, no ill effects were noticed, and the autopsies revealed no injury to the medullary substance even upon microscopic examination. THE EEGIO]^ OF THE EAE. The ear (auris), or organ of hearing, consists of two accessory portions, the pinna, or auricle, for the purpose of collecting and con- verging the aerial vibrations to the external meatus, which conducts them to the middle ear, or tympanum, and the essential portion, the internal ear, or labyrinth, where the sensation of sound is produced by their ulti- mate impression upon the auditory nerve. The pinna, or auricle (Plate 17), projects from the side of the head, being movably attached to the external auditory opening of the THE REGION OF THE EAR. 61 temporal bone by the anterior and posterior auricular ligaments, and the anterior auricular, superior auricular, and posterior auricular muscles. The anterior ligament connects the front of the pinna to the root of the zygoma, and the posterior ligament the back of the pinna to the mastoid process. The anterior and superior auricular muscles (Plate 20, No. 42) arise from the temporal arch of the aponeurosis of the occipito-frontalis muscle, and are respectively attached to the front and upper part of the pinna. The posterior auricular muscle consists of a few fleshy bundles which arise from the base of the mastoid process and are inserted into the back of the pinna. These auricular muscles are very imperfectly developed in man, and consequently the auricle possesses a limited functional capability, and persons who have been deprived of it suffer very little loss in their power of hearing. The pinna is formed of a yellow fibro-cartilage, with some fat and connective tissue, covered with integument, which is expanded from the side of the head and very closely adherent to the cartilage. The auricular cartilage is an incomplete irregular plate presenting many peculiar elevations and con- cavities. The deficiencies (or fissures of Santorini) in the cartilage are bridged over by fibrous tissue. The folded border of the pinna is called the helix (Plate 17, No. 9) ; the elevation within it, the antihelix; and the groove between them is the fossa of the helix (or fossa scaphoidea). The upper part of the antihelix divides anteriorly and encloses the fossa of the antihelix (or fossa ovalis). The concha is the deep concavity leading into the meatus. In front of the concha is the tragus (Plate 17, No. 13), a conical elevation which is usually covered with some conspic- uous hairs. Behind the tragus, at the outer part of the concha, is the antitragus. The tragus and antitragus are separated by a deep notch, the incisura. Below the concha is the soft pendulous portion of the pinna, the lobule (Plate 17, No. 16), which consists of fat and fibrous tissue covered with skin and without any cartilaginous basis. There is great variability in the development of the auricle, both as to its confor- mation and as to the manner in which it is set on the side of the head. The margin of the helix is often irregular and presents a conical process at its upper part. The skin covering the pinna is thin, with very little PLATE 9. Fig'ure The right side of the head, with the scalp removed to show the topographical survey of the skull in its relations to the brain. The temporal muscle and its fascia have also been removed to show their ridges. 1. The junction of the coronal and sagittal sutures {the bregma). 2. The cut edge of the scalp tissues. 3. The parietal eminence. 4. The junction of the lambdoid and sagittal sutures (the lambda). 5. The position of the junction of the occipital, parietal, and temporal bones {tlie aslerion). 6. The external occipital protuberance (ifie inion). 7. The coronal suture. 8. The point where the ridge for the temporal fascia crosses the coronal suture {the superior stephanion). 9. The frontal eminence. 10. The point of intersection of the ridge for the temporal muscle and the coronal suture {the inferior stephanion). 11. The superciliary ridge, covered with the tissues of the eyebrow {the ophryon). 12. The top of the squamo-parietal suture. 13. The junction of the nasal bones with the frontal (the nasion). The position of the anterior inferior angle of the pari- etal bone, and its junction with the great wing of the sphenoid and frontal and temporal bones [the pterion). 14, Figure 2. The right side of the head with the skull removed, showing the dura mater and the main branches of the great meningeal artery. This also illustrates the contiguous relations of the tissues of the scalp to the tables of the skull in their surgical application, and especially to the operation of trephining. 1. The scalp. 2. The pericranium. 3. The epicranial aponeurosis. 4. The outer compact table of the skull, 5. The diploic structure. 6. The inner compact table of the skull. 7. The posterior branch of the great meningeal artery. 8. The dura mater. 9. The anterior branch of the great meningeal artery and its vein. 10. The middle branch of the great meningeal artery and its vein. 11. The position of the anterior inferior angle of the pari- etal bone, corresponding to the root of the great meningeal artery. p]3te 9 Vol I FiP Fi0 2 £i,ssn-tixf. Plwtoirdpked mil Coloiril frmn Nature bt Gcoifsc McCimum,. M D. Copvnfhi, ISSI.by Ciom!: Mc CttLLAN^ M. a Arm.sironjtCD LilK 6^51 THE REGION OF THE EAR. 63 subcutaneous tissue, and is closely adherent to the subjacent perichon- drium, especially within the fossae or concavities. On the helix and the back of the pinna it is somewhat looser, and may become extremely swollen and painful from the tenseness produced by inflammation of the parts, as in erysipelas. There are numerous sebaceous glands within the scaphoid fossa and the concha. Besides the bands of fibrous tissue which fill up the breaches in the auricular cartilage, and which are known as the intrinsic ligaments, there are various small muscles which extend between the different parts of the cartilage. On the convex surface toward the side of the head there are some muscular fibres extending from the concha to the posterior border of the helix, called the trans- verse auricular muscle, and others from the top of the concha to the top of the back of the antihelix, called the oblique auricular muscle. On the outer or concave surface of the concha are the tragicus, consisting of ver- tical fibres on the front of the tragus, the antitragicus, which is usually well developed and extends obliquely from the antitragus to the caudate process of the helix, the helicis major, which ascends along the front part of the helix from the caudate process to the highest part, where it begins to curve backward, and the helicis minor, which passes from the floor of the concha anteriorly to the end of the helix. All these intrinsic auricular muscles are supplied by branches of the facial nerve. The arteries supplying the pinna are derived from the posterior auricular, temporal, and occipital arteries. The veins pass into the tem- poral vein. The nerves are branches from the great auricular branch of the superficial cervical plexus, the auriculo-temporal branch of the inferior maxillary, the posterior auricular branch of the facial, and the auricular branch (Arnold's) of the pneumogastric nerves. The latter especially supplies the concha. The external auditory meatus is the oval passage which extends three centimetres, or about an inch and a quarter, obliquely inward and forward from the concha to the tympanum, conforming to the petrous portion of the temporal bone. It is a curved oval canal, with the greatest diameter in the vertical direction at the concha, and in the transverse direction at the membrana tympani, which completely closes 64 THE REGION OF THE EAR. the bottom of the meatus. Owing to the oblique direction of the mem- brana tympani, the floor of the canal is a little longer than the roof, which is highest at the middle. The middle of the meatus is also the narrowest portion, and affords the greatest obstacle to the removal of foreign bodies from the bottom of the canal. The first twelve millimetres, or half-inch, of tlie meatus consists of a tubular continuation of the cartilage of the pinna, which is firmly connected with the osseous portion, although it is incomplete at the upper and back part, where the breach is filled in with fibrous tissue. The cartilaginous portion of the canal may be some- what straightened by drawing the pinna upward, outward, and backward. It is lined with integument which contains many sebaceous and ceruminous glands. The sebaceous glands are often the seat of minute abscesses which are extremely painful. The ceruminous glands secrete the cerumen or ear- wax. The osseous portion is two centimetres, or about three-quarters of an inch, in length, and more constricted than the cartilaginous portion, being formed by the auditory plate above and by the tympanic plate below. The auditory plate extends to the tympanum, while the tympanic plate at its inner end is grooved for the insertion of the membrana tympani. The upper wall of the osseous portion of the meatus is separated from the cra- nial cavity, as already stated, by only a thin layer of bone, which is apt to give way in abscess or bone-disease and occasion meningitis. The anterior wall is in relation to the condyle of the lower jaw and part of the parotid gland. The posterior wall separates the meatus from the mastoid cells, but is so thin a partition that it is liable to break down in mastoid disease. The inferior luall is very dense, and corresponds to the vaginal process of the temporal bone. The skin within the osseous portion of the meatus is very thin and adherent to the periosteum, and contains no sebaceous glands. The ceruminous glands resemble in structure hypertrophied sweat- glands, and are mainly confined to the skin lining the cartilaginous portion, although a few are placed along the roof of the osseous part of the canal. The skin at the bottom of the meatus is spread over the membrana tym- pani, where it forms a cul-de-sac, so that after maceration the pouch of cuticle may be removed, showing the exact form of the meatus. THE MEGION OF THE EAR. 65 The membrana tympani (Plate 3, Fig. 5, No. 17) is a thin, semi- transparent, oval membrane inserted obliquely downward and inward in a bony groove at tlie termination of the meatus. In children this mem- brane holds a more oblique position than in the adult, owing to the imperfect development of the bony walls of the auditory canal. There is generally, although not always, a deficiency in the upper part of the groove in which the membrane is attached, called the notch of Rivinus, which is merely covered by the skin lining of the meatus, and which may allow the escape of fluid from within the middle ear without perforation of the membrane. The membrana tympani is less securely attached at this notch than at the rest of its circumference : therefore when it is sub- jected to any violent concussion it is liable to give way at this point. The structure of the membrane is fibrous tissue, with most of the fibres radiating from the centre, which receives the handle of the malleus and is slightly drawn inward, so that this portion of the membrane is called the umbilicus. The membrana tympani is covered on the outer side by the skin lining of the meatus, as just stated, and upon its inner surface by the mucous lining of the tympanum. It is supplied by the tympanic branch of the internal maxillary artery, which enters by the Glaserian fissure, and it receives a branch from the auriculo-temporal nerve. The tympanum, or middle ear, is an irregular cavity, within the petrous portion of the temporal bone, which serves as an air-chamber between the auditory meatus and the labyrinth or internal ear, having a communication anteriorly with the pharynx by the Eustachian tube, so that the atmospheric pressure is equal on both sides of the membrane. The tympanic cavity (Plate 3, Fig. 5, No. 5) is somewhat broader behind and above than it is below and in front, and it is traversed by three little bones, the ossicles, which are movably connected with one another by ligaments and extend between the membrana tympani and the fenestra ovalis of the labyrinth, so that they serve to conduct the vibrations across the tympanum. It is not quite twelve millimetres, or half an inch, long from before backward, about six millimetres, or a quarter of an inch, in its vertical direction, and from two to four millimetres, or from one-twelfth to one-sixth of an inch, in width from its outer to its inner boundaries. The 9 66 THE REGION OF THE EAR. bony walls of this cavity are very tliin, and have important relations to the neighboring structures. The upper wall, or roof, is a thin bony plate on the anterior surface of the petrous portion and close to the junction of the squamous portion of the temporal bone. There is a squanio- petrosal suture in the roof of the tympanum in infancy which may admit of inflammation of the lining membrane being transmitted to the dura mater within the cranial cavity. The floor is a very narrow, delicate plate of bone, overlying the jugular fossa, and perforated anteriorly by a small foramen for the tympanic branch of the glosso-pharyngeal (Jacob- son's) nerve, which arises from the ganglion of Audersch and eventually passes out of the tympanic cavity through the upper tympanic canal into the middle fossa of the cranium, and is known as the lesser superficial petrosal nerve, whence it passes by the innominate canal in the sphenoid bone to join the otic ganglion. The outer wall is mainly formed by the membrana tympani and the margin of the bony groove which accommo- dates it. The latter has in it three small openings, — viz., the Glaserian fissure, a little slit at the upper and front part of the bony ring, which lodges the processus gracilis of the malleus and the so-called laxator tympani muscle, and gives jjassage to the tympanic branch of the internal maxillary artery ; the iter posterius, behind the membrana tympani, which gives entrance to the chorda tympani nerve ; and the iter anterius, which runs parallel with the Glaserian fissure and leads into the canal of Huguier, giving exit to the chorda tympani nerve. The inner wall is vertical and very uneven, and presents various objects of interest. At the upper part is the curved ridge corresponding to the aqueduct of Fallopius (Plate 3, Fig. 5, No. 9), which accommodates the facial nerve. Just below this is the fenestra ovalis, which communicates with the vestibule of the internal ear, but in the recent state is filled with a membrane to which is attached the base of the stapes. Below this is the promontory, which corresponds to the first turn of the cochlea, and is slightly grooved for the branches of the tympanic plexus of nerves. Below and posterior to the promontory is the fenestra rotunda, which is an opening at the bottom of a conical depression leading to the scala tympani of the cochlea, but in the recent state is closed by a membrane (the membrana tympani THE EEGION OF THE EAR. 67 secundaria). The conical eminence in front of the ridge of the aqueduct of Fallopius and behind the fenestra ovalis is called the pyramid. It is hollow, and contains the stapedius muscle, the little round tendon of which passes through a foramen in the apex to be inserted into the stapes. The posterior wall is perforated by openings of various sizes leading into the cellular spaces within the mastoid process, which are lined with the same mucous membrane as the cavity of the tympanum, and are mostly filled with air. Owing to the contiguity of structure, the mastoid cells are often involved in suppurative disease of the middle ear; their proximity to the lateral sinus has already been referred to (page 6). The anterior wall of the tympanum is very thin, and in direct relation with the carotid canal, from which it receives the tympanic branch of the internal carotid artery. At its upper part is an opening in a conical eminence which transmits the tendon of the tensor tympani muscles. This eminence is sometimes called the anterior pyramid. A bony septum separates it from the channel which conveys the air from the pharynx into the tympanum, the Eustachian tube. This channel begins near the processus cochleariformis in the lower part of the anterior wall, and runs for twelve millimetres, or about half an inch, to the angle of junction of the petrous and squamous portions of the temporal bone, where it has a rough, jagged extremity to which is attached a cartilaginous con- tinuation two and a half centimetres, or about an inch, in length. The mucous lining of the tymj^anum is continued through the Eustachian tube to its pharyngeal opening, which is behind the inferior meatus of the nose (Plate 12, No. 32) and in close relation with the tonsil gland. The ossicles which extend across the tympanum are the malleus (or hammer), the incus (or anvil), and the stapes (or stirrup), which are articulated to one another by ligamentous bands and so arranged that they serve to render the membrana tympani tense or loose according to the degree of impulse of the vibrations. The malleus consists of a head, which is attached by a suspensory ligament to the roof of the tympanum and articulates with the incus posteriorly ; a neck, the constriction below the head, tapering into the manubrium (Plate 3, Fig. 5, No. 14), to be fastened to the fibrous portion of the tympanic membrane along its 68 THE MEGION OF THE EAR. upper part, as far as the umbilicus, as already described ; tbe processus gracilis, a very long delicate j^roj action from a tubercle below tbe neck, extending into tbe Glaserian fissure and receiving tbe insertion of tbe ligamentous band formerly called tbe laxator tympani muscle; and tbe processus brevis, a sligbt elevation at tbe root of tbe manubrium, resting upon tbe membrana tympani and receiving tbe insertion of tbe tensor tympani muscle. Tbe incus is sbaped somewhat like a bicuspid tooth with widely separated unequal fangs. Tbe body of tbe incus has a glenoid depression for tbe reception of tbe bead of tbe malleus. Tbe long process (Plate 3, Fig. 5, No. 16) is placed nearly parallel with tbe manubrium of tbe malleus, and articulates with tbe bead of the stapes. The short process extends backward to be fixed in the neighborhood of the mastoid openings. The stapes is a beautifully constructed little bone very closely resembling a miniature stirruj). The neck is a constriction just below tbe point where the head is connected with the long process of tbe incus, and it receives tbe insertion of the tendon of tbe stapedius muscle after it comes through tbe posterior pyramid. Tbe base is the oval plate of bone, at the opposite ends of the delicate bony crura, which rests upon a membrane covering the fenestra ovalis, and thus completes the bony chain and serves to convey the impulse of the vibrations upon tbe membrana tympani to tbe fluid within the vestibule of tbe internal ear. Besides the ligamentous bands which support the ossicles and retain them in position, there are capsular bands at the articulations between tbe malleus and tbe incus, and between tbe incus and tbe stapes. Tbe amount of motion between these little bones is very slight, and is produced by the various actions of the tensor tympani and stapedius muscles. Tbe tensor tympani muscle arises from tbe apex of the petrous portion of the temporal bone and from the cartilaginous portion of the Eustachian tube, being lodo'ed within a special canal above tbe latter, and is inserted into tbe handle of the malleus. It is supplied by a nerve from tbe otic ganglion, in rela- tion to the internal maxillary artery, and by drawing the bead of tbe mal- leus inward renders the membrana tympani tense. The stapedius muscle arises from tbe hollow of tbe posterior pyramid, and its tendon, which is supplied with a synovial sheath, is inserted into THE REGION OF THE EAR. 69 the neck of the stapes. It receives a little branch from the facial nerve, which comes through an opening in the adjacent aqueduct of Fallopius, and the- action of the muscle probably serves to increase the tension upon the fluid within the vestibule. The mucous lining of the tympanic cavity is closely attached to the periosteum, except where it is pierced by the vessels and nerves, and is reflected over the membranes which fill in the bottom of the meatus and the fenestra ovalis, and completely surrounds the ossicles. It has been already stated that the mucous lining is con- tinuous from the pharynx by the Eustachian tube and is prolonged into the mastoid cells. The mucous lining is supplied with filaments from the tympanic plexus of nerves. The facial nerve (or seventh cranial nerve) enters the internal audi- tory meatus in the apex of the temporal bone, and, after interchanging a few fibres with the auditory nerve within the meatus, enters the aque- duct of Fallopius, which is a tortuous canal in the upper and posterior margin of the inner wall of the tympanum above the fenestra ovalis, and at the back of the tympanic cavity passes vertically downward to the stylo-mastoid foramen. The facial nerve within the aqueduct presents a gangliform swelling {intumescentia gangliforriiis) in the neighborhood of the hiatus Fallopii, which is an oblique slit in the anterior border of the petrous part of the temporal bone, giving passage to the large petrosal nerve, which, combining with the sympathetic branch from the carotid plexus, forms the Vidian nerve, and thus brings the facial nerve in rela- tion with the spheno-palatine (Meckel's) ganglion (Plate 3, Fig. 2, No. 6). From the gangliform swelling also arise the small petrosal nerve and the external superficial petrosal nerve, — the former passing to the otic ganglion and the latter to the sympathetic plexus around the middle meningeal artery. The tympanic branch of the facial nerve, as already stated, passes through a foramen in the descending j^art of the aqueduct to enter the base of the posterior pyramid to supply the stapedius muscle. In this vicinity the facial nerve receives a communicating filament from Arnold's nerve. Between this point and the stylo-mastoid foramen, where the facial nerve makes its exit from the skull, an important branch, the chorda tympani nerve (Plate 3, Fig. 2, No. 24), passes upward in a bony channel parallel to PLATE 10. Figure 1. The dura mater removed to show the vessels of the pia mater over the cortical surface of the right hemisphere. 1. The cut tissues of the scalp. 2. The pia mater enveloping the outer surface of the right hemisphere, and showing the complexity of the course of the external cerebral veins and arteries, which mask the underlying convolutions. 3. Section of the skull-cap. Figure 2. The pia mater removed from the right hemisphere to show the surface-markings of the iSssures and convolutions, and a topographical survey of the subdivisions of the motor area of the opercular region, according to the most recent Investigations of the localization of the centres of function of the cortical surface of the cerebrum. 1. The centre for the movements of the face (the expres- sions). 2. The centre for the movements of the fingers. 3. The centre for the movements of the thumb. 4. The centre for the movements of the wrist. 5. The centre for the movements of the shoulder and elbow. 6. The centre for the movements of the hip, knee, and leg. 7. The centre for the movements of the foot and toes. 8. The cut tissues of the scalp. 9. The fissure of Rolando (in this case joining the hori- zontal branch of the fissure of Sylvius). 10. The calloso-marginal fissure. 11. The superior parietal convolution. 12. The inter-parietal fissure. 13. The inferior parietal convolution. 14. The ascending parietal convolution. 15. The angular convolution. 16. The parieto-occipital fissure. 17. Section of the skull-cap. 18. The superior occipital convolution. 19. The superior temporal fissure. 20. The middle occipital convolution. 21. The centre for the movements of the lips, tongue, throat, and larynx. 22. The speech centre. 23. The superior frontal convolution. 24. The posterior frontal fissure. 25. The ascending frontal convolution. 26. The middle frontal convolution. 27. The inferior frontal convolution. 28. The ascending branch of the fissure of Sylvius. 29. The liorizontal branch of the fissure of Sylvius. 30. The fork of the fissure of Sylvius. 31. The superior temporal convolution. N. B.— The figures on Plates 9 and 10 were taken in succession from the head of an adult male, in remarkable physi- cal health, and represent the structures in their normal condition and position. Comparison of the series will demon- Btrate the perplexities attending the study of cerebral localization, and the parts to be encountered in cerebral surgery. Vol I Fici t Fig 2 I - ' , ■■ — ^ 'sr ^— '7 \ .-, — t* ^-4 — 2 d ,.^ — ; ,<,-,,,^A_ - 30 31 l^-.vf /)/,- .Ctfi/zlA, //A THE REGION OF THE EAR. 71 the aqueduct and enters the cavity of the tympanum through a foramen (the iter posterius) below the posterior pyramid and close to the membrana tympani. It is surrounded with the mucous lining of the tympanum, and, passing between the manubrium of the malleus and the long process of the incus, it emerges through a foramen (the iter anterius), the opening of a special bony canal (the canal of Huguier), close to the Glaserian fissure. Thence it descends between the two pterygoid muscles, behind the middle meningeal artery and in close relation to the auriculo-temporal and inferior dental nerves, and blends with the lingual branch of the inferior maxillary nerve, being eventually distributed to the submaxillary ganglion and the lingualis muscle. The chorda tympani nerve is generally believed to originate from the nerve of Wrisberg, intermediate between the auditory and facial nerves. Owing to its comparative distribution in the lower animals, it is supposed to preside over the sense of taste at the anterior portion of the tongue. Recently this nerve has been traced through the geniculate ganglion of the facial nerve to the fourth ventricle, and it is therefore considered as an independent cranial nerve, with the special function concerned in the power of speech (Sapolini). The facial nerve communicates in the temporal region by filaments with the pneumogastric, the glosso-pharyngeal, the great auricular, and the auriculo-temporal nerves, and with the carotid plexus ; and on the face with the numerous sensoiy branches from the trifacial nerve. A lesion of the facial nerve within the aqueduct of Fallopius from fracture of the base of the skull is attended by paralysis of the facial muscles, which is often a diagnostic feature of such an injury in connection with other symptoms. The tympanum is very richly supplied with blood by little arteries from various sources. The tympanic branches of the internal maxillary and internal carotid arteries, the petrosal branch from the middle menin- geal artery, and minute branches from the ascending pharyngeal artery, enter from the front, while from behind the stylo-mastpid branch from the posterior auricular artery penetrates by the aqueduct of Fallopius. The veins empty into the superior petrosal and lateral sinuses, and into the middle meningeal and pharyngeal veins. 72 THE REGION OF THE EAR. The internal ear, or labyrinth, consists of a very complex arrange- ment of spaces and channels in the most compact part of the temporal bone. There are three special compartments, known as the vestibule, the semicircular canals, and the cochlea. The vestibule is an irregular oblong cavity situated between the tympanum and the internal auditory meatus, having the fenestra ovalis on its outer wall, by which it com- municates with the tympanum when the parts are macerated, but in the recent state it is closed by the base of the stapes and its annular liga- ment, and on its inner wall there is a shallow depression in front, called the fovea hemisphcerica, the lower part of which, the macula cribrosa, is perforated by numerous foramina for the transmission of the filaments of the auditory nerve. Behind the fovea hemisphserica there is the crista, a ridge, with usually a little oj^ening, called the aqueduct of the vestibule, which gives passage to a small vein. In the roof of the vestibule there is a depression, the fovea hemi-elliiitica, which lodges the utricle. The five openings of the semicircular canals are in the posterior part of the vesti- bule, and anteriorly there is the opening into the cochlea : so that the vestibule is the common cavity in which all the others communicate. The semicircular canals are three bony canals above and somewhat behind the vestibule. Each canal forms about two-thirds of a circle ; and they differ in their directions, so that they are called superior, posterior, and external. Each canal is dilated at one end, — the ampulla, — corresponding to a similar dilatation of the membranous lining of the labyrinth. The canals all open into the posterior part of the vestibule by both of their extremi- ties, but, as one of the openings is made up of the extremities of two of the canals, there are only five distinct openings. The superior semicircular canal is vertical in direction, and arches across the anterior part of the petrous portion of the temporal bone, forming a rounded elevation on its surface. Its outer ampullated extremity opens into the upper part of the vestibule. Its non-ampullated extremity opens into the back of the vestibule by a common orifice with the similar extremity of the p)osterior semicircular canal. The latter is also vertical, but is placed at a right angle with the superior canal, being parallel to the posterior surface of the petrous bone. It is the longest of the three canals. THE REGION OF THE EAR. 73 The external semicircular canal is placed horizontally, and is the shortest. The cochlea closely resembles a common snail's shell, and is placed almost horizontally at the anterior part of the labyrinth. Its base corresponds to the bottom of the internal auditory meatus, and is perforated by the cochlear branches of the auditory nerve. Its apex is in relation with the upper and front part of the inner wall of the tympanum. The cochlea consists of a conical-shaped central axis, the modiolus, and a gradually tapering spiral canal which winds round the modiolus to the extent of two and a half turns, terminating at the apex of the cochlea in a little dome, — the cupola. The modiolus (or columella) is quite thick at its base, but gradually diminishes toward the apex, where it terminates in the infundibulum. Its interior is composed of cancellous bone, through the meshes of which vessels and nerves pass to the spiral lamina. The arteria centralis modioli is a little artery which is accommodated in a canal within the centre of the modiolus. The spiral canal is subdivided by a delicate plate, the lamina spiralis, partly bony (the lamina ossea) and partly membranous (the membrana basilaris), into two parallel tubes, called the scalce. The scala tympani is the larger and lower of these tubes, and is in relation with the tympanum by the membrane attached to the fenestra rotunda; the scala vestibuli is the upper tube, and is in direct connection with the ves- tibule. Owing to a deficiency in the top of the modiolus, the two scalse communicate with each other in the cupola by the opening called the helicotrema, which is partly bounded by a hook-shaped process at the end of the lamina (ossea) spiralis. The scala vestibuli is furthermore sub- divided by the oblique membrane of Keissner, which separates a portion of its upper part from the rest and thus forms the scala media, or cochlear canal. At the junction of the bony lamina with the modiolus there is a very small winding canal, the canalis spiralis modioli, which is occupied by an enlargement of the cochlear nerve, whence the nerves pass to the organ of Corti. The aquceductus cochlece is a small aperture leading to a canal which opens on the basilar surface of the petrous bone and trans- mits a vein from the cochlea to the internal jugular vein. The mem- branous continuation of the osseous lamina spiralis is thickened into an 10 74 THE REGION OF THE EAR. elevation, the limbus, or denticulate lamina, which overhangs the furrowed margin (the sulcus spiralis) of the bony lamina. The upper border of the sulcus is called the labium vestibulare, the lower, the labium tympani- cum. From the latter a delicate membrane (the membrana basilaris) extends to the outer bony wall of the cochlea, completing the scala tympani. Where the basilar membrane is attached to the outer wall there is a projection of connective- tissue cells, — the so-called Ugamentum spirale. The basilar membrane increases j)roportionately as the osseous lamina decreases toward the cupola. The membrane of Reissner is the oblique membrane which partitions off the cochlear canal from the scala vestibuli. It is a very delicate layer of connective tissue, covered on the cochlear surface with epithelium, and is continuous with the periosteum lining the upper surface of the lamina spiralis. The cochlear canal is formed on its inner wall by the membrane of Keissner, on its outer wall by the periosteum, on its lower wall by the limbus spiralis and the basilar membrane. Within the periosteum on the outer wall there is a conical eminence of connective tissue which accommodates a tiny vein, — the vas spirale. Between this and the attachment of Reissner's membrane there is another eminence, which consists of numerous anastomosing vessels, — the stricB vascularis. The basilar membrane sustains the complex and wonderful arrange- ment of the organ of Corti, upon which the ultimate filaments of the auditory nerves are distributed. The organ of Corti is covered over by the membrana tectoria, which is a fine layer of connective tissue extending between the labium vestibulare of the osseous lamina and the attachment of Reissner's membrane and placed parallel to the basilar membrane. The entire osseous labyrinth is lined with a very thin perios- teum, which cousists of fibro-elastic tissue with cell-elements and serves as a matrix for blood-vessels. From this tissue is secreted a small quantity of fluid known as the perilymph, or liquor Cotunnii, which surrounds and suspends the membranous labyrinth, a tubular reproduction of the osseous labyrinth, which also encloses a little fluid, the endolymph, or liquor Scarpoe. The membranous labyrinth receives the distribution of the terminal filaments of the auditory nerves, which, owing to their inter- THE REGION OF THE EAR. 75 position between tlie two fluids, are thus rendered susceptible to the most delicate vibrations. The vestibular portion of the membranous labyrinth forms two unequal communicating sacs, the utricle and the saccule. The utricle is lodged, as previously stated, in the fovea hemi-elliptica, and com- municates with the openings of the semicircular canals. It is the larger of the two pouches, and is thickest (the macula) at the crista, where the nerve-branches enter. The saccule rests in the fovea hemisphserica in front of the utricle. It is connected with the cochlear portion of the membranous labyrinth by the canalis reuniens, and in a roundabout way with the utricle by the aqueduct of the vestibule, thus establishing an uninterrupted channel for the endolymph throughout the membranous labyrinth. On the inner walls of the utricle and saccule there are many minute concretions of carbonate of calcium which seem to be in connection with the ends of some of the nerves. They are called otoliths (or ear-stones). The membranous semicircular canals correspond to the bony canals which contain them. They are connected at their ampullated extremities by the vessels and nerves to the contiguous periosteum, but in the rest of their extent they are only about one-third of the diameter of the osseous canals. The connection at the ampullated extremities with the periosteum forms a partial septum, the crista acoustica. The membranous structure consists of three layers, an outer fibrous layer, a middle, the tunica pro- pria, and an inner or epithelial layer. In the ampullated portions the epithelial layer presents spindle-shaped cells with ciliated processes, the auditory hairs. From the description already given of the relations of the membrane of Reissner, the basilar membrane, and the membrana tectoria within the scala vestibuli of the cochlea, it will be seen that they serve practically to constitute a shrunken membranous cast of the bony cochlea, resembling in a measure the membranous pouches within the vestibule and the semi- circular canals. This membranous cochlea, or cochlear duct, is the scala media above mentioned : it commences opposite the promontory of the tympanum, and, after winding along the middle of the cochlear canal, ends at the cupola in a closed extremity. It is connected with the mem- PLATE 11. Figure 1. * Transverse (coronal) section through the head just in front of the ears, passing through the ba.silar part of the occip- ital bone below and the bregma above. Showing the section of the brain, in situ, at the middle of the lateral ventricles. The figure represents the parts as seen from the front. 21. The right pneumogastric nerve. 22. The right longus colli muscle. 23. The first frontal convolution. 24. The falx cerebri, in the longitudinal fissure. 25. The second frontal convolution. The third frontal convolution. The left lateral ventricle. The internal capsule. The left fissure of Sylvius. The external capsule. The left optic thalamus. 32, 33, and 34. First, second, and third temporal convolu- tions. 35. The pons Varolii. 36. The basilar portion of the occipital bone. 37. The osseous portion of the left Eustachian tube. 38. The left ear. 39. The left parotid gland. 40. The left pneumogastric nerve. 41. The left internal carotid artery. 42. The lefL internal jugular vein. 43. The left longus colli muscle. 44. The pre-vertebral fascia. 1. Section of the superior longitudinal sinus of the dura mater, showing its triangular shape. 2. The cut tissues of the scalp. 3. The diploic structure, between the outer and inner tables of the skull. 4. The dura mater over the right cerebral hemisphere. 5. The gray involuted cortical substance of the brain. 6. The white medullary substance of the brain, showing puncta vasculosa. 7. Section of the inferior longitudinal sinus of the dura mater, showing its oval shape. 8. The corpus callosum. 9. The fornix. 10. The right lateral ventricle. 11. The right fissure of Sylvius. 12. The internal capsule. 13. The external capsule. 14. The right optic thalamus. 15. The basilar artery on the pons Varolii. 16. The right ear. 17. The osseous portion of the right Eustachian tube. 18. The right internal carotid artery. 19. The right parotid gland. 20. The righk internal jugular vein. 26, 31, Figure 2. Horizontal section of the head, with the brain in position. 1. The position of the foramen csecum. 2. The anterior median fissure (or fore part of the longi- tudinal fissure). S, The anterior cornu of the left lateral ventricle. 4. The intra-ventricular portion of the left corpus striatum (or the nucleus caudaius). 5. The position of the foramen of Monro. 6. The extra-ventricular portion of the left corpus stria- tum (or the nucleus leniicularis). 7. The left optic thalamus. 8. The left portion of the choroid plexus. 9. The splenium of the corpus callosum. 10. The posterior cornu of the left lateral ventricle. 11. The posterior median fissure (or hind part of the longi- tudinal fissure). showing the lateral ventricles and adjacent parts. The frontal sinus of the skull. The frontal lobe of the brain, with puncta vasculosa. The anterior cornu of the right lateral ventricle. The intra-ventricular portion of the right corpus stria- tum (or the nucleus caudaius). The extra-ventricular portion of the right corpus stria- tum (or the nucleus leniicularis). The right optic thalamus. The fornix. The right portion of the choroid plexus. The middle cornu of the right lateral ventricle. The posterior cornu of the rig-ht lateral ventricle. The point where the longitudinal sinus terminates at the torcular Herophili. Figure 3- Anterior posterior section of the head, with brain orbital muscles are seen in relation to the eyeball. 1. Section through the fissure of Rolando. 2. The occipito-parietal fissure. 3. The corpus callosum. 4. The corpus striatum. 5. The optic thalamus. 6. The velum interpositura. 7. Position of the fo\irth ventricle. 8. The transverse lissure, with the tentorium cerebelli. 9. The arbor vitaB of the cerebellum. 10. The inion. 11. The frontal lobe of the right hemisphere. in position, through the middle of the right hemisphere. The 12. The frontal sinus. 13. The superior rectus muscle. 14. The right eyeball. 15. The external rectus muscle. 16. The capsule of Tenon. 17. The right optic nerve. 18. The inferior oblique muscle. 19. The inferior rectus muscle. 20. The temporo sphenoidal lobe. 21. The antrum of Highmore, in the right superior max- illary bone. N. B.— The heads from which all of these figures were taken were very recent and without any hardening prepara- tion, so that the relations of the parts are perfectly preserved. (Figs. 1 and 2 are from male heads, about thirty and thirty-five years of age, and Fig. 3 from a female aged thirty-seven years.) Plate i ^\p 1 Fig 2 Vol I Fig 3 D'ssect^. Ppvto^rdphed dnd Colored from Natun; hi George Mr.. Clsllan. M D. Copyright, mi, by George Mc Cllllai., M. D. Afmjrtrong sCo LitS Bosicn. TSE REGION OF THE EAB. 77 brahous semicircular canals by tlie ductus reuniens, and is batbed without by tbe perilymph and within by the endolymph, like the rest of the mem- branous labyrinth. It is much more important, however, as it differs greatly in the character and arrangement of the complex structures con- tained within a portion of its space, which are known as the organ of Corti. This organ presents a slight elevation upon the basilar membrane, and appears to be a modification of the lining epithelium following the spiral turns of the membrane throughout its course, whence it was formerly called the papilla spiralis acoustica. Microscopic examination demonstrates that it consists of a peculiar arrangement of cells which bear a remarkable similarity to the key-board of a piano-forte. The central cells are rod-like bodies, the rods of Corti, which are disposed on the basilar membrane in two sets, an inner and an outer, in such a manner that they incline toward each other, blending at their upper extremities, forming a series of arches, the minute spiral sj)ace so enclosed by them being the tunnel of Corti. Both the outer and the inner rods are similar in structure and have a broad nucleated base, but they differ materially in shape, the outer being compared to a swan's head, which is received into the sigmoid cavities of several of the inner rods, which are in shape very like the upper extremity of the human ulna. There are a great many more inner rods than outer, and they are shorter and less obliquely placed. There are numerous stiff ciliated processes in relation to the inner and outer rods, called respectively the inner and outer acoustic hair cells. The acoustic hair cells are believed to be in direct connection with the ultimate fibrils of the cochlear nerves; and the intervals between them and the outer rods are occupied by long fusiform cells, the supporting cells of Deiters, which rest upon the basilar membrane. There is a net-like mem- brane, the lamina reticularis, spread out over the summits of the outer hair cells, through which the ciliated processes project. This net-work consists of several rows of plates, or phalanges, which dovetail with the phalangeal processes from the summits of the supporting cells. There is a some- what similar reticular membrane over the ends of the inner hair cells. The auditory nerve (or eighth cranial nerve) enters the internal audi- tory meatus (Plate 3, Fig. 1) with the facial nerve and auditory artery, 78 TEE REGION OF THE EAR. and at its bottom passes througli a perforated plate, the lamina cribrosa, to be distributed to the labyrinth, or internal ear, being divided into the vestibular and cochlear nerves. The facial nerve pursues an independent course along the aqueduct of Fallopius, as already described (page 69). The vestibular nerve becomes at first slightly enlarged, and then divides into various branches, which proceed to the utricle, the saccule, and the ampullae of the semicircular canals. The cochlear nerve immediately within the lamina cribrosa separates into numerous filaments, which enter the canals in the base of the modiolus. Thence they pass outward between the plates of the osseous lamina, through the ganglion spirale, to form a minute plexus, the ultimate filaments of which appear to be connected with the inner and outer hair cells of the organ of Corti. The labyrinth is supplied by the auditory artery, a branch of the basilar artery (Plate 5, Fig. 3) which accompanies the auditory and facial nerves into the internal auditory meatus and divides into vestibular and cochlear branches. These branches correspond to the nerves and ramify over the periosteal lining of the internal ear, receiving branches of com- munication from the vessels of the tympanic cavity and from the stylo- mastoid artery, which arises from the posterior auricular branch of the external carotid artery. In fractures involving the petrous portion of the temporal bone, attended with hemorrhage from the external auditory meatus, the source of bleeding is more generally from the minute arteries of the labyrinth and the tympanum than from the adjacent internal carotid artery or the internal jugular vein, laceration of either of which would be probably immediately fatal. The escape of cerebro-spinal fluid by the same exit is indicative of a fracture implicating the internal auditory meatus (page 7). The pressure of this fluid upon the perilymph within the labyrinth, to which have been attributed some cases of deafness, does not anatomically exist, as the only lymph-extension is by the sheaths of the auditory vessels and is too inconsiderable to admit of any degree of pressure by any amount of intra-cranial eflfusion. The auditory vein receives its blood from the veins of the labyrinth, and, passing out through the internal auditory meatus, empties it into the THE ORBITAL BEG ION AND THE EYE. 79 inferior petrosal sinus. There are also emissary veins from the cochlea and vestibule, which, passing through their respective aqueducts, terminate generally in the internal jugular vein. THE OEBITAL REGIOIT AND THE EYE. The orbits (Plate 28) are two cavities, one on each side of the upper part of the face, for the lodgement and protection of the eyeballs and their accessory apparatus. Each orbit is formed of the plane surfaces of the contiguous bones of the head and face, peculiarly disposed so that the eye is insured extensive range of vision. These cavities are pyramidal, their bases corresponding to the surface-margins, and their apices extending backward and inward in such a manner that their axes continued back- ward would meet over the body of the sphenoid bone where the optic commissure rests. The roofs of the orbits are formed anteriorly by the vaulted orbital plates of the frontal bone and posteriorly by the lesser rings of the sphenoid bone. The floors are formed chiefly -by the orbital processes of the superior maxillae, with the orbital processes of the malar bones anteriorly and the orbital surfaces of the palate bones posteriorly. They are much less concave than the roofs. The inner walls are nearly vertical and parallel with each other, while the outer walls are divergent. The inner walls are mainly formed by the ossa plana of the ethmoid bone and the orbital surfaces of the lachrymal bones, with portions of the sphenoid behind and the nasal processes of the superior maxillse in front. The outer walls are formed anteriorly by the orbital processes of the malar bones and posteriorly by the orbital plates of the great wings of the sphenoid bone. At the apices of the orbits the optic foramina transmit the optic nerves and ophthalmic arteries. External to the optic foramen at the back part of the outer wall of each orbit is the oblique sphenoidal fissure, between the greater and lesser wings of the sphenoid bone, which transmits the ophthalmic division of the trifacial nerve and the nerves to the muscles of the eyeballs (Plate 3, Fig. 2), together with the ophthalmic vein and some sympathetic filaments from the carotid plexus. Continu- ous with the sphenoidal fissure passing externally in the floor of each 80 TRE ORBITAL REGION AND THE EYE. orbit is the spheno-maxillary fissure, whicli in the recent state is bridged over by membrane. From the middle of the sj)heno-maxillary fissure in the floor of each orbit there extends outwardly a groove which leads into the infra-orbital canal and gives passage to the infra-orbital nerve and infra-orbital artery. Just within the nasal margin of each orbit is the lachrymal fossa, formed by the apposition of grooves in the nasal process of the superior maxilla and the lachrymal bone. This fossa is the opening into the nasal duct, which conveys the tears into the inferior meatus of the nose. In the sutural line between the ethmoid and frontal bones there are two foramina, the anterior and posterior ethmoidal, the former transmitting the nasal nerve and anterior ethmoidal vessels and the latter the posterior ethmoidal vessels. Tlie facial opening into each orbit is provided with a somewhat four-sided margin, peculiarly adapted above for the support of the eyebrows and at the circumference for the attach- ment of the eyelids. The external angular processes of the orbits are the outer limits of the superciliary ridges at the junction of the frontal with the malar bones. They are superficial, and important topographical landmarks, as has been j^reviously stated. Two and one-half centimetres, or about an inch, from the external angular processes inward toward the nose, on the borders of the orbital arches there are notches or foramina for the exit, upon the forehead, of the supra-orbital vessels and nerves. The bones forming the floor, the inner wall, and the roof of the orbital cavity are very fragile, the frontal portion of the roof being often only membra- nous, so that foreign bodies thrust into the orbit may readily penetrate downward into the antrum, inward into the ethmoidal cells, or upward into the cranial cavity. Owing to this latter feature, in abscess of the frontal lobe of the brain it is feasible to make an artificial oj)ening for drainage either through the orbit or through the nasal cavity. The eyebrows (supercilia) consist of the arching folds of the in- tegument connected beneath with the constrictor muscles of the eyelids, the orbicularis palpebrarum and occipito-frontales muscles, and especially the transverse fibres of the orbicularis known as the corrugator muscles (Plate 15, No. 22). They surmount the superciliary ridges of the frontal bone, supporting short, thick hairs which at the nasal side of the arch are THE ORBITAL REGION AND THE EYE. 81 directed upward and forward, and for the rest of the arch upward and outward with increasing obliquity. Below the eyebrows the skin is of very delicate texture, entirely destitute of fat, and spread over the elliptical folds, the eyelids, which consist of the so-called tarsal cartilages, attached to the margin of the orbit by the palpebral ligaments, and covered by the extremely thin inner layer of pale fibres of the orbicularis muscle, which are connected by loose cellular tissue to the skin. So exceedingly thin and delicate is the covering of the upper eyelid that when it is closed over the eye not only can its blood-vessels be readily seen, but, owing to the translucency of the tissues, often the iris may be distinguished through them. Occasion- ally there is a cutaneous fold from the upper lid overlapping the inner canthus. The laxity of the cellular tissue of the eyelids is manifest in the oedematous conditions following inflammation or contusion. The skin over the lids is wrinkled transversely, and on the upjDer lid there is a constant fold which marks the part covering the globe of the eye from that in relation to the soft structures of the orbit. The furrow which exists between the lower lid and the cheek deepens in old age and in many wasting diseases, and produces a peculiar sunken look about the eyes common to those conditions. The upper lid is larger and more movable than the lower. It is mainly by the action of the levator palpebrse muscle upon the upper lid that the eye is exposed, and by that of the orbicular muscle that the eye is closed. The interval between the two lids, ihefissura palpebrarum or rictus oculi, terminates in the inner and outer corners or canthi. The size of the rictus varies with the relation of the lids to the eyeball, according as the eyes are directed upward, forward, or downward. When the eye is looking upward (Plate 53, Fig. 1), the rictus is dilated, the upper lid arching as high as the upper margin of the cornea, while a portion of the white sclerotic coat is visible above the lower lid. When the eye is looking straight forward, the upper lid slightly covers the top of the cornea, and the lower lid is on a level with its lower border. When the eyes are downcast, the upper lid covers the cornea as far as the top of the pupil, and the lower is on a line with the lower border of the cornea. The lower lid holds the latter relation also in ordinary closure of 11 82 THE ORBITAL BBGION AND THE EYE. the eyes. The cartilage of tlie upper lid is larger than that of the lower one, broad in the middle and narrower at each end, while the lower is nearly uniform throughout. These cartilages are attached to the orbital margin by the palpebral ligaments, which are continuations of the perios- teum lining the orbit. The attachment of the cartilages to the malar portion of the orbit is by the external palpebral ligament, and that to the nasal process of the superior maxilla is by the internal palpebral ligament, or tendo oculi (Plate 15, No. 25). The latter is a fine, short cord at the inner canthus, which passes from its attachment in front of the lachrymal groove horizontally outward and divides into separate portions for the palpebral cartilages. The angular artery and vein are on the inner side of this tendon (Plate 18, No. 3). The orbicularis palpebrarum is the sphincter muscle surrounding the eyelids. It is attached to the tendo oculi and the inner and lower margin of the orbit, while above its fibres blend with those of the occipito-frontalis, and on the cheek with the elevators of the upper lip and nose, and the zygomatic! (Plate 15). The fibres of this muscle form oval loops round the eyelids and orbit, the orbital fibres being thicker and redder than those over the eyelids, as already mentioned. Forced contraction of the orbicular muscle serves to push back the eye into the orbit, and affords a soft protective pad in front of it. In winking it is only the paljjebral portion of the muscle which contracts. This momentary closure of the lids is accompanied by a slight drawing inward at the inner canthus, which directs the tears toward the punda lachrymalia. The "crow's-feet" of old age are the permanent radiating wrinkles produced by the orbital fibres drawing the brows down and the lower lids up. The corrugatores supercilii muscles (Plate 15, No. 22) are deep acces- sory portions of the orbicular muscles, which arise from the internal angular processes of the orbits, and, passing transversely outward, are inserted into the superficial muscular fibres and skin of the eyebrows. These bunches of fibres have special branches from the facial nerves, by their action wrinkle the forehead vertically, and are the proper muscles of frownino-. The levatores palpebrarum muscles arise from the lesser wings of the sphenoid bone in the back parts of the orbital cavities, above the optic THE ORBITAL REGION AND THE EYE. 83 foramina. They pass over tlie globes of the eyes, terminating in broad thin tendinous insertions at the tarsal cartilages of the upper lids beneath the palpebral ligaments. They are constantly in action when the eyes are open, becoming relaxed in sleep. The free margins of the eyelids are the thickest parts of the tarsal cartilages. They are straight, and when the eyes are closed are in accurate apposition. Upon their edges the eyelashes {cilia) are arranged in several rows. The lashes of the upper lids are longer and more numerous than those of the lower lids, and the upper ones curve upward, while the lower curve downward. The bulbs of the lashes are placed between the tarsal cartilages and the overlying muscular fibres. They are supplied with blood from the palpebral branches of the ophthalmic artery, which run parallel with and close to the borders of the lids. If the lids are everted, a number of sebaceous glands {Meibomian) are to be seen arranged in longitudinal parallel rows on the under surface of the tarsal cartilages. Their orifices are situated behind the lashes, on the margins of the lids, and their function is to prevent the lids from sticking together by their sebaceous secretion. Inflammation of one of these glands results in a small cystic abscess, known as hordeolum or stye. Within the orbit, just behind the external angular process, there is a shallow depression for the lodgement of the lachrymal gland, which is about the shape and size of an almond, and whose function is to secrete the tears. It is fastened in its place by a few fibrous bands from the periosteum attached to its upper surface, while below it rests loosely upon the eyeball and its superior and external straight muscles. Sometimes there is an accessory portion to the gland, which from its relation to the upper lid is called the palpebral portion {of Rosenynilller) . The gland is invested by a capsule of connective tissue. In structure the gland resembles very much the salivary glands, being an aggregation of lobes and lobules held together by fibro-cellular tissue. There are about a dozen excretory ducts, which take a parallel course and open in a row of orifices two and one-half centimetres, or about an inch, above the edge of the upper tarsal cartilage, upon the conjunctiva, the mucous lining of the eyelids. The tears {lachrymce) are the excessive secretion of the PLATE 12. Median antero-posterjor vertical section through the head, face, and neck of a powerfully-built man, thirty years of age. The superior longitudinal sinus of the dura mater. Section through the tables of the skull, showing the diploic structure. The cut tissues of the scalp. The falx cerebri. The inferior longitudinal sinus. The vence Galeni. The straight sinus. The fourth ventricle. Section of the cerebellum, showing the arbor vitee. The torcular Herophili. The occipital sinus. The medulla oblongata. The spine of the first cervical vertebra. The spine of the second cervical vertebra. Section through the ligamentum nuchse and muscles and fascia at the nape of the neck. The spine of the third cervical vertebra. The spine of the fourth cervical vertebra. The spine of the fifth cervical vertebra. The spine of the sixth cervical vertebra. The spine of the seventh cervical vertebra (the verte- bra prominens). The convolution of the corpus callosum and anterior cerebral vessels. Section of the corpus callosum (showing the genu). The fornix. The crista galU of the ethmoid bone. The frontal sinus. The corpora quadrigemina. The sella turcica, and position of the pituitary body. The sphenoidal sinus. The nasal meatuses. The pons Varolii, resting on the basilar portion of the sphenoidal bone. Breach through the septum of the nose, opening into the middle meatus. The opening into the Eustachian tube. The junction of the soft and hard palates. The vault of the palate. The incisor teeth of the upper jaw. The velum palati (the uvula). The incisor teeth of the lower jaw. The tongue. The pharynx. The epiglottis. The genio-hyoid muscle. The mylo-hyoid muscle. The body of the hyoid bone. The notch in the thyroid cartilage. The ventricle of the larynx. The commencement of the oesophagus. The cricoid cartilage. The spinal cord. The second ring of the trachea. The sterno hyoid and thyroid muscles. N. B.— This section was made shortly after death, and photographed immediately, so as to preserve the relations of the structures accurately. J. l„l '_ ^_ I ^ VC.i „;.: ±dlBiJ^:'MilMi.iUi-.j^.?-'!i..Mt:^aeu,i Crjpyn^ht, IS30„ by Gcomc Mc Clellak -V D. '^""SJ'ongtCoLrih Boston. THE ORBITAL REGION AND THE EYE. 85 lachrymal glands, which, under the influence of the emotions, or from the irritation caused by cold, or by any foreign substance coming in contact with the eye, overflow upon the cheek. Ordinarily the secretion of the gland serves to keep the surface of the cornea constantly moist, and to bathe the conjunctiva so that the movements of the lids and of the eyeball shall be free. The conjunctiva is reflected from the lids over the front of the eye, and the two portions are known respectively as the palpebral and the ocular. The palpebral portion is the thicker, is very vascular, and is pro- vided with numerous fine papillae, inflammation of which occasions the disease called "granular lids." At the inner canthus of the eye the conjunctiva is reduplicated, forming the plica semilunaris, and its angle of reflection from the lids to the eyeball is called the fornix conjunctivce. The continuations of the plica are the superior and inferior palpebral folds. When the lids are closed, even in the momentary action of winking, the conjunctiva becomes, as it were, a closed cavity which collects the tears and conveys them to the inner canthus, where there is an oval space between the two lids, the lacus lachrymalis. This space is occupied by the caruncula lachrymalis, a small, reddish-colored, conical body consisting of a number of follicles and resembling in structure the Meibomian glands. The caruncula secretes the whitish matter frequently noticeable at the inner angle of the eye. Near the inner canthus there are on the margin of each lid slight elevations, the papillae, with openings, the puncta, on their summits. The puncta are the orifices of the canaliculi, which pass inward toward the lachrymal sac. The manner in which these orifices are disposed for the reception of the tears is influenced by the action of a slip of muscular fibres from the orbicular muscle. This slip is called the tensor tarsi (or Horner's muscle), in consequence of its arising from the ridge of the lachrymal bone and being inserted into the tarsal cartilages of both lids near their puncta. This little muscle may also act as a compressor of the lachrymal sac. The canaliculi vary in their course, — a fact which should be thoroughly understood in undertaking to relieve obstruction of either of them by the introduction of probes or the knife. The superior 86 THE ORBITAL REGION AND THE EYE. canal first extends upward, and then, bending at an acute angle, passes inward and downward to join tlie inferior canal at its entrance into the tear-sac. The course of the inferior canal (which is the one most often affected) is first downward, and then it abruptly passes horizontally inward. These canals are dense and elastic, somewhat dilated at their angles, and have, especially the lower one, some spiral fibres from the tensor tarsi muscle wound round their walls. The lachrymal sac occupies the lachry- mal fossa within the nasal border of the orbit, with the tendo oculi and the tensor tarsi muscle in relation to it anteriorly. Sometimes in dis- tention of the lachrymal sac the tensor projects under the tendo oculi, which occasions a bulging without and within, the tense ligament depressing the top of the sac. The tendo oculi is always the guide to the sac. There are minute valvular folds in the mucous lining of the sac at the entrance of the canals, which is continuous with the conjunctiva through the canaliculi, and with the pituitary membrane of the nose through the nasal duct, the lower constricted portion of the lachrymal sac. The ocular portion of the conjunctiva is very differently arranged in its relations to the sclerotic coat and to the cornea. The sclerotic conjunc- tiva is very loosely attached to the subjacent coat, so as not to interfere with the movements of the eyeball. It is very thin, transparent, and, except when inflamed, nearly colorless. A few scattered blood-vessels extending toward the cornea are generally visible in the healthy condition of the organ ; but under the stimulus of a foreign body or of some action upon the vaso-dilator sympathetic nerves, very rapid congestion occurs, through a peculiarly intricate capillary plexus of vessels which is derived from the palpebral and lachrymal arteries. The laxity of the sclerotic conjunctiva is demonstrated in chemosis, where, owing to the distention, the patient cannot close his eye. The con- junctival vessels are so feebly supported in this loose tissue that they often rupture in paroxysms of whooping-cough or severe vomiting. Conjunctival extravasations are unlike similar conditions elsewhere, and the blood retains its scarlet arterial color, owing to the ready absorption of oxygen from the atmosphere by the blood through the delicate conjunctival membrane. In severe inflammations resulting from burns the mucous lining of the lids THE OBBITAL REGION AND THE EYE. 87 is very often so contracted that the condition of entropion is induced. The corneal conjunctiva is practically the outer layer of the cornea itself, con- sisting chiefly of epithelium, and being extremely thin, non-vascular, and transparent. There are numerous lymphatic vessels interspersed through the capillary net-work of the conjunctiva, and the membrane is everywhere extremely sensitive, owing to its abundant supply from the ciliary nerves. The cornea (pellucida) is the beautiful transparent convex struc- ture projecting from the outer coat of the eyeball, of which it constitutes about one-sixth part. It serves as a circular window by which the light is admitted into the eye. The cornea is composed of four layers of various forms of tissue. The outer layer is the delicate adherent covering of the conjunctiva, already described, which consists of several strata of epithelial cells. Beneath this is the proper substance of the cornea, which is fibrous, tough, and perfectly transparent, and upon which the thickness and strength of the cornea depend. The thickness is very deceptive, so that in oper- ating upon the cornea the knife may be thrust among the fibrous laminae of which it is composed. These laminae are demonstrable only by the use of reagents. There are some sixty laminae, the independent fibres of each being arranged in a j>arallel direction, while those of the alternate laminae cross at right angles the fibres of the laminae above and below. In the recent state there is no trace of this complex condition of struc- ture. Interposed between the lamellae are irregular spaces in which are retained the so-called corneal corpuscles, which, upon careful inspection under the microscope, appear to intercommunicate. The proper sub- stance of the cornea is continuous with the sclerotic coat, but, owing to the modified character of its connective tissue, in which the elements are so nearly alike in refractive power, in the healthy state it appears homogeneous. Immediately beneath the conjunctival epithelium there is a peculiar lamella, which has been named the anterior limiting or elastic lamina {of Bowman), in contradistinction to the posterior elastic lamina {of Descemet), which is the posterior modified lamella of the proper substance. The posterior elastic lamina is remarkable for its tendency to curl upon itself, with the corneal surface innermost, when it is separated from the rest 88 THE ORBITAL BEGION AND THE EYE. of the cornea. It probably has to do with maintaining the proper curva- ture of the cornea. The degree of curvature varies in different eyes and at different ages, being more prominent in early life, the cornea gradually flattening with age. The posterior surface of the posterior elastic lamina is covered with a continuation of the epithelial lining of the aqueous chamber, which resembles that of other serous membranes. There are no blood- vessels normally within the structure of the cornea. At its circumference the capillaries of the conjunctiva and sclerotic coat terminate in loops. In keratitis these marginal arteries furnish branches which penetrate into the interlamellated spaces. In the affection called pannus the conjunctival arteries send out radiating branches which pass over the cornea through the medium of the somewhat loosened epithelial covering and make it appear to be vascularized, whereas the vessels are entirely superficial and outside of the cornea proper. At birth the cornea is slightly opaque, but shortly afterward becomes transparent. In old age it diminishes in lustre and translucency, especially at the upper and lower borders, where, owing to fatty degeneration at these points, white crescents, forming the arcus senilis, appear. It is remarkable that wounds of the cornea heal promptly, in spite of the lack of direct blood-supply. There are very numerous branches from the ciliary nerves which enter the laminated tissue and form minute nerve-plexuses, rendering the cornea ordinarily extremely sensitive. In glaucoma it loses its sensibility, owing to the intra-ocular pressure upon the ciliary nerves before their branches reach the corneal destination. The cornea is set into the anterior border of the sclerotic coat very much as a watch-glass is received into its case, its margin being bevelled on the outside and that of the sclerotic on the inside. The sclerotic coat is the white, tough, protecting coat of the eye, which maintains the form of the globe, of which it constitutes the outer covering for tlie posterior five-sixths. It is thickest behind, and thinnest six millimetres, or about a quarter of an inch, from the cornea, where it is apt to be ruptured through violence. This is partly due to the resistance afforded by the recti muscles, which in a measure surround the globe and are inserted into the sclerotic six millimetres, or a quarter of an THE ORBITAL REGION AND THE EYE. 89 inch, from the cornea, leaving the intervening portions of the sclerotic unprotected except by the loose conjunctiva, which gives the brilliant white appearance to the front of the eyeball. The tendons of the recti muscles are exposed by removing the ocular conjunctiva, when they will be seen inserted upon the sclerotic coat in an elliptical manner, so that their central portions approach the cornea more nearly than their sides. This accounts for the unequal division of the tendons in the operation for strabismus unless the whole tendon be hooked forward and completely severed. In the case of the internal rectus muscle, which most frequently requires division, this should be especially remembered, as its tendon is nearer to the cornea than that of the others. The origins of the inferior and internal recti occur at the inner and lower margins of the optic foramen, in the apex of the orbit, from a fibrous band, — the ligament of Zinn. The external rectus muscle has two heads, the upi^er one arising from the margin of the optic foramen and the lower one from the ligament of Zinn and the lower border of the sphenoidal fissure. Between these two heads the motor oculi nerve, the nasal nerve, and the abducent nerve pass forward to their distribution, together with the oph- thalmic vein. The superior rectus muscle arises from the upper margin of the optic foramen and from the dural sheath of the optic nerve. The four recti muscles diverge from their origins and embrace the globe of the eye, being invested with a loose fascia, the capsule of Tenon (Plate 5, Fig. 2, No. 6). This fascia consists of two layers with an intermediate space, and thus resembles the tunica vaginalis. There is always a cushion of fatty tissue in the back of the orbit, even when the general state of the individual is one of extreme emaciation, and this cushion takes the shape of a cone, owing to its disposition about the globe of the eye. The prominence of the eyes depends somewhat upon the amount of this fat, and the " hollow-eyed" appearance in old age and in wasting disease is consequent upon its partial absorption. The recti muscles rest upon this orbital fat, and receive sheaths from the ocular layer of the capsule of Tenon, which is closely united with the margins of their tendons. The ocular layer of this fascia extends forward to the anterior borders of the orbit, blending with the periosteum, and 12 PLATE 13. Figure 1. The relations of the great vessels and nerves at the base of the skull to the posterior wall of the pharynx. 1. The left lesser wing of the sphenoid hone. 2. The basilar portion of the sphenoid bone. 3. The left ear. 4. The left mastoid cells. 5. The left internal jugular vein. 6. The left parotid gland. 7. The left pneumogastric nerve. 8. The left spinal accessory nerve. 9. The left sterno-mastoid muscle. 10. The left common carotid artery, at its bifurcation, 11. The right ear. 12. The right internal jugular vein. 13. The right parotid gland. 14. The right spinal accessory nerve. 15. The right pneumogastric nerve. 16. The right glosso-pharyngeal nerve. 17. The right internal carotid artery. 18. The posterior wall of the pharynx. Figure 2. The face laid open on the left side to show the relations of the salivary glands and the vessels and nerves to the tongue. The lingual branch of the trifacial nerve, or the gus- tatory (?) nerve. The tongue. The palato-glossus muscle. The sublingual gland. The lingual artery. The submaxillary gland. The genio-hyoglossus muscle. Section through the symphysis of the lower jaw. The genio-hyoid muscle. The mylo-hyoid muscle. The parotid gland. The duct of Stenson. 13. Section through the ramus of the lower jaw. 14. The uvula. 15. The tonsil gland. 16. The glosso-pharyngeal nerve. 17. The pneumogastric nerve, brought forward. 18. The internal carotid artery. 19. The hypoglossal nerve. 20. The Etylo-pharyngeus muscle. 21. The internal jugular vein. 22. The external carotid artery. 23. The hyoid bone. 24. The descending thyroid artery. 25. The superior laryngeal nerve. Figure 3. The posterior wall of the pharynx opened to show the larynx and the relations of the palate and tonsils from behind. 1. The left Internal jugular vein. 2. The left parotid gland. 3. The left palato-pharyngeus muscle. 4. The left spinal accessory nerve. 5. The left tonsil gland. 6. The left internal carotid artery. 7. The left pneumogastric nerve. 8. The left portion of the pharyngeal wall, reflected. 9. The posterior wall of the larynx. 10. The right internal jugular vein. U. The right parotid gland. 12. The right internal carotid artery. 18. The uvula. 14. The right palato-pharyngeus muscle. 15. The dorsum of the tongue. 16. The right tonsil gland. 17. The right spinal accessory nerve. 18. The epiglottis. 19. The right portion of the pharyngeal wall, reflected. 20. The right arytenoid cartilage of the larynx. Figure 4. The lower jaw removed to show the palate, the tonsils, the fauces, and the tongue extended. 1. The roof of the mouth, formed by the hard palate. 2. The right palatine artery. 8. Section of the right ramus of the lower jaw. 4. The right parotid gland. 5. The right palato-glossus muscle. 6. The right palato-pharyngeus muscle. 7. The right tonsil gland. 8. The foramen CEecum. 9. The clrcumvallate papillae. 10. The fungiform papillae. 11. The left palatine glands. 12. The left palatine artery and nerve. 13. Section of the left ramus of the lower jaw. 14. The left parotid gland. 15. The uvula. 16. The left tonsil gland. 17. The epiglottis. PJ ate 1 3 Vol 1 Fig 3 Fi0 2 F154 D'ssf.rtf^. Pf'otoqrduhed dnd Colored from Nature fa- George Mc Clsllai^, M D. Copynght, IS3I by George Mc Cuuan, M D. ArmilrongtCo Lifh &iston. THE ORBITAL REGION AND THE EYE. 91 especially with the two palpebral ligaments (formerly described). Owing to this intimate relation of the tendons of the recti muscles to their sheaths and the continuation of the latter with the anterior attachments of the capsule, the functional insertion of these muscles is greatly increased. This feature is particularly noticeable in the operation for strabismus, when the fascial connection with the tendon must be completely cut through as well as the tendon itself, or there will still be some counter- acting hold upon the globe. In this relation Tenon's capsule is of im- portance, but much undue stress has been given to it. For the rest, the outer orbital layer of the capsule, after sending areolar processes into the interstitial tissue of the fatty cushion, passes backward with the posterior part of the ocular layer to the back of the eyeball, blending with the sheath of the optic nerve. In this locality there is a delicate areolar layer which limits the so-called perineural space and allows the ciliary nerves and vessels to pass forward to where they perforate the back part of the sclerotic Coat. The superior oilique muscle, or trochlearis, is a slender muscular ribbon which arises by a tendinous slip in front of and at the inner side of the optic foramen. It passes forward along the roof of the orbit internally to the levator palpebrse muscle, and ends in a rounded tendon, which passes through a fibro-cartilaginous ring, the trochlea, which occupies a little fossa within the supra-orbital margin of the frontal bone above the internal angular process. The tendon is .provided with a syno- vial sheath as it passes through the trochlea, whence it is directed beneath the superior rectus muscle and is inserted into the sclerotic coat just without that muscle, midway between the cornea and the entrance of the optic nerve into the eye. The inferior oblique muscle is situated in the floor of the orbit, and arises from the orbital plate of the superior maxilla near the lachrymal fossa. It is directed beneath the inferior rectus muscle, to be inserted by a thin tendon at the outer part of the sclerotic coat posterior to the insertion of the superior oblique. The motor oculi nerve supplies the inferior oblique and all the recti muscles, except the external rectus, which receives the abducent nerve. The superior oblique receives the trochlear nerve. The motor oculi nerve within the sphenoidal fissure divides into two branches, which pass forward between the two origins of the external 92 THE ORBITAL REGION AND THE EYE. rectus muscle, separated from each other by the nasal nerve. The upper branch, which is the smaller, passes over the optic nerve and supplies the superior rectus and levator palpebrse muscles on their ocular borders. The lower branch subdivides into three little nerves, one directed under the optic nerve to supply the internal rectus, and another to the inferior rectus, while the third runs along the floor of the orbit to the inferior oblique muscle. The latter nerve furnishes a small branch to the ciliary ganglion. Paralysis of the motor oculi results in a drooping of the upper lid (ptosis), a fixed condition of the eye, with divergent (external) squint from un- opposed action of the external rectus muscle, and dilatation and immobility of the pupil. If the paralysis is complete there is apt to be a slight pro- trusion of the globe in consequence of the relaxation of the recti muscles. The abducent nerve also passes forward between the two origins of the external rectus muscle, above the ophthalmic vein, and terminates in fine filaments on the ocular border of the external rectus. This nerve carries with it from the cranial cavity some sympathetic fibres from the carotid plexus, and within the orbit it receives other sympathetic fibres from Meckel's ganglion, sometimes a twig from the ophthalmic nerve. Paralysis of the abducent nerve results in convergent (internal) strabismus. The trochlear is nerve (Plate 5, Fig. 2, No. 2) enters the orbit above the other nerves and crosses the origin of the levator palpebrarum to be dis- tributed to the superior oblique muscle, which it enters upon its orbital surface, sending a recurrent branch to the dura mater at the base of the cranium. Paralysis of the trochlearis nerve is attended with but little change in the condition of the eye as regards mobility, as the loss of function of the superior oblique muscle may be compensated for by the vicarious action of the other muscles. In all cases of paralysis of the orbital muscles tliere is more or less diplopia, or double vision. It will be observed from the above that the motor nerves in the orbit enter the muscles upon the ocular surfaces, except the trochlearis, which enters the superior oblique muscle on its orbital surface. The recti muscles move the eye upward, outward, downward, and inward, according to their position. Acting together they tend to retract the eye, the oblique muscles serving partially to antagonize them. The THE ORBITAL BEGION AND THE EYE. 93 superior and inferior recti muscles do not pursue a direct course, but rather one obliquely outward to their insertions, and consequently their inde- pendent action in elevating or depressing the eye would be accompanied with some deviation and rotation inward. This is overcome by the peculiar disposition of the oblique muscles, the inferior correcting the action of the superior rectus and the superior correcting the action of the inferior rectus. The independent action of the superior oblique muscle is to rotate the eyeball downward and outward, that of the inferior oblique muscle to rotate the eyeball upward and outward. The ingenious con- trivance of these ocular muscles which brings a complete picture before the eye in whatever position the head may be held can best be under- stood by remembering the rdle which the capsule of Tenon plays in blending their tendinous insertions and thereby serving to modify and harmonize their functions. The sensory nerves of the orbit are branches of the ophthalmic division of the trifacial nerve, — viz., the nasal, frontal, and lachrymal nerves. The nasal nerve, after passing through the sphenoidal fissure between the two origins of the external rectus muscle, separating the two branches of the motor oculi nerve, as has been stated, crosses over the optic nerve, beneath the levator palpebrse and superior rectus muscles, to the inner wall of the orbit, where, after giving off the infra-trochlear nerve, it leaves the orbit by the anterior ethmoidal foramen. This nerve contributes the long root to the ciliary ganglion in its passage between the origins of the rectus muscle; also the long ciliary nerves, which, passing up the inner side of the optic nerve, receive filaments from the ciliary ganglion and pierce the sclerotic coat to go to the iris. The infra-trochlear nerve passes to the inner angle of the orbit, to supply the lachrymal sac, the skin over the inner corner of the eyelids, and the adjacent side of the nose. The frontal nerve, the second branch of the ophthalmic nerve, runs along the upper surface of the levator palpebrse muscle, and about the middle of the orbit divides into the supra-trochlear and supra-orbital nerves. The supra-trochlear nerve passes above the pulley of the superior oblique muscle to the inner angle of the orbit, where it forms a connecting loop with the infra-trochlear branch of the nasal nerve, and sends a branch 94 THE ORBITAL REGION AND THE EYE. between the orbicular muscle and the orbital arch to supply the skin of the upper eyelid, forehead, and nose (Plate 53, Fig. 1, No. 13). Besides these there are several filaments which penetrate the frontal bone and supply the mucous lining of the frontal sinuses. The supra-orbital nerve is really the continuation of the frontal nerve. It passes through the su23ra- orbital notch or foramen and supplies sensation to the orbicular and occipito-frontalis muscles and the skin of the ujjper eyelid, forehead, and scalp. The lachrymal nerve passes on the outer side of the orbit, above the external rectus muscle, accompanying the lachrymal artery to supjDly the lachrymal gland. Before entering the gland it gives off a little twig which communicates with the orbital branch of the superior maxillary nerve. In front of the lachrymal gland the nerve pierces the palpebral ligament and supplies the skin at the outer border of the upper eyelid. Paralysis of the ophthalmic nerve is attended by loss of sensation in the globe of the eye and the mucous lining and cutaneous surfaces supplied by its branches, a condition which readily exposes the eye to injury. The ophthalmic or ciliary {sympathetic) ganglion is a tiny, reddish- colored, square-shaped body embedded in the orbital fat between the external rectus muscle and the optic nerve in the back of the orbit. It is in close relation to the ophthalmic artery. This ganglion has a motor root from the branch of the motor oculi nerve to the inferior oblique muscle, a sensory root from the nasal nerve, and a sympathetic root from the carotid plexus which joins it with the sensory root. From the anterior border of the ciliary ganglion about a dozen short, delicate, ciliary nerves pass forward with the ciliary arteries, in a wavy course, close to the optic nerve, and pass through the back of the sclerotic coat, where they are joined by the long ciliary branches from the nasal nerve and are distributed to the ciliary muscle and the iris. The ophthalmic artery, after its origin from the internal carotid artery near the anterior clinoid process of the sphenoid bone, enters the orbit with the optic nerve through the optic foramen. It first holds a position external to the artery, but within the orbit becomes very tortuous, crossino- over the optic nerve to the inner side of the orbit, and giving off numerous branches. The first branch of importance is the arteria centralis retince, THE ORBITAL REGION AND THE EYE. 95 whicli enters obliquely the outer side of the optic nerve close to the optic foramen and passes forward in the centre of the nerve to the retina. From the ophthalmic, near the above, are given off the internal and external ciliary branches, the former subdividing in the perineural space into six or seven minute branches, and the latter into as many more, all of which pierce the sclerotic coat. There is a long branch of each of these sets, which pass one upon each side of the optic nerve, and, after entering the sclerotic coat, continue between it and the choroid coat toward the iris. On the outer side of the optic nerve, and between the external and superior recti muscles, the lachrymal artery arises. It proceeds with the lachrymal nerve to the lachrymal gland, being finally distributed to the neigh- boring portion of the conjunctiva and eyelids. It also sends a recurrent branch through the sphenoidal fissure, which anastomoses with a branch from the middle meningeal artery. Anterior to the lachrymal artery, the muscular branches are distributed to the ocular muscles. The supra- orbital artery is a very small vessel which accompanies the supra-orbital nerve in its course and distribution. The anterior and posterior ethmoidal arteries pass out of the orbit through the ethmoidal foramina, the anterior being accompanied by the nasal nerve. The palpebral arteries supply the lids and form arches around their margins by anastomosing with the lach- rymal and infra-orbital arteries. The nasal and frontal arteries are the terminal branches of the ophthalmic. The nasal artery leaves the orbit above the tendo oculi and joins the angular branch of the facial on the nasal side of the eye. The frontal artery inosculates with the supra- orbital artery at the inner angle of the eye. There are two ophthalmic veins, which convey the venous blood from the orbit to the cavernous plexus around the internal carotid artery. The super^ior ophthalmic vein commences at the inner angle of the eye, where it communicates with the frontal and angular veins. Thence it passes along the inner and upper part of the orbit, receiving tributary veins which correspond to the arteries with which they are in relation. The inferior ophthalmic vein receives the blood from the outer and lower part of the orbit and passes along the floor to empty into the sujDerior vein, or directly into the cavernous plexus. The optic nerve, from the optic foramen to its entrance at the back 96 THE ORBITAL REGION AND THE EYE. of the globe of the eye on the nasal side of its axis, is about two and one- half centimetres, or an inch, in length. It is enveloped by a double sheath, consisting of a prolongation of the pia mater within and of the dura mater without. The dural sheath is firm and fibrous, and is continuous with the sclerotic coat, and at the optic foramen it also blends with the periosteum of the orbit from which the ocular muscles arise. The optic nerve is surrounded by the perineural space, formed by the inflection of the orbital fascia, already mentioned, in which the ciliary vessels and nerves pass forward. The orbital fat separates it from the recti muscles. It is pierced on its outer side, near the optic foramen, by the central, or retinal, artery, which, with its vein, passes forward in a central canal made up of processes from the pial sheath. The eyeball is com^^osed of three concentric coats, — an outer fibrous, strong, and protective coat, consisting of the sclerotic and cornea ; a middle or vascular coat, composed of blood-vessels, muscular tissue, and dark pig- ment cells, and consisting of the choroid, the iris, and the ciliary processes ; and an inner or nervous coat, the retina, which is the expansion of the optic nerve. Within these there are three transparent media for the trans- mission of light, — viz., the aqueous humor in front, the crystalline lens in the middle, and the vitreous body behind. The optic nerve becomes slightly constricted as it ajiproaches the sclerotic coat, and breaks up into a number of bundles of fibres, which pass through minute apertures in the sclerotic coat, giving a cribriform character to this portion of the membrane, which is therefore called the lamina cribrosa. The porus opticus is the central and largest of these apertures, and transmits the retinal vessels. Around the cribriform lamella there are many puncta for the transmission of the ciliary vessels and nerves. The anterior ciliary arteries, which are derived from the muscular arteries of the orbit, run along the tendons of the recti muscles, pierce the sclerotic coat very near the cornea, and form the circular anastomosis of the iris. There is a small oval canal running round the corneal attachment of the sclerotic, the sinus circularis iridis, or canal of Schlemm (or Fontana). At the junc- tion of the posterior elastic lamina of the cornea, or Descemefs membrane, already described, with the sclerotic coat on its inner surface, it spreads out THE ORBITAL BJ3GI0N AND THE EYE. 97 into a circle of radiating processes, — the ligamentum pectinatum iridis, — some of whicli are attached to the front of the iris at its circumference and others to the anterior part of the sclerotic and choroid coats. The intervals between these processes are called the spaces of Fontana, and these communicate with the canal of Schlemm, conveying the fluid of the anterior chamber into it. The choroid coat is the soft vascular tunic which underlies the sclerotic coat, and the space between the two is traversed by a mesh-work of connective-tissue fibres containing stellate pigment cells, the supra- choroid membrane. The connective tissue which underlies the sclerotic coat and unites it with the choroid is called the lamina fusca, and the contiguous surfaces of these two layers of tissue are lined with epithelium, having a lymph-space between them which is in reality continuous with that of the capsule of Tenon, through the prolongation of that fascia accompanying the ciliary vessels and nerves. Into this lymph-space hemorrhage may occur in injuries to the globe of the eye, and the same occurrence sometimes follows the operation of iridectomy or of extraction of cataract, owing to the sudden diminution of ocular tension. The choroid coat is deficient posteriorly where the optic nerve enters, but from this point to the iris anteriorly it consists of two layers, — the outer one con- taining principally large plexuses of veins, the vencB vorticosce, and the inner one being composed of a net-work of capillaries from the long and short ciliary arteries, the tunica Ruyschiana. The veins of the outer coat of the choroid present remarkable regularity in their arrangement, and con- verge to five or six equidistant trunks, which, after piercing the sclerotic coat at the outer side of the lamina cribrosa, terminate in the ophthalmic veins. Between the veins run forward the choroid arteries, consisting of the anterior ciliary arteries, which come from the muscular arteries of the orbit entering anteriorly, and the long and short posterior ciliary arteries, entering around the optic nerve. Interspersed between the vessels are dark pigment cells which communicate with one another by fibrous pro- longations and constitute a delicate net- work. The inner layer of the choroid, which is formed by the radiating capillaries from the choroid arteries, is the most delicate vascular net-work found in any tissue. On the 13 PLATE 14. Figure 1. Transverse section of the neck of a negro (male), aged thirty years. From the fifth cervical vertebra behind to the cricoid cartilage in front. 1. The spinous process of the fifth cervical vertebra. 2. The left transverse process of the fifth cervical vertebra. S. The left vertebral artery and vein. 4. The body of the fifth cervical vertebra. 5. The left vagus nerve (or pneumogastric nerve). 6. The left common carotid artery. 7. The oesophagus. 8. The left internal jugular vein. 9. The left lobe of the thyroid body. 10. The rima glottidis, seen through the cricoid cartilage. 11. The left external jugular vein. 12. The hoop of the cricoid cartilage in front. 13. The right trapezius muscle. 14. The right complexus muscle. 15. The medulla spinalis. 16. The right transverse process of the fifth cervical ver- tebra. 17. The right vertebral artery and vein. 18. The longus colli muscle. 19. The right vagus nerve (or pneumogastric nerve). 20. The right common carotid artery. 21. The right internal jugular vein. 22. The right lobe of the thyroid body. 23. The right omo-hyoid muscle. 24. The right external jugular vein. 25. The sterno-thyroid and sterno-hyoid muscles. Figure 2. Transverse section at the root of the neck (same as Figure 1) from the first dorsal vertebra to the top of the sternum. 1. The cut cords of the right brachial plexus of nerves. 2. Section through the apex of the right lung. 3. The right innominate vein. 4. The right vagus nerve. 5. The innominate artery. 6. The sternal end of the sterno-mastoid muscle. 7. The trachea. 8. The sterno-thyroid and sterno-hyoid muscles. 9. The recurrent laryngeal nerve. 10. The oesophagus. 11. The left common carotid artery. 12. The left vagus nerve. 13. The left Innominate vein. 14. The left subclavian artery. 15. The left scalenus anticus muscle. 16. The supra-scapular artery and vein. 17. The right scalenus anticus muscle. 18. The right transverse process of the first dorsal vertebra. 19. The head of the right first rib. 20. The medulla spinalis. 21. The spine of the first dorsal vertebra. 22. Section through the intervertebral disk. 23. The left transverse process of the first dorsal vertebra. 24. The apex of the left lung. 25. The splenius muscle. 26. The trapezius muscle. N. B.— These sections were made on a recent well-developed cadaver, placed in the horizontal position, without any freezing or hardening agent, and the plates represent the relations of the parts absolutely as they were. Plate I Vol I Dissected, Photographed and Colored from Nature tiy Georqe Mc. Clellan, M 0. Copyright, 1831,, by Gborge Mc Clellan, M D AirntlrongBCa lirS.BosWn, THE ORBITAL BEG ION AND THE EYE. 99 inner surface of tliis vascular tissue is a very thin membrane, the lamina vitrea, which separates it from the pigmentary layer of the retina. The choroid coat splits anteriorly into the ciliary muscle in front and the ciliary processes behind, both constituting the ciliary body. The ciliary processes consist of about seventy large and small, alternating, plaited folds of the tissues of the choroid, with their vessels, nerves, and pigment. They are arranged radially behind the ciliary muscle and the iris, and posteriorly fit into corresponding folds of the suspensory ligament of the lens, espe- cially into the part called the zone of Zinn, and their rounded free ends, which are devoid of pigment, project a little distance into the posterior chamber, and rest upon the capsule of the lens. The ciliary muscle is a zone of unstriped muscular fibres at the front of the choroid coat, arising close to the canal of Schlemm, at the junction of the sclerotic coat and the cornea. Some of the fibres radiate backward and blend with the ciliary processes, and others form the circular ciliary muscle (or ciliary ligament) around the periphery of the iris. Its action is to accommodate the eye to objects at various distances, which it prob- ably accomplishes by drawing on the ciliary processes and thus relaxing the suspensory ligament of the lens, rendering the anterior surface of the lens more convex. The nerves supplying the ciliary muscle are derived from the long and short ciliary nerves. The ciliary region is the danger- ous area of the eye, owing to its important vascular and nerve anastomoses and its relations to the cornea, iris, choroid coat, retina, and vitreous body. Wounds of the cornea in front of this region, or of the sclerotic coat behind it, are not so hazardous, but any traumatic affection of the ciliary body is liable to be followed by the gravest results. Not only are the contiguous parts readily involved by the spread of inflammation from this locality, but experience has shown that that terrible affliction called sympathetic ophthalmia — whatever may be the insidious and latent process by which it travels from one eye to the other — invariably has its origin in some injury to the ciliary region. The iris (a rainbow), so called from its various colors in different individuals, is the continuation of the ciliary muscle. It is a circular contractile membrane, with a round hole a little to the inner side of its Missing Page Missing Page 102 THE ORBITAL REGION AND THE EYE. the iris greatly contributes. It has been stated (page 100) that the circular fibres are the most marked in the human iris; and the many changes to which they are subjected are probably due to the influence of the vaso-motor sympathetic ciliary nerves on the capillary vessels of the iris, for not only does the influence of the light upon the retina incite by reflex action a corresponding degree of contraction or dilatation of the pupil according to its intensity, the impression probably being trans- mitted through the optic nerve to the optic lobes in the brain and thence to the motor oculi nerve and its continuations, but there are other conditions with which the light has nothing to do. The pupil is always observed to be dilated in coma, from compression of the brain in many states of shock, in many mental or nervous derangements, and in the general relaxation of the muscular system at the moment of death. One of the physiological actions of belladonna, which seems to paralyze the vaso-motor nerves, is to dilate the puj)il. Ojpium, on the contrary, by increasing the tension of the capillaries, induces contraction of the pupil. The aqueous humor consists of a few drops of clear limpid alkaline fluid, which fills the space between the cornea and the lens in which the iris is suspended, dividing the space, as already mentioned, into the anterior and posterior chambers. The posterioi' chamber is a very small angular interval between the back of the iris and the ciliary processes and the suspensory ligament and the capsule of the lens. The anterior chamber is in communication with the canal of Schlemm — the circular venous canal at the junction of the cornea with the sclerotic coat — through the spaces of Fontana. This canal therefore bi-ings the anterior chamber into relation with the venous circulation, and thus the ready absorptive power of the aqueous humor may be explained, — as is proved in the speedy removal of extravasated blood, or in the treatment of soft cataract by the " needle operation." The aqueous humor is also rapidly seci-eted after the extraction of a cataract. The crystalline lens is a perfectly translucent, biconvex, semi-solid body placed immediately behind the pupil, and completely surrounded by an equally translucent elastic capsule. The capsule of the lens resembles the elastic lamina of the cornea, and is thicker in front than behind. The THE OBBITAL REGION AND THE EYE. 103 anterior surface of the capsule is in contact with the free pupillary margin of the iris. There is no vascular connection between the lens and its capsule, but the capsule is separated from the front of the lens by a layer of epithelium which after death exhales the so-called liquor Morgagni. The capsule is retained in its position by the suspensory ligament of the lens, or the zone of Zinn, which is the continuation of the hyaloid membrane, extending from the vitreous body to the ciliary processes. The elasticity of the capsule is manifest from the curling outward of its edges in lacerated wounds, or in cataract operations. When the capsule is wounded the aqueous humor is imbibed by the fibres of the lens to a greater or less degree, with proportionate opacity. The lens consists of three triangular segments, which are composed of numerous concentric layers. It is somewhat soft and gelatinous externally, but each successive layer becomes more dense toward the centre, which is hard and is called the nucleus. The laminae consist of minute parallel fibres which are hexagonal prisms fitting accurately into one another by a dovetailing of their edges. The lens varies with age and the conditions of myopia and presbyopia. In early life it is almost spherical, but in old age it becomes flattened, yellowish, and less transparent. In the adult it is distinctly more convex behind than in front. The function of the lens is to bring the rays of light coming from any object to a focus upon the retina. The canal of Petit is the so-called encircling space between the capsule of the lens and its suspensory ligament, formed by a splitting of the latter. It probably contains a semi-fluid extension of the vitreous humor ; when inflated by a blow-pipe it presents a peculiar beaded appearance, owing to the plaiting of the suspensory ligament on the front of the lens. The vitreous body is the transparent jelly-like substance filling the cavity of the retina, immediately behind the lens, which it accommodates in front in a depression (the hyaloid fossa) adapted to its capsule. It is surrounded, except in front, by the delicate, transparent hyaloid membrane, which, as already explained, passes forward anteriorly to form the suspen- sory ligament of the lens. The latter portion of the hyaloid membrane contains longitudinal elastic fibres. The vitreous body consists of a fluid contained in cellular meshes which freely intercommunicate, as is seen in PLATE 15. Anterior view of the muscles of the face of a well-developed man, aged thirty-five years, showing the delicate inter- lacing of the fibres about the corners of the eyelids and mouth. This dissection was made with especial care to demon- strate the anatomy of expression in its application to the facial marliings now considered characteristic of disorders pertaining to mental, nervous, digestive, and respiratory functions. The epicranial aponeurosis or (galea capills). The right frontal muscle. The external lateral fibres of the right frontal muscle, some of which are attached to the external angular process of the orbit, and others blend with the adja- cent orbicularis muscle. The pyramidal slip from the frontal muscle descending upon the na.sal bone. The right temporal aponeurosis. The right orbicularis palpebrarum muscle. The right compressor naris muscle. The right levator labii superioris et alae nasi muscle. The right levator labii proprius muscle. The right levator anguli oris muscle. The depressor alee nasi muscle. The depressor septum nasi muscle. The right zygomatic muscle. The superior labial portion of the orbicularis oris muscle. The right masseter muscle. The inferior labial portion of the orbicularis oris muscle. The triangular, or depressor anguli oris (labii inferioris) muscle. The right levator menti muscle. The quadratus, or depressor labii inferioris proprius muscle. The inter-frontal aponeurosis. The peculiar looping of the fibres of the frontal muscle. The transverse fibres of the orbicularis palpebrarum muscle, which arise from the internal angular pro- cess of the orbit, called the corrugator supercUii muscle. The left pyramidalis nasi slip from the frontal muscle. The interlacing of the fibres of the frontal with the orbicularis at the inner corner of the eyelid. The tendo oculi. The left compressor naris muscle. The left orbicularis palpebrarum muscle. The left levator labii superioris et alae nasi muscle. The left levator labii superioris muscle. The left levator anguli oris muscle. The left zygomaticus muscle. The left buccinator muscle (just seen in this view). The left masseter muscle. The left depressor anguli oris muscle. The left depressor labii inferioris muscle. The left levator menti muscle. N. B.— The platysma muscles have been removed from their attachment at the outer corners of the mouth, where they form the laughing muscles of Santorini. The vessels and nerves have also been removed, as they are shown in other plates, in order to give a clearer idea of the interdependence of the facial muscles. Plate i' Vox I .W( /f/j /yii /Fii Copyn§ht, I830,by Gbohge Mc Clellan, M 0. 1 Mc.Clellan. M D. A.-riiiiro^i^ J.Co Mlh Vision THE ORBITAL REGION AND THE EYE. 105 puncture of the body, when the humor drains away. There is a central canal {of Stilling) which passes from the position of the entrance of the optic nerve to the middle of the back of the capsule of the lens : it is lined by a prolongation of the hyaloid membrane, and contains fluid. In the foetus this canal conveys the little hyaloid artery from the central artery of the retina to the capsule of the lens. On the inner side of the hyaloid membrane there are many granular corpuscles, which under the microscope exhibit amoeboid movements. The muscce volitantes which often trouble short-sighted persons are due to opaque matters suspended in the vitreous body, and closely resemble the hyaloid corpuscles. The retina is the delicate nervous membrane formed by the expan- sion of the optic nerve after its passage through the sclerotic and choroid coats, upon which the images of external objects are received. It is the so-called inner coat of the eye, and is placed between the choroid and the hyaloid membrane, extending as far forward as the ciliary ligament, where it terminates in a fine serrated border, — the ora serrata, — a single lamina of its tissue, the pars ciliaris, being continued to the ciliary processes and the iris. The retina is thickest at the entrance of the optic nerve, and gradually becomes thinner toward the ora serrata. Its internal (byaloid) surface is smooth, and during life appears as a transparent pinkish tissue. At the point of entrance of the optic nerve there is a round disk, called the porus opticus, in the centre of which may be seen with the ophthalmo- scope the central artery of the retina entering and branching above and below, and the central veins converging and passing inward. There is also a little prominence of the nerve-substance at this point, the optic papillcB. This prominence is sometimes called the blind spot (or punctum ccecum), because it is altogether insensible to the rays of light. In the recent state, at the fundus of the eye, directly opposite the pupil, in the centre of the axis of vision, there is an oval, yellow spot {macula lutea) in the retina, with a central conical pit, the fovea centralis. Here the structure is so thin that the dark pigmentary layer of the retina (the tapetum) is seen through it, and it is at this point that the impression of light is greatest and vision is considered to be most perfect. The porus opticus is about two and one-half millimetres, or one-tenth 14 106 THE ORBITAL BEGION AND THE EYE. of an inch, to the inner side of the macula lutea. After death there is a minute transverse fold in the retina extending from the centre of the fovea to the papilla. The retina appears to the naked eye as a simple, soft, trans- parent membrane, but when examined under the microscope it is found to be an exceedingly complex structure, showing the most elaborate organi- zation. It is composed of eight layers, all differing from one another, arranged in strata, and supported by an extremely delicate connective- tissue framework (the sustentacular tissue), which upon the choroid and vitreous surfaces becomes somewhat condensed and appears membranous, forming respectively the so-called membrana limita7is externa and mem- brana limitans interna. The first, outer, or pigmentary layer, the tapetum nigruvi of the retina, is a layer of hexagonal epithelial nucleated cells, containing pigment granules only on their inner portions, which, although in the closest relation with the choroid coat, are prolonged like fine tapering filaments between the numberless elongated bodies of the second layer. The pigment is probably so disposed to absorb the rays of light, and thus, preventing its reflection, to convert it into some form of nervous force. The second or columnar layer is composed chiefly of minute, bacillus-like bodies, which penetrate externally into the pigmen- tary layer and internally into the subjacent outer nuclear layer, being supported by a trabecular arrangement of the connective tissue (the mem- brana limitans externa). These bodies are also known as the rods and cones, the former being club-shaped and greatly outnumbering the cones, which are flask-shaped and isolated and scattered among the rods. The rods are longer and therefore more in relation with the pigmentary layer, while the cones are shorter ; and they are both connected with the sub- jacent outer nuclear layer by delicate fibrous prolongations. The rods are not found in the yellow spot. Little is known regarding the function of these interesting little bodies beyond the facts of comparative anatomy that among those animals and birds which seek their food by night the retina consists solely of rods, and that in the case of birds which live on brightly-colored insects the cones are about as numerous as the rods. From these facts the inference is drawn that the rods are concerned in the discrimination of the quantity of light, the cones in that of its THE REGION OF THE NOSE AND THE NASAL CAVITIES. 107 quality or color. The next succeeding four layers are alternating nuclear and molecular layers, called outer and inner, from their relative positions. They consist of strata of clear nucleated corpuscles or granules, modified in each layer so as to offer some peculiarities, and embedded in the retinal connective tissue. They are severally connected by upward and downward prolongations, the outer nuclear layer with the rods and cones as above stated, whereas the inner molecular layer joins the seventh or ganglionic layer. The last is a very clear stratum of spheroidal nerve- cells connected by oblique processes with the eighth retinal layer, which consists of the ultimate fibres of the optic nerve. The ganglionic cells are inserted into several strata in the vicinity of the yellow spot, and within it into six or seven. The layer of nerve-fibres is composed of the axis cylinders only, and is continued as far forward as the ora serrata, arranged for the most part in bundles which interchange so as to form j)lexuses. At the yellow spot this layer is interrupted by the accumulation of nerve-cells. THE EEGIOE" OF THE KOSE AND THE ]^ASAL OAYITIES. The special organ of the sense of smell consists of an external portion, the nose, and internal portions, the nasal fosscB, or nasal cavities. The nose is the prominent feature which projects anteriorly between the orbits from the upper part of the face, being connected by its summit with the forehead and by its base with the upper lip. It serves as the chief avenue of respiration when the mouth is closed. The skeleton of the nose consists of the two nasal bones and the nasal processes of the superior maxillary bones, to which is attached a cartilaginous framework composed of five peculiarly-shaped movable cartilages. The nasal bones are severally of an elongated quadrilateral shape, being narrow and thick above, where they are firmly attached by suture with the nasal spine of the frontal bone, constituting the nasion, and wide and thin below, where they form the upper margin of the anterior nasal fossce of the skull (Plate 28) and in the recent state give attachment to the upper 108 THE BEGION OF THE NOSE AND THE NASAL CAVITIES. lateral nasal cartilages. They are strongly united in the middle line, forming " the bridge" of the nose, this juncture being strengthened by their inner borders projecting as a longitudinal crest, which connects them with the ethmoidal portion of the septum of the nose. Their outer borders are bevelled, and supported by the contiguous borders of the superior maxillary bones. The width and length of the nasal bones vary greatly in different skulls, and, as they are almost immediately beneath the skin (Plate 1), they give shape and character to the organ. The under surfaces of the nasal bones are grooved for the nasal nerves, and perforated by a few small foramina for the transmission of vessels. The nasal processes of the superior maxillary bones are triangular, thick, bony plates which extend upward on each side of the nose to be joined by suture with the frontal bone. Their anterior borders are serrated for articulation with the nasal bones, — the form and dimensions of the nose being mainly dependent upon the development of these processes and the manner in which the nasal bones are set upon them. The outer surfaces of the nasal processes are serrated and concave ; the internal surfaces are rough, and present two well-marked ridges, the superior and inferior turbinated crests, the former articulating with the middle turbinated portion of the ethmoid bone and the latter with the inferior turbinated bones on each side. The cartilaginous framework of the external nose is formed of a median septum and two lateral segments on both sides. The cartilage of the septum is a smooth triangular plate inserted posteriorly into a groove in the perpendicular plate of the ethmoid bone ; anteriorly, where it is thicker, it is connected above with the nasal bones and adjacent lateral cartilage, and below with the vomer and the palatine processes of the superior maxillary bones. The septal cartilage separates the anterior portions of the nasal cavities, and up to the seventh year of age is usually straight, but subsequently it is apt to incline to one side (usually the left), according to the deviation of the vomer (Plate 28, No. 39). Sometimes it is perforated, and thus establishes a communication between the cavities. The lateral cartilages consist of an upper triangular piece and a lower oval piece on each side, which together give shape to the wings and tip THE REGION OF THE NOSE AND THE NASAL CAVITIES. 109 of the nose and support the integument. Each upper cartilage is attached above to the margin of the nasal bone and adjoining nasal process, in front to the septum, and below to the lower cartilage. The latter is curved upon itself so as to form the outer and inner boundaries of the external orifice of the nostril. It approaches its fellow of the opposite side internally, and thus forms the upper part of the columna nasi, the partition between the nostrils. When the lower lateral cartilages are not in contact there is a median furrow which is sometimes well marked at the tip of the nose. These cartilages are connected to each other and to the bones by a tough fibrous membrane, the perichondrium. In this tissue, in relation to the superior maxillae, there are usually several nodules, — sesamoid cartilages. The elasticity of these cartilages preserves the size and shape of the nostrils, and enables the muscles moving them to expand or contract the orifices so important in respiration. The skin over the root of the nose below the forehead, on the sides and the greater part of the dorsum, is thin and loose ; but over the wings {alee) and on the point it is thick and very adherent to the parts beneath, and remarkable for the number and size of its sebaceous follicles. Owing to the presence of the latter, the lower part of the nose is frequently the seat of acne. Inflammation of the skin over the cartilaginous portion of the nose is very painful, and is usually accompanied by local congestion, the pain depending upon the tenseness of the part and the congestion upon the free blood-supply of the region. There is very little fat in the cellular tissue between the skin and the alar cartilages. The muscles in connection with the nose are, on each side, the pyramidalis nasi, the compressor naris, the depressor alae nasi, and the smaller dilatator muscles. The pyramidales nasi muscles arise from the upper borders of the right and the left compressor naris muscle, having an angular interspace between them, and pass upward over the bridge of the nose, joining each other in the middle line, and blending their outer fibres with the orbicular muscles of the eyelids, their inner fibres being prolonged into the occipito-fron tales muscles (Plate 15, No. 4). The principal action of these muscles is to produce transverse wrinkles at the root of the nose, by drawing down the inner angles of the eyebrows ; 110 TRE REGION OF THE NOSE AND TEE NASAL CAVITIES. but by reversing their action and tightening the skin over the alar carti- lages they may also serve as dilators of the nostrils. The compressor muscles of the nose are triangular in shape, arising on each side of the face, from the inner sides of the canine fossae of the superior maxillae, and join by a common aponeurosis over the dorsum of the nose. These muscles compress the alse and produce the pinched appearance seen in labored breathing. Their origins are concealed by the elevator muscles of the upper lip and the wing of the nose (Plate 18, No. 4, and Plate 19, No. 5). The depressores alarum nasi muscles arise from the superior maxillary bones, above the second incisor teeth, and, being placed between the mucous lining of the upper lip and the orbicular muscle of the mouth, their fibres radiate to the septum and back parts of the alae of the nose. These muscles serve to constrict the anterior nares by drawing the alse downward. The dilatator — anterior and posterior — muscles are very delicate bundles of fibres, which pass respectively from the alar cartilage to the overlying skin, and from the sesamoid cartilages and nasal process of the superior maxilla to the margin of the nostrils. In ordinary respiration, especially in sleep, these little muscles resist the tendency of the nostrils to close from atmospheric pressure, by raising and everting the alse, but in dyspnoea their action is marked, as it also is in the expressions of pride, anger, and disdain. The arteries of the nose are the lateralis nasi from the facial (Plate 18, No. 6), the nasal branch from the superior coronary artery to the septum, and the nasal branches from the ojDhthalmic and infra- orbital arteries. The great vascularity of the skin over the nose renders it well adapted for plastic surgery in this region. The nasal veins empty into the facial and ophthalmic veins. The nerves of the ?iose are branches from the facial nerve which supply the muscles, branches from the infra- orbital and infra-trochlear nerves, and the naso-lobular filament from the nasal branch of the ophthalmic, which, after descending in a groove on the inner surface of the nasal bone, becomes subcutaneous at the junction of the nasal bone and upper lateral cartilage and supplies the tip and lobule of the nose (Plate 63, Fig. 1, No. 17). This latter nerve establishes connec- tions with the eye, as is demonstrated by the lachrymation which follows THE REGION OF THE NOSE AND THE NASAL CAVITIES. Ill any intense irritation about the nostrils. There are numerous lymphatic vessels about the nose, which follow the course of the facial vein and mostly emjDty into the lymjDhatic glands of the submaxillary region (Plate 16). Within the margins of the nostrils there are numerous stiff curved hairs, vibrissce, which grow from the inner surface of the alse and septum as far as the place where the skin joins the mucous lining of the nasal cavities. The nasal fossae, or nasal cavities, are the two very irregularly shaped air-chambers, separated by the septum nasi, which open on the face by the anterior nares and on the pharynx by the posterior nares, and communicate at their outer sides with the sinuses of the ethmoid, sphenoid, frontal, and superior maxillary bones. They also communicate with the orbits by the lachrymal canals, with the mouth by the anterior palatine canals, and with the cranium by the olfactory foramina. Each nasal fossa is narrower above than below, and higher at the centre than at either the anterior or the posterior opening. The roof of each nasal fossa is formed by the nasal bone, the nasal spine of the frontal bone, the cribriform plate of the ethmoid bone, the body of the sphenoid bone, and the sphenoidal turbinated bones. The floor is formed by the horizontal plates of the superior maxillary and palate bones, and is wider at the centre than at either end. The inner wall is the smooth septum formed principally by the perpendicular plate of the ethmoid bone, the vomer, and the septal cartilage. The outer wall is formed by the nasal processes and inner sur- faces of the superior maxillary, lachrymal, ethmoid, palate, and inferior turbinated bones, and the internal pterygoid plate of the sphenoid bone. The turbinated bones are delicate, spongy, scroll-shaped bony shelves, which give greater extent of surface to the mucous lining of the nose, pro- jecting from the outer wall and dividing each nasal cavity into the superior, middle, and inferior nasal meatuses, or passage-ways (Plate 12, No. 29). The superior meatus is the smallest, and occupies the upper and back part of thfe nasal fossa, between the superior and middle turbi- nated bones. In the dried skull the spheno-palatine foramen opens at the back part of the outer wall of the superior meatus, but in the recent state this opening is covered by the pituitary mucous membrane. The posterior ethmoidal cells communicate with the superior meatus imme- PLATE 16. Dissection of the superficial muscles of the right side of the head, face, neck, thorax, and arm. From a well- developed male, aged thirty-five years. The superficial lymphatic glands and vessels of the face and neck are drawn on the photograph (after notes of many dissections) to show their arrangement and position. 1. The epicranial aponeurosis. 2. The temporal muscle, with the temporal lymphatic vessels. 3. The posterior auricular lymphatic glands. i. The superficial jugular lymphatic glands. 6. The mastoid attachment of the sterno-cleido muscle. 6. The occipital lymphatic glands and vessels. 7. The splenius muscle. 8. The levator anguli scapulEe muscle. 9. The scaleni muscles. 10. The trapezius muscle. 11. The deltoid muscle. 12. The compressor naris muscle. 13. The buccinator muscle. 14. The anterior auricular lymphatic glands. 15. The supra-parotid lymphatic glands. 16. The masseter muscle. 17. The depressor anguU oris muscle. 18. The submaxillary lymphatic glands. 19. The digastric muscle. 20. The hyoid bone. 21. The thyro-hyoid muscle. 22. The omo-hyoid muscle. 23. The pomum Adami of the thyroid cartilage. 24. The carotid lymphatic glands. 25. The sterno-thyroid muscle. 26. The sterno-hyoid muscle. 27. The supra-clavicular lymphatic glands. 28. The clavicular attachment of the sterno-mastoid mus- cle. 29. The sternal attachment of the sterno-mastoid muscle. SO. The clavicular portion of the pectoralis major muscle. 31. The sternal portion of the pectoralis major muscle. 82. The triceps muscle. 33. The serratus magnus muscle. 84. The biceps muscle. Plate ifi Vol I i ■ Dissected, Photo^rdphed and Coiorsd from Nature by George Mc. Clellan, M D. Copynght, 1831, by George Mc Clellan, M D THE BEGION OF THE NOSE AND THE NASAL CAVITIES. 113 diately behind the superior turbinated bone in the upper walL The middle meatus is larger than the superior, is situated between the middle and inferior turbinated bones, and extends along the posterior two-thirds of the outer wall of the nasal fossa. At its anterior part a long narrow passage, the infundibuluni, leads upward into the anterior ethmoidal cells and thence to the frontal sinus. About the centre of the outer wall is the orifice, of variable size, which leads into the sinus of the superior maxillary bone, the antrum of Highmore. The inferior meatus is the space between the inferior turbinated bone and the floor of the nasal fossa, extending the entire length of the outer wall of the nose. The lachrymal canal, or nasal duct, which conveys the tears from the lachrymal sac to the nose, opens into the anterior part of the inferior meatus. The lachrymal sac occuj^ies the groove formed by the lachrymal bone and the nasal process of the superior maxillary bone (page 86). The nasal duct is twelve millimetres, or about half an inch, in length, and is directed downward, backward, and a little outward. Its opening in the in- ferior meatus in life is guarded by a valvular fold of the mucous lining, the valve of Hasner, and its position is two and one-half centimetres, or about one inch, behind the opening of the nostril, and one and three-fourths centi- metres, or three-fourths of an inch, above the floor of the nose. The pharyn- geal opening of the Eustachian tube is behind the inferior turbinated bone (Plate 12, No. 32). There is a great difference between the form and di- mensions and character of the various openings of the nasal fossse as they exist in the dried skull and as they present themselves in the recent state. This is chiefly dependent upon the arrangement of the Schneiderian or pituitary membrane, the vascular mucous membrane which lines the nasal cavities and the passages connected with them. This membrane is con- tinuous with the skin at the inner borders of the anterior nares, with the mucous membrane of the pharynx through the posterior nares, and with the conjunctiva through the nasal duct and the lachrymal canaliculi, and is prolonged into the various sinuses communicating with the nasal fossae already described. A coryza, or inflammation of the nasal mucous mem- brane, may thus implicate any of these structures, and a " cold in the head" or an attack of "hay fever" furnishes a demonstration of these 15 114 THE REGION OF THE NOSE AND THE NASAL CAVITIES. relationships. The mucous membrane varies much in thickness, vascu- larity, and appearance in these different parts. It is thickest and most vascular over the turbinated bones, where it forms projections especially in relation to the front and back part of the inferior turbinated bone, and thus encroaches upon the dimensions of the space of the nasal cavity. It is also quite thick on the septum, but in the intervals between the turbinated bones and on the floor of the fossae it is thinner. The lining membrane within the cells and sinuses is very thin and pale, and very different from the proper lining of the nose. In the middle meatus the Oldening of the infundibulum is nearly closed by a fold of the membrane, and the opening into the antrum of Highmore is greatly diminished from its size in the dried bone, appearing usually as a round hole, about the centre of the middle meatus, and nearly two and one-half centimetres, or an incli, above the floor of the nose. The mucous lining of the nasal cavi- ties is peculiarly modified in the nostrils, in the air-passages, and in the olfactory region. In the nostrils it is furnished with papillae, a few hairs, and a squamous epithelial lining; in the air-passages the epithelium is columnar and ciliated ; but upon the upper portion of the septum and upon the superior and middle turbinated bones, where the olfactory nerves are distributed, the epithelium is entirely columnar. These columnar cells terminate in fine processes, between which the microscope reveals nucleated fusiform cells, the so-called olfactory cells. The anterior nares are the oval openings of the nasal cavities on the face, and are placed horizontally, so that in order to examine the septum and inferior turbinated bones the head should be thrown back (Plate 53, Fig. 1). A finger can be readily introduced into the nostril and passed far enough back to reach another finger introduced into the posterior nares through the mouth. The posterior nares are about the same height as the anterior (three centimetres, or one and a quarter inches), and measure trans- versely in the dried state twelve millimetres, or about half an inch, but in life the mucous lining considerably diminishes them. The ordinary devi- ation of the septum may block one nostril more or less, and interfere with the clearness of the voice, especially in singing. The floors of the nasal cavities are generally wider at the centre, where the passages are also THE BEGION OF THE NOSE AND THE NASAL CAVITIES. 115 higher than elsewhere, and foreign bodies often become lodged here. The introduction of forceps to remove the latter, or for the extraction of nasal polypi, should be along the floor of the inferior meatus, and they should be opened so as to grasp the object vertically. The posterior nares when the mouth is opened are usually blocked by the folds of the soft palate being drawn upward, and are thus cut off from the pharynx. Owing to this disposition, the "nasal douche" can be used so that the fluid introduced into one nostril shall pass over the soft palate and return by the other nostril. The vascularity of the mucous membrane of the nose is due to the numerous capillaries which anastomose freely beneath its surface. The arteries of the nasal cavities are the anterior and posterior ethmoidal branches of the ophthalmic arteries, which supply the roof of the nose, the ethmoidal cells, and the frontal sinuses ; the nasal arteries, from the internal maxillary, which supply the septum, the meatuses, and the turbinated bones ; and the posterior dental arteries, from the internal maxillary arteries, which supply the antra. The veins of the interior of the nose terminate in the ethmoidal veins, which enter the ophthalmic vein. In children there is almost always a communication between the nasal veins and the superior longitudinal sinus through the foramen caecum. This is usually closed about puberty, but may continue in the adult and j^erhaps explain per- sistent hemorrhage or the spread of inflammation from the nasal cavities to the meninges of the brain. There is a venous plexus {rete nasi) about the inferior turbinated bone which resembles a kind of cavernous tissue, very prone to bleed. Bleeding from the nose — or epistazis — is generally due to some interference with the venous circulation. There are also venous communications with the frontal vein, and through the spheno-palatine foramen with the zygomatic plexus. The mucous membrane of the nose is abundantly furnished with sensory nerves. The roof is supplied by the nasal branches from the ophthalmic and filaments from the Vidian nerves; the septum, by branches from the nasal nerves, the spheno- palatine (or Meckel's) ganglions (Plate 3, Fig. 2, No. 6), and the naso- palatine nerves; the floor, by branches from the naso-palatine and anterior palatine nerves ; and the outer walls, by filaments from the spheno-palatine 116 THE REGION OF THE FACE. gaDglions, and branches from the nasal, anterior dental, and anterior pala- tine nerves. The olfactory nerves, about twenty on each side, are derived from the olfactory bulb, and pass through the foramina to the cribriform plate of the ethmoid bone. They are arranged in three sets on each side, and each nerve is invested with a fibrous prolongation from the dura mater. The inner set supply the upper part of the septum ; the middle are the smallest, and are spread over the roof of the nose ; the outer are the largest, and are divided into two groups, the anterior group supplying the mucous membrane over the superior turbinated bone, and the posterior group being distributed over the os planum and the middle turbinated bone. It will be noticed that the olfactory nerves are situated high up in the nasal cavities, and hence in the effort to smell intently the nostrils are always dilated. The partial loss of smell in some cases of facial paralysis has been ascribed to inability to dilate the nostrils. The olfactory nerves ramify between the mucous membrane and the skin, communicating freely with one another, and forming plexuses with elongated meshes. The fibres of these nerves are non-medullated, with a sparsely nucleated neurilemma. Interspersed between the columnar epithelial cells in the olfactory region there are peculiar cells having a nucleated body with two processes. These are called the olfactory cells, because one of the cell processes terminates on the surface of the mucous membrane and the other is believed to be in connection with the terminal filaments of the olfactory nerves. THE EEGION OF THE FACE. The landmarks of the face (Plates 1 and 28) include, besides the bony prominences of the orbits (page 79) and the nose (page 108), the malar eminences and their backward prolongations into the zygomatic arches, which support the cheeks, and the angles, lower border, and mental eminence of the inferior maxillary bone, the latter giving promi- nence and character to the chin. The skin of the face is generally very fine and thin, and adherent to the parts beneath, except over the eyelids, where it is peculiarly delicate and the subcutaneous cellular tissue is very loose. In relation to the alse of THE REGION OF THE FACE. 117 the nose and the chin it is more dense, and somewhat resembles the tissues of the scalp; and over the bony prominences contused wounds are often attended with a linear rupture of the skin similar to an incised wound. The lax arrangement of the cellular tissue elsewhere about the face is demonstrated in the swellings which follow inflammatory infiltration about the cheeks and mouth. There is much fat in the subcutaneous tissue of the face, especially in the anterior parts of the cheeks (Plates 18 and 19) and in relation to the zygomatic muscles. In children there is an aggregation of fatty lobules surrounded by a capsule over the buccinator muscles, called the "sucking cushions," because they are thought to be instrumental in distributing the atmospheric pressure and preventing the buccinator muscles from being pressed inward between the alveolar arches when a vacuum is created in the mouth. The skin of the face is intimately associated with many of the subjacent muscles, the habitual use of some of which produces the facial furrows and markings characteristic of certain expressions. A careful study of these lines and their varying modifica- tions will prove of great value to the physician in forming a diagnosis of many diseases, especially in young children and the ignorant, in whom the facial expression is often the sole guide in the recognition of subjective symptoms. The only way of obtaining information from an infant who cannot communicate ideas or describe sensations by speech, is by noticing the expression and gestures. Such observation teaches that contraction of the brows indicates pain in the head ; sharpening of the nostrils, pain in the chest; and drawing of the upper lip, pain in the abdominal region. There are certain lines (Jadelot's) which become marked in the face of any one suffering from serious diseases. Of these, the line which begins at the inner corner of the eye and passes outward toward the cheek-bone beneath the lower lid — the oculo-zygomatic line — is associated with disorder of the cerebro-nervous system. The line which extends from the wing of the nose round the corner of the mouth, — the nasal line, — if connected with marked dimpling of the cheek, points to disorder of the digestive tract. This is especially the case in infancy. The line which passes from the angle of the mouth to the lower part of the face — the labial line — is a sign of disease of the respiratory organs. PLATE 17. The skin removed on the left side of tlie neclc to show the platysma myoides muscle and the usual position of the great external jugular vein. 1. The anterior temporal artery, seen through the scalp. 2. The position of the temporal artery, where it emerges from the parotid gland. 3. The po.sition of the parotid gland. 4. The position of the submaxillary gland. 5. The external jugular vein, showing its course from the angle of the lower jaw to the middle of the clavicle. 6. The prominence of the thyroid cartilage (pomumAdami). 7. The platysma myoides muscle. 8. Superficial veins over the supra-clavicular fossa. 9. The helix. 10. The fossa (ovalis) of the anti-helix. 11. The fo-ssa (scaphoidea) of the helix. 12. The anti-helix. IS. The tragus. 14. The concha. 15. The anti-tragus. 16. The lobule. Plate 17 Vol I Copynghl, 1831 , A)- &onst- Mo Cllllan, M D. Dissected Photographed and Colored from Mature W Geobge Mc. Cleli-Ah, M D. Armstrongs Co Lirh Bosto THE HEGION OF THE FACE. 119 The muscles of the face, especially those called from their action the muscles of expression, are of finer texture and paler color than the muscles generally in other parts of the body. The muscles of expres- sion also have no proper tendons of origin or insertion, are destitute of aponeuroses or sheaths, and blend with adjacent muscles by the most complex and delicate interlacement of their fibres (Plate 15), so that they do not present the same arrangement in every individual. They often vary in development even on the two sides of the face, thereby influencing the character and degree of the expressions. The muscles of the forehead, orbits, and nose are described with the anatomy of those regions. The muscles which surround the mouth and are attached to its upper and lower borders are remarkable for their interdependence (Plate 15) and for their great mobility. The orbicularis oris muscle is, like other sphincter muscles, composed principally of circular fibres, and has very slight attachments to the neighboring bones. The variety in the prominence of the lips in different individuals depends upon the size and thickness of this muscle. It consists of two portions, each pos- sessing very marked differences from the other in the appearance and arrangement of its fibres. The labial portion is composed of very thin pale fibres which surround the mouth and have no bony attachment ; the facial portion is broader, its fibres at the outer borders of the upper and lower lips intermingling with the fibres of other muscles, which converge toward it from the surrounding parts of the face. It is con- nected on each side to the bone by two fasciculi in the upper lip, one to the septum nasi and the other to the alveolar border in relation to the incisor teeth, and by a single fasciculus on each side in the lower lip to the lower jaw in relation to the canine tooth. There are tiny slips extending one on each side from the orbicularis to the anterior 2Dart of the nasal septum, producing the delicate furrow, called the philtrum, from the nose to the upper lip. This muscle counteracts all the other muscles which move the lips, the infinite play and variety of expression about the mouth depending upon the counterbalancing of their opposing actions. The ordinary action of the orbicularis closes the lips, and, on account of the outer surface of the muscle being intimately connected 120 TRE BUGIOH OF THE FACE. witli the lips and the overlying skin, its forcible contraction produces radiating wrinkles about the mouth in the skin of elderly persons. The levatores labii superioris et alarum nasi muscles arise from the nasal processes of the superior maxillary bones near the inner borders of the orbits, and, passing downward, divide into inner slips, which are inserted into the alar cartilages of the nose, and outer slips, which blend with the orbicularis oris and the adjacent levatores labii superioris muscles in the upper lip. These muscles serve to dilate the nostrils and to draw upward the upper lip and the wings of the nose, and produce the changes in the countenance in the expressions of indignation, disgust, and derision. Their habitual use occasions the furrows which extend from the side of the nose to the corners of the mouth. The levatores labii superioris {proprius) muscles arise from the lower borders of the orbits beneath the orbicular muscles of the eyelids, above the infra-orbital foramina, and, overlapping the deej) origins of the compressor nasi and levator anguli oris muscles, on each side, their fibres blend with the orbicularis oris. The two levator anguli oris muscles arise underneath the preceding muscles from the canine fossae of the superior maxillse below the infra-orbital foramina, and blend at the angles of the mouth with the contiguous muscles. The zygomaticus muscle arises on each side from the malar bone near its junc- tion with the zygoma, and passes obliquely in a bed of fatty tissue across the side of the face to the angle of the mouth, where its fibres interlace with those of the other muscles of the upper Y\\). The action of this muscle is seen in laughing and snarling. Sometimes an additional muscular slip passes downward from the orbicularis palpebrarum, and, taking a course parallel to the zygomaticus, is called the zygomaticus minor. The depressor anguli oris muscle on each side has a broad origin from the oblique line of the inferior maxilla behind the mental foramen, and its fibres conversce upward to a narrow insertion at the angle of the mouth, where they intermingle with those of the zygomaticus, the orbicularis oris, and the upper portion of the platysma muscle, known as the musculus risorius (or laughing muscle of Santorini), and also with the under strata of the levator anguli oris. The peculiar arrangement of the interlacing of the fibres of this muscle at the corner of the mouth with so many others THE REGION OF THE FACE. 121 renders tliis part the most mobile in the face. The depressor anguli oris is the most expressive of all the facial muscles : it plays an important role in melancholy and sorrowful emotions. The depressores lahii inferioris muscles arise from the lower jaw, between the symphysis and the mental foramina, a quantity of fat being generally interspersed among their fibres, which are inserted into the lower lip, blending with one another and the outer portion of the orbicularis. These muscles draw the lower lip downward and a little outward, as in the expression of irony or sarcasm. The levatores menti muscles arise in conical bundles from the incisor fossae of the lower jaw, and are inserted into the skin of the lower i^ai't of the chin. Their action is to wrinkle the chin, as in doubt, and to raise the chin and protrude the lower lip. The latter action is made use of in shaving the chin. The two risorius muscles are constituted by a separation of the upper fibres of the platysma myoides muscles, which are inserted into the super- ficial layer of fibres from the depressor anguli oris and the orbicularis muscles at the angles of the mouth. A few fibres of the risorius muscles occasionally arise from the fascia over the masseter muscles. When these are pronounced, the action of these muscles is noticeable in laughter, but as they usually exist they produce the smile of scorn or derision rather than that of good humor. There is often great diversity in the develop- ment of these muscles on the two sides of the same face. Beneath the risorius and other muscles which blend at the angles of the mouth are the oral attachments of the buccinator muscles. These muscles are chiefly concerned with keeping the food between the teeth during mastication, and therefore are more properly classified with the regions of the cavity of the mouth (page 172) and of the pharynx. They arise from the molar portions of the alveolar processes of the upper and lower jaws, and posteriorly from the fibrous intersections which separate them from the superior constrictor muscles of the pharynx on each side. These fibrous bands extend from the hamular processes of the internal pterygoid plates to the posterior extremities of the mylo-hyoid ridge on each side of the lower jaw, near the last molar teeth. They are called the pterygo- 16 122 THE REGION OF TSE FACE. maxillary ligaments. The fibres of the buccinator muscles pass forward, to be inserted in a peculiar manner at the under surface of the other muscular structures at the angles of the mouth. The upper fibres join the upper lips, and the lower fibres the lower lips, while the central fibres cross one another. Unlike the rest of the facial muscles, the buccinators are covered with a sheath of fascia externally, which greatly increases their power. In relation to the masseter muscles a quantity of fat, on each side, fills up the zygomatic fossse, giving to the face a fulness or roundness in these parts. Its absorption produces the sunken condition of the cheeks in emaciated individuals. The buccinator muscles widen the aperture of the mouth by pulling upon its corners, and their power for expelling the air from the mouth is seen in whistling, or in blowing a trumpet (whence their name). The masseter muscles arise from the lower edges of the zygoma and malar bones. These muscles consist of superficial and deep strata of fibres arranged in a crossed manner which greatly augments their power. The superficial fibres constitute the principal part of each muscle, and take origin by a thick tendinous aponeurosis from the malar process of the superior maxilla and from the lower border of the anterior two-thirds of the zygoma (Plates 16, 18, and 21). These fibres pass obliquely backward, and are inserted into the angle and the lower half of the outer surface of the ramus of the jaw. The deep fibres are mainly muscular, and arise from the posterior third of the lower border and the whole of the inner surface of the zygomatic arch. They pass downward and forward, and are inserted into the upper half of the ramus and the outer surface of the coronoid process, blending with the insertion of the super- ficial fibres. The anterior border of the muscle is tlierefore formed of the two layers of fibres, and presents a thick prominence which can be readily felt by the finger inserted in the mouth between the cheek and the malar bone. The deep portion of this muscle is partly covered by the superficial portion anteriorly, and it is in relation to the parotid gland posteriorly. The masseter muscles assist largely in producing the contour of the lower part of the face. Their function is to raise the lower jaw and to assist the temporal muscles in mastication. There is a dense layer of fascia, derived THE REGION OF THE FACE. 123 from the deep cervical fascia, which covers each masseter muscle, called the masseteric fascia. It adheres intimately to the tendon of origin of the superficial portion, and binds it firmly to the ramus of the jaw. A few strong fibres also connect the origin of the deeper portion with the tendon of the temporal muscle at the coronoid process. The motor nerves of the masseter muscle are, like those of the temporal (page 14), derived from the inferior maxillary nerve. The spot where reflex contraction of the masseter muscle may be produced by electrical stimulation is four centi- metres, or about an inch and a half, in front of the ear, on a line drawn from the apex of the nose to the lobule (Plate 53, Fig. 1). The arteries of the face are very numerous, and are derived from the facial, internal maxillary, and temporal branches of the external carotid artery. The facial (or external maxillary) artery, after it has tunnelled through the submaxillary gland, appears at the side of the face, coursing over the body of the lower jaw, accompanied by the facial vein in front of the masseter muscle (Plate 18, No. 14, and Plate 19, No. 13). In this relation the artery is comparatively superficial, and its pulsation can be readily detected or checked by compression. In order to secure it with a ligature the incision should be made parallel to the anterior border of the masseter muscle, about three centimetres, or an inch and a quarter, in front of the angle of the jaw ; but it should be remembered that the vessel usually lies in a loose bed of fat, and that the skin and platysma muscle over it are freely movable, so that it will readily slip aside. It may be rendered more tense by depressing the lower jaw. From the masseter muscle the artery passes very tortuously to the corner of the mouth, where it gives off ordinarily the inferior labial and coronary arteries to the lips, and is continued up along the side of the nose to the inner canthus of the eye, terminating as the angular artery (Plate 19, No. 4). In its course over the face it gives off" branches to the masseter and buccinator muscles. The inferior labial artery passes under the depressor anguli oris and anastomoses with the mental, submental, and inferior coronary arteries. The inferior coronary artery is usually given off from the facial near the corner of the mouth, either by an independent trunk or in common with the superior coronary. It passes beneath the 124 THE REGION OF THE FACE. depressor anguli oris, pierces the orbicularis, and, running between this muscle and the mucous membrane of the lip, inosculates with its fellow and the inferior labial and mental arteries. The superior coronary is larger and more tortuous than the inferior, and arises from the facial artery beneath the zygomaticus muscle. It also runs between the muscular structure of the upper lip and the mucous membrane, and, inosculating with its opposite fellow, forms with the two inferior coronary arteries a vascular circle, which can be felt pulsating on the inside of the mouth by compressing the lips anywhere near their free borders. The superior coronary supplies branches to the septum and ala of the nose. Some- times this vessel arises independently from the transverse facial branch of the temporal artery (Plate 19, No. 9), which is then much enlarged and superficial. The lateral artery of the nose is supplied by the facial to the ala and dorsum of the nose. It anastomoses with the nasal branch from the ophthalmic artery, the septal artery, the infra-orbital artery, and the communicating vessels from the other side of the nose. The angular artery is the termination of the facial, and ascends among the fibres of the levator labii superioris et alae nasi muscle to the inner angle of the orbit, where it inosculates with the nasal branch of the oph- thalmic artery in relation to the tendo palpebrarum, on the nasal side of the lachrymal sac. The anastomoses of the facial artery are so numerous that ligature of both ends of a divided vessel in this region is often necessary. The great vascularity of the face occasions very rapid healing in wounds, which should have their edges accurately adjusted as soon as possible, to avoid distortion. The same cause also occasions the occurrence of neevi and erectile tumors about the face. The remarkable success of plastic surgery in this region is due to the great vitality of the flaps, and extensive injuries involving loss of substance are often repaired rapidly. The facial artery and its branches are surrounded by a minute plexus of vaso-motor and dilator nerves, derived from the superior cervical gan- glion of the sympathetic nerve (Plate 36, No. 49), to the influence of which is probably due the sudden blushing or pallor of the countenance which attends mental emotions, as in shame or fear. THE REGION OF THE FACE. 125 The facial vein begins at the inner corner of the eye, where it receives the blood from the frontal and supra-orbital veins, and is called the ayigular vein where it is in relation to the angular artery. Thence it passes down the side of the nose, with the lateral nasal artery, and from the alar cartilage it takes an oblique course to the anterior border of the masseter muscle, being interposed between it and the facial artery, with which it is apt to be ensheathed (Plate 18, No. 15, Plate 19, No. 13, and Plate 21, No. 32). It usually passes directly over the termination of the parotid duct (Plate 18, No. 10). The veins emptying into the facial vein are the tributary veins from the territories supplied by the branches of the facial artery ; but at the corner of the mouth it is increased in size by the communicating veins from the infra-orbital and temporo-maxillary veins. By far the most important of the communications of the facial vein are the veins which bring it in relation with the cavernous sinus at the base of the brain. This connection is twofold. There is a direct communi- cation with the angular vein through the ophthalmic vein (page 95), and an indirect communication through the deep facial vein, from the pterygoid plexus, which is in relation with the cavernous sinus by small veins through the foramen of Vesalius, in the sphenoid bone, and the fibrous tissue of the foramen lacerum medium. There are no valves in the facial vein, or at the junction of any of its branches, so that when it is involved in wounds the bleeding from it is very copious. It is also peculiar in remaining more patent after being cut than superficial veins elsewhere, which renders it liable to septic absorption. The facial vein terminates in the internal jugular vein near the bifurcation of the common carotid artery. The lyviphatic vessels of the face converge chiefly toward the submaxillary ganglia, while some go to a few lymphatic ganglia which lie superficially over the parotid gland (Plate 16). The sensory nerves of the face are mainly derived from the terminal branches of the fifth cranial, or trifacial, nerve (Plate 3, Fig. 2). An accurate knowledge of the position of the foramina through which they make their exits upon the face (Plate 28), and of their cutaneous areas of distribution (Plate 53, Fig. 1), is of the greatest value in determining the seat and treatment of neuralgic affections in this region. The oph- PLATE 18. The superficial fascia removed from the left side of the face, together with the platysma myoides muscle from the neck, to show the superficial vessels and nerves in these regions, and especially the superficial relations of the parotid gland. 1. The supra-orbital artery. 2. The anterior branch of the temporal artery. 3. The angular artery. 4. The compressor naris muscle. 5. The levator labii superioris muscle. 6. The lateral nasal artery and vein. 7. The levator anguli oris muscle. 8. The zygoraaticus major muscle. 9. Tlie transverse facial artery. 10. The duct of Stenson, from the parotid gland. 11. The infra-orbital branches of the facial nerve. 12. The orbicularis oris muscle. 13. The inferior labial artery (arising in this case from the transverse facial artery). 14. The facial artery. 15. The facial vein. 16. The depressor labii inferioris muscle. 17. The submaxillary vein, joining the facial vein with the external jugular vein. 18. The anterior belly of the digastric muscle. 19. The mylo-hyoid muscle. 20. The submaxillary gland. 21. The facial branch of the auricularis magnus nerve. 22. The oblique vein, joining the facial vein with the in- ternal jugular vein. 23. The point of bifurcation of the common carotid artery. 24. The thyroid notch (pomum Adami). Superficial branches of the superior thyroid artery. The superficial transverse cervical nerves. Tlie left stern o -thyroid muscle. The leftsterno-hyoid muscle. The fascia over the supra-clavicular fossa, Tlie sternal portion of the stern o-cleido-mastoid muscle. The clavicular portion of the sterno-cleido-mastoid muscle. The sternal and clavicular nerves, from the cervical plexus of nerves. The fascia over the clavicle. The fascia over the great pectoral muscle. The superficial temporal nerves. The auriculo-temporal nerve. The temporal artery. The orbital branch of the temporal artery. The temporal branches of the facial nerve. The parotid gland. The auricular branch of the auricularis magnus nerve. The mastoid branch of the auricularis magnus nerve. The external jugular vein in its proper position. The external and internal carotid arteries covered by their sheaths of the deep fascia. The auricularis magnus nerve. The junction of the superficial cervical veins with the external jugular vein. The acromial nerve. Dissect^, PhotD^rdphed and Colored from Nature by Geo/^oe Mc. Clellan. M D. Copyright, I89hby Georgf Mc Clellan, M AcmstrongsCo Lith BosTon THE REGION OF THE FACE. 127 thalmic division of the trifacial nerve supplies the supra-orbital, the supra- trochlear, the lachrymal, the infra-trochlear, and the naso-lobular, all of which have been described with their special regions. The superior maxillary division of the trifacial nerve terminates upon the face in the infra-orbital nerve and the temporo-malar nerve, the former of which emerges, with the infra-orbital artery, from the infra- orbital foramen under the levator labii superioris muscle. The infra-orbital foramen is six millimetres, or about a quarter of an inch, below the margin of the orbit, and directly in a straight line drawn from the supra-orbital foramen, which is three centimetres, or an inch and a quarter, from the external angular process, toward the root of the nose, to the mental foramen, which is the same distance outward from the symphysis of the lower jaw. The location of this foramen is of surgical importance, as the nerve is apt to be compressed within its bony canal. The foramen may be reached by a trap-door incision made parallel to the lower margin of the orbit, over the point just indicated. The infra-orbital canal, in which the nerve is lodged before it makes its exit at the foramen, presents considerable variations, so that the operation for resection of the nerve is better done by seeking the foramen first, and then chiselling away the bone so as to expose the nerve in the anterior part of its course. In close relation to the infra-orbital foramen is the plexus formed by the communications between the deep branches of the facial nerve, which sup- plies the adjacent muscles, and the descending branches of the infra-orbital nerve. Immediately after issuing from the foramen, the nerve separates into a leash of fibres, some of which, the palpebral, pass upward beneath the orbicularis palpebrarum muscle to supply the lower eyelid ; others, the nasal, pass to the side of the nose ; and others, the labial, and the most numerous, descend beneath the levator labii superioris muscle and termi- nate in the papillae of the upper lip and the bordering mucous mem- brane of the mouth. The temporo-malar nerve arises from the superior maxillary nerve within the spheno-maxillary fossa, whence it enters the orbit and divides into temporal and malar branches. The temporal branch runs in a groove in the malar portion of the orbit and passes through a foramen in the malar bone. It ascends under the temporal muscle, which 128 THE REGION OF THE FACE. it pierces, together with its fascia, about two and a half centimetres, or an inch, above the zygoma, and is distributed to the skin of the temple and side of the forehead (Plate 53, Fig. 1, No. 20). The malar branch issues on the face through a foramen in the malar bone, of variable size and position, and, piercing the outer fibres of the orbicularis palpebrarum muscle, supplies the skin of the cheek over the malar bone, being some- times called the subcutaneus malce. The sensory portion of the inferior maxillary division of the trifacial nerve terminates upon the face in the auriculo-temporal nerve, the buccal nerve, and the mental nerve. The auriculo-temporal nerve arises by two roots, which surround the middle meningeal artery (Plate 3, Fig. 2, No. 20), and then combine to form a single trunk, which passes behind the external pterygoid muscle and the neck of the lower jaw. It first ascends beneath the parotid gland, and then passes, with the temporal artery and vein, over the root of the zygoma and divides into anterior and posterior branches (Plate 18, No. 36, and Plate 19, No. 20). The anterior branch supplies the skin over the vertex and the temporal region ; the posterior branch supplies the ujjper part of the pinna and the adjacent integument. The auriculo-temporal nerve communicates, near its origin, with the otic ganglion. It sends auricular branches to the meatus externus and the membrana tympani (page 65), and to the tragus and auricle. It also sends branches to the temporo-maxillary joint and to the parotid gland. The buccal nerve arises usually in common with the anterior deep temporal nerve, and passes either above or between the fibres of the external pterygoid and temporal muscles to reach the buccinator muscle, where its filaments sjjread out and form with the buccal branches of the facial nerve a plexus in relation to the facial vein. The buccal nerve supjilies sensation to the skin, the mucous membrane, and the buccal glands of the cheek. This is borne out by several instances where this nerve has been found to originate from the superior maxillary nerve. The facial nerve incites the motor power of the buccinator muscle by a special branch (page 130). The mental nerve is the termination of the inferior dental branch of the inferior maxillary nerve, which emerges, with the mental artery, at the mental foramen in the lower jaw, beneath the THE RE&ION OF THE FACE. 129 depressor anguli oris muscle. It divides into a leash of fibres, some of which supply the integument over the chin, and the rest are dis- tributed to the papillae and mucous membrane of the lower lip. The skin covering the parotid gland and contiguous part of the cheek is supplied with sensation by the great auricular branch of the cervical plexus of nerves (Plate 53, Fig. 1, No. 27). The motor nerves of the face are derived from the branches of the seventh cranial or facial nerve, which emerge at the anterior border of tlie parotid gland over the masseter muscle. The origin of the facial nerve, from the lateral tract of the medulla oblongata (page 41), and its course through the aqueduct of Fallopius in the temporal bone (page 69) to its exit from the skull at the stylo-mastoid foramen, have been de- scribed. After issuing from the foramen the facial nerve sends off motor branches to the posterior auricular, occipital, digastric, and stylo-hyoid muscles, and then, in relation to the ramus of the lower jaw, divides into two primary facial branches, named, from their distribution, the temporo-facial and cervico-facial nerves, which form, by their communi- cations within the substance of the parotid gland, the plexus called by the old anatomists theses anserinus (Plate 19, No. 23), from its fancied resemblance to the outspread skeleton of a goose's foot. The temporo-facial nerve is the largest, and in passing through the parotid gland it crosses the external carotid artery and the neck of the jaw. It is joined by several sensory twigs from the auriculo-temporal branch of the trifacial nerve, and divides into temporal, malar, and infra-orbital branches. The motor temporal nerves ascend over the zygoma and supply the muscles about the orbit and eyelids, and form sensory connections with the supra-orbital nerve, with the temporal branch of the superior maxillary nerve, and with the auriculo-temporal and lachrymal nerves. The spot where reflex contraction of the temporal muscle may be produced is two and a half centimetres, or about an inch, in front of the ear, on a line drawn from the eyebrow to the top of the auricle (Plate 53, Fig. 1, No. 6). The motor malar nerves cross the malar bone to the outer angle of the orbit, supplying the contiguous portion of the orbicularis muscle, and join with sensory filaments from the lachrymal, supra-orbital, and subcutaneus malee 17 130 THE REGION OF THE PAROTID GLAND. nerves. The motor infra-orbital nerves are comparatively of larger size, and consist of sujierficial and deep branches which pass forward over the masseter muscle to be distributed to the muscles beneath the lower margin of the orbit and about the mouth. The superficial branches supply the superficial muscles of the face and form sensory connections with the nasal and infra-trochlear nerves along the nose. The deep branches pass beneath the zygomaticus and levator labii superioris muscles, which they supply, and establish sensory connections with the infra-orbital branches of the superior maxillary nerve, forming the infra-orbital plexus, already mentioned. The cervico-facial nerve is joined within the parotid gland by sensory filaments from the auricularis magnus branch of the cervical plexus of nerves. It descends toward the angle of the jaw, and divides into the buccal, supra-maxillary, and infra-maxillary nerves. The motor buccal nerves pass over the masseter muscle to supply the buccinator and orbicularis oris muscles. They join with filaments of the infra-orbital motor nerves, and form sensory connections with the buccal branch of the inferior maxillary nerve. The supra-maxillary nerves pass beneath the platysma and depressor anguli oris muscles, which they supply. They establish sensory communications with the mental branch of the inferior maxillary nerve. The infra-maxillary nerves consist of several arching branches beneath the platysma muscle, which they supply, between the jaw and the hyoid bone. One of these branches is joined by the super- ficial cervical nerve from the cervical plexus (Plate 19). THE REGIOK OF THE PAEOTID GLAITD. The parotid gland, so called because it is near the ear (Plates 13 and 18), is the largest of the salivary glands. It weighs from half an ounce to an ounce in different individuals, and is lodged in a pyramidal bed upon the side of the face, below and in front of the ear. Its external sur- face is firmly bound down by an extension of the fascia from the masseter muscle, which is here called the parotid fascia, and which serves to conceal the form of the gland from external view. The tough and unyielding nature of this fascia accounts for the intense pain often experienced in cases THE BEGION OF THE PAROTID GLAND. 131 of abscesses involving the gland, or in parotitis (raumjDs), from pressure upon the sensory nerves within the gland. From the inner layer of the parotid fascia prolongations extend into the substance of the gland, which partition off and support the lobules, the gland being of the compound racemose variety. The lobules consist of aggregations of small csecal dilatations (the alveoli) of fine canals, which are lined with a layer of epithelial cells, and supported by the connective tissue which is continued inward from the surface of the gland, as above mentioned. The peri- lobular tissue contains lymph-spaces, which are in relation to the capillary vessels and ultimate nerve filaments which preside over the nourishment and secretory functions of the glandular structure. The canals are the excretory ducts of the lobules, which empty into the main duct of the gland, called the duct of Stenson, which leaves the gland at its anterior border on the masseter muscle. Stenson's duct is a firm white tube, the size of a goose-quill, and takes a parallel course to the zygoma in close relation to the transverse facial artery, on a line drawn from the external auditory meatus to a point midway between the ala of the nose and the angle of the mouth (Plate 18, No. 10). About the middle of this line the duct, after passing over the facial vein, turns abruptly inward around the anterior border of the masseter muscle and penetrates the buccal fat and the buccinator muscle, to open upon the mucous membrane of the mouth, opposite the second molar tooth of the upper jaw, by a narrow orifice. The saliva secreted by the parotid gland is an alkaline, watery fluid, which aids in the mechanical disintegration of the food and also possesses the property of converting starch into dextrin and grape sugar. The space which the gland occupies is bounded above by the zygoma, below by the sterno-mastoid and digastric muscles, behind by the external auditory meatus and the mastoid process of the temporal bone. The gland is prolonged anteriorly over the ramus of the jaw and masseter muscle to a variable extent. It is often continuous with the structure of the sub- maxillary gland, but is usually separated from it by a fold of the deep cervical fascia, called the stylo-maxillary ligament. There is also an extension of the deep cervical fascia which is connected with the sheaths of the pterygoid muscles and the pterygoid process of the sphenoid bone. PLATE 19. The parotid gland removed from the left side of the face to show the branches of the facial nerve, and the fascia removed from the posterior cervical triangle to show more clearly the superficial cervical plexus of nerves. 1. The frontal muscle and branches of the frontal artery and snpra-trochlear nerve. 2. The supra-orbital artery and nerve. 3. The anterior branch of the temporal artery. 4. The angular artery. 5. The compressor naris muscle. 6. The lateral nasal artery and vein, 7. The levator anguli oris muscle. 8. The zygomaticus major muscle. 9. The transverse facial artery. 10. The mnsseter muscle. 11. The superior coronary artery. 12. The inferior coronary artery. 13. The facial artery and vein. 14. The depressor anguli oris muscle. 15. The carotid artery covered by its sheath. 16. The transverse cervical nerve, passing beneath the external jugular vein. 17. The sterno-hyoid muscle. 18. The interspace between the sternal and clavicular por- tions of the sterno-mastoid muscle. The posterior branch of the temporal artery. The auriculo-temporal nerve. The temporal branches of the facial nerve. The temporal artery. The remains of the parotid gland, dissected away to show the relations of the facial nerve, and the pes anse^'inus. The vessels and nerves to the buccinator muscle. The splenius capitis muscle. The auricularis magnus nerve. The cervical branch of the facial nerve. The oecipitnl artery. The trapezius muscle. The occipitalis minor nerve. The spinal accessory nerve. The descending cervical nerves (sternal, clavicular, and acromial branches). The scalenus medius muscle. Tiie external jugular vein. The supra-clavicular fossa, occupied with fat and superficial veins. N. B.— The transverse facial artery in this instance supplies the coronary arteries which usually arise from the facial artery proper. Plate! 9 Vol I l^/ssect^. Pholo^rdDhed and Cohrea from Nature by OeoffGe Mc. C/.^llan, MO. Copyn^ht,l83l_.by George Mc Clei.lan^M D THE REGION OF THE PAROTID GLAND. 133 The gland is therefore in a measure enclosed in a fascial envelope. This is normally very thin over the deeper parts, but when the gland is affected ■with any chronic morbid enlargement it is thickened, and may be then more properly regarded as a sac. There is, furthermore, a peculiar in- vagination of the deep cervical fascia between the anterior surface of the styloid process and the posterior border of the external pterygoid muscle, which reaches to the wall of the pharynx, so that in post-pharyngeal abscess there is often an external swelling in the parotid region. In several cases in the author's experience, where the pharyngeal abscess was so large that it was feared the evacuation of the pus through direct incision by the mouth might lead to suffocation by its entering the glottis, external drainage was established by careful dissection down to the stylo- maxillary ligament and tapping the space above referred to just below the lower border of the parotid gland. The dimensions of the space occupied by the gland vary with the movements of the lower jaw, and with the changes in its angle peculiar to infancy and to old age. In the two latter instances it is naturally increased at its lower part, owing to the obliquity of the angle, and it is also increased when the head is extended and the jaw moved forward. When the head is flexed it is diminished. The relations of the parotid gland are of the greatest importance from a surgical point of view, as its removal, when diseased, is one of the most difiicult and hazardous of surgical undertakings. The skin and superficial fascia over this region are loose and movable, and contain some fibres of the platysma muscle in the lower part. In the connective tissue between the superficial fascia and the deep or parotid fascia there are a few branches of the superficial cervical plexus of nerves, and several lymphatic glands, which receive the lymphatic vessels from the neighboring portion of the scalp and the superficial tissues of the face (Plate 16). These are the extra-parotid lymphatic glands, the enlargement of which by disease consti- tutes a form of false parotid tumor. There is another species of lymphatic tumor in this region which is very difficult to distinguish from enlargement of the gland itself, owing to the involvement of the intra-parotid lymphatic glands. These are usually two or three in number, though sometimes 134 THE REGION OF THE PAROTID GLAND. only one, and receive the lymph from the deep temporal and maxillary structures accompanying the vessels into the interlobular spaces within the gland. The deep surface of the parotid gland is very irregular, consisting of projections of its substance which fit into the spaces between the subjacent parts. These projections, which extend from the main body of the gland, are known respectively as the glenoid lobe, which is received into the portion of the glenoid fossa of the temporal bone not occupied by the condyle of the lower jaw, and limited anteriorly by the Glaserian fissure and posteriorly by the vaginal process; \hQ pterygoid lobe, which projects behind the ramus of the jaw, between the two pterygoid muscles and internal to the internal maxillary artery ; the carotid lobe, which is in relation to the base of the styloid process, and interposed between the external carotid artery and the internal carotid artery and internal jugular vein ; and the masseteric lobe, or soda parotidis, which is of variable size, and lies upon the masseter muscle, usually above Stenson's duct, into which it opens by a separate duct. The external carotid artery, at the angle of the jaw, gives off the posterior auricular artery and continues upward under the parotid gland for about two-thirds of its extent, and opposite the neck of the jaw it enters the gland, and, tunnelling through its substance, emerges at the upper border, where it is called the temporal artery. Just before quitting the gland the external carotid gives off the internal maxillary artery, which passes behind the ramus of the jaw ; while the temporal artery in immediate relation with the upper border of the gland sends off the transverse facial branch (Plate 18, No. 9). The lower part of the internal surface of the gland is separated from the external carotid artery by the confluence of the temporal and internal maxillary and posterior auricular veins, which empty into the external jugular vein at its commencement in the neighborhood of the angle of the jaw. The upper part of the gland, through which the external carotid artery passes, is in. immediate relation with the internal carotid artery and the internal jugular vein (Plate 22, Fig. 2), and interior to these vessels are the pneumogastric, spinal accessory, hypoglossal, and glosso-pharyngeal nerves (Plate 36). The facial nerve THE REGION OF THE PAROTID GLAND. 135 enters the parotid gland at its posterior border, on a line with the entrance of the external carotid artery, and divides into the temporo-facial and cervico-facial nerves, which, branching between the lobules of the gland, form the pes anserinus, and emerge at the superior and anterior borders, to be distributed to the region of the face (page 129). The auriculo-temporal branch of the inferior maxillary nerve penetrates the gland behind the neck of the jaw, and the auriculo-parotidian branch of the auricularis magnus nerve, from the cervical plexus, enters it near the lobule of the ear (Plate 19, No. 20). Both of these nerves supply sensation and form connections with the facial nerve within the substance of the gland ; and in rapidly-growing tumors of the gland, not only is facial paralysis apt to occur from pressure on the facial nerve, but the pain is often referred to the parts supplied by the auriculo-temporal nerve, viz., — the pinna, the temple, the meatus, and the temporo-maxillary joint. From the above description it will be understood that it is the upper part of the gland which extends most deeply toward the base of the skull and involves structures of vital importance. In some dissections the inward projections of the gland have been found to reach such a depth, and their adhesions to be so general to hard and soft structures alike, that an enucleation or extirpation of the entire glandular mass would seem to be a well-nigh impossible task ; but it has not proved such in the hands of some bold enough to undertake it, and their success has been due to the most exact knowledge of this complex region, alike in its normal condition and in the possible changes which disease may occasion in the parts, a precision of knowledge which is probably required by no other operation in surgery. The tendency of most morbid growths of the gland is outward, in spite of the resistance of the parotid fascia, and the deep portion, although the fascia over it may be thickened by in- flammation, is apparently drawn forward. This statement is based upon the author's clinical observation, and the opportunity afforded him of examining a scirrhous parotid on the dissecting-table. The cavity of the wound after complete extirpation of the parotid was found to be larger at the bottom than at the surface. The styloid process, quite uncovered by the removal of the little muscles which are attached to it, projected Missing Page Missing Page 138 THE DEEP STRUCTURES OF THE FACE. which are projected inward toward the base of the skull (page 134). The connections of the deep parts beneath the inferior maxillary articulation are so intimate that they offer great difficulty to the dissector bent upon investigating the diverse branches of the internal maxillary artery and their relations to the complex nerves which traverse this region. These can be properly displayed only after removal of the zygoma and the ramus of the jaw (Plate 22, Fig. 2) ; but before this is done the attachments of the pterygoid muscles should be understood. The external pterygoid muscle has a double origin, the upper head arising from the bony surface extending from the ridge on the great wing of the sphenoid bone to the base of the pterygoid process, and the lower head from the outer surface of the external pterygoid plate. The fibres comj)osing these two portions converge to be attached to the front of the neck of the lower jaw and inserted into the fibro-cartilage above the condyle. The internal -pterygoid muscle arises mainly from the pterygoid fossa, receiving slips from the adjacent tuberosities of the palate and superior maxillary bones. The internal pterygoid muscle closely resembles the masseter in form and in the direction of its fibres, which are inserted by a strong, broad tendon into the inner side of the ramus of the lower jaw, between the dental foramen and the angle. At their origins the pterygoid muscles rest upon and cross each other. When the muscles upon both sides of the head act in unison the lower jaw is drawn forward, so as to advance the lower teeth beyond the upper; when they act in alternation they serve as the direct agents in the trituration of food. The motor nerves to both of the pterygoid muscles are derived from the inferior maxillary nerve, like those to the masseter and temporal muscles. Trismus, or spasm, is very apt to affect the muscles of masti- cation, and may be produced by irritation of the sensory branches of the inferior maxillary nerve. The outer surface of the internal pterygoid muscle is in close relation with the internal lateral ligament of the temporo-raaxillary joint, and its inner surface is associated with the tensor palati muscle, and is separated from the pharynx by a cellular space. Between the maxillary insertions of the two pterygoid muscles pass the vessels and nerves. THE BEEP STRUCTURES OF THE FACE. 139 The internal maxillary artery arises from the external carotid artery in the substance of the parotid gland (page 130), opposite the neck of the lower jaw. It is very complex in its course, supplying numerous branches which establish free anastomoses with other arteries of the face and head (Plate 3, Fig. 2, and Plate 22, Fig. 2). In relation to the neck of the jaw, and between it and the internal lateral ligament, the artery just after its origin sends off the tympanic, middle and lesser meningeal, and inferior dental branches. The tympanic artery enters the Glaserian fissure behind the articu- lation of the jaw, to supply the cavity of the tympanum and the membrana tympani, as described in the region of the ear. It also sometimes sends a little branch through a foramen in the anterior wall of the external auditory meatus, to supply the skin lining that canal. The middle menin- geal artery ascends behind the external pterygoid muscle and enters the foramen spinosum of the sphenoid bone, whence it passes to the anterior inferior angle of the parietal bone and subdivides into radiating branches between the dura mater and the parietes of the skull (Plate 9, Fig. 2). The lesser meningeal artery usually arises independently from the internal maxillary, although it is often a branch of the middle meningeal. It enters the foramen ovale of the sphenoid bone, which also gives exit to the inferior maxillary nerve, and supplies chiefly the Gasserian ganglion of the trifacial nerve. The inferior dental artery descends to the dental foramen at the middle of the inner surface of the ramus of the jaw, which it enters with the dental nerve, and, passing through a canal in the diploic structure of the jaw, supplies the roots of all the teeth, eventu- ally making its exit upon the face at the mental foramen (page 127) and becoming the mental artery. Before the inferior dental artery enters the dental foramen the mylo-hyoid branch is given off, accompanying the corresponding nerve to the mylo-hyoid muscle. In relation to the ex- ternal pterygoid muscle the internal maxillary artery is very tortuous. It passes either over or under the muscle (in some cases through it), and subdivides into the masseteric, anterior and posterior deep temporal, ex- ternal and internal pterygoid, and buccal branches. The masseteric artery passes outward through the sigmoid notch of the jaw to the under surface PLATE 20. Dissection of the vessels and nerves of the scalp and face on the left side, and the stern o-mastoid muscle removed from its sternal and clavicular attachments to display the deep cervical plexus of nerves. The fascial slip to the centre of the omo-hyoid muscle is also removed to show the relations of the common carotid artery and the internal jugular vein. S5. The anterior branch of the temporal artery. The angular artery. The compressor naris muscle. The lateral nasal artery and vein. The levator labii superioris muscle. The zygomaticus major muscle. The orbicularis oris muscle. The tmnsverse facial artery. The infra-orbital branch of the facial nerve. The facial vein. The facial artery. The depressor labii iiiferioris muscle. The body of the lower jaw. The sub-mental artery. The anterior belly of the digastric muscle. The mylo-hyoid muscle. The facial artery, coming out of the submaxillary gland, in front of the masseter muscle. The submaxillary vein, connecting the facial vein with the external jugular vein. The position of the hyoid bone. The oblique vein, connecting the facial vein with the internal jugular vein. The external carotid artery, just above Its origin, and slightly enlarged, as it is often found to be here. The internal jugular vein. The internal carotid artery, covered by its sheath. The superior laryngeal artery. Tlie thyroid notch. The anterior belly of the omo-hyoid muscle. The left sterno-hyoid muscle. The left sterno-thyroid muscle. The phrenic nerve. The pneumogastric nerve, brought forward Into promi- nence. The scalenus anticus muscle. The junction of the external and internal jugular veins with the subclavian vein. The clavicle. The inter-muscular cleft between the great pectoral and deltoid muscles. The pectoralis major muscle. The posterior branch of the temporal artery. The temporal artery. The auriculo-temporal nerve. The superficial temporal nerves. The temporal branch of the facial nerve. The upper border of the parotid gland. The superior auricular muscle. The remains of the parotid gland. The masseter muscle. The posterior auricular artery. The temporal vein. The posterior auricular nerve. The external jugular \em, drawn aside, with the upper portion of the stern o-mastoid muscle. The submaxillary gland. The occipital artery. The upper portion of the stern o-mastoid muscle drawn outward. The second cervical nerve. The anterior branch of the second cervical nerve. The mastoid nerve. The third cervical nerve. The nerve to the levator anguli scapulse muscle. The anterior branch of the third cervical nerve. The anastomosing branch of the second cervical nerve, with the spinal accessory nerve. The fourth cervical nerve. The scalenus medius muscle, with the ascending cervi- cal artery. The acromial nerve from the fourth cervical nerve. The trapezius muscle. The clavicular nerve from the fourth cervical nerve. The sternal nerve from the fourth cervical nerve. The transversalis colli artery. The posterior belly of the omo-hyoid muscle. The brachial plexus of nerves. The supra-scapular artery. The point of entrance of the thoracic duct. The point of entrance of the external jugular vein with the subclavian vein. The fascia over the deltoid muscle. Plate 20 Vol I I D'sse:ted. Photo^rdphed end Colorec/ from /Mature d^ Geobse Mc Clbllan. M D. Copynght. 1831. by George McClellan.M D. AfnvtiranglCo Lith Bod' THE DEEP STRUCTURES OF THE FACE. 141 of the masseter muscle; the deep temporal arteries ascend to the under surface of the temporal muscle ; the pterygoid arteries supply the pterygoid muscles ; and the buccal artery passes with the buccal nerve to the bucci- nator muscle. After leaving the external pterygoid muscle the internal maxillary artery is continued through the spheno-maxillary fossa, where it gives off many terminal branches. At the tuberosity of the superior maxillary bone the superior dental artery is distributed by minute twigs to the pulps of the molar and bicuspid teeth of the upper jaw, and to the contiguous portions of the gums and the antrum of Higlimore. The infra-orbital artery passes upward through the spheno-maxillary fissure and enters the canal with the infra-orbital nerve, which it accompanies in its distribution, to emerge upon the face at the infra-orbital foramen (Plate 3, Fig. 2, No. 8). Within the canal the anterior dental branches descend to the incisor and canine teeth, and filaments ascend to the inferior oblique and rectus muscles, as well as to the lachrymal gland. The descending palatine artery, com- paratively large, enters the posterior palatine canal with the palatine nerve from Meckel's ganglion, and runs along the roof of the mouth in close relation to the alveoli supplying the gums, the glands, and the mucous membrane over the soft and the hard palate (Plate 13, Fig. 4, No. 12). The Vidian artery accompanies the Vidian nerve. It is not constant, and is always insignificant. The pterygo-palatine artery passes through the canal from which it receives its name, and supplies the Eustachian tube particularly. The nasal, or spheno-palatine, artery enters the nose with the nerve of the same name from Meckel's ganglion, supplying the ethmoidal cells, the turbinated bones, and the antrum, and terminates as the septal artery. It is noteworthy that the branches of the internal maxillary artery in the first and the last part of its course pass through bony canals, but that the branches from the intervening part go directly to muscles. The internal maxillary vein is formed by the veins which bring back the waste blood from the territories supplied by the corresponding branches of the internal maxillary artery. These tributaries form a plexus — the pterygoid plexus — in the space between the temporal and external pterygoid 142 THE DEEP STBUCTUBES OF THE FACE. muscles, which establishes communications with the cavernous sinus above, at the base of the brain, and anteriorly with the facial vein. The vein unites with the temporal vein in the substance of the parotid gland, and they empty together into the external jugular vein. The nerves which accompany the superior maxillary branches of the internal maxillary artery in their distribution are branches of the supe^'ior maxillary nerve, Avliich is the second division of the fifth cranial or trifacial nerve. It leaves the skull through the foramen rotundum, passes horizontally forward across the spheno-maxillary fossa, and enters the orbit by the fissure of the same name. Within the spheno-maxillary fossa and just below the superior maxillary nerve is situated the spheno- palatine or Meckel's ganglion (Plate 3, Fig. 2, No. 6). It is a reddish- gray, heart-shaped body, about the size of a pea. Its sensory root is received from the spheno-palatine branches of the superior maxillary nerve ; its motor root comes from the facial nerve, through the great petrosal portion of the Vidian nerve, and its sympathetic root through the sympathetic fibres of the Vidian nerve, derived from the carotid plexus. The nerves from Meckel's ganglion are distributed to the orbit, the palate, the nose, and the pharynx, and are described with the anatomy of those regions. The Vidian nerve is formed by the great petrosal branch of the facial nerve (page 69), reinforced by fibres from the carotid sym- pathetic plexus as it passes forward to the body of the sphenoid bone, which it enters and traverses through a special canal, the Vidian, to join the back part of the ganglion of Meckel. The inferior maxillary nerve is one of the most interesting of the cranial nerves, from its resemblance to a spinal nerve (page 41). It is the largest branch of the great trifacial or fifth cranial nerve (Plate 3, Fig. 2), and is composed of sensory and motor filaments, owing to the union of the proper (sensory) portion of the nerve, from the lower angle of the Gas- serian ganglion, with the distinct motor root of the trifacial nerve, just after its exit through the foramen ovale. The foramen ovale is five centimetres, or about two inches, from the outer surface of the head, on a level with the middle of the zygomatic arch. The inferior maxillary nerve is covered by the external pterygoid muscle, and is at the outer side of the Eustachian THE BEEP STRUCTURES OF THE FACE. 143 tube. Almost immediately after the formation of the trunk of the nerve, as above described, it subdivides into two portions, — the anterior, consisting mainly of motor fibres, which are distributed to the muscles of mastication and to the buccinator, and the posterior, consisting chiefly of sensory fibres, which convey sensation to the teeth and gums of the lower jaw, the skin about the temj^le and external ear, and the lower part of the face and under lip. The motor branches, from the anterior portion, have each been described with the muscles which they furnish with power. The senso7y auriculo-temporal branch has also been described in detail in its relations to the parotid gland and its distribution upon the side of the head. Its peculiar origin, from two roots which surround the middle meningeal artery and then unite to form a single nerve-trunk, should be remembered. The other important sensory branches are the inferior dental nerve and the lingual nerve. The inferior dental nerve leaves the trunk of the inferior maxillary nerve beneath the external pterygoid muscle, and descends to the dental foramen, by which it enters the inferior maxillary bone and accompanies the dental artery in its distribution to the pulps of the lower teeth (Plate 3, Fig. 2) and the adjoining gums. At the mental foramen the nerve divides into mental and incisor branches in relation to the divisions of the mental artery. The mylo-hyoid nerve, which supplies motion to the mylo-hyoid muscle and the anterior portion of the digastric muscle, appears to branch off from the inferior dental nerve just as that nerve is about to enter the dental foramen. This nerve derives its fibres from the motor root of the trifacial nerve, and is included in the sheath of the dental nerve for a short distance. The lingual nerve is at first in close relation with the inferior dental nerve beneath the external pterygoid muscle, and is very deeply situated through its entire course. About on a level with the entrance of the dental nerve into the dental foramen the lingual nerve is joined by the chorda tympani nerve (page 69), which issues from the canal of Huguier, close to the Glaserian fissure. The lingual and inferior dental nerves are frequently connected by a communicating branch underneath the internal maxillary artery. The lingual nerve descends obliquely from the pterygoid region to the inner side of the last molar tooth of the lower jaw, being here 144 THE DEEP STRUCTURES OF THE FACE. placed under the mucous membrane. In this situation it is sometimes divided to relieve the excruciating pain in cancer of the tongue. The otic ganglion is an oval, reddish-gray little body situated inter- nal to the inferior maxillary nerve, just below the foramen ovale. It is best found by tracing up the highest attachment of the internal pterygoid muscle until the nerve to that muscle is reached. By following along this nerve the ganglion will be found about its origin. It is very near the cartilaginous portion of the Eustachian tube, and the middle meningeal artery mounts upward behind it. The motor roots of the otic ganglion are derived from the internal pterygoid nerve, and the sensory root probably comes from the glosso-pharyngeal nerve; the sympathetic root is derived from the plexus which surrounds the middle meningeal artery. The ganglion is brought into relation with the facial nerve by the small petrosal nerve from the tympanic plexus (page 69). It sends a com- municating branch to the auriculo-temporal nerve in its distribution to the parotid gland. It also sends off filaments to the chorda tympani nerve and to the tensor palati and tensor tympani muscles. The superior maxillary region consists of the superior maxillary bones and the muscles, vessels, and nerves which they support. These have been described with the general anatomy of the face and pterygo- maxillary region. The superior maxillary bones are peculiarly constructed, being exceedingly fragile themselves, but very firmly connected by sutures to the other bones of the face. They are irregular in shape, assist in the formation of the cavities of the orbits, the nose, and the mouth, and are hollowed in their central portions, forming the maxillary sinuses, or antra of Highmore. Each antrum is developed very early in life, but it is not until the period of second dentition that the cavity assumes its full growth. Its facial, orbital, and nasal walls are very thin, and often yield to the pressure of growths or collections of fluid within it. The facial wall upon its external surface presents the incisive fossa, canine eminence, and canine fossa (Plate 28), which afford attachment to many of the muscles which act upon the nose, the upper lip, and the corners of the mouth (Plate 15). The infra-orbital foramen is above the canine fossa, and transmits the facial terminations of the superior maxillary nerve and the internal THE DEEP STRUCTURES OF THE FACE. 145 maxillary artery. The orbital wall or roof of the antrum is grooved ujaon the middle of its orbital surface for the lodgement of the above-mentioned artery and nerve. This groove, two centimetres, or about a finger's breadth, from the margin of the orbit, terminates in a canal which soon subdivides into two branches, one of which, the infra-orbital canal, con- tinues forward to open on the facial surface below the curved border of the orbit, giving passage to the infra-orbital vessels and nerves, and the other, the anterior dental canal, bends downward into the anterior portion of the antrum, transmitting the anterior dental Vessels and nerves to the front teeth of the upper jaw. The nasal xoall of the antrum is an incomplete partition between the cavities of the antrum and nose. The further relations of this portion of the superior maxilla are described with the formation of the nasal cavities in the region of the nose. The cavity of the antrum is often crossed by bony shelf-like projections similar to those found in the cranial sinuses, and on its posterior wall are the posterior dental canals, which convey the posterior dental vessels and nerves to the back teeth of the upper jaw (Plate 3, Fig. 2). The floor of each antrum is formed by the alveolar process, which is the thickest portion of the superior maxillary bone, is spongy in character, and is ex- cavated into eight little pits on each side, forming the alveoli, or sockets, for the corresponding teeth. These alveoli vary in size and depth, that for the canine tooth being the deepest, while those for the molars are the broadest. They encroach upon the cavity of the antrum, and esj)ecially the alveoli for the first and second molars, the fangs of which have sometimes been found to penetrate directly into the antrum, a fact which has been taken advantage of in the extraction of one of these molars to drain or explore the antrum. The knowledge of the relations of the various processes of the upper jaw-bone — i.e., the nasal, malar, alveolar, and palate processes — is of great value when surgical inter- ference is required in the many afiections to which this bone is liable. In excision of this bone it should be understood that its sutural con- nections with the contiguous bones by these jDrocesses are so strong that they must be severed by the use of the saw or bone-nippers. 19 PLATE 21. Deep dissection of the head and neck on the right side to show the temporal muscle uncovered by its fascia, and the relative positions of the deep cervical and brachial plexuses of nerves. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 28. 27. 28. 29. SO. The cut margin of the temporal fascia. The temporal muscle. The ridge for the temporal fascia. The posterior auricular arterj'. The branches of the occipital artery. The occipital artery. The upper portion of the sterno-mastoid muscle, turned upward. The mastoid nerve from the second cervical nerve. The external jugular vein, drawn outward. The anastomosing branch of the mastoid nerve with the spinal accessory nerve. The second cervical nerve. The third cervical nerve. The spinal accessory nerve. The anterior branch of the third cervical nerve. The fourth cervical nerve. The trapezius muscle. The acromial nerve from the fourth cervical nerve. The clavicular nerve from the fourth cervical nerve. The posterior belly of the omo-hyoid muscle. The right clavicle. The middle cord of the brachial plexus of nerves. The point of entrance of the external jugular vein into the subclavian vein. The deltoid muscle covered with the deep fascia. The compressor naris muscle. The lateral nasal artery and vein. The facial branches of the facial nerve. The superior labial artery. The pes anserinus of the facial nerve. The orbicularis oris muscle. The facial vein. The masseter muscle. The facial artery. The depressor labii inferioris muscle. The inferior labial artery. The mylo-hyoid muscle. The anterior belly of the digastric muscle. The hypoglossal nerve. Fascia over the submaxillary gland. The submaxillary vein, joining the facial vein with the external jugular vein. The posterior belly of the digastric muscle. The descendens hypoglossi nerve. The superior laryngeal nerve. The pneumogastric nerve. The point of bifurcation of the common carotid artery into the external and internal carotid arteries. The internal jugular vein. The common carotid artery. The thyroid notch. The oblique vein joining the facial vein with the in- ternal jugular vein. The communicating branch of the third cervical nerve with the descendens hypoglossi nerve. The anterior belly of the omo-hyoid muscle. The anterior jugular vein. The sterno-hyoid muscle. The sterno-thyroid muscle. The left clavicle. The supra-sternal notch. The inter-muscular cleft, between the great pectoral and the deltoid muscles. The pectoralis major muscle. ■i?»ll55S»*'ate5BJI*fi? \ecM, F/ioagrtiphel/ and Coloren fro.r. Manif: o> ■ G£ORr,F^ Mc Clelim. M D. C• Geofmc McldeuM. MB .^v^v^v^^v^^^^vt^t^^^^vt^^^t^t^t^^»« THE REGION OF THE NEGK. 197 over the subclavian vessels into the axilla. Back of the sternum there is a continuation of this layer of the deep fascia, which passes along the anterior mediastinum : the pus from a cervical abscess will sometimes travel along this route and point at the side of the xiphoid appendix on the surface of the abdomen. The arrangement of the layers of the deep cervical fascia in relation to the top of the sternum, to the first rib, and to the clavicle is such that the soft parts at the upper opening of the chest are protected against the pressure of the atmosphere during inspiration. The deep cervical fascia is not normally strong and unyielding, and cannot properly be compared with the fascia lata, but it may become so under the influence of pressure and inflammation ; and in many instances where growths or abscesses in this region have been influenced in their course by the denseness of the surrounding fascia, the growth or abscess has itself induced the change. This is especially noticeable where the morbid condition has become chronic. The sterno-cleido-mastoid muscle (Plates 16, 18, 19, and 23) is the great muscular landmark at the side of the neck, which serves as a guide to the position of the important vessels with which it is in immediate rela- tion. It arises by a thick, round tendon from the upper and outer surface of the manubrium sterni, internal to the sterno-clavicular joint, and by a flat, fleshy, and tendinous origin from the adjacent portion of the clavicle. Between these origins there is a variable interval, which is filled with a double layer of the cervical fascia. The sternal fibres ascend over the sterno-clavicular joint and join with the clavicular fibres, so that at the middle of the muscle its substance is strong and somewhat contracted, but toward its insertion it flattens out, to be attached to the mastoid process, the temporal bone behind the process, and the contiguous part of the upper curved line on the occipital bone. The fibres composing the external and clavicular portions, if carefully examined, will be found to overlap one another, so that the sternal fibres occupy the outer and more conspicuous position, while the clavicular fibres are deeper and mainly attached to the apex of the mastoid process. These peculiarities of the insertions of the fibres of this muscle explain the different actions of which it is capable. This will be better understood by referring to the landmarks of the articu- 198 THE REGION OF THE NECK. lated skeleton (Plate 1) than by referring to a detached skull (Plate 2), and it should be remembered that a line drawn from one mastoid process to the other will bisect the condyloid processes, as previously stated, and that the vertical axis of the skull corresponds to a perpendicular line from the vertex to the inter-mastoid line. Ordinarily the united action of the two sterno- mastoid muscles maintains the head in the erect position with the face directed forward, but if the action of the sternal fibres, which are attached to the temporal and occipital bones behind the mastoid j^rocess, is greatest, the head will be tilted backward, with the face upward, while if the action of the clavicular fibres, which are inserted into the apex of the mastoid process, predominates, the head will be bowed forward. This action is marked in raising the head from the recumbent position, and both actions may be demonstrated by the application of electrical stimulation (Plate 53, Fig. 1). In considering the action of the sterno-mastoid muscle the expan- sion of the deep fascia, which connects the upper part of its anterior border with the lower jaw, should not be overlooked, for it probably assists ma- terially the clavicular fibres. The action of one sterno-mastoid muscle draws the head obliquely toward the opposite shoulder, co-operating with the splenius muscle of the other side. The condition known as " wry-neck" is generally due to the spasmodic contraction of one sterno-mastoid muscle. When the head is fixed, the sterno-mastoid muscles elevate the sternum in forced inspiration. Each muscle is supplied principally by the spinal accessory nerve, which enters close to the mastoid process, together with the sterno-mastoid branch of the occipital artery. It also receives nerves from the second and third cervical nerves, and arteries from the superior thyroid and supra-scapular arteries. The side of the nech may be considered as divided by the oblique direction of the sterno-mastoid muscle into triangular spaces, the anterior and posterior cervical triangles. The anterior triangle is inverted, its base being formed by the body of the lower jaw, and its sides by the middle line and the anterior border of the sterno-mastoid. The posterior triangle has the clavicle for its base, while its sides are defined by the posterior border of the sterno-mastoid and the anterior border of the trapezius muscle (Plate 16). The neck is further subdivided into smaller THE REGION OF THE NECK. 199 triangles by the disposition of the digastric and omo-hyoid muscles beneath the sterno-mastoid. The digastric muscle consists of two muscular portions, united by an intermediate tendon, which pierces the tendon of the stylo- hyoid muscle and is attached to the body of the hyoid bone by a loop of the deep fascia (Plate 25, No. 4). The posterior portion arises from the digastric fossa on the temporal bone, back of the mastoid jDrocess. The anterior portion is attached to the lower jaw near the symphysis. These two portions, with the body of the lower jaw, constitute the submaxillary or digastric triangle. When the platysma is removed from this locality the deep fascia presents a dense covering to the contents of this space, the chief of which is the submaxillary salivary gland (Plate 18, No. 20, and Plate 13, Fig. 2, No. 6), which has already been described (page 164), as well as the relations of the facial and lingual arteries, for which this trian- gular space is usually topographically surveyed. The submaxillary vein, which joins the facial vein with the external jugular, is in the superficial fascia, in close proximity to the jaw (Plate 18, No. 17), and there are from six to ten lymphatic glands (Plate 16), some above and some beneath the salivary gland, which receive the lymphatic vessels from the face, the tongue, and the tonsils, already spoken of in the description of these parts. The stylo-hyoid muscle is a slender band of fibres, originally separated from the posterior portion of the digastric, with which it is in close relation at its inner side. Its upper attachment is at the outer and back surface of the styloid process, and its lower at the body of the hyoid bone near the lesser cornu, where it is pierced by the middle tendon of the digastric. The nerves which supply the posterior portion of the digastric and the stylo- hyoid muscles come from the facial nerve, and leave the lower border of the parotid gland immediately above. These muscles overlie the external and internal carotid arteries, the internal jugular vein, and the pneumogastric and hypoglossal nerves (Plate 13, Fig. 2, and Plate 22, Fig. 2). The anterior portion of the digastric muscle is superficial, and rests upon the mylo-hyoid muscle anterior to the submaxillary gland (Plates 23 and 25). The inner margins of the anterior portions of the two digastric muscles are often connected by fleshy fibres, but generally by connective tissue. Their nerves are derived from the mylo-hyoid nerves. The anterior and pos- 200 THE REGION OF THE NEOK. terior portions of the digastric muscle always act together, but the effect of their action depends upon which two of the three points of attachment are fixed. If the jaw and skull are both fixed, the muscle raises the hyoid bone, as in swallowing; if the skull and hyoid bone are fixed, the lower jaw is depressed, as in yawning ; if the chin is supported so that the jaw and hyoid bone are fixed, the muscle can draw the skull backward. The digastric and stylo-hyoid muscles, with the mylo-hyoid and genio-hyoid muscles, described in relation to the tongue (page 165), are classified as the supra-hyoid muscles. The omo-hyoid muscle is digastric, consisting of two fleshy portions connected by an intermediate tendon. Its posterior portion arises beneath the trapezius muscle from the superior border of the scapula, usually including the supra-scapular notch and its ligament, and passes forward and upward to the level of the cricoid cartilage, being attached to the clavicle by a fold of deep fascia which loops around its intermediate tendon under the sterno-mastoid muscle. The anterior portion passes vertically upward close to the outer border of the sterno-hyoid muscle, and is attached to the lower border of the hyoid bone. The course of this muscle does not change in contraction, and always maintains an obtuse angle, so that it is a reliable guide to the position of the great carotid vessels, directly over the sheath of which it passes at the point where the anterior and posterior portions of the muscle meet, on a level with the cri- coid cartilage, as just stated. The fascial expansion which binds the central tendon to the clavicle is usually reflected to the first rib, and appears to offer resistance to the pressure of the atmosphere upon the internal jugular vein and the apex of the pleura which it covers. Occasionally fieshy fibres are developed in this refiection of the fascia. The contraction of the omo- hyoid muscles takes place only during inspiration, and, owing to their influence upon the fascia enveloping the great venous trunks at the root of the neck, a dilatation of these vessels is coincident with the dilatation of the thorax, so that the flow of the blood toward the heart is facilitated. This also indicates the danger of the entrance of air in wounds involving these veins. The subdivisions of the side of the neck which may be mapped out by the disposition of the omo-hyoid muscle are known as the superior THE REaiON OF THE NEGK. 201 and inferior carotid triangles anterior to the sterno-mastoid muscle, and the occij)ital and supra-clavicular triangles posterior to it. The superior carotid triangle has for its three sides the posterior portion of the digastric muscle, the sterno-mastoid muscle, and the anterior portion of the omo-hyoid muscle. The inferior carotid triangle is bounded by the omo-hyoid and sterno-mastoid muscles, above and below, and in front by the middle line of the neck. These carotid triangles have been so called because they were considered to bear reference to the course of the carotid artery and the internal jugular vein, and to elucidate the topographical study of this very complex region. They are very misleading, and time is often wasted in attempting to acquire or recall their boundaries. The carotid artery is not within the limits of the inferior triangle at all, as the sternal end of the sterno-mastoid muscle completely overlaps the sheath of the great vessels, which is in reality in relation to the interval between the sternal and clavicular origins of that muscle. A needle introduced upon the right side above the clavicle through this interval would pierce the bifurcation of the innominate artery, and on the left side the common carotid artery (Plate 14, Fig. 2, No. 6). The course of the carotid arteries on both sides from this point to their bifurcation is similar, and approximately may be con- sidered as corresponding to the anterior borders of the sterno-mastoid muscles when either of them is brought into relief by turning the head to the opposite side. A line drawn transversely across the neck from the fifth cervical vertebra to the cricoid cartilage will indicate the position where the omo-hyoid muscle crosses the sheath of the great vessels. Above this point the carotid artery is superficial ; below it is deeply placed and covered with a quantity of fatty tissue containing many veins, nerves, and lymphatics. It is this point of crossing of the omo-hyoid muscle which should be sought for in any operation upon the carotid artery ; and by making an incision opposite the cricoid cartilage along the border of the sterno-mastoid muscle it can be readily reached. The bifurcation of the common carotid into the external and internal carotid arteries usually occurs opposite the top of the thyroid cartilage, which is on a level with the body of the third cervical vertebra, but it may be a little above or 26 PLATE 29. The anterior wall of the thorax and upper part of the abdomen removed to show the relations of the heart, lungs, diaphragm, liver, stomach, and spleen to the ribs and their sternal cartilages. The lungs are inflated (as in full inspira- tion) to indicate the so-called area of the heart's dulness. From a male subject about forty years old, with normal condition of the organs. The supra-sternal notch. The right first rib. The right second rib. The upper lobe of the right lung. The right third rib. The base of the heart. Position of the tricuspid valves. The right fourth rib. The right nipple. The right auricle of the heart. The middle lobe of the right lung. The right fifth rib. The lower lobe of the right lung, resting on the dia- phragm and overlapping the liver. The right sixth rib. The ensiform cartilage. The upper surface of the diaphragm, seen through the space between the sixth and seventh ribs. The cartilage of the right eighth rib. The right seventh rib. The left lobe of the liver. The right eighth rib, in this case a true rib, having an independent sternal cartilage. The cartilage of the right ninth rib, in its relation to the fundus of the gall-bladder. The cartilage of the right tenth rib. The lower margin of the right lobe of the liver. The great omentum. The manubrium. 26. The left first rib. 27. The left second rib. 28. The ridge at the junction of the manubrium and gladi- olus of the sternum, where it receives the cartilages of the second ribs. 29. The left third rib. 30. The position of the pulmonary valves. 31. The upper lobe of the left lung. 32. The left fourth rib. 33. The position of the mitral valve. 34. The left nipple. 36. The left fifth rib. 36. The right ventricle of the heart. 37. The position of the apex beat in the adult. 88. The upper surface of the diaphragm, seen between the fifth and sixth ribs. S9. The left sixth rib. 40. The lower border of the left lung. 41. The cartilage of the left eighth rib, independently con- nected with the sternum. 42. The left seventh rib. 43. The left eighth rib. 44. The fundus of the stomach, in ordinary distention. 45. The cartilage of the left ninth rib. 46. The cartilage of the left tenth rib. 47. The lower border of the spleen, in its relation to the cartilage of the tenth rib. 48. The branches of the gastro-epiploica dextra artery. N. B.— The subject upon which this dissection was made presented the rare anomaly of a distinct eighth true rib on either side. This is well shown in the plate. Plate 29 VOL i Cupv,i(ht, 1831 h- Geonei: Mc Clellan.M D O'ssecra'i, Pf:oio^n,ph^j dnd Colored ^^o^r h'^f_un: fjy GEo^rifc Mc. CiEu.Afi, M D. THE REGION OF THE NECK. 203 below this point. The bifurcation is often the seat of aneurism or dilata- tion, in consequence of the resistance here naturally offered to the current of the blood. The external carotid artery, just after its origin, gives off the ascending pharyngeal artery, which runs up between the external and internal carotids to its distribution (page 175), and then in successive order anteriorly the superior thyroid (page 184), lingual (page 166), and facial (page 123) arteries, and terminates in the parotid gland in the internal maxillary and temporal arteries (page 134). Posteriorly the branches from the external carotid are the occipital and posterior auricular arteries (page 8). The relative position which the external and internal carotid arteries hold to each other is worthy of careful notice. At first they are on the same plane, but the external soon crosses in front of the internal to enter the under surface of the upper portion of the parotid gland. The internal ascends close by the side of the pharynx to the base of the skull (Plate 13, Figs. 1 and 3), which it enters by the carotid canal in the apex of the temporal bone. Between the ex- ternal and internal carotid arteries, just above their bifurcation, there is a long, grayish-colored body, the inter-carotic body, which consists of a vas- cular net-work of tiny vessels from the external carotid, interwoven with some non-medullated nerves and ganglion cells and connective tissue. It is the remains of one of the foetal visceral clefts. The internal jugular vein receives the blood from the brain by the lateral sinus, and commences at the jugular foramen, where it is joined by the inferior petrosal sinus and presents a slight enlargement, the jugular sinus. The jugular foramen is formed by the apposition of the jugular fossae of the occipital and tem- poral bones, and is behind the opening of the carotid canal, two and one- half centimetres, or about an inch, from the surface over the mastoid process. The vein descends on the outer side of the internal carotid artery, and, after receiving the temporo-facial vein, becomes ensheathed with the common carotid artery, and pursues its course as the common jugular vein on the outer side of that vessel, until it empties into the subclavian vein at a right angle and forms the innominate or brachio- cephalic vein. The internal jugular receives the blood from the pharyn- geal, occipital, facial, lingual, superior thyroid, and middle thyroid veins. 204 THE BEGTON OF THE NECK. The jugular foramen also gives exit from the cranium to the pneumo- gastric, spinal accessory, and glosso-pharyngeal nerves. The pneumogastric nerve (Plate 21, No. 43, Plate 36, No. 61, and Plate 37, No. 32) within the foramen is enclosed in a sheath of the dura mater and arachnoid membrane, with the spinal accessory nerve. There is upon its root a small ganglion (Arnold's) which receives a branch from the accompanying nerve. About twelve millimetres, or half an inch, below the ganglion on the root thei'e is another ganglionic enlargement, the ganglion of the trunk, which involves only a part of the nerve. The pneumogastric is probably at its origin a nerve of sensation only, but as it is joined by filaments from the hypoglossal and from the first and second cervical nerves as well as from the superior cervical sympathetic ganglion, it becomes a compound nerve and resembles a spinal nerve. It descends upon the rectus capitis anticus major and longus colli muscles in front of the cervical vertebrae, and at the upper part of the neck becomes ensheathed with the internal carotid artery and internal jugular vein, holding a position posterior to them. This position of the pneumogastric nerve is maintained with regard to the common carotid artery and internal jugular vein until the root of the neck is reached, where the nerve, as well as the vessels, holds different relations on the two sides, which are specially described on page 317. In the upper part of the neck the pneumogastric nerve furnishes branches to the ear, to the pharynx, and to the larynx. The auricular (Arnold's) branch arises from the lower end of the jugular ganglion, and, passing through a canal in the outer wall of the jugular fossa of the temporal bone, enters the aqueduct of Fallopius and escapes to the outer surface by the auricular fissure, where it communicates with the posterior auricular nerve and supplies the back of the concha (page 63). The pharyngeal branch arises from the upper part of the ganglion of the trunk, and, being joined by filaments from the spinal accessory and sympathetic nerves, passes to the inner side of the internal carotid artery and forms the pharyngeal plexus upon the middle constrictor muscle (page 175). The superior laryngeal branch is derived from the middle of the ganglion of the trunk, and, passing downward behind the internal carotid artery, divides into the internal and external laryngeal THE REGION OF THE NECK. 205 nerves (page 185). In two dissections made within the last year the author has found distinct branches passing from the pneumogastric on the left side to the brachial plexus (one of these is seen in Plate 36). The glosso-pharyngeal nerve leaves the jugular foramen in a separate sheath of the dura mater, in front of the spinal accessory and pneu- mogastric nerves. This nerve at its exit consists of two cords, which coalesce in the jugular foramen and form a double ganglionic swelling, the upper part of which is the jugular (or Ehrenritter^ s) ganglion and the lower is the petrosal (or Andersch's) ganglion. The trunk of the nerve below the ganglionic enlargement descends between the internal carotid artery and internal jugular vein until it reaches the lower border of the stylo-pharyngeus muscle, whence it is distributed to the tongue (page 167). The hypoglossal nerve, after its exit from the skull through the anterior condyloid foramen, is in close connection with the ganglion of the trunk of the pneumogastric beneath the internal carotid artery and internal jugular vein, between which it comes forward and below the posterior portion of the digastric muscle curves round the occip- ital artery on its way to the tongue (page 167). As it crosses the occipital artery the branch called the descendens hypoglossi is given oif (Plate 21, No. 41). At first this little nerve enters the sheath of the carotid vessels, but about the level of the liyoid bone it comes through the sheath and runs along on its surface to a point below where the omo-hyoid muscle crosses. This nerve can usually be seen as a white thread on the surface of the carotid sheath, and is generally a reliable indication of its position. The descendens hypoglossi forms a loop, the ansa hypoglossi, with the communicating branches from the second and third cervical nerves (Plate 21), from which are derived the nerves which supply the omo- hyoid, sterno-hyoid, and sterno-thyroid muscles, — the depressor muscles of the hyoid bone. The descendens hypoglossi appears to consist of fibres mainly derived from a branch from the upper two cervical nerves. The spinal accessory nerve leaves the skull in a common sheath of dura mater with the pneumogastric nerve at the middle of the jugular foramen. The fibres of the original portions of this nerve, the accessory and the 206 THE REaiON OF THE NECK. Spinal, intermingle at the foramen, but separate into two portions again below the foramen. The accessory portion sends a few filaments to join the ganglion at the root of the pneumogastric nerve, and also filaments to the pharyngeal and superior laryngeal branches as they leave the ganglion of the trunk of that nerve. Below the latter ganglion the remaining accessory fibres are incorporated with the pneumogastric. The spinal portion, after leaving the accessory, curves backward and outward across the internal jugular vein and the transverse process of the atlas vertebra behind the stylo-hyoid and digastric muscles. It pierces the upper portion of the sterno-mastoid muscle in company with the sterno-mastoid branch of the occipital artery. Leaving the sterno-mastoid muscle, the nerve crosses obliquely the occipital division of the posterior triangular space of the neck to the under surface of the trapezius muscle, and is joined by branches of the second, third, and fourth cervical nerves (Plate 20, No. 58, and Plate 21, No. 10). The occipital triangle is bounded in front, behind, and below respec- tively by the sterno-mastoid, trapezius, and omo-hyoid muscles. Within this space (Plate 21) are found the deep cervical plexus of nerves, the spinal accessory nerve as above described, and a chain of lymphatic glands in relation to the posterior border of the sterno-mastoid muscle, extending from the mastoid process to the root of the neck (Plate 16). The transversalis colli artery and vein (Plate 25), and the superficial cervical branch from the transversalis colli artery to the trapezius muscle, pass outwardly in the lower portion of this space. The deep cervical lolexus of nerves (Plates 20 and 21) consists of inter- communicating branches between the anterior divisions of the upper four cervical nerves, which rest upon the levator anguli scapulae and scalenus medius muscles, close to the transverse processes of the upper four cer- vical vertebrae. Each nerve forming the plexus, with the exception of the first, divides into ascending and descending branches. The super- ficial nerves of the plexus have been already described (page 193). The deep nerves consist of external and internal branches. The external branches are, besides the communicating nerves to the spinal accessory, muscular nerves to the contiguous muscles, — viz., the sterno-mastoid, THE REGION OF THE NECK. 207 scalenus medius, levator anguli scapulae, and trapezius. The internal branches consist of the communicanies (from the second and third nerves), which, looping round the internal jugular vein, join the descen- dens hypoglossi, muscular branches from the first nerve to the prever- tebral muscles, — viz., the recti antici, rectus lateralis, and longus colli, — and branches to the hypoglossal, pneumogastric, and sympathetic nerves, and the phrenic, which arises from the third, fourth, and fifth cervical nerves and descends toward the root of the neck over the scalenus anticus muscle. The supra-clavicular triangle, called also the subclavian triangle, be- cause it contains the subclavian artery, is bounded below by the clavicle, in front by the clavicular origin of the sterno-mastoid muscle, and above by the posterior portion of the omo-hyoid muscle. The area of this space is variable, and depends upon the obliquity of the omo-hyoid muscle and the extent of the clavicular attachments of the sterno-mastoid and trape- zius muscles. The contents of the supra-clavicular triangle are described with the other parts at the root of the neck. They, together with the contents of the occipital triangle, rest upon the deep muscles of the neck, the splenius (capitis et colli), the levator anguli scapulae, the scalenus medius and posticus, and part of the serratus magnus. The splenius muscle (Plate 16, No. 7, Plate 19, No. 25, Plate 22, Fig. 1, Nos, 5 and 14) arises by tendinous slips from the spinous processes of the six upper dorsal and seventh cervical vertebrae, from the supra-spinous ligament, and from the lower portion of the ligamentum nuchae. The fleshy fibres are directed upward and outward, and are divided into two portions, an inner and an outer. The inner portion is inserted into the mastoid process and into the outer part of the superior curved line of the occipital bone beneath the sterno-mastoid muscle, and is called the splenius capitis. The outer portion is inserted into the posterior tubercles of the transverse j)rocesses of the three upper cervical vertebrae, and is called the splenius colli. These muscles are supplied by the external branches of the posterior divisions of the cervical nerves. The action of the splenii muscles aids that of the sterno-mastoid muscles. When the two muscles on both sides contract together, they assist in 208 THE REGION OF THE NECK. holding the head erect. The action of either of them (the two portions working together) is to draw the head and the upper cervical vertebrae toward its own side. When this contraction is permanent it may pro- duce " wry-neck," and may be confounded with the action of the opposite sterno-mastoid muscle, which produces the same effect (page 198). The levator anguli scapulce (Plate 16, No. 8) arises tendinously from the transverse processes of the four upper cervical vertebrae, the two upper slips being the largest. These unite to form a prismatic muscle which descends along the side of the neck and is inserted into the posterior border of the scapula from the superior angle to the root of the spine. It receives branches from the third and fourth cervical nerves of the deep cervical plexus, and a branch from the fifth cervical nerve. When this muscle is brought into action, it raises the posterior angle of the scapula, as in shrugging the shoulders. The cervical portion of the trapezius muscle covers the preceding muscles. It is superficial (Plate 22, Fig. 1, No. 4) at the back of the neck, and constitutes the lateral bulge on each side of the middle depression over the spines of the cervical vertebrae. The trapezius arises from a variable extent of the inner portion of the superior curved line on the occipital bone, from the ligamentum nuchae, from the spinous process of the vertebra prominens, and from the spines of all the dorsal vertebrae and their supra-spinous ligaments. Each trapezius muscle is triangular in shape, but the two together form a trapezoid, and between the sixth cervical and the third dorsal vertebra their origin presents a glistening semi-oval aponeurosis, the speculum rhom- boideu7)i. The fibres of each muscle converge from their extensive vertical origin toward the shoulder, to be inserted upon the scapula exactly corre- sponding to the origin of the deltoid muscle (Plate 16, No. 10). The upper fibres pass downward and outward, to be inserted into the upper edge of the clavicle, usually upon its outer third, but often extending forward as far as the posterior border of the clavicular portion of the sterno-mastoid muscle ; the middle fibres pass transversely outward to the inner border of the acromion process and upper margin of the spine of the scapula; and the lower fibres pass upward and outward and are inserted by a thin tendon THE REGION OF THE NEGK. 209 into the tubercle of the spine of the scapula. There is always a laj^er of loose connective tissue or a mucous bursa interposed between the tendon and the triangular surface at the back of the scapula. The trapezius is supplied by the spinal accessory nerve, and by the deep branches of the cervical plexus. Its nutrient arteries are derived from the superficialis colli and the dorsal branches of the intercostal arteries (Plate 22, Fig. 1, No. 10). When both trapezius muscles act from below they draw the head backward, or one muscle acting in the same manner will turn the head backward to the corresponding side. The whole of each muscle has the power to retract the scapula, and, by rotating it, to raise the shoulder. Beneath the trapezius and splenius muscles at the back of the neck is the powerful complexus muscle. This muscle is broad and thick, and arises usually by seven tendons from the tips of the transverse processes of the three upper dorsal vertebrae and the vertebra prominens and from the articular processes of the sixth, fifth, and fourth cervical vertebrae. It is inserted into the depression between the two occipital curved lines near the median ridge. Very often this muscle presents a transverse tendinous intersection, and a separate fasciculus is sometimes specialized at the spinous border, which, because it has a longitudinal tendon in its centre, is called the biventer cervicis. This muscle is separated from its fellow by the ligamentum nuchm, which is practically a continuation upward of the supra-spinous ligament. It consists of fibro-elastic tissue, and extends from the spinous processes of all the cervical vertebrae, except the atlas, to the external occipital protuberance. In a few instances muscular fibres have been found in place of this ligament, but in man it is a rudiment of the strong elastic ligament which enables some of the lower animals to sustain the weight of the head. At the outer side of the complexus are the trachelo-mastoid and trans- versalis colli muscles, which are accessory portions of the longissimus dorsi continued to the head and neck. The trachelo-mastoid muscle arises from the upper five dorsal transverse processes and from the lower four cervical articular processes by tendinous slips which unite to be inserted into the back of the mastoid process beneath the sterno-mastoid and splenius muscles. The transversalis colli 27 PLATE 30. The lungs inflated, so as to demonstrate the approximation of their edges over the heart, as in full inspiration. The right common carotid artery. The right internal jugular vein. The right scalenus anticus muscle. A rubber tube introduced into the trachea for the pur- pose of inflating the lungs. The right transversalis colli artery and vein. The right pneumogastric nerve. The sternal end of the right clavicle. The innominate artery. The right subclavian vein and artery. The sternal end of the right first rib. The right innominate vein. The ascending portion of the aorta. The right second rib. The right third rib. The cleft between the upper and lower principal lobes of the right lung. The right lung. The right fourth rib. The right fifth rib. The cleft in the lower portion of the right lung, indi- cating its division into the so-called middle and in- ferior lobes. The right sixth rib. The anterior lower border of the right lung (as in full inspiration). The upper surface of the diaphragm. The right seventh rib. The left common carotid artery. The left brachial plexus of nerves. The left internal jugular vein. The trachea at the root of the neck. The left scalenus anticus muscle. The left pneumogastric nerve. The remains of the left coraco-clavicular membrane. The sternal end of the left clavicle. The left subclavian artery. The left subclavian vein. The sternal eud of the left first rib. The left innominate vein. The left pneumogastric nerve. The left second rib. The approximation of the edges of the lungs in the median line, covering the root of the heart, as occurs in full inspiration. The left third rib. The upper lobe of the left lung. The left fourth rib. The notch in the anterior edge of the left lung in rela- tion to the apex of the heart. The left fifth rib. The right ventricle of the heart covered with the peri- cardium. The left sixth rib. The anterior lower border of the left lung (as in full inspiration). The left seventh rib. The left eighth rib. N. B.— This and the succeeding plates (31, 32, and 33) were taken from a male subject about thirty-two years of age, who died from choking. The lungs were absolutely healthy. The pleurae were removed in the dissection. Plate 30 Vol I is/^.'^r-r-y. Pr,. ^:§^a^'-'^o and toioreo '■'<. 'D^OF M' CiFl.lAN. M D. Coi)\ ni. ht, i6?~> b\ George Mc Clellan, M D. THE EEGION OF THE NECK. 211 muscle arises by delicate tendons from the six upper dorsal transverse processes, and is inserted by as many tendons into the posterior tubercles of the lower six cervical transverse processes. The last two muscles are supplied by external branches from the posterior divisions of the cervical nerves, the complexus receiving internal branches of these nerves, together with branches from the sub-occipital and great occipital nerves. The action of the trachelo-mastoid and transversalis colli muscles assists the overlying muscles in holding the head erect or in turning it back- ward to one or the other side according as both pairs of the muscles act together or the individual muscles act severally. The occipital artery, after leaving its groove in the temporal bone back of the mastoid process, passes horizontally underneath the sterno-mastoid, splenius, and trachelo-mastoid muscles to the complexus (Plate 22, Fig. 1), upon the outer surface of which it turns upward, and, piercing the attachment of the trapezius, winds tortuously over the occiput, dividing into numerous branches, which sup- ply the tissues of the scalp posteriorly. The point where the occipital artery reaches the scalp (Plate 21, No. 6) is about midway between the external occipital protuberance and the mastoid process, and it also corre- sponds to the position of the great occipital nerve, with which the vessel is in close relation. The occipital artery furnishes nutrient vessels to the digastric, stylo-hyoid, splenius, trachelo-mastoid, and sterno-mastoid muscles. It also sends a branch to the back of the concha, and one or more menin- geal branches which enter by the mastoid foramen or through the jugular foramen to supply the neighboring part of the dura mater ; but the most important branch is the princeps cervicis, which passes downward from the occipital between the complexus and splenius muscles and divides into two branches. One of these is superficial, and, penetrating the splenius, supplies the trapezius and anastomoses with the superficial cervical branch of the transversalis colli ; the other takes a deep course between the com- plexus and semispinalis colli muscles and anastomoses with the vertebral and often with the deep cervical branch from the superior intercostal artery. By means of these anastomoses the collateral circulation is mainly established after ligature of the carotid or subclavian artery. The deeper muscles beneath the complexus are the prolongations of 212 THE REGION OF THE NECK. the erector spinse mass. They are of variable develoj)ment in different subjects, and are interesting because they assist the more superficial muscles in holding the head in the various positions while the body is uiDright. The cervicalis ascendens is the upward continuation of the accessorius muscle : it arises from the angles of the four or five upper ribs, and is inserted by tendons into the posterior tubercles of the transverse processes of the sixth, fifth, and fourth cervical vertebrae. The spinalis colli is often absent, but when it exists it connects the spines of the lower cervical verte- brae, like the spinalis dorsi, and is inserted into the spinous process of the axis vertebra. The cervical portion of the muUifidus spince consists of a series of muscular slips extending from the articular processes of the lower four cervical vertebrae, each of which passes obliquely to be inserted into the si:)inous process of the vertebra above and the contiguous portions of the laminae. Besides the above there are the inter-spinales and the inter-transversales. The former are more pronounced in the neck than they are in the back, and extend between the spinous processes of the lower six cervical verte- brae, while the latter pass between their transverse processes. The anterior portions of the inter-transversales correspond to the intercostal muscles. There are seven in the neck, where they are also most marked, and they are arranged in pairs between the anterior and posterior tubercles of the contiguous vertebrae. All these deeper muscles are supi3lied with branches from the internal posterior branches of the cervical nerves. At the very top of the neck there are upon each side various small muscles which are concerned in the movements of the head upon the atlas and axis vertebrae. They are specialized as follows. The rectus capitis posticus viajor is the largest : it arises from the side of the spinous process of the axis, and is inserted into the outer part of the lower curved line on the occipital bone and the rough surface below it. The rectus capitis posticus minor is deeper than, and internal to, the major : it arises by a narrow tendon from the posterior tubercle of the atlas, and is inserted by a fan-shaped expansion between the inner portion of the inferior curved line and the foramen magnum. The action of these muscles is to raise the head. The obliquus capitis inferior passes from THE REGION OF THE NECK. 213 the spine of the axis to the under surface of the transverse process of the atlas. The obliquus capitis superior extends from the upper surface of the transverse process of the atlas, just above the insertion of the former, to the interval between the occij)ital curved lines. The action of the inferior oblique is to turn the head round to the same side by rotating the atlas upon the axis vertebra. The great occi^^ital nerve supjjHes it with a branch as it turns round its lower border. The action of the superior oblique is to draw the occiput toward the spine. This muscle and the two recti postici receive branches from the sub-occipital nerve, which is in close relation to them. The so-called sub-occipital triangle is formed by the disposition of the two oblique muscles with the rectus capitis posticus major, the obliquus superior being on the outer side, the rectus capitis posticus major on the inner, and the obliquus inferior on the lower. This triangle contains the arch of the atlas vertebra, with the vertebral artery lying in a groove on its upper surface (page 215). The posterior division of the sub-occipital (first spinal nerve) is placed between the artery and the bone. Beneath the multifidus muscles, upon the laminae of the cervical vertebrae, there is on both sides of the neck a plexus of large veins, the cervico-dorsal spinal veins, which communicate freely with the veins of the vertebral canal through the interlaminar ligaments. The interlaminar ligaments, or ligamenta suhjlava, are thick masses of elastic yellow fibrous tissue which fill in the intervals between the arches of the vertebrae. They pass from the upper edge of each vertebra to a rough ridge on the anterior surface of the vertebra above. The ligament upon one side is continuous with its corresponding fellow. In the cervical region these ligaments are thinner than elsewhere, and are directed outwardly to the inner margins of the articular processes. The interspinous ligaments in the neck are not markedly developed, and appear like projections of the ligamentum nuchae between the spinous processes. There is no inter- spinous ligament between the axis and atlas vertebrae, and none between the atlas and the occipital bone. The interlaminar ligament between the atlas and the axis, the posterior atlanto-axial ligament, and that below the occipital bone and the atlas, the posterior occipiito-atlantic ligament, 214 THE HEGION OF THE NECK. are deficient in elastic tissue, being composed chiefly of condensed areolar tissue which is closely connected with the dura mater of the spinal cord in front. The nerves at the back of the nech are the posterior divisions of the cervical nerves. The posterior division of the first cervical nerve, or sub-occipital, makes its exit from the spinal canal between the arch of the atlas and the ver- tebral artery, and thence enters the sub-occipital triangle and sends off muscular branches, as already described. The posterior division of the second cervical nerve, or great occipital, emerges between the arches of the atlas and axis vertebrae. The posterior divisions of the lower six cervical nerves divide into external and internal nerves. Of these the internal are the larger, and those from the second, third, and fourth nerves form the so-called posterior cervical plexus beneath the complexus muscle, which after supplying the muscles terminate in the skin over the trapezius. The lower three cervical nerves also give off cutaneous branches. There are eight pairs of cervical spinal nerves, and their origins from the spinal cord can be seen only by removing the posterior segments of the cervical vertebrae (Plate 4, Fig. 2). The removal of these segments exposes the theca vertebralis, or cervical portion of the spinal dura mater, through which the spinal nerves pass out, the two roots — anterior (motor) and posterior (sensory) — of each piercing the membrane by seiiarate holes and receiving from it prolongations or sheaths. The anterior roots are the smaller, and have no ganglionic enlargement upon them, while the posterior roots are larger, and have a ganglion upon each, with the exception some- times of the posterior root of the first cervical nerve. The two roots of each nerve blend with each other beyond the ganglion, and the compound trunk thus formed passes out of the corresponding intervertebral foramen and separates into an anterior division to supply the anterior part of the neck, and a posterior division to supply the posterior part, each nerve being composed of fibres from both roots. The ganglia are of oval form and proi30rtionate in size to the nerve-trunks to which they contribute, and are generally situated in the intervertebral foramina outside of the dura THE REGION OF THE NECK. 215 mater (Plate 4, Fig. 2). When the first nerve has a ganglion on its pos- terior root, it is, however, usually within the dura. The spinal cord presents an enlargement opposite the fifth cervical vertebra, where the nerves are given ofi" which form the brachial plexus on each side. The anatomy of the spinal cord is described with the region of the back in Vol. II. The vertebral arteries, after their origins from the subclavian arteries, ascend for a short distance between the longus colli and scalenus anticus muscles on each side, and, entering the foramen in the transverse process of usually the sixth cervical vertebra, mount upward through the vertebral foramina above until the interval between the axis and the atlas is reached. Here each artery makes an abrupt curve backward, being accommodated in grooves on the arch of the atlas vertebra within the sub-occipital triangle, and enters the foramen magnum after perforating the posterior occipito-atlantic ligament and the dura mater (Plate 4, Fig. 2, N^os. 9 and 25). Within the skull the two vertebral arteries unite to form the basilar artery, which occupies the anterior median fissure of the pons Varolii (page 46). The cervical branches of the vertebral arteries are small, some going to the deep muscles, and others, the lateral spinal, supplying the spinal cord and its membranes in relation to the inter- vertebral foramina and the contiguous surfaces of the bodies of the verte- brae. The vertebral veins commence by tributaries from the muscles in the neighborhood of the foramen magnum, and descend in front of the arteries through the vertebral foramina. They are often brought in relation with the lateral sinus by emissary veins through the posterior condyloid foramen on one or the other side. The characteristic curvature of the cervical portion of the spine is mainly due to the shape of the disks of intervertebral fihro-cartilage, which are here thicker in front than behind. These disks, like all the others of the spinal column, consist of outer concentric layers of fibro- cartilage surrounding a pulpy nucleus of elastic tissue. The nucleus is not quite in the centre of each disk, and contains a small irregular-shaped cavity. The fibres at the circumference cross one another, taking an oblique direction from side to side. At the margins of the disks the fibrous layers PLATE 31. The relations of the lungs, in moderate distention, to the pericardium, as iu ordinary breathing. Also the great vessels and nerves at the root of the neck. The sternum and costal cartilages are removed. The right superior thyroid vessels, and superior laryn- geal nerve. The median notch in the thyroid cartilage. The right internal jugular vein. The right common carotid artery. The right scalenus anticus muscle. The median cord of the brachial plexus. The right pneumogastric nerve. The right transversalis colli artery and veins. The right phrenic nerve. The brachial plexus of nerves, and subclavian artery and vein, below the clavicle. The innominate artery. The right recurrent laryngeal nerve. The sternal end of the right first rib. The right innominate vein. The stenaal end of the right second rib. The aorta, covered with the pericardium. The right third rib. The right lung. The right fourth rib. The right fifth rib. The right sixth rib. The upper surface of the diaphragm. The body of the hyoid bone. The left superior thyroid vessels, and superior laryngeal nerve. The left internal jugular vein. The left common carotid artery. The left brachial plexus of nerves, above the clavicle. The left phrenic nerve. The left scalenus anticus muscle. The left pneumogastric nerve. The left deltoid muscle. The left brachial plexus, below the clavicle. The sternal end of the left clavicle. The left subclavian artery and vein. The left pectoralis minor muscle. The sternal end of the left first rib. The left innominate vein. The superior vena cava. The position of the pulmonary artery, covered with the pericardium. The left second rib. The upper lobe of the left lung. The left third rib. The position of the right auricle, covered with the pericardium. The left fourth rib. The left fifth rib. The right ventricle of the heart, covered with the peri- cardium. The left sixth rib. The left seventh rib. -t'i are J Vol I Copyright, I8S0, by Geouse Ma Cluuan, M D »i»«M £afa^dil^* ' "■ '•'■'vBlnd mii Lolores from Ndturt iy GsonsE Mc. CiBLLAn, MB. ArmhriongjCo Lirh Boslor THE REGION OF THE NECK. 217 are firmly attaclied to the contiguous margins of the vertebral bodies above and below. The bodies of the vertebrae and the intervertebral disks are strongly united in front by the anterior common spinal ligament, and by a similar band within the spinal canal, called the posterior common ligament. The anterior ligament consists of several strata, the outer being composed of long fibres extending along several vertebrae, and the inner, of short fibres from one vertebra to another. This ligament is thicker over the bodies of the vertebrae than the intervertebral disks, and is attached above to the axis in connection with the longus colli muscles. Each joint between the articular processes in the cervical vertebrae is jDrovided with a synovial membrane surrounded with a loose capsular ligament, in accord- ance with the free movement in the neck. For the same reason the joint between the occipital bone and the atlas and axis vertebrae has specialized ligaments. The anterior common ligament is continued ujDward from the top of the anterior arch of the atlas to the front border of the foramen magnum, as the anterior occipito-atlantic ligament, which is thicker at the centre than at either side. The posterior occipito-atlantic ligament has been already referred to (page 213). If a section is made of the posterior arches of the two upper vertebrae and the occipital bone, the ligamentum latum axiale is exposed. This is a strong fibrous band separated from the posterior common ligament. Beneath the broad axial ligament is the remarkably strong transverse ligament, which is stretched across between the internal tuberosities of the atlas back of the odontoid process, a syno- vial bursa and a thin layer of fibro-cartilage being interposed between the process and the ligament. Some fibres of this ligament pass upward from its centre to be attached to the basilar process, and some downward to the body of the axis. The occipito-odontoid or check ligaments are placed above the transverse ligament, and extend from the inside of each occipital condyle to the same side of the top of the odontoid process. They are rendered tense by turning the head to one side or the other. A few fibro-cartilaginous fibres pass from the apex of the odontoid process to the front of the foramen magnum, and are called the suspensory ligament of the axis. In addition to the above, the articular surfaces of the occiijut and atlas are provided with synovial sacs and capsular ligaments. The 28 218 THE REGION OF THE NECK. cervical curve of the spine is considered as consequent upon the exten- sion of the neck in development, and extends from the atlas to the inter- vertebral disk between the second and third dorsal vertebrae. The weakest point, not only in the neck but also in the entire column, is between the second and third cervical vertebrae. The structures in immediate relation to the front of the cervical portion of the spinal column are the prevertebral muscles and fascia (Plate 11, Fig. 1). The longus colli muscle consists principally of a vertical portion, the fibres of which arise tendinously from the lateral ridges on the bodies of the three upper dorsal and two lower cervical vertebrae external to the common spinous ligament, and are inserted by arching tendons into the bodies of the fourth, third, and second cervical vertebrae, and into the anterior tubercle of the atlas. Besides these there are accessory portions. The inferior oblique portion arises with the vertical tendons from the three upper dorsal vertebrae, and is inserted into the transverse processes of the sixth, fifth, and fourth cervical vertebrae. Those fibres which are inserted into the sixth vertebra cover the verte- bral artery at its entrance into the foramen in the transverse process of that vertebra. The superior oblique portion arises from the transverse processes of the fifth, fourth, third, and sometimes second cervical verte- brae, and is inserted with the vertical portion into the bodies of the upper two vertebrae and the anterior arch of the atlas. The longus colli muscle is supplied by branches from the lower cervical nerves, and the action of the united portions is to bend the cervical vertebrae forward. The rectus capitis anticus major muscle arises from the transverse processes of the fifth, fourth, third, and second cervical vertebrae, and is inserted into the basilar portion of the occipital bone near the pharyngeal spine. Under this muscle there is a much smaller muscle, the rectus capitis anticus minor, which arises from the front of the root of the transverse process of the atlas, and is inserted into the basilar process of the occipital bone behind the former muscle. The two recti antici are supplied with branches of the anterior division of the sub-occipital nerve, and some filaments from the deep cervical plexus, and their action is to assist in bending the head forward. The rectus capitis lateralis muscle extends THE BEGION OF THE NECK. 219 from the transverse process of the atlas to the jugular process of the occipital bone, and is in reality the topmost of the series of inter- transversales muscles in the cervical region, which extend between the successive transverse processes in front of the exits of the spinal nerves and over the vertebral artery. The laterales are capable of bending the head slightly sideways. The cervical portion of the sympathetic nerve on each side consists of a continuous cord, on which there are three ganglia, situated in front of the transverse processes of the cervical vertebrae. The superior ganglion is the largest of the three, and is about opposite the second and third cervical vertebrae, over the rectus capitis anticus major muscle, behind the internal carotid artery, and internal to the pneumogasti'ic nerve (Plate 36, No. 49). It is an elongated, reddish-gray body, generally three centimetres, or about an inch and a quarter, in length. It is some- times marked by constrictions, and receives externally four communi- cating branches from the four npper cervical nerves. It sends branches to the upper and lower ganglia of the pneumogastric (page 204), also to the ganglion of Andersch, on the glosso-pharyngeal nerve (page 205), and to the hypoglossal nerve. From the upper portion of the superior ganglion the cord is continued into the carotid canal with the internal carotid artery, to form the carotid sympathetic plexus. Filaments leave the anterior border of the superior ganglion and accompany the branches of the external carotid artery, upon which they form plexuses and are distributed to the territories which they supply. A branch is also sent to the inter-carotic body. The superior cardiac nerve arises from the lower part of the supe- rior ganglion, and descends upon the longus colli muscle behind the sheath of the carotid vessels, in close connection with the main sympathetic cord. The middle cervical ganglion is very small and inconstant, and when present is situated opposite the sixth cervical vertebra, near the inferior thyroid artery, and about on a level with the crossing of the omo-hyoid muscle. It receives branches from the adjacent cervical nerves, and gives off thyroid branches and the middle cardiac nerve, which descends with the superior cardiac either over or under the subclavian artery to join the cardiac plexus. 220 THE REGION OF THE NECK. The inferior cervical ganglion is deeply situated between the transverse process of the vertebra prominens and the neck of the first rib (Plate 36, No. 22). It receives branches from the seventh and eighth cervical nerves, and gives off branches which form the plexuses about the subclavian and vertebral arteries and the inferior cardiac nerve, which joins the deep cardiac plexus. The scalene muscles extend from the transverse processes of the cervical vertebrae to the two uf)per ribs, in the manner of a scalene triangle, on each side, and are comparable to the intercostal muscles both in their attach- ment and in their function. The scalenus anticus arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and is inserted by a flat tendon at the inner border and ujoper surface of the first rib (Plates 31, 32, 34, 85, and 36). This muscle is usually described as being inserted into the tubercle (of Lisfranc) on the first rib, and much stress has been laid upon it as an important guide to the adjacent vessels; but, after examining several hundred specimens, the author has the recollection of seeing only four or five upon which any approach to a tubercle was develojjed. The "scalenus medius arises from the posterior tubercles of the transverse processes of the lower six cervical vertebrae, and is inserted also upon the first rib behind the scalenus anticus. This is the strongest of the three scalene muscles. The scalenus posticus arises from the posterior tubercles of the transverse processes of the three lowest cervical vertebrae, and is inserted upon the second rib external to its angle. These muscles receive their nerves from the lower cervical nerves, which they surround as they leave their grooves on the upper surfaces of the transverse processes. Their combined action is to raise the thorax, as in deep inspiration, or, being fixed below, they can bend the cervical vertebrae, as in rising from the recumbent position. The scalenus anticus is a guide in distinguishing the position of the im- portant structures with which it is in close relation at the root of the neck. The lower attachment of the scalenus anticus is usually overlapped by the clavicular portion of the sterno-mastoid muscle, but by depressing the shoulder and extending the neck the outer border of the former muscle can be readily felt. THE REGION OF THE NECK. 221 The subclavian artery and the subclavian vein are separated by the costal attachment of the scalenus anticus, as they pass in their respective grooves upon the first rib on their way to and from the axilla. The vein is in front and the artery is behind : the latter can sometimes be felt pulsating over the rib by pressing with the thumb in the supra-clavicular fossa, at the outer border of the sterno-mastoid muscle. In this way also compression of the subclavian artery may be sometimes satisfactorily effected, as is required in amputation at the shoulder. In one instance the author found both the artery and the vein in front of the scalenus anticus ; and several cases have been recorded in which the relations of the vessels were reversed, the artery being in front of the vein. In relation to the scalenus anticus muscle it should be remembered that the phrenic nerve (page 207) passes obliquely from the outer to the inner border in front of that muscle, to enter the chest between the subclavian artery and subclavian vein (Plates 25 and 31), and that it is joined on the outer surface of the muscle by a twig from the fifth branch of the cervical plexus as well as by a filament from the sympathetic nerve. The supra-scapular and transversalis colli arteries (page 233) cross over the lower part of the scalenus anticus, and between it and the sca- lenus medius and above the subclavian artery are the cords of the brachial plexus of nerves. Its inner border is in close relation with the vertebral artery, which is here covered by the internal jugular vein. The structures collected at the root of the neck (Plate 14, Fig. 2) present a complex arrangement which varies upon both sides, even in the normal condition, in consequence of the mode of distribution of the great aortic branches. The innominate artery upon the right side leaves the aorta at the commencement of the transverse portion of the arch behind the middle of the manubrium sterni, opposite the fourth dorsal vertebra, and ascends to the stern o-clavicular joint, behind which it subdivides into the right subclavian and right common carotid arteries. The innominate artery is usually four centimetres, or about an inch and a half, in length, in a well-developed adult, but it is often half an inch longer, and in some cases the vessel ascends above the clavicle close to the trachea before it divides. The innominate sometimes gives off" a branch, the thyroidea ima 222 THE REGION OF THE NECK. (Plate 43), which ascends to the lower border of the thyroid body along the front of the trachea and compensates for a deficiency in the inferior thyroid artery. In the child, owing to the greater laxity of the connective tissue and the prolongation of the cervical fascia, the innominate artery may be drawn upward into the supra-sternal notch by extending the head and neck backward, but this cannot be done in the adult if the artery is in its normal position. It has been demonstrated on the dead subject (Burns) that if the innominate artery be tied with a ligature the collateral circulation can be established both in the right side of the head and in the right arm, and the operation has been successfully performed on the living subject (Mott) ; but it is a desperate undertaking, and should not be attempted except as such. The artery lies above the bifurcation of the trachea, and is enveloped in a strong sheath prolonged from the deep cervical fascia, which continues over it to the pericardium. The two vence innominatce, or right and left brachio-cephalic veins, converge in front of the innominate artery to empty into the superior vena cava, the right vein descending on the outer side of the artery and the left vein passing across its origin. These veins thus form a triangular space (Plates 31 and 35), in which the artery appears when the loose fascia which connects it to the coat of the left innominate vein is removed. The pneumogastric nerve descends into the thorax between the right innominate vein and the innominate artery at its bifurcation into the right subclavian and common carotid arteries, and in this relation gives off the right recurrent laryngeal nerve, which turns upward under the subclavian or innominate artery, as previously described (page 186). It will be noticed that the great innominate veins, with all their tributaries, occupy a plane anterior to that of their respective arteries, which is the converse of the relation of the arteries and veins below the diaphragm (Plate 42), with the single exception of the renal vein. The innominate veins are formed respectively by the confluence of the common jugular and subclavian veins of each side. The right vein commences behind the right sterno-clavicular joint, and descends a little forward to a point opposite the first right intercostal space, where it is joined at an obtuse angle by the left vein, to empty into the superior vena cava. It is about two and a THE EUGION OF THE NECK. 223 half centimetres, or an inch, in length, and receives the right internal mammary, superior intercostal, and inferior thyroid veins. The left innominate vein is nearly three times the length of the right, being six centimetres, or two and a half inches, as it commences behind the sternal end of the left clavicle and extends across the origins of the left common carotid and innominate arteries. The left vein receives upon its under surface the left internal mammary, thymic, and mediastinal veins, and on its upper surface the left inferior thyroid, vertebral, and deep cervical veins. The tributary veins to both vessels are guarded with single crescentic valves at their orifices. In the young child the left innomi- nate vein is generally above the upper margin of the sternum. Between the innominate vessels and the sternum there is a considerable quantity of adipose and connective tissue, and in the adult the remains of the thymus gland (and in the child, up to the third or fourth year, the gland itself), with numerous veins. These veins form a plexiform net-work, and are associated with the inferior thyroid veins, which occupy the space be- tween the trachea and the top of the sternum and empty into the right and left innominate veins. The presence and proximity of these veins render any operation in this locality extremely hazardous. They are liable to become dilated and engorged from interference with the respiration, as in membranous croup, or under the influence of pressure from a neighboring growth. In a patient from whom the author successfully removed the upper portion of the sternum and adjacent third of the clavicle for osteo- sarcoma, the venous hemorrhage was appalling, and could be arrested only by sponge pressure. The right and left common carotid arteries ascend from the root of the neck by the sides of the trachea, diverging outward from the middle line to their bifurcation opposite the top of the thyroid cartilage (page 201). On a level with the top of the sternum, and three centimetres, or about an inch and a quarter, from the surface, the two carotid arteries are separated from each other by two centimetres, or less than an inch, but at their bifur- cation, owing to the breadth of the larynx, they are six centimetres, or two and a half inches, apart (Plates 31, 32, 33, and 42). In consequence of the independent thoracic origin of the left common carotid artery from the PLATE 32. The relations of tlie lungs, partially distended (as in tranquil respiration), to the pericardium. Also the vessels and nerves at the root of the neck. 1. The right facial artery. 2. The right facial vein. 3. The right lingual artery. 4. The right thyro-hyoid artery. 5. The right superior laryngeal nerve. 6. The right external carotid artery. 7. The thyroid notch. 8. The thyroid cartilage, 9. The right superior thyroid artery. 10. The right superior thyroid vein. 11. The right common carotid artery. 12. The right scalenus anticus muscle. 13. The right trapezius muscle. 14. The right internal jugular vein. 15. The right brachial plexus of nerves. 16. The right pneumogastric nerve. 17. The right phrenic nerve. 18. The supra-scapular artery and veins. 19. The right recurrent laryngeal nerve. 20. The right deltoid muscle. 21. The brachial plexus of nerves below the clavicle. 22. The right axillary artery. 23. The right axillary vein. 24. The right innominate vein. 2o. The sternal end of the right first rib. 26. The superior vena cava. 27. The right phrenic nerve. 28. The sternal end of the right second rib. 29. The upper lobe of the right lung. 30. The right auricle covered with the pericardium. 31. The sternal end of the right third rib. 32. The middle lobe of the right lung. 33. The sternal end of the right fourth rib. 34. The height to which the diaphragm arches on the right side. 35. The sternal end of the right lifth rib. 36. The lower lobe of the right lung. 37. The sternal end of the right sixth rib. 38. The branches of the right phrenic nerve on the dia- phragm. 39. The left facial artery. 40. The left facial vein. 41. The left thyro-hyoid artery. 42. The left external carotid artery. 43. The left internal jugular vein. 44. The left superior thyroid artery. 45. The left trapezius muscle. 46. The left crico-thyroid artery. 47. The cricoid cartilage. 48. The left brachial plexus of nerves. 49. The left phrenic nerve. 50. The left scalenus anticus muscle. 51. The left pneumogastric nerve. 52. The left deltoid muscle. 53. The trachea. 54. The left common carotid artery. 55. The left axillary vein. 56. The innominate artery. 57. The left innominate vein. 58. The sternal end of the left first rib. 59. The long thoracic artery. 60. The pectoralis minor muscle. 61. The left phrenic nerve. 62. The root of the heart covered with the pericardium. 63. The sternal end of the left second rib. 64. The upper lobe of the left lung. 65. The sternal end of the left third rib. 66. The sternal end of the left fourth rib. 67. The right ventricle of the heart covered with the peri- cardium. 68. The sternal end of the left fifth rib. 69. The sternal end of the left sixth rib. 70. The branches of the left phrenic nerve on the dia- phragm. 71. The sternal end of the left seventh rib. Plate 32 Vol I Copyn^ht, ISShby SfOBSf Mc Cli^llan, M. D Photographed 3'id Colored from Nature by GEor,oE Mc Clcllah. THE REGION OF THE NECK. 225 arch of the aorta, it is longer than the right, the thoracic portion being equivalent in length to the innominate artery. The thoracic portion of the left common carotid artery is crossed by the left innominate vein, and its under surface is in relation to the trachea, oesophagus, and thoracic duct (Plate 39). In the neck, between the clavicle and the position of the crossing of the omo-hyoid muscle the relations of the two cai'otids are almost identical. The right artery is usually a little nearer the surface than the left, and its calibre is larger. The right and left common jugular veins occupy separate compartments of the general sheaths on the outer sides of their companion arteries. As they approach their termination in the innominate veins they overlap the arteries, and on the left side this is more especially so than on the right (Plates 33 and 42), because of the inclination of the large veins from the left to the right side to reach the venous side of the heart. The calibre of the right common jugular usually exceeds that of the left, and they are both provided with double valves about three centimetres, or an inch and a quarter, above their terminations. The right and left pneumogastric nerves ascend also in separate com- partments of the sheath posterior to the septa between the artery and the vein, but somewhat nearer the latter. The position of the carotid vessels, on each side, may be indicated by drawing a line from the top of the sternal end of the clavicle to the parotid gland between the mastoid process and the angle of the lower jaw. As the sterno-mastoid muscle is attached to the anterior surface of the top of the sternum, with its fibres interlacing with those of the sternal portion of its fellow muscle (Plates 23 and 24), it completely covers the line of the carotid vessels, which in reality corre- sponds to the space between the sternal and clavicular attachments of the sterno-mastoid muscle (page 197). Between the sheath of the vessels and the sterno-mastoid muscles at the root of the neck there are also the sternal attachments of the sterno-hyoid and sterno-thyroid muscles, and between the latter muscles and the sheath are the intricate thyroid veins, and sometimes the external jugular vein passing into the internal jugular to empty conjointly into the subclavian (Plate 21). The sheath of the carotid vessels is separated posteriorly from the bodies 29 226 THE BEGION OF THE NECK. of the lower cervical vertebrse by the lorigus colli and rectus capitus anticus muscles. It is in close relation with the sympathetic nerve cord, and separated from the vertebral artery by the inferior thyroid artery, which winds upward and inward from the subclavian to the thyroid body. To the inner side are the trachea, the larynx, and a lobe of the thyroid body. The CBSophagus inclines to the left of the middle line at the root of the neck, so that it is in closer relation to the left carotid sheath. The recurrent laryngeal nerve on both sides ascends to the larynx between the trachea and the oesophagus, but is separated from the carotid sheath by considerable cellular tissue (Plate 24, Fig. 2). In the operation for applying a ligature upon the carotid artery it is essential to avoid as far as possible interfering with the cellular investment of the sheath and its attachment to the reflections of the deep cervical fascia (page 195). In order to reach the artery the head should be turned to the opposite side over a pillow, so as to bring into relief the anterior border of the sterno-mastoid muscle, along which an incision from three to four inches in length should be made through the skin, superficial fascia, and platysma muscle so as to intersect the line of crossing of the omo-hyoid muscle at the level of the cricoid cartilage. The carotid sheath is immediately under the omo-hyoid, and this muscle may be cut through, or the sheath can be opened above or below it as required. A finger pressed upon the vein at the root of the neck will cause it to distend and reveal its precise relation. The sheath should be opened on the tracheal side, and it is well to raise the head and to turn it to the same side before passing the artery needle, so as to relax the tissues and avoid including or injuring any of the adjacent structures. The descendens hypoglossi nerve is usually seen upon the sheath, and the sterno-mastoid branch from the superior thyroid artery crosses it near the omo-hyoid muscle. The thyroid veins are numerous over the sheath at the root of the neck; and if it is necessary to tie the artery in that locality, they must first be secured with a double ligature and severed. Upon the left side the operation low down is attended with so much difiiculty that it is well to divide the sternal attachment of the sterno-mastoid muscle, which will render the vessel more accessible. THE REGION OF THE NECK. 227 After ligation of the common carotid artery the collateral circulation is established through the anastomoses of the branches of the external and internal carotid arteries of the opposite side with the branches of the ligatured side, in which the blood-current is reversed, and between the vertebral and posterior communicating, the inferior and superior thyroids, and the profunda and princeps cervicis, of the same side. The deep cervical lymphatic glands (or glandulae, concatenatce) form a chain extending from the base of the skull to the root of the neck em- bedded in the connective tissue which surrounds the great vessels. Some of these glands are directly over the sheath of the common carotid, and others lie between it and the bodies of the cervical vertebrae, so that when they become diseased they are often so adherent to the adjoining struc- tures that their removal is extremely hazardous. These glands are con- tinuous with the thoracic and axillary glands. They are most numerous in the neighborhood of the bifurcation of the common carotid artery by the side of the pharynx, as they receive here the lymphatic vessels from all parts of the head and neck. The cervical lymphatic vessels unite at the inner border of the scalenus anticus muscle on both sides, so as to form the jugular lymphatic trunks. Upon the right side the trunk empties into the right lymphatic duct, which is about twelve millimetres, or half an inch, in length, and terminates at the junction of the common jugular and subclavian veins, and on the left side the trunk generally empties into the thoracic duct (page 318), and sometimes, by a separate orifice, directly into the angle of junction of the left common jugular and sub- clavian veins (Plate 20). The subclavian arteries differ not only in their origins but in their relations upon the two sides of the root of the neck (Plates 33, 35, and 39). Each of them pursues an arching course to pass behind the scalenus anticus muscle (page 221), which divides the vessel into three portions, — the first or pectoral portion being between its origin and the inner border of the scalenus anticus, the second or muscular portion that which is behind it, and the third or cervical portion that which is between the outer border of the muscle and the lower border of the first rib, whence the artery continues as the axillary. 228 THE REG-ION OF THE NECK. The right subclavian artery ordinarily leaves the innominate behind the sterno-clavicular joint, and its first portion is very deeply placed as it passes upward and outward to the inner border of the scalenus anticus. Any change in the position of the bifurcation of the innominate artery will of course affect the point of origin of this artery. Besides the superficial coverings, it has over it the insertions of the presternal muscles (Plate 23) and a layer of deep fascia which is projected from the inner border of the scalenus anticus muscle. Under this fascia it is crossed by the common jugular and vertebral veins (Plate 21), by the pneu- mogastric and phrenic nerves (Plates 34 and 35), and by the superior cardiac sympathetic nerves. Behind the artery are the recurrent and sympathetic nerves (Plate 36) upon the longus colli muscle and the transverse process of the first dorsal vertebra. It is here, also, in close proximity to the apex of the right lung covered with its pleura (Plate 39). The subclavian vein lies below the artery, under cover of the clavicle. Three branches are given off from the first portion of the subclavian artery, — i.e., from its under surface the internal mammary (page 257), and from its upper surface the vertebral (page 232) and the thyroid axis (page 232). The left subclavian artery commences within the thorax by an inde- pendent origin from the arch of the aorta, and its first portion is conse- quently longer than that of the right. Its calibre is less, and it is also deeper. Within the thorax the first portion is crowded by the apex of the left lung within its pleura. It is covered by the sternal end of the first rib, by the sterno-clavicular joint, and by the left subclavian vein on its way to join the jugular vein to form the left innominate vein. Between the vein and the artery in this locality the phrenic nerve descends. Be- hind the artery, and internal to it, are the trachea, the oesophagus, the left recurrent laryngeal nerve, the inferior cervical ganglion of the sympa- thetic, and the thoracic duct (Plates 36 and 39). Above the clavicle the first portion of the left subclavian artery corre- sponds very nearly in its relations to those on the right side, and its branches are similarly disposed. The second portions of both the right and left arteries very closely resemble each other as they pass between the THE REGION OF THE NECK. 229 scalenus anticus and scalenus medius muscles over the first rib, the only- difference being in the height to which the artery ascends above the clavicle, which in some cases is as high as four centimetres, or an inch and a half. The right subclavian usually arches higher than the left (Plate 35). The phrenic nerve descends across the scalenus anticus muscle, and at its anterior border passes between the artery and the vein. The superior intercostal artery is the only branch given off from the subclavian behind the scalenus anticus. The third portions of both subclavian arteries also resemble each other in their relations. Here the vessel is more superficial as it passes downward over the first rib. It occupies the supra-clavicular triangle, formed by the sterno-mastoid and omo-hyoid muscles and the clavicle; but it should be remembered that the dimensions of this triangle may be encroached upon by the approximation of the sterno-mastoid and trapezius muscles (page 207). As this portion of the artery is most readily exposed, and therefore most easily ligatured, it deserves special attention. Besides the superficial coverings in this locality, there is the double layer of deep fascia, consisting of the expansion from the omo-hyoid to the clavicle and the underlying expansion from the scalenus anticus. Within the superficial fascia the supra-clavicular nerves, the lower end of the external jugular vein, and the transverse cervical and supra-scapular veins cross this space (Plates 18 and 19). In the ordinary position of the arm the clavicle and subclavius muscle and the supra-scapular vessels lie directly over this portion of the subclavian artery, but by turning the head and neck to the opposite side and depressing the shoulder the axillary artery may be drawn upward and made to take its place. The artery rests directly in a groove upon the first rib, and the outer border of the scalenus anticus muscle is a direct guide to it (page 220). The sub- clavian vein is below and on a plane anterior to it, under cover of the clavicle. The cords of the brachial plexus of nerves and the posterior portion of the omo-hyoid muscle are placed obliquely above the artery. The supra-scapular artery usually arises from the third portion of the subclavian, although occasionally it is derived from the thyroid axis at the inner border of the scalenus anticus muscle. PLATE 33. The relations of the lungs, when completely collapsed, to the heart. Also the deeper relations of the vessels and nerves at the root of the neck. The pericardium is removed, and the ribs sawn through at their middle to give a better view into the cavity of the thorax. The clavicles are also removed. 1. The right facial artery and vein. 2. The right digastric muscle. 3. The right lingual artery. 4. The right superior laryngeal nerve. 5. The right superior thyroid artery. 6. The right common carotid artery. 7. The right internal jugular vein. 8. The right pneumogastric nerve. 9. The right phrenic nerve. 10. The right brachial plexus of nerves. 11. The right scalenus anticus muscle. 12. The right supra-scapular artery and veins. 13. The right subclavian artery. 14. The origin of the subclavian artery from the innomi- nate artery. 15. The right subclavian vein. 16. The innominate artery. 17. The right recurrent laryngeal nerve, winding under the innominate artery. 18. The right innominate vein. 19. The back of the upper part of the thoracic cavity. 20. The superior vena cava. 21. The right phrenic nerve. 22. The ascending portion of the aorta. 23. The upper lobe of the right lung. 24. The right auricle of the heart. 25. The middle lobe of the right lung. 26. The position of the tricuspid valve. 27. The lower lobe of the right lung. 28. The branches of the right phrenic nerve on the upper surface of the diaphragm. The diaphragm. The left facial artery and vein. The left digastric muscle. The body of the hyoid bone. The thyro-hyoid membrane. The thyroid notch. The left superior laryngeal nerve. The left superior thyroid vein and artery. The crico-thyroid membrane, and the crico-thyrold artery. The cricoid cartilage. The left internal jugular vein. The left common carotid artery. The left recurrent laryngeal nerve. The left scalenus anticus muscle. The left brachial plexus of nerves. The left subclavian artery. The left subclavian vein. Tlie left innominate vein. The left pneumogastric nerve giving off Its recurrent branch to pass under the aorta. The back of the upper part of the thoracic cavity. The transverse portion of the arch of the aorta. Tlie left phrenic nerve. The pulmonary artery. The upper lobe of the left lung. The right ventricle of the heart. The lower lobe of the left lung. The branches of the left phrenic nerve on the upper surface of the diaphragm. Plate 33 Vol I Copynght, m ,. by GwnGF_ Mc Clellan, M U Dissected, Photosnphd and Cohrd from NaWn br Gcofmse Mc. Cli^llan. MB. THE BEGION OF THE NECK. 231 The subclavian vein, upon either side, does not arch upward like its companion artery, but takes nearly a straight course to join with the common jugular in forming the corresponding innominate vein. It ex- tends from the lower border of the first rib to a point between the insertion of the scalenus anticus and the sterno-clavicular joint. The phrenic and pneumogastric nerves descend between it and the artery upon both sides of the neck, and it receives its blood through the anterior and external jugular veins. Before its junction with the common jugular it is guarded with a pair of valves. It should be noted that throughout its course the subclavian vein is placed on a lower plane than, and in front of, the artery. The sheath over the subclavian vessels is attached to the back of the clavicle, and, as the vein is more firmly enveloped by it than the artery, it follows the movements of that bone. This intimate relation of the vein to the clavicle renders it liable to injury in fractures of that bone. The operation for tying the subclavian artery is a difiicult task, even upon the dead subject with the parts in their normal positions. It is naturally more so upon the living, and not only is a practical knowledge of the anatomy requisite, but also a knowledge of the possible deviations which attend the structural changes in consequence of aneurism or other tumor involving this region. In ligation of the subclavian artery in the third or outer part of its course the patient's head should be turned back, the shoulders raised, and the arm pulled down to the utmost, so as to lower the clavicle. The integument should be drawn downward, and an incision several inches long should be made directly upon the clavicle through the superficial coverings. If the trapezius and sterno-mastoid muscles overlap the supra- clavicular space they must be cut and turned aside. In this incision care must be taken not to wound the external jugular vein, and, as the supra^ scapular veins are often in the way, they may require a double ligature and section. The deep fascia can be opened by following the external jugular vein as it pierces it. Much time is often lost through mistaking the cellular space above the deep fascia for that below it. In the depths of the latter the artery in question is situated. In more than one instance the lower cord of the brachial plexus has been mistaken for the artery, and on several 232 THE REGION OF THE NECK. occasions tied ; but this is not likely to happen if before securing the liga- ture the arm is raised and rotated, so as to relax the parts, when they can be better recognized. The impression conveyed to the finger by pressing over the first rib should never be relied on. The operator does not usually see the vein. It is out of the way, below the clavicle. In the deeper cellular space there is generally a quantity of fat, with some lymphatic glands, which when enlarged offer additional embarrassment to the opera- tion. The collateral circulation after the artery has been tied in its outer portion is maintained by the occluded branches of the axillary artery drawing the blood from their anastomoses with the superior inter- costal, upper aortic, intercostal, and internal mammary arteries, assisted by the communications between the dorsalis scapulae and the supra-scapular and posterior scapular arteries. The vertebral artery arises from the upper and posterior surface of the first portion of the subclavian. It ascends behind the common jugular vein, and runs between the scalenus anticus and longus colli muscles until it enters the vertebral foramen in the transverse process of the sixth cervical vertebra. On the way it is crossed by the inferior thyroid artery, and on the left side by the thoracic duct. The sympathetic nerve cord is in close relation to it, and some delicate nerves from the inferior cervical ganglion pass along with it, and others pass across, to blend with the cords of the brachial plexus. After entering the transverse process of the sixth vertebra it continues up through the corresponding foramina in the transverse processes of the vertebrae above until it arrives at the atlas in the sub-occipital triangle (Plate 4, Fig. 2), where, after it rises through the foramen in the transverse process, it turns backward round the condyle of the occipital bone to penetrate the posterior occipito-atlantic ligament and to enter the sub-dural space within the foramen magnum. Within the cranium the vertebral artery passes between the hypoglossal nerve and the anterior root of the first cervical nerve and ascends upon the basilar process to join with its fellow (page 22) and form the basilar artery (Plate 5, Fig. 3). The thyroid axis is a short trunk arising from the first portion of the subclavian at the inner border of the scalenus anticus muscle. It usually THE REGION OF THE NECK. 233 divides into three branches, the inferior thyroid, the transversalis colli, and the supra-scapular. The inferior thyroid artery ascends tortuously across the vertebral artery, the recurrent laryngeal nerve, and the longus colli muscle to the corresponding lobe of the thyroid body. The middle cervical ganglion of the sympathetic nerve is very close to it as it passes beneath the sheath of the carotid vessels. The inferior thyroid sends off branches to the pharynx, oesophagus, trachea, and the anterior mediastinal glands, and the little inferior laryngeal artery which accompanies the recurrent laryngeal nerve. Within the thyroid body it breaks up into terminal branches which anastomose freely with those of the other thyroid arteries. The transversalis colli artery usually arises from the axis and passes over the scalene muscles and the brachial plexus to reach the upper angle of the scapula, where it supplies the adjacent muscles. Its veins are in close relation with it and empty their blood into the external jugular. The transversalis colli often gives off the swperficial cervical artery, which passes upward along the border of the trapezius muscle (Plate 25) and anastomoses with the descending branch of the occipital artery. It is accompanied by two vense comites, which join the transverse veins. The supra-scapular artery arises sometimes from the thyroid axis, sometimes independently from the third portion of the sub- clavian artery (page 229). It passes behind the clavicle, separated from the subclavian artery by the reflection of the deep cervical fascia from the omo-hyoid muscle, and on reaching the scapula it enters the supra- spinous fossa. It then passes through the supra-scapular notch and eventually terminates in the iufra-spinous fossa. In its course it sends branches to the neighboring muscles, to the clavicle, to the acromion and body of the scapula, and to the shoulder-joint. This vessel is accompa- nied by two veins, which are provided with valves at their termination in the external jugular or subclavian veins. The thyroid body is the very vascular glandular organ which is situated in the neck over the front and sides of the upper part of the trachea, extending upward on each side of the larynx. It consists of two ovoid lateral lobes, united near their lower borders by a median transverse portion, the isthmus. It is of a reddish-brown color, and weighs in the 30 234 THE REGION OF THE NECK. adult about two ounces. Each lobe extends from the fifth or sixth ring of the trachea below to the side of the thyroid cartilage above, which is embraced by the narrower end. Each lobe is five centimetres, or about two inches, in length, by three centimetres, or an inch and a quarter, in breadth. The anterior surface is convex, and covered by the infra-hyoid, sterno-hyoid, sterno-thyroid, and omo-hyoid muscles (Plates 23, 24, and 25), and is overlapped at the sides by the anterior borders of the sterno- mastoid muscles. The posterior surface is adapted to and closely adherent to the parts of the trachea, larynx, and oesophagus over which it lies. The carotid sheath is usually in contact with the external border of the lobe on each side, but very often it is embraced, particularly on the right side, by the glandular structure. The isthmus is variable in size, shape, and position, and usually crosses over the second and third rings of the trachea, being firmly attached by a band of the deep cervical fascia, besides the general investment which con- nects the thyroid body to the sides of the trachea and to the cricoid and thyroid cartilages. In consequence of this intimate association the organ rises and falls with the larynx in swallowing, and thus a valuable means is afforded of distinguishing the character of any enlargement of its lobes. Very often there is an accessory •pyramidal middle lobe which extends upward from the junction of the isthmus with the left lobe to be attached to the thyro-hyoid membrane by a fascial band. This may sometimes be covered by a separate slip from the sterno-hyoid muscle, called the levator corporis thyroidei. The thyroid body varies in size in different individuals and at different periods of life. It is relatively larger in the child than in the adult, and in the female than in the male. In children the isthmus is usually very insignificant. The function of the thyroid body is unknown, but it is supposed to be in some way a blood-forming organ and to regulate the production of mucin. Each lobe consists of many irregular lobules, held together by areolar-tissue septa which are inflected from the external glandular investment. In these septa are the branchings of the vessels, surrounded not unfrequently with a colloid substance. The lobules are composed of a great number of closed follicles, the epithelial lining of THE REGION OF THE NECK. 235 which secretes a serous fluid in the child. In the adult the lining -wall degenerates and colloid matter takes the place of the earlier limpid fluid. There are fine sympathetic nerve filaments which accompany the vessels throughout the glandular structure ; and there are numerous lymphatic vessels which commence in lymph-spaces in the interlobular septa and terminate in the lymphatic ducts upon each side of the neck. There- is no proper duct to the thyroid body itself. The arteries which supply the thyroid body are remarkable for their number, size, and free inoscula- tion. The superior thyroid arteries (page 203) arise from the external carotid arteries just below the greater cornua of the thyroid cartilage, and curve downward beneath the infra-hyoid muscles to the upper and front surface of the thyroid body (Plate 24). The inferior thyroid arteries arise from the thyroid axis of the subclavian arteries (page 233) and ascend tortuously to the under surface of the thyroid body. Occasionally there is a middle thyroid artery, the thyroidea ima, which arises either from the arch of the aorta or from the innominate artery and ascends in front of the trachea to the isthmus. The thyroid veins are also remarkably large, and form a plexus upon the lobes of the thyroid body. The superior and middle thyroid veins upon each side empty into the internal jugular. The inferior thyroid veins communicate freely with each other over the trachea in the anterior part of the root of the neck, and terminate in the innomi- nate veins. The relations of the thyroid body to the great vessels and nerves of the neck explain many of the symptoms produced by the hyper- trophied condition of any portion of it, known as " bronchocele." The trachea in the neck is covered anteriorly by the sterno-hyoid and sterno-thyroid muscles (Plate 23, Fig. 2). The sterno-hyoid muscles are thin fleshy bands of parallel fibres beneath the skin, which arise on each side from the posterior surface of the sterno-clavicular joint and the con- tiguous portions of the clavicle and manubrium sterni. They ascend and converge to be inserted tendinously into the lower border of the body of the hyoid bone. The sterno-thyroid muscles arise from the posterior surface of the manubrium sterni, internal to the sterno-hyoid muscles, and from the cartilage of the first rib on each side, and ascend like two muscular ribbons, diverging a little from each other to be inserted into the oblique 236 THE REGION OF THE NECK. lines of the alse of the thyroid cartilage. Occasionally these muscles present tendinous intersections. The thyro-hyoid muscles are continu- ations upward of the sterno-thyroid muscles, and are variable in their degree of separation from them. They are somewhat broader than the sterno-hyoid, and project laterally beneath the attachments of the omo- hyoid muscles. These muscles are all brought into action in forced inspiration. The sterno-hyoid aids the omo-hyoid in depressing the hyoid bone. The thyro-hyoid elevates the thyroid cartilage, while it is depressed by the sterno-thyroid. These muscles are innervated by the communi- cating loop from the descendens hypoglossi nerve (Plate 27). In the middle line the fascial sheaths of the sterno-thyroid and sterno-hyoid muscles blend and form the linea alba cervicalis, which can be readily distinguished after incision through the integument (Plate 23.) The trachea is the cartilaginous and membranous portion of the windpipe which commences at the cricoid cartilage of the larynx opposite tlie fifth cervical vertebra (page 177) and extends medially downward to about the body of the fourth dorsal vertebra, where it divides into the right and left bronchi (page 268). It is situated partly in the neck, and partly within the superior mediastinum of the thorax (page 260). The length of the trachea in the adult is from ten to eleven and a half centi- metres, or from four to four and a half inches, and its diameter is about nineteen millimetres, or three-fourths of an inch, from before backward, and a little more than that from side to side. The dimensions vary with the age and development of the individual, and in the female the trachea is smaller than in the male. In a general way the calibre may be said to correspond to the size of the patient's forefinger. It is a cylindrical tube flattened behind, so that upon section it appears shaped like the letter D (Plate 26, Fig. 2, No. 7). It is composed of a series of incomplete carti- laginous rings, from sixteen to twenty in number, which extend round the anterior two-thirds of its circumference. At the posterior deficiency in the rings, where the trachea is in relation to the oesophagus, the tube is com- pleted by a fibro-muscular membrane, in consequence of which its calibre can be increased or enlarged. The muscular tissue consists of layers of longitudinal and transverse fibres. The spaces between the rings are filled THE BEGION OF THE NECK. 237 up witli the fibrous membrane, in which there is an additional development of elastic tissue. The hoops of the rings are generally parallel with one another across the front of the tube, but their extremities offer great diver- sity in conformation. Sometimes they fork, alternating upon the two sides, and sometimes the ends of the adjacent rings are united. The last ring is peculiar, and usually is modified by being prolonged in front in a V-shaped piece so as to conform with the first rings of the two bronchi. The top ring is always broader than the rest, and is strongly connected by fibrous tissue with the lower border of the cricoid cartilage, with which it is sometimes blended. The tracheal cartilages rarely ossify, as they are non- vascular. They are invested with a dense perichondrium which closely adheres to the entire tube. The mucous lining of this portion of the air- passage is smooth and of pinkish color, although it is but slightly vascular. Within the sub-mucous layer are the blood-vessels, lymphatics, and nerves, together with a number of small racemose mucous glands, the tracheal glands. These are situated mostly in the posterior membranous wall and along the borders of the rings, and their ducts convey their secretion to the inner lining; In bronchitis they are the sources of the abundant secretion. The tracheal arteries are supplied by the inferior thyroid arteries (page 233) and run longitudinally downward to terminate in capillary plexuses. The nerves are derived from the pneumogastrics and their recurrent branches. The trachea is surrounded by a quantity of loose connective tissue, especially in children, which allows of its free mobility. This mobility of the trachea is one of the greatest obstacles to the satisfactory performance of tracheotomy, as it is essential to fix the trachea in the middle line, which here, as elsewhere in the body, is regarded surgically as the line of safety, owing to the feeble anastomosis of the vessels from side to side. In the performance of the operation of tracheotomy, the patient's head should be extended straight backward, with the shoulders elevated over a firm pillow, so as to bring the trachea into relief and to steady it as much as possible. The landmarks, consisting of the thyroid notch, the hoop of the cricoid cartilage, and the top of the sternum, are clearly noticeable. The upper rings of the trachea cannot be detected through the PLATE 34. Preparation to show the relations of the heart, within the pericardium. 1. The thyro-hyoid membrane. 2. The thyroid notch. 3. The right thyro-hyoid muscle. 4. The right superior thyroid artery. 5. The right superior laryngeal nerve. 6. The right crico-thyroid muscle, and crico-thyroid ar- tery. 7. The right pneumogastric nerve. 8. The right common carotid artery. 9. The right supra-scapular artery. 10. The right scalenus anticus muscle. 11. The right phrenic nerve. 12. The right brachial plexus of nerves. IS. The right subclavian artery. 14. The right first rib. 15. The right pneumogastric nerve, passing behind the right innominate vein. 16. The innominate artery. 17. The right innominate vein. 18. The upper lobe of the right lung, drawn aside. 19. The superior vena cava. 20. The right phrenic nerve. 21. The middle lobe of the right lung, drawn aside. 22. The position of the right auricle, covered with the pericardium. 23. The lower lobe of the right lung. 24. The rightventricle of the heart within the pericardium. 25. The left superior thyroid artery. 26. The left thyro-hyoid muscle. 27. The crico-thyroid membrane. 28. The cricoid cartilage. 29. The left internal jugular vein. 30. The left common carotid artery. 31. The left pneumogastric nerve. S2. The left brachial plexus of nerves. 33. The left recurrent laryngeal nerve. 34. The left scalenus anticus muscle. 35. The trachea. 36. The left subclavian artery. 37. The left subclavian vein. 38. The left phrenic nerve. 39. The left innominate vein. 40. The upper lobe of the left lung, drawn aside. 41. The position of the pulmonary artery within the peri- cardium. 42. The left lung, drawn aside. 43. The left phrenic nerve. 44. The apex of the heart within the pericardium. 45. The lower portion of the lower lobe of the left lung, drawn aside. 46. The position where the pericardium blends with the central tendon of the diaphragm. N. B.— The ribs are cut away so as to give an unrestricted view. Vol I Copyright, 1830, by Georbe Mc Clellan, M 0. DisSKtsd, P.'mtognDted md Cohred from Nature t; Geouk Mc. Cucllah, MD. THE EEGION OF THE NECK. 239 integument, except in very thin subjects. The isthmus of the thyroid body crosses over the second and third tracheal rings, and is usually very closely bound down to them. It should be remembered that the crico- thyroid artery passes over the top of the crico-thyroid membrane (page 184), that occasionally the anterior jugular vein occupies the middle line (page 192), and that the inferior thyroid veins always intercommunicate over the trachea at the root of the neck (page 235). These anatomical facts indicate the isthmus of the thyroid body as the point above which or below which the operation offers special features of interest. In all cases it is well to make the incision through the superficial tissues free ; and it should be kept absolutely in the middle line. It should divide the skin over the position of the isthmus of the thyroid body, when the anterior jugular vein, if present, will be recognized, and the white aponeurotic line between the sterno-hyoid and sterno-thyroid muscles will be exposed. The surface of the crico-thyroid membrane should be carefully examined for the presence of any transverse vessel, — the crico-thyroid or superior thyroid, — and traction should be made upon the isthmus to see whether it can be drawn upward or downward. If it cannot be displaced it may be cut through upon a director, and, if necessary, between a double ligature. When the trachea is sufficiently exposed, a tenaculum should be inserted to steady it, and the upper rings cut by plunging into them the point of the knife to the extent of half an inch, so as fully to open the mucous lining. This precaution is necessary when there is a false membrane, so that the canulated metal tube when inserted may not pass between it and the tracheal wall. It is not safe to make the plunge with the knife deeper than half an inch, on account of the danger of wounding the oesophagus. It is noticeable that when air enters the lungs through the tracheal wound the engorgement of the tributary veins subsides in consequence of the relief afforded to the heart, which is thus enabled to pump out the venous blood from its right side. Below the isthmus of the thyroid body the trachea becomes deeper as it descends behind the sternum (page 190), which adds greatly to the difficulty of opening it in this situation. In little children the neck is usually very fat, and at the root of the neck, besides the intricate inferior thyroid veins, the left innominate vein, and 240 THE REGION OF THE THORAX. even the innominate artery, may be drawn upward above the margin of the manubrium sterni, in consequence of the comparatively greater laxity of the connective tissue. The upper portion of the thymus gland is also often in the way. In the adult, however, unless there is an unusual origin for the innominate artery, it can hardly be made to mount so high as the supra-sternal notch by stretching the neck, as already stated (page 222). In operating below the isthmus the inferior thyroid veins should never be forgotten, and the knife should be introduced with the back toward the sternum, to avoid the thymus gland and other structures in that situation. THE REGION" OF THE THORAX. The landmarks of this region are so obscured by the supei'ficial and external structures that they are not easily recognized without particular knowledge of the component parts in their several localities. They are of the greatest importance, on account of their medical application in the physical examination of the chest as relates to diagnosis by auscultation or percussion in affections of the thoracic organs. Attention will therefore be first drawn to the general construction of the thorax, and then to its principal features in detail, before considering its topographical relations. The skeleton of the thorax (Plate 28) is composed of the dorsal vertebrae, the ribs and costal cartilages, and the sternum, so arranged as to form a conical, movable framework, which gives attachment to the muscles of respiration, and affords protection to the heart and the lungs. The method of the articulation of the ribs with the dorsal vertebrae behind, and with the sternum through their cartilages in front, is one of the most ingenious pieces of mechanism in nature, which not only permits the unceasing momentary alterations in capacity of the thoracic cavity during respiration, but also fulfils the function of support and protection. The ribs are twelve pairs of flattened, bony hoops, which are attached to the spinal column between the neck and the loins, and so arranged that they project anteriorly and describe a series of arches which increase in length to the seventh and in obliquity to the ninth from above downward. The obliquity of the ribs is so great that the sternal end of any rib is on THE REGION OF THE THORAX. 241 a level with the vertebral end considerably below it in numerical order. Thus, the first rib in front corresponds to the fourth rib behind, the fifth to the ninth, the seventh to the eleventh. The seven upper ribs have separate cartilaginous prolongations which connect them with the sternum, and are distinguished as true or sternal ribs, whereas the lower five are called false or asternal ribs, because they are not joined directly with the sternum. Of the latter, the eighth, ninth, and tenth ribs have cartilagi- nous prolongations which unite and turn upward to join the cartilage of the seventh rib so that they are brought indirectly in connection with the sternum. The eleventh and twelfth ribs are without cartilages and termi- nate in free ends in the muscular walls of the abdomen, and hence are called floating ribs. Very rarely the eighth rib presents the anomaly of having an independent cartilaginous prolongation to the sternum (Plate 29), and therefore would then come within the classification of a true rib. Each rib is peculiarly modified in conformation to its position in the series, and from the first to the last they are so remarkably adapted that the slight rotation which can take place only at their vertebral articulations occasions not only a slight elevation of their sternal ends, but an eversion of their lateral surfaces, so that by their united action the thoracic cavity is enlarged in every direction. The vertebral extremities or heads of the intermediate ribs, which closely resemble one another in all respects, are covered with articular cartilage, which in all but the first and last three is divided by a slight transverse ridge into two facets for articulation with the bodies of two contiguous vertebrae. The lower facet is the larger, and is received upon the vertebral body which corresponds numerically with the rib. The costo-vertebral joints are each provided with a capsular ligament, including two synovial membranes separated by & fibro-cartilaginous inter- articular ligament, which extends from the intervertebral disk to the transverse ridge between the facets on the head of the rib. These joints are reinforced anteriorly by fibres which radiate from the anterior border of the head of each rib to the side of the body of the vertebra above, to the front of the intervertebral disk, and to the front of the body of the vertebra below, forming the stellate ligament. The narrowed portion beyond the 31 242 THE REGION OF THE THOEAX. head of each rib is called tlie nech. This is smooth in front, but roughened behind for the attachment of the posterior accessory ligament, consisting mostly of transverse fibres which connect it with the front of the transverse process of the corresponding vertebra. The neck is generally two and a half centimetres, or about an inch, in length, and ends in a roughened process called the tuberosity, which presents on its inner surface a smooth oval facet for articulation with the end of the transverse process of the vertebra. This is also provided with a delicate capsular ligament and encloses a synovial membrane. The fibres which connect the necks and tubercles to the transverse processes are called, from their relative jiositions, anterior, middle, and pos- terior costo-transverse ligaments. The anterior consists of a broad band of fibres extending between the upper border of each rib to the lower border of the transverse process above. It is in relation in front with the intercostal vessels and nerves. The middle consists of short fibres which pass from the back part of the neck of each rib to the anterior surface of the adjacent transverse process. Tlie posterior consists of a short, strong band which passes obliquely from the top of the transverse process to the neck of the rib just back of the tubercle. Between the last two ribs and the transverse processes of the corresponding vertebrae the middle and posterior costo- transverse ligaments are very loose and allow considerable freedom of motion to these ribs. It should be noted in this connection that the trans- verse processes of the dorsal vertebrae become more oblique from above downward, and consequently the obliquity of the neck of each rib increases. Beyond the tuberosity each rib is prolonged forward as a narrow, flattened, bony hoop, constituting the body or shaft. The inner surface is concave and smooth, and the outer surface is rough. The upper border is rounded and thick, and gives attachment to the internal intercostal muscles. The lower border is grooved for the accommodation of the intercostal vessels and nerve, and presents a sharj) external edge for the attachment of the external intercostal muscle. The body of each rib from the second to the tenth at a short distance from its neck suddenly bends forward and changes the direc- tion of its curve. At this point of divergence there is upon the external surface an oblique ridge called the angle, which upon each successive rib THE BEGION OF THE THORAX. 243 downward is situated farther outward, and corresponds to tlie insertion of the slips of the sacro-lumbalis muscle. Furthermore, as each rib approaches its sternal end there is a tendency for the body to twist in its axis, so that the posterior surface behind the angle is inclined downward and inward, while toward the middle of the body the bone is inclined downward and outward. This gives the spiral shape which can best be appreciated when an isolated specimen is placed upon a flat surface, it being then found that both ends cannot be kept down at the same time. In consequence of the obliquity and curvature of the ribs, a pistol-ball upon striking one of them may be deflected in its course, and if it has entered in front may be found in the muscles of the back, or if it has entered from behind may pass out near the sternum. The sternal portions of the ribs are broader, thicker, and more porous than elsewhere, and have cupped depressions in their ends to receive the costal cartilages. The ribs which have noteworthy individual peculiarities are the two upper and three lower ribs upon each side. The first rib is broad, nearly flat, and very curved, but without any twist in its axis. It has a small rounded head, which has only one articular facet for articulation with the body of the first dorsal vertebra. The neck is long and slender and ends in a decided tuberosity. In very pronounced specimens the upper surface presents two shallow oblique impressions in front of the middle of the body, which are separated by a slight ridge. The posterior impres- sion is for the subclavian artery, the anterior part of the ridge for the attachment of the scalenus anticus muscle (page 220), and the anterior impression for the subclavian vein. Between the tuberosity and the impression for the subclavian artery there is a rough surface for the scalenus medius muscle. The second rib is not so broad as the first, and conforms more to the succeeding ribs below, but it is without any twist and is also flatter. The head is provided with two facets for articulation with the bodies of the first and second dorsal vertebrae. About the middle of the body there is a roughness for the attach- ment of the scalenus posticus and serratus magnus muscles. On both the first and the second rib the angle is very slightly developed. The tenth rib is long and curved, and has only a single facet on its head. PLATE 35. Preparation to show the relations of the heart and the great vessels at the root of the neck, opened and held aside. The pericardium is 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. The thyroid notch. The right common carotid artery. The right superior laryngeal nerve. The right superior thyroid artery. The crico-thyroid membrane, with the crico-thyroid artery. The cricoid cartilage. The right supra-scapular artery. The right scalenus anticus muscle. The right subclavian artery. The right brachial plexus of nerves. The right first rib. The right pneumogastric nerve. The innominate artery. The right recurrent laryngeal nerve. The right innominate vein. The right phrenic nerve. The transverse arch of the aorta. The superior vena cava. The upper lobe of the right lung, drawn outward. The pericardium drawn outward to expose the root of the heart. The right auricle of the heart. The middle lobe of the right lung. The right coronary artery of the heart. The pericardium opened and resting upon the dia- phragm. The lower lobe of the right lung. The left thyro-hyoid muscle. The left superior thyroid artery. The left superior laryngeal nerve. The left internal jugular vein. The left common carotid artery. The left scalenus anticus muscle. The left brachial plexus of nerves. The left pneumogastric nerve. The left subclavian artery. The left subclavian vein. The left recurrent laryngeal nerve. The left innominate vein. The upper lobe of the left lung, drawn aside. The descending portion of the arch of the aorta. The ascending portion of the aorta. The pulmonary artery. The upper portion of the pericardium, drawn aside to show the root of the heart. The left coronary artery of the heart. The lower lobe of the left lung, drawn aside. The right auricle of the heart. The apex of the heart. The lower portion of the pericardium, drawn aside to show the apex of the heart .ridLe oo Vol I Copyright, 1830, by George Mc Clellan, M D. Dissected, Photo^rdphed and Colored from Nstunt by Georoe Mc. Clellan, M D. ArmsiTOftjACo L.th Boston. THE REGION OF THE THORAX. 245 The eleventh and twelfth ribs are less well developed in every respect than the others, and have each a single facet on the head, but are with- out neck or tubercle and terminate in sharp-pointed extremities. The difference between them is that the eleventh has a slight angle and groove on its under border, while the twelfth has neither. Occasion- ally there is found a rudimental thirteenth rib on one or both sides in either the cervical or the lumbar region. The sixth, seventh, and eighth ribs are those most frequently fractured, on account of their being usually more exposed than the others. The cartilaginous prolongations of the ribs, or costal cartilages, which bring them in connection with the sternum, resemble in shape the sternal ends of the bony ribs, into which they are fitted without articulation, being merely adjusted and enveloped in a thick perichondrium. In length they increase downward to the seventh, and thence gradually decrease. The first costal cartilage corresponds in breadth to its proper rib, and, like the second, third, and fourth costal cartilages, which are narrower, is continued to the sternum in the line of its rib. The cartilages of the lower true ribs, also narrow, converge uj)ward to be joined to the sternum ; the seventh is the largest, and receives the cartilage of the eighth rib at its under surface, as the eighth does that of the ninth and the ninth that of the tenth. The cartilages of the floating ribs are merely tips to the bones. The union of the several cartilages with the sternum offers all the characteristics of a joint, with special differences in some instances. The first chondro-sternal joint is a synchondrosis, the cartilage being continued into a depression on the outer angle of the top of the manubrium sterni, which admits of very little motion. This cartilage is often partially or completely ossified at middle life. The second chondro-sternal joint occurs at the junction of the manubrium with the gladiolus of the sternum, and consequently there are double articular surfaces, with an interarticular fibro-cartilage and a synovial membrane. This joint is of topographical value, as it can be located through the superficial structures by its relation to the constant ridge between the manubrium and gladiolus sterni (Plate 28). The succeeding costal cartilages are joined to the margins of the sternum in a manner very closely resembling the attachment of the 246 THE REGION OF THE THORAX. head of the first rib to the body of its vertebra. The seventh chondro- slernal joint often resembles the first, and has slight motion. Each of these joints is provided with a capsule from the adjoining periosteum, which is strengthened by the anterior chondro-sternal ligament, composed of fibres radiating from the ends of the costal cartilages on the front of the sternum, where they interlace with one another above and below and from the opposite side and with the tendinous attachments of the pectoral muscles. The posterior chondro-sternal ligament is the corre- sponding fibrous interlacement on the endothoracic surface of the articu- lations. The cartilages of the eighth, ninth, and tenth ribs are connected to one another and to the cartilage of the seventh rib by the interchondral ligaments. The costal cartilages are very elastic in youth, those of the lower ribs particularly so. In certain diseased conditions these cartilages become ossified and are liable to fracture. The sternum, or breast bane, consists in the adult of three light, flat, spongy bones which are supported by the costal cartilages in the front of the chest, and taken together form a narrow, long, bony mass shaped somewhat like an old Koman sword. The upper portion resembles the handle, and is called the manubrium (or presternum) , the central blade-like portion is the gladiolus (or mesosternum) , and the lower jwinted process (usually cartilaginous) is the eiisiform process (or metasternum), which, because of its variability of form and frequently forked termination, is also known as the xiphoid appendix. The manubrium is the broadest and thickest part, and presents on each lateral border three articular surfaces, the upper of which is the largest, for the articulation with the clavicle (page 324), the middle just below it for the cartilage of the first rib, and the lower half facet for the upper border of the cartilage of the second rib. The upper border of the manubrium is on a level with the lower border of the second dorsal vertebra, is smooth, and is noticeable through the skin between the two sterno-clavicular joints as a marked depression, called the supra-sternal notch. The gladiolus is ordinarily broadest between the articulations of the cartilages of the fifth ribs. Upon the lateral borders are the articular notches for the rib cartilages, and running across the bone between them THE REGION OF THE THORAX. 247 from side to side are imperfectly-marked ridges, indicating the original segmentation in its formation. Tlie ensiform cartilage is irregular, notched or bifid, and is often bent forward or to one side owing to some habitual occupation during life, as the pressure exerted by a cobbler's last. There is a chondro-xiphoid ligament which extends from the cartilage of the eighth rib on each side to this process. The chief difference in the length of the sternum in the female (seven- teen and a half centimetres, or about seven inches) and in the male (twenty centimetres, or about eight inches) is in the gladiolus, which in the former (Plate 41, Fig. 1) is shorter and broader proportionately than in the latter (Plates 28 and 29). The outer surface of the sternum is slightly convex, the inner concave. Looked at from the side, the anterior surfaces of the different portions will be seen to occupy different planes, so that there is always a slight bend at the junction of the manubrium and gladiolus. The plane of the manubrium inclines forward, that of the gladiolus less so, and the ensiform cartilage is usually vertical, although, as just stated, it is subject to variations. The outer layer of compact tissue which encases the spongy substance of the sternum affords very slight pro- tection, but the j)eriosteal covering is very dense, and thicker than usual in other bones. The joint between the manubrium and gladiolus is rarely ossified, and there is often a decided yielding or tendency to sinking back- ward of the top of the gladiolus, which has in some instances been errone- ously surmised to be the result of fracture. As stated, the ridge in this situation is constant, and of the greatest service in counting the ribs, for, as it corresponds to the attachment of the cartilage of the second rib on each side (page 245), it is easy to ascertain any other by counting down- ward. The median line of the sternum is not continuous with the median line of the abdomen, but inclines rather to the right. The intercostal spaces in relation to the sternum are noticeably wider above and narrower below. The second intercostal sjjaee is generally the widest (Plate 29), but they all vary with the expansion and contraction of the chest in respiration. They can be increased by bending the body over to the opposite side. The skeleton of the thorax, considered as a whole, is somewhat flattened 248 TEE REGION OF THE THORAX. in front and behind, so that its width from side to side exceeds its depth, which is characteristic of the human thorax as compared with that of quadrupeds, and makes the supine position naturally an easy one to man. The anterior surface is slightly convex, corresponding to the direction of the sternum and the costal cartilages by which it is formed. The lateral surfaces are convex, and formed by the arching bodies of the ribs and the intercostal spaces. The posterior surface is also convex from above down- ward, and is formed by the dorsal vertebrae and the portions of the ribs posterior to their angles. The thorax increases in dimension from the first rib to the eighth, where its transverse diameter is greatest. There is much variability in the form of the thorax at all periods of life, and very com- monly there is a want of symmetry in the two sides, the circumference of the right usually being greater than that of the left. In early childhood the thorax is relatively smaller than in the adult, the ribs are flatter and less hooped, and up to the end of the third year breathing is more abdom- inal than thoracic, while after that age, in boys, and in men too, it is effected by the action of the muscles attached to the lower seven ribs as well as the diaphragm. In adult females the upper portion of the thorax is less compressed from before backward, and the upper ribs are naturally brought more into play, even when not influenced by artiflcial pressure, so that in them breathing is thoracic. A horizontal section made through the middle of the thorax (Plate 41, Fig. 2) presents a cordiforra or heart- shaped outline, owing to the projection of the bodies of the dorsal portion of the vertebral column into the back of the thoracic cavity. Such a sec- tion will also show that the ribs are cut obliquely. In the male a section made on a level with the lower borders of the third ribs anteriorly and through the body of the eighth dorsal vertebra posteriorly will generally cut the eighth, seventh, sixth, fifth, and fourth ribs (Plate 41, Fig. 2). The dorsal vertebrce, or, more properly, thoracic vertebrce, are peculiarly adapted with facets and demi-facets for the articulation of the ribs. The first corresponds in general conformation to the vertebra prominens of the neck, and the last to the first vertebra of the lumbar region. Their bodies are thicker behind than in front, as are also the dorsal intervertebral disks, so that when they are articulated they present a natural curvature with the THE REGION OF THE THORAX. 249 convexity backward. The dorsal spines are very oblique, and it should be remembered that their tips do not correspond to the bodies. That of the first is opposite the disk between the first and second bodies ; that of the second is opposite the body of the third ; that of the fourth is on a level with the disk between the fifth and sixth ; those of the fifth, sixth, seventh, and eighth are opposite the seventh, eighth, ninth, and tenth. That of the ninth corresponds to the body of the tenth, the tenth to the eleventh, and the eleventh is opposite the disk between the eleventh and twelfth. The further description of the dorsal vertebrae will be found under the anatomy of the back, in Vol. II. The terms superior and inferior apertures of the thorax are misleading, such openings existing only in the skeleton. The superior, corresj)onding to the summit of the thorax, gives passage to the structures at the root of the neck and to the dense fibro-cellular tissue which is prolonged over them from the deep cervical fascia into the thoracic cavity. The inferior opening, or base, is closed in the recent state by the diaphragm, which forms a muscular partition between the chest and the abdomen. Although the diaphragm is arched upward to a considerable extent and its muscular portions fall and rise continually in unison with the efforts at resj)iration, thereby alternately increasing and diminishing the capacity of the thorax, the actual space occupied by the lungs and heart is very limited compared to that indicated by the outward appearance of the bony cage. The dia- phragm (page 320) is on a level with the junction of the fifth costal carti- lage and rib on the right ride, and of the sixth on the left (Plate 27), corres23onding to the height to which the liver reaches. It is attached in front to the ensiform cartilage, but it curves downward to become attached to the last rib on both sides. The skin over the anterior surface of the thorax is delicate and closely connected with the superficial fascia. It is tense and very slightly movable over the sternum, but at the sides, in consequence of the traction exerted by the underlying muscles, the pectoralis major and minor and the latissi- mus dorsi, forming the folds of the axilla, it is freely movable. The skin over the sternum in dark-hued males is usually the seat of the growth of curly black hairs associated with large sebaceous glands. The superficial 32 250 THE REGION OF THE THORAX. fascia is generally loose, and does not contain much fat except in relation to the mammse, where the fascia subdivides into two layers which surround these glands and send numerous septa between their various lobes. The ligamenta suspensoria are fibrous processes which project from the anterior layer to the skin around the nipples. The mammary glands in the female (Plate 44, Fig. 1) extend from the third to the sixth rib on each side between the axillse and the sternum. They vary in size and shape according to their functional development and the general physical condition of the individual. When fully formed, with the enveloping skin, fascia, and fat, they appear as globular promi- nences, the breasts, from which protrude conical, brownish-pink-colored eminences, the nipples, which are surrounded at their bases by a zone of colored skin, the areola. The nipple is usually situated opposite the fourth intercostal space, and twelve centimetres, or about four and a half inches, from the middle line ; but its position is variable and cannot be relied upon as a reference for definite measurement (Plate 27). The skin of the areola is extremely thin, and is covered with a number of little whitish tubercles which contain the orifices of sebaceous glands. The skin of the nipple is provided with sensitive papillse, and consists of retiform tissue interspersed with unstriped muscular fibres. It is highly vascular. The milk-ducts open upon the summit of the nipple by from fifteen to twenty orifices. The mammary gland is a racemose glandular structure, consisting of from fifteen to twenty lobes, which are supported by the septa inflected from the anterior layer of the fascial investment. The lobes are quite independent of one another, so that in mammary abscess it is often necessary to make several openings, and they should be made in a straight direction radiating from the nipple, in order to avoid as far as possible injuring the milk-ducts. The arteries which enter the margins of the gland are small and numerous, and they do not accompany the ducts. Those for the upper lobes are derived from the thoracico-acromial artery, those for the outer lobes from the long thoracic and external mammary arteries, and those for the inner lobes from the anterior intercostal arteries (Plate 44, Fig. 1). The deep veins accompany the arteries; the superficial veins form an THE BEGION OF THE THORAX. 251 anastomosing circle around the base of the nipple and end in the supe- rior thoracic veins. The lymphatic vessels are numerous, and chiefly converge toward the axillary glands, following the outer border of the great pectoral muscle (Plate 44, Fig. 2), while others terminate in the anterior mediastinal glands in relation to the internal mammary vessels (Plate 41, Fig. 1), penetrating the thoracic walls through the upper three intercostal spaces. The distinction between the sub-sternal and axillary glands with reference to their possible involvement in cancer should be clearly understood. The former receive the lymphatic vessels from the inner portion of the breast, so that in cases where they have become implicated they are anatomical obstacles to the effectual removal of a scirrhous breast, notwithstanding the most thorough enucleation of the axillary glands with the tumor. The superficial lymphatics from the vicinity of the nipple pass to a gland below the outer border of the clavicle. The nerves are chiefly derived from the anterior and lateral cutaneous branches of the intercostal nerves. The sujierficial fascia along the border of the sternum is pierced by the anterior cutaneous branches of the inter- costal nerves, which emerge with the anterior intercostal branches of the internal mammary artery, the second, third, fourth, and fifth being dis- tributed to the mammary gland. The connections of the intercostal nerves explain the diffusion of j^ain complained of in many affections of the breast. In the female there is always a loose layer of connective tissue underneath the gland, and often a bursa, which allows it to glide freely over the pectoral muscle, to which it is in no way attached in the healthy state. In the male the gland is rudimental, and, as the substratum of connective tissue is less loose, it follows to a greater extent the movements of the pectoralis major muscle. Occasionally the male mammae are developed, and in rare instances have been known to secrete milk ; and there are numerous recorded cases of supernumerary mammse in the female, variously situated in the back, axilla, groin, and thigh. In the female the various modifications which the breasts assume after puberty are coincident with the other phenomena attendant upon pregnancy. In the operation for removal of the breast the arm of the affected side PLATE 36. Dissection of the pneumogastric nerve on the left side, and its relations to the phrenic and sympathetic nerves. (From, a female, aged thirty-seven years.) The parotid gland. The digastric muscle. The styloid process. The stylo-glossus muscle. The lingual {or gustatory) nerve. The hypoglossal nerve. The glosso-pharyngeal nerve. The lingual artery. The digastric muscle attached to the hyoid bone by the loop of deep fascia. The great cornu of the hyoid bone. The attachment of the omo-hyoid muscle to the hyoid bone. Section through the symphysis of the lower jawbone. The superior laryngeal nerve. The crico-thyroid muscle. The superior thyroid artery. The top of the thyroid cartilage. The descendens hypoglossi nerve. The right sterno-thyroid and hyoid muscles. The thyroid body. The internal jugular vein. The pneumogastric nerve. The lower cervical ganglion of the sympathetic nerve. The common carotid artery. The recurrent laryngeal nerve. The innominate artery. The sternal end of the right clavicle. The left innominate vein. The U'ft first rib. The anterior margin of the right lung. The ascending portion of the arch of the aorta. The right second rib. The right auricle. The right third rib. The left phrenic nerve. The apex of the left ventricle of the heart. The branches of the posterior coronary artery. The right fifth rib. The right sixth rib. The gastric branches of the left pneumogastric nerve. The diaphragm over the liver. The right seventh rib. The sawn end of the ramus of the lower jawbone. The occipital artery. The spinal accessory nerve. The trapezius mxiscle. The internal jugular vein. The second cervical spinal nerve. The third cervical spinal nerve. The upper— long— cervical ganglion of the sympathetic nerve. The external carotid artery. The internal carotid artery. The descendens hypoglossi nerve. The omo-hyoid muscle. The scalenus anticus muscle. The sympathetic nerve. The left phrenic nerve. The cords of the brachial plexus of nerves. The subclavian artery. The subclavian vein. The insertion of the sca,lenus anticus muscle at the inner border and upper surface (tubercle?) of the first rib. The pneumogastric nerve. The oesophagus (distended). The first intercostal artery coming from the subclavian artery. The internal mammary artery. The left innominate vein. The second intercostal artery and nerve. The origin of the subclavian artery. The left third rib. The sympathetic nerve. The left third intercostal artery and nerve. The transverse portion of the arch of the aorta. The left fourth rib. The left fourth intercostal artery and nerve. The left fifth rib. The pulmonary artery. The left fifth intercostal artery and nerve. The roots of the pulmonary vessels and bronchi. The sixth intercostal artery and nerve. The oesophageal branches of the pneumogastric nerve. The great splanchnic nerve. The left auricle of the heart. The seventh intercostal artery and nerve. The lesser splanchnic nerve. The azygos minor vein. The pneumogastric nerve. The left eighth rib. The diaphragm arching over the spleen. The phrenic nerve. The gastric branches of the pneumogastric nerve pass- ing through the diaphragm to the stomach. The terminal branches of the pneumogastric nerve. The spleen. The stomach. Plate 36 Vol I Copyright, IS90, by George He. Clellan, M. D. Dissected, Photo§rdphed ^nd Colorea from Nature by George Mc. Clellan, M D. THE REGION OF THE THORAX. 253 should be drawn upward and backward, so as to put the great pectoral muscle on the stretch, and a bevelled incision should be made, first on one side and then on the other, around the base of the gland, in a direction toward the axilla. The entire gland, including the nipple, should always be extirpated, to avoid as far as possible a recurrence of the morbid state, and if the axillary glands are involved, as they generally are in cancer, the incision can be extended so as to expose them. They will be found surrounding the deep vessels (Plate 45), and often adherent to the axillary vein and its tributaries, so that their removal is very difficult and hazard- ous, whereas the excision of the gland alone is comparatively a simple and easy task. Upon complete removal of the gland, its base will be found to conform with the slight bulge of the subjacent pectoralis major muscle, which with its sheath of deep fascia will be seen usually untouched at the bottom of the wound. The deep fascia of the anterior surface of the thorax is exposed after removal of the double layer of the superficial fascia and the contained mammary gland. It serves as a thin aponeurotic sheath for the great pectoral muscle, into which it sends prolongations between its component fasciculi. This fascia is attached to the front of the sternum and to the clavicle. It is very delicate over the upper part of the pectoralis major; but, as it is reflected from the outer border of that muscle across the axillary space to the latissimus dorsi muscle, it becomes considerably thicker. It is continued under the latter muscle to the spinous processes of the dorsal vertebrae. Below the deep thoracic fascia is quite strong and blends with the sheaths of the recti muscles. The pectoralis major muscle (Plate 16, and Plate 44, Fig. 1) is the large, triangular, fleshy mass situated at the side of the chest, consisting of two special portions, the fibres of which converge toward the shoulder. The clavicular portion arises chiefly by fleshy fibres from the front of the inner half of the clavicle and the capsule of the sterno-clavicular joint, and extends obliquely outward, when the arm is at the side of the body, to the insertion of the deltoid muscle, with which it blends on the surface of the shaft of the humerus, and also gives off" an expansion to the brachial fascia. In relation to the deltoid muscle above, the clavicular 254 TSE REGION OF THE THORAX. portion is separated only by a furrow which lodges the cephalic vein and the humero-thoracic artery. When this furrow is marked, the coracoid process can be felt through it and may be a useful landmark (page 330). The sternal portion is peculiar in the manner both of origin and insertion of its fibres, which are arranged in two layers which are often quite distinct from each other, being separated by a cellular interval. The superficial layer arises by tendinous fibres from the front of the sternum interlacing with those from the opposite muscle, and usually by a slip from the sheath of the rectus abdominis muscle. The deeper layer arises by fleshy fibres from the cartilages of the five or six upper true ribs, the slip from the first costal cartilage being sometimes absent. The fibres of these two layers are directed in a radiating manner toward their insertion, being disposed in such a manner that the fibres of the deeper layer pass obliquely upward under the fibres of the superficial layer, so that their relative positions are reversed, the lower becoming the upper, as they terminate in a flat tendon at the outer margin of the bicipital groove under the insertion of the clavicular portion. The attachment of the sternal portion gives off a delicate expansion which covers the bicipital groove and is connected with the capsular ligament of the shoulder-joint. The twist in the sternal portion produces the anterior rounded border of the axilla, and covers- the axillary vessels and nerves at the upper part of that space. The pectoralis major muscle is remarkable for its tendency to separate into radial lamellae, commonly offering accessory slips which pass to the humerus or the brachial fascia. Its function is chiefly to draw the arm forward and rotate it inward upon the chest. When the arm is raised it can draw it downward, or, if the fixed point is above, the muscle can assist in raising the trunk, and also serve as an auxiliary muscle of inspiration. The arteries to this muscle come from the long and short thoracic branches of the axillary artery. The nerves are derived from the anterior thoracic branches of the subjacent brachial plexus. The cleft between the clavic- ular and sternal portions of the pectoralis major muscle, when the arm is extended outward, is often clearly indicated by a depression in the skin, and, as it corresponds to the course of the commencement of the axillary THE REGION OF THE THORAX. 255 artery, that vessel may be sought for here and a ligature applied with considerable ease (page 343). The pectoralis major muscle must be removed in order to expose the pectoralis minor and subclavius muscles. The former will be found sepa- rated from the sternal portion of the pectoralis major by a quantity of loose cellular tissue, and the latter beneath the clavicular portion, enclosed in the strong costo-coracoid membrane. The pectoralis minor muscle (Plate 44, Fig. 2) is a triangular fleshy mass composed of- fibres which arise by flattened tendinous slips from the sternal ends of the third, fourth, and fifth ribs, and from the aponeurotic expansion over the subjacent inter- costal muscles. Besides these there are often accessory slips of origin, either above or below. It ascends to be inserted by a narrow, flat tendon into the upper and inner edge of the coracoid process of the scapula, and gives a fibrous extension to the coracoid attachments of the coraco-brachialis and biceps muscles. The insertion of the pectoralis minor passes across the middle of the axillary vessels and nerves (page 339). Between the pecto- ralis minor and major muscles there are branches of the thoracico-acromial artery and the anterior internal thoracic nerve. The long thoracic artery runs along the axillary border of the pectoralis minor. The function of this muscle is to depress the shoulder, by drawing the scapula forward and downward. The costo-coracoid membrane consists of several leaflets of fascia of varying density, extending from the cartilage of the first rib to the coracoid process. Above it is attached to the outer and inner edges of the sub- clavian impression on the under surface of the clavicle, and thus com- pletely encloses the subclavius muscle. The outward and more superficial expansion is thin, and splits so as to pass over and under the coracoid attachment of the pectoralis minor muscle, to be continued with the axil- lary fascia, forming the anterior part of the sheath of the axillary vessels. This leaflet is pierced by the cephalic vein, the thoracico-acromial artery and vein, the anterior thoracic nerves, and the superior thoracic artery. The deeper portion of this membrane is called the costo-coracoid ligament, because of its strong fibrous character. It arches over the axillary vessels and nerves as they pass over the first rib. 256 THE REGION OF THE THORAZ. Tlie subclavius muscle is a round mass of fibres which arises by a strong tendon from the junction of the first rib and its cartilage, and is inserted into the subclavian impression of the clavicle as far as the coraco-clavicular ligament. It receives filaments from the lower cervical nerves, and its function is to fix and depress the clavicle. When the above muscles are completely removed from the anterior surface of the thorax there is a strong glistening aponeurotic layer of fascia spread over the intercostal spaces, which serves to bind down the fibres of the intercostal muscles and to afford additional protection to the spaces. The intercostal muscles consist of two separate layers, external and internal, the short fleshy fibres of which cross one another. There are eleven pairs of each set of intercostal muscles, and they are arranged peculiarly as they approach the vertebral and sternal ends of the ribs. The extei'tial intercostal muscles commence at the tubercles of the ribs, pass obliquely from the outer border of the rib above to the top of the rib below, throughout the series, and extend as far forward as the costal cartilages, where the muscular fibres disappear and are replaced by strong, oblique, tendinous fibres, which constitute a membranous expansion, to the border of the sternum. The internal intercostal muscles commence at the sternum and jiass obliquely in the opposite direction to the external muscles from the inner edge of tlie groove above and from the costal car- tilage to the upper border of the rib below, as far backward as the angles of the ribs, where they are reinforced by additional fibres, the subcostal muscles, which extend upward and downward, passing over one or two ribs between their attachments. The direction of the fibres of the external intercostals corresponds to the external oblique muscle of the abdomen, and that of the internal intercostals is similar to the internal oblique. The in- ternal intercostals are thicker and their muscular fibres more pronounced anteriorly (Plate 40) than they are posteriorly. The intercostal muscles are exercised chiefly in the movements of the ribs in ordinary breathing. When the first and second ribs are fixed by the scalene muscles the action of the external intercostals raises the anterior part of the ribs and everts their lower borders, thus enlarging the thoracic cavity, as in inspira- tion. The special action of the internal intercostals is not definitely THE REaiON OF THE THORAX. 257 understood, but they probably depress the ribs, as in expiration. In the spaces between the costal cartilages the two sets of fibres, it is supposed, assist each other in inspiration. The internal surface of the intercostal spaces is covered with a thin adherent fascial expansion similar to that upon the outer side of the chest wall. It is closely connected with the outer layer of the pleura. Within the thorax, on the under surface of the sternum and cartilages of the lower true ribs, there is a thin, flat muscle, of variable development, called the triangularis sterni. It arises from the ensiform cartilage and the sides of the lower part of the gladiolus and the adjacent cartilages, and ascends obliquely outward, to be inserted, by fleshy slips, into the carti- lages of the lower true ribs, generally from the sixth to the third. The fibres of the lowest slip pass transversely outward, and are in reality con- tinuous with the anterior portion of the transversalis abdominis muscle. The action of the triangularis sterni muscle is to depress the costal carti- lages in expiration. Its nerves are derived from the intercostal nerves, and its arteries are branches of the internal mammary on both sides, which are situated between it and the costal cartilages. The internal mammary artery on either side is given off from the first portion of the subclavian artery, opposite the origin of the thyroid axis at the inner border of the scalenus anticus muscle, and descends into the thorax behind the clavicle and the first rib, in close relation to the phrenic nerve, which passes over it from without inward to descend behind the artery (Plates 39 and 40) between the pleura and the pericardium. The internal mammary artery with a vein on each side of it runs parallel with the border of the sternum, and twelve millimetres, or about half an inch, from it (Plate 41, Figs. 1 and 2), on the surface of the pleura, until it reaches the fifth or sixth intercartilaginous space, where it passes between the cartilages and the triangularis sterni muscle. This artery can be easily ligated within the second intercostal space through an incision directly over its course. In relation to the seventh costal cartilage it divides into its terminal branches, the musculo-phrenic, which supplies twigs to the diaphragm and the lower intercostal muscles, and the superior epigastric, which enters the abdominal wall between the sheath of the rectus 33 PLATE 37. The posterior mediastinum, exposed on the right side by removing the ribs near their angles and drawing forward the heart and lungs, to demonstrate the entrance of the vena azygos major into the superior vena cava, and the distribu- tion of the right pneumogastrio and phrenic nerves. 1. The right occipital artery. 2. Section of the sterno-mastoid muscle. 3. The cut brachial plexus of nerves. 4. Section of tlie first rib. 5. Section of the second rib. 6. Section of the third rib. 7. The chain of ganglia of the sympathetic nerve. 8. The thoracic duct, crossing behind the oesophagus and aorta to the left side. 9. The intercostal vessels and nerve in relation to the seventh rib. 10. The seventh rib. 11. The thoracic duct. 12. The vertebral column, covered with the thoracic fas- cia. 13. The greater splanchnic nerve. 14. The descending thoracic aorta. 15. The lesser splanchnic nerve. 16. Section of the eleventh rib. 17. The hepatic arch of the diaphragm. 18. The lingual artery, 19. The descending thyroid arterj", and superior laryngeal 20. The notch in the thyroid cartUage. 21. The common carotid artery. 22. The thyroid axis. 23. The cricoid cartilage. 24. The right subclavian artery. 25. The first intercostal artery. 26. The trachea. 27. The cesophagus. 28. The innominate artery. 29. The right phrenic nerve. 30. The vena azygos major vein, entering into the superior vena cava. 31. The heart, within the pericardium, drawn forward. 32. The oesophageal plexus of nerves, from the pneumo- gastrio nerve. 33. The right auricle of the heart, within the pericardium. 34. The right lung, drawn outward. 35. The inferior vena cava, emptying into the right auricle of the heart. 36. The thoracic duct, coming through the aortic opening in the diaphragm. 37. The branches of the right phrenic nerve on the dia- phragm. PJate37 Vol I Copynjht, ISSI . k. &-OHSE Mc CU.utN, M D 'om t^oture r,y Oeoroe Mc Cit^LtAt^, ^ D THE REGION OF THE THORAX. 259 abdominis muscle and the extra-peritoneal fascia and anastomoses with the deep epigastric. In its course it distributes a branch which accom- panies the phrenic nerve, the arteria comes nervi phj-enici, branches to the structures within the anterior mediastinum, branches whicli pass to the five or six upper intercostal spaces and inosculate with the aortic inter- costal arteries, and perforating arteries which pass through the intercostal spaces and supply the j^ectoralis major muscle, the mammary gland (page 250), and the skin over the chest. At the first rib there is a lateral infra- costal branch from the internal mammary, which in intra-thoracic growths sometimes becomes greatly enlarged. The two internal mammary veins are usually of unequal size, and are provided with a number of valves. Behind the first intercostal muscle the veins unite and empty on the left side into the innominate vein, and on the right, generally, into the superior vena cava. In close proximity to the internal mammary vessels there are from six to eight lymphatic glands, which receive the lymphatic vessels from the upper part of the rectus abdominis muscle, the diaphragm, the intercostal spaces, and the inner portion of the mammary gland (page 251). They empty into the right lymphatic duct and left thoracic duct respectively. If the sternum and costal cartilages are carefully removed, the anterior wall of the thorax will be opened so as to display the prolongation of the deep cervical fascia downward and the anterior surfaces of the right and left pleural sacs. In the middle line there is a tubular expansion of fascia extending between the pleurae all the way from the neck to the ensiform cartilage of the sternum, and on each side the fascia becomes thickened and is attached to the pericardium, forming the sterno-perieardial ligaments. The sub-sternal tubular sheath can generally be demonstrated by inflation with a blow-pipe, and may allow pus to travel from the root of the neck and point below the ensiform cartilage in the upper part of the abdominal wall. Upon slitting up this layer of fascia the subdivision of the interjjleural space, called the anterior mediastinum, is exposed (Plate 26, Fig. 1). This is a shallow space included between the anterior portions of the pleurae, the pericardium, and the sub-sternal fascia just described, especially that portion of it which corresponds to the gladiolus. Its direction is usually not vertical, as it inclines to the left side because of the position of the heart, 260 THB REGION OF THE THORAX. over the root of which, opposite the origin of the great vessels, it is also narrowest, owing to the approximation of the pleurae. As the left pleura recedes from the middle line, this space is wider below than it is above. Within the anterior mediastinum there are the sub-sternal lymphatic glands, embedded in a variable amount of fatty tissue, and on the left side the internal mammary vessels for a part of their course (Plate 41). The space does not properly enclose the attachments of the triangularis sterni, sterno-hyoid, and sterno-thyroid muscles, as they are covered by reflections of the endothoracic fascia continuous with the deep cervical fascia. The so-called superior mediastinum is that portion of the inter- pleural space which extends from the manubrium in front to the upper dorsal vertebrae behind and above the j^ericardium. It contains, besides the great vessels and contiguous portions of the trachea and oesophagus, the thymus gland in the infant or its remains in the adult. It is not truly separated from the anterior mediastinum except when the expan- sion of the lungs in full inspiration brings their pleural envelopes into contact. The thymus gland is a soft, grayish-red-colored, lobulated body, of variable size and shape, situated behind the manubrium sterni and over- lapping the great vessels of the heart covered with the pericardium (Plate 26, Fig. 3, No. 6). At birth it is five centimetres, or about two inches, in length, wider below than above, and it continues to grow until the end of the second year, often ascending into the root of the neck, and sometimes reaching the lower border of tlie thyroid body. From the second year to the sixth it does not undergo much change, but after the latter age it gradually atrophies, and at puberty there is very little trace of its original glandular structure left, a fatty mass taking its place and rarely projecting above the sternum. It bears much resemblance to the racemose glands, but its function is unknown. It seems to be the great functional lymphatic gland of early life, each lobe consisting of lobules composed of clusters of lymph-follicles surrounded with vascular connective tissue and numerous lymph-cells. The branches from the internal mammary arteries furnish it with most of its blood. The pleurae (Plate 26, Fig. 1, Nos. 6 and 16) are the serous mem- THE REGION OF THE THORAX. 261 branes surrounding the lungs, and are so arranged as to form two distinct completely closed sacs, each having a parietal layer, or pleura costalis, which is in contact with the thoracic wall, and a visceral layer, or pleura pulmonis, which is reflected over the contained lung. The enclosed space between the two layers of each pleura is called the cavity of the pleura, the surfaces of which are smooth and moist, but it is not ordinarily of appre- ciable dimensions. It is now regarded as a large lymph-space, like that of the peritoneum, and communicates by stomata with the surrounding sub- pleural lymphatic vessels. During life, when healthy, the two layers glide freely uj)on each other, and thereby facilitate the movements of the lungs. The costal pleura is the thickest, and is connected especially to the inner surfaces of the ribs by a well-marked connective tissue, which allows of its being easily detached. The pulmonary pleura is very delicate and trans- parent, and is also attached to the lung tissue by elastic connective tissue, which serves as a nidus for a plexus of capillaries from the bronchial arteries, and a plexus of lymphatic vessels which communicate with the lymph-spaces in the areolar tissue of the lobules of the lung. Inflamma- tion of the pleura may produce a thickening and roughening of its lateral surfaces, so that in the expansion of the lung a friction sound is produced. This is peculiarly modified if the inflammation results in a distention of the pleural sac by serum (hydrothorax), or by pus (empyema), or by air (pneu- mothorax). When the cavity of the pleura requires tapping (paracentesis thoracis) to evacuate it of an - accumulation of fluid, the sixth or seventh intercostal space, midway between the sternum and the spine, is generally selected, and the trocar should always be introduced at the middle of the space, during inspiration, to avoid the intercostal vessels and nerves. On the right side the fifth intercostal space should be selected, in order to avoid the diaphragm (Plate 27). The right and left pleural cavities are distinct, and their respective membranes are reflected posteriorly from the roots of each lung, in connection with a fold of the prevertebral fascia, to the diaphragm below, having a free curved edge between the diaphragm and the lung. This is called the ligamentum pulmonale. As the apices of the lungs extend upward into the root of the neck behind the attachments of the scalense antici muscles on the first ribs, their pleurse naturally are 262 THE REGION OF THE THORAX. similarly expanded. On tlie right side the pleura usually reaches a little higher than on the left. In this position it bears an important relation to the subclavian artery in its first portion. At the root of the neck the endothoracic fascia is expanded somewhat in the shape of a dome, to which the deep cervical fascia is usually attached. Sometimes there is a prolongation of this fascia, which brings the dome into relation with the transverse process of the seventh or sixth cervical vertebra, and a few muscular fibres have been found in it, probably segmented from the sca- lenus posticus muscle. The parietal layer of the pleura over the apex of each lung is intimately connected with this dome-like expansion of the fascia. The presence of this ea;^ra-pleural fascia at the root of the neck, with its possible modifications consequent upon any inflammatory infiltra- tion, is worthy of the consideration of the physician, who may be confused by the adventitious sounds produced by it upon auscultation, in the same manner as the surgeon finds it often difiicult to distinguish between true and false crepitus in injuries about the joints. The extent and limitation of the reflections of the pleurae upon the inner wall of the thorax are very difficult to understand without actual demonstration. Below they practically follow the attachments of the diaphragm, which, except about its margin and at its central tendon, is covered by the pleurae. In front the right pleura holds a position more nearly the middle line, being oppo- site the junction of the seventh rib and its cartilage, while the left is placed at a variable distance away from it and a little lower, in consequence of the interposition of the heart. Posteriorly both pleuree descend as far as the head of the last rib, and laterally the right pleura is in relation to the lower border of the ninth rib, and the left pleura to the lower border of the tenth rib. In consequence of this disposition of the pleurae over the diaphragm it often happens that a pistol-ball which has penetrated the thoracic wall will roll down over the diaphragm to the lowest part of the back of the pleural cavity. The pulmonary layers of the pleura upon each side are not coex- tensive with the costal layers, except during forced inspiration. Therefore there are portions of the folds of the pleurae where their surfaces ordi- narily are in contact. These are called the pleural sinuses, and they THE REGION OF THE THORAX. 263 are found along the costal origins of the diaphragm, between the peri- cardium and the sternum, and between the pericardium and the dia- phragm (Plate 26, Fig. 1, No. 8). Upon the anterior margins of the last two sinuses there are folds which blend with the tissue of the peri- cardium, and through which the phrenic nerves on their way to the diaphragm can be seen in front of the roots of the lungs. If a trans- verse section of the thorax is made, it will be noticed that the pleurse do not come into contact, and that there is a distinct space between them extending from before backward (Plate 41, Fig. 2). This is called the interpleural space, and is subdivided into the anterior, middle, and pos- terior mediastina. Of these the middle is the largest compartment, and contains the heart within the pericardium, the vessels which pass to and from the base of the heart, the phrenic nerves, and the bifurcation of the trachea and the bronchial lymphatic glands. The anterior mediastinum is in front of the pericardium, and, as it is first exposed upon opening the thorax anteriorly, it has already been described (page 259), as being in the natural order of approaching the study of this region. The posterior mediastinum is behind the pericardium, between it and the dorsal vertebrae, from the fourth to the twelfth, and contains the descending thoracic aorta, the oesophagus, the pneumogastric nerves, the venae azygos major and minor, the thoracic duct, and lymphatic glands (Plate 38). The lungs are two large spongy organs within the pleurse, occupying during life the whole of the cavity of the thorax on each side of the mediastinum, and separated from each other by the heart enclosed in the pericardium. They vary even in health from a pale-pinkish color to a mottled gray, depending upon their vascularity and inflation. With age they generally become darker and spots are visible upon their surface, probably due to the deposition of particles of carbonaceous matter which have been inhaled. After death they usually appear of a dark-purple hue, especially at the back, in consequence of venous stagnation. When the lungs are fully distended, as in forced inspiration (Plate 30), they will be seen to conform to the shape and limitation of their respective pleura. Each lung has a rounded apex, which extends into the root of the neck (Plate 27) two and a half centimetres, or about an inch, within the pleural 264 THE REGION OF THE THORAX. domes (page 262), and a concave base, which conforms to the arch of the diaphragm upon which it rests. They fit into the pleural sinuses when fully expanded, and reach downward posteriorly as far as the eleventh rib on each side, — the right lung in the axillary line being in relation to the ninth rib, and the left lung to the tenth rib. The right lung is thicker and shorter than the left, the concavity of its base being also higher, as it corresponds to the arch of the diaphragm over the liver. It is often notched on its mediastinal surface, presenting depressions foi the superior and inferior venae cavse. The left lung is excavated on its mediastinal surface for the reception of the heart, and its apex has an impression for the left subclavian artery. The apex of the left lung does not mount quite so high above the clavicle as does that of the right. The anterior edges of both lungs present characteristic differ- ences. That of the right lung is nearly straight or vertical, and that of the left is oval or oblique. The extent to which they approach each other depends upon the degree of their expansion. In forced inspiration, when the lungs are absolutely healthy, the anterior edges of the lungs meet over the root of the heart and the origin of the great vessels within the pericardium (Plate 30). The surfaces of the pleurae are thus brought into contact to the extent of several inches, between the lower border of the manubrium sterni and the junction of the cartilages of the fourth ribs with the sternum. At such times the anterior edge of the right lung is absolutely vertical and parallel with the median line of the chest, and the area of the heart which is uncovered by the left lung is limited to the lower third of the right ventricle. In ordinary tranquil breathing the anterior edges of the lungs do not come together (Plates 31 and 32). In a state of collapse both lungs shrink back into their recesses within the thoracic cavity (Plate 33). From careful observations made upon both the living and the dead body at different ages, it would seem to the author that only when healthy do the lungs meet in front over the root of the heart upon a prolonged and full inspiration. There is generally some interspace between them in the anterior mediastinum. The right lung comes forward more readily than does the left, even in moderate inspiration, so that the anterior edge THE REGION OF THE THORAX. 265 of the right lung approaches more nearly the middle line. The lower portion of the right lung also expands more readily below in relation to the diaphragm than does the lower portion of the left lung, whereas the converse appears to he true with regard to their apices. Not only does the left lung not come forward so readily, but its lower portion does so only upon prolonged inspiration, and thereby reaches the anterior limit of its pleural sac. When both lungs are normal and fully inflated in the well- developed adult male, in the erect position, the lower front edge of the right lung corresponds approximately to the oblique line of the interspace between the cartilages of the sixth and seventh ribs (Plate 27), while the lower front edge of the left lung is in relation to the lower border of the seventh rib, and extends but a little way beyond the sternal end of that rib (Plate 30). These limitations will be lessened by the breadth of a rib if the individual be placed in the recumbent position, and in the female or poorly-nourished youth they may be lessened still more, so that the anterior lower edges of the right and left lungs may reach respectively the lower borders of the fifth and sixth ribs, corresponding to the height which the arches of the diaphragm normally reach and hold relatively (page 322) to each other. It should be therefore under- stood that in respiration the upper portions and posterior surfaces of the lungs are at all times in close contiguity with their pleural sacs, and that the anterior medial and lower edges retire and advance according to the effort of expiration or inspiration and the healthy condition of the pleurae which allows their natural freedom of motion. It is very doubtful if the anterior lower edges of the lungs ever do completely fill their proper portions of the pleural cavities, and an adhesion existing anywhere be- tween the lung and its sac will influence the degree of motion of the lung. In forced expiration the lower edges of the lungs posteriorly do not ascend higher than the lower borders of the seventh ribs. A transverse section made across the root of the neck from the first dorsal vertebra to the top of the sternum (Plate 14, Fig. 1) will show that the apex of the right lung is larger than that of the left, and that they are both in this locality of oval form. A transverse section across the thorax from the eighth dorsal vertebra to the lower borders of the third ribs (Plate 41, Fig. 2) 34 PLATE 38. The posterior mediastinum and its contents, as seen on removal of the dorsal vertebrae (from the second to the ninth) with portions of their contiguous ribs. The lungs are expanded so as to show their proper relations posteriorly. 1. The body of the first dorsal vertebra. 2. The thoracic duct, winding across the oesophagus to enter the superior mediastinum. 3. The upper portion of the left lung. 4. The descending portion of the arch of the aorta, over- lapped above by the left lung. 5.- The vena azygos major, crossing to the right of the oesophagus. 6. The CEsophagus, distended. 7. The vena azygos minor, 8. The thoracic aorta. 9. The thoracic duct, after its entrance into the thorax from the aortic opening. 10. The upper surface of the left arch of the diaphragm. 11. The spine of the ninth dorsal vertebra. 12. The upper portion of the right lung. 13. The vena azygos major entering the superior vena cava. 14. The left auricle of the heart. 15. The lower portion of the right lung. 16. The base of the left ventricle of the heart. 17. The inferior vena cava. 18. The upper surface of the right arch of the diaphragm. Plate 38 Vol I I O'sspcte^, Photographed d''d Colored from Ndzure by George Mc Clellan, M D. Copyr^^hi, IS9I . by Gropsr Ma Clellan, M. Armslron^eCo lifh B THE REaiON OF THE THORAX. 267 shows that both lungs are here somewhat palm-shaped, with their bases toward the spine and their narrower portions toward the sternum. Each lung is divided into an ufper and a lower lobe by a great fissure which commences behind about seven and one-half centimetres, or three inches, from the apex, opposite the fourth dorsal vertebra on the right and the third on the left, and descends obliquely forward to the junction of the seventh rib with its cartilage on the right, and opposite the sternal end of the sixth rib on the left. There are, however, many alterations in the relative positions of the fissures, and their terminations cannot be foretold. There is generally a deep notch in the anterior edge of the left lung over the pericardium where it is in relation to the apex of the heart (Plate 30, No. 42), and occasionally the right lung is similarly notched about the cartilage of the fourth rib (Plate 29). The right lung is subdivided by a secondary fissure which commences about opposite the sixth rib, near its angle, and extends usually to the cartilage of the fourth rib and thus marks off" a middle lobe. The lower primary lobes of both lungs are the largest, and they chiefly constitute the posterior portions, whereas the anterior portions are mainly formed by the upper lobes. Occasionally the left lobe has a semblance of a secondary fissure, and occasionally also the secondary fissure in the right lung is undeveloped. The convex outer surfaces of the lungs are free and moulded to the interior of the thoracic walls, and the concave inner or mediastinal surfaces are connected to the heart and the trachea by the bronchial tubes, with their vessels, nerves, and lymphatics, and by the pulmonary arteries and the pulmonary veins. These structures collectively form the roots of the lungs, and are held together by areolar tissue, and supported below by reflections of the pleurae, called the ligamenta lata pulmonalia. The roots of the lungs are attached to the bottom of a deep cleft, the hilum pulmonale, which is situated a little nearer the posterior than the anterior surfaces and above the middle of each lung. If the thorax be opened from behind by removing the dorsal vertebrae and contiguous portions of their ribs (Plate 39), it will be seen that the vena azygos major arches over the root of the right lung and the aorta over the root of the left lung. Behind the right root are the posterior pulmonary plexus of the pneumo- 268 THE REGION OF THE THORAX. gastric nerve and the vena azygos (Plate 37), and behind the left are the descending aorta and the posterior pulmonary plexus of the pneumogas- tric nerve (Plate 36). In front of each root are the anterior pulmonary branch of the pneumogastric and the phrenic nerve. In front of the root of the right lung is also the superior vena cava (Plate 33). The trachea at the root of the neck, as previously described (page 236), passes deeply from the outer surface in front of the oesophagus to its bifurcation into the right and left bronchi within the superior mediastinum. The bifurcation is about on a level with the body of the fourth dorsal vertebra posteriorly, and opposite the second intercostal space anteriorly. Within the chest the trachea is crossed by the arch of the aorta, the deep cardiac nerves passing between them. The oesophagus projects a little to the left of the middle line at the root of the neck, and is closely con- nected by areolar tissue to the trachea, which is placed between the upper portions of the two pleurae. The recurrent laryngeal nerves from the pneumogastric nerves ascend on each side of the neck in the grooves between the trachea and the oesophagus (Plate 39). The bronchi vary in length, direction, and diameter. The" right bronchus is about two and a half centimetres, or an inch, in length, and, passing nearly horizontally, enters the right lung about opposite the body of the fifth dorsal vertebra. Its diameter is greater than that of the left bronchus, and, as the ridge of separation between the two bronchi at the bottom of the tracheal tube inclines to the left of the middle line, foreign bodies which may chance to fall down the trachea are more likely to pass into the right bronchus. The left bronchus is about five centimetres, or two inches, in length, and descends obliquely to enter the left lung opposite the sixth dorsal vertebra.. The left bronchus passes in front of the oesoj)hagus and thoracic duct and under the arch of the aorta (Plate 38). In struct- ure the bronchi resemble the trachea (page 236), the right having from six to eight rings and the left from nine to twelve. At the roots of the lungs the bronchi subdivide into two branches, the bronchial tubes, corresponding to the primary lobes of the lungs. The lower branch of the right bronchus sends off a small branch to the third lobe on that side. The right bronchus at the root of the right lung is behind the right pulmonary artery, and THE REGION OF THE THOEAX. 269 tlie left bronchus also holds the same relative position, being behind the corresponding pulmonary artery. On both sides the pulmonary veins are in front of the arteries (Plate 41, Fig. 1). "Within the lungs the bronchial tubes divide dichotomously into posterior and anterior branches, which again subdivide into lateral branches, and these diverge in all direc- tions throughout the organs until their termination in the lobules, where they are known as bronchioles. There is no communication between the bronchioles, so that if any obstruction occurs in one branch the air cannot reach the vesicles to which it naturally leads. The pulmonary and bronchial vessels, the lymphatics and nerves, all accompany the ramifications of the bronchial tubes, and are united to them by connective tissue, the arteries always being behind and the veins in front of the tubes. Within the structure of the lungs the tubes cease to have regular cartilaginous rings, circular muscular fibres with patches of cartilage here and there constituting the walls of the branches. They are lined throughout with the mucous membrane continued from the trachea, which is covered with columnar ciliated epithelium. Gradually all traces of cartilage disappear and the walls present irregular dilatations, which commence in pouches surrounding the ultimate tubules. These enlarge in diameter and end as sacculated passages, the infundibula, whose walls consist of blind pouches, the alveoli or air-vesicles. They are surrounded and connected everywhere with an elastic tissue, in which there are only slight traces of muscular tissue, and which is derived from the peculiar elastic sub-serous tissue closely investing the surfaces of the lungs beneath the pleura. Upon this elastic tissue the remarkable expansibility of the lungs depends. When the chest is opened the lungs collapse to about a third of their ordinary bulk (Plate 33), in consequence of their elasticity. This elastic tissue is prolonged from the surfaces into the inner structure of the organs, forming numerous angular spaces of various sizes about the alveoli, and called the pulmonary lobules. When the lungs are distended, the surface is everywhere marked by polygonal areas, which vary in size at different ages. These areas are mapped out into smaller ones, which are less distinct. They indicate the lobules, which are larger on the surface than in the interior of the lung. After air has once entered into the 270 THE REGION OF THE THORAX. lobules it cannot be entirely pressed out, owing to tlieir spongy texture, and any portion of the lung will therefore float on water, but it will sink immediately if inspiration has not taken place, and owing to this property such a demonstration is frequently made use of as a test in medico-legal investigations. It should be remembered that a portion of lung-tissue from which the air has been dispelled by pneumonic exudation will also sink in water. When pressed between the fingers, the escape of air from the luHg-tissue produces crepitation. When the air-vesicles are ruptured, the air escapes into the interlobular tissue, producing pulmonary emphysema, and if there is infiltration of serum into this tissue it is called oedema of the lung. If the lung-tissue is torn, a reddish frothy liquid is exuded, consisting of mucus, air, and blood commingled. The terminal branches of the pulmonary artery form nets of capillary vessels which accompany the bronchioles in their distribution to the alveoli, where they are covered by epithelium on both surfaces and project into the air-vesicles. The pulmonary capillaries are very crowded in relation to the air-vesicles, and the plexus surrounding one air-vesicle is arranged in a single layer and has no communication with that of another vesicle. There are only the delicate wall of the vesicle and the walls of the capil- lary vessels between the blood and the air, so that the purification of the blood takes jjlace through the absorption of the oxygen and the elimination of carbonic acid and watery vapors. The blood circulating through the cap- illary plexuses is returned by the pulmonary veins, which are very minute at first, but gradually coalesce so that they form branches of increasing calibre and size, which freely anastomose, and, following somewhat the course of the arteries, eventually terminate at the root of each lung in two main trunks which convey the oxygenated blood to the left auricle of the heart. There are no valves in any of the pulmonary veins. Besides the pulmonary system of vessels there are the nutrient vessels of the lungs, de- rived from the small bronchial arteries. On the right side there is usually one bronchial artery, which arises either from the first aortic intercostal or from the aorta in common with the left bronchial artery. On the left side there are usually two bronchial arteries, both arising from the aorta. They enter at the roots of the lungs posterior to the bronchi, and are distributed THE REaiON OF THE THOBAX. 271 to the walls of the tubules, the larger pulmonary vessels and the pulmonary lymphatic glands, and the inflections of the elastic interlobular tissue. The bronchial veins mostly empty on the right side into the vena azygos major, and on the left into the superior intercostal vein, although some of them empty their blood into the corresponding pulmonary veins. The pulmonary lymphatic vessels are very numerous, and are arranged in superficial and deep sets, the former forming plexuses over the surface (sub-pleural lymphatics) and throughout the interlobular tissue, communi- cating with the cavity of the pleura by stomata, and the latter beginning in the mucous lining of the bronchial tubes and accompanying the vessels. The deep lymphatic vessels terminate in \hQ pulmonary lymphatic glands, which are situated along the walls of the smaller bronchial tubes and in the angles of their divisions. There are about forty in the right lung and thirty in the left. The efferent vessels from these pulmonary glands join with the superficial lymphatic vessels and end in the bronchial glands which are clustered about the roots of the lungs and the lower portion of the bronchi and trachea. The efferent vessels from the bronchial glands com- municate with the mediastinal glands, and are generally blackened by the deposition of carbonaceous matter. The right pulmonary lymphatics pass through the intermediation of the mediastinal glands to the right lymphatic duct, and the left pulmonary lymphatics join the thoracic duct. The pulmonary nerves are derived from the j)neumogastric and sympa- thetic nerves on each side, which form the anterior and posterior pulmo- nary plexuses in front of and behind the roots of the lungs. They enter the lungs with the bronchial tubes and accompany their ramifications. The pericardium, or heart-sac (Plate 34, and Plate 26, Fig. 1), is a dense fibrous pouch which encloses the heart and the portions of the great vessels which enter into and issue from its base. It is broadest below in relation to the diaphragm (page 320), where it is intimately adherent to the middle leaflet of the tendon about the opening for the inferior vena cava and more loosely connected to the muscular part on the left side. Above it passes into the superior mediastinum, enveloping the great vessels and becoming continuous with their sheaths. In this relation it also blends with the downward prolongations of the deep cervical fascia PLATE 39. View of the thoracic organs from behind, the dorsal vertebras (from the second to the tenth) with portions of their contiguous ribs removed. The lungs are displaced to show the relations of the heart. 1. The body of the first dorsal vertebra. 2. The left subclavian artery. 3. The upper (cut) part of the thoracic duct ascending to empty into the left subclavian vein, 4. The left common carotid artery. 6. The left recurrent laryngeal nerve. 6. The left innominate vein. 7. The arch of the aorta. 8. The left phrenic nerve. 9. The left lung pushed aside and forward to show the po- sition of apex of the heart resting on the diaphragm. 10. The thoracic aorta, with origins of the intercostal ar- teries. 11. The apex of the left ventricle of the heart within the pericardium. 12. The vena azygos minor. 13. Thelower{nut)endofthe thoracic duct coming through the aortic opening of the diaphragm. 14. The upper surface of the diaphragm on the left side. 15. The innominate artery, bifurcating into the right com- mon carotid and subclavian arteries. 16. The right internal mammary artery. 17. The vena cava superior. 18. The upper (cut) end of the oesophagus. 19. The right pneumogastric nerve. 20. The right phrenic nerve. 21. The vena azygos major, emptying into the superior vena cava. 22. The bifurcation of the trachea into the right and left bronchi. 23. The right lung pushed aside and forward to show the relation of the left auricle of the heart and the arch of the diaphragm on the right side. 24. The left (or posterior) auricle of the heart. 25. The position of the inferior vena cava. 26. The upper surface of the diaphragm on the right side. 27. The lower (cut) end of the oesophagus. 28. The spine of the tenth dorsal vertebra. Plate39 Vol I Copvr,gl,l, ISSI . by CenRBE Mc C,-U.I.AN, M D D'sspcte:] F/:oto^rtin/ir'd {ind Colored from Mciturt c> Georgf. Mc. d ellan, A^ D. TEE REGION OF THE THORAX. 273 (page 195), whicli are continued as dense bands (the suspensory ligaments) upon each side to their attachment at the diapliragm. These connections of the pericardium are of great interest, for if the entire diaphragm descends in respiration it must draw with it the heart-sac and therefore exert more or less strain upon the vessels at the base of the heart. The author inclines to the belief that the central portion or tendon of the diaphragm does not descend, although the lateral muscular portions do. On one occasion, after the excision of the sixth, seventh, and eighth ribs on the right side, he was able to examine the upper surface of the diaphragm during the forced efforts of inspiration under ether, and on another, after the evacuation of the contents of an enormous abscess involving the left lobe of the liver, he could easily introduce his hand into the abscess-cavity and detect the lateral upheaving of the diaphragm and the rapid pulsa- tions of the heart. In the latter case, during the straining of the patient in the act of vomiting it was observed that the diaphragm descended and ascended with spasmodic contractions, but only upon the sides, there being apparently little if any change in the relations of its central tendon. There can be hardly any doubt that the direct connections of the pericardium below with the central tendon of the diaphragm and with the expansions of the deep cervical fascia above play an important role in maintaining the position of the arch of the aorta, and thus admitting of sudden changes of position without injurious interference with the circu- lation of the blood at its outset from the heart. The slight descent of the larynx noticeable on deep inspiration is probably due to the expansion of the chest walls and the consequent lateral traction exerted upon the bronchi by the distended lungs. The pleurse overlap the pericardium in front, the right more so than the left (Plate 26, Fig. 1), and the phrenic nerves descend between them upon each side. Posteriorly the oesophagus is in close relation with that part of the pericardium which encloses the left auricle of the heart. After death the pericardium usually appears to be considerably larger than the heart, but this is due to the empty condition of the left side of the heart. In the healthy state, when the heart is distended, during life, it nearly fills the jjericardium, except at the lower part on the left side of the diaphragm, where the sac covers 35 274 TSE REGION OF THE THORAX. the apex of the heart and is more or less loose. Although the pericardium is not ordinarily distensible, it may be made in the adult to hold about ten ounces of fluid, and in pericarditis with effusion the accumulation of serous fluid within the sac sometimes reaches a pint or more, which may be drawn off" by tapping through the fourth or fifth interspace two cen- timetres, or about three-quarters of an inch, from either border of the sternum, so as to avoid the internal mammary vessels. The pericardium ordinarily contains several drachms of a clear straw-colored fluid. The nutrient arteries to the pericardium are derived from the internal mammary, bronchial, and oesoj^hageal arteries, and its veins mostly return their blood to the vena azygos. Its nerves are supplied by the phrenic nerves on both sides. If the pericardium is opened in front (Plate 35) the heart will be exposed glistening with the moist surface of a serous tissue which is reflected over it and the vessels at its base and also lines the fibrous sac. This serous tissue forms a shut sac, and is composed of a parietal layer in contact with the fibrous jiericardium and a visceral layer in contact with the heart and interposed between the vessels so as to form a series of pouches. The invagination of the serous layer over the vessels is not always to the same extent, but there are usually seven tubular sheaths thus formed. There is a common reflection around the aorta and pulmonary artery, completely ensheathing them. The superior vena cava is also covered by the serous layer, except where it crosses behind the pul- monary artery. The inferior vena cava is covered only in front as it enters the right auricle directly after passing through the diaphragm. The left pulmonary veins are almost surrounded, and the right are only partially covered. The reflection of the serous layer is very irregular. The pouch which extends upward from the inferior vena cava on the right to the posterior surface of the left auricle is called the great oblique sinus. There are other, smaller pouches, — i.e., between the inferior vena cava and the inferior right pulmonary vein, between the pulmonary veins, one on each side, between the upper right jralmonary vein and the superior vena cava, and one between the superior vena cava and the aorta, which, pass- ing under the aorta and pulmonary artery, reaches the left side over the left auricle. This last, from its direction, is called the transverse sinus. THE BEGIOJSr OF THE THORAX. 275 Besides these there is a fold between the left pulmonary artery and left pulmonary vein, of crescentic shape, two and a half centimetres, or about an inch, in depth, and two centimetres, or three-quarters of an inch, in length, which is the vestigial fold, and is the remains of the left superior vena cava of early foetal life. These serous reflections enable the heart and the vessels at its base to maintain their freedom of action. That portion of the visceral layer of the pericardiac serous tissue which is closely connected with the intermuscular tissue of the heart-structure is distinguished as the epicardium. There are upon the surface many stomata which open from the plexus of lymphatic vessels, especially along the auricular margins. This layer also contains the nutrient vessels and nerves, which are usually associated with more or less fat along the grooves and deeper parts of this tissue. Even in health the amount of fat deposited upon the heart is often considerable ; but this must not be confounded with the more serious condition of fatty degeneration of the muscular tissue. The heart, as it appears upon oj)ening the pericardium (Plate 35), is conical in form, and its surfaces are generally convex, with the exceiDtion of that portion which rests upon the pericardium where it is attached to the central tendon of the diaphragm, and which is flattened. It is situated obliquely as regards the middle line of the chest. Its base, to which the great vessels are attached, is directed upward and backward to the right side, where it is held firmly in relation to the spine between the fifth and ninth dorsal (thoracic) vertebrae by means of the dense cervico- thoracic fascia, which blends with the pericardium at the roots of the great vessels. Elsewhere the heart is free within the pericardium, and its apex is directed downward and forward to the left side, where during life it generally beats in relation to the interval between the fifth and sixth costal cartilages. The anterior surface of the heart consists mainly of the right auricle and right ventricle, which are brought into view when the pericardium is opened in front. The termination of the superior vena cava is also thus exposed as it enters the right auricle above, at the side of which is the ascending portion of the aorta curving upward and backward over the pulmonary artery, the root of which is over- lapped by the appendix of the left auricle. Below the latter are the 276 THE REGION OF THE THORAX. branches of the left coronary artery passing toward the apex of the heart in the groove between the left and right ventricles. On the right side the right coronary artery issues from beneath the appendix of the right auricle, which overlaps the root of the aorta. The apex is formed by the left ventricle, which projects a little beyond the right, so that normally its beat is felt against the chest wall. The posterior surface of the heart is formed chiefly by the left auricle and the left ventricle (Plate 43, Fig. 3). As the relative position of the heart to the walls of the thorax is chiefly of value with reference to the normal location of the cardiac valves, it is thought best here to refer to the anatomy of the heart removed from the body (Plate 43), in order that a clearer idea may be obtained of the topographical survey of its relations in situ. The exterior of the heart presents more or less defined grooves which indicate the division of its interior into the four compartments called the auricles and ventricles. The auriculo-veritricular groove passes obliquely around the heart between the auricles and the ventricles. The interauricular groove separates the two auricles, and the interventricular groove separates the two ventricles, the anterior portion of the latter beginning under the left auricular appendix and ending to the right of the apex. The nutrient vessels, nerves, and lymphatics to the heart are chiefly lodged in these grooves embedded in fatty tissue beneath the epicardium, as already mentioned (page 275). The right coronary artery arises from the aorta upon the right side just after it issues from the heart-structure, and, passing between the pulmonary artery and the right auricle in the auriculo-ventricular groove, distributes branches to the contiguous vessels and portions of the right auricle and ventricle. The left coronary artery arises from the back of the aorta, a little higher than the right, and, passing between the pulmonary artery and the left auricle in the auriculo-ventricular groove, gives off several large branches which occupy the interventricular grooves and anastomose freely with the branches of the right coronary artery upon the outer surface. "Within the substance of the organ the minute divisions of the coronary arteries terminate in capillary plexuses which empty into comparatively large venous radicles. It is an interesting fact that the THE REGION OF THE THOBAX. 277 origin of both coronary arteries is above the free borders of the aortic semilunar valves, the right being from the anterior sinus of Valsalva and the left from the left posterior sinus, so that there is a steady passage of the blood through them. The coronary veins receive their blood from the cardiac veins, which accompany the arteries and are provided with single valves where they are joined by their tributaries. They all end in the coronary sinus, which is two and a half centimetres, or about an inch, in length, situated at the back part of the auriculo-ventricular groove, and opens into the floor of the right auricle between the opening of the inferior vena cava and the auriculo-ventricular orifice. At its entrance into the auricle it is guarded by the coronary valve. The shape of the heart varies during life, according to its dilatation or diastole, and its contraction or systole, but its vertical measurement is not altered by its action. The dimensions of the heart naturally vary with the age, sex, and general development of the individual. The average meas- urement of the heart of a well-developed adult male is twelve and a half centimetres, or about five inches, in length, from the base to the apex, eight and three-quarter centimetres, or three and a half inches, across the base, and six and a half centimetres, or about two and a half inches, in thick- ness, between the anterior and posterior surfaces. As a rule, the dimen- sions of the heart increase up to the age of fifty, and subsequently gradually diminish. The weight is generally about ten ounces in the male, and eight in the female, but depends upon the size and general condition of the body. The right border {margo acutus) is sharp and directed obliquely downward, while the left border (margo obtusus) is thick and rounded and directed obliquely upward. From the front of the right auricle a small pouch pro- jects about the root of the aorta, which is called, from its resemblance to the ear of a setter dog, the appendix auriculce, and from the upper side of the left auricle a similar appendix extends over the root of the pulmonary artery. When the adult heart is opened so as to display the interior of its cavities (Plate 43, Figs. 2 and 4) it appears to be a double hollow mus- cular organ, so constructed that each half, separated from the other by a septum, fulfils the function of a pump, for the propulsion of the blood in its circulation. The right half of the heart propels the venous blood to the 278 THE REGION OF THE THOBAX. lungs, the left propels the arterial blood throughout the body. Each half consists of two cavities, the auricle and the ventricle, communicating by an opening, the auricuh-venti'icidar, which is peculiarly guarded by valves. The auricles are the receptacles of the blood, and are provided with com- paratively thin fleshy walls, which are always slightly thicker in the left than in the right. The ventricles, on the other hand, are composed of stout muscular walls adapted to their purpose of forcing outward the blood received from the auricles, their thickness being proportioned to the effort required of them. The left is therefore naturally thicker and stronger, as it distributes the arterial blood throughout the system, while the right sends the venous blood to the lungs. The right auricle consists of a main cavity, the atrium or sinus venosus, out of which extends the pouch called the appendix. When the anterior wall is removed tlie interior is exposed smooth and glistening, because it is lined with a delicate serous membrane, the endocardium, which is continuous with the serous coat of the vessels opening into the auricle, and through the opening into the ventricle below with the inner lining of the pulmonary artery. The opening of the supe- rior vena cava is in the upper and anterior part of the auricle, about opposite the right auriculo-ventricular opening, so that the current of venous blood which it conveys from the upper part of the body is directed immediately to the ventricle. The orifice of the superior vena cava is the only large cardiac opening without a valve. The opening of the inferior vena cava is in the lowest part of the auricle, and, owing to the slight curve which the vessel takes after passing through the dia- phragm, the venous blood which it returns from the lower part of the body is directed toward the oval depression, the fossa ovalis, in the auric- ular septum. The fossa ovalis indicates the position of the foramen ovale, which during foetal life allowed the blood from the inferior vena cava to pass through into the left auricle. At that period this course of the blood was greatly assisted by the presence of the Eustachian valve, which is situated at the right margin of the opening of the inferior vena cava and extends to the front of the annulus ovalis, the prominent border surrounding the fossa. In the adult this valve appears as a thin crescentic fold of the endocardium, and often it has dwindled into a THE REGION OF THE THOBAX. 279 mere rudimentary band, simply indicating its former position. The floor of the fossa ovalis is the thinnest part of the septum between the auricles. Between the remains of the Eustachian valve and the auriculo- ventricular opening is the entrance of the coronary sinus, which is quite large and is guarded by a duplicature of the endocardium, called the valve of Thebesius. Besides the sinus there are a variable number of little openings on the posterior wall of the auricle, called the foramina Thebesii, which are the minute apertures of little veins coming from the heart-substance. Some of these are impervious, but one, situated on the right of the septal wall, is constant, and known as the vena Galeni cordis. Interposed between the openings for the superior and inferior venae cavse there is a variable elevation termed the tubercle of Lower, which prob- ably aids in the direction of the blood from the superior cava toward the auriculo-ventricular opening in embryonic life. Within the auricular appendix, and to some degree in the lower part of the atrium, there are parallel elevations of the muscular tissue covered with the endocardium, called, on account of their resemblance to the teeth of a comb, musculi pectinati. The right auriculo-ventricular opening is of oval form, and large enough to admit three fingers. It is guarded by the tricuspid valve, which is named from the usual tripartition of the fibrous tissue of which it is composed, and invested by the endocardium ; but this arrangement is often less pronounced than it is generally described as being. When the anterior wall is removed from the right ventricle, the objects within its cavity are exposed (Plate 43, Fig. 2). At the upper part there is a smooth passage leading to the opening of the pulmonary artery, called the infundibulum, or conus arteriosus. From the walls of the ventricle, which are every- where thicker than those of the auricle, project bands of muscular tissue, the columnce carnece, of various character and arrangement. Some are short and thick, others are long and narrow. They are either mere ridges projecting from the walls, or constitute little bridges, having both ends attached and being free in the middle. There is usually a band extending from the ventricular septum to the anterior wall, called the PLATE 40. The normal position and relations of the thoracic aorta, seen from behind, the lungs being removed to show their roots. The body of the first dorsal vertebra. The left subclavian artery. The left innominate vein. The left internal mammary artery. The left common carotid artery. The arch of the aorta. The left first rib. The left phrenic nerve. The vertebral border of the scapula. The left recurrent laryngeal nerve winding upward round the aorta. The left second rib, near its cari,ilage. The left third rib. The root of the left lung. The left fourth rib.; The left fifth rib. The apex of the left ventricle of the heart (within the pericardium). The upper surface of the diaphragm on the left side. The position of the aortic opening in the diaphragm. The right subclavian artery. 20. The innominate artery. 21. The upper (cut) end of the oesophagus. 22. The right internal mammary artery. 23. The superior vena cava. 24. The right recurrent laryngeal nerve. 25. The trachea bifurcating into the right and left bron- chi. 26. The right second rib. 27. The right pneumogastric nerve. 28. The root of the right lung. 29. The right third rib. 30. The left auricle of the heart. 31. The right fourth rib. 32. The thoracic aorta, with the roots of the intercostal arteries. 33. The inferior vena cava. 34. The right fifth rib. 35. The upper surface of the diaphragm on the right side. 36. The lower (cut) end of the cesophagus, where it passes through the diaphragm. 37. The spine of the tenth dorsal vertebra. P^^l■e40 Vol I righl, 1831 . b^eeomE Mc Clilllan, M. D. D'ssected, Phoiu^rdphf^d and Loforec froir, Nature «> GeoR'jfr Mr Clfllah. M D. Armslrong eCo Lith Boston I THE BEGION OF THE TSOEAX. 281 moderator, or a number of reticular fascicles taking its place, "which pre- vents the complete reflection of the anterior wall. The most important of the columnse carneee are those which are called the musculi papillares. There are three of these, usually well formed, in the right ventricle, corresponding in number to the flaps of the tricuspid valve. They are attached by one end to the walls of the cavity, and at the other terminate in the fine tendinous cords, the chordce tendinece, which regulate the action of the tricuspid valve. The two largest of the papillary muscles arise from the anterior wall of the ventricle, and the smallest from the septal wall. Occasionally accessory fasciculi are found interposed between the regular muscles and blending with them. The auriculo-ventricular opening is surrounded by a ring of fibrous tissue which constitutes the base of the valve. The flaps of the valve are thinnest at their contiguous margins where they receive the chordae tendinese. Not unfrequently the edges of the flaps are jagged and irregular, and sometimes in the notches between them there are little projecting nodules. The Jlaps are designated according to their relative position as right and left anterior and posterior. The left anterior flap is the largest and freest, while the posterior is the shortest and least movable and is placed toward the septum. The chordae tendineae which are attached to the adjacent margins of the right and left anterior flaps and to the notch between them are furnished by the anterior papil- lary muscle ; those to the adjacent margins of the right anterior and posterior flaps and to the intervening notch come from the posterior papillary muscle; and those to the adjacent margins of the left anterior and posterior flaps and to the intervening notch come from the smaller papillary muscle, which is derived from the septal wall and often aug- mented by independent chordae which spring from the septum without any papillary muscle. The mode of attachment of the chordae tendineae to the flaps is of peculiar interest, as they serve to hold together the flaps of the valve during the systole of the ventricle and thus prevent the blood from regurgitating into the auricle. They are all fastened to the ventricular surface of the valve, and they severally separate into branches which go respectively to the base, middle, and free margins 36 282 THE REGION OF TSE THORAX. of the adjacent borders of the flaps as above described. Further- more, the component fibres of the cords interlace witli one another in the fibrous tissue of the valve. In the empty state of the ventricle the flaps appear hanging downward from the auriculo-ventricular opening, but experiment has shown that when the ventricle is full of fluid and is made to contract the fluid catches in the margin of the valve and presses the flaps upward and together, while the chordae tendinese act Like little guy-ropes and prevent the flaps from turning upward into the auricle. Their proper adjustment and tension are brought about by the action of the papillary muscles, for without them they would be naturally slackened by the contraction of the walls of the ventricle. At the upper part of the right ventricle the infundibulum leads into the common pulmonary artery, the mouth of which is guarded by three semi- lunar valves, of which one is situated anteriorly to the left and two are placed posteriorly to the right and left. At the upper and posterior surface of each valve the wall of the artery is dilated in a pouch, the pulmonary sinus {of Valsalva). The valves are formed of fibrous tissue continuous with the fibrous ring surrounding the opening, similar to the construction of the base of the auriculo-ventricular valve, and covered with a duplica- ture of the endocardium. The free margins of the valves are directed upward toward the lumen of the artery, and are each provided with a cres- centic fibrous border, the lunula, in the middle of which there is a little blunt nodule of fibro-cartilage, called the corpus Arantii. The semilunar valves are readily forced upward by the blood during the ventricular systole, but when the ventricle relaxes the blood in the artery backs up against the valves, and, being received into the sinuses, exerts pressure upon the lunulse of the valves, so as to bring them together, their closure being completed by the apposition of the nodules. The left auricle is smaller than the right, but, like it, consists of a cavity, the sinus, and the auricular appendix. When the posterior wall is removed (Plate 43, Fig. 4) the interior of the sinus is seen to be covered with the endocardium, which is continuous with the lining membrane of all the openings leading in and out of the auricle, and through them with the internal coats of the vessels. Upon the posterior wall of the auricle are the THE REGION OF THE THORAX. 283 openings of the pulmonary veins, usually four in number, two on the left and two on the right side, which return the oxygenated blood from the lungs. Sometimes the left pulmonary veins oi^en by one orifice, more rarely by three. They are not guarded by valves. Upon the inter- auricular septum is a depression which indicates the position of the foramen ovale of foetal life, which before birth admitted the venous blood brought by the inferior vena cava to the right auricle into the left auricle. The musculi pectinati of the left auricle are fewer and smaller than in the right auricle, and are confined to the lower and back part of the cavity. The left auriculo-ventricular opening is of oval shape and a little smaller than the right, and is placed at the lower and anterior part of the auricle. It is guarded by the bicuspid or mitral valve, which has two flaps, one anterior and to the right, and one posterior and to the left, with little nodules projecting at their notches, called the nodi valvules, mitralis. The right flap is the larger. The interior of the left ventricle presents a close resem- blance to the right. Its walls are very thick, especially in their upper portion, where they are also broadest, but they gradually diminish toward the apex. The columnce carnece, are smaller, more reticulated, and more numerous than in the right ventricle. Two large, variably-constituted papillary muscles project from among the columns at the bottom of the cavity, the anterior from the left wall and the posterior from the right. They terminate in chordae tendinece, which are attached to the flaps of the mitral valve. The construction of the mitral valve corresponds to that of the tricuspid valve, but it is thicker and stronger in all its com- ponent parts. The ring of fibrous tissue surrounding the auriculo-ven- tricular opening, the flaps themselves, and the chordse tendinese are all stronger. The latter are similarly attached to the adjacent margins of the flaps, the posterior papillary muscle supplying the adjacent margins on the right, and the anterior papillary muscle furnishing the adjacent margins on the left. They are both reinforced by additional cords from the contiguous portions of the walls with or without muscular origin. The action of the mitral valve is apparently the same as that of the tricuspid, — i.e., to prevent regurgitation of the blood into the auricle during the systole of the ventricle. From the upper and back part of the left ventricle a 284 THE BEGION OF THE THORAX. smootli surface leads to the opening into the aorta, which resembles that of the pulmonary artery, having three semilunar valves, with dilatations of the aortic wall {sinuses of Valsalva) behind them. The aortic opening is placed in the groove between the two auricles, and it is very close to the left auriculo-ventricular opening, being separated from it only by the larger anterior flap of the mitral valve. In framework and construction the aortic semilunar valves differ from those guarding the pulmonary artery only in being proportionately stronger, to adapt them to the greater work they have to accomplish, consistently with the greater strength of the left ventricle, in sending the arterial blood throughout the general system. The structure of the heart consists of an intricate arrangement of layers of muscular fibres supported upon a framework of fibrous tissue. The latter is disposed in rings about the two auriculo-ventricular, the aortic, and the pulmonary openings, as described in their proper relations. These rings, besides forming the bases for the attachment of the valves, receive at their external circumference the muscular fibres of the walls of the different cavities. The strongest part of the fibrous slceleton is in the inter- space between the aortic and the two auriculo-ventricular openings. This is triangular, and in some of the lower animals is substituted by a bony nodule, called the os cordis. The muscular fibres of the heart are peculiar for the comparatively small amount of connective tissue between the component fascicles, which are of the striped variety and very closely associated. They are arranged in layers, whose striae pass transversely and longitudinally. The fibres of the auricles are distinct from those of the ventricles. They consist of a superficial layer, which generally runs across the base of the heart, including both auricles, and a deep layer, composed of fibres surrounding the auricular appendix and the entrances of the ven^e cavse on the right auricle, and the auricular appendix and the entrances of the pulmonary veins on the left. The superficial fibres are most marked on the anterior surface, and send a few fasciculi inward to the interauric- ular septum. The deep fibres also blend with the muscular fibres of the ventricles in front and behind the auriculo-ventricular fibrous rings. The layers of fibres composing the walls of the ventricles are very complicated, THE REaiON OF THE THOHAX. 285 and can be satisfactorily studied only after hardening by prolonged boiling, which dissolves the connective tissue. These fibres are independent of the auricles, and are much thicker. They consist of various layers, which for the most part commence from the rings of the fibrous framework above and descend obliquely to the apex of the heart, twisting upon one another in such a manner as to produce what is called the vortex, and ascend in the interior of the walls back again to the fibrous rings, sending off in their courses fibres which constitute the columnse carnese and musculi papillares. The most superficial layer of the ventricular fibres in front of the heart descends obliquely across from right to left, many of those from the right at the anterior interventricular groove turning inward and intersect- ing with the fibres in the ventricular septum which arise from the deeper layers. Behind the heart the fibres descend from left to right, and do not enter at the posterior interventricular groove. The deeper layers of fibres which compose the chief bulk of the ventricular walls are arranged in strata, whose fascicles vary in the degree of their obliquity, diminishing from without inward, and interlacing everywhere, so that they present fibres which have been described as making annular or figure-of-eight loops. Some of the deeper layers of fibres do not appear to have any connection with the fibrous rings. The most valuable inference to be drawn from the laborious efforts of investigators, who have attempted to unravel the complications of these muscular fibres, is that the musculi papillares are integral parts of the walls from which they spring, so that they contract simultaneously with them. The nerves of the heart are derived from the pneumogastric and from its recurrent branch, and from the three cervical sympathetic ganglia on both sides (page 219), which form the great cardiac plexus in front of and behind the arch of the aorta. This consists of numerous, minute, and delicate nerves, which interlace in every direction with one another, and are known, from their relative position, as the superficial and deep cardiac plexuses (Plates 36 and 37). In relation to the concavity of the aortic arch there is sometimes found a small ganglion (the cardiac ganglion of Wrisberg). Both the superficial and deep cardiac nerves form frequent connections with each other, and thus establish the pulmonary plexuses PLATE 41. Figure 1. The thorax of a young female, with the second, third, fourth, fifth, and sixth ribs remOTed on the left side, and the left lung drawn aside to show the relations of the root of the lung and the apex of the heart to the diaphragm. 1. The manubrium of the sternum. 2. The cartilage of the left second rib. 3. The left internal mammary artery with its two com- panion veins. 4. The cartilage of the left third rib. 5. The cartilage of the left fourth rib. 6. The cartilage of the left fifth rib. 7. The left first rib. 8. The upper lobe of the left lung. 9. The root of the left lung. 10. The left phrenic nerve. 11. The coronary artery. 12. The lower lobe of the left lung. 13. The apex of the heart. 14. The relation of the phrenic nerve to the apex of the heart. 15. The diaphragm. 16. The left seventh rib. 17. The diaphragm seen between the left eighth and ninth ribs. Figure 2. Transverse section through the thorax of an adult male, on a level with the lower borders of the third ribs anteriorly and through the body of the eighth dorsal vertebra posteriorly, seen from below. 1. Section through the gladiolus of the sternum. 2. The right internal mammary vessels. 3. The anterior mediastinum. 4. Section through the right third rib. 5. The superior lobe of the right lung. 6. The right ventricle of the heart. 7. The right auricle of the heart. 8. Section through the right fourth rib. 9. The right phrenic nerve. 10. The middle lobe of the right lung. 11. Section through the right fifth rib. 12. The oesophagus. 13. The vena azygos major. 14. The inferior lobe of the right lung. 15. Section through the right sixth rib. 16. Section through the right seventh rib. 17. The right eighth rib. 18. Spine of the eighth thoracic vertebra. 19. The left internal mammary vessels. 20. The anterior margin of the superior lobe of the left lung. 21. The superior lobe of the left lung. 22. The left ventricle of the heart. 23. The left phrenic nerve. 24. Section through the left fourth rib. 25. Section through the left bronchi. 26. The left pneumogastric nerve. 27. The thoracic duct. 28. The descending aorta. 29. The Inferior lobe of the left lung. 30. The body of the eighth thoracic vertebra. 31. The spinal canal with section of the spinal cord. 32. The eighth thoracic vertebra. 33. The left eighth rib. 34. Section through the dorsal mtiscles. Pia+e 4 Voi I Fi| I Fip2 Dissected, Photogrdph/'d and Colored from Nature ny GeoeoE Mc. Cleu.au, M D. Copyright, 183/ . by Geopge Mc Clellan, M D. ArmitrongsCn Lith Soalo THE REaiON OF THE THORAX. 287 in relation to the roots of the lungs, and the coronary plexuses. The branches of the latter respectively accompany the ramifications of the coronary arteries both without and within the substance of the heart. It is said that there are minute intra-cardiac ganglia, which possibly preside over the functional contractions of the heart. The lymphatic vessels of the heart, which also occupy for the most part the interventricular grooves with the vessels and nerves, convey their lymph to the glands situated between the aorta and the trachea, and thence pass to the right lymphatic duct and the thoracic duct on either side of the root of the neck. The superior vena cava (Plate 35) is formed by the right and left innominate veins (page 222), which unite opposite the first intercostal space on the right of the border of the sternum, and descends, with a slight inclination backward,, to the right auricle, which it enters at its upper and anterior part, opposite the third right costal cartilage. It is six and a quarter centimetres, or about two and a half inches, in length, in the adult, and the lower portion is covered with the pericardium (Plate 34). Above it is covered on the right side by the pleura, between which and the great vein the phrenic nerve passes downward. The superior vena cava is without valves, and receives, besides some pericardiac and medi- astinal veins, the vena azygos major, which curves downward over the right bronchus above the pericardium (Plate 37, No. 80). The aorta (Plates 33, 35, 36, 40, 42, and 43) arises opposite the lower border of the third costal cartilage, at the upper and posterior part of the left ventricle, near the centre of the heart. Its normal course is very singular, and its shape much resembles that of an old-time shepherd's crook. At its commencement it is expanded into a bulbous enlargement, in con- sequence of the dilatations (the sinuses of Valsalva) opposite the semilunar valves at its cardiac orifice, and proceeds upward about five centimetres, or two inches, and a little to the right of the middle line, as high as the lower border of the second right costal cartilage. This portion is called the ascending (or ventral) aorta, and is enclosed in the fibrous layer of the pericardium. It is in very close relation with the under surface of the sternum, the lower margin of the thymus gland and the right pleural sac 288 THE REGION OF THE THORAX. being interposed between them. The bulbous enlargement is covered by the pulmonary artery on the left, being included with it in a common sheath of the serous layer of the pericardium, and by the appendix of the right auricle on the right (Plate 35) . The ascending aorta encroaches some- what upon the superior vena cava, and is in relation posteriorly to the right pulmonary vessels and the root of the right lung. The coronary arteries to the heart are given off from the origin of the aorta, as already described (page 276). Near the termination of the ascending portion the aorta usually presents a dilatation, the sinus maximus, which changes the lumen of the vessel in that situation from circular to oval. It is worthy of especial note that the first or ascending part of the aorta is closely covered only by the thin serous layer of the pericardium, which renders an aneu- rism in this locality very dangerous, in consequence of the easy, rapid distention of the coats of the vessel and the slight hinderance to the escape of the blood into the pericardium. From the lower border of the second right costal cartilage the aorta passes backward, at first a little upward and to the left, toward the body of the second dorsal vertebra, and then, curving across the trachea just above its bifurcation, it turns downward at its left side as far as the lower border of the fourth dorsal (thoracic) vertebra. This portion is called the transverse aorta, or arch of the aorta. Its relations are very important and interesting. On the left it is overlapped by the left pleura, beneath which the left phrenic nerve passes, and it is in close proximity to the left pneumogastric nerve, which here gives off the left recurrent laryn- geal nerve (Plates 36 and 40), which curves upward under the aorta (page 186). On the right it is in contact with the right pleura, and posteriorly it is very near the trachea, oesophagus, and thoracic duct. From the upper surface of the arch of the aorta the three normal branches arise close together, — i.e., the innominate artery (page 221), the left common carotid artery (page 223), and the left subclavian artery (page 229). Their origins are crossed by the left innominate vein (Plate 35). The orifices of the innominate and the left common carotid, when examined from within the aorta, are separated by merely a sharp edge. The cardiac nerves from the sympathetic and pneumogastric nerves also pass over the arch to their THE REGION OF THE THORAX. 289 distribution on the heart (page 219). This portion of the aorta measures four and three-quarter centimetres, or a Httle less than two inches, in length. The highest point to which its convex surface reaches in a well- formed adult is usually about two and a half centimetres, or an inch, below the upper border of the sternum, and its concavity corresponds with the ridge between the manubrium and the gladiolus ; but these points cannot be definitely relied upon, as various factors may tend to raise or lower the arch, and it is subject to modifications owing to interference with its proper development. There are various irregularities of the great vessels which probably occur more frequently than has been noted, and may be ascribed to either an ax'rest or a persistence of one or other of the primitive aortic arches of early embryonic life, out of the ordinary order of the human develop- ment. Such modifications usually result in transposition of the innomi- nate to the left side or some change in the point of origin of the carotid or the subclavian artery upon one or both sides. Anomalies of the heart and the aorta are extremely rare. It may not be inappropriate to mention in this connection such a case which the author met with in the body of a man aged twenty-seven years, whose death was caused by phthisis. The preparation (Plate 26, Fig. 4) exhibits no arch of the aorta, but independent origins of both right and left carotid and subclavian arteries from the top of the descending thoracic aorta, with the heart placed vertically, the position in which it was found within the chest. This disposition of the aortic branches is somewhat analogous to that ordina- rily observed in the horse and in the ruminating animals, but it does not appear to have been hitherto recorded as found in man. The heart was found to consist of a single auricle and a single ventricle. The common pulmonary artery (Plate 35), which conveys all the venous blood from the right side of the heart, to be aerated in the lungs, commences at the infundibulum in the upper part of the right ventricle (page 279). This vessel is nearly five centimetres, or two inches, in length, and, as has been already stated, is contained within the sheath of the serous layer of the pericardium, which is common to it and the ascending portion of the aorta. It stands out in front of all the great 37 290 THE REGION OF THE THORAX. cardiac vessels when the heart-sac is opened between the right and left auricular appendages (Plates 33 and 35). Its direction is upward and backward to the concavity of the arch of the aorta, where, in front of the bifurcation of the trachea and on a level with the sixth dorsal vertebra, it divides into the right and left pulmonary branches, which, passing through the pericardium on each side, enter the roots of the respective lungs. The right branch is larger and longer than the left, and is separated from the arch of the aorta by the deep cardiac nerves of that side, and as it enters the root of the right lung it is in front of and below the right bronchus (page 268). The left branch passes in front of the descending aorta and enters the root of the left lung in front of and above the left bronchus (page 269). Where the left branch leaves the pericardium there is a short fibrous cord extending backward to the left end of the arch of the aorta, which is the remains of the ductus arteriosus, the canal by which, in foetal life, the blood from the pulmonary artery passed directly into the aorta (page 304). The pulmonary veins, which return the blood to the left auricle of the heart after it has been re-oxygenated and transformed into arterial blood in the lungs, commence in a net-work of capillary vessels upon the walls of the air-vesicles, where they are con- tinuous with the ultimate ramifications of the pulmonary artery (page 270). They also receive part of the blood distributed by the bronchial veins in the substance of the lungs. They unite at first into single trunks corresponding to each lobule, and these in turn unite to form a trunk for each lobe, so that the right lung has three and the left lung two main efferent vein-trunks. Usually the two upper trunks of the right lung join at its root, although they sometimes remain independent of each other. The right pulmonary veins are somewhat longer than the left, and they all terminate in the posterior wall of the left auricle (page 283), the orifices of those coming from the left lung being closer together and on a lower level than those from the right. The upper one of the right and the lower one of the left are respectively larger (eighteen millimetres, or three-quarters of an inch, in diameter) than their companion veins. Both pairs in the roots of the lungs (page 268) occupy a position in front of the pulmonary arteries, and as they pass THE REGION OF THE THORAX. 291 horizontally toward the left auricle they pierce the pericardium, the serous layer of which is reflected over their anterior surface. There are no valves in the pulmonary veins. As the heart is the central organ of the vascular system, in which, by means of the great vessels at its base, the arteries originate and the veins terminate, the general anatomy of these two classes of the blood- vessels may be here properly considered. The arteries are comparatively firm, elastic tubes, which commence at the heart in two great trunks, the aorta (page 287) and the pulmonary artery (page 289), the former distributing the arterial blood from the left ventricle throughout the general system, and the latter conveying the venous blood from the right ventricle to the lungs, as described on page 306. The systemic arteries arise from the main branches of the aorta, which are directed to the head and the extremities and to the various organs of the body. The arteries generally pursue the shortest, most direct, and most protected course from their origins to the locality of their distri- bution, and this is particularly noticeable in the extremities, where they are contiguous to the bones, in the lines of flexure, so that they are less exposed to injury and less likely to be compressed by muscular action. The arteries (except within the tissues of the brain and of the bones) are provided with a special investment of the areolar tissue of the parts in which they are contained, constituting their sheaths, and in particularly exposed situations the superficial arteries are usually further protected by tendinous expansions. They also continue of uniform size until they give off a branch, when they become, as a rule, somewhat smaller in calibre. It has been estimated, however, that the combined capacity of the branches is greater than that of their original trunks, and in consequence there is naturally a diminution in the velocity of the blood-current as it proceeds farther and farther from its source. In certain localities, where the parts are freely movable, the arteries are tortuous, so that they readily accom- modate themselves to changes in position and the movements of the soft parts without being subjected to strain. The facial, lingual, and vertebral arteries are examples. Arteries branch in various ways. If they divide 292 THE MEGION OF THE THOBAX. into two equal branches, they diverge at equal angles from the line of the trunk. If the branches are unequal, the trunk is deflected from its straight course to the side opjDOsite that to which the branch is distributed, varying in degree according to the size of the branch. In fact, the branches may be given off" at any angle, but they usually proceed at an acute angle from their origin. In their course the smaller arteries fre- quently communicate with one another, constituting what is called their inosculation or anastomosis. This arrangement serves to prevent an inter- ruption in the flow of the blood in case of pressure upon one or other of the branches, and is of great value in the establishment of the collateral circulation after the ligation of any one of the principal vessels. In the brain, the retina, and the kidneys the ultimate branches of the arteries are called terminal or end arteries, because they do not anas- tomose with one another, and consequently if a supplying artery is blocked by an embolus the area of its distribution is completely destroyed by necrosis. During life the arteries possess a considerable degree of elasticity and contractility, as is often witnessed in the remarkable manner in which they escape injury in penetrating and incised wounds. In the healthy state the walls of the arteries are capable of withstanding a considerable degree of intravascular tension, and their firmness is conspicuous, for when they are cut across they do not collapse, as the veins do. They appear empty after death, and on this account were originally supposed to contain air. The elasticity of the arteries diminishes with age, and in consequence they often become spirally twisted and tortuous in localities where they are loosely embedded in the tissues. The size of the arteries is proportionate to the amount of blood required by the physiological actions of the part which they supply. The larger arteries (eight millimetres, or three-eighths of an inch, in diameter) are attended by a single large vein ; the medium- sized arteries (six millimetres, or one-quarter of an inch, in diameter) have one or two accompanying veins, and the smaller (three millimetres, or one-eighth of an inch, in diameter) usually two veins. The venoB comites of the arteries are generally included in their areolar sheath, together with the nerve-cord which passes to the same area of distribution as the artery. THE REGION OF THE THORAX. 293 The course of the arteries in the extremities is generally along the inter- muscular septa, or in the spaces between the superficial and deep muscles, so that a twig issuing among the surface-tissues, if traced backward, serves as a guide to the position of the main vessel. By this means, for example, the anterior and posterior tibial arteries within the deeper part of their course may be easily found ; and there is no safer way of reacliing the external iliac artery than by following the deep epigastric, or of reaching the axillary artery than by following the acromial. Owing to some localized arrest of development, occasioning dilatations of anastomotic branches and attended by contraction or obliteration of the main trunk, there are fre- quent variations in the arteries, and it often happens that a vessel which is usually small may become abnormally enlarged, so that it is liable to be mistaken for the main artery. It should be remembered also that a small branch arising from a large vessel will always bleed freely, and to an extent out of proportion to its size, so that its hemorrhage requires to be promptly arrested. The structure of the walls of the arteries consists of three chief layers of various formation which are intimately associated with one another. They are called the external, middle, and internal coats, or the tunicse adventitia, media, and intima. The external coat, or adventitia, on which the strength and firmness of the arteries mainly depend, is comjoosed of layers of condensed fibro-connective tissue derived from the surrounding- cellular tissue and arranged in interlacing bundles, between the meshes of which are lymph-spaces and connective-tissue corpuscles. In the larger vessels, and in the arteries which are loosely connected with their sur- roundings, as on the face and the mesentery, longitudinal muscular fibres are blended with the other elements of the outer coat, which in the latter case not only renders the mesenteric arteries thicker but enables them to offer support to the parts which they supply, the jejunum and the ileum, and to withstand the constant traction to which they are subjected in the changes of position of the intestines during life. The middle coat, or media, is the thickest portion of the wall of an artery. It consists princi- pally of unstriped muscular fibres (and therefore is sometimes also called the muscular coat), with a variable quantity of elastic connective-tissue fibres. PLATE 42. Dissection of the vascular system in a child eight months old, showing the principal arteries and veins In their proper relations and positions. The right temporal artery. The right facial artery. Branch of the right lingual artery. The body of the hyoid bone. The superior, or descending, thyroid artery. The right internal jugular vein. The right common carotid artery. The right pneumogastric nerve. The median nerve of the right arm. The thyroid body. The sternal end of the right clavicle. The axillary artery. The trachea, at the root of the neck. The right subclavian vein, branching from the right innominate vein. The right innominate vein. The right subscapular vessels and nerves. The superior vena cava. The root of the right lung, showing the pulmonary ves- 19. The right auricle of the heart. 20. The anterior coronary artery and veins. 21. The under surface of the diaphragm, showing the right phrenic arteries. 22. The inferior vena cava. 23. The right kidney, opened, showing the renal vessels. 24. The right spermatic vein, emptying into the inferior vena cava. 25. The superior mesenteric artery, drawn to the right side. 26. The right ureter. 27. The right common iliac artery. 28. The right spermatic artery. 29. The right internal iliac artery. 30. The inferior mesenteric artery. 31. The right circumflex iliac artery. 32. The right anterior crural nerve. 33. The right femoral vessels, passing under Poupart's ligament. 34. The right spermatic cord. 35. The sartorius muscle. 86. The femoral artery, passing mto Hunter's canal. 37. The gracilis muscle. The insertion of the sartorius, gracilis, and semitendi- nosus muscles. The left temporal artery. The left facial artery. The left lingual artery. The left stern o-mastoid muscle. The left pneumogastric nerve. The left internal jugular vein. The left common carotid artery. The left superior thyroid artery. The median nerve and brachial artery of the left arm. The axillary artery, surrounded by the cords of the brachial plexus. The sternal end of the left clavicle. The left carotid artery. The left innominate vein. The left subclavian artery. The left subscapular vessels and nerves. The arch of the aorta. The root of the left lung, showing the pulmonary vessels. The posterior coronary artery. The apex of the heart. The left phrenic artery, on under surface of the dia- phragm. The abdominal aorta. The cceliac axis. The left kidney, opened to show the renal vessels. The left spermatic vein, emptying into the renal vein. The left ureter. The left spermatic artery. The left internal iliac artery. The inferior mesenteric artery. The sigmoid flexure of the colon, drawn aside. The superior htemorrhoidal, or rectal, artery. The left circumflex iliac artery. The bladder. The left anterior crural nerve. The left femoral vessels. The left spermatic cord. The left adductor longus muscle. The left sartorius muscle. The left gracilis muscle. The anastomotica magna artery. N. B.— The preparation from which the photograph for this plate was taken is remarkable because it Is an actual dem9nstration of the circulation of the blood. The injection, a solution of wax in ether, was introduced into the right common carotid artery beneath the lobe of the thyroid body, and, having passed through the capillaries, filled the veins. There is some probability that the foramen ovale had remained unclosed, which would have contributed to complete the venous injection. The ductus arteriosus was obliterated. Vol I Mc Clcllah, M D. ArmslrongRCo Lilh Boslofi. THE REGION OF THE THORAX. 295 They are arranged for the most part circularly, except in the smallest arterioles, where they are spiral. The proportion of the elastic tissue apparently diminishes with the size of the artery, while the converse is true with regard to the muscular tissue, so that the smaller vessels possess greater contractility relatively to the larger. Connective tissue also enters into the construction of this coat in the larger vessels, and many of the latter are provided with an external elastic lamina (Henle). The muscle- fibres in the middle coat of the large arteries are irregular and both oblique and longitudinal, while in the small arteries they are more uniform and exhibit under the microscope longitudinal striae each containing an elliptical nucleus. The internal coat, or intima, is very delicate and thin, and com- posed of an intermixture of elastic and fibrous tissue arranged in several layers. The amount of elastic tissue also varies with the size of the vessel, being in the smallest merely a single layer. The internal surface of the intima consists of the transparent membrane, the endangium, which closely resembles the serous membranes in character and is continuous with the endocardium of the heart. The endangium has been demonstrated to be constituted of two layers, called the endotheli-mn and the membrana propria. The former consists of a single stratum of transparent fusiform cells having a central nucleus and arranged parallel to the course of the vessel. The latter consists of interlacing connective-tissue fibres con- taining branching corpuscles. The amount of muscle and elastic tissue in the walls of certain arteries is variable irrespective of their calibre, as it has been proved that the carotid and axillary arteries are provided with more elastic tissue in their middle coats than the femoral, which has a greater quantity of muscle-fibre. Upon the application of a ligature to an artery in the healthy state the internal and middle coats are completely broken, so that they retract, while the external coat is puckered up. The arteries are without valves. The veins possess much thinner walls and are generally larger in calibre than the arteries. They return the venous blood from the system by means of the superior and inferior vense cavae (pages 287 and 306), and from the walls of the heart by the coronary sinus (page 277), to the right 296 THE REGION OF THE THORAX. auricle, and the arterial blood from the lungs by the pulmonary veins (page 290) to the left auricle. The systemic veins are more numerous than the arteries, and their combined capacity is greater. They originate in radicles, which receive the blood from the capillaries everywhere in the tissues, and are generally arranged in plexuses at their commencement. From these plexuses branches are given off which unite into trunks, which are constantly increased iu size by being joined by tributaries in their course toward the heart. They consist of two chief divisions, the super- ficial and the deep veins. The former are placed between the layers of the superficial fascia beneath the skin, and the latter accompany the arteries, being known as the vence comites, or satellites. The largest arteries and their largest branches are usually accompanied by a single vein, but the medium-sized and smaller arteries have two veins, which are enclosed in their common sheaths, as previously described (page 292). In certain regions, as in the brain, the spinal canal, and the liver, the veins do not accompany the arteries ; in others, as in the head and face, they pursue a more direct course than the arteries. The veins communicate or inoscu- late much more freely than the arteries do, even among those of large size. This is conspicuous with the superficial veins, which form a net- work over the whole body. The intercommunication of the superficial veins with the dee]) is esj^ecially noticeable at the flexures of the joints, where the motions would otherwise be liable to offer impediment to the flow of the blood. This is also markedly the case in the neck and within the cranium, where any obstruction to the venous system would be followed by a dangerous stasis. The veins of the dura mater within the bead are called the sinuses, which are formed by the splitting of that membrane and lined by epithelium (page 18). In certain localities where veins are contained within masses of areolar tissue and enveloped in a dense fibrous membrane, they may anastomose, but as their walls are imperfect they allow their blood to escape into the surrounding trabeculse or spaces and thus form erectile tissue, as in the corpora cavernosa penis. The veins offer very many anomalies, but there is always a noticeable fact regarding them, — i.e., that where a vein is unusually small there is a compensating enlarge- THE REGION OF THE THORAX. 297 ment in an adjoining or neighboring vein. Such a variation is commonly noticed between the external and anterior jugular veins (page 192). The structure of the walls of the Deins is composed, like that of the arteries, of three coats, but taken together they are less uniform and thinner than the arteries, although they are more intimately connected. They possess con- siderable strength, however, and the walls of the superficial veins are generally thicker than the deeper ones. It is very difficult to separate the external and middle coats. The former consists chiefly of a compact layer of fibro-connective tissue blended with meshes of elastic fibres. The latter is mostly made up of irregular circular bands of unstriped muscular tissue, also held together in meshes of elastic fibres. The amount of fibro-connective and muscular tissue varies in the veins of different parts, and the two tissues hold variable proportions to each other in the outer and middle coats. In the great jugular and innomi- nate veins at the root of the neck there is a deficiency of muscular tissue. In the Haversian canals of the bones the walls of the veins con- sist only of fibrous tissue lined with endothelium. The internal coat, or intima, of the veins is very similar to that of the arteries, consisting of a very delicate elastic membrane, having upon its internal surface an endothelial lining and a substratum of striated con- nective tissue, often containing muscle-cells. One of the most important peculiarities of the veins is the development of valves from their internal coats in certain localities, which prevent regurgitation of the blood and therefore assist its passage toward the heart. They usually occur in pairs, placed opposite each other in the course of a vein, but are single at the orifices of the branches. The valves are not found in all veins, but they are most numerous in the superficial veins of the extremities, especially the lower, where they often appear like knots through the skin in varicosed conditions. They consist of crescent-shaped flaps composed of the inner coat, like little pockets. They are attached with their convex border to the sides of the vein and their free concave margin directed in the proper course of the blood, so that if this is interfered with by pressure and a reflux occurs the pockets become filled and close the lumen of the vein by their distention. The valves are not always equally developed, 38 298 THE REGION OF THE THORAX. as on several occasions the author has found it possible to throw an injecting material into the radicles of the hand or foot through the main venous channel of the limb : in two instances a solution of wax in ether was thus made to traverse the capillaries and fill the arteries. The relative position which the main arterial and venous trunks bear to one another throughout the body follows the rule already mentioned (page 222), that above the diaphragm the veins are superficial to the arteries, while below the diaphragm the arteries are superficial to he veins, with the single exception of the renal veins. The capillaries are the fine hair-like vessels which serve as the secret communications by which the blood passes continually from the arteries into the veins throughout the tissues of the various organs of the body. They are so minute that they can be seen only with the microscope, and so fine that it is necessary to rupture several of them to get a drop of blood. Although generally very numerous, they vary in number in the different tissues according to their requirements for nutrition, being most abundant in the tissues or organs where the greatest degree of vital activity exists. They are not found in the cartilages, ejjithelium, or epidermis. Ordinarily they are arranged in a system of net-works, which vary in the size of their meshes in different localities. They are very close in the lungs, in the gray substance of the brain and spinal cord, in the mucous membranes generally, and in the muscular and adipose tissues. In the dermis and choroid coat of the eye the net-work of capillaries is exceedingly fine and close. In the fasciae, however, and the aponeuroses, tendons, and ligaments, the capillary meshes are wider, the vessels them- selves being fewer. They are variably arranged to conform with the structure of the tissues which they occupy. This is noticeable especially in the lungs in relation to the lobules, and in the papillse of the skin or the villi throughout the intestinal canal. In their simplest form the capillaries may be considered as composed only of the delicate endothelial lining of the arteries or veins with which they are continuous. They are both elastic and contractile, so that they differ in calibre under different conditions. Under the influence of chemical reagents their walls have been shown to have a cellular construction, with the cells arranged longitudinally to the THE REGION OF THE THORAX. 299 axis of the vessel. The cells contain an oval nucleus, and they are held together by what is termed "intercellular cement," which is marked at intervals by fine dots. During the state of inflammation the capillaries become distended, and the intercellular cement in the localities of these dots yields, occasioning small openings in the walls, the stomata, through which the white blood-cori^uscles show a tendency to escape into the inter- spaces among the tissues. This is an important characteristic of these vessels, as by its means the elements of nutrition in the processes of growth, repair, and performance of function are imbibed and eliminated. When the capillaries in the web of a frog's foot or in the mesentery of a snake are examined under the microscope, they appear as transparent tubes contain- ing a clear fluid {liquor sanguinis), which moves more slowly along the walls of the vessels, being retarded by friction, than in the centre, where the corpuscles are arranged in a column and are swept onward with greater rapidity. It follows from the resistance offered by the increased wall-area of the capillaries, as well as by the minuteness of their lumina, that the blood circulates through the capillaries much more slowly than it does in the large arteries. In some tissues the blood-vessels, before they terminate in capillaries, divide into peculiar tufts of minute anastomosing vessels, such as are seen in the glomeruli or Malpighian corpuscles of the kidney. In others the separate arterial stems and venous radicles form a net-work before they break up into capillaries, and thus constitute the different forms of rete mirabile, such as occur in the choroid tela and velum interpositum of the brain. The walls of all the larger arteries and veins are provided with arteries and veins of their own, the vasa vasorum, which are derived from and terminate respectively in the neighboring vessels. It is evident to the naked eye that such vessels are furnished to the external coats of the large vessels, and it is asserted that the microscope has revealed that there are capillary vessels in relation also to the middle coat. Lymphatic vessels appear, as already stated, in and around the external coats, and about the largest vessels they establish plexuses. The arteries and veins are also supplied with nerves, the vaso-motor nerves, which form plexuses in the muscular or middle coats, more especially of the arteries. They have been shown to preside over the 300 THE REGION OF THE THORAX. contractility and dilatability of the vessels, and explain many of the physiological phenomena, as in pallor or blushing, and the changes in local temperature, owing to their influence upon the degree of blood- pressure. The vaso-motor nerves, although apparently derived as fibres from the sympathetic ganglia in the various regions of the body, have been demonstrated by experiment, in many instances, to arise originally from the nerves of the spinal cord. The so-called inhibitory or repressing effect manifested in the physiological action of certain drugs is probably ascribable to them. These nerves are now considered as consisting of two distinct sets of fibres, which from their opposing influences are called vaso- constrictor and vaso-dilator nerves. The marvellous rapidity with which the secretion and excretion of certain organs are performed, and the regu- lation of the distribution of the blood by which the various physiological processes of digestion are determined, can be understood only by taking into account the controlling influence of this special division of the intri- cate nerves, composed of fibres from the sympathetic and fibres from the spinal nerves combined, and probably presided over by some special centre in the floor of the fourth ventricle of the brain. The blood is the viscid, red-colored, ojoaque, alkaline fluid which circulates throughout the vascular system, and the function of which is to furnish the nutritive material to all the tissues and organs of the body, and to eliminate from them many of the elements of waste which are capable of being revivified and used over again. The color of the blood varies according to the conditions under which it is seen, and in the different sets of vessels in which it flows, being bright red in the arteries, and bluish-black or purple in the veins. These changes of color are due to the amount of oxygen which is in combination with the hcemoglobin, the coloring-matter of the blood. The blood has a saline taste and a peculiar odor. Its material is in a continual state of change and motion, the degree of the latter being regulated by the influence of the vaso-motor nerves and the calibre of the vessels in which it is contained. The blood consists essentially of cellular elements, the corpuscles, and an intercellular substance, the plasma. The corpuscles are of two kinds, the white, or leucocytes, which are variable in number in different parts THE REGION OF THE THORAX. 301 and in different conditions of the individual, and the red corpuscles, which in health always greatly outnumber the white and give to the blood its characteristic color. The leucocytes are colorless, nucleated cells, which under the microscope show amoeboid motions. The red corpuscles are uniform, homogeneous, flattened circular disks, concave upon both surfaces and without nuclei. There are also in the blood a quantity of minute oval disks, called blood-plates, and numberless granules, hoematoblasts. The plasma is a clear, colorless, alkaline fluid, which is capable of trans- udation through the walls of the capillary vessels into the surrounding cellular spaces of the connective tissue. These spaces are now called lymph-paths, because the lymph is formed within them as the result of the combination of unused plasma and waste tissue-cells. The lymphatic system of vessels is described with the lacteals, in connection with the anatomy of the intestinal canal, in Vol. 11. When fresh blood is examined at the temperature of the body, the white corpuscles are seen to change slowly their shape and position, re- sembling in many respects the microscopic animalcule the amoeba. This power of amoeboid movement enables the white corpuscles under certain influences to pass out with the plasma into the cellular spaces ; and hence these corpuscles are also known as the migratory cells. The white corpuscles are in fact derived from the lymph, and are supposed to be the source of the red corpuscles; but this has not yet been satisfactorily established. The red corpuscles in fresh blood exhibit a remarkable tendency to pile themselves together like little rouleaux of coin. The ■plasma consists chiefly of a permanent liquid, the serum, which is a straw- colored fluid, and of certain elements called flbrin-factors, fibrinogen and fibrino-plastin. When the blood is withdrawn from the body and at rest, there is apparently a ferment formed from the breaking down of some of the white corpuscles, which occasions the union of the fibrin- factors into a clot, or coagulum. The serum is an albuminous solution containing salts, fatty matters, sugar, etc., and readily coagulable by heat. The blood also contains in solution oxygen, carbonic acid, and nitrogen gases. The hcemoglobin, or coloring-matter, belongs to the red corpus- cles, and has a remarkable affinity for oxygen, which it absorbs when PLATE 43. Figure 1. The front view of the heart removed from the body, with the roots of the great vessels arising from the aorta. 1. The trachea. 2. The ima thyroidea artery. 3. The right common carotid artery. 4. The right subclavian artery. 5. The innominate artery. 6. The superior vena cava. 7. The ascending portion of the arch of the aorta. 8. The right coronary artery. 9. The right auricle. 10. The appendix of the right auricle. 11. The left subclavian artery. 12. The left common carotid artery. 13. The transverse portion of the arch of the aorta. 14. The descending portion of the arch of the aorta. 15. The common pulmonary artery. 16. The appendix of the left auricle. 17. The left coronary artery. 18. The right ventricle. 19. The left ventricle. 20. The apex of the heart. Figure 2. Section of the right auricle and ventricle to show the interior of their cavities. 1. The ima thyroidea artery. 2. The right common carotid artery. 3. The right subclavian artery. 4. The innominate artery. 5. The ascending portion of the arch of the aorta. 6. The superior vena cava. 7. The foramina Thebesii. 8. The openmg of the vein of Galen. 9. The annulus ovaUs. 10. The fossa ovalis. 11. The tubercle of Lower. 12. The Eustachian valve. 15. The orifice of the coronary vein. 14. The musculi pectinati. 15. The inferior vena cava. 16. The right common carotid artery. 17. The right subclavian artery. 18. The transverse portion of the arch of the aorta. 19. The descending portion of the arch of the aorta. 20. The appendix of the left auricle. 21. The pulmonary artery laid open. 22. The semilunar valves. 23. The cut edge of the right ventricle. 24. The anterior musculus papillaris. 25. A bristle passed through the right auriculo-ventricular opening. 26. The chordae tendlne;e. 27. Tlie inter-ventricular septum. 28. The columnaj carnese. 29. The apex of the heart. Figure 3. The posterior view of the heart in relation to the thoracic aorta. 1. The left common carotid artery. 2. The left subclavian artery. 3. The descending portion of the arch of the aorta. 4. The pulmonary artery. 6. The appendix of the left auricle. 6. The posterior coronary artery. 7. The thoracic aorta. 8. The apex of the heart. 9. The right common carotid artery. 10. The right subclavian artery. 11. The transverse portion of the arch of the aorta. 12. The superior vena cava. 13. The dilatation situated at the entrance of the inferior vena cava into the right auricle. 14. The inferior vena cava. Figure 4. The posterior walls of the l^t auricle and ventricle removed to show the interior of their cavities. 1. The aorta. 2. The pulmonary artery. 3. The musculi pectinati. 4. The appendix of the right auricle. 5. The anterior flap of the mitral valve. 6. The left coronary artery. 7. A needle passed through the aortic opening. 8. The apex of the heart. 9. The left pulmonary veins. 10. The right pulmonary veins. 11. Openings of the pulmonary veins in the wall of the left auricle. 12. The septum. 13. A bristle passed through the left auriculo-ventricular opening. 14. The appendix of the left auricle. 15. The posterior ilap of the mitral valves. 16. The musculus papillaris. 17. The columnae carneae. N. B.— The specimen from which these four plates were taken was the heart of an adult male, perfectly healthy and normal, excepting the little ima thyroidea artery, which arises from the innominate, as seen in Figures 1 and 2. Plate -1 3 Vol I F I '■■ Fig 3 Fip4 Copyright, ISSLbi' GeoKSE Mc Cleuan, M. D. />^3se!:tc^, P.hoto^rdphsd d"J Colored from Hfiwra '^v George Mc. CLEUi^N, MP. ArmslrongtCo Lrth Boslon THE REGION OF THE THORAX. 303 brought into relation with the air-cells of the pulmonary lobules by endosmosis. The fcetal heart, and the circulation of the blood before birth. — In the early stages of the fcetal formation the heart occupies nearly the whole of the thoracic cavity, and, comparatively speaking, is much larger than it is subsequent to birth. The auricular portion exceeds the ventricular, and the right auricle is more capacious than the left, the right ventricle being also smaller than its fellow. The organ is placed vertically within the thorax in its early stages. Just before birth, how- ever, these peculiarities disappear, and the ventricular portion becomes the larger, the left having the thicker walls, and the whole organ rapidly approaches its normal condition for life. The internal structure of the foetal heart is different from that of the adult chiefly in having an oval opening {foramen ovale) between the auricles, which allows a commu- nication from side to side, and in the large size of the Eustachian valve (page 278), which directs the blood from the inferior vena cava through the foramen ovale. The latter generally becomes closed within the first week or ten days after birth, but may remain open longer, and in some instances has been found to be slightly pervious at a great age. The Eustachian valve speedily dwindles after the establishment of the func- tion of the lungs and the proper circulation of the blood. Contemporary with these structural alterations changes occur in the great vessels which are requisite for the independent circulation of the blood. The pulmo- nary artery of the foetus, after leaving the right ventricle, gives off the right pulmonary branch, and then divides into two other branches, the first of which is as large as the pulmonary artery itself, about twelve milli- metres, or half an inch, in length, and directly joins the aorta at the termi- nation of its arch (page 290), while the other goes to the left lung. The connecting branch between the pulmonary artery and the aorta is named the ductus arteriosus. It is really the continuation of the pulmonary artery. The fostal circulation (Plate 26, Fig. 2) consists of the entrance of the arterial blood from the placenta into the body of the embryo at the umbilicus, by means of the umbilical vein, which ascends to the under surface of the liver. 304 THE REGION OF THE THORAX. Within this organ the greater part of the blood first communicates with the branches of the portal vein and with the hepatic veins, and thence passes to the inferior vena cava, but a portion of the blood conveyed by the umbilical vein is conducted by a small vessel directly to the upper part of the inferior vena cava, without passing through the substance of the liver: this vessel is called the ductus venosus (Plate 26, Fig. 2, No. 5). The inferior vena cava empties all its blood into the right auricle, whence it is directed by the Eustachian valve through the foramen ovale into the left auricle. From the left auricle it passes through the left auriculo-ventricular opening into the left ventricle, and thence by means of the aorta it is distributed chiefly to the head, neck, and upper ex- tremities. The more immediate supply of pure blood to these parts accounts for their greater proportionate development at birth. The im- pure blood from the upper part of the body is returned into the superior vena cava, and by it to the right auricle, from which it passes through the right auriculo-ventricular opening into the right ventricle. From the latter it issues by the pulmonary artery, and is chiefly conveyed by its continua- tion, the ductus arteriosus (Plate 26, Fig. 2, No. 13), into the upper portion of the descending aorta, where it mixes probably with some of the blood from the left ventricle passing through the ai'cli of the aorta. From the descending aorta the blood passes through the abdominal aorta into the iliac arteries. The external iliac arteries carry part of this blood to the lower extremities, but most of that in the internal iliac arteries is curiously returned to the placenta by means of the hypogastric arteries, which are the continuations of the superior vesical branches of the internal iliac arteries (Plate 26, Fig. 2, Nos. 22 and 24). They pass out at the um- bilicus, where, under the name of the icmbilical arteries, they twine round the umbilical vein in the substance of the cord, and return their impure blood to the placenta to be re-oxygenated. The umbilical vein and the ductus venosus become empty at birth, contract, and are ultimately con- verted into fibrous cords which occupy the fissure of the ductus venosus of the liver and become its round ligament. They are usually obliterated about the fifth day after birth. The ductus arteriosus and the hypogastric arteries also contract after birth, and become closed, the former usually THE REGION OF THE THORAX. 305 ■within the first ten days, and the latter within the first three or four days. The remains of tlie ductus arteriosus constitute the Ugamentum arieriosum, which is attached to the concavity of the aorta at tlie left end of the arch. The bands resulting from the obliteration of the hypogastric arteries form the lateral false ligaments of the bladder. The lungs previous to hirth are quite solid, and are packed into the back parts of the recesses on each side of the thorax. They receive only a slight amount of blood by their proper branches of the pulmonary artery, and return it to the left auricle by the pulmonary veins. The changes in the heart and vascular system, upon which depends the difierentiation of the circulation of the blood before and after birth, are all gradual and commensurate with the processes of development. They are almost completed by the establishment of the function of the lungs when respiration occurs and the connection with the placenta is severed. At birth, the first inspiratory effort aj)pears to be due to the stimulus of the atmosphere upon the surface nerves, which is immediately imparted to the pneumogastric and phrenic nerves, in consequence of which the phenomena of respiration ensue. The first expansion of the lungs is attended with the passage of blood through the pulmonary veins into the left auricle, which exerts a considerable degree of pressure upon the septal valve, so as to bring it in contact with the margin of the foramen ovale, and thus the blood is directed through the left auriculo-ventricular opening into the left ventricle. Coincident with this is the diminution of the tension between the auricles, owing to the arrest of the incoming blood from the umbilical vein, so that there is little obstacle to the blood from the inferior vena cava joining that from the superior vena cava in its passage through the right auriculo-ventricular opening into the right ventricle. The expansion of the lungs in inspiration induces the suction of the blood from the right ventricle into the pulmonary artery and from the left ventricle into the aorta. The passage of the blood through the ductus arteriosus ceases with the determination of the pulmonary circula- tion and the mechanical influence exerted upon the vessels at the root of the heart through their connections with the deep cervical fascia. The circulation of the blood after birth, when the organs have 39 306 THE REGION OF THE THORAX. attained their full development, consists in the reception of all the venous blood returned from the body through the venae cavse into the right auricle and its passage into the right ventricle, whence it is pro- pelled through the right and left branches of the pulmonary artery into the lungs. Here the blood is subjected to the purifying influence of the air within the lobules (page 269), and then returned by the pulmonary veins to the left auricle. This constitutes the pulmonary circulation. The pro- pulsion of the arterial blood from the left ventricle by means of the aorta to be distributed throughout the body, and its return by the capillaries into the veins which conduct it to the right auricle, constitute the systemic circulation. The latter, in reality, consists of numerous small circulations everywhere, each of which is made up of supplying arteries, intervening capillaries, and draining veins. In its passage to and from the heart the blood is propelled in a rhythmic current in consequence of the peculiar elastic and muscular contraction of the walls of the ventricles. As it is forced through the openings between the cavities or at the orifices of the vessels leading out of them, every impulse is followed by the closure of the various valves which normally prevent the regurgitation of the blood, and thus characteristic sounds are produced. The heart-sounds in health consist of a long sound {liib), succeeded by a short one {diip), which is immediately followed by a pause equal in duration to the second sound; and then the long and short sounds are repeated, and so on. The first sound is caused chiefly by the closing of the auriculo-ventricular valves, with the accompanying rush of the blood from the ventricles in consequence of their systole or contraction. This is synchronous with the beat of the apex against the chest wall. The second sound is produced by the abrupt closure of the semilunar valves which follows upon the emptying of the ventricles at the close of their contraction, and by the pressure of the blood upon them, which, after it has been driven into the pulmonary artery and the aorta, is forced into the sinuses of Valsalva in its endeavor to return. The degree of the pressure upon the semilunar valves, which is proportionate to the volume of the blood in the great vessels, causes the distinctness with which the second sound is heard, and accounts for what is called its accentuation. THE REGION OF THE THORAX. 307 Both, the right and left ventricles contract and dilate in unison, as both the right and left auricles also do. The arterial pulse is produced by, and coincident with, the ventricular contraction, as may be ascertained upon auscultation and feeling the pulse in any one of the superficial arteries at the same time. In consequence of this the second sound, which is produced by the simultaneous closing of the pulmonary and aortic semilunar valves, may be usually heard with the stethoscope placed over the carotid arteries at the root of the neck, as it is propagated in the blood-current from their origins. If a murmur is detected during the ventricular systole it is probably due to regurgitation of the blood from the pulmonary artery or the aorta, or to some obstruction at one of the auriculo-ventricular openings. If in con- nection with this there is absence of the second sound over the carotids, aortic regurgitation may be inferred. The prolongation of the first or second sounds, called their reduplication, is due to the want of harmonious closure of the flaps of the respective valves producing them. When both the auricle and the ventricle upon one side become dilated from any cause, great tension is exerted upon the fibrous ring to which the base of the auriculo-ventricular valve is attached, and it is rendered "incompetent." The tricuspid valve is peculiarly constructed so that regurgitation may take place through it whenever the right ventricle is in any way embar- rassed, and the third flap of this valve has on this account been compared to a "safety arrangement," as it provides this means of relief from the strain that would otherwise be exerted upon the pulmonary capillaries. Disease of the tricuspid valve is rare, probably on account of this anatomical provision, but when it allows of regurgitation of the venous blood back into the right auricle it is often associated with a pulse in the jugular veins. This is more especially noticeable in the right jugular vein, as the reflux blood passes more readily into the right innominate vein. What is called the respiratory pulse is often observable in the superficial cervical veins, even in health, after rapid exercise, as in dancing, when, during the rapid efforts at expiration and inspiration, and before harmonious respiration is regained, the blood is prevented from emptying itself evenly from the veins into the superior vena cava. As 308 THE REGION OF THE THORAX. the left side of the heart is always engaged in forcing the arterial blood throughout the system, it naturally follows that the mitral valve is liable to suffer in consequence of over-work. Mitral regurgitation is therefore the most frequent of valvular affections, and the murmur which charac- terizes it necessarily occurs with the ventricular systole. This murmur can be distinguished from aortic regurgitation by not being noticeable in the carotid arteries, but by being more clearly heard over the apex and below the left shoulder-blade, where the left ventricle is nearest the tho- racic wall without the intervention of any other portion of the heart. In order to determine upon a topographical survey of the chest (Plate 27) for the clinical study of the relative positions of the important parts of the heart and lungs, it is well to bear in mind certain established facts, and to pay especial attention to the landmarks of this region. There is very little possibility of change in the normal position of the base of the heart in the adult, as has been explained (page 273), in consequence of the manner in which the pericardium is attached to the central tendon of the diaphragm below and to the deep cervical fascia above. The apex of the heart, on the contrary, is continually changing its position during life, as it is free within the pericardium, and extends upon the left muscular arch of the diaphragm, which overlies the stomach, so that not only does it naturally accommodate itself to the diaphragmatic movements of respiration, but its freedom is also somewhat interfered with when the stomach is distended. In this connection it should be remem- bered that the left lobe of the liver overlaps the stomach, even so far as its cardiac extremity, and thus intervenes between the latter and the diaphragm (Plate 29). Distention of the stomach with gas from fermen- tation in digestion in various dyspeptic conditions is often attended with cardiac disturbance, but this disturbance occurs chiefly through the tension exerted upon the diaphragm and the consequent limitation of the ordinary moving space of the heart within the pericardial sac. Undoubtedly, also, many of the nervous symptoms attendant upon such a condition may be ascribed to the dragging upon the filaments of the pneumogastric nerves which accompany the oesophagus through its proper opening in the dia- phragm to their distribution over the stomach (Plate 36), The degree THE REGION OF THE THOBAX. 309 of displacement of the heart in consequence of distention of the stomach is, however, greatly exaggerated, for, except in very unusual cases, the stomach when distended must enlarge toward its free border at the ex- pense of the abdominal cavity rather than of the thoracic. The anatomy of the diaphragm is described on page 320, but its ever-changing posi- tion at the sides renders the study of its relations to the adjacent viscera of the thorax and abdomen of peculiar value and interest. After death the diaphragm is usually found arching upward to the fullest extent, owing to the collapsed state of the lungs from expiration ; but during life its lateral contractions produce changes which are more apparent than real, for there are alterations in the relative positions of the ribs and sternum above and below, which are coincident and exert a modi- fying influence on whatever effect it may have upon the neighboring viscera. It should be remembered that the ribs are raised in inspiration and lowered in expiration, and that their relations are thus materially altered. To be of assistance in arriving at any degree of accuracy in observation, these alterations are further to be considered from the stand- point of the individual peculiarities of conformation of the chest; and only by those who are most cognizant of what may be termed the normal changes are the difficulties in the way of mapping out the position of the viscera upon the living body properly aj^preciated. The shape of the thorax varies considerably in different individuals. The ribs vary in breadth, as do also the sternum and the interveniug cartilages (Plates 27, 28, 29). The uncertainty attending the many descriptions of the position of the heart within the thorax is mainly due to a want of proper consideration of the relative bearing of this important organ to the general conformation and development of the bony cage which contains it. It should be under- stood and remembered at the outset of every physical examination that the precise location of the various parts must be settled with exactness upon each individual, and that any standard of measurement can be applied only with latitude. It is easy enough to point out where things ought to be beneath the skin, but to say that they actually are at any one spot, without auscultation and percussion, is not compatible with extensive 310 THE REGION OF THE THORAX. observation upon tlie living or the dead. An allowance should always be made in fixing upon any diagnostic point, but it may be considerably diminished if sufficient attention is paid to the peculiarities of individual conformation. It has been asserted (page 245) that the ridge between the manubrium and gladiolus of , the sternum is the most reliable landmark in the front of the chest. It indicates the position of the sternal attachment of the cartilage of the second rib, and therefore by counting downward on either side the numerical order of the several true ribs may be ascertained. As already stated, the base of the heart may be considered to be anatomically fixed at the junction of the third costal cartilage with the right border of the sternum. This is fortunate for diagnostic purposes, because it assists in determining the localization of the valves of the heart. The apex of the heart in a well-formed adult may be felt beating at each contraction between the cartilages of the fifth and sixth ribs, to the left of the sternum, and about nine centimetres, or three and a half inches, from its middle. The thorax should give a clear note on percussion, except over the position of the heart, where dulness is elicited. Only a small triangular part of the heart is uncovered by the lungs and pleurae during full inspi- ration (Plates 27, 29, and 30), in consequence of the deflection of the left lung from the middle line. This is known as the area of the greatest cardiac dulness. The limitations of this area may be approximately indi- cated by drawing a line from the middle of the sternum opposite the fourth left costal cartilage to the point of junction of the left fifth rib and its cartilage, and from this point horizontally back to the mid-sternal line (Plate 27). The following survey of the anterior view of the chest is based upon many careful observations upon the living, and it is believed to be verified by the dissections of this region, as represented in Plates 29, 30, 31, 32, 33, 34, and 35. The references throughout the text, as to the position and bearing of the lungs, the heart, and the great vessels, are also the result of personal study. In the adult, standing erect, with the shoulders squared and the arms at the sides, if the breath is held upon expiration, the position of the THE REGION OF THE THORAX. 311 valves of tlie heart may be ascertained, after determining upon the rela- tions of the base and apex of the heart as above described (Plate 27). The right auriculo-ventricular or tricuspid valve is situated behind the middle of the sternum, opposite the interspace between the right fourth and fifth ribs. The left auriculo-ventricular or mitral valve is situated just above the cartilage of the left fourth rib, about two and a half centi- metres, or an inch, from the border of the sternum. The aortic semi- lunar valves are behind the sternum, between the junction of the cartilage of the left fourth rib and the mid-sternal line. The semilunar valves of the pulmonary artery are just behind the junction of the cartilage of the left third rib with the border of the sternum. If the breatli is held upon inspiration, the interposition of the lungs renders the heart-sounds obscure and uncertain. Fortunately, the structure of the sternum is such that in a measure it serves as a sounding-board, and does not interfere with the transmission of the sounds through a stethoscope. The difficulty of fixing definitely the points where the sounds of the cardiac valves can be detected by the ear applied to the chest is greatly increased in examining young children, in whom the position of the heart is relatively higher and consequently the sounds of its valves are confused with those of the respiratory organs. In infancy and throughout child- hood the heart also is proportionately of greater breadth in comparison with the chest (Plate 42), and the apex-beat will therefore generally be found at a point higher and more external than it is in the adult. The so-called nipple-line is not to be relied upon for accurate reference, as the position of the nipple, although usually occupying the fourth intercostal space upon both sides, is subject to variation, as stated in the description of the breast (page 250). With regard to the physical examination of the chest for the recog- nition of the condition of the lungs there are several points regarding which the anatomy of the region will ofier elucidation. When the hands are held in each other at the back, with the body in the upright position, percussion over the anterior wall of the chest will reveal a clear note wherever the lung-tissue is healthy. By this means an experienced ear and a light touch may enable the physician to map out the area of the 312 TEE REaiON OF THE THORAX. lungs in inspiration (Plate 27) and thus ascertain the degree of their exj)ansion. Over the apices of the lungs at the root of the neck there is a slight resonance, but it is much more clear below the clavicles, where the amount of lung tissue is greater. Generally in this locality there is upon the right side normally a comparative degree of dulness, owing to the interposition of the innominate artery and innominate vein. Both sides of the chest should always be percussed symmetrically downward, the area of the heart's dulness being allowed for upon the left side. By this means it will be found that in the middle over the sternum during inspiration the resonance is clearest along the upper part of the gladiolus, above the attachment of the cartilages of the fourth ribs. Upon the right side the resonance diminishes below the level of the fifth rib, as the lung thins out over the liver, until the upper border of the seventh rib is reached, where the absolute dulness of the liver commences. Upon the left side below the sixth rib percussion will gradually elicit the tym- panitic note of the stomach. The posterior lower level lines of the lungs are indicated in the topo- graphical survey of the back, which will be found in Vol. II. The space included between the reflections of the two pleurae posteriorly, extending from the roots of the lungs and the pericardium to the sides of the bodies of the dorsal vertebrae, is called the posterior mediastinum (page 263). It contains the descending thoracic aorta and its intercostal branches, the oesophagus, the pneumogastric nerves, the thoracic duct, the venae azygos major and minor, the splanchnic nerves, and some lym- phatic glands (Plates 36, 37, 38, and 41, Fig. 2). The descending thoracic aorta commences at the termination of the arch, about the lower border of the body of the fourth dorsal vertebra on the left side, and extends to the twelfth dorsal vertebra. It is closely connected to the spine by a strong investment of the endothoracic fascia, and it^ course is not straight, as it follows the natural curvature of the spine in this region, and gradually approaches the middle line, where it passes through its proper opening in the diaphragm to become the abdom- inal aorta. The thoracic aorta is separated from the pericardium by the oesophagus and the pneumogastric nerves (Plates 37 and 38). The root THE REGION OF THE THORAX. 313 of the left lung is in front of its upper portion (Plates 39 and 40), which also indents the lung in this relation. As it descends, this portion of the aorta diminishes slightly in calibre (from twenty-three to twenty-one millimetres, or from eleven-twelfths to five-sixths of an inch, in diameter) and gives off at intervals numerous branches. From the anterior surface arise the upper and lower right and left bronchial arteries, which accom- pany the respective bronchi into the lungs, several pericardiac arteries, and four or five oesophageal arteries, which are distributed to the walls of the pericardium and oesophagus and also to the posterior mediastinal lymphatic glands. From the posterior surface upon each side there are usually nine intercostal arteries given off". There are eleven pairs of intercostal arteries, but the upper two are derived from the superior inter- costal branch of the subclavian artery (page 229). The right aortic intercostal arteries are longer than the left, owing to the position of the aorta, being for the most part on the left side of the spine, and the upper ones upon each side ascend obliquely to pass along the intercostal spaces, while the lower ones pass transversely. Upon reaching the intercostal spaces, between the side of the vertebra and the superior costo-transverse ligament, each artery divides into an anterior and a posterior branch. The anterior branch is the largest, and at first runs along the middle of the intercostal space upon the external intercostal muscle, and, in consequence of the internal intercostal muscle being deficient here, is separated from the thoracic cavity only by the endothoracic fascia and costal reflection of the pleura. At the angle of the rib the Vessel passes between the two layers of intercostal muscles and becomes lodged in the sub-costal groove of the lower border of the rib above, with its companion vein above and nerve below (Plate 37). Before doing so it sends off a tiny branch called the collateral intercostal artery, which runs along the upper border of the rib below. This branch is sometimes large enough to cause troublesome bleeding, and in entering a trocar through any one of the spaces it is better to select the middle of the space, instead of just above the border of the lower rib as generally recommended. The anterior branches of the intercostal arteries anasto- mose with one another and with the branches from the internal mammary 40 PLATE 44. Figure 1. Dissection of the anterior thoracic region, showing the superficial fascia and mamtaary gland on the left side, and the great pectoral muscle on the right. The arms are drawn upward and outward to bring the axillary borders into prominence and expose their relations to the vessels and lymphatic glands ; of importance in operations upon the breast. From a female aged twenty-four years. 1. The converging fibres of the right pectoralls major muscle, passing to their insertion on the humerus. 2. The anterior cutaneous branch of the first intercostal nerve, and the first perforating branch of the in- ternal mammary artery. 3. The sub-scapular artery, veins, and nerves. 4. The anterior cutaneous branch of the second inter- costal nerve, and the second, or principal, perforating branch of the internal mammary artery. 5. The long thoracic nerve. 6. The anterior cutaneous branch of the third intercostal nerve, and the third perforating branch of the in- ternal mammary artery. 7. The long thoracic artery, coursing along the axillary border of the pectoralis major muscle when in this position. 8. The anterior cutaneous branch of the fourth intercostal nerve, and the fourth perforating branch of the in- ternal mammary artery. 9. The middle clavicular nerves. 10. The internal clavicular nerve. 11. The fascia over the great pectoral muscle. 12. The sternal nerves. 13. The superficial axillary veins. 14. The axillary glands. 15. The superior division of the second, or principal, perforating branch of the internal mammary ar- tery. 16. The inferior division of the second perforating branch of the internal mammary artery. 17. The superficial pectoral fascia, surrounding the mam- mary gland. 18. The left nipple, with its areola. 19. The lower portion of the mammary gland, carefully dissected to show the lactiferous lobes and ducts. 20. The superficial cutaneous veins. Figure 2, Dissection of the muscles of the shoulder and axilla on the right side. The lymphatic glands and vessels are super- posed upon the photograph, from notes of many observations, to show their proper relations. The temporal muscle. The deltoid muscle, reflected. The pectoralis major muscle, reflected. The triceps muscle. The biceps muscle. The lymphatic chain along the inner border of the coracoid head of the biceps muscle. The coraco-brachialis muscle. The sub-scapularis muscle. The latlssimus dorsi muscle. The lymphatic chain along the axillary border of the latissimus dorsi muscle. The compressor naris muscle. The buccinator muscle. The masseter muscle. The depressor anguli oris muscle. The anterior portion of the digastric muscle. 16. The mylo-hyoid muscle. 17. The thyro-hyoid muscle. 18. The head of the humerus, covered with the capsular ligament. 19. The stemo-mastoid muscle. 20. The glenoid head of the biceps muscle. 21. The sterno-thyroid muscle. 22. The sterno-hyoid muscle. 23. The coracoid head of the biceps muscle. 24. The coracoid attachment of the pectoralis mihor mus- cle. 25. The axillary glands in the apex of the axilla. 26. The pectoralis minor muscle. 27. The lymphatic chain along the axillary border of the pectoralis minor muscle. 28. The serratus magnus muscle. g l/f ■Mvnaij Off mujig Aq sjmBf/ ujojj psMjOi cue p^ Q i^'NviTnj si^i sSM.ijj -(97£-4'/''Y*''^'"^"5 ;jl;,| r T'^A THE MEaiON OF THE THORAX. 315 artery in front (page 257). They distribute blood to the contiguous ribs and muscles, and also by perforating brandies to the pectoral muscles, mammary gland, and serratus magnus muscle. The anterior intercostal vessels and nerves pass, as they enter between the intercostal muscles, beneath the chain of sympathetic nerve ganglia (Plates 36 and 37). The posterior intercostal arteries pass backward with the dorsal nerves between the transverse processes of the contiguous vertebrae, and divide opposite the intervertebral foramina into the spinal and dorsal branches. The spinal arteries enter the spinal canal and immediately subdivide and establish communications with the vessels above and below, so that there are arterial plexuses formed in front and at the back of the cord, called the anterior and posterior neural rete mirabile. A branch of each spinal artery also pierces the dura mater of the spinal cord, and with similar branches anastomoses upon the anterior and posterior surfaces of the cord itself. The dorsal arteries divide into internal and external muscular branches, which supply the various layers of dorsal muscles. The oesophagus is the continuation of the pharynx, and begins in the neck on a level with the sixth cervical vertebra and the lower border of the cricoid cartilage (Plate 12). It is the narrowest portion of the digestive canal, and leads directly into the stomach, passing in front of the spine to the transverse portion of the arch of the aorta, thence through the posterior mediastinum in front of the descending thoracic aorta (Plate 37) to its proper opening in the diaphragm opposite the ninth dorsal vertebra. It is about twenty-five centimetres, or nine or ten inches, in length. It is most constricted in relation to the fourth dorsal vertebra and at the diaphragm. Its course is somewhat peculiar, being not exactly straight, and, besides conforming to the curvatures of the spine in the different regions through which it passes, it deviates from the middle line in certain localities. At the root of the neck it bulges to the left of the trachea (Plate 36), which, with the lobe of the thyroid body and the left recurrent laryngeal nerve, is situated in front of it. It is separated from the longus colli muscles by the pre- vertebral expansion of the deep cervical fascia. The left inferior thyroid and common carotid arteries, and the thoracic duct, are close to the left 316 THE REGION OF THE THORAX. side of it. Within the thorax the oesophagus passes through the superior mediastinum, extending over a little to the right of the middle line, lying in front of the bodies of the upper dorsal vertebrse. In the posterior mediastinum it is separated from the vertebrae by the thoracic duct, the vena azygos major, and the right upper intercostal arteries. Here it passes forward and to the left, and is surrounded below the roots of the lungs by the oesophageal plexus of nerves, which are derived from the right pneumo- gastric nerve posteriorly and from the left pneumogastric nerve anteriorly. It is in relation with both pleurse, but more especially the right, and has in front of it the trachea, the left bronchus, the arch of the aorta, and the posterior surface of the pericardium in relation to the left auricle (Plates 38 and 39). The oesophagus terminates at the cardiac orifice of the stomach, about two centimetres, or three-fourths of an inch, to the left of the middle line, passing through the diaphragm, and entering the cavity of the abdomen behind the left lateral ligament of the liver and the adjoining peritoneal layers of the lesser omentum. Upon section the cesoj^hagus appears like a cord with a stellate lumen (Plate 41, Fig. 2, No. 12). It will be observed from the above that the direction of the oesophagus presents two lateral curves, one at the root of the neck and the other at the diaphragm, which should not be over- looked in the introduction of a probang or of the stomach-pump. The diameter of the canal varies, being normally at the above-mentioned points of constriction thirteen millimetres, or about half an inch, and in the rest of the passage from seventeen to twenty-one millimetres, or a little over three-quarters of an inch. These measurements are considerably increased by forcible distention : the narrowest portions, however, rarely exceed twenty-two millimetres, or seven-eighths of an inch, in diameter, while the rest of the gullet will stretch to thirty-six millimetres, or one and a half inches. It follows, therefore, that foreign bodies when swal- lowed are most apt to be arrested at either the upper or the lower portion of the oesophagus. The operation of oesophagotomy for the removal of an impacted foreign body is performed with the patient's neck turned upon the right side over a pillow, so as to render the left side prominent where the cesoph- THE REGION OF THE THORAX. 317 agus extends to the left of the middle line. The foreign body can usually be felt, and thus serves as a guide. The incision should be free and made parallel to the anterior border of the sterno-mastoid muscle, and the carotid sheath carefully exposed. The latter, together with the trachea, should be drawn forward and the sterno-mastoid muscle outward, every precaution being exercised not to injure the thyroid body, the thyroid vessels, or the recurrent laryngeal nerve, and especially to avoid tearing the surrounding loose cellular tissue, which is very prone to diffuse inflammation. The distensibility of the oesophagus is due not only to the laxity of its attachments, but also to the character of its coats. These consist of an external or muscular coat, composed of outer longitudinal and inner circular fibres, which are mostly well developed and pronounced in the upper portion ; a middle or areolar coat, consisting of elastic tissue in which are embedded masses of adenoid tissue and rows of little racemose cesophageal glands (larger below than above), and an mternal or mucous coat, which is continuous with the mucous lining of the pharynx above and with the stomach below, and which when the oesophagus is empty is folded into vertical rugae. The mucous membrane is quite thick, and is lined with scaly epithelium. The arteries to the CBsophagus are derived from various sources. In the neck it receives branches from the inferior thyroid artery, within the thorax branches from the descending thoracic aorta, and below the diaphragm a few twigs from the gastric artery. Its veins empty their blood into the gastric, the vena azygos major, and the inferior thyroid veins in their respective localities. The nerves are sup- plied from the cesophageal plexus formed by the pneumogastrics and some filaments from the first dorsal ganglion of the sympathetic nerve. The pneuviogastrie nerves within the thorax hold different relations upon the two sides. The right p7ieumogastric enters from the neck, be- tween the subclavian artery and subclavian vein, and descends by the side of the trachea to the root of the lung (Plate 39). After giving off the recurrent branches and others which communicate with similar branches from the left pneumogastric nerve and form the posterior pulmonary and oesophageal plexuses, it continues as a single cord along the posterior 318 THE REGION OF THE THORAX. wall of the oesopliagus to the stomach. The left pneumogastr'tc nerve, after entering the thorax from the neck between the left subclavian and carotid arteries and behind the left innominate vein, passes over the arch of the aorta and behind the root of the left lung to the anterior surface of the oesophagus. In its course it gives off branches which combine with those from the right pneumogastric nerve, as already stated, in the formation of the pulmonary and oesophageal plexuses, and continues as a single cord along the anterior wall of the oesophagus to the stomach. The recurrent laryngeal nerves are given off from the pneumogastric nerves within the limits of the superior mediastinum, and have already been particularly described (page 185). The thoracic duct is the upward continuation of the receptaculum chyli, which receives the converging lacteal vessels from the intestines and the lymphatic vessels from the lower portion of the body, which are described with the region of the abdomen in Vol. II. The duct enters the posterior mediastinum by the aortic opening in the diaphragm, to the right side of the aorta (Plate 37, No. 8, and Plate 38, No. 2), and ascends in a sinuous course in close relation to the right pleural boundary of this space as far as the body of the third dorsal vertebra. Here it passes across to the left side behind the arch of the aorta and the oesophagus, and curves upward to the left side of the latter, between it and the left pleura, to enter the superior mediastinum. Very often the thoracic duct in its upper portion divides into branches, and it usually presents a dila- tation where it crosses over the spine. It receives the pleural, intercostal, and left pulmonic lymphatic vessels. When dilated it appears irregular and nodulous, owing to the many pairs of valves with which it is pro- vided. The valves are most numerous in the upper portion, where it ascends between the oesophagus and the left subclavian artery into the neck as high as the seventh cervical vertebra. It then curves down- ward over the subclavian artery, near the anterior border of the scalenus anticus muscle, and empties into the back part of the confluence of the left common jugular and subclavian veins (Plate 20, No. 69). At the orifice of the duct there are two well-marked valves, which guard against any regurgitation of the blood from the veins into its canal. THE REGION OF THE THORAX. 319 The vena azygos major is the great connecting link between the superior and inferior vense cavse, making up for their dejficiency in the situation of the heart. It commences by tributaries from the right lumbar and renal veins, and often from the inferior vena cava itself, and, passing through the diaphragm at the aortic opening, ascends upon the right side of the spine over the right intercostal arteries to the third dorsal vertebra, whence it arches forward to empty into the superior vena cava as it becomes covered by the pericardium (Plate 37, No. 30). It receives the lower nine or ten right intercostal veins, the spinal veins, and the pos- terior mediastinal, oesophageal, and right bronchial veins. About the sixth dorsal vertebra the vena azygos major is usually joined by the vena azygos minor (Plate 38, No. 13), which ascends up the left side of the spine (Plate 36, No. 84). The latter vein commences in the abdo- men by tributaries from the left lumbar veins and the left renal vein, and ascends to the left of the aorta through the left crus of the dia- phragm. It receives the lower six or seven of the intercostal veins, besides some of the mediastinal and oesophageal veins. The left ujjper intercostal veins terminate in a trunk called the superior vena azygos minor, which empties into the vena azygos major generally, but some- times into the inferior vena azygos minor. All the azygos veins are provided with valves, which are not very perfect, however. The splanchnic nerves are the sympathetic nerve cords which are made up of branches from the lower thoracic ganglia, and are distributed to the abdominal plexuses under the names of the greater and lesser splanchnic nerves (Plate 36, Nos. 80 and 83, and Plate 37, Nos. 13 and 15). The sympathetic ganglia in the thoracic region vary in number upon each side from ten to twelve, in consequence of several of them being often united. The first is the largest, and they are mostly situated over the heads of the ribs. They are small, grayish-pink, irregular bodies connected by broad, thin, grayish branches, and each ganglion is also con- nected by a couple of branches, one white and one gray, with the neigh- boring intercostal nerve. It is thought that these connecting links with the spinal nerves consist of fibres which leave the ganglia at their inner branches and endow them with vaso-motor and viscero-inhibitory functions. 320 THE DIAPHRAGM. The nerves from tlie four upper ganglia are quite small, and pass inward to join the cardiac and posterior pulmonary plexuses. The nerves from the six lower ganglia constitute the greater, the lesser, and the smaller splanchnic nerves. The great splanchnic nerve is composed of the most numerous filaments from the fifth, sixth, seventh, eighth, ninth, and tenth ganglia, which combine into a single trunk, and, passing through the crus of the diaphragm on the corresponding side, join the solar, renal, and supra-renal plexuses. The lesser splanchnic nerve arises by branches from the tenth and eleventh ganglia, and passes generally to the cceliac 2')lexus; and the smallest splanchnic nerve arises as a collateral branch from the twelfth ganglion, and terminates in the renal plexus. The chains of the sympathetic ganglia and their nerve -cords are covered by the reflection of the costal pleura upon each side, which holds them in place, and which must be removed before they can be examined and followed through the diajAragm. The association of the filaments of the splanchnic nerves with the solar plexus probably accounts for many of the obscure symptoms complained of in dyspepsia, which by reflex action manifest themselves in pain in the area of distribution of the cutaneous nerves of the ujiper part of the back. THE DIAPHEAGM. The diaphragm is the thin, movable, arching partition which separates the cavity of the thorax from the cavity of the abdomen. Its construction is very peculiar, as it consists of muscular and tendinous portions which arise by numerous digitations and, arching upward and inward, converge to be inserted into a common central tendon. To the upper surface of the central tendon are attached the fibrous pericardium and the dense lateral bands which are prolonged from the deep cervical fiiscia, already described (page 259). These serve to maintain the arch of the diaphragm and to keep the central tendon in position while the muscular portions are in constant motion during respiration (page 273). When looked at from below, the whole diaphragm resembles somewhat a large palm-leaf, while the central tendon appears almost a counterpart in form : hence the differ- THE DIAPHRAGM. 321 ent portions of each, in front and at the sides, are called the leaflets. Of these the right leaflet is the largest. In structure the central tendon con- sists of intersecting fibres which pass in all directions and then radiate among the muscular fasciculi, thus affording additional strength. It is of a glistening bluish-white color. The muscular portion of the diaphragm arises by fleshy digitations from the ensiform cartilage, from the inner surfaces of the six lower ribs on each side, interdigitating with the attach- ment of the transversales abdominis muscles, and from the tendinous arches over the quadratus lumborum and psoas muscles on each side, which con- sist of condensations of the extra-peritoneal fascia in this locality, and are known, from their ligamentous nature, respectively as the ligamentum arcu- atum externum and the ligamentum arcuatum internum (Plate 63, Nos. 6 and 31, Vol. II.). The ligamentum arcuatum externum extends from the twelfth rib to the transverse process of the first lumbar vertebra, and the ligamentum arcuatum internum extends from the transverse process of the first lumbar vertebra to the body of the second. Lower down upon the lumbar vertebrae are two variably-developed and always unsym metrical fleshy portions, called the crura of the diaphragm, because their com- ponent fibres in passing upward cross each other in such a way that they usually form a figure-of-eight arrangement around the openings for the aorta and the cesophagus (Plates 62 and 63, Vol. II.). The aortic opening is in the middle line in front of the spine between the two crura, and gives passage to the descending aorta, with the thoracic duct and the vena azygos major on its right side. The oesophageal opening is in the muscular portion above and in front of the aortic opening, and transmits, besides the cesophagus, the right and left pneumogastric nerves (page 317). To the right of the latter, and in the highest part of the central tendon, is the opening for the inferior vena cava, which also gives passage upward to some of the hepatic lymphatic vessels, and occasionally to a branch of the right phrenic nerve. The wall of the inferior vena cava is adherent to the central tendon where it passes through it, so that it is not subjected to pressure in the action of the adjacent muscular leaflet. Besides these three great openings there are several smaller ones under the crura, which allow the splanchnic nerves to enter the abdomen from the 41 322 THE DIAPHRAGM. thorax (page 320). On the left side the vena azygos minor gains entrance to the thorax (page 319). On each side of the ensiform cartilage there is a triangular space which gives passage to the epigastric branch of the internal mammary artery, and to the lymphatic vessels from the anterior wall of the abdomen into the anterior mediastinum (page 259). Occasion- ally this becomes distended by an abscess or by a diaphragmatic hernia. The diaphragm receives branches from the lower intercostal and internal mammary arteries, but is mainly supplied with blood by the two phrenic arteries, which arise from the aorta just as it issues through its proper opening. The nerves of the diaphragm are the phrenic (page 207) and some of the branches of the lower five or six intercostal nerves, which are rein- forced by sympathetic fibres from the neighboring supra-renal plexuses. These fibres form the diaphragmatic plexuses, and on the right side there is a little ganglion {diaphragmaticum) , from which filaments pass to the liver. The diaphragm, next to the heart, is the most extraordinary muscular arrangement in the body. Its ujjper surface arches into the thoracic cavity, on each side, at variable heights (Plate 40), reaching during expiration about the level of the fifth rib on the right side and of the sixth rib on the left (page 265), and during inspiration sinking about an inch, and thus pushing downward the abdominal viscera to a slight degree. It is through the alternate contraction and relaxation of its muscular portions that it enters largely into the mechanism of respira- tion, aiding, in this important process, the expulsion of the air from the lungs, by acting in harmony with the rest of the thoracic walls and thus accommodating the cavity of the thorax to the degree of expansion of these elastic organs. It is concerned in coughing, sneezing, and laughing, as is manifest by its rapid contractions during those acts. It also assists the abdominal muscles in compressing the viscera in vomiting and defecation, and in the efforts of parturition. The under surface of the diaphragm is covered by the peritoneum, as described with the region of the abdomen in Vol. II. TRE REGION OF TRE BROULBER. 323 THE UPPER EXTREMITY. The region of the shoulder is formed by tlie clavicle, the scapula, and tlie upper part of the humerus (Plate 28), together with the structures surrounding them, by which the upper extremity is attached to the thorax. The skin over this region is comparatively thin, and although there may be a considerable amount of fat in the subcutaneous tissue in certain localities, which softens and subdues the surface markings, yet the promi- nences of the bony framework can always be detected by the sense of touch. The clavicle, the acromion process, and the spine of the scapula are readily felt through the skin. In order to determine with accuracy these landmarks it is advisable to refer to the corresponding points of the opposite shoulder, and to take advantage of the extreme mobility of the parts, for by rotation, abduction, and adduction many factors otherwise obscure will be explained. The clavicle and the scapula are the frame- work of the shoulder proper, and with those of the opposite side form the shoulder girdle. This girdle is incomplete posteriorly, owing to the gap between the two scapulae, which are connected with the thorax solely by muscles, while in front the two clavicles are supported upon and con- nected with the top of the sternum. The shoulder girdle is remarkable for its lightness and great mobility. The clavicle, or collar bone, is the long irregular bone which extends from the sternum outward over the first rib to the summit of the shoulder, which it forms with the acromion process of the scapula (Plate 28). In the upright position the clavicle usually inclines a little upward at its outer end, and in the recumbent position this is increased in consequence of the weight of the limb being removed. It is subject to variable physical pro- portions, much depending upon the amount of strain and effort required of the muscles which are attached to it. In the female it is usually smoother and more slender than in the male. The right clavicle is often shorter than the left. The bone presents a peculiar sigmoid curvature, so that the anterior border begins by curving forward at the sternal end, and at 324 THE REGION OF THE SHOULDEB. the middle gradually curves backward to the acromial end, where it juts outward. The posterior border is exactly the reverse. The degree of curvature of the inner portion of the clavicle is very variable, especially in men, the freedom and much of the grace of movement of the upper extremity depending upon it. The sternal end is a prominent, rough, thick, triangular-shaped process covered with a dense fibrous tissue. It is provided with an irregular facet, which at its lower part rests upon the shallow facet on the upper border of the sternum, and with the inter- position of a disk of fibro-cartilage establishes the important sterno- clavicular joint. This joint is provided with two pouches of synovial membrane, one above and the other below the interarticular cartilage, enclosed within a capsular ligament, of which there are two strong bands of fibres, one stretching in front of and the other behind the surfaces of the contiguous bones. They are called respectively the anterior and posterior sterno-clavicular ligaments. These bands are reinforced by the intercla- vicular ligament, which is in reality a differentiation of the deep cervical fascia extending between the ends of the two clavicles across the top of the sternum, and the costo-clavicular or rhomboid ligament, which ascends inward from the cartilage of the first rib to the costal tuberosity of the clavicle. This is now regarded as a differentiation of the sheath of the subclavius muscle. It is remarkably strong, and limits the elevation of the clavicle. Although the sterno-clavicular joint is the only direct con- nection between the upper extremity and the thorax, it is very rarely dislocated. It has been demonstrated that the peculiar sloping arrange- ment of the articular facets of this joint allows the sternum to advance slightly upon the end of the clavicle in inspiration (Morris). The acro- mial end is rough, broad, and flattened, and presents upon its under surface an obliquely-directed oval facet for articulation with the acromial process of the scapula, forming the claviculo-acromial joint. This joint is provided with superior and inferior ligaments, the superior being much the stronger, and a reflected synovial membrane. There is sometimes a rudimentary fibro-cartilage within. It is capable of very slight gliding motion, but, slight as this motion is, it is essential to the perfect freedom and har- monious movement of the upper extremity. This joint is liable to rheu- THE REGION OF THE SHOULDER. 325 matic inflammation, and the resulting rigidity will cause weakness iu certain movements of tlie limb. Very often tlie outer end of the clavicle appears to be tilted above the acromion process, instead of occupying the same level. This is probably due to partial separation of the connecting ligaments from some severe strain. It is not attended with any impair- ment of function. The inner two-thirds of the shaft of the clavicle are rounded, and its posterior concave surface arches over the subclavian vein and artery and the cords of the brachial plexus of nerves (Plates 30 and 31). The upper surface of the bone is smooth and subcutaneous, being readily recognizable through the skin, which is always thin and loosely attached over it. The anterior and posterior borders of the upper surface are roughened to a variable extent toward each end. The anterior border gives attachment to the pectoralis major muscle at its inner half, and to the deltoid muscle at its outer. The posterior border receives the insertion of the clavicular portion of the sterno-mastoid muscle (page 197) inwardly, and of the trapezius muscle outwardly (Plate 16). The under surface presents at the sternal end a small facet for the reception of the first rib, which is in reality a portion of the sternal articular surface. Close to the outer side of this is the rough costal tuberosity for the attachment of the rhomboid ligament, beyond which along the middle of the shaft is the subclavian impression for the subclavius muscle. The costo-coracoid mem- brane (page 255) is attached to the ridge in front of this impression and a reflection of the deep cervical fascia from the omo-hyoid muscle to a ridge behind it. Sometimes there is a rough line in the middle of the impression, in which case it afibrds insertion to a fibrous septum in the subclavius muscle. Upon the under surface of the shaft, where it spreads out to form the acromion, there is at its posterior border an eminence called the conoid tubercle, from which an oblique line extends to the outer end of the anterior border. The conoid tubercle is directly over the coracoid process of the scapula, to which it is connected by the conoid ligament. The oblique line gives attachment to the trapezoid ligament, which arises from the coracoid process, the two ligaments being practically portions of one, the PLATE 45. Figure 1. Dissection of the right axillary space and inner side of the arm to show the relation of the vessels and nerves. 1. The anterior ulnar vein. 2. The posterior ulnar vein and branches of the internal cutaneous nerve. 3. The median basilic vein. 4. The basilic vein. 5. The lesser internal cutaneous nerve. 6. The greater internal cutaneous nerve. 7. The triceps muscle. 8. The ulnar nerve. 9. The brachial vein. 10. The superior profunda artery and veins. 11. The intercosto-humeral nerve. 12. The latissimus dorsi muscle. 13. The dorsalis scapulae artery. 14. The sub-scapular artery and veins. 15. The second sub-scapular nerve. 16. The third sub-scapular nerve. 17. The axillary glands embedded in adipose tissue. 18. The long thoracic artery. 19. The serratus magnus muscle. 20. The posterior thoracic nerve, or external respiratory nerve of Bell. 21. The median vein. 22. The median cephalic vein. 23. The cephalic vein. 24. The biceps muscle. 25. The median nerve. 26. The brachial artery. 27. The coraco-brachialis muscle. 28. The deltoid muscle. 29. The cephalic vein. 30. The sternal portion of the pectoralis major muscle. 31. The right clavicle. 32. The severed trapezius muscle. Figure 2. Deep disisection of the right axilla and inner side of the arm. The deltoid and pectoralis major and minor muscles are detached and reflected to show the intricate relations of the brachial plexus of nerves to tlie artery and veins. 1. The fascia of the forearm and branches of the internal cutaneous nerves. 2. The median basilic vein. 3. The median nerve covering the brachial artery. 4. The anastomotica magna artery. 5. The lesser internal cutaneous nerve. 6. The greater internal cutaneous nerve. 7. The ulnar nerve. 8. The superior profunda artery. 9. The inferior profunda artery. 10. The triceps muscle. 11. The ulnar nerve, passing beneath the basilic vein. 12. The latissimus dorsi muscle. 13. Connecting venous link between the basilic and brach- ial veins. 14. The basilic vein before it empties into the axillary vein. 15. The axillary glands. 16. The intercosto-humeral nerve. 17. The sub-scapular artery and veins. 18. The sub-scapular nerves. 19. The blending of the veins of the forearm over the ten- don of the biceps muscle. 20. The cephalic vein. 21. The biceps muscle. The basilic vein. The brachial artery. The brachial vein. The median nerve. The coracoid attachment of the biceps muscle. The musculo-cutaneous nerve. The thoracico-humeral artery. The coraco-brachialis muscle. The coracoid attachment of the severed pectoralis minor muscle. The inner cord of the brachial plexus of nerves. The axillary artery. The main brachial vein before its entrance into the axillary vein. The brachial plexus of nerves. The acromio-thoracic artery. The severed pectoralis major muscle, reflected. The serratus magnus muscle. The posterior thoracic nerve. The short thoracic artery. The great axillary vein. The right clavicle. The trapezius muscle. Plate 4- .5 Vol I Copyright, IS3I . U fro.ist- Wc &f.tt/^^, « ft Disspct^. Pholaqr-iphed a^'d Colored frcrn Nntijm hi Georse Mc Ci sirAN, M 0. THE REGION OF THE SHOULDER. 327 coraco-clavicular ligament. They severally serve to restrain the move- ments of the shoulder. The curved formation of the clavicle renders it sufficiently elastic to compensate for its otherwise weak construction, so that it is capable of moderating the effects of ordinary concussions re- ceived through the shoulder. Its outer surfaces consist of comj)act tissue, which is much thicker at the middle of the bone, and the interior consists of large-meshed spaces of cancellous tissue containing reddish-colored marrow usually at the sternal end. The clavicle is peculiar not only in that it is the first bone of the skeleton to ossify, but also in that ossification begins in its primary fibrous substance before the deposition of cartilage. At birth the entire shaft is bony, although the ends are cartilaginous. The sternal end is the sole epiphysis to the clavicle, and it is joined to the shaft about the twenty-fifth year. It is rarely separated from the shaft by accident, owing to the close ligamentous attachments of the sterno-clavicular joint, but the powerful pectoralis major muscle might produce displacement in a young person. This bone is frequently the seat of green-dick fracture, owing to the exceedingly thick and loose periosteum which surrounds it in childhood, as well as to its more early ossification. Fractures of the clavicle occur frequently at all ages, in consequence of the manner of its construc- tion and its exposed position, and they are generally occasioned by indirect violence. The commonest form of fracture occurs at the outer end of the middle third of the bone, the resistance against concussion being weakened by the junction of the two curves of the bone at this point. The direc- tion of the fracture is oblique, and whatever degree of displacement may occur is chiefly through the agency of the weight of the upper extremity upon the outer fragment, the inner fragment rarely changing its position. The outer fragment may also be drawn inward and somewhat rotated, so that it projects in advance of the inner, by the contraction of the muscles attached to the upper portion of the humerus and the coracoid process of the scapula. The great obstacle to the complete reduction of such a fracture is the inability to maintain the scapula in position, owing to the gliding movements which are caused by its suspension in a sling of muscles at the side of the thorax. All the ingenuity which has been 328 THU REGION OF THE SHOULDEB. expended in devising apparatus to restrain tlie scapula has thus far failed, and consequently has been unsuccessful in overcoming the shortening of the bone in the process of repair. Union, however, usually occurs with marvellous rapidity (in from twelve to fourteen days), even when no dressing has been used, and with little impairment of function. The scapula, or shoulder-blade, is a flattish, triangular bone, situated at the back of the upper part of the thorax, and, in the properly articu- lated skeleton, extending between the second and seventh ribs. It consists mainly of a broad thin plate, the body, with raised and roughened borders. Its dorsal surface is smooth and slightly convex, and is divided near its upper third by a prominent projection of bone, the Sjyine, into two hollows, called the superior and inferior spinous fosscB. The supra-spinous fossa lodges the sup>ra-spinatus muscle, the fibres of which arise from its inner portion and from the dense fascia with which it is invested and converge to a strong tendon, which glides over the outer part of the fossa and across the capsular ligament of the shoulder-joint to be inserted into the superior facet on the greater tuberosity of the humerus. The infra-spinous fossa presents several faint ridges toward the vertebral border, from which and their inter- spaces the fibres of the infraspinatus muscle arise, and blend to form a tendon which passes over the upper part of the axillary border, from which it is sometimes separated by a bursa, and across the capsular ligament of the shoulder-joint, to be inserted into the middle facet on the greater tuberosity of the humerus. This muscle is also firmly bound down by an enveloping fascia. The teres minor muscle arises from the upper two-thirds of the axillary border by fibres which pass obliquely upward and form a narrow elongated mass, which mostly terminates in a tendon to be inserted into the inferior facet on the greater tuberosity of the humerus, and by a few muscular fibres into the humerus immediately below. The tendon of this muscle also passes across the capsular ligament of the shoulder-joint. The teres minor muscle is separated from the contiguous muscles by fibrous laminae, which also give origin to some of its component fibres. About the centre of the attachment of the teres minor there is a groove in the axil- lary border, which accommodates the dorsalis scapulae vessels. The teres major muscle arises by fibres attached to the lower part of the axillary THE REGION OF THE SHOULDER. 329 border, being separated by an oblique line from the preceding muscle, and by fibres extending over tlie inferior angle of the scapula. They form a broad mass which ascends outwardly, and, deviating from the teres minor, from which it is separated by the middle portion of the triceps muscle, is inserted by a flat tendon, about five centimetres, or two inches, in length, into the internal ridge of the bicipital groove of the humerus. The lower border of this tendon blends with the lower border of the latissimus dorsi muscle, forming the posterior boundary of the axillary space (page 338), and is inserted conjointly with it. The upper portion, however, is inserted independently, having a synovial bursa interposed between it and the proper attachment of the latissimus dorsi, which is at the bottom of the upper part of the bicipital groove. The latter muscle as it passes from its origin in the back (Vol. II.) crosses over the inferior angle of the scapula, to which it is usually attached by a fibrous expansion, so that it serves to retain .this portion of the scapula in place. Occasionally there is no connection between the latissimus dorsi muscles and the two scapulae, they being separated by synovial bursse. In such a condition the scapulae are apt to jut out like wings beneath the skin of the back. The vertebral border between the inferior angle and the root of the spine receives the attachment of the rhomboideus muscle. This muscle is sometimes divided by a septum into two portions. The upper portion is then called the rhomboideus minor, in distinction from the lower portion, or rhomboideus major. The fibres of the latter are inserted chiefly into a tendinous arch extending from the inferior angle half-way up the verte- bral border. The rhomboideus muscle consists of a flat mass of strongly- developed fibres which arise from the spinous processes of the vertebra prominens and the five upper dorsal vertebrae. Its action is to antago- nize the serratus magnus muscle, by drawing the scapula upward and backward. It receives a branch from the fifth cervical nerve, which also supplies the muscle immediately above, the levator anguli scapulce, which arises from the neck (page 208) and is attached to the scapula between the superior angle and the root of the spine. The smooth triangular surface over the root of the sj)ine has in the recent state a mucous bursa, or a layer of loose connective tissue, over which the trapezius muscle plays 42 330 THE REGION OF THE SHOULDER. as it passes to its insertion along the upper margin of the spine, as previ- ously described (page 208). The spine gradually projects from the dorsal surface, arising out of the smooth triangle at the vertebral border until it ends in the flattened, rough, quadrilateral acromion process, which is twisted so that it overhangs the shoulder-joint. The superior border of the scapula extends outwardly from the superior angle and ends in the curiously crooked projection called the coracoid process, at the root of which there is usually a notch, the supra-scapular, for the passage of the supra-scapular nerve, the companion vessels passing immediately over it. This notch is often a distinct foramen, or is con- verted into one, like similar notches elsewhere, by the presence of a trans- verse ligament. To this ligament, or to the inner border of the supra- scapular notch, is attached the scapular end of the omo-hyoid muscle. The coracoid process is very much like the little finger half bent, and extends forward over the shoulder-joint, where it can be felt during life below the clavicle. The inner border receives the attachment of the pectoralis minor muscle (page 255), and from its point the coraco-brachialis and short head of the biceps muscles arise by a common tendon. The coracoid and acromion processes have a strong fibrous band extending between them, called the coraco-acromial ligament, which forms an arch over the shoulder-joint and prevents the head of the humerus from being dislocated upward. The anterior or thoracic surface of the body of the scapula is concave, presenting a broad sub-scapular fossa, or venter, with three or four slight ridges at the vertebral border, which give origin to the intersections between the bundles of fibres of the sub-scapularis muscle, which completely occupies the fossa. Toward the root of the coracoid process this surface of the bone is smooth and the tendon of the sub-scapularis muscle passes over it, there being a laige bursa interposed across the capsule of the shoulder-joint to be inserted into the lesser tuberosity on the anterior part of the top of the humerus. The fibres from the axillary border of the fossa are inserted into the neck of the humerus two and a half centimetres, or about an inch, below the tuberosity. The chief action of this muscle is to rotate the head of the humerus inward. The whole of the anterior THE REGION OF THE SHOULDER. 331 surface of the vertebral border of the scapula receives the insertion of the serratus magnus muscle. This flat muscle forms the inner wall of the axilla (Plate 44, Fig. 1, and Plate 45, Fig. 2). It arises by nine digitations from the upper eight ribs (there being two attached to the second rib), which are arranged according to the direction of the fibres into superior, middle, and inferior portions. The superior is formed by the junction of the slip from the first rib with the anterior slip from the second rib by a small tendinous arch, and is inserted into the border of the superior angle of the scapula. The middle is made up of the posterior slip from the second rib with slips from the third and fourth ribs, and is inserted into the vertebral border and the neighboring fibrous arch. The inferior is the strongest part, consisting of slips from the fifth, sixth, seventh, and eighth ribs, and is inserted into the anterior surface of the inferior angle of the scapula. This muscle is covered by the contents of the axilla (Plate 45) and the skin over the side of the chest, and is sup- plied by the posterior thoracic nerve (page 345). Its function is to draw forward the scapula round the chest wall, but when the scapula is fixed its action is reversed, so that it becomes a powerful inspiratory muscle. At the external margin of the spine on the dorsal surface beneath the acromion process there is a notch by which the supra- spinatus and infra-spinatus fossae communicate: this is called the great scapular notch. Through this notch the supra-scapular artery passes and establishes the important anastomosis with the dorsalis scapulae and pos- terior scapular arteries (page 342). The anterior angle is the thickest part of the bone, and is called the head, while the constricted portion posterior to it is the nech. The head presents an oval shallow fossa, the glenoid cavity, which is narrower above than it is below, and is directed vertically outward, forward, and a little upward, for the reception of the head of the humerus. At the upper edge is the supra-glenoid tubercle, for the attachment of the long tendon of the biceps muscle, and at the lower edge is the rough infra-glenoid tubercle, for the origin of the middle or long head of the triceps muscle. This fossa is deepened in the recent state by the glenoid ligament, which consists of a prismatic fibro-cartilaginous band continuous with the expansion of the 332 THE REGION OF THE SHOULDER. fibres of attachment of the above-mentioned muscles round the margins. The central portion of the body of the scapula is extremely light, some- times being deficient in ossific matter, and the periosteum surrounding the bone is strong and laminated, and especially developed upon the various processes and borders. The upper end of the humerus consists of a smooth hemispherical head, directed upward, inward, and backward, to be received against the glenoid cavity of the scapula. The constriction about the head is known as the anatomical neck. From this the greater tuberosity extends outward. It is a rough prominence, presenting three facets, an upper, a middle, and a lower, for the attachments of the supra-spinatus, infra-spinatus, and teres minor muscles, as already described. From the anterior part of the ana- tomical neck the lesser tuberosity projects directly forward, the tendon of the sub-scapularis muscle being inserted into it. Between these tuberosi- ties there is a deep vertical furrow, the bicipital groove, for the accommo- dation of the long tendon of the biceps muscle (Plate 44, Fig. 2). Below the tuberosities, as far as the middle of the shaft, the bone is cylindrical, and is known as the surgical neck, in consequence of the frequency with which it is fractured. The shoulder-joint consists of the adaptation of the smooth surface of the head of the humerus upon the glenoid cavity of the scapula, thereby constituting an enarthrodial or ball-and-socket joint. These bony surfaces are each covered with articular cartilage in such a manner that it is thickest at the margins of the glenoid cavity and thinnest at the centre, while upon the head of the humerus the reverse is the case, the cartilage being thicker at the centre and thinner toward the anatomical neck. The capsular ligament is attached above to the circumference of the glenoid cavity and below to the anatomical neck, except at its inner and lower part, where it extends some little distance below. It is in itself a quite weak structure, being composed of a very loose layer of fibrous tissue. It is thickest at its upper part, where it is strengthened by the V-shaped coraco-humeral ligament, and serves mainly as an outer layer for the synovial membrane, offering very little security to the joint, which in reality depends upon the great strength and number of the tendons of TBE REGION OF THE SHOULDER. 333 the muscles with which it is intimately associated. When these tendons are completely severed, the head of the humerus will fall away from the glenoid cavity to the extent of two and a half centimetres, or an inch, or even more, so loose is the capsular ligament ; and likewise the arm appears to be lengthened when the muscles which ordinarily support it are para- lyzed. In fact, the capsule is large enough to accommodate the head of the femur, which is nearly twice the size of the head of the humerus. A knowledge of the arrangement of the tendons about the joint is therefore of great importance, not only in realizing the wide range of motion of which the joint is capable, but also in understanding how to readjust it in case of its dislocation. The tendons of the supra-spinatus, infra-spinatus, and teres minor muscles, as they pass over the capsule to their respective insertions upon the greater tuberosity, strengthen the upper and posterior part; the broad tendon of the sub-scapularis muscle protects it on the inner part, where it comes forward to be inserted into the lesser tuberosity ; and below it receives support from the long head of the triceps muscle. Further- more, the long tendon of the biceps muscle, which is lodged within the deep groove between the tuberosities, pierces the capsular ligament and passes over the head of the humerus to the top of the glenoid cavity, strengthens the upper anterior part of the joint, and prevents the head of the humerus from being brought against the acromion process in the upward movements of the arm. In fact, it is mainly by the normal position of this tendon, assisted somewhat by the atmospheric pressure, that the head of the humerus is retained in its natural position. Occa- sionally the biceps tendon is dislocated out of its groove onto the inner ridge, and abduction is limited by the great tuberosity thus coming almost immediately in contact with the acromion process. From a careful con- sideration of the disposition of the tendons it will be seen that they surround the capsule, except toward the axilla, where the head of the humerus can be readily felt. When the arm is raised and extended, the head of the humerus rests upon. the weak part of the capsule; and it is therefore through this part, between the tendons of the sub-scapularis and the long head of the triceps, that most of the dislocations at this 334 THE EEGION OF THE SHOULDER. joint occur. If the capsule is opened, it presents upon its interior several folds, which have been specialized as gleno-humeral folds. The synovial membrane is reflected upon the inner surface of the capsule and forms fringes at the borders of these folds, and is invaginated about the biceps tendon, which it follows as a tubular sheath down the groove to the extent of five centimetres, or two inches. There is a constant small opening at the upper and inner side of the capsule, which admits the tendon of the sub-scapularis muscle, and by which the synovial membrane communicates directly with the bursa under the tendon. There is also often an opening from the capsule leading into the bursa beneath the tendon of the infra- spinatus muscle. In chronic disease of the joint sinuses are readily estab- lished in the sites of the bursal connections. There is no anatomical communication between the capsule and the bursa under the deltoid muscle, which is interesting because the sub-deltoid bursa is peculiarly liable to independent disease. It is contained within an expansion of loose con- nective tissue beneath the deltoid and overlying the tendons of the spinati muscles. The shoulder-joint is practically a universal joint, and, as it depends upon the arrangement and power of the surrounding tendons, rather than upon the mechanical adjustment of the opposing bony sur- faces, the grouping of the muscles in effecting the various movements should be understood. Extension is effected by the teres major, latissimus dorsi, and the posterior portion of the deltoid. These are assisted in raising the arm by the teres minor and infra-spinatus muscles. Flexion is produced by the coraco-brachialis and the anterior portion of the deltoid, aided by the j^ectoralis major ; abduction, by the deltoid and supra-spinatus ; adduction, by the pectoralis major, teres major, latissimus dorsi, and coraco- brachialis. The shoulder is rotated outward by the infra-spinatus and teres minor, and inward by the sub-scapularis, latissimus dorsi, and teres major. The shoulder-joint is supplied by the circumflex nerve and circumflex artery, which are described on page 342. The deep structures of the shoulder- joint are protected by the great deltoid muscle, which forms a complete shoulder-cap. It arises from the lower border of the outer third of the clavicle, from the acromion process, and from nearly the whole of the spine THE BEGION OF THE SHOULDER. 335 of the scapula (Plate 16). This extensive origin corresponds to that of the trapezius muscle above (page 208). The muscular fibres composing the deltoid are very coarse, and are disposed in bundles or fascicles which are separated by inward expansions of the strong layer of the deep fascia enveloping the muscle upon its outer surface. The bundles thus formed by the fibres arising from the clavicle and from the spine of the scapula gen- erally converge from their origins to their insertions upon the lateral ridges of the deltoid tuberosity, but those of the outer or acromial portion are peculiarly arranged. Here there are additional fibres which originate from the sides of the intramuscular tendinous septa in a bipenniform manner and pass parallel to one another to be inserted by fleshy slips into the middle ridge of the deltoid tuberosity on the outer surface of the shaft of the humerus. The deltoid tuberosity consists, therefore, of three con- verging ridges. The tendon of insertion can be understood only by de- taching the muscle from its origin and reflecting it. When this is done, it will be seen that the insertion is about three and three-quarter centimetres, or an inch and a half, in length, extending upward upon the middle of the shaft from the deltoid ridges, whence fibrous septa are projected into the substance of the muscle between the fibres originating from the apo- neurotic expansions between the fasciculi. In this manner the several fasciculi reinforce one another, and the increased number of their fibres compensates for their length, thus greatly augmenting the functional jDower of the muscle as a whole. Looked at from in front, the insertion of the deltoid resembles the letter V. It is embraced by the fleshy origins of the brachialis anticus muscle, and thus occasions a characteristic depression of the overlying integument. The three parts of the muscle can act sepa- rately in raising the arm in different directions, and they each act to better advantage when the humerus is rotated outwardly. The power of the deltoid depends greatly upon the scapula, being steadied by the serratus magnus, the long head of the triceps, and the middle fibres of the tra- pezius muscles. When the whole muscle contracts, it raises the arm to the horizontal position (at an angle of ninety degrees) : beyond this it cannot act, further elevation being effected by the serratus magnus and trapezius, which then raise the shoulder. The deltoid muscle receives its 336 THE REGION OF THE SHOULDER. blood from the circumflex arteries (page 342), and is supplied by the cir- cumflex nerve (page 346). When the head of the humerus is dislocated into the axilla, the rotundity of the shoulder is lost, the deltoid becomes flattened, and the acromion process is rendered very prominent. In such a condition there is beneath the latter process a marked depression, into which one or two fingers can be inserted, constituting one of the diagnostic features of dis- location at the shoulder-joint. Dislocation at this joint is very common. Primarily the displacement is always downward into the axilla, because it is caused by direct violence received upon the point of the shoulder or by indirect violence while the upper extremity is abducted and the joint conse- quently placed at a disadvantage, the head of the humerus readily slipping through the lowest and weakest part of the capsule (page 832). Sometimes the head of the bone is retained in this position, when it is called a sub- glenoid dislocation. After leaving the capsule, however, the pectoralis major and other muscles having free play, it is most frequently drawn forward and inward, and assumes the character of a sub-coracoid dislo- cation. Rarely the head of the humerus is driven backward under the acromion upon the dorsum of the scapula (sub-sijinous dislocation). In every form of dislocation there will be flattening of the deltoid and more or less stretching of that muscle, and consequently abduction of the arm, with proportionate rigidity. The chief diagnostic symptoms are as follows : the elbow stands away from the side of the body, and the hand of the affected limb cannot be placed in the small of the back nor upon the top of the opposite shoulder. There have been many observations regarding the special anatomy of the various forms of dislocation of the shoulder, but they are of no practical use, beyond the inference that the head of the humerus, in order to be restored to its proper place, must be first restored to the sub-gleuoid position, and then, by circumduction or other means, its reduction may be accomplished. The proximity of the im- portant structures within the axilla renders them liable to injury from pressure of the head of the humerus when it is driven against them, and that they escape with so little damage is probably due to the relaxation of the soft parts which follows upon the shortening of the limb. THE REGION OF THE AXILLA. 337 Fractures involving the anatomical neck of the humerus are ex- tremely rare, and can only be suspected, unless an opportunity is given to explore the joint. The prolongation of the internal and lower fibres of the capsular ligament would connect the fragments unless they were also ruptured. The superior epiphyseal line is below the tuberosities, just where the shaft is widest. It does not become obliterated before the twenty-second year. The upper epiphysis may become detached prior to this period, and simulates the condition of a fracture in the upper part of the surgical neck of the humerus without overlapping. In amputation at the shoulder-joint it is essential that the incisions should be made so as to leave the division of the axillary vessels to the last moment. Whatever method is employed, the long tendon of the biceps muscle should be sought for, and by using its bony furrow as a grooved director the capsule can be slit up and the joint expeditiously opened. In the oval flap method, which the author has found to possess many advantages, the relations of the severed vessels and nerves as they present themselves in the flaps after amputation at the left shoulder are as follows (Plate 50, Fig. 2). The anterior flap is formed by the pectoralis major (No. 3), the heads of the biceps, coraco-brachialis, latissimus dorsi, teres major, and rotator muscles. The axillary vessels (Nos. 1 and 2), the cords of the brachial plexus of nerves (No. 11), and the inferior scapular artery and veins (No. 12) will be found in the axillary border of this flap ; while the long tendon of the biceps (No. 5), a branch of the anterior cir- cumflex artery (No. 7), and the cephalic vein and the descending branch of the acromio-thoracic artery (No. 8) occupy the acromial border of the flap in relation to the severed clavicular portion of the deltoid muscle. The posterior flap is formed mainly by the scapular portions of the deltoid muscle (No. 15), with branches of the posterior circumflex vessels and nerves (No. 14). THE REGION OF THE AXILLA. The region of the axilla, or armpit (Plates 44 and 45), varies in depth with the position of the arm. It is a pyramidal space, bounded internally by the side of the thorax, externally by the arm, and in front 43 338 THE REGION OF THE AXILLA. and behind by prominent muscular folds. The a?iterior fold is formed by the lower border of the pectoralis major muscle (page 253), while the pos- terior fold is formed by the lower borders of the latissimus dorsi and teres major muscles (page 329). The skin of the axilla is closely connected with the subjacent superficial fascia, is provided with long hairs which radiate toward the borders of the cavity, and contains numerous sebaceous glands of a reddish-brown color, which are liable to become inflamed and pro- duce superficial abscesses. It also has very large sweat-glands, and a dense net-work of lymphatic vessels in the corium. There is more or less fat in the meshes of the subcutaneous tissue. The deep fascia is called the axillary fascia. It is very dense, and bears important relations to the fascias of the regions of the neck, thorax, and shoulder. It consists of a close fibrous layer stretching across the base of the axilla, between the anterior and posterior folds. It is continuous with the deep fascia surrounding the pectoralis major muscle (page 255), and with the costo- coracoid membrane above, which, since it draws up the axillary fascia towai'd the clavicle, is known sometimes as the suspensory ligament of the axilla. It produces the characteristic " hollow" of this region. The space beneath the axillary fascia is mainly occupied by a quantity of very loose connective tissue and fat, in which pus or extravasated blood often collects to an extraordinary amount, being checked in its progress toward the surface by the fascia. In consequence of the barrier which this fascia also presents laterally, there is a tendency for unrelieved abscess in this region to extend into the neck along the sheath of the vessels in the direction of least resistance. In opening an axillary abscess, a small incision should first be made through the deep fascia of the floor of the space, upon the inner side, midway between the two axillary folds. As soon as the pus is reached, the opening can safely be enlarged upon a grooved director. Trifling as this operation may seem to the uninitiated, it is fraught with danger unless due precaution is taken to avoid the important structures on the outer and upper part of the space. The muscles forming the posterior wall of the axilla are the latissimus dorsi, teres major, and sub-scapularis. The anterior wall is formed by the under surfaces of the pectoralis major and minor muscles. Upon the inner wall THE REGION OF THE AXILLA. 339 are the four upper ribs, with tlieir intercostal muscles, covered by the serratus magnus. The biceps and coraco-brachialis are upon the outer wall, between the convergence of the two axillary folds. At the apex of the space the axillary vessels and nerves descend outwardly from the root of the neck, whence they bring with them a funnel-shaped prolongation of the deep cervical fascia. This communication between the neck and the axilla constitutes the cervico-axillary passage. It is bounded by the first rib, the clavicle, and the upper border of the scapula. In order to see the con- tents of the axilla, the axillary fascia must be removed. Within the layers of this fascia a small artery will sometimes be found, probably arising from the brachial artery, crossing the floor of the space quite superficially. It is noteworthy, as it is directly in the way of the usual incision for opening an axillary abscess. Whenever the knife is used in this region, great caution must be exercised, and after the preliminary incision it is better to resort to the handle of the knife or to the finger to separate the loose connective tissue and thus expose the lymphatic glands, vessels, and nerves, the relations of which deserve particular attention. Not far from the surface the posterior lateral cutaneous branches of the intercostal nerves will be found perforating the chest wall between the digitations of the serratus magnus muscle (Plate 45). Of these the posterior lateral branch of the second intercostal nerve is specialized as the intercosto-humeral nerve, because it supplies the skin of the inside of the arm as low as the internal condyle (Plate 27, No. 41). It passes across the upper part of the axilla, issuing from the second intercostal space. There is also an inter- costo-humeral nerve from the third nerve, which receives a branch from the second and accompanies it in its distribution. The anterior branches of the above two nerves supply the skin upon the side of the chest and on the axillary folds. The axillary artery is the continuation of the subclavian, and commences at the lower border of the first rib, whence it passes downward and outward along the coraco-brachialis muscle to the lower border of the posterior fold of the axilla. It is separated from the inner side of the shoulder-joint by the insertion of the sub-scapularis muscle into the lesser tuberosity of the humerus. The pectoralis minor muscle (page 255) PLATE 46. Figure 1. The anterior view of the right elbow and forearm of an adult male, with the superficial fascia carefully removed to show the relations of the superficial veins and nerves. The median nerve in the lower third of the arm, over- lapping the brachial artery. The brachial artery. The biceps muscle. The external brachial vein. The external (in this case independent) cephalic vein. The median cephalic vein. The musculo-spiral nerve. The fascia from the biceps tendon, passing beneath the superficial veins at the head of the elbow. A branch of the musculo-cutaneous nerve. A branch of the recurrent radial artery. The median veins (in this case double). The radial vein. The radial nerve. The radial artery with its vense comites. The tendon of the supinator longus muscle. The median nerve, above the wrist. The ulnar nerve. The triceps muscle. 19. The greater internal cutaneous nerve. 20. The lesser internal cutaneous nerve. 21. The internal brachial vein. 22. The anastomotica magna artery. 23. The basilic vein, 24. Branches of the ulnar nerve. 25. Branches of the internal cutaneous nerve. 26. The anastomosing vein. 27. Deep fascia over the flexor muscles. 28. The ulnar vein. 29. The flexor carpi radialis muscle. 30. Branches of the musculo-spiral nerve. 31. Carpal branch of the internal cutaneous nerve. 32. The ulnar nerve. 33. The tendon of the flexor carpi ulnaris muscle. 34. The flexor sublimis digitorum muscle. 35. The ulnar artery and its venae comites. 36. The external carpal branch of the ulnar artery. 37. The annular ligament. Figfure 2. Deeper dissection of same arm as Figure 1. The bicipital fascia and the superficial flexor muscles are renjoved, while most of the superficial veins are retained to preserve their relations. 1. The brachial artery. 2. The biceps muscle. 3. The median nerve. 4. The external brachial vein. 5. The external cephalic vein. 6. The median cephalic vein. 7. The tendon of the biceps muscle. 8. The brachial artery, surrounded by the brachial veins. 9. The musculo-spiral nerve. 10. The communication between the superficial and deep veins, by the vena anastomotica. 11. The anterior interosseous branch of the median nerve. 12. The supinator longus muscle. 13. The median vein. 14. The anterior interosseous artery, with its vense comites. 15. The radial artery, with its venffi comites. 16. The shaft of the radius. 17. The radial nerve. 18. Carpal branch from the radial artery. 19. The triceps muscle. 20. The internal cutaneous nerve. 21. The ulnar nerve. 22. The basilic vein. 23. The internal brachial vein. 24. Branches of the ulnar nerve, over the internal condyle. 25. The cut attachment of the superficial flexor muscles. 26. The deeper portion of the pronator radii teres muscle. 27. The bifurcation of the brachial artery. 28. The origin of the interosseous artery. 29. A muscular branch from the ulnar artery. 30. The ulnar nerve. 31. The flexor carpi ulnaris muscle. 32. The median nerve. 33. The ulnar artery, with its venae comites. 34. The pronator quadratus muscle. 35. Carpal branch of the ulnar artery. PJate 46 Vol I Fie Fra 2 Copyn^ht, 1830, by George Mc Ci bllan, M. D. he he he he he he he he he he he he he he he he he lue Mc. Ci.ellan, M 0. Arms1ro(ie»Ci> L.th Bosro THE REGION OF THE AXILLA. 341 passes across the middle of the artery to be inserted into the coracoid process, so that the vessel is usually described according to its position, — above, under, or below that muscle. In its course there are many branches from it distributed to the neighboring regions. Above the pectoralis minor the superior thoracic and acromio-thoracic arteries arise independently or by a common axis. The superior thoracic passes along the border of the pectoralis minor, and, descending between it and the pectoralis major, supplies them both and anastomoses with branches from the intercostal and internal mammary arteries. The acromio-thoracic artery usually divides very near its origin, as it pierces the costo-coracoid membrane, into several branches. They are the small thoracic or pectoral, to the serratus magnus and pectoralis minor muscles, the descending or thoracica humeraria (Holden), which descends in close relation to the cephalic vein between the deltoid and pectoralis major muscles, both of which it supplies, and the acromial and clavicular branches. The acromial crosses the coracoid process to the under surface of the deltoid muscle, and establishes a communication (the rete acromiale) with the posterior circum- flex and supra-scapular arteries. The clavicular supplies the subclavius muscle. The companion veins of these arteries terminate either in the cephalic or in the axillary vein, — ^generally in the latter. The alar thoracic artery arises variably from the axillary trunk or from its long thoracic branch. It suj)plies the anterior lymphatic glands embedded in the connective tissue of the axillary space. The long thoracic artery (Plate 44, Fig. 1, No. 7) descends close to the lower border of the pectoralis minor muscle. It sometimes gives off the alar artery, but its external mammary branch is usually quite large in the female and passes to the breast along the lower border of the pectoralis major. The short and long sub-scapular arteries are variable in their origin. The short sub- scapular is distributed mainly to the under surface of the sub-scapular muscle. The long sub-scapular artery is the largest of all the branches of the axillary. It descends in relation to the sub-scapularis muscle and divides into anterior and posterior branches. The anterior or thoracic branch descends in relation to the posterior fold of the axilla to the side of the chest, where it ends in the serratus magnus. It also sends a small 342 THE REGION OF THE AXILLA. twig to the inferior angle of the scapula which anastomoses with branches from the dorsalis scapulae and posterior scapular arteries. The posterior branch of the long sub-scapular artery is called the dorsalis scapulos (Plate 45, Fig. 2, No. 17). It passes into the sub-scapular triangle, which is formed by the long head of the triceps muscle passing between the sub- scapularis and teres major muscles to its insertion at the inferior border of the glenoid cavity (page 354). Here it gives oif a deep branch which breaks up into smaller branches in relation to the ridges of the sub- scapular fossa. The superior of these branches is important, because it supplies an articular artery to the shoulder-joint and the principal nutrient artery to the venter of the scapula. The main trunk of the dorsalis scapulae artery winds round and grooves the axillary border of the scapula under the centre of the attachment of the teres minor muscle. Here it supplies this muscle and the adjoining infra-spin atus muscle, and anasto- moses with branches from the posterior circumflex and posterior scapular arteries. The veins which accompany these arteries terminate in the sub- scapular veins, which empty into the axillary veins. Owing to the many sources of arterial supply to the scapula and its muscles and their free anastomoses, the removal of the scapula, or even of growths involving a portion of it, is attended with profuse hemor- rhage. All the main vessels above described require a ligature in these operations, and consequently their relative positions should be carefully studied. The posterior circumflex, artery is nearly as large in diameter as the sub-scapular. It arises opposite to it, and sometimes with it by a common trunk, and passes backward, accompanied by its two veins and the posterior circumflex nerve, round the posterior surface of the neck of the humerus, to the under surface of the deltoid muscle. This artery establishes com- munications with the branches from the acromio-thoracic and supra-scapular and the ascending branch from the superior profunda, and supplies not only the neighboring muscles, but also the head of the humerus and the shoulder-joint. The anterior circumflex artery is much smaller than the posterior, and passes under the coraco-brachialis and the coracoid head of the biceps close to the anterior surface of the neck of the bone. In relation THE REGION OF THE AXILLA. 343 to the bicipital groove this vessel gives oflf the little bicipital artery, which accompanies the long head of the biceps to the capsule of the shoulder- joint and to the head of the humerus. It enters the capsule by a foramen at the top of the bicipital groove. The anterior circumflex communicates with the posterior circumflex beneath the deltoid muscle. There is great variability in the position of the branches of the axillary artery, and sometimes, although rarely, it furnishes the radial or the ulnar artery to the forearm. When the arm is extended in the supine position, a line drawn from the middle of the clavicle to the point where the anterior axillary fold crosses the inner border of the biceps muscle corresponds to the course of the axillary artery. This line also indicates the position of the inter- muscular cleft between the sternal and clavicular portions of the pectoralis major muscle, in which the axillary artery can be most easily reached, as it lies upon the first intercostal space below the clavicle. The point where the pectoralis minor muscle crosses the artery may be designated by a line drawn from the coracoid process to the junction of the third rib and its cartilage. The artery is inaccessible for a ligature beneath the pecto- ralis minor muscle, so that its relations above and below that muscle are of peculiar interest to the surgeon. When tied in the upper part, the collat- eral circulation is established through the same vessels as after the ligature of the outer part of the subclavian artery (page 232). In the operation for tying the lower part of the axillary artery the incision should be made upon the inside of the bulge of the biceps muscle when the arm is ex- tended, and by following upward along the border of the coraco-brachialis muscle the artery will be found enveloped in its sheath and closely surrounded by the two brachial veins, the basilic vein, and the median and ulnar nerves. In this relation there are often connecting links be- tween the veins extending across the artery, and often, too, accessory slips from the latissimus dorsi muscle to the insertion of the pectoralis major, and therefore, in spite of the artery being more superficial in this locality, it is very difficult of access. The collateral circulation here is similar to that which occurs upon the ligation of the brachial artery above the origin of the superior profunda, — i.e., by the communication of that vessel with 344 THE HEGION OF THE AXILLA. the branches of the posterior circumflex and the neighboring muscular arteries. If, before applying the ligature, the forearm is flexed and the position of the arm is changed, there can be little difficulty in distin- guishing between the artery and the nerve-cord of the brachial plexus, which is close to it. This nerve-cord has been mistaken for the artery in several recorded instances. The axillary vein is the continuation of the basilic vein upward from the lower border of the posterior axillary fold to the outer border of the first rib. In its course it receives as tributaries the venae comites of the branches of the axillary artery, except the circumflex veins, which either join the sub-scapular or empty into one of the brachial veins. Either just before or at its termination in the subclavian vein the axillary vein receives the two brachial veins and the cephalic vein (Plate 45, Fig. 2). The orifices of the tributary veins are guarded by single valves, but there are double valves at the termination of the main trunk. The axillary vein is more superficial than the artery, and throughout most of its course, when the arm is at the side, the vein is in front of and internal to the artery, but when the arm is slightly raised the vein, although still in front, is below the artery. If the arm is raised to more than a right angle, the vein will overlap the artery above the pec- toralis minor. Just above its commencement the axillary vein is separated from the artery by some of the nerves of the brachial plexus. The costo- coracoid membrane is intimately adherent to the external coat of the axillary vein where it pierces that dense fascia to empty its blood into the subclavian vein. This attachment serves to keep the vessel open when it is wounded, and probably explains the great rush of blood when it is severed. Its position also renders it liable to be influenced by the inspira- tory movements of the chest, and thus air may be drawn into the heart through the vessel if the latter be wounded. In amputation at the shoulder-joint (Plate 50, Fig. 2) it is important to secure the axillary vein with a ligature immediately after tying the axillary artery. The brachial or axillary plexus of nerves is formed by the anterior branches of the fifth, sixth, seventh, and eighth cervical and first dorsal nerves, each branch consisting of muscular and cutaneous fila- THE REGION OF THE AXILLA. 345 ments in close association. The fifth receives a descending or communi- cating branch from the fourth cervical above it, and then joins with the sixth to form the upper trunk of the plexus. The seventh cervical pursues an independent course as far as the clavicle, and is the middle trunh, while the eighth cervical and first dorsal as they issue from beneath the scalenus anticus muscle unite in relation to the first rib to form the lower trunk (Plate 4, Fig. 2, and Plates 20, 25, and 33). The arrange- ment of the nerves contributing to the plexus is variable, especially upon the left side, but the following corresponds to most of the author's dis- sections. At the outer border of the scalenus medius muscle the three great nerve-trunks divide into anterior and posterior branches. The anterior divisions from the upper and middle trunks form the outer cord of the plexus, the anterior division from the lower trunk furnishes the inner cord, and the posterior divisions of the upper and middle trunks unite behind the axillary artery to form the posterior cord, which also receives the small posterior division of the lower trunk, but the latter is often found passing directly to form part of the musculo-spiral nerve. At its commencement the plexus is broad (Plate 25), but it becomes narrow opposite the clavicle (Plate 36), and forms below it an intricate interlace- ment about the axillary artery (Plate 45, Fig. 2) beneath the pectoralis minor muscle. In the root of the neck the nerve-trunks receive some filaments from the cervical ganglia of the sympathetic nerve, and the fifth cervical nerve sends a branch to join the phrenic nerve as it passes down over the scalenus anticus muscle (page 221). The branches from the brachial plexus above the clavicle, besides the one to the phrenic nerve, are smiall muscular nerves to the longus colli and scalene muscles, and a branch which pierces the scalenus medius and accompanies the pos- terior scapular artery to supply the levator anguli scapulae and rhomboid muscles. The supra-scapular nerve arises from the upper trunk of the plexus, and passes to the superior border of the scapula beneath the supra- scapular artery through the notch in the scapula. It furnishes nerves to the spinati muscles and to the shoulder-joint. 'Y\\q posterior thoracic nerve (or external respiratory nerve of Bell) arises usually from the upper trunk, at the outer border of the scalenus medius, and sometimes receives a branch 44 346 THE REGION OF THE AXILLA. from the middle trunk. It passes behind the axillary artery, and sup- plies the serratus magnus muscle, which it enters upon the outer surface (Plate 45, Fig. 2, No. 38). The branches below the clavicle are mainly for the supply of the arm. The external and internal anterior thoracic nerves arise by filaments from the anterior divisions of the three trunks of the plexus. The external anterior thoracic nerve pierces the costo-coracoid membrane in close rela- tion with the acromio-thoracic artery, and supplies the adjacent parts of the pectoralis major muscle. The internal anterior thoracic nerve is joined by a filament from the former, and, after passing between the axillary vessels, supplies the pectoral muscles. The sub-scapular nerves, three in number, arise from the posterior cord of the plexus and are distributed to the sub- scapularis, teres major, and latissimus dorsi muscles. The nerve to the last muscle is called the long sub-scapular nerve, and accomj)anies the sub- scapular artery to the lower border of the muscle. The circumflex nerve arises from the posterior cord anterior to the sub-scapular nerves. It is a large nerve, and after sending a filament to the shoulder-joint it accompa- nies the posterior circumflex artery round the surgical neck of the humerus beneath the deltoid muscle. It divides into many branches, which supply the skin over the deltoid and the upper and back part of the arm (Plate 27, No. 37). Very curiously, the branch of the circumflex nerve which supplies the teres minor muscle possesses a small pseudo-ganglion close to its origin. Branches also pass to the front and back parts of the capsular ligament. The terminal branches of the brachial plexus are described with the arm (page 357). The lymphatic glands of the axilla (Plates 44 and 45) receive the lymphatic vessels from the upper extremity, from the back, from the anterior portion of the chest, and from the outer portion of the mammary gland (page 251). They form a continuous chain with the cervical lym- phatic glands passing beneath the clavicle to the root of the neck. They are about a dozen in number, of variable size, and are mostly in close relation to the axillary vein and its larger tributaries. There is also a cluster of the glands situated more superficially than the deeper ones, and embedded in the loose connective tissue and fat of the axillary space. The THE REGION OF THE AXILLA. 347 thoracic and sub-scapular arteries furnish blood to the deeper glands, while the superficial ones are supplied by the alar thoracic artery. The lymphatic vessels from the outer side of the arm and shoulder pass to a couple of glands in the groove between the deltoid and i3ectoralis major muscles, over the costo-coracoid membrane, near the cephalic vein. The efferent vessels from these usually pass to the cervical glands directly, while the lymphatic vessels from the inner side of the arm terminate in three glands situated along the axillary vein. A gland is generally found in relation to the sub-scapular artery, and another on the tendon of the latissimus dorsi close to the humerus. The superficial lymphatic vessels of the back are derived from the whole expanse of that region, from the nape of the neck to the loins. They converge to the axilla, and end in the glands in the upper and back part of the cavity. The lymphatic vessels from the nipple, the areola, and the outer portion of the breast convey their lymph to two or three glands situated upon the serratus magnus muscle under cover of the lower border of the pectoralis major muscle. The efferent vessels from all the axillary glands resolve themselves into four lymph -trunks, which pass along with the subclavian vein and terminate upon the right side in the right lymphatic duct and upon the left side in the thoracic duct (page 318). When the axillary glands are in a normal condition they cannot be felt through the skin ; and it is not always possible to detect them even when they are slightly enlarged. Their secondary involvement in scirrhous disease of the breast is so common that it is advisable in all such cases, when an operation is resorted to, to extend the incision into the axillary space, so that the finger can thoroughly explore the cavity. With the exception of the removal of the chain of cervical glands from about the internal jugular vein, there is no operation of a similar nature more trying to the skill and patience of the surgeon than the removal of the axillary glands about the axillary vessels. They are closely associated at all times with the thin walls of the great veins in this region, but when implicated with disease their relation is of the most intimate character, and they have literally to be peeled off one by one, at imminent risk of rupturing the veins. No rough handling of the structures in the apex of the axilla 348 THE REGION OF THE ABM. during an operation would be countenanced by one whose scalpel had ever unravelled the intricacies of these parts in his student days, THE REGION OF THE ARM. The arm extends from the axilla to the elbow. It has already been stated (page 332) that the shape of the shaft of the humerus above the deltoid insertion is cylindrical ; below it is prismatic and slopes gradu- ally downward and slightly forward to the lower end, where it becomes transversely flattened (Plate 28). The central portion of the lower end of the humerus is peculiarly formed for articulation with the ulna. It is called the trochlea, and consists of a smooth, rounded, condyloid surface, which is constricted at the middle so that the inner jDortion is somewhat larger and projects lower than the outer. Above the constriction ante- riorly there is a depression for the recejition of the coronoid process of the ulna when the forearm is flexed, called the coronoid fossa. Pos- teriorly there is a similar but larger depression, the olecranon fossa, for the olecranon process of the ulna when the forearm is extended. The por- tion of bone between these fossae is exceedingly thin and translucent, and sometimes perforated, forming the supra-trochlear foramen. Jutting out from the internal portion of the trochlear surface is a prominent process, the internal epicondyle, and to the periosteum over this process the flexor muscles of the wrist and hand are attached. The internal epicondyle looks directly inward when the arm hangs naturally at the side, and occupies a lower plane than the external epicondyle, which is the corre- sponding process upon the outer portion of the trochlear surface. The latter is rough and comparatively short, and gives attachment to the origins of some of the extensor muscles. Upon the outer surface of the trochlea is a small spheroidal forward projection, called the capit- ulum, upon which the cujs-shaped depression on the head of the radius rests and glides within the elbow-joint. The outer and inner borders are directly continuous with the epicondyles, and are known as the ex- ternal and internal sujjra-condyloid ridges. Upon the posterior surface of the internal epicondyle there is a slight groove for the ulnar nerve. The epicondyles are the only parts of the humerus which are subcuta- THE REGION OF THE ABM. 349 neous, and, although the shaft of the humerus can be felt through the soft structures, there are no other bony prominences, and therefore the surface-marking, which is due to the contour of the various muscles, is of particular interest in relation to the subjacent parts. This is more pro- nounced in well-developed muscular men than among women whose arms are rounded and of regular outline. Fat, here, as in other parts of the body, always subdues the depressions and renders them less discernible. The skin on the front and inner surface of the arm is especially smooth, free from hairs, delicate, and extremely sensitive, while on the back and outer surface it is somewhat thicker and less sensitive. The skin is also loosely attached to the deeper parts by the subcutaneous fascia. This is often manifest in cellulitis, and in amputation through this part of the upper extremity the laxity of the integument allows it to be drawn away from the muscles with very little effort. For this reason the method of applying the knife from without inward in amputation through the arm is suggested to those who may be called upon to do this operation with- out much practical experience, as it secures ^^ops with bevelled edges (Plate 51, Fig. 1). The triangular depression caused by the insertion of the deltoid muscle (page 335) can generally be recognized upon the surface with ease, and, as it indicates the precise mid-point of the shaft of the humerus, it is an important landmark. Exactly opposite to it, upon the inside of the arm, is the insertion of the coraco-brachialis muscle. The bulge of the biceps muscle causes its outline to be usually well defined in the front of the arm, so that there are furrows or depressions upon each side of it. The outer bicipital depression extends from the bend of the elbow to the insertion of the deltoid, and corresponds to the position thus far of the cephalic vein (Plate- 45, Fig. 1, No. 29), which ascends above this in the groove between the deltoid and pectoralis major muscles and empties into the axillary vein. It is accompanied by the descending branch of the acromio- thoracic artery and the upper external cutaneous nerve. Sometimes there is a connecting vein between the cephalic vein and the external jugular or the subclavian, which passes over the clavicle, and, being subcutaneous, is readily seen during life. The inner bicipital depression is more notice- PLATE 47. Figure I. The radial border of the forearm and elbow, showing the relations of the superficial veins— the superficial fascia being carefully removed— to the muscles and tendons. 1. The biceps muscle. 2. The external cephalic vein, a direct continuation of the radial vein. 3. Branches of the musculo-cutaneous nerve. 4. The musculo-spiral nerve. 6. The tendon of the extensor communis digitorum mus- cle. 6. The tendon of the extensor secundl Internodil pollicis muscle. 7. The posterior annular ligament. 8. The external brachial vein. 9. The median nerve. 10. The basilic vein. 11. The bicipital fascia. 12. The median vein. 13. Branches of the musculo-spiral nerve. 14. The tendon of the flexor carpi radialis muscle. 15. The tendon of the supinator longus muscle. 16. The radial nerve passing round to the baeli of the wrist. 17. The tendon of the extensor ossis metacarpi pollicis muscle. 18. The tendon of the extensor primi internodil pollicis muscle. 19. The radial artery, seen through the deep carpal fascia. Figure 2. The anterior view of the left elbow to show particularly the bicipital fascia in relation to the superficial veins and the deep vessels and nerves. 1. The brachial artery. 2. The basilic vein. 3. The anastomotica magna artery. 4. The ulnar nerves. 5. The internal cutaneous nerve. 6. The branches of the ulnar and internal cutaneous nerves around the internal condyle of the humerus. 7. The ulnar vein. 8. The branches of the internal cutaneous nerve in the forearm. 9. The biceps muscle. 10. The median nerve. 11. The brachial vein. 12. The median basilic vein. 13. The brachial artery at the bend of the elbow. 14. The tendon of the biceps muscle. 15. The median cephalic vein. 16. The vena anastomotica. 17. The bicipital fascia. 18. The median vein. Figure 3. Dissection of the veins on the bacli of the hand and forearm, with their relations to the underlying tendons and nerves. 1. The posterior ulnar vein. 2. The common ulnar vein. 3. The posterior annular ligament. 4. The carpal branch of the ulnar nerve. 6. The vena salvatella. 6. The posterior radial vein. 7. The radial vein. 8. The radial nerve. 9. The radial artery. 10. One of the dorsal interossel arteries. Plate 47 vol i l-ip Fip 2 *N1 F:P 3 Copyright, ISSa by- Georse Mc Clellan, M. D. =d3£<££aiEdiediEdJE(£Ed3£dj£di£aiEdiediEd3£(l}Ed3Edj£diE0RGE Mc. Clellan. M D. THE BEQION OF THE ARM. 351 able than the outer ; it extends from the middle of the bend of the elbow all the way to the axilla, and indicates the course of the brachial artery and its companion veins and nerves. The deep fascia of the arm is a continuation from the fascia of the shoulder and axilla. It forms a close-fitting investment for all the mus- cles in this region, and sends into each condyloid ridge of the humerus strong septa which divide the muscles in front from those behind. In certain localities it expands so as to form protected passage-ways for im- portant vessels and nerves, as over the musculo-spiral groove on the pos- terior surface of the humerus for the nerve of that name and the superior profunda artery which accompanies it, and on the border of the humerus above the internal condyle, where it sometimes forms a dense band across the median nerve. Here its attachment to the humerus is occasionally ossified, presenting a hook-shaped process of bone, which is then called the supra-condyloid process. The deep fascia is also pierced here and there by the nerves which pass down to be distributed to the forearm, and at the middle of the internal bicipital depression there is an oval opening, the hiatus semilunaris, for the basilic vein. There is marked variability in the density of the deep fascia in its different relations. Thus, over the biceps it is quite thin, but upon the inside of the arm, where it passes between the biceps and the brachialis anticus, it is very strong, forming a dense sheath for the brachial vessels and nerves and binding them upon the surface of the latter muscle. At the back of the arm the fascia constitutes a strong envelope over the biceps muscle, and in front, as it approaches the elbow in relation to the tendon of the biceps, it is also remarkably strong. The biceps muscle is so called because it has a double origin. The long head arises by a long round tendon from the top of the glenoid cavity and the glenoid ligament, and, arching over the head of the humerus within the capsule of the shoulder-joint, pierces the latter between the two tuberosities and descends in the bicipital groove between them, covered with a reflection of the synovial membrane of the joint (page 334), which serves to lubricate it and facilitate its movements. It is held in place by the tendon of the pectoralis major muscle, which passes over it to be 352 THE REGION OF THE ARM. inserted into the outer ridge of the groove, being also connected to the latter muscle by its sheath. The short head arises by fleshy and tendi- nous fibres from the point of the coracoid process together with the coraco-brachialis muscle (Plate 44, Fig. 2, No. 23). About the middle of the arm the two heads unite and form a single mass of muscle, which is subject to great variation in development in different individuals, and terminates suddenly in a strong flat tendon. This tendon is of con- siderable length, is subcutaneous, and can be readily felt upon contrac- tion of the muscle. It twists somewhat upon itself and sinks into the ante-cubital fossa to be inserted into the lower and posterior part of the bicipital tubercle of the radius, a bursa being interposed between the tendon and the front of the tubercle. Before the tendon enters the fossa it gives off" from its inner border a semilunar fold of fascia which protects the brachial vessels and the median nerve at the bend of the elbow (Plates 46 and 47). The action of the biceps muscle is to both Jlex and supinate the fore- arm. The function of supination ensues upon the manner of its insertion into the posterior part of the tubercle of the radius, and is most effectually accomplished when the elbow is bent, because the tendon then passes at a right angle to its insertion. The peculiar ligamentous function of the long tendon at the shoulder-joint has already been described (page 333). The biceps receives two branches from the brachial artery. One of these is called the vas aberrans (page 355). It enters about the middle of the muscle, and divides within its substance into ascendino; and descending branches. Each head of the muscle receives a branch from the musculo- cutaneous nerve (page 362). The coraco-brachialis (Plate 44, Fig. 2, No. 7, and Plate 45, Fig. 2, No. 29) is a slender muscle on the inner side of the short head of the biceps, in common with which it arises by fleshy fibres from the coracoid process of the scapula. It is inserted by a flat tendon at the middle of the inner surface of the shaft of the humerus, just above the foramen for the nutrient artery to that bone. This muscle is pierced by the musculo- cutaneous nerve in its upper portion (Plate 45, Fig. 2, No. 27), which also supplies it. Its action is to draw the arm forward and inward upon the THE REGION OF THE ABM. 353 side of the chest. Not only is the upper portion of this muscle the guide to the axillary artery (page 343), but, as the brachial artery is in rela- tion to its flat tendon of insertion, it can here be effectually compressed if the pressure is directed outward. This is the usual site for the applica- tion of a tourniquet; but it should always be remembered that the close relation of the median nerve (page 357) renders it liable to be included in the pressure and therefore to cause great pain. There is a bursa inter- posed between the tendons of the coraco-brachialis and the short head of the biceps and the tendon of the subscapularis muscle over the head of the humerus. The brachialis anticus muscle arises by two fleshy portions, one upon each side of the insertion of the deltoid, and from the lower part of the front surface of the humerus, which it covers. Its inner border is also connected with the septum from the deep fascia which separates it from the triceps posteriorly. Its fibres are arranged in nearly parallel bundles, so that they form a broad thick mass superposed upon the capsule of the elbow-joint, to which it is slightly attached. Its tendon is flat, and upon the outer border extends into the substance of the muscle. It is chiefly inserted into the coronoid process of the ulna, and reflected upon a ridge from this process to the tuberosity of the ulna. It forms a pad to the elbow, upon which the brachial vessels and the median and musculo- cutaneous nerves are supported internally, as they pass across the joint under protection of the expansion from the tendon of the biceps muscle. Externally the brachialis anticus is quite superficial, and separated from the supinator longus muscle by a furrow in which is lodged the musculo- spiral nerve (Plate 47, Fig. 1, No. 4), from which it receives a small branch, although its main nerve-supply is from the musculo-cutaneous nerve upon its inner side. Its action is to flex the elbow. The triceps extensor cubiti is so called from its triple origin and its peculiar function of being the sole extensor muscle of the forearm. It is situated at the back of the arm. The long or middle head arises by a strong thick tendon from the bottom of the glenoid cavity and the lower portion of the glenoid ligament. It is closely connected with the capsule of the shoulder-joint. As it passes between the tendons of the teres 45 354 THE REGION OF THE ARM. minor and major muscles (page 329) it becomes more fleshy. The outer head begins immediately below the attachment of the teres minor muscle, and is itself attached all the way to the musculo-spiral groove and to the reflection of the deep fascia. The inner head arises close to the in- sertion of the teres major muscle, and from the posterior surface of the humerus below the musculo-spiral groove nearly as far as the inter- nal epicondyle. Its flbres arrange themselves into an oblique tendon which blends with the muscular mass composed by the union of the fleshy portions of the other two heads about the middle of the back of the arm. The combined tendon thus formed is thick and remark- ably strong. It is inserted into the summit and sides of the olecranon process of the ulna. Between the tendon and the back part of the capsule of the elbow-joint there is a cushion of fatty tissue, which has sometimes been described as a bursa. From the tendinous portion of the inner head some muscular fibres pass directly to the olecranon and the adjacent portion of the capsule, and have been specialized as the sub- anconeus muscle. The musculo-spiral nerve separates the outer from the inner heads, and sends branches to all the heads of the triceps muscle. The brachial artery is the continuation downward of the axillary artery. It commences at the lower border of the posterior fold of the axilla, at the inner border of the coraco-brachialis muscle, whence it passes along the inner border of the biceps muscle to the middle of the flexure of the elbow, where, opposite the head of the radius, it divides into the radial and ulnar arteries. The above muscles slightly overlap the artery in its course, which is at first internal to the shaft of the humerus upon the triceps and brachialis anticus muscles and sub- sequently gradually inclines to the front of the lower end of the bone beneath the bicipital semilunar fascia. The brachial artery gives off seven or eight muscular branches from its outer side to the contiguous muscles, and four principal branches from its inner side, as follows : The superior profunda artery usually arises from the brachial below the teres major muscle, although it is sometimes given off in common with the posterior circumflex from the axillary. Soon after its origin it dis- tributes muscular branches to the deltoid, the coraco-brachialis, and the THE REGION OF THE ARM. 355 long head of the triceps muscle ; also a communicating branch to the poste- rior circumflex, which plays an important rdle in the collateral circulation after ligature of the main vessel in this locality, and a nutrient branch, which enters the upper end of the humerus beneath the outer head of the triceps. About the middle of the arm the superior profunda subdivides into two principal branches, one of which, the cubital, descends through the substance of the triceps muscle to the olecranon process, where it an- astomoses with the anastomotica magna, posterior ulnar, and interosseous recurrent arteries, assisting in the formation of the rete olecrani; while the other branch accompanies the musculo-spiral nerve to the outer side of the arm, where, after piercing the intermuscular septum, it descends deeply with the radial nerve in the furrow between the brachialis anticus and supinator longus muscles to anastomose with the radial recurrent artery about the external epicondyle. The inferior profunda artery arises either in common with the superior profunda or by a separate origin at the middle of the arm, and pursues a course with the ulnar nerve through the intermuscular septum to the interval between the internal epicondyle and the olecranon, where it also terminates in the rete olecrani. The main nutrient artery is usually derived from one of the muscular branches of the brachial. It pierces the tendon of the coraco-brachialis muscle to enter the nutrient foramen, and within the medullary canal divides into ascending and descending- branches which anastomose with the nutrient vessels derived from the periosteum. The anastomotica magna arises from the brachial about six centimetres, or two and a half inches, above the bend of the elbow. It runs at first inward across the brachialis anticus muscle, and then divides into branches, one of which descends antetiorly between the brachialis anticus and pronator radii teres muscles in front of the internal epicondyle to anastomose with the anterior ulnar recurrent artery, another pierces the intermuscular septum posteriorly to anastomose with the posterior ulnar recurrent and inferior profunda arteries in the rete olecrani, while a third usually arches over the olecranon fossa and joins the superior profunda artery. Besides these regular branches of the brachial artery there is another, called the vas aberrans, which ordinarily is quite insignificant 356 THE REGION OF THE ARM. and arises near the origin of the superior profunda or in common with it, and descends over the median nerve to supply the neighboring part of the biceps muscle. This vessel occasionally plays an important role in replacing the brachial artery when that vessel has undergone some modifying change in consequence of interference with its development during foetal life. In such cases it pursues the ordinary course of the brachial artery, except that it is placed over instead of under the median nerve, and it joins the radial artery, or very rarely the ulnar. It is of variable size, and, owing to its substituting one or other of the terminal branches of the main vessel, it occasions the condition called the high bifurcation of the brachial. The possibility of such an occurrence should never be lost sight of in the operation of tying the brachial artery. The line of reference for the brachial artery is practically a continuation of the line for the axillary artery (page 343), and may be drawn along the internal bicipital depression from the middle of the axillary space to the middle of the bend of the elbow. The incision should be made along the above line, with the arm abducted and rotated outward. The basilic vein (page 351) will be found in the superficial fascia, and can be drawn aside. The deep fascia should be divided upon a grooved director, and when the biceps muscle has been drawn outward the sheath of the brachial vessels will be exposed, with the median nerve lying directly over it ; and, as the nerve may therefore receive pulsations from the artery, it requires careful examination lest it be mistaken for the vessel itself After much experience as a teacher of operative surgery, the author feels justified in stating that the inexperienced generally find more diffi- culty in securing the brachial artery properly than in securing any other artery in the body. This may be due to the belief that the task is an easy one, owing to the straight course and somewhat superficial position of the vessel. The disposition of the median nerve is most important, and if understood it may serve as a deep guide to the artery. This nerve in the upper part of the arm is generally at the outer side of the artery, but it very soon approaches the sheath of the brachial vessels and overlies it as far as the semilunar bicipital fascia, where the artery passes to the middle of the elbow-joint, and the nerve continues, at its THE REGION OF THE ARM. 357 inner side, to descend between the two beads of tbe pronator radii teres muscle, Tbere is an investment of tbe deep fascia wbicb retains the nerve in this relation to the sheath of the vessels even if the position of the arm is changed in extension, but if tbe forearm is flexed after tbe deep fascia is divided the nerve can be drawn to one side or tbe other and tbe underlying sheath exposed. When tbe latter is opened, the artery- will be found with a companion vein upon each side of it. It should be further remembered that tbe upper part of tbe artery is over tbe musculo- spiral nerve, that the ulnar nerve is close to its inner side as far as tbe insertion of the coraco-brachialis muscle, and that toward tbe elbow tbe internal cutaneous nerve is either in front of or close to its inner side. The vence comites of the brachial artery are tbe continuations of the deep radial and ulnar veins (Plate 46, Fig. 2). Tbe internal is usually much larger than tbe artery, and often overlaps it. They are frequently united by cross veins, similar to those about tbe axillary artery, either in front of or behind the artery, and they unite in a single trunk in the axilla to empty into the axillary vein near tbe tendon of tbe sub- scapularis muscle. Tbe terminal branches of the brachial plexus of nerves (page 344) are the median, tbe musculo-cutaneous, tbe ulnar, tbe two internal cutaneous, and tbe musculo-spiral nerves. The median nerve is composed of a plexi- form arrangement of fibres derived from two heads which arise respectively from tbe outer and inner cords of the brachial plexus and unite to form a single nerve-cord external to tbe axillary artery, generally beneath tbe pec- toralis minor muscle (Plate 45, Fig. 2, No. 23). In its course down the arm the median nerve does not normally give off any branches. It is usually at first at tbe outer side of the artery, near tbe axilla, although not always so, and it soon overlies the sheath of the brachial vessels until it reaches tbe elbow, where it is at the inner side of the artery, as already described. The deep fibres of origin to tbe outer head of tbe median nerve are derived from tbe sixth and seventh cervical nerves, and those to the inner head are derived from tbe eighth cervical and first dorsal nerves. Tbe musculo-cutaneous nerve arises from the outer cord of the brachial plexus in common with the external head of the PLATE 48. Figure 1. Dissection of the palm of the right hand, showing the superficial layer of the palmar fascia. 1. The abductor poUicis muscle. 2. Slip of the palmar fascia, passing to the proximal pha- lanx of the thumb. 3. Lateral nerve to the thumb. 4. Accessory transverse slip of the palmar fascia, arching over the vessels and nerves to the thumb. 5. The princeps polllcis artery. 6. The superficial layer of the palmar fascia, showing its longitudinal fibres and expansion. 7. Arch of the palmar fascia, between the metacarpal bones of the index and middle fingers, over the digital vessels and nerves. 8. Tendon of the palmaris longus muscle. 9. The ulnar artery, at the wrist. .0. The abductor minimi digiti muscle. 1. The external lateral nerve and artery to the little finger. .2. Arch of the palmar fascia, between the little and ring fingers. The branches of the median nerve. 13, Figure 2. Dissection of the palm of the right hand. The superficial layer of the palmar fascia is hooked aside to show the deep layer of the fascia and the superficial palmar arterial arch. The superflcialis volae artery. The abductor pollicis muscle. The continuation of the superficialis volee artery. The deep layer of the palmar fascia, over the median nerve and the flexor tendons. The flexor brevis pollicis muscle. The superficial palmar arch. Digital branches of the median nerve. The superficial layer of the palmar fascia, hooked aside. Branches of the median nerve, dividing at the cleft of the fingers into digital nerves. 10. The annular ligament. 11. The ulnar artery. 12. The ulnar nerve. 13. The abductor minimi digiti muscle. 14. Branches of the median nerve. 15. The external lateral artery to the little finger. 16. Branch of the superficial palmar arch. 17. Tendinous insertion of the palmar fascia to the meta- carpal bone of the ring finger. 18. Superficial flexor tendon to the ring finger. 19. Digital nerves from the median nerve. Figure 3. Dissection of the palm of the right hand, showing the position of the superficial arterial arch and the relations of Its digital branches to the nerves and fiexor tendons. 1. The fiexor carpi radialis tendon. 2. The median nerve, above the annular ligament. 8. The abductor pollicis muscle. 4. The median nerve, below the annular ligament. 5. The princeps pollicis artery. 6. The fiexor tendon to the index finger. 7. Aponeurotic arch. 8. Sheath of flexor tendons. 9. Aponeurotic arch. 10. The subdivision of the superficial flexor tendons, to be Inserted in the sides of the second, or intermediary, phalanx. 11. Anastomosing branches of the digital arteries, across the phalangeal joint. 12. Aponeurotic arch. 13. Terminal arterial plexus. 14. The ulnar artery. 15. The annular ligament. 16. The ulnar nerve. 17. The superficial palmar arch. 18. Superficial flexor tendon. 19. Aponeurotic arch of the fiexor tendon to the ring finger. 20. Deep flexor tendon of the ring finger. Figure 4. Dissection of the palm of the right hand. The tendons are cut away to show the deep palmar arterial arch and Its relations, etc. 1. The median nerve, above the annular ligament. 2. The opponens pollicis muscle. 3. The abductor pollicis muscle. 4. The superficialis volffi artery. 6. The flexor brevis pollicis muscle. 6. Branch of the median nerve to the thumb, 7. The adductor pollicis muscle. 8. The tendon of the flexor longus pollicis muscle. 9. The cut ends of the flexor tendons. 10. Sheath of the flexor tendons. 11. Aponeurotic arch. 12. Terminal arterial plexus. 13. The ulnar nerve. 14. The ulnar artery. 15. The annular ligament. 16. The median nerve, below the annular ligament. 17. The flexor brevis minimi digiti muscle. 18. The deep palmar arch. 19. The superficial palmar arch. 20. The cut ends of the flexor tendons. 21. Aponeurotic arch. 22. Insertion of superficial flexor tendon into the sides of the Intermediary phalanx of the ring finger. 23. Terminal arterial plexus. Plate 48 Vol '^G'iffGOnO-inO-iRG-iRG-iRG-iRO-iRG-iRG-iRG-iRG-iRG-iRG-iRG-iRO-iRG-iRGlROE Mc. Ci.FLLAN, MO. Copynpht, 1890. by Gi'OHGE Mc ClelLAN, M. D, THE BEGION OF THE ARM. 359 median nerve, at the outer side of the axillary artery. It pierces the coraco-brachialis muscle and passes obliquely to the septum between the biceps and braehialis anticus muscles. Above the outer side of the elbow the nerve pierces the deep fascia between the tendon of the biceps and supinator longus muscles, and becomes subcutaneous beneath the median cephalic vein (Plate 46, Fig. 1, No. 9). It supplies branches to the coraco-brachialis, the coracoid head of the biceps, and the braehialis an- ticus muscles. This nerve is sometimes derived from the median nerve, or, if it is absent, the median nerve distributes the branches ordinarily supplied by it, — the whole of the outer cord of the brachial plexus, in such instances, contributing to the formation of the median. Division of the musculo-cutaneous nerve at its origin will result in paralysis of the flexor muscles at the elbow. Its fibres have been traced to the fifth and sixth cervical nerves. The ^ilnar nerve arises from the inner cord of the brachial plexus in common with the internal head of the median nerve and the internal cutaneous nerve. In its course normally this nerve gives off no branches in the arm. At first it is internal to the brachial artery, but it soon leaves it to accompany the inferior profunda artery, with which it pierces the intermuscular septum fourteen centimetres, or about five inches, above the elbow, and descends on the inner head of the triceps muscle to reach the space between the internal epicondyle and the olecranon. Here it is accommodated in a shallow groove upon the back of the epicondyle (page 348), and can be felt through the skin. The internal cutaneous nerve, after its origin from the inner cord of the brachial plexus, descends at first beneath the deep fascia on the inner side of the brachial artery. About the middle of the arm it pierces the fascia at the hiatus semilunaris, which also admits the basilic vein (page 351), and divides into anterior and posterior branches. The anterior branch passes under the median basilic vein and supplies the skin on the forearm as far as the wrist, where it communicates with cutaneous branches of the ulnar nerve. The posterior branch soon subdivides into several branches, one of which is distributed to the back of the internal epicondyle and communicates with the lesser internal cutaneous 360 TSE REGION OF THE ABM. nerve, and anotlier to the back of the forearm as far as the wrist, above which there is a connection between it and the ulnar nerve. The fibres composing both the ulnar and the internal cutaneous nerves are originally derived from the eighth cervical and first dorsal nerves. The lesser internal cutaneous nerve {of Wrisberg) arises also from the inner cord of the brachial plexus, receiving its filaments from the first dorsal nerve. It is at first upon the inner side of the axillary vein, and near the anterior fold of the axilla it usually unites with the posterior division of the lateral cutaneous branch of the second intercostal nerve, or intercosto-humeral nerve (page 339) : the compound nerve thus formed pierces the deep fascia and supplies the skin of the inside of the arm as far as the elbow. The musculo-spiral nerve arises fi'om the posterior cord of the brachial plexus, in common with the circumflex nerve (page 346), their original filaments being derived from the sixth, seventh, and eighth cervical and first dorsal nerves. The musculo-spiral nerve is the largest of the nerves of the arm. It descends behind the upper part of the brachial artery and passes between the external and the internal heads of the triceps muscle, winding obliquely round the back of the shaft of the humerus with the superior profunda artery in the musculo-spiral groove. Thence it pierces the intermuscular septum and enters the furrow between the brachialis anticus and supinator longus muscles, both of which it supplies upon the outer side of the lower third of the arm, where it divides into two terminal branches, the radial and posterior interosseous nerves. In the first part of its course, behind the brachial artery, the musculo-spiral nerve gives off" branches as follows : the nerve to the long head of the triceps; the posterior internal cutaneous nerve, which supplies the area of skin behind that supplied by the intercosto-humeral nerve ; the nerve to the inner head of the triceps, from which a little branch sometimes passes to join the ulnar nerve; the nerve to the anconeus muscle; the nerve to the outer head of the triceps ; and the posterior external cutaneous nerve, which usually arises from the main nerve within the musculo-spiral groove and subdivides into two branches, the superior of which becomes superficial below the deltoid insertion and supplies the skin of the arm between that point and the elbow external to the cephalic vein. The THE REGION OF THE ARM. 361 inferior branch descends within the superficial fascia of the forearm and supplies the skin over the ulna (page 378). It is interesting to note that the musculo-spiral nerve supplies all the extensor and all the supinator muscles, except the biceps. In consequence of its close connection with the humerus, this nerve is frequently injured by contusions, or in fractures at the middle of the shaft of the bone. Fracture of the shaft of the hurnerus is a very common accident, both from direct and from indirect violence, but much undue stress has been laid upon the influence of muscular action upon the displacement of the frag- ments of the bone. In fact, marked displacement is rarely met with, not- withstanding the possibilities usually ascribed to the injury with reference to its occurrence above or below the insertion of the deltoid muscle. The weight of the arm tends to overcome displacement, and seldom allows much shortening. In the treatment of all fractures of the arm it is of the utmost importance that both the shoulder-joint and the elbow-joint should be properly supported, so as to maintain the fragments in perfect line. Non-union would probably be far less common if this were understood. In amputation through the middle of the arm by the antero-posterior oval- flap method, the relations of the important parts as they appear in the flaps when made upon the left arm are as follows (Plate 51, Fig. 1). The ante- rior flap consists chiefly of the biceps muscle (No. 1), while the posterior flap is composed chiefly of the triceps muscle (No. 5), containing the anastomotica magna artery (No. 11). Between the flaps on the inner side are the ulnar nerve (No. 4), the median nerve (No. 3), and the brachial vessels (No. 8). On the outer side, in the angle between the flaps will be found the severed superior profunda artery (No. 9) and the musculo-spiral nerve (No. 10). At birth the ossification of the shaft of the humerus is nearly completed, although the extremities are entirely cartilaginous. Bone is not developed in the head before the second year, or in the tuberosities before the third year. There is generally but one centre of ossification for the two tuber- osities, but there may be one for each tuberosity. The bicipital groove is produced by the constant and forcible impression of the long tendon of the biceps muscle on the growing bone. About the fifth year the centres 46 362 THE REGION OF THE ELBOW. for the head and tuberosities coalesce and form the upper epiphysis, which is not united to the shaft until about the twenty-second year. The radial portion of the articular surface of the lower end of the humerus is de- veloped by a centre of ossification in the third year, and the ulnar surface does not begin to ossify before the twelfth year. The internal epicondyle is formed about the fifth year, and the external epicondyle in the fourteenth year. The epicondyles and the trochlear surface become united about the seventeenth year and form the lower epiphysis, which generally unites with the shaft a year later. It should be noted that after the sixteenth year the growth of the humerus chiefly depends upon the upper epiphysis. THE REGION OF THE ELBOW. The elbow is formed by the lower end of the humerus and the upper end of the ulna, which are so adapted to each other that they establish a hinge-joint of very considerable strength, by which the arm is con- nected with the forearm. The peculiar conformation of the lower end of the humerus has already been described (page 348). The upper end of the ulna is one of the most remarkable portions of the skeleton, and possesses many singular features. It consists of two conspicuous processes separated by a deep hollow. The jorocess which extends backward is called the olecranon, because it forms the prominence of the elbow. It is a thick, strong, bony eminence ending in a curved tip which is received into the olecranon fossa of the humerus when the forearm is extended. The base of the olecranon process is constricted where it joins the shaft, corresponding to the line of the olecranon epiphysis, and is the usual seat of fracture when this part of the bone is broken. The upper pos- terior surface of the olecranon is somewhat square-shaped, and presents a rough impression for the attachment of the triceps muscle (page 354). The anterior surface is smooth, and forms the upper part of the deep hollow called the greater sigmoid cavity, which articulates with the trochlear surface on the humerus. The bottom of this cavity is marked transversely by a line, which indicates the constriction at the base of the olecranon above referred to. The cavity terminates below in the coronoid process, the broad projection from the shaft of the ulna which THE REGION OF THE ELBOW. 363 curves upward and ends in a point which rests in the coronoid fossa of the humerus when the forearm is flexed. The base of the coro- noid process is thick and directly conthiuous with the shaft of the ulna. There is no epiphysis for this process, and its fracture is hardly possible. The brachialis anticus muscle is attached to the base of the process and contiguous part of the shaft. Upon the outer surface of the coro- noid process there is a narrow oblong hollow, called the lesser sigmoid cavity, in which the adjacent head of the radius rolls. The upper end of the radius, although it is present within the elbow-joint, does not proj)erly take part in the function of that joint. The contiguous portions of the elbow are peculiarly adapted to the retention of the U23per end of the radius in position, so that the function which it possesses in relation to the hand through the wrist-joint may be maintained and act harmoniously with the movements at the elbow. The upper end of the radius is called its head. It consists of a round disk with a cupped depression which glides upon the capitulum on the outer condyloid surface of the humerus. The inner part of the marginal surface of the head is held in contact with the lesser sigmoid cavity of the ulna, in the ordinary position of the forearm, by means of the orbicular ligament. In the rotation of the radius the greater part of the margin of the head may revolve within the cavity. Below the head the bone is cylindrical and constricted, forming the nech, which joins the shaft at the prominent tubercle on the inner side of the bone, at the jDosterior and under surface of which the tendon of the biceps muscle is attached. The elbow-joint is a ginglymus or hinge joint. The sigmoid cavities of the ulna and the trochlear surface of the humerus are covered with a layer of articular cartilage, as are also the depression and margin of the head of the radius. As stated above, the latter is present at the elbow in order merely that its function of rotation may be properly adjusted to the contemporaneous movements of the ulna. It is therefore not attached to the humerus by any special ligament, but with the ulna it is firmly held in close relation by the orbicular ligament, which forms a sort of collar round the neck of the radius, its ends being attached to the anterior and posterior borders of the lesser sigmoid cavity. This constitutes the 364 THE REGION OF THE ELBOW. superior radio-ulnar joint, the chief function of which is to prevent the biceps muscle from dislocating the radius forward. The lower margin of the orbicular ligament is quite straight, and much narrower than the upper part, which is looser and blends with the fibres of the anterior and external portions of the capsular ligament surrounding the elbow. The capsular ligament is of unequal density, and is attached to the humerus over the coronoid fossa in front, to the margins of the olecranon fossa behind, and on each side to the lower surface of the epicondyles. Below, the capsule is attached to the ulna on the external borders of the olecranon and coronoid processes, and to the inner edge of the greater sigmoid cavity, and exter- nally it is connected with the upper part of the orbicular ligament. The capsular ligament is strengthened by accessory fibres, which are sometimes specialized as anterior, posterior, internal lateral, and external lateral ligaments. They are inseparable from the rest of the capsule, but it is important to note their peculiarities, as they in a measure limit the extent of motion at the joint. The anterior ligavient consists of an oblique band of fibres extending from the internal epicondyle to the outer part of the coronoid process and the adjacent orbicular ligament. They assist in preventing over-extension. A few of the fibres of inser- tion of the brachialis anticus muscle are attached to this part of the capsule, so that in flexion the latter is drawn upward from between the bones. The internal lateral ligament consists of strong fibres which pass from the internal epicondyle in a radiating manner, some being attached to the coronoid process and some to the olecranon process, while a small band of fibres extends transversely between the two processes across the internal notch of the greater sigmoid cavity, thus affording protection to the small vessels which here enter the joint. From the internal lateral liga- ment the flexor sublimis digitorum muscle arises (page 381). The fibres composing the external lateral ligament pass from the external epicondyle to the orbicular ligament, and receive the origin of the extensor communis digitorum and supinator brevis muscles. The posterior ligament is very weak, and is composed of thin, loose fibres which extend over the back of the joint from the margin of the olecranon fossa to the borders of the olecranon process. As some of the deep fibres of the triceps are inserted THE REGION OF THE ELBOW. 365 into it, it is drawn upward with the contraction of that muscle. When the capsule is opened, several quite large fatty masses are usually found contained within the folds of the synovial membrane, and occupying the several fossae on the end of the humerus and the notches at the sides of the greater sigmoid cavity of the ulna. The synovial membrane lines the entire capsule, and is widest and loosest beneath the tendon of the triceps muscle, as is demonstrated by the enlargement on each side of the olecranon in cases of synovitis. It is well to note here also that in all cases of chronic distention of the elbow-joint from disease the posi- tion of semi-flexion is assumed, which naturally enables the joint to hold the greatest amount of fluid. The inner surface of the orbicular liga- ment is also provided with a reflection of the synovial membrane, which facilitates the rotation of the head of the radius. There are several smaller folds of the membrane in relation to the orbicular ligament. One projects between the head of the radius and the capitulum, and another between the lower border of the lesser sigmoid cavity and the neck of the radius. The latter restrains somewhat the movements of pronation and supination. The movements of flexion and extension at the elbow are probably not hindered by the olecranon and coronoid processes of the ulna, because their respective fossse on the humerus receive them completely ; but the liga- ments and tendons in front of and behind the joint exert a considerable degree of restraint. A knowledge of this fact is of great importance in the treatment of all injuries about the elbow, as the thickening resulting from plastic inflammation occurring in such cases about these ligaments and tendons is very apt to produce ankylosis. It is one of the reasons why early and repeated passive motion should be resorted to upon the subsidence of acute inflammatory symptoms in every case of sprain or fracture at the elbow. In consequence of the obliquity of the trochlear surface of the lower end of the humerus, when the elbow is extended and the hand supinated the forearm diverges from the line of the arm at an angle of about ten degrees. A line drawn through the epicondyles on the lower end of the humerus will form a right angle with the axis of the arm, but an obtuse angle with the axis of the forearm. This explains why in flexion the PLATE 49. Figure 1. Dissection of the muscles of the right forearm and hand in pronation to show the relations of the extensor tendons of the thumb to the radial artery. 11. The tendon of the middle finger. 12. The flexor carpi radialis muscle. 13. The flexor sublimis dtgitorum muscle. 14. The tendon of the flexor carpi radialis muscle, at the wrist. 15. The extensor ossis metacarpi poUicis muscle. 16. The extensor primi internodii pollicis muscle. 17. The radial artery. 18. The abductor brevis pollicis muscle. 19. One of the tendons of the adductor interosseous muscle to the middle finger, blending with the tendon of the common extensor muscle. 1. The tendon of the biceps muscle. 2. The supinator longus muscle. 5. The extensor radialis longior muscle. 4. The extensor communis digitorum muscle. 6. The tendon of the extensor radialis brevior muscle. 6. The posterior annular ligament. 7. The tendon of the extensor secundl internodii pollicis muscle. 8. The tendon of the extensor radialis longior muscle. 9. The tendon of the extensor indicis muscle. 10. The tendon to the index finger from the extensor com- munis digitorum muscle. Figure 2. Dissection of the muscles and tendons of the back of the right forearm and hand, in extension. 1. The internal condyle of the humerus. 2. The extensor carpi ulnaris muscle. 3. The extensor communis digitorum muscle. 4. The extensor minimi digiti muscle. 5. The posterior annular ligament. 6. The tendon of the extensor radialis brevior muscle. 7. The tendon to the little finger from the common exten- sor muscle. 8. The tendinous slip connecting the tendons to the middle and ring fingers. 9. The extensor communis digitorum muscle. 10. The supinator longus muscle. 11. The extensor carpi radialis longior muscle. 12. The extensor ossis metacarpi pollicis muscle. 13. The tendon of the extensor radialis brevior muscle. 14. The extensor primi internodii pollicis muscle. 15. The extensor secundl internodii pollicis muscle. 16. The abductor pollicis muscle. Figure 3. Dissection of the tendons on the back of the left hand, showing the relations of the nerves and arteries. 1. The extensor ossis metacarpi pollicis muscle. 2. The extensor primi internodii pollicis muscle. 3. The extensor secundi internodii pollicis muscle. 4. The tendon of the extensor carpi radialis brevior muscle. 6. The tendon of the extensor carpi radialis longior muscle. 6. Branches of the radial nerve to the thumb and index finger. 7. The posterior annular ligament. 8. The common nerve to the adjacent sides of the thumb and index finger. 9. The abductor pollicis muscle. 10. The nerves to the adjacent sides of the index and mid- dle fingers. 11. The tendon of the index finger in its aponeurotic sheath. 12. The extensor carpi ulnaris muscle. 13. The shaft of the ulnar. 14. The third dorsal interosseous muscle. 15. The branches of the ulnar nerve to the ring and little fingers. 16. Common nerve to the adjacent sides of the ring and middle fingers. 17. The tendon to the middle finger from the common extensor muscle. 18. One of the dorsal interossel arteries. Plate 49 Vol I Fig ! FiiS 2 Fi2 3 Copyright, I8S0, by GioMc Mc CttuAH.M a •co/fCO/^co^cof^(of^ioffcof^(of^cjffco/^cof^cof^cof^ijffcof^cof^cjffCof^s^ Mc. Clellai^, M D. THE REGION OF THE ELBOW. 367 forearm inclines inward, so that the hand is brought toward the middle line of the body, and also why it is not possible for the hand to be placed flat upon the shoulder of the same side. When the forearm is extended, the epicondyles of the humerus and the olecranon process of the ulna will be found to lie in a direct transverse line, but when it is flexed these points form a triangle, the olecranon being brought forward in front of the transverse line through the epicondyles. The olecranon process is nearer to the internal than to the outer epicondyle. When the olecranon is very prominent, its summit will be found in extreme exten- sion above the transverse line. These bony prominences constitute the chief landmarks of this region, and, as they can always be felt through the skin, their relation in flexion and extension, as above indicated, should be carefully noted in all injuries to the elbow. It may also be observed that here, as in all other joints, much uncertainty may be removed by reference to the similar features upon the opposite limb. The skin over the front of the elbow is very thin and fine, and, although there may be more or less fat in the subcutaneous tissue, the relations of the tendon of the biceps muscle can generally be easily recognized ; whereas behind, over the olecranon, the skin is loosely attached with a thickened and roughened cuticle, which in extension is puckered into transverse wrinkles. In front of each elbow there is upon the outer side a promi- nence corresponding to the bulging of the mass formed by the supinator longus and extensor muscles, and upon the inner side there is a prominence caused by the pronator radii teres and flexor muscles. Between these the tendon of the biceps muscle descends into the ante-cubital fossa, thus formed, and in well-developed arms a groove is noticeable extending upward on each side of the tendon to blend respectively with the outer and inner bicipital depressions. The outer border of the tendon of the biceps can be distinguished better than the inner, owing to the reflection from the latter of the semilunar bicipital fascia. The superficial veins at the bend of the elbow, usually described as presenting an M-shaped figure, are not always so arranged, because the veins are liable to great diversity in their disposition (Plates 45, 46, and 47) over the bicipital fascia. The deviation is most common 368 THE BEG ION OF THE ELBOW. upon the radial side, in consequence of the radial tributary veins being deficient. Ordinarily the radial veins from the radial side of the forearm pass upward to empty into the cephalic vein (page 349), and the ulnar veins empty into the basilic vein (page 351), while the anterior median vein ascends from the wrist to the bend of the elbow, where, after receiving the blood from the deep veins of the forearm by means of the vena anas- tomotica (Plate 46, Fig. 2, No. 10, and Plate 47, Fig. 2, No. 16), it divides into two branches, respectively known as the median basilic and median cephalic veins. The median basilic vein generally occupies the inner bicipital groove and joins the posterior ulnar vein above the internal epicondyle as it empties into the basilic vein, while the median cephalic vein follows the outer bicipital groove and joins the radial veins to form the cephalic vein. These veins can usually be distinguished through the integument if there is not a great deal of fat. The median basilic vein, owing to its larger size, its prominence, and its comparatively fixed rela- tions, has been usually selected for venesection in this region. Its course is over the bicipital fascia, and corresponds so closely to that of the brachial artery beneath the fascia that it may in some thin individuals receive the pulsations from the artery. The strength and denseness of the bicipital fascia depend upon the general muscular development, as is the case with the expansions of the deep fascia elsewhere. Occasionally at the elbow two median basilic veins are found (Plate 46). Branches of the internal cutaneous nerve usually pass close to the inner side of the median basilic vein, while filaments of the musculo-cutaneous nerve pass to the skin of the forearm at its outer side. Beneath the superficial fascia the relations of the vessels and nerves on either side of the tendon of the biceps muscle are of great interest. In the outer groove between the tendon and the supinator longus muscle are the terminations of the musculo-cutaneous and musculo-spiral nerves, and the superior profunda and radial recurrent arteries (Plate 46, Fig. 1, No. 10). In the inner groove beneath the bicipital fascia are the median nerve, the brachial artery and its two companion veins, and the communi- cation between the anastomotica and anterior recurrent ulnar arteries. The median nerve at the elbow is at the ulnar side of the brachial artery, and THE REGION OF THE ELBOW. 369 descends beneath tlie fascia between the two heads of the pronator radii teres muscle (page 379), having previously distributed branches to the superficial flexor muscles and to each head of the pronator. The bra- chial artery at the elbow passes beneath the bicipital fascia to the middle of the joint, where opposite the head of the radius it bifurcates into the radial and ulnar arteries. As the brachialis anticus muscle passes over the elbow-joint to be inserted into the coronoid process of the ulna, it supports the termination of the brachial artery, besides serving as a covering to the joint. In forcible flexion of the elbow it is possible effectually to compress the artery between the masses of muscle, but such pressure, necessarily involving the median nerve also, is so painful that it cannot be endured more than a short time. When the bicipital fascia is removed, the origins of the brachial veins from the deep vense comites of the vessels of the forearm and their relations to the brachial artery are exposed (Plate 46, Fig. 2, No. 8). Between the olecranon process and the internal epicondyle the ulnar nerve is lodged in a groove, which is subcutaneous (page 359). It is in close relation with the posterior recurrent ulnar artery. Sometimes the ulnar nerve passes in front of the epicondyle instead of behind it. Just below the external epicondyle there is a depression which is always to be seen even when there is much fat in the subcutaneous tissue. This depression adds much to the graceful contour of this part of the forearm, and it is most marked when the latter is extended. The depression corresponds to the interval between the supinator longus and extensor carpi radialis muscles and the external border of the anconeus muscle. It is im- portant surgically, as the head of the radius can be felt in it when the bone is rotated, and because it thus affords a means of distinguishing the line of the elbow-joint. If the forearm is placed in the position of extreme pronation, the tubercle of the radius can be felt below the head. The superficial lymphatic vessels of the forearm accompany the superficial veins toward the inner side of the elbow, and terminate in a lymphatic gland situated just above the internal epicondyle. This gland is apt to be involved in any septic affection of the fingers or hand, and should be remembered, as it is the lowest gland in the upper extremity. 47 370 THE REGION OF THE ELBOW. There are three bursce about the elbow, one between the attachment of the tendon of the biceps and the tubercle of the radius, a small one occasionally over the internal epicondyle, and a large one over the olecranon process. The latter is frequently enlarged, and when inflamed may affect the joint, as there is a communication between it and the syno- vial membrane. The elbow-joint is supplied by filaments from both the ulnar and the median nerve. In some injuries to the joint severe pain is experienced iu the parts of the forearm corresponding to the distribution of these nerves. The anastomoses of the arteries about the olecranon process and the posterior part of the capsule of the . elbow establish the rete olecrani. The vessels forming it are deiived from the anastomotica and superior and inferior profunda arteries, which are branches of the brachial artery, and from the posterior ulnar recurrent and interosseous recurrent arteries. It is important to note that their disposition is such that the circulation through them is not interrupted by the tension of the superficial fascia in extreme flexion of the elbow, when the current in the brachial artery at its bifurcation may be arrested by pressure. It should be observed also that the arteries about the internal epicondyle are more numerous than those about the external. The commonest form of dislocation of the elbow is where the bones of the forearm are driven backward upon the lower end of the humerus. In such cases, when the displacement is complete, the coronoid process will be found opposite the olecranon fossa, with the head of the radius projecting behind the external epicondyle. The anterior and lateral ligaments of necessity are torn, the orbicular is rarely affected, and the posterior may or may not be torn, according to the nature and direc- tion of the violence. The tendon of the biceps appears like a tense cord drawn over the trochlear surface of the humerus, while the attachment of the brachialis anticus is usually ruptured. The median and ulnar nerves are necessarily stretched. Fractures of the lower end of the humerus which involve the elbow- joint occur most commonly in young persons. They are caused by direct violence received upon the point of the elbow. Sometimes the olecranon process is driven so forcibly into the olecranon fossa that the end of the THE BEG ION OF THE ELBOW. 371 humerus is split across transversely at its base, or it may be complicated by a vertical separation of the condyloid portions of the bone, thereby con- stituting a T-shaped fracture. Of the two epicondyles, it may be said that the external, on account of its slight prominence and construction, is very rarely if ever broken by itself, whereas the internal often suffers fracture. The latter, prior to the age of eighteen years, may be detached at its epiph- ysis (page 362). There is seldom displacement following fracture of the internal epicondyle, as it is enveloped by the dense aponeuroses of the common flexor muscles of the forearm. In children, when there is a sepa- ration of the lower epiphysis of the humerus there is naturally very little deformity, in consequence of the epiphyseal line being almost wholly within the capsule of the elbow. Fracture of the olecranon process occurs most frequently just above the constriction through the greater sigmoid cavity, and corresponds to the epiphyseal line. The degree of displace- ment depends upon the extent to which the periosteum and ligaments are ruptured, and the consequent unrestricted contraction of the triceps muscle. Fracture of the coronoid process of the ulna, or of the head or neck of the radius, can hardly occur except in severe injuries attended with dislo- cation and extensive contusion, owing to their anatomical relations. The relations of the parts as they are found in the flaps after ampu- tation at the elbow-joint by the antero-posterior flap method (on the left side) are as follows (Plate 51, Fig. 2). The anterior flap is composed chiefly of the biceps and brachialis anticus muscles, and contains the severed median nerve (No. 1), and the brachial artery (No. 2) and its veins (No. 3). In relation to the internal epicondyle are the ulnar nerve and the posterior recurrent ulnar artery, while the musculo-spiral nerve is in close proximity to the external epicondyle, and the radial recurrent artery is in the outer angle of the flaps. The posterior flap is com- posed of the integument and the tendon of the triceps muscle (No. 12), the latter attached to the severed olecranon process of the ulna. At the inner border of the posterior flap there is a recurrent branch of the ulnar artery, and in the inner angle between the flaps is the anastomotica magna artery. In resection of the elbow there is always danger of injuring the ulnar 372 THE REGION OF THE FOREARM. nerve, owing to its close relation to the internal epicondyle and the difficulty of detaching the soft structures from that bony prominence. It is very important to preserve the periosteum over the olecranon and the strong fascia over the anconeus muscle, so that the triceps may not be altogether severed from the ulna. The relations of the parts exposed in the procedure by a posterior vertical incision (oji the left side) are as follows (Plate 52, Fig. 6) : the severed tendon of the triceps (No. 2) will be seen just above the trochlear surface of the lower end of the humerus (No. 3) ; upon the outer side of the olecranon process, which is denuded of its periosteum (No. 8), are the head of the radius (No. 4) and the radial recurrent artery (No. 5), while upon the inner side are the ulnar nerve (No. 7) and the posterior ulnar recurrent artery (No. 9). As an illustration of the possible degree of injury which the elbow may recover from without loss of power or motion, the author may be justified in noticing in this connection a case recently under his care. The patient, a young man aged twenty-one years, received fractures of the internal epicondyle and the upper end of the ulna below the coro- noid process in consequence of a fall upon the elbow while it was in a semi-flexed position. Seven weeks later, when he was regaining the use of the elbow, after constant passive motion, he met with another fall and fractured the olecranon of the same elbow through the greater sigmoid cavity. Owing probably to the passive use to which the triceps had been so recently subjected, and certainly to the extensive laceration of the ligaments and the periosteal connections, the process was drawn a hand's breadth away from its proper site. The local contusion and extravasation in both instances were unusually great, but, by careful perseverance, within two months complete use of the joint was obtained, both as to power and as to motion, and measurement proved that the olecranon was consolidated again with the ulnar shaft without any separation, — an unusual feature. THE EEGION OF THE FOREARM. The shafts of the radius and the ulna, beyond their upper extremities, already described with the elbow, extend side by side to the wrist, and are peculiarly formed, not only to support the soft structures of the forearm, THE REGION OF THE FOREARM. 373" but also to be adapted to their respective functions, the ulna being em- ployed principally in extension and flexion, while the office of the radius is to rotate the hand in pronation and supination. The radius is external .on the side of the thumb, the ulna is internal on the side of the little finger. The shaft of the 7'adius below the bicipital tubercle is prismatic in form, and gradually increases in breadth to the lower fourth of the bone, where it is expanded into a large quadrilateral-shaped extremity for articulation with the wrist. The radius is slightly bowed forward and inward, pre- senting an external border which is convex through its whole extent, and an internal or ulnar border which presents along its middle a sharp edge for the attachment of the interosseous, ligament which connects the radius with the opposing sharp edge of the ulna. The lower extremity of the radius is the broadest part of the bone. It terminates in the carpal articular surface, which presents two concave facets, the outer of which is triangular, for the reception of the upper convex surface of the scaphoid bone, and the inner is quadrate, for the semilunar bone. The external border of the scaphoid facet is narrow, and prolonged downward in a conical projection, called the styloid process of the radius. The internal border of the semilunar facet is placed on a level considerably higher than the latter, and presents a depression for articulation with the contiguous convex border of the lower end of the ulna. The margins of the ulnar depression unite above and are continuous with the interosseous edge of the bone. The outer surface of the styloid process and the adjacent pos- terior surface of the lower end of the radius are grooved for the passage of the tendons of the extensor muscles (page 384). The anterior surface of the lower end of the radius appears vertically concave, owing to the projection forward of the irregular sharp lip of bone, the anterior crest, which is the portion of the bone supposed to be detached from the shaft in the so-called Barton's fracture of the wrist. The shaft of the ulna gradually diminishes in size from below the attachment of the brachialis anticus muscle to the lower end. It is pris- matic in form, and is twisted in its axis, so that below the elbow it inclines a little toward the radius, becomes quite straight at its middle, and arches slightly away from the radius lower down, where its rounded articular PLATE 50. Figure 1. The relations of the structures involved in the operation of trephining the skull, as in a case of cortical epilepsy. The disk of bone has been removed and the pia mater partially detached to expose the convolutions on the right hemi- sphere, supposed to include the centre of the movements of the hand, and especially of the thumb. 1. The scalp ilap, including the periosteum, reflected from the bone. 2. The skull, with the temporal ridge plainly showing. 3. The upper cut end of the temporal artery. 4. The fissure of Rolando, in this case joining the horizon- tal branch of the fissure of Sylvius. 5. The flap of dura mater, with the cut branch of the middle meningeal artery seeu through it. 6. A branch of the middle cerebral artery, lodged in the posterior part of the horizontal branch of the fissure of Sylvius. 7. A cut scalp artery, branch of the posterior temporal artery. 8. The lower cut end of the temporal artery. 9. The lower part of the anterior central, or ascending frontal, convolution. 10. The lower part of the posterior central, or ascending parietal, convolution. Figure 2. Amputation at the left shoulder-joint by the oval-flap method (of Larrey), showing the relations of the parts exactly as they appear after the completion of the operation. The anterior flap is formed by the pectoralis major, the heads of the biceps, the coraco-brachialis, the latissimus dorsi, the teres major, and the rotator muscles of the joint. The posterior flap is formed mainly by the deltoid muscle. 1. The axillary vein. 2. The axillary artery. 3. The cut pectoralis major muscle. 4. The glenoid cavity of the scapula, covered with its ar- ticular cartilage. 5. The glenoid, or long, head of the biceps muscle. 6. The clavicular portion of the deltoid muscle. 7. A branch of the anterior circumflex artery. 8. The cephalic vein and the descending branch of the acromio-thoracic artery. 9. One of the brachial veins. 20. The latissimus dorsi and teres major muscles. 11. The brachial plexus of nerves. 12. The inferior scapular artery and veins, 13. A portion of the capsular ligament. 14. The posterior circumflex vessels and nerve. 15. The cut deltoid muscle. 16. The position of the sub-deltoid bursa. Plate "50 Vol I Fi§'2 9 !Oll 1^: ^~' 14- '- 16 Copyright, 1330, by Gcorof Mc Clullah, M D 'Oissectso, PhotD%rdDhed and Coloreo from Nature- Cy Geo/^ge Mc. Clellan, M D. ArmstrongiCo Lith Coiifn TRE REGION OF THE FOREARM. 375 surface bends back again to be received upon the depression on tlie inner border of the lower end of the radius. The internal border of the ulna is irregular, being rounded and smooth above and roughened below, while the external or radial border is provided with a sharp edge, except at the lower fourth of the bone. The lower extremity of the ulna is very small, and terminates in a hollow depression adapted to the triangular fibro- cartilage which intervenes between it and the wrist-joint. From the posterior border of the lower end, on the little-finger side, extends a small blunt-pointed bony projection, called the styloid process of the ulna. Tliis is placed a little lower than the rounded bony prominence or head of the ulna, which is received against the depression on the radius, already men- tioned, and forms the inferior radio-ulnar joint. This joint is comjjleted below by the upper surface of the triangular cartilage (page 397), and is surrounded with a capsular ligameyit, which is especially loose anteriorly. Some of the fibres of this capsule have been specialized, according to their relative positions, as the anterior and posterior radio-ulnar ligaments. They are continuous with the capsule of the wrist-joint proper. The opposing surfaces of the ulna and the triangular fibro-cartilage are not moulded to each other, and the intervals between them are filled by a loose fold of synovial membrane, called the membrana sacciformis. The shafts of the two bones of the forearm are connected by the oblique and interosseous ligaments. The oblique ligament extends from the lower sur- face of the tuberosity of the ulna downward and outward to the shaft of the radius below the bicipital tubercle. It is not always present, and is regarded as a specialization of the fascia covering the supinator brevis muscle, which arches over the insertion of the tendon of the biceps. The interosseous ligament, or interosseous membrane, as it is sometimes called, consists of several layers of fibres, which pass chiefly obliquely from the sharp internal edge of the radius to the contiguous border of the ulna. This ligament is deficient above, to the extent of about two and a half centimetres, or an inch, below the tubercle of the radius, so that that process can have free play in the rotation of the bone on the ulna. In relation to the extensor muscles of the thumb there are additional fibres derived from their sheaths, which cross one another between the bones of the forearm. 376 THE BEGION OF THE FOREAHM. The interosseous ligament, besides offering a broad surface for the attach- ment of the deep flexor and extensor muscles (page 383), strengthens the two bones and enables the hand to support a weight or to push against an object in extension, as when the ulna and the humerus are in a direct line, constituting the humero-ulnar shaft. The movements of pronation and supination take place between the bones of the forearm, about an axis which corresponds to a line drawn from the head of the radius through the lower end of the ulna and the metacarpal bone of the ring finger. Pronation is mainly limited by the lower two-thirds of the interosseous ligament, the inner part of the posterior carpal ligament, and the opposi- tion of the bones. Supination is checked partially by the lowest part of the interosseous ligament and the internal lateral carpal ligament, and par- tially by the catching of the posterior edge of the ulnar depression of the radius upon the tendon of the extensor carpi ulnaris muscle, which passes over the groove on the back of the styloid j^rocess of the ulna. Owing to the loose capsular ligament about the inferior radio-ulnar joint, there is always a slight lateral motion between the bones at tliis articulation in the rotation of the radius. It should be remembered that the interosseous space is larger below than above, and that it is narrowest in complete pronation and widest in supination ; and, further, that the bones of the forearm can be said to be parallel to each other only when they are held half-way between pronation and supination, or when the forearm is at right angles with the arm and the palm of the hand is turned upward. In the treatment of fractures of the forearm too great attention cannot be given to the proper adjustment of the bones so as to secure the preservation of the interosseous space from infringement, because such infringement is almost certain to be followed by a proportionate degree of loss of the rotating power of the wrist. In this connection it should be noted that the shafts of the radius and ulna vary in size relatively to each other according as they are con- sidered near the elbow or near the wrist, the radius increasing and the ulna decreasing from above downward. This is well seen upon section of the bones, as in an amputation anywhere in this region (Plate 51, Fig. 3). Both bones are also nearer to the posterior than to the anterior surface of the forearm through their whole extent. THE REGION OF THE FOREARM. 377 The internal and posterior surfaces of the ulna are wholly subcu- taneous, and the lower part of the external surface of the shaft of the radius, as well as its head, can be readily felt through the skin, — the intervening portion of the radius being covered by the thick mass com- posed of the supinator longus and extensor carpi radialis muscles. The shape of the circumference of the upper portion of the forearm naturally depends upon the degree of muscular development, being generally oval in the male and round in the female and the child. In both of the latter the contour of the limb is influenced by the presence of a greater proportionate amount of fat upon the anterior and posterior surfaces. The variability in the transverse width in the upper part of the forearm is chiefly due to the degree of development of the muscles which take origin from the surfaces about the epicondyles of the humerus, the mass upon the radial side being the larger, already referred to as being more pronounced upon the posterior surface. On the lower third of the radial border the extensor muscles of the thumb produce a slight elevation as they pass obliquely downward (Plate 49). Above the middle of the forearm the muscles are always more developed anteriorly than they are posteriorly, while below it, where the muscles become tendinous, the two bones are more equally covered by the soft parts both anteriorly and posteriorly. The skin, like that of the arm, is thinner, more sensitive, and more loosely attached by the superficial fascia to the deep fascia on the front and inner surface of the forearm than upon the back and outer surface. The superficial veins, lymphatic vessels, and cutaneous nerves are within the layers of fatty and connective tissue which compose the superficial fascia. The veins can usually be readily seen through the skin, passing upward from the wrist to the elbow. On the anterior surface the superficial median vein ascends along the front of the forearm, while upon the ulnar surface are usually a small superficial anterior ulnar vein and a larger posterior ulnar vein. The superficial radial veins commence at the radial dorsal plexus of the hand and ascend by several branches over the lower part of the posterior or dorsal surface of the forearm (Plate 47, Fig. 3), and then wind round the radial border to empty with the other superficial veins into the venous trunks at the front of the elbow, already described 48 . 378 THE REGION OF THE FOREARM. (page 367). Besides these there are many superficial communicating veins which connect the median with the ulnar and radial veins at dif- fei'ent points in the front of the forearm. It is noteworthy that the dorsal surface to the extent of ten centimetres, or four inches, below the olecranon process is comparatively free from superficial veins. It is also a fact often unheeded, that the greater part of the blood from this region is returned by the surface veins, so that any undue or improperly-applied pressure by splints or bandaging may result in oedema. The cutaneous nerves of the forearm are derived from the branches of the musculo-cutaneous, the external cutaneous branch of the musculo- spiral, and the internal cutaneous nerves, which supply special areas and establish communications between their ultimate filaments. On the anterior surface below the elbow, the anterior branch of the musculo-cutaneous (page 357) supplies the radial border of the forearm as low down as the wrist (Plate 27, No. 56). About opposite the middle of the radius this nerve gives off the posterior branch, which winds backward to supply the skin on the dorsal surface as far as the wrist, where it joins with filaments from the radial and external cutaneous branches of the musculo-spiral nerve. A few of the lower filaments pass across the ball of the thumb and communicate with the palmar branch from the median nerve and the radial nerve in that locality. In relation to the elevation caused by the extensor muscles of the thumb the radial nerve becomes superficial, and curves over the radius to supply the back of the hand and the fingers (Plate 47, Fig. 1, No. 16, and Plate 53, Fig. 2). The external cutaneous branches of the musculo-spiral nerve (page 360) supply some filaments to the skin over the front of the forearm which join with fibres from the anterior division of its inferior branch, and some filaments to the outer and back part of the forearm, from the elbow to the wrist, by the pos- terior division. On the ulnar side the antei'ior branch of the internal cutaneous nerve (page 359) supplies the strip of skin over the ulna as far as the wrist. Below the inner side of the elbow the posterior branch passes backward to supply the upper portions of the posterior surface of the forearm. The dorsal branch of the ulnar nerve becomes subcutaneous close to the styloid process of the ulna (Plate 47, Fig. 3, No. 4), and dis- THE REGION OF THE FOREARM. 379 tributes filaments over the back of the hand, which join with the terminal filaments of the external and internal cutaneous nerves about the wrist. The deep fascia of the forearm is directly continuous with that of the arm, and forms a dense, close-fitting aponeurotic sleeve about the soft structures, being peculiarly modified above and below so as to con- tribute to the power of the muscles in their contraction and to restrain and preserve the position of tlie tendons. It is mainly composed of obliquely decussating fibres, which are reinforced in certain localities, as in front of the elbow, by fibres from the tendons of the biceps and brachialis anticus muscles, and at the wrist, where it forms the posterior annular ligament and contributes to the anterior annular ligament. The deep fascia is further attached to all the bony processes which are sub- cutaneous, especially to the epicondyles, the olecranon, and the inner border of the shaft of the ulna. The under surface of this fascia divides into septa, which not only separate the individual muscles from one another but also furnish to each of them additional surfaces for the origin of their fibres. It is perforated at intervals by the various cutaneous vessels and nerves. The muscles of the forearm are disposed in two groups, an anterior group, consisting of the flexors and pronators, which are attached about the internal epicondyle of the humerus (page 348), and a posterior, con- sisting of the extensors and supinators, which are attached to the external epicondyle and the condyloid ridge above it. Each group further consists of two layers, superficial and deep. The superficial layer of the anterior group comprises five muscles, which are arranged in the following order from within outward : the pronator radii teres, the flexor carpi radialis, the palmaris longus, the flexor sublimis digitorum, and the flexor carpi ulnaris. The pronator radii teres muscle arises by two distinct portions or heads, the most superficial being attached to the internal supra-condyloid ridge and to the adjacent intermuscular septum, and also, sometimes, to the supra-condyloid ligament (page 351), and the deeper portion by a thin tendon from the inner side of the coronoid process of the ulna. The fibres of these two portions unite and pass obliquely to be inserted by a 380 TEE REGION OF TEE FOREARM. flat tendon into the oblique line and the pronator impression on the outer side of the radius. This muscle forms the inner border of the ante-cubital fossa at the elbow, and is supplied by twigs from the median nerve, Avhich descend between its two portions (page 369). The special function of the pronator teres is to rotate the radius on the ulna, in conjunction with the pronator quadratus (page 384). The flexor carpi radialis muscle arises from the common tendon about the internal epicondyle, from the intermuscular septa on each side of it, and from the overlying deep fascia. Its fibres pass obliquely outward and end in a long tendon, which is at first flat and becomes narrow toward the wrist, where, after crossing over the anterior annular ligament, it continues beneath the short flexor muscles of the thumb, through a fibrous arch in relation to the trapezium, and is inserted into the base of the metacarpal bone of the index finger. In the lower part of the forearm the tendon of this muscle is at the inner side of the radial artery and its veins, the tendon of the supinator longus being at the outer side (Plate 46, Fig. 1, No. 14). Between the tendon and the trapezium there is usually a bursa. There is sometimes an accessory muscle beneath the flexor carpi radialis, which arises from the radius and is inserted into the metacarpal bone of the middle finger, being also connected with the otlier muscle by a few fibres at its insertion. The function of the flexor carpi radialis is to flex the wrist and to abduct the hand, or, acting from below, it may assist in flexing the elbow. It is supplied by the median nerve. The palmaris longus muscle is occasionally absent, and when present is always small. Its fibres unite into a slender flat tendon, which de- scends usually along the middle of the forearm upon the flexor sublimis muscle to the wrist, where, after passing over the annular ligament, it becomes continuous with the palmar fascia (Plate 48, Fig. 1, No. 8). In some instances the tendon of the palmaris longus is attached to the anterior annular ligament, without extending to the palmar fascia. Its muscular portion is subject also to great variety of development. The flexor carpi ulnaris muscle has a double origin, from the back of the internal epicondyle by a flat tendon, and by an expansion of the fascia over the olecranon, so that they form an arch under which pass the THE REGION OF THE FORE ABM. 381 ulnar nerve and ulnar recurrent artery. This muscle also takes origin from the fascia attached to the upper two-thirds of the ulna. The fibres from these sources present a penniform arrangement, as they enter a tendon on the radial side, which, after passing over tlie anterior annular ligament, is inserted into the pisiform bone, and to the fibrous expansion stretching across the unciform bone to the base of the metacarpal bone of the little finger. In the lower two-thirds of the forearm the ulnar artery, with its companion veins and the ulnar nerve, is placed between the tendons of the flexor carpi ulnaris and flexor sublimis muscles, the former muscle in reality overlapping the artery until within a short distance above the wrist (Plate 46, Fig. 1, No. 33). In relation to the annular ligament the ulnar vessels and nerve are protected by a fibrous expansion which extends between the ligament and the tendon of the flexor carpi ulnaris. This muscle receives twigs from the ulnar nerve as the nerve passes be- tween its two portions above. Its function is to flex and adduct the wrist. The flexor sublimis digitorum muscle is situated beneath the other muscles of the superficial layer, and arises by three separate portions, — one large, tendinous, and fleshy, from the internal epicondyle and the adjacent part of the capsular ligament of the elbow and from the inter- muscular septa between it and the two carpal flexor muscles; one, small and tendinous, from the inner side of the coronoid process above the pronator teres ; and another, thin, broad, and fleshy, from the oblique ridge on the front of the radius, extending from the bicipital tubercle to about two and a half centimetres, or one inch, below the insertion of the pronator teres, which partly overlaps it. The fibres from these difierent sources combine into one muscle, which passes down the middle of the forearm and subdivides into four distinct slips which terminate in four tendons arranged in two superposed pairs as they pass beneath the an- nular ligament into the palm. The superficial pair of tendons are con- tinued to the middle and ring fingers, while the deeper pair go to the index and little fingers. All these tendons within the palm are placed beneath the branches of the median nerve and the ulnar artery (Plate 48, Fig. 3). Each of the tendons of the flexor sublimis muscle, as it enters the aponeurotic sheath which encloses it in relation to the meta- PLATE 51. Figure I. Amputation through the middle of the left arm by the antero-posterior oval-flap method, showing the proper rela- tions of the vessels and nerves to the humerus, in a well-developed man, aged forty-eight years. , The anterior flap, composed chiefly of the biceps mus- cle. The flap of the periosteum, which was dissected from the anterior surface of the humerus before the saw was applied to the bone. , The median nerve. . The ulnar nerve. 5. The posterior flap, composed chiefly of the triceps muscle. 6. Section of the left humerus, at its middle. 7. The medullary canal of the humerus. 8. The brachial artery and veins. 9. The superior profunda artery. 10. The musculo-spiral nerve. 11. The anastomotica magna artery. Figure 2. Amputation at the left elbow-joint by the antero-posterior flap method (of Dupuytren),.showing the relations of the severed structures immediately after the completion of the operation. The olecranon process of the ulna is retained to preserve the function of extension of the triceps muscle. 1. The median nen-e. 2. The brachial artery. 3. The brachial vein. 4. The ulnar artery and the ulnar nerve. 5. The anastomotica magna artery. 6. One of the recurrent branches of the ulnar artery. 7. The anterior flap, compo.sed chiefly of the biceps and brachialis amicus muscles. 8. The musculo-spiral nerve. 9. The radial artery. 10. The lower end of the humerus, showing the trochlear surfaces of the condyles covered wilh articular car- tilage. 11. The section through the greater sigmoid notch of the olecranon process of the ulna. 12. The posterior flap, composed of integument and the tendon of the triceps muscle. Figure 3. Amputation through the middle of the left forearm by the antero-posterior oval-flap method, showing the relations of the severed structures on completion of the operation. 1. The superficial median vein. 2. The anterior flap, composed chiefly of the flexor mus- cles. 3. The median nerve. 4. Section through the middle of the left ulna. 6. The ulnar artery and veins, and the ulnar nerve. 6. The radial artery and veins, and the radial nerve. 7. Section through the middle of the left radius. 8. The interosseous artery and the interosseous nerve. 9. The posterior flap, composed chiefly of the extensor muscles. 10. The superficial radial vein. N. B.— These amputations were all done by means of a long, stout, straight bistoury, applied from without Inward, which gives a bevelled appearance to the flaps, overcomes the retraction of the skin, and renders unnecessary the after- retrenching of the muscles. In each instance the vessels were left in the wound, as they would be before the application of the ligatures, and the nerves have been left as they were severed by the knife. riate bl Vol I Fig 2 F15 3 Copynght, 1830, by- 6f OHiSE Mc Clellw, M. D. Dis dc. iHc. dc. dc. dc. dc. dc. dc. dc. dc. dc. dc. dc. dc. dc. dc. dc. idc. CtEUAt^, M D. Armslrong (Co. LiTli SosTon. THE REGION OF THE FOREARM. 383 carpo-phalangeal joint of its special finger, divides into two lateral slips, ■which diverge opposite the middle of the first or proximal phalanx so as to allow the corresponding tendon of the flexor profundus muscle to pass between them. The two lateral slips of the superficial tendon closely embrace the deep tendon, and pass behind it in such a way that their component fibres decussate before they separate again to be finally inserted into the sides of the second phalanges (page 404). The action of the flexor sublimis muscle is to flex the second joint of the fingers. The different portions of the above muscle are supplied by the median nerve. The muscles of the deep layer of the anterior group of the forearm are the flexor profundus digitorum, the flexor longus pollicis, and the pro- nator quadratus. The flexor profundus digitorum muscle is the thickest individual muscular mass in this region. It arises from the inner two- thirds of the anterior surface of the ulna as far as the origin of the pro- nator quadratus muscle, and from the interosseous ligament in relation to the ulna. The fleshy mass resulting from the fibres thus arising soon divides into two portions, the outer one of which separates from the inner and main portion above the middle of the forearm and continues inde- pendently to its insertion into the index finger, while the fibres composing the inner portion are inserted into three flat tendons which pass side by side upon the same plane with their fellow-tendons to the index finger beneath the annular ligament, under the tendons of the flexor sublimis muscle. About the middle of the first or proximal phalanges of thq fingers the deep tendons perforate the superficial tendons, to be inserted finally into the bases of the third or ungual phalanges (page 404). The tendons of the flexor profundus muscle serve to flex the finger-tips. Its nerves are branches of the interosseous branch of the median nerve and the ulnar nerve. The flexor longus pollicis muscle arises mainly from the anterior part of the shaft of the radius, below the oblique line and above the pronator quadratus muscle, and from the adjacent part of the interosseous ligament. It sometimes also receives a few fibres of origin from the coronoid process. The fleshy fibres, becoming thicker toward the wrist, terminate in a tendon, 384 THE REGION OF THE FOREARM. which passes under the annular ligament and between the two portions of the flexor brevis, to be inserted into the base of the last phalanx of the thumb. It strongly flexes the thumb, and receives its nerve from the interosseous branch of the median nerve. The pronator quadratus muscle is a square muscle arising tendinously from the lower fourth of the oblique line on the ulna, and from the strong fascia covering its anterior surface. Its fibres pass transversely to their in- sertion into the lower fourth of the anterior surface and contiguous outer border of the radius. Its function is to pronate the radius in conjunction with the pronator teres muscle. The interosseous branch of the median nerve also supplies it. Tlie muscles of the superficial layer of the postei'ior group of the fore~ arm are seven in number, and are arranged in the following order from the radial to the ulnar border: the supinator radii longus, the extensor carpi radialis longior, the extensor carpi radialis brevior, the extensor com- munis digitorum, the extensor minimi digiti, the extensor carpi ulnaris, and the anconeus. The supinator radii longus muscle arises by fleshy fibres from the external condyloid ridge of the humerus as high up as the musculo-spiral groove. It forms the outer boundary of the ante-cubital fossa of the elbow, and is the most external of the muscles covering the radial border of the forearm (Plate 49, Fig. 1, No. 2, and Fig. 2, No. 10). This muscle terminates about the middle of the forearm in a flat tendon which is inserted into the outer side of the base of the styloid process of the radius. At its insertion it is covered by the tendon of the extensor ossis metacarpi pollicis muscle (Plate 49, Fig. 2, No. 12). This muscle assists the anterior muscles in flexing the forearm, but it acts as a supi- nator upon the hand. It is supplied by a branch of the musculo-spiral nerve before its division. The extensor carpi radialis longior muscle arises from the lower part of the external condyloid ridge and the septum intervening between it and the extensor brevior muscle. It soon ends in a flat tendon which is over- lapped by the supinator longus, and, passing beneath the extensor muscles to the thumb, it traverses a groove on the outer and posterior surface of the lower end of the radius, to be inserted into the radial side of the THE REGIO:sr OF THE FOREARM. 385 cariml end of the metacarpal bone of the index finger. The tendon of this muscle occupies the second groove in the posterior annular ligament. Its nerve is derived from the musculo-spiral nerve. The extensor carpi radialis brevior muscle arises with the preceding muscle from about the external epicondyle, the intermuscular septa, and the adjacent part of the capsular ligament of the elbow. It is shorter and thicker than the extensor longior muscle, and its fibres terminate upon the under surface of a flat tendon below the middle of the forearm, where it is overlapped by the extensor longior. The tendon passes beneath the extensor muscles of the thumb, being accommodated in a special groove in the posterior surface of the lower end of the radius, and is inserted in the radial side of the base of the metacarpal bone of the middle finger. It is supplied by the posterior interosseous nerve. The tendons of both of the radial extensor muscles have usually small burste interposed between them and their insertions. They are peculiarly enclosed in a synovial sheath as they pass under the extensor muscles of the thumb, which allows them to play freely under these (page 388). Their function is to extend the wi'ist. The extensor communis digitorum muscle arises fi'om the lower part of the external epicondyle, the intermuscular septa, and the ovei'lying expansion of the deep fascia. It divides on the back of the forearm into three portions, which terminate in tendons at different points and pass under the annular ligament posterior to the radius to the back of the hand, whence they are distributed to the fingers, the third tendon dividing so that it is distributed to both the ring and the little finger. Below the annular ligament the tendons become broad and flat and diverge from one another toward the knuckle-joints of the fingers, where they change in character, becoming thicker and narrower, and give off lateral expansions, which pass to the sides of these joints and thus form the lateral metacarj)o-phalanc/eal ligaments (Plate 49, Fig. 2). On the back of the hand the two middle tendons generally pass over the corresponding metacarpal bones, while the tendon to the index finger passes obliquely across the space between the first and second metacarjial bones, and the tendon to the little finger, smaller than the other, continues in close relation to that of the ring finger until just above the metacarpo-phalangeal joint, where it diverges 49 386 THE HEGION OF THE FOREABM. abruptly to pass to its insertion. These tendons are often connected by accessory slips — vincula — above tlie knuckle-joints. They are subject to great variety, but they generally exist as strong slips extending from each side of the tendon of the ring finger to the adjacent tendon (Plate 49, Fig. 2, No. 8), so that this finger does not ordinarily admit of independent extension. The tendon of the index finger is usually free. On the back of each finger the common extensor tendon, after giving off" the bands which serve as lateral ligaments to the metacarpo-phalangeal joint, is continued as the digital aponeurosis, into which the tendons of the corre- sj^onding lumbrical and interosseous muscles are inserted in relation to the second or medial phalanx (page 403), where the aponeurosis divides into three slips, the middle one of which is attached to the base of the medial phalanx, while the two lateral slips join in front of the latter and are in- serted into the upper end of the third or ungual phalanx. This muscle is supplied by the jDOsterior interosseous nerve. Not only is the function of this muscle to act as a general extensor of the fingers, but it can also act so as to extend the first phalanges while the second and third are flexed, and to extend the second and third phalanges while the first are flexed. The extensor minimi digiti muscle arises from the external epicondyle and the adjacent intermuscular septa, and its fibres are arranged in a long slender bundle terminating in a tendon, which passes down the back of the forearm close to the tendons of the common extensor muscle, but occupying a separate compartment in the annular ligament, posterior to the inferior radio-ulnar joint. On the back of the hand the tendon divides into two slips which pass to the little finger, the slip on the radial side being joined by the tendon from the common extensor, already described, and then the tendons expand over the phalangeal joints and ter- minate in the same manner as the other extensor tendons of the fingers. It is supplied by the posterior interosseous nerve, and its special function is to extend the little finger independently. The extensor carpi ulnaris muscle arises from the common tendon about the external epicondyle, from the septum between it and the preceding muscle, and from the posterior border of the ulna in immediate proximity to the origins of the flexor carpi ulnaris and flexor profundus digitorum THE REGION OF THE FOREARM. 387 muscles. The fibres combine into a strong, broad tendon which is ac- commodated in a groove on the posterior surface of the ulna close to its styloid process, with which it is connected by a lateral expansion of fascia, and is finally inserted, after passing through a separate compartment iu the posterior annular ligament, into the ulnar side of the base of the metacarpal bone of the little finger. There is also a fibrous expansion connecting its tendon with the extensor aponeurosis at the base of the little finger. The tendon is surrounded by an extension of the synovial membrane of the wrist as it lies in the groove on the ulna. When the forearm is in the position of full pronation, the end of the ulna can be felt and seen projecting between the tendons of the extensor carpi ulnaris and extensor minimi digiti muscles. There is usually a bursa placed beneath the tendon and the end of the bone. The posterior interosseous nerve supplies its proper nerve, and its function is to extend the hand toward the ulnar side. The anconeus muscle is small, triangular, and placed at the external and posterior part of the elbow, arising by a tendon from the back of the external epicondyle and the contiguous portion of the capsule of the elbow-joint, from which diverging fibres jDass to be inserted into the tri- angular surface on the upper fourth of the ulna. It is subcutaneous, and receives a special branch from the musculo-spiral nerve, which descends to it through the inner portion of the triceps muscle just above it. This muscle may be regarded as an extension of the triceps on to the forearm, which it assists in extending the elbow. The muscles of the deep layer of the posterior group of the forearm are the supinator radii brevis, the three extensor muscles to the thumb, and the extensor indicis. The supinator radii brevis muscle arises beneath the mass of extensor muscles, from the lower and jiosterior part of the external epicondyle, from the external lateral ligament where it blends with the orbicular ligament, and from the roughened surface of the ulna below the lesser sigmoid cavity. The fibres of this muscle wind over the neck and upper part of the shaft of the radius and are inserted into the radius between the bicipital tubercle and the attachment of the pronator teres muscle. Occasionally there is a slip for this muscle attached specially 388 THE REGION OF THE FOREARM. to the orbicular ligament. The supinator brevis is supplied by the pos- terior interosseous nerve (page 394), and acts as a powerful supinator of the radius. The extensor ossis metacarpi poUicis muscle is situated immediately below the supinator brevis, and arises from the ulna below that muscle, from the interosseous ligament, and from the opposite surface of the radius. It descends obliquely, crossing over the radial carpal extensor muscles (Plate 49, Figs. 1, 2, and 3), about seven and a half centimetres, or three inches, above the wrist, passes through the annular ligament, and is inserted into the base of the metacarpal bone of the thumb, usually sending a slip to the trapezium. The extensor primi internodii poUieis muscle arises from the radius and the interosseous ligament just below the preceding muscle, which it accompanies through the annular ligament to be inserted into the base of the first phalanx of the thumb (Plate 49, Fig. 2, No. 14). This muscle is interesting as being 2^eculiar to the human hand. The extensor secundi internodii pollicis muscle partially overlaps the preceding muscle, arising from the ulna below the extensor ossis metacarpi, from the interosseous ligament, and from the sbeath of the extensor minimi digiti muscle. Its tendon passes independently through the annular ligament, in a distinct groove on the posterior surface of the radius, passes obliquely across the radial extensor tendons, and continues over the metacarpal bone and first phalanx of the thumb to be inserted into the base of the second or last phalanx (Plate 49, Fig. 1, No. 7). These tendons severally extend the portion of the thumb to which they are distributed. They can be readily distinguished through the skin, and the hollow produced by the extensor primi and extensor secundi tendons (the tabatiere anatomique) is interesting because the radial artery here j)asses across its floor (Plate 49, Fig. 1, No. 17) to enter into the palm (page 414). The extensor indicis muscle arises from the posterior surface of the ulna, below the extensor secundi pollicis, and from the adjacent part of the interosseous ligament. Its tendon passes beneath the annular ligament in the same groove on the end of the radius with the tendon of the extensor communis muscle. It proceeds to the metacarpo-phalangeal joint of the index finger, where it is joined to the tendon from the common extensor (Plate 49, Fig. 1, No. 9). THE REGION OF THE FOREABM. 389 This muscle is supplied by the posterior interosseous nerve, and its func- tion is to enable the index finger to be extended independently. The radial artery is the smaller of the two divisions of the brachial artery (page 354). It commences about opposite the head of the radius, and continues in the same line as the brachial artery as far as the wrist, being upon the radial side of the forearm, and for the most part between the supinator longus and flexor carpi radialis muscles. In the upper part of its course it is deeply situated between the pronator radii teres and the supinator longus, the fleshy border of the latter muscle usually over- lapping it. This artery is superficial to the extent of eight centimetres, or a hand's breadth, above the wrist, and rests upon the lower part of the anterior surface of the shaft of the radius (Plate 46, Fig. 2, No. 16), so that it can be easily distinguished and compressed, and is therefore chiefly used as the most convenient vessel for examining the arterial pulse. The branches of the radial artery in the forearm are the recurrent, superficialis volse, muscular, and carpal. The radial recurrent artery is of variable size, arises below the elbow, and ascends between the supi- nator longus and brachialis anticus muscles, supplying in its course the two supinators and the two radial extensors (Plate 46, Fig. 1, No. 10). It inosculates with the superior profunda artery (page 354). The arteria superficialis voice is variable both as to size and as to origin, and is some- times absent. It usually arises from the radial artery near the wrist, where it turns to pass under the extensor muscles of the thumb. It runs over the anterior annular ligament (Plate 48, Fig. 2, No. 1) and above or through the muscles of the ball of the thumb, to anastomose generally with the superficial branch of the ulnar artery and establish the superficial palmar arch (Plate 48, Fig. 4, No. 4). There are nine or ten muscular branches, which furnish blood to the muscles on the radial border of the forearm. The anterior and posterior carpal arteries are small branches which usually leave the radial artery below the pronator quadratus and join the ramifications of the neighboring arteries in the anterior and pos- terior rete carpi. The radial artery is accompanied by the tivo deep radial veins, or vence comites, one on each side, which are connected by venous links extending PLATE 52. Figure 1. The second phalangeal joint of the middle finger of the left hand laid open by an oval incision, as for the anterior flap of an amputation at this joint, to show the relations of the bone surfaces and the adjacent vessels. 1. The condyloid surface of the third or proximal phalanx of the middle finger. 2. The external lateral digital artery. 3. The glenoid surface of the head of the second phalanx of the middle finger. 4. The internal lateral digital artery. Figure 2. The metacarpophalangeal joint of the middle finger of the left hand opened, as in the first stage of an amputation (by the lateral-flap method) of the finger, to show the appearance of the ends of the bones at this joint. The position of the joint, on the dorsal surface, before the incisions were made, can be judged by comparison with the adjacent fingers. 1. The head of the metacarpal bone of the middle finger. 2. The external lateral digital artery. 3. The middle finger retained to show the character of the incisions for its removal by the lateral-flap method. i. The trochlear surface of the third, or proximal, phalanx of the middle finger. 5. The internal lateral digital artery. Figure 3. Amputation at the carpo-metacarpal joint of the thumb of the left hand (by the flap method), showing the relative positions of the structures severed in the operation. 1. The radial artery where it passes into the palm. 2. The OS trapezium. 3. The head of the metacarpal bone of the thumb drawn outward after division of the ligaments. 4. The thumb retained to show the proper character of the incisions in this amputation. 5. The external dorsal artery of the thumb. 6. The radialis indicis artery. 7. The princeps pollicis artery. 8. The internal dorsal artery of the thumb. Figure 4. The wrist-joint of the rigki hand laid open by an oval incision, as for the dorsal flap, in amputation at this joint, showing especially the appearance of the articulation between the lower end of the radius and the semilunar and scaphoid bones. 1. The lower end of the radius, showing the depression for the semilunar and scaphoid bones. 2. The triangular fibro-cartilage between the lower end of the ulna and the carpus. 3. The semilunar bone. 4. The cut tendons of the common extensor muscle to the fingers. 5. The divided radial arterj'. 6. The scaphoid bone. 7. The cut extensor tendons to the thumb. 8. The cut extensor tendon to the index finger. Figure 5. Vertical section through the articulations at the wrist of the right hand to show the synovial membranes and the cancellous structure and arrangement of the carpal bones. 1. The interosseous membrane. 2. Section through the lower end of the ulna. 3. The triangular inter-articular fibro-cartilage. 4. Section through the proximal row of the carpal bones. 5. Section through the distal row of the carpal bones. 6. Section through the heads of the metacarpal bones. 7. Section through the cuneiform bone. 8. Section through the pisiform bone. 9. Section through the unciform bone. 10. Section through the lower end of the radius. 11. Section through the semilunar bone. 12. Section through the scaphoid bone. 13. Section through the os magnum. 14. Section through the os trapezium. 15. Section through the trapezoid bone. 16. Section through the heads of the metacarpal bones. Figure 6. The left elbow-joint laid open posteriorly, as in the process of resection or excision of this articulation, to show the relations of the opposing bones and the adjacent structures. 1. The lower posterior portion of the left arm. 2. The severed tendon of the triceps muscle. 3. The trochlear surface of the lower end of the humerus. 4. The head of the radius. 5. Branch of the recurrent radial artery. 6. The upper portion of the left forearm. 7. The ulnar nerve. 8. The olecranon process of the ulna. 9. Branch of the recurrent ulnar artery. THE REGION OF THE FOREABM. 391 across the artery at frequent intervals, and join the venae comites of the brachial artery in the ante-cubital fossa. The radial nerve, which is a branch of the musculo-spiral nerve (page 360), is in relation to the outer side of the radial artery in the middle third of the forearm only. About six centimetres, or two and a half inches, above the wrist the radial nerve passes under the tendon of the supinator longus muscle, to be distributed to the back of the hand (Plate 47, Fig. 1, No. 16). Above the wrist, in the pulse-area, the radial vessels are often tortuous (Plate 46, Figs. 1 and 2). The line of reference for the radial artery may be drawn from the middle of the bend of the elbow to the ulnar side of the styloid process of the radius, or, for all practical purposes, an incision made parallel to the radial border of the forearm and two centi- metres, or a finger's breadth, from it will expose the sheath of the radial vessels. The ulnar artery is larger than the radial, with which it commences opposite the head of the radius at the bifurcation of the brachial artery. In the first part of its course it curves deeply beneath the pronator teres, the superficial flexor muscles, and the median nerve to the space between the flexor sublimis digitorum and flexor carpi ulnaris muscles, being over- lapped by the tendon of the latter, and so completely ensheathed by a re- flection of the deep fascia that its pulsation above the wrist can rarely be felt during life. Its course along the lower half of the forearm is more superficial and direct (Plate 46, Fig. 2). The branches of the ulnar artery in the forearm are the anterior and posterior ulnar recurrent, articular, common interosseous, muscular, and carpal. The anterior and posterior ulnar recurrent arteries arise gener- ally by a common trunk just after the origin of the main vessel at the elbow. The anterior passes upward to anastomose with the anastomotica magna and inferior profunda arteries. The posterior is the larger, and ascends between the two heads of the flexor carpi ulnaris muscle to the space between the olecranon and the internal epicondyle, by the side of the ulnar nerve, to communicate with the inferior profunda, anastomotica magna, and other arteries in the rete olecrani (page 370). The articular branch pierces the anterior part of the capsule of the elbow-joint at the 392 THE REGION OF THE FOREARM. outer border of tlje bracliialis anticus muscle. The common interosseous artery, which is four centimetres, or about one and a half inches, in length, arises from the ulnar artery, below the bicipital tubercle of the radius, and divides at the opening between the oblique and interosseous ligaments (page 375) into anterior and posterior branches. The anterior interosseous artery passes downward, being held in close contact with the interosseous ligament by a sheath of areolar tissue, as far as the upper border of the pronator quadratus muscle, where it subdivides into anterior and posterior branches, which join respectively the anterior and posterior carpal rete. The anterior interosseous artery in its course gives off the nutrient arteries to the radius and ulna, supplies the adjacent muscles with blood, and sends some perforating twigs through the interosseous membrane to the deep extensor muscles. , It is provided with two vence comites (Plate 46, Fig. 2, No. 14), and accompanied by a branch of the median nerve, the interosseous nerve, which overlies it superficially. The posterior interosseous artery, after reaching the posterior surface of the interosseous ligament, is in close relation with the posterior interosseous nerve (page 394). It gives off, besides muscular twigs to the superficial and deep extensor muscles, a recurrent branch, which joins the rete olecrani above, and finally ends below in the posterior carpal rete. The muscular branches of the ulnar artery are about a dozen in number, distributed to the contiguous muscles upon the ulnar side of the forearm. The anterior and posterior carpal branches arise from the ulnar artery above the wrist and join with the corresponding branches from the radial artery in forming the posterior carpal rete and the posterior palmar arch. The ulnar artery is also closely ensheathed with its two vence comites, which are connected at intervals by venous links and empty into the vense comites of the brachial artery below the elbow. The ulnar nerve takes a direct course along the ulnar side of the forearm, from the internal epicondyle to the radial side of the styloid process of the ulna, and therefore is at a considerable distance from the upper part of the ulnar artery, but for about six centimetres, or two and a half inches, above the wrist it is in close relation to the sheath of the vessels, the nerve being always to the ulnar side. Both vessels and nerve pass over the anterior an- THE REGION OF THE FOREARM. 393 iiular ligament together (Plate 48), and are held closely to the pisiform bone by an expansion of the fascia from the tendons of the flexor carpi ulnaris muscle. The lines of reference for the ulnar artery may be drawn from the tendon of the biceps at the front of the elbow to the middle of the ulnar side of the forearm, and thence straight to the radial side of the pisiform bone. Below the middle of the forearm the artery may be exposed by an incision made parallel to the ulnar border two centimetres, or a finger's breadth, from it. It should not be forgotten that the ulnar artery above the wrist is closely embraced by the border of the flexor carpi ulnaris muscle, and that therefore it is not so accessible or easy of exposure for a ligature as is the radial. The median nerve in the forearm descends, after passing between the two heads of the pronator radii teres muscle below the flexure of the elbow (page 369), along the middle of the forearm, between the flexor sublimis and flexor profundus digitorum muscles. It is quite deep at first, but gradually becomes more superficial where the flexor muscles become ten- dinous, and at the wrist it passes beneath the anterior annular ligament between the outer tendon of the flexor sublimis and the inner border of the flexor carpi radialis muscle (Plate 46, Fig. 1, No. 16, and Plate 48, Fig. 3, No. 2). Near the elbow the median nerve sends, besides the two branches to the two heads of the pronator teres muscle, muscular branches to all the flexor muscles except the flexor carpi ulnaris and the ulnar part of the flexor profundus. The anterior interosseous nerve leaves the median just below the pronator teres muscle, and accompanies the ante- rior interosseous vessels (page 392), being on their radial side. It supplies the flexor longus pollicis, part of the flexor jDrofundus, and the pronator quadratus muscles. There is also a cutaneous palmar branch, arising five centimetres, or two inches, above the wrist, which passes over the annular ligament and supplies the skin of the palm. Very often there is a branch from the median which joins the ulnar nerve where it is in more particular relation to the ulnar artery. The ulnar nerve in the forearm, as already stated (page 392), passes in a direct line from the front of the internal epicondyle to the radial side of the pisiform bone. At the elbow it gives off an articular branch to the elbow-joint, and soon after branches to both 50 394 THE REGION OF THE FOREARM. of the heads of the flexor carpi ulnaris and the contiguous part of the flexor profundus muscle. About the lower third of the forearm the ulnar nerve distributes two branches, called from their distribution the anterior and posterior ulnar cutaneous branches. The anterior passes superficially over the ulnar artery to supply the skin of the front of the wrist, and the posterior j^asses beneath the tendon of the flexor carpi ulnaris to the dorsal surface. A few twigs from the ulnar nerve also supply the wrist- joint. The branches of the musculo-spiral nerve in the forearm, besides the twigs supplied to the supinator longus and extensor carpi radialis longus muscles (page 360), which leave the nerve in the space between the brachialis anticus and the supinator longus in the outer depression of the elbow, are the posterior interosseous and the radial. The posterior interosseous nerve is the larger of the two terminal branches. It turns backward through the supinator brevis and passes downward between the superficial and deep extensor muscles to the middle of the posterior part of the forearm, curving thence under the extensor secundi internodii j^ollicis muscle to the back of the wrist. It supplies all the extensor muscles with which it is in relation throughout its course, and may be regarded exclusively as a motor nerve. The radial nerve is the cutaneous branch of the musculo-spiral in the forearm. Its course is along the middle of the forearm, under cover of the supinator longus muscle and to the outer side of the radial vessels. Above, in relation to the elbow, the nerve is placed considerably to the outer side of the artery ; below, it passes beneath the tendon of the supinator longus muscle (Plate 47, Fig. 3, No. 8), pierces the deep fascia, and subdivides into two terminal branches, which are distributed to the skin on the back of the radial border of the hand (page 408), some of the filaments communicating with the terftiinal filaments of the musculo-cutaneous nerve. Although fractures of the bones of the forearm are very common, it is surprising how little attention has been given to the anatomy of the parts involved, a knowledge of which would certainly influence the method of their treatment. These injuries may afiect both the radius and the ulna, or either of these bones. When the two bones are broken, the violence THE REGION OF THE FOREARM. 395 may be direct or indirect. Wlien the radius is broken alone, it is generally- due to indirect violence transmitted from the hand. When the ulna is broken alone, it is usually owing to direct violence and to its exposed posi- tion. Whatever shortening or displacement may occur in any form of these injuries is not so much in consequence of muscular action upon the fragments as on account of the direction from which the violence is received. The essential feature of the treatment of fractures of the fore- arm is the preservation of the normal dimension of the interosseous space, as already stated (page 376). This is generally appreciated nowadays; but it is of equal importance to remember that in all fractures, in what- ever region they occur, the bones are not the only tissues which suffer from the injury. There is always accompanying the breach in the continuity of the bones more or less damage to the soft structures about them. The interosseous ligament and periosteum, with their special vessels, must be lacerated, and although in one sense this is essential for the process of repair, yet it presents a factor which probably accounts for the frequent unsatisfactory results of treatment. It should be borne in mind that the radius supports the hand, and that therefore it is most liable to suffer from non-union. The superficial veins (page 408) play a valuable part in nature's efforts at repair, and should not be interfered with. As soon as bony union has been obtained, passive motion should be resorted to at regular intervals. The fracture at the lower end of the radius, known as Colles's fracture, usually occurs transversely from half an inch to one and a half inches above the wrist-joint. This is probably due to the character of the internal structure of the bone in this situation. The expanded lower end of the radius is mostly cancellous, while the shaft which joins it possesses a greater amount of compact tissue (Plate 52, Fig. 5). This fracture is usually caused by the weight being transmitted through the hand out- stretched in the position of pronation to break the shock in the act of falling. The degree of displacement depends measurably upon whether the ligaments of the inferior radio-ulnar joint are ruptured. The development of the radius occurs from three centres. The head is ossified in the fifth year, and joins the shaft about the eighteenth year. 396 THE REGION OF THE WRIST AND THE HAND. The lower extremity is ossified during the second year, but does not unite with the. shaft before the twentieth year. The development of the ulna also is from three centres, one for the shaft and one for each end. At birth the extremities are entirely cartilaginous. The olecranon does not begin to ossify until the tenth year, and it is joined to the shaft about the sixteenth year. The lower extremity ossifies in the fourth year, and joins the shaft in the twentieth year. It should be noted that the epiphyses which meet at the elbow unite with their shafts earlier than those at the opposite ends of the bones, also that the foramina of the medullary arteries are directed toward the elbow. In amputation through the middle of the forearm by the antero- posterior oval-flap method, the parts exposed in the flaps when made upon the left side bear the following relations (Plate 51, Fig. 3). The anterior flap is composed chiefly of the flexor muscles, in the margin of which in the superficial fascia is the cut superficial median vein (No. 1). The median nerve (No. 3) is in the middle of the flap, between the severed superficial and deep flexor muscles. The ulnar vessels and the ulnar nerve (No. 5) are close to the sawn end of the ulna, and the radial vessel and the radial nerve are close to the sawn end of the radius. The interosseous vessels and nerve are between the bones. The posterior flap is composed chiefly of the extensor muscles, and in its margin will be found the superficial radial vein (No. 10). THE REGION OF THE WRIST AND THE HAND. The skeleton of the hand consists of the carpus, or wrist, which connects the hand with the forearm, the metacaipus, or median portion of the hand, and the phalanges, or digital extremities. The carpal bones are eight in number, polygonal in shape, and are composed of cancellous tissue enclosed in a compact layer. They are arranged in two rows, each of which contains four bones, counting from the external or radial side, as follows: in the upper or proximal row, the scaphoid, semilunar, cunei- form, and pisiform ; in the lower or distal row, the trapezium, trapezoid, magnum, and unciform. Each of these little bones presents a dorsal surface which is usually comparatively smoother and larger than the THE REGION- OF THE WRIST AND THE HAND. 397 palmar surface, wliicli is rough for the attachment of the ligaments, while tlie lateral borders are covered, in the recent state, with articular cartilage. When they are collectively united they form an arch with its concavity toward the palm, the scaphoid and the trapezium, the two outer bones of the two rows, and the pisiform and the unciform, the two inner bones of the two rows, projecting laterally. The contiguous surfaces of the carpal bones are so adapted that they form with one another gliding joints, the motion between any two of them being very slight, and limited to ex- tension and flexion, with the exception of the os magnum, which appears to be also capable of a very little rotation. The articulation between the two rows, the intercarpal joint, however, admits of considerable motion, and materially contributes to the flexion and extension of the hand. The three principal bones of the upper row, the scaphoid, semilunar, and cuneiform, are connected by interosseous ligaments at their margins so that they present a convex surface which is received into the con- cavity formed by the articular surface of the lower end of the radius and the under surface of the triangular fihro-cartilage, thus establishing the important radio-carpal or wrist joint (Plate 52, Fig. 5). The triangular fibro-cartilage separates the inferior radio-ulnar joint (page 375) from the wrist. It extends transversely beneath the lower end of the ulna, being attached by its apex to the groove between the styloid process and the head of the ulna, and by its base to the ridge between the ulnar depression and the articular surface of the lower ex- tremity of the radius. Its lower surface is therefore really a continuation inward of the radial articular surface. T^he synovial membrane lining the cavity of the wrist-joint is separated from the synovial pouches between the carpal bones by the interposition of the interosseous ligaments, but there is very often a communication between the synovial cavities of the inferior radio-ulnar and radio-carpal joints through a deficiency in tlie triangular fibro-cartilage. The flexor and extensor tendons as they pass over this region afford strong protection to it, but beneath them there are fibrous bands which extend mostly from the margins of the radius and fibro- cartilage to the first row of carpal bones, and which with the intervening connective tissue constitute the capsular ligament of the wrist. Tlie 398 THE REGION OF THE WRIST AND THE HAND. various bands which have been specialized are the anterior ligament (or ligamentum arcuatum) , composed mainly of intersecting fibres which pass obliquely from the anterior lip of the radius to the palmar surface of the scaphoid, semilunar, and cuneiform bones, a few fibres being inserted also into the os magnum. This is reinforced by an additional band placed more superficially, extending from the base of the styloid process of the ulna to the cuneiform bone, and attached to the fibro-cartilage between them ; the external lateral ligament, which is short and thick and extends from the styloid process of the radius to the outer side of the scaphoid ; the posterior ligament (or ligamentum, rectum), consisting of intersecting fibres which j^ass from the posterior margin of the radius and the fibro- cartilage to the dorsal surface of the semilunar and cuneiform bones; and the internal lateral ligament, which is a round band, longer and narrower than tlie external, and extends from the tip of the styloid process of the ulna to the cuneiform bone. The movements permitted at the wrist-joint are flexion, extension, abduction, adduction, and circumduction, but not rotation. This joint acts harmoniously with the intercarpal and carpo-metacarpal joints, all of them being closely associated, so that they move simultaneously. The radio-carpal joint is supplied by filaments from the ulnar and posterior interosseous nerves. In opening the wrist-joint from the dorsal surface, as in amputation (Plate 52, Fig. 4), the peculiar convex arrangement of the upper row of carpal bones and the cup-shaped concave surface formed by the lower end of the radius and triangular cartilage present themselves, together with several bands of the capsule which project across the cavity of the joint and about which the synovial membrane is gathered into folds. The pisiform bone articulates with the cuneiform bone, and the joint thus formed is surrounded by a capsular ligament and provided with a distinct synovial membrane. It is also strongly connected by ligamentous fibres with the unciform and fifth metacarpal bones. It serves mainly to give attachment to the flexor carpi ulnaris and abductor minimi dio-iti muscles. Besides the synovial membranes peculiar to the inferior radio- ulnar joint, to the radio-carpal or wrist joint, and to the piso-cuneiforra joint, just described, there are two distinct synovial membranes, enclosed THE REGION OF THE WRIST AND THE HAND. 399 within the articulations formed by the carpal bones in relation to one another (the intercarpal joint) and to the bases of the metacarpal bones. The largest of these extends between both rows of the carpal bones, sending short pouches upward between the bones of the first row, and longer pouches downward between the bones of the second row, which are expanded between the latter and the bases of the contiguous metacarpal bones. The smaller synovial membrane is interposed between the trape- zium and the metacarpal bone of the thumb. It is not uncommon to find that the interosseous ligament between the magnum and unciform bones is attached to the ridge on the fourth metacarpal bone, and consequently there is a subdivision of the larger synovial membrane between the unciform and the bases of the fourth and fifth metacarpal bones. The carpal bones are all connected by interosseous ligaments at their dorsal and palmar margins, of variable development, which blend with the especial ligaments of the intercarpal joint, and are called, from their positions, the palmar and dorsal ligaments. The palmar consists of strong fibres which radiate from the tuberosity of the os magnum to all the adjacent bones, and therefore is sometimes known as the ligamentum radiatum. The dorsal is somewhat weaker, and consists mostly of transverse fibres which extend from the back of the os magnum over the other bones and unite with the dorsal ligaments of the radio-carpal joint above and the carpo-metacarpal joints below. The metacarpal bones, five in number, are modified long bones, each consisting of a somewhat triangular shaft, slightly bowed, with the concavity toward the palm. The proximal ends, or bases, are irregular, presenting tuberosities for the attachment of the ligaments and smooth facets for articulation with the carpal bones and the adjoining metacarpal bones, with which they are in relation. The distal ends, or heads, are quadrate, and provided with lateral depressions for ligaments, and sphe- roidal eminences for reception upon the glenoid surfaces of the proximal ends of the first phalanges. The articular processes of the heads embrace more of the palmar than of the dorsal surfaces. The metacarpal bones of the fingers are proportionately more slender than the metacarpal bone of the thumb, which is shorter and broader. They all diverge slightly PLATE 53. Figure 1. Topographical survey of the right side of the head, face, and neclt, with especial adaptation to cranio-cerebral study, the localization of the areas of distribution of the sensory nerves, and spots where electrical stimulation produces reflex contractions of some of the muscles in these regions. Also the landmarks for the operations of tracheotomy and of laryngotomy. 23. Cutaneous area of mental nerve. 24. Position where facial artery and vein pass over the body of the jaw in front of masseter muscle. 25. Spot where reflex contraction of the sterno-cleido-mastoid mus- cle may be produced. 26. Position of body of the hyoid bone. 27. Cutaneous areaof auricularis mag- nus nerve. 28. Anterior prominence of the thy- roid cartilage. 29. Point where the common carotid artery is in relation to the trans- verse process of the fourth cer- vical vertebra. 30. Position of the hoop of the cricoid cartilage. 31. Spot wliere reflex contraction of the omo-hyoid muscle may be produced. 32. Supra-sternal notch. 1. Cutaneous area of supra-orbital nerve. 2. Position of superior frontal fissure. 3. Cutaneous area of auriculo-tem- poral nerve. 4. Position of the fissure of Rolando. 5. Position of horizontal branch of the fissure of Sylvius. 6. Spot where reflex contraction of the temporal muscle may be produced. 7. Cutaneous area of occipitalis major nerve. 8. Cutaneous area of occipitalis mi- nor nerve. 9. Spot where reflex contraction of the splenius muscle may be produced. 10. Spot where reflex contraction of the trapezius muscle may be produced. 11. Posterior cervical folds of the in- tegument produced by contrac- tion of the trapezius muscle. 12. Spot indicating position of the brachial plexus of nerves. 13. Cutaneous area of supra-troohlear nerve. 14. Position of inferior frontal fissure. 15. Cutaneous area of infra-troclilear nerve, 16. Cutaneous area of lachrymal nerve. 17. Cutaneous areaof nasal nerve. 18. Position of ascending branch of the fissure of Sylvius. 19. Cutaneous area of infra-orbital nerve. Cutaneous area of temporo-malar branch of the superior maxil- lary nerve. Spot where reflex contraction of the masseter muscle may be produced, 22. Cutaneous area of buccal nerve. 20. 21, Figure 2. The left hand in the position of pronation, showing a topographical survey of the areas of distribution of the sensory nerves on the back of the hand and fingers, and spots where electrical stimulation produces reflex contraction of some of the muscles. 1. Area supplied by the median nerve on ulnar side of dorsal surface over third phalanx of middle finger. 2. Lowest distribution of ulnar nerve on ulnar side of middle finger. 8. Area supplied by median nerve on dorsal surface of radial side over third phalanx of ring finger. 4. Lowest distribution of ulnar nerve on ulnar side of dorsal surface of ring finger. 5. Ulnar nerve on radial side of little finger. 6. Ulnar nerve on ulnar side of little finger. 7. Spot where contraction of the third dorsal interosseous muscle may be produced. 8. Spot where contraction of the fourth dorsal interosseous mus- cle may be produced. 9. Spot where reflex contraction of the abductor minimi digiti mus- cle may be produced. 10. Ulnar nerve on back of wrist. 11. Median nerve on dorsal surface of third phalanx of middle finger. 12. Lowest distribution of radial nerve on radial side of middle finger. 13. Median nerve on dorsal surface of ulnar side of third phalanx of index finger. 14. Lowest distribution of radial nerve on ulnar side of index finger. 15. Median nerve on radial side of dor- sal surface of third phalanx of index finger. 16. Lowest distribution of radial nerve on radial side of index finger. 17. Eadial nerve on dorsal surface of thumb. 18. Spot where contraction of second dorsal interosseous muscle may be produced. 19. Spot where contraction of first d or- sal interosseous muscle may be produced. 20. Eadial nerve on dorsal surface of wrist. 21. Lowest distribution of musculo- spiral nerve. Figure 3. The right hand in the position of supination, showing a topographical survey of the areas of distribution of the sensory nerves ou the palm of the hand and anterior surface of the fingers, and spots where some of the muscles may be caused to contract by electrical stimulation. Also the surface-markings on the palm of the hand in relation to the arterial arches. 1. Median nerve on ulnar side of pal- mar surface of middle finger. 2. Median nerve on radial side of palmar surface of ring finger. 8. Ulnar nerve on ulnar side of pal- mar surface of ring finger. 4. Ulnar nerve on palmar surface of radial side of little finger. 5. Ulnar nerve on palmar surface of ulnar side of little finger. 6. Linca mensalis. 7. Spot where contraction of the third lumbrical muscle maybe produced. 8. Spot where contraction of the fourth lumbrical muscle may be produced. 9. LiiifL! hepatica. 10. Li7iea ceplmlica. 11. Spot where contraction of the op- ponens minimi digiti muscle may be produced. 12. Spot where contraction of the abductor minimi digiti muscle may be produced, 13. Spot where contraction of the opponens poUicis muscle may be produced, 14. Spot where contraction of the palmaris brevis muscle may be produced, 15. Ulnar nerve on front of wrist, 16. Median nerve on palmar surface of radial side of middle finger. 17. Median nerve on palmar surface of ulnar side of index finger. 18. Median nerve on palmar surface of radial side of index finger, 19. Spot where contraction of the sec- ond lumbrical muscle may be produced. 20. Spot where contraction of first lum- brical muscle may be produced. 21. Spot where contraction of the adductor poUicis muscle may be produced. 22. Internal branch of median nerve on palmar surface of thumb. 23. External branch of median nerve on palmar surface of thumb. 24. Spot where contraction of the flexor brevis poUicis muscle may be produced. 25. Liiiea vitalis. 26. Spot where contraction of the abductor poUicis muscle may be produced. 27. Median nerve below the wrist. 28. Linea tranevnm caijA. 29. Median nerve above the wrist. 30. Spot where contraction of the flex- or longus poUicis muscle may be produced. 31. Spot where contraction of the tendons of index and little fin- gers may be produced. 32. Spot where contraction of the ten- dons of middle and ring fingers may be produced. Fi0 I ■ ■ m&r — ■ T"'" 26 ■ m^ 1 ^ Eama^^ \ 9 ,-': ■ 31 Fio2 Photagf'aphed and De.:- . ■re 6y GsoRGB Mc. Clellah M. Copvn^^_hi.:83l.bvGronr,^ Ml Clllla>:.N I' THE REGION OF THE WRIST AND THE HAND. 401 from the carpus, but that of the thumb diverges more than the others. The metacarpal bone of the index finger is the longest of the series, the rest of which are successively shorter toward the little finger, its meta- carpal bone being longer than that of the thumb. The latter is peculiar in having its palmar surface turned toward the ulnar side of the hand; its base has no lateral facet, being provided with an oval facet for articu- lation with the trapezium only. The head is less pronounced than in the corresponding bones, and has two marked processes on the palmar surface for the two sesamoid bones (page 402). The joint between the trapezium and the metacarpal bone of the thumb is distinct and protected by a cap- sular ligament, which is particularly strong in the external and dorsal portions. The proximal ends of the metacarpal bones are connected by interosseous ligaments, and each carpo-metacarpal joint is provided with palmar, dorsal, and lateral ligaments. The phalanges are fourteen in number, — three in each finger and two in the thumb. They are designated as the first or proximal, the second or medial, and the third or distal. The latter are also called the ungual phalanges, because they suj)port the nails. The phalanges in each of the digital extremities successively decrease in size toward the wrist. They are all long bones with semi-cylindrical shafts. The dorsal surfaces of the first and second phalanges are slightly convex, except that of the thumb, which is rather concave and tapers toward the distal end. The upper ends of the first phalanges are severally provided with glenoid depressions variably modified for articulation with the metacarpal bones to which they belong, and their lower ends present trochlear surfaces for articulation with their proper second phalanges. The upper ends of the latter have each a double concavity for the reception of the trochlear surfaces of the first phalanges, and their lower ends are also provided with similar trochlear surfaces, but smaller than those of the first phalanges. The second phalanges of the middle and ring fingers are about equal in length, that of tlie index finger is shorter, and that of the little finger is the smallest of the series. The third or ungual phalanges are all provided with concavities at their upper ends, each presenting two depressions, for articulation with the 51 402 THE REGION OF THE WRIST AND THE HAND. second phalanges, and they terminate in the horseshoe-shaped ungual processes, which are roughened on their palmar surfaces for the attach- ment of the pulps of the fingers. The ungual process of the thumb is the largest and broadest, while the ungual processes of the middle, ring, index, and little fingers follow in order as named. The metaearpo-phalangeal joints are enarthrodial, being capable of extension, flexion, abduction, adduction, and slight rotation. The con- tiguous bony surfaces are each provided with a layer of articular cartilage and a synovial membrane, the glenoid depressions on the proximal ends of the first phalanges being deepened by small glenoid ligaments. These joints are surrounded by capsular ligaments, which being comparatively weak in their dorsal portions are strengthened by expansions from the extensor tendons (Plate 49). The fibres at each side are very strong, and have been specialized as lateral ligaments. The second and third interphalangeal joints are ginglymoid, being capable only of flexion and extension. They are constructed similarly to the metaearpo-phalangeal joints, having glenoid and capsular ligaments, the side bands of the latter being strengthened into lateral ligaments. At the metaearpo-phalangeal joint of the thumb there are always found two sesamoid bones, the outer being the larger. They are the ossified nodules of fibro- cartilage, in relation to the lateral ligaments, and receive the inser- tions of short muscles. The spaces between the metacarpal bones are occupied by the inter- osseous muscles, which are arranged in two sets, palmar and dorsal. There are three palmar interosseous muscles, each of which has a single origin. The first arises from the base and front of the metacarpal bone of the index finger, and is inserted into the ulnar side of the dorsal aponeurosis of the three phalanges belonging to the digital extremity of that finger. The second arises from the metacarpal bone of the ring finger, and is in- serted into the radial side of the dorsal aponeurosis of the corresponding phalanges. The third arises from the metacarpal bone of the little finger, and is inserted into the radial side of its phalanges. There are four dorsal interosseous muscles, each of which has two origins. The first arises from the ulnar side of the upper portion of the metacarpal bone THE RSaiON OF THE WRIST AND THE HAND. 403 of the thumb and the whole of the adjacent side of the metacarpal bone of the index finger, and is inserted into the radial side of the base of the proximal phalanx and the dorsal aponeurosis over the medial and distal phalanges of that finger. The second arises from the adjacent sides of the metacarpal bones of the index and middle fingers, and is inserted into the radial side of the aponeurosis enveloping the phalanges of the middle finger (Plate 49, Fig. 1, No. 19). The third arises from the adjacent sides of the metacarpal bones of the middle and ring fingers, and is inserted into the ulnar side of the aponeurosis over the phalanges of the middle finger. The fourth arises from the adja- cent sides of the metacarpal bones of the ring' and little fingers, and is inserted into the ulnar side of the aponeurosis over the phalanges of the ring finger. The general function of the palmar set is to adduct the fingers toward the middle line of the middle finger, while that of the dorsal set is to abduct the fingers from that line. The dorsal aponeurosis of the fingers, above mentioned, is formed by the expansion of the extensor tendons (Plate 49) after they have given off the flat bands to the sides of the metacarpo-phalangeal joints. It is con- tinued down the fingers, being attached by a middle slip to the bases of the medial phalanges, and by lateral slips which intersect and are inserted into the bases of the ungual phalanges (page 402). On the sides of the proximal phalanges the aponeurosis receives the insertions of the interosseous muscles, described above, as well as those of the lumbricales muscles. The latter are four slender bundles of muscular fibres which arise from the deep flexor tendons in the palm of the hand. The Jirst and second are attached to the radial sides of the tendons of the index and middle fingers, and are inserted into the radial sides of the digital aponeuroses below. The third and fourth arise from the contiguous surfaces of the adjacent tendons of the ring and little fingers, and are inserted into the radial sides of their digital aponeuroses. The first and second lumbricales are supplied by the median nerve, the third and fourth by the ulnar nerve. Their function is to flex the metacarpo-phalangeal joints, but they can also assist the action of the extensor tendons in maintaining the extension of the interphalangeal joints. It has already been stated 404 THE REGION OF THE WRIST AND THE HAND. that all the flexor tendons become enclosed in aponeurotic sheaths opjiosite the palmar surface of the metacarpo-phalangeal joints, and that as they enter these sheaths the superficial tendons divide into lateral slips, which diverge about the middle of the proximal phalanges, to allow the deep flexor tendons to pass between them. The two lateral slips of the super- flcial tendons blend together behind the deep tendons, and then separate again, to be finally inserted into the sides of the medial phalanges, while the deep tendons are continued on, to be inserted into the bases of the ungual phalanges. In this connection it should be noted that the meta- carpo-phalangeal joints are capable of being flexed so that the fingers may be brought into the hollow of the palm, thus forming the fist, while the heads of the metacarpal bones and the bases of the proximal phalanges are made prominent at the knuckles. The fingers can be extended only very little beyond the plane of the metacarpus, but they can be readily moved laterally. The interphalangeal joints can be flexed or extended so that the separate phalanges shall move in the same manner as the entire fingers, but they have no lateral movement. The construction of the joint of the thumb, between its metacarpal bone and the trapezium, enables it to be opposed to all the fingers. The special flexor (page 383) and extensor (page 388) muscles of the thumb have already been described. Besides these there are the muscles which constitute the ball of the thumb. The abductor pollicis muscle (Plate 48, Fig. 3, No. 3) arises .from the anterior annular ligament and the tubercle of the trapezium, and is inserted into the outer side of the proximal phalanx of the thumb. This muscle is supplied by a branch of the median nerve, and often consists of two slips, between which passes the superficialis volse artery (page 389). The action of this muscle is to draw the thumb away from the rest of the hand. The opponens pollicis muscle (Plate 48, Fig. 4, No. 2) arises beneath the abductor, also from the annular ligament and the trapezium, and is inserted into the metacarpal bone of the thumb upon the whole length of its radial border. It is supplied by a branch of the median nerve. By its action the thumb is brought forcibly in apposition with all the fingers. The fi,exor brevis pollicis muscle has a double origin, a superficial portion THE REGION OF THE WRIST AND THE HAND. 405 arising from the trapezium and annular ligament, which is inserted into the outer sesamoid bone and the radial surface of the proximal phalanx of the thumb, and a deeper portion which arises from the bases of the metacarpal bones of the index and middle fingers and the fibrous arch between them and the trapezoid and magnum and is inserted into the inner sesamoid bone and the base of the proximal phalanx of the thumb. The superficial portion is supplied by the median nerve, the deep portion by the ulnar nerve. The tendon of the long flexor muscle passes between these two portions, to be inserted into the base of the ungual phalanx of the thumb (page 383). The function of the flexor brevis is to flex the proximal phalanx of the thumb upon the palm. The adductor pollicis muscle (Plate 48, Fig. 4, No. 7) is triangular, and arises from the shaft of the metacarpal bone of the middle finger, its fibres blending with those of the deep portion of the flexor brevis, to be inserted into the inner sesamoid bone and the adjoining part of the proximal phalanx of the thumb. Sometimes two portions of this muscle are differentiated as the oblique and transverse adductors, but they are very imperfectly separable. The adductor pollicis is supplied by the ulnar nerve. Its action is to augment that of the flexor brevis, and to enable the tip of the thumb to be brought into contact with the tips of the fingers. The mobility of the thumb and the power which it possesses through its many muscles render it one of the distinguishing features of the human hand. The muscles of the ball of the little finger resemble somewhat those of the thumb. The abductor minimi digiti muscle (Plate 48, Fig. 2, No. 13) arises from the pisiform bone and its capsular ligament and is inserted into the ulnar side of the base of the proximal phalanx of the little finger, blending with its dorsal aponeurosis. It sometimes receives an accessory slip from the tendon of the flexor carpi ulnaris. The flexor brevis minimi digiti muscle (Plate 48, Fig. 4, No. 17) is really a part of the abductor. It arises from the unciform process, and is inserted also into the base of the proximal phalanx of the little finger and into the adjacent aponeurotic arch over the deep flexor tendon. The action of the abductor muscle is to draw the little finger away from the rest of the hand, and it is 406 THE REGION OF THE WRIST AND THE HAND. assisted in this effort by the flexor brevis. The opponens minimi digiti muscle arises beneath the flexor brevis from the unciform process and the under surface of the annular ligament, and is inserted on the ulnar side of the metacarpal bone of the little flnger. The action of this muscle is to draw the metacarpal bone of the little finger upon the palm,, so as to strengthen its power of grasping. All these muscles of the little finger are supplied with branches from the ulnar nerve. The surface-markings of the wrist and hand are of considerable topo- graphical importance. The positions of all the bony prominences in this region should be noticed, in extension and flexion, as well as in supination and pronation. The lower extremities of the radius and ulna can be readily defined, because they are to a great extent superficial. It has already been stated that the laxity of the capsular ligament about the inferior radio-ulnar joint permits of slight lateral motion between the bones of this articulation when the radius is rotated, and consequently it is the styloid j)rocess of the ulna which is felt in supination, and not the head of that bone. The styloid process of the radius is placed more anteriorly than the con-espouding process of the ulna, and is also twelve millimetres, or half an inch, lower. Below and in front of the radial styloid process the tubercle of the scaphoid bone can be felt, and below and in front of the ulnar styloid process is the pisiform bone. A line drawn from one styloid process to the other will be found to pass down- ward and outward, and its extremities represent the lower limits of the radio-carpal joint, the line of the joint itself being in the form of an arc with the convexity upward (Plate 52, Fig. 4). The skin over the wrist is quite loose, thin, and free from fat. In front of the wrist the skin is closely connected with the deep fascia, and is marked by transverse lines, of which the lowest is usually very distinct (Plate 53, Fig. 3, No. 28). It is about one and a half centimetres, or three-quarters of an inch, below the wrist-joint, and crosses the os mag- num in the line of the metacarpal bone of the middle finger. This line also corresponds to the upper border of the anterior annular ligament (page 412). About the middle of the anterior surface of the wrist the tendon of the palmaris longus muscle is usually plainly seen, especially when THE REGION OF THE WRIST AND THE HAND. 407 the wrist is flexed with the fingers extended. The flexor carpi radialis tendon is on its outer side. The median nerve as it descends from the forearm to enter the palm beneath the annular ligament is between these two tendons (Plate 48, Fig. 4, No. 1). The tendon of the flexor carpi ulnaris muscle can be easily distinguished as it passes to the pisiform bone on the inner side of the wrist, when that joint is slightly flexed and the little finger closed uj)on the palm. The tendons of the flexor sublimis digitorum muscle are in the depression between the tendons of the flexor carpi ulnaris and the palmaris longus. Within the superficial fascia on the palmar surface of the thumb and the fi'ont of the wrist the superfi- cial veins can be seen through the thin skin passing upward from the palmar plexus to empty into the median and ulnar veins. On the radial border of the wrist the tendons of the extensor ossis metacarpi and primi internodii pollicis muscles are brought into distinct relief when the thumb is abducted; and on the back of the wrist the tendon of the extensor secundi internodii pollicis muscle is rendered prominent when the thumb is forcibly extended and abducted. The extensor carpi ulnaris tendon can be felt upon the inner side of the posterior surface of the wrist, and to the radial side of it are the tendons of the extensor communis digitorum. If the skin is removed from the back of the hand, the above tendons will be seen as they pass beneath the posterior annular ligament (Plate 49, Fig. 3, No. 7). This consists of a special condensation of the deep fascia in this locality, which is formed by the transverse fibres of the deep fascia prolonged from the forearm and augmented by special fibres which are attached to the ridges on the back of the lower end of the radius and thence pass obliquely inward over the capsular ligament of the inferior radio-ulnar joint to the ulnar side of the carpus, where they are attached to the pisiform and cuneiform bones. The several attachments of the deep fibres to the ridges on the radius convert the grooves into canals for the passage of the extensor tendons. There are six compartments thus formed in the posterior annular ligament, as follows: one for the extensor ossis metacarpi and the extensor primi internodii pollicis ; one for the extensor radialis longior and the extensor radialis brevior; one for the extensor secundi internodii pollicis; one for the extensor indicis and the extensor 408 THE REGION OF THE WRIST AND THE HAND. communis digitorum ; one for the extensor minimi digiti ; and one for the extensor carpi ulnaris. All these compartments are lined by synovial mem- branes which envelop the tendons and accompany them nearly as far as their insertions. Sometimes there is a communication between one of the above synovial sheaths and the cavity of the wrist-joint. The skin over the bach of the hand is very fine, and but loosely attached to the annular ligament enclosing the tendons and to the deep fascia pro- longed from it to the knuckles below, owing to the extreme laxity of the subcutaneous tissue. This is manifest in oedema and extravasations which often occur here. The skin is also jirovided with numerous short fine hairs and sebaceous follicles. The hairs are so set that they have an inclina- tion toward the ulnar border, and they are extended also over the dorsal surfaces of the first and second phalanges of all the fingers. The sweat- glands are not so numerous on the back of the hand as they are on the palm, where they are remarkable for the profuseness of their perspiration under certain conditions. The skin of the back of the hand is not very sensitive to tactile impressions. The superficial veins of the hand (Plate 47, Fig. 3) arise mainly from the dorsal plexuses, which commence by radicles forming arches over the backs of the j)roximal phalanges. On the ulnar side the ulnar dorsal plexus is formed by the union of the vein from the little finger (the vena salvatella) with the veins from the third and fourth interdigital clefts. From this plexus usually two veins ascend to the forearm, a small anterior superficial ulnar and a larger posterior superficial ulnar. On the radial side the radial dorsal plexus is formed by the junction of the vein from the thumb (the vena cephalica pollicis) with veins from the index and middle fingers, which terminate in the radial veins above. There is much diversity in the arrangement of these veins on the back of the hand, and the two plexuses are frequently connected by a transverse venous link, which presents an H-shaped appearance. As the vein from the thumb passes upward it crosses the hollow formed by the extensor tendons of the thumb, and in close relation with it are the branches of the radial nerve (Plate 47, Fig. 3, No. 9) which pass to supply the dorsal surface of the thumb and the dorsal surface of the index and THE REGION OF THE WRIST AND THE HAND. 409 the radial side of the middle finger as far as their distal phalanges (Plate 53, Fig. 2). At the bottom of the hollow, beneath the tendons, the radial artery, in a bed of fat which separates it from the scaphoid and trapezium, passes (Plate 49, Fig. 1, No. 17) to the interval between the first and second metacarpal bones to enter the palm between the two portions of the abductor indicis muscle and form the deep palmar arch (page 415). Before leaving the back of the hand the radial artery gives off the pos- terior carpal artery, which passes beneath the extensor tendons, forming an arch with the corresponding branch from the ulnar artery. From this dorsal arch the dorsal interosseous arteries arise (Plate 47, Fig. 3, and Plate 49, Fig. 3). They descend to the muscles occupying the several interosseous spaces, supplying them and the other adjacent parts, and inosculating near the metacarpo-phalangeal joints with the j)erfo- rating branches from ' the deep palmar arch. On the ulnar side of the back of the hand the ulnar nerve appears just below the styloid process of the ulna, and in relation to the vein from the little finger (Plate 47, Fig. 3, No. 5) it divides into branches which supply the dorsal surface of the little finger, the whole of the dorsal surface of the ring finger, except the radial border of the distal phalanx, and the dorsal surface of the ulnar side of the middle finger, except over the distal phalanx (Plate 53, Fig. 2, No. 10). The palm of the hand presents some conspicuous features which should be closely examined. There is a large prominence on the radial side, formed by the muscles of the ball of the thumb, already described (page 404), which is called the thenar eminence; while upon the ulnar side the long prominence corresponding to the muscles of the ball of the little finger is the hypothenar eminence. The two eminences are some- times named the heel of the hand. Between them, over the annular ligament, there is a depression, which broadens toward the fingers, and when the latter are flexed forms the holloiv of the hand. The skin of the palm is attached to the fascia beneath along the many lines of flexion, three of which are especially marked and have been designated as follows. The first line, curving round the base of the thenar eminence, is caused by the constant flexion of the thumb, and is called the linea vitalis (Plate 53, 52 410 THE REGION OF THE WRIST AND THE HAND. Fig. 3, No. 25). It corresponds to the attachment of the radial margin of the palmar fascia. The second line commences at the radial side of the hand, between the index finger and the thumb, and extends across the palm to about the middle of the metacarpal bone of the little finger, is caused by the apposition of the middle and index fingers with the thumb, and is known as the linea oephalica. This line indicates the position of the metacarpo-phalangeal joint of the index finger, and is a useful guide iu its amputation. The third line, which is the lowest upon the extended palm, commences at the elevation between the index and middle fingers and runs obliquely to the ulnar border of the hand, is caused by the flexion of the middle, ring, and little fingers, and is known as the linea mensalis. The last two lines are intersected by another, less conspicuous, which takes a vertical course nearly over the metacarpal bone of the middle finger, is called the linea hepatica, and gives to these markings the characteristic outline of the letter M (Plate 53, Fig. 3). The second line where it crosses the metacarpal bone of the ring finger is about over the lowest part of the superficial palmar arch (page 414). The third line is the most important. It is one centimetre, or a little less than half an inch, above the metacarpo-phalangeal joints of the fingers which produce it, and indicates very nearly the upper limits of the synovial sheaths of the index, middle, and ring fingers. Just beyond this line the palmar fascia divides into its four slips (page 412). The position of the metacarpo- phalangeal joints can be ascertained by alternate flexion and extension, and will be found to be for each finger at a point midway between the third palmar line and the webs of the fingers. The same points refer to the bifurcation of the digital arteries (Plate 48, Fig. 4). When the proximal phalanges are extended and the medial and distal are flexed, three little elevations are noticed, formed by the pressing forward of the little cushions of fatty tissue which occupy the arches made by the digital slips of the palmar fascia over the flexor tendons. The palmar surface is further marked at the bases of the fingers by transverse flexion-folds, which are single for the index and little fingers and double for the middle and ring fingers. These folds are about two centimetres, or three-quarters of an inch, below the corresponding metacarpo-phalangeal joints. There THE REGION OF THE WRIST AND THE HAND. 411 are similar folds produced by the flexion of the interphalangeal joints, the first of which is double and the second usually single for each finger. They do not correspond to the joints, being usually from three to one and a half millimetres, or from one-eighth to one-sixteenth of an inch, above them. The thumb is provided with two folds corresponding to its two joints, the upper one of which passes obliquely over the metacarpo- phalangeal joint. The free margin of the web between the fingers is called the plica inter digitalis, and is about two centimetres, or three- quarters of an inch, from the metacarpo-phalangeal joints on the palmar surface. These measurements are exact, but it is always best for prac- tical purposes to remember the unfailing rule of exercising the functions of these joints when in doubt, which will demonstrate their position and features better than any description. The palmar ej)idermis varies in thickness mainly according to the uses to which the hands are put. There are abundant sweat-glands, as already stated. The papillse are exceedingly large and numerous, and contain touch-corpuscles. On the rounded pulps of the fingers they are arranged in irregular concentric ridges, never being precisely alike in any two hands. The subcutaneous tissue of the 'palm is scanty, and resembles the same tissue in the scalp, as mentioned in the description of that structure, as it is intimately associated with the palmar fascia beneath. Owing to the dense- ness of this tissue and the thickness of the cuticle, the hand is peculiarly adapted to sustain the effects of pressure and friction. The ulnar border of the palmar part of the hand is remarkably well provided in this respect and protected by the soft parts, without the presence of any large nerves. The pahnaris brevis muscle consists of short transverse fibres arising from the skin over the hypothenar eminence and attached to the palmar fascia. Its contraction assists in grasping. When the skin of the palm with the above muscle is carefully removed, the palmar fascia and the anterior an- nular ligament are exposed. The palmar fascia is a strong, silvery-white, glistening tissue spread over the centre of the palm, and when completely developed is really the expansion of the tendon of the palmaris longus muscle (Plate 48, Fig. 1, No. 8). In such cases it overlies the annular ligament proper; but very 412 THE REGION OF THE WRIST AND THE HAND. often it appears to be simply a downward prolongation from that ligament over the palm, the tendon of the palmaris longus losing itself in the upper margin of the ligament. The palmar fascia consists chiefly of strong longi- tudinal fibres, which constitute the outer or superficial layer, and can be separated by careful dissection (Plate 48, Fig. 2, No. 8) from a deep layer of transverse fibres which are in immediate relation with the lower border of the annular ligament. At the borders of the thenar and hypothenar eminences the palmar fascia becomes thinner, and a layer composed of the deeper transverse fibres passes over the muscles forming these emi- nences to blend with the dorsal fascia. Toward the fingers the fascia divides into four slips, which are inserted chiefly into the bases of the proximal phalanges and the anterior surfaces of the capsular ligaments of the metacarpo-phalangeal joints, while some of the deeper fibres form lateral slips which blend with the aponeurotic sheaths of the flexor tendons, and others pass round and join the dorsal aponeurosis over the extensor tendons. In the arches formed by the attachment of the slips there are little cushions of fatty tissue whicli enclose the digital nerves and arteries and the tendons of the lumbricales muscles as they pass to the fingers. Many of the fibres of the superficial layer of the fascia are associated with the skin, which renders its dissection from the fascia very tedious. From the deeper layer there are two weak slips which pass across to be attached to the lateral expansions enclosing the muscles of the thenar and hypothenar eminences. The one to the thumb is espe- cially noticeable (Plate 48, Fig. 1, No. 4). From the under surface septa also pass to the metacarpal bones. Beneath the skin of the webs of the fingers there are transverse fibres, called the superficial transverse ligaments, which cross over the vessels and nerves and afford them greater protection from pressure when the hand is used in grasping. The palmar fascia, like all the expansions of the deep fascia, is subject to great variability, depending upon development. In the hands of mechanics it is always very strong, and among persons who habitually use their fingei's requiring effort doubtless many accessory slips are produced. The ulnar artery and ulnar nerve descend to the palm over the annular ligament and between the two layers of the palmar fascia (Plate 48, Fig. 2, Nos. 11 and 12). THE REGION OF THE WRIST AND THE HAND. 413 The anterior annular ligament consists of a strong transverse band of fibrous tissue arcliing across from the unciform j)rocess and the pisi- form bone to the trapezium and the tuberosity of the scaphoid bone. It is continuous with the deep fascia of the forearm above and with the deep layer of the palmar fascia below. Most of the muscles of the ball of the thumb and of the little finger arise from it (page 404), and it holds in place the flexor tendons of the fingers and thumb and the median nerve (Plate 48, Figs. 2, 3, and 4). The anterior annular ligament is one of the most unyielding fibrous structures in the body. There are two synovial sacs placed beneath this ligament: one, the larger, lines the canal formed byihe ligament arching across the carpus, and is reflected over the flexor tendons of the fingers so as to form a loose pouch four centimetres, or one and a half inches, above the ligament, while below it sends prolongations along the several tendons, forming sheaths for them as far as the middle of their corresponding metacarpal bones, except the little finger, which usually is accompanied by an extension as far as the attachment of the flexor profundus tendon at the base of the ungual phalanx. The smaller synovial sac is in relation to the flexor longus pollicis tendon, and extends above the annular ligament not quite so far as the other sac. It accom- panies the tendon as far as its insertion into the ungual phalanx of the thumb. The tendons of the index, middle, and ring fingers are provided yfith. 'separate synovial sheaths, which rarely communicate with the other synovial sacs, they being about two centimetres, or three-quarters of an inch, apart. The highest points of the digital sheaths usually correspond to the third flexion-line on the palmar surface, while they terminate at the bases of the ungual phalanges, so that the finger-pulps rest upon the periosteum, a fact which is often demonstrated in felon, or whitlow, by the rapid necrosis affecting the bones. This arrangement explains the fact that an abscess involving the thumb or the little finger is apt to spread to the forearm, while such an extension of suppuration does not often follow a similar affection of any of the other fingers. The ulnar artery descends from the forearm in close relation to the pisiform and unciform bones, with the ulnar nerve close to its inner side. At the wrist both artery and nerve are embedded in adipose tissue and 414 THE REaiON OF THE WRIST AND THE HAND. protected by an expansion from the tendon of the flexor carpi ulnaris to the palmaris longus. Just after leaving the pisiform bone the ulnaris profunda is given off, and, accompanied by the deep branch of the ulnar nerve, passes between the abductor minimi digiti and flexor brevis minimi digiti muscles, while the main vessel continues between the two layers of the palmar fascia along the muscles of the ball of the little finger, two cen- timetres, or three-quarters of an inch, from and parallel with the linea vitalis on the surface. About midway between the latter and the linea cephalica the ulnar artery turns outward toward the web of the thumb, and, crossing over the branches of the median nerve and flexor tendons, anastomoses either with the radialis indicis or with the superficialis volse artery, and sometimes with both, thus forming the superficial arterial palmar arch (Plate 48, Figs. 3 and 4). This arch is about six centi- metres, or not quite two and a half inches, above the interdigital clefts. From the upper border or concavity of the arch several small recurrent branches arise which supply the carpal bursa and palmar fascia and inosculate with the carpal branches of the radial artery. From the lower border or convexity of the arch arise four digital arteries, which supply the fingers, except the radial side of the index and the thumb. The first descends over the muscles on the inner border of the palm to the ulnar side of the little finger, along which it runs to the tip. The* second, third, and fourth descend vertically between the flexor tendons and on a line with the clefts between the fingers. About one and a half centimetres, or half an inch, above the clefts each artery, after receiving a communicating branch from the deep arch, bifurcates into two branches, which proceed along the opposed sides of the fingers as far as their tips. The lateral digital arteries in their courses freely communicate by trans- verse branches at the several joints, which they supply, as well as the sheaths of the tendons on both the palmar and dorsal surfaces. At the ungual phalanges the digital arteries subdivide into palmar and dorsal branches, which form plexuses in relation to the pulps of the fingers and the matrices of the nails respectively. The radial artery enters the palm from the dorsal surface between the inner head of the flexor brevis and the adductor pollicis muscle (page 405), THE REGION OF THE WRIST AND THE HAND. 415 and, after giving off the arteria princeps pollicis and the radialis indicis, continues inward as the palmaris profunda, under the branches of the median nerve and the flexor tendons, to anastomose with the ulnaris pro- funda and thus form the deep arterial palmar arch (Plate 48, Fig. 4). This arch is seven centimetres, or two and three-quarter inches, above the interdigital clefts. The arteria princeps pollicis at its origin is of large size, and passes between the abductor indicis (or first dorsal interosseous) and the adductor pollicis to the ulnar side of the palmar surface of the metacarpal bone of the thumb. In the interval between the lower portions of the flexor brevis muscle it divides into two lateral branches, which run along one or each side of the thumb and inosculate with each other simi- larly to the other digital arteries. The radialis indicis artery descends from its origin to the radial side of the index finger. Usually at the lower border of the adductor pollicis muscle this vessel communicates with the superficial palmar arch, and it often receives a branch from the prin- ceps pollicis (Plate 48, Figs. 3 and 4). The deep arch receives three per- forating branches from the dorsal carpal rete through the spaces between the metacarpal bones, and from its upper border gives off branches to the adjacent muscles and branches to the anterior carpal rete. From its lower border four small branches descend in relation to the palmar interosseous muscles and communicate with the digital arteries from the superficial arch, as above described. Occasionally one or more of these interosseous branches are substituted for the regular arteries to the fingers. Wounds of the palm involving any of the principal arteries are always serious, in consequence of the free anastomoses between the vessels form- ing the arches, and of the difiiculty of reaching the bleeding vessel and securing it in the wound without damaging other important structures. Nevertheless, the above procedure is the only proper one, as the hemor- rhage can rarely be checked by tying either one or both of the main arteries above the wrist. The ulnar nerve, after passing over the anterior annular ligament at the wrist, on the inner side of the ulnar artery, divides into a deep and a superficial palmar branch. The deep palmar branch supplies the muscles forming the hypothenar eminence, and accompanies the ulnaris profunda 416 THE BEaiON OF THE WRIST AND THE HAND. artery to supply all the interosseous muscles, the two ulnar lumbricales, the adductor pollicis, the inner head of the flexor brevis pollicis, and the carpo-metacarpal and metacarpo-phalangeal articulations. The superficial palmar branch distributes filaments to the skin over the hypothenar emi- nence and the inner surface of the palm of the hand, and to the palmaris brevis muscle, and divides into two digital nerves, one to the ulnar side of the little finger and the other subdividing and supplying the opposed sides of the ring and little fingers (Plate 48, Fig. 4, and Plate 53, Fig. 3). The superficial branch of the ulnar communicates with the median nerve by a branch which passes beneath the superficial palmar arch. The median nerve (Plate 48, Figs. 3 and 4), as it descends from the forearm under the anterior annular ligament, is enveloped in a fold of the synovial membrane. It is superficial to the flexor tendons, and as it enters the palm becomes somewhat swollen, of a pinkish color, and flat- tened, and divides into two branches of nearly equal size. The external palmar branch supplies recurrent filaments to the muscles of the ball of the thumb (the abductor pollicis, the opponens pollicis, and the outer head of the flexor brevis pollicis), and ends in three digital nerves, two to the thumb and one to the radial side of the index finger. The nerves to the thumb pass one on each side of the long flexor tendon as far as the ungual phalanx, where the outermost nerve connects with the ter- minal branch from the radial nerve. The nerve to the radial side of the index finger sends a filament to the first radial lumbrical muscle, and is continued to the ungual phalanx. The internal palmar branch of the median nerve divides into two digital branches, which pass vertically in a line with the clefts between the index and middle and the middle and ring fingers. About three centimetres, or one inch and a quarter, above the webs of the fingere the digital branches subdivide into lateral digital nerves, which are distributed as follows. The nerves from the first branch pass to the opposed sides of the index and middle fingers. The first digital branch also supjilies the second radial lumbrical muscle. The nerves from the second branch pass to the opposed sides of the middle and ring fingers, receiving communicating branches from the ulnar nerve. After many careful dissections, and repeated critical examinations on THE BEGION OF THE WRIST AND THE HAND. 417 e living regarding the cutaneous distribution of the various digital jrves, the author is inclined to believe that the arrangement as shown 'late 53, Figs. 2 and 3) may be considered to represent their usual rela- )ns. It should be remembered that there is commingling of the fibres ' the median and ulnar nerves by direct intercommunicating nerves both )ove and below the wrist, which probably accounts for the discrepancy the observations on this subject. The extremities of the digital nerves e provided with peculiar little bodies, the Pacinian corpuscles, which are und in greater number on the nerves of the thumb and the index finger, heir function is unknown. The cutaneous nerve-supply of the hand is markable for the high development and the great number of the tactile rpuseles, which give to it an extraordinarily acute degree of tactile sensi- lity. The most sensitive area is the palmar surface of the tips of the igers, and especially that of the ungual phalanx of the index finger, be dorsal surface of the hand is the least sensitive, as already stated. The superficial lymphatic vessels commence by palmar and dorsal vessels 1 each finger, which unite and form plexuses on the palmar and dorsal irfaces of the hand respectively. Those of the palmar plexus are small id very close, and are arranged in an arch, from which vessels pass up e forearm accompanying the superficial veins. Those of the dorsal exus are comparatively larger and more numerous, and their vessels ind round the borders of the forearm above the wrist and join with the issels from the palmar plexus. The deep lymphatic vessels accompany e venae comites of the radial and ulnar arteries. The nails are the horny plates which surmount the finger-tips upon eir dorsal surfaces, and may be regarded as modified appendages of the )idermis. Each nail rests upon the extremely vascular and sensitive lil-bed of the dermis, the upper portion of which is called the matrix, bose papillse are arranged in ridges and protected by a fold of the skin, [le part of the nail in relation to the matrix is the root. It is the thin- ist part, and appears white and opaque just in front of the fold of the ;in, and, owing to its crescent shape, is called the lunula. The latter always more pronounced in the thumb than in the fingers. The growth ' the nails is like that of the epidermis, by an incessant production of 53 418 THE REGION OF THE WRIST AND THE HAND. nail-cells in fhe nail-bed, so that as long as the matrix is preserved the nail is capable of reproduction. The nails vary in individuals, and under certain constitutional conditions are probably influenced by impeded cir- culation, for there appears to be a direct communication between the arteries and the veins in the matrix. It is noteworthy that during con- valescence from many of the exanthematous diseases grooves make their appearance across the nails, presenting indications of growth. As the digital nerves supply large terminal filaments to the nail-beds, it is not difl&cult to account for the intense pain which is experienced when a splinter or other foreign body is thrust beneath the nails. The development of the bones of the wrist and hand occurs at varying periods. At birth the carpal bones are all cartilaginous. The os magnum becomes ossified in the first year, the unciform in the second, the cuneiform in the third, the trapezium in the foui'th, the semilunar in the fifth, the scaphoid in the sixth, the trapezoid in the seventh, and the pisiform not generally before the twelfth. The metacarpal bones and the phalanges are usually composed of a shaft and an upper epiphysis. The shafts become ossified soon after birth, and the epiphyses are all united about the twentieth year. INDEX TO VOLUME I. THE REFERENCES TO SURGICAL AFFECTIONS OR PROCEDURES (MARKED *) RELATE TO THEIR ANATOMY ONLY. A. Abducent nerve, 41, 92. * Abscess, deep-seated, of the temporal region, 150. mammary, 250. mediastinal, 322. pharyngeal, 133. post- pharyngeal, 195, Acervulus cerebri, 51. Acoustic hair-cells, 77. Acromion process, 330. Alse of the nose, 109. Alveoli of the jaws, 145. of the lungs, 269. of the parotid gland, 131. AmpiiUse of the semicircular canals, 72. *Amputation of the arm, 349, 361. of the elbow-joint, 371. of the forearm, 396. of the shoulder-joint, 337. Amygdalae of the cerebellum, 47. Anastomosis of arteries, 292. Andersch, ganglion of, 205, 219. * Aneurism of the aorta, 288. Annular ligament of the wrist, ante- rior, 413. of the wrist, posterior, 407. Annulus ovalls, 278. Ansa hypoglossi, 205. Anterior nares, 114. Antihelix, 61. fossa of, 61. Antitragus, 61. Antrum, mastoid, 6. of Highmore, 11.S, 144. walls of, 145. Aorta, 287. absence of arch of, 289. arch of, highest point to which it reaches, 289. ascending, or ventral, 287. Aorta, branches of, 288. bulbous enlargement of, 287. descending thoracic, 312. interior of, 288. normal course of, 287. opening into, 284. transverse, 288. Aponeurosis, digital, 386. dorsal, of the fingers, 403, of the scalp, 13. pharyngeal, 171. Appendix of the left anricle, 282. of the right auricle, 277. * Application of tourniquet to the brachial artery, 363. Aqueduct of Fallopius, 69, 204. of Sylvius, 39, 44, 50. of the cochlea, 73. of the vestibule, 72, Aqueous humor, 100, 102. Arachnoid fluid, or cerebro-spinal fluid, 21. membrane, 21. Arantius, ventricle of, 50. Arbor vitae of the cerebellum, 49. Arch of the aorta, 289. of the upper jaw, 147. Arciform flbres, 45. Arcus senilis, 88. Areola of the breasts, 250. Arm, bicipital depressions of, 349. region of, 348. subcutaneous fascia of, 349. surface-marking of, 349. Arnold's nerve, 63, 204. Arteria centralis modioli, 73. retinae, 94. comes nervi phrenici, 259. Arterial arch, deep palmar, 415. superficial palmar, 414. pulse, 307. Arteriosum, ligamentum, 305. Arteriosus, ductus, 290, 303. Artery ,or arteries : acromial, 341. descending, 349, acromio-thoracic, 341. alar thoracic, 341. anastomotica magna of brachial, 355. angular, 124, anterior cerebral, 22. ciliary, 96. circumflex, 342. communicating, 22. dental, 141. interosseous, 392. mediastinal, 233, 259. articular, to the elbow-joint, 391. to the shoulder-joint, 233. ascending palatine, 159. pharyngeal, 175. auditory, 23, 78. axillary, 229, 339. branches of, 341. basilar, 22, 215, 232, bicipital, 343. brachial, 354. at the elbow, 369. branches of, 354. compression of, 369. course of, 351. high bifurcation of, 356. in relation to the median nerve, 356. * ligation of, 366. venae comites of, 357. bronchial, 270, 313. buccal, 141. capacity of, 291. capillary, of the heart, 276. carotid, 223. course of, 201. * ligation of, 226. carpal, 389. circumflex, 334. 419 420 INDEX. Artery or arteries : collateral intercostal, 313. common carotid, bifurcation of, 201. interosseoos, 392. pulmonary, 282, 289. communication with veins in the matrices of the nails, 418. coronary, 148, 277. cortical, 23. course of, in the extremities, 293. in various localities, 291. crico-thyroid, 184. *in relation to laryngot- omy, 184. cubital, 355. deep temporal, 141. descending acromial (thoracica humeraria), 341. palatine, 141. digital, 414. dimensions of, 292. dorsal, 315. interosseous, of the hand, 409. of the tongue, 166. dorsalis scapulae, 331, 342. '* effect of ligation upon, 295. endangium of, 295. ethmoidal, 95. external and internal carotid, relative position of, 203. carotid, 34. branches of, 203. coat, or adventitia, 293. mammary, 250, 341. facial, 123, 203. frontal, 8, 95. ganglionic, 23. general anatomy of, 293. great or middle meningeal, 17. hypogastric, 304. inferior coronary, 123. dental, 139. labial, 123. laryngeal, 233. profunda, 355. thyroid, 233, 235. infra-orbital, 141. innominate, 121, 288, bifurcation of, 141. « ligation of, 222. intercostal, 313. dorsal branches of, 209. internal carotid, 134, 203. in relation to the phar- ynx, 176. coat, or intima, 298. Artery or arteries : internal mammary, 257. * ligation of, 257. maxillary, 134, 139, 203. interosseous, of the palm, 415. lachrymal, 95. lateral digital, 414. infracostal, 259. of the nose, 124. spinal, 215. lateralis nasi, 110. left common carotid, 288. subclavian, 288. lenticulo-striate, 23. lesser meningeal, 17, 139. lingual, 166, 203. » ligation of, 166. long and short sub-scapular, 341. thoracic, 341. lower intercostal, 257. mammary branches of anterior intercostal, 250. masseteric, 139. meningeal, 17. from occipital, 211. middle cerebral, 22. coat, or media, 293. meningeal, 139. mode of division of, 292. muscular branches of brachial, 354. of radial, 389. of ulnar, 392. musculo-phrenic, 257. mylo-hyoid, 139. nasal, 95. from internal maxillary, 115. or spheno-palatine, 141. nutrient, to the humerus, 355. occipital, 8, 203, 211. oesophageal, 313, 317. of the brain, 22. of the breasts, 250. of the choroid coat, 97. of the dura mater, 17. of the face, 123. of the larynx, 184. of the nasal cavities, 115. of the nose, 110. of the palate, 159. of the pericardium, 274. of the pinna, 63. nf the scalp, 8. hemorrhage from, 9. of the tympanum, 71. ophthalmic, 94. osculation or anastomosis of, 292. Artery or arteries : palmar and dorsal, of digital, 414. palmaris profunda, 415. palpebral, 95. perforating, of deep palmar arch, 409, 415. of the thorax, 259. pericardiac, 313. petrosal, from middle meningeal, 71. phrenic, 322. posterior auricular, 8, 134, 203. carpal, 409. cerebellar, 23. cerebral, 23. circumflex, 342, 346. communicating, 22. dental, 115. interosseous, 392. palatine, 168. scapular, 330, 342. princeps cervicis, 211. pollicis, 415. pterygo-palatine, 141. pterygoid, 141. pulmonary, 290. radial, 389. and ulnar, variable originS of, 343. in the hollow formed by the extensor tendons of tbc thumb, 409. in the palm, 414. radialis indicis, 415. ranine, 162, 166. recurrent, of posterior interos- seous, 392. radial, 389. ulnar, 392. right and left coronary, 276. septal, 141. short ciliary, 97. small thoracic, or pectoral, 341. spinal, 313. structure of walls of, 293. subclavian, 221, 227. differences of right and left, 228. » ligation of, 231. sub-lingual, 166. sub-scapular, 342. superficial cervical, 206, 233. superficialis volse, 389. superior coronary, 124. dental, 141. epigastric, 257. intercostal, 211. INDEX. 421 Artery or arteries ; superior laryngeal, 184. profunda, 354. thoracic, 341. thyroid, 203, 235. supra-hyoid, 166. supra-orbital, 8, 95. supra-scapular, 221, 229, 231, 233. stylo-mastoid, 71, 78. systemic, 291. temporal, 8, 134, 203. terminal, 23, 292. thoraciea humeraria, 341. thoracieo-acromial, 250. thyroid axis, 229, 232. thyroidea ima, 221, 235. to the concha, 211. tonsillar, of facial, 171. tracheal, 237. _ transversalis colli, 206, 221, 233. transverse facial, 124, 134. tympanic, 139. ulnar, 391, 393. at wrist, 413. recurrent, 391. ulnaris profunda, 414. umbilical, 304. vas aberrans, 352, 355. vertebral, 215, 232. groove for, on atlas verte- bra, 213. vessels of, 299. Vidian, 141. Asterion, 60. Auditory artery, 23, 78. canal, walls of, 64. hairs, 75. meatus, external, 63. cartilaginous portion of, 64. osseous portion of, 64. nerves, 41, 77. vein, 78. Auricle of the ear, 60. left, of the heart, 282. right, of the heart, 278. Auricles, walls of, 278. Auricular appendix, 282. branch of pneumogastrio nerve, 63. cartilage, 61. ligaments, 61. muscles, 61. Axilla, connective tissue of fat in, 338. lymphatic glands of, 346. region of, 337. suspensory ligament of, 338. * Axillary abscess, 338. artery, 339. « ligation of, 343. line of, 343. fascia, 338. fold, 338. glands, involvement of, in can- cer, 347. * removal of, 347. Bartholin, duct of, 164. Base of the cerebrum, 37. Basilar artery, 22. Basilic vein, 351, Basion, 35. Bell, external respiratory nerve of, 345. Bichat, fissure of, 29. Bicipital groove of the humerus, 332. Blind spot, 105. Blood, 300. amoeboid movement of, 301, arterial, 290. circulation of, after birth, 305. before birth, 303. corpuscles, red and white, 300. differentiation of its circulation before and after birth, 305, haematoblasts, 301. hEemoglobin of, 301. plates, 301. Blue line in lead-poisoning, 150. Bodies, olivary, 45. restiform, 45. Body, intercarotic, 203. thyroid, 233. Bone or bones : body of sphenoid, 111. carpal, 396. clavicle, 323. cribriform plate of ethmoid, HI. cuneiform, 396. humerus, 348. hyoid, body of, 165. greater and lesser cornua of, 165. position of, 165. incisive, 147. incus, 68. inferior maxillary, development of, 152. mylo-hyoid ridge of, 165. variations in angle of, 153. lachrymal, 79. magnum, 395. malar, 80, 145. Bone or bones : malleus, 67. maxillary, ossification of, 150. metacarpal, 399. nasal, 107. of the ear, 67. of the forearm, * fractures of, 394. of the head, 2. of the orbits, 80. of the palate. 111. of the wrist, ossification of, 418. phalanges, 401. pharyngeal spine of occipital, 172. pisiform, 396. premaxillary, 147. radius, 363, 373. ribs, 243. scaphoid, 399. scapula, 328. semilunar, 396. sesamoid, 402. sphenoidal turbinated, 111. stapes, 68, sternum, 246. superior maxillary, 144. * excision of, 145. palate processes of, 156. tuberosity of, 141. temporal, 7. trapezium, 396. trapezoid, 396. turbinated. 111, ulna, 362, 373. unciform, 396. vertebrae, cervical, 187. dorsal, 248. vomer, 108. Wormian, 5. Brachia, 52. Brachial artery, 354. high bifurcation of, 356. or axillary plexus of nerves, 344. plexus of nerves in the arm, 357. Brain, 24. area of surface of, 25. arteries of, 22, convolutions of, 25. development of, 25. fifth ventricle of, 53. fourth ventricle of, 49. furrows of, 25. lateral ventricles of, 53. lobes of hemispheres of, 26. median or longitudinal fissure of, 26. 422 INDEX. Brain, membranes of, 15. motor area of, 35. sensorial area of, 36. size and shape of, 25. structure of, 25. tliird ventricle of, 51. Breast, 250. * operation for removal of, 251, 253. Breathing, abdominal, 248. thoracic, 248. Bregma, 2, 33. Bridge of the nose, 108. Broca, convolution of, 30. Bronchi, 268. right and left, 236. structure of, 268. Bronchial glands, 271. tube, 268. Bronchioles, 269. Bronchocele, 235. Bulb, olfactory, 38. Bursa in relation to the tendon of the biceps muscle, 352. in relation to the tendon of the coraco-brachialis muscle, 353. in relation to the tendon of the flexor carpi radialis muscle, 380. in relation to the tendon of the sub-scapularis muscle, 353. in relation to the tendon of the trapezius muscle, 209. sub- deltoid, 334. Bursoe about the elbow, 370. C. Calamus scriptorius, 50. Calcar, 55. Canal or canals : anterior dental, 145. central, of Stilling, 105. infra-orbital, 127, 145. lachrymal, 113. membranous semicircular, 76. naso-palatine, 156. of Huguier, 71, 143. of Petit, 103. of Schlemm, 96, 102. palatine, 147. posterior dental, 145, semicircular, 72. spiral, 73. Vidian, 142. Canaliculi of the eyelids, 86. Canalis reuniens, 75. spiralis modioli, 73. Canthi, 81. Capillaries, 298. calibre of, 298. in various tissues, 298. medullary, 224. pulmonary, 270. structure of, 298. Capitulum, 348. Capsule, external, 54. internal, 54. of Tenon, 89, 93. Carotid tubercle, 189. Carpal bones, 396. rete, 392, 415. Carpus, 396. Cartilage or cartilages: accessory, in female larynx, 179. arytenoid, 177. auricular, 61. costal, 245. cricoid, 177. hoop of, 177, 189. relations of, 190. ensiform, 247. lateral, of the nose, 108, of Wrisberg, 178. septal, of the nose, 108. sesamoid, 109. tarsal, 81. thyroid, 176. cornua of, 176. Cartilaginous framework of the nose, 108, Caruncula lachry mails, 85. Caudate nucleus, 54. Caudo-lenticular limb, 55, Cavernous sinuses, 19. Cavity, glenoid, of scapula, 331. of temporal bone, 136. Cavum oris, 156. Cells, acoustic hair-, 77. anterior ethmoidal, 113. gustatory, 102. mastoid, 6. migratory, 301. of Dieters, 77. olfactory, 114, 116. pigment-, of choroid coat, 97. posterior ethmoidal, 113, Cerebellum, 26, 47. central lobe of, 47. function of, 49. vermiform process of, 47. Cerebrum, base of, 37. convolutions of, 25. crura of, 39. fibres of medullary substance of, 68. Cerebrum, fissures of, 27. hemispheres of, 26. lobes of, 26. lower level of, 33. ventricles of, 49, 51, 53. Ceruminous glands, 64. Cervical axillary passage, 339. Chamber, anterior, 102. posterior, 102, Cheeks, 149, Chest, physical examination of, 311, Chordse tendinese, 281, 283. vocales, 178, 179. Willisii, 19. Choroid coat of the eye, 97. plexuses, 52. tela, 21. Ciliary body, 99, processes, 99. Circle of Willis, 22. Circulation, foetal, 303. pulmonary, 306. systemic, 305. Circulus major, 101. minor, 101. Claustrum, 54. Clava, 46. Clavicle, 324. acromial end of, 324. borders of, 325. * fractures of, 327, movements of, 324, ossification of, 327. physical properties of, 323. sternal end of, 324. subclavian impression of, 325, Cochlea, 73. Cochlear canal, 73, 74. duct, 75. Cohnheim, terminal arteries of, 23. Collateral circulation, 292. after ligation of the axil- lary artery, 343. after ligation of the carotid artery, 227. after ligation of the sub- clavian artery, 232. Columnss carnese, 279, 283. nasi, 109. Commissura simplex, 47. Commissure, great transverse, 57. of the third ventricle, 67. Conarium, 51. Concha, 61, Conjunctiva, 85. blood-vessels of, 86, corneal, 87, palpebral and ocular, 85, INDEX. 42c Djunctiva, sclerotic, 86. nus arteriosus, 279. nvolution or convolutions : angular, 31. annectant, 31. anterior central, or ascending frontal, 30. ascending parietal, 31. Broca's, 30. fornicate, 32. frontal, 30. bippocampal, 32. of the brain, 25. parietal, 31. retro-insular, 32. superior marginal, 31. racoid process, 330. rd, spinal, enlargement of, opposite the fifth cervical vertebra, 215. rds of the brachial or axillary plexus of nerves, 345. rnea, 87. lamina of, 87. nerves of, 88. non-vascularity of, 88. proper substance of, 87. rneal corpuscles, 87. rniculum laryngis of Santorini, 178. rnua Ammonis, 55. of lateral ventricles, 53. rona radiata, 58. ronoid process, 362. rpora albicantia, 39. geniculata, 52. quadrigemina, 50. striata, 52. function of, 58. topographical relation of, 59. rpus albicans, 53. Arantii, 282. callosum, 57. peduncles of, 37. ventricles of, 58. dentatum, 45. fimbriatum, 53. rpuscles of the blood, 300. Pacinian, 417. rti, organ of, 74. rods of, 77. tunnel of, 77. stal cartilages, 245. sto-coracoid membrane, 338. anial nerves, 38. deep origins of, 44. inio-cerebral topography, 32, ista, 72. acoustica, 75. " Crow's-feet," 82. Crura cerebri, 39. of the cerebellum, 49. of the fornix, 52. Crusta, 39. Crystalline lens, 102. Cuneiform cartilages, 178. Cupola, 73. Curved line of the occipital bone, 6. Cutaneous muscle of the scalp, 11. D. Deciduous teeth, 151. Decussation of the optic nerve, 38. Deep fascia of the arm, 351. of the forearm, 379. Deltoid muscle, 334. insertion of, 335. Diaphragm, 249, 320. aortic opening of, 321. arteries of, 322. central tendon of, 320. crura of, 321. height of arches of, in respira- tion, 322. leaflets of, 321. muscular portion of, 321. nerves of, 322. observations upon contractions of, 273. oesophageal opening of, 321. opening for inferior vena cava, 321. relations of upper surface to contents of thorax, 309. tendinous arches of, 321. Diastole of the heart, 277. Digital extremities or phalanges, 396. Diploe, 3. Diploic structure of the skull bones, 14. veins, 15. Direct sensory tracts, 58. Disk, intervertebral, 241. » Dislocation of elbow, 370. *" of shoulder, 336. Double chin, 191. Duct, cochlear, 75. lymphatic, 227. nasal, 80, 113. of Bartholin, 164. of Rivinus, 164. of Stenson, 131, 149. of Wharton, 165. thoracic, 227, 232, 318. termination of, 318. valves of, 318. Ductus arteriosus, 290, 303, 304. reuniens, 77. venosus, 304. Dura mater, 15. arteries of, 17. lateral sinuses of, 18. nerves of, 19. sinuses of, 18. veins of, 18. E. Ear, external meatus of, 60. region of, 60. Ear-stones, 75. Elbow, dislocations of, 370. fractures in relation to, 371. landmarks of, 367. movements of, 365. passive motion of, after injuries, 365. region of, 362. superficial veins of, 367. Elbow-joint, 363. '^ amputation of, 371. injuries to, 372. resection of, 371. Eminence, auditory, 50, canine, 144. cinereous, 50. frontal, 5, 33. hypothenar, 409. parietal, 6, 33. thenar, 409. Eminentia collateralis, 55. Emissary veins, communications of, 18. from the cochlea, 79, Encephalon, 24. Endocardium, 248. Endolymph, 74. Epicardium, 275. Epicondyle, internal and external, 348. Epicranium, 13. Epiglottis, 178. Epistaxis in relation to the superior longitudinal sinus, 19. Eustachian tube, 67, 173. pharyngeal opening of, 113. valve, 278, 303. External capsule, 54. meatus of ear, 60. Extremity, upper, 223. Eye, 79. accommodation of, for vision, 101. dangerous area of, 99. 424 INDEX. Eyeball, 96. Eyebrow, SO. Eyelashes, 83. Eyelids, 81. F. Face, arteries of, 123. deep structures of, 136. development of, 150. fat in subcutaneous tissue of, 117. landmarks of, 116. lymphatic vessels of, 125. muscles of, 119. region of, 116. sensory nerves of, 125. skin of, 116. Facial artery, 123. markings, 117. nerves, origin of, 41. vein, 125. Fallopius, aqueduct of, 69. Falx cerebelli, 16. cerebri, 16. Fascia, axillary, 338. bicipital, 351, 368. bucco-pharyngeal, 149. deep cervical, 193. development of, 197. external layer of, 194. influence of, against atmos- pheric pressure, 197. internal layer of, 195. reflections of, 194. dentata, 29, 57. oxtra-pleural, 262. laryngeal, 179. masseteric, 123. of the arm, 351. over the anterior surface of the thorax, 353. palmar, 411. parotid, 130. post-pharyngeal, 175. prevertebral, 195. subcutaneous, over the arm, 349. temporal, 14. Fasciculi teretes, 46, 50. Fauces, 170. Fenestra ovalis, 66. rotunda, 66. Fibres, association, 59. of medullary substance of the cerebrum, 58. Fibro-cartiloge, inter-articular, 136. intervertebral, 215. triangular, 397. Fissura palpebrarum, 81. Fissure, anterior median, of ineduUa oblongata, 44, calcarine, 29. central, of Rolando, 30. dentate, 57. Glaserian, 66, 139. hippocampal, 29. in upper lip, 149. interparietal, 29. intra-lobular, of brain, 30. longitudinal, 26, 37. of Rolando, 27. of Santorini, 61. of Sylvius, 27. branches of, 27. parieto-OGcipital, 29. posterior median, of medulla ob- longata, 45. primary, of brain, 27. secondary, of brain, 27. spheno-maxillary, 80. sphenoidal, 79. transverse, of Bichat, 29. Flocculus of the cerebellum, 47. Foetal circulation, 303. heart, 303. Fold or folds : aryteno-epiglottic, 178. axillary, 338. gleno-humeral, 334. glosso-epiglottic, 163. vestigial, 275. Follicles, sebaceous, of nose, 109. Fontanelles, 3. Foramen or foramina : anterior condyloid, 167. caecum of frontal bone, 10, 115. of medulla oblongata, 45. of tongue, 161. dental, 139. ethmoidal, 80. in transverse process of sixth cervical vertebra, 215. infra-orbital, 127, 144. intervertebral, 315. jugular, 203. magnum, 232. mastoid, 6. mental, 139. of Magendie, 21, 50. of Monro, 51. of Scarpa, 147. of Stenson, 147. of Vesalius, 125. optic, 79. ovale, of the heart, 278. of the sphenoid bono, 139. Foramen or foramina : parietal, 6. spinosum, 139. stylo-mastoid, 69. supra-orbital, 5. supra-trochlear, 348. Thebesii, 279. * Forearm, amputation through the middle of, 396. bones of, in relation to surfaces, 376. branches of radial artery in, 389. of ulnar artery in, 391. contour of, 377. cutaneous nerves of, 378. deep fascia of, 379. movements of, in pronation and supination, 376. muscles of, 379. region of, 372. Formatio reticularis, 46. Fornix, 51. anterior pillars of, 52. conjunctivas, 85. crura of, 52. Fossa, antecubital, 352, 367. anterior nasal, 11)7. canine, 144. coronoid, 348. hyaloid, 103. incisive, 144. infra-spinous, of scapula, 233. jugular, 203. lachrymal, 80. nasal, 111. olecranon, 348. ovalis, of the antihelix, 61. of the heart, 278. scaphoidea, 61. spheno-maxillary, 142. supra-spinous, of scapula, 233. Fovea, anterior, 50. centralis of retina, 105. hemi-elliptica, 72. bemisphaerica, 72. posterior, 50. * Fracture or fractures : at base of skull, symptoms of, 7. Barton's, of wrist, 373. Colles's, 395. green-stick, of clavicle, 327. of bones of forearm, 394. of clavicle, 327. of elbow, 370. of humerus, 261. of petrous portion of temporal bone, 78. INDEX. 425 * Fracture or fractures : of ribs, 245. of shoulder, 337. of skuU by contre-coup, 15. Fraena labiorum, 149. Fraenula, 47. Frsenum epiglottidis, 163. linguae, 162. Friction-sound consequent upon in- flammation of the pleura, 261. Frontal artery, 8, 95. eminences, 5. lymphatics, 10. sinuses, 5. veins, 9. Function of the cerebellum, 49. Furrows of the brain, 25. G. Galea capitis, 11. Galen, veins of, 52. Ganglia, intra-cardiac, 287. sympathetic, in the thorax, 319. Ganglion, Arnold's, 204. cardiac, of Wrisberg, 285. ciliary, 94. diaphragmatic, 3^2, Gasserian, 41, 142. in relation to the circumflex nerve of the shoulder, 346. inferior cervical, of the sympa- thetic nerve, 220. jugular, 205. Meckel's, 69, 142. middle cervical, of the sympa- thetic nerve, 219, 233. of Andersoh, 205, 219. otic, 144. petrosal, 205. spheno-palatine, 69, 142. spiral, 78. submaxillary, 169. Superior, of the sympathetic nerve, 219. Ganglionic arteries, 23. Genu of the corpus callosum, 57. Glabella, 5. Gladiolus, or mesosternum, 246. Gland or glands : axillary, in relation to cancer, 251. bronchial, 271, buccal, 149. ceruminous, 64. labial, 149. lachrymal, 83. lymphatic, at the elbow, 369. Gland or glands : lymphatic, of the axilla, 346. mammary, 250. lobes of, 250. milk-ducts of, 250. Meibomian, 83. molar, 149. palatine, 157. , pineal, 51, pulmonary lymphatic, 271. sebaceous, 83. sublingual salivary, 164. submaxillary salivary, 164, 199. sub-sternal, 251. sweat-, of the hand, 411. thymus, 223, 240, 260. tracheal, 237. Glandulse concatenatae, 227. Glaserian fissure, 66. Glosso-pharyngeal nerve, distribu- tion of, 167. origin of, 43. Glottis, 179. respiratory area of, 180. vocal area of, 180. Groove, auriculo-ventricular, 276. bicipital, production of, 361. for the ulnar nerve, 359, 369. interauricular, 276, interventricular, 276. musculo-spiral, 351, primitive dental, 151, Gums, 150, Gyri operti, 32, Gyrus fornicatus, 57, H. Ilaematoblasts, 301. Hemoglobin of the blood, 300, Hairs, auditory, 75, of the scalp, 8. over the back of the hand, 408. Hand, cutaneous nerve-supply of, 417. heel of, 409. hollow of, 409. median portion of, or metacarpus, 396. palm of, 409. region of, 396. surface-markings of, 406. Hard palate, 147. Head, bones of, 2. development of, 1, 3. landmarks of, 1. region of, 1. surface-form of, 1. Heart, 275. 54 Heart, anomalous condition of, 289. anterior surface of, 275, area of greatest dulness, 310. development of, 305, dimensions of, 277, fibrous skeleton of, 284, foetal, 303, location of apex of, 310, lymphatic vessels of, 287. nerves of, 285, position of apex of, 308, of base of, 308, within the thorax, 275. shape of, 275. sounds, 306. propagation of, 307. reduplication of, 307. structure of, 284. within the thorax, examination of, 309. Helicotrema, 73. Helix, 61. fossa of, 61. Hemispheres of cerebellum, 47. of cerebrum, 26. Hernia, diaphragmatic, 322. Herophili, torcular, 18. Hiatus Fallopii, 69. semilunaris, 351, 359, Ilighmore, antrum of, 133, 144, Hippocampus major, 52, 57. minor, 55. Hollow formed by the extensor mus- cles of the thumb, 408. of the armpit, 338. of the hand, 409. Horner's muscle, 85. Horny band of Tarinus, 54. Huguior, canal of, 71. Humerus, anatomical neck of, 332. bicipital groove of, 332. epicondyles of, 348, 365. Hyaloid membrane, 103. Hypoglossal nerve, 167. Impression, subclavian, 255, 325. Incisura, 61. Incus, 67. Infundibula of the longs, 269. Infundibulum at the base of the brain, 39. of the nose, 5, 113. or conus arteriosus, 279, Inion, 6, Insula, 29, Intercarotic body, 203. 426 INDEX. Internal ear, or labyrinth, 60. Intumeacentia gacgliformis, 69. Iris, 99. pigment-cells of, 100. Isthmus faucium, 170. Iter a tertio ad quartum ventricu- lum, 50. anterius, 66. posterius, 66. Jadelot's lines, 117. Jaw, ramus of, 139. Joint or joints: between the metacarpal bone of the thumb and the trapezium, 401. between the pisiform and cunei- form bones, 398. carpal and metacarpal, 401. claviculo-acromial, 324. coato- vertebral, 241. elbow-, 363. enarthrodial, 332. ginglymus, 363. inferior radio-ulnar, 375. intercarpal, 397. interphalangeal, 402. knuckle, 404. metacarpal, 402. metacarpo-phalangcal, 402, 410. radio-carpal, or wrist-, 397. shoulder-, 332. sterno-clavicular, 324. superior radio-ulnar, 364. temporo-maxillary, 136. movements of, 137. Labia cerebri, 58. Labium tympanicum, 74. vestibulare, 74. Labyrinth, or internal ear, 60, 72. membranous, 74. vestibule of, 72. Lachrymal canal, 113. fossa, 80. nerve, 94. sac, 86, 113. Lacus lachrymalis, 85. Lambda, 2, 33. Lamina, anterior limiting, or elastic, of Bowman, 87. cinerea, 37. cribrosa, 78, 96. fusca, 97. Lamina ossea, 73. posterior elastic, of Descemet, 87. reticularis, 77. spiralis, 73. vitrea, 99. Larynx, accessory cartilages of fe- male, 179. arteries of, 184. cartilages of, 176, 177, 178. cavity of, 175. comparison of, in the child and in the adult, 189. extrinsic muscles of, 183. framework of, 176. intrinsic muscles of, 180. lodgement of foreign bodies in, 178. lymphatic vessels of, 186. mobility of, 186. nerves of, 185. region of, 175. sensibility of, 185. veins of, 184. ventricles of, 179, Lateral tracts, 45. ventricles, 53. cornua of, 53. digital cavities of, 55. * operation for tapping, 60. position of, 60. Lens, capsule of, 102. crystalline, 102. function of, 103. nucleus of, 103. suspensory ligament of, 102. Lenticular nucleus, 54. Leucocytes, 301. Ligament or ligaments: anterior and posterior, of elbow- joint, 364. and posterior radio-ulnar, 375. annular, 413. chondro-sternal, 246. common spinal, 217. middle, and posterior costal transverse, 242. occipito-atlantic, 217. of wrist, 398. auricular, 61, capsular, of cervical vertebrae, 217. of elbow-joint, 364. of inferior radio-ulnar joint, 375. of metacarpo-phalangeal joints, 402. Ligament or ligaments : capsular, of shoulder, 332. of temporo-maxillary joint, 37. of wrist, 397. chondro-xiphoid, 247. ciliary, 99. conoid, 325. coraco-acromial, 330. coraco-clavicular, 327. coraco -humeral, 332. eosto-clavicular, or rhomboid, 324. costo-coracoid, 255. external and internal, of tem- poro-maxillary joint, 137. external lateral, of wrist, 398. glenoid, of metacarpal phalan- ges, 402. of shoulder, 331. glosso-epiglottic, 178. hyo-epiglottic, 178. inferior thyro-arytenoid, or true vocal cord, 179. interarticular fibro-cartilagi- nous, of costo-vertebral joints, 241. interchondral, 246. interclavicular, 324. interlaminar, 213. internal lateral, of wrist, 398, interosseous, 375. interphalangeal, 402. interspinous, 213. intrinsic, of auricular cartilages, 63. lateral metacarpo-phalangeal, 385. of elbow-joint, 364, of metacarpo-phalangeal joints, 402. metacarpal interosseous, 401. oblique, 375. occipito - odontoid, or check, 217. of Zinn, 89. orbicular, 363. palmar and dorsal intercarpal, 399. palpebral, 82. posterior accessory, of costo- vertebral joints, 241. annular, 407. atl an to -axial, 213. common spinal, 217. occipito-atlantic, 213, 217, 232. of wrist, 398. INDEX. 427 Ligament or ligaments : posterior tliyro-byoid, 176, pterygo-maxillary, 122. Etellate, 241. sterno-olayicular, 324. sterno-pericardial, 259. stylo-hyoid, 165, 172. stylo-maxillary, 131, 165, 195. superficial transverse, of the webs of the fingers, 412. superior thyro-arytenoid, or false vocal cord, 179. supra-condyloid, 379. suspensory, of axilla, 338. of axis vertebra, 217. of tbe lens, 103. thyro-epiglottic, 178. transverse, of axis vertebra, 217. trapezoid, 325. Ligamenta lata pulmonalia, 267. subflava, 213. suspensoria of the breasts, 250, Ligamentous action of tendons of tbe muscles about the shoulder- joint, 333. function of long tendon of biceps muscle, 352. Ligamcntum arcuatum externum of the diaphragm, 321. internum of the diaphragm, 321. of the wrist, 398. arteriosum, 305, latum axiale, 217, nuchse, 209, pectinatum iridis, 97, 100, pulmonale, 261. radiatum, 399. rectum, 398. spirale, 74. * Ligation of brachial artery, 356. of carotid artery, 226. of lingual artery, 166. of radial artery, 391, of subclavian artery, 231, of ulnar artery, 393. Line, labial, 117, nasal, 117. oculo-zygomatio, 117, of axillary artery, 343. of brachial artery, 356. of radial artery, 391, of ulnar artery, 393, Linea alba cervicalis, 236, cephalica, 410. hepatica, 410. mensalis, 410. vitalia, 409. Lines of Jadelot, 117. transverse, over wrist, 406. Lingula, 47. Lip, hare-, 156. Lips, nasvi of, 14.9 sensory papilliB of, 148. upper and lower, 148. vermilion color of, 148, Liquor Cotunnii, 74, Morgagni, 103, sanguinis, 291. Scarpse, 74. Lobe or lobes : anterior, or frontal, of the brain, 26, 30. central, of tbe brain, 26, 32. middle, or temporo-sphenoidal, of the brain, 26. of the cerebellum, 47, of the parotid gland, 134, opercular, 31, area of, 35. parietal, of the brain, 26, 30. posterior, or occipital, of the brain, 26, 31. temporal, of the brain, 32. Lobule or lobules: crescentic, 47. cuneiform, 47. cuneus, 31. digastric, 47, infracentral, 31, marginal, 47, of the cerebellum, 47, of the ear, 61, of the parotid gland, 131. paracentral, 31. pulmonary, 269. quadrate, or prascuneus, 31. quadrilateral, of the cerebellum, 47, tonsil, of the cerebellum, 47. Lobulus gracilis, 47. Locus coeruleus, 50. niger, 39. Lower level of the cerebrum, 33, Lower, tubercle of, 279, Lungs, 263, apex and base of, 263. degree of their expansion, 264. elastic tissue of, 269. great fissure of, 267. height of, upon right and left side at root of neck, 262. limitations of their expansion, 265. lobes of, 267. lobules of, 269. Lungs, mode of detection of degree of their expansion, 312. observations on the approxima- tion of their anterior edges, 264. oedema of, 270. previous to birth, 305. roots of, 267. spongy texture of, in medico- legal investigations, 270. structure of, 269, Lympb-patbs, 301, Lymph-space, great cerebral, 23. Lymphatic duct, 227. gland or glands ; above tbe internal epicon- dyle, 369. at the back of the pharynx, 175. deep cervical, 227. extra-parotid, 133. in relation to the posterior border of tbe sterno-mas- toid muscle, 206. in the submaxillary tri- angle, 199. intra-parotid, 133. of the axilla, 346. of the lung, 271. posterior mediastinal, 313. pulmonary, 271, sub-sternal, 259. superficial, of the neck, 193, jugular trunk, 227, vessels, frontal, 10, in relation to tbe larger arteries and veins, 299. occipital, 10. of the breast, 251. of the face, 125. of the fingers and hands, 417. of the heart, 287. of the larynx, 186. of the nose. 111. of the pharynx, 175, of the scalp, 10, of the tongue, 170, of the tonsil, 171. parietal, 10. pulmonary, 271. Lymphoid tissue of the tongue, 163. Lyra, 53. M. Macula cribrosa, 72. lutea, 105, Magendie, foramen of, 50, 428 INDEX. Malleus, 67. Mammary glands, 250. development of, in the male, 251. supernumerary, in the female, 251. Manubrium, or presternum, 246. Margo acutus, 277. obtusus, 277, Mastoid antrum, 6. cells, 6. foramen, 6. processes, 6. vein, 9. Matrix of the nails, 417. Meatus, internal auditory, 78. Meatuses, nasal. 111. Meckel's ganglion, 69, 142, Mediastinum, anterior, 197, 259. posterior, 263, 312. superior, 236, 260, 318. Medulla oblongata, 44. Medullary capillaries, 24. velum, posterior, 49. superior, 49. Membrana basilaris, 73. limitans, external and internal, of the retina, 106, pupillaris, 101. sacciformis, 375. tectoria, 74. tympani, 65, secundaria, 67. Membrane, costo-coracoid, 255, 338. hyaloid, 108, interosseous, 375. mucous, of the nose, 115. of Reissner, 74. pituitary, 113. supra-choroid, 97. synovial, of elbow-joint, 365. of shoulder-joint, 334. of wrist-joint, 397. thyro-hyoid, 176. Meningeal arteries, 17. Metacarpal bones, 399, Metacarpus, 396. Middle ear, or tympanum, 60. thyroid veins, 203. Mitral regurgitation, 308. valve, 308, Moderator, 281. Modiolus, 73, Monro, foramen of, 51, Monticulus cerebelli, 47. Morgagni, sinus of, 172. Motor area of the brain, 35, of the brain-surface, 27. Motor cells, position of, in the gray matter of the brain, 35. nerves of the face, 128. oculi nerve, 91. Mouth, angles or corners of, 148. cavity of, 156. formation of, in the foetus, 156. region of, 148. roof of, 156. vestibule of, 149. MuscjB volitanfces, 105. Muscle or muscles : abductor minimi digiti, 405. pollicis, 404, anconeus, 387. antitragicus, 63. arytaenoideus, 178. aryteno- epiglottic, 183. arytenoid, 183, auricular, 61. azygos, 158. biceps, 351. function of, 352, ligamentous function of long tendon of, 352. vessels and nerves in rela- tion to tendon of, 368. biventer cervicis, 209. brachialis anticus, 353. buccinator, 121. cervicalis ascendens, 212. ciliary, 99. circular ciliary, 99. complexus, 209. compressor naris, 110. sacculi, 183. sacouli laryngis, 179. coraco-brachialis, 352. corrugator, 80. superciliary, 82. deltoid, 334. insertion of, 335. depressor anguli oris, 120. depressores alarum nasi, 110. labii inferioris, 121. digastric, 199. action of, 200, dilatator pupillse, 100. dilatators of the nose, 110. extensor carpi radialis brevior, 385. carpi radialis longior, 384, carpi ulnaris, 386. communis digitorum, 385. indicis, 388. minimi digiti, 386, 388. of the thumb, 387. ossis metacarpi pollicis, 383. Muscle or muscles : extensor primi internodii polli- cis, 388. external Intercostal, 256. rectus, 89. extrinsic, of the larynx, 183. flexor brevis minimi digiti, 405, brevis pollicis, 404. carpi radialis, 380. carpi ulnaris, 380. longus pollicis, 383. profundus digitorum, 383. sublimis digitorum, 381. genio-hyo-glossi, 164. genio-hyoid, 165. helicis major, 63. minor, 63. hyo-glossi, 164. inferior constrictor, 172. oblique, 91. rectus, 89. infra-spinatus, 328. internal intercostal, 256. rectus, 89. interosseous, palmar and dorsal, 402. interspinales, 212. intertransversales, 212, 219. intrinsic, of the larynx, 180. lateral crico-arytenoid, 183. latissimus dorsi, 329. laughing, of Santorini, 120. levator anguli oris, 120. scapulge, 208, corporis thyroidei, 234, levatores and tensores palati, * division of, 159. labii superioris et alarum nasi, 120. labii superioris proprius, 120. menti, 121. palati, 158. *division of, 158. palpebrarum, 82. uvulae, 158. linguales, 163. long tendon of biceps, 333, longus colli, 218. lumbricales, 403. massetcr, 122. middle constrictor, 172. multifidus spinas, 212. mylo-hyoid, 163, 165. oblique auricular, 63. obliquus capitis inferior, 212. occipito-frontalis, 11. of ball of little finger, 405. INDEX. 429 Muscle or muscles : of ball of thumb, 404. of crioo-thyroid, 180. of expression, 119. of face, 119. of forearm, 379. of nose, 109. of orbit, action of, 92. . paralysis of, 92. omo-hyoid, 195, 200. opponens minimi digitis, 406. poUicis, 404. orbicularis, 81. oris, 119. palpebrarum, 82. palato-glossi, 159, 164. palato-pharyngei, 159. palmaris brevis, 411. longus, 380. pectoral accessory, 255. pectoralis major, 253. clavicular portion of, 253. cleft between its two portions, 254. sternal portion of, 254. minor, 255. platysma myoides, 191. posterior crico-arytenoid, 181. pronator quadratus, 384. radii teres, 379. teres, 393. pterygoid, external, 138. internal, 138. pyramidales nasi, 109. rectus capitis anticus major, 218. capitis anticus minor, 218. capitis lateralis, 218. capitis posticus major, 212. capitis posticus minor, 212. rhomboideus, major and minor, 329. risorius, 121, 181, 191. salpingo-pharyngeus, 159. scalenus anticus, 220. guide for subclavian artery, 229. medius, 220. posticus, 220. serratus magnus, 331. sphincter colli, 191. pupillae, 100. spinalis colli, 212. splenius, 207. stapedius, 68. sterno-oleido-mastoid, 197. sterno-hyoid, 235. Eterno-mastoid, action of, 198. Muscle or muscles : sterno-thyroid, 235. stylo-glossi, 164. stylo-hyoid, 199. stylo-pharyngeus, 172. sub-anconeus, 354. subclavian, 256. sub-scapularis, 330. superior constrictor, 172. oblique, 91. rectus, 89. supinator radii brevis, 387. radii longus, 384. supra-hyoid, 200. Eupra-spinatus, 328. temporal, 14, 136. tensor tarsi, 85. tympani, 68. tensores or circumflexi palati, 158. palati, division of, 159. teres major, 328. minor, 328. thyro-arytenoid, 181. thyro-epiglottic, 181. thyro-hyoid, 236, trachelo-mastoid, 209. tragicus, 63. transversalis colli, 209. transverse auricular, 63. trapezius, action of, 209. cervical portion of, 208. triangularis sterni, 257. triceps extensor cubiti, 353. trochlearis, 91. zygomaticus major, 120. minor, 120. Muscular fibres of the heart, infer- ences drawn as to their function, 285. superficial and deep layers of, 284. Musculi papillares, 281. peotinati, 279, 283. Musculo-spiral groove, 351. N. Nail-bed, 419. Nails, 417. growth of, 417. lunula of, 417. matrix of, 417. peculiarities of, 417. root of, 417. Nares, anterior and posterior. 111, 114. Nasal artery, 95. Nasal bones, 107. cavities, arteries of, 115. veins of, 115. duct, 80, 113. fossae or cavities. 111. dimensions of, 113. walls of. 111. meatuses, 111. nerve, 93. veins, 110. Nasion, 5, 107. Nates, 50. Neck, anterior triangle of, 198. deep fascia of, 193. development of, 190. landmarks of, 187, 189. posterior triangle of, 198. region of, 187. skeleton of, 187. skin over front of, 191. over nape of, 191. structures collected at root of, 221. superficial glands of, 193. Nerve or nerves : abducent, 41, 92. acromial, 193. ansa hypoglossi, 205. anterior fora&ch of internal cu- taneous, 378. branch of museulo-cuta- neous, 378. division of external cuta- neous of musculo-spiral, 378. interosseous, 393. palatine, 115. articular, to elbow-joint, 393. auditory, 41, 77. auricular, Arnold's, 204. branch of pneumogastric, 11, auricularis magnus, 192. anriculo-temporal, 11, 128, 143. axillary or brachial plexus, 344. brachial, plexus of, in relation to subclavian artery and veins, 229, branches of fifth cranial, 41. buccal, motor, 128. sensory, 128. cardiac, 288. cells, 25. cervical plexus, 193. spinal, 214. ganglia of, 214. roots of, 214. cervico-facial, 129. chorda tympani, 69, 143. 430 INDEX. Nerve or nerves : chorda tympani, supposed func- tion of, 71. circumflex, 334, 346. clavicular, 193. cochlear, 78. communicantes, 207. communicating filaments of, in the forearm, 394. course and relations of left pneu- mogastric, 318. of right pneumogastric, 317. cutaneous palmar branch, 393. deep cervical plexus, 206. palmar branch of ulnar, 415. descendens hypoglossi, 167, 205. digital, 416. distribution of various digital cutaneous, 417. dorsal branch of ulnar, 378. eighth cranial, 41. eleventh cranial, 43. external anterior thoracic, 346. cutaneous, 349. of musculo-spiral, 378. laryngeal, 185. palmar of median, 416. superficial petrosal, 69. facial, 41, 69, 129. communications of, 71. fibres, 25. fifth cranial, 40. first cranial, 38. spinal, 213. fourth cranial, 40. from otic ganglion, 144. frontal, 93. glosso-pharyngeal, 43, 134, 169, 205. ganglia of, 205. great auricular, 63, 129. occipital, 11, 193,213,214. splanchnic, 320. groove for ulnar, 348. hypoglossal, 44, 134, 167, 265. incisor, 143. inferior cardiac, 220. dental, 143. laryngeal, explanation of its recurrent course, 186. maxillary, 41, 142. or recurrent laryngeal, 185. infra-maxillary, 130. infra-orbital, 145. infra-trochlear, 93. intercosto-humeral, 339, 360. internal anterior thoracic, 346. Nerve or nerves : internal cutaneous, 359. laryngeal, 185. palmar of median, 416. interosseous, 392. labial, 127. lachrymal, 94. lesser internal cutaneous, of Wrisberg, 360. splanchnic, 320. lingual, 143. * division of, 169. * position for division of, in cancer of the tongue, 144. long ciliary, 93. sub-scapular, 346. median, 351, 356, 357. at the elbow, 368. in relation to the anterior annular ligament, 416. in the forearm, 393. mental, 128, 143. middle cardiac, 219. motor, buccal, 130. malar, 129. oculi, 91. of face, 128. of masseter muscle, 123. to pterygoid muscles, 138. muscular branches of median in the forearm, 393. of brachial plexus, 345. musculo-cutaneous, 352, 357. musculo-spiral, 354, 360. in the forearm, 394. liability of, to injury in con- tusion or fractures, 361. mylo-hyoid, 143, 199. nasal, 93. from the spheno-palatine ganglia, 115. of infra-orbital, 127. of ophthalmic, 115. aso-lobular, 110. naso-palatine, 115. ninth cranial, 43. oculo-motor, 39. oesophageal, 317. of Lancisi, 57. of the axillary folds, 339. of the breast, 251. of the cornea, 88. of the dura mater, 19. of the heart, 285. of the iris, 101. of the larynx, 185. of the nose, 110. of the pericardium, 274. Nerve or nerves : of the pinna, 63. of the scalp, 10. of Wrisberg, 71. olfactory, 38, 116. ophthalmic, 41. paralysis of, 94. optic, 38, 95. passage of, through the sclerotic coat, 96. orbital branch of superior max- illary, 11. palatine, 161. palpebral, 127. pharyngeal, 204. plexus of, 175, 204. phrenic, 221, 268, 322, 345. plexus, posterior cervical, 214. pneumogastrio, 43, 134, 204, 222, 225. branches of, 204. communicating branches of, with the brachial plexus, 205. ganglion of the root, 204. of the trunk, 204. pulmonary plexuses of. 267. within the thorax, 317. posterior auricular branch of facial, 11, 63. branch of internal cuta- neous, 378. branch of muscular cuta- neous, 378. dental, 145. division of external cuta- neous of musculo-spiral, 378. external cutaneous, 360. internal cutaneous, 360. interosseous, 394. lateral cutaneous, 339. thoracic or external re- spiratory of Bell, 345. ulnar cutaneous, 394. pulmonary, 271. radial, 391, 394, 408. where it becomes superficial in the forearm, 378. recurrent laryngeal, 226, 268. second cranial, 38. sensory, of nose, 115. of orbit, 93. seventh cranial, 41. sixth cranial, 41. small occipital, 11, 193. petrosal, 69, 144. smaller splanchnic, 320. INDEX. 431 Nerve or nerves : spinal accessory, 44, 134, 198, 205. accessory portion of, 206. spinal portion of, 206. splanchnic, 319. splenic, 207. sternal, 193. sterno-mastoid, 207. subcutaneus malse, 127. Bub-occipital, 214. posterior division of, 213. sub-scapular, 346. superficial cervical, 130, 192. over parotid region, 133. palmar, 416. superior cardiac, 219. laryngeal, 185, 204. maxillary, 127, 142. supra-clavicular, 229. supra-maxillary, 130. supra- orbital, 10, 94. supra-scapular, 330, 345. supra-trocblear, 10, 93, sympathetic, cervical portion of, 219. in the neck, 195. temporo-facial, 129. temporo-malar, 127. tenth cranial, 43. third cranial, 39. to tensor palatine muscle, 161, triangles of, 198. trifacial, 41. trochlear, 40, 92. twelfth cranial, 44. tympanic branch of the facial, 69. ulnar, 359, 392, 393, 409. at elbow, 369. in relation to the anterior annular ligament, 415. vagus, 43. vaso-constrictor, 300. vaso-dilator, 300. vaso-motor, 299. about facial artery, 124. of iris, 102, vestibular, 78. Vidian, 69, 141, 142. Nipple, relative position of, 250. Nipple-line unreliable, 311. Nipples, 250. Nodi valvulao mitralis, 283. Nodulus of the cerebellum, 47, Nose, arteries of, 110, cartilaginous framework of, 108, Nose, lobule of, 110, lymphatic vessels of. 111, nerves of, 110. region of, 107. skeleton of, 107. Nostrils, exploration of, 114. Notch, great, of scapula, 331. of Rivinus, 65. sigmoid, 136. supra-orbital, 5. supra-scapular, 233, 330. supra-sternal, 246. thyroid, 176. Nuclei laterales, 46. Nucleus amygdalse, 54. caudate, 54. gracilis, 46. lenticular, 54. of fibro-cartilage, 215. of lens, 103. olivary, 45. O. Obelion, 6, Obex, 50. Oblongata, medulla, 44. Occipital artery, 8. lymphatics, 10. veins, 9. Ooulo-motor nerves, origin of, 39. Odontoblasts, 153. * CBsophagotomy, operation of, 315. (Esophagus, 315. arteries of, 317. at the root of the neck, 268. coats of, 317. constrictions of, 315. diameter of, 316. lateral curves of, 316. relations of, to the vertebral col- umn, 315. Olecranon process, 362. Olfactory bulbs, 38, cells, 114. Olivary bodies, 45. nucleus, 45. Opening, auriculo-ventricular, 278. left auriculo-ventricular, 283. right auriculo-ventricular, 279. * Operation of trephining for tapping lateral ventricles, 60. Opercular lobe, area of, 35. Operculum, 29. Ophryon, 5, 35. Ophthalmic artery, 94. ganglion, 94. veins, 95, Optic commissure, 38. Optic foramina, 38, lobes, 50. nerve, 95. nerves, origin of, 38. papillae, 105. thalami, 52. function of, 59. tracts, 38, Ora serrata, 105. Orbit, sensory nerves of, 93. Orbital region, 79. Orbits, bones forming, 80. walls of, 79. Organ of Corti, 74. Os cordis, 284. Ossicles, 65, 67. Ossification of the bone of the arm, 361. of the bones of the forearm, 396. of the bones of the hand, 418. of the bones of the wrist, 418. Otic ganglion, 144. Otoliths, 75. Pacchionian bodies, 16. depressions, 15. Pacinian corpuscles, 417. Palate, arteries of, 159. cleft, in association with hare- lip, 148. cleft of, 156. closure of, 156. hard, 147, 156. muco-periosteal covering of, 157. pillars of, anterior and posterior, 157, raphe of, 157, soft, 157. Palm of the hand, 409. subcutaneous tissue of, 411. Palmar arch, deep arterial, 415. posterior, 392. superficial arterial, 414, fascia, 411, development of, 412. expansions of, 412. Papilla spiralis acoustica, 77, Papillae circumvallat^, 161, filiform, 162. fungiformes, 162. of the eyelids, 85. of the hand, 411. sensitive, of the nipple, 250, sensory, of the lips, 148. Parietal lymphatics, 10. 432 INDEX. Parotid fascia, 130. gland, deep surface of, 134. dissection of, 135. extirpation of, 135. lobes of, 134. region of, 130. relations of, 131. Pars ciliaris, 105. intermedia of Wrisberg, 41, Passage, cervico-axillary, 339. Peduncles of the cerebellum, 49. of the pineal gland, 51. Pericardium, 271. attachment to the diaphragm, 273. invagination of the serous layer over the vessels at the root of the heart, 274. layers of, 274. nutrient arteries of, 274. serous fluid within, 274. Perichondrium over the nasal carti- lages, 109. Pericranium, 13. Perilymph, 74. Pes accessorius, 55. anserinu9, 129, 135. cervicis, 193. hippocampi, 52, 57. Petit, canal of, 103. Phalanges, 396, 401. proximal, medial, and distal, 401. ungual, 401. Pharyngeal recess, 173. tonsils, 173. Pharynx, 171. arteries of, 175. naso-, 173. oro-, 173. Phrenic arteries, 322. Pia mater, 21. Pineal gland, 51. Pinna, 60. arteries of, 63. nerves of, 63. veins of, 63. Piso-cuneiform joint, 398. Pituitary body, 39. Plasma, 301. Pleura, cavity of, 261. * operation of tapping, 261. costalis, 261. parietal layer of, 261. pulmonis, 261. visceral layer of, 261. Pleurse, 260. height upon right and left side at the root of the neck, 262. Pleurae, limitations of their reflec- tions, 262. Pleural sinuses, 252. Plexus, diaphragmatic, 322. cesophageal, 318. pterygoid, 141. radial dorsal of hand, 408. supra- renal, 322. tonsillar, 171. ulnar dorsal of hand, 408. Plexuses, cardiac, 285. choroid, 23, 52. coronary, 287. pulmonary, 285, 318. Plica interdigitalis, 411. semilunaris, 85. Pneumogastric nerve, auricular branch of, 11. in the neck, 204. origin of, 43. nerves within the thorax, 317. Pomum Adami, 176, 189. Pons Varolii, 46. Portio dura, 41. mollis, 42. Porus opticus, 96, 105. Posterior auricular artery, 8, veins, 9. nares, 114. Process, acromion, 330. coraooid, 330. coronoid, of lower jaw, 136, 150. of ulna, 362. ensiform, or metasternum, 246. external angular, of orbits, 5, 80. hamular, of sphenoid bones, 158. malar, 145. nasal, 145. olecranon, 362. in relation to epicondyle of humerus, 367. olivary, of sphenoid bone, 38. palate, 145, 147. styloid, 169. supra-condyloid, 351. Processes, alveolar, 145. ciliary, 99. mastoid, 6. nasal, of superior maxillary bones, 108. transverse, of dorsal vertebrae, 242. ungual, 402. Processus cochleariformis, 67. e cerebello ad testes, 49. unciformis, of brain, 32. Promontory, 66. Protuberance, external occipital, 6. Pterion, 2, 33. Pulmonary capillaries, 270. emphysema, 270. veins, 270. Pulps of the fingers, 411. Pulse, arterial, 307. respiratory, 307. Pulse-area, 391. Pulvinar of the brain, 52. of the larynx, 179. Puncta lachrymalia, 82. of the eyelids, 85. vasculosa, 58. Punctum caecum, 105. Pupil, 100. muscular fibres of, 100. size of, 100, Pyramid, anterior, of the tympanum, 67, Pyramidal tract, 58, Pyramids, anterior, of the medulla, 45. posterior, of the medulla, 45. R. Radial artery, 389. branches of, in the forearm, 389. ligation of, 391. line of reference of, 391. venae comites of, 389. Radiatio thalami, 59. Radius, anterior crest of, 373, articular surface of lower end of, 393. oarpal articular surface of, 373. fracture of lower end of, 395. head of, 363. interosseous edge of, 373. lower end of, cancellous struc- ture of, 395. extremity of, 373. neck of, 363. ossification of, 396. shaft of, 373, styloid process of, 373, tubercle of, 363, ulnar depression of, 373. Raph6 of corpus callosum, 57. posterior, of pharynx, 172. Recess, pharyngeal, 173. Region of the arm, 348. of the axilla, 337. of the ear, 60. of the elbow, 362. of the face, 116. INDEX. 433 Begion of the forearm, 372. of the hand, 396. of the head, 1, of the larynx, 175. of the mouth, 148. of the neck, 187. deep fascia of, 193. of the nose and the nasal cavi- ties, 107. of the orbit and the eye, 79. of the parotid gland, 130. of the shoulder, 323. of the thorax, 240. of the wrist, 396. pterygo-maxillary, 136. superior maxillary, 144. Reil, island of, 32. Keissner, membrane of, 74. Restiform bodies, 45. Kete acromiale, 341. carpi, 415. anterior and posterior, 389, 392. mirabile, 299. neural, anterior and poste- rior, 315. nasi, 115. olecrani, 355, 370, 392. Retina, 105. central artery of, and vein, 96. ganglionic cells of, 106. hyaloid surface of, 105. layers of, 106. rods and cones of, 106. Rib, angle of, 242. anomalous eighth true, 241, body or shaft of, 242. eleventh and twelfth, 245. first, 243. neck of, 242. occasional rudimental thirteenth, 245. second, 43. spiral shape of, 243. tenth, 243. tuberosity of, 242. Ribs, 240. false or asternal, 241. floating, 241. fractures of, 245. mode of counting, 310. obliquity of, 240, 248. relation in respiration, 309. true or sternal, 241. vertebral extremities of, 241. Rictus oculi, 81. Ridge between the manubrium and gladiolus of the sternum, 245, 310. Ridges, deltoid, 335. superciliary, 5. supra-condyloid, 348. temporal, 5. Rima glottidis, 180. Rivinus, ducts of, 164. notch of, 65. Rolando, fissure of, 27. Rostrum of corpus callosum, 57. S. Sac, lachrymal, 86. Saccule, 75. Sacculus laryngis of Morgagni, 179. Saliva, 131. Santorini, cartilages of, 178. Scala media, 73. tympani, 73. vestibuli, 73. Scalp, 7. aponeurosis of, 13. arteries of, 8. cutaneous muscle of, 11. lymphatic vessels of, 10. nerves of, 10. veins of, 9. Scalp-hairs, 8. Scapula, 328. borders of, 328. bursae in connection with, 329, glenoid cavity over, 331. head of, 331. inferior angle of, 329. neck of, 331. proper situation of, in relation to the skeleton, 328. * removal of, 342. spine of, 328. sub-scapular fossa or venter, 330. superior and inferior spinous fossae of, 328. Scarpa, foramen of, 147. Schneiderian membrane, 113. Sclerotic coat, 88. Sella turcica, 39. Semilunar fold of the bicipital fascia, 352. Semilunaris, hiatus, 359. Sensitive area of the finger-tips, 417. Sensorial area of the brain, 36, Sensory nerves of the face, 125. Septum lucidum, 63. Serum, 301. Sesamoid bones at the metacarpo- phalangeal joint of the thumb, 402. Shaft, humero-ulnar, 376. 55 Sheath, sub-sternal tubular, 259. Sheaths, tubular, of the pericardium, 274. Shoulder, * dislocations of, 336. * fractures of, 337. girdle, 323. region of, 323. Shoulder-joint, 332. * amputation of, 337, 344. arteries of, 334. bursae connected with, 334. motions of, 334. nerves of, 334. Sigmoid cavity, greater, 362. lesser, 363. Sinus circularis iridis, 96. coronary, 277. entrance of, 279. great oblique, of the pericardium, 274. jugular, 203. maximus, 288. of Morgagni, 172. of Valsalva, 277, 284, pulmonary, of Valsalva, 282. superior longitudinal, 18. transverse, of the pericardium, 274. venosus, 278. Sinuses, cavernous, 19, 125. frontal, 5. lateral, of the dura mater, 18. maxillary, 144. of the dura mater, 18, 296. petrosal, 18. pleural, 262. Skin covering the auricle, 61. of the axilla,' 338. of the eyelids, 81. over the anterior surface of the thorax, 249. over the arm, 349. over the back of the band, 408, over the elbow, 367. over the forearm, 377. over the neck, 190. over the nose, 109. over the shoulder, 323. over the temporal region, 14. over the wrist, 406. Skull-cap, inequality of its thick- ness, 14. Space, crico-thyroid, in children, 184. interosseous, 376. importance of preservation of, in the treatment of fractures of the forearm, 376. 434 INDEX. Space, interpleural, 263. occupied by parotid gland, 131. perineural, of eyeball, 91. sub-dural, 21. Spaces, anterior perforated, 22, 38, intercostal, 247, 313. of Fontana, 97, 102. posterior perforated, 22, 39. sub-aracbnoidean, 44. Speculum rhomboideum, 208. Speech-centre, 30. Spinal accessory nerve, origin of, 43. column, weakest point of, 218. Spine, cervical curve of, 218. curvature of cervical portion of, 215. Splenium of corpus callosum, 57. Spot for reflex contraction of masseter muscle, 123. Stapes, 67. Stenson, duct of, 131. opening of, 149. foramen of, 147. Stepbanion, 6. superior, 35. Stcrno-mastoid muscle, 206. Sternum, 246. differences in tbe male and tbe female, 247. inclination of middle line of, 247. Strise acousticse, 50. lateral, 67. longitudinal, 57. transverse, of fourth ventricle of the brain, 50. vascularis, 74. Subclavian artery, 211. Subcutaneous tissue of scalp, 7. Sucking cushions, 117. Supra-orbital artery, 8. Surface-markings of the wrist and hands, 406. Suture, coronal, 2. frontal, 2. interparietal, or sagittal, 2. lambdoid, 2. Sutures, 2. closure of, 3. dentate, 2. squamous, 2. Sweat-glands of the a.'iilla, 338. Sylvius, aqueduct of, 50. fissure of, 27. Sympathetic nerve in the neck, 219. in the thorax, 319, plexuses at base of brain, 24. Synovial membrane at elbow-joint, 365, between the metacarpal bone of the thumb and the trapezium, 399, of the piso-cuneiform joint, 398, of tbe shoulder-joint, 334. of the wrist-joint, 397. membranes in relation to the extensor tendons on the back of the hand, 408. sacs in relation to the anterior annular ligament, 413. sheaths in relation to the ten- dons of the fingers, 413. sheaths of the fingers in relation to felon, or whitlow, 413. Systole of the heart, 277. T. Tabatiere anatomique, 388, Table, vitreous, 15. Tables of the cranial bones, 3. Taenia hippocampi, 53, 57. semicircularis, 53. Tapetum, 105. nigrum, 106. Tarinus, horny band of, 54. Tartar, 150. Taste-buds, 162. Tears, 83. Teeth, 151. bicuspids or premolars, 153. canines, 153. development of, 151. of the permanent, 152. function of, 153. germs of the temporary, 151. incisors, 153. molars, 153, peculiarities of, 165. periods of eruption, 152, permanent, 151, wisdom, 162, Tegmentum, 39, Temporal artery, 8, anterior branch of, 8. bones, 7. fascia, 14. attachment of, 6. muscle, 14. attachment of, 6. region, 14, veins, 9. Tendo oculi, 82. Tenon, capsule of, 89, 93, Tentorium, Ifi, Testes, 50, Thalamo-lenticular limb, 55. Theca vertebralis, 214, Thenar eminence, 409. Thoracic duet, 227, 318, Thorax, apertures of, 248. base of, 249, landmarks of, 240, percussion of, 310, region of, 240. skeleton of, 240, 247. summit of, 249. surfaces of, 248. variability in form of, at difl'er- ent periods of life, 248, variation of shape, 309, Thumb, ball of, 404, extensor muscles of, 387, metacarpal bone of, 401, movements of, 404, Thymus gland, 260. lymph-follicles of, 260, probable function of, 200, Thyroid body, 233, arteries of, 235, colloid substance of, 234, isthmus of, 233. lateral lobes of, 233. pyramidal or middle lobe of, 234. size of, 234. supposed function of, 234, veins of, 235. Tongue, 161, dorsum of, 161, furring of, 161. hemorrhage in excision of, 166. intrinsic muscles of, 163, lymphatic vessels of, 170, lymphoid tissue of, 163. median septum of, 163, 166i root of, 161, source of its gustatory fnnetion, 167, tip of, 161, Tongue-tie, relief of, 162. Tonsils, 170, nerves of, 171, pharyngeal, 173, relations of, 170, vascularity of, 171. Tooth, body of, 153, cement of, 153. crown of, 153. dentine, 153. enamel, 153. neck of, 153. pulp of, 153. INDEX. 435 Topographical relation of the corpora striata to the external surfiice of the head, 59. survey of the chest, 308. Topography, oranio-cerebral, 32. Torcular Herophili, 18. Traehea, 235, 236. arteries of, 237. at the root of the neck, 263. cartilaginous rings of, 236, 237. length of, and dimensions, 236. mobility of, 237. * Tracheotomy, operation of, 237- 239. Tragus, 61. * Trephining, operation of, in relation to the fissures of the brain, 37. Triangle, inferior carotid, 201. occipital, 206. submaxillary, or digastric, 199. sub-occipital, 213. sub-scapular, 342. superior carotid, 201. supra-clavicular, or subclavian, 207. Triangles of the neck, 198. Triangular fibro-cartilage, 397. Tricuspid valve, 307. Trifacial nerves, origin of, 40. Trochlea, 91. Trochlear nerves, origin of, 40. Tuber cinereum, 38. Tubercle, bicipital, 352. carotid, 189. conoid, 325. infra-glenoid, 331. of Lisfranc, 220. of Lower, 279. supra-glenoid, 331. Tuberosity, deltoid, 335. Tunica Buyschiana, 97. Tympanic cavity, 65. Tympanum, or middle ear, 60, 65. arteries of, 71. veins of, 71. walls of, 67. U. Ulna, head of, 375. interosseous edge of, 375. ossification of, 396. shaft of, 373. styloid process of, 375. Ulnar artery, 391. branches of, in the forearm, 391. line of reference for, 393. | Umbilicus of the membrana tympani, 65. Ungual phalanges, 401. Utricle, 72, 75. Uvea, 100. Uvula, 157. V. Vagus nerve, 43. Vallecula, 27, 38. Valve or valves: aortic semilunar, location of, 311. auriculo-ventricular, flaps of, 281. bicuspid, or mitral, 283. coronary, 277. Eustachian, 303. mitral, 308. location of, 311. of Hasner, 113. of Thebesius, 279. of tributary vein to axillary vein, 344. of Vieussens, 40, 49. semilunar, of aorta, 284. of pulmonary arteries, 282. location of, 311. tricuspid, 279. location of, 311. safety arrangement of third flap of, 307. Varolii, pons, 46. Vas aberrans, 352, 355. spirale, 74. Vasa vaaorum, 299. Vascular circle of the lips, 124. Vaso-constrictor nerves, 300. Vaso-dilator nerves, 300. Vaso-motor nerves, 299. Vein or veins : angular, 125. anomalies of, 296. anterior jugular, 192. median, 268. auditory, 78. axillary, 344. influence of costo-ooraooid membrane upon, 344. relation of, to axillary ar- tery, in different positions of the arm, 344. tributaries of, 344. basilic, 351. brachial, 369. brachio-cephalic, 222. bronchial, 271. cardiac, 277. cavernous plexus of, 19. Vein or veins : cephalic, 349. cervico-dorsal spinal, 213. circumflex, 344. coats of, 297. common jugular, 203, 225. communication of, 296. coronary, 276. course of, in various localities, 296. deep facial, 125. radial, 389. diploic, 15. emissary, 9. ethmoidal, 115. external jugular, 191. valves of, 192. facial, 125, 199, 203. frontal, 9. hepatic, 304. inferior thyroid, 235, 239. infra-orbital, 145. innominate, relative position of, 222. valves of, 223. internal jugular, 134, 203. mammary, 223, 259. maxillary, 141, 192. larger posterior superficial ulnar, . 408. posterior ulnar, 377. left innominate, 2.88. lingual, 167, 203. mastoid, 9. median basilic, 363. * with reference to vene- section, 368. cephalic, 368. mediastinal, 223. middle thyroid, 203. nasal, 110. peculiarity of, in children, 115. occipital, 9, 192, 203. oesophageal, 317. of the breast, 250. of the choroid coat, 97. of the dura mater, 18, of the forearm, 377. * importance of recognition of, in the application of bandaging, 378. of the larynx, 179, 184. of the nasal cavities, 115. of the pinna, 63. of the scalp, 9. of the tympanum, 71. ophthalmic, 95. 436 INDEX. Vein or veins: peculiarities of, in certain organs, 296. pharyngeal, 203. plexus of, 175. plexus of, at root of neck, 223. portal, 304. posterior auricular, 9, 192. pulmonary, 270, 290. in relation to the pulmonary arteries, 269, 290. openings of, 283. ranine, 167. . relative position to the main trunks of the arteries, 298. renal, 222. scapular, 342. small superficial anterior ulnar, 377, 408. structure of walls of, 297. subclavian, 221. right and left, 229. submaxillary, 192, 199. sub-scapular, 344. superficial and deep, 296. at the bend of the elbow, 367. at the wrist, 407. communicating, 378. median, 377. of the hand, 408. radial, 377. superior thyroid, 203. middle, and inferior thy- roid, 235. supra-scapular, 229. systemic, 296. temporal, 9. thymic, 223. tonsillar, 171. transrersalis colli, 206, 233. transverse facial, 192. umbilical, 303. valves of, 297. vertebral, 215, 233. Velum interpositum, 23, 51. pendulum palati, 157. Vena anastomotica, 368. azygos major, 267, 319. minor, 319. cava inferior, opening of, 278. cava superior, 222, 287. opening of, 278. cephalica pollicis, 408. salvatella, 408. Vense comites, 292, 296. of brachial artery, 357. of great meningeal artery, 17. of interosseous artery, 392. of radial artery, 389. of superficial cervical ar- tery, 233. of ulnar artery, 392. Galeni, 52. cordis, 279. innominatse, 222. vorticosae, 97. Venosus ductus, 304. Ventricle, fifth, of the brain, 53. fourth, of the brain, 49. lateral, of the brain, 53. position of, 60. left, of the heart, 283. walls of, 283. of Arantius, 50. of corpus callosum, 58. right, of the heart, 279. walls of, 278. third, of the brain, 51. Vermiform process of the cerebellum, 47. Vermis, inferior, 47. superior, 47. Vertebra, dorsal or thoracic, 248, 249. prominens, 189. Vessels, axillary, sheath of, 255. carotid, sheath of, 225. position of, 225. posterior dental, 145. Vessels, palatine, 147. supra-scapular, 330. Vestibule of the mouth, 149. of the tympanum, 66.' Vibrissae, 111. Vidian nerve, 142. VieuEsens, valve of, 49. Vincula above the knuckle-joints, 386. Vitreous body, 103. Vocal cord, false, 178. true, 178. Voice, change of, 183. w. Walls of the auditory canal, 64. of the nasal fossic. 111. of the orbits, 79. Wharton, duct of, 165. Willis, circle of, 22. Wormian bones, 5. * Wounds of the palm, 415, Wrisberg's nerve, 360. Wrist, or carpus, 396. region of, 396. surface-markings of, 406. Wrist-joint, 397. movements of, 398, synovial membrane of, 397, Wry-neck, 198, 208. Xiphoid appendix, 246. Yellow spot of the retina, 105. Zinn, ligament of, 89. Zone of Zinn, 99, 103. Zygoma, 138. END OF VOL. I. !'.' :Vi, vt ibji i ;:< ■'iMV,\, JSi