DUKE HOSPITAL LIBRARY Digitized by the Internet Archive in 2016 f https://archive.org/details/lecturesonanatom4183coop LECTURES ON ANATOMY: INTERSPERSED WITH PRACTICAL REMARKS. VOL. IV. / By B. B. COOPER, F.R.S., SURGEON OF GUY’S HOSPITAL, LECTURER ON ANATOMY, &C. &C. &C. LONDON: LONGMAN, REES, ORME, BROWN AND GREEN, PATERNOSTER ROW; S. HIGHLEY, FLEET STREET; AND THE MEDICAL BOOKSELLERS IN LONDON, DUBLIN AND EDINBURGH. 1832 , F. WARR, PRINTER, RED LION PASSAGE, KOLBORN, LONDON. PREFACE. In offering this my Fourth and last Volume to the Public, I complete the series of my Anatomical Lectures ; and trust that I have fulfilled the in- tentions which I proposed in the Preface to my First Volume. From the very flattering manner in which the preceding Three Volumes have been reviewed by the periodical press, and from the readiness with which the pupils, not only of my own, but of other classes, have adopted my general classification and mode of anatomical instruction as their guide, I cannot but indulge a sanguine expectation, that the Work may be found useful, not only to the Student, but to the Profession at large. New Street; October, 1832 . \ . : CONTENTS. PART VII. LECTURE XXVI. Descriptive Anatomy of the Arteries. page. Classification. — General view of the contents of the Thorax. — Pulmonary distribution — Systemic distribution. — The Aorta — Its divisions. — Ascending Aorta — Arch of the Aorta — Thoracic Aorta — Abdominal Aorta ... 3 LECTURE XXVII. Practical Remarks. Importance of the knowledge of the Arteries. — Causes which generally lead to operations on the Arteries. — Diseases of Arteries. — Great tendency to Adhesive Inflammation. — Its consequences illustrated by reference to the preparations in the Museum of Guy’s Hospital. — Acute Inflammation — Chronic Inflammation. — Ulcerations. — Sphacelus of rare occurrence. — Morbid changes peculiar to Arteries. — Thickening of the Internal Coat. — Ossific or Calcareous, and Atheromatous Depositions. — Predisposing causes of Aneurism. — Importance of remarking pre-existing constitutional symptoms. — Causes leading to fallacious diagnosis. — The value of correct anatomical knowledge of the relative positions of the contents of the Thorax. — Various diseases resembling Aneurism in the symp- toms produced. — Cases and Preparations referred to. — Surgical operations for the cure of Aneurism. — Difficulties arising from irregular distributions of Arteries. VIII CONTENTS. — Enumeration of the principal varieties — illustrated by preparations in Guy’s Museum. — Operation for tying the Arteria Innominata. — Danger arising from the Patient being allowed to move about too soon after the Operation. — Operation for tying the common Carotids — The Upper operation — The Lower operation. — Operation for tying the External Carotid — The Ramulus Thyroideus Superior — The Ramulus Maxillaris, vel Facialis Externus — Extirpation of the Sub-maxillary Gland, and other Operations connected with this Artery.— The Ramulus Lingualis, and Operations connected with it. — The Occi- pital and Posterior Aural ramuli. — The Ramulus Tempo- ralis — Liability to spurious Aneurism of — The Subclavian artery on the outer side of the Scalenus Anticus muscle — Danger occurring from a wound of the Jugular vein in this operation. — Treatment recommended in Wounds of Arte- ries of the Hand. — Pulsating Tumour in the Abdomen, how distinguished from Aneurism. — Sir Astley Cooper’s operation for tying the Common Iliac Artery. — Various modes considered. — The lateral operation recommended and described. — The variations necessary for the Internal Iliac. — Sir A. Cooper’s operation described. — Operations for tying the Femoral Artery. — Variations required for the Popliteal Artery. — Mode of exposing the Posterior Tihial ramus — The Peroneal ramus — The Anterior Tibial ramus. — General treatment previous to the opera- tion for Aneurism. — General treatment after the operation Table of the Arteries LECTURE XXVIII. Descriptive Anatomy of the Veins. Classification, corresponding to that of the Arteries. — The four Pulmonary Trunks. — The Coronary Trunks. — The Systemic Trunks. — The Veins which unite to form the Superior Cava. — The Veins which concur in forming the Trunk of the Vena Cava Inferior ..... PAGE. 101 121 129 CONTENTS. IX LECTURE XXIX. Descriptive Anatomy of the Absorbent System. page. Consisting of Glands and Vessels.— Absorbent Glands of the Head — Of the Face — Of the Neck — of the Upper Extre- mity — Of the Thorax — The Bronchia— of the Lower Ex- tremities — Of the Pelvis. — The internal Iliac Glands — The External Iliac Glands — Sacral Glands — Absorbent Glands of the Abdomen — Mesenteric Glands — Meso-colic Glands — Ventricular Glands — Cseliac Glands — Lumbar Glands. — Of the Absorbent Vessels. — Termination in two main Trunks. — Absorbents of the Head and Neck. — Superficial and deep-seated Absorbents of the Upper Extremity. — Absorbents of the Parietes of the Thorax. — Absorbents of the Viscera, and parts withiu the Thorax. — Superficial and deep-seated Absorbents of the Lower Extremity. — Superficial and deep-seated Absorbents of the lower part of the Trunk. — Deep-seated Absorbents of the Testes, and Organs of Generation in the Male and Female. — Ab- sorbents of the Viscera in the Cavity of the Abdomen. — Absorbents of the Urinary Organs, and Capsulse Renales. — Absorbents of the Chylopoetic Viscera — Of the Liver — Stomach and Intestines. — Of the Left Thoracic Duct — Of the Right Thoracic Duct . . . . . .146 PART VIII. LECTURE XXX. Physiology of the Nervous System. Comprising the Brain, Medulla Oblongata, Medulla Spinalis, the Cerebral, and the Sympathetic Nerves. — Early Deve- lopement. — Relation of the Early Growth of the Human Brain, to its Permanent State in the Lower Orders of X CONTENTS. PAGE. Animals. — Observations of Tiedemann and Serves. — Growth of the Brain regulated by the Developement of the Arterial System. — Deviation in the case of the Ophthalmic Artery. — First Appearances of Nervous Developement. — Observations of Dr. Bennett. — Refutation of the Hypothesis of Drs. Gall and Spurzheim. — Order of Foetal Growth, by Dr. Bennett. — Construction of Nerves. — Four kinds enumerated. — Their peculiarities enumerated. Order of their Existence in the Animal Creation, and corresponding relation to their Function. — Their Mutual Dependance. — Views of Sir Charles Bell. — His arrange- ment of the Cerebral Nerves into Three Orders — Those of Motion, Sensation, and Respiration. — Comparison of Cerebral with Sympathetic Nerves arranged in a Table. — General Consideration of the Sympathetic Nerves. — Mutual Dependance on the Cerebral and Sympathetic Orders of Nerves, and their Influence over the Muscular and other vital powers. — Experiments of Majendie. — Origin of Sensation in the Tuhercula Quadrigemina. — Volition, Regulation, and Excitation of Muscular Movements, re- ferred to Peculiar Parts of the Brain. — Comparison with the Doctrines of Gall and Spurzheim. — The Observations of Dr. Foville, of Rouen — An Account of his Demonstra- tions at Guy’s Hospital — His Application of his Observa- tions and New Mode of Dissection in Explanation of the Functions of the Brain — His Views supported by numerous Pathological Facts. — Reference to Diagrams . . .165 LECTURE XXXI. Descriptive Anato»iy of the Nervous System. The Membrane of the Brain. — The Processes of the Dura Mater. — The Venous System of the Brain. — The Tunica Arachnoidea. — The Pia Mater. — Practical Remarks . 185 CONTENTS. XI LECTURE XXXII. Descriptive Anatomy of the Brain. PAGE. Of the Exterior of the Cerebrum — Its comparative Volume — Its Division into Hemispheres, and Sub-division into Lobes. — Commissure of the Optic Nerves. — Infundibulum. — Pituitary Gland. — Corpora Albucantia. — Substantia Per- forata. — Crura Cerebri. — Exterior of the Cerebellum — its Division into Lobes. — Processus Vermiformis Superior — Processus Vermiformis Inferior. — Exterior of the Pons Varolii. — Coverings of the Medulla Spinalis. — Dura Mater. — Tunica Arachnoides. — Pia Mater. — Ligamentum Denta- tum. — Extent of the Spinal Marrow — Comparative Volume. — Medulla Oblongata. — Corpora Pyramidalia. — Corpora Olivaria. — Discovery of Nervous Roots for Motion being distinct from those for Sensation, by Sir Charles Bell. — The Interior of the Brain. — Various Modes of Dissection — Method by Drs. Gall and Spurzheim — Method of Dr. Foville explained by Diagrams. — Corpus Callosum. — Medullary and Cineritious Substances. — Views of Dr. Foville in Opposition to those of Gall and Spurzheim. — Raphe. — Corpora Striata. — ’Thalami Nervosum Opticorum. — Taenia Semi-circularis. — Plexus Choroides. — Anterior Cornua. — Posterior Cornua. — Inferior Cornua. — Taenia Hippocampi. — Hippocampus Major et Minor. — Corpus Denticulatum. — Eminentia Collateral^. — Septum Lucidum. — Fornix. — Lyra Davidis. — Foramen of Monro. — Velum Interpositum. — Corpora Geniculata. — Third Ventricle. — Commissura Mollis, Anterior et Posterior. — Foramen Com- mune Anterius — Foramen Commune Posterius. — Iter ad Infundibulum. — Iter a Tertio ad Quartum Ventriculum. — Pineal Gland. — Nates. — Testes. — Processus e Cerebello ad Testis. — Valve of Vieusens. — Medulla Spinalis. — Corpora Olivaria. — Corpora Restiformia. — Corpus Rhom- boideum, vel Serratum — Arbor Vitae. — Pons Varolii. — Locus Niger 196 XU CONTENTS. LECTURE XXXIII. Descriptive Anatomy of the Nerves. page. Cerebral Nerves to the Organs of Sensation and Volition. — First Pair, or Olfactory — Controversy respecting their Function. — Second Pair, or Optic. — Third Pair, or Mo- tores Occulorum — Anomaly respecting their Function. — Fourth Pair, or Pathetici — Peculiarity in their Distribu- tion explained by Sir C. Bell. — Fifth Pair, or Trigeminus. — Sixth Pair, or Abducentes. — Seventh Pair, Portio Dura or Facial Nerve. — Eighth Pair, Portio Mollis, or Audi- tory Nerves. — Ninth Pair, or Glosso-pharyngeal. — Tenth Pair, Par Vagum, or Pneumo-gastric Nerves. — Eleventh Pair, Hypo-glossal, or Lingual Nerves .... 223 LECTURE XXXIV. Descriptive Anatomy of the Spinal Nerves. Consist of Thirty-two Pairs. — 1. Nervus Accessorius Wil- lisii. — 2. Nervi Sub-occipitales. — 3. to 9. Nervi Cervicales, Seven Pair General Description — Particular Descrip- tion. — Plexus Cervicalis formed from the Anterior branches of the 1st, 2nd, and 3rd pairs of Cervical Nerves — Plexus Axillaris formed from the Anterior branches of the 5th, 6th, and 7th pairs of Cervical Nerves. — 10. to 21. Nervi Dorsales, Twelve Pair. — 22. to 26. Nervi Lumbales, Five Pair. — Plexus Lumbalis formed from the Anterior branches of Five pair of Lumbar Nerves.*— 27. to 32. Nervi Sacrales, Six Pair. — Plexus Sciaticus formed from the Anterior branches of the Fifth Lumbar, and Four Upper pair of Sacral Nerves 251 CONTENTS. Xlll LECTURE XXXV. Descriptive Anatomy of the Sympathetic Nerve. page. General Description of the Ganglia. — Ganglia Capitis. — Ganglion Lenticulare, vel Ophthalraicum. — Spheno-pala- tine, or Ganglion of Meckel. — Ganglia Cervicales Superius, Medius, et Inferius. — Plexus Cardiacus.-— Ganglia Tho- racica. — Ganglia Abdominales. — Ganglia Semilunare. — Ganglia Lumbales. — Ganglia Sacrales. — Ganglion Impar 284 Table of the Nerves 300 PART IX. THE ORGANS OF THE SENSES. LECTURE XXXVI. Descriptive Anatomy of the Organs of Vision. Parts External to the Orbits: — Supercilia — Palpebrse — Fibro-tarsal Cartilages — Meibomian Glands — Ciliae — Tunica Conjunctiva — Caruncula Lachrymalis. — Parts Within the Orbits : — Muscles — Lachrymal Gland — Puncta Lachrymalia — Lachrymal Ducts — Lachrymal Sac — Nasal Duct. — The Composition and Function of the Tears. — Of the Globe of the Eye. — Tunica Sclerotica. — Cornea Pel- lucida. — Tunica Choroides. — Membrana Jacobi.— Liga- mentum Ciliare. — Of the Iris. — Retina. — Tunica Vasculosa Retinse. — Limbus Luteus. — Foramen Centrale. — Corpus Ciliare. — Processus Ciliares. — Aqueous Humour. — Crys- talline Lens. — Liquor Morgagni. — Canal of Petit. — Vitre- ous Humour. — Hyaloid Membrane. — Corona Ciliaris. — Physiology of the Eye. — General View of the Phenomena of Light. — Application to the Organ of Vision. — Explana- tion of the Foci produced in Myopia and Presbiopia. — View of the Mode in which the Eye is adjusted to Vision at different Distances . . . . . . .313 XIV CONTENTS. LECTURE XXXVII. Of the Organ of Hearing. Descriptive Anatomy of the Ear. page. General Division into Three Parts. — Of the External Part, or Auricle : — Helix — Anti-helix — Fossa Navicularis— Tragus — Anti -tragus —Concha — Lobulus — Ligaments — Muscles — Arteries — Nerves — Absorbents — Meatus Audi- torius Externus — Skin — Fibro-cartilage — Ceruminous Glands. — The Tympanum, or Middle Part : — Form — Di- vision into Walls — Membrana Tympani — Fenestra Ovalis — Fenestra Rotunda — Processus Pyramidalis — Eustachian Tube — The Ossicula Auditus — Muscles of the Ossicula. — The Labyrinth, or Internal Part of the Ear. — Of the Semi-circular Canals. — Cochlea. — Scala Tympani. — La- mina Spiralis. — Scala Vestibuli. — Modiolus. — Cupola. — Aqueductus Cochleae. — The Nerves. — Physiology of Hearing. — Of Sound. — Diatonic Scale. — Propagation of Sound. — Application to the Organ of Hearing. — Practical Remarks. — Diseases of the External Ear. — Diseases of the Tympanum. — Diseases of the Labyrinth . . . 339 LECTURE XXXVIII. Descriptive Anatomy of the Organ of Smell. General Remarks. — Of the Skin. — Of the Muscles. — Of the Cartilages. — Pituitary Membrane. — Of the Nerves. — And Vascular Distribution. — Practical Remarks. — Physiology of the Sense of Smell. — Definition of the Sense of Smell. — Phenomena of Odoriferous Particles.— Application to the Schneiderian Membrane . . . . . . 363 CONTENTS. XV LECTURE XXXIX. Descriptive Anatomy of the Organs of Taste. page. Bones — The Mouth. — The Lips. — Mucous Membrane. — Vascular Distribution. — The Cheeks.— Palate and Gums. — The Tonsils. — Vascular Distribution — The Tongue. — The Papillae. — Nervous and Vascular Distributions. — The Salivary Apparatus — General Description of. — The Parotid Gland — Vascular Distribution The Submaxillary Gland. — Nervous and Vascular Distributions.— Sublingual Glands — Vascular and Nervous Distributions. — Practical Re- marks. — Diseases of the Lips. — Diseases of the Tongue. — Diseases of the Tonsils Diseases of the Uvula. — Diseases of the Salivary Apparatus. — Physiology of Taste. — General Remarks. — Phenomena of Sapid Bodies — Experiments of Guyot. — Of the Saliva.— Of the Papillae. — Nervous Dis- tributions. — Experiments of Majendie. — Chemical Effects of Sapid Bodies. — Sense of Taste at Different Ages. — General View of the Function of Taste .... 369 •• ♦ LECTURES ON ANATOMY. PART VII. DESCRIPTIVE ANATOMY OF THE ARTERIES. ■v * * LECTURE XXVI. DESCRIPTIVE ANATOMY OF THE ARTERIES. x he principle which I have adopted in the following 1 de- scription of the arteries, I have taken from the example of my friend Mr. Joshua Brookes, as it possesses considerable advantage in assisting’ the memory of the student. It is to consider the two principal arteries arising 1 from the heart, as arterial trunks. The branches immediately given off from the systemic trunk, are named arteries, and num- bered in the order of their succession. The branches from arteries, are named rami ; branches from rami, ramuli ; branches from ramuli, ramusculi ; branches from ramusculi, ramifications; and their ultimate terminations, distributions. Before we commence a description of the anatomy of the arteries, it will be necessary again to take a view of the precise situation of the heart within the thorax, in order that its position in relation to the large arteries arising from it may be clearly understood. The heart is placed obliquely within the chest ; its base being opposite to the fourth dorsal vertebra, partly resting upon the diaphragm ; while its apex is directed obliquely downwards, forwards, and to the left, towards the interspace of the fifth and sixth ribs. With regard to the ventricles and auricles, — those of the right side are placed most anteriorly, and form the acute edge ; while the left auricle and ventricle form the obtuse edge, and posterior part of the heart. The pulmonary arterial trunk — already described with the organization of the lungs ( Vide Vol. III. p. 186J, is the first vessel seen in the natural position of the heart ; arising from the upper and anterior part of the base of the right ventricle, where it conceals the origin of the aorta. B 2 4 DESCRIPTIVE ANATOMY OF THE ARTERIES. The aorta — the main trunk of the systemic distribution, arises from the base of the left ventricle, and immediately takes its course obliquely upwards, and to the right ; and, like the pulmonary, appears to be directed, so as to con- vey the current of the blood in the direction of the contractile forces of their respective ventricles. The origin of the aorta is opposite to the fourth dorsal vertebra, its termination at the junction of the fourth with the fifth lumbar vertebra ; in this extent it takes a curved course, and is divided into an ascending - , transverse, and descending - portion. The ascending aorta — commences from the upper and fore part of the left ventricle, rather to the left of the fourth dorsal vertebra, and extends upwards and obliquely to the right, in the direction of the long axis of the heart, as high as the upper edge of the third dorsal vertebra, where it terminates in the commencement of the arch. In this course it is first covered by the pulmonary artery, which arises immediately in front of it ; above which is a small space, still within the pericardium ; on emerging from the pericardium, it takes its course between the pulmonary artery on the left, and the superior cava on the right ; while the right branch of the pulmonary artery is behind it. This portion of the aorta is visible on opening the cavity of the chest, having nothing in front of it, excepting the contents of the anterior mediastinum, which separates it from the second bone of the sternum. The aorta is connected with the heart in the following manner : — External!}', by a continu- ation of the pericardium ; secondly, by its fibrous coat, which is not a continuation of the muscular fibres of the heart, but commences abruptly by three semilunar folds, which are attached to the fleshy fibres of the ventricle ; thirdly, by the internal lining membrane of the ventricle, which is continued into the ascending aorta, forming at its commencement three semilunar valves. The opening of the aorta from the ventricle is of a triangular figure, and con- tracted, but almost immediately enlarges, forming three DESCRIPTIVE ANATOMY OF THE ARTERIES. O pouches corresponding' to each valve, which are termed the sinuses of Morgagni. These pouches are not produced by the pressure of the column of regurgitating blood, but are natural formations tending to facilitate the propulsion of the blood in the systole of the heart, being surrounded by the muscular fibres of the ventricle itself, which partly overlap them where they are exterior to the semilunar valves. The only branches which are given off by the ascending aorta are, the coronary or cardiac arteries, whose office it is to supply the heart itself with blood. They are two in number, and are distinguished from each other by their course. (1.) Arteria coronaria dextra vel anterior — is sent off’ from the ascending aorta, immediately above the free edge of the semilunar valve, which faces somewhat di- agonally towards the right side. It immediately after its origin takes its course downwards and forwards, in front of that portion of the aorta which is seen anteriorly before it is crossed by the pulmonary arterial trunk ; it then passes in a tortuous manner in the fissure between the right auricle and ventricle, where it divides itself into three principal Tami, — a superior, an inferior, and a posterior. (a.) Ramus superior — passes in a course between the auricle and ventricle, along the base of the latter, around which it passes until it meets a similar branch from the left coronary artery. In this course it distributes several ramifications, some of which pass upward and backward to the right auricle, and others downward and forward to the parietes of the right ventricle. (b.) Ramus inferior — is directed forwards and down- wards, along the thin edge of the right ventricle, as far as the apex of the heart, where it anastomoses with the left coronary artery, dividing in its passage into several anterior and posterior ramifications, to supply the corresponding' surfaces of the ventricles and septum cordis. (c.) Ramus posterior — passes backwards and down- wards to supply the back part of the right ventricle and 6 DESCRIPTIVE ANATOMY OF THE ARTERIES. septum cordis, and anastomoses, like the inferior branch, at the apex. (2.) Arteria coronaria sinistra vel posterior — is smaller than the right, it arises immediately above the floating- edge of the most anterior of the semilunar valves ; but, like the right, is placed rather transversely, being in- clined to the left, to take its course between the pulmonary artery and left auricle, by the apex of which it is partly concealed. It soon divides into two rami, a superior and an inferior, (a.) Ramus superior — takes its course backwards, in the groove between the left auricle and ventricle, sending off numerous ramifications superiorly and inferiorly to supply each of these cavities, and terminates by anastomosing with the superior branch of the right coronary artery. By this anastomosis, the arteries form a complete line of separation between the auricles and ventricles. (b.) Ramus inferior — descending along the septum cordis anteriorly, sends numerous ramifications into the substance of both ventricles, as well as to the fleshy partition between them ; and terminates at the apex, by freely anastomosing with the right coronary artery. The ultimate termination of the coronary arteries may be considered to be in the fleshy fasciculi of the heart ; but they also frequently anastomose with the phrenic, internal mammary, and bronchial vessels. At the third dorsal vertebra, where it has already been said that the ascending aorta terminates, there the arch of that vessel begins, — which has now to be described. The arch of the aorta — extends from the right of the upper part of the third dorsal, to the left of the same bone ; in its course it first passes upwards, backwards, and to the left, as high as the second dorsal vertebra, which it crosses, being placed in front of the trachea ; where, having gained its vertex, it is continued downwards and backwards, between the vertebrae and left lung, to arrive at the left side of the third dorsal vertebra, where the arch is completed. It is to DESCRIPTIVE ANATOMY OF THE ARTERIES. 7 be observed, therefore, that the arch is not placed trans- versely, but is directed from before to behind, from right to left, and from above to below. To facilitate a more accurate description of the relative position of the arch of the aorta, it may be divided into its right anterior, its middle, and its left posterior thirds. The right anterior third of the arch — is that portion between the ascending aorta and the arteria innominata. The middle third — where it crosses the second dorsal ver- tebra, resting upon the trachea just above its division ; and The left posterior third — where it reaches from the left of the second to the lower edge of the third dorsal vertebra. Each of these parts has some important anatomical points connected with it. The right anterior third, instead of continuing in the direc- tion of the ascending aorta, namely, in that of the axis of the heart, is directed backwards and to the left ; it passes in front of the right bronchus, is placed between the trachea and descending vena cava, and has connected with it the left vena innominata, which is just above it. It is about opposite to the junction of the cartilage of the second rib with the first two bones of the sternum. The middle third, as has been before said, rests upon the trachea, opposite the second dorsal vertebra. It may be comprehended between the arteria innominata and the left subclavian ; the left vena innominata runs immediately above it; and just where the middle becomes connected with the descending portion of the arch, the ductus arteriosus con- nects it with the pulmonary arterial trunk. The inferior third, as it lies upon the left side of the bodies of the second and third dorsal vertebrae, which are frequently indented by the pressure of this vessel, has, to the right, the oesophagus, and more posteriorly, the thoracic duct ; while immediately behind it, is the recurrent laryngeal branch of the par vagum— the par vagum being placed in front. The concavity of the arch of the aorta is directed down- wards and to the left ; and within its parabolic curve it 8 DESCRIPTIVE ANATOMY OF THE ARTERIES. encloses several important organs : first is seen the pulmo- nary trunk, and its two arteries ; behind them, the left bronchus, the oesophagus, the thoracic duot, and the left pneumogastric nerve, with its recurrent branch, besides some small dark coloured glands surrounding the bronchi. The arteries given off from the convexity of the middle third of the arch of the aorta are usually three in number, and are destined to supply the neck, head, upper extremities, and part of the chest. These are denominated the arteria innominata, the left carotid, and the left subclavian arteries. (3.) Arteria innominata — arises from the junction of the anterior with the middle third of the arch, being, therefore, from the most anterior portion of the aorta, and opposite to the junction of the cartilage of the second rib to the ster- num ; from thence it extends upwards, obliquely, to the right, as high as the sterno clavicular articulation, where it divides into the right common carotid and right subclavian vessels. In this course the arteria innominata is bounded in front by the sternum, sterno hyoideus and sterno thyroideus mus- cles, and vena innominata ; behind, by the trachea and longus colli muscle ; the latter, however, is separated from the vessel by a considerable quantity of cellular membrane. The arteria innominata, from its commencement to its division, does not usually give off any branches ; but some- times a small vessel arises from it, which passes upwards, in front of the trachea, to be distributed to the thyroid gland, and has been described as the middle thyroid artery. The origin of the left common carotid artery should next be examined, as it arises within the thorax from the arch of the aorta; and is not placed under the same circumstances as the right until it has reached the left sterno clavicular articulation; the point corresponding with the commencement of the right common carotid. (4.) The arteria carotidis communis sinistra — arises from the arch of the aorta, on a plane posterior to the arteria DESCRIPTIVE ANATOMY OF THE ARTERIES. 9 innominata, and forms very nearly a right angle with the arch, passing upwards, with a slight obliquity to the left, as high as the sterno clavicular articulation, where it is placed under precisely the same circumstances as the right carotid. By the extent of its thoracic portion it is longer than thfe right, but is somewhat smaller ; and, in this situation, is bounded in front by the sternum, by the remains of the thymus gland, and crossed by the vena innominata : it runs upwards on the left side of the trachea, to which it is nearly parallel, but partly covers it, as well as the thoracic duct and oesophagus ; then emerging from the chest, it corres- ponds to the right vessel: from hence, therefore, one des- cription answers for both arteries. (4.) The arterice carotides communes — from the sterno clavicular articulations, diverge, as they pass upwards and backwards, to reach the upper edge of the thyroid cartilage, where they each divide into an external and an internal corotid ramus. This division most frequently takes place on a plane with the lower edge of the third cervical vertebra. In this course they are placed under different circumstances as regards their relative position with neighbouring parts, being at their commencement deeply seated, covered by the platysma myoides, sterno cleido mastoideus, sterno hyoideus, sterno thyroideus, and omo hyoideus muscles ; but w’hen they reach as high as the cricoid cartilage they become superficial, in consequence of the direction the sterno cleido mastoidei muscles take upwards and backwards to gain their insertion ; so that from this point to their termination, the common carotid arteries are lying in a hollow between the inner edge of the sterno cleido mastoidei and larynx, and are only covered by the platysma myoides, fascia of the neck, and superficial veins and nerves. At their commencement, the common carotids correspond posteriorly to the bodies of the cervical vertebrae; but above, to their transverse processes: they first rest upon the longus colli muscle, and as they ascend, upon the rectus capitis anticus major ; they each cross in front of the inferior thy- 10 DESCRIPTIVE ANATOMY OF THE ARTERIES. roideal ramulus, the recurrent branch of the par vagum and the sympathetic nerve. The common carotid arteries are enclosed in a sheath of fascia, and are accompanied by the internal jugular vein, which is on their outer side, and by the pneumogastrie nerve, which runs between the artery and vein. Exterior to the sheath, and in front, the descending branch of the lingual nerve may be seen, being placed to its outer or mastoid side above, and to its inner or tracheal side below; forming, in this course, junctions with the cervical nerves. The common carotid arteries, as has been before men- tioned, diverge, as they pass from below upwards, to an extent depending more or less upon the size of the trachea and larynx ; they do not give off any branches prior to their division into an external and internal carotid, opposite to the upper edge of the thyroid cartilage. I shall now, contrary to the plan usually followed by anatomical writers, describe that portion of the left sub- clavian artery which is placed within the cavity of the chest, instead of first tracing the numerous ramuli of the exter- nal and internal carotids, as I shall then have completed the account of the origin of the vessels from the arch of the aorta (5.) Arteria subclavia sinistra — like the left common carotid, arises from the arch of the aorta, within the thorax, but posterior to it, being separated from the arch just at the junction of the middle with the descending third; from this point it ascends, nearly vertically, as high as the inner edge of the first rib, where it is placed under the same circum- stances as the right subclavian ; and from thence a common description will serve for both vessels. While this vessel is within the chest it is very deeply seated, resting upon the longus colli muscle and inferior cervical ganglion of the sympathetic nerve, running upwards parallel with the oesophagus ; it is, anteriorly, covered by the left lung and pleura, the par vagum, the left common carotid artery, the jugular vein and vena innominata, the thoracic duct, the sterno cleido mastoideus, sterno hyoideus. DESCRIPTIVE ANATOMY OF THE ARTERIES. 11 sterno thyroideus muscles ; and as to bones, by the first rib, clavicle, and sternum. This portion of the left subclavian artery, which renders it so much longer than the right, is, however, the smaller ; and is much more deeply seated than it, the arteria innominata, or the left common carotid. The common carotid arteries have already been described as passing from their origin to the upper part of the thyroid cartilage, before they divide; and in this course they do not give off any branches, but terminate by dividing’ into an external and an internal carotid ramus, which are destined to supply the head, face, and neck. (a.) Ramus carotidis externus — supplies the face and exterior of the head. It extends from the upper edge of the thyroid cartilage to the cervix of the lower jaw, where it terminates by dividing into the temporal and internal max- illary ramuli, within the substance of the parotid gland. In its course it is at first anterior, and to the inner side of the internal carotid, and runs parallel to it, in this situation being comparatively superficial; it then dips under the lingual nerve, the stylo hyoideus muscle, and at the posterior belly of the digastricus again becomes superficial, here as below being only covered by the platysma myoides ; it then passes outwards and backwards, just behind the angle of the lower jaw, where it buries itself in the substance of the parotid gland, to divide into the temporal and internal maxillary ramuli. In thus passing to its termination it does not take a straight course, but presents a convexity, looking forwards and upwards toward the pharynx and tonsil, and a concavity backward, to the sterno cleido mastoideus. It has opposed to it on its inner side the pharyngeal plexus of nerves, the stylo glossus, stylo pharyngeus mus- cles, and glosso pharyngeal nerve; and above, a portion of the parotid gland ; all of which tend to separate the external from the internal carotid artery. The ramuli which this ramus distributes may be divided into four distinct sets, from the direction of their course, viz. : — anteriorly, posteriorly, internally, and ascending. 12 DESCRIPTIVE ANATOMY OF THE ARTERIES. The anterior ramuli of the external carotid, which are given off' from the convexity of its curve, may now be ex- amined : they are three in number, — the superior thyroideal, the lingual, and the facial. ( a .) Ramulus thyroideus superior vel descendens — is the first vessel sent off' by the external carotid, and usually immediately below the cornu of the os hyoides ; it extends to the thyroid gland, in which it ramifies, taking however a circuitous course, first running upwards and inwards, and then forming its course downwards to the thyroid gland. The trunk of this vessel is only covered by the platysma myoides, being accompanied by the laryngeal nerve, which is posterior to it ; while above, but separated from it by the cornu of the os hyoides, is the lingual ramulus and nerve. The superior thyroideal ramulus is destined to supply parts between the os hyoides and thyroid cartilage, the larynx and the thyroid ; for which purpose, it sends off three principal ramusculi — ramusculus hyoideus, ramuseulus la- ryngeus, and ramusculus thyroideus. (a.) Ramusculus hyoideus — ascends from the trunk of the thyroid ramulus, and usually takes its course along the under edge of the os hyoides, anastomosing with a similar vessel of the opposite side, sending ramifications upwards to anastomose with the lingual ramulus, and to supply the thyro hyoideus, orno, and sterno hyoidei muscles, and the -thyro hyoid ligament. A superficial ramification is usually separated from the hyoideal, which runs downwards to supply the glands of the neck, sterno cleido mastoideus, and platysma myoides. (/3.) Ramusculus laryngeus — proceeds towards the upper part of the larynx, behind the thyro hyoideus muscle, accompanied by the laryngeal branch of the par vagum. This little ramusculus enters the larynx, sometimes above the thyroid cartilage, piercing the broad ligament ; at others between the thyroid and cricoid, penetrating the crico thyroid ligament ; and less frequently, passes through a foramen of the thyroid cartilage : when it has gained the interior, it DESCRIPTIVE ANATOMY OF THE ARTERIES. 13 divides into numerous distributions to supply the muscles and mucous membrane of the larynx and epiglottis, anasto- mosing’ with those of the opposite side. A small ramifica- tion should be particularly observed, which takes its course downwards and inwards over the thyroid cartilage to gain the crico thyroid ligament, where it forms an anastomosis with a similar ramification of the opposite side. This vessel should be particularly remembered in opening the larynx between these two cartilages. (y.) Ramusculus ihyroideus — seems a continuation of the original ramulus, and takes its course behind the sterno thyroideus muscle to gain the thyroid gland, where it divides pretty generally into three ramifications : one, running along- the upper edge of the gland to anastomose with its fellow; a second, passing behind the gland, between it and the trachea; and a third, taking its course downwards, along the outer edge of the gland, to anastomose with the inferior thyroideal ramulus — but all plentifully supplying the paren- chyma of the organ. Although the lingual ramulus is the next given off by the external carotid, it is better first to dissect the fascial and its ramifications, as the lingual may be more readily dis- sected afterwards. (bi) Ramulus maxillaris, vel facialis externus — is usually given off by the external carotid, behind the digastricus and stylo liyoideus muscles ; it immediately takes a tortuous course forwards and inwards, towards the submaxillary gland, behind which it passes (the gland usually separating this artery from its accompanying vein); it then runs for- wards upon the mylo hyoideus muscle, from the anterior edge of which it dips down to pass around the horizontal portion of the lower jaw to gain the face, just anterior to the edge of the masseter muscle, being covered by the platysma myoides, and some fibres of the depressor anguli oris ; here it becomes embedded in a considerable quantity of fat, lying on the buccinator muscle. It then winds under the zygomatici, and levator labii superioris alseque nasi 14 DESCRIPTIVE ANATOMY OF THE ARTERIES. muscles; and running- up by the side of the nose, terminates at the inner canthus of the eye, anastomosing- with the nasal ramusculus of the ophthalmic of the internal carotid. In this course it gives off numerous ramusculi, which may be divided into two sets, — those which are given off below the jaw, and those which are distributed to the face. Those which are given off below the jaw, are two prin- cipal ramusculi, — the inferior or ascending palatine, and the submental, besides some small ramifications to the muscles and glands. («.) Ramusculus palati inferior, vel ascendens — is given off almost immediately, at the separation of the facial from the external carotid ; it then passes upwards, in front of the stylo pharyngeus and behind the stylo glossus muscle, upon the side of the pharynx, and distributes itself to these muscles, to the tongue, the tonsils, and the eustachian tube ; and is lost by supplying the soft palate and uvula, anasto- mosing with the superior or descending palatine ramusculus of the internal maxillary rarnulus. Muscular ramifications — are sent off below the jaw to the stylo hyoideus, stylo pharyngeus, and stylo glossus muscles. (/3.) Ramusculus tonsilaris — near the insertion of the stylo glossus, is often separated from the facial rarnulus ; and penetrating the pharynx, supplies the tonsil of its own side. (y.) Ramusculi glandulares — are also distributed from this vessel to the submaxillary gland, and neighbouring absorbent glands. (5.) Ramusculus submentalis — is separated from the facial artery while it is covered by the submaxillary gland, and proceeds forwards, above the anterior belly of the digastricus, towards the symphisis of the lower jaw, being placed superior to the lower edge of the horizontal portion, resting upon the mylo hyoideus, and surrounded by a chain of absorbent glands. This ramusculus not unfrequently supplies the place of the sublingual of the lingual ra- mulus. It distributes ramifications downwards and in front DESCRIPTIVE ANATOMY OF THE ARTERIES. 15 of the digastrieus, to anastomose with a corresponding rami- fication from the opposite side ; sending some downward, to anastomose with the hyoideal ramusculi of the lingual Tamulus ; and some upward upon the chin, to anastomose with the dental of the internal maxillary, and inferior labial of the facial — supplying at the same time various muscles. After having distributed these vessels below the jaw, the ramulus facialis mounts upon the face, and distributes the following ramusculi — first externally. (e.) Ramusculi masseteres — which supply the masseter muscle ; and some take their course with the parotid duct, and supply the gland, anastomosing- with the ramusculi of the temporal. Ramifications are also distributed to the buccinator, to the platysma myoides, and to the depressor labii inferiores ; anastomosing with the submental ramusculi, and the inferior dental as it passes out of the anterior maxillar} 7 foramen. (£.) Ramusculus labialis inferior — -takes a very tortuous course towards the commissure of the mouth, and supplies both the muscles and mucous membrane of the under lip ; anastomosing with the corresponding ramusculus of the op- posite side, and also with the inferior dental and submental ramusculi. (n.) Ramusculus labialis superior vel coronarius — is given off from the ramulus facialis, above the commissure of the mouth, and gains by a very tortuous course the upper lip, into the muscles and mucous membrane of which it plentifully distributes itself, anastomosing in the centre of the lip with the opposite corresponding ramusculus, from which small ramifications mount vertically towards the par- tition of the nose, where they expand themselves, supplying the depressor muscles of the lip and alae of the nose. The coronary ramusculi are, however, very variable, both as to situation and size. One of them very frequently ex- tends to the commissure of the mouth, and there dividing, supplies the place of both. The facial ramulus is still continued upwards by the side 16 DESCRIPTIVE ANATOMY OF THE ARTERIES. of the nose, under the levator labii superiors alaeque nasi, and in its course sends off the (S.) Ramusculus lateralis nasi — which distributes itself upon the side of the nose, supplying - the compressor nasis, anastomosing with its fellow and descending ramification from the forehead. The facial ramulus terminates by giving off the (i.) Ramusculus angularis — which mounts to the inner canthus of the eye, between the two origins of the levator labii superioris alaeque nasi, where it anastomoses with the infra orbitar ramusculus of the internal maxillary, sending ramifications in this situation to the orbicularis palbebrarum; it then reaches the lachrymal sac, which it supplies, anasto- mosing here with the nasal ramusculus of the ophthalmic of the internal carotid, and terminates by ramifications to the orbicular muscle of the upper eye-lid, and by anastomosing with the supra orbitar ramusculus of the internal carotid ramus. (c.) Ramulus lingualis. — This vessel is not unfrequently given off from the external carotid, in a common trunk with the facial, but more frequently below it, and between it and the superior thyroideal. It is rather more deeply seated, and takes its course forwards, upwards and inwards, above the os hyoides, to gain the tongue. In the first part of its course it is accompanied by the lingual nerve, which is rather above it ; and until it gains the posterior edge of the hyo glossus muscle, it is only covered by the skin, platysma myoides, and fascia ; it then passes above the hyo glossus muscle, by which it is separated from the lingual nerve, which takes its course upon the inferior surface of the muscle, at the anterior edge of which they again meet, and between the hyo glossus and genio hyo glossus terminate in the tongue. In this course, the lingual ramulus gives off' the four followine - ramusculi. («.) Ramusculus hyoideus — is given off' before the lingual ramus gains the upper surface of the hyo glossus muscle ; DESCRIPTIVE ANATOMY OF THE ARTERIES. 17 this ramusculus passes along the superior surface of the os hyoides, distributing itself to the muscles of the base of the tongue, and of the lower jaw. (/3.) Ramusculus dorsalis linguae — is given off from the lingual while upon the upper surface of the hyo-glossus ; it takes its course upwards and outwards, towards the base of the tongue ; and passing between the hyo-glossus and lingualis muscles, it gains the dorsum of the tongue, where it anastomoses with the opposite ramusculus, sending rami- fications backwards to supply the fauces, tonsil, and epi- glottis, anastomosing- with the ascending palatine ramusculus of the facial ramulus. (y.) Ramusculus sublingualis — is frequently substituted by the submental ramulus of the facial ; w'hen given off by the lingual it arises just at the anterior edge of the hyo- glossus muscle, and takes its course forwards between the genio-hyoideus muscles, and the sublingual gland, — sup- plying both; it then penetrates the mylo-hyoideus, and is lost upon the chin, anastomosing with the submental, the inferior dental, and the inferior coronary ramusculi. (S'.) Ramusculus raninus — seems to be a continuation of the lingual ramus, and is continued forwards to the apex of the tongue, between the lingualis and genio-hyo-glossus muscles, distributing a ramification to them, and also to the hyo-glossus and stylo-glossus muscles, as well as to the fraenum, by the side of which it runs, being there only covered by the mucous membrane of the tongue, and accompanied by a vein and a branch of the lingual nerve. The ramuli given off from the external carotid artery, posteriorly, are the occipital and posterior aural. (of.) Ramulus occipitalis — is usually separated from the external carotid, opposite to the origin of the facial or lingual ramulus, but is smaller than either of them ; it ex- tends to the posterior part of the occipital bone, where it terminates by numerous anastomosing vessels. In taking this course, it passes backwards under the posterior belly of the digastricus, sterno cleido mastoideus, trachelo mastoideus c 18 DESCRIPTIVE ANATOMY OF THE ARTERIES. muscles, and the lingual nerve, which completely hooks around it ; it crosses anterior to the internal carotid artery, jugular vein, pneumo-gastric, and spinal accessory nerves, and then rests upon the rectus capitis lateralis, being placed between the transverse process of the atlas and the occiput, being here covered by the splenius, and complexus, the latter of which muscles it frequently perforates to gain the occiput, immediately above the attachment of the obliquus superior and rectus capitis posticus major. The first ramusculi sent off from the occipital ramulus, supply the digastric and stylo-hyoideus muscles. Ramuli also pass downward along the anterior edge of the sterno cleido mastoideus, to supply the superficial cer- vical glands, and terminate by anastomosing with the su- perior thyroideal ramusculi. While the occipital ramulus is crossing the carotid artery and internal jugular vein, it sends a ramusculus meningeus upwards on the vein which passes through the foramen laeerum basis cranii, to supply the dura mater. It also sends the ramusculus auricularis to the lobe of the ear ; and when behind the traehelo mastoideus, and splenius, it supplies them both with blood. When it gains the occiput, it sends a ramification transversely above the insertion of the obliquus, and rectus superior muscles, to anastomose with the corres- ponding vessel of the opposite side, forming an arch, with its convexity upwards and concavity downwards ; from the latter, several ramifications pass downward to supply the recti and obliqui. A deep ramification passes to anastomose with the verte- bral artery ; and a long descending ramification passes upon the semispinalis colli and under surface of the complexus, to anastomose with the ramus cervicalis profundus of the subclavian artery. From the convexity, numerous ramifica- tions pass upward on the occiput to anastomose with the temporal and posterior aural, one of which passes through the mastoid foramen to supply the dura mater. (.) Ramulus profundus — which is sometimes sent off from the ramulus circumflexus internus, takes its course in a transverse direction, behind the fascia lata, and in front of the peetineus muscle, to gain the perinseum, in which it terminates, anastomosing with the ramus pudicus internus. (c.) Ramus circumflexus ilii superflcialis — is much smaller than either of the other branches ; and although pretty constant in its origin and course, is not particularly described by anatomists. Immediately after its origin it pierces the fascia lata, takes its course outwards, along the under edge of Poupart’s ligament, as far as the spinous process of the ilium ; where it divides into numerous ramuli, to supply the parietes of the abdomen, and to anastomose with the deep circumflexus ijii, gluteal, and external circum- flex rami. (d.) Ramus profundus femoris — is separated from the posterior part of the femoral artery, usually about an inch and a half below Poupart’s ligament ; and in a space midway between the pubes and trochanter minor ; from hence it passes downwards and backwards, to about the middle part of the thigh ; where perforating the aponeurosis of the adductor longus, it gains the posterior part of the thigh, and terminates in three or four muscular ramuli. In this course, the ramus profundus is first directed slightly outwards from the femoral artery, lying - on the psoas and iliaeus muscles ; it then descends in front of the insertions of the peetineus and adductor brevis, and perfo- rates the adductor longus, as before stated. It has in front of it, in the first part of its course, where it is directed outwards from the femoral artery, only the fascia lata and common integuments ; but as it descends, it is covered by the femoral artery and vein, with which it runs parallel for some distance, but much deeper seated. Five ramuli are sent off from the ramus profundus, which have distinct names ; besides others, which are of less im- portance. (a.) Ramulus circumflexus externus -is given off while DESCRIPTIVE ANATOMY OF THE ARTERIES. 89 the ramus profundus is to the outer side of the femoral artery ; it is directed transversely outwards, and is a large short vessel, passing behind the rectus and sartorius mus- cles, and crossing in front of the psoas, iliacus, and crureus, where it is divided into three sets of ramusculi. (<%.) Ramusculi ascenclentes — are three or four in number, which run upward, behind the sartorius and tensor vaginae femoris, and then between that muscle and the gluteus medius and minimus ; anastomosing with the ramusculi inferiores, of the gluteal ramus ; and terminate by supplying the neighbouring muscles. (/3.) Ramusculi transversales — are two or three in num- ber, and continue in the direction of the main ramulus, passing still farther to the outer of the crureus muscle, as far as the origin of the vastus externus muscle, where they perforate it and the insertion of the gluteus maximus ; and gain the posterior part of the thigh, below the trochanter major, where they terminate by supplying the muscles, and anastomosing with the ramulus circumflexus internus, and the gluteal and ischiatic rami. (y.) Ramusculi descendentes — are large and numerous they pass downward, between the crureus and vastus ex- ternus muscles, and extend to the outer side of the knee- joint, where they terminate by anastomosing with the arti- cular ramuli of the popliteal artery. They also supply the rectus, crureus, and vastus externus ; in their course anasto- mosing, posteriorly, with the perforating ramuli of the ramus profundus. ( b . ) Ramulus circumflexus internus — is usually larger than the preceding ramulus, and is given off below it. It takes its course backwards and inwards, between the pectineus and the tendinous insertion of the psoas and iliacus muscles ; it then continues its course around the neck of the femur, between the inferior edge of the quadratus femoris and the superior edge of the adductor magnus, where it divides into two terminating ramusculi. In this course, the ramulus gives off small ramusculi to the neighbouring muscles, the 90 DESCRIPTIVE ANATOMY OF THE ARTERIES. capsular ligament, and others anastomosing with the ramus obturatorius 5 they together supply the interior of the hip- joint. («.) Ramusculus ascendens — is separated in the space between the quadratus femoris and adductor magnus, and is covered, posteriorly, by the gluteus maximus. It then arises outwards, along the obturator externus muscle, to gain the digital cavity of the great trochanter, where it terminates by supplying the outer rotators of the thigh, and anastomosing with the gluteal and external circumflex ramuli. (/3.) Ramusculus descendens — is rather the larger of the two, and takes a transverse course downwards, dividing into two sets of ramifications ; one set passing inwards to the tuberosity of the ischium, supplying the origin of the muscles of the ham-strings ; the other passing downwards in the course of the sciatic nerve, to terminate by supplying the adductor magnus muscle, and anastomosing with the gluteal ischiatic rami, and the superior perforating ramus- culus of the ramus profundus. The frequent anastomoses of the circumflex ramuli with the gluteal, ischiatic, pudie, and obturator rami of the in- ternal iliac artery above ; and with the articular rami of the popliteal artery below, is the principal means of carrying on the circulation, in obliterations of the external iliac. (c.) Ramulus perforans primus — is sent off from the ramus profundus, opposite to the trochanter minor ; it takes its course backwards, below the tendon of the peetineus ; and passing between the adductor longus and the adductor brevis, it perforates the adductor magnus, where it terminates in numerous ramusculi. In this course, it supplies the peetineus, and adductor muscles; afterwards the gluteus maximus and biceps ; anastomosing, above, with the is- chiatic, and gluteal rami, and the circumflex ramuli of the ramus profundus ; and below, with the inferior perforating ramusculi, ( d . ) Ramulus perforans secundus — is sent off immedi- ately below the preceding ramulus, and directly perforates DESCRIPTIVE ANATOMY OF THE ARTERIES. 91 the adductor brevis, and then the adductor magnus, to gain the back part of the thigh ; where it divides into ascending ramusculi, to supply the gluteus maximus muscle, and to anastomose with the ramulus perforans primus ; and de- scending ramusculi, which supply the biceps, semi-mem- branosus, semi-tendinosus, and triceps muscles ; and to anastomose with the ramulus perforans tertius. It sends also a ramusculus nutritius into the former ; the foramen for which is directed from below upwards, and is usually found at about the junction of the upper with the middle third of the femur, in the course of the linea aspera. (e.) Ramulus perforans tertius — is the smallest of the three ramuli, and is separated much lower down than the others. It passes to the back part of the thigh, perforating the adductor mag’nus, and immediately dividing into nu- merous ramusculi, which superiorly anastomose with the other perforating ramuli, inferiorly with the articular rami of the popliteal artery ; and terminates by supplying the surrounding muscles. (e.) Ramus anastomoticus magnus — is separated from the femoral artery, just where it enters the tendinous sheath formed for it by the tendons of the triceps and vastus ex- ternus muscles. It immediately perforates this fascia, and takes its course inwards, along the vastus internus, towards the inner condyle of the femur, where it divides into nu- merous ramuli ; inferiorly, anastomosing with the articular rami of the popliteal artery, and with the recurrent branch of the anterior tibial ramus ; superiorly, anastomosing w ith the ramusculi perforantes ; and anteriorly, behind the ex- tensor tendon of the knee-joint, with the descending ramus- culi of the external circumflex ramulus. (19.) Arteria poplitea — is so termed immediately the femoral artery emerges from the fascial sheath formed by the adductor magnus and vastus internus muscles ; from this it passes obliquely downwards and outwards, to the lower edge of the popliteus muscle, where it terminates by dividing into two rami. 92 DESCRIPTIVE ANATOMY OF THE ARTERIES. It may be observed, when taking’ a general view of the course of the femoral and popliteal arteries in the thigh, that the first third of this course is anterior, the middle third internal, and the lower third posterior, to the thigh-bone. The lower third, or popliteal artery, is bounded, above, anteriorly by the femur ; in the middle, by the posterior surface of the knee-joint ; and below, by the popliteus muscle. Posteriorly, it is bounded by the popliteal vein, which is rather external to it, and by the sciatic nerve, which is still more superficial and external to it ; above, by the semi-membranosus muscle; and below, by the heads of the gastrocnemii. It is here also crossed by the posterior tibial nerve. It has to its outer side, the biceps, external head of the gastrocnemius, and origin of the plantaris muscle : the gastrocnemius forms its internal boundary. In this course, the popliteal artery sends off numerous small muscular branches above, to supply the muscles in the lower and back part of the thigh ; and to anastomose with the perfo- rating ramuli of the ramus profundus. These vessels have, however, no distinct names. Besides the above, the pop- liteal artery gives off five rami, which are more important, and supply the knee-joint ; and then ultimately terminate, by sending off inferior muscular branches. (a.) Ramus articularis superior internus. — The precise point at which this ramus is separated from the popliteal, is very various, and may occur at any part of the distance from where it penetrates the adductor magnus, to the internal condyle. It reaches its course inwards, behind the vastus externus and adductor muscles, close upon the bone; passing forwards, above the internal condyle of the femur ; and anastomoses with the ramus anastomoticus magnus, and the ramus articularis externus. It also sends some ramuli downwards, in the direction of the tendon of the adductor magnus, to anastomose upon the inner side of the knee-joint with the inferior articular ramus. (b.) Ramus articularis superior externus — arises from the outer side of the popliteal artery, and proceeds immedi- DESCRIPTIVE ANATOMY OF THE ARTERIES. 93 ately outwards, close to the bone, behind the tendon of the biceps, winding 1 around the femur above the external con- dyle ; and having 1 g-ained the fore part of the femur, it divides into two ramuli. The superior, or deep-seated, takes its course upwards, to supply the periosteum and muscles on the fore part of the thigh, and anastomoses with the muscular rami of the femoral artery. The superficial and anterior ramulus passes forwards, above the external condyle of the femur, through the vastus externus muscle, to gain the patella, upon which it anastomoses with the internal superior articular ramus. (c.) Ramus articularius medius, vel azygos — is much smaller than the two preceding rami, and passes forwards through the posterior ligament of Winslow, to gain the interior of the knee-joint, w r here it divides into two ramuli ; one of which remains external to the synovial membrane, and supplies the adeps and cellular membrane at the back part of the joint; the other distributes itself to the synovial membrane, the crucial ligaments, and the interior parts of the joint. (d.) Ramus articularis inferior internus — arises from the outer side of the popliteal artery, immediately above the popliteus muscle, and takes its course inwards in front of the posterior tibial nerve and gastrocnemius externus mus- cle, between them and the head of the tibia, around which it runs, behind the internal lateral ligament of the knee-joint, and the tendons of the sartorius, gracilis, and semi-tendinosus muscles ; having reached the fore part of the tibia, it runs up the inner edge of the ligamentum patellae, to gain the bone ; and upon it anastomoses with the superior inner articular, and inferior external articular rami. (e), Ramus articularis inferior externus — arises from the outer side of the popliteal artery, below the knee-joint, but above the head of the fibula. It takes its course outwards, along the convexity of the external semilunar cartilage ; covered, in its course, by the gastrocnemius externus, plan- taris, external ligament of the knee-joint, and tendon of the 94 DESCRIPTIVE ANATOMY OF THE ARTERIES. biceps ; then having- g-ained the fore part of the tibia, it runs along- the outer edge of the ligamentum patellae to gain the bone, where it anastomoses with the last-described ramus. In this course, it also supplies ramuli to the muscles, and anastomoses with the superior, external, and middle articular rami. The inferior muscular branches supply the gastrocnemii and solei, and anastomose with the posterior and anterior tibial rami — these are sometimes called the surales. The popliteal artery, after having given olf the preceding vessels, continues downwards, behind and to the lower edge of the popliteus muscle, where it divides into the posterior and anterior tibial rami. (f.) Ramus tibialis posticus — is the larger of the two terminating branches of the popliteal artery, from which it separates at the superior extremity of the soleus muscle; anterior to which, it passes downwards upon the posterior surface of the flexor longus digitorum, and tibialis posticus muscles, to the malleolus internus ; passing behind which, it gains the sole of the foot ; and immediately upon the inner side of the abductor pollicis, it divides into its two terminat- ing- plantar ramuli. In its course downwards upon the leg, it passes in an oblique direction, from above to below and from without to within ; — in the upper and middle third of the leg, being covered by the g-astrocnemius, and soleus muscles ; but in the lower third, it is only covered by the skin, superficial and deep fascia. When first given off from the popliteal artery, it lies upon the tibialis posticus, then upon the flexor longus digitorum ; and below, upon the tibia, and internal lateral ligament of the ankle-joint ; separated, however, from the superficial layer of muscles, by the deep fascia of the leg. In the above course, it sends off only one ramulus of import- ance ; but it supplies small ramuli to the popliteus, soleus, and gastrocnemii muscles ; and an inch below the popliteus muscle, gives off — (a.) Ramulus peronceus — which is variable in its size, DESCRIPTIVE ANATOMY OF THE ARTERIES. 95 sometimes being 1 equal to the posterior tibial in its dimen- sions, at others being very small, or even entirely wanting. It directs itself obliquely downw'ards and outwards, along the inner edge of the fibula, nearly to the malleolus externus, where it forms two terminating ramusculi ; above, it is covered by the soleus, separated from it, however, by the deep fascia of the leg ; below, by the flexor longus pollicis : at first it rests upon the tibialis posticus, through the fibres of which it passes, and then lies on the interosseous liga- ment. In this course, it furnishes small posterior ramusculi to the muscles of the calf of the leg, and anterior ones to the deep layer of muscles ; after which it divides into — (a.) Ramus cuius per onceus posterior . — This appears tobe a continuation of the peroneal ramulus, and passes downwards behind the malleolus externus, distributing ramifications to the muscles in its course : when it has gained the posterior part of the ankle-joint, it sends a posterior malleolar rami- fication to anastomose with the posterior tibial ramulus, and to supply the adeps and cellular membrane between the tendo Achillis and posterior part of the ankle-joint. The ramuseulus peronaeus posterior, still continues behind the malleolus externus, and reaches the outer side of the foot, where it anastomoses with the external plantar ramulus; and in front of the tarsus, with ramuli from the tibialis anticus. (/3.) Ramuseulus peronaeus anterior — perforates the in- terosseous ligament, to gain the fore part of the leg, passes under the peronaeus tertius muscle, descends in front of the inferior tibio-fibular articulation, and passes to anastomose with the ramus tibialis anticus ; and together, supply the anterior malleolar ramification, and the ligaments of the tarsus. This ramuseulus is, in some eases, very large, and seems destined to perform the office of. the anterior tibial ramus, which, in such instances, is proportionably small. After the ramus tibialis posticus has given off the ramulus peronseus, in its passage down the back part of the leg, it 96 DESCRIPTIVE ANATOMY OF THE ARTERIES. gives off rarauli to the muscles, and a nutritious one to the tibia, which passes into the bone through a foramen which is directed from above downwards, and is situated about the centre of the bone. When the posterior tibial ramus has reached the inner side of the malleolus internus, it sends off small ramuli to supply the periosteum of the bone, and muscles proper to the great toe ; and usually between the origins of the abductor poilicis pedis, it divides into its two terminating plantar ramuli. (6.) Ramulus plantaris internus — is smaller than the external terminating ramulus, and passes forwards along the inner edge of the foot, upon the upper surface of the abductor poilicis muscle, and extends as far as the base of the first phalanx of the great toe. In this course, it sends off ramusculi to supply the ankle-joint, the muscles of the great toe, and the flexor brevis digitorum ; also ramusculi which wind around the inner side of the foot upon the tarsus and metatarsus, to anastomose with the ramus tibialis an- ticus, and terminate by supplying the great toe. (c.) Ramulus plantaris externus — seems like a continu- ation of the posterior tibial ramus. It immediately separates itself from the internal ramulus, and directs itself outwards and forwards ; first resting upon the upper surface of the abductor poilicis, then upon the flexor brevis digitorum com- munis, being between it and the musculus accessorius ; it still continues outwards to the metatarsal bone of the fifth toe, from the base of which it runs between the flexor digitorum brevis, and abductor minimi digiti, where it is straight in its course, and superficially placed ; it then changes its direction, passes inwards inferior to the tendons of the flexor longus digitorum and lumbricales, and is placed upon the under surface of the interossei muscles: having arrived in the interspace between the anterior extremities of the metatarsal bones of the first and second toes, it ter- minates by anastomosing with the deep communicating ramulus of the ramus tibialis anticus. In this course, the external plantar ramus forms the great plantar arch, the DESCRIPTIVE ANATOMY OF THE ARTERIES. 97 convexity of which looks forwards and outwards, and the concavity backwards and inwards. The ramulus plantaris externus, before it begins to form the plantar arch, sends off numerous ramusculi to supply the muscles of the sole of the foot, and to anastomose with the ramusculus peronseus posterior, and internal plantar ramulus. From the arch itself, ramusculi are also distributed : from the concavity the — («.) Ramusculi perforantes — which pass to the interossii muscles, and anastomose on the dorsum of the foot, with the anterior tibial ramus ; and from the convexity the — (/3.) Ramusculi cligitales . — The first of these arises from opposite the metatarsal bone of the little toe, passes for- wards between it and the muscles proper to the toe, proceeds forwards to the extreme phalanx along- its outer side, and then anastomoses at the tip of the toe, with the correspond- ing ramusculus from the opposite side. The second digital ramusculus, takes a course between the metatarsal bones of the fourth and fifth toes ; and having passed forwards to the cleft between the two, it re- ceives a metatarsal ramusculus from the anterior tibial ramus, and immediately after it divides into two ramifications — one of which passes along the tibial side of the little toe, and the other along the fibular side of the fourth toe. The third and fourth digital ramifications are distributed precisely in a similar manner ; and like the digital ramifi- cations on the fingers, are accompanied with corresponding filaments of nerves. (g.) Ramus tibialis anticus — immediately after it is sepa- rated from the popliteal artery, is directed forwards, through the fibres of the tibialis posticus muscles and the upper hiatus of the interosseous ligament, when it is placed in the foTe part of the leg, upon the anterior surface of the inter- osseous ligament, along which it proceeds downwards ; and passing behind the ligamentum annulare, gains the dorsum of the foot, continues to the cleft between the metatarsal bones of the great toe, and the toe next to it, and terminates H 98 DESCRIPTIVE ANATOMY OF THE ARTERIES. by anastomosing- with the ramulus plantaris externus. A line drawn from the head of the fibula to the base of the metatarsal bone of the great toe, will be parallel to the course of this ramus in its whole extent. In this course, before it passes throug-h the interosseous hiatus, it is placed between the fibres of the tibialis posticus and the flexor long-us dig-itorum muscles, to both of which it sends off“ ramuli. When it has reached the front part of the leg-, in the four upper fifths of its extent, it rests upon the interosseous lig-ament, but in the lower fifth, upon the tibia. Anteriorly, above, it is covered by the tibialis anticus, and extensor communis dig-itorum ; and below, by the extensor proprius pollicis; it is bounded upon its inner side, in its whole course, by the tibialis anticus and tibia ; and on its outer side, above, by the extensor digitorum communis, and below, by the extensor proprius pollicis; being accompanied by a nerve, which does not however pass through the in- terosseous hiatus with it, but winds around the head of the fibula. While upon the leg, it sends off three ramuli — (a.) Ramulus recurrens — is separated from the ramus tibialis anticus, immediately it has perforated the interosseous hiatus ; takes its course upwards and Awards, through the substance of the tibialis anticus muscle, and is distributed to the inner side, and fore part of the knee-joint, where it anastomoses with the inferior articular rami, from the pop- liteal artery. The ramus tibialis anticus, in its course downwards to the ankle-joint, distributes numerous ramuli to the neighbouring muscles; but within one or two inches of the ankle-joint, it sends off — (6.) Ramulus malleolus internus — which passes trans- versely inwards, between the tibialis anticus tendon and the tibia, to reach the malleolus internus, where it divides into numerous ramusculi to supply the ankle-joint, and to anas- tomose with the ramus tibialis posticus. DESCRIPTIVE ANATOMY OF THE ARTERIES. 99 (c.) Hamulus malleolus externus — usually arises oppo- site the last-described, but sometimes lower down, and takes its course outwards upon the fibula, behind the tendons of the extensor communis digitorum, and peronseus tertius ; in this part of its course anastomosing- with the ramusculus peronseus anterior, and supplying- the anterior ligament of the inferior tibio-fibular articulation. It still continues out- wards, gains the malleolus externus, divides into numerous ramifications, which anastomose posteriorly with the ramus- culus peronaeus posterior, and inferiorly are lost upon the dorsum of the foot — anastomosing with the ramulus plan- taris externus. The ramus tibialis anticus now proceeds over the tarsus, on the fibular side of the tendon of the ex- tensor proprius pollieis ; and having gained the dorsum of the foot, proceeds forwards to its termination. In front of the ankle-joint, and while crossing the os naviculare, this ramus gives off — (c/.) Ramulus tar sails. — This takes its course outwards, under the tendons of the extensor brevis digitorum com- munis, and the tendon of the peronaeus brevis ; and ter- minates by supplying the muscles proper to the little toe, and by anastomosing with the external plantar ramulus. The ramus tibialis anticus, having reached the metatarsus, sends off — (.) Ramuli n. profundi — divide themselves into an ex- ternal and an internal set ; they descend outwards, anterior to the iliacus muscle, and behind the sartorius and rectus, separating into numerous filaments that are distributed to the rectus, vastus externus, sartorius, and tensor vaginae femoris muscles. The internal set are distributed to the vastus in- ternus, pectineus, and triceps adductor femoris muscles. It sends off also — (<%.) Ramusculus n. saphenus — usually accompanies the femoral artery within the sheath, as far as the tendinous canal of the adductor magnus muscle; this ramusculus then leaves the artery, passes to the popliteal region, and then passing downwards between the sartorius and gracilis, and behind the tendon of the sartorius, about two inches below the head of the tibia, penetrates the aponeurosis, and be- coming sub-cutaneous, accompanies the saphena major vein as far as the great toe, distributing cutaneous filaments in its course. (d.) Ramus n. obturatorius — is smaller than the anterior crural, and arises from the second, third, and fourth pairs of lumbar nerves ; it passes downwards and inwards, along the inner edge of the psoas muscle, in the direction of the linea ilio pectinea, accompanied by the ramus arteriosus obturatorius, and gains the obturator interims muscle, which fills up the obturator foramen ; it sends off a ramusculus which is distributed to that muscle and to the levator ani ; it then passes through the foramen, reaches the upper and inner part of the thigh, and behind the adductor femoris muscle divides into an anterior and a posterior ramulus. (a.) Ramulus n. anterior — passes forwards between the adductor muscles, which it supplies, as well as the gracilis, and sends off cutaneous filaments that pierce the fascia OF THE SPINAL NERVES. 275 lata, and unite with filaments of the ramus nervosus cru- ralis. (6.) Ramuli n. posteriores — pass backwards to supply principally the adductor magnus muscle, giving filaments also to the obturator externus, and uniting with the ramus n. sciaticus. (e.) Ramus n. sacro lumbalis — is formed by filaments from the anterior branches of the fourth and fifth pairs of lumbar nerves, which having united with each other, pass downwards into the pelvis, in front of the sacrum, to be connected with the sacral nerves, which ujiite with it to form the sciatic plexus ; previous to which, however, the ramus sacro lumbalis sends off — (a.) Ramulus n. glutceus superior. — The filaments of this branch may be traced from the fourth and fifth lumbar pairs, or may be said to arise from the sacro-lumbar plexus ; im- mediately it is formed, it passes out of the ischiatic notch above the pyramidal muscle, and divides into ramusculi which take the course of the ramulus arteriosus glutseus profundus, and supply the glutceus medius and minimus muscles. Nervi Sacrales, Consist of six pairs, sometimes however of only five ; they arise from the spinal marrow by two sets of filaments, similar to the other spinal nerves, and form the termination of the cauda equina. The ganglia formed by their posterior roots are placed within the sacral canal ; the six pair of sacral nerves pass through the anterior sacral foramina, and then divide into posterior and anterior branches. (27.) Nervi sacrales primi. (a.) Ramus n. posterior — is a very small branch, and immediately it has passed through the sacral foramen, it unites with the second pair of sacral nerves, and they together form numerous filaments that supply the sacro-spinalis mus- cle, and terminates in the glutseus maximus, and integuments of the glutaeal region. (b.) Ramus n. anterior — is considerably larger than the t 2 276 DESCRIPTIVE ANATOMY preceding 1 , and unites with the sacral ganglia of the sympa- thetic nerve, and then passing outwards terminates by as- sisting in forming the sciatic plexus. (28 to 30.) Nervi sacrales — 2nd, 3rd, 4th. (a.) Rami n. posteriores — of all these nerves are alike in passing through their corresponding foramina, uniting with each other, and in being distributed to the muscles and in- teguments of the nates, hip, and margin of the anus ; they increase from the first to the fourth, and diminish then to the sixth. (b.) Rami n. anteriores — are alike in being united with the sacral ganglia of the sympathetic nerve, and in entering- into the composition of the sciatic plexus ; they diminish in volume from above downwards. (31, 32.) Nervi sacrales — 5th, 6th. (a.) Rami n. posteriores — are smaller than the posterior branches of the other nerves ; they communicate with the fourth pair, and are lost by supplying the parts about the anus. (b.) Rami n. anteriores. — That of the fifth passes through a foramen common to the sacrum and os coccygis ; that of the sixth, if it be present, through a notch in the latter bone. They unite with each other, with the fourth, and with the sacral ganglia of the sympathetic, and supply the coccvgeus, levator and sphincter ani muscles ; and assist in forming the hypogastric plexus. Plexus Sciaticus, Is formed by the anterior branches of the fifth lumbar, and of the four upper pairs of sacral nerves, which unite to produce a large nerve, termed the nervus ischiaclicus. This plexus is situated, deeply seated, in the lateral region of the pelvis, resting upon the pyramidal muscle, and being covered by the iliac vessels, and viscera of the pelvis ; it furnishes numerous rami, which may be distinguished by their distribution into an anterior and posterior set ; the ante- rior supplying the viscera within the pelvis, while the pos- terior set principally pass out of the pelvis. OF THE SPINAL NERVES. 277 (a.) Rami n. hcemorrhoidales — are small filaments, which take their origin from the anterior part of the plexus, and immediately penetrate the posterior parietes of the rectum, and then divide into ascending and descending ramuli — the former running upwards towards the sigmoid flexion of the colon, the latter to the sphincter and verge of the anus, ac- companied by the arterial ramusculi. (b.) Rami n. vesicales — are variable in number, are fre- quently united to the last-described rami, passing over the sides of the rectum, they gain the posterior part of the bladder to be distributed to its muscles, and mucous membrane ; some of these filaments pass to supply the organs of gene- ration. (c.) Rami n. vaginales, et uterini — arise from the sciatic plexus in common with the last described rami, pass around the rectum, then separate from the vesical nerves, and are distributed to the lateral regions of the vagina, and its mucous membrane ; the superior filaments are distributed to the uterus. (d.) Ramus n. glutceus inferior — arises from the posterior part of the sciatic plexus, and from the second and third pairs of sacral nerves, passes out of the pelvis through the sciatic notch, below the pyriform muscle, and then divides into three principal ramuli. (a.) Ramulus n. glutceus meclius — ascends and ramifies upon the superior part of the under surface of the glutaeus maximus muscle, taking the course of the ramulus arteriosus glutaeus superficialis ; some of its ramusculi also descend, penetrate the substance of the muscle, in which they are finally lost. ( b .) Ramulus n. sciaticus , vel pudendalis — descends downwards and inwards, then turns upwards under the tube- rosity of the ischium, when it divides into numerous filaments to supply the inferior part of the glutaeus maximus, the in- teguments upon the inner, and superior part of the thigh, and of the perineum and penis. (e.) Ramulus n. cruralis — is the largest of the three. 278 DESCRIPTIVE ANATOMY passes in front of the gluteeus maximus, then becomes sub- cutaneous, descends in the back part of the thigh, and expends itself by distributing filaments to the skin which covers the back part of the leg. (d.) Ramus n. pudicus internus — arises from the third and fourth sacral nerves, and from the sacral plexus ; it is connected above, with the inferior gluteal nerve, and passes out of the pelvis with it through the ischiatic notch, below the pyriform muscle ; it then re-enters the pelvis by the lesser sciatic notch, between the two sacro-sciatie ligaments, accompanying the ramus arteriosus pudicus, and divides into two ramuli. (a.) Ramulus n. inferior — takes its course forwards, along the inner side of the tuberosity of the ischium, sending filaments to the levator and sphincter ani muscles, and skin and fat about the anus ; it still proceeds forwards and up- wards, along the perineum, between the erector penis, and accelerator urinae muscles, to both of which it sends fila- ments, and is ultimately lost by supplying the scrotum. ( bf Ramulus n. superior — leaves the inferior branch, passing upwards from the ramus of the ischium to that of the pubes, to gain the symphysis, from whence it passes between tbe pubes and the corresponding crus of the penis, to gain the upper surface of that organ, along which it passes as far as the corona glandis, where it terminates by sending filaments to the skin of the prepuce. In this course it distributes filaments to the obturator muscle, and erector penis, as well as to the skin. In the female, the inferior ramulus is much larger than in the male ; it sends off filaments to the perineum, enters the labium externum, distributes filaments to it, to the constrictor vaginae, to the erector clitoridis, and is ultimately lost on the mons veneris. The superior ramulus, which is comparatively small, terminates on the clitoris, much in the same manner as the distribution on the penis of the male. (e.) Ramus n. ischiadicus — is the principal branch of the sacral plexus, arising from all the nerves which enter into its OF THE SPINAL NERVES. 279 formation, namely, the last lumbar, and four superior sacral ; it passes out of the pelvis through the sciatic notch, below the pyramidalis, and above the superior geminis muscle ; it then descends along- the back of the thigh, lying upon the posterior surface of the geminus superior, obturator internus, and quadratus femoris muscles ; it is then placed a little to the inner side of the centre of the space between the tro- chanter major, and tuberosity of the ischium; from this point it descends along the posterior part of the thigh, anterior to the origins of the muscles of the ham-strings, and lying upon the adductor magnus muscle, as far as the popliteal region, where it divides into two principal terminating ra- muli. In its course from the pelvis to the ham, it sends off- la.) Ramuli n. musculares — to the obturator internus, ge- mini, and quadratus muscles. (bi) Ramulus communicans — which forms a union with the inferior gluteal ramus. (c.) Ramuli musculares inferiores — to supply the biceps, semi-tendinosus, semi-membranosus, and triceps muscles. (cZ.) Ramulus n. culaneus superior — is usually separated from the ischiadic ramus, near to its exit from the pelvis ; it almost immediately divides into two ramusculi, one of which is distributed to the integuments about the tuberosity of the ischium and nates, while the other passes downwards upon the posterior surface of the thigh, distributing filaments to the skin as far as the calf of the leg. ( e .) Ramulus n. peroneus, vel popliteus externus — takes its course downwards, along the inner edge of the biceps muscle, as far as the head of the fibula ; it then passes for- wards, through the peroneus longus muscle, winds around the neck of the fibula, and then divides into two terminating ramusculi ; previous to which, it sends off— (a.) Ramusculus n. cutaneus. — This is sometimes dis- tributed in two or three filaments, which descend along the outer and back part of the leg, between the gastrocnemius externus muscle and the skin, it unites with the cutaneous 280 DESCRIPTIVE ANATOMY filaments of the posterior tibial ramusculus, together sup- plying the skin in their passage downwards, to the malleolus externus, behind which they pass to terminate by dorsal fila- ments to the fourth and fifth toes, and filaments to the integuments of the outer side of the foot. (i3.) Ramusculus n. superjicialis, vel musculo-cutaneus — is separated from the ramulus n. peroneus on the neck of the fibula, from which it passes downwards and forwards, between the peroneus longus, and brevis muscles, to both of which, as well as to the extensor longus dig'itorum, it sends filaments ; and about the middle of the leg, it perforates the fascia, becomes sub-cutaneous, passing down- wards towards the outer malleolus, a little above which it divides into an internal and external dorsal ramification ; the internal is distributed to the integuments on the dorsum of the foot, and on the first and second toes, communicating with the ramusculus n. saphenus, and with the ramusculus n. tibialis anticus ; the external supplies the third, and part of the fourth toe, and communicates with the ramusculus n. cuta- neus of the peroneal ramulus. (7.) Ramusculus n. profundus, vel tibialis anterior — passes through the fibres of the extensor digitorum com- munis, to gain the anterior surface of the interosseous liga- ment, where it meets with the ramus arteriosus tibialis anticus, in front of which it descends, they being placed first between the tibialis anticus, and extensor longus digitorum, and then between the tibialis anticus and extensor longus pol- licis muscles; they then pass behind the ligamentum annulare, to ffain the dorsum of the foot, where the nerve divides into an inner and an outer filament. In this course the ramusculus n. profundus supplies the muscles placed between the tibia and fibula, and one filament rises on the fore part of the knee-joint, and accompanies the ramulus a. recurrens. The inner dorsal filament continues along- the inner edge of the extensor brevis digitorum, which it supplies, as well as the inner interossei muscles, and passing along the space between the metatarsal bones of the first two toes, it dips OF THE SPINAL NERVES. 281 down to reach the sole of the foot, accompanying- the ramulus a. communicans, and unites with the inner plantar nervous ramification. The outer dorsal filament passes to the outer side of the dorsum of the foot, where it is distributed to the outer part of the extensor brevis digitorum communis, and the outer interossei muscles. (/!) Ramulus n. tibialis posticus, vel popliteus interims — is the larger division of the sciatic nerve, and descends nearly vertically through the popliteal region, on the outer side of the semi-membranosus muscle, and behind and to the outer side of the popliteal vessels ; it then passes behind the knee-joint, between the two heads of the gastrocnemius externus muscle, and then between the gastrocnemius and soleus muscles ; when it gains the leg, it is placed immedi- ately behind the tibia, from which situation it receives the name of the tibial nerve. It continues its course downwards, in front of the soleus muscle, and behind the tibialis posticus and flexor longus digitorum, and on the outer side of the ramus a. tibialis posticus. Towards the lower part of the leg, it becomes comparatively superficial, is placed on the inner side of the tendo Aehillis dives into the sulcus of the os calcis, between the heel and the inner malleolus, and divides into internal and external plantar ramusculi. In this course, the ramulus tibialis posticus sends off" — (a.) Ramusculus n. cutaneus tibialis, vel saphenus ex- ternus. — This ramusculus is usually given off immediately above the external condyle of the femur ; it descends along the posterior part of the leg, accompanying the saphena minor venous ramulus, and just as it gains the outer side of the tendo Aehillis, it becomes united with the cutaneous ramusculus of the ramulus n. peroneus — the two forming a considerable ramusculus ; after this union, ramifications are distributed beneath the tendo Aehillis, supplying its mem- branous sheath, and the adjacent parts ; the ramusculus then passes behind the external malleolus, takes its course along the superior and external part of the foot, as far as 282 DESCRIPTIVE ANATOMY the metatarsal bone of the little toe, where it divides into numerous filaments to supply the muscles and integument of the dorsum of the foot, and terminates by distributing digital filaments to the two outer toes. In the popliteal region, the ramulus tibialis posticus sends off muscular filaments to the gastrocnemii, soleus, popliteus, plantaris, and tibialis posticus muscles, as well as to the knee-joint; two or three filaments pass through the inter- osseous ligament, to supply the muscles on its fore part; and just above the malleolus internus, and before its ultimate division, it gives off cutaneous filaments to supply the skin about the inner side of the ankle. (/3.) Ramusculus n. plantaris internus — is given off be- hind the malleolus internus, and posterior to the ramus a. tibialis posticus, which vessel does not divide into its plantar ramuli so soon as the nerve. The ramusculus n. passes forwards along the inner side of the tarsus, above the ab- ductor pollicis muscle, and by the side of the tendon of the flexor longus pollicis, as far as the base of the metatarsal bone of the great toe, where it separates into four digital filaments. In this course, it sends off filaments to the neighbouring muscles. Its first digital filament, takes a course along the tibial side of the great toe; the second filament, sub-divides in the space between the metatarsal bone of the great toe and the toe next to it, and supplies the fibula side of the great toe, and the tibial side of the toe next to it ; the third filament, enters between the second and third metatarsal bones, supplies the lumbricalis muscle, sub-divides into two, which pass to the second and third toes ; the fourth fila- ment, is in a like manner situated between the third and fourth metatarsal bones, furnishes filaments to the corres- ponding lumbricalis muscle, and sub-dividing supplies the outer side of the third, and the inner side of the fourth toe. (7.) Ramusculus n. plantaris externus — is the smaller division of the posterior tibial ramulus ; it takes its course forwards and outwards, above the flexor brevis digitorum OF THE SPINAL NERVES. 283 muscle, to the posterior extremity of the metatarsal bone of the fifth toe, where it divides into a superficial and a deep- seated filament. The superficial filament, divides into digital filaments to supply the outer side of the fourth, and both sides of the little toe, as well as the corresponding lumbri- cales muscles. The deep-seated filament, passes obliquely inwards, between the interossei and adductor muscle of the great toe, and is lost by supplying the deep muscles of the plantar region. LECTURE XXXV. DESCRIPTIVE ANATOMY OF THE SYMPATHETIC NERVE. This nerve is termed the sympathetic, from its forming- such frequent and general communication with all the other nerves of the organismus. It differs from the cerebral and spinal nerves, from its apparent origin from ganglia, which are considered by some physiologists as so many centres of nervous influence, or little brains ; and which are placed within the cavities of the trunk, and not found any where in the extremities, or exterior of the body. The ganglia are reddish grey bodies, destitute of any envelope, of different forms, and having nervous cords, which proceed from their circumference either to be connected with other ganglia, or nerves, or to be lost in some particular organ. The cords which leave these ganglia, pass to some other, and are either to be considered as the trunk of the sympathetic nerve, or perhaps as mere cords of communi- cation between the ganglia themselves : in the first case, it premises the nervous cord as the most important part of the sympathetic nervous system, and the ganglia as merely accessory to the function ; while in the second case, the ganglia seem to be the important organs, and the cords as mere media of communication : but which ever view' we may take of the comparative importance of these parts, it is the best and easiest mode to gain a just knowledge of the system, to describe the ganglia as they are placed in the head, neck, chest, and abdomen ; and to describe their cords of junction, as mere nervous communications. OF THE SYMPATHETIC NERVES. 285 Ganglia Capitis. The first ganglion which is usually described, is the oph- thalmic or lenticular ganglion, situated within the orbit ; but Ribes, a German anatomist, has described some filaments of the sympathetic nerve continuing in the course of the internal carotid artery, as high as its division into its anterior cerebral branches ; and that there the filament on one side unites with that of the opposite, and just over the commu- nicating branch of the two anterior cerebral arterial ramuli, form a little ganglion, which has been named the ganglion of Ribes. (1.) Ganglion lenticulare, vel ophthalmicum — is placed on the outer side of the optic nerve, close to its entrance into the orbit ; it is small, somewhat oblong, presenting a convex external surface, opposed to the abductor oculi muscle, and a concave internal surface, connected with the optic nerve ; it is surrounded by a considerable quantity of semi-fluid fat : the posterior edge of this ganglion, either receives, or sends off two filaments, one of which passes to unite with the nasal ramulus of the first division of the fifth pair, and the other from its posterior and inferior edge to be connected with the outer ramulus of the third pair of nerves. The anterior edge of the ganglion supplies two sets of rami, one placed above the other, which are destined to supply the interior of the eye — these are called ciliary nerves ; they are very delicate, and of a reddish color. (a.) Rami ciliares s. superior es — composed of five or six filaments, proceed from the upper edge of the ganglion, above the optic nerve, accompanied by filaments from the nasal ramulus of the first division of the fifth, to the ball of the eye. (b.) Rami ciliares s. inferiores — composed of from eight to ten filaments, are placed below and to the outer side of the optic nerve, but frequently unite with each other so as to surround it ; arriving at the posterior part of the globe of the eye, all the ciliary filaments traverse the sclerotic coat, pass 286 DESCRIPTIVE ANATOMY forwards between it and the choroid, running parallel with each other, frequently communicating, and reach the ciliary circle or ligament, where each filament divides into two, which are lost, partly in the substance of the ligament, and partly in the iris. This ciliary circle or ligament, has been considered by some anatomists, as a true ganglion of the sympathetic nerve. (2.) The spheno-palatine, or ganglion of Meckel — is placed within the spheno-maxillary fossa, below the second division of the fifth pair of nerves ; it is small, irregular in its form, having a convexity on its outer surface, and being flattened internally towards the lateral nasal, or spheno- palatine foramen. From this ganglion, rami are sent off 1 superiorly, inferiorly, internally, and posteriorly. (a.) Rami s. superiores — from the upper part, two or three rami pass upwards to be connected with the second division of the fifth pair of nerves. The filaments given off inferiorly, are all distributed to the palate, and are termed the palatine filaments ; they are three in number. The first is termed — (a.) Ramulus s. palatmus magnus. — It enters the pos- terior palatine canal, first giving off a small nasal filament, which passes into the nose, and is distributed in the space between the tw 7 o turbinated bones. The great palatine nerve, continues its course along the palato-maxillary foramen, sending filaments into the nasal fossae, and is lost by sup- plying the palate, and gums of the upper jaw. ( b . ) Ramuli s. palatini medii — descends along the pos- terior part of the palato-maxillary foramen, and comes out of the canal through a foramen which opens in the fossa between the two pterygoid plates, and then divides to be distributed to the soft palate. (c.) Ramuli s. palatini parvi — is still posterior to the last, and like it, is distributed to the soft palate, the uvula, and the tonsil. (b.) Rami s. interni — are three or four in number, and are OF THE SYMPATHETIC NERVES. 28T destined to supply the pharynx, and the nose. They are termed the spheno-palatine, or lateral nasal nerves, and pass through the spheno-palatine foramen to gain the nasal fossa, which they enter close to the posterior extremity of the su- perior turbinated bone, and here spread out upon the pituitary- membrane of the superior and middle meatus of the nose, sending also filaments backwards, to supply the pharynx and palate. There is one filament in particular, termed the — (a.) Hamulus s. naso-palatinus — which takes its course from the superior part of the septum of the nose, descending obliquely forwards behind the pituitary membrane, to the opening of the anterior palatine canal of its own side, which it enters, and passing downwards towards the mouth, reaches the foramen incisivum, produced by the union of the canal from each nostril ; and here the naso-palatine ramulus of the one side unites with that of the other, and produces a little enlargement, which has been termed by Cloquet, the spheno- palatine ganglion. This ganglion receives a filament from the great palatine ramulus. (c.) Ramulus s. posterior, vel viclianus, vel pterygoideus— directs itself horizontally backwards, through the pterygoid foramen or canal, emerging from which, it divides into two ramuli, first sending off within the pterygoid foramen fila- ments to the septum of the nasal fossae, and to the pharynx. (a.) Ramulus s. inferior, vel carotideus — passes imme- diately in the carotid canal, applying itself upon the coats of the carotid artery, and uniting with the filament which is connected with the sixth pair of nerves ; it descends to be connected with the superior cervical ganglion of the sympathetic ; forming, therefore, a medium of communica- tion between the spheno-palatine, the cavernous, and the superior cervical ganglia. ( b . ) Ramulus s. superior, vel innominatus — passes up- wards, penetrates the fibro-cartilaginous substance, which closes the foramen lacerum basis cranii anterius, and enters the skull close to the anterior surface of the petrous portion 288 DESCRIPTIVE ANATOMY of the temporal bone, where it enters a groove, which con- ducts it to a foramen termed the foramen innominatum, and which leads to the canal of Fallopius ; here it becomes applied to the trunk of the. portio dura, with which it passes to a point, at the posterior and inner wall of the cavity of the tympanum, immediately underneath the base of the pyramid, where a foramen is placed, through which it passes; it then traverses the tympanum from behind forwards, first under the incus, then between its long crus and the upper part of the handle of the malleus, with which it is in con- tact ; it then descends forwards, and passes out of the glenoid fissure, continuing its course downwards and in- wards to be connected with the ramusculus lingualis of the third division of the fifth pair, and terminating by forming a kind of ganglion around the submaxillary gland, which has been termed the submaxillary ganglion. This filament, therefore, forms a communication between the spheno- palatine, and submaxillary ganglia, and is termed the chorda tympani. In its course, it sends olf a filament while within the cavity of the tympanum, which passes to the promontory and unites with a filament from the internal carotid filament. Besides the ganglia we have described, there is generally another, situated within the skull, within the cavernous sinus, termed the cavernous ganglion • it is very small, of a reddish grey color, placed to the outer side of the internal carotid artery, and sends filaments to be connected with the sixth, the first division of the fifth, the third pair of nerves, and the lenticular ganglion ; and also inferior filaments, which are connected with the superior cervical, and Meckel’s ganglion. Ganglia Cervicales. The ganglia which are found upon the neck, are three in number, and are named according to their relative position, with respect to each other. The ganglion cervicale superius — is of an oval form, of a reddish color, and is placed upon the rectus capitis anticus major, behind the carotid artery, and jugular vein ; reaching OF THE SYMPATHETIC NERVES. 289 from the transverse process of the first to that of the third, and sometimes the fourth cervical vertebra, or even lower. Its form and size, are variable ; it gives off rami, in the fol- lowing- directions, upwards, downwards, outwards, inwards, and forwards. (a.) Rami s. superior es .— These are two in number, they ascend to enter the carotid canal, and upon the surface of the internal carotid artery, form divisions, so frequently anastomosing- with each other, as to produce a distinct plexus ; from this plexus a ramulus is connected with the ramulus inferior of the ramus s. vidianus ; two or three other rarnuli enter the cavernous sinus, and become connected with the sixth pair of nerves, and with the cavernous g'anglion, as well as w r ith the first division of the fifth. There are other small ramuli, which pass to the pituitary shaft ; also some delicate ramuli pass into the cavity af the tympanum from the carotid canal, where on the promontory they unite with the superior ramulus of the vidian ramus, and with a filament of the g-losso-pharyngeal nerve, which latter gains the tym- panum through a foramen close to the stylo-mastoid foramen, which opens into that cavity. According to Ribes, a filament is described as taking the course of the central arterial ramulus of the retina ; which he considers as forming a communication between it and the superior cervical ganglion. (b.) Ramus s. inferior — descends from the inferior extre- mity of the superior, to the middle cervical ganglion, which is situated opposite to the fifth or sixth cervical vertebra, where it terminates; the size of this ramus is variable; its consist- ence resembles more that of the cerebral, than of the sympa- thetic nerves ; it descends vertically in front of the rectus capitis anticus major, and the longus colli muscles ; behind the carotid artery, jugular vein, and pneumo-gastric nerve, exterior to their sheath. In this tract, it receives some fila- ments from the third and fourth pairs of cervical nerves ; it also unites wdth the external laryngeal ramulus of the par vagum, and sends off two or three delicate filaments, which u 290 DESCRIPTIVE ANATOMY pass into the chest, and assist in forming- the cardiac plexus. (c.) Rami s. externi — are numerous ; above, they unite by several filaments, with an arch formed around the trans- verse process of the atlas, by the union of the anterior branches of the sub-occipital, and first pair of cervical nerves; another filament subdivides, and communicates with the an- terior branches of the second and third pairs of cervical nerves ; while the inferior of these external rami, unite with the anterior branches of the fourth pair of cervical nerves, and with the cervical plexus. (d.) Rami s. interni — are soft and delicate nerves ; they distribute filaments to the rectus capitis anticus major, and longus colli muscles ; and terminate in the larynx and pharynx — assisting the glosso-pharyngeal, and par vagum nerves in forming the pharyngeal plexus. (s.) Rami s. anteriores — are numerous and large, and have been sometimes called the nervi molles ; the upper are the shortest, and ascend to unite with the portio dura, pneumo-gastric, and lingual nerves, soon after they pass out of the skull. The inferior pass downwards, are two or three in number, directing themselves from behind, forwards, to the point of division of the common carotid artery, where they form a plexus, from which numerous ramuli are distributed, with the branches of the common carotid artery, and the carotid plexus ; uniting also with filaments from the par vagum, and portio dura. The inferior one or two of these anterior rami unite to form the ramulus cardiacus superficialis, vel superior ; of which we shall speak more particularly hereafter. Ganglion Cervicale Meclius. This ganglion does not always exist; under which circum- stance, the inferior ramus of the superior cervical ganglion descends to the neck of the first rib, to terminate in the inferior cervical ganglion ; but when present, it is situated close to the ramulus a. thyroidalis inferior, opposite to the OF THE SYMPATHETIC NERVES. 291 sixth cervical vertebra. Its form is somewhat rounded ; it is bounded behind, by the longus colli muscle, on which it rests ; before, by the carotid artery, jugular vein, and pneumo-gastric nerve. It sends off inferior, external, internal, and anterior rami. (a.) Rami s. inferiores — small, usually from five to six in number, descend — some posterior, and some anterior to the subclavian artery, to terminate in the inferior cervical ganglion. (b.) Rami s. exterm — sometimes emanate in a single branch, pass outwards usually through the scalenus antic-us muscle, and unite with the three inferior cervical nerves. (c.) Rami s. interni— accompany the inferior thyroideal arterial ramulus, around which they form a plexus. Some pass to the thyroideal gland, oesophagus, and trachea, uniting with the recurrent laryngeal ramus n. of the par vagum ; and one filament unites with the phrenic nerve. (d.) Rami s. anterior es — are two or three in number, which unite in forming the ramulus s. eardiacus medius, which will be hereafter described. Ganglion Cervicale Inferius. Is very irregular in its form, frequently appearing to consist of several small ganglia, connected by a reddish in- termediate tissue ; it is situated behind the vertebral artery, between the transverse process of the seventh cervical verte- bra, and the neck of the first rib, as well as between the scalenus anticus, and the longus colli muscles ; it furnishes superior, inferior, external, internal, and anterior rami. (a.) Rami s. superiores. — Some of these communicate with the middle cervical ganglion, others pass upwards upon the vertebral artery, forming a plexus upon it, and are de- scribed as passing upwards as high as the second cervical vertebra, where they unite with the sub-occipital nerve. Small filaments from this vertebral plexus, unite with each of the cervical nerves, as they emanate from the interver- tebral foramina. u 2 292 DESCRIPTIVE ANATOMY (b.) Ramus s. inferior — communicates with the first thoracic ganglion. (c.) Rami s. externi—are very numerous, surround the subclavian artery, around which they form a plexus, and subdivide to accompany the branches of that artery. Some of these rami also unite with the anterior branches of the last four pairs of cervical, and with the first dorsal nerve. (d.) Rami s. interni — are few in number, and take their course partly to the longus colli muscle, and in part assist in forming the pulmonary plexus, and unite with the recur- rent laryngeal ramulus of the par vagum, and with the phrenic nerves. (e.) Rami s. anteriores — form the inferior cardiac nerve. The cardiac nerves should now be described. These are three in number on each side ; and as they arise from the superior, middle, and inferior sympathetic ganglia, they are accordingly named the superior, middle, and inferior cardiac rami. (a.) Ramus cardiacus superior, vel superjicialis — arises by four or five lower anterior filaments of the superior cervical ganglion; these having united, form a small cord, which descends along the neck, by the side of the trachea and thyroid gland, behind the carotid artery, to the chest. In this course, it sends filaments to assist in forming the pharyngeal plexus ; it also sends some to the thyroid gland, and others to be connected with the pneumo-gastric nerve. As it arrives in its descent opposite to the middle cervical ganglion, it sends off a filament, which becomes connected with the inferior tbyroideal plexus of that ganglion, and unites with the descending cervical ramus of the hypo- glossal nerve. The superior cardiac ramus then enters the chest, behind the subclavian vein, and there becomes inti- mately connected with the recurrent laryngeal ramus of the par vagum, and with the inferior cervical ganglion. The superficial cardiac nerve of the left side, descends into the chest, between the common carotid, and the subclavian arteries, where it divides into numerous filaments ; some of OF THE SYMPATHETIC NERVES. 293 which pass over the aorta, to unite with the inferior cardiac ramus, and cardiac filaments of the pneumo-gastric nerve ; while others pass behind the aorta, and assist in forming- the posterior cardiac plexus. (b.) Ramus s. cardiacus medius, vel magnus — is upon the right side larger than the other cardiac nerves ; it arises by four or five of the anterior filaments from the middle cervical ganglion, and descends along the inner side of the common carotid artery, passes in front of the subclavian artery to gain the chest ; here uniting in its course with the recurrent laryngeal ramus, and pneumo-gastric nerve. It then descends obliquely inwards, passing along the outer side of the arteria innominata, to reach the space between the arch of the aorta and the trachea, where it terminates in the cardiac plexus. On the left side, the middle cervical cardiac ramus s. is not unfrequently wanting, and generally receives its principal branch from the inferior cervical ganglion. (c.) Ramus s. cardiacus inferior. — The filaments which form this ramus on the right side, spring from the inferior cervical ganglion, and immediately form a, plexus, which descends vertically behind the subclavian artery, uniting with filaments from the recurrent ramus ; they then pass along- the left side of the arteria innominata, upon the anterior surface of the arch of the aorta, and between it and the pulmonary artery, assisting in forming the anterior cardiac plexus. Most frequently, on the left side, the middle, and inferior cardiac rami unite to form a single trunk ; under which circumstance, the cardiacus superior, and the cardiacus profundus pass separately to the heart ; and on the right side, the cardiacus superior and inferior unite, leaving the cardiacus medius to pass separately. Plexus Cardiacus. This plexus is placed behind the ascending aorta, near its origin from the left ventricle, and in front of the right pul- monary artery ; it is of an irregular form, and is made up of filaments proceeding from the cardiac rami of the opposite 294 DESCRIPTIVE ANATOMY sides, as well as of filaments from the pneumo-gastric nerves, and their recurrent rami. In this plexus several small ganglia are enclosed, and to the whole of them the term of cardiac ganglion is sometimes applied. This plexus receives at its upper part, the right and left middle cardiac rami ; on the left side, principally fila- ments from the cardiacus superficialis ; and on the right side, from the ramus cardiacus inferior: while there emanate from this ganglion, anterior, inferior, and posterior rami. (a.) Rami s. anterior es — are small and few in number, and are distributed to the anterior parietes of the aorta. (b.) Rami s. posteriores — terminate in the pulmonary plexus. (c.) Rami s, inferiores — are very numerous, and are dis- tributed especially to the heart ; some of them pass back- wards, encircling the posterior coronary artery, and forming a complete plexus around its branches, pass into the sub- stance of the heart, where they terminate ; others pass forwards, surrounding the aorta, and produce the anterior cardiac plexus, between the aorta, pulmonary artery, and vena cava. From the cardiac ganglion, numerous filaments take the course of the pulmonary vessels, unite with fila- ments of the pneumo-gastric nerve, and assist in forming the pulmonary plexus, which upon the left side surrounds the ductus arteriosus. Ganglia Thoracica. There are twelve ganglia on each side of the thorax, placed behind the pleura, one anterior to the head of each rib : sometimes there are but eleven, the last cervical, and the first dorsal being united. Each of these ganglia is small, and triangular in figure, the first being the largest; they communicate with one another, and send off external, and internal rami. (a.) Rami s. communicantes. — These are single branches of considerable size, and extend from the inferior edge of the ganglion above, to the superior edge of the ganglion below. (b.) Rami s. externi — ’from two to four in number from OF THE SYMPATHETIC NERVES, 295 each g’anglion, take their course upwards and outwards, and almost immediately unite with a small branch from the anterior ramus of each dorsal nerve, as it emanates from the intervertebral foramen. (c.) Rami s. interni — are very numerous, and variable in their distribution. Those from the upper ganglia, are the shortest, and terminate in the interior of the chest, communi- cating frequently with each other in front of the vertebral column, and uniting with the pulmonary plexus. While those from the inferior ganglia are longer, and generally from the sixth to the twelfth, unite to form the two splanchnic rami. (d.) Ramus s. splanchnicus major — arises from the inner edg-es of the thoracic g’anglia, from the sixth to the ninth or tenth, by four or five filaments, which take their course downwards along the sides of the vertebral column, and opposite to the tenth dorsal vertebra unite to form a single branch, which passes through the lesser muscle of the dia- phragm into the abdomen ; and immediately above the capsula renalis, it divides into numerous filaments to unite with the ramus splanchnicus major of the opposite side, through the medium of the g’reat semilunar ganglion, at the root of the eoeliac axis. (e.) Ramus s. splanchnicus minor — is formed by the junc- tion of rami arising from the two or three inferior thoracic ganglia ; it passes into the abdomen by perforating the dia- phragm behind the great splanchnic branch, and terminates partly by uniting with the greater splanchnic, and in part by forming the renal plexus. Ganglia Abdominales. Ganglion Semilunare. One on each side placed on the pillars of the diaphragm, partly upon the aorta, at the root of the coeliac artery, above and a little behind the capsula renalis; above, the semi- lunar ganglia receive the greater splanchnic rami ; and below, as they converge towards each other, they sometimes unite directly, so as to form but one ganglion ; more fre- 296 DESCRIPTIVE ANATOMY quently, however, this union is only by small filaments. That of the right side, is the larger of the two ; it is placed between the right pillar of the diaphragm and the vena cava : that of the left side, is placed upon the left pillar of the diaphragm, and generally lies upon the right dia- phragmatic artery, being covered by the tail of the pancreas. It is also between the splenic vein, which is above it, and the left renal artery, which is below it. Both the semilunar ganglia are surrounded by several other ganglia, termed the cceliac, which are connected with each other by numerous short filaments, the whole producing the solar plexus ; from which, sets of filaments again are sent off, forming plexuses, taking the course of the arteries from the aorta, and are named accordingly. (a.) Plexus s. diaphragmaticus — arises from the superior part of the solar plexus ; there are but few 7 filaments which enter into its composition, and they terminate by taking the course of the diaphragmatic arteries, and by uniting with the phrenic nerve. (b.) Plexus s. coeliacus. — The filaments forming this plexus, are sent off from the inferior part of the solar plexus, assisted by filaments of the pneumo-gastric, and phrenic nerves ; when thus produced, it subdivides into three other plexuses. (a.) Plexus s. coronarius — takes its course with the ramus arteriosus coronarius of the cceliac artery, which it embraces near its origin ; following the course of the lesser curvature of the stomach, it is distributed to its coats, and commu- nicates with the pneumo-gastric nerve. (b.) Plexus s. hepaticus — much larger than the former, surrounds the hepatic artery, and vena portse, passing- with them through Glisson’s capsule to the substance of the liver, to which it is distributed, accompanying the ramifica- tions of the hepatic vessels. It also sends filaments to the ductus communis cholidochus, duodenum, greater curvature of the stomach, and gall bladder ; and receives filaments from the right pneumo-gastric nerve. OF THE SYMPATHETIC NERVES. 297 (c.) Plexus s. splenicus — accompanies in a similar manner the ramifications of the splenic artery into the spleen, and like the ramifications of that artery, supplies the pancreas, the left extremity of the stomach, and the omentum. (c.) Plexus s. mesentericus superior. — The solar plexus continues along- the fore-part of the aorta, from the coeliae, as low as the superior mesenteric artery, where filaments accompany that vessel, and form the superior mesenteric plexus. This plexus then descends with the superior mesen- teric artery, between the pancreas and duodenum, then be- tween the two layers of the mesentery, where it forms a net-work surrounding the mesenteric glands, and which sends off filaments, that follow the course of the arterial rami to the pancreas, duodenum, colon, and caecum. (d.) Plexus s. mesentericus inferior — is composed of fila- ments, which proceed along the front of the aorta, down as low as the inferior mesenteric artery, where they take the course of that vessel, and form the inferior mesenteric plexus, being distributed with the arterial branches. Just as it is passing into the pelvis, this plexus divides into two portions — the inner of which takes the course of the common iliac artery, and its distributions ; the outer portion passes with the haemorrhoidal branch of the superior mesenteric artery to the meso-rectum. (e.) Plexus s. renalis— one on each side is made up of filaments from the solar, and coeliac plexus, and from the lesser splanchnic nerve. It is furnished with small ganglia, situated behind the emulgent artery and vein, the ramifications of which they accompany into the substance of the kidney. (f.) Plexus s. spermaticus — formed principally from the renal plexus, and partly also from the superior mesenteric ; its filaments take the course of the spermatic artery, in the male, to the testicle, and in the female, to the ovaria and Fallopian tubes. Ganglia Lumbales — Are usually five on either side, placed on the lumbar ver- tebrae, behind the vena cava on the right, and the aorta on 298 DESCRIPTIVE ANATOMY the left side. They send off communicating external, and internal rami. (a.) Rami s. communicantes — are filaments which unite the five ganglia with each other ; these filaments are some- times united in one cord, at others separated into three or four. The first connects the last thoracic ganglion with the first lumbar, and the lower one, the last lumbar with the first sacral. (b.) Rami s. externi — are usually two or three from each ganglion ; they cross in front of the lumbar arteries, the upper filaments being directed obliquely upwards, the middle ones transversely, and the lower ones downwards. They pass between the origins of the psoas muscle, and opposite to the intervertebral foramina unite with the anterior rami of the lumbar nerves. (c.) Rami s. interni — are numerous, but extremely delicate, frequently uniting with each other in front of the aorta; they form the aortic plexus ,* from which filaments are distributed to be united with the several plexuses we have described, and the inferior filaments unite with the hypogastric plexus. Ganglia Sacrales. Are three or four on either side, placed upon the anterior surface of the sacrum, behind the peritoneum ; like the lumbar, they send off communicating, external, and internal rami— the two latter, concurring in forming the hypogastric plexus. (a.) Rami s. communicantes — form a junction between each of the sacral, and between the last lumbar and first sacral ganglia. (b.) Rami s. externi — are of considerable size, and unite with the anterior branches of the sacral nerves, partly to be distributed to the levator ani muscle. (c.) Rami s. interni — are small, and unite within the middle of the sacrum from the opposite side ; from which union filaments are sent off} that assist in forming the hypo- gastric plexus. OF THE SYMPATHETIC NERVES. 299 Plexus Hypogastricus. This plexus is formed by filaments derived from the sciatic, inferior mesenteric, and aortic plexuses, as well as by fila- ments from the sacral ganglia. The hypogastric plexus distributes ramifications to the rectum, bladder, vesieulse seminales, in the male ; uterus, and vagina, in the female ; accompanying the arterial branches which are distributed to those parts. The last pair of sacral ganglia sends off filaments, which pass downwards and inwards on the anterior surface of the os coecygis, on which they unite, producing a little ganglion, which has been termed the ganglion impar ; from the under surface of which, delicate filaments are distributed, which lose themselves on the extremity of the os coecygis. TABLE OF THE NERVES. CEREBRAL NERVES. 1. First pair, or olfactory. 2. Second pair, or optic. 3. Third pair, or motores oculorum. a. Ramus nervosus superior. a. Ramulus n. musculi recti superiors. b. Ramulus n. m. levatoris palpebrae superioris. B. Ramus n. inferior. a. Ramulus n. m. adduetoris oculi. b. Ramulus n. m. recti inferioris. c. Ramulus n. m. obliqui inferioris. 4. Fourth pair, or pathetici. 5. Fifth pair, or trigeminus. a. Ramus n. ophthalmicus. a. Ramulus n. laelirymalis. a. Ramusculus n. spheno-maxillaris, vel commu- cans. f$. Ramusculus n. malaris. b. Ramulus n. frontalis. x. Ramusculus n. super-trochlearis. 13. Ramusculus n. supra-orbitalis. c. Ramulus n. nasalis. x. Ramusculus n. ganglionicus. /3. Ramusculus n. nasalis internus. y. Ramusculus infra-trochlearis. b. Ramus n. maxillaris superior. a. Ramulus n. orbitalis. x. Ramusculus n. malaris. /3. Ramusculus n. temporalis. b. Ramuli n. dentales posteriores. TABLE OF NERVES. 301 c. Ramulus n. infra-orbitalis. a. Ramusculi n. externi et interni. /3. Ramusculus n. dentalis anterior, c. Ramus n. maxillaris inferior. a. Ramulus n. superior. «. Ramusculi n. temporales profundi /3. Ramusculi n. masseteres. y. Ramusculus n. buccales. £. Ramusculi n. plerygoidei. b. Ramulus n. inferior. a. Ramusculus n. lingualis, vel gustatorius. /3. Ramusculus n. dentalis inferior. y. Ramusculus n. auricularis, vel temporalis su- perfieialis. 6. Sixth pair, or abducentes. 7. Seventh pair — portio dura, or facial nerve. a. Rami n. muscular es. b. Ramus n. auricularis posterior. a. Ramulus n. anterior. b. Ramulus n. posterior. c. Ramus n. stylo-hyoideus. d. Ramus n. digastricus. a. Ramulus n. superior. b. Ramulus n. inferior. E. Ramus n. temporo-facialis. a. Ramuli temporales. b. Ramuli malares. c. Ramuli buccales. f. Ramus n. cervico-facialis. a. Ramuli n. supra-maxillares. b. Ramuli n. infra-maxillares. 8. Eighth pair — portio mollis, or auditory nerve, a. Ramus n. cochlearis. B. Ramus n. vestibuli. a. Ramulus magnus. b. Ramulus medius. c. Ramulus minimus. 302 TABLE OF NERVES. 9. Ninth pair, or glosso-pharyngeal nerves. a. Ramus n. anastomoticus. b. Rami n. communicantes. c. Rami n. pharyngei. D. Ramus n. lingualis superior. a. Raraulus n. tonsillaris. e. Ramus n. lingualis inferior. F. Ramus n. lingualis medius. 10. Tenth pair — par vagum, or pneumo-gastric nerves. a. Rami. n. communicantes. b. Ramus n. pharyngeus. c. Ramus n. laryngeus superior . a. Ramulus n. laryngeus externus. b. Raraulus n. laryngeus internus. a.. Ramusculi n. superiores. /S. Ramusculi n. inferiores. d. Rami n. cardiaci. e. Ramus n. laryngeus inferior, vel recurrens. a. Ramuli n. cardiaci. b. Ramuli n. pulmonares. F. Rami n. pulmonares. g. Rami n. cesophagei. h. Rami n. ventricular es. 11. Eleventh pair — hypo-glossus, or lingual nerve, a, Ramus n. cervicalis descendens. a. Ramuli n. musculares. b. Ramulus n. lingualis. a. Ramusculi n. musculares. SPINAL NERVES. 1. Nervus accessorius Willisii. a. Ramus n. communicans. b. Ramus n. pharyngeus accessorius . 2 . Nervi sub-occipitales. a. Ramus n. anterior. a. Ramuli n. musculares. TABLE OF NERVES. 303 b. Ramus n. posterior. a. Ramulus n. occipitalis superior et internus. b. Raraulus n. occipitalis superior et externus. c. Raraulus n. occipitalis inferior, vel eerviealis. Nervi Cervicales. 3. Nervi cervicales primi. a. Ramus n. anterior. a. Raraulus n. aseendens. a. Ramusculi n. comraunicantes. b. Ramulus n. descendens. b. Ramus n. posterior, vel occipitalis magnus. a. Ramuli n. musculares. 4. Nervi cervicales secundi. a. Ramus nervosus anterior. a. Ramulus n. aseendens. b. Ramulus n. descendens. b. Ramus posterior. 5. Nervi cervicales tertii. a. Ramus n. anterior. b. Ramus n. posterior. Plexus Cervicalis. a. Ramus n. descendens internus. b. Ramus n. diaphragmaticus, vel phrenicus. c. Rami n. descendentes externi. a. Ramuli n. supra-elaviculares. b. Ramuli n. supra-acromiales. c. Ramuli n. sub-elaviculares. d. Ramuli n. cervicales profundi. D. Rami n. ascendentes. a. Raraulus n. superficial^ colli. b. Ramulus n. auricularis. c. Ramulus n. occipitalis minor. 6. Nervi cervicales quarti. 7. 8, 9. Nervi cervicales — 5th, 6th, 7th. 304 TABLE OF NERVES. Plexus Axillaris, a. Rami n. thoracici. a. Ramulus n. anterior. b. Ramulus n. posterior. B. Ramus n. suprascapular is. c. Rami n. infra subscapular es. d. Ramus n. articularis, vel circumjlexus. e. Ramus n. cutaneus internus. a. Ramulus n. externus. b. Ramulus n. internus. f. Ramus n. cutaneus internus minor. g. Ramus n. cutaneus externus, vel musculo-cutaneus. a. Ramulus n. posterior. b. Ramulus n. anterior. h. Ramus n. medianus. a. Ramuli n. musculares. b. Ramulus n. interosseous. c. Ramulus n. palmaris cutaneus. d. Ramulus n. digitalis primus. e. Ramulus n. digitalis secundus. f. Ramulus n. digitalis tertius. g. Ramulus n. digitalis quartus. h. Ramulus n. digitalis quintus. i. Ramus n. ulnaris, vel cubitalis. a. Ramulus n. palmaris. a. Ramusculus n. profundus. /3. Ramusculus n. superfieialis. b. Ramulus n. dorsalis. a. Ramusculus n. internus. /3. Ramusculus n. externus. k. Ramus n. radialis, vel spiralis. a. Ramuli n. musculares. b. Ramulus n. cutaneus posterior. c. Ramulus n. anterior, vel superfieialis. a. Ramusculus n. externus. /3. Ramusculus n. internus. TABLE OF NERVES. 305 d. Ramulus n. posterior. x. Ramuseuli n. posteriores. /3. Ramuseuli n. anteriores. Nervi Dorsales. a. Ravii n. posteriores. a. Ramuli n. interni. b. Ramuli n. externi. b. Rami n. anteriores. 10. Nervi dorsales primi. b. Ramus n. anterior. b. Ramulus n. descendens. 11. Nervi dorsales secundi. b. Ramus n. anterior. a. Ramulus n. intercostalis. b. Ramulus n. brachialis. 12. Nervi dorsales tertii. b. Ramus n. anterior. a. Ramulus n. intercostalis. b. Ramulus n. brachialis. 13 to 16. Nervi dorsales — 4th, 5th, 6th, 7th. b. Rami n. anteriores. a. Ramuli n. interni. b. Ramuli n. externi. 17 to 20. Nervi dorsales — 8th, 9th, 10th, Uth. b. Rami n. anteriores. a. Ramuli n. interni. x. Ramuseuli n. profundi. /3. Ramuseuli n. superficiales. b. Ramuli n. externi. 21. Nervi dorsales — 12th. b. Rami n. anteriores. a. Ramulus n. communicans. Nervi Lumbales. 22. Nervi lumbales primi. a. Ramus n. posterior. x 306 TABLE OF NERVES. b. Ramus n. anterior. 23 to 26. Nervi lumbales — 2nd, 3rd, 4th, 5th. Plexus Lumbalis. a. Ramus n. spermaticus ext emus. a. Ramulus n. internus. b. Ramulus n. externus. b. Ramus n. cutaneus externus, vel musculo-cutaneus. a. Ramulus n. abdominalis. a. Ramusculus n. externus. /3. Ramusculus n. internus. b. Ramulus n. descendens. c. Ramulus n. cutaneus. c. Ramus n. cruralis. a. Ramuli n. superficiales. b. Ramuli n. profundi. a. Ramusculus n. saphaenus. d. Ramus n. obturatorius. a. Ramulus n. anterior. b. Ramuli n. posteriores. e. Ramus n. sacro-lumbalis. a. Ramulus n. glutaeus superior. Nervi Sacrales. 27. Nervi sacrales prime a. Ramus n. posterior. b. Ramus n. anterior. 28 to 30. Nervi sacrales — 2nd, 3rd, 4th. a. Rami n. posteriores. b. Rami. n. anteriores. 31, 32. Nervi sacrales — 5th, 6th. a. Rami n. posteriores. b. Rami n. anteriores. Plexus Sciaticus. a. Rami n. hcemorrhoidales. b. Rami n. vesicates. TABLE OF NERVES. 307 c. Rami n. vaginales, et uterini. d. Ramus n. glutceus inferior. a. Ramulus n. g-lutaeus medius. b. Ramulus n. seiaticus, vel pudendalis. c. Ramulus n. cruralis. d. Ramus n. pudicus interims. a. Ramulus n. inferior. b. Ramulus n. superior. e. Ramus n. ischiadicus. a. Ramuli n. musculares. b. Ramulus n. communicans. c. Ramuli n. musculares inferiores. d. Ramulus n. cutaneus superior. e. Ramulus n. peroneus, vel popliteus externus, «. Ramusculus n. cutaneus. /3. Ramusculus n. superficial^, vel musculo cuta- neus. y. Ramusculus n. profundus, vel tibialis anterior f. Ramulus n. tibialis posticus, vel popliteus internus. a.. Ramusculus n. cutaneus tibialis, vel saphenus externus. /3. Ramusculus n. plantaris internus. y. Ramusculus n. plantaris externus. 308 TAELE OF NERVES. NERVUS SYMPATHETICUS. Ganglia Capitis. 1. Ganglion lenticulare, vel ophthalmicum. a. Rami sympathetici superior es, et inferiores, vel ci- liares. 2 . Ganglion spheno-palatine, or ganglion of. Meckel. a. Rami s. superior es. b. Rami s. inferiores, vel palatini. a. Raraulus s. palatinus magnus. b. Ramuli s. palatini medii. c. Ramuli s. palatini parvi. c. Rami s. inter ni, vel spheno-palatini, or lateral nasal, a. Ramulus s. naso-palatinus. d. Ramus s. posterior vidianus, vel pterygoideus. a. Ramulus s. inferior, vel earotideus. b. Ramulus s. superior, vel innominatus. Ganglia Cervicalia. Ganglion cervicale superius. a. Rami s. superiores. b. Ramus s. inferior. c. Rami s. externi. d. Rami s. interni. e. Rami s. anteriores. Ganglion Cervicale Medium, a. Rami s. inferiores. B. Rami s. externi. c. Rami s. interni. d. Rami s. anteriores. Ganglion Cervicale Inferius. a. Rami s. superiores. B. Ramus s. inferior. c. Rami s. externi. D. Rami s. interni. e. Rami s. anteriores. TABLE OF NERVES. 309 Rami s. Cardiaci. a. Ramus s. cardiacus superior, vel superficialis. b. Ramus s. cardiacus medius, vel magnus. c. Ramus s. cardiacus inferior, vel parvus. Plexus Cardiacus, or Cardiac Ganglion. a. Rami s. anteriores. b. Rami s. posteriores. c. Rami s. inferiores. Ganglia Thoracica. a. Rami s. communicantes. b. Rami s. externi. c. Rami s. interni. d. Ramus s. splanchnicus major. e. Ramus s. splanchnicus minor. Ganglia Abdominalia. Ganglion Semilunare. a. Plexus s. diaphragmaticus. b. Plexus s. coeliacus. a. Plexus coronarius. b. Plexus liepaticus. c. Plexus splenicus. c. Plexus s. mesentericus superior. D. Plexus s. mesentericus inferior. e. Plexus s. renalis. f. Plexus s. spermaticus. Ganglia Lumbalia. a. Rami s. communicantes. b. Rami s. externi. c. Rami s. interni. Ganglia Sacralia. a. Rami s. communicantes. b. Rami s. externi. c. Rami s. interni. Plexus Hypogastricus. LECTURES ON ANATOMY. *’*.%* * ".•***” PART IX. THE ORGANS OF THE SENSES. X - r * ■ 'h\ * LECTURE XXXVI, THE ORGANS OF THE SENSES. Descriptive Anatomy of the Organs of Vision. These organs are placed within those cavities formed by the junction of the bones of the face, which are termed the orbits. They have already been described with the bones of the head. (Vide Vol. I. p. 10.) The student, after referring to the osteological description . of these cavities, should next examine them in reference to the eyes, and observe how well they are adapted, not only for the purposes of protection, but also to afford a varied range of motion for the purposes of vision. In aid of this object, we find the situation of the orbits contributes much to the perfection of this function ; thus the superior and fore part of the head is admirably chosen for many important purposes in the animal economy, as their vicinity to the immediate seat of the intellect, and nervous communication with the brain, render them capable of being adapted, by their exalted position and extensive motion, for the perception of sur- rounding objects. It may also be observed, that the orbits are much larger than the globes of the eyes ; this is not only for the purposes of enclosing, at the same time, the numerous muscles, nerves and blood-vessels, which contribute to the function of vision ; but also to admit a motion of the eyes, independent of all the other parts of the body. Besides this protection from the bony orbits, the external delicacy of the eye re- quires an apparatus for the purpose of defending it from the effects of the air, and other external objects, as well as to moderate and modify the degree of light passing to the organ. 314 THE ORGANS OF THE SENSES. Thus we have surrounding the orbits, the eyebrows, eye- lids, eyelashes, meibomian glands, and lachrymal apparatus ; all performing their separate functions, in aid of the perfec- tion of vision. These parts have been termed by Haller, the tutamina oculi. Of the eyebrows, or supercilia . — These are two eminences, resting upon the superciliary ridges of the frontal bone, covered by short hairs, which are directed from within out- wards. They are larger internally, which extremity is called their head, they are arched in their centre, and their thinner and outer extremity is sometimes called their tail. The color of these hairs is usually that of the hair of the head. A con- siderable quantity of fat is placed between the skin of the eyebrows, and the superciliary ridges of the frontal bone, admitting of a motion produced by the orbiculares palpebra- rum, corrugatores superciliorum, and the occipito frontalis muscles. • , ' The eyebrows are supplied with nerves from the first division of the fifth pair, and from the facial ; they derive their blood from the temporal, and palpebral ramusculi of the internal carotid arterial ramus. Use . — To protect the eyes from perpendicular rays of light, to prevent the perspiration of the forehead from lodging on the eyelids ; and also they may be considered as organs of mental expression, indicating thought, surprise, and anger. The eyelids, or palpebrce — are two moveable curtains, placed in front of the eye, and are distinguished into an upper and a lower. The upper is bounded above by the eyebrow, and the lower one below by the cheek. When the eyelids are closed, so that their free extremities are in contact with each other, the upper, it may be ob- served, from its larger size, descends so as to form the greater portion of the covering to the eye ; and the motion of the lower eyelid, is comparatively limited. Both lids are convex externally, and concave internally, in a degree cor- THE ORGANS OF THE SENSES. 315 responding- to the convexity of the anterior part of the lobe of the eye. They unite at their transverse extremities, forming- two angles, the inner is the greater ; which dispo- sition depends upon the arrangement of the fibres of the orbicularis palpebrarum, having' a tendon between thfern internally and not externally. The skin of both eyelids is thrown into numerous folds, by the action of the orbicular muscles ; they are more numerous upon the upper, which are concave downwards, while those of the lower have their concavities directed upwards. The free extremities of each eyelid, present numerous small orifices ; towards the internal angle, one may be ob- served on each lid, which is termed the punctum lachrymale. Besides these, there are little orifices that point out the ter- mination of the ducts of the meibomian glands, along the whole length of the lids ; these open inwards, towards the eyes ; and in front of them are placed the eyelashes, which are short stiff hairs — those on the upper lid being directed upwards, and those on the lower, downwards. The following tissues, enter into the composition of the eyelids. The skin — which differs only from the cutaneous covering of the other parts of the body, in being extremely delicate, in not being connected to the sub-cutaneous tissues by adi- pose membrane, and in being semi-transparent. Underneath the skin is situated the orbicularis palpebrse muscle ; towards the outer circumference of this muscle, the fibres are sepa- rated widely from each other, so as to afford an indistinct appearance of musclar fibre ; but towards the free edges of the lids, the fibres are closer, larger, and straighter, forming what has been considered by some anatomists as a distinct muscle, which they have named the m. tarsahs. A fibrous tissue — is situated under this muscular layer of each eyelid, which is stronger on the outer side, and is placed on the upper lid, between the orbicularis and the tendon of the levator palpebrss superioris, and in the lower lid, between the orbicularis and the tunica conjunctiva. It 316 THE ORGANS OF THE SENSES. is inserted into the tarsal cartilages, and is connected with the circumference of the orbits ; it is particularly obvious on the outer side, but becomes so attenuated on the inner, as to be lost in cellular membrane. The tendinous expansion of the levator palpebral superioris, crosses this fibrous layer, as it passes to be inserted into the tarsal fibro-cartilage, and serves to strengthen the fibrous tissue of the upper eyelid. Fibro-tarsal cartilages — are one to the upper, and another to the lower lid of each eye. They have their elastic laminae, placed in the free edges of the lids, at the termination of the fibrous tissues just described. At the inner canthus, the cartilages of the two lids are connected with the tendon of the orbicularis muscle ; and at the outer, they terminate by uniting, through the medium of the fibrous tissue, with each other. The fibro-cartilage of the upper lid is larger than that of the lower, and of a different form, so as to enable the one to be distinguished from the other ; it is broad in its centre, and contracted at its extremities ; the broadest part of the upper measuring usually about six lines, while in the lower it is not more than two ; but it presents nearly the same measurement in its whole length. They are convex upon their anterior, and concave upon their pos- terior surfaces ; the latter presenting many vertical grooves, which lodge the meibomian glands. The adherent edges of these cartilages, are attached to the fibrous layers of the eyelids ; their free edges are thick, and somewhat bevelled, so that when the eyelids are brought in contact, a little groove is formed by their approximation, which is supposed to be for the purpose of conveying the tears from the outer, to the inner canthus of the eye. The meibomian glands — are small rounded follicles, of a yellow color, which are placed between the tarsal cartilages, and the tunica conjunctiva, arranged in parallel vertical lines. These are described by Soemmerring as being about forty in the upper, and not more than twenty on the lower lid. These follicles communicate with each other, and open at the free extremities of the eyelids, upon the fore part of THE ORGANS OF THE SENSES. 317 the eye, through very minute apertures, which are placed behind the cilise in two transverse rows. The substance which is secreted by these glands, is of a sebaceous quality, and sufficiently firm to be squeezed out in a cylindrical form. The cilice, or eyelashes — are strong hairs, placed in rows upon the anterior free extremity of each eyelid, but are more numerous and stronger upon the upper, than on the lower. They are so disposed, that those on the upper are directed upwards, with a slight curve, and those on the lower lid, with a curve downwards ; so that the convexities formed by these curves, are opposed to each other when the eyelids are closed ; but the free extremities of the hairs of each eyelash are so separated, as to prevent their entanglement. Tunica conjunctiva, or membrana adnata. — This mem- brane belongs to the mucous system, and not only covers the posterior surface of the eyelids, but also the anterior surface of the globe of the eye. It is still a matter of dis- pute, whether or not this membrane is continued over the transparent cornea ; the distinct fibrous or laminated struc- ture of the cornea, and the complete absence of such an appearance in the conjunctiva, would lead one to doubt this being the case: while, again, the continuity of pustular disease over this portion of the globe of the eye from the eyelids, seems to argue for the continuation of this mem- brane over the whole of the fore part of the org’an. At the free edges of the eyelids, the tunica conjunctiva is con- tinuous with the cutis, and is pierced by the ducts of the meibomian glands ; or more properly, should be considered as passing into their apertures to form the follicular appa- ratus, as it passes through the puncta lachrymalia, to form the lachrymal duct and ductus ad nasum. At the inner canthus of the eye this tunic forms a fold, presenting a small projection of a pale red color, which is termed the caruncula lackrymahs ; in which may be observed small follicles, and very minute hairs ; and immediately to the outer side of the caruncula, another indistinct fold may be observed, which 318 THE ORGANS OF THE SENSES. from its situation, and resemblance to a similar structure, but much more developed in certain animals, has been termed the membrana nictatans. Practical Remarks . , , > The use of the eyelids is to protect the eye from light bodies, which are constantly floating in the atmosphere, as well as, by their frequent involuntary closing, to offer a relief to the retinee by an alternate ex- clusion and admission of light. They also, by the same motion, convey the tears from the upper and outer part of the orbit to the puncta lachrymalia, which are situated at the inner canthus ; this object is not merely to lubricate the surface of the eye, or to wash off light bodies which are brought in contact with it ; but to spread over its anterior surface a thin layer of tear, which produces a refractive medium between that of the atmosphere and of the transparent cornea : — a theory, which is proved by the power of vision becoming imperfect when the tear is wiped off the globe of the eye. The eyelids are liable to numerous diseases, from the derangement of the several structures entering into their formation ; namely, those of the skin, cellular membrane, muscle, fibrous membrane, fibro-cartilage, meibomian glands, and hairs ; each of which are liable to peculiar diseases. Of the Parts contained within the Orbit. It has already been said, that the globe of the eye only in part fills up the orbits ; the remaining- space being- occu- pied by a considerable quantity of fat, by the muscles, arteries, veins, nerves, and absorbents of the organs. The adeps contained within the orbit, so surrounds the globe of the eye, as completely to imbed, and form a soft cushion for it, protecting the globe from friction on the bone; and perhaps at the same time, may be useful in moderating the action of the muscles, and preventing too great an altera- tion in the refractive power of its transparent parts. For these purposes, the adeps within the orbit is found enveloped in large cells, and of a very soft consistence. The muscles of the eye, are six in number — four of which, from their direction, are named the straight, and two the oblique. The levatores palpebrarum superiorum, have al- ready been mentioned (VideV ol. II. p. 71,) as moderators to the orbiculares palpebrarum. THE ORGANS OF THE SENSES. 319 The recti muscles — are named according - to their use, as levator, depressor, abductor, and adductor muscles. Musculus levator oculi — arises from the upper surface of the foramen opticum, immediately beneath the levator palpe- brse superioris, and is somewhat connected with the neurileraa of the optic nerve ; it then passes forwards on the upper surface of the ball of the eye, where it becomes aponeurotic, and is inserted into the sclerotic coat, anterior to the trans- verse axis of the globe ; its upper surface is covered by the levator palpebrae superioris, from which, anteriorly, it is se- parated by the tunica conjunctiva. Its inferior surface rests upon the optic nerve, the ramulus a. ophthalmicus, and the nasal n. ramulus of the first division of the fifth pair. Use . — To raise the eye. M. depressor oculi — arises from the under surface of the optic foramen, by a tendon common to it, the adductor and abductor oculi muscles ; it passes forwards, along the under surface of the globe of the eye, anterior to the great diameter of which it is inserted, similar to the last-described muscle. Its inferior surface is in contact with a quantity of adeps, and its tendinous insertion is covered by the tunica conjunctiva; its upper surface is in connection with the optic nerve, and the inferior ramus of the third pair. Use . — To antagonize the levator oculi, and consequently to direct the pupil downwards. M. abductor oculi — is placed on the outer side of the orbit; it has a double origin, partly from the optic foramen, and partly from a tendon which is attached to the edge of the foramen lacerum orbitale superius ; between which two origins, the third pair of nerves, the sixth, and the ramulus nasalis of the first division of the fifth, enter the orbit. The muscle passes horizontally outwards and forwards, beyond the transverse axis of the globe, to be inserted by an apo- neurosis into the sclerotic coat. Its external surface is in contact with the orbitar process of the sphenoid bone, and more anteriorly with the lachrymal gland; its internal sur- 320 THE ORGANS OF THE SENSES. face, with the optic nerve, the lenticular ganglion, and sixth pair of nerves, which ramify on it. Use . — To direct the pupil outwards. The peculiarity to be observed with respect to these muscles, is, that they receive a distinct pair of nerves, namely, the abducentes, which receive a filament from the sympathetic. No clear physiological theory has been formed upon this anatomical fact. M. adductor oculi — arises from the inner side of the optic foramen, from which it passes forwards, anterior to the diameter of the globe, where it becomes aponeurotic, and is inserted into the sclerotic coat. Its internal surface corres- ponds to the orbitar process of the oethmoid bone, its ex- ternal to the optic nerve. Use . — To direct the pupil inwards. In taking a view of the direction given by each of these muscles to the globe of the eye, first, by their separate, and secondly, by their collective action, it will be obvious, that the field of motion is as extensive and varied, as the sphere of vision can require ; and yet a mystery hangs over the action of two other muscles, which are connected with this organ. M. obliquus superior oculi — arises by a short aponeurosis from the upper and inner part of the optic foramen, where it is somewhat connected with the origin of the levator palpebrse superioris. It proceeds forwards along the orbitar process of the oethmoid bone, towards the internal angular process of the frontal bone, where a cartilaginous pully is fixed, through which the tendon of this muscle passes, and is then reflected, passing from above downwards, backwards, and outwards, to be inserted by aponeurosis midway between the vertical diameter of the globe, and the entrance of the optic nerve. Use . — To draw the point of insertion of the muscle forwards, in- wards, and upwards, making the globe of the eye perform a rotatory motion, which directs the pupil downwards, and outwards. These muscles receive the fourth pair of nerves, which are wholly distributed to them. M. obliquus inferior oculi — is situated at the under and fore part of the orbit, arising from the orbitar process of the THE ORGANS OF THE SENSES. 321 superior maxillary bone, above the infra-orbitar foramen, and just to the outer side of the lachrymal groove ; from this origin it passes obliquely outwards, backwards, and up- wards, to be inserted by a tendinous expansion into the sclerotic coat, behind the transverse axis of the eye, close to the entrance of the optic nerve ; its inferior surface lies upon the orbitar process of the superior maxillary bone, the upper is connected with the ball of the eye, and the de- pressor oculi muscle. Use . — To draw the point of insertion of this muscle forwards, in- wards, and downwards, and consequently to direct the pupil backwards, outwards, and upwards. Such would be its separate action ; but when in combination with the preceding muscle, they draw the eye forwards, and counteract the combined power of the four straight muscles. The lachrymal apparatus — consists of the lachrymal gland, and lachrymal passages, which are placed within the orbits. The lachrymal gland — is a conglomerate gland, placed in a depression in the upper and outer part of the orbit, on the inner side of the external angular process of the os frontis, above the abductor oculi, and covered by the tunica conjunctiva. It is about the size of a small almond, of a pale red color, of an oval figure ; it may be separated in two or three lobes, which are further separable into small granules, connected by cellular tissue. Each of these granules receives a small ramification from the ramulus a lachrymalis, and from which a small ramification of a vein commences, as well as a distinct excretory duct, which unites with others, so that the whole gland does not produce more than seven or eight ducts, opening upon the inner side of the upper eyelid, arranged in a curved row — the convexity of which is directed upwards. The whole gland is surrounded by a distinct capsule. The puncta lachrymalia — are two small orifices to each eye, one on either eyelid ; they occupy the centre of a little tubercle, more or less obvious in different individuals, situated about a line and a half from the inner canthus. That of the Y 322 THE ORGANS OF THE SENSES. upper eyelid is directed downwards, outwards, and back- wards ; and that of the lower, upwards, backwards, and out- wards ; both are therefore curved in such a manner that their convexities are directed towards each other. These puncta are the orifices of the — Lachrymal ducts — which extend from the puncta to the lachrymal sac ; the upper is rather longer than the lower, and more curved ; both of them open into the sac, rather above the centre of its outer side, and immediately behind the tendon of the orbicularis muscle. They usually open separately into the sac ; but sometimes they unite before they reach it. Lachrymal sac — is a small membranous pouch, composed of mucous membrane, placed at the inner eanthus of each eye, and lodged in a bony groove formed by the os unguis and superior maxillary bone. This sac is closed above, and rises superior to the tendon of the orbicularis muscle, which covers its anterior surface, as well as some of the fibres of the orbicular muscle, and the integuments ; its inferior extre- mity is continuous with the nasal ducts. The interior of the lachrymal sac is lined by a continuation of the tunica conjunctiva, which afterwards lines the nasal duct and nose itself ; its color is red, and it is always moist- ened by mucus. Its outer surface is covered by some mus- cular fibres, besides those of the orbicularis palpebrae, which have been spoken of by anatomists as a distinct muscle ; but they appear to me to be part of the obliquus inferior, which may contribute in some measure to press its fluid contents towards the nose. It receives its blood from the ramusculi a. palpebraies of the ophthalmic ramulus, and its nervous filaments from the ramulus n. nasalis. Nasal duct . — The bony canal which has already been described in Vol. I. p. 72. It is lined by a continuation of the mucous membrane of the sac, which adheres very firmly to the periosteum, and opens in the inferior meatus of the nose, under the inferior turbinated bone, by a small orifice, which is surrounded by a circular projection of pituitary membrane; THE ORGANS OF THE SENSES. 323 the direction of the duet, from its commencement at the sac to its termination in the nose, is obliquely backwards, and a little outwards. The tears — which are secreted by the lachrymal glands, and directed downwards and inwards by the action of the orbiculares palpebrarum muscles to the puncta, to be ultimately conveyed to the nose; are a muco-serous fluid, the specific gravity of which is somewhat greater than water; and according to Fourcroy, contains water, mucus, muriate of soda, soda, phosphate of lime, and phosphate of soda. The saline parts amount only to about O' 01 of the whole. Under common circumstances, the tears are principally, at any rate, in a great measure removed by evaporation; as may be proved by the liability of the tears to flow over upon the cheek, when the atmosphere is loaded with moisture; but when from mental emotion, or any other cause, the lachrymal gland is excited to inordinate secretion, then the tears fall upon the cheek, producing what is termed weeping. The secretions from the Meibomian glands prevent the tears, in a great measure, from pas- sing over the lids ; as do also the cilise, excepting between the puncta laclirymalia and the inner angle of the eye, where there are no hairs placed, and where the tears therefore most readily accumulate and pour over. Towards this part of the eye, the tears are conveyed by the closing of the lids ; and here the puncta absorb them, probably by capillary at- traction, and they flow into the lachrymal sac, from which they are pro- pelled by the action of the orbicular, and perhaps inferior oblique muscles, into the nasal duct, and from thence into the nose. Any interruption of the flow of the tears through the lachrymal passages, produces a consequent weeping; it may depend upon disease of the puncta, lachrymal sac, or duct. If the symptoms depend upon disease of the puncta, or sac, they may usually be removed by injecting warm water through the lower punctum ; but when they are produced by obstruction in the nasal duct, the sac should be laid open, and a style passed through the duct into the nose, and allowed to remain there until the passage is re-established — or a probe may be passed up the nasal duct from the nose. Of the Globe of the Eye. The parts which compose the globe of the eye, are the membranes or tunics, the humours, and also substances of a peculiar nature, as the crystalline lens, and the ciliary bodies ; beside numerous vessels and nerves. The ball of the eye is spherical, its greater diameter is from before to behind, in which direction it is usually about eleven lines in length ; while its other diameters are only ten lines. The F 2 324 THE ORGANS OF THE SENSES. globe of the eye is not completely circular, the transparent cornea being a portion of a smaller sphere, projecting’ on its anterior part. This projection forms about a fifth of the ball of the eye. The eye is bounded anteriorly, by the tunica conjunctiva ; posteriorly, by the straight and oblique muscles, vessels, and nerves, and a considerable quantity of fat ; above and to the outer side, by the lachrymal gland; below and to the inner side, by the lachrymal passages. Tunica sclerotica — extends from the entrance of the optic nerve, to the circumference of the transparent cornea, forming about four-fifths of the circular investment of the eye ; it is a dense, fibrous substance, of a pearly whiteness, and is thicker posteriorly than anteriorly ; its external surface is convex, and is covered by the muscles of the eye, and their tendinous insertions, and by the tunica conjunctiva ; its inner surface is covered by the choroid coat, with which it is con- nected by blood-vessels, and nerves, and a delicate cellular membrane. A little to the nasal side, on the posterior sur- face of the sclerotic coat, is found a perforation for the entrance of the optic nerve ; this is sometimes a single foramen, at others a cribriform plate. There are also nu- merous small foramina, for the passage of the ciliary vessels and nerves. Anteriorly, the sclerotic coat terminates by a circular opening, the edge of which is bifid, to receive the transparent cornea, in a similar manner to that in which the rim of a watch receives the glass ; of these bifid edges, the exterior is the largest. At the point where the muscles of the eye become ten- dinous, the sclerotic coat acquires the metallic lustre of tendon ; while posterior to this point, it presents an opaque whiteness, in which situation it is stronger, and more dis- tinctly fibrous. At the point where the optic nerve leaves the skull, the dura mater forms a distinct envelope to it, accompanying it as far as the entrance into the sclerotic coat, where it leaves the nerve, and connects itself with that tunic. THE ORGANS OF THE SENSES. 325 Cornea pellucicla — forms the anterior fifth of the ball of the eye ; it is not perfectly circular, its vertical being* less than its transverse axis, which is seven lines in length. Its anterior surface is convex, more or less prominent in different individuals, and is supposed by some anatomists to be covered by the tunica conjunctiva, and by others, by a mucous layer of a nature peculiar to itself; its posterior surface is concave, and covered by the serous membrane of the aqueous humor: its circumference is received within the sclerotic coat, in a manner which has already been described, its edge corres- ponding to the bifid groove which receives it. The cornea is thicker than the sclerotic, being one third of a line, but is not like it fibrous; being composed of five or six concentric lamellee, united by a very delicate cellular mem- brane, containing an aqueous fluid. Tunica choroides — is placed between the sclerotic coat and the retina, and extends from the entrance of the optic nerve to the ciliary ligament ; it is of a dark brown color, being composed of a congeries of minute blood-vessels, united by a thin cellular tissue ; posteriorly, it presents a narrow opening for the optic nerve ; while anteriorly, it unites itself intimately to the ciliary ligament; its outer sur- face is covered with a brownish pigment, formed of small globules, which after death tinge the inner surface of the sclerotic coat. The inner surface is covered much more abundantly by the pigmentum nigrum, which does not stain the retina, being separated from it by a reflected serous membrane, first discovered by Mr. Jacobs, of Dublin, and now termed the membrana Jacobi. The choroid coat consists of two layers, which are sepa- rable posteriorly, but inseparable when connected with the ciliary ligament ; here it becomes puckered, forming a number of delicate folds, which surround the crystalline lens and anterior surface of the vitreous humor. This coat appears to be composed entirely of blood-vessels ; the arteries are divided into two sets, the long, and the short ; the former are two in number, pass forwards by the sides of the choroid 326 THE ORGANS OF THE SENSES. coat, and reaching the ciliary ligament are directed inwards, to be distributed to the iris : the vessel on the outer side, is a little above that which runs on the inner side of the eye. The short ciliary arteries are much more numerous than the former, pierce the sclerotic coat sooner, and then immediately divide into numerous ramifications, which anastomose upon the choroid coat. The veins of the choroid coat are larger than the arteries, and pass from before backwards, describing arches, and converging towards the posterior part of the eye, where they form three or four distinct venous trunks, w’hich pierce the sclerotic coat, and terminate in the ophthalmic vein, which empties itself into the cavernous sinus. Ruysch separated these vascular distributions from each other, di- viding them into two layers, the inner of which has gained the name of the membrana Ruyschiana, and secretes the pigmentum nigrum. Ligamentum ciliare — is a grey ring, of considerable firm- ness, forming a boundary to the anterior extremity of the choroid coat, and a bond of union between the sclerotic and choroid coats, and the iris. Its broadest part is not more than two lines in breadth, it is of a pulpy consistence, and from receiving the distribution of the ciliary nerves, and sending off other nerves to the iris, it has been considered by some anatomists as a ganglion, although its structure is unknown. Of the iris . — This is a delicate circular membrane, sus- pended vertically from the ciliary ligament, and behind the transparent cornea, so as to separate the space between the crystalline lens and the cornea into chambers, the anterior of which is much the larger of the two. They communicate with each other freely through the central aperture of the iris, which is called the pupil. The pupil is not placed in the centre of the iris, but rather nearer to its nasal than its temporal side. The iris has the power, during life, of con- tracting and expanding, so as to vary the dimension of the pupil. The circumference of the iris corresponds to the ciliary ligament ; the opening in its centre forms the limits of the THE ORGANS OF THE SENSES. 327 pupil ; its anterior surface, forming 1 the posterior boun- dary of the anterior chamber of the eye, is covered by the membrane of the aqueous humor, and presents different colors in different individuals, but which in some measure correspond with the color of the hair. On this surface may be observed striae, passing- from the outer circumference to- wards the pupil, where they meet other striae, appearing- like a fasciculus of circular fibres surrounding the pupil. These fibres have been supposed by some anatomists to be mus- cular ; and Dr. Maunroir, of Geneva, considered the radiating fibres were for the purpose of dilating', while the circular fibres were for the purpose of contracting' the pupil, and forming a sphincter muscle. There is every reason to believe that the pupil is under the influence of a sphincter muscle, which, like the other sphincters in the body, has a tendency to remain permanently closed — and to be opened only by the action of its moderators. This is evinced by the circumstance which occurs upon the exhibition of a powerful narcotic, which, overcoming the action of voluntary muscles, leaves the pupil permanently contracted. This occurred but a short time since at Guy’s Hospital, in a woman who made an attempt to destroy her- self, by taking- a large quantity of laudanum. The posterior surface of the iris is covered by pigmentum nigrum, which, in the intervals of the ciliary processes, is continuous with the inner surface of the choroid coat ; and when the posterior surface of the iris is washed, a number of converging striae may be observed, passing from the cir- cumference of the pupil, where they become blended, so as to form a membranous zone. The iris is abundantly supplied with nerves and arteries, in a manner which has already been described. In the foetus, the pupil, up to the seventh month of utero-gestation, is closed by a delicate vascular membrane, termed the mem- brana pupillaris ; which is supposed to be formed of a division of the aqueous membrane into two distinct bags, uniting at the pupil, and which afterwards becomes ruptured. 328 THE ORGANS OF THE SENSES, On the choroid coat, ciliary ligament, and iris being dis- sected off, the retina is exposed — which should next be considered. The retina — as usually described, is placed between the choroid coat, and the vitreous humour ; but there is, in fact, placed between them Jacob’s membrane, which will be afterwards noticed. The retina extends from the optic nerve, with which it is continuous, nearly as far forwards as the corpus ciliare, within about two lines of which it terminates by a distinct edge. Its structure is soft, and pulpy ; and from the manner in which it commences from the optic nerve, it does not seem to be the expansion of that nerve, but rather, as considered by M. Ribes, as a membrane to receive the distribution of its medullary structure. After death, the retina is semi-transparent, and of a pale white color ; it appears to be formed of two layers, which are separable, and more readily so when the central artery has been injected. Upon the inner layer, the distribution of this vessel may be traced, rendered quite vascular, while the outer layer is medullary. This division may also be demonstrated by macerating the eye for some days, when the medullary sub- stance may be washed off, and the vascular coat left entire. Anterior to the apparent termination of the retina, just poste- rior to the corpus ciliare, there is a structure proceeding forwards to the crystalline lens, of which various opinions have been formed. Many anatomists consider it as a con- tinuation of the retina, which they describe therefore, as terminating at the circumference of the lens. The late Sir William Adams considered it as a distinct structure, and from its tenacity and firmness named it the ligament of the retina. At any rate, it is demonstrable that there is a substance resting on the hyaloid membrane, and placed be- tween the defined line, forming the apparent termination of the retina, and the crystalline lens ; which to me appears to be a continuation of the tunica vasculosa retinae — the me- dullary layer terminating at the point described, two lines posterior to the corpus ciliare; anterior to which its prolong- THE ORGANS OF THE SENSES. 329 ation could afford no service to vision, as the rays refracted by the lens could not impinge it. The inner layer is termed the tunica vasculosa retince. On the inner surface of the retina, about two lines to the outer or temporal side of the entrance of the optic nerve, a yellow spot (termed by Soemmerring the “ limbus luteus ,”) may be seen, in the centre of which is situated the “ foramen centrale .” These appearances being placed immediately in the axis of vision, have led to much physiological speculation with respect to their use, although little or nothing seems to be known about them. Besides the two layers of the retina, which have been described, it receives a distinct external covering from Jacob’s membrane, which, according to some dissections made by my friend Mr. John Dalrymple, seems to be a dis- tinct serous membrane, covering both the external surface of the retina, and the internal surface of the choroid coat. That a membrane did exist between the retina and choroid coat, was first demonstrated by Mr. Jacob, of Dublin, whose name has been given to it ; but he did not describe it as a closed serous bag. This membrane may be shewn, by care- fully tearing the choroid through, and everting it, when small portions of Jacob’s membrane may be detached from the retina, and by inflation, rendered distinct from the medul- lary layer. The corpus ciliare — is a dark ring, constituted by the union of all the ciliary processes, posteriorly ; it is bounded behind, by the retina ; before, by the ciliary processes ; on its outer circumference, by the choroid coat; and on its inner, by the hyaloid membrane. From its anterior edge from sixty to eighty small vasculo- membranous bodies project, placed beside each other, which are the — Ciliary processes. — They pass forwards, surround the cir- cumference of the crystalline lens, projecting into the poste- rior chamber, and are placed behind the iris and the ciliary ligament. These processes are alternately, long' and short ; 330 THE ORGANS OF THE SENSES. and as there is a space between each two of them, the hyaloid membrane and circumference of the crystalline lens become stained in these spaces by the pigmentum nigrum, in consequence of the choroid and hyaloid membranes coming in contact. The form of each ciliary process is triangular ; the base is attached to the ciliary body, the apex is free in the posterior chamber of the eye ; the superior surface is directed for- wards to the iris, and the inferior backwards to the lens. The Humours of the Eye. The aqueous humour — enclosed within its proper mem- brane, is placed immediately behind the transparent cornea, and occupies the anterior and posterior chambers of the eye, so as to be opposed both to the anterior and posterior surface of the iris, and the anterior surface of the crystalline lens. Its quantity is about six grains ; it is secreted by its mem- brane, which is capable of reproducing it in a very short space of time, if it be evacuated either by accident, or during any operation. The aqueous humour is slightly viscid ; it does not co- agulate, either by acids or alcohol ; nor if submitted to heat, does it deposit any residuum. Its s. g. is 1 • 0003 ; it con- tains, according to Brande, a minute quantity of albumen ; and according toChenevix, gelatin, albumen, and some small quantity of salines. In the foetus, the aqueous humour has a reddish tint. The crystalline lens — is placed between the aqueous and the vitreous humours ; and with respect to its situation in the eye, is at about the junction of the two posterior thirds with the anterior third of the organ. It is not exactly placed in the centre of the antero-posterior axis of the globe, but rather to its nasal side — its axis corresponding to that of the pupil ; it presents two convex surfaces, the posterior of which is more prominent than the anterior. It is surrounded by a fine capsule proper to it, which is described as being denser, and more elastic anteriorly, than posteriorly; its THE ORGANS OF THE SENSES. 331 specific gravity is 1 • 0790. As to its chemical composition, it differs from the aqueous humour in containing a greater quantity of gelatin, and albumen, and in the absence of saline substances ; upon the application of heat, it becomes perfectly opaque. Within its capsule, a small quantity of fluid is contained between it and the lens, which is termed the liquor Morgagni — the lens itself being composed of a concentric laminated structure, soft and semi-fluid at its outer surface, and harder as it approaches the centre, where it has a nucleus, nearly of a solid consistence. The crystalline lens is held in its situation by the splitting of the hyaloid membrane, one layer of which passes anterior, and the other posterior to it. Where the two layers of the hyaloid membrane reach the circumference of the crystalline lens, a triangular space is left, which runs around the lens, and is termed the canal of Petit. This canal is intersected by small septa, which give to it a vesicular appearance when inflated. Such is the description of the canal of Petit, given by most anatomists ; but there are others, who believe that the hyaloid membrane does not pass in front of the lens, but that it is situated wholly behind it ; and that the membrane of the aqueous humor covers the lens in front, and uniting at its circumference with the hyaloid membrane, assists in forming the canal of Petit. If the lens be boiled, or exposed to maceration, it will separate into a number of triangular pieces, the apices of which are all directed towards the centre. In the foetus, the lens is of a reddish color, and soft ; in the adult, it is transparent ; and in old age, it becomes yellow, or of an amber color. The density of the lens gives to it a great refractive power, and its double convexity tends to draw the rays to a focus upon the retina. The vitreous humour — occupies the two posterior thirds of the globe of the eye. It is fluid, perfectly transparent, and when contained within its membrane, forms a tremulous mass. This membrane enters so intimately into the compo- 332 THE ORGANS OF THE SENSES. sition of this part of the eye, that it may be described in two parts — the vitreous fluid, and the hyaloid membrane. The vitreous humour mingles readily with water, does not coagulate by heat ; its s. g. is 1 * 0009, and is therefore rather denser than the aqueous humour ; but by chemical analysis, it is found to contain the same principles. The quantity of this humour, 'is computed to be not less than one hundred grains. The hyaloid membrane — not only surrounds the vitreous humour, but sends off" innumerable processes into it, so as to divide the whole mass into cells, which communicate very freely with each other, so that if one cell be laid open, the whole fluid escapes, although but very slowly, in conse- quence of the minuteness of the cells. The anterior part of the hyaloid membrane, between the corpus ciliare and the crystalline Jens, receives the ciliary processes in little grooves, producing therefore small projections, corresponding with the interspaces of the processes, which are marked by the pigmentum nigrum, in a striated manner, so as to give it the appearance of a disk of a flower, and is sometimes called the corona ciliaris. The use of the vitreouos humour, is to give a general support to the tunic of the eye ; and from its density being less than that of the crys- talline lens, it tends to diverge the rays, and to form a larger picture upon the retina Physiology of the Eye. The function of the eye is termed vision, or the sense of sight, and consists in the perception of the color, form, size, and distance of sur- rounding objects. In order to comprehend fully the uses of the several parts of the organ of vision, it is necessary to make a few observations upon the nature, and properties of light; which is the intermediate agent between objects, and the eye, and the cause of those impressions upon which vision depends. It is unnecessary to enumerate here all the phenomena and properties of light, as this rather belongs to the science of optics. Presuming, therefore, that the student has made himself acquainted with the elements of that science, from the “ Lectures on Natural Philosophy,” so ably given by my colleague, Mr. Barry, at Guy’s Hospital, 1 shall THE ORGANS OF THE SENSES. 333 touch upon those parts only, which directly bear upon the organization of the eye — and, first, of the nature of light. Light has been admitted to be one of the imponderable substances, emanating from the sun, and all luminous bodies. It is of two kinds, natural, and artificial. Natural light is that which is derived frein the sun, and fixed stars ; and is so termed, to distinguish it from artificial light, which is derived from the combustion of inflam- mable substances, and from bodies heated to a state of incandescence. To these sources, may perhaps be added some minor causes, such as, the state of bodies which, from certain chemical changes, become phosphorescent, or are naturally so, as the glow-worm and fire-fly ; or which emit it in concurrence with electrical phenomena. From either of these sources, light emanates in the form of rays, passing in straight lines, and with a velocity almost inconceivable. It has been computed, that light travels two hundred thousand miles in a second, or twelve millions in a minute. Light was, at first, considered as homogeneous ; but Sir Isaac Newton discovered, that when a solar ray is made to pass through a prism, it is separated and refracted into rays of different colors, producing what has been termed the solar spectrum : this consists of an oblong image, consisting of rays of seven different colors ; namely, violet, indigo, blue, green, yellow, orange, and red, blended into each other, the violet ray forming one boundary, and the red the other. These rays not only differ from each other in their color, but in their illuminating powers, and other circumstances. The greatest illumin- ating power resides in the lightest yellow, and palest green ; the least, in the violet rays. Dr. Herschel discovered that light also is accompanied by rays which excite heat, and that this power was greater in the red, and least in the violet rays ; he also observed a spot, a little beyond the red, in the solar spectrum, where there was no light, but which was even hotter than the red itself ; and inferred, that these rays must be less refrangible than those of light. Considerable variation has, however, been found in the situation of these calorific rays, apparently depending on the different powers of refracting caloric, in different transparent media. Another curious effect, produced by the decomposition of light by the prism, is, the exhibition of its chemical properties in rays, which excite neither light nor heat, but cause rapid chemical effects — hence termed chemical rays. These, according to Ritter and Wollaston, are most powerful just beyond the violet ray, and diminish from thence progressively to the green, beyond which they are wholly lost ; hence the chemical rays are more refrangible than the luminous ones. Another remarkable property 334 THE ORGANS OF THE SENSES. of light has been ascertained by Mrs. Somerville, to belong to the most refrangible or chemical rays ; namely, that of imparting magnetic powers to needles, after an exposure of about two hours to a focus of the violent rays. Certain bodies, as the diamond, and a compound named Canton’s phosphorus, have the power of absorbing light upon being exposed to the sun’s rays ; and are capable of again emitting it for a time, when removed from their influence. Rays of light, under common circumstances, pass in straight lines, and the bodies through which they pass, are termed media. Now these media, have a power of altering and modifying the course of the ray. This modification is called refraction, the light appearing as if bent or broken ; and it depends upon two circumstances : — first, upon the density, secondly, upon the combustibility of the medium through which the ray passes. Thus, when a ray of light passes from a denser to a rarer medium, as from water into air, it is refracted from a line drawn perpendicular to the point of contact ; and this refraction will be greater in proportion to the rarity of the fluid into which it passes. When, however, a ray passes from a rarer to a denser medium, as from air into water, a contrary effect ensues ; the ray is drawn or attracted towards the perpendicular ; and this in proportion to the density and combusti- bility of the medium. It was formerly supposed, that this refraction was increased by giving a peculiar shape to the medium, if solid ; but this is not the case ; for lenses have merely the power of altering the disposition of one ray with respect to another, causing them to approximate, if convex, or recede from each other, if concave. Now a piece of glass with parallel surfaces, of equal density with a convex lens, would produce an equal degree of refraction : in the former instance, passing out or emerging in a direction parallel to that of their impingence, or in which they had passed in, owing to the density being- the same throughout ; in the latter case, their direction would be unequal, and they would tend to meet in a point or focus, owing to the density, and consequently the degree of refraction being unequal. The distance of this focus may always be determined by referring to the convexity of the lens : for if it be spherical, the focus will be at the distance of one quarter of its diameter ; if for a double convex lens, the focus will be situated at the distance of the semi-diameter, of the sphere of which the surfaces of the lens form a part ; and if for a plano-convex lens, it will be seen at double the distance of a double convex lens, or at the distance of the diameter, of the sphere of which the lens forms a part. While in concave lenses, their foci will be found bearing the same relation to the concavities of the spheres of which their surfaces form parts. THE ORGANS OF THE SENSES. 335 Concave lenses have the power of diverging the rays of light, as if they proceeded from a point anterior to the lens, and this in proportion to the degree of their concavity. There are besides what are termed multiplying lenses, consisting of numerous facettes, each of which receiving the light at a separate angle, gives rise to a separate impression upon the retina, and the optical illusion of so many distinct objects. So far with respect to light passing through transparent media. Now whenever a ray of light meets a body, which is not transparent, hence termed opaque, we find that it rebounds, or is reflected from the surface, and at an angle equal to that at which it falls ; thus the angle of reflection is equal to the angle of incidence, and is opposed to re- fraction ; though it may be observed, that a body which refracts light always in some measure reflects it. Thus the modifications of light, are either transmission, reflection, or refraction ; from which modifications, the color and appearance of all surrounding bodies depend. Thus, a body which transmits some rays, and reflects others, has a translucent appearance ; such bodies as absorb all the prismatic colors hut one, will appear visible by that color or modification which it reflects. It is curious that some bodies appear very different by the light which they reflect, from that which they transmit. Thus, gold by reflected light, is of a brilliant yellow, but by refracted, of a muddy green color. The operation of light in producing the phenomena of vision, may be considered under two heads ; — the perception of color and form, de- pending directly on the rays of light ; and the perception of distance and size of objects, which is attributable to habit and experience, assisted in many instances by the sense of touch. We will now trace the progress of a ray of light, through the different transparent structures of the eye, in its passage to the retina ; and we shall find the organ a most beautifully constructed achromatic instru- ment, capable of adapting itself not only to the quantity, but the modi- fication of the light which it admits. Light reflected from opaque bodies, pass off in straight lines in every direction. Some of these rays impinge the transparent cornea ; and it is believed that they undergo some slight change in passing through the moisture which covers its anterior surface ; which may therefore be considered as essential to perfect vision. The rays which strike the opaque cornea, are reflected, and according to the laws of optics, at the angle at which they impinged ; and do not therefore interfere with the rays to be transmitted. The rays which impinge the transparent cornea, are refracted towards the perpendicular by the density of this structure ; and by its convexity, they have a 336 THE ORGANS OF THE SENSES. tendency towards a focus, so as to collect the rays in quantities corres- ponding to the size of the opening of the pupil: and, indeed, there is reason to believe that a reciprocal accommodation occurs between the re- fractive power of the transparent cornea, and the contraction or dilatation of the pupil ; which, perhaps, we may account for, by the changes which must necessarily take place in the aqueous humour upon any motion of the iris. Thus, when the pupil contracts upon the membrane containing the aqueous humour, the fluid must necessarily be pushed forwards, and the transparent cornea rendered more convex, so as to alter the focus to the contracted dimensions of the pupil ; and, on the contrary, when the pupil is large, there is more space through the pupil, for the fluid in its membrane ; consequently, less pressure, and less convexity of the transparent cornea, and a proportionable divergent direction of the rays of the enlarged opening. Those rays, however, which do not pass through the pupil, are reflected from the iris, and denote its color. The rays transmitted by the transparent cornea and aqueous humour, through the pupil to the crystalline lens, now undergo such changes as are produced by a double convex lens, modified, however, by the variety of density in its different layers, as well as by the means which the eye itself possesses of altering its own refractive power. All the light which passes upon the anterior surface of the crystalline lens, is not transmitted, part of it being reflected upon the posterior surface of the iris, where it is absorbed by the pigmentum nigrum. These rays seem to have a considerable effect upon the iris ; for the rays which fall upon its anterior surface do not excite its contraction : but those reflected from the anterior surface of the crystalline lens, are absorbed by the pigmentum nigrum, and perhaps produce those particular effects upon the iris. The rays which pass through the crystalline lens, converge so as to form a focus somewhat anterior to the surface of the retina. Were the two convex surfaces of the crystalline lens segments of the circle formed by the vitreous humour, the focus would then be in its centre; but as the posterior convexity is more prominent than the anterior, the focus cannot be in the centre of the vitreous humour. As soon as the rays emerge from the crystalline lens, they are passing from a denser to a rarer medium, and consequently diverge ; by which divergence, a larger picture is presented to the surface of the retina. In myopia there is a superabundance, in presbyopia a deficiency, in the refracting powers of the eye. In the former instance, the cornea is more prominent, and the crystalline lens more convex than natural; consequently, according to the laws of optics, the focus must be con- siderably anterior to its natural situation, though this will depend upon THE ORGANS OF THE SENSES. 337 the distance of the object; thus, an object which is near, forming a greater angle, will have its focus still farther removed, so that it will be about its natural situation, Nowit is obvious, that any thing which will increase the angle formed by an object, must produce the same effect; this is done by means of a concave lens. In presbyopia, we find the cornea and crystalline lens considerably flattened ; so that according to the laws of optics, the focus will be prolonged beyond its natural situation. Here, therefore, any thing which will diminish the angle, will remove this defect: this is done either naturally, by removing the object to a greater distance, or artificially, by means of a convex lens, which, by converging the rays, must necessarily increase the angle at which they fall. There is considerable difficulty in comprehending how the eye adjusts itself to the examination of objects at different distances ; but it is evident that changes do take place ; for if the eye be examined when a person abstractedly brings his mind to dwell upon the consideration of a minute object, the pupil will be seen to contract ; and again, if the mind be directed to the imaginary examination of an extended landscape, the pupil will as immediately dilate. These phenomena seem to prove the necessity for some alteration in the adjustment of the globe of the eye ; and as we know of no structure capable of being stimulated by the influence of the mind, but muscle, we have some right to infer, that the muscles are the principal regulators of the adjusting powers of the eye. Let us therefore examine the attachment of these muscles, and we shall find, that they are not only capable of directing the whole organ ; but also of producing such changes in its figure, as must materially affect its foci, and refractive powers. With respect to the iris, no one has yet proved its muscularity ; and there are as many reasons to believe it is composed of an erectile tissue, as to admit of its muscular contraction. The ciliary processes, also, yet open a considerable field for investigation to the anatomist, and physiologist. Of these structures, nothing has yet been satisfactorily given. The pupil becomes motionless, and dilated, upon the division of the fifth pair of nerves ; and, according to some anatomists, the same effect takes place after the division of the third pair; and sight is also lost upon the division of the optic nerve. It is evident, that the black pigment is of considerable utility, from the defective vision of albinos, in whom it appears to be deficient of color. The picture formed on the retina, communicates the impression of dis- tance to the brain, very much by the size of the picture, and the intensity of the light ; thus, when two objects are placed at a distance, one Z 338 THE ORGANS OF THE SENSES. behind the other, if that which is farthest from the eye receives the brightest light, it will appear the nearest. I might here dwell upon the diversity of opinion with respect to the central foramen of the retina, placed as it is in the very centre of the axis of vision, whether or not it receives any impression from light. I might speak also of the points of entrance of the optic nerves, which are denied the power of the other parts of the retina, of receiving- any impression from light. But these are subjects more for the direct consi- deration of the physiologist, and therefore should not be here discussed. I would, however, strongly recommend the perusal of Potteriield, on the eye ; and the article on optics, by Dr. Brewster, in Reeces Encyclopedia. The diseases of the eye, have been so ably and frequently written on by various surgeons, and in itself offers so very extensive a subject, that I shall not here enter upon it; but refer my readers to authors who have exclusively paid attention to this branch of surgery. LECTURE XXXVII. OF THE ORGAN OF HEARING. Descriptive Anatomy of the Ear. The eav may be divided into three parts : the external or outer, which is for the purpose of collecting" sound, and conveying" it to the middle part, or cavity of the tympanum, which modifies it, and the internal part, the seat of sensation, and which is capable of appreciating" sound. Of the external part of the Ear, or Auricle. The auricle in man, although furnished with small muscles, enjoys little or no voluntary motion ; but in most animals is capable of both extensive and variable movements. It is situated on either side of the head, at the posterior part of the face, beneath the temple, and in front of the mastoid pro- cess of the temporal bone. Its figure is irregularly oval, being’ larger above than below, and having its greater diameter vertical. The circumference of the oval is free above, poste- riorly, and below ; while anteriorly, it is connected with the posterior part of the cheek. Upon the external surface of the auricle, there are nu- merous elevations and depressions, which form a series of parabolic curves, for the purpose not only of collecting, but also for directing sound into the tympanum. These eleva- tions and depressions have had names given to them, and therefore must be described. The helix — forms the outer inverted rim, commencing in the middle of the auricle, above the opening of the meatus, and directing itself first forwards, then upwards and baek- z 2 340 THE ORGANS OF THE SENSES. wards, forms the circumference of the auricle, and terminates below at the commencement of the lobe. Its inferior ex- tremity is somewhat bifid ; its upper litnb is connected with another eminence, which is termed the anti-helix, while the lower one is continuous with the lobe. A groove is pro- duced between the helix and the other part of the auricle, which commences in the concha, takes its whole course, and has been termed the fossa innominata , which is more or less distinctly marked in different individuals. The anti-helix — commences behind the helix, where it is rising' upwards from the concha to form the superior part of the auricle, by two crura, the upper one of which is broader, and more obtuse than the lower or narrower one ; they pass backwards, and uniting - form one prominence, which is thicker than the helix, becomes thinner however as it passes downwards to terminate just above the anti- tragus, from which it is separated by a depression. The depression between the two crura by which the anti-helix commences, is termed the fossa navicularis. The tragus — is a small triangular projection, which over- laps the opening of the meatus auditorius ; the base of the triangle is directed forwards towards the cheek, with which it is continuous ; and the apex overlaps the meatus. Above it is separated from the helix by a notch, and also below from the anti-tragus, which is posterior to it. The anti-tragus — is in form very similar to the tragus; it is situated below the anti-helix, and behind the tragus, from which it is separated by a notch ; its base is towards the lobe of the ear, and its apex is directed upwards, and slightly forwards towards the concha. The concha — is a deep cavity, which is bounded above and behind by the anti-helix, and below by the tragus and anti-tragus ; it is divided into two parts, an upper and a lower, by the commencement of the helix ; the lower por- tion of the concha is continuous with the meatus auditorius. The lobe of the ear — is a rounded soft eminence, void of elasticity, which forms the termination of the circumference THE ORGANS OF THE SENSES. 341 of the auricle inferiorly ; it does not appear in any way destined to perform any office in the function of the auricle. The inner surface of the auricle, does not correspond in its convexity to the irregularities produced on the external surface ; it is directed towards the head, having generally a slight inclination backwards, which would be more obvious but for the means adopted to prevent this tendency. The parts which enter into the composition of the auricle, are the skin, fibro-cartilage, ligaments, and muscles. The skin — is extremely thin, and firmly united to the fibro-cartilage by a most delicate cellular membrane, which never contains any fat, as that substance would have pre- vented the reverberation of sound ; but at the lobe, which has nothing to do towards the function of hearing, there we find the skin containing a considerable quantity of adeps. The integument of the auricle, is also furnished with a great number of sebaceous follicles, and on the inner side of the tragus with some small hairs, which seem to be for the purpose of preventing light bodies floating in the at- mosphere, from passing’ into the ear. The fibro-cartilage — is the structure which constitutes the form of the auricle, and possesses flexibility enough to admit of its motions, and elasticity sufficient to maintain its form, and offer the best possible substance to admit of the reverberation of sound. It is this substance which gives the general figure to the auricle, and produces the various eminences and depressions which have been named ; but it does not, however, continue throughout the whole surface of the organ, being in some situations deficient: for instance, it is wanting between the helix and the tragus, and also between the termination of the helix and the anti-tragus. It cannot, however, be properly said to be entirely deficient in these parts, as its fibrous tissue continues, but the car- tilaginous does not. The lobe also has no fibro-cartilage entering into its composition. The ligaments of the auricle — are three in number, and are for the purpose of fixing it to the side of the head ; from 342 THE ORGANS OF THE SENSES. their relative positions, they are termed superior, anterior, and posterior. The superior ligament — passes upwards, from the inner surface of the concha, over the posterior extremity of the zygomatic arch, and is lost by expanding upon the temporal aponeurosis. The anterior ligament — connects the auricle to the zygo- matic process ; it is attached to it, and to the base of the tragus, being continuous with its fibro-eartilage. The posterior ligament — proceeds from the convexity of the concha, and is directed backwards to the mastoid pro- cess, with which it is connected. The muscles of the auricle — are of two kinds ; those which are destined to move the whole auricle, and those which act only upon its individual parts. They are all, however, but very indistinct, and by some anatomists the existence of the second class is entirely denied; but as they are frequently found, it is right to describe them, and to consider their absence as the result of disease, and the tenacity with which children’s ears are kept confined to the side of the head, for fear they should be directed forwards, as intended by nature. The muscles common to the auricle, are three in number. M. attollens aurem — is of a thin triangular figure, arising from the temporal aponeurosis, from whence its fibres de- scend, converging as they pass downwards to be inserted into the superior part of the inner convex surface of the concha. The external surface of this muscle is covered merely by the skin ; its internal surface covers the aponeu- rosis of the temporal muscle ; its anterior edge is longer, and more oblique than its posterior edge. Use . — To elevate the auricle, and at the same time to draw it for- wards ; by which action it enlarges the concha, and opens the meatus auditorius externus. M. auricularis anterior — is smaller than the last-described muscle, and arises from the temporal aponeurosis, at the THE ORGANS OF THE SENSES. 343 posterior extremity of the zygomatic arch, from which point its fibres pass backwards to be inserted into the inner surface of the helix; above, it is bounded by the last-described muscle ; while its lower edge has immediately below it, the zygoma. Use . — To assist the attollens in drawing the auricle upwards and forwards. M. auricularis posterior, vel retrahens auriculam. — This muscle is usually composed of three or four distinct bundles, which proceed forwards from the anterior edge of the mastoid process, to be inserted into the inner surface of the lower part of the concha, by distinct aponeurotic fibres. Use . — To draw the auricle backwards, and to contract in some measure, the opening of the meatus externus. The muscles proper to the auricle, are five in number. M. fragicus — is the largest of the five, and may almost invariably be found ; it is of a triangular form, corresponding to the figure of the tragus ; it arises from the base of the tragus, and passes forwards, the fibres converging to be inserted at the apex of that body. Use . — To draw the apex outwards and backwards, and to enlarge the opening of the meatus externus. M. anti-tragicus — passes from the upper part of the fibro- cartilage, supporting the anti-tragus, and fills up the space or notch between the anti-tragus and anti-helix, to the fibro- cartilage of which it is also connected. Use . — Either to direct the apex of the anti-tragus outwards, by which action it enlarges the opening of the meatus, or else to draw downwards the anti-helix ; and in this action, perhaps, it renders the whole auricle a better vibratory medium. M. helicis major — is attached to the helix major, just where it is passing above the tragus ; from whence it passes downwards to be inserted into the fibro-cartilage of the helix, where it arises from the concha. Use . — To render the commencement of the helix major tense, and to deepen the concha. 344 THE ORGANS OF THE SENSES. M. helicis minor — is situated behind and below the pre- ceding- muscle, within the concha, being- attached to the commencement of the helix major. Use . — To assist in increasing the concavity of the concha. M. transversus auriculce — is placed upon the inner or convex surface of the auricle ; it arises from the prominence produced by the fossa innominata, and is lost upon the con- vexity of the concha. Use — -To diminish the depth of the concha, and antagonize the helices muscles. The arteries of the auricle are dervived from the ramulus a. auricularis posterior, and ramulus a. temporalis, of the external carotid ramus. The nerves spring- from the auricular ramus n. of the third division of the fifth pair, from the posterior auricular ramus of the portio dura, or seventh pair, and from auricular filaments from the cervical plexus. Its absorbents pass to glands which are placed behind the temporo-maxillary articulation, upon the outer surface of the sterno-cleido mastoideus muscle. The meatus auditorius externus — leads from the auricle to the cavity of the tympanum, and is placed between the mastoid process of the temporal bone, which is behind it, and the temporo-maxillary articulation in front of it, the zyg’omatic process above it, and the vaginal and styloid processes below it. In the adult subject, it is from eleven to twelve lines in extent, but does not pass in a straight direction, having an obliquity forwards as it passes inwards. It is also curved in this direction in such a manner that its calibre presents a convexity upwards, and a concavity down- wards. Its inner extremity terminates obliquely, as if truncated from above downwards, and from without to within, so that its inferior surface is longer than its superior. The meatus auditorius is formed of skin, fibro-cartilage, ceruminous glands, and bone. The skin — is a continuation of the integuments of the THE ORGANS OF THE SENSES. 345 auricle passing into the meatus, and forming upon the external surface of the membrana tympani, a cul de sac, from which it is very readily separated by a putrifactive pro- cess. As it first enters the meatus, it is of the same thickness as on the auricle, but becomes more and more attenuated as it approaches the tympanum. In its course it is fur- nished with very small hairs, which are most evident at the commencement of the meatus. It is also perforated by a number of small openings, which are the mouths of the excretory ducts of the ceruminous glands. These are prin- cipally situated in the upper and posterior part of the meatus. The jibro- cartilage — is continued from that of the tragus, and also from the inferior part of the concha, forming only a portion of a canal, the interspaces being filled up so as to complete the circle by fibrous tissue ; thus connecting the soft w r ith the bony structures of the meatus. The spaces between the fibro-cartilaginous portions, which are filled up by the fibrous tissue, have been termed the fissurse of Santorini ; the larger of which is at the upper and back part of the meatus. The ceruminous glands — are placed between the skin and the fibro-eartilage, imbedded in cellular membrane ; they are most numerous in the upper, and back part in the fissure of Santorini ; they are of a reddish yellow color, each being furnished with an excretory duet, to convey their peculiar secretion into the meatus. This secretion is a thick bitter fluid, but slightly soluble in w r ater, and according to Vauquelin, contains an oil, albumen, and coloring matter. Of the Tympanum. The tympanum — or middle portion of the ear, is that cavity placed between the meatus auditorius externus, and the labyrinth. The tympanum is very irregular in its form, but it presents parts of so much importance to the function of hearing, as to 346 THE ORGANS OF THE SENSES. render it quite necessary to subdivide this cavity into different surfaces or walls. It presents, therefore, an external wall, filled by the membrane of the tympanum, and opposed to the meatus auditorius externus ; an internal wall, which separates the cavity of the tympanum from the labyrinth ; an anterior wall, which is bounded by the eustachian tube; a posterior wall, opposed to the mastoid process of the temporal bone ; a floor, bounded by the carotid canal, and fossa jugularis; and a roof, which is bounded by the opening to the mastoid cells, which pass upwards, backwards, and downwards, to the mastoid process. The external wall — admits of little farther description than that of the membrana tympani, which principally composes it; unless, indeed, we describe the rim of bone which re- ceives that membrane. This aperture, or rim of bone, forms three-fourths of an oval figure ; the upper fourth not pre- senting a continuation of the oval, but an irregular hori- zontal line, passing from before backwards. The principal irregularity in this line is produced at its upper, and anterior part, for the purpose of containing a membrane, which has been discovered by my friend Mr. Shrapnell ; and of which I shall give a short description, with the rest of the mem- brana tympani. The membrana tympani — forms by far the larger portion of the outer wall, presenting an obliquity from above down- wards, and from without to within, so as to form a very acute angle with the inferior surface of the meatus auditorius externus. The membrana tympani, is covered externally, by the skin of the meatus auditorius, and internally, by the lining mucous membrane of the cavity of the tympanum ; while the middle fibrous tissue, is composed of radiating fibres, emanating from the manubrium of the malleus, to pass to the groove which is lodged in the bony ring just described. This membrane then, in fact, admits the manubrium of the malleus, so that the upper two thirds of the membrane are divided into two by this process of bone. THE ORGA.NS OF THE SENSES. 347 From the upper and anterior part of the membrana tym- pani, and occupying’ the irregularity which has been de- scribed, in the horizontal upper fourth of the oval rim of bone, there is a membrane differing from the larger portion, in its structure, in the distribution of its fibres, in the plane of its surface, as well as in not being received into a groove. These circumstances, prove the necessary physiological difference between this portion and the rest of the membrana tympani ; the latter being- in every way adapted, from its tension, to vibrate ; while the former is, from its flaccid state, constituted, rather to annihilate, than to propagate vibration. This portion of the membrane, Mr. Shrapnell has termed the membrana flaecida : — a name aptly chosen, as it points out at once, that the membrana tympani is not only for the purpose of increasing, but under certain circumstances of diminishing the force of vibration. The particular direction of the plane of the membrana tympani, will be mentioned when describing the manubrium of the malleus, upon its attachment to which it depends. The inner wall — presents the following important parts. The fenestra ovalis — has its long axis placed horizontally, and is situated in about the centre of the inner wall, but rather more to its upper and posterior part. The upper part of this oval foramen, has passing over it a projection, which marks the course of the canal of Fallopius ; below the fe- nestra, there is a projection of bone termed the promontory, beneath which, and rather posterior to the centre of the fenestra ovalis, is situated the — Fenestra rotunda — which is so overlapped by the pro- montory, as to require the temporal bone to be held in a particular direction to bring it into view. At the junction of the inner with the posterior wall of the tympanum, foramina are found, which admit of the passage of nerves from the canal of Fallopius, as well as from a distinct foramen, through which a filament passes from the glosso-pharyngeal nerve. At the junction of the anterior and inner wall, the 348 THE ORGANS OF THE SENSES. two surfaces concur in forming- passages for the entrance of the eustachian tube, and the tensor internus muscle. The anterior wall — in the dry bone, presents little to be observed, beyond the spaces for the eustachian tube, and tensor tympani muscle ; there is, however, above this a small opening, which leads to the fissura Glasseri, to transmit the chorda tympani nerve, and admit the laxator tympani muscle. The posterior wall — is almost a cribriform plate of bone, some of the foramina admitting of the nerves to enter the tympanum from the canal of Fallopius, and others leading into the mastoid cells. Upon this wall is to be observed, pointing to the long axis of the fenestra ovalis, a hollow projection of bone, which is termed the processus pyra- midalis, and which gives attachment to, and contains the museulus stapedius. On the outer side of this pyramid being nearer to the outer than the inner wall, it is, that the foramen is situated, for the passage of the filament of the glosso- pharyngeal nerve ; and above the pyramid nearest to the inner wall, small foramina are placed, which admit of the nervous filaments from the canal of Fallopius. The floor of the tympanum — furnishes foramina for the entrance of nervous filaments from the carotid canal, which, with the fossa-jugularis, forms its boundary. The roof of the tympanum — presents an opening of con- siderable size, which leads backwards and downwards, into the mastoid cells, but nothing further worthy of observation. Th e eustachian tube — which has been described as opening into the anterior part of the cavity of the tympanum, leads from the upper part of the pharynx to the ear, and is termed the iter a palato ad aurem. It is composed of bone, fibro- cartilage, and membrane, is about two inches in length, and in its course from the ear to the pharynx, is directed for- wards, inwards, and downwards, terminating near the inner lamina of the pterygoid process of the sphenoid bone, by a large aperture, the sides of which, however, so approximate as to form it into a kind of fissure. The bony part of the eustachian tube, is placed above the THE ORGANS OF THE SENSES. 349 carotid canal, and on the inner side of the fissura Glasseri, in the angle formed by the junction of the squamous with the petrous portion of the temporal bone. The fibro-carti- laginous portion does not form the whole circumference of its calibre, but only the inner, and anterior part of the outer wall of the canal ; it commences by being attached to the bony irregularities of the eustachian tube ; and as it passes forwards, towards the pharynx, it assists in filling up the foramen lacerum basis cranii anterius. The fibro-cartilage of the eustachian tube — gives attach- ment to the pterygoideus intern us, circumflexus palati, levator palati, and the tensor tympani muscles. The membranous portion of the eustachian tube, forms the principal part of its outer parietes, and unites the two edges of the fibro-cartilage — thus completing the canal. It seems to be a continuation of the mucous membrane of the pharynx, but much lighter in color, as it approaches the ear ; and having gained the tympanum, its texture and secretion are quite altered, so as to have led some anatomists to deny the lining of the tympanum by raucous membrane. At its pharyngeal extremity, the mucous membrane is much thicker and redder, and furnished with numerous mucous follicles. The ossicula auclitus — or bones contained in the tym- panum, are four in number ; and are termed the malleus incus, os orbiculare, and stapes. Malleus — is placed on the superior part of the inner side of the membrana tympani, and is furnished with a head, neck, processus gracilis, and the manubrium. The head forms the upper part of the bone, is ovoid, presenting posteriorly, a double, smooth, articulatory surface, to be articulated with the incus ; this surface is divided into two by a slight non-artieulatory process. The neck is very small, being scarcely more than a line in leng’th, and unites the head to the manubrium ; it is situated at the upper part of the membrana tympani, and gives attachment to a deli- cate lengthened process, which is termed the processus gracilis. This process, passes horizontally outwards and 350 THE ORGANS OF THE SENSES. forwards, to traverse the fissura Glasseri, and gives attach- ment to the laxator tympani muscle. The manubrium — of the malleus, is narrower than the neck, and passes obliquely downwards, forwards, and out- wards, so as to be connected with the membrana tympani, terminating by a thin rounded extremity, which corresponds to the junction of the middle with the inferior third of the membrane. From the upper and outer part of the manu- brium, there projects a short process, which is sometimes termed the processus obtusus, which is attached by ligament to the bony rim of the outer wall of the tympanum, and forms a fulcrum for the motions of the malleus. This little process, close to its origin from the manubrium, gives attach- ment to the tensor, or internal muscle of the malleus. Incus — is situated behind the malleus, and to its inner side, nearer to the mastoid cells. It presents a body, and two crura, which are separated from each other, and are of unequal length. The body — or head, is directed forwards, and slightly upwards, and presents a concave, semilunar, articulatory cavity, which is divided into two surfaces to receive the head of the malleus. The superior crus — is the shorter, is strong and thick, and is directed downwards and backwards, to be connected by iig'ament to the posterior wall of the tympanum, close to the openings of the mastoid cells. This crus forms another fulcrum for the motions of the bones of the ear. The inferior crus — is much the longer, and is directed downwards, forwards, and inwards, to be articulated to the os orbiculare, so that its inferior extremity on its inner side presents a small articular surface ; in this course, the inferior crus of the incus runs nearly parallel with the manubrium of the malleus. Os orbiculare — is a small round bone, placed between the inferior crus of the incus, and head of the stapes; it presents, therefore, an inner, and an outer articular surface, for these two bones. THE ORGANS OF THE SENSES. 351 Stapes — is situated between the os orbiculare, and the fenestra ovalis, the long- axis of its base being placed hori- zontally; it is divided into its head, neck, two cruTa, and base. The head — is directed outwards, and presents a small concave articular surface, to receive the os orbiculare ; it is connected to the rest of the bone, by a small neck, which results from the union of the two crura, the neck giving attachment to the stapedius muscle. The crura are placed horizontally, one before the other: the anterior crus, is longer than the posterior, and both of them are curved ; they pass to be attached to the base, forming a space, of a parabolic figure, which is filled up by a membrane. The base — forms the inner part of the bone, is a broad and thin plate, of an oval figure, its long axis being placed horizontally, and applied to the fenestra ovalis, which it imperfectly closes, but is connected to its circumference by the membranes of the tympanum, and vestibule. Muscles of the Ossicula. M. tensor tympani, vel internus malleus — arises from the petrous portion of the temporal bone, and the osseous canal of the eustachian tube ; from this point, it takes its course backwards and outwards, parallel to and above the eusta- chian tube, enclosed in a distinct canal ; when it reaches the cavity of the tympanum, it becomes tendinous, and passes through a hamulary process, at the termination of the canal, and taking its course slightly upwards and outwards, to be inserted into the processus obtusus of the malleus. Use . — To draw the manubrium of the malleus, and consequently the membrana tympani forwards, upwards, and inwards — thus rendering it tense. M. laxator tympani, vel malleus externus. — This muscle arises from the little styloid process, at the extremity of the spine of the sphenoid bone, and from the cartilaginous por- tion of the eustachian tube, and then passes backwards to enter the glenoid fissure, and thus gain the cavity of the 352 THE ORGANS OF THE SENSES. tympanum, where it is inserted, by passing slightly outwards, into the processus gracilis of the malleus. Use . — Is not, as usually described, to relax the tympanum; this must be obvious at once to any one who examines the direction of its course, and point of attachment to the malleus, which must produce a motion of the membrane, similar to the last-described muscle; and conse- quently, in concert with it. It may properly enough, therefore, be called the m. tensor t3 r mpani externus. M. stapedius — is a delicate round muscle, contained in the cavity of the processus pyramidalis, from the interior of which it arises ; its tendon passes out of the foramen at the apex of the pyramid, to be inserted into the posterior crus of the stapes, close to its neck. Use . — To draw the head of the stapes backwards, and elevate the anterior extremity of its base ; it may also act upon the whole chain of the ossicula, rendering- them tense. The tympanum is lined by membrane, which is continued from the pharynx, and is therefore a portion of the gastro- pulmonary mucous membrane ; but in different parts of its course along the eustachian tube, and more particularly in the cavity of the tympanum itself, its structure and secretion differ so much, as frequently even to lose the character of mucous membrane, and has led some physiologists to deny its existence in these parts. The Labyrinth. The labyrinth — is the third, or internal portion of the ear; it is placed between the tympanum, and the meatus audito- rius internus, and is composed of the vestibule, semi-circular canals, and cochlea. The vestibule . — In prosecuting the dissection of the ear according to the plan I have here adopted, I should wish first to direct the student’s attention to the precise position of the vestibule, which is a cavity placed immediately to the inner side of the fenestra ovaiis. This cavity is of an irre- gular figure, about the size of a swan-shot, presenting strong parietes in every direction ; and the following fora- mina opening into, and from it. THE ORGANS OF THE SENSES. 353 The first opening-, is the one we have already described from the tympanum, the fenestra ovalis, which forms the greater portion of the outer wall, or boundary of the vestibule. Posteriorly, there are five openings from the semi-circular canals, the relative position of which will be immediately described. Upon the posterior part of the inner wall, a sixth is found, the entrance of the aqueduetus vestibuli, which, externally has already been described to open immediately behind the foramen auditivum internum. The last or seventh opening, is the scala vestibuli, which leads down to, and indeed assists in forming the cochlea. This opening is placed in the inferior part of anterior wall of the vestibule There might also be mentioned some very minute foramina, which give passage to the filaments of the portio mollis. Of the Semi-circular Canals. These are three in number, placed within the substance of the petrous portion of the temporal bone, above and be- hind the vestibule. Their direction differs ; and with respect to the long axis of the petrous portion of the temporal bone, they may be named the vertical, the oblique, and the hori- zontal canal. The vertical — usually called the superior vertical canal, is intermediate in size, between the oblique and the hori- zontal ; it presents an internal and external crus, and its convexity faces immediately upwards. It is hollow, as its name would imply ; and its outer crus opens upon the outer side of the roof of the vestibule, near to the posterior wall. Its inner crus forms a common opening with the superior crus of the oblique canal on the internal w-all. The oblique canal — is placed on the inner side of the other two canals, and is nearly parallel with the posterior surface of the petrous portion of the temporal bone ; its convexity is directed towards the mastoid process of the temporal bone ; its superior crus opens in common with the internal of the vertical, and its inferior near to the commence- ment of the scala vestibuli. 2 A 354 THE ORGANS OF THE SENSES. The horizontal canal — is the smallest of the three, and is placed below, — each crus opening- separately into the vesti- bule. The outer crus opens immediately below the outer crus of the vertical canal, and the inner opens between the two crura of the oblique canal. The convexity of this canal is directed backwards, towards the mastoid process of the temporal bone. Where these semi-circular canals terminate in the vestibule, they each enlarg-e at one of their extremities, — forming what is termed the ampulla. The ampullae of the vertical and the horizontal canals, are formed by their outer crura ; and in the oblique canal, by its inferior crus. The continuation of these ampullae, seem to form a larg-e proportion of the cavity of the vestibule ; and that of the inferior crus of the oblique, may be traced as continuous with the scala vestibuli. The cochlea — forms a part of the labyrinth ; but it may also be said, in some measure, to belong to the cavity of the tympanum, below, and to the inner side of which it is placed. The cochlea is made up of two canals, separated from each other by a spiral process of bone, which are winding around a central pillar called the modiolus, and are all enclosed in the substance of the petrous portion of the temporal bone. The first canal to be described, is the scala tympani — which commences from the fenestra rotunda, passing down- wards, forwards, and inwards, and taking the two turns and a half around the modiolus, it terminates at the apex of that pillar of bone in an opening. The roof of this canal is in its whole course formed by the lamina spiralis. Lamina spiralis — commences from the vestibular side of the inner wall of the tympanum, between the fenestra ovalis, and the fenestra rotunda, separating those foramina from each other as the promontory does upon the inner wall of the tympanum; from that point it passes forwards and inwards, until it meets the modiolus, around which it takes two turns and a half ; and at the apex or outer extremity of this pillar, it projects a little over the opening of the scala tympani, and THE ORGANS OF THE SENSES. 355 terminates in what is called the hamulary process. From the anterior part of the vestibule, and consequently above the lamina spiralis, the scala vestibuli commences. This canal passes downwards and forwards, until it meets with the modiolus, around which it takes two turns and a half, terminating- at the apex of the modiolus, above the hamulary process of the lamina spiralis. The modiolus — is a pillar, which crosses at right angles the petrous portion of the temporal bone, extending from the ter- mination of the foramen auditivum internum, obliquely out- wards, to the cupola of the cochlea. The modiolus is conical in its form, its base is towards the foramen auditivum internum, and is cribriform for the passage of the portio mollis. The apex which terminates the modiolus, as well as the scala vestibuli, the scala tympani, and the lamina spiralis, are all overlapped by the concave portion of bone termed the cupola, in which there must therefore be placed two open- ings — one, the termination of the scala tympani, and the other, the termination of the scala vestibuli. If a fluid were injected from the vestibule into the cochlea, it would fill both scalae, but not pass into the cavity of the tympanum, as the fenestra rotunda is closed by a membrane. The bony cavities of the labyrinth are lined by a very delicate membrane, which proceeds from the cavity of the vestibule into all the semi-circular canals, forming within them smaller canals than the bones themselves ; and from the anterior part of the vestibule, it also passes down the scala vestibuli, covering the upper surface of the lamina spiralis ; it then proceeds to the hamulary process within the cupola, winds around it to gain the scala tympani, lining it in a similar manner. It should be remarked, however, that the lamina spiralis in separating the scalse from each other, does not form a com- plete bony partition ; one half being membranous, but that part of the lamina spiralis which is next to the modiolus, is bony. The cavity of this mambrane, contains a fluid which is somewhat viscid, fills all the cavities of the labyrinth, and 2 a 2 356 THE ORGANS OF THE SENSES. is opposed to the ultimate and sentient extremities of the portio mollis. From the scala tympani, just within the membrana fenestra rotunda, a minute opening - , named the aqueductus cochlece, leads to the base of the petrous portion of the temporal bone, where it opens under the dura mater, between the fossa jugularis and carotid canal. The nerves which supply the organs of hearing, are the portio dura, portio mollis, glosso-pharyngeal,and sympathetic. The portio dura and the portio mollis together pass into the foramen auditivum internum, at the bottom of which they separate — the portio dura to enter the canal of Fallopius, and the portio mollis to pass through the cribriform openings of the labyrinth. But just before these two nerves sepa- rate, according to the recent dissections of my friend Mr. Shrapnell, they decidedly communicate with each other; which circumstance has been denied by most anatomists. The portio dura, soon after it has entered the canal of Fallopius, receives the superior nervous ramulus from the ramus vidianus of Meckel’s ganglion, which enters at the foramen innominatnm; and these nerves also unite with each other, and together proceed along the canal of Fallopius, in a direction upwards and backwards, over the inner wall of the tympanum, and immediately above the fenestra ovalis ; it is then directed downwards and backwards to gain the foramen stylo-mastoideum, where it passes out to be distri- buted upon the face. In this course, however, immediately behind the fenestra ovalis, and at the base of the processus pyramidalis, there is a foramen which leads from the canal of Fallopius, and through which a nerve passes into the cavity of the tympanum : this nerve has always been hitherto described as the chorda tympani, and taking its course for- wards between the manubrium of the malleus and the long crus of the incus, to gain the fissura glasseri, and to be ulti- mately connected with the ramusculus gustatorius of the ramus n. maxillarius inferior, of the third division of the fifth pair. THE ORGANS OF THE SENSES. 357 Mr. Shrapnell, however, describes the nerve which passes out of this foramen, as dividing into two or three filaments — one passing upon the promontory, to unite with filaments from the carotid canal ; another, which passes to the mem- brane of the stapes ; and a third, to the stapedius muscle : while the chorda tympani, he considers as emanating from the glosso-pharyngeal nerve, entering a foramen immedi- ately anterior to the stylo-mastoid foramen, passing up in the direction of the canal of Fallopius, as far as the posterior wall of the tympanum, upon the outer side of which it opens close so the junction of the straight portion of the bony rim of the membrane of the tympanum with the posterior wall. Through this foramen, the filament of the glosso- pharyngeal nerve passes, and becomes the chorda tympani, taking’ the course before described. I think it right, knowing the numerous preparations Mr. Shrapnell has made in the examination of this question, to take this early opportunity of publishing his opinions ; although I have not yet satisfied myself of the propriety of his describing the chorda tympani as a branch from the glosso-pharyngeal nerve. But as he is now preparing a work upon the anatomy of the ear, the result of his dissec- tions will soon be laid before the public. It is quite clear, that the nervus innominatus, glosso-pharyngeal, filaments from the portio dura, and from the superior cervical ganglion of the sympathetic nerve, all concur in supplying the parts within the tympanum, and form intimate junctions with each other. The portio mollis within the meatus auditivus internus, divides into two rami ; one passing to the cochlea, the other to the vestibule; the latter enters the vestibule by three ramuli, and is distributed as described, page 241. Physiology of Hearing. The ear perceives sounds, and distinguishes their variety, distance, and intensity : sound bearing the same relation to the ear and its perceptions, that light does to the eye in vision. It will be necessary, 358 THE ORGANS OF THE SENSES. in order to understand the function of the several parts of the ear, to examine and make a few observations upon the nature and properties of sound. Sound is the result of a vibratory motion among the particles of elastic bodies, which motion is caused by exterior forces, and is capable of being communicated to surrounding bodies, and of being propagated by them. Thus, the air is the general medium of communication between sonorous bodies and the ear; but as solids also communicate sounds, they also may be made the means of communication, either, directly, through their substance, or by being hollowed so as to concentrate the vibrations— thus increasing the effect of those communicated by the air. The vibratory motion of sounds, may he either slow, or rapid, producing what has been termed acute and grave sounds. It has been calculated, that the gravest sound consists of thirty-two vibrations in a second, and the most acute, of twelve thousand; these limits constituting the range of appreciable sounds. Appreciable sounds or tones, are found to bear a certain relation to each other, constituting harmony. Thus, a distinguishable sound or tone of double the number of vibrations of another, has an harmonious relation to it, and is termed its octave ; while the intermediate vibrations between one octave and another, produce seven appreciable sounds; these constitute the gamut, or diatonic scale of music, distinguished in musical writing as the notes of the octave, and are lettered a. b. c. d. e. f. g., and are designated by the names ut, re, mi, fa, sol, la, si ; the further consideration of which, belongs to the science of music. Sounds which are not appreciable by the ear, from the number of vibrations, are termed noises. Besides the tones or notes of the gamut, the ear distinguishes the expression or timbre, depending upon the nature of the sonorous body; thus, when wood or metal is struck, or in the still more familiar instance of the voice, the ear instantly distinguishes each variety of expression. Sound travels, or is propagated through bodies with various degrees of rapidity. Thus, in air at the rate of one thousand one hundred and thirty feet in a second, or about thirteen miles in a minute; and according to Cladni, in water four thousand nine hundred, in wood twelve thousand feet in a second ; it however loses its force or intensity in exact proportion to the square of the distance from whence it emanates ; and all sorts of sounds are propagated with the same rapidity, and without change. When sound meets a body that prevents its passing, it is reflected in angles equal to those of incidence : and the impression on the ear of reflected sound, is termed echo. Reflected THE ORGANS OF THE SENSES. 359 sounds are capable of concentration, and will be heard more distinctly at the point of focus. We should now examine how well the organs of hearing are appro- priated to the collection, modification, and perception of sound. The external ear is placed in the most advantageous situation to be impressed by the air, when influenced by the motions of the particles of a sonorous body Its form and tissues admit of the impinging air being collected and reflected so as to form a focus upon the meatus auditivus externus : this is produced by the parabolic curves of the eminences and depressions of the external ear. In most animals, the auricle enjoys a considerable degree of motion, so as to be directed either towards or from a sound, as it may either be agreeably or too violently impressed — making this part of the organ a safeguard to the more delicate struc- tures. Man, however, possesses but little of these powers, although more perhaps than at first view we are led to expect; for we have reason to believe, that the external ear performs its part in modifying an intense sound, when by the will it is prepared for any violent concussion. The undulating air thus collected by the auricle, and conveyed into the meatus auditorius externus, impinges the membrane of the tympanum, which becomes affected, and as is believed by some physi- ologists, is in itself capable of modifying the degree of sound it should communicate to the ossicula auditus. The late Sir Everard Home was of opinion, that a muscular structure entered into the composition of this membrane; while it is generally believed, that this membrane is only capable of modifying sound by the action of the muscles of the ossicula. From the membrane of the tympanum, some doubt may arise as to the means by which the sound is conveyed to the labyrinth. By some it is believed, that the small bones alone communicate the sound ; by others, that the air contained within the tympanum is the means by which it is conducted : it is right, perhaps, to consider that each assists in the function of the tympanum ; as either destruction of the hones, or the absence of air from the tympanum from diseases of the eustachian tube — each causes deafness. Deafness, however, occurring from obliteration of the eustachian tube, does not necessarily prove that the air contained within the tympanum is for the purpose of conveying sound : for its absence may produce deafness, by the outer atmosphere pressing so forcibly upon the membrane of the tympanum, as to prevent the motion of the small bones. When the fingers are pressed into the meatus, and the outer ear thus closed, hearing is rendered imperfect only, in consequence of the communication being cut off from the external air ; but yet certain sounds, such as rumbling noises, are still distinct; which seems to 360 THE ORGANS OF THE SENSES. prove, that there are different means of conveying sounds to the internal ear, by which the nerves inay be sensibly affected, whether it be trans- mitted through the organ of hearing itself, or through the substance of the body. The small bones of the ear, are so articulated and influenced by muscles, as to form a chain of communication between the membrane of the tympanum and the base of the stapes, which is in contact with the membrane lining the vestibule. Whether these bones actually convey the sound, or only modify its degrees of intensity, is a subject not yet clearly understood by physiologists. The sound having reached the labyrinth, perhaps partly through the medium of the bones impressing the vestibule, partly by the air in the tympanum impinging the mem- brane of the fenestra rotunda, and probably also assisted by the stapedius muscle, which prepares the labyrinth for the due perception and appreciation of the most delicate varieties in sound. The mode by which the stapedius muscle assists in this function, I shall leave the description of to my friend Mr. Shrapnel!, the discoverer of its parti- cular attachments. Whatever may be the means by which sound is conveyed to the labyrinth, little is known how its intricate structures are capable of communicating its influence to the sensorium. Practical Remarks. The ear is liable, as would naturally be inferred from the delicacy of its structure and variety of its tissues, to numerous diseases; the slightest of which interfere with their function. The diseases of the auricle are most easily treated, because they are more readily detected, and remedies can be more readily applied. Mal- formation, however, sometimes leads to defective hearing; thus the auricle may be wanting entirely, or its form may be so unnatural as to render it ill fitted to convey sound to the meatus; under these circum- stances, acoustic instruments are required. The integument sometimes closes the external opening of the meatus, requiring to be punctured for the purpose of establishing a passage ; this, however, is not always effected, as the meatus is occasionally filled up entirely by a fibro-carti- laginous tissue ; under which circumstances, the operation must ne- cessarily fail. Sir Astley Cooper, in his lectures frequently mentioned two cases of malformation of the meatus. In the one, a servant of Dr. Girdleston, of Yarmouth, at the age of fourteen years was restored to hearing, by puncturing the skin which covered the meatus: while in the other, a Scotch boy who called at his house, the removal of the skin produced no good effect — the meatus being filled up. The meatus itself is some- times so small, as to interfere with the function of hearing; for which THE ORGANS OF THE SENSES. 361 no remedy has been found effectual, although sponge tents, and other modes of dilation, have been attempted. When the meatus is the subject of inflammation, it is always accompanied with a great degree of general excitement; and the strictest antiphlogistic plan should be immediately adopted, to prevent the formation of matter. This, however, does occasionally occur, producing an aggravation of symptoms, and having a tendency to evacuate itself, either into the meatus, or between the auricle and the mastoid cells. As soon as matter can be detected, an opening should be made. When the abscess opens into the meatus, granulations of a peculiar kind form, depending upon the structure of the part ; these are sometimes mistaken for polypi ; and fatal conse- quences have ensued from attempts to remove them with forceps. Mild astringent injections, with alterative and tonic medicines, are the means to be adopted in such cases. The diagnostic mark by which these granulations may be distinguished from true polypi, is to be gained by desiring the patient, while closing the nose and mouth, to attempt to blow; when, if it be polypus, air will rush through the membrana tympani by the side of the polypus, as it invariably arises from the cavity of the tympanum, and cannot therefore make its appearance within the meatus without absorption of that membrane. Extraneous substances, indurated cerumen, and small excrescences from the cuticle of the meatus, should be carefully removed. Diseases of the Tympanum When inflammation first begins, considerable pain is produced, at- tended with slight deafness, pain in the head, and even sometimes delirium. The patient should immediately be bled, and a few leeches also applied around the ear, saline aperients administered, and indeed the most strict antiphlogistic regimen prescribed. These means may not always be effectual, and matter may form, and make its escape through the membrana tympani; the discharge is ichorous, sometimes tinged with blood, and imparts a yellow tinge to a silver instrument. Great care must be taken in the local treatment of this disease ; the mildest astringent injections should be used, with the adoption of the antiphlogistic regimen before prescribed. Several instances have occurred of fatal consequences, produced by too strong injections. Matter has been found in the cerebellum, and between tbe dura mater and the temporal bone, the occurrence of which has been frequently recorded ; and some have come under my own notice. This discharge of pus is sometimes followed by polypi ; these must be removed by the most gentle mechanical means that can possibly be adopted. Inflammation of the tympanum occasionally produces the destruction of the ossicula auditus — generally indicated by a foetid dis- 362 THE ORGANS OF THE SENSES. charge, and greater degree of deafness than in the other instances. Such cases must he treated rather by constitutional than by local remedies, although mild astringent injections will be found beneficial. Obstruction of the eustachian tube, frequently arises from syphilitic ulcers, cynanche, or polypi of the nose ; deafness is the consequence of this disease, which may be detected by the inability to inflate the mem- brane of the tympanum ; if this effect has been produced by exposure to cold, producing inflammation, it is usually removed by those remedies which relieve the cause ; if by polypi pressing on the tube, their removal also effects a cure ; if by cicatrix, instruments should be passed through the nose, either to dilate or puncture the commencement of the eusta- chian tube : but as all these means have in some instances failed, Sir Astley Cooper recommends puncturing the membrane of the tympanum, which immediately restores the patient to hearing. The good effect is, however, but of short duration ; for the opening soon closes again, or the membrane is wholly destroyed : either of which circumstances places the patient much in the same situation as he was before the operation. In two or three instances, however, the operation has proved perma- nently successful. Of the diseases of the labyrinth, leading to deafness, little or nothing is known; violent concussion, altered function of nerve, inflammation of the lining membrane, may all tend to produce deafness, without leaving any means by which the cause of loss of hearing can be detected : but the local symptoms produced by any of these causes, must be alleviated by such remedies as the circumstances indicate, as they depend principally upon the general health of the patient. LECTURE XXXVIII. DESCRIPTIVE ANATOMY OF THE ORGAN OF SMELL. The bony parts of the nose, which are destined to protect the more delicate structures, which enter into the compo- sition of the organ of smell, have already been described ; vide Vol. I. page 72 ; but the cartilages, and softer parts, are now to be considered. The nose, with respect, both to its bony and soft parts, although varying much in form, may be described as a pyramidal eminence, reaching from the centre of the forehead to the upper lip, and bounded on either side by the eyes, and cheeks. Its lateral surfaces are flattened, and are posteriorly connected to the cheeks by a deep groove marking the separation of the alee, at the lower part; while anteriorly, the sides meet to form what is termed the bridge of the nose, which differs in shape in different people, and terminates by a rounded portion, which is called the lobe ; beneath which are placed two apertures, termed the nostrils. The upper part of the nose is completely fixed, and the bones entirely belong to it, which may be considered as con- taining the true organ of smell ; while the lower part is perfectly moveable, capable of great dilatation and contrac- tion ; and although belonging to and assisting in the function of smell, is to be considered as more important as a respi- ratory organ. Besides the bones, skin, muscles, cartilage, fibro-cartilage, and mucous membrane, enter into the composition of this organ. Of the skin . — Little or no difference is observable between the skin covering the nose and the rest of the face, excepting 364 THE ORGANS OF THE SENSES. that it is not covered with hair. It is connected to the sub- jacent parts by a delicate cellular membrane, which never secretes adeps, but unites it with different degrees of firm- ness in different parts of the nose ; for instance, more firmly in the mesian line of the bridge, and with the alae, than in the other parts. The skin is furnished with a number of small follicles, which secrete a sebaceous fluid, more espe- cially in the groove attaching the alee to the cheeks. These follicles open into a small oval sac, from which their secre- tion may be pressed somewhat in the form of a little worm, The muscles of the nose — have already been described with the muscles of the face. Vide Vol. II. p. 69, et seq. The cartilages — are three in number, namely, a middle one, forming a cartilaginous septum, and the two lateral. The cartilage of the septum, is triangular in its form, and vertically placed, being connected above with the nasal process of the ethmoid bone, behind and below with the anterior edge of the vomer, which has a deep groove to receive it ; while anteriorly, it is placed between and con- nected with the two lateral cartilages of the nose, and with the fibro-eartilages which form the boundaries to the nasal openings. It is to the anterior edge of this septum that the two lateral cartilages are connected; and from which they pass to be attached to the nasal, and to the anterior edge of the nasal processes of the superior maxillary bones. They are triangular in their form, are covered externally by the compressores narium muscles; and internally they are lined by the pituitary membrane. The fibro-eartilages of the nose — produce the apertures of the nostrils, as well as the alae. Those of the opening are very irregular in their form, but are curved upon them- selves, so as to produce an inner and an outer crus ; the inner curved forwards, and uniting to be connected by liga- ment with the cartilaginous septum, assist in forming a septum between the two nostrils ; while the posterior crura pass backwards to be connected with the fibro-cartilages of the alae ; they thus produce apertures of an elleptical form. THE ORGANS OF THE SENSES. 365 which are influenced by the muscles of the upper lip, and by the compressores narium. The fibro-eartilages of the alse, are also very irregular in their form, are inconsiderable in size, and are connected with the preceding' fibro-cartilages, and with the lateral cartilages of the nose. They seem to be for the purpose of keeping the nostrils constantly open, without the necessity of muscular exertion. All these parts, as well as the osseous structures before de- scribed, are lined by a continuation of the gastro-pulmonary mucous membrane, usually termed either the Schneiderian, or the pituitary membrane. The pituitary membrane — lines the whole of the internal parts of the nose, being continuous at the edges of the nostrils with the common integuments of the face, above with the continuation of the tunica conjunctiva, and behind with the mucous membrane lining the eustachian tubes, pharynx, and larynx. Within the nose, it forms numerous folds and duplicatures, corresponding with all the irregularities of the internal surface of this organ ; presenting therefore a very extended secreting surface. To trace it from its commence- ment at the nasal fossae, through all its intricate folds, would only be to reiterate the irregularities on the surfaces of the bones which have already been described. It presents through its whole course, an external surface, which is connected with the bones of the nose ; while its internal surface presents a spongy red appearance, with distinct vil- losities, furnished with small follicular openings. The color of the pituitary membrane, is not the same throughout its whole course, being lighter as it approaches the nostrils near which part small hairs, called vibrissse, may be observed, and are supposed to be for the purpose of preventing foreign substances passing into the nose. The pituitary membrane wdiich lines the different sinuses opening into the chambers, does not seem to be furnished with follicles, and is of a much whiter color than in the nose. The secretion from this membrane constantly covers its 366 THE ORGANS OF THE SENSES. surface ; it is a viscid mucilaginous substance, but little soluble in water, and of a slightly salt taste. It is secreted more abundantly by those parts of the membrane which is least covered by epidermis ; the quantity secreted varies from different circumstances, and is superabundant from the in- fluence of cold. The blood which supplies the nose, is conveyed by three or four ramusculi from the ramulus a. maxillaris internus, and also from the ramulus a. ophthalmicus of the internal carotid artery. The nose receives its nervous influence from the first pair, or olfactory, from which it derives its perception of smell, from the first and second divisions of the fifth pair of nerves, and from Meckel’s ganglion. Its absorbent vessels, pass principally to the glands situ- ated about the internal jugular vein. Practical Remarks. The nose, from the various structures which enter into its composi- tion, and from the different functions which it assists in performing, is rendered peculiarly subject to disease. Perhaps among the most de- structive to it, are the diseases of its bones, which, from their extreme delicacy, become quickly destroyed, and leave an irreparable deformity. Hence the necessity of the earliest attention to the first symptoms indi- cating these maladies, which are so frequently found to follow an injudicious use of mercury, and are considered as syphilitic, when in- deed they are only mercurial. Still, however, small doses of mercury must be exhibited; and I have usually found the red oxyd, combined with opium, as the best form of mercury in these cases. The fibro-cartilages and cartilages of the nose, are not unfrequently the subject of diseases ; and from the little degree of vitality these structures possess, they have a great tendency to slough, and produce the most distressing consequences. This disease is usually considered of a specific character, and is termed lupus or noli me tangere ; but as far as my experience goes, I am more inclined to attribute the ravages produced, to the peculiarity of the structures affected, and the particular functions they have to perform keeping them in constant motion, than to any specific diseased action. Polypi very frequently form within the cavities of the nose, and when pendulous, they should be early removed, taking care in the operation THE ORGANS OF THE SENSES. 367 to use as little violence as possible; remembering, any injury to the delicate bones to which they are attached, may lead to their destruction. Constitutional means, such as alterative and tonic medicines, are to be administered after the removal of the polypus, to prevent its recurrence. In diseases of the antrum, the nose may become secondarily affected; and indeed, the diagnosis maybe difficult; but upon examination of the nose, and finding it free from disease, while at the same time there is a foetid smell, and a discharge of unhealthy mucus or perhaps pus, the surgeon’s attention should be directed to the antrum ; and usually, by striking the second molar tooth with any metallic instrument, a pain shooting into the superior maxillary bone, will indicate the seat of the disorder. Physiology of the Sense of Smell. This sense consists of the perception of odorous particles, emanating from bodies which are termed odoriferous, and which, being given off in all directions, are by the air conveyed into the nose in the act of respiration, and then impressing the sentient extremities of the olfactory nerve convey to the brain the peculiar sense termed smell. The senso- rium receiving this impression, if pleasurably affected may particularly exert the organ of smell for a more perfect sensation ; and by the will, the moveable parts of the nose are arranged in such a manner as to draw the air more forcibly into the nostrils, so that the odorous particles may not only be more abundant, but be forced upwards into the superior meatus, where the olfactory nerve is distributed : hence it is, that the snufftaker draws down the upper lip to narrow the passages and force the powder into contact with the olfactory nerve. It may be observed, that odorous particles emanate from a great variety of bodies, from some constantly, and in great abundance ; and yet these particles are so infinitely minute, that no sensible diminution of weight occurs, although the odoriferous body may have given off its scent for many years. The circumstances which occasion the odoriferous particles of bodies to be given off, as well as the nature of the particles themselves, are but little understood ; it is not however to all bodies that this property belongs, and those in which no scent is perceptible, are termed in- odorous. Some physiologists have attempted to classify odours ; but little seems to have been effected in such an arrangement, beyond the natural expressions of weak and strong, agreeable and disagreeable : — dis- tinctions which, however, will vary as frequently as the capricious fancies of different individuals. It has been asserted, that some odours possess poisonous properties ; but there is some doubt, whether or not these effects are attributable to absorption, either in the lungs or in the 368 THE ORGANS OF THE SENSES. stomach ; whether they may have been conveyed by respiration to the former, or by deglution to the latter. The atmosphere is the general medium by which odorous particles are transported ; but they are also said to be given off with considerable force in vacuo; and it has been conjectured, that they obey laws of reflection similar to light. Little, however, is yet known upon this subject. Odours combine with various substances, both liquid and solid ; and in this way are preserved for a considerable length of time. When an odoriferous body is applied to the nose, its odorous particles are drawn up upon the extended surface of the Schneiderian membrane, and there mingle with its mucous secre- tion, which may be rendered more abundant if the odour be too powerful, so as to dilute them, or by entangling them, assist in retaining the weaker impressions. For this purpose, the membrane lining the upper meatus secretes the mucous in the greatest quantity, the cells being most capacious, and the nerves most abundantly distributed. LECTURE XXXIX. DESCRIPTIVE ANATOMY OF THE ORGAN OF TASTE. The mouth might have been described when speaking of the organs of digestion; but as it is so particularly connected with the function of taste, and the salivary apparatus, it may perhaps be as properly considered now, as with the function of degdutition. The bones which enter into its composition, have already been described (p. 74, Vol. I.) ; but the lips, cheeks, gums, palate, tonsils, salivary glands, and tongue, all concur in the performance of the function of taste, and many of them assist in other functions. The mouth — is placed between the two jaws, below" the nasal fossae, and in front of the pharynx ; it presents an oval cavity, which opens anteriorly by an horizontal aperture, capable however of considerable variety of figure from the muscles of the lips. The interior of this cavity is lined by a mucous membrane, which, commencing from the cutaneous edge of each lip, passes to the anterior surface of either jaw, covering the gums, and forming in the mesian line a frenum to each lip. It then passes over the gums, dips down into the alveolar processes, thus enclosing the roots of the teeth ; which cir- cumstance has led some physiologists to describe the teeth as products of the mucous membrane ; from the alveolar processes, both above and below-, it proceeds into the ca- vity of the mouth ; above covering the palate, below the muscles of the tongue and the tongue itself, forming a frenum for that organ to unite it with the symphysis of the lower jaw. It then proceeds backwards, surrounding the 2 B 370 THE ORGANS OF THE SENSES. pillars of the fauces* covering' the tonsils, and terminates by being connected with the mucous membrane of the pharynx, larynx, and eustachian tubes. In its course, however, it enters into the excretory ducts of all the glandular and folli- cular apparatus opening intd the mouth. The lips — form the anterior parietes to the mouth, and are connected with the upper and lower jaw, from which they are respectively named. Laterally, they are connected with the cheeks, where they meet, forming their commissure ; th4|^ each present an attached edge to their respective jaws,*«.nd a free edge, which come in contact with each other, are covered by mucous membrane, and form the anterior opening of the mouth. Their free edges can be so perfectly approximated, that all the power of the muscles of expiration is incapable of forcing air between them, although there appears to be but little muscular power used in their approximation. The external surface of each lip is covered with skin, which, . after the age of puberty, in the male, is furnished with hair, forming a large portion of the beard. The internal surface is lined by mucous membrane, which in the mesian line forms a frenum to each lip. ‘Between the skin and the mucous membrane, the muscles of the lip§ are placed, which have been described (vide p. 71, et seq. Vol. II.) ; and be- tween the muscles and the mucous membrane, there are numerous follicular sacs, which are termed the labial glands, and which have their excretory ducts opening into the interior of the mouth. The lips are supplied with blood by ramusculi from the facial ramuli of the external carotid ; and the blood is re- turned by corresponding venous ramuli, into the internal jugular vein. Their nervous influence, is derived from the second and third divisions of the fifth pair, and from the facial nerve. Their absorbents, terminate in the glands situated under the chin. The cheeks — which form the lateral boundaries to the mouth, are composed of skin, a layer of adeps, muscles, THE ORGANS OF THE SENSES. 371 raucous membrane, and the excretory duct of the parotid gland. There is but little to observe with respect to them ; the quantity of fat which they contain, gives a general con- tour to the face ; the muscles which particularly enter into their composition, are the buccinatores — by the action of which, they assist in the function of mastication and deglu- tition ; and by pressing the saliva from the ducts of the parotid glands, they perform, in part, the function of taste ; and farther, by forcing and directing the air through the mouth, the cheeks become important organs in respiration and voice : but. these muscles have been particularly de- scribed, as in the above reference. Some mucous follicles are also placed between the muscles of the cheeks and mucous membrane, which are termed the buccal glands. The cheeks are supplied with blood, by the facial and internal maxillary ramuli of the external carotid ramus, and the venous branches accompanying the arterial, terminate partly in the internal, and partly in the external jugular vein. Their absorbents, pass to the glands of the neck, and in an absorbent gland generally situated on the parotid. The roof of the mouth, or bony palate, as well -as the alveolar processes of the two jaws, are covered by a peculiar structure, which is termed the — Soft palate , and gums . — They seem to be a thickening of the common mucous membrane of the mouth, connected by a very dense cellular tissue to the periosteum of the bones to which they are attached. The structure is but little sen- sible, forming therefore a protection to the osseous parts of the mouth ; and being covered by the mucous membrane, it affords a continuous secreting mucous surface. The gums, which are composed of the same tirm compact tissue, which covers the palate, surround the necks of the teeth, and fill the intervals between them, so as to protect all their bony parts which are not covered by enamel. The soft palate, as well as the gums, receive blood-vessels 2 B 2 372 THE ORGANS OF THE SENSES. and nerves ; but their degree of sensibility is very slight in a healthy state, although in disease they become highly painful. The arterial distribution to the palate and gums, proceeds from the ramifications of the external carotid ramus, and principally from its facial and internal maxillary ramuli. The nervous distributions, are derived from the second and third divisions of the fifth pair, and from Meckel’s ganglion. The tonsils — are placed one on either side of the fauces, between the pillars ; they are about the size of an almond, somewhat of that shape, and are placed with their larger extremity upwards, towards the junction of the two pillars of the fauces with the velum pendulum palati; and their smaller extremity points downwards, resting upon the tongue; exter- nally, they are bounded by the superior constrictor of the pharynx ; anteriorly, by the constrictor isthmi faucium ; and internally, they are directed towards each other. The tonsil seems to be made up of a number of mucous follicular sacs, united to each other by a firm, dense, cellular tissue, covered by the mucous membrane of the mouth. If a section be made of the tonsil, it presents a honey-comb appearance, from the numerous cells which are laid open, and which are larger nearer their upper than their lower ex- tremities. All these cells are lined by the mucous membrane of the mouth, which enters them by their excretory ducts. Ramusculi from the lingual, facial, and internal maxillary ramuli, send blood to the tonsils. The nervous filaments, are supplied by the lingual, and glosso-pharyngeal nerves. The tongue — has already been partly described by the anatomical account of its muscles, as far as refers to it as an organ of deglutition ( vide p. 91, Vol. II.) ; but we have now to consider it as the principal organ of taste. The tongue is placed within the cavity of the mouth, be- hind the teeth, in front of the epiglottis, above the os hyoides and the pharynx, and below the arch of the palate : it is divided into its body, base, and apex. THE ORGANS OF THE SENSES. 373 The body — presents a superior and an inferior surface, and two edges. The superior surface, or dorsum of the tongue — presents in its centre a longitudinal furrow, which divides it into symmetrical halves, and which terminates posteriorly in the foramen ccecum — an opening of mucous follicles. The inferior surface — is smooth anteriorly, free, and covered by the mucous membrane of the mouth ; which membrane posteriorly connects the tongue to the os hyoides, and parts below — producing what is termed the frcenum linguce. The lateral edges — are rounded, thicker posteriorly than anteriorly, are fixed behind, by the mucous membrane and muscles, to the lower jaw, and styloid processes of the tem- poral bones. The base — 4s the fixed point, is the thickest and broadest part of the tongue, and is united to the os hyoides, epiglottis, and pillars of the fauces, by muscles and mucous membrane. The apex — is free and rounded, and capable of the greatest mobility from the numerous muscles which form the tongue. The tongue is composed of muscles, which have been described ; and also of th# mucous membrane of the mouth, which on the tongue bears great resemblance to the common integuments — being covered by a thin epidermis, and fur- nished with numerous follicles, forming what are termed the papillce. These are divided into three sets. The papillce capitatce, vel lenticular es — are usually from nine to fifteen in number, presenting a rounded head, con- nected with the tong’ue by a narrow neck. They are placed on the posterior part of the dorsum, and are so arranged as to commence from the foramen caecum ; from thence they pass forwards in two diverging lines, so as to present the appearance of the letter V, with the angle directed backwards. The papillce fungiformes, vel semi-lenticular es — are much smaller than the former, but much more numerous ; they present small round eminences, and are dispersed over the 374 THE ORGANS OF THE SENSES. whole surface of the tongue, but are most developed on the edges ; they are separated by slight intervals from each other. The 'papilla; conicce — are very numerous, like the pre- ceding, occupy a great part of the superior surface of the tongue, but are most numerous towards its apex, although those placed posteriorly are the larger. These papillae are supposed to be supplied by, if not formed of, the termination of the gustatory nerve. The tongue receives nervous influence from the hypo- glossal nerve, which supplies its muscles, and imparts to it voluntary motion for the purposes of deglutition, speech, &c. ; from the third division of the fifth pair, which is sup- posed to form the true organ of taste ; and from the glosso- pharyngeal, which is supposed to impart to it functions sympathetic, with the respiratory organs. Of the Salivary Glands. There are three pair of glands, which are constantly pouring- their secretion into the cavity of the mouth, and which may be considered, perhaps, equally important to the function of digestion, as to taste ; but as no substance can produce any sapid sensation without being dissolved in this fluid, they may be properly enough considered with those organs, which are excited in the function of taste. The pancreas has sometimes been considered as one of the salivary glands, and there are many circumstances in which they are very similar ; as for instance, the disposition of their lobules, the absence of every distinct capsule, the mode of distribution of their blood-vessels, and the strong resemblance of their secretion : but the different situation of the pancreas, and its close connection with the digestive organs, seems to indicate the propriety of describing it, as I have done, with the chylopoietic viscera. The salivary glands — are the parotid, the sub-maxillary, and the sub-lingual, more or less connected with each other, and extending from the temporo-maxillary articulation on THE ORGANS OF THE SENSES. 375 either side to the symphysis of the lower jaw, where they in some measure unite. The parotid — is the largest of the salivary glands ; one is placed on either side of the head, reaching from the zygo- matic process to the angle of the lower jaw, behind the posterior edge of its ascending plate, between it and the mastoid process of the temporal bone. It is somewhat pyramidal in its form, its sides being flattened, and its largest extremity placed above ; it is bounded externally, by the platysma myoides muscle, and the skin of the face ; inter- nally, by the temporo-maxillary articulation, ascending plate of the lower jaw, masseter, and pterygoideus internus muscles ; and behind, it is opposed to, and by condensed cellular membrane, connected with, the fossa parotidea, and auditory process of the temporal bone, the anterior edge of the sterno-cleido mastoideus, and the posterior belly of the digastricus ; and below, with the styloid process of the temporal bone, to which it is firmly united by the deep cervical fascia. The parotid gland is composed of numerous small lobules, united to each other by a condensed cellular membrane, so as to form small lobes, producing a conglomerate gland, of a greyish yellow color, firm in its texture, and not en- closed in a distinct capsule. In each of its granules, or lobules, a distinct ramusculus of an artery passes, a ramus- culus of a vein commences, and a little excretory duct is mven off which soon unites with the duct of another lobule, and this duct again with a third, and so on, until they all form one great duct, which passes out of the anterior edge of the gland to open into the mouth. The parotid duct, sometimes termed Stenon’s duct, is about two inches and a half to three inches long, and about a line in diameter; it leaves the outer surface of the anterior edge of the gland, and takes its course forwards, across the masseter muscle ; having traversed which, it becomes em- bedded in a considerable quantity of adeps, and gains the buccinator; this it perforates, forming a right angle with 376 THE ORGANS OF THE SENSES. the fibres of that muscle, and opens into the mouth through its lining mucous membrane, opposite to the second, or rather between the second and third upper molar teeth. The parotid duct is composed of two coats ; an outer one, which is peculiarly firm and resisting’, possessing almost a cartilaginous firmness ; and an inner, thin delicate continu- ation of the mucous membrane of the mouth. The arterial ramifications to the parotid gland, are derived from the temporal, posterior aural, and facial ramuli of the external carotid ramus ; they are numerous, but very small, dividing again, and again, before they enter the substance of the organ. The venous, correspond with the arterial ramifications, and terminate in the internal and external jugular veins. It derives its nervous ramifications from the facial nerve, the third division of the fifth pair, and from the cervical plexus. The sub-maxillary glands . — One is placed on either side of the upper part of the neck, immediately below the base of the lower jaw, in a triangular space, bounded above by the jaw, and below by the junction of the common tendon of the anterior and posterior bellies of the digastric muscle, to the os hyoides. The exact position of this gland, is very difficult to under- stand, unless the student first considers how r much its rela- tive situation is altered according to the view which is taken of it, whether in the erect, or in the recumbent posture. In the course of its dissection, and consequently in the recumbent posture of the subject, it would be described as being placed beneath the skin, platysma myoides, and fascia of the neck ; resting upon the mylo-hyoideus muscle ; bounded externally and posteriorly, by the angle of the jaw, parotid gland, and posterior belly of the digastric muscle; and anteriorly, by the hyo-glossus muscle, the hypo-glossal nerve, and the sub-lingual gland. But when described, as other parts usually are, in the erect posture of the body, then the sub-maxillary gland is placed above the platysma my- oides and skin, below the mylo-hyoideus and sub-lingual THE ORGANS OF THE SENSES. 377 gland ; bounded on the outer side, by the angle of the jaw, and pterygoideus interims muscle ; and on the inner, by the hyo-glossus muscle, and hypo-glossal nerve. The sub-maxillary gland — is, like the parotid, composed of numerous little lobes connected by a condensed cellular membrane, and not possessing any distinct envelope. The junction of all the ducts from each lobule, produce one excretory duct, which emanates from the upper surface of the gland, then passes forwards and inwards upon the under surface of the hjo-^glossus muscle, between the hypo- glossal and gustatory ramulus of the third division of the fifth pair; and passing between the genio hyo-glossus muscles, and sub-lingual glands, opens into the mouth, on either side of the fraenum of the tongue, by a small orifice placed in the centre of a projecting tubercle. This duct, like that of the parotid, is lined by the mucous membrane of the mouth. The sub-maxillary gland is furnished with blood by the facial, and lingual ramuli, of the external carotid. Its venous blood passes into the internal jugular. Its nervous ramifications, are derived from the third divi- sion of the fifth pair, and sub-maxillary g’anglion. The sub-lingual glands — are placed, if considered in the erect posture of the body, above the myio-hyoidei muscles, below the genio hyo-glossi, behind the genio hyoidei, and in front of the sub-maxillary glands. In form they are some- what lengthened from before to behind, and flattened late- rally ; they are organized in a similar manner to the other salivary glands, excepting that they are furnished with several excretory ducts, which in part open by the sides, and part on the fraenum of the tongue. They derive their blood from the facial, and lingual ramuli. Their nervous influence, is derived from the third division of the fifth pair of nerves, and from the sub-maxillary ganglion. The chemical analysis, and the properties of the saliva, have been described; vide p. 82, Vol. III. 378 THE ORGANS OF THE SENSES. Practical Remarks. It sometimes happens, that at birth the mouth is imperforate, re- quiring prompt assistance, by making an horizontal incision so as to divide the two lips ; and by the application of some mechanical means, to prevent reunion of the edges of the incision, and at the same time by bringing the cheeks forward to prevent the antagonizing muscles producing too great a distention of the orbicularis oris, The upper lip is also at birth subject to a malformation, termed a hare-lip ; generally there is but one fissure, but sometimes more ; and these require a sur- gical operation, to remove the deformity. This disease is sometimes complicated with a fissure extending through the roof of the mouth ; if only through the palatine processes of the superior maxillary bone, the fissure will frequently close after the common operation for the hare lip ; and in such cases the operation should be performed as early as possible : but if the fissure extends through the palate bones, and soft palate, a further operation is required, to close the cavity. This may be effected by paring the edges of the fissure, and by making two longitudinal incisions, one on either side of the fissure, and at some little distance from it, so as to detach the soft palate from the bone; and then by sutures, to draw the edges of the incised portions together. In the soft palate, the edges alone require paring. In simple hare-lip, the edges of the cleft are to be pared, and the incisions are to be brought in close contact, either by sutures or pins ; at the same time bringing the cheeks forwards, to prevent the action of the antagonizing muscles upon the orbicularis oris. The sutures or pins should be allowed to remain three or four days; and when they are removed, the means employed for bringing the cheeks forwards, should still be continued, lest the action of the muscles should tear open the newly-formed cicatrix. If the deformity of the lip is not so great as to prevent the infant sucking, it is better not to perform the operation until after the child be weaned, and has learned to take its food ; but if the malformation is so great, as to prevent the child sucking, it must be performed as early as possible. Cancer of the lip — a disease which occurs almost always in the under lip, may be known by its hardness, wart-like appearance, lancinating- pain, and age of the patient — as it rarely occurs before the age of forty. Men are more liable to it than women ; and extirpation is the only cure : at the same time, administering alterative medicines, and paying great attention to every means which can be adopted for the improve- ment of the general health. After the disease has been removed, the edges of the wound are to be brought together, in the same manner as in hare-lip. THE ORGANS OF THE SENSES. 3T9 The tongue is not unfrequently the subject of disease, and ulcer ig that of the most frequent occurrence, being often produced by the rough edge of a tooth ; if this be the cause, filing the tooth, or extracting it, will prove its infallible remedy. Ulcers in the tongue, sometimes are concomitant with a deranged state of the digestive organs, pro- ducing little aphthous sores on the mucous membrane of the tongue and lips. In these cases, the ulcers should be touched with nitric acid, and blue pill, with neutral salts and bitters, used as constitutional remedies. The tongue is also liable to malignant diseases, and cancerous ulcera- tion is not very unfrequent. In this situation, as in other parts of the body, extirpation of the diseased part is the only hope ; and when it can be effected, is to be performed in the following manner : — a needle is to be passed through the centre of the tongue, opposite to the disease, armed with two ligatures, and by this means the tongue is readily held by an assistant, which cannot in any other way be commanded ; one ligature is then to be tied tightly behind, and one in front of the ulcer, including between the ligatures a sufficient portion of healthy parts, as to allow of the complete extirpation of the disease ; these ligatures preclude the possibility of any alarming haemorrhage. The exposed surface should either be touched with nitric acid or actual cautery, with the hope of inducing a new action; and the constitution should be affected by alterative, and tonic medicines. As far as my experience goes, however, this disease soon returns in the absorbent glands under the lower jaw ; and five months is the longest period I have known any patient survive the extirpation of a cancerous ulcer from the tongue. The fraenum of the tongue may require to be cut, for the purpose of liberating- the organ when the fraenum is too short, either to allow the tongue to be brought out of the mouth, or to be raised up to the palate. In performing this operation, the scissors should be directed downwards, so as to avoid the ranine artery. The tonsils are sometimes inflamed, so much so as to interfere with deglutition and respiration. Relief may immediately be obtained, by scarifying the tonsils, and by the use of restringent lotions, and altera- tive medicines. The inflammation, however, sometimes goes on to form abscess, which not only produces mechanical obstruction to deglutition, but also such constitutional derangement us occurs in the formation of matter in other parts of the body. The matter should be immediately evacuated, by passing either the point of a lancet or a phymosis knife into the tonsil, directing it backwards, downwards, and inwards, so as to avoid injury to the internal carotid ramus, which is behind it and to its outer side. The extirpation of a part of the tonsil, is some- times required, in consequence of chronic inflammation, producing 380 THE ORGANS OF THE SENSES. such a permanent enlargement, as to interfere with deglutition and breathing. This operation is best performed by the application of a ligature, which is applied by means of what is called a tonsil needle, and being - tied tightly around the diseased part, it is to be twisted tighter every day until the included portion of the tonsil sloughs off. The tonsil needle may either be passed through the nose, or mouth, as may be found most convenient to the operator. The uvula is not unfrequently elongated ; astringent gargles are usually sufficient to efFect its contraction ; but it sometimes will not yield to this treatment, and requires excision ; and the superfluous portion may be removed with scissors, without any fear of ill effects from haemorrhage. The diseases of the gums and teeth, I have intentionally omitted, as my friend and colleague Mr. Thomas Bell, not only lectures most ably, but has written a most excellent work upon the subject. From ulcer or wound in the cheek, it sometimes happens, that the parotid duct, or the parotid gland itself, is injured, so that the saliva is constantly pouring upon the face, and the wound thereby prevented from being healed, soon puts on a fistulous character. If the accident be a wound of the duct, — either from any accidental cause, or perhaps from surgical operation, as removing a small tumour from the face, — the aperture should be immediately closed ; and every attempt made to unite the outer wound, by a just adaptation of the parts, and desiring the patient not to masticate for a few days, so that the part may not only be kept in a perfect state of rest, but that also the salivary appa- ratus may not be stimulated to secretion. If the wound has been open for some time, these means will prove ineffectual, and an operation is usually necessary to produce a cure. This operation is performed in the following manner : — a needle armed with a thread is passed through the opening in the duct, directly into the mouth, and a knot being tied at the farther end of the thread, the ligature is drawn tight so as to keep a constant pressure upon the knot, and induce its ulceration into the mouth ; by which means a passage is established, and the saliva no longer passes through the outer wound, which soon heals. Desault recommends as a cure for salivary fistula, such a degree of pressure upon the salivary gland, as to induce its absorption ; hence, no saliva being secreted, the fistula heals, and it is found that no ill effects are produced by the diminution of the quantity of saliva secreted. I have myself, in removing a small diseased absorbent gland, wounded the parotid gland, and a quantity of saliva was immediately poured out. Considerable difficulty occurred in the reparation of this wound ; but after caustic, actual cautery, and other means had failed, THE ORGANS OF THE SENSES. 381 sprinkling the red oxyd of mercury two or three times a day upon the wound, ultimately succeeded in curing it. The sub-maxillary and the sub-lingual ducts, are sometimes rendered impervious, either from the thickening of the lining' mucous membrane, or from minute calculi obstructing them; the result of which is, great distention of their salivary ducts, producing a considerable tumour underneath the tongue : this disease is termed — Ranula — and maybe known at once by its fluctuating feel, and by its semi-transparency. It sometimes produces great difficulty of breath- ing, from pressing the tongue backwards so as to close the glottis. The late Mr. Cline heard a person fall in his anti-room, and running in to see what was the matter, he found a gentleman lying on the floor, with his countenance livid, and apparently struggling in the last agonies of death. Mr. Cline immediately passed his finger into the mouth, to observe what might be the cause of this asphyxia, and there discovered a large ranula, into which he directly thrust his lancet, let out the saliva, and the patient was immediately restored by the prompt application of Mr. Cline’s surgical knowledge. When the disease is recent, the contents of the tumour have perfect resemblance to the white of an egg: but they soon become more viscid, and of a darker color. Whether the tumour affects deglutition and respiration, or not, it should be laid open, as its pressure is sure tc cause injury to the lower jaw. They produce but little or no pain, and are generally cured by laying the tumour open, and cutting out a portion of the sac : some surgeons further recommend a stimulating application to the inner surface of the sac, to secure adhesive inflamma- tion. If the ranula be very small, and a small calculus the cause of the obstruction of the duct, the removal of the calculus will usually be found sufficient, without any further operation. Physiology of Taste. The sense of taste, informs us of the flavor or sapid qualities of bodies dissolved in saliva. Certain bodies, however, that are soluble, are yet destitute of tase; while others, apparently insoluble, have yet a distinct flavour. Hence it has been conjectured, that the chemical properties, and their peculiar connection with the animal economy, may therefore contribute to the sense of taste. Such bodies as produce an agreeable flavour, are generally useful and nutritious ; while those which are pernicious, occasion a disagree- able sensation in the mouth. Bodies are said to be bitter or sweet, sour, acid or acrid ; but like the classification of odours, no satisfactory arrangement has yet been made of sapid bodies. 382 THE ORGANS OF THE SENSES. The tongue, is the principal organ of taste ; but it is evident, that the lips, internal surface of the cheeks, palate, pharynx, oesophagus, and even the stomach itself, are capable of receiving - impressions from the contact of sapid bodies, which contribute to the perfection of this seYtse — the actual seat of which has so long been a matter of controversy amongst physiologists. The experiments of Guyot, detailed in the Bibliotheque Universelle, appear, however, to set this matter at rest. The tongue was enclosed in a case of soft parchment, which only ex- tended from the tip to about the middle; sapid bodies then introduced, gave no taste: — proving, that the anterior extremity of the tongue was the essential organ of taste. The tongue was next covered entirely, when common bodies being introduced gave no taste ; but extract of aloes, and other bodies very highly sapid, gave a slight taste at the posterior part of the tongue, corresponding to the velum palatum. No other sensation than that of touching was excited on the application of extract of aloes to the palate, roof of the mouth, or cheeks. It is the anterior and upper part of the velum palatum which possesses the sense, in a space, however, small and undefined in its limits. It was further observed, that when the tongue was covered with parchment, and a hole being left in the middle of its posterior surface, that on the application of sapid bodies to this exposed portion, the sense of taste was not produced until the sapid body was dissolved in saliva, and gained access to the tip of the tongue. And Guyot found, that only certain parts, namely, within a space of about one or two lines at the sides, three or four at the tip, and within a curved space at the back, were the only seats of the organ of taste. The saliva poured into the mouth from the salivary glands, possesses a peculiar power as a solvent; and in the act of tasting, it is evident that the operation consists in applying the tongue in such a manner as to expose its papillae to the sapid substance mixed with the saliva. Mere contact, however, may be sufficient for fluid, or gasseous bodies ; but solid bodies appear to require actual solution, before their flavour can be tasted. The arrangement of the papillae is so made, that those which dis- tinguish flavour are protected, and as it were separated from those which secrete the mucus, lubricating the mouth, and fauces, contri- buting to the act of swallowing. The papillae conicae — are disposed in two rows, wider at the tip and back part of the tongue, than at the sides, and are probably those destined particularly to the sense of taste The nerves which supply the tongue, are derived from several sources; thus we have the inferior, and a few ramuli from the superior maxillary rami, filaments also from the spheno-palatine ganglion, the naso-palatine of Meckel, the lingual, and the glosso-pharyngeal nerves. THE ORGANS OF THE SENSES. 383 The lingual, or gustatory branch of the fifth pair, has been traced to the villi, and papillae conicae, and has therefore been considered as the principal nerve of the sense of taste ; but other nerves may also contri- bute, although they cannot be traced distinctly. Majendie asserts, that on the division of the lingual gustatory nerve, the tongue continues the power of motion, but loses the sense of flavour; but the palate, gums, and internal surface of the cheeks, preserve their aptitude for the exercise of taste : but if the trunk of the fifth pair be divided in the cranium, then the property of recognising flavours is completely lost. The same occurs in diseases affecting the fifth pair. When sapid bodies are brought into contact with the mucous surface of the tongue, such as vinegar, mineral acids, alkalies, and many others, the color of the membrane has been observed to change — becoming sometimes white, at others yellow : from whence it has been conjectured, that some chemical change has been effected, and that the durability of an impression depends upon their changes. For instance: — acrid bodies leave an after-impression in the pharynx; acids, on the lips, and teeth ; peppermint, through the mouth and pharynx. These impressions obtain a wonderful degree of delicacy and accuracy, by exercise and habit of the parts, as may be evinced by those who have exercised it in distinguishing the flavour of wines. In old persons, this sense becomes weak, and requires stimulating things to excite it: it appears, also, that young infants do not fully acquire the sense of taste, until some time after they are born ; they however possess it at birth, as may be seen by placing a bitter or saline substance on the lips. Taste presides over the choice of food, and enables us to distinguish between wholesome and noxious substances; and when exercised with agreeable food, is a source of considerable pleasure, but which, if too much indulged, will form an epicure, whose wants are an evident abuse of this sense. FINIS. fstg&si ramtatt S s -^Cooper v.U 1832 \ — ■