LaIBRARY . OF . 'f 'fc §«s'V.>i.:v,^^^V; '^ ' Jn^v io-^itv Digitized by the Internet Archive in 2010 with funding from Boston Library Consortium IVIember Libraries http://www.archive.org/details/anatomyofhumanboOOcruv THE ANATOMY OF THE BUMA]« BOHY. BY J. CRUVEILHIER, i>HOFESSOR OF ANATOMY TO THE FACULTY OF MEDICINE OF PARIS, PHYSICIAN TO THE HOSPITAL OF SALPETRIERE, AND PRESIDENT OF THE ANATOMICAL SOCIETY OF PARIS. THE FIRST AMERICAN, FROM THE LAST PARIS EDITION. EDITED B Y GRANVILLE SHARP PATTISON, M.D., PKOFESSOR OF ANATOMY IN THE UNIVERSITY OF NEW-YORK, MEMBER OF THE MEDICO-CHIRUKGICAL SOCIETY OF LONDON, OF THE WARNERIAN SOCIETY OF NATURAL HISTORY OF EDINBURGH, OF THE SOCIETE MEDICALE D'EMULATION, AND SOCIETE PHILOMATIQUE OF PARIS. THl NEW-YORK: PUBLISHED BY HARPER & BROTHERS, No. 82 Cliff- Street. 18 44. ^ho . q ^1 ^ ■^ a. \ \ . Entered, according to Act of Congress, in the year 1844, by Hakper & Brothers, In the Clerk's Office of the Southern District of New- York. * > k ;• ■">?; EDITOR'S PREFACE. Numerous and excellent as the works on Anatomy are which have lately been reprinted in this country, still they are, all of them, so de- cidedly inferior to the " System of Anatomy by Cruveilhier," that the editor feels it unnecessary to offer any apology for having under- taken its republication. Occupying, however, as he does the Chair of Anatomy in the Metropolitan University of the United States, the pro- fession may perhaps think that it would have been more becoming of him to have published a System of Anatomy of his own, rather than to have undertaken the humble office of editing the work of a European anatomist. The reasons which have influenced him in the course he has pur- sued are the following : The science of Anatomy, viewed abstractly, and without reference to its connexion with Physiology, Pathology, and the Practice of Med- icine and Surgery, is to the student just commencing a very dry and uninteresting study. Yet in this way it is generally taught in the schools, each system being demonstrated separately, without refer- ence to the others, or to the Physiological and Pathological facts which its demonstrations tend to illustrate. The course followed by the editor, as a teacher of Anatomy, as his numerous students are aware, is very different. His great object has always been to endeavour to give interest to every lesson, by making it not a mere lecture on Anatomy, but a discourse illustrating Physiological and Pathological science, and elucidating the principles which should guide the practitioner in the practice of his profession. For the editor to have prepared a mere system of Anatomy would have been, in fact, merely to have undertaken the work of a compiler ; originality was out of the question, and no industry nor effort could have enabled him to have produced, on this plan, a better work than the systems of Wilson, Quain, or the numerous other systematic trea- tises on Anatomy which have already been published. The editor having been a teacher of Anatomy for more than thirty years, from his experience is fully aware of the vast importance to the successful performance of his duties as an anatomical professor, of his being en- abled to interest his pupils and to fix and enchain their attention, that he is very unwilling to do anything which could have the effect of taking from the interest or diminishing the freshness of his lectures. To pub- IV EDITOR S PREFACE. lish a system of Anatomy on the same plan as that adopted in his lec- tures, he would, of necessity, requii'e to imbody in it the same Phys- iological, Pathological, and practical views with which they are illus- trated ; and to have done so,, he cannot doubt but that the interest of his lectures would have been diminished, and that he would in future have found it much more difficult to fix the attention of his pupils. This consideration has decided him never to publish, so long as he is engaged in the duties of teaching, an original work on Anatomy. The system of Anatomy of Cruveilhier has recommended itself to the editor for publication : First, on account of its decided superiority to any other work on Anatomy which has ever been published ; and, secondly, from its being prepared, in some measure, in accordance with the plan which he follows in his lectures, many of its details be- ing illustrated by Physiological and Pathological references. In republishing the work, the editor has so restricted himself in the performance of fiis task that he feels it can neither add to nor take from his reputation. He has merely furnished to the members of the profession in the United States The System of Anatomy of Cru- veilhier. Several reasons have influenced him in being sparing in the introduction of notes or additional matter. First. The work is in itself so perfect as not to require them. Secondly. It is very volumi- nous, and to have increased its size would have been to have diminish- ed its value. Thirdly. The editor has ever thought that an inde- pendent mind will shrink from mixing up and incorporating his thoughts with those of another. If a man wishes to obtain reputation as an author, let him publish an original work, and not attempt to gain popularity by illustrating and enlarging the labours of another. The editor, in disclaiming all credit to himself in the publication to which he has affixed his name, cannot allow the opportunity to pass without calling the attention of the profession to the obligations under which they have been placed by the liberality of the enterprising pub- lishers. The Messrs. Harper and Brothers have commenced a new era in medical publications. Before they entered the field, although a number of the best works on Medicine and Surgery were republished in this country, when every other kind of literature was furnished on very cheap terms, the prices required for medical books was such as to debar the great body of the profession from procuring them. The Messrs. Harper, since they have engaged in medical publications, have entirely reformed this matter. Feeling assured that the excellence of the works they repubUsh will command extensive sales, they are con- * tent with very moderate profits. This fact is fully established by their republications of " Kane's Chemistry" " Magendie's Physiology" and " Chailly's Midwifery ;" works which they furnish for two dollars each, being not much more than half the price which would have been asked for similar books before they engaged in this department of pub- EDITOR S PREFACE. V lication, and still more so by the low price at which they sell Cruveil- hier's Anatomy. The English edition of this work costs thirteen dol- lars, while they furnish it to the members of the profession in the United States for three dollars. That the liberal course adopted by these gentlemen might create some feeling among the members of the trade, is not to be wondered at. We can understand the feelings of " Demetrius, the silversmith, who made silver shrines for Diana, which brought no small gain to the craftsmen;" but we confess we could hardly have believed that any of the medical censors of the country, men of science, could have expressed any other feeling but that of unmixed satisfaction ; for the Messrs. Harper have diminished nearly 100 per cent, the price of med- ical books. The remarkable course, however, followed by the medical journals of Philadelphia, in reference to the publications of the Messrs. Harper, only proves how little reliance can be placed on the opinions of reviewers when self-interest interferes with its candid expression. It is very possible, from the course which these gentlemen reviewers have pursued in reference to the publications which have received the imprimatur of the professors of the University of New- York, that the System of Anatomy of Cruveilhier may, when reviewed by them, fare no better than the other medical works published by the Messrs. Har- per, under the sanction of the medical department of New- York. It is, however, a matter of very little consequence. " Good wine requires no hush ;" and a good book, if furnished at a low price, must and will always command an extensive sale. New- York is the great metropolis of the Union, and must very soon become, like London and Paris, how- ever distasteful it may be to those who may have other interests, be- come the great centre, not only for medical publications, but also of medical education. Since the English edition of Cruveilhier has been published in Lon- don, the first and second volumes of a second edition of the work have been published by the author in Paris. The editor has carefully com- pared the second edition with the first, so far as it has been published, and has incorporated in the American edition whatever he thought could increase its value. He has, however, only followed the second edition when he thought that the changes introduced were improve- ments. In many instances, with the view of keeping down the size of the book, he has condensed into a few short paragraphs the substance of several pages. In the department of Myology the author has in his second edition made very numerous alterations from the first. As these, in the opinion of the editor, have rather diminished than in- creased the value of the work, he has only in a very few instances adopt- ed them. The student, he feels satisfied, will find the description of the muscles sufficiently minute. The subdivisions introduced, and the minutiae which are added to their descriptions in the second edition, VI EDITOR S PREFACE. would rather embarrass than promote their improvement ; he has, therefore, very generally preferred to follow the first edition in the de- scription of the muscles. In the original work there are no engravings ; this is a great desidera- tum, which has been removed in the English edition by the introduc- tion of numerous woodcuts, selected with care from the best anatomi- cal engravings, and marked with letters of reference. This greatly enhances the value of the work. The translation, which is an excel- lent one, was made by Dr. Madden. Systems of Anatomy generally offer little interest except to the anatomical student. This cannot be said of the system of Anatomy of Cruveilhier. It im bodies a fund of information, in connexion with Physiology and Pathology, which will, in the opinion of the editor, pro- cure for it a place in the library of every physician and surgeon who feels any interest in his profession. If the members of the profession only procure the book and peruse it, he cannot doubt but that the cause of Anatomical science will be greatly promoted in the United States ; and should this be the case, the editor will be amply repaid for any trouble he may have had in undertaking the republication of Cru- veilhier. University of New-York, Sept. 1st, 1844. AUTHOR'S PREFACE. The study of -man offers three very different objects for contemplation ; viz., his or- ganization, his vital functions, and his moral and intellectual faculties. The organization or structure of man is the object of anatomy, a science which in- vestigates every distinguishable material condition of the different parts that enter into the construction of his frame. Anatomy is a science of observation, and is, in this re- spect, susceptible of mathematical precision and physical certainty. The vital functions of man are the objects of physiology, which reveals to us the ac- tions of organs, with whose structure anatomy has previously made us acquainted. The science of physiology inquires into the various motions that occur within the human body, just as anatomy investigates the form of its component parts. All that we know, m fact, concerning material objects, may be resolved into a knowledge of their motions and their forms. As a moral and intellectual being, man is the object of the science of psychology, which contemplates him in the exercise of thought and volition, analyzes the operations of his mind and will, and classifies them according to their supremacy. A perfect acquaintance with man necessarily presupposes a combination of all that is taught by these three sciences ; and it is because his anatomy, his physiology, and his moral and intellectual endowments have not been studied by the same class of philoso- phers, that in the sciences relating to himself so much yet remains to be desired. Anatomy — the immediate object of this work — constitutes the foundation of medicine- In order to discover the precise seat of a defect in some complicated machine, and the means to be adopted for the reparation of its disordered mechanism, it is necessary to be acquainted with the relative importance, and the particular action of all its constitu- ent parts. " The human body," says Bacon, " may be compared, from its complex and dehcate organization, to a musical instrument of the most perfect construction, but ex- ceedingly liable to derangement." And the whole science of medicine is therefore re- duced to a knowledge of the means by which that harmonious instrument, the human frame, may be so tuned and touched as to yield correct and pleasing sounds. But since anatomy forms, as it were, the vestibule of medical science, it is of im- portance that he who is entering upon its pursuit should fully understand the path he is about to tread ; it is necessary, therefore, to assign, on the one hand, the rank which medicine holds as a natural science, and, on the other, the position of anatomy among the various sciences relating to medicine. The term science, according to the admirable definition of the Roman orator, signifies certain knowledge, deduced from certain principles — cognitio ccrta ex ■principiis certis ex- orta. Sciences are divided into the metaphysical, the mathematical, and the natural ; but since the two former are not connected with our present subject, we shall direct atten- tion to the natural sciences only. The object of the natural sciences, or of physics, taken in its widest signification, is a knowledge of the materials of which the universe is composed, and of the laws by which they are governed. They are subdivided into the physical, and the physiological or zoo- logical. The physical sciences take into consideration all the phenomena presented by inor- ganic bodies; they comprise, 1. Astronomy, which studies the heavenly bodies as they revolve in space, and estimates, by the aid of numbers, the laws by which their move- ments are governed ; 2. Physics, properly so called, or the study of the properties of matter in general ; in aid of which, experiments are performed in order to exhibit phe- nomena in every possible light, and calculation is employed to render fruitful the results of experiment ; 3. Geology, or that science which studies the surface of the globe, and the successive strata which are met with in its interior ; which goes back far beyond all historical traditions, brings to light, as it were, the very depths of the earth, and traces, with a sure hand, the history of the globe, and the various revolutions it has undergone ; 4. Chemistry, which consists in the study of the reciprocal actions of bodies, when re- duced to their atomic condition. The zoological or physiological sciences embrace all the phenomena presented by living bodies. The science of botany examines into the structure and functions of plants ; but zoology, properly so called, investigates the organization and the life of animals. The examination into structure or organization constitutes anatomy. Physiology embraces the study of functions or of life. The facts presented to us in the zoological are of a totally different character from those comprised in the physical sciences. Inorganic bodies, in fact, are governed by constant and immutable laws, acting in perfect harmony with each other ; but living bodies are subject not only to physical, but also to vital laws, tbe latter of which are constantly struggling against the former. This struggle constitutes life ; death is the triumph of the physical over the vital laws. In consequence, however, of this continual strife, derangements of structure and disordered functions very often occur ; and these become more frequent and more complicated, in proportion as the organization is more highly developed, and the animal more elevatrd in the scale of creation. A knowledge of these derangomcnts an.l of the proper means for restoring both or- Viil AUTHOR S PREFACE. ganization and life to a healthy condition, constitutes the science of medicine ; and the station which I have just assigned to this most important branch of zoological science will prove, better than any arguments, that the study of the physiological or healthy state of organization and of life should precede that of their pathological or diseased conditions ; and that anatomy forms the first link in the chain of medical science. Each science has its own methods of investigation, and its peculiar elements of cer- tainty. Metaphysics and moral philosophy have a metaphysical and moral certainty. The mathematical sciences set out from a small number of self-evident propositions or axioms founded upon the nature of things, proceed gradually from the known to the un- known, and trust to problems already demonstrated as to so many axioms, by means of which, as steps, they again ascend towards new truths. The natural sciences, again, are founded upon observation, and observation is merely the evidence of our senses ; hence arises the necessity of exercising them, in order to increase their acuteness and their activity. Facts, therefore, constitute the elements of the natural sciences ; and then reasoning follows, founded upon those facts and upon analogy. It would be absurd to study the natural sciences after the same method as metaphysics. It may readily be understood, that as the purely physical sciences are based upon con- stant phenomena, mathematics are directly applicable to them, and hence they are termed physico-mathematical sciences ; but in the zoological sciences, effects are continually varying, according to their causes. Any attempts, therefore, to apply the art of numbers to the elements of medicine, would be to imitate the philosopher, Condorcet, who enter- tained the whimsical notion of subjecting moral probabilities to the test of mathematical precision ; who was anxious to substitute a-\-b for either oral or written legal testimony ; who admitted half proofs and fractional proofs, and then reduced them to equations, by means of which he supposed he could arrive at arithmetical decisions, regarding the lives, the fortunes, and the characters of his fellow-men. It must, however, be reluctantly confessed, that we can acquire a knowledge only of the surfaces of a body ; and that to say we are acquainted with its texture, is to state, in other words, that we have a knowledge of the smallest surfaces comprised within its general surface. Sight, touch, &c., the only means of investigation by which we can appreciate the qualities of matter in general, can recognise nothing but surfaces, appear- ances, and relative properties. Absolute properties they are unable to detect. With our organization, we shall never know of what material objects essentially consist, but only what they are in relation to ourselves. This work being essentially of an elementary nature, and in some measure adapted for the lecture-room, I have endeavoured to confine myself within narrow limits, and strictly to avoid all considerations which are not immediately connected with the anato- my of organs. At the same time I have not forgotten that this work was intended for the student of medicine, and not for the naturalist ; I have, therefore, been induced, in the following pages, if not expressly to indicate, at least to direct attention to the more immediate applications of anatomy to physiology, surgery, and medicine. The objects which I have constantly had in view have been to exhibit the actual state of the science of anatomy ; to present its numerous facts in their most natural order ; to describe each fact clearly, precisely, and methodically ; to adopt such a method as would form an easy guide to the student, and not involve him in confusion ; and, lastly, to give to each detail its pecuhar value, by invariably directing particular attention to the more important points, instead of confounding them with matters of less consequence, in an indigested and monotonous enumeration of facts. The following is the order in which the principal divisions of the subject have been treated. The first division comprises Osteology, Arthrology or Syjidcsmology, and Odontology. 1. Osteology, which, notwithstanding the great number of works on the subject, seems always to offer some new facts to those who study it with zeal, has been treated with the attention it deserves, as forming the basis of anatomical knowledge. An account of the development of the osseous system has appeared to me necessary for the comple- tion of its history. I have therefore considered the following points in connexion with the development of each bone : the number of ossific points ; the time of appearance of the primitive and complementary ossifie points ; the periods at which the several points unite, and the changes occurring in the bone subsequently to its growth. By adopting this method, the most complicated ossifications are reduced to a few propositions easily retained in the memory. The inconvenience arising from including in a description of the bones all the attach- ments of the muscles, and nearly the whole anatomy of the part, is so totally at variance with a methodical arrangement of facts, that it is unnecessary to offer an apology for the changes made in this respect. Occasionally, however, I have mentioned those muscu- lar attachments which might serve to characterize the osseous surfaces on which they are situated. 2. Under the title of Syndcsmology, or Arthrology, are united all the articulations of the human body. Assuming as the only basis of classification the form of the articula- ted surfaces, which is always in accordance with the means of union and the movements of the joint, I have been induced to modify the divisions usually adopted. Tlie condylar- AUTHOR S PREFACE. IX tkrosis, or condyloid artindation, and the articulation by mtitual reception, form quite as natural genera as the enarthrosis and the arthrodia. It will, perhaps, be found that the characters of the different kinds of articulation, and in particular those of the angular ginglymus, which I have called the trochlear articulation, and those of the lateral gingly- mus, or the trochoid articulation of the ancients, are more clearly defined than in other anatomical works. The mechanism, i. e., the movements of a joint, is so intimately connected with its anatomy, that it was impossible to pass it over in silence ; on the other hand, it was sometimes difficult to determine the limit which ought to distinguish an anatomical from a physiological treatise. I have endeavoured to avoid both extremes, by confining my- self strictly to the mechanism of each joint in particular, referring to works on physiol- ogy for the principal movements of locomotion, and of animal statics, such as walking, running, standing, &c. 3. Odontology, or the description of the teeth, concludes the first division. I have ta- ken care to point out that this juxtaposition of the bones and the teeth was founded upon their common indestructibility, and not upon the identity of their nature ; the bones be- ing organs composed of living tissues, while the hard portion of the teeth, on the other hand, is but the solidified product of secretion.* The second division includes Myology, Aponeurology, and Splanchnology. 1. In treating of Myology, I have preferred the topographical to the physiological ar- rangement of the muscles, for this reason only, that it admits of all of them being studied upon the same subject. To unite, as far as was practicable, the undoubted advantages possessed by both methods, I have given, at the conclusion of myology, a general sketch of the muscles, arranged according to their physiological relations ; and by grouping them, not after their order of super-imposition, but according to their several actions, I have arranged them around the articulations to which they may belong, and have point- ed out the extensors, the flexors, &c. A muscle being known when its attachments are ascertained, I have thought it advi- sable to commence the description of each by a brief announcement of its origin and in- sertion, as a sort of definition or summary. The particular details concerning its mode of insertion, whether it be aponeurotic or fleshy, and concerning the direction of its fibres, complete the description of each muscle considered by itself; the history of which is concluded by an examination of its relations to neighbouring parts, and of its uses. The individual or combined action of the muscles, for the production of simple movements, follows so naturally after their description, and presupposes so correct and positive a knowledge of their anatomy, that it can be treated of with propriety only in a work on anatomy. The compound movements necessary for the consecutive or simultaneous action of a great number of muscles come within the province of physiology. 2. The aponeuroses, those important appendages of the muscular system, are separ- ately noticed, in connexion with the muscles to which they belong ; but I have also de- scribed them together under the head oi' Aponeurology. This combination of analogous parts possesses the twofold advantage of simplifying the science, by enabhng one part to elucidate the structure of another, and of permitting us to discover the general laws according to which these structures are disposed. 3. With some modification, I have adopted that old division of anatomy, which treats of the viscera and organs, and which is known by the name of Splanchnology. The brain and the organs of the senses, which were included in this division m all anatomical works preceding those of ScBmmering and Bichat, have been removed from it, and described with the other portions of the nervous system. The description of the heart, in like manner, will be found with that of the other organs of circulation. In short, the old classification of the viscera, according to their locality, that is, into those of the head, the neck, the chest, &c., has been replaced by a more physiological arrange- ment. Splanchnology will therefore comprehend a description of the organs of digestion and their appendages, of the organs of respiration (among which is included the larynx, or the organ of voice), and, lastly, the genito-urinary organs. To the inquiry why I have departed from the usual custom of placing splanchnology at the end of anatomy, I reply that, in order to study, with advantage, the vessels and the nerves, it is necessary to have a previous acquaintance with the organs to which they are distributed. The importance of the parts described in this division, and the practical results which flow from even the most superficial knowledge of their forms, connexions, and intimate structure, are at once my reason and excuse for extending, to so great a length, this portion of the work ; and, moreover, it is necessary to state, that there are many medi- cal practitioners who learn anatomy only from elementary works. The third and the last division treats of the organs of circulation, viz., the heart, arter- ies, veins, and lymphatics ; and of the sensory apparatus, viz., the organs of the senses, the brain, and the nerves. 1. No part of anatomy, perhaps, has been better known than the arteries, since the appearance of Haller's admirable works ; I could neither have followed a better guide nor a more perfect model. * See note, p. 183. B X AUTHOR S PREFACE. 2. The study of the veins has acquired an unexpected degree of importance, in conse- quence of the works of various physicians on phlebitis ; and our knowledge of them has been mucli extended by the researches of M. D&puytren into the veins of the spine, and the excellent plates of this order of vessels published by M. Breschet. 3. The study of the lymphatics has been almost abandoned since the very remarkable publications of Mascagni : I have endeavoured to ascertain what credit was to be given to the assertions of some modern writers concerning the frequent communication be- tween the veins and the lymphatics. 4. The work of Soemmering'on the organs of the senses constitutes, perhaps, the high- est title to fame possessed by that great anatomist ; and it might even be said that he has left nothing for his successors to accomplish, did not the constant study of a science of observation unceasingly proclaim this important truth, that it is in the power of no man to declare, beyond this limit thou shalt not pass. The brain and the nerves, to which so many able and laborious inquirers have lately directed their attention, have been my favourite objects of investigation ; on account of their importance, and perhaps, also, from the difficulties attending their study. Not sat- isfied with simply tracing the nerves to the various organs in the body, I have studied them in the interior of those organs, and have endeavoured to ascertain the precise branches that are distributed to each particular part. I may add, that, in order to facilitate the dissection of the nervous system, and, indeed, of all the other parts of the body, I have presented, whenever it was necessary, a short account of the best method of preparation. With regard to the general spirit of this work, I have been anxious to render it clas- sical ; and have avoided, most scrupulously, that species of induction and analogical rea- soning, which, in a great measure, constitutes philosophical anatomy. To this kind of anatomy I have never even introduced any allusions, except when its general ideas and views (almost always ingenious, but usually bold and speculative) might elucidate our own subjects. All the descriptions have been made from actual dissections. It was only after hav- ing completed from nature the account of each organ that I consulted writers, whose imposing authority could then no longer confine my thoughts, but always excited me to renewed investigations wherever any discrepancy existed. Anatomy being, as already stated, the basis of medical science, we should greatly misapprehend its nature did we not consider it the chief of the accessory sciences of medicine. Without it, the physiologist rears his structure upon sand ; for physiology is nothing more than the interpretation of anatomy. It is anatomy that guides the eye and the hand of the surgeon ; that inspires him with that ready confidence, which leads him to search among structures, whose lesion would be dangerous or mortal, for some vessel that must be tied, or for a tumour which must be extirpated. Nor is it less indispensa- ble to the physician, to whom it reveals the seat of diseases, and the changes of form, size, relation, and texture, which the affected organs have undergone. Anatomy is, moreover, the science which, of all others, excites the greatest curiosity. If the mineralogist and the botanist are so eager, the one to determine the nature of a stoae, the other to ascertain the characters of a flower ; if the love of their particular science induces them to undertake the most dangerous voyages, in order to enrich it with a new species, what ought to be our ardour in pursuing the study of man, that masterpiece of creation, whose structure, possessed of both delicacy and strength, ex- hibits so much harmony as a whole, and displays so much perfection in its parts ! And while contemplating this marvellous organization, in which all has been provided and prearranged with such intelligence and wisdom, that no single fibre can acquire the slightest addition, or undergo the least diminution of power, without the equilibrium be- ing destroyed and disorder being induced — what anatomist is there who would not feel . tempted to exclaim, with Galen, that a work on anatomy is the most beautiful h3Tnn which man can chant in honour of his Creator !* May this work inspire among students an ever-increasing ardour for the study of the organization of man, which, even if it were not the most eminently useful, would still be the most interesting, and the most beautiful of all the sciences. And what more powerful motive for emulation can present itself to a generous mind, than the idea, "that every acquisition of knowledge is a conquest achieved for the relief of suffering humanity !" Let it neveV be forgotten that, without anatomy, there is no physiology, no surgery, no medicine ; that, in a word, all the medical sciences are grafted upon anato- my as upon a stock ; and that the deeper its roots descend, the more vigorous will be its branches, and the more abundantly laden with flowers and with fruit. I must here express my acknowledgments to M. Chassaignac, the anatomical assist- ant to the Faculty, who has distinguished himself in several concours, and who has as- sisted me with the greatest zeal in the execution of this work. * " Sacrum sermonem quern ego Conditovis nostri verum hymnum compono, existimoque in hoc veram esse pietatem, non si taurorum hecatombas ei sacrificaverim, et casias, aliaque sexcenta odoramenta ac unguenta suffumigaverim, sed si noverini ipse primus, deiiide et aliis exposueriiii qua)nam sit ipsius sapientia, quie virtus, qus bomtas." — (Galen, De tisu part., lib. iii.) CONTENTS. INTRODUCTION. Object and DUision of Anatomy. — General View of the Human Frame. — Apparatus of Sensation — of Lo- comotion— ofMutrilion — of Reproduction. — General Plan of tlie Work Page 1 APPARATUS OF LOCOMOTION. OSTEOLOGY. Of the Boves in General. The Bones — Importance of their Study —General View of the Skeleton.— Number of the Bones.— Method of Description. — Nomenclature. — Situation in general. — Direction. — Size, Weight, and Density of Bones. — Figure. — Distinction into long, broad, and flitt Bones. — Regions of Bones. — Eminences and Cavities. — Internal Conformation. — Texture. — Development, or Osteogeny. — Nutrition 5 The fertebral Column. General Characters of the Vertebrae. — Characters peculiar to the Vertebrs of each Region. — Characters proper to certain Vertebrae. — VertebriE of the Sacro-coccygeal Region. — The Vertebral Column in general. — Development 18 The Scull. Composed of the Cranium and Face. — Cranial Bones — Occipital — Frontal — Sphenoid — CEthnioid — Parietal — Temporal. — The Cranium in general. — Development. — Bones of the Face — Superior Ma.xillary. — Palate. ' — Malar. — Nasal. — Lachrymal — Inferior turbin;ited. — Vomer— Inferior Maxillary. — The Face in general. — Cavities. — Development 33 Tkc Thorax, or Chest. The Sternum. — Ribs. — Costal Cartilages. — The Thorax in general. — Development 64 The .Superior, or Thoracic Extremities. The Shoulder.— Clavicle.— Scapula.— The Shoulder in general.— Development.— Humerus.— Ulna.— Radius, — The Hand. — The Carpus and Carpal Bones. — The Metacarpus and Metacarpal Bones. — The Fingers. General Development ol the Superior Extremities 73 The Inferior, or .Ibdominal Extremities. The Haunch.— Os Coxee.— The Pelvis.— Development.— Femur. — Patella. — Tibia.— Fibula.— The Foot.— The Tarsus and Tarsal Bones. — The Metatarsus and Metatarsal Bones. — The Toes. — Development of the Lower Extremities. — Comparison of the Upper and Lower Extremities. — Os Hyoides . . . .87 The Articulations, or Arthrology. General Observations.— .■Articular Cartilages.— Ligaments.— Synovial Membranes. — Classification of the Joints. — Diarthroses. — Synarthroses. — .-imphiarthroses, or Symphyses HI Articulations of the Vertebral Column. Articulations of the Vertebra; with each other. — Those peculiar to certain VertebrEe. — Sacro-vertebral, Sa- cro-coccygeal, and Coccygeal Articulations. — Articulations of the Cranium — of the Face — of the Tho- >^ 115 Articulations of the Superior or Thoracic Extremities. Articulations of the Shoulder.— Scapulo-humeral.—Humero-cubital.— Radio-cubital. — Radio-carpal. Of the Carpus and Metacarpus. — Of the Fingers 135 Articulations of the Inferior or Abdominal Extremities. Articulations of the Pelvis.— Coxo-femoral.— Knee-joint.— Peroneo-tibial. — Ankle-joint.— Of the Tarsus.— Tarsometatarsal. — Of the Toes I54 ODONTOLOGY. Circumstances in which the Teeth ditfer from Bones. — Number. — Position. — External Conformation. Gen- eral Characters. — Classification — Incisor — Canine — Molar. — Structure. — Development .... 177 MYOLOGY. The Muscles in general. — Nomenclature.— Number.— Volume and Substance.— Figure.— Dissection. Rela- tions.— Attachments. — Structure. — Uses. — Preparation. — Order of Description 190 Muscles of the Posterior Region of the Trunk. The Trapezius.— Latissimus Dorsi and Teres Major.— Rhomboideus —Levator Anguli Scapulas.— Serrati Postici.—Splenius.— Posterior Spinal Muscles.— Complexus. — Inter-spinales Colli. — Recti Capitis Postici, Major et Minor.— ObUqui Capitis, Major et Minor.— General View and Action of the Posterior Spinal Muscles 198 Muscles of the Anterior Abdominal Region. The ObliquusExternus Abdominis.— Obliquuslnternus and Cremaster.—Transversalis Abdominis.— Rectus Abdominis. — Pyramidalis 208 Diaphragmatic Region 212 Lumbar Region. The Psoas and Iliacus. — Psoas Parvus. — Quadratus Lumborum 314 Lateral Vertebral Region. Tho Inter-transversales and Rectus Capitis Lateralis. — Scaleni ......... 217 XU CONTENTS. Deep Anterior Cervical, or Prevertebral, Region. The Recti Capitis Antici, Major et Minor. — Longus Colli. — Action of these Muscles . . .Page 213 Thoracic Region. The Pectoralis Major. — Pectoralis Minor. — Sub-clavius. — Serratus Magnus. — Intercostales. — Supra-costales. — Infra-costales. — Triangularis Sterni 220 Superficial Jlnterior Cervical Region. The Platysma Myoides. — Sterno-cleido mastoideus 234 Muscles of the Infra-hyoid Region. The Sterno-hyoideus. — Scapulo- or Omo-liyoideus.— Sterno-thyroideus. — Thyro-hyoideua , . . 226 Muscles of the Suprahyoid Region. The Digastxicus. — Stylo-hyoideus. — Mylo-hyoideus. — Genio-hyoideus. — Their Action .... 228 Muscles of the Cranial Region. Occipito-frontalis. — Auricular Muscles 230 Muscles of the Palpebral Region. Orbicularis Palpebrarum. — Superciliaris. — Levator Palpebrfe Superioris .... . . 231 JVasal Region. The Pyramidalis Nasi. — Levator Labii Superioris Al^que Nasi. — Transversalis, or Triangularis Nasi. — De- pressor Alffi Nasi. — Naso-labialis 233 Muscles of the Labial Region. The Orbicularis Oris. — Buccinator. — Levator Labii Superioris. — Caninus. — Zygoniatici, Major et Minor. — Triangularis. — Cluadratus Menti. — Levator Labii Superioris. — Movements of the Lips and those of the Face 234 Muscles of the Temporo-maxillary Region. The Masseter and Temporalis 239 The Ptery go-maxillary Region. The Pterygoideus Internus. — The Pterygoideus Externus 240 Muscles of the Shoulder. The Deltoideus. — Supra-spinatus. — Infra-spinatus and Teres Minor. — Sub-scapularis .... 241 Muscles of the Arm. The Biceps. — Brachialis Anticus. — Coraco-brachialis. — Triceps Extensor Cubiti 244 Muscles of the Forearm 249 Muscles of the Hand. The Abductor Brevis Pollicis. — Opponens Pollicis. — Flexor Brevis Pollicis. — Adductor Pollicis. — Palmaris Brevis. — Abductor Digitl IMinimi. — Flexor Brevis Digiti Minimi. — Opponens Digiti Minimi. — The Interos- seous Muscles, Dorsal and Palmar 260 Muscles of the Pelvis. The Glutaei Maximus, Medius, et Minimus. — Pyriformis. — Obturator Internus. — Gemelli, Superior et Inferior. — Uuadratus Femoris. — Obturator Externus. — Action of these Muscles 264 Muscles of the Thigh. The Biceps Cruris. — Semi-tendinosus. — Semimembranosus. — Tensor Vagina Femoris. — Sartorius. — Triceps Extensor Cruris. — Gracilis. — Adductor Muscles of the Thigh 2(j9 Muscles of the Leg. The Tibialis Anticus. — The Extensor Communis Digitorum — Extensor Proprius Pollicis. — Peronei Longus et Brevis. — Gastrocnemius, Plantaris and Solaris. — Popliteus. — Tibialis Posticus. — Flexor Longus Pol- licis 277 Muscles of the Foot. The Extensor Brevis Digitorum.— Abductor Pollicis Pedis.— Flexor Brevis Pollicis Pedis. — Adductor Pollicis Pedis.— Transversus Pollicis Pedis. — Abductor Digiti Minimi.— Flexor Brevis Digiti Minimi. — Flexor Bre- vis Digitorimi. — Flexor Accessorius. — Lumbricales. — Interossei 286 APONEUROLOGY. General Observations on the Aponeuroses. — Structure. — Uses 294 Particular Aponeuroses. Superficial Fascia. — Aponeuroses of the Cranium — of the Face — of the Neck — of the Thorax — of the Abdo- men— of the Pelvis — of the Thigh, Leg, and Foot — of the Shoulder, Arm, Forearm, and Hand . . 297 SPLANCHNOLOGY. General Observations on the Viscera. — External Conformation.- trueture. — Development. — Functions. — Dissection 320 The Organs of Digestion and theie Appenbages. Alimentary or Digestive Canal. General Observations. — Division. — Mouth and its Appendages. — Lips. — Cheeks. — Hard and soft Palate. — Tonsils. — ^Tongue. — Salivary Glands. — Buccal Mucous Membrane. — Pharynx. — QEsophagus. — Stomach. — Small Intestine. — Large Intestine. — Muscles of the Perineum. — Development of the Intestinal Canal . 322 Appendages of the Alimentary Canal. The Liver and its Excretory Apparatus. — The Pancreas. — The Spleen 384 The Organs of Respiration General Observations. — ^The Lungs and Pleurae. — The Trachea and Bronchi. — Development of the Lungs. — The Laiynx — its Structure, Development, and Functions. — The Thyroid Gland .... 409 CONTENTS. XIU The Genito-Urinary Organs. The Urinary Organs. Division. — The Kidneys and Ureters. — The Bladder.— The Supra-renal Capsules . . . Page 435 The Generative Organs. The Generative Organs of the Male. The Testicles and their Coverings. — The Epididymis, the Vasa Deferentia, and Vesiculse Seminales. — Tlie Penis.— The Urethra.— The Prostate and Cowper's Glands 446 The Generative Organs of the Female. The Ovaries.— The Fallopian Tubes.— The Uterus.— The Vagina.— The Urethra.— The Vulva . . 461 The MamTiue. Number. — Situation. — Size. — Form. — Structure. — Development 473 The Peritoneum. The Sub-timbilical Portion. — The Supra-umbilical Portion.— General Description and Structiue . . 479 ANGEIOLOGY. Definition and Objects of Angeiology 479 The Heart. General Description. — External and Internal Conformation. — Structure. — Development. — Functions. — ^The Pericardium 479 The Arteries. Definition. — Nomenclature. — Origin. — Varieties. — Course. — Anastomoses. — Form and Relations. — Termina- tion.— Structure.— Preparation 496 Description of the Arteries. The Pulmonary Jirtery. Preparation. — Description. — Relations. — Size. — Development 499 The Aorta. Preparation. — Definition. — Situation. — Direction. — Size. — Division into the Arch of the Aorta, the Thoracic Aorta, and the Abdominal Aorta 501 Collateral Branches of the Aorta. Enumeration and Classification. — Arteries arising from the Aorta at its Origin, viz., the Coronary or Car- diac—Arteries arising from the Thoracic Aorta, viz., the Bronchial, the OEsophageal, the Intercostal. — Arteries arising from the Abdominal Aorta, viz., the Lumbar, the Inferior Phrenic, the Coeliac A.\is, in- cluding the Coronary of the Stomach, the Hepatic, and the Splenic, the Superior Mesenteric, the Inferior Mesenteric, the Spermatic, the Renal, and the Supra-renal or Capsular 503 Arteries arising from the Arch of the Aorta. Enumeration and Varieties. — The Common Carotids. — The External Carotid — the Superior Thyroid — the Facial — the Lingual — the Occipital — the Posterior Auricular — the Parotid — the ascending Pharyngeal — the Temporal — the Interna! Maxillary. — The Internal Carotid — the Ophthalmic — the Cerebral Branches of the Internal Carotid. — Summary of the Distribution of the Common Carotids. — Artery of the Upper Extremity. — The Brachio-cephalic. — The Right and Left Sub-clavians — the Vertebral and its Cerebral Branches, with Remarks on the Arteries of the Brain, Cerebellum, and Medulla — the Inferior Thyroid — the Supra-scapular — the Posterior Scapular — the Internal Mammary — the deep Cervical — the Superior Intercostal. — The Axillary — the Acromiothoracic — the Long Thoracic — the Sub-scapular — the Posterior Circumflex — the Anterior Circumflex. — The Brachial and its Collateral Branches. — The Radial, its Col- lateral Branches, and the deep Palmar Arch.— The Ulnar, its Collateral Branches, and the Superficial Palmar Arch. — General Remarks on the Arteries of the Upper Extremity 513 Arteries arising from the Termination of the Aorta. Enumeration. — The Middle Sacral. — The Common Iliacs. — The Internal Iliac, or Hypogastric — the Umbil- ical— the Vesical — the middle HEemorrhoidal — the Uterine — the Vaginal — the Obturator — the Ilio-lumbar — the Lateral Sacral — the Glutoeal — the Sciatic — the Internal Pudic. — Summary of the Distribution of the Internal Iliac. — Artery of the Lower Extremity. — The External Iliac — the Epigastric— the Circumflex Iliac. — The Femoral — the Superficial Epigastric — the External Pudic — the Muscular — the deep Femoral, its Circumflex and Perforating Branches. — The Popliteal, and its Collateral Branches.— The Anterior Tibial and the Dorsal Artery of the Foot. — The Tibio-peroneal — Peroneal — Posterior Tibial, and the In- ternal and External Plantar. — Comparison between the Arteries of the Upper and Lower Extremities . 552 The Veins. Definition. — The Venous System. — Origin of the Veins. — Course. — Anastomoses and Plexuses. — Varieties. —Termination. — Valves. — Structure.— Preparation.— Method of Description . .... .573 Description of the Veins. The Pulmonary Veins Preparation. — ^Description. — ^Relations. — Size. — Peculiarities 577 The Veins of the Heart. The Great Coronary or Cardiac Vein.— The Small Cardiac Veins 577 The Superior, or Descending Vena Cava and its Branches. The Superior Vena Cava.— The Brachio-cephalic Veins— the Inferior Thyroid— the Internal Mammary — the Superior Phrenic, the Thymic, Pericardiac, and Mediastinal— the Vertebral. — The Jugular Veins, viz., the External — the Anterior — and the Internal. — The Encephalic Veins, and the Sinuses of the Dura Mater, viz., the Lateral — the Superior Longitudinal — the Straight— the Superior and Inferior Petrosal — the Cavernou.=i — the Coronary — and the Anterior and Posterior Occipital Sinuses — the Conflux of the Sinuses. — The Branches of Origin of the Jugular Veins — the Facial — the Temporo-maxillarv — the Pos- XIV CONTENTS. tenor Auricular — the Occipital — the Lingual — the Pharyngeal — the Superior and Middle Thyroid — the Veins of the Diploe. — Summary of the Distribution of the Veins of the Head. — The deep Veins of the Upper Extremity — the Palmar, Radial, Ulnar, Brachial, and Axillary— the Sub-clavian. — The Superficial Veins of the Upper Extremity — in the Hand — iu the Forearm — at the Elbow — and in the Arm. — General Remarks on these Superficial Veins Page 578 The Inferior, or Ascending Vena Cava and its Branches. The Inferior Vena Cava — the Lumbar or Vertebro-lumbar Veins — the Renal — the Middle Supra-renal — the Spermatic and Ovarian — the Inferior Phrenic. — The Portal System of Veins — the Branches of Origin of the Vena Portas— the Vena PortEe — the Hepatic Veins. — The Common Iliacs — the Internal Iliac — the Hemorrhoidal Veins and Plexuses — the Pelvic Veins and Plexuses in the Male and in the Female. — The deep Veins of the Lower Extremity — the Plantar, Posterior Tibial, Peroneal, Dorsal, Anterior Tibial, and Popliteal — the Femoral — the External Iliac. — The Superficial Veins of the Lower Extremity — the Inter- nal Saphenous — the External Saphenous 596 The Veins of the Spine. General Remarks. — The Superficial Veins of the Spine. — The Anterior Superficial Spinal Veins, viz., the Greater Azygos — the Lesser Azygos — the Left Superior Vertebro-costals — the Right Vertebro-costals — the Vertebro-lumbar — the Iliolumbar, and Middle and Lateral Sacral — the Anterior Superficial Spinal Veins in the Neck. — The Posterior Su|ierficial Spinal Veins. — The deep Spinal or Intra-spinal Veins — the Anterior Longitudinal, and the Transverse Veins or Plexuses, and the Veins of the Vertebrae — the Posterior and the Posterior and Lateral Transverse Veins or Plexuses — the Medullary Veins. — General Remarks on the Veins of the Spine 605 The Lymphatic System. Definition, History, and general View of the Lymphatic System. — Origin. — Course. — Termination and Structure of the Lymphatic Vessels. — The Lymphatic Glands. — Preparation of the Lymphatic Vessels and Glands 611 Description of the Lymphatic System. The Thoracic Duct — the Right Thoracic Duct. — The Lymphatic System of the Lower Extremity — of t e Pelvic and Lumbar Regions — of the Liver — of the Stomach, Spleen, and Pancreas — of the Intestines — of the Thorax — of the Head — of the Cervical Regions — of the Upper Extremity and Upper Part of the Trunk 6S20 NEUROLOGY. The Organs of the Senses. The Skin — its External Characters, Structure, and Appendages. — The Tongue considered as the Organ of Taste. — The Organ of Smell — the Nose— the Pituitary Membrane. — The Organ of Sight — the Eyebrows — the Eyelids — the Muscles of the Orbit — the Lachrymal Apparatus — the Globe of the Eye, its Meia- branes and Humours — the Vessels and Nerves of the Eye. — The Organ of Hearing — the External Ear — the Middle Ear or Tympanum — the Internal Ear or Labyrinth — the Nerves and Vessels of the Ear . 629 The Cerebro-spinal Axis. General Observations ' 681 The Membranes of the Cerebro-spinal Axis. General Remarks. — The Dura Mater — the Cranial Portion, its Structure and Uses— the Spinal Portion. — The Arachnoid— its Cranial Portion — its Spinal Portion— the Sub-arachnoid Fluid — their Uses. — The Pia Mater — its External Cerebral Portion 662 The Spinal Cord, and the Medulla Oblongata. General View of the Cord — its Limits and Situation — the Ligamentum Denliculatum. — Size of the Spinal Cord — Form, Directions, and Relations — the Cord in its Proper Membrane — the Proper Membrane, or Neurilemma of the Cord— the Cord deprived of its Proper Membrane.— Internal Structure of the Cord — Sections — Examination by means of Water, and when hardened in Alcohol — the Cavities or Ventricles of the Cord. — The Medulla Oblongata— Situation-External Conformation — Anterior Surface, the Ante- rior Pyramids and the Olivary Bodies— the Posterior Surface — the Lateral Surfaces— the Internal Struc- ture— Sections— Examination by Dissection, and imder Water. — Development of the Spinal Cord. — De- velopment of the Medulla Oblongata.— Comparative Anatomy of the Spinal Cord. — Comparative Anatomy of the Medulla Oblongata 693 The Isthmus of the Encephalon. General Description and Division.— The Pons Varolii and Middle Peduncles of the Cerebellum— the Pedim- cles of the Cerebrum— the Superior Peduncles of the Cerebellum and the Valve of Vieussens— the Cor- pora auadrigemina.— Internal Structure of the Isthmus, viz., of its Enferior, Middle, and Superior Strata. — Sections. — Development. — Comparative Anatomy 710 The Cerebellum. General Description.— External Characters and Conformation— Furrows, Lobules, Laminae, and LamellsB. —Internal Conformation— the Fourth Ventricle, its Fibrous Layers, its Inferior Orifice, and its Choroid Plexus.— Sections of the Cerebellum, Vertical and Horizontal.— Examination by Means of Water, and of the hardened Cerebellum.— General View r)f the Organ.— Development.— Comparative Anatomy . 715 The Cerebrum, or Brain Proper. Definition— Situation— Size and Weight— General Form —The Superior or Convex Surtace.— Jt ne Inferior Surface or Base— its Median Region, containing the Inter-peduncular Space, the Corpora Albicantia, the Optic Tracts and Commissure, the Tuber Cinereum, Infnndibulum, and Pituitary Body, the Anterior Pah of the Floor of the Third Ventricle, the reflected Part of the Corpus Callosum, the Anterior Part of the Longitudinal Fissure, the Posterior Part of the Longitudinal Fissure, the Posterior Extremitv of the Corpus Callosum and Median Portion of the Transveree Fissure, and the Transverse Fissure. — The Lateral Re- gions, including the Fissure of Sylvius and the Lobes of the Brain.— The Convolutions and Anfractuosi- ties of the Brain, upon its Inner Surface, its Base, and its Convex Surface— Uses of the Convolutions and Anfractuosities.— The Internal Structure of the Brain— Examination by Sections— Horizontal Sections showing the Corpus Callosum, the Septum Lucidum, the Fornix and Corpus Fimbriatum, the Velum In- terpositum, the Middle or Third VenU-icle, the Aqueduct of Sylvius, the Pineal Gland, the Lateral Ven- tricles, their Superior and Inferior Portions, the Choroid Plexus, and the Lining Membrane and the Fluid of Uie Ventricles — Median Vertical Section— Transverse Vertical Sections — Section of Willis. — General CONTENTS. XV Remarks on this Method of examining the Brain.— Methods of Varolius, Vieussens, and Gall.— Gall and Spurzlieim's Views on the Structure of the Brain.— General Idea of the Brain. — Development. — Compar- ative Anatomy P^^ge 725 The Nerves, or the Peripheral Portion of the Nervous System. General Remarks. — History and Classification. — Origin, or Central Extremity.— Different Kinds. — Course, Plexuses, and Anastomoses. — Direction, Relations, and Mode of Division. — Termination. — Nervous Gan- glia, and the great Sympathetic System. — Connexions of the Ganglia with each other, and with the Spi- nal Nerves. — Structure of Nerves.— Structure of Ganglia. — Preparation of Nerves . . . .759 Description of the Nerves. General Remarks. — Division into Spinal, Cranial, and Sympathetic Nerves ...... 769 The Spinal JiTerves. Enumeration and Classification. — The Central Extremities, or Origins of the Spinal Nerves — Apparent Ori- gins— Deep or real Origins. — The Posterior Branches of the Spinal Nerves — Common Characters— ^the Posterior Branches of the Cervical Nerves, their Common and Proper Characters — the Posterior Branches of the Dorsal, Lumbar, and Sacral Nerves. — The Anterior Branches of the Spinal Nerves — their General Arrangement 770 The interior Branches of the Cervical JVerves. Dissection. — Anterior Branch of the First, Second, Third, and Fourth Cervical Nerves. — The Cervical Plexus— its Anterior Branch, the Superficial Cervical — its Ascending Branclies, the great Auricular and the External or Lesser Occipital — its Superficial Descending Branches, the Siipra-clavicular — its deep De- scending Branches, the Nerve to the Descendens Noni and the Phrenic — its deep Posterior Branches. — The Anterior Branches of the Fifth, Sixth, Seventh, and Eighth Cervical, and First Dorsal Nerves. — The Brachial Plexus — its Collateral Branches above the Clavicle — its Muscular Branches, Posterior Thoracic, Supra-scapular — opposite to the Clavicle the Thoracic, below the Clavicle the Circumtle.x — its Terminal Branches, the Internal Cutaneous and its Accessory, the Musculo-cutaneous, the Median, the Ulnar, the Musculo-spiral or Radial. — Summary of the Distribution of the Branches of the Brachial Plexus . 776 The -interior Branches of the Dorsal Jfcrves, or the Intercostal J^Terves. Dissection. — Enumeration. — Common Characters. — Characters proper to each 794 The Anterior Branches of the Lumbar JVerves. Enumeration. — The Lumbar Plexus. — Collateral Branches, Abdominal and Inguinal. — Terminal Branches — the Obturator Nerve — the Crural Nerve and its Branches, viz., the Musculo-cutaneous — the Accessory of the Internal Saphenous — the Branch to the Sheath of the Vessels — the Muscular Branches — the Inter- nal Saphenous 7% The Anterior Branches of the Sacral JVerves. Dissection. — Enumeration. — The Sacral Plexus. — Collateral Branches, viz., the Visceral Nerves — the Mus- cular Nerves — the Inferior lleninrrhoidal — the Internal Pudic audits Branches — the Suvierior Gluteal Nerve^the Inferior Gluteal, or Lesser Sciatic Nerve — the Nerves for the Pyramidalis, (iuadratus Fe- moris, and Gemelli. — Terminal Branch of the Sacral Plexus, or the great Sciatic Nerve. — The External Popliteal and its Branches — the Peroneal, Saphenous, Cutaneous, and Muscular Branches — the Musculo- cutaneous— the Anterior Tibial. — The Internal Popliteal and its Branches — the Tibial or External Saphe- nous— Muscular and Articular Branches — the Internal Plantar — the External Plantar. — Summary of the Nerves of the Lower Extremity. — Comparison of the Nerves of the Upper with those of the Lower E.v- tremity 804 TTie Cranial JVerves. Definition and Classification. — The Central Extremities of the Cranial Nerves, viz., of the Olfactory — of the 0|)tic — of the Common Motor Oculi — of the Pathetic — of the Trigeminal — of the External Motor Oculi — of the Portio Dura and Portio Mollis of the Seventh — of the Glosso-pharyngeal, Pneumogastric, and Spinal Accessory Divisions of the Eighth — and of the Ninth Nerves 816 Distribution of the Cranial JVerves. The First Pair, or Olfactory Nerves. — The Second, or Optic Nerves. — The Third, or Common Motor Nerves. — The Fourth, or Pathetic Nerves. — The Fifth, or Trigeminal Nerves — the Ophthalmic Division of the Fifth, and its Lachrymal, Frontal, and Nasal Branches — the Ophthalmic Ganglion — the Superior Maxil- lary Division of the Fifth, and its Orbital Branch — the Spheno-palatine Ganglion, and its Palatine, Spheno- palatine, and Vidian Branches — the Posterior and Anterior Dental, and the Terminal Branches of the Su- perior Maxillary Nerve — the Inferior Maxillary Division of the Fifth — its Collateral Branches, viz., the deep Temporal, the Masseteric, Buccal, and Internal Pter>-goid, and Auriculo-temporal — its Terminal Branches, viz., the Lingual and Inferior Dental — the Otic Ganglion. — The Sixth Pair, or External Motor Nerves. — The Seventh Pair— the Portio Dura, or the Facial Nerve— its Collateral Branches — its Terminal Branches, viz., the Temporo-facial and Cervicofacial — the Portio Mollis, or Auditory Nerve. — The Eighth Pair — its First Portion, or the Glossopharyngeal' Nerve — its Second Portion, or the Pneumogastric Nerve, divided into a Cranial, Cervical, Thoracic, and Abdominal Part — its Third Portion, or the Spinal Acces- sory Nerve.— The Ninth Pair, or the Hypoglossal Nerves.— General View of the Cranial Nerves . 824 The Sympathetic System of JVerves. Ceneral Remarks.— The Cervical Portion of the Sympathetic— The Superior Cervical Ganglion— its Supe- rior Branch, Carotid Plexus, and Cavernous Plexus— its Anterior, External, Inferior, and Internal Branch- es.—The Middle Cervical Ganglion. — The Inferior Cervical Ganglion. — The Vertebral Plexus. — The Cardiac Nerves ; Right, Superior, Middle, and Inferior ; Left.— The Cardiac Ganglion and Plexuses.— The Thoracic Portion of the Sympathetic— The External and Internal Branches.— The Splanchnic Nerves, Great and Small.— The Visceral Ganglia and Plexuses in the Abdomen, viz., the Solar Plexus and Semi- lunar Ganglia. — The Diaphragmatic and Supra-renal, the Cceliac, the Superior Mesenteric, the Inferior Mesenteric, and the Renal, Spermatic, and Ovarian Plexuses.— The Lumbar Portion of the Sympathetic. — The Communicating, External, and Internal Branches. — The Lumbar Splanchnic Nerves and Visceral Plexuses in the Pelvis. — The Sacral Portion of the Sympathetic. — General View of the Sympathetic System 854 DESCRIPTIVE ANATOMY. INTRODUCTION. Object and Division of Anatomy. — General Vieio of the Human Frame. — Apparatus of Sen- sation— of Locomotion — of Nutrition — of Reproduction. — General Plan of the Work. Considered in its most extended signification, Anatomy* is the science which has for its object the structure of living beings. Living beings are divided into two great classes, vegetables and animals ; there is, therefore, a vegetable anatomy and an animal anatomy, ^^^len anatomy embraces, in one general view, the whole series of animals, comparing the same organs as they exist in the different species, it receives the name of zoological, or comparative anatomi/. Zoological anatomy is denominated philosophical or transcendental, when from the com- bination and comparison of particular facts it deduces general results, and law^s of orga- nization. "SMien anatomy is confined to the examination of one species only, it receives the name oi special ; such as the anatomy of man, the anatomy of the horse, &c. Physio- logical anatomy considers the organs in their healthy state. Pathological anatomy regards them as altered by disease. When physiological anatomy is confined to the examination of the external conforma- tion of organs, that is to say, of all their qualities which may be ascertained without di- vision of their substance, it is called descriptive anatomy. If, on tlie contrary, it pene- trates into the interior of organs, in order to determine their constituent or elementary parts, it receives the name general anatomy, or of the anatomy of textures. Descriptive anatomy informs us of the names of organs (anatomical nomenclature), their number, situation, direction, size, colour, weight, consistence, figure, and relations ; it traces, in fact, tlie topography of the Imman body. In more than one respect, it is to medicine what geography is to history. The anatomy used by painters and sculptors may be regarded as one of its dependances, and may be defined to be the knowledge of the external surface of the body, in the different attitudes of repose, and in its various move- ments. On this subject it may be observed, that the precise determination of the ex- ternal eminences and depressions may afford most important indications regarding the situation and state of deeply-seated parts, and is therefore worthy the attention of the physician. Descriptive anatomy, in the sense here meant, has arrived at a high degree of perfec- tion. It is to this branch that reference is made by those who affirm that nothing now remains to be done in anatomy. But although descriptive anatomy may be all that the surgeon requires to enable him to comprehend the lesions which most commonly fall under his notice, and to perform operations, it will by no means suffice for the physician or the physiologist. For their purposes, anatomical investigations must not be confined to the surface, but penetrate into, and analyze the substance of organs. Now such is the object of general or textural anatomy. By its means the different organs are re- solved into their component tissues : these tissues, again, are reduced to their simple elements, which are then studied by themselves, independently of the organs which they form ; and subsequently, by considering the elementary constituents as combined in va- rious proportions, the organization of even the most comphcated and dissimilar parts is made manifest. There is one species of anatomy which has of late been cultivated with the greatest success. I mean the anatomy of the fcetus. The anatomy of the fcctus, or the anatomy of the body at different periods of life, named the anatomy of evolution, has for its object the study of the development of organs, their successive modifications, and sometimes even the metamorphoses which they undergo, from the time of their first appearance until they arrive at perfection. Lastly, there is a species of anatomy to which the term of " applied anatomy''^ may be given, because it comprehends all the practical apphcations of the science to medicine * The word Anatomy is derived from the Greek (ava, up, and tcuvoi, I cut). It is, in fact, by means of dissection principally that we are enabled to separate and study the different organs. But injections, desicca- tion, the action of alcohol, concentrated acids, &c., are also means employed by the anatomist. A 2 INTRODUCTION. and surgery. With this view, the body is divided into regions or departments, and ezdh region into successive layers. The relation of the different layers is pointed out, and in each layer the parts which compose it. In a word, the constant object is the solution of the following question : A region, or any part of the surface of the body being given, to determine the subjacent parts which correspond to it at different depths, and their order of superposition. This has generally been denominated the anatomy of regions, topographical or surgical anatomy, because it has hitherto been studied only with refer- ence to its uses in surgery. It may easily be shown, however, that with the exception of ^ the limbs or extremities, the anatomical knowledge of which has few applications to medicine, properly so called, the study of regions is no less important to the physician I than to the surgeon. To give it, therefore, a name corresponding with its use, it should be called ^nedico-chirurgical topographical anatomy. Such are the different aspects under which anatomy may be regarded. The following work is essentially devoted to descriptive anatomy.* Geneeal View of the Human Body. Before entering on a detailed description of the numerous organs which enter into the composition of the human body, it is advisable to present a rapid sketch of the whole. Such general views, instead of embarrassing the mind, at once enlighten and satisfy it, by exhibiting the objects of its research in their true relations, and showing the end to be attained. There is one general covering, which, like a garment, envelops the whole body, and is moulded, at it were, round all its parts. This covering is the skin, of which the nails and hair are dependances. The skin presents a certain number of apertures, by means of which a communication is established between the exterior and the interior of the body. These apertures, however, are not formed by a mere perforation or breach of continuity in the skin ; on the contrary, this membrane passes inward at the circumference of these openings, and having undergone certain important modifications in its structure, forms the mucous membranes, a kind of internal tegument, which may be considered as a prolongation of the external envelope. We might, therefore, strictly speaking, regard the human body as essentially composed of a skin folded back upon itself This idea is, indeed, realized in some of the inferior animals, which consist of a mere tube or canal. In proportion, however, as we ascend in the scale, we find the layers which separate these two teguments become more and more increased in thickness, and cavities are at length formed between them. Nevertheless, however widely these membranes may be separated from each other, and however different they may be in external aspect, there are abundant analogies to establish unequivocally their common origin. Under the skin there is a layer of adipose cellular tissue, which gently elevates it, fills up the depressions, and contributes to impart that roundness of form which character- izes all animals, and particularly the human species. In some parts, there are muscles inserted into the skin, which are intended for its movement ; these are the cutaneous muscles. In man they are very inconsiderable, and are confined to the neck and face, where they play an important part in giving expression to the physiognomy ; but in the larger animals they line the whole skin, and in certain classes, of very simple organiza- tion, they constitute the entire locomotive apparatus. Tlie superficial veins and lymphatics traverse the subcutaneous cellular tissue : the latter, at various parts of their course, pass through enlargements denominated lymphatic ganghons, or lymphatic glands, which are grouped together in certain regions. Below the cellular tissue are the muscles, red, fleshy bundles, arranged in many layers. In the centre of all these structures are placed the bones, inflexible columns, which serve for a support to all that surrounds them. The vessels and the nerves are in the immediate neighbourhood of the bones, and, consequently, removed as much as possible from external injury. Lastly, around the muscles and under the subcutaneous adipose tissue are certain strong membranes, which bind the parts together, and which, by pro- longations detached from their internal surface, separate and retain in their situation the different muscular layers, frequently each particular muscle : these envelopes are the aponeuroses. Such is the general structure of the limbs or extremities. If next we examine the trunk, we find in its parietes a similar structure, but more in- ' ternally are cavities lined by thin transparent membranes, named serous, on account of a liquid or serosity with which they are moistened. In these cavities are situated or- gans of a complex structure, called viscera, of which we shall give a rapid enumeration in an order conformable to the offices they perform in the animal economy. The human body, as well as that of other organized beings, is composed of certain parts, denominated organs {opyavov, an instrument), which differ from each other in * Descriptive anatomy ought, in strictness, to be confined to the consideration of the external characters of organs, or what is understood by the term external conformation ; nevertheless, in order to present a complete view of each organ, after having described its exterior, we shall give a short account of its texture and dc'-ej- opment. GENERAL VIEW OF THE HUMAN BODY. 3 their structure and use, but are all combined, for the double pui-pose of the preservation of the individual, and the continuance of the species. To accomplish these purposes, the organs are distributed in a certain number of groups or series, each of which has a definite end to fulfil. This end is denominated a function .- the series of organs receives the name of an apparatus. Of those necessary for the preservation of the individual, some are designed to place him in relation with external objects, and these constitute the apparatus of relation: the others are destined to repair the loss which the parts of the body are constantly suffering ; they form the apparatus of nutrition. The apparatus of relation may be subdivided into two classes; 1. The apparatus of sensation. 2. The apparatus of motion. Apparatus of Sensation. — The apparatus of sensation consists, 1. Of the organs of sense ; 2. Of the nerves ; 3. Of the brain and spinal cord. The oro-ans of the senses are, 1. The skin, which possesses sensibility, the exercise of which constitutes tact. The skin being placed under the direction of the will, and rendered mobile in consequence of the peculiar mechanism of the human hand, is called the orr^an of touch. 2. The organ of taste, the seat of which is in the cavity of the mouth, that is, at the entrance of the digestive canal. 3. The organ of smell, placed in the nasal fossae, the commencement of the respiratory passages, by which we are en- abled to recognise the odorous emanations of bodies. 4. Tlie organ of hearing, con- structed in accordance with the principles of acoustics, and placed in relation with the vibrations of the air. 5. The organ of sight, which bears relation to the light, and ex- hibits a construction in harmony with the most important laws of dioptrics. The organs of sense receive impressions from without. Four of them occupy the face, and are, therefore, placed in the vicinity of the brain, to which they transmit im- pressions ■with great rapidity and precision ; and that organ seems, in its turn, to extend into them, so to speak, by means of the nerves. Indeed, the impressions received by the external organs would be arrested in them, were it not for certain conductors of such impressions ; these conductors are the nerves — white, fasciculated cords, one ex- tremity of which passes into the organs, while the other is connected to the spinal mar- row and the brain, which are the central parts of the nervous system, the nerves con- stituting the peripheral part. Apparatus of Locomotion^ — The apparatus of locomotion consists, 1. Of an active or contractile portion, the muscles. These are terminated by tendons, organs of a pearly white colour, which direct upon a single point the action of many forces ; 2. Of a pas- sive portion, the bones, true levers, which constitute the framework of the body, and the extremities of which, by their mutual contact, form the articulations : in the latter we perceive (a) the cartilages, compressible, elastic substances, which deaden the violence of shocks, and render the contact uniform ; (b) an unctuous liquid, the synovia, secreted by membranes denominated synovial : this liquid performs the office of the grease em- ployed in the wheel-work of machinery ; (c) bands or ligaments, which maintain the con- nexion of the bones. Such is the apparatus designed to establish the relation between man and external objects. Apparatus of Nutrition. — The apparatus which performs in the human body the im- portant office of nutrition consists of the following parts : A. The digestive apparatus, which consists essentially of a continuous tube or canal, denominated the alimentary canal. This canal has not the same form and structure throughout the whole extent : on the contrary, it is composed of a series of very dissim- ilar organs, all, however, contributing to the formation of one common passage. These organs are, 1. The mouth ; 2. The pharynx ; 3. The asophagus, or gullet ; 4. The stom- ach ; 5. The ijitestines ; which are farther subdivided into the small intestines, consisting of the duodenum, jejunum, and ileum, and the large intestines, comprising the coecum, colon, and rectum. To this long tube, the greater part of which is contained in the abdomen, where it forms numerous reduplications, are annexed, 1. The liver, a glandular organ, whose office it is to secrete the bile, and which occupies the superior and right portion of the abdomen ; 2. The spleem, whose functions are involved in great obscurity, but which may, perhaps, be termed an appendix to the liver, on the left side ; 3. The pancreas, which pours a fluid into the duodenum, by an orifice common to it and the biUary duct. B. On the internal surface of the digestive canal, and particularly that portion of it which bears the name of the small intestine, certain vessels open by numerous orifices or mouths,* and carry off the nutritive fluids prepared by the process of digestion : these are the ckyliferous or absorbent vessels, which are also called lacteal vessels, on account of the white, milky aspect presented by their contents while absorption is going on. The absorbent apparatus consists, also, of another set of vessels denominated lymphatics, be- cause they contain a colourless liquid named lymph, which they collect from all parts of * [Tkis must not be uaderstood literally. See account of the lacteals, infra,} ■4 INTRODUCTION. the body. All the absorbent vessels, of whatever order they may be, traverse at differ- ent parts of their course certain grayish bodies, called lymphatic ganglions or glands, and finally terminate in the venous system. C. The venous system arises from all parts of the body : it takes up, on the one hand, all those matters which, having been employed a sufficient time as part of the body, must be eliminated from it ; and, on the other hand, all those substances which are carried into the system, to contribute to its reparation : it is composed of vessels denominated veins, which at various distances are provided with valves, and at last unite in forming two large veins called vencB cavcB, of which one, the superior, receives the blood from the upper part of the body ; the other, the inferior, brings back that which has circulated in the lower portion. These two venae cavae terminate in the central organ of the circulation, the heart, a hollow muscle, containing four contractile cavities -. two on the right side, the right au- ricle and ve7itricle, and two on the left, the left auricle and ventricle. D. Next to these in order of function is the respiratory apparatus, composed of two spongy sacs, placed on each side of the heart, and occupying almost the whole of the chest : these are the lungs. They receive the air from a common tube, the trachea, which is surmounted by a vibratile organ, the larynx, which opens externally by the nose and mouth, and constitutes the organ of voice. E. From that cavity of the heart which is called the left ventricle, arises a large ves- sel, the aorta : this forms the principal and primitive trunk of the whole class of vessels named arteries, whose office it is to convey red blood to all parts of the body, to main- tain their heat and life. F. There still remains one other portion of the nutritive system, the urinary appara- tus, consisting of, 1. The kidneys, organs which secrete the urine : 2. The ureters, by means of which the urine, as soon as secreted, passes off into a spacious receptacle, the bladder, from whence it is at intervals expelled along a passage which has received the name oi urethra. Apparatus of Reproduction. — ^The apparatus above mentioned is destined for individual preservation : the organs which secure the continuance of the species constitute the generative or reproductive apparatus. They differ in the male and in the female. In the male they are, 1. The testicles, which prepare the spermatic or fecundating fluid ; 2. The vasa defcrentia, tubes which transmit this fluid from the testicle where it is se- creted to the vesiculaj seminales ; 3. The vesiculcz scminales, or receptacles of semen ; 4. The ejaculatory ducts, through which the seminal fluid passes into the urethra ; 5. The prostate and Coioper^s glands, glandular appendages of the organs for the transmission of the semen ; 6. The penis, by means of which the fecundating fluid is conveyed into the interior of the genital organs of the female. The generative apparatus in the female is composed of the following organs : 1. The ovaries, the function of which is to produce, or keep in readiness, the ovulum or germ ; 2. The uterine tubes, which transmit the germ, when fecundated, to the uterus ; 3. The uterus or womb, in which the product of conception remains and is developed during the pei'iod of gestation ; 4. The vagina, a canal which permits the passage of the foetus at its final expulsion ; 5. As appertaining to the system should be mentioned the mammary glands, which secrete the milk destined for the nourishment of the new-born infant. General Plan of the Work, There are two methods by which the numerous facts that come within the range of anatomy may be explained. The different organs may be studied in their order of super- position, or in the topographic order, a capite ad calcem ; in this way the most dissimilar parts are brought together, while others are separated which have the greatest analogy ; or they may be considered in a. physiological order, i. e., an order founded upon the same grounds as serve for the classification of functions. This is clearly the most rational, because it has the incontestable advantage of preparing for the study of the functions by that of the organs. It may be easily seen, however, that this physiological an-angement should be modified according to the relative difficulty in the study of the different parts of the body ; for the great aim in a work of instruction should be to conduct the mind, by degrees, from simple and easy objects to those which are more complicated. It is for this reason that the consideration of the nervous system, which, in strict accordance with physiological arrangement, should be placed near to that of the locomotive appara- tus, is deferred. The object proposed has been to adopt an arrangement which would, as far as possible, reconcile both these views, and, at the same time, be compatible with the greatest economy of subjects for dissection ; and this appears to be secured by the method o-enerally adopted, at least with a few slight modifications. The following table presents a view of the general plan of this work : {1. Of the bones — Osteology. 2. Of the articulations — Sjmdesniologv. 3. Of the muscles— Myology. 4. Of the aponeuroses — Aponeuvolog /. GENERAL OBSERVATIONS. 2. Apparatus of digestion, apparatus of respiration, j t; i h ol »v genito-urinary apparatus . . . . J '"'^ °^' f Heart . ~i 3. Apparatus of the circulation .... ■{ y'^.®'^'^^ ' >Angeiology. I Lymphatics J r Organs of the senses "1 4. Apparatus of sensation and innervation . . ■{ g^'"^ '^"^ ' ' > Neurology. L Nerves . . .J APPARATUS OF LOCOMOTION. OSTEOLOGY. OF THE BONES IN GENERAL. The Bones — Importance of their Study. — General View of the Skeleton. — Numher of the Bones. — Method of Description. — Nomenclature. — Situation in general. — Direction. — Size, Weight, and Density of Bones. — Figure. — Distinction into Long, Broad, and Flat Bones. — Regions of Bones. — Eminences and Cavities. — Internal Conformation. — Texture. — De- velopmcTit of Osteogeny. — Nuiritvon. The bones are parts of a stony hardness, but yet organized and living. They serve as a support to all other parts of the body, are a means of protection to many, and afford points of attachment to the muscles, in the midst of which they are situated. All the hard parts of the body, however, are not bones. The fundamental character of a bone consists in its being at once hard and organized. As the bones receive vessels for the purpose of nutrition at every part of their surface, they are surrounded on all sides by a membrane which is fibrous and vascular, named the Periosteum (Kepi, around ; ogteov, a bone). According to this definition, the teeth, horns, nails, and, in articulated animals, the ex- terior skeleton, are not to be considered as bones, but merely ossiform concretions. We may add, that true bones belong exclusively to vertebrated animals. The study of the bones constitutes Osteology, which may be regarded as the basis of anatomy, for without a knowledge of the bones it is impossible to become acquainted with the muscular insertions, or the exact relations between the muscles, nerves, vis- cera, and, above ail, the vessels, for which the bones afford the anatomist invariable points of reference. Osteology has, therefore, ever since the time of the Alexandrian school, formed the commencement of the study of anatomy. In the present day, the transcendental anatomists have particularly engaged in the study of the osseous system, doubtless on account of the facility with which it may be investigated ; and from their labours, though in many respects speculative, a more ac- curate knowledge has been obtained of some of the nicer points of osteology, which had scarce attracted notice from the older anatomists. Lastly, from the admirable researches of Cuvier respecting fossil animals, osteology has become one of the most important bases of comparative anatomy and geology. By the study of bones the anatomist has been enabled to determine genera and species, no longer existing on the face of the globe, and to give, as it were, new hfe to these old and disjointed relics of the antediluvian aniinal kingdom. Thus the fossil bones, deposited in an invariable order of superposition in the crust of the earth, have been transformed into monuments more authentic than historical records. General View of the Skeleton. — The bones form a system or whole, of which the different parts are contiguous, and united to each other. The only exception to this rule is the OS hyoides, and yet the ligaments by which it is connected with the rest of the system are evidently the representatives of the osseous pieces, which in the lower animals con- nect this bone with the temporal. The assemblage of the bones constitutes the skeleton. It is called a natural skeleton when its different parts are connected by their own ligaments ; an artificial skeleton, on the other hand, is one of which the bones are joined together by artificial Connexions, such as metallic wires, &c. The result of this union is a symmetrical and regular structure, essentially composed of 3 central column, denominated the vertebral column or spine, which terminates superi- orly in a considerable enlargement, the cranium, and inferiorly in certain immovably united vertebra;, which constitute the sacrum and coccyx. To this column the following appendages are attached : 1. In front of and below the cranium, a complicated osseous structure, the /ace, divided into two maxillae, the superior and iriferior. 2. On each side twelve bony arches, flexible, elastic, and curved — the rihs, which are united in front to another column, the sternum. These parts, taken together, form the thorax. 3. Four prolongations, called limbs or extremities : two superior, or thoracic, as they are termed because they correspond with the chest or thorax ; and two inferior or pelvic, so nam^' O- OSTEOLOGY. on account of their connexion with the basin or pelvis, but better named aliormnal ex- tremities. The thoracic and abdominal extremities are evidently modifications of the same fundamental type, and are essentially composed of the same number of analogous parts, viz. : 1. An osseous girdle, the superior constituted by the bones of the shoulder, the inferior by the pelvis. 2. A part which may be in some measure regarded as the body of the limb, viz., the humerus, in the thoracic extremity, the femur in the abdominal. 3. A manubrium or handle, to use an expression of Galen, above the forearm, below the leg. 4. Lastly, digitated appendages which form, the extremities, properly so called, viz., the hand and the foot. Number of the Bones. — Authors do not agree respecting the number of the bones. Some, for instance, describe the sphenoid and the occipital as forming only one bone, while most anatomists consider them two distinct bones. Some admit three pieces in the sternum, which they describe separately. Many, after the example of the older writers, divide the haunch into three distinct bones — the pubes, the ischium, and the ileum : others recognise five pelvic or sacral vertebrae ; three or five parts of the os hyoides ; and, lastly, the ossa sesamoidea and the ossa wormiana- are omitted by some, but by others are reckoned in the enumeration of the bones. The ideas of certain modem authors with respect to the development of the bones, in- stead of dispelhng the uncertainty which attaches to the enumeration of the parts of the skeleton, have tended not a httle to increase the confusion, because many of them have made no distinction between bones, properly so called, and pieces of ossification. AH doubt, however, in this respect will cease, provided we consider as distinct bones only those portions of the skeleton which are separable at the time of complete development. The time at which the osseous system arrives at its perfect development is betweea the twenty-fifth and thirtieth year. According to these views, we may count in the human body 198 bcaies, viz. : Vertebral column, including the sacrum and coccyx .... 26 Craniimi 8 Face 14 Os hyoides 1 Thorax (ribs, sternum) 25 Superior extremities, each 32, viz., shoulder, arm, forearm, and hand 64 Inferior extremities, each 30, viz., pelvis, thigh, leg, and foot . . 60 198 This enumeration does not include the ossa wormiana, nor the ossa sesamoidea, among which we include the patella. Of these 198 bones, 34 only are single : all the others are in pairs, which reduces the number to be studied to 116. Before proceeding to examine each piece of the skeleton in particular, we shall state the method we intend to pursue in the description. The chief points embraced by de- tailed descriptions of a bone are, K Its name; 2. Its general situation; 3. Its direction ; 4. Its bulk and weight ; 5. Its figure ; 6. Its regions ; 7. Its relations ; 8. Its internal conformation ; 9. Its intimate texture ; 10. Its development. Nomenclature. — Osteological nomenclature has many imperfections. Persuaded of the importance of a suitable choice of language in the study of all the sciences, some anatomists have endeavoured to introduce reforms, but with little success, the old de- nominations being still for the most part retained. From these modem systems of no- menclature we shall adopt only such terms as are strikingly appropriate, or such as have already been sanctioned by usage. "VVe may here observe that the denominations of bones have been derived, 1. From their situation ; as the fronlal, which is so called be- cause it is situated in the forehead : 2. From a resemblance, usually very obscure, to some well-known object, as the bones named tibia, scaphoid, malleus, incus, stapes ; or to some geometrical figure, as the cuboid : 3. From their size ; as the os magnum of the carpus, and the small bones or ossiada of the ear : 4. Fi-oni some circumstance of their external conformation ; as the cribriform or ethmoid bone, the unciform or hooked bone : 5. From the name of the author Avho first most carefully described them ; as the ossicles of Ber- tin, of Morgagni — swings of Ingrassias, &c. General Situation of Bones. — The situation of a bone is determined by comparing the place which it occupies with that occupied by other bones of the skeleton. In order to make this comparison, the skeleton is supposed to be surrounded by certain planes, which are thus denominated: 1. An anterior plane, passing before the forehead, the breast, and the feet ; 2. A posterior plane, passing behind the occiput and the heels ; 3. A superior plane, placed horizontally above the head ; 4. An inferior plane, which passes be- low the soles of the feet ; 5 and 6. The two lateral planes, which complete the sort of case or parallelepiped with which we suppose the skeleton to be surrounded. Lastly, the skeleton being symmetrical, i. e., exactly divisible into two similar halves, we admit a seventh imaginary plane, the median or antero-posterior, separating these two halves. By the term median line is understood an imaginary line traced so as to mark exteriorly the division of all the symmetrical bone= of the skeleton into two similax halves. GENERAL OBSERVATIONS. 7 Tliese points being understood, nothing is more easy than to determine the position of a bone. If it approach nearer to the anterior plane than others with which it is com- pared, it is said to be anterior to them ; if it be nearer the posterior plane, it is said to be posterior to them. Let us take, for example, the malar or cheek bones. With respect to the whole face, they are placed at the anterior, superior, and in some degree the lateral part; relatively to the neighbouring bones, they are situated, 1. Below the frontal; 2. Above and a httle external to the maxillary ; 3. Before the great wings of the sphenoid and the zygomatic process of the temporal. Direction of Bones. — The direction of a bone is absolute or relative. The absolute di- rection is expressed by the terms straight, curved, angular, or twisted ; in a word, it is the direction of a bone considered by itself, or independently of its situation in the skeleton. The long bones are never quite straight : sometimes they present a slight degree of cur- vature, as the femur ; sometimes their extremities are curved in opposite directions, like the letter S, as the clavicle : sometimes, again, they are twisted upon their own axes, as the humerus, the fibula, &c. The relative direction is determined by reference to the planes which circumscribe the skeleton. Viewed in this manner, a bone is vertical, horizontal, or oblique. It is needless to enter into any explanation of the terms vertical and horizontal ; but with re- gard to the oblique direction, it may be stated that this is determined by the respective situations of its two extremities. For example, a bone is oblique when one extremity approxnnates the superior, the median, and the posterior planes, while the other ap- proaches nearer to the inferior, lateral, and anterior planes ; such a bone is said to be obhque from aJbove downward, from within outward, and from behind forward. It is easy to see that in Uiis way the situation of a bone relatively to the different planes may be determined with the greatest exactness. It should be observed, that in describing the direction of a bone, we should always set out from the same point. Thus, if the direc- tion of a bone from above downward is spoken of in determining its obliquity from be- fore backward, and from within outward, we should always commence with the supe- rior extremity. Size, Weight, and Density of Bones. — The size of a bone may be measured by the ex- tent of its three dimensions ; but as an exact estimate is not in general required, it is sufficient to indicate the volume of each bone relatively to others, whence has arisen the division of bones into great, middle-sized, and small ; a distinction, however, altogeth- er vague and futile, since from the largest to the smallest bones there is so regular a gradation that the limits assigned must be quite arbitrary. The weight, or the mass of the skeleton compared with the rest of the body, the weight of each bone, and the comparative weight of different bones, are points of little inter- ■est; such, however, is not the case with the specific weight or density of bones. In respect of density, viz., the number of molecules in a given volume, the bones are the heaviest of all organs. The truth of this assertion is by no means contradicted by the lightness of certain bones, which is only apparent, and which is caused by vacant spaces or cells in their substance. This density varies in different kinds of bones, in bones of the same kind, and even in different parts of'the same bone. Thus, in the long bones, the greatest density is in the middle : the extremities of the long bones and the short bones have a much lower density. The broad or flat bones hold a middle place between the shaft of long bones and the short bones. Of tliese broad bones, those of the cranium are heavier than those of the pelvis. Age has a remarkable influence upon the specific weight of bones. It has been said that the bones of the aged are specifically more heavy than those of the adult, just as the bones of the adult are specifically heavi- er than those of the infant ; and this assertion appears the more probable, from it being generally admitted, as a law of organization, that the phosphate of lime increases in bones with the progress of age ; and it is well known that the weight of bones depends, in part, on the presence of this calcareous phosphate. But on this point, as on many others, experience has refuted these preconceived opinions. Thus, it is certain that the specific, as well as the absolute weight of bones, is much less considerable in the old person than in the adult ; and this difference depends upon the loss of substance which the bones undergo, in coimnon with all other tissues, during the progress of age : thus, in aged subjects, the walls of the cylinder of the long bones are remarkably diminished in thickness, while the medullary cavity is proportionally increased. We may even af- firm, with Chaussier, that the medullary cavity of the shaft of long bones has a greater diameter, in proportion as the individual is advanced in age. In like manner, the cells of the spongy tissue become much larger, and their walls acquire an extreme tenuity. It may, nevertheless, be contended, that the weight of the osseous fibre, or, rather, of the osseous molecules of the old people, is greater, comparatively, than that of the same parts in the adult ; and this presumption is almost converted into certainty by chemical analysis, which shows an excess of phosphate of lime in the bones of the aged : to re- move all doubts upon this point, it would be necessary to grind an adult bone and an old one, and to weigh in the balance an equal bulk of each powder. In this way the contra- dictory statements of certain authors might be reconciled. 8 OSTEOLOGY. Tlie increasing fragility of bones, and the consequent frequency of fractures in old age, are easily explained, since along with the accumulation of phosphate of lime, which di- minishes the elasticity while it increases the brittleness, there occurs a diminution of bulk, and, consequently, there is less resistance. It is with respect to the quantity of calcareous phosphate alone that the osseous system can be said to preponderate in old age. Shafe of Bones. — The shape of a bone is determined, 1. By comparison either with different known objects, or with geometrical figures : thus the frontal bone has been compared to the scallop-shells of pilgrims, the sphenoid to a bat with extended wings, ■ &c. It may be readily conceived that, notwithstanding its want of exactness, this meth- od of comparison, so familiar to the ancients, cannot be altogether proscribed. The comparison of bones whose forms are so irregular with the regular solid figures of which geometry treats is no less inaccurate than the preceding ; nevertheless, we shall con- tinue, like other anatomists, to speak of the short bones as cuboidal, the shafts of long bones as being prismatic and triangular, the lower maxillae parabolic, &c. We sliall speak of spheres, of cones, of ovoids, of cylinders, &c. 2. The symmetry or want of symmetry of bones is a fundamental point in the deter- mination of their figure : thus, some bones are divisible into two halves exactly resem- bling each other ; these are the symmetrical or azygos bones, also called median, be- cause they always occupy the middle line. The others can not be divided into two sim- ilar parts : these are the asynunetrical bones, called also lateral or corresponding, because they are always in pairs, and situated on opposite sides of the median line. 3. The figure of a bone comprehends, also, the proportion which its three dimensions bear to each other. When the three dimensions, length, breadth, and thickness, are nearly equal, the bone is said to be short ; when the length and breadth are almost the same, and both greater than the thickness, the bone is called broad or flat. Lastly, the predominance of one dimension over the two others constitutes the character of long bones. The distinction here dravm, however, is not altogether exact, because there are certain mixed bones which partake at the same time of the character of the long and the broad bones. Some general observations upon the three great classes will not be out of place here, as they will be applicable in the description of the individual bones. General Characters of Long, Flat, and Short Bones. Of Long Bones. — The long bones are situated in the extremities, in the centre of which they form a set of pillars or levers placed upon each other. The bones of the abdominal extremities are generally longer and larger than those of the thoracic. The longest bones are in the upper part of the limbs ; it may be said, indeed, that the length of bones is in the direct ratio of their proximity to the trunk. The diameter of the long bones is smallest in their middle. From this part, as from a centre, they gradually increase in volume, and at their extremities are much enlarged, so as to present a diameter double or treble that of the shaft. Every long bone, therefore, presents a biconical form, i. e., is shaped like two cones united by their summits. A long bone consists of a shaft and extremities. The shaft of the long bones is almost always prismatic and triangular ; so much so, that in this respect the bones seem to be an exception to the general rule of organized bodies, which have usually a rounded form, and to approach nearer that of the mineral kingdom, the characteristic shape of which is angular. The extremities of long bones are enlarged, that they may serve, 1. For articula- tions ; 2. For the insertion of hgaments and muscles ; 3. For the reflection of tendons, the direction of which they alter. Each extremity presents a smooth articular surface, covered with cartilage in the fresh state, and not perforated by any foramina, and a non-articular portion, rough, pierced with apertures, and covered with eminences and depressions. Of Broad w Flat Bones. — These bones, intended to form the parietes of cavities, are more or less curved, and present for consideration a circumference and two surfaces ; the internal concave, the external convex. No single broad bone constitutes a cavity ; there are always a certain number united for this purpose. Some broad bones are alter- nately concave and convex on the same surface, as the haunch bones. In flat or broad bones there is no accurate correspondence between the inequalities, ridges, or depres- sions of the two surfaces. Thus, the iliac portion of the haunch bones, instead of pre- senting a convexity on the inner surface, to correspond with the external iliac fossa, is hollowed out into another depression, the internal iliac fossa. In like manner, in the cranium certain impressions and eminences exist on the internal surface, while the ex- ternal is uniformly convex, and almost smooth. The parietal, and even the occipital protuberances, would be twice or three times more prominent if the interior concavity were faithfully represented by a corresponding external prominence, and if this concav- ity were not in a great measure hollowed out from the substance of the bone. The circumference of broad bones being intended either for articulations or for inser- tions, is for this purpose greatly thickened. Thus the parietal bones, which are very GENERAL OBSERVATIONS. Q thin at their centre, become considerably thicker at the circumference. Tlie broad bones present at their circumference sometimes a simple enlargement, when it is in- tended for muscular insertions only ; for example, the haunch bones : sometimes indent- ations of various kinds, and sinuosities, when it is to serve the purpose of articulation ; for.instance, the bones of the cranium. Of Short Bo7ies. — These are principally met with in the vertebral column, the carpus, and the tarsus ; in fact, wherever great solidity is required in connexion with slight mo- bility : several of them are always grouped together ; their form is extremely irregular, but generally cuboid ; ihey have also numerous facettes for articulation. The non-artic- ular portion is rough, for the insertion of ligaments and tendons. Regions of Bones. — There are so many objects to be considered on the surface of a bone, that it is necessary, in order to prevent the omission of any essential detail in the description, to divide the surface into a certain number of parts or regions, which should be successively examined. These different parts or regions have been denom- inated faces, borders, and angles. Thus, in the prismatic and triangular shafts of long bones, there are three faces and three borders to be considered ; in the flat bones, two faces and a circumference, which is again subdivided into borders and angles formed by the meet- ing of these borders. There are six faces in the short bones. These faces and borders are named sometimes, from their situation, superior, inferior, anterior, posterior, &c. ; some- times from the parts which they contribute to fomi, such as the orbital and palaiine fa- ces of the superior maxillary bone ; sometimes from their relations to other parts, as the cerebral and cutaneous face of the bones of the cranium, fhe frontal, occipital, and tem- poral borders of the parietal bones. WTien the borders give insertion to a great number of muscles, it has been deemed advisable to divide these into three parts or parallel hues : the middle is then called the interstice, and the two lateral are named lips, the in- ternal and external hp ; the superior border of the haunch bone, and the linea aspera of the femur, are examples. Eminejices and Cavities of Bones. — The bones present certain eminences and cavities, of which it is proper to take a general survey in this place. Eminences of Bones. — The osseous eminences or processes were divided by the an- cients into two great classes, apophyses and epiphyses, distinguished by the difference of their mode of development. According to their view, some of these eminences arise from the body of the bone, appearing to be nothing more than prolongations or vege- tations of its substance : these they called apophyses ; others, on the contrary, are formed by separate osseous centres or nuclei, which make their appearance at various times during the process of the development of bone : to these they gave the name of epiphyses. This distinction, however, founded upon incomplete observation, has been totally rejected, since the researches of M. Serres on Osteogeny have rendered it evi- dent that almost all the osseous eminences are developed from isolated nodules ; so that an eminence, which at one time is an epiphysis, becomes afterward an apophysis. If, therefore, the majority of eminences are formed from separate osseous points, the dif- ference between them can apply only to the relative periods at which they become uni- ted to the body of the bone. A far more important distinction is that by which the eminences are divided into articular and non-articular. The articular eminences have received different names. 1. They are called dentic- ulations when they form angular eminences resembling the teeth of a saw ; these are best seen in the bones of the cranium. This kind of eminence is employed only in im- movable articulations. The others belong to joints which admit of motion, and have received the following names : 1. They are called heads when they represent a portion of a sphere supported by a more contracted portion, to which the name of neck is given ; for example, the head and neck of the femur. 2. The term condyle is applied to them when they resemble an elongated head, or a portion of an ovoid cut paraUel to its greatest diameter ; for exam- ple, the condyles of the inferior maxilla. The non-articular eminences are, for the most part, designed for muscular insertions. Their appellations are in general derived from their shape. Thus, they are denominated, 1. Prominences. When they are but slightly elevated, smooth, and almost equally ex- tended in all directions ; as the parietal and frontal eminences. 2. Mamillary Processes. When they resemble papillae ; for instance, the mamillary processes of the internal surface of the bones of the cranium. 3. Tuberosities. When they are of a larger size, round, but uneven ; for example, the occipital protuberance, the bicipital tuberosity (or tubercle) of the radius. 4. Spines or Spinous Processes. When, from their acuminated, but generally rugged form, they bear some resemblance to a thorn ; as the spine of the tibia, the spinous pro- cesses of the vertebrae. 5. Lines. When their length greatly exceeds their breadth ; as the semicircular lines of the occipital bone. When these lines' are more prominent, and covered with asper- ities, they receive the name of hneee asperae ; as the linea aspera of the femur. B 10 OSTEOLOGY. 6. Crests. When they are elevated, and have a sharp edge ; as the external and inter- nal crest of the occipital bone, the crest of the tibia. One of these eminences has been denominated the crista galli, because it bears some resemblance to the comb of a cock. 7. The term apophyses (or processes) has been retained for those eminences which are of a certain size, and appear to form, as it were, a little bone superadded to that from which they spring ; they are distinguished, for the most part, by epithets derived from their shape. Thus, the clinoid processes of the sphenoid are so called from their supposed resemblance to the supporters of a bed {kHvj}, a bed ; eUo^, shape). Pterygoid processes are those which are like wings (Trrepv^, a wing). Mastoid, such as resemble a nipple {fiacTog, mamma). Zygomatic, such as have the form of a yoke {l^vyoc, a yoke). Styloid, such as are like a style. Coronoid, such as are shaped like one of the angular projec- tions of a diadem.* Odontoid, such as resemble a tooth ; as the odontoid process of the second cervical vertebra. Coracoid, such as have the form of a raven's beak (Kopa^, a ' raven) ; as the coracoid process of the scapula. Malleoli, such as are like a hammer {malleus, a hammer). Some processes have received names, 1 . From the parts they contribute to form — orbitar processes, malar processes, olecranon {uMvri, the elbow ; Kpdvov, head) ; 2. From their direction ; as the ascending process of the superior maxilla : 3. From their uses ; as the trochanters {rpoxuiJ, to turn), because they serve for the insertion of muscles, which rotate the leg on its own axis. No part of the language of osteology, perhaps, is more faulty than the nomenclature of the eminences. Thus, how unlike is the spine of the scapula to the spinous processes of the vertebrae, or the styloid process of the temporal to the diminutive projection call- ed styloid of the radius ! Many eminences which perform analogous offices have re- ceived different names : thus, the eminences of the humerus, which give attachment to its rotating muscles, are called the great and small tuberosities ; while the correspond- ing parts of the femur have been denominated trochanters. While, therefore, we retain the names consecrated by usage, we shall be careful to point out the more rational terms substituted by modern anatomists, and particularly by Chaussier. The size of the eminences of insertion is in general proportional to the number and strength of the muscles and ligaments which are attached to them. To be convinced of this fact, it is only necessary to compare the male and female skeleton, or that of a man of sedentary habits and that of a person devoted to athletic exercises. This re- markable correspondence between the size of osseous eminences and the strength of the muscles which are inserted into them, has given rise to the opinion that these eminences are formed by muscular traction. It is easy to refute this notion, and without entering into details which belong to general anatomy, we shall prove, by facts, that the osseous projections enter into the primordial plan of organization, so much so, that they would have doubtless existed, even though the muscles had never exercised any traction upon the bones. I have twice had occasion to dissect the thoracic extremities of individuals, who, in consequence of convulsions during their earliest infancy, had suffered complete paralysis of these parts. The limb affected had scarcely the proportions of that of a child of eight or nine years, while the opposite limb was perfectly developed. Never- theless, in this atrophied limb, the smallest as well as the largest projections were per- fectly marked. Moreover, very powerful muscles are often inserted into cavities, as, for instance, the pterygoid cavity of the sphenoid. Cavities of Bones. — Besides the great cavities of the skeleton, cavities in the formation of which many bones concur, and which are destined to lodge and defend the organs most important to life, there are a great number of smaller excavations formed in the substance of the bone itself These cavities, like the eminences, are divided into two great classes, articular and non-articular. The articular cavities have received different names. 1. The term cotyloid designates the articular cavity in the haunch bone, because it is deep and round, like a vessel known by the ancients under the name of kotvXt). 2. The name glenoid (from yl-^vr]) is applied to many articular cavities, which are more shallow ; for example, the glenoid cavity of the scapula, the glenoid cavity of the temporal bone. 3. The term al- veoli has been assigned to the cells or sockets in which the roots of the teeth are lodged. It is not correct, however, to consider as an articulation the union of the teeth with the jaws, because, as we shall afterward show, the teeth are not true bones. The non-articular cavities are to be considered with reference both to their figure and their uses. From their figure, they have received the following denominations : 1 . Fossct, or pits, are cavities largely excavated, wider at the margin than at the bottom ; e. g., the parietal fossae. 2. Sinuses are cavities with a narrow entrance ; as the sphenoidal sinus, maxillary sinus, &c. 3. The term cells is applied when the cavities are small, but nu- merous, and communicating with each other ; as the ethmoidal cells, &c. 4. Channels (gutters) are cavities which resemble an open semi-cylindrical canal ; as the channels for the longitudinal and lateral sinuses of the scull. 5, These take the name of grooves * [Also from Kopiivrj, a crow — like a crow's beak.] GENERAL OBSERVATIONS. H (coulisses) when they are lined by a thin layer of cartilage, for the passage of tendons ; as the bicipital groove of the humerus. The term pulley or trochlea is applied to grooves which have their two borders also covered with cartilage. 6. Furrows are superficial impressions, long, but very narrow, and intended for the lodgment of vessels or nerves, as the furrows for the middle meningeal artery. 7. When more deeply excavated than the last, and angular at the bottom, they are named by the French anatomists Rainures. 8. A notch {incisura) is a cavity cut in the edge of a bone.* The cavities which we have described exist only on one surface of a bone ; those which perforate its substance are usually denominated foramina or holes. 1. When a foramen has an irregular, and, as it were, lacerated orifice, it is named a foramen lacerum. 2. When its orifice is very small and irregular, it is called hiatits ; when the opening is long, narrow, and resembling a crack or slit, it is denominated a fissure ; as the sphenoidal fissure, the glenoid fissure, &.c. 3. If the perforation runs some way through the substance of a bone, it is called a conduit or canal ; as the Vidian canal, carotid canal, &c. There are some canals which lodge the vessels intended for the nourishment of the bone : these are called nutritious canals. They are divided into three kinds. The first, which belong exclusively to the shafts of long bones, and to some broad bones, penetrate the substance of the bone very obliquely. These are the nutritious canals prop- erly so called. Anatomists carefully point out their situation, size, and direction, in de- scribing each bone. The second kind are seen on the extremities of long bones, on the borders, or adjoin- ing the borders, of broad bones. Canals of this kind are generally near the articular sur- faces. Their number is always considerable. Bichat has counted 140 on the lower end of the thigh bone, twenty upon a vertebra, and fifty upon the os calcis. The third kind of nutritious canals are exceedingly small, and might be denominated the capillary canals of bones. They are found in great numbers on the surfaces of all bones. They may be easily seen by the aid of a good magnifying glass ; their presence is also indicated by the drops of blood which appear upon the surface of a bone on tear- ing off the periosteum ; for example, on the internal surface of the cranium, after sep- arating the dura mater. The diameter of these little canals has been calculated to be about the I-20th of a line. The farther progress of the above-mentioned canals is as follows : those of the first kind, which belong to the long bones, soon divide into two secondary canals, one ascend- ing, the other descending, and communicating with the central or medullary cavity. Those which are situated in the broad bones form winding passages, which run for a considerable distance in the substance of the bone. The canals of the second kind sometimes pass completely through the bone (as in the bodies of the vertebrae), and they communicate with the spongy tissue. The canals of the third kind terminate at a greater or less depth, in the compact substance of the long bones, and in the spongy tissue of the short bones. Such are the forms and general ar- rangement of all the cavities which exist on the surface of the bone ; the following are their uses : 1. They serve for the reception and protection of certain organs ; ex., the occipital fossae, which receive a portion of the cerebellum. 2. For insertion or surfaces of attachment, as those on which muscular fibres are implanted, as the temporal and pterygoid fossae. 3. For the transmission of certain organs, such as vessels and nerves which have to pass into or out of an osseous cavity ; such are the fissures, canals, fora- mina, &.C. 4. For increasing the extent of surface ; as the sinuses and cells connected with the organ of smelling, the surface of which they greatly enlarge by their numerous anfractuosities.t 5. For the easy passage of tendons, and sometimes for their reflec- tion, so that the original direction of the force is changed. To this class belong the bi- cipital groove of the humerus, that for the tendon of the obturator internus, &c. They are generally converted into canals by means of fibrous tissue, which lines and com- pletes them. 6. For the nutrition of bones, such being the use of the three orders of nutritious canals already described. We must mention, along with these osseous cavi- ties, other markings or impressions seen on the surface of many bones ; for example, the shallow depressions in the lower jaw bone for the sub-lingual and sub-maxillary glands, the impressions named digital on the internal surface of the cranium. As the eminences of bones have been attributed to the mechanical effect of muscular traction, so the various impressions and vascular furrows upon the internal surface of the cranium have been considered to be the result of pressure and pulsation ; but it would be more correct to limit ourselves to the simple statement, that the impressions and eminences on the inside of the cranial bones exactly correspond with the elevations and depressions on the surface of the brain, and also that the osseous furrows for the middle meningeal artery correctly represent the ramifications of that vessel. * [There is great latitude among anatomical writers in the use of these terms. ] t [Whatever other purpose they may serve, such cells and sinuses are, in most instances, to be regard- ed as a provision for increasing the bulk and strength of bones without a corresponding augmentation at weight.] 12 OSTEOLOGY. We may here point out certain rules to be followed in describing the external confor- mation of bones. 1. In describing the surface of a bone, it should be so divided that the description may comprehend but few objects at a time. Thus, a broad bone is to be di- vided into two surfaces, into angles and borders, which are to be successively studied. 2. The bone being thus subdivided into regions, each of these is then examined, care being taken regularly to proceed from one part to its opposite, i. e., to pass from the su- perior to the inferior surface, and from the anterior to the posterior. This is the only method which, in a long description, will guard against omissions and avoid tiresome repetitions. 3. It is also of great importance, in considering the objects presented by each region or surface, to follow an invariable and regularly progressive order. Thus, after exposing the objects placed in front, the examination should be continued uninter- ruptedly from this point backward. 4. In the symmetrical bones, it is advisable to de- scribe, first, the objects situated in the median line, and afterward those placed laterally. Internal Conformation of Bones. — The tissue of bones, like that of most other organs, presents the appearance of fibres, whose properties are throughout identical, but which, by certain differences in their mode of arrangement, give rise to two forms or modifica- tions of structure. To one of these the name of compact substance has been given ; to the other, that of spongy or cancellated substance. A subordinate modification of the lat- ter has long been described under the name of reticular tissue. The spongy or cellular substance has the appearance of cells and areolae, of an irregu- lar shape and variable size, all of which communicate with each other, and their walls are partly fibrous, partly lamellar. The compact substance seems to consist of fibres strongly compressed, so as to form a close, firm tissue. It is both fibrous and areolar. By means of careful inspection, softening the bone in nitric acid, and studying its devel- opment, it has been clearly proved that it is fibrous, and that in long bones the fibres are arranged longitudinally, while in broad bones they seem to diverge like rays from the centre to every part of the circumference ; and that in the short bones they are disposed irregularly, so as to form a superficial layer or crust. The researches of Malpighi have conclusively shown that it is also areolar or spongy. By examining a bone softened by nitric acid, or studying it in the fcetal state, it may be seen that, in fact, the compact tis- sue is nothing more than an areolar substance, the meshes of which are extremely close and much elongated. Accidental ossifications, and the diseases of bone which so fre- quently exhibit the compact tissue converted into spongy, and the spongy changed into compact, complete the demonstration.* In strictness, therefore, but one form of osseous tissue can be admitted, namely, the areolar, which presents itself under two aspects, sometimes being close, compact, and fasciculated ; sometimes spongy and cellular. Having thus become acquainted with these two forms of osseous tissue, their general arrangement in the different kinds of bones is next to be examined. Internal Structure of Long Bones. — A vertical section of a long bone presents, in the body or shaft, a cylindrical cavity, which, in the fresh state, is filled with a soft, fatty substance, named the marroiv. This cavity, or medullary canal, is of greatest diameter at the middle of the shaft ; and, as it recedes from this point, it is narrowed and inter- sected at various parts by lamellae detached from the sides, and forming a sort of incom- plete partitions. Sometimes, however, there is a complete partition ; thus, I have seen the cyhnder of a femur divided into two distinct halves by a horizontal partition situa- ted precisely in the middle of the bone. The medullary canal is not regularly cylindri- cal, nor does it correspond in figure with the external surface of the bone. It commu- nicates with the exterior by means of the nutritious canals, which sometimes run, for a considerable distance in the substance of the bone, parallel to the medullary cavity, with which they communicate by numerous apertures, and transmit the vessels as far as the extremities of the bone. Some have supposed that the cavity existed only in order to receive the marrow, while, on the other hand, it has been maintained that the marrow existed only to fill up the cavity. Whatever be the uses of the marrow, it is certain that the existence of a cavity in the centre of long bones is an advantageous provision for strength ; for it is proved in physics, that, of two cylinders, composed of the same material in equal quantity, the one which is hollow, and whose diameters are, conse- quently, greater, wiU offer greater resistance than that which is solid. By the contri- vance, therefore, of the medullary canal, there is an increase of strength without aug- * [The description in the text applies to the more obvious structure of bone ; but, when examined with the microscope, the osseous substance, both compact and spongy, is seen to consist of exceedingly fine lamellae laid on one another. In the compact external crust of bones, these lamella run parallel with the surface ; they also surround, concentrically, the small cavilies of the compact substance and the cells of the spongy texture, the parietes of which they form. They are not to be confounded with the coarser layers and plates described in the compact substance by Gagliardi, Monro, and others of the older writers. Along with the la- mellcE there are minute, opaque, white bodies, with extremely fine lines irregularly branching out from thera. These bodies, which can be seen only with the aid of the microscope, are named the osseous corpuscules ; they obviously contain calcareous matter, and are, probably, minute ramified cavities lined with earthy salts. The earthy matter of bone, however, is not confined to the corpuscules, for the intermediate substance is also impregnated with it. For a representation of the minute structure of bone, see jUiiller's Physiology, translated by Baly, plate 1.] GENERAL OBSERVATIONS. 13 mentation of weight. There is another advantage in this arrangement, viz., the in- crease of volume without corresponding increase of weight ; for, since tlie bones are intended to give insertion to numerous muscles, it is necessary that their surfaces should not be reduced to too small dimensions ; but this must have been the result had the walls of the hollow cylinder been compressed so as to form a solid rod. The mar- row consists of two distinct parts : 1. The medullary membrane, which lines the walls of the canal. 2. The fatty tissue, properly so called, or the medullary liquid. The membrane, higUy vascular, serves to nourish the internal layers of the bone ; it possesses great sensibility and a high degree of vitality. The fatty tissue, on the con- trary, is altogether insensible. If a probe be introduced into the centre of the medulla of a long bone in a living animal, no sign of pain is evinced so long as the instrument does not touch the walls of the cavity ; but whenever the walls are rubbed or scratched, the pain becomes excessive, and is manifested by piercing cries and violent struggles. The proportion between the thickness of the walls of the cylinder and the diameter of the medullary canal varies not only in different individuals, but in the same person at dif- ferent periods of hfe. In the aged, the thickness of the walls is proportionally much less than in the adult : tliis is one cause of the great fragility of the bones in old age. Some- times in the adult the walls are so thin, that the bone breaks by the slightest force : in such cases, there is in some sort hypertrophy of the medulla and atrophy of the bone. It is in such cases that fractures occur from the simple effect of muscular contraction, or even from moving in bed. It is in the central canal of long bones that those very delicate osseous filaments are observed, which, interlacing with each other, and forming large meshes, give rise to that variety of spongy tissue which has received the name of reticular, and which appears in- tended to give support to the medulla. The compact tissue diminishes, and the cells increase in number, the greater the distance from the centre of the bone, so that the ex- tremities are entirely composed of spongy substance covered by a thin layer of compact tissue. It appears that the compact tissue which forms the shafts of the bones divides and subdivides into lameUae, in order to form the cells of the extremities. It is easy to perceive the advantage of a spongy structure in the usually voluminous extremities of the long bones : they could not have been compact without a great increase of weight, while the additional strength thus acquired would have been redundant, and altogether useless. The cells of the spongy substance are filled by an adipose tissue, similar to that which exists in the bodies of long bones : from its greater fluidity, it has been denominated medullary juice. Inter7ial Structure of Broad Bones. — If the surface of a broad bone be scraped, or if the bone be sawn across perpendicularly or obliquely, it will be found to consist of two lamellce. or talks, separated by a greater or less thickness of spongy tissue. Hence the two plates are insulated, and one may be fissured or broken without injury to the other. The thick- ness of the compact laminae and of the spongy tissue is not uniform throughout the whole extent of a broad bone. At the centre, for example, there is scarcely any spongy tissue, and hence the transparency of the bone at this part. Towards the circumference, on the contrary, the spongy tissue forms a very thick layer. In the bones which form the vault of the cranium, the spongy substance takes the name of diploe {6nr?.6og, double), because it occupies the interval between the two tables. From what has been said regarding the internal structure of broad bones, it is evident that their distinctive character depends as much upon their internal as their external conformation, and therefore the ribs, which, according to their external characters, seem rather to belong to the long bones, have been classed among the broad, because they exhibit in their internal structure the characters of the latter kind of bones. Internal Structure of Short Bones. — The extremity of a long bone, if separated from the shaft, would represent a short bone, both in its external and internal conformation ; for a short bone is a spongy mass, covered by a thin layer of compact tissue. To their spongy structure the short bones, as well as the extremities of the long, owe their specific hghtness. It should be observed, that what has been said concerning the internal structure of bones applies, in strictness, only to those of the adult, because the younger the subject, the less are the cells of the spongy tissue developed. And, in like manner, as the walls of the cylinder of long bones diminish in thickness, and the medullary cavity increases in diam- eter in the aged, so by the progress of age the walls of the ceUs become extremely thin, and the cells themselves very large. In some cases of disease, for example, after white swelling of the ankle-joint, I have observed true medullary canals in the cuboid bone and calcaneum ; and I have remarked in one case of cancer of the breast, that the ribs adjoining the tumour were hollowed out by a sort of medullary canal. It is to this dimi- nution of the osseous substance, this kind of atrophy of the bone, that I am disposed to attribute the fragihty so often observed in the whole osseous system in cancerous diseases. Chemical Composition of Bones. — The bony tissue consists essentially of two distinct elements, one inorganic, the other organized. When a bone is subjected to the action of dilute nitric acid, the salts are removed ; it becomes flexible and elastic hke cartilage, and though retaining its original bulk and fonn, it is found to have lost a great part of 14 OSTEOLOGY. its weight. By this process its saline ingredients have been dissolved, and nothing re« mains but its organic constituents, which, being subjected to boiling, present all the characters of gelatine. On the other hand, if a bone be calcined, the whole of its organic matter is destroyed, giving out during the process the odour of burned horn. A substance remains which preserves exactly the shape and size of the original bone, but at the same time is very light, porous, and so friable that it crumbles to powder under the slightest pressure. If the calcination be complete, the bone is rendered perfectly white, but it is black when the burning has not been carried sufficiently far ; it may even be vitrified by a more in- tense heat applied for a longer time. Prolonged exposure to the action of air and moist- ure in like manner remove the organized substance, and leave only a calcareous residue. The two elements of bone do not bear the same proportion at different ages. Certain diseases greatly affect the predominance of one or the other, producing almost the same effects as chemical agents. To the inorganic matter the bones owe their hardness and durability ; to the organized substance they are indebted for their vitality and the slight degree of flexibility and elas- ticity which they possess. The following are the results furnished by the chemical analysis of M. Berzelius : , f, ,^, Tj.„^ J 1. Animal matter reduced to gelatine by boiling .3217 1. Organized Part J 2 i^^.j^(^l^^„.^^l^^jj^^ . . . . . 113 ( Phosphate of lime 51-04 {Carbonate of lime 11 "30 Fluate of lime 2-0 Phosphate of magnesia 1"18 Soda and chloride of sodium 1'20 The bones are furnished with vessels : by one set arterial blood is transmitted, by another venous blood is returned. 1. The arteries are of three orders, corresponding with the osseous canals, which have been described in speaking of the cavities of bones. First Order, or Arteries of the Medullary Canal of Long Bones. — In each medullary canal there is at least one principal artery which enters by the nutritious canal and divides almost immediately into two branches, one ascending, the other descending. These subdivide into an infinite number of small branches, the interlacements of which form that vascular network called the medullary membrane. With this network the vessels of the second order freely anastomose after their entrance at the extremities of the bone. In consequence of this important communication, the vessels, notwithstanding the great difference in the manner of their entering the bone, can reciprocally supply each other with blood. In illustration of this, Bichat relates a singular case, in which the nutritious foramen of a tibia was completely obliterated, and yet the nutrition of the bone was un- impaired. The medullary artery gives off the twigs for those layers of compact tissue which form the parietes of the medullary cavity. The arteries of the second order, destined for the spongy tissue, enter the bones by the nutritious foramina of the second order ; but their number by no means corresponds with that of the foramina, which are for the most part destined for the transmission of veins. These arteries communicate both with the medullary artery already mentioned and with the arteries of the periosteum. The arteries of the third order, or the periosteal arteries, are exceedingly numerous. This class comprehends the innumerable little arteries which, after ramifying in the perioste- um, enter the bone by the minute canals of the third order. These small vessels, spe- cially distributed to the exterior layers of compact substance, anastomose with the two preceding orders of vessels. 2. The veins of bones follow the course of the arteries. But there are peculiar venous canals in the interior of the broad and the short bones, and in the spongy extremities of the long bones. These canals were first described by M. Dupuytren in the cranial bones, where they are very obvious : they are perforated with lateral openings, by which they receive blood from the adjoining parts ; their parietes are formed by a very thin plate of compact tissue, and they are hned by a prolongation of the internal membrane of the veins. We shall afterward see that there is a complete analogy between these venous canals and the sinuses of the dura mater, the only difference being in the nature of their parietes, which are fibrous in the sinuses, but bony in the canals in question. I have remarked, that in the foetus and new-born infants, the cells of the spongy tissue, which subsequently contain adipose matter, are filled with venous blood. Lymphatic vessels have not yet been actually demonstrated in the bony tissue ; but it is probable that they really exist there ; at least, the process of nutrition in bones, and certain morbid phenomena which they present, lead to the belief of their existence. The cellular tissue also enters into the composition of the bones : it contributes to form their fibrous structure. Nerves can be demonstrated in connexion with most of the bones of the skeleton. But it is necessary to distinguish those nerves which merely pass through the bones from those which are distributed on their substance. DEVELOPMEJJT OF DONES. 15 Development of Bones, or Osteogeny. From the time of their first appearance in the foetus, to the period of their complete development, the bones pass through a series of changes, which constitute one of the most important circumstances in their history. The investigation of these changes, or of the successive periods of development, is the object o( osteogeny. The development of the bones, considered generally, presents three phases or periods, designated by the name mucous, cartilaginous, and osseous stage. 1. The mucous stage. The mucous condition, the cellular of some authors, has not been vrell defined. Some apply the term to that period of formation in which the bones and the other organs of the body form but one homogeneous mass of a mucous aspect : others use the term to signify a more advanced stage, in which the bones, acquiring a greater consistence than the surrounding parts, begin to show their development through these more transparent tissues. In the latter sense, the mucous stage is obviously no- thing but the commencement of the cartilaginous, and therefore the first acceptation is the only one to be retained. 2. The cartilaginous stage succeeds the mucous, though the time of the transition from the one to the other has not been precisely ascertained. Several anatomists are of opin- ion, with Mr. Howship, that the cartilaginous state does not necessarily intervene be- tween the mucous and osseous conditions ; that its occurrence is only satisfactorily de- monstrated in such bones as are late in ossifying, and that it constitutes a sort of provis- ional condition, in which the cartilage is employed to perform the office of bone. But when we take into consideration, in the first place, the rapid transition from the cartila- ginous to the osseous stage in certain bones, and, secondly, the translucency of newly- formed cartilage when of inconsiderable thickness, as in the cranium, where the carti- lage is scarcely to be distinguished from the two membranes between which it is placed, we can conceive that the cartilaginous stage may easily have been overlooked. On the other hand, the constant result of my observations proves that, in the natural process of ossification, every bone passes through the state of cartilage. When the different pieces of the skeleton assume the cartilaginous condition, the change occurs throughout their whole substance at once. The notion of central points of cartilaginification, corresponding with the points of ossification, is purely hypotheti- cal : a bone becomes cartilaginous in all parts simultaneously, and never by insulated points. The cartilage has the same figure as the future bone. Bones which are to be permanently united by intermediate cartilage, are formed from one primitive piece of cartilage, as those of the cranium and face : those, on the other hand, which are connected together only by ligaments, are distinct and separable while in the cartilaginous state. 3. The osseous stage. The cartilaginous condition of the skeleton is completed by the end of the second month ;* but ossification commences in several places long before this period. The first point of ossification appears after the fourth week in the clavicle ; the second, in the lower jaw. From the thirty-fifth to the fortieth day points of ossifica- tion appear sometimes successively, in other cases simultaneously, in the thigh-bone, the humerus, the tibia, and upper jaw-bone. From the fortieth to the fifty-fifth day, points of ossification appear at short intervals in the annular portion of the uppermost vertebrae, in the bodies of the dorsal vertebrae, in the ribs, the tabular bones of the scull, the fibula, the scapula, the ilium, the nasal, palatine, and metacarpal bones, the phalan- ges of the fingers and toes, the metatarsus, &,c. Once commenced, the ossification pro- ceeds with more or less rapidity in the different bones during the remainder of intra- uterine life. In the child at birth, the shafts of the long, as well as the broad bones, are far advan- ced in development. As to the short bones, the vertebrae are scarcely less early in their evolution than the long and broad bones ; the calcaneum, cuboid, and sometimes the as- tragalus, have points of ossification, but only commencing. The extremities of the long bones, with a single exception, the lower end of the femur, are as yet without ossifying points. The remaining short bones and extremities of long bones ossify subsequently. Of the tarsal bones, the scaphoid is the last to ossify ; the pisiform is the latest among the carpal bones ; the patella is ossified at the age of three years. In regard to the process of ossification, a question of the highest interest presents it- self, viz., 7s the successive appearance of the centres of ossification governed by any general law? The order of commencement of the points of ossification is in no way dependant on the size of the bones. It is true that the smaller bones, excepting the ossicles of the ear, are later in appearing ; but, at the same time, it is not the largest bones that are the earliest ; thus, the bones of the pelvis appear long after the clavicle. * [The relative time of ossification of the diiTerent bones, or, at least, the order in which it commences in them, is easily determined ; but owing to the uncertainty respecting the age of the embryo in its early stages, the absolute time of fcetal life at which each bone begins to ossify is very uncertain, and, accordingly, the statements of many anatomists differ from that given in the text : thus the seventh week is assigned by soma as the period when ossification commences in the clavicle. The age fised by the author appears too early.] 16 OSTEOLOGY. Proximity to the heart or great vessels has no effect on the precocity of development. Though the ribs which are near the heart ossify speedily, the breast-bone, on the other hand, which is still nearer, is one of the bones latest in ossifying. Again, the anterior and inferior angle of the parietal, which is close to the anterior branch of the middle meningeal artery, is the part of the bone which last ossifies. The femoral artery lies on the confines of the os pubis and ilium, which at that part long remain cartilaginous. The true law which governs the order of appearance of the points of ossification is this, viz., that the period of formation is earlier or later in the several bones according to the period at which they are required to fulfil their office in the economy. Thus, the jaws being required to act immediately after birth, are ossified before the other bones of the head. In the same way, the ribs, destined for a function which must commence from the moment of birth, are for this purpose completely ossified : the vertebrae and bones of the cranium appear early, because of their use as protecting the spinal cord and brain ; and it is thus that the pretended correspondence between the rapidity of ossifica- tion and proximity to the nervous centres is explained. Although several of the bones are completed solely by an extension of the primitive nuclei of ossification, the greater number acquire, in addition to these principal or es- sential pieces, complementary points of ossification named epiphyses. Thus, while in the frontal the two original points of ossification suffice by their extension for the- com- pletion of the bone, the vertebrae, on the other hand, have three primary osseous nuclei, one for the body, and two for the laminae and processes ; and five complementary pieces of ossification, namely, two for the body, and one each for the tips of the spinous and transverse processes. The transition from the state of cartilage to hone is attended with the following phenom- ena : the cartilage becomes more dense ; its colour is at first a dull white, but subse- quently changes to deep yellow ; small irregular cavities are formed in its substance ; red vessels show themselves ; a bony point appears in the midst of these vessels, and this bony nucleus is spongy and penetrated with blood. The ossification spreads by lit- tle and little, always preceded by a great development of vessels ; so that, in attentively examining an ossifying cartilage, we find first an osseous point, then a red zone, next an opaque layer of cartilage which is permeated by canals, and, lastly, the remaining car- tilage traversed only by a few vascular canals which run towards the point of ossifica- tion. Moreover, it is always at some depth within the substance of the cartilage that the first osseous points appear, and never at the surface. It is only in cases of accident- al or diseased ossification, as in the cartilages of the ribs, that it occasionally begins at the surface. It is unnecessary to pursue farther the immediate process of ossification : nor need we here discuss the purely speculative question, whether the bone is really a new part essentially distinct from the cartilage, which is absorbed and gives place to it, or merely a deposite of earthy phosphate in a cartilaginous tissue. In admitting that ossification is always preceded and accompanied by a great devel- opment of vessels, a fact proved incontestably by HaUer and Bichat, I must, neverthe- less, decidedly dissent from the opinion that the appearance of blood in a cartilage is a constant indication of approaching ossification ; for several cartilages have naturally bloodvessels, as may be seen in the cartilages of the ribs and larynx. The study of the development of the bones does not consist merely in determining the number and time of appearance of their points of ossification : it comprehends, also, the ulterior changes which take place in the osseous system, viz., the union of the ■primitive points of ossification, and the appearance and junction of the complementary points of ossifica- tion. It is to be remarked, that the order of development and union of the points of os- sification does not always correspond with that in which they originally appear ; nay, it is often the reverse. Thus, the lower epiphysis of the femur is the earliest in appearing, and it is the last in joining ; while, on the other hand, the upper end of the radius is one of the latest of the epiphyses in appearing, but is joined to the bone before all, or nearly aU, the rest. The junction of the pieces of ossification is not complete till about the age of twenty-five years, at which time the lower epiphysis of the femur unites with the body of the bone. General Mode of Ossification of Eminences and Cavities. — M. Serres, in a very remarka- ble work, has given, under the title of General Laics of Osteogeny, the results of his ob- servations concerning the development of azygos or median bones, and of eminences and cavities ; and with a rapid notice of these, we shall conclude what is to be said on the points of ossification. 1. By the law of symmetry, which, according to M. Sen'es, governs the development of all bones situated on the median line, every such bone is originally double, that is, composed of two separate halves, which, advancing to meet each other, are at last join- ed. Thus there are originally two osseous halves of the spinal column, and two demi- stema. The basilar portion of the occipital, the body of the sphenoid, the cribriform plate of the ethmoid, the vomer, and the spinous processes of the vertebrae, have, ac- cording to this view, originally been double. But this law has many exceptions. Thus, although some of the pieces of the sternum are commonly formed from two lateral DEVELOPMENT t)F BONES. 17 points, the first and the last are alwaj^s, or almost always, developed from a single point in their middle. The bodies of the vertebra? are most commonly formed from a single primitive nucleus : the same is the case u'ith the basilar portion of the occipital, the per- pendicular plate of the ethmoid, the vomer, and the spinous processes of the vertebrae. Instances of incomplete division of bones on the median line must not be adduced in proof of the existence of two primitive points of ossification. 2. Every eminence, according to M. Serres, is developed by a special point of ossifi- cation. This is true generally : but how many eminences are formed merely by the ex- tension of ossification from the piece which supports them ! Where, it may be asked, is the special point of ossification for the articular processes of the vertebra?, the coronoid process of the ulna, the external and internal protuberances of the occipital, Ac. 1 There are even double eminences developed from a single point, as the condyles of the femur. 3. Every cavity is formed by the union of at least two pieces of ossification ; so that, when a bone furnished with a cavity consists of several pieces, the place of junction of these pieces is at the cavity. Thus, the three pieces of the os innominatvun meet together at the cotyloid cavity. The same law, according to M. Serres, regulates the formation of the foramina and osseous canals of every kind, as the medullary cavity of the long bones, all the canals for vessels and nerves, as the carotid, vidian, i&c. : according to the same law, all the foramina in the bones of the scuU are formed originally of two halves. But the facts are opposed to this doctrine when apphed so universally. Progress of Ossification in the three Kinds of Bones. — 1. In the long bones. Ossifica- tion commences in their middle part. A small cylinder of bone appears, narrow in the middle, expanded at the ends, tubular within, perforated already with the nutritious fo- ramen, which is very obvious, and receives very large vessels. This little cylinder grows gradually thicker and longer, extending towards the extremities of the bone, which it reaches about the time of birth ; while at this period the ossification is so far advanced in the body of the long bones, their extremities are not yet osseous. It is only at later periods, varying in diflerent bones, that an osseous nucleus appears in the cartilaginous extremities, increasing and encroaching upon the portion of cartilage which separates it from the bony shaft, until that cartilaginous partition, gradually becoming thinner, is at last itself invaded by the ossification. AD the long bones have two essential or princi- pal epiphyses, to which complementary epiphyses are sometimes added. The phalan- ges* are an exception ; they have only one. It is this process which is named junction of the epiphyses. The time of its completion is not confined to any very definite limits, but it is over by twenty or twenty-five years. Throughout the whole time of development the growth in length takes place, chiefly by ossification of the intermediate cartilage, which separates' the epiphyses from the shaft, but partly, also, by longitudinal expansion of the ossified shaft itself The foimer mode of increase has been satisfactorily established by Hunter ; the latter is proved by the following experiment of Duhamel : Three needles being fixed in the shaft of a long bone of a bird, at measured distances, it is found that after a certain time they become farther separated, which proves that the osseous cylinder has undergone an elongation. 2. In the broad bones. 1. Among the broad bones, those which are symmetrical often commence by two points placed one on each side of the median line. 2. The asymmet- rical bones are developed sometimes from a single point of ossification, as the parietal ; sometimes by several, as the temporal. One of the most remarkable circumstances in the development of broad bones is the sort of radiation by which the deposition of calcareous phosphate extends, which spreads from the centre where the first osseous point was deposited, and advances by divergent rays to all points of the circumference, forming bony stria? separated by intervals, which are soon filled up by new osseous rays. As these rays are of unequal length, and are separated at the circumference by intervals of greater or less extent, it follows that a broad bone in the process of ossification must have at its circumference a scalloped or jagged border, like the toothed edge of a comb. It is this form of ossification which gives rise to the serratures of the sutures. The broad bones are proportionally much thinner in the early periods of ossification than subsequently, because ai first the spongy texture is scarcely developed. At the time of birth, the primary pieces of ossification not having united except in very few places, and the ossification which spreads from the centre of the bones not having yet reached the limits of their circumference, it follows that the constituent parts of bones, and the edges of different bones which are destined in the end to meet together, are at this period separated by cartilaginous, and, in some measure, membranous intervals, which in the cranium constitute the fontanelles. After birth, ossification spreads more and more in the broad bones ; at the same time they increase in hardness and thickness, appearing as if to separate into two plates or tables, the interval between which be- comes filled with spongy tissue. The epiphysary or complementary points of ossification of some of the broad bones * [Also the clavicle, the metatarsal, and usually the metacarpal bones.] c .^ 18 OSTEOLOGY. represent, in a certain degree, the epiphyses of the long bones. They occupy the cir- cumference, and are thence named marginal epiphyses. Thus, in the cartilaginous bor- der of the haunch-bone, which represents the crest of the ilium, a point of ossification commences, and extending along its whole length, forms a marginal epiphysis, which subsequently joins the rest of the bone, and in this respect is perfectly analogous to the epiphyses at the extremities of the long bones. The epiphyses, then, are not an exclu- sive attribute of the long bones, as Bichat maintained. They are found, also, in some of the short bones. But it would be indulging in a false analogy to class the Wormian bones, formed during the development of the cranium, with the epiphyses of the long and the broad bones ; for they have peculiarities which are never found in true epiphy- ses. Thus, 1. They are not joined by osseous union, as is the case with epiphyses, but / always by sut\ire. 2. There is no constancy in their time of appearance, nor in their figure, which is irregular, nor in their size, which is, in general, greater the earlier they have appeared, because they have then had longer time to extend themselves before meeting the neighbouring bones. From what has been said, we conclude that the broad bones have a twofold mode of mcrease in breadth, namely, the successive addition of bony substance to their borders, and the formation of marginal epiphyses. In every broad bone which is formed from several pieces, and which has on its surface a part for articulation, this last becomes the centre in which the different pieces meet, and are ultimately joined when the ossi- fication is completed. 3. In the short bones. These are the latest in being ossified ; a gi-eat number of them are still cartilaginous at birth. The short bones are not destitute of epiphyses, as is proved by the ossification of the vertebrae and calcaneum. Their ossification, in fine, presents the same phases, and follows the same progress, as that of the extremities of the long bones, which they resemble in so many respects. Changes which take place in Bones after Maturity. To obtain a complete notion of the development of the bones, we must not rest satis- fied with ascertaining the number of points of ossification, their successive appearance, and their mode of junction ; we must also study the changes which they undergo after they have attained their full growth. The increase of the bones in height terminates when their several pieces have become united : the time when this is accomplished varies from the age of twenty to thirty years ; but they continue to increase in thickness for a considerable time longer. In proof of this, we need only compare the bones of a young man with those of an adult of forty. In old age the bones still undergo important changes : the medullary canal of the long bones augments in width, and the thickness of its parietes diminishes in proportion ; and something similar takes place in the broad and the short bones. Another important fact to be here mentioned is, that the relative proportion of calca- reous phosphate and animal matter undergoes continual changes in the course of life. Thus, by an analysis of Dr. I. Davy, it was shown that the proportion of calcareous phos- phate was a fifth less in a child of fifteen years than in the adult. The same chemist found that the proportion of phosphate of lime in an adult occipital was to that in an occipital bone of an aged person as sixty-four to sixty-nine. JVutrition of Bones. The fact of the nutrition of bones, and the process of composition and decomposition in which it consists, appear to me to be demonstrated by the experiment with madder. If an animal is fed for some time with food impregnated with the juice of madder, its bones soon become coloured red, as may be ascertained by amputating a limb ; but, by suspending the use of that substance for some time, the bones recover their natural col- our. In this experiment, there is no doubt that the calcareous phosphate is the vehicle of the colouring matter, for the bones are the only parts that become coloured ; all that is cartilaginous remains free from colour. We may infer from this that a twofold move- ment continually goes on in bones, by which new molecules are first deposited and then removed, after they have for a longer or shorter period formed part of these organs.* The administration of madder, moreover, demonstrates a fact, which was proved by Duhamel du Monceau in a very curious set of experiments, namely, that the growth of bones takes place by the successive deposition of new layers, formed by the undermost '' or contiguous layers of the periosteum. Thus, let a pigeon be fed with food impregnated with madder, suspend the use of the madder for a time, then renew it ; after this, the bones, when cut through, exhibit a red layer next their surface, then a white layer, then a red layer again. Thus the bones grow in two ways, namely, by the interstitial mode of growth, or by intussusception, which they have in conmion with the other tissues ; and, secondly, by juxtaposition. * A somewhat subtle objection would be the following : May not the colouring' matter be deposited and again carried oif without the particles of phosphate of lime being necessarily subject to the same vicissitudes 1 THE VERTEBRAL COLUMN. 1& THE VERTEBRAL COLUMN. General Characters of the Vertebrae. — Characters peculiar to the Vertebra of each Region. — Characters proper to certain Vcrtebrcc. — Vertebra of the Sacro- Coccygeal Region. — The Vertebral Column in general. — Development. The vertebral column (from the Latin word vertere, to turn, because ,, ^* ^' the body turns round this as an axis), spine, or rachis, is that long, flex- ible, hollow, bony stem, the principal lever of the body, which affords support to almost the entire skeleton, and, at the same time, shields and protects the spinal marrow. It is situate^ at the posterior and median portion of the trunk, extending from the cranium to the pelvis, where it terminates in two osseous pieces, the sacrum and coccyx, which may, in fact, be. regarded as a continuation of the column. The sacrum and the coccyx have been separated from the vertebral column merely on account of the osseous junction of the vertebras of which they are composed.* It is articulated with the base of the cranium at the part where the posterior joins the two anterior thirds of this cavity : it corresponds with the posterior portion of the pelvis, an ar- rangement most favorable for maintaining the erect position. The vertebral column is situated behind the alimentary canal in man, above it in the lower animals. In front are suspended the or- gans of respiration and circulation, to which it affords protection, and which constantly tend to incline it forward : to its sides are attached the ribs and the extremities, the thoracic having an indirect and movable, the abdominal a fixed connexion. From the limits here assigned to the vertebral column, it follows that this part of the skeleton extends the whole length of the trunk, forming tlie entire osseous support of the neck and loins, the poste- rior column of the thorax, and even the posterior wall of the pelvis. Hence it is divided into four regions, viz., a cervical, a dorsal or tho- racic, an abdominal, and a pelvic or sacro-coccygeal region. The vertebral column {fg. 1) is composed of twenty-six bones piled above each other ; the last two have received the names of sacrum and coccyx, and the others, which constitute the vertebral col- umn, properly so called (a d), are denominated vertebra: : they have also been called true vertebra:, as distinguished from the false verte- bra, which, by their osseous union, fonu the sacrum {d e) and coccyx (e/). The sacrum is composed of five of these false vertebra?, and the coccyx of four, in a rudimentary state. The description of these latter bones will be deferred, in the mean time. The first seven true vertebra; form the cervical region (a h) ; the twelve which succeed constitute the dorsal (6 c) ; and the last five the lumbar region (c d). There are occasionally, but very rarely, some variations in the number of vertebra;. In a few cases only six cervical vertebra; have been found ; and Morgagni, who first observed this anomaly, consid- ers it to be a predisposing cause of apoplexy, on account of the ac- companying shortness of the neck, and consequent approximation of the heart and brain. There are sometimes tliirteen dorsal ver- tebrae : sometimes the fifth lumbar is united to the first sacral, and there are then only four lumbar vertebrae. In other cases, the first sacral vertebra is distinct from the rest, and the lumbar portion of the column then consists of six. The vertebra; present general characters, which distinguish them / 1^"^^^ from all other bones : they have also characters peculiar to each particular region ; and in each group or region certain vertebra; have individual distinctive characters. General Characters of the Vertebrcs. Every vertebra {figs. 2, 3, 4, 5, 6, 7) is essentially a symmet- rical ring, a segment of the cylinder which protects the spinal marrow, and is, consequently, perforated by a foramen, denom- inated the vertebral or rachidiaii foramen {l,fig. 2). As it con- curs also to form part of a supporting column, it presents a kind of enlargement or solid cylinder, of which the posterior fifth has been removed. I'his enlargement is the body of the ver- tebra (2). Each vertebra gives attachment to numerous mus- cles, by very marked eminences for insertion — the spinous (3) and transverse processes (4 4). It is articulated with the other * The same is true of anchylosis, as of certain differences of form and development, viz., that thev lead to the establishment of varieties, but cannot form the ground of total separation. ct Fig. 2. 20 OSTEOLOGY. vertebrae by four articular -processes (5 5), two superior and two inferior. Lastly, it pre- sents two superior and two inferior notches (7, figs. 4, 5), which unite to form the inter- vertebral foramina, through which the vessels and nerves are transmitted. Fin. 3. -A.. The body of the vertebra (2) occupies the anterior portion of the vertebral ring, and presents /owr surfaces. The superior and inferior surfaces are connected with the contiguous vertebra, and are slightly hollowed for the reception of the intervertebral sub- stance. This double excavation is the vestige of the deepbicon- ical cavity, so remarkable in the vertebrae of fishes. The ante- rior surface is convex transversely, and presents a horizontal 2^ groove (2, figs. 4 and 5), which is deeper laterally than in the me- dian line, and in cases of abnormal curvature is greater on one side than on the other. This groove is the rudiment of that circular constriction which exists in the vertebrae of reptiles and fishes, and in the cervical vertebrae of birds : it has the double advantage of economy, both as to the weight and the bulk of the bone. The posterior surface is concave, and forms part of the vertebral canal. It is pierced by numerous foramina of considerable size, which are the orifices of venous canals hollowed out in the substance of the vertebra. Smaller foramina of the same nature exist also on the anterior surface. B. The vertebral foramen {I, fig. 2) exhibits certain variations in form and dimensions in the dilferent regions of the spine ; but in nearly all the vertebrae it approaches more or less to the triangular form. The differences which it presents in the extent of its diameters bear reference partly to the size of the spinal marrow, and partly to the ex- tent of motion in each region. C. The spinous process (3, figs. 2, 3, 4, 5) is that eminence of considerable size which arises in form of a spine from the posterior part of the vertebral arch. It forms a lever for the extensor muscles of the trunk, and accordingly varies in length, shape, and di- rection, in the different regions. It bifurcates, as it were, at its base, and passes into the two lamincB {b b, fig. 2), w'hich constitute the lateral and posterior portions of the arch. D. The articular processes {5 5) arise from the lateral portions of the arch near its junc- tion with the body of the vertebra : their direction is in general vertical, i. e., perpendicu- lar to the direction of the articulating surfaces of the body, which are horizontal. They are four in number, two superior or ascending, and two inferior or descending ; they are placed symmetrically on each side of the median line, and are covered with cartilage in the fresh state, to form a movable joint with the articular processes of the adjacent vertebrae ; they project beyond the level of the bodies of the vertebrae, so that their artic- ulations correspond with the intervertebral substances. Hence the vertebral column presents two successive series of articulations : one constituted in front, by the union of the bodies ; the other behind, by the articular processes. E. The transverse processes (4 4) are lateral prolongations, which arise from each side of the vertebral ring, pass horizontally outward, and vary in length and size in the dif- ferent regions. F. In front of the articular and transverse processes, immediately behind and at the side of the body of the vertebra, are four notches cut in the lateral parts of the ring (7, figs. 4 and 5) : the inferior are generally deeper than the superior, but their depth varies considerably in the different regions. The part of the vertebral ring between the upper and lower notches is reduced to a sort of pedicle ; it is the weakest part of the vertebra, and, consequently, it is the principal seat of torsion in curvatures of the spine. The con- stituent parts of a vertebra are,, therefore, 1. In the median line, the body, the foramen, the spinous process, and the lamince ; 2. On each side, the articular and transverse processes, the notch, and the pedicle. Characters peculiar to the Vertebrce of each Region. The characters distinctive of the vertebrae of each region of the spine are most marked in those placed in the middle of the respective region, for at its extremes the vertebrae acquire intermediate or mixed characters belonging to the two regions near the confines of Avhich they are situated. It may be remarked, that the vertebrae of each region may be at once recognised by Fig. 5. one single distinctive iS!!>^.'> character : thus, the cer- vical vertebrae are al- ways known by a fora- men in the base of the transverse processes (a, fig. 2) ; the dorsal vertebrae by facettes hollowed out on the sides of the bodies (6 6, fig. 4) ; and the lum- bar {fig. 5) by the absence of the two preceding marks." The characters just mentioned might, then, suffice as mere distinctive marks, but THE VERTEBRAL COLUMN. 21 they would not answer the purposes of exact anatomical description. Indeed, a vertebra is cervical, dorsal, or lumbar, rather in virtue of its entire form and structure than by- reason of any single circumstance pertaining to it. We shaU examine in regular order each part of a vertebra, as it exists in the different regions. Bodies of the VertebrcB in different Regions. The first distinctive character is their size. This prcgressively increases from the cer- vical to the lumbar regioyi (a, b, c, d,fig. 1) : talcing the size of the bodies of the lumbar vertebrae as unity, that of the dorsal would be two thirds, and that of the cervical one half The second distinctive character is the proportion of the diameters. In all vertebra the transverse diameter is the greatest, and the vertical the smallest. In the lumbar verte- brae the height or vertical diameter is twelve hues (one inch), in the dorsal nine lines (three quarters of an inch), and in the cervical six lines (half an inch). In the cervical and lumbar regions, the vertical diameter of the body is less behind than before, which inequahty gives rise to the anterior convexity of these regions. In the dorsal region, on the other hand, the vertical diameter is shortest anteriorly. In the lumbar region, the transverse diameter does not exceed the vertical and the antero-posterior by more than one third at most. In the dorsal region no one diameter is strikingly predominant ; but in the cervical the transverse is almost double that of the antero-posterior and the ver- tical diameters. The third distinctive character is formed by the lateral ridges of the bodies of the cervi- cal vcrtebrcz. From the twn sides of the superior surface of the bodies of the cervical vertebra arise two small ridges {fig. 2, on each side of 2), which are received into corresponding depressions on the inferior surface of the vertebra above. This mutual fitting-in of the bodies of the cervical vertebra3 compensates for the less secure connex- ion of their articular processes, and which insecurity is, moreover, of less importance, from the bodies being united by disks of intervertebral substance. The fourth distinctive character consists in the two demi-facettes on each side of the bodies of the dorsal vertebra: (6 6, fig. 4). These demi-facettes, when united with the cor- responding parts of the neighbouring vertebrae, form angular excavations, in which the posterior extremities of the ribs are received. This character belongs exclusively to the dorsal vertebras. The fifth distinctive character is the excavation of the superior and inferior surfaces of the bodies, which is lessjn the dorsal region than in the cervical or lumbar. From this dis- position it results, that a lenticular space of a much greater size intervenes between every two of the lumbar and cervical vertebra; than between the dorsal : the mobility is consequently much increased, from the greater size of the intervertebral substance. The specific characters, then, of the bodies of the vertebrae in the different regions are the following: 1. Lateral ridges on the superior surface of the cervical vertebra. 2. Lateral faccttes on the dorsal vertebra. 3. The absence of these two characters, and the preponder- ance of size in the lumbar vertebra. If the body of a vertebra be presented for our inspec- tion, we can at once determine from these characters the region to which it belongs. The Vertebral Foramen and the JVotches in the different Regions of the Spine. The vertebral foramen and the notches present certain marked distinctions in the ver- tebrae of the three regions, by which they may be recognised by a practised eye. 1. In the cervical region, the transverse diameter of the foramen il,fig. 2) considera- bly exceeds the antero-posterior. 2. In the dorsal region, the two diameters are almost equal, but there is this much which is remarkable, that a very considerable depression exists on the posterior surface of the body of the bone. 3. In the lumbar region, the transverse diameter is the greater, but the difference is much less remarkable than in the cervical. The following is a comparative table of the diameters in the three regions ; Transverse diameter. Antero-posterior diameter. In the neck, 6 lines, back, 6 lines, loins, 8 lines. In the neck, 11 lines, back, 7 lines, loins, 10 lines. It may be remarked here, that these differences correspond with the extent of motion in each region. In the lumbar region, which is more movable than the dorsal, the fora- men is larger ; and in the cervical region, where the lateral motions are more extended than in the loins, the transverse diameter is still greater, in the proportion of eleven to ten. It must be observed, however, that the diameters of the foramen bear reference not only to the mobility of the part, but also to the size of the spinal marrow. The notches present also certain differences in the different regions ; thus, in the dor- sal and lumbar regions {7, figs. 4 and 5), the inferior are much deeper than the superior ; in the cervical region_they are of almost equal depth {fig. 3). It may also be remarked, tliai the depth of the notches, and, consequently, the size of the intervertebral foramina, 22 OSTEOLOGY. are generally proportional, not only to the size of the spinal ganglions, but also to the capacity of the venous canals, which establish a communication between the external and internal veins of the spine. It is then possible, when only the vertebral foramen and the notches are seen, to determine the region to which the bone belongs. The Spinous Processes and Laminm in the different Regions. 1. In the cervical region, the spinous processes are prismatic and triangular {3, figs. 2, 3), grooved inferiorly for the reception of the spinous process of the vertebra below du- ring the movements of extension, and bifurcated at their summit, for the purpose of muscular insertion. Their direction is horizontal, and, consequently, favourable to extension. 2. In the dorsal region (3, fig. 4) they are prismatic and triangular, wjth a tubercle at their summit ; their direction is extremely oblique, approaching to the vertical. This direction, together with their great length, causes them to descend considerably below the inferior surface of the body of the vertebra. Hence a sort of imbrication, and to such a degree that a very slight movement of extension causes them to touch each other. 3. In the lumbar region the spinous processes (3, fig. 5) are broad, thick, and quadrilat- eral, presenting on their sides a large surface for muscular insertion ; their posterior border is thick, tuberculated, and triangular. Their direction, being horizontal, presents no obstacle to extension. The two laminae {b b, fig. 2), which form the posterior arch of the vertebra, are con- tinuous with the base of the spinous process. Their length is directly proportionate to the dimensions of the part of the canal to which they correspond, and their thickness is in proportion to the size of the spinous process. 1. In the cervical regian the laminae are thin, very long, and so inclined that when the head is erect, i. e., in a position intermediate between flexion and extension, the inferior edge of the superior laminse passes beyond the superior border of the vertebra below, so that there is a true imbrication of these laminae, not less marked than that which we have observed of the spinous processes in the dorsal region. There has been, conse- quently, no case recorded of the entrance of any penetrating instrument into the spinal canal, in the situation of the undermost five cervical vertebrae ; which fact is the more easily conceivable when we reflect that the least impression upon the back of the neck excites, instinctively, an extension of the head, and thus increases the imbrication of the laminae. 2. In the dorsal region the thickness of the laminae is greater than in the neck, but still inferior to that in the loins ; they are comparatively much shorter than in the cervical region, and, instead of forming an elongated rectangle, they represent a square — nay, their vertical dimension almost exceeds the transverse. 3. In the lumbar region they are characterized by great thickness, by diminution of the transverse, and marked increase of the vertical diameter. In general, it may be stated that the height of the lamina corresponds with the thickness of the body of the vertebra to which it be- longs ; hence they are so narrow in the cervical region. To sum up, then, the characters of the spinous processes and the laminae : 1. Cervical Region. — Processes prismatic and triangular, grooved inferiorly, bifurcated with tivo tubercles at their summit, horizontal, short, and continuous, with long, Tiarrow, and thin lamince, inclined so as to become imbricated. 2. Dorsal Region. — Spiiious processes prismatic and triangular, long, oblique, and tuberculated at their summit, ivith short vertical lamina:. 3. Lumbar Region. — Spinous processes quadrilateral, strong, and horizontal, with very short, thick, and vertical lamince. It is possible, then, from the spinous process and its laminae alone, to determine the region of any vertebra. The Articular Processes in the different Regions. In the cervical region (5 5, figs. 2 and 3) the articular processes form small columns, and are so directed that their articular surface makes, with the horizon, an angle of about 45° ; the superior look upward and backward, the inferior downward and forward. It is important to remark this direction, because it permits the movements of flexion, extension, and lateral inclination : it is owing to the same circumstance, also, that lux- ations of the cervical vertebrae may occur without fracture of their articular processes. It should be also observed that the articular surfaces of the right and left sides are in the same plane. 2. In the dorsal region (5 5, fig. 4) the articular processes are simple laminae, the di- rection of which is vertical and the surface plane. The superior look backward and out- ward, the inferior forward and inward. The articular facette of the right side is not on the same plane as that of the left. I should observe that, in certain cases, the dorsal articular processes are found, as it were, locked together, the extremity of the superior process being received into a deejx notch on the surface of the inferior process of the vertebra above. 3. In the lumbar region (5 5, fig. 5) the articular processes are very strong, with curved THE VERTEBRAL COLUMN. 23 surfaces. The superior concave look backward and inward, the inferior convex forward and outward. They both represent two segments of a cylinder, one of which complete- ly surroimds the other, or, rather, the inferior resemble half hinges, which are received into the half rings formed by the superior processes. It should be observed here, that the superior articular processes are prolonged by certain tubercles, to which the name of apophysary may be correctly applied, and which serve for the insertion of muscles. To sum up, tfien, what has been said : The cervical articular processes are small columns, cut with plane faces, at an inclination of 45°, those of both sides on the same plane ; the dor- sal arc thiyi lamina, plane and vertical, but not in the same plane ; the lumbar strong, vertical, and tuberculatcd lamince, xcith a curved articular surface. The region of any given verte- bra may be easily recognised from its articular processes alone. The Transverse Processes in the different Regions of the Spine. No part of the vertebrae presents more decided variations in the different regions than the transverse processes. 1. In the cervical region (4 ^,figs. 2 and 3) they are grooved superiorly for the lodg- ment of the anterior branches of the cervical nerves ; their base is perforated {a, fig. 2) for the passage of the vertebral artery ; they have two borders, an anterior and posterior, to which the inter-transversal muscles are attached ; their free extremity is bifurcated for the attachment of muscles. It should be added, that these transverse processes, be- ing on the same plane with the bodies of the vertebra?, double their transverse diameter in front, and enable them to afford support to a great number of parts. 2. In the dorsal region (4, fig. 4) they are large and horizontal, much stronger than in the other regions, and twice or three times the size of the spinous processes ; they are much inclined backward, and the anterior surface of their extremity has a depression for articulation with the tubercle of the ribs. Some anatomists have attached great im- portance to the direction of the articular facettes, making it the basis of their notions of the mechanism of respiration. The important modifications which the transverse pro- cesses of the dorsal vertebra? present are evidently connected with the nature of their functions, which are not only that of affording points of insertion to muscles, but also of supporting the ribs with which they are articulated. 3. In the lumbar region, the transverse processes (4, ^o-. 5) are thin, narrow laminae, flattened from before backward. They are situated in a plane anterior to that which the transverse processes of the dorsal vertebra? occupy, and almost correspond with that of the ribs, with which, also, they have numerous other analogies : hence the name costi- form processes given them by some anatomists.* The characteristics, then, of the three kinds of transverse process are, jn the cervical region, a grooved projection with a foramen at the base ; in the dorsal region, a strong process inclined backward, tuberculatcd, and artic- ular at the extremity ; in the lumbar region, a small, thin, blunted projection. It is, therefore, extremely easy to determine the situation of a vertebra by the transverse process. The truth of what we formerly remarked will be now evident, viz., that a vertebra is distinguished as cervical, dorsal, or lumbar, by the form of all its constituent parts. Uni- form in their fundamental type, these bones present, in each region, and in each part, certain differences adapted to their respective uses. Characters proper to certain VertehrcE. We have now noticed, 1. The general characteristics of the vertebra?, by means of which they may be recognised from all other bones ; 2. The peculiar distinguishing chraracters of the vertebra? in each region. We have now to examine in each region those vertebra? which are distinct from all the others of that part of the spine. The place of each vertebra might, strictly speaking, be determined by comparing it with all the other vertebrge of the same region : in this way, those who are accustomed to artic- ulate skeletons acquire surprising readiness. But a few vertebrae only possess suffi- ciently characteristic peculiarities to determine their situations without comparison with the others. It is only in the vertebra? at the extremity of each region, and which, on account of their position, have a mixed character, that such distinctive and individual attributes can be observed. The first, second, and seventh cervical vertebrae, the first, eleventh, and twelfth dor- sal, and the fifth lumbar, require special description. First Cervical Vertebra, or Jltlas (fig. 6). In the first vertebra, or atlas, the place of the body is supplied by an arch (a g), flattened * The description which, -we have given of the transverse processes is in accordance with that usually found in works on human anatomy. Several modem anatomists, however, do not admit of the arrangement which we have adopted. From the e.xislence of cervical and lumbar ribs in the skeletons of many vertebrated ani- mals, they maintain that in man the anterior half of the cervical transverse processes, and the thin plates of the lumbar transverse processes, represent the ribs of the dorsal region ; while the parts truly analogous to the dorsal transverse processes are, 1. lu the ccn'ical region, the posterior half of the transverse process ; 2. la the lumbar region, those projections which we have called apophysarj- tubercles. 24 OSTEOLOGY. from before backward, the anterior arch of the first verte- bra. Its convexity, turned forward, is marked by a tu- bercle (a), the anterior tubercle of the atlas. Its concav- ity, looking backward, presents an oval facette, slightly hollowed for articulation with the odontoid process of the second vertebra. The superior and inferior borders afford attachment to ligaments. The foramen of the first vertebra is much larger than that of all the others. The antero-posterior diameter, ^ which in the neck and back is six lines, and in the loins eight, is here fourteen ; the transverse diameter, eleven lines in the neck, seven in the back, and ten in the loins, is here thirteen. This remarkable extent of all the diameters is not simply owing to the size of the spinal marrow at this point, for the anterior por- tion of the foramen (/, g, f) gives lodgment to the odontoid process of the second verte- bra, so that the antero-posterior diameter of the part which contains the spinal cord does not greatly exceed that of the foramen in the succeeding vertebrae. The transverse di- ameter alone is more considerable, whence the possibility of lateral displacements or incomplete luxations of the first upon the second vertebra without any marked com- pression of the cord. The notches (h h) are situated on the posterior arch at its junction with the lateral masses. They are posterior to the articular processes, while in all the other vertebrae they are anterior. The superior are very deep, often converted into foramina by a bridge of bane, and seem to be continuous with the foramen in the base of the trans- verse process, by means of a horizontal groove which winds round behind the articular process. This groove is sometimes almost converted into a complete canal. From the union of these parts, viz., the notch, groove, and foramen, a twisted canal results, verti- cal at first, and afterward horizontal, along which the vertebral artery runs in its pas- sage into the cranium. Through the superior notch, which almost forms by itself the first intervertebral foramen, the vertebral artery and vein and the first cervical nerve pass. The inferior notches present nothing remarkable, excepting that they are suffi- ciently deep to form, by themselves, the intervertebral foramina between the first and second vertebrae. There is no spinous process : its place is supplied by a posterior tubercle (i) for muscu- lar insertion, analogous to the anterior tubercle, or, more correctly, resembling a spinous process truncated. Sometimes, instead of a tubercle, there are only some inequalities. The posterior a-rch (h, i, h), which forms more than half the circumference of the verte- bra, consists of two strong and long plates. The articular processes or columns, which we have remarked throughout the whole cer- vical region, are very large in the atlas, and bear the name of lateral masses. This struc- ture is connected with the use of the bone, which is to support the occipital condyles, and, consequently, the weight of the head. Of the four articular processes, the superior (b b) are concave, slanting inward, oval, and obliquely directed from behind forward, and from without inward. Their form ex- actly corresponds with the convexity of the occipital condyles (7 7, fig. 10), which they receive, and for this purpose their external borders and posterior extremities are con- siderably elevated. Within and below the articular surface are certain inequalities (//' fis- 6), which give attachment to the transverse ligament. The inferior articular processes are circular and plain ; they look downward and a little inward. The transverse processes (c c) are very large and triangular : they have only one tuber- cle, into which are inserted the principal rotatory muscles of the head : they are per- forated by a foramen (e) at the base, but are not grooved on their surface. The characteristics, then, of the atlas are, an annular form ; great lateral dimensions, so that it surmounts the vertebral column like a capital ; a very large vertebral foramen ; no body, nor spinous process ; large lateral masses, supporting very strong transverse processes, which are not grooved, and have only one tubercle. Second Vertebra, ^xis, or Vertebra Dentata (Jig. 7, side view). The body is surmounted by an eminence (g, a, I, fig. 7), which, in the connected skel- Fig. 7. eton, corresponds with the anterior arch of the atlas. This em- inence has received the name odontoid process, or processus dcn- tatus, from its tooth-like form. It constitutes a species of cylin- drical pivot, about half an inch in length, round which the head turns ; and hence the name axis given to the entire vertebra. It is attached to the body of the bone by a broad basis, is then constricted, and terminates superiorly in an enlargement called the head, which is rough at its summit (a), and gives attachment to the odontoid ligaments. The contracted portion {I) is called the neck ; it is the weakest part of the process, and is, conse- quently, the invariable seat of its fractures. This circular con- THE VERTEBRAL COLUMN. 25 striction of the inferior part of the odontoid process contributes to maintain it in the semi-osseous, semj-ligamentous ring in which it turns. Two articular facettes are seen on this process : one in front (g), corresponding with the anterior arch of the atlas ; the other behind (at I), for the transverse ligament. The body (c) of the axis presents anteriorly a triangular vertical ridge, which separ- ates two lateral depressions for the attachment of muscles. The posterior surface cor- responds with the vertebral canal. The greatest diameter of the inferior surface is the antero-posterior : it is obliquely sloped downward and forward, and slightly concave, for the reception of the body of the third cervical vertebra. This mutual reception of the two bones does not take place between any of the succeeding vertebrae. The foramen is shaped like the figure of a heart on playing cards : its antero-posterior diameter is eight lines, which is two hnes more than in the other cervical vertebrae, and its transverse diameter is the same. This great size of the foramen of the second ver- tebra corresponds with the extent of the movements between it and the atlas. There is no superior notch, the inferior notch of the atlas forming by itself the inter- vertebral foramen. The inferior notch presents nothing peculiar. The spinous process {k, m), though of great length, is even more remarkable for its breadth and thickness, presenting, as it were, in an exaggerated degree, the characters of the cervical spinous processes : its form is prismatic and triangular ; it is grooved inferiorly, and terminates by two tubercles for the attachment of powerful muscles. The spinous process is for the axis that which the transverse process is for the atlas, both giving insertion to powerful muscles, which move the head upon the vertebral column. The lamincB, which correspond, as usual, with the size of the spinous process, are re- markably strong. The superior articular processes (d) are placed on each side of the body. Their facettes are broad, flat, and almost horizontal, being slightly inchned outward. This direction permits the atlanto-axoidean articulation to be the centre of all the rotatory movements of the head. The inferior articular processes (e) resemble those of the other cervical vertebrae. The transverse processes («) are small, witli only one tubercle, triangular, bent down- ward, and perforated at the base by a foramen (/), or, rather, a bent canal, which is hol- lowed out on each side of the body of the hone ; and is vertical in the first part of its course, then horizontal. This canal, and that which we have described upon the atlas, mark the winding course of the vertebral artery hcfore it enters the cranium. The specific characteristics, then, of the second vertebra are, the odontoid process, the great size of the spinous process and the lamincr., the large size and horizontal direction of the superior articular processes, ichich arc placed on each side of the body, and the shortness of the transverse processes, which are triangular, and have one tubercle. Seventh Cervical Vertebra, or Vertebra Prominens {b, Jig. 1). The body has the ordinary characters observed in the cervical vertebrae, but in size it resembles that of the dorsal vertebrae, and frequently presents laterally a small impres- sion for articulation with the head of the first rib. The spi?ious process bears the greatest resemblance to those of the dorsal vertebrae : it is pyramidal, terminates in a single tu- bercle, and is of great length, projecting considerably beyond the level of the other cervi- cal vertebrae ; hence its name of vertebra prominens. The articular processes are almost vertical, and are not supported by small columns. The transverse process, although groov- ed and perforated at the base, as in all the other cervical vertebrae, closely approaches to the characters of the dorsal. The posterior border of the groove, or posterior root of the process, is thick, tubercular, and exactly similar to a dorsal transverse process, while the anterior is thin and rudimentary, excepting in cases where it is separated from the body of the bone, and forms a supernumerary rib.* The foramen in the base of the trans- verse process is very rarely absent, but is most commonly small : in one case only I have found it double. It is never traversed by the vertebral artery. First Dorsal Vertebra. This vertebra resembles the cervical, in having its body surmounted laterally by two hook-like processes or ridges, but, in all other respects, it is strictly analogous to the other dorsal vertebrae. It should be also observed, that the body presents an entire facette for the first rib, and a third or fourth part of another for the second. Eleventh and Twelfth Dorsal Vertebrae. The eleventh dorsal vertebra presents on each side of the body an entire facette for the eleventh rib. Its body is very large, and the place of the transverse process is supplied by a tubercle. The twelfth dorsal vertebra (c, fig. 1) resembles the lumbar in its body, which is scarcely * This circumstance is one of the facts appealed to with most success by those who mate the distinction of transverse and costiform processes. 26 OSTEOLOGY. smaller than that of the lumbar vertebrae, and of which the transverse diameter begins to predominate. The spinous process is horizontal, strong, and quadrilateral. The transverse processes are represented by tubercles, which, like those of the preceding bone, are evidently continued in the lumbar region by those tubercles which we have denominated apophysary. Lastly, the body presents entire articular facettes. It is distinguished from the eleventh dorsal vertebra by the curved surface of the inferior articular processes. ^ Fifth Lumbar Vertebi'a. The inferior surface of the body slopes very obliquely downward and forward. The transverse processes vary in size, but are generally much larger than those of the other lumbar vertebrae ; the inferior articular processes, which are farther separated from each other, have a flat surface, and look directly forward. These are the only vertebrae which in each region present peculiarities. Excepting the first and second cervical, which have many characters quite foreign to the vertebrae of the region to which they belong, it might be said of those peculiar vertebra which have been specially described, that their peculiarities are comprehended in the general statement that those vertebra; which are placed at the limits of any two regions possess characters belonging to both regions. VertebrcB of the Sacro-coccygeal Region. All the vertebrae of this region, nine in number, are in the adult state united into two bones : the five superior form the sacrum, the four inferior the coccyx. The Sacrum (rf, e,figs. 1 and 8). The sacrum has received its name from the alleged practice of the ancients of offering this part of the victim in sacrifice. It occupies the posterior and median part of the pelvis, behind the point where this cavity articulates with the thigh bone, an arrange- ment advantageous for the erect position. It is inserted, hke a wedge, between the two haunch bones. Above, it corresponds with the true vertebral column ; below, with the coccyx. It is directed obliquely backward and downward ; hence the column represent- ed by the sacrum forms an obtuse angle with the lumbar column, the projection of which is anterior. This angle is denominated the promontory, or the sacro-vcrtebral angle (d, Jig. I) : it is an important object of study, both with reference to the mechanism of standing, and in the practice of midwifery.* The sacrum is curved upon itself from behind forward, so as to present an anterior concavity. It is the largest of all the bones of the vertebral column ; hence the name of great vertebra applied to it by Hippocrates. It is proportion- ally more developed in man than in any other mammiferous animal, which is connected with the erect bipedal attitude and the sitting attitude which belong to him in a special manner.! The form of the sacrum is that of a quadrangular pyramid with a truncated apex, the base looking upward. It is symmetrical, like all the median bones, and pre- sents for consideration a?i anterior, a posterior, and two lateral surfaces, a base, and a summit. The anterior, pelvic, or rectal surface {fig. 8) forms part of the cavity of the pelvis. Its concavity varies much in different individuals, and in the two sex- es : but on this latter point there is great diversity of opinion among anatomists. Some believe that it is greater in the female, whence, it is said, results the advantage of a larger capacity of the pelvis, and, consequently, an increased facihty for the passage of the head of the foetus during parturition. Others, on the contrary, contend that the male sacrum is more curved, and that of the female al- most straight ; and they argue that, had the opposite been the case, the coccyx, which forms a continuation of the curve of the sacrum, would have been directed forward, and thus diminished the ante- ro-posterior diameter of the outlet of the pelvis ; whereas, with a slight curve of the sacrum, the coccyx has no tendency to project, but is easily bent backward during labour, t In order to determine the validity of these opposing statements, I have compared a great number of sacra from both sexes, but I could never detect any difference sufficiently marked or constant to be considered as characteristic of the sex. * The sacro-vertebral angle is most remarkable in man, because he alone is destined for the erect posture. By this angle the impetus of movement transmitted from the vertebral colunm to the sacrum is in part de- etroyed. In midwifery it explains the rarity of median positions of the vertex. t Birds, ■which, like man, are biped, are also remarkable for the size of their sacrum. t A very great curvature of the sacrum diminishes not only the antero-posterior diameter of the inferior, but also that of the superior aperture of the pelvis ; and it thus opposes the ascent of the uterus from the true into the false pelvis. Accouclieurs cannot too carefully study the varieties presented by the curvature of this bone. The sacrum is often affected by a species of rickets, when the other bones of the pelvis are free from deformity : and this fact may be easily explained by a reference to the uses of this bone in supporting the whole weight of the trunk. THE VERTEBRAL COLUMN. 27 The anterior .concavity of the sacrum is interrupted by four transverse projections (1 1 1 I, fig. 8), which correspond with the points of union of the sacral vertebrae, and are analogous to the intervertebral prominences. The first is sometimes so prominent, that it might be mistaken for the sacro-vertebral angle in an examination per vaginam. On each side of the median line are the anterior sacral foramina (2 2 2), four in number, the two superior much greater than the two inferior. They give passage to the anteri- or branches of the sacral nerves, to the sacral veins, and some small arteries. External to these are grooves for the nerves, and the attachment of the pyramidalis muscle. The anterior surface of the sacrum is contiguous to the rectum, which follows its curvature. Posterior, spinal, or cutaneous surface. Its convexity is exactly proportioned to the an- terior concavity. 1. In the median line it presents the sacral ridge, formed by a continu- ation of the spinous processes of the vertebral column. This is often entire in its whole length, but sometimes interrupted : it bifurcates inferiorly, and forms the borders of the groove which terminates the sacral canal. The sacral ridge is rarely found cleft through- out its whole length. 2. On each side of the median line are two shallow grooves, named the sacral grooves : they are continuations of the vertebral grooves ; they are pierced hy four posterior sacral foramina, smaller than the anterior foramina, and differing less from each other in diam- eter. These afford passage to the posterior branches of the sacral nerves, to some veins and arteries. They are bordered by two ranges of unequal projections : the first row, placed interior to the foramina, represent the articular processes united together; the second, external to the foramina, are more marked, and correspond with the transverse processes also united. The lateral surfaces {d, e,fig. 1) are triangular, broad above, narrow below, where they constitute mere borders. They slope obliquely from before backward and from without inward, so that the sacrum is wedged between the haunch bones in an antero-posterior as well as in a vertical direction. In front is a demi-oval or crescentic surface (7, fig. 8), compared from its shape to the human ear, and hence denominated auricular surface. In the fresh state it is covered with cartilage, and articulates with the os innominatum. Behind it is a very rugged surface with irregular depressions, giving attachment to the posterior sacro-iliac ligaments. The sinuous border which terminates each lateral sur- face inferiorly gives attachment to the sacro-sciatic ligaments. The base presents, 1. In the middle an oval facette {'i,fig. 8), in all respects similar to the body of a lumbar vertebra, with the last of which bones it is articulated. Behind this is a triangular aperture resembling the foramen of other vertebra;, and completed posteriorly by two laniince, which unite, and form a spinous process,* the commencement of the sacral ridge. 2. On each side two triangular surfaces (4 4), smooth, looking for- ward and upward, and constituting part of the greater or false pelvis. They are separ- ated from the anterior surface of the sacrum by a blunt edge, which forms, as we shall afterward see, a portion of the superior aperture of the pelvis. Behind the oval surface of the body are notches, which complete the last intervertebral foramina; and behind these notches are the articular processes (5 5), which resemble the superior articular processes of the fiftli lumbar vertebra, and receive the inferior processes of that bone. The apex (6) is truncated, and presents a transverse elhptical surface, which articu- lates with the base of the coccyx. Behind it is the termination of the sacral groove, bounded by two small apophyses, intended to unite with two similar projections of the coccyTL. These are the small curnua of the sacrxim. The sacral canal. The termination of the vertebral canal is prismatic and triangular, wide superiorly, contracted and flattened inferiorly, where it degenerates into a groove, which is converted into a canal by ligaments. This canal lodges the sacral nerves, and conmiunicates both with the anterior and posterior sacral foramina. The Coccyx (8, 9, jig. 8). This consists of four, rarely of five, pieces of bone : they are flattened from before backward, and diminish successively in size from the first to the last : they are common- ly united together, rarely separate, the largest corresponding with the apex of the sa- crum ; the smallest is a mere nodule of bone, generally unattached. The whole knot- ted-hke bone, thus constituted, has a triangular shape, and follows the direction of the lower part of the sacrum. It may be regarded as the rudiment of the tails of the lower animals. In some cases I have seen it form a right angle, or even an acute angle with the sacrum. 1 . The posterior, spinal, or cutaneous surface, is rough, for the insertion of the aponeuro- sis of the gluteus maximus. 2. The anterior surface resembles the same part of the sacrum in miniature, and, like it, is in immediate proximity to the rectum. 3. The borders are narrow, sinuous, and tubercular, and give attachment to the sacro- sciatic ligaments. * I have seen this spinous process completely bifurcated. 28 OSTEOLOGY. 4. The base is often united by bone to the sacrum, even in young subjects ; it pre- sents an elliptical articular surface, exactly corresponding with that on the lower end of the sacrum. Behind are two processes directed upward (cornua of ihc coccyx, 8 8, fig. 8), which are sometimes continuous with the small cornua of the sacrum. Externally are two notches, which are converted into foramina by means of ligaments, and afford passage to the fifth pair of sacral nerves. 5. The apex (9), which is sometimes enlarged and sometimes bifurcated, gives attach- ment to the levator ani muscle. It is not uncommon to find the last pieces of the coc- cyx deviating from the median line. Of the Vertebral Column in general. Having already described the situation of the vertebral column, we shall now consid- er its dimensions as an entire piece of the skeleton. Dimensions of the Vertebral Column. 1. The length or height of the vertebral column does not correspond with the length of the spinal marrow, which does not extend below the first lumbar vertebra. It varies at different ages : most commonly it increases up to the twenty-fifth year, but occasionally its growth is completed before this period. In the adult it remains unaltered, but in old age it becomes shortened by the incurvation of the trunk forward, and the yielding of the bodies of the vertebrae and the intervertebral substances. This latter cause is also productive of a very appreciable shortening of the trunk, sometimes to the extent of half an inch, after long walking or standing. When measured along its curvatures, the length of the column is generally two feet four inches ; in vertical height it is two feet two inches. These dimensions are not ex- actly proportional to the height of the individual, which depends principally upon the length of the lower extremities. In this respect I have never found any marked differ- ence between tail and short persons. In an adult of medium stature, the cervical por- tion measures five inches and a half, the dorsal nine inches and a half, the lumbar six inches and a half, and the sacro-coccygeal six inches and a half It may be easily conceived that, in cases of abnormal curvature, the vertical height must present considerable differences, while the actual length of the column may remain almost constant. In the skeleton of a female affected with rickets, a vertical line, stretched from the tubercle of the atlas to the base of the sacrum, measured one foot, six inches, and six lines ; while a hne which followed the inflections of the column, meas- ured two feet eighteen lines — giving a difference of seven inches. Hence the possibil- ity of a rapid and considerable increase in length in those patients who are submitted to continued extension. 2. Antero-posterior dimensions. The antero-posterior diameter, at the sacro-vertebral angle and in the lumbar region, is three inches ; in the dorsal region, two inches, four lines ; in the middle of the cervical region, one inch, six lines. 3. Trarisverse dimensions. The transverse diameter is eighteen lines in the lumbar region, thirteen in the middle of the dorsal, and twenty-two in the cervical. It shoidd, however, be remarked, that the transverse processes are included in this measurement of the cervical region, but not in the others. Direction. The general direction of the spinal column is vertical, but it presents certain alternate curvatures. There are four antero-posterior curvatures, viz., in front, a convexity in the neck {a, b,fig. 1), a concavity in the dorsal region {b, c), a convexity in the loins (c, d), and a concavity in the sacro-coccygeal region (d, e,f). Behind, the opposite curvatures are observed. The degree of each curvature is always proportioned to that of the oth- ers ; thus, if there be a remarkable projection in the cervical region, there is a corre- sponding degree of concavity in the dorsal, and a proportional convexity in the lumbar regions. So great, indeed, is the mutual dependance of these curvatures, that the slight- est modification of one produces corresponding alterations in ah the others. There are many individual varieties of these curvatures ; their effect appears to be that of augmenting the power of resistance in the vertical direction, or, at least, of di- minishing the effect of vertical pressure. It may be physically demonstrated, that of two similar rods made of the same materials, that which presents alternate curves will sup- port a greater amount of pressure in the vertical direction than that which is straight, on account of the decomposition of forces which occurs at each curvature.* In addition to these antero-posterior curvatures, there is at the level of the third, " Some physiologists have even gone so far as to express by figures what the difference of resistance of a recto-lineal vertebral column would be, as compared to one formed with curves like the spine, and have made it as 1 ; 16. It has also been asserted, that the curvatures of the spinal column were the result of muscular action. This is certainly not the fact. These curves are too fixed and too important to be made to depend on an agent so variable as that of muscular contraction. They are produced by the general law which regu- lates the organization of the body. THE VERTEBRAL COLUMN. 29 fourth, and fifth, dorsal vertebree a lateral inclination, the concavity of which is on the left side. This being the exact situation in which the aorta, the principal artery of the body, makes a curve downward, the older anatomists have ascribed the concavity of which we speak to the curvature of this vessel. Bichat imagined it to be owing to the almost universal habit of employing the right hand, in which action the upper part of the trunk is inclined to the left, so as to afford a point of support, and, as it were, a counterbalance to the action of the right arm, which inchnation, by frequent repetition, becomes perma- nent. According to this hypothesis, left-handed individuals should present a curvature in the opposite direction, and Beclard has shown that such is in reality the case. I may add, that I have always found the deviation greatest in those who used their right arm in the most laborious employments. Of late years it has been supposed that the lateral curvature depended upon the position of the foetus in utero ; had this been the case, it should exist at birth, which, as I can affirm, it never does. Notwithstanding the likeli- hood of Bichat's opinion, yet, if we consider that in every case in which an artery is im- mediately contiguous to a bone, that bone presents a corresponding depression, it may be questioned whether the opinion of the older anatomists has not more foundation than is generally admitted.* However slight this lateral incurvation may be, it always pro- duces a correspondent one in the lumbar region, though in the majority of cases this is scarcely perceptible. The history of abnormal curvatures or deviations belongs to pathological anatomy. I shall only observe, that they are all due to the following causes : 1 . The wasting of the vertebrae by caries or softening. 2. Want of equilibrium between the strength of the vertebral column and the weight of the body, either alone or when loaded with burdens. 3. Muscular traction. 4. The frequent repetition of any attitude in which the column is curved. Figure and Aspects. Viewed in front, the vertebral column represents two pyramids united by their bases. The inferior p3Tamid is constituted by the sacrum and coccyx ; the superior pyramid is the true spine ; its base rests on the former, and its summit is surmounted by the atlas. The contraction which exists at the fourth and fifth dorsal vertebra has led to the subdivision of this superior pyramid into two others, united by their summits. Other subdivisions have been instituted, which we shall not point out, since they are useless. What it is important to know is, that the vertebral column increases progressively in size from above downward, which satisfactorily proves that man was formed for the erect posi- tion. There are partial enlargements in different parts, as, for instance, in the first two cervical vertebrae, in the seventh cervical, and last dorsal, &c. Upon the whole, it may be said that the vertebral column presents in front the appear- ance of a knotted cylinder ; behind, that of a triangular pyramid, bristled with eminences and perforated with holes. How irregular does the spine appear when cursorily exam- ined ! Yet, when viewed as a whole, and when we examine its figure and processes in reference to its uses, we are lost in admiration in perceiving that there is not the small- est tubercle, nor the most minute hole, nor the most trifling circumstance in its configu- ration, which is not of great importance in securing the perfection of the entire column. The vertebral column presents for consideration an anterior, a posterior, and two lat- eral surfaces, a base, and a summit. Anterior Surface. — Here are observed, 1. The curvatures already described ; 2. The range of bodies of the vertebrae, having the form of small columns piled on each other, and separated in the fresh state by certain prominent disks of a white colour and fibrous structure. 3. A range of transverse grooves on the bodies of the vertebrae, which are deeper in the aged than in the young subject. This surface presents in its transverse diameters those variations which we have already noticed. The parts placed in front of the vertebral column are, 1 . Immediately on its anterior surface a ligamentous layer, which completely invests it, with the anterior recti muscles of the head, the longi colli, the crura of the diaphragm, and the psose muscles. 2. At a greater distance the aliment- ary canal, which rests on the spine at its commencement and termination, and is attach- ed to it by membranous connexions, even where it advances forward to form its numer- ous convolutions. 3. The organs of circulation, viz., the heart, the aorta, in almost its whole extent, the carotid, vertebral, and conmion iliac arteries, the venae cava;, the ju- gular and conunon iliac veins, the vena azygos, and the thoracic duct. From this posi- tion of parts arises the possibility of effectually compressing the arteries against the ver- tebral column, a method which has been successfully adopted with the carotid arteries and abdominal aorta. It also explains the marked pulsations in the abdominal region frequently observed in emaciated subjects, and often giving rise to an erroneous suspi- * This opinion .seems to be still farther corroborated by a case lately reported to the Academy of Medicine by Doctor G6ry, of complete inversion of the viscera, where the aorta was placed on the right side of the ver- tebral column, and where the concavity, or, rather, lateral depression, was situated on the right side. The facts of the case are satisfactorily established by JM. Bonamy, who examined the subject. Positive proof was obtained that this individual was not left-handed. 30 OSTEOLOGY. cion of aneurism. 4. The trachea and the lungs. 5. The great sympathetic nerves are connected with it in its entire extent, and the ganglionic enlargements of which corre- spond in number to the number of its different pieces. Posterior Surface. — 'This presents, 1. In the median line^ the row of spinous processes, the whole of which constitute a vertical crest or ridge denominated spine, and hence the names spinal column and rachis {paxh, spine). This ridge is far from being regular, but its irregularities are all perfectly adapted for the fulfilment of the movements of the dif- ferent regions. It commences with the tubercle of the first vertebra, is suddenly en- larged at the second, diminishes again at the third, fourth, and fifth cervical vertebrae, and projects anew at the sixth, and more remarkably at the seventh ; thence named vertebra prominens. Below this point the processes become oblique, prismatic, trian- gular, and with one tubercle : their obliquity increases, but they become more slender from the first to the tenth : in the tenth, eleventh, and twelfth dorsal, they become hor- izontal, shorter, and stronger ; and they are bVoad, square, rectangular, and horizontal in the lumbar region. Lastly, the ridge gradually sinks down in the sacro-coccygeal re- gion, when it ends by dividing into two smaller ridges, leaving between them a furrow, which is continued along the coccyx. We cannot fail to perceive the importance of the most trifling circumstance in the conformation of the spinal ridge, whether examined in reference to physiology or pathology. 1st. In reference to physiology. This ridge must be viewed as the lever of those powers which produce extension. We know that the movements of extension are greatest in the cervical portion, that they scarcely exist in the dorsal, and are again considerable in the lumbar. The interval between the spinous processes measures the extent of motion. The three enlargements above referred to, viz., that of the second cervical vertebra, that of the seventh cervical and first dorsal, and that of the twelfth dorsal and first lumbar, explain these movements. The first is for the articulation of the particular movements of the head, the second for the move- ments of the neck, and the third for the insertion of the extensor muscles of the loins. 2d. In reference to pathology. The spinal ridge being the only part of the vertebral column which we can see or feel in the living subject, it is clearly of the greatest im- portance to study the slightest differences which it presents, because it is thus alone that we are able to judge of the extent of deviation in the column ; and yet the indica- tions it aflbrds are not absolutely certain, because the pedicles of the vertebrae being susceptible of torsion, a curvature may exist in the bodies of the vertebrae without any corresponding alteration of the spinous processes. 2. On each side of this median ridge are two grooves, broad and shallow in the cervi- cal, broad and deep in the upper part of the dorsal region, contracted at the lower part of the back, enlarged again in the loins and at the base of the sacrum, contracted, and final- ly obliterated, at the lower part of this bone. These grooves are filled by a muscular mass, which, in robust individuals, projects beyond the spine, while in those who are emaciated the ridge forms the most prominent part. Lateral Surfaces. — These present, 1. In front, the sides of the bodies of the vertebrae and their transverse grooves, which are deeper at the sides than in front, also deeper in the loins than in the neck and back ; 2. In the dorsal region, facettes for the costo-ver- tebral articulations ; 3. Still more posteriorly, the intervertebral foramina, equal in number to that of the vertebrae. The largest of these foramina is the one situated between the fourth and fifth lumbar vertebrae : from this point they gradually diminish in size to the upper part of the back : in the cervical region, again, they are somewhat larger ; and in the sacro-coccygeal they are double, with an anterior and a posterior opening,* in con- sequence of the lateral conjunction of the false vertebrae of the sacrum. In general, their dimensions are in proportion to the size of the veins which communicate between the intra and the extra vertebral venous system. Between these foramina are the transverse processes, which contribute to form the sides of the posterior grooves, and, between the transverse processes, the articulating processes are visible. The base and the summit of the vertebral column have been already considered, in the special description of the atlas and the fifth lumbar vertebra. Vertebral Canal. — This canal, into which the intervertebral foramina open, follows all the curves of the spinal column, but does not altogether correspond in shape with its external figure. It may be even said that its dimensions, at different heights, bear an inverse proportion to those of the column ; thus, while the canal is most capacious in the neck, the column, on the other hand, is largest in the loins. It has been said that the widest portions of the canal correspond with the enlargements of the spinal cord : but this is not correct. The capacity of the canal is proportioned to the mobility of the respective portion of the column, so that, in the most extensive movements, the spinal marrow is effectually guarded from compression : thus it is largest in the neck and loins, and smallest in the back and sacrum, t * [The foramina which lead from the sacred canal are single at their internal orifices, though, for the rea- son given in the text, they open externally by two orifices. It is the internal orifice which answers to the intervertebral foramen of tlie other vertebra.] t In the Philos. Trans., 1822, Mr. Earl has published a paper to establish this fact from observation in comparative anatomy. THE VERTEBRAL COLU^II'J. 31 The canal is almost equally well protected in front and behind ; anteriorly by the bodies of the vertebras, posteriorly by the spinous processes, v,1iich, as it were, ward off mischief from the spinal canal. Laterally it is defended by the articular and transverse processes. Behind, on each side of the median ridge, it is protected by the lamina?, the intervals of which are filled up by what are named the yellow ligaments. Any loss of se- curity occasioned by the existence of these yellow ligaments is compensated by the fol- lowing circumstances : 1. The ligaments are very short, so that the edges of the laminae are almost contiguous. 3. In the neck, where the intervals are greatest, the laminas are so inclined, that the inferior border of the one above overlaps the superior border of the one below. 3. In the loins, where the intervals are nearly as great, the lamina are small, and their place is in a great measure occupied by the lateral masses and the pedi- cles, which are proportionally increased in development. It is impossible for an instru- ment to penetrate into the canal in the lumbar region, excepting between the spinous processes. The same difficulty exists in the cervical region during extension, on ac- count of the imbrication of the laminae. During forcible flexion, however, an instrument may enter between them, when directed from below upward. Internal Structure of the Vertebrce. Excepting the thin external layer of compact tissue, the bodies of the vertebras are almost entirely composed of open, spongy texture. The different processes, on the other hand, have a considerable quantity of compact tissue ; but, in all places where they undergo any enlargement, they are cellular. The laminse are formed almost exclusively of compact tissue. This abundance of the spongy tissue explains the fact of the weight of the spinal column being so inconsiderable in proportion to its size. The venous canals are larger in the vertebrae than in any other bones. They are, for the most part, arranged within the body of the bone in the following manner : A single canal, directed horizontally, and from behind forward, commences at the posterior surface of the body of the vertebra ; at the distance of a few lines from its commencement, it divides into two, three, or four canals, which diverge from each other, and terminate partly upon the anterior surface of the bone, partly in the cells in its interior ; all these canals are lined by a thin layer of compact tissue, and perforated by foramina. Development. The development of the vertebral column comprises, 1. That of the vertebrae in gen- eral ; 2. That of certain vertebra; which differ from the rest ; and, 3. That of the column considered as a whole. Development of the Vertebrce in general. — Each vertebra is developed at first from three points of ossification,* viz., one median for the body, and two lateral for the rest of the vertebral ring. To these primitive points are added, at different periods, five secondary or epiphysary points, viz., one for the summit of each transverse process, one for the summit of the spinous process, and two for the body, the one on the superior surface, the other on the inferior surface, where they form two very thin plates, so that at one tune the body of every vertebra of the spine is, in fact, a triple disk. Lastly, there is a complementary point for each apophysary tubercle of the lumbar vertebrae, which gives to this class of vertebrae seven secondary points of ossification. The first osseous points generally appear in the lamina? ; they precede, by some days, the deposition of bone in the bodies. This law, however, as Beclard has remarked, is by no means general. The first ossific points are visible from the fortieth to the fiftieth day ; that in the body occupies the centre of the cartilage, under the form of an osseous granule, which ex- tends horizontally, so as to present a lenticular aspect. The points of ossification of the laminae appear in the situation of the future transverse and articular processes. The complementary osseous points are not formed until the fifteenth or eighteenth year. Sometimes, however, as Bichat has observed, the point for the summit of the spinous process is included among the primitive nuclei, and in such cases it is situated at the place where that process becomes continuous with the laminae. The lateral osseous points are always united together before joining the body of the bone : this union commences about a year after birth ; they are not united with that of the body until about four years and a half The lateral points are so joined to the cen- tral one that they form the sides of the body, and in the cervical region, from their more rapid increase, they constitute of themselves fully two fifths of the body of the vertebra. It is, then, on the body of the vertebra, or on what is essentially the articular part of the bone, that the three primitive points are united together. The epiphysary points of the transverse and spinous processes are joined to the rest from the twentieth to tlie twen- ty-fifth year ; the union of the epiphysary laminaj of the bodies is not completed until from the twenty-fifth to the thirtieth year. * Some anatomists admit two primitive points for the body of the vertebra. It would exceed our limits to give an account of the discussions to which this question of osteogeny has given rise. 32 OSTEOLOGY. Development of particular Vertchrce. — Those vertebrae which present great differences of form present striking differences, also, in their mode of development ; such are the atlas, axis, seventh cervical vertebra, first lumbar, and those which constitute the sa- crum and coccyx. Atlas. — Modern anatomists admit five or six points of ossification for this bone ; one or two for the anterior arch, two for the lateral masses, and two for the posterior arch. I have never observed more than two lateral points, the same point belonging at once to the lateral masses, and half of the arch on each side. They appear in the following order : those for the posterior arch make their appearance from the fortieth to the fiftieth day ; those for the anterior arch not until during the first year after birth. The two osseous points of the posterior arch unite together, those of the anterior arch do the same, and then the anterior is united to the posterior arch. Axis. — There are often two osseous points for the body of this bone, and always two lateral ones for the odontoid process : it has, therefore, in all, five or six points, viz., two for the laminaj or posterior arch, one or two for the body, and two for the odontoid process. Meckel and Nesbit admit one other nucleus between the odontoid process and the body, which appears in the course of the first year after birth. The points in the laminee appear from the fortieth to the fiftieth day ; those in the body during the sixth month ; and those in the odontoid process, a short time after. At birth the body of the axis is proportionally more developed than that of the other vertebrae. The union of its several parts takes place in the following order : the two laminae are joined together shortly after birth ; the two points of the odontoid process remain distinct during the whole of the first year ; the body and the odontoid process are united in the course of the third year ; and the laminae and the body during the fourth or fifth year. Seventh Cervical Fcr^cJra.— Independently of the osseous points common to all the vertebra, this bone has two others situated on each side of the body in the cartilage which forms the anterior half of the transverse process. The existence of this point, which was described by Hunauld, but which does not appear to me to be constant, establishes an analogy between the transverse processes of the cervical vertebrae and ~ the ribs ; it represents in a rudimentary state the permanent cervical ribs of some ani- mals ; and explains an anomaly which is not very uncommon in the human subject, viz., the existence of a supernumerary cervical rib. First Lumbar Vertebra.— Its transverse process is sometimes developed by a point which remains separate from the body of the bone, and forms a supernumerary lumbar rib. Development of the Sacrum and Coccyx.— The first three sacral vertebrae each present five primitive points, viz., one for the body, two for the lamina?, and two for the anterior portion of the lateral masses. The last two sacral vertebra; have only three points. Each of the coccygeal vertebra; is developed from one point only, but it is not uncom- mon to see the first two formed by two lateral points, which subsequently unite in the median line : there are, therefore, twenty-one primitive points in the sacrum, and four in the coccyx. Subsequently two epiphysary lamina; are formed for the body of each sacral vertebra, making ten new complementary osseous points. At a still later period two laminae are developed, one on each side of the sacrum, corresponding with the au- ricular surface, so that the whole number of osseous points in the sacrum is thirty-three. Ossification proceeds more slowly in the sacral and coccygeal vertebra; than in the others : it commences in the body, the first points appearing from the second to the third month in the first three sacral vertebrae, from the fifth to the sixth month in the fourth and fifth vertebra; ; the lamina; begin to ossify in the interval between the sixth and ninth month : the first vertebra of the coccyx usually begins to ossify during the first year after birth ; the second, from the fifth to the tenth ; the third, from the tenth to the fifteenth ; and the fourth, from the fifteenth to the twentieth year. The union of the osseous points takes place at different times ; the osseous pieces of each vertebra are first joined together, and subsequently the vertebrae themselves. 1. Union of the Ossemis Nuclei of each Vertebra. — The osseous points of the laminae are first united ; these then join with the anterior lateral nuclei of the first three vertebrae : at a much later period the lateral masses become connected with the body. The union of the lateral masses with the body takes place much earlier in the fourth and fifth sacral vertebra; than in the three others, though these latter first showed osse- ous points. After the union of the lateral masses, the sacrum is composed of five pieces, which remain separate until the fifteenth year. 2. Union of the Sacral Vertebra icith one another. — This process commences between the fifteenth and eighteenth year, at which time the epiphysary lamina; of the bodies of the sacral vertebra; are developed. At the age of twenty-five the epiphysary laminae of the iliac surface of the sacrum are developed. The union commences with the lower vertebrae, and proceeds upward. The first is not completely joined to the others until from the twenty-fifth to the thirtieth year. The union of the body of each vertebra with its epiphysary laminae proceeds from the circumference to the centre, so that, in a vertical section of a sacrum, which is com- pletely ossified externally, we often find an intermediate lamina of cartilage. I have THE SCULL. 33 t observed this cartilage between the first and second sacral vertebrae in subjects of a very advanced age. The union of the pieces of the coccyx takes place sooner than those of the sacrum. It commences with the first two pieces ; the third and fourth then follow ; and, in the last place, the second and third are united. Towards the fortieth or fiftieth, or some- times the sixtieth year, the coccyx becomes united to the sacrum. This junction is later in the female than in the male ; sometimes it never takes place. Development of the Spine in general. — Up to the end of the first month of conception, the length of the spine is commensurate with that of the body, the extremities as yet only existing under the form of small tubercles. This disproportion between the spine and members is gradually effaced by the elongation of the limbs, so that at birth the vertebral column does not constitute more than three fifths of the height of the subject. In the adult it forms only two fifths. All the parts which concur in forming the canal for the defence of the spinal cord are developed prior to those which are specially devoted to locomotion, as is shown in the development of the laminae, as compared with that of the body and processes. The os- sification of the laminae proceeds in regular succession from above downward, from the neck to the sacro-coccygeal region. The ossification of the bodies takes a different course, commencing in the dorsal region as a centre, and proceeding to either extremity of the column. The ossification of the bodies of the vertebrae conmiences in the centre of the bone, and accordingly, if the spine of a foetus be dried, the cartilages shrink, and the series of osseous nodules, which represent the bodies of the vertebrae, look like grains of Indian corn strung together. In the first periods of its development, the spinal column presents the following re- markable differences from its subsequent condition. It is completely devoid of curva- ture, and instead of resembling in shape a pyramid with the base below, it is precisely the reverse, the base of the pyramid being uppermost. As the child grows up, the spine gradually acquires those characters which it presents in the adult. In the old subject it is always more or less bent forward. It is not uncommon to meet with several dorsal or lumber vertebrae more or less completely united by a layer of bone, which forms a sort of sheath or clasp. To this I have applied the name of anchylosis by invagination. THE SCULL. Composed of tlie Cranium and Face. — Cranial Bones. — Occipital. — Frontal. — Sphenoid. — Ethmoid. — Parietal. — Temporal. — The Cranium in general. — Development. — Bones of the Face. — Superior Maxillary. — Palate. — Malar. — Nasal. — Lachrymal. — Inferior Tur- binated.— Vomer. — Inferior Maxillary. — The Face in general. — Cavities. — Development. The scull is the most comphcated portion of the skeleton. It has been more minute- ly investigated than any other part, probably on account of the difficulty of the study. It is composed of two distinct portions : one, the cranium, designed to enclose and protect the brain ; the other, the face, which affords lodgment to almost all the organs of the senses, and, at the same time, is employed in the function of mastication. The Cranium. The cranium {npavo^, a helmet) is a round osseous case, composed of eight bones, that is, of eight pieces, distinct and separable after the complete development of the skeleton. Four of these are single, and placed on the median line, viz. (counting from behind forward), the occipital, the sphenoid, the ethmoid, and the frontal ; the remaining four are in pairs, and are situated laterally, viz., the two parietal and the two temporal. To these must be added the two small supernumerary bones denominated ossa wormiana, or triquetra. The Occipital Bone {figs. 9 and 10). The occipital bone occupies the posterior, inferior, and middle portion of the cranium, a great part of the base of which it constitutes.* Below it is articulated with the ver- tebral column ; in front with the sphenoid ; and it is, as it were, wedged in between the parietal and temporal bones of the right and left sides. It is broad and symmetrical ; in shape, an irregular segment of a spheroid, notched round the circumference. It has an anterior and a posterior surface, and a circumference having /owr borders and /owr angles. The posterior or cutaneous surface {fig. 9) is convex, and presents the inferior orifice of the occipital foramen (1, fig. 9 ; d, fig. 21), (foramen magnum), the largest of all the fora^ mina in the skeleton, excepting the sub-pubic, or obturator foramen of the os innomina- * It is the OS prorcE of Fahricius of Aquapendente, who, following out the same metaphor, has given the name of os puppis to the frontal, and os carina: to the sphenoid. E 34 OSTEOLOGY. Fii^. 9. turn. It gives passage to the spinal marrow with its envelopes, the spinal accessory nerves, and vertebral arteries. In front of the foramen is the inferior surface of the basilar process C^, fig- 9; n, fig. 21), which forms the bony roof of the pharynx ; it is placed hor- izontally, is rough, and has a ridge in the median line, more or less prominent in different subjects. Behind the foramen, and in the median line, is the external occipital ridge {-perpendic- ular spine) (3 A, fig. 9; c a, fig. 21), extending from the poste- rior edge of the foramen to the exter^ial occipital protuberance. This projection is wanting in some individuals, and in others its place is occupied by a depression. On each side of the ridge are unequal surfaces, bounded above by a line, with the concavity looking downward. Thus, the siiperior semicircular line (5 5, fig. 9 ; a b,fig. 21) commences at the occipital protu- berance (4, fig. 9 ; a, fig. 20), and proceeds horizontally out- ward. The irregular surface included between this line and the foramen is again divided by a line whose concavity is directed upward (6 6, fig. 9), and which is called the inferior semicircular line. These lines and these inequalities are destined to receive the insertion of a great number of muscles. On each side of the occipital foramen, and towards the fore part, are the condyles (7 7, fig. 9 ; e,fig. 21), two articular eminences, convex, elhptical, directed from behind for- Avard, and from without inward, their surfaces looking downward, and somewhat out- ward. They articulate with the atlas. Behind these are two fosssg -. the posterior con- dyloid, which are often perforated by an aperture ; the posterior condyloid foramen {9>, figs. 9 and 21), giving passage to a vein. In front, and external to the condyles, are the an- terior condyloid fosscz and foramina (9 9, fig. 9) ; the latter are really flexuous canals, through which the hypoglossal nerves pass out of the scull. External to the condyles is a rough surface, the jugular surface {i,fig. 21), which gives attachment to the recti laterales muscles of the head. The anterior internal or encephalic surface (fig. 10), in common with all the other bones Fig. 10. of the cranium, is lined by the dura mater. It presents, 1 . The internal orifice of the occipital foramen {I, fig. 10), which is larger than the external. 2. Before the foramen the ba- silar groove (2), sloping gently from above downward and backward : the sides of the groove are marked by other very small grooves, which concur in forming the inferior petrosal groove. 3. On each side of the occipital foramen, and towards the fore part, is a projection (3 3) which corre- sponds with the condyle, and particularly with the anterior condyloid canal. 4. A little more external and posterior is a small portion of a groove (4), which contributes to form the termination of the lateral sinus. 5. Behind the foramen are the four occipital fosscE, two superior or cerebral (5 5), and two inferior or cerebellar (6 6), separated from each other by a crucial ridge. The vertical branch of this ridge (g a) joins the termination of the sagittal groove above ; below it is formed by the internal occipital crest (7). The horizontal branches (g b) correspond with the grooves for the lateral sinuses of the dura mater. The internal occipital protuberance (g) is situated at the conflu- ence of the four branches. The right and left lateral grooves are rarely of the same size and depth ; the right is generally the larger, and forms by itself the continuation of the sagittal or longitudinal groove. The circximfercnce presents four borders and four angles. The superior or parietal bor- ders {a b, a b), which are remarkable for the length of their indentations, articulate with the posterior borders of the parietal bones forming the lamdoidal suture. The inferior or temporal borders (b c, b c) are divided into two equal portions by the jugii- lar eminence (rf), which articulates with the temporal bone. This eminence, in most sub- jects small, in some instances is largely developed, so as to form a true jugular process. I have seen this process articulated to the transverse process of the atlas. The part » (b d) above this eminence is slightly denticulated, and united to the mastoid portion of the tenriporal bone ; the part {d c) below is thick, sinuous, but without indentations, and articulates, by juxtaposition, with the petrous portion of the temporal. In front of the jugular eminence is a deep notch, sometimes divided into two parts by a process of bone, which contributes to form the foramc7i lacermn postcrius. The superior angle (a) is acute, and is received into the retreating angle formed by the posterior borders of the parietal bones. Its place is sometimes supplied by a Wor- mian bone. In the young subject, the posterior fontanelle is placed here. The inferior angle (c) is truncated, and very thick ; it forms the basilar process, which presents a rough articular surface for union with the body of the sphenoid. The connexion is established FRONTAL BONE. 35 by means of a. cartilage, which becomes ossified at a very early period, so that many anatomists describe the sphenoid and occipital as one bone.* The lateral angles {b b) are very obtuse, and are received into the retiring angle formed by the union of the parietal with the temporal bone. At these angles the lateral and pos- terior font aneUes are situated. Conrnxions. — The occipital articulates with six bones ; the two parietal, the two tem- poral, the sphenoid, and the atlas. Structure. — The part of this bone which forms the occipital fossae consists almost ex- clusively of compact tissue. It is here extremely thin, especially at the inferior fossae. In the rest of its extent there is spongy tissue between the two tables. The external table is much thicker and less brittle than the internal, which is named vitreous, on ac- count of its fragility. The spongy tissue is very abundant in the condyles and in the ba- silar process. Development. — The occipital bone is developed from four points : one for the squamous portion, that is, the part of the bone behind the foramen magnum ; one for each lateral condyloid portion of the occipital, and one for the anterior or basilar portion. These four parts are considered by some anatomists as so many distinct bones, which they de- scribe under the names of posterior or superior occipital, lateral occipitals, and anterior occipital or basilar bone. The first point of ossification appears in the squamous or back part of the bone, under the form of a small oblong plate, placed transversely in the situ- ation of the protuberances. I have never seen this piece formed by two lateral points. The part of the bone of which we are speaking is always visible towards the middle of the second month. The condyloid portions make their appearance next,- and, lastly, the basilar portion, which I have never seen developed from two lateral points. In a foetus of two months and a half, tlie ossified part of this process presented the appearance of a linear streak, situated exactly in the median line, and directed from before backward. The four points of ossification are finally united at the foramen magnum. Anatomists, however, are not at all agreed respecting the number of points of ossifi- cation. Meckel admits eight for the posterior part of the bone, two for the condyles, and one for the basilar process. Beclard, on the other hand, admits only four in the poste- rior part of the bone. His opinion is founded upon the existence of four fissures or di- visions at the circumference of this portion ; viz., one at the superior angle, Avhich sometimes gives to the posterior fontaneUe the lozenge shape of the anterior ; one be- low, which is nothing more than a slight notch in the back of the foramen magnum ; and two on each side, corresponding to the posterior lateral fontanelles. The opinion of Meckel is perhaps grounded upon certain abnormal cases, in which this pa.rt of the bone is divided into a considerable number of pieces, resembling so many Wormian bones united by suture. The Frontal or Coronal Bone {figs. 11 and 12). The frontal bone is situated at the anterior part of the scull, and above the face. It is symmetrical, and represents a considerable segment of a hollow sphere. From its shape it has been compared to a shell. The superior three fourths are curved, placed vertically, but more or less inclined from above downward and forward ; the inferior fourth is flat and horizontal. It has an anterior, a posterior, and an inferior surface, and three borders. The anterior cutaneous or frontal sxvrface is smooth and convex ; there is a suture in the median line in young subjects, which in the adult is pi^_ H. obliterated, leaving scarcely any trace of its existence, ex- cepting at its termination below. At this spot there is a prominence named nasal eminence or glabella (or middle frontal eminence) {I, fig. 11). On the sides of the median line, proceeding from above downward, we observe two smooth surfaces ; then the frontal emi7ie?ices (2 2), two projections which are most strongly developed in young subjects ; and below these, on each side of the glabella, the superciliary ridge, an arched ^^ ,. - elevation which forms the margin of the orbit, and is more ^ '^ prominent towards the nose than externally. Quite at the outside of the anterior sur- face of the frontal, there is a small, depressed, triangular surface (4), which looks directly outward, and is separated from the frontal eminence by a sort of crest, running upward and backward (5) : it forms the anterior part of the temporal fossa. The anterior surface of the frontal bone is separated from the skin by the frontal, or- bicular, and corrugator supercihi muscles, and the anterior portion of the cianial apo- neurosis. The inferior or orbito-cthmoidal surface {fig. 12) presents in the middle a lar} forms tlie upper SPHENOID HONE. 39 part of the zygomatic fossa, and gives attachment to the external pterygoid muscle. On this last part we perceive the inferior orifices of the oval and spinous foramina. Anterior or Orbital Surface. — This surface {lo iv) is four-sided and smooth, and forms the greater part of the external wall of the orbit. Its superior border unites with the frontal bone ; the inferior forms part of the spheno-maxiUary fissure. The internal border con- tributes to form the sphenoidal fissure, and has a small tubercle near its inner termina- tion. The external joins the malar bone. Internal Border. — This border is convex, and commences in front by a triangular and very rough surface (y y,fig. 13), which articulates with a corresponding surface on the frontal bone ; it then forms part of the sphenoidal fissure (2), and finally bends outward, to join the petrous portion of the temporal bone : in this place it is grooved for the lodg- ment of the cartilaginous portion . of the Eustachian tube. The sphenoidal fissure, or foramen lacerum superius (2 2, figs. 13 and 14), partly formed in the way we have described, is completed by the lesser wing of the sphenoid. Wide at its internal extremity, it be- comes narrow at its outer end, where it is closed by the frontal bone at e. It gives pas- sage to the third, fourth, the ophthalmic branch of the fifth, and the sixth pair of nerves, to the ophthalmic vein, and to a prolongation of the dura mater. At the internal extremity of the fissure there is a furrow, which is occasionally converted into a foramen for the pas- sage of a recurrent branch of the ophthalmic artery, which goes to the dura mater. The external border is concave, bevelled on the outside superiorly, and on the inside inferiorly, for articulation with the temporal bone. The anterior extremity is very thin (behind y, fig. 13), and bevelled on the inner side for articulation with the anterior and inferior angle of the pai'ietal. The posterior extremity presents a vertical process (z), the spine or spinous process of the sphenoid, which is received into the angle formed by the union of the squamous and petrous portions of the temporal bone, and gives attachment to the internal lateral liga- ment of the inferior maxilla, and the external or anterior muscle of the malleus. Connexions. — The sphenoid articulates with all the bones of the cranium, and with the palatine, vomer, and malar bones of the face. Structure. — The most remarkable circumstance in the structure of the sphenoid is the presence of the sinuses, which convert the body of the bone into two or more cells (5, fig. 23). The compact tissue prevails in the lesser and the greater wings, and in the pterygoid processes, the thick part only of these containing spongy substance. Development. — In the foetus, as we have already mentioned, the sphenoid is divided into two quite distinct parts : 1. An anterior sphenoid, consisting of the lesser wings and the portion of the body which supports them ; and, 2. A posterior sphenoid, formed of the great wings and the part of the body which corresponds to the sella turcica. 1. The anterior sphenoid is developed from four points of ossification; two for the body, and two for the alas minores.* 2. The posterior sphenoid is also developed from four points ; two for the body, and two for the great wings. Besides these eight points, there are two others on each side ; one for the internal plate of the pterygoid process, and one for the sphenoidal turbinated bone ; so that the whole number of centres of ossification of the sphenoid is twelve. The osseous points of the great wings are the first to appear ; they are visible from the fortieth to the forty-fifth day ; a short time afterward, those of the lesser wings, which are situated on the outside of the optic foramen. At the end of the second month the osseous points of the body of the posterior sphenoid are distinct ; at the end of the third month, those of the body of the anterior sphenoid, and the internal pterygoid plates : the sphenoidal turbinated bones begin to ossify, according to Beclard, in the seventh month of intra-uterine life ; according to Bertin, in the second year after birth. The two points of the body of the posterior sphenoid are united from the third to the fourth month ; the great wings are joined to the body in the course of five or six months after birth. The two points of the body of the anterior sphenoid are joined to those of the small wings about the third or fourth month ; they then unite together in the me- dian plane from about the eighth to the ninth month. The union of the internal ptery- goid plates takes place during the sixth month. t The anterior and posterior sphenoid are united from the eighth to the ninth month. The sphenoidal turbinated bones are not joined to the body of the bone until from the fifteenth to the eighteenth year. The otlier changes which the sphenoid afterward undergoes are connected with the development of the sinuses. It is united with the occipital bone from the eighteenth to the twenty-fifth year. * According to Albinus, the anterior sphenoid is formed exclusively by the union of the osseous points of the lesser wings in the median lino. B6clard observes, that the process takes place sometimes as described by Albinus, but that occasionally there is a median point ; and that at other times there are two points for each of the smaller wings, the internal of which forms the base of the process, and the inner half of the optic fora- men ; and the e.xternal forms, the remainder of tlie wing. These are the two points which I conceive to form the body of the anterior sphenoid. The very numerous osseous points which some anatomists have described are nothing more than irregular grains, which have been mistaken for constant centres of ossirication. t In the lower animals the two sphenoid bones remain separate daring' the whole of life, The inner plate ef tha pterygoid process is also a distinct bone. 40 OSTEOLOGY. one side.* The Ethmoid Bone (Jigs. 15 and 16). The ethmoid is so named from the Greek word r)dfj.bc, a sieve, because it is perforated with a number of foramina ; it is placed in the anterior and middle part of the base of the cranium, but belongs rather to the face and nasal fossee. It is included between the median notch of the orbital part of the frontal and the sphenoid. It is a symmetrical bone of a cuboidal figure, consisting of three parts — a middle part or cribriform plate, and two lateral masses. Cribriform Plate. — This is a lamina situated on the median line, horizon- tal, quadrilateral, and pierced with numerous foramina. It has two surfa- ces, and two borders. On the superior surface (a a, fig. 15) we observe in the middle a vertical triangular process, the crista galli {b and n, fig. 22) ; the summit of this eminence gives attachment to the falx cerebri ; the an- terior border terminates in front in two smaU processes {ala) (/), which articulate with the frontal bone, and often complete the foramen caecum ; the posterior border is very obhque, and is continued to the posterior edge of the cribriform plate by a marked thickening. There are many varia- tions in the size and direction of this process : it is frequently deflected to On each side is the ethmoidal groove (a), deeper and narrower in front than behind ; it is pierced throughout its whole extent with numerous foramina, which have been very accurately described by Scarpa, and which form two rows ; the internal, sit- uated along the base of the crista galli, being the largest. They all transmit filaments of the olfactory nerves ; they are funnel-shaped, and are the orifices of canals, which subdivide in traversing the cribriform plate, and terminate in grooves, either upon the turbinated bones or the perpendicular plate of the ethmoid. Among these openings is one which has the form of a longitudinal fissure by the side of the crista gaUi, and trans- mits the ethmoidal or nasal branch of the ophthalmic nerve. The inferior surface of the cribriform plate {fig. 16) forms part of the roof of the nasal Fig 16 fossa; ; it presents on the median hue a vertical plate {g g, fig. 16), which / passes from before backward, and divides it into two equal parts. This .A is the perpendicular plate of the ethmoid, continuous with the base of the y 6. The superior or spheyioidal border is connected with the sphenoid in ahnost the whole of its extent. It presents a deep notch, forming three fourths or sometimes the entire sph£no-palatine foramen i&,fig. 25 ; o, figs. 26, 27 ; 7i, fig. 37), which corresponds with the sphcno-palatine ganglion, and gives passage to the vessels and nerves of the same name. This border is surmounted by two processes, an anterior or orbital (4, fig. 25 ; a, figs. 26, 27), and a posterior or sphe- noidal {h,fig. 25 ; m,figs. 26, 27). The sphenoidal process is the broader, particularly at its base, but is not so elevated as the anterior : it presents three facettes — an internal, which forms part of the nasal fossa ; an external, which is visible in the zygomatic fossa ; and a superior, which articulates with the sphenoid, and presents a groove, which con- tributes to form the ptcry go-palatine canal. The orbital process, inclined outward, and supported by a constricted portion or neck, has five facettes. Three of these are articular ^y'lz., the internal {n, fig. 27), which is concave, and unites with the ethmoid, covering and completing its cells ; the anterior {p,fig. 27), which joins the maxillary bone ; and the posterior {q,fig. 26), which is united to the sphenoid by certain asperities surrounding a cell, which exists in the substance af the pi^ocess, and com- municates with the sphenoidal sinus. The other two are non-o,rticular, viz., the superior {r, fig, 26), which fonns the deepest part of the floor of the orbit, and the external {s,fig. 26), which forms part of the zygomatic fossa, and is separated from the preceding by a small edge, which constitutes a portion of the spheno-maxillary fissure. Internal Structure. — The palate bone is compact throughout, excepting in the palatine process, where it is thick and cellular. Connexio7is. — The palate bone articulates with its fellow on the opposite side, with the maxillary, the sphenoid, the ethmoid, the inferior turbinated bone, and the vomer. Development. — This bone is developed from a single point of ossification, which ap- pears from the fortieth to the fiftieth day, at the point of union of the vertical and hori- zontal portions, and the pyramidal process. During its development, the bone appears as it were crushed down, so that the vertical portion is shorter than the horizontal, and there is a marked predominance in the antero-posterior diameter. This disposition is in accordance with the shortness of the vertical diameter of the superior maxilla. ^s-^- The Malar Boms (Jig. 28). The malar bones, called also cheek, jugal, or zygomatic bones, are situated in the superior and lateral part of the face : their form is that of a very irregular four-sided figure. They have three sur- faces, an anterior, a posterior, and a superior ; four borders, and four angles. The anterior or cutaneous surface (a) looks outward, is convex and smoothj and presents the openings of several foramina (A^, NASAL BONES. 55 named malar, which are intended for nerves and vessels. This surface gives attach- ment below to the zi/gomaticus major muscle. It forms the most prominent part of the cheek, and is covered only by the skin and orbicularis palpebrarum muscle : it is, conse- quently, much exposed to injury. The superior or orbital surface (b) is supported by a thick curved process, the orbital pro- cess, which arises from the bone almost at a right angle. This surface is concave, and of small extent : it forms part of the orbit, exhibits the internal openings of one or more malar foramina, and terminates behind by a rough, serrated edge, which articulates above with the frontal and sphenoid bone, and below with the superior maxillary. The same maxillary edge presents in the middle a retiring, smooth angle, which constitutes the anterior extremity of the spheno maxillary fissure. The posterior or temporal surface is concave, and presents a smooth surface behind, which contributes to form the temporal fossa, and on which one or more malar foramina open ; and a rough surface in front, which unites with the malar process of the superior maxilla. Of the four borders, two are superior ; of these, the anterior or orbital {d e) is semi-lunar, rounded and blunt, and forms the external third of the base of the orbit ; the posterior or temporal {e f) is thin, and curved like the letter S, and bounds the temporal fossa in front. Of the two inferior borders, the anterior or maxillary (d g) is very rough and articulates with the maxillary bone ; the posterior or masseteric (gf) is horizontal, thick, and tubercular, and gives attachment to the masseter muscle. Of the four angles, the superior ox frontal (e), which is much elongated, and vertical, is the thickest part of the bone, and articulates with the external angular process of the frontal bone : the posterior or zygomatic (/), broader and thinner than the preceding, is serrated, and slants downward and backward, for articulation with the zygomatic process of the temporal bone, which rests upon it. The internal or orbital angle (d) looks in- ward and forward, is very acute, and articulates with the superior maxillary near the infra-orbitary canal. The inferior or malar angle (g) looks downward, is obtuse, and unites with the outer part of the malar or jugal process of the superior maxillary. Internal Structure. — The malar bone is almost entirely compact, possessing spongy tissue only in the anterior and inferior edge, and in the part where the orbital portion is given off. It is constantly traversed by a canal called zygomatic. This passage is gen- erally simple, but sometimes double or even multiple, and opens by at least three orifices. The superior or orbital orifice is visible on the surface of the same name ; the next or external zygomatic foramen is on the cutaneous surface of the bone ; and the third or internal zygomatic on the inner surface of the vertical portion. Connexions. — The -malar bone is articulated with the superior maxillary, the frontal, the sphenoid, and the temporal. Development. — It is developed from one point of ossification, which appears about the fiftieth day of foetal life. The ulterior changes which it undergoes do not require par- ticular notice. The J\''asal Bones (Jigs. 29, 30). The nasal bones are two in number, asymmetrical, and very small in the human sub- Fig. 29. Fig. 30. ject ; they are closely contiguous to each other, sometimes united into one piece superiorly. They are situated at the upper and middle part of the face, and form, as their name indicates, the osseous part of the nose, of which they constitute the root. They are directed obliquely downward and forward, but with various degrees of inclination in dif- ferent subjects ; and hence the varieties in the shape nnd prominence of the middle or bridge of the nose. Their figure is rectangular and oblong ; they are thick and narrow above, broad and thin below ; and have two surfaces, an anterior and a posterior, and four edges. The ajiterier or cutaneous surface {fig. 29) is covered only by the skin and pyramidalis nasi muscle, and hence the ease with which these bones are fractured : it is concave above, flat or even convex below : the orifice of a vascular canal is always very distinctly seen, which is variable in its situation, sometimes single, but often accompanied by others of smaller size. The posterior or pituitary surface {fig. 30) is concave, and forms the anterior part of the roof of the nostrils : it is marked by vascular and nervous furrows, and in the fresh state is covered by the pituitary membrane. Of the four edges, the superior {a, figs. 29, 30), short, thick, and serrated, articulates with the nasal notch of the frontal bone. The inferior (d), very thin, and more elonga- ted, has a slight notch in the centre for the passage of a nervous filament, and forms part of the anterior orifice of the nasal fossaj : it unites with the lateral cartilage of the nose. The interyial (b) edge is thick above, and bevelled, so that, when approximated to the other bone, the two constitute a furrow, in which the nasal spine of the frontal and the perpendicular lamella of the ethmoid bone are received. The external (c) edge is some- what longer than the internal, is slightly bevelled on the outer table, and indented for articulation with the ascending process of the superior maxilla, which rests upon it. 56 OSTEOLOGY. Connexions. — The two bones are articulated together : they unite also with the frontal, the ethmoid, and the superior maxilla, and likewise with the lateral cartilages of the nose : they afford passage to the vessels which establish a communication between the skin of the nose, and the mucous membrane of the nasal fossae. hiternal Structure. — The nasal bones are thick and cellular in their upper parts, thin and entirely compact in their lower, and are traversed by nervous and vascular grooves. Development. — The nasal bone is developed from one single osseous point, which ap- pears before the end of the second month. Ossa Unguis, or Lachrymal Bones {Jigs. 31, 32). These are the smallest bones of the face : they are thin, like paper, and have the trans- Fig. 31. Fig. 32. parence, tenuity, and even the shape of a nail, from which circvim- stance one of their names has been derived. They are situated at the internal and anterior part of the orbit : their figure is irregularly quadrilateral : they are two in number, and, therefore, asymmetri- cal. They have two surfaces and four edges. The external or orbital surface {fig. 32) is divided into two unequal parts by a vertical ridge {a b), which terminates below in a sort of hook. The portion anterior to the ridge is narrow, and marked by a porous groove (c), which, when joined to the channel on the ascending process of the superior maxilla, forms the lachrymal groove (hence the name of lachrymal bone).* The portion (d) of the os unguis, which is posterior to the ridge, completes the inner wall of the orbit. The internal or ethmoidal surface {fig. 31) presents a furrow {a' b), which corresponds to the external ridge ; the portion (c') in front of the furrow forms part of the middle meatus ; behind is a rough surface {d'), which covers the anterior cells of the ethmoid. Of the four borders, the superior{a a') is rough, and articulates with the internal angu- lar process of the frontal bone ; the inferior {h b') articulates with the inferior turbinated bone by a small tongue which passes backward, and which contributes to form the nasal canal, and with the internal edge of the orbital surface of the superior maxillary. The anterior edge {e e') unites with the ascending process of the maxillaiy bone ; and the ■posterior edge {f f), slightly denticulated, joins the orbital portion or lamina papyracea of the ethmoid. Connexions. — The os unguis articulates with the frontal, the ethmoid, the superior maxillary, and the inferior turbinated bone : they assist in the formation of the lachrymal sac, the nasal canal, and the internal wall of the orbit. Structure. — The os unguis consists of a very thin layer of compact tissue, and is the most brittle of all the bones. It is of importance to note its tenuity and fragility, be- cause it is concerned in the operation for fistula lachrymalis. Development. — The os unguis is ossified at the commencement of the third month, from one single point. The Inferior Turbinated or Inferior Spongy Bones (Jigs. 33, 34, and d, fig- 37). The inferior turbinated bones, so called on account of their curved figure, are situated at the lower part of the external wall of the nasal fossse {d, fig. 35), below the ethmoid, whence the name sub-ethmoidal turbhiated bones. They are two in munber, asymmetrical, and their greatest diameter is directed from before backward. They have two surfaces, two edges, and two extremities. The internal surface {fig. 34, and d,fig. 37) is convex, and looks towards the nose, which it sometimes touches when that part deviates from the straight direction ; the external sur- face {fig. 33) is concave, and forms part of the middle meatus. Both are rough, and, as it were, spongy, which has given rise to the assertion that these bones form an exception to the general rule of the spongy tissue being in the interior of bones : this appearance, however, is owing to the multi- plicity of canals intended for nerves, and more particularly for the veins which expand over the bone. The superior or articular edge {abed, figs. 33, 34) is very irregular, and presents from before backward, 1. A thin edge {a b), which articulates with the ascend- ing process of the superior maxilla. 2. A small eminence bearing the name of 7ia.sal or lachrymal process {h), which articulates by its apex with the os unguis, and by its two edges with the two lips of the ascending process of the superior maxillary, to complete the nasal canal. 3. A ciuved plate, called aitricular process {e, fig. 33) by Bertin, who com- pared it to the ear of a dog ; this plate is directed downward, and applied partially upon the orifice of the maxillary sinus, which it assists in closing. 4. Behind this process * The existence of lachrymal bones is subordinate to that of the lachrymal secretion. They are not met with in those animals which live in the water, and which have neither lachrymal glands nor passages. VOMEK. INFERIOR MAXILLA. 57 we find a thin edge (e d, figs. 33, 34), -which articulates with a small ridge on the palate bone. 5. Between the auricular and the lachrymal processes are small prominences which unite with the ethmoid. The inferior or free border (a d) is convex, and thicker in the middle than at its ex- tremities : it is separated from the floor of the nostrils by an interval (m o,fi.g. 37) of un- certain extent, a circumstance to be remembered during the introduction of instrmnents into the nasal fossa;. The anterior extremity {a) is a httle less pointed than the posterior {d), which distin- guishes the bone of the right from that of the left side. Connexions. — The inferior turbinated bones articulate with the superior maxillary, the palate bones, the ethmoid, and the ossa unguis : they have important relations with the inferior orifice of the nasal canal, which they defend from the contact of foreign bodies. Structure. — Their external spongy appearance depends upon the multitude of canals with which their surface is furrowed, but they are ahnost exclusively formed of compact tissue. Development. — Their ossification commences about the fifth month of fcetal life, by a point situated in the centre. The Vomer {fig. 35, and 10, ^g-. 22). The vomer is so called from its supposed resemblance to a ploughshare. It is situated in the median plane, and forms the posterior part of the sep- pjv 35 tum of the nostrils. It is thin, flat, and quadrilateral, and has two surfaces and four edges. The surfaces are placed laterally (as at a, fig. 35), and are generally plane, but they are often bent to one side or the other, and are then convex and concave in opposite directions : they are always smooth, and covered by the pituitary membrane, and present small vascular and nervous furrows. The superior or sphenoidal border {b,fig. 35, and 3, fig. 22) is the shortest and thickest : it is marked by a deep groove, which receives the in- ferior crest of the sphenoid ; the two lips of the groove are bent outward, and received into furrows on the inferior surface of the same bone, and thus complete a small chan- nel for the passage of vessels and nervous filaments. The inferior or maxillary (c) bor- der is the longest, and is received into the furrow which is formed by the union of the two palate bones behind and of the two superior maxillary in front : it sometimes termi- nates by a more or less prominent process behind the anterior nasal spine. The anterior or ethmoidal border {d,fig. 35, and 3 4, fig. 22) presents the continuation of the groove on the superior edge, and receives the inferior border of the perpendicular plate of the eth- moid. There is no groove where it is attached to the cartilaginous septum. The pos- terior or guttural edge {c,fig. 35, and t, 10, fig. 22) is free : it is thin and sharp, and in- clines downward and forward : it separates the posterior openings of the nasal fossae. Conncxio?is. — The vomer is articulated with the sphenoid, the ethmoid, the superior maxillary, the palate bones, and the cartilage of the septum. Internal Structure. — The vomer is composed of two very thin compact lamina, which are distinct above, but united below. Some anatomists have called these plates aicE of the vomer. Development. — It is developed from one point of ossification, which is situated at the lower part of the bone, and appears before the end of the second month. It then pre- sents the form of a deep groove, embracing the cartilage just as, at a future period, it embraces the sphenoidal crest. At birth the vomer is still only a groove ; afterward this condition is confined to the sphenoidal and ethmoidal edges of the bone. It is not uninteresting to note the peculiar and uncommon manner in which the ossification pro- ceeds from the surface to the interior of the cartilage. Inferior Maxilla (fig. 36). While, as we have before observed, a considerable number of bones to enter into the formation of the upper jaw, the lower jaw consists of one pig_ 35. bone only. The inferior maxilla occupies the lower part of the face. From the number and importance of the practi- cal points connected with this bone, too much attention cannot be bestowed on the study of its form and connex- ions. It has the shape of a parabolic curve, the two ex- tremities of which, called rami, form a right angle with the middle portion or body. Of the body or middle portion (a). — The body represents a curved plate, convex in front and concave behind. It of- fers to our notice an anterior and a posterior surface, and a superior and inferior border. The anterior surface has in the middle a vertical hne, called symphysis menti (c d) ; it H 58 OSTEOLOGY. marks the place of union of the two pieces of which this bone is composed in yoimg subjects, and which, in a gi-eat number of animals, remain distinct through life.* The mode in which the two halves of the body of the inferior maxilla are united, forming an arch instead of an angle, as in other animals, constitutes one of the distinc- tive characters of the human species ; and the vertical direction of the symphysis, com- pared with its ver)" obhque inclination downward and backward, or almost horizontal position in the lower animals, is a no less characteristic mark of man, who alone can be said to possess a chin.f In front the sjmphysis terminates by a triangular eminence called mental process (d). Behind, it presents below four small tubercles, two superior and two inferior, known by the collective appellation of genial processes {yeveiov, the chin), and give attaclmient tc the genio-hyoid and genio-glossal muscles. On each side of the si/mphysis, we observe on the anterior or cutaneous surface of the body of the inferior maxilla, 1 . A small depression for the attachment of muscles, named mental fossa (e e). 3. A line, which commences at the mental process, passes obhquely upward, and becomes continuous with the anterior edge of the ramus of the jaw : it is named the external oblique, or external maxillary line {e f), and is also intended for muscu- lar insertions. 3. Above this Hne, the mental foramen (g), the orifice of the inferior dental carud, which transmits the mental vessels and nerves. 4. The anterior surface of the alveolar arch (c h), marked by a series of projections corresponding to the alveoh, and separated by vertical depressions, which point out the situation of the inter-alveolar sep- ta. 5. Below the external obhque line, a smooth surface (a), separated from the skin by the platysma myoides muscle. The posterior or lingual surface is in some measure moulded upon the tongue : it pre- sents, 1. The mylo-hyoidean line (k) (jiv/.og, dcTis molaris). called also internal oblique or in- ternal maxillary, which commences at the genial processes, and passes upward and back- ward, becoming more prominent opposite the last molar tooth. 2. Below this line, a broad but superficial depression, which lodges the sub-maxillary gland. 3. Above the obhque hne, and near the symphysis, & fossa, which lodges the sub-hngual gland, and a smooth surface covered by the mucous membrane of the mouth and gums. These two lines, the external and internal obhque. divide the body of the inferior max- illa into two parts, a superior or alveolar, and an inferior or basilar. The first named constitutes almost the entire body of the bone in the foetus and the infant ; in the adult it forms only two thirds of the depth of the bone, the other third being the basilar portion : last- ly, in the aged, the alveolar portion almost entirely disappears, and the basilar only is left. The superior or alveolar border describes a smaller curve than the corresponding alveo- lar edge of the superior maxiha ; so that, in a regular conformation of the parts, the in- ferior incisor teeth are overlapped by the superior. This border is less thick in front than behind, where it projects inward ; it is pierced by a series of sockets or alveoli, re- sembling those of the superior maxiUa, and, like them, variable according to the kind of teeth which they are intended to receive. The niferior border or ba^e of the jaw {d m) is the thickest part of the bone ; it forms part of a larger curve than the superior border, so that the jaw projects forward in some measure at the lower part : this projection varies much in different subjects. Rami of the inferior maxilla {b b). — These are quadrilateral, and present, 1. Aji external surface (b) covered by the masseter muscle, which is inserted into it, especially below, where we may observe depressions and ridges, and where the bone itself is more or less bent outward ; in front of these ridges is a shght mark, which corresponds with the situation of the facial artery. 2. An internal or pterygoid surface, also rough, for the at- tachment of the internal pterygoid muscle, and on which is observed the superior orifice (/) of the inferior dental canal, which is wide, and has a sort of spine, to which the in- ternal lateral hgament of the temporo-maxiUary articulation is attached : a small groove passes from this orifice in the same direction as the canal, and bears the name of mylo- hyoidean furrou-, because it lodges the nerve of that name. 3. A posterior ox parotid edge, which is round, and gives attachment below to the stylo-maxillary ligament : it is em- braced by the parotid gland. 4. An anterior edge (r), marked by a groove, which is the continuation of the alveolar border ; the anterior and posterior lips of this groove being formed by the external and internal obhque hnes. 5. A superior edge, very thin, and hol- lowed out into a deep notch, caUed sigmoid notch {n o). on account of its shape, giving passage to nerves and vessels. 6. An inferior edge, which is nothing more than a con- tinuation of the inferior border of the body of the bone. The angle which the rami form with the body of the bone is named the angle of the jaw (m). It is a right angle in the adult, but very obtuse in the infant, as also in the * In serpents these pieces form a movable joint ; and as a similar arrangement obtains between the two halves of the upper jaw, these reptiles are enabled to swallow an object much larger than their head, or even than their boOy. t It IS interesting to remark the difference in the dissection of the symphysis in the Caucasian and Ethi- opian varieties of the human family. In the former it is placed nearly vertically, slightly oblique from above to below, and from behind to before. In the latter it is oblique from before to behind, and in this respect re- sembles the confonnation in the inferior animals, more especially in the Simia. INFERIOa MAXILLA. 59 carnivora and some of the rodentia, this disposition enabhng its muscles to act with greater power. The rami of the inferior maxilla are terminated above by two processes : the anterioi; called the coronoid process (n) ; the posterior, named the condyle (p). The coronoid process is triangular, and inclined for^vard ; broad at its base, and pointed at its summit ; it gives attachment to the temporal muscle. The size of this process in the ditferent species of animals bears an exact and constant proportion, both to-'the depth and extent of the temporal fossa, and to the strength and curvature of the zygomatic arch. The condyle articulates with the glenoid cavity of the temporal bone ; it is an oblong eminence, the greatest diameter of which is directed slightly inward and backward. It IS supported by a contracted portion, called the necf: of the condyle (cervu) (o). This neck is turned inward in such a manner that the condyle, which it supports, does not project beyond the external plane of the ramus of the jaw ; it is also pretty deeply excavated internally, to afford attachment to the external pter}"goid muscle. The neck of the con- dyle is the weakest part of the inferior maxilla. Connexions. — The inferior maxilla articulates with the temporal bone, and lodges the lower range of teeth. Structure. — The external surface of the inferior maxilla is composed of compact tis- sue ; the interior of the bone assumes the form of diploe, and is traversed for a great part of its extent by the dental or inferior maxillary canal, which transmits the vessels and nerves that are distributed upon the teeth of this jaw. This canal commences at the middle of the ramus, by a groove covered Avith a fibrous lamina, the only use of which, as it appears to me, is to protect the vessels and nerves, and to separate them from the internal pterygoid muscle. From this point it proceeds forward and inward be- low the mylo-hyoidean line, the curvature of which it follows ; it gradually becomes con- tracted in diameter ; and in the situation of the second small molar or bicuspid tooth, it divides into two canals, the larger of which is verj' short, and opens upon the external surface of the body of the bone at the mental foramen already described ; the other, very minute, pursues the original track, and is lost near the midrlle incisor tooth. In its pas- sage the inferior dental canal communicates with the alveoli, by one, and sometimes two foramina, through which the vessels and nerves of the teeth are transmitted. The sit- uation of the dental canal varies much in different periods of life. In the new-born in- fant, before the appearance of the teeth, it occupies the lowest portion of the jaw ; after the second dentition, it corresponds pretty nearly with the mylo-hyoidean line ; and after loss of the teeth, it runs along the alveolar border. In the inferior maxilla of the old subject, the anterior orifice of the dental canal, or the mental foramen, is close to the su- perior border of the bone. The dimensions of the dental canal are no less remarkable for their variations ; it is very large in the fcetus, and in the chdd before the appearance of the second set of teeth ; it diminishes during adult age, and is much contracted in the old subject. Development. — The inferior maxilla is developed by two points of ossification, one for each lateral half Antenrieth admits, in addition, three complementary points ; one for the condyle, one for the coronoid process, and one for the angle ; but I have never ob- serA-ed them. The case is different, however, with a point of ossification described and figured by Spix, which forms the inner side of the alveolar border, or, rather, of the den- tal canal. In a fcetus of about fifty or sixty days, I have seen a kind of bony spiculum, which passed along the internal surface of the body and ramus of the bone ; on the one half of the maxillary bone this spiculum was entirely free ; but that of the other side ad- hered by the internal third of its length. The spine which surmounts the dental canal is nothing more than the extremity of this bony spiculum. It follows, therefore, that the inferior maxilla is developed from four points of ossification. The inferior maxilla takes precedence of all the bones of the head in its development, and, indeed, of all the bones of the skeleton, excepting the clavicle. The inferior edge of the body of the bone appears cis early as the thirtieth or thirty-fifth day ; this extends backward to form the ramus, and in front to form the portion which supports the incisor teeth ; it is probable that the osseous point of the dental canal, mentioned above, appears at the same time. From the fiftieth to the sixtieth day, each half of the bone appears already marked by a groove common to the dental can^ and the alveoli. At a later period, the groove becomes verj' considerable, and is divided into alveoli by septa, which at first are incomplete, but afterward become perfect ; the alveoU and their septa occupy at this time the entire depth of the bone. The point of ossification described by Spix is united to the rest of the bone from the fiftieth to the sixtieth day. (Spix affirms that it remains separate until the fourth month.) The two halves of the maxdla are joined together during the first year after birth. The traces of this union exist for some time, but are afterward effaced ; in the lower animals the suture remains throughout life. The changes which the inferior maxilla undergoes after birth, relate. 1. To the angle which the ramus forms with the body of the bone, whieli is very obtuse at birth, and be- comes a right angle after development is completed. 3. To the alterations effected ia 60 OSTEOLOGY. the body of the bone, by the first and second dentitions, the loss of teeth in the aged, and the subsequent absorption and disappearance of the alveoli. The Face in general. The fourteen bones which we have described, united to each other, and joined to the bones of the cranium, form a piece of bony sculpture, symmetrical, extremely comphca- ted, destined to lodge the organs of smell, sight, and taste, and to be the instrument of mastication. This bony sculpture forms the face, which is situated below the cranium, above the neck, and in front of the vertebral column, from which it is separated by the pharjTix, and is bounded on each side by the zygomatic arches. Dimensians of the Face. In order to form a just idea of the dimensions of the face, it is necessary to examine a scull cut vertically from before backward (as in Jig. 22). We then perceive that the face is comprised within a triangular space, which is bounded above by an irregular line that separates it from the cranium ; in front by the face, properly so called ; and below, by a line passing below the symphysis menti. If a line be drawn above the inferior maxiUa, and under the arch of the palate, when prolonged backward, it will be in the plane of the foramen magnum ; for the cranium having much less depth in front than behind, a horizontal line, which touches the cranium behind, is separated from it in front by the entire height of the upper jaw. The vertical diameter, which extends from the frontal protuberance to the chin, is the longest of all the diameters of the face. It gradually diminishes from before backward. The transverse diameter is of considerable extent in the situation of the cheeks, but di- minishes above and below this point. The aTitero-posterior diameter stretches above from the nasal spine to the basilar process ; below it is greatly contracted ; and at the level of the chin only measures the thickness of the symphysis. With regard to the dimensions of the face as a whole, we shall only refer to what has been already stated concerning the inverse proportion of the area of the cranium, and that of the face, in different species of animals.* The face represents a triangular p}Tamid, and offers for consideration three surfaces or regions : an anterior, a superior, and an inferior. Anterior or Facial Region. The numerous anatomical differences which this region presents form distinctive characters, not only of different nations, but also of different individuals. It is bounded above by the forehead, below by the base of the inferior maxiUa, and laterally by a line which passes along the external angular process, the malar bone, and the ridge which separates the canine fossa from the tuberosity of the maxiUa. In this region we observe, in the median line, the nasal eminence ; a transverse suture, formed by the union of the proper nasal bones with the os frontis, the fronto-nasal suture ; below this suture, the nose, a pyramidal eminence, narrow above or at its root, broad below or at its base, and formed by two bones, which are united together by juxtaposition in the median line, and externally to the ascending process of the superior maxilla. Below this eminence is the anterior orifice of the nasal fossa, which has the form of a heart on playing cards, and presents at the bottom the anterior nasal spine, and below this a ver- tical suture, the maxillary, the interval which separates the middle incisor teeth, the opening of the mouth, and the symphysis menti. On each side, we find the opening or base of the orbit, directed obliquely outward, of an irregular square form, and presenting above the supra-orUtary foramen ; below, the infra-orhitary foramen; on the outside, the fronto-jugal suture ; and, on the inside, the fronto-maxillary suture. Below the opening of the orbit is the canine fossa, then the alveoli and teeth of the two jaws, the extern^ obUque hne, the mental foramen, and the base of the inferior maxiUa. Superior or Cranial Region. This region is so united with the inferior surface of the cranium, that the scull and the superior maxiUa form only one piece, and cannot be removed from each other. It presents, in the median line, counting from behind forward, the articulation of the vomer with the sphenoid, in which articulation there is a mutual reception of parts, the sphe- noidal crest being received between the laminae of the vomer, and these, in their turn, being lodged in corresponding fissures in the sphenoid ; the articulation of the vomer with the posterior edge of the perpendicular plate of the ethmoid; the articulation of this perpendicular plate with the nasal spine of the frontal bone ; and the articulation of this spine with the proper bones of the nose. On each side, proceeding from within out- ward, we observe, 1. The roof of the nasal fossae, formed behind by the inferior surface of the body of the sphenoid ; in the middle by the cribriform plate of the ethmoid ; and in front by the posterior surface of the nasal bones. 2. More externally, the base of the * Vide of the cranium in general ; of the facial angle of Camper ; the occipital angle of Daubenton, and the measurement of Cnvier, p. 45. THE FACE IX GEXEEAL. 61 pterygoid processes, the articulation of the palate bone with the sphenoia, the pterv^o palatine canal, and the spheno-palatine foramen. 3. The articulation of the lateral mass- es of the ethmoid ^vith the sphenoid behind, and with the frontal bone in front. 4. The articulation of the internal angidar process of the frontal bone witli the os unguis. 5. The articulation of the nasal notch of the frontal bone with the ascending process of the su- perior maxilla, and the proper bones of the nose. 6. More externally still, the roof of the orbit, bounded externally by the articulation of the frontal with the malar bone and the sphenoid, and by the sphenoidal tissm-e. 7. The anterior surface of the great wing of the sphenoid, which forms the largest portion of the external wall of the orbit ; 8. Out- side the orbit, the zygomatic arch. Inferior or Guttural Region. This region forms part of the pharynx and cavity of the mouth. It presents from be- hind forward, 1. A vertical portion ; 2. A horizontal portion ; and, 3. Another vertical portion. The rerticd portion {fig. 21) exhibits in the median line the posterior edge of the sep- timi narium, formed by the vomer ; the posterior extremity of the articulation of the vo- mer with the sphenoid (o, fig. 21) ; and the posterior nasal spine. On each side, the pos- terior opening of the nasal fosscE (/; o, y), which is quadrilateral, longer in its vertical than in its transverse diameter, and formed internally by the vomer, externally by the ptery- goid process (r), above by the sphenoid united ^\ith the palate bone, and below by the palate bone. More externally is the pterygoid fossa (r). formed by the sphenoid, and a small part of the palate bone. Still more externally, we find a deep fossa, or, rather, a large space bounded internally by the external plate of the pter-'goid process and the tu- berosity of the maxiHar." bone, and externally by the ramus of the inferior maxilla ; it is known by the name of the zygomatic fossa. The hcrizontal portion is the arch of the palate (?' x y, fig. 21). It is of a parabolic form, extremelj- rough, and, in the fresh state, covered by the palatine mucous membrane. It is constituted by the palatine processes of the maxillar}" bones (z), and by the horizontal portions of the palate bones {y), and presents, in consequence, a crucial suture, at the cen- tral point of which the vomer is attached : hence the piece of anatomical nicety which consisted in asking at what part of the skeleton it is possible to touch five bones at once with the point of a needle. The arch of the palate is pierced by several foramina ; we find here the inferior opening of the anterior palatine canal (1), which is single below, but double above, so as to open into each nostril separately ; the posterior palatine canals (2), which open at the posterior and external part of the arch of the palate ; and a groove, which nms along the external edge of the arch, and lodges the posterior palatine vessels and nerves at their exit from their canals. The third portion is also vertical : it presents, 1. In the median line, the suture of the two superior maxillarj' bones, the interval between the middle incisor teeth of each jaw, the sjTnphysis menti, and the genial processes. 2. On each side, the posterior surface of the alveolar border of the upper jaw, and the two rows of teeth which he across each other hke the blades of scissors in the middle, but meet posteriorly. 3. The posterior surface of the inferior maxilla, the internal oblique Line, the sub-lingual and sub-maxillary fossae, and, lastly, the base of the inferior maxilla. Zygomatic or Lateral Regions. These regions are bounded above and on the outside by the zygomatic arch ; above and on the inside by the transverse ridge which separates the temporal from the zygo- matic fossa. The}' present first a plane surface, formed by the ramus of the inferior maxilla ; when this part is removed, we obsers'e the zygomatic fossa, the superior wall of which is formed by the inferior surface of the great wing of the sphenoid, the anterior by the maxillary tuberosit)-, the internal by the outer plate of the pterj'goid process, and the external by the ramus of the inferior maxilla. The posterior and inferior walls are wanting. At the bottom of this fossa, between the maxillary bone and the anterior surface of the pterygoid process, is a large vertical fissure, named by Bichat the ptcry go-maxillary fissure ; this opening leads into a sort of fossa, denominated by the older anatomists iot- tom of the zygomatic fossa, and by Bichat sphcno-maxillary fossa, which it is important to study carefully, because five foramina or canals open into it, viz., three behind ; the fora- men rotundum, the vidian or pterygoid, and the pterygo-palatinc canals : a fourth on the in- side, the spheno-palatine ; and a fifth below, the superior orifice of the posterior palatine canaL Lastly, the spheno-maxillary fossa presents, at the union of its superior with its ante- rior wall, the spheno-maxillary fissure (fig. 21, before 3), which, on the one hand, makes an acute angle with the sphenoidal fissure (or foramen lacerum orbitale). and, on the other, a right angle with the pter)"go-maxillar\- fissure. The spheno-maxillarA.' fissure, which is traversed solely by some nerves and vessels, is formed internally by the max- illary and palate bones, externally by the sphenoid, and at its anterior extremity, which is very broad, it is completed by the malar bone. 62 OSTEOLOGY. Catiities of the Face. The study of those bones which we have been engaged in examining has made us ac- quainted with the existence of a great number of cavities, which considerably augment the size of the face, and multiply its internal surfaces, without proportionally increasing the weight. All the cavities of the face may be reduced to three principal : viz., 1. The orbital cav- ities ; 2. The nasal fossae, of which all the sinuses are dependances ; and, 3. The buc- cal cavitv, or mouth. The Orbits. These cavities, two in number, have the form of quadrangular pyramids, the axes of which, prolonged backward, would intersect each other in the situation of the sella tur- cica. It should, at the same time, be remarked, that the internal wall of the orbit does not participate in this obliquity, but is directed straight from before backward. We have to consider in each orbit, a superior, an inferior, an external, and an internal wall ; four angles which correspond to the intersection of these surfaces ; a base and an apex. The superior wall, or roof of the orbit, formed by the frontal bone in front, and by the orbital or lesser wing of the sphenoid behind, is concave, and presents from before back- ward, 1. Towards the outside, the lachrymal fossa. 2. On the inside, the slight depres- sion in which the pulley for the superior oblique muscle is attached. 3. The suture be- tween the lesser wing of the sphenoid and the orbital plate of the frontal.bone. 4. The foramen opticum. The inferior wall, or floor, forms a plane inclined outward and dovniward, and pre- sents from before backward, 1. The infra-orbital canal. 2. A suture which marks the union of the malar bone with the superior maxilla. 3. The orbital surface of the superior maxilla. 4. A suture which marks the union of the superior maxilla with the palate bone. 5. The orbital facette of the palate bone. The external wall, formed by the sphenoid and the malar bone, presents an almost ver- tical suture, which indicates internally the spheno-jugal suture. The internal wall, formed by the os unguis, the ethmoid, and the sphenoid, presents two vertical sutures : in front, that which unites the os unguis to the ethmoid, and be- hind, that which unites the ethmoid to the sphenoid. In front of these sutures is the lachrymal groove, formed by the union of the os unguis and the ascending process of the superior maxilla ; at the lower part of this groove we find the wide and very oblique ori- fice of the nasal canal or duct, which opens into the middle meatus of the nose, and es- tablishes a direct communication between the orbital and nasal cavities. Of the four angles, two are superior and two inferior. Of the two superior, one is in- ternal, the other external. The external superior angle presents the sphenoidal fissure behind, and the inner aspect of the spheno-frontal and fronto-jugal sutures. The internal superior angle presents the suture of union of the frontal bone with the ethmoid behind, and with the os unguis in front. The orifices of the two internal orbital foramina are seen in the situation of this suture. Of the two inferior angles, the external presents the spheno-maxillary fissure, a portion of the malar bone, and the opening of the jugal canal. The internal presents an uninter- rupted horizontal suture, which unites in front the maxillary bone to the os unguis ; more posteriorly, the maxillary bone, and then the palate bone, to the ethmoid. The bast of the orbit is cut obliquely from within outward, and from before backward ; its ver- tical diameter is, for the most part, quite perpendicular to the horizon, but is sometimes rendered slightly oblique by the projection of the frontal sinuses. At the apex of the or- bit is the union of the sphenoidal, the spheno-maxillary, and pterygo-maxillary fissures. The Nasal Fossa. These fossae are two in number, separated from each other by a vertical septum di- rected from before backward ; they are situated in the middle of the face, and are pro- longed into the interior of several of the bones of the face and cranium by means of the cavities called simis^s. To describe their situation more exactly, we may say that they are placed below the anterior and middle part of the base of the cranium, above the cav- ity of the mouth, between the orbits, and the canine and zygomatic fossae of each side. In order to have an exact idea, either of the dimensions or the shape of the nasal fossas, it is necessary to have recourse to horizontal and vertical sections, of which the latter should be made both from before backward and from side to side. With regard to their dimensions, the nasal fossae (see figs. 22 and 37) present, 1. A vertical diameter, larger in the middle than before or behind. 2. A transverse diameter much shorter than the other two, and gradually contracted* from the lower to the uppei part, on account of the obliquity of the external wall. 3. An antero-posterior diameter, which measures the whole of the interval between the anterior and posterior openings of the nares. * This progressive contraction of the nasal fosss from below upward, and the obliquity of the external wall, ought to be remembered during the iutruduction of instruments into the nose. THE FACE IN GENERAL. 63 The nasal fossae have a horizontal direction, but are nevertheless slightly inclined backward and downward ; this is caused by the sloping of the inferior wall and the ob- liquity of the body of the sphenoid, which forms part of the superior wall. They are irregular cavities, and have four walls ; a superior, an inferior, an internal, and an ex- ternal ; and two orifices, an anterior and a posterior. The superior wall or roof of the nasal fossa presents a concavity looking downward : it is formed, 1. In front by the proper bones of the nose, and in a small degree by the na- sal spine of the frontal bone. 2. In the middle, by the cribriform plate of the ethmoid. 3. Behind, by the body of the sphenoid. In this wall are two transverse sutures, name- ly : before, the suture which indicates the union of the nasal and frontal bones, and be- hind, that which marks the union of the ethmoid and sphenoid. At the back part of this wall the opening of the sphenoidal sinus is seen. The inferior wall ox floor, much broader but shorter than the superior, presents a trans- verse concavity ; it is directed from before backward, and slightly from above downward, which arrangement concurs in determining the obliquity of the nasal fossae. It is form- ed, in front by the superior maxilla ; behind, by the palate bone ; a transverse suture marks the union of these bones. Near its anterior extremity, and at the side of the me- dian line, the floor of the nasal fossae shows the superior orifice of each branch of the an- terior palatine canal {g, fig. 22, and o, fig. 37). The internal wall (see fig. 22) formed by the septum is generally flat, but sometimes concave or convex, according as it is bent to one or the other side.* We find here the suture which indicates the union of the vomer with the perpendicu- lar plate of the ethmoid (3 4, Jig. 22) ; the septum in the skeleton is deeply notched in front, and this notch (14 8), which is formed above by the perpendicular plate of the eth- moid, and below by the vomer, is occupied in the fresh state by a cartilage, called the cartilage of the septum. The external wall {fig. 37), remarkable for its anfractuosities, is formed by the ethmoid {b c), the OS unguis, the palate bone {m y), the superior maxillary j,- ^^ {s u o), and the inferior turbinated bone (d). It presents from above downward, 1. The superior turbinated bone, superior concha, or concha of Morgagni (b), in front of which is a rough square sur- face. 2. The superior meatus (between b and c), at the back part of which we find the spheno-palatine foramen (w), and the open- ing of the posterior ethmoidal cells. 3. Below the superior mea- tus, the middle turbinated bone, or middle concha (c). 4. Below, the middle meatus (between c and d), at the back of which is the open- ing of the maxillary sinus already described {see maxillary bone, fi.g. 25) ; and in front, the infundibulum {s, fig. 37), which leads into the anterior ethmoidal cells. 5. The inferior turbinated bone, or inferior concha {d). 6. The inferior meatus {m o), in which we find the inferior orifice of the nasal canal. The anterior and posterior openings of the nasal fossae have been described with the anterior and inferior regions of the face. General Development of the Face. The development of the face is not effected solely by an equable increase of its dimen- sions ; for certain regions are at one period of life predominant, at another period rela- tively smaller, which circumstances give rise to very characteristic differences of form at different ages. State of the interior Region of the Face at different Periods of Life. In the Fastus. — The upper part of the face shows a remarkable predominance, depend- ant upon the early development of the frontal bone and the great capacity of the orbits. The middle portion, or the superior maxilla, on the contrary, is very much contracted by the absence of the maxillary sinus and canine fossa ; the vertical dimensions of the superior maxilla and of the palate bone are so small, that the edge of the orbit and the alveolar border are almost contiguous. We should mention here that the prominence of the alveolar border, which still encloses all the germs of the teeth, is the principal cause of the absence of the canine fossa. Lastly, the inferior maxilla is contracted in its vertical diameter, like the superior, and, like it, presents a decided prominence in front, by reason of its enclosing the germs of the teeth in the alveoh. The inclusion of the dental germs also, by causing the alveolar border to project, produces a degree of obliquity downward and backward of the symphysis ; to these causes of the small extent of the vertical dimension of the face, we must add also the inconsiderable height of the ethmoid at this period. * Sometimes the deviation of the septum is sd considerable that the internal touches the external wall, and, consequently, there is great difficulty in the passage of the air. This circumstance has given rise in some cases to a suspicion of the existence of polypus. 64 OSTEOLOGY. The transverse dimensions of the face are very considerable at the level of the orbits ; at the lovi'er part of the face, on the contrary, they are proportionally much less than in the adult. The characteristics, then, of the face of the foetus are, 1. The smallness of its verti- cal dimension. 2. The predominance in size of its upper over its lower part. In the adult, the development of the maxillary sinus, the widening and vertical exten- sion of the alveolar arches, give to the face the expression which characterizes it at that period of hfe. In the aged, the loss of the teeth, and the disappearance of the alveolar edge, partly restore to the face the expression which it had in the foetus ; but the elongation and prom- inence of the chin, which, from the diminution of the vertical diameter, approaches the nose, and the symphysis of which is now oblique from behind forward and downward, impress upon it a peculiar character. The obliquity of the chin, just mentioned, is pre- cisely the reverse of that which exists in the foetus. State of the Lateral Regions in different Ages. These regions undergo the fewest changes of all ; for if, on the one hand, the devel- opment of the maxillary sinus tends to increase the prominence of the maxillary tuber- osity in the adult, on the other, the inclusion of the dental germs in the superior max- illa, during foetal life, compensates for the want of the sinus. State of the Posterior Region of the Face at different Ages. In the guttural portion, this region presents, in the foetus and the infant, the followmg circumstances : the posterior borders of the rami of the jaw are very oblique, instead of being almost vertical, as in the adult ; the pterygoid processes, and the posterior nasal openings, are also directed very obliquely downward and forward, instead of vertically, on account of the absence as yet of the maxillary sinus, which, during its development, carries them backward. From the obliquity of the posterior border of the ramus of the jaw, it follows that the articular surface of the condyle which surmounts it looks back- ward instead of upward. In the horizontal or palatine portion, the inferior region of the face has proportionally less extent from before backward than in the adult, on account of the obliquity of the pterygoid process, and the slight development of the maxillary sinus. We perceive, then, how great an influenee the varying conditions of these sinuses exercise over the whole configuration of the face, at the different periods of life. It may be easily conceived that the cavities of the face must undergo important chan- ges during these alterations in the shape of the face which we have been describing. The most remarkable is the tardy development of the nasal fossae compared with that of the orbits. It may even be said that they proceed in an inverse ratio. The orbital cavity, intended to receive the globe of the eye, which is already highly developed at the time of birth, is of great capacity. This magnitude it owes entirely to the rapid growth of the frontal and sphenoid bones ; because the malar bone and the superior maxilla con- tribute but little towards it, and the height of the ethmoid is so small, that the vertical diameter of the orbit, which depends upon that of the ethmoid, is less considerable than its transverse diameter. The nasal fossae, which are very small in the foetus, gradually acquire an increased extent of surface, by the growth in height of the ethmoid, the pal- ate bone, the superior maxillary, and the vomer, and by the augmented size of the turbi- nated bones ; and their surface is still farther extended by the enlargement of the max- illary, sphenoidal, and frontal sinuses, and the ethmoidal cells. The development of the frontal sinus, it may be observed, is owing chiefly to the separation of the two tables of the bone, the anterior of which is almost always thrown forward, the posterior remain- ing stationary. There are, however, some examples on record, in which it was evident that the sinus was formed almost exclusively by the retrocession of the posterior table. THE THORAX, OR CHEST. The Sternum. — Ribs. — Costal Cartilages. — The Thorax in general. — Development. The thorax {dupa^, the chest) is a sort of bony cage intended to contain and protect the principal organs of respiration and circulation. The parts which enter into its com- position are twelve dorsal vertebrae behind, the sternum in front, and twelve flexible bones named ribs, on each side. We have already described the dorsal vertebrae, and have now, therefore, only to notice the sternum and the ribs. The Sternum {a b c, fig. 38). The sternum, so named from the Greek word arepvov, the breast, is a kind of flat- tened, symmetrical, bony column, which occupies the anterior and middle part of the thorax. It is situated between the ribs, which support it like props. The clavicles, STERNUM. 65 and through them the upper extremities, rest upon its upper part as a basis, during their movements. The sternum is not immovably fixed in its place ; it is raised and de- pressed, as we shall point out in describing the mechanism of the thorax. The length of the sternum, which is proportionally smaller in the female than in the male, varies from 5^ to 7^ inches. At its upper part its breadth is from H to 2 inches ; it then becomes contracted, then again expands, and terminates below in a very nar- row extremity. Its thickness above is about 6 lines ; at its lower part it is much thin- ner, never exceeding 3 lines. With regard to figure, the sternum was compared by the ancients to the sword of a gladiator, and from this have arisen the denominations given to its various parts. The upper part (a), which is broadest, has been called the handle {manubrium) ; the middle part {h), the body {mucro) ; and the lower extremity (c), the point ; xiphoid appendix (pro- cessus ensiformis). This division of the bone into three parts has been retained by some modern anatomists, who describe the three pieces of the sternum separately as so many distinct bones. We shall adhere to it only, however, in speaking of the development of the bone. The sternum presents two surfaces, two borders, and two extremities. 1. The anterior or cutaneous surface is slighly convex, and forms an oblique plane do\vn- ward and forward ; it presents three or four projecting transverse hues, which are tra- ces of the union of the original pieces of the bone, and divide it into surfaces of unequal size. The hne which marks the union of the first two pieces of the bone is the most remarkable ; it causes a projection of variable size in different individuals, which has been sometimes mistaken for a fracture or exostosis. At the lower part of this surface, we find in some subjects a foramen which perforates the bone : sometimes, in place ot this foramen, there is a considerable aperture, to which much importance has been attached, as affording a proof of the primitive separation of the bone in the median line. The existence of this opening explains how purulent matter, deposited behind the ster- num, may in certain cases make its way outward without any absorption of the bone. The anterior surface of the sternum is covered by the skin, and an interlacement of very numerous aponeurotic fibres. 2. The posterior, mediastinal, or cardiac surface {a b c), is slightly concave from above downward, and presents, in young subjects, lines (e e) corresponding to those which occupy the anterior ; but all which, excepting the one between the first and second pieces of the bone, are eflfaced at a more advanced age. This surface is in relation with many organs contained in the chest, and especially the heart, in front of which the sterniun forms a kind of shield.* At the lower part of this surface are several nutritious foramina. 3. The borders, very thick and sinuous, present seven articular cavities (d d, &c.), sep- arated from each other by semilunar notches, which are longer above than below, where the facettes closely approach one another. The uppermost of these seven cavities is shallow, triangular, and at an early age becomes ingrained with the cartilage of the first rib ; those which follow are deeper, angular, and situated at the extremities of each of the lines (e e) above mentioned ; they are all intended to articulate with the cartilages of the first seven ribs. When examined in a dried specimen, they appear more angular and deeper in proportion to the youth of the subject. 4. The superior or clavicular extremity is the broadest and thickest part of the whole bone, presenting a notch, transversely concave, which bears the name of fourchette (/) of the sternum (or semilunar notch) ; on each side (g- g) is an oblong articular surface, concave from without inward, convex from before backward, articulated with the clav- icle, and surrounded with inequalities for the insertion of muscles and ligaments. It frequently happens that the two clavicular facettes are not at the same height ; a fact which was noticed by Morgagni, and which I have attributed to the unequal wearing of the two articular surfaces. 5. The inferior or abdominal extremity is formed by the xiphoid appendix (c) i^i(poc, a sword), called also xiphoid or ensiform cartilage, because it often remains cartilaginous to adult age. In length, shape, and direction, it presents numerous varieties ; it is fre- quently bifid, sometimes pierced by a foramen, and is accasionally bent forward, or to one side, and, in certain cases, much depressed : its summit gives attachment to an ap- oneurotic structure, called the linea alba ; behind, it indirectly corresponds with the stomach, which rests upon it when the body is placed in a prone position.! * This use of the bone is exemplified in many animals which are provided with a sternum, though they have no ribs ; for example, the frog^. This bone has attracted much of the attention of the modem transcendentalists. By them it is regarded as a vertebral column anterior to the intestinal canal in man, and inferior to it in the lower animals. Many ol them have conceived that they have found in it a cervical, a dorsal, and a lumbar region, &c., u, both), because they partake of the characters of both, viz., mobdity, and continuity of surfaces.! For the determination of the secondary divisions, regard has been had both to the shape of the articular surfaces, and to the movements of which the joint is capable. * AU the joints which possess the four movements of opposition necessarily possess those of ctrcumducHoa. t This kind of articulation was known to Galen, and named by him neuter, or doubtful articulation. 114 AETimOLOGY. Thus, the diarthroscs have been subdivided into, 1. Enarthroses, when the head of one bone is received into the cavity of another ; 2. Arthrodia, when the articular surfaces are plane, or nearly so ; 3. Ginglymus, when the joint is only capable of opposition, that is, of alternate movements in opposite directions in the same plane. This latter class is again subdivided into (a) angular ginglymus or hinge-joints, when the movements are an- gular, as- in flexion or extension : the angular ginglymus is said to be perfect, when these movements alone are possible, as in the elbow ; and imperfect^ when a slight degree of lateral motion may take place, as in the knee : (b) lateral ginglymus (or diarthrosis tro- choides), when rotation is the only possible movement. It also is subdivided into simple, when the bones touch only by one point ; and duuble, when they have two points of contact. The synarthroses, or immovable joints, have been divided, according to the nature of ' their articular surfaces, into, 1. Suture, when they are furnished with teeth, by means of which they are locked together, as in the squamous suture ; 2. Harmonia, when the sur- faces are nearly smooth, and are merely in juxtaposition ; 3. Gomphosis, when one part is implanted in another, as the teeth in the alveoli ; 4. Schindylesis, when a plate of one bone is received into a groove of another : in this way the osseous projection of the an- terior edge of the palate bone is attached to the opening of the maxillary sinus.* There are many advantages in the above classification, but many imperfections also, I would characterize, as especially objectionable, the class arthrodia, which comprises the most dissimilar articulations, as the shoulder-joint, the articulations of the lower jaw, of the wrist, of the bones of the carpus, and of those of the tarsus. We should also notice, as another cause of imperfection, the want of unity in the basis of the classifi- cation, which is sometimes founded upon the shape of the surfaces, sometimes on the motions. By adopting the shape of the articular surfaces alone as a basis, we shall find the ar- rangement of the ligaments and the motions to be in some measure dependant upon this. On this principle, we shall divide all the joints into three classes : 1. The diarthroses (SiapOpovf), or those which are formed by bones the surfaces of which are contiguous, but free ; 2. Synarthroses {avv, with), or all the joints whose surfaces are continuous ; 3. Amphiarthroses, or symphyses (uficpu, both), or those joints whose surfaces are partly contiguous, and partly continuous by means of fibrous tissue. I. Diarthroses. Characters. — Contiguous or free articular surfaces, shaped so as to fit exactly upon each other, and each provided, 1. With an incrusting layer of cartilage ; 2. With syno- vial membranes ; 3. With peripheral ligaments ; joints always movable. This class is divided into six subdivisions : 1. Enarthrosis. Characters. — A head, or portion of a sphere, more or less completely received into a cavity. Examples : hip and shoulder joints {fig. 76, and figs. 69 and 70). Ligaments. — A fibrous capsule. Motions. — In every direction ; viz., flexion, extension, abduction, adduction, circum- duction, and rotation. 2. Articulation by mutual Reception. Characters. — Articular surfaces, concave in one direction, convex in the direction per- pendicular to the first, and so fitted as to embrace each other reciprocally. Example ; articulation of the trapezium with the first metacarpal bone {m,fig. 75).| Ligaments. — Two or four ligaments, or, rather, an orbicular or capsular ligament. Motions. — In all directions, like the enarthroses, excepting rotation, 3. Articulation by Condyles, or Condylarthrosis. Characters. — An elongated head, or condyle, received into an elliptical cavity. Ex- amples : articulation of the forearm and hand (fig. 75), of the lower jaw and the temporal bo7ie (fig. 65). Ligaments. — Two or four ligaments. Motions. — In four directions; viz., flexion, extension, abduction, and circumduction, but no rotation. There are always two principal movements in these joints, and, con- sequently, two which are limited. 4. Trochlear Articulation, or Ginglymus. Characters. — A mutual reception of the articular surfaces. The pulley or trochlea belongs to this mode of articulation. Examples : the elbow (figs. 71 and 72), the knee ifig. 78), the joints of the phalanges (figs. 73 and 74). * [The rostrum of the sphenoid, and the descending plate of the ethmoid, are united in this manner to the vomer, and aflford, perhaps, a better example.] t The particle ha always siprnifies separation. I The cervical vertebrie of the swan present a beautiful specimen of this kind of articulation. This gives • 1 the movements of the neck of these birds that elegance and grace for which they are so remarkable. AUTICULATIONS OF THE VERTEBRAL COLUMN. 115 Ligaments. — Two lateral ligaments generally placed nearer the side of flexion than that of extension. Sometimes there are likewise anterior and posterior ligaments, but they are always weak, and are often replaced by tendons. Motions. — Two motions in opposite directions, 5. Trochoid Articulations.* Characters. — An axis received into a ring, which is partly osseous and partly fibrous. Examples : articulatmi of the atlas and axis (e. Jig. 64), of the radius and ulna (Jigs. 71 ahd 72). Ligaments. — An annular ligament. Motions.— Rotation. 6. Arthrodia. Characters. — Articular surfaces, plane, or nearly so.t Examples; articulations of the carpal and tarsal bones (figs. 75 and 84), and of the articular processes of the vertebra {g,figs. 61 and 63). Ligaments. — Fibres placed irregularly round the joint. Motions. — Gliding, II. Synarthroses. Characters^ — ^Articular surfaces armed with teeth or other inequalities, which are mu- tually dovetailed, and from which the name of suture is derived. Examples : articula- tions of the hones of the cranium {figs. 21, 22, and 23), Means of Union. — Remnant of the cartilage of ossification, which is gradually en- croached on during the progress of age. t There are no incrusting cartilages, synovial membranes, ligaments, nor motions, Monro enumerates seven kinds of sutures, and these might still be multiplied, if we regarded all the varieties presented by the articular surfaces. Three kinds may be ad- mitted with propriety: 1. Indented sutures; 2. Squamou.s sutures; and, 3. Harmonic su- tures ; the distinctions depending upon the articular surfaces being provided with teeth, or overlapping like scales, or being simply rough and in juxtaposition. These even are only unimportant varieties, Monro added the schindylesis, or ploughshare articulation of Keil. We shall content ourselves with simply mentioning it ; and we also omit the division gomphosis {-y6/x(poc, a nail), which is appropriated to the mode of implantation of the teeth; because the teeth are not bones, and are lodged in the jaw, not articulated with it III. jlmphiarthroses, or Symphyses. Characters. — Flat, or nearly flat, articular surfaces, which are partly in contact, and are partly continuous, by means of fibrous tissue. Examples : articulation of the bodies of the vertebrce {b,fig. 58), symphysis pubis (e,fig. 77), sacro-iliac symphysis {b,fig. 76). Means of Union. — Interosseous and peripheral ligaments. Motion. — Very slight, gliding ; an arthrodia is a necessary element of an amphiarthro- sis. Thus, in the symphysis pubis the bones are partly in contact, partly continuous. ARTICULATIONS OF THE VERTEBRAL COLUMN, Articulations of the Vertebra with each other. — Those peculiar to certain Vertebra. — Sacro- vertebral, Sacro-coccygeal, and Coccygeal Articulati-ons. — Articulations of the Cranium — Of the Face — Of the Thorax. The articulations of the vertebral column {figs. 58, 59, and 60) are divided into the extrinsic and the intrinsic. The first comprise the articulations of the vertebral column with the head, the ribs, and the ossa innominata. The intrinsic comprise the articula- tions of the vertebree with each other. These last are also divided into those which are common to all the vertebrae, and those which are peculiar to some. We shall describe each in succession. .Articulations of the Vertebrcs with each other. Mode of Preparation. — Remove completely all the soft parts which surround the ver- tebral column ; saw off vertically all that part of the head which is in front of the column, and separate the bodies of the vertebra from the posterior arches by dividing the pedi- cles. When the section reaches the axis, carry the instrument behind the superior ar- * The trochoid (rp/xw, to turn), or pivot-joint, corresponds to the simple or double lateral ginglymus of modem anatomists, or the rotatory diarthrosis of the ancients. t These articular surfaces are very variable in the arthrodial articulations. Sometimes they are angular, sometimes spheroidal. As respects the ligaments, they arc sometimes loose, sometimes firm. t Some anatomists have rejected this kind of articulation, adopting the opinion of Columbus, who affirms that there can be no joint where there is no motion. 116 ARTHROLOGY. ticular processes of this vertebra, and of the atlas, and behind the condyles of the occipi- tal cone : remove the spinal marrow and its membranes. In this way the vertebral col- umn will be divided into two parts : an anterior, formed by the series of the bodies of the vertebras, on which we find the anterior and posterior comvion ligaments, and the interver- tebral substances ; and a posterior, formed bV the series of laminae, and the articular and spinous processes. The intervertebral substances require a special preparation, which consists in making vertical and horizontal sections of a portion of the column, or which may be more simply effected by maceration in diluted nitric acid, which allows the bodies of the vertebras to be removed without injuring the intervertebral substance. The vertebrae are united, 1. By their bodies ; 2. By their articular processes ; 3. By thefr laminae ; and, 4. By their spinous processes. Articulation of the Bodies of the Vertebra. The bodies of the vertebrae are united together by amphiarthrosis. The arthrodial por- tion, or the contiguous surface, is represented by the articular processes. The articular surfaces are the upper and under surfaces of the body of each vertebra. It follows, from the concavity of these surfaces, that, instead of fitting each other exact- ly, they leave considerable lenticular spaces between them ; these appear to be the ves- tiges of the biconical cavity between the vertebrae of fishes. The depth of these spaces is not the same throughout the entire column ; it exactly measures the thickness of the intervertebral substance. By measurement, I have ascertained that the height of the in- tervertebral substance in the loins is one half of that of the bodies of the vertebra, in the back one third, and in the neck a little more than the half From the size of the bodies of the vertebra, it follows that the interval between the bodies is largest in the lumbar re- gion. The articular surfaces of the bodies of the vertebra are covered by a very thin layer of cartilage intermediate between the bones and the fibrous tissues. The means of union are of two kinds, as in all the amphiarthroses : 1 . They surround the joint ; 2. They proceed from one articular surface to the other : in one word, some are peripheral, and the others interosseous. 1. Peripheral Ligaments. — The most general idea which can be formed of these liga- ments is that of a fibrous sheath, surrounding the column formed by the bodies of the vertebrae, and uniting in one Avhole the different pieces of which it is composed. The part, of the sheath which covers the anterior aspect of the bones is called the anterior common ligament of the vcrtcbrcs ; and that which covers the posterior surface is called the posterior common ligament of the vertcbrcc. The anterior common vertebral ligament {a, figs. 58, 60) presents the appearance of a Fig. 58. white pearly-looking membrane stretched from the axis to the upper part of the sacrum. This ligament, which is thicker in the dorsal region than in the neck or the loins, is composed of three '/At^a very distinct parts : a thick one in the middle, and two lateral, ^,l_^ which are separated from it by a series of openings that give pas- sage to some vessels (see fig. 58). Its anterior surface is in con- tact with the organs of the neck, the thorax, and the abdomen, and united with them by very loose cellular tissue. The tendons of the longi colli and anterior recti muscles, and the pillars of the diaphragm, mix their fibres with this ligament. The psoae mus- 'i cles correspond to its lateral portions below. Its posterior surface adheres more closely to the intervertebral substances, and to the projecting rims of the bodies of the vertebrae, than to the trans- verse grooves of the bodies. This ligament is composed of sev- eral planes of fibres, of which the most superficial are the longest. The deepest pass from one vertebra to the next, and are lost on the periosteum. The superficial stretch over four or five vertebrae. Posterior common vertebral ligament (a, fig. 59). This is thicker than the anterior, but (Fig. 59.) has the same white pearly appearance. It conmiences at the oc- cipital bone, and terminates at the sacrum. It resembles a fibrous band, which expands at the intervertebral substances, and is con- tracted over the bodies of the vertebrae ; hence it has a regular fes- tooned appearance. Its posterior surface is united to the dura mater at its upper part, but is separated from it by a delicate cellular tis- sue throughout the rest of its extent. Its anterimr surface adheres intimately to the intervertebral substances ; it is separated from the middle of the bodies of the vertebrae by the veins, which pass from the interior of the bone into the vertebral venous sinuses which run along the edges of the ligament. Like the anterior com- mon vertebral ligament, it is composed of several planes of fibres, the posterior of which are the longest. It is formed of more com- pact tissue than the anterior. 2. The intervertebral substance or interosseous ligament (b, figs. 58, ARTICULATIONS OF THE VERTEBRAL COLUMN. 117 59, 60, and 68) consists of a kind of disc, which fills up the lenticular space between the bodies of the vertebrae, and might, with propriety, be called intervertebral disc. Each disc has the form of a double convex lens, and is so closely united by its upper and under surfaces to the corresponding vertebrae, that it is easier to break the bones than to destroy this connexion. Its circumference adheres to the anterior and posterior com- mon ligaments, and contributes to form the intervertebral foramina. In the dorsal region it also forms part of the angular facette wliich articulates with the ribs. The thickness of the intervertebral substance is not the same in all the regions of the spinal column, be- ing greatest at the lower parts. The proportion between the thickness of the discs and the bodies of the vertebrae is exactly measured by that of the intervertebral space, and is not the same in all the regions. In the lumbar region the thickness of the disc is half that of the corresponding vertebrae ; in the dorsal region it is a third ; and in the cervi- cal region it is a little more than a half* The intervertebral substance is not equally thick throughout. From its lenticular form, it must be thicker at the -centre than at the circumference ; in the neck and in the loins it is thicker in front than behind ; in the back the opposite prevails, and by this inequality the discs concur in producing the alternate curves of the vertebral column. Abnormal curvatures are in a great measure caused by unequal thickness of these dies, and I have often had opportunities to convince myself that compression of this substance on the side towards which the inclination takes place is the most common origin of the deformity. The thickness of the discs varies in different circumstances. Thus, after prolonged standing in the erect posture, the height of the body becomes diminished from eight to ten lines, which is owing to compression of the intervertebral substances. Each disc is composed of concentric layers ifigs. 60 and 68) closely pressed together at the circumference, but more separate towards the centre, where we find a soft spongy substance, moistened by a viscid fluid resembling synovia. This soft substance is nearer the posterior than the anterior aspect of the body of the vertebra ; it escapes, and forms, as it were, a hernia, when the parts are cut either horizontally or vertically. It varies much at different ages. It is moist, soft, spongy, and white in the infant and in youth, which accords with the suppleness of the vertebral column at that period of life. Where this substance is situated, we may inflate an irregular cellular cavity in it, which may be regarded as the rudiment of the large synovial cavity which these parts exhibit in fishes. M. PaiUoux believes that this cavity is lined by a synovial membrane. In old age it be- comes dry, friable, and yellowish, or brown. Monro attributes the elasticity of the ver- tebral column to the displacement of this soft central substance in the different move- ments ; for, according to his theory, the movements of the bodies of the vertebrae take place upon it as upon a movable pivot or a liquid fulcrum. The intervertebral substance is called a cartilaginous ligament by Vesalius ; by others, a cartilage ; and by Bichat, & fibro-cartilage ; but they evidently belong to the fibrous tis- sues. This may be shown by macerating a portion of the spinal column for some days, or even by rubbing the surface with a rough cloth. It will then appear that this pretend- ed fibro-cartilage is nothing more than a series of concentric fibrous layers, strongly com- pressed together ; that each layer is formed of parallel fibres, directed very obliquely from the lower surface of the vertebra above to the upper surface of the vertebra below, and regularly crossing with the fibres of the next layer {b', fig. 58). This regular cross- ing, which we shall meet with in other parts, is evidently very conducive to sohdity. Union of the Articular Processes. These articulations are arthrodia. Articular Surfaces. — The corresponding surfaces are covered by a thin layer of cartilage. The means of union consist of some irregular ligamentous fibres (d d, fig. 60), which sur- round the outside of the joint, and are more numerous in the dorsal and cervical regions than in the loins, the internal side of the articulation being occupied by the yellow liga- ment. These articulations are provided with synovial membranes of greater extent in the cervical than in the other regions. Union of the Lamince. p^- gO^ The spaces between the vertebral laminae are occupied by ligaments of a particular description, which are called yellow ligaments, ligamenta sub- jiava, on account of their colour. They are composed of two halves uni- ted at an angle like the laminae (c c,fig. 60). Their lower edge is implanted upon the upper edge of the laminae below, and their upper edge is attached to the anterior surface of the corresponding laminae. From this it fol- lows, that the height of the ligamenta subflava is much greater than would be necessary to reach from one lamina to another ; it is almost equal to that of the corresponding vertebral lamina. Their length is measured by that of the laminae, and is, consequently, * A curious preparation may be made by taking- away all the bodies of the vertebrae in a spine softened by nitric acid. A column then remains, formed by the series of discs, which may be compared with a column formed by the bodies of the vertebriE. 118 ARTHROLOGT. greater in the neck than in the back and loins. They are of ^eater thickness in the loins than in the back and the neck, and the thickest part corresponds to the base of the spinous process. There are also some re-enforcing bundles, which constitute a sort of median yellow ligament. Their anterior surface is separated from the dura mater by cel- lular tissue, and by veins. It is remarkable for its smooth and polished appearance. Their posterior surfaces are in contact with the vertebral laminae, which cover them al- most completely, except in the cervical region, where they may be seen between the lam- inae, when the head is slightly inclined forward ; this circumstance renders it possible for a penetrating instrument to enter between the cervical laminae, while it is almost impossible in the dorsal and lumbar regions. Structure. — These ligaments are composed of parallel vertical fibres very closely ar- ranged. They are extensible, and, when stretched, immediately recover themselves, and are therefore very elastic. They are as strong as ordinary ligaments. Their extensi- bility is brought into action during flexion of the vertebral column, and their elasticity during extension. They have great effect in maintaining the erect posture,, which would otherwise have required a constant expenditure of muscular power. Union of the Spinous Processes. The spinous processes are united by the supra-spinous and the fnter-spinous ligaments. The supraspinous ligament (d d, figs. 5& and 59) is a fibrous cord, which extends from the seventh cervical vertebra to the sacrum, along the summit of the spinous processes of the dorsal and lumbar vertebrae. This ligament can be only distinguished from the aponeurotic fibres, which are inserted into the spinous processes, by the longitudinal di- rection of its fibres. It is larger in the lumbar than in the dorsal region. It is expand- ed, and becomes even sometimes cartilaginous in the interval between the processes. It is inextensible. I regard a fibrous cord which extends from the seventh cervical ver- tebra to the external occipital protuberance as a continuation of the supra-spinous liga- ment ; it appears to be the vestige of the posterior cervical ligament, of quadrupeds, and is of considerable size in some subjects ; from its anterior surface, prolongations are given off to the spinous processes of all the cervical vertebrae, excepting the first.* The inter-spinous ligaments (e e, fig. 58) do not exist in the neck, where their place is supplied by small muscles ; they are very thin in the back, where each has the form of a triangle with the base looking backward. They are thick and quadrilateral in the loins. Their upper and lower edges are attached to the corresponding spinous processes. Their surfaces are in contact with the muscles of the vertebral grooves. M. Mayer speaks of synovial capsules, which he has met with between the lumbar spinous processes, and especially between the third and the fourth in this region ; these membranes are by no means constant. Articulations peculiar to certain Vertebrcs (Jigs. 61 to 64). Although the articulations of the atlas and of the axis, with the occipital bone, do not properly belong to the articulations of the vertebral column, yet the connexion between these articulations and that of the atlas with the axis is so intimate, that it is impossi- ble to separate them. We shall describe these three articulations in succession ; first noticing the articulation of the atlas with the occipital bone (occipito-atlantoid articulation}. Qccipito-atlanfoid Articulatioyi. Preparation. — Remove the part of the scull which is in front of the vertebral column, taking care to leave the basilar process. The muscles which surround the joint, being closely applied to the ligaments, should be very carefully detached. The atlas unites witli the occipital bone, 1 . By its anterior arch ; 2. By its posterior arch ; 3. By the base of its transverse processes ; 4. By its two articular surfaces. 1. The anterior arch of the atlas is united to the circumference of the foramen mag- y. gj num by two anterior occipito-atlantal ligaments. One of these, the superficial (a, figs. 61 and 64), is a very strong cylindrical cord situated in the median line, where it forms a very marked projection, and stretches from the basilar process of the occipital bone to the an- terior tubercle of the atlas. The other (5, fig. 61), which is deep-seated, is pretty thick, consists of several layers, and extends from the upper edge of the anterior arch of the atlas to the occipital hone. ^^^^/MMd^^ ^- Mo^t anatomists admit the existence of a liga- "" ment stretching from the posterior part of the foramens magnum to the upper edge of the posterior arch of the atlas, tlie posterior occipito-atlantal ligament {b, figs. 62 * This ligament is the result of the intersection of the aponournses, of the trapezius, splenius, 3ffc- just described has no effect in giving strength to the joint, it may be wondered that there is only one ligament for the articulation ; but it should be observed that, as the lower jaw is articulated in the same manner at both its extrem- ities, the external lateral ligament of the one exactly per- forms the functions of an internal lateral ligament to the other. The stylo-maxillary ligament {d, figs. 65, 66, and 67) ap- pears to me to hold the same place as the preceding ; it is a fibrous band extending from the styloid process to the angle of the inferior maxilla. It has no relation to the union of the articular surfaces. Its use appears to be that of giving attachment to the stylo- glossus muscle. Meckel calls it the stylo-mylo-hyoid ligament, 3. There are two synovial capsules in this joint, one on the upper and the other on the lower surface of the inter-articular cartilage {see fig. 65). Sometimes they commu- nicate by an opening in the cartilage ; the superior is looser than the inferior ; and thus the articular cartilage is more closely united to the condyle of the lower jaw than to the glenoid cavity. These two synovial capsules are in contact on the outside with the external lateral ligament, and elsewhere with a thin layer of fibrous tissue. Mechanism of the Temporo-maxillary Artieulation. In considering the action of this joint, the lower maxilla may be regarded as a ham- mer which strikes against the anvil represented by the upper jaw ; it is a double angu- lar lever, the axis of its motion being represented by a horizontal line that would pass through the middle of the rami. This articulation, which belongs to the class of condy- loid joints, has been ranged among the angular ginglymi, on account of the great extent of its movements in two opposite directions, during its elevation and its depression ; but it differs from them in being so constructed as to admit of slight lateral movements. It can also be moved forward and backward. 1. Depression. — In this movement each condyle rolls forward in its glenoid cavity, and then passes upon the transverse root of the zygoma, with a sudden jerk, which may be easily felt by placing the finger on the condyle while the mouth is being opened ; at the same time the angle of the jaw is moved backward. The condyle carries with it the inter-articular cartilage ; for the union of these two parts is of such a nature that, even in dislocation of the jaw, they are never separated. This depends not only upon the comparative tightness of the lower synovial capsule, but also on the mode of insertion of the external pterygoid muscle, which, being attached both to the neck of the condyle and the inter-articular cartilage, acts simultaneously upon them. The other parts of th& joint are affected in the following manner : During depression of the lower jaw, the ex- ternal lateral ligament is stretched ; the upper synovial capsule is distended behind, but readily yields on account of its laxity. The spheno-maxillary band, or internal lateral ligament, which is inserted at an almost equal distance from the condyle, which is car- ried forward, and from the angle of the jaw, which is carried backward, remains unal- tered, being neither stretched nor relaxed. When the depression is carried too far, either from the effect of a blow upon the bone, or during a convulsive yawn, the condyle is dislocated into the zygomatic fossa?, tearing the superior synovial capsule, and carrying with it the inter-articular cartilage.* This mode of displacement is impossible in the infant ; for, from the obliquity of the ascend- ing ramus of the jaw, the upper part of the condyle looks backward, and, in order to be * This luxation would be much more common were it not for the inter-articular cartilage, which, by al- ways accompanying the condyle, presents a smooth surface, over which the latter may g^lide in returning into its pr ippr cavity. R 130 ARTHROLOGY. luxated forward, would have to traverse a much larger space than it does even when the mouth is opened to the greatest possible extent. 2. In elevation, the condyle rolls backward, upon the transverse process, into the gle- noid cavity. The external lateral ligament is relaxed. The obstacles to too great an elevation are, 1. The meeting of the dental arches. 2. The presence of the vaginal process and the anterior wall of the auditory meatus ; and it is very probable that the extensive movements of the jaw in the old subject, when the teeth are lost, are permit- ted by the size of the glenoid cavities. Without that portion of the glenoid cavity which is behind the fissure of Glasserus, the toothless alveolar edges of the aged could never be brought in contact. The forward motion is not, like the preceding, the motion of a lever in which the jaw turns upon its axis ; it is a horizontal nriovement, in which the condyle is brought under the transverse root of the zygoma. A preliminary and indispensable condition to this movement is a slight depression of the whole of the lower maxilla. In this movement all the ligaments are stretched ; if it were carried too far, the coronoid process would strike against the bone in the zygomatic fossa, and this circumstance would prevent the possibility of luxation of the condyle. The backward motion requires no special remark. The lateral movements differ from the preceding in the mechanism by which they are effected. In the first place, the whole bone does not move from its place. One of the condyles alone escapes from its socket, while the other remains in the glenoid cavity. The bone, therefore, turns upon one of the condyles as on a pivot. The external lateral ligament of that articulation in which the condyle moves is much stretched. The lateral motions vv^ould have been much more extensive had not the two condyles mutually obstructed each other in all movements but that of depression, by reason of their opposite directions. This may be shown by sawing a maxilla through the middle, and moving each of the halves. Moreover, the styloid and vaginal processes, and the spine of the sphenoid, prevent displacement inward. Articulations of the Thorax. Tlie articulations of the thorax comprehend, 1 . The costo-verteoral articulations ; 2. The cliondro-sternal ; 3. The articulations of the cartilages of the ribs with each other ; 4. The junction of the cartilages and the ribs. The Costo-vertehral Articulations {figs. 58 to 60, and 68). Preparation. — Saw the ribs across at their posterior angles. Remove with care the pleura and the subjacent cellular tissue in front, and the muscles of the vertebral grooves behind. After having studied the superficial ligaments, expose, 1. The costo-transverse interosseous ligament by a horizontal section of the rib, and the transverse process to which it is attached ; 2. The costo-vertebral interosseous ligament by a similar horizon- tal section, including one vertebra and one rib, and passing above the angular part of the joint. This last ligament may be also exposed by a vertical section of the rib and the two vertebrae with which it is connected. The costo-vertebral articulations have some characters which are common to them all, and others that are peculiar to a few. General Characters of the Costo-vertebral Articulations. Articular Surfaces. — In this joint, the head of the rib is applied to the angular surface formed by the two half facettes (//, fig. 58) upon the sides of the bodies of the dorsal vertebrae, so that each rib is articulated with two vertebra {costo-vertebral articulation, fropcrly so called) ; and, in addition, the tubercle of the rib is applied to the facette {g,figs. 58, 60, and 68) on the fore part of the transverse process {costo-transverse articulation). With regard to the costo-vertebral articulation, it is to be remarked, 1. That it affords an example of a projecting angular facette received into a retreating angular facette, which has given rise to the mistaken notion that this joint is an angular ginglymus ; and, 2. That in each articulation the lower half facette is twice as large as the upper. The surfaces of the costo-transverse articulation are, a convex facette belonging to the tubercle of the rib, and a concave one belonging to the tranverse process. Sabatier af- firms that the articular surfaces of the transverse processes look forward and upward in *he upper vertebrae, and forward and downward in the low^er, and directly forward in those which occupy the middle of the column. This arrangement has been referred to in explanation of the mechanism of the dilatation of the thorax, by depression of the low- er, and elevation of the upper ribs ; but this explanation is unfounded. In addition to the costo-vertebral and costo-tranverse articulations, the neck of the rib (c, fig. 68), without being in immediate contact with the tranverse process, is, in some degree, united with it by symphysis. Means of Union. — These joints are examples both of symphysis and arthrodia. Some of the ligaments are external to the articulation, the remainder are interosseous. The ligciinciits external to the articulation arc, the anterior costo-vertebral or stellate lig- ARTICULATIONS OF THE THORAX. 131 ament, the superior and the inferior ligaments, the posterior costo-transverse, and the superior costo-transverse. 1. The anterior costo-vertebral, or stellate ligament {I, Jig- 58), arises from the two verte- bra with which the rib is connected, and from the corresponding intervertebral substance. From these points its fibres converge, and are inserted in front of the extremity of the rib. 2 and 3. Besides the stellate ligament there are two small ligamentous bundles, a su- perior and an inferior, which extend from each of the vertebrae, concurring to form the articulation, to the extremity of the rib. 4. The posterior costo-transverse ligam£nt {m,Jig. 59 : transverse ligament of Boyer, poste- rior costo-transverse ligament of Bichat) is a fibrous band stretched from the apex of the transverse process, in an obUque direction, to the non-articular portion of the tubercle of the rib. 5. The superior costo-transverse ligament {n, figs. 58, 59 : costo-transverse of Boyer, infe- rior costo-transverse of Bichat) consists of a band, which arises from the lower edge of each transverse process, passes obliquely, and is inserted, not into the rib, which articu- lates with that process, but into the upper edge of the neck of the rib below. At the place of this insertion, we always find a crest or spine. This ligament is sometimes di- vided into two or three bundles ; it forms the continuation of a thin aponeurosis, which covers the external intercostal muscle, and completes the external wall of the opening through which the posterior' branches of the intercostal vessels and nerves are transmit- ted. This ligament is interposed between the anterior and posterior branches of these vessels and nerves. The interosseous ligaments are two in number. 1. A costo-vertebral interosseous ; 2. A costo-transverse interosseous. 1. The costo-vertebral interosseous ligament {o,fig. 58) is a small bundle of fibres, very short and very thin, extending horizontally from the projecting angle on the head of the rib to the retreating angle of the vertebrcil facette, where it is continuous with the inter- vertebral substance. 2. The costo-transverse interosseous ligament {a, fig. 68) is formed by some ligamentous bundles intermixed with reddish adipose tissue, which stretch from the anterior surface of the transverse process to the pos- terior surface of the neck of the rib. An idea of the strength of this ligament may be formed by attempting to separate the rib from the transverse process, after the anterior costo-ver- tebral and the posterior costo-transverse ligaments have been divided. There are three synovial capsules in the articulations of the ribs with the vertebrae : one between the tuberosity and the transverse process, and two small ones for the two surfaces which are separated by the costo-vertebral interosseous ligament. Characters peculiar to certain Costo-vertebral Articulations. The articulations of the first, eleventh, and twelfth ribs alone present peculiarities. 1. Costo-vertebral Articulation of the First Rib. — The rounded head of the first rib is re- ceived into a cavity on the side of the body of the first dorsal vertebra ; the articulation is, therefore, a species of enarthrosis ; there is neither a costo-vertebral interosseous lig- ament, nor a superior costo-transverse ligament ; the synovial membrane is much looser than in the corresponding articulations. 2. The costo-vertebral articulations of the eleventh and twelfth ribs present the same char- acters as the preceding in this respect, that the articular cavity for the head of the bone is situated upon one vertebra alone. The head of the rib is flattened, or very slightly convex, and there is no interosseous costo-vertebral ligament. The superior costo-trans- verse ligament is much broader and stronger than in the other articulations. As the eleventh and twelfth ribs have no tuberosities, and the transverse processes of the cor- responding vertebras are but little developed,* it follows that there is no costo-transverse articulation ; but yet there is a costo-transverse interosseous ligament. All -these liga- ments are much more loose than in the other articulations. TTie Chondro-sternal Articulations {fig. 69). There are seven in number on each side, formed by the internal angular end of the cartilages, which are received into the angular cavities on the side of the sternum. The means of union are, 1. A radiated or anterior chondro-sternal ligament {a, fig. 69), which is tolerably strong : it crosses in the median hue with the corresponding ligament of the opposite side, and is blended both with the periosteum and the aponeurotic insertions ot the greater pectoral muscles, in the thick fibrous layer which covers the sternum ; 2. Two small ligaments, a superior and an inferior ; 3. A radiated or posterior chondro-sternal ligament, much weaker than the anterior. The existence of a synovial membrane is * Sometimes, however, the transverse process of the eleventh dorsal vertebra is enlarged, and articulated to the eleventh rib. 133 ARTHROLOGY. merely inferred from analogy, for it cannot be demonstrated. {Vide Articu;.ations in GENERAL.) The first, second, sixth, and seventh chondro-stemal articulations present some pe- culiarities. 1. The cartilage of the first rib is sometimes continuous with the sternum, and is sometimes articulated like the cartilages of the other ribs. I found in one sub- ject the first rib excessively movable, because its cartilage, instead of being continuous with the sternum, had its upper edge applied to the side of that bone to which it was united by ligaments, and was ultimately articulated by a narrow extremity immediately above the second rib. 2. The second cartilage (b) is much more angular at its inner ex- tremity than any of the others ; it is received into the retreating angle formed by the union of the first two pieces of the sternum. Sometimes there is an interosseous liga- ment in this joint, running from the angle of the cartilage to the bottom of the cavity, and there are then two synovial capsules : in other cases there is only one (c), but it is always more marked than in the other joints. 3. The articulations of the sixth and sev- enth cartilages, besides the anterior ligaments, have also a chondro-xiphoid ligament more or less strong, which crosses with the ligament of the opposite side in front of the ensi- form cartilage and the lower end of the sternum. Sometimes this ligament only exists for the seventh cartilage ; it is intended not only to strengthen the chondro-stemal ar- ticulations, but also to maintain the xiphoid appendix in its place. The Chondro-costdl Articulations. The cartilages are immovably united to the ribs ; the anterior extremity of the rib is hollowed to receive the external end of the cartilage : there is no ligament. The perios- teum is the only bond of union between the costal cartilage and the rib, as in the articu- lations of the cranial bones. The Articulations of the Costal Cartilages. The first, second, third, fourth, and fifth costal cartilages do not articulate together, unless the aponeurotic laminae, sometimes very strong, which form the continuation of the external intercostal muscles, and occupy the whole length of the cartilages,- be con- sidered as uniting media. The sixth, seventh, and eighth cartilages, frequently the fifth, and sometimes the ninth, present true articulations. Some cartilaginous processes arise from the neighbouring edges, and come in contact with each other : there are sometimes two articular facettes between the sixth and the seventh cartilages. The means of union are some vertical fibres united in bundles so as to form two ligaments, the one anterior and thicker, the other posterior and thinner. There is a much more distinct synovial membrane than in the chondro-stemal articulations. The seventh, eighth, and tenth cartilages haye not always articulq.r facettes, but are simply united by vertical ligaments. Mechanism of the Thorax. As the thorax performs the double office of protecting the organs which it encloses, and of assisting by its movements in the function of respiration, we must consider its mecha- nism with, reference to bpth these ends. Mechanism of the Thorax for the Protection of the contained Organs. 1. The following is the mechanism by which the thorax is enabled to resist pressure or violent blows directed from before backward. The sternum is supported by the four- teen ribs, which, like buttresses, oppose their united strength to any causes of displace- ment or fracture ; it is therefore very rare to find the sternum driven backward, and all the ribs broken, however great the violence may have been. The elasticity of the car- tilages and of the ribs, and the number of articulations which exist in the thorax, are all circumstances most favourable to strength, because they diminish the intensity of exter- nal blows by neutralizing a certain amount of impulse : yet I have met with one case in which all the sternal ribs were broken by a fall, as completely as if the anterior wall of the thorax had been divided for an anatomical preparation. I should remark, also, that the flexibility of the ribs and their cartilages permits great depression of the sternum without fracture ; and this explains the possibility of contusion, and even mpture of the heart, lungs, or great vessels, without fracture of the bones of the thorax. The degree of resistance of the anterior wall of the thorax may be also considerably varied by the state of relaxation or contraction of the muscles, which should be considered as active and contractile supports to the arch, of which the stemum forms the key-stone. 2. In the case of lateral pressure or blows, the thorax resists, like an arch, the vault of which is represented by the convexity of the twelve ribs, and its pillars by the ster- num in front and the vertebrae behind. External violence cannot act upon the whole side of the chest at once, as it does upon the front, and therefore the ribs offer a more partiaJ resistance laterally, and are accordingly much more easily broken by -direct blows. In this case, also, as in the former, when the elevator muscles of the ribs are in action, the resistance is considerably increased ; and individuals have been then able to bear ARTICULATIONS OF THE RIBS. 133 enonnous weights, ■which would, in all probability, have fractured the ribs, had the mus- cles been reliaxed. What has been said above of the manner in which the ribs withstand violence is not however, applicable to the false ribs, which, having no fixed point on the sternum, are depressed into the abdominal cavity. Mechanism of the Thorax with reference to Mobility. The thorax is not equally movable throughout. The middle portion, which corresponds to the heart, and which is formed by the sternum and vertebral column, has a very limit- ed degree of mobility, while the sides which correspond to the lungs are endowed with the power of extensive motion. The movements of the thorax consist of alternate dilatations and contractions, from which its mechanism has been compared to that of a pair of bellows. They result from the motions which take place at the costo-vertebral and chondro-sternal articulations, and at the articulations of the cartilages with each other. We cannot explain the move- ments of each rib, and of the entire thorax, without first analyzing the motions at each of the above joints, Movements of the Costo-vertebral Articulatiojis. These articulations permit only very limited gliding motions. In these movements, '*ach rib represents a lever, which moves upon the fulcrum afforded by the vertebral col- umn. It may describe the movements, 1 . Of elevation ; 2. Of depression ; 3. It may be carried inward ; 4. It may be carried outward ; 5. It may perform a revolving motion around the cord of the arc which it represents. These different movements, which are very obscure in the immediate neighbourhood of the joint, are more evident the greater the distance is from the posterior end of the rib. The means of union between the ribs and vertebrae are so strong, that luxation of the ribs is impossible ; and the causes which would tend to produce it would break the neck of the rib. Each rib is capable of performing all these motions ; but, as they vary in degree in the •difierent ribs, we must examine them comparatively in the series of costo-vertebral ar- ticulations. The eleventh and the twelfth ribs possess the most extensive power of motion. They owe this, 1. To the circumstance of their being scarcely at all united to the very small transverse processes ; 2. To the loose state of their ligaments ; and, 3. To the almost perfect flatness of their articulated surfaces. The extent of their move- ments inward and outward should also be noticed. We shall find these movements but less pronounced, in the eighth, ninth, and tenth ribs, they scarcely exist in the first seven ribs.. The shape of the head of the first rib is undoubtedly favourable to mobility, and has suggested the idea that it is the most movable of all the ribs ; but the articulation of its tubercle with the transverse process of the first dorsal vertebra, and the tightness of its ligaments, sufficiently explain why this opinion is erroneous. The movements which take place in the second, third, fourth, fifth, sixth, and seventh costo-vertebral articulations do not differ sufficiently to require any special mention. Movements of the Choniro-sternal Articulations. In these articulations there is even less gliding than in the preceding. The anterior ■extremity of the first rib, or, rather, of the cartilage which forms its continuation, is the least movable of all ; more commonly, it is completely fixed on account of its continu- ity with the sternum, a circumstance which neutrahzes the favourable conditions for mobihty presented by its posterior extremity. The eleventh and twelfth ribs, whose anterior extremities are connected only to soft parts, are the most movable. The mo- bility of the ribs in front decreases from the lower to the upper part of the thorax ; to this rule the second rib is an exception, chiefly on account of the two synovial mem- branes at its chondro-sternal articulation, which permit of greater motion. This, how- ever, is variable, depending as it does on the absence or presence of an articulation be- tween the first and second bones of the sternum, and upon the more or less variable mode in which these two pieces are articulated. Movements of the Cartilages upon each other. The movements of this kind are restricted to the sixth, seventh, eighth, ninth, and tenth ribs, the cartilages of which alone are articulated to each other. They are simple, gliding motions, and this gliding is proportionate to the looseness of the ligaments. Hence it follows, that the ribs which I have just mentioned are always moved simul- taneously as they glide slightly upon each other ; whereas the superior ribs are inde- pendent in their movements. This independence, however, is not as great as it might appear at first sight, on account of the interosseous aponeuroses, the interosseous mus- cles, and the superior transverso-costal ligament, which is very narrow above, and forms below large and shining aponeurotic laminae. It results, from the facts above stated, that the most movable ribs are the twelfth and the eleventh, which may be moved upward and downward, and, at the same time, 134 AETHBOLOGY. enjoy, in the highest degree, the movements of projection inward and outward ; that the first rib is the least movable of all ; that the superior ribs may be moved isolatedly ; that the inferior ribs are moved all together. Movements of the entire Rib. Since we now know all the elements of which the movement of the ribs is composed, we shall easily comprehend the play of each of these bones isolatedly, and the play of the whole thorax. The movements of the entire rib are composed, 1. Of those which take place at the sternal and vertebral articulations ; and, 2. Of those which result from its own flexibility and elasticity. "We shall endeavour to reduce the subject to its most simple elements. Let us suppose, then, that the ribs are straight, inflexible levers ; from their oblique po- sition in reference to the vertical axis of the spinal column, their elevation will increase the width of the intercostal spaces ; for it is a law of physics, that hnes which are ob- lique with regard to another line, and parallel to each other, become farther separated when they are placed perpendicularly to that line. Hence it foUows, that the contact or the overlapping of the ribs is impossible during the movement upward of these bones. A second effect of the elevation of this oblique lever is the advancement of the anterior extremity of the rib, which movement increases proportionately to the length of the le- ver ; hence results an increase of the antero-posterior diameter of the thorax. But as the ribs are curved levers, and not rectilinear, in assuming the horizontal position, their concavity must come to be directed perpendicularly to the median plane formed by the mediastinum. It may be shown, geometrically, that the concavity of an arc which falls perpendicularly upon a plane includes a greater space than when it falls obliquely. From the elevation of the ribs results, therefore, an increase of the transverse diameter of the thorax.* The arcs of the ribs, however, have not all the same curvature : each rib has its own peculiar perimeter, and it may be proved that the more curved the rib, the greater is the projection outward which it forms when elevated. Lastly, as in some ribs the upper border forms the segment of a smaller circle than the lower, the movement of projection outward is proportionally greater in these than in the other ribs. This assertion may be experimentally proved by imitating the movements of elevation and depression on the second rib.t The greater the disproportion between the curvature of the superior and that of the inferior border, the more marked will be the projection outward. This is the reason why the elevation of the second and third ribs, when they are bent at once, hoth by their faces and their borders, produce such a remarkable increase of the thoracic capacity. If the ribs and their cartilages were inflexible levers, the movements of elevation would be much restrained ; but, by a mechanism, of which we find no instance elsewhere, the flexibility of these levers introduces into the problem a power which is most impor- tant and very variable, so that their movements are much more marked than would arise from the mobility of the articular surfaces. These movements cannot be determined by calculation. Now this flexibihty, whence results a movement of torsion in the rib, or of rotation round an axis, represented by the cord of the arc which the rib forms, is in a direct ratio to the length of the ribs and their cartilages, and the flexibihty of either. Indeed, the movements of the ribs are much more considerable in children and women than in old men ; and the deficiency of mechanical power in regard to breathing, which corresponds to the smallness of the power of locomotion in old men, explains the sever- ity which characterizes asthma and all the diseases of the lungs at this age. We shall now examine the movements of the thorax in general Movements of the Thorax in general. The general movements of the thorax, which result from those partial motions we have been engaged in considering, are, I. A movement of dilatation, corresponding with the act of inspiration ; 2. A movement of contraction, corresponding with that of expi- ration. 1. The dilatation of the thorax is caused by the elevation of the ribs. By this move- ment, the anterior extremity of each rib is carried forward, and the antero-posterior di- ameter of the thorax is thus increased ; the most eccentric portion of the rib is carried outward, and the transverse diameter of the thorax is thereby augmented. There is a sort of antagonism between the upper and lower part of the thorax, with regard to the direction in which the increase of its capacity is effected : in the upper part the trans- verse diameter is most augmented ; in the lower, the antero-posterior diameter. The most movable point in the superior ribs is at the centre of the curvature : the most movable point of the inferior ribs is at the junction of the ribs and the cartilages. But the columns to which the extremities of the ribs are attached are not equally mo- * Borelli, t. ii., p. 177. t From measurements taken by Haller, it appears that the second rib is the most elevated during inspira- tion ; and if this may be doubted, it cannot be demed that its eccentric movement is greater tb.an that of auj of the other nbs. ARTICULATIONS OF THE SHOULDER. 135 vable : if the posterior extremity is fixed, the anterior extremity may be moved from its place. This circumstance does not oppose the transverse enlargement being produced by the elevation of the arcs of the ribs, though it introduces a new condition into the problem, to wit, the elevation of the anterior column or the sternum. So long as the movement of elevation of the ribs is limited to the costo-vertebral articulations and a slight flexibility of the ribs and their cartilages, the sternum scarcely participates in the motion •, but when the elevation is carried beyond a certain point, when all the powers of inspiration are in activity, when there is an integral movement of the thorax, which has not been sufficiently distinguished from the partial movement, then the sternum is carried upward with the ribs, then the first two ribs, which we have represented as the essential props of the sternum, are themselves elevated, and this elevation must be the same as that of all the other ribs, and must, therefore, be proportionately more consider- able. Does the sternum perform an angular motion during its elevation, as Haller ima- gined 1 On placing the thorax between two parallel planes, and on executing a forci- ble movement of inspiration, we feel at the inferior portion a pressure, which seems to indicate, in this inferior portion, a movement of projection forward. The lever formed by the inferior ribs being longer, it seems, indeed, as though there ought to be an angular motion ; but it will be observed that there is no pression tending to diminish the curve which is described by the ribs ; that therefore the two halves of the arc which the curves represent do not recede from each other, and that the powers of elevation simply draw all the anterior extremities of the ribs upward ; indeed, the sternum is simply elevated near the cervical region, retaining its primitive direction, as Borelli had previously well pointed out ; considering the flexibility of the cartilages, the angular motion is almost impossible. The enlargement of the thorax is effected by the elevation of the ribs, and takes place either transversely forward or backward. The enlargement of the thorax in a vertical direction is produced by a totally diflferent mechanism, the contraction of the diaphragm, of which we shall speak hereafter. 2. Let us now speak of the contraction of the thorax. This contraction is effected by the depression of the ribs. In the first stage, the contraction is passive, because it re- sults from the elasticity of the cartilages, which, on account of the relaxing of the eleva- tor muscles, cease to be maintained in a state of torsion, and therefore react and restore the rib to its primitive position, so that the rib and cartilage, according to the ingenious remark of Haller, are alternately the cause of their respective movements. It ought to be remarked, that the movement of depression is much more limited than the movement of elevation ; and I may justly regard the superior transverso-costal ligament as being destined to impose particular limits to that depression, during which the intercostal spaces are narrowed. We may regard as a powerful auxiliary of the depression and the contraction of the thorax the movement of projection inward, especially in the last five ribs, which are in certain respects depending upon each other. This movement of pro- jection invi'ard is opposed to the transverse dilatation or the movement of projection out- ward, which takes place especially at the superior portion, as has been seen above, and as is shown every day by the use of the corsets. Afterward we shall see that the great inspiratory powers, or powers of elevation, occupy the superior portion of the thorax, as the great expiratory powers occupy the inferior portion. To the integral elevation of the thorax, in the most considerable degree of contraction, corresponds an integral de- pression, and this depression of the ribs is directly produced by muscles which bear the name of expiratory muscles. ARTICULATIONS OF THE SUPERIOR OR THORACIC EXTREMITIES. Articulations of the Shoulder. — Scapulo-humeral. — Humero-cubital. — Radio-cubital. — Radio- carpal.— Of the Carpus and Metacarpus. — Of the Fingers. Articulations of the Shoulder. The two bones of the shoiilder are articulated together ; the clavicle is also united ■with the sternum and the first rib. There are, therefore, two orders of articulations : 1. The intrinsic articulations of the shoulder, viz., the acromio- and coraco-clavicular artic- ulations ; 2. The extrinsic, or the sterno- and costo-clavicular. The Acromio- and Coraco-clavicular Articulations. i The clavicle is articulated, 1 . With the acromion by its external extremity, the acro- mio- clavicular articulation ; 2. With the coracoid process by its lower surface, the coraco- clavicular articulation. Preparation. — Remove the skin, the cellular tissue, and the muscles which surround the joints ; separate the acromion from the spine of the scapula ; remove, in succession, the different layers of the superior acromio-clavicular ligament, so as to be able to judge of its thickness. Make a vertical section of the acromio-clavicular articulation, so as to be able to observe the thickness of the ligaments and articular cartilages. 136 ARTHROLOGT. Fig. 69. u /7 Acromio-clavicular Articulation (fig. 69). Articular Surfaces. — The clavicle and the acromion process oppose to each other a plane, elliptical surface, with its greatest diameter directed from before backward. The articular surface of the clavicle looks somewhat obliquely downward and outward, the acromial facette looks obliquely upward and inward. The extent of these surfaces va- ries greatly in individual cases, dependant on the degree of exercise to which the joint is subjected.* Means of Union and Provision for facilitating Motion. — These are, 1. An inter-articular cartilage, first pointed out by Weitbrecht ; it is by no means constant, and, when it does exist, occupies only the upper half of the articulation. 2. An orbicular fibrous capsule (d, fig. 69), which is very thick above and behind, and very thin below. It is composed of distinct bundles, which are much longer behind than in front, and are strengthened by some fibres belonging to the aponeurosis of the trapezius muscle ; it is not only attached to the upper edge of the articular surface, but also to some inequalities upon the upper surface of the acromion. It is composed of several layers, the deepest being the shortest. 3. A synovial membrane, of a very simple construction, supported below by adipose tissue. Coraco-clavicular Articulation {fig. 69). There can be no doubt concerning the existence of an articulation, where two surfaces are contiguous, and capable of a gliding motion on each other ; one of them, the coracoid, being almost always covered with carti- lage and a synovial membrane ; and the other, the clavicular, presenting some- times a considerable process for this ar- ticulation. The means of union are two ligaments, or, rather, two distinct ligamentous bun- dles, a posterior and an anterior : they are called coraco-clavicular. 1. The posterior ligament, named also the conoid or radiated (c, fig. 69), is trian- gular, and directed vertically ; it com- mences by a narrow extremity, at the base of the coracoid process, and is inserted into a series of tubercles on the posterior edge of the clavicle, near its outer extremity. 2. The anterior ligament (/) {trapezoid ligament of Boyer) arises from the internal edge of the coracoid process, and from the whole extent of the rough projection on the base of this process : from this it proceeds very obliquely to the ridge on the lower surface, near the external end of the clavicle. The two coraco-clavicular ligaments are continuous, and can only be distinguished by the direction of their fibres. We might with propriety range among the means of union of this joint an aponeurotic lamina, to which much importance has been attached in surgical anatomy, and which is known by the name of the costo-clavicular aponeurosis, or costo-coracoid ligament. It may be-easily felt under the pectoralis major in emaciated individuals : it extends from the inner edge of the coracoid process to the lower surface of the clavicle, and converts the groove for the subclavius muscle into a canjd. Mechanism of the Acromio- and Coraco-clavicular Articulations. The acromio- and coraco-clavicular articulations perform well-marked gliding move- ments ; and, in addition, the scapula rotates forward and backward upon the clavicle to a considerable extent. In order to have a correct idea of these motions and their mecha- nism, it is necessary to procure a shoulder with the ligaments still attached, and to ro- tate the scapula backward and forward. It will be then seen that the scapula turns round an imaginary axis passing through its middle. The looseness of the posterior half of the orbicular and of the coraco-clavicular ligaments permits this rotatory motion ; of the two «oraco-clavicular ligaments, one limits the rotation forward, while the other, which, as we have observed, runs in an opposite direction, limits the rotation backward. Although these motions are pretty extensive, they never give rise to dislocation, which can only be produced by falls on the top of the shoulder, the coraco-clavicular ligaments being lacerated if the luxation be complete. Incomplete luxations may, however, take place without laceration of these ligaments. The Sterno-clavicular Articulation {fig. 69). The articulation of the inner end of the clavicle is composed of the sterno-clavicular and the costo-clavicular articulations. Preparation. — Saw through the clavicles vertically at their middle, and also the first ribs at corresponding points ; and meet these two sections by a horizontal division of the * In individuals who have exercised the upper extremilies very much, these surfaces are uneven, and unequally incrusted with newly-formed cartilage. ' • ARTICULATIONS OF THE SHOULDER. 137 Sternum. In order to see the interior of the sterno-clavicular joint, open the fibrous cap- sule along the edge of the sternum above, or, rather, make a horizontal cut, which wOl divide it into two parts, an upper and an under. In order to examine the costo-clavicular articulation, open the synovial membrane be- hind. The sterttO'clavicular articulation belongs to those which are formed by mutual reception. Articular Surfaces. — The articular surface of the sternum is transversely oblong, con- cave in the same direction, and convex from before backward ; it looks obliquely upward and outward, and is situated on the side of the notch on the upper part of the sternum. 1. The articular surface of the clavicle is oblong from before backward, slightly concave in the same direction, and convex transversely. From the respective configuration of these surfaces a mutual jointing results, and the short diameter of the one corresponds to the long diameter of the other ; so that the end of the clavicle overlaps the surface of the sternum in front and behind, and the surface of the sternum projects beyond that of the clavicle on the inside and the outside.* 2. There is an inter-articular lamina of cartilage (i, fig. 69) between the articular sur- faces, which is moulded upon them, and is very thick, especially at the edges. It is sometimes perforated in the centre. t It is so closely united by its circumference to the orbicular ligament that it is impossible to separate them-: it adheres below to the carti- lage of the first rib, and above and behind to the clavicle. Means of Union. — These are, 1. The orbicular ligament {I, fig. 69). This name may be given to the fibrous capsule which surrounds the joint in all directions. The fibres which compose it have been regarded as forming two distinct bundles, known by the name of anterior and posterior ligaments ; but it is impossible to distinguish between them. Fi- bres proceed from all parts of the circumference of the articular surface of the clavicle, obliquely downward and inward, to the circumference of the articular surface of the ster- num. The capsule is not of equal thickness throughout ; it is thinner, and somewhat looser, in front than behind, which may partly account for the more frequent luxations of the clavicle forward than backward. 2. The inter-clavicular ligament (rti, fig. 69), consisting Of a very distinct bundle stretch- ing horizontally above the fourchette of the sternum, from the upper part of the inner end of one clavicle to the inner end of the other. This ligament, which is much nearer the posterior than the anterior part of the joint, establishes a sort of continuity between the clavicles. It is the only direct means of union between the two shoulders. 3. There are two synovial capsules in this joint. That which is between the sternum and the inter-articular cartilage is more loose than that between the cartilage and the clavicle. The Cos to-clavicular Articulation (fig. 69). The articulation between the clavicle and the cartilage of the first rib is an arthrodia. It is formed between an articular surface, which ahnost always exists on the lower sur- face of the clavicle, and a corresponding facette on the upper surface of the inner end of the first rib, at its junction with the cartilage. There is, in this articulation, a syno- vial membrane, which is loose, especially behind. There is only one ligament, the cos- to-clavicular {g, fig. 66), a thick, strong bundle of fibres, quite distinct from the tendon of the subclavius muscle, which is placed in front of it. It is fixed to the inner part of the first costal cartilage, and is directed very obliquely upward and outward, to be inserted into the under surface of the clavicle, to the inner side of the articular facette. Mechanism of the Sterno-clavicular Articulation. This articulation is the movable centre of the motions of the shoulder and of the whole upper extremity ; and hence the utility of an inter-articular cartilage, to obviate the effects of blows or pressure : hence, also, the wearing away of this cartilage, the de- formity and wasting of the articular surfaces, the depression of the right sternal facette, and, lastly, the difference in the size of the sternal extremities of the right and left clavicles. This articulation, like all those effected by mutual reception, admits of motions in every direction : viz., upward, downward, forward, backward ; and of circumduction, resulting from the preceding, but not of rotation. 1. Movement of Elevation. — In this the sternal facette of the clavicle glides downward upon the corresponding surface of the sternum ; the inter-clavicular ligament is relaxed ; the cartilage of the first rib comes in contact with the inner extremity of the clavicle, limits the degree of elevation, and prevents displacement. 2. Movement of Depression. — In this the sternal end of the clavicle glides in the oppo- site direction ; the articular surfaces of the costo-clavicular articulation press strongly * Bichat considers that this arrangement of the articular surfaces predisposes to luxation ; it appears to me to have a precisely opposite effect, as it permits the surfaces to move upon each other to a considerable extent without being separated. T III a great number of cases this ligament is found partially wasted by the continued pressure to which the joint is subjected. s 138 ARTHROLOGY. against each other, and limit the extent of this movement. It should be remarked, that in this movement the subclavian artery is compressed between the clavicle and the first rib, sometimes so completely as to arrest the circulation in the limb. 3. In the movement of the shoulder backward, the inner end of the clavicle glides for- ward upon the surface of the sternum ; the anterior part of the orbicular capsule is stretched ; and if the movement is carried beyond a certain point, the capsule is torn, and the clavicle dislocated forward. 4. In the forward movement of the shoulder, the inner end of the clavicle glides back- ward. The anterior part of the orbicular ligament is relaxed, and the posterior part stretched ; as, also, the inter-clavicular ligament, which, as we have seen, is nearer the back than the front of the joint. In this motion luxation may take place backward. It may be remarked that, of all the movements of the shoulder, the one described, in which the clavicle is likely to be dislocated backward, is the most uncommon. The movement of circumduction is more extensive forward and upward than backward. The motions at the sterno-clavicular articulation are very circumscribed in themselves ; but when transmitted by the lever of the clavicle, they become very considerable at the apex of the shoulder. Mechanism of the Costo-clavicular Articulation. This articulation, which may be regarded as a dependance of the sterno-clavicular, admits of very limited motions, subordinate to those of the joint last described. The Scapulo-humeral Articulation {figs. 69 and 70). Preparation. — Separate the upper extremity from the trunk, either by disarticulating the clavicle at its sternal end, or by dividing it through the middle ; 2. Detach the del- toid from its origin ; 3. Detach the supra and infra spinati muscles, the teres minor and subscapularis, proceeding from the scapula to the humerus ; 4. Observe the adhesion of the tendons of these muscles to the capsular ligament ; 5. Divide the capsule trans- versely, after having studied its external aspect. The scapulo-humeral articulation belongs to the class of enarthroses. Articular Surfaces. — These are the glenoid cavity of the scapula, slightly concave, of an oval form, with the large end downward, and looking directly outward ; and the head of the humerus, consisting of about a third of a sphere, and presenting a surface three or four times more extensive than the glenoid cavity. The axis of the head of the hume- rus forms a very obtuse angle with that of the shaft of the bone.* These two surfaces are covered by a layer of cartilage, which, on the head of the hu- merus, is thicker at the centre than at the circumference ; while the reverse obtains in the glenoid cavity. Glenoid Ligament (a, fig. 70). — This is a fibrous circle, which surrounds the margin of Ftg 70. the glenoid cavity, and appears to be formed by the bifur- cation of the tendon of the long head of the biceps ; but it is also partly composed of fibres proper to itself, which stretch along the margin, arising from one point and ter- minating in another. Notwithstanding this addition, the head of the humerus is still too large to be received into the cavity, so that a portion of it is always in contact with the capsular ligament ; an inconvenience that is obviated, in some measure, by the existence of a supplementary cavity, as we shall presently see. The scapulo-humeral ar- ticulation is therefore one formed by juxtaposition, and not by reception ; from which arrangement it has lately been classed among the arthrodial articulations. Means of Union. — Like all enarthroses, there is here z. fibrous capsule, or capsular lig- ament {r,figs. 69 and 70), a sac with two openings, which extends from the margin of the glenoid cavity to the anatomical neck of the humerus, t This capsule is remarkable for its laxity. In fact, it is so capacious that it could lodge a head twice as large as that of the humerus, and is so long that it will allow the articular surfaces to be separated for more than an inch ; the only example of so great a separation without laceration of the ligament. t There is this peculiarity in the fibrous capsule of the shoulder-joint, that it is incom- plete in one part, its place being there supplied by the tendons of the surrounding mus- cles. In no joints, in fact, have the muscles and tendons more effect in strengthening the articulation : they are, in a manner, identified with it. There are a great many varie- ties in this respect. The fibrous capsule is so much stronger, as it is less adherent to the * Such is the shortness of the neck of the humerus, that its head, which looks upward and inward, would be almost entirely included between the prolonged planes of the body of the humerus. t It should be remarked, however, that the fibrous capsule does not terminate directly at the anatomical neck of the humerus, but is prolonged a little downward, and becomes blended with the insertions of the ten- dons of the supra and infra spinati and subscapularis. t In paralysis of the deltoid, the head of the humerus is so far separated from the glenoid cavity thai two fingers may be inserted between the articular surfaces. ARTICULAXrONS OF THE SHOULDER. 139 surrounding tendons. The following are the relations of the capsule : 1. Below, in the variable space between the subscapularis and teres minor, it corresponds to the cellular tissue of the axilla, or, rather, to the thin edges of the muscles just mentioned : the head of the humerus may, therefore, be easily felt by the fingers introduced deeply into the axilla. 2. Above and on the outside, it is in contact with the tendon of the supra-spi- natus, from which it is difficult to separate it, and is also in relation, though not immedi- ately, with the arch formed by the acromion and clavicle with the deltoid muscle. 3. In front, it corresponds to the subscapular muscle, from which it may be easily separated. 4. Behind, it corresponds to the tendons of the supra and infra spinatus, which are more or less adherent to it, and the teres minor, which does not adhere to it. As to its struc- ture, it is composed of fibres stretched irregularly from the neck of the humerus to the circumference of the glenoid cavity. Its thickness is not great, nor is it equal through- out, being most considerable below and in front ; but the capsule is strengthened above by a considerable bundle of fibres {s,fig. 69), called the coracoid ligament, coracn-humeral ligament, or accessory ligament of the fibrous capsule, which arises from the anterior edge of the coracoid process, and spreads out on the capsule. This capsule always presents an opening or an interruption above and before,* on a level with the superior border of the subscapularis, which covers the opening in part ; or, rather, between this border and the coracoid process. This opening is of an oval form ; its greatest diameter is horizontal ; its large extremity is turned outward, and its small extremity inward. The circumference of this opening, which is large enough to admit the point of the index fin- ger, is perfectly smooth, thick, and looks like mother-of-pearl, especially in its inferior half This opening is traversed by a considerable prolongation of the synovial mem- brane, which reaches the basis of the coracoid process, and then extends between the tendon of the subscapularis and the cavity which bears the same name. This cone- shaped prolongation is variable with respect to its extent, and appears to have no other object except to facilitate the gliding of the tendon of the subscapularis under the cora- coid arch and against the border of the glenoid cavity. By distending the articular cap- sule in several subjects, Mr. Bonamy has demonstrated this disposition to my perfect satisfaction. I have been able to see that the synovial prolongation is sometimes divi- ded into several cells by incomplete walls, by which this distended prolongation acquires a crimpled aspect. Sometimes several of these cells are totally distinct from the syno- vial membrane. Inter-articular Ligament. — This name may, with propriety, he applied to the tendon {t, fig. 70) of the long head of the biceps, which, arising from the upper part of the glenoid cavity, turns hke a cord over the head of the humerus, and passes along the bicipital groove. It acts by keeping the head of the humerus applied to the glenoid cavity, and forms a sort of arch that supports the bone when it is forced upward. In two subjects, I found this tendon terminating by a strong adhesion in the bicipital groove, and thus justifying the name of inter-articular ligament, which I have applied to it : the tendon for the long head of the biceps took its origin from the same groove. I consider this division of the tendon to have been accidental, for the bicipital groove was depressed, and the inter-articular ligament flattened, and, as it were, lacerated. The synovial capsule is the simplest of all in regard to its disposition. It lines the fibrous capsule and the tendons which replace it, and is reflected, on one side, on the neck of the humerus, and, on the other, upon the border of the glenoid cavity, to be lost upon the circumference of the articular cartilages. It is remarkable, inasmuch as, 1. It forms a fold round the tendon of the biceps, which is prolonged into the bicipital groove, and terminates below by a cul-de-sac or circular fold, which prevents the effusion of the synovia ; 2. It is open in one or two points,! and presents two prolongations communi- cating with the synovial bursae of the subscapularis and infra-spinatus. Supplementary Cavity. — We may regard as a dependance of the scapulo-humeral artic- ulation the vaulted arch formed by the coracoid and acromion processes, and the liga- ment which unites them. In shape it corresponds to the head of the humerus, and is so constructed that the coracoid process prevents displacement inward ; the acromion pre- vents it upward and outward ; and the ligament between them opposes dislocation di- rectly upward. This provision evidently compensates for the incomplete reception of the head of the humerus in the glenoid cavity. A circumstance which proves the use- fulness of this vault, and the frequent contacts which it must have with the humerus, is the presence of a synovial capsule, situated between the coraco-acromion vault on one * I have seen this opening- divided into two unequal portions by a fibrous bundle, strong, looking- like mother- of-pearl, and resemliling a little tendon. Often 1 have met a second interruption of the fibrous ca))sule on a level -with the concave border of the acromion process, which concave border acts as a real returu-puUey for the infra-spinatus muscle, and is analogous to the return-pulley presented l)y the basis of the coracoid process to the subscapularis muscle. When the capsule is perforated at this point, the synovial membrane gives off a prolongation, which serves as a gliding capsule for the tendon of the infra-spinatus. t [Although the synovial capsule of the shoulder-joint is thus occasionally prolonged into the bursa; mucosa connected with the tendons of these muscles, it must not, therefore, be supposed that it is an exception to tha general rule that membranes of this nature always form shut sacs ; in stich cases, the three structures consti- tute one continuous cavity.] 140 ARTHaOLOGY. side, and, on the other, the tendon of the infra-spinatus and the ^eat trochanter of the humerus. The study of the coraco-acromion vault cannot, therefore, be separated from the study of the scapulo-humeral articulation, either under an anatomical and physiolo- gical or surgical .point of view. The Coraco-acromial Ligament. This ligament (m, figs. 69 and 70) forms part of the vault we have described : it is a triangular bundle of radiating fibres, which extends from the apex of the acromion to the whole length of the posterior edge of the coracoid process. Its external edge becomes thinner, and is continued into an aponeurotic lamina below the deltoid muscle, and sep- arating that muscle from the joint. Its anterior and its posterior bundles are very thick, folded upon each other, and look like mother-of-pearl ; its middle bundles are much less thick. It is lined below by a synovial membrane, and is separated from the clavicle by fatty tissue.* Mechanisiti of the Scapulo-humeral Articulation. The scapulo-humeral articulation admits of the most extensive movements of any joint in the body : it is capable of every kind of motion, viz., forward and backward, and also those of adduction, abduction, circumduction, and rotation. Forward and Backward Motions.— In these the head of the humerus rolls upon the gle- noid cavity, and moves round the axis of the neck of the humerus, while the lower extrem- ity of the bone describes the arc of a circle, of which the centre is at the joint, the radius being represented by the humerus, t The for^vard movement is very extensive, and may be carried so far that the humerus may take a vertical direction exactly opposite to the natural one. The motion backward is produced by the same mechanism ; the head of the humerus turns upon its axis. This movement is limited by the contact of the head of the humerus with the coracoid process, without which dislocation fon\^ard would he very easily produced. It should be remarked that, in any considerable movement of th€ humerus forward, the scapula is also moved, performing that sort of rotation which we spoke of when considering the mechanism of the shoulder. And this combination of the movement forward of the arm and the movement of rotation of the shoulder renders every kind of displacement extremely difficult in exercising the movements of the arm forward. The movement outward, or abduction, is the most remarkable. It belongs exclusively to animals possessed of a clavicle. In it the head of the humerus does not turn upon an axis ; it glides do^^iiward upon the glenoid cavity, and presses upon the lower part of the capsule. The shape of the glenoid cavity, which has its long diameter vertical, and its broad part below, is advantageous as regards this motion. When abduction is car- ried so far that the humerus forms a right angle with the axis of the trunk, a great part of the head of the bone is below the glenoid canty. If, while in this condition, the arm be moved forward or backward, the great tuberosity of the humerus rubs against the coraco-acromial arch, and forms with it a sort of supplementary articulation, lubricated by the bursa situated between the coraco-acromion vault and this great trochanter. t The movement of abduction may be carried so far as to allow the arm to touch the head without dislocation ; for the capsular hgament is sufficiently loose, especially below, to receive almost the Avhole head of the bone without being torn. It should be remarked, that during abduction the scapula is fixed, which explains the frequency of luxations of the humerus downward. Adduction is limited by the ai-m meeting with the thorax. "VMien it is combined with ■ftie for\vard motion, the upper and back part of the capsule, and the muscles which cover it, are considerably stretched. The scapula does not participate in this movement, du- ring which luxation can be occasioned only by a very strong impulse on the arm upward and backward. Circumduction is nothing more than the transition of the humerus from one to another of these motions. The cone which it describes is much more extensive in front than behind, a circumstance tending greatly to facilitate the prehension of external objects, which is the chief purpose of the upper extremities. This predominance of the forward motions has been already noticed in the sterno-clavicular articulation, and wiM be fotiH^ also in many others. ♦ [This is the Ugamentum proprium imttriua of authors ; but the author has taken no notice of another ligw- ment proper to the scapula, viz., the hgamentum proprium posterius, a thin band of fibres stretched across the notch at the base of the coracoid process, which it thus converts into a foramen. The supra-scapular nerve generally passes below, and the arterj' abore it.] t It is through this ingenious and simple mechanism, of -which we shall soon see another example in the ftrticulation of the femur with the os innominatum, that the movement forward of the humerus may be carried fel- enoug-h to describe a demi-circle, without the bone being displaced. t If theory has led ns to believe that the coraco-acromion vault contributed to luxation, by offering- a poi-nt of support to the lever represented by the Ixumerus abducted from the body, a more careful observation, on the contrar}-, has demonstrated that this supporting of the humerus was impossible, as the anterior border of the coraco-acromion ligament is alone pressing against the humerus in the forcible abduction, and luxation is al- ways produced in a middle abduction of the arm. ARTICULATIONS OF THE ELBOW. Ill Fig. 71. Fig. 72. Rotation. — In this movement the humerus does not turn upon its own, but upon an imaginary axis, directed from the head of the humerus to the epi-trochlea, parallel to the bone. The manner in which the rotatory muscles embrace the head of the humerus is highly favourable to this motion, by compensating for the shortness of the neck, which serves as a lever for the rotatory movements. The Humero-cubital Articul.vtion, or Elbow-joint {figs. 71 and 72). Preparation. — 1. Remove carefully the brachialis anticus muscle ; 2. Detach the ten- don of the triceps from above downward, without opening the synovial capsule ; 3. Re- move the muscles which are attached to the internal and external tuberosities, keeping in mind that the lateral ligaments are intimately connected with the tendons of these miiscles. This articulation belongs to the class of trochlear joints (angular ginglymi). Articular Surfaces. — On the humerus we find, 1. An almost perfect trochlea or pulley, presenting two edges, of which the internal is the more prominent, so that, when the end of the bone rests upon a horizontal plane, its shaft is directed very obliquely from above downward and inward ; 2. The small head, or articular condyle, separated from the trochlea by a furrow, which is also articular ; 3. Two cavities, a pos-^ terior, which is very deep, and is intended to receive the olecranon process, and an anterior, which is shal- lower, and receives the coronoid. The articular surfaces of the forearm are, 1. The greater sigmoid cavity of the ulna, which exactly em- braces the trochlea ;* 2. The glenoid cavity of the ra- dius, which receives the small head of the humerus. The means of union consist of four hgaments, two lateral, an anterior, and a posterior. 1. The external lateral ligament {a, figs. 71, 72) is blended with the ten- don of the supinator brevis ; it is of a triangular form, and stretches from the external tuberosity of the hu- merus to the annular ligament, with which it becomes continuous, and which seems to be in part formed by it. Some fibres of this ligament are also inserted into the outer part of the sigmoid cavity of the ulna. This connexion of the lateral with the annular ligament is of great importance with reference to the production of luxations of the upper end of the radius, f 2. The internal lateral hgaments are two in number : one internal, properly so called, or humero-coronotdian ; the other internal and posterior, humero-olecranian. The former, or humero-coronoidian, which is partly confounded with the aponeurotic tendon of the superficial flexor muscle of the fingers, is a thick, rounded bundle, which arises below the internal tuberosity of the humerus, and is inserted into the whole internal side of the coraeoid process, and more especially, in its tubercle. The second, or humero-olecranian, which might be described as a posterior ligament of the articulation, is thin and radiating; it arises from the posterior portion of the epi- trochlea, and irradiates to be inserted into the whole extent of the internal border of the olecranon ; the inferior bundles are the strongest, and come in part from the humero- coronoUian ligament. The superior bundles are thin and slender, and reach beyond the olecranon, in order to expand over the synovial membrane. 3. The anterior ligament (c) is a very thin layer, in which, however, three orders of fibres can be recognised. The first, directed vertically, form a bundle which extends from the upper part of the coronoid cavity to the lower part of the coronoid process ; the second are transverse, and intersect the first at right angles ; and, lastly, the third are obliquely directed downward and outward to the annular ligament, t We shall see, hereafter, that the brachialis anticus renders an anterior resisting ligament entirely use- less ; moreover, the most inferior and deepest fibres of this muscle are directly inserted ift this aaterior Iigana.€jit. * There is here, indeed, a hinge : it is the ifiost remarkable example of a hin?e in the system ; it is the most perfect angular ginglymoid. The two articular surfaces present a sinuous surface, which is alternately concave and convex, a sort of catching which is seen nowhere else. t These relations between the annular ligament and the external lateral ligament are so intimate that these two ligaments are seldom torn independently of each other ; hence the consecutive dislocation of the radius upon the cubitus in the luxations of the elbow ; hence, also, the luxations of the radius upon the humerus^ the uhia remaining in its place. (See an example of the luxation backward of the radius upon the humerus, the ulna remaining in its place, Anat. Puthel., with plates, 8th number.) X It should be remarked, that none of these ligaments of the elbow-joint are attached directly to the radius., but that the fibres which are directed towards this bone join the annular ligament. This arrangement allows the radius to rotate with perfect freedom within its rifig, whidi would have been impossible hail the fibiea linen directly inserted into the bone. 142 ARTHEOLOOY. 4. The posterior Vi We should observe that it is almost impossil)le to separate the mechanism of the carpal articulations I'rom that of the radio-carpal joint ; the latter is noticed here by itself only in order to conform with the ana- T;>n)ical divisions. ARTICULATIONS OF THE CARPUS. 147 the direction of the long diameter of the articular surfaces, dislocation must be very dif- ficult, and that, when it does occur, it must be incomplete. The movement of circumduction is nothing more than a succession of the ditTer^nt mo- tions which have been already pointed out. The hand describes a cone, of greater ex- tent behind, that is, in the direction of extension, than in front, or in the direction of flexion. It is also still more restricted in adduction and abduction. Articulations of the Carpus {figs. 73 to 75). These articulations comprise, 1. The articulations of the bones of each row together ; and, 2. The articulations of the two rows. Articulations of the Bones of each Row. PreparaHon. — 1. Remove the extensor and the flexor tendons ; 2. Separate the hand from the forearm, then the first row from the second, and, lastly, the bones of both rows from each other, examining their means of union before completing the separation. Artkul&r Surfaces. — The articulations of the bones of each row are amphi-artkroses, and, consequently, present one part continuous and another contiguous. The bones of' the first row correspond to each other by oblique surfaces, those of the second row by vertical and more extensive surfaces. Mean^ of Union. — Two classes of ligaments belong to these joints : the one is extend- ed between the corresponding surfaces, the interosseous ligaments; the other set are peripheral, and are divided into palmar and dorsal. The palmar and dorsal ligaments are fibrous bundles, stretched transversely or oblique- ly from each of the bones of the carpus to those which are contiguous to it. The dorsal are much thinner than the palmar. The interosseous ligaments are not disposed in an exactly similar manner in the two Fig. 73. rows, and we shall, therefore, examine them separate- ly. 1. The interosseous ligaments of the first row (e e, fig. 73) occupy only the upper part of the corresponding y',, facettes ; they are nothing more than small fibrous bun- dles, one extending from the scaphoid ( 1 ) to the semi- lunar (2) ; the other from the semilunar to the cunei- form (3) ; they are sometimes partially interrupted, and present openings, which establish a communication be- tween the general synovial membrane of the carpus and that of the radio-carpal articulation. These inter- osseous hgaments are reddish, scarcely fasciculated, very loose, so as to admit of pretty extensive gliding motions. 2. The interosseous ligaments {d d d) of the second row are much thicker than those of the first ; the whole non-articular portion of the corresponding facettes gives insertion to these hgaments, which are very compact, and of a much more dry and close tex- ture than the reddish tissue connecting together the bones of the first row. It follows, therefore, that the bones of the second row are more firmly united than those of the first, whose interosseous hgaments are loose, and permit a certain degree of mobility. The articulation of the pisiform bone with the cuneiform merits a special description. Articulation of the Pisiform and Cuneiform Bones. For this articulation, the pisiform bone presents a single articular surface, which unites with the anterior facette of the cuneiform bone. There are four ligaments in this little joint, which is nothing else but a hose arthrodia: 1. Two inferior {e,fig. 75), which are very strong, viz., an external, stretched obliquely from the pisiform to the hook-like process of the unciform bone ; and an iiUernal, vertical, which is inserted into the upper end of the fifth metacarpal bone. These two ligaments appear partly to re- sult from the bifurcation of the tendon of the flexor carpi ulnaris, this tendon being in the place of the superior ligament, which is wanting. The internal lateral ligamenrof the radio-carpal articulation may also be considered as entering into the structure of the superior ligament. 2. An anterior and a posterior ligament, thin and radiating, which strengthen the synovial capsule in front and behind. The synovial capsule is, most commonly, a smaU isolated pouch ; and sometimes it is a prolongation of the radio-carpal synovial membrane. This capsule is very loose, and the ligaments are not very tight ; hence the great mobility of the articulation. Articulation of the two Rows of Carpus together. The articulation of the two rows of the carpus together presents an enarthrosis in th« middle, and an arthrodia on each side. The articular surfaces consist of a head or spherical eminence received into a cavity, constituting the enarthrosis, and of plane surfaces on the inside and the outside, which form a double arthrodia. The head is formed by the os magnum i(i,fig. 73) and the sn- 148 ARTHROLOGY. perior process of the os unciforme (7) : the cavity is constituted by the inferior surfaces of the scaphoid (1), the semilunar (2), and the cuneiform (3) bones. This cavity, vv'hich is deeply notched in front and behind, is completed in these situations by two ligaments, an anterior and a posterior, which might be called glenoid ligaments, considering their po- sition on the edge of a cavity, and their use in increasing its depth. The posterior glenoid ligament is composed of transverse fibres, which are inserted into the first row, closing up the posterior notch. The anterior glenoid ligament, much stronger than the other, belongs to the second row ; it is confounded with the anterior ligaments of the articulation, between the two rows, and extends transversely from the os unciforme to the trapezium, passing in front of the neck and the head of the os magnum. Besides these ligaments, we also find, 1. An anterior ligament {i, Jig. 75), which is very thick, and stretches from the anterior sur- face of the os magnum, by diverging rays, to those three bones of the first row that form the enarthrodial cavity, in which the head of the os magnum is received, viz., the sca- phoid, the semilunar, and the cuneiform. 2. A posterior ligament {i, fig. 74), which con- sists merely of some fibres extending obliquely from the bones of the first row to those of the second. On the inside and the outside of this carpal enarthrosis we find an arthrodia. On the inside is the articulation of the cuneiform (3, fig. 73) with the unciform (7) bone, consti- tuted by plane surfaces, and strengthened by a very thin posterior ligament, an anterior ligament, much thicker than the preceding, and an internal lateral ligament (c). On the outside is the articulation of the scaphoid with the trapezium and the trapezoid. The ar- ticular surface of the scaphoid (1) is a sort of head or elongated convexity, and those of the trapezium (4) and the trapezoid (5) are two facettes, that unite in forming a concavity, into which the convexity of the scaphoid is received. This small articulation is strength- ened by two anterior ligaments, both of which proceed from the scaphoid, and are connected one to the trapezium, and the other to the trapezoid ; and two posterior, arranged in a sim- ilar manner with the preceding, but much thinner. A single synovial capsule (see fig. 73), very loose, especially behind, covers the corre- sponding articular surfaces of the two rows. But it is also provided with small culs-de- sac, which penetrate into the intervals between the bones of each row, there being three below and two above. Mechanism of the Carpus. The mechanism of the carpus must be considered as providing both for strength and mobility. The conditions favourable to strength are, 1. The number of bones in the car- pus ; 2. The reciprocal dovetailing of the two rows, the anti-brachial row joining in this fashion the metacarpal, and vice versa ; 3. The numerous ligaments connecting the bones of each row together. The carpus, therefore, has power to resist the most violent shocks, chiefly on account of the expenditure offeree at each of its numerous articulations. With regard to mobility, the movements between the bones of each row must be distinguished from those which take place between the two rows. 1. The partial movement between the component bones of each row is scarcely appreciable, and requires no consideration. 2. The mobility of the two rows upon each other is, however, more marked. The enar- throdial articulation of the head of the os magnum can only perform forward and backward motions, for the arthrodial joints on each side prevent any lateral movements. Mechanism of the Carpal Enarthrosis. — The movement of extension is very limited, on ac- count of the resistance of the anterior hgaments. The movement of flexion, on the con- trary, is much more considerable : it may be carried sufficiently far to cause luxation of the head of the os magnum backward. The slight structure and the looseness of the pos- terior ligaments, and also the looseness of the synovial membrane behind, explain the fa- cility which this articulation enjoys in the movements of flexion. It is of importance to remark, that the carpal enarthrosis performs a more active part in the flexion of the hand than even the radio-carpal articulation ; a circumstance of the highest interest in relation to the mechanism of the carpus. Metacarpal Articulations. The metacarpal bones are united at their extremities, but separated along their shafts. We shall examine the articulations, 1. Of their carpal ; and, 2. Of their digital extremities. 1. Articulations of the Carpal Ends of the Metacarpal Bones. These are symphyses or amphi-arthroscs. The articular surfaces {see fig. 73) occupy the sides of the carpal ends of the metacarpal bones, and are partly contiguous and partly con- tinuous. The contiguous portion consists of a facette covered with cartilage, and is, in fact, an extension of the surface that articulates with the carpus. The part intended to become continuous is rough. The means of union arc the interosseous, the dorsal, and the palmar ligaments. The inter- osseous ligaments (//, fig. 73) are short, close, and very strong bundles of fibres, interposed between the rough portions of the lateral facettes of two neighbouring metacarpal bones. They constitute the principal means of uniting these bones, as may be seen by attempting METACARPAL ARTICULATIONS. 149 to separate them after dividing the dorsal and palmar ligaments. The dorsal (Z, fig. 74) and palmar ligaments (m, fig. 75) consist of fibrous bundles, stretched transversely from one metacarpal bone to another. The palmar ligaments are much larger than the dorsal. 2. Articulation of the Digital Ends of the Metacarpal Bones. Although the digital extremities of the metacarpal Fig 75 bones are not, prop- erly speaking, artic- ulated together, yet as they are contigu- ous, and move upon each other,their sur- faces are covered by a synovial mem- brane, vi^hich facil- itates their move- ments ; moreover, a palmar ligament (n, Jigs. 74, 75) is stret- ched transversely in front of these ex- tremities, and unites them loosely together. This lig- ament (called also transverse) is common to the last four metacarpal bones, but it does not reach the met- acarpal bone of the thumb. It may be considered as formed by the union of all the anterior ligaments ol the metacarpo-phalangal articulations, and as being destined to render these ligaments continuous. In order to expose this ligament, and to study with atten- tion its connexions with the anterior ligaments of the metacarpo-phalangal articulation, it is sufficient to open the fibrous sheaths of the flexor tendons of the fingers, and to remove the small lura- bricales muscles, together with the nerves and vessels of the fingers. We may consider the interosseous palmar aponeurosity as representing, in respect to the shafts of the metacarpal bones, the aponeurosis called the interosseous ligament in the forearm. Strictly speaking, the thickened inferior border of the dorsal interosseous aponeurosis, which is continuous with the tendons of the extensor muscles, might be con- sidered as a dorsal transverse ligament, much weaker than the preceding. The interosseous muscles, as we shall afterward see, complete the means of union of the metacarpal bones. Carpo-metacarpal Articulations. The articular surfaces are the inferior facettes on the bones of the second row of the carpus, and the facettes on the upper ends of the metacarpal bones. We may consider all the carpo-metacarpal articulations as forming only one joint with a broken surface. The articulation of the trapezium with the metacarpal bone of the thumb, and that of the fifth metacarpal bone with the os unciforme, require each a special description. Articulations of the Second, Third, and Fourth Metacarpal Bones with the Carpus. Articular Surfaces {see fig. 73). — The articulation of the second, third, and fourth met- acarpal bones with the carpus presents a sinuous line, which might, perhaps, be sub- jected to certain rules of disarticulation, if this disarticulation seemed to be of the least use. It constitutes a tight arthrodia, with an angular surface. Proceeding from within outward, the fourth and third metacarpal bones form a regular curve, with the concavity looking upward ; but the second, which unites by three facettes with the trapezium, the trapezoid, and os magnum, presents an angular surface. The second metacarpal bone is jointed, by its transversely concave surface, with a facette on the trapezoid, which is concave, but in the opposite direction, and by two lateral facettes, with the os magnum and the trapezium, so that it enters, as it were, into the carpus by two angular projec- tions, which are received into the intervals between the three bones with which it is articulated. From this it follows, that the carpo-metacarpal articulations present not only concave and convex surfaces, favourable to mobility, but also angular surfaces that evince the immobility of these joints. Means of Union. — Some ligaments, distinguished as dorsal and palmar, both very strong, short, and compact, retain the articular surfaces as immovably in contact as if the joints were symphyses. 150 ARTHROLOGY. The dwsal ligaments are much stronger than the palmar, and are composed of severai layers, the deepest being the shortest. There are three dorsal ligaments for the second metacarpal bone : a median (o, Jig. 74), stretched to it from the trapezoid bone ; an exter- nal (p), which comes from the trapezium, and covers the insertion of the extensor carpi radialis longior ; and an internal, arising from the os magnum : the first of these is ver- tical, the last two are oblique. There are two dorsal ligaments in the articulation of the third metacarpal bone : a vertical, which comes from the os magnum ; and an oblique (?), from the os unciforme. In the articulation of the fourth metacarpal bone there is one dorsal ligament, longer and looser than the preceding. The palnmr ligaments are much less marked than the preceding ; contrasting thus with the palmar ligaments of the carpus. There is none for the second metacarpal bone ; the tendon of the flexor carpi radialis appears to supply the place of this ligament. There are three ligaments for the third metacarpal bone : an external, which comes from the trapezium ; a middle, proceeding from the os magnum ; and an internal, from the os unci- forme. Lastly, for the articulation of the fourth metacarpal bone, there is one palmar ligament from the os unciforme. The synovial Tnembrane {see fig. 73) of the carpo-metacarpa! articulations is a continu- ation of the synovial membrane of the carpus, and is prolonged between the upper ends of the metacarpal bones ; and, as the synovial membrane of the carpus communicates also with the radio-carpal joint, it can be conceived what ravages may be produced by inflammation attacking any one of these parts. I must here point out an interosseous, or lateral ligament (I, fig. 73), which arises from the os magnum, and slightly, also, from the OS unciforme, and is attached to the inner side of the third metacarpal bone. It al- most completely isolates the articulations of the last two metacarpal bones. Tliis liga- ment being attached to the third metacarpal bone, which is already provided with very strong ligaments, increases in a remarkable manner the strength of the joint. Carpo-metacarpal Articulation of the Thumb. — This joint {m,fig. 73), which is very dis- tinct and completely separated from all the others, is remarkable, also, for the arrange- ment of the Articular surfaces. There is a mutual jointing between the trapezium, which is concave transversely, and convex from behind forward ; and the first metacarpal bone, which is concave and convex in precisely opposite directions. It is the type of all ar- ticulations by mutual reception. The means of union consist of a capsular ligament {s,figs. 74 and 75), imperfect on the outside, where its place is occupied occasionally by the tendon of the abductor longus poUicis (extensor ossis metacarpi pollicis) : it is much thicker behind than in front, and is sufficiently loose to permit extensive motions in all directions. There is a separate syyiovial membrane for this joint, which is remarkable in respect of its relations : viz., 1. Behind, with the extensor muscles of the thumb ; 2. On the outside, with the expanded tendon of the abductor pollicis ; 3. On the inside, with the interosseous muscles and the radial artery, where that vessel penetrates into the palm of the hand, to form the deep palmar arch ; and, 4. In front, with the muscles of the ball of the thumb. Carpo-metacarpal Articulation of the fifth Metacarpal Bone {see fig 73). — The artictilation of the fifth metacarpal bone with the os unciforme is, in many respects, analogous to the preceding ; for there is here, also, a sort of mutual reception between their correspond- ing articular surfaces. There is, also, a kind of capsular ligament {t, fig. 74), very strong in front and thin behind, and incomplete on the outside, on account of the presence of the fourth metacarpal bone : it is rather loose, and maintains the relation of the articular surfaces. The tendon of the extensor carpi ulnaris strengthens this joint behind, in the same manner as the tendon of the long abductor of the thumb strengthens the articula- tion of the trapezium and the first metacarpal bone. The synovial membrane of this joint belongs also to the fourth metacarpal bone. The fourth and fifth metacarpal bones may, indeed, be strictly considered as forming only one joint, and the lateral interosseous ligament as completing the capsular ligament. On the other hand, the second and third metacarpal bones form a very distinct articulation with the OS magnum, the trapezoid, and a small facette upon the trapezium ; lastly, there is another joint peculiar to the first metacarpal bone and the trapezium. There are thus three distinct joints (see fig. 73) in the carpo-metacarpal articulation, in one of which the articular surfaces are simple, while in the two others they are broken. Mechanism of the Carpo-metacarpal Articulations. The mechanism of the carpo-metacarpal articulations should be studied, both as re- gards strength and mobility. 1. With regard to strength, the metacarpal bones mutually support each other, and resist in common the action of external agents : they can only be broken, therefore, by violence sufficient to fracture several at the same time. In order that any one should be broken alone, the violence must be applied directly to it. In this manner I have seen the third metacarpal bone fractured by the stick of a rocket. The great strength of the metacarpus depends not only on the simultaneous resistance ARTICULATIONS OF THE FINGERS. 151 of its component parts, but also on the intervening articulations, each of which becomes the seat of a certain expenditure of force ; for part of this being employed in moving the articular surfaces upon each other, is necessarily lost as far as its direct transmission is concerned. With regard to mobility, these articulations, which might be called tight angular arthro- dias, are only possessed of slight gliding motions, on account of the angular disposition of the articular facettes, the sinuosity of the common articular line, and the strength and shortness of both the external and the interosseous ligaments. At the same time, the mobility of all the metacarpal bones is not equal. Thus, the articulation of the trape- ziimi with the first metacarpal bone holds the first rank ; it is in some degree different from the others in this respect as well as in position, and merits particular description. The articulation of the fifth metacarpal bone holds the second place, and that of the fourth the third. The articulations of the second and third metacarpal bones are as im- movable as symphyses. Mechanism of the Articulation of the Trapezium and the first Metacarpal Bone. — From the mutual reception of the articular surfaces, this articulation permits four motions, viz., flex- ion, extension, abduction, and adduction, and, as a consequence of these, circumduction. Flexion is not performed directly, but obliquely inward and forward. This oblique mo- tion produces the movement of opposition, which characterizes the hand ; it is very exten- sive, and, when carried too far, may produce luxation backward with the greater facility, because the capsular ligament is very thin in that direction. Extension may be carried so far that the first metacarpal bone may fonn a right angle with the radius. It is con- ceivable that luxation forward might be produced by this motion ; but there are very few causes that would tend to increase extension to such a degree, and, moreover, the ante- rior part of the capsular ligament is extremely strong, so that no example of this luxa- tion has ever been recorded. Abduction is very extensive ; when carried beyond a certain point, it may give rise to dislocation inward, for the trapezium, being situated on a plane anterior to the root of the metacarpus, the neighbouring metacarpal bones offer no obstacle to such a displacement. Lastly, direct adduction is limited by the meeting with the second metacarpal bone. Mechanism of the Articulation of the fifth Metacarpal Bone with the Cuneiform. — This ar- ticulation in some degree resembles the preceding, and, like the last, it would be liable to dislocation, were it not for its intimate connexions with the other metacarpal bones, so that the same cause that would tend to displace the fifth metacarpal bone would also tend to displace the fourth. Articulations of the Fingers {figs. 74 and 75). These comprise, 1. The articulations of the fingers with the metacarpal bones. 2. The articulations of the phalanges together. Metacarpo-phalangal Articulations. These belong to the class of condyloid articulations. The articular surfaces in each are formed by the head of the metacarpal bone, flattened from side to side, increasing in breadth from the dorsal to the palmar aspect, and pro- longed much farther in the latter direction, where it presents the trace of a division into two condyles ; and by the shallow glenoid cavity of the first phalanx, whicli is trans- versely oblong, and, consequently, has its long diameter at right angles to that of the head of the metacarpal bone, which is oblong from before backward. We see, then, that an articular head, elongated from before backward, is adapted to a transversely oblong cav- ity. This arrangement favours the movements of flexion and extension, as well as the lateral motions, which are as extensive as they would have been had all the diameters of the articular surfaces been equal to those which are actually the longest. It is on account of the lateral flattening of the heads of the metacarpal bones that, in amputations at these joints, surgeons make choice of lateral, in preference to antero- posterior flaps. Mea-ns of Union. — On account of the disproportion just noticed as existing between the articular surfaces of this joint, the glenoid cavity of the first phalanx not being equal to more than one half of the articular surface on the metacarpal bone, this cavity is pro- vided with a ligament called the anterior ligament {u,fig. 75), which was confounded by the older anatomists with the fibrous sheaths of the flexor tendons. This ligament I have called the glenoid ligament, and its use is to complete the cavity of reception of the metacarpal condyle. It is situated on the palmer aspect of the joint, and is grooved anteriorly, to correspond with the flexor tendons. It is concave, forming, so to say, a demi-capsule behind, to correspond with the metacarpal condyle. By its edges it is con- tinuous not only with the transverse metacarpal ligament, which is one of its appurte- nances, but also with the sheath of the flexor tendons, and with the lateral ligaments of the joint. By its superior border this ligament is continuous with the palmar interos- seous aponeurosis, and with the digital bands of the palmar aponeurosis. By its lower edge it is firmly fixed to the anterior part of the margin of the first phalangal articular 152 ARTHROLOGY. surface ; its upper edge is loosely connected by some ligamentous fibres to the contract- ed neck which supports the head of the metacarpus, and is accurately adapted to that neck. The anterior or capsular ligament is very thick, unyielding, formed of fibres that cross each other, and look like mother-of-pearl, and is as compact as cartilage. Several times I have found a sesamoid bone in the substance of the anterior ligament of the in- dex and the middle finger. The whole tendinous sheath of the tendons of the flexor muscles may be considered as making part of this anterior ligament, and we ought not to overlook these tendons in estimating the solidity of the joint with regard to flexion. This joint has two lateral ligaments, which are extremely unyielding, an internal and an external ; they are inserted into a marked tubercle existing posteriorly on each side of the lower extremities of the metacarpal bones, and into a very remarkable depression below and before this tubercle ; hence these ligaments extend very obliquely from be- hind forward and from above downward, in the shape of a strong and flat band, looking like mother-of-pearl, which continually expands and irradiates, and finally terminates, 1. In a tubercle existing anteriorly, and on each side of the margin of the upper end of the first phalangal bone. 2. By its superior fibres into the borders of the anterior ligament. These lateral ligaments extend, therefore, obliquely from the posterior tubercle of the lower end of the metacarpus to the anterior tubercle of the upper end of the first phalan- gal bone ; they are stretched by flexion, which cannot be extended beyond the right angle without the ligaments being torn ; and they are relaxed by extension, except that portion of these ligaments which goes to the anterior ligament, and which limits the ex- tension by its resistance. It may be interesting to remark, that the external lateral lig- ament is much stronger than the internal ; the former of these ligaments is inserted not only into the tubercle, but also into the whole extent of the subjacent depression. There is no dorsal ligament properly so called ; its place is evidently supplied by the corresponding extensor tendon (w, fig. 74). This extensor tendon, after having reach- ed the level of the joint, becomes narrow, and contracts, as it were, upon itself, in order to form a thick and extremely compact cord. From each edge of this ligament an apo- neurotic expansion arises, which is inserted into the sides of the joint. The synovial capsule is extremely loose, especially on the aspect of extension ; it does not adhere to the tendon, but is folded upon itself during extension, and is stretched du- ring flexion : it lines the inner surface of the lateral ligaments, and is reflected upon the articular cartilages. Metacarpal-phalangal Articulation of the Thumb. — Two sesamoid bones (x, figs. 73 and 75) are annexed to this articulation in front, and are constantly found in the glenoid lig- ament ; they afford insertion to the lateral ligaments and to all the short muscles of the thumb. If we examine these articulations in connexion, we shall find that they are disposed in a curved line, with the convexity looking downward. This curvature is slightly in- terrupted at the articulation of the fourth metacarpal bone, which is not on a level with those of the index and the middle fingers. Mechamsm of the Metacarpo-phalangal Articulations. We shall take as an example the metacarpo-phalangal articulation of the middle fin- ger. From the arrangement of the articular surfaces, it is evident that this articulation can execute movements in four principal directions, and, consequently, those of circum- duction also. From a simple inspection of the surfaces, it might be inferred that the movement of flexion must be very extensive, while that of extension (or flexion back- ward) and the lateral motions of abduction and adduction are exceedingly limited. The arrangement of the ligaments amply confirms these suppositions. It should be noticed, as a rare exception, that in the movements executed by this joint, it is not the head that moves upon the cavity, but the cavity that moves upon the head. In flexion, the first phalanx glides forward upon the head of the corresponding metacar- pal bone ; the extensor tendon and the back of the synovial capsule are stretched by the projecting head of this bone : the posterior fibres of the lateral ligaments are also stretch- ed ; they limit the movement of flexion, allowing it only to proceed so far that the pha- lanx forms a right angle with the metacarpal bone. Lastly, flexion can be carried some- what farther by the thumb, the ring, and the little fingers, than by the others. In ex- tension, the phalanx glides backward upon the head of the metacarpal bone supporting it : this head corresponds almost entirely with the anterior ligament, which, as we have seen, is disposed in the shape of a fibrous demi-capsule. The posterior fibres of the lateral ligaments are relaxed, and the anterior stretched. The motion is evidently limited by the anterior or capsular ligament, and by the anterior fibres of the lateral ligaments, which are inserted into this anterior ligament. I may remark, that the upper border of this anterior hgament forms a sort of ring or collar, which surrounds almost entirely the neck of the corresponding metacarpal bone, without adhering to it. According to the relative size of this ring, and the comparative looseness of the glenoid ligament, will the movement of extension be more or less considerable. In all persons it may be carried so far as to form an obtuse angle behind ; in some, until a right angle ARTICULATIONS OF THE FINGERS. 153 is formed ; and in a few, even so far as to produce an incomplete luxation, reducible by the slightest muscular effort. If extension be carried beyond these limits (for which, however, considerable violence is necessary), the head of the metacarpal bone will escape from the kind of collar formed by the superior border of the capsular ligament and the anterior fibres of the lateral ligaments, sometimes by extensively lacerating it, but at others only by stretching it very much ; in both cases the first phalanx is dislocated back- ward, or the metacarpal bone forward. When the collar is not torn, reduction is al- most impossible, because the glenoid ligament is always interposed between the articular surfaces. It should be remarked, that the metacarpo-phalangal articulation of the thumb is the only one which is not capable of flexion backward. This is probably owing to the want of looseness in its anterior or capsular ligament. In this joint, the movement of extension does not go beyond the straight line ; in this respect it resembles the ar- ticulations which the phalanges form with each other.* Adduction and abduction consist of simple lateral glidings, limited by the meeting of the other fingers. Articulations of the Phalanges of the Fingers. These are pulley-like joints, or perfect angular ginglymi. There are two articulations of this kind in each finger, but only one in the thumb. Articular Surfaces. — The lower end of the first phalanx, flattened from before back-- ward, presents a trochlea, broader on the palmar than on the dorsal aspect, and prolonged much farther in front than behind. The trochlea of the phalanx resembles the lower end of the femur, with this difference, that its two condyles are not separated from each other. The upper end of the second phalanx, also flattened from before backward, pre- sents two small glenoid cavities, separated by an antero-posterior ridge. The ridge cor- responds to the groove of the pulley, and the glenoid cavities to the two condyles. Means of Union. — 1. An anterior ligament {y, fig. 74), grooved anteriorly, to serve the tendon as a sheath, and exactly resembling what exists in the metacarpo-phalangal ar- ticulations, and performing the same office of deepening the glenoid cavity, which by it- self only imperfectly receives the pulley of the first phalanx. 2. Two lateral ligaments, an internal {z) and an external {z'), arranged precisely in the same manner as the lateral ligaments of the metacarpo-phalangal articulations. They are attached to tubercles situated behind the lateral depressions, on the lower end of the first phalanx, and pass obliquely forward, to be inserted both into the glenoid ligament and the second phalanx. There is no posterior ligament, its place being supplied by the extensor tendon. This tendon is disposed in a peculiar manner : it gives off constantly a prolongation {w) from its anterior aspect, which is inserted into the upper end of the second phalanx, so that this bone presents a somewhat similar arrangement behind, as it does in front, with the flexor tendon. This prolongation has a cartilaginous aspect. The synovial capsule is precisely similar to that of the metacarpo-phalangal joints. The foregoing description applies equally well to the articulation of the second with the third phalanx. There is often a sesamoid bone in the substance of the glenoid ligament of the two phalangal joints of the thumb. Mechanism of the Phalanges. The fingers are essentially the organs of prehension and of touch. In the mechanism of touch, the fingers are moved over the surfaces of bodies, and are moulded upon even their slightest inequalities, sometimes acting together, sometimes separately, seizing and moving between them, as between the blades of sentient forceps, even the most dehcate objects. For the performance of this function, great mobility must be conjoined with great precision of movement. On the other hand, for the purpose of seizing bodies, of retaining, repulsing, or breaking them, as well as of acting as the means of attack and defence, considerable power is required ; all which qualities are united in the mechanism of the hand. Observe the number of the fingers and their complete isolation, so that they can act either together or separately, and even in opposite directions. Notice the number of the phalanges, their successive decrease in size, and the facility with which they can be separated or made to approach each other, so as to be applied around spher- ical bodies. Note, also, the inequality of the fingers in length and power, enabling each to act a determinate part in prehension ; and, above all, remark the shortness of the thumb, which only reaches the base of the first phalanx of the index finger ; but which, placed as it is upon a plane anterior to the rest, and endowed with a greater degree of mobili- ty, can be opposed to all the fingers together, to each finger separately, and to every pha- lanx of each, thus constituting the principal blade of the sentient forceps represented by the hand ; for, being more strongly constructed, and provided with more powerful mus- cles than the other fingers, it in some degree counterbalances them all. * This is, I believe, the anatomical reason why a reduction of the dislocations forward of the metacarpo- phalangal articulations of the thumb and the other fingers is difficult, and sometimes impossible. The most skilful practitioners have sometimes failed in this reduction, and especially in dislocations of the thumb ; gan- grene and death have often taken place in consequence of the violent attempts at reduction. I am certain that the vertical section of the anterior ligament would obviate the difficulty at once. u 154 ARTHROLOGY. Mechanism of the Phalangal Articulations . From the shape of the articular surfaces, which form a miniature representation of the knee, it is evident that the only motions of which these joints are capable are flex- ion and extension. The flexion of the second upon the first phalanx is as extensive as it could possibly be, for it is only limited by the meeting of the anterior surfaces of these bones. The amount of flexion of the third phalanx upon the second is less considerable. The extension of the second phalanx upon the first, and that of the third upon the second, are limited, as in the metacarpo-phalangal joints, by the anterior glenoid and the lateral ligaments. This motion of the phalanges is extremely slight ; I have never seen them carried farther back than to form a straight hne. From what has been observed, it follows that, as regards its movements, each finger represents a shortened or miniature limb ; that, at its articulation with the metacarpus, it is capable of motions in every direction, and also of circumduction ; that, from the joints between the phalanges, it is endowed with the power of strong, extensive, and accurate flexion ; and that, from the double bending of the second upon the first, and the third upon the second phalanges, the fingers represent a true hook for seizing and cling ing to external objects. ARTICULATIONS OF THE INFERIOR OR ABDOMINAL EXTREMITIES. Articulations of the Pelvis. — Coxo-femoral. — Knee-joint. — Peroneo-tibial. — Ankle-joint. — Of the Tarsus. — Tarso-metatarsal. — Of the Toes. Articulations of the Pelvis (figs. 76, 77). The articulations of the pelvis are, 1. The sacro-iliac symphysis ; 2. The s)nnphysis pubis ; and, 3. The sacro-coccygeal articulation. The last has been already described with the other articulations of the vertebral column. Sacro-iliac Symphysis. Preparation. — 1. Detach the pelvis from the rest of the trunk ; 2. Saw through the hor- izontal ramus and arch of the pubes at the distance of about eighteen hues on each side of the symphysis ; 3. Dislocate the os innominatum of one side ; 4. Dissect the anterior ligaments of the sacro-iliac symphysis upon the other ; 5. Then make a horizontal section of that articulation, dividing it into an upper and a lower half. The sacro-iliac articulation belongs to the class of symphyses or amphi-arthroses. The articular surfaces are formed on the sacrum and os innominatum, and are partly contiguous and partly continuous. The contiguous surfaces of these two bones are an- terior to the others, and are shaped like an ear, with the convex edge turned forward ; hence they are called the auricular surfaces. The parts which are rendered continuous by means of ligamentous fibres consist of the entire space comprised between the auric- ular portion and the posterior border of the os innominatum, and of all the lateral sur- face of the sacrum not occupied by the auricular facette. The continuous portions are both marked with very rugged eminences and depressions. These articular surfaces are also remarkable from being sinuous and alternately concave and convex, and from their presenting a well-marked obliquity in two directions, viz., from above downward, and from before backward and inward, so that the sacrum is, as it were, wedged between the ossa innominata both in a vertical and an antero-posterior direction. Means of Union. — The auricular surfaces are covered with cartilage, which is thicker upon the sacrum than on the os innominatum, and is remarkable for the roughness of its surface, which contrasts with the smooth ap- pearance of other articular cartilages. There is a distinct synovial membrane in this joint in the infant and pregnant female, but it can scarcely be detected in the adult and the aged. The ligaments are, 1. An anterior sa- cro-iliac ligament (b, figs. 76, 77), a very thin layer which passes in front of this articula- tion, and composed of fibres stretched trans- versely from the sacrum to the ilium. 2. A superior sacro-iliac ligament (4:, fig. 52), a very thick bundle, extending transversely from the base of the sacrum to the contiguous portion of the ilium. 3. An interosseous lig- ament, which forms the strongest bond of union fn this joint, composed of a great number of ligamentous fibres, stretched horizon- tally from the ilium to the sacrum, crossing each other, and filling up almost the whole of the deep excavation comprised between the two bones ; these fibres leave small inter- ARTICULATIONS OF THE PELVIS. 155 vals between them, which are occupied by fat, and traversed by numerous small veins. One of these bundles merits a special description : it consists of a long and strong band extending almost vertically from the posterior superior spinous process of the ilium to a thick tubercle on the third sacral vertebra ; it may be called the posterior vertical sacro-iliax: ligament. 4. The ilio-lumbar ligament (c, figs. 76, 77) may be considered as belonging to this joint ; it extends from the summit of the transverse process of the fifth lumbar ver- tebra to the thickest part of the crest of the ilium, that is, to the enlargement situated about two inches in front of the posterior superior iliac spine. It is a thick and very strong triangular bundle. Symphysis Pubis. Preparation. — This requires no special direction : only, in order to become acquainted with the respective extent of the contiguous and continuous portions, it is necessary to make two sections, a horizontal section, and also a vertical one from before backward. The articular surfaces (e, fig. 77) are oval, having their longest diameters directed ver- tically ; they are flat, and obliquely cut from behind forward and outward. They are, therefore, separated by a triangular interval, the base of which is directed forward, and the apex backward. We should observe, concerning this articulation, that there are many varieties in the respective extent of the contiguous and continuous portions of the artic- ular surfaces. Sometimes they are almost wholly continuous ; at other times, on the contrary, they are nearly altogether contiguous. I have observed this latter disposition in a very remarkable degree in the symphysis of a young woman who died in the sixth month of pregnancy. The 7neans of union are the following : 1. An anterior pubic ligament (d,fig. 76), a very thin fibrous layer, the posterior portion of which is blended with the interosseous liga- ment : it is composed of fibres extending from the spine of each os pubis obliquely to the anterior surface of the opposite pubic bone ; those from the left side pass in front of those from the right. 2. A posterior pubic ligament, extremely thin, and covering the prominence formed by the ossa pubis behind, at the place of their articulation. This prominence, which is very marked in old subjects, seems to be produced by a jutting out of the poste- rior table of the bone backward, apparently caused by the pressure of one articular sur- face upon the other ; these surfaces being, as we have described, in contact behind, but separate in front. In a female who died of peritonitis soon after delivery, I found this posterior prominence of the pubes forming a sort of spine of some lines in diameter from before backward. 3. A superior pubic ligament {e, fig. 76), very thick, and continuous on each side, with a fibrous cord, that covers the upper edge of the os pubis, and effaces its irregularities. 4. An inferior pubic or triangular ligament ( /", fig. 76), which is exceed- ingly strong ; it forms a continuation of the anterior and interosseous hgaments, and is composed of interlacing fibres : this ligament renders the angle formed by the ossa pubis obtuse, and gives to the arch of the pubes that regular curve presented by it to the head of the foetus during labour. 5. An interosseous ligament {e,fig. 77), which occupies the whole non-contiguous portion of the articular surfaces, and varies greatly in thickness in different individuals. This ligament forms the principal means of union between the bones of the pubes ; it fills up the vacant space of a line and a half to two lines, which exists between the articular surfaces, and is composed of fibres, which cross each other like those of the intervertebral substances.* Of the Sub-pubic or Obturator Membrane, and the Sacro-sciatic Ligament. "We place the description of the obturator and sacro-sciatic ligaments next to that of the articulations of the pelvis, simply remarking that they can scarcely be considered true ligaments, but rather aponeuroses, which serve to complete the parietes of the pel- vis, without contributing anything to the strength of the pelvic articulations. In trying to account for the great obturator foramen and the great sciatic notch, I have asked my- self the question whether these great openings, independently of their transmitting ves- sels, nerves, and muscles, did not result from that law of osteology, by means of which the bones, the levers of the muscular power, are formed with the least possible weight and volume. How much heavier would the pelvis have been, if the obturator foramen and the great sciatic notch had been filled with osseous tissue. It would have been use- less, for the strength of the pelvis would not have been increased in any way by such an arrangement. Perhaps these strong but flexible membranes are also useful during the progress of labour, by diminishing the pressure of the soft parts of the mother between the head of the child and the bones of the pelvis. * From analogy, we may infer an identical disposition in the pubic and vertebral symphysis. Thus it will be seen that the articular surfaces in these two articulations are not fitted to each other. In the symphyis pubis, however, we discover an additional degree of mobility ; the articular surfaces are contiguous to a greater ex- tent, and the synovial membrane is so perfect that no anatomist has yet doubted it. The symphysis pubis might, therefore, be regarded as the transition between the movable articulations and the mixed or symphy- ses. The obliquity in an inverse direction of the articular surfaces is the cause why the symphysis pubis is much larger in front than behind ; hence, in symphyseotomy or a section of the sy/nphysis, the knife must be ap- plied to the anterior portion of the symphysis, so that the articulation may be entered into with more safety. It is clear that a trocar could not be thrust into the bladder through the symphysis, on account of its being tQQ narrow behind to admit of its passage. 156 ARTHROLOGY. Sub-puhic or Obturator Membrane {g, figs. 76, 77). — This membrane closes the obtura- tor (sub-pubic) foramen, excepting at its upper part, where we find a notch, by which the groove for the obturator vessels and nerves is converted into a canal. The external half of its circumference is attached to the corresponding margin of the obturator fora- men, and the internal half to the posterior surface of the ascending ramus of the ischi- um ; its two surfaces give attachment to the obturator muscles. The obturator mem- brane is composed of aponeurotic bundles, which look Uke mother-of-pearl, and are in- terlaced in every direction. An interesting point of its structure is its being formed of several layers of fibres, and small bristle-shaped collections of fibres arising constantly from the internal half of the margin of the obturator foramen, which expand upon the anterior surface of the membrane, and afterward intermingle with the periosteum. There is also to be found a very strong parcel arising from a sort of spine upon the mar- gin of the obturator foramen, immediately above the level of the great cotyloid notch. Sacro-sciatic Ligame?its. — These are divided into the great and the small : we apply the term ligaments to them rather on account of their fasciculated shape than from their use, which scarcely has reference to the union of the bones of the pelvis. The great sacro-sciatic ligament {I, figs. 76, 77) arises from a ridge situated on the in- ternal lip of the tuberosity of the ischium, and also from the ascending ramus of the same bone, by a curved margin of considerable extent, having its concavity directed up- ward, which, with the inner surface of the tuberosity of the bone, forms a groove for the protection of the internal pubic vessels and nerves. The most superficial fibres of this ligament are partly continuous with the common tendon of the biceps and the semi-ten- dinosus. Iminediately after its origin, from its fibres being collected together, it be- comes very narrow and thick, and is directed upward and inward ; it then expands con- siderably, and is inserted into the edges of the sacrum and coccyx, and more slightly into the posterior part of the crest of the ilium, as far as the posterior and superior spi- nous process of this bone. Its upper edge, or, rather, its external, is vertical, and is continuous with the aponeurosis, extending over the pyriformis muscle. Its internal edge, which forms a curve, and which is almost horizontal, makes part of the inferior circumference of the small pelvis ; it lines the small sacro-sciatic ligament, to which it adheres at its insertion into the coccyx, and from which it is separated externally by a triangular space, where it is in relation with the internal obturator muscle ; it is covered by the gluteus maximus, to which it furnishes a great number of aponeurotic insertions. This disposition increases the thickness of this ligament considerably, and gives to its posterior surface the rugged, rough, and, as it were, lacerated aspect, which is a char- acteristic of that surface. The great sacro-sciatic ligament is composed of bundles, sev- eral of which, on a level with the narrowest portion of this ligament, are interlaced in the shape of the letter X. Several of these ligaments, which are external at their sci- atic insertion, become internal at their insertion into the coccyx, and vice versa. The great sacro-sciatic ligament and the posterior and superior sacro-iliac ligaments consti- tute a fibrous plane in the shape of bundles, arising from the superior posterior spinous process of the ilium, and extending in various directions. Fig. 77. The small sacro-sciatic ligament (m,figs. 76, 77), placed in front of the preceding, and extremely thin, arises from the suirunit of the spine of the ischium, passes inward, and, becoming thinner, is lost upon the anterior surface of the great sacro-sciatic ligament. The two sacro-sciatic liga- ments divide the great sacro-sciatic notch into two distinct foramina : the upper (n, fig. 77) is very large, and shaped like a triangle with the angles rounded off, and is in a great measure filled up by the coccygeus and pyriformis muscles ; it gives passage also to the great and small sciatic nerves, to the ischiatic vessels, and to the gluteal and internal pu- dic vessels and nerves, and to a large quantity of cellular tissue. That form of hernia which is called sciatic takes place through this foramen. The lower {o,fig. 77) is much smaller ; it is situated between the spine and tuberosity of the ischium, and gives passage to the obturator internus muscle, and to the internal pudic vessels and nerves. Mechanism of the Pelvis. The mechanism of the pelvis should be regarded in four distinct points of view : 1. As affording protection to the contained viscera ; 2. In relation to the part which it per- forms in the mechanism of standing and progression ; 3. In connexion with the phenom ena of parturition ; and, 4. In reference to the motions which take place at its articula tions with other bones, and those between its own component parts. 1. Mechanism of the Pelvis considered as a Protecting Structure. — The following are the conditions in the structure of the pelvis, having reference to its office as a protector of the contained viscera : 1. Behind ; the presence of the sacrum, which is itself protected. ARTICULATIONS OP THE PELVIS. 157 as well as the nerves that pass through it, by the great prominence of the posterior iliac tuberosities, which project considerably beyond it ; 2. On the sides, by the crest of the ilium, and the prominence of the trochanters, which so often preserve the pelvis from ex- ternal violence. With regard to the large notch in front, which leaves the viscera situ- ated on a level with it, unprotected, it may be remarked, that the viscera contained in the small pelvis, being hable to considerable changes of volume, require to leave the osseous and unyielding space which contains them when empty, in order that they may extend into a cavity the walls of which are soft, and may be dilated almost indefinitely ; 3. In front the means of protection are much less efficacious, in consequence of the vast notch which is situated in this region. The partial absence of the bony parietes in front has reference to the great variations in size which the viscera of the pelvis can undergo, and which would have been incom- patible with the existence of an osseous cincture, incapable of dilatation. Tlie absence of bony walls in the situation of the three great notches, presented by the outlet of the pelvis, is also unfavourable to its solidity ; but it has many other important uses, partic- ularly in the mechanism of labour. The pelvis, especially at its upper part, where it is most exposed to injury, is enabled to resist external violence by virtue of its vaulted con struction. Part of the impulse, also, is lost in producing the slight degree of gliding mo tion permitted at the symphysis pubis. Where, however, the power of resistance pos- sessed by the pelvis is overcome, it will be seen at once that the parts most liable to fracture are the ascending rami of the ischia at their junction with the descending rami of the ossa pubis. 2. Mechanism of the Pelvis with regard to Standing and Progression. — The part perform- ed by the pelvis in standing is connected with the transmission of the weight of the trunk to the lower extremities ; this is effected by means of the sacrum, which rests upon the ossa innominata. We should add, that a small portion of the weight is directly trans- mitted to the femurs by the iliac bones, which support the viscera of the abdomen. The following arrangements should be noted, as being concerned in the transmission of the weight by means of the sacrum : 1. The great size of that bone, affording evidence of the destination of man for the erect posture. 2. The obtuse angle at which the sacrum unites with the vertebral column, peculiar to the human species, and which becomes the seat of a decomposition of the force transmitted by the spine. Part of the momentum acting in the direction of the axis of the column has no other effect than that of increas- ing the sacro-vertebral angle, at the expense of the flexibility of the inter-articular car- tilage ; the rest is transmitted to the sacrum, and then to the lower extremities. 3. The double wedge shape of the sacrum itself In order to understand the advantage arising from this form, it is necessary to remark, first, that the weight of the trunk is transmit- ted in the axis of the upper half of the sacrum, and, consequently, in the direction of a line sloping downward and backward ; from this it follows, that the sacrum must have a tendency to be displaced either downward or backward, but the displacement down- ward is prevented by the position of the ossa innominata, which are nearer to each other below than above. The displacement backward is obviated by the oblique direction of the articular surfaces of the same bones backward and inward, while the obliquity of the sacrum itself is in the opposite direction, for it is broader in front than behind.* 4. The distance intervening between the sacro-iliac and the coxo-femoral articulations. The articulation of the vertebral column with the pelvis being situated at the back part of that cavity, while those of the femurs are situated towards the front and the side, the distance between them increases the space in which the centre of gravity can oscillate, without being carried so far forward as to pass beyond the perpendicular let fall from the coxo- femoral articulation to the base of support. In man alone is found a large pelvian basis of support, and thus the erect posture has been rendered possible in him, without an ex- cessive extension in front. In quadrupeds, the antero-posterior diameter of the bones of the ihum is rather short and their haunch bones are elongated behind, and placed in almost the same plane as the vertebral column. The foetus and new-born infant somewhat resemble the lower animals in this respect, and, therefore, in the human subject there is a great tendency to assume the attitude of a quadruped during the first year of existence. The weight received by the sacrum and transmitted to the haunch bones is divided, sometimes equally and sometimes unequally, between the sacro-iliac symphyses. One portion of the impulse calls into action the mobility of the symphyses, and the remainder is transmitted to the cotyloid cavities. It should be remarked, that this transmission is effected along the triangular prismatic columns, which form the sides of the inlet of the pelvis, and are the thickest and strongest parts of that structure. At the foot of these * Without admitting that the influences to which the sacrum is subjected have a tendency to force it back- ward as well as downward, it is impossible to explain either the use of its being shaped like a wedge, with the base turned forward, or of that powerful apparatus of posterior ligaments which can only resist its disloca- tion backward. The idea that these forces tend to press it forward is manifestly at variance with the natur* of the uniting media ; for the sacro-iliac symphyses are only maintained in front by a very thin ligamentous layer, and the breadth of the space between the iliac bones is also greater in front than behind ; circumstan- ces that would evidently facilitate displacement forward. 158 ARTHROLOGY. columns, which form curves, we find, dug, as it were, into their substances, the cotyloid cavities, to which the weight of the trunk is transmitted. During the sitting posture, the weight of the body is transmitted to the tuberosities of the ischia, which, from their great size, are well fitted to support it. As these processes are a little anterior to the cotyloid cavities, and, therefore, situated in a plane very near the front of the pelvis, the centre of gravity of the trunk has a tendency to fall behind the basis of support represented by them ; and, therefore, it is easy to push an individual backward when in the sitting pos- ture, inasmuch as in front the basis for the support of the pelvis is increased by the length of the femurs and the length of the foot while man is seated on a chair, and the whole length of the abdominal extremity while he is seated on a horizontal plane. The mode in which the pelvis resists violence applied to the tuberosities of the ischia in falls, is some- what connected with its mechanism as adapted to the sitting posture. The shock is, in these cases, transmitted directly upward in the direction of the acetabula, the lower hem- ispheres of which offer resistance like two arches : from the acetabula the impulse is communicated backward, by the thick columns extending from behind these cavities, to the sacro-iliac symphyses ; and forward, to the symphysis pubis ; so that falls upon the tuberosities are almost always accompanied with painful concussion both of the sacro- iliac and pubic symphyses. In order to complete our account of the mechanism of the pelvis in standing, we must examine its mode of resistance in falls upon the knees or soles of the feet. In this case, the shock is conununicated from below upward to the upper halves of the cotyloid cavi- ties, which are supported by the prismatic columns already described. The anterior part of each acetabulum presents a large notch, and is altogether unconcerned in the transmission of these shocks ; so, also, is the very thin lamina constituting the bottom or inner wall of the cavity, which can only suffer compression in falls upon the great tro- chanter. The great difference existing between a fall upon the knees and the tuberosi- ties of the ischia, and the fall upon the points of the feet, with regard to a commotion of the brain and the spinal marrow, may be easily conceived. While standing on one foot the weight of the trunk is transmitted to the femur by the sacro-iliac symphyses, and by the curve-shaped column of the side which bears upon the ground. In this position a fall readily takes place, on account of the facility with which the centre of gravity passes the basis of support. During progression, the pelvis affords to each thigh alternately a solid fulcrum, and re- ceives itself a fixed point of support from the femur of that leg which rests upon the ground. While one side of the pelvis is thus supported upon one of the thigh bones, the other side is projected forward. These alternate movements of projection of either side of the pelvis take place at the coxo-femoral articulation of the extremity which rests upon the ground. The alternate movements of projection increase in proportion to the breadth of the pelvis. It is for this reason that women, in walking, move the hips more than men. The remark of a witty author, that " running is the only thing which women are unable to do gracefully," is an allusion to this rather awkward motion of the pelvis. We may form a correct idea of the share which the pelvis takes in the act of walking by studying the mode of progression of persons with wooden legs. In these unfortunate beings the lateral inclinations of the pelvis are sufficient for progression by transporting the centre of gravity alternately to the two inflexible columns substituted for the lower extremities. 3. Mechanism of the Pelvis with regard to Parturition. — The art of midwifery depends, in a great measure, upon the study of the pelvis ; it is impossible to form a true concep- tion of the mechanism of natural labour without being acquainted with the axes of the pelvis, its dimensions as compared with the size of the foetus, the sacro-vertebral angle, the inclined planes of the true pelvis, the diameters of the brim and the outlet, and the malformations to which it is liable. Any lengthened details upon these points would be out of place here. I shall only remark, 1. That the existence of the arch of the pubes is peculiar to the human species ; and, 2. That the sciatic notches and the obturator foramina are not only useful from economizing weight, but also because, corresponding as they do to the oblique diameters of the head of the foetus during parturition, they ren- der less painful the pressure attendant upon that process ; 3. That the pyramidales, the internal obturators, and the psoaj and iliaci muscles perform, so to speak, the office of mat- tresses in the pelvic cavity ; 4. That parturition, consisting in the expulsion of the foetus along the line of the pelvis, natural parturition, provided the expulsive power exists in its normal conditions, depends partly on a true conformation of the pelvis, and partly on a true conformation and position of the foetus ; 5. That a general idea of all the defects which may occur in the conformation of the pelvis may be expressed by stating, that this cavity- is liable to all the malformations which may result from a pressure upon its whole brim or only a part of it, from above downward, from below upward, from before backward, or from side to side. 4. Mechanism of the Pelvis with regard to its own Movements. — The intrinsic movements of the pelvis are very obscure, being confined to mere gliding or swinging motions, the production of which destroys part of the momentum from any external violence. By COXO-FEMORAL ARTICULATIO.V. 159 some admirable contrivance, the mobility of the intrinsic articulations of the pelvis is considerably increased during the latter periods of pi-egnanc'y, so that the coccyx may be pressed backward, causing an increase of five or six lines in the antero-posterior diam- eter of the outlet ; while the symphysis pubis* becomes susceptible of a slight separa- tion, which increases (in a very slight degree, it is true, but sufficiently to merit notice) the dimensions of the brim of this cavity. This mobility, which is especially remarkable in a narrow pelvis, favours the process of labour in a singular degree. The natural mobil- ity of the symphysis pubis has suggested the operation of symphyseotomy, by which the diameters of the pelvis, however, are but little increased, unless the severing of the bones of the pubes should be carried far enough to result in a separation of the sacro- ihac symphysis. A relaxation taking place in the symphysis of the pelvis may give rise to strange errors in diagnosis. The extrinsic movements of the pelvis are those of flexion, extension, lateral inclina- tion, and rotation : these motions, which are all very hmited, have been indicated in describing the mechanism of the vertebral column. The motions of the pelvis upon the thighs are very considerable : they will be examined with the mechanism of the hip-joint. Coxo-FEMORAL Articulation {fig. 76). Preparation. — Remove with care all the muscles that surround the joint, preserving the reflected tendon of the rectus femoris. The psoas and iliacus muscles, the synovial capsule of which so often communicates with the articular synovial membrane, must be removed with particular care. After the fibrous capsule has been studied upon its exter- nal surface, a circular division should be made round its middle portion, for the purpose of uncovering the deep-situated parts. This articulation is the type of the order enar- throsis, being a true ball and socket joint. The articular surfaces are the globular head of the femur, and the cotyloid cavity of the OS innominatum. There is a striking diflference between this joint and that of the shoul- der, as far as regards the size of the articular head and the depth of the articular cavity. While the head of the humerus and the glenoid cavity are simply in juxtaposition with- out any reception of the former into the latter, so that the scapulo-humeral articulation has for a long time been, and is now considered as an arthrodia, there is a deep and com- plete fitting of the head of the femur into the cotyloid cavity, which we have pronoun- ced to be the deepest articular cavity of the body. Both of the surfaces above named are covered with cartilage, with the exception of two depressions, one of which is situa- ted on the head of the femur, the other at the bottom of the cotyloid cavity : the latter is filled with a reddish adipose tissue, improperly caUed the cotyloid gkmd. It is analo- gous to the adipose tissue found in the neighbourhood of all the joints ; its use is not well known. I have often asked myself the question. Why should there be this poste- rior cotyloid cavity \ On submitting the joint to an antero-posterior vertical section, slightly encroaching on the margin of the posterior cotyloid cavity, it will be seen that the object of this cavity is to protect the round ligament in all the possible positions of the head of the femur ; and that, without this cavity, the round ligament could not have existed without its being compressed between the articular surfaces. Now, as the intra- articular vessels enter this cavity, and go to the head of the femur along the round lig- ament, it is not impossible but that the exclusive use of this posterior cotyloid cavity should be to protect the vessels destined to the head of the femur, and that the round ligament itself should have no other use than to support these vessels, and to transmit them to the head of the femur. The cotyloid adipose tissue does not seem to have any other object, except to fill the empty space of this posterior cavity. It appears to me that the round hgament of the coxo-femoral articulation of the poste- rior cotyloid cavity serves the same purpose as the space between the condyles of the lower end of the femur and the crucial ligaments of the knee-joint. Means of Union. — The cotyloid ligament {n, fig. 76). This band, improperly called co- tyloid ligament, is attached to the margin of the acetabulum, which it, as it were, com- pletes ; it augments the depth of the cavity, and renders smooth its sinuous and notched circumference. It is of greater size at the notches than in any other part : by its means the in-egularities of the edge of the acetabulum are effaced, and the deep- notch in front and below is converted into a foramen for the passage of vessels to the fatty tissue, the inter-articular ligament, and the head of the femur. The cotyloid band is much thicker above and behind than below and in front, and it is precisely against the first two points that the head of the femur constantly presses. It is also remarkable, in this respect, that the diameter of its free borders is smaller than that by which it is attached ; and this circumstance assists, in some degree, in retaining the head of the femur in the cotyloid cavity, t It consists of fibres which arise succes- * In a female seventy-nine years of age, the mother of nineteen children, I found the symphysis pubis ex- tremely movable : the two articular surfaces of the pubes were contiguous ; the interosseous ligament had disappeared ; and a very thick, fibrous capsule, of recent formation, surrounded the articular surfaces in front, above and below, being inserted at some distance from them. It was a symphysis changed to a loose arthrodia. t I have never seen this disposition better exhibited than in a subject in which the cotyloid band was ossi- fied in its whole extent, except at the place on a level with the anterior and inferior notch. The head of the 160 ARTHKOLOGY. sively from all points of the circumference of the acetabulum, and interlace at very acute angles. This interlacement is especially visible in the situation of the great anterior notch, where the fibres may be seen arising from each side of the notch, and passing across each other. The orbicular ligament, or fibrous capsule (p, fig. 76). This represents a fibrous sac, having two openings, by one of which it embraces the acetabulum, outside the cotyloid ligament, while the other surrounds the neck of the femur. The femoral insertion of the capsular ligament requires to be carefully studied, for the purpose of explaining the difference between fractures within, and fractures beyond, the capsule. This insertion is so arranged, that at the upper part and in front of the joint it corresponds with the base of the neck of the femur, while beneath and behind it is situated at the junction of the external with the two internal thirds of the neck. The insertion of the capsule in front takes place not only at the base of the neck of the femur, but also internally to this base, to the extent of several lines, as may be ascertained by an incision being made along this insertion in the direction of the axis of the neck. The length of the orbicular ligament is exactly equal to the distance between its insertions, excepting at the inner part, where it is much more loose. Hence the extent of the motion of abduction, which is so remarkable in some jugglers, that they are able to separate their legs until they form right angles with the body, without producing dislocation. The thickness of this ligament is not equal throughout : it is greatest above and on the outside, where the reflected tendon of the rectus muscle is situated ; it is yet very considerable in front and above ; it is less thick behind, and still thinner on the inside. In some subjects the thickness of the superior part of the capsule is to that of the inferi- or as five to one. In front, the capsule is strengthened by a bundle of fibres stretched obliquely, like a sling, from the anterior inferior spinous process of the ihum to the inside of the base of the neck of the femur. It is called by Bertin the anterior and superior lig- ament (r, fig. 76). This band, which serves as a re-enforcement to the capsule, lies un- der that portion of the iliacus muscle which arises from the anterior spinous process of the ilium, and follows the direction of this muscle ; it is composed of parallel fibres, and closely adheres to the capsule, without adhering in the least to the muscle. Within this bundle the capsule is often imperfect, and permits a comnmnication between the synovial membrane of the joint and the bursa of the psoas and iliacus muscles. This last syno- vial membrane may be considered as a prolongation of the articular synovial membrane ; this prolongation is analogous to the one which we have described at the scapulo-hume- ral articulation for the subscapularis muscle. In one subject that I dissected, the com- municating orifice was so large, that the common tendon of these muscles was in imme- diate contact with a considerable portion of the head of the femur ; the tendon itself be- ing split into several bands, some of which had been lacerated, and, as it were, worn away by friction. The external surface of the capsular ligament is in relation with the psoas and iliacus muscles in front, being separated from them by a bursa at the upper part, in those cases where the fibrous capsule is not interrupted, and giving insertion to many of their fibres below. On the inside, it is in relation with the obturator externus and the pectineus ; on the outside, with the gluteus minimus ; behind, with the quadratus femoris, the ge- melh, the pyriformis, and the obturator internus. Several of these muscles send fortify- ing bundles of fibres to the capsule. I may point out an aponeurotic expansion coming from the gluteus minimus, which establishes a close connexion between this muscle and the capsule ; a second expansion, furnished by the pyriformis and the gemelli ; and a third, which is furnished to the capsule by the tendon of the vastus externus. The internal surface is lined by the synovial membrane. The orbicular ligament of the hip-joint differs from the generality of such structures in being of a dull white instead of a pearly white colour, and in being composed of ir- regularly interlaced fibres, except the superficial fibres, which are disposed in parallel lines. I have also observed a very remarkable fact, apparently overlooked by anatomists, viz., that it is extremely thin at its inferior orifice, but especially behind ; and that near this insertion it is strengthened by some circular fibres which embrace the neck of the bone like a collar, but without adhering to it ; and that in its different movements this sort of collar rolls round the neck, but is retained in its place by small bundles of fibres, reflected from the capsule upon the neck of the bone, which raise the synovial mem- brane from the surface. The inter-articular, which is improperly called round ligament {t, fig. 76). This ligament arises, under the form of a fibrous band, folded backward upon itself, from the depression on the head of the femur, which depression is not entirely filled by it. It is twisted around this head, and is divided into three bands, one of which, after having again been subdivided, traverses the adipose tissue and is fixed into the bottom of the cotyloid cav- ity, while the two others are attached to the two edges of the cotyloid notch, below the cotyloid band, by which this insertion, with which it is often continuous, is concealed. femur wtis mechanically and solijly retained in the acetabulum, whose bottom, being partly ■worn out and pressed inward, formed a prominence in the interior face of the pelvis. COXO-FEMORAL ARTICULATEON. 161 In one case a prolongation of this ligament traversed the cotyloid notch, and was at- tached to the part nearest the capsule. The thickness and the strength of this inter-ar- ticular ligament are extremely variable ; sometimes it is extremely strong, sometimes very weak ; sometimes it adheres to one edge only of the notch ; sometimes it consists mere- ly of a few ligamentous fibres, contained within the substance of the reflected synovial membrane ; sometimes in its place is found a fold of that membrane, which may be torn by the slightest force ; and, lastly, it is not uncommon to find that it is altogether wanting. The synovial memhrane lines the whoie internal surface of the capsular ligament, the two non-adhering surfaces of the cotyloid ligament^, and that part of the neck of the fe- mur contained within the joint ; it embraces the round ligament, and sends off a pro- longation from it to a quantity of fatty matter at the bottom of the acetabulum ;* an ar- rangement which led the older anatomists to believe that the round ligament was in- serted into the bottom of tlie cotyloid cavity. Mechanism of the Coxa-femoral Articulation. Like all enarthroses, the coxo-femoral articulation can execute movements of flexion, extension, abduction, adduction, circumduction, and rotation. 1. Inflexion, the head of the femur rolls in the cotyloid cavity around an imaginary axis corresponding with that of the neck of the bone, while the lower end of the femur is carried from behind forward, and describes the segment of a circle, whose radius is represented by the shaft of the bone. In the mechanism of this movement, the neck of the femur has the effect of substituting a rotatory motion of the head of that bone upon a fixed point, without changing the relation of the head with the acetabulum, and, con- sequently, without any tendency to displacement, for a very extensive movement back- ward and forward, which would otherwise have been necessary, and in which the sur- faces would have been liable to separation from each other. We can, indeed, scarcely believe that luxation would be possible during this motion, although it can be carried so far that the front of the thigh and the fore part of the abdomen may be brought in contact. 2. Extension is effected by the same mechanism, the head and the neck of the femur rolling upon themselves from behind forward, while large arcs of a circle, from before backward, are described by the body of the bone ; but such is the obliquity of the acetab- ulum, which looks both forward, outward, and downward, that when the femur is in the vertical direction, the head projects and carries forward the fibrous capsule. The anterior re-enforcing bundle is stretched. The psoas and iliacus muscles perform the ofiice of an active ligament. Luxations of the femur forward are not common, for the movement of extension is limited by the meeting of the edge of the acetabulum and the back part of the neck of the femur ; and the ligament and muscles above named also tend to counteract it. 3 and 4. The mechanism of adduction and abduction is altogether different from that of the preceding movements, where the articulation forms the centre of a circle descri- bed by the femur, the radius of which is measured by a line stretched from the head of the bone to the space between the condyles. In abduction, the head of the femur presses against the inner part of the capsular ligament ; and, on account of the looseness of this ligament, the obliquity of the acetabulum, and the arrangement of the inter-articular lig- ament, this movement may be carried very far without displacement, and is only limited by the meeting of the upper edge of the neck of the femur with the rim of the cotyloid cavity. But this very Uiceting may itself become the cause of luxation, and then the edge of the cotyloid cavity may be regarded as the fulcrum of a lever of the first order with unequal arms, the whole length of the femur being the arm, to which the power is applied, and the neck of the bone, that by which the resistance acts. In adduction, the femur moves in precisely the opposite direction ; this motion is lim- ited by the mutual contact of the two thighs, but, by means of slig-ht flexion, it may be carried so far as to throw one over the other. The great depth oi the upper and exter- nal part of the cotyloid cavity, and the strength of the capsular Jigament in the same di- rections, would seem to oppose all displacement. But it should be observed, that falls upon the knees almost always happen during adduction of the thighs, for this is an in- stinctive movement of preservation. However slight the adduction may be, the inter- articular ligament is of necessity stretched ; and from this it follows, as my colleague, M. Gerdy, has ingeniously remarked, that the head of the femur is detached from the bottom of the cavity by a kind of rolling of the round ligament upon it, and comes to press against the fibrous capsule. The rupture of the inter-articular ligament is not al- ways necessary in luxation. I have seen several instances of a so-called incomplete lux- ation inward, without this ligament being torn. 5. Circumduction consists in the transition from one of these motions to another. The * The synovial membrane is often seen, being: interposed and descending- between the adipose substance and the posterior cotyloid cavity. I may also point out semilunar folds, which are often formed by the syno- vial membrane round the neck of the femur. These folds are supported by some detached fibres of the cap- sule, so that the neck, oq a level with those fibres, is lined with synovial membrane only in the neighl)our- hood of the head of the femur. The synovial folds appear to me destined to conduct vessels to the margin of the head of the femur. Round the head of the femur, at its point of union with the neck, are constantly found very small adipose bundles. X 162 ARTHROLOGY. femur circumscribes a cone, of which the apex is in the joint, while the base is described by the lower end of that bone. The axis of the cone is represented by a hne drawn from the head of the femur to the interval between the condyles ; and the length of the femur accounts for movements which are scarcely felt at the coxo-femoral articulation, being so considerable at the lower end of the bone. 6. Independently of the movements above described, the coxo-femoral articulation per- forms motions of rotation, arising by no means from its enarthrodial shape, but from the presence of the neck of the femur. Generally no movement appears to require a greater expenditure of power on the part of nature than the rotatory movements, and these move- ments are not always regulated by the same mechanism. We have already seen an ex- ample of this movement in the atlo-axoidian articulation, where a cylinder formed by the odontoid process rolls in the partly osseous and partly fibrous ring of the atlas, as an axle- tree in a wheel. Here the arrangement is quite different ; the rotatory movement is ob- tained simply by the lever being bent like an elbow in such a manner as to make the rota- tory movements of the femur upon its axis result from the movements forward or backward of the bent portion. This movement should be studied both at the upper and at the lower part of the femur. At the upper part it is a motion of horizontal displacement, the radi- us being represented by the head and neck of the bone ; at the lower part it is a rotatory motion of the femur, not precisely upon itself, but upon an imaginary axis placed on the inside of, and parallel to, the shaft. It follows that there can be no rotation in cases of fracture of the neck of the bone, and this is one of the diagnostic signs of that accident. Lastly, it may be observed that rotation is performed from without inward, or from within outioard : the latter is the more extensive and more natural movement ; it is produced by a great number of muscles, and, therefore, during repose, the point of the foot is slightly inclined outward. The Knee-joint {Jigs. 78 to 81). Preparation. — 1. Make a crucial incision in front of the knee and dissect back the flaps. 2. Detach the aponeurosis of the thigh, preserving the fibrous band, which forms the con- tinuation of the tensor vagina femoris, and which forms, as it were, a superficial ligament. 3. Remove the aponeurosis of the triceps on the sides of the patella, taking care to avoid opening the synovial capsule. 4. Remove the tendon of the biceps, and turn downward the tendons of the sartorius, gracilis, and semitendinosus. 5. Remove the popliteal ves- sels and nerves behind, and also the gastrocnemii. 6. After having studied the ligaments situated around the synovial capsule, isolate the latter as much as possible by dissecting off the lateral ligaments, and the ligamentum patellae. 7. Open the synovial capsule above the palate. 8. Make a horizontal section of the femur immediately above the con- dyles, and a vertical section from before backward between the condyles. These two sections are intended to expose the crucial hgaments. The articulation of the knee belongs to the class of angular ginglymi ; it is the largest and most comphcated joint in the human body ; it is, perhaps, the most important, both in regard to the part which it plays in the mechanism of the animal economy, and the fre- quency and the gravity of the maladies which it is liable to. Articular Surfaces. — The lower end of the femur and the upper end of the tibia are the essential constituents of this joint, which is completed in front by the patella. The ar- ticular surface of the femur is formed in front by the trochlea, and behind by the two condyles, separated by the intercondyloid fossa ; the articular surface of the tibia con- sists of the glenoid cavities, separated by the spine of the tibia, in front of and beliind which are some irregular projections. The patella presents two concave surfaces, sep- arated from each other by a vertical ridge corresponding to the groove of the trochlea. These surfaces are aU covered with a thick layer of cartilage. It should be remarked, w-ith regard to the knee-joint, 1. That the articular surfaces are rather placed in juxta- position than jointed together ; 2. That the articulation is in some measure double, since two very distinct condyles correspond to two equally distinct cavities. These two con- dyles being turned in opposite directions, viz., the external backward and outward, the internal backward and inward, they are opposed to each other ; like the articulation of the two condyles of the occipital bone with the atlas, which are opposed both to the lat- eral and the rotatory motions, and, in regard to these motions, constitutes an angular ginglymus, so in the case in the knee, its two condyles constituting, as it were, a double condylian articulation, transformed into an angular ginglymus. Liter-articular Cartilages. — Like all joints that are exposed to much pressure, the knee is provided with inter-articular cartilages. They are two in number, and are named, from their figure, semilunar or falciform cartilages (a, b, fig. 78). Their upper surfaces, corresponding to the convexity of the condyles, are concave ; their external circumfer- ence is very thick, and the internal sharp and thin : they therefore assist in deepening the concave surfaces of the tibia. The section of these cartilages forms an elongated isoscele triangle, with its base outward. The external inter-articidar cartilage (a) cov- ers almost the whole of the external glenoid cavity of the tibia, forming nearly a com- plete circle ; while the internal cartilage {b), which is, indeed, semilunar, leaves a great ARTICULATIONS OP THE KNEE-JOINT. 163 Fig. 78, part of the corfesponding cavity uncovered.* In this respect ihe inter-articular cartilages of the knee differ from all others of the same kind, for they do not establish a complete separ- ation of the articular surfaces, between which they are placed. These falciform cartilages are inserted into the tibia by means of ligaments, which deserve a particular description. Ligaments ef the External Semilunar Cartilage. — These are two : the one anterior, and the other posterior ; both of them are very strong. The anterior is inserted in front of the spine of the tibia, outside of the anterior crucial ligament, into a deep depression situated near the external glenoid cavity of the tibia. This anterior ligament of the external semilunar cartilage sends off a bundle which intermingles with the ante- rior crucial ligament. Tlie posterior is inserted into the spine of the tibia, in the unequally-divided interval situated between the two prominences of the spine. The posterior ligament sends off a considerable bundle of fibres to be inserted into the posterior crucial ligament. The circular form of the external semilunar cartilage is owing to the insertions of the two an- terior and posterior ligaments being separated from each other only by a few lines. Ligaments of the Internal Semilunar Cartilage. — These are much weaker than the for- mer. The anterior is inserted a good deal before its fellow, the anterior ligament of the external semilunar cartilage, and the posterior is inserted a good deal behind the corresponding ligament of the external semilunar cartilage ; hence the semilunar shape ■of the internal semilunar cartilage, which does not send off" any fibrous prolongation to the anterior or posterior crucial ligaments. The ligaments of the inter-articular cartila- ges being inserted into the tibia, these cartilages follow the tibia throughout its course. Means of Union of the Kfiee-joint are two lateral ligaments, a posterior and an anterior, two crucial ligaments, and a synovial capsule. 1. Lateral Ligaments. — The external lateral ligament {a, Jigs. 79 and 80) appears as a rounded cord ; it is inserted into the exter- nal tuberosity of the femur, at the point of union of the five anterior sixths with the first posterior, on the prolongation of the line of the fibula ; the precise point of this insertion is a small eminence surmounting a depression which is destined to the tendon of the popli- teus muscle, and is situated in front of an- other depression destined to the external ge- mellus ; thence this ligament descends, in a vertical line, to be inserted mto the external face of the head of the fibula. This ligament has the appearance of a tendon ; it extends along the anterior border of the tendon of the biceps, with which it may be readily con- founded. We should have but an incomplete idea of the means of union which the knee-joint pos- sesses on the outside, if we did not add to the number of its ligaments the tendon of the bi- ceps, which unites in some sort its inferior insertions with those of the external lateral ligament, and the small band of the fascia lata inserted into the anterior tubercle of the tibia^ and sending to the external edge of the rotula an expansion, which unites with the tendon of the vastus externus The internal lateral ligament (b c, figs. 79 and 80), which is much longer than the exter- nal, has the shape of a broad, thin, pearly- coloured band, arising from the posterior part Fig. 79. Fig. 80. * On asking myself the question why there should be this difference between the two semilunar cartila<;es, I have come to the conclusion that the external condyle of the femur, pressing much more upon the tibia than the intemai, on account of the external following the axis of the femur, while the internal is turned away from it to the inside, the external iater-artictilar cartilage had to piotect a greater ] the tibia rtion of the articular surface of 164 ARTHROLOGY. of the internal tuberosity of the femur, on a level with the external lateral ligament, im- mediately below the tubercle into which the third adductor muscle is inserted ; it is turned downward, and a little outward ; it widens in its course, and is inserted, by a broad surface, into the internal border and the anterior surface of the tibia : at this in- sertion, which is at least an inch wide, it is covered by the tendons of the sartorius, gracilis, and semitendinosus muscles, which glide over this ligament by means of an in- tervening synovial bursa. Its deep surface is applied to the anterior or reflected tendon of the semi-membrano- sus, to the internal semilunar cartilage, to which it intimately adheres, and to the inter- nal inferior articular vessels, which are protected by it. When the layers of this ligament are removed in succession, it will be seen that the deepest fibres are attached to the superior part of the internal tuberosity of the tibia, and adhere to the synovial membrane. The lateral hgaments are situated much nearer to the flexing or the back part, than to the extending or the fore part of the joint, so that they are stretched during extension, and assist in limiting that motion, but are re- laxed during flexion, to the performance of which they oiTer no obstacle. The posterior ligament, or ligament of Winsloic {c,figs. 79 and 81), is much complicated, and is composed, 1. Of a fibrous capsule for each condyle ; 2. Of a median posterior lig- ament, the only one which has been described by authors. 1. Fibrous Capsule of the Condyles. — -Each condyle is enveloped with a fibrous husk; that of the external condyle is covered by the external origin of the gemellus, and that of the internal condyle by the internal. The fibrous capsule of the internal condyle is completed by the internal origin of the gemellus turning around the highest and most in- ternal portion of this condyle. The semi-membranosus muscle sends a fibrous expansion from above downward to this same internal capsule ; the external head of the gemellus is still much more than the internal identified with the corresponding fibrous capsule, which furnishes a great number of insertions to that muscle. When there is a sesa- moid bone in the external gemellus, it is found in the substance of the external capsule, 2. The Median Posterior Ligament. — It is composed of severtil sets of fibres : 1. Some pass obhquely upward and outward, being formed by a considerable expansion of the semi-membranosus ; 2. Others proceed from the tendons of the popliteus and the ge- meUi ; and, lastly, 3. Some fibrous bundles, partly vertical and partly oblique, arise from above the condyles of the femur, and are attached to the tibia. From tins collection of fibres running in difl!erent directions, there results an irregularly-interwoven ligament, perforated by foramina that transmit the ramifications of the middle articular artery ; several of the most deeply-seated ligamentous bundles are inserted into the edges of the inter-articular cartilages. 3. Anterior Ligament, or Ligamcntum Patellfe {d,figs. 80 and 81). — This name is given Pig_ 81. to that portion of the tendon of the extensor muscles which ex- tends from the patella to the tibia. This ligament has the shape of a very broad, thick, ahnost triangular band. Its fibres arise by a broad insertion, of from five to six lines, from the apex of the patella and from the anterior surface of this bone ; they are parallel, pearly-white, and become nearer to each other as they approach the most prominent and lower portion of the anterior tuberosity of the tibia, to which tuberosity they are attached. It should be remarked, that this ligament is by no means inserted into the rugged projections which are found on the back part of the apex of the patella. Behind this ligament is a considerable mass of adipose tissue {e,fig. 81), which separates the hgament from the articular synovial capsule , a synovial bursa if fig- 81) separates it from the anterior portion of the tuberosity over which it glides. This synovial bursa sometimes communicates with the articular synovial capsule, and sometimes is totally dis- tinct from it.* Crucial or Interosseous Ligaments. — In the interior of the knee- * I should remark that this bursa extends partly over the lig-ament, which it covers from side to side, and partly over the anterior tuberosity of the tibia, which is at this point completely deprived of inter-articular car- tilage ; so that the facility with "which the synovial membrane of the tibia is removed contrasts with the diih- culty which is experienced in dissecting the synovial membrane which covers the inter-articular cartilages, provided it exists there. The ligamentum patella; forms only a part of the anterior ligament of the knee-joint ; this anterior ligament is completed by the rotula and by the united tendons of the rectus femoris, the vastus intemus and extemns, of which united tendons the ligamentum patells is evidently a continuation. We see here a very remarkable application of this law, by means of which the articular ligaments are fortified by ten- dons, and sometimes completely replaced by them ; and I have taken care to observe that it is generally the trochlear joints which exhibit examples of this replacing of ligaments by tendons in regard to extension, be- cause, in the movement of extension, a ligament, being a purely passive means of union, was not sufficient. What would take place if an ordinary ligament were to be substituted for the tendon of the extensor muscles 7 In the first place, this ligament would have to be extremely long to permit flexion ; but in case it should l»e long enough for flexion, what would become of it in the movement of extension ? Unless it were endowed with the extensibility and the elasticity of the yellow ligaments, it would become folded, and would thrust itself between the articular surfaces. It is for this reason that a ligament was required which might be short- ARTICULATIONS OF THE KNEE-JOINT. 165 joint there are two interosseous ligaments {g i,fig- 78), so arranged as to admit of the most extensive flexion, but to limit the movement of extension. They are called crucial, because they cross each other like the letter X. They are situated in the deep inter- condyloid fossa, whose sole destination appears to be that of protecting them. The an- terior {g,figs. 78 and 81) arises from the external condyle, and passes to the fore part of the spine of the tibia. The posterior {i,fig. 78) arises from the internal condyle, and is fixed to the back part of the spine. Both are continuous, by a distinct bundle, with the external inter-articular cartilage ; never with the internal. The names anterior and posterior have been given these ligaments, from their inferior insertion ; for superiorly they arise on the same level. Here follows a more minute description of their inser- tions above and below, and of their direction. The anterior crucial ligament arises, as a little band flattened from side to side, from the semilunar depression, which is concave superiorly, and is situated on the internal or median surface of the external condyle ; thence it extends from above downward, from without inward, and from behind forward, flattens from before backward, and is inserted in front of the spine of the tibia, upon which spine it encroaches a little by means of some insertions which it takes between the two articular projections constituting the spine. From the external edge of this ligament a few fibres are given off, which extend into the external part of the semilunar cartilage. The posterior crucial ligament arises from the external or median surface of the inter- nal condyle in a semilunar depression, entirely similar to the one which is destined to the anterior crucial ligament ; like the latter, it presents a threefold obliquity from above down- ward, from before backward, and from within outward ; it sends a considerable expan- sion to the external inter-articular cartilage, and is inserted back of the spine of the tibia. Thence it follows that the crucial ligaments present a double crossing : 1. A crossing in an antero-posterior direction, and this alone has been observed with attention ; 2. A crossing in a transverse direction ; when the tibia is rotated from within outward, the crossing of these two hgaments increases to such an extent that these two ligaments, strongly pressed against each other, limit the motion ; in the movement of rotation from without inward, on the contrary, as the crossing diminishes, they become relaxed and parallel ; both are stretched during extension, and relaxed during flexion ; there is an exception for the most anterior fibres of the anterior crucial ligament, which are relaxed in the middle state of extension, and stretched during flexion ; but when the extension is considerable, the anterior crucial ligament is also stretched in its anterior fibres, which, being pressed by the condyles, describe a curve anteriorly concave. The synovial capsule of this joint is the largest and the most complicated of all that ex- ist in the body. In tracing it from the upper edge of the patella, we find, behind the ten- don of the extensor muscles, a large cul-de-sac {s,fig. 81), sometimes replaced by a dis- tinct synovial capsule, interposed between that tendon and the surface of the femur. In many subjects, this bursa communicates with the synovial capsule of the knee-joint by a more or less considerable opening, and in such cases a circular constriction forms the only trace of separation. On each side of the patella the synovial membrane extends beneath the two vasti, and is sometimes elevated from one and a half to two inches above the articular surfaces ; the prolongation under the vastus externus is much more considerable than that under the vastus internus. The existence of these two prolonga- tions affords an explanation of the swellings observed at the sides of the knee in dropsy of this joint ; and the greater extent of the external prolongation explains, also, the great- er size of the prominence on the outside. In the inter-condyloid notch the synovial mem- brane envelops the crucial ligaments ; then it is reflected upon the posterior ligament, the lateral ligaments, the semilunar cartilages, the articular surfaces of the tibia, and, lastly, the back of the ligamentum pateUse ; it next sends off a prolongation, containing a few ligamentous fibres, and extending from the lower border of the patella to the front of the inter-condyloid notch. This fold has been incorrectly termed the adipose ligament ened or elongated as might be necessary, a tendon beingf the continuation of a muscle, that is, of an org-an at ouce capable of extension, contraction, and endowed with elasticity. Besides this, a bone was required that might complete the articulation on the outside, that might fill the large space wliich, during- the movement of flexion, would have remained empty between the articular surfaces, and might glide without injury over osseous surfaces, and facilitate, at the same time, standing upon the knees. Tiiis threefold object has been attained byihe patella, a sesamoid bone, which is developed in the substance of the tendon of the extensor muscle of the leg, viz., of the triceps fenioris, whose parallelism, at its insertion into the rotula, is destroyed by this bone. Independently of the anterior ligament, the knee-joint exhibits a large aponeurotic surface, formed by the femoral apooeurosis, by an aponeurotic expansion of the fascia lata, and by another aponeurotic expansion fur- nished by the tendons of the sartorius, gracilis, and semi-tendinosus muscles ; to this latter expansion is joined a fibrous lamina, given off by the tendon of the vastus externus and internus, which is attached to the tibia. This large anterior aponeurotic surface exhibits, on a level with the tendon of the triceps, a saltier-shaped in- terlacing, which closely adheres to this tendon, and seems destined to serve it as a bridle ; on a level with the patella it exhibits a thin layer, which is sometimes interrupted, and, so to say, lacerated, in consequence of the sub-cutaneous synovial capsule being present ; and on a level with the ligamentum patelliE it exhibits fibres running obliquely from above downward and from without inward. Finally, I shall point out as appendages of the anterior ligament two proper ligaments of the patella, one in- ternal, the other external, extending from the edges of tlie patella to the posterior part of each tuberosity ; these ligfaments are broad and thin, and strongly adhere to the synovial capsule. 166 ARTHROLOGT. (ligamentum mucosum, t,figs. 78 and 81). After having furnished this fold, the syno- vial membrane lines the posterior surface of the patella, and becomes continuous with the cul-de-sac behind the extensor tendon. Sometimes the prolongation, known as the adipose ligament, does not exist ; at other times there is more than one. I have seen a fold of the same nature extending from that part of the synovial membrane which lines the extensor tendon to the surface of the femur above the trochlea. No other synovia! membrane in the body is provided with so large a number of villous prolongations, which, in some subjects, may be said to give it a shaggy appearance ; they are especially met with around the pateUa* and the semilunar cartilages. To these prolongations Clopton Havers has given the name of synovial fringes. Some deep fibres of the triceps cruris have been regarded as a special tensor muscle of the synovial capsule. (Vide Triceps Cruris, Myology.) Sub-synovial Adipose Tissue. — From the abundance of this tissue in the knee-joint, its disposition requires some special notice. It is chiefly met with behind the ligamentum patellae {e,fig. 81), where it forms a very thick layer, filling up the interval between the patella and the synovial membrane. This adipose mass, which raises the ligamentum patellae in the extension of the knee, and which, during flexion, fills the empty space which the movement of flexion produces between the condyles of the femur and the tibia, is situated to the outside of the joint, between the ligamentum patellae and the synovial capsule, which is raised by the mass. This mass, on being examined on the side which is contiguous to the joint, exhibits several prolongations, which are somewhat similar to the fatty appendages of the epiploon. These appendages are all Uned by a fold of the synovial capsule ; one of these appendages, supported by a fibrous bundle, is attached to the inter-condyloid space, under the name of ligamentum mucosum patella, which hg- ament is sometimes multiple, and has no other object except to draw to it the fatty mat- ter between the tibia and the femur during flexion of the knee, and to keep that matter in its place during the movement of extension. A large quantity of fatty matter is also found behind the tendon of the triceps above the condyles, where that matter fills the in- terval between this tendon and the corresponding part of the femur. Bundles of fatty matter are, lastly, found all around the condyles, as well as in the inter-condyloid notch, and around the insertions of the crucial ligaments. This fat, which may be observed even in individuals in a state of marasmus, except that, under those circumstances, it is more serous and infiltrated, is nowhere more evidently than in the knee-joint, destined to fill the intervals produced betw'een the articular surfaces by certain attitudes. Mechanism of the Fcmoro-tilial Articulation. 1. With regard to Strength. — The strength of articulations is generally in direct pro- portion to the extent of the articular surfaces, and there is no joint more advantageously constructed in this respect than the one we have been examining. The reception of the spine of the tibia into the inter-condyloid fossa also tends greatly to increase the strength of the joint, although it forms but an imperfect kind of dovetailing. A tliird and last con- dition conducive to strength is, the multipUcity of the ligaments, and of the tendons, sup- plying, in some respects, the deficiencies in the fitting. 2. With regard to Mobility. — The knee, being a hinge-joint, has two principal move- ments, in opposite directions, \[z., flexion and extension; but, as the mutual reception of the surfaces is very imperfect, it is also capable of some slight rotatory motions. In flexion, the surfaces of the tibia, defended by their inter-articular cartilages, glide backward upon the condyles of the femur ; and, from the great extent of the articular surfaces of the last bone in that direction, the movement can be carried so far as to per- mit the leg and thigh to touch. In this movement, the lateral, the posterior, and the cru- cial ligaments are relaxed, except the anterior fibres of the crucial ligament, which are stretched ; the ligamentum patellae is stretched ; the patella is firmly applied to the front of the joint, and can neither be moved to the right nor to the left,, as may be done during extension. In the position of flexion, the patella fills up, as it were, the great hiatus then existing at the front of the joint between the femur and the tibia. Luxation is impossible during this movement, which is only limited by the mutual contact of the leg and the thigh. In extension, the tibia and the inter-articular cartilages glide in the opposite direc- tion. The movement is arrested when the leg is in the same line as the thigh, and whatever muscular effort be then made, the leg never will pass that Hmit, excepting from malformation of the parts. A greater amount of extension is rendered impossible, both by the shape of the articular surfaces, and by the stretching of all the ligaments, ex- cepting that of the patella, which is completely relaxed, and permits of a great mobility of that bone in all directions. One circumstance in the shape of the articular surfaces, which appears to be opposed to any extension beyond the straight line, is the small extenc of the trochlea in front ; for, could such extension take place, the glenoid cavities of the tibia would then be applied to a portion of the trochlea, much smaller than themselves. The crucial ligaments are especially intended to limit the movement of extension, as the * [Two slight folds of the memln-ane formed at the sides of the patella, have been particularly descriheij ■under the very inappropriate name of tlve alar Ugaments.l PERONEO-TIBIAL ARTICULATIONS. 167 following experiment will at once demonstrate. Divide all the external ligaments of the joint ; the crucial ligaments will then alone remain ; then endeavour to extend the leg beyond the ordinary limits ; this will be found impossible until these ligaments are divided. That both the crucial ligam.ents oppose the extension of the limb beyond a cer- tain limit, is proven by dividing these ligaments separately. So long as one remains, no matter which, the extension is limited. An analogous experiment, in which all the liga- ments of the joint (even including the crucial) are divided, excepting the lateral, proves that these are not only opposed to lateral movements, but also limit extension with much force ; this they are enabled to do from being situated nearer to the back than to the front of the joint. Complete luxation can only be effected after laceration of all the liga- ments which limit extension. An interesting remark, which has been suggested to me by M. Martin, is, that the crucial ligaments are not only destined to limit the movement of extension, but also — and this is, perhaps, their principal object — to prevent the articu- lar surfaces from leaving each other in the anterior posterior direction during a forcible extension. Thus, the anterior crucial ligament will prevent, in a movement of exten- sion, both the displacement of the tibia backward, and that of the femur forward, and the posterior crucial ligament will prevent both the displacement of the tibia forward, and that of the femur backward. It is also important to remark, that while standing upon the feet, the ham-strings being stretched, these extensor muscles of the leg, which are situa- ted upon the thigh, the rectus femoris, and the vastus externus and internus, are entirely inactive, as is proved both by the extreme mobility of the patella and the relaxed state of these muscles in a standing position, and by the absence of all sensation of lassitude in these muscles after the vertical position upon the feet has been continued for a long time. The extension of the knee, therefore, takes place without any co-operation on the part of the muscles, simply through the articular surfaces being juxtaposed in all their breadth, and by the tension of the lateral and crucial ligaments, which keeps the articular surfaces mechanically upon each other.* In all these motions the patella is fixed ; it is the femoral trochlea which glides upward or downward upon the posterior surface of that bone. This almost invariable position of the patella depends on the inextensibility of its ligament. The existence of the patella has no effect in limitin^he movements of extension ; its only uses, as far as the joint is concerned, are to protect it in front, and to prevent painful pressure in the kneeling posture. Its other and chief uses are connected with the functions of the triceps ex- tensor muscle, in the tendon of which it is developed; it removes the axis of the muscle from the parallel direction of the lever which it is destined to move. It is movable and depressed during extension of the leg, but during flexion it becomes prominent and fixed, t Rotation. — When the leg is semi-flexed upon the thigh, it can be very slightly rotated inward and outward. These movements are performed, not upon the external, but upon the internal condyle as a pivot, so that the external part of the head of the tibia glides forward during rotation inward, and backward during rotation outward. The difference in the part performed by the two condyles in the movement ©^.rotation does not depend upon any peculiarity of structure in the joint, but exclusively upon the arrangement of the acting forces, as we shall see when treating of the muscles. Rotation inward is limited by the mutual contact of the crucial ligaments, whose decussation is increased during this movement. Rotation outward is more extensive, because in this movement the liga- ments are uncrossed, and become parallel. We shall see hereafter that the biceps is the agent of rotation outward, and the popliteus of rotation inward. Peeoneo-tibial Articulations {figs. 79 and 80). Preparation. — 1. Remove carefully the muscles of the anterior and posterior regions of the leg, which will expose the interosseous ligament, and the anterior and posterior ligaments of these joints. 2. In order to see the interior of the articulations, saw through the two bones in the middle, and then separate them. 3. To gain an idea of the interosseous * M. Robert, one of our most disting-uished young surg-eons, has observed a fact which sustains thpse ideas, which had already been demonstrated by the artificial legs of M. Martin. An individual in whom the patella •was fractured, had recovered %vith a distance of about ten centimeters. The movement of extension by mus- cular contraction was impossible ; but when the limb was extended, it maintained itself in that position with the same force as the limb upon the healthy side. The patient had succeeded, by a sort of artifice, in exe- cuting spontaneously the movement of extension ; he brought the trunk and the pelvis forcibly forward : the femur followed the pelvis, and extension being once effected, this inferior limb, being very strong and immo- vable, assisted in the standing position just as much as the healthy limb. t It is during flexion of the leg, and, consequently, when the patella is most immovable, that this bone maybe displaced in consequence of some external violence, and in this case, the dis|)laceinent always takes place to the outside. However, one should suppose that the external condyle of the femur, being much more prominent than the internal, would be opposed to the luxation outward, and favour the luxation inward. But we may remark, that the patella, when displaced inward, cannot remain in this position, in which nothing maintains it, and from which the oblique direction of the triceps tends, on the contrary, to bring it back to its natural place ; whereas, when the patella is displaced outward, the prominence of the external condyle op- ooses the reduction of the patella, which can only be eflfected by artificial means. It should be remarked, that ttie obliquity downward and inward of the femoral trochlea gives a tendency to the patella of being continually drawn outward by the tendon of the extensor muscles, which is slightly oblique in the same direction as the trochlea. This is so true, that in white swellings of the knee-joint, the spontaneous displacement of the pa^ tella always takes place outward. 168 ARTHROLOGY. ligament of the inferior articulation, saw perpendicularly through the lower ends of the bones of the leg, so as to divide them into an anterior and a posterior portion. The tibia and the fibula, which are contiguous at their extremities, are separated from each other along their shafts, the interval being occupied by an aponeurosis, improperly called the interosseous ligament. We have, then, a superior and an inferior peroneo-tibial articulation, and an interosseous ligament or aponeurosis. 1. Superior Peroneo-tibial Articulation. This articulation is an arthrodia. The articular facette of the tibia, looking downward and outward, is situated behind its external tuberosity. The facette of the fibula looks upward and inward ; it occupies the inner part of the upper end of the bone. The means of union are two ligaments : an anterior {g,fig. 80) and a posterior {d,fig. 79). They are composed of parallel fibres, directed obliquely downward and outward from the exter- nal condyle of the tibia to the head of the fibula. There is generally a distinct synovial membrane for this joint, but sometimes it is a prolongation from the capsule of the knee. This communication frequently existing between the synovial capsule of the knee and the peroneo-tibial articulation, should condemn, in an amputation of the leg, the practice of extirpating the superior extremity of the fibula. The formidable accidents which might be consequent upon such an extirpation may readily be conceived, and should for- bid the operation, although it has been accomplished without any accident. Its only ob- ject is to prevent the fibula from pressing upon the soft parts. 2. Inferior Peroneo-tibial Articulation. This articulation is an amphi-arthrosis, that is, it is formed between surfaces that are partly contiguous and partly continuous. The former consists of two articular facettes, narrow from above downward, and oblong from before backward ; of these, one is con- vex, and situated upon the internal surface of the lower end of the fibula above the mal- leolus ; the other is concave, and continuous with the inferior or tarsal articular surface of the tibia. They are both covered with cartilage. The continuous surfaces are rough, and much more extensive ; they are triangular in shape, having their bases directed down- ward : the one situated upon the fibula is convex, that upon thg tibia is slightly concave. The means of union are, two ligaments external to the joint, and an interosseous Uga- ment connecting the two triangular surfaces just mentioned. Of the two external liga- ments, one is anterior (i, fig. 80) and the other posterior (e, fig. 79). Tliey are both very strong, and composed of thick, shining, parallel fibres, which pass obliquely downward and outward from the tibia to the fibula. They are almost always divided into two dis- tinct bundles. They are both remarkable from descending beyond the articular surfa- ces, so that they increase the depth of the cavity for the reception of the astragalus. The synovial membrane of this articulation is a prolongation from that of the ankle-joint. The interosseous ligament consists of fibrous bundles, mixed with adipose tissue, which unite the two triangular surfaces so firmly that the fibula is sometimes fractured in at- tempting to rupture the ligaments. 3. Interosseous Aponeurosis. The name of interosseous ligament is given to an aponeurotic septum (b, figs. 79 and 80) placed between the muscles of the anterior and those of the posterior aspect of the leg ; it should rather be regarded as serving to multiply the points of insertion for fibres of those muscles, than as a means of union between the bones of the leg. It is nan'ow- er below than above, and is composed of fibres running obliquely downward and outward from the outer edge of the tibia to the longitudinal crest on the inner surface of the fibula. As in the interosseous ligament of the forearm, we find some other fibres cross- ing the former at an acute angle. The septum thus formed is interrupted above and be- low for the passage of the tibial vessels ; the peroneal artery and veins traverse the low- er opening ; the anterior tibial artery and veins pass through the upper. Mechanism of the Peroneo-tibial Articulations. The fibula is only capable of almost imperceptible gliding movements upon the tibia. This arrangement is directly connected with the mechanism of the ankle-joint. Ankle, or Tibio-taksal Joint {figs. 79 and 80).* Preparation. — Cut and turn back the tendons that are reflected round the joint, and remove the sheaths of those tendons by which most of the hgaments are covered. The peroneo-calcanean ligament is seen after the tendons of the peroneal muscles have been removed ; the synovial membrane of these tendons only covers it. The peroneo-astra- galian ligament is the most difficult to uncover, on account of it 3 being deeply seated, and separated from the sheath of the muscles of the posterior region by a large quantity of adipose tissue. The internal lateral ligament is seen immediately beneath the sheaths of the tibiaUs posticus, the common flexor tendon of the toes, and the proper flexor of the * We should remark that, in order to study tWs as well 33. ah the other articulations efficiently, it is a g^reat advantage to be provided with two joints, of which one is opened, while the other has its ligaments untouched- ARTICULATIONS OP THE ANKLE-JOINT. 169 great toe. In order to see the deep layer of this hgament, the superficial layers must be removed one after the other. The tibio-tarsal articulation belongs to the class of angular ginglymi. Articular Surfaces. — Both bones of the leg participate in this joint, their lower extrem- ities being united to form a transversely oblong socket, of which the tibia constitutes by far the greater part. On this articular surface there is an antero-posterior ridge, corre- sponding to the groove of the trochlea on the astragalus, and separating two shallow cav- ities. The socket is bounded by the malleoli on each side. The internal or tibial mal- leolus corresponds to the internal lateral articular surface of the astragalus ; and the ex- ternal or fibular malleolus, to the external lateral facette of the same bone. The tibio- peroneal cavity is completed forward and backward by the lower part of the anterior and posterior peroneo-tibial ligaments. The superior articular surface of the astragalus is a trochlea ; it is oblong from before backward, thus contrasting with the cavity on the lower extremity of the leg,* which is transversely oblong. This trochlea presents a shaUow depression, running from before backward, and having an external and an internal edge, the external being the more elevated of the two. The pulley of the astragalus is continuous with its lateral articular surfaces, of which the external is by far the larger. The means of union are three external lateral ligaments, two internal lateral hgaments, an anterior (r, fig. 80) and a posterior (s, fig. 79) ligament, and a synovial capsule. The external lateral or. j>eroneo-tarsal ligaments are three in number ; they all proceed from the fibula, either to the astragalus or the os calcis. 1 . The external lateral Hgament, properly so called (ligamentum fibulae medium vel per- pendiculare, m,.figs. 79 and 80), is situated beneath the sheath of the peroneus longus and brevis. It arises from the summit of the external malleolus, is directed downward and slightly backward, to be attached to the outside of the os calcis. It is rounded, and composed of parallel fibres. 2. The anterior external lateral ligament (ligamentum fibulae anterius, ?i, fig. 80) arises from the anterior edge of the external malleolus, and proceeding downward and forward, is fixed to the astragalus in front of its external malleolar facette. It is very short, and broader below than above : it forms one of the two anterior hgaments described by Bi- chat in this joint. 3. 'The posterior lateral ligament (hgamentum fibulas posterius, o,fig. 79) is very deeply seated behind ; it extends from the excavation on the inside and behind the external mahcolus to the posterior border of the astragalus, immediately above the pulley of this bone. It is directed almost horizontally, or in a shght degree obliquely downward and inward, and is almost parallel to the posterior ligament of the lower peroneo-tibial ar- ticulation. It is composed of very distinct parallel fibres, which are arranged in several layers, the deepest of which are attached to the astragalus behind the facette of the ex- ternal malleolus. The posterior peroneo-astraglagean ligament is very strong. Bichat calls it the posterior ligament of the joint. The internal lateral ligament is much stronger than the three external hgaments taken together. It is composed of two very distinct layers : 1. A superficial layer, consisting of fibres stretched from the apex and the anterior and posterior borders of the internal mal- leolus to the os calcis, and the upper edge of the lower calcaneo-scaphoid ligament, which it maintains in a state of constant tension. The fibres are long and slightly divergent, but still sufficiently so to have given origin to its name of the deltoid ligament {p,figs. 79 and 80). The fibres which are most anterior pass directly forward to the neck of the astragalus, and to the scaphoid ; they form a very thin layer, which has been improper- ly cahed the anterior ligament of the ankle-joint. 2. Below the above is a deep layer of much greater extent, composed of short and strong bundles, passing downward and out- ward from the summit and sides of the internal malleolus, to the inner surface of the as- tragalus, below the articular facette. t Synovial Capsule. — The external surface of this membrane is brought into view in front and behind by removing the tendons and their sheaths ; and if the external and in- ternal lateral hgaments be divided, it wih be seen to extend into the inferior peroneo- tibial articulation. It will also be observed that it is tense at the sides, but very loose behind, and more particularly so in front. A great quantity of adipose tissue covers its external surface in these situations. Mechanism of the Ankle-joint. This articulation not only constitutes the point at which the weight of the body is * Hence, the longest diameter of the astraglagean cavity is from before backward ; the longest diameter of the tibio-peroneal cavity is transversely. The extent of the movements of flexion and extension of the foot depends upon the disproportion between the antero-posterior diameter of the pulley of the astragalus and the socket of the leg. t [The author has omitted, perhaps intentionally, to give a special description of the anterior and posterior ligaments of the ankle-joint, already alluded to by him. The former extends from the anterior margin of the articular surface of the tibia to the corresponding border of the astragalus, and is called the tibio-tarsal lig- ament ; it is very thin, and covered by the tendons of the extensor muscles. The posterior can scarcely be said to exist as a distinct ligament.] Y 170 ARTHROLOGY. transmitted to the foot, but also performs a very active part in the movements of pro- gression ; it is therefore so constructed as to unite great strength with the capabiUty of tolerably extensive motion. With regard to strength, the following arrangements should be noticed as especially ad- vantageous : 1. The leg being articulated with the foot at a right angle, transmits the weight of the body directly to it, and this transmission being effected in the perpendicular direction, i. e., in a direction in which the articular surfaces mutually oppose each other, has no tendency either to produce fatigue or to rupture the ligaments. The perpendic- ular position of the leg upon the foot during standing is worthy of notice, because of it- self it proves that man was intended for the erect posture, since in this attitude alone does the entire inferior surface of the foot rest upon the ground. It should be also re- marked, that there is no other articulation, excepting that of the head upon the verte- bral column, in which the parts united are habitually perpendicular to each other. 2. The dovetailing eifected at this joint, by the reception of the astragalus into the socket, formed by the bones of the leg, is also highly conducive to its strength. This dovetail- ing results both from the pulley-like surface of the astragalus, and from the angular form of the tibio-fibular socket ; and it should be observed, that this latter condition is, as it were, peculiar to the ankle-joint, for in no other do we meet with such abrupt angles. With regard to mobility, the tibio-tarsal articulation admits of flexion and extension. There is no lateral motion, the movements of the foot in this direction being almost ex- clusively performed at the tarsal joints. In flexion, the astragalus glides backward upon the tibia and fibula, and the back part of the pulley projects behind. Luxation, from an excess of this movement, is almost impossible, for it is limited by the meeting of the neck of the astragalus and the anterior edge of the tibio-fibular sockets. In this movement, the posterior external lateral liga- ment, and the middle and posterior fibres of the internal lateral ligament, are put upon the stretch. In extension, on the contrary, the trochlea of the astragalus glides forward upon the corresponding surface ; the synovial membrane is borne upward in front ; the anterior external lateral ligament, and the anterior and middle fibres of the internal lateral liga- ment, are stretched. Luxation is possible during this motion, but is very rare. Lateral Movements. — Although the shape of the joint is opposed to movements of this kind, yet it cannot be doubted that the elasticity of the fibula, by allowing the external malleolus "to yield a little, may permit them in a slight degree. Nevertheless, the fibula must be fractured, if any force, exerted by the astragalus against the external malleolus, be carried so far as to thrust it much outward. Articulations of the Tarsus {figs. 80, 82, 83, 84). The intrinsic articulations of the tarsus comprise, 1. The articulations of the compo- nent bones of each row. 2. The articulation of the two rows together. jij g2_ Preparation. — 1. Remove the tendons situated upon the dor- sum of the foot, and also the extensor brevis digitorum mus- cle. 2. Remove all the muscles of the plantar region. 3. Rub off, by means of a rough cloth, the adipose tissue covering the ligaments (a subject much infiltrated with serum is best adapted for this purpose). 4. In order to gain a clear comprehension of the articulation of the two rows together, remove the astrag- alus from the sort of box in which it is contained, by divi- ding the interosseous ligament which unites it to the os calcis. 5. For the examination of the interosseous ligaments, it is ne- cessary to separate the bones by laceration or section of those ligaments ; the resistance experienced in doing this, and the portions of the ligaments remaining attached to the bones, will give a good idea of their strength and situation. 6. In order to obtain a correct notion of all the ligaments together, it is necessary, while studying each, at the same time to examine a foot in which all the joints have been opened above, while the bones are still retained in their situations by means of the plantar ligaments . Articulation of the CompoJicnt Bones of the First Row, or Articula- tion of the Astragalus with the Os Calcis. This is a double arthrodia, in which each of the bones pre- sents two articular facettes, separated by a furrow deeper on the outer than on the inner side. The posterior surface of the astragalus (1, fig. 84) is concave, that of tjie os calcis (2) is convex ; in front (1) the opposite obtains, so that there is a mu- tual reception of parts. The means of union, properly speak- ing, consist only of an extremely strong interosseous ligament (a, ARTICULATIONS OF THE TARSUS. 171 fig. 84) formed by ligamentous bundles, of which some are vertical, and others oblique ; they are mixed with fat, and occupy the considerable interval formed by the grooves of the two bones, and which is larger towards the outer end. To form a complete idea of this ligament, it is necessary to make a vertical section from before backward, through the middle of the astragalus and os calcis (as in_^^. 84). A loose synovial membrane lines the posterior articulation, which is strengthened on the inside by the fibrous sheaths of the tendons of the tibialis posticus, the flexor longus digitorum, and the flexor longus polhcis. There are also about this joint two very small fibrous bundles, one of which is posterior {t, fig. 80 ; a, fig. 83), and the other external {b, fig. 83) : some anatomists have described them by the names of ■posterior and external ligaments. The anterior por- tion of this articulation is often double, from the division of the anterior articular sur- faces'into two smaller facettes : it forms part of the astragalo-scaphoid articulation, with which it wOl be described. Articulations of the Component Bones of the Second Row. All these joints are very compact, for the five bones which constitute this row act as one only in the movements performed by the foot at its tarsal pig, 83. articulations. They present for the most part angular facettes ; they have also interosseous ligaments, and are true symphyses or amphiarthroses. Articulations of the Cuneiform Bones with each other. * '^ ^>~y^^ Articular Surfaces. — The corresponding surfaces of the first and second cuneiform bones present contiguous as well as con- tinuous portions. The contiguous portions are square, and sit- uated at the upper and back part of each surface. The con- tinuous portions are placed in front of the preceding. The corresponding articular surfaces of the second and third cunei- form bones are smooth and contiguous behind, but rough and irregular in front. Means of Union. — 1. ^y dorsal ligaments (cc, fig. 83). This name is given to some very compact fibrous bands stretching transversely from one bone to the other. By their upper sur- faces, on which the longest fibres may be seen, they are in re- lation with the extensor brevis digitorum and with the tendons of the other extensor muscles. Their lower surfaces, the fibres of which are shorter, correspond to the articulations, and to the periosteum of the cuneiform bones, with which they in- terlace. 2. By plantar ligaments. This name may be given to some of the fibres of the interosseous ligaments. 3. By in- terosseous ligaments. These, which are very strong, consti- tute the principal means of union of these joints, and occupy all the rough portions of the corresponding facettes. They so closely unite the bones, that, even when the dorsal liga- ments are removed, it is not easy to open the joints. The synovial membrane is merely a portion of the general synovial membrane of the tarsus. Articulations of the Scaphoid with the Cuneiform Bones. Articular Surfaces. — The scaphoid presents the only example in the body of a single articular surface being divided into three facettes by well-marked ridges. Each of these facettes is triangular, and corresponds to a surface of the same form on one of the cunei- form bones. The base of the triangular facette for the first cuneiform bone is below ; the bases of the other two are above (3, fig. 80). Means of Union. — 1. Dorsal ligaments. There are two for the first cuneiform bone, a superior (<^, _^^. 83), and an internal {e,figs. 83 and 84) ; and only one for each of the oth- ers iff, fig. 83). The dorsal ligaments of the first cuneiform bone pass directly back- ward ; those of the other two are stretched obliquely forward and outward. 2. Plantar ligaments. A very strong plantar hgament (a, fig. 82) extends from the tubercle of the scaphoid to the corresponding tubercle of the first cuneiform bone ; it is blended with the tendon of the tibialis posticus, which furnishes a considerable expansion that crosses the direction of the tendon of the peroneus longus, and extends to the third cuneiform, and the corresponding metatarsal bone ; it may be considered as an inferior ligament of the tarsus. The name of plantar ligaments can scarcely be given to some irregular fibres (b,fig. 82) passing from the lower surface of the scaphoid to the second and third cunei- form bones. A synovial membrane, common to the three articulations, is continuous with that of the three cuneiform bones. 172 ARTHROLOGY. Articulation of the Third Cuneiform Bone with the Cuboid. This articulation resembles in every respect those of the cuneiform bones. The means of union are a dorsal ligament {g, fig. 83), consisting of a very strong transverse bundle ; an interosseous ligament, which occupies the entire non-articular portion of the correspond- ing surfaces ; and an ill-defined plantar ligament, consisting of some irregular transverse fibres. The synovial membrane communicates vi^ith that of the cuneo-scaphoid articulations. Articulation of the Scaphoid with the Cuboid. The scaphoid and the cuboid often unite by a small facette. The means of union are an oblique dorsal ligament {i, fig. 83), a very strong interosseous ligament, occupying the whole of the corresponding surfaces of the bones, excepting the small portions which are contiguous ; and a very thick transverse plantar ligament, extending somewhat ob- liquely from the tuberosity of the scaphoid to the cuboid. These ligaments exist even when there are no articular facettes. Articulation between the two Rows of the Tarsal Bones. The articulation between the two rows consists of the articulation of the astragalus with the scaphoid and os calcis, the articulation of the os calcis with the cuboid, and, lastly, the union of the os calcis to the scaphoid by means of several ligaments. 1. Articulation of the Astragalus with the Scaphoid. The articular surface on the head of the astragalus (1,^^. 84), elongated from without Fig. 84. inward, and from above down- ward, is larger than the glenoid cavity of the scaphoid (3), and pro- jects considerably below it, where it articulates with the anterior fa- cette, or the two anterior semi- facettes of the os calcis. The cavity of reception is completed by a ligament called the inferior calcaneo-scaphoid {b), which occu- pies the triangular interval be- tween the small tuberosity of the _ OS calcis and the scaphoid, and y^~ forms by itself the inner side of the cavity of reception. In order to obtain a good view of this ligament, it is advisable to remove the astragalus by cutting and tearing the interosseous ligament that unites it to the OS calcis ; it will then be seen that the ligament we are describing is very strong and triangular, and that it covers not only the lower, but the inner part also of the head of the astragalus. It is often divided into two parts : one being external, narrow, and shaped like a band ; the other internal, much broader and thicker, in relation below with the sesamoid bone of the tendon of the tibialis posticus, and presenting a cartilaginous thickening at the corresponding point. Another ligament, called the superior calcaneo-scaphoid {I, fig. 83), must also be regard- ed as contributing to wedge in the astragalus ; it extends from the inside of the anterior extremity of the os calcis to the outside of the scaphoid. It is situated upon the dorsum of the foot, in the deep hollow occupied by fat, on the outer side of the astragalus. These two ligaments (the inferior and superior calcaneo-scaphoid) constitute the means of union between the os calcis and the scaphoid. These bones are in no part contigu- ous ; but occasionally we find the os calcis continued into the scaphoid, through the me- dium of an osseous lamina, which replaces the lower calcaneo-scaphoid ligament.* The OS calcis being very securely articulated with the astragalus, and at the same time very firmly connected with the scaphoid, it follows that the articulation between the scaphoid and astragahis possesses great strength, although the ligaments directly uniting them are by no means powerful ; just as the atlas, which is but slightly connected with the occipital bone by means of its own ligaments, is very firmly fixed by the ligaments stretching from the occipital bone to the axis. Nevertheless, the absence of any very strong and direct means of union between these bones renders it possible for the astrag- alus to be forced by external violence out of the sort of osseo-fibrous socket in which it is placed. The superior aslragalo-scaphoid ligament {s,fig. 80 ; m, figs. 83 and 84) is the only one proper to this joint ; it is semicircular in form, and extends somewhat obliquely forward and outward, from the neck of the astragalus to the margin of the facette on the sca- phoid. It is thin in texture, and consists of parallel fibres ; it is covered by the ex- tensor brevis digitorum above, and is lined below by the synovial membrane of the articu- lation between the scaphoid and the astragalus. * I have represented a case of this nature (vide Anat. Pathol, avec Planches, liv. ii., pi. iv.). ARTICULATIONS OF THE TARSUS. 173 2. Calcaneo-cuboid Arliculalion. This articulation is upon the same hne as the astragalo-scaphoid ; an anatomical fact which has suggested the ingenious idea of a partial amputation of the foot between the two rows. It belongs to the class we have designated articulations by mutual reception, and of which we have found examples in the stemo-clavicular joint, and the carpo-meta- carpal articulation of the thumb. Articular Surfaces (2, fig. 80). — The facette of the os calcis is concave from above downward, while the surface of the cuboid is concave transversely, that is, in a direc- tion at right angles to that of the former. At the lower part of the facette of the os cal- cis there is a horizontal projection, which sometimes stops the knife during the disartic- ulation of the two rows. The means of union consist of three ligaments : an inferior or plantar, an internal, and a superior. The inferior plantar, or calcaneo-cuboid ligament (ligamentum longum plantae, c d,figs. 82 and 84), is the strongest of all the tarsal ligaments, forming a broad band of pearly- white fibres, directed from before backward. These fibres constitute a very thick bundle, and extend from all the under surface of the os calcis, excepting the posterior tuberosities, to the posterior margin of the groove of the cuboid. If the fibres of this ligament be removed layer by layer, we soon arrive at a more deeply-seated ligament, separated from the first by some fatty tissue : it extends obliquely inward, from a tuber- osity at the forepart of the under surface of the os calcis, to all that portion of the infe- rior surface of the cuboid, situated behind its groove. There are, therefore, two inferior calcaneo-cuboid ligaments : a deep (c) and a superficial (d). The internal calcaneo-cuboid ligament (n, fig. 83) is short, narrow, quadrilateral, and very strong ; it is placed at the side of the superior calcaneo-scaphoid ligament, in the deep excavation between the astragalus and the os calcis. These two ligaments are separated in front, but blended together behind, so as to resemble the letter Y. They may be considered as in some measure fonning the key of the articulation of the two rows of tarsal bones ; for, during disarticulation, the articular surfaces are easily separ- ated as soon as they are divided. The superior calcaneo-cuboid ligament (a, fig 83) is only a very thin, small band of fibres, extending directly forward, from the os calcis to the cuboid. Mechanism of the Tarsal Articulations. We should examine the mechanism of the tarsal articulations both as regards their strength and their mobility. With regard to Strength. — The tarsus forms the fundamental part of the foot ; one might, in fact, consider the metatarsus and the toes as superadded structures, for, even when they are removed, the foot fulfils its office as a basis of support very efficiently. Surgeons avail themselves of this fact in performing partial amputations of the foot at the tarsal and tarso-rnetatarsal articulations. The construction of the tarsus is, in every respect, adapted to ensure strength ; the number of its pieces, the breadth of the articular surfaces, the strength of the interosse- ous hgaments, and even the mobility of its component bones, all conduce to this end. Suppose, for example, that a single bone had occupied the place of the seven bones in the tarsus, how liable would this long and cancellated lever have been to fractures from the violent shocks to which it is constantly exposed, or from the influence of muscular contraction 1 The tarsus is narrow behind, but enlarged before, so as to increase the transverse extent of the supporting base in that direction ; it is articulated with the leg at a right angle, and, therefore, receives directly the weight of the body, and as directly transmits it to the ground. In order to provide the arm of a lever for the power which raises the weight of the body, it projects behind the leg ; indeed, the fitness of an indi- vidual for running and leaping may be, in some degree, calculated from the length of his heel, or, what is the same thing, from the prominence of the tendo Achilles. In stand- ing upon the sole of the foot, the weight of the body is transmitted by the tibia to the astragalus, and from thence to the os calcis. Part of the momentum is lost at the artic- ulation between these bones, and it is easy to comprehend why they are super-imposed, and not arranged in mere juxtaposition. But the astragalus is not placed horizontally above the os calcis, for it inclines inward, downward, and Ibrward ; and from this cir- cumstance, even in standing upon the soles of the feet, the weight of the body is distrib- uted between the os calcis and the anterior range of the tarsus, which is itself subdivi- ded into two rows, but only on the inside, because it is there chiefly that the weight of the body is transmitted by the astragalus. In one attitude, this weight is communicated by the astralagus exclusively to the front row, viz., in standing upon the point of the foot ; and it is then that the division of the tarsus into several bones is especially useful in preventing the injurious effects of shocks transmitted from below. There is an im- mense difference, also, as regards their effects on the system, between falls upon the heels and those upon the points of the feet. The mechanism of the tarsal articulations with respect to mobility should be first studi- ed in the two ranges separately, and afterward in the articulation of the two rows to- gether. 174 ARTHROLOGY. 1. The bones of the first range, viz., the astragalus and the os calcis, glide upon each other from before backward and from side to side. The lateral glidings assist in the torsion of the foot, which, however, is chieiiy pertormed at the articulation between the two rows. The antero-posterior glidings take place under the following circumstances : when the weight of the body presses upon the upper part of the astragalus this bone slips a little forward, and the foot has a tendency to become elongated, or flattened from above downward, as Camper has remarked. When the pressure ceases, the astragalus returns to its original position. The truth of the assertion, that the foot is an elastic arch, is chiefly established by reference to the nature of the astragalo-calcanian joint. 2. The bones of the second row are capable of such very slight gliding movements, that they may be considered as forming but a single piece. However, the articulation between the scaphoid and the cuneiform bones is somewhat more movable than those of the cuneiform bones with each other and with the cuboid. 3. The chief movements of the tarsus take place between the two rows, and the ar- ticular surfaces are there very favourable to mobility ; for there is in one part a head re- ceived into a cavity (at the astragaio-scaphoid articulation), and in another a mutual re- ception (at the calcaneo-cuboid articulation). These movements consist of a sort of tor- sion or rotation, by means of which the sole of the foot is carried either inward or out- ward. Assisted by slight lateral motions of the astragalo-calcanian joint, they consti- tute what is called adduction and abduction of the foot. They are generally attributed to the ankle-joint ; but, as we have seen, that articulation is limited to flexion and exten- sion ; the sprains, therefore, which result from too extensive movements, either outward or inward, take place at the articulation of the two tarsal ranges, and not at the ankle- joint. When the movement of torsion is carried too far, the external malleolus is forced somewhat outward ; slight gliding motions occur at the tibio-fibular articulations ; the elasticity of the fibula is called into play ; and, if the violence be innmoderate, the fibula is fractured. Tarso-metatarsal Articulations {figs. 82 to 84). In the formation of these joints, the wedge-shaped tarsal extremity of each metatarsal bone is opposed to one of the bones of the tarsus, the corresponding surfaces being plane and triangular. The fi.rst metatarsal bone articulates with the first cuneiform ; the sec- ond metatarsal with the second, and slightly with the first and the third cuneiform bones ; the third metatarsal with the third cuneiform ; the fourth and fifth metatarsal with the cuboid. From this there results an angular articular line, commencing on the outside, at the projection formed by the tuberosity of the fifth metatarsal bone. This line is directed obliquely forward and inward ; it forms an angle at the third, and again more particularly at the second metatarsal bone, because the third cuneiform bone projects, and is wedged in between the second and fourth metatarsal bones, while the second metatarsal bone projects into the tarsus between the first and the third cuneiform bones. The articular surfaces are held together by dorsal, plantar, and interosseous ligaments. We shall now study each of these articulations separately. Articulation of the First Metatarsal Bone loith the Tarsus. — There are two semilunar facettes in this articulation, one belonging to the first metatarsal, the other to the first cuneiform bone ; the long diameter of these surfaces is directed vertically. The strength of the joint is maintained by a very strong plantar (/, figs. 82 and 84), and a thinner dor- sal {p, fig. 83, and e, fig. 84) ligament. Both these consist of bands directed from before backward. There is a distinct s3Tiovial membrane for this joint. We may include among the ligaments of this articulation the aponeurotic expansion given off by the pe- roneus longus to the first cuneiform bone, and also that derived from the tibialis anticus, and attached to the first metatarsal bone. The articulation of the second mctitarsal bone with the tarsus is effected by the reception of the posterior extremity of that bone within the recess formed by the three cuneiform bones. We met with a similar arrangement, tliough less perfectly developed, in the carpo-metacarpal articulation of the second metacarpal bone. It is the strongest of all the joints of this kind, and is provided with, 1. Three dorsal ligaments, as in the corre- sponding articulation in the hand ; one median, (r, fig. 83), broad, and constantly divided into two bands, which proceed from the second cuneiform bone ; a very strong internxil ligament, extending from the first cuneiform bone, the third being external, thin, and at- tached to the third cuneiform bone. 2. M'ith two plantar ligaments, one of which {g, Jig. 82) is very strong, extends obliquely from the first cuneiform to the second metatarsal bone, and is prolonged upward, so as to become interosseous ; the other is very small, and proceeds from the sharp edge of the second cuneiform to the second metatarsal bone. 3. With an interosseous or lateral ligament, extending from the external lateral surface of the first cuneiform bone to the internal lateral surface of the second metatarsal bone. The articulation of the third metatarsal bone with the tarsus is maintained by a dorsal liga- ment {s, fig. 82) from the third cuneiform bone. There is no plantar ligament, properly so called, unless an oblique bundle of fibres from the first cuneiform bone be considered as such ; but the fibrous layer, which, after forming the sheath of the tendon of the pe- ARTICULATIONS OF THE METATARSUS. 173 roneus longus, is prolonged to the third metatarsal bone, appears to me to act as a plantar ligament. There is also an external lateral or interosseous ligament, which separates the articulations of the third and fourth metatarsal bones. The fourth and fifth metatarsal bones together present a slightly concave surface, which articulates with the convex surface of the cuboid. The means of union consist of a dorsal ligament {t, fig. 83) for the fourth, and an oblique ligament (?/), running outward and forward, for the fifth metatarsal bone : they are both loose, but especially the latter. There is no plantar ligament, excepting the sheath of the tendon of the peroneus longus, and a very strong tendinous expansion of the tibialis posticus. The tendon of the pe- roneus brevis acts as an external lateral ligament ; and, besides this tendon, there ex- ists a very strong fibrous band, derived from the external plantar aponeurosis, which extends from the os calcis to the process of the fifth metatarsal bone ; and, moreover, an expansion of the tendon of the peroneus longus, given off as it passes over the cuboid. The articulation of the fifth metatarsal bone is very loose. There is a very strong iii- terosseous ligament, stretched from the external lateral facette of the third cuneiform bone to the internal lateral facette of the fourth, and the external lateral facette of the third metatarsal bones. This ligament is analogous to one that separates the articula- tion of the fourth and fifth metacarpal bones from the other carpo-metacarpal articula- tions, and it fulfils a similar purpose here ; so that there are three distinct articulations between the tarsus and the metatarsus, and, therefore, three separate synovial mem- branes ; one for the fourth and fifth metatarsal bones, one for the second and third, and another for the first. Articulations of the Tarsal Extremities of the Metatarsal Bones. — These are true amphi- arthroses. The corresponding surfaces are partly contiguous and partly continuous. The contiguous part is nearer to the tarsus ; it is flat, and presents on each bone two small secondary facettes. Contrary to what obtains in the metacarpus, the continuous por- tions are larger than the articular surfaces. There are interosseous, dorsal, and plantar ligaments. The interosseous consist of very strong, short, and compact bundles of fibres, which extend between the rough surfaces of two neighbouring metatarsal bones. The dorsal {b, fig. 83) and plantar {i, fig. 82) pass transversely from one metatarsal bone to another, the plantar being much the larger. Articulations of the Digital Extremities of the Metatarsal Bones. — Although the digital ends of these bones do not articulate together, yet, as they are in contact and move upon each other, a synovial membrane covers the continuous surfaces and facilitates their movements ; a ligament, also, the transverse ligament of the metatarsus (x, figs. 82 and 83), is stretched transversely in front, and unites them loosely together. This ligament is common to the five metatarsal bones ; it is formed by the junction of all the anterior ligaments of the metatarso-phalangal articulations, by means of small bundles passing from one to another. It is exposed by opening the sheaths of the flexor tendons. Mechanism of the Metatarsal Articulations, With regard to Strength. — 1. The five component bones of the metatarsus are so strong- ly united that it is very uncommon for one of them to be broken by itself; the metatar- sus, therefore, can be only fractured by violence sufficient to crush it. 2. The slight mobility of the bones also concurs in increasing the strength of this part of the foot, by permitting it to yield slightly to external impulse. 3. The metatarsus is not uniformly strong throughout ; the first of its bones is the strongest, and upon it a great portion of the weight of the body rests during standing. The mobility possessed by the tarsal and the digital extremities of the metatarsal bones requires to be separately noticed. 1 . In the tarsal extremities, the angular arrangement, the mutual wedging of the tar- sus and the metatarsus, as well as the strength and shortness of the external and inter- osseous ligaments, admit of only very obscure ghding movements ; a proof of which ex- ists in the fact, that no example of the luxation of these bones upon the tarsus has, per- haps, ever been recorded. 2. Obscure, however, as these movements may be. they give rise to considerable motions in the digital ends of the bones, where the mobility is fa- voured by the looseness of the transverse metatarsal hgament, and the presence of a sy- novial membrane between the heads of the bones. The first metatarsal bone is not more movable than the others, contrasting remarkably in this respect with the first met- acai-pal bone. Akticulations op the Toes (figs. 82 to 84). Metatarso-phalangal Articulations. These articulations belong to the class condyloid, and offer a nearly perfect similarity to the metacarpo-phalangal joints. Articular Surfaces. — The head of each metatarsal bone is flattened on the sides, and elongated from above downward, so that it forms a condyle. Each phalanx presents a shallow cavity, the greatest diameter of which, contrary to that of the metatarsal surface, is transverse. 176 ARTilROLOGY. Means of Union. — 1. There is an inferior or glenoid ligament (I, fig- 82), situated On the plantar aspect of the joint ; it is very tliick, of the density of cartilage, and consists of interlacing fibres : its edges are continuous, partly with the sheath of the flexor tendons, partly with the transverse metatarsal ligament, but especially with the lateral ligaments of the joint. It is grooved below for the flexor tendons, concave above, to correspond with the convexity of the head of the metatarsal bone, and completes the cavity in which that head is received. Its anterior edge is very firmly fixed to the plantar border of the cavity of the phalanx, of which it seems a continuation ; its posterior edge is free, or, rather, is loosely connected by some ligamentous fibres to the inequalities behind the head of the metatarsal bone, upon the contracted neck of which it is moulded very ex- actly, so that, while protecting the lower part of the joint, it serves also to increase the extent of the surfaces included in the articulation. 2. There are two very strong lateral ligaments {y, figs. 82 and 83), an internal and an external, inserted, not into the depres- sions on each side of the head of the metatarsal bone, but into tubercles situated behind them ; from this origin they proceed very obliquely forward and downward, like flat bands, spreading out as they advance, and terminating partly in the inferior ligament, and partly on the sides of the phalanx. There is no dorsal ligament, properly so called, but the corresponding extensor tendon evidently occupies its place. It is not uncommon to observe a prolongation from the anterior surface of this tendon united to the metatar- sal end of the first phalanx. Synovial Capsule. — Under the extensor tendon we find a very loose synovial capsule ; it covers the internal surface of the ligaments as well as the articular cartilages. The metatarso-phalangal articulation of the first metatarsal hone presents some peculiar- ities which merit special description. 1. The articular surfaces are much larger than in the other similar joints. 2. The head of the first metatarsal bone presents two pulleys on its plantar aspect, separated from each other by a prom.inent ridge directed from be- fore backward. This construction is connected with the presence of two sesamoid bones (g, fig. 84), developed in the substance of the inferior hgament, which is three or four times thicker than in the other joints. The lateral Hgaments are ahnost exclusively fixed into these sesamoid bones. This joint has also a sort of fibrous ring surmounting the border of the glenoid cavity of the phalanx. Articulations of the Phalanges of the Toes. These are perfect angular ginglymi. Each toe has two such joints, with the excep- tion of the great toe, which has only one. Articular Surfaces. — The anterior extremity of the first phalanx, flattened from above downward, presents a trochlea, which is broader, and prolonged farther on the plantar than on the dorsal surface. On the second phalanx there are two smaU glenoid cavities separated by a ridge, the cavities corresponding to the smaU condyles, and the ridge to the groove of the trochlea just described. Ligaments. — 1. As the articular pulley of the first phalanx projects considerably below the second, it is covered in this direction by an inferior or glenoid ligament {m,fig. 82), exactly resembling those of the metatarso-phalangal joints, and perfoming the same functions. 2. The two lateral ligaments (y, Jigs. 82 and 83) are fixed precisely like the corresponding ligaments of the metatarso-phalangal joints, viz., into the tubercle above the lateral hollow on the anterior extremity of the first phalanx ; and they extend ob- liquely forward to the glenoid ligament and the second phalanx. 3. There is no superior ligament, its place being supplied by the extensor tendon. This tendon is arranged in a particular manner, for it frequently sends off a prolongation (r, fig. 83) from its anterior surface, which is attached to the upper end of the second phalanx. 4. The synovial cap- sule is arranged as in the metatarso-phalangal articulations. There is often a sesamoid bone in the inferior ligament of the phalangal articulation of the great toe. Mechanism of the Metatarso-phalangal Articulations. Like all condyloid joints, these admit of movements in four principal directions, and, therefore, are also capable of circumduction. Extension or flexion backward can be car- ried much farther than in any other similar joints. The lateral movements of abduction and adduction are very limited. Let us examine what takes place during each of these movements, in which the glenoid cavity of the first phalanx glides upon the head of the corresponding metatarsal bone. Inflexion, the first phalanx glides downward upon the head of the metatarsal bone ; the extensor tendon and the upper part of the synovial capsule are stretched by the projecting head ; the upper fibres of the lateral ligaments are also stretched ; these fibres then limit the motion, which, nevertheless, may be car- ried so far that the phalanx may make a right angle with the metatarsal bones. In extension, the phalanx glides upward upon the head of the corresponding metatarsal bone ; the superior fibres of the lateral ligaments are relaxed, while the inferior are stretched : these latter and the inferior ligament evidently limit the motion. In aU sub- jects it maybe carried so far as to make an obtuse angle behind ; in some so as even to form a right angle. The movements of abduction and adduction are limited by the meet- ing of the toes. ODONTOLOGY. 177 Mechanism of the Phalangal Articulations. As the mechanism of these joints is in every respect identical with that of the fingers, %ve shall refer to what has been said upon that subject, merely remarking that, either from original constmction, or from the continued confinement of the toes in tight shoes, their movements, which consist exclusively of flexion and extension, are much more limited than those of the fingers. Note on Arthrology. —\lt has been considered advisable to include in a single note the following observations on the general anatomy of the several tissues that enter into the construction of the articulations : Cartilages (p. 111). — The substance of the articular cartilages, in many joints, appears to be arranged in masses placed side by side, and perpendicularly to the surface of the bone ; and hence the fibrous character presented by them after slight maceration : nevertheless, they are composed of pure cartilage, unmiied with fibrous tissue. When viewed under the microscope, cartilage is found to consist of a transparent substance, in which are imbedded numerous corpuscles, either placed singly or aggregated in groups. The interme- diate substance is homogeneous in youlh, but becomes more or less laminated as age advances. The corpuscles, which are, in fact, metamorphosed primitive cells, are of irregular forms, contain nuclei and nucleoli, and are somewhat flattened near the surface of the cartilage. Occasionally, several are seen occupying a distinct cavity in the intermediate substance. Their average size is -pA^jth of an inch in length, byYT^Wth in breadth. Neither nerves, bloodvessels, nor lymphatics are found in the articular cartilages, which, al- though non- vascular, can scarcely be considered unorganized. Cartilage contains 66 per cent, of water ; its principal solid constituent is an animal matter, resolved by boiling into a peculiar variety of gelatin, called chondrin ; it also contains salts of soda, lime, magnesia, and potash. The inter-articular cartilages having free surfaces (as those of the knee-joint), are composed of true carti- lage interwoven with fibrous tissue, which particularly abounds at their attached margins. The inter-verte- bral substances, and aU other interosseous cartilages, have a similar structure, but contain a greater propor- tion of fibrous tissue. From the two anatomical elements of which these structures consist, they are called Jibro-cartilages. The articular borders surrounding the glenoid and cotyloid cavities, generally described with the ligaments, are also composed of fibro-cartilagiuous tissue. Ligaments (p. 112). — The articular ligaments consist entirely of fibrous tissue, the obvious component fibres of which are divisible into parallel micro.«;opic filaments, exactly similar to those of cellular tissue (see note on Aponeurologt, infra). They are supplied with but very few vessels and nerves ; they contain 62 per cent, of water, the remainder being almost entirely converted into gelatin by boiling. The yellow elastic tissue, of which the ligamenta subflava are composed, differs in minute, as well as in ob- vious characters, from the white fibrous tissue of ordinary ligaments. It consists chiefly of peculiar filaments, intermixed with a few of those of cellular tissue. The proper elastic filaments, examined with the micro- scope, are yellowish and transparent, have a bright aspect and dark outline (very unlike the delicate appear- ance of the cellular filaments), and are usually curied or bent at iheir torn extremities. The peculiar char- acter of dividing and uniting again, often assigned to them, is thought to be rather apparent than real, and to depend on an imperfect separation of the larger into their component filaments. The elastic is more vascular than the fibrous tissue. It contains less water (only 29 per cent.), and yields much less gelatin when boiled: the insoluble residue somewhat resembles coagulated albumen. Synovial Membranes (p. 112). — The basis of an articular synovial membrane is cellular tissue, which be- comes more and more condensed towards the free surface of the membrane. The smoothness of this surface is due to a covering of flattened scales (metamorphosed primitive cells) lying upon it, and constituting what is termed an epithelium. The recent discovery of this epithelium upon the surface of the articular cartilages is sufficient to establish the continuity of the synovial membrane over them ; a fact which, though doubted by many, is assumed by M. Cruveilhier upon analogical grounds. No nerves have been traced into these mem- branes, and the vessels existing in the sub-synovial tissue cease at the margin of the cartilage. The syno%-ia secreted by these membranes is an aqueous solution of albumen and saline matters. It contains more albu- men than the fluid of serous cavities, the lining membranes of which (as we shall hereafter notice) have a similar structure to those just described. Besides the articular synovial membranes, two other kinds are usually mentioned, viz., the bursal, including the various bursae, erroneously called bursae mucoss ; and the vaginal, examples of which are met with in the sheaths of tendons. These two forms will be again referred to in the note on Aponeurology, infra. Adipose Tissue. — The constant occurrence, especially in the larger articulations, of masses of fat beneath the synovial membranes, affords an opportunity of alluding in this place to the minute anatomy of the adipose tissue generally. It may be briefly stated to consist of an aggregation of distinct spherical or oval vesicles, containing the adipose substance, and having numerous vessels ramifying on their transparent and homoge- neous parietes. They are held together by the branches of those vessels, and bj' cellular, tissue. In man, the adipose substance is liquid during life, but separates, when obtained in any quantity, into an oily fluid called elaine, and a solid residue, consisting of two fatty substances, stearine and margarine.] ODONTOLOGY. Circumstances in which the Teeth differ from Bones. — Number. — Position. — External Confor- mation. — General Characters. — Classification — Incisor — Canine — Molar. — Structure. — Development. The teeth, the immediate instruments of mastication, are those ossifonm concretions which surmount the edges, and are implanted in the substance of both jaws. The teeth are not bones, though, from possessing an apparent analogy to them, they have long been considered as such. They differ from bones in many respects. 1. With regard to positimi. The teeth are naked and visible at the surface, while the bones, and this is one of their most important characters, are covered by periosteum. 2. In anatomical characters. The teeth consist of a bulb or thick papilla, surrounded by a calcareous envelope, composed of two substances, the enamel and the ivory. This calcareous envelope is not traversed by vessels, nor can any trace of cellular tissue be discovered in it. 3. In regard to their mode of development. In the teeth, the formation of the hard or ossiform matter takes place by successive depositions, from the circumference to the cen- Z 178 ODONTOLOGY. tre ; while bones are developed in a precisely opposite direction- No nutritive chang'gs are carried on in the teeth as in bones. Moreover, the teeth are renewed by means of the second dentition ; but there is no analogous phenomenon in the development of bone. 4. In physiological relations. The teeth do not participate in the diseases of bone, being susceptible only of chemical and physical alterations ; nor is the period of their existence, like that of the bones, of equal duration with the life of the individual. 5. In regard to chemical composition. They contain a much larger proportion of saline matters, and the enamel is entirely destitute of gelatine. All these circumstances prove that the teeth are not bones. We shall now show that they belong to the epidermoid system, and are analogous to the nails and hair. 1. When examined in the lower animals, they are found to present an uninterrupted ■^ series, from such as closely resemble horns or nails to such as present the most perfect- ly characteristic appearances of bone. 2. They have a lamellated structure, like the nails and hair : in some animals this is very manifest, but is rendered obscure in others from the abundance of calcareous deposite. 3. They are developed in the same manner as horns, nails, and hair. 4. Like them, they present no nutritive phenomena ; they are formed layer after layer, and undergo no renewal of their constituent parts ; they are* inorganic bodies, the products of transudation. 5. According to M. GeofFroy St. Hilaire, the beak of birds, which is evidently a horny structure, belongs to the dental system. Number. — In young subjects, at the period of the first dentition, there are twenty teeth, ten in each jaw : in the adult there are thirty-two, sixteen in each jaw. Man, therefore, during the course of his Ufe, has fifty-two teeth, twenty temporary, and thirty-two per- manent. The varieties in the number of the teeth are either the result of a deficiency or an excess. The varieties /rom deficiency consist, 1. In the absence of all teeth, examples of which have been recorded by Fox and Sabatier ; 2. In the absence of a great number of teeth, as occurred in an individual who had only the four incisors in each jaw. These deficien- cies are chiefly observed to affect the posterior molares, and frequently they are merely apparent in them from the teeth remaining concealed within the alveoli for a much longer period than usual. Besides, Fox remarks, that there is no tooth which has not occa- sionally been observed to be wanting, either alone or in conjunction with others. The varieties from excess are observed in the existence of supernumerary teeth, which may or may not range with the ordinary teeth. The supernumerary teeth either exist in distinct alveoli, or are blended with some other teeth. There are two varieties of this latter condition ; for the supernumerary tooth may either appear to gi-ow upon a primitive or parent tooth {dens prolifer of Bartholin), or several teeth may seem as if united into one. Position. — The teeth are arranged in two parabolic curves, constituting the dental arches, and con-esponding to the alveolar arches, which support them. Into these arches the teeth are fixed, not by articulation, but by the implantation of their roots into the al- veoli, which are moulded exactly upon them. This arrangement induced those anato- mists who regarded the teeth as true bones to admit a peculiar mode of articulation for them, called gomphosis {yo/Lt^oc, a nail). The teeth are mechanically fixed in their alveoli ; but yet we must consider the gums and the alveolo-dental periosteum as also forming uniting media. The importance of the latter will be acknowledged, if we consider the effects of scurvy in loosening the teeth, and the ease with which they drop out from the skeleton. Each dental arch forms a regular, uninterrupted curve, an arrangement peculiar to man, for in the lower animals the teeth are .of unequal length, and the dental arches have irreg- ular edges ; moreover, instead of their teeth being uninterruptedly contiguous, very con- siderable intervals, at some points at least, are left between them. Each dental arch presents an anterior convex, and a. posterior concave surface ; an adherent or alveolar bor- der, which is regularly scalloped ; and a free edge, thin and cutting at the middle, thick and tubercular at the sides ; in the latter situations it has two lips, of which the external is sharper in the upper teeth, and the internal in the lower. The free edge is so arran- ged that all the teeth are upon a level. As the superior dental arch fonns a greater curve than the inferior, it necessarily fol- lows that the two arches meet like the blades of a pair of scissors ; but the mode in which they meet is not the same in the middle region, occupied by the incisor teeth, as on the sides, where the molares are placed. Thus, the upper incisors pass in front of the lower, while the external tubercles of the superior molares pass to the outside of the external tubercles of the inferior molares, so that these latter tubercles are applied to the furrow formed between the two rows of tubercles of the upper molares. The teeth of the upper jaw, with the exception of the great molares, are larger, in gen- eral, than those of the lower. I should also remark, that no tooth is placed quite per- pendicularly to its fellow in the other jaw ; for the summit of a tooth in one jaw always corresponds to the interval between the sunmnits of two in the other ; so that the two rows of teeth are not simply in contact, but are really locked together. * See note, p. 183. THE INCISOR TEETH. 179 External Conformation. — The teeth, considered in reference to their form or configura- tion, present some general characters which distinguish them from all other organs of the body ; and also certain specific characters^ by which one tooth may be distinguished from another. General Characters {Jigs. 85 to 92). — Each tooth is composed of tw^o very distinct parts : a free portion, projecting beyond the alveolus, named the crown or body (a. Jigs. 85, &c.}, and a portion implanted in the bone called the root or fang (b), the constricted portion between these two constituting the neck (c). The rim of the alveolus or socket does not exactly correspond to the neck of the tooth, but rather to the root, at some dis- tance from the neck, the intervening space being occupied by the gum. The asis of the teeth is vertical. This direction is peculiar to the human species. The projection of the teeth forward gives a disagreeable aspect to the countenance, and is al- most invariably connected with a diminution of the facial angle. The axis of all the teeth is slightly inclined, so as to converge somewhat towards the centre of the alveolar curve. The length of the teeth (that is, of their crowns) is very nearly uniform. The advan- tage of this arrangement, in preventing one tooth from projecting beyond another, is very obvious. When the teeth are not equal in length, mastication is evidently imperfect ; and therefore the principal object, in cases of fracture of the lower jaw, is to prevent the inconvenience that would arise from irregularity of the dental edge, and which is actu- ally observed when the fragments unite in a wrong position. The teeth are only separated from each other by very small triangular intervals, so that they are almost contiguous. When the intervals are very considerable, mastica- tion is imperfect. The general form of the teeth is that of a slightly elongated cone, flattened in opposite directions, the base of which is formed by the crown and turned towards the free edge of the dental arch, while the summit, formed by the simple or compound root, presents an opening that penetrate* into the cavity of the tooth. The conical form of the root, and the accuracy with which the alveolus is moulded upon it, have a twofold result, viz., that the etfort of mastication is disseminated over all points of the socket, and that no pressure is ever experienced at the extremity which receives the vessels and nerves. The differences presented by the teeth, more especially in the crown, have led to their arrangement into three classes, viz., incisors, canhic, and molais: the latter have been subdivided into the great and small tnolars. The crown of the mci-sor teeth (figs. 85, 86) resembles a wedge with the sharp border shaped like a chisel ; as their name implies, they serve the purpose of cutting the food. The crown of a cojiine tooth {figs. 87, 88) forms a cone with a free pointed apex ; these teeth serve to tear the food, whence their name of lamaires : Hunter called them cuspi- dati, from their having only one point. The crown of a 7nolar tooth (figs. 89 to 92) is cuboidal, the free extremity being provided with tubercles or points, intended to bruise the food as in a mill. The small molars, which have only two tubercles, are called by Hunter bkuspides {figs. 89 and 90). Man alone, of the entire animal series, is possessed of the three kinds of teeth in an almost equal state of development. TAe Incisor Teeth {figs, 85 and 86). These are eight in number, four in either jaw. They occupy the middle of the dental arches, and, consequently, the anterior extremity of the lever of the third order, repre- sented by each half of the jaw. Their position is unfavourable, and, consequently, they are intended only to divide substances that offer but little resistance. This class of teeth attain their utmost development in rodentia ; as in the rabbit, beaver, &c. General Characters. — The crown (a) is wedge-shaped ; its anterior surface {fig. 85) is convex, and the posterior concave ; its sides {fig. 86) are triangular ; its _,. „, _. g, base is thick and continuous with the root, and its free edge sharp, some- ^' ,^ " ^^' what broader than the base, and cut obliquely upward and backward in the upper teeth, and downward and forward in the lower. This obliqui- ty of the surfaces, by which the incisors of the two jaws correspond, is the result of their constant friction upon each other, for they cross like the blades of scissors. The cutting edge of an incisor tooth, before it is worn down, is marked by three small denticulations. The root {b) has the form of a cone flattened on the sides ; the anterior border is thicker than the posterior. A small vertical furrow (see fig. 86) occasionally ex- ists on each side, appearing to indicate an original division ; and some- times the point of the root is bifid. Two curved lines, having their concavities directed downward, and united on the sides of the tooth, separate the root from the crown.* Differential Characters. — The iipper incisors are distinguished from the lower by their much greater size, the former being almost twice as large as the latter. In the upper jaw, the middle are distinguished from the lateral incisors, also, by their well-marked su- ' [It maybe well to observe, that the illustrations are all taken from teeth of the upper jaw, in which the general characters of each class are more strongly marked than in those of the lower.] 180 ODONTOLOGY. periority in size. In the lower jaw, on the contrary, the lateral incisors are the larger, though the difTerence is but slight. The Canine Teeth {Jigs. 87, 88). These are four in number, tivo in each jaw. They are situated on either side exter- nally to the incisors, and therefore are nearer to the fulcrum, so that they can overcome a greater resistance. These teeth are most completely developed in the carnivora. The tusks of the boar and of the elephant are also canine teeth. General Characters. — They are the longest of all the teeth, both in the crown and in Fi--. 87. Fig. 88. the root ; they therefore project a little beyond the incisors, particu- t^ larly in the upper jaw. Their croivn (a) is thick and irregularly conoid ; it is somewhat enlarged immediately above the neck, and terminates in a blunt point cut obliquely at the sides (see^o-. 88), and grooved be- hind. The anterior surface {fig. 87) is convex, the posterior concave. The canine teeth have much longer and larger roots (b) than any oth- er, and their alveoli are remarkably prominent. The root is flattened on the sides, each of which presents a vertical groove traversing its- entire length {see fig. 88). Differential Characters. — The superior canine teeth are distinguished from the inferior by their greater length and thickness. The roots cor- respond to the ascending process of the superior maxilla, and in some subjects are prolonged to the base of that process. The length of their root explains the difficulty of extracting them, and the accidents by which this operation is sometimes fol- lowed. There are several preparations in the museum of the Faculty of Medicine, in which the canine teeth are seen developed in the substance of the ascending process, and reversed, so that the crown is turned upward and the root downward. The Molar Teeth {figs. 89 to 92). The molar teeth are twenty in number, ten in each jaw. They occupy the last five alveoli on either side, and, consequently, are nearer to the fulcrum than all the other teeth : they are, therefore, most advantageously placed for exercising a powerful pressure upon any substances we may desire to break between the teeth. The instinctive motion by which, in order to crusli a very hard body, we place it between the molars, is evidently connected with this arrangement. These teeth are most highly developed in herbivora. The geyieral characters which belong to all the molars are the following : 1. The great extent of their grinding surfaces, which far exceed those of the incisors and canine ; 2. The absence of all obliquity at their summit, the anterior and posterior surfaces be- ing parallel, instead of approaching e.ach other, so as to form a cutting or angular bor- der : this character is evidently connected with the preceding one ; 3. The inequalities of their grinding surfaces, which are marked by eminences and depressions ; 4. The round or even cubical form of the crown ; 5. The shortness of the vertical diameter of the crown ; 6. The multiplicity of roots. The molars are divided into two classes, according to their difference in size, and the number of tubercles upon their grinding surfaces. The smaller are called small molars, or bicuspides ; the larger, great molars, or multicuspides. It should be remarked, that in the first dentition, all the molars, without exception, are multicuspides. The small molars or biscuspides {figs. 89 and 90) are eigV»t in number ; four in each, jaw, two on the right, and two on the left side. They are distinguished by the names first, second, &c. They are situated between the canine teeth and the great molars. The small molars of the upper jaw correspond to the canine fossae. General Characters. — The crown (a) is irregularly cylindrical, flattened from before Fis 89 Fig 90 backward, with its long diameter directed transversely. The anterior and posterior surfaces, which correspond to the two neighbouring teeth, are plain (see fig. 90). The internal and external {fig. 89) sur- faces are convex ; the free or grinding surface is armed with two tu- bercles or points, separated from each other by a furrow. Of the two tubercles the external is the larger. The crown of the small molars has been compared to that of two small canine teeth united. The root (b) is generally simple, but sometimes double or bifid. When simple, it has a deep vertical groove upon each side ; w^hen it is bifid, the sep- aration is never so deep as in the great molars. Differential Characters. — The lower bicuspides are distinguished from the upper by their smaller size, by a slight projection of the crown inward, and by the external tuber- cle being worn down. In the upper bicuspides, the tw^o tubercles are separated by a deep furrow ; in the lower, on the contrary, the fun-ow is more shallow, and the tuber- cles are sometimes united by a ridge. The second upper bicuspid has generally two roots ( iigs. 89 and 90), by which it is distinguished from the others. The first lower bicuspid, somewhat smaller than the second, has most commonly but one tubercle, viz., the external. This gives it more resemblance to a canine tooth. STRUCTURE OF THE TEETH. 181 The great molars or multicuspides {figs. 91 and 92) are twelve in number ; six in each jaw, three on one side, and three on the other. They are named f^. 91. p^ gg numericahy, proceeding from before backward, first, second, and third. The last is also called deiis sapientice, on account of its tardy appearance. They occupy the most remote part of the alveolar border. General Characters. — The crou-n (a) is pretty regularly cuboid. The anterior and posterior surfaces (see fig. 92), by which these teeth correspond, are flat ; the external and internal surfaces {fig. 91) are rounded. The grinding surface is armed with four tubercles {denies quadricuspides), separated by a crucial furrow, which is occasionally replaced by small depressions. In some teeth a fifth tubercle may be found. In almost all the tubercles are of unequal size, and cut into facettes. The crown of the great molars resembles two small molars united. The root {b) is always compound ; it is most commonly double or triple, and, in this case, one of the roots has a longitudinal furrow. Sometimes it is divided into four or five parts, variable both in length and direction. The roots are either divergent or parallel ; and occasionally, after separating, they approach each other again, curving like hooks, so as to embrace a more or less considerable portion of the jaw bone. Such teeth (which are called dents harries) it is impossible to extract without pulling away the included portion of the jaw also. Each root of these teeth exactly resembles the single roots of the teeth already descri- bed, with the exception of being smaller. Differential Characters of the Upper compared ivith the Lower Molars. — 1 . Contrary to what was observed with regard to the other teeth, the crowns of the lower great molars are a little larger than those of the upper. 2. They are shghtly bent inward, while those of the upper great molars are quit« vertical. 3. The lower great molars have only two roots, an anterior and a posterior. These roots are very strong and broad, flattened from before backward, deeply grooved longitudinally, and bifurcated at the points. The upper great molars have at least three roots {figs. 91 and 92), one internal and two external. It is very easy, then, to distinguish between the molar teeth of the two jaws. Individual Characters of the Great Molars. — 1. The first great molar is distinguished from the other two by its size, in which it generally exceeds them. 2. The third great molar, or wisdom tooth, is distinguished from the first and second by its evidently smaller size ; by its crown having only three tubercles, two external and one internal ; by its shortness ; and by its roots being, in certain cases, more or less completely joined together. However, even where the roots of these teeth are united, we always find the trace of the characters proper to the series of molar teeth to which they belong ; i. e., the vestige of three roots, an internal and two external for the upper wisdom teeth, and of two roots, an interior and a posterior for the lower. No teeth present so many varieties as the last molares, which occasionally even remain buried in the substance of the maxillary tuberosity. Structure of the Teeth. The crown of each tooth contains a cavity {d, figs.. 93, 94) corresponding with it in shape. This cavity is prolonged with contracted dimensions into „. g, the centre of the root, and opens by an orifice of variable size at the apex of the simple or compound cone, represented by the fang. The dimensions of this cavity are in an inverse proportion to the age of the tooth ; so that it is largest at the earliest periods, but during the progress of years it becomes entirely obliterated. It contains a soft substance constituting the dental pulp. A tooth, therefore, is composed of two substances, an external hard or cor- iical portion, which is unorganized,* and an internal organized pulp. The dental pulp, contained in the cavity of the tooth as in a mould, has the same form as the tooth to which it belongs. This pulp is connected with the dental vessels and nerves by means of a nervous and vascular pedicle, which, after penetrating the dental cavity through the orifice in the apex of the root, and traversing the small canal, becomes continuous with it. From analogies, the accuracy of which will be seen in studying the development of the teethr the pulp may be regarded as a bulb or large papilla, and appears to consist of a nervous expansion traversed by a great number of vessels. Its arteries are derived from the internal maxillary ; the nerves belong to the superior and inferior maxillary branches of the fifth pair. A membrane, rather difficult of demonstration on account of its tenuity, envelops the pulp, which is extremely sensitive, is the seat of toothache, and to it alone must be referred all that has been said regarding the vitality and sensi- bility of the teeth. The hard or cortical portion is composed of two substances, one of which covers the * See note, p. 133. 182 ODONTOLOGY. crown, and has been called the enamel (e, figs. 93 and 94), from a comparison with the vitreous layer or glaze of porcelain ; the other, constituting the entire root and the in- terior of the crown, is the ivori/ (/), improperly designated the bony portion of the tooth. The enamel is thickest on the grinding surface of the tooth ; it diminishes in thickness as it approaches the neck, at which part it terminates abruptly. The prominence of the curved line, indicating the termination of the enamel, gives rise to the constriction call- ed the neck. By comparing, and, in some degree, contrasting the peculiar characters of the enamel and the ivory, we shall be better able to assign to each their respective properties. 1. The enamel is of a bluish-white, milky colour, and semi-transparent ; the ivojy is yellowish-white, and has an appearance like satin. 2. The enamel, examined in fragments of the crown, exhibits fibres perpendicularly implanted upon the ivory, and pressed closely to each other. The ivory, on the contra- ry, is formed of concentric layers,* the fibres of which are generally parallel to the long diameter of the tooth. 3. Both substances are excessively hard ; but in this respect the enamel is superior to the ivory, for it will strike fire wath steel, and is much less easily worn down by use ; it can even turn the edge of a file. This excessive hardness, a principal element of im- mutability, explains how the teeth are preserved uninjured as long as the enamel re- mains entire, and, on the other hand, the facility with which they decay when once it has been removed. The great brittleness of the enamel, which is one of its most char- acteristic properties, is also owing to this extreme hardness. 4. In chemical composition, the enamel and ivory present important differences, indi- cated in the following tables : Ivory. EnameJ. Phosphate of lime ... 61-95 Phosphate of lime - . - 85-3 Fluate of lime . . - - 210 Fluate of lime - - - . 3-2 Carbonate of lime ... 5.30 Carbonate of lime ... 8-0 Phosphate of magnesia 1-25 Phosphate of magnesia 1-5 Soda and chloride of sodium 1-40 Membranes, soda and water 2-0 Cartilage and water - . - 28-00 It follows, therefore, that the principal chemical distinction 'between these substances depends on the existence of cartilage, that is, of an animal matter in the ivory, and on its absence in the enamel. The presence of cartilage in ivory forms a trace of resem- blance between this substance and bone ; and this is farther strengthened by the result of the action of heat, by which both are similarly affected. Between the true bones and the ivory there is, however, all that difference by which a living tissue is distinguished from a solidified product of secretion. I admit, then, a complete want of vitality both in the ivory and the enamel of the tooth ; nevertheless, there are some phenomena which appear to contradict such an opinion, 1 . The cortical substance of the tooth affords a much more perfect sensation of such bodies as come in contact with it than either the nails or hair. 2. Weak acids, particularly vegetable acids, cause a peculiar sensation when they are applied to the teeth, rendering the slightest touch extremely painful ; a sensation gener- ally expressed by saying that the teeth ai-e set on edge. But if, on the other hand, we reflect that the substance of the teeth is never affected by inflammation, that it never becomes the seat of any tumour or diseased product, and that it is worn av/ay by rubbing and by the file, in the same way as an inorganic body, without any attempt at reparation or any evidence of the existence of a nutritive pro- cess, we must be led to admit the absence of vitality in these organs, and to explain the foregoing facts as dependant simply upon transmission. Lastly, the hardness, fragility, and mutability of the enamel and ivory vary in differ- ent individuals ; hence the difference in the durability of the teeth, and their liability to change. It must not be imagined that the ivory, when exposed, is susceptible of caries or necrosis ; its changes are entirely of a chemical nature. The contrary opinion pre- vailed only so long as the teeth were considered true bones, and yet it has exercised an influence over the language of surgery which is not yet removed ; thus, we are in the habit of speaking of a carious or necrosed tooth, and to describe them as affected witti exostosis, and even with spina ventosa. It follows, from all that has been said, that the human teeth are simple, i. e., formed by one centre of ivory covered with one layer of enamel. Compound teeth exist only in herbivora, in which animals mastication consists of a most extensive grinding move- ment ; nor are they met with except among the molar teeth. The characteristic feature of a compound tooth is the division of the crown into a greater or smaller number of lesser crowns, each of which consists of a centre of ivory covered by a layer of enamel. /Ul these crowns are united into one by a third substance, called the cement or crusta pe- trosa, of which the tartar of the human teeth will afford a sufficiently good idea.t * See note, infrd, t [Recent researches into the structure of the teeth have brought so many interesting facts to light, that it is necessary to notice the result of these discoveries. DEVELOPMENT OF THE TEETH. 183 Development of the Teeth, or Odontogeny. The study of the development of the teeth is one of the most interesting parts ol their history. It embraces the description of the phenomena that precede, accompany, and follow the eruption of the first and second sets of teeth. First, Temporary, or Provisioned Teeth. Phenomena which f recede their Eruption* — If the jaws of a foetus of two or three months be examined, it will be seen that they are marked by a broad and deep groove, divided by very thin septa into so many distinct sockets for the reception of the dental germs. The alveolar groove is closed at its free border by the membrane of the gum, which is stretched over a sort of thin, and, as it were, indented crest. This crest is formed by a tissue to which some anatomists have given the name of dental cartilage ; it is a pale, very strong fibrous tissue, and does not extend either upon the anterior or posterior surface of the bone, which are only covered by the mucous membrane, the gum being as yet confined to the alveolar border. The gingival fibrous tissue sends a pro- longation into each alveolus {alveolo-dental periosteum), that forms a fibro-mucous sac upon Three different structures at least enter into the formation of the human teeth, viz., the ivory, the enamel, and the cortical substance- The ivory (a. Jig. 95) consists of a hard, transparent substance, traversed by numerous tubes, about .=-iTth of a line in diameter, which commence by open orifices at the cavity of the pulp, and extend in an undulating, but nearly parallel direction, towards the suiface of the ivory. In this course the tubes pig, 95. present secondary and smaller undulations, underg'o a dichotonious division, diminish in size, at first gradually, then rapidly, give off numerous lateral twigs, and, finally, divide into extremely minute ramifications, of which some anastomose together, others commu- nicate with small irregular dilatations called calcigerous cells, situated in the transparent inter-tubular substance, while the remainder appear to be lost at or near the surface of the ivory. The cells and tul>es both contain calcareous matter, and seem to be analogous to the corpuscles of bone and the ramified lines radiating from them. In human teeth the cells are very minute , but in those of many animals they are much more distinct, and present a striking analogy to the osseous corpuscles. The hard inter-tubular substance is not homogeneous, but, as may be clearly seen in young and growing teeth, is composed of fibres arranged parallel to the tubes, which ap- pear to have distinct parietes. It consists of animal tissue, combined with a large amount of calcareous salts ; and it is the seat of by far the greater proportion of the earthy matter contained in the ivory of the tooth. The enamel (b,fig. 95) is composed of hexagonal and transversely striated fibres, about j4-Tyth of a line in diameter, arranged parallel to each other, and applied by their internal extremities to numerous corresponding depressions on the surface of the ivory, a delicate intervening membrane serving to connect the two structures. Near the neck of the tooth, the enamel fibres rest almost perpendicularly, near the apex of the crown, more or less obliquely upon the surface of the ivory ; moreover, they are often slightly waved or curved. Previously to the eruption of the tooth, each fibre contains an appreciable i^uantity of organic matter, which, at later periods, almost entirely disappears. The cortical substance (c, fig. 95) consists of a thin osseous layer developed on the ex- ternal surface of the fangs, and, as life advances, extending even into their interior, and encroaching upon the cavity of the pulp. It differs in no essential particular from true bone, containing the characteristic corpuscles, and anastomosing tubuli of that tissue. It has been found, also, on the fangs of the teeth of most mammalia, and of a few reptiles and fishes ; in some instances, direct communications have been discovered between the tubes of the ivory and the cells and tubuli of the cortical substance. The cement, or crusta petrosa, existing on the crowns of the compound teeth of the lower animals, also contains corpuscles and tubuli like those of bone, and may, per- haps, be regarded as an analogous deposite to the preceding, differing from it only in situation. From a perusal of the preceding summary, it will be seen that not only has much additional knowledo-e been acquired regarding the structure of the teeth, but that many of the statements of M. Cruveilhier must now undergo considerable modification. Thus, 1. The crusta petrosa bears no resemblance to the tartar of the teeth, which is merely a deposite from the saliva. 2. Even simple teeth contain a third element in their struc- ture, besides the ivory and enamel. S. Instead of being inorganic bodies, the teeth are possessed of a complex organization, which, we may add, is uniform throughout each species, and often sufficiently characteristic to be of the highest utility to the zoologist, &c. 4. A remarkable affinity has been established between the teeth and bone, as far as regards the structure of the cortical substance and the ivory.] * [The earbest stage in the development of the teeth, described in the text, is that in which the dental pulps are situated at the bottom of closed sacs ; it has long been familiar to anatomists, and is now called the saccu- lar stage. A. condition antecedent to this, in which the future sacs are as yet open follicles, was first described by Arnold, but we are indebted to Mr. Goodsir (Edin. Med. and Surg. Journ., No. cxxxviii.) for the following connected history of the origin of the pulps and sacs of the temporary and permanent teeth : Origin of the Pulps and Sacs of the Temporary Teeth. — In the upper jaw of a fojtus, about the sixth week, between the lip and a semicircular lobe constituting the early condition of the palate, is situated a dc-dssion of the form of a horseshoe. During the seventh week, this begins to be divided by a ridge (i.jinmencing from behind) into two grooves, of which the outer forms the recess between the lip and the lULure external alveolar process, while the inner constitutes the primitive dental groove. The mucous membrane along the floor of this groove is then thickened, and from it a single papilla is developed, and subsequently four others arise from the external lip of the groove, in either half of the jaw. In the mean time, membranous laminae projecting from the external lip, and at first only partially surrounding the papillis, unite with similar but smaller processes from the infernal lip, so that each papilla (p, 3, Jig. 97) becomes enclosed in a separate follicle (/, 3,/^. 9"). com- municating with the cavity of the mouth, and lined by its mucous membrane. The papilla; now increase in size, and gradually assuming the form of ihe future temporary teeth, sink within the yet open follicles. At this period, the edges of the latter appear to be developed into opercula (o, i,fig- 97), which differ in number and arrangement according to the shape of the crowns of the different teeth, there being two for the incisors, three for the canine, and four or five for the molars. The formation of the bony alveoli, by the development of an external and internal alveolar process, and of inter-alveolar septa, closely follows the preceding changes in the soft parts. The order and time of appearance of these ten papillas in the upper jaw are as follow : First, those of the 184 ODONTOLOGY. each follicle, perforated at the bottom of the socket for the passage of the dental vessels and nerves. As these prolongations or sacs are intimately connected to the gingival {Fig. 96, magnified three diameters.) anterior temporary molars during the seventh week ; of the canine teeth at the eighth ; of the central, and then of the lat- eral incisors, about the ninth ; and in the tenth week those of the posterior molars. The formation of the inter- follicular sep- ta, and the other changes in the papilliE, follicles, and alveolar borders described above, proceed in the same order, and are completed about the thirteenth week. The condition of the upper jaw at that period, constituting the end of the follicular stage in the development of the temporary teeth, is seen in Jig. 96, in which the follicles are shown as if held open ; the diagrams 1 to 5 in fig. 97, representing perpendicular sections across the jaw, may serve to illustrate the successive changes in the mucous membrane, from the commencement of the groove to the completion of the follicles. During the fourteenth week, a small crescentic depression (c, b,fig. 97) is formed immediately behind each of the foUi-' cles, the mouths of which are now closed by their opercula, but without adhesion ; the lips of the groove, which at this time is called the secondary dental groove, axe now applied to each other \G,fig. 97), With the exception of the ten depressions just mentioned, and a small por- tion situated beyond the posterior temporary molar follicle, adhesion of every part of the groove now takes place, proceeding from before backward. The follicles are thus converted by the fifteenth week into shut sacs (s, T,fig. 97), while the enlarged papillae constitute the dental pulps (p, 7). The relation of the parts in this, the saccular, stage in the development of the temporary teeth, is represented at 7, fig. 97. Independently of a few subordinate differences, the changes in the lower jaw are similar, and occur in the same order, each step in the process being somewhat later than the corresponding one in the upper. Origin of the Pulps and Sacs vf the Permanent Teeth. — It has been stated above, thai during the general adhesion of the dental groove occurring at the fifteenth week, the part posterior to the second temporary molar follicle (in either half of the jaw) still remains open ; in this situation, a papilla, sunk in an open follicle, ap- pears during the sixteenth week. At the twentieth, the fundus of this follicle is converted into a sac, and the papilla into the pulp of the anterior permanent molar tooth, which is thus the earliest to appear of those of the second set, and is farther characterized by being developed (like the papillae of the temporary teeth) from the primitive dental groove, and on the same level with them. At the end of this week the hitherto open portion of the groove is entirely closed by adhesion of its lips, but its walls still remain disunited, and a cavity is thus formed, situated between the sac of the anterior permanent molar and the surface of the gum ; this is the posterior cavitt/ of reserve, from which the pulps and sacs of the second and third molars are subsequently developed. The ten depressions (c, 6) formed behind the follicles of the temporary teeth during the secondary condi- tion of the dental groove (G,fig. 97), in consequence of theii escaping the general adhesion of its lips and sides, Fig. 98. Fig. 98.* are converted into as many cavities, called the anterior cav- ities of reserve (c, 7), which gradually elongate and recede into tiie substance of the gum. Pulps and folds (analogous to the opercula of the temporary follicles) are developed within them, appearing first in the anterior cavities ; and they eventually become the sacs of the ten anterior perma- nent teeth, assuming a position behind and above those of , and the milk teeth in the upper, and behind and below them in the lower jaw (see 7 to K,fig. 97 ; aXso fig a, figs. lOJ, 102), each occupying corresponding recesses {a, fig. 102) in the alveolar liorder. At this time, owing to the great relative increase in the size of the dental sacs, that of the anterior perma- nent molar (o, ^,fig. 98*) is forced backward and upward into the maxillary tuberosity of the upper, and into the coronoid process of the lower jaw (a 2) ; and the large posterior cavity of reserve (4 2) is drawn in the same direction. At birth, the length of the alveolar border increases relatively, and this sac again sinks to a level with those of the temporary teeth (a 3). Tlie cavity of reserve (63), having now resumed its former posittoa DEVELOPMENT OF THE TEETH. 185 membrane, by pulling gently upon the latter we can raise the follicles from their recep- tacles, and completely lay bare the alveoli. The follicle or dental germ consists essentially of a membrane, containing a sort of pe- diculated papilla, known as the bulb or dental -pulp. 1. The membrane oi the follicle, after having clothed the sac just described as lining the alveolus, is reflected upon the vessels and nerves which form the pedicle of the bulb, and appears to be prolonged upon the bulb itself: this, however, has not yet been demon- strated. The membrane of the follicle, therefore, resembles the serous membranes in forming a shut sac, the inner surface of which is free and smooth, and the outer adhe- rent. A transparent viscid fluid occupies the space between the bulb and the alveolar portion of the membrane. The following is the order in which the follicles of the first set of teeth appear. To- wards the middle of the third month of foetal life there are four distinct follicles in each jaw ; at the end of the third month a third follicle appears in each half of the jaw, and a fourth and a fifth towards the end of the fourth month. 2. Of the dental bulb. In the earliest stages the membrane of the dental follicle only contains a fluid, which is at first reddish, and afterward yellowish-white ; but towards the third month a small body makes its appearance, rising as a papilla from the bottom of the alveolus.* This papilla is abundantly supplied with vessels and nerves, and pro- gressively increases in firmness and in size. A very thin pedicle, consisting of the den- tal vessels and nerves, affords attachment to it, so that it is suspended like a grape. This papilla, dental bulb, or pulp, gradually acquires the characteristic form of some par- ticular tooth, of which it presents an exact model, constituting the nucleus around which the tooth itself is deposited. The first part developed upon this papilla is the crown of the tooth, on which we already find indications of the various eminences and depressions subsequently exhibited by it. The development of the hard portion commences towards the middle of pregnancy. The production of the ossiform matter upon the surface of the bulb is effected by a pro- cess of secretion ;t it begins by the deposition of some small laminae, or very delicate scales {\,fig- 99), upon each projection of the pulp : they are at first pHable and elastic, but gradually become more consistent. These laminae or scales constitute so many formative points for the tooth, and have been compared to the points of ossification in bones. The incisor and canine teeth have only one scale ; the bicuspides have two, and the great molares as many as there are tubercles. These small scales so intimate- ly embrace the pulp upon which they are moulded, that it requires some force to detach them ; and yet their inner surface, as well as the outer, is very smooth. It should be remarked, that the pulp has a much more vividly red colour at the points covered by the scales. The scales are visible in the lower jaw at an earlier period than in the upper. The following is the order in which they appear : the middle incisors are visible from the fourth to the fifth month ; they are soon followed, 1. By the lateral incisors. 2. By the first or anterior molar, which appears from the fifth to the sixth month. 3. At a short and shape, elongates backward, and a pulp is developed in its fundus, which is conTerted before the fourth year into the sac of the second permanent molar. About the sixth or seventh year, the remaining part of the cavity once more elongates bacltward, and forms the pulp and sac of the third permanent molar, or wisdom tooth. Each of these sacs undergoes changes in its relative position in the jaws, similar to those experienced by the anterior permanent molar, at first receding backward and upward, and then descending behind, and on a level with the sac immediately anterior to it. From the preceding observations, it follows that the pulps and sacs of both the temporary and permanent teeth have a common origin from the gastro-intestinal mucous membrane ; that a papilla is first formed, after- ward surrounded by and sunk into a follicle, which latter is then converted into a closed sac ; and hence the origin of the terms papillary follicular, and saccular, applied to these several conditions. It moreover appears that all the temporary teeth, and also the anterior permanent molar, originate from the primitive dental groove ; and that all the permanent teeth, except the anterior molar, are developed from cav- ities of reserve commenced during its secondary condition. For an account of the changes occurring in the pulps and sacs of the two sets of teeth during the saccular and eruptive stages, the reader may now refer to the text, remembering, however, that the term, follicle is there applied to the entire dental germ in its saccular condition, consisting of a closed sac and its contained pulp.] * [The papilla of a temporary tooth appears even before the formation of the open follicle, and therefore long prior to its conversion into a shut sac. (See note, p. 183.)] t [The ivory is no longer regarded, by the best authorities, as a secretion from the surface of the dental pulp, nor the enamel as a similar product from the parietal layer of the lining membrane of the sac. A micro- scopic examination of these two structures in their perfect condition is, indeed, alone sufficient to throw con- siderable doubt on the old opinion adopted in the text. The researches of Schwann into their mode of devel- opment have again elucidated the subject. It has been observed that the globules in the centre of the dental pulp are primitive nucleated cells, analogous to those found in the early condition of all organic tissues ; that at the surface of the pulp these cells assume a cylindrical form and a perpendicular arrangement, but still con- tain nuclei ; that they adhere in places to the ossified scales, and correspond in size (not to the tubuli) but, to the fibres of the inter-tubular substance in a growing tooth. From these facts Schwann concludes that the formation of the ivory, like that of all other organized tissues, is effected by a metamorphosis of primitive nu- cleated cells ; in other words, that it is developed by a progressive transformation and ossification of the superfi- cial cells of the dental pulp — a theory which recent observations in Great Britain would seem to have confirmed. Similar evidence is advanced by him to prove that the enamel is formed in a similar manner from the pulpy enamel membrane, occupying the upper portion of the sac. The hexagonal fibres, of which the surface of this membrane consists, arc, in fact, prismatic, nucleated cells, resting perpendicularly on a tissue, in which are other cells of a vesicular form. The hexagonal fibres correspond, therefore, both in form and direction, with those of the perfect enamel ; and, moreover, they are found to agree in size with the membranous reinains of the enamel fibres of a growing tooth, after the removal of their earthy matter by means of a dilute acid.] A A 186 ODONTOLOGY. interval from each other, by the canine and the second molar : the scales of all the teeth of the first set have made their appearance by the seventh month, according to the ob- servations of Meckel ; but at the eighth month, according to Blake. As development advances the scales enlarge, and gradually uniting (2, fig. 99), form a sheath or shell of ivory, which, during its growth, encloses the pulp, and, by degrees, ex- tends to the vascular and nervous pedicle at the part where it penetrates the alveolus.* The outermost sheath being formed, a second is deposited within it, then a third within that, and so on. The external surface of the bulb secretes the ivory. The enamel is formed from the parietal or alveolar layer of the follicular membrane : at the commence- ment of its formation it is so soft that, in a foetus at the full time, it can be very easily separated from the ivory. It has been asserted by some that the enamel, as well as the ivory, is the product of a secretion from the bulb, from which it has transuded in a liquid state through the different layers of the ivory, and has then solidified upon its surface ; others affirm that the enamel is a sort of crystalline deposite from the fluid surrounding the tooth ; but the greater number of anatomists admit, with Hunter, that the enamel is a product of secretion from the parietal layer,! as the ivory is from the layer of the fol- licular membrane, reflected upon the bulb. This opinion appears to me the more proba- ble, because, on examining with attention the parietal layer, we find on its inner sur- face, near the crown of the tooth, a sort of pulp, or very evident enlargement, particular- ly in the follicles of the molar teeth. This external pulp becomes atrophied as soon as the enamel is formed ; and hence the fang is not covered with enamel, although, after the eruption of the tooth, that part occupies the former position of the crown. This ex- ternal pulp does not exist in some of the dental follicles of certain animals, and we can- not, therefore, be astonished that such teeth have no enamel. Lastly, when this ex- ternal pulp remains after the eruption of the teeth, the secretion of the enamel also con- tinues, like that of the ivory. This is the case with the incisors of the rabbit and the beaver. In these animals the enamel occupies only the anterior surface of the tooth ; consequently, the edge always remains sharp, from the unequal wearing of the anterior and posterior surfaces. From what has been said concerning the phenomena of the formation of the provision- ary teeth before their eruption, we may draw the following conclusions : 1 . Of the two constituent parts of a tooth, viz., the corticle or hard portion, and the medullary portion or pulp, the latter is first developed ; and of the two distinct elements of the hard por- tion, viz., the ivory and the enamel, the formation of the ivory is first commenced. 2. The deposition of the cortical substance of the tooth begins at the crown ; the roots are not formed until a subsequent period. 3. The bulb being enclosed within the solidified products which it has furnished, diminishes gradually in size as these press upon it. Phenomena which accompany the Eruption of the First or Temporary Teeth. — At the time of birth all the teeth are still contained within their alveoh. Exceptions to this rule have been met with in cases where infants have been born with one or two teeth. If the anterior wall of the alveoli be removed at this time, the teeth will already be found considerably, but unequally developed, none having yet reached the bottom of the socket. But after birth, and at periods to be presently indicated, the extremity of the root having reached the bottom of the alveolus, and the farther growth of the tooth in that direction being impossible, it is effected in the direction of the gum, which is compressed, becomes inflamed, and is perforated ; this perforation, however, is not exclusively the result of distension, for the gum is but very slightly stretched when it opens ; and in other cases where it is greatly distended, as by polypi or other tumours, it is not lacerated at all. The tooth gradually rises, and the gum moulds itself successively upon the different portions of the crown, and, lastly, upon the neck of the tooth. The division of the gum is a severe process, but still it cannot altogether explain those serious symptoms which frequently accompany the first dentition. The eruption of the teeth does not take place simultaneously, but in succession, and in a regular order that admits of but few exceptions. 1. The teeth of the same kind ap- pear in pairs, one on the right side, the other on the left ; 2. The teeth of the lower jaw * [The vascular pulp of either a temporary or permanent tooth having more than one fang is, after the formation of the crown, divided into as many processes by the advancement into it of the gray membrane of the sac. The dental substance still continuing to be produced on every part of the surface of the divided pulp, a bridge of ivory is thus formed across the area of the cavity of the tooth betvpeeu each process (3, i,fig. 99), (Fig- 99.) around vfhich separate fangs are subsequently developed (5, 6, 7), in the same manner as that around the un- divided pulp of an incisor tooth.] + See note, p. 184. DEVELOPMENT OF THE TEETH. 187 precede those of the upper in their appearance ;* 3. The middle incisors are cut before the lateral, these before the first molars ; after these come the canine, and then the sec- ond molars. The eruption of the first set of teeth commences towards the sixth month after birth, and terminates at the end of the third or the commencement of the fourth year. The middle lower incisors appear from the fourth to the tenth month, and, soon afterward, the upper middle incisors ; the inferior lateral incisors appear from the eighth to the sixteenth month, and then the superior lateral incisors. The first lower molars are cut from the fifteenth to the twenty-fourth month ; the lower canine from the twen- tieth to the thirtieth ; and the upper first molars and canine soon afterward. In some cases the eruption of the canine and the first molar teeth takes place simultaneously ; sometimes even the canine teeth take the precedence. The second great molars appear from the twenty-eighth to the fortieth month, and thus complete the twenty teeth of the first set. Second or Permanent Teeth. Phenomena which precede the Eruption.f — The second dentition consists of the eruption of the teeth called permanent, to distinguish them from the temporary teeth. They are thirty-two in number, so that there are twelve additional teeth in the second set. In this dentition, as in the former, we have to study the phenomena which precede, ac- company, and follow the eruption of the teeth. The follicles or germs of the second set of teeth correspond to the row of teeth already formed, bony septa intervening between them. They have the following relations with the follicles of the provisionary teeth : 1. The folhcles of the additional teeth in the sec- ond set, viz., the last three molars, are situated in the same curve as the milk teeth, but they occupy, of necessity, the lateral extremities of these curves (fig. 100). 2. The fol- licles of those teeth of the second set that replace others of the first are, on the contrary, situated precisely behind the teeth to which they correspond {a, Jigs. 100, 101, 102). These follicles are at first contained in the same alveoli as the temporary teeth ; but, after a certain time, septa are grad- pig_ loo. ually formed between them, pro- ceeding from the bottom of each alveolus towards its orifice (figs. 101, 102). Nevertheless, for a long time after the formation of these septa, the temporary (a" a", Jig. 102) and the permanent Cb ''b) alveoli communicate by tolerably large or- ifices (c' c',Jigs. 101, 102), through which proceed the cords (c, Jig. 102) connecting the two teeth. The follicles of the permanent teeth do not sensibly differ in their mode of development from those of the provisionary teeth, only the increase of the vascular system of the former coincides with the progressive atrophy of the vessels of the latter. Phenomena which accompany their Eruption. — As long as the development of the per- manent teeth can be effected in a direction towards the bottom of their sockets, the tem- porary teeth remain uninjured ; but when the growth of the permanent teeth influences their upper edges, the alveoli of the first set are compressed, and afterward destroyed at the parts corresponding to the crowns of the permanent teeth Ptg. 101. {see Jig. 101). After this time the alveoli of the first and sec- ond sets form common cavities : the roots of the milk teeth being compressed by the crown of the permanent teeth, under- go a loss of substance, become loosened, and may be detached by the slightest effort, each tooth being retained in its place only by the sort of ring formed by the gum around its neck. The shedding of the milk teeth is not always effected in the way we have described, viz., by a previous destruction of their root. Sometimes, in fact, the permanent tooth does not pen- etrate into the alveolus of the corresponding milk tooth ; but this alveolus is gradually wasted away by the constantly in- creasing development of the neighbouring permanent socket. teeth may fall without destruction of their roots, which, however, are then almost always slender, and, as it were, atrophied. Some compression, either exercised upon the pa- rieties of the temporary sockets, or upon the roots of the milk teeth, is almost indispen- sable for their expulsion. When, in fact, the permanent tooth deviates from its natural direction, and, consequently, does not press upon the milk tooth, this latter remains, and forms a supernumerary tooth. We cannot, then, doubt the influence of this compression upon the fall of the milk teeth ; but anatomists are not agreed as to the immediate cause of the destruction of the temporary alveoli, and of the roots of the teeth contained within * [Although the papills, it will be remembered, appear earlier in the upper jaw.] t See note, p. 183. In this case, the milk 188 ODONTOLOGY. them. How does this compression act 1 Does it produce the fall of the milk teeth in a purely mechanical manner, or does it effect this indirectly by the destruction of the den- tal vessels and nerves ! One author believes the latter to be the principal cause ; but what we have already said regarding the want of vitality in the teeth will abundantly prove that the wearing away of the alveolus and the milk tooth is the result of mechan- ical pressure. At the same time it should be observed, that, since the destruction of the roots of the milk teeth leaves no debris, a process of absorption must, therefore, be performed, the ex- citing cause of which is, undoubtedly, the compression above alluded to. It is not neces- sary, as some authors have believed, to assume the existence of a peculiar absorbent ap- paratus, appropriated to this office. The teeth of the first dentition are shed in the space comprised between the sixth and „. .„„ the eighth year, the fall of each tooth °' ' taking place in the same order as its ap- pearance. Blake was the first to point out the existence of a cord {c,fig. 102) passing from the follicle of the perma- nent tooth, along a small, long canal (c' c'), behind the alveolus of the milk tooth, and becoming continuous with the gum. It has been supposed that the canal, and the cord placed within it, were intended to direct the tooth during the progress of its eruption. Hence the name of iter dentis given to the canal, and gubernac- ulum dentis applied to the cord, which has been ingeniously compared by M. Serres to the guhcmaculum testis. This cord appears to me to be solid,* not hollow ; it is very well marked in the incisor teeth, but forms a mere thread in the molars. Upon the whole, the influence exerted by the iter dentis and gubernaculum upon the direction of the permanent teeth during its erup- tion is by no means constant. Order of Eruption. — The first permanent teeth which appear are the first great molars ; they precede the other permanent teeth by a considerable interval, and immediately suc- ceed the milk teeth, coexisting with them for some time ; they have been, therefore, im- properly classed among the first set of teeth in some anatomical treatises. The first great molars are known by the vulgar name of seveii years' teeth. The eruption of the permanent teeth takes place in the same order as that of the milk teeth. Below are sta- ted the periods at which each pair are protruded : Middle lower incisors from Middle upper incisors Lateral incisors First small molar Canine teeth Second small molar Second great molar Third great molar The greatest irregularity exists in the eruption of this last molar tooth, which is often wanting, and frequently remains, during the whole of life, either partially or entirely en- closed within the substance of the jaw. The incisor and canine teeth of the second set are much larger than the corresponding milk teeth. The opposite is the case with regard to the first two permanent molars, viz., the small molars, or bicuspides. It was ascertained by the inquiries of Hunter, that, in this way, there is such a compensation, that the twenty teeth of the first set occupy pre- cisely the same space as the twenty corresponding teeth of the second. This is not a purely speculative question, but one of singular interest in relation to the practice of ex- tracting the milk teeth. The truth of Hunter's assertion may be confirmed by measuring with a thread the space occupied by the twenty temporary teeth, and comparing it with the space occupied by the corresponding teeth of the second set. M. Delabarre has done this upon the same individual at the period of the two dentitions. Phenomena which follow the Eruption of the Permanent Teeth. — These relate, 1. To their growth ; 2. To their decadence. 1. Growth of the Teeth. — The teeth of man are not, like those of some animals, the ro- dentia in particular, susceptible of unlimited growth. The enamel of the crown wears away without ever being reproduced. All the facts brought forward in support of the idea of its reproduction are either erroneous observations, or may be interpreted in a different manner. Nevertheless, some changes take place in the interior of the tooth wliich are worthy of notice. New layers of ivory continue to be secreted; anf^ the cavity of the * [Arising from the adhesion of the sides of the elongated part of the cavity of resen'e.] 6 to 8 years. 7 " 9 8 " 10 9 " 11 10 " 12 11 " 13 12 " 14 28 " 30 DEVELOPMENT OF THE TEETH. 189 tooth is gradually encroached upon, and finally obliterated. Thus the teeth of the aged have neither pulp nor dental cavity. 2. Decadence of the Teeth. — The fall of the teeth in aged persons is the etfect of a con- traction of the alveoli, produced in the following manner : The teeth are dependances of the buccal mucous membrane, and are, as it were, only accidentally placed in the alveo- lar borders, which, from the tonicity or elasticity of their bony tissue, have a constant ten- dency to displace them. In one word, the tooth is to the alveolus like a foreign body, of which it is incessantly tending to free itself This tendency to contract on the part of the alveolus is etfectually resisted, so long as the root of the tooth has a tendency to in- crease towards the bottom of the socket ; but it acts with full force when this resistance ceases in consequence of atrophy of the pulp. Then the alveolus, shrinking upon it- self, expels the tooth by a mechanism similar to that by which, during the progress of syphilitic affections, the most healthy-looking teeth are displaced, solely in consequence of the vitality of the pulp being destroyed by the influence of the virus. The fall of the teeth in the aged is regulated by no law, either as regards the time or the order in which it is effected. Differences between the First and Second Sets of Teeth. — The teeth of the first dentition are distinguished from those of the second by the following characters : 1 . Their colour, instead of being white, like ivory, or clear yellow, is of a bluish or azure white hue. 2. The temporary incisor and canine teeth are always distinguished from the corresponding permanent teeth by their smaller size and the shortness of their roots. 3. The two mo- lars of the first set differ from the two small permanent molars or bicuspids which take their place, and approach nearer in character to the great molars ; from these, however, they are distinguished, by the shortness of their crowns, and by the number of tubercles on them, viz., five ; three on the outside, and two on the inside. 4. Comparative chem- ical analyses of the teeth of the two sets have shown that the milk teeth contain some- what less phosphate of lime than the permanent, and to this circumstance their greater susceptibility of change is due. General Observations. — From the description we have given of the teeth, it will be seen that these organs should be looked upon merely as large vascular and nervous papillag, covered by an unorganized calcareous sheath, which is formed by a species of crystalli- zation.* The diseases of the teeth offer nothing incompatible with this theory, for, with the exception of toothache, and the sensation of being set on edge, which are evidently seated in the pulp, the other alterations of which the teeth are susceptible are either me- chanical lesions, such as splitting, cracking, wearing, &c., or chemical changes, as the dry or moist caries, or, lastly, alterations appearing to have their seat in the hard sub- stance of the tooth, but which are really situated elsewhere. Of this nature are the in- crustations with tartar, the product of a vitiated secretion, attributed by several anato- mists, and especially by M. Serres, to some small follicles, the function of which, before the eruption of the teeth, is to produce a fluid to soften the gum preparatory to its perfo- ration by the teeth. Again, exostosis and spina ventosa of the teeth evidently depend upon irregular secretion of the enamel and ivory. The consolidation of fractures of the teeth is explained by the formation of new layers, resembling those which have been seen surrounding bullets in the substance of an elephant's tusk. Lastly, the coloration of the teeth, from the action of madder, is only observed in the layers deposited during its use, and therefore does not prove the existence of any nutritive process in these or- gans, such as takes place in bone. With regard to the evolution of the teeth in two distinct sets, it may be inquired what is the object of such an arrangement. Without entering here into the discussion of final causes, it cannot be denied that the second set of teeth would not accord with the com- paratively small size of the jaws in the foetus. Use. — 1. The teeth are the immediate agents of mastication. The incisors cut, the canine tear, and the molars grind the food, the position of each being regulated by the resistance they have to overcome. 2. The teeth form a kind of elevated border, which prevents the constant escape of sahva from the mouth. 3. They assist in rendering sounds articulate, by affording a fixed point to the tongue in the pronunciation of certain consonants, called by grammarians dental. 4. The teeth furnish important characters for zoological classifications. Indeed, as they bear a necessary relation to the mode of feeding in different animals, a circumstance that exercises so great an influence over their entire organization, it may easily be conceived that the form of the teeth is, to a certain extent, one of the characters by which a summary idea is conveyed of the nature of that organization. At the same time, it is necessary to guard against the evidently erroneous conclusions which some philosophers have delighted in deducing from the ar- rangement of the dental apparatus in man with regard to his fitness for a purely animal or exclusively vegetable diet. Above all, it should be remembered that the mechanical ingenuity of mankind must always form an indispensable element in the solution of eveiy problem of this nature. * [It is necessary, in some degree, to modify this definition of the hard portion of the teeth, which, though extra-vascular, and, on that account, probably subject neither to interstitial absorption nor nutrition, cannot be regarded with propriety as unorganized or crystalline bodies. 190 MYOLOGY. MYOLOGY. The Muscles in general. — Nomenclature. — Number. — Volume and Substance. — Figure. — Di- rection.— Relations. — Attachments. — Structure. — Uses. — Preparation. — Order of Descrip- tion. The active organs of locomotion are called muscles.* They are composed of bundles of red or reddish fibres, consisting of fibrin as their basis, and possessing the essential property of contractility, that is, the power of contracting or shortening upon the apphca- tion of a stimulus, t J^omenclature of Muscles. The names applied to the various muscles have not been founded upon uniform prin- ciple. Before the time of Sylvius the muscles of any region (of the thigh, for exariiple) were designated numerically, first, second, &c., in the order of their super-position or of their uses. Sylvius first gave particular names to the greater number of the muscles ; and he was followed by almost all succeeding anatomists, especially by Riolanus. In this nomenclatare, which is still generally adopted, the names of the muscles are deri- ved, 1. From their situation, as radialis, ulnaris, peroneus, &;c. ; 2. From their size, as glutaeus maximus, minimus ; palmaris longus, brevis, &c. ; 3. From their direction, as rectus abdominis, obliqui capitis ; 4. From their shape, which is generally an imperfect representation, either of certain geometric figures, as rhomboideus, pyramidalis, and sca- lenus, or of well-known objects, as deltoideus, lumbrici, and soleus (from solea, the sole fish) ; 5. From their divisions or comphcations, as digastricus (from having two bellies), triceps (from having three heads), biceps, complexus, &c. ; 6. From their insertions, as sterno-hyoid, sterno-thyroid, &c. ; 7. From their uses, as flexors, abductors, &c. In modern times many attempts have been made to substitute in the place of these vague and generally arbitrary denominations, a uniform nomenclature, derived from the most important consideration, viz., the attachment of the muscles. The nomenclature of Chaussier, however, which is undoubtedly superior to all others, has not been adopt- ed ; first, because a knowledge of the old names cannot be neglected, since they are the only ones employed in a great number of works on medicine and surgery ; and, second- ly, because even the most imperfect denominations, when they have been long in use, are, from this circumstance alone, preferable to any new appellations. J\''u7nber of the Muscles. Upon this point, likewise, authors are but little agreed. According to most, the num- ber of muscles is four hundred. Chaussier reduced it to three hundred. These differ- ences arise partly from the fact that the natural limits of the different muscles are not so well marked as those of the bones, for example, and partly because the grounds of de- marcation between the various muscles have not been sufficiently established. The fol- lowing rules maybe adopted with advantage : 1. When a number of fasciculi unite, and fonn a mass, which is isolated both in its body and at its extremities, and fulfils distinct and determinate uses, such a collection should be considered a separate muscle. 2. A muscle should also be regarded as distinct when it is separated from others at one por- tion only of its body, and at the most movable of its attachments. On the whole, what- ever be the mode of demarcation adopted, it will be seen that the number of the muscles greatly exceeds that of the bones ; the reason of this is, that each bone acts as a lever in a great variety of movements, while each muscle acts only in a very limited number of motions. Volume and Substance of the Muscular System. Of all the systems of organs in the body, the muscular is predominant both in substance and in volume. This great mass of muscular apparatus is a necessary consequence of the unfavourable position of most of the levers represented by the bones. There is very great variety in different individuals, as regards both the volume and substance of the muscular system. Compare, in this respect, the glutaeus maximus of a robust man, and the same muscle in a thin, nervous individual, much emaciated, but yet in perfect health, for still greater differences are produced by disease : size and strength of the muscular system may also be natural or acquired, partial or general. Partial preponderance is most usually acquired, and is commonly the result of exercise. To be convinced of this, it is only necessary to inspect the muscles of certain regions, in individuals whose em- ployment requires the special exercise of those parts. The preponderance of the mus- cles on the right side is produced solely by the habit of using this side more than the other ; it is not, as has been alleged, the result of congenital difference. Lastly, the size of one or the other region of the muscular system, in different anunals, * From iivHv, a muscle, or fjuj, a mouse. t It will be seen, that, in constructing this definition, the only object has been to distinguish the muscles g-en- erally from other organs, by pointing out their two characteristic properties, viz., their fihriaous compos tion and their contractility. FIGURE A\D DIRECTION OF THE MUSCLES. 191 is in relation either with their instinctive propensities, their mode of feeding, or their natural attitude, or with some other important peculiarity in their organization. Hence we find, 1. In the lion, the tiger, and other carnivorous animals that tear their prey in pieces, the muscles connected with the inferior maxilla, the most highly developed ; 2. In the bear, which is a climbing animal, the muscles of the back ; 3. In the hare, whose mode of progression is by successive leaps, the muscles of the hind limbs ; 4. The mus- cles of the wing in birds ; and, 5. Those of the lower extremities and the vertebral grooves in man, to whom the erect position is peculiar. Figure of the Muscles. The figure of the muscles is determined upon the following data : 1. From a compari- son of them with geometric figures or with famihar objects. 2. From the respective ar- rangement of their surfaces, edges, and angles. 3. From their being symmetrical or otherwise. In this latter respect there is a remarkable difference between the osseous and the muscular systems : many bones are symmetrical, or azygos, while almost all the muscles, on the contrary, are asymmetrical, and arranged in pairs. 4. From the relative proportion between their three dimensions ; from this latter consideration, muscles have been divided into three classes, viz., long, broad, and short, concerning each of which we shall make some general remarks. The long muscles are chiefly met with in the limbs. Their length is sometimes con- siderable ; and the longest are always most superficial. Very long muscles generally pass over several articulations, and can therefore assist in moving them all. This great length of certain muscles has also another advantage, viz., that it enables them to obtain a fixed point of attachment upon a less movable part, as the trunk, from which they can then act upon the more mobile parts : such is the case with the muscles that move the thigh or the leg. Long muscles are either simple or divided. Sometimes the division occurs at the more movable attachment ; sometimes at that which is habitually fixed. The broad muscles occupy the parietes of cavities ; they are quadrilateral when all their points of attachment are on the trunk, and triangular when they extend from the trunk to the extremities. When several broad muscles are super-imposed, the fibres of one always cross those of another at an angle ; and this an-angement, by forming a sort of interweaving, greatly augments the strength of the parietes which they assist in forming. This is particularly well shown in the broad muscles of the abdomen. The short muscles are generally met with in the same situations as the short bones. It is not the shortness of its fibres, but of its fleshy body that characterizes a short mus- cle. It is important to notice, with regard to these muscles, that a number of them are often arranged in succession, so as to resemble a long muscle. Of this we shaU find many examples in the muscles of the vertebral grooves. Direction of the Muscles. The direction of the muscles is one of the most important points in their history, since, without a knowledge of this, it is impossible to appreciate their uses. Each muscle has an axis or middle line, in which the general action of its fibres takes effect. Few mus- cles are altogether rectilinear ; most are angular or curved ; and almost all undergo cer- tain deviations or reflections in passing round the joints : some, indeed, take a direction at right angles to their primitive course, when they pass over pulleys or hook-like pro- cesses. In muscles of this kind the action is in the direction of the reflected portion. The direction of muscles must be studied with reference to the axis of the body, but especially to the axis of the limb or lever, in relation to which they represent the moving power. Many muscles are almost parallel to the axis of the lever upon which they act ; but it should also be remarked that, in certain positions, these same muscles form great- er or smaller angles with their corresponding levers, and may even become perpendicu- lar to them. In this respect the direction of the muscles is not absolute, but is subordi- nate to the position of the levers. Some muscles are constantly perpendicular to the levers upon which they act. The angles of incidence of the muscles upon their points of attachments are very va- riable, but generally they are more nearly parallel than perpendicular to those points. As the axis of a muscle is not the same as that of its component fibres, it is necessary to study, in each muscle, not only the direction of the fleshy belly, but that of the fibres also. Relations or Connexions of the Muscles. In reference to surgery, the relations or connexions of the muscles are among the most important circumstances in their history. Relations of the Muscles to the Skin. — Those muscles only which are caUed cutaneous are immediately connected with the skin ; the remainder are separated from it by apo- neuroses of greater or less density, so that the skin does not participate in the move- ments of the muscles, and vice versa. Nevertheless, the changes produced in the form and size of the muscles during their contraction are so decided, that those which lie near the surface are more or less defined through the integuments ; but the projections 192 MYOLOGY. corresponding to the bodies of the muscles and the depressions at their attachments are, in a measure, obhterated by adipose tissue, the quantity of which varies in the two sexes and in different individuals. To this latter circumstance are due the differences in the outward characters of the muscular system of the female, as compared with the male ; and of a fat individual, as compared with the one who is emaciated. Relations of the Muscles to the Bones. — In the limbs where the muscles form several par- allel layers around the bones, the belly or thickest part of the muscle always corresponds with the shaft or most slender portion of the bone ; while the ends of the muscle, where it is thinnest, correspond with the expanded extremities of the bone. The relations of the bones with the muscles vary, according as the latter are deep-seated or superficial. The superficial are only in contact with the bones by their extremities or their tendons : the deep-seated muscles alone correspond to the bones by their entire length. Relations of the Muscles to each other. — The muscles are arranged upon each other in successive layers ; each muscle is covered by a sort of fibro-cellular sheath ; and a loose and moist cellular tissue is interposed between the different sheaths, so as to facilitate the gliding movement and independent contraction of each muscle. This isolation of the muscles does not exist throughout their entire length ; several are often blended together in one common insertion, from which they proceed as from a centre, afterward separating from each other. This community of attachment is principally observed in those muscles that perform analogous offices, or that, usually at least, act simultaneously. Most muscles are enclosed in a separate fibrous sheath, which isolates them in their actions, and also in their diseases. Of this we shall find remarkable examples in the rectus abdominis and sartorius. With regard to the relations of their edges, the muscles are sometimes contiguous throughout their entire course, and sometimes separated by intervals, generally of a triangular figure ; and principally important in surgical anatomy, because incisions, for the exposure of vessels, are almost always made in such intervals. Relations of Muscles to the Vessels and Nerves. — The muscles serve to protect the ves- sels and nerves, not only in consequence of the thickness of the layers which they form in front of them, but also by the resistance they oppose during their contraction to ex- ternal violence. Near the centre of a limb there is generally a considerable cellular in- terval between the muscular layers, which is intended for the principal vessels and nerves. The existence of such spaces prevents the injury which these vital parts would sustain from compression during the contraction of the muscles. It is also worthy of notice, that whenever a vessel passes through the body of a muscle, we find an aponeurotic arch or ring, which is non-contractile, and in some degree, therefore, obviates the danger of compression during the action of the muscular fibres. I say in some degree, because, in order to render compression of the vessels impossible, the muscular fibres attached to these rings must have proceeded from them as from a centre, diverging in all directions. In this case, the action of the muscles would not change the form of the rings, but would tend to increase their diameters in every direction. It is found, however, that they are invariably elongated in one direction and diminished in another, when the fibres of the muscle contract. BernouiUi, indeed, has shown that it is impossible to change the form of a circle, by making one of its diameters greater than the others, without, at the same time, diminishing its capacity ; because, within a given periphery, the most regular fig- ures have the greatest capacity, and the circle is more regular than either the oval or the ellipse. On the whole, however, it must be understood that the contraction of the fibrous rings does not, in any material degree, impede the circulation. It should also be remarked, that a distinct fibrous sheath surrounds the vessels and the nerves, serving to isolate and protect them amid the various muscles by which they are surrounded. Most of the arteries have accompanying muscles, which may be called their respective satellites : thus, the sartorius is the satellite muscle of the femoral artery, the biceps of the brachial, the sterno-mastoid of the carotid, &c. Attachments or Insertions of Muscles. The attachments or insertions of muscles constitute one of the most important points in their history, and one which requires to be studied with the greatest care, because the uses of a muscle can be determined from a knowledge of its insertions alone. These insertions should be considered in two points of view ; 1. As to the direct insertion of the muscular fibres into the tendons, aponeuroses, or other structures ; 2. As to-the in- sertion of the tendons and aponeuroses into the levers represented by the osseous system. The muscular fibres themselves are attached, 1. To the skin, of which mode there are numerous examples in the muscles of the face ; 2. To other muscular fibres, as in many muscles of the face and of the tongue ; 3. To cartilages, as in several of the muscles of the chest and larynx ; 4. To aponeuroses, of which they act as tensors, and whose power of resistance they thereby increase ; lastly, to tendons or aponeuroses * that are them- selves attached to the bones. The fleshy fibres are inserted into, or become continuous with, the tendons and apo- * [The tendons afford examples of the fascicular form of fibrous tissue, for a notice of which see note, infrii.1 ATTACHMENTS AND STRUCTURE OF MUSCLES. 193 neuroses in the -following manner : The tendon is prolonged under the form of a mem- brane, either upon the surface or in the substance of the muscle. The results of this arrangement are, 1 . An increase of surface for the attachment of the muscular fibres, which the tendon gathers up, as it were, in order to concentrate their efforts upon one point ; 2. An obliquity in the insertion of the fibres, in reference to the axis of the entire muscle, by which the direction of the power is represented. It may easily be conceiv- ed that this obliquity is of the gceatest interest as regards the dynamic relations or ac- tive property of the museles.* One of the most curious circumstances respecting the continuity of a tendon or an aponeurosis with a muscle is the very intimate union between the muscular and fibrous tissues, which is so complete that they are scarcely ever separated by external violence, which, moreover, tends to lacerate the muscle rather than the tendinous fibres. It is a fact worthy of notice, and one which we have already had frequent occasion to remark, that the adhesion of any two organic tissues is stronger than the respective co- hesion of each ; so that the tissues themselves will sooner break than admit of separa- tion from one another. Insertion of the Aponeuroses and Tendons into the Bones. — A tendon or an aponeurosis forms a species of ligament, by means of which the action of a very large muscle is transmitted to the lever intended to be moved, by a fibrous cord or aponeurotic lamina of small size. A great advantage arises from this mode of economizing the extent of bony surface required for muscular attachments ; for, notwithstanding the extent of surface afforded by the expanded ends of the bones, and by the eminences and ridges with which they are covered, it would be evidently insufficient, were the muscular fibres to be directly attached. The existence of tendons and aponeuroses produces also this remarkable result, viz.„ that the muscular insertions are much stronger than they would otherwise have been.. The aponeurotic tissue acts as a transition structure, being in some points of its organic zation analogous to bone, and in others approaching that of muscle. The analogy be^. tween the bony and fibrous tissues is confirmed by the frequent occurrence of ossifica- tion in the latter, even under normal conditions, as may be observed in the formation^of the sesamoid bones, and also in the mode by which tendons are attached. It has been; observed, in fact, that at the point of junction of the tendons with the bones there isa. sort of mutual fusion of the tissues, from which so intimate a connexion results, that the- proper substance of the tendons always gives way before they can be separated- from the bones, their attachments to which even maceration will scarcely destroy. Of the different bones with which a muscle is connected, some remain immovable du- ring its contraction, while others are put in motion ; hence the distinction helvteen fixed and movable attachments. But this eminently useful distinction must not be taken in an absolute sense ; it is only rigorously true of a very small number of muscles, which, like some of those found in the face, being connected by one extremity with the skin, and by the other with the bones, can give rise to movements only at their cutaneous at- tachments. In the greater number of muscles, on the contrary, although one of the at- tachments is most commonly fixed and the other movable, yet their relative condition may be changed, and they may become alternately fixed and movable ; it is therefore necessary, in explaining the action of a muscle, carefully to notice the supposed mobility or fixedness of the different attachments at the time. In comparing such attachments as are habitually fixed with those that are constantly movable, we shall observe that the former are either numerous or spread out by means of aponeuroses, whereas the latter consist of very accurately-circumscribed tendons. The figurative expressions of head and tail, given to the ends of a muscle, refer to this arrangement. The fixed attachment of a muscle is usually blended with those of several others, while the movable one is distinct. t In order to facilitate our description, we shall invariably designate the fixed attachment of a muscle, its origin, and the movable attachment, its termination or insertion. Structure of Muscles. Muscles are composed of two kinds of fibres : 1 . Of red or contractile fibres, which form the muscular tissue properly so called ; 2. Oi white, strong, and non-contractile fibres, con- stituting the tendons and aponeuroses. In speaking of the ligaments, we mentioned the general properties of tendons and aponeuroses as belonging to the fibrous tissues ; we shall now make a few remarks on the peculiar characters of muscular tissue. 1. Colour. — Muscular tissue is of a reddish colour, the intensity of which varies in dif- ferent muscles and in different individuals. This colour is not an essential character even in the human subject, for the contractile fibres of the intestinal canal are very * In fact, as the tendon, and the aponeuroses by which it is continued into the muscle, represent the direc- tion ol'the power, the fleshy fibres must necessarily be attached to it more or less obliquely. It is not our in- tention to examine here the great loss of power which this arrangement involves. t [This assertion must be taken with some limitation. We shall find many exceptions to this general rule, as we proceed in the description of the muscles.] Bb 191 MYOLOGY. pale ■* still less is it so in the lower animals, some of which have the entire muscular system perfectly colourless. The red colour of the muscular fibre is independent of the blood contained within the vessels of the muscle. 2. Consistence. — The consistence of the muscular fibres varies in different subjects : in some it is soft and easily torn ; in others it is firmer and more resisting, and retains for some time after death a degree of rigidity which yields with difficulty to forcible ex- tension. Structure. — The muscles may be divided into bundles or fasciculi of different orders, and these, again, into distinct fibres, wliich are visible to the naked eye, and rendered more apparent, either by dissection, or by the action of alcohol, of diluted nitric acid, or even of boiling water. They are of a variable shape, resembling prisms of three, four, 'five, or six surfaces, but are never cylindrical. Their length also varies in different muscles, in but a few of which do they extend parallel to each other tliroughout the en- tire length of the fleshy belly. Each muscle is surrounded by a sheath of cellular tissue, which also penetrates into its substance, and surrounds both the fasciculi and fibres. Tliis cellular tissue permits the free motion of the different fasciculi upon one another, while it serves, at the same time, to isolate each and combine the whole. t The chemical analysis of muscular tissue shows that it is composed of a small quan- tity of free lactic acid (Berzelius) ; gelatin; some salts; osmazome in greater or less quantity, according to the more or less advanced age of the individual ; and leucine, a substance extracted from this tissue by the process described by M. Braconnot. (Ann. de Chim. et de Phys., tom. viii.)1: In addition to the tendinous and fleshy fibres, vessels, nerves, and cellular tissue also enter into the composition of muscles. We have already described the disposition of the cellular tissue contained in these organs ; the mode of distribution of their vessels and nerves will be more appropriately alluded to in the description of the vascular and ner- vous systems, ij Uses of Muscles. The muscles are the active organs of motion, constituting the source of the power * [The involuntary muscular tissue, of which the above-named fibres afford examples, are, with the excep- tion of the heart, of a much paler colour than the voluntary muscles, to which this division, of the present work exclusively refers.] t [In reference to the microscopic structure of the voluntary muscles, or those of animal life, it has been ascertained that the smallest fasciculi (C(irresponding with the prismatic fibres of our author, and with the -secondary fasciculi of .MiJller), the size of which varies in different muscles, are divisible into transversely-slri- ./aUd fibres (the primitive fasciculi of Miiller), having a uniform diameter in all muscles in the same species, and being themselves composed of still smaller elementary parts na.meii filaments (the primitive fibres of Miil- ler), All these elements of the muscular tissue extend parallel to each other, from one tendinous attachment :to aaother, never having been seen to bifurcate or coalesce. In .man Ihe fibres vary from xATjtli to -g-^-gth of an inch in diameter; the trans\-erse striiE upon them are parallel, generally straight, b Jt occasionally slightly waved or curved ; they are situated at intervals of from . Jl ^ tfa to y-o g-Q^th of an inch. The f.laments are varicose or beaded, i. e., alternately enlarged and contracted ; their diameter is from .1 th to —^- — th of an inch. According to the general opinion, thev are held together in each fibre by 1 g 0 001 ^000 means of a glutinous substance, which latter, according to Skey, constitutes the entire centre of the fibre, the circumference alone being occupied by the filaments. In the lan-ie of insects, a delicate membranous sheath, sometimes observed projecting beyond the filaments, has been described by Schwann as forming a proper in- vestment of the fibre ; and, by analogy, this is also presumed to exist in man and the other vertebrata. Be this as it may, it is certain that the fibres have no separate sheaths uf cellular tissue derived from the common gheath of the muscle, the prolongations of which appear to extend only so far as to enclose the smallest fasciculi. The cause cf the striated appearance has, perhaps, not been quite satisfactorily ascertained ; but since the enlart'ements on the varicose filaments are darker than the constricted portions, and since ihey are situated at intervals precisely similar to those between the transverse stris of the corresponding fibre, and from some other additional considerations, it has been supposed, with great probability, to result from the enlarged and dark portions of the filaments being arranged side by side. For an account of the microscopic characters of the involuntary or organic muscular fibres, .see the notes on the structure of the several viscera, &c.,in which they are found, viz., the alimentary canal, trachea, genito- nrinary organs, and iris. We may remark here, that the muscular fibres of the heart and of the upper part of the oesophagus are striated, and approach very closely in character to those of animal Ufe.] t [The following analysis of the muscles of the ox is on the authority of Berzelius . Water 77-17 Fibrin (with vessels and nerves) 15.8 Cellular tissue convertible into gelatin . . . . . 1"9 Albumen and colouring matter 2'2 Alcoholic extract, or ozmazome, with lactic acid and lactates 1'8 Watery extract, with phosphate of soda ..... 1'05 ;Phosphate of lime '08 100- The inadvertent omission, on the part of M. Cruveilhier, of ^irin as one of the proximate principles of mus- cle will serve to impress on the mind of the reader its importance as a constituent of that tissue, in which it exists in greater abundance than in any other. The substance called leucine, mentioned in the text, is a product resulting from the action of concentrated sulphuric acid on muscular fibre, and therefore must not be regarded as previously existing in it.l 6 As it is our intention to introduce, after Myology, an account of the Aponeuroses, we shall be content at present with the general ideas that have been already stated regarding this important division of the fibrous tissues. USES OF MUSCLES. 195 that is applied to the various levers represented by the component parts of the skeleton. The movements produced are the result of that peculiar property possessed by the mus- cles of shortening themselves, which is called muscular contractility {myotiliU). The shortening of a muscle is termed its contraction, and the opposite state its relaxation. Phenomena of Muscular Contraction. — During contraction the muscular fibres become folded in a zigzag manner throughout their entire length ; the muscle itself becomes hardened, and broader and thicker in proportion to the amount of shortening. There is no oscillation in a muscular fibre during a normal contraction.* The aponeuroses and the tendons take no part in the contraction ; they are entirely passive. The degree of shortening of which the muscular fibre is susceptible cannot be precisely determined ; as far as we know, the shortening, and, consequently, the ex- tent of the resulting movement, is proportional to the length of the fibre. A distinction should be drawn between the force and the velocity or rapidity of muscular contraction. Again, the velocity is very different from the extent of motion : the latter depends upon the length of the fibres ; the former has no connexion with it, but varies according to the constitution of the individual, and is probably dependant on a more or less rapid influx of nervous influence. The muscular force is composed of a great number of elements. According to Borel- li, an intrinsic and an effective force may be distinguished in each muscle. The in- trinsic force is that power which the muscular fibres would exert if they were in the most favourable position for contraction : the effective force is measured by the result. The estimation of the force of a muscle presupposes a knowledge, 1. Of the number of its fibres. 2. Of ther quality or constitution. 3. Of the nature of the lever upon which it acts. 4. Of the angle of incidence of the muscle upon that lever ; and, 5. Of the angle of incidence of the fibres with respect to the imaginary axis of the muscle. 1. Each muscular fibre, being distinct from those around it, may be considered as a small power ; it may, therefore, be easily conceived that the greater the number of fibres in any muscle, the more energetic will be its contraction. 2. The quality and constitution of the fibre, and the intensity of the stimulus, have no less an influence upon the contractile force of a muscle than the number of its fibres. To be convinced of this, it is sufficient to compare the energy of movement in an individual excited by anger with that in one who is calm. 3. The determination of the kind of levert represented by the bone upon which the muscle acts, is a fundamental point in studying muscular action. It is a law in mechan- ics, that the power acts with greater effect in proportion as its arm of the lever exceeds in length that of the resistance. The most common lever in the human body is that of the third order, in which the power, being applied between the fulcrum and the weight, is therefore most disadvantageously situated for action. 4. As far as regards energy of movement, the lever to which the power is applied is as unfavourable as possible, because the muscles are generally inserted near the fulcrum. * The observations of Rogerus tend to show that rapid contractions and relaxations are constantly taking place in muscles, especially during their contraction. — {Tr.) " De Perpetua Fibrarum Muscularium Palpitatione," 1760. Fi^. 103. t A lever, in mechanics, signifies an inflexible rod capable of turning round a point. The point upon which the lever turns is called the ful- crum (ftjigs. 103, 104, lO.")) ; the cause of motion is called the power (p) ; and the obstacle to be surmounted is the resistance (r) ; the space be- tween the fulcrum and the power is the poirer-arm of the lever ; the space between the fulcrum and the weight is the resistance-arm of the lever. There are three kinds of levers, distinguished by the respective arrange- ment of the three parts: 1. A lever of the first order (fig. 103) has the ful- crum between the power and the resistance. 2. A lever of the second or- der (fig- 104) has the resistance between the fulcrum and the power. 3. A lever of the third order (fig. 105) has the power between the re. Fig. 106. posterior region of the trunk, covers the nape of the neck and the back. It is a broad triangular, rather than trapezoid muscle, thick in the mid- dle, thin and elongated at its supe- rior and inferior angles. Attachments. — It arises from the spinous processes of all the dorsal and the seventh cervical vertebrae, from the corresponding supra-spi- nous ligaments, from the posterior cervical ligament (ligamentum nu- chcE;, and from the internal third of the superior occipital line, and is in- serted into the entire length of the spine of the scapula, into the poste- rior border of the acromion, and into the external third of the posterior border of the clavicle. The fixed attachments or origins of this mus- cle present, 1. A broad, semi-ellipti- cal aponeurosis, which, when united to the one on the opposite side, forms an ellipse, occupying the space be- tween the sixth cervical and the third dorsal vertebrae ; 2. A very thin fibrous lamina, not having the ordi- nary shining appearance of an apo- neurosis, which is firmly adherent to the skin, and forms the truncated occipital angle of the muscle ; 3. A great number of tendmous fibres, constituting all those attachments to the vertebra; that are independ- ent of the two preceding aponeuro- ses. From these origins all the fleshy fibres proceed mitward, the mferior fibres from below upward, the superior from above downward, and from behind forward, and the middle ones horizontally. They terminate in the following manner : the lower or ascending fibres are collected together, and at- tached to a triangular aponeurosis, which, gliding over the small facette at the internal extremity of the spine of the scapula, is inserted into the tubercle immediately connect- ed with it ; the middle or horizontal fibres terminate at the posterior border of the spine of the scapula, by tendinous fibres which are very distinct, especially towards the acro- * [The transversa- spinalis muscle includes the semi-spinalis colli, the semi-spinalis dorsi, and the multifidas spinse of Alhinus.] THE LATISSIMUS DOKSI AND TERES MAJOR. 199 mion ; the upper or descending fibres are inserted into the convex portion of the posterior border of the clavicle, many of them being also attached to the upper surface of that bone. Relations. — The trapezius is covered by the skin, from vk^hich it is separated by an aponeurotic lamina, except at the upper part, where tiie muscle and integuments are intimately adherent. It covers the complexus, splenius, rhomboideus, and levator an- guli scapulae, in the neck ; and the serratus posticus superior, the supra-spinatus, the pos- terior spinal muscles, and the latissimus dorsi, in the back. The most important rela- tions of this muscle are those of its superior and external or occipito-clavicular margin : this forms the posterior boundary of the supra-clavicular triangle, which is limited in front by the sterno-mastoid muscle, and below by the clavicle. It should be observed in reference to the indications regarding the supra-clavicular space, furnished by this margin of the trapezius, that it sometimes advances as far as the middle of the clavicle, and has even been observed to become blended with the posterior edge of the sterno-mastoid. Action. — 1. The upper or descending portion elevates the clavicle, and, consequently, the apex of the shoulder ; but if the shoulder be fixed, this portion of the muscle inclines the head to one side and extends it, and, moreover, rotates it, so that the face is turned to the opposite side. 2. The middle or horizontal portion carries the shoulder back- ward, but, from the obliquity of the spine of the scapula, it also rotates that bone, so that the apex of the shoulder is carried upward. 3. The lower or ascending portion draws the posterior costa of the scapula inward and downward ; and, by a species of rotation, which was alluded to when treating of the scapulo-clavicular articulations, also elevates the apex of the shoulder. 4. When the whole of the muscle contracts at once, the scap- ula is drawn inward, and the apex of the shoulder is raised. The Latissimus Dorsi and Teres Major. Dissection. — 1. Render the latissimus dorsi tense by the same means as were employ- ed for the trapezius, and also by withdrawing the arm from the side. 2. Make an incis- ion in the median line from the tenth dorsal vertebra to the sacrum, and another trans- versely from the same vertebra to the posterior border of the axilla, dividing in the lat- ter incision a fibro-cellular membrane, which adheres very firmly to the fleshy fibres. 3, Dissect the humeral insertion very carefully, and at the same time prepare the teres major, which is very intimately related to this extremity. The Latissimus Dorsi. The latissimus dorsi {b,Jig. 106, p,Jigs. 109, 110) occupies the lumbar and part of the dorsal region, and the posterior border of the axilla. It is the broadest of all the mus- cles, and shaped like a triangle, having its inferior angle truncated, and its upper and external angles considerably elongated. Attachments. — It arises from the spinous processes of the last six or seven dorsal, of all the lumbar, and of the sacral vertebrae, from the posterior third of the crest of the ilium, and from the last four ribs, and is inserted into the bottom of the bicipital groove of the humerus, not into its posterior border. Its origin from the crest of the ilium and from the vertebrae is effected through the medium of a triangular aponeurosis, narrow and thin above, broad and very strong be- low, where it is blended with the aponeuroses of the serratus posticus inferior and ob- liquus internus abdominis, and with the posterior layer of the aponeurosis of the trans- versus abdominis. This aponeurosis assists in forming the sheath of the sacro-lumbalis, longissimus dorsi, and transverso-spinalis. The costal origins consist of fleshy tongues or digitations, which are interposed between similar processes of the external oblique. From this threefold origin the fleshy fibres proceed in the following manner : the upper pass horizontally, the middle are directed obliquely, and the lower vertically upward ; they all converge, so as to form a thick fasciculus, directed towards the inferior angle of the scapula, from which it often receives some accessory fibres. The muscle is then twisted upon itself, so that the inferior or vertical fibres become first anterior and then superior, while the superior or horizontal fibres become first posterior and then inferior. This torsion may perhaps be intended to prevent displacement of the fibres. They all terminate in a flat quadrilateral tendon, which is inserted into the bottom of the bicip- ital groove, above the insertion of the tendon of the pectoralis major. This tendon fur- nishes a fibrous expansion continuous with the fascia of the arm, and also a band which; extends to the lesser tuberosity of the humerus. Relations. — This muscle is covered by the skin (from which it is separated by a close- s ly-adherent fibro-cellular sheath), and by the inferior angle of the trapezius. It covers the posterior spinal muscles, the serratus posticus inferior, the external intercostals, the serratus magnus, the lower angle of the scapula, the rhomboideus, and, lastly, the teres major, by which muscle it is itself covered in its turn. Its external margin is in relation with the posterior border of the external oblique, from which it is separated below by a small triangular interval. The upper part of the external margin, together with the teres major, forms the posterior border of the axilla ; and from the same margin a muscular fasci- culus occasionally extends beneath the axilla to the lower edge of the pectoralis major.. 200 MYOLOGY. The Teres Major. This muscle (c c, Jig. 106), which, both in its uses and its anatomical arrangements, should be considered an accessory to the latissimus dorsi, is situated behind the slioulder. Attachments. — It arises from the quadrilateral surface, situated at the inferior angle of the scapula, to the outer side of the infra-spinous fossa, and is inserted into tiie j osterior border of the bicipital groove. The scapular attachment consists of short tendinous fibres, some of which are fixed directly to the bone, and some into the fasciae, which separate this muscle from those of the infra-spinous and subscapular fossae. The fleshy fibres arising from these different attachments form a thick fasciculus, flattened from be- fore backward, not cylindrical, and about two or three fingers in breadth, which is direct- ed outward and upward, and becomes slightly twisted, so as to be inserted by a broad and flat tendon into the posterior border of the bicipital groove. Relations. — The latissimus dorsi at first covers its scapular extremity, and then, turn- ing round its lower edge, becomes anterior to it. The tendon of the latissimus dorsi is, therefore, applied to the anterior surface of the tendon of the teres major ; but since the former is attached to the bottom, and sometimes even to the anterior border of the bi- cipital groove, and the latter to the posterior border of the same groove, they are separ- ated at their insertions by an interval, in which there is almost always a synovial mem- brane, and which forms a true cul-de-sac below, for the lower margins of the two tendons are blended together. The posterior surface of the teres major is covered by the skin, from which it is sep- arated on the inside by the latissimus dorsi, and externally by the long head of the tri- ceps. Its anterior surface is in relation with the subscapularis, the coraco-brachiahs, the short head of the biceps, the brachial plexus, the axillary vessels, and the cellular tissue of the axilla. Its upper margin is at first in contact with the teres minor, from which it is separated above by the long head of the triceps ; its lower margin forms, in conjunction with the latissimus dorsi, the posterior border of the axilla. Action of the Latissimus Dorsi and Teres Major. — The latissimus dorsi adducts the arm, rotates it inward, and at the same time draws it backward (hence its name, ani scalptor). "When only the upper or horizontal fibres contract, the arm is carried inward and backward ; when the lower fibres act alone, it is can-ied downward. The uses of the teres major are precisely similar to those of the latissimus dorsi, to which it is congenerous and accessory, and with which it is always associated in ac- tion, drawing the humerus inward, backward, and downward. When the humerus is the fixed point, the latissimus dorsi raises the trunk, and with the greater facility, be- cause it is attached to the ribs, the spine, and the pelvis. In consequence of its costal attachments, the latissimus dorsi is a muscle of inspiration ; and it should be observed, that the direction of its fibres, which is almost perpendicular to the ribs, enables it to act with great power. The Rhomboideus. Dissection. — Divide the trapezius by an incision extending from the third dorsal ver- tebra to the lower angle of the scapula : dissect back the flaps, taking care to remove a fibro-cellular layer which adheres closely to the trapezius. The rhomboideus {d d, fig. 106), situated in the dorsal region, on the posterior aspect of the trunk, approaches closely to the form of a rhomboid or lozenge ; it is broad and thin, but thicker below than above, and is almost always divided into two parts. Attachments. — It arises from the bottom of the ligamentum nuchae, from the spinous processes of the seventh cervical and five superior dorsal vertebrae, and from the corre- sponding interspinous ligaments, and is inserted into all that part of the posterior costa of the scapula situated below its spine. The spinal or internal attachments consist of tendinous fibres, the most inferior of which are the longest. From these points the fleshy fibres proceed, parallel to each other, downward and outward, to a very thin ten- don, which runs along the posterior costa of the scapula, but only adheres to it above and below : the greater number of fibres are inserted into the lower angle of the scapula by a very strong tendon, which forms the principal attachment of the muscle, and to which the tendon mentioned above is merely subordinate. The upper part of this mus- cle {e,fig. 103), which arises from the ligamentum nuchae and the seventh cervical ver- tebra, is inserted by itself opposite the spine of the scapula. It is distinct from the re- mainder of the muscle, and from this fact Vesalius, Albinus, and Scemmering gave it the name of rhomboideus minor or superior. Relations. — This muscle is covered by the trapezius, the latissimus dorsi, and the £kin. It covers the serratus posticus superior, part of the posterior spinal muscles, the xibs, and the intercostal muscles. Action. — The rhomboid raises the scapula and draws it inward. As it acts principal- ly upon the lower angle of that bone, it rotates it in such a manner that the anterior angle, and, consequently, the apex of the shoulder, is depressed. It assists the trape- zius in carrying the entire shoulder inward, and is also associated with the upper fibres THE SERRATI POSTICI. 201 of the same muscle in raising that part ; but, on the other hand, it antagonizes the tra- pezius by depressing the apex of the shoulder. The Levator Anguli Scapulce. Dissection. — Detach the trapezius from the spine of the scapula with care ; divide the upper part of the sterno-mastoid, so as to expose the transverse processes of the three or four superior cervical vertebrae. The levator anguli scapula (levator scapulae, Albinus, f, figs. 106, 110, 113, 114), situ- ated at the posterior and lateral part of the neck, is an elongated bundle, having its up- per portion flattened from without inward, and divided into three or four fasciculi, while the lower part is flattened from behind forward. Attachments. — It arises from the posterior tubercles of the transverse processes of the three or four superior cervical vertebrae, externally to the splenius, and behind the sca- lenus posticus ; it is inserted into the superior angle of the scapula (whence its name), and into all that portion of its internal costa situated above the spine. The cervical attachments of this muscle consist of four tendons, to which succeed an equal number of fleshy fasciculi, at first distinct, but afterward united into one bundle, which proceeds downward, backward, and outward, and spreads out to be inserted into the scapula by short aponeurotic fibres. Relations. — It is covered by the trapezius, the sterno-mastoid, and the skin ; and it lies superficially to the splenius, the sacro-lumbalis, the transversalis colli, and the ser- ratis posticus superior. Action. — When its upper attachment is fixed, this muscle carries the posterior angle of the scapula upward and forward, and, consequently, rotates that bone, so as to depress the apex of the shoulder. It conspires with the rhomboid and the trapezius in elevating the entire shoulder, and with the rhomboid in depressing its apex, in this respect acting as an antagonist to the trapezius. When the fixed point is below, which must be very rarely, it inclines the neck backward and to its own side. The Serrati Postici. These are two in number, a superior and an inferior. Dissection. — 1. To expose the superior muscle, divide and reflect the trapezius and the rhomboid, and draw the scapula forward ; 2. To display the inferior, raise the latissimus dorsi with great care, as its deep aponeurosis is blended with that of the serratus posticus inferior ; 3. Preserve the thin aponeurosis extending between the two serrati muscles.* 1 . The serratus posticus superior is situated at the upper and back part of the thorax, and is of an irregularly-quadrilateral figure. Attachments. — It arises from the ligamentum nuchae and the spinous processes of the seventh cervical and of the two or three upper dorsal vertebrae, and is inserted into the upper borders of the second, third, fourth, and fifth ribs. The vertebral attachment con- sists of a very thin aponeurosis, the fibres of which are parallel, and inclined downward and outward. From this aponeurosis, which constitutes at least the inner half of the muscle, the fleshy fibres proceed in the same direction, and almost immediately divide into four digitations, which are inserted into the ribs by means of short tendinous fibres. The superior digitation is attached near the angle of the corresponding rib, and each of the others at successively greater distances from it. 2. The serratus posticus inferior (lumbo-costalis, Chaussicr, g,fig. 106) is also of an ir- regularly-quadrilateral form, and is situated at the lower part of the back and the upper part of the loins. It arises from the spinous processes of the two lower dorsal and three upper lumbar vertebrae, and is inserted into the inferior borders of the last four ribs. The vertebral or internal attachment consists of an aponeurosis similar to that of the prece- ding muscle, but its fibres have an inverse direction, i. e., obliquely outward and upward. From this aponeurosis, which forms the internal half of the muscle, the fleshy fibres pro- ceed in the same direction, and divide into four flat digitations, progressively decreasing in size from above downward, which are inserted into the ribs by means of tendinous laminae, the superior digitation near the angle of its corresponding rib, and the others, successively, farther beyond it. Relations. — These two muscles have certain relations in common, and there are some peculiar to each. They both cover the longissimus dorsi, the sacro-lumbalis, the trans- verso-spinalis, the ribs, and the corresponding intercostal muscles. The superior is cov- ered by the rhomboideus, the trapezius, and the serratus magnus, and covers the splenius and transversalis colli. The inferior is covered by the latissimus dorsi, with the apo- neurosis of which muscle its own aponeurotic lamina is so closely united that it is impos- sible to separate them completely ; and it covers the posterior layer of the aponeurosis of the transversalis. Action. — Besides certain common uses, each muscle has its own peculiar action. One * [This exceeding-ly thin and semi-transparent lamella has received the name of the vertebral aponeurosis. See Aponeurology,] Co 202 MYOLOGY. important common use is, to retain in the vertebral groove those muscles of the back which, from their extreme length, are the most liable to displacement. This effect is produced by their fleshy portions rendering tense their aponeurotic expansions. With regard to the actions proper to each, 1. The superior elevates those ribs into which it is inserted, and is, consequently, a muscle of inspiration ; 2. The inferior, on the other hand, is a depressor of the ribs, and, therefore, a muscle of expiration. The Splenius. Dissection. — Merely remove the trapezius, the rhomboid, and the serratus posticus su- perior. The splenius {i.figs. 106, 113, 114), so named because it has been compared to the spleen {airTajv), is situated at the posterior part of the neck and upper part of the back. It ^ is a broad muscle, terminating in a point below, and dividing into two portions above. Attachments. — It arises from the spinous processes of the four or five superior dorsal and the seventh cervical vertebrae, from the corresponding supra-spinous ligaments, and also from the ligamentum nuchae, between the seventh and the third cervical vertebra ; it is inserted, 1. Into the transverse processes of the first, second, and often the third cer- vical vertebrae ; 2. Into the external surface and posterior border of the mastoid process, and the external third of the rough space beneath the superior semicircular line of the occipital bone. The spinal attachments consist of tendinous fibres, the most inferior of which are the longest. From these the fleshy fibres proceed obliquely upward and out- ward, the lower being longer and more vertical, and form a broad, flat muscle, which is much thicker externally, and soon becomes divided into two portions : one smaller, infe- rior and external ; the other much larger, superior and internal. The former is called the splenius colli ; it is sometimes distinct, even from its origin, and soon subdivides into two or three fasciculi, which terminate in as many tendinous processes, that are in- serted into the atlas, the axis, and often into the third cervical vertebra. The fascicu- lus proceeding to the atlas is usually the largest. The second, or the upper and internal portion of the muscle, is connected with the head, and is called the splenius capitis. Relations. — The splenius is covered by the trapezius (the rhomboid and the serratus posticus superior intervening below), by the sterno-mastoid, and by the levator anguli scapulae. It covers the complexus, the longissimus dorsi, the transversalis colli, and the trachelo-mastoid. The levator anguli scapulae is in contact with its outer border, and rests upon it above, the cervical insertions of the two muscles being blended togeth- er ; below they are separated by the transversalis colli and sacro-lumbalis. The inter- nal edge is very thin, and separated from the muscle of the opposite side by a triangu- lar interval, in which the complexi are visible. Actions. — The splenius extends the head, inclines it to its own side, aivd rotates it so that the face is turned to the same side. This action of the splenius depends on its at- tachments to the occipital bone, the mastoid process, and the atlas. By its insertions into the second and third cervical vertebrae it tends to rotate these in the same direction. When the two muscles act together, the head is drawn directly backward. The splenius is therefore an extensor and rotator of the head and of the neck ; it assists in supporting the head in the erect position, and prevents it from inclining forward in obedience to the force of gravity. The Posterior Spinal Muscles. As these muscles are arranged in a peculiar manner, we shall adopt a method of de- scription in some measure different from that which we have elsewhere employed. The posterior spinal, or long muscles of the back (see_^^. 107), are three in number, viz., the sacro-lumbalis, the longissimus dorsi, and the transverso-spinalis muscle. These three muscles, which extend the entire length of the spine, form a very large muscular mass, completely filling up the corresponding vertebral groove. This mass is small at the lower part of the sacral groove, becomes much enlarged in the loins, then diminishes in the back, and again acquires a considerable size in the neck. Chaussier has given a description of them under the collective name of the sacrospinal muscle ; and they have also been denominated the erector spina. I shall describe the three muscles together ; but, in order to adopt some arrangement in a matter so complicated, I shall divide them into three portions, viz., a lumbro-sacral, a thoracic, and a cervical, Lumbro-sacral Portion of the Posterior Spinal Muscles, Dissection.— \. Render this portion of the muscle tense, by placing a block under the abdomen. 2. Divide by a vertical incision the trapezius, splenius, rhomboideus, latis- simus dorsi, and serrati postici ; reflect the divided portions inward and outward. A young subject, from ten to twelve years of age, is best adapted for the study of these muscles, from the facility with which the different fasciculi may be separated. For the same reason, one that is much infiltrated with serum is preferable to one in which the parts are dry. THE POSTERIOR SPINAL MUSCLES. 203 The lumbo-sacral portion is usually called the common mass of the sacro-lumbalis and longissimus dorsi. It forms the fleshy part of the loins, and is called the fillet in the low- er animals : it is the most highly developed in man, in whom it exerts a constant and powerful action during the erect posture : it appears to be the common origin of the pos- terior spinal muscles, whence the name of eommon mass : it fills up entirely the lumbo- sacral groove, and even projects backward and laterally in robust subjects. It is of small size in the sacral region, is much enlarged at the middle of the lumbar region, at the upper part of which it again diminishes, so as to resemble two cones uni- ted by their bases. Attachments. — The common mass arises from the whole extent of the sacro-iliac groove, and from the anterior surface and external border of an extremely strong apo- neurosis, formed of parallel vertical fibres, and strengthened by a superficial layer direct- ed obliquely. This aponeurosis of origin for the posterior spinal muscles (d,fig. 107) is in- serted on the inside to the sacral ridge, to the summits of the spinous processes of the lumbar and three lower dorsal vertebrae, and to the corresponding supra-spinous liga- ments : on the outside, to the series of eminences representing the transverse processes of the sacral vertebrae, and to the back part of the crest of the ilium : it gives attach- ment to many of the fibres of the gluteeus maximus. It is short on the outside, and very long on the inside, reaching in the latter direction to the middle of the dorsal region, un- der the form of parallel and regular bands {d,fig. 107). Arising from these dilferent origins, the common mass appears at first extremely sim- ple in its composition, consisting of fibres passing vertically upward. But if the aponeu- rosis be detached from its spinal insertions, and turned outward, it will be seen that the common mass is essentially composed of two portions : one internal and anterior, the lumbosacral portion of the transverso-spinalis ; and the other external and posterior, the lumbo sacral portion of the sacro-lumbalis and longissimus dorsi. 1. The lumbosacral portion of the transverso-spinalis* occupies all the sacral groove, and that part of the lumbar groove situated within the articular processes. It is perfectly distinct in the loins, being separated from the common mass by loose cellular tissue trav- ersed by vessels and nerves. It arises from the articular processes of the lumbar verte- bra by flat tendons, directed obliquely inward and upward, and terminating upon the pos- terior surface of the muscle : by the union of their contiguous edges an aponeurosis is formed, which is itself blended along one of its borders with the deep surface of the com- mon aponeurosis of origin. From these tendons the fleshy fibres arise, and having united into bundles, terminate by other tendons at the spinous processes of the vertebrae above. In the sacral region this portion of the transverso-spinalis is less distinct, but it may be easily seen that it occupies the whole of the sacral groove, and that the corresponding por- tion of the aponeurosis of origin affords attachments to it alone. 2. The external and posterior portion of the com- mon mass, or lumbosacral portion of the sacro-lumbalis and longissimus dorsi, is entirely without the sacral groove, but occupies that part of the lumbar groove situated on the outer side of the articular processes. It arises, 1. From aU the lumbar portion of the com- mon aponeurosis. 2. From an extremely strong ten- don, which is attached to the posterior superior spi- nous process of the ilium. 3. From the posterior ' fourth of the crest of the ilium, internally by tendi- nous, and externally by muscular fibres. The thick fleshy mass proceeding from these different origins ,i is disposed of in the following manner : the greater part of the fibres pass directly upward to the dorsal region, forming the proper commencement of the sacro-lumbalis {a a, fig. 107). The remaining fibres are directed forward, and are arranged into two sets of bundles, one of which is inserted into the summits of the transverse processes, forming the external or transverse fasciculi ; and the other into the tubercles of the articular processes, forming the internal or ar- ticular fasciculi. These two sets of fibres constitute the proper origin of the longissimus dorsi (d d, fig. 107). Relations.— The common mass is covered behind Fig. 107. * [This corresponds to the inferior or lumbo-s^cral fasciculi of the multifidus spinje.J 204 MYOLOGY. bv the united aponeuroses of the latissimus dorsi and serratus posticus inferior, and by the posterior layer of the aponeurosis of the transversalis ; in front, it corresponds to the lumbar groove, the inter-transversales muscles of the loins, and the middle layer of the aponeurosis of the transversalis, which separates it from the quadratus lumborum ; on the inside, it corresponds to the spinous processes ; and on the outside, to the angle of union bettveen the posterior and middle layers of the aponeurosis of the trcinsversalis. In this way it is completely enclosed in an osteo-fibrous sheath. Thoracic Portion of the Posterior Spirud Muscles. The transverso-spinalis muscle may be completely isolated from the others in this region. AVe have seen the distinction between the sacro-lumbalis and longissimus dorsi commenced at the upper part of the lumbar region ; in the back they are completely sep- arated by some loose cellular tissue and the posterior branches of the dorsal nerves and vessels. The thoracic portion of the sacro-lumbalis (h h'.fig- 107) consists of a continuation of the Tertical or external fibres of the common mass ; as it proceeds upward it becomes more and more slender, and is divided into a series of fascicuh, which are inserted successive- ly into the angles of the ribs, by means of tendinous prolongations, that extend for a considerable distance upon the posterior surface of the muscle. It was the existence of these aponeurotic processes, the contiguous edges of which are often united, that in- duced Winslow to compare the muscle to a palm leaf In this manner the muscular fascicuh are soon expended, terminating at about the sixth rib, but the muscle itself is continued into the neck by means of accessory fibres, which may be exposed by turning the muscle outward, after separating it from the longissimus dorsi (as at h') : twelve long, thin tendons wdl then be seen to arise from the upper portion of the angles of the twelve ribs, and to pass outward and upward : to these succeed fleshy fascicuh, which terminate in aponeurotic processes, situated on their posterior surfaces, and ha\ing pre- cisely the opposite direction. These accessory bundles {cc'.fig. 107; i.fig. 108) have been xery well described by Diemerbroek under the name of ccrvicales descendens, and by Steno under that of muscidus accessorius ad sacro-lumbalem ; the four or five superior bun- dles form the transversaire grele of Winslow, and the cerricalis desceiidciis of Albinus. The thoracic portion of the longissimus dorsi {e e', fig. 107) is larger than the preceding muscle, to the inner side of which it is situated : it diminishes much less rapidly, because the common aponeurosis (d) is extended in the form of bands upon its posterior aspect, vrhich atFord attachment to additional fleshy fibres. This muscle is a continuation of the internal or articular, and the external or transverse fascicuh, described as existing in the lumbar region, and is itself divided into three orders of fasciculi, one external and two internal. 1 . The external or costal fasciculi form the continuation of the transverse bun- dles of the lumbar portion of the muscle, and are inserted by ver\- thin tendons into the space between the angles of the ribs and the summits of the dorsal transverse processes (c', lisr. 107). 2. The first set of internal, or the spinous fasciculi, are inserted into the spi- nousprocesses of the five or six superior dorsal vertebrae ; and as they arise from tendi- nous bands attached to the summits of the spinous processes of the lower dorsal vertebrae, and of that of the first lumbar vertebra, Winslow considered them as forming a separate muscle, which he called le loiig epineux du dos (spinalis dorsi, f, fig. 107). 3. The second set of internal, or the transverse fasciculi, are a continuation of the articular fasciculi of the lumbar region; they constitute the principal termination of the longissimus dorsi, and are attached by very long and thin tendons to the transverse processes of the dorsal Tertebrse. The thoracic portion of the transverso-spinalis"^ (partly seen in.%. 108) is reduced to a very narrow band, concealed by the longissimus dorsi : it arises by very long and delicate tendons from the lower dorsal transrerse processes, and is inserted by others equally similar, long and slender, into the summits of the superior dorsal spinous processes, some pale fleshy fibres connecting the two series of tendons. Connexions. — The dorsal portion of the posterior spinal muscles entirely fills the dor- sal groove, limited on the outer side of the angles of the ribs. They are covered by several muscular layers, the nearest of which is formed by the two serrati postici and their connecting aponeurosis, which completes the sheath enclosing the long muscles of the back : they are, moreover, separated from the skin by the rhomboid, trapezius, and latissimus dorsi. The Cervical Portion of the Posterior Spinal Muscles, the Transversalis Colli, and the Trachelo-mastoideus. Cervical portion of the sacro-lumbalis, or cerricalis descendens. The sacro-lumbalis, whose original fibres are found to terminate at and upon the sixth rib, is continued, by means of its accessory fasciculi (c e',fig. 107), up to the transverse processes of the four or five inferior cervical vertebrae {i,fig. 108), into the summits of which it is inserted by very slender tendons. The number of these terminating fasciculi varies in a remarkable * [Tkis corresponds to tke semi-spinalis dqrsi, and to the dorsal portion of the multii5das spiuE of Albinus.J THE POSTERIOR SPINAL AND COMPLEXUS MUSCLES. 205 manner. Indeed, the splenius, the transversalis colli, the sacro-lumbalis, and even the levator angnli scapulas, are so closely connected, that, upon examining their cervical in- sertions only, these might all be ascribed to a single muscle. The cervical portion of the sacro-lumbalis is covered by the levator anguli scapulae, and can only be exposed by turning this muscle outward. The cervical portion of the longi^simus dorsi, or the transversalis colli, and the tra- chelo-mastoid. The extent of the longissimus dorsi is limited to the back ; its highest internal or spinous fasciculus seldom reaches the spinous process of the first dorsaf ver- tebra : its highest external or costal fasciculus is attached to the second, sometimes even to the fourth rib, and its highest transverse fasciculus is inserted into the transverse process of the first dorsal vertebra. In some very rare cases, a few internal fasciculi reach the cer\'ical vertebrae : I have seen one of them terminate by becoming attached both to the transverse process of the third cervical vertebra and to the complexus. The longissimus dorsi is, however, prolonged by accessory fasciculi as far as the third cervi- cal vertebra. These fasciculi can only be identified by their direction (for they can never be completely separated from this muscle) : they form a distinct muscle, known as the transversalis colli (transversalis cervicis, Albinus, g g,fig- 107). By reflecting outward the upper part of the longissimus dorsi, they may be exposed, varying in number, and arising from the summits of the transverse processes of the third, fourth, fifth, sixth, and sometimes seventh and eighth dorsal vertebrae, by long, thin ten- dons, and inserted by other tendons into the posterior tubercles of the transverse pro- cesses of the five inferior cervical vertebrae {Ufig. 108) : the transversalis coUi is covered by the longissimus dorsi, the splenius, and levator anguh scapulae, and rests upon the trachelo-mastoid and complexus. The trachelo-mastoideus (complexus minor, i i, fig. 107) may be regarded as another accessory muscle to the longissimus dorsi, which it continues up to the head. In order to expose its origin, the transversahs colli must be reflected outward (as in fig. 107). It arises from the angles between the transverse and articular processes of the four in- ferior cervical vertebrae, by four small tendons, or sometimes by a continuous aponeu- rotic plane. From thence the fibres proceed upward, and form a small muscle, which is inserted into the mastoid process, in a small furrow to the inside of the digastric groove. This small muscle is almost always interrupted by a tendinous intersection near its mastoid insertion. The cervical portion of the transverso-spinalis.* AMiile the preceding muscles present only a few fasciculi in the neck, the transverso-spinalist undergoes an enlargement in this region, so as to occupy the entire cervical groove {a and h,fig. 108). In camivora, this portion of the muscle is enormously developed (much more so than in man), in con- sequence of those animals using the head and neck in seizing or struggling with prey. In manunalia, as in man, the dorsal portion of the transverso-spinalis is, as it were, but a rudiment in the lumbo-sacral region ; the muscle is larger in man than in other animals, on account of his erect posture. Albinus described the enlarged cervical portion as a separate muscle, viz., the spinalis cervicis. In the neck, as in the other regions, the transverso-spinalis is a collection of super- imposed fasciculi, which arise from the transverse processes of the five or six upper dorsal, and from the articular processes of the five lower cervical vertebrae, and are in- serted mto the spinous processes of the six lower cervical vertebrae : the highest and the largest fasciculus is attached to the axis. This muscle, which would have been much better named articulo-spinalis, is composed of several layers of fasciculi, placed one above the other, and extending from the whole length of the articular processes and laminae of the vertebrae below to the whole length of the spinous processes and laminae of the vertebrae above. The length of these layers diminishes progressively from the more superficial {a, fig. 108) to the deep-seated ones (b) ; the latter extend only from one ver- tebral lamina to another, and might be considered as proper muscles of the laminae, and not as a part of the transverso-spinalis muscle. The most superficial layer is composed of radiating fasciculi, diverging from one articular process to the summits of several of the spinous processes. The Complexus. Dissection. — Divide the splenius perpendicularly to the direction of its fibres, and re- flect the two parts upward and downward ; turn outward the upper portions of the lon- gissimus dorsi, the transversahs colh, and the trachelo-mastoid (see^o-. 107). The complexus {I, fig. 107) is situated beneath the splenius at the posterior part of the neck and upper part of the back. It is a flat muscle, broad above, but terminating in a point below. Attachments. — It arises, 1. From the transverse processes of the five or six superior * If we were to follow the order of super-imposition rig-ornusly, the complexus should be described before this muscle, which canaot be brought into riew until the former is removed. + [Th.s iiortiun of tlie transverso-spinalis corresponds to the semi-spinalis colli {a, fig. 106), and the ceni- cal fasciculi (A) of the multifidus spinE of Albinus.j 206 MYOLOGY. dorsal vertebrae ; 2. From the articular tubercles and the angular depression formed be- tween them and the transverse processes of the four inferior cervical vertebrae ; 3. Some- times from the spinous processes of the seventh cervical and two upper dorsal vertebrae : it is inserted upon the side of the external occipital crest into the inner half of the rough space comprised between the two semicircular lines. The origins of this muscle con- sist of tendons, from which the inferior fleshy fibres pass vertically upward, the superior ones obliquely inward and upward, becoming gradually shorter and more nearly horizon- tal. The muscular fibres are interrupted by some very remarkable tendinous intersec- tions. Thus, on the inside, the fleshy fasciculus arising from the sixth, fifth, and fourth dorsal vertebrae, gives origin to a tendon, which proceeds along the inner edge of the muscle, and, at the distance of an inch and a half or two inches, becomes the origin of another fleshy fasciculus, which is attached to the side of the occipital crest ; hence the name of biventer cervicis, given by Eustachius to the whole complexus, and by Albinus to this inner portion only (m, Jig. 107). More externally, there is another flat tendon ex- tending along the posterior surface of the muscle, from the outer edge of which an apo- neurotic intersection passes in a zigzag course obliquely outward and upward. It is not uncommon to find another small digastric fasciculus with a separate tendon, on the an- terior surface of the muscle. Relations. — The complexus is covered by the trapezius, splenius, longissimus dorsi, transversalis colli, and trachelo-mastoid, and covers the transverso-spinalis and the recti and obliqui capitis. Its inner edge is separated from the muscle of the opposite side by a considerable quantity of adipose tissue, and by a prolongation of the ligamentum nuchae. The Inter-spinales Colli. The inter-spinales muscles are distinct in the neck only. It is generally admitted that there are five pairs, the first of which extends between the axis and the third cervical vertebra, and the last between the seventh cervical and first dorsal vertebrae. They are small quadilateral muscles, extending from one of the borders of the groove in the spinous process below to the corresponding lip of the next process above. Externally, they are in relation with the transverso-spinalis, and are separated from each other internally by cellular tissue and an aponeurotic lamina. ^ig_ 108. The Recti Capitis Posiici, Major and Minor. The rectus capitis posticus major {e, Jig. 108) may be regarded as an axoido-occipital, and the rectus minor (d) as an atloido-occipital intcr-spi- nalis muscle. They both arise tendinous, the smaller from the tubercle on the posterior arch of the atlas, and the greater from the superior tubercle of the spinous process of the axis (2) ; and, increasing in size, they both pass obliquely upward and outward. The rectus major, -Z/ which is much the larger and more oblique, is inserted to the outer , side of the inequalities situated below the inferior semicircular line of the occipital bone ; the rectus minor is inserted to their inner side. The name of recti is not, therefore, very appropriate, for both of them (but more especially the larger one) are directed obliquely ; but they are so called in contradistinction to two neighbouring muscles which are much more oblique. The obliquity of these muscles (by increas- ing their length) allows of more extended movements, and, at the same time, enables them to assist in rotating the head. The Obliquus Capitis Major or Inferior, and Obliquus Minor or Superior. The obliquus major or inferior (/, Jig. 108), as far as its insertions are concerned, may be called the axoido-atloid spino-transversalis ; it resembles, in fact, a thick fasciculus of the longissimus dorsi. The obliquus minor or superior (g) may, for the same reason, be called the atloido-occipital transverso-spinalis, resembling a thick fasciculus of that mus- cle. The obliquus major arises from the apex of the spinous process of the axis, on the outer side of the rectus major (e), and above the transverso-spinalis (i. e., the semi-spi- nalis colli and multifidus spinae conjoined, a and b) ; it forms a tnick, cylindrical bundle, passes almost horizontally outward, and is inserted behind and below the transverse process of the atlas, which is excavated for this purpose. It is the axoido-atloideus of Chaussier. The obliquus minor (atloido-sub-mastoideus) arises by some very long tendi- nous fibres from the upper part of the transverse process of the atlas, proceeds at an angle of about 45° towards the occipital bone, into which it is inserted not far from the mastoid process, by some tendinous fibres, less distinctly marked than those of its origin. From this difference of direction, it follows that the rectus major and the two obliqui form on each side an equilateral triangle ; in the interval between the two triangles a considerable part of the recti minores is seen. Relations. — The recti and obliqui capitis are covered behind by the complexus, from which they are separated by a very strong aponeurotic lamina and much cellular tissue ; 4m^ THE POSTERIOR SPINAL MUSCLES. 207 they cover the p'osterior arch of the atlas, with the posterior hgaments of the atloido-oc- cipital and atloido-axoid articulations. General View of the Posterior Spinal Muscles. After the preceding description, it will now be easy to comprehend the general guiding principles in the arrangement of the innumerable, and, at first sight, inextricable fasci- culi which constitute the fleshy mass known by the general name of the posterior spinal muscles. We shall first recall to mind, that the levers to which all these muscles are ultimately attached are, 1 . The row of spinous processes ; 2. The row of articular pro- cesses ; and, 3. The row formed by the transverse processes and the ribs, which, for many reasons, may be regarded as extensions of those processes. We shall suppose these three series of levers, and therefore the several points of in- sertion, to be represented by three vertical lines. We must remember, also, that the dorsal transverse processes are upon the same line as the lumbar and cervical articular processes, and that the ribs are upon the same line as the lumbar transverse processes and the anterior roots of the cervical transverse pro- cesses. (See Osteology, p. 5.) These data being admitted, we can now reduce all the posterior spinal muscles into the four following orders of fascicuh, two being vertical and two oblique. 1. The internal vertical or spinous muscles, comprising the spinalis dorsi {i. e., the in- ternal and superficial portion of the longissimus dorsi), the inter-spinalis of the neck, and the recti postici of the head. 2. The external vertical lateral, or transverse muscles, con- nected with the transverse or costiform processes. They comprise the sacro-lumbalis and the inter-transversales, among which the quadratus lumborum may be included. 3. The spino-transvcrse and spino- articular* oblique muscles, including the longissimus dorsi, with its accessories, the transversalis coUi and trachelo-mastoid, the splenius and the obliquus major. 4. The transverso-spinous and articulo-sprnous* oblique muscles, viz., the transverso-spinahs, the complexus, and tlie obliquus capitis minor. Action of the Posterior Spinal Muscles. Having once established the general principles according to which the posterior spinal muscles are arranged, it is very easy to determine the mode of action of each, and to re- duce to very simple elements a mechanism to all appearance so complicated. 1. The long and short spinous fasciculi being vertical, directly extend the vertebral column ; such is the action of the spinahs dorsi and inter-spinahs colli ; the recti capitis, at the same time that they extend the head, rotate it also to the side on which the mus- cles are acting. When the recti muscles of both sides act simultaneously, the head is drawn directly backward. 2. The fasciculi of the sacro-lumbalis being vertical and lateral, erect the vertebral column, and incline it to one side, when only one set of muscles acts ; when both sets act together, they extend it directly backward. 3. As the fasciculi of the longissimus dorsi, belonging to the spino-transverse and spi- no-articular group, have their fulcra upon the spine, and are inserted into the articular and the transverse processes or ribs, they conspire in erecting the vertebral column, and keeping it in that position. But, from their obliquity, they produce a slight movement of rotation, those fibres which are attached to the articular processes having less effect than those connected with the transverse processes. In this movement, the front of the body is turned to the side on which the muscles are situated. When the muscles of both sides act together, the spine is extended directly backward. The splenius, which is the representative of the longissimus dorsi for the neck and head, acts in the same way, but with greater efl^ect. Thus, by the contraction of the left splenius, the face is turned to the left side, and the head is drawn backward and to the right side. The obliquus infe- rior also acts in the same direction. When the two splenii and the two inferior oblique act together, the head is inclined directly backward. 4. The fixed insertions of the transverso-spinalis being at the articular or transverse processes, and their movable points at the spinous processes, besides the common effect of erecting the vertebral column, they are also able to rotate it, so that the anterior re- gion of the trunk is turned to the opposite side. From its obliquity, this muscle is the principal rotator of the vertebral column. The complexus, which is its representative in the neck, acts upon the head in the same manner, but in a more remarkable degree. Thus, by the contraction of the complexus of the left side, the face is turned to the right side, and the head is inclined backward upon the left side, so that, in rotation, it acts in a precisely opposite direction to the splenius. When all these muscles act together, the trunk is simply drawn erect. The superior oblique assists the complexus in the move- ments of the head. Lastly, we may now understand the successive actions which take place along the * [The terms spino-transverse and spino-articular are applied to fasciculi passing upward from the spinous to the tran.sverse and articular processes ; transverso-spinous and artirjjlo-spinous, to such as proceed upward from the transverse and articular to the spinous processes.] 208 MYOLOGY. whole extent of the posterior spinal muscles. The sacrum and the iliac bones furnish a fulcrum for the fasciculi which move the lumbar region : this latter being fixed, then be- comes the fulcrum for those that move the dorsal region, and so on to the head, vi'hich alone has independent muscles. It is impossible to extend backward the dorsal region, and the lower part of the cervical, without at the same time erecting ihe lumbar region ; but the head may be moved at will, independently of the vertebral column. The posterior spinal muscles maintain in equilibrium the weight of the whole trunk ; hence the lassitude experienced in the back, but especially in the loins, by long-contin- ued standing, walking, or even sitting without a support to the back ; and hence the re- lief afforded by the recumbent posture. Rotation, we have seen, scarcely exists in the loins, the back, or the lower part of the neck ; but at the upper part of the neck it is very extensive, and here the rotator mus- cles are proportionally strong, and directed very obliquely. MUSCLES OF THE ANTERIOR ABDOMINAL REGION. The Ohliquus Externus Abdominis. — Ohliquus Internus and, Cremaster. — Transversalis Ah- daminis. — Rectus Abdominis. — Pyramidalis. The muscles of the anterior abdominal region are, the external oblique, the internal oblique, the transversalis, the rectus, and, occasionally, the pyramidalis ; being ten in the whole, five on each side. The Ohliquus Externus Abdominis. Dissection. — 1. Make an incision through the skin of the abdomen extending from the cartilage of the eighth rib obliquely downward and inward, dividing, at the same time, the very firm layer of cellular tissue which immediately covers the muscle. 2. During the preparation of this, as well as all the other abdominal muscles, place a block under the loins, and in the dissection follow exactly the direction of the muscular fibres. The great or external oblique muscle of the abdomen (o, fioc, the temple), is a broad, radiated muscle, resem- bhng a triangle with the base turned upward. Attachments. — It arises from the whole extent of the temporal fossa, and from the in- ner surface of the superficial temporal fascia, and is inserted into the edges and summit of the coronoid process. The fleshy fibres all arise directly, either from the temporal fossa, or from the inner surface of the fascia, which, being attached above to the entire length of the temporal semicircular line, and below to the upper edge of the zygomatic arch, is very tense, and thus affords a solid and very strong surface of origin. From these two parts the fleshy fibres converge, and proceeding downward, the anterior ob- liquely backward, the posterior obliquely forward, and the middle vertically, form a fleshy mass, which gradually increases in thickness until its fibres are attached, partly to the external, but chiefly to the internal surface and borders of the terminal aponeurosis. The fibres of this aponeurosis, which are very strong, and radiated at its commence- ment, are collected into the form of a very thick tendon, inserted into the coronoid pro- cess, and cahed the coronoid tendon. The temporal muscle, in its course from the tem- poral fossa to the coronoid process, undergoes a sort of reflection over the groove at the base of the zygoma. I have often seen a very strong muscular fasciculus arising from the lower part of the temporal fossa and the ridge bounding it below, and inserted by a separate tendon into the internal border of the anterior surface of the ramus of the jaw. Relations. — It is covered by the skin, the aponeurosis of the occiplto-frontalis, the an- terior and superior auricular muscles, the superficial temporal arteries, veins, and nerves, and more immediately by the superficial temporal aponeurosis, the zygomatic arch, and the masseter. It covers the temporal fossa, the external pterygoid muscle, a small part of the buccinator, the internal maxillary artery, and the deep temporal vessels. Its thickness is in proportion to the depth of the temporal fossa and the strength of the coronoid process. Action. — The strength of the temporal muscle, therefore, may be in some degree measured by the depth of the temporal fossa and the size of the coronoid process. This fact may be demonstrated by an examination of these regions in the skeletons of carniv- orous animals, in which the elevators of the lower jaw are most highly developed. The use of the temporal muscle, like that of the masseter, is to elevate the lower jaw, but the mechanism of its action is different. In fact, the masseter raises the jaw by a direct action ; the temporal muscle, on the contrary, raises it by a sort of siving motion, acting principally upon the back part of the coronoid process. In a word, the temporal muscle acts upon the vertical arm of the bent lever represented by the maxillary bone, while the masseter, on the contrary, acts upon its horizontal arm, the movement depending on the action of the temporal muscle : the lower jaw resembles the curved lever represent- ed by the hammer of a bell. THE PTERYGO-MAXILLARY REGION. The Pterygoideus Internus. — The Pterygoideus Externus. The muscles of this region are the external and the internal pterygoids. Fig. 115 The Pterygoideus Internus vel Magnus. Dissection. — Separate the face and that part of the cranium which is situated anterior to the ver- tebral column from the remainder of the scull, and divide the face into two lateral halves by an antero-posterior section. This muscle may also be dissected in the fol- /i lowing manner : saw through the lower jaw ver- tically at the junction of the body and ramus ; re- move the zygomatic arch ; cut through the base of the coronoid process and the neck of the con- dyle, and then disarticulate the latter. The internal pterygoid (a, fig. 115) is deeply seated in the zygomatic fossa, along the inner surface of the ramus of the jaw (tertius musculus qui in ore latitat, Vesalius). It is thick and quad- THE PTEUYGOIDEUS EXTERNUS, ETC. 241 riiateral, and in its' form, structure, and direction, bears a remarkable resemblance to the masseter ; hence Winslow called it the internal massetcr. Attachments. — It arises from the pterygoid fossa, from the hamular process, at the apex of the internal pterygoid plate, and from the lower surface of the p)Tamidal process of the palate bone ; and is inserted into the inner surface of the angle of the lower jaw. Its origin consists of a tendon resembling that of the masseter, prolonged upon the in- ternal surface, and into the substance of the muscle. From this the fleshy fibres pro- ceed dmcnward, outward, and backward, to be inserted, by very strong tendinous laminae, into the lower jaw. Relations. -^On the inside it is in relation with the external peristaphyline muscle {tensor palati), and with the pharynx, a triangular interval existing between it and the latter, occupied by a considerable quantity of cellular tissue, vessels, nerves, and the sub-maxillary gland : on the outside it corresponds with the ramus of the lower jaw, from which it is separated above by the dental and lingual nerves, the inferior dental vessels, and the so-called internal lateral ligament of the temporo-maxillary articulation. Action. — As this muscle is inserted almost perpendicularly into the lever upon which it acts, it has very great power. Mast of the remarks already made concerning the mas- setor apply to this muscle, which is a true internal masseter. It has only this peculiar- ity, that as its origin is nearer the median line than that of the external masseter, it •assists in producing a slight lateral movement of the jaw, which is very useful in bruis- ing the food. The Pterygoideus Externus vel Parvus. Dissection. — This, like the preceding muscle, may be exposed by two opposite methods The external pterygoid {b,fig. 115) is very short, thick, and conoid, smaller than the preceding, and situated in the zygomatic fossa, extending horizontally from the outer surface of the external pterygoid plate to the neck of the condyle of the lower jaw. It ■arises from the whole outer surface of the external plate of the pterygoid process, and from the facette of the palatine process, at which it terminates below, from the ridge separating the temporal and zygomatic fossae, and from a spinous process at the extrem- ity of this ridge, wtiich appears to me worthy of notice. It is inserted into the fossa in front of the neck of the condyle of the lower jaw, and into the border of the interarticu- lar cartilage. Its origin consists of a strong tendon, prolonged into the substance of the muscle. From this the fleshy fibres proceed horizontally outivard and backward. forming, at first, two distinct portions, between which the internal maxiUary artery often passes : these two portions then converge, are blended together, and terminate by some small tendinous fibres, which form the truncated summit of the cone represented by the muscle, and are attached to the neck of the condyle and to the inter-articular cartilage. Relations. — This muscle is deeply situated, and is in relation on the outside with the ramus of the lower jaw, the temporal muscle, and the internal maxillary artery ; on the inside with the internal pterygoid, and above with the upper wall of the zygomatic fossa. Action. — The axis of the external pterygoid being directed outward and backward, and its origin being at the pterygoid process, it may be readily imagined that its con- traction will produce a horizontal motion in two directions, viz., forward and to the op- posite side from that on which the muscle is acting. WTien the two external pterygoids act together, the jaw is carried directly forward. From the insertion of this muscle into the inter-articular cartilage, the latter is never separated from the condyle during these several movements. It is principally this muscle which causes displacement of the con- dyle in cases of fracture of the neck of the bone, and it is also the chief agent in bruis- ing the food. MUSCLES OF THE UPPER EXTREMITIES The muscles of the upper extremities may be divided into those of the shoulder, oi the arm, of the forearm, and of the hand. MUSCLES OF THE SHOULDER The Deltoideus. — Supra-spinatus. — Infraspinatus and Teres Minor. — Subscapularis. The muscles of the shoulder are the deltoid, the supra-spinatus, the infra-spinatus and teres minor (which I regard as only one muscle), and the subscapularis. The teres major, generally arranged among the muscles of this region, has already been described with the latissimus dorsi, of which it may be regarded as an accessory. The Deltoideus. Dissection. — Make a horizontal incision through the skin, round the summit of the shoulder, extending from the external third of the clavicle to the most distant point of the spine of the scapula : from the middle of this incision let another be made, descend- Hh 242 myologv. ing vertically half way down the humerus ; dissect back the two flaps, taking care to raise at the same time a very thin aponeurosis, which is closely applied to the fibres. The deltoid {I, figs. 106, 109), so named from its resemblance to tlie Greek delta, A, re- versed, is a thick, radiated, triangular muscle, bent in such a way as to embrace the scapulo-humeral articulation before, on the outer side and behind. It is the muscle of the top of the shoulder. Attachments. — It arises from the entire length of the posterior border of the spine of the scapula, from the external border of the acromion, and from the external third, i. e., from the concave part of the anterior border of the clavicle : it is inserted into the del- toid impression on the humerus. The scapulo-clavicular origin of the deltoid corre- sponds exactly to the inferior attachment or the insertion of the trapezius, so that these! two muscles, although separate and distinct in man, appear to form a single muscle di- vided by an intersection : a view that is perfectly confirmed by a reference to compara- tive anatomy. The origin consists of tendinous fibres ; of these the posterior are the longest, and are blended with the infra-spinous aponeurosis, which also gives origin to some of the fibres of the deltoid. Three or four principal tendinous laminae, attached at regular intervals to the clavicle and the acromion, penetrate into the substance of the muscle, and give origin to a great number of fleshy fibres. The largest of these laminae extends from the summit of the acromion, and its situation is sometimes indicated by a prominence of the skin, particularly during contraction of the muscle. From this very extensive origin the fleshy fibres proceed downward, the middle vertically, the anterior backward, and the posterior forward : they form a thick, broad mass, moulded over the top of the shoulder, and, gradually converging, are at length inserted into the deltoid impression of the humerus by three evry distinct tendons, the two principal of which, the anterior and posterior, are attached to the bifurcations of that V-shaped impression. Not unfrequently some fibres of the pectoralis major are connected with the front of this tendon. Relations. — It is covered by the skin, the platysma intervening between them, by some supra-acromial nerves, and by a thin fascia extending from the infra-spinous apo- neurosis, the spine of the scapula and the clavicle, and becoming continuous with the fascia of the arm. It covers the shoulder-joint, from which it is separated by a tendi- nous layer continued from the infra-spinous and coraco-acromial ligaments, and which terminates on the sheaths of the coraco-brachialis and biceps muscles. Between this lamina and the greater tuberosity of the humerus there is a quantity of filamentous cel- lular tissue, and frequently a synovial bursa. The deltoid, therefore, is enclosed in a proper fibrous sheath, and glides over the articulation. It also covers the upper third of the humerus, the coracoid process, the tendons of the pectorales, coraco-brachialis, biceps, supra-spinatus, infra-spinatus and teres minor, teres major, and biceps muscles, «lso the circumflex vessels and nerves. The anterior border of the deltoid, directed ob- liquely downward and outward, is separated from the external margin of the pectoralis major by a cellular interval, but is frequently in contact with it. The cephalic vein and a small artery define the hmits of the two muscles. The posterior border is thin above, where it is applied to the infra-spinatus muscle, and becomes thick and free below. The inferior angle of the deltoid is embraced by the brachialis anticus. Issues are generally established over this situation. Remark. — The structure of this muscle has been patiently investigated by some anat- omists, who have counted the exact number of its component fasciculi. These are sep- arated by fibro-cellular prolongations, like the fasciculi of the gluteus maximus ; some- times, even, the muscle is divided into three distinct portions above, viz., a clavicular, an acromial, and a spinal. Eighteen or twenty small penniform fasciculi, the bases of which are generally turned upward, are collected into a small space by mutually over- lapping each other, and are united by their terminating tendons. Albinus admits ten of these bundles, which he has described separately. Action. — The deltoid elevates the shoulder {elevator, attollens humerum). From the threefold direction of its fibres, it has a different action, according to the particular set of fibres employed. Tlie middle fibres raise the humerus directly, the anterior raise and carry it forward, the posterior raise and carry it backward. When the arm is raised, Bichat states that the anterior and posterior fibres can depress it ; but I do not think this possible. There has been no example recorded of luxation from the over-action of this muscle. When the arm is fixed, as in the act of climbing, the shoulder is moved upon the head of the humerus. The trapezius must be regarded as the most powerful antagonist of the deltoid, since the scapulo-clavicular attachments of both muscles are the same. Thus, we have seen that the diaphragm and the transvcrsalis abdominis are separated only by their costal insertions. The most complete antagonism follows from such an arrangement, for then one fibre is, as it were, opposed to another, having ex- actly an opposite direction. The action of the deltoid is, however, less powerful than might have been supposed from its size ; it is, in fact, parallel to the lever on which it acts. \^Tiile almost all other muscles have a movuntmn, occurring at the period when their fibres are inserted at the THE SUPRA AND INFRA SPINATUS AND TERES MINOR. 243 most favourafeie angle, the deltoid, properly speaking, has none ; it is parallel to the lever during the entire period of its action. This is the reason why the elevation of the arm is so feeble a movement, and why contraction of the deltoid is always accompanied by considerable fatigue. The Supra-spinatus. -Disstctimi. — Take off the trapezius, and, in order to see the whole extent of the mus- cle, remove the clavicle, and saw through the base of the acromion. The supra-spinatus (r,Jig. 106) is a thick, triangular muscle, broad on the inside, nar- row without, occupying the supra-spinous fossa, and retained therein by a strong apo- neurosis, which completes the osteo-fihrous sheath in which the muscle is enclosed. AttachmeTits. — It arises from the internal two thirds of the supra-spinous fossa, and is inserted into the highest of the three facettes on the greater tuberosity of the humerus. Its origin from the supra-spinous fossa is partly tendinous and partly fleshy, and some fibres arise from its aponeurotic investments. From these points the fleshy fibres con- verge to a tendon, which is found among thern where the muscle reaches the upper part of the joint, and which is slightly reflected over the head of the humerus before reaching its insertion. This has not the shining appearance of other tendons, but has the dull aspect of many ligaments ; it is blended with the fibrous articular capsule, from which it cannot be separated near its insertion. It may even be regarded as forming the upper part of the capsular ligament. Relations. — It is covered by the trapezius, the clavicle, the coraco-acromion ligament, and the deltoid ; and it covers the supra-spinous fossa, the supra-scapular vessels and nerves,* and the upper part of the shoulder-joint. Its tendon is often blended with that of the infra-spinatus, and is separated from that of the sub-scapularis by the long head of the biceps, and the accessory hgament of the capsule. Action. — It raises the humerus, and therefore assists the deltoid. Notwithstanding the number of its fibres, and its perpendicular insertion into its lever, it has very little power, on account of the proximity of that insertion to the fulcrum. Its principal action appears to me to have reference to the joint, affording a support to it above, and forming a sort of active arch, the resisting power of which is in proportion to the force tending to thrust the humerus upward against the osteo-fibrous arch, composed of the acromion and coracoid processes and their connecting ligament. There is no muscle, then, to which the nanrie of articular can be more correctly applied. The use of the deep fibres in preventing the folding of the fibrous and synovial capsules, and their compression be- tween the two articular surfaces, though much insisted on by Winslow, appears to me very problematical. The Infra-spinatus and Teres Minor. Dissection. — Detach the scapular origin of the deltoid, and saw through the base of the acromion. The infraspinatus (s) and teres minor {t, Jig . 106) constitute a single, thick, triangular muscle, broad on the inside and narrow externally, and occupying the infra-spinous fossa, in which it is retained by an aponeurosis, exactly resembling that of the supra-spinatus muscle. It arises from the internal two thirds of the infra-spinous fossa, from a very strong fascia interposed between it and the teres major and long head of the triceps, and by a few fibres from the infra-spinous aponeurosis : it is inserted into the middle and inferior facettes on the greater tuberosity of the humerus, below the insertion of the supra-spi- natus. It arises from the infra-spinous fossa, directly by fleshy fibres, and also by means of tendinous fibres attached along the ridges of that fossa. One of these laminae is con- stantly found attached to the ridge situated on the outer side of the infra-spinous groove : this has doubtless given rise to the division of the muscle into two parts, called the in- fra-spinatus and the teres minor. From these origins the fleshy fibres proceed, the su- perior horizontally, the next obliquely, and the inferior almost vertically outward : they form a thick, triangular, fleshy body, and become attached to the anterior surface and margins of a flat tendon, which glides upon the concave humeral border of the spine of the scapula, to be inserted into the humerus. Not unfrequently we find the lower fibres of the portion called the teres minor, arising from the posterior surface of the tendon of the triceps, becoming applied to the under part of the capsular ligament, and inserted into the humerus immediately below the great tuberosity. Relations. — These two united muscles are covered by the deltoid, the trapezius, the latissimus dorsi, and the skin ; and they cover the infra-spinous fossa, from which they are separated by the supra- scapular nerves and vessels ; they also cover the capsular ligament of the joint, and a small portion of the long head of the triceps. Their lower or external border corresponds internally or inferiorly with the teres major, an aponeu- rotic septum intervening-between them, and externally or superiorly with the long head of the triceps. * The supra-scapular nerve generally passes through the coracoid notch by itself, and the supra-scapular artery above the ligament. 244 MYOLOGY. Action. — This muscle rotates the hxunerus outward and a little backward. When the arm is raised, it assists in keeping it in this position, and carries it backward. But an important use of this muscle is that of retaining the head of the humerus in its place, pre- venting its displacement backward, and protecting the posterior part of the articulation. The Sub-scapularis. Dissection. — Detach the upper extremity, including the shoulder, from the trunk of the body ; remove from the inner surface of the muscle the cellular tissue, the lymphatic glands, the brachial plexus, the axillary vessels, and the serratus magnus ; and dissect off, with care, the thin fascia which invests it. The sub-scapularis {o,figs. 110, 116) is a thick triangular muscle, occupying the whole of the sub-scapular fossa, beneath the axillary border of which it passes : by itself it rep- resents the supra and infra spinatus and teres minor, upon the posterior scapular region. We not unfrequently meet with tendinous laminae dividing it into three parts, which cor- respond to those three muscles. Attachments. — It arises from the internal two thirds of the sub-scapular fossa, by ten- dinous laminae attached to the oblique ridges already described as existing on that part of the scapula ; also from the anterior lip of the axillary border of the scapula by an apo- neurosis, which separates this muscle from the teres major and the long head of the tri- ceps. Very frequently the lowest fibres arise from the anterior surface of this head of the triceps, just as we have seen that the lower fibres of the teres minor take their ori- gin from the posterior surface of the same head of that muscle. From these different origins the fleshy fibres all proceed outward, the upper horizontally, and the lower ob- liquely, gradually approaching more and more to the vertical direction. The muscle, therefore, becomes progressively narrower and thicker, until its fibres are attached to the two surfaces and borders of a tendon which is inserted into the entire surface of the lesser tuberosity of the humerus. Some of the muscular fibres are inserted below the tuberosity ; and I have seen the inferior fibres of the muscle attached for a certain extent to a fibrous prolongation that completes the bicipital groove behind. Relatione. — The posterior surface of this muscle hues the sub-scapular fossa, which it entirely fills, and from which it is separated at the outer third by some cellular tissue and the sub-scapular vessels and nerves ; more externally, it covers the upper and anterior part of the capsular hgament of the shoulder-joint, turning around it, and becoming iden- tified with it at its insertion. Its anterior surface is in relation with the serratus magnus, the sub-scapular fascia, and some very loose cellular tissue intervening between them ; also with the axillary vessels and nerves, and with the coraco-brachialis and deltoid muscles. The itpper border of its tendon glides in the hoUow of the coracoid process, which serves as a pulley, and forms with the coraco-brachiahs and the short head of the biceps a sort of ring, partly bony and partly muscular, in which the tendon is retained. Between this tendon and the coracoid process there is also a synovial bursa, which some- times extends over the tendons of the biceps and coraco-brachialis, and always commu- nicates with the synovial capsule of the shoulder-joint.* Action. — It is essentially a rotator inward of the humerus. In proof of this, we find that the muscle is stretched when the arm is rotated outward, and relaxed when it is ro- tated inward. The movement of rotation is much more considerable than the length of the neck of the humerus would lead us to imagine, and this arises from the muscle turn- ing round the head of the bone. As a rotator muscle, then, it is congenerous with the latissimus dorsi. When the humerus is raised, the sub-scapularis tends to draw it down- ward. And farther, this muscle, as well as the supra-spinatus, infra-spinatus, and teres minor, is essentially an articular muscle, and is sometimes completely identified with the anterior part of the fibrous capsule : in all cases it offers an active resistance to displace- ment forward, and is, therefore, always torn in this kind of dislocation. MUSCLES OF THE ARM. The Biceps. — Brachialis Anticus. — Coraco-brachialis. — Triceps Extensor Cubiti. The muscles of the arm have been divided into those of the anterior region, viz., the biceps, the coraco-brachialis, and the brachiahs-anticus ; and those oi the posterior region, which constitute the single muscle called the triceps. Anterior BRAcni.iL Region. The Biceps. Dissection. — Make a vertical incision through the skin from the middle of the clavicle to the middle of the bend of the elbow ; direct back the flaps, and divide longitudinally the brachial fascia, which is united to the biceps by very loose cellular tissue ; preserve the vessels and nerves which lie along the inner border of the muscle. Expose the up- per part of the muscle by detaching the pectorahs major and deltoid from their clavicu- * See note, p. 22. THE BICEPS, 245 lar origins, and tumjng them inward and outward. In order to trace the whole extent of the long head of the biceps, open the capsular hgament above ; and to see the radial insertion of the muscle, flex the forearm to a right angle upon the arm, and supinate it forcibly ; it is better, however, to wait until the muscles of the anterior region of the fore- arm are dissected. The biceps flexor cubiti (a, fig. 1 16) is a long muscle forming the superficial layer of the Fig. llfi. anterior region of the arm ; it is divided above into a short and long head ;* and hence its name biceps. Attachments. — It arises by its short head from the apex of the coracoid process, and by its long head from the top of th-e glenoid cavity ; and is inserted into the bicipital tuberosity of the radius. The origin of the short or coracoid head {b,fig. 116) consists of a flat and very thick tendon, common to it and the coraco- brachialis, and terminating in front of this part of the muscle in an aponeurosis, from which is given off a tendinous septum, be- tween the biceps and the coraco-brachialis. The long, glenoid, or reflected head arises by a tendon apparently forming a contin- uation of the glenoid articular border, which penetrates into the interior of the joint, turns over the head of the humerus, upon which it is reflected, and thus reaches the bicipital groove. It is retained in this groove by a sort of fibrous bridge or canal, traverses the whole of its extent, and ends in a sort of tendinous cone open behind, from the interior of which the fleshy fibres take their origin. These fibres are collected into a rounded belly, which, about the middle of the arm, is applied to the muscular belly of the short portion, equally rounded and of variable size, and ultimately becomes identified with it. The single muscle {a, fig. 116) thus formed is very thick, flattened from before backward, and directed vertically like the two original fasciculi. Its fibres are attached to the surfaces and edges of an aponeuro- sis, which gradually becomes narrower and thicker, until it emerges in the form of a free tendon opposite the lower end of the humerus, a httle nearer to the outer than the inner side. This flattened tendon sinks downward and backward into the triangular space be- tween the supinator longus and the pronator teres, and is then so folded and twisted upon itself that its anterior surface becomes posterior, its internal margin becomes anterior, and its external margin at first posterior and then superior. This folding and torsion are of extreme utihty in preventing displacement of the muscle, which thus fastens down it- self The tendon of insertion having given off from its anterior surface and external margin a broad aponeurosis, constituting the principal origin of the fascia of the fore- arm, glides over the bicipital tuberosity of the radius, from which it is separated by a bursa, and is inserted into the posterior part of that process. Relations. — The upper third of the two heads of the biceps, as well as the coraco-brach- iaUs, and the axillary vessels and nerves, are contained in the cavity of the axilla, be- tween the pectoralis major and the deltoid in front, and the latissimus dorsi and teres major behind. In this part of its course, the short head of the biceps is in relation with the coraco-brachialis on the inside, and behind with the sub-scapularis, which separates it from the shoulder-joint ; a bursa intervenes between these two muscles. The tendon of the long head is in contact with the head of the humerus, and surrounded by the sy- novial membrane, which isolates it from the cavity of the joint, and accompanies it, for a greater or less distance, along the bicipital groove. Below the axiUa the biceps is sub- cutaneous in front, the brachial fascia intervening between it and the skin, through which it is very clearly defined ; behind, it is in relation with the musculo-cutaneous nerve, and the coraco-brachialis and brachialis anticus muscles ; on the inside, with the brachial ar- tery and its accompanying veins, and with the median nerve, all of which lie along its in- ternal border, by the projection of which they are protected. The tendon is embraced at its insertion by the supinator brevis, and it is separated from that of the brachialis anti- cus by a bursa. Great attention should be paid to the relation of this muscle to the brach- ial artery. I am accustomed, when speaking of the surgical anatomy of these parts, to call the biceps the satellite muscle of the brachial artery. It is worthy of remark, that the relative positions of the long and the short head are altered as the humerus is rota- ted inward or outward ; in rotation inward, the long head is placed behind the other, or even crosses to the inner side of it ; but in rotation outward, the interval between the two heads is considerably increased. Action. — "The biceps flexes the forearm upon the arm, and at the same time supinates it. This last effect results from the insertion of the muscle into the inner and back part of the bicipital tubercle of the radius. The momentum of the biceps occurs during semi- * Not unfrequently the biceps is trifid above. The supernumerary head is internal, and arises from the in- ner border of the humerus, below the coraco-brachialis, which may be regarded as the continuation of this head, for they correspond in size. This supernumerary portion is attached to the inner edge and posterior surface of the lower tendon of the biceps. I have twice seen this disposition of parts. 246 MYOLOGY. flexion of the forearm ; its insertion being at that period perpendicular to the lever, the disadvantage arising from its proximity to the fulcrum is then counteracted. The length of its fibres explains the extent of the movement of flexion. By means of its scapular attachments, the biceps acts upon the arm, either secondarily, after bending the forearm, or primarily, when the forearm is extended. By means of both its heads, it carries the arm forward, and thus co-operates with the anterior fibres of the deltoid and coraco-brach- ialis. The two heads also assist in strengthening the shoulder-joint. The long head forms a sort of fibrous arch, which supports the head of the humerus, and retains it in the glenoid cavity. The short head, together with the coraco-brachialis, forms a continuation of the hook of the coracoid process, and protects the anterior and inner part of the joint. The biceps is, as Winslow first showed, one of the principal supinators of the forearm : and it is in this movement that the tendon glides over the bicipital tuberosity of the ra- dius by means of the intervening bursa. This tuberosity is almost entirely intended for the tendon to glide over ; it is, therefore, incrusted with cartilage. Dense and reddish granulations, as pointed out by Haller, are found upon the synovial bursa of the tendon. When the forearm is fixed, as in climbing, the biceps flexes the arm upon the fore- arm, and the scapula upon the arm. Lastly, it is a tensor of the fascia of the forearm, upon which the internal fibres of the muscle often terminate. The Brachialis Anticus. Dissection. — Cut the biceps across, opposite the insertion of the deltoid, and turn down the lower part upon the forearm. T.he brachialis anticus (brachialis internus. Alb., d d,fig. 116; d,fig. 117) is a thick, prismatic, and triangular muscle, situated behind the preceding. It arises from the hu- merus, below the insertion of the deltoid, which it embraces by a well-marked bifurca- tion ; and since the point of insertion of the deltoid is not always the same, it follows that this origin of the brachialis anticus is also variable ; it also arises from the internal and external surfaces, and from the three borders of the humerus, and from the external and internal inter-muscular septa. It is inserted into the rough surface on the fore part of the coronoid process of the ulna. The different origins from the humerus are fleshy, the fibres being of very various lengths, and proceeding in different directions ; the middle pass vertically downward, the external somewhat obliquely inward, and the internal out- ward ; they all terminate on the posterior surface of an aponeurosis, which is broad and thin above, and thick below, especially on the outer side, where it turns round so as to embrace the outer border of the muscle, and forms a deep aponeurotic lamina. The fleshy fibres, therefore, are received into a semi-cone of tendinous substance, open on the inside, the fibres of which are collected together, and finally inserted into an oblique line, running downward and outward, below the coronoid process of the ulna. Relations. — The anterior surface of the brachialis anticus is in relation with the biceps, the musculo-cutaneous nerve, the brachial fascia, the brachial artery and veins, and the median nerve ; its internal surface, with the pronator teres muscle, the ulnar nerve, and the triceps, from which it is only separated by the internal inter-muscular septum ; its external surface, with the supinator longus and the extensor carpi radialis longior, which are received into a sort of groove presented by it, the radial nerve establishing the limit between these two muscles and the brachialis anticus. The posterior surface embraces the internal and external surfaces of the humerus, to which it is attached ; below, it em- braces, and effectually protects the front of the elbow-joint, into the anterior ligament of which many of its fibres are inserted. Actioji. — The brachialis anticus flexes the forearm upon the arm, and, reciprocally, the arm upon the forearm. Its moraentum takes place, like that of the biceps, during semi- flexion. It is worthy of remark, that this muscle acts with greater precision than the bi- ceps upon the forearm, because it arises from the humerus only, and, besides that, it be- longs more especially than that muscle to the elbow-joint. I have already said that it may be regarded as the active anterior ligament of this articulation. In fact, it so com- pletely limits the movement of extension, that we cannot imagine the possibility of lux- ation of the forearm backward without rupture of this muscle. From the insertion of the biceps into the radius, and of the brachialis anticus into the ulna, it follows that the flexor muscles of the forearm are divided between the two bones, in the same manner as those of the leg are distributed to the tibia and fibula Thus, the contraction of the brachialis anticus has a tendency to carry the forearm outward as well as to flex it, while that of the biceps tends to draw it inward. When the two muscles contract si- multaneously, direct flexion is the result. The Coraco-brachialis. Dissection. — The upper part is exposed as soon as the deltoid is detached ; the middle is situated between the pectoralis major and the latissimus dorsi ; and the lower part is seen upon the inner surface of the humerus, near the tendon of the deltoid. The coraco-brachialis {e,Jigs. 116, 117) is the smallest muscle of the arm. It is situa- ted at the inner and upper part of the arm, and was confounded by most of the older THE TRICEPS EXTENSOR CUBITI. 247 anatomists with the short head of the biceps, with which, indeed, it is intimately united at its upper part. Attachments. — It arises from the apex of the coracoid process, and is inserted towards the middle of the internal surface and border of the humerus. It arises from between two tendinous layers, the most superficial of which is common to it and the short head of the biceps, and also from the septum between these two muscles. From this origin the fleshy fibres proceed, forming an elongated, thin, and flat bundle, the size of which is always in an inverse ratio to that of the short head of the biceps ; this bundle passes downward, backward, and a little outward, to be inserted into the humerus, between the brachialis anticus and the triceps. Its insertion is effected by means of a flat tendon, which receives the fleshy fibres successively upon its edges and external surface, and is accompanied by them even to its attachment to the bone. The precise situation of the attachment varies like that of the deltoid, and hence the different statements of authors regarding this point. According to Winslow, the coraco-brachialis is inserted at the up- per part of the middle third of the humerus ; according to M. Boyer, in the middle of the bone ; and according to Bichat, a little above its middle. I have found it inserted at the junction of the lower with the two upper thirds. Relatione. — It is covered by the deltoid, the pectoralis major, and the biceps, and it covers the sub-scapularis, the latissimus dorsi, and the teres major. Its relations to the axillary and brachial arteries, and the median and musculo-cutaneous nerves, are the most important. Above, it covers these parts, and then it is in relation with the outer side of the brachial artery and median nerve, so that its tendon alone separates the ves- sel from the bone. The musculo-cutaneous nerve passes through it ; hence the name of ■perforatus Casserii has been given to this muscle. It is also very frequently perfora- ted by one of the branches of origin or roots of the median nerve. Action. — It carries the arm forward and inward, and, at the same time, elevates it. It co-operates with the anterior fibres of the deltoid, and the superior fibres of the pecto- ralis major. If the arm be fixed, it depresses the top of the shoulder ; when the arm is carried backward and turned inward, it draws it forward again, and rotates it outward.* Posterior Brachial Region. The Triceps Extensor Cubiti. Dissection. — It is exposed by simply removing the skin and the fascia from the back of the arm, by removing the deltoid, or turning it upward, and by tracing the long head of the muscle between the teres major and minor to the axillary border of the scapula. In order to render it tense, and thus faciUtate the dissection, the forearm must be flexed and the humerus abducted. The triceps extensor cubiti {i f g,'fig. 117) is a very large muscle, divided above into three portions, named the external, internal, and middle, or long heads. It constitutes by itself the entire muscular apparatus of the posterior region of the arm. Attachments. — It arises, 1. By its lo77g head, from the low- er part of the glenoid cavity of the scapula, and from a rough, triangular depression existing on the contiguous portion of its axillary border ; 2. By its external head (vastus externus), from all that portion of the posterior surface of the humerus which is above the groove for the radial nerve, from the external border of that bone, and from the external inter-muscular septum ; 3. By its inter- nal head (vastus internus), from the whole of the poste- rior surface of the humerus below the groove for the ra- dial nerve, from the internal border of the bone, and from the internal inter-muscular septum. It is inserted into the back of the olecranon. The origin of the middle or long head (which we shall find to be analogous to the rectus cruris)t consists of a tendon that is blended with the glenoid ligament, nearly in the same manner as the long tendon of the biceps. This tendon is flattened from before backward, and soon splits into two layers, united by their outer edges, the posterior of which is thin and short, while the anterior is very thick, especially at its outer edge, and prolonged to the middle of the muscle. The head of the humerus, therefore, is bound by the long head of the triceps below, in the same manner as by the long tendon of the biceps * I have seen a small supernumerary coraco-brachialis extending from the base of the coracoid process tj below the lesser tuberosity of the humerus, immediately beneath the insertion of the sub-scapularis : the same arrangement existed on both sides. This small muscle described a cune in front, of the sub-scapularis. t The older anatomists regarded this long portion as a separate muscle : longus {Riolanus AlOinus), cubitum eitendentium primus {Vesalius), le grand ancon6 {Winslow). 248 MYOLOGY. above. The fleshy fibres arise from between the two layers above mentioned, and form a bundle flattened in front and behind, which immediately turns upon itself, so that its anterior surface becomes posterior, and vice versa. From this sort of torsion the strong- est layer of the tendon, which was originally in front, eventually occupies the posterior surface of the muscle. The fleshy fibres arising from between the two layers, and es- pecially from the anterior surface and borders of the now posterior tendon, pass down- ward and a little outward, to be inserted, some into the anterior, but the greater number into the posterior surface of an aponeurotic expansion, the external border of which is continuous with a similar structure belonging to the external division of the muscle. The aponeurotic fibres are collected together into a very thick tendon, which is folded into a semi-cone, within which the fleshy fibres terminate ; the tendon itself is inserted by a thick mass into the inner and back part of the olecranon, on the outer side of the internal portion of the muscle, and closely united with the posterior aponeurosis of the external portion. A synovial capsule intervenes between this tendon and the olecranon. The origins of the external and internal portions from the humerus divide between themselves, so to speak, the posterior surface of that bone, to which the long head has no attachments. The external head {f,figs. 116, 117), which is larger than the internal, and, from analo- gy, may be termed the vastus externus of the triceps brachii (cubitum extendentium secun- dus, Vesalius ; ancon6 externe, Winslow), arises partly by fleshy and partly by tendinous fibres. They are bounded above by a rough line, which is very well marked in powerful individuals, extending obliquely from the lower part of the head of the hmnerus to its external border. From these different origins the fleshy fibres proceed downward and inward, become partly blended with the internal head, and are almost all attached to the anterior surface of the terminal aponeurosis of the long head, and to the anterior sur- face and external edge of a very broad and strong tendon, which occupies the posterior aspect of the muscle. This latter tendon is united internally with the tendon of the long head, is folded upon itself, and receives the fleshy fibres as far as its insertion into the olecranon, on the outside of the long head. The inferior fleshy fibres of this portion of the muscle are very short and horizontal, and seem to be continued by the anconeus. The internal head of the triceps (tertius cubitum extendentium, Vesalius ; ancone in- terne, Winslow, g,figs. 116, 117), which we denominate the vastus internus of the triceps brachii, might be called the deep and internal portion of this muscle, for, as we find with regard to the vastus internus of the thigh, it is almost entirely covered by the other two portions. Its origins are partly fleshy and partly tendinous. The fibres pass in diflTer- ent directions, the external downward and inward, a few to the anterior surface of the aponeurosis of the external head, by which they are concealed, but the greater number directly to the olecranon, in front of the insertion of the other portions. The internal pass downward and outward, and terminate, some upon the inner edge and anterior sur- face of the tendon of the long head, but the greater number directly upon the olecranon, to the inside of that tendon. The lowest of these fibres are almost horizontal. Some of the deepest fasciculi are generally given off from the body of the muscle, to be insert- ed into the synovial capsule of the elbow-joint. Relations. — It is covered through nearly its whole extent by the brachial fascia, and separated by it from the skin, through which it is distinctly defined ; it covers the poste- rior surface of the humerus, the back of the elbow-joint, the radial nerve, and the deep humeral artery. It is separated from the muscles of the anterior region of the arm by the external and internal inter-muscular septa. Its long or scapular portion is in relation with the deltoid and the teres minor behind, and with the sub-scapularis, the teres major, and the latissimus dorsi in front. Aetion. — The triceps extends the forearm upon the arm, but in order that its longhead may act with effect, the scapula must be fixed by other muscles. The power of this muscle is not so great as its size and the number of its fibres would indicate, on account of its disadvantageous insertion near the fulcrum. It is true that here, as in the case of the triceps femoris, nature has, as much as possible, counterbalanced this disadvan- tage by inserting the muscle, not into the apex, but into the back part of the olecranon. We even find, as we have said, a synovial bursa between the tendon and that part of the olecranon with which it is in contact. It would appear, at first sight, that the momentum. of this muscle would occur during semi-flexion, but a little consideration would show that, like the triceps femoris, it has, properly speaking, no momentum ; and that the ole- cranon, which may be regarded as the ossified tendon of the muscle, always has the same relation to the ulna, whatever be the position of the forearm. It should also be observ- ed, that this muscle has not nearly so much power during semi-flexion as during exten- sion, because, in the former case, it is opposed by the flexor muscles, which, in that po- sition, act with the greatest possible effect ; while in the latter, when the arm and fore- arm form an obtuse angle, the extensor muscle has the advantage. Lastly, the predom- inance of the extensor over the flexors is less marked in the arm than in the thigh ; and even supposing the extensor to possess more intrinsic power, it has less active force, in consequence of the insertions of the flexors being m.uch more favourable, both as THE PRONATOR TERES. 249 regards their distance from the fulcrum, and their nearer approach to a perpendicular direction. Thus flexion evidently predominates at the elbow, and extension at the knee. This, indeed, ought to be the case, for in the upper extremities the flexion of the elbow- is the movement of attraction and prehension ; while in the lower extremities, the ex- tension of the knee is an essential position in standing, walking, running, and leaping. We might suppose the possibility of rupture of the olecranon at its junction with the coronoid process, during violent extension of the forearm, an accident that would be anal- ogous to fracture of the patella, or rupture of its ligament. The longhead of the triceps assists in drawing the humerus backward, and slightly adducts the arm. By means of its tendon of origin from the scapula, and especially by the outer edge of that tendon, which is thick, and, as it were, arched, so as to fit the head of the humerus, the long head also forms a cord which supports the bone during abduction, and tends to prevent its displacement ; but, as the glenoid cavity is directed forward, and as its inferior ex- tremity is situated almost at the junction of the two anterior thirds with the posterior third of the cavity, it follows that this tendon is well calculated to prevent dislocation backward, but offers no resistance to displacement forward. Sometimes the lower ex- tremity of the triceps becomes its fixed point, and then it extends the arm upon the fore- arm, and the shoulder upon the arm. MUSCLES OF THE FOREARM. The Pronator Teres. — Flexor Carpi Radialis. — Pahnaris Longus. — Flexor Carpi Ulnaris. — Flexor Sublimis Digitorum. — Flexor Profundus Digitorum. — Lunibricales. — Flexor Longus Pollicis. — Pronator Quadratus. — Sicpinator Longus. — Extensores Carpi Radia- lis, Longior et Brevior. — Supinator Brevis. — Extensor Communis Digitorum. — Extensor Digiti Minimi. — Extensor Carpi Ulnaris. — Anconeus. — Abductor Longus Pollicis. — Ex- tensor Brevis Pollicis. — Extensor Proprius Indicis. The muscles of the forearm are divided into those of the anterior, the external, and the posterior regions. Muscles of the Anterior Region. These muscles form four very distinct layers. The first consists of the pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor carpi ulnaris ; the second is formed by the flexor sublimis digitorum ; the third by the flexor profundus digitorum and the flexor longus pollicis ; and the fourth by the pronator quadratus. The Pronator Teres. Dissection. — This muscle is exposed when the inner and anterior part of the fascia of Fig. 118. the forearm is removed. Its origin should be carefully studied. The pronator teres, or rotundus {a, fig. 118), the most superficial mus- cle on the anterior and inner aspect of the forearm, foims an oblique ridge under the skin, upon the inner side of the bend of the elbow. It is attached above to the inner condyle of the humerus, or epitroch- lea (a, fig. 119), and is inserted below into the middle of the radius {a'). It arises from the lower part of the inner border of the humerus, from the inner condyle, from a large inter-muscular septum, separating it from the flexor carpi radialis and the flexor sublimis, and from the coronoid process of the ulna on the inner side of the brachialis anti- cus, by means of a tendinous and fleshy bundle, which is separated from the rest of the muscle by the median nerve. From these ori- gins the fleshy fibres proceed obliquely downward and outward (pro- nateur oblique, Winsl.), surrounding a flat tendon, which appears first on the anterior surface of the muscle, and then turns over the ante- rior and external surfaces of the radius, to be inserted at the middle of that bone. The muscle, therefore, turns spirally around the radius, but not so completely as the supinator brevis. Its insertion may take place opposite any point in the middle third of the bone. Relations. — It is covered by the fascia of the forearm, by the su- pinator longus and extensor carpi radialis, and by the radial artery and musculo-spiral nerve : it covers the brachialis anticus and flexor sublimis, the median nerve by which it is first perforated, and the ulnar artery. Action. — The greater the amount of supination of the forearm, the more effectual is the action of this muscle as a pronator, because then it is much more completely rolled around the radius. I may remark that, on account of its obliquity, it is inserted into the radius at an angle of 45'' ; and that, consequently, the direction in which it operates is rather favourable. It acts with greater advantage in pro- portion as it is mserted nearer to the upper end of the radius ; and, for this reason, its Ii 250 MYOLOGY. power must vary considerably in different individuals. When pronation is carried as far as possible, the muscle then becomes a flexor of the forearm. After the preceding ex- amination of this muscle, we need no longer be surprised at the great energy of the move- ment of pronation, which is much more powerful than that of supination ; nor yet that it is the most natural position of the forearm, for the pronator teres can more than coun- teract the two supinators taken together. In fracture of the bones of the forearm, this muscle tends to obliterate the interosseous space. The Flexor Carpi Radialis. Dissection. — It is sufficient to divide and dissect off the anterior part of the fascia of the forearm, in order to expose this muscle, which may be recognised by the following description : The flexor carpi radialis (radialis internus, Albinus, I, fig. 118) is situated inunediately within the pronator teres, occupying the superficial layer of the anterior aspect of the forearm, and being, as far as its tendon is concerned, the most superficial of all these muscles. It arises from the lower part of the internal border and from the inner con- dyle of the humerus {b,fig. 119), and is inserted (b') into the second metacarpal bone. Its origin consists of a tendon common to it and to the pronator quadratus, palmaris longus, flexor sublimis, and flexor carpi ulnaris. The fleshy fibres immediately arise from within a sort of pyramidal aponeurosis given off by this common tendon, and from the body of the muscle, at first slender, then increasing in size, and again tapering to- wards its attachment to the two surfaces and edges of a tendon, which forms the lower two thirds of the muscle, and passes obliquely outward and downward to the level of the OS scaphoides ; it there penetrates into a groove formed by the scaphoid and the trape- zium, is reflected inward along this oblique groove, and terminates upon the second met- acarpal bone, spreading out so as to embrace its upper extremity ; it also gives off a ten- dinous expansion to the trapezium, and sometimes one to the third metacarpal bone. Relations. — It is covered by the fascia and the skin, through which it is very clearly de- fined : it is in relation behind with the flexor sublimis ; on the outside, with the tendon of the flexor pollicis, over which it passes at an acute angle, so as to bind it down ; and lower down, with the wrist-joint. A very strong tendinous sheath, concealed by the ab- ductor brevis and opponens pollicis, completes the groove formed by the scaphoid and trapezium for its tendon, the movements of which are facilitated by a well-marked sy- novial membrane.* Its most important relation is that of the external border of its ten- don with the radial artery. The superficial position of the tendon prevents our feeling the artery when the muscle is contracted. Action. — It flexes the second row of the carpus upon the first, and this, again, upon the forearm. Moreover, on account of its reflection, it is a pronator, and, according to Winslow, it is a more powerful supinator than the supinator longus. Its obliquity down- ward and outward explains why it inclines the hand to the radial border of the forearm, and thus acts as an abductor. The Palmaris Longus. Although this small muscle is rather a tensor of the palmar fascia than a flexor of the hand, I have yet judged it proper to describe it in this place, in connexion with the flexor carpi radialis, which, in contradistinction to this muscle {le •petit palmaire), has also been called le grand palmaire (Bichat). It is a small fusiform, slender, fleshy bundle {c,fig. 118), of about four inches in length, arising {c,fig. 119) from the inner condyle of the humerus to the inner side of the preceding muscle, and from a small tendinous cone, which isolates it from that muscle, the flexor sublimis, and the flexor carpi ulnaris. The fleshy fibres terminate around a flat tendon, which constitutes the lower two thirds of the muscle (whence the name palmaris longus), proceeds vertically downward and a little outward, and terminates by expanding in front of the anterior annular ligament (g, figs. 118, 119) of the wrist, and becoming continuous with the middle palmar fascia (c', fig. 118). This muscle is subject to a great many varieties, and is often wanting ; its fleshy belly is sometimes very long, and occasionally occupies the middle of the muscle. Relations. — The same as those of the preceding muscle {flexor carpi radialis) ; its ten- don is very superficial. It is separated from the neighbouring muscles by a very strong sheath. Action. — It is a tensor of the palmar fascia. When this effect has been produced, it flexes the hand upon the forearm. According to Winslow, it would assist the flexor carpi radialis in pronation. The Flexor Carpi Ulnaris. Dissection. — Remove the superficial layer of the fascia covering the inside of the fore- arm, taking care, in dissecting this as well as the other muscles of tlie forearm, to stop at the points where that fascia adheres intimately to the fleshy fibres. * See note, p. 296. THE FLEXOR SUBLIMIS DIGITOEUM. 251 This is the most deep-seated of all the muscles of the superficial layer of the forearm (ulnaris internus, Alhinus ; cubital interne, Winslow, d,Jigs. 118, 119, 121, 122). It arises from the inner condyle of the humerus and from the inner edge of the ole- cranon, these two origins forming an arch under which the ulnar nerve passes. It also arises sometimes, though sUghtly, from the coronoid process of the ulna, from the upper half of the posterior border of the ulna, through the medium of the fascia of the forearm, and from the septum between itself and the flexor sublimis. It is inserted into the pisi- form bone. The origin from the ridge on the ulna is remarkable ; it consists, indeed, of the fascia of the forearm, which becomes thickened and divided into two layers, one deep and very thin, the other superficial and very thick ; in the interval between these the fleshy fibres arise. These fibres are attached to the surfaces and edges of a very strong tendon, which then appears upon the anterior border of the muscle, and continues to re- ceive the fleshy fibres on its posterior edge until its insertion into the pisiform bone. This takes place upon the anterior surface of the bone, like those of the triceps muscles of the arm and thigh into the olecranon and patella. The tendon then becomes continu- ous with the inferior vertical ligament of the articulation between the pisiform and cunei- form bones, so that the muscle may, in fact, be regarded as inserted into the fifth meta- carpal bone. Relations. — It is covered by the fascia, and is intimately united with it for a consider- able extent : it covers the ulnar artery and nerve, the flexor sublimis, the flexor profun- dus, and the pronator quadratus. The most important of all its relations is that with the ulnar artery, which is at first under it, and then lies along the external edge of its ten- don, which protects the artery, and serves as a guide in the application of a ligature to it. I have, therefore, been in the habit of calling this muscle the satellite of the ulnar artery. Action. — This muscle acts as if it were inserted into the upper extremity of the fifth metacarpal bone. Were it not for the peculiar mode of its attachment to the pisiform bone, it would have been inserted parallel to its lever ; whereas it is really inserted at an angle of about 45°. It flexes the second row of the carpus upon the first, and this upon the forearm ; at the same time it inclines the hand towards its ulnar side. Its mo- mentum, as well as that of the preceding muscle, occurs during semi-flexion of the hand upon the forearm. The Flexor Sublimis Digitorum. Dissection. — The portion of this muscle, situated in the forearm, is exposed by cutting across the middle, and turning aside the pronator teres, the flexor carpi radialis, and the palmaris longus, which form a superficial layer in front of it. With a little care, the ori- gin of this muscle may be separated as far as the inner condyle of the humerus. In re- moving the pronator teres, it is necessary to be extremely careful to avoid dividing the radial origin of the flexor sublimis, which forms a very thin prolongation under the pro- nator. The dissection of the palmar and digital portions of the mus- cle is the same as thai of the flexor profundus. Divide the anterior annular ligament of the carpus vertically, and remove the palmar fascia ; examine the disposition of this structure opposite the heads of the metacarpal bones, and also the relations of the tendons of the flexor sublimis and flexor profundus in the palm of the hand ; then dissect the digital sheaths, which must be divided in order to display the singular manner in which the ten- dons of the flexor sublimis bifurcate and turn round, so as to em- brace the corresponding tendons of the flexor profundus. The flexor superficialis, sublimis, or perforatus {e e,fig. 118 ; e, fig. 119), is a broad, flat, thick muscle, divided into four portions below. It arises from the internal condyle or epitrochlea of the humerus, and from the ulnar and radius, and is inserted into the second pha- langes of the fingers. It arises from the epitrochlea by the common tendon, from a rough surface on the fore part of the inner side of the coronoid process of the ulna, and also from about two inches of the radius. This latter origin consists of tendinous fibres attach- ed to that obhque portion of the anterior border of the bone which extends inward towards the bicipital tuberosity, and from which arise the supinator brevis above, the flexor longus pollicis below, and the muscle we are now describing in the middle. A great number of fibres also arise from the broad aponeurotic septa which divide this muscle from the flexor carpi ulnaris, and from the other muscles of the superficial layer, viz., the pronator teres, the flexor carpi radialis, and the palmaris longus. From these different origins the fleshy fibres proceed vertically downward, forming a broad and thick belly, which is almost imme- diately divided into four portions. These at first are in juxtaposi- tion, but soon become arranged in two layers, like the tendon^ of 252 MYOLOGY. the extensor communis, viz., one anterior and larger, consisting of the divisions for the median and ring fingers (the latter not being so strong as the former), and another pos- terior, formed by the divisions for the index and little finger. Each division is, indeed, a small muscle, having its own particular tendon, around which the fleshy fibres are ar- ranged, at first regularly, and afterward on one side only : they are thus semi-penniform muscles. The two posterior divisions are not so distinct as the anterior, and have a pe- culiar arrangement : they generally constitute two small digastric muscles ; that is to say, a fleshy belly terminates upon a flat tendon, which, becoming enlarged, gives origin, in its turn, to a new fleshy belly. The four tendons, after emerging from the fleshy fibres, pass together under the annular ligament {g) of the carpus, in conjunction with the me- dian nerve, which lies on their outer side, and is often mistaken for a tendon, and with the tendons of the flexor profundus digitorum and the flexor longus pollieis. This thick bundle of tendons having reached the palm of the hand, is then distributed in a manner to be noticed after the description of the flexor profundus, with the tendons of which those of the flexor sublimis are intimately connected. Relations. — It is covered by the pronator teres, the flexor carpi radialis, the palmaris longus, the flexor carpi ulnaris, and the fascia of the forearm ; and it covers the flexor profundus digitorum, from which it is separated by the ulnar vessels and nerves ; it also covers the median nerve and the flexor longus pollieis, to which it generally sends a tendinous and fleshy prolongation. The Flexor Profundus Digitorum. Dissection. — This muscle is exposed by cutting across the flexor sublimis and the flex- or carpi ulnaris. The flexor profundus or jperforans {i, figs. 119, 120) is situated under the superficial flex- Fig. 120. or, which it exceeds in size, but resembles it in being divided below into four portions. Attachments. — It arises from the upper three fourths of the internal and anterior surfaces of the ulna, from a well-marked cavity situated on the inner side of the coronoid process behind the rough eminence which gives attachment to the internal lateral ligament of the elbow, from the inner two thirds of the interosseous ligament, from that part of the fascia of the forearm which covers the inner surface of the ulna, and, lastly, by a few fibres, from within and below the bicipital tuber- osity of the radius. It is inserted into the front of the bases of the last phalanges of the fingers {i,figs. 119, 120). The fleshy fibres arise directly from these numerous origins, and proceed vertically downward, the internal fibres alone being directed somewhat obliquely forward and outward. The belly of the muscle thus formed continues to increase in size, and is then divided into four unequal portions, each constituting a semi-penniform muscle. These four smaU muscles are in juxtaposition, and terminate in as many flat tendons, which occupy the lower two thirds of the anterior surface of the entire muscle, and are remarkable for being divided into very reg- ular and closely-united parallel bands of a nearly white colour. The four tendons emerging from the fleshy fibres at various heights, but always above the anterior annular ligament of the carpus, pass under this ligament conjointly with the tendons of the flexor sublimis, the flexor pollieis longus, and the median nerve. In this situation they are placed behind the tendons of the flexor sublimis, which are ar- ranged in two layers, as we have already seen. The tendons of the flexor profundus are always in juxtaposition, and, moreover, are united together by means of dense cellular tissue and tendinous bands pass- ing from one to the other : the fasciculus for the index finger alone remains distinct ; and, therefore, the flexion of this finger is almost as independent of that of the others as its extension, for which latter movement it receives a special muscle. Immediately below the annular ligament the tendons separate from each other ; the two anterior tendons of the flexor sublimis no longer cover the two posterior, but all four become situated in front of the corresponding tendons of the flexor profundus, and arrive together at the raetacai-po-phalangal articulations : here they are received, at first, into a very strong fibrous sheath, resulting from the division of the palmar fascia, and afterward into an- other sheath {s,figs. 118, 119), which converts the groove in front of the phalanges into a canal. If we divide any of these digital sheaths, we find the tendon of the superficial flexor becoming flattened and hollowed underneath, as it were, into a groove, which is exactly moulded upon the tendon of the deep flexor. About the middle of the first pha- lanx the tendon of the sublimis (e,fig. 119) bifurcates, and gives passage to that of the profundus, which it embraces by turning round it like the thread of a screw, and be- coming posterior instead of anterior, as it was before. The two halves of the tendon then reunite to form a groove having its concavity directed forward, and again separate THE LUMBRICALES AND THE FLEXOR LONGUS POLLICIS. 253 to be inserted into the rough edge of the groove on the second phalanx. The tendon of the flexor profundus {i' i', figs. 119, 120), on the contrary, passes directly through the Bheath formed by that of the flexor sublimis, and is inserted into the third phalanx. The tendons of the flexor profundus, moreover, present in their whole course very slightly apparent traces of division. From the relation of the tendons of the two flexors to each other, the superficial muscle has been called the perforatus, and the deep one the perforans. Relations.— These should be examined in the forearm, in the palm of the hand, and along the fingers. In the forearm the flexor profundus is covered by the flexor sublimis, from which it is separated by an incomplete tendinous septum, and by the median nerve. It covers the ulna, the interosseous ligament, and the pronator quadratus ; it corresponds within to the flexor carpi ulnaris, and without to the flexor longus poUicis. The ulnar vessels and nerves are at first situated between this muscle and the flexor subhmis, and after- ward separate it from the flexor carpi ulnaris. In the pahn its tendons are subjacent to those of the flexor sublimis, and cover the interosseous muscles and the adductor poUicis. The lumbricales muscles take their origin from them. Along the fingers its tendons are in relation behind with the grooves of the phalanges, and with the metacarpo-phalangal and phalangal articulations, and in front with the tendons of the subhmis and the fibrous sheaths of the fingers. Action of the two Flexors. — These muscles flex the third phalanx upon the second, the second on the first, this, again, upon the corresponding metacarpal bone, and, lastly, the hand upon the forearm. The flexor subhmis has no action upon the third phalanges. Its origin from the internal condyle of the humerus enables it to act upon the forearm, and to assist in flexing it upon the arm. It is scarcely necessary to say that the bifur- cation of the tendons of the flexor sublimis is intended to afford a sheath to, and bind down, those of the flexor profundus. The flexor profundus flexes the third phalanx upon the second, the second upon the first, the first upon the corresponding metacarpal bone, and, lastly, the hand upon the forearm. The Lumbricales. The lumbricales {x,figs. 119, 120) are small fleshy tongues, which may be regarded as accessories of the flexor profundus. They are four in number, distinguished as the_^rs^ second, &c., counting from without inward. They extend from the tendons of the flexor profundus to the first phalanges of three or four fingers. They arise from the tendons after these have passed through the annular ligament : the first and the second in front of the tendons for the index and middle fingers, the third in the interval between those for the middle and ring fingers, and the fourth in the interval between those for the ring and little fingers. From these origins they proceed, those near the median line verti- cally, and those at either side obliquely downward to the outer side of the metacarpo- phalangal articulations of the corresponding fingers, where they terminate by a broad tendinous expansion inserted into the edges of the extensor tendons, and completing the sheath which those tendons form on the back of the first phalanges. The tendon of the third lumbricalis appears to me to be almost always inserted, not into the outer side of the ring finger, but into the inner side of the middle finger : an arrangement that cannot well be accounted for. It is not unconunon to find this third lumbricalis bifurcated, and attached, not only to the inner side of the middle, but to the outer side of the ring finger. Relations. — They are placed between and upon the tendons of the flexor profundus, and have, therefore, the same relations as those tendons in the palm of the hand ; they are also in relation with the sides of the metacarpo-phalangal articulations, and the ten- dons of the interosseous muscles. Action. — It is difiicult to determine their actions precisely. Vesalius has described them as adductors, and Spigelius as flexors. I agree with Riolanus in regarding them as specially intended to keep the extensor tendons closely applied to the phalanges, and to serve instead of a proper sheath. They are of use also in binding together the ex- tensor and flexor tendons, and preventing the displacement of either. The Flexor Longus PoUicis. Dissection. — The same as that of the flexor profundus. The flexor longus poUicis {I, figs. 119, 120) is situated upon the same plane as the flex- or profundus digitorum, of which it may be considered a division ; it is thick, elongated, and penniform. Attachments. — It arises from the upper three fourths of the radius, from the contiguous portion of the interosseous ligament, from the anterior border of the radius, and not un- frequently by a prolongation, tendinous at its extremities and fleshy in the middle, from the flexor subhmis digitorum. It is inserted into the upper end of the second phalanx of the thumb. The fleshy fibres arise directly from these origins, pass vertically down- ward, and are attached to the posterior surface of a flat tendon, which forms a continu- ation of the series of tendons of the flexor profundus on the outside, and, like them, is 254 MYOLOGY. divided into bands. The fleshy fibres accompany the tendon as far as the anterior an- nular ligament of the carpus ; it then passes beneath this ligament, is reflected over the inside of the trapezium, and proceeds obliquely outward along the first metacarpal bone. When it reaches the metacarpo-phalangal articulation of the thumb, it is received in an osteo-fibrous sheath, resembling in every respect that of the tendons of the other fingers, and, like them, is inserted in front of the upper extremity of the ungual phalanx of its corresponding finger (/, ^^. 120). Relations. — It is covered by the flexor sublimis, the flexor carpi radialis, the supinator longus, and the radial artery ; it covers the radius and the interosseous ligament, from vi'hich it is separated above by the interosseous vessels and nerves, and below by the pronator quadratus. Its tendon is the most external of those which pass under the an- terior annular ligament of the carpus, after leaving which it is received into a deep mus- cular groove formed by the muscles of the ball of the thumb, and is ultimately enclosed in its own osteo-fibrous sheath. Action. — It flexes the last phalanx of the thumb upon the first, this upon the first met- acarpal bone, and then the hand upon the forearm. In order to understand its action precisely, we must suppose the muscular force to be concentrated upon the upper end of the reflected portion ; it is then easy to see that it draws the phalanges inward, while flexing them. It is, therefore, an opponens muscle. The Pronator Quadratus. Dissection. — Cut across all the tendons occupying the lower part of the anterior region of the forearm, and this muscle will be exposed. This small muscle (le petit pronateur, Bichat, m,figs. 119, 120) is situated at the low- er part of the anterior region of the forearm, and forms the deepest layer of this region. It is regularly quadrilateral, and thicker than at first sight it appears to be. AttachmeTits. — It arises from the lower fourth of the internal border of the ulna, which is directed so decidedly backward inferiorly, that the muscle is rolled round the bone ; also, from an aponeurotic layer much thicker below than above, directed obhquely up- ward and outward, and occupying the inner third of the muscle, upon which it terminates in a number of elegant intersections ; lastly, from all that portion of the anterior surface of the ulna upon which it lies. From these origins the fibres proceed horizontally out- ward (le pronateur transverse, Winslow), becoming longer as they are more superficial, to the lower fourth of the external border, anterior surface, and internal border of the radius. Relations. — It is covered by the flexor profundus digitorum, the flexor longus pollicis, the flexor carpi radialis, and the radial and ulnar arteries, and it partially covers the two bones of the forearm and the interosseous ligament. Action. — The pronator quadratus tends to approximate the two bones of the forearm ; but as it is rolled around the ulna, which is immovable, it causes the radius to turn upon that bone, and is therefore a pronator. Its action is much more energetic than would at first sight appear : this depends on the number of its fleshy fibres, which are arranged in several layers, the most superficial being the longest. The Muscles of the External Region of the Forearm. The muscles of this region are, the supinator longus, the extensores carpi radiales, longior and brevier, and the supinator brevis. The Supinator Longus. Dissection. — The brachial portion of this muscle is exposed in the dissection of the brachialis anticus and the triceps, and the portion situated in the forearm, by removing the fascia from the outer and anterior aspect of the muscles of this region. The supinator longus {f,figs. 118, 121), which is the most superficial muscle of the ex- ternal and anterior aspect of the forearm, belongs both to the arm and the forearm (bra- chio-radialis, SiEmmering), and constitutes, in a great measure, the oblique ridge forming the external boundary of the bend of the elbow. It is a long, flat muscle, fleshy in its upper two thirds, and tendinous in its lower third. Attachments. — It arises from the outer border of the humerus, and from the external inter-muscular septum of the arm ; the extent of its humeral attachment varies from the lower fourth to the lower third of that bone, and is limited above by the groove for the musculo-spiral nerve. It is inserted, into the base of the styloid process of the radius. The fleshy fibres proceed from their origins downward, forward, and a little inward, to form a fleshy belly, which is flattened from without imvard, and is applied to the brachi- alis anticus. After reaching the lower end of the humerus, the fleshy belly becomes flattened from before backward, and passes vertically downward. At first it is thick, but, during its progress, it expands, and becomes thin, until its fibres terminate successively upon the anterior surface of an aponeurosis, which becomes entirely free from fleshy fibres above the middle of the forearm, and is gradually contracted into a flat tendon, that is inserted into the styloid process of the radius. Relations. — It is covered bv the fasciae of the arm and forearm : in the arm it is en- THE EXTENSORES CARPI RADIALES, LONGIOR ET BREVIOR. 255 closed in the same sheath with the brachialis anticus, from which it is separated by the radial or musculo-spiral nerve ; in the forearm it has a sheath proper to itself: it is in relation with the brachialis anticus, which is at first within, and afterward behind it - then with the extensor carpi radialis longior, the tendon of the biceps, the supinator bre- vis, the pronator teres, the flexor carpi radialis, the flexor digitorum sublimis, the flexor longus pollicis, the radial artery and veins, and the radial nerve. Its inner border limits the bend of the elbow on the outside : the radial artery emerges from beneath this bor- der, and then lies parallel to it. Its outer border is separated from the extensor carpi radialis longior by cellular tissue, and, inferiorly, is in contact with the dorsal branch of the radial nerve, which, at first, was situated beneath it. The most important of all these relations is that with the radial artery, of which the long supinator may be consid- ered ths satellite muscle, and might be designated the muscle of the radial artery. Action. — It might be asked. Why does the supinator longus form an exception to the general rule, in being inserted into the lower end of the lever which it is intended to movel for, while the forearm is in a state of supination, the axis of the muscle is verti- cal, and its action appears limited to that of flexing the forearm ; but if the limb be pro- nated, the direction of the muscle becomes oblique from without inward, and, therefore, supination is the result of its contraction. After this effect has been produced, if the muscle still continues to act, the forearm is flexed upon the arm. It is needless to state that the distance of its insertion from the fulcrum gives the muscle great power, not- withstanding its disadvantageous angle of incidence. The Extensor Carpi Radialis Longior. Dissection. — This muscle, as well as the succeeding one, wiU be exposed at the same time as the supinator longus, beneath which it is placed. The lower end of its tendon occupies the dorsum of the wrist, and should also be exposed. The extensor carpi radialis longior (le premier ou long radial externe ; radialis externus longior, Albinus, n,figs. 119, 121) is situated on the external and posterior aspect of the forearm, below the supinator longus, of which it seems to be a continuation at its origin from the humerus : like that muscle, it is flattened from within outward in the arm, and from before backward in the forearm : it is fleshy in its upper third, and tendinous in its lower two thirds. Attachments. — It arises from the rough triangular impression terminating the external border of the humerus, from the external inter-muscular septum, and from the anterior surface of the common tendon. It is inserted into the back of the upper end of the sec- ond metacarpal bone. The fleshy fibres arising directly from the parts mentioned con- stitute a bundle, at first flattened on the sides, and forming a continuation of the supina- tor longus, from which it is often difficult to separate it : it afterward becomes flattened from before backward. The fibres pass vertically downward, and are attached to the anterior surface of a tendon, a little beyond the upper third of the forearm. The tendon then becomes narrower and thicker, proceeds along the outer border of the radius, pass- es under the tendons of the abductor longus and extensor brevis pollicis, which cross it obliquely, and turns a httle outward, and then backward, to arrive at a groove common to it and the extensor carpi radialis brevior ; it is then crossed at an acute angle by the tendon of the extensor longus pollicis, and is finally inserted, by an expanded termina- tion, into the second metacarpal bone {n',fig. 121). Relations. — It is covered by the supinator longus and the fascia of the forearm ; on the outside of the forearm, it is covered and crossed obliquely by the abductor longus and ex- tensor brevis poUicis, and in the wrist by the tendon of the extensor longus pollicis. It covers the elbow-joint, the extensor carpi radialis brevior, and the back of the wrist-joint. The Extensor Carpi Radialis Brevior, The extensor carpi radialis brevior (le second ou court radial externe ; radialis externus brevior, Albinus, o,figs. 119, 121, 122) is thicker, but shorter, than the preceding, below which it is placed. It arises from the external condyle or epicondyle of the humerus, by a tendon common to it and the extensor muscles of the fingers ; also, from a very strong aponeurosis, situated upon its posterior surface ; and from another tendinous septum, which divides it from the extensor communis digitorum. It is inserted into the back part of the upper end of the third metacarpal bone. The fleshy fibres, thus arising from the external condyle by means of an aponeurotic pyramid, are attached to the posterior sur- face of a tendon, which becomes gradually narrower and thicker as it receives them. The fibres themselves terminate about the middle of the forearm, and then the flat ten- don passes backward into the same groove on the radius as that of the last-named mus- cle, the two tendons being retained in it by the same fibrous sheath, and lubricated by the same sjmovial membranes, but separated from each other by a small vertical ridge of bone. After leaving the common sheath, the tendon of the short separates from that of the long radial extensor, passes still more posteriorly, and is inserted into the third metacarpal bone (o',/5-.s. 121, 122), Relations. — It is covered by the preceding rr.uscle, and, like it, is crossed obliquely on 256 MYOLOGY. the outside by the long abductor, the short, and then the long extensor muscles of the thumb : it covers the external surface of the radius, from which it is separated by the supinator brevis above, and the pronator teres in the middle. Its tendon covers and protects the back of the wrist. In consequence of the different length of their fleshy fibres, the supinator longus and the two radial extensors of the carpus are arranged one above the other, the highest being the supinator longus, and the lowest the extensor carpi radialis brevior. Actio7i of the two Radial Extensors. — These two muscles, which, from their insertions, might be called the posterior radials, extend the second row of the carpus upon the first, and this upon the forearm ; they are also abductors of the hand, for they incline it to- wards the radial side of the forearm. The extensor carpi radiahs longior being attach- ed to the humerus, can assist in flexing the forearm. The Supinator Brevis. Dissection.— Vronate the forearm forcibly. In order to expose this muscle completely, divide the two radial extensors of the carpus, and even some of the muscles of the su- perficial layer, on the back of the forearm. The supinator brevis (■p,figs. 119, 120, 122) is a broad muscle curved into the form of a hollow cylinder, and rolled round the upper third of the radius : it forms by itself the deep layer of the external region of the forearm. Attachments. — It arises from the external lateral ligament of the elbow, with which it is blended, and by this means from the external condyle ; from the annular ligament of the radius ; from the external border of the ulna, which is provided with a projecting ridge for this purpose ; from a deep triangular excavation., in front of this ridge, and below the lesser sigmoid cavity of the ulna ; and, lastly, from the deep surface of an expansion of its tendon of origin and the external lateral ligament, which covers the greater part of the muscle. From these different origins (fig. 122) the fleshy fibres pass round the ra- dius, into the posterior, external, and anterior surfaces of which bone they are inserted, embracing in front the bicipital tubercle and the tendon of the biceps {figs. 119, 120). I have seen a fleshy prolongation of this muscle, covering the anterior half of the annular ligament of the radius, of which it might be regarded an extensor. Relations. — The supinator brevis is covered by the radial extensors, the supinator lon- gus, the pronator teres, the extensor communis digitorum, the extensor digiti minimi, the extensor carpi ulnaris, the anconeus, and the radial artery and vein : it covers the upper third of the radius, and also its annular ligament, the elbow-joint, and the inter- osseous ligament. It is perforated by the deep branch of the radial nerve, which is dis- tributed to all the muscles on the back of the forearm. Action. — No muscle in the body is so completely rolled around the lever that it is in- tended to move, for it forms five sixths of a cylinder ; it is, therefore, the chief agent in supination, and the supinator longus can only be regarded as an accessory. Muscles of the Posterior Region of the Foeeaem. The muscles of the posterior region of the forearm constitute two very distinct layers : one superficial, comprising the extensor communis digitorum, the extensor digiti minimi, and the extensor carpi ulnaris ; the other deep, comprising the abductor pollicis longus, the extensor brevis and extensor longus pohicis, and the extensor indicia Muscles of the Superficial Layer. One mode of dissection is common to all these muscles. Make a circular mcision through the skin at the lower part of the arm ; pronate the arm, and make a perpendic- ular incision from the external condyle of the humerus to the third metacarpal bone, entirely dividing the sub-cutaneous cellular tissue down to the fiiscia ; remove this fascia by careful dissection, except where it is very adherent. Trace the tendons of the ex- tensor muscles along the back of the fingers. The Extensor Communis Digitorum. The extensor communis digitorum {b,fig. 121), situated at the back of the forearm, sim- ple above and divided into four portions below, arises from the external condyle of the humerus, and is inserted into the second and third phalanges of the four fingers. Its ori- gin consists of a tendon common to it, and to the extensor carpi radialis brevior, exten- sor digiti minimi, and extensor carpi ulnaris. This tendon consists of a four-sided pyra- mid, and is formed by the fascia of the forearm, by a lamina separating this muscle from the extensor carpi radialis longior, by another lamina separating it from the extensor digiti minimi and the extensor carpi ulnaris, and, lastly, by another situated between it and the supinator brevis. The fleshy fibres arising from the interior of this pyramid form at first a thin, but afterward a much larger muscle, which becomes flattened from before backward, and soon divides into four fasciculi. The two middle fasciculi, intended for the middle and the ring fingers, are stronger than those destined for the index and little fingers, i. e., the two extreme fasciculi, which, lower down, become placed in front of THE EXTENSOR DIGITI MIMMI. 257 the middle fasciculi.' In this manner they all pass under the dor- Fig 121. sal ligament ir,Jig- 121) of the carpus in a proper sheath. After leaving this sheath, in which they are provided with a synovial capsule,* extending both above and below the dorsal ligament, the four tendons become situated on the same plane, and diverge from each other ; the two middle tendons proceed along the backs of the corresponding metacarpal bones ; tlie external and internal ten- dons (b' b',Jig. 121) correspond to the interosseous spaces, which they cross obliquely, in order to assume a position behmd the heads of the metacarpal bones, to which they belong. Having reached the metacarpo-phalangal articulations, the tendons become nar- rower and thickened, and give off on each side a fibrous expansion, attached to the sides of the joint ; they then enlarge again so as to cover the dorsal surface of the first phalanges, receive and are re- enforced by the tendons of the lumbricales, and opposite the ar- ticulation of the first with the second phalanx, they divide into three portions, one median, which is implanted upon the upper end of the second phalanx, and two lateral, which pass along the sides of the second phalanx, approach each other at the lower half of the dorsal surface of the second phalanx, unite by their neighbouring edges, and are inserted into the upper end of the third phalanx. Opposite the metacarpal bones they sometimes split into two or three small juxtaposed tendons, and at the lower end of these bones the tendons for the little, ring, and middle fingers commu- nicate with each other by expansions of variable size, and some- times by a true bifurcation (see fig. 121). The tendon for the in- dex finger is alone free. The communication of the tendon of the little with that of the ring finger takes place opposite the metacar- po-phalangal articulation, by means of a transverse band, which forms a projection under the skin. Lastly, we not uncommonly see a tendinous prolongation arising from the anterior surface of these tendons, and in- serted into the upper end of the first phalanx. Relations. — The extensor communis digitorum is covered by the fascia of the forearm, from which a great number of its fibres arise superiorly, by the dorsal hgament of the carpus and the dorsal fascia of the metacarpus, which separate it from the skin : it cov- ers the supinator brevis, the three long muscles of the thumb, the extensor proprius in- dicis, the lower radio-cubital articulation, the carpus, the metacarpus, and the fingers. Action. — This muscle extends the third phalanx upon the second, the second upon the first, the first upon the corresponding metcarpal bone, then the carpus, and, lastly, the •radio-cubital articulation. It is necessary for me to mention the independence of the muscular fasciculi proceeding to each finger : this is pecuhar to man, and is much more remarkable in some individuals than in others. By continual exercise, the faculty of extending one finger without the others may be acquired. The tendon for the index is generally the only one not united to the others, and therefore the movements of this finger are by far the most independent. The Extensor Digiti Minimi. This is a very slender muscle (extensor proprius auricularis, Alhinus, c, Jig. 121) placed on the inner side of the common extensor, to which it appears to be an appendix. It is difl^cult to trace its origin as far as the common tendon, with which it is connected only by an aponeurotic prolongation. Its fleshy fibres arise from this prolongation, and from a fibrous pyramid which separates it from the muscles of the deep layer, from the exten- sor communis digitorum externally, and internally from the extensor carpi ulnaris, and is completed superficially by the fascia of the forearm. The fibres constitute a small, fusiform, fleshy belly, which accompanies the tension (at least on one side) as far as the head of the ulna; there the tendon enters a special fibrous sheath formed behind the head of that bone ; it is then reflected inward to the fifth metacarpal bone, behind which it is retained in a thinner sheath, which, like the preceding, is lined by a synovial mem- brane.t The tendon then splits into two bands, of which the external (or radial) re- ceives the inner bifurcation of the extensor communis. The three tendinous prolonga- tions becoming united, envelop, as in a sheath, the dorsal aspect of the first phalanx of this finger; having reached the articulation of the first with the second phalanx, they divide into three portions, which are attached precisely in the same manner as the ten- dons of the extensor communis. Action. — As its name indicates, this muscle extends the little finger. It might at first sight be imagined that this finger might be moved independently, since it receives a sep- arate muscle ; but the connexion of its tendon with that of the extensor communis ren- See note, p. 29C. Kk t See note, p. 296. 258 MYOLOGY. ders any such independent action as difficult as in the other fingers, and much more so than in the index finger. The Extensor Carpi Ulnaris. The extemor carpi ulnaris (e, Jig. 121), the most superficial and the most internal* of the muscles on the back of the forearm, arises from the external tuberosity of the humerus ; from the posterior surface of the ulna, which is a little excavated for this purpose ; from the middle third of the posterior border of that bone ; and from the anterior surface of an aponeurosis covering the muscle behind. It is inserted behind the upper end of the fifth metacarpal bone. Its origin is effected by means of a fibrous pyramid, the apex of which is attached to the outer tuberosity of the humerus. From the interior of this pyr- amid, and from the other origins above mentioned, the fleshy fibres proceed to a tendon, which, by a very uncommon arrangement, extends through the substance of the muscle, even from its superior attachment, without commencing in the form of an aponeurosis. At the lower third of the forearm, this tendon appears on the posterior border of the then semi-penniform muscle, and continues to receive fleshy fibres on its anterior edge until it enters the groove intended for it on the ulna. This oblique groove is continued as far Fig. 132. as the insertion of the tendon into the metacarpal bone, by means of a long, fibrous sheath, and is lined throughout by a synovial membrane. Relations. — The extensor carpi ulnaris is covered by the fascia of the forearm : it covers the ulna, the supinator brevis, and the mus- cles of the deep layer. Action. — It extends the second row of the carpus upon the first, and this upon the forearm. It is, at the same time, an adductor of the ,g hand, which it inclines towards the ulnar border of the forearm. The Anconeus. The anconeus (brevis anconeus, Eustachius ; le petit ancone, Wins- low, g, Jigs. 121, 122) is a short, triangular muscle, so named from its situation {ayKuv, the prominence of the elbow). It appears to be a continuation of the external portion of the triceps, from which it is only separated by a very slight cellular interval. Attachments. — It arises from the back part of the outer tuberosity of the humerus, and is inserted into the outer side of the olecranon, and a triangular surface bounded internally by the posterior border of the ulna. Its origin from the condyle consists of a tendon quite dis- tinct from that common to the muscles on the back part of the fore- arm. This tendon splits into two diverging bands. The fleshy fibres arising from these proceed inward, the upper horizontally, the lower obliquely downward, and are inserted directly into the outer side of the olecranon, so as to be continuous with the triceps, and into the surface of the ulna. Relations. — It is covered by a prolongation from the fascia of the triceps, and it covers the radio-humeral articulation, the annular lig- ament of the radius, the ulna, and a small portion of the supinator brevis. jietion. — It extends the forearm upon the arm, and vice versa ; from its oblique direc- tion, it can also rotate it inward. Muscles of the Deep Layer. Dissection. — This is the same for all the muscles of the deep layer of the forearm, and consists in removing the muscles of the supei-ficial layer, especially the extensor com- munis digitorum and the extensor digiti minimi. The Abductor Longus Pollicis. The abductor longus ■pollicis (extensor ossis metacarpi poUicis, i,Jlgs. 121, 122) is the broadest, thickest, and most external muscle of the deep layer (le grand abducteur, Bichat). Attachments. — It arises from the ulna below the origin of the supinator brevis, from the interosseous ligament, from the radius, and from a tendinous septum between it and the extensor longus poUicis. It is inserted into the upper end of the first metacarpal bone. From tlie above-mentioned origins the fleshy fibres proceed obliquely downward and outward, constitute a flattened fusiform belly, and are successively attached to the posterior surface of an aponeurosis, which becomes condensed into a flat tendon ; this tendon turns round the radius, crossing over the radial extensors of the carpus, and, at the same time, ceasing to receive any fleshy fibres ; it is then received into the outer groove on the lower end of the radius, conjointly with the tendon of the extensor brevis * It is needless to remark that this internal situation presupposes the supination of the forearm. In prona- ! tion, this muscle may be correctly termed ulnaris extemus, and le cubital externe, according to Albinus and •iWinslow, THE EXTENSOR BREVIS POLI.ICIS, ETC. pollicis, a small fibrous septum intervening between them, and, finally, is inserted into the first metacarpal bone. This tendon is almost always divided longitudinally into two equEil parts, and not unfrequently the division extends up to the fleshy portion. Of these two divisions, one is inserted into the first metacarpal bone, the other furnishes attach- ments to the abductor brevis poUicis. Relations. — It is covered by the extensor communis digitorum and extensor digiti min- imi : it lies immediately under the fascia, from the outer side of the radius to its termi- nation. It covers the interosseous ligament, the radius, the tendons of the radial exten- sors o-f the carpus, and the outer side of the wrist-joint, where it may be easily distin- guished under the skin. Action. — It extends and abducts the first metacarpal bone : for a long time it was called the extensor of the thumb ; but its chief use is, as Albinus first remarked, in ab- duction. Winslow observes that, from its obliquity, it can act as a supinator ; lastly, it assists in extending the hand. The Extensor Brevis Pollicis. This muscle (extensor primi intemodii pollicis, I, figs. 121, 122) is situated internally to the preceding, which it exactly resembles- in figure and direction, and with which it was for a long time confounded (partie du premier extenseur du pouce, Winslow). It is, however, shorter and more slender (petit extenseur du pouce, Bichat). It arises from the radius, occasionally from the ulna, and from the interosseous liga- ment ; and is inserted into the upper end of the first phalanx of the thumb. Its origin consists of short, tendinous fibres, the fleshy fibres proceeding from which constitute a slender fasciculus, having a similar arrangement to that of the preceding muscle ; its tendon is received into the same fibrous sheath, but is divided from the other by a small septum, and passes on, to be inserted into the first phalanx. Relations. — The same as those of the abductor longus. Action. — It extends the first phalanx upon the first metacarpal bone, and then becomes an abductor and extensor of the metacarpal bone of the thumb. The Extensor Longus Pollicis. This muscle (extensor secundi intemodii pollicis, m,figs. 121, 122) is much larger than the extensor brevis, within and parallel to which it is situated. It arises from a consid- erable extent of the ulna, from the interosseous ligament, and from the tendinous septa, dividing it from the extensor carpi ulnaris, and the extensor proprius indicis : it is insert- ed into the upper end of the second phalanx of the thumb. The fleshy fibres form a flat fusiform bundle, directed obliquely like the preceding muscle ; they terminate in succes- sion around a tendon, which emerges from them at the carpal extremity of the ulna, en- ters a special osteo-fibrous sheath, and crosses obliquely over the tendons of the two ra- dial extensors, being separated from the tendons of the abductor longus and extensor brevis pollicis by an interval which may be readily distinguished through the integu- ments, and gives rise to the hollow on the outer side of the wrist, commonly called the salt-cellar. The tendon next crosses obliquely over the first interosseous space, gains the inner edge of the first metacarpal bone, and then that of the first phalanx, upon which it is expanded, and proceeds to be inserted into the second or ungual phalanx of the thumb. Relations. — Its general relations are the same as those of the preceding muscle. Action. — Its uses are also the same j but it acts in a special manner upon the second phalanx of the thumb, which it extends upon the first before exerting any influence upon this last-mentioned bone. It has less power in abduction than the preceding muscles. The Extensor Proprius Indicis, This is an elongated fusiform muscle (indicator, Albinus, r,fig. 122) like the preceding, below and parallel to which it is situated. It arises from the ulna, the interosseous liga ment, and a septum intervening between it and the extensor longus pollicis ; it is insert- ed into the last two phalanges of the index finger. The fleshy fibres proceed obliquely from their origins and terminate around a tendon, which they accompany as far as the sheath of the extensor communis digitorum : into this sheath the tendon enters, and, having escaped from it, crosses obliquely over the carpus and the second interosseous space, becomes situated on the inside of the tendon given off to the index finger by the extensor communis, unites intimately with that tendon opposite the lower end of the metacarpus, and terminates with it in the manner already indicated. Its relations are the same as those of the preceding muscles. Action. — It enables the index finger to be extended independently of the others, and hence, without doubt, arises the particular use of that finger. I should add, that the union of its tendon with the one furnished by the common extensor is, so intimate, that its in- dependence of action would have been much less, had not the fleshy fasciculus of the common extensor destined for it been itself almost isolated. 260 MYOLOGY. MUSCLES OF THE HAND. The Abductor Brevis Pollicis. — Opponens Pollicis. — Flexor Brevis Pollicis. — Adductor Pol- lids. — Palmaris Brevis. — Abductor Digiti Minimi. — Flexor Brevis Digiti Minimi. — Op- ponens Digiti Minimi. — The Interosseous Muscles, Dorsal and Palmar. The muscles of the hand occupy the entire paknar region. They are divided into those situated on the outer side, viz., the muscles of the thenar eminence, or ball of the thumb ; those on the inner side, viz., the muscles of the hypothenar eminence, or of the little finger ; and those which occupy the interosseous spaces. All the muscles of the thenar eminence belong to the thumb ; they are, in the order of their superposition, the abductor brevis, the opponens, the flexor brevis, and the ad- ductor pollicis. Those of the hypothenar eminence all belong to the little finger, and are the abductor, the flexor brevis, and the opponens. The palmaris brevis may be in- cluded in this region. The interosseous muscles are seven in number — four dorsal and three palmar. The lumbricales, which belong to this region, have been already described with the tendons of the flexors of the fingers. Muscles of the Thenar Eminence, or Muscles belonging to the Thumb. I divide these into three muscles inserted into the outer side of the first phalanx of the thumb, or into the first metacarpal bone, and a single muscle inserted into the inner side. The former are the abductor brevis, the opponens, and the flexor brevis ; the lat- ter consists of the adductor, in which I include a part of the flexor brevis of authors generally. Muscles inserted into the Outer Side of the First Phalanx of the Thumb, or into the First Metacarpal Bone. Dissection. — Make an oblique incision from the middle of the annular ligament of the carpus to the outer side of the first phalanx of the thumb, and a circular incision round the wrist ; detach the flaps, raise the external and middle palmar fascias, and then cau- tiously separate the muscles of this region, which are recognised by the following char- acters. The Abductor Brevis Pollicis. This is the most superficial of the muscles constituting the ball of the thumb {q, fig. 119). It arises by tendinous and fleshy fibres from the os scaphoides, from the upper, anterior, and external part of the anterior annular ligament of the carpus, and almost always from an expansion of the tendon of the abductor longus pollicis. It is a small, thin, flat muscle, passing outward and downward, and inserted by a flat tendon into the outer side of the first phalanx of the thumb. A very narrow cellular line separates it on the inside from the flexor brevis, which is situated on the same plane. It is covered by the external pahnar fascia, and it covers the opponens muscle, from which it is distin- guished by the direction of its fibres, and by a thin intervening aponeurosis. Action. — It draws the thumb forward and inward, and therefore might be termed the superficial opponens. From its attachments, it might be called scaphoido-phalangal. The Opponens Pollicis. The opponens pollicis (r, figs. 119, 120), a small triangular muscle, arises from the trape- zium, and the anterior and external part of the anterior annular ligament of the carpus, in front of the sheath of the flexor carpi radialis. From these origins, which are partly fleshy and partly tendinous, the fleshy fibres radiate downward and outward, the highest being the shortest and the most horizontal. They are inserted into the entire length of the outer border of the first metacarpal bone. This muscle is covered by the abductor brevis, which projects a little beyond it on the outside, and from which it is separated by a more or less distinct aponeurosis. It cov- ers the first metacarpal bone, and its articulation with the trapezium. Action. — It draws the first metacarpal bone inward and forward, thus opposing it to the others, as its name indicates. From its attachments, it may be called trapezio-mctacarpal. The Flexor Brevis Pollicis. It is difficult to point out the limits of this muscle, or, rather, they have hitherto been quite arbitrary. Its inferior attachment has been usually divided between the external and the internal sesamoid bones (Boyer, Traite d' Anatomic, torn, ii., p. 307 ; Bichat, Ana- tomic Descriptive, torn, ii., p. 272) ; but we shall consider that portion only which is at- tached to the external sesamoid bone as belonging to this muscle, referring the entire fleshy mass that is inserted into the internal sesamoid bone to the adductor pollicis.* * The arrangement 1 have adopted is founded upon the inferior attachments of the muscles, for at their origins they are so blended that their division is more or less arbitrary. I divide the muscular fasciculi con- nected with the thumb, therefore, into two sets, viz., those proceeding from the carpus to the first metacarpal THE ADDUCTOR 1>0LLICTS, ETC. ggj This division is, moreover, established by the tendon (/,.%. 120.) of the flexor Ion "lis pollicis. Proceeding then from below upward, in th6 dissection of the flexor brevis'(<, Jigs. 119, 120), we shall see that it is triangular, much larger than the preceding two muscles, bifid above, and channelled in front. It arises by tendinous and fleshy fibres from a process on the trapezium, from the lower edge of the annular ligament, from all the reflected portion of that ligament forming the sheath of the flexor carpi radialis, and extending as far as the os magnum, and from the os magnum itself by a portion which is usually distinct. From these different origins the fleshy fibres proceed downward and outward, the internal being the most obhque ; and, converging so as to form a thick fas- ciculus, are inserted, through the medium of the external sesamoid bone, into the first phalanx. RelatioTis. — It is covered by the external palmar fascia, which is prolonged in front of it ; it covers the tendon of the "flexor longus pollicis, and more internally those of the common flexor. It also covers a small portion of the outer border of the adductor pollicis, and the tendon of the flexor carpi radiahs. Its outer border, or, rather, side, is in relation with the short abductor, from which it is easily separated, and with the opponens, some- times being continuous with it. Its inner border is distinct from the adductor below, but is confounded with it at its origin. Its tendon of insertion into the phalanx is cov- ered by that of the short abductor, which hes externally to it. From its attachments, it might be called trapesio-phalangal, and, from its uses and position, the oppoiiens internus. Action. — It is evidently not a flexor pollicis, but, like the preceding muscles, it draws the thumb forward and inward, and it acts more decidedly in producing the latter effect, because it is inserted in a more favourable manner than the other muscles. This, there- fore, is also an opponens muscle. Muscle inserted into the Inner Side of the First Phalanx of the Thumb. The Adductor Pollicis. This is the largest of all the muscles of the thumb (u, figs. 119, 120) ; it is very ir- regularly tri-angular, and arises from the entire extent of the anterior border of the third metacarpal bone, from the anterior surface of the os magnum, from the anterior and up- per part of the trapezoides, from the anterior part of the trapezium by a tendinous and fleshy fasciculus, and from the palmar interosseous fascia, near the third metacarpal bone. From these different origins the fleshy fibres proceed, the lower horizontally, the rest more and more obliquely outward ; they all converge to form a thick fleshy bundle, which is inserted through the m^edium of the internal sesamoid bone into the first pha- lanx of the thumb. Relations. — Its inner two thirds are deeply situated, and covered by the tendons of the flexor profundus digitorum, by the lumbricales, and by an aponeurosis, which, becoming continuous vdth the deep interosseous fascia, constitutes the sheath of the muscle. It is sub-cutaneous near its lower border. It covers the tirst two interosseous spaces, from which it is separated by a very strong aponeurosis. It is again sub-cutaneous behind, also along its lower border, which may be easily felt under the fold of skin, extending from the thumb to the index finger. Action. — It is an adductor ; it draws the thumb towards the median hue or axis of the hand, represented by the third metacarpal bone. Muscles of the Hypothenar Eminence., or Muscles belonging to the Little Finger. These muscles correspond exactly to those of the thumb : the reason that three only are described is, that the one which represents the adductor of the thumb is situated in the fourth interosseous space, and is, therefore, classed with the interosseous muscles, to be hereafter described. All the muscles of the hypothenar eminence are inserted into the inner side of the first phalanx of the little finger, or into the third metacarpal bone. We find also a cutaneous muscle in this region, viz., the palmaris brevis. .The Palmaris Brevis. This is a very thin square muscle (care quaedam quadrata, S, fig. 118), situated in the adipose tissue covering the hypothenar eminence. It arises from the anterior annular ligament of the carpus, and the inner edge of the middle palmar fascia, by very distinct tendinous fasciculi, succeeded by equally distinct fleshy bundles, which pass horizontally inward, and terminate in the skin. Relations. — It is covered by the skin, to which it adheres intimately, especially by its inner extremity (le palmaire cutane, Winslow ) ; it covers the muscles of the hypothenar bone and to the outer side of the first phalanx of the thumb, and those extending from the carpus to the inner side of the same phalanx. The first set, which might be regarded as a single muscle, comprises the abductor brevis, the opponefis, and the flexor brevis ; the other constitutes the abductor pollicis, vv'hich I regard as the first palmar interosseous muscle. The action of the first set is common, viz., to carry the thumb forward and inward ; they are, therefore, all muscles of t.pposition (perhaps no muscles are so badly named as those of the thenar eminence) ; the muscle foriiip.l by tin second set is reall}' an adductor, as its name implies, and so are all the palmar interossei, among ./lii.;!i Jt s! . uld be included. MYOLOGY. eminence and the ulnar artery and nerve, from all of which it is separated by the inter- nal palmar fascia. Action. — It corrugates the skin over the h}-pothenar eminence. The Abductor Digiti Minimi. It arises from the pisiform bone, and from an expansion of the flexor carpi ulnaris, by tendinous fibres ; these are succeeded by a fusiform fleshy belly {v^fig. 119), which passes TerticaUv along the internal (or ulnar) surface of the fifth metacarpal bone, and is inserted by a flat tendon into the inner side of the first phalanx of the little finger. Relations. — It is covered by the external pahnar fascia, and covers the opponens digiti minimi. Action. As it name denotes, it abducts the little finger from the axis of the hand. The Flexor Brevis Digiti Minimi. This muscle (w,Jiz. 119) is situated on the outer or radial border of the preceding, from which it is distmguished by arising from the unciform bone. The two muscles are separated bvthe ulnar vessels and nerves, which pass between them, in order to penetrate into the deep palmar region. In other respects, as in direction, insertions, and relations, the muscles resemble each other ; they have accordingly been described by Chaussier as a sinfrle muscle, under the name of Zc carpo-phalangien du petit doigt. This muscle is often wanting, but the fleshy fibres which usually constitute it are then always found in some measure blended with the other muscles. Adion. — It produces slight flexion of the httle finger. The Opponens Digiti Minimi. This muscle {Tj,fig. 119) is generally distinct from the preceding, and is the represent- ative of the opponens pollicis. It arises from the hookhke process of the unciform bone, and from the contiguous part of the annular ligament : from these points the fibres pro- ceed downward and inward (i. e., towards the ulnar border of the hand), the highest be- ing the shortest and the most horizontal : they are inserted into the whole length of the inner or ulnar margin of the fifth metacarpal bone. Relation. — It is covered by the preceding muscles and by the internal pahnar fascia : it covers the iifth metacarpal bone, the corresponding interosseous muscle, and the ten- don of the superficial flexor proceeding to the httle finger. Action. — ^It opposes the httle finger to the thiunb by drawing it forward and outward. The Interosseous Muscles. Dissection. — Remove the tendons of the extensor muscles behind, and those of the flexor muscles in front, together with the lumbricales, preserving, at the same time, the digital insertions of these smaU muscles. Dissect and study the deep palmar fascia, a fibrous layer covering the interosseous muscles in the palm of the hand, wiiich sends prolonga- tions between the two kinds of these muscles, and is inserted into the anterior borders of the metacarpal bones, enclosing each interosseous muscle in a proper sheath. After having studied the palmar and dorsal fascia, separate the bones of the metacarpus by tearing their connecting hgaments, and the interossei wll then be completely exposed. The interossei, so named from their position, and distinguished from each other by the mmierical appellations first, second, third, &c., are divided into palmar {p p p. Jig. 123) and dorsal {d d d d), according as they are situated nearer to the palm or to the back of the hand. They are also distinguished into adductors and abductors of the fingers. There are two in each interosseous space, one occupying its dorsal, the other its pal- mar aspect ; and, as there are four interosseous spaces, it would seem that there should be eight interosseous muscles ; nevertheless, seven only are admitted by modern anat- omists, in consequence of the first palmar interosseous muscle, which belongs to the thumb, being separately described as the adductor poUicis. This separation is founded upon the peculiar arrangement presented by that muscle, which is not attached from the first to the second, but extends from the first to the third metacarpal bone ; an important fact, that explains the great extent to which the thiunb can be adducted. A minute description of the interosseous muscles would be both useless and tedious. I shall content myself with pointing out their general conformation, and the law which regulates their arrangement. In taking a general view of the interosseous muscles, they must be considered with regard to the adduction or abduction of the fingers ; but these terms must not be under- stood in reference to the axis of the skeleton, but to the axis of the hand, which is rep- resented by a line passing through the third metacarpal bone and the middle finger. This being admitted, aU the dorsal interossei will be found to be abductors, and all the palmar interossei adductors. Thus, the first dorsal interosseous muscle proceeds from the first and second meta- carpal bones to the outer or radial side of the first phalanx of the index finger : it is there- fore an abductor of that finger. The second extends from the second and third meta- THE DORSAL INTEROSSEI. 263 carpal bones to the outer or radial side of the first phalanx of the middle finger, and is an abductor of that finger. The third extends from the third and fourth metacarpal bones to the inner or ultmr side of the phalanx of the middle fingers, and is also an abductor of the same, because it separates it from the supposed axis of ! the hand. The fourth extends from the fourth and fifth metacarpal bones to the inner or ulrwj- side of the first phalanx of the fourth finger, and it again is an abductor of that finger from the axis of the hand, although, as well as the preceding muscle, it is an adductor as regards the axis of the body. In order to render this view more intelligible, I have been accustomed to rep- resent the five fingers by five lines (see diagram d), to prolong the middle line for the axis of the hand, and then to draw other lines (the four fine lines) representing the axes of the muscles ; the demonstration is thus rendered complete. In the same manner, all the palmar interossei are adductors as regards the axis of the hand. Thus the first, which is represented by the adductor pollicis, and extends from the third metacarpal bone to the inner or idnar side of the first phalanx of the thumb, is an adductor as regards the axis of the hand as well as that of the body ; the second, ex- tending from the second metacarpal bone to the inner or utnar side of the first phalanx of the index finger, is an adductor both as regards the axis of the hand and that of the body ; the third, extending from the fourth metacarpal bone to the outer or radial side of the first phalanx of the ring finger, is an adductor as regards the axis of , #the hand ; and, lastly, the fourth, extending from the fifth metacarpal bone to the outer or radial side of the first phalanx of the little finger, is an adductor as regards the axis of the hand, but an abductor in reference to the axis of the body. A similarly-constructed figure, as that employed for the dorsal interossei, will always keep this arrangement in the memory (see diagram p ; the four fine lines represent the axes of the palmar muscles). The gen- eral disposition of the interossei may be summed up in the following very simple law ; All the dorsal interossei have their fixed attachments farther from the axis of the hand than their movable one ; all the palmar interossei have their fixed attachments nearer to the axis of the hand than their movable one. We may now consider the general arrangement of these little muscles. The Dorsal Interossei. These are short, prismatic, and triangular muscles {d to d,fig. 123), extending from the two metacarpal bones, between which they are placed, to pig. 123. the first phalanx and the extensor tendon of one of the corre- sponding fingers. They arise by a double origin, between which the perforating arteries pass. But while one of these origins is limited to the back part of the lateral surface of one of the metacarpal bones, the other occupies the whole length of the corresponding lateral surface of the other metacarpal bone. From this double origin the fleshy fibres pass obliquely forward round a tendon, which only emerges from them near the metacarpo-phalangal articulation ; it then expands, and is inserted partly to the upper end of the first phalanx and partly to the outer edge of the corresponding extensor tendon. Relations. — The dorsal interossei correspond behind with the dorsal surface of the hand and the extensor tendons, from which they are separated by a very thin aponeurosis ; in front, they are visible in the pahn of the hand by the sides of the palmar interossei, and, like the latter, are covered by the muscles and tendons of the palmar region, being separated from those parts by the deep palmar fascia. A distinct cellular line, or, rather, an aponeurotic septum, intervenes between one of their lateral surfaces and the corresponding palmar interosseous muscle ; the other lateral surface is in relation, through its entire length, with the metacarpal bone on which it is implanted. Acticm. — These muscles are evidently abductors of the first phalanges of the fingers, the axis of the hand being taken as the point of departure. Their insertion into the ex- tensor tendons explains why previous extension of the fingers is necessary to the move- ment of abduction. The Jirst dorsal interosseous muscle merits a special description. It is larger than thc others, on account of the greater size of the space occupied by it ; it is flat and triangu- lar, and arises by two origins, separated, not by a perforating branch, but by the radial artery itself A fibrous arch completes the half ring formed by the interval between the first two metacarpal bones for the passage of this artery. The external head of the muscle arises from the upper half of the inner border of the first metacarpal bone ; the internal from the entire length of the external surface of the second metacarpal bone, and from the ligaments which unite it to the trapezium. From these points the fleshy fibres proceed, forming two thick bundles, which are perfectly distinct above, and con- verge to a tendon that is attached to the outer side of the first phalanx of the index finger. 264 MYOLOGY. Relations. — It is covered behind by the skin ; it corresponds in front to the adductor and flexor brevis polhcis, excepting below, where it is sub-cutaneous. Its lower edge, directed obliquely downward and inward, is immediately sub-cutaneous, and crosses the corresponding edge of the adductor pollicis at a very acute angle. The Palmar Interossei. These, like the preceding, are short, prismatic, triangular, and penniform muscles. They are three in number {jp p p,fig- 123) according to most authors, but four if we in- clude the adductor pollicis. They all occupy the palm of the hand, as their name indi- cates, and extend from the entire length of one of the metacarpal bones bounding the interosseous space in which they are situated to the first phalanx of one of the corre- sponding fingers, and to its extensor tendon. They arise from about the anterior two thirds of the lateral surface of only one meta- carpal bone ; they are, therefore, covered behind by the dorsal interossei, which, being attached to the entire lateral surface of the other metacarpal bone, project equally into the palm. Lastly, their insertions into the phalanges and their extensor tendons corre- spond precisely with those of the dorsal interossei. Relations. They are covered by the flexor tendons and by the muscles of the palmar region : each is in relation behind with a dorsal interosseous muscle ; on one side with the dorsal muscle of the corresponding finger, and on the other with the metacarpal bone from which it arises. Action. — They are evidently adductors, as regards the axis of the hand, and, like the dorsal interossei, they bind down the extensor tendons ; they can only act effectually when the fingers have been previously extended. MUSCLES OF THE LOWER EXTREMITIES. The muscles of the lower extremities may be arranged in four groups, viz., those of the pelvis, of the thigh, of the leg, and of the foot. MUSCLES OF THE PELVIS. The Glutcei, Maximus, Medius, et Minirmis. — Pyriformis. — Obturator Interims. — Gemelli, Superior et Inferior. — Quadratus Femoris. — Obturator Externus. — Action of these Muscles. Fig. 124. '^^'^ muscles of the pelvis are divided into those occupy- ing the posterior and those occupying the anterior region. The former are very numerous, consisting of the three glutaei, maximus, medius, and minimus, the pyriformis, the obturator intemus, the gemelli, the quadratus femoris, and the obtura- tor externus. The iliacus, which may with propriety be considered as be- longing to the pelvis, and as forming its anterior region, has been already described, together with the psoas, under the name of the ^'soas-zYiac muscle. The Glutceus Maximus. Dissection. — Having placed the subject on its face, raise the pelvis by a block, flex the leg forcibly, and rotate it inward ; then make an oblique incision along the middle of the but:- tock, from the sacrum towards the great trochanter, dividing botli the skin and fascia covering the muscle : dissect up the two flaps, one from below upward, the other from above down- ward, following the direction of the muscular fibres. The giutcBus maximus {a, fig. 124) is the most superficial of the muscles on the posterior aspect of the pelvis ; it is broad, thick, and pretty regularly quadrilateral ; it is the largest mus- cle of the human body, in this respect coinciding with the great size of the pelvis and femur in man ; it causes the prom- inence of the buttocks. Its great size is one of the most dis- tinctive characters of the muscular system of man, and has reference to his biped position. Attachments (see a, fig. 125). — It arises fi'om the posterior semicircular line of the ihum, and the portion of the bone be- hind that line ; from the vertical sacro-iliac ligament, and the outer margin of the common aponeurosis of the posterior spi- nal muscles ; from the crest of the sacrum, sometimes only from the tubercles which form a continuation of the trans- verse processes of the vertebrse on the outside of the posterior THE GLUTEUS MEDIUS. 265 sacral foramina ; from the edges of the coccyx, and the notch terminating the crest of the sacrum below, this origin being often effected by means of a tendinous arch, under which the last posterior sacral nerves pass ; from the posterior surface of the great sacro-sci- atic hgament ; and, lastly, from the posterior surface of the aponeurosis of the glutseus medius. It is inserted {a, Jig. 125) into the rough line leading from the great trochanter to the linea aspera of the femur. The fleshy fibres arise either directly or by short tendinous fibres, and proceeding par- allel to each other outward, and a little downward, unite into large distinct fasciculi, ca- pable of being separated through their entire length, and constituting an extremely thick, quadrilateral, and very regular muscle, which, having reached the outside of the thigh, terminates by tendinous fibres. These are received between two layers of the fascia lata, which is here very thick ; in passing downward they converge, escape from the fascia lata, curve round the base of the great trochanter, or, rather, the tendon of the vas- tus externus, from which they are separated by a synovial bursa, and are successively" inserted by so many large fasciculi into the series of tubercles and depressions, extend- ing from the great trochanter to the linea aspera, and from the external bifurcation of that hne. The lower fleshy fibres are attached directly to the linea aspera, and a cer- tain number are inserted merely into the fascia lata. In order to obtain a good view of the femoral insertions of this muscle, its tendon must be separated from the fascia lata. Relations. — It is covered by a large quantity of fat, being separated from it by an ex- pansion from the aponeurosis of the glutaeus medius, from which are given off the cellu- lar prolongations that divide the muscle into thick, parallel, and easily separable fasciculi. It covers the glutaeus medius, the pyriformis, the gemelli, the obturator internus, the quadratus femoris, the great sciatic notch, and the tuberosity of the ischium, together with the muscles attached to it, viz., the semi-tendinosus, the semi-membranosus, and the long head of the biceps. It covers also the great trochanter, the adductor magnus, and the triceps femoris, the glutaeal, ischiatic, and internal pudic vessels and nerves, and the great sciatic nerves. Its upper border is very thin, and rests upon the glutaeus me- dius ; its lower border forms a very marked prominence beneath the skin, that affords the surgeon very precise indications, both in the diagnosis of many diseases of the hip- joint ; in operations performed for the purpose of reaching the tuberosity of the ischium, when it is either carious or necrosed ; in those for the relief of sciatic hernia ; or, lastly, in searching for the sciatic nerve, whenever it becomes necessary to operate upon it. Several bursas mucosae, which have been well described by Monro, separate the glutaeus maximus from the eminences which are covered by it. One of these separates it from the great trochanter, and is almost always multi-locular : I have seen it filled with a san- guineous synovia. A second exists over the tuberosity of the ischium, but is often want- ing ; and a third between the tendon of this muscle and the vastus externus.* Action. — The glutaeus maximus is an extensor, an abductor, and a rotator of the thigh outward. When the femur is fixed, as in standing, it acts upon the pelvis, which it draws backward and to its own side, and rotates so that the anterior surface of the trunk is turned to the opposite side. Besides this, it is easy to see that the lower fibres can act as adductors. By its connexions with the fascia lata, it is one of the principal tensors of this structure ; by its attachment to the coccyx, it tends to prevent that bone from being thrown backward, forward, or to one side. The Glut (BUS Medius. Dissection. — Make a vertical incision through the middle of the glutaeus maximus, or detach that muscle from the pelvis ; remove the adipose tissue from the sub-cutaneous portion of the muscle, and also the fascia lata ; dissect the tensor vaginae femoris, which covers the anterior fibres of this muscle. The glutaus medius {b,figs. 124 to 127) is intermediate to the other two glutsei, both as regards size and position ; it is a broad, thick, radiated muscle, situated more deeply than the preceding, beyond which it projects upward and forward {fig. 124). The glu- taeus maximus is attached to a small portion only of the ihac fossa : the glutaei medius and minimus share almost the whole of it between them. Attachments. — It arises from the whole extent of the curved triangular surface included between the superior semicircular hne behind, the anterior three fourths of the crest of the ihum above, and the inferior semicircular line below ; from the anterior superior spine of the ilium and the notch immediately below it ; from the deep surface of a dense aponeurosis, which is inserted into the outer lip of the crest of the ilium, covers all the upper portion of the muscle, and becomes continuous with the fascia lata : opposite the junction of the anterior with the middle third of the crest of the ilium, at which point a large tubercle exists upon the bone, this aponeurosis is so dense as to resemble a tendon. The muscle also arises from a deep aponeurosis, extending from the anterior part of the inferior semicircular line, and giving attachment, on its external surface, to a great num- ber of fleshy fibres ; and, lastly, from the fascia lata internally to the tensor vaginae femo- ris. It is inserted into the external surface of the great trochanter {figs. 125, 127). * See note, p. 296. L L 266 MYOLOGY. From these numerous origins the fleshy fibres proceed in different directions ; the pos- terior forward, the middle vertically, and the anterior backward, becoming more and more horizontal in front. They all terminate upon the two surfaces and edges of a radiated aponeurosis, the fibres of which are gradually concentrated, and folded upon themselves, so as to form a flat tendon, inserted, not into the upper border, as it is generally said, but into the external surface of the great trochanter, along an oblique line running downward and forward, so that the anterior fibres of the muscle are inserted into the anterior ex- tremity of the lower border of the great trochanter, and the posterior fibres into the back part of the upper border ; at this latter point a well-marked projection sometimes exists, the size of which generally indicates the power of the glutaeus medius. A synovial bursa intervenes between the tendon and that part of the great trochanter over which it passes.* Relations. — It is covered by the glutaeus maximus, the tensor vaginae femoris, and the skin : it covers the glutaeus minimus, with which its outer border is blended, and the gluteeal vessels and nerves. Its lower border is parallel with the pyriformis {fig. 125). Action. — The glutaeus medius is both an extensor and an abductor of the thigh. More- over, the anterior fibres rotate the femur inward, and the posterior outward ; but the for ■ mer have the greater power, for they are more numerous, the muscle being twice or thrice as thick in front as behind ; it is, therefore, an extensor, an abductor, and a rotator inward of the thigh. Winslow denies that it is an extensor, and considers it only as an abductor ; this is only true in the position of standing upon both feet. In the sitting pos- ture, again, this muscle in some degree loses its power as an extensor and abductor, and acts merely as a rotator. When the femur is fixed, as in standing, the glutaeus medius extends the pelvis, draws it to its own side, and rotates it, so that the front of the trunk is turned towards the same side. It co-operates with the glutaeus maximus in the first two motions, but antagonizes it in the last. Finally, its anterior fibres appear to me calculated to flex the thigh upon the pelvis, especially when the flexion has been already conmienced by other muscles. The Gluteus Minimus. The glutceus minimus (c, fig. 127) is exposed by simply cutting across the preceding muscle, beneath which it lies ; it is thinner, and more regularly radiated. It arises from the anterior part of the crest of the ilium, below the glutaeus medius, from the outside of the sciatic notch, and from all that part of the external iliac fossa situated below the in- ferior semicircular line : from these points the fibres converge, the middle passing ver- tically, the posterior forward, and the anterior backward, to the deep surface of a radia- ted aponeurosis, the fibres of which are collected together into bands, that are inserted separately into the anterior border and anterior half of the upper border of the great tro- chanter. Most conamonly the posterior band is intimately attached to the tendon of the pyriformis. Relations. — It is covered by the glutaeus medius, with which its anterior fibres are blended ; it covers the external iliac fossa, the reflected tendon of the rectus femoris, and the upper part of the hip-joint, from which it is separated by some fatty cellular tissue. Action. — It is much more directly an abductor than the preceding muscles. Its ante- rior half rotates the thigh inward, and its posterior half outward. If the femur be fixed, it extends the pelvis, inclines it to its own side, and turns the anterior aspect of the trunk to the same side ; by its anterior fibres it assists slightly in producing flexion. General Remarks upon the Action of the Glutczi. — The three muscles we have just ex- amined generally have their fixed points upon the pelvis ; and, in this point of view, are of the greatest importance in the standing posture. By their means the pelvis, finiily held down from behind, is enabled to resist the effects of the weight of the trunk, which tends to throw it forward : hence the enormous development of these muscles in man, evidently proving his destination for the erect position. These same muscles are the principal agents in the position of standing upon one foot, inclining the pelvis to their own side, and balancing the entire weight of the opposite side of the trunk. They also rotate the trunk when the individual is standing upon one foot. They are all extensors and abductors ; the glutaeus maximus is a rotator outward ; the other two are rotators inward. Hence we may understand how the thigh can be so powerfully rotated inward, although there are no direct muscles for that purpose ; while a great number are spe- cially intended to produce rotation outward, which movement, indeed, is performed much more energetically than rotation inward. The Pyriformis. Dissection. — Detach the glutaeus maximus, and separate the pyriformis from the lower border of the glutaeus medius, to which it is parallel. In order to see the sacral attach- ments of the muscle, make an antero-posterior section of the pelvis. The pyriformis or pyramidalis {d, fig. 125) is sometimes double : it is a flat muscle, of a pyriform, or, rather, pyramidal shape, lying almost horizontally along the lower margin of the glutaeus medius, with which it seems to be continuous, and is sometimes intimately * See note, p. S296. THE OBTURATOR INTERNUS. 267 united : it is partly situated in the cavity of the pelvis, and assists in filling up the sciat- ic notch. Attachments. — It arises from the anterior surface of the sacrum {p,fig. Ill), in the in- tervals between the grooves forming the continuations of the anterior sacral foramina, and also opposite those grooves, by three or four digitations, vi^hich are sometimes trav- ersed by the great sciatic nerve : these origins are sometimes concentrated into a small space around the second and third anterior sacral foramina. It also arises from the an- terior surface of the great sacro-sciatic ligament, and from the upper part of the sciatic notch. It is inserted into the back part of the upper edge of the great trochanter. The fleshy fibres pass from their origins almost horizontally outward and a little backward, and form a muscle which fills up the upper part of the great sciatic notch, and, becoming much narrower immediately after emerging from the pelvis, from the convergence of its fibres, terminates on the posterior surface and edges of an aponeurosis, which is after- ward converted into a round tendon, and is fixed to the upper border of the great tro- chanter, behind the glutaeus minimus, and above the gemelli and obturator internus, with which it is almost always intimately connected. Relations. — Its anterior surface is in relation with the rectum, the sciatic plexus, and the hypogastric vessels within the pelvis, and with the hip-joint outside that cavity ; its posterior surface, with the sacrum and the glutaeus maximus ; its upper margin, with the glutseal vessels and nerves, which separate it from the glutseus medius ; its lower mar- gin, with the ischiatic vessels, and with the great and small sciatic nerves. Sciatic her- niae take place between the upper margin of this muscle and the sciatic notch. Some- times the muscle reaches the summit of the notch ; occasionally, a considerable interval exists between them ; in such cases, there is a predisposition to this species of hemiae. The Obturator Internus. The obturator internus {e,fig. 125) is a triangular reflected muscle, extending from the inner surface of the margin of the obturator foramen to the digital cavity of the great trochanter. Its course and direction are alike remarkable. Attachments. — It arises from the posterior surface of the obturator ligament, from the pelvic fascia lining the inner surface of this muscle, and from the tendinous arch which converts the sub-pubic groove into a canal ; also, from the entire circumference of the ob- turator foramen, viz., from the internal surface of the descending ramus of the pubes and the ascending ramus of the ischium, and from the whole extent of the quadrilateral sur- face situated between the obturator foramen and the sciatic notch ; and, lastly, by a few fibres from the brim of the pelvis. It is inserted into the digital cavity of the great tro- chanter. The fleshy fibres arise directly from this extensive surface, and, converging downward and outward, pass out of the pelvis through a triangular opening formed by the spine of the ischium and lesser sacro-sciatic ligament above, by the great sacro-sciatic ligament on the inside, and by the body of the ischium on the outside. At its exit from the pelvis the muscle becomes much narrower, is reflected at a right angle over the body of the ischium as over a pulley, is next received into a groove formed for it by the gemelli, and proceeds horizontally outward, to be inserted into the digital cavity of the great tro- chanter below the p3Tiformis. In order to obtain a good view of the structure of this muscle, it must be detached from its insertion and turned inward. We shall then per- ceive that the tendon divides into four or five diverging portions upon the deep surface of the muscle, which are lost in its interior. A well-marked synovial membrane* inter- venes between the tendon and the trochlear surface on the body of the ischium, which is covered with cartilage that is streaked, as it were, in the direction of the movements. Cowper and Douglas alluded to the presence of this bursa when they named the muscle marsupialis vel bur salts. Relations. — In the pelvis the obturator internus is in relation with the obturator liga- ment and the circumference of the obturator foramen, by its anterior surface ; and with the pelvic fascia and levator ani muscle, which separates it from the bladder, by its pos- terior surface. During its passage through the orifice I have described, it is in relation with the internal pudic vessels and nerves ; externally to the pelvis, it is covered by the great sciatic nerve and the glutaeus maximus, and it covers the hip-joint. From the great extent of the pelvic origins of this muscle, ahnost the whole of the an- terior and lateral parietes of the pelvis are covered internally by a layer of muscular tis- sue ; the posterior wall is also in a great measure covered by the pyriformis. The origins of the muscular fibres from the tendinous arch of the obturator ligament are so arranged, that the contraction of the muscle can have no eflect in diminishing the size of the sub-pubic foramen intended for the passage of vessels and nerves. There are sometimes two small tendinous arches ; one for the nerve, the other for the artery and vein. The Gemelli^ Superior et Inferior. The gemelli (gemini, Albinus ; les petits jumeaux, Winslow, f and g, fig. 125), two small * See note, p. 295. 268 MYOLOGY. fleshy fasciculi, accessories to the obturator intemus, are generally distinguished by anat- omists into the superior (/) and the inferior (g) ; they are separated from each other by the tendon of the obturator intemus, for the reception of which they form a groove. Above and below this groove they take their origin ; the superior from the spine of the ischium, and the inferior, which is the larger, from the tuberosity of that bone, immedi- ately above the attachment of the great sacro-sciatic ligament, and even slightly from the ligament itself. They both pass horizontally outward, are sometimes united either behind or in front of the tendon of the obturator intemus, which they then completely embrace, and with which they are entirely or partially blended, being inserted with it into the digital cavity of the great trochanter. Their relations are the same as those of the reflected portion of the obturator intemus. The gemellus superior is often wanting, and the inferior is frequently double. I have several times seen the superior terminate in the tendon of the pyriformis, and the in- ferior in the tendon of the obturator intemus. Action. — They rotate the thigh outw-ard. Their relations with the synovial capsule of the obturator intemus led to their being designated marsupiales by Cotoper, and by Portal, le muscle capsulaire de la capsule du tendon de I'obturateur interne. The Quadratus Femoris. This muscle (i, fig. 125), shaped like a parallelogram, is situated immediately below the gemellus inferior. It arises from the extemal border of the tuberosity of the ischium, in front of the semi-membranosus, from which it is separated by adipose tissue. From this point the fibres proceed horizontally outward, parallel to each other, and are inserted into " an oblong ridge* projecting partly from the back of the root of the great trochan- ter, and partly from the femur inmiediately below it ;" but above the attachment of the adductor magnus, with which, at first, it appears to be continuous, but from which it is always separated by the internal circumflex vessels. This muscle is sometimes wanting ; but very frequently its pelvic attachments are pro- longed as far as the ascending ramus of the ischium ; in which cases it is twisted inferi- orly upon itself, so as to oppose a surface, not a border, to the adductor magnus. Its re- lations behind are the same as those of the preceding muscles ; in front, it covers the obturator externus and the lesser trochanter, from which it is often separated by a sy- novial capsule. The Obturator Externus. Dissection. — The lower or horizontal portion of the obturator externus is exposed, by dividing the quadratus femoris into two equal parts by a vertical incision. In order to see the upper or pelvic portion, it is necessary to detach the gracilis, pectineus, psoas, Ui- acus, and adductor brevis. This is a triangular, flat muscle (e, fig. 127), of the same shape, but thinner and smaller than the obturator internus, and, like it, reflected, though at an obtuse angle. It arises from the circumference of the obturator foramen, from the obturator ligament, and from the tendinous arch which completes the sub-pubic canal for the vessels and nerve. It is inserted into the deepest and lowest part of the digital cavity of the great trochanter. The fleshy fibres arise directly, the lower ones proceed horizontally outward, and the upper obliquely downward, backward, and outward ; thus converging, they form a fleshy belly, which turns round the neck of the femur, and terminates in a tendon that passes horizontally outward, to be inserted into the digital cavity, below the gemelli and the ob- turator internus. Relations. — Its outer and anterior surface is in relation with the pectineus, the adduc- tors, the psoas and iliacus muscles, and more externally with the neck of the femur and the lower part of the capsular ligament of the hip-joint. Its inner and posterior surface is in contact with the obturator foramen and the quadratus muscle. Action of the preceding Muscles. The last six muscles are evidently rotators of the thigh outward. The pyriformis, the gemelli, and the obturator internus, which are almost always united at their insertions, would deserve the name of quadri-gemini, given by the older anatomists to the gemeUi, the pyriformis, and the quadratus. WTien they take their fixed point upon the femur, as, for example, in standing upon one foot, they become rotators of the pelvis, and turn the anterior surface of the trunk to the opposite side. They are only rotators when the limb is extended ; in the sitting posture, they become abductors. Winslow, who first demon- strated their use in abduction in the semiflexed position, attached great importance to the connexion of so many of these muscles with the capsular ligament, which he believed prevented pinching of the capsule during the different movements of the joint. The insertion of these muscles is exceedingly favourable. Moreover, we shall find, that besides the glutaeus maximus and the posterior fibres of the glutaeus medius and * [M. Cruveilhier states the insertion of the quadratus femoris to be into the inter-trochanteric line. The description in the text, copied from Albinus, gives a more accurate idea of the insertion of this muscle.] THE BICEPS CRURIS. 269 minimus, they have many other muscles as accessories in rotation. The effects pro- duced by the contraction of the two obturators can be easily understood, if we bear in mind that the action of a reflected muscle is to be calculated from the point of reflection, leaving the rest of the muscle out of consideration. Thus, with regard to the obturator internus, the sciatic notch acts as a pulley, and may be regarded as the fixed point. MUSCLES OF THE THIGH. The Biceps Cruris. — Semi-tendinosus. — Semi-memlranosus. — Tensor Vagince Femoris. — Sartorius. — Triceps Extensor Cruris. — Gracilis. — Adductor Muscles of the Thigh. The muscles of the thigh are divided into those of the posterior region, viz., the biceps, the semi-tendinosus, and the semi-membranosus ; those of the external region, viz., the tensor vaginee femoris and the vastus extemus ; those of the anterior region, viz., the sartorius, the rectus, and the triceps extensor cruris of authors ; and, lastly, those of the internal region, viz., the gracilis, the pectineus, and the three adductors. Posterior Region. The Biceps Cruris. Dissection. — This is the same for the biceps, the semi-tendinosus, and the semi-mem- branosus. Place the subject upon its face, with a block under the pelvis, and allow the leg to hang over one side of the table. Make an incision from the middle of the space between the tuberosity of the ischium and the great trochanter to the interval between the two condyles of the femur. Both the skin and the fascia of the thigh must be di- vided in this incision. Cautiously remove the cellular and adipose tissue surrounding the subjacent muscles, the relations of which w-ith the popliteal vessels and nerves must be carefully studied. In preparing the superior attachments of these muscles, the glu- taeus maxiraus must be divided in the middle, perpendicularly to its fibres. The biceps femoris (biceps cruris, Albinus, I, figs. 124, 125), so named because it con- sists of two fleshy bodies or heads above, is a long, large muscle, situated on the poste- rior and external aspect of the thigh. Attachments. — It arises from the tuberosity of the ischium and the linea aspera of the femur, and is inserted into the head of the fibula, and slightly pig 125 into the external tuberosity of the tibia. Its origin from the ischium (I, fig. 125) is common to it and the semi-tendinosus ; it takes place, not from the tuberosity properly so called, but from the highest and most external part of the tuberosity, above and behind the adductor magnus, and immediately be- low the gemellus inferior. It arises by a tendon which is sel- dom completely free from muscular fibres. This tendon, at first very thick, and separated from the tuberosity of the ischium by a synovial bursa, expands into an aponeurosis, ■which gives origin to the fleshy fibres of the biceps by its ex- ternal edge and posterior surface, and to those of the semi- tendinosus by its internal surface. Up to this point the biceps and semi-tendinosus are blended together so as to form a single fleshy belly, which, after extending from two to four inches, is divided into two portions : one posterior and external, consti- tuting the long head, or ischiatic portion of the biceps ; the other anterior, forming the origin of the semi-tendinosus, which we shall next describe. Arising thus in succession, the fleshy fibres of the long head of the biceps form a fusiform belly passing obliquely downward and a little outward, and termina- ting on the anterior surface of an aponeurosis, which extends for a considerable distance on the posterior surface of the muscle, and which gradually becomes contracted, so as to form the terminal tendon. Just where these fleshy fibres are about to terminate (hfig- 125), the aponeurosis receives upon its anterior surface and external edge the fleshy fibres of the short head, or femoral portion of the biceps. This portion of the muscle {I', fig. 125) arises from the greater part of the in- terval between the two margins of the hnea aspera, and the posterior surface of the external inter-muscular septum of the thigh ; it passes downward, inward, and backward, to be at- tached to the common tendon, almost as far as its insertion. This insertion is not confined to the head of the fibula, but extends also to the external tuberosity of the tibia by means of a strong division of the tendon, which, at the same time, gives off an expansion to the fascia of the leg. The insertion into the fibula is ef- 270 MYOLOGY. fected on the outer side, in front of and behind the external lateral ligament of the knee- joint, which ligament it embraces in a bifurcation. Relations. — The biceps is covered by the glutaeus maximus and the femoral fascia. It covers the semi-tendinosus, semi-membranosus, and vastus extemus. It is in relation, also, with the great sciatic nerve, which is placed at first externally, then in front, and, lastly, on the inside of the muscle ; finally, its short head is in relation with the popliteal vessels. The biceps forms the external border of the popliteal space ; near its termination it is in relation with the outer head of the gastrocnemius and with the plantaris longus muscle. Actioyi. — The biceps flexes the leg upon the thigh. When this movement is com- pleted, its long portion extends the thigh upon the pelvis. From its obliquity downward and outward, it rotates the leg outward during semi-flexion ; but this rotation is impos- sible when the leg is extended, in consequence of the tension of the crucial ligaments. The fixed point of this muscle is as often below as above, and it then performs an im- portant part in the mechanism of standing ; for it tends to prevent the individual from falling forward, because it holds back the pelvis. When the pelvis is thrown quite back- ward, this muscle can then flex the thigh upon the leg. The Semi-tendinosus. The semi-tendinosus {m,figs. 124, 125), so named on account of the great lengtn of its tendon, is situated on the posterior and internal aspect of the thigh. Attachments. — It arises from the tuberosity of the ischium, and is inserted into the an- terior tuberosity of the tibia. Its origin {m,fig. 125) consists of a tendon common to it and the long head of the biceps, which is prolonged in the form of an aponeurosis, upon the external (or popliteal) border of the muscle. Some of the fleshy fibres are attached directly to the tuberosity of the ischium. Having arisen in this manner, it enlarges and constitutes a fusiform bundle, which passes at first vertically downward, and then ob- liquely inward. About four or five fingers' breadth above the knee-joint it terminates in a long, thin tendon, which turns round the internal tuberosity of the tibia, describing a curve having its concavity directed forward, and is then reflected horizontally forward, to be inserted into the anterior teberosity of that bone, behind the tendon of the sarto- rius, and parallel with the lower edge of that of the gracilis, to which it is united. The union of these three tendons constitutes the patte d'oie (goose's foot). The length of its tendon of insertion is the most characteristic feature of the muscle ; and hence its name, semi-nervosus {Spigelius), and le demi-nerveux ( Winslaw), for which the term semi-tendinous has now been substituted. The structure of this muscle is re- markable. The fleshy fibres are interrupted across the middle by a tendinous intersec- tion, analogous to that of the great complexus, which gives origin to new fleshy fibres. Relations. — It is covered by the glutseus maximus and the femoral fascia, and it cov- ers the semi-membranosus and part of the upper portion of the adductor magnus. Its tendon is first placed behind the semi-membranosus, and then, before it turns round the internal tuberosity of the tibia, between the tendon of that muscle and the inner head of the gastrocnemius. Action. — The same as that of the biceps. It is a very powerful flexor, on account of the reflection of its tendon. Its oblique direction enables it to rotate the tibia inward du ring semi-flexion of the leg. It is, therefore, a congener of the pophteus. The Semi-membranosus. The semi-membranosus {n,figs. 124, 125) is situated upon the posterior aspect of the thigh, thin and aponeurotic above, thick and fleshy below. Attachments. — It arises from the upper and outermost part of the tuberosity of the is- chium, in front of the biceps and semi-tendinosus ; and is inserted into the internal tuber osity of the tibia, and also, by an expansion of its tendon, into the femur. It arises by means of a very thick tendon, which becomes wider immediately after its origin. From its inner border is given off" an aponeurotic lamina, that splits into two layers, from the in- terval between which the superior fleshy fibres arise. Lower down, the muscular fibres proceed directly from the tendon itself, which runs along the outer (or popliteal) border of the muscle, as far as the lower fourth of the thigh, but is afterward buried in its sub- stance. The union of all these fibres constitutes a very thick, four-sided, fleshy belly, which is received into a tendinous semi-cone, open on its outer side, and soon becoming converted into a thick tendon, which, after a passage of a few lines, separates into three divisions, terminating in the following manner : the posterior division passes inward and upward, forms the chief part of the posterior ligament of the knee-joint, and is inserted into the femur ; the middle division is attached to the back of the internal tuberosity of the tibia, below the articular surface ; the third is horizontal, and turns round the inter- nal tuberosity of that bone in the horizontal furrow existing there, and is inserted on the inner side of the tuberosity. A synovial bursa intervenes between it and the bone. Relations. — The semi-membranosus is covered by the glutaeus maximus, the semi-ten- THE TENSOR VAGINiE FEMORIS. THE SARTORIUS. 271 dinosus, the biceps, and the femoral fascia : it covers the quadratus femoris, the adduc- tor niagnus, and the inner head of the gastrocnemius. A synovial membrane separates it from the knee-joint. It also covers the popliteal artery and vein, w^hich soon come into relation with its outer or popliteal border. The sciatic nerve lies parallel with its outer border through the whole of its extent ; the gracilis is in contact with its inner border. I shall remark here, that the biceps on the outside, and the semi-membranosus and semi-tendinosus on the inside, constitute the lateral boundaries of a cellular interval which extends along the whole of the back of the thigh, and is continuous with the pop- liteal space. This large cellular interval communicates above with the cellular tissue of the pelvis at the sciatic notch, and below with the fossa of the ham. It is in this di- rection that purulent matter so readily escapes from the pelvis. The greater part of this interval is destined for the great sciatic nerve, which, however, is soon accompani- ed by the popliteal vessels. Action. — Precisely similar in nature to that of the preceding muscle, but much more powerful. The momentum of all these flexor muscles occurs, on the one hand, during semi-flexion of the leg upon the thigh ; and, on the other {i. e., when their lower attach- ments are fixed), during semi-flexion of the thigh upon the pelvis. External Region. The Tensor Vagina. Femoris. Dissection. — In order to expose this muscle, it is sufficient to make a vertical incision through the thick, tendinous layer given off from the anterior portion of the crest of the ilium, and to dissect back the two flaps of that aponeurosis. The tensor vagina femoris (le muscle du fascia lata, o,fig. 126) is the largest of all the extensor muscles of aponeuroses : it is a short, flat, quadrilateral muscle, contained within the substance of the fascia lata, and occupying the upper third of the external region of the thigh. It arises from the anterior part of the outer margin of the crest of the ilium, and from the outer border of the anterior superior spinous process of the ilium, between the sartorius and the glutaeus medius, by means of a tendon, which also furnishes some points of attachment to the anterior fibres of the last-named muscle. From these points the fleshy fibres proceed downward and a little backward, and, at about the upper fourth or third of the thigh, terminate in a series of smaU tendinous bundles, the anterior of which become continuous with the fascia lata, while the posterior cross obliquely over the vertical fibres of the fascia, with which they are very soon blended. Relations. — It hes between two layers of the fascia lata, the external layer being much thicker than the internal. It is covered by the skin, and it covers the glutaeus medius, the rectus, and the vastus externus. Its anterior border is in contact with the outer edge of the sartorius, but is soon separated from it by a triangular space, in which the rectus femoris may be seen. Action. — It is a tensor, not only of the entire femoral fascia, but particularly of the very dense portion or band of the fascia lata, which, being continuous with it, may be regard- ed as an aponeurotic tendon to this muscle (muscle aponeurotique de la bande large, Winslow), and which is inserted into the outer tubercle of the anterior tuberosity of the tibia, and into the adjacent part of its external tuberosity. When the tensor vaginae is in action, this band compresses the vastus externus, which has so great a tendency to displacement ; by means of this band, also, the muscle acts upon and extends the leg. Lastly, on account of its slight obliquity downward and backward, it may be regarded as a rotator of the thigh inward ; it is but Uttle concerned, however, in the production of this movement, which, as I have already said, is chiefly effected by the anterior fibres of the glutaei medius and minimus. Anterior Region. The Sartorius. Dissection. — This is common to all the muscles of the anterior and inner regions of the thigh. Make a horizontal incision along the femoral arch, and another perpendicu- larly from the middle of that to the anterior tuberosity of the tibia. Dissect the fascia of the thigh with care. As all the muscles of the anterior and inner region are separa- ted from each other by distinct sheaths, their dissection consists simply in opening these sheaths successively, and removing the cellular tissue that fills up the inter-muscular spa- ces. It is necessary to preserve the vessels, in order to obtain a good view of their rela- tions : avoid opening the vena saphena, as it generally contains a large quantity of blood, the escape of which will impede the dissection. If the vein should be opened, it must be tied above and below the orifice, and then cut across. When the superficial muscles have been studied, they must be divided in the middle, in order to expose the muscles of the deep layers. The sartorius {p, fig. 126), so named on account of its uses, crosses diagonally over the anterior, and then the inner part of the thigh, to the top of the leg. It is the longest mus- cle in the body, both as regards its total length, and more especially in reference to the 272 MYOLOGY. Fig. 126. length of its fibres ; whence the name of longus, given to it by Riolanus. This is the case even although it be measured by a line stretched directly between its two extremities. Attachme7its. — It arises from the anterior superior spinous pro- cess of the ilium, from the upper half of the notch below that pro- cess, and from a tendinous septum between the muscle and the fascia lata. It is inserted into the inner margin of the crest of the tibia, situated beneath the ligamentum patellas. Its origin con- sists of some tendinous fibres, which are more marked behind and on the outer side than in front and within. The fleshy fibres coimnence almost immediately, and form a flat, riband-like mus- cle (fascialis, Spigelius), which in reality is prismatic and trian- gular, as well as the tendinous sheath in which it is enclosed, s j-p. The muscle increases in breadth as far as the lower third of the |[ll 1. thigh, and passes obliquely downward, inward, and a little back- ward ; it becomes internal and vertical at the lower third {p, figs. 134, 125), and reaches the back part of the inner condyle of the femur, to turn round the knee-joint, tendinous fibres having al- ready commenced on the anterior edge of the muscle. The fleshy fibres terminate precisely where the muscle changes its direction to pass forward. The flat tendon by which they are succeeded is at first narrow, but becomes considerably expanded, to be inserted into the crest of the tibia, in front of the tendons of the semi-ten- dinosus and gracilis muscles, with which it is united, so as to form what is called the fatte d'oie (goose's foot). A synovial membrane separates it from the tendons of these muscles. A considerable tendinous expansion is given ofl!"from its lower edge, and contributes to form the inner part of the fascia of the leg. Relations. — The sartorius is the most superficial muscle in the anterior aspect of the thigh ; it lies beneath the femoral fascia, and covers the psoas and iliacus, the rectus, the vastus internus. the adductor longus, the gracilis, the adductor magnus, and the internal lateral ligament of the knee-joint. The borders of this muscle deserve particular attention, because incisions for ligature of the femoral artery must be made along them. Its most important relation, indeed, is with the femoral artery and vein ; it is the satellite muscle of the femoral artery. Thus, in the upper third of the thigh, it forms, with the adductor longus and femoral arch, an isosceles triangle, having its base turned upward, and the femoral artery represents a perpendicular drawn from the apex to the base of the triangle. In the middle third of the thigh, the artery is in relation, first, with the inner border, then with the posterior surface, and, lastly, with the outer border of the muscle. In the lower third, the sarto- rius occupies a deep groove, formed by the gracilis and vastus internus ; from the latter muscle it is separated below by an interval containing adipose tissue, of which circum- stance advantage maybe taken in the application of issues. It also covers the saphenus nerve (a deep branch of the anterior crural), which emerges from beneath its anterior bor- der, opposite the lowermost point of insertion of the adductor magnus. Near the knee- joint, the saphena vein is in relation with the posterior border of the muscle. The structure of the sartorius is very simple. The fleshy and tendinous fibres are all parallel, and the former correspond exactly with the length of the muscle. Action. — The sartorius flexes the leg upon the thigh, which it draws inward, so as to cross one leg over the other. When this movement is produced, it flexes the thigh upon the pelvis. If the fixed point of the muscle be at the leg, it then flexes the pelvis upon the thigh, and rotates it, so that the anterior surface of the trunk is directed to the op- posite side. The Rectus Femoris and Triceps Extensor Cruris., or the Triceps Femoralis, I have included under the name triceps femoralis the two muscles, or, rather, the two parts of the same muscle, which are described separately in most anatomical works. The reasons for this arrangement will be understood after the following description of the muscle : I shall consider the triceps femoralis as composed of three portions, viz., a middle or long portion, the rectus femoris of authors ; an external and an internal portion, which constitute together the triceps cruris of authors ; for these I shall retain the names of vastus internus and extcrnus, including in the former the middle portion or crureus, prop- erly so called, of most anatomists. The long portion of the triceps femoralis, or the rectus femoris (r, fig. 126), is situated in the anterior region of the thigh, extending from the anterior inferior spinous process of the ilium to the patella : it is vertical in its direction, thick and broad in the middle, and narrower at its extremities THE RECTUS PEMORIS AND TRICEPS EXTENSOR CRURIS. 273 It arises by a very strong tendon (r, fig. 127), which embraces the anterior inferior spinous process of the iUum, and is proportioned to the power of the muscle. This ten- don receives on its outer side another flat tendon, arising from a groove upon the rim of the cotyloid cavity, and following its curvature ; this is the reflected tendon, which is Wended with and strengthens the straight tendon. It then expands into a broad aponeu- rosis, the outer portion of which is very thin and prolonged over the anterior surface of the muscle as far as the middle, while the inner portion is very thick, and penetrates into its substance nearly as far as its insertion. The fleshy fibres arise from the poste- rior surface and edges, and also from the anterior surface of the inner portion of this aponeurosis ; they all pass downward and backward, the internal inward and the exter- nal outward, and form a fleshy belly, which increases as it proceeds downward, and then terminates on the anterior surface of a broad, thick, and shining aponeurosis, occupying the lower two thirds of the posterior surface of the muscle, and soon becoming contract- ed into a flat tendon, which receives upon its inner edge the superficial fibres of the vastus internus, again expands, and is finally blended with the common tendon of the two vasti. Triceps Femoris of Authors, or Vastus Internus and Ezternus. — This is a voluminous mass of muscular tissue, situated behind the preceding muscle, and extending from the three surfaces of the shaft of the femur to the patella and tibia. It is commonly but er- roneously considered to be divided above into three heads, which are described under the names of vastus internus, vastus externus, and crureus. I have searched in vain for the middle portion, but have never been able to find more than two separate parts : one external, very large and superficial, viz., the vastus externus ; the other internal, anteri- or, and even external, viz., the vastus internus ; it is much smaller than the vastus ex- ternus, and is partly covered by it and by the rectus. The external portion^ or vastus externus {s, figs. 124 to 127). This is the largest portion of the triceps femoralis. It arises from a projecting border or horizontal crest, situated at the base of the great trochanter, and from a vertical edge in front of that trochanter, which forms a continuation of its anterior border, and sometimes presents a very prom- inent tubercle : in the angle formed by these two attachments is situated the tendon of the glutasus medius. It also arises along a line running from the great trochanter to the linea aspera, and from the whole extent of the external lip of the linea aspera itself All the preceding origins are effected by means of a broad aponeurosis which covers the superior three fourths of the muscle, and from the deep surface of which almost aU the fleshy fibres proceed. Lastly, some of these arise from the tendon of the glutaius max- imus, and from the tendinous septum intervening between the vastus externus and the short head of the biceps. From these origins the fleshy fibres proceed, some vertically downward, the others somewhat obliquely downward and forward, the lowest being the shortest and the most oblique ; they form a large bundle, which partially covers the an- terior portion of the vastus internus, but is separated from it by vessels, nerves, and cel- lular tissue. After a course of variable length, some of the fleshy fibres are attached to the deep, but the greater number to the superficial surface of another equally strong apo- neurosis : this becomes thickened and contracted into a flat tendon, which is sometimes divided into thick parallel bands, emerges from the fleshy fibres at the external margin of the rectus, and is inserted into the outer half of the upper border of the patella, being blended on the inner side with the rectus and the vasttis internus. The lower fleshy fibres which arise from the inter-muscular septum are attached directly to the outer bor- der of the patella.* The internal or anterior portion, vastus internus {t and u,jig. 127), is much smaller than the external, and surrounds the femur. Its inner portion lies immediately under the fas- cia, and is the only part which is generally described as the vastus internus {t,figs.l2(}, 127). Its anterior portion is covered by the rectus, or long portion, and is usually called the crureus (cruralis. Alb., u,fig. 127). Its outer portion is covered by the vastus externus. with which many of its fibres are blended : but they may always be separated by cutting along the outer margin of the middle aponeurosis. Thus defined, the vastus internus arises from a rough oblique line, extending from the front of the neck of the femur to the linea aspera, and from the internal hp of the linea aspera itself, in front of the adductor muscles : both of these origins are effected by means of an aponeurosis, which is weaker and smaller than that of the vastus externus, and is blended with that of the adductors, concurring with it in the formation of a canal for the femoral artery. It also arises from almost the whole of the internal, anterior, and external surfaces, and from the two ante- rior borders of the femur ; lastly, the lower fibres arise from the internal inter-muscular septum. From these different origins the fleshy fibres pass in various directions ; the external inward, the middle vertically, and the internal, which are the most numerous, downward, forward, and outward ; they thus form a fleshy belly, thicker below and with- in than above and without, and are successively attached to both surfaces, and espe- cially to the posterior surface of a broad aponeurosis, which is covered by the tendon of * The anterior border of this tendon is free, and perfectly distinct from the tendon of the rectus, which is lined by it ; and also from the expanded tendon of the vastus internus. Mm 274 MYOLOGY. the vastus externus, but can be easily separated from it. The inner fibres are attached to the anterior surface of the aponeurosis, and terminate very regularly opposite a verti- cal line, running parallel to the inner margin of the rectus femoris. The aponeurosis extends over the anterior surface of the middle portion of the mus- cle, which lies behind the rectus : this fact has, doubtless, given rise to its division into two parts, viz., a middle, or the crureus, and an internal, called the vastus inlernus. The superficial layer of the internal fleshy fibres is attached below to the inner margin of the rectus, or long portion of the triceps femoralis : the lowest of these fibres, which arise from the inner and inferior bifurcation of the linea aspera, and from the corresponding inter-muscular septum, are almost horizontal, and accompany the tendon as far as its in- sertion into the inner border of the patella. Lastly, the terminating aponeurosis is pro- longed inward to the internal tuberosity of the tibia, below which it is inserted, being covered by the tendons of the semi-tendinosus, semi-membranosus, and gracilis muscles, on the inner side of the internal lateral ligament of the knee. This very strong aponeu- rotic insertion represents the fascia lata on this aspect of the limb, and forms an acces- sory internal lateral ligament. From the above description, it follows that the triceps femoralis is composed of three muscles and three tendons, super-imposed upon each other, viz., the rectus femoris, the vastus externus, and the vastus internus. Relations. — The long portion of the triceps, or the rectus femoris, is covered by the fascia lata in its lower three fourths. Its upper part is covered by the sartorius, by the anterior fibres of the gluteeus medius, and by the psoas and iliacus. It covers the hip- joint, the anterior circumflex vessels, and the two vasti muscles. The vasti surround the femur as in a muscular sheath, and have relations with all the muscles of the thigh. They are superficial in a great part of their extent : in front, they are in relation with the psoas and iliacus, the rectus femoris, and the sartorius, and they lie immediately under the fascia, in the triangular spaces left between these muscles : behind, they are in relation with the biceps and semi-membranosus ; on the inside, with the adductors, with the femoral artery, the sheath of which the vastus internus contributes to form, and with the sartorius ; on the outside, with the glutaeus maximus, which ghdes over the upper end of the vastus externus, and is separated from it by a synovial bursa ; and, lastly, with the tensor vaginas femoris, and the fascia lata. It is necessary to allude here to a small fleshy bundle, formed by the deepest and lowest fibres of the vastus in- ternus, which is always distinct from the rest of the muscle, and is inserted into the up- per part of the synovial membrane of the knee. This bundle has been regarded by Wins- low as an articular muscle, intended to prevent the synovial membrane from being pinched between the surfaces of the joint. Action. — This muscle extends the leg upon the thigh ; its action is facilitated by the existence of the patella, which serves to increase the angle of insertion, and which we have described as a sesamoid bone, developed in the substance of the tendon. We must, therefore, regard the triceps as inserted into the anterior tuberosity of the tibia, or, rath- er, into the lower part of that tuberosity. It should be observed, that the tendon is in- serted into the patella, in front of its base, and not into the base itself, in the same man- ner as the ligamentum patella; is attached to the anterior surface of that bone, and not to the rough mark on its posterior surface : this important arrangement increases the angle at which the moving power operates. The triceps femoralis is the most powerful muscle in the body, no other having such large surfaces of origin, and, consequently, so great a number of fibres. By itself it supports, in a state of eciuilibrium, the entire weight of the body in standing, and may be adduced as a striking example of the pre- dominance of the extensors over the flexors ; it is also this muscle which raises the whole trunk in progression and in the act of leaping. We cannot, therefore, be astonish- ed at rupture of the pateha, of its ligament, or of the common tendon, during a violent contraction of this muscle, notwithstanding its disadvantageous insertion so near to the fulcrum. The rectus necessarily acts with the two vasti, but it can also flex the thigh upon the pelvis. The somewhat oblique direction of the tendon of the triceps down- ward and inward, and of the ligamentum patellce downward and outward, so that they form an obtuse angle, open to the outside {see fig. 126), and more especially the predom- inance of the vastus externus over the vastus internus, sufficiently account for the oc- currence of luxation of the patella outward, and for the impossibility of its being dislo- cated inward. When the patella is forced inward by external violence, the contraction of the vastus externus draws it back into its original position : on the other hand, the action of this muscle has a tendency to displace it outward ; and when this is accomplished, the same muscle keeps it in its abnormal position. Luxations of the patella, therefore, if not al- together irreducible, can only be temporarily replaced ; whenever the hand ceases to re- tain the bone in its proper place, the contraction of this muscle again dislocates it. Pro- fessor Ant. Dubois has informed me of an individual whose knees were bent very much inward, who could not contract the triceps femoralis Avith any force without dislocating the patella outward. THE GRACILIS, ETC. 275. Internal Region of the Thigh. The muscles of the internal region of the thigh are the gracilis and the adductors, among which I include the pectineus. The Gracilis. The gracilis (le grele interne, ou droit interne, Winslow, r, figs. 124, 125, 126) is a long, straight, and slender muscle, and the most superficial of those situated on the inside of the thigh. Attachments. — It arises from the s3TTiphysis pubis, between the pubic spine and the ascending ramus of the ischium, and is inserted into the spine of the tibia. It arises by some long, shining, and parallel tendinous fibres, which bind down a perpendicular fibrous bundle that lies on the inner side of the line of attachment. The fleshy fibres succeed- ing to these are at first parallel, and form a broad, thin bundle ; they then converge to- wards each other, so that the entire muscle resembles a much elongated isosceles tri- angle. It is rounded below, and terminates in a long, thin tendon, which runs for a con- siderable distance upon its posterior border, and receives all the fleshy fibres in succes- sion. This tendon becomes free immediately above the knee-joint, is then situated be- hind the internal condyle of the femur, turns round this process and the corresponding tuberosity of the tibia, and is inserted into the spine of the last-mentioned bone, behind the tendon of the sartorius, and above that of the semi-tendinosus, with both of which it is united so as to form the trifid aponeurotic interlacement, denominated la patte d'oie (goose's foot). Relations. — The gracilis is covered by the femoral fascia, and slightly by the sartorius at its lower part : it covers the three adductors, the inside of the knee-joint, and the in- ternal lateral ligament, from which it is separated by a synovial bursa common to it and the semi-tendinosus : the vena saphena interna crosses the inner surface of this muscle obliquely, near its lower extremity. Action. — It flexes the leg, and carries it slightly inward, at the same time, by means of its reflection round the knee ; in this part of its action it assists the sartorius ; it also ad- ducts the thigh. In the position of standing, its movable point is at the pelvis. The Adductor Muscles of the Thigh. There are three muscles on the inner aspect of the thigh which are called adductors ; with these the older anatomists were acquainted under the collective name of the triceps adductor. Modern writers, however, describe them either in the order of their super- imposition, as the first, second, and third {Boycr) ; or in the order of their size, as the mid- dle, small, and great adductors (Bichat). These vague denominations are the source of much confusion, for the one which occupies the middle place as regards size is the first as regards its position. I have therefore thought it right to modify these names, and have, at the same time, included the pectineus among the adductor muscles. I consider, therefore, that there are four adductors, which I shall divide into superficial and deep ; the two superficial are the pectineus and the first or long adductor ; these I shall term the first and second. Superficial Adductors. — The two deep are the short and the great adductors, which I shall denominate the small deep adductor and the great deep adductor. Strictly speaking, we could only admit the existence of two adductors, one superficial, the other deep; and this mode of division would perhaps be preferable. Dissection. — This is common to all the adductors. Abduct the thigh so as to render these muscles tense. Make an incision through the integuments from the middle of the femoral arch to the patella, and a semicircular incision at either end of this ; preserve the vessels and nerves, in order to examine their relations ; tie and cut across the vena sephena where it enters the femoral vein ; divide the fascia lata, and dissect the mus- cles, which will then be brought into view. The First Superficial Adductor, or Pectineus. The pectineus (pcctcn, the pubes) is a square muscle {w,fig. 126) situated at the upper anterior and inner aspect of the thigh, on the inner side of the psoas and iliacus (c). Attachments. — It arises {w, fig. 127) from the spine and crest of the pubes, from the trian- gular surface in front of this crest, and from the lower surface of a very strong tendinous and arched prolongation of Gimbernat's ligament, which is attached to the crest of the pu- bes, and is continuous with the fascia covering the muscle. It is inserted (w, fig. 127) below the lesser trochanter, into the ridge extending from that process to the linea as- pera. With the exception of the spine of the pubes, where there are always some well- marked tendinous attachments, the fleshy fibres commence directly from the several ori- gins : they proceed downward, backward, and outward, and constitute a bundle, which is at first flattened from before backward, and afterward from without inward : the fibres of this after a short course converge, and are inserted into the internal bifurcation of the linea aspera, in part directly, and partly through the medium of an aponeurosis which oc- cupies the anterior surface of the muscle. 276 MYOLOGY. F^. 127. Relations. — The pectineus is covered by the deep layer of the femoral fascia, and by the femoral vessels. It covers the capsular ligament of the joint, the smaU deep adductor, and the obturator externus, from which it is separated by the ob- turator vessels and nerves. Its outer border is parallel with the inner border of the conjoined portions of the psoas and iliacus, and is separated from them by a cellular interval, over which the femoral artery passes ; so that, were it not for the projection of this outer border, this vessel would be in imme- diate contact with the bone. Its inner border is in relation with the second superficial adductor, and is sometimes blend- ed with it, except below, where it is separated by an interval in which the small deep adductor may be seen. It has an im- portant relation with the anterior orifice of the sub-pubic canal, which corresponds with the posterior surface of the muscle. When hernial protrusions, therefore, take place at the fora- men ovale, the displaced parts are always covered by the pec- tineus muscle. The Second Superficial Mductor, or Adductor Longus. The adductor longtts of Albinus (le premier adducteur, Bo- yer ; le moyen adducteur, Bichat, x, jig. 126) is a flat, triangu- lar muscle, situated on the same plane as the pectineus, of which it seems to be a continuation, and with which it is often blended above. For this reason, Vesalius made of these two muscles his eighth pair of muscles of the thigh, under the name of pars octava femur moveniium. It is certain that there is a sort of consolidation between these two muscles, and that a small pectineus is always observed in conjunction with a large adductor longus. Attachments. — It arises (x, Jig. 127) from the spine of the pubes, and is itiserted (x) into the middle third of the linea as- pera of the femur. Its origin consists of a narrow, flat ten- don, which expands anteriorly, and gives origin to a thick and broad fleshy beUy ; this passes downward, backward, and out- ward, and is inserted into the middle third of the linea aspera of the femur, between the triceps femoralis in front, and the great deep adductor behind : with the latter of these muscles it becomes blended at its insertions. It is attached to the bone by means of two tendinous layers, between which the fleshy fibres are receiv- ed. A number of foramina, intended for the perforating arteries, are observed in the neigh- bourhood of this attachment. Relations. — Its upper part lies immediately under the fascia, and it becomes gradually deeper as it passes downward. It is in relation with the sartorius, from which it is sep- arated by the femoral artery and veins. This relation is one of great importance, as I shall hereafter have occasion to point out. The SmaU Deep Adductor y or Adductor Brevis. The adductor brevis oi Alhinus (le seconde of Boy er ; le petit of Bichat, y,fig. 127) is of the same form as the preceding muscle, and is the second in the order of super-im- position, but the smallest in size. It arises below the spine of the pubes on the outer side of the gracilis and the inner side of the obturator externus, from a variable extent of surface. The fibres proceed outward, downward, and a little backward, and form a thick bundle, at first flattened from within outward, and then from before backward, which increases in breadth, and terminates at the middle of the linea aspera of the femur, in front of the great deep adductor, and behind the two superficial adductors, with which it is blended at its insertion. Relations. — It is covered by the superficial adductors, and it covers tlie great deep ad- ductor, or adductor magnus. Its outer border has a relation with the obturator externus, and the conjoined psoas and iliacus muscles ; its inner border is at first in contact with the gracilis, and is then applied to the adductor magnus, from which it is sometimes difl5cult to separate it. The Great Deep Adductor, or Adductor Magnus. Dissection. — In order to obtain a good view of this muscle, it is not sufficient to study its anterior surface only, which is exposed after the preceding muscles have been divi- ded ; its posterior surface must also be examined ; and for this purpose it is necessary to remove the three muscles of the posterior region of the thigh, viz., the biceps, the semi-tendinosus, and the semi-membranosus. THE ADDUCTOR MAGNUS, ETC. 277 The adductor magnus of Albinus (le troisieme of Boyer ; le grand of Bichat, z, z', Jigs. 124 to 127) is a very large, triangular muscle, extremely thick internally, where it con- stitutes almost the entire substance of the inside of the thigh {fig. 127). It arises from the whole extent of the ascending ramus of the ischium, from a small part of the de- scending ramus of the pubes, and from the apex, i. e., the lowest portion, of the tuberos- ity of the ischium. It is inserted into the whole extent of the interval between the two iips of the linea aspera, and into a very prominent tubercle upon the inner condyle of the femur, above the depression for the insertion of the tendon of the inner head of the gas- trocnemius. Its origins, especially those from the ischium, which are the principal, can only be seen on the posterior surface of the muscle (see fig. 125). They consist of ten- dinous bundles, giving origin immediately to fleshy fibres, which form an extremely thick mass, directed downward and outward, and presenting coarse bundles, almost as large and as easily separable as those of the glutaeus maximus. The muscle soon divides into two portions, or, rather, into two distinct muscles, an internal and an external. The internal portion {z, figs. 125, 127) forms the inner border of the adductor magnus, the original course of which it follows. About the lower third of the thigh, its fibres are received into a tendinous semi-cone, open on the outside, and terminating in a shi- ning tendon, which is inserted into a well-marked tubercle on the upper and back part of the internal condyle of the femur. Throughout its whole course, this tendon lies close to the aponeurosis of the vastus intemus. The external portion (2:',^^. 125), abandoning the primitive direction of the muscle, is directed outward, and separates into thick bundles, which are inserted into the whole extent of the interval between the lips of the linea aspera by means of a very large aponeurosis, which is intimately united to the tendons of the other adductors, and forms a series of arches (see fig. 125) for the passage of the perforating arteries. These two divisions of the adductor magnus are separated below by the femoral ar- tery and veins and their sheath, and are generally distinct for a considerable extent, and sometimes entirely so. I have met with a case of this kind. That portion of the mus- cle which was inserted into the internal condyle arose entirely from the apex of the tu- berosity of the ischium ; while the origin of that portion which was attached to the linea aspera took place from a prominence situated on the external side of that tuberosity, and projecting outward from it, and also from the ascending ramus of the ischium, and the descending ramus of the pubes, externally to the gracilis muscle. The superior fibres (fig. 126) are horizontal, and, forming a distinct, and, as it were, a radiated bundle, turn in front of the succeeding fibres, and are inserted into the line leading from the great trochanter to the linea aspera, internally to the glutaeus maximus. Relations. — The adductor magnus is covered by the superficial adductors and by the small deep adductor : it covers the semi-tendinosus, the biceps, the semi-membranosus, and the glutaeus maximus. Its inner border is bounded by the gracihs above, and by the sartorius below: its upper border is in contact with the obturator externus (e, fig. 127) on the inside, and with the quadratus femoris (i,fig. 125) more externally. Its most important relation is that with the femoral artery and vein, which pass through it before reaching the popliteal space. At the place where this perforation occurs we observe a tendinous arch, or, rather, canal, into which the fleshy fibres are inserted ; and so, also, where the perforating arteries pass through this muscle. Action of the Adductor Muscles. — The muscles we have just described are both flexors and rotators outward ; but their principal office, as their name indicates, is to perform adduction, a very energetic movement, as might be anticipated from the strength of the muscles concerned in its production. We have seen, indeed, that the line of origin ex- tends from the ilio-pectineal eminence as far as and including the tuberosity of the ischi- um, and that the insertions occupy the entire length of the linea aspera, the two branch- es of its superior bifurcation, and the inner condyle of the femur. These muscles are powerfully exerted during equestrian exercise ; it is by their means that the horse is firmly grasped between the knees. The two superficial adductors and the adductor bre- vis are also flexors, because their insertions are posterior to their origins. All the ad- ductors are, as it were, rolled around the femur during rotation inward. MUSCLES OF THE LEG. The Tibialis Anticus. — Extensor Communis Digitorum. — Extensor Proprius Pollicis. — Pe- roneus Longus and Brevis. — Gastrocnemius, Plantarus, and Soleus. — Popliteus. — Tibia- lis Posticus. — Flexor Longus Pollicis. The muscles of the leg may be divided into those of the anterior, those of the exter- nal, and those of the posterior regions. Muscles of the Anterior Region of the Leg. The muscles of the anterior region of the leg are the tibialis, the extensor communis digitorum, and the extensor proprius pollicis pedis. The anterior peroneus, or peroneus 278 MYOLOGY. tertius, when it exists, is nothing more than an accessory fasciculus of the extensor communis. The Tibialis Anticus. Dissection. — Make a vertical incision through the skin from the anterior tuberosity of Fig. 128 the tibia to the middle of the inner border of the foot ; dissect back the two flaps of skin, and expose the fascia of the leg ; di- vide this fascia vertically, commencing from the middle of the leg, and terminating at the lower end of the tibia, taking care to preserve the annular ligament ; prolong the dissection and sep- aration of the fascia as far upward as possible ; lastly, remove the fascia on the dorsum of the foot, which covers inferiorly the tendon of the tibiahs anticus. The tibialis anticus {a, fig. 128) is a long, thick, prismatic, and triangular muscle, placed superficially along the outer side of the tibia. Attachments. — It arises from the crest which bounds the ante- rior tuberosity of the tibia on the outside, and from the tubercle terminating this crest above ; from the external tuberosity of the tibia, and the superior two thirds of its external surface, which presents a depression proportioned to the strength of the muscle ; from all that portion of the interosseous ligament situated to the inner side of the anterior tibial vessels and nerves ; from the deep surface of the fascia of the leg ; and, lastly, from a tendi- nous septum intervening between this muscle and the extensor communis digitorum. It is inserted into the tubercle on the first or internal cuneiform bone, and sends off a tendinous expansion to the first metatarsal bone. It arises from the internal surface of an osteo-fibrous quadran- gular pyramid formed by the tibia, the fascia of the leg, the inter- osseous ligament, and the inter-muscular septum ; from these points the fleshy fibres proceed vertically downward, and termi- nate around a tendon which commences in the substance of the muscle above its middle third ; the anterior fibres cease at the lower third of the muscle, the posterior accompany the tendon to the point where it passes under the dorsal ligament of the in- step (seen in fig. 128). As soon as the tendon appears on the anterior border of the muscle, it is deflected forward in a similar manner to the external surface of the tibia, and follows the same oblique course, after having left the common sheath of all the muscles of the anterior region of the leg. Another sheath, which is nothing more than the condensed dorsal fascia of the foot, re- ceives the tendon at the point where it passes vertically downward, to be inserted into the tubercle of the first cuneiform bone. Relations. — The tibialis anticus is covered by the fascia of the leg and the dorsal fascia of the foot ; on the inside it is in relation with the external surface of the tibia ; on the outside, at first with the extensor communis digitorum, and then with the extensor pro- prius pollicis, from which it is separated behind by the anterior tibial vessels and nerves. Action. — It flexes the foot upon the leg ; and, from the obliquity of its tendon, it raises the internal border of the foot, and, consequently, produces that sort of rotation inward at the articulation of the two rows of the tarsus which we have already alluded to. It tends, also, to adduct the ankle-joint, and is, consequently, opposed to dislocation out- ward. The absence of a proper sheath for this muscle explains the considerable pro- jection formed by its tendon during contraction, which may serve as a guide to the pre- liminary incisions in ligature of the dorsal artery of the foot. Spigelius called this mus- cle the musculus catence, because fetters applied around the ajikles of criminals press chiefly upon the projection formed by its tendon. The Extensor Longus Digitorum Pedis, and the Pero7ieus Tertius vel Anticus. Dissection. — Remove the fascia of the leg and the dorsal fascia of the foot. This is an elongated, semi-penniform, and reflected muscle (b c, Jig. 128), flattened from within outward, single above, and divided into four or five tendons below. Attachments. — It arises from the external tuberosity of the tibia, on the outer side of the tibialis anticus ; from the whole of the internal surface of the fibula in front of the interosseous ligament, and slightly from that ligament ; from the upper part of the fascia of the leg, and from the tendinous septa interposed between this muscle and the tibialis anticus within, and the peroneus longus and brevis without. It is inserted into the sec- ond and third phalanges of the last four toes. From these numerous origins the fleshy fibres proceed in different directions ; the su- THE EXTENSOR PEOPRIUS POLLICIS. 279 perior vertically' downward, the rest obliquely downward and forward, the lowest being the most oblique ; they all terminate around a tendon, which appears upon the anterior border of the muscle below the upper third of the leg. This tendon soon divides into two portions : one internal, and itself subdivided into three tendons for the second, third, and fourth toes ; the other external, and generally split into two tendon-s, one of which is intended for the fifth toe, while the other is fixed to the posterior extremity of the cor- responding metatarsal bone. This last subdivision is often wanting : it is but imperfect- ly separated from the fasciculus belonging to the fifth toe, to which it almost always sends off an accessory tendon : it has been generally described as a separate muscle, under the name of the peroneus tertius or anticus (c,Jig. 128). I have thought it right, however, to connect this muscle with the extensor longus digitorum (6), from which it can be so imperfectly separated that it has been designated by Cowper, pars extensoris digitorum pedis longi ; and by Morgagni, quintus tendo extensoris longi digitorum pedis. The extensor communis is directed vertically as far as the ankle-joint, where it enters a sheath common to it and the flexor proprius pollicis, is next reflected under this sheath, becomes horizontal, passes obliquely inward and opposite the tarsus, is received into a much stronger proper sheath, after leaving which the five tendons separate so as to cov- er the dorsal surface of the metatarsal bone of the toes, to which they correspond. In this course they cross the extensor brevis digitorum at a very acute angle, reach the dorsal surface of the metatarsal phalangal articulations, apply themselves to the inner edges of the corresponding tendons of the extensor brevis, receive some expansions from the interossei and lumbricales, and are arranged in precisely the same manner as the ex- tensor tendons of the fingers, forming a fibrous sheath on the dorsal surface of the first phalanx of the toes ; and like these, having arrived at the articulations of the first with the second phalanges, each divides into three portions : one median, attached to the pos- terior extremity of the second phalanx ; and two lateral, which unite upon the dorsal sur- face of the second phalanx, to be inserted into the posterior extremity of the third. Relations. — Internally this muscle is in relation with the tibialis anticus, from which it is soon separated by the extensor proprius poUicis, and externally with the peroneus longus and brevis. It is covered by the fasciee of the leg and foot, and it covers the fibula, the interosseous ligament, the ankle-joint, the extensor brevis digitorum, which separ- ates it from the tarsus and metatarsus ; lastly, it covers the toes. Action. — As in aU reflected muscles, we must suppose the power to be exerted imme- diately after its reflection, and in the direction of the reflected portion : in this way, it will be seen that it extends the third phalanges upon the second, and the second upon the first ; and having produced this effect, it flexes the foot upon the leg. From its obliqui- ty, it also draws the toes outward, and turns the sole of the foot inward. The Extensor Proprius Pollicis. The extensor proprius pollicis {d,Jig. 128) is an elongated, thin, flat muscle, placed in front of the leg, between the extensor longus digitorum and the tibialis anticus. Attachments. — It arises from the internal surface of the fibula, and slightly from the adjacent part of the interosseous ligament, within and behind the extensor coimnunis. This origin is situated at variable heights, but commonly not above the middle third of the leg. It is hiserted into the posterior extremity of the second phalanx of the great toe. The fleshy fibres arise directly from the fibula and the interosseous ligament, and proceed at first vertically around, and then obliquely behind a tendon, which occupies the anterior border of the muscle, and to which the fleshy fibres are all attached in a sloping manner, like the barbs of a feather, as far down as below the proper sheath formed for it at the tarsus. From thence the tendon is reflected at a right angle, proceeds obhque- ly and horizontally forward and inward upon the dorsum of the foot, passes along {he dorsal surface of the first metatarsal bone and first phalanx of the great toe, to the latter of which it gives off a prolongation on each side, and is then inserted into the second phalanx. Relations. — Internally, it is in relation with the tibialis anticus, from which it is sep- arated behind by the anterior tibial nerve and vessels ; and externally, with the extensor longus digitorum. Its anterior border, at first concealed between the preceding muscles, is soon situated inunediately beneath the fascia, and during its contraction forms a pro- jection, which it is important to know, because it serves as a guide in searching for the dorsal artery of the foot, which will always be found on the outer margin of the tendon : it may be called the muscle of the arteria dorsalis pedis. In the foot it crosses superfi- cially to the extensor brevis digitorum. Action. — It extends the second phalanx of the great toe upon the first, and that upon the metatarsus ; when this is accomplished, it flexes the foot upon the leg. In conse- quence of its obliquity, it tends, like the preceding muscle, to turn the toes outward, and slightly to elevate the inner border of the foot. External Region of the Leg. , In this region are found the peroneus longus and peroneus brevis muscles. 280 MYOLOGY. The Peroneus Longus. Dissection. — This is common to both muscles. Remove the skin on the outer side of the leg ; make a vertical incision through the fascia ; reflect the tvi^o flaps, in order to ar- rive at the tendinous septa dividing the peronei from the muscles of both the anterior and posterior regions of the leg. To expose these muscles in the foot, remove the outer portion of its dorsal fascia, and divide obliquely inward and forward all the muscles of the plantar region, from the groove of the cuboid to the posterior extremity of the first metatarsal bone. The peroneus longus {e,figs. 128 to 130) is a long, thick muscle, prismatic and trian- gular at its upper part, and superficially situated on the outer side of the leg (peroneus primus, Spigelius). Attachments. — It arises externally from the outer and anterior part of the head of the fibida ; from a small portion of the contiguous part of the external tuberosity of the tibia ; from the upper third of the external surface of the fibula ; and from the anterior and pos- terior borders of that bone, by means of very strong tendinous septa, interposed between it and the anterior and posterior muscles of the leg ; lastly, from the fascia of the leg superiorly. It is inserted into the posterior extremity of the first metatarsal bone, on the outer side of which a process exists for this purpose. From these very numerous origins, the fleshy fibres proceed vertically and form a bun- dle {e,fig. 130), thick above, thin and flat below, and terminating in a tendon which is at first concealed in the substance of the muscle, but appears in the form of a band on its outer side, a little above the middle of the fibula, and becomes narrower and thicker as it proceeds. The tendon soon leaves the fleshy fibres, and accompanies the external sur- face of the fibula as it turns backward (peroneus posticus, Rial), then passes behind the external malleolus in a groove common to it and to the peroneus brevis, and is reflected forward and downward to the outer side of the os calcis, upon which it is held by a sep- arate sheath. Having reached the outer side of the cuboid bone, it is again reflected, enters a groove running obliquely inward and forward upon the lower surface of that bone {e,figs. 132, 133), where it is retained by a very strong and compact sheath, and continues its oblique course, without any deviation, along the lower surface of the tarsal bones ; as far as the posterior extremity of the first metatarsal bone. In this way the tendon of the peroneus longus undergoes a double reflection : first, behind the external malleolus, in which situation a thickening or knot is often seen ; and, secondly, at the cuboid bone, opposite which a sesamoid bone almost always exists. There are also three fibrous sheaths, and three synovial membranes belonging to this tendon, one be- hind the external malleolus, one upon the outside of the os calcis, and a third under the cuboid bone. Relations. — In the leg, the peroneus longus is covered by the skin and the fascia of the leg : it covers the peroneus brevis. In front, a tendinous septum intervenes between it and the extensor longus digitorum : behind, another inter-muscular septum exists between it and the soleus above, and the flexor proprius below. On the outside of the foot, its tendon corresponds to the skin externally, and to the os calcis internally. In the plantar region, it is covered below by the entire thickness of the soft parts, and corresponds above to the inferior tarsal ligaments. Action. — As we have already so frequently observed, a reflected muscle acts as if the power were appUed at the point of reflection. In this way, by transferring the power to the outer end of the groove on the cuboid bone, we shall find that the foot is abducted, or, rather, rotated outward by this muscle ; by next supposing the power to act from the other point of reflection, i. e., from behind the external malleolus, we may observe that the foot is extended upon the leg, and its outer border turned upward. In this move- ijient, the lower end of the external articular surface of the astragalus tends to carry the external malleolus outward, and to increase the curvature of the fibula, which is some- times fractured in consequence. It may be easily conceived that if the fibula be frac- tured, the contraction of this muscle will no longer be counteracted, and accordingly will turn the sole of the foot outward, and may luxate the astragalus inward. This is the mechanism of luxation of the foot occuning after fracture of the fibula, the only species of lateral dislocation of this part which has ever been observed.* The Peroneus Brevis. The peroneus brevis of Albinus (peroneus secundus, Spigel ; le petit peronier, Wins- iow,f,figs. 129, 130) is a flat, penniform, and reflected muscle, smaller and shorter than the preceding, beneath which it lies. Attachments. — It arises from the lower half, sometimes from the lower two thirds of the external surface of the fibula, which is more or less excavated for this purpose ; from the anterior and posterior borders of the same bone, and from the tendinous septa exist- ing between this muscle and those of the anterior and posterior regions of the leg. It is inserted into the posterior extremity of the fifth metatarsal bone, and sometimes * See the admirable memoir by M. Diipuytrpn, on fracture of the fibiila. THE GASTROCNEMIUS. 281 even, by a tendinous expansion, into the fourth metatarsal bone ; it often gives off a pro- longation to the extensor tendon of the little toe. The fleshy fibres proceed successively from their different origins to the internal sur- face and edges of a tendon, situated upon the outer surface of the muscle ; the bundle which they form gradually increases in size, and then diminishes, is at first penniform, and afterward semi-penniform, and accompanies the tendon as far as the fibrous sheath behind the external malleolus : after leaving the sheath, the tendon enters another, prop- er to itself, upon the outer side of the os calcis, above that for the tendon of the peroneus longus, and passes somewhat obliquely downward and forward, to be inserted into the base of the fifth metatarsal bone. Relations. — It is covered by the peroneus longus, and covers the fibula and the outer side of the os calcis. It is, therefore, only in comparison with the peroneus longus that Riolanus and others have called this muscle the anterior peroneus. Action. — The same as that of the peroneus longus, with the exception of that of its subtarsal portion. Thus, supposing the power to be appUed at the external malleolus, we have extension of the fifth metatarsal bone upon the cuboid ; extension and rotation inward of the second row of the tarsus upon the first ; rotation of the calcaneum upon the astragalus ; extension, and a tendency to abduction of the entire foot, which is therefore considerably everted when the fibula is fractured. Posterior Region. There are two layers in this region : one superficial, formed by the gastrocnemius and soleus (or triceps suralis) and the plantaris ; the other deep, consisting of the popliteus, the tibialis posticus, the flexor longus digitorum, and the flexor longus pollicis. The Gastrocnemius and Soleus, or Triceps Suralis, and the Plantaris. Dissection. — Make a vertical incision from the upper part of the popliteal space to the heel ; at right angles to this, above, make another horizontal and semicircular incision, embracing the back part of the thigh ; divide and dissect the fascia of the leg. The gas- trocnemii will then be exposed, and must be dissected very carefully at their origins. In order to study the structure and attachments of these muscles properly, they must be cut transversely in the middle, and the superior half turned upward. In dividing the outer head of the gastrocnemius, be caijpful not to cut the plantaris, which seems to be merely a small fasciculus detached from that muscle. The soleus is exposed by simply removing the gastrocnemius ; but, in order to study its structure and attachments, it must be divided vertically from behind forward at the side of a median tendinous raphd, and the fibres which conceal this median aponeurotic lamina of the muscle must be scraped away. From this division we have a fibular and a tibial portion of the soleus. The gastrocnemius {g g) and the soleus (i i',Jig. 129) together constitute a very powerful triceps muscle (musculus surae. Seem.), which, by itself, forms the fleshy part of the leg, commonly called the calf The great development of these muscles is one of the most marked characteristics of the muscular apparatus of the human sub- ject, and is connected with his destination for the erect position. The three portions of the triceps suralis are united together below in a common tendinous insertion, constituting the tendo AcUllis {t, fig. 129), but are divided above into two very distinct planes : one, anterior or deep, formed by the soleus ; the other, posterior or su- y, perficial, consisting of the two heads of the gastrocnemius. We shall describe these in succession. Gastrocnemius. The gastrocnemius, from yaarrjp, a belly, and kvtj/lcti, the leg (ge- mellus, Albinus ; primus pedem moventium, cum secundo, Vcsali- us), is the most superficial muscle on the back of the leg : it con- sists of two heads above {g g',fig. 129), but forms a single fleshy belly, which is thick and flattened from before backward. It arises from the condyle of the femur by two perfectly distinct but similar heads, viz., an outer or smaller, called the gemellus ex- ternus {g), and an inner or larger, named the gemellus internus (,§■'). They take their origin from the bone, by two very strong and flat tendons, which are attached on the outer side, and behind the con- dyle of the femur, to two well-marked digital impressions, that for the outer head being situated above a much deeper impression for the popliteus muscle, and that for the inner head immediately be- hind the tubercle into which the adductor magnus is inserted, so that the inner head is situated upon a plane a little posterior to that of the outer head. They also arise, by tendinous fasciculi, from Nn Fig. 129. 282 MYOLOGY. the rough triangular surfaces surrounding the digital impression, and terminating at the inferior bifurcation of the linea aspera. Each tendon of origin (that for the inner being much larger than that for the outer head) expands into an aponeurosis upon the posteri- or surface of that portion of the muscle to which it belongs. The aponeurotic expansion of the inner head is, moreover, thicker and longer than the other, and embraces the inner border of that part of the muscle, like a tendinous semi-cone. The fleshy fibres arise from the anterior surface of these tendinous expansions, and are disposed in the follow- ing manner : those in the middle, which are few in number, are strengthened by fleshy fibres proceeding from the rough projections of the bifurcation of the hnea aspera, pass inward and downward, and are united together like the limbs of the letter V opening up- ward, upon a median raphe, which consists either of a simple thickening of the termina- ting aponeurosis, or of a small tendinous septum : the other fibres, constituting almost the entire muscle, arise from the anterior surface of the tendons of origin, and from the aponeurosis in which they terminate, and proceed vertically downward to the back of an- other very dense aponeurotic expansion, which covers the whole anterior surface of the muscle. This last aponeurosis commences above by two very distinct portions ; at first it is of equal breadth with the muscle, then becomes narrower and thickened, and, finally, closely united with the terminal tendon of the soleus. At the lower part of the calf the fleshy fibres terminate suddenly upon the posterior surface of this aponeurosis, forming a V opening downward. Although the two portions of the gastrocnemius become inti- mately united shortly after their origin, they are not confounded together, and the inter- nal portion forms on the inside of the tibia the greatest part of the fleshy mass called the calf of the leg. Relations. — The gastrocnemius is covered by the fascia of the leg, and it covers and adheres intimately to the capsular ligament, which envelops the back part of the con- dyles of the femur. It is also in relation with the popliteus and the soleus. The tendon of the inner head corresponds to the posterior surface of the internal con- dyle ; that of the outer head to the outer side of the external condyle. We often find at the upper part of the tendon of each head, but most commonly in the substance of that of the outer head, a sesamoid bone, that glides upon the back of the condyle, and belongs to the sort of fibrous capsule or hood by which the back of each condyle is cov- ered. (Vide Syndesmology, Articulation of the Knee.) The Plant aris. This little muscle (le plantaire grele, 1 1', fig. 129) should be regarded as an accessory of the outer head of the gastrocnemius, or, rather, as a rudimentary muscle in the hu- man subject. Its small fusiform, fleshy belly, varying much in size, is found beneath the outer head of the gastrocnemius. It arises (1) from the fibrous capsule covering the external condyle, and sometimes from the lower part of the external bifurcation of the linea aspera. From these points, it pass- es obliquely downward and inward, and after a course of from two inches and a half to three inches, ends in a long, flat, and slender tendon, which is at first situated between the gastrocnemius and soleus, and afterward {I') lies parallel with the inner edge of the tendo Achillis, and is inserted into the os calcis, either at the side, or in front of that ten- don. Sometimes, however, it is lost in the sub-cutaneous adipose tissue. This muscle, which is often wanting, is occasionally double.* The Soleus. The soleus (partly seen at i i',fig. 129) is so called because it has been compared to the fish called a sole, or to the sole of a shoe. Attachments. — It arises from the fibula and tibia, and is inserted into the os calcis. Its f,bular origins {i) consist, first, of a tendon attached behind, and on the inner side of the head of that bone ; this tendon is extremely strong, especially on the inside, opposite a process existing on the fibula for its attachment ; it is prolonged within the substance, and along the anterior surface of the muscle : and, secondly, of some tendinous fibres attached to the upper half of the external border of the fibula, and the upper third of the posterior surface of the same bone. The tibial origins {i') take place from the oblique line on the posterior surface of the tibia below the popliteus, and from the contiguous portion of the aponeurotic expansion of that muscle ; from an aponeurosis which arises from the middle third of the inner border of the tibia, and is prolonged upon the anterior surface, within the substance of the muscle ; and, lastly, by a few fleshy fibres from a tendinous arch extending between the head of the fibula and the oblique line on the posterior surface of the tibia. From these different origins, the fleshy fibres pass in dilTerent directions to the anterior sur- face and edge of an aponeurosis, which covers the posterior surface of the muscle, be- comes narrower and thickened as it proceeds downward, unites with the terminal ten- don of the gastrocnemius about the middle third of the leg, and is soon blended with it to form the tendo Achillis. * Fourcroy, in his sixth memoir upon the bursae mucosae, states that the plantaris, whose tendon, according to Albinus, is received into a groove along the inner border of the tendo Achillis, is the tensor muscle of the synovial capsule of that tendon. This is an error. THE POPLITEUS. 283 • In order to study accurately the structure of the soleus, divide it longitudinally at the side of the raphe or tendinous septum existing in the middle of the lower half of this muscle, and then» hy scraping off some of the fleshy fibres, it will be seen that a dense, fibrous septum given off by the terminal aponeurosis, separates the muscle into two equal halves, and forms with that aponeurosis two tendinous semi-cones, in the interior of which the fleshy fibres are received. It wiU now be understood why Douglas, who had designated the gastrocnemius the two exterr.al and superficial heads of the great extensor of the tarsus, should call the soleus the two internal and deep heads of the same muscle. There are, in fact, two principal aponeuroses of origin, and two hollow tendons of inser- tion ; each aponeurosis of origin covers almost the entire anterior surface of the corre- sponding half of the muscle. Relations. — It is covered by the gastrocnemius, which projects beyond it on both sides, but especially on the inner side, and from which it is separated by the plantaris. It is thickest immediately below the largest part or belly of the inner portion of the gastroc- nemius, and, consequently, it prolongs the swelling of the calf downward. It covers the muscles of the deep layer, viz., the flexor communis digitorum, the flexor proprius polli- cis, and the tibialis posticus ; it also covers the posterior tibial and the fibular vessels and nerves. The TendoAcMllis. — The tendo Achillis {I, figs. 129, 130) results from the union of the tendons of the gastrocnemius, plantaris, and soleus. It is formed in the following man- ner : the terminal aponeurosis of the gastrocnemius, shortly after leaving the fleshy fibres, is intimately united to that of the soleus, which still continues to receive fleshy fibres upon its anterior surface and its edges, and gradually becoming narrower, is soon joined by the antero-posterior septum of this muscle. All these tendinous fibres are col- lected together to form the strongest and largest tendon in the body, known by the name of the tendo Achillis, which, after a course of about an inch and a half or two inches, glides over the smooth surface presented by the superior two thirds of the back of the OS calcis, with the intervention of a synovial bursa, and is expanded a little, in order to be inserted into the rough surface on the lower part of the same bone. Action of the Gactrocnemius and Soleus. — These muscles extend the foot upon the leg. In no other part of the body do we find so advantageous an arrangement for an immense development of power. 1. These muscles are very large, and particularly remarkable for the number of their fleshy fibres, in which respect they exceed all other muscles in the body. 2. The mode of insertion is nowhere else so favourable, for it is absolutely per- pendicular. 3. We have here a lever of the second order, in which the fulcrum is at the ball of the toes, the resistance in the middle of the foot, being represented by the weight of the body resting upon the ankle-joint, and the power at the extremity of the heel (see fig. 104). The length of that portion of the lever which projects behind the joint varies much in different individuals ; it scarcely exists in the peculiar malfonnation denominated fiat-foot. These muscles are the principal agents in walking and leaping ; they raise the weight of the whole body, even when loaded with heavy burdens. Hence it is not surprising, that occasionally an energetic contraction of these muscles may rupture the tendo AchiUis, or fracture the os calcis. Frequent exercise appears to be necessary for these muscles ; for when they remain inactive, they become atrophied, and are speedily affected with fatty degeneration. The action of the soleus, which reaches only from the leg to the heel, is limited to extension of the foot ; but the gastrocnemius, which is at- tached to the femur, after having extended the foot, can flex the leg upon the thigh ; but, from its proximity to the fulcrum, this last action is very slight. When the foot is fixed, as, for example, in standing, the soleus acts upon the leg, and tends to prevent one from falling forward, to which there is a constant tendency from the weight of the body ; the action of the gastrocnemius, on the contrary, is to flex the thigh, and in this respect it is altogether independent of the soleus. The plantaris can only be regarded as rudimentary in man ; in the lower animals it is a tensor of the plantar fascia ; it has been, as it were, cut short in man, in conse- quence of his destination for the erect position. Sometimes, as we have already stated, it is lost upon the fatty tissue covering the os calcis. The Popliteus. This is a small, triangular, and very thin muscle (m,fig. 130), situated in the popliteal space. It arises from a deep fossa, resembling a groove running from behind forward, on the back of the external condyle of the femur, below the origin of the outer head of the gas- trocnemius. It is inserted into the entire extent of the triangular surface, on the upper part of the posterior aspect of the tibia. It arises by a very strong tendon, which bears no proportion to the diminutive size of the muscle. This tendon, at first concealed by the external lateral ligament, contain- ed, as it were, in the cavity of the joint, and completely enveloped by the synovial mem- brane, passes obliquely behind the articulation, and, after extending for about one inch, 284 MYOLOGY. divides, like the tendon of the obturator internus, into four or five small diverging bun- Fig. 130. dies, which soon surround the fleshy fibres on ah sides. The lat- ter then become attached in succession to the triangular surface of the tibia, the lowest being the longest and the most oblique. The superficial fibres are inserted into a tendinous expansion from the semi-membranosus, which covers the posterior surface of the popliteus muscle, and forms a very strong sheath for it. Relations. — It is covered by the gastrocnemius and the plantaris, from which it is separated by the popliteal vessels, and the inter- nal popliteal branch of the sciatic nerve. It covers the tibio-fibu- lar articulations and the back of the tibia. Action. — It flexes the leg upon the thigh, and, at the same time, rotates it inward (oblique movens tibiam, Spigelius). In this last respect it antagonizes the biceps. The Tibialis Posticus. Dissection. — Remove the gastrocnemius and soleus ; separate the tibialis posticus from the flexor longus digitorum, which par- tially covers it ; carefully remove from the posterior surface of the tibialis posticus a very broad aponeurosis, together with a portion of the long flexor of the toes, which arises from the posterior sur- face of that aponeurosis ; completely separate the tibialis posticus from the interosseous ligament, and the adjacent portions of the tibia and fibula ; lastly, be careful to preserve the tendinous expan- sions always given off by this muscle to the fourth and fifth meta- tarsal bones. The tibialis posticus 'ji,fig. 130) is the most deeply seated of all the muscles on the back of the leg ; it is very thick, and occupies the whole depth of the excavation between the tibia, fibula, and interosseous ligament. Attachments. — It arises from the tibia, the fibula, and the interos- seous ligament, and is inserted into the scaphoid bone. Its tibial and fibular origins form a bifurcation for the passage of the poste- rior tibial artery. Its tibial attachment takes place on the oblique line situated below the popliteus, soleus, and flexor longus digitorum. Its fibular origin is from the inner border of that bone, below the soleus, and from all that portion of its inner surface which is behind the interosseous ligament. It also arises from the entire posterior surface of this ligament. Lastly, a few fibres take their origin from the deep surface of an aponeurosis which separates the deep from the superficial layer of muscles, and from the tendinous septa interposed between this muscle itself and the flexor lon- gus digitorum on the inside, and the flexor proprius pollicis on the outside. From these numerous origins the fleshy fibres proceed vertically downward, around a tendon which may be distinguished near the upper extremity of the muscle, under the form of a ten- dinous sheaf, which afterward appears along its posterior border, and receives the fleshy fibres on its anterior surface, like the barbs of a feather upon the shaft. This tendon, however, is nothing more than the thickened posterior edge of an aponeurosis occupy- ing the entire substance of the muscle '"rom before backward, and receiving the fleshy fibres upon its two lateral surfaces as far down as opposite the internal malleolus. The thick tendon resulting from the union of these aponeurotic fibres then becomes free, and enters a proper sheath on the outer side of that belonging to the tendon of the flexor longus digitorum, in front of which it then passes behind the internal malleolus, where it is also enclosed in a separate sheath {n,jig. 129). On the inner side of the internal lateral lig- ament of the ankle, and below the lower calcaneo-scaphoid ligament, it enters another sheath, and is finally inserted {n,fig. 133) into the tubercle of the scaphoid bone, a very thick sesamoid bone existing near its insertion. In some subjects this sesamoid bone is found at the point of insertion ; in others it is situated opposite the calcaneo-scaphoid ligament. Besides this, the tendon of the tibialis posticus gives oflT a very strong ex- pansion to the first cuneiform bone, and on the outside an oblique expansion to the sec- ond and third cuneiform bones, and even to the third or fourth metatarsal bones. Relations.— It is covered by the flexor longus digitorum, slightly by the flexor proprius pollicis, and entirely by the soleus : it covers the interosseous ligament and the adjacent parts of the tibia and fibula. Action. — The tibialis posticus extends the foot upon the leg. As it is a reflected mus- cle, all the fibres must be considered as acting from the point of reflection that is be- hind the inner ankle. It is evident, then, that this muscle extends the foot, both by its action upon the astragalo-scaphoid articulation, and also by that upon the ankle-joint. It also tends to turn the sole of the foot inward ; and, consequently, it co-operates with the tibialis anticus in this respect, and antagonizes the peroneus longus and brevis. It may also be understood why some persons, in whom the tendo Achillis has been cut oi THE FLEXOR LONGUS POLLICIS. 285 ruptured, are yet capable of walking, and why the foot can in all cases be extended after this accident ; but under these circumstances the lever formed by the foot is changed, and the power represented by the tibialis posticus is applied between the fulcrum and the resistance ; so that we have, then, a lever of the third, not of the second order, as when the tendo Achillis is uninjured. The Flexor Longus Digitorum Pedis. This is a penniform, elongated, and reflected muscle {o,figs. 130, 132), situated along the posterior surface of the tibia and in the sole of the foot ; it is the most internal mus- cle of the deep layer, is flattened from before backward, and terminates below in four tendons. Attachme7its. — It arises from the tibia, and is inserted into the last phalanges of the last four toes. It arises from the oblique line of the tibia, below the popliteus and the sole- us, and from the middle three fifths of the posterior surface of the same bone. Some fibres also proceed from the tendinous septum intervening between it and the tibialis posticus. From these different origins the fleshy fibres proceed obliquely backward and downward, to the anterior surface and edges of a tendon which commences near the upper end of the muscle, and gradually disengages itself from the fleshy fibres, being accompanied by them anteriorly as far as the internal malleolus. It passes behind this projection in the same sheath as the tendon of the tibialis posticus, from which it is sep- arated by a fibrous septum ; it soon leaves that tendon, passing to its outer or fibular side (o, fig. 129), and is then reflected at an obtuse angle upon the internal malleolus. It now becomes horizontal, and is buried under the astragalus and the small anterior tubercle of the os calcis, where it is contained in a proper sheath. Having thus reached the sole of the foot (o, figs. 131, 132), it passes obliquely outward and forward, crosses under the tendon of the flexor longus pollicis at a very acute angle, receives from it a strong tendinous communication, and at the same time becoming expanded, is joined by its accessory muscle, and finally divides into four tendons for the last four toes. The tendon for the second toe proceeds directly forward. The tendons for the other toes in succession pass more and more obliquely. Having reached the metatarso-phalaogal ar- ticulations, these tendons are received, together with those of the flexor brevis digitorum, into the sheaths upon the first and second phalanges ; and they have precisely the same relations to the tendons of the last-mentioned muscle as the flexor profundus is observed to have with regard to the flexor sublimis digitorum in the hand ; and hence the name of perfora7is given by Spigelius to the long flexor of the toes. The tendons are finally inserted into the posterior extremities of the third phalanges. The tendinous parts of this muscle are lubricated by synovial membranes where they pass through the different sheaths. Relations. — It is covered by the soleus, the posterior tibial vessels and nerves, and it covers the tibia and the tibialis posticus. In the foot, it is covered below by the flexor brevis digitorum and the adductor pollicis. Action. — It flexes the third phalanges upon the second, the second upon the first, and the first upon the corresponding metatarsal bones. When these movements have, been accomplished, it extends the foot upon the leg. From the obliquity of its reflected por- tion, it would turn the toes and the sole of tue foot slightly inward, if the accessor}' mus- cle did not, as it were, rectify its action, as well as co-operate with it. In standing, it op- poses flexion of the leg forward. The Flexor Longus Pollicis. The flexor longus •pollicis is the most external and the largest muscle in the deep re- gion of the leg : it is prismatic and quadrangular, vertical and fleshy in the leg (/>, figs. 129, 130), tendinous and horizontal in the foot {p,figs. 131, 132). Attachments. — It arises from the fibula, and is inserted into the last phalanx of the great toe. Some of the fibres arise directly from the inferior two thirds, and from the internal and external borders of the fibula ; others arise from the fascia covering the tibialis pos- ticus (its origin from the fibula, and that from the fascia of the tibialis muscle, are sep- arated from each other by the peroneal vessels) ; from a tendinous septum between it and the peroneus longus and brevis ; and from a small portion of the lower part of the interosseous ligament. From these numerous points of origin the fleshy fibres pass ob- /iquely downward and backward, around a tendon which occupies the entire length of the muscle, and may be seen at the lower part of the leg, through a thin layer of muscu- lar fibres. These fibres terminate abruptly, behind the ankle-joint, at the oblique groove on the astragalus, in which the tendon is lodged ; it then turns into a groove on the os calcis, forming a continuation of the preceding {fig. 133), and situated below that for the tendon of the flexor longus digitorum, and dips into the sole of the foot. It is retained in these two grooves, which run obliquely downward, inward, and forward, by a very strong and continuous sheath {fig. 132). In the sole of the foot, the tendon is deeply situated {p, fig. 131), passes forward, and crosses {p, fig. 132) at an acute angle above the tendon of the flexor longus digitorum, to which it gives off a considerable fibrous 286 MYOLOGY. prolongation. It is then received in a groove formed betvv'een the flexor brevis digito- rum and the obhque adductor of the great toe, passes below the anterior glenoid liga- ment of the metatarso-phalangal articulation of that toe, between the two sesamoid bones, and is received into the osteo-fibrous sheath of the first phalanx, to be inserted into the posterior extremity .of the second. Relations. — It is covered by the soleus, being separated from it by a fascia, which in- creases in thickness as it passes downward ; it is also covered by the tendo Achillis ; it covers the fibula, the tibialis posticus, the peroneal artery, and the lower part of the in- terosseous ligament. Externally, it is in relation with the peroneus longus and brevis ; internally, with the flexor longus digitorum. Action. — It flexes the second phalanx of the great toe upon the first, and this upon the first metatarsal bone ; having produced these movements, it then extends the foot upon the leg. From the obliquity of its fleshy belly, it has a tendency to turn the great toe and the foot outward. In this respect it antagonizes the flexor longus digitorum and the tibialis posticus. The very strong tendinous expansion which unites it to the long flexor of the toes consohdates the two muscles ; in fact, it is very uncommon to find either of them acting independently. MUSCLES OF THE FOOT. The Extensor Brevis Digitorum. — Abductor Pollicis Pedis. — Flexor Brevis Pollicis Pedis. — Adductor Pollicis Pedis. — Transversus Pollicis Pedis. — Abductor Minimi Digiti. — Flexor Brevis Minimi Digiti. — Flexor Brevis Digitorum. — Flexor Accessorius. — Lunibricales. — Interossei. The muscles of the foot are divided into those of the dorsal and plantar aspects and the interossei. The muscles of the plantar aspect may be again subdivided into three regions, viz., those of the middle plantar region, those of the i7iternal plantar region, and those of the external plantar region. A single muscle occupies the dorsum of the foot, viz., the extensor brevis digitorum. The muscles of the internal plantar region are four in number, viz., the abductor, the flexor brevis, and the oblique and transverse adduc- tors of the great toe. The last two muscles may be regarded as forming part of the middle plantar region. The muscles of the external plantar region are the abductor and the flexor brevis of the little toe. The muscles of the middle region are the flexor brevis digitorum, the flexor accesso- rius, and the lumbricales. The interosseous muscles are seven in number, and are divided into the dorsal and plantar. Dorsal Region. The Extensor Brevis Digitorum. Dissection. — Remove the dorsal fascia of the foot, and the tendons of the muscles of the anterior region of the leg. The extensor brevis digitorum (q, jig. 128) is a thin, flat, quadrilateral muscle, situated on the dorsum of the foot ; it is divided into four portions anteriorly, and is an accessory of the extensor longus digitorum. It arises from the os calcis, and is inserted into the first four toes. It arises, by a rounded extremity, from a small excavation on the outside of the foot, formed by the os calcis and the astragalus {the astragalo-calcanean fossa), and from the os calcis, in front of that excavation. Its origin from these parts is both fleshy and tendi- nous. The muscle then passes forward and inward, and soon divides into four fleshy fasciculi,, each representing a little penniform muscle, and terminating quickly in a small tendon, the size of which is proportioned to the strength of the fasciculus. The inter- nal tendon is the largest, because it is intended for the great toe ; it is situated below the tendon of the extensor proprius pollicis, which it crosses at a very acute angle, and is inserted into the dorsal surface of the proximal end of the last phalanx. The second, third, and fourth tendons, intended for the second, third, and fourth toes, are subjacent to the corresponding tendons of the extensor longus digitorum, which they cross at a very acute angle. Having reached the metatarso-phalangal articulations, the tendons of the short extensor are situated to the outside of those of the extensor longus, and are blended with them, so as to complete the fibrous sheath on the dorsal surface of the first phalanx, and to terminate in a similar manner. Relations. — It is covered by the dorsal fascia of the foot, by the tendons of the exten- sor longus digitorum and extensor proprius pollicis ; it covers the second row of the tar- sal bones, the metatarsus, and a small portion of the interosseous muscles and the pha- langes. The arteria dorsalis pedis runs at first along the inner border of this muscle, which overlaps the artery, where the latter perforates the first interosseous space, in order to reach the sole of the foot. THE FLEXOR BREVIS POLLICIS PEDIS. 287 Actioyi. — It extends the first four toes ; it acts upon the first phalanx only of the great toe. Its obliquity enables it to correct the contrary oblique movement communicated to the toes by the contraction of the extensor longus digit orum ; so that the opposite ac- tions of these two muscles are mutually destroyed, and the foot is extended directly. Not uncommonly, the extensor brevis presents a fifth fasciculus, which is lost upon some one of the metatarso-phalangal articulations. Internal Plantar Region. The muscles of the ball of the great toe may be divided, like those of the thumb, into two orders, viz., those which pass from the tarsus to the inner side of the first phalanx, and those which pass from the tarsus to the outer side of the same phalanx. Here, as with the muscles of the thumb, the tendon of the flexor longus divides the flexor brevis pollicis pedes of authors into two parts: one internal, forming the flexor brevis of the great toe, properly so called ; the other external, which is found to be connected with the oblique adductor of this toe. Muscles inserted into the Inner Side of the First Phalanx of the Great Toe, Dissection. — In order to expose the abductor brevis, it is sufficient to remove the in- ternal plantar fascia ; the flexor brevis will be found under, i. c, deeper than the tendon of the abductor brevis. The muscles inserted into the inner side of the first phalanx of the great toe are the abductor brevis and the flexor brevis. They are distinct at their origins, but are often blended at their insertions ; so that Winslow united them together under the name of le thenar du pied. Fiz. 131. The Abductor Pollicis Pedis. "''^ This muscle (le court adducteur,* Cruveilhier, r,fig. 131) is the most superficial in the internal plantar region ; it arises on the inside, from the internal posterior tuberosity of the os calcis ; from the internal annular ligament under which the posterior tibial vessels and nerves pass ; from the upper sur- face of the internal plantar fascia ; and from the lower sur- face of a tendinous expansion, which occupies the entire ex- tent of the deep or superior surface of the muscle. From these points the fleshy fibres proceed to the circumference of a tendon (r, figs. 132, 133), which emerges from them infe- riorly near the first cuneiform bone, but is often accompanied by them superiorly as far as its insertion into the internal ses- amoid bone, opposite the first phalanx of the great toe. Relations. — It is covered below by the internal plantar fas- cia, and is divided from the muscles of the middle plantar re- gion by a tendinous septum, which gives attachment to some of its fleshy fibres. It is superficial to the flexor brevis polli- cis, the flexor accessorius, the tendons of the flexor longus digitorum, and that of the flexor longus pollicis, the tarsal in- sertions of the tibialis anticus and posticus, the plantar vessels and nerves, and the internal articulations of the tarsus. Action. — It is, properly speaking, a flexor of the great toe. The Flexor Brevis Pollicis Pedis. Adopting a similar plan in the definition of this muscle as in that of the short flexor of the thumb, I shall describe as the short flexor of the great toe that portion {s, fig. 133) only of the flexor brevis of authors which extends from the second row of the tarsus to the internal sesamoid bone of the metatarso-phalangal articulation of the great toe, and shall refer to the oblique adductor that portion (t) which is attached to the external ses- amoid bone. This change appears to be warranted by the rule already laid down for the distinction of muscles. Community of the fixed points of origin is not sufficient to es- tablish the unity of two muscles, provided tl\eir movable insertions are distinct. A cel- lular interval and the tendon of the flexor longus pollicis establish anteriorly the line of demarcation between the flexor brevis and the adductor obliquus pollicis. According to this view, the flexor brevis pollicis {s, figs. 131, 132, 133) arises from the second row of the tarsus, particularly from the cuboid and the third cuneiform bones, by some tendinous fibres which are formed by a continuation of the inferior ligaments of the tarsus, and are common to this muscle and the internal portion (/) of the oblique ad- ductor of the great toe. The tendon of the tibialis posticus {n,fig. 133), or, rather, the prolongation which this tendon gives off to the fourth metatarsal bone, also furnishes some points of origin. The fleshy fibres proceeding from these different attachments form a bundle that gradually increases in size, becomes separated from the oblique ad- * See note, next page. 288 MYOLOGY. ductor, and terminates in a tendon which is inserted into the extci^Sl sesamoid bone, and also into the glenoid ligament of the metatarso-phalangal articulation. Not unfre- quently the greater number of the fleshy fibres are attached to the tendon of the abduc- tor brevis, and thus constitute the short head of a biceps muscle. Relations. — The flexor brevis pollicis is in relation below with the internal plantar fas- cia, and with the tendon of the abductor brevis pollicis, being moulded upon it, and usu- ally separated from it by a tendinous sheath, except in those cases where the two mus- cles are blended together. Observe that, at the point where the fleshy belly of the ab- ductor terminates, the flexor brevis is in relation above with the tendon of the peroneus longus ie,fig. 133) and the first metatarsal bone. Action. — The same as that of the preceding muscle, but it is much less powerful, and less extensive. Muscles inserted into the External Side of the First Phalanx of the Great Toe. These are the oblique and transverse adductors.* Dissection. — They are exposed by cutting across, and turning forward the flexor brevis digitorum, the tendons of the flexor longus digitorum, and the flexor accessorius : par- ticular care should be taken, when the dissection has extended as far as the heads of the metatarsal bones, to avoid cutting the small transverse adductor. The Adductor Pollicis Pedis. This (I'abducteur oblique, Cruveilhier, 1 1', fig. 133) is the largest of all the plantar mus- cles ; it is prismatic and triangular, and occupies the great hollow formed by the last four metatarsal bones, and is bounded by the first metatarsal bone on the inner side. It ex- tends from the second row of the tarsus to the external sesamoid bone of the great toe. It arises by two very distinct portions : the smaller {t,figs. 131, 132, 133), common to it and to the flexor brevis, proceeds from the cuboid bone ; the other {t') is much larger, and arises from the sheath of the tendon of the peroneus longus («), from the posterior extremities of the third, fourth, and fifth metatarsal bones, and from the transverse lig- aments by which they are united. From these different origins the fleshy fibres pass more or less obliquely inward, and are inserted by a tendinous bundle into the external sesamoid bone of the metatarso-phalangal articulation of the great toe, and into the pos- terior edge of the glenoid ligament of the same joint. Relations. — Its inferior surface is in relation with the long and short flexors of the toes, with the flexor accessorius, the lumbricales, and the plantar fascia ; its superior surface, with the interosseous muscles and the external plantar artery ; and its inner surface, with the first metatarsal bone, the tendon of the peroneus longus, and with the flexor brevis pollicis. Action. — It is a powerful adductor and flexor of the great toe. The Transversus Pollicis Pedis. This small transverse bundle (I'abducteur transverse, Cruveilhier, u,fig. 133) forms an appendage of the preceding muscle, and is represented in the hand by the transverse fibres of the adductor pollicis ; it extends from the fifth metatarsal bone to the external sesamoid bone of the metatarso-phalangal articulation of the great toe. This muscle, which is of variable size, arises externally from beneath the head of the fifth metatarsal bone, by a tendinous and fleshy tongue, which is directed transversely inward, is strengthened by other fibres arising from the anterior transverse ligament of the metatarsus, and from the interosseous aponeurosis, and is inserted into the outer side of the first phalanx of the great toe, where it is often blended with the attachment of the oblique adductor. Relations. — It is in relation below with the tendons of the long and short flexors of the toes and with the lumbricalis, and above with the interosseous muscles. It is lodged in the anterior part of the deep concavity of the metatarsus, and is provided with a proper sheath. Actions. — It adducts the great toe, and draws the head of the metatarsal bones toward* each other. * [The terms adductor and abductor are applied by M. Cruveilhier to the muscles of the great toe, from their respective actions upon it, in reference to the axis of the body ; the muscle attached to the inner side of that toe being- called its adductor, and those to the outer side its abductors. In the translation, however, the nomen- clature of Albinus has been adopted, in which the terms adductor and abductor have reference to the axis of the limb: first, because it is followed by the majority of authors ; and, secondly, because it is in accordance with the principle obsen-ed by M. Cruveilhier himself, in describing not only all the muscles of the hand, but some even of those of the foot, viz., the interossei, which are classed by him as abductors or adductors, accord- ing as they draw the several toes from or towards an imaginary axis passing through the second toe. By this change much risk of perplexity will be avoided, and a uniform principle of nomenclature preserved as regards all the muscles of the hand and foot. In the description of each muscle of the great toe, the synonymes of Cruveilhier are given between brack- ets ; but in all instances, both here and hereafter, where these muscles have incidentally to be mentioned, the names adopted from Albinus will be strictly adhered to. It is scarcely necessary to observe that tlie abductor of the little toe will still retain its name.] THE ABDUCTOR DIGITI MINIMI, ETC. 289 External Plantar Region. The Abductor Digiti Minimi. Dissection. — This is common to the abductor and the flexor brevis. The first is ex- posed by simply removing the external plantar fascia, and the second by removing or re- flecting down the first. ,. The abductor digiti mi)umi {v,fig. 13l) is of the same form, the same structure, and al- most the same size as the abductor pollicis, and extends from the os calcis to the first phalanx of the little toe. It arises by tendinous and fleshy fibres from the external pos- terior tuberosity of the os calcis, from the outer side of the internal posterior tuberosity, and from an aponeurosis occupying the upper surface of the muscle. The fleshy fibres having arisen in succession from these different points, proceed obliquely round a tendon, from which they emerge, opposite the posterior extremity of the fifth metatarsal bone. The fleshy belly of the muscle appears to end at this point, but it is continued by other fibres, arising from the upper surface of the external plantar fascia, and inserted either into the common tendon, or separately, by the side of this tendon, into the outer part of the first phalanx of the little toe. A small fleshy bundle is frequently detached from the body of the muscle, and implanted into the posterior extremity of the fifth metatarsal bone, together with a prolongation of the external plantar fascia, which serves as a ten- don for it. Action. — It is an abductor and flexor of the little toe. The Flexor Brevis Digiti Minimi. This is a small fleshy fasciculus {x,figs. 131, 132, 133), situ- ated along the external" border of the fifth metatarsal bone, and forming a continuation of the series of interosseous muscles, with which it was for a long time confounded (interosseus, SpigcVnis) : it extends from the second row of the tarsus, and from the fifth metatarsal bone, to the first phalanx of the little toe. It arises from the ligamentous layer covering the plantai surface of the metatarsal row of the tarsal bones, and from the posterior extremity of the fifth metatarsal bone ; it is inserted into the outer side of the first phalanx of the little toe, or, more correctly, into the posterior edge of the glenoid ligament of the metatarso-phalangal articulation of that toe. Some of the fleshy fibres will be found attached to the entire length of the external border of the fifth metatarsal bone ; and these some- times form a small and very distinct muscle, representing the opponens digiti minimi of the hand. Relations. — It is covered below by the plantar fascia, which is here very thin, and also by the tendon of the abductor digiti minimi ; it is in relation above with the fifth metatarsal bone and the first plantar interosseous muscle. Action. — The same as that of the preceding muscle with re- gard to flexion, but its action is less powerful and less exten- sive. Middle Plantar Region. The Flexor Brevis Digitorum. Dissection. — Remove the plantar fascia, whic:^ is intimately united to this muscle pos- teriorly. The flexor brevis digitorum {y,Jig. 131) is a short, thick muscle, narrow behind, and divided into four tendons in front. It arises from the inside of the external tuberosity of the OS calcis, from the upper surface of the middle plantar fascia, from a special ten- dinous expansion occupying the lower surface of the nuiscle, and appearing to be a de- pendance of the plantar fascia ; and, lastly, from an aponeurotic septum, situated between it and the muscles of the external plantar region. It forms a fleshy belly, which is nar- row and thick behind, passes directly forward, increases in breadth, and soon divides into four, sometimes only into three fasciculi, constituting as many small and perfectly distinct penniform muscles, the long and delicate tendons of which emerge from the fleshy fibres before reaching the metatarso-phalangal articulations, become flattened, and are then situated below and in the same sheath with the tendons of the flexor longus. Opposite the first phalanx each tendon of the short flexor bifurcates, to allow the passage of the corresponding tendon of the flexor longus, is formed into a groove, becomes re- united above the latter tendon, and once more bifurcates, in order to be inserted along the borders of the second phalanx (hence it was named perforatus by Spigehus, and le perfore du pied by Winslow). The short flexor of the toes is, therefore, analogous to the superficial flexor of the fingers. Relations. — It is covered below by the plantar fascia and the skin; it is in relation Oo 290 MYOLOGY. above with the plantar vessels and nerves, with the tendon of the flexor longus digitorum, and with the flexor accessorius and the lumbricales, from which it is separated by a tendi- nous lamina. On its outer and inner side it is completely isolated from all the adjacent muscles by prolongations of the plantar fascia. Action. — It flexes the second phalanges of the last four toes upon the first phalanges, and these upon the corresponding metatarsal bones. The Flexor Accessorius. This is a flat, quadrilateral muscle, forming a considerable fleshy mass (massa carnea, Jacobi Sylvii, z,jig. 132) ; it anses, by a bifurcated extremity, from the lower part of the groove of the os calcis, and a small part of the calcaneo-scaphoid ligament by fleshy fibres, and by means of a tendon from the lower surface of the same bone, this tendon sometimes extending as far as the external posterior tuberosity of the os calcis. From these points the fleshy fibres pass directly forward, and terminate in the following man- ner : the lower fibres become inserted, into the outer margm, and a small portion of the inferior surface of the tendon of the flexor longus digitorum ; while the upper are inserted into several small fibrous bundles, which unite together, receive a considerable expan- sion from the tendon of the flexor longus pollicis, and are ultimately blended with, and increase the size of the divided tendon of the flexor longus digitorum. Relations. — This muscle is in relation helow with the flexor longus digitorum and the plantar vessels and nerves, and above with the os calcis and the inferior calcaneo-cuboid ligaments. Action. — It is a muscle of re-enforcement, and assists in flexing the toes ; from its obli- quity, it rectifies the oblique action of the flexor longus digitorum in the opposite direction. The Lumbricales. The lumbricales {I I, figs. 131, 132), which form a second class of accessory muscles belonging to the flexor lo'ngus digitorum, exactly resemble the lumbricales of the fingers ; they consist of four small fleshy tongues, decreasing in size from within outward, the two outer of which are not unfrequently atrophied ; they extend from the angles formed by the division of the tendons of the flexor longus to the inner or tibial borders of the first phalanges of the last four toes, and to the corresponding margins of the extensor tendons. They are distinguished by the numerical names of first, second, third, and fourth. The first is situated parallel with the flexor tendon of the second toe. Relations. — They are covered below by the flexor brevis digitorum ; they emerge from beneath the plantar fascia, in the interval between the sheaths furnished by it to the flexor tendons, gain the inner side of the corresponding metatarso-phalangalarticulation,^ and terminate upon the first phalanx and inner margm of the tendons of the extensor longus digitorum. They have the same action as the lumbricales of the hand. Interosseous Region. The Interossei. The interosseous muscles of the foot correspond exactly with those of the hand, and require the same consideration. They arise from the lateral surfaces of the interosseous spaces in which they are placed ; and are inserted into the sides of the first phalanges and the corresponding mar- gins of the tendons of the extensor muscles. They are seven in number, viz., four dorsal (three of which are seen at d d d,fig. 133), and three plantar {p p p); to the latter, however, the ob- lique adductor of the great toe may be added, for it is nothing more than a very large plantar interosseous muscle. As in the hand, the dorsal interossei are abductors, their origins being situated externally to the axis of the foot ; the plantar inter- ossei, again, are adductors ; but the axis of the foot must be suppo- sed to extend through the second, and not through the middle toe. As we observed in the hand, the dorsal interossei project into the plantar region, by the side of the plantar muscles ; and so narrow are the interosseous spaces in the foot, that these dorsal muscles are much more completely situated in the plantar than those of the hand in the palmar region. The palmar interossei correspond- ing to the fourth and fifth toes, arise not only from the lower two thirds of the internal or tibial side of the corresponding metatar- 7* sal bone, but also from the lower surface of the posterior extrem- ity of the same bone. It follows, therefore, that the interosseous muscles, viewed from below, appear one continuous muscle, in which it would be difficult to separate the muscles of each space, if the interosseous plantar fascia did not give off prolongations between them ; elsewhere, a cellular line defines the limit be- tween each plantar and dorsal muscle. PHYSIOLOGICAL ARRANGEMENT OF THE MUSCLES. 291 Again, as in the hand, the dorsal interossei arise from two corresponding metatarsal bones at once, but more especially from the lateral surface of that metatarsal bone which is directed/rom the axis of the foot : as in the hand, also, their posterior extremities are perforated by the posterior perforating arteries, the first being perforated by the arteria dorsalis pedis. The plantar interossei arise from only one of the metatarsal bcnes, and from the lateral surface that is directed towards the imaginary axis of the foot ; moreover, they do not arise from the entire thickness of the bone, but only from its inferior two thirds, since the upper third is covered by the dorsal muscle. The following are the general relations of the interossei : they are separated above from the tendons of the extensors by a layer of fibrous tissue, and by the dorsal inter- osseous fascia ; and below from the proper muscles of the foot, by the deep plantar in- terosseous fascia, which is muc^ stronger than the corresponding structure in the hand, and give^ off septa between the differerit jpairs of interosseous muscles. PHYSIOLOGICAL ARRANGEMENT OF THE MUSCLES. However important it may be to become acquainted with the order of super-imposi- tion, or the topographical arrangement of the muscles, it is no less necessary to study the retrospective uses, in other words, the physiological arrangement of these organs.* In order to obtain, as much as possible, the advantages of each of these two methods, having already described each muscle in its topographical order, I shall now give a table of the muscles, arranged according to their physiological relations. It is important to observe that the terms muscles of the arrn^ of the thigh, SfC., have not the same accepta- tion in the two arrangements. Tlius, by the term muscles of the arm, in the topograph- ical order, we mean the muscles which occupy the region of the arm, as the deltoid, bi- ceps, &c. ; but, in the physiological arrangement, the same term is apphed to the mus- cles which move the arm, viz., the pectoralis major, latissimus dorsi, &c- Muscles of the Vertebro-cranial Column. These are divided into the extensors, the flexors, and the lateral muscles or lateral flexors, which incline the vertebral column to one side or the other. There are no rota- tors, for rotation is performed by the extensor muscles. Extensors. — These occupy the posterior region of the vertebral column. They con- sist, on each side, of, 1. The posterior spinal, or long muscles of the back, divided into the sacro-lumbalis, longissimus dorsi, and transverso-spinahs ; 2. Of the transversalis colli and the trachelo-mastoideus, which may be regarded as accessory fasciculi to the longissimus dorsi ; 3. Of the splenius, or representative of the longissimus dorsi of the neck and head ; 4. Of the complexus, or transverso-spinalis of the head ; .5. Of the in- ter-spinales, in which the two recti postici of the head may be included ; 6. Of the ob- liquus major, or spino-transversalis of the atlas ; 7. Of the obliquus minor, or transverso- spinalis of the head. Flexors. — These are situated on the anterior region of the vertebro-cranial column. The most important of these muscles are carried forward, and attached to the sternum, and to those long transverse processes called the ribs. They are on each side, 1. The rectus abdominis ; 2. The sterno-cleido-mastoideus. The other muscles that co-operate inflexion occupy the deep anterior cervical region, viz., 1. The rectus capitis anticus major ; 2. The rectus capitis anticus minor ; 3. The longus colli. Lateral Muscles. — These are, 1. The inter-transversales of the neck and loins, among which I include the rectus capitis lateralis ; 2. The scaleni anticus et posticus ; 3. The quadratus lumborum. Muscles of the Ribs, or of the Thoracico- abdominal Parietes. These are, 1. The inter-costales, externi and interni, which are both elevators and depressors ; 2. The small accessory muscles, viz., the infra-costales of Verheyen and the supra-costales, or levatores costarum, the latter being always elevators ; 3. The ser- rati postici superiores, which are elevators ; 4. The serrati postici inferiores, depressors ; 5. The triangularis sterni, or small anterior serratus, also a depressor ; 6. The diaphragm, a muscular septum, the contraction of which increases the vertical diameter of the tho- rax, and draws the ribs inward. The muscles of the abdominal parietes are so intimate- ly connected in action with those of the thorax, that the description of the former nat- urally fohows that of the latter. The abdominal muscles, then, may be regarded as mus- cles of expiration, and are all depressors of the ribs. There are, 1 . The obliquus exter- * Custom, rather than conviction, has induced me to prefer the topographical to the physiological arrange- ment. The only objection which can be urged against the latter is, that it does not permit all the muscles to be dissected upon the same subject ; but this objection applies only to a few regions ; and as these regions exist in pairs, the superficial muscles on one side might surely be sacrificed. Moreover, there is no reason why the exammntion of the deep-seated muscles should not be postponed until the superficial ones have been studied. I therefore direct students to dissect these parts sometimes according to their topographical, and at others after their physiological order 293 MYOLOGY. nus, which is nothing more than a large external intercostal muscle, extending between the ribs and the pelvis ; 2. The obliquus internus, which may be regarded as a large internal intercostal muscle, of which the cremaster is a dependance ; 3. The transversa- lis, which we may consider as forming with the diaphragm a single muscle, interrupted by its costal attachments. Muscles which move the Lower Jaw. As the bones of the upper jaw are immovably articulated together and to the cranium, they have no proper muscles. The muscles of the face do not belong to them, but are true cutaneous muscles, attached to the different bones only for the purpose of having fixed origins. The lower jaw, on the contrary, is provided with two principal orders of muscles, elevators and depressors, to which are added didxictors (from didu^co, to draw aside). The elevators and diductors preponderate ; the only office of the depressors is to bring down the jaw into a position from which it may then be raised. 1. Elevators. — These are the masseters, the temporales, and the pterygoidei intemi. 2. Diductors, viz., the pterygoidei extemi. 3. Depressors, consisting of the muscles of the supra- and infra-hyoid regions, and more particularly of the two digastrici. Muscles which move the Os Hyoides. These are divioed into elevators and depressors. All the elevators belong to the supra-hyoid region, and are, 1. The stylo-hyoidei ; 2. The mylo-hyoidei ; 3. The genio-hyoidei. The depressors consist of the muscles of the infra-hyoid region, viz., 1. The stemo- hyoidei ; 2. The sterno-thyroidei ; 3. The thyro-hyoidei ; 4. The omo-hyoidei. Muscles which move the Pelvis, There are no muscles proper to the pelvis. The ischio-coccygeus is the only intrinsic muscle. The extrinsic muscles attached to the pelvis do not belong to its cavity, but merely take their fixed points from its parietes. It is only under particular circumstan- ces that the pelvis changes its usual office, and becomes the movable point ; for exam- ple, in the horizontal position, in the action of climbing, and in the reversed attitude of a tumbler, the pelvis is moved upon the vertebral column on the one hand, and upon the femur on the other. Muscles which move the Shoulder. The muscles of each shoulder are divided into elevators and depressors, both of which are also rotators. The elevators are, 1. The trapezius ; 2. The rhomboideus ; 3. The levator anguli scapulae. The depressors are, 1. The pectoralis minor ; 2. Tlie subclavius ; 3. The serratus magnus. The elevators and depressors of the entire shoulder must be carefully distinguished from those which raise or depress its apex. Muscles which move the Thigh upon the Pelvis. These muscles are divided into extensors, flexors, adductors, abductors, and rotators. The extensors aiXiA abductors are the same, viz., the three glutaei. The conjoined psoas magnus, iliacus, and psoas parvus constitute the only flexor. Adduction is performed by four muscles, viz., the pectineus and the three adductors. Rotation outward is performed by six muscles, viz., the pyriformis, the two gemelli, the obturator internus, the quadratus femoris, and the obturator externus. Rotation inward is performed by the tensor vaginee femoris, and especially by the an- terior fibres of the glutaei, medius et minimus. Muscles which move the Arm upon the Shoulder. These muscles are divided into abductors, which are at the same time flexors, and into adductors and rotators. There are no proper muscles for the movement forward or flexion, nor for the movement backward or extension, both of which motions are effected by the adductors and abductors. The abductors are, 1. The deltoideus ; 2. The coraco-brachiahs ; 3. The supra-spi- natus. The adductors are, 1. The pectoralis major ; 2. The latissimus dorsi ; 3. The teres major. The rotators are, 1. The external, viz., the infra-spinatus and the teres minor ; 2. The internal, viz., the sub-scapularis. Muscles which move the Leg upon the Thigh. These are divided into flexors and extensors. The flexors are, 1. Tlie biceps femoris ; 2. The semi-tendinosus ; 3. The semi-membranosus ; 4. The popliteus ; 5. The sarto- rius ; 6. The gracilis. Extension is performed by one muscle only, viz., the triceps femoralis, the long head PHYSIOLOGICAL ARRANGEMENT OF THE MUSCLES. 293 of which is formed b}' the rectus femoris, and the other two heads by the triceps cruris of authors, viz., the vastus externus and vastus internus, including the crureus. I should remark, that all these muscles which arise from the pelvis perform the double ilmction of moving the leg upon the thigh, and the thigh upon the pelvis. Muscles which move the Forearm upon the Arm. These are divided into flexors and extensors. The flexors are the biceps and the brachialis anticus. The extensors are, 1. The triceps (of which the long head resembles the rectus femoris) ; 2. The anconeus. Muscles which move the Radius upon the Ulna. These are rotators inward, ox ■pronators, viz., 1. The pronator teres; 2. The pronator quadratus ; and rotators outward, or supinators, viz., 1. The supinator longus ; 2. The supinator brevis. The pronators occupy the anterior region, the supinators the poste- rior region of the forearm. Muscles which move the Hand upon the Forearm. These are divided into flexors and extensors. T\xe flexors are, 1. The flexor carpi radialis ; 2. The palmaris longus ; 3. The flexor carpi ulnaris. The extensors are, 1, The extensores carpi radiales, longior et brevior ; 2. The extensor carpi ulnaris, Adduction and abdvxtion are also performed by these muscles- Muscles which move the Fingers. Tliese are divided into extensors, flexors, adductors, and abductors. The extensors are, 1. The extensor communis digitorum ; 2. The extensor digiti minimi; 3. The ab- ductor longus poUicis ; 4 and 5. The extensor brevis and extensor longus pollicis ; 6. The extensor proprius indicis. The j?ezors are, 1. The flexor subltmis digitorum ; 2. The flexor profundus digitorum, and its accessories, the lumbricales ; 3. The flexor longus pollicis. The extensors and the flexors of the fingers are all situated in the forearm ; the ad- ductors and abductors belong to the hand : they consist of the interossei, which are seven in number, four dorsal, constituting the abductors, and three palmar, which are adductors. Other muscles are also superadded to the thumb and the little finger. The muscles superadded to the thumb are, 1. Those which constitute the thenar eminence (ball of the thumb), viz., the abductor brevis, the opponens, and the flexor brevis ; 2. The ad- ductor pollicis, which is nothing more than a palmar interosseous muscle. The mus- cles superadded to the little finger constitute the hypothenar eminence (ball of the little finger), and form, as it were, a repetition of those of the thenar eminence, viz., the ab- ductor brevis, the flexor brevis, and opponens. But although three only are thus de- scribed, it is because the palmar interosseous muscle of the little finger, which repre- sents the adductor pollicis, presents no peculiarities, and is, therefore, classed with the other palmar interossei. Muscles which move the Foot upon the Leg. These are divided into flexors and extensors : the same'muscles also produce, at the articulation of the two rows of the tarsal bones, movements of rotation, which corre- spond to adduction and abduction. The extensors are, 1. The gastrocnemius and soleus, or the triceps suralis, with which we describe a small rudimentary muscle, the plantaris- 2. The tibialis posticus. 3. The peroneus longus et brevis. There is only one ficxor, viz., the tibialis anticus. The peroneus tertius, when it ex- ists, is merely a dependance of the extensor longus digitorum. There are no muscles in the leg analogous to the pronators and supinators of the fore- arm. Muscles which move the Toes. These are divided into extensors and flexors. The extensors are, 1. The conjoined extensor longus digitorum and peroneus tertius. 2. The extensor proprius pollicis. 3. The extensor brevis digitorum. The flexors are, 1. The flexor longus digitorum, and its accessories, the lumbricales. 2. The flexor brevis digitorum ; the flexor longus pollicis. Contrary to what we have seen with regard to the fingers, many of the flexors and ex- tensors of the toes form part of the intrinsic muscles of the foot. As in the hand, the ad- ductors and abductors of the toes occupy the thenar, hypothenar, and interosseous regions. The interosseous muscles are adductors and abductors of the toes ; they are seven in number, four dorsal, being the abductors, and three plantar, actingr as adductors. The superadded muscles of the great toe are, 1. The muscles ot"the thenar eminence, viz., the abductor brevis and the flexor brevis. 2. The adductor obliquus, and the ad- ductor transversus. The muscles superadded to the little toe are the muscles of the hy- pothenar eminence, viz., the abductor and the flexor brevis. 294 APONEUROLOGY. Cutaneous Muscles. These musdes, which are inserted into the skin by one of their extremities at least, are in the human subject concentrated round the openings in the face, with a single ex- ception, viz., the palmaris brevis. The cutaneous muscles of the ear belong to the orifice of the external auditory meatus, and are all rudimentary in man. They form the three auricular muscles. The muscles of the eyelids, on either side of the face, are divided into constrictors and dilators. There is only one constrictor, the orbicularis palpebrarum, of which the corru- gator supercilii may be considered an accessory. There are two dilators, viz., the levator palpebraa superioris and the occipito-frontalis. The cutaneous muscles of the nose consist of four or five pairs, s. e., on each side of the face, of the pyramidalis nasi, the levator labii superioris alseque nasi, the transversalis nasi', the depressor alae nasi or myrtiformis, and the naso-labialis of Albinus. The cutaneous muscles of the lips are, 1. A constrictor, viz., the orbicularis oris. 2. Nine pairs of dilators, consisting, on each side, of the levator labii superioris alaeque nasi already mentioned, the levator labii superioris, the zygomaticus major, the caninus, the buccinator, the triangularis oris, the quadratus mentr, the levator labii inferioris, the pla tysma myoides ; and often of two accessory muscles, viz., the risorius of Santorini, and the zygomaticus minor. APONEUROLOGY. General Observations on the Aponeuroses. — Structure. — Uses. The aponeuroses are fibrous membranes, arranged in the form of inextensible textures, which constitute sheaths for the muscles, and, at the same time, afford them broad sur- faces for attachment. The aponeuroses are generally known, at the present day, by the name of fascia {fascia, a band), an expression wluch was at first applied exclusively to the strong, broad aponeurotic band, forming the termination of the tensor vaginee femoris, and part of the fascia lata of the thigh. The aponeuroses constitute important adjuncts to the system of locomotion. They were for a long time neglected, or, rather, studied independently of each other, and then only partially, until Bichat gave a general view of them, in his division of the fibrous sys- tem, including the membranous forms of that tissue, of which the apoueuroses form the greatest part. As the aponeuroses have now become the object of numerous researclies, and even the subject of some special treatises,* I have considered that it would be useful to offer a description of all the aponeuroses of the human body under the head of Aponeurology. This grouping together of analogous parts will have the double advantage of simplifying the description of the particular aponeuroses, by making them elucidate each other, and of bringing into prominent notice a system of organs, the study of which is generally neg- lected in anatomical lectures. General Observations. — The aponeuroses are divided by Bichat into two distinct class- es, one serving for the insertion of muscles, viz., the aponeuroses of insertion ; the other for investing or containing the muscles, called the investing or confiniug aponeuroses. Many aponeuroses serve both these purposes at the same time ; but, in general, one or the other function predominates in each. The aponeuroses of insertionf are subdivided into those formed by the expanded con- tinuations of tendons, and those which do not originate in tendons. The aponeuroses of the gastrocnemius and soleus belong to the first class ; those of the broad muscles of the abdomen are examples of the second : in the latter case, the aponeuroses serve both for the insertion and investment of the muscles. Sometimes the aponeurosis occupies the middle of a muscle ; as, for example, the cordiform tendon of the diaphragm, and the aponeuroses of the occipito-frontalis. The use of the aponeuroses of insertion evident- ly has reference to the great number of muscular fibres, all of which could not have been attached to the limited superficies of the skeleton. The investing aponeuroses occasionally form a sheath for the entire limb, sometimes for only a single muscle, and at others for several muscles. The first set are called gen- eral, the other two partial aponeuroses. The aponeuroses are found not only in the extremities where they perform such im- portant offices, but also in the trunk. As a general rule, wherever there exists a muscle fulfilling any special purpose, and susceptible of displacement during its contraction, we find an aponeurosis, or, rather, an aponeurotic sheath ; and the thickness of this sheath is proportioned to the length and strength of the muscle, and especially to its tendency to displacement. * Godman, of Philadelphia, published in 1824 a special work upon the fascis ; and Paillard a treatise upon tke aponeuroses of the human body in 1827. t See note, p. 296. GENERAL REMARKS UPON THE APONEUROSES. 295 Each aponeurosis presents for our consideration an external and an internal surface, a superior border or circumference, sometimes termed its origin, and an inferior border or circumference, sometimes called its termination. 1. The external surface of the general investing aponeuroses is in contact with the sub- cutaneous cellular tissue, from which it is separated by the superficial veins, lymphatics, and nerves. The skin is therefore movable upon these aponeuroses, excepting in some situations, as in the palms of the hands and soles of the feet, where it is intimately uni- ted to the fascia; by prolongations from the inner surface of the cutis. What, indeed, would be the consequences with regard to the sense of touch, or in the attitude of stand- ing, if the skin over those regions were as movable as it is upon the thigh 1 The same adhesion is also observed between the hairy scalp and the subjacent aponeurosis. The mobihty of the skin upon the aponeuroses depends upon the following contrivance : From the inner surface of the skin are given off a great number of prolongations, which, having intercepted the areolcc containing the adipose tissue, unite together, and expand into a membrane, which glides over the aponeuroses and the superficial vessels and nerves : the sub-cutaneous membrane thus formed bears the name of the/ascm supcrfici- alis : it is only distinctly seen in regions that are traversed by supei-ficial vessels and nerves, as in the lower part of the abdomen, and on the extremities. 2. The deep surface of a general investing aponeurosis presents fibrous prolongations passing between the different layers of muscles, and even between the muscles of which these layers are composed. Moreover, this surface and its several prolongations some- times afford attachments to the superficial muscles, and sometimes it glides over the mus- cles and their tendons by means of a very loose filamentous cellular tissue — an arrange- ment that prevails throughout the greater part of the extent of this surface. Lastly, amid all these sheaths for the nmscles, there exists a proper sheath for the principal vessels of the extremities. These aponeurotic sheaths are not so exactly moulded upon the muscles as not to ad- mit of the accumulation of a certain quantity of fat in their interior; nevertheless, their capacity is so far proportioned to the size of the muscles, that the latter, during their contraction, experience a degree of pressure from them which is highly favourable to their action, at the same time that it prevents all displacement. In emaciated individuals, these sheaths are no longer filled by their respective mus- cles ; and, without doubt, the want of a due compression upon the muscles has some in- fluence in producing the weakness experienced by convalescents, or by those wasted by some chronic disease. 3. The borders or circumferences of aponeuroses, incorrectly named their origin and ter- mination, are either continuous with the aponeuroses of the adjacent regions, or are at- tached to the processes on the articular extremities of the bones, or result, in part, from the expansion of tendons. The aponeuroses are perforated by vessels and nerves, which, in such cases, are gui- ded and protected by arches, rings, or canals of fibrous tissue : of this nature are the sheaths of the femoral artery and vein, and of the brachial artery and veins, the femoral aich, the canal and arch of the adductor muscles of the thigh, tlie arch of the obturator foramen, and the aortic arch of the diaphragm ; these canals and arches tend to prevent any injury to the vessels and nerves by which they are traversed during the contraction of the muscles. We must not suppose, however, that the vessels are exempt from all pressure -, for experience has proved that arteries are particularly liable to become affect- ed with aneurism in the neighbourhood of such arches ; as, for example, the popliteal and femoral arteries and the aorta. The muscular fibres, in fact, are not attached to these arches in such a manner as to dilate them in all directions during their contraction, but rather in such a way as to elongate them in one direction and contract them in another. All the aponeuroses, whether of insertion or investment, have their tensor muscle. With regard to the aponeuroses of insertion, this requires no proof; for the action of the muscle or muscles to which they afford attachment must necessarily render them tense. It is no less true, however, of the investing aponeuroses, some of which have even a sep- arate muscle for this purpose. Thus, the occipital and frontal muscles are tensors of the occipito-frontal aponeurosis. The fascia lata is rendered tense by the tensor vagina; fe- moris, the palmar fascia by the pahnaris longus, &c. The aponeuroses of both kinds are inextensible, resisting, and insensible membranes, their thickness and strength being exactly proportioned to the resisting power and strength of the muscles which are invested by them, or to which they afford the means of inser- tion. Thus, the fascia of the thigh is very much stronger than that of the arm : the thick- ness of the aponeuroses increases from the upper to the lower part of the limbs ; and, again, the powerful vastus externus is provided with a much stronger sheath than the muscles of the posterior, or of the internal region of the thigh. We may, then, consider it as a general law, without exception, that the aponeurotic system invariably presents a corresponding degree of development to that of the muscular system. We should, there- fore, study the aponeuroses, as well as the muscles, upon robust subjects ; their pearly aspect is destroyed in individuals wasted by chronic diseases. The aponeurotic and 296 APONEUROLOGY. muscular systems are both most fully developed in camivora, in which class of animals the peai"ly appearance is pecuharly well marked, and the cellular tissue is often replaced by a fibrous texture ; a transformation which proves the analogy of the cellular and fibrous tissues in organization, vitality, and function.* The thinner fasciae are composed of a single layer of parallel fibres, which have be^ tween them intervals of diiferent sizes : stronger aponeuroses are composed of several planes, the fibres of which intersect each other at various angles. The vessels and nerves of the aponeuroses are little known ; but I believe that I have traced nerves into them. I have certainly done so with regard to the dura mater.* I shall include among the aponeuroses the fibrous sheaths of tendons * which are some- times presented under the form of imperfect rings, or canals of different lengths, which retain the tendons in contact with the bones. They serve to confine the tendons, to keep them applied against the bones, and to favour their reflection. The periosteum* must also be annexed to the aponeurotic system ; it is a true aponeu- rosis, covering every part of the bones, and constituting a fibrous sheath for them. We may consider the periosteum as the central point of the aponeurotic system, proceeding- from which, we find either tendons expanding upon the surface or in the substance of muscles, and constituting the aponeuroses of insertion ; or else those fibrous cones or pyr- amids, from the interior of which the fleshy fibres take their origin. From the perioste- um, or, rather, from the ridges or clefts by which the surfaces of bones are marked, both, the partial and general investing aponeuroses arise. In this way the muscles of the ex- tremities are situated between two fibrous layers ; the deep layer consisting of the peri- osteum, the superficial layer of the general investing fascia : numerous septa pass from one to the other, and divide the limb into a number of compartments, intended to isolate, confine, and protect the different muscles. Use of the Aponeuroses. — Forming, as they do, an important division of the fibrous tex- tures, tiiey partake of the physical, chemical, anatomical, physiological, and pathological properties of that tissue. 1. From their great strength, they are enabled to resist the powerful traction and dis- tension exercised upon them by the muscular fibres. Their division or destruction is accompanied by displacement of the parts which they are intended to bind down. Be- tween the different layers of the regions of the body they establish very precise limits, a knowledge of which is of the greatest importance, in enabling us accurately to account for many morbid phenomena, and in guiding us in the performance of surgical operations. 2. They are inextensible ; hence the resistance which they oppose to the development of subjacent parts, and the tension produced by inflammation of organs situated beneath them. They yield to gradual distension, but then become thinner and weaker, and can only imperfectly fulfil their proper oflices. 3. They are totally inelastic, and, therefore, when distended beyond a certain point, never return to their original dimensions. Of this we have an example in the condition of the abdominal parietes after utero-gestation, or ascites. 4. The low degi-ee of vitality they possess explains why they are so slightly involved in inflanamation or other morbid conditions of the adjacent structures, and also the fact of their establishing limits beyond which these diseases seldom pass. They are insen- sible to all ordinary stimuli, but become painful when they are violently overstretched. The plantar fascia, under such circumstances, becomes extremely sensitive. Having made these general remarks, we shall now describe, in succession, the prin- cipal aponeuroses of the human body.t * See note, infra. t Note on Aponeurology. — [The analogy existing between tbe cellular and aponeurotic investments of various organs renders it advantageous to consider in this place the general anatomy of the ceWu/ar and _^frrous tissues. The ultimate elements of both these kinds of tissue are precisely similar, though s.miewhat differently ar- ranged in each ; they consist of delicate transparent filaments, varj-ing in diameter from ^ ^^ j ^ ^ th to jj-jj-q-q th of an inch, and having a peculiar sinuous or undulating direction ; they are insoluble in cold water, but by long-continued boiling are almost entirely converted into gelatine. In cellular tissue these undulating filaments are arranged side by side, either into larger compound and flex- uous fasciculi, or into thin, transparent laminae, which cross and intersect one another in all directions, so as to leave interstitial cavities or areuke, freely communicating with each other, and moistened by an albuminous fluid. The tissue thus formed, more properly called areolar, or filamentous, is of a grayish aspect, and highly elastic ; the latter property depending not on any innate elasticity in the ultimate filaments, but on the sinuous disposition of those filaments, and of the fasciculi into which they are collected. But few vessels, and still fewer nerves, are believed to terminate in this tissue. It is continuous over the whole body ; hence the great extent to which it may be affected with diffuse inflammation ; it also invests and isolates parts, forms the ma- trix of nearly all organs, and the basis of many membranei ; and is called, according to its position, investing, intermediate, penetrating, parenchymatous, or sub-membranous. The characters above described are most strongly marked in the loose cellular tissue, examples of which are met with in the axilla, under the sub-scap- ular muscle, between the free surfaces of muscles and their sheaths, behind the kidneys, &c. In other situ- ations it is more condensed, as in the sub-serous, sub-mucous, and sub-cutaneous cellular tissues ; in the latter of these, or the superficial fascia, and also in the cutis itself, it approaches to the fibrous tissue Ixith in density and in the mode of arrangement of its elementary filaments, and is therefore termed fibro-cellular tissue. From this variety the transition is natural to the fibrous tissues, properly so called. In fibrous tissue the undulating primitive filaments are also arranged side by side into fasciculi, which differ from those of cellular tissue in being much larger, more dense and more opaque, and in being straight in- stead of flexuous. They are white, shining, strong, and almost inelastic, qualities depending on the compact SUPERFICIAL FASCIA. 297 PARTICULAR APONEUROSES. Superficial Fascia. — Aponeuroses of the Cranium — of the Face — of the Neck — of the Thorax — of the Abdomen — of the Pelvis — of the Thigh, Leg, and Foot — of the Shoulder, Arm, Forearm, and Hand. The Superficial Aponeurosis, or Superficial Fascia. From every point of the deep surface of the skin fibrous cellular lamellae arise, which intersect each other in various directions, so as to form meshes or areolae, containing adipose tissue in ordinary circumstances, and a serous fluid in cedema.* The cutaneous muscle {panniculus carnosus) of the lower animals is developed in these lamina? ; and among them are situated the sub-cutaneous vessels and nerves, and the lymphatic glands. The name of fascia superficialis has been of late applied to this assemblage of laniellge. It was pointed out in a particular manner by Glisson, who described it under the name of the general investment of the muscles, proceeding from the spine, and covering the whole body; Camper, Cowper, Scarpa, Hesselbach, Lawrence, J. Cloquet, &c., have described it upon the abdomen, in its relation with herniae ; Godman has spoken of its existence over the entire surface of the body : M. Paillard, in his inaugural dissertation, traced it with still greater exactness ; MM. Velpeau and Blandin, in their Traites d'Ana- tomie Chirurgicale, consider it as existing in almost all regions of the body. But if the word aponeurosis be employed in its ordinary acceptation, it will be found that a fascia superficialis, consisting of a fibrous texture capable of anatomical demon- stration, exists only in two kinds of situations, viz., in those where the skin is extreme- ly movable, and in those where there is a layer of sub-cutaneous vessels and nerves : in both these cases the fibrous prolongations from the skin are expanded into a thin lamina, constituting a superficial covering for these vessels and nerves, and separated from the fibrous investment of the muscles by a layer of cellular and adipose tissue, of variable thickness. In all other parts, the fibro-cellular prolongations of the skin become contin- uous either with the investing aponeuroses, or with the proper fibro-cellular sheaths of the muscles, or are lost in the sub-cutaneous cellular tissue. So true is this, that this thin areolar layer, which can with diflSculty be separated from the skin in emaciated persons, disappears altogether in those whose cellular tissue is distended by fat or se- rous effusion. Having made these remarks, I shall describe the superficial fascia in those regions only where it can be easily demonstrated, viz., in the lower part of the abdomen, and in the extremities. The Superficial Fascia of the Abdomen. This aponeurosis, from its constituting the first sub-cutaneous covering of herniae, has particularly engaged the attention of authors who have specially treated of the patho- logical anatomy of those diseases. It becomes evident in the neighbourhood of the umbilical region, but is much more dis- tinct at the fold of the groin, where it divides into two layers, one of which is attached to the femoral arch, and the other is prolonged upon the lower extremity. It is bound- ed on the inside by the median line, and on the outside by another line, extending per- pendicularly upward from the anterior superior spinous process of the ilium. It is pro- longed over the inguinal ring, and over the spermatic cord in the male subject. parallel disposition of the component filaments, and the slight amount of elasticity in particular on the ab- sence of sinuosity in the compound fasciculi. According- to the manner in which these fasciculi or fibres (as they are termed) are arranged and combined, we have either the membranous or the fascicular form of fibrous tissues. In the membranous form there are some which closely resemble the fibro-cellular membranes already allu- ded to, and consist of the shining fibres crossing each other in all directions (without anastomosis), and inter- mixed with more or less condensed cellular tissue ; for example, the thinner investing aponeurosis, the capsu- lar ligaments, the pericardium, tunica albuginea, periosteum, and dura mater. In others, again, the fibres are more parallel, though stiU intersected, and combined with cellular tissue, as in the fascia lata of tlie thigh, and in other strong investing aponeuroses. In the aponeuroses of insertion of the broad muscles, and in the expanded terminations of tendons, there is scarcely any cellular tissue, while the parallel arrangement is yet more perfect ; and, finally, the latter attains its utmost perfection in the round ligaments, and in tendons, which constitute the fascicular form of fibrous tissue, and the type of the tissue itself. These textures contain but few nerves and vessels. The distribution of a branch of the fourth cranial nerve to the dura mater, alluded to in the text, has been confirmed by other anatomists. Bloodvessels abound in the periosteum, but they merely divide in that membrane, so as to enter the bone at a great number of points. The sheaths of tendons (classed among the fibrous tissues by M. Cruveilhier) display a tendency to become fibro-cartilaginous, especially at and near their attachments to the bones. They have hitherto been described (ex. gr., p. 250, 257) as if lined by vaginal synovial membranes (note, p. 177). According to Dr. Ilenle, how- ever, their interior is not covered by an epithelium. The bursce, or so-called bursal synovial membranes, formed between the tendons of muscles (p. 265), between tendons and bones (p. 265, 266, 267), and between the skin and projecting parts of bones, as over the patella, the olecranon, &c., according to the same authority, are also destitute of epithelium. It would appear, therefore, that although these cavities resemble in function the true synovial membranes, they differ anatomically from them, and consist merely of shut sacs formed in the (general cellular texture of the body. Such bursas, however, as communicate with the synovial capsules of joints (p. 216, 244), are probably lined by an epithelium.] * [Adipose tissue is never deposited m the sub-cutaneous tissue of the eyelids, nor in the male organ of gen- eration. These parts, however, may become much distended from serous infiltration.] Pp 298 APONEUROLOGY. It has been said that in the foetus, before the descent of the testicle, the superficial fas- cia dips into the inguinal canal, and forms an infundibuliform prolongation, reaching up to the lower part of that gland ; and the dartos has been supposed to result from the ex- pansion of this fascia — a description which can be regarded only as an ingenious specu- lation, which has not been confirmed by actual dissection. Lastly, the external surface of the superficial fascia of the abdomen is in relation with the skin, separated from it, however, by a layer of adipose tissue of variable thickness, in which the sub-cutaneous vessels and nerves are situated. Its deep surface corre- sponds with the aponeurosis of the external oblique muscle, and with a portion of its fleshy fibres : from these parts it is separated by a layer of serous cellular tissue, which enables it to be moved easily upon this muscle and the sub-cutaneous vessels and nerves. The Superficial Fascia of the Upper and Lower Extremities. These are thin fibrous sheaths, separated from the skin by a greater or less quantity of adipose tissue, and from the investing aponeurosis of the muscles by the sub-cutaneous vessels and nerves. It does not exist around the joints, nor in the palms of the hands and soles of the feet, for in these places the skin adheres to the subjacent aponeuroses The Aponeuroses of the Cranium. The Occipito -frontal or Epi-cranial Aponeurosis. This is a sort of tendinous or cutaneous cap {galea capitis), stretched between the two frontal and two occipital muscles. Its superficial surface is intimately adherent to the skin by means of very short and strong fibrous prolongations, between which the fatty matter is deposited : the frontal, occipital, temporal, and auricular vessels and nerves traverse this adipose tissue. Its deep surface glides upon the periosteum of the scull (pericranium) by the intervention of a very delicate cellular tissue, in which fat is never found. Its anterior margin receives the fibres of the frontal muscles, forming a trian- gular point between them ; its posterior margin receives the fibres of the occipital mus- cles, and also occupies the interval between them. These two muscles act as tensors of the aponeurosis. Its outer margin gives attachment to the superior and anterior auricular muscles. It is composed behind of shining fibres, which seem to form a ten- don of insertion to the occipitalis muscle, but it soon loses its pearly appearance, and becomes more adherent to the skin : it is thick and strong at the upper part of the head, but thin and almost cellular at the sides : it may be regarded as a dependance of the su- perficial fascia. It gives rise to the tension which is so common and so dangerous in inflammations of this region. Its adhesion to the skin explains the shallow character of ulcers, and the flatness of the small abscesses occurring in these parts. The Temporal Aponeurosis. Besides the tendinous origin of the temporal muscle, which has been already descri- bed, there is also a very strong investing aponeurosis, arising from the upper border of the zygomatic arch, and inserted into the curved line bounding the temporal fossa above. This aponeurosis completes the sort of case in which the muscle is contained ; and the space between it and the temporal fossa corresponds with the thickness of the muscle. It differs from the epicranial aponeurosis, which is more superficial and covers it su- periorly, in not adhering to the skin, which glides very easily upon it. Its deep surface adheres to the upper part of the muscle, and furnishes it with numerous points of at- tachment ; below it becomes free, and is separated from the fleshy fibres by a consider- able quantity of fat ; hence the depression formed in this situation in emaciated persons. It increases in thickness from above downward ; it divides below into two layers : one superficial and thinner, inserted into the outer edge of the upper border of the zygoma ; the other deep and thicker, attached to the inner surface of that process. In tolerably stout persons, a considerable quantity of fat is situated between these two layers, and a remarkable branch of the temporal artery also occupies the same situation. This fat must not be confounded with the larger mass which lies beneath the aponeuroses. The resistance of this fascia explains the reason why abscesses in the temporal fossa never point outward, but rather tend downward into the zygomatic fossa. The Aponeuroses of the Face. The Parotid Aponeurosis. This is a sheath of great thickness, especially that part which covers the outer surface of the gland ; it is continuous below with the cervical fascia. It belongs especially to the gland, for which it forms a framework by means of fibrous prolongations from its deep surface. The density of this sheath explains both the pain caused by inflammation of the gland, and the difficulty with which pus makes its way from within it to the surface. The Masseteric Aponeurosis. This is a thin tendinous layer covering the masseter muscle, and continuous below with the cervical fascia ; it appears to divide behind into two layers, one of which con- THE CERVTCAl. FASCIA, ETC. 299 stitutes the parotid fascia, and the other penetrates between that gland and the masse- f.er ; above and anteriorly, it becomes merged into the cellular tissue. Purulent matter situated beneath this fascia tends downward into the neck, but when situated superfi- cially to it, points towards the skin. The Buccinator Aponeurosis. The buccinator is covered by a closely adherent fibrous layer, which is regarded as the expansion of the fibrous sheath of the Stenonian duct ; it is thickest behind, where it is termed the buccinato-pharyngeal aponeurosis, because it gives attachment behind to the superior constrictor of the pharynx, and to the buccinator in front. This aponeurosis prevents superficial abscesses from opening into the mouth, and is also opposed to the extension outward of diseases attacking the mucous membrane. The Cervical Aponeurosis, or Cervical Fascia. In the cervical region we find, 1. The cervical fascia ; 2. The prevertebral aponeurosis. The Cervical Fascia. The cervical aponeurosis covers the whole anterior region of the neck ; it extends from the base of the lower jaw to the sternum and clavicles, and is insensibly lost on either side in the sub-cutaneous cellular tissue. It is thick in the median line, and forms a sort of cervical linea alba. From this linea alba two layers proceed in the supra-hyoid region, and four in the infra-hyoid region, which are arranged in the following manner : 1. The superficial layer, or the superficial cervical fascia, covers the whole anterior and lateral regions of the neck, is prolonged downward in front of the clavicle, to become continuous with the proper aponeurosis of the pectoralis major, is attached above to the masseteric and parotid fascia;, and, internally to the masseter muscle, is fixed to the base of the lower jaw. It fills up the interval between the two platysmata, and is prolonged behind these mus- cles to form the anterior layer of the sheath of the sterno-mastoid. The external jugu- lar vein is superficial to this layer in the sub-hyoid, and lies beneath it in the supra-hyoid region. 2. The deep layer passes beneath the sterno-mastoid, on the outer border of which it unites with the preceding layer, and completes the sheath for that muscle. It covers the internal jugular vein, the common carotid artery, the pneumogastric nerve, the great sympathetic, and its cervical ganglia. Its upper margin is attached to the base of the lower jaw ; its lower margin to the posterior surface of the clavicle, and to the posterior edge of the fourchette of the sternum. It is necessary to examine this deep layer, both in the supra and sub hyoid region. In the supra-hyoid region its middle portion is very strong, and occupies the triangu- lar space between the anterior bellies of the digastric muscles ; it is fixed by its lower margin to the os hyoides, and on each side to the tendon of the digastricus. The lat- eral portions of this aponeurosis pass beneath the sub-maxillary glands, and are attached to the rami of the lower jaw. Externally to these glands they join the parotid aponeu- roses, and form a tolerably thick septum between the sub-maxillary and parotid glands of either side. In the sub-hyoid region this deep layer is divided into three very distinct parts, a mid- dle and two lateral. The middle is the stronger ; it occupies the triangular space be- tween the two omo-hyoid muscles, and becomes continuous with their median tendons : the muscles may, therefore, be regarded as the tensors of this facia. It binds down the muscles of the infra-hyoid region : its arrangement explains why abscesses situated in front of it discharge their contents through the skin, and not into the thorax, as those do that are subjacent to it. The lateral parts of the aponeurosis constitute the supra-clavic- ular fascia, a very strong layer, in which the superficial layer already described, and the two which yet remain to be noticed, all terminate. It occupies the whole triangular space between the trapezius and the sterno-mastoid, is continuous with the fibro-cellular sheath of the former muscle, and adheres below to the clavicle. The latter circumstance is of great importance in relation to surgical anatomy. The superficial and deep layers which we have now described are common to both the supra and sub hyoid regions. In the sub-hyoid region there are two other aponeurotic layers : one, very thin, separating the superficial from the deep muscles, i. e.. the omo and sterno hyoidei from the sterno-thyroidei and thyro-hyoidei ; the other, thicker, pass- ing between the sterno-thyroidei and the trachea. The latter is the fourth layer, which Godman incorrectly describes as continuous with the pericardium. The Prevertebral jiponeurosis. This aponeurosis covers the muscles of the prevertebral region, viz., the longi colli, and the great and small anterior recti : it is prolonged on each side upon the scaleni, the levator anguli scapulae, and the brachial plexus ; and is attached to the upper border of the scapula, and to the outer half of the posterior border of the clavicle. It completely 300 APONEUROLOGY. separates the axilla from the neck, and is perforated by several vessels. It prevents large abscesses of the neck from opening into the axilla ; and, in caries of the cervical vertebra, it retains the pus poured out against it, so as to form abscesses by accumulation. The Thoracic Aponeuroses. The Intercostal Aponeurosis. Independently of the semi-tendinous structure of the intercostal muscles, we find sev- eral fibrous layers in each intercostal space : one layer in front, continuous with the ex- ternal intercostal muscle ; another behind, continuous with the internal intercostal mus- cles ; and, situated within these muscles, a third layer, which lines them and separates them from the pleura. The existence of this sub-serous aponeurosis accounts for the rare occurrence of the bursting of an external abscess of the chest into the cavity of the pleura ; and, on the other hand, of the escape of collections in the pleura by external openings. The Aponeurosis of the Serrati Postici. In the dorsal region of the trunk, we find a very thin fibrous layer (sometimes called the vertebral aponeurosis), extending between the two serrati postici. It is of a quadri- lateral form ; its inner margin is attached to the summits of the dorsal spinous process- es ; its outer margin to the angles of the ribs, and its lower margin to the upper border of the serratus posticus inferior ; it seldom terminates at the lower border of the serratus posticus superior, but generally passes beneath it, and becomes the investing aponeuro- sis of the splenius. The use of this aponeurosis is evidently to confine the posterior spi- nal or long muscles of the back. The Abdomimal Aponeuroses. The parietes of the abdomen are partly muscular and partly aponeurotic : the muscu- lar portions are situated at the sides of the abdomen. The aponeurotic portions occupy the anterior and posterior regions, and form the anterior and posterior abdominal aponeu- roses. The extensibility, elasticity, and, above all, the contractility of the abdominal pa- rietes, depend on the three intersecting muscular layers ; whde to the aponeuroses must be attributed their capability of resistance and want of extensibility. The Anterior Abdominal Aponeurosis. The anterior abdominal aponeurosis forms the greater part of the anterior wall of the abdomen. It consists, 1. Of a fibrous column, which is continuous with the osseous col- umn of the sternum ; and, 2. Of two perfectly corresponding halves, one right, the other left. These two halves are united in the linea alba, which may be regarded as their com- mon origin. The Linea Alba. The linea alba {i,figs. 109, 110) is a tendinous raphe, extending from the ensiform cartilage to the symphysis pubis ; it constitutes the anterior median line of the abdomen. In a theoretical point of view it may be regarded as a continuation of the sternum, which, in some animals, is prolonged as far as the pubes.* Anatomists are not agreed as to the acceptation of the term linea alba. According to some, it is a mathematical line produced by the intersection of the aponeuroses of one side with those of the other : according to others — and this meaning appears to me preferable — it consists of the tendinous band comprised between the inner borders of the recti. Thus defined, the breadth of the linea alba corresponds to the interval between these muscles, and, as they are directed somewhat obliquely upward and outward, it follows that the upper or supra-umbilical portion of the linea alba is broader than that portion which is below the umbilicus. This remarkable arrangement, by which the strength of the lower part of the abdomen is secured, affords an explanation of the uniform occur- rence of hernias through the linea alba above, not below, the umbdicus. It should also be observed that, during exertion, the viscera are chiefly forced against the lower part of the abdominal parietes, and also that the gravid uterus rests upon it. The sub-umbilical portion of the linea alba forms a mere line, while the supra-umbili- cal is about a quarter of an inch in breadth. Its transverse dimensions are much in- creased in persons whose abdomen has been greatly distended. Thus, during and after pregnancy and certain dropsies, it in some cases acquires a considerable breadth, and does not return to its original size, even after the distension has ceased to exist. In a female who died a short time after delivery, I found the linea alba three inches across at the umbdicus, and fifteen lines in the narrowest part. In cases of this kind, the linea alba forms a sort of long pouch, which receives the intestines, and becomes very prom- inent during the contraction of the recti. The linea alba presents several elliptical openings for the passage of nerves and ves-* * The analogy has even been carried so far, that the tendinous intersections of the recti have been com- pared to the ribs, for they seem to come oif from the linea alba like abdominal ribs. THE AISiTERIOR ABDOMINAL APONEUROSIS. 301 seis. In these foramina, round masses of fat are developed, which dilate them, and draw down the peritoneuin into them, or are absorbed in consequence of emaciation, and thus open an easy way for the production of hernia of the hnea alba. Of all these orifices, the most remarkable is the umbilical ring, which gives passage to the umbilical vessels in the foetus, but becomes cicatrized after birth, at least in the majority of subjects.* The situation of the umbilicus varies at different ages. The middle point of the length of the body is situated above the umbilicus before the sixth month of foetal existence, and coiTesponds with it after that period. In the adult it is situated below the umbil- icus. Its situation with regard to the abdomen varies in different individuals. Thus, the umbihcal cicatrix, which is generally a little below the middle of the abdomen, is sometimes exactly in the middle. I have even seen it at the point of junction of the lower with the upper two thirds. This cicatrix, moreover, is much stronger than the neighbouring parts. Thus, an im:ibilical hernia, which, in a new-born infant, always occupies the navel itself, in an adult is almost invariably situated a little above the umbilicus. Still it occasionally yields, either in cases of dropsy or of hernia ; and I have records of several instances of hernia in the adult, that have occurred through the umbilical ring. The linea alba is in relation, in front, with the skin, which adheres more closely to it than to the neighbouring parts, especially opposite the umbilicus. In the male, it is sep- arated from the skin below by the suspensory ligament of the penis, which sometimes extends as far as the middle of the space between the pubes and the umbilicus : behind, it is in relation with the peritoneum, separated from it, however, by the remains of the urachus, and by the bladder itself when that viscus is distended. It is, then, through the linea alba that the bladder is punctured in cases of retention of urine, and that the incision is made in the high operation of lithotomy. The peritoneum does not adhere more closely to the umbilicus than to the other parts of the abdomen, and therefore um- bilical hernice, like all others, are invariably provided with a proper sac. The upper extremity of the linea alba is attached to the ensiform appendix, a flexible, elastic, cartilaginous body, constituting, as it were, a transitional structure between the sternum and the part we are now describing. The lower extremity corresponds to the symphysis pubis. If we examine the structure of the linea alba, we shall see that it is formed by the in- tersection of the layers of the anterior abdominal aponeuroses. One remarkable circum- stance is, that the intersecting fibres do not stop at the median line, but pass from one side to the other ; so that the tendinous fibres of the external oblique of the right side become the tendinous fibres of the internal oblique of the left ; and, again, that the inter- section occurs not only from side to side, but also from before backward. Below the umbilicus the point of intersection is elevated by some longitudinal fibres, constituting 4 small and very distinct cord, which appears to form a septum between the recti mus- chs ; it increases in thickness as it proceeds downward from the umbilicus to the sym- physis,, and may be easily felt under the skin in emaciated individuals. We may add, that Uie fibres of the linea alba have no resemblance to the yellow elastic tissue ; they are neither extensible nor elastic, at least in the human subject. Its uses entirely re- fer to Its cbpability of offering resistance. The pyraiRidales are its tensor muscles. The Four Layers of the Anterior Abdominal Aponeurosis. From each side of the linea alba [a, Jig. 134, a diagram representing a horizontal sec- tion of the abdominal parietes) two fibrous layers proceed pig. 134. out'vard, one anteriorly, the other posteriorly, to the rec- tus muscle (r). The anterior layer (6), having arrived near the outer bor- der of the muscle, subdivides into two other layers : one superficial, constituting the aponeurosis of the external ob- lique (rf) ; the other deep, forming the anterior layer of the fj aponeurosis of the internal oblique (e). The posterior lay- er (c) is also simple as far as the outer border of the rec- tus, and then separates likewise into two layers : one an- terior, which becomes united with the aponeurosis of the internal obhque («), and is regarded as the posterior layer of that aponeurosis ; the other -posterior, which continues its course outward from the rectus, and forms the aponeu- rosis of the transversahs muscle (/). We shaU describe these different parts in succession. The Aponeurosis of the External Oblique. — ^This is the most superficial layer, and is of a quadrilateral figure {a, fig. 109) ; it is broad below, where it corresponds to the in- * Some cases are on record of the persistence of the umbilical vein, and, consequently, of the umbiliciilring'. I have narrated a case where a sub-cutaneous abdominal vein, prodigiously developed, lierame continuous with the vena cava, which was also very large. — (Anal. Path., 1. xvi., pi. 6.) S02 APONEUROLOGY. terval between the anterior superior spinous process of the ilium and the linea alba, be- comes narrower immediately above, and again expands .at the upper part, but to a less extent than below. It is covered by the skin and the superficial fascia, and it covers the aponeurosis and the anterior portion of the fleshy fibres of the internal oblique. It adheres intimately to the aponeurosis of the internal oblique, as far as the vicinity of the outer border of the rectus, excepting below, where the two fasciae are perfectly distinct, and can be easily separated throughout their entire extent. Its external margin, slightly concave and denticulated, presents irregular prolongations, with which the fleshy fibres become continuous. A line extending from the anterior superior spinous process of the ilium to the extremity of the cartilage of the eighth rib, will indicate with tolerable accuracy the direction of this margin, which appears to be divided into two layers, one superficial, very thin, and continuous with the proper cel- lulo-fibrous sheath of the muscle ; the other deep, and giving origin to fleshy fibres. Its upper margin is narrow, and cannot be exactly defined ; it often gives attachment to some fibres of the pectoralis major. Its lower margin consists of two very distinct portions : one, extending from the ante- rior superior spinous process of the ilium to the spine of the os pubis, is called the fem- oral arch {p p'.figs. 136, 137) ; the other, stretching between the spine and the symphy- sis pubis, offers for consideration the pillars and the cutaneous orifice of the inguinal canal {m, figs. 109, 136, 137). The aponeurosis of the external oblique is composed of tendinous fasciculi, directed obliquely downward and inward, like the fleshy fibres with which they are continuous. It is also perforated, especially in the neighbourhood of the linea alba, by a considerable number of bloodvessels and nerves. Not unfrequently the component fasciculi have between them, especially near the femoral arch, linear or triangular spaces of variable size, through which the fibres of the internal oblique are visible. The component fas- ciculi are also intersected at right angles, and, as it were, bound dowTi by other tendi- nous fibres, which are more or less developed in different individuals, and are most usu- ally situated in the neighbourhood of the femoral arch. Having made these preliminary observations, we shall now describe in detail, 1. The lower margin of the aponeurosis of the external oblique, or the femoral arch; and, 2. The inguinal ring and canal. The Femoral or Crural Arch. — ^When the aponeurosis of the external oblique has ar- Fig. 136. rived opposite a hne extending from the anterior superior spinous pro- cess of the ilium to the spine of the pubes, it suddenly terminates, be- comes thickened, and is reflectei (a a', fig. 137) from before back- ward upon itself. The rcflerted \)orAer{pp',figs. 136, 1371 ha? been variously denominated the femoral or crural arch, the refiictei margin of the tendon of the eztemal ohlique, Pouparfs ligament, and /he ligament of Fallopius. This aich, which is stretched like a cord, corresponds to the fold of the groin, and defines the limits of the abdomen and the lower extremity : it forms the ar terior border of a considerable tri- angular space, which is completed by the ilium (1,.^^- 136) on thr. out- side, and by the os pubis (2) behind. This space establishes a communi- cation between the lower extremi- ty and the abdomen, and is occupied (proceeding from without inward) by the psoas and iliacus muscle (? to i), the crural nerve (n), the femoral artery (a) and vein (v), and the pectineus muscle.* The crural arch is directed somewhat obliquely downward and inward ; and as its out- er third is more oblique than the inner two thirds, it describes externally a slight curve, having its concavity directed upward. Its loicer or reflected border is continuous with the fascia of the thigh. This adhesion occasions the tension of the arch, as may be shown by cutting the femoral fascia at the point of its junction with the arch : hence the precept of Scarpa, who recommended incisions to be made in this situation, in order to relieve the constriction in femoral hernias. The free margin of the reflected portion of the aponeurosis, of which the femoral arch * This is not represented in the woodcut. THE CRURAL ARCH. 303 consists, is continued backward into the iliac fascia {s') externally ; and internally, into the fascia transversalis (/)• Externally near the psoas and iliacus (beyond a'. Jig. 137), the posterior or reflected portion of the arch is closely blended with its anterior or direct portion, as well as with the ihac fascia and the fascia of the thigh, so that, in this situation, there is a thickening rather than an actual reflection of the aponeurosis. Internally to the psoas and iliacus, however (at a), the direct and reflected portions are perfectly distinct, and form a groove with its concavity upward, which we shall find to assist in the formation of the inguinal canal. These two separate portions of the inner part of the femoral arch require a spe- cial description. The direct portion (part of which is shown turned downward at d, fig. 137) passes on to be attached to the spine of the pubes {p,figs. 136, 137), becoming more and more prominent, so that it can be easily felt under the skin, especially when the thigh is ex- tended upon the pelvis. The reflected -portion, externally, is narrow, and, as it were, folded ; but internally it becomes expanded, from its fibres slightly changing their direc- tion, and diverging, so as to be inserted into the spine of the pubes behind the direct portion, and also into the pecten or crest of the pubes. This reflected and expanded portion, described even in the oldest anatomical works, has become celebrated in recent times under the improper name of Gimbernat's ligament {g,fig- 136), from a Spanish surgeon, Avho pointed out its importance as the seat of stric- ture in femoral hernia. It is triangular in shape ; its anterior margin corresponds to the crural arch ; its posterior margin to the crest of the pubes ; its outer margin is free, con- cave, tense, and sharp, and forms the inner part of the circumference of the crural ring (r). This concavity, against which the protruded intestine becomes strangulated, has obtained for the ligament the name of the falciform ligament or fold* ■ Its strength is very considerable ; but, occasionally, intervals are left between its fibres, through which hernial protrusions may take placet From the lower surface of Gimbernat's ligam.ent a fibrous prolongation is given off, which sometimes represents a second arch below the femoral arch, and assists in form- ing the superficial layer of the fascia lata of the thigh. This tendinous expansion has a great effect in rendering the arch tense. We may add, that there is considerable vari- ation in different subjects, both in the strength and development of Gimbernat's hga- ment ; varieties that must have great influence on the position of crural hernise, and on the seat of strangulation in that disease. Behind the femoral arch, on the outer side of Gimbernat's ligament, is an opening (a to r. fig. 136) or ring, intended to give passage to the femoral artery (a) and vein (v), and to a gi'eat number of lymphatic vessels and glands : this is the crural ring.t The sub-peritoneal cellular tissue sometimes acquires great strength opposite this ring, and constitutes what is called the crural septum, (situated at r). The form of the crural ring is that of an isosceles triangle, the base of which is very long, and formed by the crural arch, the inner border by the pectineus, and the outer by the psoas and iliacus muscles. Of the three angles, the internal is rounded, and corre- sponds to the concave margin of Gimbernat's ligament ; the external angle, opposite which the epigastric artery is situated, is very acute, and corresponds to the point at which the femoral arch separates from the iliac fascia ; the posterior angle is very ob- tuse, and corresponds to the ilio-pectineal eminence (d). The femoral vein is in relation with the inner or pectineal border of this triangular space ; the femoral artery with the ilio-pectineal eminence and the outer border. The crural nerve (n) lies behind and externally to the artery, being separated from it only by the iliac fascia (.s'). Crural hernias descend through the inner portion of the crural ring.ij The femoral arch is formed by proper fibres, arising from the anterior superior spinous process of the ilium ; and also by those fibres of the aponeurosis of the external oblique, which, after having arrived at the arch, change their direction, become reflected inward, and are collected together, so as to form a strong and tense cord. The Inguinal Ring and Canal. — On the inner side of the spine of the os pubis, between the spine and the symphysis, the aponeurosis of the external oblique divides into two almost parallel, or at least very slightly diverging, bands, which leave between them an opening for the passage of the spermatic cord in the male, and of the round ligament in the female. This opening is the inguinal ring {m,figs. 109, 136, 137), and the bands which form its limits are called the pillars (o p,figs. 136, 137). The inguinal ring is oval or triangular ; its greatest diameter has the sarne direction as the fibres of the external oblique, viz., obliquely downward and inward. Its base corresponds to the interval be- * [This term is now generally applied (after Bums) to the external margin of the saphenous opening (n,_/ig-. 137) in the fascia lata.1 t M. Laugier has lately recorded a case of hernia through the fibres of Gimbernat's ligament. Ihave since had an opportunity of seeing, m an old woman at the Salptr^iere, two hernial sacs near each other, one of which protruded through the crural ring, and the other internally to the ring; the necks of these sacs were separated by a fibrous band, which appeared to me to be formed by the external fibres of Gimbernat's ligament. t [The term "crural ring,"' it must be remembered, is limited by British anatomists and surgeons to the small space (r), bounded internally by the free margin of Gimbernat's ligament, and externally by the femoral vein. It is through this space, and therefore through the intenial portion only of the " crural ring" of M. Cruveilhier, that crural herniiE descend.] I) See note, suptd. 304 APONEUROLOGY. Fie. 137 tween tlie spine and symphysis pubis. Its apex is not always well defined, and is generally truncated by fibres which pass at right angles to its pillars. From the up- per part of the margin of the ring a tendi- nous prolongation is given off, which ac- companies the sper- matic cord in the male, and the round ligament in the fe- male. Of the pillars, one is external or inferior, the other internal or superior. The external pillar (p) is attached, not to the spine of the OS pubis, but into the fore part of the symphysis : this pillar is nothing more than the in- ternal extremity of the direct portion of the femoral arch. Moreover, some anatomists consider Gimbernat's ligament as the reflected portion of the external pillar. The internal pillar (o) is broader than the external, and intersects the corresponding structure of the opposite side in front of the symphysis, not unfrequently some fibres of the right internal pillar intersecting those of the left external pillar. Inguinal Ca7ial or Passage. — The inguinal ri7ig (?n) is the anterior or cutaneous orifice of an oblique passage, formed in the substance of the lower edge of the inferior parietes of the abdomen opposite the crural arch, and destined to transmit the cord (s) of the spermatic vessels in the male, and the round ligament of the uterus in the female. This passage, which modern writers only have correctly described, has been styled by them the inguinal canal {t c m). Its length varies from an inch and a half to two inches and a half; it is directed obliquely downward, forward, and inward. The inguinal canal is formed, in reality, by the groove resulting from the reflection backward of the aponeurosis of the external oblique (at a), the posterior border of which groove is continuous with the fascia transversalis, and its anterior border with the apo- neurosis of the external oblique itself We may, then, consider this passage as having an inferior concave wall (at a) formed by the groove of reflection ; an anterior wall, formed by the aponeurosis of the external oblique (shown turned downward at d) ; and a posterior wall, formed by the fascia transversalis (c). There is no superior wall, or, rather, it is sup- plied by the lower margins of the internal oblique (c) and transversalis (/) muscles, which occupy the groove of the crural arch, and receive from it externally numerous points of attachment. Internally the margins of these muscles are separated from the groove by the spermatic cord, or the round ligament. It has been supposed that this canal is lined by a funnel-shaped prolongation of the fascia transversalis. The peritoneal or internal orifice {t, figs. 110, 137) of the inguinal canal is much less accurately defined than the external, or, rather, its inner border alone is well defined, consisting of a concave fibrous edge formed by the fascia transversalis, and somewhat analogous to the concave edge of Gimbernat's ligament. The strangulation of the intestine in inguinal hernia sometimes occurs against this edge. The peritoneal orifice of the ingumal canal is closed by the peritoneum, and the epigastric arteiy runs aloiig its inner border. The testicle, which is originally situated within the abdomen, descends through the inguinal canal ; so, also, do those hernia?, conunonly called oblique inguinal hernias, in order to distinguish them from the direct or internal inguinal herniee. The Anterior Aponeurosis of the Ohliquus Internus and Transversalis. — The aponexirosis of the internal ohlique commences at the linea alba, and immediately divides in its upper three fourths into two layers, one of which passes in front, and the other behind the rectus (r, fig. 134). The lower fourth passes entirely in front of the same muscle without division (as shown in fig. 135). The anterior layer is very closely united with the aponeurosis of the external oblique (at h), from which it can be distinguished only by the direction of its fibres. In some parts there is even a true interlacement between the tendinous fibres of these two muscles ; the lower or undivided portion of the aponeurosis of the internal oblique may, on the contrary, be easily separated from that of the external oblique. The posterior layer of the aponeurosis of the internal oblique is no less intimately blended with that of the transversalis (at c), from which, also, it is to be distinguished by the direction of its fibres only. At the outer border of the rectus muscle the anterior layer of the apo- THE FASCIA TRANSVERSALIS, ETC. 305 neurosis of the internal oblique separates from that of the external oblique, and the pos- terior layer from that of the transversalis, and then immediately unite together, and give origin to the fleshy fibres. The outer margin, therefore, of the aponeurosis of the internal oblique exactly corresponds to the outer border of the rectus, and is directed vertically. The aponeurosis of the transversalis (/, figs. 134, 135) is the deepest layer of the an- terior abdominal aponeurosis : it is very narrow above, increases in breadth as far down as opposite the crest of the ilium, and then progressively diminishes towards its lower portion. It commences at the linea alba, and is divided into two portions : one inferior (below s,fig. 110), consisting only of the lower fourth of the aponeuroses, and passing in front of the rectus (asf in fig. 135) ; the other superior (above s, fig. 110), which passes behind the rectus (as in^^. 134), and is formed by the upper three fourths of the apo- neurosis. Its external margin is convex, and gives origin to the fleshy fibres of the muscle. Its anterior surface is closely united to the aponeurosis of the internal oblique, beyond which it passes on the outside ; its posterior surface is loosely connected with the peritoneum, excepting in its lower fourth, which, as already stated, passes in front of the rectus muscle. The tendinous fibres of the transversalis, which have the same direction as its fleshy fibres, are occasionally found not to terminate abruptly behind the lower part of the rectus ; but the aponeurosis merely becomes thinner, and its fasciculi separated from each other. The Fascia Transversalis and Sub-peritoneal Aponeurosis. In order to complete the description of the anterior abdominal aponeurosis, it only re- mains for me to describe the fascia transversalis, which I regard as a thickened portion of the sub-peritoneal fascia. The fascia transversalis (seen at a' and c,fig. 137) was first pointed out by Sir Astley Cooper, but has been more correctly described by Lawrence and J. Cloquet : it com- mences below at the reflected border {a a') of the crural arch, so that it may be regard- ed as a thin prolongation of the reflected portion of the tendon of the external oblique. It also frequently arises from the brim of the pelvis, as well as from the crural arch. From these points it passes upward, becoming more and more attenuated as it approach es the umbilicus, at which point it cannot be distinguished from the sub-peritoneal apo~ neurosis. The fascia transversalis is situated between the abdominal muscles and the peri- toneum. Its internal margin is continuous with the outer border of the rectus muscle ; and its external margin, which gradually becomes thinner, is blended with the sub-peri- toneal aponeurosis. The only part deserving a special description is that portion which lies between the outer border of the rectus muscle and the abdominal opening of the in- guinal canal. In this situation it assists in strengthening the parietes of the abdomen,, which are here remarkably weak ; and it is to the existence of this fascia that we may attribute the extreme rarity of direct inguinal herniae*, which, in fact, can only result from a congenital weakness, or a relaxation of this fascia. A very interesting portion of the fascia transversalis is an infundibuliform prolonga- tion, given otffrom it to the spermatic cord. It is impossible, indeed, to conceive the descent of the testicle to occur without its pushing before it a portion of the fascia, which then constitutes the immediate investment of the cord upon which the cremaster muscle (b,fig. 137) is spread out. The peritoneal orifice of the inguinal canal is, there- fore, the superior opening of the infundibuliform process, furnished by the fascia trans- versalis to the testicle and its cord. The Sub-peritoneal Aponeurosis. The peritoneum, throughout the whole extent of the abdominal parietes, is strength- ened on its outer surface by a very thin tendinous layer, the existence of which may serve to explain why abscesses, formed in the parietes of the abdomen, so seldom open into the cavity of the peritoneum ; and, on the other hand, why collections within the peritoneal cavity so seldom open externally. The Posterior Abdominal Aponeurosis. The posterior abdominal aponeurosis is much smaller and of less importance than the anterior: it consists of three layers, one anterior (k, in diagram, ^o-. 134)^ and very thin, which cominences at the base of the transverse processes of the lumbar vertebra;, and passes in front of the quadratus lumborum (q) ; another, 7niddle (i), and much stronger, commencing at the summits of the same transverse processes, and passing behind the quadratus lumborum ; and a third, posterior (k), which arises iVom the summits of the lumbar spinous processes, and passes behind the sacro-lumbalis, longissimus dorsi, and transverso-spinalis muscles (s). This last-mentioned layer is connected both with the internal oblique (e) and with the transversalis muscle (/), and is blended with the apo- neuroses of the serratus posticus inferior, and of the latissimus dorsi (Z). The two an- * IF. e., hemiffi occurring directly downward and forward through the inguinal rin^ {'"jfig. 137), and not descending along the inguinal canal.} Qq 306 APONEUROLOGY. terior layers are connected with the transversahs only. The posterior abdominal apo- neurosis has, therefore, nearly the same relation to the quadratus lumborum and the common mass of the sacro-lumbalis, longissimus dorsi, and transverso-spinalis muscles, that the anterior aponeurosis has to the rectus muscle. The Lwnho-iliac Aponeurosis. The lumho-iliac aponeurosis, or fascia iliaca of modern authors, forms the tendinous sheaths of the abdominal portion of the psoas and iliacus muscles, and is, therefore, bi- furcated at its upper part. That portion which invests the psoas commences at the ten- dinous arch of the diaphragm, already described as embracing the nipper end of this mus- cle. The iliac portion arises from the whole extent of the inner border of the crest of the ilium. The circumflex ilii artery is situated in the substance of this iliac portion, at its origin. The internal margin of the fascia iliaca is attached to the sides of the lumbar vertebrae, and, lower down, to the brim of the pelvis ; it is arranged in arches, which give passage to the lumbar vessels and to the nervous cords, establishing a communica- tion between the lumbar plexus and the lumbar ganglia of the sympathetic nerve. The centre of each arch is opposite to the groove on one of the bodies of the lumbar verte- brae, the intervals between the arches corresponding with the intervertebral substance. The largest arch extends from the last lumbar vertebra to the brim of the pelvis, and is opposite to the base of the sacrum. The obturator and lumbo-sacral nerves pass under it. Opposite the femoral arch, the fascia iliaca adheres intimately to the outer part of Poupart's hgament ; but towards the median line it separates from that ligament, passes behind the femoral vessels, and forms the posterior half {s, fig. 136) of the crural ring. Below the femoral arch, the fascia is prolonged upon the thigh ; on the outside («') it completes the sheath of the psoas and iliacus, accompanies them as far as the lesser trochanter, and becomes continuous with the iliac portion {g,fig. 137) of the femoral fascia ; on the inside, it forms the posterior wall {s,fig. 136) of the canal for the femoral vessels, and forms the deep layer or pubic portion Oi,fig. 137) of the femoral fascia. Relations. — It lies beneath the peritoneum, to which it is united by a very loose cellu- lar tissue ; it covers the psoas and iliacus, but is not adherent to them, in consequence of the interposition of some equally delicate cellular tissue. All the nerves from the lumbar plexus are subjacent to this fascia, excepting one very small cord, which perfo- rates it at the side of the sacrum, and becomes situated in the sub-peritoneal cellular tissue. The femoral vessels are situated on the inner side of the fascia, and are separ- ated by it from the crural nerve, which lies on its outer side, and underneath it. Structure. — The upper part of the fascia is extremely thin, but it increases in thick- ness as it approaches the femoral arch. It is formed of well-marked transverse fasci- culi, intersected perpendicularly by the tendon of the psoas parvus, when that muscle exists. This tendon is blended with the fascia, and is distinguished from it only by the different direction of its fibres ; it is inserted by spreading out, at the side of the pelvic ■brim, into a tendinous arch which lines this brim, and with which the psoas parvus and the iliac fascia are continuous above, and the pelvic fascia below. Few aponeuroses are more deserving the attention of anatomists than this, on account 'Of the practical consequences resulting from its arrangement. In fact, notwithstanding its tenuity, it forms a boundary between the sub-peritoneal and sub-aponeurotic cellular tissvie, which is very rarely passed by inflammatory action. When inflammation termi- nates in suppuration, the pus, whether it be beneath the peritoneum or beneath this fas- cia, descends towards the femoral arch ; but if the inflammation be sub-peritoneal, the femoral vessels lie behind the purulent collection ; and should it be sub-aponeurotic, the ■vessels will be in front of it. The latter is especially the case in abscesses following caries of the vertebras. The Aponeuroses of the Pelvis. The aponeuroses of the pelvis should be distinguished into the pelvic, properly so called, and the perineal : the former constitute essential parts of the pelvis, and are deeply seat- ed. The others belong to that part of the floor of the pelvis which is called the perineum. I shall commence with the description of the latter. The Jlponeuroses of the Perineum. These are two in number ; one superficial, the other deep. The Superficial Perineal Fascia.* Dissection. — Remove tne sub-cutaneous adipose tissue very cautiously, layer by layer, commencing the dissection along the edges of the pubic arch. This aponeurosis (which is very distinct from the fibrous laminae, intercepting spaces iilled by fat, and forming what is called the fascia superficialis) is of a triangular shape, and consists of well-marked transverse fibres. The outer margin of each half of the fas- cia is attached to the descending ramus of the os pubis and the ascending ramus of the ischium : its inner margin is lost at the raphe, along the median line : its posterior mar- * M. Bo'uvier, in his thesis, and M. Blandin, in his Traiti d' Anatomic Chirurgicale, first described this fascia THE DEEP PERINEAL APONEUROSIS. 307 Fig. 138. gin is bounded by a line extending from the tuberosity of the ischium to the anus ; it cor- responds with the posterior edge of the transversus perinei muscle, and appears to be reflected behind it, so as to line the corresponding perineal or ischio-rectal fossa.* Relations. — It is covered by a prolongation of the dartos, to a greater extent in the me- dian line than on each side ; also by the sub-cutaneous adipose tissue, which is thicker behind than in front, and by the sphincter ani, above which it terminates in the median line : it covers the transversus, the bulbo-cavernosus, and the ischio-cavernosus mus- cles, the fibrous sheaths of which may even be regarded as a prolongation of this aponeu- rosis. It also covers the superficial perineal vessels and nerves, which are sometimes lodged within its substance. The existence of this membrane explains why, in cases of perforation of the urethra, the urine is infiltrated forward, and very rarely backward. The Deep Perineal Aponeurosis. Dissection. — Remove with great care the ischio- and bulbo-cavernosus and the trans- versus perinei muscles. This aponeurosis, which was well described by M. Carcassone under the name of ^ c. rineal ligament, and called by modern writers the middle pe- rineal fascia, appears to me perfectly distnict from the aponeuroses of the pelvis. It is an extremely strong trian- gular layer {b a. Jig. 138t), oc- cupying the pubic arch, and apparently forming a continu- ation of the sub-pubic ligament {b). It is vertical near the arch, as far as the ball of the urethra, below which it be- comes horizontal, or, rather, oblique, from before back- ward. Its lateral margins are attached to the descending ra- mi of the ossa pubis, and the ascending rami of the ischia (d d), above the attachment of the ischio-cavernosi muscles. Its posterior margin becomes blended with the posterior margin of the superficial perineal fascia, behind the transversi muscles, in front of the perineal fossae, of which it forms the anterior boundary. Relations. — Its lower surface is in relation with the ischio- and bulbo-cavernosus mus- cles, and gives off, in the median line, a fibrous septum, which passes between these muscles, and affords them points of attachment. Its upper surface is in relation with the artery or arteries (e e) of the bulb, which are sometimes contained within its sub- stance : it is also in contact with a very remarkable plexus of large veins, with which it is very closely united, so that, when divided, they remain open : these veins are also fre- quently enclosed within its substance. It is also in relation with the levator ani. There constantly exists another transverse muscle, very distinct from the transversus perinei generally described, which is situated farther behind. This muscle (^transversus perinei alter. Alb.) is applied to the lower surface of the perineal fascia, and passes trans- versely inward to the bulbous portion of the urethra. The deep fascia of the perineum is perforated (at c) by the posterior part of the bulb of the urethra, or, rather, by the point of union (c, fig. 181) between its bulbous and membranous portions : it gives off prolongations upon the sides of the bulb, and serves to support the membranous portion of the urethra : whence the name, triangular liga- ment of the urethra, given to it by Colles. It is also perforated, beneath the arch of the pubes, by a great number of veins, and by some arteries Uses. — This remarkable aponeurosis evidently supports the canal of the urethra. It has been correctly regarded as an obstacle to the introduction of the catheter, the point of which strikes against it, however slightly it may deviate from the direction of the ca- nal. The prostate gland is situated above it. The Pelvic Aponeuroses. From the sides of the pelvis, and from the entire circumference of the brim (which, as * See note, p. 309. t [The triang-ular lig-ament consists of two layers, which approach each other more nearly above than below , in. fig 138. the anterior layer has been removed. Between tlie two layers are situated the sub-pubic lig-umca (i), perforated by the veu« dorsales penis, the pudic arteries (//), the arteries of the bulb (e e), the great part of the membranous portion of the urethra, with its compressor muscle, to be described hertaft>-.". ani.- lastly, Cowper's glands (g g). In the female, the triangular ligament is perforated by the vagina, as wsl by the urethra. J S08 APONEUROLOGY. we have seen, is covered and rendered smooth by a thick layer of fibrous tissue, that forms a hmit to the lumbo-ihac aponeurosis), a tendinous lamina is given off, which pass- es into and lines the pelvis, and is soon divided into two distinct layers : one external, the lateral pelvic or obturator fascia, which continues to line the sides of the pelvis, and covers the obturator internus muscle ; the other internal, or superior, which passes in- ward upon the side of the prostate gland, bladder, and rectum, in the male, and of the bladder, vagina, and rectum, in the female, in order to form the floor of the pelvis. This is the superior pelvic aponeurosis, with the description of which we shall commence. The Superior Pelvic Aponeurosis, or Recto-vesical Fascia. Dissection. — This aponeurosis must be studied both from the cavity of the pelvis and from the perineum. It is exposed in the pelvis by removing the peritoneum, and the loose cellular tissue beneath that membrane : this should be done without any cutting instrument. To view this fascia from the perineum, it is necessary to take away the adipose tissue that occupies the perineal fossae, and also the levator ani muscle. The superior pelvic aponeiirosis forms a complete floor for the pelvis. Anteriorly it is remarkable for its strength and shortness ; in fact, it does not reach the inlet in this sit- uation, but arises on each side from the symphysis pubis, presenting the appearance of bands or columns, which are more or less separated from each other, and become at- tached to the front of the neck of the bladder, whence the name of anterior ligament of the bladder, which the older anatomists gave to this part of the aponeurosis. More exter- nally, it forms a strong arch (the sub-pubic arch), which completes the posterior orifice of the obturator or sub-pubic canal («, fg. 48). This arch is not unfrequently double, and then one of the foramina gives passage to vessels, and the other to nerves. Still more externalli/, it is attached to the brim of the pelvis, in the manner I have al- ready pointed out. Posteriorly it is extremely thin, passes in front of the sciatic plexus, and is lost upon the sacrum. Sometimes it appears to be divided into two laminae, the posterior of which passes in front of the sciatic plexus, and the anterior in front of the internal iUac vessels, to which it would seem to furnish sheaths. Relations. — Its upper surface is concave, and connected with the peritoneum by loose cellular tissue, containing more or less fat. Its lower surface is convex, and covered by the levator ani : it forms part of the great perineal excavation, and is in relation with the pyriformis and obturator internus mucles, with the sacral plexus, &c. This aponeurosis is perforated by a great number of openings : in the male it is pierced by the prostate {i, fig. 181) and the bladder (h), on the sides of which it is prolonged, and reflected on to the rectum, whence the name of the recto-vesical aponeurosis, given to it by M. Carcassone. In the female it is also perforated by the vagina. On each side of the bladder and prostate it is strengthened by two tendinous bands, which run from before backward. These are sometimes very strong ; they extend from the symphysis pubis (i) to the spine of the ischium (e), pass along the bladder and the prostate, and are re- flected upon their sides. In front, it has some openings for the vesical and prostatic vessels. Behind it presents a considerable opening, which corresponds to the outlet of the pel- vis, and gives passage to the lumbo-sacral nerve and the gluteal vessels. The extrem- ity of the arch formed by it corresponds to the anterior border of the sciatic notch. It is through this opening that sciatic hernije protrude. We not uncommonly find larger or smaller openings in this fascia, of an oblong or cir- cular shape, leading into conical culs-de-sac, which are filled with fat. Lastly, it is per- forated behind by the ischiatic and internal pudic vessels. It does not appear to be in- tended for the passage of the vessels which are distributed in the interior of the pelvis, for it seems to invest these in fibrous sheaths. Uses. — The superior pelvic aponeurosis forms the floor of the pelvis ; it is pushed downward by the action or the diaphragm and abdominal muscles, and tends to prevent the occurrence of perineal herniae, which otherwise would be extremely common : it forms a boundary between the sub-peritoneal and the perineal cellular tissue, and also hmits the progress of inflammation and infiltrations. Infiltration of urine above the fas- cia can only be caused by rupture of the bladder itself The prostate {_i,fig. 181) is al- most entirely below the fascia, and therefore, in the lateral operation for stone, in which this gland is the principal structure to be divided, inflammation and infiltration of the ceUular tissue are extremely rare. When they do occur, the section or laceration must have been prolonged into the body of the bladder. The Lateral Pelvic Aponeurosis, or Fascia of the Obturator Muscle. Dissection. — This aponeurosis is more advantageously studied, at least in its most im.por- tant part, from the perineum, than from the cavity of the pelvis : it is exposed on eiiher side by removing the adipose tissue, which fills up the perineal fossa. This aponeurosis, which is quite distinct from the obturator ligament, commences at the upper part of the circumference of the obturator foramen, and at the brim of the p(?lvis, in connexion with THE FEMOKAL APONEUROSIS. 309 the superior pelvic aponeurosis, which it soon leaves, and is applied to the obturator in- ternus muscle : it then unites below with the reflected portion of the great sacro-sciatic ligament, and is prolonged upon that portion of the anterior surface of the glutajus max- imus which projects beyond the ligament, and also upon the coccygeus muscle. Relations. — On the inner side and above, it is only separated from the superior pelvic aponeurosis by the levator ani, which is applied to that aponeurosis ; lower down, the two aponeuroses are separated by a considerable interval, which is occupied by fat : this interval forms the perineal fossa' On the outside it is in contact with the obturator in- ternus, and lower down with the internal pudic vessels and nerves. Uses. — It binds down the obturator internus muscle, and protects the internal pudic vessels and nerves, which are, therefore, rarely cut in operations in the perineum. It forms the external boundary of the perineal fossa. Tlie Perineal Fosscb. — Situated between the superior pelvic aponeurosis (which is lined below by the levator ani) and the lateral pelvic aponeurosis, there is found on each side of the anus a conical space, the base of which is directed downward, and corresponds to the skin: it is formed behind by the lower border of the gluteeus maximus ; in front, by the transversus perinei muscle ; on the inside, by the levator ani and the superior pel- vic aponeurosis ; and on the outside, by the tuberosity of the ischium.* Each of these fossa; is filled by a large quantity of fat, and traversed by fibrous lamina;, some of which extend vertically from the apex to the base, and divide the contained adipose cellular tissue into several distinct portions. When an abscess occurs in either of these fossse, it may be easily conceived how difficult it is for the inner surface of its parietes to come into opposition : hence the pathology of fistula;, and the modes of cure which are adopted. The Aponeuroses of the Lower Extremity. The aponeuroses of the lower extremity comprise the /ejHoraZ fascia; the fascia of the leg ; the annular ligaments, which bind down the tendons of tlie muscles of the leg, as they are passing upon the dorsal or plantar surface of the foot ; the plantar and dorsal fascicE of the foot ; and, lastly, the fibrous sheaths, which maintain the tendons in con- tact with the phalanges of the toes. We shall describe these in succession. The Femoral Aponeurosis, or Fascia Lata. After the remarks which we have already made upon the aponeuroses generally, it may be easily conceived that the muscles of the thigh, which are so numerous, of such great length, and so loosely united together, and almost all of which are reflected to a greater or less amount over the knee, require to be kept in close contact with each oth- er and with the bones ; hence the necessity for the femoral aponeurosis, consisting of a large fibrous sheath, that confines without compressing the muscles, and the strength of which is directly proportioned to the force of the muscles, and their tendency to dis- placement. Its superficial or sub-cutaneous surface (g h,fig. 137) is separated from the skin by a very thin fibrous layer, the fascia svperfieialis (not shown in fig. 137), which can be more easily demonstrated immediately below the femoral arch, and along the sa- phenous vein. Between the femoral aponeurosis or fascia lata and this superficial fas- cia, which results from the union of the fibrous prolongations given off by the deep sur- face of the skin, the sub-cutaneous vessels and nerves take their course, and communi- cate with the deep vessels and nerves, either by simple openings or by fibrous canals, of variable length. Under this fascia, also, are situated the superficial lymphatic vessels and glands of the groin. A great number of the superficial nerves of the thigh have special sheaths, which are hollowed out, as it were, in the substance of this aponeurosis. The femoral aponeurosis is perforated with a great number of foramina opposite the femoral vessels, from Poupart's ligament to the entrance of the vena saphena {z) into the femoral vein (y). These foramina, which occupy a triangular space, of which the base is above and the apex below, are intended for the passage of a great number of lymphatic vessels, which pass through it to join the deep set. This has been called the sieve-like portion of the fascia lata, or the fascia cribriformis (v) : it has been said by some, that the aponeurosis is altogether wanting in this situation.! We not unfrequently find a lymphatic gland occupying one of the foramina. * [These spaces are the ischio-rectal fossa: of Velpeau ; they are described by him as if lined by an aponeu- rosis (the ischio-rectal) composed of two layers, one external or ischiatic, corresponding to the lateral pelvic aponeurosis of M. Cruveilhier, and another internal or rectal, which covers the lower surface of the levator ani from the coccyx to the posterior border of the transversus perinei, and unites with the other layer before, above, and behind. This latter layer is very thin, and continuous with the united margins of the superficial perineal fascia and the triangular ligament, behind the transverse muscle, and is alluded to by M. Cruveilhier (p. 307) as a reflection of the superficial fascia. 1 t [And then the cribriform fascia is regarded, not as belonging to the fascia lata, but as formed by a deep layer of the superficial fascia, situated beneath the sub-cutaneous vessels, adherent to the borders of the saphe- nous opening in the fascia lata, and perforated by those vessels. The saphenous opening is, according to this view, not the foramen (t) through which that vein passes, but the aperture (n) left between the iliac (§■) and pubic (A) portions of the fascia lata, and is bounded externally by the crescentic margin of the iliac portion, or the falciform process of Burns (see the left side oi fg. 137, where the cribriform fascia has been entirely removed).] 3i0 APONEUROLOGY. The most remarkable of all these openings is undoubtedly that (i) for the vena saphena interna, where that vessel enters the femoral vein, at the upper part of the thigh, eight or ten lines below Poupart's ligament. The margin of this opening, which has been improperly called the mferior orifice of the crural canal, can only be demonstrated in its low- er half, on account of the almost complete absence of the aponeurosis above it : this is the reason of the semilunar form of the portion of the fascia over which the vein passes. The deep surface of the fascia lata gives off a great number of prolongations, which pass between the muscles, and form their proper investments or sheaths. The largest of these prolongations form two lateral septa, called the inter-muscular sep- ta, which extend from the fascia to the linea aspera ; each has the form of a triangle, having its base directed downward and its apex upward ; they are extremely thick, es- pecially below. The Inter-muscular Septa of the Femoral Aponeurosis. Of these there are two, one internal and the other external. The Internal Inter-muscular Septum. — This serves at once as a septum, an aponeurosis of insertion, and a sheath for the vastus internus : it extends from the anterior inter- trochanteric line to the inner condyle of the femur. Its anterior surface affords attachments to the vastus internus throughout its whole extent : its posterior surface is in opposition with the adductors, and is intimately uni- ted to their aponeuroses. Its outer margin is attached to the linea aspera : its inner margin is very thick, and prominent below, where it is strengthened by the inferior ten- don of the adductor magnus, and may be felt under the skin like a cord. It appears to become continuous below with the internal lateral ligament of the knee. It is composed of very strong vertical fasciculi, passing somewhat obliquely down- ward and inward. These fasciculi are bound together above the inner condyle by oth- ers passing transversely, and are crossed almost at right angles by the tendinous fibres of the adductors. Lastly, the internal septum is perforated, near the linea aspera, by a number of orifices destined for the passage of vessels, and forming communications between the anterior and the internal sheath of the muscles of the thigh. The External Inter-muscular Septum. — This serves as a septum, an aponeurosis of in- sertion, and as a sheath for the vastus externus. It extends from the great trochanter to the external condyle, above which it forms a projecting cord : it affords attachments to the vastus externus in front, and to the short head of the biceps behind. Its inner margin is attached to the linea aspera : its outer margin forms a prominent cord, especially below. It consists of fibres directed vertically, or somewhat obliquely outward, and strength- ened by transverse fibres above the condyle. Like the internal septum, it is perforated, especially above and below : above, for the passage of the circumflex vessels ; below, for the passage of the articular vessels of the knee. We shall now examine the different sheaths furnished by the femoral aponeurosis. One of the most important of these is, as it were, hollowed out of the sides of the others, and belongs to the femoral vessels. The Sheath of the Femoral Vessels. The femoral artery (z,fig. 137) and vein (y) are enclosed in a prismatic and triangular tendinous canal, which protects them in their course amid the muscles of the thigh. The portion of the canal (laid open in^o-. 137) included between the femoral arch and the point where the vena saphena opens into the femoral vein, has received the name of the crural canal, a term to which I have always objected, since it was first introduced into anatomical nomenclature, because it establishes a false analogy between the ingui- nal canal and this upper portion of the sheath of the femoral vessels ; for, while an oblique inguinal hernia traverses the entire length of the inguinal canal, ci-ural herniae, as far, at least, as my own observation extends, never protrude through the saphenous opening, but escape immediately below the femoral arch, and lift up the cribriform por- tion of the fascia lata.* The anterior ivall of the sheath of the femoral vessels is formed above by the cribri- form portion of the femoral fascia {g',fig. 137), then by the fascia itself, and, lastly, by the posterior layer of the sheath of the sartorius, in which place it is thin and transparent. The internal wall is formed above by the very strong layer covering the pectineus ; be- low, by the weaker layer investing the adductors. The external wall consists of the very strong sheath {s',fig. 136) of the psoas and ilia- cus : externally to this wall is situated the crural nerve, a branch of which perforates * [The term "crural ring" is, in this country, commonly limited to the space (r,jfig. 136) situated internal- ly to the femoral vein. By the term " crural canal" is generally understood that portion only of the canal de- scribed by M. Cruveilhier as the " crural canal," which is situated on the inn^r side of the femoral vein, and is occupied by cellular tissue, lymphatic vessels, and sometimes by a lymphatic gland. If the term crural ca- nal be thus defined, if the cribriform fascia be regarded as a part of the superficial fascia, and the saphenous aperture as the space between the iliac and pubic portions of the fascia lata (see note, p. 309), the analogy be- tween the crural and inguinal canals will not be so very reraote.3 THE FEMORAL APONEUROSIS. 311 ■the sheath and joins the vessels. Lower down, the external wall is formed by the apo- neurosis of the vastus internus. The three great Muscular Sheaths of the Femoral Aponeurosis. By means of the internal and external inter-muscular septa, the muscles of the ante- rior region of the thigh are separated from those of the posterior and internal regions ; a weaker septum than the preceding intervenes between the muscles of the internal and posterior regions. It follows, then, that the femoral aponeurosis presents three great tendinous sheaths : an anterior, an internal, and a posterior. The great posterior sheath is undivided : it is common to the biceps, the semi-tendino- sus, and the semi-membranosus. The great anterior and internal sheaths are subdivided into a number of secondary sheaths, in most cases corresponding with the number of the muscles. The great Anterior Sheath. — The sartorius has a proper sheath, remarkable for its pris- matic and triangular form. The rectus femoris, or long head of the triceps, is separated from the two vasti by a tendinous layer, very thin below, but strong above, and com- posed of vertical fibres. The tensor vaginae femoris is contained in the strongest sheath in the human body, for it is formed by the fascia lata itself The deep layer of this sheath is much thinner than the superficial ; it commences at the anterior inferior spinous process of the ilium, below the rectus, and may be regarded as the deep origin of the broad band in which the tensor vaginae femoris terminates : it is composed of vertical fibres, prolonged be- tween the rectus and the vastus externus. Lastly, above and on the outside, we find the sheath of the psoas and iliacus {s',fig. 136), which forms a continuation of the lum- bo-iliac aponeurosis, or fascia iliaca. The great internal sheath furnishes a number of tendinous lamellae, which separate the different muscles of this region. Thus, there is a proper sheath for the gracilis, a com- mon one for the pectineus and the adductor longus, one for the adductor brevis, and an- other for the adductor magnus. The sheath of the obturator externus is continuous with that of the adductor brevis ; it commences by a very strong fibrous lamina or arch, which arises from the anterior edge of the pubes, and is directed obliquely outward to the fibrous capsule of the hip-joint. This arch conceals the anterior orifice of the obtu- rator canal, and protects the obturator vessels and nerves. Lastly, the two vasti, which extend into all the regions of the thigh, have sheaths formed by the femoral fascia, where they are superficial, and by the internal and exter- nal inter-muscular septa, and the posterior laminae of the other sheaths in their more deeply-situated portions. In the midst of the sheaths of the anterior and internal regions we find the sheath of the femoral vessels already described. The Superior Circumference of the Femoral Apo?ieurosis. In front the femoral aponeurosis arises from the femoral arch, with which it is so per- fectly continuous as to render the arch tense : hence the plan, already mentioned as proposed by Scarpa, of endeavouring to remove the constriction in cases of strangulated crural hernia, by puncturing the femoral aponeurosis. But the mode of origin and continuity of this fascia with the femoral arch is not the same on the inner and outer sides. On the outside, the iliac portion of the femoral apo- neurosis ig,fig. 137) arises by a single very thick layer ; more internally, in the situation of the femoral vessels, it arises by two layers, one superficial, thin, and perforated by foramina (the cribriform portion, v) ; the other deep, called its pubic portion (h), which is continuous with the fascia iliaca {s,fg. 136), covers the pectineus, and sends off a pro- longation between that muscle and the psoas. This deep layer forms the posterior wall of the canal of the femoral vessels. On the inside of the thigh, the femoral aponeurosis arises from the body of the os pu- bis and the ascending ramus of the ischium. On the outside and behind, it arises from the crest of the ilium by very numerous ver- tical fibres, which are strengthened, especially behind, by other horizontal fibres. Be- tween the posterior superior spine of the ilium and the crest of the sacrum there is a. tendinous arch, which is common to the femoral fascia and the aponeurosis of the long; muscles of the back. The Glutceal Aponeurosis. j The glutaeal aponeurosis forms the upper and back part of the femoral fascia. It cov- ers the glutaeus medius, in which situation it is extremely thick, and is continuous with the broad band of the tensor vaginae femoris. Having reached the upper border of the glutaeus maximus, it is divided into two layers : one superficial and very thin, which covers the outer surface of the glutaeus maximus, becomes thinner below, and continu- ous with the femoral fascia ; the other deep and thicker, especially above and behind, where it affords attachment to the glutaeus maximus, and is blended with the great sa- qro-sciatic ligament. It becomes very thin where it separates the glutaeus maximus. 312 APONEUROLOGY. from the deep-seated muscles. A synovial capsule intervenes between this fascia and the great trochanter, and another between it and the tuberosity of the ischium. It presents a very remarkable opening called the glutaal arch, for the passage of the gluteal vessels and nerves. Lastly, over that portion of the glutaeus maximus which enters into the formation of the corresponding perineal fossa, it acquires a great degree of thickness, and, at the lower border of the muscle, is blended with the superficial layer of the gluteal fascia. The Inferior Circumference of the Femoral Aponeurosis. The femoral aponeurosis terminates below, around the knee-joint, where it becomes continuous, partly with the fascia of the leg, and partly with the fibrous structures cov- ering this articulation. Concerning the arrangement of these fibrous laminae we shall offer a few remarks. Behind, the femoral aponeurosis passes over the popliteal space, and is continuous with the fascia of the leg. In front, it is prolonged over the patella, from which it is separated by a synovial bur- sa; it is very thin, and is continued in front of the ligament of the patella, upon which it forms a thin layer of transverse fibres. On the inside, it is at first blended with the sheath of the sartorius, and then with the horizontal portion of the tendon of this muscle ; it crosses the fibres of that portion per- pendicularly, and becomes continuous with the fascia of the leg. Under this layer of fibrous tissue we find, on the inside of the knee, another very dense layer, formed by vertical tendinous fibres derived from the vastus internus, and inserted into the upper part of the inner surface of the tibia, beneath the tendon of the sartorius. This fibrous layer, which may be regarded as the lower or tibial insertion of the vastus externus, occupies the interval between the internal lateral ligament of the knee-joint and the patella. Its vertical fibres are crossed by others at right angles, extending from tne internal tuberosity of the femur to the corresponding margin of the patella. Lastly, under this we find another very thin layer, belonging to tlie synovial capsule. On the outside, the femoral aponeurosis is blended with the broad band of the tensor vaginsB femoris, from which it can be distinguished only by the horizontal direction of its fibres. Beneath this very thick layer we find a thin one, composed of fibres stretching from the external tuberosity of the femur to the patella ; and, lastly, another thin layer be- longing to the synovial membrane. Structure of the Femoral .Aponeurosis. It is thin behind and on the inside, thicker in front, and extremely thick on the out- side of the thigh, where, indeed, it may be said to exceed all other fibrous membranes in thickness and in strength. This thickened portion is bounded in front by a line extend- ing vertically downward from the anterior superior spinous process of the ilium. Its Um- its behind are no less distinctly defined ; hence the name given to it of the broad band {fascia lata). This great density is owing to some very strong vertical fibres, arising from the front of the crest of the ilium. It is connected with the great force and tendency to displace- ment of the vastus externus. 'We may add, that the femoral aponeurosis is composed of horizontal fibres, sometimes regularly parallel, as in its thinnest portions, and sometimes intersecting each other. These horizontal fibres are even seen opposite the broad band on the outer side, from which they are distinguished by their direction. There is a very beautiful preparation of this aponeurosis in the Museum of the Facul- ty of Medicine : similar preparations should be made by those who wish to obtain a good idea of the tendinous sheaths, and the shape of the muscles of the thigh. It is to be made by removing all the muscles from their sheaths by means of longitudinal incisions, and substituting for them a quantity of tow, which must be taken out when the aponeu- roses are completely dried. The form of the sheaths exactly represents that of the cor- responding muscles. A tolerably accurate idea of these sheaths may also be obtained by cutting across each sheath and the muscle which it contains, in a fresh subject. The circumference of the section of the portion of the sheath that becomes visible after the retraction of the muscle will give an excellent idea of the figure of the different sheaths, which are all angular and polyhedral like the muscles, but never rounded : during health they are completely filled by the muscles, which in emaciated persons, on the contrary, .do not occupy more than a half, a third, or a sixth of the area of their sheaths. Such is the femoral fascia. Its tensor muscles consist of the tensor vaginae femoris and the glutaeus maximus, the tendon of which is received between two layers of this fascia. ApONEUEOSES of the liEG AND FoOT. aponeurosis of the Leg. The aponeurosis of the leg forms a strong general investment for the whole leg, except- ANNULAR LIGAMENTS OF THE TARSUS. 313 ing the internal surface of the tibia, which is covered by it only at its lower part, a little above the malleoli. Its external surface is separated from the skin by the superficial vessels and nerves, several of which perforate it, either directly, or after having run for a short distance in its substance. The external saphenous vein and nerve receive from it a complete sheath. Its internal surface covers all the muscles of the leg, and does not adhere to them ex- cepting above and in front, where it gives attachment to the tibialis anticus and the ex- tensor communis digitorum. From the internal surface there proceeds on the outer side of the leg two principal tendinous septa, one situated between the muscles of the ante- rior tibial region and the peronei, the other between the peronei and the muscles of the posterior region of the leg. There are, therefore, three principal sheaths in the leg, an anterior, an internal, and a posterior. The latter is subdivided into two other sheaths by a very strong transverse lamina, becoming still stronger below, which separates the muscles of the deep posterior layer and the posterior tibial and peroneal vessels and nerves from the superficial layer of muscles, or the triceps suralis. Lastly, some tendi- nous laminae, more or less complete, are interposed between the different muscles of each region. Thus, a tendinous layer separates the tibialis anticus, at first from the ex- tensor communis digitorum, and then from the extensor proprius pollicis : this layer dis- appears in the middle of the leg. Another very strong tendinous lamina separates the tibialis posticus from the flexor longus digitorum on the one hand, and from the flexor longus pollicis on the other. Superior Circumference. — If we now examine the manner in which the aponeurosis of the leg becomes continuous with that of the thigh, we shall find that, posteriorly, the femoral fascia is prolonged directly upon the leg, in order to form the posterior part of its aponeurosis, which, in this situation, also receives an expansion from the ten- dons of the biceps, sartorius, gracilis, and semi-tendinosus, and from the broad band of the fascia of the thigh. Anteriorly the fascia of the leg is continous with that of the thigh over the patella, and appears also to arise directly from the outer edge of the ante- rior tuberosity of the tibia, from the head of the fibula, and from the tendon of the biceps, which, as we have already seen, gives off an aponeurotic expansion backward. By its lower circumference this fascia is continuous with the annular ligaments of the ankle, which w^e shall presently describe. Structure. — On examining the direction of the fibres and the thickness of the fascia of the leg, it is found that it is much thicker in front than on the outer side of the leg, and still more so than behind ; that, in the first situation, in the upper three fourths of its ex- tent, it is composed of obliquely interlaced fibres, some of which descend from the spine of the tibia, and others from the anterior angular surface of the fibula ; and that in the lower fourth of the anterior region of the leg, and in the whole extent of the posterior re- gion, it is composed of circular fibres. At the point where the muscles of the leg become tendinous, and are reflected over the ankle, they require very strong sheaths to keep them in contact with the joint ; the fascia of the leg, therefore, forms, opposite this part, the anterior, internal, and external annular ligaments. The Annular Ligaments of the Tarsus. The annular ligaments of the tarsus are three in number : an anterior or dorsal, an in- ternal, and an external. The dorsal annular ligament of the tarsus. The aponeurosis of the leg is thicker at the lower and anterior part of the leg, and binds down the corresponding portion of the mus- cles in that region. But there is, in addition to this, a dorsal annular ligament of the tarsus {see fig. 128), which arises, by a narrow but thick extremity, in front of the as- tragalo-calcanean fossa, becomes broader as it extends inward, and is divided into two bands. The superior band passes upward and inward above the internal malleolus, and is split into two layers, in such a way as to foi'm two complete sheaths : one internal, for the tibialis anticus ; the other external, for the extensor longus digitorum and the peroneus tertius. Between these two complete sheaths, which are separated from the synovial capsule of the joint by a layer of cellular tissue, we find an incomplete sheath (for the annular ligament is not split into two layers in this situation), intended for the extensor proprius pollicis and the anterior tibial vessels and nerves : the internal sheath is the higher, and situated opposite the lower extremity of the tibia ; the external sheath is lower, and corresponds to the ankle-joint. The inferior hand, or the lower bifurcation of the annular ligament, passes forward and inward to the front of the tarsus, and be- comes continuous with the internal plantar aponeurosis. This lower band forms a sec- ond annular ligament, which furnishes to each of the three preceding muscles, upon the dorsum of the foot, a less powerful sheath than that afforded by the upper band ; it keeps the tendons closely applied to the bones. The external and internal annular ligaments of the tarsus are two fibrous bands, contin- uous with the fascia of the leg on the one hand, and with the plantar aponeurosis on the other. Rr 314 APONEUROLOGY. The internal annular ligament arises from the borders and summit of the internal mal- leolus, and proceeds in a radiating manner to the inner side of the os calcis, and the in- ner margin of the internal plantar aponeurosis. Beneath this sheath, which is thick- er below than above, and closes in the concavity on the inner surface of the os cal- cis, proceed the posterior tibial vessels and nerves, and also the tendons of the tibialis posticus, the flexor longus digitorum, and the flexor longus pollicis. For these several parts there are four very distinct sheaths : the most superficial is that for the vessels and the nerves ; two sheaths, placed one over the other (see fig. 130), and behind the internal malleolus, belong, the anterior to the tibiahs posticus (w), and the posterior or more superficial to the flexor longus digitorum (o). These two sheaths soon separate as the two tendons diverge from each other towards their insertions : as the sheath of the tibialis posticus is continued as far as the insertion of that muscle, the sheath of the ^ flexor longus digitorum accompanies it to where it gets beneath (i. e., deeper from the surface than) the plantar fascia. The sheath of the flexor longus pollicis (p) is lower than the preceding, and extends obliquely along the astragalus and os calcis, to be cov- ered by the internal plantar fascia. The external annular ligament forms a common sheath for the two peronei, longus et brevis : it extends from the border of the external malleolus to the os calcis, and is completed on the inside by the external lateral ligaments. It is at first single, but soon becomes subdivided into two other sheaths, one of which is destined for the tendon of the peroneus brevis, and the other for that of the peroneus longus. The aponeuroses of the Foot. These are divided into the dorsal and plantar. The Dorsal Aponeuroses of the Foot. These comprise the dorsal aponeurosis, properly so called, the pedal aponeurosis {Vapo- neurose pedieuse), and the dorsal interosseous apaneuroses. Dorsal Aponeurosis of the Foot. — While the upper margin of the annular ligament is blended with the fascia of the leg, which appears to be inserted upon it, the anterior margin of the same ligament becomes continuous with the dorsal aponeurosis of the foot. This dorsal aponeurosis is a thin layer, which forms a general sheath for all the tendons situated upon the dorsum of the foot : it gradually disappears in front, opposite the an- terior extremities of the metatarsal bones, and is attached at the sides to the borders of the foot, becoming continuous with the plantar fascia. These tendons, again, are sep- arated from the extensor brevis digitorum by another and still thinner layer, which in- vests that muscle : this is the pedal aponeurosis ; lastly, upon the same surface of the foot we find the four dorsal interosseous aponeuroses, viz., one for each interosseous space. The Plantar Aponeuroses. The plantar aponeuroses or fasciaj are three in number : one middle, the other two lateral. The middle plantar aponeurosis is very strong, is attached to the inner of the posterior tubercles of the calcaneum, becomes suddenly contracted, and afterward gradually ex- pands without diminishing perceptibly in thickness. Opposite the anterior extremities of the metatarsal bones, it divides into four bands, which are themselves bifurcated al- most immediately, so as to embrace the flexor tendons of the four outer toes. Becom- ing moulded on the sides of these tendons, they furnish those of each toe with an almost complete sheath, which is attached to the upper and lateral borders of the anterior gle- noid ligament of the corresponding metatarso-phalangal articulation, and becomes con- tinuous with the tendinous sheath of the corresponding toe. These four sheaths are separated by three arched openings, through which proceed the lumbricales and interos- seous muscles, and the plantar vessels and nerves. There is a perfect analogy between the middle plantar and the middle palmar aponeurosis ; but the former is by far the stronger. It constitutes, indeed, a true ligament for the foot, offers a powerful resist- ance to the forced extension of the phalanges upon the bones of the metatarsus, and sup- ports the antero-posterior arch of the sole of the foot. I have known exceedingly vio- lent pain to be produced by distension, and, probably, laceration of some of the fibres of this aponeurosis. The margins of the middle plantar aponeurosis are curved upward, so as to embrace the flexor brevis digitorum on each side ; they become continuous with the external and internal plantar aponeuroses, and form septa between the muscles of the middle and those of the external and internal plantar regions : in front these septa are complete, but only partial behind. The upper surface of this fascia gives attach- ment, posteriorly, to the short flexor of the toes : the proper tendinous expansion of this muscle appears to be given off" from the upper surface of the plantar aponeurosis. Some transverse fibres strengthen this fascia in front, and I shall also notice some other transverse fibres, perfectly distinct from the preceding, which form a true trans- verse ligament for the four outer toes : it is situated opposite the middle of the lower surface of the first phalanges, and is admirably adapted for opposing their dislocation. The E.xtcrnal and Internal Plantar Aponeuroses. — The external plantar aponeurosis, very THE APONEUROSES OF THE SHOULDER. 315 thick behind and thin in front, gives attachment by its upper surface to the abductor muscle of the little toe, and is bifurcated at the posterior extremity of the fifth metatar- sal bone. The external division of this bifurcation is very strong, is inserted into the enlarged posterior extremity of the fifth metatarsal bone, and may be regarded as a povi^- erful medium of connexion between that bone and the cuboid. The internal plantar apo- neurosis is thin in comparison with the external ; it commences behind by an arch, ex- tending from the inner malleolus to the os calcis ; its inner margin is attached to the corresponding border of the tarsus, and is continuous with the dorsal annular ligament and with the dorsal fascia of the foot ; its outer margin is blended with the middle plan- tar fascia, or, rather, is reflected upward, to complete the sheath for the internal mus- cles of the foot. These three plantar fasciee just described form three sheaths, which are quite distinct in their anterior five sixths, but communicate with each other behind. The internal plantar sheath includes the abductor and the short flexor* of the great toe, which are separated from each other by a layer of fibrous tissue ; it also contains the internal plantar artery and nerves. The external plantar sheath includes the abductor and the flexor of the little toe, which are also separated by a tendinous layer. Lastly, the middle plantar sheath includes the short flexor of the toes, the tendon of the flexor longus digitorum, the flexor accesso- rius, the lumbricales, the tendon of the flexor longus poUicis, the oblique adductor,t the transversus pedis, and the external plantar vessels and nerves. The sheath of the flexor brevis digitorum is completed above by an aponeurotic layer, which separates it from the tendons of the long flexor and from the accessorius. A propev sheath exists for the oblique adductor,! and a subdivision of the same sheath for the transverse ad- ductor. It is formed above by the interosseous aponeuroses, and below by a thin layer attached to the circumference of the deep hollow in which the adductors are lodged. Lastly, the inferior interosseous aponeurosis is remarkable for its thickness, and for the septa which it gives off" between the interosseous muscles. The sheaths into which the flexor tendons of the toes are received opposite the pha- langes resemble so exactly those of the fingers, that I shall not anticipate what will be said hereafter regarding the latter. We find the same system of synovial membranes, and the same loose, membranous, and extensible cellular tissue for the flexor tendons of the toes as for those of the fingers. In all sheaths that are partly osseous and partly tendinous, we find a synovial membrane ;$ but, on the other hand, there is nothing more than a loose cellular tissue in situations where a tendon or muscle glides in the interior of a confining aponeurosis. The Aponeuroses of the Upper Extremity. These comprise the aponeuroses of the shoulder ; the brachial aponeurosis ; the apo- neurosis of the forearm ; the dorsal and anterior annular ligaments of the carpus ; the palmar aponeurosis ; and, lastly, the sheaths for the tendons of the flexor muscles of the fingers. The Aponeuroses of the Shoulder. These are the supraspinous, the infra-spinous, the subscapular, and the deltoid aponeu- roses. The supraspinous aponeurosis is a thick layer of fibrous tissue, attached to the entire circumference of the supra-spinous fossa, and converting it into a sort of osteo-fibrous case, that serves as a sheath for the supra-spinatus muscle, to which it also affords sev- eral points of attachment. This tendinous layer is gradually lost, externally, under the acromio-coracoid arch. The infraspinous aponeurosis is an equally dense and strong fibrous lamina, attached to the entire margin of the infra-spinous fossa, and completing the osteo-fibrous sheath of the infra-spinatus muscle : it is continuous on the outside with the brachial fascia, and gives off" from its anterior surface a thick septum intervening between the scapular at- tachments of the teres major and those of the teres minor, and also some thinner septa interposed between the teres minor and the infra-spinatus, and between the different portions of the infra-spinatus muscle itself The deltoid aponeurosis. The infra-spinous aponeurosis having reached the posterior border of the deltoid muscle, splits into two layers : of these, the superficial layer invests the deltoid, and terminates in the brachial aponeurosis ; the deep layer continues to cover the tendon of the infra-spinatus, and becomes attached to the tendon of the short head of the biceps. Some very loose cellular tissue, or even a synovial bursa, separates this aponeurosis from the head of the humerus, and the tendons inserted around it. The sub-scapular aponeurosis is a very thin membrane, which completes the sheath of the sub-scapularis, and gives the muscle some points of attachment. It is fixed to the entire margin of the sub-scapular fossa. * [/. f., the inner half of the flexor brevis poUicis of anatomists generally.] t [Including the outer portion of the flexor brevis pollicis of most anatomists.] i See note on Aponeuboloov, p. 296. 316 APONEUROLOGY. The Brachial Jlponeurosis. The brachial aponeurosis commences above at the clavicle, the acromion, and the spine of the scapula, and is continuous with the infra-spinous aponeurosis : on the inner side it arises from the tendons of the pectoralis major and the latissimus dorsi ; and, in the interval between them, from the cellular tissue of the axilla ; it envelops the arm as far down as the elbow, where it becomes continuous with the fascia of the forearm, and is attached to the different bony projections presented by the surface of that joint. Its sii- perjicial surface is separated from the skin by vessels and nerves, to which it furnishes sheaths of greater or less extent. We may admit the existence of a superficial fascia between the vessels and the skin. Its deep surface presents various septa, dividing its interior into a certain number of thin sheaths for the several muscles. It is composed almost entirely of circular fibres, some of which have a somewhat spiral direction : these fibres are intersected at right angles by others passing vertically downward to the fascia of the forearm. The brachial aponeurosis is so loose as to permit the free exercise of the muscles con- tained within it, yet sufficiently tense to prevent their displacement. It is slightly thickened on either side, along the outer and inner borders of the humerus, and gives off in those situations two very strong inter-muscular septa : one external, the other internal. These septa are in every respect analogous to those of the femorzil fascia, and divide the brachial sheath into two great compartments : an interior, contain- ing the muscles on the anterior aspect of the arm, viz., the biceps, the brachialis anti- cus, and the coraco-brachialis, also the upper or brachial portion of the supinator longus, and the extensor carpi radialis longior ; the posterior compartment belongs to the triceps. The external inter- muscular septum arises from the anterior border of the bicipital groove, by a narrow and very thick extremity, blended with the posterior margin of the tendon of the deltoid ; it reaches the outer border of the humerus, expands and becomes somewhat thinner, and separates the anterior from the posterior muscles, more espe- cially the triceps from the brachiahs anticus, affording attachments to them both. It is perforated very obliquely by the musculo-spiral or radial nerve, and the superior profunda artery, which at first lie behind, but are afterward in front of it. The sheath of this nerve and artery establish a free communication between the anterior and posterior com- partments already alluded to. The internal inter-muscular septum, broader and thicker than the preceding, but, like it, of a triangular form, arises from the posterior border of the bicipital groove, below the teres major, is continuous with the tendon of the coraco-brachialis, crossing it at a very acute angle, and becoming partially united to and blended with it, proceeds along and adheres closely to the inner border of the humerus, and terminates at the inner condyle or epitrochlea of that bone. Both of these septa are formed by bands and fibres given off in succession from the corresponding borders of the humerus, and they both afford attachments to the brachialis anticus in front, and to the triceps behind. The ulnar nerve is anterior to the internal septum in the upper part of the arm, but perforates it, and remains in contact with its posterior surface, passing between the attachments of the triceps. From these two great sheaths the proper sheaths of the muscles proceed. First, the deltoid has its proper sheath : another thin aponeurotic layer, gradually becoming thicker from above downward, consisting almost entirely of vertical fibres, and forming one of the origins of the aponeurosis of the forearm, separates the biceps from the brachiahs anticus ; again, the brachial vessels and the median nerve have a special sheath, which also receives at its upper part the basilic vein, and the ulnar and internal cutaneous nerves ; this is the brachial canal, the counterpart of the femoral canal ; it establishes a communication between the cellular tissue of the axilla, and that in the bend of the elbow ; lastly, a tendinous layer separates the upper half of the long head of the triceps from the other portions of that muscle : the sheath of the coraco-brachialis is given ofT from the inner edge of the biceps. We must consider as dependances of the common brachial investment the several sheaths furnished by it to the cephalic, basilic, and median veins, to the branches of the internal cutaneous nerve, and to the superficial ramifications of the musculo-cutaneous nerve. When an artery or a vein previously situated under an aponeurosis becomes sub-cutaneous, the perforation in the aponeurosis is almost always of an arched form. The brachial aponeurosis has no muscle analogous to the tensor vaginae femoris ; the pectoralis major and the latissimus dorsi are sufficient to effect its tension. The Aponeurosis of the Forearm and Hand. The Jlponeurosis of the Forearm. Dissection. — ^Make a circular incision through the skin, immediately above the elbow, and from this let two vertical incisions be carried downward to the wrist, one in front and the other behind ; let the incisions extend through to the fascia, without dividing it : then cautiously remove the skin, being careful to take with it the sub-cutaneous adipose THE APONEUROSIS OF THE FOREARM. 317 tissue ; the superficial veins and nerves may be preserved. The external surface of the fascia may be studied first, and its several sheaths afterward opened in succession. The aponeurosis, or fascia of the forearm, ■^omis a general sheath, entirely surrounding or embracing that portion of the upper extremity, with the exception of the posterior border of the ulna. It is semi-transparent, and hence can be seen to be traversed by white lines, generally vertical in their direction, which indicate a corresponding number of thickenings of the sheath, and inter-muscular septa given off from them. It is separated from the skin by the superficial veins and nerves ; by its upper part it gives numerous attachments to the subjacent muscles, and this renders the dissection very difficult. By making a vertical incision, however, along the separate sheath which it furnishes to each of the muscles, and then carefully removing the latter, a good idea may be formed of the numerous angular compartments into which the common cavity of the fascia is subdivided. In the first place, it will be seen that this fascia, like all other investing aponeuroses, is composed of proper and superadded fibres ; that the proper fibres are nearly or quite circular, are more or less oblique, and more or less in- terlaced, but the superadded fibres are vertical. It wiU be found that it is twice as thick upon the dorsal as upon the palmar surface of the forearm ; that its thickness and its strength increase from above downward ; and that it is strengthened by a great number of superadded fasciculi, consisting of aponeurotic expansions from the tendons of the adjacent muscles. Thus, the brachialis anticus on the outside, the biceps on the inside and in front, and the triceps behind, give off tendinous expansions to this aponeurosis : of these the most remarkable is, without doubt, that given off from the biceps, which muscle may be regarded, indeed, as the tensor of the anterior portion of the fascia. This expansion constitutes, in fact, one of the terminations of the biceps, with the ex- ternal fasciculi of which it is continuous, and, moreover, arises from the outer edge and the anterior surface of its tendon. This expansion, so important in consequence of its relations with the brachial artery, passes obliquely inward and downward, and, as it ex- pands, intersects at right angles the vertical fasciculi proceeding from the epithrochlea and epicondyle of the humerus. These last-mentioned fasciculi also appear to me to be supplementary ; they are continuous with the common tendons of origin of the external and internal muscles of the forearm, and constitute the anterior walls of those two mul- tilocular pyramids, of which one is on the inner, the other on the outer side of the fore- arm, or of that series of trumpet-shaped cavities (cornets), as M. Gerdy calls them, from each of which the muscles of these regions take their origin. I must not omit to men- tion the thick tendinous band, which arises from the entire length of the posterior border of the ulna, divides into two layers to give origin to the flexor carpi ulnaris, and by its internal or deep surface affords attachment to the flexor sublimis. In the fascia of the forearm there are numerous foramina for the passage of vessels and nerves, but I shall direct attention to one very large orifice existing in front, at the bend of the elbow, and bounded on the inside by the outer margin of tlie tendinous ex- pansion of the biceps. This opening establishes a free communication between the sub- cutaneous and the sub-aponeurotic cellular tissue at the bend of the elbow, and leads into a sort of fossa, in which are found the tendon of the biceps, the brachial artery, the commenceaient of the radial artery, and the median nerve. This fossa is lined by apo- neurotic laminae : on the outside, by the layer which covers the inner surface of the supi- nator longus, the radial extensors, and the flexor sublimis ; on the inside, by the layer which completes the sheath of the pronator teres : it communicates above with the canal of the brachial artery, and below with the canals through which the radial, ulnar, and interosseous arteries and the median nerve proceed downward to the forearm. From the internal surface of this fascia a number of lamina? are given off, to form the following muscular sheaths : In the anterior region of the forearm, a transverse septum, thicker below than above, divides the superficial layer of muscles from the middle layer, consisting of the flexor sublimis, and also from the deep layer, composed of the flexor profundus digitorum and the flexor longus pollicis. Other septa, passing from before backward, divide the mus- cles of the superficial layer from each other. Lower down the sheaths of the flexor carpi radialis and palmaris longus, which are perfectly distinct from each other, are situated in front of the remainder of the fascia ; and this has led to the statement of some anat- omists, that the fascia is perforated by the tendons of these muscles, especially by that of the palmaris longus. The ladial artery has a special sheath throughout its whole ex- tent ; the ulnar artery and nerve have a proper sheath only in the lower part of the forearm. In the posterior region of the forearm, the fascia is much stronger than in the anterior. A transverse layer separates the muscles of the superficial from those of the deep layer; and septa, passing from behind forward, subdivide these common sheaths into several smaller ones, corresponding in number to that of the muscles. Thus, we find a sheath for the extensor communis digitorum, a second for the extensor digiti minimi, a tlurd for the extensor carpi ulnaris, and a fourth for the anconeus. The supinator longus and the two radial extensors of the wrist appear to be in the same sheath ; but a more or less distinct membrane surrounds the first of these muscles ; the supinator brevis has 318 APONEUROLOGY. also a proper sheath. We find a common sheath for the extensor longus pollicis and tlie extensor proprius indicis. The abductor longus and the extensor brevis poUicis, which, properly speaking, constitute but one muscle, have also a common sheath accompanying them as far as the dorsal annular ligament of the wrist. The Dorsal Annular Ligament of the Wrist, and the Dorsal Aponeurosis of the Metacarpus. The dorsal annular ligament of the wrist (r, fig. 121) may be considered as a depend- ance of the fascia of the forearm, which in this situation is strengthened by a great number of fibres. It is a band of six or eight lines in width, passing obliquely inward and downward over the extensor tendons of the hand, perforated by a number of open- ings for the passage of vessels, and distinguishable from the fascia of the forearm only by its somewhat greater thickness and by the parallel arrangement of its fascicuh. It arises internally from the pisiform bone and the palmar fascia, passes first over the ulnar side, and then the posterior surface of the carpus, is interrupted by the outer mar- gin of the groove for the two radial extensor muscles, takes a fresh origin from that mar- gin, covers the radial side of the wrist, and is inserted partly into the radius, and partly into the fascia of the forearm. From the anterior surface of this thick fibrous band arise several small prolongations, which are interposed between the numerous tendons passing over the dorsal and radial aspects of the carpus, and convert the grooves upon the lower extremities of the radius and ulna into canals. Thus, proceeding from with- out inward, and from before backward, we find, 1. A sheath for the united tendons of the abductor longus and extensor brevis pollicis ; 2 and 3. Two distinct sheaths opposite the radius : one for the two radial extensors of the carpus, the other for the extensor longus pollicis, which sheaths become blended together lower down into a single com- pletely fibrous sheath ; 4. A fourth sheath, stronger than the preceding, for the extensor communis digitorum and the extensor proprius indicis ; 5. An entirely fibrous sheath for the extensor digiti minimi ; 6. A very strong sheath for the extensor carpi ulnaris, which is prolonged below the ulna, and accompanies the tendon as far as the fifth meta- carpal bone. All these sheaths are lined by synovial membranes,* which extend some distance above the dorsal annular ligament, and, on the other hand, accompany the ten- dons very far down, sometimes even to their insertions. The dorsal aponeurosis of the metacarpus is a continuation of the dorsal annular liga- ment : it is composed of a very thin layer of transverse fibres, and separates the exten- sor tendons from the sub-cutaneous vessels and nerves. A very loose, extensible, and elastic cellular tissue takes the place of the synovial membranes over these tendons, and greatly facilitates their movements. The Anterior Annular Ligament of the Carpus. The deep groove upon the anterior surface of the carpus is converted into a canal by a very thick fibrous band, viz., the anterior ligament of the carpus ig,fig. 118). It com- mences internally by two well-marked origins, separated from each other by the ulnar nerve, one being from the pisiform bone and the tendon of the flexor carpi ulnaris, the other from the unciform bone. The first bundle passes downward, the second trans- versely, and their united fibres, some of which are transverse and others interlaced, ter- minate at the trapezium and the scaphoid, giving off an expansion to the fascia cover- ing the ball of the thumb, with which they are continuous. This ligament is continuous above with the fascia of the forearm, which is much thickened in this situation : it re- ceives in front the expanded tendon of the palmaris longus, and terminates below in the palmar fascia. Its anterior surface gives attachment to most of the jnuscles of the the- nar and hypothenar eminences. A small portion only of this ligament is generally seen and described, viz., the free portion. If it is wished to obtain a perfect conception of it, the muscles attached to its anterior surface should be carefully removed ; it will then be seen that, on the outside, it describes a curve having its conca^^ity directed inward, in order to be attached to the scaphoid and the trapezium, and that the sheath of the flexor carpi radialis is contained in its substance : this sheath is entirely fibrous above, and partly fibrous and partly osseous below, where it converts into a canal the groove on the trapezium. "VVliile there are almost as many synovial membranes a^ there are sheaths under the dorsal ligaments of the carpus, on the palmar aspect nine cendons with the median nerve form but a single bundle, which is lubricated by one or two synovial membranes. This synovial membrane* presents a curious arrangement, subject, moreover, to numerous varieties. It lines the posterior surface of the anterior annular ligament of the carpus is prolonged above and below that ligament, and is reflected (without passing between the different tendons) upon the anterior surface of the bundle formed by them and by the median nerve, which is to their outer side. In order to obtain an accurate idea of the termination of this synovial membrane, cut across the tendons at the lower part of the forearm, and turn them forward upon the palm of the hand : it will then be seen that the * See note, p. 296. THE PALMAR APONEUROSIS, ETC. 319 synovial membrane is reflected upon the ulnar border of tlie bundle of tendons ; that it lines the posterior surface of this bundle, passing more or less between the tendons, and separating them from each other in a rather irregular manner ; that it is reflected upon the groove of the carpus, prolonged upward and downward much farther than it was in front, and divided below into four small prolongations corresponding to the flexor ten- dons of each finger. Nor is this all, for there is a special synovial membrane for the flexor longus pollicis. In order to expose this, the synovial membrane must be cut through where it is reflected, on its radial side, from the annular ligament on to the me- dian nerve and the anterior surface of the bundle of tendons : a special and very exten- sive synovial membrane will then be seen to pass high up along the tendon of the flexor longus poUicis, and to be prolonged downward as far as the last phalanx of the thumb. The Palmar Aponeurosis. The ■palmar fascia {c,fig. 118) forms a common sheath for all the muscles of the palm of the hand, and is divided into three portions, a middle and two lateral. The middle portion. This is the only part generally described as the palmar fascia ; it is triangular and strong, but of variable thickness : it binds down the numerous sub- jacent tendons. It arises from the anterior surface and lower margin of the anterior annular ligament of the carpus, and from the tendon of the palmaris longus, which may be regarded as its tensor muscle. Between these two origins the ulnar artery pene- trates into the palm of the hand. Not unfrequently the expanded tendon of the palma- ris longus forms a fibrous layer in front of the proper palmar fascia. This fascia is nar- row and thick at its origin, but expands as it proceeds from above downward, and, op- posite the heads of the metacarpal bones, divides into eight prolongations for the four inner fingers. At the seat of this division we find very strong transverse fibres binding the prolongations together, and preventing disjunction of the fingers and laceration of the fascia. By this arrangement four arches are formed, under which the tendons of the flexor muscles pass : between these four arches there are three smaller ones, giving passage to the collateral vessels and nerves of the fingers, and to the lumbricales, so that al- together there are seven arches. These arches are true fibrous canals. In order perfect- ly to understand their structure, make a vertical incision through the palmar fascia ; it will then be seen that, opposite the arches, tendinous prolongations or tongues are detached from the deep surface of the fascia : these prolongations turn round the sides of the ten- dons so as to embrace them, and become continuous with the anterior or glenoid liga- ment of the metacarpo-phalangal articulations : the same arrangement obtains with re- gard to the three small arches for the vessels and nerves situated between the four prin- cipal tendinous arches. The palmar fascia is, moreover, intimately united to the skin by very numerous prolongations : its deep surface covers the superficial palmar arch of the arteries of the hand, the median and ulnar nerves, and the flexor tendons ; a very loose and extensible cellular tissue separates it from these parts, and facilitates the move- ments of the tendons. From its inner margin is given oif a very strong layer, which becomes continuous with the interosseous aponeurosis, and separates the middle from the internal palmar region ; a thinner layer proceeds from its outer margin, and passes down between the muscles of the thenar eminence and the first lumbricalis muscle. This small muscle, called the palmaris brevis {b, fig. 118), arises from the inner margin of the middle palmar fascia, and is merely a cutaneous muscle. The external and internal palmar fascia, or the thenar and hypothenar aponeuroses. These consist of two rather thin fibrous layers, forming the sheaths of the muscles of the ball of the thumb and those of the little finger : they are both continuous with the middle palmar fascia : the external appears to consist, in a great measure, of an expan- sion from the tendon of the abductor longus pollicis ; and the internal, of an expansion from that of the flexor carpi ulnaris. At the limits between these aponeuroses and the middle fascia are formed two septa, passing from before backward, and dividing the palm of the hand into three distinct sheaths : one median, completed by the interosseous apo- neurosis, and intended for all the flexor tendons and the principal vessels and nerves of the hand ; the other two placed on either side, and binding down the muscles of the the- nar and hypothenar eminences. The Sheaths of the Flexor Tendons of the Fingers, and their Synovial Mem- branes. After leaving the arches, or, rather, the curious sheaths, formed by the palmar fascia immediately above the corresponding metacarpo-phalangal articulation, each pair of flex or tendons is received into a special sheath, by which they are accompanied down to the last phalanx. It will be remembered that the anterior surfaces of the first and sec- ond phalanges are marked by a longitudinal groove ; to the two borders of this groove is attached a very regular semi-canal of fibrous tissue, which is exactly large enough to contain the two flexor tendons. This very strong sheath preserves its shape when the tendons have been removed ; and a correct idea of its importance may be obtained by observing the eflfects of contraction of the flexor muscles after it has been divided. This 320 SPLANCHNOLOGY. sheath is formed of parallel semicircular laminae, placed one above the other, densely ag- gregated over the bodies of the phalanges, and, for the most part, forming a continuous sheath, but becoming more and more separated, and sometimes even completely disap- pearing opposite the articulations and the articulating extremities of the bones. It ap- pears to me that, in the movements of flexion, these articular rings are pushed into each other. The sheath ceases altogether above the articulation of the second with the ter- minal phalanx. A very remarkable synovial membrane,* which is prolonged upward beyond the arch- es formed by the palmar fascia, lines the whole lenth of each osteo-fibrous sheath on the one hand, and on the other is reflected upon the two flexor tendons, affording each of them a sheath, and forms two, often three or four triangular folds, having their bases directed upward, and being perfectly analogous to the so-called adipose ligament of the knee- joint. Of these folds, the superior is situated opposite the upper extremity of the first phalanx, and extends from the tendon of the flexor sublimus to that of the flexor pro- fundus ; the inferior fold passes from the bifurcation of the superficial tendon to the deep tendon ; the others are intermediate, and proceed from the phalanx to the two tendons. These synovial folds can be very well seen by raising and separating the flexor tendons from the phalanges. Not unfrequently the synovial membrane forms a hernia between two of these tendinous rings, either opposite the body of a phalanx, or, still more com- monly, over one of the articulations. We may add, that these synovial folds are proba- bly intended to support the nutritious vessels of the tendons, and not to connect these tendons together. SPLANCHNOLOGY. General Observations on the Viscera. — External Conformation. — Structure. — Development. — Functions. — Dissection. Splanchnology (from oTrldyxvov, viscus) is that division of anatomy which treats of organs more or less compound in their structure. Some of these are contained within the three great visceral cavities {the viscera), while others are situated without these cavities {organs, properly so called). t The brain, the spinal cord, the heart, and the organs of the senses, are generally in- cluded in this division. I have thought it advisable, however, to confine myself here to the description of the digestive, respiratory, and genito-urinary apparatus. The organs of the senses, the brain, and the spinal cord will be studied more advantageously in con- nexion with the rest of the nervous system, and the heart with the other organs of the circulation. As the organs we are about to examine have few relations with each other, they do not admit of such extended and important general remarks as those which preceded the osteological and myological divisions. I shall content myself with explaining briefly the method in which the description of each organ should be pursued. Every organ presents for consideration its external conformation, its internal confor- mation or its structure, its development, and its functions. The External Conformation of Organs. The description of the external conformation of organs includes that of their nomen- clature, number, situation, direction, size, shape, and relations. Nomenclature. — The nomenclature of organs has not been subjected to so many chan- ges as that of the bones and muscles : the names adopted by the oldest authors have been retained in modern science, and are even used in common language. The names of organs are derived, 1. From their uses, as the oesophagus (from olu, I convey, and ^ayu, I eat) ; also, the lachrymal and the i^alivary glands. 2. From their length, as the duodenum. 3. From their direction, as the rectum. 4. From their shape, as the amygdalce (the tonsils). 5. From their structure, as the ovaries. 6. From the name of the authors who have best described them, as the Schneiderian membrane, the FaUopian tubes. Lastly, they are conventional words ; for example, the tongue, the liver, &c. Number. — Some organs are single ; others exist in pairs. Varieties in number are very common, both by excess and by defect. Thus, three kidneys have been found in the same individual, and there is often only one. Examples have been recorded of in- dividuals having three testicles ; one is imcommon. Lastly, varieties by excess almost always result from the division, and those by defect, from the union or fusion of organs. Situation. — This must be considered with regard to the region of the body occupied by an organ, i. c., its general or absolute situation; and also with regard to its relations with neighbouring organs, ?. e., its relative situation. Thus, when it is stated that the stom- * See note, p. 296. t All tlio viscera are organs, but all the organs are not viscera. The ■word viscus is probably derived from vescor, I eat, because a great number of the viscera are engaged iu the functions of nutrition. STRUCTURE AND DEVELOPMENT OF ORGANS. 321 ach occupies the left hypochondrium and the epigastrium, its absolute or general situa- tion is indicated ; but when it is added that this viscus is situated between the oesopha- gus and duodenum, below the diaphragm, and above the transverse mesocolon, its relative situation is implied. Many of the organs are subject to varieties of position ; and this constitutes an im- portant point in their history. These varieties of position depend upon congenital oi upon accidental displacement, either affecting the particular organ only, or consequent upon displacement of the neighbouring organs ; or they may result from a change in the size of the organ itself Size. — The absolute size of an organ is determined by linear measurements, by the quantity of water which it displaces, and by its weight ; its relative size, by comparison with bodies of a known size, or with other organs. The size of organs is subject to a great number of varieties. These depend either on age, as in the liver, testicles, and thymus gland ; on sex, temperament, or on individual peculiarities ; also on the state in which an organ is found : for example, the uterus, pe- nis, and spleen. Lastly, there are some pathological variations, which should not be omitted in a treatise upon descriptive anatomy. Figure. — The figure of the organs treated of in splanchnology appears to follow these rules. The double organs do not exactly resemble each other on the right and left sides of the body. The single organs, occupying the median line, are symmetrical ; but most of those which are removed from that line are not symmetrical. Nevertheless, symme- try is not so completely wanting in the viscera belonging to nutritive life, as stated by Bi- chat, for the stomach and the small and great intestines may be divided into two equal halves. In regard to their forms, organs are compared, in general, either with familiar objects, or with geometric figures. Thus, a kidney is said to resemble a kidney-bean, and either hing, a cone. In very irregular organs, we merely describe the surfaces and the borders. We shall not find in the viscera the same constancy of form as exists in the organs of relation. Direction. — The direction of an organ is determined in the same manner as that of the bones and muscles, viz., by its relations with the imaginary planes surrounding the body, or with the mesial plane. Relations. — The figure of an organ being determined, its surface is then divided into regions, the relations of which are accurately ascertained. These regions are generally termed surfaces and herders. As the situation of many organs is subject to great varie- ties, their relations must also vary. Too much cannot be said of the value of an accu- rate knowledge of these relations, from which a number of the most important practical inferences may be derived. The Internal Conformation or Structure of Organs. The surface of an organ being well understood, we next proceed to the study of its structure, comprising its colour, its consistence, and its anatomical elements. Colour. — The colour both of the surface and the substance of an organ requires to be studied. All variations of colour should be very carefully noted. Age and disease have much influence over it ; and it is often difficult to distinguish positively between its physiological and pathological condition. Consistence. — The consistence, density, and fragility of organs are connected with their structure. The specific gravity or density of a single oi-gan only, the lung, has been ac- curately studied, and that in a medico-legal point of view. In estimating the consistence and fragility of organs, we can only approximate the truth. It is desirable that some more methodical and accurate means should be devised for the estimation of these qualities. Anatomical Elements. — The determination of the immediate anatomical elements, or tissues, which enter into the composition of an organ, together with their proportions and their arrangement, constitutes the knowledge of its structure. Every organ has either a cellular, fibrous, cartilaginous, or bony framework. Some organs are provided with muscular fibres, or even with distinct muscles ; they all contain the several kinds of vessels, viz., arteries, veins, and lymphatics ; and they all possess nerves. The glan- dular organs have excretory ducts. In explaining the structure of organs, we shall, generally, confine ourselves to a brief enumeration of their constituent parts, referring to works on the anatomy of textures for details which would be misplaced in an elementary treatise. The Development of Organs. The study of the development of organs, and the changes which they undergo at the different periods of intra- and extra-uterine life, is of the greatest interest, at least as re- gards some among them. The formation of the soft parts, however, is not nearly so well understood as that of the hard tissues, because the most important phenomena of devel- opment occur during the first weeks after conception. The remarks upon this subject, will, therefore, generally point out some hiatus to be fUled up. Ss 322 SPLAyCHXOLOGT. The Functions of Organs. The foncrions or uses of organs flow so naturaDy from their anatomical description, that we shall follow the example of the greater number of anatomists, in adding to SQch description a short account of the functions of an organ. "We shall only notice particn- lariy those uses of organs which depend immediately upon their structure, referring to physiological works for the details and discussions of yet disputed points in the science of functions. No part oi anatomy excites so much curiosity and interest as splanchnol- ogy, in consequence of the importance of the organs of which it treats. Without a knowledge of this department of anatomy, it is impossible to understand the mechanism of functions the most indispensable to life ; and as the organs themselTes are the seat of the greater part of the lesions which are assigned to the physician, as well as of many of those which fall under the care of the surgeon, most of the fundamental qt^stions of the healing art require a profound knowledge of these organs. The Dissection of the Viscera. The dissection of organs does not consist in merely isolating them fi-om surrounding parts, which, as far as regards those contained in the visceral cavities, is done by sim- ply laying open the latter, but in the separation of their anatomical elements or tissues. For this purpose, injections of the most delicate kind, maceration, boiling, preservation in alcohol, desiccation, the action of acids, in short, all the resources of his art. are em- jdoyed by the anatomist. Having made these preliminary observations, we shall now describe in snccessitHi the organs of digestion, the organs of respiration, and the genito-urinary apparatus. THE ORGAX.S OF DIGESTION AND THEIR APPENDAGES. ALDCEXTARY OR DIGESTTTE C-\NAL. GeTieTol Observations. — Dinsion. — Mouth and Us Appcndagts. — L\ps. — ChccLs. — Hard and Soft Palate. — Tonsils. — Tongue. — SaliTary Glands. — Buccal Mucous Membrane. — TJia- ryrcx. — (Esophagus. — Stomach. — SnuiU Intestine. — Large Intestine. — Muscles of the Pe- rineum.— Detelfpment of the Intestinal Canal. The organs of digestion form a long canal, the alimentary or digestire canal, extending from the mouth to the anus, which receives alimentary substances, induces in them a series of changes, by which they are rendered fit to repair the losses incurred by the body, and. moreover, presents a vast absorbent surface for the action of the lacteal ves- sels. The entire series of these organs constitutes the digestive apparatus. The existence of an alimentary canal is one of the essential characters of an animal. In consequence of possessing it, aninnals may be detached from the soil, so as to move from place to place. In the lowest species, the entire animal is nothing more than an alimentary sac. having a single opening, and formed by a reflection of the skin : so that, according to the beautiful observation of Trembley. when polypes are turned inside out, the digestive process is performed as well by their external as by their internal surface. Ascending in the scale of animals, the canal soon presents two openinss. acquires larger dimensions, becomes more or less convoluted, and is distinct from other systems of or- gans. A skeleton clothed by muscles is interposed between it and the skin. It becomes more and more voluminous, in proportion as the nutritive materials and the textures of the body differ more widely in their chemical composition. ^Vlial a difference there is, in this respect, between certain fishes, in which the alimentary canal is not nearly so long as the animal, and son^ herbivora : the ram. for example, in which it is twenty- seven times the length of the body. Carnivorous animals, again, have a short and nar- row alimentar^i- canal. Man. being destined to Irre both upon animal and vegetable sub- .■jtances, occupies, as it were, a middle station between the herbivora and camivora. General Situation. — The digestive canal is situated in front of the vertebral column, with the direction of which the straight portion of the canal accurately corresponds, while its tortuous part is distant from, though invariably connected with it by means of membranous attachments. It commences at the lower part of the face, traverses the neck and the thorax, penetrates into the abdominal cavity, which is almost exclusively intended for it. and the dimensions and mechanism of which bear strict relation to the functions of the alimentary canal ; and it terminates at the outlet of the pelvis, anterior to the coccyx, by the anal orifice. Its upper part is in immediate relation with the or- gans &f respiration : its lower, with the genito-urinary apparatus. Dimensions. — The length of the digestive canal has been calculated to be seven or eight times that of the body of the individual. Its diameter is not equal through its whole extent ; and its alternate expansions and contractions establish very distinct lim- its between its several portions. The largest portion is, undoubtedly, that which re- ceives the name of the stomach : the narrowest parts are the cervical portion of the (Esophagus, the pyloric opening of the stomach, and the ileo-caecal orifice. It is impor- GENERAL REMAEKS. 323 tant to remark, that the transverse dimensions of an alimentary canal have, to a certain extent, an inverse ratio to its length. Thus, a very wide intestinal canal is generally less remarkable for length. This remark is illustrated by comparative anatomy in the fact that, in the horse, an herbivorous animal, the intestinal canal is shorter, but, at the same time, of a much greater calibre than in the ruminantia, which are also herbivorous. Directio7i. — The upper or supra-diaphragmatic portion of the alimentary canal, through "which the food merely passes, is straight ; the sub-diaphragmatic portion is very much convoluted upon itself but again becomes straight before its termination. General Form. — The digestive apparatus forms a cylindrical continuous canal, in which we have to consider an external and generally free serous surface, and an internal mu- cous surface. Structure. — The digestive canal is composed of four membranes or tunics : 1. The most external is the serous or peritoneal coat, also named the common tunic, because it is coQunon to almost all the organs in the abdominal cavity. This membrane, which may be regarded as an accessory tunic, is often incomplete, and even entirely wanting through- out the supra-diaphragmatic portion of the digestive canal. At the same time thai it constitutes the external covering of this canal, it separates it from the neighbouring parts, faciUtates its movements, and forms certain bands, which maintain the several portions of the canal more or less fixedly in their proper situations. The serous membranes, of which this external tunic is only a dependance, are shut sacs, which, on the one hand, line the walls of the cavities to which they belong, and, on the other, are reflected upon the organs contained therein,* without, however, including them within their own prop- er cavity. A serous membrane may be compared to a baUoon, or, rather, to a double nightcap ; its internal surface is free, smooth, always moistened "with serosi*y, and its parietal and visceral portions are in contact with each other : its external surface is adherent. t 2. Beneath the serous coat is situated the muscular coat, consisting of two layers : one su- perficial, composed of longitudinal fibres ; the other deep, and composed of circular fibres. These fibres are colourless, like almost all the muscles of nutritive or organic life.t 3. The fibrous coat, interposed between the muscular and mucous coats, maybe regard- ed as constituting the framework of the alimentary canal. It consists of dense areolar cellular tissue.^ 4. The mucous coat or membrane forms the internal lining of the digestive canal. Ev- ery cavity having a conamunication with the exterior is lined by a mucous membrane, so called on ac^-ount of the mucus with which it is constantly lubricated. In mucous membranes generally, we find, 1. A dermis or chorion, 2. Papilla or villosi- ties, which give them a velvety appearance ; hence the designation papillary, villous, or velvety membrane frequently given to them. 3. On the outer surface of the dermis we find a ver>' dense network of capillary vessels, which may be completely injected from the veins, but less easily and less completely from the arteries. 4. Either follicles or small closed sacs are seen here and there in the substance of mucous membranes ; but they are not essential, as the name follicular, given to these membranes by Chaussier and some other anatomists, would seem to indicate. * [Hence the terms parietal and visceral, applied to these two portions of a serous membrane (see Hg. of the testis, letters p and e). In consequence of the existence of an aperture in the free extremitv of each Fallopian tube, the peritoneal cavity in the female is an exception to the general rule, that serous membranes form shut sacs, not communi- cating- with the external medium.] t [Serous membranes are transparent, colourless, extremely thin, and highly distensible and elastic. They are composed of a basis of cellular tissue, loose and connected to the adjacent tissues externally, more or less condensed towards the inner and free surface of the membrane, and covered with an extra- vascular epithelium, consisting of a single layer of nucleated cells, flattened into the form of scales, and arranged parallel to that surface. Cilia have been detected on many serous membranes, as on the peritoneum and pericardium of the frog ; on the same part^, and also on the pleura and lining membrane of the ventricles of the brain in certain mammalia ; and in the latter situation in man. Bloodvessels ramify in the sub-serous cellular tissue, but do not penetrate far towards the free surface, where they are entirely wanting. Lymphatics also exist in the sub-serous tissues, but have not been found in the membranes themselves ; nor have nerves been traced into them. The fluid secretion found in serous cavities appears to be of an albuminous nature.] t [The involuntary muscular fibres of the alimentary canal (according to Dr. W. Baly) consist of bands, va- rying from ^ y th to . g*-^ ^ th of an inch in diameter, apparently formed of flattened tubes, in the parietes of which are seen, at irregular intervals, numerous transparent oval or linear bodies, sometimes ver>" djflicult of detection ; they are believed to be the nuclei of the primitive cells, from which the libre itself is developed. These fibres contain no varicose filaments, nor do they present any transverse stria>, like those of animal life (see p. 194). Moreover, although they have a parallel arrangement in the fasciculi into which they are col- lected, the fasciculi themselves are irregularly interlaced, at the same time that they all pursue a common direction. The muscular coat of nearly the entire alimentary canal consists essentially of these involuntary or organic muscular fibres ; but at the commencement and termination of the canal, where the muscular systems ot aju- mal and organic life come into relation with each other, this tunic appears also to consist of fibres resembling those of the voluntary muscles. Thus, at the upper part of the cesophagus. fibres containing varicose filaments, and possessing tlie cross strire, were detected by Schwann ; and it has been shown by Valentm and Ficinus, that these exist all along the cesophagus, and that indistinctly striated fibres are found even at the cardiac end of the stomachs of many mammalia, and of man. Similar fibres were observed by Ficinus in the rectum, near the sphincter ani.] >> [It IS frequently called the cellular coat ; and, ftom its white appearance, has been termed (like all other white textures) the nervous tunic] 324 SPLANCHNOLOGY. All mucous membranes. are covered by an extremely delicate peUicle, which may be readily detected by means of a simple lens. Injections made by the arteries and veins never penetrate it, nor is it reddened by inflammation. I have accidentally injected it, how^ever, by means of a tube containing mercury, used for injecting the lymphatics by pricking the mucous membrane in different places as superficially as possible. The vas- cular network, thus injected, is exceedingly delicate ; the small globules of mercury traversing it in all directions, so as to form rapidly a silvery areolar layer. I have seen this in the mucous membrane of the nose ; on the conjunctiva, both over the sclerotic and over the cornea ; on the mucous membrane of the vagina, of the tongue, and of the cheeks. It is very remarkable that the mercury never passes from this network ei- ther into the veins or the arteries ; and, moreover, that if the tube pierces a little too deeply, the veins are injected, but not the epidermic capillary network. It is evident, therefore, that this network has no conamunication either with the arteries or the veins. It probably belongs to the lymphatic system, although I have never observed the lymphat- ic vessels filled from it.* Vessels and Nerves. — Vessels and nerves also enter into the formation of the aliment- Pi^_ 139. ary canal : for example, we find a very abundant supply of branches from the adjacent arterial trunks ; an immense num- ber of veins, of which those from the sub-diaphragmatic por- tion of the canal terminate in the vena portas ; absorbent ves- sels, divided into lymphatics and lacteals ; and, lastly, nerves, almost all of which proceed from the ganglionic system, ex- cepting the pneumogastric and glosso-pharyngeal nerves. Division of the Digestive Canal. — The digestive canal has been divided into several parts, from differences both in their anatomical characters and their functions. One principal di- vision, which deserves to be retained, is into a supra-diaphrag- matic and a sub-diaphragmatic portion. The supra-diaphragmat- ic portion comprehends the mouth, the pharynx, and the oesoph- agus. The infra-diaphragmatic portion includes the stomach (a b,fig. 139), the small intestine, subdivided into the duodenum {b c), and the jejunum and ileum (c d) ; and the large intestine, somewhat arbitrarily divided into the caecum (d e), the colon {d h\ and the rectum (h i). The appendages of the digestive ca- nal consist of the salivary glands, connected with the mouth , of the liver and the pancreas, connected with the duodenum ; and of the spleen, which may be regarde'' as an appendage of the liver. The Mouth and its Appendages. The mouthi is a cavity situated at the entrance of the digestive passages. It occu- pies the lower part of the face, and is situated between the two jaws, below the nasal * [The lining membrane of the digestive apparatus, forming part of the gastn^pulmonary system of the mucous membranes, e.xtends not only throughout the entire alimentary canal, but also along the ducts of the various glands which pour their secretions into it. Structure m general. — Mucous membranes are usually soft, pulpy, incapable of great distension, easily la- cerated, somewhat opaque, and when free from blood, of a pale grayish or ashy hue. The dermis or chorion (analogous to that of the skin) is a basis of cellular tissue, of very variable thickness ; its attached surface is connected to the subjacent textures, either immovably, as in the nasal cavities and on the tongue, or loosely, as in the gullet and stomach. The peUicle or epithelium with which its suiface is always covered (correspond- ing to the epidermis of the skin) also varies much in thickness in different situations ; it consists of transpa- rent nucleated cells, according to the form and arrangement of which it receives its name. Thus, in the squamous epithelium, there are generally (as in the mouth and gullet) several layers of cells ; of these the deepest are vesicular, and contain a comparatively large nucleus ; those on the surface are flattened out into polygonal scales, from the centro of which the nucleus has nearly disappeared, while the intermediate cells present intermediate transitional forms. The nucleated cells of the columnar epithelium (found, for example, in the stomach and intestines) are developed into oblong cylinders, arranged in a single series, like basaltic columns, perpendicularly to the surface of the dermis. In some situations, as in the nasal cavities and air passages, cilia are attached to the free extremities of the cylinders of the columnar epithelium, but no cilia have been detected in any part of the alimentary canal of man, or the warm-blooded animals : the superficial cells of the epithelium of mucous membranes are continually being thrown off by a process of desquamation. The different mucous membranes differ in vascularity ; the network of capillary vessels in the dermis becomes closer or denser near its surface ; the lymphatic vessels also form a network in the same situation ; but the epithelium, though organized, is, as stated in the text, perfectly extra-vascular. Mucous membranes are also more or less abundantly supplied with nerves. When boiled they yield no gelatine, or, rather, only as much as would proceed from the cellular tissue and vessels they contain. The fluid secreted by them, or mucus, is viscid, transparent, and colourless, miscible with, but not soluble in water, and not coagulated by heat. It contains, besides the desquamated epithelium scales, proper granular globules, j-jVo ^^'^^ '" diameter, and having a very close resemblance to the globules of pus.. According to Berzelius, mucus consists of water, a few salts, albumen, and a peculiar animal sub- stance, -vyhich he calls mucous matter. This latter, when dried, swells on being placed in water, but, like fresh mucus, is insoluble in that fluid, either hot or cold; it is slightly soluble in dilute acetic and nitric acids, and in caustic alkalies. The peculiarities presented by particular portions of the mucous membranes, and the structure of the pa- pillae, villi, follicles, Toid muscle (ji,fig. 114), the thyroid body (c), the left recurrent laryngeal nerve, and the inferior thy- roid vessels, which cross it at right angles. The relation of the cesophagus to tlie tra- chea explains how foreign bodies arrested in the former passage may compress the tra- chea, and impede or even prevent respiration. The deviation of the oesophagus to the left is the reason for selecting that side for the performance of cesophagotomy. Behind, it corresponds to the longi coUi muscles and to the vertebral column, being united to them by loose cellular tissue, so that it is enabled to execute those movements which are necessary for the performance of its functions. Laterally, it corresponds to the thy- roid body, the common carotid artery, and the internal jugular vein ; but these relations are somewhat modified on each side, in consequence of the deviation of the cesophagus. Thus, the relations of the cesophagus with the left common carotid are much more im- mediate than those with the right. The left recurrent nerve lies in front of the oesopha- gus, the right nerve a little behind it. Its thoracic portion {o, fig. 161) is situated in the posterior mediastinum, and is in rela- tion in front, commencing from above, with the trachea, then with its bifurcation, and slightly also with the left bronchus, which crosses it obliquely, and which may be com- * [Opposite the cricoid cartilage.! THE (ESOPHAGUS. 351 pressed by it during the retention of a foreign body (an example of this accident has been recorded by Habicot) ; lastly, it is situated opposite and behind the ascending portion of the arch of the aorta, and the base and posterier surface of the heart, from which parts it is separated by the pericardium. Behind, it is in relation with the longus colli and the vertebral column, to which, however, it is not so closely applied as in the neck ; nor does it follow the curvature of the spine in the dorsal region, but is separated from it by a space, filled with cellular tissue, lymphatic glands, the vena azygqs, and the thoracic duct, the latter being placed to its right side, at the lower part of the thorax, but passing be- hind it above, so as to reach the left side. Below, at the point where the oesophagus deviates to the left side, in order to gain the opening of the diaphragih, it lies in front of the aorta. On each side it forms a projection along the wall of the mediastinum, which is thus brought into relation with the corresponding lung ; it is much more prominent on the right than on the left side. On the left side it is also in contact, in its entire extent, with the thoracic aorta {h,fig. 161), which is situated a little behind it. Above, it has immediate relations with the arch of the aorta, as that vessel is passing backward and to the left side of the vertebral column. It is commonly, at this point, that aneurisms of the aorta open into the oesophagus. In all this region the oesophagus is enveloped by a serous cellular tissue, extremely loose and very abundant ; it is surrounded by a great number of lymphatic glands, which have been improperly named cEsophageal. These glands, when enlarged, sometimes compress the gullet so much as completely to arrest deglutition. Lastly, the two pneu- mogastric nerves run along each side of the oesophagus ; inferiorly the left comes in front, and the right retires behind the canal : they communicate with each other throughout their course by loops or arches, which, perhaps, explains the pain caused by swallowing too large a mass of food. In its abdominal portion (if such can be said to exist), the oesophagus is in relation with the oesophageal opening of the diaphragm, below which it is entirely covered by the peritoneum. On the right side and in front it is embraced by the left extremity of the liver ; behind, by the lobulus Spigelii. In some subjects the abdominal portion of the oesophagus is an inch in length,, but this, I think, is occasioned by descent of the stomach. The internal surface is remarkable for its pale colour, which contrasts strongly with the rosy hue of the stomach and the upper part of the pharynx, for the wrinkling of its pa- rietes and their contact with each other, and, lastly, for its longitudinal folds, which seem to have reference to the necessity for its momentary distension during the mere passage of the food through it. Structure. — The oesophagus is essentially composed of two cylindrical membranes, one internal or mucous, the other external or muscular. The muscular coat is remarkable for its thickness, which greatly exceeds that of any other part of the alimentary canal, and is connected with the necessity for the rapid pas- sage^of the alimentary mass from the pharynx into the stomach. It is susceptible of hy- pertrophy, as we find in cases of stricture of the lower part of the gullet. I have seen it five or six lines thick. In all herbivorous animals in which the oesophagus is almost incessantly in action, in those in which the food is carried upward in opposition to grav- ity during the act of deglutition, in the horse and in ruminants, the muscular coat is still more developed than in man. The muscular coat is of a red colour immediately below the pharynx, and rosy through the rest of its extent, but of a darker tint than in the succeeding portion of the aliment- ary canal. It is of a vivid red in herbivora.* This coat is composed of two very distinct layers, the external consisting of longitu- dinal fibres regularly disposed upon all sides of the oesophagus ; the internal, of circular fibres, in which we shall in vain seek for the spiral arrangement described by some anat- omists as existing in animals and in man.f The longitudinal fibres seem to arise, at least in part, from the posterior surface of the cricoid cartilage, in the median line, be- tween the two posterior crico-arytenoid muscles ; they evidently become continuous be- low with the longitudinal muscular fibres of the stomach. The first muscular ring of the oesophagus appears to arise from the cricoid cartilage ; it has been designated the crico- asophageus. There is no sphincter, as some anatomists have affirmed, round the lower extremity of the oesophagus. The Mucous Mevilrane. — As Bichat has remarked, the mucous membrane of the oesoph- agus is, perhaps, next to the buccal, the thickest in the alimentary canal. By a remark- able exception (also observed in the rectum), its outer surface is united to the adjacent membrane by a very loose cellular tissue ; so that the whole mucous cylinder may be removed entire from the sort of muscular sheath in which it is contained. It has even been said that the muscular coat can force the mucous membrane downward by its con- traction, so as to produce a projecting rim around the cardiac orifice of the stomach, analogous to that which is formed at the anus in prolapsus. The longitudinal folds of * [It consists of involuntary muscular fibres (note, p. 323), intermixed with fibres possessing transverse striae.] 1 [These fibres are obviously spiral in the ruminant, and many other mammalia ] 352 SPLANCHNOLOGY. the mucous membrane are not caused by the contraction and elasticity of the circular fibres of the muscular coat, but depend upon a peculiarity of structure. If the first hy- pothesis be correct, why should not the mucous membrane also present transverse folds from the action of the lono-itudinal fibres ■! for the extremities of the oesophagus are not so fixed nor is its tension so great that it could not be shortened by the action of these fibres. Besides the lonfitudinal folds, there are also in the oesophagus a number of icnnkles analoo-ous to those of the skin, and, therefore, irregular ; they appear to me to be caused by the elasticity of the muscular fibres. The mucous membrane of the oesophagus has a thick epithelium, which may be easily shown by maceration and the action of acids, or even without preparation, and which terminates at the cardiac orifice of the stomach by an irregularly fringed or festooned border.* When examined by the microscope, the free surface of the mucous membrane pre- sents a number of small linear ridges, running vertically, and united together by other oblique ridges, so that the whole surface has a reticulated aspect. These ridges are formed by papillae or villosities, the arteries and veins of which have been accurately figured by Bleuland. The surface of the mucous membrane is raised in various places by small, oblong, and flat glands found here and there over the entire oesophagus. They were first described by Steno, and should be carefully distinguished from the oesophageal lymphatic glands : the latter are external to the oesophagus, and, in certain animals, frequently contain small entozoa : they have been supposed to open into the oesophagus, and to deposite within it a fluid containing these animalcules, which some physiologists have regarded as the chief agent in digestion. Any communication, however, between these lymphatic glands and the cavity of the gullet is purely accidental. The true oesophageal glands are very numerous, t In the oesophagus, there is only a trace of the fibrous membrane, which forms the frame- work of the alimentary canal ; it adheres to the muscular coat, and is, therefore, but loosely attached to the mucous membrane. There is no external serous membrane ; it would not have yielded to the instantane- ous dilatation required in the oesophagus. The two laminee of the posterior mediasti- num corresponding to its sides may be regarded as forming the rudiment of a serous coat. Vessels and Nerves. — The (esophageal arteries are numerous, and arise from several sources. They may be distinguished into the cervical, proceeding from the inferior thy- roid ; the thoracic, given off either directly from the aorta or from the bronchial and in- tercostal arteries, and sometimes from the internal mammary : and, lastly, the abdominal, arising from the coronary artery of the stomach, and the inferior phrenic. The veins terminate in the inferior thyroid, the superior cava, the azygos, the internal mammary, the bronchial, the phrenic, and the coronary of the stomach. The lymphatic vessels enter the numerous glands which surround the oesophagus. The nerves are very numerous, and are derived from the pneumogastrics, which sur- round the oesophagus with a series of loops ; these are joined by some branches from the thoracic ganglia of the sympathetic. The development of the oesophagus presents nothing worthy of notice. Functions. — The oesophagus is intended to convey the food rapidly from the pharynx to the stomach. This function is performed by its longitudinal fibres shortening the pas- sage, and by its circular fibre's contracting it successively from above downward during deglutition ; in vomiting or regurgitation, the contraction proceeds from below upward. The Stomach. The stomach (jaGTTjp, ventrictdus), one of the princi- pal organs of digestion, is that wide dilatation {s, fig. 139) of the alimentary canal, intervening between the oesophagus (a) and the duodenum (b c), in which the food is collected and converted into chyme. Situation. — It is situated at the junction of the upper tenth with the lower nine tenths of the alimentary ca- nal, between the organs of deglutition and those of chyhfication. It occupies the upper part of the abdom- inal cavity {s, figs. 155, 161), almost entirely fills the left hypochondrium, and advances into the epigastri- um, as far as the limits of the right hypochondrium. J * [The epithelium is, in fact, continued on through the rest of the alimentary canal, but becomes thinner, and assumes a different character : in the oesophagus it is squamous.] t [Especially around the lower extremity of the gullet.] , t [In order to facilitate the description of the viscera contained in the abdominal cavity, anatomists have adopted the following ar- tificial division of that cavity into several regions: The abdomen is first divided into three zones by two horizontal lines, one (a o, Fig. 148. THE stoma'ch. 353 It is maintained in its place by the oesophagus and duodenum, and also by some folds of the peritoneum, which connect it with the diaphragm, the liver, and the spleen. The stomach is, therefore, less subject to displacement than most of the abdominal viscera. It may even be generally stated, that almost all the changes in the relative situation of this organ are the results of displacements or alterations in the size of those organs which are connected with it, I do not here refer to examples of complete transposition of the viscera, nor to those cases of malformation of the diaphragm, in which the stom- ach has been found in the thorax. Direction. — The stomach is directed obliquely downward to the right side, and a little forward ; this direction affords some explanation of the almost constant habit of lying on the right side during sleep, and why the rest is disturbed and digestion rendered diffi- cult in those who lie upon the left side. Changes in direction of the stomach depend upon the same causes as changes in its situation. Thus, dragging produced by displace- ment of the small intestine or the omentum, enlargements of the liver or spleen, or the use of too tight stays,* must necessarily affect the direction of this organ. We not un- frequently find stomachs having a vertical direction. Number. — The stomach is single in the human subject as well as in the greater num- ber of animals. The examples of double or triple stomachs in the human subject are merely cases of single stomachs having one or more circular constrictions.! The es- sential character of a double stomach is not an accidental or even a congenital contrac- tion, but a difference in structure. Bihcular stomachs, indeed, are very common ; but this form (resembling that of some kinds of calabash-gourds), though sometimes extreme- ly well marked when the stomach is empty, disappears almost entirely when it is much distended by inflation. Size. — In all animals, the stomach is the most capacious part of the alimentary canal ; so that, in many species, where its limits are not so clearly defined as in man, the ex- istence of a stomach is determined only by the presence of a dilatation. It is of consid- erable size in herbivora, but comparatively much smaller in camivora. The human stomach is intermediate between these extremes — a fact which affords evidence of its adaptation to both vegetable and aliment diet. The human stomach, however, presents innumerable varieties in size, from a state of extreme contraction, in which it scarcely exceeds the duodenum, to such an enormous degree of dilatation that it occupies a third, a half, or even almost the whole, of the abdominal cavity. These differences depend, less upon original variations, than upon its peculiarly dilatable and elastic structure^, which enables it to contain a large quantity of food, and to contract more or less com- pletely upon itself when empty. Thus, the stomach has a much greater capacity in those who adopt the bad habit of eating only one very full meal in the twenty-four hours, than< in those who eat more frequently, but less abundantly. In some cases of stricture at the pylorus, it becomes enormously distended. Long-continued abstinence occasions such> an amount of contraction, that it has even been asserted, that pain resulting from the rubbing of its parietes together gives rise to the feeling of hunger ; but this completely mechanical hypothesis should be rejected. In a great number of cholera patients,, the stomach was found to be exceedingly small. In a female, who died a month after hav- ing voluntarily swallowed a small quantity of sulphuric acid, the contracted stomach was not larger than a moderately-sized gall-bladder. Figure. — The stomach resembles a flattened cone, curved upon itself backward and upward, and having a rounded base ; it has been compared to the bladder of a bagpipe. Sections made at right angles to its axis represent circles gradually decreasing in size from the entrance of the oesophagus to the pylorus. We have to examine its external and its internal surface. The external surface. From the peculiar form of the stomach, we are enabled to con- sider an anterior and a posterior surface, a convex border or great curvature, and a con- cave border or lesser curvature, a great cul-de-sac or tuberosity, an oesophagal extremi- ty, and a pyloric extremity. The anterior surface (upper surface of some anatomists, s,fig. 155) is directed forward, and a little upward. Wheh inflated in the dead body with the abdomen open, it is turn- ed directly upward ; but such cannot take place, either in the living or dead subject, Jig. 148) extending between tlj^ most prominent points of the cartiiag-es of the ribs, and the other (b b) be- tween the crests of the iliao bones. The superior zone is called the epigastric ; the middle, the umbilical ; and the inferior, the hypogastric. These three zones are then subdivided by two vertical parallel lines drawn from the cartilages of the eighth rib down to the centre of Poupart's ligament. The epigastric zone is thus divided into two hypochondriac (1 l),and a middle epigastric region (2) ; the umbilical into two lumbar (33), and a middle umbilical region (4) ; and the hypogastric into two iliac (5 5), and a middle hypogastric region (6).] * It is impossible to insist too strongty upon the influence of too tight stays on the situation, and even the form, of the viscera occupying the base of the thorax. Thus, changes in the situation and direction of the stomach are much more frequent in females than in males. Soemmering observed, but without stating the cause, that the stomach is more rounded in the male, and more oblong in the female. t It may, strictly speaking, be stated that ruminants have only one stomach, the rennet or obomasum; and that the first three, viz., the paunch, the reticulum, and the manypUes or omasum, are nothing more than dila- tations of the (Esophagus, in which the food undergoes a preparatory elaboration. The same observation ap- plies to birds, in which the crop and the gizzard are not organs of chymification, the first being merely an or-- gan of insalivation, the second one of trituration. Yy 354 SPLANCHNOLOGY. when the abdominal pavietes are entire ; in which case the distended stomach passes in the direction of the least resistance, i. e., forward and downward, and its anterior sur- face cannot then be completely turned up. This surface is in relation with the diaphragm, and is separated by it from the heart : with the liver, which is prolonged upon it to a greater or less extent ;* with the last six ribs, being separated from them by the diaphragm ; and with the abdominal parietes in the epigastrium : hence the name given to that region. It is not uncommon to find the great omentum turned upward between the stomach and the liver. When distended, the stomach has much more extensive relations with the epigastrium, or, rather, with the abdominal parietes, both in a vertical and transverse direction. All these relations are of the greatest importance ; and, with the exception of those which concern the epigastrium, they are constant. In fact, it rarely happens that the stomach precisely corresponds to the sub-sternal or xiphoid depression, which has been called the pit of the stomach, or the scrobiculus cordis, but which belongs neither to the heart nor the stomach. In exploring this depression, it is almost always the liver which is felt ; the stomach lies lower down, and is generally below the ensiform appendix. The posterior surface {inferior surface of some anatomists, seen turned up at s,fig. 154) is directed downward and backward, and is seen in the sac of the omentum, of which it forms the anterior wall. It has relations with the transverse mesocolon, which serves as a floor for it, and sep- arates it from the convolutions of the small intestines ; with the third portion of the duo- denum (e' to b), by some of the older anatomists called the pillow of the stomach (ven- triculi ■pulviyiar) ; and, lastly, with the pancreas (o). The duodenum, the pancreas, the aorta (a), and the pillars of the diaphragm {d d), separate it from the vertebral column, upon which it rests obliquely. These relations are modified by the emptiness or fulness of the stomach. Tlie great curvature " i] end of the small intestine ; they become more and more I '"'"■ - J scattered as we approach the duodenum, in which, how- |f\.^ r „ > -, ^ ever, Peyer once met with a single patch. Their number varies considerably, twenty, thirty, and even more having been counted. Are they ever entirely wanting ^ The dif- ficulty of detecting them in some subjects has led to their being rejected altogether, or considered as the results of a pathological condition ; but this opinion is clearly at va- riance with observation. Again, these patches are not j* f' constant either in situation, form, or dimensions. Some- 't ,' . times they assume the appearance of bands two or three K;" . ' inches in length {fig. 158), and sometimes they form cir- I; ' cular or irregular clusters. The largest are found near '■ the ileo-caecal valve. It is not rare to find the termina- c- >' *• ■ tion of the small intestine surrounded by a circular patch ; 5''V,';/' » in other cases, the patches termi- L^J!^- . " I Fig. 157. jj^jg g^j^g inches above the ileo- a?-'W.(- , " ,'' ' ^] caecal valve, and their place is sup- ||fj.-j s...^ I'l^ ■■* ' ' phed by simple follicles. * [According to Dr. Boehm (De Gland. Inteshn. Struct, peniiiori), thi.>! is not the case, the compound glands of Brunner not existing below the commencement of the jejunum.] t iFig. 157 is a solitary gland magnified ; it is represented, after Boehm, as a closed vesicle, filled with whitish matter, which contains granules smaller than those of mucus. Villi are seen upon the free surface of its capsule, and it is sur- '^'^yy/z'/yym'/xtsmmp rounded by the crypts of Lieberkuhn (the mouths of which are indicated by the ^^^•^^^ Mignified. " spots), which have no communication with the vesicle itself (see also note, p. 370).] A A A f V-T" ^\ 370 SPLANCHNOLOGY. These patches are generally contained in the substance of the mucous menabrane, to which they give a much greater density, so that, in these situations, it will bear to be scraped. In some cases they appear to be imbedded in the fibrous coat. They should be examined both from the external and internal surfaces of the mucous membrane.* When they are filled with their secreted fluid, and are exam- ined by transmitted light, they may be compared to the vesicles in the skin of an orange : this observation may be easily made in the day. They evidently consist of collections of glands, exactly resembling the solitary glands {fig. 159). Each depression appears to be the orifice of one of the follicles, which are quite independ- ent of each other ; so that we sometimes find two or three altered in the middle of a patch, which is other- !''«,"■ J"..'*,* ^" ♦ , "VJ" wise perfectly healthy. Lastly, villi are found upon the E" UD-Z' vl -V ' * '*•)*? - .i. ..'.♦- -J patches of the glandulae agminatse : they occupy the in- ...-„ tervals between the depressions.! The Follicles or Corpusculcs of Liebcrkuhn. — Lieberkuhn speaks, also, of innumerable, rounded, whitish follicles, which are seen between the villi, and of corpuscules which are visible between these follicles. He calculates that there are eighty follicles for eighteen villi, and eight corpuscules for each follicle. I am disposed to think that these follicles and corpuscules, which have never been seen excepting by the microscope, should be refer- red to those globules which are revealed in all the tissues by the aid of a magnifying power, t The Vessels and Nerves. — All the arteries of the small intestine, properly so called, are branches of the superior mesenteric. They are very numerous. Those of the duodenum arise from the hepatic. The branches from the superior mesenteric are remarkable for the numerous anastomotic loops which they form before reaching the intestine, for their flexuous course within its coats, and for the series of vascular layers formed by them between the peritoneal and muscular, the muscular and fibrous, and the fibrous and mu- cous coats. The last layer forms a very complicated network, from which the vessels of the mucous membrane are derived. The vei>is are much larger than the arteries, and present a similar arrangement, except in regard to the flexuous course, which is peculiar to the arteries ; they constitute the superior mesenteric vein, which is one of the prin- cipal branches that contribute to form the vena portas. The lymphatic vessels are of two kinds, viz., lacteals and lymphatics, properly so called ; they both enter the numerous lymphatic glands, situated in the mesentery ; those which belong to the duodenum enter the glands above the pancreas. The nerves are derived from the solar plexus. The development of the small intestine will be noticed in conjunction with that of the large intestine. Uses. — Chyhfication, i. e., the transformation of the chyme into chyle, is effected in the ■duodenal portion of the small intestine. The essential agents of this process are the bile and the pancreatic fluid. In the remainder of the small intestine (the jejunum and ikum), the absorption of the chyle takes place. The numerous convolutions, the valvu- lae conniventes, and the villi, all tend to increase the extent of the absorbing surface. The products of exhalation and of follicular secretion serve to complete the digestive process. The contents of the bowels are forced along by the shortening of the longitu- dinal, and the contraction of the circular fibres, the latter producing the vermicular mo- tion of the intestines. The Large Intestine. The large intestine is that part of the alimentary canal which extends from the end of the small intestine {d,fig. 139) to the anus (i). It commences in the right iliac region {c,fig. 161), and passes upward (a) as far as the right hypochondrium ; then, having reached the liver, it makes a sharp flexure (the right or hepatic flexure), and proceeds * [Their contents are sometimes transparent, and they are then very difficult of detection.] t Qln^^. 159, representing part of a patch of Peyer's glands magnified, are seen some of the elevated white bodies descriWd by Boehm as resembling the solitary glands, except in not generally having any villi situated directly upon Ihem. Each is surrounded by a zone of dark points, the elongated openings of the crypts of Lieberkuhn. Many of these crypts are also seen scattered irregularly between the numerous villi ; none of them communicale with the interior of the whitish bodies, in which, whether solitary or agminated, Boehm could discover no opening, at least, not in a healthy human intestine. He considers them, therefore, to be closed ■vesicles, not follicles. More recently, however, Krause has observed that, in the pig's intestine, they are occasionally open, independ- ently of disease ; and Dr. Allen Thomson has lately made a similar observation in reference both to the pig and to the human subject.] X [The follicles or crypts of Lieberkuhn are tubes placed more or less perpendicularly to the surface of the mucous membrane, like those in the stomach, but situated more widely apart ; their open mouths are .seen scattered over the whole surface of the membrane, or collected around the solitary and agminated glands I. figs. 157, 159). The corpuscules (corpora albicantia), described by the same observer as being situated in the bot- tom of the crypts, are probably collections of desquamated epithelium within them.] THE INTESTINES. 371 transversely (t) from the right to the left side {transverse arch of the colon) ; in the left hypochondrium, below the spleen, it again makes a sharp bend and becomes vertical {d), {left or splenic flexure). In the left iliac region (/) it is twice bent upon itself, like the Ro- man letter S {iliac or sigmoid flexure), and it then dips into the pelvis (r), and terminates at the anus. The large intestine, therefore, describes within the abdomen a nearly complete circle, which surrounds the mass of convolutions of the small intestine ; and it occupies the right and left iliac regions, the right and left lumbar, the base of each hypochondriac, and the adjacent borders of the epigastric and umbilical regions. Although it is much more firmly fixed in its place than the small intestine, and is, therefore, less liable to displacement, yet it presents some varieties in length and curvature which have a con- siderable influence over its position. The large intestine is more deeply situated than the small in one part of its extent, but in another is at least quite as superficial. From its long course, and from the different relations piesented by its different parts, it has been divided into the cacum, the colon, which is itself subdivided into several parts, and the rectum. Dimensions. — The length of the large intestine is four or five feet, and, compared with the small intestine, is as one to four ; but it varies considerably, rather, it would seem to me, from the effects of repeated distension, than from any original conformation ; for it may be easily imagined that the bowel cannot be distended transversely without lo- sing somewhat in length, and that, on returning to its former diameter, it must be elon- gated in proportion to the distension it had previously undergone. The large intestine has also generally appeared to me longer in persons advanced in age than in adults. Its caliber or diameter usually exceeds that of the small intestine, but may become so reduced that the gut resembles a hard cord, about the size of the little finger. In other cases it is so large that it occupies the greatest part of the abdominal cavity : this is ob- served in tympanitic distension of the large intestine. It is not of uniform caliber throughout, as the following measurements will show. The circumference of the caecum, moderately distended, and taken immediately below the ileo-caecal valve, was found to be eleven inches and three lines in one subject, and nine inches and a half in another ; the right colon in the loins and the right half of the arch were eight inches and nine lines in the first, and five inches some lines in the second subject. The circumference of the left half of the arch of the colon, and of the left lumbar colon, was six inches in the first and five inches and a half in the second. The circumference of the sigmoid flexure was five inches and a quarter ; that of the rectum was three inches until near its termination, where it presented a dilatation four inches in circumference in one, and five inches in the other subject. It follows, therefore, that the large intestine, like the small, has an infundibuhform shape ; it resembles, indeed, two funnels, the base of the one corresponding to the caecum, and its apex to the sigmoid flexure, while the base of the other is at the dilated portion of the rectum, and its apex is applied to that of the first. It is probable that this infundibuhform arrangement has some reference to the passage of the faecal matters. It also follows that there is no uniform relation between the diameters of the different portions of the large intestine : thus, a very large caecum and ascending colon may co- exist with a small descending colon In some cases we find in the large intestine con- siderable dilatations, separated from each other by such constrictions that the caliber of the corresponding part of the gut is obliterated. These strangulations from a con- traction of the circular fibres are very different from those produced by organic diseases ; they probably take place during life, and may account for the affection known as the windy colic. In some chronic diseases, accompanied with diarrhoea, the large intestine, contracted and containing no gases, is not as large as the small intestine. The Cacum. — The caecum {e,fig. 139), so named because it resembles a cul-de-sac, is the first part of the large intestine The existence of a caecum is one of the numerous indications of the line of separation between the large and the small intestine. Its up- per boundary is altogether arbitrary ; it is determined by a horizontal plane intersecting it immediately above the insertion of the small intestine. It is single in the human sub- ject, but is double in some species of animals. It is situated {c,fig. 161) in the right ihac fossa, and occupies it almost entirely. It is one of the most fixed portions of the ali- mentary canal, for the peritoneum merely passes in front of it, and binds it down into the iliac fossa. It is not, however, so firmly fixed in all subjects ; it is often enveloped by the peritoneum on all sides, and floats, as it were, in the region which it occupies, its capability of motion depending on the looseness of the right lumbar mesocolon. This arrangement of the peritoneum is not necessary, however, to explain the great amount of displacement which the caecum undergoes in certain cases. It is not uncommon to find it in the cavity of the pelvis : it occasionally enters into the formation of herniae. and, what is somewhat remarkable, it has been at least as frequently found in herniae upon the left as upon the right side. Its direction, which is in general the same as that of the ascending colon, is not alway vertical as may be seen by examining a moderately-distended intestine, but it passt 372 SPLANCHNOLOGY. obliquely upward and to the right side, so that it forms with the colon an obtuse angle projecting on the right side ; and I have even seen it form a right angle with the colon. This arrangement, connected with the obliquity of the plane of the ihac fossa, explains why, when its attachments are relaxed, it has less tendency to be displaced towards the right inguinal ring and femoral arch than to the same parts on the left side. In some subjects, the cescum and its vermiform appendix are applied to the lower part of the small intestine, so that the caecum and the neighbouring part of the colon describe a curve, the concavity of which embraces the lower end of the ileum. In size it is generally larger than the portion of the intestine which succeeds it : this, perhaps, depends less upon its primitive conformation than upon the accumulation of faecal matters resulting from the inclined position of this intestine, and from the direc- tion in which its contents are moved. It may be said, as a general rule, that, next to the stomach, the caecum is the largest part of the alimentary canal. There are many individual varieties in the length and capacity of this intestine, in which the faecal mat- ters are liable to be retained. These accumulations occasion great pain ; they have been much studied lately, and have been often mistaken for inflammations. The caecum is very slightly developed in carnivora, but, on the other hand, it is very large in her- bivora. Figure. — The caecum is a sort of rounded ampulla, all the diameters of which are nearly equal ; it is also sacculated like the rest of the large intestine. Upon it we ob- serve the commencement of the three longitudinal bands, which I have already noticed : of these, the anterior is, in the caecum, twice as broad as either of the two posterior ; some folds of peritoneum, loaded with fat. which are called fatty appendages (appendices epiploiccB) ; and, lastly, some protuberances, separated by parallel depressions, an ar- rangement which exists in the colon also, and is produced by the longitudinal bands. Relations. — In front, the caecum is in relation with the abdominal parietes, through which it can be felt when it is distended with gases or faecal matters. When the cae- cum is collapsed, the small intestine is often interposed between it and the parietes of the abdomen. Behind, it rests upon the iliacus muscle, from which it is separated by the lumbo-iliac fascia. The cellular tissue uniting it to this aponeurosis is extremely loose, and, there- fore, offers no opposition to displacement of the intestine. When the peritoneum forms a complete covering for the caecum, that intestine is, of course, in indirect relation with the iliacus. The vermiform appendix is often turned back behind the caecum. On the inside, the caecum receives the small intestine ; the angle at which they unite (the ileo- caecal angle) varies much. Sometimes the small intestine is inserted at a right angle ; most commonly the angle of incidence is obtuse above and acute below (fig. 160). Some- times the ileum, instead of passing upward, is directed downward, and then the angle of incidence is changed. A circular depression indicates the limit between the two in- testines. Below, upon the free extremity or cul-de-sac of the caecum, is seen the ver- miform appendix (»), situated behind and on the left side, a few lines below the ileo- caecal angle. The arrangement of the internal or mucous surface of the caecum is in accordance with that of its external surface : thus, three projecting ridges correspond with the three lon- gitudinal bands ; some cavities or pouches with the protuberances ; and some transverse projecting folds, forming incomplete septa, which are easily seen in a dried specimen, correspond with the parallel depressions. Upon this surface, to the left and a little be- hind, we also find the ileo-caecal valve {a b,fig. 160), and the orifice (o) of the vermiform appendix (v). The Ileo-cacal Valve. — This is also called the valve of Bauhin, from the name of the anat- omist to whom its discovery is attributed, although it had been described before his time. To obtain a perfect knowledge of it, it should be examined upon a fresh specimen under water, and also upon an inflated and dried intestine. In a fresh specimen, when viewed from the caecum, it presents the appearance of a projecting cushion, oblong from before backward, and fissured in the same direction. It is a membranous and movable cushion, and was incorrectly compared by Riolanus to the pyloric ring. It has two lips and two commissures ; the two hps are in contact, except during the passage of the contents of the bowels. Two folds, proceeding from the two commissures, one of which is anterior and the other posterior, are lost upon the corre- sponding surfaces of the intestine. The posterior fold is much longer than the anterior ; Morgagni called them ihefrana of the valve. When viewed from the ileum, it presents the appearance of a funnel-shaped cavity, directed upward and to the right side. In a dried intestine, the ileo-caecal valve is seen to consist of two prominent valvular segments, projecting into the caecum, so as to form an angular riige. The upper, or ileo- colic segment \b,jig. 160), is horizontal ; the lower, or ileo-cacal (a), forms an inclined plane of about 45*^, and both are parabolic. The upper segment is fixe 1 by its adherent convex border to the semicircular line, along which the upper part of the tube of the ileum is united with the colon ; the adherent border of the lower segment, which is also convex, is continuous with the semicircular hue of junction between the lower half of the ileum THE INTESTINES. 373 and the caecum. The free borders of the segments are directed to- wards the right side, and are semilunar ; they are united at their ex- tremities, but in the middle leave between them (between a and h) an opening like a buttonhole, which becomes narrower as the intes- tine is more distended. The diameter of this opening is in proportion to that of the small intestine. The free border of the lower segment is more concave than that of the upper. When examined from the ileum, the valve presents an angular excavation exactly correspond- ing to the projecting edge found in the cavity of the large intestine. The lower surface of the upper valvular segment is slightly concave ; the corresponding surface of the lower segment is slightly convex. This double ileo-caecal valve differs widely from the ring of the py- lorus ; it offers no obstruction to the passage of the contents of the small into the large intestine ; but in ordinary cases, it will not per- mit their regurgitation from the latter into the former. The lower or ileo-cascal segment is elevated so as to prevent reflux from the caecum, and the ileo-colic segment becomes depressed, and opposes any return of the contents of the colon. Still, from a great num- ber of experiments which I have performed on this subject, I am satisfied that both wa- ter and air injected into the large intestine most frequently overcome the resistance offer- ed by this valve, though with different degrees of facility in different subjects. This re- gurgitation, however, only takes place with gaseous or liquid matters ; such as have a greater degree of consistence cannot pass back, and therefore the reflux of faecal matter is impossible.* Structure. — The structure of the ileo-caecal valve was perfectly demonstrated by Albi- nus. If we follow his example, and remove the peritoneal coat from a distended intes- tine, at the point where the ileum enters the large bowel, we shall at once perceive most distinctly that the small intestine seems to sink in there ; and if, by means of careful and gradual force, we attempt to disengage it from the large intestine, it may be drawn out, as it were, from the colon to the length of an inch or an inch and a half; and then, on inspecting the inside of the large intestine, we shall find that the valve has altogether disappeared, and that the ileum communicates with the caecum and colon by a large ap- erture. The precise structure of the valve is as follows : it is composed of the circular muscu- lar fibres of the ileum, which are prolonged as far as its free edge ;t of the fibrous coat, and of the mucous membrane. A similar fact has been observed regarding this mucous membrane to one we have already several times noticed in describing the alimentary ca- nal, viz., a sudden change in its character opposite the free margin of the valve. That portion of the membrane which lines the surface turned towards the large intestine has all the characters of the mucous membrane of that bowel, while that hning the surface directed towards the ileum has those of the mucous membrane of the small intestine. The limit between them is generally observed in diseases. The Appendix Vermiformis . — The appendix vermiformis {v,figs. 139, 160, 161), so na- med from its resemblance to an earth-worm, commences at the posterior lower and left portion of the caecum, of which it may be considered an appendage (the cacal appendix) ; it resembles a small, hollow, and very narrow cord (duodecies nascente colo angustior, says Haller). In length and in direction, it presents much variation : its length is from one to six inches. It is somewhat wider at its point of junction with the caecum than in any other part, and is in general about the diameter of a goose-quill. Its direction is sometimes vertically downward, sometimes upward, and often tortuous. I have found it spiral, and at other times contained in the substance of the mesentery, parallel to the ileum, and only free at its extremity. In some subjects it is funnel-sha- ped, widening out to become continuous with the caecum, which, in such cases, is very narrow. Its situation and relations are equally variable. Thus, most commonly, it oc- cupies the right iliac fossa, near the brim of the pelvis : it is attached to the caecum and to the iliac fossa by a triangular or falciform fold of the peritoneum, which extends only to one half of its length, and allows it a greater or less capability of movement. It is still more movable when it is entirely surrounded by the peritoneum, and has no mesentery. From this it may be conceived that it may enter into the formation of herniae, and may be twisted around a knuckle of the small intestine, so as to cause strangulation. It is * Nevertheless, if we consider that the large intestine must always be very much distended in order to pro- duce a reflux of gases and liquids, it may be questioned whether the passage of gaseous or liquid matters from the large to the small intestine can take place during life. I have been able to determine the mechanism of the resistance offered by the valve from the efl^ects of distension. The two segments are turned back, the lower one upward, and the upper one downward ; their corresponding surfaces become convex, and they are pressed together the more and more forcibly in proportion to the amount of distension. In some subjects dis- tension may be carried so far as to rupture the longitudinal bands, and yet not overcome the obstacle. In most cases, the free edge of the lower segment glides from right to left under the upper one, which remains immovable ; and the gas and liquids escape with more or less facility according to the degree of disturbance in the parts. t [The longitudinal muscular fibres and the peritoneal coat pass directly from the small to the large intes- tine, without entering into the formation of the valve.] 374 SPLANCHNOLOGY. often turned back behind the ascending colon between that intestine and the kidney : in one case of this kind, I found the free extremity of the appendix in contact with the lower surface of the liver. I have also once seen it turned up behind the lower end of the small intestine, and, at another time, embracing that bowel in front. None of these dif- ferences, however, depend on the situation of its point of attachment to the caecum, which is always on the left side, below and behind the cul-de-sac, at a short distance from the ileo-caecal valve. When divided lengthwise, the cavity within it is seen to be so narrow that the walls are always in contact. A small quantity of mucus is found in it, and it often contains small scybala ; cherry-stones and shot have also been found in it. The whole of its internal surface has a honeycomb appearance, like that at the lower end of the small intestine.* A valve of different size in different subjects, but never sufficiently large to cover the orifice entirely, is found at the point (o, fig. 160) where the appendix conunu- nicates with the caecum. The cavity of the appendix, like the caecum, terminates be- low in a cul-de-sac ; and in this, which is extremely narrow, foreign bodies may be lodged, and may then sometimes become the cause of those spontaneous perforations which are occasionally seen. The uses of this appendix are altogether unknown ; in the human subject, it is merely a vestige of an important part in many animals. Haller says that he has twice seen the vermiform appendix obliterated, i. e., without any cavity. I presume that this was the effect of morbid adhesion. Lastly, I once found this appendix as large as the index finger, and two inches in length ; its cavity contained some thick, transparent mucus. The orifice by which it should have communicated with the caecum was obliterated. The Colon. — The colon {itulvu, to impede, dfg h,fig. 139) constitutes almost the whole of the large intestine. It extends from the caecum to the rectum, and, as we have al- ready seen, there is no line of demarcation between these different parts. In the first part of its course it ascends vertically, then becomes transverse, next descends vertical- ly, and is then curved like the Roman letter S, and becomes continuous with the rectum. From this long course, and also from its direction and numerous relations, the colon has been divided into four portions, viz., the ascending or right lumbar colon, the transverse colon, or arch of the colon, the descending or left lumbar colon, and the iliac colon, or sigmoid flexure. Each of these parts requires a separate description, at least with regard to its relations. Let us first point out the general form of the colon. The colon presents a sacculated appearance throughout, which gives it some resem- blance to a chemical apparatus, consisting of a long series of aludels. The sacculi of the colon are arranged in three longitudinal rows, separated by three muscular bands. Each of these rows presents a succession of enlargements and constrictions, or deep grooves, placed across the length of the intestine. These enlargements and grooves are produced by the longitudinal bands, which, being much shorter than the intestine, cause it to be folded inward upon itself at intervals. It follows, therefore, that division of these bands by means of a bistoury, or, rather, their rupture, from great distension of the gut, should de- stroy this sacculated appearance, and such, indeed, is the result of the exper- iment ; at the same time, the large in- testine becomes twice or three times as long as it was before, and forms a regular cylinder, like the small intes- tine. An incontestable proof of the relation between the cells of the colon and the muscular bands, is the con- current absence of both in a great num- ber of animals. Lastly, the three rows of sacculi vary much in different sub- jects, and also in different parts of the great intestine. The descending colon and the sigmoid flexure have only two rows of sacculi, and, consequently, two intermediate bands. The saccuU al- most entirely disappear in the sigmoid flexure. The Ascending or Right Lumbar Colon {a, figs. 155, 161).— This portion of the colon is bounded below by the caecum, * [Nevertheless, the structure of the munou.» membrane in the two situations is very different (see notes, p. 370, 379).] THE INTESTINES. 375 and above by the transverse arch, with which it forms a right angle, near the gall-blad- der. It is more or less firmly held in its place by the peritoneum, which in some sub- jects merely passes in front of it, and in others forms a fold or lumbar mesocolon. The ascending and descending colon may be included among the most fixed portions of the alimentary canal. In front of it are the parietes of the abdomen, from which, excepting when greatly distended, it is separated by the convolutions of the small intestine. Be- hind, it is in immediate relation with the quadratus lumborum and the right kidney, no layer of peritoneum intervening. It is united to these parts externally by loose cellular tissue. This relation accounts for the bursting of abscesses of the kidney into the colon, and explains the possibility of reaching the colon in the lumbar region without wound- ing the peritoneum. On the left side, advantage has been taken of this fact in attempt- ing to form an artificial anus. On the inside and on the outside it is in relation with the convolutions of the small intes- tine ; and on the inside also with the psoas muscle, and with the second portion of the duodenum. The Transverse Colon, or Arch of the Colon. — This {t) is the longest portion of the large intestine ; it extends from the ascending to the descending colon, from the right to the left hypochondrium, and generally occupies the adjacent borders of the epigastric and umbilical regions. It is not unfrequently found opposite the umbilicus, and even in the hypogastrium. Its right extremity corresponds to the gall-bladder {g), its left is below the spleen (k). It describes a curve having its convexity directed forward, and its con- cavity backward ; hence the name, arch of the colon. In some subjects it is two or three times its ordinary length, and hence it presents various inflections. I have seen its middle portion descending as low as the umbilical or hypogastric region, and even reach- ing the brim of the pelvis ; in other cases it descends parallel to, and on the inner side of, the ascending colon, and then passes upward again, or it describes curves of different extent. The arch of the colon is supported by a very remarkable fold of peritoneum, called the transverse mesocolon, which forms a horizontal septum between the small in- testine below, and the stomach, the liver, and the spleen above. The extent of this fold, which is one of the largest of all those formed by the peritoneum, explains the great freedom of the movements of the transverse colon, which, next to the small intestine, is the part of the aliinentary canal most frequently found in hernia. Relations. — Above, it has relations with the liver {I), which generally presents a slight depression, corresponding to the angle formed by the ascending and transverse colon ; with the gall-bladder {g), whence the discoloration of the right extremity of the arcli from the bile ; it is not rare to find the gall-bladder opening into the colon ; with the stomach (.thyroid membranes, the superior vocal cords, and the aryteno-epig-lottid ligaments are also composed of this tissue, which, he says, exists even in the thyro-epiglottid, hyo-epiglottid, and glosso-epiglottid ligaments.] 428 SPLANCHNOLOGY. Their action is not yet well determined. By taking their fixed point upon the cricoid cartilage, it appears to me that they would move the thyroid cartilage in such a way as to increase the antero-posterior diameter of the glottis, and thus act as tensors of the vocal cords. The Crico-arytenoidcus Posticus. Dissection. — This muscle is exposed by removing the mucous membrane from the posterior surface of the larynx. It is a triangular muscle {g,figs. 171, 177), situated at the back of the cricoid carti- lage. Its fibres arise from the lateral depression, which we have described on the pos- terior surface of the cartilage, and pass in different directions ; the upper fibres are the shortest, and are almost horizontal ; the middle are obhque, and the lower are nearly vertical ; they all converge towards the posterior and external process on the base of the arytenoid cartilage, behind the crico-arytenoideus lateralis. Relations. — It is covered by the mucous membrane of the pharynx, to which it is very loosely united, and it covers the cricoid cartilage. Action. — It is a dilator of the glottis. It carries the base of the arytenoid cartilage backward, outward, and downward, and thus renders the inferior vocal cord tense The Crico-arytenoideus Lateralis. Fig. 177. Dissection. — Remove with care one of the lateral halves of the thyroid cartilage (as in Jig. 177). It is impossible to separate this muscle from the thyro-arytenoideus. This is an oblong muscle (/), situated deeply under the thyroid cartilage. Its fibres arise from the side of the upper border of the cricoid cartilage, in front of the crico-arytenoid articulation ; from this point they proceed obliquely upward and backward, to be insert- ed into the posterior and external process of the arytenoid cartilage, by a tendon common to them, and to the thyro-arytenoideus. It is covered by the thyroid cartilage and by the crico-thyroid muscle, and it covers the lateral crico-thyroid membrane (d). The Thyro-arytenoideus. Dissection. — The same as for the preceding. This muscle may be dissected from the interior of the larynx, by removing the vocal cords. I describe the thyro-arytenoideus and the crico-arytenoideus lateralis separately, merely in accordance with custom, for in no instance, not even in large animals, such as the ox, have I ever been able to separate them completely. They have the same arytenoid insertion; their fibres are situated upon the same plane, without any line of demarcation, and they fulfil the same uses. We might, therefore, unite them under the name of the thyro-crico-arytenoideus. The thyro-arytenoideus (e) is a broad muscle, very thin above and very thick be- low. It arises on each side from about the lower two thirds of the retreating angle of the thyroid cartilage. The greater number of its fibres arise from the lower part of the angle, and form a very thick fasciculus. From these points they pass horizontally back- ward and outward, and terminate in the following manner : The thick fasciculus above mentioned is inserted into the outer surface of the anterior process of the arytenoid car- tilage, and into a depression on the outer side of the base of that cartilage, between the two processes. The upper fibres are attached to the outer border of the arytenoid car- tilage. In the larger animals, the upper fibres of the muscle evidently proceed to the epiglottis, and form the thyro-epiglottideus of some authors. Relations. — On the outside it corresponds with the thyroid cartilage, from which it is separated by loose and sometimes adipose cellular tissue ; on the inside it is in contact with the vocal cords and the ventricle of the larynx. The thickest part of the muscle corresponds with the inferior vocal cord, and is almost the only cause of its projecting into the interior of the larynx. This fasciculus may even be considered as contained within the substance of the inferior vocal cord, and the two structures are so closely adherent that great care is required to separate them. Many anatomists, indeed, have thought that the fibres of the thyro-arytenoideus terminate in the vocal cord, which they therefore regarded as the tendon of the muscle ; but the cord and muscle may always be completely separated. Action. — It carries the arytenoid cartilage forward, and would thus seem to relax the inferior vocal cord, as Haller believed : " Cartilagines guttales (the arytenoid) antrosum dvxunt, glottidem dilatant, ligamentorum glottidis tensionem minuiint." {Elementa Physiol., t. iii., liv. ix., p. 387.) But if we consider the mechanism of the crico-arytenoid articula- tions, and the mode of insertion of the thyro-arytenoid muscles into the outer side of the bases of the arytenoid cartilages, we shall perceive that, at the same time that these cartilages are carried forward, they undergo a partial rotatory movement, by which their anterior processes are turned inward. The ligaments of the glottis are, therefore, ren- THE LARYNX. 429 dered tense, and approximated towards each other. This movement may be carried to such an extent that the anterior processes may touch, and the antero-posterior diameter of the glottis be diminished accordingly.* The thyro-arytenoideus is, then, both a tensor and a constrictor of the glottis. This, moreover, was the opinion of both Cowper and AlbinuSj but Haller attempted to re- fute it.t The sudden action of the thyro-arytenoid muscle, pressing upon the ventricle of the larynx, may expel any mucus collected within it. The Arytenoideus. Dissection. — Remove the mucous membrane and glandular masses which cover it be- hind. Detach it along one of its borders, so as to be enabled to examine its thickness. The arytenoideus {a, fig. 171) is a single, short, thick, trapezoid muscle, situated be- hind the arytenoid cartilages, and filling, up the concavity on their posterior surfaces, as well as the interval between them. It arises from the whole length of the outer border of the right arytenoid cartilage, and is inserted into the corresponding part of the left. Some of the fibres arise from the upper border of the cricoid cartilage. The fibres have a triple direction, and form three layers, which have been regarded as so many distinct muscles. The two more superficial layers are obhque, and cross each other, one passing from the base of the right arytenoid cartilage to the apex of the left, and the other following the opposite direction ; they constitute the arytenoideus ohliquus of Albinus : both of these layers are thin. The third and deepest layer is very thick ; it is composed of transverse fibres, and forms the arytenoideus transversus of Albinus. None of the fibres reach the comicula. Under the name of the aryteno-epiglottideus, muscular fibres have been described, extending from the arytenoid muscle to the mar- gins of the epiglottis. Some fibres of the arytenoideus are also said to be continuous with the thyro-arytenoideus. Relations. — Behind, with the mucous membrane and some glandular masses, which ad- here to the muscle by means of loose cellular tissue ; in front it is in relation with the posterior surface of the arytenoid cartilages, and in the interval between them with a thin fibrous membrane, extending from the upper border of the cricoid cartilage to the whole extent of the inner borders of the arytenoid cartilages. Action. — It would appear, at first sight, that this muscle must forcibly approximate the two arytenoid cartilages, and therefore constrict the glottis ;t but if we remember that it is attached to the outer borders of these cartilages, we shall understand that, besides drawing them together, it must produce in them such a movement as will carry their an- terior processes outward, and stretch the vocal cords, but, at the same time, separate them from each other. And if we call to mind that the thyro-arytenoideus occasions an ex- actly opposite movement, it will be understood that the simultaneous action of the two muscles must produce tension of the cords, and. at the same time, fix the processes. Having thus obtained a knowledge of the cartilages of the larynx, the articulations by which they are united, and the muscles which move them, we shall now proceed to give a general description of this organ. The Larynx in general. The larynx, the general position of which has been already described, presents certain differences in its dime7isions, depending either upon the individual, upon sex, or upon age. These ditferences affect both the whole of the larynx and its constituent parts. Thus, the larynx of the female may always be distinguished from that of the male by being smaller, i. e., about two thirds the size of the male larynx ; and by the angles and pro- cesses of its cartilages being less prominent, and their depressions less marked. These differences are connected with the characters of the voice, and affect principally the di- mensions of the glottis. The individual differences in the size of the larynx have not been thoroughly examined. The differences depending on age wiU be noticed when speaking of its development. The larynx presents for our consideration an external and an inter7ial surface. The External Surface of the Larynx — Anterior Region {fig. 170). — In the median li?ie'we observe a vertical ridge, formed by the angle of the thyroid cartilage ; beneath this the crico-thyroid membrane, and still lower the convexity of the cricoid cartdage. On the sides we find the oblique laminae of the thyroid cartilage, a portion of tlie cri- coid covered by the crico-thyroid muscle, and the thyro-cricoid articulation. Sub-cutaneous in the median line, where it is only separated from the skin by the linea alba of the neck, the external surface of the larynx is covered on each side by the mus- cles of the sub-hyoid region, the inferior constrictor of the pharynx, and the thyroid gland. * [The effect of this will be, as stated by Ilaller, to relax the vocal cords, which is considered by the latest observers to be the action of these muscles.] 1 Loo. cil. " Cum rnagni viri glottidem dixerint ab islis musculis arctari, experimento facto diducere didici. Neque potest ille ad latus cartilaginis arytsenoidae musculus terniinari quin earn rimam diducat." X [When acting- together with the lateral crico-thyrjid muscles, this is certainly their action.] 430 SPLANCHNOLOGY. The superficial position of the surface enables us to examine its different parts through the integuments, and renders it liable to wounds. Its still greater proximity to the skin in the median line has suggested the operation of laryngotomy. Posterior Region {figs. 141, 171). — In the median line we observe a prominence like a small barrel, on either side of which the thyroid cartilage projects. This prominence is formed by the back of the cricoid, and by the arytenoid cartilages, the expanded portion corresponding with the bases of the latter, which are covered by folds of a pale mucous membrane. Under this membrane we find, proceeding from above downward, the ary- tenoideus muscle, the vertical ridge of the cricoid cartilage, the crico-arytenoidei posti- ci, and the crico-arytenoid articulations. On each side of the barrel-shaped prominence is a deep angular groove, formed by the meeting of two flat surfaces, which are separated above, but approximated below ; along these grooves it is supposed that liquids flow during deglutition. The external wall of each groove is formed by the posterior surface of the thyroid cartilage, the os hyoides, and the thyro-hyoid membrane. The internal wall is formed by the upper and lateral part of the barrel-shaped prominence. The grooves are lined by a closely-adherent mucous membrane ; and it should be observed, that they exist only on a level with the aryte- noid cartilages, and, consequently, in this region alone is the larynx protected by the thyroid cartilage, the posterior borders of which rest upon the vertebral column. The back of the cricoid cartilage is on a level with the posterior borders of the thyroid {fig. 174), and, like them, rests upon the vertebral column. The Internal Surface of the Larynx. — The internal surface of the larynx does not cor- respond, either in shape or dimensions, with its outer surface ; and this depends princi- pally on the fact that the retreating angle of the thyroid is the only part of that cartilage which enters into the formation of the laryngeal cavity, the lateral laminae being alto- gether unconcerned in it'. Cylindrical below, where it is formed by the cricoid cartilage, the cavity of the larynx is prismatic and triangular above, where it is constituted by the epiglottis in front, the arytenoid cartilages and the arytenoid muscle behind, and on the sides by the two mu- cous folds which extend from the margins of the epiglottis to the arytenoid cartilages. The dimensions of the lower of these two portions of the laryngeal cavity undergo no change, always remaining the same as those of the cricoid cartilage ; while the upper, on the contrary, which is broadest in front, varies much in size, in consequence of the mobility of the epiglottis and the arytenoid cartilages. Between these two portions, and about the middle of the larynx, a fissure exists, which is narrower than the rest of the cavity, and oblong from before backward ; this is the glottis, or vocal apparatus, properly so called. It can be seen without any dissection by looking down into the larynx {fig. 178), and requires a very particular description. The Glottis, or Vocal Apparatus. — The glottis {yTiuTTig, from yTiuaari, the tongue), fre- Fig. 1V8. quently confounded with the superior orifice of the larynx,* is a trian- gular opening or fissure {o,fig. 178) {rima), elongated from before backward, and included between the vocal cords of the right and left sides. It represents two isosceles triangles, placed one above the other, and having perfectly equal borders, the base of each being directed backward, and its apex forward. The lower isosceles tri- angle is formed by the inferior vocal cords (r), and the upper one by the superior vocal cords {s). The inferior vocal cords are situated nearer to the axis of the larynx than the superior, so that a vertical plane let fall from the latter would leave the inferior vocal cords on its inner side. Many authors limit the term glottis to the lower tri- angle. This view is supported by the absence of the superior vo- cal cords in a great number of animals, the ox in particular. Dimensions of the Glottis. — The glottis is the narrowest part of the larynx, and hence the danger from the introduction of a foreign body into it, and from the formation of false membranes in this situation. The only action of the intrinsic muscles of the larynx is to dilate or contract the opening of the glottis. We have seen that, with the exception of the crico-thyroidei, they are all, in some measure, collected round the crico-arytenoid articulation, the movements of which determine the dimensions of the glottis. The individual differences which constitute the tenour, baritone, or bass voices in sing- ing, df'pend upon the size of the glottis ; to which, also, must be attributed the difference between the male and female voice, and the change produced in its tone at the time of puberty. A deep voice coincides with a large glottis, and a shrill voice with a small one. In the adult male the antero-posterior diameter of the glottis is from ten to eleven lines, in the female it is only eight lines ; in the male, the greatest transverse diameter is from three to four lines ; in the female, from two to three lines. t This error is, perhaps, to be attributed to the use of the word epiglottis, so much do words influence our s. It was committed even in Haller's time, who says, " Etiani hoc (laryngis) ostium non bene pro gloltide sumitur.'" t Tiiess measurements are taken at the level of the inferior vocal cords ; the transverse diameter is rather longer opposite the superior vocal cords ideas sumit THE LARYNX. 43l From these dimensions, it may be understood how a Louis d'or might pass edgewise through the glottis, and thus fall into the trachea. In a case of this kind, most of those who were called in consultation rejected the idea of the presence of the coin in the Avind- pipe, because, said they, the glottis cannot admit it. The patient died in about a year, and the Louis d'or was found in the trachea. Ventricle of the Larynx. — Between the superior and inferior vocal cords of each side there is a cavity, called the ventricle or sinus of the larynx {v,figs. 176, 178) ; it is oblong from before backward, and of the same length as the cords ; its depth is determined by the interval separating the cords from the thyroid cartilage, or, rather, from the thyro- arytenoid muscle, which forms the bottom of the corresponding ventricle. The opening of the ventricle is somewhat narrower than the bottom, is elliptical in its longest diame- ter, and has admitted the introduction of a foreign body. To each ventricle there is a supplementary cavity, which is accurately described and figured in the works of Mor- gagni.* This cavity resembles in shape a Phrygian cap; it has a broad base, opening into the ventricle, and a narrow apex ; it is found at the anterior part of the ventricle, and is prolonged on the outer side of the superior vocal cord, between it and the thyroid cartilage, upon the side of the epiglottis. Its dimensions vary much. In one case its ver- tical diameter was six lines, and it was divided into two parts by a transverse band. The Circumferences of the Larpix. — The superior circumference of the larynx (fig. 178) is much wider than the inferior, and presents the following objects ; the superior angu- lar border of the thyroid cartilage, and the great cornua, in which it terminates ; behind the thyroid cartilage, the epiglottis (/) ; and between the cartilage and the epiglottis, a small triangular space, filled by a compact fatty mass, which has been incorrectly descri- bed as the epiglottid gland. I have already said that this fatty mass is bounded above by a fibrous membrane, extending from the epiglottis to the posterior surface of the os hyoides. Behind the epiglottis, we find the dipper orifice of the larynx, which must not be con- founded with the glottis ; it slopes obliquely from before backward and from above down- ward, having the form of a triangle, with its base directed forward and its apex back- ward, consequently in the opposite direction to the glottis. This orifice is formed in front by the free margin of the epiglottis, which is shghtly notched ; on each side, by the upper part of the lateral margin of the epiglottis, and by the free edge of the aryteno- epigloitid fold (b) ; and behind, by the cornicula laryngis, and by the summits of the ary- tenoid cartilages (a), and the deep notch between them. The superior orifice is the widest part of the larynx, and admits foreign bodies which cannot pass through its lower portion. The epiglottis, when depressed, generally cov- ers it completely, and may even overlap it at the sides. The inferior circumference of (he larynx is perfectly circular, is formed by the cricoid cartilage, and is continuous with the trachea. The Mucous Membrane and Glands of the Larynx. — The mucous membrane of the la- rynx is a continuation of that of the mouth and pharynx. The larynx presents the only example in the body of an organ, part of whose external surface, namely, the posterior, is covered with mucous membrane ; and this depends upon the circumstance of its form- ing part of the parietes of the pharynx. The mucous membrane is disposed in the following manner : From the base of the tongue it is reflected upon the anterior surface of the epiglottis, forming the three glos- so-epiglottid folds already described, one in the middle and one on each side ; it adheres pretty closely to the epiglottis, is reflected over its free margin, covers its posterior sur- face, and penetrates into the larynx : on each side it passes from the epiglottis to the arytenoid cartilages, and becomes continuous with the pharyngeal mucous membrane, which covers the back of the larynx. At the superior orifice of the larynx, it is reflect- ed upon itself, to form the aryteno-epiglottid folds, which constitute the sides of the su- pra-glottid region of the larynx ; it then covers the superior vocal cord, and lines the ven- tricle, sending a prolongation into its supplementary cavity. In the ventricle it is re- markable for its slight adhesion to the subjacent parts. It is reflected from the ventri- cle upon the inferior vocal cord ; there, as well as opposite the superior cord, it is so thin that it does not conceal the pearly appearance of the ligament beneath, to which it adheres so closely that it is difficult to separate them. Lastly, it covers the internal sur- face of the cricoid cartilage, and the middle and lateral crico-thyroid membranes. The laryngeal mucous membrane is characterized by its tenuity, its adhesion to the parts beneath it, and by its pale pink colour.f It is perforated by the openings of a num- ber of mucous glands. Its extreme sensibility, especially at the upper orifice and in the * I first saw this cavity in a patient affected with laryngeal phthisis, in whom it was vpry much dereloped. I then examined the larynx in other individuals, and found it to be constant. I did not tlien know tliat IVIor- gagni had pointed it out and figured it {Advcrs. i., Epist Anat., viii.). t [The epithelium of the laryngeal mucous membrane is, in the greater part of its extent, columnar and cil- iated. The cilia urge the secretion upward ; according to Dr. Henle, they extend higher up in front than on each side and behind ; on the sides, for example, as high as the border of the superior vocal cords, or about two lines above them, and in front upon the posterior surface of the epiglottis, as high as its base or widest por- tion. Above these points the epithelium gradually assumes the laminated form, like that in the mouth and pharynx.] 432 SPLANCHNOLOGY. supra-glottid portion of the larynx, is well known.* The aryteno-epiglottid folds, which include the ligaments of the same name, and some muscular fibres in the larger animals, are remarkable for the great quantity of very loose cellular tissue which they contain : this fact explains their liability to a serous infiltration, called oedema of the glottis, which proves rapidly fatal. The Glands of the Larynx.— The glands of the larynx are the epiglottid and the aryte- noid. The thyroid gland, or body, cannot be considered as belonging to the larynx ; if it belongs to any organ, it must be to the trachea. The EpiirlotHd Glands.— The name of epiglottid glands is generally given to the fatty mass already described as being situated between the thyroid cartilage and the epiglot- tis ; and it has even been asserted that it opens by special ducts on the posterior surface of the epiglottis. But there is no other epiglottid gland besides those situated in the sub- stance of the epiglottis, which is perforated with innumerable holes for their reception : these small glands'are so numerous, that Morgagni {Advers., i., 2 ; v., 68) regarded them as forming a single gland ; they all open upon the laryngeal surface of the epiglottis by very distinct orifices, from which a considerable quantity of mucus can be pressed. The Arytenoid G lands .—These were well described by Morgagni, who very properly considered them as forming a single glandular mass, situated in the substance of the ary- teno-epiglottid fold. They are arranged in two lines, united at an angle, like the letter L ;t the vertical line runs along the anterior surface of the arytenoid cartilage and its corniculum, and produces a slight prominence, perfectly distinct from that made by the cartilages ; the horizontal line is less prominent, and is situated in the superior vocal cord. The arytenoid glands open separately upon the internal surface of the larynx. Vessels and Nerves. — The arteries are derived from the superior thyroid, a branch of the external carotid, and from the inferior thyroid, a branch of the subclavian. The veins enter the corresponding venous trunks. The lymphatic vessels, which are little known, terminate principally in the glands of the supra-hyoid region, if we may judge from the frequency of their inflammation in cases of acute laryngitis, &c. The nerves are branches of the pneumogastric, viz., the superior and the inferior, or recurrent laryngeal. The superior laryngeal nerves are not exclusively distributed to the muscles called constrictors of the glottis (the arytenoideus and the crico-thyroidei) ; nor do the inferior laryngeals belong exclusively to those called dilators (the crico-arytenoi- dei postici and laterales, and the thyro-arytenoidei), as a celebrated physiologist has af- firmed. (See Neurology.) The peculiar rotatory movement of the arytenoid cartilages somewhat interferes with any classification of these muscles into dilators and constrictors. Development. — The evolution of the larynx is remarkable in this respect, that, after hav- ing attained a certain size, it undergoes no appreciable change until the time of puberty. The ventricles are as yet so slightly developed that their existence has been denied. The prominence of the os hyoides in some measure conceals that of the larynx. M. Rich- erand (Mem. de la Sociele Med. d' Emulation, torn, iii.) has proved that there is no very remarkable difference between the larynx of a child at three years of age and of one at twelve Up to the age of puberty the larynx presents no trace of the sexual differences which afterward become so evident ; and to these anatomical conditions are owing the shrillness and uniformity of the voice in the youth of both sexes. At the period of puberty, at the same time as the genital organs, the larynx increases so rapidly as to attain its full development in the space of one year ; the voice then loses its uniformity, and acquires its peculiar timbre and quality, and then also the sexual dif- ferences in the vocal apparatus become manifest. Is it from an unequal development of the different parts of the larynx, or from want of a certain degree of education, that the voice at this period is so discordant, especial- ly in singing, or breaks, as it is said 1 The simultaneous development of the genital organs and the larynx has led to the opin- ion that they stand to each other in the relation of cause and effect; and observation has established that the vocal apparatus is in some measure under the influence of the generative organs ; for < in eunuchs the larynx remains as small as it is in the female. (M. Dupuytren, Mem de la Soc. Phil., tom. ii.) At the age of puberty the size of the glottis is increased by one third in the female, and is nearly doubled in the male. After puberty, any changes which the larynx may undergo are the result of exercise, not of development, properly so called. Ossification of the cartilages of the larynx is not always the effect of age. I have seen it at the thirtieth year quite independently of disease. Chronic inflammation of the la- rynx induces a premature ossification of the cartilages. The thyroid has the greatest tendency to this change, then the cricoid, and, lastly, the arytenoid cartilages ; I have never observed it in the epiglottis. Functions. — The larynx is the organ of voice. Numerous experiments upon living animals, and many surgical facts, show that the vocal sound is produced exclusively in * It has been observed, in experiments upon animals, and in introducing- the oanula after the operation of laryngotomy, that the sensibility of the mucous membrane beyond the glottis is much less acute, t " Gnomonis, sed obtusanguli figurara utervis acervus habet.'' — {Haller.) THE THYROID GLAND. 433 the larynx. The lungs, the bronchi, and the trachea perform, with regard to the voice, the office of an elastic conductor of air capable of contraction and dilatation, of shorten- ing and elongation. The thorax acts like a pair of bellows, by which the air is driven into the larynx with any wished-for degree of force ; and hence the quantity of air pass- ing through the larynx, and the rapidity with which it moves, may vary to a very great extent. What, then, is the mechanism of the voice 1 Is it the same as that of a horn (Dodart), of a stringed instrument {Ferrein), of a flute {Cuvier), of a reed instrument {Biot and Ma- gendie), or of a bird-call* (Savart) I Is it produced by the vibration of the tense vocal cords, or merely by the vibration of the air while passing through a narrow opening, which is itself incapable of vibrating 1 We shall leave these questions to the decision of physiologists. It is sufficient for our purpose to know that the action of the muscles of the larynx and the arrangement of the vocal apparatus are perfectly fitted to produce either dilatation or contraction of the glottis ; and such is the mechanism of this part, that, from the rotatory movement of the arytenoid cartilages, the vocal cords are always rendered tense, whatever may be the other actions of the muscles. The voice as it issues from the larynx is simple, for the larynx is, with regard to the voice, what the mouth-piece is in the flute, or the reed in the bassoon ; but during its pas- sage through the vocal tube, composed of the epiglottis, the pharynx, the isthmus of the fauces, the mouth, and the nasal fossae, the voice becomes modified. According to a very ingenious theory of M. Magendie, the epiglottis resembles those soft and movable valves which M. Grenie places in the pipes of an organ to enable the sound to be increased without modifying the tone. The isthmus of the fauces resembles the superior larynx of birds, which consists of a contractile orifice that can be diminished, and even closed at pleasure ; and it is princi- pally owing to this mechanism that the small glottis of birds can execute such an exten- sive range of notes. We know, in fact, that the tone of a wind instrument is reduced an octave lower by completely closing the lower orifice of the tube, and that, when it is only partially closed, the tone is depressed in proportion. Now the isthmus of the fau- ces acts exactly like the superior larynx of birds. On watching a person who wishes to utter a very low note, we see that he depresses and flexes the head slightly upon the neck, so as to approximate the chin to the thorax : by this means the vertical diameter of the isthmus of the fauces is diminished, the larynx being carried upward, while the velum palati is depressed ; and from this we may judge of the important part performed by the velum in producing modulations of the voice. If to this we add the changes which may be effected in the length and diameter of the pharynx (see Pharynx), and if we remember that, by diminishing by one half the length or diameter of the tube or body of a wind instrument, its tone is raised one octave, we shall be able to understand how the human voice can execute so extensive a scale of notes, although the glottis is so small. The voice is also modified while traversing the buccal and nasal cavities. Do the nasal fosscr. favour the resonance of the voice ! or does the air, when passing through them, merely give rise to certain sounds denominated nasal ! The latter opin° ion, which is supported by Mr. Gerdy, appears to me the most consistent with facts. MM. Biot and Magendie had already correctly observed that the voice becomes nasal only when it traverses these passages. The voice becomes articulate in passing through the mouth, i. e., the vocal sound is interrupted, and modified by the more or less rapid percussion of the lips and tongue against the teeth and the palate. Articulate voice is very distinct from speech. Animals which differ much from man in the conformation of their vocal organs, the parrot, for example, may be made to artic- ulate ; but speech is the peculiar attribute of man, because he alone is possessed of in- telligence. The Thyroid Gland. The thyroid gland, or thyroid body, is a glanduliform organ, the uses of wmch are un- known : it is situated hke a crescent with its concavity directed upward, in front of the first rings of the trachea, and upon the sides of the larynx. In describing this organ in connexion with the larynx, I foUow the usual custom, which has arisen not from any direct relation between their functions, but from their contiguity to each other. The thyroid body varies much in size in different individuals ; there are few organs which present greater varieties in this respect. The sexual differences in the size of this organ, like all those relating to the vocal ap- paratus, are very well marked, but in an inverse manner, that is to say, the thyroid body is larger in the female, in whom it forms a rounded projection, which assists in making the thyroid cartilage in that sex appear still less prominent. * A bird-call is a cavity with elastic walls, perforated upon the two opposite sides. The cavity is repre- sented by the ventricles, and the openings by the intervals between the vocal cords. If a tube capable of contracting and dilating be fitted to such an instrument, an infinite variety of sounds may be produced. Ill 434 SPLAXCHNOLOGY. Climate, and more especially certain qualities in the water used as drink, have a re- markable influence upon its size, which, in many cases of goitre, is enormous. These differences in size affect either the whole of the gland equally, or only one lobe, or occasionally the middle portion alone. The weight of the thyroid body, which is about an ounce, may be increased to a pound and a half, or even more. Form. — The thyroid l>ody is generally composed of two lateral hies or cornua, united by a contracted portion, flattened from before backward, and called the isthmus. The varieties in shape principally affect the isthmus, which may be very narrow, long or short, regular or irregular, or entirely absent, or it may be as thick and as long from above downward as the lobes themselves. I have seen one case in which the thickest part of the thyroid gland was in the middle, and the lobes terminated above in a very narrow point. The opinion of the ancients, and which is also met with in Vesalius, that the human subject has two thyroid glands, no doubt arose from the narrowness or absence of the isthmus, or, rather, from the separation and complete independence of the two lobes in a great number of animals. The surface of the thyroid body is smooth and well defined, and sometimes divided into lobules by superficial furrows. We shall examine in succession the relations of the middle and lateral portions : The middle portion or isthmus is convex in front, and is separated from the skin by all the muscles of the sub-hyoid region. Behind, where it is concave, it is in contact with the first rings of the trachea. Moreover, this middle portion descends to a greater or less distance in different subjects, and sometimes so low, that there is not room to per- form tracheotomy between it and the sternum. Each lateral lobe is convex in front, and corresponds with the muscles of the sub-hyoid region : in particular, I ought to mention the sterno-thyroid, by which it is directly cov- ered, and the breadth of which seems to be proportioned to the size of the lobe : in many cases of goitre I have seen this muscle twice or three times as broad as in the natural state. On the inside, each lateral lobe is concave, so as to be applied to the side of the trachea and cricoid cartilage, to the lower and latter part of the thyroid cartilage, to the lower part of the pharynx, and to the upper part of the oesophagus. The two lobes, to- gether with the middle portion or isthmus, form a half or sometimes three fourths of a canal, which embraces all those parts ; an extremely important relation, which explains how, in certain goitres, the trachea is flattened on the sides, deglutition is impeded, and true asphyxia by strangulation is the final result. Behind, each lateral lobe coiresponds with the vertebral column, from which it is separated, on the outside, by the common carotid artery, the internal jugular vein, and the pneumogastric and great sympathetic nerves, which, according to the size of the gland, are either covered by it, or are merely in relation with its outer surface. The upper extremity of each lateral lobe terminates in a point, and hence the two- horned figure assigned to the thyroid body. It is situated on the inside of the carotid artery, in contact with the lateral and back part of the thyroid cartilage, and sometimes extends nearly to its upper border. Its loiuer extremity is thick and rounded, descends to a greater or less distance in different individuals, and corresponds to the fifth, sixth, or seventh rings of the trachea : it is situated between the trachea and the common ca- rotid. The inferior thyroid artery enters the gland at its lower extremity. Its upper border is concave and notched in the middle ; the superior thyroid arteries run along it. A prolongation extends from this border, which has been correctly repre- sented by Bidloo, and named the pyramid by Lalouette. It almost always exists ; it passes perpendicularly upward, either on the right or left side of the median line, and presents numerous varieties in several respects. Thus it varies in its origin, sometimes arising from the isthmus, and sometimes from one of the lobes at one side of the isth- mus ; also in its termination, sometimes ending opposite the notch in the upper border of the thyroid cartilage, sometimes opposite the thyro-hyoid membrane, and at other times even on a level with the body of the os hyoides ; but always firmly adherent either to the membrane or the bone. It also varies in its structure : sometimes it is a fibrous cord, and sometimes a reddish linear band, which has all the appearances of a muscular fasciculus, and has even been described as a muscle ; it often consists of a series of granules arranged in a line ; sometimes, again, we find, in the middle, or at one end of the cord, a glanduliform enlargement, exactly resembling the tissue of the thyroid gland ; lastly, it may be double, or bifurcated, or even completely wanting ; in which case, how- ever, there exists a glanduliform mass of a certain height. This prolongation, in which I and many others have in vain attempted to find an excretory duct, is evidently of a compact nature. Is it the remains of a foetal structure, or the trace of a normal dispo- sition in some animals 1 The lower border of the thyroid body is convex, more or less deeply notched in the cen- tre, and is in contact with the inferior thyroid arteries. Structure. — The proper tissue of the thyroid gland is of a variable colour, sometimes resembhng the lees of Port wine, and sometimes of a yellowish hue. It is of tolerably THE URINARY ORGANS. 435 firm consistence, and feels granular. This organ presents all the anatomical characters of glands, and, like them, may be separated by dissection into glandular grains ; but with this difference, that these grains communicate with each other, while, in ordinary glands, they are independent. The communication of the glandular grains may be shown in the following manner : if the tube of a mercurial injecting apparatus be inserted into the thyroid gland, the mercury will enter into and distend the cells, and after a certain time all the grains will be injected ; it is easy to satisfy the mind that the mercury is not in- filtrated into the cellular tissue, but is contained in the tissue of the gland itself, in the centre of the granulations. The right and left lobes do not conmiunicate, but all the granulations of each lobe communicate with each other. The thyroid gland has, therefore, a vesicular structure ; and we have seen that the glandular grains of all glands are spongy and porous, and that the products of their secre- tion may be accumulated in these pores. The glandular nature of the thyroid body is also shown by the viscid, limpid, yellowish fluid which pervades it in certain subjects, and which may be collected in sufficient quantity for chemical analysis ; and also by the retention of this matter within a greater or less number of the vesicles when their orifices of communication with the neighbour- ing vesicles become obliterated. But, in connexion with this view regarding its glandular nature, we seek in vain for an excretory duct. If we examine the trachea and the larynx, or lay open the oesophagus, and then press the thyroid gland, we shall see that no fluid escapes into those canals. It has been asserted, indeed, that the excretory duct of the thyroid gland terminated in the foramen ccecum of the tongue, in the ventricles of the larynx, or in the trachea opposite its first ring ; but, after the example of Santorini, we are compelled to reject these fancied and too hastily announced discoveries. I may here notice the intimate adhesion of the side of the thyroid gland to the first ring of the trachea. This can be very well shown by detaching the gland from behind for- ward ; it is of a .fibrous nature, and I have sometimes thought that I saw a duct in the centre of it, passing through the membrane which connects the trachea with the cricoid cartilage, though I have never been able satisfactorily to demonstrate it. Still, I do not think that the absence of an excretory duct should remove the thyroid from among the glandular organs ; for I believe that there exist in the body glands with- out excretory ducts, a§ the thymus, the supra-renal capsules, and the thyroid body. The secretion of the gland is entirely absorbed, and fulfils certain unknown uses. Arteries. — The size and the number of the arteries distributed to the thyroid gland in- dicate that something more than a mere nutritive process must be carried on in it. The arteries are sometimes four, sometimes five in number ; two superior arise from the ex- ternal carotid ; two inferior from the subclavian, and the fifth, or the thyroid artery of Neubauer, where it exists, arises from the arch of the aorta. The veins are proportionally as large as the arteries, and form so considerable a plexus in front of the trachea, as, in certain cases, to have prevented the completion of the operation of tracheotomy. The lymphatic vessels terminate in the cervical lymphatic glands. The 7ierves are derived from the pneumogastrics, and the cervical ganglia of the sym- pathetic. A thin cellular membrane envelops the gland, and sends very deh'cate prolongations into its substance, where we find a very firm cellular tissue, always destitute of fat. Development. — The thyroid gland is developed in two lateral halves, which are after- ward united by a median portion. It is not uninteresting to remark, that this dispo- sition, which is transitory in the fcetus, represents the permanent condition of the gland in a great number of animals. During intra-uterine life and infancy it is relatively larger than at subsequent periods. Nevertheless, the changes which it afterward undergoes are not to be compared with those that occur in the thymus ; and we cannot say, as of the latter structure, that the existence of the thyroid body has any peculiar relations with fcetal life. Functions. — It is a secreting organ, but the uses of its fluid are not known. THE GENITO-URINARY ORGANS. I HAVE thought it proper to describe the genital and the urinary organs together, because, although their functions are very distinct, yet they have the most intimate anatomical, physiological, and pathological connexions. THE URINARY ORGANS. Division. — The Kidneys and Ureters. — The Bladder. — The Supra-renxil Capsules The urinary organs form a very complex secretory apparatus, consisting of two secre- ting organs, the kidneys ; of two provisional reservoirs, the calyces and the pelvis of each kidney ; of two excretory ducts, the ureters ; of a second and final reservoir, the bladder; 436 SPLANCHNOLOGY. and, lastly, of a second and final excretory canal, which, in the male, is common to both the genital and the urinary organs, viz., the canal of the urethra. The Kidneys. The kidneys {vE(l)pol) are glandular organs, intended to secrete the urine. They are deeply situated {k k,fig. 199) in the lumbar region, hence called the region of the kidneys, on each side of the vertebral column, externally to the peritoneum, vi^hich merely passes in front of them ; they are surrounded by a great quantity of fat, and, as it were, suspended by the vessels which pass into and emerge from them. Fixed firmly in this situation, they are but httle liable to displacement. Most of the changes in their position are congenital. The right kidney generally descends a little lower than the left, doubtless on account of the presence of the liver. One of the kid- neys may not uncommonly be found in front of the vertebral column, or even in the cavity of the pelvis ; and this unusual arrangement may, in certain cases, render diag- nosis very obscure.* I have frequently found the right kidney in the corresponding ihac fossa in females who had been in the habit of wearing very tight stays. This displace- ment happens when the pressure of the stays upon the liver forces the kidney out of the depression in which it is lodged in the lower surface of that organ. Number. — The kidneys are two in number. It is not very uncommon to find only one, which is almost always formed by the union of the two, by means of a transverse portion crossing in front of the vertebral column, and having its concave border directed upward. Sometimes the two united kidneys are situated in the right or left lumbar region, or in the cavity of the true pelvis. Cases of union of the two kidneys should be distinguish- ed from those in which one of them is atrophied. Again, Blasius, Fallopius, Gavard, &c., relate examples of individuals having three kidneys ; in some of these cases, two were situated upon the same side, in others the supernumary kidney was placed in front of the vertebral column. Size. — The kidney is not subject to such great variations in size as most other organs. Its ordinary dimensions are from three and a half to four inches in length, two inches in breadth, and one inch in thickness. Its weight is from two to four ounces.t I have found them more than three times their ordinary size in a diabetic patient. When one kidney is atrophied, the other becomes proportionally enlarged, sometimes even to twice the usual dimensions. Atrophy of the kidney may be so extreme as to reduce it to a drachm and a half or two drachms in weight, and make it appear to be lost among the surrounding fat ; but the presence of this fat distinguishes such a case from one of con- genital absence of the kidney, t Density and Colour. — The tissue of the kidney is harder than that of other glands. Its fragility accounts for its laceration by direct violence, or by a concussion produced by a fall from a great height. Its colour is that of the lees of red wine, somewhat analogous to that of the muscular tissue, but oifers several different shades. Figure. — The shape of the kidney may be well compared to a bean, with the hilus turned inward. This form enables us to consider its two surfaces and its circumference. Relations. — The anterior surface of the kidney is directed slightly outward ; it is con- vex,ves, mixed with some elastic tissue. In the penis of the horse there are pale red fibres, dLfenn;; from cellular^ tandinous, and elastic tissue, but which, according- to Miiller, do not possess muscular coatractilit/.] 456 SPLANCHNOLOGY. The arteries arise from the internal pudic, and enter the substance of the corpus ca- vernosum. Injection of these arteries does not produce erection until the fluid has pass- ed from them into the veins.* The lymphatic vessels are little known. No nerves have been traced into the interior of the corpus cavernosum.+ The Triangular Suspensory Ligament of the Penis. — This ligament is composed of yel- low elastic tissue, and extends in the median line from the symphysis pubis to the cor- pus caveniosum. Muscular fibres have been described as existing in it ; but it is prob- able some fibres prolonged from the bulbo-cavernosus, and now known as the muscle of Houston, have been regarded as forming part of this ligament. I have seen the sus- pensory hgament reach along the linea alba, half way up to the umbilicus. Muscles of the Penis. These are eight in number, four on each side, viz., the ischio-cavernosus, the bulbo-ca- vernosus, the pubio-urethralis, and the ischio-bulbosus. The Ischio-cavernosus, or the Erector Penis. The ischio-cavernosus {c,Jig. 163) is an elongated muscle, situated upon the corre- sponding root of the corpus cavernosum ; it is curved upon itself, and is aponeurotic in part of its extent. It arises from the inner lip of the tuberosity of the ischium, below the transversus pe- rinaei, by tendinous and fleshy fibres, and also from the surface of the root of the corpus cavernosum. From these points its fibres pass inward, and are inserted, after a short course, into the edges of the upper surface of a very strong, shining, and fasciculated aponeurosis, having its fibres directed from behind forward, which covers the correspond- ing root of the cavernous body, upon which it is then prolonged. The fleshy fibres, ter- minating at the edges of the aponeurosis, form two bundles ; one internal, and extend- ing upon the inner side of the root, the other external, which passes on the outer side of the same, and is prolonged, much farther than the internal fasciculus, upon the cav- ernous body. In order to see the structure of this muscle, it is necessary to make a longitudinal incision into the aponeurosis, which entirely covers its lower surface ; we then observe a muscular layer, which is tolerably thick behind, but thin in front, and is formed partly by the original fibres, and partly by others arising from the root of the corpus cavernosum itself Relations. — Below, with the cellular tissue and the dartos ; above, with the root of the corpus cavernosum, upon which it is closely applied ; on the inside, with the bulbo-cav- ernosus, being separated from it by a triangular space, the base of which is directed backward. Uses. — It acts solely upon the corpus cavernosum, drawing the root of the penis down- ward and backward ; instead of compressing the root of the corpus cavernosum by the contraction of its fibres, it tends, on the contrary, to dilate its cavity, by separating the wer from the upper wall, and, in this manner, facilitates erection. The Bulbo-cavernosus, or Accelerator JJrina. This muscle {d,fig. 163) is much larger than the preceding ; it is situated in front of the anus, extending along the lower surface of the bulb and the spongy portion of the urethra, upon which it seems to be moulded. It arises in front of the sphincter ani by a median fibrous raphe, which is common to the two muscles of this name, and which appears to arise from the bulb, to which it ad- heres closely ; while the external fibres arise from the posterior margin of the triangu- lar ligament, or deep perineal fascia, and frequently from the rami of the ossa pubis, op- posite that margin. From this double origin the fibres pass forward, and terminate in the following manner : the outermost fibres form a thin layer upon the lower surface of the triangular ligament, and are inserted by short, tendinous fibres to the inner side of the root of the corpus cavernosum ; the middle fibres, which are larger, are directed oblique- ly inward, and are inserted by very distinct tendinous fibres immediately in front of the point of junction of the roots of the corpus cavernosum, in the sort of groove between that body and the urethra ; the innermost fibres are the longest ; they pass directly for- * [Miiller has described, besides the nutritious arteries of the corpus cavernosum, which terminate, as usual, jn the veins, a peculiar set of vessels, called the arteria: helicina:. They are short, curled branches, much larger than capillaries, and ending abruptly in free rounded extremities ; they project either singly, or in tufts arising from one stem, into the venous cells, by the lining membrane of which they are supported and invested. They are found principally in the posterior portions of the cavernous and spongy bodies, and are more marked in man than in animals. In the horse they are very indistinct ; in the elephant they do not exist at all. Miil- ler believes that the blood, during erection, is poured out directly from these vessels into the venous cells ; but no openings through which the blood could escape have been detected, either in their sides c at their ex tremities, nor is analogy in favour of their existence. According to Valentin, the so-called helicine arteries are the divided branches of common arteries curled up (after having been injected), in consequence of the retraction of the elastic trabeculie on which they are sup- ported ; to this it is replied, by Mullcr, that these vessels may be seen in cells deeper than the surface o Ihe ■section. Valentin farther maintains that the arteries terminate in the veins by wide, funnel-shaped orifices.] t [Numerous nerves enter the corpus cavernosum ; they are derived from the internal pudic and sympathet- ic nerves, and have been carefully traced by Miiller.] THE URETHRA. 457 ward, and, at the point where the penis is bent in front of the pubis, are inflected out- ward {e,fig. 163), pass upon the sides of the penis, and terminate on its dorsal surface, becoming continuous with the suspensory ligament. The last-named termination ap- pears to me to constitute the muscle described by Houston, which, according to that anatomist, is intended to compress the dorsal veins of the penis* in man and other ani- mals ; but it is evident, on the one hand, that it cannot compress the veins of the penis ; and, on the other, as M. Lenoir has pointed out, that the dorsal veins of the penis are cutaneous veins, which do not communicate with those of the corpus cavernosum.t Relations. — Below, the bulbo-cavernosus corresponds with the dartos, from which it is separated by the superficial perineal fascia by a very thin layer of fat, and by a proper fibrous sheath. Above, it is in relation with the bulb of the urethra, which it embraces, like a contractile sheath, resembling the sheath around the stems of grasses. The inner border is continuous with the muscle of the opposite side ; so that, at first sight, it might be thought that there is but one bulbo-cavernosus. Uses. — Its attachment to the inner side of the corpus cavemosum enables it to separ- ate the lower wall of that body from the upper, and, consequently, to induce the entrance of the blood. It therefore contributes powerfully to erection. On the other hand, by compressing the urethra, it accelerates the expulsion of the urine and semen. The Puhio-urcthralis. This muscle, known also as the muscle of Wilson, because it was described by that anat- omist, may be regarded as the continuation of the levator ani. The two muscles arise from the middle of the sub-pubic arch, and descend first upon the sides and then on the lower surface of the membranous portion of the urethra, which they surround as in a ring. They are situated behind the triangular ligament, or deep perineal fascia.t When spasmodically contracted, it is said that they may arrest the point of a catheter. The Ischio-bulbosus. We may describe under this name a small muscle situated below the deep perineal fascia. It is stronger than the transversus perinaei ; it arises from the ascending ramus of the ischium and the descending ramus of the pubis, and terminates on the sides of the bulb. This muscle, which is of a triangular shape, is separated from the one last de- scribed by the deep perineal fascia, so that it cannot be regarded as a dependance of the levator ani.^ The Urethra. The urethra is the excretory passage for the urine, and in the male it serves the same purpose in regard to the semen. Its direction has been particularly studied. Commencing at the neck of the bladder, it passes forward and downward ; having arrived beneath the symphysis pubis, it de- scribes a slight curve, with the concavity directed upward, embraces the symphysis, ri- ses a little in front of it, and then enters the groove on the lower surface of the corpus cavernosum. Beyond this point its direction is determined by that of the penis ; and it * [The compressores vense dorsalis penis, according to Houstou (Dublin Hasp. Reports, vol. v.), arise from the rami of the pubes above the erectores penis and the crura of the corpus cavernosum, expand into a thin layer, pass upward, inward, and forward, and unite in a common tendinous band over the dorsal vein. They are separated by the crura from the erectores penis, of which muscles, he says, they might otherwise be re- garded as portions : the anterior layer of the triangular ligament and the pudic artery are interposed between them and the muscles of Wilson.] t Dissertation sur quelques Points d'Anatomie, de Physiologic, et de Pathologie, No. cccxv., 1833. [The dorsal veins return the greater part of the blood from the glans penis and corpus spongiosum, as well as the skin, and are also joined by branches from the corpus cavemosum. {See M. Cruveilhier's own descrip- tion of these veins, Angeioloqy).] I [In the descnption of the muscles given by Wilson himself (Med. Chir. Trans., vol. i., p. 176, 177), it is stated, that " the line of tendon connecting the two bellies of these muscles is, in general, very distmctly seen running from the apex of the prostate gland, along the under surface of the membranous portion of the ure- thra, until it enters the corpus spongiosum penis." From this it would appear that the muscles discovered by him are placed between the two layers of the ligament, not behind its posterior layer. On the same plane with Wilson's muscles, i. e., between the layers of the ligament, are situated two small transverse muscles, which arise, one on each side, by broad thin tendons, from the rami of the ischia, near their junction with those of the ossa pubis, immediately above the crura penis and their erector muscles ; from thence the fleshy fibres pass transversely inward and upward, and are inserted along the median line of the upper and under surface of the membranous portion of the urethra by means of two tendinous structures, which extend, one above the urethra, from the fascia covering the prostate to the union of the crura penis in front of the triangular ligament, and the other below that canal, from the fascia on the prostate to the central point of the perineum : to this tendinous structure the vertical muscles of Wilson are also attached. The pu die arteries run either above or below these transverse muscles, the lower fibres of which pass below Cow- per's glands, i. e., more superficially, when viewed from the perineum. These transverse muscles are described and figured by Santorini (Observ. Anat., c. X., ^ viii., t. 3, fig. 5; also, Sepiemdecim Tabula, t. 16, fig. 1), who states, however, that (hey are attached only to the lower surface of tlie urethra, behind the bulb ; he named them elevatores urethrte, or ejaculatores. It has been recently shown by Mr. Guthrie (Land. Med. and Surg. Journ., 1833, p. 491, 402; also, On the Anatomy and Diseases of the Neck of the Bladder and of the Urethra. 1834, p. 34, &c.) that the transverse muscles of Santorini are inserted, as already described, both above and below the urethra : and that the vertical muscles of Wilson are lilended with them at their insertions : he therefore proposes to regard them as one muscle, which has been termed the compressor urethra:.] i [The description of this muscle corresponds exactly with that of the transversus perina:i alter of Albinus.l M M M 458 SPLANCHNOLOGY. describes, with that organ, a second curve, much more marked than the preceding, hav- ing its concavity dii-ected downward, but only in the state of relaxation, for the curve no longer exists when the penis becomes elongated, either from erection, or from direct traction. It follows, therefore, that, except during erection, the urethra describes two curves, like the letter S ;* but when the penis is elongated, it forms only a single curve, which is permanent. Although the cur^'ature of the urethra is not so rigid as to prevent the introduction of a straight instrument into the bladder, it would be wrong to conclude that the canal it- self is straight. It must be remembered that organic membranous ducts are sufficiently pliable to accommodate themselves to the direction of instruments introduced into them ; but the effacing, or the artificial removal of the curves, is very different from their non- existence. Moreover, the curvature of the urethra is demonstrated by the impossibility ' of drawing a straight line from the neck of the bladder, and passing a short distance be- low the symphysis to the point where the urethra joins the corpus cavernosum ; also by the curve acquired by bougies after remaining for some time in the urethra ; and, lastly, by the curvature presented by a mould obtained by injecting the bladder and urethra with any substance capable of becoming solid. Dimensions. — The length of the urethra is from eight to nine inches ; it is sometimes less than eight. The extreme dimensions noticed by Whately,t in measurements taken from forty-eight subjects, are nine inches six lines and seven inches six lines. It is dif- ficult to estimate the width of the urethra. According to Home, it is four lines, except at the orifice, where it is only three. It is quite impossible to judge of its width exter- nally, on account of the thickness of its walls, and especially on account of their being unequal. The extreme dilatability of the canal allows the introduction of instruments of considerable cahber, as in the operation of lithotrity. The urethra is considered as divided into three portions, as different in their structure as in their relations ; these are the prostatic, the memhranous, and the spongy portions. The Prostatic Portion. — This part of the urethra, which forms, as it were, a continua- tion of the bladder, and the commencement of the urethra, is called prostatic, because it appears to be hollowed out of the glandular body called the prostate, the description of which must be inserted here, on account of its intimate connexion with the urethra. The prostate {i,fig. 181), a whitish glandular body, is situated in front of the neck of the bladder, and embraces it ; it is behind the symphysis pubis, and in front of the rec- tum. It is shaped like a cone, with its base turned backward, and its truncated apex forward. Its axis or long diameter is horizontal, but slopes a little from behind down- ward and forward. It has often a bi-lobed appearance in man, but it is never truly double, as in a great number of animals. The size of the prostate varies greatly in different subjects. The following dimen- sions have been taken from the measurements of the prostates of adults : Vertical di- ameter, twelve lines ; transverse, eighteen ; antero-posterior, or length, fifteen. Some- times it acquires three or four times its nominal size ; the increase may aifect either the whole gland or one half, or the middle lobe only. Relations. — We shall examine the relations of the prostate with the parts correspond- ing to its outer surface, and with those which are situated within it. Relations of the Outer Surface of the Prostate. — The lower surface corresponds with the rectum, adhering to it by tolerably dense cellular tissue, in which there is never any fat or serum ; and hence the rule of examining the prostate by the rectum. In consequence of alterations in the condition of the rectum, that intestine sometimes projects on each side beyond the prostate, as during distension ; and sometimes, as when it is contract- ed, the prostate projects beyond it laterally. The lower surface of the gland is smooth, and is traversed in the median line by an antero-posterior furrow, which is well marked in some subjects, and divides it into two equal portions. The upper surface is in relation with the recto-vesical fascia (9, _^^. 181), or, rather, with some very strong ligamentous bundles, which extend from the pubes to the blad- der, and are called the ligaments of the bladder. This surface has no immediate rela- tions with the arch of the pubes, behind which it is placed ; it is always some lines dis- tant from it. Nevertheless, by means of a silver catheter or sound, introduced into the bladder, we may draw the prostate under the pubes, and make it project in the perineum. The sides are embraced by the levator ani and the levator prostatae. When the prostate is pushed downward by the catheter, its sides are embraced by the circumference of the arch of the pubes, and they then approach very near the trunk of the internal pudic artery. The Jftse of the prostate embraces the neck of the bladder, and is prolonged a little upon that organ, so as to surround the vas deferens and the neck of the vesiculae semi- nales. * It was this direction of the canal which suggested to J. L. Petit the idea of making silver bougies, shaped like the letter S, to remain in the passage. t An Improved Method of treating Stricture of the Urethra, 1816. THE URETHRA. 459 The apex terminates behind the membranous portion of the urethra. Relations of the Prostate icith the Paris situated in its Interior. — The prostate is perfo- rated by the urethra, by the ejaculatory ducts, and by its own excretory ducts. The relations of the urethra with the prostate vary in different subjects : thus, sometimes its lower three fourths only are surrounded by the gland, which is accordingly wanting above, and is merely grooved, not perforated by a canal ; sometimes the prostate forms a complete hollow cylinder around the urethra. The portion of the prostate situated above the urethra is scarcely ever thicker than the part beneath it. In some cases, however, the urethra has been found occupying the lower part of the prostate, and only separated from the rectum by a very thin layer of glandular substance. When such is the case, the rectum is very hable to be wounded in the ditferent steps of the operation of lithotomy.* In the natural state the prostate does not project into the urethra ; but not unfrequent- ly we find a prominence, of greater or less size, rising from the lower part of the urethra, opposite the base of the prostate, and obstructing more or less completely the com- mencement of that canal : this tubercle was named by Lieutaud la luette visicale {uvula vesicce) ; by Sir Everard Home, an enlargement of the middle lobe of the prostate. But, in the iirst place, this prominence only exists in disease ; and, secondly, there is no middle lobe, unless that term be applied to the slightly-grooved, and, therefore, thinner portion by which the two lateral halves of the prostate are united. Relations of the Ejaculatory Ducts with the Prostate. — The ejaculatory ducts {d,fig. 186), which lie close to each other, are received into a sort of conical canal, formed in the prostate. Some loose cellular tissue separates them from the substance of the gland, of which they are altogether independent ; it was chiefly to the portion of the prostate which is situated above this canal that the name middle lobe was given by Home. Density. — The density of the prostate is considerable, and yet the tissue of this gland is friable, and can be very easily torn after having been once divided. It is of the greatest importance to remember this friability in performing the operation of lithotomy. The prostate, in fact, is the only obstacle to the extraction of the calculus ; and when this gland has been divided in its antero-posterior diameter, the bladder itself may be torn with the greatest facility. Structure. — The structure of the prostate can only be properly studied in the adult. In certain cases of hypertrophy without alteration of tissue, its characters are, as it were, exaggerated. It consists of a collection of glandular lobules, which may be subdi- vided into granules pressed close to each other in the midst of a tissue that appears to me to be muscular, for it is continuous with the muscular coat of the bladder, and bears the most perfect resemblance to it in cases of hypertrophy. From these granules, which are generally of unequal size, small excretory ducts proceed, and unite into an irregular number of prostatic ducts that open, not upon the verumontanum itself, but upon its sides {see fig. 182), in the whole extent of the lower wall of the prostatic portion of the ure- thra, or prostatic sinus. I have assured myself of tj;ie existence of these ducts and their orifices in many cases where I have found them filled with innumerable small calculi, resembling grains of brownish sand. The orifices of the prostatic ducts may be easily detected by pressing the gland, when the fluid secreted by it will be observed to exude at several points. The Membranous Portion. — The membranous portion of the urethra {c,fig. 181) ex- tends from the prostatic portion to the bulb, and passes upward and forward, t It is in relation above and laterally with the arch of the pubes, from which it is separated by some considerable veins, or, rather, by a sort of erectile tissue ; below it corresponds • with the rectum, but is separated from it by a triangular space, having its base directed forward and downward, and its apex backward and upward. It is generally in this tri- angular space that the urethra is divided in the operation of lithotomy. Its upper concave surface is about an inch long ; its lower surface is from four to six lines. This difference in length is caused by the bulb projecting backward upon the lower surface of the membranous portion of the urethra. This part of the canal is embraced laterally and below by the two muscular bundles which have been already described as the muscles of Wilson ; and also by the transverse muscular fasciculi described by Santorini and Guthrie. The Spongy Portion. — The spongy portion (/) constitutes the greatest part of the length of the urethra ; it commences opposite the symphysis pubis by a very considerable ex- pansion, called the bulb (below /), and terminates at the extremity of the penis by an- other and still larger expansion, which constitutes the glans penis. * The varieties in the situation of the urethra, in relation to the prostate, were well pointed out by M. Senn, in an inaugural dissertation in 1825. According to his ob.servatiuns, the portion of the prostate situ- ated below the canal is seven or eight lines thick in the middle, and ten or eleven lines when measured down- ward and outward. t [The membranous portion perforates both layers of the triangular ligament, about an inch below the arch of the pubes {see Jig. 138) ; but as the two layers are separated from each other below, the greater part of this portion of the urethra is included between them ; a very small part is situated behind the posterior layer ; both layers are prolonged over the urethra, one forward and the other backward.] 460 SPLANCHNOLOGY. The hull occupies the highest part of the pubic arch, and fills the interval between the crura of the corpus cavernosum. Its size varies in different individuals, and according to the state of the penis ; it projects several lines below the level of the membranous portion, which is partially covered by it in this direction, and seems to open into its up- per part. As the bulb is directed very obliquely upward and forward, we might be inclined to consider the urethra to be much more curved than it actually is, if we judged of it only by the external appearance of the canal. The bulb is embraced below and upon the sides by the bulbo-cavernosi muscles, which have numerous points of insertion upon it. Between these muscles and the bulb we find Cowper's glands. The bulb terminates insensibly in front, becoming continuous with the spongy portion : the angle of union of the crura of the corpus cavernosum may be assigned as its anterior boundary. The Glands of Cowper.— These are two small, rounded bodies {g g,Jigs. 168, 181, 182) (so called after the anatomist who has given the best description of them), situated against the bulb, in contact with which they are retained by a tolerably dense layer of fibrous tissue.* From each of these glands, which are of variable dimensions, an excre- tory duct proceeds, and after a course of an inch and a half or two inches, opens into the canal of the urethra upon the sides of the spongy portion (c. Jig. 182), passing ob- liquely through its parietes.t In front of the bulb, the spongy portion of the urethra enters the groove on the lower surface of the corpus cavernosum, and is in relation below, in the first part of its course, with the bulbo-cavernosi muscles, which separate it from the cellular tissue of the scro- tum, and more anteriorly with the skin of the penis. The glans, so called from its shape, is the conical enlargement which forms the ex- tremity of the penis. It is covered by the prepuce, which is united to it below by means of the fraenum ; its base projects considerably beyond the end of the corpus cavernosum, and forms what is called the corona glandis. This circular projection is grooved perpen- dicularly throughout its entire extent by some large nervous papillae, which are visible to the naked eye. The base of the glans is cut very obliquely, so that its upper surface is twice as long as its lower. Below, and in the median line, the corona glandis pre- sents a groove, in which the fraenum is received. At the extremity of the glans is situated the orifice of the urethra, meatus urinarms, a vertical fissure, three or four lines in extent, and placed in the same line as the frae- num, from which it is separated by a very short interval. Sometimes this orifice is placed exactly opposite the fraenum, and, like it, is directed downward : this malforma- tion constitutes what is called hypospadias. Internal Surface of the Urethra. — Upon this surface (see fig. 182) we find no trace of the distinction established between the different portions of the urethra, considered from without, except that the prostatic portion of the canal is of a white colour, while all the rest of it is of a more or less deep violet hue. Dimensions. — Opposite the prostate the urethra becomes dilated, sometimes to a con- siderable extent (sinus prostaticus) ; at the commencement of the membranous portion it suddenly contracts, and then continues cylindrical as far as the glans, where it again dilates so as to form the fossa navicularis (o), and terminates by an orifice, which is the narrowest part of the entire canal, t In order to obtain more exact ideas of the comparative dimensions of the different portions of the urethra, M. Amussat inflated this canal, and then carefully removed all the structures superadded to its proper parietes, so as to reduce the latter to the mu- cous membrane only, and thus leave them of almost uniform thickness, instead of being very unequal. According to this mode of appreciation, which, however, is not free from objection, he has shown that the narrowest part of the canal is the bulbous, not the membranous portion ; that the canal, after being contracted opposite the bulb, again ex- pands at the spongy portion, and then gradually contracts as it proceeds forward. He denies the existence of a dilatation opposite the fossa navicularis ; and attributes the dilated appearance of that part to the fact of the tissue of the glans being very dense, and closely adherent to the mucous membrane of the urethra, so as not to allow it to collapse, like that of the other parts of the canal. However, the extreme dilatability of the walls of the urethra render an exact deter- mination of its dimensions less important than might be imagined. Besides the extensibility of the tissues, there is another anatomical condition which favours the extreme dilatability of the urethra, viz., the existence of longitudinal folds on the inner surface of the canal, which are effaced by distension. These folds must * [They are placed between the two layers of the triangular ligament : the transverse muscles of Santorini cover them below, and the arteries of the bulb (e e,_fig. 168) cross above them : they are compound glands.] t 1 have never seen the gland called, by Litre, the anti-prostatif; ; nor have I seen the third gland of Cow- per, which is said to be situated below the arch of the pubes. t [Three dilatations in the urethra are usually described, viz., the prostatic sinus, the sinus of the bulb, and the fossa navicularis. The first and the third of these are described above ; the second is at the commence- inent of the suongy portion, in the inferior wall of the urethra.] THE OVARIES. 461 not be confounded with certain small longitudinal fasciculi which lie beneath the mu- cous membrane throughout the whole extent of the canal, and appear to me to be of a muscular nature. The whole of the inner surface of the urethra presents a number of obhque orifices, which lead into culs-de-sac of variable depths. These sinuses, the ori- fices of which are always directed forward, are sometimes large enough to receive the extremities of bougies ; they were very well described by Morgagni, and, therefore, they are generally called the sinuses of Morgagni. I have seen them more than an inch long. No glands open into them.* The Verum.07itanum, or Crest of the Urethra. — The lower wall of the membranous por- tion of the urethra presents, in the median line, a crest, which has been named the ve- rumontanum, caput gallinaginis, or urethral crest {a to d). This crest commences in front by a very delicate extremity ; is directed backward along the median line, and termi- nates at the anterior part of the prostatic portion by an enlarged extremity (a), upon which the ejaculatory ducts open by two distinct orifices. From this posterior extrem- ity several radiated folds proceed on either side, called the frana of the verumontanum, which are lost in the opening of the neck of the bladder ; they were carefully described by Langenbeck. The prostatic ducts open at the sides of the verumontanum. Structure of the Urethra. — A very fine transparent mucous membrane, of an epidermic character, lines the inner surface of the urethra ; and is continuous, on the one hand, with the mucous membrane of the bladder, and, on the other, with that covering the glans. It is also continued through the ejaculatory ducts, into the vasa deferentia and the vesiculae seminales.t The structure of the urethra, as regards the coats external to the mucous membrane, is not the same in the different portions of the canal. In the prostatic portion, we find the same elements as in the bladder, which seems as if it were continued into the cavity of the prostate. The deepest layer of the muscular coat of the bladder is prolonged between the mucous membrane and the prostate, while the other layers form different planes which penetrate into the substance of the gland. The membranous portion would be more correctly denominated the muscular part of the canal, for it is surrounded by a layer of muscular fibres. A plexus of veins sur- rounds these muscular fibres. The spongy portion Q f,fig. 182; c,fig. 187) has a similar appearance to that of the cavernous body ; it is an erectile structure, composed of a fibrous framework, formed by numerous prolongations interlaced in all directions, so as to resemble areolar tissue. It is probable that the internal coat of the veins lines all the cells, which contain more or less blood, according to the state of the penis. In the tissue of the corpus spongiosum, as well as in that of the corpus cavernosum, are found longitudinal muscular fibres, very evident to the naked eye in the larger ani- mals, and the existence of which appears to be shown by the microscope in the human subject. The structure of the glans (//) is exactly the same as that of the bulb, only its tissue is more dense. The corpus spongiosum urethrae does not communicate with the corpus cavernosum, although at first sight it appears to be nothing more than a con- tinuation of it. The blunt extremity of the corpus cavernosum is evidently embraced by the base of the glans, but no communication exists between the erectile tissue com- posing these two bodies, so that it is possible to inject them separately. THE GENERATIVE ORGANS OF THE FEMALE. The Ovaries. — The Fallopian Tubes. — The Uterus. — The Vagina. — The Urethra. — The Vulva. The genital organs of the female consist of the ovaries, the Fallopian tubes, the uterus, the vagina, and the several parts forming the vulva. With these we may include the mamma, as appendages to the generative apparatus. The Ovaries. The ovaries (ovaria), so called on account of the small vesicular ova which they con- tain, are the representatives of the testicles in the male ; the product secreted by both the one and the other is absolutely indispensable for reproduction. From this analogy between the ovaries and testes the ancients called them testes muliebres (Galen). The ovaries {a a, fig. 188) are two in number, and are situated one on each side of the uterus, in that portion of the broad ligament {d d') termed the posterior ala (i^), and be- hind the Fallopion tube. They are retained in this position by the broad ligament, and by a proper ligament called the ligament of the ovary (c). * [One of these sinuses or lacunae, larger than the rest, and situated on the upper surface of the fossa na- vicularis, is called the lacuna magna ; they appear to be mucous crypts.] t [It is prolonged into the ducts of Cowper's glands and the prostate, into the vesiculae seminales, vasa def- erentia, and tubuli seminiferi, and through the ureters into the uriniferous ducts ; in the female it also lines the vagina, uterus, and Fallopian tubes ; the whole forms the genito- urinary system of mucous membranes ; it is covered throughout with an epithelium, which, in the male generative apparatus, approaches the columnar fi>rm.] ASH SPLANCHNOLOGY. Ther situation varies at different ages, and also according to the state of the uterus. In the foetus, they are placed in the lumbar regions, like the testicles. During pregnan- cy they are carried up into the abdomen with the uterus, upon the sides of which they are applied. Immediately after dehvery, they occupy the iliac fossae, where they some- times remain during the whole period of life, being retained there by accidental adhe- sions. It is extremely common to find them thrown backward,* and adhering to the pos- terior surface of the uterus. The ovary has sometimes been found in inguinal or femoral herniae : by descending into the labia majora, they have simulated the appearance of testicles. The size of the ovaries varies according to age, and according as the uterus is gravid or unimpregnated, healthy or diseased. They are relatively larger in the foetus than in the adult ; they diminish in size after birth, again increase at the period of puberty, and become atrophied in old age. During the latter periods of pregnancy, they sometimes acquire double or triple their ordinary size. The ovaries are of an oval shape, a little flattened from before backward ; they are of a whitish colour ; their surface is rough, and, as it were, cracked, and is often covered with very dark-coloured cicatrices, which have been incorrectly regarded as remains of ruptures in their external coat, to allow of the escape of the fecundated ovum. The ovary is free in front, behind, and above, but is attached by its lower border to the broad ligament, by its outer end to the trumpet-shaped extremity of the Fallopian tube, and by its inner end to the corresponding side of the uterus, some lines below the upper angle of that organ, by means of a ligamentous cord, called the ligament of the ovary (c) ; which was for a long time regarded as a canal {ductus ejaculans), intended to convey an ovarian fluid into the uterus. The tissue of this ligament strongly resembles that of the uterus, and seems to be a prolongation from it.t Structure. — The ovary is composed externally of a dense fibrous coat, covered by the peritoneum, which adheres so closely to it that it cannot be detached ; and, internally, of a spongy and vascular tissue, the areolae of which seem to be formed by very delicate prolongations from the external coat ; in the midst of this tissue (the stroma, from arpu/xa, a bed) the Graafian vesicles are deposited. These vesicles vary in number, from three or four to fifty. The structure of the ovary is most evident in the recently-delivered fe- male. At that time its tissue, expanded, and, as it were, spongy, appears to me to re- semble that of the dartos, and is traversed by a great number of vessels. I have also seen, in recently-delivered females, the ovaries from twelve to fifteen times larger than ^ usual, and converted into a f^ac, having very thin parietes, which were easily torn ; the ovary itself was of a spongy, vascular, and diffluent texture, in the midst of which the vesicles were seen unaltered. The vesicles are nothing more than small cysts of variable size, with very thin trans- parent walls, adhering to the tissue of the ovary, and containing a limpid serosity, either colourless, or of a citron yellow. According to Von Baer, the most superficial vesicles which approach the expanded extremity of the Fallopian tube, contain a floating body, which was imperfectly seen by MaJpighi, and constitutes the germ or ovum.J I have often met with ovaries destitute of vesicles ; but then they had undergone some change, that of induration, for example. May the absence of these vesicles be regarded as a cause of sterility ■! The corpora lutea, according to the observations of Haller, consist of the remains of vesicles that have been ruptured in consequence of the act of impregnation ; they are brownish-yellow masses, of a tolerably firm consistence, and which I have found as large as a cherry-stone in females recently delivered. These bodies have been ascertained to exist in females who have never borne children, and this anomaly has been explained by supposing that they may be produced in consequence of masturbation. We would re- mark, however, that there is no constant relation between the existence of these bodies and the occurrence of fecundation. In some females who have had many children, no corpora lutea can be detected, and, on the other hand, a corpus luteum has been found in a girl of five years of age. The bloodvessels and veins of the ovary correspond exactly with those of the testicles. * The situation of the ovaries, behind the Fallopian tubes, prevents their displacement forward. t It has even been stated that this so-called efferent duct of the ovary divides into two branches, one of which opens directly into the uterus, while the other runs along- its border, and opens near the os uteri. t [The vesicles of De Graaf vary from the size of a pea to that of a pin's head ; they have two tunics, one external and vascular, the other called the ovi-capsule, which, according to Schwann, is lined internally with epithelium (membrana granulosa, Bacr). In each vesicle there is usually but one ovum, which at first occu- pies its centre, but in the mature condition approaches the inner surface of its internal coat, and, surrounded by a granular covering (tunica granulosa, Barry), is held there by retinacula {Barry). The ovum is a perfect- ly spherical body, of uniform size (about ^4'?)^^' "f ^" i"<^^ '" diameter) ; it consists of a thick but very trans- parent coat (zona pellucida, Valentin; chorion, Vl^a^ner), which surrounds the substance of the yolk ; within the yolk is situated the germinal vesicle of Purkinj<5 (about i^-^gth of an inch in diameter), and within that the germinal spot of Wagner (aboutTy^'j^-gth or g^xo^jth of an inch). The changes incidental to impregnation, according to Dr. Barry, commence in the germinal spot and vesicle. For farther information, and for a list of works upon this subject, see Mullefs Physiology, translated by Dr Baly, and Wagner's Physitlogy, transla- ted by Dr. Willis.] THE FALLOPIAN TUBES. 463 Uses. — Without precisely determining the part performed by the ovaries in reproduc- tion, it may be said that they are indispensable to that function. Extirpation of these bodies is followed by sterility. And, again, ovarian fcetation proves that fecundation may occur within the ovary. The use of the Graafian vesicles in generation is not well known.* The Fallopian Tubes. The tuhcB uterina {ff,fig. 188) are two ducts, situated in the substance of the upper margin of the broad hgament. They are "^S- 188. also called the tubae Faliopianffijt the Fal- lopian tubes, after Fallopius, who first gave a good descrip- tion of them ; they ex- tend from the upper angle of the uterus to the sides of the cavity of the true pelvis. Situation and Di- rection.— Floating, as it were, in the cavity of the pelvis, between the ovaries behind, and tlie round ligaments {g g) in front, they pass transversely out- ward, and at the point where they terminate, bend backward and inward, in order to approach the outer end of the ovary, to which they are attached by a small ligament. Each Fallopian tube is straight in the inner half of its course, but describes certain wind- ings in the remaining outer portion, which are so considerable in certain cases, and especially when the tube has been the seat of chronic inflammation or of dropsy, as to i-esemble in some degree the windings of the vas deferens. Moreover, accidental adhe- sions of the expanded extremity very frequently give it an entirely different direction from the one it usually takes. The tubes may be drawn down with tire ovaries into a hernial sac, as I have several times observed. The length of the Fallopian tube is four or five inches, but it sometimes varies on the two sides. The canal in their interior is very narrow along their inner half, but gradu- ally enlarges as it proceeds outward to their termination, which is expanded and divided into irregular fringes, like the calyces of certain flowers ; this expanded end constitutes the mouth of the trumpet, or Xhe fimbriated extremity (c) of the Fallopian tube. In order to obtain a good view of this structure, it is necessary to place the tube in water, and then a number of fringes or small shreds of unequal length will be seen floating in the liquid, and consisting of folds divided unequally, and sometimes forming two or three concentric circles. It is generally said that one of these fringes, longer than the rest, is attached to the outer end of the ovary; but this connexion appears to me to be effected by means of a small ligament. All these folded fringes terminate around a circle some- what narrower than the adjoining portion of the tube ; this circle constitutes the free orifice, or ostium abdominale of the tube. The outer portion of the tube will admit the end of a moderate-sized catheter, while the inner portion will scarcely admit a bristle. The diameter of that portion of the tube which traverses the uterine walls is capillary, and it is very difficult to detect with the naked eye its uterine orifice, or ostium uterinum (o o,fig. 189). As the canal of the tube opens into the uterine cavity on the one hand, and into the cavity of the peritoneum on the other, it forms a direct communication between the two ; and hence certain cases of peritonitis have been supposed to depend upon the passage of a fluid from the uterus into the peritoneal sac. Not very unfrequently the fimbriated orifice of the tube is ob- literated ; in this case the tube becomes dilated like a cone, having its base directed out- ward, and it also becomes much more flexuous. When opened longitudinally, and placed under water, the outer or wide portion of the tube presents longitudinal folds of unequal breadth, and touching by their free edges. There is no valve, either in the course or at the orifices of the tube. Its nanow por- tion is hard to the touch, inextensible, and closely resembles in appearance the vas def- erens ; its wide portion is collapsed, and its walls are thin and extensible. Structure. — The peritonium adheres closely to it, and forms its outer coat ; it is lined by a mucous membrane, which can be easily shown in the whole extent of the broad and folded portion, and appears to form of itself the longitudinal folds already described. This lining membrane is continuous, on the one hapd, with the uterine mucous mem- brane, and on the other, with the peritoneum, at the fimbriated extremity of the tube ; it thus presents the only example in the human body of the direct continuity of a serous * See note, p. 462. t [Literally, the Fallopian trumpets, from their expanded abdominal extremities.] 464 SPLANCHNOLOGY. and mucous membrane. Between the peritoneal and the mucous coats is found a proper membrane, which appears to be a prolongation of the tissue of the uterus, and is proba- bly muscular.* Uses. — The Fallopian tubes, which represent in the female the vasa deferentia in the male, serve not only to transmit the fecundating principle of the male, but also to con- duct the fecundated ovum into the uterus. These uses are proved by the sterility of females in whom the tubes have been tied ; and by the occurrence of tubal fcetations, in v/hich the fecundated ovum is arrested in the cavity of the tube, and there passes through the several stages of development. The fimbriated extremity of the tube is intended to embrace the ovary during the act of fecundation, and to apply itself to the spot from which the ovum is to be detached ; it follows, therefore, that any adhesion of the ovary or of the tube which prevents this, acts as a cause of sterility. The Uterus. The uterus {uter, a leather-bottle), matrix (mater), or womb, is the organ of gestation. It is situated {u,fig. 190) in the cavity of the pelvis, in the median line, between the bladder and the rectum, and is retained in that position by the round and broad ligament on each side, and by the upper end of the vagina below. The looseness and extensibility of its connexions enable it to float, as it were, in the cavity of the pelvis, and to be moved to a greater or less extent. The facility with which it can be drawn towards the vulva in certain surgical operations, and its displace- ment during pregnancy, when it rises into the abdomen, are proofs of its great mobility. Direction. — Its long axis is directed obliquely downward and backward, i. e., it coin- cides with the axis of the brim of the pelvis. Its direction is liable to frequent varia- tions, the history of which belongs to midwifery ; but one of them, viz., the obliquity downward, and from the right to the left side, is so frequent that it has been regarded as natural, and, according to some anatomists, appears to be connected with the posi- tion of the rectum on the left side of the pelvis. In pregnancy, this inclination is almost constant, and has some relation with the most usual position of the child, viz., that in which the occiput is turned towards the left acetabulum of the mother. Number. — The uterus is single in the human species ; it is double in most animals. The cases of double uterus observed in the human subject are nothing more than bifid uteri, or such as are divided by a septum : this state may exist either in the body of the uterus alone, or at the same time in the body and neck, and even in the vagina. Size. — The size of the uterus varies according to age, and certain physiological con- ditions pecuhar to this organ. It is very small until puberty, and then acquires the size which it subsequently presents. In females who have borne children it never returns to its original size. It becomes enonnously enlarged during pregnancy, or from the de- velopment of certain tumours. In old age it becomes atrophied, and is sometimes as small as it is in newborn infants. The following are the measurements of the uterus after puberty : length, two and a half to three inches ; breadth, at the fundus, sixteen to eighteen lines, at the neck six lines ; antero-posterior diameter, or thickness, six lines. f Weight. — The weight of the uterus is from six to ten drachms at puberty, an ounce and a half or two ounces in females who have had children. T have seen it from one to two drachms in aged females, in whom it had become atrophied. At the end of preg- nancy the weight of the uterus is from a pound and a half to three pounds. Form. — The uterus is shaped like a small gourd, or a pear flattened from before back- ward. It is divided into a body {u), and cervix or neck (A) ; the distinction between these two parts being established by a more or less marked constriction. Relations. — These must be studied in front, behind, on the sides, at the upper border or fundus, and at the lower or vaginal extremity. The anterior surface is covered by the peritoneum in its upper three fourths, and is in- directly in relation with the posterior surface of the bladder, from which it is often sep- arated by some convolutions of the small intestine ; in its lower fourth it is in imme- diate contact with the inferior fundus of the bladder, and is united to it by rather loose cellular tissue. The latter relation explains why cancerous affections of the uterus so often extend to the base of the bladder. The posterior surface is entirely covered by the peritoneum, and is in relation with the anterior surface of the rectum, from which it is often separated by some convolutions of the small intestine. This surface is much more convex than the anterior ; it may be examined from the rectum. Its sides are slightly concave, and give attachment to the broad ligaments (d d', d d'), which are two quadrilateral folds of peritoneum, extended transversely from the lateral * [Muscular fibres have not yet been demonstrated in the human subject, thoug-h in some animals circular and longitudinal contractile fibres have beenfound. The epithelium of the mucous membrane is columnar and ciliated : by the action of the ciUa the contents of the tubes are urged towards the uterus : Dr. Ilenle has found cilia on both surfaces of the fimbriae.! t [The body of the uterus, at its thickest part, viz., immediately below the fundus, is from eight to twelve lines thick.] THE UTEKUS. 465 borders of the uterus to the sides of the pelvis. Their upper margin is divided on each side into three folds or ridges, formed in the following manner : a posterior fold formed by the ovary (a) and its ligament (c), an anterior one by the round ligament (g), and a middle fold by the Fallopian tubes (/). Hence some anatomists have described three wings [alcB vcspcrtilionis) in each of the broad ligaments. The broad ligaments may be regarded as forming across the cavity of the pelvis a transverse septum, within which the uterus and its appendages are contained. This septum divides the cavity into two portions : one anterior, containing the bladder, the other posterior, in which are situated the rectum, and almost always some intestinal convolutions. Besides the broad ligaments, there are also the ligaments of the ovary and the round ligaments, proceeding from the sides of the uterus. The round ligaments (g g) have a filfrous appearance, but are evidently continuous with the tissue of the uterus. They arise from the side of the uterus, below and in front of the Fallopian tubes, pass upward and outward in the anterior fold of the broad ligament to the abdominal orifice of the inguinal canal, into which they enter, being ac- companied by a prolongation of the peritoneum, which forms around them a cylindrical sheath called the canal of Nuck. In females far advanced in life, this sheath may be traced as far as the external oiifice of the inguinal canal. Besides the uterine fibres which enter into its composition, the round ligament also contains a great number of veins, which may become varicose, especially near the ex-* ternal orifice of the inguinal canal, where they sometimes simulate a hernia. The upper border ox fmidits (*) of the uterus is convex, and is directed upward and for- ward ; it is covered by convolutions of the small intestine ; when not distended, it never reaches as high as the brim of the pelvis, and cannot, therefore, be felt by the fingers in the hypogastric region. The lower or vaginal extremity of the uterus, called also the os tinea, from its shape, is directed downward and backward ; it is embraced by the vagina, into which it projects, and is divided by a transverse fissure into two lips, one anterior, the other posterior. The OS tinccE is small, and perforated by an almost circular opening (w) in females who. have not borne children ; but in those who have been mothers it forms a more consid- erable projection, and its fissure is more marked and longer transversely.* In some females the os tincae is of considerable length, and, as it were, hypertrophied, although, the uterus is healthy. The anterior lip is thicker than the posterior, which is a little longer than the other. It frequently happens that in old females every trace of the lips of the os tincae disap- pears ; the orifice alone remains, and in some cases even that is obliterated. In such a case the vagina terminates in a cul-de-sac, at the bottom of which a round and yielding point may be felt. This disappearance of the two lips is much more common than the elongation of the neck of the uterus, which was pointed out by my venerable colleague, M. Lallemand. Cavity of the Uterus. — The cavity of the uterus is extremely small in comparison with the size of the organ ; its figure is that of a curvilinear triangle ; its walls are in con- tact, and are smooth, and covered with a layer of mucus. We shall examine it in the body and neck of the uterus. The cavity of the body of the uterus (u, fig. 189) is of a triangular form, and has an opening at each angle. The inferior opening (ostium internum, h) Fig lb9 establishes a free communication between the cavities of the body and neck ; it is often obliterated in old women.! The other two '' orifices (o o) are those of the Fallopian tubes; they are scarcely visible to the naked eye, and are situated at the bottom of two funnel-shaped cavities formed at the superior angles of the uterus, and constituting the remains of the division of the body of the ute- rus into two halves or cornua. This division, which is normal in many animals, is sometimes met with in the human female. Congenital deficiency of the cavity of the uterus is very rare. My colleagueTProfes- sor Rostan, kindly sent me a specimen, in which there was no trace of a cavity in the body of the uterus, although the cavity of the neck remained. The female to whom it belonged had never menstruated. It is unnecessary to say that she was barren. The cavity of the neck {h to n) represents a cylinder flattened from before backward, and has upon its anterior and posterior walls certain ridges, which form upon each wall' along the whole length of the neck a tolerably regular median column, from which pro- ceed, at more or less acute angles, a certain number of smaller columns, t which pro- ject to a greater or less degree. The whole appearance resembles that of a fern-leaf, * I have seen the os tines lacerated and fissured in different directions, in consequence of parturition. t This obliteration, which causes retention of mucus and blood, and, consequently, distension and ramol-- lissement of the body of the uterus, is so common that M. .Mayer regards it as normal. t These ruga;, which vary considerably in their arrangement, have been described in detail by Haller, Bo-- yer, and others. N N N 466 SPLANCHNOLOGY. and has been called the arbor vita. It generally disappears after the first labour, at least only traces of it are left. Nevertheless, it is not unfrequently found perfect, even after several accouchements — a circumstance of some importance in legal medicine. The internal surface of the body of the uterus is much more vascular than the neck. This difference is particularly observed in females who have died during a menstrual period, in whom the vessels of the body of the womb are much developed, and that or- gan itself is swollen and softened, while the cervix retains its accustomed whiteness and consistence. Another character of the uterine cavity is the existence of a gi-eater or less number of transparent vesicles, which were mistaken by Naboth for ova {ova of Naboth), but are only muciferous foUicles. They exist both in the body and neck of the uterus, but are more numerous in the neck, near the vaginal orifice, and only become apparent when the mucus accumulates in them from obliteration of their orifices. They are sometimes much enlarged, and have then given rise to the opinion that some more serious disease has existed. The orifices of the uterine sinuses, described by the older anatomists at the fundus of the uterus, cannot be detected. They are only to be seen after dehvery in the situa^ tion where the placenta had been attached. The parietes of the unimpregnated uterus are from four to six lines in thickness. The thinnest part is at the entrance of the Fallopian tubes, where they are not more than two lines thick. The parietes of the cervix are thinner than those of the body. Structure of the Uterus. — The constituent parts of the uterus are, a proper tissue, an external peritoneal coat, an internal mucous.membrane, and some vessels and nerves. The proper tissue is of a grayish colour, very dense and strong, and creaks under the knife hke cartilage. The body appears less consistent than the neck, but this depends upon the fact of its being more frequently the seat of sanguineous congestion. It is com- posed of fibres, i. e., it has a linear arrangement. It may be asked, with regard to the nature of these fibres, Do they consist of fibrous tissue 1 are they muscular, or are they analogous to the yellow tissue of the arteries 1 The following considerations will de- termine this question : The walls of the unimpregnated uterus appear to be composed of a fibrous tissue, trav- ersed by a great number of vessels. During pregnancy, or in consequence of the devel- opment of tumours, or the accumulation of fluid in the cavity of the uterus, its proper tissue acquires all the properties of the muscular tissue, as it exists in the viscera of organic life, and, like it, is endowed with contractility. Can, therefore, the presence of a fcetus or a foreign body in the uterus cause a transformation in the tissue of that organ 1* Assuredly not ; but the great influx of blood into the uterus, and the conse- quent distension and development of its fibres, reveals a structure which before was con- cealed by the state of condensation and atrophy kept up by inactivity. This view is fully confirmed by the microscopical observations of Rcederer, and the chemical experiments of Schwilgue ; and also by the results furnished by comparative anatomy, which has shown circular and longitudinal muscular fibres in the uteri of some animals, even when not in a gravid condition, t The nature of the fibres of the uterus being determined, we may now examine their direction. Some anatomists agree with Malpighi and Monro, that they have no regu- larity in their disposition, but are interlaced in an inextricable manner. It must be con- fessed that, in the unimpregnated uterus, such is the case ; but during gestation, the ar- rangement of the greater number of fibres can be traced. t In the body the external thin layer is composed of two median vertical fasciculi, one on each surface of the uterus ; of another fasciculus occupying the fundus, and of some oblique ascending and descending fibres, which converge towards the Fallopian tubes, the round ligaments, and the ligaments of the ovaries,' which contain prolongations of these fibres.^ This first, or superficial layer, belongs exclusively to the body of the ute- rus. The deep layer of the body consists of two series of circular fibres ; each series forming a cone, the apex of which corresponds to the Fallopian tube, while the base is directed towards the median hne, and is there blended with that of the opposite side. The neck is composed entirely of circular fibres, which intersect each other at very acute angles. The facts furnished by comparative anatomy perfectly accord with the preceding de- scription Thus, in the uterus of a sow, which had littered, I found that the cervix was composed exclusively of circular fibres ; and that the cornua (aduterum of M. Geoffrey * I conceive that I have proved by facts, that only three tissues, viz., the muscular, the nervous, and the glandular, are never the products of organic transformations. — {Vide Essai sur V Anatomic Pathol, 1816.) t [The muscular fibres of the gravid uterus have been described by Dr. Baly (translation of Miiller's Phys- iology). Like other inorganic muscular fibres, they have no transverse stnie ; they are much broader than those of the alimentary canal, and taper very much at their extremities, which are sometimes split into two or three points : the corpuscles upon them are comparatively small.] t Hunter, Anatomia uteri. Rosemberger in Schlegel, Syllog. Oper. Minor, ad Artem Obstetric. Lipsi^, torn, ii., p. 296. Mtiinoire pr6sent6 4 rAcad6mje de M6decine, par Mme. Boivin. Oct., 1821. t) I. e., in the gravid state. THE UTERUS. 467 St. Hilaire), which represent the body of the uterus of the human female, were formed by two layers of fibres, one external and longitudinal, the other deep and circular. From this arrangement, we may therefore conclude that the human uterus results from the union of two cornua, which communicate directly with each other, instead of opening separ- ately into the cavity of the cervix. When examined in the state of pregnancy, the tissue of the uterus is found to be trav- ersed by venous canals, or uterine sinuses, which are of very considerable size, especial- ly opposite the attachment of the placenta. This great number of vessels gives to the tissue of the uterus the appearance of an erectile or cavernous structure, having muscu- lar parietes.* The External or Peritoneal Coat. — The peritoneum, after covering the posterior surface of the bladder, is reflected upon the anterior surface of the uterus, of which it covers only the upper three fourths, the lower fourth being in immediate contact with the blad- der. At the fundus of the uterus, it passes to the posterior surface, which it covers en- tirely, is prolonged a short distance upon the vagina, and is then reflected upon the rec- tum. The broad ligaments are formed by a transverse duplicature of this coat. Two falcifomi folds, formed by this membrane between the bladder and the uterus, are called the vesico-uterine ligaments, and two others, between the uterus and the rectum, are na- med the recto-uterijie ligaments. The peritoneum adheres very loosely to the borders of the uterus, but much more closely as it approaches the median line. When enlarged during pregnancy, the uterus becomes covered with the peritoneum of the broad ligament, a species of mesentery, the folds of which become separated, and yield to the increasing size of the organ. The Internal or Mucous Membrane. — The existence of a mucous membrane upon the internal surface of the uterus has been denied by those anatomists who have examined it after parturition, especially by Morgagni and Chaussier, and so, also, by those who do not admit the presence of a mucous membrane unless it can be demonstrated over a certain space. But the existence of a mucous membrane on the internal surface of the uterus appears to me incontestably proved by the following considerations : First, every organized cavity which communicates with the exterior is lined by a mu- cous membrane ; why, therefore, should the uterus form an exception to this rule ! Sec- ondly, by dissection it is shown that the mucous membrane of the vagina is continued into the neck of the uterus, and then into the body ; but in this latter situation it is des- titute of epithelium.! Notwithstanding the difficulty of dissecting this membrane, on account of its tenuity, and its close adhesion to the tissue of the uterus, its presence is demonstrated by the following observations : Under the microscope, the internal surface of the uterus presents a papillary appearance, but the papilla; are very small ; it is pro- vided with follicles or crypts, from which mucus may be expressed by a number of points, and which form small vesicles when distended with mucus, in consequence of obstruction or obliteration of their orifices. Thirdly, it is extremely vascular, and pre- sents a capillary network of the same appearance as that of the other mucous mem- branes ; and, lastly, it is constantly lubricated with mucus. Pathological observations also show that the internal surface of the uterus, like all mucous membranes, is liable to spontaneous hemorrhages from exhalation, without breach of continuity, to catarrhic secretions, and to those growths which are denominated mucous, vesicular, and fibrous polypi : and it is generally admitted that, where there is an identity of disease, there is also identity of structure. During pregnancy, the elements of the mucous membrane are separated ; the vessels become penicillate, and greatly increased in size ; but in proportion as the uterus returns to its original dimensions, the mucous membrane regains its primitive form, and its dis- sociated elements approach each other. It seems as if this membrane was destroyed by a true exfoliation, and then entirely reproduced. The arteries of the uterus are derived from two sources : the principal, called the ute- rine, arise from the hypogastric ; the others proceed from the spermatic or ovarian ar- teries to the borders of the uterus, and are distributed upon it : both sets are very tor- tuous. The veins are remarkable for their enormous size during pregnancy and after parturi- tion. The term uterine sinuses has been given to the large veins which are then found in the substance of the organ ; and this term is not altogether without foundation, for these venous canals are formed by the lining membrane of the veins which adlieres to the proper tissue of the uterus, just as, in the sinuses of the dura mater, it adheres to the fibrous tissue of that membrane. The lymphatics, which have been well examined only during pregnancy and after par- * This combination of the erectile and muscular tissues is found in the penis of the horse, and perhaps, also, in that of man. t [The mucous membrane of the uterus contains numerous tubular glands, or crypts, resembling-, in form and direction, the tubuli of the stomach, and the crypts of Lieberkuehn, found in the intestinal canal. The epithelium of this mucous membrane is, according to IIenl6, columnar, and also ciliated from the fundus to tixe middle of the cervix uteri ; below that point it passes into the scjuamous form of epithelium found in the vagina and ou the labia.] 468 SPLANCHNOLOGY. turition, at which time I have often seen them full of pus, are, like the veins, extremely large (see Anat. Path., avec planches, liv. xiv.); they form several layers in the sub- stance of the uterus, the most superficial of which is the most developed. They termi- nate in the pelvic and lumbar lymphatic glands ; some accompany the ovarian veins. The nerves, as seen in the pregnant condition, have been well described and figured by Tiedemann. Some of them are derived from the renal plexus, and surround the ovarian arteries ; others proceed from the hypogastric plexus, and are formed by some of the anterior branches of the sacral nerves, and by branches from the lumbar ganglia of the sympathetic. Development. — It is generally agreed that the body of the uterus is always bifid, or two- horned, in the embryo, up to the end of the third month ; and that, towards the end of the fourth month, the two halves are united to form a single cavity. I have not observed this in the earhest periods of intra-uterine life. During fcetal life, the uterus, instead of presenting the same form as it subsequently possesses, is decidedly larger at the neck than in the body : at this period the broadest part of the uterus is its vaginal extremity. After birth, and up to the time of puberty, the development of the uterus is almost stationary ; so that, according to the observations of Rcederer, which are confirmed by Professor Duges, it is from twelve to fourteen hues long in the new-born infant, and only an inch and a half at ten years of age. At puberty, the uterus rapidly acquires its full dimensions, and at the same time be- comes the seat of a periodic and sanguineous exhalation, the occurrence of which con- stitutes menstruation. In old age, the uterus becomes atrophied, and altered in shape ; the cervix and body are separated by a much more decided constriction. These two parts of the uterus seem to become more independent of each other. The lips of the os tincae are general- ly efihced in old women. The tissue of the body preserves its softness, while that of the neck acquires an extreme density. The situation of the uterus is very different at different ages. In the foetus it projects beyond the brim of the pelvis, and is in the abdominal cavity, after birth, and in conse- quence of the development of the pelvis, it seems gradually to sink into that cavity. At the age of ten years, the fundus of the uterus is on a level with the brim ; afterward it is lower down. In old women it is generally inclined to one side, or reversed upon the rectum. Functions. — The uterus is the organ of gestation ; the fecundated ovum is deposited in its cavity, and there meets with the most favourable conditions for its development. The uterus is also the principal agent in the expulsion of the fcetus. The Vagina. The vagina is a membranous canal, extending from the vulva to the uterus ; it is the female organ of copulation, and also forms the passage for the menstrual blood, and the product of conception. It is situated in the cavity of the pelvis between the bladder and the rectum, and is held in that situation by tolerably close adhesions to the neighbouring parts, but stiU is so loose that it can be everted like the finger of a glove. Direction.— It is directed obliquely forward and downward, i. e., it coincides with the axis of the outlet of the pelvis ; and as the direction of the uterus corresponds with the axis of the brim, these two parts form an angle or curvature with each other, having its concavity directed forward. Shape and Dimensions. — The vagina is shaped like a cylinder, flattened from before backward, and having its walls in contact, as may be seen upon applying the speculum. It is from four to five inches long ;* sometimes it is much shorter : I have seen it as short as an inch and a half This congenital shortness must be distinguished from the apparent shortness produced by prolapsus uteri. The vagina is not of the same diameter throughout. Its lower orifice is the narrow- est part, while its upper extremity is the widest. In females who have borne children, the bottom of the vagina forms a large ampulla, in which the speculum may be moved about extensively, and in which, also", a considerable quantity of blood may accumulate during hemorrhage. It is, moreover, a dilatable canal, as is proved during parturition ; and is, at the same time, elastic, and contracts after delivery, so as almost to return to its original dimensions. It would appear, also, to be capable of a vermicular contraction. Relations. — In front, where it is slightly concave, it corresponds to the inferior fundus of the bladder, to which it is united by very dense filamentous cellular tissue, resembling the dartos ; it cannot be separated from the urethra, which appears to be hollowed out of the substance of its walls. The close adhesion of the vagina to the bladder and ure- thra accounts for these latter organs always following the uterus in its displacements. Behind, the vagina corresponds with the rectum, through the medium of the peritoneum in its upper fourth, and immediately in its lower three fourths. It adheres to the rec- * iFrom the nature of the curve formed by the vagina, its anterior wall is shorter than the posterior.] THE VAGINA. 469 turn by cellular tissue resembling the dartos, and analogous to that existing between it and the bladder, but much looser, so that the rectum does not follow the vagina in its displacement. The sides of the vagina give attachment to the broad ligaments above, and to the superior pelvic fascia and the levatores ani below, and they are in relation with the cellular tissue of the pelvis and with some venous plexuses. Internal Surface. — The internal surface of the vagina is covered with an epithelium, which can be very easily demonstrated, and which is prolonged as far as the os uteri, where it terminates by a sort of indented margin, in the same manner as the epithelium of the cEsophagus ceases at the stomach.* This surface presents on both walls, but es- pecially in front and near the orifice of the vulva, some transverse rugae, or, rather, prominences, which very nearly resemble the irregular ridges upon the palate ; they all pass from a median prominent line, which is often prolonged like a median raph6 along the whole anterior wall of the vagina ; the raphe on the posterior wall is not so well marked. These two median raphes are called the columns of the vagina. They are the remains of the median septum, which generally coexists with a bifid uterus, but ex- ists sometimes independently of it. The transverse rugae of the vagina are very numerous in the new-born infant and in virgins ; they are partially effaced after the first labour, at the upper part of the vagina, but always remain at the lower part. These rugaj are not folds, and do not appear to assist in the enlargement of the vagina. The up-per extremity of the vagina embraces the neck of the uterus, upon which it is prolonged without any line of demarcation, and forms a circular trench around the os tincee, which is deeper behind than in front. The lower extremity, or opening into the vulva, presents a corrugated transverse pro- jection in front, which is exposed by separating the labia and nyinphse ; it narrows, and seems even to close the entrance of the vagina. In virgins, the orifice of the vulva is provided with a membrane, concerning the form and existence of which there have been numerous disputes ; it is called the hymen, and is a sort of diaphragm interposed between the internal genitals on the one hand, and the external genitals and urinary passages on the other. This membrane is of a crescentic shape, having its concavity directed forward, and closing up the posterior and lateral parts of the vagina: it sometimes forms a complete circle, perforated in the centre. Its free margin is fringed ; it varies in breadth in different individuals, and thus regulates the dimensions of the vaginal orifice. The hymen sometimes forms a complete mem- brane, constituting what is called imperforate vagina. The hymen is composed of a duplicature of mucous membrane, varying in strength, and containing within it some cellular tissue and vessels. The debris remaining after its laceration constitute the carunculm myrtiformes, which vary in number from two to five. Structure. — The walls of the vagina consist of an erectile spongy tissue interposed be- tween two very strong fibrous layers, of which the external is the thicker. Around this erectile tissue we find a tolerably thick layer resembling the tissue of the dartos con- densed. I cannot agree with some anatomists in admitting an identity of structure in the walls of the vagina and uterus, for in no case does the vagina assume a muscular character like the latter organ. From the presence of the dartoid tissue an obscure ver- micular movement may take place, and assist the elasticity of the walls of the vagina. The posterior wall and the upper part of the anterior wall are thin ; the vagina is very much thicker opposite the urethra, which seems to be hollowed out of its substance, and terminates by a rugous enlargement, which forms, at the entrance of the vagina, the pro- jection already mentioned, and which is only a very dense spongy tissue. The mucous membrane of the vagina is remarkable for the thickness of its epitheli- um,! for its close adhesion to the proper membrane, and for its highly developed papillae, especially at the entrance of the passage, where the rugaj are nothing more than papilla in an exaggerated form. The mucous follicles can be easily demonstrated. The Bulb of the Fa^wia.— Besides the spongy expansion at the orifice of the vagina, there is in front and on each side of this orifice an enlargement or cavernous body, occu- pying the interval between the entrance of the vagina and the roots of the clitoris. It is not very thick in the middle, where it is placed between the meatus urinarius and the union of the roots of the clitoris, but gradually enlarges from this point, and terminates below, upon each side of the vagina, by an enlarged extremity. The posterior wall of the vagina is the only part in which it does not exist. In position, as well as shape, it resembles the bulb of the urethra in the male. J The Constrictor VagincB. — This consists of two muscles, one on each side of the ori- fice of the vagina, the arrangement of which very nearly resembles that of the bulbo- * [In both of these situations the epithelium does not cease, but is merely changed in its character (see note, p. 467).] t [The epithelium in the vagina, and also in the vulva, is .squamous.] t In one subject, on the outer side of this vaginal bulb, I found a smooth sero-fibrous pouch, containing a transparent mucous fluid. A narrow canal, proceeding from this pouch, passed directly towards the entrance of the vagina. I could not find the orifice of this canal, which was probably obliterated. The same disposi- tion existed on both sides. 470 SPLANCHNOLOGY. cavemosus in the male. Each muscle commences in front of the rectum, by an inter- lacement of fibres common to it, to its fellow of the opposite side, and to the sphincter ani, passes forward under the form of a flattened band, and terminates upon the sides of the clitoris, a portion being continued above it, and blended with the suspensory hga- ment of that body. Relations. — It is covered on the outside by the skin and the fatty cellular tissue of the labia majora ; it corresponds on the inside with the bulb of the vagina, which it must strongly compress. The proper vaginal arteries arise from the hypogastric. The uterine arteries also send numerous branches to the vagina. The veins are very numerous, form plexuses, and terminate in the hypogastric veins. The nerves are derived from the hypogastric plexus. Development. — The rugae of the vagina are not visible until about the end of the fifth month of intra-uterine life ; from the sixth to the eighth they become much more devel- oped than they are subsequently. The transverse rugae are visible in the whole length of the vagina, and are placed closely to each other. The hymen does not make its ap- pearance until about the middle of fcetal life ; it is directed forward, and is rough and jagged. It is always present. The Urethra in the Female. This canal, which is, as it were, hollowed out of the anterior wall of the vagina, dif- fers considerably from the male urethra, of which it represents the membranous portion only. It is about one inch in length. It is very difficult to determine its diameter, on account of its dilatability ; but it is about three or four lines when quite undilated. Its lower end is somewhat contracted. It is directed obliquely downward and forward, and is slightly concave in front. Relations. — Anteriorly, while behind the symphysis, it is in contact with the cellular tissue of the pelvis ; opposite the symphysis, it is in relation with the angle of union of the two crura of the clitoris. The pelvic fascia, or, rather, the anterior ligaments of the bladder, form a half sheath for it above, but are separated from it by numerous venous plexuses. Posteriorly, the canal is so closely united to the vagina, that it is impossible to separate them. The vesical orifice of the female urethra is similar to that of the male, only there is no prostate gland. The internal surface is of a deep colour, and is remarkable for certain longitudinal folds or parallel ridges, the majority of which are not effaced by distension ; one of these folds is in the median line of the lower wall of the canal. We also find the orifices of mucous crypts or lacunae, and some parallel longitudinal veins. Structrirc. — It is muscular and erectile, like the membranous portion of the male ure- thra. It is surrounded by a thick layer of circular muscular fibres, which seem to be continuous with the fibres of the bladder, some of the longitudinal fibres of that organ being prolonged upon the outside of these.* A thin layer of spongy or erectile tissue lies subjacent to the mucous membrane, which is very thin. The Vulva. ^ Under the term vulva we include all the external genitals of the female, viz., the mens Veneris, the labia majora and minora, the clitoris, and the meatus urinarius, to which we may add the orifice of the vagina already described. The mons Veneris is a rounded eminence, more or less prominent in different individ- uals, situated in front of the pubes, and surmounting the vulva ; the prominence of this part is owing partly to the bones, and partly to a collection of fatty tissue beneath the skin ; it is covered with hair at the time of puberty. The labia majora are two prominent cutaneous folds, which form the limits of an an- tero-posterior opening, by most anatomists named the vulva. They are flattened trans- versely, and are thicker in front than behind ; their external surfaces are covered with hairs ; their internal surfaces are moist and smooth, and in contact with each other ; their free borders are convex, and provided with hair ; their anterior extremities are con- tinuous with the mons Veneris ; their posterior extremities unite to form a commissure called the fourchette, which is almost always lacerated in the first labour. The interval between the fourchette and the anus constitutes the perineum, which is generally from * [The female urethra perforates the triangular lig^ament precisely in the same way as the membranous por- tion of the urethra in the male ; and, moreover, between the two layers of the ligament it is surrounded by mus- cular fibres corresponding exactly with the compressor urethra: in the male sex. The vertical fibres, or Wil- son's muscles, were noticed by hira Ooc. cit.), descending from the symphysis, separating on the urethra, and passing around it : the transverse fasciculi, which are often very large, form together the depressor urethra of Santorini, and were described and figured by that author {Ohs. Anat.) as arising by a broad tendon from the lower part of the rami of the pubes, above the erectores clitondis, passing obliquely upward and inward, and uniting with each other above the urethra. Mr. Guthrie has sliown [loc. cit.) that the relations of the verti- cal and transverse fasciculi to each other, to the urethra, and to the layers of the triangular ligament, are pre- cisely the same as in the male.} THE VULVA. 471 feight to ten lines long. The interval between the fourchette and the entrance of the vagina is called the fossa navicularis. The constituent parts of the labia majora are, a cutaneous layer, a mucous layer, both provided with numerous sebaceous follicles.* In fat persons, a great quantity of adipose tissue, a layer of dartoid tissue next the mucous membrane, and some arteries, veins, lymphatics, and nerves. They are therefore very analogous to the scrotum in the male, and, like it, are liable to serous infiltration in anasarca. The labia mi7iora, or nymphcz, are seen after separating the labia majora, under the form of two layers of mucous membrane ; they are narrow behind, where they commence upon the inner surface of the labia majora, and they enlarge gradually as they converge towards each other in front. At the clitoris they become sligiitly contracted, and bifur- cate before their termination. The lower division of the bifurcation is attached to and continuous with the glans of the clitoris ; the upper division unites with that of the op- posite side, and forms a hood-like fold above that body, called the preputium cUtoridis. The nymphae are provided with very large crypts, which are visible to the naked eye, and secrete an abundance of sebaceous matter. They vary much in size, according to age : thus, in new-born infants, they project beyond the labia majora, principally on ac- count of the imperfect development of the latter. They also vary in different individ- uals : in some females being extremely small, and in others always projecting beyond the labia majora ; and, lastly, in different countries ; for in certain African nations, among the Hottentots, for example, they are of a disproportionate length, and constitute what is called in females of that race the apron. The clitoris is an erectile apparatus, forming a miniature representation of the corpus cavernosum of the penis. Its free extremity is seen in the anterior part of the vulva, about six lines behind the anterior commissure of the labia majora, and resembles a tu- bercle situated in the median line, covered, as by a hood, with the upper divisions of the bifurcated nymphaj, and continuous with the lower divisions of the same. This tuber- cle, which, though imperforate, has been compared to the glans penis {glans cUtoridis), is generally very small. Sometimes, however, it is very long, so as to have excited a sus- picion of the existence of hermaphrodism. In one instance that came under my obser- vation, the free part of the clitoris was two inches long, and extremely slender. Like the corpus cavernosum in the male, the clitoris arises from the ascending rami of the ischia by two roots, which expand and converge until they arrive opposite the symphysis, where they unite and form a single corpus cavernosum, flattened on each side ; this, after passing for some lines in front of the symphysis, separates from it, and forming a curve with the convexity directed forward and upward, and the concavity downward and backward, gradually becomes smaller towards its free extremity. It has a suspensory ligament precisely resembling that of the penis, and ischio-caver- nosi muscles, similar to, but smaller than those of tlie male. We have already said that the constrictor vagina;, which represents the bulbo-cavernosi of the penis, has a similar arrangement to those muscles, i. «., it passes upon the sides of the clitoris, and then be- comes continued on to its suspensory ligament. The last circumstance which completes the analogy between the clitoris and the corpus cavernosum of the penis, is the reception of the canal of the urethra into the V-shaped interval formed by the union of the two crura of the clitoris. The corpus cavernosum of the clitoris forms a longitudinal ridge between the labia ma- jora, extending from the anterior commissure to the glans of the clitoris. The Meatus Urinarius. — About an inch below and behind the clitoris, we find in the median line, immediately above the projecting margin of the opening of the vagina, tte meatus urinarius, or the orifice of the urethra, which constantly appears closed. The Mucous Membrane of the Vulva. — The mucous membrane lining the vulva is con- tinuous, on the one hand, with the skin at the internal surface of the labia majora, and with the mucous membrane of the vagina on the other ; upon the labia majora and nym- phae it has a great number of sebaceous follicles visible to the naked eye, and yielding a cheesy, odorous secretion ; and also mucous follicles, which are most numerous near the meatus urinarius, and open into culs-de-sac, the orifices of which are visible to the na- ked eye, and are often large enough to admit the blunt extremity of a probe. Development. — In the foetus th.e labia majora are small, and separated from each other by the nymphae, which are much larger in proportion, and also by the clitoris, which pro- jects beyond them to a greater extent in the earlier periods of development. This pre- dominance of the clitoris is still so decided at birth, that it has occasioned mistakes con- cerning the sex of the infant. THE MAMM^. Number. — Situation. — Size. — Form. — Structure. — Development. The mammcE or breasts {jiaarb^, from nd(j, to seek eagerly, because the infant seeks * It is not rare to see small and very short hairs growing from the sebaceous follicles on the inner surface of the labia majora ; they are analogous to those of the carunculse lachrymales. 472 SPLANCHNOLOGY. them for the milk) are glandular appendages of the generative system, which secrete the milk, and even after birth establish intimate relations between the mother and the infant. The important office performed by the mammaj has led zoologists to arrange in the same class, under the term mammalia, all animals having an apparatus for lactation. We may mention here another character peculiar to this class of animals, because it is in- timately connected with the existence of mammae, viz., that aU mammalia are vivip- arous, that is to say, give birth to their young freed from all their fcetal envelopes. The mammce exist in both sexes, but are rudimentary and atrophied in the male, and belong essentially to the female. Number. — They are two in number in the human species, which is uniparous ; in the lower animals they are generally double the number of the young. Examples of three or four mammag in the human subject are very rare, and the supernumerary mammae are generally nothing more than simple nipples, or, rather, masses of fat. Situation. — They are situated on the anterior and upper part of the chest, the trans- verse enlargement of which in the human subject is so favourable to their development. In the lower animals they occupy the abdominal region. They are situated on each side of the median line, over the interval between the third and the seventh ribs. They are therefore placed at the same height as the arms, and occupy this region, says Plutarch, in order that the mother may be able to embrace and support her infant while she is suckling it. Size. — In the male they are rudimentary during the whole of life ; in the female until the period of puberty only, when they become much enlarged as the generative appara- tus is developed more completely. They again increase in size during pregnancy, and especially after delivery ; they become atrophied in old age. In some females who are still young, the size of the mammae by no means corresponds to their stature, strength, and soundness of constitution ; while, on the other hand, it is not uncommon to see thin, phthisical individuals with very large breasts. In judging of the size of the mammae, we must not confound that depending upon the gland itself with that due to fat. The lar- gest breasts are not always those which furnish the most milk, because their extreme size often depends on an accumulation of fat, the gland itself being small. The left mam- ma is almost always a little larger than the right. Form. — The mammae represent a semi-sphere surmounted by a large papilla called the iiipple. The skin covering the mamma is remarkably delicate. Surrounding the nipple is an areola or aureola of a pinkish hue in young girls, but of a brownish colour in most females who have borne children ; it has also a rough appearance, owing to a number of sebace- ous glands, which yield a kind of waxy secretion that prevents the irritating action of the saliva of the infant. Morgagui, Winslow, and Meckel state that they have observed milk to escape from them ; but if there was no error in their observations, it must be admitted that, by some unusual anomaly, a lactiferous duct opened at the side of one of these little glands. The mammilla or nipple is of a pinkish or brown colour, rough, and, as it were, crack- ed at the summit, and capable of undergoing a sort of erection ; it varies in form and size in different subjects ; it is either cyhndrical or conical, and sometimes so short that the lips of the infant cannot lay hold of it ; in certain cases it is even depressed. In the centre of the nipple we observe one or more depressions, in which the lactiferous ducts open by a variable number of orifices. The papilla is provided also with a great number of sebaceous glands having the ap- pearance of tubercles, and secreting a substance which prevents the nipple from being chapped by the act of sucking and the sahva of the infant.* Structure. — The breasts consist of the mammary glandular tissue and of fat. The Mammary Gland. — When freed from the fat by which it is surrounded, the mam- mary gland appears like a mass flattened from before backward, and thicker in the cen- tre than at its circumference, which is irregular, but less so on the inside than on the outside. Its base, which is plane, and even slightly concave, rests upon the pectoralis major, and sometimes beyond it upon the serratus magnus ; a continuation of the fascia superficialis separates it from these muscles, to which it adheres by very loose serous cellular tissue only, and hence it is very movable. The cutaneous surface of the mammary gland is very unequal, and forms alveoli filled hy fat, by which means the inequalities are concealed. The proper tissue of the gland is considerably denser than that of most glandular or- gans. It should be examined both during lactation, and when that function is not being performed. In the absence of lactation, the gland has the appearance of a very compact, whitish, * [Sir A. Cooper has described numerous cutaneous papillae upon the nipple and areola ; they are highly vascular and nervous. He has also shown that the glands found in the areola and at the base of the nipple have branched ducts, endinfj in blind extremities : in the female, from one to five open on each tubercle. — \Anatomy of the Breast, 1840.)] THE MAMM^. 473 fibrous tissue, divided into unequal lobes, which cannot be compared to anything better than to certain fibrous tumours of the uterus. The granular structure proper to the tis- sue of glands is not visible during this state. During lactation, the granular structure becomes very evident. The following are the results of my observations respecting it at this period : The glandular granules or lobules are united into small clusters, forming flattened lobes, placed one upon another. From each httle lobe proceeds an excretory duct, which may be recognised by its white colour, is easily injected, and is formed by the union of a number of smaller ducts cor- responding to the number of lobules. Having had an opportunity of dissecting the mam- ma of a female recently delivered, in which the cellular tissue between the lobules was infiltrated with serum, the lobules themselves, as it were, dissected, and the lactiferous ducts injected with yellowish coagulated milk, I found that some of the lobules were iso- lated, and, as it were, pediculated, while others were collected into regular or irregular clusters. In one of these clusters the lobules had a circular arrangement, small ducts proceeded from each lobule, and, passing from the circumference towards the centre of the circle like radii, opened into a common efferent duct, which issued from the central point. Another cluster was elongated and swollen at intervals, and in the centre was a duct which received the smaller ducts from the several lobules. Each lobule had a central cavity, from which a worm-shaped mass of coagulated caseous matter could be expressed. When examined by the simple microscope, the parietes of these cavities had a spongy aspect hke the pith of the rush, a character which I have already noticed as belonging to all glandular organs.* The Fibrous Tissue of the Mamma. — Besides the lobules, a large quantity of fibrous tis- sue also enters into the structure of the gland, forms a complete investment for it, and then sends more or less loose prolongations into its substance, and unites the lobes to- gether. It is to the great quantity of fibrous tissue that the hardness of the mammary gland is to be ascribed. Sometimes the enlargement of the mamma at the time of pu- berty is confined entirely to the fibrous tissue ; in such a case, the organ may acquire an enormous size, the glandular tissue disappears, and the mamma is transformed into a many-lobed fibrous mass, which has been sometimes mistaken for a degenerated lipoma. The Adipose Tissue. — The alveoli on the outer surface of the mamma are filled with masses of fatty tissue, which are separated by fibrous laminae extending from the gland to the skin. The cells in which these masses are contained do not communicate with each other, and hence the frequency of circumscribed abscesses in the mamma. The relative quantities of fat and glandular tissue have an inverse ratio to each other. The great size of the mammae in some men is owing to development of the fatty tissue. Haller says that it is an essential element in the structure of the gland, and that he has several times seen lactiferous ducts arise from it. The Lactiferous Ducts. — If the mamma of a female who has died during lactation be divided, the milk will be seen to exude from a number of points, as from the pores of a sponge ; these points correspond to sections of the thin, whitish, semi-transparent ex- cretory ducts of the mammary glands, which are called lactiferous, or galactophorous ducts. They arise from the lobules, and perhaps, also, from the fatty tissue, as was thought by Haller ;t they unite successively like the veins, converge from the circumference to the centre, traverse the substance of the gland, and at length form a variable number of ducts, which reach the centre of the gland, opposite the areola. In that situation they acquire their utmost size, and form considerable ampullae or dilatations, between which scarcely any intervals are left. According to some anatomists, the number of these am- pullae is not less than twenty; I have never counted more than ten. They are of un- equal size. At the base of the nipple they become contracted, straight, and parallel, and open upon its summit by orifices, which are much narrower than the ducts themselves. Thus, then, although there is no reservoir properly so called in the mammary gland, the ampullae above described may be regarded as such ; with this difference only, that in- stead of one reservoir there are several. The lactiferous ducts, moreover, are surrounded, both in the mammilla and opposite the areola, with a dartoid tissue, the existence of which explains the state of orgasm and erection of the nipple, as well as the expulsion of the milk in a jet when the gland is excited. There is no trace of the cavernous structure described by some anatomists as existing in the nipple. The lactiferous ducts do not communicate with each other in any part of their course ; neither in their terminating canals, nor in their ampullae, nor in their smaller ducts ; this may be proved by mercurial injections, or by filling each duct with a differently-coloured injection. The mammary gland, like most others, is therefore divided into a certain number of distinct compartments, which may perform their functions independently of each other. Injections also show that the lactiferous ducts have no valves. Their structure is little * [The ultimate structure of the mammary gland consists of the terminations of the lactiferous ducts in clusters of microscopic cells within each lobule ; these cells are round, and have a diameter twenty times as great as that of the capillaries which ramify upon them. t (Our present knowledge of the minute structure of glands has proved the inaccuracy of this supposition ol HallerJ O o o .4714 SPLANCHNOLOGY. known. It is generally admitted that they consist of an internal memhrane continuous "With the skin, and which must be analogous to the mucous membranes, and of an exter- nal fibrous coat, which I am inclined to regard as analogous to the tissue of the dartos. The arteries of the mamma arise from the thoracic, especially that which is called the external mammary, also from the intercostals and the internal mammary. The veins are very large, and of two kinds, sub-cutaneous and deep ; the latter accom- pany the arteries, the former are visible through the skin. The lymphatics are very numerous, and enter the axillary glands. The older anato- mists admitted a direct communication between the thoracic duct and the glandular tis- sue of the breast ; but this opinion, suggested by the resemblance in colour between the chyle and milk, is altogether erroneous. The nerves are derived from the intercostals and the thoracic branches of the brachial plexus. Development. — The mammae become visible after the third month of intra-uterine life. At birth they are more developed than at a subsequent period, and contain a certain quantity of milky viscid fluid. Until puberty the manmiae of the two sexes differ only in the nipple being larger, and the gland somewhat larger in the female than in the male. In the female, at puberty, they gradually acquire the size which they subsequently re- tain, their development coinciding with that of the genital organs. Most commonly the change precedes, but sometimes it follows, the appearance of the menses. The mammae of the male also participate in the development of the generative appara- tus at the time of puberty, and in some subjects even a milky secretion is formed.* The mammae become atrophied in old age, and are sometimes replaced by fibrous tis- sue ; in several old women I have found the lactiferous ducts distended with a dark, in- spissated mucus, of a gelatinous consistence which has enabled me to trace the ducts even to their most delicate radicles. THE PERITONEUM. The Suh-wmbilical Portion.- -General Description and -The Supra-umbilical Portion.- Structure. The peritoneum (nept, around, and reivu, to extend) is a serous membrane, which, on the one hand, lines the abdominal parietes, and, on the other, invests nearly all the vis- cera contained in the cavity of the abdomen. As it enters into the formation of almost all the abdominal viscera, it has been already Fig. 190. partially examined while describing them. It remains for us to demonstrate these parts as a whole, and for this purpose, we shall suppose the membrane to com- mence at one particular point, and shall trace it with- out interruption in a circular course until we again ar- rive at the point from which we started. The peritoneum is the largest and most complica- ted of the serous membranes ; it forms, like all of them, a shut sac, the external surface of which ad- heres to the parts over which it is reflected, while its internal surface is free and smooth. Taking the umbilical region as a point of departure, we shall divide the peritoneum into two portions, a superior, epigastric or supra-imibilical, and an inferior or sub-umbilical portion. The Inferior or Sub-umbilical Portion of the Peritone- um.— The inferior or sub-umbilical portion, supposed to commence at the umbilicus, lines the whole of the parietes of the abdomen {a, fig. 190) below that point. In so doing, it is raised up by the urachus and the two umbilical arteries, or, rather, by the ligaments repla- cing those arteries, so as to form three falciform folds, one median and two lateral, which converge towards their termination at the umbilicus, but diverge in the direction of the bladder ; the peritoneum then dips into the pelvis, and covers the fundus, the sides, and the posterior surface of the bladder (J), but to a varia- ble extent, according as that organ is distended oi empty. When the bladder is contracted, the perito- neum descends behind the symphysis ; when, on the * [It has been shown by Sir A. Cooper, that the mammary gland of the male has a system of ducts and cells like those of the female gland, but very much smaller.] THE PERITONEUM. 475 Other hand, it is distended and rises into the abdomen, the peritoneum retires before ii, and the bladder then comes into direct contact with the anterior wall of the abdomen, so that it can be reached by the surgeon without wounding the peritoneum. From the posterior surface of the bladder the peritoneum is reflected upon the other pelvic organs, being arranged differently in the two sexes. In the male it is reflected from the bladder upon the rectum, forming two lateral semilunar folds, called the pos- terior ligaments of the bladder, and a cul-de-sac between them of variable depth, wliich sometimes reaches as low as the prostate.* In the female it is reflected from the pos- terior surface of the bladder upon the neck of the uterus (m), forming a cul-de-sac between the two, so that the inferior fundus of the bladder is entirely uncovered by it. It then covers the two surfaces and the superior border of the uterus, and forms two lateral, broad, transverse folds (the ligamenta lata), each of which is subdivided superiorly into three smaller folds, the ala vespertilionis or alee of the broad ligament, the anterior fold corresponding with the round ligament, the middle one to the Fallopian tube, and the posterior fold to the ovary. The peritoneum has no relation with the front of the vagina (v), but it covers the up- per third of that canal behind ; from thence it is reflected upon the rectum (r), and has then the same arrangement in both sexes. Inferiorly it is hmited to the anterior sur- face of the gut, but superiorly it entirely surrounds it, excepting behind, where it forms a duplicature known as the mesorectum. After leaving the cavity of the pelvis, the peritoneum continues to ascend, so as to cover the posterior wall of the abdomen ; in this situation we shaU examine it in the middle and at the sides. In the middle it passes in front of the sacro-vertebral angle, then in front of the lumbar vertebrae, and having arrived opposite an oblique line, extending from the left side of the second lumbar vertebra to the right iliac fossa, it is reflected forward to constitute the left layer (m) of the mesentery {niao^, middle, evrepov, an intestine) ; it immediately ex- pands, so as to correspond to the whole length of the small intestine (i), lines the left lateral half, the convex borders, and the right lateral half of that intestine, and then pass- ing from before backward (m'), is applied to the back of the layer just described, and in this manner forms the mesentery (m m'), the largest of all the duplicatures of the peri- toneum, and remarkable for its resemblance to a plaited ruffle. On the left side, the peritoneum, after having formed the mesorectum, then forms the iliac mesocolon, a considerable fold, which allows great mobility to the sigmoid flexure of the colon. From the sigmoid flexure it is prolonged upon the left lumbar colon, cover- ing the anterior five sixths of that part of the intestine, and applying it against the kidney, but without forming any duplicature for it ; so that the kidney and the colon are in im- mediate relation. Still, the left lumbar colon is not unfrequently entirely surrounded by the peritoneum, so as to have a duplicature behind it, called the left lumbar mesocolon. Along the whole course of the great intestine, the peritoneum usually forms a number of small folds containing fat, and named the appendices epiploicm. On the right side the peritoneum arrives at the caecum, and may be arranged in one of two modes : it either entirely invests that portion of intestine, which is then very mo- vable ; or else, and this is the most common arrangement, it passes inunediately in front of the caecum, which is thus applied against the right iliac fossa, and is attached there by rather loose cellular tissue. The peritoneum sometimes forms a small mesentery for the vermiform appendix, sometimes fixes it against the posterior surface of the caecum, or against the ileum, or, lastly, against the lower portion of the mesentery. Above the Cfficum the peritoneum covers the right lumbar colon, and has the same arrange- ments as on the left side. Such is the course of the sub-umbilical portion of the peritoneum. The Superior or Supra-umblical Portion of the Peritoneum. — We shall trace the superior or supra-umbilical portion from the umbilicus to the posterior wall of the abdomen, op- posite to the mesentery and the lumbar mesocolon, to which points we have already traced the lower portion. Commencing at the umbilicus and proceeding upward, the peritoneum (e) lines the an- terior abdominal parietes ; on the right side it meets with the umbilical vein, or the fibrous cord to which that vein is reduced in the adult, covers it, and forms a falciform duplicature, named the suspensory ligament of the liver, or falx of the umbilical vein ; this fold is of a triangular shape, its apex corresponds with the umbilicus, and its base with the upper surface of the liver, which is divided by it into two lateral portions or lobes, t From the umbilicus, then, as from a centre, proceed four peritoneal folds : one superior or ascending, for the umbilical vein ; and three descending, one for the urachus and two for the umbilical arteries. From the anterior wall of the abdomen, the peritoneum is continued upon the lower * The peritoneum, forming the cul-de-sac between the bladder and the rectum, sometimes has a fissured ap- pearance, like that seen upon the parietes of the abdomen in women who have had many children. t [Its lower free margin encloses the umbilical vein, and its upper or interior border is attached to the ab- dominal parietes.] 476 SPLANCHNOLOGY. surface of the diaphragm (/), and is arranged differently on the right and left sides and in the middle. The Right or Splenic Portion. — The peritoneum, after having lined the lower surface of the diaphragm as far as the vertebral column, is reflected upon the posterior surface of the vascular pedicle of the spleen, covers the posterior half of the internal surface of that organ, its posterior border, the whole of its external surface, the anterior half of its internal surface, and the anterior surface of its vascular pedicle, from which it is pro- longed upon the great end of the stomach, and becomes continuous with the anterior layer of the great omentum. The two layers which are applied to each other, one in front of and the other behind the vessels of the spleen, constitute the gastro-splenic omen- tum. Below the spleen, the peritoneum forms a horizontal fold, or septum, by which that organ is separated from the viscera below it. The Middle or Gastro-epiploic Portion. — In the middle the peritoneum lines the lower surface of the diaphragm, as far back as the cardiac extremity of the oesophagus, is re- flected over the anterior surface of the stomach (*), and descends into the abdomen in front of the arch of the colon and the convolutions of the small intestine, to form the an- terior layer (w) of the great omentum. After descending towards the lower part of the abdomen for a distance, which varies in different individuals and at different ages, it is folded backward upon itself, and passes upward to form the posterior layer (o) of the great omentum. Having arrived at the con- vex border of the arch of the colon (c), it covers the lower surface of that intestine, and passes horizontally backward (q) to the anterior surface of the vertebral column, in front of which it is again reflected, and becomes continuous with the right layer (m') of the mesentery. The horizontal portion, which extends from the arch of the colon to the vertebral column, forms the tJiferior layer (q) of the trayisverse mesocolon. It follows, then, that the portion of the peritoneum which is continuous with that upon the anterior surface of the stomach, forms below that organ a kind of bag, which has a direct or descending layer, and a reflected or ascending layer, in the interval between which are placed the stomach (s), the pancreas {p), the duodenum {d), and the arch of the colon (e). We shall afterward find that each of these layers is lined internally by another layer of peritoneum, so that the great omentum consists of four layers of serous membrane. The Right or Hepatic Portion. — On the right side the peritoneum is reflected from the diaphragm upon the convex surface of the liver {t), and forms the coronary ligament of the liver (at g), being continuous with the suspensory ligament, the direction of which is at right angles to its own. From the convex surface of the liver, the peritoneum is reflected over its anterior margin, and then upon its concave surface, investing the gall-bladder, sometimes almost entirely, but generally on its lower surface only. At the transverse fissure it is reflect- ed downward in front of the vessels of the liver, and to the left of those vessels reaches the lesser curvature of the stomach, and is continued upon the anterior surface of that organ. That portion of the peritoneum which extends from the transverse fissure to the lesser curvature of the stomach, constitutes the anterior layer (h) of the gastro-hepatic or lesser omentum. To the right of the vessels of the liver and to the right of the gall- bladder, the peritoneum covers the lower surface of this viscus, and becomes directly continuous with the portion which covers the right lumbar colon. As the peritoneum is reflected from the diaphragm upon the right and left extremities of the liver, it forms two folds, one on each side, caUed the triangular ligaments of the liver. The Foramen of Winslow and Sac of the Omentum. — Behind the vessels of the liver, and under the anterior root of the lobulus Spigelii, is an opening which leads into a cav- ity situated behind the stomach and the gastro-hepatic omentum. This opening is the orifice of the omental sac, or the foramen of Winsloio (in which a probe is placed in the figure) ; the cavity is called the posterior cavity of the peritoneum, or the sac of the omen- tum (i). The foramen of Winslow is semicircular, sometimes triangular in shape, and about one inch in its longest diameter. It is bounded in front by the vessels of the liver, behind by the vena cava inferior, below by the duodenum, and above by the neck of the gall-bladder, or, rather, by the lobulus caudatus, or anterior root of the lobulus Spigehi, these several parts being covered with peritoneum. Through this opening the perito- neum enters the sort of pouch formed between the two layers of the great omentum. In tracing the course of the reflected portion of the peritoneum, we shall commence at this opening, and shall return without interruption to the same point. The perito- neum is first applied to the posterior surface of the anterior layer of the gastro-hepatic omentum already described, and forms the posterior layer (t) of that omentum ; it then covers the posterior surface of the stomach ; below that organ it is applied (w) to the descending or anterior layer of the great omentum, behind and parallel to which it passes down ; having arrived at the point where the anterior layer of the great omentum is re- flected, the layer we are now describing is itself reflected (x) in the same manner, and becomes applied to the anterior surface of the posterior layer of that omentum ; con- THE PERITONEUM. 477 tinuing to ascend, it gains the convex border of the transverse colon, covers the upper surface of that intestine, and, farther back, is applied to that layer of the great omentum which is continued over the lower surface of the colon ; it thus forms the upper (?/) of the two layers of which the transverse mesocolon is composed. Having reached the front of the vertebral column, it leaves the inferior layer of the transverse mesocolon, covers the anterior surface of the third portion of the duodenum (d), the anterior surface of the pancreas (p), the lobulus Spigelii and the anterior part of the vena cava, and ar- rives at the transverse fissure of the liver, opposite the foramen from which we began to trace it. It follows, therefore, that the great omentum, notwithstanding its thinness and trans- parency, consists of four perfectly distinct layers, two of which, united together in front, and two behind, constitute the parietes of a cavity called the posterior cavity of the peri- toneum, or the sac of the omentum. We may, however, describe the omentum in a different mode, as follows : Two lay- ers of peritoneum applied to each other pass off from the transverse fissure of the liver, separate along the lesser curvature of the stomach, in order to enclose that organ, again unite along its greater curvature, then pass downward, and, opposite the brim of the pelvis, are reflected backward upon themselves, and proceed upward. Having reached the convex border of the colon, they separate to receive that intestine between them, become reunited at its concave border to form the transverse mesocolon, and then sep- arate finally. The inferior layer is reflected downward, to become continuous with the right layer of the mesentery ; the superior is reflected upward, to cover the third portion of the duodenum, the pancreas, and the lobulus Spigelii, and then becomes continuous with the rest of the peritoneum at the foramen of Winslow.* General Description of the Peritoneum. — From the preceding description, it follows that the peritoneum forms a continuous membrane, so that, if it were possible to unfold all its duplicatures, and to detach it entire from the surface of all the organs covered by it, it would form a large membranous sac without an opening. Nevertheless, in the fe- male there is a remarkable interruption at the point corresponding to the free extremity of the Fallopian tube, in which situation we find the only example in the body of a serous and mucous membrane being continuous with each other. The peritoneum has two surfaces, an external and an internal. The internal surface is free, smooth, and moist, and is the seat of an exhalant and absorbent process, which, in the natural condition, exactly counterbalance one another. The external or adherent surface lines the parietes of the abdominal cavity, covers most of the abdominal viscera, of which it forms the externaror common coat, and is in con- tact with itself in the different folds formed by the peritoneum. The attachment of this surface is effected by means of cellular tissue, the character of which varies in different situations. We shall examine the external surface of the portion of the peritoneum applied to the abdominal parietes, or the parietal peritoneum ; of that upon the viscera, or the visceral peritoneum ; and also of that forming the different folds. The Parietal Portion of the Peritoneum. — Upon the diaphragm it is attached by a very dense cellular tissue ; nevertheless, it may be torn off in dissecting that part. Upon the anterior wall of the abdomen it adheres most strongly opposite the linea alba and the sheath of the rectus muscle, and more loosely opposite the crural arches than in any other part. Still, it is not very difficult to separate the whole of the membrane correspond- ing to the parietes of the abdomen. In the lumbar region the adhesion is extremely loose, and also in the iliac fossae on the front of the vertebral column : the same is the case in the cavity of the pelvis. The cellular tissue on the outside of the peritoneum, which most anatomists have re- garded as forming the external tissue of that membrane, sends prolongations through the numerous openings with which the walls of the abdomen are perforated. These prolongations connect the sub-peritoneal cellular tissue with that of the lower extremi- ties on the one hand, and with the cellular tissue external to the pleura on the other. The peritoneum is supported throughout by a fibrous layer, and this accounts for the dif- ficulty with which abscesses of the abdominal parietes open into the cavity of the peri- toneum. The Visceral Portion of the Peritoneum. — x\mong the viscera of the abdomen some re- ceive a complete investment from the peritoneum, always excepting the point at which their vessels reach them ; to this class belong the spleen, the stomach, and the small intestines. Others have a less complete covering, so that a portion of their surface is in immediate relation with surrounding parts : of this number are the ascending and de- scending colon and the caecum. Lastly, others have only very slight relations with the peritoneum, which merely pass over them, and do not appear to enter into their forma- * Tn many subjects the existence of the sac of the omentum may be demonstrated by introducing- a large catheter into the foramen of Winslow, and by blowincf carefully through it ; the air will enter between the two anterior and the two posterior layers of the great omentum, and form a large and more or less rtgular bladder. For this experiment to succeed, the omentum must be perfectly uninjured, and free from adhesions. 478 SPLANCHNOLOGY. tion : to this class belong the bladder, the lower part of the rectum, the pancreas, the two lower portions of the duodenum, and the kidneys. To the last-named organs the peritoneum is connected only by very loose cellular tissue. The visceral portion of the peritoneum is not strengthened by the fibrous layer met with in its parietal portion, and, therefore, perforation of the serous coat of the viscera is much more common than perforation of the parietal portion of the serous membrane. The Folds of the Peritoneum. — Among the folds of the peritoneum, most of which have been already described, and which need be only recapitulated here, some bear the name of ligaments, viz., the triangular, coronary, and falciform ligaments of the liver, the pos- terior ligaments of the bladder, and the broad ligaments of the uterus. Others are called mesenteries, viz., the mesentery, properly so called, or the mesentery of the small intestine, the transverse mesocolon, the right and left lumbar mesocolon when they exist, the iliac mesocolon, and the mesorectum. With these we should in- clude the duplicature extending from the transverse fissure of the liver to the lower cur- vature of the stomach, and known as the lesser omentum ; it really constitutes the me- sogastrium. Lastly, there are certain folds, named omenta or epiploa {enl, upon, tt/I^w, to float), viz., the great, or gastro-colic, small, or gastro-hepatic, gastro-splenic, and colic omenta.* With this class we may connect the appendices epiploicae. It may be well to make a few observations upon the great and lesser omenta. The Great Omentum. — The great or gastro-colic omentum, so called because it is at- tached, on the one hand, to the stomach, and on the other to the colon, scarcely exists in the new-born infant ; it is gradually developed as age advances, and about the period of the termination of growth it reaches to the brim of the pelvis. It has been remarked that it descends a little lower on the left than on the right side. When the stomach and the colon are distended, this omentum is reduced to a more or less narrow border extending along the arch of the colon. It presents also a number of individual varieties : sometimes it is very regularly sus- pended in front of the intestinal convolutions ; sometimes it is folded upon itself, and carried to one side or the other ; occasionally it adheres at some point, becomes stretch- ed like a cord, and may then give rise to strangulation ; and, lastly, it is not very rare to find it turned upward and backward between the diaphragm above and the stomach and liver below. It is so transparent and thin that it is difficult to conceive it to be formed of four lay- ers. In some individuals it is even perforated with holes like a piece of lace. The great omentum is found, in very fat persons, to be loaded with an immense quantity of adipose tissue, deposited chiefly along the vessels ; so that it may acquire a very con- siderable size, and a weight of several pounds. The great omentum has an anterior and posterior surface, both of which are free, an upper adherent border, a lower border, free, convex, and more or less sinuous, which cor- responds with the crural arches, and the internal openings of the inguinal canals ; it is, therefore, very often found in hernial sacs. The lower border is more liable to adhesions than any other part of the omentum. The lateral borders have nothing remarkable ; they proceed parallel to the ascending and descending portions of the colon, which are sometimes covered by them. The arteries of the great omentum are furnished by the right and left gastro-epiploic arteries ; they descend vertically between its two anterior layers, scarcely diminishing in caliber. At its lower border they turn upward, and ascend between the two posterior layers as far as the arch of the colon, where they communicate with the arteries of that intestine. The veins follow the same course as the arteries, and assist in forming the vena portae. Some lymphatic glands are found in the great omentum along the curvatures of the stomach and the arch of the colon. Nerves. — Some nervous filaments from the solar plexus can be traced upon the arter- ies of the omentum ; it is doubtless from them that the epiploon derives its peculiar sen- sibility, and on them that the phenomena of strangulation depend when it is constricted in a hernia. The uses of the omentum are not known. The Lesser Omentum. — The lesser omentum, a true mesentery, the mesogastrium, pre- sents a lower concave border, attached to the lesser curvature of the stomach, and an upper border, attached to the transverse fissure of the hver, to that part of the antero- posterior fissure which is behind the transverse fissure, and also to the oesophagus and the diaphragm ; its right border contains the ducts and vessels of the liver, and behind the border thus formed is seen the foramen of Winslow ; on the left it is bounded by the cesophagus.t * [The colic omentum consists of two layers of peritoneum, with intermediate vessels and fat, which de- scend, behind the great omentum, from the upper part of the ascending colon.] t [The cellular tissue surrounding the vessels, ducts, and nerves, contained between the layers of this smaU omentum, has been described as giving origin to Glisson's capsule.] THE HEART. ^ 479 Structure of the Peritoneum. — The peritoneum, like all other serous membranes, has neither arteries, veins, nor nerves. Those which are contained within the omenta and the mesentery do not properly belong to this membrane. The finest capillary injections, either natural or artificial, form an extremely delicate network below the peritoneum, but never penetrate it.* ANGEIOLOGY. Definition and Objects of Angeiology. Angeiology {ayyelov, a vessel) is that division of anatomy which treats of the organs of the circulation. The circulating system consists of a central organ, the heart, the agent for propelling the blood ; of the arteries, vessels through which the blood is conveyed from the heart to all parts of the body ; of the veins, through which the blood is returned from all parts of the body to the heart again ; and, lastly, of the lymphatic vessels, appendages of the venous system, into which their contents are ultimately poured. THE HEART. General Description. — External and Internal Conformation. — Structure. — Development. — Functions. — The Pericardium. Dissection. — In order to study the external conformation of the heart, inject the cavi- ties of the right side of that organ by the pulmonary artery, or by one of the venae cavae, taking care to tie the other ; the cavities of the left side may be filled from the aorta, or one of the pulmonary veins. Tallow, wax, and glue-size are the most suitable materials for this purpose. The heart {Kapdia), the central part of the circulating apparatus, is a hollow muscular organ, divided into several compartments, and intended for propelling through the arter- ies into all parts of the body the blood which is poured into it from the veins. The heart is one of the most important organs in the body. In a zoological point of view, the presence or absence of a heart, and the complexity or simplicity of its struc- ture, deserve particular attention, because such variations in regard to the central organ of the circulation are accompanied by very great modifications in the entire organism, t Congenital absence of the heart is extremely rare, and is always accompanied with other malformations, more especially with absence of the brain. These deficiencies are incompatible with life. Number. — Man and vertebrated animals have only one heart ; in mollusca it is double, or even triple. This plurality of hearts, instead of being an index of perfection, should be regarded as a subdivision, and less perfect condition of the organ. We shall see that man, as well as mammalia and birds, has, in reality, two hearts united into one. Situation. — The heart is situated at the junction of the upper third with the lower two thirds of the body ; hence the upper parts of the system are more immediately under the influence of this important organ. t The heart {I, fig. 170 ; o,fig. 171) occupies the middle of the thoracic cavity; it is sit- uated in the mediastinum, in front of the vertebral column, behind the sternum, which forms a kind of shield for it, and beyond which it projects on the left side ; it is placed between the lungs, and above the diaphragm, by which it is separated from the abdom- inal viscera. It is retained in this situation by the pericardium (p p,fig. 170), a fibro-serous cover- ing, which is itself closely adherent to the diaphragm (x) ; by the pleurae {q q), which are reflected on each side of it, to form the parietes of the mediastinum ; and, lastly, by the great vessels which pass out or enter at its base. * [The basis of the peritoneum is cellular tissue ; its smooth surface is covered with a squamous epithelium.] t Vertebrata and mollusca are the only animals which are provided with a heart. Mammalia and birds alone possess a double heart, i. e., a heart with two auricles and two ventricles. Fishes and reptiles have a simple heart, i. e., a heart with only one auricle and one ventricle, this ventricle being pulmonary m fishes, and both systemic and pulmonary in reptiles.* t The distance from the heart to the brain varies in different individuals, according- to the length of the tho- ra.\- and the neck. This difference may amount to two inches, and mayexercise some influence upon the cere- bral circulation. In consequence of this observation, extreme shortness of the neck has been regarded as a predisposing cause of apoplexy. " [A central pulsating vessel is found in some of the higher radiata, and in the articulata ; in some of the latter it constitutes a strong muscular ventricle, but the addition of a systemic auricle to this ventricle is first observed in the mollusca ; in the invertebrata, generally, the ventricle is entirely systemic : in the higher ce- phalopods there are two branchial hearts. In fishes the heart consists of a systemic auricle and a pulmonary ventricle, and is preceded by a sinus venosus, and followed by a bulbus arteriosus. In the early condition of the biitrachia the same conformation exists ; but in their adult state, and also in all reptilia, there are two auricles and one ventricle, the additional auricle being pulmonary, i. e., receiving the blood from the lungs. In the higher reptilia, the single ventricle, which is both systemic and pulmonary, is divided by an imperfect septum ascending from the apex of the heart. In the crocodilus lucius, as well as in birds and mammalia, this interventricular septum is complete, so that in them the heart is divided into two auricles and two ventri- cles, the cavities of one side being systemic, and of the other pulmonary.] 480 " ANGEIOLOGY. These means of attachment are not such as to prevent the heart from undergoing re- markable changes of position, depending upon pecuHar attitudes, upon shocks acting on the body, or upon diseases of the surrounding organs. Thus, in a case of hydrothorax on the left side, the apex of the heart struck against the right side, and gave rise to the suspicion that the viscera were transposed. Size and Weight. — Neither the size nor the vi'eight of the heart can be estimated with exactness, oh account of the numerous individual varieties in both. It is very difficult to determine the limits, in either the one or the other, between a healthy and a morbid con- dition ; and a heart which would be considered normal in one individual would be re- garded as hypertrophied in another. The defects of the method proposed by Laennec for obtaining an approximative esti- mate of the size of the heart, by comparing it with that of the closed hand of the same subject, afford sufficient evidence of the difficulty of arriving at an accurate result in this matter.* No organ in the body is more subject to enlargement than the heart ; when caused by dilatation of the cavities, it constitutes aneurism of the heart {dilatation) ; when due to thickening of the parietes, it is termed hypertrophy. When enlargement occurs from both these causes, the heart acquires an enormous size, and has been called bullock's heart {hypertrophy with dilatation). The size of the heart may be estimated directly by ascertaining the quantity of water displaced by it, and by admeasurement ; it may also be determined, in an approximate manner, by its weight, which bears a certain relation to the size. In making these estimates, it is necessary to distinguish the size and weight depend- ant upon thickness of the parietes of the heart, from the increase occasioned by blood contained in its cavities. In order to obtain comparative results upon this point, the heart must be weighed and measured both in its empty and its distended state. The average weight of the empty heart is from seven to eight ounces. Some atrophied hearts do not weigh more than two ounces : dilated and hypertrophied hearts, when empty, may weigh twenty-two ounces. The ordinary weight of the heart distended with tal- low is twenty-four ounces. I have seen dilated hearts, also, filled with tallow, which weighed three pounds. As to the admeasurement, we shall apply it in succession to the ventricles and to the auricles. Form, Direction, and Divisions. — The heart has the form of a flattened cone, the axis of which is directed obliquely from above downward, from the right to the left side, and from behind forward. This direction, which is peculiar to the human species (for in the lower animals the heart is vertical), appears to have some relation to the erect position. The heart is not symmetrical in reference to the median line of the body, nor yet in re- gard to its own axis. The general relations of the heart will be indicated when we describe the pericardium. I shall here simply state that the heart is in relation with the left lobe of the lungs, which is deeply notched to receive it ; that that portion of the heart which is uncovered in front between the lungs, after the sternum and the ribs have been removed, is extremely vari- able in different subjects ; that independently of the volume of the heart, the adhesions of the lungs exercise a very great influence upon the extent of these direct relations of the heart with the anterior part of the sternum. In an old woman, whose lungs were closely adhering to the walls of the thorax, the anterior face of the heart was almost en- tirely bare behind the sternum and the cartilages of the ribs on the left side.t That the posterior face of the heart deserves the name of vertebral surface just as well as that of diaphragmatic surface ; that this surface occasions a marked impression upon the liv- er ; that the relations of the posterior surface of the heart with the oesophagus are such as will cause the distended oesophagus to raise the corresponding portion of the pericar- dium, and that the posterior surface of the heart is not only separated from the vertebral column by the oesophagus, but also by the aorta, which is situated between the oesopha- gus and the bodies of the dorsal vertebra. The heart is divided into ventricles and auricles. The ventricles {I o,figs. 191, 192) constitute the chief part, in some measure the body of the organ, the conical form of which is determined by them ; the auricles {m n) are a kind of appendices, which can be well seen only when the heart is raised ; they occupy the base of the organ ; the hmit between the auricles and the ventricles is indicated by a circular furrow. » External Conformation of the Heart. The External Surface of the Ventricles. The external surface of the ventricles, or the ventricular portion of the heart, called also * The large hand of a wurkman does not imply the existence of a larger heart than the small hand of a fe- male, or of a man exempt from manual labour. t The heart descends as far as the middle portion of the xiphoid appendix. The upperhalf of this appendix is, therefore, in direct relation with the heart, and the inferior half in direct relation with the liver. Should not this circumstance be of some weight in explaining the acute pains by which a pressure upon this appendix IS accouipauied ? THE HEART. 481 by the ancients the arterial portion, because the arteries arise from it, presents for our consideration an anterior and an inferior surface, a right and a left border, a base and an apex. The anterior or sternal surface (fig. 191) is convex, and is divided into two unequal parts, a larger on the right, and a smaller on the left side, pig, 191. by the anterior furrow of the heart {e b), which passes verti- cally from the base towards the apex, is occupied by the an- terior coronary artery, and is often obscured by fat. All that part of the organ which is to the right of the furrow be- longs to the right ventricle (/), all on the left belongs to the left ventricle (0). The furrow itself corresponds to the sep- tum between the ventricles. This surface, or, rather, the pericardium which covers it, is in relation with the sternum, more especially in that part which lies to the right of the furrow ; also with the fourth, fifth, and sixth costal cartilages of the left side, and with the lungs, which cover it more or less completely. It should be remarked that, in large hearts, this surface, or its peri- cardium, corresponds immediately to the sternum, while in the natural state it is situated at some distance from that bone. The relations of the heart with the anterior wall of the thorax enable us to examine its condition by means of percussion and auscultation. The inferior or diaphragmatic surface (fig. 192) is plane and horizontal ; it rests upon the diaphragm, which forms a sort of floor for it, and separates it from the liver and the stomach. Like the anterior surface, it is marked by a longitudinal furrow, the posterior furrow of the heart {e b), which is traversed by vessels and concealed by fat. It diflfers from the anterior furrow in running parallel to the axis of the heart, and dividing its diaphragmatic surface into two nearly equal parts, excepting near the apex. In conse- quence of the relations of this surface, pulsations are observed in the epigastrium, which are sometimes much more distinct than those felt upon the anterior wall of the thorax. Another result of these relations is, that the same meaning is attached to the terms scrobiculus cordis and pit of the stomach, and also to the expressions pain at the heart, pain at the slonmch, c^-c. The r7ght or lower border is thin and horizontal, and rests upon the diaphragm ; it is straight near the apex, but becomes convex towards the base. The left border (0 b,fig._ 191) is very thick, convex, and almost vertical; it resembles a surface rather than a border, and corresponds to the left lung, which is deeply notched to receive it. The base of the ventricular portion of the heart is turned upward, backward, and to the- right side. From it arises, upon an anterior plane, an artery, which immediately passes from the right to the left ; this is the pulmonary artery (k) ; the portion of the ventricle- from which it proceeds forms a prominence on the right side of the anterior furrow of the heart, and is prolonged towards the left, becoming narrower at the same time, so as to form a funnel-shaped projection (infundibulum, conus arteriosus) (a), extending a little beyond the base of the ventricles. Upon a second plane we find the aorta (/), the origin of which, from the left ventricle, is concealed by the funnel-shaped prolongation of which we have just spoken. On a third plane we find a circular furrow (0 u,fig. 195), separa- ting the auricles from the ventricles. Its posterior half is occupied by the coronary ar- teries and veins, and the anterior and posterior furrows of the heart terminate in it at right angles. This circular furrow at first sight appears to be superficial, but is very deep in its pos- terior half If we dissect carefully down to the bottom of this furrow, it is found that the base of each ventricle is, as it were, turned inward, so as to be in contact by a broad surface with the base of the auricle. We find, also, that the base of the ventricles is cut obliquely, and hence the anterior surface of the heart is longer than the posterior surface. The difference in length between these two surfaces is about fifteen lines upon the right, and from nine to ten lines upon the left ventricle. Thus, in a heart of the ordinary size, the length of the ventricles in front was three inches three hues, and behind two inches three lines. In a very large heart the length in front was four inches, and behind only three. The circumference of the base of an injected heart, of the average size, measured ten inches ; that of a large heart was thirteen inches six lines. The apex {h) or poirU of the heart is slightly curved backward in the majority of sub- jects, and is notched opposite the junction of the two longitudinal furrows. This notch, which is partially concealed by vessels and adipose tissue, divides the apex of the heart into two unequal portions ; a right and a smaller, belonging to the right ventricle, and a left and larger portion, belonging to the left ventricle. The relative size of the two por- tions of the apex of the heart is not constant. In some cases of hypertrophy of the left ventricle, the apex of the heart is entirely formed by it ; in other cases, on the contrary, the apex of the heart is nearly equally subdivided. Ppp 4S2 ANGEIOLOGY, The apex of the heart is directed forward, downward, and to the left, and corresponds to the cartilages of the fifth and sixth ribs of the left side, and therefore to the region of the corresponding mamma ; the left lung is notched opposite the apex of the heart, so that the latter strikes directly against the parietes of the thorax. The External Surface of the Auricles. The auricles (m n,figs. 191, 192), forming the mrkular ■portion of the heart, are saccular cavities in which the veins terminate ; they may, in fact, be regarded as dilatations of those vessels, and hence this portion of the heart is called the venous portion, in contra- distinction to the ventricles. They are situated upon the hindermost portion of the base of the heart {fig. 192). Their size varies in different individuals ; in an injected heart, the average height of the auricular portion is two inches ; its antero-posterior diameter is nearly the same ; and when the auricles are distended, its transverse diameter extends beyond the ven- tricles on each side. The shape of the auricular portion of the heart, which can only be accurately deter- mined by means of injection, is irregularly cuboid. It therefore presents several sur- faces ; its anterior surface is situated on a plane much farther back than that of the front of the ventricles {fig. 191). It is concave, and describes three fourths of a circle, so as to embrace the aorta and the pulmonary artery, being moulded upon those vessels, and completely concealed by them. The anterior surface of the auricular portion has no anterior furrow along the middle line. The posterior surface {fig. 192) is convex, and is continuous with the inferior surface of the ventricles ; it presents a vertical furrow, which is prolonged upward from the posterior furrow of the ventri- cles, then deviates to the left side, and forms a curve, the concavity of which is directed towards the right ; it corre- sponds to the septum of the auricles. Immediately to the right of this furrow we find the termination of the vena cava inferior (r), and lower down, that of the great coronary vein. The posterior surface of the auricles is turned towards the vertebral column, from which it is separated by the cEsopha- gus and the aorta. The superior surface of the auricular portion forms the highest part of the heart, and is directed backward and to- wards the right side. It is divided by a furrow, which is convex on the right side, is continuous with the furrow upon the posterior surface, and, like it, corresponds to the inter- auricular septum. Upon this surface we find the termina- tions of five different veins ; one only of these is to the right of the furrow, viz., that of the vena cava superior {d,fig. 191); the other four are on the left of the furrow, and are those of the four pulmonary veins, which are arranged in pairs (c c,fig. 192), two at the extreme left of the auricles belonging to the left pulmona- ry veins, and two immediately in the neighbourhood of the posterior furrow belonging to the right pulmonary veins. This surface corresponds to the bifurcation of the trachea, which, as it were, rides upon it. The extremities of the auricles, or the auricula, are free, and somewhat resemble the pendulous portion of a dog's ear ; hence the term auricles. They are indented hke a cock's comb ; the right auricula is anterior, the left posterior. The right auricula (c, fig. 191) is broader and shorter than the left ; it is triangular and concave, so as to embrace the aorta, in front of which it projects ; the left auricula (?) is narrower and longer, it is sinuous, and curved twice upon itself like an italic S ; it em- braces the pulmonary artery, and terminates opposite the highest part of the anterior fur- row of the ventricles. The right auricula is continuous with the rest of the corresponding auricle, without any well-marked line of separation ; but the left auricula is very distinct from its auricle ; and upon this latter side, the distinction pointed out by Boerhaave, between the sinuses and the auricles properly so called, may be particularly observed : according to him, the sinus constitutes the body of the auricle, and may be regarded as a dilatation of the veins, while the auricular appendix forms the proper auricle. The Internal Conformation of the Heart. The heart is divided internally into four cavities, which are separated from each oth- er by complete or incomplete septa ; two of these cavities belong to the auricles, and two to the ventricles. There are a right ventricle and auricle, and a left ventricle and auri- cle. The auricle and ventricle of the same side are separated by incomplete septa or valves, and communicate with each other. The cavities of the opposite sides are sep- arated by complete septa, and do not communicate. The heart is therefore, in this lat- ter respect, truly double. The right ventricle and auricle constitute the right heart, also THE HEART. 483 named the caur a sang noir, from the colour of the blood which it contains ; and the pul- monary heart, because it propels the blood into the lungs. The left ventricle and auricle constitute the left heart, called also the cceur a sang rouge, or the aortic heart, because it throws the blood into the aorta. The Internal Conformation of the Ventricles. Dissection. — In order to obtain a general idea of the internal conformation of the heart, make a series of sections at right angles to its length, or else make an incision along its borders parallel to its long axis. To obtain a more exact notion of the ventricles, make a V-shaped incision in the right ventricle, letting one branch of the incision extend along the anterior furrow, and the other along the right border, while the angle at which they meet should correspond to the apex of the ventricle. The best method of opening the left ventricle consists in making a vertical section through the septum ; but in doing this, the right ventricle must be sacrificed. In order to obtain a general view of the appearance of these cavities, they may be pre- pared in the dried state. For this purpose, the heart is to be injected with tallow, and then, after being dried sufficiently, to be opened in the manner above described, and im- mersed in warm turpentine, which will dissolve the tallow,and leave the ventricles dilated. Interior of the Right Ventricle. The right ventricle occupies the right anterior and inferior portion of the heart, and has, therefore, been called the anterior or the inferior Fig. 193. ventricle. Its cavity {fig. 193) has a three-sided pyramidal form. Its inner wall {b) is convex, and is formed by the septum of the ventricles ; in its lower half it has a well-marked reticulated appear- ance, which is almost entirely absent in the upper half (a). The anterior and inferior walls (partly re- moved in fig. 193) are both concave, and are re- markable for their thinness, so that they are al- ways collapsed when the ventricle is empty. The base of this ventricle presents two openings, which are separated from each other by a projecting part, and which may be compared to the wide circular end, and the narrow mouthpiece of a huntsman's horn. The opening into the auricle (in which a bristle is placed) corresponds to the wide end of the horn, a;id the infundibulum (a) to the narrower end. The transverse diameter of the base of this ventricle is nearly equal to its height. The sum- mit (A IS turned towards the apex of the heart. The walls of the right ventricle are very remark- able for their reticulated or areolar character ; this areolar portion might be termed the corpus cavernosum of the heart, for it presents the spongy structure of the erectile tissues. The fleshy columns which form the areolae are observed not only upon each of the walls of the ventricle, but they also pass across the cavity of the ventricle near its summit, extending from one wall to the other ; in conse- quence of which the capacity of the ventricle is singularly diminished. The cylindrical fleshy columns {columnce carnecB, terctcs lacerti), which separate the meshes or areolae, are of three kinds. Some (e) are attached to the parietes of the heart by one of their extremities, and are free in the rest of their extent ; they terminate by a kind of simple or double mammillated projection, from which proceed small tendinous cords {chorda tendinea), that are inserted into the auriculo-ventricular valves (c). They are very few in number, and have been named the muscles of the heart {musculi papillares). The fleshy columns of the second kind are free throughout the whole of their extent, ex- cepting at their extremities, which are attached to the walls of the ventricle. These col- umns, which are the most numerous, are divided and subdivided to form the areolae. The third kind of columnae carneae adhere to the walls of the ventricle by one of their sides ; they are therefore sculptured like pilasters upon the walls of the ventricle. Most of the columnae carneaj pass from the apex towards the base of the heart. In all their free portion, the columns of the two first kinds are attached to each other or to the walls of the ventricle, by means of small tendinous cords, which are much more deli- cate than those proceeding to the valves. The areolar muscular structure just described is the essential constituent of the walls of the ventricle ; but in addition to it there is a rather thin, compact, and non-reticulated layer of superficial fibres, on which depends the smooth appearance of the external surface of the ventricle. The Orifices of the Right Ventricle. — At the base of the right ventricle there are two orifices, one auricular, which establishes a communication between the ventricle and the 484 ANGEIOLOGY. Fig. 195. auricle ; the other arterial, which leads into the pulmonary artery. They are both fur- nished with valves. The right auricular or auriculo-ventricular orifice (through which the bristle is inserted, fig. 194. fig. 193) is placed at the posterior and right part of the base of the ventricle ; it is elliptical, and is provided with a mem- branous structure, called the tricuspid or triglochin valve (c), which projects into the interior of the ventricle. This valve is of an annular form {annulus valvulosus). Its ventricular sur- face {t 1 1, fig. 194) is directed towards the parietes of the ven- tricle, and receives a great number of small tendinous cords, which, being attached to it at different points, give it an ir- /m regular aspect. Its auricular surface {t t t,fig. 195), which is turned towards the axis of the ventricle, is smooth. The ad- herent border is fixed to the margin of the auricular orifice. The free border or margin forms a ring, the diameter of which is equal to that of the adherent border : this margin is irregularly divided, so that, in- stead of the three segments {t t t) generally described, and from which the name of the valve has been derived {rpelc, ires, three, and ylwxli, cuspis, a point), some authors admit four, or even six segments. The construction of the tricuspid valve can be understood only by regarding it as composed of two parts, an anterior, cor- responding to the anterior half of the elliptical auriculo-ventric- ular orifice, and a posterior, corresponding to the posterior half of the same. The tricuspid valve is not unfrequently in- terrupted on the left side opposite the junction of these two valves. This valve might, with as much propriety, be termed mitral, as that which is attached to the left auriculo-ventricular opening. To the free margin of the valve, upon which some small nodules are occasionally found, are attached a number of tendinous cords of a nacreous aspect, which are ex- trem,ely strong considering their tenuity. These small cords, or, rather, tendinous fila- ments, always arise in greater or less number from the summits of the columnae car- neae ; diverging from thence, often bifurcating during their course, and sometimes be- coming united together, they terminate, some at the free margin, others at the ventric- ular surface of the valve, and others, again, at its adherent border. All the smalll tendinous cords do not arise from the columnas carneae of the first kind ; many of them proceed directly from the parietes of the heart. We constantly find a fasciculus of diverging cords arising from the septum. These cords are so arranged, that, by drawing upon them, the valve is depressed and stretched. We find, in fact, that both in the anterior and posterior part of the tricuspid valve, those cords which arise from the free margin on one side converge towarte those of the opposite side, some even crossing each other in the form of the letter X The arterial or pulmonary orifice (ostium arteriosum, d,fig. 194) is placed at the anterior part of the left side of the base of the right ventricle. It is sep- arated from the auricular orifice by a tolerably prominent mus- cular band, which is concave on its lower surface, and divides the right ventricle into two portions, an auricular and a pulmo- nary portion or infundibulum. This orifice is circular, and is provided with three very distinct valves, which are named sig- moid or semilunar (ffig. 195 ; a a a, fig. 196).* Although thin ^^- and semi-transparent, they are very strong. They are directed vertically as the blood is passing from the ventricle into the artery, and become horizontal when it tends to flow back from the artery into the ventricle. Of their two surfaces, the ven- tricular corresponds to the cavity of the ventricle ; the other, or arterial surface, includes between it and the walls of the artery a small cul-de-sac, which has been compared to a pigeon's nest. The adherent border of each valve is convex, and directed to- wards the ventricle ; its free margin presents in the middle a small nodule, by which it is divided into two semilunar halves. Wlien depressed, the valves completely close the vessel, the three nodules filling up the triangular interval left between the approximated free mar- gins. These valves must, therefore, oppose the reflux of the blood into the ventricle ; but the resistance offered by them is easily overcome by an injection thrown into the pulmonary artery. Interior of the Left Ventricle. The left ventricle occupies the left upper and back part of the heart ; it is evidently * It is extremely rare to find any anomaly in the number of these valves, either by an increase or a dimi- nution of them. Fig. 196. THE HEART. 485 constructed upon the same fundamental type as the right ventricle, but differs from it in many respects, as we shall now proceed to show. Difference in Situatioii. — The different positions of the two ventricles are sufficient- ly known from what has already been stated ; but it is important to remark, that the left ventricle projects beyond the other at the apex of the heart {fig. 197), while the right is more prominent at the base, in consequence of the existence of the infundibulum. Difference in Shape. — The right ventricle is pyramidal, and becomes collapsed when not distended ; the left is conical and convex, not only on its free surface (b), but even at the septum (a, Jig. 194), where it seems to project into the interior of the right ven- tricle. Difference in Size. — It is generally stated, in accordance with Senac, Winslow, and Haller, that the right ventricle is more capacious than the left : this statement is found- ed upon direct observation, which proves that the right ventricle gains more at the base than the left does at the apex ; also upon deductions made by comparing the right auri- cle and the pulmonary artery with the left auricle and the aorta ; and, lastly, upon the results obtained by injecting the cavities of the heart. No two observers agree as to the exact numbers which would represent the capacities of the two ventricles, as the fohowing different estimates will show. The capacity of the left ventricle to that of the right has been stated as 31 to 33, as 10 to 11, as 5 to 6, as 2 to 3, and as 1 to 2. — {Hal- ler, t. i., 1. iv., sect. 3, p. 327 ) Now the discrepancies in these estimates prove either the deficiency of the methods of observation, or the existence of real differences resulting from a greater or less amount of accidental obstruction to the pulmonary circulation occurring shortly before death. In the great majority of subjects, the right ventricle is proved to be more capacious than the left, and this, according to the judicious remark of Sabatier, depends upon the state of the circulation through the heart during the last moments of life, at which time the blood flows back from the lungs into the right ventricle, while the left ventricle, not ex- periencing a similar obstruction, and, moreover, acting with greater vigour, empties it- self, more or less completely, of the blood contained within it. After death by decapita- tion, the right ventricle is as much contracted as the left ; also, in individuals that have died without any agony or exhaustion, the cavity of the left ventricle has been com- pletely contracted.* The condition of the heart, then, in the dead body, in which that organ is found as it was at the moment of death, affords us no means of judging of the relative capacity of its cavities during life. If, by tying the aorta in a living animal, we cause stagnation of the blood in the left ventricle, while the exit of that fluid from the right cavities through the pulmonary artery remains unimpeded, the relative capacity of the two ventricles will be found to be exactly the reverse of what is generally indicated. The gradual injection of the heart with wax or tallow, so as to distend the ventricles without producing laceration, enables us to determine the size and the weight of the mass of injection contained within each cavity of the heart, and also to measure these cavities under similar conditions, that is to say, in a state of distension. From obser- vations which I have made in this way, it appeared that the left ventricle was rather more capacious than the right. Difference in the Appearance of the Cavity and in the Structure of its Parietes. — In the left ventricle we find the three kinds of columna; earner. Of y^ jg» the columns of the first kind there are only two (i i,fig. 197), ^^^ which are remarkable for their great size. Their summits are almost always bifurcated, and sometimes they are divided into three parts ; not unfrequently each of these columiiae results from the apposition of two or three others, which are united by small fibrous cords or filaments. The fleshy columns of the second kind are smaller in the left than in the right ventiicle. The areolar arrangement is less strongly marked, and is observed only in the innermost layer, excepting always at the apex, the whole thickness of which, with the exception of the most superficial layer, pre- sents the cavernous arrangement. Moreover, the areolae are remarkable for their small size, and for the slenderness and number of the columnae by which they are surrounded. These muscular areolae are often completed by fibrous cords. Difference in Thickness. — The walls of the left ventricle are much thicker than those of the right {Jigs. 193, 194, 197). The proportion of one to two, arrived at by Laennec, is too slight ; it is one to four, or even one to five. It i» gener- ally said that the muscular tissue of the heart is more compact on the left than on the right side. * The concentric hypertrophy mentioned by authors appears to apply to ordinary hearts, or to hearts m a state of hypertrophy, with their cavities closed, in cimsequenc* of the eontraction contiriuiuj to the last mo- uent. I, therefore, am opposed to admitting concentric hypertrophy as a pathological state. 486 ANGEIOLOGY. Difference in the Orifices. — The left auriculo- ventricular orifice (through which a bristle is inserted, ^o-. 197) exactly resembles the right one, and, like it, is provided with a valve {g) analogous to the tricuspid, and named by Vesalius the mitral valve, from its being regularly divided into two opposite segments {mm, figs. 194, 195). The mitral valve is stronger than the tricuspid, it is thicker and longer, and receives stronger and more numerous chordae tendineae. These differences are more particularly observed in the right segment of the mitral valve, which projects, like an incomplete septum, into the cavity of the ventricle, and appears to divide it into an aortic and an auricular por- tion ; the left segment of the valve {g,fig- 196), on the contrary, is applied against the walls of the ventricle. The aortic orifice {e,fig. 194) exactly resembles the pulmonary orifice of the right ven- tricle ; like that opening, it is also provided with three sigmoid valves (e, fig. 195), which differ from those of the pulmonary artery merely in being stronger, and in having larger nodules or globules upon their free borders ; and, as Arantius admitted their existence only in these valves, they are therefore called globuli, noduli or corpora Aranlii.* The right auriculo-ventricular and arterial orifices are placed at a" distance from each other, but the corresponding orifices of the left side are contiguous, so that the adherent border of the right half of the mitral valve is continuous with the adherent border of the corresponding sigmoid valve ; and hence it follows, that when these valves are removed, the base of the ventricle presents only one orifice. Interior of the Auricles. Dissection of the Right Auricle. — Make a horizontal incision from the auricula to the inferior vena cava, and then a vertical one from the vena cava superior perpendicularly to the first. Of the Left Auricle. — Make a vertical incision from before backward, between the right and left pulmonary veins, including the entire posterior wall of the auricle. In or- der to have an accurate idea of the shape of the interior of the auricles, inject a heart with taOow or wax, and then examine the cast thus taken of their cavities. Interior of the Right Auricle. The shape of the right auricle, when distended, may be compared to the segment of an irregular oval, the long diameter of which is directed from before backward. It has three walls : an anterior, which is convex ; an internal, which is slightly concave, and corresponds to the septum ; and a 'posterior, also concave, which forms the greatest part of the auricle, and is remarkable for the existence upon it of fleshy columns. The right auricle has four orifices in the adult, and five in the foetus, viz., the auriculo-ventricular orifice, the opening of the vena cava superior, that of the vena cava inferior, that of the coronary vein, and, in the foetus, the foramen ovale {trou de Botal), the situation of which is occupied in the adult by the fossa ovalis. The' auriculo-ventricular orifice {see fig. 195), the largest of all, is of an elliptical form, from sixteen to eighteen lines in its longest diameter, which is from before backward, and about twelve lines in its shortest diameter. It is surrounded by a whitish zone (a q), to which is attached the adherent border of the tricuspid valve {t 1 1). The cavity of the auricle presents a sort of constriction opposite the auriculo-ventricular orifice. The orifice {h,fig. 193) of the vena cava superior {d) is circular, and is directed down- ward and a little backward ; it has no valves ; it is bounded on the left by a projecting muscular band, which separates it from the auricle, and on the right by a less prominent band intervening between it and the vena cava inferior. The former of these two bands, which are distinctly marked upon the cast of wax, separates the fasciculated portion of the auricle from the non-fasciculated portion, which seems to be formed by an expansion of the venaj cavae. The orifice {i) of the vena cava inferior (r) opens into the auricle, near the septum, not perpendicularly upward, but horizontally, and at right angles to the original direction of the vein, which is vertical. The orifice is circular, and larger than that of the superior cava ; the inferior cava sometimes forms an ampulla or dilatation before it enters the auricle ; its orince, unlike that of the superior cava, is provided with a remarkable semi- lunar valve, the valvula Eustachii (n), which surrounds the anterior half, and sometimes two thirds of this opening. Its free margin is concave, and directed upward ; its adhe- rent border is convex, and directed downward : one of its surfaces is turned forward to- wards the auricle, the other backward towards the vessel ; one of its extremities ap- pears to be continuous with the margin of the fossa ovalis {s), and the other is lost upon the margin of the opening of the inferior cava. The valve of Eustachius closes the orifice of that vein very imperfectly. In its upper two thirds it is extremely thin, and resembles the valves of the veins ; its lower third contains a muscular fasciculus. * The three sigmoid valves of the aona are generally very similar in form ; in one case, however, which I examined, one of these valves had twice the si'/e of the others. I have lately observed, in a njan of sixty, who died of a disease of the heart, the rare sight of an aorta provided with only two sigmoid valves; these two valves were very large, and in relation with the diameter of the aortic orifice, which they covered completely THE HEART. 487 The orifice of the coronary vein is placed immediately in front of the preceding, from which it is separated by the Eustachian valve. It is sometimes situated at tlie bottom of a small cavity or vestibule. It is provided with a very thin semilunar valve {valvula Thebcsii, below and behind the bristle), which exactly resembles the valves of the veins, and completely covers the mouth of the vessel. The upper extremity of this valve is continuous with the lower end of the Eustachian valve. The Intcr-auricular Orifice. — In the foetus, the inter-auricular septum is perforated be- hind and below by an opening improperly called the foramen of Botal, for it was known to Galen, who described a free communication between the auricles. After birth, we find in the situation of the foramen ovale a fossa (fossa ovalis, vestigium fora^nims ovalis), or, rather, a plane surface, which is generally smooth, but occasionally uneven, and, as it were, reticulated ; it is bounded in front and above by a semicircular ridge or border (s), which is improperly called the isthmus or aiinulus Vieussenii, and may be regarded as a more or less perfect sphincter. Behind, the fossa ovalis is continuous with the vena cava in- ferior ; the semicircular ridge or border of the fossa ovalis is formed by a curved mus- cular fasciculus, sometimes very thick, the concavity of which is directed backward ; the inferior extremity of the fasciculus is continuous with the Eustachian valve. The fossa ovalis is frequently found to be prolonged beneath the semicircular border or annulus, so as to form a sort of cul-de-sac, the bottom of which is often perforated, and the handle of a scalpel may not unfrequently be introduced through this opening into the left auricle, although no morbid phenomenon may have been observed during life. The Fasciculated and Reticulated Portion of the Auricle. — Upon the internal surface of the auricle, to the right of the vena cava, are observed certain muscular fasciculi or fleshy columns {musculi pectinati auriculae), which are directed vertically from the auric- ula towards the auriculo-ventricular orifice. These fasciculi adhere to the auricle on one side only ; they are intersected by other oblique and smaller bundles, which give a reticulated aspect to the inner surface of the auricle. Cavity of the Auricula. — The auricula, or that portion of the auricle which extends from the vena cava superior to the bottom of the appendix, consists of an areolar or cav- ernous structure, exactly resembling that which has been described in the ventricles. The same cavernous structure is found in other parts of the auricle, and in particular near the orifice of the coronary vein. I agree with Haller* and Boyer, in denying the existence of the tubercle of Lower, described by that anatomist as situated (at m) between the openings of the venae cavae. It is generally admitted that a certain number of small veins open into the right auri- cle by minute orifices without valves We find, in fact, some openings resembling vas- cular orifices, and known under the name of the foramina Thebcsii; they are constantly found below the orifice of the vena cava superior, but most of them only lead into small groups of areolae, and injections do not demonstrate the existence of any corresponding vessels. The only true vascular orifices are those for the anterior coronary veins. Interior of the Left Auricle. The cavity of the left auricle {fig. 197) differs from that of the right in the following circumstances ; in being less capacious tlian the right auricle, the proportion between them being four to five ; in its form, which is irregularly cuboid ; in the number of its orifices, of which there are five after birth, and six in the foetus ; in the character of those orifices : thus the left auriculo-ventricular orifice (see fig. 195) is smaller than the right ; its long diameter, which is transverse, is from thirteen to fourteen lines, its short diameter is from nine to ten lines ; the four other openings belong to the pulmonary veins, two (c) on the right, and two (c c) on the left side, and all are without valves ;t in the structure of its auricula, which is perfectly distinct from the rest of the auricle, and con- tains a central conical cavity, leading into the auricle by a well-defined circular open- ing ; in the left auricle, nothing is seen on the septum corresponding to the fossa ovalis,t at least we perceive neither band nor ring by which it is circumscribed. When the two auricles communicate by an oblique passage, we find a very thin fibrous band, beneath which the scalpel may be introduced into the right auricle. Structure of the Heart. The heart is essentially a muscular organ, and has a framework consisting of certain fibrous rings or zones ; it is covered by a layer of serous membrane ; the left cavities -- are lined by a membrane continuous with the internal coat of the arteries, and the right * " Id tuberculum cupide reoeptum est, ut fere fit, ab iis scriptoribus quibus occasio ad propria experimenta nulla est, deinde etiam ab iis qui tandem onmind in corporibus humanis dissecandis se exercuerunt." — (HaUer Elem. Pkys., t. i., lib. iv., sect. 2, p. 314.) t It is not uncommon to meet with five openings, three on the right and two on the left side ; in other cases, the two left pulmonary veins open by a common orifice. J [The situation of the fcetal opening (a, fig. 197) is very commonly indicated by a recess of variable depth opening between the left surface of the septum ami the (still free) crescentic border of the valve of the fora- laen ovalf.J 488 AXGEIOLOGT. cariries bj one coritinuots with the lining- membrane of the veins.* Seme nerves, prop- er Tessels, and cellular tissue, also enter into its stracture. The Framexjcork of the Heart. This term may be applied to four r:f rou^ zones (the tendinous circles of Lower), which may be regarded as affording both origin and insertion to aD the muscular fibres of the heart. These zones are situated at the four orifices of the ventrieles, tIz., the two au- licnlo-T'entricular and the two arterial orifices. Digscdion. — ^Remore with care the adipose tissce, and the vessels which occupy the farrows of the heart. Examine the fibrous zones from the internal surface of the heart. In order to study the relations of the orifices with each other, remove the auricles, the aorta, and the pulmonary artery, a little above those orifices. T%« Auriado-rcntricular Zones- — Each axriculo-reniriadar zone is a tolerably regular fibiois circle, which surrounds the opening between the auricle and ventricle, and de- tennines its form and dimensions. These fibrous circles give off expansions of a sim- ilar natnre. which enter into the formation of the tricuspid and mitral valves, and thus add to their strength. The chordce tendines of the heart also terminate in these zones, either directly or through the medium of the valves. The left auricnlo-ventricular zone is stronger than the right. The Arterial Zones. — ^These are two circular rings, the diameter of each of which is somewhat less than that of its corresponding artery, so that there are some very distinct folds or wrinMes produced. These two zones are exactly alike in form, but differ some- what in strength, the aortic being stronger than the pulmonary. From these zones are given off three very thin but very strong prolongations, which occupy the angular inter- Tals formed by the indented border by which the aorta and pulmonary anery commence ; and three other prolongations extend into the substance of the sigmoid valves. These prolongations form very distinct fibrous bundles in the sigmoid valve of the aorta-t Relaiire Position of tne On rices of the YentricUs (see Jig. 195). — ^The two auriculo-vec- trieular orifices are situated upon the same plane, posterior to the other orifices, and ap- proach each other at their middle. The long diameters of these two orifices are at right angles to each other : thus, the long diameter of the right auricnlo-ventricular orifice is directed from before backward, while that of the left orrSce is directed transverselv. In thr i-g;:li7 ir:^^ .' '. :': between these two orifices in front, the aortic opening (f) is clos-^.; _r,::-i : :. : so that the posterior half of the circumference of the aor- tic ZCT- - :.^r > .:. nriculo- ventricular zones. At the point of junction be- twee- : r . ^ ir:;.ijr. us. and in the larger animals a bony, arch, which was descT.: ^ " : :i :: :r: :ie name of the lone of the heart: in this situation, also, ■^^ ::^ - -'-V ~ - " ;-;::::- ; Tzcretions of the orifices. - - ; ;" i " -^^ " : : : and on the left of the aortic opening, and about five or s_--^ 7. - ^ : - :: :? ;;: i:Ti ■ r orifice (/) of the puhnonary artery. -T :r:- : : v; ^ n^ s i::-;ted towards the right side, that of the pulmonary ar- '^~ ' .: - ^^ vf: - '.'-.:.'- ".aese two vessels cross each other, so as to represent the It \ . :: ; : ::re, that the pulmonary orifice is separated from the right ^- ■ .'^r ::.- ;y the orifice of the aora. ;-- -Ai:...:::.j : rir ;_t: .:._5. —^ observe that the plane of the auriculo-ventricular or- i^>^- -5 :;:i:.-: ::1 lUr!;- i^j.ivird and downward: this explains the difference in the i^r ^ ;.: ; ■ -;.e Tenrricles before and behind. We also notice the reflection or turning iii- ■^ ' '■'---- base of each ventricle {g a,p h) upon itself, so as to form a circular groove cr -.:-:. :_ :- the inner surface of its cavity, running entirely round the margin of the cor- r^i.- i-i-Li auriculo-ventriculaT orifice. The Muscular Fibres of the Heart. The Muscular Fibres of the Tentrtdes. Dissection. — The mtiscular fibres of the heart may sometimes be traced without any preparation : but, generally speaking, either commencing putrefaction, maceration in vinegar, or, stiU better, hardening and separation of the fibres by means of alcohol, and especiaDy by boiling, are necessary for this purpose. This being done, remove first the * [Tl>e imJsealar Sbres of the lieait, ihssoA mrcfemlarj', veir closelT resemble in stmetaxe lliose of the tuluMaiy miisdes (see note, p. 194K liQt tbe transverse scria npcn them are less distinirt. ThefiBBig' metAaaaea oi the two aides <^ the heart are cohered by epitheliom, asd faaa what is termed Uie I aMmrm'iimu ] t I lar a Iod^ time beliered that the sismmd valres, both the aortic and the pnlmocarT. -vsrere formed by two jmJiwtitiiiii of the interaal Baemhtane of the heart reflected npon itself ; bot I hare from pathcdogical £actB tatetf die positiTe demonstiation that eadi sigm" arteries of the heart and of the lips. Again, the serpentine course of an artery, by increasing its length in a given space, adds to the extent of surface from which collateral branches may arise. The curvatures of the internal maxillary and of the ophthalmic arteries evidently have this advantage ; and it is highly probable that the arch of the aorta may serve a similar purpose. The arteries are tortuous in certain parts also, in which this arrangement would seem to diminish the force and rapidity of the current of blood ; it cannot fail to be perceived * The word oriffin must not be taken here in its exactly literal sense, for it has br no means been shown that the arteries are developed from the heart towards the extremities. A very ingenious theory tends, on the con- trary, to prove that development proceeds from the extremities towards the heart. t 1 should add ihat the proper tissue of the aorta only touches the fibrous arterial zone opposite the angle, or at the summit of the three festmins which the origin of the aorta exhibits. The arterial zone may be con- sidered as the taagent of the three festoons. X While the oriifin of the nerves exercises a great influence on their functions, the place from whence the arteries originate appears to be of but little consequence, and is, at all events, very secondary. We cannot asree in the opinion of Walther, that the origin of the arteries of an organ are intimately connected with the mode of its existence, and with the functions which it performs. I) rFor sf»ecial information on the varieties in the disiribution of the arteries, the reader is referred to Hal- ler, Icones Anatom'cee, 1T56; Murray, Defcriptio Arteriarum, Sec, 1783-9"<; Barclay, Description of the Ar- teries, (fee, I»18 ; Tiedemann, Taiulee Arlerianim, (fee, 1822; and to R Quain's Anaiomy of the Arteries, &c., with drawings by J. Maclise, 1840, 1841.] THE ARTERIES. 497 that such is the intention of the curvatures described by the internal carotid and the vertebral arteries. Bichat, it is true, has objected to this, that, in a system of commu- nicating and permanently distended canals, the curvature can have no influence upon the rapidity of the fluid circulating through them. But I would answer, that this prin- ciple, though true in reference to a system of inextensible tubes, is not so when applied to a system of dilatable canals like the arteries. In the latter case, in fact, part of the momentum acts against the curvature itself, and straightens it in a certain degree, and in this way there is a loss of some portion of the original momentum. In some arteries this tortuous condition is acquired, in others it results from the prog- ress of age. It proceeds from elongation of the arteries, which is itself produced in the following manner : sA.t each ventricular systole, the arteries tend to become elongated as well as dilated. In the aged, and especially in those whose heart is very powerful, this tendency to become elongated produces an actual and permanent elongation, as may be seen in the abdominal aorta and in the common iliac, the humeral, and the radial arteries, which, in almost all old subjects, present alternate curvatures, that are never met with in the infant and the adult. It has been incorrectly stated, that at each sys- tole of the heart the curves were diminished, or manifested a tendency to be dimin- ished : on the contrary, the curves increase. This increase of cu^ve is evidently per- ceived in observing the temporal artery during the systole of the ventricles. If an ar- tery is injected, its branches, at each stroke of the piston, become more flexuous. If the arteries were straightened, the dilatations and the calcareous deposites would not be constantly observed on the side of the convexity of the curves. Let us remark, that the dilatation of the arteries is, just as much as their elongation, a cause of the increase of their flexuosity. The flexuosities of the arteries are of a twofold order, zigzag and spiral. The former are more frequent ; the latter are especially noticed in the ovarian or testicular, uterine. and sometimes facial arteries. "V^^e may also consider as acquired the tortuous condition assumed by collateral arte- rial branches, after the obliteration of the main trunk.* Anastomoses of the Arta-ies. During their course, the arteries communicate with each other by certain branches, which sometimes unite two different trunks, and sometimes form a connexion between two parts of the same trunk. This mode of communication is called anastomosis (ava, by, and cr-d^o, a mouth). There are several kinds of anastomoses. Atitistomesis bj/ mosculatien^ or b}" loops, in which two vessels running in opposite di- rections open into each other by their extremities and form a loop. Anasta>nosis by tya.>tsrc.rse com-munication^ as v^hen two parallel trunks are united by means of a branch at right angles to their own direction : for example, the anterior com- municating artery of the brain. Afi/istomosis by conrcrgencc, in which two arterial branches unite at an acute angle to form a larger artery, as in the union of the vertebral arteries to form the basilar trunk. By means of the anastomosis by inosculation or by loops, which is the roost common method of communication, uninterrupted collateral channels are establislied along the great arterial trunks, the place of which they may even supply. The existence of these anastomoses, and the power possessed b^- arteries of becoming enlarged to an almost indefinite extent, originated the bold idea of attempting to tie even the largest arte- rial trunks. Anastomoses by inosculation are sometimes useful in regulating the distribution of blood,t and spreading out the origins of arteries over a men' extended space. Thus, by means of several series of arches, the superior mesenteric artery gives offbranches which proceed at right angles* to the small intestine throughout its whole length. Forms and Rtlatzons. The arteries represent regular cylinders when they give off no branch, and cones, or. rather, a series of decreasing cylinders, when they gradually diminish by giving off a certain number of branches. Their cj^lindrical form, together with the looseness of the surrounding cellular tissue, preserves them from a number of accidents. Thus, the hu- meral and tlie femoral arteries glide over the head of the humerus and femur in disloca- tions of these bones ; and so the carotid arteries, contrary to all apparent probability, sometimes escape uninjured in incised wounds of the neck. The arteries have relations with many other parts. With the bones, being supported by them, and more or less closely approximated to them. Thus, the aorta is applied to the vertebral column, and the arteries of the limbs, after escaping from the trunk, become * There are fiexuositie-s originating in malformation, by deviatiou or by fracture. In a case of fracture of the neck of the femur, the femoral artery described very marked inflections at the hip. This was also the case in a luxation of the femur with considerable shortening. The aorta becomes very flexuous in cases of hunch- bacJis. ■f [The retia mirabilia of arterial vessels, found in some animals, are examples of the repeated subdivisioc and anastomosis of arteries.] R R R 498 ANGEIOLOGY. appliea to the corresponding bones, their course along which is marked by a depression, and against which they may easily be compressed (see Osteology). From the relations of the arteries with the articulations, some important practical in- ferences are derived. The arteries always occupy the aspect of flexion ; and as flexion is performed in the larger articulations of a limb alternately in opposite directions, the arteries are observed to alter their relative position, as it were, to regain the aspect of flexion. This is seen in the femoral artery as it becomes popliteal, and also in the brachial, which at first lies in the cavity of the axilla, and then turns forward at the bend of the elbow. In consequence of this arrangement, the arteries are protected by the habitual, and, as it were, instinctive, position of the limbs. On the other hand, the proximity of certain arteries to articulations, and the absence of any curvatures in such situations, may explain the occurrence of rupture of these vessels in dislocation, and often, also, in immoderate attempts at reduction. With the Muscles. — The muscles are the essential protectors of the arteries, which they separate from the skin. There are large cellular spaces in the centre of the limbs for the reception of the principal arteries, which are thus removed from the influence of external violence. Most arteries have a special muscle, which may be termed their satellite muscle. Thus, the sartorius is the satellite muscle of the femoral artery ; the sterno-cleido-mastoideus of the common carotid ; the biceps of the brachial artery, &c. With the Skin. — Some arteries are sub-cutaneous, or, rather, sub-aponeurotic, in a certain part of their extent ; and in large arteries, this is almost always at the point where they emerge from the trunk, as in the femoral artery. The arteries of the cra- nium are situated between the skin and the epicranial aponeurosis in the whole of their extent. The importance of these relations in reference to compression of the vessels may be easily conceived. With the Veins. — The arteries are always in relation with certain veins, which are ap- plied to them. When there are two satellite veins {vena comites) for one artery, the lat- ter vessel is constantly placed between the two veins. With the Nerves. — The arteries support the plexuses of nerves distributed to the or- gans of nutritive life. We may even regard their plexuses as forming an accessory coat to this set of vessels. Other nerves, though not so immediately in contact with the ar- teries, have a constant relation with them. This it is of importance to know, so that the nerves may be avoided, or that they may direct the operator in applying a ligature to the vessels themselves. For each artery it may be said there is one satellite nerve. With the Aponeurotic Sheaths. — The principal artery of a limb is provided with a fibrous sheath, which belongs to it in common with its veins, and often with its accompanying nerve. When an artery perforates a muscle, it is protected in its passage by a sheath or aponeurotic arch, which prevents, or at least moderates, the compression during the contraction of the muscle. Lastly, the arteries are surrounded by a loose cellular sheath, which allows of their dilatation and their alterations in position. The looseness of this cellular tisssue favours the displacement of arteries during the infliction of wounds, and enables us to isolate these vessels by blunt instruments, which cannot injure them.* As the nutritious ves- sels reach the coat of the arteries through this sheath, we can easily understand the im- propriety of separating the vessel from it too extensively in tying the arteries, t Termination of the Jlrteries. The divisions of the arteries are not so numerous as would at first sight appear. The number of successive divisions, commencing at the aorta, is not more than twenty. The arteries terminate in the substance of organs. The number of arteries distrib- uted to each organ is in proportion to the activity of its functions^ secreting organs are much more plentifully supplied with vessels than those in which the function of nutri- tion only is performed. Soemmering, Prochaska, and others, have observed that the actual termination of the arteries is diffprent in different organs. Referring for farther details upon this subject to textural anatomy, I shall content myself with stating here, 1st, that the arteries terminate in the capillary system, through the medium of which they become continuous with the veins, as is demonstrated even by the coarsest in- jections ; 2d, that the arteries enter only in a very slight degree into the composition of the capillary system, which is essentially venous ; this may be ascertained by in- jecting the arteries of an organ, the venous capillary system of the same having been previously injected by the veins ; it will then be perceived that the arteries enter but very little into the formation of the capillary system, and that they cease to exist as soon as they have communicated with it. If it were objected that, through this prep- aration, the injected liquid might have passed over from the venous capillaiy system into * [Another important result of this is, that a divided artery is enabled to retract within its sheath. In the abdomen and head this sheath scarcely exists.] t i have seen a ligature of the primitive carotid which had been laid bare to too great an extent followed by a consecutive hemorrhage and death. THE ARTERIES. 499 the arterial, I would remark, that the impossibility of this reflux is one of the most clear- ly demonstrated facts in anatomy. Structure of Arteries. The walls of an artery are composed of three coats : an external, a middle, and an in- ternal.* The External Coat. — This is generally called the cellular coat, because it is in some measure continuous with the surrounding cellular tissue. Scarpa erroneously regarded it as not forming an integrant part of the arteries. It consists of a filamentous, areolar, and, as it were, felted tissue, which is never charged with fat or infiltrated with se- rum, and which appears to me to present all the characters of the dartoid tissue. I believe that the contractility which has been attributed to the middle coat is altogether dependant upon this, t It is the only coat which remains undivided after the applica- tion of a ligature. The Proper or Middle Coat. — The characteristic properties of arteries are chiefly de- pendant upon this coat. It is composed of circular fibres, which interlace at very acute angles, but which do not present the spiral arrangement admitted by some authors. From its yellow colour and its elasticity, it has been called the yellow or elastic coat. It is ex- tensible longitudinally and transversely. It is very fragile, is easily torn by longitudinal extension, and is cut by a ligature. It is proportionally thinner in the great than in the small arteries. This coat is of the same nature as the yellow elastic ligaments, and is therefore not muscular. Moreover, chemical analysis shows that it contains no fibrine ; direct irritation develops no contractility in it ; and the supposed phenomena of irrita- bility pointed out by Haller may be entirely attributed to elasticity. It should be re- marked that the middle coat may be separated in several distinct layers, which are, how- ever, not independent of each other ; while the most external layers present a strongly- marked fibrous linear disposition, the most internal exhibit an equally marked lamellar one ; indeed, to such extent, that authors have considered as a dependance of the inter- nal coat the layer of yellow tissue which is in contact with the internal membrane, properly so called. The Internal Coat. — It is a transparent pellicle of extreme tenuity ; it must be care- fully distinguished from the subjacent layer, which is almost always dissected off with it. It is of a pale pink colour, and is lubricated with serosity. It appears to be of the nature of serous membranes, of which it presents the chief characteristics, viz., tenuity and non-vascularity.t It may even be said that, like the serous membranes, it is ex- clusively formed by a lymphatic net. I do not think that this interna^ coat of the arter- ies, which may have been considered as a sort of inorganic glue, is extensible or elas- tic ; on the contrary, in arteries in a non-distended state, this coat exhibits the appear- ance of folds which disappear by distension. Vessels and Nerves. — The arteries and veins distributed to the coats of the arteries are called vasa vasonim. In regard to the question whether the arteries receive any nerves, or whether the nervous plexuses which accompany them are only intended for the or- gan to which the vessels are distributed, I would observe, that it has appeared to me that several filaments of the great sympathetic nerve were lost in the thickness of the aorta, and it is probable that the same disposition exists in regard to the less consid- erable arteries. As to the vasa vasorum, some believe they arise from the neighbour- ing vessels, while others are of opinion that they are derived from the vessels them- selves to which they belong. I adopt the latter opinion, and believe that they mostly arise from the arteries to which they are attached. The venous vasa vasorum of the arterial coats join the nearest veins. Preparation, The preparation of an artery consists in separating it from the neighbouring parts, at the same time preserving its relations. Most of the arteries may be studied without any other preparation than a careful dissection ; but injections are necessary in order to follow the smaller branches. Tlie most convenient injection with which I am acquaint- ed is the following :§ Tallow, nine parts ; Venice turpentine, one part ; ivory black, mix- ed with spirits of turpentine or varnish, two parts. * All the Tessels, and all the tubes of the body, are formed of different layers. t All experimenters have observed that, in an animal which dies of hemorrhag-e, the arteries, during- the last moments of its life, lose a consideralile part of their caliber, which is restored to them immediately after death. This phenomenon, which appears at first sight to be in opposition to the absence of the contractility, properly so called, of the middle coat, may be easily accounted for by the tonic contractility of the dartoid tissue. The presence of this tissue may also account for the smallness or the contraction of the pulse, in op- position with its fulness, a double character which is sometimes met in the same individual, and in the same diseases, at short intervals. I [It consists of longitudinal fibres, which are slightly interlaced, and are covered with a squamous epithe- lium. The longitudinal wrinkles observed in arteries contracted after death are produced in this coat.] i) [The paint or cold injection is one of the most useful ; it consists of either red or white lead, mixed as a paint, witii a small quantity of boiled linseed oil, with spirits of turpentine, and also with some driers, viz., sugar of lead and litharg-e.J 500 ANGEIOLOGY. The best injection for preparations intended to be preserved is wax, one part ; taUow, three parts ; vermilion, indigo, or Prussian blue, first mixed w^ith spirits of turpentine. It is advantageous, before making the general injection, to throw in some turpentine or spirit varnish, coloured with the substances mentioned above. For a very fine injection it is necessary to use glue-size, coloured either with lamp- black or vermilion ; but this mode of injection is not suitable where the preparation is to be preserved. In order to place a tube in the aorta, saw through the sternum longitudinally ; keep the two halves apart by means of a small piece of wood ; open the pericardium ; be care- ful not to mistake the pulmonary artery for the aorta ; raise up the aorta by a ligature ; make an incision in it anteriorly, and introduce the pipe. Injections of the whole body may also be made by introducing the tube into a large artery, such as the primitive ca- rotid ; this mode of injection permits of injecting the heart and the cardiac arteries, and of avoiding the mutilation of the arch of the aorta. The partial injections in a whole subject are preferable to the general injections, especially when such substances as tal- low are used, which are easily solidified. Of course, an indispensable condition for the success of these partial injections is the previous isolation of the arterial system that you wish to prepare. This isolation is eflfected by ligatures which are put upon the large arteries communicating with the small arteries that are to be injected. In injecting the coronary arteries, the pipe must be introduced into one of the carotids. DESCRIPTION OF THE ARTERIES. THE PULMONARY ARTERY. Preparation. — Description. — Relations. — Size. — Dcvclopme^it. Preparation. — In order to inject the pulmonary artery, the injecting pipe mast be in- troduced into one of the venae cavae. The pulmonary artery, called vena arteriosa by the older writers, because having all the external characters of an artery ; it nevertheless contains black blood, extends from the right ventricle to the two lungs. It arises {k, fig. 191) from the infundibuliform pro- longation of the right ventricle, and then passes upward and to the left side, crossing in front of the aorta, which is embraced by its concavity ; having reached the left side of this artery, after a course of about fourteen or fifteen lines, it divides into two trunks {k k, fig. 192), whifih proceed transversely, one to the riglit, the other to the left lung {kk, fig. 171), where they terminate by dividing into branches. From the point of di- vision into the right and left branches* a fibrous cord, the remains of the ductus arteri- osus, proceeds in the original direction of the artery, and is attached to the concavity of the arch of the aorta opposite the left subclavian artery. At its origin the pulmona-y artery is covered externally by the highest fibres of the infundibuluni ; internally it is provided with three sigmoid movable valves (a a a, fig. 196), which, when depressed, completely close the mouth of the vessel. By careful dis- section, it is found that the pulmonary artery is cut at its origin into three festoons, cor- responding to the sigmoid valves, and that it is connected to the tissue of the heart by its internal coat, which is contiguous with the lining membrane of the right cavities of the heart ; and also by prolongations given off from the fibrous zone, and attached to the convex borders of the three festoons, and to the angular intervals between them. Relations. — In front and on the left side the pulmonary artery is convex, and covered by the serous layer of the pericardium, which is often separated from it by some fat ; be- hind and on the right side it is concave, and is in relation with the aorta, which it em- braces. The right and left auricles are in contact with its corresponding sides. Size. — The left branch of the puhnonary artery is about one inch in length ; it is in relation behind with the left bronchus, one of the bronchial arteries often passing between them ; it is in direct relation with the aorta. In front, it is covered by the serous layer of the pericardium, excepting near the lungs, where the pulmonary veins are placed in front of the arterial branches. The right division of the pulmonary artery is from sixteen to eighteen lines in length ; . it is in relation in front with the vena cava superior, and with tijp, ascending portion of the aorta, but not immediately, for the serous layer of the pericardium covers both the aorta and the corresponding part of the pulmonary artery. Behind, it is in relation with the right bronchus, and passes above the right auricle. Development. — In the foetus, instead of the fibrous cord, which we have described as proceeding from the point at which the pulmonary artery divides into its two branches,! there is a canal called the ductus arteriosus, almost equal in diameter to the pulmonary * See note, infra. t [It was noticed by Hallex and Senac, that the ductus arteriosus in the fcetus, and the cord to which it is reduced after birth, arise, not from the angle of division into the right and left pulmonary arteries, but from the left pulmonary artery itself: this is an interesting and important fact in reference to the development of the great vessels issuing from the heart.l THE AORTA. 501 artery itself, the course of which vessel it pursues ; at this time the right and left branch- es of the pulmonary artery are very small. At birth the whole of the venous blood pro- ceeds to the lungs, none of it passing through the ductus arteriosus, which then becomes obliterated. THE AORTA. Preparation. — Definition. — Situation. — Direction. — Size. — Divisio7i into the Arch of the Aor- ta, the Thoracic Aorta, and the Abdominal Aorta. Preparation. — The aorta may be studied without having been injected.* In order to study it in an injected subject, the median incision made for the purpose of introducing the injection must be prolonged down to the pubes. Then disarticulate the clavicles, separate the two sides of the thorax, even so far as to break some of the ribs, and keep them separate by introducing a piece of wood ; cut through the abdominal parietes, and turn the left lung over to the right side. The aorto {aoprri, arteria magna, arteriarum omnium mater, ah c d.fig. 198), the com- mon origin of all the arteries of the human body, commences at the left ventricle, and terminates by bifurcating (at d) opposite the fourth lumbar vertebra. Situation. — It is situated deeply in the thoracic and abdominal cavities, along the ver- tebral column, which affords it both support and protection. In those animals in which the aorta is prolonged beyond the trunk, the vertebral column accompanies the vessel, and forms a bony canal or sheath for it, distinct from the canal for the spinal cord. Direction. — Immediately after its origin, the aorta advances towards the right side {a, Fig. 198. Jig. 198), and almost directly afterward pro- ceeds upward, describing a slight curve, the con- vexity of which is turned forward and to the right, and the concavity backward and to the left. After leaving the pericardium, it changes its direction, becomes suddenly curved, and passes almost horizontally from the right to the left, and from before backward, to reach the left side of the vertebral column, on a level with the third dorsal vertebra, at which point (b) it makes a third curve, and becomes vertical and descend- ing. Having reached the diaphragm (at c), it inclines a little to the right side, in order to gain the median line, and to pass through the ring, or, rather, the canal, formed for it by the pillars of the diaphragm. From this point to its ter- mination, it rests upon the middle of the anteri- or surface of the vertebral column. Varieties in its Direction. — It is not a very rare occurrence to find the aorta curving over to the right instead of the left side — a disposi- tion which may either be accompanied with a complete transposition of the thoracic and ab- dominal viscera, or may be independent of it. Size. — The several portions of the aorta have not a uniform caliber ;t but its gradual decrease, in this respect, bears no direct proportion to the number and size of the branches given off from it. At its origin it always presents three ampul- lae, which correspond to the sigmoid valves ; they are called the sinuses of the aorta, or sinuses of Valsalva. They exist originally, and must, therefore, be distinguished from a dilatation found on the convex side of the arch of the aor- ta in old subjects, and called the great sinus of the aorta. This dilatation resuhs entirely from the impulse of the current of the blood. The caliber of the aorta, moreover, differs exceedingly in different subjects, even when there is no appreciable organic lesion :t it should be remarked, however, that the thickness of its coats is not at all in proportion with its caliber. * It will be advantageous to study the aorta in the same subject in which the viscera have already beea ex- amined. t Thus, the caliber of the commencement of the aorta, compared with that of its termination, is g^enerally as five to three ; hence the diminution is not by any means proportionate to the number of branches arising from it, for the united calibers of its collateral branches would much exceed that of the main vessels. t Thus, I have seen a case in which the aorta was 4 inches 8 lines in circumference opposite the arch, and 2 inches 6 bnes at its lower end : the latter is the usual size of the vessel. 502 ANGEIOLOGY. The aorta is generally divided into three portions, viz., the arch of the aorta, the tho- racic aorta, and the abdaminal aorta. The tvi'o latter portions form together the aorta de- sccndcns. The Arch of the Aorta. I shall give this name to all that pait of the aorta {a b,fig. IQS) which is comprised between its origin from the left ventricle and the point where it is crossed by the left bronchus.* The direction of the arch of the aorta is neither transverse nor antero-posterior, but oblique from the right to the left side, and from before backward ; so that it is anterior, median, and substernal in its first portion, and posterior at its termination, and in rela- tion with the left side of the vertebral column. In consequence of these relations, aneu- risms of the anterior part of the arch of the aorta frequently affect the sternum, while aneurisms of the posterior portion affect the vertebral column. Relations. — We shall examine the relations of the arch of the aorta, first in its pericar- diac or ascending portion, and then in its horizontal and descending portions taken to- gether. The Pericardiac Portion {f,fig. 191). — Concealed, as it were, in the substance of the heart at its origin, it is in relation in front with the infundibulum of the right ventricle, and behind with the concavity of the auricles, which are moulded upon it. On the right, it rests upon the groove between the infundibulum and the right auriculo-ventricular or- ifice ; on the left, it is in relation with the pulmonary artery. It is important to note the practical consequences of these relations. I have recently seen a communication between the aorta and the infundibulum. Again, aneurisms of the origin of the aorta may burst into the auricles. After leaving the heart, this portion of the aorta is surrounded on all sides, but to a greater extent in front than behind, by the serous layer of the pericardium, which forms a sort of additional coat for it, excepting in front, below, and on the left side, where it is in immediate contact with the pulmonary artery, as that vessel turns round it. Behind, this portion of the aorta is in relation with the right division of the pulmonary artery ; on the right, with t'ne vena cava superior. It follows, therefore, that the pulmonary ar- tery on the one hand, and the aorta on the other, form two half-rings, like the branches of the letter x, which embrace each other by their concavities. The pericardiac portion of the aorta is situated oeneath the sternum, from which it is separated by the pericar- dium and the anterior mediastinum The Second Portion, comprising the Horizontal and Descending Pwtions of the Arch. — On the outside of the pericardium, the aorta is in relation, in front and on the left side, with the left pleura, and is separated by it from the corresponding lung, which is exca- vated at that point. The phrenic and pneumogastric nerves are also in immediate con- tact with it. Behind, and on the right side ( /, fig. 171), it is in direct relation with the tra- chea, the commencement of the left bronchus, the oesophagus, the thoracic duct, the re- current nerve, the vertebral column,t and a great number of lymphatic glands. By its convexity, which is directed upward, it gives origin to three large arterial trunks, viz., proceeding from the right to the left side, the hrachio-cephaUc (e, fig. 198) or iimom- inate, the left common carotid (/), and the left subclavian (g) arteries. The highest point of tlie arch is opposite the origin of the brachio-cephalic artery in the infant, and that of the left subclavian in old subjects. The distance between the fourchette of the sternum and the highest point of the aortic arch varies in different ages and individuals : it is generally from ten to twelve lines in the adult ; it is much less in the aged and in the newborn infant, but for very different reasons ; in the infant it is owing to the undevel- oped condition of the sternum, but in advanced age it depends upon dilatation of the arch of the aorta ; in some adults, also, we find the distance very inconsiderable, and this is important in reference to the operation of tracheotomy. I3y its concavity, which is directed downward, the arch of the aorta is in relation with the left recurrent nerve, which embraces it, as it were, in a loop, having its concavity turned upward; with the left bronchus ip,fig- 171 ; also,.;?^. 198), which is placed be- hind the horizontal portion of the arch, and then becomes situated in front of its descend- ing portions, so that the aorta, during its curvature, has two different relations with this air-tube ; and, lastly, with a very great number of lymphatic glands, which in some measure fill up the concavity of the aortic arch. Anomalies of the Arch of the Aorta. — A very remarkable anomaly of the arch of the aorta has been observed, in which the vessel, being simple at its origin, divides into two trunks, which pass, one in front and the other behind the trachea, and then reunite to form the descending aorta. The aorta sometimes presents traces of a subdivision into * The limits of the arcn of the aorta are not weJ defined ; most authors exohide the first curve of the ar- tery The lower boundary is marked by the origin of the left subclavian, according to some ; by the left bron- chus, according to others : and. lastly, according to a great many, by the articulation of the fourth with the fifth dorsal verteora. t I have, I believe, satisfactorily demonstrated, in another part of this work, that the left lateral concavity of the vertebral column was owing tu the presence of the arch of the aorta BRANCHES OF THE AORTA. 503 two from its origin ; such a case appears to indicate a fusion of two aortas into one, for we then find five sigmoid valves. The Thoracic Aorta. The thoracic aorta (b c, fig. 198) is situated in the posterior mediastinum, along the left side of the vertebral column, and it projects into, and encroaches upon, the left cavity of the chest. Relations. — It corresponds, on the left side, with the lung, from which it is separated by the left wall of the posterior mediastinum ; on the right, it is in relation with the cesophagus, the vena azygos, and the thoracic duct ; in front, with the left pulmonary ar- teries and veins above ; with the cesophagus (h) below, which canal becomes anterior to it before passing through the oesophageal opening in the diaphragm, and with the peri- cardium in the middle, by which it is separated from the posterior surface of the heart ; iehind, it is in relation with the vertebral column, the thoracic duct passing between them above. The thoracic aorta is surrounded by an abundance of cellular tissue, and by a number of lymphatic glands. Diaphragmatic Portion of the Thoracic Aorta. — The diaphragm does not form a simple orifice or an aponeurotic arch for the aorta, but its crura {s s,fig. 199) are arranged into a muscular semi-canal, from fifteen to eighteen lines in length, and terminating below by a tendinous arch. The aorta is accompanied, while passing through this canal, by the thoracic duet* and the vena azygos, and it inchnes a little to the right side, in order to become anterior to the vertebral column. The Abdominal Aorta. The abdominal aorta (c d,fig. 198) occupies the middle part of the anterior surface of the vertebral column, and is in relation on the right side with the vena cava inferior, and in front with the pancreas and the third portion of the duodenum, which rests immedi- ately upon it ; in the rest of its extent it corresponds with the adherent borders of the mesentery, and with the peritoneum covering the lumbar region of the vertebral column. The stomach and the convolutions of the small intestine separate the aorta from the an- terior parietes of the abdomen. When the small intestine falls down into the pelvis, the abdominal aorta may be felt immediately behind the wall of the abdomen, and may be easily compressed there, so as completely to intercept the passage of the blood, t BRANCHES FURNISHED BY THE AORTA IN ITS COURSE. Enumeration and Classification. — Arteries arising from the Aorta at its Origin, viz., the Cor- onary or Cardiac. — Arteries arising from the Thoracic Aorta, viz., the Bronchial, the Oesophageal, the Intercostal. — Arteries arising from the Abdominal Aorta, viz., the Lum- har, the Inferior Phrenic, the Caeliac Axis, including the Coronary of the Stomach, the He- patic and the Splenic, the Superior Mesenteric, the Inferior Mesenteric, the Spermatic, the Renal, and the Supra-renal or Capsular. The aorta is the common trunk of all the branches and twigs given off" by the arterial tree. It alone furnishes, therefore, all the arteries of the human body. The branches which come from it I shall divide into terminal and collateral branches. The terminal branches of the aorta consist of the middle sacral and the two common iliac arteries. The collateral branches are very numerous : they may be divided into those arising from the pericardiac portion of the aorta, viz., the coronary or cardiac ar- teries ; those arising from the aortic arch, viz., the brachio-cephalic, the left common carotid, and the left subclavian : these we may consider as terminal arteries, wliich, ta- ken together, have been termed the ascending aorta in opposition to the descending aorta ; those arising from the thoracic aorta, which may be subdivided into the parietal branches, viz., the intercostals and the visceral, viz., the bronchial, oesophageal, and mediastinal arteries ; and, lastly, those arising from the abdominal aorta, which may also be distinguished as the parietal, viz., the lumbar and inferior phrenic arteries, and the visceral, viz., the coeliac axis, the superior and inferior mesenteric, the supra-renal, the renal, and the spermatic arteries. Arteries arising from the Aorta at its Origin. The Coronary or Cardiac Arteries. Dissection. — Take off the serous membrane from the heart, and also the fat which oc- * It is a mistake to say that the right azygos vein passes through the same opening as the thoracic duct. The azygos vein traverses the opening which is destined to the passage of the great splanchnic branch of the sympathetic nerve. t This compression is very easily applied in women immediately after parturition, both in consequence of the relaxed state of the abdominal parietes allowing them to be readily depressed, and also from the facility, with which the small intestines are moved aside. 504 ANGEIOLOGY. cupies the furrows ; in order to see distinctly the origin of these arteries, remove the pulmonary artery and the infundibulum of the right ventricle. The cardiac or coronary arteries {see figs. 191, 192), the nutritious vessels of the heart, or, as it were, its vasa vasorum, are two in number, and are named right and left on ac- count of their origin, and also anterior and posterior from their distribution. Their number is not constant. Thus the two coronary arteries sometimes arise by a common trunk, to the left of the puhnonary artery.* Sometimes there are three coronary arter- ies ; Meckel has seen four ; but these varieties in number do not affect their distribu- tion, for the supernumerary arteries merely represent branches, which, instead of arising from the coronary arteries themselves, proceed directly from the aorta. I have recently seen the right coronary artery arise from the aorta by three branches in juxtaposition, one of which was of considerable size : the others were small. Origin. — They arise from the anterior part of the circumference of the aorta, imme- diately above the free margin of the sigmoid valves, at the highest points of the two corresponding sinuses. The origins of these vessels are so situated, that their orifices are not covered by the valves when these latter are apphed to the walls of the aorta, so that the heart receives its arterial blood at the same time as all the other organs. The angle at which the coronary arteries arise is extremely obtuse, so that the course of the blood in them is completely retrograde. The coronary arteries differ from each other in caliber, the right being larger than the left, and also in their course, so that a special description is requisite for each. The left or anterior coronary artery is destined principally for the anterior furrow of the heart ; it is concealed, at its origin, by the infundibulum, from between which and the left auricula it then escapes, and entering {e,fig. 191) the anterior furrow of the heart, traverses it in a very tortuous manner, and anastomoses, at the apex, with the right or posterior coronary artery. Not unfrequently this artery divides into two branches, one of which runs along the anterior furrow, while the other passes upon the anterior sur- face of the left ventricle. In this course, opposite the base of the ventricles, the artery gives off an auriculo- ventricular branch, which, arising at a right angle, enters the left auriculo-ventricular furrow, and, passing along it, turns round the base of the left ven- tricle, as far as the posterior inter-ventricular furrow {e,fig. 192), where it anastomoses with the right coronary artery. The right or -posterior coronary artery is larger than the left ; it arises to the right of the infundibulum, between that part and the right auricle. Immediately after its origin it is surrounded with a large quantity of fat, and turns directly, so as to gain the right auriculo-ventricular furrow. At the upper end of the posterior inter- ventricular furrow (c, fig. 192) it bends at a right angle, and entering the furrow, runs along it to the apex of the heart, where it anastomoses with the left coronary artery. At the point where it changes its direction, the right coronary artery gives off a branch, which anastomoses with the auriculo-ventricular branch of the left artery. From this description, it follows that the cardiac arteries and their principal divisions occupy the furrows of the heart ; that they form two vascular circles, which are placed at right angles to each other like the furrows themselves ; that the auriculo-ventricular circle is formed on the right by the trunk of the right cardiac, and on the left by a branch of the left cardiac artery ; that the vessels forming these two circles are tortuous, but especially those on the ventricles, because that part of the heart is subject to greater variations in its dimensions than the part with which the auriculo-ventricular circle is in relation ; and, lastly, that both coronary arteries anastomose by inosculation, and therefore can easily supply each other. All the arteries of the heart proceed from these two circles. The auriculo-ventricular circle gives off some ascending or auricular branches, an aortico-pulmonary branch to the origins of the aorta and pulmonary artery, and an adipose branch, all of which were pointed out by Vieussens ; also some descending or ventricular branches, the two prin- cipal of which run somewhat obliquely along the right and left borders of the heart. The ventricular circle gives off branches which penetrate the fleshy fibres at right an- gles. A large artery, which has been described as the artery of the septum, appears to be one of the terminal branches of the left coronary artery ; it dips into and is lost in the substance of the septum. Lastly, the coronary arteries communicate with the bronchial. They are very liable to calcareous deposites.f Arteries arising from the Thoracic Aorta. These may be divided into visceral branches, all of which arise from the front of the * The coronary arteries were denominated by the older anatomists, and especially by Bartholin, coronarite modo simplex, modo gemina. Meckel, Harrison, and others have described oases in which there was but one coronary artery. According to the descriptions of writers on comparative anatomy, that disposition is natural with the elephant. t It is not uncommon from such deposites to find cardiac arteries which are extremely narrowed, and even obliterated. Several pathologists have considered this ossification of the cardi.ic arteries as the cause of those phenomena which are designated by the name of angina vectoris ; but tlus opinion is a mere hypothesis. - THE AORTIC INTERCOSTAL ARTERIES. 505 aorta, viz., the bronchial and the oesophageal, and parietal branches, which arise from the back of the aorta, viz., the aortic intercostals. The Bronchial Arteries, Dissection. — Carefully take away the heart and pericardium, dissect the bronchi, and trace these arteries both to their origin and towards their termination. Number and Origin. — The bronchial arteries (see^^. 198) vary much both in number and origin. There are generally two on each side ; but sometimes there are three, or even four, arising either at different heights or by a common trunk. Occasionally, one of them arises from the subclavian, or from the internal mammary, or, rather, from the first intercostal, or, lastly, from the second, or even the third intercostal artery. I have seen the inferior thyroid artery give off a bronchial artery, which, after run- ning along the trachea, passed in front of the right bronchus, and anastomosed freely with the right bronchial furnished by the aorta. The right bronchial artery is always larger than the left. Whatever be their origin, the bronchial arteries pursue a tortuous course to the cor- responding bronchus, and are usually situated on its posterior surface. When the right bronchial artery arises from the aorta, it crosses obliquely over the lower part of the tra- chea. The bronchial arteries always give some branches to the cesophagus ; a very great number to the bronchial glands ; also several to the left auricle : they anastomose with the coronary arteries on the one hand, and with the inferior thyroid and the supe- rior intercostal arteries on the other. Haller believes that the terminations of the bronchial arteries anastomose with the di- visions of the pulmonary artery, and says that he has seen free and evident communica- tions between them.* The (Esophageal Arteries. The (esophageal arteries {h,fig. 198) vary in number from three to seven, and are re- markable for their slenderness and length. They arise in succession from the front of the aorta, which they leave at right angles, and immediately curve downward to reach the front of the cEsophagus, where they divide into extremely slender ascending, and into very long descending branches, from which are given off a numerous series of twigs. The superior cesopliageal artery almost always anastomoses with the bronchial arteries, and the oesophageal branches of the inferior thyroid. The i'nferior cesophageal artery anastomoses with the cesophageal branches derived from the left inferior phrenic, and from the coronary artery of the stomach. The branches from the oesophageal arteries perforate the muscular coat of the oesoph- agus, ramify in the sub-mucous cellular tissue, and terminate in a network in the sub- stance of the mucous membrane. The Aortic Intercostal Arteries. Dissection. — In order to see the posterior branches, dissect the posterior spinal mus- cles, and open the vertebral canal. To see the anterior branches or the intercostals, properly so called, expose these vessels on the inside of the parietes of the chest in the first half of their course, and then on the outside of the chest to their termination. The aortic or inferior intercostals {i i i' i', fig. 198), so named to distinguish them from the superior intercostal, a branch of the subclavian, and from the anterior intercostals, derived from the internal manunary, are generally eight or nine in number, the upper two or three intercostal spaces being supphed by the superior intercostal branch of the subclavian. The varieties in their number depend upon the number of intercostal spaces which are supplied with branches frorfi the subclavian, and also upon the number of intercostal ar- teries which arise by a common trunk. Origin. — They arise at various angles from the back of the aorta ; the superior gen- erally at an obtuse angle to gain the spaces situated above them ; the succeeding ones at different angles, which are less and less obtuse, and sometimes right angles, or even acute angles. In the latter case, the vessel immediately ascends to reach the intercostal space for which it is intended. The right and left intercostals are of equal size, and there is little difference in this respect between the superior and the inferior intercostals. In consequence of the aorta being situated towards the left side, the right intercostals (i' i') are longer than the left. They turn over the body of each dorsal vertebra, passing behind the cesophagus, the thoracic duct, and the vena azygos, and reach the correspond- ing intercostal space. The left intercostals enter their proper spaces at once. Both are in relation with the costal pleura and the thoracic ganglia of the great sympathetic nerve, behind which they are situated. The lower intercostals on the left side are covered by the vena azygos minor. The two lower intercostals on both sides are covered by the pillars of the diaphragm. In their course over the bodies of the vertebraj, the intercos- tals give off numerous nutritious branches, which enter the foramina on the anterior sur- face of these bones. See note, p. 421. S s S 506 ANGEIOLOGY. On reaching the intercostal space, each artery immediately divides into an anterior and a posterior branch. The anterior or intercostal branches are larger than the posterior, and may be regarded as the continuation of the arteries themselves in their original course. They are at first situated in the middle of the intercostal spaces, between the pleura and external inter- costal muscles ; they then pass between the external and the internal intercostals, reach the lower border of the rib above them, and are lodged in the grooves found in that sit- uation ; having reached the anterior third of the intercostal spaces, where they have be- come extremely small, they quit the grooves, and again become placed in the middle of the spaces ; the superior intercostals then terminate by anastomosing with the intercostal branches of the internal mammary, and the inferior intercostals with the epigastric, the phrenic, the lumbar, and the circumflex iliac arteries During its whole course, each intercostal branch is in relation with the corresponding intercostal vein and nerve. The inferior intercostal arteries, commencing at the fifth, after leaving the intercostal spaces, are lost in the external and internal oblique muscles of the abdomen, which, as we have seen, form, as it were, continuations of the intercostal muscles (see Myology). The intercostal branch furnishes numerous ramusculi to the intercostal muscles, the ribs, the sub-pleural cellular tissue, the muscles which cover the thorax, and even to the integuments. A very small, but tolerably constant branch, is given off at an acute angle from the artery, at the moment where it dips between the two sets of intercostals, gains the upper border of the rib below, and is lost in the periosteum and the muscles, after running a variable distance. The fosterior or dorsi-spinal branches pass directly backward between the transverse processes of the vertebrae, on the inner side of the superior costo-transverse ligaments, and each of them immediately divides into two branches : one, the spinal, wiiich enters the inter-vertebral foramen, and again divides into a vertebral branch for the bodies of the vertebrae, and a inedullary branch for the coverings of the spinal cord, and for the cord it- self, to the distribution of which we shall hereafter return. The second, or dorsal branch, is larger than the spinal, and forms a continuation of the dorso-spinal ttunk ; it escapes behind between the transverso-spinalis and longissimus dorsi, sends some ramifications between the longissimus dorsi and sacro-Iumbalis, and terminates in the muscles and the skin. Arteries arising from the Abdominal Aorta. The branches furnished by the abdominal aorta are parietal, viz., the lumbar and the inferior phrenic arteries ; and the visceral branches, viz., the cceliacaxis, the superior and inferior mesenteric, the spermatic, the renal, and the middle supra-renal arteries. In refer- ence to their place of origin, these arteries may be divided into those which arise from the anterior aspect of the aorta, viz., the coeliac axis, the superior and inferior mesenter- ic, and tne spermatic arteries ; and those which arise from its sides, viz., the renal, the middle supra-renal, and the lumbar arteries. The lumbar arteries might be regarded as arising from the back of the aorta. The Lumbar Arteries. Fig. 199. Dissection. — Remove the pillars of the diaphragm and the psoas muscles. In order to expose the dorsi-spinal branches, dissect the posterior spinal muscles, and open the vertebral canal. To ex- pose the anterior branches, dissect the abdominal muscles carefully. The lumbar arteries {I I, fig. 199) continue the series of intercostals, with which they present nu- merous analogies in reference to their origin, course, and termination. They vary in num- ber from three to five, but there are usually four. These varieties depend either upon the greater or less size of the ilio-lumbar artery, which bears the same relation to the lumbar arteries as the superior intercostal does to the aortic intercostals, and which sometimes takes the place of the last, some- times of the last two lumbar arteries ; or the va- rieties may depend on several lumbar arteries ari- sing from a common trunk. Origin. — The lumbar arteries are given off at right angles from the back of the aorta. Very rarely the right lumbar arteries arise by a common trunk with the left. Course. — They proceed transversely in the grooves on the bodies of the vertebrae, and pass - THE INFERIOR PHRENIC ARTERIES, ETC. 507 under the tendinous arches of the psoas, by which muscle they are covered. They send a great number of branches to the bodies of the vertebras ; and having reached the base of the transverse processes, each of them divides into two branches, a posterior or dor- si-spinal, and an anterior or abdominal branch. The posterior branch, which is analogous to the dorsi-spinal of an intercostal artery, di- vides into two branches : one, the spinal, which enters the spinal canal through the in- ter-vertebral foramen, and subdivides into a vertebral branch for the body of the vertebra, and a medullary branch for the cord and its coverings ; the other branch is the dorsal, which terminates in the muscles and integuments of the lumbar region. The anterior branch is smaller, and analogous to the anterior branch of an intercostal artery : it is situated between the quadratus lumborum and the middle layer of the apo- neurosis of the transversalis, and ramifies in the substance of the abdominal muscles. The anterior branch of the first lumbar artery runs along the lower border of the twelfth rib, passes obliquely downward and forward, and divides into two ramusculi, one of which continues in the same course, while the other turns downward to the crest of the ilium. The anterior branches of the second and third pair of lumbar arteries are generally small : not unfrequently the third artery is wanting. The anterior branch of the fourth lumbar artery runs along the crest of the ilium, and sends branches to the muscles of the abdo- men and to the iliacus and glutaei muscles. The Inferior Phrenic Arteries. Dissection. — CarefuLy detach the peritoneum from the lower surface of the diaphragm. The inferior phrenic or diaphragmatic, or the sub-diaphragmatic arteries (d d, fig. 199), so named in contradistinction to the superior phrenic, which are branches of the internal mammary, are so frequently derived from the coeliac axis, that some anatomists, Meckel among others, describe them as branches of that trunk. They are two in number, a right and a left. They arise from the aorta, immediately below the cordiform tendon of the diaphragm, either side by side, or by a common trunk. Sometimes they arise from the cceliac axis itself, or, rather, from the coronary artery of the stomach, from the renal, or from the first lumbar artery ; in some subjects we find as many as three or four. Each artery passes upward and outward in front of the corresponding pillar of the dia- phragm, gives some twigs to this pillar, and one to the supra-renal capsule, and then di- vides into two branches, an internal and an external. The internal branch passes direct- ly forward, ramifies and anastomoses by loops with the vessel of the opposite side around the oesophageal opening, behind the cordiform tendon of the diaphragm. The external branch is larger and more tortuous than the preceding ; it proceeds obliquely outward, between the peritoneum and the diaphragm, and divides into a great number of branches, which extend as far as the attachments of this muscle, where they anastomose with the intercostal and the internal mammary arteries. The right inferior phrenic artery, moreover, sends some branches into the coronary ligament of the liver ; the left artery gives off a branch to the cEsophagus, which enters through the oesophageal opening in the diaphragm, and joins the oesophageal branches derived from the coronary artery of the stomach and from the aorta. The Cceliac Axis. Dissection. — Elevate the liver by means of hooks, or by a ligature fixed to the right side of the chest ; depress the stomach ; divide the fold of peritoneum by which these two viscera are united ; and search for the coeliac axis between the pillars of the dia- phragm, by removing the solar plexus of nerves, which forms a thick layer in front of it. The celiac axis or artery (from KoilLa, the belly or stomach, y,fig. 199), le tronc opis- thogastrique, Chauss. {owiaOtv, behind, yaarijp, the stomach), supplies the stomach, the liver, the spleen, the pancreas, and the great omentum. It is remarkable for its size, being larger than any of the other branches of the abdominal aorta, not excepting the superior mesenteric ; for arising at a right angle from the front of the aorta, immediate- ly below the phrenic arteries ; for its horizontal course, which is rarely more than five or six lines in extent, and for its very early division into three branches, ad modum tri- dentis. These three branches are of unequal size : they are the coronary artery of the stomach {b, fig. 200), the hepatic (c), and the splenic (d), which, together, are called the coeliac tripos, or the tripos of Haller. In its short course the coeliac axis is in relation with the lesser curvature of the stom- ach, or, rather, with the gastro-hepatic omentum, behind which it is situated ; on the left side, it is in relation with the cardia ; below, with the upper border of the pancreas, upon which it rests ; above, with the left side of the lobulus Spigelii. It is surrounded by so large a plexus of nerves, that it cannot be exposed until the plexus is removed. The Coronary Artery of the Stomach. The coronary artery of the stomach, or the superior gastric (b,figs. 200, 201), is the small- est branch of the coeliac axis. It is directed upward and to the left side, to reach the oesophageal orifice of the stomach ; it then turns suddenly to the right side, pursues a 508 ANGEIOLOGY. Pig. 200. semicircular course along the lesser curvature (arteria coronaria ventriculi), and terminates by in- osculating with the pyloric artery (e), a branch from the hepatic. In this course it gives off from its convex bor- der ascending (Esophageal branches, which pass through the oesophageal opening of the dia- phragm, ascend upon the oesophagus, and are there distributed like the aortic oesophageal branches, with which they anastomose ; also car- diac branches, which form a vascular network around the oesophageal opening of the stomach, and pass transversely upon its great tuberosity ; and a series of gastric branches, which arise along the lesser curvature, and are divided into two sets, an anterior set for the front, and a posterior set for the back of the stomach. No branch ari- ses from the concavity of the curve formed by this artery. Not unfrequently the coronary artery of the stomach gives off an hepatic branch, and hence the first branch of the coeliac axis has been called the gastro-hepatic by some anatomists. In such cases, as may be conceived, this artery is very large. It is also not uncommon to find the left inferior phrenic arising from it. The Hepatic Jlrtery. The hepatic artery (c, figs. 200, 201) is larger than the preceding. It passes trans- versely from the left to the right side, describing a curve, having its concavity directed upward, and moulded, as it were, upon the lobulus Spigelii. Near the pylorus it chan- ges its direction, and passes upward to the transverse fissure of the liver, where it di- vides into two branches. In the latter part of its course it is contained within the gas- tro-hepatic omentum, in front of the foramen of Winslow, and is in relation with the ductus choledochus and the vena portae, the vein being placed behind both the artery and duct. It is not uncommon to find two hepatic arteries, one derived from the coronary of the stomach, and the other from the superior mesenteric. Sometimes there are even three hepatic arteries, one from the coronary of the stomach, a second from the superior mes- enteric, and a third from the coeliac axis. Collateral Branches. — The hepatic artery gives off three collateral branches, the pylo- ric, the right gaslro-epiploic, and the cystic. The pyloric artery, also named the small right gastric artery, to distinguish it from the coronary artery of the stomach, which was called the left gastric (e), is a small vessel which arises from the hepatic, near the pylorus : it runs from right to left along the pylorus and the lesser curvature of the stomach, and inosculates with the coronary ar- tery {b) of that viscus. Two sets of branches, an anterior and a posterior, arise from its convex border, and are distributed to the stomach and the first part of the duodenum, in the same manner as those from the coronaria ventriculi itself Not unfrequently the pyloric artery terminates near the pylorus, without anastomosing with the coronary. The right gastro-cpiploic artery {f,figs. 200, 201) is remarkable for its size and for its length. It passes vertically downward, behind the first portion of the duodenum, near the pylorus. Having reached below the duodenum, it changes its direction, passes from right to left {I) along the great curvature of the stomach, where it inosculates with the left gastro-epiploic (h, fig. 201). In one case, where the hepatic artery was given off by the superior mesenteric, the right gastro-epiploic arose directly from the coeliac axis. The first portion of this vessel, usually called the gastro-duodenal artery, furnishes sev- eral branches to the pylorus, which may be called the inferior pyloric ; it then gives a branch to the duodenum and the head of the pancreas, named the pancreatico-duodena- lis (k), and remarkable for its anastomosing with the superior mesenteric ; an arrange- ment that leads, as it were, to the cases in which the hepatic itself is derived from the last-mentioned artery ; it is also remarkable for its size, which is sometimes such that the continuation of the vessel, the right gastro-epiploic artery proper, is only half the size of the trunk from which it is given off (the gastro-duodenal). In its horizontal portion along the great curvature of the stomach, the right gastro- epiploic sends both ascending and descending branches : the former, or gastric branches, divide into two sets ; one for the anterior, and one for the posterior surface of the stom- ach. The latter, or epiploic branches {g g, fig. 200), are extremely long and slender ; THj: SPLENIC AND SUPERIOR MESENTERIC ARTERIES. 509 they pass downward parallel to each other, without any windings, in the substance of the two anterior layers of the great omentum, are reflected upward at its lower border, just as the two layers are themselves, and accompany them as far as the transverse colon, to which they are distributed. The cystic artery '{i, fig. 200) is a small vessel which almost always arises from the right of the terminal divisions of the hepatic artery, reaches the neck of the gall-blad- der, and divides into two branches ; one superior, running between the liver and the vesicula, the other inferior, which pursues a tortuous course between the peritoneum and the proper coat of the gall-bladder, divides and subdivides, and is finally distributed to the mucous membrane. Terminal Branches.— Of the two terminal branches of the hepatic artery, one dips into the right extremity of the transverse fissure of the liver, and the other into the left ex- tremity of the same fissure : in these situations they become apphed to the correspond- ing branches of the vena portse and hepatic duct, are enclosed with them in the capsule of Glisson, and closely accompany the corresponding ramifications of those vessels through all their divisions and subdivisions. The Splenic Artery. The splenic artery {d, figs. 200, 201) is larger Fig- 201. than either of the other divisions of the coeliac axis. Immediately after its origin it is received into a slight groove formed along the whole of the upper border of the pancreas (z). It passes from the right to the left side, and is exceedingly tor- tuous in its course :* having reached the hilus of the spleen, it divides into a great number of terminal branches (n, fig. 201), which enter that organ separately. It is not rare to find one of these branches detached from the others, to be distributed either to the upper or the lower end of the spleen. Near the spleen, the splenic artery and its di- visions are enclosed within the gastro-splenic omentum. The relations of the splenic artery to the posterior surface of the stomach explains how, in certain cases of ulceration of the stomach opposite the pancreas, this artery may become the source of haematemesis. The splenic artery gives off several collateral branches : The pancreatic arteries (i i), which are variable in number, and are very large, consid- ering the size of the organ to which they are distributed. The left gastro-epiploic artery (h), which often arises from one of the divisions of the splenic, passes vertically downward, behind the great end of the stomach, gains the great curvature, along which it runs from left to right, and anastomoses with a branch of the hepatic, viz., the right gastro-epiploic (/) ; like which artery, it sends oS ascending or gastric, and descending or epiploic branches. The size of the gastro-epiploica sinistra varies much, and has an inverse proportion to that of the gastro-epiploica dextra. The vasa hrevia (o o), which are remarkable for their number and shortness, generally arise from one or several of the terminal branches of the splenic artery, just as these are entering the spleen ; they pass directly, by a retrograde course, from that organ to the great cul-de-sac of the stomach, as far as the cardia, where they anastomose with the cardiac branches of the coronary artery of the stomach. From the preceding description of the branches of the cceliac axis, we perceive that the stomach is surrounded by an uninterrupted arterial circle, formed by the right and left gastro-epiploic, by the pyloric, and by the coronary arteries ; and that, secondly, the branches derived from this circle constitute an anastomotic network upon the anterior and posterior surfaces of the stomach. The Superior Mesenteric Artery. Dissection. — Look for the origin of the artery between the pancreas and the third por- tion of the duodenum ; turn the whole of the small intestines to the left side ; remove with care the right layer of the mesentery, the left layer of the right lumbar mesocolon, the inferior layer of the transverse mesocolon, and the numerous lymphatic glands which conceal the artery and its divisions. The superior mesenteric artery (below y,fig. 199) is the artery of the small intestine, • and of the right half of the large intestine. It arises from the front of the aorta, imme- * I have seen some splenic arteries not at all tortuous ; ana at other times I have found the curvatures so decided that the lower part only of the curves came in contact with the pancreas. Why do these curvatures exist? It cannot be to accommodate the variations in tlie su", of the spleen; but is it to retard the flow of the blood ? There is no proof of it ; indeed, the law which governs the existence of a tortuous condition of certain arteries is yet to be discovered. The caliber of the splenic artery is strictly proportioned to the size of the spleen. Where it is strophicd the artery ir small where hypertrophied, it becomes enormously enlarged. 510 ANGEIOLOGY. diately below the coeliac axis, and very rarely from a common trunk with it. It is at first situated behind the pancreas, and then passes vertically downward, between that gland and the third portion of the duodenum, which is crossed at right angles by it, and of which it forms the lower boundary (vide Duodenum) ; it at length reaches the mesentery, opposite the point (a, Jig. 202) where that fold meets the transverse meso- colon. Continuing its course within the sub- stance of the mesentery, and following its ad- herent border, it describes a slight curve, with the convexity directed to the left and the con- cavity to the right side : gradually diminish- ing in size as it advances, it proceeds to oppo- site the ileo-csecal valve (b), and then becomes so small that it can no longer be distinguished from the branches given off from it. It fol- lows, therefore, that the trunk {a b) of the su- perior mesenteric artery corresponds with the adherent border of the mesentery, with the length of which it, as it were, agrees. Collateral Branches. — While behind the pan- creas, the superior mesenteric sends off pan- creatic branches (k), which anastomose with those derived from the hepatic and the splenic arteries ; it rather frequently gives off the he- patic, and it is then larger than the ccEliac axis. In the mesentery, the superior mesenteric gives off two sets of branches : one set ari- sing from its convexity, and forming the arter- ies of the small intestine ; the other set from its concavity, viz., the arteries of the great intestine, called the right colic arteries. The arteries of the small intestine have received no particular name ; they are large branches, directed obliquely downward and forward, all of which proceed parallel to each other in the substance of the mesentery, towards the concave border of the small intestine. Their number is irregular, and their size unequal : seven or eight of them are at least equal in size to the radial artery, others are smaller ; the superior branches are generally the largest. Their number is calculated at from fifteen to twenty. After a course of about two or three inches, each of them bifurcates ; the branches of the bifurcation separate from each other, and, curving into arches, inosculate with the neighbouring branches. From the convexity of this series of arches, which is turn- ed towards the intestine, a multitude of branches arise, which soon bifurcate, and form anastomotic arches {d d d), which, as they are nearer the small intestine, describe a curve of much greater extent in the mesentery than the first series. From the con- vexity of this second series of arches a great many more branches arise than were given off from the first series. Lastly, from the division of these branches a third series of anastomotic arches is formed, which is still nearer the concave border of the intestine than the second. There are only three series of arches at the commencement and the termination of the small intestine ; but in the middle there is a fourth, sometimes even a fifth. From the convexity of the arches nearest to the small intestine arise two sets of ves- sels, intended for the two halves of the cylindrical gut. Each of these sets of vessels divides into sjiperficial branches, which, ramifying beneath the peritoneum, form a super- ficial network, and anastomose upon the convex border of the intestine ; and into deep branches, which perforate in succession the muscular and cellular coats, and terminate in an inextricable network in the mucous membrane. The series of anastomotic arches formed by the divisions of the superior mesenteric artery, not only regulate the current of the blood, but also enable a small number of branches, occupying a very limited space at the root of the mesentery, to supply branches to so great an extent of surface as the entire length of the small intestine, which is from fifteen to twenty-one feet. This spreading out of the vessels over a large surface will be still better seen in the arrangement of the arteries of the great intestine. ^, The arteries for the great intestine, or the right colic arteries, are two or three m num- ber, and are distinguished into the superior (e), middle (/), and inferior (A). They arise from the concavity of the curve formed by the superior mesenteric artery, and pass from the mesentery, in which they are enclosed at their origin, into the right lumbar meso- colon. The superior is ascending, the middle horizontal, and the inferior descending ; near the great intestine they bifurcate. The branches of the bifurcation anastomose, and form very large arches, with their convexities turned towards the great intestine. From these arches the intestinal branches take their origin directly, and divide into two THE INFERIOR MESENTERIC ARTERY, ETC. 511 Fig. 203. sets of parallel ramifications, an anterior and a posterior, which, like those of the small mtestine, subdivide into the sub-peritoneal and the deep branches, and terminate in the different coats of the intestine. Where the primary anastomotic arches are situated at a certain distance from the intestine, for example, opposite the angles of bifurcation of the arteries, or opposite the angles formed by the ileum with the caecum, and by the as- cending with the transverse colon, we find one, or even two, small arches filling up the angular interval. The upper branch (g) of the right superior colic artery (e, figs. 202, 203), which sup- plies the right half of the arch of the colon, anastomoses with the upper branch of the left colic artery (/, Jig. 203), which is derived from the inferior mesenteric (c). This re- marlcable anastomosis between the superior and inferior mesenteric arteries has been pointed out by anatomists as the most important anastomosis in the body. The lowest branch of the right inferior colic artery (/;, Jig. 202) anastomoses with the termination (b) of the superior mesenteric, which becomes exceedingly slender. This right inferior cohc, or ileo-colic artery (h), supplies the ceecum, the ileo-cascal angle, and the appendix vermiformis. The Omphalo-mesenteric Artery. — In the early periods of intra-uterine life, the superior mesenteric artery gives olf a branch, called the omphalo-jneseyitenc, which reaches the umbilicus, passes out of the abdomen, traverses the entire length of the cord, and is dis- tributed upon the umbilical vesicle. I have found this artery perfectly distinct in an anencephalous fcetus at the full term ; it is generally obliterated towards the end of the second month of intra-uterine hfe. The Inferior Mesenteric Artery. Dissection. — Turn the small intestines to the right side ; spread out the arch of the colon, the right lumbar colon, and the sigmoid flexure ; remove the peritoneum, which forms the inferior layer of the transverse mesocolon, and the right layer belonging to the descending colon and sigmoid flexure. The inferior mesenteric artery (m,Jig. 199 ; c,Jig. 203) is much smaller than the supe- rior. It arises from the front of the aorta, about two inches above the bifurcation of that vessel. It descends vertically in front of, and in contact with the aorta, and then in front of the left com- mon iliac artery. It is at first enclosed in the ili- ac mesocolon, but afterward enters the meso-rec- tum, where it divides into two branches, which are named the superior hemorrhoidal (h, Jig. 203). In this course, the inferior mesenteric gives off no branch on the right side ; on the left it gives two, more frequently three branches, called the left colic arteries (/), which are distributed in pre- cisely the same manner as the right colic arteries. I have already said that the upper division of the left superior colic artery (/) inosculates with the upper division (g) of the right superior colic (e). IS'ear the sigmoid flexure we find two, and some- times three series of arches from the sigmoid branch, so arranged that the last may reach the intestine. The superior hemorrhoidal arteries are distribu- ted to the rectum, in the same manner as the other intestinal arteries ; near the sphincter, they anas- tomose with the middle hemorrhoidals, which are derived from the internal iliac arteries. The Spermatic Arteries — the Arteries of the Testicles in Man, and the Utero- ovarien in Woman. Dissection. — Remove carefully the mesentery and the peritoneum. Follow these ar- teries, in man, through the inguinal passages imbedded in the substance of the sper- matic cord, down to the testicle and the epididymis ; and in woman, follow them into the substance of the broad ligament as far as the ovaries on one side, and on the other, as far as the bottom and the body of the uterus. To inject perfectly these arteries to their termination, recourse must be had to very penetrating liquids, or, what is better, to par- tial injections. The spermatic arteries (o o,Jig. 198 ; ff,Jig. 199) are distributed to the testicles in the male, and to the ovaries in the female. They are two in number, and are as variable in their origin as they are regular in their course and distribution. Their origin is remarkably distant from their termination ; an unsatisfactory attempt 512 ANGEIOLOGY. has been made to explain this circumstance by referring to the situation of the testicle in the foetus. Varieties of Origin. — These arteries generally arise from the front, sometimes from the side of the aorta, below the corresponding renal artery, rarely above it, and still more rarely from the renal itself It is rather rare for the right and left spermatics to come off at the same heights. I have seen the right spermatic artery arise below the renal, and the left by the side of the inferior mesenteric* Whatever may be their origin, these arteries pass directly downward. Sometimes they come off at a right angle, and then curve downward, so as to descend almost ver- tically upon the sides of the spine, behind the peritoneum, in front of the corresponding psoas muscle and ureter, and on the inner side of the spermatic veins. The right sper- matic artery is in relation with the vena cava inferior, and almost always passes in front, but sometimes behind it ; the artery of the left side is situated behind the sigmoid flex- ure of the colon. On both sides, having reached the side of the pelvis, the artery is sit- uated on the inner side of the psoas, in front of the external iliac artery, and is then dif- ferently distributed in the two sexes. In the male {f, fig. 199), it enters the abdominal orifice of the inguinal canal, along which it proceeds, and, together with the vas deferens and the spermatic veins, forms the spermatic cord ; it escapes from the canal, and, at a greater or less distance from the ring, divides into two branches, one of which enters the head of the epididymis, while the other, the testicular, penetrates the testicle at its upper border, and is then distribu- ted as already described (see Testicles). In the female, the ovarian arteries (o o,fig. 198), which are much shorter than the spermatics of the male, dip into the pelvis, reach the upper border of the ovaries, supply them, and also the Fallopian tubes, with a great number of branches, and terminate upon the sides of the uterus, by anastomosing freely with the uterine arteries {n 7i').i The ovarian arteries are distributed more to the uterus than to the ovary, as may be proved by the post mortem examination of the body of a pregnant or puerperal female : for it is then seen that the ovarian arteries also become largely developed as well as the uterine, and that the branches sent to the uterus are enormous in comparison with those given off to the ovaries. The ovarian arteries are very tortuous, especially opposite the brim of the pelvis : they are quite as much convoluted as the uterine arteries. The Renal or Emulgent Arteries. Dissection. — The renal arteries are prepared after the intestines, the peritoneum, the renal adipose tissue, and the numerous nervous filaments by which the arteries are sur- rounded, have been removed. The renal or emulgent arteries {e e,fig. 199) arise at right angles from the side of the aorta, above the inferior mesenteric : the left renal artery often arises a little higher than the right, doubtless on account of the size of the liver. These arteries are very large in comparison to the kidney, for they are nearly equal in size to the coeliac axis, or the superior mesenteric ; they are remarkable for their transverse, and, generally, straight direction ; for their shortness ; and, lastly, for their numerous varieties. These we shall now mention. Varieties as to Number. — There is generally one for each kidney, but frequently there are two, three, or four. Varieties as to Origin. — Not uncommonly the renal arteries arise from the aorta lower down than usual, or even from the common iliac or the internal iliac. The two latter modes of origin are scarcely observed, excepting when the kidney is displaced, and occupies either the iliac fossa or the cavity of the pelvis. In a case which I recently examined, the kidney occupied the cavity of the pelvis, and there were two renal arteries, one of which arose from the aorta at its bifurcation, and the other near the inferior mesenteric. Lastly, I should add that Meckel has seen the two renal arteries arise by a common trunk from the front of the aorta. Varieties in Direction. — When two renal arteries arise from the same side, or when one divides into two branch- es, 1 have found them, in several cases, twisted spirally round each other, like the um- bilical arteries. Varieties as to Division. — The renal artery sometimes divides immedi- ately after its origin ; and then one of the branches, separating itself from the others, proceeds to one or other extremity of the kidney. Such a mode of division leads to those cases in which there is more than one artery. Relatio)is. — The renal arteries are covered by the peritoneum and the corresponding renal veins ; they are surrounded by a quantity of adipose cellular tissue, and they rest behind upon the bodies of the vertebrae. The right renal artery is also covered by the inferior vena cava. In one case, where there were two renal arteries on the right side, one of these was in front, and the other behind the vena cava. * It IS not uncommon to meet witn two spermatic anenes on one sme t We kno-w that the development of the uterus, during the first five months of pregnancy, takes place al- most exclusively at the expense of the body, and that the neck of the uterus begins to be developed from the fifth to the sixth month. I have seen some diseases of the uterus in which a sort of independence might have been traced between the neck and the body of the womb. THE CAPSULAR ARTERIES, ETC. .513 Collateral Branches. — The renal arteries give off some small twigs to the supra-renal capsules, which are called the inferior capsular or supra-renal, and also some small branch- es to the adipose tissue which covers the kidney, and to its proper cellular coat. Terminal Branches. — At the hilus of the kidney, the renal artery divides into three or four branches, all of which enter the hilus, between the pelvis of the ureter, which is behind, and the branches of the renal vein, which are in front. The arteries subdivide in the kidney so as to form a network at the limits between the tubular and cortical sub- stances. (See Kidney.) A very few of the branches from this network proceed to the tubular substance, almost all of them being distributed to the cortical substance. Most anatomists have remarked the facility with which even coarse injections pass from the renal arteries into the veins and ureters. The Middle Supra-renal^ or Capsular Arteries. The middle supra-renal arteries {s s,fig. 199), so named in contradistinction to the supe- rior vessels of the same name, derived from the diaphragmatic and the inferior, pro- ceeding from the renal, are of large size in comparison with the organ to which they are distributed. They arise from the sides of the aorta, above the renal, supply twigs to the surrounding fat, and to the pillar of the diaphragm, run along the concave border of the corresponding supra-renal capsule, give off anterior and posterior branches, which enter the furrows on the surface of that organ, and penetrate and rami/y in its interior. ARTERIES ARISING FROM THE ARCH OF THE AORTA. Enumeration and Varieties. — The Common Carotids. — Ths External Carotid — the Superior Thyroid — the Facial — the Lingual — the Occipital — the Posterior Auricular — the Parotid — the Ascending Pharyngeal — the Temporal— the Irdernal Maxillary. — The Internal Ca- rotid— the Ophthalmic — the Cerebral Branches 0/ (he Internal Carotid. — Summary of the Distribution of the Common Carotids.— Artery of tie Upper Extremity. — The Brachio-Ce- phalic. — The Right and Left Subclavians — tkc Vertebral and its Cerebral Branches, with Remarks on the ^Arteries of the Brain, Cerebelhim, and Medulla — the Inferior Thyroid — the Supra-scapular — the Posterior Scapular— the Internal Mammary— the Deep Cervical — the Superior Intercostal. — The Axillary— the Acromio-thoracic — the Long Thoracic — the Sub-scapular — the Posterior Circumflex— the Anterior Circumflex. — The Brachial and its Collateral Branches. — The Radial, its Collateral Branches, and the Deep Palmar Arch. — The Ulnar, its Collateral Branches, and the Superficial Palmar Arch. — General Remarks on the Arteries of the Upper Extremity. Three arterial trunks, intend.id to supply the head and the upper extremities, take their origin from the arch of tte aorta. Proceeding in the order in which they arise, i. e., from right to left, they are tte innominate or brachio-cephalic {c,fig. 198), which soon sub- divides into the rio-ht commni carotid (/) and right subclavian (g), the left common carotid (/') and the left subclavian (g). The direction of that portion of the arch of the aorta which gives origin to these arter- ies is such, that they are arranged one after the other upon a plane which slopes down- ward, backward, and to the left ; so that the trunk of the innominate artery lies almost immediately beh'fld the sternum, while the left subclavian is near the vertebral column. Varieties. — These three arteries present numerous varieties in their origin, all of which appear to me co be referrible to the three following heads : varieties by approximation or fusion, varieties by multiplication, and varieties by transposition of their origins. In many cases, several of these kinds of varieties may coexist.* Varieties by Approximation or Eusion of Origins. — Sometimes the left common carotid becomes closely approximated to the brachio-cephalic trunk ; and this condition leads us to the not very uncommon variety in which these two vessels arise by a common trunk.f Again, two brachio-cephalic trunks may be given off from the arch of the aorta, one on the right, the other on the left side.t Of these two trunks which arise from the aorta, the first, which is the most voluminous, gives origin to the two carotid arteries, and to the right subclavian ; the second, which is the smallest, gives origin to the left subcla- vian. The greatest amount of variety of this kind is observed in the case where the three branches which usually arise from the arch are united into one common trunk,, which forms an ascending aorta. In this case, there is no arch of the aorta ; the aorta,. * [A variety, affecting merely the situation of the three primary vessels upon the arch, is noticed by Pro- fessor R. Quain {Opera cit.). It consists in those vessels arising to the rigjit of their usual position, i. e., near- er to the origin of the aorta.] t I have often seen these three brar-shes, viz., the brachio-cephalic trunk, the left primitive carotid, and the left subclavian, arising by the side of each other, so that their three oriiices were only separated, as it were,- by a spur. } This variety, which, together with the preceding, constitutes the normal state of some animals, seems, moreover, the reproduction of the normal disposition of the venou.s system, in which there are two cephalic venous trunks, one right, tlie other left, which unite for the purpose of forming the superior vena cava. Meck- el, I believe, was the first to remark that certain anomalies of the arterial system might be attributed to the normal disposition of the venous system. — (See the excellent article of Dr. Rendu, Memoir on the History of Arterial Anomalies, Gazette Medicate, 1842, vol. x., p. 129.) Ttt 514 ANGEIOLOGY. immediately after its origin, is divided into ascending and descending. This arrange- ment is normal in the ox, the horse, the sheep, the goat, and some other animals.* Varieties by Multiplication of Origin. — Sometimes the two common carotids arise sep- arately in the interval between a right and a left subclavian, a condition that leads us to the case in which the two carotids arise by a common trunk between the separated sub- clavians. Again, the left vertebral artery may arise directly from the aorta, between the left carotid and subclavian ; this is very common : or the two vertebrals, the two carotids, and the two subclavians may all arise separately ; or the inferior thyroid, or the thyroid of Neubauer, from the name of the anatomist who first described this variety, may arise directly from the curvature of the aorta ; lastly, the right internal mammary and the left vertebral may arise directly from the arch of the aorta. Varieties by Transposition or Inversion of Origin. — The brachio-cephalic trunk is some- times found on the left side instead of the right ; still more frequently the right subcla- vian arises separately below the left subclavian, and then passes upward and to the right side, most commonly behind the trachea and oesophagus, but sometimes between these two canals. Again, the trunks arising from the arch of the aorta have been seen to be given off in the following order : a single trunk for both common carotids ; then the left subclavian , and, lastly, the right subclavian, which arose from behind the arch of the aorta, and passed as in the preceding case. A fifth variety consists in a combi- nation of the variety by transposition either with the variety by fusion or with the vari- ety by multiplication. The Common Carotid Arteries. Dissection. — Dissect the anterior cervical region, preserving all the parts in relation to the vessels. In order to see the thoracic portion of these arteries, remove the upper part of the sternum. The primitive or common carotid arteries {ff, fig. 198 ; a, fig. 204) are the arteries of the head. Their limit above is marked by the upper border of the thyroid cartilage, op- posite which they divide into the external and internal carotids.! They are two in number, distinguished as the right and left : they differ as to their origin, their length, and their directions ; thus, on the left side, the common carotid ari- ses directly from the aorta ; on the right, it arises from a trunk common to it and to the subclavian, viz., the innominate, or brachio-cephalic artery {e,fig. 198). As the brachio- cephalic and the left common carotid are given off from the aorta nearly at the same level, it follows that the left common carotid is longer than the right by the entire length of the brachio-cephahc. It follows, also, from the obliquity of the arch of tht aorta, that the left common ca- jotid is placed much deeper than the right at its origin ; but, in the cervical region, the !two carotids are upon the same plane. They pass somewhat obliquely upward and outward immediately after their origin, but they are directed vertically and parallel to each other in ti,e cervical region. t The interval between them is occupied by the trachea and the oesop'aagus below, and by the larynx and pharynx above. Their course is straight, and without any winding. Their diameter is uniform throughout, a circumstance which is connecter! with the absence of any collateral branches. The caliber of these arteries is relatively hrger in man than in other animals ; and this has reference to the greater size of his brain. I have not ob- served any difference in diameter between the right and left common carcitids. As about one inch in length of the left common carotid lies in the thorax, its relations must be separately studied in that situation. Relations of the Thoracic Portion. — Li front, with the left subclavian vein, and the ster- no-hyoid and sterno-thyroid muscles, which separate it from the sternum ; behind, with the trachea and oesophagus, and with the left subclavian and left vertebral arteries ; on the outside, with the pleura or the left wall of the mediastinum ; on the inside, with the brachio-cephalic trunk, from which it is separated by a triangular interval, in which the trachea is visible. Relations of the Cervical Portion. — These are the same for both arteries. In front, each common carotid is covered below by the sterno-mastoid, and more immediately by the sterno-hyoid, sterno-thyroid, and omo-hyoid muscles, the latter of which crosses the artery obliquely.iji In its upper half it corresponds to the platysma myoides, which separates it from the skin. The cervical fascia, the superior thyroid vein, and the de- scendens noni, a branch of the hypoglossal nerve, are in more immediate relation with * Some anomalies of the arterial system of man may be in some measure explained from the normal state of the arterial system of certain auicaals ; but the number of such cases,is extremely limited. 1 do not know whether any one has ever thought of applying to these anomalies the rule of the arrest of development, which eome have lately made to play such an exaggerated part in the theory of the vices of conformation. t [The, common carotid has been seeu to divide above the os hyoides, also opposite the thyroid cartilage, and even low down in the neck.] t [In consequence of the larynx being wider than the trachea, the common carotids are not quite parallel in the neck, but are somewhat farther apart above than below.] () In order to omit nothing, I should say that the conunon carotid is crossed obliquely by a branch which i» given off from the superior thyroid artery to the stemo-mastoid muscle. THE EXTERNAL CAROTID ARTERY. 515 it. The most important of these relations is that with the sterno-mastoid, which, in a surgical point of view, may be regarded as its satellite muscle. Behind, the common carotid is the vertebral column, from which it is separated by the pre-vertebral muscles, the great sympathetic nerve, and below by the recurrent nerve and inferior thyroid artery.* On the inside, it is in relation with the trachea, cesophagus, larynx, and thy- roid gland, which passes in front of the artery when larger than usual ; on the outside of the artery is the internal jugular vein. The pneumogastric nerve lies at the back, between the artery and vein. The common carotids are also surrounded by much loose cellular tissue, and by some lymphatic glands. The left common carotid is in more direct relation with the cesophagus than the ar- tery of the right side. The common carotids give off no branch during their course : nevertheless, it is not very rare for this artery to give off the inferior thyroid artery, or a supernumerary branch known as the middle thyroid.i Neabauer has seen the common carotid give off a thy- roid artery, and the internal mammary of the right side. Terminal Branches. — Having reached the upper border of the thyroid cartilage, at a variable height, according to the subject, the common carotid divides into two branches, called the external and internal carotids, which, by no means a common arrangement, do not leave each other at an acute angle, but remain in contact, and even freq^uently be- come crossed before they separate. The point of division is also remarkable for a sort of ampulla or dilatation, which the primitive carotid exhibits. Sometimes the primitive carotid bifurcates much sooner than usually. Morgagni relates a case in which the bifurcation took place at the distance of an inch and a half from the origin of the ar- tery. Sometimes the primitive carotid does not terminate in a bifurcation. In such a case, all the branches given off by the external carotid arise successively from the prim- itive carotid, which penetrates the cranium and terminates as the internal caiotid. The External Carotid Artery. Dissection. — Prolong the incision made for exposing the common carotid as far as the neck of the condyle of the lower jaw. Dissect carefully the styloid muscles and the digas- tricus, and cautiously separate the artery from the surrounding tissue of the parotid gland. The external or superficial carotid artery (b,fig. 204) is, in a great measure, intended for the face, and has, therefore, been ptg. 204. called the facial carotid by Chaussier. It arises from the common carotid, forming one of its two divisions, and extends as far as the neck of the con- dyle of the lower jaw, where it termi- nates by dividing into the temporal and internal maxillary arteries. The origin of this artery is remark- able for being situated on the inner side of the internal carotid. It as- cends vertically as high as the digas- tricus, and passes under that muscle ; it is then directed a little backwarii and outward, leaves the vertebral c^)!- umn, reaches the angle of the lowex' jaw, and again becomes vertical as it proceeds upward to the necA of the condyle, opposite to whick it termi- nates. It is very slightlv tortuous in the adult, and in the ip/api is almost straight. In the adult it \s nearly equal in size to the internal carotid, but it is much smaller in voung subjects. It diminishes rapidly in diameter, on account of the number of brancAes given off from it, so that at its termination it is scarcely one third its original si/d. Sometimes it divides immediately into a sort of bunch of arterial ves- sels ; in other cases its branches arise in succession from the common carotid, which is then direciJly continuous with the internal carotid.! * A va/iet; of relations which it is important to know m a surgical point of view is the relation which often exists l^hi'id, between the right primitive carotid and the trachea. Where this anomaly exists, the brachio- cepha.'ic trunk arises a little more to the left side than usually. t This supernumerary artery arises at different elevations, 'in a case which has been communicated to me br Professor Dubreuil, the middle or supernumerary thyroid artery was given off by the right primitive ca- rotid at the distance of a centimeter from the innominata. It passed up in a straight line into the gland, where it was lost, and anastomosed freely with the superior and inferior thyroidian arteries on each side. The right inferior thyroidian artery was not half as voluminous as usual. Mr. Dubreuil, who teaches anatomy with so much talent at Montpelier, has communicated to me several arterial anomalies, which are to be inserted in a professional work that he is preparing on that subject in a surgical point of view. ; It is doubtless on account of the numerous branches given off by the external carotid that several ancient 516 ANGEIOLOGY. Relations. — It is superficial at its origin, like the upper part of the common carotid, and, like it, is merely separated from the skin by the platysma myoides ; but it then dips into the supra-hyoid region, below the digastricus, the stylo-hyoideus, and the hypo- glossal nerve.* Higher up it is situated deeply in the parotid excavation, surrounded on all sides by the tissue of the parotid gland, which, on this account, cannot be entire- ly extirpated without wounding the vessel. Collateral Branches. — These are six in number, and are arranged into three sets, viz., an anterior set, consisting of the superior tm/roid, the facial, and the lingual ; a posterior, including the occipital and the auricular ; and an internal'Set, formed by one vessel, the inferior, or ascending pharyngeal. The terminal branches are two in number, the superficial temporal and the internal max- The Superior Thyroid Artery. The superior thyroid artery (d, fig. 204) belongs both to the larynx and the thyi'oid gland. It is the first branch given off from the external carotid ; it rather frequently arises opposite the bifurcation of the common carotid, which in this case would seem to divide into three branches. In some cases it arises directly from the common carotid ; at other times it has been seen to come off by a common trunk with the lingual. It is always of considerable size, but varies in this respect, maintaining either a direct rela- tion to the size of the thyroid body, or an inverse proportion to that of the other thyroid arteries. Direction. — It is at first airected horizontally forward and inward ; but it almost im- mediately bends, and proceeds vertically to the upper end of the corresponding lobe of the thyroid gland, in which it terminates. Relations. — It is superficial at its origin, where it is covered only by the skin and the platysma ; it then dips under the omo-hyoid, sterno-hyoid, and sterno-thyroid muscles, and it is also covered by the cervical fascia and the superior thyroid veins. This artery furnishes several collateral branches, viz., the superier laryngeal, the inferior laryngeal or crico- thyroid, and the sterno-mastoid branch. t The Superior Laryngeal Branch. — This (e) comes off from the thyroid, at the point where the latter changes its direction ; sometimes it arises from the external carotid. In certain cases it is so large that it may be regarded as formed by a bifurcation of the thyroid. In one case where it was wanting on the left side, I found it replaced by the right superior thyroid, which was almost double its usual size. This artery passes transversely inward between the thyro-hyoid muscle and the membrane of the same name, which it perforates along with the superior laryngeal nerve ; having reached the cellular tissue behind this membrane, it divides into two branches, an ascending, or cpi- glottid branch, which passes upon the side, then in front of the epiglottis, and ramifies upon it ; and a descending, or laryngeal branch, properly so called, which passes behind the thyroid cartilage, between it and the thyro-arytenoid muscle, and is distributed upon the muscles and mucous membrane of the larynx. Not unfrequently the superior laryn- geal branch enters the larynx through a foramen existing in the thyroid cartilage in some subjects. The Inferior Laryngeal or Crico-thyroid Branch— This arises from the internal termina- ting branch of the superior thyroid artery ; it is more remarkable for its constant presence than for its size. It is sometimes wanting on one side, but it is then replaced liy the superior thyroid artery of the other side. It passes transversely inward, in front of the crico-thyroid membrane, along the lower border of Uie thyroid cartilage, and inosculates with the branch of the opposite side. From the arcli thus formed twigs proceed, which perforate the crico-thyroid membrane, and ramify in th& muscles and the mucous mem- brane of the larynx. It is not uncommon to find the inferior laryngeal artery dividing into two branches : one superficial and transverse, the other ascending, which passes up behind the thyroid cartilage. M. Chassaignac has exhibited, at the Anatomical Society, a prfc(;)aTation, in which the trunk of the superior thyroid artery, instead of giving off the inferior laryngeal branch, passed itself transversely over the crico-thyroid ligament. The Sterno-mastoid Branch. — This is constant, but of variable size. \x tomes off from the superior thyroid, a little below the superior laryngeal, and passes dow^ward to reach the deep surface of the sterno-mastoid muscle, to wliich it is distributed. Terminal Bra.nches. — Having reached the gland, the thyroid artery divides i^to three branches, viz., one which passes between the gland. and the trachea; another, which authors have not descr'beci this vessel as a particular artery, but have contented themselves with descn'.iin^ the branches which it gives off. * [It crosses over the styloid process, the stylo-glossus and pharyngeus muscles, and the glosso-pharyngeal nerve, whicli lie between it and the internal carotid.] t [The first branch ts usually a small one, named the hyoid, which arises opposite the ereat comu of the OS hyoides, passes inward on the thyro-hyoid membrane, and anastomoses with the vessel of the opposite side.l THE FACIAL ARTERY. 5l7 proceeds along the outer border of the corresponding lobe ; and a third, which runs along the inner border, and anastomoses in the median line with the corresponding branch of the opposite side. It is this vessel which sometimes gives off the inferior laryngeal.* The Facial, the Labial, or External Maxillary Artery. Dissection. — Let the head fall backward by means of a billet placed under the neck, and incline it towards the side opposite to that on which the artery is to be laid bare ; dissect carefully the digastricus and stylo-hyoid muscles, which must be cut superiorly at their origin from the styloid process ; dissect the sub-maxillary gland, then the mus- cles of the face, avoid injuring the numerous branches which may come under the scalpel. The facial artery {f,figs. 204, 206), so called from its distribution, is given off from the front of the external carotid, a little above the os hyoides : it is so large in some subjects that it seems to be formed by a bifurcation of the external carotid. It pro- ceeds in a tortuous course from below upward, and then from behind forward, along a groove formed in the sub-maxillary gland. After leaving this groove, it passes verti- caOy upward, crosses the body of the lower jaw at right angles in front of the masseter muscle, becomes oblique, arrives near the commissure of the lips, reaches the furrow between the ala nasi and the cheek, and terminates near the inner angle of the eye, by anastomosing with one of the branches of the ophthalmic, and with the infra-orbital ar- tery. The termination of the facial artery is subject to numerous individual varieties. The vessel is also remarkable for being extremely tortuous, a condition which is con- nected with the mobility of the parts supplied by this artery, which runs in succession over the supra-hyoid, the inferior maxillary, the buccal, and the nasal regions Relations. — In the supra-hyoid region the facial artery is covered by the digastric and stylo-hyoid muscles ; then, along the base of the jaw, it is in relation with the outer sur- face of the sub-maxillary gland, and is separated from the skin by the platysma and a great number of lymphatic glands. In the facial region, the artery is covered below by the platysma, higher up by the triangularis oris and the zygomaticus major, and in all the rest of its extent by a greater or less quantity of fat, which separates it from the skin ; it lies upon the inferior maxilla, against which it may be compressed in front of the masseter, also upon the buccinator, the orbicularis oris, the levator communis, and the levator proprius. Collateral Branches. — The following branches are given off by the facial artery in the supra-hyoid region. The ijiferior palati?ie, a small branch which is sometimes derived from the external carotid, or from the ascending pharyngeal artery, passes up behind [or between] the stylo-glossus and stylo-pharyngeus muscles, to which it furnishes some branches, gains the side of the pharynx, and is distributed to the tonsil, which it covers with its ramifications, and also to the velum palati and the pillars of the fauces, oppo- site which it anastomoses with several branches of the ascending pharyngeal artery. I have seen the palatine branch of the facial extremely large, and taking the place of the tonsillar and palatine branches of the ascending pharyngeal artery. The sub-mental branch {g,fig. 204^ runs along the inner side of the lower border of the ramus of the jaw, between the digastricus and mylo-hyoideus, passes upward in front of the bone, on the outer side of the anterior attachment of the digastricus, and ramifies in the skin and muscles of the chin, anastomosing with the ramifications of the inferior dental artery. Sometimes the sub-mental divides into two or three branches, all of which terminate in the same manner, after perforating the digastric muscle. Branches for the Sub-maxillary Gland. — These are three or four in number, and are large in proportion to the organ which they supply. The Pterygoid Branch. — This is a small branch which passes iato the internal ptery- goid muscle. The collateral branches of the facial region are divided into external and internal. The external branches ramify in all the muscles and integuments of the cheek, and anastomose freely with the transversalis faciei, a branch of the superficial temporal : the most re- markable of these branches are the two given to the masseter and buccinator muscles. Among the internal branches, besides a number of small twigs which have received no names, we remark the following . The inferior coronary or labial artery (h), which is given off from the facial, a little be- low the commissure of the lips ; it pursues a serpentine course in the substance of the lower lip, between the muscular and glandular layers, at a greater or less distance from the free border of the lip, and anastomoses, in the median hne, with the corresponding vessel of the opposite side. I have seen this artery occupy the lower or adherent border of the lower lip until it reached the median line, when it ascended vertically to the free border, where it divided into two equal branches, which passed, horizontally, one to the ♦ I have seen rlie branch winch runs along tiie inner border of the thyroid gland pass transversely to the left side, above and at a certain distance from this border ; having reached the median line, it proceeded ver- tically downward, in front of the crico-thyroid ligament, to the middle of the thyroid gland, where it gave oif the right and left inferior laryngeal branches. The left thyroid was very small, and only furnished the ex- ternal branch for the thyroid gland. 518 ANGEIOLOGY. right and the other to the left, in order to fonn a second coronary artery, smaller than the first. The superior coronary, or labial, arises opposite the commissure, passes in the upper lip between the muscular and glandular layers, and inosculates, in the median line, with the vessel on the opposite side. Branches are given off from this arch to the mucous membrane, the gums, the muscles, and the skin. One branch only of this artery requires a special description ; it is known by the name of the artery of the septum nasi (i). It comes off, in the median line, by one, two, and sometimes three branches, which pass vertically upward, and then horizontally beneath the skin, covering the under surface of the septum as far as the tip of the nose, where they anastomose with the artery of the ala. The artery of the ala nasi, or lateral artery of the nose (1), which is very often the ter-' mination of the facial, divides into two branches ; a small one, that runs along the lower border of the cartilage of the ala, and anastomoses with the artery of the septum ; and a larger one, that runs along the upper convex border of that cartilage. A small branch pen- etrates into the interior of the nares, between the cartilage and the opening of the nostril. Termination of the Facial Artery. — The facial artery having become extremely slender, sometimes terminates, under the name of the angular branch (m), upon the side of the nose, by anastomosing with the nasal branch of the ophthalmic, and with the infra-orbit- al. At other times its termmation is formed by the artery of the ala of the nose, or by the superior coronary of the lip, or even by the inferior coronary. I have seen it termi- nate in the artery of the septum. We seldom find the facial arteries of both sides ahke. Sometimes there is merely a trace of one, while the other is very much developed, and supplies by itself alone all the nasal and labial branches. No artery varies more than the facial, both in size and extent of distribution. Its anastomoses with the inferior dental and infra-orbital arteries, branches of the in- ternal maxillary, as well as those with the ophthalmic, a branch of the internal carotid, should be particularly noticed. The Lingual briery. Dissection. — Cut the hyoidian insertions of the mylo-hyoid muscle, which is to be turned up from below upward ; saw the inferior maxillary bone, either at the symphysis or on each side of it. Hook the tongue and draw it out of the mouth, and maintain it in that position while you follow the artery as situated at its inferior surface. The lingual artery {n, Jigs. 204, 205), which is very large considering the size of the Fig 205. organ to which it is distributed, comes off from the front of the ex- ternal carotid, between the facial and the superior th3'roid, and often by a common trunk with the facial ; it passes at first obliquely up- ward, and then transversely inward and forward, along the upper margin of the corresponding great cornu of the os hyoides : oppo- site the lesser cornu of that bone it changes its direction, and runs in a serpentine course from behind forward, in the substance of the tongue as far as the apex, where it terminates by anastomosing with the artery of the opposite side ; in the latter part of its course it is named, we know not why, the ranine artery {g, fig. 205 ; rana, a frog). Its remarkably tortuous course is connected with the lia- bility of the tongue to undergo great changes in its relative dimenr feions. Relations. — It is deeply seated, at its origin, under the digastric " and stylo-hyoid muscles and the hypo-glossal nerve ; opposite the OS hyoides (at n.fig. 205) it is situated between the hyo-glossus (the nerve passing over that muscle) and the middle constrictor of the pharynx ; in the substance of the tongue it is placed between the genio-hyo-glossus and the lingaalis, and is accompanied by the lingual branch of the fifth nerve : consequently, it occupies the inferior surface of the tongue. Collateral Branches. — A small transverse branch, the hyoid (e), forms an anastomotic arch with the vessel of the opposite side, upon the bodv of the os hyoides. between the genio-hyo-glossus and the genio-hyoideus. The dorsal artery of the tongue (/), generally small and difficult to demonstrate; it arises opposite the great cornu of the os hyoides, ascends upon the lateral border of the tongue, near the anterior pillar of the fauces, to which it gives branches, then passes forward and inward, and giving several epiglottid branches, which anastomose with those of the opposite side, is finally distributed to the caliciform papillae. In the whole of its course, this artery lies immediately beneath the mucous membrane. The suh-lingual artery (i) is large enough to be regarded by some as resulting from the bifurcation of the lingual, which, according to them, takes the name of raninal only after it has furnished the sub-lingual branch. It arises as often from the facial, by a common trunk with the sub-mental, as from the lingual itself It passes horizontally forward be- tween the mylo-hyoideus, which separates it from the sub-mental, and the genio-hyo- glossus, and, in company with the Warthonian duct, runs along the lower border of the THE OCCIPITAL ARTERY, ETC. 510 sub-lingual gland, to which it furnishes numerous twigs, and then divides into two branches : the larger, or the artery of the frcenum, anastomoses, in an arch, with the ves- sel of the opposite side above the fraenum ; while the smaller, or ascending branch, pass- es upon the sides of the symphysis menti, and sends twigs into the several incisor fora- mina, situated behind the teeth of the same name. It is this artery of the fraenum, not the ranine artery, which is liable to be wounded in division of the fraenum. Not unfre- quently the sub-lingual artery gives off a superficial branch, which passes through the an- terior belly of the digastricus, and ramifies upon the region of the chin, like the analo- gous branches of the sub -mental. Lastly, in the substance of the tongue, the lingual artery gives off superior, internal, and external branches, which supply the muscles and the papillary membrane of that organ. The Occipital Artery. Dissection. — Detach the sterno-mastoideus and the splenius at their superior inser- tions. To uncover more completely this artery, which is deeply situated between the mastoid process and the transverse process of the atlas, cut with a chisel or saw the mastoid process at its base, turning it from above downward with the muscles which are inserted into it ; cut the styloid process at its base, and turn the styloid muscles down. Remove carefully the skin of the occipital region, so as to enable you to follow the sub- cutaneous branches. The occipital artery (o o, fig. 204), which is distributed to the posterior region of the head, is smaller than the three branches of the external carotid already described. It arises from the back of the external carotid, on a level with the lingual or the facial, sometimes immediately below the parotid gland : it passes obliquely upward and back- vward, as high as the apex of the mastoid process ; it then passes horizontally backward, and on the inner side of the splenius muscle, divides into two ascending branches : one external, which immediately bends upward ; the other internal, which is continued hori- zontally, and is then reflected vertically upward on the side of the occipital protuber- ance. These two branches, which are very tortuous, cover the occipital region with their numerous ramifications, and reach as high as the vertex, anastomosing with each other, and with the superficial temporal arteries. It is situated deeply at its origin, and is covered by the digastric muscle and the hypo- glossal nerve ; it is still more deeply situated as it passes between the mastoid process and the atlas, where it is covered by the digastric and the sterno-mastoid ; its horizon- tal portion is situated between the obliquus capitis superior and the splenius muscle, then between the complexus and the splenius, running along the occipital insertion of the lat- ter muscle, on the inner side of which it becomes sub-cutaneous. The two brand es into which this artery divides, and all its succeeding ramifications, are situated between the skin on the one hand, and the occipital muscle and the occipito-frontal aponeurosis on the other. Collateral Branches. — Among a great number of small and unnamed ramusculi. we shall distinguish the following branches : a superior sterno-mastoid artery, which constant- ly exists, but is sometimes given off from the external carotid itself: it forms a curve, with its concavity directed downward, under which the hypo-glossal nerve turns ; it then penetrates the deep surface of the upper portion of the sterno-mastoid : a stylo-mastoid branch, which is often derived from the posterior auricular artery : a meningeal artery, or posterior mastoid, which enters the cranium, either by the foramen mastoideum, the fo- ramen lacerum posterius, or even the foramen magnum, and is distributed to the dura mater : a. cervical artery {priTiceps cervicis), which descends between the splenius and com- plexus muscles, and may be followed down to the lower part of the neck; this branch is sometimes of considerable size ; lastly, very often, a terminal branch, the parietal, which enters the cranium by the parietal foramen, and ramifies in that portion of the dura ma- ter which forms the superior longitudinal sinus. 2'he Posterior Auricular Artery. Dissection. — Avoid cutting this artery at its origin in preparing the trunk of the exter- nal carotid ; turn the pinna of the ear forward ; seek for the trunk of the artery between the meatus auditorius externus and the mastoid process ; follow up the dissection on one side towards the origin, on the other towards the termination of this artery, being guided by the description. The posterior auricular artery {s,fig. 204) is intended for the pinna, the internal ear, and' the neighbouring parts of the cranium : it is usually smaller than the occipital, but is sometimes as large ; it arises from the back of the external carotid, a little above the occipital, and rather often by a common trunk with that artery. It passes vertically up- ward, being deeply seated under the digastricus ; it is then covered by the parotid gland, which it perforates to gain the posterior border of the mastoid process, upon which it di- vides into two branches, a mastoid and an auricular. In this course it gives off several parotid and muscular branches, and the stylo-mastoid' artery, which is sometimes derived from the occipital. The stylo-mastoid artery, so re- 620 ANGEIOLOGT. markable for the length of its course, dips into the stylo-mastoid foramen, runs the whole length of the aqueduct of Fallopius, giving off, as it proceeds, some twigs to the internal ear, and terminates by anastomosing with a branch of the middle meningeal artery, which enters by the aqueduct of Fallopius. The terminal mastoid branch of the posterior auricular passes upward and backward be- tween the mastoid process and the skin, and subdivides into two sub-cutaneous ramus- culi : one horizontal, which passes inward along the occipital attachment of the stemo- mastoid and splenius ; the other ascending, which continues in the original course of the vessel, and is lost in the skin upon the outer margin of the occipitalis muscle. The terminal auricular branch almost always divides into two : a superior and an infe- rior. The superior branch runs along the anterior border of the mastoid process, rami- fies upon the upper half of the internal surface of the pinna, and turns round its free mar- gin, so as to reach the external surface. The inferior branch passes behind the auditory meatus, supplies the lobule of the ear, insinuates itself into the fissure in the cartilage, between the helix and concha, and thus gains the external surface of the pinna, upon ■which it passes upward in the furrow between the hehx and antihelix. It terminates by anastomosing with the superior branch. I have seen the auricular artery of great size, to supply the place of the posterior branch of the superficial temporal. The Parotid Arteries. While passmg through the parotid gland, the external carotid gives off four or five large branches to that organ, which deserve special description. They arise from the carotid at right angles, cross the ramus of the lower jaw also at right angles, and divide into a great number of ramifications, most of which are lost in the substance of the gland ; the remainder are distributed to the skin and muscles. One or more of these branches pass between the parotid gland and the masseter muscle, parallel to the trans- versalis faciei artery, and reach as far as the zygomaticus major ; others gain the angle of the jaw, and are lost in the supra-hyoid region. The Inferior or Ascending Pharyngeal, or Pharyngo-meningeal Artery. Dissection. — Make the section necessary for examining the pharynx, as described in a former part of this work when on the Anatomy of the Pharynx. The steps required for this purpose render it advisable that the study of this artery should be postponed until after that of the internal maxillary. The ascending pharyngeal is the smallest branch of the external carotid ; it arises from the inner side of that artery opposite the lingual. I have seen it arise from the occipital. Not unfrequently it is given off either from the angle of bifurcation of the common caro- tid, or from the internal carotid ; and in this last case, there is almost always a very small pharyngeal branch arising from the external carotid, and passing transversely in- ward to the pharynx. It varies in size to a certain degree, and, as it appears to me, in an inverse ratio to that of the palatine branch of the facial. I have seen it almost as large as the occipital. Immediately after its commencement the ascending pharyngeal passes vertically up- ward, at first between the external and internal carotid, and then behind the internal ca- rotid, with which latter vessel it is found in the triangular interval between the pharynx and the internal pterygoid muscle ; it then almost immediately divides into two branch- es, a meningeal and a pharyngeal. Before dividing, it gives off an inferior pharyngeal branch, which passes transversely inward, and subdivides into ascending and descending branches, the latter of which an- astomose on the pharynx with some twigs of the superior thyroid. The meningeal branch, which is situated behind the internal carotid, passes vertically upward, gives off twigs to the superior cervical ganglion of the sympathetic nerve, to the pneumogastric, glosso-pharyngeal, and hypo-glossal nerves, and to the accessory nerve of Willis, enters the cranium through the foramen lacerum posterius, and ramifies upon that portion of the dura mater which lines the inferior occipital fossa. I have seen this vessel divide into a great number of branches, one of which entered the cranium by the carotid canal, and another by the foramen lacerum anterius. The meningeal branch, and sometimes even the trunk of the pharyngeal, gives off a prcBvertebral branch, which passes upward in front of the longus coUi and the recti antici major et minor, supplying these muscles, and anastomosing with the cervicalis ascen- dens. I have traced a branch into the cranium through the first intervertebral foramen (i. c, along the superior notch of the atlas), and another which entered the vertebral ca- nal between the atlas and axis. I regard this pra3vertebral branch as supplementary to the ■ cervicalis ascendens (a branch of the inferior thyroid), for it has a similar distribution. The pharyngeal branch passes in front of the mternal carotid, and having reached the base of the cranium, divides into numerous branches, which ramify in the very dense fibrous tissue found at the occipital attachment of the pharynx : they are all reflected downward, and are distributed upon the Eustachian tube and the muscles of the pharynx. THE TEMPORAL ARTERY. 521 In a case in which the palatine branch of the facial artery was absent, this pharyngeal branch was very large and supplied the tonsil, and, finally, ramified in the velum palati. The Temporal Artery. Dissection. — Turn bacK the parotid gland ; seek for the artery under the skin of the temporal region ; follow its different collateral and terminal branches upon the cranium as far as the vertex, on the face, and on the ear. The temporal or superficial temporal artery (p, fig. 204) appears, by its direction, to form the continuation of the external carotid. It commences opposite the neck of the con- dyle of the lower jaw, between it and the external auditory meatus, which is behind ; it passes vertically upward, immediately behind the zygomatic arch, reaches the temporal region, where it describes some curves, still continuing its vertical course, and termi- nates by bifurcating at the middle, or sometimes the upper part of that region. Relations. — It is covered at its origin by the parotid gland ; it becomes subcutaneous as soon as it passes beyond the zygomatic arch, and then rests upon the temporal fascia at first, and upon the epicranial aponeurosis afterward. Its superficial position, added to its proximity to a bony surface, render it easily compressible, and explain why this artery, and especially its anterior or frontal branch, is generally chosen for arteriotomy. Collateral Branches. — These are divided into anterior, posterior, and internal. The Ariterior Branches. — The most remarkable of these is the transversalis faciei {u), which arises from the temporal immediately after its origin, opposite the neck of the condyle of the lower jaw. and, consequently, in the substance of the parotid gland : it very often comes directly from the external carotid. It varies much in its size, which is generally in an inverse proportion to that of the facial artery. It proceeds horizon- tally forward, across the direction of the neck of the condyle and the masseter muscle, about six lines below the zygoma, above the Stenonian duct, which runs parallel to it. The transversalis faciei gives an articular branch to the temporo-maxillary articulation, and several deep masseteric branches, of which one of considerable size penetrates the back part of the muscle, and anastomoses with the masseteric branch of the internal maxillary. It also gives a small twig, which runs along the Stenonian duct. At the anterior margin of the masseter the transverse facial artery subdivides into a great num- ber of cutaneous, muscular, and anastomotic branches. Among the first we should notice a malar cutaneous branch ; and among the muscular branches, those which are distributed to the great zygomatic muscle. The muscular branches of the transversalis faciei may be traced in one direction as far as the orbicularis palpebrarum, and in another into the levator pvopnus labii supenoris. The anastomotic branches establish an intimate com- munication between the temporal artery and the buccal, infra-orbital, and facial arteries. A second anterior branch of the temporal artery also requires special notice, viz., the orbital, v.hich is given off above the zygomatic arch, passes from behind forward, be- tween the superficial and deep layers of the temporal fascia, then behind the orbicularis muscle, which it supplies, as well as the corresponding skin, and anastomoses with the superior palpebral branch of the ophthalmic. This artery is very variable in regard to size. I have seen it very large and reflected upward, between the frontalis muscle and the skin, parallel to the supra-orbital branch of the ophthalmic, and capable of being fol- lowed as far as the parietal region. From the bend which it forms by turning upward, it gives off a palpebral branch, which completes the superior palpebral arch, and also a branch which anastomoses with the supra-orbital. This orbital branch of the temporal does not exist in all subjects ; the branches which it furnishes are then given off direct- ly from the temporal. The posterior branches consist of the anterior auriculars yv), which are irregular as to number ; the lower branches are distributed to the lobule, the middle ones to the exter- nal auditory meatus, and the upper branches to the highest part of the pinna. The internal branch is the middle deep or sub-aponeurotic temporal artery ; it arises from the temporal above, sometimes on a level with the zygoma, perforates the fascia, and is distributed to the temporal muscle, anastomosing with the anterior and posterior deep temporal branches derived from the internal maxillary. Terminal Branches. — Of the two branches into which the temporal artery divides, the anterior or frontal (q) passes forward and upward towards the frontal region, upon which it ramifies, anastomosing with the branches of the frontal and supra-orbital arteries, and with the temporal of the opposite side. This branch is divided in the operation of arte- riotomy. The posterior or parietal branch (y) is larger than the anterior : it passes up- ward and ramifies upon the parietal bone, anastomosing with the auricular and occipital arteries, with the frontal branch of the temporal, and with the temporal of the opposite side. It is sometimes derived from the auricular artery. The Internal Maxillary Artery. Dissection. — Saw through the zygomatic arch in two places, and turn it downward to- gether with the masseter muscle, taking care not to tear the masseteric artery. Dissect the temporal muscle, and saw through the coronoid process of the inferior Uuu 522 ANGEIOLOGY. maxilla. Saw through the cranium circularly, and remove the brain, which may be put into diluted nitric acid or alcohol, to be hardened for the subsequent dissection of the cerebral arteries. The artery may then be exposed in two ways, either from the outer or else from the upper wall of the zygomatic fossa. It may be reached from the outer wall of the zygomatic fossa by sawing through the lower jaw in front of the masseter, by disarticulating the condyle, or, rather, by sawing it across its neck, and by carefully dissecting the pterygoid muscles The artery can be reached from the upper wall by making two sections in this part of the bone, which will meet at an acute angle in the foramen spinosum of the sphenoid bone. The branches of this artery, especially those which are enclosed in bony canals, such as the dental, the ptery go-palatine, the vidian, &c., must be dissected by carving out their courses in the bone. A vertical section, made from oefore backward through the middle of the face, facili- tates the examination of this artery, and enables us to see the terminations of its nasal, palatine, and pharyngeal branches. The internal maxillary artery (e, fig. 206), little known to the older anatomists, but ac- Fig. 206. curately described by Haller, is the continuation of the external carotid, at least as far as size is concerned. Immediately after its origin, it forms a curve, and passes deeply to the inner side of the neck of the con- dyle of the lower jaw. Tortuous and horizontal in the first part of its course, it traverses the zygomato-maxillary fossa diagonally, passes forward, inward, and a little upward, to reach the highest part of the tuberosity of the superior max- illary bone, upon which tuberosity it describes a very considerable curve with the convexity turned for- ward, and then dips into the bottom of the zygomat- ic fossa, i. e., the spheno-maxillary fossa, where it ter- minates by one or several branches, called the sphe- no-palatine. The tortuous course of the internal max- illary is connected with the great number of branches given off from it. Relations. — Opposite the neck of the condyle, it is situated between the condyle, to which it is applied, and the styloid process — an important relation in a surgical point of view. Its relations in the zygomato-maxillary fossa are not very definite. Some anat- omists, with Bichat and Meckel, state that it is situated between the internal and exter- nal pterygoid muscles ; others, with Haller, that it is placed in front of the extemal pte- rygoid, i. e., between that muscle and the temporal. Both modes of distrilmtion are equally common, and I have even seen one existing on the right, and the other on the left side in the same subject. If the internal maxillary is situated between the ptery- goids, it passes directly forward, on the outside of the dental and lingual nerves ; when it has to get between the external pterygoid and the temporal, it bends downward and then upward, so as to embrace the lower half of the circumference of the external pte- rygoid : in this manner it gains the outer surface of that muscle, appears opposite the sigmoid notch of the lower jaw, and passes from behind forward, between the external pterygoid and temporal muscles; in both cases it passes between the two origins of the external pterygoid, in order to reach the pterygo-maxillary fissure. Collateral Branches. — These are thirteen in number, and are divided into those arising on the inner side, and near the neck of the condyle, viz., the tympanic, the middle menin- geal, and inferior deiital, the posterior deep temporal, the masseteric, the pterygoids, and the small meningeal arteries ; those arising near the maxillary tuberosity, viz., the buccal, the anterior deep temporal, the alveolar, and the infra-orbital arteries ; and those arising with- in the spheno-maxillary fossa, viz., the vidian or pterygoid, the pterygo-palatine, and the superior palatine arteries. Branches arising near the Neck of the Condyle. The tympanic artery is a very small branch, which sometimes arises from the tempo- ral, and sometimes from the inferior dental ; it is distributed to the external auditory meatus and the temporo-maxillary articulation, and penetrates through the Glasserian fissure into the cavity of the tympanum, to the muscles and walls of which it sends its ramifications. The middle or great meningeal artery, or spheno-spinous artery, is destined for the dura mater and the bones of the cranium ; it almost always arises from the internal maxilla- ry before the dental, but sometimes in the same situation ; it passes vertically upward, behind the neck of the condyle, and gains the foramen spinosum in the sphenoid bone, through which it enters into the interior of the cranium ; it is then reflected upon the anterior margin of this foramen, becomes horizontal, and divides into two branches, an anterior and a posterivr. The anterior branch is the larger ; it runs upon the outer ex- THE INTERNAL MAXILLARY ARTERY. 523 tremity of the lesser wing of the sphenoid, and reaches the anterior angle of the parietal bone, where it is received into an imperfect, and sometimes even into a complete bony canal, and then divides and subdivides in the ramified grooves upon the internal surface of the parietal bone. Its branches may be traced even into the walls of the longitudinal sinus. The posterior branch is smaller, and passes backward and upward upon the squamous portion of the temporal bone, and upon the internal surface of the parietal bone, enters into the ramified grooves upon that surface, and terminates in the dura mater and the bones of the cranium. The ultimate twigs of the middle meningeal artery anastomose with those of the opposite side, and with the branches of the anterior and posterior me- ningeal arteries. Relations. — In the first part of its course, it is very deeply situated, and is in relation in front with the condyloid attachments of the external pterygoid muscle ; in the crani- um it is situated on the outer surface of the dura mater, between that membrane and the bones, into the substance of which it sends a number of extremely fine ramusculi. The relation of the two divisions of this artery with the two inferior angles of the parietal bone deserves notice in a surgical point of view. In consequence of its sending branch- es into the bones, separation of the dura mater is always followed by effusion of blood. The middle meningeal artery also gives off some collateral branches. On the outside of the cranium it furnishes some unnamed twigs. Within the cranium it gives a small branch, named the vidian, which enters the aqueduct of Fallopius through the hiatus Fal- lopii, and supplies the facial nerve, ramifying in its neurilemma, and anastomosing with the stylo-mastoid branch of the occipital artery ; some small branches, which supply the fifth or trigeminal nerve, and evidently anastomose with the meningeal branches of the internal carotid ; a small twig, which enters the canal for the internal muscle of the malleus, and is distributed upon that muscle ; opposite the sphenoidal fissure, several orbital branches, which enter the orbit at the narrowest part of that fissure, or even by proper canals in its neighbourhood; and, lastly, some rather large temporal branches, which pass into the great alas of the sphenoid at their orbital surface, and anastomose in the temporal fossa with the deep temporal arteries : not unfrequently the lachrymal ar- tery, or a small supplementary lachrymal artery, is furnished by the middle meningeal. The inferior dental artery {d) is the artery of the lower jaw : it generally arises on a level with the middle meningeal, but sometimes before and sometimes after that vessel ; it passes downward, along the inner surface of the ramus of the jaw, between the bone and the internal pterygoid, sending off branches to that muscle, but being separated from it by the fibrous band called the spheno-maxillary ligament ; it thus reaches the superior orifice of the dental canal, before entering which it gives off a small branch that passes downward and forward in a groove on the inner surface of the jaw, and ter- minates in the mylo-hyoid muscle. The inferior dental artery traverses the entire length of the dental canal, accompanied by the nerve of the same name. Opposite the bicuspid teeth it divides into two branch- es : a mental branch, the larger, which escapes through the mental foramen, and anasto- moses with the submental artery and the inferior coronary artery of the lip ; and an iri- cisor branch, which continues in the original course of the artery, passes beneath the canine and incisor teeth, and is lost in the diploe opposite the symphysis. During its course, the dental artery, as well as its incisor branch, gives off a great number of twigs, which are lost in the diploe of the bone ; and a series oi dental branches, which correspond in number with the roots of the teeth, penetrate into the alveoli, and from thence into the teeth through the foramen observed at the apex of each fang. The posterior deep temporal artery (g) arises opposite the sigmoid notch, passes verti- cally upward between the external pterygoid and the temporal muscles, gains the pos- terior border of the latter muscle, gets between that border and the temporal fossa, re- mains in contact with the periosteum, and then divides and subdivides so as to termi- nate partly in the temporal muscle and partly upon the periosteum, anastomosing with the middle and anterior deep temporal arteries. It often gives off the masseteric, and sometimes the buccal artery. The masseteric artery is a small branch, the size of which is inversely proportioned to that of the masseteric branch of the transversalis faciei. It often arises by a common trunk with the posterior deep temporal, passes outward in front of the condyle, and, there- fore, in the notch between the condyle and the coronoid process, and enters the internal surface of the masseter, in which muscle it anastomoses with the masseteric branches given off by the transversalis faciei and facial arteries. The pterygoid arteries are irregular in number ; some of them arise directly from the internal maxillary, others from the posterior deep temporal and the middle meningeal. The small meningeal artery is not constant, but I have seen it in one case as large as the middle meningeal ; it arises at the same height as the inferior dental, passes between the pterygoid muscles, and divides into two branches, one of which turns round the ori- gin of the internal pterygoid, and terminates in the velum palati and the nasal fossae ; and another, which passes vertically upward, between the external pterygoid and th© 524 ANGEIOLOGY. upper wall of the zygomatic fossa, enters the cranium by the foramen ovale, and sup- plies the trigeminal nerve and the dura mater, anastomosing with smaU branches given off from the internal carotid. Branches arising near the Tuberosity of the Superior Maxillary Bone. The buccal artery (h) is a small branch of variable size, and sometimes exists only in a rudimentary state. It rather frequently arises by a common trunk with the superior dental artery, passes in a tortuous course from behind forward, between the ramus of the lower jaw and the internal pterygoid muscle, emerges in front of the ramus, and is lost in the buccinator muscle, anastomosing with the buccal branches of the facial and transversalis faciei. The anterior deep temporal artery (i) is of considerable size : it passes vertically up- ward, along the anterior border of the temporal muscle, with which it is in contact, is lost in that muscle, anastomosing with the posterior deep temporal and the middle tem- poral. It gives off some extremely delicate orbital branches, which traverse the canals in the malar bone, and are lost in the adipose tissue of the orbit. The alveolar or superior dental (I) often arises by a common trunk with the infra-or- bital, passes in a very tortuous manner forward and downward upon the tuberosity of the superior maxilla, and divides into several branches ; some of these, having reached the alveolar border, are reflected upon the margins of the alveoli, pass into their cavities, and ramify in the alveolo-dental periosteum ; other branches enter the small posterior dental canals, penetrate into the alveoli of the molars and bicuspids, and divide into as many ramusculi as there are roots to each of those teeth. Several of these branches penetrate into the maxillary sinus. I have seen one which ran along this sinus from behind forward near its lower wall, was reflected upward on the anterior wall of the same cavity, and entered the base of the ascending process of the superior maxilla, at which point I could no longer follow it. This branch was situated between the lining membrane of the sinus and the bones. All the divisions of the alveolar artery furnish branches to the superior maxillary bone, and, at the same time, supply them to the cor- responding teeth. Lastly, some very delicate twigs of the superior dental artery enter the buccinator muscle. The infra-orbital artery arises from the internal maxillary opposite the spheno-maxil- lary fissure, sometimes alone, sometimes by a common trunk with the superior dental, immediately enters and then traverses the infra-orbital canal, emerges at the infra-or- bital foramen, and divides into a great number of branches (m), which are distributed to the skin and mucous membrane of the cheek, anastomosing with the facial artery, the transversalis faciei, and the alveolar and buccal branches just described. Several branch- es enter the alveoli of the canine and incisor teeth at their borders : others penetrate into the nasal fossae at the nostril. During its course, the infra-orbital artery furnishes a very remarkable branch, which enters the cavity of the orbits, where it divides into two branches, one of which passes directly forward, and is lost in the lower eyelid, while the other, which is larger, turns inward, and inosculates with the inferior palpebral branch of the ophthalmic artery ; an- other branch of the infra-orbital artery enters the anterior dental canal, to supply the canine and incisor teeth, penetrating into the foramina at the points of their fangs, in the same way as in the other teeth. Branches arising .in the Ptery go-maxillary Fossa. The vidian or pterygoid artery is a very smaU vessel, which, immediately after its com- mencement, enters the vidian canal, traverses its whole length, and then ramifies in the pharynx and around the Eustachian tube. The ptery go-palatine artery is as small as the preceding, below and to the inner side of which it is situated : it traverses the pterygo-palatine canal, and terminates in the pharynx and on the Eustachian tube. It sometimes arises from the spheno-palatine artery. The superior palatine artery is larger than the preceding branches, and pursues a down- ward course : it arises opposite the pterygo-maxillary fissure, passes vertically down- ward, enters the posterior palatine canal, and, having emerged from its inferior orifice, is reflected from behind forward, advances in a tortuous manner (r, fig. 205) between the hard palate and the mucous membrane, in the groove which runs along the alveolar border, and forms an anastomotic arch in the median line, with the palatine artery of the opposite side. Before entering the posterior palatine canal, it gives off some branch- es, which run through the accessory palatine canals, and ramify upon the velum palati. While upon the hard palate, it sends off branches, which are distributed to the glands of the mucous membrane ; others, which are distributed to the gums, and enter at the margins of the alveoli, and supply the alveolo-dental periosteum ; and, lastly, a smaU nasal branch {t, fig. 205), which enters the anterior palatine canal, bifurcates above like that canal itself, so as to penetrate into each of the nasal fossae, and anastomoses with the spheno-palatine artery of both sides.* * There are, in the interior of the bones of the face, as in all spongy hones, true arterial canals, the study of which, is not less important than that of the veaous canals found in similar situations. THE INTERNAL CAROTID. 525 Terminal Branch of the Internal Maxillary Artery. This is named the sphe7io-palatine ; it is a large vessel, often multiple, and is intended exclusively for the pituitary membrane ; it passes from below upward, in a tortuous man- ner, to penetrate the corresponding nasal fossa, by the spheno-palatine foramen, that is, at the back part Of the superior meatus, where it immediately divides into two branches : one internal {s, fig. 205), which passes obliquely downward and forward, covers the sep- tum with a complicated network, and anastomoses in front with the nasal branch of the superior palatine ; the other external, which divides into three ramusculi for the three meatuses, and ramifies in them and upon the turbmated bones. Some of the twigs en- ter the sphenoidal and maxillary sinuses, the posterior and the anterior ethmoidal cells, the frontal sinus, and the lachrymal canal All these arteries form areolas of different sizes in the pituitary membrane, and give it, in successful injections, a reticulated aspect ; they are situated between the periosteum and the pituitary membrane, properly so called. The arteries of the turbinated bones are lodged in the areolar cells on the surface of those bones, and in the arterial canals which are hollowed out of them Summary of the Distribution of the Internal Maxillary Artery The internal maxillary sends branches to the organs of mastication and deglutition, to the nasal fossae, to the bones and fibrous membranes of the cranium, to the fiice, and to the organ of hearing. Its different branches are distributed in the following manner : To the passive instruments of mastication, viz., the jaws and teeth, the inferior dental, the superior dental, and the infra-orbital arteries ; to the active organs concerned in that process, the masseteric, the anterior and posterior deep temporal, and the pterygoid arteries. To the organs of deglutition, viz.. the hard and soft palate and the pharynx, the siipe- rtor palatine, the small meningeal, the vidian, and the pterygo-palannc arteries. To the nasal fosses, some branches of the infra-orbital, and the whole of the spheno- palatine artery ; the latter vessel, and, consequently, the internal maxillary artery also, are very large in those animals which have a highly-developed olfactory apparatus. To the organ of hearing, the tympanic artery, those branches of the middle meningeal which enter the hiatus Fallopii, and also those which enter the canal of the internal muscle of the malleus. To the face, viz., to the muscles and integuments, the buccal, the infra-orbital, and the mental arteries. The region of the eye is the only part not supplied by the internal max- illary. To the bones of the cranium, and to the dura mater, the middle and the small meningeal arteries. The Internal C.\rotid. Dissection. — The simplest method of exposing this vessel is to make the section for examining the pliarynx. The carotid canal must be opened with a chisel, and the outer wall of the cavernous sinus removed. The internal carotid is distributed to the anterior part of the brain, and to the eye and its appendages. It is one of the two branches into which the common carotid divides : situated, at its origin, on the outside of the external carotid, it passes sometimes vertically upward, par- allel to, and in contact with, that artery, and sometimes behind it. by crossing it at an acute angle opposite the digastric muscle ; ii then leaves tne external carotid to pass deeply into the triangular space between the pharynx and the ramus of the lower jaw, and reaches the base of the cranium, into which it penetrates by the carotid canal. After emerg'ing from this canal, it is situated in the cavernous sinus, upon the sides of the sella tuvcica, is reflected upward on the inner side of the anterior clinoid process, and terminates by dividing into three branches. The size of this artery, wiiich is always exactly proportioned to that of the brain, is, in the adult, pqual to that of the external carotid ; in the infant it is much larger (ramus grandior carotidis, Vcsal.). In man, as in the whole series of animals, the relative size of the internal and external carotids is determined by the relative development of tlie brain and the face. Tlie internal carotid is remarkable for retaining the same diameter from its commencement to its termination. Its direction is generally straight until it reaches the base of the cranium, but some- times it describes a single curve immediately after its commencement, sometimes sev- eral curves having opposite directions. At the base of the cranium, before entering the carotid canal, it becomes horizontal, and then vertical and ascending. In traversing the carotid canal, it follows the angular course of that passage ; in the cavernous sinus, it passes directly forward and upward, like the carotid groove ; at oth- er times it describes two distinct curves ; lastly, on the inside of the anterior clinoid process, it is reflected directly upward and a little backward. The double curvature which it describes in traversing the carotid canal and the cavernous sinus has been well compared to the Roman letter S. The numerous inflections of the internal carotid form 526 ANGEIOLOGY. one of the most decided arguments in favour of the opinion that the use of these wind- ings is to retard the passage of the blood. Relations : from its Origin to the Base of the Cranium. — At its origin, the internal carot- id is situated as superficially as the termination of the common carotid, and is crossed by the hypoglossal nerve and the occipital artery ; it soon passes behind the external carotid, and becomes deeper and deeper Protected by its position m the triangular space, which is bounded on the inside by the pharynx, and on the outside by the ramus of the lower jaw, it rests behind upon the vertebral column, from which it is separated by the prasvertebral muscles and aponeurosis ; it is in relation in front and to the outer side with the stylo-glossus and stylo-pnaryngeus muscles, which pass between it and the external carotid ; on the inside, with the pharynx ; and on the outside and behind, with the internal jugular vein The ascending pharyngeal artery is, moreover, in rela- tion with it behind, and the great sympathetic nerve on the inside : the pneumogastric, glosso-pharyngeal, and hypoglossal nerves are situated behind the internal carotid at their exit from the cranium, but soon get to its outer side, between it and the internal jugular vein. The relation of the artery with the external surface of the pharynx explains how this vessel may be wounded from the interior of that cavity. Sometimes one of its curves approaches the region of the tonsil ; and this may, perhaps, have been the case when the artery has been wounded by an instrument directed transversely outward and car- ried into the tonsil, either to open an abscess or to excise the gland. In the carotid canal, t'ne artery is in relation with the nervous filaments ascending from the superior cervical ganghon. A very thin fibrous lamina, a prolongation of the dura mater, separates the vessel from the bony walls of the canal. Its proximity to the internal ear while traversing the petrous portion of the temporal bone, is probably the cause of the arterial pulsations which are heard in certain cases. In the cavernous sinus, the artery is applied against the inner wall of that cavity, and IS, therefore, placed on the inner side of the nerves which pass through the sinus, and more particularly of the sixth pair ; it is said that the artery is not bathed in the blood contained in the sinus, but is protected from it by a very thin layer of membrane, con- tinuous with the internal coat of the veins. However careful I may have been, I have never succeeded in separating this membrane. On the inner side of the anterior clinoid process, the artery is upon the outer side of the optic nerve ; and at the point where it emerges from the dura mater, above the an- terior clinoid process, it is received in a sheath formed by the arachnoid. Branches of the Internal Carotid. — On the outside of the cranium it gives ofFno branch, excepting in a few cases where it furnishes the ascending pharyngeal, or. rather, only a supplementary pharyngeal branch ; and, lastly, when it gives off the occipital. In the carotid canal, it sends a twig into the cavity of the tympanum by a special opening. In the cavernous sinus, it furnishes several small branches {arterice receptaculi), some of which are reticulated, and distributed to that portion of the dura mater which lines the basilar surface of the occipital bone, and to the walls of the inferior petrosal sinus ; while others ramify upon the pituitary body, the fifth pair of nerves, and the adjacent portion of the dura mater : a larger branch anastomoses with the middle meningeal ar- tery. Lastly, on the inner side of the anterior chnoid process, just as it passes above that process, the internal carotid gives off in front a remarkable artery, named the ophthalmic. The Ophthalmic Artery. Dissection. — Make a partial injection, either from the common or internal carotid. Remove the roof of the orbit, after having carefully detached the integuments and peri- osteum of the frontal region : leave a small bridge of bone on the inner part of the margin of the orbit for the supra-orbital artery, or, rather, open the supra-orbital fora- men and disengage the artery from it. Dissect the muscles of the eye with great care, preserving all the vessels which present themselves. The study of the branches of the ophthalmic artery, which are distributed to the ball of the eye, requires a perfect knowl- edge of that organ. This artery is principally destined for the eye and its appendages, and is less remark- able for its size, which is inconsiderable, than for the number of its branches. Imme- diately after its origin, it enters the optic foramen {b,Jig. 207), on the outer side of and below the optic nerve.* The artery is at first contained in the same sheath as the nerve, but, soon escaping from it, penetrates into the orbit between the abducens oculi nerve and the external rectus muscle of the eye, turns inward and crosses the optic * A very remarkable variety in the origin of the ophthalmic artery is that m %vhich this artery arises by a common trunk with the middle meningeal or arteria media dura mstris, which is a branch of the internal maxillary. In a case of this kind, which has been communicated to me by M. Dubreuil, the ophthalmic ar- tery arose from the anterior branch of the meningeal ; when this branch reached the canal at the anterior in- ferior angle of the parietal bone, it entered the orbit by the e-xternal extremity of the foramen lacerum or- bitale, and successively gave off the branches furnished by the ophthalmic artery. THE orHTIlALMIC ARTERY. 527 nerve, sometimes at right angles and sometimes obliquely, and is then placed above the nerve. Having reached the inner wall of the orbit, it again changes its direction, passes horizontally and in a slightly tortuous manner along the lower border of the superior oblique muscle of the eye, and terminates by bifurcating at the margin of the orbit. Not un- frequently, the ophthalmic artery, immediately after its origin, is placed on the inner side of and below the optic nerve, and then pass- es directly forward along the inner side of that nerve ; so that, in these cases, the nerve and artery do not cross each other. The ophthalmic artery gives off a great number of branches, which, according to their origin,* may be divided into those ari- sing on the outside of the optic nerve, viz., the lachrymal artery and the central artery of the retina ; those arising above the nerve, viz., the supra-orbital, the short ciliary, the middle or anterior ciliary, the superior and the inferior muscular arteries ; those arising on the ^5^ > inner side of the optic nerve, viz., the posterior and anterior eth- moidal and the inferior ajid superior palpebral arteries ; in all, eleven branches, to which may be added the terminal branches, viz., the nasal and the frontal arteries. It is well to remark, that the origins of most of the above-named branches are subject to extreme variety. Branches arising on the Outer Side of the Optic Nerve. — The lachrymal artery (c, fig. 207), one of the largest branches of the ophthalmic, arises immediately before the en- trance of the latter into the orbit. Not unfrequently it is given off from the middle me- ningeal artery. The lachrymal artery passes from behind forward along the outer wall of the orbit, between the periosteum and the external rectus muscle, and enters the lachrymal gland (I), supplying it with a great number of branches. Emerging from the gland very much reduced in size, it terminates partly in the conjunctiva, and partly in the structures com- posing the upper eyelid. In its course it sometimes gives off a small meningeal branch, which passes back- ward through the sphenoidal fissure, and enters the dura mater, in which it anastomoses with the middle meningeal artery. This branch may be considered, in some subjects, as one origin of the lachrymal artery ; a condition that leads to those cases in which the lachrymal artery arises from the middle meningeal. It often gives off a long ciliary artery, and always some twigs to the neurilemma of the optic nerve, and muscular branches to the levator palpebra; superioris and the superior rectus ; lastly, it furnishes a muscular branch, the malar, which perforates the malar bone, and anastomoses in the temporal fossa with the anterior deep temporal artery, and upon the malar bone itself with the transversalis faciei. The central artery of the retina {arteria centralis retina, i), quite distinct from the twigs supplied to the neurilemma of the optic nerve, is an extremely delicate vessel : it arises either from the ophthalmic, or from one of the ciliary arteries, penetrates obliquely into the substance of the nerve, runs along its centre from behind forward, enters into the globe of the eye, and expands in diverging ramifications, which are applied to the inter- nal surface of the retina, and accompany it as far as the ciliary processes. A branch very distinct from those just mentioned traverses the vitreous body from behind forward, in the axis of the eye, and reaches the capsule of the crystalline lens, after having fur- nished some extremely fine twigs to the hyaloid membrane. Branches arising above the Optic Nerve. — The supra-orbital or superciliary artery (d) arises from the ophthalmic as that vessel is crossing the optic nerve ; it is sometimes given off from the lachrymal. It is very variable in size, and appears in certain cases to be partially replaced by the orbital branch of the temporal, or by the frontal branch of the ophthalmic. It passes horizontally between the periosteum of the roof of the or- bit and the levator palpebrae superioris, accompanied by the frontal nerve ; it escapes from the orbit at the superciliary notch, is reflected over it as over a pulley, ascends vertically, and divides into two branches, one of which passes upward between the skin and the orbicularis and occipito-frontalis muscles, and the other is situated between the muscles and the periosteum, and ramifies in that membrane. The sub-cutaneous branch often divides into an internal and an external twig. It is also said constantly to furnish a branch to the diploe of the frontal bone, as it is passing through the superciliary notch. It appears to me that this branch is often wanting. The ciliary arteries may be divided into the posterior or short, the middle or long, and the anterior. The posterior cuiary arteries (r) distributed to the choroid coat and the ciliary processes (arteres uveales, Chauss.) are irregular in number which is stated to be thirty, or even * The branches given off by the ophthalmic artery might be more philosophically divided as follows : 1st. Those which are destined to the globe of the eye, viz., the arteries of the retina, the short ciliary or choroi- dian, the middle or long ciliary, and the anterior ciliary ; 2d. Those which are distributed to the parts con- tained in the orbital cavity, lachrymal and muscular arteries ; 3d. Those which are on the outside of the orbital cavity, the palpebral, sub-orbital, ethmoidal, frontal, and nasal artenes. 628 ANGEIOLOGY. forty; they arise from two trunks : one inferior, which as given off from the ophthalmic artery on the outer side of the optic nerve ; the other is superior, and arises above that nerve. Not unfrequently the lachrymal artery gives off the inferior long ciliary trunk. They run in a very tortuous course along the optic nerve, and, having reached the ball of the eye, twist spirally and immediately expand into a tuft of tortuous ramusculi, which surround the optic nerve, perforate the sclerotic coat around the entrance of the nerve, and then ramify, as will be elsewhere stated, in the choroid coat and ciliary pro- cesses. The middle or long ciliary arteries (arteres iriennes, Chauss.), which are distributed to the iris, are two in number, an internal and an external ; they perforate the sclerotic at some distance from the optic nerve, and pass between the sclerotic and the choroid membrane on the sides of the eyeball. Having reached the ciliary ring, each of them divides into two branches, which anastomose together, and form the great vascular circle of the iris. Numerous radiating branches proceed from all points of the inner border of this circle towards the free margin of the iris, where they subdivide and anastomose to form the lesser vascular circle of that membrane. The anterior ciliary arteries are irregular in number, and are derived from the muscu- lar branches, and sometimes from the lachrymal and infra-orbital ; they give some branches to the conjunctiva, penetrate the sclerotic at a short distance from the cornea, and terminate in the great circle of the iris. The muscular arteries are two, viz., the superior and the inferior. The superior is the smaller : it is often wanting, and is then replaced by branches from the lachrymal, infra- orbital, or ciliary artei'ies. It is distributed to the levator palpebrEe superioris, the supe- rior rectus, and the obliqiuis superior. The inferior, which always exists, passes from behind forward between the optic nerve and the inferior rectus, gives off most of the anterior ciliary arteries, and is distributed to the external and inferior recti, and to the obliquus inferior. Sometimes the inferior muscular is not entirely distributed to the mus- cles, but forms an anastomotic arch with the infra-orbital branch of the internal maxillary. Branches arising on the inner Side of the Optic Nerve. — The ethmoidal arteries are two, viz., the anterior and the posterior. The posterior ethmoidal (e) is given off the first from the ophthalmic, and is sometimes as large as the continuation of that artery : at oth- er times merely a trace of it exists. It runs from without inward, passes through the posterior internal orbital canal to reach the ethmoidal groove within the cranium, and then divides into a meningeal and a nasal branch. The meningeal ramifies in the dura mater, particularly in the falx cerebri ; the nasal branch enters the nasal fossa, through the foramina of the cribriform plate, and anastomoses with the ultimate divisions of the spheno-palatine artery. The anterior ethmoidal (/) is mversely proportioned, as regards size, to the posterior artery, which is sometimes replaced by it ; it enters the cranium through the anterior internal orbital canal, and divides into a meningeal brajich, distributed upon the falx cer- ebri, and a nasal branch, which penetrates the olfactory cavities by the foramina of the cribiform plate. The branches to the falx are remarkably tortuous. The palpebral arteries are divided into the superior and the inferior. Both arise from the ophthalmic, opposite the cartilaginous pulley of the superior oblique. Sometimes they arise by a common trunk. Most commonly the inferior palpebral is given off a lit- tle before the superior. Sometimes the superior is so large that it appears to result from a division of the ophthalmic itself into two equal branches. The inferior palpebral passes vertically downward, behind the tendon of the orbicularis muscle, proceeds outward to reach the lower eyelid, along the whole length of which it runs in the form of an arch without any winding, and is gradually lost at the external canthus or angle of the eyelids. The vascular arch thus formed, the inferior palpebral, is situated between the muscular fibres of the eyelid and the tarsal cartilage, immediately below the free border of tJiat cartilage. At the point where it enters the eyelid, it gives off a very remarkable branch, which anastomoses with the orbital branch of the infra-orbital artery. From the arch of anas- tomosis a branch arises, which enters the nasal duct (branch of the nasal duct), and ram- ifies in the mucous membrane of that passage, as far as the inferior meatus. The superior palpebral passes downward behind the orbicularis palpebrarum, and, having reached the superior punctum lachrymale, is reflected outward, between the muscular fibres and the tarsal cartilage, immediately above its free border, along which it forms an arch, and terminates by anastomosing with a palpebral branch derived from the su- perficial temporal. Terminal Branches of the Ophthalmic. — At the anterior extremity of the angle formed by the upper and internal walls of tlie orbit, the ophthalmic artery terminates by divi- ding into a nasal, and ci frontal branch. The nasal branch varies in size, and is often larger than the ophthalmic artery itself, so that some anatomists have regarded it as a branch of the facial, with which it always anastomoses. It emerges from the orbit above the tendon of the orbicularis, and liav- CEREBRAL BRANCHES OP THE INTERNAL CAROTID. 529 ing given off a small branch, which afterward enters the groove in the os unguis, to be distributed to the mucous membrane of the lachrymal sac, it divides into two branches : one, named the angular artery, runs in the groove formed by the nose and cheek, be- tween the pyramidalis nasi and the levator labii superioris alaeque nasi ; it is accompa- nied by the vein, which lies to its outer side, and it is continuous with the facial artery, without any line of demarcation, the two vessels inosculating so completely, that it is impossible to define their respective limits : the other branch, the dorsal artery of the nose, runs along the dorsum of the nose, and terminates opposite each ala by anastomo- sing with its corresponding artery. These two divisions of the nasal branch of the oph- thalmic are sub-cutaneous, and give off numerous ramifications, which cover the whole surface of the nose. The frontal branch is smaller than the nasal, and generally smaller than the supra- orbital or superciliary ; it passes upward upon the forehead, parallel to the supra-orbital, with which it communicates above by a transverse branch ; it divides into sub-cutaneous twigs, situated between the skin and the muscles, and into muscular and periosteal twigs. Summary of the Distribution of the Ophthalmic Artery. — The ophthalmic sends branches to the ball of the eye, to its appendages, viz., the muscles, eyelids, and lachrjTnal appa- ratus, to the frontal region, and to the nose and nasal fossas. To the ball of the eye it gives the arteria centralis retinae, which supplies the retina, the hyaloid membrane, and the capsule of the crystalline lens ; the posterior, middle, and anterior ciliary arteries, which are distributed to the choroid membrane, the ciliary processes, and the iris. It supphes proper muscular branches, and also twigs from its other branches, to the muscles of the eye. To the eyelids it gives off the palpebral arteries. To the lachrymal apparatus it sup- plies the lachrymal artery for the gland, and the two branches for the lachrymal sac and the nasal duct. The frontal region receives its frontal and supra-orbital branches ; the nose, the nasal branch, and the nasal fossse, the anterior and posterior ethmoidal arteries. The Cerebral Branches of the Internal Carotid Artery. When the internal carotid has given off the ophthalmic artery, it enters {c,fig. 208) a deep fossa seen on the base of the brain at the inner end of the fissure of Sylvius, and immediately divides into three branches, which spread out from each other. Of these three branches, the anterior is called the anterior cerebral, or artery of the corpus callosum ; the external is named the middle cerebral, or artery of the fissure of Sylvius ; and the third, or posterior, is the posterior communicating artery. Not unfrequently the carotid gives origin to the pos- terior cerebral artery, from which, in that case, the posterior communicating artery is then given off, and immediately joins the anterior extremity of the basi- lar artery. The Anterior Cerebral Artery. Dissection. — The study of these arteries requires no preparation ; it is sufficient to overturn the brain in a manner which will bring its base into view. Each artery will be recognised by the following description : This vessel {d d, fig. 208), also called the artery of the corpus cal- losum, passes, immediately after its origin, forward and inward, towards the median line, and thus reaches the longitudinal fissure between the right and left anterior lobes of the brain. There it approaches its fellow of the op- posite side, and communicates with it by a transverse branch, which passes at right an- gles between them. This anastomotic branch (a), so remarkable for its size, shortness. and direction, is called the anterior communicating artery ; instead of one, there are some- times two smaller branches ; sometimes it is so short that the two anterior cerebral ar- teries may be said to be apphed to each other, and blended together at this point : most commonly it is from one to two lines in length, and it then gives off some small twigs, which penetrate into the third ventricle. After communicating in this manner, the anterior cerebral arteries become parallel, run from behind forward, turn upward in front of the anterior extremity of the corpus callosum, and then run backward upon its upper surface, as far as its posterior extremity, describing a curve, which exactly corresponds with that of the corpus callosum itself Before turning over the anterior border of the corpus callosum, the anterior cere- bral arteries give off some ramusculito the optic and olfactoiy nerves, to the third ven^ tricle, and the adjacent part of the anterior lobe of the brain, and also a series of large branches, which are distributed to the inferior surface of the same lobe. At the point X X X 530 ANGEIOLOGY. where the arteries are reflected, and also along the upper surface of the corpus callosum, large branches arise from the convexity of the curve described by these vessels, and ramify upon the inner surface of the two hemispheres ; the anterior branches run from behind forward, and the others from before backward, and from below upward ; most of them reach the convex surface of the brain. Some capillary twigs proceed from the con- cavity of the curve, and penetrate the substance of the corpus callosum. We may regard as the termination of each anterior cerebral artery a very small branch which continues in the same course, reaches the posterior extremity of the corpus callo- sum, is there reflected downward, and terminates in the adjacent convolutions of the brain. The Middle Cerebral Artery. — This is larger than the preceding vessel ; it passes (/, fig. 208) outward and backward to enter the fissure of Sylvius, having previously given off a great number of rather large branches, which run perpendicularly upward into the very thin layer of cerebral substance situated at the junction of the longitudinal fissure of the brain with the fissure of Sylvius.* As soon as the middle cerebral artery has entered the fissure of Sylvius, it divides into three branches : an anterior, which is applied to the anterior lobe ; a posterior, which lies upon the middle lobe ; and a median branch, Avhich corresponds to the small lobe that is concealed within the fissure : they all follow the direction of this fissure, and are concealed within it, but soon emerge so as to ramify upon the convolutions and anfrac- tuosities of the brain, anastomosing with each other, and with the branches of the ante- rior and posterior cerebral arteries. It is of importance to remark, and this observation applies to all the cerebral arteries, that the arterial ramifications destined for the surface of the brain are extremely tortuous, that they dip into the anfractuosities, and cover the free borders and the two surfaces of the convolutions, between which they are situated ; that they ramify very freely, and run a very extensive course ; and that they do not divide gradually into smaller and smaller branches, but that bundles of very fine capillary vessels arise from every part of the cir- cumference of vessels of a certain size, and immediately penetrate the cerebral substance. The Posterior Commu7ucating Artery, or Communicating Artery of Willis. — This artery varies exceedingly in size, being generally small, but sometimes forming the largest di- vision of the internal carotid. It arises from the back of the carotid, runs from before backward (r), and terminates in the posterior cerebral branch of the basilar artery. In certain cases, the communicating artery of Willis may be regarded as the chief origin of the posterior cerebral, which then seems to result from the union of this communica- ting artery with the anterior bifurcation of the basilar. The Choroid Artery. — A very small but constant branch {s) arises from the back of the internal carotid, on the outer side of the communicating artery of Willis. This is the artery of the choroid ■plexus, which passes backward and outward, along the optic tract, and, consequently, along the crus cerebri, to both of which it sends branches, and then en- ters the lateral ventricle at the anterior extremity of the great transverse fissure of the brain, gives twigs to the hippocampus major and corpus fimbriatum, and terminates in the choroid plexus, t Summary of the Distribution of the Common Carotid Arteries. The common carotids are distributed to the head, and to the organs which occupy the front of the neck. The internal carotid belongs exclusively to the brain, and to the organs of vision ; and hence, doubtless, at least in part, arises that intimate relation between the condition of the brain and of the eye, which is expressed by the common saying, that the eye is the mirror of the soul. Although the size of the internal carotid is almost always in proportion to that of the brain, yet this artery is not the only one by which that organ is supplied with blood. The vertebral artery, a large branch of the subclavian, completes the arterial system of the brain ; and the fact of an artery, principally destined for the upper extremity, also send- ing a branch to the brain, proves that there is nothing peculiar in the quality of the blood transmitted to the encephalon. We have already seen that the ophthalmic artery communicates by its nasal branch with the facial artery, and by its inferior palpebral branch with the infra-orbital branch of the internal maxillary. But the internal carotid has no direct communication with the external, unless when it gives origin to the ascending pharyngeal and the occipital arter- ies. I may remark, however, that some meningeal branches are given off by the inter- nal carotid within the cavernous sinus. The external carotid differs from the internal, in giving origin to a very great number of branches, which are distributed to the face, to the parietes of the cranium, to the or- gans of respiration, and, lastly, to the organs of digestion. The /acta/ branches may be divided into the superficial and the deep-seated. * We shall see hereafter that this region of the brain belongs to the corpus striatum. t See vertebral artery (p. 533), for the completion of the arterial system of the enceohalon. ARTERY OF THE UPPER EXTREEITY. .531 The superficial arteries of the face are derived from many sources. The principal one is furnished by the facial or external maxillary ; the others are the transverse artery, or transverse arteries of the face, coming from the temporal ; the nasal, a descending branch of the ophthalmic ; the buccal, masseteric, infra-orbital, and mental — all derived from the internal maxillary. The arteries of the right side communicate very freely and fully with those of the left ; and on each side, branches from the diiferent sources communi- cate as freely with each other ; so that, in hemorrhage from any of them, the injured vessel must be tied on both sides of the wound. I may call attention to the abundance of arterial vessels in the face, and to the number and size of the muscular and cutaneous branches ; this is evidently connected with the extreme susceptibility of the skin of this region, the existence of the hair-bulbs, and the action of the muscles in giving expression to the features. The deep arteries of the face are principally derived from the internal maxillary. Thus, the spheno-palatine supplies the nasal fossae : some branches of the infra-orbital enter the orbit. We shall afterward allude to the branches which are furnished to the buccal cavity and the zygomatic and spheno-maxillary fossae. Lastly, the superficial and deep arteries of the face are united by numerous anastomoses. The first set of cranial branches, derived from the external carotid, are the arteries of the hairy scalp, viz., the occipital, temporal, posterior auricular, supra-orbital, and frontal. With regard to these arteries, it is important to notice their large size, which is connect- ed with the great vitality of the skin of the head, and with the existence of the bulbs of the hair ; also, that they are extremely tortuous, which appears to me to be in corre- spondence with the great number of branches which they give off; and, lastly, that they are situated in the dense cellular tissue which connects the skin with the muscles and the epicranial aponeurosis. Besides these, small branches are found upon the pericranium, under the muscles and epicranial aponeurosis : they are seen on the forehead, where tliey arise from the fron- tal and infra-orbital arteries, and also in the temporal region, where they are called the deep temporals ; these branches are both periosteal and muscular. The secojid set of branches to the cranial parietes are arteries of the interior of the cra- nium, viz., the meningeal, the chief of which is the middle meningeal, a branch of the in- ternal maxdlary : the others, or small meningeals, enter through most of the foramina at the base of the cranium. Among these latter we would mention the meningeal branches of the ascending pharyngeal artery, and meningeal branches from the ethmoidal arteries, to which may be added some small twigs given off from the internal carotid, while enclosed in the cavernous sinus. We may also refer the arteries of the organ of hearing to those of the cranial parietes. They are the posterior auricular and the anterior auricular, which are distributed to the pinna and to the external meatus ; the tympanic, which passes through the fissure of Glasserus, and a small branch of the middle meningeal, which enters through the hiatus Fallopii. The branches of the external carotid distributed to the organs of digestion belong to the following parts : To the organs of mastication, viz., the alveolar, the infra-orbital, and the inferior den- tal arteries, which go to the teeth and the jaws ; the superior palatine, which supplies the roof of the palate ; and, lastly, the deep temporal, the masseteric, and the pterygoid, which are distributed to the muscles of mastication. To the salivary organs : thus, the parotid receives its branches from the external carotid and the temporal ; the sub-max- illary gland from the facial ; and the sub-lingual gland from the sub-lingual branch of the lingual artery. To the velum palati and the tonsils we find the ascending or inferior palatine branch of the facial artery, the superior palatine branch of the internal maxillary, and the ascending pharyngeal. To the pharynx, the pharyngeal twigs from the superior thyroid, the ascending pharyngeal, the pterygo-palatine or superior pharyngeal, and the vidian from the internal maxillary, and the inferior palatine branch of the facial. To the oesophagus there are the descending cesophageal branches of the superior thyroid. The branches given by the external carotid to the air-passages are the superior and infe- rior laryngeal, from the superior thyroid artery, which is essentially distributed to the thyroid gland. Artery of the Upper Extremity. A single arterial trunk, called the brachial trunk ( Chaussicr), is destmed for the upper extremity. On the left side it arises directly from the arch of the aorta, and on the right side from the innominate artery ; it emerges from the thorax, between the first rib and the clavicle, traverses the axiUa, runs along the inner side of the arm, passes in front of the elbow-joint, and divides into two branches, which supply the forearm and the hand. As the brachial trunk has some highly important relations during its course, and, moreover, furnishes a very great number of branches, it has been artificially divided,, in order to facilitate its study: each of the divisions has received a particular name, ac- cording to the region through which it passes : thus, the arterv of the upper extremity 532 AKGEIOLOGY. is caDed snccessivelT the m^-e^oriax. the czxSsry, and the htmeral arteiT ; and its tenoi- nal drrisHHis are named the radial and ulnar arteries. The Beaceio-cephjxic Axteet. The hT&chxo-uflialic or innominate artery {arteria atumyma of many authors, e. Jig. 198) is the comnuHi tnmk of the ri^it sob-claTian and lidxt common carotid arteries, and has m tnms been regarded as a portion of the carotid, and as a part of the suh-claTian. It arises from the aorta, at the point where that vessel changes its direction from vertical to horizontaL It is situated in front and to the right of the other arteries given off from the arch of the aorta. It is from one ioch to fifteen lines in length. It is directed ob- Cqaely upward and outward. Rdadma- — JnfronX of the mnoimnate artery is the stermmu beyond the npper end of which the aiteiy almost always projects, and from which it is separated by the left brachio-ce^ialic vein, by the remains of the thymus, and by the sternal attachments of the ste^no-hyoid and stemo-thyroid muscles. BeJdrid. it is in relation with the trachea, which it crosses obliquely ; on the ouier side, with the pleura and mediastinum, which separate it fix>m the lungs : on its iiuier side is the left common carotid, frcan w^hich it is separated by a triangular interval, ra which the trachea is seen. Prom a knowledge of these relations, modem surgeons have succeeded in applying a ligature to the innominate artery. Its relations, however, vary in different individu^. In some cases almost the whole length of the vessel projects beyond the sternum ; and it is then extremely accessible, either to accidental woimds, or to the surgeon in the ap- plication of a ligature. It has been thouoh^ that the presence of the innominate artery esplaiss the predominance of the ri^it over the left upper extremity ; but this opinion is entirely unfounded. The arteria innominata grres off no collateral branch, except in those cases in which it affords origin to the thyrwd artery of Xeuhauer, so named from the anatomist who called attention to this anatomical variety.^ The same anatomist has seen the right in- ternal mammary artery arise from the brachio-cephahc tmnb The Right atd Left Scb-clatia!? Akteeixs. The right suh-clavian artery (£■, fig. 198 : /. Jig. 204) arises from the innominate (e) ; fbe left sub-clavian {g% frtwn the arch of the aorta. Varieties of Origin.— One very common variety is that in which the right sub-clavian arises feelow the Left, frtsn the posterior and inferior part of the arch of the aorta, from which it passes upward and to the right side, generally behind the trachea and cesopha- gus. somerimes between the two, and rarely in front of the tracheal The precise termination of this artery is not well defined. By some authors it is said to end, and the vessel to take the name of axiUary artery as it passes between the sca- leni-± It appears to me more convenient to take the clavicle as indicating the respect- ive hmits of the two vessels. AH above the clavicle, then, belongs to the sub-clavian. and an below it to the axillary artery, o From the difference, as to origin, between the right and left sub-clavians, they differ from, each other remarkably in length, direction, and relations. IhjfereTvceg in Length. — ^The right sub-clavian is shorter than the left by the length of the innominate artery -. and we should, moreover, bear in mind the slight difference in the height between the origin of the innominate and the left suh-clavian. The dijfereru:' in the size of the two sub-cVavian arteries requires no special notice. IHfferenee^ in IHreetir/n. — ^The right sub-clavian passes at first obhquely outward and a little upward, and then bends over the apex of the lung, describing a curve with the con- cavity looking downward. The left snivclavian passes vertically upward before curving over the apex of the lung, opposite which it changes its direction abruptly, and becomes horizontaL Differeyi/ce* in Relaivms. — ^In describing these, we shaD divide the sub-clavian artery into three portions : the JirH, extending from the origin of the artery to the scaleni mus- cles : the ttr.rmi, gitoated between the scaleni : and the third, extending from the scale- ni to the clavicle. The relations of the right and left sub-clavians differ from ea.:-h other only in the first of these portions. The fr»t y/rtir/a <\.f.g- 204> of the right sub-clavian Ls in relation in front with the inner end of the clavicle, the stemo-clavicular articulation, the platysma, and the clavicular attachment of the stemo-mastoid muscle, with the stemo-hyoid and stemo-thyroid miis- des, with the termination of the internal jugular and vertebral veins in the snb-clavian * Vm nfeiior diTniideaa arterf ariaea, periiaf , note freqweady from Ae an^ of tlie amta, between the teaelnaHKpbalic trmtk aad die left yoMitiie earotid. t CIt raxAj paaees lietweea die XtailOtA and OESCfiba^TU ; and it ajqpean diere is do reeoid of its liaTing been •etaaBj' aeea ia frost of the tia^ea(aee (itmm u^fhe Arteries). 1 % ActmHag to tamtt antitoa, the aztety ehaagea its name as it eaeigea from benreea the acaleid ; accord- mg to othen, while it is yet between Oose moadea. 4 We are in the haixt a( diTiding this arterr iato three fomoaa : a ezziiae, a middle, aad an aziliarj por- ooB. The firat, ttat port between its otigin and the scaleni ; die second, the portioa ealiraced between tbe •calen ; sad Ae drosA, the reauiaiagr fort af die azteiy<— £0. THE y£ETEBRAL ASTEET. 533 Tein, and vrith the right pnemnosastric and phrenic nerves : behind, with the recnrrent larjmgeal nerve and the transverse process of the seventh cervical vertebra : on the otit- er side, with the mediastinal pleura, which separates it iroin the lung. On the inner side, it is separated from the common carotid by a triangular interval* It is surround- ed by loose ceUular tissue, a great number of lymphatic glands, and nervous loops formed by the great sympathetic. The nrst portion of thf left sub-clavian is in relation with the same parts, though to a somewhat different extent : thus, its relations with the left mediastinal pleura and lung are much more extensive. The sub-olavian vein crosses it at right angles, instead of being parallel to it ; but the left pneumogastric and phrenic nerves run parallel to. in- stead of crossing it. It is parallel to the left common carotid, instead of forming an an- gle with it : and. instead of being near the clavicle, the left sab-clavian is close to the vertebral column, and rests on the longus coUi. the inferior cervical ganglion of the sym- pathetic nerve, and the thoracic duct, which is there to its inner side. The second portion of both the rifht and kft sub-clavian arteries, situated between the scaleni. is in close relation below with the middle of the upper surface of the first rib. on which there is a corresponding depression behind the tubercle for the attachment of the anterior scalenus : above, with the two scaleni. which are in contact with each other above the vessel ; behind, with the brachial plexus : in front, with the scalenus anricus, which separates the sub-clavian artery from the sub-clavian vein. This separation of the artery from the vein is one of the most important points in its history, i The third portion of the sub-clavian, or that extending from the scaleni to the clavide, corresponds to a triangular space, bounded in front by the stemo-mastoid and anterior scalenus, above by the omo-hyoid. and below by the clavicle -. this space is named the lower or clavicul2ir portion of the posterior triangle of the neck, which is bounded in front by the stemo-mastoid. behind by the trapezius, below by the clavicle. In front of. but somewhat lower than the artery, is the clavicle, that bone being separated from the ves- sel by the sub-clavian vein, which is here below and in contact with the artery, and by the sub-clavius muscle : behind and to the outside of the artery is the brachial plexus of nerves, which surroimds the vessel in the axilla : it is covered by the deep cervical fascia, the platysma, the superficial fascia, and the skin, and is crossed by the descend- ing cutaneous branches of the cervical plexus, and obliquely by the supra-scapular ar- tery and vein ; below, it rests upon the first rib. In consequence of these relations, the sub-clavian artery may be compressed, and the circulation of the upper extremity stopped by forcible depression of the clavicle ; the sub-clavian may be easily felt, compressed, and tied above the clavicle : and. lastly, it follows that the sharp fragments of a broken clavicle can wound the coats of the artery only after having transfixed the sub-clavius muscle and the sub-clavian vein. This artery, moreover, presents individual varieties both in regard to its direction and relations ; it usually rises shghdy above the clavicle, but in persons with short necks and high shoulders it is situated deeply imder the clavicle, while in those who have long necks and low shoulders it may even slightly raise up the platysma and the skin. But the most important variety is that in which the relations of the sub-clavian with the sca- leni muscles are changed. It is not imcommonr to see the sub-olavian artery situated in front of the scalenus anticus. forming immediate relations with the sub-clavian vein. 4 CoiUUcral Bramkes. — The sub-clavian artery. gives off certain collateral branches, which may be divided into the superior, infcnor. and e^^nai. The superior are the «t- tebrai and the mfcrwr thyroid ; the inferior are the intcma] tmimntartf and the superior in- tercostal : the external are the sitpra-sciwu-dr. the posterior scspular or transrrrsnlis eolJi, and the dt-ep cfmeaJ. Besides these, the sub-clavian aneries sometimes give off. near their origin, pericar- diac, thjTnic. and oesophageal branches ; not unlrequently the left sub-clavian gives ori- gin to the bronchial artery of that side. The Vertebral Artery. The Tcrtfbral artery, destined for the cerebro-spinal nervous centre, supplies more panicularly the spinal cord, the pons Varohi. the cerebellum, and the posterior portion of the cerebrum. It is the first and largest branch of the sub-clavian. and in some subjects is about equal in size to the continuation of that vessel. A rery great inequal- ity in the size of the two venebrals is rather irequently met with. Moreagni states * [It has been observed bv Professor R. Quain (^v. cit. ^ that the oHsin o?" the nght stib-claviaa is stanetjiues putiallr or compieteiy corered br the ncht oaroiid, a piwess of the cerri-^al fascia separsrinff the rwo ressels.] t iProft'ssor Qnain has sieen. in a few cases, the ar:err perforanns' the anterior scalenus ; and it has eT^ been found, by himself and others, antenor to that muscle, ana thereA'>re la contact irith the rein.] t Acoordinsr to our observation, this 55 a most rare variety. — Ed. t Im a case of this kind, -which has been communicated to ice by M. IVmeaui. »d!ttnct of anaWmT to t^ Faculty, (here was no brachio-cephalic trunk, but a bi-carotid trunk ; the ncht sab-c}avian arT."has-as. (This p-eitaratioji has been deivsatied in the I able, was formed as usual. It gave off the external collateral of the thumb and the common trunk of the in- ternal collateral of the index, and the external collateral of the middle finger. This common trunk was the continuation of the non-flexed portion of the radial artery. The radial artery iu this case was much larger than the ulnar. REMARKS ON THE ARTERIES OF THE UPPER EXTREMITY. 551 from the superficial arch ; they are rarely of the same size, but always bear an mverse ratio to them ; the bifurcation of each digital branch of the superficial palmar arch takes place two or three lines below the metacarpo-phalangal articulation, opposite the junc- tion of the body with the upper end of the first phalanx ; the collateral arteries of the fingers are situated upon the anterior aspect of the phalanges, on each side of the sheath of the flexor tendons ; they give off dorsal and palmar branches, and anastomose with each other in front of the body of the phalanges by small transverse branches ; having reached the middle of the last phalanx, they anastomose in an arch, from the convexity of which a great number of anterior branches pass to the skin, over the last phalanx, and some dorsal branches to the matrix of the nail ; one of these branches runs along the curved adherent border of the nail. The termination of the superficial palmar arch is subject to variety : thus, it terminates either by anastomosing with the radio-palmar or superficialis volae, of the same size as itself, or by receiving a very small radio-palmar branch, and being prolonged so as to con- stitute the common trunk of the internal collateral artery of the thumb, and the external collateral artery of the index finger ; or else it terminates in the external collateral of that finger ; or, lastly, after having given off the internal collateral of the thumb and the external collateral of the fore-finger, it ends in the external collateral of the thumb. At other times, again, there is no superficial palmar arch properly so called, and the ulnar artery terminates by furnishing the collaterals of the little and ring fingers, and the in- ternal collateral of the middle finger, the other collaterals being derived from the radio- palmar, which is then very large. In certain cases, a very small transverse branch forms the communication between the radial and the ulnar arteries. General Remarks on the Arteries of the Upper Extremity. A single trunk, which may be called the brachial trunk, supplies the whole of the up- per extremity ; it forms, in succession, the sub-clavian, the axillary, and the brachial ar- tery, which latter bifurcates near the bend of the elbow into the radial and ulnar arteries : these form the palmar arteries, from which the arteries of the fingers take their origin. The difference in the origin of the right and left brachial trunks has been considered to account for the difference in strength between the two arms ; and the different size of the two vessels has also been supposed to be connected with the same fact, which, however, in reality, depends upon the more frequent exercise of the right than of the left arm. The brachial trunk is not exclusively distributed to the upper extremity, but supplies the most dissimilar parts ; a fact which shows that the conditions of origin, which have so great an influence in regard to nerves, are altogether without importance in reference to the arteries. Thus, the brachial trunk sends branches to the following parts : the ver- tebral artery to the brain, the cerebellum, the pons varolii, the medulla oblongata, and the spinal cord ; the inferior thyroid artery, to the thyroid gland, the larynx, the trachea, the oesophagus, and sometimes the bronchi ; the internal mammary and thoracic arteries, to the corresponding mamma ; and the same arteries, together with the superior inter- costal, to the parietes of the thorax and abdomen ; the ascending cervical, to the praever- tebral muscles and the spine ; and, lastly, the deep cervical, sub-scapular, and posterior scapular arteries, to the superficial and deep muscles of the back of the neck. Setting aside those branches which do not belong to the upper extremity properly so called, we find that, during its course along the limb, the artery always occupies the as- pect of flexion, which is at the same time the position where it can be best protected ; and that, for this purpose, it is directed from the axilla to the bend of the elbow : we find, also, that it gives off a great number of anastomotic branches around the articula- tions, and thus establishes a collateral circulation, through which the blood can pass when the principal artery is obliterated. This anastomosis, and, consequently, the col- lateral circulation, is effected by the cutaneous, muscular, and periosteal branches, and even by those distributed to the nerves. Thus, along the clavicle, we find the acromio- thoracic in front, and the supra-scapular or transversus humeri behind ; around the scap- ula there are the supra-scapular on the upper border, the posterior scapular on the ver- tebral border, and the sub-scapular on the axillary border ; so that that bone is complete- ly surrounded by an anastomotic triangle. Around the elbow-joint are the external and internal collateral branches of the brach- ial artery, and the radial, ulnar, and interosseous recurrents. Around the wrist we find the anterior and posterior carpal arteries, and also anasto- motic arches around the metacarpo-phalangal and phalangal articulations. On comparing the size and number of the arteries of the arm and forearm with the size and number of the arteries of the hand, it will be seen that the latter has greatly the advantage : indeed, in this part of the body, there is an unusual distribution of the arterial system into a deep and a superficial set of vessels, precisely as is the case with the veins. Why is this 1 Is it not extremely probable that, as the deep veins are in- tended to supply the place of the superficial, when the circulation in the latter is for a tune impeded, so in the hand the arteries are arranged in a similar manner, because the- 552 ANGEIOLOGY. superficial circulation is liable to be interrupted by pressure from grasping bard bodies firmly in the hand for a longer or shorter period 1 and is it not for the same reason thai the superficial system derived from the ulnar artery has so many communications with the deep system given off from the radial 1 It is worthy of remark that the radial, which is the superficial artery of the forearm, becomes deep-seated in the hand ; and that the ulnar, which is deep-seated in the fore- arm, becomes superficial in the hand. The great quantity of blood circulated through the hand is connected with the active use of that part, in the almost constant exercise of the sense of touch, and in prehension. ARTERIES ARISING FROM THE TERMINATION OF THE AORTA. Enumeration. — The Middle Sacral. — The Cominon Iliacs. — The Internal Iliac, or Hijpogas- tric — the Umbilical — the Vesical — the Middle Hemorrhoidal — the Uterine — the Vaginal — the Obturator — the Ilio-lumbar — the Lateral Sacral — the Glutaal — the Sciatic — the Inter- nal Pudic. — Summary of the Distribution of the Internal Iliac. — Artery of the Lower Ex- tremity.— The External Iliac — the Epigastric — the Circumflex Iliac. — The Femoral — the Superficial Epigastric — the External Pudic — the Muscular — the Deep Femoral, its Cir- cumflex and Perforating Branches. — The Popliteal and its Collateral Branches. — The An- terior Tibial and the Dorsal Artery of the Foot. — The Tibio-peroneal — Peroneal — Poste- rior Tibial, and the Internal and External Plantar. — Comparison between the Arteries of the Upper and Lower Extremities. The arteries arising from the termination of 'the aorta are the middle sacral and the two common iliac arteries. The Middle Sacral Artery. The middle or anterior sacral artery {n,fig. 199), the small median artery of the sacrum, arises from the lower and back part of the aorta, a little above its termination. Like the aorta, it is a single vessel, and seems to be the continuation of it, as far as direction is concerned ; which, indeed, is really the case in such animals as are provided Avith a tail. Sometimes, but rarely, it arises from the left common iliac, or the last lumbar ar- tery. I have seen it arise by a common trunk with the two lower lumbar arteries.* It passes vertically downward in front of the fifth lumbar vertebra, the sacrum and the coccyx being closely applied to them all. It is situated in the median line at its origin, but sometimes deviates to one side or the other. In size it is scarcely equal to one of the lumbar arteries, and it gradually diminishes from its origin to the first bone of the coccyx, towards the apex of which it terminates in a very variable manner. The size of the middle sacral is generally inversely proportioned to that of the lowest lumbar arteries. When the aorta divides higher than ordinarily, and the last lumbar is given off from the middle sacral, the last-named artery is of course unusually large. During its course, the middle sacral gives off, opposite the fifth lumbar and each of the sacral vertebrae, a right and left lateral branch, which correspond with the series of intercostal and lumbar arteries. The two lumbar branches are generally small, but are very large when the fifth lumbar arteries are neither furnished by the aorta, nor by the fourth lumbar, nor by the ilio-lumbar. The lateral branches given off upon the sacrum pass transversely outward, supply twigs to the periosteum and bone, and anastomose with the lateral sacral, the place of which they sometimes supply within the interior of the sacral canal. The middle sacral having become very slender near the base of the coccyx, bifurcates in order to form an anastomotic arch with the right and left lateral sacral arteries. I have seen its lower end divided into three branches, of which the median was prolonged as far as the tip of the coccyx, while the lateral branches anastomosed with the lateral sacral arteries. The Common Iliac Arteries. The primitive or common iliac arteries {t i,figs. 199, 212), the two branches into which the aorta subdivides, commence opposite the lower margin of the fourth lumbar vertebra, and terminate by bifurcating opposite the base of the sacrum ; they separate from each other at an acute angle, pass obliquely downward and outward, and form the two sides of an isosceles triangle, the base of which corresponds with the transverse diameter of the fifth lumbar vertebra. These arteries are generally straight, but not unfrequently they are tortuous in aged persons. In the adult they are about two inches long, the right being rather longer than the left, from the position of the aorta ; but they are often much shorter, on account of their bifurcating higher than usual. Meckel has remarked that this premature bifurcation is more common on the left than on the right side. In .a specimen deposited in the museum of the Ecole de Medecine, the right common iliac * I have geen the middle sacral artery arise from the renal artery. In this case, the renal artery came from the angle of bifurcation of the aorta. THE INTERNAT. ILIAC ARTERY. 553 is entirely wanting ; the aorta dividing into three branches, two on the right, viz., the in- ternal and external iliacs, and one on the left, viz., the common iliac, which is distributed in the usual manner. In this case the descending aorta resembled, to a certain extent, the ascending aprta, and, like it, gave off three trunks Relations. — They are covered by, and loosely connected with, the peritoneum ; they are crossed by the ureters and the spermatic vessels, besides which, the left common il- iac is crossed by the inferior mesenteric artery ; they are surrounded by a great number of lymphatic glands, and rest above upon the vertebral column, and on the outside and below upon the inner side of the psoas muscle. It is of great importance to comprehend their relations with the common iliac veins. The veins are situated behind the arteries ; but as the right and left vein unite on the right side of the vertebral column, the left common ihac vein comes into relation with both common iliac arteries. The common iliac artery gives off no collateral branch ; it merely supplies some twigs to the cellular tissue, the lymphatic glands, and the coats of the common iliac veins. It occasionally gives off one of the renal arteries ; and it has been seen to supply the sper- matic and the ilio-lumbar arteries. Terminal Branches. — The common iliac artery terminates by dividing into two branch- es, which remain in contact with each other for a short distance : the internal branch dips into the pelvis, and is called the internal iliac or hypogastric artery ; the external branch continues in the original course of the common iliac, and is termed the external iliac artery. The Internal Iliac or Hypogastric Artery. The internal iliac or hypogastric artery (t, figs. 199, 212) is distributed to all the organs contained in the cavity of the pelvis ; to the muscles pig_ 212. which line it within and cover it without ; to the exter- nal and internal organs of generation, and to the integ- uments. It passes at first obliquely downward and forward, and, as it were, in contact with the external iliac ; it then dips vertically into the pelvis in front of the sacro- iliac synchondrosis, describing a short curve ; and, after a course of about one inch or one inch and a half in length, divides opposite the upper part of the sacro-sciatic notch into a greater or less number of branches, which do not always arise in the same way from the principal trunk, but whose ultimate distribution is constant. It is cov- ered by peritoneum, and is crossed by the ureter ; it rests behind on the lumbo-sacral nerve and pyriformis muscle-; and the internal iliac vein is behind and to its outer side. Its branches, all of which sometimes arise from two principal trunks, one anterior and the other posterior, may be divided into an anterior set, consisting of the umbilical, vesical, obturator, middle hemorrhoidal, uterine, vaginal, sci- atic, and internal pudic arteries ; and a posterior set, including the ilio-lumbar, lateral, sa- cral, and gluteal arteries. Altogether, there are nine in the male and eleven in the female. The Umbilical Artery. The umbilical artery, which is so large in the foetus, is converted into an impermeable cord {u,fig. 212) in the adult, excepting near its origin (a), where it gives off some ves- ical branches : the examination of the umbilical arteries belongs, therefore, more espe- cially to the anatomy of the foetus. They are intended to convey the blood of the foetus to the placenta, and are then the continuations of the common iliac arteries. The ex- ternal and internal iliacs, being very small at that period, in correspondence with the small size of the abdominal extremities, appear to be nothing more than divisions of the umbilical. The umbilical arteries pass downward, forward, and outward, and, having arrived at the sides of the bladder, run along them, in order to reach the umbilical ring, through which they emerge from the abdomen, and, having traversed the whole length of the umbilical cord in a spiral and tortuous manner, are at length distributed to the placenta.* The vesical, middle hemorrhoidal, uterine, vaginal, and obturator arteries are given off in succession from the apparently ligamentous cord formed by the umbilical artery near its origin. The Vesical Arteries. These are variable in number : the principal of them on each side are given off from * It is curious to study the variable manner in which the umbilical arteries are converted, after birth, into a fibrous tissue. Sometimes these arteries are converted into two regular cords, which converge towards the umbilicus. At other times each of these cords is subdivided into irregular bundles which it is difficult to trace to their true origin. 4A 554 ANGEIOLOGY. the umbilical artery (a), which seems to be converted into a ligamentous cord (u) at the place where the vesical arteries arise, but which is in reality pervious. This ligament- ous appearance of the umbilical arteries depends upon the narrowness of their canal, as compared with the thickness of their coats. Other vesical branches arise from the mid- dle hemorrhoidal and obturator arteries, and in the female from the uterine and vaginal. We shall divide the vesical arteries into the posterior, the anterior, and the inferior. The posterier vesical artery {b,fig. 212) frequently arises, in the female, by a common trunk with the uterine. It reaches the base of the bladder, on the outer side of the ure- ter, passes inward and upward upon the posterior surface, as far even as the summit of that viscus. I have seen the right posterior vesical artery, of large size, running along the posterior surface of the bladder in the median line, and prolonged upon the urachus ; the left posterior vesical was very small, and, in fact, rudimentary. The anterior vesical (c) arises from the umbilical, from the obturator, and sometimes ' from the internal pudic artery. When it arises from the umbilical, it is given off from that artery opposite the sides of the bladder, and passes downward and inward along its anterior surface. I have seen it given off near the summit of that organ. When it ari- ses from the obturator or the internal pudic, it traverses the anterior ligament of the blad- der, and passes upward upon the front of that organ. I have seen a very large vesical artery given off from the obturator, which, in that case, arose from the epigastric, and farther the vesical artery arose by a common trunk with the artery of the corpus cavernosum. The inferior vesical (d), which often arises direct from the internal iliac, reaches the inferior fundus of the bladder, and ramifies abundantly upon it and the commencement of the urethra : in the male it also supplies the corresponding vesicula seminalis and vaa deferens, the branch to which is called the deferential artery, and the prostatic portion of the urethra. I have seen the dorsal artery of the penis arise from the inferior vesical. The Middle Hemorrhoidal Jlrtery. This is a small artery (c), which is sometimes wanting, its place being then supphed by branches from different sources, but especially from the sciatic or the internal pudic ; it passes upon the sides of the anterior surface of the rectum, where it terminates by anastomosing with the superior and inferior hemorrhoidal arteries. The Uterine Jlrtery. The uterine artery {n n,jig. 198) arises from the umbilica., near the posterior vesical, and frequently by a common trunk with it ; passes transversely inward to the corre- sponding lateral border of the uterus, a little above the os tincae ; is reflected upward along the uterus, and terminates by expanding into several ascending branches, of which the anterior reach the front, the posterior the back, and the middle the upper border of the viscus, and inosculate either with their fellows of the opposite side, or with the uter- ine branches of the ovarian artery. The uterine arteries are remarkable for the great size which they acquire during pregnancy, and also for their tortuous and spiral course, even to their smallest branches : a disposition which no other artery presents in the same degree. These tortuosities, instead of diminishing, appear to increase during pregnancy : a fact which seems opposed to the view generally adopted regarding the use of arterial flexuosities in organs liable to variations in their size. Collateral Branches. — At the point of its reflection, each uterine artery gives off one or more descending branches between the vagina and the bladder to supply both parts ; in their course along the borders of the uterus, they furnish a series of anterior and poste- rior ascending branches, which are distributed in the same way as the terminal ascending branches ; they all anastomose in the median line with their fellows of the opposite side. Relations. — The trunks of the uterine arteries are beneath the peritoneum ; the prin- cipal branches are situated under a thin layer of the substance of the uterus, and the ul- timate divisions and subdivisions enter its tissue. The Vaginal Artery. The vaginal artery arises from the umbilical, sometimes before, sometimes after the origin of the uterine, which is sometimes given off from a common trunk with it. It is as large as the uterine in young subjects, but is smaller than it after puberty. It de- scends directly upon the sides of the vagina, to which it gives off a numerous series of branches, supplies a considerable branch to the neck of the bladder and the urethra, gives an equally large one to the bulb of the vagina, and then passes backward between the orifice of the vagina and the rectum, and anastomoses with its fellow of the oppo- site side. The Obturator Artery. The obturator artery {f,Jig. 212) is remarkable for the varieties of its origin, and for the important consequences which result from those varieties, in reference to the oper- ation for femoral hernia. THE ILIO-LUMBAK ARTERY. . 555 It generally arises from the internal iliac by the side of the umbilical, but sometimes above the gluteal ; it is almost as frequently given off from the external iliac, either di- rectly,* which is rare, or by a common trunk with the epigastric. Lastly, and much more rarely, it arises from the femoral artery. The course of the obturator artery is modified by these differences of origin, which, notwithstanding the assertion of some anatomists, are as common in the male as the fe- male, and which may occur on one side only, or on both sides of the same subject. Thus, when the obturator comes from the femoral, it passes upward on the inner side of the femoral vein, enters the pelvis through the crural ring, is reflected upon the upper surface of the body of the os pubis, then passes behind it and gains the internal opening of the sub-pubic canal. When it arises by a common trunk with the epigastric, it dips vertically behind the os pubis to the same opening. In its ordinary mode of origin, it passes horizontally forward upon the sides of the brim of the pelvis, being bound down by the peritoneum, runs parallel with the obturator nerve (n), which is placed above it, gains with it the internal orifice of the sub-pubic canal, and, having traversed this pas- sage, divides into an internal and an external terminal branch. Collateral Branches. — Near its origin, the obturator artery gives off a tolerably large branch, the iliac, which perforates the iliac fascia, dips between the iliacus muscle and the iliac fossa, and anastomoses with a branch of the circumflex iliac artery. t As it enters the sub-pubic canal it gives off a small branch, which passes transversely behind the body of the pubis, and ramifies upon the side of the symphysis, anastomo- sing with its fellow of the opposite side ; also a small ascending branch (*), which anas- tomoses with the epigastric artery, and which may be regarded, according to Meckel, as one of the origins of the obturator ; so that the variety in which the obturator arises from the epigastric is often nothing more than an unusual development of this commu- nicating branch. In support of this view, we may quote the very rare case, in which the obturator arises by two roots of almost equal size, one coming from the epigastric, and the other from the internal iUac. Terminal Branches. — The internal branch passes between the obturator externus mus- cle and the conjoined rami of the pubes and ischium, so as to describe a semicircle around the inner half of the obturator foramen, gives branches to the periosteum of the OS pubis, muscular branches to the two obturator and to the adductor muscles, some genital branches to the coverings of the testis in the male and to the labia majora in the female, and, lastly, some very important anastomotic branches, which join those of the internal circumflex. The external branch runs along the outer half of the obturator foramen ; it is placed, like the preceding, between the two obturator muscles, and terminates between the neck of the femur and the quadratus femoris muscle by anastomosing with the sciatic artery. This anastomosis is very remarkable. During its course, the external branch supplies the obturator muscles and the hip-joint ; the articular branch enters by the notch of the cotyloid cavity, and is lost in the reddish, fatty tissue situated at the bottom of it. The distribution of the obturator artery is much more limited than that of the ob- turator nerve. The Ilio-lumbar Artery. The ilio-lumbar artery (h) arises from the back of the internal iliac, and, tolerably fre- quently, from the gluteal. There are often two ilio-lumbar arteries. This vessel bears the same relation to the lumbar arteries that the superior intercostal does to the aortic intercostals ; its size and distribution vary according to the presence or absence of the fifth lumbar artery. It has a retrograde course, running upward and backward in front of the lumbo-sacral nerve, and behind the psoas muscle, and soon divides into two branches : an ascending or lumbar, and a transverse or iliac. The ascending or lumbar branch passes vertically upward along the bodies of the lumbar vertebra^, hidden by the psoas, and subdivides into a muscular branch, which corresponds to the abdominal branches of the lumbar ar- teries, and is distributed to the psoas and to the quadratus lumborum ; and a spinal branch, which enters the vertebral canal by the foramen between the fifth lumbar verte- bra and the sacrum, and is distributed in the same manner as the other spinal arteries. * The cases where the obturator artery arises separately from the external iliac are not unfrequent. The following description may serve as an example. In one Usually, there are two veins of unequa size for each internal mammary artery, which is placed between them. The two almosi. always unite into a single trunk, which ter- minates on the right side at the junction of 4;e two brachio-cephahc veins, or in the up- per and ft-ont part of the superior cava, and ^n the left in the corresponding brachio- cephalic vein. Among the veins which open into the internariqammary, I should mention the proper veins of the sternum, which form a very remarkably venous network in front of and be- hind each piece of that bone beneath the periosteum. , The Superior Phrenic, and the Thymic, Pericar&iac, and Mediastinal Veins. These are small veins which unite into two groups, one for the right side, terminating at the junction of the two brachio-cephahc veins, or at the uijper and anterior part of the superior vena cava ; the other for the left, and temiinating la the left brachio-cephalic vein. The pericardiac and mediastinal veins commence upon the pericardium and the anterior mediastinum. The thymic veins, which are very large in the fcetus, may still be seen in the adult and the aged, for the thymus gland is never completely absorbed. The superior phrenic veins are remarkable for their length as well as for their small size ; they accompany the phrenic nerve and the superior phrenic artery : the left supe- rior phrenic vein often enters the corresponding superior intercostal vein, and frequent- ly the internal mammary vein. THE JUGULAR VEINS. The Vertebral Veins. The vertebral vein corresponds to the cervical portion of the artery of the same name, ■and, like it, is contained in the canal formed by the series of foramina at the base of the transverse processes of the cervical vertebrae ; it opens into the braehio-cephalic vein im- mediately behind the internal jugular ; and it is said to open occasionally into the last- mentioned vein. Not unfrequently, as Eustachius remarks, this vein divides into tvro branches near its termination, one of which emerges vs^ith the artery, between the fifth and sixth vertebrae, while the other, either alone or accompanied by a small arterial twig, escapes by the foramen of the seventh cervical vertebra. I have seen these two branch- es emerge, one at the foramen of the fifth, the other at that of the sixth cervical vertebra. This vein commences in the deep muscles at the back of the neck, communicates by a large branch with the occipital vein, and sometimes receives a small branch, which passes out at the posterior condyloid foramen ; it enters the canal of the transverse pro- cesses, between the occipital bone and the atlas ; and while within this canal, it receives anterior muscular branches from the praevertebral region, posterior branches from the external spinal veins, and vertebro-spinal branches from the interior of the spinal canal. At the point where it opens into the braehio-cephalic vein, it receives a large branch, which corresponds in its course to the ascending cervical artery ; it also receives the deep cervical vein, which has the same distribution as the artery of that name. The Jugular Veins. The jugular veins (from jugulum, the throat) are three in number on each side, viz., the internal ox deep jugular {n,fig. 219), the external jugular (A), and the anterior jugular (m). The two latter veins form part of the superficial or sub-cutaneous venous system ; but the internal jugular is the satellite vein of the common carotid artery and its branch- es. I shall describe these three veins in succession, but shall not notice the veins with which they are directly continuous, nor yet their branches of origin, until I have described all three of them, because those branches terminate almost indifferently in either of them. The External Jugular Vein. The external jugular {h), one of the supplementary veins of the internal jugular, is a sub-cutaneous vein of the neck, on the lateral and ^. ^jg anterior aspect of which it is situated. It is bound- ed above by the angle of the lower jaw according to some authors, by the neck of the condyle of that bone according to others ; the former mode of limitation seems to me to be preferable. It is bounded below by the clavicle, behind which it ends in the sub-cla- vian vein (o), immediately to the outer side of the internal jugular, and sometimes even opposite that vein, but upon a plane anterior to it. The external jugular is generally single, but is sometimes double ; and this depends either upon some of its branches of origin not joining it until they reach the lower part of the neck, or else upon the existence of a small collateral branch, which ari- ses from the upper part of the external jugular, runs along its outer side, and opens into it below, imme- diately before its termination ; at other times the external jugular bifurcates before it ends in the sub- clavian. The external jugular varies extremely in size, which frequently differs on the two sides, and is not uniform throughout its whole length. Thus, it al- most always presents an ampulla, or ovoid dilatation of variable dimensions, near its termination. In size it is inversely as that of the other jugular veins of the same and the opposite side, and its differences are either congenital or acquired ; the former depending upon the fact of its receiving more or fewer branches, while acquired alterations in size are occasioned either by some occupation requiring violent respiratory efforts, or by the venous circula- tion being impeded by disease. Direction. — The external jugular vein passes obliquely downward and backward in the opposite direction to the sterno-cleido-mastoideus, which it crosses at a very acute an- gle, and then runs parallel to the posterior border of that muscle. A line drawn from the angle of the jaw to the middle of the clavicle will exactly indicate its direction. Op- posite the clavicle, the external jugular vein turns forward and opens into the sub-clavi- an, either directly, or after running horizontally for some lines. Relations. — The external jugular vein runs first across the stemo-mastoid, and then the supra-clavicular region of the neck. In the whole of its extent it is covered and 582 ANGEIOLOGT. separated from the skin by the platysma ; hence the rule to open this vein across the fibres of the platysma, when it is desirable that the orifice should be free, and favourably disposed for the flow of blood. By its deep surface it is in relation with the stemo mastoid, which it crosses obliquely, so that it rests above upon the anterior border of that muscle, and below upon its external surface, and parallel with its outer border. In the supra-clavicular region it is in relation behind with the omo-hyoid and scalenus anticus muscles and with the brachial plexus. It is always separated from these differ- ent parts by the cervical fascia, which is perforated by it as it curves forward to enter the sub-clavian vein. The external jugular vein is surrounded by the superficial nerves of the cervical plex- us, some of which pass in front, and others behind it. The auricular nerve runs behind its upper portion. This vein has generally two valves, one in the middle, the other near its termination ; sometimes only the latter exists. These valves do not appear, in general, to oppose any great obstacle to an injection thrown from the heart towards the extremity of the vein. Collateral Branches. — The external jugular vein receives, in front, branches of variable size and number, which communicate with the anterior jugular vein, and others which pass directly out of the sterno-mastoid muscle ; behind, it receives the superficial occip- ital veins (k), and several superficial branches from the posterior and lateral regions of the neck ; lower down, it also receives the supra-scapular and posterior scapular veins (l), which exactly correspond to the arteries of the same names. A constant branch passes beneath the clavicle, and establishes a communication between the external jugidar vein and the upper part of the veins of the arm. Branches of Origin. — These are extremely variable ; most commonly the external jug- ular is formed by the junction of the temporal (/) and the internal maxillary veins. Some- times it is formed by a branch resulting from the bifurcation of a trunk common to those two veins ; at other times, by the successive juction of the temporal, internal maxillary, facial, lingual, and superior laryngeal veins. In all cases the external communicates either directly or indirectly with the internal jugular vein in the substance of the parotid gland by means of a communicating branch, which may be regarded as a branch of origin, and which sometimes is the only branch of origin. The interior Jugular Vein. The anterior jugular is a sub-cutaneous vein {m,fig. 219), supplementary to the exter- nal and even to the internal jugular, and collects the blood from the parts situated in the middle of the anterior region of the neck. It varies in size in different individuals, is almost always inversely proportioned to the extetnal jugular, and is often larger than that vein. We frequently find both a right and a left anterior jugular vein ; but then they are rarely of equal size. Rather frequently, however, there is only one, scarcely a trace of the other existing. Lastly, instead of' these veins, there are occasionally only some small branches, which scarcely deserve notice. Direction. — ^From the supra-hyoid region, where it commences, this vein passes verti- cally downward, between the median line and the inner border of the sterno-mastoid mus- cle ; opposite the fourchette of the sternum it bends abruptly, passes horizontally out- ward behind the two lower fasciculi of the sterno-mastoid, and enters the sub-clavian vein on the inner side of the external jugular, sometimes opposite to, but in front of the internal jugular ; lastly, in other cases, it terminates by a common orifice with the ex- ternal jugular. During its course it runs in the substafice of that median layer of fibrous tissue which we have called the cervical linea alba, and it receives several collateral branches. Collateral Branches. — The anterior jugular veins communicate with the external by one or two branches of variable size ; they also communicate freely with the internal jugular veins ; the communicating branches often form the origins of this vein. The an- terior jugular receives some laryngeal branches, and sometimes an inferior thyroid vein. At the point where it bends at the lower part of the neck it receives a sub-cutaneous vein, which comes from the upper part of the thorax, and passes above the fourchette of the sternum. At the same point, also, the right and left anterior jugular veins communicate with each other by a transverse branch {r,fig. 223), into which branches derived from the inferior thyroid vein, or even some branches coimnunicating directly with the left brachio-cephalic vein, pour their contents. Branches of Origin. — The anterior jugular vein often commences by sub-cutaneous and muscular branches, derived from the supra-hyoid region, and corresponding in their several courses to the branches of the sub-mental artery, i have seen it arise from one end of a loop, the other end of which was continuous with the external jugular vein ; at other times it commences by a common trunk with the facial and lingual veins. Lastly, I have seen the anterior jugular form the continuation of the facial vein. THE INTERNAL JUGULAR VEIN, ETC. 583 The Internal Jugular Vein. The internal jugular vein {n,fig. 219), the principal vein of the head, collects the blood from the interior of the cranium and from the greater part of the face and neck ; it com- mences at the posterior lacerated foramen, and terminates in the brachio-cephalic vein (r), which is formed by the junction of the internal jugular with the sub-clavian vein (o). Its direction is vertical, without any deviation or bending. It is of considerable size, but varies in different individuals ; it is seldom of equal size on both sides, and is inversely proportioned to the external and anterior jugular veins ; it becomes extremely large in such chronic diseases as impede the entrance of blood into the cavities of the heart. I have sometimes seen the internal jugular vein of the left side very small, its place being then supplied, as in the lower animals, by a very large external jugular. Moreover, the internal jugular is not of uniform size throughout its whole length. It commences at the posterior lacerated foramen by a dilatation, which is called the gulf of the internal jugular vein ; it continues of the same size until opposite the larynx, where it becomes greatly enlarged in consequence of receiving several branches ; it terminates b^low in an oblong dilatation, and is again slightly contracted as it opens into the brachio- cephalic vein. This oblong dilatation in some asthmatic persons is very large, and might be called the sinus of the intcryial jugular vein. That part of the internal jugular vein which extends from the os hyoides to the brachio- cephalic vein represents the common carotid artery ; the part included between the os hyoides and the posterior lacerated foramen represents the internal carotid ; and the se- ries of branches which terminate in it represent the external carotid and the ramifica- tions of that artery. These branches of the internal jugular, however, do not unite into a common trunk corresponding to' the trunk of the external carotid artery, so that the distribution of this vein represents very nearly that variety in the distribution of the ar- teries of the neck, in which there is no external carotid artery ; the branches usually given from it arising from the common carotid artery, which then terminates in the in- ternal carotid. Relations. — In that portion of its course which corresponds to the internal carotid ar- tery, the internal jugular vein has almost the same relations as that vessel : thus, it is situated in the triangular interval between the pharynx and the ramus of the lower jaw ; the artery, together with the pneumogastric, hypo-glossal, glosso-pharyngeal, and spinal accessory nerves, lie to the inner side and in front of it ; the styloid and vaginal pro- cesses, and the styloid muscles, are also anterior to the internal jugular vein. That por- tion of the vein which represents the common carotid artery lies on the outer side of that vessel and in contact with it, excepting below, where the carotid is directed some- what inward to reach the arch of the aorta, while the vein continues to be vertical, and is therefore separated from the artery. During its course it has the same relations as the artery, only on account of being situated to the outer side of that vessel, it follows that it is not covered by the platysma myoides to so great an extent as the artery, and, therefore, that it is covered for a greater length by the sterno-mastoid ; and, indeed, its lower end is inclined to project beyond the outer border of that muscle, so that in asth- matic persons the skin covering the anterior part of the supra-clavicular triangle be- comes elevated when the enlarged part of the vein is dilated. The pneumogastric nerve is situated behind, between the artery and the vein. A very important relation of the internal jugular vein is that which it has with the sub-clavian artery, which is situated between it and the vertebral vein, the internal jugular being in front, and the vertebral vein behind the artery. The internal jugular vein returns all the blood from the interior of the cranium, re- ceiving it from the lateral sinus, which may \te regarded as the origin of this vein, and as the common trunk of all the veins within the cranium. Its collateral branches, several of which belong sometimes to the internal, and at others to the external jugular, are the facial (e), lingual, inferior pharyngeal, superior thyroid (all which open by a common trunk), and middle thyroid veins, sometimes also the temporal (/), internal maxillary, and deep oc- cipital veins. We shall describe in succession the branches of origin, and then the col- lateral branches of the internal jugular vein. The Encephalic Veins and the Sinuses of the Dura Mater. The commencing twigs and the branches of the cerebral veins are like all other veins, but their trunks are essentially different, for they consist of fibrous canals, formed, as it were, in the substance of the dura mater ; the lining membrane of these canals is the only part in which they correspond in structure with the rest of the venous system, the dura mater forming their outer coat. These canals are called the sinuses of the dura mater. They receive the blood from the brain, cerebellum, and medulla, from the eye, and from the bones of the cranium. All the sinuses of the dura mater have a similar situation ; they all occupy grooves form- ed for them upon the internal surface of the bones of the cranium, and which we have already described. They are, for the most part, situated opposite the intervals betweea 584 ANGEIOLOGT. the great divisions of the encephalon : thus, the superior longitudinal sinus occupies the fissure between the two hemispheres of the brain ; the lateral sinuses are situated op- posite the great fissure which separates the cerebrum from the cerebellum. All the sinuses communicate with each other, and form an uninterrupted series of canals ; they all open into the lateral sinuses, which are to the other sinuses what venous trunks are to their branches. There are twelve sinuses in all, not including the inferior longitudinal sinas, which may be regarded as a vein. Eight of the sinuses exist in pairs, the remaining four are sin- gle, and occupy the median line. The single sinuses are the superior longitudinal sinus^ the straight sinus, the coronary sinus, and the transverse occipital sinuses. The eight sinuses which exist in pairs are placed four on each side of the cranium ; they are the two superior and two inferior petrosal, the two occipital, and the two lateral sinuses. As the lateral sinuses form, as it were, the common trunks of aU the others, I shall describe them first. The Lateral Sinuses. The lateral or transverse sinuses (a a, fig. 221) are situated in the lateral grooves {vide Osteology, p. 80) ; each of them commences, like those grooves, at the internal occip- ital protuberance^ and passes horizontally outward as far as the base of the petrous por- tion of the corresponding temporal bone, at which point it dips obliquely downward and inward into the inferior occipital fossa, turns round the base of the pars petrosa, and again ascends to reach the posterior lacerated foramen of its own side (s s,fi^. 221), where it terminates in the internal jugular vein. Like the corresponding grooves, the right and left lateral sinuses are of unequal size, the right being almost always the lar- ger. Both of them gradually increase in size from their posterior extremity, which may be regarded as their origin, to their anterior extremity. A section of the horizontal portion of each lateral sinus, which is situated in the outer margin of the tentorium cerebelli, is triangular, while that of its vertical or curved por- tion is semi-cylindrical. In the first part of its course it projects beyond the correspond- ing groove in the occipital bone, so as to occupy the fissure between the cerebrum and cerebellum. In the remamder of its course it does not project into the interior of the cranium, or pass beyond the groove, which is exactly suited to its dimensions. The internal surface of each lateral sinus is smooth, and it is not traversed by bands like those found in the other sinuses. However, I once found in the horizontal portion of this sinus some of the white bodies called glandulae Pacchioni. One of the lateral sinuses has been found divided, in front, into two equal parts, a su- perior and inferior, by a perfect horizontal septum ; it is very common to find a fibrous lamina indicating a trace of this subdivision. The anterior extremity of each lateral sinus is continuous with the gulf of the corre- sponding internal jugular vein, and the inferior petrosal sinus of its own side opens into it at the same point. During its course it receives some inferior cerebral veins, some cere- hellar veins, and the superior petrosal sinus (/), which enters it at the point where it chan- ges its direction from horizontal to oblique, i. e., opposite the base of the petrous portion of the temporal bone. The lateral and inferior cerebral veins commence partly on the lateral and inferior parts of the convex surface of the. cerebrum, and partly on the base of the brain ; they unite so as to form a group of three, four, or five veins, which open into the horizontal por- tion of the lateral sinus. They enter from before backward, that is to say, in an oppo- site direction to the course of the blood in the sinus. One of these veins is sometimes observed to run along the tentorium cerebelli, with which it is maintained in contact by the parietal layer of the arachnoid for aboutan inch before it opens into the lateral sinus. The lateral and inferior cerebellar veins are very large ; they commence upon the lower surface of the cerebellum, and terminate in two or three trunks, which are found upon the circumference of the cerebellum, and open into the horizontal portion of the lateral sinus by perforating its lower wall. A large mastoid vein, which may be regarded as one of the principal origins of the oc- cipital, also opens into the lateral sinus, and thus establishes a free and direct commu- nication between the venous system within and that outside the cranium. The Superior Longitudinal Sinus. The superior longitudinal sinus (b b, fig. 220) is a single and median sinus, which occu- pies the longitudinal groove, and accordingly extends from the crista galh to the inter- nal occipital protuberance; it is formed within the substance of the convex border of the falx cerebri, and is three-sided ; a section of it represents an isosceles triangle (b, fig. 221), with its base turned upward and its apex dovvnAvard. It is small at its anterior extremity, but gradually increases in size as it approaches the confluence of the sinuses (n, fig- 221), in which it terminates. It not unfrequently bifurcates near its posterior ex- tremity ; sometimes it is directly continuous with the right lateral sinus. The internal surface of this sinus is remarkable for the transverse bands found in it. THE SUPERIOR LONGITUDINAL SINUS, ETC. 585 especially along its inferior angle. These bands Fig- 220. consist of fibrous tissue covered by the lining mem- brane of the sinus, and they conceal the orifices of the veins which open into it ; in some points they are so numerous as to form an areolar tissue. Lastly, we almost always find on the internal sur- face of the sinus some small white projecting bod- ies, the glandulm Pacchioni. The following veins open into the superior lon- gitudinal sinus : some from the internal or flat sur- face of each cerebral hemisphere, called the inter- nal cerebral veins ; others from the upper half of the convex surface of the brain, or the external cere- bral ; and, lastly, several veins from the dura mater and the bones of the cranium. The internal cerebral veins, three or four in number on each side, return the blood from all the convolutions of the flat surface of the corresponding hemisphere of the brain, and enter the superior cerebral veins at the point where these are applied to the surface of the falx. The superior cerebral veins vary in number, but are generally seven or eight on each side. The anterior of these veins are very small ; the posterior are much larger. There is al- most always one of greater size than the rest, which may be named the great superior cerebral vein : it appears to commence in and run along the fissure of Sylvius, is then prolonged obliquely backward, and turning forward upon the convex surface of the brain, so as to describe a curve having its concavity directed forward, it becomes applied to the falx cerebri, and opens into the longitudinal sinus, after having run for about one inch in the substance of its walls. During its course this vein receives a great number of branches, some anterior and others posterior, which, although corresponding to the arter- ies in their origin and in a part of their course, are completely separated from those ves- sels at their termination. The common trunks pass inward towards the great median fissure of the brain ; near the sinus they become attached to the dura mater, being held down by the arachnoid membrane, which is reflected from the brain upon the dura ma- ter; they then change their direction, turn forward in the substance of the falx cerebri, beneath a very thin layer of the dura mater, and after a course of from six to ten lines in length, terminate in the longitudinal sinus by one or more openings. The manner in which the cerebral veins open into the sinus varies : for some there are lateral openings, as if made by a punch ; others open by means of an areola fibrous tissue, which, as I have already stated, is found in certain parts of the walls of the sinuses. All the venous ori- fices are concealed by fibrous areolae, none of the veins opening directly into the sinus. Most of them run for a certain distance from behind forward, i. c, in an opposite direction to the course of the blood, before they open into the sinus ; the most anterior veins, which run from before backward, are the only exceptions to this rule. Moreover, the fold or bands which are formed in this and other sinuses do not perfoma the functions of valves, for they permit fluids to pass from the sinus into the veins. The inferences drawn by physiologists from the direction in which the cerebral veins open into the sinuses ap- pear to me to be erroneous, for that direction facilitates instead of opposing the reflux of the blood. I have satisfied myself that the cerebral veins have no valves in any part of their extent. The superior longitudinal sinus also receives proper veins from the dura mater, some venous or diploic veins, and several veins which commence in the pericranium, and es- tablish a communication between the external and internal veins of the cranium. Among the communicating veins are those which traverse the parietal foramina, and are called the veins of Santorini. A very great number of veins penetrate through the longitudinal suture, to open into the corresponding sinus in young subjects ; the communication of the diploic veins with those of the dura mater, and with the sinuses and cerebral veins, may be shown by perforating with a pin, in a young subject, the very thin and brittle external bony table which covers one of the numerous veins of the diploe, and then inserting into the orifice the fine point of a mercurial injecting apparatus : the mercury will fill the diplo- ic veins, and will pass into the sinuses, the veins of the dura mater, and the cerebral veins. The Straight Sinus. The straight sinus {c,fig. 220) occupies the base of the falx cerebri, corresponding with the line of junction of the falx with the tentorium cerebelli. The straight sinus is therefore single, and situated in the median line ; it is directed somewhat obliquely backward and downward, and it opens into the confluence of the si- nuses or torcular Herophili (n), by one or sometimes two orifices, according to the pres- ence or absence of a vertical band across its termination. It is three-sided, and a sec- tion of it represents an isosceles triangle {c,fig. 221), having its base turned downward. This sinus increases in size as it proceeds backward. 4 £ 586 ANGEIOLOGY. The straight sinus receives by its anterior extremity the inferior longitud'mal vein or sinus, the two great ventricular veins or vcn(£ Galeni, the inferior median cerebral veins, and the superior median cerebellar vein. The inferior longitudinal vein {d), which is generally but incorrectly described as the inferior longitudinal sinus, may be regarded as an ordinary vein enclosed within the pos- terior half of the free margin of the falx cerebri. This vein increases in size from be- fore backward, and enters directly into the straight sinus. It sometimes bifurcates be- fore its termination, and then the lower branch of the bifurcation opens into the anterior extremity of the straight sinus, and the upper describes a decided curve, and enters at the middle of that sinus. The inferior longitudinal vein receives the proper veins of the falx cerebri. It seldom receives any vein belonging to the brain itself The ventricular veins, or venm Galeni (e), are two in number, one proceeding from the left, and one from the right lateral ventricle. Each of them is formed by the union of two branches, viz., the choroid vein, and the vein of the corpus striatum. The choroid vein runs along the whole length of the outer border of the choroid plexus, in a direction from behind forward. During this course it receives the vein from the hippocampus major, one from the fornix, and one from the corpus callosum, and having reached the anterior extremity of the choroid plexus, it turns back again within the sub- stance of the plexus, and unites with the vein of the corpus striatum. The vein of the corpus striatum is much smaller than the preceding ; it commences be- hind in the furrow between the corpus striatum and the thalamus opticus, traverses the whole length of that furrow, covered by the taenia semicircularis, receives, during its course, a great number of small veins from the corpus striatum and thalamus opticus, and having arrived behind the anterior pillow of the fornix, unites with the choroid vein to form one of the vena; Galeni. The two vena Galeni proceed parallel with each other, and horizontally backward be- neath the velum interpositum, pass out from the brain beneath the corpus callosum, and immediately enter the straight sinus below the opening of the inferior longitudinal vein without crossing each other, as is stated by some anatomists. Not unfrequently we find an anterior and superior cerebellar vein opening into the ve- nsE Galeni, as the latter enter the straight sinus. The inferior median cerebral veins are very large. One is anterior, and commences upon the fore part of the lower surface of the cerebrum, and turns round its correspond- ing crus ; while the other, which is posterior, arises upon the posterior convolutions ; they both enter the anterior extremity of the straight sinus, behind the vense Galeni. The superior median cerebellar vein passes upward between the valve of Vieussens and the superior vermiform process, and opens into the anterior extremity of the straight sinus. The Superior Petrosal Sinuses. The superior petrosal sinuses {fffig- 221) are situated along the upper border of the Fig. 221. petrous portion of the temporal bones, and are partly lodged in the small corresponding grooves ; they are continuous as regards their direction with the horizontal portion of each lateral sinus, and occupy the anterior half of the lateral or adherent borders of the tentorium, the lateral sinuses occu- pying the posterior half. They are very small, and, like the part of the lateral sinus with which they are continuous, they are three-sided. The anterior extremity of each su- perior petrosal sinus communicates with the corresponding cavernous sinus {h h) ; and its posterior extremity opens into the corresponding lateral sinus at the point where the latter leaves the tentorium cerebelli to turn round the base of the petrous portion of the temporal bone. The superior petrosal sinuses, therefore, estabhsh a di- rect communication between the cavernous and the lateral sinuses ; they sometimes receive an inferior lateral cerebral vein, but always an anterior lateral cerebellar vein, which passes upward under the free margin of the tentorium cerebelli, behind the fifth pair of nerves. The veins which come from the sides of the pons VaroUi also enter the an- terior extremity of this sinus. The Inferior Petrosal Sinuses. The inferior petrosal sinuses (g g) are situated, one on each side, upon the petro-occip- ital sutures, and lie in corresponding grooves ; each of them extends from the anterior to the posterior lacerated foramen of its own side. They are larger than the superior petrosal sinuses, and are semi-cylindrical, like the anterior part of the lateral sinuses, with which they are continuous. The anterior extremity of each opens into the anterior THE CAVERNOUS SINUSES, ETC. 587. occipital sinus (r) and into the cavernous sinus of its own side ; while its posterior ex- tremity opens into the anterior end of the corresponding lateral sinus, opposite the com- mencement of the internal jugular vein (s). These sinuses establish a free anastomosis between the anterior and posterior sinuses found at the base of the cranium. Excepting one vein which comes from the base of the cranium through the foramen lacerum anticus, the inferior petrosal sinus receives no vein of importance. The Cavernous Sinuses. The cavernous sinuses (A A), so named from their reticulated, and, as it were, spongy structure, occupy the sides of the sella turcica and the grooves on the body of the sphe- noid bone. Each cavernous sinus is bounded in front by the inner part of the sphenoidal fissure, and behind by the apex of the petrous portion of the temporal bone : its cavity (shown on the right side in the figure) is larger than it at first sight appears to be, but is encroached upon by the internal carotid artery, which curves twice upon itself during its passage through the sinus, and also by the abducens oculi, or sixth cranial nerve. The motor oculi or third nerve, the trochlearis or fourth, and the ophthalmic branch of the fifth cranial nerve, are situated in the substance of the outer wall of the sinus. It is traversed by reddish reticulated filaments, the nature of which is unknown. The older anatomists said that the internal carotid artery and the sixth nerve were bathed in the blood of the sinus ; but it is now generally believed, in accordance with the opinion of Bichat, that they are protected by the hning membrane of the veins ; it is difficult to prove the accuracy of this opinion, although analogy is in its favour. Bichat also thought that the reticulated filaments mentioned above were folds of the lining membrane of the vein. The anterior extremity of each cavernous sinus has been named the ophthalmic sinus, doubtless on account of its being prolonged outward. Its posterior extremity opens into the corresponding superior and inferior petrosal sinuses, and into the transverse oc- cipital sinus. On the inner side it receives the coronary sinus, which establishes a di- rect communication between the right and left cavernous sinuses. Lastly, each cavern- ous sinus receives below several branches, which connect the veins within with those outside the base of the cranium, more particularly with the pterygoid venous plexuses. The cavernous sinuses receive in front the inferior and anterior cerebral veins, which commence upon the lower surface of the anterior lobe of the cerebrum. The largest of these veins on each side reaches the sphenoidal fissure, turns backward over the lateral and middle fossa of the base of the cranium, and enters the middle meningeal vein. Several anatomists state that they have seen the middle meningeal veins open into the cavernous sinuses. Lastly, the anterior extremity of each of these sinuses receives the ophthalmic vein. The ophthalmic vein is a very large vessel, which commences on the inner side of the orbit as a continuation of the frontal vein, and terminates by opening into the anterior extremity of the corresponding cavernous sinus ; and it thus establishes a very free com- munication between the veins of the interior and exterior of the cranium. It pursues the same course as the ophthalmic artery, but without any windings, and receives venous branches corresponding to the ramifications of that artery. Among them, I shall men- tion particularly the ciliary veins, which commence in the choroid membrane of the eye, where they are called vasa vorticosa, on account of being arranged in whirls. The Coronary Sinus. The coronary sinus, or circular sinus of Ridley (i), runs round the margin of the pituitary fossa, and completely surrounds the pituitary body. Its posterior is much larger than its anterior half In old subjects it is not rare to find the quadrilateral plate of the sphe- noid bone behind the pituitary fossa worn away, as if corroded by the blood of the sinus, so that it may easily be broken. At this period of life, the coronary sinus is larger than in young subjects, and extends under the pituitary body itself The coronary sinus only receives osseous veins from the sphenoid, some veins from the dura mater, and those from the pituitary body. It opens freely on each side into the cavernous sinuses, which thus communicate with each other. The Anterior Occipital, or the Basilar Sinus. The anterior or transverse occipital sinus (r) is median and single ; it extends trans- versely across the basilar groove from the foramen lacerum posticus of one side to that of the other ; it is of an irregular form, much larger in the aged than in adult and young subjects, and connects the superior and inferior petrosal sinuses and the cavernous sinus of one side with the corresponding sinuses of the opposite side. In old subjects, the basilar surface not unfrequently appears as if corroded opposite this sinus, the cavity of which often presents a cellular or spongy structure. The Posterior Occipital Sinuses. These {k k) are the smallest of all the sinuses of the dura mater ; they commence one at each foramen lacerum posticus, pass from thence upon each side of the foramen 588 ANGEIOLOGY. magnum, converge towards the falx cerebelli, enter its substance, and open separately into the confluence of the sinuses : they receive some small veins from the bones of the cranium and from the dura mater : the posterior occipital sinuses may be said to repre- sent the chord of the arc formed by the lateral sinuses.* The Confluences of the Sinuses. From what has been stated above, it appears that there are three central points in which all the sinuses meet : one situated behind and in the middle line, and one on each side of the middle line in front. The term confluence of the sinuses might be applied to all three points, but it has hitherto been confined to the posterior and median central point, or occipital confluence. All the sinuses open directly into one of these three points, the inferior longitudinal, if it be considered a sinus, forming the only exception. The Posterior or Occipital Confluence, or Torcular Herophili. — If that portion of the dura mater which corresponds to the occipital protuberance be opened from behind, six ori- fices will be exposed to view, viz., a superior, which belongs to the superior longitudinal sinus ; an anterior, sometimes divided into two by a vertical band, which belongs to the straight sinus ; two lateral orifices, which belong to the two lateral sinuses ; and two in- ferior, which belong to the posterior occipital sinuses. The point at which these sinuses meet is named the torcular Herophili {n n,figs. 220, 221), because it is supposed that the columns of blood flowing from the different sinuses must, in some degree, press against each other. The Anterior or Petro-sphenoida.l Confluence. — Between the apex of the petrous portion of the temporal bone and the sphenoid bone, there is on each side another confluence, at which a great number of sinuses meet, viz., in front, the cavernous sinus and the cor- onary sinus ; on the inside, the transverse occipital sinus ; and behind, the superior and inferior petrosal sinuses. The Branches op Origin of the Jugular Veins. The Facial Vein. The facial, or external maxillary vein {e, fig. 219), represents the artery of the same name ; also the terminal divisions of the ophthalmic artery ; and, lastly, some of the branches of the internal maxillary artery. It commences in the frontal region, where it is called the frontal vein ; at the inner angle of the eye it is named the angular vein ; and afterward the facial vein until its ter- mination. The frontal vein (la vein preparate, a, fig. 219) is a sub-cutaneous vein, which was se- lected by the ancients for phlebotomy : it is sometimes single, and is then placed in the median line ; but there are generally two frontal veins united by a transverse anasto- mosis. Among the numerous varieties which this vein presents, I shall point out one in which the two frontal veins are united into a single trunk, which bifurcates above the root of the nose. These veins do not exactly follow the course of the frontal arteries ; they descend from the vertex, where, by their numerous anastomoses, either with each other or with the temporal veins, they form a venous plexus large enough to cover the whole frontal region. They open into a transverse venous arch, having its concavity directed downward ; it is sometimes tortuous : it is situated at the root of the nose, and is named the 7iasal arch (b). This arch is also joined by the supra-orbital vein, a deep- seated vessel (indicated by the dotted lines c), which runs transversely along the upper part of the orbit, receives the superior internal palpebral vein, and opens into the ex- tremity of the arch, on the outer side of the frontal vein : the ophthalmic vein also termi- nates in the nasal arch of the vein, between which and the cavernous sinus it establishes a free communication. Thus the upper parts of the face, more particularly the eye and its appendages, are intimately connected with the brain through the medium of the veins as well as of the arteries. Moreover, the dorsal veins of the nose, which run on each side of the ridge of that organ, open into the concavity of the nasal arch. The angular vein^ are given off from the right and left extremities of the nasal arch, and may be regarded as the continuations of the frontal veins ; like the corresponding arteries, each of them (d) is situated in the furrow between the nose and the cheek. The inferior palpebral vein and the vein of the lachrymal sac and nasal duct enter the outer side of each angular vein, which is joined on its inner side by the veins of the corre- sponding ala of the nose. The veins of the ala nasi form a very dense network between the cartilage and the skin, and also between the cartilage and the mucous membrane ; from these networks two branches are given off: a superior, which runs along the convex border ; and an infe- rior, which runs along the lower border of the inferior lateral cartilage, or the cartilage of the ala. These two branches unite into a very large conunon trunk, which passes upward, often very obliquely, into the angular vein. The facial vein (e) commences in the angular vein, at the point where the latter is * [They sometimes join the lateral sinuses in front, as shown in the figure.] THE TEMPORO-MAXILLARY VEIN. 589 joined by the Veins of the nose ; it proceeds very obhquely downward and outward, passes under the great zygomatic muscle, reaches and then runs along the anterior bor- der of the masseter, crosses at right angles over the base of the jaw, is received into a groove in the sub-maxillary gland, and terminates in several different modes. Most commonly, it unites with the Ungual to form a common trunk, which enters the internal jugular ; it is into this common trunk of the facial and lingual veins that the su- perior thyroid and the pharyngeal vein, and the common trunk of the temporal and inter- nal nlaxillary veins, sometimes open. In other cases the facial vein passes obliquely across the outer surface of the sterno-mastoideus, and enters at some point of the exter- nal jugular vein. I have seen it directly continuous with the anterior jugular, also with the external jugular of the same or of the opposite side, or it may enter the convexity of an arch of conmmnication between the external and anterior jugular veins. Collateral Branches. — During its course the facial vein in joined on its outer side by the alveolar venous trunk, which is very large, and may be regarded as the deep branch of origin of the facial vein, which, in fact, becomes much larger, sometimes even twice as large, after its reception. This alveolar trunk commences in a very remarkable venous plexus, named the alveolar plexus, in which the alveolar veins properly so called, together with the infra-orbital, superior palatine, vidian, and spheno-palatine veins terminate, and which communicates with the pterygoid plexus. All these veins accompany the branches of the internal maxillary artery having the same names. From the alveolar plexus the alveolar trunk runs forward and downward below the malar bone, and unites obliquely with the fecial vein. The facial is also joined on its inner side by the superior and infe- rior coronary veins of the lip, which are distributed like the arteries, but are not tortu- ous ; by the buccal vein or veins ; and by the anterior masseteric veins. Below the base of the jaw, the facial vein is joined by the sub-mental vein ; by the in- ferior palatine, which is remarkable for the plexus around the tonsils, which is formed al- most entirely by it ; also by the vein or veins from the sub-maxillary gland, and some- times by the ranine vein. During its course the facial vein is, in general, more superiicial than the facial artery, and does not accompany it on the face, but is situated more to the outside, and is not tortuous. The Temporo-maxillary Vein. The temporo-maxillary vein, or venous trunk, represents the temporal artery, a part of the internal maxillary, and the upper part of the external carotid : many authors follow Walther in naming it the posterior facial vein, in contradistinction to the facial vein prop- erly so called, which they name the anterior facial. The temporo-maxillary is formed by the junction of the temporal and internal maxillary veins : it most frequently termi- nates in the external jugular vein. The Temporal Vein. — This vein commences above by superficial, middle, and deep branches. The superficial temporal veins {f,fig. 219) commence upon the crown of the head by anterior or frontal branches, which communicate freely with the origin of the frontal vein, by middle or parietal branches, which communicate with the corresponding branches of the opposite side, and by posterior or occipital branches, which communicate with the branches of the occipital vein. These form a very open network over the greater part of the cranium. From this network anterior and posterior branches arise, and unite with each other above or opposite to the zygomatic arch. During this course the veins do not exactly follow the direction of the corresponding arteries. It might be said that the veins of the scalp partake of the characters both of the venae comites and the sub- cutaneous veins. These venous networks are, moreover, situated in the substance of the hairy scalp, and, like the arteries, are placed between the skin and the occipito- frontalis muscle. The middle temporal vein is a very large vessel, often much larger than the common trunk of the superficial veins. It is situated (as indicated by the dotted lines, g,fig- 219) beneath the temporal fascia, between it and the temporal muscle. It is sometimes formed principally by the junction of the palpebral with the external orbital veins, which, corresponding in their distribution to the arteries of the same name, unite into a common trunk that runs backward at first between the two layers of the temporal fascia, then be- tween the muscle and the fascia, is directed backward and downward, again perforates the fascia from within outward above the antero-posterior root of the zygomatic process, and unites with the superficial temporal vein in front of the external auditory meatus. The trunk resulting from the junction of the superficial temporal and middle temporal veins passes vertically downward, between the external auditory meatus and the tem- poro-maxillary articulation, dips into the substance of the parotid gland, and, having ar- rived behind the neck of the condyle, receives the internal maxiUary vein, which consti- tutes the deep origin of the temporo-maxillary trunk. The Internal Maxillary Vein. — This vein, the deep origin of the temporo-maxillary trunk, is called by Meckel the internal and posterior maxillarv, in opposition to the alveolar branch 590 ANGEIOLOGY. of the facial vein, which he calls the internal and anterior maxillary : it corresponds to all the branches given off from the internal maxillary artery behind the neck of the condyle, in the zygomato-maxillary fossa ; while the alveolar vein, the deep branch of the facial, corresponds to all the branches given off by the internal maxillary artery upon the tuber- osity of the superior maxilla and in the pterygo-maxillary fossa. Thus it is joined by the middle meningeal veins. The vena comites of the middle me- ningeal artery, the existence of which has been erroneously denied, are two in number, and are situated, one in front, the other behind the artery. These veins often I'eceive some inferior and anterior cerebral veins, which enter them near the foramen spinosum of the sphenoid ; they always receive veins from the bones of the cranium and from the dura mater, and communicate with the superior longitudinal sinus ; they are sometimes so large, especially the anterior branch, that they have deep grooves formed for them upon the sphenoidal fossa, reaching from the foramen spinosum to the point of the great ala of the sphenoid bone. Lastly, the distribution of the middle meningeal veins is sim- Uar to that of the corresponding artery. The internal maxillary vein is also joined by the inferior dental, by the deep temporal, by the pterygoid, and by the posterior masseteric veins. AH of these veins communicate with a very large and important venous plexus, the pterygoid plexus, situated between the temporal and external pterygoid muscles, and between the two pterygoid muscles. In this plexus, which communicates freely with the alveolar plexus, so freely, indeed, that they may be regarded as forming but a single plexus, the internal maxillary vein commences and joins the temporal vein, behind the neck of the condyle of the lower jaw. The temporo-maxillary trunk, thus formed by the junction of the temporal with the internal maxillary vein, is much larger than the former vein, and continues its course through the substance of the parotid gland ; it is joined directly by some parotid veins, by the posterior and anterior auricular veins, and, lastly, by the transverse veins of the face. The last-named veins form, between the parotid gland and the masseter muscle {i, fig. 219), between that muscle and the ramus of the lower jaw, and around the temporo-max- illary articulation, a very large plexus, named the masseteric plexus, which communicates freely with the pterygoid plexus through the sigmoid notch. Termination of the Temporo-maxillary Trunk. — Most conmionly the temporo-maxiUary vein or trunk terminates directly in the external jugular vein (h) ; at other times it enters the internal jugular, and then there is merely a trace of the external jugular, which is formed principally by the superficial branches of the occipital vein, and by some commu- nicating branches from the anterior jugular. In some cases, the temporo-maxillary vein is almost equally divided between the internal and external jugulars ; lastly, it is some- times united to the lingual and the facial vein : when it ends in the external jugular, it sends to the internal jugular a large communicating branch which passes above the di- gastric muscle. The Posterior Auricular Vein. The posterior auricular vein follows the distribution of the artery of that name ; it re- ceives the stylo-mastoid vein, and enters the external jugular, or, rather, the temporo- maxillary vein, which does not take the name of external jugular until after it is joined by this vein. The Occipital Vein. The occipital vein is distributed in the same manner as the occipital artery ; it com- mences at the back of the cranium, passes beneath the splenius muscle, and is joined opposite the mastoid process by one or more large mastoid veins, which come from the corresponding lateral sinus, establishing a direct and free communication between the venous circulation in the interior and exterior of the cranium. It was this that led Mor- gagni to prefer the occipital veins for the purpose of bloodletting; in apoplexy. The oc- cipital vein ends in the internal, and sometimes in the external jugular. The Lingual Veins. The lingual veins, being intended for a contractile organ, the circulation in which is on that account liable to be much interfered with, are divided, like the veins of the limbs, into the superficial or sub-mucous, and the deep veins. The superficial veins of the dorsum of the tongue, which are generally named the lingual veins, occupy the dorsal region of the tongue, ramifying in a remarkable manner between the mucous membrane and the muscular fibres of that organ : all these veins open into a dorsal or superior lingual plexus, which is situated at the base of the tongue, and is joined by a great number of veins from the tonsils and epiglottis. The satellite vein of the lijigual nerve emanates from this plexus, accompanies the lin- gual nerve, receives some branches from the sub-lingual glands and the tissue of the tongue, and enters the facial or the pharyngeal vein, or terminates directly in the exter- nal jugular, communicating freely with the ranine veins. The ranine veins are the superficial veins of the lower surface of the tongue. They THE PHARYNGEAL VEIN, ETC. 591 are seen one upon each side of the fraenum, where they form a ridge beneath the mucous membrane. Each of them accompanies the corresponding hypoglossal nerve, between the genio-hyoglossus and hyoglossus muscles, and tenninates either in the common trunk of the Ungual and facial veins, or directly in the facial vein. The ranine veins communicate upon the sides of the tongue with a very large plexus, the vessels composing which are sometimes provided with valves, so that it is impossi- ble to inject it in a direction from the heart towards the extremities of the veins, which, in other cases, may be done with the greatest facihty. Lastly, the lingual veins, properly so called, are extremely small ; they are two in number, and accompany the lingual artery throughout the whole of its course. Not un- frequently the veins of the tongue terminate directly in the internal jugular : I have seen them open into the anterior jugular. The Pharyngeal Vein and Pharyngeal Plexus. The Pharyngeal Plexus. — In making the section already described for examining the pharynx, we observe round the back of that organ a considerable venous plexus, which forms loops or rings for embracing the pharynx ; several meningeal branches, and some derived from the vidian and spheno-palatine veins, open into this plexus ; from which a variable number oi pharyngeal branches arise, and terminate by a common trunk, or by several distinct branches, in the lingual vein, sometimes in the facial or the inferior thy- roid, and frequently in the internal jugular. Besides this plexus, which may be called the superficial pharyngeal plexus, an ex- tremely dense network is found beneath the mucous membrane, from which branches proceed to join with those that arise from the superficial plexus just described The Superior and the Middle Thyroid Veins. The superior thyroid, or thyro-laryngeal vein, commences upon the thyroid gland by branches corresponding to the thyroid arteries, and upon the larynx by branches corre- sponding to the ramifications of the superior laryngeal artery. The thyroid and laryn- geal branches unite and end in the internal jugular vein, opposite the upper part of the larynx ; they perhaps end more frequently in the coimnon trunk of the facial and Ungual veins. It is not uncommon to find the superior laryngeal branch terminating directly either in one or the other of these veins, or in the anterior jugular. The middle thyroid vein arises from the lower part of the lateral lobe of the thyroid gland, and is joined by some branches from the larynx and the trachea. By their union they form a trunk, which ends in the lower part of the internal jugular vein. The con- stant existence of this vein explains in some degree a rather frequent variety in the ar- teries of the thyroid gland, viz., the existence of a middle thyroid artery given off by the common carotid. Not unfrequently there are two middle thyroid veins on each side. These, as weU as all the other thyroid veins, are much enlarged in goitre The Veins of the Diplo'e. To complete the description of the vessels of the head, it only remains for me to no- tice the diploic veins, or the proper veins of the bones of the cranium. They were first described by M. Dupuytren, in his inaugural thesis, under the name of venous canals of the bones : they were afterward figured by M. Chaussier {Traite de V Encephale), and, to- gether with their principal varieties, they have lately been represented with uncommon accuracy by M. Breschet, in his admirable work upon the veins. In the substance of the cranial bones there are found ramified venous canals, which are occupied by veins, having only their internal membrane, the bony canals themselves serving for an external coat. These venous canals are not exclusively confined to the bones of the cranium : they exist in all spongy bones, and even in compact bones ; but, while the canals are found in the entire substance of spongy bones, in the compact part of the long bones they are situated near the medullary canal. The venous canals of the bones of the cranium vary much in their size, and in the extent to which they are distributed : they are independent of each other as long as the cranial bones remain distinct and separable ; but they almost always communicate when, in the progress of age, those bones become united together. They get larger and larger as life advances, and their size is indirectly proportioned to the number of their ramifi- cations : they sometimes present ampuUaj or dilatations, and at other times are suddenly interrupted, and terminate in culs-de-sac, reappearing again farther on, or ceasing alto- gether : these peculiarities depend upon the venous canal opening at different points into the middle meningeal veins. Moreover, these venous canals communicate by a number of orifices of different sizes, either in the interior of the cranium with the me- ningeal veins, and with the sinuses of the dura mater, or on the exterior with the veins which Ue in contact with the bones of the scuU. In some heads of old subjects, these canals are found blended with the furrows for the branches of the meningeal arteries; those furrows themselves present some large foramina, which open into the cranium in ijarious places. 592 ANGEIOLOGY. In new-born infants there are no venous canals, properly so called ; but the whole substance of the bones is traversed by a venous network, which may be seen when its constituent veins are naturally injected with blood, or when they have been filled with mercury, by which as delicate a network of vessels can be shown in the diploe as in in- jections of the soft parts. At this period all the cells of the bones are filled with venous blood. On the roof of the cranium the canals of the diploe are divided into the frontal, tempo- ral, parietal, and occipital. The frontal diploic canals are two in number, one on the right, the other on the left side : they commence by numerous ramifications upon the upper part of the frontal bones, increase in size as they approach the lower part of the roof of the scull, commu- nicate with each other by transverse branches, and also with the periosteal or the me- ningeal veins, open externally by vascular foramina, and then enter the supra-orbital and frontal veins. The temporo-parietal diploic canals are divided into anterior and posterior : they corre- spond to the furrows which contain the ramifications of the meningeal artery, and open into those furrows by a great number of foramina, which become very distinct in advanced life : they also communicate with the deep temporal veins on the exterior of the scull. The occipital diploic canals, two in number, a right and a left, communicate with each other by a great number of branches, and open below into the occipital veins. Summary of the Distribution of the Veins of the Head, Circulation in the Brain. — Corresponding to two of the arterial trunks, the common carotids, which convey blood to the head and neck, there are six veins, to return it back to the heart from the same parts, viz., the two internal, the two external, and the two anterior jugulars. This arrangement tends to prevent interruption of the venous circu- lation in the head, which, from so many causes, is liable to be disturbed. The external and anterior jugular veins belong to the sub-cutaneous venous system, and may be re- garded as supplementary veins which have no corresponding arteries, and which would be sufficient of themselves to carry on the venous circulation ; and as the veins of the right and left sides communicate very freely with each other, it follows that one of them would suffice to return the blood from the head. It will be seen hereafter, when de- scribing the veins of the spine, that the obliteration of all the six jugular veins would not of necessity be followed by interruption of the venous circulation in the cranium. Lastly, it is important to observe, that the external and anterior jugulars open into the sub-clavian vein, while the internal jugular joins the inner end of the sub-clavian, to form the brachio-cephalic vein. We have seen that the lower part of the internal jugular vein represents the common carotid, and the upper part of it the internal carotid ; and that the external carotid is represented by all the veins of the face and neck, which open into the internal jugular either by a common trunk, or by several distinct branches. The cerebral venous system is remarkable for the extreme thinness of the parietes of the veins upon the brain, and for the existence of the sinuses, which take the place of the venous trunks, and differ so much in their distribution from the arteries. The cerebral veins are divided into the ventricular veins, which go to form the venffi Galeni, and the superficial veins of the brain. All of them run towards the sinuses, in which they terminate in succession like the barbs of a feather upon the common shaft, but do not acquire a great size. From the absence of valves at their orifices into the sinuses, the blood may regurgitate into them. The presence of the spongy areolar tissue at the or- ifices of these veins, together with their oblique course through the walls of the sinus, must diminish this regurgitation : the communication of the cerebral veins with each other, and the continuity of the several sinuses, explain the varied means contrived for carrying on the cerebral circulation, which can only be interrupted by obliteration of the lateral sinuses. Lastly, the position of the principal sinuses opposite the fissures between the great di- visions of the encephalon, and the resisting nature of the walls of the sinuses themselves, prevent the fatal effects which might otherwise ensue from compression produced by obstruction of the venous circulation. Circulation in the Parietes of the Cranium. — In the parietes of the cranium we find the veins of the dura mater, the veins of the diploe, the periosteal veins, and the veins of the hairy scalp. The numerous communications existing between these four systems of veins, and the direct communications estabhshed between the sinuses of the dura mater and the veins on the exterior of the scull, are worthy of particular attention. I would observe that the principal veins of the scalp, like the arteries of the same part, are situated between the skin and the epicranial aponeurosis. I have ascertained the existence of free and frequent anastomoses among these veins. As at the back of the cranium there is a very free communication between the occipital vein and the lateral sinus by means of a large vein, so, also, along the superior longitudinal groove, and op- posite the sutures upon the base of the scull (through most of the foramina found in that THE DEEP VEINS OF THE UPPER EXTREMITY. 693 situation), an uninterrupted communication is established between the veins within and those outside the cranium. VcTious Circulation of the Face. — All the veins of the face and of the parietes of the cranium end in two principal trunks, the facial and the temporal. The facial vein cor- responds to a part of the internal maxillary artery, to a part of the ophthalmic artery, and to the facial artery properly so called. One of the most remarkable circumstances connected with the distribution of the facial vein is the communication between it and the cavernous sinus, established at the inner angle of the orbit by means of the ophthal- mic vein, so that the veins on the inside and on the outside of the cranium are most in- timately connected.* The temporal vein represents the temporal artery, a part of the internal maxillary ar- tery, and the upper part of tho external carotid, and returns the blood from the entire side of the head. With regard to the veins of the tongue, we should remark the existence of two sub- mucous veins, corresponding to the sub-cutaneous veins in the limbs, and intended to return the blood, instead of the deep veins of the tongue, during the contractions of that organ. The size of the superior middle thyroid veins, their number, which exceeds that of the arteries, and their free anastomoses with the inferior thyroid veins, render them an important medium of circulation when the passage of the blood from the head is obstruct- ed, and, at the same time, a diverticulum in great impediments to the circulation. The irregularity which exists in the relative size of the internal, external, and ante- rior jugular veins, and also in the distribution of the veins of the hefJ between these three trunks, proves that, in the venous as well as in the arterial sj-stem, the origin or termination of the vessels is of little importance, and that, alter the venous system of any part is once formed, it matters but little with which of the great vascular trunks it is connected. Lastly, the free communications which exist between aU the preceding veins afford sufficient evidence that but little interest need be attached to their termination in one or another of the principal venous trunks. The Deep Veins of the Upper Extremity. The veins of the upper extremity are divided into the dee^ and the superficial or sub- cutaneous. The Palmar, Radial, Ulnar, Brachial, and Axillary Veins. The deep veins of the upper extremity exactly follow the course of the arteries, form their venae comites, and take the same names : there are almost always two to each ar- tery. The large venpus trunks alone form exceptions to this rule. Thus, there are two superficial and two •^^^i' palmar veins ; two deep radial and two deep ulnar veins ; we also find two brachial veins ; but there is only one axillary and one sub-clavian vein. All these venae comite? receive branches formed by the union of still smaller ones, which are them- selves the venae comites of the ramifications of the arteries, there being two veins with each small artery. The sub-clavian vein, however, is an exception to this, for it does not receive all the veins which correspond to the branches of the sub-clavian artery ; while, on the other hand, it receives other veins that are totally unconnected with the distribution of that artery. I ought to allude, in this place, to a mode of termination of the collateral veins, which is frequently observed, especially in the brachial vein. The circumflex veins, for example, instead of entering the brachial vein directly, terminate in a collateral branch, which runs parallel to the brachial vein, like a canal running along- side a river, and communicates with that vein above and below. Several large veins have these collateral canals, which establish a conxmunication between different points of their length. Thus, I have seen a venous trunk proceed from the external jugular, de- scend through the brachial plexus of nerves, and enter the lower part of the axillary vein. The deep veins, moreover, communicate freely and frequently with the superficial veins. They are also provided with valves, like the superficial veins, and, it appears, even with a greater number : an injection thrown from the heart towards the extrem- ities will not enter more readily into one than into the other set. We always find two valves at the mouth of a small vein where it opens into the larger trunk ; and it is a re- markable fact that, while the valves situated in the course of the veins are sometimes passed by the injection, those which are placed at the mouths of the small veins are scarcely ever overcome. The Sub-clavian Vein. The term sub-clavian is generally given to all that portion of the brachial venous trunk * The study of these anastomoses ought to lead us again to have recourse to those local venesections which have fallen into disuse since the discovery of the circulation ; and it will enable us to determine, on anatomi- cal grounds, the proper places at which they should be performed. Thus, it appears to me that we might ad- vantageously introduce into practice bleeding from the angular vein in diseases of the eye ; from over the mas- toid region, and the point which corresponds to the junction of the longitudinal with the larabdoidal suture, in cerebral affections ; and bleeding from the ranine vein in diseases of the pharjmx. 4 F 594 ANGEIOLOGY. which extends from the vena cava superior to the scaleni muscles ; but this vein may be described more naturally, as being limited internally by the brachio-cephalic vein, or, rather, by the junction of the internal jugular vein vs'ith the venous trunk of the upper extremity, and externally by the clavicle, or, rather, by the costo-coracoid, or sub-cla- vian aponeurosis. If the sub-clavian veins be thus defined, they wiR be of equal length on both sides ; and the left vein, and even the right vein also, will be shorter than the corresponding artery. The direction of the sub-clavian veins differs much from that of the arteries : we have seen that the sub-clavian arteries describe a curve over the apex of the lung, with its concavity turned downward ; the sub-clavian veins, on the contrary, proceed directly outward as far as the first rib, over which they bend, so that they resemble the cord of the arc described by the sub-clavian artery. We have seen, also, that the inferior- thy- roid vein, the internal mammary, the vertebral, the supra-scapular, the posterior scapu- lar, the deep cervical, and the left superior intercostal veins, enter not into the sub-cla- vian, but either into the superior vena cava, or into the brachio-cephahc vein. The right superior intercostal vein, when it exists, that is to say, when the branches which should form it do not terminate separately in the vena azygos, is the only one of the veins cor- responding to the branches of the sub-clavian artery which opens into the sub-clavian vein. The external jugular, the anterior jugular, and a small branch from the cephalic vein of the arm, also terminate in the sub-clavian vein. It would therefore, in some respects, be proper to describe the external and anterior jugulars in connexion with the sub-cla- vian veiri, instead of with the internal jugular. I would remark, that the external and anterior jugidars frequently terminate, not in the sub-clavian vein, but at the point where it ends in the brachio-cbphalic vein, in front of the internal jugular. Relations.— In front of fhe sub-clavian vein is situated the clavicle, which is separated from the vein only by the sub-clavian muscle, so that this vessel may be wounded in fractures of the clavicle ; a very dense fibrous sheath binds it down to the sub-clavius muscle ; and it perforates tke costo-coracoid or sub-clavian aponeurosis, which adheres to it, and keeps it open when cut across ; behi7id the vein is the sub-clavian artery, from which it is separated, towards the inner part, by the scalenus anticus ; below, it is in re- lation with the pleura and with the first rib, on which there is a corresponding but slight depression ; above, it is covered by the cervical fascia, which separates it from the skin : a considerable swelling is often seen in this region when the venous circulation is ob- structed. The Superficial or Sub-cutaneous Veins op the Upper Extremity. The sub-cutaneous veins of the zipper extremity belong essentially to the skin and to the subjacent adipose tissue, since all the branches from the muscles enter the deep veins. The superficial are larger than the deep veins, with which they communicate freely at a great number of points ; and it may be remarked, that the size of the one set of vessels is always inversely proportioned to that of the other set. We proceed t^ describe them in succession in the hand, the forearm, and the arm. The Superficial Veins of the Hand. All the largest veins of the hand are situated upon its dorsal aspect ; and it is worthy of notice, that the largest arteries, on the contrary, occupy the palm of the hand. If the superficial veins had existed on the palmar aspect, the venous circulation would have been impeded whenever the hand was used in prehension. Entering into the large sub- cutaneous network of veins situated upon the back of the hand are several branches, which constitute the superficial, external, and internal collateral veins of each finger ; they occupy the outer and inner borders of the dorsal surface of the fingers, and communi- cate frequently on the dorsal surface of each phalanx and around the phalangeal artic- ulations, but not upon the articulations themselves. Opposite the lower part of each interosseous space, these collateral veins unite at an acute angle, just as the digital arteries bifurcate at the same point. All the superficial digital veins ascend vertically between the metacarpo-phalangeal articulations, which they seem to avoid, and then enter into the convexity of a very irregular venous arch, which is formed by a series of loops, at each of the junctions of which one of the digital veins is seen to terminate. From the concavity of this irregular arch, which is turned upward, are given off a greater or less number of ascending branches, which are sometimes formed directly by the junction of the digital veins, without the intervention of an arch. Among these branches, we should especially notice the external branch, which is situated nearest to the first metacarpal bone, and is called the cephalic vein of the thumb ; also the innermost branch, which corresponds to the fifth metacarpal bone, and, for some reason not very well known, has been named the vena salvatclla. The Superficial Veins of the Forearm. The superficial veins are much more numerous on the anterior than on the posterity THE SUPERFICIAL VEINS AT THE ELBOW, ETC. 595 aspect of the forearm. We find there the radial vein or veins, the ulnar vein, and the median vein. The superficial radial vein (r, in the representation of the superficial nerves of the arm) is the continuation of the cephalic vein of the thumb ; it is situated along the outer side of the carpus and of the radius, and it soon unites with some branches from the vena salvatella, or with the salvatella itself. The superficial radial vein often divides into several branches, which are joined by others from the venous arch at the back of the hand. There are sometimes two superficial radial veins. The vein or veins having reached the middle of the forearm, turn forward upon the outer border of the radius, and then continue to ascend vertically along the outer side of the anterior surface of the fore- arm, up to the bend of the elbow. The ulnar vein (m) commences partly from the vena salvatella, and another vein on the dorsal region of the forearm, and partly from some branches which arise from the lower part of the back of the forearm, and even from some small veins proceeding from the thenar and hypothenar eminences. The branches which arise from the vena salvatella and the back of the wrist pass for- ward ; the other branches run backward ; the common trunk or trunks resulting from their union are directed at first vertically upward, parallel with the superficial radial vein, then somewhat obliquely forward, to anastomose with the median basilic vein, above the bend of the elbow. When there is a second or posterior ulnar vein, it ends in the basilic higher up, or else it anastomoses with the anterior ulnar vein. Between the anterior radial and ulnar veins we find the common median or median vein (m), formed by the anterior veins of the carpus and forearm. There may be more than one median vein, and it is not unfrequently wanting, in which case its place is supplied by a venous network, the branches from which enter separately into the radial and ulnar veins. In some cases its place is supplied by an additional radial vein, and at other times by the deep veins. The Superficial Veins at the Elbow. At the elbow all the veins are on the anterior aspect. The most common arrangement is the following : on the outer side we find the upper portion of the radial vein or veins ; on the inner side, the upper portion of the ulnar vein or veins, which pass in front of the internal condyle of the humerus ; between the radial and ulnar veins is the median, which divides into two branches : one external (a), which unites with the radial to form the cephalic vein (c), and is called the median cephalic ; the other internal (e), generally smaller, but more superficial than the preceding, which unites with the ulnar to form the basilic vein {b), and is called the median basilic. Several varieties are observed in the arrangement of the veins of the elbow ; some- times the common median vein is wanting ; but then its cephalic and basilic branches are given off by the radial, and the cephalic vein is almost always very small. In other cases we only find two veins at the bend of the elbow, viz., the radial and the ulnar, which are directly continuous with the cephalic and basilic. I once saw the common median vein replaced by the anterior radial, and by a branch from one of the deep ulnar veins. The Superficial Veins in the Arm. In the arm there are only two superficial veins, an external, named the cephalic vein, and an internal or basilic. The cephalic vein (c) is formed by the junction of the radial with the median cephalic vein, which junction may occur at very different heights. It ascends vertically along the outer border of the biceps ; then, running a little inward, it gains the furrow be- tween the deltoid and pectoralis majer, passes over the summit of the coracoid process, above or in front of which it curves backward, so as to enter the axillary vein immedi- ately below the clavicle. From this curve the cephalic vein gives off a branch, which passes in front of the clavicle, crosses at right angles over the middle of that bone, and enters the sub-ciavian vein. Not unfrequently the cephalic vein is replaced by a very small branch. The internal vein of the arm, which is called the basilic vein (b), is generally larger than the cephalic. It is formed by the junction of the ulnar with the median basilic vein, passes at first obliquely backward, and then vertically upward, in front of the internal intermuscular septum, and enters either the brachial or the axillary vein. General Remarks upon the Superficial Veins of the Upper Extremity. From the preceding description, it follows that the cephalic vein forms the continua- tion of the radial, which is itself the continuation of the cephalic vein of the thumb, and that the basilic is a prolongation of the ulnar, which is a continuation of the vena salva- tella. The median vein, placed as it is between the radial and ulnar veins, bifurcates so as to terminate equally in the two latter veins, and establishes a free anastomosis be- tween them. 596 ANGEIOLOGY. The anastomoses of the several sub-cutaneous veins together are very numerous, and enable them mutually to supply the place of each other. The anastomoses between the sub-cutaneous and deep veins are not less numerous. Thus, the superficial collateral veins of the fingers communicate with the deep collat- eral veins : communications exist between the superficial and deep veins of the carpus ; very large communications exist between the two sets of vessels at the bend of the el- bow, so that, in fact, they are continuous with each other ; thus, the superficial radial vein is sometimes continuous with one of the deep radials, and the median, as it divides into the median basilic and median cephalic, occasionally sends a very large branch to the brachial. In one case, where the median vein was wanting, I found that the ulnar, the deep interosseous, and the deep radial veins, formed a plexus, which gave off two branches, an external to the cephalic, and an internal, which formed the deep brachial vein. The superficial ulnar veins often communicate freely with the deep ulnar, beneath the muscles attached to the internal condyle. Along the arm, the basilic vein communicates with one of the brachial veins by several transverse branches. Not unfrequently the basilic vein communicates with the brachial by a very delicate branch, which forms a lateral canal. Valves. — The valves are more numerous in the deep than in the superficial veins ; they increase in number as we approach the upper part of the arm, and are much more numerous in the basilic than in the cephalic vein. There are three in that part of the cephalic which corresponds to the furrow between the deltoid and the pectoralis major. There is one at the opening of the cephalic into the axillary ; another at the opening of the basilic into the brachial ; all the small veins which enter the cephalic and basilic, as well as those which terminate in the deep veins, are also provided at their openings with valves, which prevent the regurgitation of the blood during life, and the passage of an injection from the heart towards the extremities. General Relations. — The sub-cutaneous veins are separated from the skin by the super- Jicial fascia, and by the layer of fat above it. The median basilic is the only exception, for it is in contact with the skin, at least in the majority of subjects. The sub-cutaneous veins must be carefully distinguished from the cutaneous veins, prop- erly so called, which are in contact with the true skin, or even ramify in its substance, and which are sometimes of considerable size, especially in the neighbourhood of certain tumours. From the relation of the median basilic vein with the brachial artery, over which it crosses at a very acute angle, and from which it is separated only by the fibrous expan- sion from the tendon of the biceps, it follows, that in emaciated persons the vein is al- most in contact with the artery ; so that, in bleeding from the median basilic, if the vein be perforated quite through, the artery may be wounded. The practical rules to be de- rived from this anatomical fact are, in the first place, to avoid bleeding in the median basilic as much as possible, and whenever it must be chosen, to open it either below or above the point where it crosses over the artery. In the description of the lymphatics and nerves of the arm, I shall point out their re- lations with the superficial veins. I may now state, however, that the musculo-cutane- ous nerve passes behind the median cephalic vein, and that the internal cutaneous di- vides into several branches, some of which pass in front, and others behind the median basihc vein. THE INFERIOR OR ASCENDING VENA CAVA AND ITS BRANCHES. The Inferior Vena Cava — the Lumbar or Vertehro-lumbar Veins — the Renal — the Middle Supra-renal — the Spermatic and Ovarian — the Inferior Phrenic. — The Portal System of Veins — the Branches of Origin of the Vena Porta — the Vena Porta — the Hepatic Veins. — The Common Iliacs — the Internal Miac — the Hemorrhoidal Veins and Plexuses — the Pelvic Veins and Plexuses in the Male and in the Female. — The Deep Veins of the Lower Extremity — the Plantar, Posterior, Tibial, Peroneal, Dorsal, Anterim- Tibial, and Pop- liteal— the Femoral — the External Iliac. — The Superficial Veins of the Lower Extremity — the Internal Saphenous — the External Saphenous. The vena cava inferior or ascendens, or the abdominal vena cava (I, fig. 222), is the large venous trunk which returns the blood from all the parts below the diaphragm to the heart. It is formed below by the junction of the two common iliac veins {n n), opposite the intervertebral substance between the fourth and fifth lumbar vertebrae ; it passes verti- cally upward, and, having reached the lower surface of the liver, inclines a little towards the right side, to gain the groove formed for it in the posterior border of that organ. At the upper end of that groove the vena cava inferior perforates the tendinous opening in the diaphragm, and also the fibrous layer of the pericardium, which is, as it were, blend- ed with the cordiform tendon at this point ; the vein then curves suddenly to the left, and opens {r,fig. 192) horizontally into the posterior inferior part of the right auricle. THE VERTEBRO-LUMBAR VEINS, ETC. 597 It is larger than the vena cava superior, but is not of uniform caliber throughout ; for example, it increases in size in a marked degree immediately above the renal veins. The vena cava inferior presents also a second still larger dilatation opposite the liver, where it is joined by the hepatic veins ; in comparison with its diameter at that point, the vena cava inferior appears to be slightly contracted as it passes through the dia- phragm. Relations. — The inferior cava is in contact with the anterior surface of the vertebral column, and runs throughout the whole of its extent along the right side of the aorta ; it inclines somewhat obliquely to the right as it is about to pass into the groove on the liver. In front it is covered by the peritoneum, the third portion of the duodenum, the pancreas, the vena portae, which crosses it at a very acute angle, and at its upper part by the liver, which forms a semi-canal, or a complete canal for it. It adheres closely to the margins of the tendinous opening in the diaphragm, and to the fibrous layer of the pericardium, as if its outer coat were blended with those struc- tures. The serous layer of the pericardium covers the vein, but the fibrous layer does not form a sheath for it. The relations of the inferior cava with the liver account for the erroneous notion of some old anatomists, that this organ was the centre from which all the veins of the body proceeded. There is no valve in the inferior cava ; but at its termination we find the Eustachian valve, which has been already described with the heart. Branches of Origin. — We have stated that the junction of the common iliac veins con- stitutes the origin of the inferior cava. It is very rare to find these veins uniting above the intervertebral disc between the fourth and fifth lumbar vertebras ; but in some few cases the junction has been observed to take place opposite the renal veins. Collateral Branches. — The vena cava inferior receives all the veins corresponding to the branches of the abdominal aorta, excepting the veins from the alimentary canal and its appendages, of which it only receives those from the liver, viz., the hepatic veins. All the abdominal veins which do not open directly into the inferior cava unite to form a large venous trunk, called the vena porta. Thus, the vena cava inferior receives the renal, the spermatic or ovarian, the lumbar, the supra-renal, and the inferior phrenic veins ; while the superior and inferior mesenteric, the splenic, the pancreatic, and the gastric veins open into the vena portae. It may still be said, however, that the vena cava inferior receives all the abdominal veins ; for, in fact, the veins of the portal sys- tem terminate in the vena cava through the medium of the hepatic veins. The portal system is, therefore, an appendage to the inferior cava. For this reason, and also for the sake of economizing subjects, I shall not describe the vena portae and its branches until I have noticed the collateral veins of the vena cava inferior. The Lumbar or Vertebro-lumbar Veins. The verlebro-lumiar veins are three or four on each side, and correspond to the arteries of the same name ; they have two branches of origin : an external or abdominal branch, which represents the intercostal veins, and a posterior or dorso-spinal branch, which is itself formed by the union of two other branches ; one muscular or cutaneous, which com- mences in the muscles and integuments, and the other a proper spinal branch, which forms part of the rachidian venous system, to be hereafter described. By the junction of these two branches a lumbar vein is formed, which runs forward and inward in the groove on the body of the corresponding lumbar vertebra, and enters the vena cava at a right angle. The left lumbar veins are longer than the right, in con- sequence of the vena cava being situated towards the right side of the vertebral column : they pass under the aorta. The Renal Veins. The renal veins are remarkable for their size, and occasion a great increase in the diameter of the inferior cava, above the point where they open into it ; they are of un- equal size on the two sides, and are unequal in length, on account of the vena cava be- ing placed towards the right side of the vertebral column, and, therefore, nearer the right than the left kidney : they also run more obliquely on the right side, on account of the right kidney being generally situated lower down than the left. These veins commence in the substance of the kidney by a number of minute divisions, which unite into small, and then into larger branches, gain the surface of the organ, and are collected into a single trunk, either in the hilus or at some distance from it. The trunk of each renal vein is always placed in front of the corresponding artery. The left renal vein passes in front of the aorta. We sometimes find one division of the left renal vein in front of the aorta, and another behind it. Plurality of the renal vein appears to me less common than an excess in the number of the arteries. The renal veins receive the inferior supra-renal and several veins from the surrounding ANGEIOLOGY. adipose tissue. The left renal vein is almost always joined by the spermatic or ovarian vein of that side. In some cases we find several communicating branches between the left renal vein and the superior mesenteric, which is one of the branches of the portal system. The Middle Supra-renal Veins. The middle supra-renal or capsular veins, which are often numerous and very large, are found on the surface of the supra-renal capsules, while the arteries enter into their sub- stance from every point. The venous trunks run in the grooves seen upon the surface of the organ. The left middle supra-renal vein almost always enters the renal vein of the same side ; the right vein generally opens into the vena cava inferior. The Spermatic or Ovarian Veins. The spermatic veins commence in the interior of the testicle, where they form a great number of those filaments which traverse the proper substance of the gland : they aU terminate in branches, which are applied to the inner surface of the tunica albuginea, and are bound down to it by a thin layer of fibrous tissue, a disposition somewhat resembling that of the sinuses of the dura mater. The spermatic veins perforate the tunica albu- ginea on the inner side of the epididymis, not opposite that body. They are soon joined by the veins of the epididymis, so as to form a plexus, which communicates with the dor- sal veins of the penis, and with the external and internal pudic veins. The spermatic veins soon unite into five or six trunks, which pass upward in front of the vas deferens, and, together with that canal and the spermatic artery, enter into the formation of the spermatic cord. These veins are tortuous ; they divide, and anastomose so as to form the spermatic venous plexus, which is often the seat of varicose dilatations. The veins ascend through the inguinal ring and canal, and having reached the interior of the pel- vis, they leave the vas deferens, accompany the corresponding spermatic artery along the psoas muscle, and terminate either in the renal vein, or in the inferior vena cava of their own side. In some cases the right spermatic vein opens both into the renal vein and the inferior cava. When there are two veins on one side, they communicate with each other by a great number of transverse branches, and, before terminating, unite into a single trunk. The name plexus pampiniformis is given to a plexus generally formed by the spermatic veins before their termination : this plexus is more frequently found on the left than on the right side, according to the observations of Meckel. The spermatic veins sometimes communicate with some branches of the portal system. The left spermatic vein passes under the sigmoid flexure of the colon, which may per- haps account for the greater frequency of varicocele on the left side. The ovarian veins accompany the arteries of the same name : they commence by sev- eral sets of branches, viz., uterine branches, which communicate very freely with the uterine sinuses ; ovarian branches, properly so called ; branches from the round ligaments ; and, lastly, some from the Fallopian tubes. All these unite within the substance of the broad ligaments, and pass vertically upward, without being at all tortuous : in some ca- ses they form a plexus pampiniformis. The ovarian veins, hke the uterine veins, become much enlarged during pregnancy. • The Inferior Phrenic Veins. These exactly follow the course of the inferior phrenic arteries, to each of which there are two veins. Tlie hepatic veins do not in any way correspond to the artery of that name ; they form a separate system, or, rather, they are connected with the portal venous system, of which they may be regarded as an appendage. The Portal Systkm of Veins. The system of the vena porta {vena portarum), or the portal system, constitutes a spe- cial venous apparatus, appended to the general venous system, and representing by it- self a complete circulatory tree, having its roots, trunk, and branches. The first, or ve- nous portion of this system of veins, is arranged like the veins of the other parts of the body, and has its roots of origin in the spleen and pancreas, and in the sub-diaphragmatic portion of the alimentary canal ; while the second, or arterial portion, sends its branches, like those of an artery, into the interior of the liver. The hepatic veins, which perform the functions of ordinary veins in reference to the second or arterial portion of the vena portae, connect the system of the vena portse with the general venous system. The Branches of Origin of the Vena Porta. The branches of origin of the vena portae (i, fig. 222) consist of all the veins which return the blood from the sub-diaphragmatic portion of the alimentary canal, and also from the spleen and pancreas. They correspond to the branches of the coehac axis, THE VENA PORTiE. 599 ■with the exception of the hepatic artery ; they unite Fig, 222. into three trunks, the great mesenteric (a), small mes- enteric (b), and splenic (c) veins. These veins are arranged like venee comites to the corresponding arteries. The Great and Small Mesenteric Veitis. — The intes- tinal or mesenteric veins commence just as the ar- teries terminate, by two layers of vessels, viz., a sub-serous layer, the vessels of which ramify be- neath the peritoneum, and a deep layer, formed by the vessels of the coats of the intestinal canal. These small vessels unite into anastomotic meshes, which always lie subjacent to the arterial network, and which terminate in larger branches, and thus con- stitute a series of veins corresponding to the arter- ies of the intestine. The right colic veins {dd) and the veins of the small intestine (shown cut short at e) terminate, the one in the right and the other in the left side of the superior mesenteric or great mes- araic vein (a) : this vein, in the early periods of in- tra-uterine life, receives the omphalo-mesenteric vein, a branch which corresponds to the omphalo-mesen- teric artery, and commences upon the vesicula um- bilicalis ; the artery and the vein disappear about the third month of utero-gestation, but the vesicle remains for a longer period. On the other hand, the left colic veins (/) enter the inferior mesenteric or small mesaraic vein (b) : this vessel forms the continuation of the superior hemorrhoidal veins {g), which commu- nicate very freely with the middle and inferior hemorrhoidal branches of the internal iliac vein. The splenic vein (c), which is proportionally larger than the artery, arises in the cells of the spleen by a great number of roots, which gradually unite in the hilus of that organ, and form the same number of branches as there are arteries, each coming from a dis- tinct compartment of the organ. All these branches soon unite into a single trunk, which passes across to the right side behind the pancreas, and, therefore, behind the splenic artery, which it accompanies without being tortuous : it is one of the branches immediately concerned in forming the trunk of the vena portae. During its course, the splenic vein receives the venous vasa hrevia {h h) from the stomach. The inferior mesenteric vein opens into the splenic ; so that there are only two venous trunks, the union of which constitutes the vena portae, viz., the splenic and the great or superior mesenteric. The Vena P or tee. The trunk of the vena porta (i) is formed by the union of the splenic and superior mes- enteric veins at an acute angle, behind the right extremity of the pancreas, in front of the vertebral column, and to the left of the vena cava inferior. The vena portae is larger than either of its two branches of origin, but is smaller than the two taken together. It passes obliquely upward and to the right side ; and, after running for about four inches, reaches the left extremity of the transverse fissure of the liver, where it terminates by bifurcating. The following are its relations during its course : anteriorly it is covered by the head of the pancreas, the second portion of the duodenum, the hepatic artery, the biliary ducts, and the lymphatics of the liver, and also by some branches from the hepatic plexus of nerves ; posteriorly it is covered by that portion of peritoneum which dips be- hind the vessels of the liver into the foramen of Winslow, to line the sac of the great omentum. By this foramen it is separated from the inferior vena cava, the direction of which it crosses at a very acute angle. The two branches into which the vena porta? divides in the transverse fissure of the liver separate so widely from each other, that they seem to form a trunk, at right angles to which the vena porta? itself is attached. Some anatomists apply the term sinus of the vena porta to that portion of the vein which is situated in the transverse fissure ; that part of the vein which adheres to the liver is more commonly called the hepatic portion of the vena portae, to distinguish it from the free and floating part, which is named the abdom- inal portion. The two divisions of the vena portae pass horizontally each towards the correspond- ing lobe of the liver ; they soon divide and subdivide into diverging branches, which sup- ply all the granules or lobules of the liver. The branches of the vena portae are accom- panied by the ramifications of the hepatic artery and biliary ducts. The capsule of Glis- son, or the fibrous coat of the liver, is reflected upon them, and forms a common sheath for them. (See Liver.) Before birth, the hepatic portion {p, fig. 164) of the vena portae receives, besides the 600 ANGEIOLOGY. abdominal portion of the same vein, the umbilical vein («), which is obHterated soon after birth. Nevertheless, I once found it perfectly permeable in an adult.* Before birth the ductus venosus (d) extends from the hepatic portion of the portal vein to the vena cava inferior, between which and the vena portae it establishes a direct com- munication. This hepatic portion might, therefore, be named the confluence of the veins of the liver. The Hepatic Veins. The capillary radicles of the hepatic or supra-hepatic veins commence in the capillary divisions of the vena portae, and, gradually uniting into larger and larger branches, con- verge towards the posterior border of the liver, or, rather, towards the fissure for the vena cava inferior, at which point they terminate by an indefinite number of small branches, named the small hepatic veins, which open all along the fissure ; and also by two principal trunks, the great hepatic veins, which end in the vena cava inmiediately before it passes into the opening in the diaphragm. One of these great hepatic veins comes from the right lobe, and the other from the left lobe of the liver. The vein of the left side often receives a great number of branches from the right lobe of the liver, and is larger than the vein of the right side. The vena cava inferior is always dilated into a large ampulla opposite the openings of the hepatic veins. It follows, from the previous description, that, in the liver, the branches of the hepatic veins and those of the vena portae run directly across each other, since the latter diverge from the centre of the organ towards its right and left extremities, while the former con- verge from the anterior towards the posterior border. Moreover, the branches of the hepatic veins are unaccompanied by other vessels, and are in direct contact with the tissue of the liver ; while those of the vena portae are sep- arated from it by the capsule of Glisson, and are accompanied by the ramifications of the artery, the nerves, and the hepatic ducts. I shall farther remark, that although the hepatic veins gradually unite, like other veins, into branches, which decrease in number, but increase in size, they most of them receive besides, during .their course, a multitude of capillary vessels, the inter-lobular hepatic veins, from the neighbouring lobules ; so that their internal surface is perforated with in- numerable foramina. The cribriform structure of their internal surface is therefore a peculiar characteristic of all the hepatic veins [except the very large ones], and enables us always to distinguish them from the branches of the vena portae. Lastly, the capillary communication between the extremities of the vena portae and hepatic veins is extremely free, as may be shown even by very coarse injections. AH the veins of the portal system are without valves,t and they can therefore be in- jected with the greatest ease from the trunks towards the extremities. An injection thrown in towards the intestine penetrates very readily into the interior of the alimentary canal, so that the minute branches of the vena portae appear to open at the apex of each villus. This can be made evident by throwing mercury into the vena porta, and then forcing it on by an ordinary injection ; drops of the mercury will then be seen in the open mouth of each villus, t The system of the vena portae is not so completely isolated from the general venous system as is commonly stated. It always communicates with branches of the internal ihac veins by means of the middle hemorrhoidal veins, and communicating branches with the renal veins have also been noticed ; and hence injections of the vena cava in- ferior always enter in a greater or less degree into the veins of the portal system. The Common Iliac Veins. The common iliac veins {n n, fig. 222) correspond exactly to the arteries of the same name ; they commence opposite the sacro-vertebral articulation by the junction of the internal and external iliac veins, and terminate by uniting at an acute angle to form the vena cava inferior or ascendens, the point of union being opposite the articulation of the fourth and fifth lumbar vertebrae, to the right side of, and a little below, the bifurcation of the aorta. The common iliac veins have the same relation to the lower extremities that the ' brachio-cephalic veins bear to the upper ; and as the right brachio-cephalic vein is shorter and more vertical than the left, so also is the right common iliac vein shorter and more vertical than the left. The relations of the common iliac veins with the corresponding arteries are remarkable, inasmuch as they are placed between these vessels and the vertebral column. The right common iliac vein is situated to the outer side of and behind the corresponding ar- * Anat. Pathol., livraison 17. t M. Bauer says that he has seen valves in the venous vasa brevia of the stomach ; I have never been able to discover them. t [The escape of the mercury is due to rupture of the bloodvessels. In the villi, the minute branches af the vena porta commence in the capillary network described and figured at page 339.] THE INTERNAL ILIAC VEIN, ETC. 601 tery, and is parallel to it ; while the left common iliac is situated on the inner side, and behind the corresponding artery, and is covered by its lower part. At the point where the left common iliac vein joins the vena cava inferior, it is also crossed obliquely by the right common iliac artery. It follows, therefore, that the left common illiac vein is covered, and may be compressed by both common iliac arteries, while the right common iliac vein cannot be compressed by either of them, and probably this is partly the reason why anasarca of the left lower extremity is more common than in the right extremity m atonic diseases. The right common iliac vein receives no collateral branch ; the left common iliac (n, fig. 223) is joined by the middle sacral vein {h). The middle sacral vein is situated in the median line, and its size depends upon that of the artery of the same name ; it belongs to the rachidian veins, with which it will be described The Internal Iliac Vein. The internal iliac or hypogastric vein exactly represents the internal iliac artery, on the inner side of which it is situated, separated from it, however, by a very thin fibrous layer, which holds it down against the walls of the pelvis. The internal iUac vein receives the venae comites of the branches of the internal iliac artery, the umbilical arteries in the fcetus alone being excepted ; for their satellite vein, the umbilical vein, which is also peculiar to the foetus, terminates in the hepatic portion of the vena portae, as we have already seen. The internal iliac vein, therefore, receives the blood returned from the parietes of the pelvis, from the organs contained within the cavity of the pelvis, and from the external genitals. There are always two veins for each artery ; but the two unite into a single vein at their point of termination in the principal trunk. The veins belonging to the parietes of the pelvis, viz., the gbiteal, obturator, and sciatic veins, are arranged precisely like the corresponding arteries. The ilio-lumbar and lateral sacral veins {i,fig. 223) form part of the rachidian system, which will be specially described. The veins belonging to the genito-urinary organs present a plexiform arrangement both in their trunks and in their roots, which deserves particular attention. Some of the venous plexuses of the pelvis are found both in the male and female, as the hemorrhoidal, while some are peculiar to one or the other sex, as the vesico-prostatic and the plexuses of the penis to the male, and the vaginal and uterine plexuses to the female. The Hemorrhoidal Veins and Plexuses. The hemorrhoidal veins and plexus form a venous network, surrounding the lower end of the rectum. They are formed by the superior hemorrhoidal veins, which form the com- mencement of the inferior mesenteric, and by the middle and inferior hemorrhoidal veins, which are branches of the internal iliac. We ought to notice in particular the sub-mu- cous venous network near the anus. The plexus formed by it is analogous to that found in all other mucous membranes ; its vessels are liable to become varicose, a condition which constitutes the greater number of hemorrhoidal tumours. The Pelvic Veins and Plexuses in the Male. Preparation. — Introduce one injection-pipe into the corpus cavernosum, and another into the glans penis, and then push an injection simultaneously into both of them, and also into the crural vein. The superficial scrotal veins terminate partly in the superficial veins of the perinaeum, and partly in the external pudic branches of the femoral vein ; they communicate with the superficial veins of the under surface of the penis. The Vesical Veins, or Vesico-prostatic Plexus. — The prostate gland and the neck of the bladder are covered by a very complicated plexus of veins, which become exceedingly developed in chronic inflammation of the bladder ; it receives the superficial veins of the penis, and gives oft" the vesical veins. This plexus, which communicates with the hemorrhoidal plexus behind, is supported by a very thick fibrous layer, which is continuous with the pelvic fascia, and which lim- its the degree of dilatation of the veins of the plexus in the same way as the dura mater limits the dilatation of the sinuses contained between its layers. The Veins and Plexuses of the Penis. — The veins of the penis are divided into a superfi- cial and deep set, the former representing the sub-cutaneous veins of the limbs. They commence in the skin of the prepuce, and run backward along the upper and lower sur- faces of that organ. The superior are called the dorsal veins of the penis ; they commu- nicate freely with each other by large branches ; most of them run beneath the arch of the pubes, between it and the corpus cavernosum, passing through some openings or fibrous canals in the sub-pudic ligament, which have the effect of keeping the veins al- ways open ; they end by assisting in the formation of the prostatic plexus. These veins communicate freely with the deep veins, especially opposite the junction of the two crura 4 G 602 ANGEIOLOGY. of the corpus cavernosum : this communication is proved by the fact that the superficial vessels are always filled when the injection is thrown into the deep veins. The areolar tissue of the corpus cavernosum and that of the corpus spongiosum may be regarded as composed of a venous network or plexus at its maximum of development. Branches proceed from this plexus, which correspond to the divisions of the internal pudic artery, and follow the same course. These veins, and the vesico-prostatic plexuses, are liable to become varicose ; hard earthy concretions, called phlebolites, are also frequently found in them. The Pelvic Veins and Plexuses in the Female. The vesical, or vesico-urethral plexus of the female, is less developed than that of the male, on account of the absence of veins corresponding to the superficial veins of the pe- nis, which are represented by a few branches from the labia majora. This plexus commu- nicates with the veins of the clitoris, and also very freely with the vaginal plexus behind. The vaginal plexus is a vascular network, extremely well developed, especially oppo- site the orifice of the vulva, which is entirely surrounded by it with several series of cir- cular anastomosing veins : it communicates with the vesical plexus in front, and with the hemorrhoidal plexus behind ; so that all the plexuses in the pelvis are involved in the state of turgescence, which accompanies the phenomenon of erection in the female. The radicles of this vaginal plexus commence in the mucous membrane of the vagina, and especially in the erectile tissue surrounding the orifice of that canal ; some large veins arise, in particular, from the bulb of the vagina, forming a true erectile apparatus, which we have already described. (See Splanchnology, p. 320.) The Uterine Plexus. — The veins contained in the substance of the walls of the uterus do not present any trace of the tortuous arrangement of the corresponding arteries. In order to obtain a satisfactory idea of them, they should be studied in a gravid uterus. The uterine veins, like the uterine arteries, are then found along the sides and upper an- gles of the organ ; opening into these veins are found larger venous canals, which run from side to side through the substance of the uterus, and anastomose frequently with each other. These venous canals are called the uterine sinuses, on account of their great size during gestation, and from the dilatations presented by them at the confluence of sev- eral secondary veins : they are also entitled to be so named from their structure, which has some analogy with that of the sinuses of the dura mater, inasmuch as only the lining membrane of the veins is prolonged into them ; their outer coat is formed by the proper tissue of the uterus, and hence the walls of these veins are contractile. I have stated elsewhere that, in reference to its veins, we may consider the uterus as consisting of an erectile tissue with muscular walls ; it is scarcely necessary to add, that these sinuses are unequally developed in different parts of the uterus, and that the point to which the placenta has been attached may be recognised by the greater size of the adjacent ute- rine sinuses. The veins contained within the substance of the walls of the uterus do not open into the uterine veins alone ; several of them terminate in the ovarian veins, which commu- nicate freely with the uterine, and may, if necessary, supply their place. The great size acquired by the uterine veins, both in the substance and on the surface of the uterus, proves that the venous apparatus plays an important part in the intersti- tial development of this organ. Moreover, the size of the veins and venous plexuses belonging to all the genito-urinary organs, and the essentially venous structure of such organs as are capable of being erect- ed, prove that the venous system performs an essential part in the truly active phenom- ena of erection. It is partly upon these anatomical and physiological arguments that I have endeavoured to show the active part performed by the veins in all the great phe- nomena of the economy, such as nutrition, secretion, inflammation, &c. The pelvic veins are provided with a great number of valves, which prevent injections from passing from the heart towards their extremities ; it ought to be remembered, that the venous plexuses of the pelvis establish a very important and verv free communica- tion between the veins of the right and left sides of the body. The Deep Veins of the Lower Extremity. The veins of the lower extremities, hke those of the upper, are divided into the deep veins or venae comites of the arteries, and the superficial veins. The Plantar^ Posterior Tibial, Peroneal, Dorsal, ^Interior Tibial, and Pop- liteal Veins. The external and internal plantar veins unite to form the posterior tibial, which accom- panies the artery of that name, and soon joins the peroneal vein, to constitute the tibio- peroncal vein : again, the anterior tibial vein, which commences by the vena dorsalis pedis, perforates the upper part of the interosseous ligament, joins the tibio-peroneal vein, and in this way forms the popliteal vein Up to this point there are two venae comites for each artery, one of the veins being placed on each side of the artery, across which thev THE FEMORAL VEIN, ETC. 603 very frequently send communicating branches. The peroneal veins are generally larger than the posterior tibial, and receive all the muscular veins from the posterior and outer regions of the leg. Commencing with the popliteal, there is only one vein for the main artery of the limb ; but the arteries of the second and third order always have two veins. The popliteal vein is situated in the pophteal space, behind and in contact with the ar- tery. Its coats are remarkably thick, so that when cut across it remains open, and in the dead body has been sometimes mistaken for the artery. Below, and opposite the articulation of the knee, the vein is situated immediately behind the artery ; above the joint it is behind, and a little to the outer side. The pophteal vein receives the large bundles of veins, the sural veins, from the gas- trocnemius muscle : they are remarkable for the number of their valves ; also the articvr- lar veins, and generally the external saphenous vein. I have seen a small vein having very numerous valves, and being analogous to the collateral venous canals of which I have already spoken, extend from the upper part of the anterior tibial to the middle of the popliteal vein. The Femoral Vein. The femoral vein, like the artery of that name, is bounded below by the ring in the tendon of the adductor magnus, and above by the crural arch ; it has different relations with the femoral artery in various parts of its course : thus, below, it is on the outer side of the artery ; higher up, it is situated behind that vessel ; lastly, from the entrance of the vena saphena interna to the crural arch, it is placed to the inner side of the artery, and is in close contact with the posterior part of the opening for the femoral vessels ; so that femoral herniae descend in front of the vein, but not of the artery. The femoral vein is single, hke the artery ; nevertheless, there are one or two collateral venous canals, which run parallel with the lower half, or lower two thirds of that vein ; some commu- nicating branches from the internal saphenous vein, and some muscular branches, open into these venous canals, which are always abundantly supplied with valves. The femoral vein receives all the branches corresponding to the divisions of the fem- oral artery, excepting the external pudic veins and the cutaneous veins of the abdomen, which terminate in the internal saphenous vein. The great deep vein (profunda) opens into the femoral about ten or twelve lines be- low the crural arch. The External Iliac Vein. The external iliac vein is bounded below by the femoral arch, and terminates at the up- per part of the sacro-iliac symphysis by uniting with the internal iliac vein ; it has the same relations as the artery, and is placed behind and to the inner side of that vessel, excepting over the os pubis, where it is exactly to the inner side of the artery. In one case I found the left common iliac receiving the right internal iliac, so that the right ex- ternal iliac was prolonged into the vena cava. The external iliac receives the epigastric and the circumflex ihac veins. These two veins are double, but each pair unites into a single trunk, as it is on the point of open- ing into the external iliac vein. All the deep veins of the lower extremity, excepting the external iliac, are provided with valves. There are four in the deep femoral, the same number in the popliteal, and many more in the tibial and peroneal veins ; the mouths of all the small veins which open into them are provided with a pair of valves. The Superficial Veins of the Lower Extremity. The superficial veins of the lower extremity are much less numerous than those of the upper, and all terminate in two trunks, viz., the internal saphenous vein and the exter- nal saphenous vein. As in the hand, they are all situated upon the dorsal region of the foot. All the col- lateral veins of the toes enter the convexity of a venous arch, which is more regular and constant than that in the hand, and which is placed on the fore part of the metatarsus. From the inner end of this arch is given off a large branch, named the internal dorsal vein of the foot, which is the origin of the internal saphenous vein ; the outer extremity also gives off a somewhat smaller branch, called the external dorsal vein of the foot, which forms the commencement of the external saphenous vein. The Internal Saphenous Vein. The internal or great saphenous vein {saphena interna, s, in the representation of the superficial nerves of the leg) is a collateral vein of the femoral venous trunk, and is con- tinuous with the internal dorsal vein of the foot. The last-mentioned vein commences at the inner extremity of the dorsal venous arch of the foot, into which the collateral veins of the great toe open ; it runs along the dorsal surface of the first metatarsal bone and the corresponding part of the tarsus, and receives, during its course, a deep branch from the internal plantar vein and all the superficial veins of the internal ulantar region, 604 ANGEIOLOGY. and particularly the internal calcaneal vein, which is sometimes large, and which, in cer- tain cases, does not terminate in the saphenous vein until it has reached above the in- ternal malleolus, around the posterior border of which it turns. The internal saphe- nous vein succeeds to the one just described ; it is reflected upward in front of the internal malleolus, and continues to ascend upon the inner surface, then along the pos- terior border of the tibia, and upon the back of the internal tuberosity of that bone and the internal condyle of the femur. In this place it is situated on the inner side of the tendons of the semi-tendinosus, gracilis, and sartorius ; it then inclines forward, descri- bing a slight curve, with its concavity directed forward ; ascends along the anterior bor- der of the sartorius, and crosses obliquely over the adductor longus ; having arrived at the saphenous opening in the fascia lata, about eight or ten inches below Poupart's lig- ament, it immediately curves backward, passes through that opening, and enters into the femoral vein, just as the vena azygos enters into the superior vena cava, that is to say, it describes a loop having its convexity directed downward. Several lymphatic glands are found near this curve. Relations. — The internal saphenous vein is separated from the skin by a very thin fibrous layer, the superficial fascia, and is in relation with the internal malleolus, the tibia, the tibial origin of the soleus, the tendons of the semi-tendinosus, gracilis, and sar- torius, with the last-named muscle itself, and with the adductor longus. It is accompa- nied by the internal saphenous nerve, from the knee down to the internal malleolus. During its course it receives all the sub-cutaneous veins of the thigh, most of the sub- cutaneous veins of the leg, the sub-cutaneous veins of the abdomen, the external pudic veins, and several communicating branches from the deep veins. The sub-cutaneous femoral veins of the back of the thigh sometimes unite into one rath- er large trunk, which appears like a second internal saphenous vein ; it runs parallel with the regular vein, and enters it at a greater or less distance from its termination. I have met with an anterior superficial vein which commenced around the patella, ascended vertically along the anterior region of the thigh, and might be regarded as a third saphe- nous vein. In one case of this kind, these three saphenous veins, viz., the anterior, posterior, and internal, entered separately into the femoral vein, or, rather, into a dilata- tion in which the internal saphenous vein terminated. The internal saphenous vein often presents the following arrangement : opposite the lower part of the leg, or at the lower end of the thigh, it divides into two equal branches which pass upward, communicate with each other by transverse branches, and unite af- ter running a variable distance ; in these cases the two branches represent a very elon- gated ellipse. I have even seen this arrangement in both the thigh and leg of the same subject, that is to say, the saphenous vein divided into two branches in the leg, which united opposite the internal tuberosity of the tibia, and again divided in the thigh. It is not uncommon to find a venous network supplying the place of the internal saphe- nous vein in the thigh. The sub-cutaneous abdominal veins should be arranged among the superficial and sup- plementary veins, although there is a small artery, the superficial epigastric, which cor- responds to them. There are three or four of these veins, which are joined by one from the gluteal region ; they open sometimes by a common trunk, sometimes by three or four distinct trunks, into the internal saphenous, just as that vein is passing through the fascia lata. In a case of obliteration of the vena cava I found these veins very large, and prolonged over the thorax into the axilla, where they anastomosed with the cuta- neous branches of the intercostal and thoracic veins. In a case in which the umbihcal vein was persistent, the right and left internal saphenous veins were tortuous, and as large as the little finger.* The internal saphenous also receives the external pudic veins; and I have seen it joined by the obturator vein, which commenced by a common trunk with the epigastric. The communicating branches of the internal saphenous with the deep veins are very nu- merous, and should be studied in the foot, the leg, and the thigh. The origin of the in- ternal saphenous vein gives ofT a branch, which communicates with the internal plan- tar vein. Along the leg several other branches exist, which estabhsh a communication between the internal saphenous and the posterior tibial veins ; these branches perforate the tib- ial origins of the soleus muscle. There is a very remarkable communication between the anterior tibial and internal saphenous veins in the middle third of the leg, by means of a branch which proceeds from the anterior tibial vein in front of the fibula, becomes sub-cutaneous, is reflected inward and upward between the fascia of the leg and the skin, and terminates in the in- ternal saphenous. Again, an inferior, internal, articular vein enters the internal saphenous. Lastly, the anastomoses in the thigh, between the deep and the superficial veins, are less numerous than those in the leg ; at most we only find two such describing loops, with the concavity directed upward. * Anat. Path., liv. xviii. THE VEINS OF THE SPINE. 605 Vahes. — The number of the valves appears to me variable : I have counted six along the internal saphenous, but at other times I have not found more than two or four. There is a greater number of valves in this vein in the thigh than in the leg. The External or Posterior Saphenous Vein. The external saphenous vein (la peroneo-malleolaire, Chauss. ; see figure of nerves of leg), smaller and much shorter than the internal saphenous, is a branch of the popliteal vein ; it forms a continuation of the external dorsal vein of the foot, which commences from the outer extremity of the dorsal venous arch ; it passes behind the peroneo-tibial articulation, crossing it from before backward ; it receives, as it runs outward, a great number of branches, the chief of which come from the external plantar region ; also an external calcaneal vein, which is sometimes of considerable size, and comes from the outer side of the os calcis ; the vein then runs along the outer border of the tendo Achil- lis, and crosses it at a very acute angle, to reach the middle hne of the posterior aspect of the leg : commencing at this point, it passes directly upward, crosses the internal popliteal nerve, and terminates in the popliteal vein between the internal and external pophteal nerves, between the two heads of the gastrocnemius, and by the side of the in- ternal inferior articular vein. In some subjects the external saphenous, at the moment when it bends to dip into the popliteal space, gives off an ascending vein, which runs along the posterior border of the semi-membranosus muscle, as high as the upper third of the thigh, where it then turns forward to open into the internal saphenous, or one of the branches of that vein, immediately below its opening into the femoral. Relations. — The external saphenous vein is covered by the superficial fascia, which separates it from the skin, and it covers the external saphenous nerve, from which it is separated by a layer of fascia ; it crosses this nerve twice, being at first situated to the inner side, then to the outer side, and again on the inner side of the nerve. The external saphenous vein communicates with the deep veins only, behind the ex- ternal malleolus, and upon the dorsum of the foot. This vein has only two valves, one of which is situated immediately before its open- ing into the popliteal vein. Such are the veins of the lower extremity. The analogy which exists between the in- ternal dorsal branch of the foot and the cephalic vein of the thumb ; between the exter- nal dorsal branch and the vena salvatella ; between the external saphenous and the ra- dial and cephalic veins ; between the internal saphenous and the ulnar and basilic veins, cannot be doubted. There is no branch in the lower extremity analogous to the median vein. THE VEINS OF THE SPINE. General Remarks.- — The Superficial Veins of the Spiyie. — The Anterior Superficial Spitial Veins, viz., the Greater Azygos — the Lesser Azygos — the Left Superior Vertebro-costals — the Right Vertebro-costals — the Vertebro-lumhar — the Ilio-lumbar, and Middle and Lat- eral Sacral — the Anterior Superficial Spinal Veins in the Neck. — The Posterior Superfi- cial Spinal VeiTis. — The Deep Spinal or Intraspinal Veins — the Anterior Longitudinal, and the Transverse Veins or Plexuses, and the Veins of the Vertebrce — the Posterior and the Posterior and Lateral Transverse Veins or Plexuses — the Medullary Veins. — General Remarks on the Veins of the Spine. The spinal or rachidian veins constitute a very important part of the venous system, which has only recently been specially studied. These veins differ, in many respects, from the spinal arteries, so that the description of the one does not afford much assistance in the study of the other ; nevertheless, I shall frequently have occasion to point out some remarkable analogies between these two sets of vessels. The spinal veins are arranged most distinctly as venae comites and supplementary veins. We shall divide them into the veins exterior to the spine or the superficial veins, and the veins in the interior of the spinal canal, or the deep veins. The Superficial Veins of the Spine. The superficial veins of the spine may be subdivided into the anterior and posterior. The Anterior Superficial Rachidian Veins. The anterior superficial rachidian or spinal veins (see fig. 223) comprise the vena azy- gos major, the vena azygos minor, the common trunk of the right superior intercostals, that of the left superior intercostals, the vertebro-lumbar and iho-lumbar veins, and the lateral and middle sacral veins ; in the neck, the ascending cervical and the vertebral veins. The Greater Azygos Vein. The vena azygos major (a a', fig. 223) is a large single \em{a^vyoc, without a rdlow), 606 ANGEIOLOGY. Vig. 223. situated along the vertebral column ; it commences {a!) in the lumbar region, and termi- nates at the upper part of the thorax by opening into the vena cava superior. Its origin is subject to much variety. It very rarely arises from the trunk of the infe- rior vena cava itself, with which, however, it almost always communicates by small branches. It generally forms the continuation of a series of anastomoses, which sur- round the bases of the right transverse processes of the lumbar vertebrae, and which may be called after some authors the ascending lumbar vein {h, on the right side) ; sometimes it arises from the trunk of the last vertebro-costal, or the first vertebro-lumbar vein : we rarely find a branch of origin from the renal or supra-renal veins. It often has two ori- gins, one from the ascending lumbar, and the other from the first vertebro-lumbar, or last vertebro-costal vein. The vena azygos, almost immediately after its origin, passes from the abdominal into the thoracic cavity, through the aortic opening in the diaphragm, ascends upon the right side of the bodies of the thoracic vertebrae, as high as the third intercostal space, i. e., between the third and fourth ribs, where it curves forward, forming, like the aorta, an arch, which passes over and embraces the right bronchus, and opens into the back of the vena cava superior, as that vein is enter- ing the pericardium. During its course the vena azygos is in contact with the vertebral column, and is situated in the posterior mediasti- num, on the right side of the aorta and of the thoracic duct (t t), which runs parallel to it ; it lies in front of the right in- tercostal arteries, and crosses them at right angles. It va- ries in size, according to the number of branches which it re- ceives, but gradually increases from below upward. The question of the existence of valves in the vena azy- gos has given rise to much discussion. It appears to me to be settled in the negative. The vena azygos is joined in front by the right bronchial vein and some (Esophageal and mediastinal veins ; on the right side by the eight mferior vertebro-costal veins (c c) of that side ; and on the left by the lesser azygos (d) and the common trunk (e) of the left superior intercostal veins. Before opening into the superior vena cava, opposite the third intercostal space, the azygos vein receives at its curve, either by a common trunk, or by two or three separate branch- es, the three superior right vertebro-costal veins, which some- times enter the right brachio-cephalic vein, and sometimes the vena cava superior, above where it is joined by the vena azygos. In the last case they pass vertically upward ; in the second they are directed almost vertically downward. The Semi-azygos, or Lesser Jlzygos Vein. The lesser azygos vein {d d,' azygos minor, semi-azygos) may be regarded as the common trunk of the three, four, or five inferior vertebro-costal veins (c' c') of the left side : it opens into the great azygos vein. It commences below {d') in as many different ways as the great azygos vein, but it communicates with the renal vein much more frequently. It runs upward upon the left of the vertebral column, approaches the median line, and opens into the great azygos at a different height in different subjects. It joins the great azygos either at right angles or obliquely, passing behind the thoracic duct. The lesser azygos vein may be regarded as the left branch of origin of the greater azy- gos : sometimes it is extremely large ; in that case the great- er azygos is directly continuous with it, and the right branch is very small. The lesser azygos vein is joined by the four or five inferior vertebro-costal veins (c' c') of the left side. It also frequent- ly receives the common trunk of the superior vertebro-costal veins, which might be said to form a superior lesser azygos vein. The Left Superior Vertebro-costal Veins The common trunk (e) of the left superior intercostal veins (//) might be called the left superior lesser azygos, for it has the same relation to these veins that the lesser azy- gos has to the inferior intercostals of the same side. It runs downward upon the left of the vertebral column, increasing in size as it approaches its termination, which is THE INTERCOSTAL VEINS, ETC. 607 either near the_end of the lesser azygos, or in the greater azygos. Not unfrequently the common trunk of the left superior intercostals bifurcates and opens both into the lesser azygos and into the left brachio-cephahc vein. In some cases it terminates entirely in the left brachio-cephahc vein : I have myself met with this disposition. I have seen the left superior phrenic and the mediastinal veins enter the trunk of the lesser vena azygos immediately before its termination. The number of the left vertebro-costal veins which unite to form the lesser azygos vein varies from three to seven ; when only three or four of the highest of these verte- bro-costal veins end in it, the two or three lower ones enter directly into the greater azygos vein. General Remarks on the Vena Azygos Major. — This vein returns the blood of the right and left vertebro-costal vems to the heart ; its presence is rendered necessary, first, in con- sequence of the inferior vena cava not being able to receive any veins from the point where it enters the groove in the liver to its termination in the right auricle ; and, sec- ondly, because the superior vena cava is also unable to receive any veins while it is within the pericardium. The greater azygos is, therefore, a supplementary vein, a true collateral canal which supplies the place of the venae cavse, and receives aU the veins corresponding to the branches given oft" by the aorta during this long course. These ob- servations are, for the most part, applicable to all the azygos veins. Anatomical Varieties of the Azygos Veins. — It would be both useless and tedious to no- tice here all the varieties that have been observed in the distribution of the azygos veins. M. Breschet has described six, but there are many more. The following is a very cu- rious variety : the greater azygos occupies the median line of the dorsal portion of the vertebral column, and is divided below into two equal branches, a right and a left, each of which receives the three inferior vertebro-costal veins of its own sides ; all the other vertebro-costal veins end directly in the greater azygos. Another not less curious variety is the following : there are two equal and parallel azygos veins, a right, which receives all the right intercostal veins, and a left, which re- ceives all the left intercostals : the two main trunks communicate with each other oppo- site the seventh or eighth dorsal vertebra by a very large transverse branch. The Intercostal or Vertebro-costal Veins. The intercostal or vertebro-costal veins of both sides (c c, c' c',f f) correspond to the in- tercostal or vertebro-costal arteries, the distribution of which it is important to call to mind. We have seen that each of these arteries divides into two branches : an intercos- tal branch, properly so called, intended for the intercostal spaces ; and a spinal branch, the dorsal division of which terminates in the spinal muscles and the skin, while its ver- tebral, or intra-spinal division, is distributed to the vertebrae, to the spinal cord, and to its coverings. In like manner, the vertebro-costal veins are formed by the junction of the spinal branch, to which we shall presently return, and the intercostal branch. These two sets of branches unite into a common trunk, the vertebro-costal vein, which passes transversely along the groove on the body of each vertebra, receives some veins from the bone in that situation, and enters at a right angle into the corresponding axygos vein. The Lumbar or Vertebro-lumbar Veins. In the lumbar region there are no azygos veins, and each vertebro-lumbar vein en- ters separately, or by a common trunk, with its fellow of the opposite side, into the back of the vena cava inferior. Not unfrequently two of the vertebro-lumbar veins of the same side open by a common trunk ; and it is not rare to find the left superior vertebro- lumbar vein enter the renal vein. The vertebro-lumbar veins {g) are distributed very differently from the corresponding arteries. Opposite the bases of the transverse processes there are a series of anasto- motic arches, which together constitute, on each side, an ascending branch, called the a^coiding lumbar vein (b b), which communicates above with the corresponding azygos veiii, and below with the ilio-lumbar veins, and which might be regarded as a lumbar azygos vein. The trunks of the vertebro-lumbar veins proceed from this series of arches to the Vena cava ; and all the intra-spinal and dorsi-spinal veins terminate in it. T'he Ilio-lumbar, Middle Sacral, and Lateral Sacral Veins. The ilio-lumhar vein, which opens into the common iliac, is distributed like the artery of that name ; it sometimes receives the last vertebro-lumbar vein : it is joined by the great veins which f^merge from the lower inter- vertebral foramina of the lumbar verte- brae ; by the branch which is continuous in front of the fifth lumbar vertebra, with the series of arches formmg what may be called the lumbar azygos ; and, lastly, by a com- municating branch from the lateral sacral veins. The middle sacral and lateral sacral veins represent the azygos veins in the sacral re- gion ; they are joined by all the dorsi-spinal branches passing out from the inter-vertebral foramina, and end in the common iliac veins. The middle sacral vein (h) often commences below by three branches, a median in 608 ANGEIOLOGY. front of the coccyx, and two lateral and anterior branches. One of these joins the ves- ical plexus, while the other communicates with the hemorrhoidal veins, and establishes a remarkable communication between the general venous system and the system of the vena portse. The middle sacral vein passes vertically upward, somewhere near the middle line, and opens into the left common iliac vein (w) at a greater or less distance from its junction with the right common iliac. I have seen it bifurcate above to enter both common iliacs. During its course it is joined opposite each vertebra by some transverse, plexiform branches, which establish a free communication between it and the lateral sacral veins, and which receive some large branches from the bodies of the sacral vertebrae. These transverse branches represent the vertebro-costal and vertebro-lumbar veins, which also receive the veins which issue from the bodies of the vertebrae, through the foramina, upon the inner surface of those bones. The lateral sacral veins {i), of which there are always more than one on each side, are continuous with the dorsi-spinal veins, which emerge from the anterior sacral foramina ; there are generally two, a superior, which enters the common iliac vein, and an inferior, which forms a very remarkable plexus, opposite the great sciatic notch, and ends in the internal iliac vein, or in its gluteal and sciatic branches. The Anterior Superficial Spinal Veins in the Jfeck. In the anterior cervical region we find transverse plexiform branches (k) opposite each vertebra, more particularly opposite the first and second ; these plexuses open partly into the ascending cervical vein, which corresponds to the ascending cervical artery, but principally into the vertebral vein, which is contained within the canal formed by the series of foramina at the base of the transverse processes of the cervical vertebrae. These plexiform branches, which cover the sides of the bodies of all the vertebrae, are joined by the veins from the praevertebral muscles, by the articular veins, and by the anterior osseous veins from the bodies of the corresponding vertebrae. The vertebral veins and the ascending cervical veins may therefore be said to repre- sent the azygos veins in the cervical region. The Posterior Superficial Spinal Veins. The posterior superficial spinal veins commence in the skin, and in the muscles of the vertebral grooves : some of them closely accompany the arteries ; for example, those that pass between the muscles of the vertebral grooves ; the others have a peculiar dis- tribution, and require a special description. These veins, which are called dorsi-spinales by MM. Dupuytren and Breschet, form an exceedingly complicated network, the meshes of which surround the spinous process- es and laminae, and the transverse and articular processes of all the vertebrae : these meshes are more numerous in proportion as the injection is more perfect. After a successful injection, we sometimes find along the summits of the spinous pro- cesses, especially in the dorsal and cervical regions, certain median longitudinal veins, from which the interosseous branches proceed. These latter run forward, on each side of, and in contact with, the inter-spinous ligaments. Having reached the base of the corresponding spinous process, they pass outward, opposite the intervals between the laminae of the vertebrae, as far as the bases of the transverse processes, and then divide into two branches : one of these ascends, and anastomoses with the descending branch from the vein above ; while the other branch descends, and anastomoses with the as- cending branch of the vein below. It follows, therefore, that around the transverse pro- cesses and the laminaj of the vertebrae there is a series of venous circles, which com- municate, opposite each inter-vertebral foramen, with the veins contained in the interior of the spine. The posterior superficial spinal veins in the neck have a much more complicated ar- rangement, and, indeed, form a plexus. Moreover, we generally find, between the coik- plexus and the semi-spinalis coUi, two longitudinal veins, which appear to me to deserve a particular description, under the name of the posterior jugular veins. The posterior jugular veins commence between the occipital bone and the atlas, pass tortuously out from the interval between these bones, run downward and in^rard, and, opposite the spinous process of the axis, the veins of the two sides anastomose by a transverse branch. They then change their direction, pass downward and outward, and having reached the lower part of the neck, turn forward, between the seventh cervical vertebra and the first rib, and open into the back of the brachio-cephal/c vein behind the vertebral vein. The two posterior jugular veins are therefore arranged in the form of the letter X. The posterior jugular vein, which does not always exist, for its branches of origin sometimes remain separate, seems to be inversely proportioned to the vertebral vein, with which it communicates opposite each inter-transverse space. It has appeared to me to communicate above with the deep occipital and the mastoid veins, with the veins situated in the spinal canal, and with the internal jugular vein. Throughout the whole THE INTRA-SPINAL VEINS. 609 ©f its course, it communicates freely, opposite each inter- vertebral foramen, with the veins contained in the interior of the spinal canal, and with the vertebral vein. The Deep Spinal oe Intra-spinal Veins. The veins in the interior of the spijie comprise the proper veins of the spinal cord, and the veins situated between the bones and the dura mater, which are subdivided into the anterior and the posterior longitudinal veins or plexuses, and the transverse veins or plexus- es ; the latter establishing a free communication between all four of the longitudinal veins or plexuses, opposite each vertebra. Before describing the veins situated between the bones, and the dura mater, I must state, in a few words, what is the arrangement of the proper arteries of the vertebrae. The spinal branches which are given off on each side of the body by the vertebral ar- tery in the neck, by the intercostal arteries in the back, by the lumbar arteries in the loins, and by the lateral sacral arteries in the pelvis, enter the spinal canal through the several inter-vertebral foramina, and then each of them divides into an ascending and a descending branch ; the ascending branch runs upward upon the lateral part of the body of the vertebra above, and anastomoses with the descending branch of the spinal artery above it, while the descending branch anastomoses with the ascending branch of the artery below. Each of the anastomotic arches thus formed has its concavity directed outward; so that there is a series of arterial arches, united at their extremities, situ- ated upon each side of the posterior sur/ace of the bodies of all the vertebra. From the convexity of each arch two transverse branches are .given off, one running above and the other below the small ibramina upon the posterior surface of the body of the corre- sponding vertebra. The cribriform portion of the bone is thus surrounded by the arte- rial arches with their transverse branches ; and from all points of the polygon which they form small arteries are given off, which penetrate into the substance of each ver- tebra, and anastomose with the arterial twigs that enter the anterior surface of the body of the vertebra The arrangement of these arteries gives a perfect idea of that of the veins known as the anterior longitudinal veins or plexuses, and of the transverse plexuses, which pass from one to the other. The Anterior Loi^itudinal Intra-spinal Veins or Plexuses, the Transverse Plexuses^ and the Proper Veins of the Bodies of the Vertebrce. Dissection. — Remove the arches of the vertebrae, and the spinal cord and its coverings. The plexus may also be viewed from the front, by carefully sawing through the pedicles and then removing the bodies of the vertebrae. The anterior longitudinal plexuses, described by Chaussier, but still more correctly by Breschet, form two venous trunks, named the great anterior longitudinal veins, extending from the foramen magnum to the base of the coccyx, one on each side of the posterior common vertebral ligament, and therefore upon the sides of the posterior surface of the bodies of the vertebrae, and on the inner side of their pedicles. These veins, improperly called vertebral sinuses, communicate together opposite each vertebra by a transverse plexus, situated between the body of the vertebra and the posterior common ligament. These longitudinal plexuses are less developed in the cervical and sacral regions. It is probable that in the neck their place is supphed by the vertebral veins. It would be in vain to consider these plexuses as having a distinct origin, course, and termination ; the description given above of the distribution of the arteries is applicable to the veins in every respect : thus, the venous plexuses are formed by a series of plex- iform arches, which embrace the pedicles of each vertebra, have their concavity directed outward and their convexity inward, and the extremities of which anastomose together opposite the inter- vertebral foramina, where they communicate with the branches on the outside of the spine, and assist in the formation of the vertebro-lumbar and vertebro- costal veins, and, consequf ntly, of the azygos veins. From the convexity of each arch proceeds a transverse plexus, which goes to join with its fellow of the opposite side ; and, just as we have seen that the transverse arteries extending from one arterial arch to another give off branches to the bodies of the vertebrae, so, in like manner, the trans- verse venous plexuses receive the veins which emerge from the body of each vertebra. The arrangement of the veins or plexuses just described explains the alternate en- largements and contractions observed in different parts of the anterior longitudinal plex- uses. The rare interruptions described by M. Breschet, I believe to depend upon im- perfect injections, which succeed so differently in different subjects. The anterior longitudinal veins or plexuses cannot be regarded as sinuses, for they are not contained in a fibrous sheath, like the veins of the dura mater, nor are they reduced merely to the lining membrane of the veins. Notwithstanding their extreme tenuity, we can recognise an external coat, and the posterior common ligament does not cover them behind. Nor is the term sinus more applicable to the transverse plexuses, although they are situated betwe'en the bodies of the vertebrae and the posterior common ligament,, for the ligament merely covers them without forming a sheath for them. 4H 610 , ANGEIOLOGY. The Proper Veins of the Bodies of the Vertebra. — The foramina upon the posterior sur- face of the body of each vertebra, which are generally proportioned to the size of the ver- tebra, are principally intended for the proper veins of the bodies of their bones : the ar- teries are much smaller, and though they enter by the same openings, they occupy but a small part of their areas. These veins belong to that system of venous canals found in the substance of bones, which we have already noticed as existing in the bones of the cranium. Their chief varieties have been correctly described and delineated by M. Bres- chet. These venous canals, which are more developed in the old than in young sub- jects, occupy the centre of the body of the vertebra, and always run parallel to the up- per and lower surfaces of the bone ; they arise from all parts of the circumference of the vertebra, communicating with the veins which enter by the foramina on its anterior sur- face, and converge towards the principal foramen, or foramina, upon its posterior as- pect. They frequently enter a semicircular canal, which has its convexity directed for- ward, and gives off from its concavity a venous canal, which opens directly into the transverse plexus ; the lateral veins of the body of the vertebra open into the extremities of this semicircular canal; while within the venous canals of the vertebra?, the veins are reduced to their lining membrane, like the veins in the canals of the cranial bones. The transverse plexuses, therefore, collect the blood from the bodies of the vertebra;, and transmit it to the anterior longitudinal plexuses. The Posterior Intraspinal Veins or Plexuses, and the Posterior and Lateral Transverse Plexuses. The posterior intraspinal plexuses, much smaller than the anterior, are situated one on each side between the vertebral laminaj and ligamenta subflava behind, and the dura mater in front. These veins are rarely injected along the whole length of the spine, and hence they sometimes appear to exist only in the dorsal region. They communicate op- posite each vertebra, by means of posterior transverse plexuses, or by transverse veins. They communicate with the anterior longitudinal plexuses by small lateral transverse plexuses, which pass from behind forward. It follows, therefore, that ihe veins within the spine, but external to the coverings of the cord, consist of four longitudinal plexuses, all of wliich are connected by a transverse circular plexus opposite each vertebra. A strict analogy may be said to exist between the sinuses of the cranium and the iniTa-spi- nal plexuses ; an analogy which did not escape the notice of the ancients, as the com- mon application of the term sinus by them to the veins of the cranium and to those of tl\e spine would seem to indicate. Thus, in the cranium Ave find certain longitudinal sinus- es, that is, those which run from before backward, viz., the superior longitudinal sinus, the straight sinus, and the posterior occipital sinuses ; also, the superior and inferior pe- trosal sinuses, the cavernous sinuses, and the right and left lateral sinuses. The former set represent the posterior intra-spinal plexuses ; the latter correspond to the anterior in- tra-spinal plexuses. In the cranium we also find certain transverse sinuses, viz., the basilar or transverse occipital sinuses and canals, and the coronary sinus, which exactly correspond to the transverse plexuses, extending from one anterior intra-spinal plexus to the other. We sometimes find two or three transverse venous plexuses in the basilar groove of the oc- (cipital bone. Lastly, may we not compare the veins on the outer surfaces of the spine to the occipital, frontal, and temporal veins ; and do not the veins passing through the posterior lacerated foramen and the sphenoidal fissure, Avhich we have regarded as representmg the inter- vertebral foramina (see Osteology), establish a communication between the veins on the inside and those on the outside of the cranium, just as the veins which escape through the inter-vertebral foramina connect together the superficial and the intra-spinal veins ? The anterior and posterior deep spinal veins communicate with the superficial veins of the spine at the inter-vertebral foramina so freely, that the circulation would not be interfered with even if a considerable amount of obstruction existed. I have already stated (see Vertebr.ts) that the diameter of the inter-vertebral foramina is in relation, not with the size of the nervous ganglia, but rather with that of the veins, which estab- lish a communication between the superficial and intra-spinal venous systems. The Proper Veins of the Spinal Cord, or the Medullary Veins. If we examine the pia mater of the spinal cord, even without having injected it, in the body of a person who has die<' tiddenly, as in that of a new-born infant after death from asphyxia or apoplexy, the suriace of the pia mater will be found covered by very tortu- ous veins, which emerge from the posterior median furrow of the spinal cord. This ve- nous network, which is spread over the whole surface of the cord, gives off opposite the roots of each nerve a small vein, which runs directly between those roots, enters the corresponding inter-vertebval foramen, is enclosed with the nerve in the sheath formed by the dura mater, and having emerged from that sheath, opens into the large vein sit- uated in the inter-vertebral foramen. There is, therefore, this difference between the proper veins and arteries of the spinal THE LYMPHATIC SYSTEM. 811 cord, that the number of veins is equal to that of the nerves ; AVhile the arteries are less numerous, and enter the fibrous sheaths of the nerves only at intervals, and in propor- tion as the preceding arteries are exhausted. Moreover, the anterior and posterior spi- nal veins, like their corresponding arteries, may be regarded as belonging only to the up- per part of the cord, and not as being intended to traverse its whole length. General Remarks on the Veins of the Spine. The veins of the spine may be regarded, in reference to the general circulation, as es- tablishing an unbroken communication between the veins of all parts of the trunk ; so that we can suppose one of the venae cavas to be obliterated, without the venous circu- lation being interrupted. The greater azygos itself, which is generally regarded as the principal means of communication between the two venae cavae, is not, however, neces- sary, when we consider the arrangement of the anterior and posterior spinal plexuses. Thus, I have sometimes seen the inferior, and sometimes the superior vena cava oblit- erated without any apparent increase in the diameter of the vena azygos, and, what will perhaps be thought surprising, without oedema, either of the upper or lower extremities. Supposing the vena cava ascendens to be obstructed from the entrance of the hepatic veins down to the renal veins, the blood would then flow back by the vertebro-lumbar veins into the plexuses contained within the spinal canal ; through these plexuses, it would ascend to the vertebro-costal veins, from thence to the azygos veins, and through them into the superior vena cava. If all the jugular veins were obliterated, the venous circulation in the head would still continue, and would be carried on through the spinal veins. I have tied the two exter- nal jugular veins in a dog. The animal showed no sign of cerebral congestion : after opening the body, I did not find any increase of size in the small veins which accom- pany the carotid arteries, and which in those animals are naturally very small. In this case, the circulation was evidently carried on by means of the spinal veins. THE LYMPHATIC SYSTEM. Definition, Histmy, and general View of the Lijmvliatic System. — Origin. — Course. — Termi- nation and Structure of the Lymphatic Vessds. — The Lymphatic Glands. — Preparation of the Lymphatic Vessels and Glatids. The term lymphatic vessels is apphed to certain transparent tubes provided with valves, and conveying either lymph or ctiylrf, which pass through small, rounded, glanduliform bodies called lymphatic gland.", and in all cases empty themselves into the venous sys- tem, to which, indeed, they may be said to form an appendage. From their tenuity and transparence, these vessels for a long time escaped the notice of anatomists. The thorsoic duct was discovered by Eustachius in 1565. The lac- teals were discovered in 1622 by Gaspard Asellius, who, by a lucky chance, while seek- ing quite another object, discovered certain vessels filled with chyle. In 1641, Pecquet discovered the receptaculum chyli, and showed that the lacteals entered the thoracic duct, and not the Jiver, as AseUius and all his contemporaries believed. Rudbeck, Thomas Bartholin, and JolyfT dispute the honour of having discovered the lymphatic vessels, properly so called, in contradistinction to the lacteals or chyliferous vessels. Mascagni devoted a great part of his life to the study of the lymphatic system ; and his work, ornamented by magnificent plates, is a monument of science, which should be taken for a model by all who are engaged in anatomical inquiries. Lastly, within the last few years, MM. Fohmann, Lauth, Lippi, Panizza, and Rossi have thrown light upon some most important points in the anatomy of this system. In describing this system of vessels, the lacteals, or the lymphatics containing chyle, have commonly been separated from the lymphatics, properly so called, or the vessels containing lymph. This distinction, however, is not warranted by anatomy, for the two sets of vessels are perfectly identical in structure. The lymphatic system oflers many analogies with the venous system ; but there are also no less remarkable differences between the two. Like the venous system, it consists, as a whole, of afferent or converging vessels, which arise from all parts of the body, and run from the periphery towards the centre. Like the veins, the lymphatics are divided into two sets : a sub-cutaneous set, which, in general, accompanies the superficial veins of the limbs ; and a deep set, which follows the course of the deep arteries and veins ; and, lastly, the lymphatics resemble the veins in being provided with valves. The lymphatics differ from the veins in passing through certain bodies improperly called glands, which, at intervals, intercept their course. They differ from the veins, also, in their arrangement ; for they do not successively unite into larger and larger branches, and these into trunks, but they scarcely increase in size from their origin to their termination ; and, though they communicate with each other by numerous anasto- 612 ANGEIOLOGT. moses, each of them follows, as it were, an independent course : lastly, the blood which circulates in the veins is still, though indirectly, under the influence of the heart's ac- tion, while the onward movement of the lymph is exclusively dependant upon the pari- etes of the vessels. Before proceeding to the special description of the lymphatics, we shall make some general remarks upon the origin, course, and termination of these vessels. Origin of the Lymphatics. The origin of the lymphatics, like every point connected with the minute structure of the tissues, is yet a new subject for inquiry.* It has been said that the lymphatics are continuous with the arteries, so that, accord- ing to this hypothesis, the arteries are continuous with two kinds of vessels, viz., with the lymphatics, which carry off the serum, and with the veins, which transmit the col- oured part of the blood. The continuity of the arteries with the lymphatics has been admitted, in consequence of its having been observed that injections thrown into the arteries passed into the lymphatics. I have frequently seen this in injecting the spleen and the liver ; but it was only when the injection was pushed in with great and contin- ued force : so that it is possible, as thought by Hunter, Monro, and Meckel, that, in these cases, some of the vessels had been ruptured, and the injection extravasated ; or, what is still more probable, there may have been transudation through the pores of the tis- sues. Microscopical observations show most distinctly that the arteries are continuous with the veins ; but there is no fact to demonstrate the continuity of the arteries with the lymphatics. The origin of the lymphatics can be actually shown only upon free surfaces, such as the raucous membranes, the skin, the serous and synovial membranes, and the lining membranes of arteries and veins ; so that, in the actual state of our knowledge, it might be maintained that the lymphatic vessels arise exclusively from all the free surfaces. All the lymphatics arise by a network of such tenuity that, when. injected with mer- cury, the whole surface appears changed into a metallic layer. About eight years since, having introduced at random a tube filled with mercury for injecting the lymphatics into the pituitary membrane in a calf, I was astonished to find the surface covered by a metallic pellicle : I repeated the experiment frequently, and constantly found that the pellicle was not caused by extravasation, for the mercury ran in determinate lines, forming plexuses of different kinds ; also that, to succeed in this experiment, it was necessary to puncture the niembrane very superficially, or the mer- cury would run into the subjacent plexus of veins-, and, lastly, that there was no com- munication between that plexus of veins and the more superficial network, which I sus- pected to consist of lymphatic vessels, for it exactly resembled the network of those vessels in the peritoneum covering the liver. I ascertained that the same structure ex- isted in the skin ; in the lingual, buccal, and vaginal mucous membranes ; in the con- junctiva ; and, lastly, in the uterine mucous membrane of a sow which had lately ht- tered. I showed this lymphatic network of the pituitary membrane in several of my lectures ; and lately, having again examined the subject for the purposes of the present work, I have ascertained that this network exists upon all the free surfaces, that it com- municates with the lymphatics, and that it is possible to inject thosje vessels and the lymphatic glands by introducing the pipe very superficially into the surfaces of these membranes.! I may be permitted to observe, that it is only a few monttts since I be- came acquainted with the splendid work of M. Panizza, of Pavia, upon the lymphatic ves- sels of the testicles (^Osservazioni Antropo-zootomico Fisiologiche, 1830) ; and withM. Foh- mann's last very important memoir {Mdmoire sur Us Vaisseaux Li/mphatiques de la Peau des Membranes Muqueuses, Sercuscs, du Tissu Nerveux, et des Muscles, 1833). Origin of the Lymphatics from the Mucous Membranes. — The villi found upon the mu- cous membrane of the small intestines contain, in their centre, a cavity, named the am- pulla of Lieberkuhn, which I have seen in one instance filled with tuberculous matter. (_Anat. Pathol., \w. ii.) Still, I have never been able to discover any open orifice on the summit of that villus, t Independently of these cavities within the villi, which are proper to the system of lacteal vessels, the thin pellicle of the mucous membranes which can- not be injected from the arteries or veins (vide p. 370), Avhen carefully and very super- ficially punctured by the pipe of a mercurial injecting apparatus, is covered by a metallic pellicle. Panizza and Fohmann have proved that the membrane which covers the glans penis has two sets of lymphatics : a superficial and a deep. M. Fohmann has figured, in some very beautiful plates, the lymphatic network of the mucous membranes of the glans penis, bladder, urethra, trachea, bronchi, oesophagus, stomach, ileum, and colon. This network is so superficial, that the mercury appears almost uncovered ; it does not com- * Do lymphatics commence in all parts of the body ? It is true that absorption is carried on in every part, for absorption is one element of the process of nutrition ; but, as it can be effected by other vessels besides the lymphatics, its occurrence in any part does not necessarily involve the presence of this peculiar class of vessels. t These preparations were made by M. Bonarai, my prosector, under my direction, with extreme skill, and a zeal above all praise. i [For what is known concerning the structure of the villi, see note, p. 369.] ORIGIN OF THE LYMPHATICS. '613 Tnunieate either with the arteries or the veins, but communicates freely with the lym- phatic vessels. It was correctly delineated by Mascagni : according to that anatomist, it covers all the intestinal villi, as with a sheath, and does not appear to have any open- ings on the exterior. Origin of the Lymphatics from the Skin. — Are the openings or pores so evident upon the skin when viewed through a lens, and from which drops of sweat may be seen to exude, intended to serve the purpose both of exudation and absorption '\ or are there rather two distinct kinds of orifices for these two functions 1 or, lastly, are these orifices altogether unconnected with the absorbent vessels'!* If we puncture the skin very superficially, so that the injecting pipe may enter imme- diately below the epidermis, the mercury will be seen to run with great rapidity into some very small vessels, and to form a metallic network, precisely like that already de- scribed as existing in the mucous membranes ; from this layer proceed sub-cutaneous lymphatics, which may be traced filled with mercury as far as the adjacent lymphatic glands, or even beyond them. In order that this experiment may succeed, it is neces- sary that the skin to be injected should be plunged into hot water. I made the following experiment in order to detect, if possible, in the lymphatics of the skin, the mercury absorbed during mercurial frictions. I caused two dogs to be rubbed with mercurial ointment night and morning ; and, that the absorption might be more complete, I enveloped their bodies in a frock made of skin. These animals died in about eight days with gangrene of the gums ; but I could not find in any part the slight- est trace of mercury, although the frictions were continued up to the period of their death. Origin of the Lymphatics from the Serous and Synovial Membranes. — The same results as those above stated are obtained by injecting the serous and synovial membranes. The portion of peritoneum covering the liver is generally chosen for injecting the lym- phatic network of serous membranes, because the tension and adhesion of the perito- neum over the liver renders it more easy to inject. The same results may be obtained by injecting the costal or pulmonary pleura, the tunica vaginahs, or the parietal and vis- ceral portions of the arachnoid. The synovial membranes may be injected with the greatest facihty, either near the cartilages, where they are more tense than in other parts, or upon the ligaments, to which they adhere. Origin of the Lymphatics from the Lining Membrane of the Veins and Arteries. — The lymphatic plexuses upon the lining membrane of veins and arteries have hitherto been only partially displayed, but the analogy between these and serous membranes is so close, that I have no doubt of their identity in this respect. I have, moreover, found the lymphatic vessels of the aorta filled with blood in several cases of degeneration of the coats of that vessel. Origin of the Lymphatics in the Free Cellular Tissue. — In order to exhibit the origin of the lymphatics in this situation, I injected coloured liquids, such as ink, into the sub- cutaneous and inter-muscular cellular tissue in several animals, and I found the lym- phatic vessels and the corresponding lymphatic glands of a jet-black colour. I made a great number of experiments to induce absorption of mercury, by injecting it either into the cellular tissue, or into a serous cavity ; but the metallic mercury always acted like a foreign body, the mechanical effect of which produced more or less inflammation, but it was never absorbed. I have found pus in both the superficial and deep lymphatics, and in the lymphatic glands of the groin, after phlegmonous erysipelas and acute abscesses of the leg ; but it is not proved that the presence of this pus was the result of absorption. It is more probable that it had been produced by inflammation of the lymphatics themselves. Although it is impossible to demonstrate, anatomically, the presence of lymphatics in the free cellular tissue, it is most probable that that tissue, as well as the serous mem- branes, with which it has so many analogies, is formed by this kind of vessels. Mas- cagni stated that all the white tissues consist of lymphatic vessels, and that the lym- phatic system forms the basis of the whole body. From the preceding observations, it may be stated that, with the exception of the lacteals which open upon the summits of the villi,! all the lymphatic vessels of free sur- faces arise by an exceedingly delicate network ; M. Fohmann believes that all the lym- phatics commence by a network of closed vessels, t I have never been able to discover the lymphatic networks, either in the nervous sub- stance, in muscles, glands, or in the fibrous, cartilaginous, and osseous tissues. * [These pores are the orifices of the ducts of the sudoriferous glands, which are imbedded in the true skin, or the sub-cutaneous cellular membrane, and have no direct connexion with the lymphatics.] t [Whether the lacteals commence in each villus by a network, or by free closed extremities, is not yet de- termined; but they form no pvception to the rule that the absorbent vessels arise by closed extremities, and not by open mouths. See p. 370.] t [These networks are arranged in layers, the most superficial of which is formed by the finest vessels, and has the smallest meshes.] 614 ANGEIOLOGT. Course of the Lymphatics. From the networks above described, the lymphatics themselves arise, and, in all the organs, are divided into a deep and a superficial set. The former set accompany the deep vessels of the organ, while the others follow the superficial veins in such parts of the body as are provided with them. In those organs which are covered with a serous coat, they appear to be contained within the substance of that membrane. The lymphatics run parallel with each other, and communicate pretty frequently by bifurcating, and then joining the neighbouring vessels ; but they do not converge towards each other, nor do they, like the veins, unite successively into a smaller and smaller number of larger and larger branches ; thus, their increase in size is not progressive ; and it might even be said that, throughout their whole course, they undergo no decided increase nor dimi- nution: Their direction is slightly tortuous. (In^^o-. 224 are shown short portions of lymphat- ics of different sizes.) Anastomoses. — We do not find in the lymphatics those numerous and important anas- tomoses which form such characteristic points in the history of the arteries and veins. These vessels present only one kind of anastomosis, which is accomplished in the fol- lowing manner ; A lymphatic, after a certain course, divides into two equal branches, which diverge at a very acute angle ; these two branches anastomose with two other lymphatics, each of which communicates either by bifurcation or directly with the neigh- bouring lymphatic vessel. This explains how, by injecting a single lymphatic, a certain group of these vessels may be filled. Not unfrequently, a lymphatic divides into two branches, which, after a certain distance, again unite. During their course, the lymphatic vessels meet certain small glanduliform bodies, the conglobate glands of the ancients, but which are also called lymphatic ganglia, on account of the analogy pointed out by Soemmerring between them and the ganglia of nerves ; the lymphatic glands form centres, to which a number of lymphatic vessels proceed, and are lost in them for a time, but from which they afterward emerge. The name of afferent lymphatics (vasa afferentia, a a a, fig. 225) is applied to those which enter a gland, and those which emerge from it are called efferent lymphatics (vasa efferentia, h b). Do all the lymphatics necessarily traverse one or more of these glands 1 Mascagni has successfully maintained the affirmative in opposition to Hewson and others, who as- sert that they have seen lymphatics entering directly into the thoracic duct. Mascagni states that he invariably found that these vessels passed through one or more glands. As to the argument derived from the absence of dropsy in cases of obstruction in the lymphatic glands, Mascagni explains this by the frequent anastomoses of the lymphatic vessels, the result of which is, that they communicate with several series of glands, some of which are situated at very great distances. The most numerous anastomoses of the lymphatics take place within tlie lymphatic glands ; thus, if we inject the afferent vessels of a lymphatic gland, the mercury escapes by its efferent vessels. In injecting a gland, it frequently happens that the mercury passes not only into the efferent, but also into some of the afferent vessels. Size of the Lymphatics. — The lymphatics are generally so small as to escape the no- tice of the observer ; but they may become enlarged to a remarkable degree. Thus, I have seen the lymphatics of the groin and of the uterus as large as the thumb. An attempt has been made to draw some comparison between the total capacities of the lymphatic, venous, and arterial systems ; but all that has been said respecting this is founded upon no positive data. I would, moreover, observe, that in all probabihty we are acquainted with but a portion of the lymphatic system. Termination of the Lymphatics. According to the most generally received opinion, all the lymphatics terminate in two trunks, the thoracic duct and the great right lymphatic duct ; tlie latter vessel receives the lymph from the right upper extremity, and from the right half of the head, neck, and tho- rax ; the lymphatic vessels of all the other parts of the body end in the thoracic duct ; the lymphatic vessels enter successively into these two trunks, as the plumes of a feath- er are attached to its shaft. The two trunks themselves end as follows ; the thoracic duct enters the left sub-clavian vein, at the junction of that vein with the internal jugu- lar ; the great right lymphatic duct terminates in the right sub-clavian vein ; hence it is that the lymphatic system may be regarded as an appendage of the venous system. Are the thoracic and the great right lymphatic ducts, notwithstanding their small size, the only terminations of the lymphatic system 1 With this question may be connected another : Are the lymphatics the exclusive agents of absorption, or do they share this function with the veins ! Mascagni appeared to have established, beyond dispute, that absorption was performed by the lymphatics to the exclusion of the veins ; when Magendie* and Delille in France, * It is established, says M. Magendie, that the lacteals absorb the chyle, and that the intestinal veins ab- TERMINATION OF THE LYMPHATICS. G15 Tiedemann and Gmelin in Germany, and Flandrin and Ennmert in England, relying upon some ingenious experiments, again attributed a power of absorption to the veins, and hence led other anatomists to undertake still farther researclies. The inquiry was soon entered upon by M. Fohmann in 1820 and 1821, by M. Lauth in 1824, and by M. Lippi in 1825, all of whom again referred the phenomena of absorption exclusively to the lymphatics, and supported that opinion both by arguments and facts. MM. Fohmann and Lauth admit two other modes of termination of the lymphatic sys- tem in the veins besides the one already indicated : first, a direct termination of the lymphatic radicles in the radicles of the veins, which is supposed to occur in the sub- stance of organs ; and, secondly, a communication between the lymphatics and veins within the lymphatic glands. This opinion, which seems reconcilable with the fact that the area of the thoracic and right lymphatic ducts is very small as compared with that of all the lymphatic vessels, appears, a priori, to be exceedingly probable. But an anatomical fact must be shown anatomically before it can be admitted. Now there is no proof of the communication of the lymphatic and venous radicles. M. Foh- mann relies upon certain more or less ingenious inductions, but not upon direct ana- tomical facts. I am, therefore, still compelled to doubt the existence of these commu- nications, and to class them with the vasa serosa, or serous veins of Haller. Again, a communication between the lymphatics and the veins in the substance of the lymphatic glands had been conjectured by many anatomists ; the elder Meckel had seen mercury, when thrown into the lumbar lymphatics, pass into the abdominal veins ; but this fact was attributed to rupture in the interior of the glands. — (Hewson, Cruickshank.) This apparent communication had also frequently been observed by Mascagni, and was attributed by him to rupture. M. Fohmann urges in reply, that this communication takes place under too shght a pressure to be referred to rupture, that actual extravasations may be easily recognised, and that the mercury is then infiltrated into the cellular tissue with much greater facility than it can enter the veins. " Why," he asks, " supposing the existence of rupture, does the mercury never pass from the lymphatics into the arteries'!" He also adduces in support of his opinion a considerable number of facts, which show that injections thrown into the lymphatic glands sometimes escape by the lymphatics alone, sometimes by the veins alone, and sometimes by both the lymphatics and the veins. He states that, having emptied the veins passing out from a mesenteric gland in a horse which had been killed while digestion was going on, and having replaced the intestines in the ab- domen, he found some streaks of chyle in the veins. Lastly, he has seen, in birds, the renal lymphatic vessels, which represent the lymphatic glands in those animals, opening directly into the renal and sacral veins. M. Lauth has repeated these experiments, and obtained the same results. But, however imposing the authority of the authors just ci- ted may be, I must confess that I am far from being convinced, and that the facts stated by them do not appear to me to be conclusive. I have made a great number of injec- tions of lymphatics, and in by far the greater number of cases the mercury passed from the atferent into the elTerent lymphatic vessels, and not at all into the veins. In some cases, it passed from the glands into the veins ; but it appeared to me that the glands had then undergone a change in their texture, more particularly a red softening. It does not seem to me, then, to be shown that there is any direct communication be- tween the lymphatics and the veins within the substance of the lymphatic glands. Lippi (of Florence) denies the communication of thelymphatics with the veins within the lymphatic glands ; but believes that, besides the terminations of the lymphatics in the venous system through the thoracic duct and the great right lymphatic trunk, there are a great number of direct communications between the lymphatics and the vena por- tae, the internal pudic and the renal veins, and the vena cava ascendens and vena azygos. Several anatomists, indeed, had already met with lymphatic vessels opening directly into the venous system ; among whom were Waloeus, Wepfer, Abraham Kaw, Heben- streit, the elder Meckel, Galdani, and Vrolyk ; but the isolated facts recorded by them were regarded by Haller, Mascagni, and Soemmering as anomahes, or as the results of rupture. The memoir pubUshed by Lippi excited new investigations on all sides. I was the more inclined to subscribe to the opinions of that observer, because, in 1825, I had most distinctly seen a large lymphatic trunk opening directly into the external iliac vein ; be- cause it appeared to me rational to admit that the communications between the lymphatic and venous systems would not be restricted to the internal jugular and sub-clavian veins ; because the communications supposed to exist by Fohmann and Lauth had not been de- monstrated ; because ligature of the thoracic duct does not prove fatal to all animals subjected to that experiment, even when the duct is single ; and, lastly, because the thoracic duct has been found obliterated in many individuals. There seemed, besides, a difficulty in admitting that the thoracic and right lymphatic ducts formed the termination sorb other substances. It is shown that the veins are the absorbing- agents in other parts of the body, but it is not shown that the lymphatics absorb. Some authors have stated that the veins absorb only when the lym- phatic system is diseased. 616 ANGEIOLOGY. of the whole of the lymphatic vessels. It appeared, moreover, at variance with the gen- eral laws of the animal economy to suppose that two sets of organs should be devoted to the same functions ; fbr, if the veins absorb, the lymphatic system would seem to have no special use. Nevertheless, truth compels me to state that, after the most minute and frequent re- searches which I have been able to make, I have not obtained a single result confirma- tory of the statements of M. Lippi ; and that, with his plates before me, I have searched for the communications in all the points which he has indicated, and have never found any. I am, therefore, obliged to conclude, with MM. Rossi, Fohmann, and others, that the vessels which M. Lippi has described as lymphatics opening into different parts of the venous system are nothing more than veins. Structure of the Lymphatics. The lymphatics, as well as the veins, have two coats. This structure can be readily shown in the thoracic duct of the human subject, and still better in that of the horse : the existence of these two coats may also be shown by a method suggested by Cruickshank, which consists in turning the thoracic duct iaside out, and forcibly introducing a tube into it ; the lining membrane, which is then on the outside, being less extensible than the external coat, becomes lacerated. The external coat is considered to be fibrous by some, and muscular by others. Shel- don says that he has distinctly seen muscular fibres arranged circularly around the tho- racic duct of the horse. It appears to me that this external coat resembles the dartoid tissue, like the outer coat of the veins. It is not uninteresting to remark, that the outer surface of the lymphatics is often covered by a thin layer of fat, which has deceived sev- eral anatomists. The internal coat of the lymphatic vessels appears to be of a serous nature, like that of the veins. Some arterial and venous twigs ramify in their parietes ; but no nerves have yet been traced into them. Minute lymphatics probably arise from the coats of the larger ones. Mascagni believes that their lining membrane is entirely lymphatic. Notwithstanding their excessive tenuity, the lymphatics are tolerably strong ; less so, however, than is generally stated, for they are often lacerated by the weight of a small column of mercury. They do not appear to me to be stronger than the veins. They are much less extensible. When the thoracic duct, or any other lymphatic vessel, is punc- tured, it inunediately collapses, and forces out its fluid contents sometimes in a jet. Some admit the existence of muscular contractility in them. The vermicular motion caused by contraction of their external coat is sufficient to explain the above-named fact.* The lymphatics are much more abundantly supplied with valves than the veins. The Fig. 224. valves (a a, fig. 224) are parabolic, and are arranged in pairs ; they have an adherent border turned towards the commencement, and a free border towards the termination of the vessel ; they are generally sit- uated at very short intervals apart, as is shown by the knotted ap- pearance of the vessels (see fig. 224), and occasionally they present a circular or annular arrangement, from which they have been re- garded as true sphincters. In general, these valves are strong enough to prevent the retrograde course of the lymph, and, consequently, of injections also. Never- theless, Hunter inflated all the lacteals from the thoracic duct ; Hal- ler filled all the lymphatics of the lung from the upper part of the same canal, and Marchettis says that he has injected the whole of the lym- phatics from the reservoir of Pecquet. The valves are extremely numerous in the lymphatics ; they have sometimes appeared to me to be wanting in the thoracic duct. Like those of the veins, the valves of the lymphatic vessels appear to be formed by a fold of the internal membrane. The Lymphatic Glands. Sylvius was the first to distinguish the lymphatic glands under the term conglobate glands, from the glands properly so called, which he named conglomerate. Chaussier called these little bodies lymphatic ganglia, following Soemmering, who first pointed out the analogy between them and the venous ganglia. The lymphatic glands are situated along the course of the lymphatic vessels, in refer- ence to which they may be regarded as centres in which a certain number of the ves- sels open ; those of the extremities are chiefly found at the upper part of the limbs on the aspect of flexion ; those of the thorax, the abdomen, the head, and the neck are pla- ced along the vertebral column and the great vessels ; they are found also in the sub- stance of the mesentery, in the mediastina, at the roots of the lungs, &c. * [The lacteal vessels have been seen to undergo a sloio contractility on exposure to air, or to the action of any other stimulus ; but there is no evidence of the muscularity of any part of the lymphatic system of mam- malia. In certain reptilia and amphibia there are pulsating muscular sacs connected with the lymphatic sys- tem, which are called It/mphatic hearts.] PREPARATION OF THE LYMPHATIC VESSELS AND GLANDS. 617 Their size varies from that of a millet seed to that of a large filbert. The smallest are situated in the epiploon, the largest at the roots of the lungs. They are often greatly enlarged by disease. They are generally of a reddish-gray colour, excepting at the root of the lungs, when they are black. Their form is irregularly spheroidal ; and they have been distinctly shown by Malpighi to have a cellular structure.* If we examine with a lens a lymphatic gland distended with fluid, we observe that it contains cells ; the same fact is clearly demonstrated by injecting it with mercury, which shows, moreover, that the cells communicate freely with each other. It is, nevertheless, doubtful whether all the cells communicate. The researches which I have made upon this subject appear to show that each lymphatic vessel is connected with a distinct portion of the lymphatic gland ; and diseases of the glands establish the same fact, by attacking one part only of a gland, the rest continuing unaffected. Several lymphatic vessels enter each gland, and several emerge from it. Each affer- ent vessel (ffl a a, Jig. 225), as it reaches the circumference of the gland, divides into a considerable number of branches, which diverge and run for a short distance upon the surface of the gland, and then dip into its substance. t The efferent lymphatics {b b) commence in precisely the same manner as the afferent vessels terminate. The study of these vessels in the larger animals appears calcula- ted to clear up all doubts as to the structure of the lymphatic glands. Abernethy having injected the mesenteric arteries and veins of a whale, saw the fluid run into pouches about the size of an orange ; he then injected mercury into the lacteals, and found that it flowed into the same cavities ; he therefore concluded that the arteries, veins, and lacteals all opened into the same cavities. This fact ap- pears to confirm the observations quoted by MM. Fohmann and Lauth, relative to the conununications of the lymphatics with the veins within the substance of the glands ; but the objections already urged against those observations will apply to this one also. The lymphatic glands are enclosed in a fibrous membrane ; I have in vain attempted to find the fleshy coat described by Malpighi, and which he imagined sent prolongations into the substance of these glands. The lymphatic glands are supplied with very large arteries for their size, and they give off still larger veins : a proper tissue (d) appears to enter into their composition. The lymphatic glands may be said to consist essentially of an inextricable interlace- ment of lymphatic vessels, their structure having some analogy to that of the corpus cavernosum penis, and to that of the spleen. This opinion is confirmed by reference to the anatomy of birds, in which lymphatic glands exist only in the neck, their place being supplied by plexuses in all other parts. Preparation of the Lymphatic Vessels and Glands. I have already said, that in order to inject the network of lymphatics, the pipe should be very superficially introduced into the free cutaneous, serous, or mucous surfaces. When the injection is successful, the mercury passes from this network into the vessels which emerge from it, reaches as far as the lymphatic glands, and even penetrates through several series of them. The great number and peculiar arrangement of the valves prevents the injection of the lymphatics from the centre towards the extremities ; I have attempted to do this several times, without success, by introducing the tube into the thoracic duct. From the small caliber of the lymphatics, it is necessary to use a capillary tube for these injections. Mercury, notwithstanding the inconvenience of its fluidity, and in- capability of being made solid, is the most convenient material for the purpose ; the weight of a column of mercury about fifteen or eighteen inches in height affords suffi- cient power for the injection. Anel's syringe is well adapted for injecting the thoracic duct, which may be filled with a solution of isinglass, or, still better, with milk, which be- comes coagulated by the alcohol. The best apparatus for injecting the lymphatics is a glass cylinder, to the lower end of which is adapted a flexible tube, which is terminated by a metal pipe, provided with a stopcock, and supporting a capillary tube of glass, which is better than one made of steel or platinum, like those generally used in Germany. A ring is attached to the upper end of the glass tube, by means of which the apparatus may be suspended : this greatly facilitates the employment of the apparatus. In order to inject the lymphatics, one of these vessels should be exposed at a greater or less distance from the centre ; for example, in the lower extremity, upon either the internal or external malleolus, or, what is still better, over the metatarso-phalangal artic- ulations, in the way practised by Mascagni ; the vessel must then be punctured, and the tube introduced into its interior ; the stopcock is then opened, and the mercury runs * See note, infra. t [Within the gland the lymphatics form a dense network (c) ; when the vessels of which this network is composed are distended, they give the cellular appearance to a sectioa of the gland noticed by Malpighi, Cruickshank, d in front of the sacrum, pass through other lymphatic glands, and arrive at the brim of the pelvis. At this point, the lymphatics of the right and left sides unite together. These vessels pass through one or several series of lumbar lymphatic glands, and at last open into the thoracic duct. This collection of lymphatic vessels and glands forms the internal and external iliac lymphatic plexuses. The inter- nal ihac lymphatic plexus is placed in the cavity of the pelvis, and surrounds the inter- nal iliac vessels : the external iliac lymphatic plexus is situated along the vessels of that name. All the lymphatics of the lower extremities, after having passed through a greater or less number of glands, open at last into these lumbar glands, so that the vessels and glands together may be said to form an uninterrupted chain. Thus, passing from plex- us to plexus, and from gland to gland, the lymphatics of even the most distant parts ar- rive, at length, at the thoracic duct. The lateral lumbar lymphatic glands, viz., those which occupy the spaces between the transverse processes of the lumbar vertebrae, receive the lumbar l)Tnphatics, properly so called, which correspond to the bloodvessels of that name. From these glands, commu- nicating vessels pass to the aortic lumbar glands. The collection of lymphatic vessels and glands occupying the lumbar region is called the lumbar lymphatic plexus. The following lymphatic vessels also enter directly into the lumbar glands : the lymphatics of the testicles in the male ; the lymphatics of the ovaries and Fallopion tubes, and also of the body and upper part of the neck of the uterus, in the female ; and the lymphatics of the kidneys in both sexes. The Lymphatics of the Testicle. — It has been already stated that the lymphatics of the covering of the testicle enter the superficial inguinal glands ; those which belong to the gland itself are divided into the sxiperficial and deep. The superficial lymphatics may be injected with the greatest facility by puncturing the serous membrane covering the tu- nica albuginea ; the tunica vaginalis will then appear as if covered with a coat of silver. (See the beautiful plates of Panizza.) These superficial vessels have numerous commu- nications with the deep-seated lymphatics, so that both sets are injected at the same time. All the l)Tnphatics from the epididymus and the body of the testicle, which are very numerous and large, ascend with and assist in forming the spermatic cord, pass through the inguinal canal, follow the course of the spermatic vessels, and enter the lumbar lymphatic glands. The Lymphatics of the Uterus. — Having, in diseases of the uterus incidental to the pu- erperal state, frequently detected pus in the lymphatics of the uterus (vide Anat. Path., liv. xiii., pi. 1, 2, 3), I have been able to trace the exact distribution of these vessels, and would divide them into superficial and deep. The superficial lymphatics are situated im- mediately under the peritoneum ; the deep lymphatics form several successive layers, which occupy different planes within the substance of the uterus. The lymphatics near the neck of this organ enter the pelvic and sacral Ijmiphatic glands. A certain number of the uterine lymphatics enter a lymphatic gland situated at the internal orifice of the obturator canal. All the uterine lymphatics, excepting those near the neck of that organ, pass towards the sides and upper border of the uterus ; some run within the substance of the broad lig- aments, and they aU reach the upper or tubal angles of the viscus. They are joined by the lymphatics of the ovaries, broad ligaments, and Fallopian tubes, and then ascend in front of the corresponding ovarian artery and veins. Having arrived in front of the lov/er part of the kidneys, they incline towards the middle line, and enter the glands which are situated in front of the vena cava and aorta. Without having witnessed it, it is impos- sible to form any idea of the enormous size which the uterine lymphatics may acquire during pregnancy : several of these vessels, when filled with pus, become so dilated that one would at first sight believe that an abscess had been formed. The Lymphatics of the Kidneys and Supra-renal Capsules. — These are divided into super- ficial and deep. The superficial lymphatics have never been injected directly ; but if a fine injection be thrown into the renal arteries and veins, the injection, freed from col- THE LYMPHATICS OF TiJE LIVER. 623 During matter', passes into the lymphatics. This was the only way in which Mascagni could inject the superficial lymphatics of the kidney, which he has represented m hi§ beautiful plates. The deep lymphatics, which are very numerous, pass out of the fissure of the kidney, and enter the glands in front of and behind the aorta and vena cava. The lymphatics of the supra-renal capsules are remarkable for their size and number ; they unite with those of the kidneys, and terminate in the same manner. The Lymphatic System of the Livee. Preparation. — Of all the lymphatic vessels, those of the liver are the most easily de- monstrated. Before they are injected, they may be rendered more apparent, and even be fiUed, by throwing water either into the hepatic arteries, the vena portae, the hepatic veins, or the hepatic ducts. In order to inject them, it is sufficient to make a superfi- cial puncture in any part of the peritoneum covering the liver ; but it is most convenient to operate upon one of the lymphatic trunks which run upon the surface of that organ. It is of importance that the tube should be introduced between the peritoneal covermg and the fibrous coat, without perforating the latter. It is sufficient to inject from a sin- gle vessel in order to fill all the others. The mercury generally runs as far as the near- est lymphatic gland, the resistance in which causes the fluid to flow back into the sur- rounding branches, even as far as their most delicate ramifications, so that, in successful injections, the whole surface of the liver has a silvery aspect ; the possibility of injecting the lymphatics of the liver, from the trunks towards the branches, nmst lead us to sup- pose that there are fewer valves in them than in the lymphatics of other parts of the body. The Lymphatic Glands of the Liver. ' ' These are situated along the hepatic vessels, behind the pylorus, and are continuous with the coeliac lymphatic glands. I have seen them of a jet-black colour ; a liquid may be expressed from them, resembling that contained in the bronchial lymphatic glands. • The Lymphatic Vessels of the Live?'. The IjTnphatics of the liver may be divided into the superficial and the deep. The Superficial Lymphatics. — These are subdivided into those of the convex and those of the concave surface. The lymphatics of the convex surface of the liver consist of a certain number of trunks, some of which belong to the right and the others to the left lobe. Some of them run from behind forward, others from before backward, towards the posterior border of the organ. The first set, or those which run from behind forward, reach the suspensory ligament of the liver, and unite into several trunks, some of which perforate the diaphragm, enter the anterior mediastinum, behind the xiphoid cartilage, and terminate in the mediastinal lymphatic glands ; while others are reflected over the anterior margin of the liver, to gain the longitudinal fissure, along which they run as far as the gastro-hepatic omentum, by which they are conducted to the lymphatic glands placed round the pylorus, to those around the cardiac orifice of the stomach, and to those which lie along the lesser curva- ture of that organ, and near the lobulus Spigelii. The second set of the lymphatics of the convex surface of the liver, or those which run from before backward, having reached the posterior border of the liver, divide into three distinct groups of vessels : those on the left enter the substance of the left triangu- lar hgament of the liver ; those on the right pass into the right triangular ligament ; while the remainder, which occupy the middle, enter the substance of the coronary ligament. Those lymphatics of the second set that do not perforate the diaphragm enter the lymphatic glands along the vena cava, and from thence reach the thoracic duct. Some of them run along the lower border of the twelfth rib, and open into the glands situated near its posterior extremity, and into another gland which rests upon the twelfth dorsal vertebra. Those lymphatics of the second set which do perforate the diaphragm pass through its crura, and proceed, some to the intercostal lymphatic glands, or into those which he along the vena azygos and the aorta, and thence into the thoracic duct ; while others enter that duct directly. I have seen a very large lymphatic trunk open directly into the thoracic duct, opposite the fifth dorsal vertebra. Mascagni pointed out some lym- phatic vessels which, after having perforated the fleshy fibres of the diaphragm, ran be- tween the pleura and that muscle, re-entered the abdomen through the aortic opening in the diaphragm, and then passed into the glands surrounding the aorta and vena cava, or entered the thoracic duct at no great distance from the reservoir of Pecquet, without passing through any lymphatic glands. The lymphatics of the concave surface of the liver consist of several trunks, which are all directed from before backward, and are divided into three sets : those which are situ- ated to the right side of the gall-bladder ; those which surround it ; and those v/hich are situated to its left side. 624 ANGEIOLOGY. Those situated on the right of the gall-bladder partly enter the lumbar glands, and partly terminate in the glands around the vena cava and aorta. Those which surround the gall-bladder form a remarkable plexus, which accompanies the hepatic vessels, and terminates in the lymphatic glands which lie along those ves- sels, and in the glands situated in the substance of the gastro-hepatic omentum. Among this set of lymphatics I would point out one considerable trunk, which runs in the cellu- lar tissue connecting the gall-bladder to the liver. The lymphatic trunks on the left of the gall-bladder end in the oesophageal lymphatic glands, and in those which occupy the lesser curvature of the stomach. The Deep-seated Lymphatics of the Liver. — These vessels accompany the hepatic ducts and the vena portae, and are contained with them in the capsule of Glisson ; they emerge from the transverse fissure of the liver, penetrate the substance of the gastro-hepatic omentum, and enter the lymphatic glands situated along the lesser curvature of the stomach and behind the pancreas. Those lymphatics of the liver which accompany the hepatic artery and duct and the vena portae are extremely large, and are often filled with yellow lymph : they are some- times found distended with gas in cases of commencing putrefaction. They were known long before the lacteals ; indeed, they were the first lymphatic vessels that were dis- covered. The Lymphatic System or the Stomach, SpLEE^, and Pancreas. The Lymphatic Glands of the Stomachy Spleen^ and Pancreas. Those of the stomach accompany the coronary vessels along the great and lesser cur- vatures of the stomach ; some of them are situated within the gastro-splenic omentum, and a great number surround the pyloric and cardiac orifices. The lymphatic glands of the spleen occupy the hilus of that organ. The pancreatic lymphatic glands are ranged along the splenic artery, and, consequently, along the upper border of the pancreas ; several of them are grouped around the cceliac axis. They receive a very great number of lymphatic vessels. The Lymphatic Vessels of the Stomach, Spleen, and Pancreas. ■ The lymphatic vessels of the stomach are divided into the superficial and deep. The superficial lymphatics form a network beneath the peritoneum ; the deep lym- phatics arise from an equally complex network situated in the mucous membrane. They follow different directions : a great number of them pass to the great curvature, and enter the glands situated there ; others proceed to the lesser curvature, and pass through the glands in that situation. Several run towards the spleen, and enter the splenic lymphat- ic glands ; and, lastly, others go to the lymphatic glands around the pylorus. It has been stated that the lymphatics of the stomach have been seen filled with chyle : this is at least doubtful. The Lymphatics of the Spleen. — The superficial lymphatics of this organ cannot be seen unless the splenic bloodvessels have been previously injected with size injection : the size freed from the colouring matter will pass into them. I have seen tallow, thrown into either the arteries or veins of the spleen, pass into the superficial lymphatics. It is true that the injection was made forcibly, and kept up for some time. The deep lym- phatics of the spleen are not known. The proper lymphatics oiihe pancreas are little known. The Lymphatic System of the Intestines. The Lymphatic Glands of the Intestines. The lymphatic glands of the small intestine, or the mesenteric glands, are extremely nu- merous. Several anatomists, who have had the patience to count them, have arrived at very different results, partly on account of individual varieties, and partly because sev- eral, having chosen tuberculated subjects for the purpose, have mistaken the tubercles for lymphatic glands. The mesenteric glands are situated between the folds of the mesentery, in the meshes of the network formed by the arteries and veins. Those which are nearest to the intestine are found in the intervals observed between the vessels of the mesentery close to the in- testine. Those which are most distant from the intestine are situated near the adherent border of the mesentery, along the trunk of the superior mesenteric artery. The largest of these glands are found near the origin and termination of that artery. Thus we find, below, a group of large lymphatic glands, the ileo-colic, opposte the termination of the il- eum in the colon. Another cluster, named the duodenal, is situated above, in front of the du- odenum : they are extremely large. We generally find one larger than the rest : it is repre- sented in the oldest works on anatomy, and has been sometimes mistaken for the pancreas. The group of ileo-colic lymphatic glands is remarkable for frequently becoming inflamed in follicular enteritis. The lymphatic glands of the great intestine, or meso-colic glands, much less numerous than those of the mesentery, generally lie along the vascular arches formed by the colic arteries and veins : several of them are situated near the posterior border of the intes- THE LYMPHATICS OF THE INTESTINES, ETC. 025 liKe-, and some are even found upon the intestine, accompanying those bloodvessels which run for a short distance beneath the peritoneal coat, and then penetrate the mus- cular coat. The meso-colic lymphatic glands are not nearly so numerous along the transverse colon as along either the ascending or descending colon. Those situated in the transverse meso-colon form an uninterrupted chain with the mesenteric glands. The Lymphatic Vessels of the Intestines. The Lymphatics of the Small Intestine. — These vessels are divided into two sets, the lymphatics, properly so called, and the lacteals. The lymphatics, properly so called, like those of the stomach and great intestine, arise from two sets of networks ; one in the serous, the other in the mucous coats. The ves- sels which pass out from these networks have a remarkable character, which was well described by Mascagni ; instead of passing directly into the mesentery, they first proceed for a short distance along the intestine, and then curve and enter the mesenteric glands. The lacteah, or lacteal vessels of the small intestine, can be easily seen in an animal that has been killed while the absorption of chyle is going on in the intestine ; and they have occasionally been observed in the human subject, in cases of accidental death. They then appear as white, nodulated, and slightly flexuous lines, which communicate occa- sionally with each other, pass from one mesenteric gland to another, enter the lymphat- ic glands situated in front of the aorta and vena cava, and terminate in the thoracic duct by a variable number of trunks ; the lymphatic plexuses of the left side pass behind the aorta. The lacteals commence, according to Lieberkiihn, upon the summit of each of the villi of the small intestines, run down to its base, and then enter at right angles into the sub- mucous lacteal vessels, which invariably perforate the other coats of the intestine, on its concave border. This arrangement was very evident in a case in which the lacteals were filled with tuberculous matter. — (Anath. Pathol. ,\iy. ii., pi. 2.)* The Lymphatics of the Great Intestine. — We m.ay, with Mascagni, divide these lymphatics into two sets, according to the glands in which they terminate, viz., those of the ccecum and of the ascending and transverse colon, which pass through the meso-colic lymphatic glands, and then terminate in the mesenteric glands ; and those of the descending colon and rectum, which enter the lumbar lymphatic glands together with the lymphatics of the genital organs, and of the lower extremities. The Lymphatic System of the Thorax. The Lymphatic Glands of the Thorax. The thoracic lymphatic glands are divided into those of the parietes of the thorax, those of the mediastinum, and the bronchial or pulmonary glands. The lymphatic glands of the parietes of the thorax are very small, and are thus arranged : the intercostal gland.s are situated on each side of the spine near the costo-vertebral ar- ticulations ; some are placed between the two layers of the intercostal muscles : they are very small, and irregular in number. The siib-sternal or mam.mary glojids are found at the anterior extremity of the intercostal spaces near the internal mammary vessels, and applied along the borders of the sternum ; there is one for each intercostal space. The mediastinal lymphatic glands are divided into those of theposterior mediastinum, which are arranged along the oesophagus and aorta, and form a continuation of the intercostal glands : they have been known to become enlarged and press upon the oesophagus, so as to cause dysphagia ; and into those of the anterior mediastinum, the principal of which lie upon the diaphragm in front of the pericardium, and around the great vessels connected with the base of the heart. The bronchial or pulmonary glands were noticed by the oldest anatomists, and espe- cially by Vesalius, whence the name oi glandulce. Vesalianm, by which they are still known : they are remarkable for their situation, number, size, and colour. They are situated along the bronchi and their first divisions. The largest are generally placed opposite the bifurcation of the trachea. The smallest lie within the substance of the lungs, around the first divisions of the bronchi ; some of them are seen in the inter-lobular fissures. Their number is very considerable. In disease, they may acquire such a size as to compress and narrow the bronchi, and thus prevent the passage of the air through those tubes. In infancy they do not differ in colour from the other lymphatic glands, but they are black in the adult, and especially in the aged. They are also hable to become the seat of depositions of phosphate of lime. Senac considers them to be secreting glands quite distinct from the lymphatic glands. Portal divided them into true glands and lymphatic glands ; but no one has been able to demonstrate the excretory ducts, which, according to Portal, proceed from the lymphat- ic glands upon the trachea. The communications between these and the trachea, ob- served in some cases of disease, are altogether accidental. * See also note, p. 369. 4K 626 ANGEIOLOGY. The Lymphatic Vessels of the Thorax. The lymphatic vessels of the thorax are divided into those of the parietes and those of the organs contained in the thoracic cavity. The Lymphatics of the Thoracic Parietes. — We shall here merely notice the deep-seat- ed lymphatics. They are divided into the intercostal, the sub-sternal or internal mam- mary, and the diaphragmatic. The intercostal lymphatics accompany the arteries and veins of that name ; they re- ceive the lymphatic vessels of the intercostal muscles and costal pleura, run along the grooves of the ribs, pass through the intercostal lymphatic glands, reach the sides of the vertebrae, unite with other lymphatics from the back of the thorax and from the spinal canal, enter the lymphatic glands on the sides of the vertebral column, and are for the most part directed downward to terminate in the thoracic duct. The sub-sternal or interiial mammary lymphatics arise from the supra-umbilical portion of the anterior walls of the abdomen : they pass into the thorax, behind the ensiform cartilage, and form two bundles, which run upon the sides of the sternum, unite with the anterior intercostal and external mammary lymphatics, and enter the internal mammary lymphatic glands. From the lowest of these glands other lymphatics proceed, and as- cend in succession from one gland to another up to the inferior cervical lymphatic glands ; on the left side they enter the thoracic duct, and on the right, the gi-eat lym- phatic trunk. Sometimes, but rarely, the mammary lymphatics open directly into the internal jugular and sub-clavian veins. The lymphatics of the diaphragm for the most part unite with the intercostal and he- patic lymphatics ; the others run forward between the pleura and the ileshy fibres of the diaphragm ; some of them enter the inferior mediastinal glands, and the others, the in- ternal mammary lymphatic glands. The Lymphatics of the Thoracic Viscera. — The lymphatics of the lungs are divided into superficial and deep : the superficial lymphatics may be injected in the same manner as those of the liver ; they form an extremely close network beneath the pleura pulmonalis, and frequently present a number of, as it were, varicose enlargements : these were no- ticed and figured by Mascagni ; and the frequency of their occurrence led him to inquire whether such was not the natural structure of lymphatics. Some of the vessels which proceed from this network run in the inter-lobular fissures, and enter the lymphatic glands situated at the bottom of these fissures ; while the others reach the internal surface of the lung, and terminate in the bronchial glands. These superficial lymphatics also communicate with the deep lymphatics in the cel- lular intervals between the lobules of the lung. The deep lymphatics of the lung are very numerous : the manner in which they com- mence in the lobules is not well known : they run in the inter-lobular cellular tissue, and all proceed towards the root of the lung, in order to terminate in the glands situated around the bronchi, and in several which lie along the oesophagus. It is doubtful wheth- er a single pulmonary lymphatic vessel enters directly into another lyiriphatic gland without first going through a bronchial gland. Other lymphatics proceed from these bronchial glands ; some of which pass in front of the trachea to enter the tracheal lymphatic glands, while the others proceed to the lymphatic glands upon the oesophagus. On the left side both sets enter the thoracic duct, at a short distance before its termination ; these are more numerous than those on the right side, which enter the right lymphatic duct. Some of them terminate in the thoracic duct, before it emerges from the thorax; several of these vessels are also seen to enter the internal jugular and sub-clavian veins. I should observe that, in consequence of the above-mentioned anatomical fact, the cervical lymphatic glands sometimes become enlarged in diseases of the lungs. The Lymphatics of the Heart, Pericardium, and Thymus. — The lymphatics of the heart are divided into superficial and deep ; the superficial vessels commence by a sub-serous network, and, for the most part, run along the right border of that organ ; the deep lym- phatics arise from the internal membrane of the heart, in which I have never been able to inject a perfect network : they all accompany the coronary vessels, and all pass out of the pericardium ; some of them unite with the lymphatics of the lung ; the others en- ter the glands in front of the arch of the aorta and pulmonary artery, and from thence pass to the thoracic duct. The lymphatics of the pericardium and thymus enter the internal mammary, anterior mediastinal, and bronchial lymphatic glands. The Lymphatic System of the Head. The Lymphatic Glands of the Head. There are more lymphatic glands in the face than in the cranium. All the lymphatic glands of the cranium are found upon its posterior region : some of them are situated behhid the ear, along the attachments of the occipito-frontalis ; several are placed beneath the upper end of the sterno-mastoid ; they are very small, and often THE LYMPHATICS OF THE HEAD, ETC. 627 escape notice in a hasty dissection : they become very distinct in diseases of the scalp. Are there any deep lymjihatics of the cranium 1 The pituitary body, the pineal gland, and the white bodies known as the glanduls Pacchioni, have been regarded as belonging to the lymphatic system. Some authors have even considered the tubercles, so fre- quently found in the brains of infants, and which are evidently accidental formations, to be of the same nature. Certain bodies found in the carotid canal, and which are evi- dently enlargements of the ganglionic nerves, have also been described as lymphatic glands ; but this opinion is now completely rejected. Of the lymphatic glands of thi: face, the largest occupy the base of the lower jaw, and are called the sub-maxillary lymphatic glands : several of them are situated upon the outer surface of the maxillary bone, along the facial vessels, in front of the masseter muscle. We find, also, in the face, the parotid lymphatic glands, some of which are superficial and others deep, the latter being situated in the substance of the gland : we find some, also, between this gland and the masseter : lastly, there are the zygomatic glands, situ- ated under the zygoma, and the buccinator lymphatic glands. The Lymphatic Vessels of the Head. These belong either to the cranium or to the /ace. The Lymphatics of the Craniuvi. — The superficial or suh-cxitaneous cranial lymphatics are divided into two sets : the temporal lymphatics, which run along the superficial tem- poral artery, and pass through the parotid lymphatic glands, from which vessels proceed to the glands in the anterior region of the neck ; and the occipital lymphatics, which fol- low the occipital artery, and terminate in the mastoid and the occipital lymphatic glands. The deep lymphatics of the cranium, the lymphatics of the dura mater, or the meningeal lymphatics, accompany the meningeal vessels, escape through the foramen spinale of the sphenoid bone, and enter the jugular lymphatic glands. Ruysch appears to have been the first who noticed lymphatics in the brain ; he has named them vasa pseudo-lymphatica. Mascagni could only show the presence of the su- perficial lymphatics of the brain by injecting coloured size into the carotid arteries. The size freed from the colouring material passed into the lymphatics. The lymphatics of the brain are but little known. M. Fohmann has described and fig- ured a lymphatic plexus situated between the arachnoid and pia mater, and precisely resembling those found in other parts of the body. This network dips into the sulci, and appears to be continued into the substance of the brain, where it is no longer possi- ble to follow it. From this network some small lymphatic trunks proceed, and accom- pany the arteries and veins as far as the foramina, in the base of the cranium, beyond which M. Fohmann was never able to trace them ; so that he inquires whether these vessels do not form an exception to the general rule from their want of connexion with the absorbent system generally, and whether they do not enter directly with the veins upon which they are placed. On the other hand, Mascagni has figured some lymphatics around the internal carotid, within the carotid canal, and also around the vertebral ar- teries and internal jugular vein. The existence of these trunks leads us to suppose that there must be cerebral lymphatics. M. Fohmann has also found lymphatics in the choroid plexuses of the lateral ventri- cles of the brain : these vessels were remarkably dilated, so as to present ampullae. The Lymphatic Vessels of the Face. — These are divided into the superficial and deep. The superficial lymphatics are much more numerous than those of the cranium. They commence upon all parts of the face ; those from the frontal region accompany the fron- tal vessels : the others accompany the adjacent bloodvessels ; several of them pass through the buccinator glands, and they all finally enter the submaxillary lymphatic glands. The lymphatics of the face are to be injected by introducing the pipe into the plexus contained in the skin. The deep lymphatics of the face accompany the bloodvessel. They are divided into tliose of the temporal fossae, those of the zygomatic awd ptery go-maxillary fossa?, and those of the nasal fossae. The lymphatics . of the pharynx, velum palati, mouth, tongue, and larynx, enter the deep parotid and the cervical lymphatic glands. The lym- phatic plexuses of the pituitary membrane, and of the lingual, buccal, and pharyngeal mucous membranes, may be perfectly injected. Indeed, it is only in that way that we can demonstrate the lymphatic vessels which emerge from these difTerent parts. The Lymphatic System of the Cervical Regions The Cervical Lymphatic Glands. The lymphatic glands of the neck are concentrated in the anterior region of the neck. They are divided into the superficial and deep. The superficial lymphatic glands of the neck are found principally along the external jugular vein ; they are therefore situated between the platysma and the sterno-mastoid ; and in the supra-clavicular triangle, that is to say, in the triangular interval between the 628 ANGEIOLOGY. clavicle, the sterno-mastoid, and the trapezius. We also find several very small super- ficial glands between the os hyoides and the thyroid cartilage, and upon the sides of the larynx. The deep lymphatic glands of the neck are very numerous, and form an uninterrupted chain around tlie internal jugular vein and the carotid artery, from the mastoid process to the superior opening of the thorax, in front of the vertebral column, and upon the sides of the pharynx and oesophagus. The tracheal lymphatic glands are also continuous with the deep cervical glands. The cervical glands form a continued series with the facial and sub-maxillary lym- phatic glands on the one hand, and with the lymphatic glands of the thorax and axdla on the other. The Cervical Lymphatic Vessels. The cervical lymphatics consist of those which have passed through the sub-maxillary and facial lymphatic glands, and which afterward traverse the chain of glands along the jugular veins. They are joined by those of the pharynx, oesophagus, larynx, trachea, and thyroid gland. They then proceed from one lymphatic gland to another, and from one plexus to another, down to the lower part of the neck, where they are joined by some lymphatics from the lung, which also pass through some of the cervical glands : they terminate on the left side in the thoracic duct, and on the right side in the right lymphatic duct. The Lymphatic System of the Upper Extremity. The Lymphatic Glands of the Upper Extremity and of the Upper Part of the Trunk. There are generally no lymphatic glands in the hand or forearm, but Meckel found several very small ones along the ulnar and radial bloodvessels. There are two or three which are sub-cutaneous in the front of the bend of the elbow, and one or two above the internal condyle of the humerus, behind the basilic vein ; in the arm we also find a se- ries of small lymphatic glands, which are never numerous, along the inner side of the humeral artery. The axillary lymphatic glands are situated deeply in the axilla, and are very numerous ; some lie along the great vessels, others are scattered through the axilla: they are often of a very large size. The following may be regarded as appendages of the axillary glands : a small sub-cla- vicular gland, situated deeply beneath the costo-coracoid membrane, opposite the trian- gular interval between the pectoralis major and the deltoid, and two or three small glands situated along the attachments of the pectoralis major, as far as the mammary gland. Mascagni has figured a small lymphatic gland near the umbilicus. The Lymphatic Vessels of the Upper Extremity and of the Upper Half of the Trunk. The Lymphatics of the Upper Extremity. — The superficial set of these vessels arise from the skin of the hand, and run parallel to the fingers : they are, for the most part, sit- uated upon the back of the hand ; they cross obliquely over the metacarpal bones, pass over the carpus, and thus reach the forearm. In the forearm they are distributed almost equally upon its anterior and posterior aspects. The anterior lymphatics are collected upon the inner and outer sides of the forearm ; having reached the elbow, some pass in front of the epitrochlea and its muscles ; others in front of the epicondyle. In this place they are re-enforced by the lymphatics from the posterior aspect of the forearm, which are also collected into an outer and inner group. Not unfrequently a certain number of the posterior lymphatics, which arise from the outer side of the l>and and forearm, after ascending almost vertically for some dis- tance, pass obliquely, or <^ross transversely inward, above and below the olecranon, and unite with the inner group. In the arm some of the inner group of lymphatics pass to the lymphatic glands above the epitrochlea ; the others run along the inner border of the biceps muscle and basilic vein, and then pass backward aM upward to reach the axillary glands. The external lymphatics cross 'very obliquely over the anterior aspect of the ann, to terminate, like the preceding, in the axillary glands. One of them has a remarkable course ; it runs along the cephalic vein, gains the cellular interval between the pectoral- is major and the deltoid, dips down over the upper edge of the pectoralis minor and be- low the costo-coracoid membrane, and describes a curve so as to enter the sub-clavicu- lar lymphatic ganglion. The deep lymphatics of the upper ejctremity exactly follow the course of the bloodves- sels ; they often communicate with the superficial lymphatics, and tenninate in the ax- illary glands. I have seen some of the deep lymphatics of the forearm communicate at the bend of the elbow with the superficial lymphatics on the outer part of the back of the arm, and enter the glands above the epitrochlea. THE SKIN. 629 The Lymphatic Vessels of the Upper Half of the Trunk. — We have seen that all the lym- phatics of the sub-umbilical portion of the trunk enter the inguinal glands ; and so all the lymphatic vessels of the supra-umbilical portion terminate in the axilla. The anterior a7id lateral lymphatics pass upward upon the pectoralis major and the ser- ratus magnus, to gain the axilla. The posterior lymphatics are divided into those of the neck and those of the back ; the ^posterior cervical lymphatics descend upon the trapezius and the deltoid, and are reflected over the posterior border of the last-named muscle, in order to reach the cavity of the axilla ; the posterior dorsal lymphatics run in different directions ; some horizontally, the others from below upward, to be reflected into the axilla below the tendons of the la- tissimus dorsi and teres major. NEUROLOGY. Neurology is that part of anatomy which treats of the apparatus of sensation and in- nervation : this apparatus consists of the orgaiis of the senses, of the cerebrospinal axis, or central portion of the nervous system, and of the nerves, or peripheral portion of that system. THE ORGANS OF THE SENSES. The Skin — its External Characters, Structure, and Appendages . — The Tongue considered as the Organ of Taste. — The Organ of Smell — the Nose — the Pituitary Membrane. — The Or- gan of Sight — the Eyebrows— the Eyelids — the Muscles of the Orbit — the Lachrymal Ap- paratus— the Globe of the Eye, its Membranes and Humours — the Vessels and Nerves of the Eye. — The Organ of Hearing — the External Ear — the Middle Ear or Tympanum — the Internal Ear or Labyrinth — the Nerves and Vessels of the Ear. The organs of the senses are certain parts of our bodies which are intended, by means of the sensibility they possess, to establish relations between us and external objects. The organs of the senses, to use a strong figurative expression, are, as it were, the bridges which connect the individual with the world around him. — {MeckeVs Anatomy, by Jourdan, p. 471.) The organs of the senses, being placed between the brain and surrounding objects, have the following characters in common : they occupy the surface of the body ; they communicate with the brain by means of nerves of greater or less size ; and, lastly, each of them has a peculiar structure in harmony with that particular quality of matter, the perception of which it is intended to convey to us. Anatomists generally admit five organs of sense, which we shall name, and then de- scribe in the following order : the skin, or the organ of tact and touch, the organ of taste, the organ of smell, the organ of sight, and the organ of hearing. The Skin. General Remarks on the Skin. The skin, the proper organ of tact and of touch, is a membrane which serves as a cov- ering or integument to the body, and is so accurately moulded upon it as to preserve the form, and yet conceal the inequalities, of its entire surface. It may be regarded as form- ing an external surface or limit, endowed at the same time with sensibility and a power of resistance ; enabhng us by the one to perceive such qualities of bodies as are distin- guishable by the touch, and by the other preserving us, to a certain extent from their ac- tion. It forms, moreover, an exhalant surface, or sudorific organ, by which the system is freed from noxious substances, and also an inhalant surface, by which fluids may be absorbed.* External Characters. " Examined in reference to its external characters, the skin presents an external or free surface, and an internal or adherent surface. The Free Surface. — Upon the free surface of the skin the following objects require at- tention : its folds, or wrinkles, and its furrows ; a peculiar colour, which is subject to * Some ancient authors, Marcus Aurelius Severinus among- others, adhering- closely to the order of super- imposition, which is sometimes called the anatomical order, commenced the description of the human body ■with the skin ; and the same part, though for a very different reason, is described first by M. de Blainville, in his Anatomie Comparee : that celebrated naturalist, carrying out analogical induction to its utmost limits, makes the skin the fundamental organ of the body, connecting ivith it all the organs of the senses, which he regards as analogous to hairs, and names phanera: (a word constructed by M. Blainville in opposition to the term cryptic, hidden, and derived from (pavepai, evident, manifest, apparent). lie considers that the appa- ratus of locomotion is a development of the elastic element of the skm, which becomes endowed with contractili- ty ; the digestive and respiratory organs he regards as modifications of the absorbent apparatus of the skin ; and the organs of secretion and generation as developments of its e.vhalant structure. The circulatory appa- ratus alone is not derived by him immediately from the external integuments ; yet he almost believes that it is an eitcnsioa or prolongation of the meshes of the cutaneous cellular tissue. 630 NEUROLOGY. variety in different races of men, and in different individuals ; certain horny growths, as the nails and hairs, which are appendages of the skin ; and, lastly, numerous orifices for the escape of the cutaneous secretions, some of them being the orifices of the sebaceous follicles, others of the sudorific glands, while others, again, are tlie foramina, or depres- sions through which the hairs protrude. The horny growths of the skin will be noticed presently ; and its colour and orifices, or pores, will be examined under the head of its structure. We shall here make a few remarks upon the different folds or wrinkles fonnd in the surface of the skin : they are of several kinds. Some of them may be termed folds of locomotion ; they are permanent, and are inhe- rent, as it were, in the skin itself, and have distinct relations to the various movements of the body. They are of two kinds : the larger folds are observed around the joints, both on the aspect of flexion, and that of extension ; for example, over the knuckles and in the palms of the hands ; the small folds are found over the whole surface of the skin, which is divided by them into irregular lozenge-shaped intervals ; it is to these folds that the skin owes its extensibility. Other folds, called wrinkles, are produced by the contraction of sub-cutaneous muscles ; such as the transverse wrinkles produced by the action of the occipito-frontalis, the ver- tical wrinkles by that of the corrugatores supercilii, and the radiated folds caused by the contractions of the orbicularis palpebrarum, the orbicularis oris, and the sphincter ani. Th-ese wrinkles, like the contraction of the muscles by which they are produced, are only transitory ; but they become permanent when their causes are frequently repeated. In the same class as these we must include the corrugations of the skin of the scrotum, from contraction of the dartos. The folds or wrinkles resulting from age and from emaciation depend upon the skin be- coming, after more or less distension, too much stretched, and, therefore, too loose to fit closely to the parts beneath. Hence, emaciation in young subjects does not produce the same effects as in the aged ; for in the latter, the wrinkles are caused by the want of elasticity in the skin, and they are more distinct in proportion as that property is lost. In cases of extreme distension, when the skin has been altered in its texture, the wrinkles are more marked, and are permanent ; as, for example, those observed on the abdomen of females after pregnancy, and of either sex after dropsy. Furrows hetivcen the Pa.piUcE. — It is necessary carefully to distinguish from the folds or wrinkles of the skin those more or less regular but slight furrows which exist between the linear ridges or eminences formed by the cutaneous papillae in the palm of the hand and the sole of the foot, and which are also found, though in a less marked degree, in all other parts of the body. Adherent Surface of the Skin. — In mammiferous animals the skin is lined throughout, the gi-eater part of its extent by a layer of muscular fibres, which are intended to act upon it, and constitute the cutaneous muscle or panniculus carnosns ; but in man the only traces of this structure are the platysma myoides and the palmaris brevis. The sub-cutaneous muscles of the human subject are concentrated in the face. It follows, therefore, that, although in animals the passions can be expressed by move- ments of the entire surface of the body, in man their expression is limited to the face. It has been erroneously supposed that the phenomenon termed cutis anserina, or goose- skin, a corrugated condition of the skin, in which the bulbs of the hairs are rendered prominent by being forced outward, depends upon the contraction of a layer of muscular fibres situated beneath the integument. But the most careful examination has demon- strated no muscular fibres there ; we do not even find a dartoid tissue, such as is ob- served wherever there exists a certain kind of active contractility independent of the will. Beneath the skin of the human subject we find a layer of adipose tissue, ■panniculus adiposus ; it varies in thickness, and is contained in the meshes formed by the fibrous lamella;, which extend from the internal surface of the skin, and are then either attached to the investing aponeuroses where the skin is said to be adherent, or become expanded into a very thin aponeurotic membrane, called the fascia superficiaHs, in which case the skin is movable. The quantity of sub-cutaneous adipose tissue, and the fixed or mo- vable condition of the skin, have a constant and necessary relation with the functions of each particular region. Thus, while adipose tissue is very abundant in the palm of the hand and sole of the foot, where we always find a cushion of fat, it is never present in the skin of the eyelids and penis. When the skin over any bony eminence is required to be very movable, and at the same time is exposed to continual friction, we find beneath it a sort of synovial capsule, or bursa, as it is called ; some of these bursse exist at birth, and belong to the original organization ; while others are accidental, and result from friction. We must regard the sub-cutaneous adipose tissue as a dependance, or even as a con- stituent part, of the integument, for it is impossible to separate one completely from the other. The adipose tissue, in fact, penetrates into, and entirely fills the areolar spaces in the skin. The cutaneous vessels enter or pass out, and the cutaneous nerves penetrate at the STRUCTURE OF THE SKIN. 631 adherent surface of the skin, and more particularly opposite the areolas observed on that surface ; so that whenever the skin is stripped off for a certain extent, it either sloughs off, or its vitality is so greatly impaired as to be incapable of completing the process of cicatrization. An accurate idea is, perhaps, not generally entertained of the enormous quantity of nervous filaments and of the immense number of arteries which enter the skin, or of the number of veins which issue from it. Its importance, both in a healthy and in a diseased condition, is sufficiently explained by these anatomical facts regarding it. Structure of the Skin. The skin consists essentially of the cutis, dermis, or true skin {a, fig. 226) ; of the pa- pillcB, which project upon its external surface ; of the pigmentum, or colouring matter (6') ; of the lymphatic network; and of the epidermis, or cuticle {b) ; as accessory parts, it also contains the sebaceous follicles, as well as arteries, veins, lymphatics, and nerves ; and has connected to it the hairs and the nails. The Cutis or ChorioR. — The dermis, ckorioii, or cutis vera (a, fig. 226 ; e,fig. 227), is the fundamental part or the basis of the skin ; and to it the skin owes p^ gofi its strength, extensibility, and elasticity. If the skin be regarded as formed of several distinct layers, the dermis constitutes the deepest of these. The thickness of the dermis varies in different parts, but is always in proportion to the amount of resistance which it is required to offer. Thus, in the cranium, it is very thick and dense ; on the face, generally, it is thinner than on the cranium, but not in every part of the face. Compare, for example, its density and thickness in the skin upon the lips with its tenuity and delicacy in that of the eyelids. On the trunk it is almost twice as thick behind as in front ; and upon the penis, scrotum, and mamma it is much thinner and finer than upon any other part of the anterior aspect of the body. skinofWegro. In the limbs the dermis is much thinner on the surfaces which are turned towards the median line and on the aspect of flexion, than it is on the outer side of the limbs and on the aspect of extension, which are more exposed to the action of external objects. On the palms of the hands and soles of the feel, which are almost incessantly in contact with external objects, the dermis is very thick. The thickness of the dermis varies in different individuals, and also according to sex and age. In old persons it participates in the general atrophy of the tissues, and be- comes so thin as to be somewhat translucent, and enables us in certain regions to dis- tinguish beneath it the pearly aspect of the tendons, and the reddish colour of the muscles. The dermis has a deep surface, and an epidermic or papillary surface. The deep surface presents a number of conical depressions, the base of each of which corresponds to the sub-cutaneous layer of adipose tissue, while its summit is directed towards the outer surface of the skin, and is pierced with very fine openings. These depressions or alveoli, which are most strongly developed in the soles of the feet and palms of the hands, are filled with conical prolongations or masses of fat, which, when inflamed, give rise to boils, and in a state of gangrene, constitute the slough from such sores. When examined in reference to its structure, the dermis is found to be composed of bundles of cellulo-fibrous tissue, interlaced with each other, and becoming closer and closer towards its external surface : this fibrous tissue is scarcely extensible or elastic, so that the extensibility and elasticity of the skin are due, not to the nature of the der- moid tissue, but to the arrangement of its component bundles.* The elasticity of a tis- sue may depend, like that of caoutchouc, upon the nature of its material, or, like that of a spiral piece of brass wire, may result from the arrangement of that material. The elas- ticity of the skin appears to be of the latter kind. The PapillcE. — Upon the external or epidermic surface of the cutis are found a multi- tude of small eminences, which are either arranged side by side, in rows or ridges {d. fig. 227), as in the palms of the hands and soles of the feet, or are irregularly scattered over the surface. These eminences are called the cutaneous papilla; ; together, they con- stitute the papillary body {corpus papillare). To understand them properly, we must ex- amine a section of a portion of skin from the palm of the hand or the sole of the foot, which section should be made transversely to the direction of the papillary ridges (see fig. 227) : numerous small eminences are then seen projecting from the dermis into the substance of the epidermis, which may be distinguished from these projections by its transparency and its horny appearance. The papillae are still more distinctly seen by re- moving the epidermis from a piece of skin, and then examining the latter under a thin layer of fluid. The papillae consist of a spongy erectile tissue,t containing pervous filaments, arter- ies, and veins. * The dermoid, like other cellular and fibrous tissues, is resolved into g-elatine by boiling. It acquires great density and strength in the process of tanning, by which it is converted into leather. t It is impossible to doubt the analogy of the papiUffi of the skin to those of the tongue, and even to the ia- 632 NEUROLOGY. Tlie nerves of the papillas are very numerous. In reference to this point, it is observed that the number of nervous filaments distributed to the skin is always in a direct ratio with the number and size of the cutaneous papillae ; and hence the nerves of the skin covering the palm of the hand are exceedingly numerous. Several anatomists state that they have seen the nerves spreading out like pencils in the papillae themselves.* The papilla; receive both arteries and veins ; in successful injections with mercury, or with glue-size, spirit-varnish, or turpentine, coloured with vermilion, all the papillae are penetrated by the injection, and exhibit, both in their interior and on their surface, a vascular network, which might be called an erectile tissue.! Lymphatics of the Skin. — If we introduce the pipe of the mercurial injecting apparatus very obliquely beneath the epidermis, the mercury, if the process is successful, will run into a sub-epidermic network of vessels, and will soon cover the skin with a metallic lay- er. These vessels arfe most evidently lymphatics, for the mercury soon passes from them into the sub-cutaneous lymphatic vessels, and from them into the adjacent lym- phatic glands : in no case does it enter the bloodvessels. Mascagni, who has given so many representations of the vessels of the skin in his beautiful plates, has delineated in several of them this lymphatic network, lying super- ficially to the layer of bloodvessels. The universal prejudice against microscopical observations had very improperly thrown some discredit upon the positive results obtained by this great anatomist, when an accidentally successful injection enabled Haase to trace and delineate the cutaneous lymphatics of the groin from the skin to the inguinal glands. J M. Lauth, also, by acci- dent, injected the lymphatic network of the same region. Panizza, in 1830, clearly de- monstrated the arrangement of the superficial lymphatic network upon the glans penis and the prepuce, in his beautiful injections of that organ in the human subject and in an- imals. Lastly, M. Fohmann (Essai sur les Vaisseaux Lymphatiques de divers Ordres, 1833) has made some special researches upon this subject, viz., upon the lymphatic network in the skin and in other parts. Two beautiful plates, one representing the skin of the mamma, and the other that of the scrotum, glans penis, and prepuce, give a perfect idea of the arrangement of this network, which, when filled with mercury, forms a silvery layer beneath the epidermis. From this network branches are given off which perforate the dermis in all directions, and enter the sub-cutaneous lymphatic vessels proceeding from its internal surface. We have succeeded perfectly in injecting the sub-cutaneous lymphatic vessels in the entire lower extremity of a new-born infant, merely by introdu- cing the pipe into the sole of the foot. This lymphatic network is remarkable for being situated superficially to the bloodves- sels, as Mascagni had correctly observed, and for being completely independent of any other system of vessels ; also, for its vessels being dilated into ampulla; at various pla- ces, for being destitute of valves, and for not opening anywhere upon the surface of the skin ; so that, excepting from laceration, the mercury does not escape through the pores of the epidermis. Lastly, the network generally consists of two very distinct layers, sit- uated between the epidermis and the dermis ; one extremely delicate and superficial, the other lying immediately upon the dermis, and belonging to deeper vessels.^ The Pigmentum. — All the different shades of colour observed in the skin of the sev- eral races of mankind belong to either the white, the black, or the copper-coloured va- riety : they depend upon the presence of a colouring matter called the pigmentum, which exists in the European as well as in the negro, though in a less marked degree, and which is deposited beneath the epidermis. This colouring matter, or pigmentum {b', fig. 226 ; c, fiff. 227), may be demonstrated in the skin of the negro (represented in fig. 226) with the greatest facility by means of maceration. It is then found not to be contained in special vessels, as Bichat supposed, but to be deposited beneath the epidermis, where it constitutes a uniform layer, that either comes off with the epidermis or remains attached to the dermis, but is independ- ent of either. II The epidermis, the papilla;, and the chorion are of precisely the same colour in the negro as in the white races. The pigmentum of the skin is identical in testinal villi. Although we are unacquainted with their precise structure, it is enough to know that they are composed of an erectile spongy tissue, in which both nerves and vessels terminate. The nervous filaments can be traced by dissection as far as the bottom of the alveolar depressiuns in the dermis. * Analysis of a furmer Memoir upon the Structure and Functions of the Skin, by MM. Breschet and Rous- sel de VauzSme. These authors state that they have ascertained that the nerves of the skin terminate in loops or arches, as had been pointed out by .MM. Prevost and Dumas, in regard to the nerves of the muscles. We shall elsewhere see what is to be thought concerning the existence of these terminal loops of the nerves in muscles, and the theory of muscular contraction founded upon it. t [The papilla; are prolongations of the vascular and nervous chorion,] X be Vasis Cutis et Intestinorum Absorbentibus, Lipsiffi, 1789. In the plate given in this work, the lym- phatic plexus is very badly represented. ^ According to M. Fohmann, .the skin is composed of the following parts proceeding from within outward : 1. The pannicaliis adiposus. 2. The internal layer of the dermis, characterized by its fibrous meshes. 3. A vascular layer composed of lymphatics, and the terminations of ihe bloodvessels and veins, united by a smail quantity of animal matter. 4. A vascular network, formed exclusively by the ultimate ramifications of the lym- phatics. 5. The rate mucosum of Malpighi. 6. The epidermis. Il See note, p. 635. THE PIGMENTUM. 633 every respect with the choroid pigment in the eye, and is formed of black molecules in- soluble in water. Blumenbach conjectured that this black matter was nothing more than carbon : several experiments appeared to confirm this opinion, but it is now gen- erally believed to be formed by the colouring matter of the blood.* In the European it escapes observation, because it does not differ much in colour from the epidermis and dermis. The colour of the skin, which is a matter of such interest in the natural history of mankind, and which forms one of the principal characters of the several human races, has a tolerably constant relation to the colour of the hair : thus, individuals with light hair have generally fairer skins than such as have dark hair ; and thus, also, red hair is accompanied with a somewhat analogous colour of the skin. In albinoes the colouring matter is deficient in the skin, as it is in the hair, and in the interior of the eye. More- over, the transition, in regard to the colour of the skin, from the white to the black races of mankind, occurs through a succession of intermediate shades : thus, I have found a colouring matter precisely similar to that of the negro's skin beneath the epidermis of several Europeans, particularly upon the scrotum, and upon the tanned faces of those who have lived exposed to a strong solar heat. In the disease called black or green jaundice, the skin of white persons becomes black or olive-coloured. A superficial chronic irritation produced by blisters, or certain skin diseases, or by an adjacent wound, will also sometimes cause a black discoloration of the skin. As to the source of the pigment of the skin, it is thought by M. Gauthier that it is yielded by the bulbs of the hairs. M. Breschet describes a series of glandular organs for secreting this pigment, which, according to him, are situated in deep furrows in the outer portion of the dermis, and are surmounted by a great number of excretory tubes, from which the globules of pigment are poured out beneath the epidermis. I have never been fortunate enough to ascertain the existence of these glandular organs and their ex- cretory tubes. It is generally supposed that the vessels of the cutaneous papillae are the source whence the pigment is derived ; the mechanism of its formation must be the same as that of the formation of the choroid pigment in the eye, and it is quite as little understood.* The Epidermis. — The epidermis, or cuticle {b, fig. 226 ; a b, fig: 227), is the outermost of the several layers of the skin ; it is a semi-transparent, horny layer, which is moulded upon the surface of the dermis and its papiUee like a coat of varnish, and protects them from the action of external agents. Its internal surface is, in fact, marked by a multi- tude of little pits, into each of which a papilla is received ; so that this surface of the epidermis may be said to form a mould of the papillary surface of the skin. In the skin of the negro, the colouring matter occupies the little pits in the epidermis, and is found in greater abundance between the papillae than upon them. In order to obtain a good view of the structure of the internal surface of the epidermis, various sections may be made of the skin upon the palms of the hands and soles of the feet. It will then be seen that the papillas dip, as it were, into the epidermis, which fur- nishes a kind of sheath for each of them. This arrangement is exceedingly distinct in the skin upon the lower surface of the bear's foot. I have alluded to this structure in ray Anatomie Pathologique (-'Diseases of the I^ymphatics," liv. ii.). M. Breschet has recently observed it in the skin of the whale, in which animal the epidermis forms a complete tube for each of the papillae. These sheaths, or tubes, are united by a gluti- nous matter, and may be separated, at least in the bear, with the greatest facility. The internal surface of the epidermis is Intimately adherent to the external surface oi the dermis ; but this adhesion may be destroyed in the living subject by the application of a blister, and after death by maceration. If in a piece of macerated skin the epider- mis be carefully separated from the true skin, it will be seen that the adhesion of one to the other is in part effected by a number of very delicate transparent filaments, which may be stretched to the extent of several lines without breaking. On examining the in- ternal surface of the epidermis under water, these filaments are seen floated out. What, then, is their nature 1 Are we to regard them, with Cruickshank, as prolonga- tions of the epidermis which dip into the areolae of the true skin 1 or, with Beclard, as strings of mucus formed by the stretching out of the viscid mucous matter situated be- tween the dermis and the epidermis 1 or, on the other hand, are they canals 1 and if so, are they to be regarded as exhalant vessels, as Kaaw, Boerhaave, and W. Hunter be- lieved 1 are they exhalant and absorbent vessels too, as Chaussier and Bichat imagined ] or are they not, rather, special vessels, the vasa sudoris of Bidloo, and the vasa sudatoria of Eichhorn, the latter of whom attributed to them both an exhalant and an absorbent function 1 These questions are not yet satisfactorily solved. The very great activity, both of exhalation and absorption of the skin, necessarily supposes the existence of some special apparatus for these processes. Steno, Malpighi, and others admitted the existence of certain sudoriferous glands, sit- uated in the adipose cellular tissue, and consisting of tubes which opened on the exte- * See note, p. 635. 4L 634 NEUROLOGY. Fig. 227. rior by means of an orifice provided with a valve. (Vide Haller, t. v., lib. xii., p. 42.) This description, when somewhat modified, agrees with the statements recently made by M. Breschet, who has described sudoriferous glands (g g, figs. 227, 228) having a saccular form, and situated in the substance of the dermis. A spiral canal* (h,fig. 227), proceeding from each of these sacs, traverses the dermis and epidermis, and, after having made several turns, opens upon the external surface of the skin (at i).t Besides these filaments, the deep surface of the epidermis presents certain irregularities, which may be felt by the finger, and which, under the microscope, appear pointed like thorns ; they seem to be prolongations of the epidermis, but I have not been able to determine their precise nature. The external surface of the epidermis presents corresponding folds and furrows to those already described upon the free sur- face of the skin. It also has numerous orifices or pores, visi- ble to the naked eye on the palms of the hands and soles of the feet, and very distinctly seen by the aid of a lens. Along each of the ridges formed by the rows of papillae are found a series of orifices, arranged in a regular manner, and resem- bling in appearance the puncta lachrym.alia in the eyelids. If the skin be examined with a lens during life, while the person is perspiring, drops of the excreted fluid are seen to exude, and form into a small globule, which is soon lost by evaporation, and, after a few seconds, another globule makes its appearance. It is impossible to conceive how several celebrated anatomists could have denied the existence of pores in the skin.t Delia Torre, Fontana, and Mascagni believed that the epidermis was organized, and that it consisted of a network of lymphatic vessels. But as Panizza has clearly proved (Osservazio7ii Antropo-zootomico Fisiologiche, 1830, p. 83), the lymphatic network always lies beneath the epidermis, which may, by maceration, be raised up from it. After the example of Panizza, I have endeavoured to inject the epidermis upon the soles of the feet, and upon other parts of the body, but without being able to find a single vessel. As for the opinion that the epidermis contains arterial and venous capillaries, it is so at variance with the results of observation that it does not require refutation. The epi- dermis, then, is unorganized [non-vascular]. It is a product of secretion, a layer of concrete, transparent, and very hygrometric mucus ; a sort of horny matter, of variable thickness, capable of reproduction after hav- ing been destroyed, and the morbid alterations of which result, not from any proper vital action in itself, but from a diseased condition of those living parts of the skin by which it seems to be produced. As to the structure of the epidermis, it has been repeatedly stated to consist of imbri- cated scales ; but the most careful examination discloses nothing more than a layer of uniform structure, into which the papillae enter ; so that it may be decomposed, hypo- thetically and even actually, by the aid of the scalpel, in some animals, into a number of agglutinated tubes or sheaths, each of which belongs to a single papilla. The different forms of the fragments of epidermis, detached either spontaneously or in consequence of disease, depend upon accidental circumstances, and show the continuity of this mem- brane in the human subject.^ I shall presently describe the relations of the epidermis to the hair, the nails, and the sebaceous follicles. * Fontana had previously spoken of serpentine vessels, which he had seen beneath the epidermis by means of the microscope. t [The sudoriferous glands, discovered by Breschet, Purkinj6, and Wendt, may be seen best by examinin_^ under the microscope a thin perpendicular section of a piece of skin taken from the palm of the hand (as in Jig. 227), and hardened in a solution of carbonate of potash. They are situated in the sub-cutaneous adipose cellular tissue (/) ; they consist of a long convoluted tube (or of two tubes which unite together), ending in an efferent duct {h), which opens (i) upon the free surface of the epidermis, and is lined by ilatteued epidermic corpuscules. Where the epidermis is thin, these ducts are nearly straight, as in the scalp (seefg. 228), and their orifices are scattered irregularly over the surface ; where it is thick, they have a spiral course, as in the palm and sole (ftg. 227), where their orifices are arranged in single rows on the papillary ridges. These spi- ral ducts are turned in opposite directions on the right and left extremities ; the average number of their ori- fices is fifty in the siiuare line ; the filaments described in the text as connecting the epidermis to the dermis are the epidermic linings drawn out of these ducts, and out of the sebaceous and piliferous follicles.] t See note, p. supra. it) The epidermic portion of the skin has been so long supposed to consist of several distinct structures, that it is still convenient to describe separately an epidermis, a pigmentum, and a rete mucosum ; but modern re- search has shown that these are merely difi'erent layers of the same structure, in difl"erent stages of develop- ment. The most superficial and hardest of these layers, which is separated from the skin in vesication during life, and by maceration after death, is the epidermis described in the text, and by authors generally ; the deeper, more recently formed, and softer portions, which may be displayed and subdivided into several layers by maceration and dissection, constitute the pigmentum and the rete mucosum : together, these insensible, extra-vascular, but not inorganic layers, form what is now called the epidermis. Thus defined, the epidermis exactly resembles the epithelium of mucous membranes, in consisting of a number of adherent nucleated corpuscules, each of which undergoes an independent development. Immedi- APPENDAGES OK THE SKIN. 635 According to M. Breschet, certain minute reddish glands are situated among the sub- cutaneous adipose vesicles, and constitute the secreting apparatus of the epidermis. Ex- cretory ducts are said by him to proceed from the summits of these small glands, to trav- erse the dermis, and to open at the bottom of the furrows found upon its external sur- face. According to the same observer, these ducts generally resemble rows of regular- ly-arranged columns, and the glands are sometimes situated at unequal depths from the surface, and communicate with each other by intermediate ducts. I have never suc- ceeded in verifying these observations ; and I have equally failed in attempting to decom- pose the epidermis into a series of layers, becoming less and less compact in proportion to their distance from the surface. The Corpus Mucosum, or Corpus Reticulaire of Malpighi. — Malpighi applied the term reticulum, and others, following that great anatomist, have given the names corpus retic- ulaire, corpus mucosum, and rete mucosum, to a gelatiniform layer {d, jig. 227) of what is regarded as a concrete mucus, situated beneath the epidermis and perforated by the pa- pillae, which thus give it a reticulated appearance. This inorganic [non-vascular] layer, which Malpighi first demonstrated beneath the thick epithelium of the tongue of the ox, after it had been boiled, and which he then supposed to exist also in the skin, cannot be demonstrated anatomically ; so that the expressions corpus mucosum, corpus reticulaire, have lost their original signification, and have been interpreted in a different sense. Haller, and several anatomists quoted by him, regarded the corpus mucosum as a deep layer of the epidermis, some of them confounding it with the pigmentum, and others dis- tinguishing it from that body. Bichat considered the corpus mucosum to be an extreme- ly delicate network of vessels, or system of capillaries, which formed, with the papillas, an intermediate layer between the chorion and epidermis, and was partly intended to convey the blood, and partly the colouring matter of the skin. M. Gauthier, in examining the skin of the heel in the negro, recognised four distinct layers in the corpus mucosum, arranged in the following manner, from within outward : 1. Vascular processes containing red blood (bourgeons sanguins), which are situated upon and adhere to the papillae ; 2. A deep white layer, composed of serous vessels, and moulded upon the vascular processes and papillae ; 3. A layer of gemmules, forming a kind of coloured membrane, excavated upon its deep surface, and separated from the vascular processes and papillae by the deep white layer ; 4. A superficial white layer, which he regards as formed of serous vessels, as well as the deep white layer. Exter- nally to this is the epidermis. M. Dutrochet, founding his opinion upon the examination of the skins of quadrupeds, admits the different layers of M. Gauthier, excepting the vas- cular processes, which he very properly regards as forming parts of the papillae : he calls the deep white layer of M. Gauthier the epidermic memhrane, the gemmules he terms the coloured layer, and the superficial white layer he names the horny layer. Lastly, Gall regarded the corpus mucosum as a layer of gray nervous matter, precisely similar to that of the gray substance of the brain and of the nervous ganglia. I agree with Chaussier that we ought altogether to reject the corpus mucosum, in whatever sense that term may be understood ; and I beheve there are good grounds for supposing that the different layers described as forming this body belong, in reahty, some to the papillae, and others to the epidermis.* Appendages of the Skin. Under this title may be included the sebaceous follicles and the horny growths, viz., the nails and hairs. The Sebaceous Follicles. — The skin contains within its substance certain sebaceous fol- licles (i i, fig. 228) ; these consist of small pouches, or bags, about the size of a miUet seed, which form projections beyond the epidermis, but are lodged in the substance of the dermis, and open externally by very small orifices, which are visible under a lens, and, in some persons, even to the naked eye. From these orifices an unctuous matter is con- stantly poured out upon the surface of the skin, and assists in preserving its pliability ; in some individuals this unctuous matter may be expressed from the folhcles upon the ately upon the surface of the true skin, these corpuscules are soft, roundish vesicles, containing a distinct nu- cleus and peculiar pigment granules, and adhering together by a viscid matter, the cytoblastema, in which they are first developed. In approaching the surface of the cuticle, they become larger and more compressed, their walls become thicker and denser, their nuclei less distinct, and their pigment paler, until, at length, they form the thin, flattened, horny, nucleated, colourless discs, which, adhering to each other firmly in an imbricated manner, constitute the upper and horny portion of the epidermis, from the free surface of which they are con- stantly being thrown off as minute scales, to be continually replaced by others having a similar origin, and un- dergoing the same changes : these imbricated scales were described by Leuwenhoek and Baker. The epidermis is insoluble, even in boiling water ; but it swells and becomes softened and transparent, in these respects resembling mucus and epithelium ; it consists of a substance called keratin. The pigment granules contained in the deeper epidermic corpuscules are the cause of the colour in the skin ; they are black in the negro, &c., of lighter hues in other dark races, and fawn-coloured in the Euro- pean ; in all cases they are darkest in the deeper and newly-formed corpuscules, and fade as these approach the surface : in albinoes they are either absent or colourless. The pigment contains iron and carbon, both in a combined state, phosphate of lime, and animal matter ; but as it is bleached by chlorine, it contains no free carbon, as supposed l)y some.] * See note, p. 634. 636 NEUROLOGY. Section of skin from the head, magnified U tinies. Fig. 228. alae of the nose, in masses which look like small worms. These sebaceous follicles are somewhat analogous to the follicles of the mucous membranes ; they are not found in the palms of the hands and soles of the feet ; but, in all probability, they exist in every part of the body : they are especially observed in the axiUa, on the hairy scalp, and around the margins of the anus and vulva, and the openings of the nose and mouth : they are very much developed in the new-born infant. The sebaceous follicles appear to me to have a glandular structure ; and this is particularly evident in those of the axilla, the organization of which seems to me to be more complex than that of those found in other parts. The supposition that these follicles are formed by the reflection of the thin portion of the skin is altogether fanciful.* The Nails and the Hair. — In man the horny growths of the skin are less developed than in any animal expo- sed to similar atmospheric conditions ; and in man, also, we find the highest development of the sense of touch. The nails of the human subject are hard, yet flexible and elastic, semi-transparent scales, and present the ap- pearance of laminae of horn : they are situated upon the dorsal surface of the last phalan- ges, which are therefore called the ungual phalanges ; and they appear rather to be in- fended for the support and protection of the pulpy extremities of the fingers, than as weap- ons of attack, or instruments of defence and prehension. In a state of civilization it is customary, therefore, to cut off that part of the nail which projects beyond the end of the finger. The ingenuity of man enables him to provide himself with offensive weapons amply sufficient to compensate for the weakness of those provided by nature, which, in- deed, are quite rudimentary in him, and if more fully developed, would greatly interfere with the delicacy of his sense of touch. The peculiarity of the human nail consists in its only covering the dorsal surface of the last phalanx, and in its being of considerable breadth, corresponding, in this respect, with the horseshoe-like enlargement at the end of the phalanx. It follows from this, that the whole of the pulp of the finger is concerned in the exercise of the sense of touch, t The nail is divided into the root, the body, and the free portion : the root is that part of the nail which is covered on both surfaces ; the body is that part which has one sur- face free ; while the third, or entirely /rce portion, projects beyond the end of the finger, and has a tendency to become incurvated when left to grow naturally. In order to obtain a correct idea of the anatomy of the nails, we should, by a longitu dinal incision, make a vertical section of the ungual portion of one of the fingers {see Jig. 229). We shall then perceive that the root is about one fourth of the length of the body of the nail (b) ; that it is also the thinnest part of the nail ; that it diminishes in thick- ness towards its posterior edge, which is slightly indented, and that it increases towards the body of the nail ; that it is flexible, and is received into a duplicature of the skin (c c), to which it is attached by both surfaces ; that the posterior edge and lower surface of the root adhere so slightly to the skin, that they may be said to be merely applied to it ; that the upper surface of the root, though it adheres move closely to the skin than the lower surface, is yet much less firmly attached to it than tlie under surface of the body of the nail, which cannot be torn off without great violence ; that the nail is separated from the phalanx by a very thick dermis (c') ; that this skin is of a white colour at the root of the nail, and for some distance in front of it, where it occasions a semilunar white mark, visible through the transparent nail, and called the lunule {lunula) ; anti, lastly, that the dermis, which corresponds to the body of the nail, is extremely vascular, and hence the nail has a rosy hue, because its semi-transparency enables us to perceive the colour of the subjacent tissue. One of the most important points in the anatomy of the nail is the nature of its con- nexion with the dermis. The fold of the skin, which is called the matrix of the nail, is formed in the following manner : the skin (c, fig. 229, being the dermis) is prolonged * [The sebaceous glands (ii, Jig.22S) are multilocular follicles ; their ducts are lined by epidermic cor- pnscules, and open upon the surface of the skin in parts without hairs ; where hairs exist, they open into the hair follicles (c), to each of which two sebaceous glands (it) are generally attached. On the face, very mi- Bvite hairs have been found around the orifices of the ducts of these glands : their secretion is albuminous as ■well as fatty.] t The hoof, of which a very perfect example is met in the horse, is nothing more than a nail which enclo- ses the united phalanges on all sides, like the wooden shues sometimes worn ; the claw of carnivorous animals is a nail which covers two thirds of the slender ungual phalanx, is compressed at the sides, and terminates in a pointed hook. The nail, properly so called, is found only in man and in quadrumana, and in the latter it approaches in character to the claw. The division of mammalia into ungulated and unguiculated is exceed- ingly natural, and is, in some measure, represented by certain correlative and constant differences in all other parts of the system. — (See Anatomie Comparee cle M. de Blainville.) THE APPENDAGES OF THE SKIN. 637 from the finger on to the dorsal surface of the nail, as far as the curved line that marks the posterior boundary of the body of the nail ; from thence it is reflected back- ward, folded upon itself, as far as the posterior bordc r «^ of the root of the nail. At this point it is again reflected forward upon itself by passing behind that border, and then (c' c') between the under surface of the nail and the dorsal aspect of the phalanx : in consequence of this two- fold reflection, it follows that it is always the epidermic S"''"' of kinonmni. surface of the true skin that is in contact with tlie nail : at the anterior extremity of the nail the skin again meets, as it were, the epidermis {a'), and becomes continuous with the integument upon the tip of the finger. But what is the arrangement of the epider- mis at the point where the skin is first reflected backward ! It is prolonged forward (a), slightly beyond the curved line formed by the reflection of the dermis, and forms a semicircular zone or band, which terminates by a smooth border, and adheres intimately to the nail. As to its arrangement beyond this point authors are not agreed. Some are of opinion that it would be prolonged upon the free surface of the nail, if it were not de- stroyed by friction ; but they overlook an objection to this view to be derived from the accustomed regularity of the epidermic border : others, again, believe that the epidermis is reflected backward like the dermis, but differ among themselves as to its ultimate dis- position ; some, for example, conceiving, with Bichat, that the epidermis is continuous with the posterior border of the nail, and some supposing that it is again reflected for- ward beneath the nail, together with the dermis (see dotted line), which, according to this hypothesis, it never quits.* A very simple experiment most clearly demonstrates the nature of the connexion be- tween the epidermis and the nail : it consists in submitting a finger to the process of maceration, by means of which the nail and epidermis come off" together in the form of a partly epidermic and partly horny sheath. In this the epidermis {a) is found to be re- flected backward upon the dorsal surface of the root of the nail, and to become blended with it {see Jig. 229) without ever passing beyond its posterior border ; while in front, at the hmits between the body and the free portion of the nail, the epidermis (a') is mani- festly continuous with the deepest layer of the horny lamina ; so that it cannot be doubt- ed that there is an identity of nature between the nail and epidermis. Structure and Growth of the Nail. — On examining the two surfaces of the nail, and es- pecially its deep surface and posterior border, it is found that they are marked by very distinct longitudinal lines or striae, which appear to indicate a corresponding linear tex- ture. It would seem, accordingly, that the nail was formed by the agglutination into laminae of a number of longitudinal fibres ; but, if we examine the free surface of the nail attentively, we find that it is marked by curved striae, which intersect the longitudinal ones. These curved striaa are particularly distinct in the not uncommon cases in which the nail of the great toe is much hypertrophied, and becomes incurvated upon the plantar surface of the toe : the enlarged nail is found to consist of imbricated laminae, received one into the other like the several laminae in the hoof of an animal. We may even sep- arate these diflferent layers by aid of maceration, and find that they are fitted one into the other, the deepest being that which was last secreted. The nails, therefore, are developed by a method very analogous to that by which we have already stated the teeth are formed. (See p. 179.) The nails, then, like the hoofs of animals, and like the epidermis, are products of se- cretion : they receive neither vessels nor nerves : alterations in their texture are not de- pendant upon diseases inherent in themselves, but result from some morbid condition of their formative organ. The fold of the dermis, which is called the matrix of the nail, is not the only part by which the substance of the nail is secreted, but the whole papillary surface of the dermis, to which the nail adheres, is concerned in its formation. The papillffi are arranged in longitudinal rows, and hence the substance of the nail is depos- ited in longitudinal striae, t The nail grows continually in length ; it does not increase sensibly in thickness, ex- cepting during disease. The layers that have been deposited the longest time are the most superficial, and occupy the free extremity of the nail, in precisely the same manner as the oldest- formed ivory in the tooth is nearest to the enamel. t * See note i, below. t The arrang-ement of the papillary dermoid layer which covers the dorsal surface of the ungual phalanx is worthy of notice : it adheres intimately to the periosteum, and forms an extremely dense, grayish stratum, penetrated by vessels and nerves; so that, if the mode of termination of the nerves in the papilla; can ever be as- certained, It IS, without doubt, beneath the nail, where these papiUas present their highest state of development. t [The nails are found by Schwann to consist of nucleated corpuscles, which, like those of the epidermis, are formed upon the surface of the dermis, where they are soft and vesicular, and afterward become hard, flattened, and firmly agglutinated together, as in the substance of the nail. These corpuscles are developed, not only opposite the matrix of the nail, but beneath the whole of its attached surface ; the nail is thus elon- gated, and, at the same time, its thickness is maintained, notwithstanding the flattening of the corpuscles formed at the root as they approach the surface. The thin layer of epidermis, described by Weber, Lauth, and Gurlt, as continued under the whole attached surface of tlie nail, is nothing more than the soft stratum gf growing corpuscles, which pass insensibly into those of the true epidermis. Like the spidermis, the nails consist of keratin.J 638 NEUROLOGY. The Hairs. — The hairs are filiform productions of the epidermis, generally flexible, va- riable in length, size, and colour, and bearing different names, according to the region on which they are situated.*' The surface of the human body, with the exception of the palms of the hands and the soles of the feet, is covered by very fine and short hairs, which form a light down, as it is named ; but the hairs, properly so called, are collected upon particular parts of the sur- face of the body, where they serve some special purpose. Thus, they exist in great abundance upon the cranium, where they are called the hair ; on the face, where they form the whiskers and beard ; the hairs upon the margins of the eyelids are called the eye- lashes ; the arched row over each orbit is called the eyebrow ; the hairs upon the lips con- stitute the mustache. On the trunk the hairs are collected, in more or less abundance, around the genital or- gans : they exist, also, in the axiUae of both sexes ; and on the chest, between the breasts, in the male. The hairs present well-marked differences, according to sex, age, and the pecuhar race to which the individual belongs. The pilous system is most developed in the Caucasian race, and least so in the negro. The hair, eyelashes, and eyebrows exist before birth : before birth, also, the whole body is clothed with a ver>- thick down, which is shed during the first few months after- ward. At the period of puberty, hairs are developed upon the pubic region, and in the axillag of both sexes, upon the labia majora of the female, and upon the scrotum and around the anal orifice in the male : the beard also appears in the male, and the ante- rior aspect of the trunk, and the limbs are covered with hairs of variable length in dif- ferent persons. I should observe, that the development of the hairs is not always in proportion to the personal strength, as is asserted by certain authors, who regard an abundance of hair as an attribute of strength and virility. But, although some men with hairy skins have robust constitutions, a great number are deUcate, and are even affected with tubercular phthisis. In mammalia, the hairs upon the posterior or dorsal region of the trunk are more de- veloped than those upon the anterior or abdominal aspect, a proof that they are destined to the quadruped attitude : in some animals, which turn upon their backs to protect them- selves, the hairs upon the abdominal surface are most highly developed. The hair of the head may grow to a verv' considerable length : it has been seen to reach as low down as the middle of the leg, and, when thrown around the trunk, sutBciently abundant to cover it like a garment. The length and the direction of the hair upon the head evidently prove that man is destined for the erect posture ; for, if he assumed the attitude of a quadruped, it would trail upon the ground, and fall over the face. The hair also presents pecuharities, or differences, in many respects ; for example, in direction, some hair being long and smooth, some crisped and woolly ; this latter kind is peculiar to the negro race, and it never grows to a very great length : also in diameter, some hair being excessively fine, and some large and coarse. t It differs, again, as to quantity, for, in general, the hair of the head is more abundant in the female than in the male, as if the activity of the pilous system was principally confined to the hairy scalp in the former sex ; and, lastly, in its colour, from which certain very important distinc- tions among men are established. Ever}' different shade in the colour of the hair may be referred to three principal va- rieties, the black, the flaxen, and the red. The flaxen hair belongs particularly to the inhabitants of the north, and to persons ofl}Tnphatic and sanguineous temperaments; the black is characteristic of the inhabitants of the south, and of those of a bilious and sanguineous temperament ; the red belongs to no particular temperament ; and in our ideas of beauty, this coloured hair, which is usually accompanied with a disagreeable odour of the perspiration, is regarded as a natural misfortune. The beard and VN'hiskers are peculiar to the male sex ; they occupy the lower part of the face, and, consequently, leave uncovered aU those parts which are principally con- cerned in giving expression to the physiognomy, viz., the ocular, nasal, and frontal re- gions. AVe cannot insist too strongly on the connexion existing between the develop- ment of the genital organs and that of the beard. The eunuch is almost destitute of that appendage. The great attention rendered necessary by wearing a long beard and long hair has led to the custom of cutting the hair and shaving. It is remarkable that the most effemi- nate nations, the Orientals, for example, are those among whom long beards are in high- est estimation. The influence of these different customs upon the health are deservedly subjects of examination for those who study Hygiene. Structure and Growth of Hairs. — The only method of obtaining an accurate knowledge of the structure of hairs is to study their growth. The extremity of the hair which is inserted into the skin is contained in a sort of follicle, verj^ analogous to the dental foUi- * The spines of the hedg'ehog-, the bristles of the boar, the hair of horses, the wool of sheep, and the fur of most mammalia, are different kinds of hair. t [The hair of the head also varies in its form; a section being a more or less flattened oval, or even reni- form, from the hair being excavated along one side. On the face, the hairs are still more flattened.] THE ORGAX OF TASTE. 639 cles. This hair-folUde {e, fig. 230), -which is the formative organ of the hair, is imbedded in the sub-cutaneous cellular tissue {g), and is prolonged to the surface of the skin by a sort of membranous canal, which was well described by Bichat. The hair-follides consist es- sentially of a pouch or sac. and a papilla. The membranous pouch or sac (c c), called the bursal membrane by Heusinger, forms a sort of cul-de-sac. having a narrow neck, and opening externally by a contracted orifice, through which the hair {b) passes without adhering to it at all. Its walls are sufficiently transparent to allow the hair contained in its cavity to be seen. If this cavity or sac, which, according to M. Dutrochet, is formed merely by the inversion of a portion of the skin, be laid open, its in- ternal surface (e) is found to be smooth, not adherent to the hair, but separated from it by a reddish liquid, first pointed out by Heusinger. Majaifiai. From the bottom of this sac, i. e.. from the part farthest from the orifice through which the hair protrudes, a papilla (a), called the pulp of the hair, arises ; this papilla is of a conical form, its base being adherent, while its apex is free : it reaches nearly to the orifice of the sac, and even projects beyond it in the disease called pHca polonica. Bloodvessels and ner^'es pass to the bottom of the hair-follicle, and are probably distrib- uted upon the papilla. It is upon the papilla that the hair is formed. At its commencement it resembles a conical horny sheath, which is exactly moulded upon the apex of the papiUa. On the in- ner side of this horny cone another is formed, which raises up the preceding one, and so on in succession, the entire hair constantly maintaining a conical form. According to the experiments of Heusinger, who plucked out at intervals the hairs from the whis- kers of a dog, and afterAvard killed the animal, so as to observe the successive changes which took place in the hair-follicles during the development of the new hairs, a rather long period elapses before the hair projects beyond the epidermis ; but, when once it has overcome that obstruction, its growth proceeds rapidly. "\Miat is the arrangement of the epidermis at the point where the hair emerges beyond its surface ! According to some, it is prolonged upon the hair, and forms its outer coat ; according to others, it dips into the cavity of the hair-foUicle, and is reflected upon the base of the hair, so as to form upon it an epidermic tube, which falls off in scales as the hair is prolonged outward ; according to others, again, the epidermis has no connexion with the hair ; and I am the more inclined to subscribe to such an opinion, because the hair is of the same size both before and at^er it has left the follicle.* The hair is the product of a secretion, and, therefore, destitute of vitality, being form- ed by a series of small horny cones fitted one into the other. It is generally admitted that it is composed of a homy, colourless, transparent, epidermoid sheath, containing a sort of coloured pith in its interior. Bichat presumed that this central substance was formed of certain bloodvessels wliich contained the colouring matter : but the mode in which the hair is developed proves that it is not tubular, and also that the colouring matter itself is produced by the papilla at the same time as the epidermoid sheath. The white hairs of old people are merely deprived of colouring matter.! The Orgax of Taste. The structure of the tongue, the organ of taste, which has already been described (see p. 332), presents a greater analogv" to that of the skin than any other of the organs of the senses. The sense of taste resides essentially in the papillary membrane which covers the up- per surface of the tongue. i It has already been stated that the perforated eminences found at the base of the tongue are not papillee, but glands ; and the true papiUa? have been divided into the large or cahciform papillse, which are arranged in the shape of the letter V at the base of the tongue, and the small papillee ; which may be again subdivided into the conical, the fJiform,.and the lenticular or fungiform, according to their respect- ive shapes. Every special sense, by which term is understood all such as receive sensations dif- ferent from that of touch, properly so called, presents for our consideration a special ap- * [The root of some hairs is larger than the shaft, and is named the bulb ; this, however, does not depend on the hair being- covered by the epidermis, a thin layer of which (d d.fig. 230) lines the follicles, and is be- lieved to terminate at the root of the hair. Into each hair-foUicle one or more sebaceous glands (i i.fig- ~~) pour their secretion.] t [Hairs, like the nails, consist, according to recent researches, of nucleated corpuscles, which ditier in form, density, and arrangement, in ditferent parts of the hair. At the root, U[>on the surface of the papiUa, where they are first developed, they are SLift and vesicular : in the central medullan- part of the shaft they are harder, compressed, and polyhedral ; in the cortical part they form an immense number of very long anii tine fibres, and, on the outside of these, a layer of short, hard scales. The hairs consist principally of keratin and an oily matter ; besides which, they vield sulphur, phosphorus, iron, salts of lime, and traces of manganese, silica, and masnesia.] ' ' t [The mucous membrane on the under surface of the tongue, and that covering the buccal surface of the soft palate and the immediately adjacent parts of the fauces, alsj possess the sense of taste.j 640 NEUROLOGY. paratus, on which the impressions act, and a special nerve or nerves, adapted to receive those impressions and transmit them to the brain. The muscular structure of the tongue, which at first sight appears to be useful only in mastication, deglutition, and the articulation of sounds, is intimately connected with the sense of taste, which would have been exceedingly imperfect, had not the gustatory membrane been capable of being moved over the bodies to be tasted. The gustatory apparatus of the tongue consists, then, of a papillary membrane stretched over a muscu- lar surface, and united so closely to it that it is impossible to separate one from the oth- er. Moreover, this membrane is constantly kept in a state of humidity, and occupies the first cavity presented by the digestive apparatus. The Gustatory Papillary Membrane. — All the elements of the skin are found in the gus- tatory membrane. The chorion is as dense as the densest part of the chorion of the skin : a very great number of muscular fibres are inserted into it, so that the gustatory membrane can be moved not only as a whole, but each part of it has its own separate movements. The papilla, by which the surface of the tongue is rendered so rough, may be said to represent the papillary body of the skin in a very highly-developed state.* The lingual papillte are supplied with nerves, which can be more easily showTi than those in the cutaneous papillse. Haller has traced them into the papillae ; and I have suc- ceeded in doing the same, but without being able to ascertain their mode of termination. The papillae also receive bloodvessels, which are so abundant that, in successful injec- tions, the papillary body appears to be altogether vascular. The Lymphatic Network. — By making a superficial puncture into any part of the mem- brane which covers the dorsum or the borders of the tongue, we may inject a lymphatic network upon it, precisely similar to that found in the skin. The mucous body, or rete mucosum, does not exist as a distinct membrane upon the tongue any more than in the skin. I have already stated that it was while examining the boiled tongue of the ox that Malpighi discovered a glutinous stratum situated be- tween the epidermis and the papillaj, and perforated by a number of openings, coiTe- sponding to that of the papilla; themselves ; hence the name of reticulum which he gave it ;t but it is as impossible to demonstrate it upon the tongue as in the skin. The Pigmentum. — There is never any black colouring matter in the tongue of the hu- man subject ; but it is distinct upon the tongue of some animals, as the ox, and can be easily demonstrated between the papillae and the epithelium. $ The Epithelium. — Each papilla is covered with a sort of epidermic sheath, wliich, ac- cording to Haller, was discovered by Mery and Cowper, and which has been perfectly described by Albinus under the name of the periglottis. This epidermis, or epithelium, so easy of demonstration in the lower animals, in which it has the consistence of horn, may be also readily shown in the human subject, although, in accordance with the great- er perfection of the sense of taste in man, the epithehum is comparatively thin. If the upper surface of the tongue be examined with a lens, especially after maceration, the lingual epithelium will be seen to be arranged in precisely the same manner as the epi- dermis of the skin, and to form a protecting sheath for each papilla. In persons who have sunk after long abstinence, the epithelial covering forms several imbricated layers, which can be rubbed off; the fur which adheres to the tongue is in a great measure formed by this debris of the epithelium somewhat dried. The epithelium of the tongue can be removed by friction ; and, in certain inflammatory diseases, the tongue is denuded of it. When one of the Ungual papillae is thus exposed, it becomes excessively painful. The Nerves of the Tongue. — No other organ, perhaps, of equal size, receives so many nerves as the tongue : one pair, the ninth or hypoglossal, is exclusively appropriated to it ; and it also receives, on each side, the glosso-pharyngeal branch of the eighth, and the lingual branch of the fifth of the cerebral nerves. "VVhich of these nerves must be regard(?d as the nerve of taste in the tongue 1 Evidently the one that is distributed to the papillae. On this account, since the time of Galen, the lingual branch of the fifth pair, or the lingual nerve, as it is called, has been regarded as the gustatory nerve ; though it would seem more natural to admit, with Boerhaave, that the hypoglossal nerve, which is distributed exclusively to the tongue, should, as it were, preside over the spe- cial sense situated in this organ. But the lingual nerve is found to enter the tongue at its corresponding border, and to spread out into branches which pass vertically upward, and are, exclusively distributed to the papillary membrane of the anterior, or free portion of the tongue. The ninth or hypoglossal nerve of each side runs from behind forward, between the ge- nio-glossus and stylo-glossus muscles, and communicates with the lingual nerve, so as to form the lingual plexus. It is not certain that some of the filaments of the hypoglos- * If the epidermic tubes, which are so remarkably distinct on the foot of the bear, be removed from the pa- pilla, the latter, when exposed, exactly resemble those of the tongue.] t " Hanc fabricam a Malpighio inventam, et a Bellino libenter acceptam, scriptores anatomicorum, et phys- iologicorum operum iconihus ctiam pictis expresserunt." — (Haller, t. v., lib. xiii., p. 107.) t [The pigment in these cases, and the lingual rete mucosum also, are the lowermost layers of the extra- vascular squamous epithelium.] THE NOSE. 641 sal nerve do not' reach the papillae ; but there is no doubt but that almost all of them are lost in the intrinsic muscles of the tongue. The right and left glosso-pharyngeal nerves supply the base of the tongue, and are ex- clusively distributed to the mucous membrane covering that part. No filament of the glosso-pharyngeal nerve is intended for the muscular fibres ; and it is a remarkable fact, that in one case in which the facial nerve sent a branch to the tongue supplementary to the glosso-pharyngeal, that branch was distributed precisely in the same manner as tlie glosso-pharyngeal itself; that is, it was exclusively distributed to the mucous membrane at the base of the tongue. From what is stated above, then, it is anatomically shown that the lingual branch of the fifth nerve and the glosso-pharyngeal nerve are the special nerves of the tongue.* The following case is no less demonstrative of the same fact : An individual had com- plete paralysis of the right half of the tongue. That side of the tongue became atrophied, and had scarcely one third of its natural thickness. Both its tactile and gustative sen- sibility were equally acute on the two sides of the organ. After the death of the person thus afflicted, an acephalo-cyst was found in the right posterior condyloid foramen, which had caused a complete atrophy of the right hypoglossal nerve. The corresponding half Qi the tongue had undergone the fatty degeneration. The Organ of Smell. The organ of smell is situated in a cavity formed within the bones of the face, as, in- deed, are most of the other senses ; it is placed at the entrance of the respiratory pas- sages, and above the organ of taste, with which it has many points of relation. Although situated in the median line, it is a double organ. It consists of an external apparatus, which serves to protect the organ, to keep it in the necessary state of moisture for the proper exercise of its functions, and to direct the air towards that part of it which is en- dowed with the greatest olfactory sensibility : this is the nose, properly so called. And, secondly, of two complicated and winding cavities, the nasal fossa, lined by a mucous membrane, czdled the pituitary membrane, which is the essential seat of the sense of smeU, Th:e JVose. The Mose resembles in form a three-sided pyramid, directed vertically, and projecting from the middle of the face, so that the olfactorj'^ organ is the most anterior of all the or- gans of the special senses. Its numerous varieties in shape and size fall under the consideration of painters rather than anatomists ; for these varieties have greater effect upon the physiognomy than upon the exercise of its functions. On each side of the nose, at its lower part, is observed a semicircular furrow, having its concavity directed downward, and forming the upper border of the alae nasi ; from this furrow, on either side, the naso-labial furrow of the semeiologists commences. The lateral surfaces of the nose form, by their union, the dorsum, which is either straight, convex, or concave, according to the subject ; differences which, in a great measure, determine the national or individual forms of this part of the face. The term lobe of the nose is applied to the rounded eminence in which the dorsum nasi terminates below. The summit, or root of the nose, is separated from the nasal protuberance by a trans- verse furrow. The base of the nose presents two elliptical or semilunar orifices, called the nostrils (nares) : the long diameters of these two orifices are directed horizontally backward and outward, and they are separated from each other by an antero-posterior septum ; they are provided with stiff hairs, or vibrissee, which serve to arrest any small particles floating in the air.t The direction of the nostrils is a proof that the erect position is natural to man ; for, if he were to assume the attitude of a quadruped, only the dorsum of the nose would be directed towards odoriferous bodies. The situation of the nostrils above the orifice of the mouth explains how no alimentary substance can be introduced into that cavity without having been previously examined by the sense of smell. The nose consists of a skeleton or basis, and of certain muscles ; it is covered by the skin externally, and by a mucous membrane internally ; and it receives both vessels and nerves. The Structivre of the Nose. The bo.sis ox: framework of the nose is composed of bone, cartilage, and fibrous tissue. * [The result of the vast number of experiments and observations made upon this subject, by persons of op- posite opinions, would appear to be, that the lingual nerve (a branch of the fifth), and the lingual portion of the glosso-pharyngeal nerves, are both of them gustatory nerves, and also nerves of ordinary sensibility to the tongue. The portion of the palate and fauces endowed with the sense of taste derives its power from the pal- atine nerves, which are given off from a ganglion (Meckel's) connected with the second division of the fifth nerve. 3 t This use of the vibrissEe becomes very evident in serious diseases ; when, in consequence of the hurried respiration, dry particles floating in the air become attached like a fine powder to these hairs. The collection of particles of dust around the nostrils often warns the practitioner of the serious nature of a disease 4M 642 NEUROLOGY. The osseous portion occupies the upper part of the organ, and consists of the proper nasal bones, and of the ascending processes of the superior maxillary bones. The cartilaginous part consists of the two lateral cartilages of the nose, to which we may add the cartilage of the septum, although it rather forms part of the nasal fossae than of the nose properly so called ; and, secondly, of the two alar cartilages, or cartilages of the nostrils, making five in all. To this we must add certain cartilaginous nodules, situated between the lower part of the cartilages of the alae and that of the septum. Santorini described eleven cartilages in the nose, doubtless because he reckoned certain cartila- ginous nodules, which are sometimes accidentally developed in the substance of the fibrous tissue.* The fibrous portion of the nose consists of a fibrous layer, which occupies the interval between the lateral cartilages of the nose and the cartilages of the alae. From this structure, it follows that the nose is inflexible above, flexible in the middle, and extremely movable below. This arrangement has the threefold advantage of pro- viding against fractures of the most prominent part of the nose, of permitting the dilata- tion of the nostrils, and, lastly, in consequence of the solidity of the highest and narrow- est part of the nasal fossae, of ensuring a free passage to the air. The lateral cartilages of the nose (a a, fig. 231) are of a triangular form ; and they are Fig. 231. united together along their anterior margins, which are thick above, so as to form a sharp ridge, which constitutes the dorsum of the nose. Along the line of union there is a sort of furrow or groove, which can be felt even through the skin. By their upper and posterior margins, they are articulated with the nasal bones ; I say articulated, because there is no continuity of substance, but the parts are connected by fibrous tissue, which allows a considerable degree of motion. Their lower margins are convex, and correspond in front to the cartilages of the alae of the nose, and behind to the fibrous tissue which occupies the intervals between the cartilages. The lateral cartilages are intimately united with the cartilage of the septum, along the dorsum of the nose ; so that we might regard these three pieces as forming a single cartilage. The thickest part of each lateral cartilage is above and in front. The cartilages of the nostrils are generally called, after Bichat, the fibro-cartilages of the alee of the nose; but we have already seen that some of the fibro-cartilages of Bichat are thin layers of ordinary cartilage, while others consist merely of condensed fibrous tissue. The so-called fibro-cartilages of the nostrils belong to the former kind. There is but a single cartilage on each side (b b,fig. 231) for the ala nasi, the lobe, and the in- ferior portion of the septum ; it consists of an irregular lamina folded upon itself into a semi-eUipse or parabola, opening behind. We shall examine its external and internal portions. The external portion (b) is extremely thin, and corresponds to the ala of the nose ; it is not situated in the substance of the ala, but is placed above it, so that its lower margin corresponds to the curved furrow which forms the upper boundary of the ala.+ The internal portion {b, fig. 232) is thicker than the external, and is situated upon a lower plane than it : it corresponds, on the inside, to the internal portion of the cartilage of the opposite side, from which it is separated above by the cartilage of the septum. The internal portions of the two alar cartilages are separated from each other by some rather loose cellular tissue, which allows them to move upon each other, and also per- mits the cartilage of the septum to extend between them, without interfering with them at all. The internal portions of the cartilages of the alae do not reach the anterior nasal spine, but terminate abruptly at a certain distance from it, by forming a projection, which is very distinct, especially in some individuals, and which sensibly elevates the mucous membrane at the entrance of the nostrils. At the point of union between the internal and external portions of each alar cartilage, that is to say, at the summit of the parabola, the cartilage itself becomes wider and excavated behind, and assists in forming the lobe of the nose. The margins of these cartilages are irregularly notched or scolloped. The upper margins are united to the other cartilages by means of a fibrous tissue, which al- lows them to move freely, both upon the cartilage of the septum and upon the lateral cartilages of the nose. A small cartilaginous nodule is found on either side, between the lobe of the nose and the cartilage of the septum ; the only use of these nodules is to facilitate the movements of the lobe upon the septum. The cartilage of the septum nasi (c, fig. 232) occupies the triangular interval between the perpendicular plate of the ethmoid bone and the vomer. It consists of two parts : one, wide and free, which is that generally described ; the other, which is narrow, and may be called the caudal prolongation of the cartilage, is received into the bony portion of the septum, between the two lamellae of the vomer * See note, infra. t [Two or three cartilaginous nodules (e e,Jig. 231) are generally found appended in a curved line to the posterior extremity of this portion of the cartilage of the ala.] THE PITUITARY MEMBRANE. 643 The free •portion of the cartilage is thick and triangular ; it has Fig- 232. the same direction as the bony septum, and presents tivo lateral surfaces, covered by the pituitary membrane ; an anterior margin, of which the upper half (c, fig. 231) is blended with the lateral cartilages along the dorsum of the nose, while its lower half is free, convex, directed downward, and received between the two cartilages of the nostrils ; a superior and posterir margin, which is extremely thick and rough, and is intimately united to the corre- sponding margin of the perpendicular plate of the ethmoid bone (e, fig. 232) : the mode in which this union is effected is not by articulation, but by a continuity of tissue, like that between the costal cartilages and the ribs ; lastly, an inferior margin, which is received between the two plates of the vomer (»). The groove into which it is received is very deep ; and as the two plates of the vomer become more and more separated in extending forward, so does the corre- sponding margin of the cartilage increase in thickness ; hence the lower extremity of the septum frequently projects considerably into one or other of the nostrils. The caudal prolongation of the cartilage of the septum may be seen by carefully exam- ining the retreating angle formed by the perpendicular plate of the ethmoid and the vo- mer ; in which situation the cartilage of the septum gives off a considerable prolonga- tion, in the form of a band, which occupies the interval between the two plates of the vomer, and is attached to the rostrum of the sphenoid bone. This cartilaginous band is contained entirely within the substance of the middle portion of the bony septum : its upper margin is thin, and, as it were, toothed ; the loioer margin is thick and rounded. The two naso-palatine nerves are situated in the same canal as the cartilage, and are placed one on each side of it. The muscles of the nose are the pyramidalis nasi, the levator labii superioris alsque nasi, and the transversalis nasi, or compressor narium, which we have described as a dependance of the depressor alee nasi, or myrtiformis : an accurate description of these muscles is still to be desired. The skin covering the nasal bones and the lateral cartilages of the nose has no par- ticular character : it is thin and movable. That which covers the alae and the lobe of the nose is very thick and extremely dense ; it crepitates under the knife, to such a de- gree, that cartilages have been supposed to exist in the substance of the alae. We have seen, however, that the cartilages of the nostrils are not prolonged into the alae, which are composed essentially of the dense integument just described, and which is reflected inward upon itself around the margins of the nostrils. I should remark, that the antero-posterior diameter of the opening of each nostril is much less than that of the corresponding cartilage ; this depends upon the fact that the skin is prolonged anteriorly, and is reflected for some lines below, and behind the lower margin of the cartilage. The skin of the nose is remarkable for the great development of its sebaceous follicles. The orifices of these follicles are shown in many individuals by certain black points, which are nothing more than the sebaceous matter discoloured. When forced out of the follicles by lateral pressure, the masses of sebaceous matter resemble in form small worms. The skin, which is reflected upon itself around the margins of the nostrils, preserves the character of integument as far as where it is provided with hairs, and then suddenly assumes the characters of mucous membranes. The Pituitary Membrane. The pituitary or Schneiderian* membrane, the immediate seat of smell, is a fibro-mucous membrane, which lines the whole extent of the nasal fossae, and is prolonged, with some modifications of texture, into the different cells and sinuses which open into those fossae. When covered with this membrane, the nasal fossae present a configuration differing in many respects from that which they have in the skeleton. Many of the foramina and canals are closed, and several are contracted in their dimensions. The irregularities of the surface of the turbinated bones are, in some measure, concealed. Besides this, the mucous membrane, where it is reflected upon itself, forms a number of folds, some of which prolong the turns of the turbinated bones ; while others, more or less, contract the orifices of communication between the various cells and sinuses and the nasal fossae. The pituitary membrane, originating, then, on the one hand, from the skin, which is reflected at the margins of the nares, and provided with hairs (h,fig. 233), is, on the other hand, continuous, without any hne of demarcation, with the mucous membranes of the pharynx and velum palati (at t s), of the Eustachian tubes (at m), and of the nasal ducts (at r). In the roof of each nasal fossa {u v) it closes the foramina of the cribriform plate * Conrad Victor Schneider (de Catarrho) gave his name to this membrane, because he was the first to refute successfully the erroneous notion of the ancients, that the secretion of the nasal fossse descended from the ven tricles of the brain ; the common term cold in the head still remains as a vestige of this error. 644 NEUROLOGY. of the ethmoid bone, and those of the nasal bones, so that all the vessels and nerves which pass through these foramina enter the mucous membrane by its external surface ; before it enters into the sphenoidal sinus, it forms a fold around the orifice of that sinus, by which the opening is narrowed, so as to have the form of a vertical fissure (see the bristle marked d). Upon the external wall of each nasal fossa (see fig. 233)* it covers a great number of Fig. 233. parts, counting from below upward, viz., the inferior meatus, at the upper and anterior part of which it meets with the lower orifice of the nasal duct ir,figs. 233, 234) ; around this opening it forms a semilunar valvular fold, the free margin of which is directed down- ward, and which prolongs the canal of the ducts to a greater or less distance in differ- ent subjects ; in passing a probe into the na- sal duct from the inferior meatus, this valve must, almost of necessity, be torn. From the inferior meatus the pituitary membrane is reflected upon the inferior tur- binated bone (c c,figs. 233, 234), which appears longer in the recent state, in consequence of a fold of the mucous membrane being con- tinued in front, and another still more marked behind the bone : this is the thickest part of the nasal mucous membrane. In the middle meatus (i) the pituitary membrane covers the infundibulum, at the lower extremity of which is an ampulla or dilatation, where the orifice of the maxillary sinus is generally found. This orifice (see bristle a, fig. 234) has a very different appearance from that which it presents in the dried scull : it is extremely nan-ow, scarcely admit- ting the blunt end of a common probe. It sometimes appears as if it were wanting ; but it will then be found opposite the middle of the infundibulum ; in this case, the max- illary sinus might be said to communicate directly with the frontal sinus. Not unfre- quently the maxillary sinus opens both into the middle meatus and the infundibulum. The pituitary membrane is prolonged from the infundibulum into the anterior ethmoidal cells (e e, fig. 234), and into the fi-ontal and maxillary (m m) sinuses. If we remove the middle turbinated bone, we find a considerable projection, which bounds the infundibu- lum above (w, fig. 233), and corresponds to a large ethmoidal ceU. Upon the back part of this projection, on which the middle turbinated bone is moulded, an opening (see bris- tle) is often found leading into this great cell, and on its fore part (at e), one or more or- ifices leading into the anterior and superior ethmoidal cells. From the middle turbinated bone (Jb, figs. 233, 234), which is continued backward by a fold of the membrane, the pituitary membrane passes into the superior meatus, where I have fre- quently met with four or five openings leading into as many of the posterior ethmoidal cells, which, in this case, did not communicate with each other : I have even seen the orifice of an etlmioidal cell upon the superior turbinated bone (a). The pituitary membrane dips into all the ethmoid- al cells, and into the fi'ontal sinuses, either directly or indirectly, but it does not enter the spheno-pala- tine foramen, which, on the contrary, is completely closed by it. Upon the septum the pituitary membrane is remark- able for its thickness, being exceeded in this respect only by the membrane covering the inferior turbinated bone. We do not find in man that prolongation or cul-de-sac, which is so very distinct in some animals, in front of the lower border of the septum ; but at this point the pituitary membrane closes the two superior orifices of the anterior palatine canal. Structure.— TYie pituitary membrane is a mucous membrane, and its peculiarity con- sists in its being extended over osseous and cartilaginous surfaces. Its free surface is smooth, red, and scattered over with foramina, from which a great quantity of mucus maybe expressed, t Its adherent surface is intimately united to the periosteum and perichondrium of the bones and cartilages of the nasal fossae, so that it is classed among the fibro-mucous membranes. * [In this figure, portions of the middle and inferior conchae are represented as cut away, to show the parts in the middle and inferior meatuses.] t [In the nasal fossa the epithelium of the pituitary membrane is columnar and ciliated ; in the sinuses it approaches the squamous m character, but yet it is provided with cilia, the movements of which have been observed in the lower animals to produce currents towards the openings of the respective sinuses.] Fig. 234. THE ORGANS OF SIGHT. 645 The pituitary membrane is generally thicker than the other mucous membranes, so that it is very easy to determine the highly vascular and truly erectile structure of this membrane. If it be punctured, and the tube of a mercurial injecting apparatus intro- duced, the mercury will immediately enter the cells of the erectile tissue, and from thence pass into the veins arising from those cells. If a more superficial puncture be made, a lymphatic network will be injected, situated so superficially, that the mercury exhibits all its metallic lustre. This lymphatic network has no communication with the venous cells just mentioned.* This lymphatic network, which is common to all the mucous membranes, gives to the non-vascular layer by which they are covered the appearance of a serous membrane. The pituitary membrane receives a great number of arteries, which penetrate it by sev- eral points, and which are almost all derived from the same source, viz., the internal maxillary artery ; as, for example, the spheno-palatine, the infra-orbital, the superior al- veolar, the palatine, and the pterygo-palatine. Some arise from the ophthalmic artery, viz., the supra-orbital and the ethmoidal ; and others from the facial artery, viz., the dor- salis nasi, the artery of the alae, and the artery of the septum. The capillary veins are so numerous, that they in a great measure form the basis of the pituitary membrane ; the larger veins which proceed from them follow the course of the arteries, and enter, by very large trunks, into the internal maxillary, the facial, and the ophthalmic veins. There are numerous communications between these last-named veins and those of the ethmoidal region of the base of the cranium. The spongy character of the internal surface of the nasal fossae, and more particularly of the surface of the turbinated bones, is due to certain grooves and foramina intended for the reception and transmission of bloodvessels. I am only acquainted with the superficial lymphatic network already noticed. In order to inject it, it is necessary to scratch the membrane with the injecting pipe. Are there any glands ox follicles in the pituitary membrane 1 Steno has described cer- tain glands which I have not been able to find. The follicles in this membrane are rather difficult to be shown. Like all the organs of the special senses, the pituitary membrane is provided with a special nerve, called the olfactory, the nerves of the two sides constituting the first fair of cerebral nerves. Comparative anatomy shows that the development of the olfactory nerves is in relation with the development of the sense of smell, and thus establishes, in a most positive manner, the generally-received opinion regarding the function of this pair of nerves. Without entering here into the description of the olfactory nerves, which will be given hereafter, I would observe, that they pass through the foramina and canals of the cribriform piate of the ethmoid bone, at the same time becoming enveloped in fibrous sheaths ; that they enter the pituitary membrane by its external surface ; and that they expand into a plexus in its substance. The branches of these nerves cannot be traced lower than the middle turbinated bones on the one hand, and the middle of the septum on the other. Thus, while the upper and extremely narrow part of each nasal fossa {s,fig. 234) is the essential seat of the sense of smell, the lower and much wider part only gives passage to the air during the act of respiration. Besides the special nerve of smell, the pituitary membrane receives other nervous fil- aments, all of which are derived from branches of the fifth nerve, viz., from the internal nasal and the frontal branches of the ophthalmic division of that nerve, and from the spheno-palatine, the great palatine, the vidian, and the anterior dental branches of its second or superior maxillary division. The experiments of modern physiologists have shown that the integrity of these different branches of the fifth pair is necessary for the perfect possession of the olfactory sense. This, however, is very different from saying that the seat of that sense is in the branches of the fifth pair. The membrane which lines the several sinuses, although it is continuous with the pi- tuitary membrane, does not resemble it in character ; it is exceedingly thin and trans- parent, and appears like a serous rather than a mucous membrane ; that it is a mucous membrane, is satisfactorily estabhshed only by certain pathological facts. The mucous membrane of the sinuses has a very close resemblance to the conjunctiva. + The Organs of Sight. The eyes, or the organs of sight, are situated at the highest part of the face, so that they are enabled to explore objects at a distance. They are two in number ; but they co-operate in their function so as to act like a sin- gle organ. The result of this is, that vision is rendered more certain, and its field of operation more extensive, at the same time that, from the unity of action of both eyes, it is single. The eyes are protected by the orbital cavities in which they are contained ; they are covered by the eyelids, and these are surmounted by the eyebrows. They are surround- ed by six muscles, by which they can be moved in all directions ; they are divided into * It was in the pituitary membrane of the calf that, about eig-ht years ago, I first accidentally injected the superficial lymphatic network. f See note, p. 648. 646 NEUROLOGY. the straight and the ohlique muscles. There is also a secreting apparatus, the apparatus of the lachrymal passages, the secretion from which lubricates the anterior surface of the ball of the eye, and facilitates the exercise of its functions. The study of the organ of sight, therefore, is not limited to that of the eyes alone, but includes that of the means of protection, viz., the orbital cavities (see Osteology), the eyelids, and the eyebrows ; that of the muscles, or moving organs ; and that of the lachrymal passages, or lubricating apparatus. These accessory parts, or appendages of the organ of vision, have been collectively named by Haller the tutamina oculi. We shall commence our description with them. The Eyebrows. The eyebrows are two arched ridges, which are covered with short stiff hairs, that are directed from within outward, and overlap each other ; the eyebrows are situated at the lower part of the forehead, and form the boundary of the upper eyelid. Their direc- tion corresponds precisely with that of the orbital arch. The hairs upon them are more numerous, and longer at the inner extremity, which is called the head, than at the outer, which is denominated the tail of the eyebrow. The heads of the two eyebrows are sep- arated from each other by an interval which corresponds to the root of the nose ; some- times, however, they are blended together. Structure. — The skin in which the hairs of the eyebrow are implanted is thick, and very closely united beneath to a muscular layer formed by the frontalis, the orbicularis palpebrarum, and the corrugator supercilii, the last-named muscle being situated beneath the other two. The orbital and superciliary arches serve as a basis to support the eye- brows ; the nerves of these parts are very numerous, and are derived from the facial and the fifth nerves ; their vessels arise from the ophthalmic and temporal arteries. Uses. — The eyebrows, which give a peculiar character to the human countenance, pro- tect the eye, and, when depressed in front of it, intercept a great number of the rays of light ; they assist in a remarkable degree in giving expression to the face. The Eyelids. The eyelids are two movable and protecting curtains, placed in front of the ball of each eye, which they conceal or leave uncovered, according as they are in a state of approx- imation or separation. The eyelids are two in number — a superior and an inferior. In a great number of ani- mals there is a third eyelid, of which merely a trace exists in man. The eyelids are large enough to close the base of the orbit completely, and to intercept entirely the pas- sage of light. Each of the eyelids presents for our consideration a cutaneous surface, which is con- vex, and marked with concentric semilunar folds that become effaced when the lids are closed ; an ocular surface {fig. 235), which is concave, is accurately moulded upon the ball of the eye, and presents a series of yellowish vertical lines, formed, as we shall see, by the Meibomian glands ; an adherent border, which is indicated by the orbital arch in the upper eyelid, but is less clearly defined in the lower lid, in which it is continuous with the cheek ; lastly, a free border, or margin, which, in both eyelids, is straight when the lids are closed, and curved when they are open : in the latter position they enclose an elliptical space {rima palpebrarum), the dimensions of which vary in different persons, and hence give rise to the expressions large eyes and small eyes, which have no refer- ence to the actual size of the globe of the eye, but merely to the size of that part which is exposed to view. The free margins of the eyelids are not cut obliquely from before backward, so as to intercept, when they are closed, a three-sided interval or channel, which is completed behind by the globe of the eye, and which is supposed to become larger from without inward, in order to conduct the tears towards the larchrymal punc- ta. On the contrary, these margins are cut horizontally from before backward (see sec- tion, ^^. 240) ; and when approximated, they leave a narrow fissure between them, which may serve as a channel for the tears during sleep, quite as well as the three-sided canal which is generally supposed to exist. The margins of the eyelids, moreover, are tolerably thick, and are furnished at their anterior lip with three or four rows of hard, stiff, and curved hairs, which are more nu- merous and longer on the upper than on the lower eyehd, and at the middle than at either end of each : these are the eyelashes. Their direction is worthy of notice : in the upper eyeUd they are at first directed downward, and are then curved upward, so as to de- scribe an arc having its concavity turned upward ; the eyelashes of the lower lid have just the opposite arrangement. From this it follows, that the convexities of the eye- lashes of the two lids are turned towards each other ; and thus, when the eye is shut, they touch each other without being able to interlace. Serious inconvenience is pro- duced when the eyelashes deviate from their proper course, and are turned inward ; when the eyelashes are wanting, the free margins of the lids are attacked with chronic inflammation. Along the posterior lip of the free raai-gin of each eyelid, or, rather, along the angular ridge formed by the union of that margin with the posterior surface of the THE EYELIDS. 647 lid, are placed a very regular series of foramina (figs. 235, 236), from which the sebace ous matter secreted by the Meibomian glands may be expressed in masses having the form of small vs^orms. At the junction of the external five sixths with the internal sixth of the free margins of the two eyelids are found two very remarkable tubercles, the lachrymal papilla or tu- bercles (a, Jig. 239; also seen injigs. 235, 236), each of which is perforated by an open- ing, visible to the naked eye ; these openings are the puncta lachrymalia, the orifices of the corresponding lachrymal canals. That part of the free margin of each eyelid which is on the inner side of the corresponding lachrymal papilla is straight, rounded, and destitute of hairs or follicular orifices : in the space enclosed between this part of the eyelids, and called lacus lackrymalis, is situated the caruncula lackrymalis (*, fig. 239). The upper eyelid, moreover, is twice as deep as the lower ; so that, when depressed, it descends below the transverse diameter, or equator of the eye, to use an expression invented by Haller. The terms angles of the eye, or commissures of the eyelids, are applied to the angles formed by the junction of the extremities of the free margins of the eyelids. The ex- ternal angle, external or temporal commissure {b,fig. 239), is also named the little angle {canthus mi?ior).* The internal angle, internal or nasal commissure (e), improperly called the great angle of the eye {canthus major), corresponds to the posterior border of the ascending process of the superior maxillary bone. Structure of the Eyelids. — The constituent parts of the eyelids are, the tarsal cartilages, a fibrous membrane, a muscular layer, two integumentary layers, one mucous and the other cutaneous, and certain follicles, with vessels, nerves, and cellular tissue. The tarsal cartilages, which resemble in their use the cylinders of wood attached to the bottom of a map or diagram, to prevent it from hanging in folds, are two in number, one for each eyelid ; they are cartilaginous plates, situated within the free margin and the contiguous portion of the lids. The tarsal cartilage of the upper eyelid {a, figs. 235, 236) is semilunar ; that of the lower eyelid (h) has the form of a small, narrow band ; neither of them occupies the entire length of the corresponding lid. Their anterior sur- face is convex, and is covered by the fibres of the orbicularis palpebrarum muscle. Their posterior surface (fig. 235) corresponds to the conjunctiva, and is closely adherent to it. The Meibomian glands are situated between the conjunctiva and the cartilage, or, rath- er, in the substance of the cartilage. The adherent border of each tarsal cartilage is thin, and affords attachment to the » fibrous membrane of the lids ; the adherent border of the cartilage of the upper eyelid, which is convex, also gives attachment to the levator palpebrae superioris muscle. The free margins of these cartilages are their thickest parts, and occasion the thickness of the free margins of the eyelids, t The cutaneous layer is remarkable for its excessive tenuity and semi-transparency : the eyelashes are appendages of this part of the integument. The cellular layer is no less remarkable for the absence of fat than for its extreme delicacy : it is the type, indeed, of serous ceUular tissue, and is frequently the seat of serous infiltrations. The muscular layer is formed by the palpebral portion of the orbicularis muscle, the pale colour of which, as I have already noticed, contrasts with the dark-red hue of the orbital portion of the same muscle. Besides this, the upper eyehd has an extrinsic mus- cle, the levator palpehra superioris (a, fig. 237), the tendon of which, however, is alone concerned in the formation of that eyelid, by being attached to the upper border of the corresponding tarsal cartilage. The fibrous layer consists of a fibrous membrane, which arises from the margin of the orbit, and is attached to the corresponding borders of the tarsal cartilages. This mem- brane is very strong and unyielding in the outer half of the base of the orbit, but dimin- ishes in thickness towards the inner half of that base, especially on the inner portion of the upper eyelid, where it degenerates into cellular tissue. The term ligament of the external canthus might be applied to a fibrous raphe, which extends horizontally from that angle to the base of the orbit. This raphe bifurcates op- posite the outer canthus, so as to become attached to the outer end of each tarsal car- tilage, and it exactly corresponds to the tendon of the orbicularis palpebrarum, which is situated at the inner canthus, and which is also bifurcated, to join the inner ends of the same cartilages. <^n cutting through this raphe, some very strong fibrous bundles are exposed, which arise from the external wall of the orbit, and spread out into the substance of the upper eyelid. * The external commissure does not correspond to the outer extremity of the transverse diameter of the base of the orbit, but is situated about three lines nearer to the nose ; hence the necessity of dividing this commissure in extirpation of the eye. t [The substance of the tarsal cartilages differs from that of ordinary cartilage in being more opaque, and also in having a fevy microscopic filaments scattered through it; in this respect approaching in character to fibro-cartilage.] 648 NEUROLOGY. The expanded tendon of the levator palpebral superioris, which is subjacent to the fibrous layer, completes the fibrous structure of the upper eyelid. The tarsal cartilages and the fibrous layer are situated upon the same plane. The mucous layer, or palpebral conjunctiva, consists of a membrane which lines the posterior surface {Jig. 235) of the eyelids, and is, moreover, extended over the globe of Fig. 235. the eye. This membrane is called the conjunctiva, or tunica adnata, because it connects the eyelids with the ball of the eye. In order to facilitate our description, we shall suppose it to commence at the free margin of the upper eyelid {a'. Jig. 240), where it is continuous with the skin : having covered the whole thickness of this margin, it then lines the posterior surface of the tarsal cartilage (c'), to which it is intimately adherent, and continues in the same direction as far as beneath the orbital arch. At this point it is reflected upon the anterior surface of the globe of the eye, so as to form a cul-de-sac between that organ and the eyelid : upon the eyeball, where it is called the ocular conjunctiva, it adheres to the sclerotic coat by means of cellular tissue, which is at first loose, but gradually becomes closer and closer as it approaches the transparent cornea. Upon the cornea (d') its adhesion is so intimate that some anatomists have denied its existence in that situation. In fact, it can only be anatomically demonstrated in the healthy state upon the margin of the cornea, but its ex- istence over the whole of that part of the eye is shown in some diseases. After having covered the anterior and inferior part of the sclerotic (c"), the conjunctiva is reflected upon the posterior surface of the lower eyelid (b'), lines its tarsal cartilage, covers its free margin, and then becomes continuous with the skin. On the inner side of the ball of the eye the conjunctiva forms a small semilunar fold, the plica semilunaris {e, Jigs. 235, 239), which has its concavity turned outward, and which may be regarded as the vestige of the third eyelid found in animals : it is misnamed the vnembrana nictitans (la membrane clignotante). On the outer side, the conjunctiva dips between the eyelids and the ball of the eye, and forms a deep cul-de-sac. Opposite the lachrymal papillae the conjunctiva passes into the puncta, and lines the lachrymal passages. From what has been stated above, it will be seen that the conjunctiva would form a shut sac, like the serous membranes, if the eyelids were supposed to be united. Like the serous membranes, it covers two surfaces that rub one upon the other. Its tenuity, its transparency, and the filamentous adhesions which are sometimes observed between its contiguous surfaces, have induced some anatomists to place this membrane among the serous rather than the mucous membranes ; but its continuity with the skin, its ex- treme vascularity, and its uses, which require it to be ia contact with the air, prove that it should be retained among the latter class of membranes.* The glands Jound in the eyelids consist of an appendage of the lachrymal gland, which will be described with it, of the Meibomian glands, and of the caruncula lachrymalis. The Meibomian glands {m m. Jig. 236) are situated upon the posterior surface of both Fig 236 eyelids, opposite the tarsal cartilages ; they resemble yellowish vertical and parallel lines, sometimes straight and sometimes curved ; their length is proportioned to the depth of the cartilages, and they never project upon the inner surface of the eyelids. Each of these lines, of which there are from thirty to forty in each eye- lid, consists of a tortuous canal, folded upon itself a great number of times, and having a considerable number of small follicles open- ing into it on each side. All these canals open very regularly upon the posterior lip of the free margin of the lid by a row of orifices arranged in a single line. I have never seen two rows of openings, as Zinn states he has observed. If the eyelids be compressed over the tarsal cartilages by a pair of pin- cers, masses of a waxy substance exude from these orifices, having the form of small worms twisted frequently upon themselves. Sometimes these small linear canals com- municate with each other opposite the adherent border of the tarsal cartilage ; at other times they bifurcate. It is the waxy sercetion from the Meibomian glands which pre- vents the tears from trickhng in front of the eyelids. These glands are lodged in the deep grooves in the tarsal cartilages ; they are, therefore, as visible upon the external as the internal surface of the cartilages. The Meibomian glands belong to the class of sebaceous follicles, and form a transition, as it were, from follicles to glands. The caruncula lachrymalis {c,Jig. 235,* Jig. 239) consists of a small, oblong group of follicles, situated at the inner angle of the eyelids, and on the inner side of that semilu- nar fold of the conjunctiva, which we have spoken of as the trace of a third eyelid. It is about the size of a grain of wheat. It is interposed between the free margins of * The absence of villi has been stated as characteristic of the conjunctiva ; but villi or papillte are found upon that portion v^hioh lines the superior tarsal cartilage. [The epithelium of the conjunctiva is squamous, and consists of several layers : according- to Henl6, it is ciliated upon the inner surface of the eyelid ; but cilia have not been observed upon the eyeball.] THE MUSCLES OF THE EYE. 649 the eyelids, in that part of those margins which extends between the lachrymal tuber- cles and the internal commissure ; but it is upon a plane posterior to these margins, so that it does not prevent their mutual contact. It is covered by a fold of the conjunctiva, which gives it a reddish aspect ; it presents a great number of openings, through which a waxy secretion exudes, and projecting from it are several small hairs, which may be- come so long as to produce ophthalmia. The caruncula lachrymalis is composed of se- baceous follicular glands, of the same nature as the Meibomian glands. It was for a long time considered to be a second lachrymal gland. In order to obtain a good view of the orifices, and of the light-coloured and sometimes very numerous hairs of the carun- cula lachrymalis, that body should be covered with ink or a solution of carmine, and then examined with a lens. Vessels and Nerves of the Eyelids. — The arteries are the internal and external palpe- bral branches of the ophthalmic, and the palpebral branches of the temporal, infra-orbital, and facial arteries. I have already said that the palpebral arteries form two arches, one for each eyelid. The veins have the same name, follow the same direction, and open into the corre- sponding venous trunks. The nerves are derived from two sources, viz., the facial and the fifth nerve. Uses. — The eyelids protect the eye from the action of light and air, and of any parti- cles floating in the latter ; by a sweeping movement, they clean the surface of the or- gan, over which they also spread the lachrymal fluid, which serves as a protection to the eyeball against the action of the air. The eyelids, from their capability of being inter- posed between the eye and external objects, place the exercise of vision under the con- trol of the will. The Muscles of the Eye, and the Levator PalpebrcR Superioris. The muscles of the eye are six in number, and are distinguished into the straight and the oblique. There are four straight and two oblique muscles. With these we shall also describe the levator palpebrae superioris. Dissection. — Remove the roof of the orbit by two cuts with the saw, meeting each oth- er at an acute angle opposite the optic foramen ; be careful that the inner cut does not injure the cartilaginous pulley of the superior oblique muscle. Dissect the origins of these several muscles from the deepest part of the orbit with the greatest care. They are arranged completely round the optic nerve (o, figs. 237, 238) and the motor oculi nerves. Those which arise above the optic nerve are attached to the dura mater and periosteum, but not to the bone ; but those which arise below the nerve adhere more closely to the bone. The inferior or small oblique muscle is the only one which does not arise from the bottom of the orbital cavity. The Levator Palpchra Superioris. The levator palpebra superioris {a, figs. 237, 238), much thinner and narrower than the rectus superior, which is subjacent to it, arises from the bottom of the orbit, at the upper part of the mar- gin of the optic foramen, or, rather, from the fibrous sheath given off from the dura mater around the op- tic nerve. It arises by short and radiated tendinous fibres, to which the fleshy fibres succeed, in the form of a thin, flat muscle, that passes outward in a line parallel with the axis of the orbit, is reflected upon the globe of the eye, and ends in an aponeurotic ex- pansion, which is inserted in the upper border of the tarsal cartilage of the upper eyelid. Relations. — It is covered by the periosteum of the roof of the orbit, it is covered obliquely at its origin by the ophthalmic nerve, and it covers the superior rectus muscle. Action. — This muscle raises the upper eyelid, and draws it backward, so that the up- per border of the eyelid is concealed under the orbital arch. The Rectus Superior, or Levator Oculi. The superior rectus (b) has two very distinct origins. The first resembles that of the levator palpebrae superioris in being from the upper part of the fibrous sheath of the optic nerve, but it is on a lower plane than that muscle ; the second is from the inner margin of the sphenoidal fissure, i. e., between that fissure and the optic foramen. The latter origin, which is continuous with those of the external rectus, appears to take place from the sheath furnished by the dura mater to the third cranial or motor ocuh nerve. The fleshy fibres arising from this radiated tendon form a flat bundle, which passes for- ward and outward in the direction of the axis of the orbit, and is reflected upon the eye- ball, where it becomes converted into a broad and thin aponeurosis, and is inserted into the sclerotic coat, at a short distance from the cornea. This muscle, like all the other recti, is in relation with the periosteum of the orbit, 4N 650 NEUROLOGY. from which it is separated towards the inner side by the levator palpebrae superioris ; it covers the optic nerve and the eyeball. The Rectus Inferior, or Depressor Oculi. The inferior rectus (c) arises, together with the internal and external recti, by a common tendon, called the tendon or ligament of Zinn, which is attached to the lower half of the optic foramen, and more particularly to a depression which is seen to the inner side of the sphenoidal fissure. Almost immediately after its commencement this tendon divides into three branches, from the middle one of which the inferior rectus muscle arises, and then passing horizontally forward and outward, is reflected upon the globe of the eye, and terminates in a similar manner to the preceding muscle. The Rectus Internus, or Adductor Oculi. The internal rectus (d) has two very distinct origins : one from the tendon of Zinn, the other from the inner side of the fibrous sheath of the optic nerve ; the latter origin is continuous with those of the superior rectus. From these points it passes forward along the internal wall of the orbit, is reflected upon the globe of the eye, and terminates like the preceding muscles. The Rectus Externus, or Abductor Oculi. The external rectus (e) also has a double origin : one inferior, derived from the liga- ment of Zinn ; the other superior, from the fibrous sheath of the sixth cranial or abdu- cens oculi nerve, and continuous with the external origin of the superior rectus. A fibrous arch, under which certain veins pass, unites these two origins, and also serves as a point of attachment to the muscular fibres. From these points the muscle passes obhquely forward and outward along the external wall of the orbit, is reflected upon the eyeball, and terminates like the other recti muscles. General Description and Action of the Recti Muscles. The four straight muscles of the eye arise from the bottom of the orbit, and terminate upon the eyeball, a few lines from the cornea. They all have the same form, viz., that of a long isosceles triangle, having its base turned forward and its apex backward. Their relations are also similar : thus, they cor- respond, on the one hand, to the periosteum of the orbit, and on the other to the optic nerve and the globe of the eye, from which they are separated by some fat and vessels. In consequence of their being inserted in front of the transverse diameter of the eye, they are all reflected upon the eyeball ; this fact is rendered much more evident when the eye is drawn in an opposite direction to that in which the particular muscle under examination would act. Their tendons are surrounded with a whitish, and, as it were^ elastic cellular tissue, by which the movements of these muscles are facilitated.* The recti differ from each other, both in length and thickness. Thus, the internal rectus is the shortest and thickest, the external rectus is the longest, and the superior rectus is the smallest. Action. If these muscles were not reflected upon the globe of the eye, their actiou would be simply to draw it forcibly backward towards the bottom of the orbit ; but, in consequence of this reflection, they can give it a rotatory motion. Thus, the superior and inferior recti rotate the eyeball upon its transverse axis, while the internal and ex- ternal recti rotate it upon its vertical axis. After either of these effects is produced, the eye is then drawn backward. The direct movement backward is produced by the si- multaneous contraction of the four muscles. When any two adjacent recti act together, the eye is moved in the diagonal of the two forces exerted by those muscles ; and hence the eye, and therefore the pupil, can pass over all the radii of the circle represented by the base of the orbit ; this arrangement is not only highly favourable to the exploratory power of the eye, but also assists in placing the function of vision under the control of the will, since it enables us to turn away the eyes from any offensive object. The straight muscles of the eye, as well as the oblique muscles, also aid in expressing the passions ; and hence the following names have been given to them by the ancients. The superior rectus is called superhus (mirator, Haller) ; the inferior rectus, humilis ; the external rectus, indignatorius ; the internal rectus, amw- torius seu bibitorius. Lastly, it has been supposed that the muscles of the eye, by compressing that organ, can alter the distance between the retina and the crystalline lens ; and a theory to ex- plain the power we possess of adapting the eye for distinct vision at different distances has even been constructed on the supposed possibility of this compression. The necessarily simultaneous and co-ordinate action sometimes of the same muscle, and sometimes of different muscles in the two eyes, is a remarkable physiological fact. Thus, the contraction of the superior rectus of the right eye is of necessity accompanied by contraction of the corresponding muscle of the left eye ; while the contraction of the external rectus of one eye is accompanied by contraction of the internal rectus of the * [Small synovial bursE have been described as existing between these tendons and the globe of the eye.} THE OBLiaUE MUSCLES OF THE EVE. 651 Other eye, and vice versa : the will can neither prevent nor disarrange these co-ordinate contractions. However, even without much practice, it is possible to overcome them, so far as to squint by endeavouring to look at the nose. It is not uninteresting to remark, that the sixth cranial nerve, or the abducens oculi, is destined exclusively for the external rectus muscle ; and that the third cranial nerve, or motor oculi, supphes the three other recti, the levator palpebr^ superioris, and the obliquus minor. No other muscles in the body receive such large nerves in proportion to their size as those of the eye. The Oblique Muscles of the Eye. These are two in number, the superior or great oblique, and the inferior or lesser oblique. The Obliquus Superior. The superior or great oblique muscle of the eye (/, Jig. 238) is a long filiform muscle, which is reflected over a pulley or trochlea, and hence has been r,^ gss termed the trochlearis muscle ; it arises from the fibrous sheath of the optic nerve, between the superior and internal recti, in the same maSner and upon the same plane as those muscles ; from this point it passes forward along the angle formed by the junction of the roof with the inner wall of the orbit, and forms a rounded muscular fas- ciculus, which ends in a rounded tendon near the cartilaginous pulley intended for its reception ; the tendon passes through this pulley, is Veflected upon itself at an acute angle, so as to be directed down- ward, outward, and somewhat backward ; gets beneath the superior rectus, where it spreads out, and is then inserted into the sclerotic coat on a level with the longest transverse diameter of the eyeball, and, consequently, farther back than the insertion of the recti. The superior oblique is the longest muscle of the eye. The trochlea, or pulley of the superior oblique, is a small cartilage, which forms five sixths of a short cylinder or ring ; the edges of this imperfect cylinder are attached to the slight bony ridges which bound a depression upon the superior wall of the orbit. Its attach- ment is effected by means of loose ligamentous fibres, so that the pulley itself has a certain degree of mobility. The fehding of the parts is facilitated by a synovial membrane, which is reflected from the tendon upon the pulley, and is prolonged in front of and behind the latter. Beyond the pulley, a whitish filamentous tissue takes the place of the synovial membrane. The relations of the superior oblique are similar to those of the superior rectus. Action. — Like all reflected muscles, the superior oblique must act from the point of its reflection. It follows, therefore, that this muscle rotates the eye upon itself from with- out inward, that is, around its antero-posterior axis. From the oblique direction of its tendon from before backward, after it is reflected, it can draw the eye forward, and tends to bring it out beyond the orbit. This muscle is behoved to assist in the expres- sion of the tender passions {musculus patheticus). The fourth cranial nerve, also called the trochlear or pathetic nerve, is destined exclusively for this muscle. The Obliquus Inferior. The inferior or lesser oblique (g, Jig. 237, 238) is the shortest muscle of the eye, and the only one which does not arise from the bottom of the orbit ; it arises from the inner and anterior part of the floor of that cavity, and, therefore, from the orbital surface of the superior maxillary bone, immediately behind the margin of the orbit, and often even from the lachrymal sac. From this origin it passes backward, in the form of a flat bun- dle, which turns round the lower surface of the globe of the eye, situated at first between the eyeball and the inferior rectus, then between it and the external rectus, and at length ends in an aponeurotic expansion, which is blended with the sclerotic, near the outer border of the superior rectus. Its insertion into the sclerotic is farther back than that of the superior oblique, and. therefore, much farther back than those of the recti. Action. — It rotates the eye in the opposite direction to the superior oblique. Its turn- ing round the lower surface of the eyeball renders its action extremely effective. From its obhque course from before backward, it can draw the eye slightly forward. The Lachrymal Passages. The term lachrymal passages includes both the apparatus for secreting and that for con- veying away the tears, consisting of a secreting organ, named the lachrymal gland ; of excretory ducts, which pour out the tears upon the conjunctiva ; and of a second set of ducts, intended to absorb the tears and convey them into the nasal fossae, comprising the puncta lachrymalia, the lachrymal canals, the lachrymal sac, and the nasal ducts. Such is the order in which we shaU describe this apparatus. 652 NEUROLOGY. The Lachrymal Gland. The lachrymal gland (glandula innominata of the ancients) consists of two very distinct parts : an orbital portioii, situated in the fossa on the roof of the orbit ; and a palpebral pcrr- tion, which is enclosed in the substance of the upper eyelid. The first or orbital portion [I, fig. 207), the only part generally described, is of an irreg- ular semi-ovoid form, having its long diameter placed transversely. It varies in size in different subjects, but is generally about as large as a filbert.* Its upper surface is con- vex, and corresponds to the fossa in the frontal bone, to which it adheres, especially in front, by very distinct fibrous bands : its interior surface is concave, and is in relation with the external rectus, and with a small part of the superior rectus. Its anterior bor- der corresponds to the orbital arch, or, rather, to the fibrous membrane of the eyelid, im- mediately behind which it is situated ; hence it maybe exposed by an incision along this arch. By its posterior edge it receives its vessels and nerves. The second or palpebral portion, though continuous with the first, is separated from it by several fibrous bands. It forms a thin granular layer, which is covered and concealed by a very dense lamina of fibrous tissue that appears to be prolonged into its interior. This palpebral portion occupies the outer portion of the upper eyeUd, and extends almj^t as far as the upper border of the tarsal cartilage. The Excretory Ducts of the Lachrymal Gland. — Before the discovery of these excretory ducts, it was only by inference that the so-called glandula innominata was regarded as the secreting organ of the tears. In 1661 Steno discovered these ducts in the sheep, in which animal they are large enough to admit bristles. He described thirteen or fourteen ducts. The difficulty of detecting these ducts in the human subject is sufficiently proved by the fact that neither Morgagni, Zinn, nor Haller could ever find them ; the second Monro, however, succeeded in filling them with mercury, and described them accurate- ly. They are from ten to twelve in number ; they run parallel to each other beneath the palpebral conjunctiva, and open upon the inner surface of the eyelid by a corresponding number of orifices {d,fig. 235), placed very regularly about a line from the tarsal cartilage, along its outer half. MM. Chaussier and Ribes have succeeded in filling them with mer- cury, by injecting them from the gland towards the eyelids. Having sought in vain, both with the naked eye and with a lens, for the orifices of the excretory ducts of the lachrymal gland in the human subject, I thought of dipping the eye and eyelids in a so- lution of carmine or slightly-diluted ink ; and I then saw distinctly a dozen openings ar- ranged in a line along the point of reflection of the palpebral conjunctiva upon the eye- ball, and occupying the outer half of the eyelid, t The Lachrymal Puncta and Canals. The puncta lachrymalia {a, fig. 239), two in number, one for each eyelid, are those small Fis 239 orifices or foramina which are visible to the naked eye in the centre of the lachrymal papillae : they are perfectly circular, are always open, and are directed backward, the upper one being turned down- ward, and the lower one upward. These openings, which are kept apart from each other by the caruncula lachrymahs, are the capil- lary orifices of two small canals, called the lachrymal canals. The lachrymal canals (/ 1) are small tubes, extending from the puncta lachrymaha to the lachrymal sac. They are two in num- ber, a superior and an inferior, each being somewhat larger than the corresponding lachrymal punctum. Their angular course is very remarkable. They pass at first vertically, the superior duct upward, and the inferior duct downward, and after a short course they bend abruptly at right angles, run inward, and open by separate orifices, never together, into the anterior and external part of the lachrymal sac. The direction of the second portion of each of the lachrymal canals varies according as the eyelids are closed or open : the duct of the lower eyelid is directed somewhat obliquely upward, that of the upper eyelid downward, even when the hds are completely closed ; but they are both very oblique when the eyelids are separated ; and as this separation is principally due to the elevation of the upper eyelid, it follows that the obUquity of the upper lachrymal canal must be very well marked. The coats of the lachrymal canals are dense and elastic, so that they do not collapse when empty, and must, therefore, act as capillary tubes. We do not find any sphincter, either at their palpebral or their nasal orifice ; they appear to be formed in the sub- stance of the free margin of each eyehd ; they are lined by a prolongation of the con- junctiva, and are covered by the fibres of the orbicularis palpebrarum muscle. Behind them are found some muscular fibres, forming a dependance of a small fasciculus, called the muscle of Horner, or the lachrymal muscle, which was believed by that anatomist to serve in drawing the lachrymal ducts inward. * [It has all the anatomical characters of a compound gland.] t T find in Haller that it was in a human eye which had been macerated for some time in water tinged witli blood, that Monro (Secundus) discovered these orifices. After they have been discovered, it is easy to intro- duce the end of the mercurial injecting pipe into them. THE LACHRYMAL PASSAGES. 653 The Muscle of Hffmer. Dissection. — Turn the eyelids inward, and carefully remove a fibrous layer which cov- ers this muscle upon the lachrymal sac. This small muscle arises from the vertical ridge of the os unguis, which forms the pos- terior border of the lachr)Tnal groove ; from this point it passes transversely outward along the posterior tendon of the orbicularis palpebrarum, and divides into two tongues, a superior and an inferior, which correspond to the lachrymal canals, and terminate at the respective lachrymal puncta. I regard these fibres as a dependance of the orbicularis palpebrarum. The Lachrymal Sac and Nasal Duct, or Lachry mo-nasal Canal. The lachrymal sac and 7iasal duct constitute a single canal, which extends from the up- per part of the lachrymal groove to the inferior meatus of the corresponding nasal fossa. The lachrymal sac (m), that portion of the lachrymo-nasal canal which occupies the lachrymal groove, represents the half of a cylinder terminating above in a cul-de-sac. It is buried, so to speak, in the substance of the inner wall of the orbit, immediately be- hind the margin of that cavity, and is in relation with the inner angle of the eyelids, the caruncula lachrymalis, the adipose tissue of the orbit, and the tendon of the orbicularis muscle. The last-named relation is one of the most important points in the anatomy of the lachrymal sac. If a circular incision be made through the eyelids from their outer angle along their adherent borders, and the lids be then turned inward, by then careful- ly dissecting the tendon of the orbicularis, it will be found that that tendon divides into three branches ; that the anterior branch, called the straight tendon, is inserted in front of the ascending process of the superior maxillary bone ; that the posterior branch, which is of equal size with the anterior, is inserted into the ridge upon the os unguis, behind the lachrymal groove ; that the middle branch ascends to be attached to the upper part of the lachrymal groove ; and, lastly, that the lower part of the tendon gives off a fibrous expansion, which forms the outer side of the lachrymal sac, and which may be regard- ed as a fourth tendinous expansion. The muscle of Horner lies upon the posterior of these tendons, and must be regarded as a portion of the orbicularis itself The tendon of the orbicularis palpebrarum corresponds to the upper part of the lachry- mal sac, only its cul-de-sac projecting above the tendon. The greatest part of the sac is, therefore, situated below it. The internal surface of the lachrymal sac presents the ordinary appearance of all ca- nals lined by mucous membrane : a considerable quantity of mucus is often found in it. At the anterior part of its external wall, and at about an equal distance from the top and bottom, are the two orifices of the lachrjmnal canals ; above, is the narrow cul-de-sac, in which it terminates in that direction ; and below, it becomes continuous with the nasal duct : in this place there is rather frequently found a semilunar, sometimes even a cir- cular valve ; this is the kind of diaphragm spoken of by Zinn, but the existence of which was denied by Morgagni. Haller says that he only met with it once. The lachrymal sac consists of a partly bony and partly fibrous canal, lined by a mu- cous membrane. The bony portion of this canal is formed by the groove upon the as- cending process of the superior maxillary bone, and upon the os unguis ; the last-men- tioned bone, which is thin and pierced with foramina, may be easily perforated ; and hence the facility of making an artificial passage for the tears. The lachrymal sac is opposite to the middle meatus of the corresponding nasal fossa. The fibrous portion forms the external flattened wall of this canal ; it is very strong and unyielding, unless to long-continued extension. The slight muscular layer, described as the muscle of Horner, may be regarded as be- longing to the lachrymal sac : this muscle is itself covered by a layer of fibrous tissue. The lining mucous membrane of the lachrymal sac is reddish, and, as it were, pulpy, and closely resembles the pituitary membrane ;* from its close attachment to the peri- osteum of the walls of the canal, it might be called afibro-mucous membrane. ' The nasal duct («), which may be said to be formed in the outer wall of the corre- sponding nasal fossa, extends from the lachrymal sac to the anterior part of the inferior meatus of the nose. It is of a cylindrical shape, slightly flattened on the sides, and rath- er narrower at the middle than at its extremities. It is directed vertically, but forms a slight curve, having its concavity turned forward and outward. It may be also readily conceived that the relative breadth of the root of the nose must affect the direction of this canal. It corresponds, on the inner side, to the middle meatus of the nose, and the inferior tur- binated bone ; on the outer side, to the maxillary sinus, from which it is separated by a very thin lamina of bone. This latter relation has doubtless led one anatomist to state that the nasal canal opens both into the maxillary sinus and the nasal fossa. The nasal canal consists of a bony canal lined by a fibro-mucous membrane ; the bony canal is complete, and is formed by the superior maxillary bone, the os unguis, and the inferior turbinated bone. It is very strong in the part formed by the superior maxillary * See note, p. 654. 654 NEUROLOGY. bone, excepting opposite to the sinus in that bone, but it is very thin and fragile where it is formed by the os unguis and inferior turbinated bone. Its hning membrane is of a fibro-mucous structure ; it adheres very slightly to the walls of the canal, and is contin- uous, on the one hand, with the mucous membrane of the lachrymal sac, and, on the other, with the pituitary membrane.* This Iming membrane is often prolonged for sev- eral lines beyond the nasal duct, so as to form a valvular fold (o). Where this fold ex- ists, the inferior orifice of the nasal duct (see r, fig. 233) is always closed, and, there- fore, difficult to be detected, even when the inferior turbinated bone has been taken away or displaced, so that, in order to discover it, it becomes necessary to introduce a probe through the lachrymal passages from above. In catheterism (if the nasal duct from below upward, according to the method practised by Laforest, this fold of mucous membrane must of necessity be torn. It has been stated by some authors, that the lower orifice of the nasal duct is prece- ded by an ampulla, or infundibuliform dilatation. I have met with this disposition, but regarded it as morbid. I am convinced that a great many lachrymal tumours depend upon contraction or obliteration of the lower orifice of this canal. The Globe of the Eye. The globe of the eye {v,fig. 240) is situated in the fore part of the orbital cavity ; it is retain- ed in this situation by the optic nerve (o), the straight and oblique muscles (beg), the vessels, the conjunctiva (rf), and the eyehds ; these parts, however, do not con- fine it in a fixed position, but allow it great mobility. In fact, the eye can be rotated around all its axes, and can even be drawn forward and backward (see Mus- cles of the Eye). The eyes are small in comparison to the orbital cavities ; and they present some slight dif- ferences as to size in different persons, which have not yet been properly estimated. The common terms large and small eyes apply less to the eyebaU than to the opening between the eyelids. The eye is propor- tionally larger in the foetus and new-born infant than in the adult and aged. In /orm, the globe of the eye resembles a regular spheroid, to the front of which is at- tached a segment of a smaller sphere (see^^. 241) : by this arrangement, the antero- posterior diameter of the organ is increased to the length of eleven lines, while its oth- er diameters are only ten lines. It is said that the form of the eyeball can be altered by the contraction of its muscles, but, in consequence of the great tension of this organ, the alteration produced is so shght that it scarcely deserves to be mentioned. The general relations of the eyeball are the following : in front, it is covered by the conjunctiva and the eyehds, which defend it from hght and from dust, rather than from external violence. It results, also, from the obliquity of the margin of the orbit, that, on the outer side, the eye projects considerably beyond the bones. In every other part of its surface the eye rests upon an elastic cushion of fat (//), which separates it from the muscles and nerves, fills up all intervals, and facihtates the movements of the organ. The absorption of this fat in emaciated individuals causes the depression of the eye into the orbital cavity. A membranous cellular tissue, or, rather, a rudimentary synovial membrane, exists between the eye and this fat. Structure.— Uke all the other organs of the senses, the eye consists essentially of a membrane provided with a special nerve, and of a particular apparatus, placed in relation with the external agent by which the organ is to be acted upon. In the organ of vision, the sentient membrane is the retina, which is the immediate seat of the sense of sight ; the other parts of the eyeball form nothing more than a very complicated dioptric instru- ment, a dark chamber, in which the rays of light are refracted, and concentrated so as to form a vivid image, and which is, moreover, provided with a movable diaphragm to regulate the number of rays to be admitted. In an anatomical point of view, the eye is said to consist of certain membranes and humours. The membranes, counting from without inward, are the sclerotic coat and cor- nea, the choroid coat and iris, and the retina. The humours are, the vitreous body and its hyaloid membrane, the crystalline lens and its capsule, and the aqueous humour. The Sclerotic. Dissection. — Clean the globe of the eye, leaving the attachments of the muscles to the sclerotic coat ; with a pair of strong scissors divide this coat circularly into an anterior and posterior portion, taking care to avoid the choroid coat ; turn the one portion for- ward and the other backward. It is easier to make this section, without injuring the choroid, upon a slightly flaccid eye than upon one which is perfectly fresh. The sclerotic {aK%r}pd^, hard), or the opaque cornea {b,fig. 241), is the outermost of the * [The epithelium of the mucous membrane of all the lachrymal passages is columnar, and, according to Henle, is provided with cilia, although Perkinj6 and Valentin failed to discover them in these situations. J THE CORNEA. 655 coats of the eye, and forms, as it were, the shell of that organ ; it is of a pearly- white colour, and very strong : it is perforated behind to give passage to the optic nerve (o), and presents a circular opening in front (from a lo a), into which the cornea is fitted. Its external surface forms the outer surface of the eyeball, and therefore has the same relations. Thus, it is covered in front by the conjunctiva, which adheres to it by means of very loose cellular tissue, that is liable to infiltration. The straight and oblique mus- cles of the eye are implanted into it. An imperfect or rudimentary synovial capsule separates it from the cushion of fat, and gives it a smooth aspect. Its internal surface has a dull, rough appearance, very different from that of its exter- nal surface : it is, moreover, of a deep-brown colour, from the choroid pigment ; it cor- responds to the choroid coat (c), and is united to it by a very delicate cellular tissue, and by the ciliary vessels.* The ciliary nerves run from behind forward between the scle- rotic and the choroid, occupying shght grooves upon the internal surface of the fonner. Both the ciliary vessels and nerves perforate the sclerotic coat very obliquely. Structure. — The sclerotic is one of the thickest and strongest fibrous membranes in the body : it is not of uniform thickness throughout ; it is thickest behind, at the entrance of the optic nerve, and thinnest in front, near the cornea. Like all the fibrous mem- branes, it is unyielding ; and on this depends the firmness and tense condition of the globe of the eye : it is also the cause of the intense pain produced by inflammation of the interior of the eye and by certain cases of hydrophthalmia. The older anatomists considered the sclerotic to be composed of two layers, the inner of which was, according to Zinn, a prolongation of the pia mater, and, according to Meckel, of the arachnoid. But, independently of the fact that the division of the sclerot- ic into two layers is purely artificial, it may be stated that neither the pia mater nor the arachnoid is prolonged upon the optic nerve. Lastly, the sclerotic has been regarded as a continuation of the dura mater, through the medium of the neurilemma of the optic nerve ; and this view is supported by dissection, which shows clearly that the sheath furnished by the dura mater to the optic nerve is prolonged upon the sclerotic. It has, moreover, been stated, but incorrectly, that the anterior part of the sclerotic has an ad- ditional layer, formed by the union of the tendons of the recti muscles. The sclerotic is composed of fibrous bundles which interlace in all directions. Its use is especially to protect the globe of the eye, of which it forms the covering and determines the shape. The Cornea. The transparent cornea (a a, fig. 241) completes the external shell of the eye in front : in reference to the sclerotic coat, it represents a segment of a smaller sphere superadded to a larger sphere ; its circumference is circular, or, rather, slightly elliptical, for its transverse diameter is half a hue longer than its vertical diameter. Its anterior surface is convex, and projects forward beyond the sclerotic ; it is covered by the conjunctiva, which adheres to it so closely, that the existence of that membrane upon it has been denied by some anatomists. t Too great a convexity of the cornea, by increasing the refracting power of the eye, occasions myopia, or short-sightedness. Its -posterior surface is concave, and forms the anterior wall of the anterior chamber of the eye. A thin membrane (m) covers this surface, and is called the membrane of the aqueous humour. The circumference of the cornea, which is fitted into the opening in the front of the scle- rotic, is cut obhquely, so that its external surface is smaller than its internal surface ; the oblique edge of the sclerotic, to which it corresponds, is sloped in the opposite direction. The cornea and sclerotic adhere so closely that they were for a long time regarded as forming but one coat ; but, independently of their difference in appearance and texture, they may be separated by boiling or by long-continued maceration. Structure. — The cornea is thicker than the sclerotic : it may be separated into a great number of lameUae, united by very thin layers of cellular tissue ; but this separation is purely artificial, so that the number of lamella; is indefinite. The thinnest layer of fluid interposed between the lamellae is sufficient to impair the transparency of the cornea; maceration, accordingly, gives it a milky appearance. The opacity of the cornea, which occurs in some cases of ophthalmia, depends upon the infiltration between the lamella; of a certain quantity of fluid, after the absorption of which the cornea recovers its ori- ginal transparency. No vessels can be shown in the cornea, even by the aid of the finest injections of the arteries and veins of the eye: its superficial layer, which is continuous with the con- junctiva, contains a network of lymphatics communicating with those of the conjunc- tiva, and capable of being demonstrated by puncturing any part of the superficial layer of * See note, p. 656. t A careful dissection, especially after prolonged maceration, shows the continuity of the most superficial layer of the cornea with the conjunctiva. A malformation sometimes occurs in which on« part of the cornea is covered by a prolongation of the conjunctiva. 656 NEUROLOGY. the cornea. It is useless to introduce the tube deeper, for the lymphatic network is en- tirely superficial. Uses. — The transparent cornea is the first medium through which the rays of light have to pass ; in consequence of its density and its convexity, it refracts the rays of light, and causes them to converge. The density of the cornea is the same in different per- sons ; but its convexity is subject to variations, upon which depend, in a great measure, the states of myopia (short sight), presbyopia (long sight), and natural vision. The Choroid Coat, and the Ciliary Circle and Processes. The choroid (indicated by the thick black line, c,Jig. 241), so called from its extreme vascularity,* is the second membrane of the eye, proceeding from without inward ; it is a vascular membrane, covered with a thick layer of pigment : it exactly lines the sclerotic, and terminates, like it, at the circumference of the cornea. Its external surface (c, jigs. 242, 244) adheres to the schlerotic by means of the ciliary vessels and nerves, and by a thin and very delicate cellular tissue, which is easily lacer- ated, and when raised appears like a spider's web.f This surface, when magnified, has a flocculent appearance. Its iTiternal surface is in relation with, but does not adhere to, the retina {r,fig. 241), by which it is lined nearly throughout its whole extent. Both surfaces of the choroid are covered with a pigment, which resembles the pigment of the skin of negroes ; this pigment is much more abundant on the internal than on the external surface, and less so behind than in front, where it forms a thick layer, in the form of a zone surrounding the corona ciliaris. Upon both surfaces are found innumerable longitudinal and contorted lines, which correspond to the vessels of the choroid. In a great number of animals, in the ox, for example, the pigment on the internal sur- face of the choroid at the back of the eye is replaced by a brilhant metallic-looking sub- stance called the tapetum. When deprived of its pigment, the internal surface of the choroid presents a smooth aspect, and is not flocculent like the external surface. It is of a grayish- white colour, and anteriorly, where it is covered by a thick layer of pigment, it becomes white and shining when the pigment is removed. Behind, the choroid is pierced by a circular opening for the passage of the optic nerve ; in front, it terminates in the ciliary circle and ciliary processes, which must be regarded as appendages to it. The Ciliary Circle. — The ciliary circle, ring, or ligament (n, fig, 241 ; b, fgs. 242, 244), is a circular zone, from a line to a line and a half in breadth, of a grayish col- our, and soft consistence, which bounds the choroid coat (c c) in front. It is of con- siderable thickness. Its external surface corresponds to the sclerotic, to which it is slightly adherent. Its internal surface cor- responds to the ciliary processes (e, fig. 241) ; by its outer or larger border, which is distinguished from the choroid by a slight ridge, it receives the ciliary nerves {a a, fig. 24«), which bifurcate, and appear to anastomose with each other before they enter the substance of the ciliary .circle : by its lesser or inner border, which corre- sponds to the iris (/), it adheres intimately to the circumference of the cornea, exactly where that membrane is continuous with the sclerotic (at a a, fig. 241). The older anatomists called this structure the ciUary liga- ment. From the great number of the nerves which enter the ciliary circle, from its gray- ish colour, and its pulpy aspect, modern anatomists have regarded it as a nervous gan- glion (annulus gangliformis, or annular ganglion, Sammering). Some anatomists describe, under the name of the ciliary canal, or the canal of Fontayia, a very small and extremely narrow cir- cular space {v V, fig. 241), which is formed between the ciliary circle, the cornea, and the sclerotic. This space can be filled with injection, and it is not certain that it is not the cavity of a bloodvessel. The Ciliary Processes and the Ciliary Body. — If the back part of the sclerotic, choroid, and retina be cut away, or even if the globe of the eye be merely divided into an anterior and posterior * Choroid is synonymous with vascular. t [A serous cavity is said by some to exist between the sclerotic and choroid ; the lining membrane of this supposed cavity is named the arachnoid membrane of the eye.] THE IRIS. 657 Posterior or iou* half by a circular incision, on looking into the anterior half a perfectly regular radiated disc {d, fig. 241 ; a b, fig. 243) will be seen around the crystalline lens. This disc, which Jias been very correctly compared to a radiated flower, is called the ciliary body, or corona ciliaris ; each of the rays is called a ciliary process or ray (rayon sous-irien, Chaussier). If, after a correct idea of the arrangement of this radiated disc has been obtained, the choroid coat be separated from the humours of the eye, it will be found that there are two perfectly distinct discs : one of these remains attached to the choroid coat, and constitutes the ciliary disc or ciliary body of the choroid {a b, fig. 243) ; the other remains attached to the vitreous body and to the crystalline lens, and is the ciliary zone of pig. 243. Zinn, which may be termed, after M. Ribes, the ciliary processes " ^ of the vitreous body (a b,fig. 248). We shall now describe the cil- iary processes of the choroid coat only, leaving the ciliary pro- cesses of the vitreous body to be described together with that part of the eye. The ciliary processes of the choroid coat, so well described by Zinn, who enumerates sixty of them, are regarded as so many folds of the internal layer of the choroid. They may be divided into great and small, the latter occupying the intervals between the former. They all increase in size (from b to a, fi^: 243) as they approach the outer border of the iris, behind which they are prolonged without adhe- ring to it, and are then bent forward upon themselves, to be attached to that border. These ciliary processes, the sides of which are turned towards each other, have, therefore, a posterior adherent or choroid portion (b), and an anterior free or iridian portion (a). The free portion (e e, fig. 241 ; a, fig. 244) floats am.ong the humours of the eye like a fringe ; the slightest agitation of the vessel or of the liquid in which the cihary processes are contained is immediately communicated to this free portion of the corona ciliaris. The ciliary body or disc, which is formed by the union of all the ciliary processes or rays, is in relation behind with the vitreous body {v in the centre, _%. 241), and advances {e,fig. 241 ; a, fig. 244, in which the iris is removed) over the circumference of the crystalline lens. It is not simply in contact with the vitreous body, but is rather firmly adherent to it ; and we shall afterward see that they are dovetailed together, that is, the ciliary processes of the vitreous body are fitted into the intervals between the ciliary pro- Anterior view-iris removed cesses of the choroid, and vice versa. If the thick layer of pigme.nt with which they are covered be removed, the ciliary processes of the choroid, when examined through a lens under water, have a white colour. In their substance are seen irregular cells which are filled with the brown pigment, and which give them a spongy, and, as it were, jagged appearance. They are evidently con- tinuous with the choroid, which immediately around them presents a zone of a whiter colour than the rest of the inner surface of that membrane. Structure of the Choroid Coat and its Ciliary Processes. — The structure of these parts is essentially vascular. Fine injections thrown into the carotid artery and internal jugular vein, in young subjects, fih a beautiful network of vessels in this membrane. The vor- ticose arrangement (v, fig. 244) of some of these vessels is then clearly displayed ; and, indeed, this is very well indicated, without the aid of an injection, by the strise already described as visible upon the surfaces of the choroid. The short ciliary arteries belong exclusively to the choroid coat. From a great number of experiments made by M. Ribes, it would appear that injections pushed into the arteries do not enter the vilh and fringes of the ciliary body, but that their vessels may be filled from the veins ; so that, accord- ing to this, the structure of the free and fringed portion of the ciliary processes is alto- gether venous, like the cavernous or erectile tissues.* From the different appearance of the external and internal surfaces of the choroid, anatomists have regarded this coat as being composed of two layers, of which the in- ternal is called the membrana Ruyschiana, after Ruysch, who has given the best descrip- tion of it. According to one view, which is not ahogether unsupported, the internal layer alone concurs in the formation of the ciliary processes, while the external layer corresponds to the ciliary ring. The Iris. The iris {i, figs. 242, 243), so called on account of the varied colours which it presents, is a membranous vertical septum, perforated in the centre, like the diaphragm of an op- tical instrument. By means of this septum (i, fig. 241 ), the space (p) between the cornea (m) and the crystalline lens (l) is divided into two parts or chambers, an anterior and a posterior. The iris is circular, and perforated in its centre by an opening which consti- tutes the pupil (p, fig. 242), vulgarly, the apple of the eye, and which is surrounded by the lesser or iniier border of the iris ; the pupil is circular in the human subject, and oblong, * Unsuccessful injections, arterial as well asrenous ramifications are demonstrated in the ciliary processes.] 40 658 NEUROLOGY. either transversely or vertically, in the lower animals ; the number of luminous rays STJf- fered to impinge upon the retina are regulated by variations in the size of this opening; We constantly find in several kinds of animals, and occasionally in the human subject, small fringes attached to the lesser border of the iris, which float in the aqueous humour. The outer or greater border of the iris is, as it were, fitted in between the ciliary liga- ment, which projects beyond it slightly in front, and the ciliary processes, which encroach upon it behind {see fig. 241). The manner in which it adheres to these parts is not well understood. There is a true continuity of tissue, and yet they may be separated by a slight degree of force ; on this is founded the operation for artificial pupil by detaching the iris. The outer border of the iris is not continuous with the circumference of the cornea. The anterior surface of the iris (i, fig. 242), with its different shades of colour, is the part which is seen through the transparent cornea ; it is plane, not convex. The inter- val between it and the cornea constitutes the anterior chamber of the eye (fig. 241). The form and size of this interval can be correctly estimated in a frozen eye ; it is filled with the aqueous humour ; its longest diameter from before backward is about one line. When examined with a lens, the anterior surface of the iris has a flocculcnt appear- ance, more distinct than, but similar to, that of the external surface of the choroid. It appears as if it were fissured here and there, and in the human subject presents some very well-marked radiated bands. When the pupil is contracted these radiated bands are straight, but during its dilatation they become flexuous. They appear to interlace, and thus to become blended with each other near the pupil. It is generally admitted that the membrane of the aqueous humour covers the anterior surface of the iris ; but it cannot be demonstrated in that situation. The colour of this surface differs in different individuals, and it has geneiiilly some relation to that of the hair ; upon these differences depend the colour of the eye«, whether blue, black, gray, &c. Whatever may be the colour of the iris, two shades of different intensity may be distinguished in it, and occa- sion the appearance of two concentric coloured zones in this membrane ; the smaller and deeper-coloured zone is situated near the pupil ; the larger and hghter-coloured one in- cludes the two outer thirds of the membrane. It is not always easy to distinguish these two zones. The posterior surface (z, fig. 243) of the iris corresponds to the crystalline lens, from which it is separated by an interval filled with the aqueous humour, and called the pos- terior chamber of the eye {fig. 241). The two chambers of the eye, therefore, communicate at the pupil {p). The posterior surface of the iris is covered by a thick layer of pigment, which is con- tinuous with the pigment of the choroid ; near its outer border it is also overlaid by the free or iridian portion (e c) of the ciliary processes of the choroid, which can be easily turned back so as to expose the entire posterior surface. It presents extremely well- marked radiated bands, which can be well seen, even before the choroid pigment is re- moved. The aspect of the posterior surface of the iris differs essentially from that of the an- terior surface ; it is white and smooth, and resembles in many respects the internal sur- face of the choroid. Some anatomists are of opinion that the posterior surface of the iris is covered by the membrane of the aqueous humour. If such be the case, it is diffi- cult to comprehend how that membrane is arranged with reference to the pigment. Structure. — The iris is three or four times as thick as the choroid ; it diminishes in thickness from its outer to its inner border. Its real structure is but little understood. The old opinion of its muscularity, which was refuted by Weitbrecht and Demours, has been revived by M. Maunoir, who admits f.vo sets of muscular fibres, viz., radiated fibres, which correspond to the external coloured ring, and circular fibres, which correspond to the internal coloured ring, and form a sort of sphincter around the pupil ; but no circular fibres can be distinguished around the pupil. An appearance as if such were the case, is occasioned by a peculiar arrangement of the radiated fibres, which seem to bifurcate opposite the internal coloured ring, to interlace with each other, and then terminate ab- ruptly around the pupil ; so that the inner border of the iris, or the pupil, appears to be formed by the blunt extremities of these radiated fibres. In the ox and the sheep, the iris has two very distinct sets of fibres : an anterior and circular layer, which occupies the whole of the anterior surface ; and a posterior and radiated set of fibres, which converge from the outer to the inner border. The anterior set of fibres does not exist in the human subject. Another and much more plausible opinion regarding the structure of the iris is, that it consists of a vascular or erectile texture.* If we examine an oblique section of the iris under a lens, we find, indeed, that it has an areolar spongy structure ; and the extreme vascularity of this part also supports the same view. * A case is related of a young man who could produce contraction of the pupils by holding his breath. [The muscularity of the fibres of the iris is now established beyond a doubt ; the fibres of the iris of the pig are described by Schwann as being very minute, cylindrical, and not beaded ; they therefore resemble th© muscular fibres of organic hfe.] THE MEMBRANA PUPILLARIS, ETC. 659 Artenes of the Iris. — The arteries of the iris are principally derived from the two long ciliary arteries, which bifurcate and anastomose after they have reached the ciliary liga- ment, and form a vascular circle, which gives off radiated vessels that converge from the outer border of the iris towards the pupil. There are also some anastomotic arches near the pupil. Vei7is of the Iris. — The veins of the iris are much more numerous than the arteries ; they terminate in the venae comites of the long ciliary arteries, and in the vasa vorticosa. Nerves. — The nerves of the iris, or ciliary nerves {a a, fig. 242), are very large ; as we have stated, they gain the ciliary circle, and then pass through it in great numbers, to enter the iris, and be distributed in its substance. Most of these nerves are given off from the ophthalmic ganglion : some of them are derived directly from the nasal nerve, which is a branch of the fifth cranial nerve. The older anatomists distinguished two layers in the iris : one anterior, which they called the membrane of the iris ; the other posterior, covered with pigment, which they called membrana uvea. By examining an oblique section of the iris with a lens, two layers may, in fact, be seen, separated by the spongy tissue of which I have spoken The Membrana Pupillaris. Dissection. — By opening the eye of the foetus from behind, this vascular membrane may be easily seen through the vitreous body and the crystalline lens. In the foetus, the opening of the pupil is closed by a membane, called the membrana pupillaris, which was discovered and very well described by Wachendorf, but more per- fectly so by Haller and Soemmering, and recently by M. Jules Cloquet. It may be seen about the third month of intra-uterine life, and generally disappears towards the seventh month. When persistent, it may occasion congenital blindness. Wachendorf and Soemmering have demonstrated the vessels of this membrane, which are continuous with those of the iris. During the existence of the membrana pupillaris, the membrane of the aqueous humour forms a shut sac. From the researches of M. Jules Cloquet con- cerning the pupillary membrane, it appears that it consists of two thin layers, between which the bloodvessels are arranged in loops ; that the convexities of these loops are turned towards each other, but that the loops which approach each other from opposite sides do not anastomose together ; that between these loops, and towards the centre of the pupil, there is a small irregular portion of the membrane which is destitute of ves- sels, and is, therefore, weaker than any other part ; that the formation of the pupil is effected by the rupture of this membrane, and that this rupture is occasioned by the re- traction of the vascular loops, which ultimately occupy the lesser border of the iris. Uses of the Iris. — The iris regulates the quantity of light that is admitted into the in- terior of the eye. The contraction of the pupil is an activfl movement, and its dilatation is passive •, facts which are opposed to the doctrine of its muscularity, but support the idea of its being a vascular and erectile structure. It has been stated that the movements of the iris are intended to enable us to judge of the distance and size of objects, or, rather, to enable us to see objects at different dis- tances: this is erroneous, for the pupil remains ^f ^he same size, under the action of a similar quantity of light, whether the object looked at be near or distant.* The effect of narcotics, and especially of belladonna, eitter applied topically, or taken internally, in producing dilatation of the pupil, is one of the most curious facts concerning the iris. The direct action of the rays of light upon the iris has no influence upon the size of the pupil, the dimensions of which are altered either by the action of light upon the retina, or in consequence of a peculiar condition of the optic nerve of the brain Th^ Pigment of the Eye. It has been stated that the external surface of the choroid and the internal surface of the sclerotic are coloured by a very thin layer of pigment ; and also that the internal sur- face of the choroid is covered with a thicker layer, which is itself thickest on the fore part of that surface, near the ciliary body, between the greater ciliary processes, and be- hind the iris. By means of this piginent the interior of the eye is converted into a true dark chamber. Still, it may be asked why the pigment is less abundant behind than in front. The choroid pigment is not black, but of a very dark-brown colour, like bistre ; in this respect resembling the pigment of the skin of the negro ; it consists of molecules or globules insolubie in water. The pigment of the choroid of the iris is wanting in albinoes, as well as the cutaneous pigment. Both have the same chemical composition, t * [The pupil certainly dilates in looking- at distant objects, and contracts under the opposite circumstances ; but it is by no means certain that the adjustment of the eye to objects at different distances depends on these alteratitms in the condition of the iris.j t [The pig^ment of the eye consists of nucleated cells containing the pigment granules ; on the inner surface of the choroid these cells are flattened and hexagonal, and their sides fit accurately together, so as to present an appearance like mosaic work ; on the back of the iris the cells are irregularly rounded. In albinoes the cells contain no coloured granules.] 660 NEUROLOGY. In some animals the pigment of the eye has a metaUic lustre, and an iridescent aspect in a great part of its extent. The Retina. The retina (r,figs. 241, 245), counting from without inward, is the third membrane of the eye ; it is the immediate seat of vision, and is an essentially nervous membrane, sit- uated within the choroid and the sclerotic. Its external surface {r,fig. 245) corresponds to the choroid, from which it is separated by the pigment, which, in eyes that have un- dergone shght decomposition, forms an irregular layer upon it, hke a web. Dr. Jacob {Philosoph. Trans., 1819) has described a serous membrane between the retina and the choroid, in the cavity of which a dropsical effusion may occur, and constitute what is called posterior staphyloma of the eye. M. Weber believes that this membrane is prolonged forward to the circumference of the crystalline lens, and is then reflected over the pos- terior surface of the iris, where it becomes continuous with the membrane of the aque- ous humour. I have not succeeded in demonstrating the membrane of Jacob.* The internal surf ace (r, fig. 246) of the retina is applied to the vitreous body, but does not adhere in the slightest degree to it. The point at which the retina terminates in front is still regarded by most anatomists as undetermined. Several, with the older authors, describe it as extending to the cir- cumference of the crystalline lens. Some entertain a modification of this opinion, be- lieving that an extremely thin membrane is given off from the rim {r'r', fig. 241) in which the retina seems to terminate, and that this membrane advances upon the inner surface of the ciliary body to the front of the capsule of the crystalline lens, to which it is attached. M. Duges, in an excellent work upon the comparative anatomy of the or- gan of vision, expresses a somewhat different opinion : according to his view, the retina having reacT^ved the ciliary processes, divides into numerous tongues, each of which passes between two of the ciliary processes, and terminates by expanding upon the circumfer- ence of the crystalline lens. A careful examination has proved to me distinctly that the retina terminatea by a defined edge (marge dentatus, r'r',fig. 241 ; Tn,fig. 245) at the posterior extremities of the ciliary processes of the vitreous body (a), to which processes it adheres rather firmly, though it can be sometimes separated from them without laceration. Is the retina an expansion of the medullary part of the optic nerve, or is it a special organ continuous with that nerve 1 Although the former of these opinions appears more probable than the latter, still it is liable to objections. The optic nerve is constructed in a particular manner as it passes through the sfclerotic, and the corresponding nervous substance is so ar- ranged that pressure upon the nerve does not force the ner- vous substance into the interior of the eye, though pressure upon every other part of the nerve causes a white pulpy matter to exude from its divided surface. The retina is semi-transparent, like a thin layer of opal : it scarcely holds together, and can be torn with the greatest fwjilHy. It does not appear to me to be thicker be- hind than in front. The radiated lines stated by several of ft»e older anatomists, and also by M. Dnges, to exist in the retina, can only be distinguished behind at the entrance of the optic nerve. This radiated character was evident in the eye (^ an ox which I recently examined. The optic nerve divided into three thick diverging buhdles, which expanded into a layer ; but this filamentous arrangement was soon succe^^de^ by what appeared, at least, to be a pulpy structure. Two layers are described in the retina : an external, which is pulpy and nervous ; and an internal, which is vascular, and is formed by the ramifications of the arteria centralis retinae ; but this subdivision of the retina is purely fictitious. Soemmering has given a good representation of the vascular network, which seema. in some manner to support the nervous substance. The Foramen Centrale, the Fold, and the Limbus Lutcus of ike Retina. — Soemmering was the first to describe in the retina a foramen {foramen ccntra}<:), which had escaped the researches of Ruysch, Zinn, and Haller, doubtless because it is hpncealed by the folds formed by the retina at this point. It is doubtful whether these folds of the retina result from the collapsed condition of the eyeball, which necessarily follows the dissection required for the examination of its interior ; or whether they are really part of its structure, and should be regarded as the vestige of the singular folds existing in different kinds of animals, and especially in birds, the visual powers of which are thereby greatly increased. However this may be, the foramen, which is always situated to the outer side of the entrance (6, fig. 246) of the * [If the posterior part of the sclerotic and choroid be carefully removed from a fresh eye (leaving the optic nerve untouched), and the eye be then macerated a few hours in water, portions of Jacob's membrane will either separate, or they can easily be separated from the outer surface of the retina.] THE VITREOUS BODY. 661 Fig. 246. optic nerve, is surrounded with a zone of a canary-yellow colour : this is the limbus lu- Uus foraminis centralis (Scemmermg), or the yellow spot of Scem- mcring (a). The foramen centrale and the limbus luteus exist in man and th p quadrumana only ; that is to say, in those cases only in which tli visual axes of the two eyes are parallel to each other, as in mai I have not found that the yellow spot corresponds to the thicl est part of the retina It should, moreover, be observed, that the foramen centrale, not the entrance of the optic nerve, corresponds to the antero-posterior axis of the globe of the eye, and is the true centre of the retina. The uses of the central foramen and the yellow spot are not known. The j'ellow spot does not exist in the foetus.* The Humours of the Eye. The media through which the light passes in the eye, besides the transparent cornea already described, are the vitreous body, the crystalline lens, and the aqueous humour. The Vitreous or Hyaloid. Body. The vitreous or hyaloid body {v, figs. 247, 248) (from va'ko^, glass), so called from its re- semblance to glass, is an imperfectly spheroidal, and quite transparent mass, which oc- cupies the posterior three fourths {v,Jig. 241) of the globe of the eye ; it is covered im- mediately by the retina {v, fig. 245), which is simply in contact with it, and indirectly by the other coats of the back part of the eye, which are accurately moulded upon it. It pre- sents a slight depression in front, for the reception of the posterior surface of the crys- talline lens (l). The vitreous body and the crystalline lens together very nearly resem- ble in form the entire globe of the eye, the projection of the crystalline lens representing the prominence of the cornea (compare figs. 241 and 245). The vitreous body is composed of a liquid, named the vitreous humour,i and of the hy- aloid membrane. The hyaloid membrane {h,fig. 241), which was first discovered by Fallopius, can be easily demonstrated by puncturing the vitreous body, and allowing the vitreous humour to escape. U it be then dipped in diluted nitric acid, the membrane will become opaque, and easily distinguishable. This membrane not only forms a general investment or cap- sule for the vitreous body, but gives off lamellar prolongations from its internal surface, which separate the vitreous humour into an irregular number of compartments, or cells. The existence of these cells can be easily proved by moving the vitreous body between the fingers ; and if this body be frozen, their shape is shown by that of the masses of ice which may be taken from them. It is generally admitted that all these cells communicate with each other ; because, when one of them only is punctured, all the vitreous humour will gradually escape. Still, I have several times observed that the eye did not collapse when a part of the vit- reous body had escaped in the operation for extracting a cataract ; this, however, might have depended upon any farther escape being opposed by the approximation of the lips of the incision. The manner in which the hyaloid m.embrane is arranged with reference to the crys- talline lens is still a disputed point. It is generally admitted that, about a line from the margin of the crystalline lens, the hyaloid membrane divides into two layers, one of which passes behind (h,fig. 241) and the other in front of the lens. The three-sided interval (s s) which exists all round the crystaUine lens, and which has been described by Francois Petit, under the name of canal godronni, is formed between these two layers and the lens. This circular canal, or canal of Petit, can be very easily shown by blowing air into it (as in p, fig. 247) ; it is then seen to be constricted at intervals, as if by small folds or bands, so that it presents a knotted or plaited appearance. Other anatomists, on the contrary, state that the hyaloid mem- brane does not split into two layers, but passes altogether behind the crystalline lens, in order to cover the front of the vitreous body. It is certain that * [From recent researches, especially those of Valentin and Hanover, the following- appears to be the mi- nute structure of the retina : 1. The membrane of Jacob consists of minute cylindrical or prismatic bodies, placed closely together, and perpendicularly to the surface of the membrane ; among- these are somewhat lar- ger bodies, "coni gemini," which might be compared in shape to two cylinders applied to each other length- -wise. Both kinds of bodies are attached by one extremity to the inner surface of the choroid, being received into exceedingly minute sheaths, which rise from ihe surface of the pigment cells. 2. The filaments of the optic nerve spread out on the inner surface of this structure, and, according to Valentin, have a plexiform ar- rangement, but their mode of termination seems doubtful. This nervous expansion is covered on its outer and also on its inner surface by a layer of ganglionic globules.] t [The vitreous humour, according to Berzehus, contains 98-4 per cent, of water; its solid matter consists of albumen, extractive matter, and chloride of sodium.] 662 NEUROLOGY. a circular layer, having the form of a radiated crown, is given off from the anterior part of the hyaloid membrane ; this circular radiated disk w^as described by Petit and Cam- per, but it is called the corona ciliaris, or the zonula Zinni : it corresponds accurately to the ciliary processes and ciliary body of the choroid coat. The ciliary zone of Zinn (a, Jig. 245, b, figs. 247, 248), or the ciliary processes of the vit- Fie 248 reous body, can be seen through that transparent body {d,fig. 241) .^e^^^^ when the several coats are removed from the back part of the - , JK globe of the eye : it is completely exposed to view when the cho- j*^*' J^ * ^^^^ ^°^^ ^^^ ^^^^ ^^^^ ^^® separated from the vitreous body (fig. ^^"'^^ 248). It is this structure which constitutes the beautiful radiated ^ 1 crown situated in front of the vitreous body around the crystalhne " ~ ' lens, and which extends considerably beyond the ciliary body of ' *^ the choroid ; it consists of alternate black and transparent rays, and is generally regarded as a reverse impression of the ciliary ._ ^ processes of the choroid. The ciliary processes of the vitreous ^ '^ body correspond to the black lines, and the intervals between the processes to the transparent rays. The cihary processes of the vitreous body are not so thick as those of the choroid ; but the folds of which they consist commence farther back than the ciliary processes of the choroid, so that the radiated disc formed by them is larger than that formed by the processes of the choroid. These folds of the vitreous body have the same spongy and jagged appearance as those of the choroid : they have no free portion, or, rather, that part of the zone of Zinn (a, fig. 248) which corresponds to the free portion of the ciliary processes of the choroid is apphed to the crystalline lens. The ciliary processes of the choroid and those of the vitreous body are so arranged that those of the one are received in the intervals between those of the other. It ap- pears to me difficult to determine whether they are simply applied to each other, or whether their structure is continuous. However, on examining these parts through a lens while they are being separated, it has appeared to me that a sort of cellular struc- ture was lacerated, and that the black pigment, which had been hitherto confined, es- caped together with a little fluid. M. Ribes believes that, during this separation, some shreds of the hyaloid membrane are drawn away with the ciliary processes of the choroid. The inner border (a) of the ciliary zone of Zinn is in contact with the margin of the crystalline lens (Z), and adheres rather firmly to it. Around the outer border, which ex- tends beyond the ciliary body of the choroid, are found the origins of certain radiated folds (i), which form, as it were, the commencement of the ciliary processes. This bor- der adheres to the anterior margin of the retina {m,fig. 245), which appears to me to be thickened and slightly uneven in this situation, and not to be continuous with the hya- loid membrane. From what has been stated, it follows that the canal of Petit is formed between the hyaloid membrane and the zone of Zinn, and that the crystalline lens is fixed by this zone to the anterior margin of the vitreous body ; that the anterior surface of the crys- talline lens is not covered by a prolongation of the hyaloid membrane, besides its own capsule ; and that the retina does not reach as far as the margin of the crystalline lens. M. Jules Cloquet has described, under the name of the hyaloid canal, a cylindrical pas- sage, which is formed by the reflection of the hyaloid membrane into the interior of the vitreous body around the nutritious artery of the lens, and which, like that artery, trav- erses the vitreous body from behind forward. I have never been able to see this canal. No vessels have been demonstrated in the hyaloid membrane ; it does not receive any from the retina, and yet we cannot doubt that it is provided with them. Although the structure of the ciliary processes of the vitreous body is little known, yet, as it is probable that it is similar to that of the ciliary processes of the choroid, and, therefore, essentially vascular, it may be, as stated by M. Ribes, that the materials for the forma- tion and nutrition of the lens and of the ciliary processes of the vitreous body are con- veyed to both of these parts through the vascular ciliary processes of the choroid. The Crystalline Lens and its Capsule. The crystalline lens {I, figs. 241, 244, 245, 248) is a transparent body, having the form of a lens, as its name implies ; it is situated at the junction of the posterior three fourths with the anterior fourth of the globe of the eye, and is placed between the vitreous body, which is behind, and the aqueous humour, which is in front {see fig. 241). Its axis corresponds to the centre of the pupil. It is shaped like a double convex lens, the posterior surface of which is more convex than the anterior. From some very exact and minute investigations which have been made upon this point by Francois Petit and others, it appears that both the relative and the absolute convexity of the two surfaces of the crystalline lens are subject to great varieties in different individuals ; that, in general, the posterior convexity forms part of a circle from four to five lines in diameter, while the anterior forms part of one from six to nine lines in diameter. In some subjects the degree of curvature of the two surfaces THE CRYSTALLINE LENS AND ITS CAPSULE. G63 of the crystalline lens is almost equal. In the foetus the crystalline lens approaches the spheroidal form, which is that which it has in fishes. The anterior surface of the crystalline lens corresponds to the iris, from which it is separated by the aqueous humour. It has been incorrectly stated by Winslow that the crystaUine lens pushes the iris forward : there is a space between the crystalline lens and the iris which constitutes the posterior chamber of the eye. The anterior surface of the lens may be seen through the pupil, so that slight shades of difference in the col- our of the lens may be detected. When the pupil is very much dilated, the anterior sur- face of the lens is entirely exposed. Its posterior surface is in relation with the vitreous body, which is depressed so as to receive it. This surface does not adhere to the hyaloid membrane. When dissecting a subject of twenty-seven years of age who had suffered with hydrophthalmia in both eyes, M. Ribes found about six grains of a limpid fluid between the hyaloid membrane and the crystalline lens ; so that the space occupied by this fluid might have been taken for a third chamber. The margin of the lens {I, fig. 248) is set (like the stone of a brooch) in the ciliary pro- cesses (a) of the vitreous body, which cover and adhere to the fore part of that margin, so that the lens is kept firmly in its place. Its margin is surrounded by the canal of Petit {fig. 247). The crystalline lens presents different shades of colour at different periods of life. It is reddish in the fcetus, but is perfectly transparent after birth ; in the adult, it becomes slightly opaline at the centre ; in the aged, it acquires a yellowish opacity, which ap- proaches somewhat to the colour of amber or topaz. Morbid opacity of the lens consti- tutes lenticular cataract. The crystalline lens consists of a capsule, and of a proper substance enclosed within it. The Substance of the Crystalline Lens. — When stripped of its capsule, the crystalline lens is found to have three degrees of consistence, at different parts : thus, at its sur- face, it is almost of a hquid softness ; below this, it is soft and gelatinous, and may be crushed by the finger — this is the cortical layer ; and, lastly, it is hard in the centre, which is called the nucleus, and closely resembles a mass of gum-arabic. The most superficial and fluid layers constitute the liquor Morgagni. The substance of the crystalline lens consists of concentric layers {b c,fig. 249), which Fig. 249. can be very easily demonstrated, even without any previous preparation, but are rendered most distinct by boiling, or immersion in a diluted acid. The crystalline lens then separates into su- perimposed laminae or scales, like the biilb of the onion. The different degrees of consistence observed in the substance of the lens do not depend upon differences in na- ture, but upon mere modifications. When hardened by an acid, the structure of the lens is exactly the same throughout : even the liquor Morgagni appears to become laminated. Each of these concentric lamina; is itself composed of radiated fibres (a, fig. 249), which can be readily seen without dissection, by placing one of them upon a black sur- face, and examining it through a lens, or even by a strong light. Lastly, the crystalline lens, when boiled, or submitted to the action of an acid, splits into three, four, or even a greater number of triangular segments {ab), all of which unite by their summits at the centre of the lens, so that its anterior and posterior surfaces have a stellate appearance.* Pathologists have successfully applied this anatomical fact to the explanation of the stellate forms of cataract, in which the opacity branches out in three or more directions. What is the nature of the crystalline lensl Is it the product of a secretion 1 or is it an organized structure 1 M. Duges has recently supported by his authority and by ad- ditional facts the opinion of Dr. Young, who believed that the crystalline lens is not only an active organized structure, supplied with vessels and veins, but that it is even mus- cular and possessed of contractility, so as to be able of itself to increase or diminish its curvatures and its density, thus endowing the eye with the power of adjusting itself to the different distances of the objects to be seen. The substance of the laminEe of the crystalline lens has, indeed, a linear structure ; but it does not at all resemble muscular tissue, either in its consistence or in its regularly stratified character. I conceive, therefore, that I am warranted in regarding the superimposed layers of the crystalline lens as the solidified product of a secretion formed by its capsule, t * See note, infra. t [The lines indicating the divisions between the triangular segments of the lens {a, fig. 249) are called sep- ta; the septa of the anterior surface are placed opposite the intervals between the septa of the posterior sur- face. The fibres of which the laminte are composed have a linear arrangement, and, as discovered by Sir D. Brewster, are fitted into each other by indented margins {fig. 250). Schwann has shown that these fibres are developed from rounded, nucleated cells, which become elongated into fibres, the margins of which sub- 664 NEUROLOGY, The capsule of the crystalline lens {t,fig. 241) is accurately fitted to the lens itself; in the healthy state it is transparent, but may become opaque, and thus constitute a mem- branous or capsular cataract. Its external surface is free in front, where it is bathed by the aqueous humour : it is merely in contact with the hyaloid membrane behind, &ut its circumference adheres in- timately to that membrane, or, rather, to the ciliary zone of Zinn. Its internal surface does not appear in the slightest degree adherent to the lens. If an incision be made into this capsule in the living subject, the lens is forced out merely by the tonicity of tfie coats of the eye. The anterior segment of the, capsule is twice as thick as the posterior : it might be compared to a layer of the cornea.* It receives bloodvessels derived from the arteria centrahs retince.t These vessels, according to Meckel, are distributed only upon the posterior half of the capsule ; those which belong to the anterior half arise from the vessels of the ciliary processes. Some anatomists believe that these vessels send ramifications between the different concentric laminae of the crystalline lens for its nutrition ; but I am not aware that they have ever been demonstrated. No nerves have been discovered in the crystalline lens. M. Duges believes that the retina gives off some nervous filaments which reach as far as the lens, and spread out upon its capsule ; but, after the most careful examination, I am convinced that such is not the case. The Aqueous Humour and its Membrane. The term aqueous humour is applied to a perfectly limpid and transparent fluid, which occupies the two chambers of the eye. These two chambers, which have been correctly understood only since the discovery of the true seat of cataract in the crystalline lens, correspond to that small portion of the cavity of the eye which is situated between the cornea and the lens {see fig. 241). The space between these two parts is divided un- equally by the iris (i) into two chambers : an anterior and larger, which is called the a7i- terior chamber; and a posterior and smaller, named the posterior chamber. These two chambers communicate through the pupil (p). The existence of the posterior chamber was long disputed, but it may easily be proved by freezing the eye ; and by the same experiment we may obtain an approximation to the relative capacity of the two cham- bers, which will be found as 3 to 1, the anterior being decidedly the larger. The total quantity of the aqueous humour is about five grains; 100 parts of it are found to contain 98 1 of water, with traces of albumen and chloride of sodium. The Membrane of the Aqueous Humour. — It is now generally admitted that the aqueous humour is secreted by a special membrane, called the membrane of the aqueous humour, or membrane of Demours, although it had been previously described by Zinn and Descemet. This membrane, according to Demours, hues the posterior surface of the cornea {m,fig. 241), and is reflected upon the front of the iris. At this point, according to most anat- omists, it is lost, and cannot be traced to the pupil ; but, according to others, it proceeds as far as the pupil, and there terminates ; and, lastly, some believe that it is reflected through the pupil, in order to cover the posterior surface of the iris, where it retains the pigment in its situation. It is easy to detach a tolerably thick and strong layer, of a cartilaginous aspect, from the posterior surface of the cornea, either after long-continued maceration, or after shght boiling; but it is not shown that this is anything more than the posterior layer of the cornea, which it resembles in appearance. It is only from analogy that the existence of the membrane of the aqueous humour can be admitted. We cannot demonstrate anatomically its reflection upon the outer border of the iris ; and, moreover, it is certain that it does not exist upon either surface of that membrane. According to M. Ribes, the aqueous humour is supplied by the vitreous body, and is poured into the posterior chamber by the canals said by him to exist in the substance of the ciliary processes of the vitreous body. This opinion is founded, 1. Upon an exper- iment which consists in carefully removing the cornea, and suspending the eye by the optic nerve, when the vitreous humour wiU exude from the wound of the cornea, so that, in less than twenty-four hours, two thirds of that body will have escaped ; and, 2. Upon the observation of cases of imperfect iris, in which, according to M. Ribes, the aqueous ° ' " sequently tecome dentated ; the lens, therefore, resembles some other non- vascular parts (as the horny tissues) in its mode of growth. It consists, according to Berzelius, of 58'0 per cent, of water, 3-7 of extractive and salts, 24 of membrane, and 35-9 of a peculiar substance, which, except in its colour, resembles the colouring matter of the blood. * According to M. Ribes, whom I always have pleasure in quoting, because his re- searches are worthy of every confidence, " by examining the internal surface of the crys- taUine capsule in a good light, and with a good lens, a series of transverse fissures are observed around its entire circumference, where the anterior and posterior segments of the capsule unite. I could never satisfy myself whether these fissures corresponded to the ciliary processes of the vitreous body, or to the villous fringes of the ciliary processes of the choroid." T Vide fig. v., pi. 6, of ScEmmering's Icones OcuU Humani. THE ORGAN OF HEARING. 665 humour is contained entirely in the posterior chamber. He believes that the free por- tion of the vitreous ciliary body has the power of absorbing this liquid. M. Duges adopts the following modification of this' opinion : the canal of Petit, accord- ing to him, is divided into as many compartments as there are ciliary processes. It re- sembles, therefore, a collection of short canals directed from before backward, rather than a single circular canal ; these short canals communicate behind with the vitreous body, and open in front by certain slits or perforations existing in the zone of Zinn, which enable the aqueous humour secreted by the vitreous body to escape in front of the crys- talline lens. Haller has stated all the opinions which have been entertained regarding the produc- tion of the aqueous humour, which has been said to be secreted by the vitreous body, as believed by MM. Ribes and Duges, by the ciliary processes, by the choroid, by the iris, and, lastly, by certain special ducts proceeding from without the eye, and perfora- ting the sclerotic at its junction with the cornea. The Vessels and JVerves of the Eye. The arteries of the eye are the following : a considerable number of short posterior cil- iary arteries, which surround the optic nerve, perforate the sclerotic near it, and ramify in the choroid, in the ciliary processes, and in the iris ; the anterior short ciliary, which perforate the anterior part of the sclerotic, and are distributed to the iris ; the long cilia- ry arteries, two in number, which run between the sclerotic and the choroid, as far as the outer border of the iris, and then, bifurcating and curving inward, anastomose with each other around that border. From the vascular circle thus formed most of the ves- sels of the iris are given off. The central artery of the retina {artcria centralis retina) en- ters the globe of the eye through the centre of the optic nerve (at the porus opticus, b, jig. 246), and, sending off a branch to the crystalline lens, which traverses the vitreous body from behind forward, covers the internal surface of the retina with its other rami- fications. The veins correspond to the arteries, but are much more numerous. The posterior, or short ciliary veins, form vortices or whorls in the choroid, and are hence called vasa vorticosa {v,fig. 244). All the veins of the globe of the eye open into the ophthalmic and angular veins. The 7ierves of the eye consist of a special nerve called the optic 7icrve, the origin, course, and structure of which will be described hereafter (see Cranial Nerves) ; and, second- ly, of the ciliary nerves, which are derived from the fifth nerve, either directly from its nasal branch, or indirectly from the ophthalmic ganglion. These nerves {a a, fig. 242) are distributed to the cihary ligament, and to the iris. The Organ of Hearing Hearing is that sense by which we perceive the vibrations of the air, which produce sound. The organ of hearing is not situated in the face, like those of the other senses, but is contained in the substance of the base of the cranium, in the petrous portion of the tem- poral bone, its deep situation preserving it from external violence : it is composed essen- tially of a membranous and nervous apparatus contained in an extremely complicated osseous cavity, named the labyrinth or internal ear. The labyrinth {f,fig. 251) communicates with the exterior by means of an acoustic trumpet formed by the auricle, or pirina (a), and external audita- p^ 251 ry meatus (b), and named the external ear, which may be regard- ed as an apparatus for collecting sonorous undulations. The term middle car, or tympanum, is applied to a cavity {d) which is placed between the labyrinth and the external ear, and may be considered as an apparatus for modifying sounds, the intensity of which is increased or diminished by it, according as they happen to be weak or loud.* It follows, therefore, that the ear is formed by a succession of cavities, which, proceed- ing from without inward, are, the external ear, consisting of the auricle and external auditory meatus, of the middle ear, or tympanum, and of the internal ear, or labyrinth. I shall de- scribe the ear in this order, and shall thus proceed from the less to the more complica- ted parts of this organ. The External Ear. The extexnal car resembles a funnel or ear-trumpet, the expanded part of which rep- resents the auricle, while the contracted portion corresponds to the external auditory meatus.! * M. Richerand (Elemens de Physiologic, first edit.) has drawn an excellent comparison between tiie uses of the tympanum in hearing-, and those of the iris in vision. f The e-xternal ear, properly speaking, only exists in mammalia ■ and even among mammalia, those which do not live constantly in the air are not provided with it. 4P 666 NEUROLOGY. The Auricle. The auricle of the ear {auricula, ■pinna), commonly called the ear, is placed at the side of the head, behind the articulation of the lower jaw, and in front of the mastoid process ; it is an oval elastic lamina, folded in various ways upon itself, and having an undulated surface. The auricle or pinna is free above, behind, and below, but is so firmly attached in front and on the inner side, that the two ears can support the weight of the entire body. The individual varieties in the shape, direction, prominence, and size of the auricle are generally known. Of these varieties, some are congenital, and others acquired. Among the latter should be noticed the effects produced by the habit of confining the entire ear more or less closely by the head-dress. The direction or prominence of the auricle is not without some influence upon hearing, the perfection of which sense, ac- cording to Mr. Buchanan, depends on the kind of angle formed by the auricle with the side of the face, and which should be from 25° to 30°. The internal or mastoid surface of the auricle presents certain eminences and depres- sions, which correspond inversely with those on its external surface. The external surface is remarkable for the alternate ridges and depressions observed Fig 252 upon it : at its centre, but somewhat nearer to the lower than the up- per part, we find the concha {a, fig. 252), a funnel-shaped excavation, the form and expansion of which are familiar to all, and at the fore part of the bottom of which is found the orifice of the external audito- ry meatus. The concha is bounded in front by the tragus (b ), a triangular pro- cess, the adherent base of which is turned forward and inward, while its free apex is directed backward and outward : it advances hke a lid over the orifice of the external auditory meatus, which is com- pletely closed by its depression. The posterior surface of the tragus, which forms part of the concha, is covered with stiff hairs, especially in old subjects ; whence its name of tragus, from rpdyoc, a goat. The use of these hairs is to arrest any small particles that are floating in the air. Behind and below, that is, opposite the tragus, the concha is bounded by the anti-tra- gus (c), a triangular tongue, which is smaller than the tragus, and is separated from it by a wide, deep, and rounded notch, named the notch of the concha {incisura tragica). Behind and above, the concha is bounded by the anti-helix (e), a curved fold, which commences above the anti-tragus, being separated from that part by a slight depression, passes upward and forward, bifurcates, and then ends in the groove of the helix. The superior branch of the bifurcation of the anti-helix is broad and smooth, while the inferi- or is sharp ; between them is situated a slight depression, called the scaphoid, or navicu- lar fossa, but which would be more correctly named i\ie fossa of the anti-helix (/). The term helix (ell^, a roU, from kliaau, to roll around) is applied to a curved fold {g g), which forms the external border of the auricle : it commences in the cavity of the concha, which it divides into two unequal parts, one superior and narrow, the other in- ferior and broader ; gradually increasing in size, it then passes upward and forward above the external meatus, then above the tragus, from which it is separated by a very distinct furrow : it next runs directly upward, curves backward, descends to form the posterior margin of the auricle, and terminates by becoming continuous with the anti-helix in front, and with the lobule {I) behind. The groove or fiirrow of the helix is the groove (i) which surrounds the helix, and sep- arates it from the anti-helix. The lobule occupies the lower or small extremity of the auricle, from the rest of which it is distinguished by its softness ; it is surmounted by the tragus in front, by the anti- tragus behind, and by the notch of the concha in the middle. The lobule of the ear va- ries exceedingly in size in different individuals, and is the part to which ear-rings are generally appended. The Structure of the Auricle.— T\ie cartilage of the ear {figs. 253, 253*) constitutes the framework of the auricle, in a great measure deter- mines its shape, and is the cause of its pliability and elasticity. When the skin is removed from it, this cartilage, therefore, presents certain eminences and depressions, corresponding, with some exceptions, to those already described as existing upon the surface of the auricle. The cartilage of the ear has no part corresponding with the lobule : again, the cartilaginous fold which consti- .r? tutes the helix terminates at the middle of the concha, from whence it is continued by a fold of skin, which, moreover, covers it throughout, and increases its prominence. Upon the cartilage of the auricle we also observe the following parts : 1. A manmiillated eminence {a, fig. 253), Fig. 253. Fig. 253.* THE AURICLE, 667 called the process of the helix : it is of considerable size, is very dense, and arises from the anterior margin of the helix, above the tragus. This process gives attachment to a ligament. 2. A tail-shaped tongue of .cartilage (i), separated from that of the anti-tragus and concha by a very long lissure, which is occupied by ligamentous fibres. This tongue is formed by the united ends of the helix and anti-helix, and is very thick and dense ; it may be called the caudal extremity of the helix and anti-helix ; it supports the base of the lobule. 3. A well-marked thickening, situated opposite the concha, and characterized by a dead white colour. This thickening occupies a vertically elongated portion of the mas- toid surface of the concha, and terminates at the lower part of the auricular cartilage : it seems to be intended to preserve the form of the concha, which cannot be flattened unless this thickened portion of the cartilage is first divided. Several fissures or notch- es are also found in the cartilage of the ear, which is thus imperfectly divided into sev- eral pieces that are movable upon each other, and united together by ligaments. The principal fissure, independently of that already described as existing between the anti- tragus and the caudal extremity of the helix and anti-helix, are, a small vertical fissure upon the anterior margin of the hehx ; another vertical fissure upon the tragus ; several irregular notches in the helix ; and, lastly, a much more important fissure, to which I shall have to allude in describing the external auditory meatus. It is situated between the helix and the tragus, and is prolonged upon the outer half of the orifice of that ineatus. The skin of the auricle is remarkable for its thinness and transparency : hence the sub-cutaneous vascular network can be seen through it without dissection ; it is no less remarkable for its tension, and its close adhesion to the cartilage, upon which it is mould- ed, so as accurately to reveal its form. The portion of skin which covers the concha is especially remarkable for its great tenuity and intimate adhesion to the cartilage. The skin upon the free border of the auricle adheres but slightly to, and projects be- yond the helix ; the same fold of skin, when doubled upon itself and prolonged below the helix, constitutes the lobule, which, together with the adjacent part of the free border of the auricle, is nothing more than a duplicature of the skin, containing some soft fat. A small quantity of fat is formed around the entire circumference of the auricle, but none exists in other situations. The skin of the ear is provided with sebaceous follicles, which can be easily shown by maceration, after the method employed by Soemmering, and which are most numerous in the concha and the scaphoid fossa. The ligaments of the auricle are divided into the intrinsic and the extrinsic ligaments. The extrinsic ligaments are, iYie ■posterior ligament, which is a thick, tendinous layer, ex- tending from the concha to the mastoid process ; the anterior ligament, which is a triangu- lar, very broad, and very strong ligament, arising from the process of the helix and the ad- jacent part of the border of the helix, and terminating at the zygomatic arch, where it is blended with the superficial temporal fascia ; and, lastly, the ligament of the tragus, which is very strong, and extends from the tragus to the adjacent part of the zygomatic arch. The intrinsic ligaments, the object of which is to keep the cartilage of the auricle fold- ed upon itself, are, the ligament which keeps the caudal extremity of the helix applied to the concha ; the very strong ligament which extends from the tragus to the helix, and unites the outer half of the auditory meatus to the cartilage of the auricle ; some very strong bundles, which are situated upon the mastoid surface of the auricle, and are in- tended to preserve its convolutions, for when they are divided the auricle may be un- folded ; lastly, those most remarkable ligamentous bundles, which occupy the fold pre- sented by the inferior branch of the bifurcation of the anti-helix. The three extrinsic muscles of the ear, which exist in a rudimentary condition in the human subject, but are so highly developed in timid animals, are intended to move the auricle as a whole (see Myology). The intrinsic muscles move the different parts of the auricular cartilage upon each oth- er. Like the extrinsic, they are quite rudimentary. There is no difference in their size in savage and civilized races. They are five in number, four of them being situated on the concave, and one only on the convex, or mastoid surface of the auricle. The great muscle of the helix (helicis major, c,fig. 253) is situated vertically upon the anterior part of the helix, near the tragus ; it is a narrow, oblong tongue, fleshy in the middle, and tendinous at its extremities ; its fibres are vertical. The small muscle of the helix (helicis minor, d), the smallest of the intrinsic muscles of the ear, lies upon that portion of the helix which divides the concha into two parts. The muscle of the tragus (tragicus, e) is a broad band, lying upon the external surface of the tragus ; its fibres are directed vertically. The muscle of the anti-tragus (anti-tragicus,/) is a tongue-like bundle, which covers the external surface of the anti-tragus, and is inserted by a tendon to the upper part of the caudal extremity of the helix. Its use may be to move this caudal extremity upon the anti-tragus. The fifth is the transverse muscle (transversus auriculae, a, fig. 253*), which is situated 4K 668 NEUROLOGY. on the mastoid surface of the auricle. According to Soemmering, it consists of a trans- verse layer of fibres of unequal length, which spread out in a semicircular form from the convexity of the concha to the ridge, corresponding to the groove of the helix. I doubt the muscularity of these fibres, which I am inclined to regard as constituting an intrin- sic ligament intended to preserve the fold of that portion of the anti-helix by which the concha is bounded behind and above. The arteries of the auricle are the posterior auricular, a remarkable branch of which passes through the cartilage, between the caudal extremity of the helix and the concha, so as to ramify in the cavity of the concha. All the branches of the posterior auricular arteries turn over the free border of the helix, so as to reach the concave surface of the auricle. The anterior auricular arteries arise from the external carotid and the tempo- ral, and divide into inferior branches or arteries of the lobule and ascending branches. The veins have the same names and follow the same course as the arteries. The nerves of the auricle are derived from the auricular branch of the cervical plexus ; three or four of them ramify upon the internal surface of the auricle. A remarkable branch perforates the cartilage between the anti-tragus and the caudal extremity of the helix, and is distributed to the skin which lines the concha.* The External Auditory Meatus. The external auditory meatus {h,fig. 251) is a partly cartilaginous and partly osseous canal, extending from the concha (a) to the membrane of >;he tympanum (c). It forms the narrow portion of the ear-trumpet represented by the external ear. It is about an inch in length. Its section represents an ellipse, of which the longest diameter is vertical. Its direction is transverse, and it describes a very shght curve, having its convexity turned upward. Moreover, near its external orifice it is bent at an ano-le which projects upward, and hence it is necessary to draw the auricle upward and backward, if we wish to examine the bottom of the external auditory meatus. The external meatus is in relation with the temporo-maxillary articulation in front, with the mastoid process behind, and with the parotid gland below. Its external orifice, which is vertically oblong, more oi; less widened out in different in- dividuals, and covered with hairs in old age, occupies the anterior and inferior part of the concha behind the tragus, which serves as a lid for it. It is bounded behind by a sort of semilunar ridge, which projects more or less forward in different individuals, so as to contract its orifice to a greater or less extent. In front of the auditory meatus there is an excavation or fossa concealed by the tragus, and named the tragic fossa of the concha ; it forms, as it were, the vestibule of the meatus. The internal orifice of the auditory meatus is circular : it is directed very obliquely downward and inward, and is closed by the membrana tympani. Structure. The auditory meatus consists of an osseous portion, and of a cartdagmous and fibrous part. The osseous portion has been already described with the temporal bone, as the external auditory meatus. It is wanting in the fffitus, and in the new-born inlant, in which its place is supplied by the tympanic ring or circle. We have stated that, in the adult, this ring forms an osseous lamina distinct from the rest of the temporal bone, that it rests behind upon the mastoid and styloid processes, for the latter of which it forms the vagi- nal process, and that it is separated in front from the auricular portion of the glenoid cavity by the fissure of Glasserius ; this lamina forms both the anterior and inferior walls of the auditory meatus and cavity of the tympanum. The cartilaginous and fibrous portion forms the outer half of the external auditory mea- tus, and may be separated from the cartilage of the auricle by a careful dissection. If an incision be made over the similunar ridge which constitutes the outer border of the orifice of the auditory meatus, it will be seen that this ridge is formed by the juxtaposi- tion of two cartilaginous borders, one of which belongs to the concha, and the other to the auricle, and which are united by fibrous tissue. If the dissection be continued be- tween the tragus and the corresponding part of the helix, the auricle may be separated from the auditory meatus, exceping below, where their continuity is established by means of a tongue or isthmus of cartilage. The tragus belongs essentially to the auditory meatus, the cartilage of that canal being merely a prolongation of the tragus folded upon itself (see b, fig. 253*), so as to form the lower two thirds or three fourths of a cylinder. The inner end of this imperfect cylm- der is attached to the rough external rim ot the osseous portion of the meatus by means of a fibrous tissue, which extends farther above and behind than below and in front, and ■which gives the cartilage a great degree of m.obility ; there is a thick prolongation or process at the lower and anterior part of the inner end of the cartilage of the meatus. The fibrous portion of the auditory meatus forms the upper third or fourth of that canal, and also fills up the large notch in the inner end of the cartdaginous portion. * [The auricle also receives twigs from the posterior auricular branch of the facial nerve, from the anriculo- temporal branch of the inferior maxillary division of the fifth nerve, and from a small branch of the pneumo- gastric nerve. See description of those nerves.] THE TYMPANUM. " 669 Near the tragus there are two or three fissures or divisions in this cartilage, named the fissures of Santorini, which give it some resemblance to the rings of the trachea : these fissures are at right angles to the length of the canal, and are filled up with a fibrous tissue, which some anatomists have conceived to be mixed with muscular fibres, or to consist entirely of muscular fibres intended to move the small and partially separa- ted portions of the cartilage. It is evident that the mode in which the partly cartila- ginous and partly fibrous portion is united with the osseous portion of the canal, and also the existence of the fissures just described, have reference to the mobility of the entire canal. The internal surface of the auditory meatus is lined by a prolongation of the skin, which is remarkable for its extreme thinness. It becomes thinner and thinner in ad- vancing from the orifice to the bottom of the meatus ; and the fineness and extreme del- icacy of that portion of the skin which corresponds to the osseous part of the meatus deserves special attention. The skin of the meatus is also characterized by being cov- ered in all parts with fine downy hairs ; a fact which proves that it is of a cutaneous structure, and not a mucous membrane. In old subjects, there are some tolerably long hairs at the commencement of the auditory meatus, as well as upon the internal surface of the tragus ; they prevent the entrance of dust and insects, which, moreover, get in- volved in the ceruminous secretion. The skin of the meatus is farther characterized by the presence of a number of se- baceous follicles, or glands, called the ceruminous glands,* the orifices of which are vis- ible to the naked eye, and give the skin an areolar appearance. These small glands oc- cupy the entire inner surface of the cartUaginous and fibrous portions of the auditory meatus : from their yellowish-brown colour, they can be readily seen in oblique sections of the skin. They secrete a rather thick unctuous substance, resembling wax, whence it is called cerumen (cera, wax). It is very bitter, and is partially soluble in water, with which it forms an emulsion which leaves a greasy stain upon paper ; it sometimes be- comes exceedingly hard from remaining long in the passage, and then acts as a mechan- ical cause of deafness. By analysis, this substance, according to Berzelius, yields a fatty oil, an albuminous substance, and a colouring matter, and, according to Rudolphi, a bitter principle like that of the bile. Nature intended, says Soemmering, that there should be a sufficient quantity of cerumen, not only to keep out insects, but also to di- minish the intensity of sonorous vibrations. It is, therefore, a bad habit to remove it artificially, unless there be an abnormal accumulation of this substance. The Middle Em; or Tympanum. Dissection. — The cavity of the tympanum may be laid open, either from its external wall, by removing the membrana tympani, or from its upper wall, by cutting away the anterior part of the base of the petrous portion of the temporal bone with a strong scal- pel ; the situation in which this may be done is indicated by a fissure, or, rather, a su- ture, which exists between the petrous and squamous portions ; lastly, the tympanum may be opened from its lower wall, by breaking down the osseous plate of the auditory meatus. In order to show all the parts contained in the cavity of the tympanum, several speci- mens should be prepared in different ways. It is of importance, moreover, to study the ear in the temporal bones of the adult subject and the foetus, as well in macerated speci- mens as in such as have been dried without previous maceration. The tympanum, tympanic cavity, or drum of the ear {tympanum, a drum, d, fig. 251), is a cavity situated between the external auditory meatus {b) and the labyrinth or internal ear (/) ; it communicates with the pharynx, and, consequently, with the air-passages, by means of the Eustachian tube (e, fig. 255) ; it is prolonged into the mastoid process, by means of the mastoid cells (c), and it is traversed by a chain of small bones (1, 2, 3), named the ossicula auditus. The tympanum is placed in the anterior part of the base of the petrous portion of the temporal bone, above the osseous lamina of the external meatus, and in front of the mastoid process ; it is directly continuous with the osseous portion of the Eustachian tube, of which it seems only to be a dilatation. From its form, which is otherwise irregular, or, rather, from the two dry membranes formed upon its opposite walls, it has been compared to a military drum ; it is flattened from without inward, so that its transverse diameter is the shortest. It presents for our consideration an internal and an external wall, and a circumference. The External Wall of the Tympanum. — This wall is formed by the membrana tympani, and by that portion of the temporal bone in which the membrane is fitted. This portion of the temporal bone is a compact lamina, which is flat in the hmnan subject, but ex- tremely prominent in some animals. The membrana tympani {c,fig. 251) is a nearly circular, semi-transparent membranous septum, dry-looking like parchment, and vibratile ; it is situated between the externa! * [The ceruminous glands consist of a long convoluted tube, closed at one end, and opening by the other upou the internal surface of the meatus.] 670 NEUROLOGY. auditory meatus, at the bottom of which it may be seen in the living subject, and the cavity of the tympanum. It is directed very obliquely downward and inward ; so that, instead of passing perpendicularly across the auditory meatus, it is continuous, at a very slight angle, with the upper wall of that canal. In consequence of this obliquity, the membrana tympani unites with the lower wall of the meatus at an angle of about 45°, and the meatus itself terminates in such a manner that its lower wall is much longer than the upper. The external surface of the membrana tympani is free, and is directed downward and outward ; the internal surface is turned upward and inward, and adheres very firmly to the handle of the bone of the ear, called the malleus, by which it is drawn inward, so that its centre presents a funnel-shaped depression, which is concave externally and convex within. The circumference of the membrane is fitted, Hke a watch-glass, into a circular furrow formed at the inner end of the external meatus in the adult, and into the tympanic ring in the foetus. Above and behind, near its insertion into its bony frame, the membrana tympani is elevated by a small process (the short process) of the malleus. Immediately on the inner side of the insertion of the membrana tympani, opposite the posterior extremity of a line drawn across its middle, is situated a small foramen, the orifice of a canal which transmits the chorda tympani nerve. Is the membrana tympani perforated ! Some anatomists have asserted that there is an aperture between the membrane and the bone, at one point of its circumference ; and others have believed that an oblique slit traverses the membrane. But these perfora- tions do not exist in the natural state ; so that the membrana tympani forms a complete septum between the tympanum and the external auditory meatus. Notwithstanding its tenuity and transparency, the membrana tympani consists of three very distinct layers. The external or epidermic layer is a prolongation of the epidermic portion only of the skin which lines the external meatus. The internal or mucous layer is a prolongation of the extremely thin mucous mem- brane which lines the tympanum. The handle of the malleus is situated between this and the middle layer. The middle or proper layer, on which the strength of the membrane depends, appears to be of a fibrous nature. According to Sir Everard Home, it is muscular; he states^ that he distinctly saw muscular fibres radiating from the centre to the circumference, first in the elephant, and afterward in the ox, and in the human subject.* By fine injections some very delicate vessels are demonstrated in the membrane. The network represented by Soemmering, who only injected the arteries, is not nearly so dense as that which may be displayed by filling the veins. If a blue injection be thrown into the jugular vein of the foetus, the whole membrane will become of that col- our, and will present an exceedingly fine vascular network under a lens. In a new-born infant, which had died with inflammation of the tympanum, the membrane was found quite red. The bloodvessels appear to be situated entirely in the internal layer ; they run from the circumference towards the centre of the membrane ; and this arrangement has probably led to the supposition of the existence of radiated muscular fibres. The use of the membrana tympani is to transmit the sonorous vibrations received through the external auditory meatus to the air contained within the tympanum, and to the ossicula of the ear. Its obliquity, besides increasing the dimensions of this vibratile membrane, has certainly some use in the reflection of sonorous vibrations. As it ad- heres to one of the chains of small bones of the ear, it is influenced by their movements ; and in this way it maybe either stretched or relaxed. The Internal Wall of the Tympanum. — The inter- nal wall of the tympanum {figs. 254, 255), which is perfectly exposed when that cavity is opened from its external wall, presents a great number of objects for our consideration. At its upper part is situated the fenestra oralis {fjig. 254), the long diameter of which is directed transversely, but rather obliquely down- ward and forward ; the upper border of this fenestra {ffig. 25S) is semi-elliptical, while the lower border is straight, or, rather, it projects somewhat into the opening. The fenestra ovalis, called also the vestib- ular orifice of the tympanum, would establish a free communication between the tympanum and the ves- tibule if it were not closed by the base of the stapes {d,fig. 255 ; n,fig. 257), which is accurately fitted to it. The fenestra ovalis is placed at the bottom of a depression, which is named the fossette of the fe- ^ nostra, and the depth of which depends upon the de- " * Philosophical Transactions, p. 23, 1823. To his paper are annexed three plates, representing the membrana tympani in the Naiural size, elephant, the ox, and man. (Section of ihe tympanum.) THE TYMPANUM. 671 gree of projection of the aqueduct of Fallopius, which bounds it in front, by that of the promontory, which is below, and by an osseous tongue which passes up to the pyramid behind. Below the fenestra ovahs is the promontory (r, figs. 254, 255), an eminence which corresponds to the first turn of the cochlea, and has three grooves upon its surface, that diverge above and converge below, where they terminate in a common canal, which opens upon the lower surface of the petrous portion of the temporal bone, be- tween the carotid canal and the groove for the internal jugular vein. This canal (ca- nalis tympanicus, Arnold) may be called the canal of Jacobson, because it contains Jacob- son's nerve, a branch given off from the glosso-pharyngeal, which establishes a very re- markable anastomosis between the glosso-pharyngeal and the nervi moUes derived from the vidian and great sympathetic nerves.* The furrows upon the promontory are in- tended to lodge this anastomosis. They are often formed into complete canals. Behind the fenestra ovahs, and opposite its transverse diameter, is a small projection of variable size, called the pyramid {t, figs. 254, 255). There is an opening upon it which is distinctly visible to the naked eye, and makes the pyramid appear tubular. From this opening emerges a small cord (o, fig. 255), the nature of which is not known, but which is called the stapedius muscle. A bristle passed into this opening enters the canal of the pyramid, which canal is generally described as ending in a cul-de-sac, but this is not the case. M. Huguier, prosector of the faculty, has clearly demonstrated, in a series of preparations, that the canal of the pyramid is a long passage, which passes backward and downward below the aqueduct of Fallopius, becomes vertical like the aqueduct, is separated from it only by a thin lamina of bone, communicates with it by a small open- ing, and at length abandons it below, to open upon the inferior surface of the petrous bone, on the inner side of the stylo-mastoid foramen, at a variable distance from it. Sometimes this canal bifurcates below ; so that two bristles introduced into the small openings near the stylo-mastoid foramen will both enter the canal of the pyramid. A small, very short, and horizontal passage, which terminates in the diploe of the tem- poral bone, may be regarded as a diverticulum of this canal. I have already stated that a librous-looking cord, named the stapedius muscle, emerges from the canal of the pyramid. It is not yet known what structures are transmitted through the divisions of this canal. Below the fenestra ovalis, and behind the promontory, is situated the fenestra rotunda {s, figs. 254, 255) ; it is placed at the bottom of a funnel-shaped depression, which was well described by M. Ribes as the fossa of the fenestra rotunda, at the bottom of which is found a partly membranous and partly osseous lamina, which is the commencement of the spiral septum of the cochlea. In a dry bone, which has been previously macerated, the membranous part being destroyed, the fossa of the fenestra rotunda communicates with the vestibule. Below this compound lamina, i. e., at the lower part of the fossa just described, is found the fenestra rotunda {s, fig. 257) properly so called, which leads into the tympanic scala of the cochlea {1} ; whence the term cochlear orifice of the tym- panum is applied to the fenestra rotunda, in contradistinction to the term vestibular orifice, which is given to the fenestra ovalis. The fenestra rotunda is closed, in the fresh state, by a membrane called the secondary membrana tympani, which is said to be composed of three layers — a middle layer, an external or tympanic, and an internal or cochlear layer. The two last named are mucous membranes.! Under the pyramid, and behind the fenestra rotun- da, is seen a deep fossa, the sub-pyramidal fossa {.v,fig. 254), remarkable for its constancy, and pierced by several foramina at the bottom. Upon the internal waU of the tympanum, in front of the fenestra ovalis, somewhat above the trans- verse diameter of that opening, and under the prom- inence of the aqueduct of Fallopius, is the internal orifice {n, figs. 254, 255) of the canal {m) for the internal "¥^p muscle of the malleus, or tensor tympani muscle. This ''^'^" orifice is wide and cup-shaped, and is supported by a hollow eminence (x, fig. 254), which is itself sustain- ed by several ridges ; so that there is the greatest analogy between it and the hollow projection consti- tuting the pyramid. Both of them transmit a tendon. One is situated in front, and the other behind the fe- nestra ovalis. M. Huguier, who has paid much at- tention to this subject, has shown that the cochleari- * This can be clearly seen in some preparations in the museum of the Faculty at Pans. t [The internal or cochlenr layer is merely apart of the common lining mcmhrane of the labyrinth, and is, most probably, a. fibre- Natural size. terous membrane, see p. 661. J (Sectionofllie tympanum.) Fig. 255. 672 NEUROLOGY. form process of anatmnisis [n, fig. 255) is nothing more than the remnant of the hollcw projection (.r, fig. 254) just described, one half of which is very thin and fragile, and ia sometimes destroyed by long-continued maceration. The so-called cochleariform pro- cess, therefore, is merely the reflected canal for the internal muscle of the malleus. The Circumference of the Tympanum. — We shall examine this circumference above, be- low, in front, and behind. Above, the tympanum corresponds to the projection formed on the anterior part of the base of the petrous portion of the temporal bone. In it there is formed a recess, which may be named the recess of the tympanum., and which is intended for the reception of the head of the malleus (1,.^^. 255), and the body and posterior ramus of the incus (2). It is thin and spongy, and is separated from the squamous portion of the temporal bone by a suture, which persists even to the most advanced age. This suture is traversed by a great number of canals, through which conununicating vessels pass from those of the dura mater to those of the tympanum. BeloiD, the tympanum is very narrow, and has the form of a trench, in which there is nothing particular to notice. The wall of the tympanum is here formed by the osseous lamina of the external meatus. At the upper and back part of the circumference of the tympanum is situated a large opening which leads into the mastoid cells (c c, figs. 254, 255). These cells are extremely numerous, and of very unequal size ; they occupy the whole of the mastoid portion, and the adjacent parts of the petrous portion of the temporal bone, and are prolonged even above the external meatus. We may therefore regard the mastoid portion of the temporal bone as an appendage to the tympanum. The mas- toid cells have a very regular arrangement in the ox and horse, in which animals they are disposed in a series radiating from the surface of the mastoid process towards the tympanum ; their arrangement is much more irregular in the human subject. Two large cells are almost always found, one near the apex, and the other at the posterior border of the mastoid process. In one case I found the whole mastoid process forming a single large cell, having extremely thin parietes. The mastoid cells are lined with a very delicate fibro-mucous membrane, which is con- tinuous Avith the mucous membrane of the tympanum. They contain air, and it is only in some cases of disease that any quantity of mucus is found in them. The mastoid cells represent, in the auditory apparatus, the cells and sinuses which are connected with the organ of smell. It may be easily conceived that the intensity of sounds may be increased by being reverberated from so considerable a surface. In the foetus there are no mastoid cells ; but there exists instead, in the base of the petrous portion of the temporal bone, a cavity prolonged from the recess already de- scribed in the upper wall of the tympanum, for the ossicula of the ear. In front, the tympanum is contracted like a funnel, to become continuous with the Eustachian tube {e, fig. 255) ; it might even be said that the tympanum and the Eustachian tube form together a single funnel-shaped cavity, the expanded portion of which is con- stituted by the tympanum, and the contracted portion by the tube of Eustachius. The canal for the internal muscle of the malleus is formed in the upper wall of the Eu- stachian tube ; it is a narrow tubular canal (?)i), which, having reached the anterior part of the tympanum, becomes applied to the internal wall of that cavity ; it passes horizon- tally backward, forming a projection upon this wall, and is then reflected outward, at a right angle, to form the hollow eminence already described. This canal is separated only by a very thin osseous lamina from the Eustachian tube ; so that the two passages, placed one above the other, have some resemblance to a double-barrelled gun. The Eustachia7i Tube. The Eustachian tube (more correctly called the Eustachian trumpet, from tuba, a trumpet, e,fig. 255), or the guttural meatus of the ear, is a straight, funnel-shaped canal, flattened upon its outer side, and about two inches in length ; it extends from the tym- panum to the upper and lateral part of the pharynx, where it terminates by a free, ex- panded extremity (m, fig. 234), directed inward and downward, named the guttural orifice, or the mouth of the Eustachian tube. This orifice is wide and dilatable, of an oval shape, the larger end of the ovoid being turned upward, and being exceedingly dilatable ; but beyond its mouth the tube almost immediately contracts, and will scarcely admit an or- dinary probe. It continues narrow as far as its tympanic orifice, where it again becomes sensibly dilated. It is directed obliquely inward, forward, and downward ; hence the facility with which the mucus of the tympanum flows into the back of the throat. The Eustachian tube consists of an osseous portion and of a cartilaginous and fibrous portion. The osseous portion, which is about seven or eight lines in length, is situated at the re- treating angle formed between the squamous and petrous portions of the temporal bone A triangular cartilaginous plate, formed into a groove, constitutes the inner half of the tube ; a fibrous layer, which is at first applied against the circumflexus palati muscle, and is then lodged in the groove between the petrous portion of the temporal bone and the THE OSSICULA OF THE EAR. 673 posterior border of the sphenoid, forms the external wall of the canal, which is habitu- ally collapsed. The base of the triangular cartilage, which forms the guttural orifice of the tube, is notched in the middle, and terminates in two thickened elongated angles ; of these, the posterior one, which is more distinct, is movable, and may be pushed upward and backward. The anterior angle is firmly fixed to the posterior margin of the pteiy- goid process. As catheterism and injection of the Eustachian tube have become com- mon operations in treating diseases of the ear, it is of importance to define the exact position of its guttural orifice ; it is situated (m, fig. 234) upon the side of the pharynx, immediately behind, and a little above the inferior turbinated bone. The mucous membrane which lines the Eustachian tube is thin, but at the mouth of the tube it assumes the characters of the mucous membrane of the pharynx and of the pitui- tary membrane, with both of which it is continuous ; it is also continuous with the mu- cous membrane of the tympanum ; hence the close sympathy which exists between the lining membrane of these several parts.* The use of the Eustachian tube is to renew the air contained within the tympanum ; but it also gives exit to the mucous secretion of that cavity, t Besides the orifice of the Eustachian tube, and that of the canal for the internal mus- cle of the malleus, the anterior funnel-shaped part of the circumference of the tympanum presents two orifices placed one above the other : the uppermost of these is the internal orifice of the canal for the chorda tympani nerve ; the lower one is an oblique fissure, which transmits a fibrous cord called the anterior muscle of the malleus. M. Huguier has shown me a number of preparations. in which the chorda tympani nerve does, not escape through the fissure of Glasserius, but runs in a very narrow special canal, about five or six lines in length, which is situated on the inner side of the Glasserian fissure, and opens at the base of the scull in the retreating angle formed between the squamous and petrous portions of the temporal bone, upon the outer side of the Eustachian tube, be- hind the spinous process of the sphenoid, and sometimes upon that bone itself The fissure of Glasserius, then, merely transmits a fibrous bundle, named the anterior muscle of the malleus, and some small arteries and veins. We may now describe the course of the chorda tympani nerve. In its course this nerve passes through two canals, entering the tjonpanum by one, and escaping from it by the other. The canal by which it enters commences at the vertical portion of the aqueduct of Fallopius, in which the facial nerve is situated, passes upward and forward, and opens immediately on the inner side of the posterior margin of the membrana tympani, on a level with the horizontal diameter of that membrane, and al- most in the groove into which it is inserted. Having entered the tympanum through this canal, the chorda tympani describes a curve, having its concavity directed down- ward, passes between the handle of the malleus and the long ramus of the incus, enters its proper canal upon the inner side of the fissure of Glasserius, and emerges at the point already mentioned. The Ossicula of the Ear. The tympanum is traversed from without inward by an osseous chain, which describes several angles, and consists of four bones articulated with each other, and extended from the membrana tympani to the fenestra ovalis. These little bones, forming the hnks of the chain, are named, from their respective shapes, the malleus, or Fig. 256. hammer {I, fig. 256) ; the incus, or anvil (2) ; the os orbiculare, or round bone (4) ; and the stapes, or stirrup bone (3) : the os orbicu- lare, however, appears to be merely a tubercle belonging to the incus. The Malleus. — The malleus {I, fig. 256) is the most anterior of the bones of the ear; it is divided into a head, a neck, and a ha7idle, and it has also two processes. The head of the malleus (a, fig. 257) is situated in the recess of the tympanum, in front of the incus, and above the membrana tympani. It is ovoid, and smooth, excepting behind and below, where it is concave, in order to be articulated with the incus. Soemmering has figured a small fibrous cord, which he caUs the proper ligament of the malleus, extending from the head of this bone to the upper part of the recess of the tympanum. The head is supported by a constricted neck (b), which is slightly twisted and flattened, and serves also as a support for the two processes. The handle (manubrium, c) is directed vertically, and, Magnified three diameters. * CAccording- to Dr. Henl6, the mucous membrane of the Eustachian tube, like that of the upper part of the pharynx, is covered with a columnar ciliated epithelium ; but in the tympanum and mastoid cells the epithelium is squamous, and not ciliated.] t [The Eustachian tube, by establishing a communication between the tympanum and the external air, en- sures an equal atmospheric pressure on the two surfaces of the membrana tympani, so that the necessary cou- iitiou of that membrane, and of the ossicula auditOs, as conductors of vibrations, is not interfered with.] 4Q 674 NEUROLOGY. with the head and neck, fonns a very obtuse angle, which retreats on the inner side ;. it is in contact with, and adheres firmly to the internal surface of the membrana tyra- pani, opposite the centre of which its rounded extremity is placed ; it therefore forms a radius to the circle represented by the membrana tympani. The lower part of the handle of the malleus is distinctly curved, having its concave side turned outward ; this ex- plains the funnel-shaped depression upon the external surface of the centre of the mem- brana tympani. The ■processes of the malleus are two in number : the external, or short process {d), is directed slightly outward, and rests against the upper part of the margin of the mem- brana tympani, so as to make it project outward ; the other, or long process, is very slender {processus gracilis of Raio, e), and is shaped like a thorn {processus spinosus) : it arises from the anterior part of the neck, enters the Glasserian fissure, and affords at- tachment to a muscular or fibrous cord. I have several times found a simple ligament- ous cord instead of this process. The Incus. — This bone (2, fig. 256) has been well compared to a bicuspid tooth, the body of which would be represented by the body of the incus, and the fangs by its two processes. The body (/, fig. 257) is contained in the recess of the tympanum, behind the malleus, with which it is articulated by a very concave surface, directed forward and somewhat upward ; so that the articulation between the head of the malleus and the body of the incus is effected by mutual reception. Of its two rami, the superior or short one {g) is thick, conoid, and directed horizontally backward : it is situated upon the same plane as the body, and, like it, is contained in the recess of the tympanum, in which it terminates ; its extremity does not appear to me to be free. The inferior, or long ramus (A), is longer and thinner than the superior one ; it passes vertically downward, parallel to the handle of the malleus, on a plane internal and some- what posterior to it. Its lower portion is bent into a hook, the concavity of which is turned inward ; and at its point is formed a sort of lenticular and distinctly defined tu- bercle {4:, fig. 256 ; i,fig. 257), which has been regarded as a separate bone, and named the OS orbiculare, or as lenticulare ; it appears to me to be merely a dependance of the in- cus, with which I have always found it united, even in the foetus. The Stapes. — The stapes (3, fig. 356), which is shaped like a stirrup, extends horizon- tally from the extremity of the long process of the incus to the fenestra ovalis (see fig. 257), and is situated upon a lower plane than the rest of the small bones of the ear. Its head presents a small articular cavity, for the reception of the orbicular tubercle of the incus. Its base («) is directed inward, and consists of a thin plate exactly corre- sponding to the fenestra ovalis, which is rather accurately filled up by it, and to draw it away from which a slight force is necessary, so that it has a greater tendency to fall into the vestibule than into the cavity of the tympanum. The slight obliquity of the long diameter of the fenestra ovalis causes an inclination of the stapes in the same di- rection. Of its two crura, or branches {fig. 256), the anterior is the shorter and straight- er. Upon those surfaces of the crura which are turned towards each other there is found a groove, which appears to indicate the existence of a membrane stretched be- tween the crura. I have found the stapes very small, and, as it were, atrophied. In one case, the two crura of the stapes were united together. Muscles belonging to the Ossicula of the Ear. Most modem anatomists agree with Soemmering in admitting four muscles for the -ossicula of the ear, viz., three belonging to the malleus, and one to the stapes. The incus has no proper muscle, because it is merely an intermediate bone between the malleus and the stapes. It is certain, however, that only one of these muscles has been actually demonstrated, viz., the internal muscle of the malleus ; but it is so easy to fall into en-or when examining such minute objects, that I feel bound to suspend my judg- ment as to the existence or non-existence of the other muscles. The internal muscle of the malleus, or tensor mcmbrance tympani of Soemmering {e,fig. 251), is an elongated, fusiform muscle, contained within the bony canal formed in the retreating angle of the temporal bone, above the Eustachian tube, with which it exactly corresponds in dii'ection. It arises from the cartilaginous portion of the tube, from the adjacent part of the sphenoid bone, behind the spinous foramen, and from the bony canal which forms its sheath. The fleshy fibres converge around a tendon, which*appears from among them, before it passes out from the bony canal. This tendon is reflected at a right angle, like the canal in which it is contained, and then passes directly outward, to be inserted into the anterior and superior part of the handle of the malleus, below the processus gracilis of Raw. The muscularity of the band or cord named the anterior muscle or ligament of the mal- leus, or the great external muscle of Meckel, is doubted by a great number both of pres- ent and former anatomists.* I have never seen anything more than a fibrous cord, which " Fu^re autem et dudum et nuper clari viri qui de veris hujus musculi fibris carneis dubitarunt, cum THE OSSEOUS LABYRINTH. 675 commenced at the tip of the processus gracilis of the malleus, traversed the glenoid fis- sure, was re-enforced by other fibres arising from that fissure, and became continuous with a fibrous layer arising from the spinous process of the sphenoid bone, and generally regarded as the internal lateral ligament of the temporo-maxillary articulation. The same remarks will also apply to the ^mall external viusclc of the malleus, or small muBcle of the malleus of Casserius. This muscle is figured by Soemmering, who says that he found it exceedingly developed in one subject. All that I have clearly seen is a cylindrical cord, extending from the upper part of the frame of the membrana tympani to the short process of the malleus, or, rather, below it, according to the observations of Soemmering {ad manubrium mallei, infra brevem ejus processum). This small muscle would relax the membrana tympani ; hence it has been named by Scemmering the lax- eter membrana. tympani. The muscle of the stapes, or stapedius muscle (o, fig. 355), which is the smallest in the body, has, since the time of Varolius, by whom it was discovered, been regarded as a ligament by some anatomists ; nevertheless, it is more generally admitted to be muscu- lar than that last described. It arises from some part of the interior of the pyramid, and, escaping from that process, passes forward, and terminates at the back of the neck, or constricted part of the head of the stapes, behind its articulation with the incus, Soem- mering has not only represented its fleshy belly and its tendon, but also (see fig. 20, tab. 11) a filament of the facial nerve terminating in it. It is difficult to conceive that such a serious mistake should have been committed by this great anatomist. I have exam- ined this cord under a lens, and have never been able to discover any muscular fibres in it. We do not conceive how a muscle should exist in so delicate a cord. Supposing, however, that it does exist, it must move the stapes in such a way that the posterior ex- tremity of the base of that bone would be pushed into the fenestra ovalis, while the an- terior extremity would be carried outward. Movements of the Ossicula. — The chain of small bones in the ear is so arranged, that any movement of one of its extremities is communicated to the entire chain. Their mo- tion is precisely similar to that of a bell-crank. M. Huguier is inclined to believe that the processus gracilis of Raw serves as a fulcrum, around which the malleus performs a rotatory movement, the effects of which are transmitted to the stapes through the in- cus. The contraction of the internal muscle of the malleus, or tensor membranae tym- pani, must draw the handle of the malleus inward and its head outward ; the incus, from its firm connexion with the head of the malleus, follows that bone, and as it swings upon its short horizontal process, its vertical process is carried inward, and therefore presses the stapes into the fenestra ovalis. The Lining Membrane of the Tympanum. The tympanum is lined by a very thin membrane, which not only covers the walls of this cavity, but also forms a very evident investment for the ossicula, and is, moreover, prolonged into the mastoid cells, lining them throughout, and forming small duplicatures around the vessels by which some of the cells are traversed. This membrane is con- tinuous with the mucous membrane of the Eustachian tube, and therefore indirectly with that of the pharynx.* It serves at once as an internal lining for the tympanum, and a periosteum for the os- seous walls of that cavity, and should therefore be regarded as a fibro-mucous membrane. It secretes a mucus, which in the natural state simply moistens its surface, but in some cases of disease occupies the whole cavity. The catarrhal character of the products of suppuration in the tympanum, the continuity of this lining membrane with the mucous membrane of the pharynx, and its extreme vascularitj^ leave no doubt of its being a mu- cous membrane. The Internal Ear, or Labyrinth. The internal ear, or labyrinth (ffig. 251), the deep-rooted and essential portion of the organ of hearing, is situated on the inner side of the tympanum, in the substance of the petrous portion of the temporal bone. It consists of the osseous labyrinth, which forms a receptacle for the membranous labyrinth, which is the immediate seat of the sense of hearing. No part of the body has a more corefplex and delicate structure. The labyr- inth is composed of three very distinct compartments, which have been named the ves- tibule., the semicircular canols, and the cochlea. The Osseous Labyrinth. Preparation. — This is justly regarded as one of the most diflicult dissections, even when the parts are previously known. The dissection should be made upon temporal bones from subjects of different ages, upon bones that have been macerated, upon oth- ers that have been dried without maceration, and also upon bones in the fresh state. nmltam quidem membranam a periosteo propagatam, sulcuro maxillie repleri viderent, et processui longissimo circumnasci, CEeterum in eo carneam nataram non deprehenderent. Neque mea experimenta rem expediunt. Mnsculum quoties volui, ostendi, num veras fibras viderem, plerumque dubius hxsi."— (.Haller, torn, v , lib, rv,, p. 218.; * See Dote, p. 673. 67d NEUROLOGY. Commence with a fcetal temporal bone, in which the labyrinth can very easily be isola- ted, in consequence of its being surrounded only by a spongy texture, readily yielding to the knife. In the adult, the labyrinth is, in proportion, much less developed than in the fcEtus, and is surrounded with so compact a tissue, that, in order to cut it, it is necessa- ry to use a chisel, a file, or a very strong scalpel. It is important to have a great num- ber of temporal bones, so as to be able to make several different sections. Preparation of the Vestibule. — Open the vestibule through its upper wall, which corre- sponds to the upper surface of the petrous portion of the temporal bone, opposite the fe- nestra ovalis, between the superior vertical semicircular canal and the internal auditory meatus. Preparation of the Semicircular Canals. — In the foetus, one of the semicircular canals projects upon the base of the petrous portion of the temporal bone ; it is easy to isolate it, as well as the other canals, by removing, with a strong scalpel, the spongy tissue in which they are imbedded. It is useful to have two preparations of the semicircular ca- nals ; one in which the canals remain entire, and another in which they have been opened. Preparation of the Cochlea. — Remove layer by layer that part of the petrous portion of the temporal bone which corresponds to the bottom of the internal auditory meatus. A layer of very thin spongy tissue shows, in the foetus, that we have arrived at the coch- lea ; remove this spongy tissue with care, and expose the cochlea, both on its upper and lower surfaces. In one preparation, the cochlea should be merely isolated ; in another, it should be carefully opened, and for this purpose it is sufficient to make a simple cut into each of its turns : it is of importance not to remove the summit of the cochlea. The Vestibule. If a probe be passed from the tympanum through the fenestra ovalis (/, fg. 258), it Fig. 258. enters an ovoid cavity (a b t, fig. 259) called the vestibule. The vestible is the centre of the internal ear, and forms an intermediate cavity or passage (fo- rum fodinae metallicas, Vesalius) between the semicircular canals (o p q,fig. 258), which are on its outer side, and the cochlea (?), which is to its inner side. It is situated in a line with the axis fg of the internal auditory meatus. It is remark- able for having a great number of both large and smaU openings into it. The large openings are seven in number : the first is the fenestra ovalis (/, figs. 258, 261), which would establish a free communication between the vestibule of the tympa- num if it were not for the base of the stapes, which closes it hermetically, as we may be convinced by examining it from the vestibule, when the stapes remains m its place.* There are>e openings (,o' p' q',fig. 259 ; o' a', fig. 261) for the three semicircular canals ; p- 259 and the seventh is the orifice {t) of the vestibular scala of the cochlea. In macerated bones we find, besides, an eighth opening, situated below the fenestra ovalis, having an oblong shape, and leading into the highest part of the fenestra ro- tunda. Of the small openings, the first is the orifice (r, fig. 259) of the aqueduct of the vestibule, which opens upon the posterior wall of this cavity to the inner side of the common opening for the two rw , ,, .V f ... , f, •., vertical semicircular canals {i. e., in the recessus Osseons labvnnth of the left side. .v^iiiv^i. , r ^\. iui* Magnified two diameters. sulciformis). The aqueduct of the vestibule turns a short distance around that common opening, and then, bending at a right angle, ter- minates upon the posterior surface of the petrous portion of the temporal bone by an orifice already described (see Osteology). The other small openings in the vestibule are foramina for the passage of vessels and nerves ; they form the macula cribrosa, which corresponds with the bottom of the internal auditory meatus. The character of the vestibule is irregularly ovoid, and is divided by a crista into two fossae : one inferior and hemispherical, named the fovea hemisphcrica {a, fig. 259) ; the other, superior and semi-elliptical, called the fovea semi-elliptica {h). Morgagni has de- scribed a third groove-like fossa (;recessus sulciformis), situated at the mouth of the com- mon orifice of the two superior semicircular canals. The Semicircular Canals. The semicircular canals, three in number, represent three cylinders or tubes (tubaeformes canales, Sammering), of equal diameters, and curved very regularly, so as to describe * [The base of the stapes is retained in its situation, and the complete closure of the fenestra ovalis is ef- fected, by the reflection of the lining membrane of the tympanum on the one hand, and by that of the lining membrane of the labyrinth on the other.] THE COCHLEA. 677 portions of circles ; they are situated within the substance of the base of the petrous portion of the temporal bone, behind the vestibule, into which they open by the five ori- . fices already described. They have been named the great, the middle, and the small semicircular canals ; terms which have caused much confasion, because the differences between them, in regard to length, are not alone sufficient to distinguish them from each other. Their direction forms a much better ground of distinction between them. Two are vertical, and one is horizontal: there is an anterior and superior vertical, and a posterior and inferior vertical canal ; the horizontal canal is external, and is situated between the . two others. The superior vertical canal {p, figs. 258, 260), which describes two thirds of a circle, is placed at the highest part of the labyrinth, immediately to the outer side of the vestibule. A plane passing through the two branches of this canal would cut the base of the petrous portion almost at a right angle. The convexity of this canal is turned upward, and its concavity downward. In the foetus, its concavity is free, so that it can be seen without any dissection ; but in the adult it is filled up with osseous tissue. The anterior and outer extremity {p',figs. 258, 259) of this canal is dilated into an ampulla, and opens separately at the upper and outer part of the vestibule. The poste- rior and inner extremity unites with the corresponding extremity of the inferior vertical canal to form a common canal (a, fig. 260), which opens without any dilatation into the upper and inner part of the vestibule (a', fig. 261). Fig. 260 The inferior vertical canal {q, figs. 258, 260) is placed at right angles to the preceding, and par- allel with the posterior surface of the petrous portion. It commences at the inner and upper part of the vestibule, by the common canal (a. Jig. 260) already described, passes almost di- rectly outward, curves at first downward, and then forward, and becomes dilated into an am- pulla (q', fig. 258) near the vestibule, into which cavity it opens {q',fig'. 259), about the distance of a line from the point at which it commences. This canal, therefore, describes nearly a com- plete circle ; and hence the term canalis major et longior, still given to it by Soemmering, in contradistinction to the superior vertical semi- circular canal, which he calls minor et hrevior. The horizontal canal (o, figs. 258, 260), canalis minimus, hrevissimus, site exterior of Soemmer- ing, commences in the vestibule {o',figs. 258, 259) between the fenestra ovalis, which is be- low, and the ampullar opening of the superior vertical canal, which is above ; it becomes dilated into an ampulla, describes a horizontal curve having its convexity turned out- ward, and opens {o',fig. 261) upon the inner wall of the vestibule, between the common opening (a') of the two vertical canals and the proper opening (q') of the inferior vertical canal. It appears, then, that each of the three semicircular canals has one of its extremities dilated into an ampulla, and the other not dilated ; that the two vertical canals unite by their non-dilated extremities ; that of the five openings belonging to the semicircular canals, two occupy the outer, and three the inner wall of the vestibule, and that the three last consist of the common canal formed by the two vertical canals, by the ampullar ex- tremity of the posterior vertical canal, and by the non-ampuUar extremity of the horizon- tal canal. The Cochlea. The cochlea {I, fig. 258), or snail, so called from its resemblance to the shell of that molluscous animal, may be said to consist of a conoid tube, which is subdivided into two cavities, called scala, by a septum extending from its base to its apex, and is coiled upon itself into a spiral containing two turns and a half The cochlea is the most anterior part of the internal ear ; it is situated on the inner side, and in front of the tympanum ; its base {d, fig. 260) rests upon the bottom of the internal auditory meatus.* Its external surface is blended, in the adult, with the substance of the petrous portion of the temporal bone, so that it requires much skill to carve it out without breaking into its cavity : in the foetus, on the contrary, such a dissection is extremely easy, on ac- count of the thin layer of spongy osseous tissue by which it is separated from the rest of the bone. * [The summit of the cochlea is directed forward, downward, and outward. coiled in a direction from below upward, and from without inward.] The gyri of the cochlea are 678 NEUROLOGY. The following- parts of the cochlea are separately described : the tuhe of the cochlea or lamina gyrorum, the lamina spiralis, the axis or columella, the two scalce, and the aqueduct. The Tube of the Cochlea. — The tube of the cochlea {canalis spiralis cocMcb, or lamina gy- rorum) is the compact lamina (I, figs. 258, 262) which forms the external walls of the cochlea. If we imagine a hollow osseous cone, coiled spirally, cicut circa fulcrum convol- vulus (Haller), or like a winding staircase ; and farther, that the lowest turn of the spire embraces the turn above it, and that the walls of the different turns are blended with each other, we shall have a correct idea of the tube of the cochlea : as before stated, the spire thus formed describes two turns and a half The Spiral Lamina of the Cochlea. — The spiral canal, or tube of the cochlea, is subdi- vided lengthwise into two secondary cavities (c e, c e, figs. 263, 264), called scalcB (scala, a staircase), by a septum (a), which is named the spiral lamina of the cochlea {lamina spi- ralis cochlea). Commencing at the base of the cochlea (f, fig. 259 ; also^^. 263), and at the fenestra rotunda, where it can be very easily seen, the spiral lamina winds edgewise around the axis or columella (6 b, fig. 262), and is continued without any interruption to the sunmiit or cupola (/) of the cochlea, the several turns of which it exactly follows. Its internal border is applied against the axis of the cochlea, and adheres intimately to it, excepting above, where it is free for a short distance, and leaves a communication in,fig. 263) be- tween the two scalae. Margo liber lamina spiralis quo fit ut ulriusque scales sit communica- tio (Sammering). Its external border adheres to the inner surface of the lamina gjrrorum, or tube of the cochlea. In consequence of the conical form of this tube, the lamina spi- ralis would, if unrolled, represent an isosceles triangle, the base of which had corre- sponded to the fenestra rotunda, and the apex to the summit of the cochlea. The spiral lamina consists of two portions — an internal osseous and an external mevi- hranous portion. * The osseous portion (lamina spiralis ossea, d, figs. 259, 261, 262, 264) predominates in the first turn, diminishes gradually in the second, and ceases at the commencement of the third, where it termi- nates in a kind of hook or beak {hamulus vel rostrum, e, fig. 262). This bony portion is thick, and consists of two la- mellae, between which are found a great number of very delicate canals, through which the nerves of the cochlea f.-. pass. These two lamellae form two distinct furrows upoa the columella. The membranous portion {lairdna spirahs membranacea, a a, figs. 263 to 265) completes the septum, forming its outer part. It is narrow in the first turn of the cochlea, becomes broader in the second, and constitutes the entire septum in the third. The bony and membranous portions of the spiral lamina, therefore, represent two isosceles triangles, so arranged that the base of the one corresponds to the apex of the other, and vice versa. Moreover, as Comparetti remarks, three zones can be distinguished in the membranous portion of the spiral lam- ina, the consistence of which diminishes progressively from the margin of the osseous lamina towards the inter- nal surface of the tube of the cochlea. TheAxisor Columella of the Cochlea. — From the bottom, or, rather, from the posterior part {d, fig. 260) of the bottom of the internal auditory meatus, arises a bony process, which is directed almost horizontally outward ; it occupies the centre or axis of the cochlea, and around it both the tube and spiral lamina describe their several turns. This bony process is called the axis of the cochlea, columella, modiolus, or nucleus {b, figs. 262, 264). It extends from the base to the summit of the cochlea, but undergoes certain changes during its course. Opposite the first turn it is extremely thick, but becomes much thinner in the first half of the second turn. In the second half of the second turn, and in the last half turn, it is replaced by a cup-shaped lamella, called the infundibulum (scyphus, Vicussens, c,fig. 262), the expand- ed portion of which is turned towards the cupola (/) of the cochlea. The modiolus or axis of the cochlea, then, has three perfectly distinct parts. The base of the modiolus, which is seen at the bottom of the auditory meatus, is marked by a very distinct spiral tract {d, fig. 260), perforated with foramina, through which the filaments of the auditory nerve are transmitted. It is the tractus spiralis foramirmlentus of Cotugno. The apex of the modiolus, when examined in a cochlea which has been opened from the under surface of the petrous portion of the temporal bone, presents a decidedly in- fundibuliform figure. But in a cochlea which has been opened from its upper surface Cochlea (dry) znagnified four tijne«. Fig. 263. Cochlea (recent). * [In the dried cochlea (fig. 262), the two scalse communicate along their whole course.] THE COCHLEA. 679 {fig. 264), on the contrary, it has the appearance of a very slender stalk, continuous with the rest of the modiolus, and proceeding directly to the cupola of the cochlea. This two- fold structure depends upon the fact that the terminal lamella of the modiolus forms only half a funnel, which half is turned towards the lower half of the cochlea. This terminal lamella of the modiolus, which has been very well described by Huguier, is of a triangular form, extends through half a turn of a spiral, and adheres to the inner surface of the tube of the cochlea by its external convex border. Its internal border or margin is straight and free, and is the only part of this lamella which is seen when the cochlea is opened from above, while its convex border and its surfaces are distinctly seen when the coch- lea is opened from below. The hamulus (e, Jig. 262) of the osseous portion of the lamina spiralis terminates opposite the middle of this free border or margin. The surface of the modiolus is marked like a screw by two furrows corresponding to the two lamellae of the osseous part of the spiral lamina ; this surface is pierced with foramina for the branches of the auditory nerve. If the modiolus be divided longitudinally (fig. 264), it will be seen that its centre is traversed by a number of canals, for the passage of the branches of the auditory nerve. These canals open by the foramina on its surface. In the centre of the half funnel formed by the ter- minal lamella of the modiolus is an opening, through which the terminal filament of the cochlear branch of the auditory nerve passes out ; it is the orifice of the tubulus centralis modioli. The Scala. of the Cochlea. — The spiral lamina {d d, fig. 264) di- vides the cavity of the tube of tne cochlea into two secondary cavities (c e, c e), called the scalce of the cochlea. They are dis- tinguished as the external, superior, or vestibular scala (scala ves- tibuli, c c, figs. 263, 264), and the internal, inferior, or tympanic scala (scala tympani, e e). The first (c c, fig. 265) communicates ^ directly with the vestibule (between t and s) ; the second, which cocUei mignified. commences at the fenestra rotunda (s,_^^. 258), would communicate with the tympanum if that fenestra were not closed by a membrane ; hence the term scala clausa. The tympanic scala is decidedly larger than the vestibular. The section of either of the scalae, at right angles to its axis, is semicircular. The two scalae communicate near the summit of the cochlea (at n, figs. 263, 265). Both the situation and nature of this communication can be easily ascertained, and have been well described by ScEmmering, and more recently by MM. Breschet and Huguier. The lamina spiralis, which, we have seen, adheres closely to the modiolus, continues to wind spirally around the half-funnel-shaped termination of the modiolus, but when it arrives opposite the concavity of this half funnel, it ceases to be attached to that con- cavity, its internal border becomes free, and is then continued on to the inner surface of the summit of the cochlea. It follows, therefore, that the free concave border of the lamina spiralis is opposite to the concavity of the infundibulum ; and hence there is an interruption in the septum, in the form of a circular opening, the canalis scalarum commu- nis o{ Cassebohm, the helicotrema of Breschet {71, figs. 263, 265), which establishes a com- munication between the two scalae : moreover, this opening is not situated precisely at the summit of the scalae, but a little below that point ; nor is the opening of communica- tion (between t and *, fig. 265) between the vestibular scala and the vestibule situated at the lowest part of that scala. The Aqueduct of the Cochlea. — The aqueduct of the cochlea opens at one end {n,fig. 259) into the tympanic scala of the cochlea, near the fenestra rotunda ; and at the other, by an expanded extremity, upon the lower border of the petrous portion of the temporal bone, near the jugular fossa. It does not appear to have any such use as was attributed to it by Cotugno. Like the aqueduct of the vestibule, it is merely a canal for a vessel, and as such was denominated by Wildberg canalis venosus cochlecc. The liquor Cotunnii could not pass through this canal, for it is closed by the dura mater. Ilg has taken a very ingenious view of the structure of the modiolus and cochlea. According to that author, the modiolus is not an osseous centre independent of the lamina gyrorum, but rather the internal wall of the spiral tube of the cochlea, which, in describing its first turn, intercepts a considerable cylindrical space of about two lines and a half in diam- eter, and then a smaller, but still cylindrical space, of about half a line in diameter, in its second turn ; while in the third turn there is no space, and therefore the axis or modiolus is wanting, but it is replaced by the internal wall of the spiral tube of the cochlea itself The terminal lamella of the modiolus would therefore be formed by the internal wall of the spiral tube. This view is supported by the structure of the bottom of the internal auditory meatus, on which is found a turn and a half of a spiral groove, precisely corresponding to the spire of the cochlea, and by sections of the cochlea made after Scemmering's plan, from the apex to the base. {Vide figs. 11, 12, 13, 14, 15, of ScBmmering's fourth plate.) The Membranous Labyrinth. The membranous labyrinth, discovered by Comparetti and Scarpa, has been correctly 680 NEUROLOGY. described and figured by Scemmering. M. Breschet has recently enriched onr knowl- edge of this intricate anatomical subject with many most interesting facts. {Etudes anatomiques et physiohgiques sur Vorgane de I'ouie et sur Vaudition dans I'homme et les ani- maux vertcbres, 1833.) It is useless to attempt the examination of the membranous labyrinth in the human subject without some previous preparation. If the labyrinth be opened, it is found to contain a fluid; the eye can detect nothing else. By previously macerating it in diluted nitric acid, the twofold advantage is gained of softening the bones, so that they can be cut with a scalpel, and of hardening and rendering opaque the nervous tissues. Before studying the membranous labjTinth in the human subject, it should first be examined in the large cartilaginous fishes, such as the ray and the turbot, in which it is most highly developed. It is then seen that the semicircular canals and the vestibule contain, be- sides a fluid, certain semi-trarisparent membranous tubes and sacs, the aspect of which closely resembles that of the retina. The membranous labyrinth {fig. 265) is not so extensive as the osseous labyrinth : thus, it does not enter the cochlea, and its diameter is much less than that of the bony labyrinth. It scarcely occupies one half the cavity of the latter. The space between the bony and membranous lab- yrinths is filled with a limpid fluid, named, after Co- tugno, the liquor Cotunnii, although it had been no- ticed by several anatomists before that author. (De f~y aqucE ductiius auris humancE interna. Cotugno, 1760.) It is the perilymph of M. Breschet. There is no air in the labyrinth, and it is somewhat MembraLous ubyrinth (lefiside). slugular that SO accuratic an anatomist as M. Ribes should have recently defended a contrary opinion, although it has been repeatedly refuted. The membranous labjTinth is itself filled with a fluid which was correctly described by Scarpa, and which might be named \.\ie fluid of Scarpa. M. de Blainville has com- pared it to the vitreous humour of the eye, and has named it la vitrine auditive : it is the endo-lymph of M. Breschet. The membranous labyrinth consists of membranous semicircular canals, and of a ves- tibular portion. The Membranous Semicircular Canals. The membranous semicircular canals {op q,fig. 265) were regarded as nervous cords by Scarpa, who first described them ; they have precisely the same form as the osseous semicircidar canals, although they do not completely fill them. Soemmering improperly calls them tubuli membrano-cartilaginosi. Each membranous canal, like the corresponding osseous one, has its ampulla, or ovoid muscle (o' p' q'). The two vertical membranous canals unite at one end into a common canal, and, therefore, the three membranous semicircular canals, like their osseous investments, open into the membranous vestibule by five distinct orifices. The membranous vestibule consists of two very distinct parts, the common sinus and the saccule. The sinus communis vestibuli, or r-^.stibular utricle {u),* as was first shown by Scarpa, forms the confluence of the membranous semicircular canals which open into it by five orifices. The utricle is situated in the fovea semi-elliptica of the vestibule, and floats, as it were, in the liquid of Cotugno ; it is distended by the liquid of Scarpa, so as to re- semble an oblong bulla. The liquid of Cotugno separates it from the base of the stapes, as Scarpa very well pointed out. The sacculus vestibuli, or vestihnlar saccule (sacculus proprius sphaericus, Scemmering, a), is much smaller than the utricle. Its connexions with the utricle have been com- pared by Fischer to those of the crystalline lens with the vitreous body : it occupies the fovea hemispherica of the vestibule, and is therefore situated below the utricle. Accord- ing to Soemmering, it does not adhere to the utricle ; that author has even represented a small space between these two parts. t According to others, there is a communication between them, and the saccule is merely a supplementary cavity to the utricle. I have not yet been able to satisfy myself concerning this point. The membranous labyrinth, then, is quite distinct from the membrane which lines the labyrinthic cavities. This periosteal membrane, which analogy would lead us to regard as a fibro-serous membrane, is the only membrane which is prolonged into the cochlea. We might, however, regard that portion of the lamina spiralis which is next to the in- ner surface of the lamina g>Torum as a portion of the membranous labyrinth. * Alvcus utrieulosus of Scarpa, vtriculvs communis of Sopmmering, sinus median of M. Breschet. t Sacculus teres eum utriculo communi nuUibi coharet, et ubi cultri apice aperitur, sphaericam ormam re- tinet. {Explanation of fig. 2, pi. 3.) According to M. Brcscliet, the sacculus and utriculus adhere intimately, and he is inclined to believe that their cavities even communicate ; but, from the extreme delicacy of these , structures, he has been unable to confirm this supposition. THE AUDITORY NERVE, ETC. 681 The Calcareous Matter of the Vestibule. — The examination of the ear of fishes, which has proved of such assistance in investigating the structure of the human membranous labyrinth, has also led to the inquiry, whether there existed anything in the human ear analogous to the solid calcareous concretions found in the labyrinth of the ear of fishes. From the researches of M. Breschet, it appears that the labyrinthic stones, or otolithes, of fishes, are represented in all the mammalia, and, consequently, in man, by a cretace- ous powder, which he has named otoconia (ovc, utoc, the ear, and kovic, dust) ; and that this powder exists both in the utricle and the saccule, collected together into two white shining masses, which were seen and described by both Comparetti and Scarpa, but were mistaken by them for the dried acoustic nerve. Does it fulfil the same uses as the otolithes in fishes ^ or should it be regarded as a rudimentary condition of an important structure in other animals 1 The Auditory JVerve and the Vessels of the Ear. The auditory nerve, or special nerve of the organ of hearing, is remarkable for its soft- ness, and hence it has been named the portio mollis of the seventh cranial nerve. The auditory nerve arises, at least in part, from the anterior wall of the fourth ventricle ; having reached the bottom of the internal auditory meatus, it divides into two branches : an anterior and larger, distributed to the cochlea, and a ■posterior, intended for the vesti- bule and semicircular canals. The anterior or cochlear branch (t, fig. 264) has a spiral arrangement, like that portion of the bottom of the auditory meatus {d,fi^. 260) to which it proceeds, and it enters through the foramina in the tractus spiralis of the lamina cri- brosa. One set of nervous filaments enters the small canals in the centre of the modi- olus {b,fig. 264) ; the others are applied to the surface of the modiolus {t,fig. 263) ; the latter filaments spread out upon the first turn of the lamina spiralis {t, fig. 265), radiating in the most regular manner, and having arrived near the outer border of the spiral lam- ina, they each divide into two or three ramuscules, which anastomose together, so as to form a nervous expansion.* These radiating filaments are more distinct upon the lower than upon the upper surface of the spiral lamina. Those filaments of the nerve which are not spread out upon the first turn of the lami- na spiralis pass through the foramina in the centre of the modiolus, and spread out upon the second turn, in the same manner as those already described. Lastly, the highest filaments emerge from-the opening at the apex of the modiolus, and terminate in a sim- ilar manner. It follows, therefore, that the nerves of the cochlea successively diminish in length, as the spiral lamina does in width ; and thus the radiating nervous filaments resemble the strings of a harp, in becoming successively shorter and shorter. It is probable that this arrangement is not without its influence upon the function of hearing. In a temporal bone softened by the action of nitric acid, the auditory nerve, the modi- olus, the spiral lamina, and the periosteal membrane which lines the cochlea, may be dissected with the greatest facility. The posterior or vestibular division of the auditory nerve is subdivided into three branches, the largest of which {v, fig. 265) is distributed to the utricle («) and to the am- pullae {o' p') of the superior vertical and horizontal membranous semicircular canals ; the middle-sized branch is distributed to the sacculus (s), and the smallest ends in the am- pulla {q') of the inferior vertical membranous semicircular canal, t Bloodvessels may be traced into the membranous labyrinth ; most of them enter by the internal auditory meatus ; those which belong to the cochlea pass through the fora- mina in the modiolus, and are distributed in a radiating manner like the nerves. THE CEREBRO-SPINAL AXIS. General Observations. The cerebrospinal axis constitutes the central portion, while the nerves form the periph- eral portion of the nervous rystem. The apparatus of innervation formed by the cerebro-spinal axis and the nerves togeth- er, and named the nervous system, is the most important part in the animal machine ; it is the source not only of sensation and motion, but of the universal sympathy existing between the several parts of the animal economy ; and that part of it called the brain performs the highest function allotted to organized beings, by becoming the immediate instrument of the soul in the exercise of the intellectual faculties. * [According to observations made by Treviranus, Gottsche, and others, the filaments of the cochlear nerve in animals do not anastomose, but terminate in isolated extremities, which are in some cases papillary (7>e- viranus), and in others club-shaped (Gottsche).'\ t [The nervous filameiit« proceeding to the utricle and saccule form a fan-like expansion upon those sacs, penetrate into their interior, and spread out as a nervous layer on their internal surface. Each of the nerves which are distributed to the membranous ampulla appears to bifurcate, so as partially to embrace its corre- sponding ampulla in a transverse direction ; the nervous filaments then penetrate into the ampuUa, and spread out upon a transverse septum, formed in its interior by the folding inward of the walls of the cavity, and also upon the adjacent parts of those walls. (See Steifensand , Miiller's Arch., 1835.)] 4R 682 NEUROLOGY. The cerebro-spinal axis consists of that soft, pulpy, elongated, and symmetrical mass of nervous substance, which, becoming enlarged at its upper part, occupies the vertebral canal and the cavity of the cranium, and forms the centre from which the nerves of all parts of the body take their origin, or in which they all terminate. The structure of no other organ in the tody excites so much curiosity, and, unfortu- nately, there is none whose structure is involved in greater obscurity. Notwithstand- ing the real advances that have recently been made in our knowledge of the anatomy of the brain, we must still acknowledge, with Steno, that the human mind, which has car- ried its investigations even into the heavens, has not yet been able to comprehend the nature of the instrument by which its own operations are performed, and that its pow- ers seem to abandon it as soon as it turns its attention to the organ in which it resides. Until the end of the last century, the study of the central portion of the nervous system consisted in a simple enumeration of its parts, or, rather, in a more or less imperfect description of its external surface, and of the ditferent objects" displayed by various sec- tions. The nomenclature of the different parts of the encephalon* is alone enough to show with what limited views the researches of those anatomists must have been made, who did not suspect that this pulpy-looking mass — a sufficient definition of which they believed to be, that it held an intermediate place between the solids and the fluids of the body — was as wonderful in the delicacy and intricacy of its structure, as in the impor- tance and elevated character of its functions. In the present day, anatomists include in the study of the encephalon not only the topographical study of its various constituent parts, but also the determination of the mode in which those parts are connected togeth- er. To ascertain this latter point, apart from all questions as to origin, formation, gen- eration, and re-enforcement, with which the subject has lately been embarrassed, should constitute the special aim of every inquiry into the anatomy of this part of the nervous system. The central portion of the nervous system consists, 1. Of the spinal cord; 2. Of the tu- ber minulare, the ■peduncles of the cerebrum and cerebellum, and the txibercula quadrigemina ; these together constitute a very constricted portion, which forms the bond of union be- tween the other parts of the encephalon, and which I shalll accordingly name le nocud de I'encephale ;i 3. Of the cerebellum ; 4. Of the cerebrum. The cerebro-spinal axis is surrounded by three membranes or coverings, called the meninges (from fiyviy^, a membrane), which perform some important functions in regard to it, and which must in the very first place occupy our attention. THE MEMBRANES OF THE CEREBRO-SPINAL AXIS. General Remarks. — The Dura Mater — the Cranial Portion, its Structure and Uses — the Spinal Portion. — The Arachnoid — its Cranial Portion — its Spinal Portion — the Sub- arachnoid Fluids — their Uses. — The Pia Mater — its External Cerebral Portion. But few parts of the body are so effectually protected as the cerebro-spinal axis ; this protection is afforded in part by the vertebral column,1: and by the cranium, the mechan- ism of which we have already described as being so eminently calculated to defend the parts situated within them. Besides the osseous case formed by the vertebro-cranial column, we find, surrounding the cerebro-spinal axis, a fibrous sheath, named the dura mater ; a serous membrane, called the arachnoid ; and a proper membrane, named the pia mater, in which the vessels of the nervous centre ramify. The Dura Mater. ^ Dissection of the Dura Mater of the Scull. — Make either a crucial incision, or one ex- tending from before backward, or from ear to ear, through the integuments of the head ; turn back the flaps, taking care to remove the periosteum with the hairy scalp. The bones of the cranium being thus exposed, the scull-cap may be removed, either with a sort of hatchet {marteau-hachette) or a saw. This hatchet is the most expeditious and the best instrument. There is no fear of shaking or lacerating the brain, if the instrument be properly used ; but it is almost im- possible to avoid cutting the brain with the saw, the only advantage of which over the other is, that it makes an even section. The section should be carried quite round the cranium, about a finger's breadth above * From iv, in, and KKpaKfj, the head ; a convenient term, used to signify that part of the cerebro-spinal axis which is situated within the cranium. + [It is necessary to bear in mind that the equivalent term, nodus encephali, has been assigned by Sosmmer- ing to the pons Varolii.] X A vertebrated animal may also be defined to be an animal provided with an encephalon ; an inter-vertebra- ted animal is one having no encephalon. 4 The application of the term muter to the meninges of the brain is derived from the Arabians, who regard- ed these membranes as the origin, or mothers of all the other parts of the body ; or, perhaps, as Haller has ob- served, this use of the term depends upon an Arabic idiom, by which the covering of any body whatsoever is called its mother. EXTERNAL SURFACE OF THE DURA MATER. 683 the orbital arches, the scull-cap being raised and removed by means of the narrow end of the hatchet, or by means of a hook attached to the extremity of its handle. If the brain is not to be preserved, a somewhat different method of proceeding is adopt- ed. Two parallel cuts must be made with the saw, one on each side of the superior lon- gitudinal sinus, along its whole extent. Each of these cuts should then be met by anoth- er, carried horizontally through the corresponding side of the scull. When the two por- tions of bone included between these sections are removed, there remains an intermedi- ate portion of bone, about an inch wide, extending from the nasal eminence to the occip- ital protuberance. The dura mater should then be divided along the borders of this in- termediate portion of bone, and the brain and cerebellum removed. If, however, it be intended to preserve the brain and cerebellum, after the entire scull- cap has been removed in the ordinary manner, the dura mater must be divided circularly, along the cut edge of the cranium, the anterior extremity of the falx cerebri must be di- vided with the scissors, and the whole fibrous cap turned backward. Another mode, and one which I prefer, is, to make an incision through the dura mater along each side of the superior longitudinal sinus, and then to divide the anterior ex tremity of the falx, and reflect that part backward. Dissection of the Dura Mater in the Vertebral Canul. — This part of the dura mater ma be exposed, either by removing the arches of the vertebrae, or by taking away the bodie of these bones. The latter method is but seldom adopted. The arches of the vertebras may be removed by means of a chisel and mallet, or, stil better, by the rachitome. An instrument has lately been invented, consisting of two parallel saws, slightly con vex on their toothed edges, firmly connected together, but capable of being separated o, approximated as may be desired. Preference is justly given to the rachitome over this complicated instrument. The important object in opening the spine is, to make the sec- tion opposite the junction of the laminae with the transverse and articular processes. In order to display the continuity of the cranial and spinal portions of the dura mater, it is necessary to connect the sections already made in the head and spine, by removing with the saw the intervening portion of the occipital bone. A beautiful preparation of the dura mater may be made by removing the roof and sides of the scull, and the arches of all the vertebrae ; by then taking out the encephalon and spinal cord through incisions in the dura mater, which may be readily concealed ; and by filling the cavity thus left with tallow, which is afterward to be dissolved out by spir- its of turpentine, or, what is easier to do, the cavity of the dura mater may be filled with fine sand. The dura mater (meninx crassa, Galen; le meninge, Chauss.) is a fibrous membrane which covers and protects the cerebro-spinal axis, and the roots of all the nerves which arise from or terminate in that portion of the nervous system. It is the most external of the membranes of the brain and spinal cord (meninx exteri- or, Sammering) ; it consist of a cranial and a spinal portion. The Cranial Portion of the Dura Mater. The cranial portion of the dura mater forms a fibrous sac, which lines the internal sur- face of the bones of the cranium, forming their internal periosteum, and at the same time serves as a covering for the encephalon, and separates its different parts by means of prolongations or incomplete septa. The dura mater in the scull presents for our consideration an external and an internal surface. External Surface of the Dura Mater. Its external surface is accurately moulded upon the internal surface of the bones of the cranium, to which it adheres by a multitude of small fibrous and vascular prolongations, which can be readily displayed by putting the membrane under water. These prolonga- tions give the external surface of the dura mater a rough appearance, which contrasts strongly with the smooth aspect of its internal surface. The ramifications of the mid- dle meningeal arteries and veins are seen on the external surface of the membrane, and project from it, as if they were only laid upon it. The dura mater adheres to the parieties of the cranium with different degrees of firmness in different situations. Thus, it is generally less firmly adherent to the roof of the scuU than to its base, where it is impossible to separate it from the bone. The upper border of the petrous portion of the temporal bone, the posterior border of the lesser wings of the sphenoid, and the margin of the foramen magnum, are points to which it is very firmly attached ; but the dura mater adheres more strongly opposite the sutures than in any other situation. Upon the orbital plates, on the occipital fossae, and upon the squamous portion of each temporal bone, it adheres so shghtly, that it has been conceived to be altogether unattached in those regions.* * An erroneous opinion for a long time prevailed that the adhesions between the dura mater and the bones 684 NEUROLOGY. The firmness of the adhesion between the dura mater and the bones varies at differ- ent periods of life, and also the manner in which it is effected. Thus, in old subjects, the parts are so closely united, that it is almost impossible to take off the roof of the scull without, at the same time, removing portions of the dura mater. When this hap- pens, there is ossification of the outermost layers of this membrane. In the new-born infant, the adhesion is firmer than in the adult, especially opposite the sutures. As to the mode in which this adhesion is effected, it may be stated, that in the infant it appears to be exclusively by means of vessels ; in old age, almost entirely by fibrous tissue ; and in the adult, by partly vascular and partly fibrous prolongations. The dura mater is, moreover, attached to the bones of the cranium by means of the fibrous canals formed by this membrane for the nerves and vessels which pass through the foramina in the base of the scull. The most remarkable prolongations of the cranial portion of the dura mater, except- ing that for the spinal cord, are those given off opposite the right and left sphenoidal fissures. Each of these prolongations separates into two layers, one of which forms the sheath of the corresponding optic nerve, while the other blends with the periosteum lining the cavity of the orbits. The Internal Surface of the Dura Mater. The internal surface of the cranial portion of the dura mater appears smoothly polished, and is constantly lubricated with serosity ; its polished appearance is owing to a layer of arachnoid with which it is covered ; this layer is so thin that one might be disposed to deny its existence, and it is so firmly united to the dura mater that its demonstration is extremely difficult. E.xcepting at the points where the cerebral veins enter the dif- ferent sinuses, the internal surface of the dura mater lined by the arachnoid is free, and is in contact with the cerebral arachnoid, and indirectly with the outer surface of the encephalon. From this surface certain prolongations or imperfect septa are given off, by which the cavity of the cranium is divided into several compartments. These septa are three in number, viz., \he falx cerebri, the tentorium cerehelli, and t\\efalx cerelelli. The Falx Cerebri. — This is a fibrous lamina {d, fig. 220), which is placed vertically along the median line, is shaped like a sickle, and extends from the foramen caecum to the tentorium cerebelli. Its point, which is in front, dips into the foramen caecum, and envelops the crista galli ; its base is behind, and rests perpendicularly upon the middle of the tentorium cerebelli. The venous canal, called the straight status, is situated along the line in which the falx and the tentorium meet. The upper border of the falx is con- vex, and extends from the foramen caecum to the internal occipital protuberance. In this border is placed the superior longitudinal sinus. The lower border is concave, thin, sharp, and free, and corresponds to the corpus cal- losum, touching that body, however, only at the back part, and, according to some anat- omists, making a rather deep furrow upon it. This free border, which is thicker behind than in front, contains within it a small vein, which has been named the inferior longi- tudinal sinus. The two surfaces of the falx correspond to the internal surfaces of the two hemispheres of the brain. Not unfrequently the faLx cerebri is found as if torn through in some points, and I once observed the two hemispheres continuous with each other through an opening in this septum. The use of the falx is evidently to obviate the effects of lateral concussion of the brain, and to prevent one hemisphere from pressing upon the other, while the person is lying upon his side. The Tentorium Cerebelli. — This is an imperfect horizontal septum (le septum trans- verse, Chauss.), which is, as it were, notched in front, and which separates the cerebrum from the cerebellum. It is constantly in a state of tension ; a condition which depends upon the permanently tense state of the falx cerebri. These two parts, indeed, mutually preserve each other's tension, and when either of them is cut, the other necessarily be- comes relaxed. It is, therefore, only when the tentorium is examined i« situ, and the falx is left uninjured, that the anatomy of the former can be properly understood. It is then seen that it represents two planes, inclined upward, and united in the middle line at an obtuse angle, so as to form a sort of arch, upon the top of which the base of the falx cerebri rests. The concavity of this arch corresponds to and is accurately fitted upon the convex upper surface of the cerebellum below ; the convexity corresponds to the slightly concave under surface of the posterior lobes of the cerebrum. Its outer or convex border is directed horizontally ; it corresponds behind to the posterior portion of the lateral grooves, and in front to the upper border of the pars petrosa. The lateral sinus occupies the whole occipital portion of this border. Its inner or concave border is parabolic ; between it and the basilar groove, in front, a small space is intercepted, which is occupied by the nodus enc.ephali, being accurately were the results of disease ; and it has even been believed that a space existed between the dura mater and the bones of the cranium. These errors resulted from a physiological hypothesis, which attributed the move- jnents of the brain to contraction of the dura mater. STRUCTURE OP THE DURA MATER. 685 adapted to that part of the brain. The extremities of the external and internal borders cross each other on each side Mke the letter X ; the extremities of the outer border are attached to the posterior clinoid processes, and form on each side a sort of bridge, near the apex of the pars petrosa, beneath which the fifth cranial nerve passes ; the extremi- ties of the inner border are prolonged above those of the outer border, and are attached to the anterior clinoid processes. They form the sides of the pituitary fossa, and con- tain in their substance the cavernous sinuses. The Falx Cerebclli. — This is a small falciform fold, situated vertically in the median line (le septum median du ceverlet, Chauss.) ; Winslow remarks that it is sometimes double. It extends from the internal occipital protuberance to the foramen magnum, and separates the two hemispheres of the cerebellum. Its base, directed upward, cor- responds with and is attached to the tentorium cerebelli ; its apex bifurcates upon the sides of the foramen magnum. Its posterior border corresponds with the internal crest of the occipital bone, and its anterior border with the bottom of the median fissure of the cerebellum. Structure. The dura mater is perhaps the thickest and strongest of all the membranous invest- ments of the viscera. It may be regarded as consisting of two very distinct fibrous lay- ers : of an external or periosteal layer, which forms the internal periosteum of the bones of the cranium ; and of an internal or proper cerebral layer, which, though blended with the preceding throughout the greatest part of its extent, is separated from it at certain points, in order to form both the fibrous canals, which are called the sinuses, and also the sev- eral folds just described as projecting from the internal surface of the dura mater. Thus, the periosteal layer of the dura mater enters into and lines the longitudinal groove, but the central layer passes off from it on either side ; and the two laminae thus formed by the right and left portions of the cerebral layer approach each other, so as to include between themselves and the periosteal layer lining the groove a long three-sided inter- val, which forms the superior longitudinal sinus. The internal layer of the dura mater, which is essentially fibrous, must not be con- founded with the arachnoid membrane by which its internal surface is lined, and which will be presently described. The dura mater is evidently composed of fibrous, not of muscular tissue, as was for a long time believed.* It consists of fibres which interlace in various directions Anatomists generally describe, in connexion with the dura mater, those white granu- lar bodies which are chiefly collected into clusters along the superior longitudinal sinus, and which are improperly called glands (the glands of Pacchioni, from the name of the author who first gave a good description of them). These bodies are not found in infants, but exist almost constantly in the adult, and are very numerous in old subjects. They are sometimes single and sometimes collect- ed into groups ; they are, at first, formed upon the internal surface of the dura mater, but after a time they displace the fibres of the internal layer, and separate them into small, parallel, or reticulated fascicuh, and, in this way, insinuate themselves between the two layers of the membrane. In this situation they form tumours, which project upon the external surface of the dura mater, and occupy corresponding depressions form- ed in the bones of the cranium. The rough and irregular depressions so frequently found in the parietal bones of old subjects, and ascribed by the older anatomists to caries of the bone, are occasioned by the clusters of these granular bodies. These bodies often insinuate themselves along the obliquely running veins into the substance of the walls of the sinuses, and project into the interior of the veins and si- nuses, so as apparently to be in direct contact with the blood ; but they are, in reality, separated from that fluid by the lining membrane of the vessels and sinuses. Although these bodies are principally collected along the superior longitudinal sinus, they are also found, as Haller remarks, opposite the anterior extremity of the straight sinus. I have seen a small pedunculated mass of them, which projected into the inte- rior of the horizontal portion of one of the lateral sinuses, and might have impeded the circulation. I consider that the bodies in question are seated in the sub-arachnoid cellular tissue ; in fact, they are often found beneath the arachnoid, at some distance from the longitu- dinal sinus, along the superior cerebral veins. They always project at first upon tlie in- ternal surface of the dura mater, and then insinuate themselves into the substance of that membrane. What is the nature of these bodies 1 Ruysch noticed them, and considered them to be of a fatty nature. Some authors have likened them to the granulations so frequently * Pacchioni, who wrote a treatise of some length upon this membrane, even went so far as to admit the exist- ence of three fleshy belhes, viz., one for each hemisphere, and a third for the cerebellum. The same author gives a very minute description of the direction of the different layers of fibres in the dura mater. I do not believe that there exists in the history of our science a more striking- example of the misapplication of textu- ral anatomy. €86 NEUROLOGY. found in the choroid plexuses ; but there is not the shghtest resemblance between the two. Pacchioni regarded them as glands which secreted a peculiar lymph. He has even described certain, so called, excretory ducts, which have been said by others to enter the superior longitudinal sinus. Those clusters which project into the sinuses have been supposed to act as valves. It has been said that these bodies are lymphatic glands ; this, also, is erroneous ; and, indeed, it is better to confess our ignorance of their nature. They occur so frequently that they cannot be regarded as morbid productions. Their absence in the infant, and their much greater abundance in the old subject than in the adult, are the principal features in their history. Vessels. — In respect of the number and size of its vessels, the cranial dura mater seems to form an exception to fibrous membranes in general, which are remarkable for their slight vascularity. It receives, in fact, the following arteries : the middle menin- geal, which is a branch of the internal maxillary artery ; the anterior meningeal, from the ethmoidal artery ; and the posterior meningeal, from the ascending pharyngeal, or pharyngo-meningeal. Nevertheless, if we consider that these vessels are situated be- tween the dura mater and the bones, and that they are almost entirely distributed to the bones, we shall be able to account for the apparent anomaly in the nmnber and size of these vessels. The veins of the dura mater are two venas comites for each meningeal artery, and the small veins which enter the sinuses ; the venous sinuses themselves are situated be- tween the two layers of this membrane. The lymphatics form a network upon the internal surface of the dura mater, but do not appear to belong to the proper fibrous tissue. Nerves of the Dura Mater. — On consulting the various writers upon this subject, it is found to be involved in the strangest perplexity : some authors admit, while others deny in the most positive manner, the existence of nerves in this membrane ; and those who do admit their existence, differ altogether in regard to their origin. Modern anatomists, with Haller, Wrisberg, and Lobstein, state that there are no nerves in the dura mater ; on the other hand, Vieussens, Winslow, Lieutaud, Lecat, Val- salva, and others, declare that they have observed them. Valsalva says that they are derived from the seventh pair ; all the other authors state that they arise from the fifth ; but they do not agree as to the exact point of origin, which, according to some, is the Gasserian ganghon ; and according to others, either the ophthalmic, or the superior or inferior maxillary divisions of that nerve. Chaussier admits their existence, and says that they are derived from the ganglionic system ; but it is evident that he has been led to this conclusion from theory, and not from actual observation. Accident has enabled me most distinctly to demonstrate nerves in the dura mater. In a head which had been macerated in diluted nitric acid, and afterward in water, the dura mater having become transparent and jelly-like, I was surprised to see within its substance certain white hnes exactly resembling nervous filaments. I cut down to these white lines, ascertained that they were nerves, and dissected them throughout their whole course. I recognised on each side of the middle line two nervous filaments which came from the fifth nerves, and reached nearly to the superior longitudinal sinus. There was a third nervous filament in the substance of the tentorium cerebeUi, but I could not ascertain its origin.* Uses of the Cranial Dura Mater. — The dura mater serves as an internal periosteum for the bones of the cranium, with which it has numerous vascular connexions ; and it also covers and defends the encephalon. Its prolongations separate from each other the dif- ferent parts of the encephalon, and in some measure prevent the effects of concussion. It also contains within its substance certain venous canals, in which aU the blood is re- turned from the encephalon. The Spinal Portion of the Dura Mater. The spmal portion of the dura mater forms a long fibrous tube, which is prolonged from the cranial dura mater, and extends from the occipital foramen to the termination of the sacral canal. In order to ascertain the capacity of this fibrous sheath, it must be first distended -with an injection : it is then seen to form a funnel-shaped tube, which is of considerable size in the cervical region, becomes contracted in the dorsal region, is again expanded in the lumbar region, and terminates in the sacral region by subdividing into a number of sheaths for the sacral nerves. When distended, the spinal portion of the dura mater almost en- tirely fills the bony canal formed by the vertebral column. Why the cavity of the dura mater {d.fig. 266, A B) should be larger than the spinal cord (s), a question the solution of which had exercised the ingenuity of almost all anatomists, has been well answered by Cotugno — it is for the purpose of containing a serous fluid, t * [The tentorium receives a branch from the fourth cranial nerve (see description of that nerve).] t " Quidrjuid autem spatii est inter vaginam duree matris et medullam spinalem, id omne plenum etiam sem- per est ; non meduUS. quidfim ipsft. in viventibus turfridiori, non nube vaporosa, quod in re adhuc obscur^ sus- picantur samnii viri ; sed aqirii ci qviidem simili,quam circa corcontinet pericardium, quae caveas cerebri ven- triculorum adimplet, quae auris labyrinthum, quiE reliquas tandem complet corooris caveas, libero aeri, nequa- qnam adeundas."— (iye Jschiade Nervosa, p. U.) THE CRANIAL PORTION OP THE ARACHNOID. 687 The external surface of the spinal portion of the dura mater, unlilie, in this respect, to the cranial portion, scarcely adheres to the bony parietes of the spinal canal. Covered by a plexus of veins behind, it has no attachment at all to the arches of the vertebrae, nor to the yellovs^ ligaments ; the intervals between those parts and the membrane is occu- pied by a soft, reddish, adipose tissue intermixed with veins, which, in the foetus, and during infancy, is infiltrated with serosity. This fat, which is most abundant in the sa- cral region, may be most aptly compared to the marrow of the long bones, with which it has so much analogy in respect of its use. In one class of vertebrated animals, viz., fishes, a precisely similar kind of fat is accumulated in large quantities in the cranium, always filling up the spaces left by the contained organs. In front, the external surface of the dura mater adheres to the posterior common ver- tebral ligament by fibrous bands prolonged from it at intervals. On each side, the spinal portion of the dura mater gives off fibrous sheaths {I, fig. 266 ; b',fig. 267) for the roots of the spinal nerves («), which sheaths accompany the nerves beyond the inter-vertebral foramina, and are lost in the cellular tissue. The internal surface of this part of the dura mater is smooth and moist, in consequence of being covered by a serous layer, viz., the arachnoid (a). Down each side of this sur- face are seen the double orifices of the several fibrous canals, which transmit the ante- rior and posterior roots of the spinal nerves. It is very rarely found entirely free from adhesions to the arachnoid ; and it is necessary to be careful not to confound these ad- hesions, which are always met with at isolated points, with such as are the result of morbid action. The inferior extremity of the spinal portion of the dura mater is situated opposite the bottom of the lumbar region, and it therefore extends much lower than the spinal cord ; this extremity is formed into a large ampulla around the cauda equina, which enlarge- ment seems to be of use only as a reservoir for the cephalo-rachidian fluid. Its superior extremity is firmly attached to the margin of the foramen magnum, and is continuous with the cranial portion of this membrane. In consequence of the firm ad- hesion of this membrane to the margin of the foramen magnum, and of its attachment to the sacrum by means of the sheaths for the sacral nerves, and to the sides of the ver- tebral column by those for the cervical, dorsal, and lumbar nerves, it is constantly main- tained in a state of tension highly favourable to its use as a protecting covering of the spinal cord. Vessels. — The vessels of the spinal dura mater are much less numerous than those of the cranial portion ; for these belong exclusively to it, and not to the surrounding bones. Its arteries arise from the spinal branches of the arteries of the cervical, dorsal lum- bar, and sacral regions. Its veins terminate in the intra-spinal veins. The lymphatic vessels observed appear rather to belong to the arachnoid. The nerves of this membrane have not yet been demonstrated ; but experiments upon living animals, especially upon dogs, have convinced me that the cranial, and probably, also, the spinal portion of the dura mater, although insensible to the knife, are extreme- ly sensible to laceration. The Arachnoid. The cerebro-spinal axis is surrounded by a serous membrane named the arachnoid, which, like all membranes of this kind, forms a shut sac, adherent by its external sur- face, but free and smooth on its internal surface. We shall first describe the cranial, and then the spinal portion of the arachnoid. The Cranial Portion of the Arachnoid. Dissection. — The arachnoid may be shown upon the convex surface of the brain with- out any preparation, if the sub-arachnoid cellular tissue be infiltrated. It can also be very easily demonstrated by blowing air under it. The arachnoid membrane, which, from its extreme tenuity, was for a long time con- founded with the pia mater, was demonstrated by Ruysch upon the convex surface of the brain by injecting air beneath it ; it was shown by Varolius upon the base of that organ, and its arrangement in that situation was figured by Casserius. It was descri- bed first by the Anatomical Society of Amsterdam as a special membrane covering the brain, under the name of the arachnoid; and Bichat, reasoning from analogy, demonstra- ted that it not only forms a covering for the brain, but is also reflected upon the dura mater, and lines it through its whole extent. He also believed that it was continuous with the Hning membrane of the ventricles, an error which has been successfully refu- ted by M. Magendie. Like all serous membranes, the arachnoid presents a visceral and a parietal layer The Visceral Layer of the Arachnoid. The visceral layer of the cranial portion of the arachnoid requires to be exammed upon the convex surface and the base of the brain. Upon the base of the brain, the arachnoid is separated from this organ in a gi'eat nura- 688 NEUROLOGY. ber of points, and more particularly as it is passing from one lobe to another. We shall examine in detail the arrangement of this part of the membrane. In the median line, \n front, it dips between the anterior lobes of the brain, but only at the fore part ; behind, it connects these lobes by passing directly from one to the other ; it covers the lower surface of the optic nerves and optic commissure, then the tuber cinereum and the infundibulum, for the latter of which it forms a sheath, and is then re- flected above the pituitary body ; from the tuber cinereum it passes across to the pons Varolii, leaving a hollow space between it and the brain, which is traversed by a few dense fibrous filaments. I shall call this space the anterior sub-arachnoid space ; it may be regarded as the prin- cipal reservoir of the serous fluid of the cranium. In the median line, behi7id, the arachnoid lines the furrow between the posterior lobes of the brain, and is reflected from the corpus callosum upon the superior vermiform pro- cess of the cerebellum : at this point it meets with the venae Galeni, and generally forms a circular fold around them, which was compared by Bichat to the foramen of Wins- low in the peritoneum, and which he supposed to be the orifice of an arachnoid canal, which opened into the third ventricle beneath the velum interpositum. The arachnoid covers the whole upper surface of the cerebellum ; and, having reached the great circumference of that organ, it passes like a bridge from one hemisphere to the other, and from the cerebellum itself to the posterior surface of the spinal cord. In thus passing from one hemisphere of the cerebellum to the other, and from the cerebellum to the spinal cord, the arachnoid leaves a considerable space or reservoir for serosity, which may be called the posterior sub-arachnoid space. Laterally, the arachnoid covers the inferior surface of the anterior lobes of the cere- brum and the olfactory nerves, which are thus held in contact with the anterior lobes ; it then passes from the anterior to the posterior lobe, without entering the fissure of Sylvius, and from the posterior lobe to the tuber annulare and the cerebellum. It fol- lows, therefore, that there are certain small sub-arachnoid spaces which communicate with the great anterior sub-arachnoid space of the brain ; so that in the dead body there exists, between the arachnoid and the pia mater, at the base of the brain, a large space, the centre of which corresponds to the median excavation of the base of the cerebrum, and which is prolonged forward between the anterior lobes of the brain, laterally along each of the fissures of Sylvius, and backward, around the peduncles of the cerebellum. By this last-named prolongation a communication is established between the anterior and posterior sub-arachnoid spaces. All these spaces contain serum in the natural state, and coagulable lymph in some cases of inflammation of the sub-arachnoid cellular tissue. The arachnoid is arranged in a uniform manner in reference to all the nerves situated at the base of the brain ; it passes over their lower surface, and therefore holds them firmly against the under surface of the brain ; but where these nerves are separated from the brain it furnishes a tubular prolongation around each, and again leaves them as they are about to enter the foramina in the base of the scull, and is reflected upon the dura mater. Upon the upper surface of the brain, the arachnoid dips into the median fissure, and is reflected from one hemisphere to the other immediately below the free margin of the falx cerebri ; and as this margin is nearer to the corpus callosum behind than in front, it fol- lows that the anterior portions of the two hemispheres are in contact with each other for a certain distance, or, rather, they are merely separated by the pia mater. The cerebral arachnoid adheres intimately to the arachnoid of the dura mater, along the sides of the superior longitudinal sinus, by means of the tubular prolongations which it forms around the cerebral veins that enter that sinus. This adhesion is also strength- ened by the granular bodies called the glands of Pacchioni, which, as we have already stated, lie in the substance of the dura mater. Moreover, on the convex surface, as well as upon the base of the brain, the arachnoid, in covering this organ, passes, like a bridge, from one convolution to another, never dip- ping into the intermediate sulci. The cellular tissue, which unites the arachnoid to the pia mater, is of a serous nature and extremely delicate, so that the two membranes can be easily separated, excepting in cases of inflammation. When air is blown beneath the arachnoid, the extreme tenu- ity of this cellular tissue becomes evident : it is very frequently infiltrated with a serous fluid. The sub-arachnoid cellular tissue never contains any fat. The fat which Ruysch, Haller, and other anatomists say they have observed, must have been that yello\^«ish, gelatiniform lymph so commonly met with in cases of inflammation.* In some parts the arachnoid is lined by a fibrous tissue, which gives it great strength. This fibrous tissue, which may be regarded as a prolongation of the neurilemma of the spinal cord, is especially distinct in the great furrows of the brain. Thus we find it * I once found in an old woman an adipose cyst, about the size of a small grape, arising by a very thin ped- icle from the upper surface of the pituitary body. THE PARIETAL LAYER OF THE ARACHNOID. 689 around the great anterior sub-arachnoid space, where it constitutes, as it were, a very strong fibrous band, which surrounds the arterial circle of WilUs, situated at the base of the brain ; it also retains the dilTerent parts of the brain in their relative positions, even when that organ is removed from the cranium, and is laid with its base uppermost. The Parietal Layer of the Arachnoid. The internal surface of the dura mater is lined with a very delicate and closely-ad- herent serous membrane, which, owing to these two qualities, for a long time escaped the notice of anatomists. It was only by reasoning analogically from the structure of all other serous membranes, that Bichat was led to enter upon the inquiry which ended in the discovery of the parietal portion of the arachnoid. This portion is quite distinct from the internal layer of the dura mater, the existence of Avhich we have admitted with several anatomists. Upon a mere inspection, we should say that it does not exist, because, from its transparency, the fibrous bundles of the dura niater can be seen as dis- tinctly as if they were not covered. But if a very superficial incision be made upon the inner surface of the dura mater, some extremely thin shreds may be detached by the aid of the forceps. Lastly, ecchymosis not unfrequently occurs between the dura mater and the arachnoid.* Ossific deposites in the dura mater, especially those found in the falx cerebri, being found beneath the arachnoid, sometimes enable us to detach this lat- ter membrane in the most distinct manner. It still remains, however, to describe the mode in which the parietal and cerebral por- tions of the arachnoid become continuous with each other. It has been stated that the arachnoid membrane forms tubular prolongations around each of the nerves which are given off from the base of the brain, and around each of the veins which enter the dif- ferent sinuses ; these prolongations just enter the fibrous canals formed by the dura mater for these nerves and veins, and almost immediately terminate by being reflected upon the dura mater itself; so that the arachnoid forms a sort of cul-de-sac around the cranial orifice of each fibrous sheath of the dura mater. In order to see the funnel- shaped prolongations of the arachnoid, it is convenient to examine them when the brain is being lifted up from before backward, in order to expose and divide the nerves which are attached to the base of the scull. The tubular prolongations being then dragged upon, they become very distinct. Not unfrequently, the development of adventitious false membrane on the base of the brain also extends along these prolongations. The arachnoid does not enter into the interior of the ventricles, below the posterior border of the corpus callosum. The arachnoid canal, called the canal of Bichat, does not exist, but it is formed by the very experiment made to demonstrate it. The following is the statement of Bichat regarding this alleged canal ; " The brain being exposed from behind and allowed to remain in its natural position, the back part of each posterior lobe is to be raised, and drawn gently outward ; the ve- na3 Galeni are then seen emerging from the canal by which they are embraced, and the oval orifice of which is now very apparent. Sometimes, however, the margin of this orifice embraces the veins so closely, that it can only be recognised by a small fissure on each side, and the parts, at first sight, would appear to be continuous. If a probe be then glided from behind forward along these vessels, and when it has penetrated a short distance, if it be turned all round the veins it will destroy the adhesions^ a7id the opening will become very evidcTit. " In order to be convinced that this opening leads into the middle ventricle of the brain, a grooved director must be introduced below the vense Galeni and pushed gently forward : it will enter the ventricle without difficulty. The corpus callosum and the for- nix are then to be removed, and the velum interpositum left untouched. Next, dividing the velum on the director, the membrane wiU be found to be smooth and polished in the whole of its course, and nowhere lacerated by the introduction of the director. Occa- sionally some resistance is experienced to the entrance of the director, lohich may even be com- pletely arrested : this depends upon the fact that the ecins ivhich enter the vence Galeni inter- lace in all directions ivithin the canal, so as to form a network, which arrests the instrument. If this be the case, it should be withdrawn, and, in order to demonstrate the communi- cation, some mercury should be poured into the external opening, and, by inclining the position of the head, this fluid will flow into the middle ventricle. Air blown into the canal wiU also enter that ventricle, and wdl pass from it into the lateral ventricles through the openings behind the anterior pillars of the fornix. If the fornix be removed, and the velum be exposed, the latter will be seen to be elevated each time that the air is blown in. " The internal orifice of this communicating canal is at the lower part of the velum interpositum ; in order to see it, this membrane must be reflected backward, either with the fornix, the under surface of which it covers, or after it has been separated from that part of the brain. The pineal gland which adheres to the velum is also to be turned * As to the collections of blood which are said to have been met with between the arachnoid and the dura mater, M. Baillarget has clearly shown, in several preparations which he presented to the Anatomical Soci- ety, that the supposed laver of arachnoid is a newly-formed membrane, having all the appearances of a serous iBezabrane. 4S 690 NEUROLOGY. back ; below and in front of this gland is then seen a row of cerebral granulations, ar- ranged in the form of a triangle, having its point turned forward. The internal orifice of the canal of the arachnoid is at the base of this triangle." Now, if we make the dissection described by Bichat, it is easy to see that there exists at the back part of the brain, below the corpus callosum, a circular or oval opening, lead- ing into a sort of cul-de-sac, which is of variable depth, and is formed by the reflection of the arachnoid around the venae Galeni : it is seen, also, that the bottom of this cul-de- sac may be easily lacerated by a blunt probe, which may then be passed beneath the velum interpositum, as Bichat has pointed out ; but it is through an artificial canal- Moreover, if a coloured liquid be injected into the ventricles, it can never be made to escape through this imagined canal of Bichat ; and so, on the other hand, if a liquid be thrown into the orifice of this canal, it never enters the third ventricle : mercury enters only by lacerating the parts ; and the same is the case with air. Analogy, which has so often conducted Bichat to beautiful and grand discoveries, has, therefore, misled him in this particular. Since, then, the arachnoid canal of Bichat does not exist, it will be necessary to de- termine how the ventricles communicate with the external arachnoid cavity. This question we shall discuss presently.* The Spinal Portion of the Arachnoid. The spinal cord, besides its own proper investment, is covered by a transparent mem- brane of extreme tenuity, and only to be demonstrated properly by raising it with the forceps, or by subjecting it tothe mode of preparation above described : this is the vis- ceral layer of the spinal portion of the arachnoid. The visceral layer (b, fig. 266, A B) forms a membranous sheath, which is much larger than the spinal cord (s) ; hence it is named the loose arachnoid. It is prolonged around the bundle of nerves called the cauda equina, and forms around each nerve a funnel-shaped sheath, which terminates in a cul- de-sac at the corresponding inter- vertebral foramen, by being reflected upon the inner surface of the fibrous sheath formed for the nerve by the dura mater (see^^. 266, B). There exists, then, between the spinal cord and the visceral portion of the arachnoid a considerable space {e,fig. 266, A B), which can be best displayed by inflating it, or injecting it with some liquid. This space, as we shall immediately show, contains a serous fluid. We have seen that, opposite the median excavation at the base of the brain, the arachnoid adheres to the cerebral pia mater only by means of long fibrous filaments. The spinal arachnoid also adheres to the proper covering of the cord by means of fibrous filaments ; but in no part does there exist any delicate sub- arachnoid cellular tissue, like that found beneath the cerebral arachnoid. t Another peculiarity in the visceral layer of the spinal portion of the arachnoid is this, that it adheres to the parietal layer in a number of points. The parietal layer (a) of the spinal portion of the arachnoid is arranged precisely in the same manner as the parietal layer of arachnoid in the scull. It becomes continuous with the visceral layer opposite the sheaths which are formed by the latter around the spinal nerves. The Sub-arachnoid Fluid. There exists around the spinal cord a serous fluid, in quantity sufficient to occupy the interval left between the cord and the dura mater : this fluid is seated in the sub-arach- noid space (e). A similar fluid exists in the ventricles of the brain and in the sub-arach- noid cellular tissue, and fills the free spaces of the cranial cavity, t The existence of the sub-arachnoid fluid was pointed out by Haller (Elementa Physi- ologic, t. iv., 87), and most explicitly and completely demonstrated by Cotugno (i)e ischi- ade nervosa commcntarhim), but the fact was neglected by anatomists, and the fluid re- garded by some as the result of cadaveric exudation, and by others as that of a morbid action. The existence of this fluid has been again confirmed by M. Magendie, who, moreover, has clearly proved that it is seated in the sub-arachnoid tissue. In order to prove the existence of the sub-arachnoid fluid, or cephalo-rachidian fluid * [The existence of the canal of Bichat is admitted by Arnold, a recent authority. Perhaps the opposite statements of anatomists concerning this canal may depend on the fact that the canal itself, though originally present, is sometimes closed subsequently, and at other times remains open.] t [The spinal sub-arachnoid space is divided behind by a thin, and, in some parts, cribriform longitudinal septum, which extends from the loose arachnoid to the posterior median fissure of the cord. This space is probably lined throughout by a serous membrane, which contains the rachidian fluid, and which might be named the internal arachnoid. The septum just mentioned may be supposed to consist of two layers of this membrane reflected from the loose arachnoid to the cord, and having the same relation to it as the mesentery has to the intestine ; and the membrane itself may be conceived to.be prolonged through the foramen described by Magendie at the Ijottom of the fourth ventricle (see p. 718), so as to form the lining membrane of the fourth, third, and lateral ventricles ; and, farther, in case of the existence of the foramen of Bichat, to become con- tinuous with the external or true arachnoid through that foramen.] THE SUB-ARACHNOID FLUID. 691 of Magendie, it- is necessary to open the lumbar region of the spinal canal in a certain number of subjects. If an incision be very carefully made through the dura mater, it will be seen that the serous fluid raises the visceral layer of the arachnoid, so as to make it protrude like a hernia through the incision : if this layer of arachnoid be then divided, the liquid will escape. Cotunni, who performed this experiment upon twenty subjects, collected from four to five ounces of fluid in each case. To the objection that this fluid is found after death, but does not necessarily exist in the living subject, we may answer thus : There is a space between. the spinal cord and the dura mater, and the brain itself does not exactly fill the cranial cavity. Now in no part of the animal body does there exist any vacuum ; the spaces between the solids are always filled either with liquids or gaseous fluids. But if it be said that in this situation the space is filled by a serous vapour, the elasticity of which might establish an equilib- rium with the external air, it may be replied, that this vapour would not be sufficient to produce so large a quantity of fluid as is found in the spinal canal. Moreover, all these objections, and also the supposition that the brain and spinal cord may be smaller after death than during life, are overthrown by the following experiment. If the posterior cervical muscles be divided in a living dog, at their occipital attachments, the posterior occipito-atlantoid ligament will be exposed. The parts being well cleansed from blood, the ligament must be cut away, layer by layer, with a scalpel held flat against it. The ligaments will scarcely be cut through before a small hernial protrusion, con- taining a fluid, will be seen ; this consists of the visceral arachnoid raised by the rush of fluid. If a crucial incision be then made in the occipito-atlantoid ligament, by the aid of a director,* a fluid as limpid as distilled water will be seen beneath the visceral layer of the arachnoid, which fluid is agitated by two kinds of motion, one of which is isochro- nous with the pulse, and the other with the respiratory movements. If the arachnoid be next punctured, the fluid will immediately escape in jets, and its quantity may be as- certained. The difficulty of not wounding the visceral layer of the arachnoid explains why, until recently, it was thought that the spinal fluid was contained within the arachnoid cavity {c,Jig. 266), i. e., between the two layers of the arachnoid membrane, although most ob- servers had noticed that the serous fluid in the cranium occupied the sub-arachnoid cel- lular tissue. It follows, therefore, that besides the fluid which is exhaled from the free surface, i. e., into the cavity of the arachnoid, a certain quantity of a similar fluid fills up the areolar tissue of the sub-arachnoid space : in this respect the arachnoid differs es- sentially from other serous membranes, all of which pour their secretions into their cav- ities, and not into the subjacent cellular tissue. This peculiarity depends simply upon the non-adhesion of the arachnoid to the spinal cord ; it may be stated as a law, that serous membranes exhale almost indiflferently from either their internal or their external surface, when the latter surface is not adhe- rent. The arachnoid exhales a fluid from both surfaces ; a certain quantity of fluid is rather frequently found between its two layers ; and although, in acute inflammations, the deposite of purulent matter or of false membranes most generally takes place in the sub-arachnoid cellular tissue, yet these morbid products are not unfrequently found in the cavity of the spinal arachnoid itself The sub-arachnoid fluid exists not only in the vertebral canal, but also within the cra- nium, in which it fills up all the spaces between the brain and the dura mater. Now these spaces are subject to much variety in size in different individuals, or from age or from disease : thus, in atrophy of the brain and spinal cord, from old age or dis- ease, the interval between the dura mater and the cerebro-spinal axis is augmented, and the quantity of fluid increases in the same proportion. The quantity of the sub-arachnoid fluid is in a direct ratio with the progress of age ; in aged lunatics, in whom the convolutions of the brain are much atrophied, the quanti- ty of this fluid contained within the cavity of the cranium is very great, t The sub-arachnoid fluid in the cranium is not distributed equally around the brain, but is chiefly seated at its base. In order to show this fluid, it is merely necessary to raise up the brain carefully from before backward, when it will be seen distending all the fun- nel-shaped prolongations formed by the arachnoid around the nerves, and it will escape as soon as the membrane is divided. As regards quantity, the sub-arachnoid fluid at the base of the brain and the fluid of the ventricles are always directly proportioned to each other, but are inversely propor- tioned to the sub-arachnoid fluid upon the convex surface of the brain. Upon opening the head of infants who have died from acute ventricular hydrocephalus, we sometimes * It is highly important to make the transverse incision very short, in order to avoid injuring the very large vertebral veins ; for if these vessels be cut, the hemorrhage will be so abundant as to prevent the continuation of the experiment. + None of these facts escaped the notice of Cotugno : " Nee lantum hsc aqua complens ab occipite ad usque imum os sacrum, tubum durte matris . . . sed et in ipso redundat calcarise cavo omniaque complet intervalla quse inter cerebrum et dur2E matris ambitum inveni- untur .... quantum autem magnitudinis cerebrum in his perdit, tantum a contactu subtrahitur durae matris, et quidquid Joci decrescendo reliquit, aquosus vapor collectus lotum adimplet."-^(0^. cit., p. II, 12.) 692 NEUROLOGY. find the convex surface of the brain dry, and, as it were, adhesive. It is of importance to determine whether the cavities containing the cephahc and the spinal fluids commu- nicate with each other. There can be no doubt that the sub-araciinoid spaces of the brain communicate with the sub-arachnoid space around the spinal cord; but do the cavities of the ventricles communicate with the sub-arachnoid space 1 Haller admitted that the fluid could flow from the ventricles into the spinal canal, and he believed that this was effected by a communication between the ventricles and the cavity of the arachnoid itself* Cotugno expresses the same opinion still more distinct- ly. Both HaUer and Cotugnot thought that this communication occurred at the bottom of the fourth ventricle, but they neither indicated the exact situation, nor the mode in which it is effected. M. Magendie has pointed out that it occurs at this very spot, near the point of the calamus scriptorms. Bichat stated that the communication between the ventricles and the arachnoid cavity was at the so-called canal of Bichat. The mode in which the fourth ventricle communicates with the sub-arachnoid space will be much better understood if stated in our description of that ventricle, t Uses of the Arachnoid and of the Sub-arachnoid Fluid. Uses of the Arachnoid. — Like all serous membranes, the essential use of the arachnoid is to lubricate the surface of the brain and spinal cord, and thus facilitate their move- ments. No other membrane more completely fulfils such a use, for the arachnoid is moistened in both its external and internal surfaces. It would, in fact, be an error to suppose that the serous secretion is poured out solely by that surface of the arachnoid which is turned towards the pia mater : the fluid is exhaled upon its internal surface also, as in all other serous membranes, so that we sometimes find serum, pus, and false membranes in the cavity of the arachnoid itself Uses of the Sub- arachnoid Fluid. — The sub-arachnoid fluid forms a sort of bath around the spinal cord, which effectually protects it during the various motions of the vertebral column. It might be said that the spinal cord, being, in reference to its delicacy, in con- ditions somewhat analogous to those of the foetus in utero, requires a similar method of protection ; and in this point of view the sub-arachnoid fluid exactly represents the liquor of the amnios. As to the other uses which have been attributed to it, they are all more or less hypo- thetical. If we open the spinal canal of a dog, between the atlas and the occipital bone, some fluid wiU immediately gush out ; air is drawn in, which is forced out in bubbles during expiration, and again enters during inspiration. If the animal be then left to himself, he will stagger like a drunken man ; he will crouch into a corner, and remain in a drowsy state for some hours. On the next day he will walk about again perfectly well. I have repeated this operation several times upon the same dog, until at last he became accus- tomed to it, at least as far as regards the physiological effects resulting from the remo- val of the fluid, by which means the slight pressure usually exercised upon the spinal cord was removed. The Pia Matee. The pia mater is the innermost of the three membranes of the encephalon and spinal cord. It consists of an extremely delicate membrane, or, rather, of a vascular network, which immediately invests the nervous axis, and which may be regarded as the nutri- tious membrane of the parts that are covered by it. In fact, the arterial vessels divide into an infinite number of branches within this membrane before they enter the nervous substance, and so, also, the veins which pass out from the brain and spinal cord unite into small, and then into larger vessels, which form part of this same network. These vessels are supported by a very delicate serous cellular tissue : to this is added, in some regions, a certain amount of fibrous tissue, which converts the membrane into a very strong fibrous structure, having all the characters of the neurilemma, or proper invest- ment of the nerves. The characters of the spinal portion of the pia mater are so distinct from those of the cranial portion, that it will be better to postpone the description of the former until we are treating of the spinal cord, of which it constitutes the proper covering. The Cranial Portion of the Pia Mater. This portion, or the cerebral pia mater, does not merely enclose the brain like the arach- noid, but dips into the sulci or anfractuosities on its external surface, and penetrates into the interior of the ventricles. That portion of the pia mater which invests the brain is * " Qua prodit de ventriculo aqua, facili in meduUae spinalis circumjectum spatium etiam parat ; earn aquam enim difficulter omnino in tertium ventriculum et ad infundibulum redderet, quoad pei-pendiculum oportet as- cendere (Holler, torn, iv., sect. 3, p. 77) . . . Non dubito quiu collecta ex ventriculis cerebri aqua eo descen- dere possit." — (Ibid., sect. 3, p. 87.) t " His spinffi aquis eas etiam subinde commisceri, qnas, sive a majoribus cerebri ventriculis per lacunar et Sylvii aqueductum, sive a propriis exhalantibus arteriis, cerebelli ventriculus accipiat ; cujus positio perpen- diculata et via ad spins cavum satis patens defluxum humoris in spinam manifesti persuadent." — (.Cotugno-, p. 18, 19.) i See note, p. 960. THE EXTERNAL CEREBRAL PIA MATER, ETC. 693 called the external pia mater, and that which is continued into the ventricles is denomi- nated the internal, pia mater. The internal pia mater cannot be satisfactorily studied until the internal conformation of the brain is understood, and itwiU therefore be describedtogetherwith the ventricles. The External Cerebral Pia Mater. Dissection. — At the base of the brain, the pia mater is naturally separated from the arachnoid by a considerable space, which is occupied by the sub-arachnoid fluid ; but it is ea^y to separate these two membranes everywhere by introducing air or water be- tween them. The arachnoid may be easily distinguished from the pia mater in cases of serous or purulent infiltration into the sub-arachnoid cellular tissue. The external pia mater is subjacent to the arachnoid, and is connected with it by a very delicate serous cellular tissue ; it not only covers the free surface of each convolution, but also dips into the adjacent sulci ; it passes down on one side of a sulcus, and then, being reflected upon the other, is continued over the free surface of the next convolu- tion, and so on. It follows, therefore, that this part of the pia mater is in contact with itself to a great extent ; and also that its superficies is much larger than that of the arachnoid, so that if the brain could be unfolded, as Gall supposed, its surface would be entirely covered by the pia mater. These remarks apply equally to tlie pia mater of the cerebellum, for every one of the numerous laminae of that organ is covered on each side by a fold of the pia mater. The internal surface of the pia mater is in contact with the brain, and is united to it by innumerable vessels, which penetrate into the substance of that organ. This adhe- sion, however, is such, that the pia mater can generally be detached without injuring the surface of the brain. I do not think, however, with some pathologists, that the adhesion of this membrane to such a degree that it cannot be removed williout injuring the substance of the brain is any evidence of disease.* For displaying the vessels which pass into the substance of the brain from the pia mater, an asphyxiated subject is very well adapted. But an injected condition of these vessels may be produced by allowing the head of the subject to hang down for some hours. The pia mater will then be not only black from its congested state, but it will be infiltrated with serum ; and if it be detached slowly, an immense number of vascular filaments, looking like hairs, will be seen emerging from the substance of the brain, re- markable for their extreme tenuity and length, and for having no anastomoses. Some drops of blood will indicate the points upon the surface of the brain from which the ves- sels escape, and which, when examined through a lens, prove to be foramina. The use of the pia mater is connected solely with the circulation of blood through the brain. This membrane affords to the vessels a very large surface, on which the arteries divide into their capillary branches, and the veins unite into their larger and larger trunks. According to my observations, five sixths of the vessels of the pia mater belong to the venous system. The pia mater is the nutritious membrane of the brain, and may thus be regarded as its neurilemma. It will afterward be seen that the internal pia mater is connected with the arteries and veins of the walls of the ventricles, ^ust as the external pia mater is with the ex- ternal vessels. THE SPINAL CORD AND THE MEDULLA OBLONGATA. General View of the Cord — its Limits and Situation — the Ligamentum Denticulatum. — Size of the Spinal Cord — Form, Directions, and Relations — the Cord in its proper Membrane — the proper Membrane, or Neurilemma of the Cord — the Cord deprived of its proper Mem- brane.— Internal Structure of the Cord — Sections — E.'camination by Means of Water — and, when hardened in Alcohol — the Cavities or Ventricles of the Cord. — The Medulla Oblonga- ta—Situation — External Conformation — Anterior Surface, the Anterior Pyramids, and the Olivary Bodies — the Posterior Surface — the Lateral Surfaces — the Internal Structure- Sections — Examination by Dissection, and under Water. — Development of the Spinal Cord. — Development of the Medulla Oblongata. — Comparative Anatomy of the Spinal Cord. — Comparative Anatomy of the Medulla Oblongata. The spinal cord {p,ve?iO^ ^dxiTijc, medulla spinalis, a b e,fig. 268) is that white, round- ish, symmetrical, nervous trunk, which occupies the spinal canal ; it is continuous with the encephalon, of which it has been alternately considered the origin and the termina- tion. It is called the medulla, in consequence of a rude analogy between it and the mar- row of the long bones, in regard to its situation and consistence. Chaussier has sub- * In some cases the membranes are so dry that the pia mater cannot be removed without tearing the sub- •tance of the brain, even when that organ is perfectly healthy. 694 NEUROLOGY. stituted for this term the title of rachidiaii prolongation, but the generally received naiiie of spinal marrow, which can give rise to no error, might be retained.* The Extent and Situation of the Spinal Cord. Authors are not agi-eed as to the superior limit of the spinal cord. The natural limit is evidently at the groove, between the medulla oblongata (a, fig. 268) and the pons Varolii (e), which groove, on account of the great size of the pons in man, is much more distinctly marked in him than in those vertebrated animals in which the pons is also found. The spinal cord is situated in the median line, at the back part of the trunk ; it is be- hind the organs of digestion, circulation, and respiration.! The vertebral column, the dura mater, the arachnoid, and the pia mater form a fourfold sheath for the spinal cord ; the first being osseous ; the second, fibrous ; the third, serous ; and the fourth, or proper sheath, both fibrous and vascular : this last-named membrane is accurately adapted to the cord, so as to support it, and gently compress it on all sides. The spinal cord is not suspended freely in the vertebral canal, but is attached on each side by a hgament called the ligamentum dcnticidatum. The Ligamentum Denticulatum. The ligamentum denticulatum (c c, fig. 267), so called from the toothlike prolongations which proceed from its outer border, is an extremely slen- der, fibrous band, which runs along the side of the spinal cord, and adheres to the proper sheath of the cord by its inner border, which is very thin. The outer edge is free, thicker than the inner portion, and gives off certain tooth- like prolongations, which are attached to the dura mater in the intervals between the canals formed by that membrane for the spinal nerves : the first denticulation of this liga- ment, which may be regarded as its origin, is very long, and is found opposite the margin of the foramen magnum, be- tween the vertebral artery and the hypoglossal nerve ; the last, which is the twentieth or twenty-first, forms the ter- mination of the hgament, and corresponds very nearly to the lower extremity of the spinal cord. The form, thin- ness, and length of these toothlike processes are subject to much variety. The ligamentum denticulatum is evidently fibrous, and cannot be regarded, as Bonn imagined, as a prolongation of the arachnoid. J The ligamentum denticulatum appears to answer the twofold use of assisting in fixing the spinal cord, and of separating the anterior (a) from the posterior (b) roots of the spi- nal nerves. The Dimensions of the Spinal Cord. The length of the spinal cord in the adult is from fifteen to eighteen inches. Its cir- cumference is twelve lines at the thinnest part and eighteen at the thickest. But it is of much less importance to determine the actual dimensions of the spinal cord than to estimate its relative size as compared with that of the brain, or in reference to the ca- pacity of the vertebral canal, or than to examine the differences in size which it pre- sents at different parts of its extent. If the size of the spinal cord be compared with that of the whole body, throughout the series of vertebrated animals, we shall perceive that it always bears a direct ratio to the vital activity of the animal. Thus^considered, the spinal cord is small in fishes and rep- tiles, and large in birds and the mammalia. Size and Weight of the Spinal Cord compared with the Size and Weight of the Brain. — It ■was while studying the spinal cord and the brain in serpents and fishes that Praxagoras, as quoted by Galen, originated the idea that the brain was a production of the spinal cord. All the old anatomists, on the other hand, who studied the brain and cord in man, in mammalia, and in birds, regarded the medulla spinalis as a prolongation or appendix of the brain (tanquam cerebri effusionem, Rufus) ; indeed, it was for a long time consid- * The first description of the spinal cord which is worthy of notice was given by Huber (J. Huber, De Me- dulld Spinali, Goettingse, 1741) ; it served as the basis for the works of Haller {Elevi. Physiol., torn, iv., sect. 1) ; of Mayer, who published a beautiful plate of it in 1779; and perhaps of Alexander Monro, Secundus (Ob- servations on the Structure and Functions of the Nervous Si/stem, 1783). Soemmering, Reil, and Gall, who so successfully studied the other parts of the nervous system, have noticed the spinal cord in a superficial man- ner. Chaussier {De F Encephale en general et en particulier) ; Keuffel, in his inaugural dissertation {De Me- dulld Spinali, 1810, dedicated to Reil, his preceptor) ; and Rolando {Richerchc Anatomiche sulla Struitura dti Midollo Spinale, Torino, 1824), have supplied many of the deficiencies in our knowledge of this part. There is a good description of the medulla in M. OUivier's work upon the diseases to which it is subject. t The position of the nervous axis behind the alimentary canal constitutes one of the great differences which exist between the nervous system of the vertebrated and the invertebrated animals ; in the latter, the nervous system lies below, i. e., in front of the alimentary canal. t It is idle to inquire whether it should be considered a prolongation of the dura mater, or an extension of the neurilemma, or a proper ligament. DIMENSIONS OF THE SPINAL OORD. 695 «red that the medulla was the principal nerve in the body, summus in corporc humano ner- vus. In the present day, anatomists have returned to the opinion of Praxagoras, and the spinal marrow is generally regarded (Reil, Gall, Tiedemann) as the fundamental part of the nervous system, and that the brain is merely a production, an appendage, or an expansion of the cord. I shall not here enter into these purely speculative questions of production or emanation, origin, and relative importance, for the spinal cord no more produces the brain than the brain produces it. Soemmering has shown that, in man, the spinal cord is smaller in proportion to the size of the encephalon than in the lower animals ; and of this there can be no doubt ; but it does not follow that the lower animals have a larger spinal cord than man in propor- tion to the size of their bodies : on the contrary, from actual observation, I should say that, if we except birds, man has a relatively larger spinal cord than any other animal. Compare, indeed, the medulla of the horse, or of the ox, with that of man, and it will at once be found that the last is the largest and heaviest in proportion to the rest of the body. According to Chaussier, the weight of the spinal cord in the adult is from the nine- teenth to the twenty-fifth part of that of the brain, and in the newborn infant about the fortieth part. According to Meckel, this last is also the proportion in the adult. It must be remembered, however, that Meckel examined the cord when deprived of its proper membrane, and, therefore, after the roots of the nerves were detached from it. Size of the Spi?ial Cord compared with the Capacity of the Spinal Canal. — The spinal cord does not, by a great deal, fill up the vertebral canal, and a considerable interval oc- cupied by fluids exists between it and the sides of the canal. What is the object of this disproportion 1 and why is there any interval 1 We have already stated (see Osteol- ogy) that the dimensions of the canal are in relation, not only with the size of the cord, but also with the extent of motion of the vertebral column. The opinion of Vieussens, that this space is intended to allow of certain movements of elevation and depression in the spinal cord analogous to those which have been observed in the brain, is sufficiently refuted by the fact that, although the latter organ is affected by movements synchronous with the respiration and with the pulse, it stdl fills the cavity of the cranium.* The length of the spinal cord does not correspond with that of the vertebral canal, for the cord terminates near the first lumbar vertebra (between 20 and 21, _^^. 268), while the canal is prolonged into the sacrum. The position of the lower end of the spinal cord has not been determined with the pre- cision which so important a question demands. According to Winslow, it terminates opposite the first lumbar vertebra ; Morgagni has seen it reach down to the second ; Keuffel has observed it to descend as low as the third lumbar vertebra in one subject, and to terminate opposite the eleventh dorsal vertebra in another. The discrepancy be- tween various authors upon this subject depends upon individual varieties irt the point of termination of the cord, and upon the different acceptation of the term lower extremity of the spinal cord ; some regarding the thick swollen part as the end of the cord, while others include in it the tapering portion also. From some experiments which I made upon this subject by thrusting a scalpel horizontally from before backward through the inter- vertebral substance between the first and second lumbar vertebrae, I ascertained that there are varieties in different subjects in regard to the point of termination of the spinal cord, and that it was influenced by the position of the body, and by the state of flexion or extension of the head and spine, but that, in general, the widest part or base of the cone in which the cord ends corresponds to the first lumbar vertebra, and the apex of the cone to the second. During the early periods of foetal life, the cord descends as low as the sacrum ; but in foetuses at the full time, I have never found so marked a difference as has been descri- bed by some modern anatomists.! Differences in the Size of the Spinal Cord at different Points of its Extent. — The spinal cord is not of uniform dimensions throughout its whole extent : it is much enlarged at * From several experiments which I have made upon this subject, it appeared that the spinal fluid seen (con- fined in its membranes) in the cervical region, between the occipital bone and the axis, was agitated by move- ments synchronous vrith the pulse and the respiration ; but that, when this fluid had been evacuated, the spi- nal cord did not move at all. I have examined with the greatest care the tumours existing in the lumbar re- gion in infants afllicted with spina bifida ; I could never detect in them any movement corresponding with the pulse, but the movement of respiration exerted a manifest influence upon them ; thus, when the sac was emp- tied by compression, the cries of the infant, excited by pain, were almost instantly followed by extreme ten- sion of the sac. As the spinal cord is not affected by the great arteries at the base of the brain, it cannot par- ticipate in the slightest degree in those movements which are observed in the spinal fluid at every pulse of the heart, and which are communicated to that fluid by the cerebral arteries. t The spinal cord is capable of elongation and retraction ; it is elongated during flexion, and returns to its original condition during extension of the vertebral column ; the difference between the two states appears to me to be from an inch to fifteen lines. In the body of an infant at the full time, which was afiiected with spina bifida in the sacral region, and died a short time after birth, the spinal marrow descended as low as the sacrum, and there was no cauda equina. Malacarne had already observed a similar fact ; this peculiarity depends not upon an arrest of development ia the cord, but upon adhesions contracted by it at an early period of ftetal life. — (See Anat. Pathol., Uv. xvii., art. Spina Bifida.) 696 NEUROLOGY. its upper part, opposite the basilar groove, where it constitutes the superior or occipital rachidian bulb, or the medulla oblongata (a) ; it becomes narrowed immediately after hav- ing emerged from the foramen magnum. This constriction, which is named the neck of the rachidian bulb, is regarded by many anatomists as the commencement of the spinal cord. Another oblong enlargement, extending over a much greater length than the prece- ding, and named the middle, cervical, or brachial rachidian bulb, or cervical enlargement (b), commences opposite the third cervical, and terminates opposite the third dorsal vertebra. The spinal cord again becomes considerably contracted from the first to the eleventh dorsal vertebra, and then presents a third enlargement of less extent than either of the other two, constituting the inferior lumbar or crural rachidian bulb, or lumbar enlargement (c) ; it then immediately tapers like a spindle, and terminates in an exceedingly slender semi-transparent cord, which has a fibrous, fihform aspect, is concealed among the nerves of the cauda equina (d), and is always accompanied by a vein. This cord may be distinguished from the surrounding nerves by its being situated in the median line, and by "its thinness, its fibrous character, and its termination. It may be traced as far as the base of the sacrum, when it terminates in the dura mater. In some cases the narrow portion of the inferior rachidian bulb is bifurcated, but the two branches of the bifurcation terminate in a single fibrous cord. Huber, Haller, and Scenunering describe the spinal cord as terminating below by two small globular enlarge- ments, of which the superior is oval, and the inferior conical. They have evidently mis- taken an exception for the rule. These three enlargements of the spinal cord constitute a totally different structure from that admitted by Gall, who, comparing with Haller the spinal cord of man, and the vertebrata generally, to the double series of gangha in annelida and insects, maintained that there are as many enlargements of the cord as there are pairs of nerves. A strict examination into facts is completely at variance with this opinion, for even in the fcetus, the temporary conditions of which so frequently resemble the permanent state of the lower animals, we find no trace of this series of enlargements. An erroneous inference, together with the aspect of the cord when surrounded by its nerves, have misled this celebrated physiologist, who should have sought for the representatives of the gangha of insects, not in the spinal cord itself, but in the series of ganglia on the spinal nerves.* The existence of the three enlargements of the spinal cord above described is in ac- cordance with two general laws relating to the nervous system, viz., 1. That the size of the spinal cord is in proportion to the size and number of the nerves which arise from and tenninate in it, and to the functional activity of the organs to which those nerves are distributed ; and, 2. That the exercise of sensibihty is connected with larger nerves than that of muscular contractility. Now the most numerous and the most important nervous communications take place opposite those three enlargements. The nerves of the lower extremities correspond with the inferior or lumbar enlargements ; those of the upper extremities, with the mid- dle one ; and the nerves of respiration, the nerves of the tongue, and a part, or perhaps the whole of the nerves of the face, with the superior enlargement. The cervical enlargement, which corresponds to the upper extremities, is certainly larger than the lumbar one, but this is because the upper extremities possess a greater degree of muscular activity than the lower, and also because they are the organs of touch. This explanation is completely justified by comparative anatomy, and is applicable also to the differences in the length of the spinal cord : thus, it is found that in the dif- ferent species of animals, the length of the spinal cord depends, not upon that of the vertebral canal, nor upon the presence or absence of a tad, but is proportionate to the muscular energy, and to the degree of sensibility. Desmoulins, a young anatomist, too soon lost to science, has established this fact by incontrovertible evidence.! The Form, Direction, and Relations of the Spinal Cord. The spinal cord has the form of a cylinder flattened in front and behind (D, fig. 269). * These supposed enlargements are not to be found even in the spinal cord of the calf, which Gall took as offering the type of this structure. The committee of the institute likewise failed to discover them in the dog-, the pig, the deer, the roe-buck, the ox, and the horse, in which Gall asserted that he had found them. The beautiful researches of Tiedemann into the development of the spinal cord have completely overthrown Gall's opinion, which rested merely upon unsubstantiated analogies. [It may be remarked, that though Gall's anatomical statement is not correct, his view as to the analogy is more in accordance with received doctrines than that of the author.] t The spinal cord of birds furnishes a striking proof of the law which presides over the development of this part of the nervous system. There are no movements performed by animals which require greater force and agility than those observed in the act of flying. It is tberofore not astonishing to find that the spinal cord is enlarged opposite the nen'es which go to the muscles of the wings. It would be supposed that the portion of the cord which corresponds to the lower extremities should be much smaller than that corresponding to the upper, but yet the inferiiir enlargement is equal to the one for the wings, because, according to a more inge- nious than probable idea, the lower extremities are the organs of touch in birds. The spinal cord of the tortoise most clearly confirms the law which we have adoiited from Desmoulins. The sort of calcareous and homy case m which the trunk of that animal is enclosed is destitute of all power of motion or sensation ; and it is found, the enlarged part of the spinal cord which corresponds to the upper ex- tremities is united to that which corresponds to the lower by an extremely slender portion. NEURILEMMA OF THE SPINAL CORD. 697 It exactly corresponds in direction with the vertebral column, every deviation of which it closely follows ; and it is an interesting fact, that it escapes compression, even in an- gular curvatures of the spine. The right and left halves of the spinal cord are perfectly symmetrical. There is less symmetry between the anterior and posterior halves, and still less between the upper and lower halves of the cord. The spinal cord is divided by anatomists into a body and extTcmitics. The body of the cord requires to be examined, both when covered by its proper sheath, and after the re- moval of that membrane. The Body of the Spinal Cord enveloped in its Proper Membrane. The surface of the cord everywhere presents certain transverse folds, united by oth- ers running obliquely, so as to form zigzag folds, which were compared by Huber to the rings of a silkworm, and regarded by Monro as so many small articulations ; these folds are situated in the sheath of the cord, and are precisely analogous to those which have been noticed in the tendons during relaxation of the muscles, and those which we shall hereafter have to describe as appearing in relaxed nerves ; they are effaced by exten- sion of the spinal cord, and are reproduced when it resumes its original length. The existence of these folds prevents that stretching of the cord which would other- wise occur in the different movements of the vertebral column. They endow the cord with a certain degree of elasticity. The spinal marrow presents for consideration an anterior, posterior, and two lateral surfaces. The anterior surface presents in the median line a fibrous band, which runs along the entire length of the medulla, and conceals the anterior median groove. The posterior surface, at first sight, presents no trace of a median groove. Many anatomists, therefore, and especially Huber, have denied its existence ; but with a little care we may detect a very delicate line which indicates the situation of the posterior median groove, to which we shall presently advert. On each side of the median line, both on the anterior and posterior surfaces of the cord, are seen the roots of the spinal nerves (1 to 31, %. 268), which are arranged in four regular lines down the cord, and are divided on either side into the anterior {a, fig. 267) and the posterior (b) roots. The dif- ferences which we shall hereafter describe as existing between these two sets of roots, both in their number, size, and mode of attachment, enable us, at first sight, to distin- guish between the anterior and posterior surfaces of the cord. If these roots be detached, it will be seen that their place of insertion is marked by a series of depressed points, which together constitute two furrows both upon the front and back of the cord, accurately described by Chaussier under the name of the collateral fur- rows of the spinal cord. We cannot deny the existence of the posterior collateral fur- rows, but I do not think that the anterior collateral furrows should be admitted. The sides of the spinal cord are rounded, and narrower than either the anterior or the posterior surface : there is no furrow upon these sides, as described by some authors. The two ligamenta denticulata are attached to them. We must next examine the proper membrane of the cord, or the rachidian pia mater, which we shall name the neurilemma of the cord, from its analogy to the neurilemma of the nerves ; we shall then describe the cord itself. Neurilemma of the Spinal Cord, or Rachidian Pia Mater. Dissection. — It is difficult to separate the rachidian pia mater from the cord, in the greater number of subjects, on account of the softness of the cord itself, and of the rapid changes which it undergoes after death. In order to succeed in doing so, it is advisable to select the body of a person who has died from an acute disease or from an accident. The spinal cord of new-born infants is more fitted for this purpose than that of adults, not only from its relatively greater density at that period of life, but also from its adhesion to the neurilemma being less firm. In the bodies of infants, after making a circular incision through the neurilemma op- posite the medulla oblongata, the sheath may be drawn downward, in the same manner as an eel is skinned, or a stocking drawn off by turning it inside out. When the sheath is more adherent to the cord, it must be very carefully divided along each side of the median furrows, and then detached by breaking down, with the handle of a scalpel, the cellular and vascular prolongations which connect it with the cord. Although the proper covering of the brain, or cerebral pia mater, consists essentially of an interlacement of vessels, the proper sheath of the spinal cord, or rachidian pia mater, is a fibrous, and, therefore, a strong membrane, which supports and protects that part of the cerebro-spinal axis, as the neurilemma does the nerves. The external surface of this membrane is surrounded with a network of remarkably tortuous bloodvessels ; and vessels are also found in its substance. The spinal cord is visible through this semi-transparent membrane, which is naturally of a pearly-white 4T 698 NEUROLOGY. colour, but IS sometimes dull, yellowish, blackish, or even covered with black spots, es- pecially in the cervical region.* This surface of the rachidian neurilemma is also rough, being covered with small cel- lular and fibrous filaments which float under water, and are the remains of small fibrous cords, which extended from the neurilemma to the arachnoid. The internal surface of the neurilemma adheres to the spinal cord by a great number of cellular and vascular prolongations, which form areolae or meshes in its interior, and which have been well described and figured by Keuffel. Along the anterior median furrow, the neurilemma sends off a prolongation, which, en- tering that furrow, lines one of its walls, and is then reflected at its bottom, so as to line the other wall ; within the substance of the duplicature thus formed, the bloodvessels penetrate. A simple prolongation of the neurilemma, of extreme tensity, also enters into the posterior median furrows, and forms a line of separation between the two pos- terior halves of the spinal cord. The neurilemma is prolonged below the lower extremity of the spinal cord as a fibrous filament, very well described by Huber, which is inserted into the base of the coccyx. This filament the older anatomists regarded as a nerve, and named it the nervus impar ; it is very strong considering its thinness ; it is always tense, and appears to be intended to fix the lower end of the spinal cord ; in this respect serving a similar purpose with the ligamentum denticulatum. Its upper part is hollow, and is filled with a gray and ex- tremely soft substance. The ligamentum denticulatum, which has been considered as a prolongation of the prop- er membrane of the cord, is attached to the external surface of this membrane ; and the proper neurilemma of each nervous filament is also given off from this surface. Monro has stated that a soft layer of gray substance covers the white substance of the spinal cord, and separates it from its neurilemma, but such a layer does not exist, t While the other membranes of the spinal cord are much larger than the part which they have to invest, the neurilemma of the cord is exactly moulded upon it, and even exerts a certain degree of pressure upon it, as is evident from the manner in which the substance of the cord protrudes when this covering is punctured ; this compression oc- casions the apparent consistence of the cord when it is enveloped in its sheath ; a con- dition which contrasts so strongly with its soilness when that sheath has been removed. This compression, as well as the absolute inextensibility of the neurilemma, accounts for the rarity of effusions in the cord, and also for the fatal effects of even the slightest effusions within its substance when they do occur. Structure. — The proper membrane of the cord is essentially fibrous ; nor has it any claim to be termed a vascular membrane (tunica vasculosa, Scemmering). Its component fibres interlace in every direction, but the majority of them are longitudinal. It is quite evident that the vessels which ramify upon its surface, and afterward penetrate it, do not belong to the membrane itself Uses. — The neurilemma is essentially a protecting structure ; it constitutes the frame- work of the spinal cord, and serves, at the same time, as a support for the nutritious ves- sels of that organ ; in this latter respect it has been compared to the pia mater of the brain. The transition from the spinal into the cerebral portion of the pia mater takes place gradually. The fibrous character of this tunic diminishes upon the medulla oblon- gata and tuber annulare, and is entirely lost opposite the peduncles of the brain ; while its vascular character, on the contrary, becomes gradually more and more marked as it passes from the cord towards the brain. It has been stated that the neurilemma is the secreting organ of the spinal cord ; one might as well say that the testicle is secreted by the tunica albuginea, and the heart by the pericardium. The Body of the Spinal Cord deprived of its J^eurilemma. When the neurilemma of the cord is removed, the spinal nerves are also taken away. We shall hereafter have to inquire whether this fact should lead us to conclude that the nerves do not enter into the substance of the cord, but merely come into contact with it. We would observe, however, in this place, that the posterior roots of the spinal nerves arise in a perfectly regular line, while the anterior roots come off irregularly from differ- ent points of the corresponding medullary column, t The Anterior Median Groove and the Commissure. — The anterior median groove, or fissure * These different shades of colour are much more common in certain animals, in the sheep, for example, than in man ; they result from the deposition of a colouring matter, and are in no way connected with any recent or previous morbid action. t In several subjects, I have most distinctly seen a very thin yellowish layer over the medulla oblongata, ■which dipped between the pyramidal bodies, and filled up the shallow groove which separates the olivary from the pyramidal bodies. t This mode of origin of the anterior roots is perfectly distinct in the spinal cord of the foetus or new-bom infant ; up to this period, the tract from which the anterior roots arise is still formed of gray substance. The roots, which are white, emerge fmm this gray tract, and when the neurilemma is removed, their small, white, ruptured ends which remain may bo traced into the substance of the cord. THE SPINAL CORD DEPRIVED OF ITS NEURILEMMA. GOD {fig. 268 ; f, fig. 269, D), penetrates to about one third of the thickness of the cord. At the bottom of the groove, which is occupied by a prolongation of the neurilemma and a great number of vessels, is seen an extremely thin white layer, perforated with foramina, which is named the anterior com- missure (commissure longitudinale, Chaussicr). The foramina in this structure are intended for the trans- mission of tufts of vessels, which enter the sub- stance of the cord. The alternate arrangement of these foramina greatly increases the difficulty of drawing out the vessels, and gives to the commis- sure the appearance of being formed by interlacing fibres ; and, in fact, several anatomists have not only admitted such an interlacement, but have ex- pressly stated that it was produced by the spinal nerves themselves.* According to Gall and Spurzheim, the bundles of which this commissure consists are directed trans- versely, and are fitted into each other like the mo- lar teeth ; but I repeat, that the most careful ex- amination demonstrates nothing in the commissure, besides a white lamella, perforated for the transmis- sion of bloodvessels. The Posterior Median Groove. — The posterior me- dian groove or fissure (a) not only exists, but is much deeper than the anterior one. Its narrow- ness, and the tenuity of the membranous prolon- gation which enters it, have alone concealed it from the observation of anatomists ; there is no white band analogous to that of the anterior median fis- sure at the bottom of this fissure, but the gray sub- stance of the commissure is all that is seen. As there are two median furrows, it follows that there are really two distinct spinal cords, connected together by an extremely thin band or commissure. The Furrows opposite the Posterior Roots of the Nerves, or the Posterior Lateral Furrows. — Immedi- ately to the outer side of the line of origin of the posterior roots of the spinal nerves, there is a gray- ish line or furrow (i), which extends the whole length of the cord. If a stream of water be allowed to fall upon this line, the continuity of the cord is soon destroyed, and the water penetrates to the centre of the organ. But there are no true fissures in these situations analogous to the anterior and posterior median fur- rows. The separation is effected by the destruc- tion of the gray substance, a prolongation of which reaches to the surface of the cord opposite these points. We shall, nevertheless, suppose these fur- rows to exist in accordance with the views of Scem- mering and Rolando, who divided each half of the spinal cord into two columns : a posterior column, consisting of that portion (e) which is comprised be- tween the posterior median furrow (a) and the posterior roots (i) ; and an antero-lateral column, including all that portion {d) which is situated between the anterior median fur- row (/) and the supposed posterior lateral furrow (i). We must also admit, with Haller, Chaussier, Gall, and Rolando, a third column on each side ; these may be called the pos- terior median columns, and are continuous with the projecting bundles which form the borders of the calamus scriptorius, and which are each limited externally by a slight groove. These small and exceedingly narrow columns, the existence of which is admit- ted by most anatomists in the cervical region only, are prolonged through the whole ex- tent of the spinal cord. Is there an anterior lateral furrow ? If the line on the outer side of the attachment of the anterior roots of the spinal nerves be closely examined, the appearance of a furrow is seen along the whole of the cord. But if water be allowed to fall upon that line, it is * There is no physiological or pathological fact which demonstrates the crossing eflfect of lesions of the spi- nal cord. 700 NEUROLOGY. found that there is no fissure or furrow properly so called, and that the jet of water has no more effect upon this line than on the adjoining parts ; we are therefore led to reject, with Rolando, both these anterior lateral furrows and the lateral tracts described by Chaussier, which would be bounded in front by the furrow of the anterior roots, and be- hind by that of the posterior roots ; these lateral tracts have, nevertheless, become cele- brated, since so much importance has been attached to them by Sir C. Bell and BeUin- geri as the lateral columns of the spinal cord. From what has been stated above, it follows that each half of the cord is composed of two columns, a posterior and an antero-lateral, and as an appendage to the posterior column, of a small column, which forms the border of the posterior median furrows. Internal Structure of the Spinal Cord. The following results regarding the structure of the cord have been obtained by va- rious modes of investigation : by making sections of it ; by acting upon it with a stream of water; by hardening it in alcohol and dissecting it; by studying its development; and, lastly, by a reference to its comparative anatomy, which appears to be necessary to complete the knowledge acquired by the other means of investigation. Sections of the Cord. 1 1t appears, from an examination of the external structure of the spinal cord, that it consists of two white, juxtaposed cylinders ; that the surfaces by which these cylinders correspond are flat, closely in contact, and united together by a median commissure ; and that each of them may be divided into two columns, the one 'posterior and smaller, of which the posterior median column is only an appendage; the other, antero-lateral, which forms two thirds of the circumference of the cylinder. Horizontal Sections. — If various horizontal sections be made through different parts of the spinal cord, we see that each half consists of a cylinder of white substance, containing gray substance in its interior (see fig. 269, D) ; that the median commissure is composed of a white layer {ichite commis- sure) and a gray layer {gray commissure) ; and that in each section the gray matter has a tolerably close resemblance in form to the letter x, the two halves or curves of which are joined in the middle by a horizontal line, while the extremities of the curves are directed towards the ori- gins of the anterior and posterior roots of the nerves. The posterior extremities reach much nearer to the surface than the anterior. We perceive, also, in these different sections, that the circumference of the cord is not perfectly regular, but is somewhat sinuous, as we shall pres- ently mention. The size of the central gray mass in each half of the spinal cord, the length and thickness of the prolongations or points, which it sends off towards the anterior and posterior roots, and, lastly, the thickness of the gray commissure, present many varieties, according to the place of section ;* and hence there is a discrepancy between different authors as to the appearances of this section. Thus, Huber compared the sec- tion of the gray matter to an os hyoides ; Monro, to a cross ; KeufTel, to four rays converging towards a central point. Rolando has given figures of sections of the cord at every part of its length. From sections of the cord the general fact is established, that the white substance en- closes the gray matter. The thin layer of gray matter on the surface of the cord ad- mitted by Monro has been justly rejected by all anatomists. The relative situation of the two substances in the cord, which is the reverse of what is observed in the brain, has attracted the attention of anatomists, and various explanations, of greater or less ingenuity, but all hypothetical, have been given of this fact. According to Rolando, there are two kinds of gray matter m the cord, one occupymg the anterior, and the other the posterior half of the cylinder ; and these two halves are fitted into each other by a series of indentations, hke the bones of the cranmm. I have never been able to convince myself of the existence of these two kmds of gray matter, but I have distinctly observed the denticulated appearance of the cn-cumference of the gray matter, which indicates that the gray and white matter mutually penetrate into each other. . . , . . , The colour of the gray substance varies considerably. In some subjects it is whitish, and can only be distinguished from the white matter by its softness, its vascularity, and its not having a fibrous structure. The younger the individual, the more marked is the difference in colour between the two substances. The two substances appear also to differ in their relative proportions in different m- dividuals. Keuffel has ascertained that the gray matter is more abundant in man than * I would recommend five sections of the cord, which appear to me to give a very accurate notion of its in- ternal structure : the first should be immediately below the decussation of the pyramids j tlie second through the middle of the brachial enlargement ; the third through the dorsal constricted part , the fourth through the middle of the lumbar enlargement ; and the fifth near the apex of the cone formed by the lumbar enlargement. INTERNAL STRUCTURE OF THE SPINAL CORD. 70l in the lower animals ; and this fact would account for the pre-eminent sensibility of the human subject, in accordance with the view of Bellingeri, who considers that the gray matter is the seat of sensation. These horizontal sections enable us not only to determine the relative position and proportions of the white and gray substances, but also to distinguish the superficial fur- rows from those which really enter into the cord ; the existence of these columns in the spinal cord, which have already been described, is in this way fully estabhshed. Vertical Sections. — The most important of these is one made from before backward in the median line, so as to separate the two halves of the cord. Each of these halves may then be unfolded like a riband, on the inner surface of which the gray matter forms a thin layer. A transverse vertical section, through the centre of the cord, displays the mode of origin of the anterior and posterior roots of the nerves. Examination of the Spinal Cord under a Stream of Water. The different sections above mentioned expose the general internal arrangements of the cord rather than its actual structure. Until lately, authors had regarded the spinal cord as consisting of a semi-fluid pulp, which oozed out when the neurilemma was divided. Several had said, incidentally, and without distinguishing between the white and the gray substance, that the cord had a fibrous structure, and that its fibres were directed longitudinally. Gall supposed the cord to consist of a series of ganglia, arranged one upon the other ; but it is now gener- ally admitted that the white matter is fibrous, and that its fibres have a linear arrange- ment ; and this is clearly shown by examining this organ by means of a stream of water, the force and size of which may be varied at will. When directed upon the surface of a vertical section, made from before backward down the middle hue, the stream of water penetrates the substance of the cord through the gray commissure, breaks down the central gray matter, and spreads the cord out like a riband, from which it is very difficult to wash off all the gray matter. When treated in this way, each half of the cord is almost immediately subdivided into two col- umns, and if the stream of water be now directed upon the internal surface of the col- umns themselves, they may be separated into a great number of wedge-shaped vertical lamellae, directed from the circumference to the centre, the thick external backs of which are turned towards the surface, and the thin internal edges towards the centre of the cord. Now, as all these lamellae are not of equal depth from back to edge, their internal edges reach to different distances from the centre ; hence the denticulated appearance of the circumference of the gray matter in a section ; and hence, also, the mistake of Rolando, in describing the white matter as formed by a medullary layer, folded a very great many times upon itself* According to my observations, each lamella is completely independent of the adjacent ones ; and pathological anatomy fully confirms this observation, by showing that one only may be altered or atrophied, while the others remain unaffected. If the action of the stream of water be continued, these medullary lamellae are decom- posed into very delicate juxtaposed filaments, which extend along the entire length of the cord ; they are all independent of each other, and are merely connected by cellular tissue and some vessels. The structure of the spinal cord is therefore filamentous or fasciculated ; its filaments are almost perfectly identical with those which constitute the proper substance of the nerves. Each filament in the cord traverses its entire length, as each nervous filament extends along the whole nerve. The very important inference to be drawn from these facts is the independence, not only of each lamella, but, I may venture to say, of each filament, t * Rolando has even counted these folds : he numbers fifty in the spinal cord of the ox, opposite the orig-in of the sixth pair of sacral nerves, and about thirty opposite the third pair of sacral nerves ; both of these ob- servations refer to the anterior columns only, for in the two figures which he gives of them the posterior col- umns appear to have no folds. Rolando made his observations upon spinal cords which had been macerated either in pure water or in salt and water. t [The microscopic structure of the white and gray substances of the brain and spinal cord has been inves- tigated by Fontana, Ehrenberg, Weber, Remak, Valentin, and others. The fibres of the white matter consist of coherent threads of a soft, semi-transparent, tenacious substance, enclosed in an extremely delicate homo- geneous or structureless sheath, which is very difficult of detection : these fibres are smaller than those of the nerves ; they differ much in size, but each of them is of uniform diameter throughout ; when submitted to the slightest pressure during examination, they have a remarkable tendency to become varicose or beaded, a property which is peculiar to them and to the fibres of the olfactory, optic, and auditory nerves, which also re- semble the fibres of the brain in other respects. The gray matter of the brain and spinal cord consists of large reddish gray globules, containing a nucleus and one or more nucleoli, and having spots of pigment upon them, in situations where the gray matter is dark- er than usual. Surrounding and attached to these globules there are minute jointed fibres, which are marked at intervals with granules (nuclei) ; by Ehrenberg these jointed fibres were considered to be of the same na- ture as the fibres of the white matter, differing from them only in size ; by Miiller and Schwann they are re- garded as organic nervous fibres, resembling those found in such abundance in the sympathetic nerves and ganglia ; while by Valentin and others they are supposed, not only in the brain, but also in the ganglia and nerves, to be the filaments of a delicate cellular tissue. The mode in which the white fibres of the brain and spinal cord end in the gray substance is not well made TOS NEUROLOGY. Examination of the Spinal Cord hardened in Alcohol. When deprived of its humidity by alcohol, the spinal marrow becomes very firm, ex- tensible, and elastic. Its filamentous texture becomes very apparent, and the filaments themselves, which, from the contraction of the cord, are flexuous, may be separated from each other, either by the handle of the scalpel, or by slight traction. I have not seen that interlacement of the fibres of the cord which is figured in the beautiful plates of Herbert Mayo, and which, in my opinion, is only apparent, and is produced by drawing the parts under examination in different directions. The Cavities or Ventricles of the Spinal Cord. Several anatomists are of opinion that there is a canal in each half of the spinal cord.* Morgagni has slightly alluded to its existence, which he had not leisure to trace for a greater extent than about five fingers' breadth, t Gall relates that, in examining the body of an infant affected with spina bifida, he cut transversely through the cord, and found that it contained two canals, which he traced into the substance of the medulla oblongata and tuber annulare, beneath the tubercula quadrigemina, and as far as the optic thalami, where they terminated in a pouch as large as an almond, t It is certain that, up to the fourth month of foetal life, each half of the spinal cord con- tains a canal precisely similar to that which exists in fishes ; but after this time the gray matter takes the place of the gelatiniform fluid which had occupied the canal. However, in one case I found the canal persisting after birth. The Medulla Oblongata. Situation. — The medulla oblongata, the rachidian bulb, or cranial enlargement, is that conoid enlargement (a, fig. 268) which forms the upper part of the spinal cord, crowning it like the capital of a column : it is situated upon the basilar groove of the occipital bone, and connects the spinal cord with the cerebrum and cerebellum. It was named medulla oblongata by Haller ; but it has also been called the cauda or tail of the medulla oblongata, this term being derived from a comparison of the pons Varolii, the four pe- duncles, and the medulla oblongata to an animal, the body of which was represented by the tuber, the arms by the anterior pedimcles, the legs by the posterior peduncles, and the tail by the rachidian bulb. External Conformation of the Medulla Oblongata, The medulla oblongata is received into the deep groove on the fore part of the cir- cumference of the cerebellum {see fig. 276), so that its anterior part only is exposed. In man and the mammalia the medulla oblongata is bounded above and in front by the tuber annulare or pons Varolii {a, fig. 270) ; but above and behind its limits are quite arti- ficial, for it is prolonged upward beyond the pons, as we shall presently see. Its limits below are altogether arbitrary : the medulla oblongata, in fact, does not contract abrupt- ly, as the term neck of the bulb, applied to its lower extremity, would seem to imply, but it is very gradually narrowed, so as to become continuous with the spinal cord. A plane, which is a tangent of the lower surface of the condyles of the occipital bone, would correspond with the lower boundary of the medulla oblongata. ^ I think, however, that it is more rational to fix this boundary according to the precise point where the me- dulla undergoes some decided modifications ; and this point is immediately below the decussation of the pyramids. The medulla oblongata is from fourteen to fifteen lines in length, nine lines in out ; according to Valentin, they separate to admit the gray globules between them, and then unite with one another so as to form loops. . „„ - ■ i-j The substance of the brain and spinal cord, according to Vauquelm, contains 80 per cent, of water ; its solid constituents consist of albumen, stearine and elaine, phosphorus (1-5 per cent.), osmazome, some acids and salts, and sulphur.] , , • j t i. • •» * It is unnecessary to say, that the existence of the single central canal admitted by some authors, is qnrfe irreconcilable with the real structure of the cord. t Adversaria Anat.,vo[. i., p. 17. Morgagni relates that, having separated the medulla oblongata from the rest of the spinal cord by a horizontal section, he saw in the substance of the cord, and for the space of about five fingers' breadth (etforlasse etiam longius si quis tunc otium habuisset ulteriorum medullam e vertebns exi- mendi), a cavity which admitted the end of the finger; everything appeared to be in a natural state, except- ing this cavity. He adds, that he had never met with so large a ca^^ty ; which seems to imply that he had seen ca.vities of this kind before.— Neque enim alias tantam aut guw liuic accederet vidi. t Spina bifida and hydrocephalus have no direct relation with the persistence of the canals of the spmal cord • and on this point.'l can remove all the doubts expressed by Keuffel (/)e Medulld Spinali, 02) concerning Moro-'agni's observation. " Forsau nos quoque," says Keuffel, " earn (scilicet meduUfe spinalis caveam) inve- nissemus, si medullam spinalem ex homine hydrocephalico aut spinft bifida laborante, mquirere potuissemus.^ Utinam huiusmodi opportunitas, si occurreret, a nemnie negligatur, ut tandem de h^c re certiores fiamus. In five infants affected with spina bifida, and two who died of chronic hydrocephalus, which I examined for this purpose, the spinal marrow was perfectly normal. Tiedemann regards the canals described by GaU as produced by insufflation. , i, ui 6 I have made experiments upon several subjects, which show that the relations of the medulla oblongata to the foramen magnum vary according as the head is directly vertical, flexed, or extended ; an instrument thrust horizontally between the atlas and occipital bone divides the medulla oblongata at different parts in these various positions of the head. THE MEDULLA OBLONGATA, ETC. 703- breadth, and six in thickness ; it is therefore much broader and thicker than the spinal cord. The medulla oblongata is directed obhquely, like the inclined plane of the basilar groove, so that it forms with the spinal cord a very obtuse angle, which projects back- ward. In shape it resembles a cone flattened in front and behind, and having its base turned upward and its apex downward ; it has, therefore, four surfaces, viz., an anterior, a pos- terior, and two lateral. Anterior Surface of the Medulla Oblongata. ■ "J- This surface {fig. 270) is directed downward, and is therefore named inferior by some anatomists ; it is convex, and is lodged in the basilar groove of the occipital bone ; it can be properly examined only after its neurilemma has been dissected oflT, which is easily done, because its substance is denser than the spinal cord. On this surface we observe a median furrow (/), into which numerous vessels enter : this furrow, which is not nearly so deep as the anterior median furrow of the spinal oord, with which it is continuous, is interrupted by a decussation of fibres about ten lines below the pons Varolii (below n), and terminates above in a tolerably deep fossa {Ic trou borgne, or foramen ccecum, of Vicq d'Azyr), at the point where the furrow meets the pons. Not un- frequently some transverse fibres occupy the place of this median furrow, in which case the anterior surface of the medulla ob- longata resembles the pons Varohi ; sometimes these transverse fibres are found upon only a part of the medulla oblongata. On each side of this median furrow are seen two eminences, which seem as if mould ■ ed in relief upon the part, and which form two planes, succeeding one another like steps from within outward. The two internal eminences are called the anterior pyramids ; the two external are named, from their shape, the olivary bodies. The interior Pyramids. The anterior pyramids {Vieussens, h b), situated on each side of the median line, and to the inner side of the olivary bodies, are two white pyramidal bundles (bandes medul- laires, Malacarne), which extend through the entire length of the medulla oblongata ; they project in rehef upon the body of the medulla, and seem to emerge or originate near its narrow portion or neck, where they separate from each other the anterior col- umns of the spinal cord, from which columns they are quite distinct : at their point of emergence they are closely approximated and narrow, being about a line and a half in width ; they pass somewhat obliquely upward and outward, become more prominent, and about three lines wide ; having reached the pons Varolii, they become rounded and cylindrical, and are constricted before they enter the substance of the pons, in which we shall afterward trace them. When the two pyramids are gently held apart, it is said that some transverse fibres are seen passing from one to the other, along the bottom of the median furrow ; and it is even stated that there is a decussation of their fibres : this, however, is only apparent, and I cannot here too particularly caution the student against those illusive appearances, which depend either upon the existence of foramina for the passage of vessels, or may be produced by pulhng about the scattered fibres in drawing the parts asunder. It wiU soon be shown that there are no transverse fibres here, and that there is no decussation of fibres at an acute angle along the whole length of the anterior pyramids, as was ad- mitted by Petit, Winslow, Santorini, and others. The two halves of the medulla oblongata are, in fact, merely applied to each other, and agglutinated together. There is no decussation excepting at the point where the pyramids emerge. The Olivary Bodies. Upon the anterior surface of the medulla oblongata, to the outer side of the anterior pyramids, and upon a plane somewhat posterior to them, are found two white ovoid bodies (corpora ovata), sometimes projecting in relief; these are peculiar to the human subject, and are more prominent in the foetus and new-born infant than in the adult. They were first described by Eustachius, and afterward more accurately by Vieussens, who, on account of their shape, gave them the name of olivary bodies {corpora olivaria, c c) ; they are much shorter than the anterior pyramids, being not more than six lines in length ; they are directed obliquely downward and inward. The upper extremity of the olivary body does not reach the pons Varolii, but is separated from it by a deep furrow ; the lower extremity, which is less prominent than the upper, is bound down by a bundle of arched fibres, the concave borders of which are directed upward {processus arciformcs, e). The outer border of the anterior pyramids and the series of nervous filaments which unite to form the hypoglossal nerve {9, fig. 276) constitute the internal boundarv of each 704 NEUROLOGY. olivary body ; and a deep furrow, directed vertically, separates them on the outer side from the inferior peduncles of the cerebellum or the restiform bodies.* It is of importance to observe, that that portion of the olivary body which projects on the outer side of the p)Tamid is only the external half of the ohvary body, its internal half being imbedded in the substance of the medulla oblongata, so as to reach behind the anterior pyramid.! The Posterior Surface of the Medulla Oblongata. This surface is partly concealed by the cerebellum, being received into a groove on Fig. 271. its under surface, and cannot be completely exposed unless the ■ medulla oblongata be forcibly bent forward, or the middle part of the cerebellum be divided vertically. It is then seen that the cord appears to open out {t,fig. 271) opposite the upper part of this surface, and to be turned inside out, so that the gray sub- stance is exposed. In consequence of this separation of the posterior columns of the cord, there is left between them a shal- ^■^ low, triangular, or V-shaped depression {p), the bottom of which is smooth, and forms the anterior wall of the fourth ventricle ; Herophilus named this depression, from its appearance, the cal- amus scrijptorius. A vertical median groove corresponds to the shaft of the quill ; while its barbs are represented by certain white medullary lines, which vary exceedingly in number, and are not symmetrical ; some of these lines are lost upon the walls of the ventricle, and others turn round the lateral surface of the medulla oblongata, and constitute, in part, the origin of the auditory nerves. The point of the pen is represented by the very acute inferior angle formed by the sides of the depression, which terminates below in a cul-de-sac, the/o5- sttte of the fo^irth ■centricle, also called the ventricle of Arantius. According to some au- thors, at the point of the calamus is situated the upper orifice of a canal, which runs through the whole length of the spinal cord ; such a canal, however, does not exist, but is, in fact, produced by the means employed to demonstrate it, for example, by insuifla- tion, by the introduction of a probe, or by the weight of a column of mercury. A shght V- shaped deposite of corneous matter is constantly found inserted within the corresponding- ly-shaped bifurcation of the columns of the cord : between the branches of the V is found the prolongation of gray substance, which is continuous with the gray matter of the cord. The medullary columns which immediately bound the calamus on each side, and which result from the separation of the elements of the cord, are formed by the posterior me- dian columns {c,fig. 269, B C, &nA fig. 271), already described, which become slightly enlarged where they separate from each other, so as to form a mammiUary projection, and then terminate insensibly upon the back of the restiform bodies : we shall call the upper part of these columns the mammiUary enlargements of the posterior median columns, and not "posterior 'pyramids. ^^X On the outer side of these mammiUary enlargements are found the restiform bodies (d, fig. 269, C ; fig. 271), which, as we shall afterward describe, pass to the cerebellum, and may be said to form its root ; they are also called the inferior peduncles of the cerebellum, or processus a cerebello ad mcdullam oblongatam. Ridley named them the restiform bodies, or cord-hke processes ; and others, again, call them the posterior pyramids. The Lateral Surface of the Medulla Oblongata. These present {fig. 272), in front, the olivary bodies (c), which we have already seen upon the anterior surface. Behind them are the restiform bodies (d) ; and, lastly, about three lines below the lower extremity of each oUvary body, is found an oblong projection, the colour of which is intermediate between that of the white and that of the gray substance : this projection is continuous with the gray matter of" the furrow, from which the posterior roots of the spinal nerves arise ; and Rolando, who first directed attention to it, has named it the ash-coloured tubercle (tuberculo cinereo). The arched fibres, or processus arciformes {c,fig. 270), pointed out by Santorini, and still better described by Rolando, are principally found upon the lateral surfaces of the medulla oblongata ; they con- sist of filaments of medullary substance, which vary exceedingly in * I do not say, wifh. some authors, that the filaments of origin of the g-losso-pharyngeal and pneumogTistric nerves (8, fie. 270) bound the olivary bodies behind, for these filaments arise from the inferior peduncles of the cerebellum, or the restiform bodies, not from the furrow between those peduncles and the olivary bodies. t In the body of a female who died at the Maternite, the left pyramidal and olivary bodies were not more than half their usual width. It might have been supposed that they were atrophied ; but the patient had ex- hibited no symptom indicative of so serious and uncommon a lesion. With a little attention, I could easily see that the pjTamid was divided into two portions, the anterior of which occupied the usual position, while the posterior covered the posterior half of the olivary body. T [The term posterior pyramids is, nevertheless, applied to these bodies by many modem anatomists.] Fig. 272. JNTERNAL STRUCTURE OP THE MEDULLA OBLONGATA. 705 number and arrangement ; they appear to arise from the anterior median furrow of the medulla oblongata, to turn like a girdle around the pyramidal and olivary bodies, and, having reached the restiform bodies, to pass obliquely upward and outward to terminate upon the sides of the restiform bodies. These arched fibres sometimes seem to be en- tirely wanting ; at other times they are collected on each side into two bundles ; one superior, which turns round the anterior pyramid, as that body is about to enter the pons ; the other inferior, which covers and circumscribes the lower extremity of the olivary body. Lastly, the pyramidal and olivary bodies are not unfrcquently found to be completely and regularly covered by a thin layer of circular fibres : it will be presently shown that these fibres dip into the anterior median furrow of the medulla oblongata, and reach as far as the posterior median furrow.* Internal Structure of the Medulla Oblongata. The internal structure of the medulla oblongata should be examined by lAeans of sec- tions, by the ordinary method of dissection, by separating its elements by means of a jet of water, and by dissecting it after it has been hardened in alcohol or boiled in oil. Sections. Horizontal Sections. — Following the example of Ptolando, we shall examine four sec- tions of the medulla oblongata. The first should be made immediately below the decussation of the pyramids ; the second, opposite the middle of the decussation ; the third, through the middle of the oli- vary bodies ; and the fourth, immediately below the pons. The Jirst section presents exactly the same appearances as a section of the spinal cord. The second presents a very different arrangement : the decussating bundles of the p)Tamids are of very considerable size, and occupy the anterior two thirds of the sub- stance of the medulla ; their section represents a triangle having its base turned for- ward, and its truncated apex backward. The gray matter is not circumscribed, as in the first section, but appears to penetrate irregularly into the white substance of wliich the remaining part of the medulla consists. The white substance itself has not the pure whiteness of medullary substance ; nor does the gray matter resemble that of the rest of the spinal cord, but it is of a yellowish-gray colour, and is much denser. The third section through the middle of the olivary bodies {Jig. 269, C) presents, be- sides the triangular section of the pyramidal bodies (i), the serrated section of the corpus dentatum (c') of the olivary bodies (c) ; it enables us to form an accurate idea of the shape and size of these bodies, which extend to each side of the median line ; it shows that they are directed obliquely inward and backward, and that they consist of successive layers, viz., of an external white layer, of an interrupted yellowish layer, and of a sec- ond white layer, which lines the inner surface of the yellowish one. It is seen that the corpora dentata of the olivary bodies are interrupted, or, rather, open on the inner side towards the median line, so as to admit the white fibres with which their interior is filled. The waving gray line seen on these sections depends upon the yellow layer be- ing frequently folded inward and outward upon itself; and from this appearance the terms corptis dentatum, or corps fcstonnc, have been applied to the gray substance of the olivary bodies. The remaining part {d) of the medulla oblongata consists of a substance which is of the colour of coffee mixed with milk, and which offers more resistance to the knife than other parts of the medulla, and consists neither wholly of white matter nor wholly of gray, but of a mixture of both. The fourth section, made immediately below the pons {Jig. 269, B), presents a trian- gular surface, on which we remark, at each of the posterior angles, a thick white bun- dle, almost as large as the posterior pyramidal body, and which will be hereafter shown to constitute one of the roots of the fifth nerve : these bundles are also seen upon the third section made through the olivary bodies, but they are much smaller than in this section. The section of the two anterior pyramids {b) is circular at this point. The centre of this section of the medulla consists entirely of a grayish- white or coffee-col- oured substance {i c'), covered by a white layer. The grayish-white substance belongs specially to the medulla oblongata ; the surrounding white layer is the continuation of the columns of the spinal cord.f The oblique sections display appearances corresponding with those of the horizontal section. Vertical Section. — A very interesting section of the medulla oblongata is a vertical one, extending from before backward through the median line. I prefer the plan of forcibly separating the two halves of the medulla to that of dividing it with a scalpel. By this means it may be shown that there are in the median line of the medulla some an- * Ought we to regard as a part of this system of arched fibres a small, slender cord which surrounds the upper part of the anterior pyramids, and which in other respects has a similar arrangement to the arched fibres generally ? t The medulla oblongata of a child seven or eight years old is much better adapted for the examination of these sections than that of an adult or old subject, because the two substances are blended in the latter ; a stream of water directed upon the sections wiU greatly assist the examination, by making the colours more distinct. 4U 706 NEUROLOGY. tero-posterior fibres, which appear to me to vary in number in different subjects : fliese fibres {o,fig. 274) run from behind forward through the whole antero-posterior diameter of the medulla ; having reached the anterior median furrow, they pass horizontally out- ward to cover the pyramids and olivary bodies, and form the arched fibres already de- scribed. These antero-posterior fibres are limited below by the decussating fibres of the pyramids. Examination of the Medulla Oblongata by Dissection under a Jet of Water, and when hardened in Alcohol. The anterior -pyramids may be separated by ordinary dissection, and a tolerably accu- rate view obtained of their decussations ; and, moreover, the medulla oblongata may be divided into two lateral halves, and its principal parts may then be isolated. The ex- amination of the medulla when hardened in alcohol, or boiled in oil, or in a solution of salt, leads to important results, by enabling us to dissect it fibre by fibre, and to trace these fibres above and below their points of decussation. Together with these different modes of investigation I have employed another, viz., that of acting upon the medulla and its parts by a jet of water, the force and size of which is to be varied at pleasure, and the drops of which insinuate themselves between the fibres and separate them from each other.* If a stream of water be directed upon the anterior pyramids, the fasciculated ar- rangement of their component fibres, all of which are parallel, will be clearly demonstra- ted ; and it will also be seen that these two bodies are not mere medullary bands, but are two three-sided bundles occupying an angular groove between and in front of the two olivary bodies {fig. 269, C). The decussation of the anterior pyramids demands attention, as one of the most impor- tant points in the anatomy of the cerebro-spinal axis. On examining the anterior median groove of the medulla oblongata (see figs. 270,276), it will be found that, at a distance from the pons Varolii of about ten lines (Gall says an inch and some lines), the anterior pyramids divide into three or four bundles, which al- ternately interlace in a regular manner (below n), so as to form a plaited structure of from two to four hues in length. Is this decussation only apparent 1 and if so, does the ap- pearance result, as has been said, from the traction of parallel fibres in opposite direc- tions 1 or do the pyramids commence by alternate bundles arising from each side of the middle line, and does this alternate arrangement occasion the appearance of a decussa- tion 1 or, lastly, do the right and left pyramids actually cross like the limbs of the letter X "i On consulting the various authorities on this subject, it is found that the decussation of the pyramids, first pointed out by Aretseus, renoticed by Fabricius Hildanus, and de- monstrated by Mistichellit and Pourfour Dupetit.t has been admitted by Santorini, Wins- low, Lieutaud, Duverney, Scarpa, and Soemmering ; and that the opposite opinion has been maintained by Morgagni, Haller, Vic d'Azyr, Sabatier, Boyer, Cuvier, Chaussier, and Rolando. ij As to Gall and Spurzheim, they do not seem to have had a decided opinion upon this point ; for, after having appeared to admit the decussation in some passages of their work, they say elsewhere that the small cords of the pyramids do not form a true decussation, but merely intersect and pass over each other obliquely. In order to settle the question of decussation, I submitted the medulla oblongata to the action of a jet of water upon both its anterior and posterior surfaces ; and by then examining it from behind forward, I was able to ascertain that the right and left pyram- idal bundles do most evidently decussate (a, fig. 273) ; that this decussation is effect- ed, not only from side to side, but also from before backward (b, fig. 274) ; that the left pyramidal bundle (6) passes downward to the right side and backward (jr), traverses the gray matter of the cord, and becomes continuous with the right lateral column of the cord, and vice versa ; and, lastly, that the anterior pyramids are not in the slightest de- gree continuous with the anterior columns of the spinal cord. The Olivary Bodies. — When the anterior pyramids are removed, it is seen that the olivary bodies {d, figs. 273, 274) do not consist merely of the prominent masses which ^project beyond and on the outer side of the anterior pyramids, but that they extend in- 'ward to the median line behind the pyramids, which are received in a slight concavity formed by the anterior surfaces of the olivary bodies {fig. 269, C). This arrangement is ■very evident, without any preparation, in anencephalous infants, or in such as are born * If we employ a stream of water in the examination of a fresh meduUa oblongata, it may easily be con- ceived that the results will be much more conclusive than if we had thus examined one which had already been subjected to different modes of preparation that may have altered its structure. t Trattato dell' Apuplessia, 1709. t Letters d'un Med6cin des Hopitaux, 1710. t) Of all who have denied the reality of the decussation, Rolando appears to me to have opposed the doctrine with the greatest force. He examined the subject with the greatest attention ; he made horizontal sections of the meduUa oblongata, but he could never see anything more than the alternate origin of the fasciculi which constitute the anterior pyramids ; he could never find tliat the bundles of the right side passed over to the left, and vice versd. In reply to the objection, that without admitting the decussation it is impossible to ac- count for the cross effects of injuries or diseases of the brain, he states that these are explained by the inti- mate union between the optic thalami and tuberculaquadrigemina of the two sides, and between the two halves of the pons Varolii and medulla oblongata. The error of Rolando evidently arose from his attaching such ex- clusive importance to sections, as a means of determining the structure of the meduUa oblongata. INTERNAL STRUCTURE OF THE MEDULLA OBLONGATA. 707 with very imperfectly-developed brains ; the situation of the atrophied pyramids is then occupied by two tracts of gray matter, and the olivary bodies, more developed than usual, reach as far as the median line. When a jet of water is directed against the median line between the olivary bodies, it encounters a white and very dense tissue, upon which it produces little effect.* As soon as this tissue has been removed with the knife, the water insinuates itself into the substance of the olivary bodies, which, as we have seen, are open towards the inner side ; each olivary body is then spread out, its anterior half is turned outward, and assumes the appearance of a dense yehowish layer folded upon itself, like a leaf while within its bud ; after some white lamellae are removed by the action of the water, the posterior half is exposed, and displays a similar appearance to that of the anterior half. Rolando compares the arrangement of this yellow folded layer, or corpus dentatum of the olivary body, to a flattened purse (borsa appiattita), the neck of which is open, some- what constricted, and directed backward and towards the median line. Gall and Spurzheim regarded the olivary bodies as ganglia, but these anatomists ap- pear to me to have singularly misapplied the term ganglion, which they have given to such dissimilar parts as the olivary bodies, the corpora striata, and the tuber annulare. Lastly, by directing the stream of water against the median line, and by assisting its action by gently drawing the parts asunder, the medulla oblongata becomes divided into two perfectly similar halves, excepting opposite the decussation. A beautiful prepara- tion may thus be made, exhibiting the separation of the two halves of the medualla ob- longata and spinal cord, and leaving the decussation of the anterior pyramids. It appears, then, on the one hand, that the anterior pyramids are not formed by the anterior columns of the spinal cord ; and, on the other hand, that the posterior columns of the cord become separated from each other behind when they have reached the me- dulla oblongata. What, then, becomes of the white bundles of the cord in the medulla ob- longata 1 Having arrived opposite the neck of the bulb, the white matter of the cord is divided into two bundles ; one anterior, which forms the anterior pyramid (i. Ji^. 273), and may be called the cerebral bundle, because it passes up (i') to the brain ; the other posterior, or the restiform body (c e), which may be called the peduncle of the cerebellum, because it is exclusively intended (n) for that organ ; the former is composed of white bundles, which emerge from the interior of the spinal cord, and the latter of the anterior columns, and of the remaining white bundles of the cord. The olivary bodies (d) are situated between these two sets of white fibres. When, by means of the stream of water, the anterior pyramids and the restiform bodies have been removed, it is seen that each half of the medulla oblongata is formed principally of a very dense nucleus, consisting of a mixture of gray and white substances. This nucleus, or fasciculus of re-eiiforcement of the medulla oblongata, which we shall call the unnamed fasciculus {faisceau innomini) of the medulla, commences opposite the de- cussation of the pyramids by a narrow extremity, increases in size as it proceeds up- ward, passes above {l,fig. 274), i. e., deeper than the pons, and becomes continuous, as we shall afterward see, with the corresponding optic thalamus. Each half of the medul- la oblongata has its fasciculus of re-enforcement, of which the internal surface, viz., that turned towards the middle line, corresponds to the fasciculus of the opposite side, but is separated from it by the white fibres {o,fig. 274) already described (p. 706) as passing horizontally from before backward, in the median hne of the medulla. The posterior surface of these fasciculi {p,fig. 271) constitutes the anterior wall of the fourth ventricle. The corresponding peduncles of the cerebellum, or the restiform bodies, embrace them on the outside, and form, as it were, grooves for them. On examining thoroughly the internal or median surface of each re-enforcing fascicu- lus of the bulb, it is found that there are two vertical bands upon that surface, one an- terior, the other posterior ; and that the fibres which pass horizontally from before back- ward in the median line of the medulla oblongata are situated between the bands of the right and left sides. Each fasciculus of re-enforcement is divided above into two parts, one of which forms the centre of the corresponding restiform body, while the other becomes continuous with the optic thalamus above the pons Varolii. I have not alluded to the olivary fasciculi admitted by some anatomists, for the white bundles so called do not even come from the olivary body, but form the continuation of the lateral columns of the spinal cord, which embrace the olivary bodies on the outer side, without being re-enforced by any bundles derived directly from them.f * I have frequently been led to regard the white medullary substance which is situated between the olivary bodies, and passes into each of them, as a transverse commissure, which might be called the commissure of the olivary bodies. t [The bundles, named faisceaux innommines in the text (fasciculi teretes of some other authors), which M. Cruveilhier describes as taking- their rise at the lower end of the medulla oblongata, are more generally con- sideied to be prolonged from the lateral columns of the cord ; and on comparing the statements of recent in- quirers concerning the anatomy of the medulla oblongata, the following appears to be the arrangement which the columns of the cord undergo in passing through it, viz., the posterior columns (including the posterior me- dian fasciculi, which correspond with the posterior pyramids) separate laterally from one another (e,Jigs. 273, 708 NEUROLOGY. Development of the Spinal Cord. As soon as the spinal cord has passed through its original condition of an almost transparent pulp, it assumes the appearance of a lamina, the edges of which are rolled back upon themselves so as to enclose a canal, continuous with the cavity of the fourth ventricle, which might be regarded as the expanded extremity of the canal. This canal is narrowed along the middle by the reflection of the pia mater into it : it is thus con- verted into two canals, the walls of which are at first thin, but afterward increase in thickness, gradually encroach upon the caliber of the canals, which finally disappear be- tween the sixth and seventh month. At this period a thin, white, outer layer covers the whole medulla : the posterior median columns are very large, and of a white colour, while the antero-lateral columns are still semi-transparent, the gray matter is soft and diffluent, like a pulp ; and, by the slightest insufflation, a canal may be formed along the centre of each half of the cord. The spinal cord occupies the whole length of the vertebral canal until the third month ; but after this time, its lower extremity becomes relatively higher up to the period of birth, when it corresponds to the second lumbar vertebra. The spinal cord is larger, in proportion to the brain, during the early periods of foetal life, than afterward. The more rapid development of the brain, at later periods, gives that organ the advantage. '■ From studying the development of the spinal cord, Tiedemann infers that the white substance exists before the gray, and therefore that the latter cannot be the nutritious organ or matrix of the white substance, as Gall had affirmed. It is quite certain that the white parietes of the medullary canal are developed pre- viously to the gray matter. Development of the Medulla Oblongata. During the first three months of intra-uterine life, the upper limit of the medulla ob- longata is not defined, because there is no pons Varolii. The foetal brain, therefore, in this condition, resembles the brains of birds, reptiles, and fishes. The transverse fibres of the pons make their appearance during the fourth month, and the upper limit of the medulla oblongata is then established. The two halves of the medulla oblongata are perfectly distinct, and each half is divi- ded into three columns : one for the brain properly so called, viz., the anterior pyramidal bundle ; another for the tubercula quadrigemina, which may be called, with Tiedemann, the olivary bundle, remembering, at the same time, that this term has a very different meaning from what was attached to it by Gall ; and a third or cerebellar bundle, which is the restiform body. r The anterior pyramidal bodies are at first flattened like those of manunalia, but during the latter months they acquire their characteristic size and prominence. In the medulla oblongata of a foetus, from the seventh to the ninth month, the anterior pyramids are of a reddish-gray colour, while the anterior columns of the spinal cord are as white as they appear afterward. Those pyramids, therefore, are not the continuation of the anterior columns of the cord. The decussation of the pyi-amids is perfectly distinct after the fourth week of foetal existence.* The ohvary bundles of Tiedemann, which are situated to the outer side of the anterior pyramids, and, like them, traverse the pons, gain the sides of the tubercula quadrigemina, beneath which they form an arch, which constitutes the upper wall of the aqueduct of Sylvius. The olivary bodies, which are wanting in birds, reptiles, and fishes, do not ap- pear until the end of the sixth or the commencement of the seventh month of foetal life. The cerebellar bundles, or restiform bodies, are perfectly distinct from the preceding. The small mammillated bundles which bound the sides of the posterior longitudinal groove can also be distinguished in the foetus. Comparative Anatomy of the Spinal Cord. Mammalia. — The spinal cord of manunalia precisely resembles that of the human sub- 274), and enter the cerebellum, forming- the principal part of its inferior peduncle (n). The fibres of the lat- eral columns are disposed of iu three ways: 1. A part of them cross the median plane to the opposite side (w. Jig. 273), and form tlie chief part of the pyramidal body (6) of that side. 2. Another set join the inferior pe- duncle of the cerebellum. 3. The remaining fibres are continued along the floor of the fourth ventricle i.p,fig. 271), as the fasciculi iunominati or fasciculi teretes. The anterior columns {a, fig. 273) of the cord, on enter- ing the medulla oblongata, are thrown aside by the decussating filires coming from the lateral columns, and then one portion of each anterior column forms the outer i>art of the coiTesponding pyramid (A) ; another por- tion (c,fig. 274) passes partly behind and partly on the outer side of the olivary body, and is then chiefly con- tinued into the fillet (h) ; the remaining part passes into the cerebellum, joining its inferior peduncle (n). The connexion of the cerebellum with the anterior columns of the cord was pointed out by Mr. Solly. — {Phil. Trans., 1836, p. 567.) Arnold describes the posterior pyramids (fa.sciculi graciles) as passing into the crura cerebri. For farther details on the anatomy of the meduUa oblongata, the reader is referred to Arnold's Bemerkungen ilber den Ban des Hims nnd Riichenmarks, Zurich, 1838 ; also his Icones Anatomicic, fasc. i. , and to a paper by Dr. .T. Reid in the Edin. Med. and Surg. Journ. for January, 1841.3 * [The fourth or fifth month, accordm" to Tiedemann ; though in one part of bis work " week" has been, by an error, printed for " month."] COMPARATIVE ANATOMY OP THE MEDULLA OBLONGATA. 709 ject : its length, its size, its enlargements, are exactly proportioned to the size and ac- tivity of the muscles, and to the sensibility of the organs with which it is connected by means of the nerves. Birds. — The spinal cord in birds is proportionally both longer and larger than in other animals ; and this has reference to the enormous muscular effort required in flying. It presents two great enlargements ; one of these corresponds to the wings, and the other, which is larger, and contains a ventricle, corresponds to the lower extremities ; this ventricle was known to Steno, who described it under the name of the rhomboidal sinus. According to Nicolai (Dissertatio de Medulla Spinali Avium, Halle, 1811) and Tiede- mann, the spinal cord of birds contains a central canal, which is lined by a thin layer of gray matter, not only in the embryo, but also in the adult. Reptiles. — In all reptiles the spinal cord contains a canal, which is lined, according to Tiedemann, by a thin layer of gray substance. In the batrachian reptiles (the toad, frog, &c.), the spinal cord occupies only the anterior or upper part of the vertebral canal. M. Desmoulins says (t. i., p. 187) that the gray matter in these species surrounds the white substance. This opinion appears to me to be erroneous. In ophidian reptiles (serpents), the spinal cord occupies the whole length of the verte- bral canal ; there is no gray matter,* but its place is occupied by a fluid, so that each half of the medulla contains a canal. In the saurians (crocodiles, lizards), the spinal cord is slender, of almost uniform size throughout, and occupies the whole length of the vertebral canal. The spinal cord of the chelonian (tortoises, &c.) is the most remarkable of all, as re- gards its shape, and is peculiarly illustrative of the law which regulates the dimensions of this organ. There are three fusiform enlargements separated from each other by two very narrow portions ; the middle enlargement corresponds to the upper extremities, and the inferior one to the lower extremities ; the first constriction corresponds to the neck, the second to the thorax. Fishes. — In ail Jishes the spinal cord occupies the entire length of the vertebral canal. It is of uniform size in its anterior five sixths, but diminishes like a cone in the posterior sixth. There is no gray matter, t so that the cord is hollow. According to Arsaky {Dissert, de Piscium Ccrebro) and Tiedemann, the medullary canal is lined by a thin layer of gray matter. The lophius piscatorius and the male tetrodon present remarkable anatomical peculi- arities ; in the lophius, the spinal cord is diminished in size opposite the third cervical vertebra ; all at once it becomes extremely slender, and then terminates in a point op- posite the eighth cervical vertebra. Twenty-six pairs of nerves arise from the enlarged portion, and only five or six pairs from the slender portion. In the tetrodon there is no spinal cord, properly so called, or, rather, this part of the cerebro-spinal axis is reduced to a medulla oblongata, from which arise thirty-two pairs of nerves. From these facts, it follows that the length and size of the spinal cord bear an exact proportion to the muscular power and sensibility of the parts supplied by it ; and farther, that the gray matter of the cord is not nearly so important as the white substance, since it is absent in a great number of species. J Comparative Anatomy of the Medulla Oblongata, In the mammalia, the medulla oblongata is constructed upon the same plan as in the human subject, but the anterior pyramids are much smaller, and the olivary bodies ap- pear to be completely effaced. The tubercula cinerea of Rolando exist only in man ; in whom alone do we find those white streaks of meduUary substance upon the anterior wall of the fourth ventricle, which are regarded as forming, at least in part, the origins of the auditory nerves. The medulla oblongata of birds and reptiles presents no striking peculiarities. In the different species its size is always in proportion to that of the fifth, and especially the eighth pair of nerves, which take their origin from this part. \n jishes a peculiar pair of lobes correspond to the medulla oblongata ; these lobes were for a long time erroneously supposed to be the lateral lobes of the cerebellum, and have thus led to much obscurity concerning the anatomy of the encephalon in these animals. Desmoulins calls them the lobes of the fourth ventricle ; we shall call them the lobes of the eighth pair of nerves. In the ray and sturgeon this lobe is so highly developed, that it forms half of the encephalic mass. In the carp, besides the lateral lobes which are traversed by some white fibres, there is also a median lobe. Moreover, as a general rule, whenever the spinal cord has to furnish any nerves, there is an enlargement or a lobe. In the torpedo, in which the eighth pair of nerves are of enorcous size, and sup- ply the electrical organ, these lateral lobes are in an extraordinary degree developed. la the trigla there are certain small lobes behind the cerebellum, which correspond to the pe- cuUar digitiform prolongations serving as organs of progression in the animals in question, * [The spinal cord of serpents forms no exception to the general rule ; gray matter has been recognised in It, as in the cord of other vertebrated animals. The same is true of tishes. — (See Leuret, Anatomie Com- farie du SijsUme Nerveux, 4fC., Paris, 1839.)] t See note, supra. t See note, supra. 710 NEUROLOGY. The olivary bodies are most highly developed in the human subject ; they exist alsd, but are very small, in some mammalia ; they disappear in birds, reptiles, and fishes. I consider the olivary bodies as lobes in a rudimentary state. THE ISTHMUS OF THE ENCEPHALON. General Description and Division. — The Pons Varolii and Middle Peduncles of the Cere- bellum— the Peduncles of the Cerebrum — the Superior Peduncles of the Cerebellum and the Valve of Vieussens — the Corpora Quadrigcmina. — Internal Structure of the Isthmus, viz., of its Inferior, Middle, and Superior Strata. — Sections. — Development. — Comparative Anatomy. I SHALL, with Ridley, apply the term isthmus of the encephalon to that narrowed and constricted portion of the encephalic mass which is situated between the cerebrum, cere- bellum, and medulla oblongata, which corresponds to the free margin of the tentorium cerebelh, and comprises the pons Varohi and middle peduncles of the cerebellum, the peduncles of the cerebrum, the tubercula quadrigcmina, the superior peduncles of the cerebellum, and the valve of Vieussens. The isthmus of the encephalon is the common point of union between the three great divisions of the cerebro spinal axis, viz., the medulla spinalis, the cerebrum, and the cerebellum. It contains within it the media by which they all communicate, or, as it may be said, the elements of each reduced to their most simple expression. It is of a cuboid form, and therefore presents six surfaces for our consideration : An inferior surface {fig. 276), on which we observe the pons Varolii, or tuber annulare {d), the middle peduncles of the cerebellum {m\ and the peduncles of the cerebrum (//). A superior surface {fig. 271), which is covered by the superior vermiform process of the cerebellum, by the velum interpositum, and by the posterior border of the corpus cal- losum. In order to expose this surface, supposing the brain to be with its base upward, the cerebellum must be turned forward, and the pia mater should be separated, taking care to lift up with it the pineal gland. Proceeding from before backward, the following parts come into view : the tubercula quadrigcmina {f g), resting upon them the pineal gland (c), the superior peduncles of the cerebellum (shown in cut at r ; also r,fig. 272), and the valve of Vieussens {l,fig. 271). The lateral surfaces {fig. 272) are each divided into two distinct parts or stages, by a furrow which runs from before backward (the lateral furrow of the isthmus) ; the inferior stage consists of the pons Varolii (a) and the middle peduncles of the cerebellum {m), while the superior is narrower, lies closer to the median hne than the preceding, and presents a triangular fasciculus {h), having its base directed downward, and its apex turn- ed upward, so as to reach the corresponding inferior quadrigeminous tubercle or testis {g). The anterior surface of the isthmus is continuous with the optic thalami (s, fig. 272). The posterior surface is much narrower than the anterior, and is continuous with the base of the medulla oblongata. We shall examine the several parts of the isthmus in the following order : the pons Varolii and middle peduncles of the cerebellum, the peduncles of the cerebrum, the superior peduncles of the cerebellum, the valve of Vieussens, and the tubercula quadrigcmina. The in- ferior peduncles of the cerebellum have been already described with the rest of the medulla oblongata, under the name of the restiform bodies. The Pons Varolii and Middle Peduncles of the Cerebellum. The pons Varolii, or tuber annulare,* is that white cuboid eminence {d, fig. 276) situa- ted between the cerebrum and cerebellum, upon the base of the encephalon, and form- ing, as it were, its centre (mesocephale, Chauss. ; nodus encephah, Soemm.). From this centre the several parts proceed as follows : backward, the medulla oblongata (e) ; for- ward, two thick white bundles, which pass into the brain, and form the anterior or cere- bral peduncles {ff); laterally, two thick bundles, which enter the cerebellum, and are named the posterior peduncles, or middle cerebellar peduncles {in). The pons Varolii, the cerebral and cerebellar peduncles, and the medulla oblongata proper, are together called the medulla oblongata by some authors ; several of the older anatomists, in fact, compared the pons to the body of an animal, of which the anterior peduncles represented the arms ; the posterior, the legs ; and the medulla oblongata proper, the tail ; and hence the terms still in use of the arms, legs, and tail of the so- called medulla oblongata. It was Varohus who compared this part to a bridge, under which the several branches of a stream, supposed to be represented by the peduncles and the medulla oblongata, joined each other ; hence the terms pons Varolii and pons cerebelli. The pons is free below, but is blended above with the upper portion of the isthmus ; it is bounded in front by the peduncles of the cerebrum, and behind by the medulla ob- longata ; and it is continuous, laterally, with the middle peduncles of the cerebellum (?n), * The term tuber annulare is derived from the fact that this part of the encephalon seems to embrace the several prolongations of the medulla oblongata like a ring. THE PEDUNCLES OF THE CEnEBRUM, ETC. 711 forming with them but one system of fibres ; its lateral boundaries are, therefore, alto- gether artificial. The size of the pons, which is very considerable in the human subject, is always in relation with the development of the lateral lobes of the cerebellum ; comparative anat- omy, embryology, and the study of malformations completely establish this fact.* Its inferior surface is covered by the pia mater, which can be easily stripped off; it rests upon the anterior part of the basilar groove, and slopes backward and downward like the inclined plane of that groove. It presents along the median line a slight furrow, which is broader in front than be- hind, and corresponds to the basilar artery : this groove appears as if it were caused by the presence of the artery ; nevertheless, I must say, that not unfrequently the basilar artery is found to deviate to one side or the other, or to be more or less tortuous, and yet that the median groove is as distinctly marked as usual. I believe there is good ground for entertaining the opinion that this groove results from the prominence of the anterior pyramids, which raise up the surface of the pons on each side of the median line. The inferior surface of the pons presents certain transverse bundles or fibres, which appear to cross each other at very acute angles, and which, according to Rolando, may be divided into three sets : superior bundles, which turn upward, to constitute the upper part of the middle peduncles of the cerebellum ; inferior bundles, which pass transversely outward ; and middle bundles, which are directed obliquely downward and outward, pass in front of the inferior bundles, and then form the anterior border of the cerebellar pedun- cles. The origin of the fifth pair of nerves is between the superior and middle sets of fibres. Not unfrequently the middle bundles are not to be seen. It follows, therefore, that the middle peduncles of the cerebellum are merely the trans- verse fibres of the pons condensed and twisted upon themselves. The pons and these peduncles of the cerebellum constitute one and the same system of fibres. We might therefore, with Gall, designate the pons and the middle peduncles of the cerebellum as the commissure of the cerebellum, or corpus callosum of the cerebellum. The Peduncles of the Cerebrum. The peduncles of the cerebrum (fffig- 276), sometimes regarded as prolongations of the cerebrum to the medulla oblongata ( processus cerebri ad medullam oblongatam, ad pon- tem Varolii), sometimes as the arms, legs, or thighs of the cerebrum {brachia, crura, femo- ra, cerebri), and by others as prolongations of the medulla towards the cerebrum ( ^jroces- sus medullcR oblongatce ad cerebrum), are two thick, white, fasciculated columns, which arise from the anterior angles of the pons Varolii, and enter the substance of the cere- brum, after a course of about six lines. They are cylindrical, and in contact with each other as they emerge from the pons ;. and they gradually increase in size, and become flattened as they advance forward, up- ward, and outward. The optic tracts (s 2, fig. 272) circumscribe and bound them in front. Tlieir size corresponds to that of the cerebral hemispheres. They are of equal di- mensions in a well-formed brahi, but they are liable to become atrophied with their cor- responding hemisphere, as I have had frequent occasion to observe. Each of them is free below, and on its outer and inner side, but is blended above with, the upper portion {h if g, fig- 272) of the isthmus of the encephalon. Their white fasciculi are slightly divergent, and are often intersected at right angles bj certain white tracts, some of which emerge from the testes and the valve of Vieus- sens, while others proceed from the internal surfaces of the peduncles themselves. This arrangement Gall and Spurzheim have named the transverse interlacement of the great fibrous bundles {see Jig. 272). Owing to the oblique and diverging direction of the cere- bral peduncles, there is left between them a triangular inter-peduncular space (between r and t, fig. 276), which is occupied in front by the corpora mammiUaria or albicantia {z) and the tuber cinereum {v), and in which is observed behind two white triangular bun- dles, separated from the peduncles by a blackish hue. We shall see that these inter-pe- duncular bundles are merely the under surface of the bundles of re-enforcement of the pieduUa oblongata, or the " faisceaux innomines" {l,fig. 274). The Superior Peduncles of the Cerebellum and the Valve of Vieussens. The superior peduncles of the cerebellum (r, figs. 271, 272, 280) are more commonly known as the processus cerehelli ad testes, a name given to them by Pourfour Dupetit. I should observe, however, that this name sanctions an anatomical error ; for the superior pedun- cles of the cerebellum do not go to the testes at all, but pass under them, and are cover- ed by the corresponding lateral triangular bundle of the isthmus ; they should rather be called processus cerebelli ad cerebrum (Drelincourt.) The inferior peduncles of the cerebellum consist of two lamellae, which arise from the * Animals which have no lateral lobe of the cerebellum have no pons Varolii, and this part is small in such as iiave very small lateral cerebellar lobes. In a young girl ten years of age, who had no cerebellum, I found, that the pons was also wanting. 712 NEUROLOGY. interior of the cerebellum, one on each side of the median line, pass upward and forward parallel to each other, and appear to be continuous with the testes. Their upper convex surface is covered by the cerebellum {see fig. 280), and is separated from it by a double layer of the pia mater. Their inferior surface is free, and assists in forming the upper wall of the aqueduct of Sylvius. Their external borders are each sep- arated from the pons by a furrow, which we have already described under the name of lateral furrow of the isthmus. Their internal borders are connected together by means of the valve of Vieussens, which is distinguished by its colour from the peduncles. Their inferior extremities pass deeply into the central white substance of the cerebellum. The valve of Vieussens (valvula magna cerebri, I, fig. 271 ; v, fig. 280 ; g to lo, fig. 282) is a thin, semi-transparent lamina, which occupies the interval between the two superior peduncles of the cerebellum ; it is the velum medullare or velum interjectum of Haller. Its posterior surface is concave, and is in relation above with the superior vermiform process ; in its lower portion it adheres to the transversely-notched imperfect lamella (linguetta laminosa, Malacarne), in which the superior vermis ends. The median line of this posterior surface is marked by a line {fig. 271), which Rolan- do considers as the trace of the line of junction between the two laminae, of which, ac- cording to him, the valve consists. The anterior surface is convex, and forms the posterior wall of the aqueduct of Sylvius (leading from v to I, fig. 282). Tlie borders of the valve are not only in juxtaposition with the corresponding borders of the superior peduncles of the cerebellum, but appear to be continuous with them. The superior extremity is narrow, and presents a transverse band, which may be re- garded as the commissure of the superior peduncles of the cerebellum and of the fourth pair of nerves. The inferior extremity is broad, very thin, and continuous with the central portion of the median lobe of the cerebellum (w). The Tuber cula Quadrigemina. Dissection. — Place the brain with its base upward, turn the cerebellum forward, and remove the pia mater. The term tubercula quadrigemina or bigemina (corpora bigemina, Soemmering, optic lobes of the lower animals) is applied to four tubercles {f g f g, figs. 271, 272) situated regu- larly upon the upper surface of the isthmus, two on each side of the median line. They form two pairs : the anterior or superior (/) are the larger, and are called the notes {emi- nentia natiformes) ; the posterior or inferior {g) are the smaller, and are called the testes {eminentice testiformes). These tubercles are placed between the cerebriun and cerebellum, and are situated above the peduncles of the cerebrum, and, consequently, upon a plane anterior to that of the pons, and cannot consistently be named the tubercles of the mesocephalon, as was done by Chaussier. The anterior part of the aqueduct of Sylvius passes beneath them {fg,fig- 282), and establishes a communication between the third (l) and fourth {v) ventricles. They are comparatively small, indeed merely rudimentary in the human subject, for their development in the animal series is inversely as that of the cerebrum and cerebel- lum. The space which they occupy is a parallelogram of ten Mnes by eight. The anterior tubercles are always larger than the posterior ;* they are of a gray col- our, oblong, ellipsoid, and diverging ; their longest diameter is directed obliquely forward and outward. The posterior tubercles are smaller, and more detached ; they are almost hemispherical, and of a white colour ; but not so white as the fasciculated medullary sub- stance. A furrow, curved like a parabola opening forward, separates the anterior from the pos- terior tubercles. The antero-posterior furrow along the median line separates the tu- bercles of the right from those of the left side. From this furrow, a small, grayish, and tolerably dense cord proceeds backward, and descends perpendicularly upon the valve of Vieussens, or, rather, upon the transverse commissure by which it is surmounted, and then divides into two or three branches. This cord might be named the pillar of the valve of Vieussens {columella frenulum). The lateral triangular bundle {h,figs. 271, 272) of the isthmus terminates in the poste- rior tubercle. This fasciculus, which was pointed out by Reil (" schleife," lemniscus, fillet), Tiedemann, and Rolando, who described it as arising from the olivary bodies, pre- sents an anterior border, which is directed obliquely forward and outward, proceeds along the anterior tubercle, and terminates in a small body called the corpus genicidatum inter- num {iyfigs. 271, 272). Its posterior border inclines downward, backward, and outward, and forms a slight prominence above the superior peduncle of the cerebellum, which is covered by it. Its base corresponds to the lateral groove of the isthmus, which separ- ates it from the pons and the peduncle of the cerebrum. Its apex extends to the eorre- * Therelativesizeof the tubercula quadrigemina varies somewhat in cUffereat animals. The anterior tuber- cles are much larger than the posterior in ruminants, solipeds, and rodentia ; they are smaller than the pos- terior in carnivora — in the dog, for example. INTERNAL STRUCTURE OF THE ISTHMUS OF THE ENCEPHALON. 713 spending posterior tubercle or testis. The anterior tubercles or nates are continuous with the optic thalami {a, fig. 271), being separated from them by a slight depression. Some white fibres proceed from the anterior extremity of these tubercles, and, as we shall afterward see, form a thin layer above the corresponding corpus geniculatum ex- ternum (;■), and assist in the formation of the optic nerves. These white bands are gen- erally proportioned to the size of the nates.* The Internal Structure of the Isthmus of the Encephalon. Dissection. — By antero-posterior and transverse sections of the isthmus. The parts to be examined by laceration, by submitting them to the action of a stream of water, and also after they have been hardened in alcohol, or by being boiled in oil, or a solution of salt. The internal structure of the isthmus presents three very distinct strata placed one upon the other : an inferior, formed by the pons, the middle peduncles of the cerebellum, and the fasciculated portion of the peduncles of the cerebrum ; a middle stratum, form- ed by the prolongation of the bundles of re-enforcement of the medulla oblongata ; and a superior stratum, which consists of the triangular lateral bundles of the isthmus, the su- perior peduncles of the cerebellum, the valve of Vieussens, and the tubercula quadri- gemina. Internal Structure of the Pons and the Peduncles of the Cerebellum. It has been stated that the lower surface of the pons presents some white transverse fibres (see left side, fig. 273), which twist upon each other to form the middle pedun- cles of the cerebellum. On making a very superficial incision into the pons, we find, beneath the external layer of white matter, which is very thin behind, and a little thick- er in front, a grayish-yellow substance, which is traversed by the transverse fibres of the pons, so that the part (m, fig. 274) has a striated appearance. If the handle of the scalpel be passed be- neath the anterior border of the pons, so as to remove all that part which projects be- yond the level of the peduncles of the cere- brum, it will be seen that the pons is trav- ersed longitudinally by certain white bun- dles of fibres {b',figs. 273, 274) ; and if, moreover, the handle of the scalpel be insinuated beneath the posterior border of the pons, and all that part be removed which projects be- yond the pyramidal bodies of the medulla oblongata, these white longitudinal bundles which traverse the pons are found to be the prolongation of the pyramids (b), and are themselves continuous with the peduncles of the cerebrum {n,fig. 282). By thus separ- ating the pons into very thin horizontal layers, it will be found that the longitudinal {¥) and transverse (m) fibres form several alternate layers, above which we arrive at the middle stratum of the isthmus. The peduncles of the cerebrum are continuous with the longitudinal fibres of the pons, and the middle cerebellar peduncles with the transverse fibres of the same part ; the gray matter of the pons extends into the substance of the latter, and gives them a stria- ted appearance. At the boundary between the pons and the middle peduncles of the cerebellum there is on each side a very considerable longitudinal bundle, which forms the origin of the fifth nerve, and which, therefore, does not belong to the anterior pyram- idal bodies.! ui The absolute continuity of the anterior pyramids with the peduncles of the cerebrum, through the pons, may be regarded as a type of the structure of the nervous centre. The two sets of fibres are intermixed in the pons, so as to intersect each other at right an- gles, but they maintain their individuality. J The pons presents neither a raphe nor a septum in the median line : the fibres of the right half are continuous with those of the left. The white fasciculated fibres (b') of the * They are very large in the sheep : it appears that it was chiefly from the anatomy of the brain in this an- imal that Gall founded his opinions as to the optic nerves, which he regards as arising from the tubercula quadrigemina. This opinion is very doubtful as far as concerns the human subject. t The most anterior and the most posterior transverse fibres of the pons have a very peculiar arrangement ; the anterior are inflected {o,Jig. 282) between the peduncles of the cerebrum, and completely occupy the in- terval between them ; so that each of these peduncles is embraced by a distinct ring, formed by the fibres of the pons ; and, again, the most posterior fibres of the pons dip between the anterior pyramids, each of which is also embraced by a distinct ring. t The continuity of the pyramids with the peduncles of the cerebrum, through the inferior portion of the pons, was accurately described and figured by Varolius (De Nervis Opticis nonnullisque aliis, J573), by Vieus- sens (Neurographia Universalis, tab. 16), by Morgagni (Adversaria Anatomica, v.), and by Vicq d'Azyr. Vieus- Bens showed this continuity by lacerating the pons. Vicq d'Azyr showed it by successively removing the thin layers of the pons by means of a cutting instrument. The plates given by Gall surpass those of his predeces» sors in execution, but not in a scientific point of view. 4X 714 NEUROLOGY. peduncles of the cerebrum, which are continuous with the anterior pyramids (b), form part of the inferior stratum of the isthmus ; these fasciculated fibres are parallel and per- fectly white, without any intermixture of gray matter. Internal Structure of the Middle Stratum of the Isthmus. When the pons, or, in other words, the successive layers of the inferior portion or stratum of the isthmus, have been removed, the middle stratum is exposed. This may Fig 274. be very easily displayed in a brain that has been well hardened in alcohol. It is then seen that this middle stratum is formed by a prolongation of the fasciculi of re-enforcement {faisceaux innomines) of the medulla oblongata, which becomes enlarged in passing above the pons, and still more so opposite the peduncles of the cerebrum, above which we shall trace them presently. This prolongation {I, fig. 274) then passes through the pons at right an- gles. It was doubtless to illustrate this arrange- ment that Varolius described the medulla, when viewed from below, as passing beneath the pons like the water of a canal under a bridge. This re-enforcing bundle, pointed out by Ro- lando (Recherches sur la Moelle Alongee, 1822) under the appellation of the middle fasci- culus, has been correctly represented by Mr. Herbert Mayo. Those portions (c, fig. 269, A) of the bundles of re-enforcement which correspond to the peduncles of the cerebrum are separated from the superficial part of the peduncles themselves (a) by a layer of black or blackish matter (b) : opposite the peduncles, these two bundles are intimately united,* but they soon diverge to enter the optic thalami. Are they simply in juxtaposition, or do they interlace at the point in which they appear to be blended ? I am inclined to believe that they do interlace ; but I have not yet been able to demonstrate this clearly, because they do not consist of very distinct bundles. The Internal Structure of the Upper Stratum of the Isthmus. The superior peduncles of the cerebellum are fasciculated : their lower extremities {r,jig. 274) assist in forming the central nucleus of the cerebellum ; their upper extremities (r') expand into a great number of fibres, some of which terminate upon the anterior wall of the fourth ventricle, on each side of the median line, while others form a loop below the tubercula quadrigemina. Structure of the Tubercula Quadrigemina. — Reil, who first examined the structure of the tubercula quadrigemina, considers them as consisting of four rounded masses of gray matter, placed upon the radiated fibres of a white bundle, which spreads out beneath them. This white bundle (forming part of the bundle h, fig. 274), which he calls the fil- let or loop, is derived (c), according to him, partly from the anterior pyramidal, and part- ly from the olivary body (d). It appears to me to be nothing more than the above-men- tioned loop formed by the superior peduncles of the cerebellum, below the tubercula quadrigemina. The tubercula quadrigemina themselves seem to me to be rather of a laminated than of a fasciculated structure. Mayo represents them as having a fasciculated texture. The triangular lateral fasciculus of the isthmus {h,fig. 272) passes in one direction be- tween the upper and middle strata of the isthmus, and in another it may be traced (form- ing the other part of the bundle h, fig. 274) downward as far as the olivary body. The anterior fibres extend from the testis {g) to the corpus geniculatum internum (y), pass beneath that body, and penetrate into the interior of the optic thalamus. This triangu- lar fasciculus forms a layer upon the superior peduncle of the cerebellum, from which it is perfectly distinct. Sections of the Isthmus of the Encephalon. A vertical section made from before backward through the median line of the istnmus will give an excellent view of its three portions or strata : the section should include the medulla oblongata (see fig. 274). Upon it are seen the white and gray striated mass (m V m) which constitutes the pons, the re-enforcing fasciculus (l) of the medulla oblon- gata becoming much thicker opposite the peduncles of the cerebrum than in the pons. Transverse vertical sections will display the arrangement of the pyramidal bodies and the re-enforcing fasciculi as they pass from the medulla oblongata into the isthmus. In these sections a thick bundle belonging to the fifth nerve is always seen. Sections of the tubercula quadrigemina show that they are neither distinct from each Other, nor from the external and internal corpora geniculata, nor from the re-enforcing fasciculi of the medulla oblongata ; but that these latter fasciculi and the tubercula qua- drigemina form a single system, surmounted by masses of nervous matter, which are the tubercles themselves. * [They here constitute the so-called iniegumentum (c,fig. 269, A) : the black substance is called the locus niger (6), and the superficial part of the peduncle is named the crust or basis (o).] THE CEREBELLUM. 715 Development of the Isthmus Encephah. The development of the pons and of the peduncles of the cerebellum is in relation with that of the cerebellum ; and the development of the cerebral peduncles with that of the cerebrum. In the embryo of two months, the tubercula quadrigemina consist merely of two lam- inae, which curve upward and outward, and become united at the end of the third month. At this period the tubercula quadrigemina of the human subject are in the same con- dition as those of the lower animals. They are as yet, indeed, only two in number, one on each side of the middle line ; and they are hollow, as in birds. At first they are com- pletely exposed, but are gradually covered by the hemispheres of the cerebrum, as those parts are prolonged backward. The transverse groove which divides the hitherto single pair of tubercles into an an- terior and a posterior tubercle on each side does not appear until about the sixth month, at which time the cavity in their interior has been obliterated by the thickening of their parietes.* Comparative Anatomy of the Isthmus. The pons Varolii and middle •peduncles of the cerebellum exist only in the human subject and in mammalia generally ; these structures, which may be regarded as forming the com- missure of the cerebellum, are developed exactly in proportion to the size of the lateral lobes of that organ ; so that they attain their utmost development in the human subject, and are smallest in rodentia. The pons and cerebellar peduncles do not exist in the re- maining three classes of vertebrata (birds, reptiles, and fishes), because those animals have no lateral lobes of the cerebellum. The tubercula quadrigemina are less developed in man than in the lower animals. It may even be said that the development of these tubercles is inversely in proportion to that of the lateral lobes of the cerebellum and the hemispheres of the cerebrum. The anterior tubercles are a little larger than the posterior in the human subject : in the ruminants, solipeds, and rodentia, on the contrary, the anterior tubercles are twice or three times as large as the posterior. In the carnivora the posterior are somewhat larger than the anterior. They are covered by the cerebrum in the human subject and the highest orders of mammalia, but are in a great measure exposed in the rodentia and cheiroptera. In birds, reptiles, and fishes, the tubercles are only two in number (the tubercula bige- mina), and attain their maximum development : sometimes they are even larger than the cerebral hemispheres ; they are hollow, and form true lobes, which are called the optic lobes, because, in fact, the optic nerves arise exclusively from them. In birds, the optic lobes are situated at each side of the base of the cerebrum. The optic lobes of birds are not the thalami optici, as was at first believed : in this class of animals the optic thalami are thrown forward. In reptiles, the tubercula quadrigemina consist, as in birds, of two large, ovoid, and contiguous lobes. In fishes, it is extremely difficult to determine what are the tubercula quadrigemina ; so much so, indeed, that the lobes of which they are composed have been taken some- times for the cerebral hemispheres, and sometimes for the optic thalami. M. Arsaky (De Piscium Cerebro) has successfully refuted both of these errors. THE CEREBELLUM. General Description. — External Characters and Conformation — Furrows, Lobules, LamincB, and Lamella. — Internal Conformation — the Fourth Ventricle, its Fibrous Layers, its In- ferior Orifice, and its Choroid Plexus. — Sections of the Cerebellum, Vertical and Horizon- tal.— Examination by Means of Water, and of the Hardened Cerebellum. — Gc7ieral View of the Organ. — Development. — Comparative Anatomy. The cerebellum {■KapeyKEi^a'XLg, Aristotle, 1 1, fig. 276 ; h h, fig. 280), or little brain, is that part of the encephalon which occupies the right and left inferior occipital fossae. It exists in all animals which have a cerebrum and spinal cord, and, therefore, in all the vertebrata. Cases of congenital absence of the cerebellum are extremely rare.t Though for a long time neglected, the anatomical examination of the cerebellum was commenced with considerable talent by Petit, of Namur {Lettre d'un Medecin des Hdpi- tau-x du Roi, Namur, 1710), and Malacarne (Enccphalotomia nuova Universale, Torino, 1780). Vicq d'Azyr and Chaussier have described its external conformation with ex- traordinary accuracy; and Reil, Gall, and Rolando, have more particularly investigated its structure. * In a foetus of seven months, I found the tubercula quadrigemina not yet divided into the nates and testes, t Vide Anat. Pathol., avec fig., for a case of absence of the cerebellum. 716 NEUROLOGY. The External Characters and Conformation of the Cerebellum. Situation. — The cerebellum is enclosed between the inferior occipital fossae and the process of the dura mater, called the tentorium cerebelli. It is placed {see fig. 282) at the top of and behind the spinal cord, and the isthmus of the encephalon. It is covered by the cerebrum in the human subject only, whence the name cerebrum inferius. It is posterior to the brain in the lower animals, and is therefore called cerebrum, posterius. The dura mater, the arachnoid, and the pia mater form a threefold investment around it, the arrangement of which has been already described. Size and Weight. — The cerebellum is larger in man than in any other species. It has been stated by Cuvier, that its size in the human subject is so exactly proportioned to that of the brain, that correct tables may be formed of their relative weights ; but it ap- pears to me that facts are opposed to this view. The mean weight of the cerebellum, including the pons Varolii and medulla oblongata, is from four to five ounces ; the proportion between the cerebrum and cerebellum may be estimated approximately to be as 7 to 1.* According to Gall and Cuvier, the cerebellum of the female is proportionally larger than that of the male. Gall believes that its size is in a direct ratio with the energy of the generative function, and that this is indicated externally by the relative size of the inferior occipital protuberances. t The cerebellum is proportionally much smaller in the infant than in the adult ; the relation between the cerebrum and cerebellum in the infant is as 20 to 1. Density. — The consistence of the cerebellum has been much studied by anatomists, who are far from being agreed upon this subject. The great difficulty depends upon the ■want of accurate means of estimating its consistence. In fact, it may be readily con- ceived that the conversion of its substance into a pulp, by letting weights fall upon it from a determinate height, is at once a most inconclusive and almost inapplicable meth- od of ascertaining the point. Another source of difficulty consists in the fact that the cerebellum is not homogeneous ; so that results obtained in reference to the gray matter do not apply to the white substance. Out of fifty cerebella which Malacarne compared with the corresponding brains, twenty-three were softer than the brains in both the me- dullary and cortical substances ; in thirteen the cortical substance was equally firm, but the medullary substance more consistent and elastic than that of the brain ; ten were more dense in texture, and the remaining five were much harder than the corresponding brains. In some cerebella one of the hemispheres was much more firm than the other. The results of my observations are, that the medullary centre of the cerebellum is of a firmer consistence than that of the cerebrum ; that the gray substance of the cerebel- lum is softer than that of the cerebrum ; and that the gray substance of the former be- comes softened in the dead body with such extreme rapidity, that it is difficult to meet ■with a cerebellum in which this substance is in the normal state. Form. The general outUne of the cerebellum is that of an ellipsoid flattened from above downward ; its long diameter is transverse, and measures from three and a half to four inches ; its antero-posterior diameter is from two to two and a half inches, and its vertical diameter two inches in the thickest part, and about six lines in the thinnest part, that is, at its circumference. The figure of the cerebellum may also be compared to that of a heart on playing cards, the notch of which is directed backward, and the truncated apex forward ; or, rather, as was done by the old anatomists, to two flattened spheroids, united together at their points of contact. The cerebellum is perfectly symmetrical, but yet a marked difference between the right and left half of this organ is not unfrequently observed.! The cerebellum presents for our consideration an upper and a lower surface, and a circumference. The upper surface (h h, fig. 280) presents along the median line an antero-posterior em- inence (d), which is rather j>rominent in front, but gradually disappears as it extends backward : it is named the superior vermiform process (vermis superior). This eminence, which covers the valve of Vieussens and the tubercula quadrigemina, should be regard- ed, as Malacarne states, as the upper part of the median lobe of the cerebellum. On each side (h h) the upper surface of the cerebellum fornis an inclined plane. This surface is separated from the posterior lobe of the cerebrum by the tentorium cerebelli. * Chaussier says, " In a considerable number of comparative experiments, we sometimes found that the adult cerebellum was ith or ith,'and at other times, but rarely, y^th or yy-th the weight of the cerebrum. In the infant, at birth, we found it to be y gth, yyth, yS,th, -gy-st, -^t^, and, in one case, even ^Ld the total weight of the brain."— (Uc V Encephale, p. 77.) + In my opinion, this idea can only be regarded as an ingenious hypothesis. The aptitude for the generative act is not dependant upon the cerebellum, for all invertebrate animals are destitute of this organ ; and in cer- tain vertebrata, where the generative orgasm is quite remarkable, the cerebellum is extremely small. Some observations, however, are quoted, which appear to show that diminution of the occipital protuberance has followed extirpation of the corresponding testicle ; but it must first be proved that these observations are cor- rect ; for example, that the inequality of the occipital protuberances did not exist previously to the castration. X In four cases which have come under my own observation, atrophy of the right hemisphere of the cerebrum coexisted with atrophy of the left hemisphere of the cerebellum ; I am, therefore, led to conclude that there are certain intimate relations between the opposite hemispheres of these two portions of the encephalon. THE FURROWS, LOBULES, ETC., OF THE CEREBELLUM. 717 Tlie lower surface of the cerebellum {figs. 275, 276) is received into the concavity ol the occipital fossae, to which it is exactly fitted : it is divided into tv?o rounded, lateral halves {h,fig. 275), the lobes of the cerebellum, by an antero-posterior fissure (a to n), the great median fissure of the cerebellum (vallecula, Haller). Th^ back part of the cerebellum is completely subdivided by this fissure (see fig. 282), which receives the falx cerebelli ; in front, the fissure opens into a wide furrow, into which the medulla oblongata is received (see fig. 276) ; in the middle of the fissure is a lozenge-shaped interval, at the bottom of which is seen the base of a pyramidal emi- nence {a h c, fig. 275), divided transversely Fig, 275. into rings like a silkworm, and named, ac- cordingly, by the older anatomists, the in- ferior vermiform process {vermis inferior, pyr- amid of Malacarne). This eminence is de- veloped into four prolongations or branch- es, arranged in the form of a cross ; the posterior prolongation (c) is tapering, and occupies the back part of the great median fissure ; the two lateral processes dip (on each side of b) into the adjacent portion of the fourth ventricle ; and the anterior {b) tapers from behind forward, and terminates in a mammillary enlargement (a), which is free, and projects into the fourth ventricle. It has been unnecessarily distinguished from the rest of the inferior vermiform process by Malacarne and Chaussier, under the name of the laminated tubercle of the fourth ventricle {tubercle lamineux du quatrieme ventricule).* The inferior vermiform process is merely the lower part of the median lobe of the cere- bellum, of which the superior vermis constitutes the upper part. The superior vermis is continuous, without any line of demarcation, with the two hemispheres of the cerebel- lum, so that the upper part of that organ appears undivided. The inferior vermis, which seems at first sight to be intended to separate the two hemispheres, nevertheless forms the means of connexion between them, as may be easily seen by drawing them apart from each other. The circumference of the cerebellum is somewhat elliptical, or, rather, resembles the heart upon playing cards ; behind and in the middle line it presents a notch {71), between the convex margins of which a triangular interval is left, into which the falx cerebelli and the internal occipital crest are received. At the bottom of this notch the surface of the cerebellum is transversely grooved ; this part unites the superior to the inferior vermiform process, and belongs to the median lobe of the cerebellum. The rounded margins of the notch are continuous with the circumference of the cere- bellum. In front, the circumference of the cerebellum appears to be formed by the pons Varolii {d,fig. 276) and middle cerebellar peduncles {m), which are in relation with the posterior surface of the petrous portion of the temporal bones, and are therefore straight, and form a truncated angle, which projects forward, and corresponds to the pons Varolii. All the bundles of fibres which connect the cerebellum with the cerebrum and spinal cord enter at the anterior part of its circumference : thus, besides the middle peduncles of the cerebellum, we find in this situation its superior peduncles {r,fig. 272), or pro- cessus ad testes, and its inferior peduncles (cut at n), or processus ad medullam oblongatam, to which we shall presently return. The Furrows, Lobules, LamincR, and Lamella, of the Cerebellum. The whole surface of the cerebellum is traversed by curved lines or furrows, which are, for the most part, concentric and horizontal, but not very regular. These furrows are not parallel, but are inflected towards each other, and intersect at very acute angles. They may be divided into four sets, according to their depth. The first set of furrows are the deepest : they reach as far as the central nucleus, and divide the cerebellum into segments or lobules {g, h, I, fig. 275). 0M.I These segments are divided into secondary segments by the second set of furrows. The secondary segments are again subdivided into lamina or folia, and these laminee into lamellcB, by two sets of yet smaller furrows. Pourfour du Petit, Malacarne, and Chaussier have studied the segments, laminae, and lamellae of the cerebellum with great care, and have even counted them. The differen- ces in their resultst are not so much a proof of varieties in the structure of the organ as of the want of some uniform method of enumeration. * [The inferior vermiform process is usually described as consisting of three portions ; the pyramid ic,fig. SJ75), the uvula (i), and the nodulus (o).] t Winslow admitted 3 lobules, Collins 6, Pourfour du Petit 15, Malacarne 11, and Chaussier 16. Chaus- sier counted 60 laminse, and from 600 to 700 lamellae ; Malacarne had previously counted from 700 to 800 la- mellie. It is a very curious fact that Malacarne only found 324 lamellse in an individual labouring under mental alienatioa 71'8 NEUROLOGY. The segments which occupy the circumference of the organ are the largest : they rep- resent segments of an ellipsoid, and are very broad in the middle, and narrowed at each extremity. The segments of the upper surface are concentric, and their curvature cor- responds to that of the entire cerebellum. The segments of the lower surface are also concentric in each half or lobe of the cerebellum, but the curves of one side are inde- pendent of those of the other. The laminae or folia of the cerebellum are applied to each other like the leaves of a book ; they are separated from each other in their whole length, and are attached to the rest of the cerebellum by their adherent borders only. The lamellae, however, are ar- ranged in a different manner, for they pass from one lamina to another, and even from segment to segment. In fact, if the segments of the cerebellum be drawn asunder, the furrows between them are seen to be traversed obliquely by a great number of lamellae, which extend from one segment to another. The arrangement of the segments, laminae, and lamellae in the median line deserves particular attention. Opposite the superior vermiform process, they are not interrupted, but are merely bent slightly, so that the middle portion of each of the anterior segments is, as it were, drawn forward, so as to describe a curve, having its concavity turned backward. Upon this surface some slight peculiarities are observed in the arrangement of the parts. Along the median line there seems, indeed, to be an interchange of lam- inae and lamellae, some of each of which become thin, and end in points, from which oth- ers appear to originate. Opposite the inferior vermiform process the two hemispheres of the cerebellum are connected together by means of the lateral prolongations of that process. But in front, i. e., opposite the medulla oblongata, the two hemispheres of the cerebellum are perfect- ly distinct from each other (see Jig. 275). From these facts we may estimate to what extent the comparison is correct which was drawn by Haller between the superior ver- miform process and the corpus callosum. At the back part of the cerebellum, opposite the notch in that situation, the two hem- ispheres are connected by means of certain small transverse rings, of which we have already spoken. The superior and inferior vermiform processes and the portion situated at the bottom of the notch constitute together the middle lobe of the cerebellum, which Gall and Spurz- heim named the primitive or fu7idamental part of the cerebellum, because it exists in all vertebrata, and because, in a great number of them (as in birds, reptiles, and fishes), where the lateral lobes of this organ are altogether wanting, it constitutes the entire cerebellum. It is well to add, that the lateral lobes are relatively larger, and the medi- an lobe smaller in man than in other mammalia. A rudimentary median lobe, and very large lateral lobes, are the characteristics of the human cerebellum, while a very large median lobe, and rudimentary lateral lobes, form the characters of the cerebellum of the lower animals. All the segments of the cerebellum, of which there are from ten to twelve, might with propriety be distinguished by particular names. The following segments, however, re- quire special mention : the segment or lobule of the circumference {I, fig. 275), which is the largest ; the lobules of the medulla oblongata (lobuli medullae oblongatae), which are situa- ted behind that part (see fig. 276), are concave on their internal surface, which is accu- rately adapted to the medulla, and convex on their external and posterior surface, which dips slightly into the foramen magnum. These lobules (removed from f, fig. 275), which have been noticed by all anatomists, are separated from one another by the inferior vermi- form process (the uvula, b), and each of them terminates in front and on the inner side by a mammillated extremity (called the amygdala or tonsil), which partially fills up the fourth ventricle. The other inferior segments of each lobe of the cerebellum describe concen- tric curves around this segment. The lobule of the pneumogastric nerve {d) is a sort of prominent tuft (flocculus), situated {u, fig. 276) behind the pneumogastric nerve (8), and below the facial and auditory nerves (7). The Internal Structure of the Cerebellum. It is convenient to include under this head the description of the fourth ventricle, as well as that of the substance of the cerebellum. The Fourth Ventricle. Dissection. — Divide the median lobe of the cerebellum vertically ; make a vertical section of the pons along the median line ; draw asunder the medulla oblongata from the cerebellum. By means of the first section the anterior wall of the fourth ventricle is exposed, and by the second its posterior wall ; by drawing apart the medulla oblongata and cerebellum, the ventricle is reached by its inferior extremity, and its whole depth can be seen. It is important to examine the fourth ventricle in all its aspects. The fourth ventricle {v to y, fig. 282) is that rhomboidal cavity situated between the medulla oblongata and isthmus of the encephalon {q n), which forms its anterior wall, and the cerebellum (lo), which constitutes its posterior wall. The old anatomists follow- THE FOURTH VENTRICLE. 719 ed Galen in calling it the ventricle of the cerebellum. Tiedemann speaks of it as the first ventricle, because it is developed before the other ventricles, and is constant in all mam- malia. The fourth ventricle terminates in a point below^, expands considerably in the middle, and is again contracted at its upper part, vi^here it becomes continuous with the third ventricle. We shall consider separately its anterior and posterior walls. The anterior or inferior wall is formed by the posterior surface of the medulla oblonga- gata (see_^^. 271) and that part of the upper surface of the isthmus of the encephalon which corresponds to the pons. In shape it resembles a lozenge or diamond, truncated at its upper point ; the upper borders of the lozenge being represented by th-e superior peduncles of the cerebellum (r to g), and the lower by the restiform bodies (e) : the poste- rior surface of the re-enforcing fasciculi {faisceaux innomines) of the medulla oblongata constitutes this anterior wall, which is lined by a dense and easily separable membrane. The posterior or superior wall represents a vaulted roof, which is formed above by the superior peduncles of the cerebellum (r to g) and the valve of Vieussens {I, fig- 271 ; I, fig, %lb ; g w, fig. 282), lower down by the cerebellum {w), and below by a fibrous mem- brane, continuous with the neurilemma of the spinal cord. Opposite the middle, i. c., the broadest part of this posterior wall (see fig. 275), are sit- uated three mammillary projections — one median and two lateral : the first {b, the uvu- la) is the anterior segment of the median lobe of the cerebellum ; the other two (the amygdalse) are formed by the innermost laminee of the lobule of the medulla oblongata (cut away at/). These latter are not bathed in the fluid of the ventricle, but are sep- arated from it by the fibrous membrane lining that cavity. The median mammillary projection (b), named by Malacarne and Chaussier the lami' nated tubercle of the fourth ventricle, resembles a movable valve. It is attached to the cerebellum by two white pedicles, which pass outward and backward upon the lateral processes of the crucial eminence formed by the inferior vermis. Connected to its an- terior extremity (the nodulus, a) are seen two broad folds {semilunar folds, e), which arise from it, one on each side, and tiecome continuous with the roots of the corresponding sub-peduncular lobules or flocculi (' branches, and those into the ultunate ramifications. A yellowish fayer covers each of these successive divisions, and upon that a gray layer, about a line in thickness, is accurately moulded. Upon sections of this kind it is easily seen that the segments of the cerebellum are very unequal in size, in direction, and in their manner of division ; that the superior segments are the smallest, the segments of the circumference the largest,! and the in- ferior segments of aii intermediate size ; that there is no vacant space between the seg- ments, but that both laminaj and lamella; occupy the intervals ; and, lastly, that all of these segments curve forward upon themselves, so as to form a series of horizontal wheels or ci.njles, the plane of which is at right angles to that of the wheel-shaped mass of the middle lobe. In the centre of the white nucleus of each half of the cerebellum is the corpus rhom- boideum, or corpus dentatum :% these bodies are of an ovoid form ; their yellowish invest- ing layer is dense, and folded backward and forward upon itself, and exactly resembles that of the olivary bodies; and I have been accustomed to speak of these bodies as the olivary bodies of the cerebellum. Gall and Spurzheim regarded them as ganglions of re-enforcement, and called them the ganglions of the cerebellum. Their shortest or verti- cal diameter is about one third of their long or horizontal diameter ; in one case, where the latter was fifteen lines, the former was five lines : moreover, the size of the corpora dentata of the cerebellum varies in different subjects, and is in proportion to the size of * Rolando (Oss^rvazioni suV Cervehtio, p. 1-87, 1623)appears to me to Imve been the first to establish the fact of the existence of three substances ; the medollare, the cinereu rossigua, and the cinerea esterna e corticale. t The segment of the circumference, which is the largest of all, immediately divides into two smaller seg- ments ; It has been incorrectly stated that there is a horizontal fissure along- the circumference of the cere- bellum, exlendmg from one of the middle peduncles to the other. t In order to divide the corpus dentatum, the section must be made opposite the corresponding inferior pe-- duncle of the cerebellum. I would recommend that one section be made to extend through the corpus denta- tum of the cerebellum, and also through the olivary body, so that some idea may be formed of the analogy be- tween these two parts, 4Y 722 NEUROLOGY. the lateral lobes of that organ : they are, therefore, much less developed in the lower animals than in man. The ■peduncles of the cerebellum are six in number, three on each side, namely, a supe- rior, a viiddle, and an inferior ; they all originate, or, it may be said, terminate in the cen- tral nucleus. The superior peduncles of the cerebellum are generally known as the processus cerebelli ad testes ; they are seen (r, fig. 280) in front of the superior vermiform process, and seem to pass up to the tubercula quadrigemina. We shall afterward see that this is only ap- parent. The inferior peduncles {processus cerebelli ad medullam oblongatam) are, in fact, the resti- form bodies ; they estabhsh a direct and intimate communication between the cerebel- lum and the spinal cord. Lastly, the middle peduncles {m,fig. 276), which are anterior to the two preceding sets, occupy the fore part of the circumference of the cerebellum, and are continued into the pons Varohi without any line of demarcation. They are called also the cerebellar pedun- cles {processus cerebelli ad pontem), and the crura or legs of the medulla oblongata. Horizontal Sections. Horizontal sections of the cerebellum have been studied with very great care, and have been well figured by Vicq d'Azyr ; they show that the dimensions of the central nucleus are much greater in the horizontal than in the vertical direction.* Upon these sections, which should be made parallel to the upper surface of the cere- bellum, is seen the relative disposition of the laminae, which are sometimes parallel and sometimes oblique in reference to each other, and which either extend around the entire circumference of the organ, or terminate in tapering extremities and again commence, and pass from one segment to another. Lastly, these horizontal sections show the continuity of the right and left lobes of the cerebellum by means of the middle lobe. In this middle lobe the lamellae are more ir- regular than in the lateral lobes ; they intersect each other at various angles, and be- come again united mto new combinations, so that several anatomists have admitted the existence of a true decussation in this middle portion of the cerebellum. The middle lobe also has its medullary centre, which connects the lateral medullary centre in such a manner that, by a successful section, a sort of cerebellar centrum ovale is obtained, analogous to tt^e centrum ovale of Vieussens in the cerebrum. Examination of the Cerebdlum by means of a Stream of Water, and Dissec- tion of the Hardened Cerebellum. A stream of water directed upon vertical sections of the cerebellum decomposes the white nucleus of each lateral lobe into a great number of extremely thin leaves, which constitute the different laminae or lamellai; of the cerebellum. All these laminae and la- mellae terminate in the central nucleus of We corresponding lobe. Each lamella is fan- shaped, its adherent border being very narrow, concave, and applied to the central nu- cleus, with which it is evidently continuous, while its convex margin corresponds to the surface of the cerebellum. The arrangement of t\iese lamellae is very beautiful and cu- rious : some of them ascend to form the segments, laminae, and lamellae of the upper surface of the cerebellum ; others descend to form the corresponding parts of the lower surface, and the intermediate ones pass horizontally to the circumference, and are dis- posed in a similar manner. Opposite each point of subdivision there seems to be an en- largement of the white substance, but this depends not upon an actual increase of that . substance, but upon the divergence of the lamellae. The structure of the cerebellum, therefore, considered generally, is lamiinted. From the central white nucleus proceed innumerable lamina?, which, though in juxtaposition, are never blended together, and which form groups, that are themselves subdivi6ed again and again, like the branches of a tree, the ultimate lamella always containing a. least two leaflets. Can anatomy teach us anything beyond this laminated arrangement'. In each lamella certain radiated striae are seen ; and it may be asked. Whether these prove the existence of a linear or fibrous structure ] It is certainly true that the lamellae mas- be divided in the direction of these stria;, but it is far from being evident that they con- sist of linear fibres. In the central nucleus, the laminae, being more firmly pressed together, are separated by the stream of water with greater difficulty than the laminae near the surface : the corpora dentata of the cerebellum are peculiarly firm. The stream of water insmuates itself into these bodies opposite their internal extremity, which appears to be naturally open, and divides them into two halves, a superior and an inferior. It is then seen that the dentated appearance of their section resuUs from the reduplication of the dense yel- lowish layer in which they are enclosed ; also, that the white substance penetrates into the interior of these bodies at their internal surface, accompanied by a great number of * In each lobe of the cerebellum there is a medullary centre, that is, a spot in which the section of the white substance is larger than at other points. GENERAL VIEW OP THE CEREBELLUM. 723 vessels -, and that this white substance is arranged in lamella;, which terminate at three different points of the yellowish layer, so that each of the corpora dentata resembles a small cerebellum. Examination of the Hardened Cerebellum. — The examination of the cerebellum, when hardened by alcohol, or by boiling in oil, or salt and water, or by maceration in a solu- tion of salt and bichloride of mercury, of the strength recommended by Rolando, confirms all the results which have been obtained by the preceding method of investigation. These modes of preparation, moreover, enable us to examine more completely than in any other way the relations of the central nuclei of the lobes to the peduncles of the care- bellum. It is seen most distinctly that these peduncles (m n, fig. 273 ; n r, fig. 274) emerge from or terminate in the central nuclei {p p), but it is very difficult to ascertain their precise arrangement within the nuclei. All that we know is the fact that, as soon as they emerge from the central nuclei, they assume a fasciculated character, and that all the lamellae and laminae of the cerebellum seem to terminate in the fibres of the mid- dle peduncles. General View of the Cerebellum, From the preceding statements we may draw the following conclusions : The cerebel- lum consists of two lateral lobes and a middle lobe ; the lobes are formed by a consider- able number of segments, which are subdivided into smaller segments, and these into laminae and lamellae ; each lobe contains a central medullary nucleus, upon which all th§ segments rest, and which constitutes the termination or the origin of the several pedun- cles ; the substance of these peduncles is fibrous or fasciculated, and that of the central nucleus has a similar character, but not so well marked ; the medullary substance of each segment is formed by laminae applied to each other, but not actually continuous ; each of these laminae is fan-shaped, and those Avhich constitute the central nucleus of each segment become separated from each other to form the secondary segments, the laminae, and the lamellae ; the ultimate lamellae of the cerebellum consist oi two leaflets of white matter covered externally by a very thin yellowish layer, which is itself cover- ed by a rather thick layer of gray matter ;* the corpora dentata, or olivary bodies of the cerebellum, consist of fibres or laminae of medullary substance, which are spread out so as to terminate at different points upon the iiuier surface of the dense yellow membra- nous layer which constitutes their external investment. A very ingenious explanation of the structure of the cerebellum has been proposed by Gall, and is now rather generally adopted. The opposite directions of the inferior and middle peduncles of the cerebellum sug- gested to him the idea of diverging and converging fasciculi, and to this he has added his theory regarding the ganglia, which he considered as apparatuses of re-enforcement, that is to say, as points of origin for new fascicuU. According to Gall, then, the inferior peduncles of the cerebellum or the restiform bod- ies (n,fig. 274), which he calls the primitive fasciculi of the cerebellum^ are the roots, or fasciculi of origin of the cerebellum. After they have penetrated a few lines into the substance of the organ, they meet with and join the corpus dentatum, which Gall regards as a true ganglion, or apparatus of origin and re-enforcement for a great part of th^ nervous mass of the cerebellum. According to him, a principal nervous fasciculus corresponds to each of the folds of the corpus dentatum, from which ganglion arise all those prolonga- tions of medullary substance which, together with the gray matter upon them, consti- tute the middle and lateral lobes of the cerebellum. Besides the preceding fascicuU, which are named by Gall the diverging fasciculi, and are said by him to constitute the formative system of fibres, there are certain converging fasciculi, which constitute the uniting system of fibres, or the commissures of the cerebellum. These are supposed to have no direct connexion either with the primitive fasciculi or the corpus dentatum, but to emanate from the gray matter upon the surface of the cere- beUum, and to pass in different directions {p q, fig. 273) between the diverging fasciculi, so as to enter into and constitute the middle peduncles of the cerebellum (w) and the pons Varolii, which Gall regarded as forming together the commissure of the cerebellum. The superior peduncles of the cerebellum (?', fig. 274) he considered as fasciculi of communication between the middle median lobe of the cerebehum and the corpora quad- rigemina, and the valve of Vieussens as the commissure of these peduncles. We can only regard Gall's view concerning the structure of the cerebellum as an in- genious speculation. Why should the inferior fasciculi be the roots or primitive bundles of the cerebellum rather than the superior 1 Who has seen the re-enforcement of these primitive fasciculi in the corpus dentatum 1 Why should the corpus dentatum be regard- ed as a ganglion ! Whence is this distinction between converging and diverging fasci- culi 1 1 and, finally, Why are figure and metaphor employed in reference to strictly ana- tomical questions 1 * [The white substance of the laminae is said to consist of two sets of fibres — one coming' from the central mass, and passing up the centre of the laminse, and the other set lying upon the first, and passing from one lamina to another.] t " These converging fibres," says Tiedemann (French translation by Jourdan, p. 169J, " are merely chimer- 724 NEUROLOGY. Another theory regarding the structure of the cerebellum has been offered by Rolan- do, who, by combining the results derived from an examination of the human cerebellum, when hardened in a strong saline solution, with those furnished by the anatomy of the brain of the shark, and those obtained by studying the development of the brain of the fowl, was led to regard the human cerebellum as formed by the folding and refolding upon themselves of the parietes of a large bladder or vesicle, so as to give rise to innumera- ble laminae.* The facts we have already stated sufficiently refute this hypothesis. It is quite cer- tain that the cerebellum is formed by the union of one middle and two lateral lobes : the lobes themselves are composed of a considerable number of segments, which are subdi- vided into smaller segments, laminae, and lamellae. The general structure of the cere- bellum is laminated, and these laminae are striated ; each lamella contains two leaflets of white substance covered with gray matter. The cerebellum is connected with the medulla oblongata by the inferior peduncles, and with the brain by the superior pedun- cles ; the middle peduncles and the transverse fibres of the pons establish an intimate connexion between the two lobes of the cerebellum-t Development of the Cerebellum. The cerebellum does not appear until some time after the spinal cord : it consists, at first, of two laminae and plates prolonged from the cord, which approach each other to- wards the median line ; these are the inferior peduncles of the cerebellum, or the resti- form bodies. The human cerebellum in this condition has a close resemblance to the same organ in fishes and reptiles. At the fourth month, the cerebellum forms a sort of uniform girdle, four lines in width, around the tubercula quadrigemina and the medulla oblongata ; the pons Varolii is already visible ; there is a rudiment of the corpus denta- tum, and the surface of the cerebellum is entirely devoid of fissures. At the fifth month there are four transverse fissures : a vertical section of the cerebellum presents five branches ; but there are as yet neither laminae nor lamellae, nor is there any distinction between the middle and lateral parts. At the sixth month, the cerebellum is divided by the posterior notch, the different orders of fissures are visible, and the corpus dentatum has acquired considerable size. During the last three months of intra-uterine existence, the lateral lobes generally acquire that predominance over the middle lobe which is found to hold after birth. As the development of the spinal cord precedes that of the cerebellum, and as the cer- ebellum appears to be formed by a prolongation of the posterior fasciculi of the cord, does it follow that that organ is a production or an expansion of the cord 1 Certainly not ; all that we can conclude is, that they are developed in succession. Reil and Tiedemann have advanced the opinion that the cerebellum is secreted by the pia mater, and that the gray matter is deposited the last ; but this is only an assertion vyithout demonstration. The cortical substance is formed at the same time as the medullary, and neither of them can be considered as the product of the other. Comparative Anatomy of the Cerebellum. In fishes the cerebellum is generally small, but in the ray and shark it is large, subdi- vided into convolutions, and prolonged above the optic lobes in front, and above the lobe of the eighth pair of nerves behind. In the silures, as Weber has observed, the cere- bellum is relatively as large as the human cerebrum ; for it covers the posterior half of the cerebral lobes, as the cerebrum in man covers the cerebellum. In aU fishes the cer- ebellum contains a considerable cavity. In some of this class of animals it is subdivi- ded into segments, laminae, and lamella?. J Reptiles. — There is no cerebellum in the batrachia (as in the frog, toad) and ophidia (serpents) ; most anatomists, however, admit its existence in a rudimentary state. It is very small, and shaped like a roof, or vaulted, in the chelonians (tortoise) ; it is very long in the saurians (lizard, crocodile). Birds. — The cerebellum is very large, and represents an eHipsoid, having its long di- ameter directed vertically. It is deeply and regularly traversed by horizontal fissures, which are curved downward on the upper half, and upward on the lower half of the or- ical ; for the pons Varolii, and the medullary fibres of which it consists, are found in the fcetus at tlie fourth month, that is, at a period when there are no laminae nor lamellae, nor even any leaflets covered with gray mat- ter. Gall, therefore, assumes these converging fibres to originate from parts which do not appear until after those fibres themselves." The refutation of Tiedemarm appears to me to be itself founded on an ass-umption, for there is no proof that the gray matter is formed after the white. ■^ Osservazioni sul' Cerveletto, p. 187. In the shark, the cerebellum consists of a gray and a white layer united together and folded a great number of times upon themselves, t It IS not yet ascertained whether the lateral halves of the cerebellum act upon the same or opposite sides of the body ; some cases, in which atrophy of one hemisphere of the cerebrum coexisted with atrophy of the op posite hemisphere of the cerebellum, would appear to show that the action of the latter is not crossed. The laminated structure of the cerebellum and its twofold composition suggested to Rolando the idea of comparing it to a voltaic pile, or electro-motive apparatus. t tit is divided into segments by deep transverse furrows in some cartilaginous fishes.l THE CEREBRUM. 725 gan. They all terminate opposite two small tubercles or appendages, situated one at each extremity of the transverse diameter. Upon a section of the cerebellum of birds is seen an arbor vitae, composed of white substance covered with gray matter. Mammalia. — In the three classes already examined, the cerebellum has merely a mid- dle lobe : in all mammalia there are also lateral lobes. They are at first small, like ap- pendages, as in the rodentia, in which the cerebellum differs but little from that of birds ; they gradually increase in size as we proceed upward in the scale, until they reach their highest state of perfection in man, the development of whose cerebrum and cerebellum exceeds that of the same parts in all the lower animals. In mammalia the size of the lateral lobes of the cerebellum is directly proportioned to that of the olivary bodies, the existence of which in this class Vicq d'Azyr has erroneously denied. THE CEREBRUM, OR BRAIN PROPER. Definition — Situation — Size and Weight — General Form. — The Superior or Convex Surface. — The Inferior Surface or Base — its Median Region, containing the Inter-peduncular Space, the Corpora Albicantia, the Optic Tracts and Commissure, the Tuber Cinereum, Infundibu- lum, and Pituitary Body, the Jjiterior Tart of the Floor of the Third Ventricle, the reflected Part of the Corpus Callosum, the Anterior Part of the Longitudinal Fissure, the Posterior Part of the Longitudinal Fissure, the Posterior Extremity of the Corpus Callosum and Me- dian Portion of the Transverse Fissure, and the Transverse Fi.ssure. — The Lateral Regions, including the Fissure of Sylvius and the Lobes of the Brain. — The Convolutions and Anfrac- tuosities of the Brain, upon its Inner Surface, its Base, and its Convex Surface — Uses of the Convolutions and Anfractuosities. — The Internal Structure of the Brain — Examination by Sections — Horizontal Sections showing the Corpus Callosum, the Septum Lucidum, the For- nix and Corpus Fimbriatum, the Velum Interpositum, the Middle or Third Ventricle, the Aqueduct of Sylvius, the Pineal Gland, the Lateral Ventricles, their Superior and Inferior Portions, the Choroid Plexus, and the Lining Membrane and the Fluid of the Ventricles — Median Vertical Section — Transverse Vertical Sections — Section of Willis. — General Re- marks on this Method of Examining the Brain. — Methods of Varolius, Vieussens, arvi Gall. — Gall and Spurzheim's Views on the Structure of the Brain. — General Idea of the Brain. — Development. — Comparative Anatomy. The cerebrum or brain, strictly so called, is that portion of the encephalon which occu- pies the whole of the cavity of the cranium, except the inferior occipital fossae. It forms, as it were, the crown or summit of the spinal axis, surmounting it {cerebrum superius), and, at the same time, lying in front of {cerebrum anterius) the spinal cord, as the origin and termination of which it has been alternately regarded. By the pons Varolii and the anterior or cerebral peduncles it is intimately connected with the cerebellum and the spinal cord. The tentorium cerebelli completes the cavity in which it is enclosed, and separates it from the cerebellum, which is situated below its posterior lobes. The cra- nium, the dura mater, the arachnoid, and the pia mater form a fourfold investment for it. Size and Weight of the Cerebrum. The great size of the cerebrum is undoubtedly one of the most characteristic points in the structure of man : in several animals, the entire encephalon is relatively as large, and even larger {ex., the canary bird, the sapajou, the dolphin) ; but in reference to the size of the brain properly so called, i. e., of the cerebral hemispheres, even the most fa- voured animals are much inferior to man.* In the adult, the weight of the cerebrum, detached from the cerebellum and the pons by a section through its peduncles, varies from two to three pounds. t I believe it to be impossible to construct a table of the comparative size and weight of the brain and of the body. Is it not evident, indeed, that one element in the comparison, namely, the weight of the body, is subject to great variety 1 Haller has recorded the resuUs of all the cal- culations which have been made upon this subject, and the diversity of those results is the best comment that can be made upon this mode of comparison. These remarks do not apply to the relative proportions between the cerebrum and • The weight of the cerebrum of the horse and the ox is scarcely lialf that of the human cerebrum. t [From the statements given by Tiedemanu {Hirn des Negers, &c., p. 6, Heidelb., 1837), it appears that the prevalent weight of the brain (entire encephalon) in the adult male is about from 44 to 48 oz. troy ; in the adult female, from 40 to 44 oz. The results deducible from Dr. Sims's tables do not materially differ from the above. In thirty-nine males, varying in age from 22 to 80, Tiedemann found the minimum weight of the brain 38 oz. 20 gr., the maximum 59J oz. In eleven females, from 20 to 80 years of age, the minimum was 32 oz. 5 drs. 50 grs., the maximum 46 oz. 2 drs. The extremes, according to Dr. Sims's observations, were in about seventy males from 20 to 91 years, lowest, 33 oz. 80 grs. ; highest, 54 oz. 6 drs., troy weight. In ninety females, between the ages of 20 and 89, the low- est was 27 oz. 80 grs., the highest 51 oz. 6 drs. J 726 NEUROLOGY. cerebellum. According to my own observations, the weight of the cerebellran is froln the twelfth to the eighth part of that of the cerebrum.* It is important to obtain some approximation to the relative size of the brain in differ- ent individuals in the two sexes, and at different ages. It results, from a great number of facts, that the size of the brain is independent of the stature of the individual ; that the size of the brain is also independent of sex, although, since the time of Aristotle, it has been the custom to repeat that the female brain is smaller than that of the male ; that in the foetus and the infant the cerebellum is rela- tively much larger than the adult ; and that in old age the brain is often atrophied like other organs, and then does not completely fill the cranial cavity. Can the size of the brain be increased by exercise, and diminished by inaction 1 It cannot be doubted that the brain must, in this respect, obey the laws which regulate all other organs ; but the bony parietes of the cranium must offer great obstruction to its development ; indeed, examples have been recorded of compression of the brain, and even of death, produced by hypertrophy of this organ. If it be true that the power of an organ depends upon its size, it follows that the size of the brain, and, consequently, the capacity of the cranium, must have a tolerably close ralation to the development of the cerebral functions ; but the activity of these functions is connected with so many circumstances besides the size and quantity of brain, that any estimate of the intellectual powers founded exclusively upon these data is very often faulty and inexact. t The specific gravity of the brain, as compared with that of water, is, according to Mus- chenbroek, as 1030 to 1000. It would be interesting to determine whether its specific gravity varies according to age and in disease, and also whether it differs in different animals. According to Soemmering, the specific gravity of the brain in old persons is less than in those of middle age. General Form of the Cerebrum. The form of the cerebrum corresponds exactly to that of the cranial cavity, which is, as it were, moulded on it ; it is, therefore, variable like that of the cavity itself, which, during early infancy, is capable of assuming all sorts of shapes from the application of external pressure. If the entire cranial cavity, exceping the posterior occipital fossse, be filled with plas- ter of Paris, an exact representation will be obtained of the general form of the brain which had been removed. The cerebrum, therefore, is like the cranium of an ovoid fig- ure, having its large end turned backward, and its small one forward. It is divided on its under surface into lobes, which occupy the different compartments in the base of the cranium. The entire surface is marked by deep tortuous furrows (see Jigs. 276, 282), called anfracluosities, which occasion an appearance like that of the convolutions of the small intestines, and hence the term convolutions is applied to the eminences resembling folds, by which the anfractuosities are bounded. The Soperiok or Convkx Surface of the Brain. A median vertical fissiire rtmning from before backward, called the longitudinal fissure^ divides the cerebrum into two exactly similar lateral halves, which are improperly called cerebral hemispheres, for each of them resembles the fourth part of an ovoid ; but would be more correctly designated the right and left brain, as was done by Galen.t The lon- gitudinal fissure divides the cerebrum in its whole depth, both in front and behind (i i/, fig. 277 ; also_^^. 282) ; but in the middle it is interrupted by the corpis callosum (d d). There are two brains, as there are two spinal cords and two cerebella.^ The cerebrum is therefore symmetrical, but it is less completely so than the spinal cord ; I should even say that a decided disproportion is very commonly observed between the right and left hemispheres. It does not appear that this want of symmetry exerts that influence upon the intellectual faculties which was imagined by the ingenious Bichat, whose own unsyrometrical brain was in direct contradiction to his doctrine. It is, nev- ertheless, possible that a want of symmetry, when carried to a certain point, may affect the intellect ; in the brains of several idiots, their want of symmetry has been very re- * In three young subjects I found as follows : lb. oz. I oz. Cerebrum ... 2 2 Cerebellum . . . 4J " . . . . 2 8i " . . . 3i " .... 2 5 1 " ... 5 + Persons endowed with strong- memories hare always appeared tn nie to have large brains ; and the part which the memory performs in the exercise of mind is of such a nature that we cannot be surprised if the persons alluded to are frequently men of superior intellect. 1 have known many persons, having heads of considera- ble size, who had merely a good memory, but none of the characteristics of genius. Those in whom the brain is large seem to me to resist the power of disease better than such as have small brains. i Chaussier applies the term lobe to the hemispheres, reserving that of lobule for the secondary divisions. ^ Galen inquires why there should be two brains ; and replies, that it is to ensure a more perfect perform- tnce of the cerebral functions. I have seen several hemiplegic individuals in whom the whole of oae hemi- sphere was atrophied, but who, notwithstanding, possessed ordinary intellectual faculties. THE BASE OF THE BRAIN. 727 Fig. 276. markable. I have seen the longitudinal fissure of the brain deviate to the right or left side at an angle of from 15° to 20° degrees from its usual direction. Each cerebral hemisphere presents three surfaces for our consideration : An internal surface {fig. 282), which is flat, vertical, and separated from that of the opposite hemisphere by the falx cerebri ; but as the falx does not extend so low as the corpus callosum, it foltows that the two hemispheres are in contact below, the pia mater, however, intervening between them. In those rare cases of absence of the falx cerebri, the corresponding faces of the two hemispheres are in contact with each other through- out their whole extent. I have seen one case in which the falx was imperfect, and the two hemispheres were united. An external surface, which is convex, and resembles the surface of the fourth part of an ovoid, having its great end directed backward ; it corresponds to the concavity formed by the frontal, parietal, and occipital bones. An inferior surface, which fonns part of the base of the brain in general, and will be next described. The Inferior Surface or the Base of the Brain. The base of the brain {fig. 276), admirably described and correctly figured bv Soemmer- ing in a special treatise upon the subject,* presents a great number of objects for our consideration. In order to obtain a perfect knowledge of it, it is advisable to examine it while the brain is still enclosed ia its membranes, and placed in the scull-cap, with its base uppermost; and also upon a brain from which the membranes have been remo- ved, and which is placed in the same position, but on a flat surface. In the former case, the parts form- ing the base of the brain are press- ed together, and may be studied as a whole ; and in the latter, they are separated, and may be examined in detail. It is at its base that the brain is connected with the other parts of the cerebro-spinal axis by means of the right and left •peduncles {ff), which may be regarded as the roots of the two hemispheres. The Median Region. — In the me- dian line, opposite the centre of ■the base of tlie brain, and in front of the pons Varolii {d), is situated an excavation, which may be called the median excavation of the base of the brain. This excavation has already been alluded to in the description of the arach- noid membrane and the sub-arachnoid fluid, with which this excavation is filled : it is formed by the brain being curved upon itself, and is partially effaced when that organ is placed with its base uppermost upon a flat surface : this excavation is of a pyram- idal form, the apex being directed upward and the base downward. The borders of the excavation form a hexagon, and contain the arterial hexagon of the base of the cra- nium, named the circle of Willis. The posterior borders of the hexagon are formed by the peduncles of the brain, the lateral borders by the inner part of the posterior lobes [c, middle lobest] of the cerebrum, and the anterior borders by the inner and back part of the anterior lobes (a) of the cerebrum. From the six angles of this hexagon, six furrows proceed in different directions : from the anterior angle, the fissure which separates the anterior lobes, or the great longitudi- nal fissure {x) of the brain ; from the two anterior lateral angles, the corresponding fis- sures of Sylvius {j/ y) ; from the posterior lateral angles, the two extremities (external to //) of the great cerebral fissure, or great transverse fissure of the brain ; and from the pos- terior angle (r), which corresponds to the interval between the cerebral peduncles, the longitudinal groove {d) upon the pons Varolii. * De basi Encephali (Ludwig, Scriptores Neurologici, L ii.). t I. e.,o( the middle lobes of anatomists generally (c, fig. 276), which, it must be remembered, the author, agreemg with ScEmmenng, does not regard as distinct from the posterior lobes (b), and to which, therefore, he does not apply the term "middle lobes." This term is, however, for the most part added [between brack- et*] in the translation, as it is generally used in anatomical descriptions in this country.] 728 NEUROLOGY. In the area of this median excavation are seen the inter-peduncular space (above rj, the mammillary tubercles (z, corpora mammillaria vel albicantia), the optic tracts {s) and optic commissure {t), the posterior part of the floor of the third ventricle, or the tuher cinereum (■»), the infundibulum (i), and the pituitary body.* In front of the median excavation are situated, counting from behind forward, the an- terior part of (he floor of the third ventricle (lamina cinerea, m, fig. 282), the under or reflect- ed portion of the corpus callosum (e), and the infenor part of the longitudinal fissure of the , cerebrum (x, fig. 276). Behind the median excavation is the pons Varolii, and, behind that, the middle part (r, fig. 282) of the great transverse fissure, by which the pia mater enters (above p) the third ventricle, the thick posterior extremity (/) of the corpus callosum, and the posterior part of the longitudinal fissure of the cerebrum. The Lateral Regions of the Base of the Brain. — Upon each of these regions are seen the inferior surface of the correspondiiig anterior lobe (a) of the cerebrum, the fissure of Sylvius (y), by which this lobe is separated from the posterior lobe [middle lobe of others, c], and the inferior surface of the posterior lobe itself (c b). There is no distinct middle lobe.f I shall now describe, successively and in detail, the several parts just enumerated, with the exception of the cerebral peduncles and the pons Varolii, which have already been noticed as constituent parts of the isthmus of the encephalon. The Median Region of the Base of the Brain. The Inter-peduncular Space. This space (above r) is of a gray colour, it is perforated by numerous openings for the transmission of vessels, and is termed the middle or posterior perforated spot {locu.s per- foratus] ; it contains the origin of the third pair of nerves (3). A longitudinal groove and two fasciculi, separated from the corresponding cerebral peduncle by a blackish line, are seen in this spot. These inter-peduncular fasciculi are formed by a prolongation of the fasciculi of re-enforcement {faisceaux innomines) of the medulla oblongata. The Corpora Albicantia. The mammillary tubercles (corpora albicantia vel mammillaria, z] are two small pisiform, or, rather, hemispherical globules, composed externally of white, and internally of gray substance, situated behind the tuber cinereum, which is accurately adapted to their an- terior surface, also behind the infundibulum, and between the peduncles of the brain. They are separated from each other by a deep fissure, excepting at their highest part, where they are connected by means of a thin layer of gray matter, which is very easily torn ; they correspond (z, fig. 282) to the floor of the third ventricle (/). It will be hereafter seen that the white covering of these small bodies is formed by the termination of the anterior pillars of the fornix, and hence the name given them by Cas- serius, the bulbs of the anterior pillars of the fornix {bulbi priorum crurum farnicis), a name which should be preserved. The two corpora albicantia are generally of equal size. In several cases of atrophy of one of the hemispheres of the cerebrum, I have found the corresponding mammillary tubercles also atrophied. We are completely ignorant of the function of these bodies. In man and the carnivora only are there two mammillary tubercles, and in aU the oth- er vertebrata there is but one. They attain their highest state of development in fishes, if, as stated by Vicq d'Azyr, they are represented by the two larger lobes, which occupy a corresponding situation in that class of animals. During the early periods of foetal life they are blended together into one tolerably large mass, and do not become distinct from each other until about the seventh month. The Optic Tracts arid Commissure. At the point where the peduncles of the cerebrum pass into the brain, each of them is surrounded by a white band, named the optic tract, or tract of the optic nerve. Each of those tracts commences, behind, at an eminence called the corpus geniculatum externum {j,fig. 271), which will be seen, hereafter, to be an appendage of that part of the brain named the optic thalamus. The corpus geniculatum internum (i,figs. 271, 272) of au- thors is merely a tubercle inserted into the bend or knee formed by the corpus genicula- tum externum. The optic tract (2, fig. 272), then, is the continuation of the corpus ge- niculatum externum, from which it is distinguished by its whiteness, which contrasts strongly with the gray colour of that body : it is at first broad, flattened, and thin, and is applied to the corresponding cerebral peduncle, being distinguished from the peduncle only by the direction of its fibres. It then turns horizontally around the peduncle, is de- tached from it, and at the same time becomes narrower and thicker ; having reached the front of the peduncle, it changes its direction, passes forward and inward is,fig. 276), and is united with its fellow of the opposite side, to form the commissure or chiasma (t) of the optic nerves (2). The optic tracts may be regarded as forming a commissure to the two optic thalami. * [To avoid confusion in the drawing, the pituitary body is not represented in Jig. 276 ; its point of attach- ment is to the infundibulum (i) .1 + See note, p. 727. , THE BASE OP THE BRAIN. "729 These tracts and the cerebral peduncles of the two sides enclose a lozenge-shaped in- terval, in which are situated the posterior perforated spot, the corpora albicantia, the tu- ber cinereum, the infundibulum, and the pituitary body. The Tuber Cinereum, the Infundibulum, and the Pituitary Body. The term tuber cinereum (v) has been applied by Soemmering to the soft gray mass which occupies the triangular interval between the corpora albicantia and the optic tracts. It is also called the floor of the third ventricle, because it closes that cavity be- hind and below, and the base of the infundibulum, because that part is attached to it. The infundibulum (la tige pituitaire, Lieutaud ; la tige sus-sphenoidale, Chauss.) is a reddish process (2), about two lines in length, directed very obliquely downward and for- w^ard (i, Jig. 282), and applied to the lower surface of the tuber cinereum : it is broad at its upper extremity, but soon diminishes in diameter, and descends, to be inserted into, and become continuous with, the pituitary body. Is the infundibulum hollow, or is it a solid stem 1 The term infundibulum, or funnel, applied to this part by the older anatomists, and the following synoxiymes, pelvis colatoria, scyphus, aqua ductus, encephali sentina, alTord ample evidence of both their anatomical and physiological views regarding it. Galen and Vesalius, who are so often at variance, are perfectly agreed upon this subject, and describe the infundibulum with a minute ex- actness ; but since the communication supposed by Galen to exist between the nasal fossae and the brain by means of passages through the ethmoid and sphenoid bones, and the equally hypothetical communication admitted by Vesalius, are known to have no ex- istence, anatomists have rejected the notion of the passage of a fluid from the brain in this direction, and they no longer regard the infundibulum as a funnel intended for its transmission. Haller has collected, in some learned notes, the contradictory opinions of his predecessors, but has left the question still in doubt. Nor has Soemmering him- self, after a long detail of investigation into the subject, arrived at a more satisfactory result.* A careful examination of the infundibulum has convinced me that there is, at least in a certain number of cases, a funnel-shaped canal, precisely similar to that which was described and figured by Vesalius : it is wide above, where it communicates with the third ventricle, and narrow below, where it reaches the pituitary body, a body which the ancients had not named, but which Vesalius called glans pituitam excipiens. In order to demonstrate this canal, the optic tract must be turned backward, and the semi-transpa- rent corneous lamina, which forms the anterior part of the floor of the third ventricle, must be divided ; behind a white band, which is quite distinct from the anterior com- missure of the brain, there is then seen a circular opening sufficiently wide to admit the blunt end of a large probe, which may accordingly be passed through the entire length of the infundibulum as far as the pituitary body. Again : by cutting the infundibulum across, and then blowing upon it through a blowpipe, or letting some drons of water fall upon it, a perfectly circular opening may be demonstrated, which cannot be produced by the means employed in the demonstration. Lastly, we may adopt the method of Vesalius, who filled the third ventricle with a coloured liquid, which soon reached the pituitary body. The same experiment succeeds still better with mercury. Nevertheless, I ought to state, that in two cases of dropsy of the third ventricle, no fluid escaped from the infundibulum when it was cut across. It is easy to show the structure of the infundibulum. A fibrous and vascular mem- brane, continuous with the pia mater, forms its external covering, and this is lined by a thin layer of gray matter, which is continuous with that of the floor of the third ven- tricle. This gray matter forms a solid cord when the infundibulum is not tubular. The pituitary bodyi is a small body, weighing from five to ten grains, which occupies the sella turcica, or supra-sphenoidal fossa (appendice sus-sphenoidale du cerveau, Chauss. ; hypophysis, Seem.). The better to appreciate its size, it is convenient to break down, with a chisel, the quadrilateral plate which forms the posterior wall of the sella turcica or pituitary fossa, and which is itself hollowed in front, so as to increase the antero-posterior diameter of that cavity. t Enclosed in the sella turcica, the pituitary body is kept in that situation on each side by the fold of the dura mater, which constitutes the cavernous sinus, and above by a portion of the same membrane, which forms a circular orifice around the infundibulum. The coronary sinus, which is situated between the pituitary body and the margin of the sella turcica in front and behind, and the cavernous sinuses on each side, form a vascular circle around this body, but it is not bathed in the blood, as stated by some. * Ludwig, Script. Neurolog-. ; Soemmering-, De basi Encephali, p. 41. " Quibus omnibus absque partium studio rite mecuni perpensis, non potui non complecti illorum vironim sententiam, qui infundibulum, si non perfecte solidum, certe non adeo conspicuo, uti veteres opinati sunt, canali perforatum esse, censuerunt." Hunter and Cruickshank say that the infundibulum is sometimes solid, and sometimes tubular. t Not shown mfigs. 276, 282. X In order to obtain a perfect examination of the pituitary body and infundibulum, it is well to sacrifice a brain and the base of the cranium, and to remove, by a circular incision, the body of the sphenoid bone, to- gether with the corresponding part of the base of the brain. 4Z 730 NEUROLOGY. The upper surface of the pituitary body is slightly excavated, still it is not unfrequent- ly convex, so as to project more or less above the level of its fossa. On removing the pituitary body, it is seen to be formed of two distinct lobes, of which the anterior is the larger, while the posterior occupies the small cavity in the quadrilat- eral plate. These two lobes have been very well described by the brothers Wenzel ; they are not of the same colour, the posterior lobe being grayish white, like the gray substance of the brain, and the anterior yellowish gray. If the anterior lobe be pressed between the fingers, a yellowish-white pulp escapes from it, very nearly resembhng mixed plaster of Paris. An antero-posterior section of the pituitary body shows, also, that the two lobes are perfectly distinct, being separated by a fibrous layer. They are provided with a great number of small vessels. It has been stated, but not proved, that the infundibulum contains two canals, one for the an- terior, and the other for the posterior lobe. It is extremely rare to find any hard con- cretions in the pituitary body like those met with in the pineal gland. It is, perhaps, not uninteresting to remark, that the pituitary body is most highly de- veloped in fishes, in which animals it forms a true lobe ; and that it is proportionally more developed in mammalia, birds, and reptiles, than in the human subject. It is hol- low in all the lower animals. It is larger at the fourth, fifth, and sixth months of foetal life than after birth, and con- tains a cavity which communicates with the third or middle ventricle. I once found a considerable cavity in the pituitary body of an adult. The functions of the pituitary body are enveloped in the greatest obscurity. Its con- stancy in all vertebrated animals and its great vascularity are sufficient evidence of its importance. It certainly communicates with the third ventricle, but for what purpose 1 Does it pour a peculiar fluid into that cavity, or does it absorb a portion of the ventricu- lar fluid 1 Whatever may be the use of the communication just alluded to, the pituitary body does not communicate directly with the venous sinuses around it : it is not a lym- phatic gland, as maintained by Monro ; nor is it a nervous ganglion of the great sympa- thetic, as some have recently conjectured, because they fancied they saw some very fine nervous filaments anastomosing upon it. The branches of the fifth and sixth nerves, which Litre and Lieutaud say they have seen penetrating this body, have not been de- monstrated. The Anterior Part of the Floor of the Third Ventricle. The anterior part {in, fig. 282) of the floor of the third ventricle, which cannot be well seen until the commissure of the optic nerves is turned backward, forms -an inclined plane directed downward and backward. It consists of a fibrous layer, which is contin- uous with the neurilemma of the optic nerves ; and of a very thin, semi-transparent, but very strong corneous layer (lamina cinerea), from which prolongations are given off to the upper jurface of the optic commissure, and continued upon the optic nerves : these prolongations might be called the gray roois of the optic nerves. On dividing this horny layer, the third ventricle (Z) is laid open ; and it is seen that this layer forms a part of the general system of gray substance, which, on the one hand, is prolonged upon the lat- eral wall of the third ventricle, and surrounds the anterior pillars of the fornix, and, on the other, is continuous with the tuber cinereum, above the optic commissure. The Reflected Portion of the Corpus Callosum. In front of the anterior part of the floor of the third ventricle is a transverse white mass, which is nothing more than the fore part (e to m) of the reflected corpus callosum. Terminating at this cross tract are two white fasciculi, which commence on each side at the point where the corresponding fissure of Sylvius meets the great transverse fis- sure of the brain ; they then pass inward and forward, along the outside of the optic tracts, form the lateral boundaries of the anterior part of the floor of the third ventricle, and terminate by becoming appUed to, but not blended with each other, behind the re- flected portion of the corpus callosum. Vicq d'Azyr has described these bands as the veduncles of the corpus callosum. The Anterior and Inferior Part of the Longitudinal Fissure. This {x, fig. 276) is situated in front of the reflected portion of the corpus callosum, and can only be seen in its entire extent after the removal of a very dense fibrous layer which connects, sometimes very firmly, the back part of the right and left anterior lobes of the cerebrum. Not unfrequently one of these lobes is seen to encroach upon the oth- er : the falx cerebri, which is very narrow in front, occupies only a very small portion of this fissure. All the parts belonging to the median region of the base of the brain, which we have hitherto described, are situated in front of the pons Varolii ; those which remain to be examined are placed behind it : they are, counting from behind forw^ard, the back part of the longitudinal fissure, the posterior extremity of the corpus callosum, and the great horizontal or transverse fissure. ■yHE BASE OF THE BRAIN. 731 The Back Part of the Longitiullnal Fissure. This is bounded in front by the posterior extremity of the corpus callosum (/) ; and as that extremity is at a greater distance from the back of the cerebrum than the anterior extremity of the corpus callosum is from the front of the brain, it follows that the back part of the longitudinal fissure is of much greater extent than the forepart (see figs. 277, 282). Moreover, this part of the fissure is free throughout its whole extent, for it is en- tirely occupied by the base of the falx cerebri, while the fore part is only partially filled with the apex of the falx : it might even be said that the posterior lobes have a tenden- cy to separate from each other in this situation. The Posterior Extremity of the Corpus Callosum, and Middle Portion of the Great Trans- verse Fissure. The posterior extremity (f,fig. 282) of the corpus callosum is named the hourrelet* in consequence of its being so much enlarged. This enlarged extremity, which we shall afterward find is continuous with the posterior pillars of the fornix, constitutes the up- per border of a fissure (r), the lower border of which is formed by the tubercula quadri- gemina {f g). The pia mater (r to near k) enters at this median fissure, and forms the velum interpositum, or tela choroidea : in this situation, also, is found the conarium or pi- neal gland ; and it is here that Bichat described the orifice of his arachnoid canal. This median fissure becomes continuous with a lateral fissure on each side, so as to form the great transverse cerebral fissure. The Great Transverse Cerebral Fissure. The great cerebral fissure {Bichat), or the great transverse or horizontal fissure, follows a semicircular direction, having its concavity directed forward ; it commences at the fis- sure of Sylvius on one side (Ji,fig. 276 ; above 2, fig. 282), turns round the opposite cere- bral peduncle, and ends at the opposite Sylvian fissure. The peduncle of the cerebrum and the optic thalamus may be regarded as forming the root of each cerebral hemisphere. Now the lateral part of the great transverse fissure passes round the posterior half of this root, because it is in this situation that the cor- responding cerebral hemisphere is turned inward upon itself It is this reflected and concave surface of the hemisphere that forms the outer border of the corresponding lat- eral portion of the transverse fissure, while the optic thalamus forms its inner border. This fissure communicates directly with the inferior cornua of the lateral ventricles, and through it the pia mater enters those ventricles, to form the interjialpia mater of the brain. The Lateral Regions of the Base of the Cerebrum. The base of the cerebrum is divided on each side into two lobes, an anterior and a posterior, separated by X\\e fissure of Sylvius. i The Fissure of Sylvius. This is a fissure of considerable size (grande scissure interlobulaire, Chauss.), which commences at the corresponding anterior extremity of the great transverse fissure, with which it forms an obtuse angle. At the point where they meet is found a white sub- stance,t perforated with large openings for bloodvessels ; this Vicq d'Azyr has named the anterior perforated substance ; it is the locus perforatus anterior (h). The fissure of Sylvius (y, fig. 276) is directed outward, and describes a slight curve, having its convexity turned forward : it corresponds to the posterior border of the lesser wings of the sphenoid bone, which are received into it. The fissure of Sylvius cannot be properly examined until both the arachnoid and pia mater have been removed. It is then found to be very deep ; it is seen that the middle cerebral artery runs along the bottom of it, that the pia mater lines it throughout, and that it soon divides into two branches, of which the anterior is the smaller, and contin- ues in the original course of the fissure ; while the posterior, which is of much greater extent, passes upward and backward, along the convex surface of the hemisphere, and terminates after proceeding a variable distance ; the interval between these two second- ary furrows is occupied by a sort oi islayid (insula, Reil), which might be called the lobule of the fissure of Sylvius, or the lobule of the corpus striatum. This lobule is of a triangular form, having its base directed upward and its apex do\vn- ward ; it is marked by certain small superficial convolutions, which radiate from below upward. It will be found immediately that this lobule corresponds to and is moulded upon the corpus striatum, which is sometimes so large as to push the lobule beyond the fissure, so that it reaches the surface of the brain, and appears to belong to the ante- rior lobe. The Anterior and Posterior Lobes of the Cerebrum. Several anatomists describe three lobes in each hemisphere upon the base of the brain, * Cushion, thick border. t [Three, according to other anatomists; an anterior (a, fig. 276), a middle (c), and a posterior (b) ; the anterior separated from the middle by the fissure of Sylvius (j/), the posterior resting on the cerebellum, or, rather, on the tentorium.] J [Light gray,] 733 NEUROLOGY. namely, an anterior (a), a middle (c), and a posterior (b) ; but there are only two : an ante- rior (a), which rests upon the orbital plate of the frontal bone, is moulded upon its irregu- larities, and is received into the concavity of that bone ; and a posterior (c b), which rests upon the corresponding sphe no-temporal fossa and the tentorium cerebelli. The an- terior third of this posterior lobe, or the portion which corresponds to the spheno-tem- poral fossa, is convex, and projects from six to nine lines below the level of the inferior surface of the anterior lobe. The posterior two thirds are slightly concave ; they corre- spond to the tentorium cerebelli, and are placed upon the same level as the anterior lobe. The convex sphenoidal portion of the posterior lobe forms what is generally called the middle lobe, and the posterior, or cerebellar portion, what is then named the posterior lobe. I believe that it is useful, in many respects, to apply the terms frontal horn (cornu fron- tale) to the anterior extremity of the cerebrum, which is received into the concavity of the frontal bone, sphenoidal horn to the anterior extremity of the posterior lobe, and oc- cipital horn to the posterior extremity of the same lobe. The Convolutions and Anfractuosities of the Cerebrum. The entire surface of the cerebrum is marked by a great number of deep, winding fur- rows, which divide it into as many oblong eminences, turned in different directions, and themselves subdivided by secondary furrows. These eminences have some resemblance to the convolutions of the small intestine, and have been named, on this account, convo- lutions, gyri, meandri, processus enteroidei. The furrows by which they are separated are called aiifractuosities or sulci. A more accurate notion of the general character of these convolutions and anfractu- osities may be obtained by supposing a bladder to be expanded round a compact central mass, at a certain distance from it, and in this condition too large to be contained with- in the cranium ; and then, that by means of threads proceeding from different points of the centre, the corresponding parts of the bladder are drawn inward, so that it is folded upon itself, and can now be contained within the cranial cavity. The various winding folds and furrows produced in the walls of the bladder by drawing them from above and from all sides towards the centre, will give some idea of the arrangement of the surface of the cerebrum. Some of the convolutions and anfractuosities are constant, because their forms are de- termined by those of the central mass ; others are subject to variety, and seem to de- pend upon no determinate cause : these varieties occur not only in different brains, but also in the two hemispheres of the same brain. In this respect the human brain differs from that of the lower animals, in which the cerebral convolutions present much less variety, though they are not so constant as Vicq d'Azyr has stated. The human brain is distinguished from the brains of the lower animals, not only by its size and weight, but also by the number and size of its convolutions. Tiedemann has given excellent representations of the progressive diminution of the cerebral convo- lutions (which is accompanied by a diminution of the cerebellum) from the apes to the rodentia and edentata.* In the human subject, as in the series of lower animals, the development of the convolutions has always appeared to me to be directly proportioned to the development of the entire brain. In this point of view, as in many others, the human foetus presents a similar structure to that found in the lower animals. The furrows or anfractuosities in the brain of the human foetus at the fifth month are neither deeper nor more numerous than those in the brain of the rabbit ; and it is important to study these primitive furrows, because they correspond to certain anfractuosities which ultimately regulate the whole system of con- volutions. Thus, at the fifth month, the great anfractuosity, which is called the fissure of Sylvius, exists, but its borders are apart from each other ; the island of Reil, or the lobule of the corpus striatum, is found upon the surface of the brain, and there is a lon- gitudinal furrow at the lower and back part of the internal surface of each hemisphere , it corresponds to the occipital prolongation or posterior cornu of the lateral ventricle ; there is also a furrow above the corpus callosum ; and, lastly, the furrow of the olfactory nerve is visible. At birth, all the convolutions exist, but they are not completely devel- oped until about the age of six or seven years. It is impossible to determine the number of the convolutions, for they have no appre- ciable limits •, and although some of them end betvi^een two adjacent ones, it is easy to see that this termination is merely apparent, and that near the point where it seems to take place, the convolution is continued into another without any line of demarcation. The ancient comparison, therefore, between the convolutions of the brain and those of the intestines, not only applies to their direction, but also to their continuity. There are several orders of convolutions. In fact, simple convolutions are seen to be divided, excavated, and furrowed, more or less deeply ; but there are no regular and con secutive subdivisions, as in the laminae of the cerebellum. Vertical sections made in * [See also Leuret's figures in the work already referred to, in which will be fdund a comparative view of the number and arrangement of the convolutions of the brain in man and mammalia] CONVOLUTIONS AND ANFRACTUOSITIES OF THE BRAIN. 733 different directions will show the arrangement of the convolutions much better than the most careful observations of the external surface of the brain. Each convolution presents to our notice two surfaces, a base or adherent harder, and a free border. The surfaces of the corresponding convolutions are moulded upon each other, and separated by a duplicature of the pia mater. The base or adherent border of each convolution is continuous with the central portion of the hemisphere (see section, fig. 211). The/r«e border is slightly rounded, so that between any two contiguous convolutions there is a small groove, which is very distinct in cases of purulent infiltrations or depo- sitions of lymph in the sub-arachnoid cellular tissue. At the points where these convolutions meet, a triangular depression is observed. These spaces are smaU in the natural state, but become very evident in cases of atrophy of the convolutions. The free border of some convolutions is frequently marked by an oblong depression or groove, varying in depth and extent, and following the direction of the convolutions ; these depressions are sometimes sharp, and radiate into three or four branches ; at other times they are superficial, or, lastly, deep and narrow. The arteries and veins which pass over the free borders of the convolutions form grooves upon them of various depths. The free borders of most of the convolutions generally reach the surface of the brain ; but besides the secondary convolutions, several of which remain concealed throughout their whole length, between two adjacent convolutions, there are some principal convolu- tions, which descend at one of their extremities between two adjacent convolutions ; and there are others, again, which are depressed at one or at several points of their extent. The depth of the convolutions varies from ten to fourteen lines, but it is extremely variable in different individuals ; moreover, there are perhaps not two convolutions, nor two parts of the same convolution, which correspond in thickness in the same brain ; some are considerably swollen, while others are narrow ; there is almost always an en- largement at the point where two convolutions become continuous. Eustachius and Vieussens have erred, then, in representing all the convolutions as perfectly similar. It would be undoubtedly curious to describe minutely all the convolutions. Vesalius, who appears to have entertained the idea of so doing, likened the appearance of the sur- face of the brain to those irregular forms which are traced by unskilful painters in de- lineating clouds. Vicq d'Azyr made an unsuccessful attempt to elucidate this subject ; Gall and Spurzheim, who were interested in giving a minute description of each convo- lution, abandoned the task ; I have myself attempted, and so has Rolando, to describe and name some of them. The description, however, to be understood, would require the assistance of figures ; I shall, therefore, content myself with noticing, in this place, the most important convolutions upon the internal surface, upon the inferior surface, and upon the external surface, or convexity of each hemisphere. Convolutions and Anfractuosities upon the Internal Surface. The convolution of the corpus callosum is one which predominates over all those of the internal surface of the hemisphere ; it is that which embraces the corpus callosum, and hence its name. It commences in front, below the reflected extremity of that body, to which it adheres, passes forward and upward, turns round its anterior extremity, then extends backward, and having reached beneath the posterior extremity of the corpus callosum, continues its course, and is arranged, in a manner to be presently described, upon the lower surface of the cerebrum. It is narrow at its anterior extremity, which Rolando regards as the principal root of the olfactory nerve ; it increases in size as it proceeds, and opposite the middle of the corpus callosum it is elevated like a crest, becomes much broader, and is marked by sev- eral furrows, of which some are superficial and others deep. The circumference of this broad crest is divided into several branches, which become continuous either with the superior convolutions of the convex surface, or with the posterior and superior convolu- tions of the internal surface of the hemisphere. Vicq d'Azyr first pointed out this crest of the convolution of the corpus callosum, and it was named by Rolando processo enter- oido cristato. The internal convolution of the anterior lobe is eccentric in reference to the one just de- scribed, upon which it is moulded, a deep anfractuosity intervening between them. It is very large at its origin in front of the fissure of Sylvius ; it forms the internal part of the anterior lobe of the cerebrum, and having arrived in front of the crest of the convolution of the corpus callosum, it passes upward, and becomes continuous with the convolutions of the convex surface of the hemisphere. This convolution is divided throughout its entire extent by a secondary anfractuosity, which is at first straight, and then sinuous. Convolutions and Anfractuosities of the Digital Cavity. A very deep longitudinal furrow, which corresponds to the digital cavity of the lateral ventricle, and, like it, constantly exists, extends from the convolution of the corpus cal- 734 NEUROLOGY. losum, near the posterior extremity of that body, directly backward along the posterior lobe of the brain, which it divides into a superior and inferior portion. This anfractU' osity of the digital cavity forms a division between the internal and inferior surfaces of the hemisphere. The convolutions of the digital cavity are the two longitudinal and tortuous convolu- tions which bound this anfractuosity ; the upper convolution belongs to the internal sur- face of the hemisphere, while the lower one forms part of the inferior surface. Convolutions and Anfractuosities upon the Inferior Surface. The great anfractuosity, called the fissure of Sylvius, divides the convolutions of the inferior surface into those of the anterior and those of the middle and posterior lobe. The convolutions of the anterior lobe constantly found are, the two small, straight, longi- tudinal convolutions which bound the groove of the olfactcry nerve (I, fig. 276), and the flexuous convolution, which extends obliquely forward and outward, along the border of the fissure of Sylvius, and is continuous behind with the external straight convolution of the olfactory nerve. The small convolutions and intervening anfractuosities are very irregular, and differ in different individuals, and even on the two sides in the same individual ; into the de- pressions formed between these convolutions are received the prominent ridges seen upon the orbital plate of the frontal bone. The Convolutions of the {Middle and) Posterior Lobe. — The convolution which runs along the great transverse fissure is the continuation of the convolution of the corpus callosum, and terminates in front by an unciform enlargement, which corresponds to the dilated extremity of the cornu Ammonis ; it forms the outer boundary of the great transverse fissure. The convolution of the corpus callosum and its continuation, viz., that of the transverse fissure, represent an ellipse, which is broken only at the fissure of Sylvius. On the outer side of this convolution is a longitudinal anfractuosity, which corresponds to the lower wall of the inferior cornu of the lateral ventricle. This anfractuosity is bounded by certain longitudinal convolutions, all of which pro- ceed from the convolution of the transverse fissure, and are remarkable for their size and windings. The most internal of these convolutions forms the lower boundary of the anfractuosity which I have said corresponds to the posterior cornu of the lateral ventricle. From the anterior part of the convolution of the transverse fissure some extremely flexuous convolutions proceed from behind forward, assist in forming the sphenoidal horn (point of the middle lobe), and become continuous with the convolutions of the ex- ternal face of the hemisphere. Convolutio7is and Anfractuosities of the Coiivex Surface. The convolutions upon the convex surface of the hemisphere are, undoubtedly, the most complicated ; on separating the borders of the fissure of Sylvius, within which the island of Reil is contained, it is seen that the fissure is triangular, and presents three sides : an inferior border, formed by the external convolution of the anterior lobe of the cerebrum ; a posterior border, directed very obliquely upward and backward, which ap- pears to receive all the occipital convolutions, and consists of a very tortuous convolu- tion ; and a superior border, also consisting of a very winding convolution, in which the majority of the superior convolutions terminate. The convolutions upon the convex surface of the brain may be divided into the frontal, the parietal, and the occipital. The frontal convolutions are three or four in number, and are directed from before back- ward. The parietal convolutions are three in number ; they pass in a serpentine direction from within outward, and become continuous with the convolution which forms the su- perior border of the fissure of Sylvius. The occipital convolutions are directed from before backward, and proceed either from the posterior parietal convolution, or from the pos- terior border of the fissure of Sylvius. The occipital convolutions are the narrowest and the most sinuous of all, so that the sides of the sinuosities of each convolution are in mutual contact in the greatest part of their extent, and touch the adjacent convolutions only at the points at which they are bent.* The frontal convolutions are also very flexuous, and have similar characters to the occipital, but not so distinctly marked. They are larger than the occipital convolutions, but smaller than the parietal, which are, moreover, less tortuous than either of the others. The unusual details with which I have described the convolutions can only be justified by the importance which has recently been attached to them. In the preceding descrip- tion the following points have been noticed : Their general disposition, their windings, and their mutual adaptation ; their continuity, and the impossibihty of drawing any pre- cise limits between them ; their general configuration, according to a common type, and the want of uniformity in their details, not only in different brains, but also in the oppo- * In senile atrophy, the occipital convolutions are chiefly affected. FUNCTIONS OF THE CONVOLUTIONS AND ANFRACTUOSITIES. 735 site hemispheres of the same brain ; their variable dimensions in different individuals, both in respect of depth and width, these being alM^ays directly proportioned to the size of the cerebral hemisphere : the individual differences both in the size of the brain and in that of the convolutions are very great.* We have also seen that the internal surface of the cranium is exactly moulded upon the surface of the brain, the digital impressions in the cranial bones corresponding to the convolutions, and the ridges or eminences to the small spaces intervening between the free borders of the convolutions. Functions of the Convolutions and Anfractuosities. • The convolutions and anfractuosities render the surface of the brain of much greater extent than it would otherwise have been. According to Vesalius, they are of use in multiplying the surface, through which the bloodvessels carry nutritious matter into the, interior of the organ, t The opinion that the anfractuosities and convolutions are intended to increase the surface has been lately revived ; but the supposed object of this increase is very differ- ent from that stated by Vesalius : thus, it has been agreed that, as there is an undoubt- ed analogy between electrical phenomena and those manifested by the nervous system, and as electrical phenomena are developed, not in proportion to the quantity of matter concerned, but in proportion to the extent of surface, so the energy of the brain's action may be in a direct ratio with the extent of its surface. In support of this opinion, the phenomena of arachnitis are quoted, in which disease delirium more frequently occurs than in inflammation of the cerebral substance itself. Allusion is also made to the folds observed in the retinae of birds, which greatly increase the intensity of vision : M. Des- moulins, who is a principal supporter of this theory regarding the use of the convolu- tions, states that he has observed these folds to disappear in birds which had been kept in the dark, in the same way that the cerebral convolutions become atrophied, either from the continued absence of all cerebral excitement, or from any other cause of intel- lectual weakness. The anatomists and philosophers of antiquity, considering that the convolutions were more highly developed in man than in the lower animals, concluded that the intellectual superiority of the former was owing to this circumstance. Such was the opinion of Erasistratus, facetiously refuted by Galen. t Gall and Spurzheim have recently revived this old opinion, and assuming, with some philosophers, the existence of a plurality of mental functions, they have arrived at the conclusion that there is also a plurality of material instruments or organs, by which those functions are performed. These material organs are supposed by them to be the convolutions, upon which they accordingly placed numbers corresponding to the differ- ent mental faculties admitted by their philosophy : the difficulty was to settle on the number of primitive mental faculties and their corresponding organs. According to Gall and Spurzheim, the highest intellectual faculties of man are seated in the anterior lobes of the cerebrum. On the other hand, from an examination of the brains of fifty insane patients, M. Neu- mann has been led to think that the occipital portion of the cerebrum is the seat of in- telligence : this opinion derives some support from a fact which I have myself often ob- served, viz., that atrophy of the brain of old persons in insanity affects the occipital more than the frontal convolutions ; and also by the fact, that, as we descend in the ani- mal series, the posterior part of the brain is observed to be the first to diminish, and then entirely to disappear. It is unfortunate for the system of Gall that the convolutions form a continuous whole, and are not separated into distinct organs ; and it is also unfortunate that, upon the base of the cerebrum, and upon the internal surface of each hemisphere, there are convolu- tions as distinctly marked as those upon the convex surface ; and yet, in the system of Gall, the convolutions upon the base and internal surface of the hemispheres have been, so to speak, disinherited ; for all the mental faculties have been located by him in the convolutions of the convex surface. The Internal Structure of the Cerebrum. In order to make as complete an examination of the internal conformation of the brain ^as is possible in the actual state of science, it should be prosecuted by means of sections * Comparative anatomy fully confirms this fact : the convolutions of a small hemisphere are very slightly developed, and they do not exist at all when the hemispheres are very thin, as in birds. t The substance of the brain, says Vesalius, is not firm enou^^h for the arteries and veins to traverse it with impunity ; on the other hand, it is so thick that bloodvessels distributed over its surface would not have been sufficient to nourish the entire mass ; and, therefore, nature has provided certain deep and winding furrows upon the brain, into which the pia mater can penetrate, so as to convey to the deep-seated parts the materials for their nutrition ; for the same reason, the cerebellum has been divided into laminae and lamelhc. Vesalius even states that the division of the cerebrum into two hemispheres is for no other purpose (Ub. vii., cap. 4, p. 542). t " Quum asini etiam admodum multipliciter cerebrum habent complexum quod deceret, quantum ad mo- rum ruditatem attinet, omnifariam simplex et minime varium nancisi cerebrum." If this theory be true, says Galen, the ass ought to have a brain with a smooth surface, and no convolutions ; but it has numerous and deep convolutions : the intellectual faculties, therefore, are independent of the convolutions. The conclusion is not obviously contained in the premises. 736 NEUROLOGY. in diiferent directions ; by tearing the brain, and by acting upon it with streams of wa- ter ; and by dissecting brains that have been hardened by alcohol, or by being boiled in oil or in a strong solution of salt. Examination of the Internal Structure of the Brain by Sections. This mode of examining the brain was the one employed by Galen ; it was revived by Vicq d'Azyr, and is now generally adopted. By means of these different sections it is easy to study the internal conformation of the brain in its principal details. The other methods are more especially adapted for determining the connexions of the several parts of the cerebrum with each other, or with the other portions of the cerebro-spinal axis. I shall commence by an examina- tion of horizontal sections of the brain.* Horizontal Sections of the Brain. On making an incision into the brain, this organ is found to consist of two substances : a gray cineritious or cortical substance, and a ivhite or medullary substance, which is sur- rounded on all sides by the gray.t First Section. — A horizontal section, made so as to remove the ufper half of the supe- rior convolutions of the cerebrum, shows that each convolution consists of a central white portion, surrounded on all sides with a layer of gray substance ; that the gray substance is accurately moulded upon the white, the form of which determines that of the corre- sponding convolution ; that the thickness of the gray matter varies from half a line to a line and a half; and that it is far from being uniform, either in the same or in different convolutions. In judging of the thickness, it is important to have regard to the direc- tion of the section ; for it is easy to understand that an oblique section of the gray mat- ter wdl give a very different result from one made perpendicularly. The section de- scribed above also shows that the convolutions are continuous with each other, and it enables us to comprehend their irregular, complex, and sinuous arrangement better than could be done without cutting into the brain. The relative proportion of the gray and white substances in each convolution may be determined approximately by macerating a brain for some days ; the gray substance be- ing softer and more readily decomposed, is thus converted into pulp, and may be easily removed. The convolutions being thus reduced to the white substance only, appear like short, white lamellae, arising from different points of the surface of the central me- dullary mass. I estimate the gray matter at about five sixths of each convolution. Second Section. — A horizontal section made beneath the base of the convolutions of the convex surface of the hemispheres presents an appearance like that of a geographical chart of a deeply and irregularly in- dented coast ; an appearance which cannot be described without fig- ures. It consists of a central mass of medullary substance, which is narrowed like an isthmus behind : extending from this central mass are certain prolongations, which may be divided into several orders, and which are themselves subdivi- ded, so as to form the medullary centre of each convolution. Third Section. — A horizontal sec- tion, made on a level with, or, rath- er, just above, the corpus callosum, displays a great medullary centre in each hemisphere (centre medullaire hemispheral ; centrum ovale minus ; acb, ac b, fig. 277). The two centres of the opposite sides, together with the corpus cal- losum {d d), form the centrum ovale of Vicussens. The centrum ovale of Vieussens is contracted in the middle line, where it is formed by the corpus callosum, but is much larger in each hemi- sphere. The anfractuosities by which the circumference of this section is indented are seen to be deeper on the outside and behind, than on the inside and in front. * The sections should be made with a very sharp instrument, a razor, for example. t See note, p. 701. THE CORPUS CALLOSUM. 737 By the three horizontal sections just described, it is shown that eacti convolution (// /) consists of a white, central portion, surrounded by a thick layer of gray substance, having a precisely similar shape ; that it is the gray matter which predominates in the convolutions ; that the central portions of all the convolutions are continuous with each other, and form the most complicated windings ; that they all rest upon a hemispherical central mass, which becomes larger and larger towards the corpus callosum, on a level with which it attains its greatest dimensions ; that the centrum ovale of Vieussens, which, however, is not oval, represents the largest medullary surface of the brain, and might be regarded as a centre, from which all the radiations that enter the convolutions are given off in one direction, and, in the other, all those which establish connexions be- tween the brain and the other parts of the cerebro-spinal axis ; lastly, that the centrum ovale and the convolutions are always developed in a corresponding ratio. The Corpus Callosum. If, when the brain is resting upon its base, the two hemispheres be drawn asunder, a transverse white band is seen at the bottom of the longitudinal fissure, extending from one hemisphere to the other, and connecting them together, and forming their commis- sure : this band is the corpus callosum* (mesolobe, Chatissier ; commissura cerebri mag- na, maxima, Reil, So^rnmeritig, d d). On removing the upper part of the two hemi- spheres by a horizontal section made about a line or two above the corpus callosum, it is seen that each hemisphere encroaches upon the corpus callosum, and overhangs it without adhering to it : the interval between the hemisphere and the corpus callosum has been improperly termed the ventricle of the corpus callosum. But there is no cavity here, nor is there a smooth exhalant and absorbing surface ; it is merely an anfractuos- ity, separating the corpus callosum from the convolutions, and lined by the pia mater, like all other anfractuosities. On continuing to remove successive portions of the hem- isphere, it is found that it can be separated without any laceration from the corpus cal- losum, much farther than the point at which the pia mater is reflected, and that the hemisphere and corpus callosum are simply in contact with each other ; the fibres of the hemisphere are seen to be longitudinal, while those of the corpus callosum are transverse. From this observation, it follows that the middle or free portion of the corpus callo- sum (shown in^^. 277) is but a small part of that body. The corpus callosum reaches much nearer to the anterior (x) than to the posterior (y) extremity of the cerebrum, being an inch and some lines distant from the former, and from two to three inches from the latter. Its length is about three inches and a half; it is broader behind than in front ; its breadth behind varies from eight to ten lines, if we include the part which is covered by the hem- ispheres : its thickness, which can be properly shown only upon a vertical section (see fig. 282), along the middle line, is not uniform throughout ; its thickest part is at the posterior extremity ( f), which is about three lines thick : in front of this extremity it diminishes abruptly, and is scarcely a line or a line and a half in thickness (d) ; it then gradually increases I'rom behind forward, and is about two lines thick at its anterior ex- tremity, opposite the point of its reflection (e). In form the corpus callosum resembles an arch or vault, so that it would deserve the name of vault or fornix better than the part usually so called. Its vaulted form is distinctly shown upon a longitudinal vertical section {fig. 282), and at the saine time it is seen that the posterior extremity of the corpus callosum is rolled up, as !C were, so as to form an enlargement, whde its anterior extremity is merely re- flected downward and backward, and after its reflection becomes gradually thinner as it descends, and terminates in a very delicate lamella. The corpus callosum presents for our consideration a superior and an inferior surface and two extremities. The superior surface is convex, and, as it were, arched from be- fore backward {medullaris arcus) ; it has no raphe along the median line, but presents in that situation a slight groove (e, fig. 277), depending on the existence of two white Ion gitudinal tracts, one on each side the middle line, which were regarded by Lancisi as constituting a nerve, the longitudinal ?icrve of Lancisi. These tracts are subject to variations : thus, they are sometimes slightly flexuous, and contiguous to each other, and at other times they unite, and then separate. Duver- ney has described certain ash- coloured longitudinal tracts, but their existence has been denied by most anatomists. The white longitudinal tracts are intersected at right angles by transverse fasciculi, which constitute the corpus callosum. The upper surface of the corpus callosum corresponds to the hemispheres on each side ; it is free in the middle, where it corresponds to the arteries of the corpus callosum and to the free margin of the falx, which has appeared to me to approach very closely to * According- to Haller, its name is derived from its whiteness, which has been compared to the colour of a cicatrix ; according- to others, it was given on account of the consistence of this part, which has been errone- ously regarded as exceeding that of other parts of the brain 5 A 738 NEUROLOGY. the posterior extremitj" of this body, but not to touch it, so that it could not occasion any depression upon it. The inferior surface of the corpus calhsum is concave, and is free over a greater extent than the superior • it forms the upper wall or roof of the lateral ventricles (r i.fig- 278, in ^vhich figure only ihe anterior and posterior extremities, e and d, of the corpus callo- sum are left).* This surface is covered by the serous membrane of the ventricles, and, like the superior surface, it is fasciculated. Along the median line it corresponds, in front, to the septum lucidum (f, figs. 278, 282), and behind to the fornix (A-), "^vith which it even seems to be united at this point. In consequence of the somewhat regular arrangement of the fibres constituting the two posterior piUars of the fornix (r r,figs. 278, 279), which diverge in this situation, and also of that of the transverse fibres of the corpus callosum, the back part {s,fig. 279) of the inferior surface of the corpus callosum has received the names of lyra, corpus psaU hides, psalterium. The posterior extremity of the corpus callosum (bourrelet, Reil), which, as we have al- ready stated, is its thickest part, is slightly concave transversely, but presents no other notch, excepting the median depression, between the longitudinal tracts. t The anterior extremity of the corpus callosum does not terminate in an enlargement, like the posterior, but it is reflected, and embraces the anterior extremity of the corpus stri- atum : it then passes downward and backward {e.fig. 282), and terminates insensibly in front of the anterior portion (??;) of the floor of the third ventricle. Reil applies the term knee (genu) to the point of reflection, and that of beak (rostrum) to the posterior and thin extremity of the reflected portion. This reflected portion of the corpus callosum is seen upon the base of the brain, between the anterior lobes r the convolution of the corpus callosum also accompanies its reflected portion, and, instead of being merely in contact, becomes continuous with it, so that the gray matter rests immediately upon the corpus callosum. The longitudinal tracts arise from the reflected portion of the corpus callo- sum ; and the inferior peduncles of the corpus callosum (Vicq d^Azyr), already mention- ed, terminate upon this portion. The right and left borders of the corpus callosum enter deeply into the substance of the hemispheres. Beneath the corpus callosum are smiated, in the median line, the septum lucidum (t t, fig. 278), ihe fornix (k), the velum- interpositum (v, fig. 279), and the median or third ven- tricle (c to X, fig. 280) ; and at the side, the lateral rentricles (i i, fig. 278). We shall pro- ceed to examine these different parts in the above-mentioned order. To obtain a good idea of their form and relations, it is important to study them upon two brains, one rest- ing upon its convex surface, and the other upon its base. The Septum Lucidum. The septum lucidum. or transparent septum, so called because it separates the lateral ventricles from each other and is semi-transparent, is situated in the median line (sep- tum median, Chauss.). It is very well seen (f,fig. 282) when the corpus callosum has been divided longitudinally on each side of the middle line. It appears like a thin lami- na given otf from the anterior and inferior part of the corpus caUosnm. and passing ver- tically downward in front of the fornix ; it is of a triangular shape, broad in front and narrow behind ; its lateral surfaces constitute the internal walls of the lateral ventricles ; its upper border is continuous with the corpus callosum, its posterior with the fornix, and its inferior with the reflected portion of the corpus callosum in front, and with the inferior peduncles of that body farther back. Hence Vicq d'AzjT imagined that the sep- tum lucidum was a continuation of these peduncles. The septum lucidum is composed of two very delicate and completely distinct lamel- lae (t t fig. 278), between which, in fi-ont, a cavity is enclosed, containing a few drops of a serous fluid ; this small cavity is called the ventricle of the septum, the first ventricle (Wenzcl), the fifth ventricle (Cuvier), and the si^ius of the median septum (Chauss.); it is not very unfrequently the seat of dropsical effusion. I have found it filled with blood in several subjects after death from apoplexy. As to whether this ventricle of the septum communicates with the other ventricles, opinions are divided. Tarin describes a small fissure opening between the anterior pil- lars of the fornix, but the majority of anatomists have not been able to demonstrate it. It appears to me that the absence of all communication is a well-ascertained fact. Each of these lamellaj of the septum lucidum consists of a meduhary layer, covered on the outside by the membrane of the corresponding lateral ventricle, and on the inside by the membrane of the fifth ventricle. The existence of this last-mentioned membrane is proved by the smooth appearance of the ventricle, and it may be demonstrated by re- * The best mode of examining the lower surface of the corpus callosum is to view it by opening- the Tentri- cles from the base of the brain. t One is astonished to read, in Chaussier's work, that the notch of the posterior extremity of the corpus callosum is caused bv the alternate movements of elevation and depression of the brain. At each elevation, according to him, this extremity of the corpus callosum strikes against the free margin of the falx cerebri, al- though that margin is at some slight distance from it. THE FORNIX AND CORPUS FIMBRIATUM. 739 Hiovrng, in succession, layers from the outer surface of the lamella. The gray matter of the third ventricle is prolonged upon the external surface of each lamella of the septum. The Fornix and Corpus Fimbriatum. The fornix (la voute a trois piliers, k, r r, Jig. 278.) is a medullary arch, situated (i, Jig. 282) beneath the corpus callosum, ^^^ 2_y with which it is continuous behind, ^^ but which it leaves in front, and then passes perpendicularly dow^mvard, de- scribing a curve within the curvature of the corpus callosum. The interval between the anterior part of the fornix and the corpus callosum is occupied by the septum lucidum. To the term fornix, used by the older writers, the epithet a trois pliers has been improp- erly added by Winslow, inasmuch as it expresses a mere appearance ; for there are in reality /oz«- pillars, the two anterior of which are closely approxi- mated to each other, while the two posterior are widely apart. The fornix resembles an isosceles triangle {trigone cerebral), having the anterior angle very much elongated and soon bifurcated ; its posterior an- gles sudderdy diverge, pass downward and outward, and are prolonged (r ) into the inferior or reflected portions or descending cornua of the lateral ventricles, where they constitute the corpora Jimbriata (s) ; or, rather, the fornix may be said to be composed of two perfectly distinct medullary cords, which are applied ctosely to each other, become broader and flatter as they proceed backward and downward, and separate from each other opposite the reflected portions of the lateral ventricles, into which they enter. The fornix, therefore, resembles the letter X placed horizontally, the anterior limbs of which are close to each other (be- tween q q) and very short, while the posterior limbs (r r) are very long and widely apart. The term fornix is really applicable only to that portion which is applied to the corpus callosum. Red, who has described and figured this part better than any of his prede- cessors, not even excepting Vicq d'Azyr and Scemmering, calls the fornix the twain-band. The superior surface of the fornix corresponds, in the median line, to the septum luci- dum in front, and to the corpus callosum behind : on each side it is free, and forms a part of the floor of the lateral ventricles. The choroid plexuses (p p) are sometimes reflect- ed upon the surface of the fornix. In order to understand the relations of the fornix with the corpus callosum, it is ne- cessary to bear in mind that it is composed of two flat medullary bands. Now the inter- nal contiguous borders of these bands are turned upward, and adhere to the lower sur- face of the corpus callosum., so as to form a small vertical septum, which is continuous with the back part of the septum lucidum. The medullary fibres of the septum lucidum are therefore generally considered to be continuous with those of the fornix. The inferior surface of the fornix (r r. Jig. 279) rests upon the velum interpositum {v), which separates it from the third ventricle (c b x, Jig. 280) and the optic thalami {I I), the internal portion of which bodies is covered by the fornix {see fig. 278). It is upon the posterior portion of this inferior surface, where the two medullary bands of the fornix separate from each other to enter the descending cornua of the lateral ventricles, that we find that regular though variable arrangement of transverse fibres {s), abutting on certain longitudinal fibres (r r), which has been named the lyra, corpus psalloldcs or psal- terium. I have already noticed this structure, which was erroneously regarded by Gall as composed of the uniting fibres of the fornix. The edges of the fornix are thin and free, and are bordered by the choroid plexuses. The anterior pillars of the fornix {k, figs. 279, 280), which Vieussens, Tarin, and others described as arising almost indifferently either from the cerebral peduncles, or from the anterior commissure (c, fig. 280, situated in the third ventricle), can only be well seen in a longitudinal vertical section of the cerebrum made exactly in the median line. Each half of the cerebrum will contain the corresponding band of the fornix ; and it will then be seen, as was first described by Santorini, that each anterior pillar (seen below k and behind c, fig. 282) arises from the corpus albicans {z) of its own side ; hence these bodies 740 NEUROLOGY. have been called the lulls of the fornix. The whole of the white covering of each of the corpora albicantia {I, fig. 283) appears to be fomred into a thick white fasciculus or cord, which passes upward, and may be very easily traced with the handle of the scalpel through the soft gray matter which forms the inferior and anterior portion of the wall of the third ventricle. While passing through this gray matter the cord describes a curve, having its concavity turned backward, and is situated between the optic thalamus and the corpus striatum, and behind the anterior commissure {c,fi.g. 282 ; m, fig. 283) ; having emerged from the gray matter, which is still prolonged along its anterior surface and thus reaches the septum lucidum {t), the anterior pillar is reflected backward (k, fig. 283) in front of the optic thalamus, and becomes changed into a flat band {k, fig. 282), which is applied to the thalamus {I), and follows the contour of that body : at the point where the anterior pillar of the fornix changes from an ascending to a horizontal direction, it forms half a ring (situated behind and below k, fig. 282), which is completed by the an- terior part of the optic thalamus. This is the opening of the foramen of Monro, by which a communication is established (opposite q q,fig. 278) between the third and the corre- sponding lateral ventricles. The Posterior Pillars. — Having arrived opposite the back part of the optic thalamus, each of the lateral bands of the fornix, which had already been directed somewhat ob- hquely outward, passes abruptly and very obliqely outward and downward (r r) into the descending cornu (h) of the corresponding lateral ventricle, and is there divided into two parts, one of which forms the superficial medullary substance of the cornu ammonis, or hippocampus major (m), while the other follows the concave border of the hippocampus, and takes the name of corpus fimlriatwm {s), corps fra?igd, corps lorde. We shall again al- lude to these parts in describing the lateral ventricle. I have said that the anterior pillars arise from the corpora albicantia, but they have a much deeper origin, which was figured by Vicq d'Azyr, and has been still better descri- bed by Reil. According to that anatomist, they arise within the optic thalami. I have traced them much farther than Reil, as far as the tania semicircularis on each side ; or, rather, each tcenia semicircularis {?i, fig. 278), which is situated in the lateral ventricle be- tween the corpus striatum {i) and the optic thalamus (l), and which is continuous with the anterior corpus quadrigeminum or natis of its own side, becomes subdivided into two bands, which may be regarded as the roots of the corresponding anterior pillar of the for- nix. Of these two roots, one is superficial (n), and easily seen without dissection ; the other is deep-seated {v, fig. 283), enters into the substance of the optic thalamus, runs forward to the corpus albicanus (Z), spreads out and forms the surface of that body, and then curves upward to constitute the anterior pillar of the fornix {h), at the point where it emerges from the gray matter. The two bands of the fornix also receive some other white fibres, which greatly mul- tiply its connexions. Thus, as they are traversing the gray matter, the anterior pillars receive additional medullary fibres, some arising from the gray matter itself, and others firom the commissure of the optic nerves ; again, just as they emerge from the gray mat- ter to become horizontal, they receive a considerable cord, fonned conjointly by the white fibres covering the optic thalamus {g, fig. 283) by a white band, which runs longitudinal- ly along the optic thalamus, and is continuous with the corresponding peduncle of the pineal gland, and by the superficial fibres of the taenia semicircularis, of which I have al- ready spoken. These three sets of fibres form a cord of considerable size, which is bent abruptly backward, and becomes continuous with the fornix. Lastly, the fornix receives, or, perhaps, it gives origin to, the white radiated fibres of the septum lucidum. The Velum Interpositum. Beneath the fornix is situated a vascu ar memorane, a pro- longation of the external pia mater : this is the velum interposi- tum, or tela choroidea {v, fig. 279), so named by Herophilus from its tenuity, which he compared to that of the foetal membrane called the chorion. It is thus formed : the external pia mater, having arrived be- low the enlarged posterior extremity of the corpus callosum, penetrates (at r,fig. 282) into the interior of the brain between that body and the tubercula quadrigemina, and forms a sort of triangular web {v, fig. 279), the base of which is turned back- ward, and the truncated and bifurcated apex forward. The tip- per siLrface of the velum is covered by the fornix (reflected at r r), to which it transmits a great number of vessels. Its infe- rior surface forms the root of the third ventricle, and corresponds on each side to the upper and to a small part of the inner sur- face of the optic thalami (/ /). The velum is also in relation with the venae Galeni and with the pineal gland {p, fig. 282), adhering very closely to that body, and forming a nearly complete invest- ment for it, so that they are almost always removed together. THE MIDDLE OR THIRD VENTRICLE. 741 Bichat described his so-called arachnoid canal as passing beneath the velum interposi- tum. Upon the lower surface of the velum, which can only be properly examined from below, are found two small trains of red granulations, precisely similar to the choroid plex- uses of the lateral ventricles, with which they are continuous in front : they may be call- ed the choroid plexuses of the third ventricle. The lateral borders of the velum are continuous with the upper part of the choroid plex- uses (p p,figs. 278, 279) of the lateral ventricles. The anterior extremity, or apex of the velum, is bifid ; each branch of the bifurcation passes from the third into the corresponding lateral ventricle (behind k, jig. 282, opposite } q, fig. 278), behind the anterior pillar of the fornix, and constitutes the anterior extrem- ity of the choroid plexus. The velum interpositum is formed by the pia mater, supported by a tolerably strong fibrous layer. When the fornix and the velum (as in fig. 280) are removed, we arrive at a cavity call- ed the middle or third ventricle. The Middle or Third Ventricle. Dissection. — In order to expose the third ventricle from the base of the brain, the right peduncle of the cerebrum and the right corpus albicans should be separated '^' from those of the left side by a longi- tudinal section in the median line. There is another section, which I rec- ommend as exceedingly well adapted to exhibit all the parts contained in the third ventricle ; it is made from before backward, and on either the right or left side of the median line, so as to leave both of the lateral walls of the third ventricle uninjured. The third ventricle (c to x, figs. 280, 282') is situated in the median line, near the base of the brain, between the op- tic thalnii (l I, fig. 280) and in front of the tubercula quadrigemina {fg) : it ap- pears like a very narrow cavity, oblong from before backward, and of greater extent below than above ; it is not so much a cavity as a fissure between the two optic thalami. Vesalius compared this ventricle to a valley, the hills on either side of which were very closely approximated to each other, and uni- ted by a sort of bridge, represented by the commissura mollis (i). The superior orifice of the third ven- tricle is surrounded by a white rim or border (s), which forms, behind and on either side, the peduncles of the pineal gland. The lateral zcalls {I, fig. 282) are plane, smooth, and of a gray colour ; they are formed by two very distinct parts, viz., above and behind by the internal surface of the optic thalamus, and below and in front by the internal surface of a gray mass, which appears to me to deserve a particular description under the name of the gray mass of the third ventricle. That part of the internal wall of the ventricle which is formed by the optic thalamus is marked off by a horizontal groove from the part formed by this gray mass. The internal surface of this gray mass is smooth, and lined by the membrane of the ventricle. The external surface is continuous with the rest of the brain ; below, it forms the tuber cinereum. or base of the infundibulum, passes around the corpora albicantia, the anterior pillars of the fornix and their roots, is prolonged upward upon the sides of the septum lucidum, and downward as far as the upper surface of the optic commissure, the posterior border of which is imbedded in this gray mass, and receives from it a short white root on each side. The lateral walls of the third ventricle are united together, opposite the anterior part of the optic thalami, by a gray substance called the soft commissure, commissura mollis (A), the gray commissure, and also the vascular commissure of the optic thalami; it varies much in size, and is very easily torn ; but I have always found the remains of it in those cases 742 NEUROLOGY. in which it appeared at first sight to be wanting.* I regard the soft commissure as a prolongation of the gray mass of the third ventricle, and this substance appears to me to be of the same nature as the gray matter of the convolutions. The floor of the third ventricle is of greater extent than the walls of that cavity ; it is concave upon its upper or ventricular surface, and convex below. We shall divide it into three portions : the posterior portion of the floor (above n, fig. 282) is deeply grooved along the median line, forms an inclined plane sloping downward and forward, and cor- responds to the interval between the peduncles of the cerebrum ; its white colour, which is scai-eely concealed by the thin layer of gray matter upon it, contrasts strongly with the distinct gray colour of the lateral walls. The middle portion of the floor is funnel- shaped, and corresponds to the corpora albicantia {z), and to the infundibulum (s) ; it leads to the canal in the infundibulum. The ajiterior portion of the floor (w) is inclined down- ward and backward, and is formed by a very thin, semi-transparent layer of gray sub- stance {lamina cinerea), which we may call, with Tarin, the pars pellucida, and which is supported by a fibrous layer derived from the pia mater. In front, the third ventricle presents the anterior pillars {k, fig. 280, below k, and be- hind c, fig. 282) of the fornix, in front of which is situated a white cylindrical cord (c), directed transversely, and visible only in its middle portion ; this is the a?iterior commis- sure, beneath which the ventricle extends as far as opposite the posterior border of the optic commissure. Behind the anterior pillars of the fornix, and somewhat above the anterior commissure, are the two openings by which the third ventricle communicates with the lateral ventricles {foramen Monroi) ; these openings (of which one is seen be- tween b and k, fig. 282) are of an oval shape, are sometimes of unequal size, and become much enlarged in chronic effusion into the ventricles. The two divisions of the ante- rior extremity of the velum interpositum pass through these openings, to become con- tinuous (at q q,fig. 278) with the choroid plexuses. Haller erroneously regarded them as accidental ; an opinion that was founded upon several pathological observations, from which it appeared that the lateral ventricles were distented with a considerable quantity of fluid, while the third ventricle remained empty. At the back part of the third ventricle is seen the posterior commissure {z, figs. 280, 282), a transverse cylindrical cord, situated in' front of the tubercula quadrigemina, and below the commissure of the pineal gland, with which it is continuous. The posterior commissure is smaller than the anterior ; it may be regarded as a white commissure of the optic thalami, for its extremities are lost in their interior. It forms a sort of bridge above the anterior orifice of the aqueduct of Sylvius. The Aqueduct of Sylvius. The aqueduct of Sylvius, or aqueduct of the corpora quadrigemina, which was descri- oed by both Galen and Vesalius, and by the latter quite as perfectly as by the anatomist after whom it was named, is a canal which establishes a communication between the third and fourth ventricles {I v, fig. 282) — iter a tertio ad quartern ventriculum ; it passes through the isthmus of the encephalon, in the median line, below the tubercula quadri- gemina {f g). It is directed obliquely downward and backward. Its walls are dense, and lined by the membrane of the ventricles. This canal presents both on its upper and its lower wall a longitudinal groove or median furrow, bounded by two small longitudi- nal cords. The median furrow on the lower wall is continuous with the longitudinal groove of the calamus scriptorius. The brothers Wenzel have given a minute descrip- tion of these two furrows, and they have also noticed two lateral furrows. It was stated by Vieussens that the opening of the aqueduct into the fourth ventricle was provided with a valve. But his statement is at variance with the results of observation. It follows, therefore, from the preceding description, that the third ventricle has four openings, two of which communicate with the lateral ventricles, the third opens into the fourth ventricle, and the fourth (between b and x, 280) leads into the infundibulum. The third ventricle, moreover, has three commissures : one composed of gray matter, viz., the commissura mollis, or commissure of the optic thalami ; the other two of white substance, one being anterior and the other posterior. The Conarium, or Pineal Gland. The conarium, pineal gland, or pineal body, is a small grayish body ( p, figs. 280, 282) situated in the median plane, behind the posterior commissure of the third ventricle, and between the nates, upon which it rests. It is retained in this situation by two small medullary cords, which are called its ped- uncles, and by the velum interpositum, below which it is placed, and by which it is almost completely invested as with a closely-adherent sheath : the adhesion between these parts is so intimate that they are almost always removed together ; and hence some anato- mists have regarded the conarium as a dependance of that membrane, and others, who * Out of sixty-six brains of subjects of all ages examined by the brothers Wenzel, the soft commissure was found in fifty-six. It was, therefore, wanting in ten cases. The facility with which it is lacerated may have misied these industrious investigutors into a belief that its absence was more frequent than it actually is. THE CONARIUM, OR PINEAL GLAND. 743 haTe not been careful in their examinations, have declared that it is sometimes want- ing in the human subject. This body, however, always exists in man and the mamma- lia. It is wanting in birds and fishes, and in reptiles, with the exception of the tortoise, in which it is so remarkably large that it forms by itself a kind of brain. — (Desmoulins, Anoit. du Syst. Nerv., t. i., p. 211.) This body is shaped hke a cone, having its adherent base turned forward and its free apex backward ; hence its name of cojiarium ( Oribasius, Galen) ; it has also been com- pared to a pine cone, and has been named the pineal gland, or -pineal body. Its form, however, is subject to some variety ; it is sometimes spheroidal, and at other times cor- diform, from being notched at the base. The pineal body is small, being only about four lines in length, and from two to three lines wide at the base. Its size, in the animal series, does not appear to bear any pro- portion to the size of the cerebrum, or of the cerebellum, or of the tubercula quadrigem- ina, so that comparative anatomy throws no light upon this obscure subject. Neither age nor sex has any influence upon the development of this small body. Relations. — The conarium or pineal gland, enclosed in the pia mater, like the cere- brum and cerebellmn, rests upon the slight triangular depression between the nates : the venae Galeni run along its sides. When stripped of the pia mater, it is free in all directions, excepting at its base, which is connected with the encephalon by a transverse commissure, situated above the posteri- or commissure of the cerebrum, and hy four slender peduncles, two of which are superior and two inferior. The superior peduncles (s, figs. 280, 282), which are the only ones gen- erally described, form together a sort of loop, the two ends of which run along the tops of the optic thalami ; they have been named the reins of the pineal body {habena). We have already seen that they are continuous with the fornix. The inferior pcdmicles, which are distinctly seen only upon a longitudinal vertical section through the middle of the cerebrum, arise from the base of the pineal body, pass vertically downw'ard upon the back part of the internal wall of the third ventricle, and may be traced to the lower part of that cavity.* Colour and Consistence. — The reddish-gray colour of the pineal body contrasts strong- ly with the whiteness of its commissure and peduncles. The colour and consistence of this body exactly resemble those of the gray matter of the cerebral convolutions. If it be compressed between the fingers, a viscid juice exudes, and certain small concretions are found in it, which I shall notice after having described the structure of this organ. Structure. — At the base of the pineal body are seen some white or medullary fibres, which arise from the commissure and from the superior peduncles of that organ. These white fibres spread out into a tuft, and terminate abruptly. All the rest of the conarium consists of gray matter. On making a horizontal section of this body, it is sometimes found to be solid, and sometimes to be hollow, and to contain a transparent, viscid fluid. The cavity is lined by a vascular membrane, and, according to Meckel, by a layer of medul- lary substance, which I have never seen. It has been stated that it communicates with the third ventricle ; but I am inclined to beheve, with Santorini and Gerardi, that the communicating orifice admitted by some authors is the result of traction upon the base of the conarium in attempting to remove the pia mater. When the pineal body contains no distinct cavity, which is not unfrequently the case, the viscid fluid is distributed through it as through a sponge. As to the nature of this body, it appears to consist of a soft gray substance, traversed by a great number of bloodvessels, having a very close resemblance to the gray matter of the brain, but none whatever to glandular tissues. Concretions of the Conarium. — One of the most curious circumstances in regard to this body is the existence in it of certain hard concretions, which Ruysch and others regard- ed as small bones, an error which was successfully combated by Soemmering. The use of them is utterly unknown. Are these concretions constant 1 The brothers Wenzel found them wanting in six brains out of one hundred. Soemmering states that he found them in fifteen" brains, among which were some of very young infants, and he adds that they exist in the foetus before the full period. Meckel says they do not appear until the sixth or seventh year, beyond which age he always found them. These concretions sometimes form a single mass (acervulus, Soemmering), resembling a granular lump of salt ; sometimes, and most commonly, there are a great nmnber of them. They appear as aggregated granules, which the Wenzels believed to be connected by means of a proper membrane. Seat of the Concretions. — When the pineal body is hollow, they are found in its interi- or ; but when it is solid, they are situated upon the surface of this body. I have found them several times upon its peduncles. ■' Ridley describes certain white strise, arising from the pineal body, and terminating in the testes. Gall says that the inferior peduncles are directed backward, and somewhat downward, to become continuous with the subjacent white lamina. Plate xi., text, p. 223. 744 NEUROLOGY. They are of an opaline yellow colour in old subjects, and are whitish in the young'. According to Pfaff, they consist of phosphate of lime, carbonate of lime, and an animal matter. They were incorrectly regarded as morbid deposites by Morgagni, who supposed, with- out proof, that they might produce cerebral atfections of greater or less severity. Function of the Pineal Gland. — The hypothesis of Des Cartes concerning the function of this body, which was so completely refuted by Steno, is a striking example of the abuse of an imperfect knowledge of anatomy ; according to Des Cartes, the soul is seated in the pineal gland, and it directs all the movements of the body by means of the pedun- cles, which he regarded as the gubernacula or reins of the soul. M. Magendie thinks that this body performs certain functions having reference to the cerebro-spinal fluid : he has regarded it as a kind of plug, which would obstruct the orifice of communication between the third and fourth ventricles ; but, in the first place, it is completely fixed by the pia mater ; and in the second case, even if it were free, it could not in any case close the orifice alluded to. Morbid conditions of this body will perhaps throw some light upon its functions, but they have not yet been sufficiently studied. The existence of a cavity within the pineal gland, added to the fact that it is sometimes the seat of dropsy, would seem to indicate that its functions are connected with secretion. The Lateral Ventricles. Dissection. — The lateral ventricles are exposed by the same dissection as that which we have pointed out for the examination of the fornix and septum lucidum, that is to say, by removing the upper parts of the hemispheres and dividing the corpus callosum on each side of the median line (as in_^^. 278, on the left side). In order to trace the reflected portion or descending cornu, it should be laid open by cutting through its outer wall from behind forward. There is also a great advantage in studying this part of the lateral ventricles from the base of the brain. The lateral ventricles {figh, Jig. 278) are two in number ; they are much larger than the other ventricles ; are placed symmetrically one on each side of the median line ; they are separated from each other, but communicate through the medium of the third ventricle ; their upper part is nearer to the base of the brain than to its upper surface, and they approach still nearer to the base by their reflected portion or descending cornu. Each lateral ventricle commences (/) in the substance of the anterior lobe (a), a little in front of the third ventricle, and behind the anterior reflected extremity of the corpus callosum (c), by which it is bounded in front ; from this point it passes verticaUy upward and backward, describing a curve with its convexity directed inward ; having reached (r) opposite the posterior part of the third ventricle, it changes its direction, so as to turn downward and forward round the optic thalamus (l), and then terminates (h) in the substance of the sphenoidal portion of the posterior lobe [i. e., in the middle lobe] (c) be- hind the fissure of Sylvius, and, consequently, a little below and behind the point (/) at which it commences. At the point of its reflection it also sends a prolongation (g) backward into the occipital portion of the posterior lobe (b). From this it will be under- stood why each lateral ventricle has been compared to a capital italic X turned upside down, and why the cavity is said to have three cornua, viz., an anterior or frontal (/), 071 inferior, descending or sphenoidal (h), and a -posterior or occipital cornu (g) ; on this ac- count the lateral ventricles are frequently denominated ventriculi tricornes. It is also seen that the ventricles are applied to each other at their anterior extremi- ties, but diverge behind like the limbs of the letter x. The general form of the lateral ventricles is very well shovsm upon a longitudinal sec^ tion of the cerebrum through the median line ; each of these ventricles is then seen to be nothing more than an elliptical canal or passage, \vhich runs around the large ellip- soid mass formed by the optic thalartius and corpus striatum. This elliptical canal is only interrupted below and in front opposite the fissure of Sylvius. Anatomists describe in each lateral ventricle a superior portion, an inferior portion, and a posterior portion or digital cavity. The Superior Portion of the Lateral Ventricle. This portion, called the body of the ventricle (?'), is broader in front than behind, and presents for our consideration a superior, an inferior, and an internal wall. The superior vrall, or the roof, is formed by the under surface of the corpus callosum. The inferior wall, or the _/Zoor, is formed by the ventricular surfaces of the corpus striatum {i) and optic thalamus (1) ; between these two bodies are found the lamina cornea and tccnia semicircular is (n). The Corpus Striatum. — When examined from the lateral ventricle, each of the corpora striata {i i,figs. 278, 280) appears like a pear-shaped or conoidal eminence, having its larger end turned forward, and its other end, which is very narrow, prolonged backward, into the reflected portion of the ventricle. Its gray colour contrasts with the whiteness of the surrounding parts. Its free surface is covered by the lining membrane of the ven- tricles, and is very regularly marked by certain large veins which run across it. THE LATERAL VENTRICLE. 745 The ventricular surface of the corpus striatum forms only one portion of this body, which has received its name from the white bundles or striae which traverse the gray matter, of which it is principally composed. The corpus striatum, considered as a whole, is an ovoid gray mass, lodged in a deep excavation formed opposite the insula or island of Reil, which is situated in the fissure of Sylvius, and which I propose to name the lohde of the corpus striatum. It will be seen, hereafter, that the corpus striatum is covered on the outer side by the convolutions of the insula, that it corresponds on the inner side with the optic tlialamus and the gray matter of the third ventricle, and that it is exposed below, at the back part of the ante- rior lobes of the brain, behind the convolutions which form the sides of the furrow for the olfactory nerve. The optic thalami (/ /, fig. 280), which, as we have already seen, constitute the lateral walls of the third ventricle, form also, by their upper surface, a part (/, fig. 278) of the floor of the corresponding lateral ventricle ; this surface, which is oblong from before backward, commences about six lines from the anterior extremity of the lateral ventri- cle : it is covered by the choroid plexus {p) and the fornix {k) : the corresponding ante- rior pillar of the fornix turns round its anterior extremity, and the interval between the pillar and the thalamus forms the opening of communication between the third and the corresponding lateral ventricle. The brownish-white colour {couleur cafe au lait) of the optic thalamus distinguishes it from the corpus striatum, which lies along its outer side, tlie lamina cornea and the taenia semicirciilaris marking the limits between these two bodies. The lamina cornea is a thick, semi-transparent band, of a horny aspect, which was com- pared by Tarin to a plate of horn, and which appears to be nothing more than a thick- ened portion of the lining membrane of the ventricle. Beneath and protected by it is found the vein of the corpus striatum, which receives the venous branches already de- scribed upon the surface of that body. Beneath the vein is seen a small, white, linear band {n), to which Willis first directed attention as the limbus posterior, and which is now called the tcenia sermcircularis. I would observe, that the lamina cornea and the tajnia semicircularis are two very distinct structures, whicli most anatomists have erroneously confounded. More deeply, the limits between the corpus striatum and optic thalamus are marked by a white layer, described by Vieussens as the geminum centrum semicirculare, or double semicircular centre. The lateral portion of the fornix and the choroid plexus (see fig. 278) must also be re- garded as entering into the formation of the floor of the lateral ventricle. This lateral portion of the fornix resembles a band apphed upon the optic thalamus, but separated from it by a fissure through which the choroid plexus becomes continuous with the ve- lum interpositum :* the choroid plexus runs along the free edge of this band, and is some- times turned up on to its upper surface. The internal wall, or septum of the lateral ventricles, is much deeper in front, where it is formed by the septum lucidum, than behind, where it consists of a small vertical portion of the fornix, with which it terminates. We ought also to regard as forming a part of the septum of the lateral ventricles a prolongation on each side of the gray matter of the third ventricle, which passes round the corresponding anterior piUar of the fornix, and upon the lower part of the septum lucidum. The Inferior or Reflected Portion of the Lateral Ventricle. Dissection. — As the reflected portion or descending cornu belongs to the base of the brain, it is well to place the brain upon its convex surface, and then proceed to open it. This cornu may also be reached from the great transverse fissure, by first removing the pia mater which enters there, and then partially dividing the lower wall of the cornu from the fissure of Sylvius backward, and turning back the lower wall on itself The descending cornu {h,fig. 278) of the lateral ventricle has two walls, a superior and an inferior. The superior wall {b, fig. 281) is concave, and, being moulded upon the pes hippocampi or cornu ammonis {m), which forms the inferior wall, is named the sheath of the pes hippocampi. Upon the inferior wall are found the pes hippocampi or cornu ammonis, the corpus fim- bria turn, the fascia dcntata, the great cerebral fissure, and the reflected portion of the choroid plexus. The cornu ammonis or ram's horn, pes hippocampi,f or foot of the sea-horse, is a conoidal eminence (m,fig. 278)t curved upon itself, and having its larger end turned forward, and * [A comparison oi figs. 278 and 279 will facilitate the comprehension of this statement; in the latter /g-. the fornix is reflected backward, and the continuity of the choroid plexus (p) with the velum (f) is shown.] t [The term pes hippocampi is generally applied to the anterior part only of this structure, the whole being usually called hippocampus major. X I have not found, like Treviranus, the medullary substance of the anterior ex'tremity of the cornu ammo- nis either continuous or communicating in any manner with the external root of the olfactory nerve ; I cannot, therefore, admit that the functions of the cornu ammonis have any relation with those of the nerves in ques- tion. Treviranus believes that it assists in the remembrance of olfactory impressions. It is unfortunate for 5B 746 ■ NEUROLOGY. its small end backward. Its concave border, which is directed inward and forward, is bounded by a narrow, thick, and dense band, which forms a continuation of the posterior pillar of the fornix ; this is the tmiia, hippocampi, so improperly named the corpus fimhri- atum, or fringed body (s). On raising up the taenia hippocampi {s,Jig. 281), there is seen beneath it a band of F!> 281. gray matter (d), which runs along the inner border of the cornu am- monis : this gray matter, which is, as it were, crenated by transverse furrows, has been well described by Vicq d'Azyr, under the name of corps godronne, or fascia, dentala. To obtain an accurate idea of the cornu ammonis, it is necessary to examine vertical sections of it, as was done by Vicq d'Azyr, who has given very good figures of such sections : it is then seen (as in fig. 281) that the hippocampus major (?n) is formed by a reflection of the hemisphere inward upon itself, as the brothers Wenzel have very well shown ; and that it is composed of a convolution doubled or turned upon itself like a horn, so that the white convex part expands in the interior of the lateral ventricle, while the gray concave part is upoa the surface of the cerebrum.* The surface of a vertical section of the hippocampus major also pre- sents a white spiral line (below m), which is the section of the white covering of this eminence, and a rather thick gray layer (a), which is subdivided into two smaUerlayers by a white streak (c) ; all these are arranged in a spiral manner. The white layer which forms the covering of the cornu ammonis is continuous, on the one hand, with that which lines the rest of the lateral ventricle, and on the other (by means of the corpus fimbriatum, s) with the corpus callosum and the fornix. Not un- frequently a second pes hippocampi is found on the outer side of the first, to which it is concentric ; it is called pes accessorius {emincntia collateralis). Meckel erroneously re- gards it as the result of an arrested development. The inferior wall of the descending portion of the lateral ventricle farther presents for our consideration, The reflected or descending portion of the choroid plexus (see fig. 278) ; and also the great trajisverse fissure, through which the choroid plexus becomes continuous (opposite s,fig. 281) with the external pia mater : the lower border of this fissure is formed by the hip- pocampus major and corpus fimbriatum ; and the upper border by the lower surface of the optic thalamus, which presents in this situation the corpus geniculatum externum (j, ficr. 271), an oblong eminence, which is continuous with the optic tract, and the corpus geniculatum internum («), a small rounded eminence, which is circumscribed by the corpus geniculatum externum. The Posterior Portion of the Lateral Ventricle. The digital or ancyroid cavity {ayKvpa, a hook) is the occipital portion {g, fig. 278) of the lateral ventricle. The term digital cavity has arisen from its having been compared to the impression which the finger would leave if pushed backward into the substance of the brain. It commences at the point where the ventricle is reflected upon itself, passes horizontally backward, describing a curve with the convexity turned outward, and becomes gradually narrower, until it terminates in a point. The dimensions of this cavity are extremely variable, not only in different individuals, but even in the same sub- ject. Thus, a very large digital cavity is often found on the right side, while on the left there is only a trace of it. Acute ventricular hydrocephalus affects the digital cavity more than any other part of the ventricle.! In some cases the bottom of the digital cavity is not more than half a line from the surface of the brain. In the natural state, the upper wall of the digital cavity is exactly fitted to a conoidal eminence, which occupies the lower wall or the floor of that cavity, and which differs in its dimensions according to the size of the cavity itself This eminence (w), which is variously named the unciform eminence, collieulus, ealcar, unguis, was very well described by Morand.t under the name of the ergot, and is therefore generally called the ergot of Morand. In form it rather closely resembles the hippocampus major, so that we ought, perhaps, to prefer, with Vicq d'Azyr, the name of hippocampus minor. There is not only a cor- respondence in form, but also in structure, between the two hippocampi ; and the broth- ers Wenzel appear to me to have clearly shown that the ergot of Morand, like the hip- this hypothesis, that the animal in which the cornu ammonis is most developed, viz., the hare, is precisely that in which there is least evidence of memory. ,,, , • j- ■ * I could never perfectly understand the structure of the cornu ammonis until I had examined it m rumi- nantia and rodentia, but especiallv in the latter, in which it is most developed. In the rodentia the reflected portion of the hemisphere is almost as large as the hemisphere itself, and the connexions of the cornu ammo- nis with the fornix are seen most distinctly. It is quite evident that the fornix, the cornu ammonis, and the corpus fimbriatum, form only one system of fibres, and are continuous with each other. t It is probable that this is simply the mechanical effect of long-continued hing upon the back. t Mem. de I'Acad. des Sciences, 1744. Observ. Anatomiques sur Quelques Parties du Cerveau. THE CHOROID PLEXUSES, ETC. 747 pocampus major, is nothing more than a special convolution projecting into the ventri- cle. It, in fact, consists of a white layer, enclosing a thick mass of gray substance. A longitudinal anfractuosity, the depth of which depends on the prominence of the ergot, denotes on the surface of the brain the situation of the digital cavity : this anfractuosi- ty is constant, and I have already described it as the anfractuositij of the digital cavity. There is also another circumstance which favours the analogy between the ergot and the hippocampus major, and that is their continuity ; for there is only a depression be- tween them, and the white layer which connects them is continuous in both cases with the fornix. Gredinsh as described several varieties of the ergot ; not unfrequently it is double, and, as we have mentioned, so is the hippocampus major. The absence of the ergot is re- garded by Tiedemann as the result of defective development. The ergot and the digital cavity scarcely exist except in man, doubtless because he alone has the occipital portion of the brain greatly developed. The Choroid Plexuses. The choroid •plexuses of the brain, which have already been noticed in the descriptions of the third and lateral ventricles, form a continuous system of vessels, as can be easily shown by examining the brain from the base upward. Upon the under surface of the velum interpositum, and on each side of the median line, are two small, red, granular bands, running from behind forward, bordered by the veins of the corpora striata, and terminating in front upon the convexity of an arch which forms the boundary of the ve- lum in that direction. This arch is formed by the junction of the anterior extremities of the choroid plexuses. It is situated behind the anterior pillars of the fornix, at the point where those pillars unite, and is crossed at right angles by the veins of the corpus striatum, which pass above it ; after this junction, the choroid plexuses again separate and enter the lateral ventricles through the foramen (foramen of Monro) which leads from the third to the lateral ventricles ; within each of the lateral ventricles they de- scribe an elliptical curve {p, Jig. 278), which is accurately moulded upon the optic thala- mus, and runs along the fornix in the upper part of the ventricle, and along the corpus fimbriatum in the descending cornu or reflected portion. The upper part of the choroid plexus is very narrow ; the lower part is three or four times broader than the upper ; its upper and under surfaces are free, and also its outer border, which contains a large vessel ; its inner border is continuous with the velum in- terpostum* in the upper part of the lateral ventricle, and in the descending cornu with the pia mater, at the base of the brain. The lining membrane of the ventricle adheres intimately to the inner border of each choroid plexus, so that the lateral ventricles are completely closed, and no fluid can es- cape through the semicircular fissure which extends along their entire course. The choroid plexuses are granular, or, rather, consist of vascular tufts, which are un- like any other structure in the body, and their uses are quite unknown. The Lining Membrane and the Fluid of the Ventricles. The middle and lateral ventricles are lined by a transparent and tolerably strong mem- brane, of which the horny lamina between the corpus striatum and thalamus opticus is a part. On tracing this membrane from the third ventricle, it is seen to pass into the lateral ventricles through the foramen (of Monro), behind the anterior pillar of the for- nix. From the third ventricle it also descends into the fourth through the aqueduct of Sylvius. It is extremely easy to demonstrate this membrane, especially upon the septmn luci- dum and corpora striata, and in the digital cavities. In order to separate it to any extent, it must be dissected from without, by gradually removing the layers of cerebral substance by which it is covered. This separation oc- curs in acute ventricular hydrocephalus, in consequence of the pultaceous softening of the surrounding tissue. In the fcBtus and new-born infant, this membrane can be sep- arated with the greatest facility, on account of its density and the softness of the sur- rounding parts. Three questions present themselves regarding the ventricular membrane : Is it a se- rous membrane ! Does it communicate with the arachnoid, so that it ought to be re- garded as a continuation of that membrane 1 How is it arranged along the fissure of each lateral ventricle ! That the ventricular membrane is a serous membrane is shown by the nature of the fluid exhaled into the cavity of the ventricles ; by the structure of the membrane itself, which consists entirely of lymphatic cellular tissue ; and by the diseases of the ventricles, which are precisely similar to those of other serous cavities. t * Compare figs. 278 and 279. t The occurrence of acute and chronic serous effusions, of purulent formations, and of miliary granulations in the ventricles, are proofs of the serous nature of their lining membrane. [The ventricular membrane has a ciliated epithelium on its inner surface.] 748 NEUROLOGY. The number of veins which are situated beneath the ventricular membrane has sug- gested the notion that it was a prolongation or continuation of the pia mater ; but these vessels do not belong to the membrane. The continuity of the ventricular membrane with the arachnoid on the surface of the brain has not been demonstrated. I have already said that the so-called canal of Bichat does not exist. It has been stated that each lateral ventricle is divided, both in its direct and reflected portions, by a circular fissure which turns round the optic thalamus, and through which the pia mater becomes continuous with the choroid plexus. This fissure is closed by blood- vessels, and some very dense cellular tissue, and in the interior of the ventricle by the li- ning membrane, which is firmly attached on both sides of the fissure to the adherent borders of the corresponding choroid plexus. It cannot be admitted that it passes from one side of the fissure to the other, so as to enclose the plexus. It is this membrane which prevents any fluid contained in the ventricles from infiltra- ting into the sub-arachnoid cellular tissue at the base of the brain. The very frequent coincidence of ventricular dropsy with the formation of false mem- brane in the cellular tissue at the base of the brain shows the relation between that tis- sue and the lining membrane of the ventricles, but by no means establishes the exist- ence of any direct communication between the ventricular cavities and the cellular tis- sue at the base of the brain. The Ventricular Fluid. — The existence of a serous fluid in the ventricles was general- ly admitted by the older anatomists, who named it pituita, and considered it to be an excrementitious fluid, which was evacuated through the nasal fossae. During the last century, anatomists were so convinced of its existence in all subjects, that they regard- ed those cases in which it was not found as exceptions ; a recentissimis cadaveribus abcst nonnunquam, says Haller, in speaking of an observation made by Verduc upon the brain after death by decapitation. But the anatomists of the last century differed from the ancients in regarding the existence of fluid in the ventricles as a post-mortem phenome- non, depending on the condensation, by cold, of a vapour which, in their opinion, alone exists in the ventricles during life. This vapour, the only use of which, according to the view stated, would be to prevent adhesion of the opposite walls of the ventricles, was compared by them to that which is found in the pleura, pericardium, and peritoneum of a living animal. The experiments of M. Magendie have proved the existence of a ventricular fluid du- ring life ; and farther, that it may flow backward and forward into the spinal sub-arach- noid space, through the opening {y,fig- 282) in the lower part of the fourth ventricle. The quantity of fluid in the several spaces found in the cranial cavity is extremely variable, for it increases or diminishes according to the relative bulk of the brain in ref- erence to the osseous case of the scull. Having thus examined the brain by horizontal sections, made at different heights from the convex surface towards the base, it is important, in order thoroughly to under- stand the .parts we have described, to study them under different aspects, either by means of particular sections, or by the aid of the various methods adopted by different anato- mists. j1 Median Vertical Section of the Brain. Upon this section {Jig. 282), which divides the brain into two perfectly similar halves, a great many objects are seen : and first, the optic thalamus and corpus striatum, which might be said to form the central nucleus or root of the ce'-ebrum. The optic thalamus is now seen to be smooth and free on its inner surface, where it forms the lateral wall (/) of the third ventricle ; it is con- vex and free above, where it forms part of the floor of the lat- eral ventricle, and it is also free below, where it presents to our notice the corpora ge- nicnlata. Behind, it is continuous with the tubercula quadrigemina, and in front with the corpus striatum ; on the outer side it is blended with the corresponding cerebral Fig. 282. VERTICAL SECTION OF THE BRAIN. 749 hemisphere, and below it is deeply notched for the reception of the corresponding cere- bral peduncle. The corpus striatum forms a concentric curve along the outer side of the opic thala- mus ; it commences in front by a large pyriform extremity, diminishes in size as it pro- ceeds backward, and terminates in a very narrow gray band, which turns round the op- tic thalamus as far as the termination of the descending cornu of the lateral ventricle, i. e., as far as the large end of the cornu ammonis. The lateral ventricle forms a circular or eUiptical trench around this central nucleus, formed by the thalamus opticus and corpus striatum (see Jig. 278). It commences in the substance of the anterior lobe of the cerebrum {anterior ox frontal cornu), mounts up upon the corpus striatum, passes horizontally backward, and, becoming widened, divides into two prolongations : one horizontal {digital cavity, occipital or -posterior cornu), which dips into the substance of the posterior lobe, and terminates near the surface of the brain ; the other reflected, which runs from behind forward, and terminates behind the fissure of Sylvius, so that the lateral ventricle would describe an almost complete ellipse if it were not for the layer of cerebral substance which forms the bottom of the fissure of Sylvius, and which separates the commencement (/) from the termination (A) of the ventricle. Upon the longitudinal section is also seen the regular curve of the corpus callosum (e ^fifig- 282), which runs around the central nucleus. The unequal thickness of the dif- ferent parts of the corpus callosum, its reflection in front so as to embrace the anterior extremity of the corpus striatum, its posterior enlarged extremity or protuberance, and its continuity with the fornix, are shown ; and farther, it is seen that the space between the corpus callosum and the central nucleus of the brain constitutes the upper part of the lateral ventricle, and that the interval between the cornu ammonis and the nucleus con- stitutes its reflected portion. In this section we also notice the septum lucidum {t), the fornix {k), the mammillary tu- bercle {z), the tuber cinereum, the gray commissure {b) and gray mass of the third ven- tricle, the infundibulum (i), the optic nerve (2), the section of the anterior commissure (c), also that of the posterior commissure {x), and the peduncle (s) of the pineal gland {p). The longitudinal section also shows that the third ventricle is formed by the juxtapo- sition of the two central nuclei of the cerebral hemispheres ; that these hemispheres are only connected to each other by the corpus callosum and the cormnissures, and there- fore that it is by studying these parts that the system of communicating fibres between the two hemispheres is displayed. It is moreover seen that each hemisphere may be regarded as composed of a white and gray covering which surrounds a central nucleus. And it is between the general central nucleus and the hemispheres, or, rather, between the fornix and its prolongations on the one hand, and the optic thalami on the other (as at s,fig. 281, for example), that the ventricles would communicate with the exterior if the ventricular membrane were not firmly attached to the choroid plexus : it is also in the same situation that the exter- nal pia mater passes into the internal. The Central Nucleus. — A very curious preparation may be very easdy made upon this vertical median section, to show the central nucleus separated from the other parts. If the handle of a scalpel be introduced between the corpus striatum and the reflected por- tion of the corpus callosum, it will be found that the ventricular membrane is the only means of connexion between them, and that the corpus callosum forms, at this point, a sort of outer case of medullary substance for the corpus striatum, the entire anterior portion of which may be exposed without breaking through any connecting fibres. The anterior part of the corpus striatum may also be exposed from below, that is to say, by dissecting from the base of the anterior lobe of the cerebrum towards the lateral ventri- cle ; for this purpose, the handle of the scalpel must be inserted along a curved whitish line, the concavity of which is turned forward, and which limits the anterior lobe behind. The corpus striatum can be completely isolated only in front and opposite the fissure of Sylvius, in which situation it is covered by only a slight thickness of cerebral sub- stance, which is seen to consist of four very distinct layers, viz., the external gray layer of the convolutions ; a very thin white layer ; an equally thin gray layer ; and, lastly, another layer of medullary substance. Transverse Vertical Sections. I am in the practice of making five transverse sections of the cerebrum : the first, im- mediately in front of the corpus callosum ; a second through the largest part of the cor- pora striata ; a third through the anterior part of the optic thalami ; a fourth through the middle of the thalami ; and a fifth through the occipital portion of the posterior lobes. I shall not here enter into a detailed description of these several sections, which appear to me to convey a more correct idea of the structure of the brain than any other sec- tions, but which cannot be well understood without figures. They disclose, in fact, a medullary centre giving oflf three or four prolongations of white substance, which con- stitute, in their turn, the medullary centres of a certain number of convolutions to which they are distributed ; this ramified disposition of the medullary substance warrants the 750 NEUROLOGY. application of the tern arbor vitct of the cerebrum to the appearances seen upon these dif- ferent sections. The most interesting of these sections is undoubtedly that which passes through the cerebral peduncles, and which discloses the following appearances : Each hemisphere is formed by a medullary centre, which gives off three principal pro- longations, around which all the convolutions are arranged, and are thus collected into three groups, viz., a superior, an external, and an inferior group ; the last of these is con- nected with the medullary centre by a long narrow pedicle which corresponds to the white matter on the outside of the corpus striatum. The corpus striatum and optic thalamus are situated opposite to this pedicle or prolongation of the medullary centre. The medullary centres of the two hemispheres are connected together by the corpus callosum, which forms an arch with the concavity directed downward. Moreover, either the section of the septum lucidum, or of the fornix, is seen according to the point at which the knife has been carried through. The transverse section through the corpora striata and optic thalami deserves special attention. If the section be made through the anterior part of the corpus striatum, and therefore in front of the optic thalamus, the former body presents an oval gray surface, dotted with white points, which are sections of medullary fibres ; the middle of this oval surface is traversed by a series of small, parallel, white fasciculi, which are sections of the medullary bands that pass through the corpus striatum. On the outer side of the corpus striatum are seen distinctly the four layers formerly mentioned as corresponding to the island of Reil. The white layer which turns round the outer surface of the corpus striatum may be said to be reflected upward to form the septum lucidum. Several of these sections appear to me to show that certain white fibres, which arise in the interior of the corpora striata, pass to the circumference of the optic thalami ; or it may be said that certain white fibres arise in the optic thalami, spread out, and are lost in the substance of the corpora striata, beyond which it is impossible to trace them. This beautiful section suggested to M. Foville* some ideas respecting the structure of the brain, to which I shall presently have occasion to refer. The Section of Willis. Previously to the time of Varohus and Willis, anatomists were contented with making successive horizontal sections of the brain from the vertex towards the base, and study- ing minutely the parts thus exposed ; and each anatomist believed that he had described different objects when chance presented him with some arrangement that had not been previously described. Willis insisted upon the necessity of carefully removing the mem- branes from the surface of the brain, and he objected to the usual method of examining this organ by making sections, which destroy the connexions between its different parts ; he considered the brain to be composed of parts folded upon themselves, collected into a globular fonn, and connected to each other by mutual prolongations. He also pointed out the importance of first examining the brains of animals, which are much more sim- ple than the brain of man, the size and complexity of which render its study one of great difficulty. After having made these judicious remarks, Willis proceeds to describe the following mode of making the section which he had contrived, for the purpose of unfolding the cerebrum and opening out this spheroidal mass into a flat surface :t Place the brain, completely stripped of its membranes, upon its convex surface ; turn forward the cerebellum and the medulla oblongata ; introduce the knife into the fissure of Sylvius, and carry it backward as far as the digital cavity ; a flap will thus be detached, comprising all the lower wall of the descending cornu of the lateral ventricle. Repeat this section on the opposite side ; and, after having turned backward the flaps thus form- ed, another section must be made on each side of the brain, extending from behind for- ward along the corpus striatum, on a level with the outer border of the corpus callosum, and reaching to the anterior extremity of the lateral ventricle. Turn forward the inter- mediate flap, which will comprise the cerebellum, the pons Varohi and peduncles, the optic thalami, and the corpora striata. The whole of the interior of the ventricle is thus exposed, so that we can examine the lower surface of the corpus callosum, and its continuity with the centrum ovale of each hemisphere, or the centrum ovale of Vieussens seen from below. The continuity of the fornix with the cornu ammonis is also well displayed. t * Note sur la Structure du Cerveau, 24e Bulletin de la Soci6t6 Anatomique. — (Nouvelle Bibliotheque Midi- cole.) ■ r ^■ t The brains of animals being much less complicated than that of man, ai-e more convenient for this purpose. The brain of a sheep thus unfolded is represented by WUlis in his Cerebri Analome, fig. vii. X This section, which, however, like all similar methods, is liable to the objection that it destroys the con- nexion of parts, suggested to M. Laurencet the idea of comparing the cerebral mass to a nervous loop, analo- gous to the loops described by MM. Prevost and Dumas as forming the terminations of the nerves. According to tliis view the nervous system would represent an elongated ellipse, one end of which would be represented by the brain and the other'by the extremities of all the uen-es ; but both loops are equally inadmissible. GALL AND SPURZHEIM S VIEWS OF THE BRAIN. 751 General Remarks upon the Method of examining the Brain by successive Sections. The method of examining the brain by successive sections has been carried farthest by Vicq d'Azyr, whose beautiful plates are entirely devoted to the demonstration of the objects seen upon various sections of the brain made in succession either from below or from above. This method unfolds to us the relative disposition of the gray and white substances, shows the manner in which the ventricles are formed, and displays to us the real nature of parts which, in consequence of their projecting and being free at some part of their surface, have received particular names. But this mode of examining the brain can only be regarded as a preliminary means calcidated to give an idea of this organ as a whole ; and it tends to perpetuate the er- roneous opinion that the brain is a pulpy mass, consisting of a semi-fluid substance, and displaying no more evidence of contrivance in its structure than a ball of wax. The method adopted by Varolius and Vieussens, which fell into disuse after the pub- lication of the beautiful work of Vicq d'Azyr, and which consisted in determining the connexion of the different parts of the brain, has been revived and improved by Gall and Spurzheim, who have thus opened up the path which modern anatomists have so eagerly pursued. Methods of Varolius, of Vieussens, and of Gall, or the Examination of the Connexions of the Different Parts of the Brain. Varolius was the first to perceive that the essential point in the study of the brain was to ascertain the connexion of its several parts. He was also the first who dissected the brain from below, and who specially examined its connexion with the spinal cord ; Be described the spinal cord as originating from the brain, not opposite the foramen mag- num, but from the lower part of the cerebral ventricles. Vieussens traced the bundles of the pyramids through the pons Varolii to the pedun- cles of the brain, and followed these peduncles through the optic thalami and the corpora striata into the centrum ovale, which is named after him. But there his inquiries ended, for, according to him, it was in this centre that the linear or radiated structure termina- ted ; and his preconceived notion of a nervous centre (centrum ovale), from which, with Varolius, he described all the fibres as proceeding downward, prevented him from carry- ing his researches farther. Gall followed up the investigations of Varolius and Vieussens, but instead of dissect- ing the fibres from above downward, or from the brain towards the medulla, he traced them from below upward, or from the medulla towards the brain, and followed them through the centrum ovale as far as the convolutions. The method adopted by Gall in order to separate the fibres of the cerebrum and show their connexions was to scrape them with the handle of a scalpel. But, from the nature of this proceeding, only those white fibres can be conveniently traced which pass through gray matter, but the white fibres themselves can never be separated from each other. Hardening the brain in strong alcohol, in nitric or muriatic acid, or by boiling it in oil, or by macerating, or boiling it in a solution of salt, facilitates the separation of its fibres ; but, as the results obtained in these modes might be considered as purely artificial, the action of a stream of water is preferable to any of them. The results obtained by acting on the brain by streams of water fully confirm those which are arrived at by the examination of the hardened brain. Again, the anatomy of the fcetal brain and comparative anatomy have also aided in throwing light upon the connexion between the different parts of the brain. As the works of Gall were the commencement, if not the foundation, of all that has since been done, I have thought it necessary to give a brief summary of his views re- garding the structure of the brain ; and as a knowledge of its structure consists in a great measure in that of its connexions with the cerebellum and spinal cord, the examination of these two subjects cannot properly be separated. Gall and Spurzheim' s Views of the Structure of the Brain. Gall and Spurzheim commence by stating, 1. That as the brain consists of several departments, the functions of which are totally different, there are several primitive fas- ciculi which, by their development, assist in the formation of that organ. 2. That these fasciculi are composed of medullary fibres arising successively from the gray matter, which, with Vicq d'Azyr, they regard as the matrix or generator of the white substance. 3. That there exist in the brain a formative system of fibres, or a formative apparatus, and systems of uniting fibres, called commissures. In the first, or formative system, Gall describes four primitive fasciculi ; namely, the anterior pyramids, the posterior pyramids, the olivary fasciculi, the longitudinal fascicuh, which assist in forming the fourth ventricle, and some others which are yet imperfectly understood.* * It will be observed that Gall's fundamental statements are hypothetical : that the brain is developed from certain pnmitive fasciculi, that there is a successive increase of these fasciculi from below upward, aud that 752 NEUROLOGY. Formative System of Fibres. — The anterior pyramidal fasciculi decussate at their origin, but the other fasciculi arise on the same side as the hemisphere to which they belong. The anterior pyramidal fasciculi {b\figs. 273, 274) are re-enforced as they pass through the pons Varolii (m), which is therefore, according to Gall's view, a ganglion, named by him the ganglion of the anterior pyramidal fasciculi ; these pyramidal fasciculi constitute the cerebral peduncles {x, fig. 283), and diverge (y y') so as to enter the inferior, ante- rior, and external (i and m, fig. 284) convolutions of the anterior and middle lobes. Gall, in his beautiful plate, No. V., shows the expansion of the fibres of the peduncles, their distribution, their unequal lengths, and the manner in which their expanded ex- tremities are covered with gray matter to form the convolutions. It still remains to determine how the superior convolutions and those of the posterior lobe are formed : the following are the statements of Gall on this point : The olivary bodies of the medulla oblongata are nothing more than ganglia, from each of which a very strong bundle, the olivary fasciculus (see p. 708), emerges, and ascend- ing behind the pons, where it is considerably re-enforced, passes through the gray mat- ter which lies upon the white fibres of the cerebral peduncle, where it again receives some additional fibres ; this gray matter constitutes a rather firm ganglion on eacTi side ; these are the optic tkalami, which, according to Gall, do not assist in the formation of the optic nerves, and bear no proportion to them in size. The olivary fasciculi, which are divided into very delicate filaments in traversing the optic thalamus, are again collected together as they emerge from its upper border. They then pass through a thick mass of gray matter, the corpus striatum, half of which projects into the ventricular cavity, while the other half is surrounded by the convolu- tions of the island of Reil. The radiated fasciculi {k,fig. 284) are again re-enforced in traversing the corpus striatum, which is regarded by Gall as another ganglion, and are then sufficient to form all the posterior convolutions, and also those which are situated along the upper border of each hemisphere, in the median line (h h A). It therefore follows, according Gall, that the convolutions are nothing more than the Fig. 283. perfecting of all the preceding structures, which should be regarded as preparatory systems of fibres destined to form a whole. Uniting System of Fibres or Commissures. — Even the oldest anatomists regarded the corpus callo- sum as the connecting medium between the two hemispheres ; Vicq d'Azyr, who described several other commissures besides the corpus callosum, regarded them as intended to establish sympathet- ic connexions between the different parts of the brain. Gall, taking a more comprehensive view of this subject, attempted to determine what parts of the brain were connected by this means, and to discover the general law which governs the ar- rangement of the commissures, which he believ- ed to be formed by a system of fibres and bundles, named by him faisccaux rentrans ou convcrgens. We have seen that Gall traces the pyramidal and olivary fasciculi to the gray matter of the con- volutions. According to him, all the extremities of the medullary fibres penetrate the gray matter, which is therefore whiter internally than on the surface. Gall acknowledges that he has not been able to determine their ultimate distribution ; he docs not know whether they terminate in the gray matter, or turn back again towards the interior. Nevertheless, he considers it very probable that new medullary filaments originate in this gray lay- er, and that there is thus produced a system of fibres which re-enforces the preceding one, and is connected with it internally.* the gray substance is the matrix of the white, are so many suppositions. Of the primitive fasciculi, the anterior pyramids alone are well defined ; the inaccuracy in the representation of the posterior pyramids disfigures his "'* Nothing certain appears likely to arise from this proposition, and yet Gall immediately adds (p. 202), "It is certain that the existence of two systems of fibres in the brain can be distinctly demonstrated, and that the convern-ino- system contains more fibres and stronger fasciculi than the radiating system. On seeking lor his proofs,' we find that he infers that converging fibres must necessarily exist, from the disproportion between the white matter of the hemispheres and the fibres which come to them from the fasciculi of origin. "The con- verging fibres,'- says he, " at the bottom of all the convolutions, are seen to enter between the diverging fibres, and interlace with them." It is very evident, from an examination of the proofs adduced by Gall in support of the existence of converging fibres, that the distinction between the converging and diverging fibres is purely hj'pothelical. GENERAL IDEA OP THE BRAIN. 753 According to Gall, the commissures are, the corpus callosum, t\ve fornix, and the ante- rior and posterior commissures. The corpus callosum (fd e,fig. 283) is intended to unite the convolutions of the two hemispheres. Its anterior reflected portion unites the inferior convolutions of the two anterior lobes {f p a a). The enlarged posterior extremity (e) receives the fibres {s s) of the posterior convolutions (b) and the middle portion of those of the middle convolu- tions (c). The anterior commissure, which can be so easily traced (m) through the corpus stria- tum into the convolution of the sphenoidal extremity of the posterior [middle] lobe, is regarded by Gall as the means of connecting certain corresponding convolutions in the sphenoidal portions of the two posterior [middle] lobes. The posterior commissure, which is lost in the substance of the optic thalami, and which is much smaller than the anterior, fulfils the same purpose for those bodies. The posterior pillars (k) of the fornix are regarded by Gall as forming a commissure for the posterior convolutions of the two middle lobes. The fornix appears to him to result from the connexion of these parts, and he considers the interlacement called the lyra, to be composed of the connecting filaments. His error here is evident, for the for- nix results from the juxtaposition of two medullary cords. The fornix may be regarded as an antero-posterior {h h), but not as a transverse commissure. The Ventricles ani Convolulions. — The formation of ventricles is considered by Gall to be the necessary result of the divergence of some fasciculi and the convergence of others. His description of the convolutions is entirely new, and one cannot but regret that it should be disfigured by the hypothesis of converging and diverging fibres. The follow- ing is his mode of describing these parts, which he regards as the completion and final object of the organization of the brain, and as performing the most elevated functions. Gall admits two layers in each convolution ; and he finds that these two layers can always be readily separated, but only in the median line. He successfully proves, in op- position to the commission of the Institute, that the convolutions are not composed of a white, soft, and pulpy matter, resembhng pomade or jelly, but that they have a fibrous or linear structure.* Unfolding of the Cerebrum. — The idea of unfolding the brain, which is nothing more than opening out the convolutions, was derived by Gall from his view of the structure of the convolutions, which he regarded as formed of two layers united by very delicate cel- lular tissue. It was also suggested to him by the examination of hydrocephalic brains, in which he conceived there was no disorganization, but merely an unfolding of the con- volutions. The following is his method of unfolding the brain : after having very care- fully removed the meninges, he introduced his fingers into the great transverse fissure between the optic thalamus and the hippocampus major, and thus penetrated into the lateral ventricles : he then pressed gently against the outside of the ventricles ; he broke down the white matter of the hemispheres until he reached the base of the convolutions, which then necessarily became unfolded, so as to be moulded upon the back of his hand ; the astonished spectators would have wondered less if they had seen the lacerations ne- cessary to produce this result. The unfolding of the brain is impossible if Gall's views be correct ; for, according to him, the white fibres of the brain are not all of equal length, and those which correspond to the anfractuosities are much shorter than those corresponding to the convolutions ; besides, I am convinced that, in hydrocephalus, the convolutions are not unfolded, but are atrophied, flattened, and compressed against each other. Such are the principal ideas of Gall regarding the structure of the brain, t His system undoubtedly contains numerous errors and imperfections ; but, nevertheless, it has estab- lished a new era in the study of the anatomy of this organ. General Idea of the Brain. 1. The decussation of the pyramidal fasciculi of the medulla oblongata, their passage through the pons Varolii, their continuity with the cerebral peduncles, of which they form the lower portion, their passage through the optic thalamus, and their expansion within the corpora striata {k, fig. 284), through which they may be traced {h h h) as far as the convolutions, are incontestable facts. 2. Again : it is no less certain that the fasciculi of re-enforcement of the medulla are * See note, p. 756. t The following- is the completion of these ideas : 1. As the peripheral extremities of the nerves expand in all the organs of our body to form an immense surface (and of this expansion the retina is an excellent exam- ple), so do the primitive fasciculi of the brain, after being re-enforced in their passage through the different masses of gray substance, finally expand in the convolutions, and receive a covering of gray matter. 2. There are as many particular systems as there are different functions, but they are all connected together by anas- tomoses. 3. The nervous system is double, but is united into one whole by the commissures. 4. There is not, and there cannot be, any common centre of all the sensations, thoughts, and volitions. 5. Personal unity will always remain a mystery. Each of these propositions might form the subject of ample commentary. I will merely remark the incon- gruity between the acknowledged fact of personal unity, and the singular proposition that there neither is, nor can be, any common centre of all the sensations, thoughts, and volitions. 50 754 NEUROLOGY. prolonged above the pons into the cerebral peduncles, of which they form the upper por- tion {x, fig. 283), and become continuous, without any line of demarcation, with the optic thalamus. Do these fasciculi decussate 1 They remain distinct until they reach oppo- site the pons, behind the tubercula quadrigemina, where they unite ; they appear to me to decussate, but not so evidently as the anterior pyramids, and I cannot venture to state this positively. 3. Fasciculi of white fibres radiate in all directions {y y', fig. 283) from every part of Fig. 284. the surface of the optic thalamus {g g), excepting its inner side, which is free, and corresponds to the third ventricle ; the an- terior of these fibres pass directly forward, the mid- dle fibres outward, and the posterior fibres backward, forming the radiating crown of Reil (k,fig. 284). As these radiating fibres emerge from the optic tha- lamus, they are bound down, as it were, by cer- tain white curved fibres, which constitute the taenia semicircularis. 4. All the white fasciculi of the corpora striata, excepting those which are continuous with the anterior pyramids, proceed from the optic thalami. Some of tliem appear to me to terminate in the corpora striata in the form of extremely delicate filaments, but the greater number pass through the corpora striata without either increase or diminu- tion, and then pass into the hemispheres. The corpora striata of Willis are, therefore, nothing more than gray pulpy masses, which are traversed both by the white fibres ra- diating from the circumference of the optic thalami, and by those which are derived from the anterior pyramids. The gray matter is not arranged in alternate linear stris with the white substance. So far from thinking, with Reil, Gall, and Tiedemann, that the fibres which emerge from the corpora striata are much more numerous than those which enter it, I have been led to a precisely opposite conclusion, namely, that a certain num- ber of fibres, proceeding from the optic thalami, terminate in the interior of the corpora striata, the gray matter of which, in reference to these fibres, represents the gray sub- stance in the convolutions. 5. From the anatomical fact that a certain number of white fibres terminate in the corpora striata, and also from the size of those bodies being in some animals inversely proportioned to that of the hemispheres, it appears to me to follow that the corpora stri- ata may be regarded as internal convolutions, in which a certain number of medullary fibres terminate.* 6. It is extremely easy, by means of a stream of water, to separate, and, as it were, enucleate the corpus striatum from the sort of shell formed for it by the cerebrum oppo- site the fissure of Sylvius. The corpus striatum is only connected with the cerebrum by the radiating fibres which emerge from its upper circumference near the corpus cal- losum. The optic thalamus and its fasciculus of origin present no trace of a linear structure. Nor can we discover in it the concentric layers admitted by Herbert Mayo. With a lit- tle attention, certain extremely delicate white filaments are seen in the optic thalamus, which cannot be separated, on account of their tenuity and the adhesion of the surrounding tissue to them. If the term ganglion be applicable to any part of the cerebrum, it cer- tainly is so to the optic thalamus ; for a nervous ganglion is nothing more than a pecu- liar apparatus in which nervous filaments become separated and spread out, in order to enter into new combinations. We must agree with Reil and Tiedemann in regarding the optic thalami as appendages of the cerebral peduncles : Tiedemann calls them the enlargements of the cerebral peduncles. 7. The essential points to be made out in the structure of the cerebrum are the ulti- mate course of the fibres radiating from the optic thalami and corpora striata, and the relations of those fibres with the convolutions of the brain and the corpus callosum. I by no means agree with Reil in thinking that we must not attach so much importance to the continuity of fibres in the cerebrum, and that their contiguity is a sufficient guide to its anatomy : on the contrary, I regard the determination of their continuity as the key to the structure of this organ. 8. There is no median raphe in the corpus callosum, the right half of its transverse fasciculi being continued into the left half, without any line of demarcation. * In several cases of chronic hydrocephalus, in which the hemispheres were reduced to a very thin lamina, J have found the optic thalami atrophied, and the corpora striata of enormous size. GENERAL IDEA OF THE BRAIN. 755 9. It appears, at first sight, that the fibres of the corpus callosum {edf,fig. 284), and the white radiating fibres {k), which emerge from the optic thalami and corpora striata, decussate (as at g) ; but on separating the fibres of the cerebrum, either after it has been hardened in alcohol or by the action of a stream of water, it is most distinctly shown that these two sets of fibres are continuous. 10. Again : the continuity of the fibres of the corpus callosum with those of the hem- ispheres is no less evident; the middle fibres {s,fig. 283) of the hemispheres are seen to pass transversely inward, the anterior fibres {ap) backward, the posterior fibres («) forward, and the inferior fibres to beiid and turn upward, to become continuous with the corpus callosum. I have in vain endeavoured to determine by actual dissection whether there is a de- cussation of the fibres of the corpus callosum itself; I still entertain many doubts regard- ing this subject ; we shall presently find, when speaking of the development of the brain, that the corpus callosum does not appear until after the hemisphei es ; and that compara- tive anatomy, by showing that the corpus callosum does not exist in the three lower classes of vertebrate animals, is opposed to the idea that the hemispheres are composed of certain fihres which decussate in the corpus callosum. 11. The doctrine of converging and diverging fibres, advanced by Gall and Reil,* can- not explain the continuity of the fibres of the coi-pus callosum with the radiating fibres of the corpora striata and optic thalami. Tiedemann, from his researches into the anatomy of the fcetal brain, states that the corpus callosum is formed by the reunion of the fibres of the cerebral peduncles after they have expanded to form the hemispheres. He says that he has traced the fibres of the peduncles as far as the median line of the corpus callosum, where those of one side unite and are blended with those of the other ; but a careful examination of the cere- brum, either by means of a stream of water, or by hardening it, shows that the fibres of the corpus callosum terminate in the convolutions, without presenting any sort of re- flection, or forming any median raphe. 12. The dissections of M. Foville seem to establish the continuity of the corpus callo- sum both with the radiating fibres of the corpora striata and with the fibres of the hem- ispheres. According to his dissections, which consist essentially in transverse vertical sections, the radiating fibres of the optic thalami and corpora striata divide immediately into three very distinct superimposed planes. The first or superior plane is reflected upward and then inward, so as to describe a curve with its convexity turned outward, passes horizontally inward to form the corpus callosum, and unites with the corresponding fibres of the opposite side. The second or middle plane, the plane of the hemisphere, ascends parallel to the corpus callosum up to the point where the fibres of that body are reflected inward ; it then con- tinues in an almost vertical direction, and thus reaches the gray matter. The ihird or inferior plane, much smaller than either of the preceding, is extremely thin, and follows a very different course : immediately after emerging from the common place of origin, it descends on the outer side of the corpus striatum, turns round its low- er part, approaches the median line, and then mounts upward, in contact with the cor- responding plane of the opposite side, through the middle of the ventricles, where the two juxtaposed planes form the septum lucidum. 13. Is the fornix an antero-posterior commissure 1 In support of this opinion, I may state, that I have seen the right half of the fornix atrophied in a case of destruction of the convolutions corresponding to the tentorium cerebelli. 14. The anterior commissure (m, fig. 283), which was regarded by Willis as the com- missure of the corpora striata, and by Reil as intended to connect the anterior convolu- tions of the middle lobe and some convolutions situated at the bottom of the fissure of Sylvius, belongs to the system of converging fibres, according to Gall, who describes them as commencing in the gray matter of the convolutions. According to Tiedemann, this commissure is a continuation of the cerebral peduncles, each of which, after having traversed the corpora striata, expands in the corresponding hemispheres, and gives off" several radiating fasciculi which incline forward and inward, are collected together into a cord, and unite with those of the opposite side ; the anterior commissure, therefore, according to this view, is a bond of union between the radiating fibres of the cerebral peduncles and those of the right and left middle lobes of the brain. Chaussier had al- ready derived the fibres of this commissure from the cerebral peduncles. All that is certainly known regarding it is, that the cord of which it consists passes through the an- terior portion of each corpus striatum, and expands in the anterior and inferior convolu- tions of the sphenoidal horn of the posterior [middle] lobes, behind the fissure of Sylvius. 15. The cornu ammonis is formed by the reflection of the lower part of the hemi- sphere : the white laminae which cover it, the corpus fimbriatum along its border, and the * The following- is Reil's statement on this subject : " Both of these two systems of fibres spread out into rays and meet each other ; the cerebral peduncles ascend from below, and expand into the form of an invert- ed cone ; the system of the corpus callosum, on the contrary, comes from above, and its fibres insinuate them- selves between the preceding ones {sue g, fig. 284), and form, as it were, the Ud of the cup." 756 NEUROLOGY. fornix, constitute but one system, which evidently belongs to the antero-posterior com- missures. 16. Each convolution is composed of two precisely similar semi-convolutions ; the two halves, which can be readily separated by a stream of water, may be decomposed into a considerable number of striated lamellae, arranged like a fan, the margin of which would correspond to the free border of the convolution, and the narrow end to the ad- herent border ; these striated lamellaj are separated from each other by vascular fila- ments ; their number seems to vary in different subjects ; they seem, moreover, to be • altogether independent of each other. The stream of water detaches a corresponding layer of gray matter with each white lamella. This layer of gray matter is also striated, and appears to be composed of fibres implanted upon the white matter, as Mr. Herbert Mayo has very clearly pointed out. 17. It follows, therefore, that in the convolutions, a lamellar striated arrangement suc- ceeds to the fibrous or linear arrangement of the medullary centres and radiating fibres of each hemisphere.* These lamellae are evidently continuous with the radiating fibres of the corpus striatum and optic thalamus. Still, there is in each convolution a proper lamella, the continuity of which with the radiating system of the hemispheres I have not been able to trace. 18. We should not regard the convolutions as so many sinuous eminences separated by the anfractuosities : on the contrary, the bottom of the anfractuosity forms the mid- dle part or fold of a layer of white and gray matter, half of which layer belongs to one convolution and half to the next convolution (71 n, fig. 284). Now it is these white lamel- lae which line the gray matter that appear to be proper to each convolution ; and be- tween these proper lamellae are situated the white striated plates that are continuous with the radiating fibres of the hemispheres,t which fibres are not arranged in lamellae, but merely in lines. It follows from aU that has been stated, that there are yet several deficiencies in our knowledge of the anatomy of the brain, which prevent us from forming a complete idea of its structure. Development of the Cerebrum.X In the early periods of foetal life, about the end of the second month, the hemispheres are represented by a very thin membrane, which is turned backward and inward, so as to cover the corpora striata. The optic thalami, which appear as enlargements of the cerebral peduncles, the tuber- cula quadrigemina, and the cerebellum, are completely exposed. The corpus callosum does not yet exist. The human brain may, then, be considered as resembling the brain of fishes. Towards the end of the third month, the membrane of the hemispheres has acquired a farther development, and covers not only the corpora striata, but also the optic thalami. The tubercula quadrigemina and the cerebellum are still exposed. The anterior lobes only of the cerebrum are formed. The posterior lobes seem to be merely appendages. The hemispheres, then, constitute at this period a membranous sac, which is open on the inner side and behind, and may be regarded as representing the brain of reptiles. The * M. Lemet has been led to the same conclusion reg-arding- the lamellar structure of the convolutions, by- studying the brain hardened by boiling it in a solution of salt. t Mr. Herbert Mayo (a series of engravings intended to illustrate the structure of the brain and spinal cord in man, 1825), who has followed the example of Reil, in examining the brain with so much care after it has been hardened in alcohol, admits the existence of three sorts of fibres in each convolution, viz., fibres which pass from one convolution to the next (u u,fig. 283), and also to more distinct convolutions ; fibres which come from the commissures (s s p) ; and fibres derived from the spinal cord. According to this anatomist, the fibres which pass from one convolution to another constitute the principal part of each convolution ; the other white fibres which form the centre of each convolution are derived partly from the commissures and partly from the optic thalami and corpora striata. According to him, the white fibres (y' q) which form the inferior layer of the cerebral peduncles radiate in the substance of the cerebrum, and constitute its anterior and middle fibres. The fibres proceeding from the optic thalami form the posterior cerebral fibres (y). There is, he afiimis, one point in which the radiating fibres evidently decussate with the fibres from the great commissure of the brain or corpus callosum (as at g, fig. 284). The posterior radiating fibres do not present this decussation. The two most remarkable fasciculi of communication between the convolutions are the following : that which occupies the bottom of the fissure of Sylvius (I, fig. 283 ; m,fig. 284), and which unites the convolu- tions of the anterior and posterior lobes ; and that { p p,fig. 283 ; I, fig. 284) which runs above the corpus cal- losum, crossing at right angles the direction of its fibres, and connects the anterior and superior with the pos- terior and inferior convolutions. Rolando has not been so successful in his researches into the structure of the cerebrum as in his investiga- tions into that of the cerebellum : the following are the results which he obtained by tearing the brain, and by examining this organ in the foetus. According to him, the brain is composed of fibres arranged in layere in the following order, proceeding from without inward : 1. A white layer reaching into the fissure of Sylvius, and covered by gray matter ; 2. A layer from which the fibres of the external convolutions arise ; 3. A layer which is formed by the fibres of the peduncles, and supplies the convolutions of the inner border of the hemi- sphere ; 4. A plane which extends from the optic thalami to the parietes of the lateral ventricles, to form the corpus callosum ; 5. A system of longitudinal fibres which form the convolutions situated upon the inner sur- face of the hemispheres ; 6. A system of medullary fibres which constitute the fornix and comu ammonis ; 7. Internal and external corpora striata, to which must be added the anterior commissures, the perforated layer, and the fasciculus of the external corpus geniculatum. t Vide Tiedemann (translated by M. Jourdan). COMPARATIVE ANATOMY OF THE CEREBRUM. 757 corpus callosum begins to appear under the form of a narrow commissure, which unites the two hemispheres in front, they being completely separated behind. In the fourth and fifth months, the cerebrum covers the anterior part of the tubercula quadrigemina. The posterior lobe exists, the fissure of Sylvius, which is well-marked, separating it from the anterior lobe. We observe here and there some small depres- sions, the traces of anfractuosities. The olfactory nerves, which are very large, and are said to have been found hollow, as in the lower animals, appear to arise from the Sylvian fissure. The corpus callosum is still very small, so that the optic thalami and the third ventricle are exposed. At this period the human brain has some analogy with that of the rodentia. In the sixth month, the cerebrum covers the tubercula quadrigemina and the greater part of the cerebellum. The only traces of convolutions are found upon the internal surface of the hemispheres. The corpus callosum is prolonged backward with the hem- ispheres, and from being vertical, now becomes horizontal. At the seventh month, the corpora albicantia, which had hitherto formed a single mass, as in the lower animals, become separated. The convolutions are defined, and the cere- brum projects behind the cerebellum. The changes occurring in the eighth and ninth months appear to be the development of the convolutions and the perfection of the other parts of the brain. At this period the characters of the human brain are well-defined. It may not be impossible, perhaps, to recognise, in the rapid phases of this development, the characters of the brain in the different orders of mammalia, but it is necessary to observe greater caution in admit- ting these analogies than has been evinced by various naturalists. As the corpus callosum continues to be developed backward, it ends by reaching the anterior tubercula quadrigemina. The corpora striata do not exhibit their white, radiating fibres until near birth, or soon after it. The originating fasciculi of the fornix are not seen in the interior of the optic thalami until the latter months of intra-uterine life ; and until then, also, the transverse eonmiissures and the white fibres of the optic commissure do not appear.* The lateral ventricles are formed by the turning backward and inward of the membrane which constitutes the hemispheres. And as this membrane is very thin until the end of the third month, it follows that at this period the lateral ventricles are proportionally much larger than they are afterward. The anterior cornua of these ventricles are developed before the descending cornua, and these before the posterior cornua. During all this pe- riod, the anterior cornua communicate with the cavities in the olfactory nerves. At the sixth month, the lateral ventricles are completely closed. The choroid plexuses, which exist in all animals provided with lateral ventricles, begin to appear as soon as these cavities. The distinction between the gray and white matter does not become evident until af- ter birth. Tiedemann is of opinion that the formation of the gray matter takes place after that of the white. This appears to me a pure hypothesis. The two substances are formed at the same time ; but, properly speaking, they are neither white nor gray, and they do not acquire their distinctive characters until some little time afterward. Comparative Anatomy of the Cerebrum. The Optic Thalami and Corpora Striata. In analyzing the brains of the lower animals, it is of the utmost importance clearly to distinguish the hemispheres, properly so called, from the optic thalami and corpora striata. The optic thalami are recognised by their having a ventricle (the third) between them, by being connected by an anterior and a posterior commissure, and, moreover, by being continuous with the cerebral peduncles. The size of the optic thalami is always proportioned to that of the hemispheres. In fishes, the cerebrum appears to be almost entirely formed by the optic thalami. There are no traces of corpora striata in fishes. Their existence in reptiles cannot be doubted. They are of enormous size in birds, in which they constitute almost the entire hemispheres. If it be true that, in the animal series, the size of the hemispheres is always directly proportioned to that of the optic thalami, such is not the case with the corpora striata, which, as I have already stated, are a kind of internal convolutions, and are often inversely proportioned, in size, to the hemispheres, properly so called. Thus, the corpora striata are very large in proportion to the hemispheres in the ro- dentia : in this respect, as in many others, the brain of this order of mammalia approach- es very near to that of birds. In the higher orders of mammalia, as the carnivora and quadrumana, the proportion between the corpora striata and the hemispheres is nearly the same as in the human subject. * [Tiedemann describes fibres as distinctly appearing- in the corpus striatum in the sixth month, though not so abundantly as afterward. He recognised the anterior and posterior commissures before the end of the third month ; at the same time, also, the anterior pillars of the fornix rising from the united mass of the cor- pora albicantia ; the fasciculi from the thalami to the corpora albicantia were quite distinct in the fifth month, and could be recognised even somewhat earlier.] 758 NEUROLOGY. The Cerebral Hemispheres and Olfactory Lobes. In Mammalia. — Man surpasses all the mammalia in regard to the size of the cerebral hemispheres and the number of their convolutions. The quadrumana stand next to man. The dolphin, perhaps, exceeds the ape in both respects, and this would tend to support the relations of travellers respecting the won- derful intelhgence of this cetaceous animal. In the carnivora and ruminantia the hemispheres are smaller, the occipital lobe of the cerebrum does not exist, and the anterior part only of the cerebellum is covered. There is no fissure of Sylvius, and no lobe of the corpus striatum. In all these animals, the number of the convolutions and the depth of the anfractuosities have appeared to me to be as great as they are in man, in proportion to the size of the hemispheres. I have not observed that regularity of the convolutions which several anatomists have pointed out as contrasting with their irregularity in man. The lowest order of mammalia, namely, the rodentia, have the least complicated brain. It is shaped like the heart on playing cards, almost resembling the brain of birds. The cerebellum is completely exposed, and the tubercula quadrigemina are but partially cov- ered by the cerebrum. There are scarcely any traces of convolutions, and the henu- spheres are reduced to a membrane folded upon itself The corpus callosum is extremely small, but the cornu ammonis is very large. These two parts seem to be developed inversely to each other. Thus, the corpus callosum is larger and the cornu ammonis is smaller in man than in the lower animals. In the rodentia, the gray matter of the convolutions is reflected beneath the fornix.* In all mammalia, excepting the dolphin, the olfactory nerves, which are so delicate in man, form two thick pedicles lying under the anterior lobes of the cerebrum, and termi- nating in front by large ovoid bulbs, corresponding in size to that of the ethmoidal fossae ; these enlargements are named olfactory lobes. They are continuous with the innermost convolutions of the sphenoidal horn of the posterior lobe, which presents, above and be- low, certain white fibres or striae, that are continuous with the cerebral peduncles. The olfactory lobes have no relation with the corpora striata, as Cuvier was the first to observe. In the dolphin, as in man, the corpora striata are very much developed. The development of the olfactory lobe is inversely proportioned to that of the cornu ammonis. . In Birds. — The cerebral hemispheres in birds are shaped like a heart on playing cards> as in the rodentia ; there are no lobes and no convolutions, excepting a very superficial longitudinal furrow, situated on each side of the median hne. The brain almost entire- ly consists of the corpora striata. The hemisphere is formed by a very thin gray lamina, upon which are observed certain white radiated fibres. This lamina commences at the inner part of the corpus striatum, turns outward round that body, and is continued to the upper part. The interval between this lamina and the corpus striatum forms the lateral ventricle. There is no trace of the corpus callosum, but there is evidently an anterior commissure, which expands in the corpora striata. In all birds of prey, two medullary bands arise in front of the commissure of the optic nerves, and, having reached the front of the hemispheres, are expanded to form the ol- factory lobes. In the other tribes, as in the gallinaceae, there are no olfactory lobes, but certain small cords, which are merely the tapered extremities of the hemispheres. In Reptiles. — The hemispheres are larger in the chelonians (tortoise) than in birds, though they are very similar in many respects : as in birds, there are no olfactory lobes, but merely two bands. In the saunans (crocodile, lizard) the olfactory lobe is continued into the tapering point of the cerebral lobe by a very long pedicle. The batrachians and ophidians have olfactory lobes in front of the hemispheres, from which they are separa- ted by a circular constriction. In Fishes. — Like reptiles, fishes have sometimes a single pair, sometimes two pairs of lobes in front of the optic lobes. When there is only one pair, it must not be conclu- ded that they represent the cerebral hemispheres ; if that pair is continuous with the ol- factory nerves, they constitute the olfactory lobes. Whenever there is a pair of lobes between the olfactory and the optic lobes, such pair belongs to the hemispheres. The olfactory lobes and the cerebral hemispheres are so independent of each other, that they are often inversely proportioned in regard to size, so that the cerebral hemi- spheres are larger in man than in any of the lower animals, while the olfactory lobes are smaller. On the other hand, the olfactory lobes are the most highly developed in the ray ; they are united together, are hollowed in the centre, grooved on the surface, ac- cording to the observation of Vicq d'Azyr, and present some traces of convolutions. Now, in the ray, there are no cerebral hemispheres, at least, unless we agree with Tiede- mann in regarding the olfactory lobes as anologous to the corpora striata. In some fish- es the olfactory lobe is supported by a pedicle of variable length. As to the cerebral hemisphere, it is a mere tubercle, which appears to represent the optic thalamus. * [Mr. Owen has discovered Ihat the brain of marsupial animals resembles that of birds, in wanting the cor- pus callosum (see his Memoir in Phil. Trans., 1837).] THE NERVES, 759 The corpus callosum, the fornix, and the septum lucidum do not exist either in birds, reptiles, or fishes. The corpora albicantia, which are wanting in birds and reptiles, are of enormous size in fishes, and constitute a true lobe, according to Vicq d'Azyr and Arsaky. The encephalon of fishes presents five pairs of lobes, which are, proceeding from be- hind forward, 1. The lobes of the pneumogastric nerve, or lobe of the medulla oblongata ; 2. The cerebellum ; 3. The optic lobes ; 4. The cerebral hemispheres ; 5. The olfactory lobes. If we now generalize, with M. de Blainville, the notions we have formed respecting the encephalon of vertebrate animals, we may regard the different pairs of lobes of the encephalon as so many pairs of ganglia situated upon the prolongation of the spinal cord ; these he names ganglions sans appareii extirieur. The first or the most anterior pair consists of the olfactory lobes, which are rudimentary in man. The second is the cere- brum, properly so called. The third is formed by the tubercula quadrigemina or optic lobes, which are rudimentary in man. The fourth is the cerebellum. The ganglia which constitute each pair communicate with each other ; each ganglion communicates with that which precedes and that which follows it • and, lastly, they all communicate with the spinal cord.* THE NERVES, OR THE PERIPHERAL PORTION OF THE NERVOUS SYSTEM. General Remarks. — History and Classification. — Origin, or Central Extremity. — Different Kinds. — Course, Plexuses, and, Anastomoses . — Direction, Relations, and Mode of Divis- ion.— Termination. — Nervous Ganglia, and the Great Sympathetic System. — Connexions of the Ganglia with each other, and loith the Spinal Nerves. — Structure of Nerves. — Struc- ture of Ganglia. — Preparation of Nerves. General Remarks. The nerves, which are concerned in the transmission of sensations and of motor influ- ence, are white cords, attached to the cerebro-spinal axis by one extremity (the central extremity), and distributed to the different organs by the other, or peripheral extremity. They have a pearly-white aspect, like the tendons, with which they were for some time confounded. Their surface is smooth, and presents a number of folds or zigzag marks, which are effaced by extension. t Lastly, if a nerve be cut across, it is seen to be com- posed of a certain number of cords, the divided ends of which project beyond the cut surface. By these characters it will always be easy to distinguish a nerve from any other white tissue in the body. All the nerves are arranged in pairs : they differ from each other in their point of junction with the central portion of the nervous system ; in their consistence ; in the place at which they emerge from the cranio-vertebral cavity ; in their distribution ; and in their functions. These points of difference have served as the foundations of the dif- ferent classifications of the nerves proposed at various periods. History and Classification of the JVerves. The nerves, which had been at first confounded with the tendons and ligaments under the name of white tissues, were distinguished from those parts by Herophilus and Galen. The subdivision of the nerves into the cerebral or cranial nerves, which pass out of the foramina in the base of the scull, and the spinal or rachidian nerves, which emerge from the inter-vertebral foramina, was so natural, that it suggested itself to the earliest anat- omists who directed their attention to this system. The cranial nerves alone have pre- sented some difficulties in their study and their classification. Marinus, whose work has been long regarded as classical, admitted only seven pairs of cranial nerves, among which neither the olfactory nor the pathetic were included. Achillini was the first who described the latter as a special nerve ; and it was Massa who classed the olfactory rib- and among the nerves. Willis divided the cranial nerves (and his division is still adopt- ed) into ten pairs, including the sub-occipital nerve. He also, like his predecessors, ad- mitted thirty pairs of spinal nerves, and regarded the great sympathetic as forming the forty-first pair. According to Willis, the olfactory nerves form the first cranial pair ; the optie nerves, the second ; the common motor nerves of the eyes, the third ; the pa- thetic nerves, the fourth ; the trigeminal nerves, the fifth ; the external motor nerves, the sixth ; the facial and auditory nerves together, the seventh ; the pneumogastric, glosso-pharyngeal, and spinal accessory, the eighth ; the hypoglossal nerves, the ninth ; and the sub-occipital nerves, the tenth. This last pair, which was with so much reason * [There is still considerable uncertainty as to the parts of the encephalon which correspond in the higher and lower vertebrata. For farther information on this point, as well as on the comparative anatomy of the brain generally, see Leuret, Anatomic Comparee du Systeme Nerveux, Paris, 1839.] t [These zigzag folds led some anatomists to believe that the nerves have a sinuous arrangement. Monro has even commemorated this anatomical error by a figure. The sinuous appearance common to the nerves and tendons disappears in both by stretching.] 760 NEUROLOGY. classed by Haller among the spinal nerves, has been alternately and arbitrarily removed from one to the other class of nerves. Scemmering divided the seventh pair of Willis into two distinct pairs : the seventh, or the facial nerves ; and the eighth, or the audi- tory nerves : he subdivided the eighth pair of Willis into three pairs, namely, the ninth, or the glosso-pharyngeal ; the tenth, or the pneumogastric ; and the eleventh, or the spinal accessory nerves of Willis. But Scemmering's modification, as well as Mala- carne's, who admitted fifteen pairs of cranial nerves, and also Paletta's, who described as a particular nerve that branch of the fifth pair which is distributed to the temporal and buccinator muscles, appear to me to be faulty, because they cause a confusion of ideas without leading to any advantage. We shall, therefore, adhere to the classifica- tion of WilUs, which is most generally adopted. Nevertheless, with Vicq d'Azyr, we shall prefer a nomenclature founded upon the distribution of the nerves to one w-hich is purely numerical. Willis conceived the grand idea of separating the nerves of voluntary from those of involuntary motion. Bichat seized upon this idea, which had already been rendered fruitful by Winslow and Reil ; he unfolded it even to the minutest detaOs, and appropri- ated to himself, in some measure, the distinction of the nerves into those of organic and those of animal life. The cerebro-spinal nerves constitute the nervous system of ani- mal life ; the great sympathetic nerve forms by itself the nervous system of organic life. This last-named nerve consists of a series of ganglia, or small nervous centres, distinct from each other and from the brain. Bichat, moreover, anticipating all the importance of the origin of the nerves, endeavoured to class them, not according to the points at which they emerged from the cranium, but according to their origin, viz., into the nerves of the cerebrum, which are ten in number ; the nerves of the pons Yarohi, six in num- ber ; and the nerves of the spinal marrow, thirty-four in number ; the only disadvantage of this classification consists in its having been premature. Other less important, and, in general, rather physiological than anatomical subdivis- ions of the nerves, have been established. Thus, in reference to their consistence, the nerves have been divided into the hard, which are motor nerves, and the soft, which are sensory ; the former are said to come from the spinal cord, the latter from the brain. The old distinction of the nerves into nerves of sensation and nerves of motion has been lately revived ; and we shall have occasion to recur to it, as well as to Sir Charles Bell's classification of the nerves into the symmetrical or primitive, and the superadded or respi- ratory system. The nerves might also be classified according to their size, but this mode of distinc- tion would be completely useless. Every nerve presents for our consideration a central extremity, a course, and a peripheral extremity. The Central Extremity of the JVerves. The central extremity of the nerves is that part by which they communicate or are connected with the cerebro-spinal axis. It is generally called the origin of the nerves. The use of such metaphorical expressions as origin, production, and effiorescence, has not been without disadvantage to science ; for by the majority of anatomists they are employed not in a figurative, but in a literal sense.* The examination of the central extremity of the nerves is, perhaps, the most impor- tant part of their study, because the properties of the nerves depend in a great measure upon their point of connexion with the central part of the nervous system. This point is, in reference to each nerve, constant and invariable, not only in man, but throughout the animal kingdom, so that its exact determination enables us to estabhsh what are the analogous parts of the encephalon in different species. Each nerve has an apparent and a real central extremity or origin. The apparent ori- gin is the exact point at which the nerve is given off from the surface of the cerebro- spinal axis ; but, as several nerves can be traced into the substance of the cerebro-spinal axis to a variable depth, it is probable that all of them have a much deeper real origin. The older anatomists proceeded on this supposition, when they described all the nerves as originating from the cerebrum, and more particularly from the corpus callosum, or, rather, from the optic thalami and corpora striata. We are still ignorant of any central point, or sensorium commuyie, forming the point of termination or of origin to all the nerves of the body, In respect of their origin, we might regard all the nerves as proceeding from the spi- nal cord : the nerves of the face, and those of the organs of respiration and deglutition, arise from the medulla oblongata and its cranial prolongations ; the nerves of the upper extremity proceed from the cervico-dorsal enlargement of the cord ; and the nerves of the lower extremity from the lumbar enlargement : the nerves of the trunk arise from the spinal cord, between its three enlargements. The optic and olfactory nerves alone appear to form exceptions to this rule. All the spinal nerves present the greatest uniformity in reference to their origin, * Comparative anatomy, and the anatomy of the fetus, prove the independent formation of the different parts of the nervous system. DIFFEREXT KIXDS OF NERVES. 761 course, and termination. The arrangement of the cranial nerves, which appears at first sight to be uninfluenced by the laws which regulate the distribution of the spinal nerves, may yet be referred to those laws to a certain extent, notwithstanding its apparent ir- regidarity and complexity. The seneral remarks which foUow apply more particularly to the spinal nerves. The spinal nerves arise by two sets of roots, the anterior {a^fig. 267) and the poste- rior (b). GaU advanced the notion that the posterior roots of the spinal nerves preside over ex- tension, and the anterior roots over flexion of the trunk and limbs, and he explained the predominance of extension over flexion by the greater size of the former roots.* Al- though the fact of this predominance appears to me indisputable. Gall"s explanation is nevertheless rendered void, for it supposes a separation of the fibres of the anterior and posterior roots in reference to their distribution, and no such a separation exists. Sir Charles Bell, having proved by experiments that the facial nerve and the fifth cerebral nerve had different properties, the former being devoted to motion and the lat- ter to sensation, was led to examine whether there did not exist something analogous in the other parts of the body ; and the double roots of the spinal nerves must have natural- ly suggested themselves to his mind. Might not the object of this double origin be to concentrate a double property in each pair of nerves ? Experiments were instituted, and the}' confirmed the preconceived ideas of this ingenious physiologist. They were soon followed by the perfectly contirmator\- experiments made by Magendie, who. by also adducing facts in pathological anatomy, threw so much hght upon this subject, that most modem ph3'siologists have admitted that the posterior roots belong to sensation, and the anterior to motion. Now, notwithstanding the imposing authorities which I have quoted, I must say that I am by no means convmced of the reality of this distinction, and that, in repeating both Bell"s and Magendie's experiments, the section of the anterior and that of the posterior roots appeared to me to produce precisely the same effects.! I have also endeavoured to determine the question anatomically. Some anatomists have thought that, after emerging from the ganglion, the filaments from the two roots become so intimately mingled that" the smallest nervous cord would contain filaments from both the anterior and the posterior roots : as far as 1 have been able to ascertain, the lilaments are interlaced, but never enter into a regular combination. Again, in order to render the dissection more easy and conclusive, having macerated a portion of a body in water containing nitric acid, and having thus destroyed the neuri- leimna or fibrous covering of the nerves. 1 endeavoured to trace some nervous filaments, both cutaneous and muscular, to their origin : but 1 never could succeed in this, so nu- merous are the combinations into which the filaments enter. However, having directed my attention more particularly to certain filaments given off from the cervical nerves to be distributed to the scaleni muscles, I succeeded in tracing them into the correspond- ing spinal gangU. Now the tilaments which proceed directly from the spinal gangUa are, according to the theory just alluded to. exclusively connected with sensation, and, con- sequently, should not be distributed to the muscles. The question of the anterior and posterior roots is connected with another more gen- eral question, viz., Are there different kinds of nerves ! Different Kinds of J\''erve3. The natural distinction of the nerves into those of sensation and of motion dates as far back as Erasistratus, who described the sensory nerves as arising from the meninges, and the motor from the cerebriun and cerebellum. This opinion was often revived and always abandoned, and it was only when direct experiment appeared to conlirm the an- ticipations of theorj" that it became generally adopted. Bichat, after the example of Winslow and Reil. divided the nervous system into two great sections, one of which belongs to animal and the other to organic life. The spinal cord and encephalon form the common centre of the nervous si/stem of amnud life ; the organs of the senses and the muscles are imder its influence. AH the organs supplied by it are subject to vohtion and consciousness. The nerrous systein of organic lift is formed by the gangha of the great sjTiipathetic. which Bichat agrees ^^ith Winslow in regarding as so many little brains. The organs of digestion, respiration, circulation, and secretion are under its influence. All of the organs which it sup'phes are withdrawn from the control of the will and of consciousness. The subdivision adopted by Reil and Bichat prevailed in the science until Sir Charles Bell was led back to the opinion of the ancients by some highly interesting observations and experiments ; he associated with that opinion the ideas of Bichat, and also estab- * In tliis matter Gall has caug-ht sig^ht of a troth which I beliere I have established upon incontestable evi dence. in describing the apparatus of locomotion ; namely, that in all parts of the body, excepting in the mna- cles of the fingers, the extensors are more powerful than the flexors. t [The accuracy of the experiments has now been amply confirmed ; and there is no doubt that the ante- rior are the motor, and the posterior the sensory roots : no difference of structure has been detected between them.J 5D 762 NEUROLOGY. lished an entirely new class of nerves, which he named nerves of expression or respiratory nerves. According to this view, there are live kinds of nerves : nerves intended for special sensations, as the nerves of smell, of vision, and of hearing ; nerves of common sensation; nerves of voluntary motion ; nerves of the respiratory movements ; and sympathetic 7ierves, which appear to unite the body into a whole in relation to its nutrition, its growth, and its decay. By a still wider generalization, Sir Charles Bell admits two systems of nerves, viz., the the primitive or symmetrical nerves, which exist in all animals, and by the aid of which they feel and move ; and, secondly, the superadded, irregular, or respi- ratory nerves, the number of which is proportioned to the perfection of the general organ- ization. It is the latter system of nerves that regulates the partly voluntary and partly mvoluntary act of respiration, and also the several movements connected with it, such as those of speaking, laughing, sighing, and sneezing. According to Bell, these nerves arise from a special tract in the cord, and sometimes proceed separately or distinct from he other nerves, and are sometimes blended with them, this occurring in such a man- ner that neither their union nor their separation in any way impedes their functions. This theory of superadded or respiratory nerves is very ingenious, but altogether hy- pothetical. Besides, it is only strictly applicable to the case of four nerves, viz., the pneumogastric, the glosso-pharyngeal, the spinal-accessory, and the facial. Sir C. Bell's opinion concerning the existence of a column situated between the anterior and poste- rior roots of the nerves, along the whole extent of the spinal cord, and giving origin to certain filaments which combine with those coming from the two roots so as to cause them to participate in the great phenomenon of respiration, is quite gratuitous. On endeavouring to decide whether there are several kinds of nerves, by anatomical investigation, it is found that, excepting the olfactory, optic, and acoustic nerves, which have altogether a peculiar arrangement, and the ganglionic nerves, which are generally gi'ayer and more slender, there is no difference in the character and structure of the nerves of different parts of the body. The cutaneous nervous filaments are exactly sim- ilar to the muscular nervous filaments. From the law of organization, that identity of structure is always connected with iden- tity of function, I have been led to admit that the nerves are homogeneous ; that the dif- ferent properties attributed to them belong to the organs to which they are distributed ; and that they perform no other office in the economy than that of co7iductors — conductors of sensatio7i when they are distributed to a sensory organ, and conductors of motor influence when they enter a motor organ.* This view of the homogeneous structure of the nerves explains much more readily than the opposite one all the phenomena of innervation, and, in particular, the unity of all parts of the nervous system. Moreover, if we admit the existence of special nerves to preside over some special phenomena, and to be distributed to particular organs, why not admit them for all special actions and for all organs 1 There would then have to be digestive nerves, generative nerves, and secreting nerves of different kinds. Course^ Plexuses, and Anastomoses of the JYerves. The course of the nerves must be examined both while they are within and while they are outside the cranio-vertebral cavity. Within this cavity the extent of their course is variable ; and their distribution, after they have emerged from it, is more or less com- plicated. All, or nearly all, the cerebro-spinal nerves communicate with the great sym- pathetic system. When the parts to which they are destined are not complicated, their distribution is very simple, as, for example, the nerves of the thoracic and abdominal parietes ; but when those parts are complicated, the arrangement of the nerves is pro- portionally intricate ; and they then unite so as to form certain interlacements called plexuses, as, for example, the thoracic and abdominal plexuses. The nervous plexuses, which Bichat regarded as so many centres in which the branch- es of origin of the nerves ended, and from which their terminal branches commen- ced, are formed by the division and subdivision of a certain number of nerves, which enter into new combinations, and form an almost inextricable interlacement. Within these plexuses there is generally so intimate a combination of the different elements of which they are composed, that it is almost impossible to determine exactly what branches of origin are concerned in the formation of any particular tenninal branch. A branch of a nerve issuing from a plexus belongs, therefore, to all the nerves which en- ter into the composition of that plexus. The plexuses do not consist of actual anastomoses of the nervous cords ; nor do they, as Monro believed, contain any gray matter : they do not afford origin to any new ner- vous filaments, but they merely give off those which they have received. The most careful examination reveals nothing more than an interchange of nervous cords, which, although they enter into new combinations, still remain independent of each other. * The homogeneous structure of the different nerves is proved by the anatomical fact, that the same nerve is distributed to a great number of organs having very different functions, as, for example, the eighth pair; and also by a fact in comparative anatomy, namely, that the same pair of nerves may, in different species, pre- side over totally different functions ; for example, the fifth pair. DIRECTION OF THE NERVES. 763 The term nervous anastomoses is applied to the communications by loops, or at more or less acute angles, which take place between the nervous filaments. The older anat- omists, governed by the idea that there existed a fluid circulating in the nerves, sup- posed that in the anastomoses of nerves there was a mixture of nervous fluids, nearly similar to that which takes place in vascular anastomoses, where two different columns of blood are intermixed. They regarded the nervous anastomoses as the most active source of sympathies. Bichat also admits the existence of these anastomoses, in which, he says, there is not only a contiguity, but also a continuity of nervous filaments. Be- clard* defends the use of the term anastomosis, and endeavours to define its meaning thus : " There is not merely an application of nervous filaments in the anastomoses, but a true communication, a junction {abouchemenl) of their canals, which, in truth, contain a fixed substance, not a circulating fluid, as was formerly believed." But, on examining the structure of the nervous anastomoses, it is seen that there is simply a juxtaposition of filaments derived from two different sources. The examina- tion also proves most distinctly that the anastomoses are merely small plexuses, so that the only difference between them is, that iji the plexuses there is an interchange of nervous cords, while in the anastomoses there is an iiiterchajige of nervous filaments or of primitive fibres. The anastomoses, like the plexuses, are intended to concentrate the action of several nerves upon any given point, as on a centre, from which their action may ex- tend to certain parts necessarily connected in function. The nervous loops described by Bichat upon all points of the median line of the body, and by the existence of which he supposed that he could explain the return of sensation and voluntary motion to paralytic parts of the body, do not exist. The only anastomoses in the middle line with which I am acquainted are those of the two pneumogastric nerves behind the lower extremity of the trachea, that of the two solar plexuses, and that of the cardiac nerves. The Direction, Relations, and Mode of Division of the JVerves. The nerves are very deeply situated at their egress from the cranio-vertebral cavity. Thus, the brachial plexus is protected by the osseous girdle of the shoulders, and the sacral plexus by the pelvic bones. The nerves then pass into the great cellular inter- vals, which we have already described as existing in the limbs for the reception of the principal vessels and nerves, and for the preservation of those parts from pressure. The direction of the nerves is generally straight, and their length corresponds exact- ly with the distance from their point of origin to that of their termination, so that, if the movements of the limbs exceed their ordinary extent, the nerves may suffer severe in- jury by being stretched. This straight direction is, in general, an essential character of a nerve. Nevertheless, a considerable number of nerves deviate from their primitive direction,! so as to describe a portion of a circle, or are seen reflected upon themselves in a direction precisely opposite to their original one. Others describe a zigzag course, like the arteries ; but these flexuosities are effaced in certain positions of the body, or during the distension of particular organs. Although ther-j is but one arterial trunk for each limb, there are always several nerves, the number of these being variable. As the arteries often deviate from their original direction, they describe certain turns, so as to occupy alternately the opposite sides of a limb. Now, as the nerves pass in a straight direction, and the arteries describe cer- tain curves, it follows that the same nerves cannot accompany the same arteries during the whole of their course. Thus, when an artery deviates from its primitive direction, it has two satellite nerves, one during the first, and the other during the second part of its course. For instance, the crural nerve accompanies the femoral artery, and the sciatic nerve the popliteal artery. When an artery bifurcates or otherwise divides, there is often a particular nerve for each subdivision : thus, the median nerve is the satellite of the brachial artery, the radial nerve accompanies the radial artery, and the ulnar nerve the ulnar artery. It follows, also, from what has been said, that the nerves have no accompanying ves- sel for a more or less considerable portion of their course ; such is the case with the great sciatic and the pneumogastric nerves. The relations of the arteries with the nerves are constant, so that modern surgeons attach great importance to these relations ; in fact, as a nerve, on account of its white- ness, is more easily recognised than an artery, as soon as the former is exposed the latter is immediately met with. It is important, moreover, to determme with the great- est accuracy what nerves are contained within, and what nerves are situated without, the sheath of their corresponding artery. Besides its principal nervous trunk, an artery is also accompanied by certain nervous filaments, which are closely applied to the ves- sels, which are very diflScult to separate from it, and which often escape observation * Anat. G6n6rale, p. 659. t I do not think that a straight direction is necessary for the transmission of the nervous influence, for this takes place in a flexed limb along a curved nerve, as well as hi an e.\tended limb along a straight nerve ; but it is probable that it sliortens the duration of this transmission. 764 NEUROLOGY. from their tenuity. These are the filaments which render ligature of the arteries so painful. Division of the Nerves. — During their course, the nerves do not divide, like the vessels, by ramifying into smaller and smaller branches ; but they give off in succession, as they proceed, branches to the different parts through which they are passing, and thus be- come gradually exhausted, until, reduced to mere filaments themselves, they terminate in the same manner as their branches. The subdivision of nerves, therefore, does not con- sist in a ramification, hut in a process of separatimi or emission. There is one circumstance which has attracted the attention of all anatomists, viz., that the nerves do not diminish in size in proportion to the number of filaments given off from them : some of them even appear to increase in size after having given off several filaments. This apparent singularity is explained, not by the fact that new filaments are added, but by the flatten- ing of the nerve, the separation of its filaments, the addition of a certain quantity of adi- pose tissue, or the thickening of the neurilemma. , Termination of Jferves. The distribution of the nerves is perfectly determinate : each nerve, indeed, has its own distinctly limited department ; an arrangement which, connected with what has al- ready been said regarding the anastomoses, explains why the nerves cannot supply the place of each other. When the principal arterial trunk of a limb is tied, the circulation is re-established by the collateral vessels ; but when a nerve is cut across, all the parts to which it is distributed are paralyzed. The termination of the nerves is, undoubtedly, one of the most important points in their anatomy. In the skin, the nerves terminate in the papillae, not one of which is destitute of them ; in the muscles, they terminate in extremely delicate filaments, which pursue a very long course in the substance of these organs, before they become invisible to the naked eye or to the eye aided by a lens : it has appeared to me that each nervous filament was so arranged as to be in contact with a very great number of muscular fibres, situated either in the same or in different planes. It is probable that there is not a single muscular fibre which is not thus lightly touched by a nervous filament ; this anatomical fact may suggest, instead of Reil's ingenious hypothesis of an atmosphere of activity around each nervous filament, the important conclusion that the nerves act upon the muscular fibre by the effect of contact.* MM. Prevost and Dumas believe that the nervous filaments terminate by loops in the substance of muscles ; and upon their incomplete observations they have founded a theory of muscular contraction. Nervous loops may certainly be observed in the substance of the recti muscles, which they selected as examples ; but these loops are not the termina- tion of the nerves, for a number of filaments are seen to issue from them, and to be dis- tributed in the manner just pointed out.t The different organs vary much in regard to the number of nerves which they receive ; the organs of the senses — the eyes, the ears, the nasal fossae, the tongue, and the skin — stand first in this respect. Next to these rank the muscles, vi'hich receive nerves in proportion to the number of their fibres and to their activity. The organs of nutritive life are far removed from the preceding in regard to the quantity of nerves distributed to them. No proper nerves have yet been discovered in cellular tissue, serous mem- branes, tendons, aponeuroses, and articular cartilages. AU the articulations are provided with nerves, called articular, which may be traced into the ligaments, and even upon the synovial membranes. The long bones, in addition to their central or medullary nerve, have certain periosteal nerves which are lost in the periosteum, and also proper nerves of the spongy tissue, which enter the foramina at the extremities of these bones. The Nervous Ganglia and the Great Sympathetic System. The nervous ganglia are certain grayish knots or swellings situated along the course of the nerves, and having a rather close resemblance to the lymphatic glands or ganglia. Considered generally, the ganglia are a kind of nervous centres, towards which a certain number of filaments converge, and from which they again pass out under new combina- tions. Hence arose the ingenious idea of Winslow, who compared the gangha to little * This hypothesis of a nervous atmosphere was suggested to Reil by the theory of a nervous fluid, which he regarded as analogous to and almost identical with the electric fluid ; and also by the fact that the nervous ap- paratus is not able to supply filaments to all the muscular fibres. t [The loops described by Prtvost and Dumas seem to have consisted of small nervous cords ; but Valentin, Emmert, and Burdach have obseri'ed that the ultimate filaments (primitive fibres of Mijller) have a loop-like termination in the muscles. In reference to the nerves of sensaticm, it has been obseri'ed by Valentin and Burdach, that in the frog's skin the primitive fibres end in loops ; this mode of termination has also been seen by Schwann in the tail of the larva of the toad, and in the frog's mesentery. Schwann farther states, that in both these cases the nervous fibres gave off exceedingly small fibrils, on which minute swellings (ganglia) were placed, and which in some situations formed a network. In the papillte of the human skin, IJreschet thought he saw the nerves ending in loops ; and Gherber believes that he has seen these terminal loops in the skin of quadrupeds. Observers diflFer in their account of the mode of termination of the optic and auditory nerves (see Obgans of Sight and Hearing).] CONNEXIONS OF THE GANGLIA. 765 brains ; an idea which was revived under a modified form by Bichat, who made it the basis of his admirable chapter upon the nervous system of organic hfe. The nervous system of invertebrate animals is reduced to a series of ganglia and gan- glionic nerves ; Swammerdam, Haher, and the older anatomists regarded this series of ganglia as a spinal cord enlarged at intervals. But there is no point of comparison be- tween these two parts ; in a word, the enlargements of the spinal cord and brain cannot be likened in any respect to the ganglionic enlargements. There are three series, or, as some say, three kinds of ganglia : viz., the spinal or rachulian ganglia ; the intercostal ganglia ; and the splanchnic gajiglia ; these last are situ- ated near the viscera for which they are intended. The first series, or the spinal ganglia, belong to the organs of relation. They are con- stant, regular, and symmetrical, hke the nerves upon which they are placed. The other two series are destined for the apparatus of nutritive life, and constitute the great sym- pathetic system, improperly called the ganglionic system. The identity in nature between the spinal ganglia and the ganglia of the great sympa- thetic, and also between the cerebro-spinal and the ganglionic system of nerves, is de- monstrated by the fact that in a great number of animals the ganglia are blended, or, as it were, fused together. M. Weber {Anat. Comparee du Nerf Sympathique, 1817) has ob- served, that in animals the development of the great sympathetic is always inversely pro- portioned to that of the spinal cord. He has established a similar relation between the great sympathetic and the pneumogastric nerve ; and, indeed, in certain species the latter nerve entirely replaces the former. The experiments of M. Legallois upon the spinal cord led him to admit that the vis- ceral nerves are under the influence of the spinal cord, and that the roots of the great sympathetic are in the cord. There are as many spinal ganglia on each side as there are spinal nerves. The gan- glia of the great sympathetic in the sacral, lumbar, and dorsal regions, are as numerous as the spinal ganglia ; in the cervical region, there are only two or three sympathetic ganglia to correspond to the eight spinal ganglia. The superior cervical ganglion may be supposed to represent several ganglia. In the cranium it is difficult to find any ganglia corresponding to the spinal ; still, the Gasserian ganglion, and the ganglion of the eighth pair, may be regarded as analogous to them. On the other hand, we may regard the ophthalmic ganglion, the spheno-palatine or Meckel's ganglion, the otic ganghon, and even the upper part of the superior cervical ganglion, as forming the cranial ganglia of the sympathetic system. Nevertheless, it would, perhaps, be more rational to regard the ophthalmic and otic ganglia as quite independent of the three above-mentioned series of ganglia, and as con- nected with certain local functions. There are a considerable number of these local gangha, which have received no particular names, and which I shall hereafter point out. Connexions of the Ganglia with each other, and with the Cerebro-spinal Jferves. The spinal ganglia belong specially to the posterior roots of the spinal nerves ; but it will preseiitly be seen that the anterior roots are not altogether unconnected with them. From the spinal ganglia proceed three branches, viz., a middle branch, forming the continuation of the spinal nerve ; an anterior or ganglionic branch, proceeding to the cor- responding ganghon of the great sympathetic ; and a posterior branch, which is distribu- ted to the muscles and skin on the posterior region of the trunk. Each of the ganglia of the great sympathetic receive one or several filaments from the spinal ganglia, and also a connecting cord from the sympathetic ganglion immediately above it ; and each of them gives off a connecting cord to the ganglion next below it, and also certain visceral branches, which sometimes terminate directly in the viscera, and sometimes, when their distribution is complicated, proceed to the splanchnic ganglia. Not unfrequently the communicating cords between some of the ganglia of the sym- pathetic are wanting, and the continuity of this nerve is then interrupted. Bichat relies chiefly upon this interruption in support of his opinion, that the great sympathetic is not a nerve properly so called, but that each of its ganglia is the centre of a small special ner- vous system, equally distinct from the cerebro-spinal system and from the other ganglia. The splanchnic ganglia are the centres or points of convergence of a great number of nerves, of which some are derived directly from the cerebro-spinal system, and others from the ganglia of the great sympathetic. In those splanchnic ganglia which approach the median line, the nerves of the right side become blended with those of the left by a great number of plexiform branches, which have a ganglionic aspect, surround the vis- ceral arteries, and are subdivided with them to enter the substance of the viscera. It follows, then, from what has been just stated, that the great sympathetic is neither a continuous nerve, differing from other nerves only by having enlargements, as was be- lieved by the older anatomists, who described the right and left sympathetic as consti- 766 NEUROLOGY. tuting a special pair ; nor is it, as Bichat conceived, a linear series of small nervous centres or little brains, which give off in all directions connecting filaments, both to the spinal and to the visceral nerves ; it is a series of ganglia connected with one another in their action, and originating' from each of the spinal nerves given off from the cerebro- spinal axis. It does not arise from the sixth cerebral nerve, nor from the vidian or carotid filaments, more than from any other spinal nerve ; but it takes its origin from the whole spinal cord ; and if it does not diminish in size as it recedes from the brain, but even increases at some points, this is because it receives new filaments of origin during its course. According to an ingenious hypothesis, which is fully confirmed by anatomical facts, the viscera, which receive their nerves from the gangha of the great sympathetic, derive their principle of action from the whole spinal cord, so that an affection of one nerve, or of one visceral ganglion, must affect the whole ganglionic system, in consequence of the intimate connexions between all the ganglia ; and also the cerebro-spinal system, from the connexions between the sympathetic ganglia and the spinal cord. It would follow from this, that the sympathetic and the splanchnic ganglia together constitute one vast plexus, which connects, in an intimate manner, the several viscera with each other and with the rest of the body. This mutual dependance and sympathy is the chief charac- teristic of the organs of nutritive life, that is to say, of the organs which receive their nervous filaments from the splanchnic and sympathetic ganglia. Structure of the JVerves. Prochaska was the first to throw any light upon the obvious structure of the nervous cords, and to prove that they consisted of true plexuses. Reil, not being contented with noticing the plexiform arrangement of the nervous cords, endeavoured especially to de- termine their structure ; and he failed only because he selected the optic nerve as the type of the other nerves, whereas its structure happens to be exceptional. Each nerve consists of a plexus enveloped in a common fibrous sheath. If this sheath be opened, and the small nervous cords contained within it are spread out by tearing the cellular tissue, it is found that these small cords, which at first seem to be parallel and in juxtaposition, anastomose in a great number of ways, so as to form an extremely complicated plexus. It is also seen that the cords are of unequal size, not only in the same nerve, but also in different nerves ; they are smallest in the branches of the great sympathetic and pneumogastric, and are largest in the nerves of the arm and in the great sciatic nerves. On spreading out a nerve, with its component cords separated from each other, upon a plate of wax, and keeping those cords asunder by pins stuck at intervals, the absolute impossibihty of following them through their successive subdivisions, and the multiplicity of their combinations, will become quite apparent. The nerves consist essentially of two parts, viz., the nervous matter properly so called, and its envelope or fibrous sheath, which has been called the neurilemma. There is a common neurilemma or common fibrous sheath for each nerve. Besides this, each small nervous cord and each fibre is provided with a proper sheath or neuri- lemma. The neurilemmatic canals divide, subdivide, and anastomose like the small nervous cords themselves. The neurilemmatic canals are composed of fibrous tissue : their shining aspect (Avhich has caused them to be frequently mistaken for tendons), their strength, their inextensi- bility, their low degree of vitality, in fact, aU their characters, clearly prove their fibrous nature and exclusively protective function.* The neurilemma of the nerves is continuous with the neurilemma of the spinal cord. Nervous Matter. — If, as was shown by Reil, a nerve be immersed in diluted nitric acid, its neurilemma will be dissolved (rendered transparent), while its nervous matter will become remarkably dense and opaque. We shall hereafter see how valuable is this double property of acids in their action upon nerves for determining the true character of fibres supposed to be nervous. In a nerve thus prepared, it is seen most clearly, that the nervous filaments of which it is composed are continually anastomosing by loops or at certain angles ; and that the addition of one set of filaments to the trunk of the nerve, or the separation of others from it, necessarily interrupts the chain of their relations at the very point where it seemed possible to ascertain them, so that, after every few inches, the component parts of a nerve are completely changed. What is the structure of the nervous matter 1 It is not a pulp, but is composed of pencils of exceedingly fine filaments, which may be compared to the fibres of raw silk : these filaments are parallel and in juxtaposition ; they are free throughout the whole length of the nerve, and may be distinctly separated from each other ; when not stretched, they are flexuous like a waved line. Each nervous filament reaches the entire length of the nerve. In each nerve, the filaments of which the fibres are composed pass con- * It may be said that the neurilemma owes its fitness as a protecting organ as well to its low vitalitj- as to its strength. This low degree of vitality of the neurilemma is the cause why nerves are constantly seen pass- ing through inflamed or degenerated parts without being affected themselves. STRUCTURE OF THE NERVES. 767 tinually from one fibre to another, and enter into an immense number of combinations, without ever becoming blended together. This structure, which is so evident in a nerve hardened by nitric acid, is not less dis- tinct in nerves which have undergone no preparation.* On puncturing the neurilemma, the nervous matter protrudes through the opening, precisely in the same way as the substance of the spinal cord protrudes under similar circumstances. On dividing the neurilemma along the whole length of the nerve, the nervous matter appears like long, parallel filaments, of a milk-white colour, which float in water if the nerve be immersed in that fluid. Every nervous filament (and this is a fundamental point in their anatomy) has its central extremity in the cerebro-spinal axis, and its peripheral extremity at its point of termination. During the whole of its long course, it only enters into new combinations, without ever being interrupted. Continuity is a laio of the structure of the nervous filaments, i Can the nerves be injected 1 The doctrine of a nervous fluid, which so long prevailed in the schools, led physiolo- gists to admit the existence of canals for the circulation of this fluid. Several experi- mentalists stated that they had collected the nervous fluid, and they even described its properties ; and anatomists instituted no researches to confirm or refute these asser- tions. Malpighi himself, who, in reference to the study of anatomy, carried to such an extent that system of philosophical skepticism which has completely revolutionized all science, believed that he saw the nervous fluid escape from the cut end of a nerve, like a glutinous juice, which he compared to spirits of turpentine, t Reil and some others have injected the neurilemma. Reil describes a very ingenious method of injecting the optic nerve, which consists in opening the transparent cornea, and injecting mercury into the globe of the eye : the mercury passes through the fora- mina, which transmit the filaments of the optic nerve at the point where these becoijie continuous with the retina. Such was the state of our knowledge when Bogros, prosector to the Faculty, having accidentally punctured a nerve with the tube of a mercurial injecting apparatus, observ- ed that the mercury ran along the punctured nervous fibre, and also into the adjacent nervous fibres ; he repeated and varied his experiments in a great number of ways, and soon published a memoir, in which he formally announced as a demonstrated fact that, in each nervous fibre, there was a central canal capable of being injected ; and, in his enthusiasm at liis discovery, he thought that he had realized the desire of Ruysch,1: and that he could henceforth trace the nerves to their very finest terminations. The work of Bogros was in general received with little favour, and, I think, has not been estimated at its real worth. Having renewed his experiments, I have arrived at the following result : If, with a pair of blunt pincers, a nervous fibre be raised from the centre of the nerve to which it belongs (from the middle of the median nerve, for exam- ple), and if the tube of the lymphatic injecting apparatus be inserted accurately intb its centre, the mercury will be seen to run by jerks, either downward or upward, along the centre of the nervous fibre, and to pass into a variable number of the adjacent fibres ; if the injection be a successful one, the greater number of the fibres of the nerve will be injected throughout their whole length. Gentle pressure with the finger, or with the handle of the scalpel, greatly facilitates the progress of the mercury ; but it often hap- pens that the parietes of the canal through which the mercury is passing yield at some point, a rupture ensues, and the fluid is extravasated. When the nervous fibre has not been punctured in the centre, the mercury is seen to run along the injected fibre, and even into some of those near it ; but the mercurial col- umn is never regular ; it does not occupy the centre of the fibre, but only one side of it ; and it is soon extravasated into the neurilemmatic sheath, which in a short time bursts. This second kind of injection, which may be made at will by puncturing the fibre su- * I have also examined this structure in living animals, while endeavouring- to determine the insensibility of the neurilemma and the sensibility of the nervous filaments. t [The nervous filaments (primitive fibres of Miiller) are simple tubes, containing a thread of a soft, semi- transparent substance ; they are continuous with the white fibres of the brain and spinal cord at the apparent origin of the nerves. The primitive fibres of the nerves resemble those of the brain and cord in the nature of their contents, but they are larger, and their tubular, homogeneous sheath is much more distinct, and is firmer, so that they do not become varicose. The olfactory, optic, and auditory nerves, however, are exceptions to this rule ; their fibres resembling those of the brain and cord, in their size, delicacy, and liability to become varicose. No differences have been observed between the fibres of the other cranial and spinal nerves, nor yet between those of the motor and sensory roots. The sympathetic nerve, and all which receive fibres from it, contain, besides the ordinary nervous fibres, a greater or less number of jointed fibres {gray fibres, Miiller ; organic nervous fibres, Schwann ; cellular tissue, Valentin), exactly like those found in the gangha and in the gray matter of the brain and spinal cord.] i But, as Haller remarks, iUalpighi only saw this upon cutting through the Cauda equina, and never ob- served it in the section of any other nerves ; now, it is extremely probable that he saw merely the serous fluid which is most commonly found in the lower infundibuliform portion of the spinal dura mater: "Quim vehe- menter suspicor eum clarum virum humorem vidisse viscidum, quo infnndibulum durce membrane spinalis fre- quentissime plenum est, et qui idem in spinam bifidam anctus aliit."— (Ilaller, Ele7n. Physiol., t. iv., p. 197.) i) Ruysch said that he should have nothing to desire if ho cculd succeed in injecting the nerves as he had done the vessels. *768 NEUROLOGY. perficially, differs essentially from the former one, obtained by introducing the pipe into the centre of the fibre. In the latter case, the small column of mercury is uniform and regular, and its metallic lustre is, as it were, observed ; the fluid runs rapidly ; the ner- vous canal is less easily ruptured ; and, when this does happen, it is preceded by a pro- trusion of the nervous matter ; then the mercury is extravasated into the neurilemmatic sheath, and it pursues the same course as it would have taken if the nervous fibre had been punctured superficially in the first instance. Where do the injections pass in these two cases 1 In the second method, that is to say, when the nerve is punctured superficially, it is the neurilemma that is injected. But in the method of central injection, is the nervous matter itself injected] Bogros be- lieved that it was, and he even asserted that he had seen a central canal with the naked eye ; but no such canal exists ; and the one which he showed after desiccation of an in- jected nerve was artificially made, as we shall immediately find. How, indeed, can we admit the existence of a canal in nervous matter, which we have shown to consist of a pencil of parallel and juxtaposed filaments 1 If, therefore, in the central injection, the mercury neither enters into the nervous mat- ter, nor is contained in the neurilemma, where is it situated 1 Is it in lymphatic ves- sels ] We do not know ; for lymphatics have not been shown by any one. Are they arteries or nerves 1 To this it may be answered, that the bloodvessels do not follow the direction of the nerves. All this is explained by the following fact : each nervous fibre, besides its common neurilemmatic sheath, has also a proper sheath, in contact with the neurilenama by its outer surface, and with the bundle of nervous filaments by its inner surface, which is smooth and moist. This sheath may be demonstrated by cutting a nerve across, and seizing one of the tufts which project beyond the retracted neurilemma ; a nervous fibre can then generally without efl^ort be drawn out several inches, having a smooth surface, and being completely freed from its common neurilemma. Now this fibre consists not only of nervous matter, but also of a proper sheath perfectly distinct from the neurilem- ma. It may now be injected, and will then present all the characters of the central in- jection already mentioned ; and, upon examining it with a lens, it will be seen that the nervous filaments of which it is composed are regularly distributed around the column of mercury. It follows, then, that, in the central injection of a nerve, it is neither the neurilemma, nor the nervous matter, nor the vessels that are injected, but the proper sheath of each nervous Jibre ; and that the passage of the injection from one fibre to a great number of others depends on the canals formed by the proper sheaths anastomosing with each other. I shall farther remark, that in this injection the mercury evidently penetrates into a regular canal, and not into one produced by its own weight, for a column of a few lines is suificient for the purpose. Again, the mercury runs more easily from the peripheral towards the central extrem- ity of a nerve than in the opposite direction, and when the injection is successful, the spinal ganglia are filled with the mercury, which is then either extravasated into the cav- ity of the dura mater, or escapes by the veins. If it be asked why the mercury does not pass into the anterior and posterior roots of the nerves 1 I should answer, that it is not certain that the fibres of these roots have any proper sheaths ; or, if so, they are very readily lacerated. As to the passage of the mercury from the nervous ganglia into the veins, it is probable that the proper sheaths terminate in the ganglia, so that the mercu- ry is extravasated into the tissue of which the ganglia consist. Injections afford a good means of tracing the nervous filaments into the substance of organs. An injection thrown into the lingual branch of the fifth nerve penetrates as far as the papillae of the tongue. Structure of the Ganglia. Meckel, in his excellent monograph upon the fifth pair, advanced the opinion that the nerves divided in the ganglia into a multitude of fibres which are intended for a great number of parts. Zinn (Acad. Berlin, 1755) said that the nerves not only divided within the ganglia into a great number of fibres, and were directed by them from the centre to the circumference, but that they were also mingled and combined in the ganglia in such a manner that a great number of fine fibres united into a smaller number of fibres of greater diameter. But this doctrine, however specious it may be, not resting upon any anatomical fact, was rejected by Haller. Scarpa undertook a series of researches in order to render our knowledge more complete regarding this subject. Instead of boiling the ganglia or ma- cerating them in vinegar, urine, and other liquids, Scarpa was contented with macera- ting them in pure water frequently renewed — a method practised by Ruysch in his del- icate investigations ; by means of this simple proceeding, he was able to demonstrate that the ganglia are formed by a number of nervous filaments surrounded by cellular tis- sue, and by a gray matter which is destroyed by maceration.* - * [The gray matter of the gangha consists, like that of the brain and spinal cord, of reddish nucleated glob- DESCRIPTION OF THE NERVES. 769 He carried his researches not only into the anatomy of the spinal, but also into that of the visceral ganglia, and he discovered a wonderful uniformity in the structure of the one and the other. He compared their structure to that of the plexuses ; both of them receive nerves from all sides, which nerves are then intermixed without becoming uni- ted ; and both generally give off a greater number of nerves than have assisted in their formation. The injection of the nervous ganglia from the nerves has enabled me to discover that these ganglia have a precisely similar structure to that of the lymphatic glands ; they are composed of cells communicating with each other, and among which the nervous fibres are scattered. In attempting to draw a comparison between the nervous plexuses, anastomoses, and gangha, it might be said that in the plexuses there was an exchange of nervous cords, in the anastomoses, an exchange of nervous fibres, and in the gangha, an exchange of nervous filaments. Preparation of the J^erves. For dissecting the nerves, a very emaciated subject, either young or old, should be chosen. Old wasted subjects appear to me at least as favourable as young subjects. The dissection of the spinal nerves is easy. Such is not the case with the cranial nerves, the dissection of which is undoubtedly the most difficult part of practical anat- omy. In order to facilitate the study of these nerves, and to aid in the distinction of the nervous filaments from small vessels and portions of fibrous tissue with which they are often confounded, I am in the habit of submitting the head to the action of dilute nitric acid. After having macerated it lor some time in this acidulated fluid, I immerse the preparation in pure water, which I renew from time to time : the tissues generally, as well as the neurilemma, become perfectly transparent, and like jelly ; the nervous mat- ter alone remains whiter and more consistent, and then all error becomes impossible. Besides, the bones, when thus deprived of their phosphate of lime, may be cut like the soft parts. In this way I have succeeded in separating the entire cerebro-spinal nervous system from the other organs, retaining the great sympathetic in connexion with the rest of the nervous system. DESCRIPTION OF THE NERVES. General Remarks. — Division into Spinal, Cranial, and Sympathetic Nerves. The nerves are divided into two very distinct sets : the cerebrospinal nerves, which have their origin or central extremity in the spinal cord or its cranial prolongations : these are the nerves of relation or of animal life ; and the ganglionic nerves, or jierves of the great sympathetic, which end in or emanate from certain ganglia : these belong to the system of nutrition or of organic life. The cerebro-spinal nerves are divided into the spinal or rachidian, and the cranial nerves: the first consist of all those which emerge from the inter-vertebral foramina;* the second, so improperly termed the cerebral or encephalic nerves, emerge from the foramina at the base of the cranium. As the line of demarcation, which seems, at first sight, to separate the cranium from the spinal column, disappears on an analytical study of the scull and on a comparison of it with the vertebrae, so it will be found that the cranial nerves, notwithstanding their apparent irregularity, approach, in many respects, to the simplicity and regularity of the spinal nerves. From such a comparison of the cranial with the spinal nerves we shall derive the general principle, that the situation at which the nerves emerge from their osseous cavities is altogether of secondarj' importance, while the fundamental points in their anatomy are the exact situation of their ccjitral extremity, and their mode of distri- bution to their peripheral extremity; we shall also find that the only rational basis of a good classification of the nerves must be derived from the consideration of their origin. In my opinion, the only difference between the cranial and spinal nerves is, that the former arise from the medulla oblongata and its cranial prolongations, while the latter arise from the spinal cord below the medulla oblongata. Just as in the osteological di- vision of this work I have described the vertebra before the cranium, so I shall now de- scribe the spinal before the cranial nerves ; this slight modification in the order gener- ally adopted will enable the student to pass from the simple to the complex, and to defer the study of the very complicated nerves of the cranium until he has been accustomed to the dissection and examination of other nerves. The following is, therefore, the order I shall adopt in describing the nerves : the spi- nal nerves, the cranial nerves, the ganglionic or visceral nerves. ules, and of gray, jointed fibres, which surround and adhere to the g-lobules, and which are most abundant in the ganglia of the sympathetic. The white fibres in the ganglia are like those of the nerves with which they are continuous ; they interlace among the globules, but do not anastomose : it has been supposed that some- white fibres may originate or terminate in the ganglia, but this is not established. J * Jt will be recollected that we have included the sacral foramina among the invertebral. 5E 770 NEUROLOGY. THE SPINAL NERVES. Enumeration and Classification. — The Central Extremities or Origins of the Spinal Nerves — Apparent Origins — Deep or Real Origins. — The Posterior Branches of the Spinal Nerves — Common Characters — the Posterior Branches of the Cervical Nerves, their Com- mon and. Proper Characters — the Posterior Branches of the Dorsal, Lumbar, and Sacral Nerves. — The Anterior Branches of the Spinal Nerves — their General Arrangement. The number of the spi?ial nerves, that is to say, of the nerves which pass through the inter-vertebral foramina, including the sacral foramina, is entirely dependant on the number of the vertebrae.* There are eight pairs (1 to 8, fig. 268) of cervical nerves, including the sub-occipital; twelve of dorsal (9 to 20) ; five of lumbar (21 to 25) ; and six of sacral nerves (26 to 31) ; in all, thirty-one pairs. They all have certain characters in common ; and there are also characters proper to certain regions, and, lastly, characters proper to each nerve. We shall proceed to examine, under these three points of view, the central extrem- ity, the course, and the termination of the spinal nerves. The Central Extremities or Origins of the Spinal Nerves. The Apparent Origins of the Spinal JSTerves. Dissection. — The same as that of the spinal cord. Common Characters. There are very close analogies, and only slight differences, between the different spi- nal nerves, in regard to their origin and course within the spinal canal. This circum- stance, added to the fact that the same dissection is required to expose the origins of the whole series of spinal nerves, has appeared to me a sufficient reason for including them all in one common description. Such a plan, the object of which is to study anal- ogous parts by comparison, is infinitely preferable to one in which the origin of each pair of nerves is separately described. The spinal nerves arise from the spinal cord by a double row of filaments, or by two series of roots. These roots are distinguished into the anterior {a a, fig. 267), which come off from each side of the anterior surface of the cord, and the posterior {b h), which come off also from each side of the posterior surface. The latter are also named the ganglionic roots, because they are more particularly connected with the spinal nervous ganglia {b b). The ligamentum denticulatum (c c) is situated betAveen these two series of roots. Immediately after leaving the cord, both the anterior and posterior roots are collected into a number of groups corresponding to the number of the spinal nerves ; the nervous cords of which each' group consists converge towards each other, the superior cords de- scending to meet the inferior, which is soon accomplished from the latter being less ob- lique in their direction. It follows, therefore, that the filaments of each root, situated one above the other, widely separated from each other on the inside, and approximated on the outside, represent a triangle, the general inclination of which to the axis of the cord varies in each particular region. Not unfrequently the filaments, especially those of the anterior roots, form two secondary groups. As they are about to enter the separate fibrous canal formed for them by the dura mater, the fibres of each of the anterior roots, and also those of each posterior root, are collected into a flattened cord. There is one fibrous canal for each cord of the anterior roots, and another for each cord of the posterior roots. The arachnoid membrane, which forms a common funnel-shaped sheath for both roots of each spinal nerve, is re- flected from them at the points where they enter the fibrous canals of the dura mater, to which the nervous cords are rather firmly attached. Although the corresponding groups of anterior and posterior roots approach each other to pass through the fibrous canals of the dura mater, there is never the slightest com- munication between them. It is curious to see the long and numerous cords or fila- ments which constitute the cauda aguina running parallel to each other without any an- astomoses, while, as soon as they emerge from the spinal canal, their communications are almost continual. Communications between the filaments of the same series, whether anterior or pos- terior, are not rare ; they take place in several different ways : thus, sometimes two filaments belonging to the same nerve unite, sometimes the filaments of two different nerves are combined, and at others, again, a filament intermediate to two nerves bifur- cates and is divided between them. Moreover, the oblique direction of the roots of the spinal nerves, and the variable length of their course within the spinal canal, are the necessary consequences of the * This relation between the number of the spinal nerves and the number of the vertebrae prevails through- out the whole series of vertebrate animals ; and, accordingly, there are about sixty spinal nerves in certain mammalia, and several hundred in some serpents. APPARENT ORIGINS OF THE NERVES. T71 relative shortness of the cord, which, as it terminates opposite the first lumbar vertebra, cannot give origin to all the nerves opposite the inter- vertebral foramina, through which they have to pass.* The differences between the anterior and posterior roots may be collected under the following heads ; The anterior roots arise nearer to the median line than the posterior ; they approach nearer and nearer to that line, towards the lower part of the cord, so that in this situa- tion they arise from each side of the median fissure. While all the posterior roots are given off from a longitudinal furrow of gray sub- stance, from which they never deviate, the anterior roots arise somewhat irregularly, and, as it were, confusedly, from a small white column about half a line in breadth. In regard to size, the posterior roots, taken separately, are much larger than their corresponding anterior roots ; besides this, the filaments of the posterior roots are more numerous, so that the posterior roots, taken together, are larger than the anterior, as Soemmering, Chaussier, and Gall have very well established. It is difficult to conceive how some authors should have entertained the opinion that the proportion between them is just the reverse, at least in some regions ; this error has, doubtless, arisen from the varieties which exist in different regions of the medulla, in the relative sizes of the an- terior and posterior roots, but which are never such as to give the advantage in point of size to the anterior roots : opposite the inter-vertebral foramina, the series of cords formed by the anterior roots have a different arrangement from those formed by the pos- terior roots. The cord formed by each of the posterior roots immediately swells out and forms an ohve-shaped ganglion, which is caUed a vertebral or spinal ganglion (b b,Jig. 267). Haase, and then Scarpa, clearly proved that, in general, the posterior roots alone passed into the spinal ganglia, and hence they are often denonainated the ganglionic roots : the spinal ganglia are situated in the inter-vertebral foramina, those of the sacral region are en- closed in the sacral canal. Though it is generally to the nervous cord which emerges from this ganglion that the cord of the anterior root is applied and united, yet I would hasten to observe, that the anterior root is not so completely unconnected with the ganglion as is commonly stated ; thus, not unfrequently the fibres of the anterior root are united either to the outer end or to the middle of the ganglion ; and, moreover, in the lumbar and sacral regions there is half a ganglion on each root. There are thirty pairs of spinal ganglia, and occasionally thirty-one, when the first pair of cervical nerves or the sub-occipital nerves are provided with them : the size of the ganglia bears no proportion to the diameter of the intei -vertebral foramina, but de- pends on the number and size of the filaments of origin wkich pass into them, and of the nerves which are given off from them. The cord which emerges from the ganglion is cylindrical, has a plexiform structure, and a furrowed aspect ; it is impossible to ascertain what part of it belongs to the ante- rior and what to the posterior root ; it gives off tiiree sets of branches : the posterior spinal branches, which supply the muscles and integuments of the posterior spinal region ; the anterior spinal branches (see Jig. 268), the true continuation of the nerve, which are distributed to the lateral and anterior parts of the trunk, and to the upper and lower ex- tremities ; and the ganglionic spinal brawlies, which pass to the ganglia of the great sympathetic (/ i u). The ganglionic branches will be descrii»ed with the ganglia of the great sympathetic. . As the posterior branches have a close analogy in their mode of distribution, and may be exposed in the same dissection, they will be described under one head. The aiUerior branches being destined for dissimilar parts, their individual distribution is exceedingly varied and complicated, so that a particular description is requisite, if not of the anterior branches of each nerve, at least of those of the several sets of nerves. Such are the characters common to all the spinal nerves at their central extremities, during their course within the vertebral canal, and at their exit from the inter-vertebral foramina. Let us next examine the characters proper to the nerves of each region. Proper Characters of the Apparent Origins of the Nerves. Proper Characters of the Cervical Nerves. — The roots of these nerves (I to 8,^^. 268) are much less oblique than those of the other spinal nerves. The first cervical nerve slopes a little upward and outward, like the cranial veins, which it resembles in this re- spect. The second nerve is transverse ; the succeeding nerves slope downward and outward, the lowest being the most obUque ; but their obhquity never exceeds the depth of a single vertei)ra. The proportion between the size of the posterior and anterior roots is as 3 to 1 ; and * Gall believed that he had solved this question, by saying that the length and obliquity of the coarse of the spinal nerves is a necessary result of the erect position of man. It is certain that the nerves are less ob- lique and have a shorter course within the vertebral canal in the lower animals ; but this difference is ex- plained by the greater length of the spinal cord in them, and has nothing to do with the attitude. 772 NEUROLOGY. this difference, which is much greater than is observed in any other region, obtains not only in reference to the filaments taken altogether, but also to each particular filament. The cervical nerves increase rapidly in size from the first to the fifth, and then main- tain the same size to the eighth. The first cervical nerve, so well described by Asch, has some peculiarities : its pos- terior filaments of origin are much less numerous than the anterior, the spinal accessory of Willis appearing to supply this deficiency ; it is also frequently without a ganglion.* Proper Characters of the Dorsal Nerves. — Excepting the first, which has all the charac- ters of the cervical nerves, the roots of the dorsal pairs of nerves (9 to 20) present the following peculiarities : A small number of filaments or roots ; so that, with the exception of the sacral, the dorsal are the smallest of all the spinal nerves. Uniformity in the number of the filaments, i. e., in the size of their roots. The dorsal nerves are almost of equal size, the twelfth nerve alone being somewhat longer than the rest. A considerable interval between their roots, and a want of regularity in this interval. Frequently a portion of the spinal cord, from eight to ten lines in length, gives origin to only a small pair of nerves. A more marked slenderness of the filaments of origin than in any other region. The slight disproportion between their anterior and posterior roots when compared filament for filament. The direction of their roots, which remain in contact with the cord for some distance, and then leave it ; this circumstance is calculated to give rise to errors concerning the precise situation of their origin. The length of their course within the spinal canal ; this length is equal to the height of at least two vertebrae. Proper Characters of the Lumbar and Sacral Nerves. — The roots of these nerves form the Cauda equina ; their characters are, the great number of their filaments of origin, which exceeds those of the dorsal, and even those of the cervical nerves. The extreme closeness of these filaments, which form an uninterrupted series. The proportion between the filaments of the anterior and those of the posterior roots, which is as 2 to 1. The uniformity in point of size between the two sets of filaments, the anterior fila- ments, taken individually, being as large as the posterior. The continuance of the origin of the posterior roots to take place at the groove, while the anterior approach nearer and nearer to the median line towards the lower part of the cord, and almost touch iljose of the opposite side. The concurrence of both thg anterior and posterior roots in the formation of the spi- nal ganglia. The almost vertical direction of the roots, a character conunon to both the lumbar and sacral pairs of nerves. The singular length of their course before they emerge from the spinal canal.t The Real Origins of the Spinal JSTerves. The apparent central extremity or origin of the spinal nerves is very different from their real central extremity or real origin. On examining the spinal cord of an adult, for the purpose of determining this important point, one is inclined to admit that the point of " contact between any nerve and the cord is the real origin of the nerve, so readily can the latter be separated from the cord without leaving any trace of the separation. It has even been stated by some that the nerves arise from the neurilemma of the spinal cord. Chaussier believed that the two series of roots arose from two lateral furrows, one anterior and the other posterior ; but Gall has with reason regarded these furrows as formed by pulling off the roots. Others agree with the older anatomists in regarding the spinal cord as a large nerve formed by the junction of all the nervous filaments which are given off from it. But this idea is refuted by the fact that the cord does not progressively diminish in size from above downward, as it must have done if formed by the junction of the roots of the spi- nal nerves. The ingenious and correct observation made by Vicq d'Azyr, that the gray matter is always found in large quantity at those parts from which a great number of nerves ori- ginate, and that it bears a proportion to the number of these nerves, and the confirma- tory observations of Gall and Spurzheim, seem to prove that the nerves originate from the gray matter. This presumption is also strengthened by the consideration, that the * According to the principles of classification which I have already stated, I should range the spinal acces- sory nerve among the cervical nerves, because it originates from the cervical portion of the spinal cord : iu classing it among the cranial nerves, I yield to general usage. t [Lastly, the situation of the ganglia of the sacral nerves within the sacral canal, and of the lowest of them within the cavity of the dura mater.l POSTERIOR BRANCHES OF THE CERVICAL NERVES 773 central gray substance of the cord is more abundant opposite the posterior roots, which are the larger, than opposite the anterior roots, which are the smaller. On examining the spinal cord of an adult by means of a stream of water, it is seen that, after tearing away the filaments of the nerves, a small conical depression remains where each fila- ment had been attached, and that the real origin of the filaments is not in this depression, but is much more deeply seated. This is all that can be discovered from an examina- tion of the spinal cord of the adult ; but in the foetus, at the seventh or eighth month, a considerable part of the cord is semi-transparent, so that the already white filaments by which the nerves arise can be traced into its interior. On making a vertical section transversely through the spinal cord of the foetus, just level with the commissure, and then directing a strong light on the surface of the section, it will be seen that the great number of very delicate filaments of which the anterior and posterior roots of the spinal nerves are composed traverse the central gray matter, are arranged like the teeth of a comb, and may be traced into the posterior median columns ; these small filaments are, moreover, all parallel. The white commissure might almost be regarded as the com- missure of these nerves. This view is very different from that of Bellingeri, who, entertaining certain physio- logical ideas, supposes that the anterior as well as the posterior roots of the spinal nerves consist of three sets of filaments, some of which come from the surface of the cord, others from the interior of the white matter, while the third set traverse the white matter, so as to reach the extremities of the eornua of the gray substance. Lastly, some anatomists agree with Santorini in believing that the nerves decussate at their origin ; but they have not attempted to demonstrate this. The Posterior Branches of the Spinal Nerves. Dissection. — Divide the integuments from the external occipital protuberance down to the coccyx. Dissect off the skin over the spinous processes with great care, especially opposite the trapezius. Be particularly cautious opposite the cellular interval between the sacro-lumbalis and the longissimus dorsi. Common Characters. The posterior branches of the spinal nerves, which are generally smaller than tne ante- rior branches, emanate from the plexiform cords which form the continuation of the cor- responding spinal ganglia, are directed backward, and immediately pass through the fora- mina, which I may regard as posterior inter-vertebral foramina.* These branches sub- divide into several twigs, which enter the great cellular intervals between the long mus- cles of the back, and are distributed to the muscles o-r the integuments. The greatest uniformity prevails among such of these nerves as are distributed to the same kinds of organs, and their differences depend on peculiarities in the parts to which they belong. We shall now study in succession the posterior branches of the cervical, dorsal, and lumbar spinal nerves. The Posterior Branches of the Cervical JVerves. Common Characters. All the posterior branches of the cervical nerves (z to o',Jig. 300) pass transversely inward between the complexus and the semi-spinalis colli, having first given off some very small twigs : having reached the sides of the posterior cervical ligament, they per- forate the aponeurotic attachments of the trapezius from before backward, lie close be- neath the skin, and are directed transversely outward. The course of these branches, therefore, is at first inward, and then outward. The posterior branch of the first cervi- cal nerve is the only one which presents any exception to these general characters. Proper Characters. The Posterior Branch of the First Ccrtical Nerve. The posterior branch of the first cervical or sub-occipital nerve, larger than the anterior branch, escapes between the occipital bone and the posterior arch of the atlas, on the inner side of the vertebral artery, with which it is in contact, below the rectus capitis posticus major, and in the area of the equilateral triang'e formed by that with the two oblique muscles ; in this situation {i, fig. 300) it is concetled by a large quantity of fatty tissue, which renders it rather difficult of dissection ; and it immediately divides into several branches, which may be arranged into the i7iternal, which go to the great and email recti muscles ; external, which supply the great and small oblique muscles ; and inferior or anastomotic, which, by uniting with the second cervical nerve, assist in the formation of the posterior cervical plexus. The branch to the rectus minor passes at first between the rectus major and the com- plexus, and then reaches the rectus minor. * Vide Osteology (vertebral column in general). These foraniiua are situated between the transversa processes, aJul in the dorsal region are completed on the outside by the superior costo-transverse ligament. 774 NEUROLOGY. The principal branch for the inferior oblique, before ramifying in that muscle, forms an arch or loop, which has been well described by Bicha:t. It follows, therefore, that both of the recti and both of the obhque muscles are supphed by the first cervical nerve, which gives no filament to the complexus,* and none to the skin. The Posterior Branch of the Second Cervical Nerve. This is the largest of all the posterior branches of the cervical nerves, and is three or four times larger than the anterior branch of the same nerve ; it emerges {g, jig. 300) from the spine, between the posterior arch of the atlas and the corresponding lamina of the axis, in the same line as the posterior branch of the first nerve, immediately below the lower border of the obhquus major, and is reflected upward between the hairy scalp on the one hand, and the occipitahs muscle and epicranial aponeurosis on the other ; it passes horizontally inward between the obliquus major and the complexus, perforates this last muscle in the outer side of its digastric portion (the biventer cervicis), then changes its direction, and turns outward between the complexus and the trapezius, through which latter it passes to become sub-cutaneous and accompany the occipital ar- tery ; it is here called the great occipital nerve (occipitalis major, a, fig. 285). Hither- to cylindrical, this nerve, on becoming sub-cutaneous, is flattened, and increased in width, and then, passing upward, spreads out into a considerable number of diverging branches, internal, middle, and external, which cover the occipital region ■\\ith their ramifications, and may be traced even to the parietal region : the internal branches are the shortest, and are successively lost in the skin of the occipital region. It supplies several branches, as follows : Some anastomotic branches to the first and third cervical nerves. Opposite the lower border of the obliquus major, it gives off a considerable vniscular branch {w,fig. 300), which is distributed to that muscle, to the complexus, and especial- ly to the splenius {w, fig. 298) ; the branches to the splenius are of great size, and spread upon its deep surface into diverging twigs, which anastomose both with each other and with branches derived from the third cervical nerve. During its passage between the obliquus major and the complexus, and between the last-named muscle and the trapezius, the posterior branch of the second cervical nerve suppUes these different muscles with a rather large number of nervous twigs. Its sub-cutaneous portion is distributed exclusively to the hairy scalp. The occipi- talis muscle, upon which it ramifies, does not receive any branch from it : as we shall elsewhere show, this muscle is supphed by the auricular branch of the facial nerve. The subdivisions of the sub-cutaneous portion of the second cervical nerve may be tra- ced into the hair follicles, and several of its external branches anastomose with the mas- toid branch of the anterior cervical plexus. Tlie Posterior Branch of the Third Cervical Nerve. The posterior branch of the third cervical nerve, smaller than that of the second, but much larger than that of the fourth nerve, and partially intended for the occipital region, emerges between the transverse process of the atlas and that of the third cervical ver- tebra, and, consequently, farther outward than the posterior branches of the first and sec- ond ner^^es ; it is immediately curved, and passes transversely inward {t, fig. 300) be- tween the complexus and the semi-spinalis colli. Having reached the inner border of the complexus, it divides into two cutaneous branches : an ascending or occipital, which perforates the innermost fibres of the complexus, passes vertically upward upon one side of the median line, apphed to the under surface of the skin, and ramifies upon the occip- ital region, near the median line, and to the inner side of the branch from the second cervical nerve ; and a horizontal or cervical branch, which perforates the aponeurosis of the trapezius between the complexus and the posterior cervical ligament, and passes horizontally outward beneath the skin, to which it adheres, and in the substance of which it terminates As the posterior branch of the third cervical nerve emerges from the posterior inter- vertebral foramen, it gives off an ascending branch, which forms an anastomotic arch with the descending branch of the second nerve : the succession of arches formed by the anastomoses of the first, second, and third nerves, and the very numerous branches which arise from their convexities, constitute a plexus, which may be called the posterior cervical plexus : it is situated beneath the complexus, near its external attachments, and it supphes both that muscle and the splenius. The direct anastomoses between the pos- terior branches of the three superior cervical nerves appear to me to be sometimes want- ing ; but then the branches given off from them still exist, and form a plexus between the splenius and the complexus. The Posterior Branches of the Fourth, Fifth, Sixth, Seventh, and Eighth Cervical Nerves. The posterior branches of the fourth, fifth, sixth, seventh, and eighth cervical nerves are much smaller than the preceding, and diminish in size successively from the fourth to the * [Asch saw and has described a twig (m, Jig. 300) proceeding from the posterior branch of the first cerri- cal nerve to the complexus muscle ; Swan and Arnold Iso observed it.] POSTERIOR BRANXHES OF THE DORSAL NERVES. 775 seveuth. Inimediately after their exit from the posterior inter-vertebral foramina, they are reflected inward and downward m the followmg manner : the fourth and fifth (o') in- cline downward upon the semi-spinalis colli, between it and the complexus ; the sixth, seventh, and eighth descend almost vertically beneath the lowest fasciculi of the semi- spinalis colli, supply that muscle and the multifidus spinae, and having reached the side of the median line, perforate the aponeuroses of the splenius and trapezius, become ap- plied to the skin, and ramify in it. The Posterior Branches of the Dorsal, Lumbar, and Sacral JS''erve. The Posterior Branches of the Dorsal Nerves. — These are intended for the dorsal region of the trunk, and resemble each other closely in their distribution, presenting only a few dif- ferences connected with the arrangement of the particular muscular layers of each region. The posterior branch of the first dorsal nerve has the same muscular and cutaneous re- lations as the corresponding branches of the lower cervical nerves ; it is of the same size, and is distributed in precisely the same manner. The posterior branches of the second, third, fourth, fifth, sixth, seventh, and eighth dorsal nerves are destined for the thorax, properly so called, and present the greatest uniformity in their size and distribution. They all emerge from the posterior inter-vertebral foramina, inomediately on the outer side of the semi-spinalis dorsi and multitidus spina;, and divide into tAvo branches. The external or muscular branch is directed towards the cellular interval between the sacro- lumbalis and longissimus dorsi, and subdivides into a great niunber of twigs, which are distributed to these two muscles [and to the levatores costarum]. The internal or mus- culo-cut-aneous branch has a very remarkable course. It is reflected inward over the semi- spinalis dorsi, embracing the outer border of that muscle, and supplying it with nervous twigs ; having reached the side of the spinous process, it is reflected backward along that process, perforates the spinal attachments of the latissimus dorsi, and thus gains the under surface of the trapezius ; in this situation it is reflected outward between the latissimus dorsi and the trapezius, perforates the latter muscle ver>' obliquely, and be- comes sub-cutaneous ; it then passes horizontally outward in the fonn of a small nervous riband, the distinct fibres of which do not disunite and spread out in the substance of the skin until they have arrived at the scapular region. The cutaneous branch, which belongs to the second dorsal nerve^ always corresponds to the triangular surface on the spine of the scapula, over which the aponeurosis of the trapezius glides. In one subject which I examined, the musculo-cutaneous divisions of the posterior branches of the third, fourth, and fifth dorsal nerves presented two ganglia at the point where they bifurcated into their muscular and cutaneous branches ; in another, the ganglia were situated upon the cutaneous branches belonging to the first and third dor- sal nerves. All these cutaneous branches are horizontal, parallel, and separated from each other by an interval corresponding to the height of one vertebra. Such of the pos- terior branches of the dorsal nerves as are in relation with the trapezius always present the preceding arrangement. But the branches lower down than that muscle are dis- tributed in the following manner : The posterior braiichcs of the ninth, tenth, eleventh, and twelfth dorsal nerves are distribu- ted in precisely the same way as the posterior branches of the lumbar nerves, and, like them, are intended for the abdominal parietes. There is no longer any internal or musculo-cutaneous branch, the external branch representing both the muscular and the cutaneous branch.* Immediately after emergmg from the inter- vertebral foramina, these posterior branches pass very obliquely downward and outward, gain the cellular interval between the sacro- iumbalis and the longissimus dorsi, or, rather, pass very obliquely through the common mass formed by the union of the sacro-lumbalis and longissimus dorsi, and almost al- ways communicate with each other during their long course through the fleshy fibres : having arrived opposite the outer border of the latissimus dorsi, or of the common mass, these branches, diminished fuUy one third in consequence of having supplied the poste- rior spinal muscles, perforate very obliquely the aponeurotic layer formed by the union of the aponeuroses of the latissimus dorsi and serratus posticus inferior, whh those from the internal, oblique, and transverse muscles of the abdomen, and become sub-cutaneous ; they then divide into some very small internal cutaneous filaments, which are directed inward upon the side of the spinous processes, and some large external cutaneous fila- ments, which descend to terminate in the skin of the gluteal region. I would especially notice several large nerves, which, either joined together, or only in contact,' descend vertically, cross perpendicularly over the crest of the ilium in front of the outer border of the common mass of the lumbar muscles, and become apphed to the integuments of the gluteal region, upon which they may be traced as far as the great trochanter. * [The internal branclies of the four lower nerves are not absent, but are much reduced in size, do not reach the surface, and are distributed principally to the multifidus spinae : the external branches give the cutaneous twigs. (Demonstrations of Anatomy, by G. V. Ellis, of whose labours in reference to the anatomy «f the neryes, free use has been made in this and many of the succeeding notes. ;j 776 NEUROLOGY. The Posterior Branches of the Lumbar Nerves. — These resemble in their distribution the corresponding branches of the four lower dorsal nerves ; they gradually diminish in size from above downward ; the fifth is extremely small, and is entirely expended in the common mass of the lumbar muscles. The Posterior Branches of the Sacral Nerves. — These branches emerge from the poste- rior sacral inter-vertebral foramina. It is difficult to dissect them, because they are extremely small, and penetrate immediately into the muscular mass which occupies the sacral groove ; they moreover decrease in size from above downward, and are uniformly arranged in the following manner : immediately after their exit from the posterior inter- vertebral foramina, they form anastomotic arches with each other, from which muscular and cutaneous filaments are given off. The former are distributed to the common mass and the glutaeus maximus, and the latter are intended for the skin of the sacral region.* The Anteeior Branches op the Spinal Nerves. The anterior branches of the spinal nerves, which are generally larger than the posterior, are the trae continuations of these nerves, and supply the lateral and anterior parts of the trunk, and also the upper and lower extremities. Such of these branches as are intended for the trunk of the body have an extremely- uniform and very simple mode of distribution ; to this class belong the intercostal nerves : those, on the other hand, which are intended for the upper and lower extremi- ties, present, in their distribution, a degree of complexity which depends on that of the parts which they supply. To this class belong the anterior cervical, anterior lumbar, and anterior sacral branches. The three last-named sets of branches, ahnost immediately after their exit from the spinal canal, communicate with each other, so as to form interlacements or plexuses, from which are given off the nerves, that ultimately ramify in all parts of the body. There are four great plexuses : two for the region of the neck and the upper extrem- ity, viz., the cervical plexus {x,fig. 268) and the brachial plexus (A), which might be re- garded as a single plexus, the cervico-brachial ; and two for the lumbar region and the low- er extremity, viz., the lumbar (l) and the sacral or crural plexus {s}, which also might be regarded as one, the lumbosacral plexus. After these preliminary observations, I shall now describe, in succession, the anterior branches of the cervical, dorsal, lumbar, and sacral nerves. THE ANTERIOR BRANCHES OF THE CERVICAL NERVES. Dissection. — Anterior Branch of the First, Second, Third, and Fourth Cervical Nerves. — The Cervical Plexus — Its Anterior Branch, the Superficial Cervical — Its Ascending Branches, the Great Auricular and the External or Lesser Occipital — Its Superficial De- scendins^ Branches, the Supra-clavicular — Its Deep Descending Branches, the Nerve to the Descendins Noni and the Phrenic — Its Deep Posterior Branches. — The Anterior Branches of the Fifth, Sixth, Seventh, and Eighth Cervical, and First Dorsal Nerves. — The Brach- ial Plexus. — Its Collateral Branches above the Clavicle — Its Muscular Branches, Poste- rior Thoracic, Supra-scapular, opposite to the Clavicle, the Thoracic, below the Clavicle, the Circumflex — Its Terminal Branches, the Internal Cutaneous ajid its Accessory, the Mus- culo-cutaneous, the Median, the Ulnar, the Musculo-spiral or Radial. — Summary of the Distribution of the Branches of the Brachial Plexus. Dissection. — It is convenient to dissect the sub-cutaneous branches which emerge from the cervical plexus before examining the anterior branches of the cervical nerves : one side of the neck may be reserved for the superficial, and the other for the deep branches. The Anterior Branches of the First, Second, Third, and Fou-rth Cervical Nerves-. The Anterior Branch of the First Cervical Nerve. — This branch (u, fig. 300) emerges from between the occipital bone and the posterior arch of the atlas in the groove for the vertebral artery, and beneath that vessel ; opposite the foramen in the transverse pro- cess of the atlas, it leaves the artery, passes in front of the base of that process, is re- flected downward, and descends to form an anastomotic arch with the anterior branch of the second nerve. As all the branches belonging to the first nerve come off from this anastomotic arch, they will be described with the second nerve. The Anterior Branch of the Second Cervical Nerve. — This is much smaller than the pos- terior branch of the same nerve ; it passes horizontally forward between the transverse processes of the atlas and axis, is reflected in front of the axis, and divides into an as- cending and a descending branch. * Among- the cutaneous filaments which proceed from the arch formed by the posterior branches of the first and second sacral nerves, there is one which passes below the posterior and inferior spinous process of tho ilium, is directed vertically downward between the g-lutiEUS muxiraus and the lesser sacro-sciatic ligament, perforates the glutEeus maximus, aud is then reflected outward in contact with the skia. THE CERVICAL PLEXUS. 777 The ascending branch curves upward in front of the transverse process of the atlas, and anastomoses in an arch with the anterior branch of the first nerve. The descending branch {z, fig. 298) subdivides into two others of almost equal size : the one internal (see also fig. 300), which constitutes the internal descending cervical nerve (before s, fig. 298) ; the other external (behind s), which anastomoses with the third nerve (above s), to form the superficial cervical nerve {k) and the great auricular nerve {q). Several large filaments for the rectus capitis anticus major are given off from the angle of bifurcation of the ascending and descending branches. The anastomotic arch formed by the anterior branches of the first and second cervi- cal nerves gives off three or four very large grayish branches and several small white filaments, which go to the superior cervical ganglion of the sympathetic ; above these it gives a short gray filament, which almost immediately swells into a ganglion, from which a long, slender, descending filament proceeds to join the internal descending nerve ; lastly, it furnishes two ascending filaments, the lower one of which joins the pneumogastric nerve, and the upper one the hypoglossal or ninth nerve. The Anterior Branch of the Third Cervical Nerve. — This (above s, fig. 298) is twice as large as the preceding ; it at first passes forward to emerge from the inter-transverse space, then downward and outward, and having gained the under surface of the sterno- mastoid muscle, it expands into a great number of branches, which constitute the cervi- cal plexus properly so called, and may be divided into a superior and an inferior portion. The superior division passes outward and backward beneath the sterno-mastoid mus- cle, and bifurcates upon its posterior borders. One of the branches of the bifurcation as- cends, and is called the mastoid nerve (y) ; the other, which is reflected over the posterior border of the muscle, anastomoses by one or two filaments with the anterior branch of the second cervical nerve, and subdivides into the superficial cervical nerve {k) and the auricular nerve (q) : both of the branches of the bifurcation anastomose with the second cervical nerve. This superior division, moreover, gives off a small nerve, which as- cends between the auricular and mastoid nerves ; also a communicating branch to the superior cervical ganglion ; and, lastly, a series of branches (»), which anastomose with the spinal accessory nerve of Willis {t), some immediately, and others while v/ithin the substance of the sterno-mastoid muscle. This superior division of the third nerve some- times joins the lowest branch of the second nerve. The inferior or descending portion passes vertically downward in front of the scalenus anticus, gives off a long slender filament to the internal descending cervical nerve, and ter- minates partly by anastomosing with the fourth cervical nerve (below s), and partly by becoming continuous with the clavicular nerves (m). A considerable branch which enters the levator anguli scapulas may be regarded as be- longing to this inferior portion. This branch for the angularis sometimes arises at the point of bifurcation of the anterior branch of the third nerve. The Anterior Branch of the Fourth Cervical Nerve. — This branch (below s) is of the same size as the preceding ; it gives off the phrenic nerve (1), which sometimes arises in the inter-transverse space ; it then passes downward and outward in contact with the scalenus anticus for about ten lines, and divides into two terminal branches, the one in- ternal, the other external, which soon subdivide and cover the supra-clavicular triangle with their diverging ramifications : these branches constitute the supra-clavicular and acromial nerves (m). Just opposite its division the anterior branch of the fourth cervi- cal nerve receives a branch from the third, which appears to be shared between its two terminal divisions. The fourth cervical generally sends off a small communicating branch to the fifth cer- vical nerve. The Ckrvical Plexus. The term cervical plexus is applied to the series of anastomoses {z s) formed by the an- terior branches of the first, second, third, and fourth cervical nerves. Some anatomists call it the deep cervical plexus, in contradistinction to the superficial branches given off from it, which, according to this view, constitute the superficial cervi- cal plexus. This plexus, which occupies the anterior and lateral aspect of the four superior cer- vical vertebrae, is situated beneath the posterior border of the sterno-cleido-mastoid mus- cle, to the outer side of the internal jugular vein, between the rectus capitis anticus ma- jor and the cervical attachments of the splenius and levator anguli scapulae : it is con- cealed by a considerable quantity of fat, and by a great number of lymphatic glands : it is also covered by an aponeurotic lamina, which adheres to it intimately, and is prolong- ed upon the nerves which emanate from it. After the example of Bichat, this plexus may be regarded as a centre in which the anterior branches of the four superior cervical nerves terminate, and from which a great number of branches proceed. This plexus is by no means inextricable ; it is always easy to determine the origin of the branches which come from it. These branches consist of one anterior branch, the superficial cervical {k) ; of ascending 5 F 778 NEUROLOGY. branches, viz., the great mastoid (y), the small mastoid, and the great auricular (q) ; and of descending branches, subdivided into the deep and the superficial ; the deep ones consisting of the internal descending branch (before s), the phrenic nerve (l), and the branch- es for the trapezius, levator anguli scapula, and rhomboideus ; the superficial descending branches are the supra-clavicular and the acromial (m). According to their distribution, they may also be divided into muscular and cutaneous branches ; the muscular consist of the internal descending, the phrenic, the branches for the trapezius, the levator anguli, and the rhomboideus ; all the others are cutaneous, and are flattened like ribands. The Anterior Branch. The Superficial Cervical JVerve. The superficial cervical nerve (superficialis colli, s, fig. 285), vphich is often double, Fig-. 285. in consequence of dividing earlier than usual, is des- tined exclusively for the skin of the neck and lower part of the face (sous-mentonniere, Chauss.), and is formed by the anastomoses of the second and third cervical nerves ; it emerges from the plexus opposite the middle of the neck, beneath the posterior border of the sterno-mastoid, around which it turns in the form of a loop, and then passes horizontally forward between that muscle and the platysma, runs at right angles beneath the external jugular vein, and divides into two branches — one ascending and larger, the oth- er descending ; these two branches often form two distinct nerves. The descending branch passes downward and in- ward between the sterno-mastoid and the platysma, is reflected upward so as to form a loop, having its con- cavity turned upward, 'perforates the platysma, and then lies in contact with the skin, beneath which it may be traced as far as opposite the os hyoides. One of its twigs, which appears to me to be constant, having reached the side of the median line, is reflected upward in front of the anterior jugular vein, ascends vertical- ly, and may be traced into the skin of the supra-hyoid region. The ascending branch, which sometimes arises by a common trunk with the auricular nerve, immediately divides into four or five very slender and slightly waving filaments, which, situated at first between the sterno-mastoid and the platysma, generally perfo- rate the last-named muscle, to become sub-cutaneous ; two of these diverging filaments, which remain subjacent to the platysma, are very slender, and run along the external jugular vein, one in front of and the other behind that vessel. All the other filaments pass upward and inward in contact with the skin, and subdi- vide into a great number of filaments, which may be traced as far as the skin of the chin and lower part of the cheek ; I have seen two of these filaments anastomose with the facial nerve. It is important to observe, that the cervical filaments of the facial nerve occupy a deeper plane than those of the superficial cervical nerve, and are separated from these latter in front by the platysma. The Ascending Branches. The Auricular J^erve. The auricular nerve (auricularis magnus, d, fig. 285), the ascending anterior branch of the cervical plexus, arises from the second and third cervical nerves by a trunk which is common to it and to the superficial cervical ; it emanates from the plexus immediate- ly above the last-named nerve, like which it embraces the posterior border of the sterno- mastoid so as to form a loop with the convexity turned backward, and then passes up- ward and a little forward between the platysma and the sterno-mastoid, and reaches the anterior border of that muscle opposite the angle of the lower jaw. In this situation it gives oflT several facial or parotid filaments, and terminates by dividing into a superficial and a deep branch. The facial or parotid branches are very slender ; some of them pass between the parot- id and the skin, with which they are in contact ; the others pass through the parotid gland from behind forward, and from below upward, to be distributed to the skin of the cheek ; I have traced them as far as the skin which covers the malar bone ; it has not been shown that some of them terminate in the substance of the parotid, as has been stated.* The superficial auricular branch ascends vertically, in the substance of the very dense * I have seen two of these parotid filaments terminate in a small abnormal gangliou, from which other fil- aments were given oif and distributed in the manner above described. THE SUPRA-CLAVICULAR NERVES. 779 fibrous tissue which connects the parotid to the skin ; it gains the lower part of the concha opposite to the anti-tragus, and then divides into several filaments, the distribu- tion of which is remarkable : the largest passes above the lobule in the fissure between the concha and the caudal extremity of the helix, and is distributed to the skin on the concave surface of the auricle, and especially to the skin of the concha ; another fila- ment turns round the margin of the auricle, and gains the groove of the helix, which it follows even to its upper part. The deep auricular branch, which may be called the anterior mastoid, perforates the substance of the parotid gland, and gains the front of the mastoid process ; here it crosses at an acute angle over the auricular branch of the facial nerve, which is more deep- ly seated, and with which it anastomoses by a rather large branch ; it then passes be- hind the posterior auricular muscle, and divides into two secondary branches : a poste- rior, which passes upward and backward, and may be traced as far as the outer border of the occipitalis muscle, where it anastomoses with a very delicate filament of the ex- ternal occipital nei-ve ; and an anterior, which runs upon the upper part of the cranial surface of the auricle. The superior filaments are reflected over the upper margin of the auricle, and are distributed to the skin which covers its external or concave surface. From what has been just stated, it follows that the auricularis magnus gives off no muscular filament. The posterior auricular and occipitahs muscles are supphed entire- ly from the auricular branch {v) of the facial nerve. The Mastoid or External Occipital Kerve. The 7nastoid or external occipital nerve (occipitalis minor, b), the posterior ascending branch of the cervical plexus, rises from the second cervical nerve ; it comes off from the plexus above the preceding nerve, describes a loop with the convexity turned up- ward upoft the posterior border of the sterno-mastoid, ascends almost vertically, parallel to the great occipital nerve and to the posterior border of the sterno-mastoid, crosses the posterior occipital attachments of that muscle, continues to ascend upon the occipi- tal region, and then upon the parietal region, and may be traced as far as opposite the anterior border of the parietal bone. During this course it is situated between the sple- nius and occipitahs muscles and epicranial aponeurosis on the one hand, and the skin on the other. This nerve gives off in the occipital region some external branches, which are distrib- uted to the skin, and anastomose with a filament of the auricular nerve, but none of them pass to the auricle. The term occipito-auricular (Chauss.) is, therefore, not applicable to it ; it should rather be called the external occipital (occipitalis minor, b),* to distinguish it from the internal occipital (occipitalis major, a), given off by the posterior branch of the second cervical nerve. It also supphes some internal branches, which anastomose several times with the in- ternal occipital nerve, and are distributed to the skin. It gives no filament to the occipitalis muscle, nor does it anastomose with the facial nerve The mastoid or external occipital nerve is essentially a cutaneous nerve. We sometimes find a small supplementary branch between the great auricular and external occipital nerves, which runs parallel to them, and may be called the small mas- toid nerve (c). The Superficial Descending Branches. The Supra-clavicular J^erves. The Supra-clavicular Nerves (e, fig. 285 ; u, fig. 298). — The terminating branches of the cervical plexus are two in number : one internal, or the supra-clavicular nerve, properly so called ; the other external, or the acromial nerve ; they come off from the plexus at the posterior border of the sterno mastoid, descend perpendicularly towards the clavicle and divide into several branches, which again subdivide before reaching that bone, so that they cover the supra-clavicular triangle with their diverging filaments. All these branches cross over the clavicle at almost regular intervals, and are lost upon the upper and anterior part of the thorax. The innermost or sternal branches cross very obliquely over the external jugular vein, then over the clavicular and sternal attachments of the sterno-mastoid, and ramify in the skin, where they may be traced as far as the median line. The external or acromial branches pass obliquely over the external surface of the tra- pezius, cross the outer end of the clavicle, and are distributed to the skin over the acro- mion and the spine of the scapula. I have followed some filaments over the top of the shoulder as far as the lower borders of the pectoralis major. The intermediate or clavicular branches cross the clavicle at right angles, are in con- tact with the skin upon the upper part of the thorax, and maybe traced to within a short distance of the nipple, t * The name mastoid branch is bad, for this branch has no relation with the mastoid process, t Not unfrequently the supra-clavicular nerve passes through a foramen in the clavicle, at the junction of the external third with the internal two thirds of that bone ; sometimes, instead of a bony canal, there ia a 780 NEUROLOGY. All these branches lie at first beneath the platysma, and then become sub-cutaneous. A layer of fascia and the omo-hyoid muscle are interposed between them and the scaleni muscles and brachial plexus. Some loose cellular tissue separates them from the clav- icle, upon which they glide with the greatest freedom. The Deep Descending Branches. The Internal Descending Cervical Iferve. The internal descending cervical nerve (before s, fig. 298), which is destined exclusively for the muscles of the sub-hyoid region, may be considered as the inferior branch of the bifurcation of the second cervical nerve, although the first and third nerves each give to it a small re-enforcing filament. It passes vertically downward, on the outer side of the internal jugular vein, along which it runs, is joined on its inner side by a filament from the first cervical nerve, and having reached a little below the middle of the neck, is reflected inward in front of the internal jugular vein, and forms an anastomotic loop, which is sometimes plexiform, with the descending branch (descendens noni. A) of the hypoglossal nerve ; this is a remark- able anastomosis, and presents many varieties in its arrangement. The convexity of this loop is turned downward, and from it arises a branch, which sometimes scarcely ex- ceeds in size either of the formative branches of the loop, and which expands into sev- eral filaments {g). One of these ascends and supplies the superior attachments of the sterno-hyoid and omo-hyoid ; a transverse filament proceeds to the bodies of the sterno- hyoid and sterno-thyroid muscles. Several filaments can be traced as far as the lower part of the latter muscle, that is to say, down to opposite the second rib. The inferior fleshy belly of the omo-hyoid is supplied by some twigs derived from the filaments which enter its superior belly. The PhreTiic or Diaphragmatic Jferve. The phrenic nerve {I, figs. 298, 302) is a branch derived from the fourth cervical nerve, sometimes re-enforced by a very small filament from the third nerve, and almost al- ways by a larger branch from the fifth.* Not unfrequently one of the formative branch- es of the loop of the hypoglossal nerve just described joins the phrenic nerve. The right and left phrenics are rarely of the same size. After its origin, the phrenic nerve descends vertically in front of the inner border of the scalenus anticus, with which it is held in contact by a fascia. It is round at first, but becomes flattened as it passes between the sub-clavian vein and artery (I have seen it pass in front of the vein), and is then inclined slightly inward, to enter the superior orifice of the thorax. In the thorax il,fig. 302) it continues its vertical direction, runs along the brachio-cephalic vein on the left side, and along the vena cava superior on the right side, is then applied against the pericardium, to which it is bound down by the pleura, and, having reached the diaphragm, ramifies in that muscle. It is accompanied by the superior phrenic artery, which is a branch of the internal mammary, and the su- perior phrenic vein. The phrenic nerve gives off no branches in the thorax : at a short distance from its origin, it anastomoses with the great sympathetic by a transverse branch : at the lower part of the neck, it sometimes gives off a filament, which forms an anastomotic arch with a branch derived from the fifth and sixth cervical nerves. I have never seen it com- municate with the inferior cervical ganglion. The distribution of this nerve in the diaphragm is curious. Some of its expanded, di- verging, and generally very long filaments, run between the pleura and the diaphragm, and enter the muscle from its upper surface ; others pass through the diaphragm, run between it and the peritoneum, and enter the fleshy fibres from below ; they may be traced as far as the costal attachments of the muscle. The right phrenic nerve termi- nates by a transverse branch which passes behind the vena cava, and anastomoses with certain transverse branches of the left phrenic, before it enters the pillars of the dia- phragm, in which it terminates. I have never seen any filament of the phrenic nerve pass either to the cEsophagus or to the solar plexus. The Posterior Deep Cervical Branches. These are, an anastomotic branch {v, fig. 298) from the cervical plexus to the spinal ac- cessory nerve of Willis (0 ; it is of considerable size ; it conies off from the second nerve at the same point as the external occipital nerve, and anastomoses at an acute angle tendinous arch upon the posterior border of the bone. In this case the clavicular branches are not scattered, but closely aggregated together : the internal branches then pass horizontally inward between the clavicle and the skin as far as the sternum ; and I have even seen a small twig enter the attachments of the pectoralis ma- jor. The external branches proceed horizontally outward upon the anterior border of the clavicle as far as the acromion. * The communication between the phrenic nerve and the fifth cervical nerve occurs in many different modes. Sometimes the phrenic supplies the communicating filament, instead of receiving it ; most commonly the phrenic branch of the fifth arises by a common trunk with the nerve for the sub-clavius muscle, crosses in front of the sub-clavian vein, between it and the cartilage of the first rib, with which it is in contact, and passes behind the internal mammary artery, to join the phrenic nerve at a very acute angle. THE BRACHIAL PLEXUS. 781 with the spinal accessory, between the cervical fasciculi of the splenius and the sterno- mastoid. Also, a branch for the trapezius, which arises from the third nerve, passes obliquely downward and backward to the deep surface of the muscle, and anastomoses with the spinal accessory of Willis, which it re-enforces, and with which it may be traced as far as the lower angle of the muscle. Lastly, the branches for the levator anguli scapula and the rho7nboideus ; these are rath- er small branches, which arise from the back part of the third and fourth cervical nerves, as they emerge from between the transverse processes of the vertebrae, pass obliquely downward and backward, turn round the scalenus posticus in contact with it, and are distributed to the levator anguli scapula; and the upper part of the rhomboideus. The same branches appear to supply both muscles. The Anterior Branches of the Fifth, Sixth, Seventh, and Eighth Cervical AND First Dorsal Nerves. These branches are remarkable for their size, in which respect they surpass the pre- ceding, and are almost all equal. On emerging from the inter-vertebral foramina, they come into relation with the two scaleni muscles, which are separated from each other, and sometimes are perforated by them ; they give off some very slender filaments to these muscles, and, converging, anastomose together so as to form the brachial plexus, from which all the nerves of the upper extremity are derived. The Brachial Plexus. • ' The brachial plexus {h, fig. 268) extends obliquely from the lateral and inferior part of the neck to the cavity of the axilla, or, rather, to the inner side of the head of the hume- rus, where it terminates by dividing into the nerves of the upper extremity ; it is formed in the following manner : The fifth and sixth cervical nerves (5, 6, fig. 286) unite at a short distance from the scaleni, and the cord thus formed passes very obliquely downward and outward, and then bifurcates. Again, the eighth cervical (8) and the first dorsal (1) nerves unite immediately after converging from the scaleni, and sometimes even between those muscles ; and the com- mon cord passes almost horizontally outward, and bifurcates near the head of the humerus. Between these two anastomotic cords is the seventh cervical nerve (7), which pur- sues a much longer course than the others, and bifurcates on a level with the clavicle ; the upper branch of its bifurcation joins the lower branch of the bifurcation of the first- named cord, and its lower branch unites with the upper branch of the second-named cord. From these several bifurcations and subsequent anastomoses, all of which take place at very acute angles, results the interlacement known as the brachial plexus. The brachial plexus is broad at its upper part, contracted in the middle, and broad again at its lower part, on account of the divergence of its terminating branches ; it com- municates with the cervical plexus by a considerable branch, which it receives from the fourth cervical nerve, and also by the filament which it gives to the phrenic nerve ; it is not so complicated but that the origins of the branches which emanate from it may be traced ; I shall take care to do this for each nerve. Relations. — At its origin it is situated between the scaleni, which cover it for a great- er extent below than above. A very strong aponeurosis, which extends over it and the scaleni also, completely isolates it from the surrounding parts. Lower down, it is situated between the clavicle and sub-clavius muscle on the one hand, and the first rib and upper part of the serratus magnus on the other. Still lower, it is contained in the cavity of the axilla, separated from the pectoral- is major in front by the costo-clavicular aponeurosis, and resting upon the scapulo-hu- meral articulation behind, from which it is separated by the tendon of the sub-scapularis. The following are its relations with the axillary artery : Between the scaleni and be- low them, the artery is situated upon the same plane as the brachial plexus, and lies be- tween the plexus and the first rib. Lower down it is placed on the anterior part of the plexus ; at the lower extremity of the plexus it passes under the angle of union of the two roots of the median nerve, by which it is embraced ; the axillary vein always lies in front of the artery, and therefore has less direct rela- tions with the plexus. The branches of the brachial plexus may be divided into the collateral and the terminal. The terminal branches are five in number, namely, the internal cutaneous (g, fig. 286) and its accessory, the mus- culo-cutaneous (b), the median (c), the radial or musculo- spiral (/), and the ulnar (d) nerves.* The collateral branches may be divided into those giv- * I think it right to class the circumflex nerve among- the collateral branches, and not, like most authors, among the terminal branches of the plexus. 782 NEUROLOGY. en off above the clavicle, namely, the nerve for the suh-davius, those for the levator angu li scapxda. and rhomboideus, the posterior thoracic or nerve for the serratus magnus, the su- pra-scapular nerve (a) or nerve for the supra- and infra-spinati muscles, and the superior sub- scapular nerve ; those given off opposite the clavicle, namely, the thoracic branches ; and those given off in the axilla, namely, the circumflex nerve (e) and the sub-scapular branches, which comprehend the nerve for the latissimus dor si, the nerve for the teres major, and the inferior scapular nerve. One branch only, namely, the nerve for the sub-clavius muscle, arises from the front part of the brachial plexus : all the other collateral branches are given off from the back of the plexus. The Collateral Branches of the Brachial Plexus. The Branches given off below the Clavicle. The Nerve for the Sub-clavius Muscle. — This is a small but constant branch, which comes off from the fifth cervical nerve, immediately before its junction with the sixth, passes vertically downward in front of the sub-clavian artery, and then enters perpendic- ularly into the middle of the sub-clavius muscle. This small nerve, before reaching the sub-clavius, always gives off a phrenic branch, which passes obliquely inward in front of the sub-clavian vein, and anastomoses with the phrenic nerve. The Nerve for the Levator Anguli ScapulcE. — This branch arises as frequently from the cervical as from the brachial plexus ; in the former case, it arises from the fourth cervi- cal nerve, in the latter from the fifth. It arises from the nerve immediately after its exit from the canal of the transverse processes, turns round the scalenus posticus to gain the deep surface of the levator anguli scapulae, enters the muscle, supplies it with a great number of filaments, and perforates it to reach the rhomboideus, under which it passes. One of its terminating filaments anastomoses with a filament from the proper nerve for the rhomboideus. The Nerve for the Rhomboideus. — This arises from the fifth cervical nerve, immediately below the preceding ; I have seen it arise by a common trunk with the superior branch of origin of the nerve for the serratus magnus ; it passes downward and backward be- tween the scalenus posticus and the levator anguli scapulae, and then beneath the last- mentioned muscle, nearly as far as its scapular attachments, in order to get between the rhomboideus and the ribs ; it may be traced as far as the lower part of that muscle. One of its filaments perforates the rhomboideus, and anastomoses in the trapezius with the posterior spinal nerves. The Nerve for the Serratus Magnus (Posterior Thoracic Nerve of authors ; External Res- piratory Nerve, Sir C. Bell). — This branch, which is very remarkable for the length of its course, is derived from the fifth and sixth cervical nerves, immediately after their exit from the canal of the transverse processes ; it arises by two roots, which are sometimes equal and sometimes unequal in size ; it passes vertically downward behind the brachial plexus and the axillary vessels, in front of the scalenus posticus, reaches the side of the thorax (e', fig. 287), between the sub-scapularis and the serratus magnus, runs the whole length of the last-named muscle, and ramifies in its lower portion. During this course, it gives off a great number of filaments to the muscle : the lowest of these may be traced as far as the lowest digitation. The branch which it gives to the upper part of the muscle is remarkable for its size. I have seen a branch from the seventh cervical nerve join the external thoracic nerve upon the upper part of the serratus magnus, so that this nerve would then be derived from the fifth, sixth, and seventh cervical nerves. The Supra-scapular Nerve, or Nerve for the Supra- and Infra-spinati Muscles. — This branch {a, fig. 286) is given off from the back part of the fifth cervical nerve at its junc- tion with the sixth ; it passes obliquely backward, outward, and downward, dips beneath the trapezius, and then under the omo-hyoid, the direction of which it nearly follows, and gradually increases in size as it approaches the coracoid notch of the scapula, and passes by itself under the ligament which converts this notch into a foramen ; the supra- scapular artery and vein, which had hitherto been in contact with the nerve, leave it op- posite this notch to pass above the ligament, and then join it again in the supra-spinous fossa. The nerve then runs from before backward in the supra-spinous fossa, protected by a thick fibrous lamella, reaches the free concave border of the spine of the scapula, against which it is held by a fibrous band, is then reflected inward and downward over this con- cave border to gain the infra-spinous fossa, and immediately divides into two branches, one of which spreads out in the upper part, and the other in the lower part of the infra- spinatus muscle. During its course through the supra-spinous fossa, the supra-scapular nerve gives off two supra-spinous branches, one of which is detached opposite the coracoid notch, and the other upon the spine of the scapula. They both enter the supra-spinatus muscle. BRANCHES BELOW THE CLAVICLE. 783 The supra-scapular nerve is exclusively destined for the supra- and infra-spinati mus- cles. It gives no filament to the sub-scapularis. The Superior Subscapular Nerve. — This is a very small branch which arises imme- diately above the clavicle, and passes downward and forward to reach the upper border of the sub-scapularis, and then enters that muscle. The Branches given off opposite to the Clavicle. These, which are named the thoracic branches,* are generally two in number, one aw terior, the other posterior : they arise from the anterior part of the brachial plexus, oppo- site the sub-clavius muscle. The anterior branch, or nerve for the pectoralis major, which is the larger, passes downward and forward between the sub-clavius muscle and the sub- clavian vein, and divides into two branches : an external, or anastomotic, which some- times arises directly from the brachial plexus, and forms a loop around the axillary ar- tery, by anastomosing with the posterior thoracic branch ; and an internal, which runs along the deep surface of the pectorahs major, and expands into a great number of re- markably long and slender filaments, which enter the muscle very obliquely, and may be traced as far as its sternal attachments. A very slender filament is constantly found running along the clavicle. The posterior thoracic branch, or nerve for the pectoralis minor, passes behind the axillary artery, below which it curves forward, to form, with the external branch of the anterior thoracic, the anastomotic loop of which I have already spoken. From this loop or arch, in forming which the nervous filaments are separated from each other, two sets of branches proceed : the one set runs between the pectoralis major and minor, closely applied to the former muscle, which they then enter, diverging to its lowest part ; the others pass beneath the pectorahs minor, and penetrate its deep surface ; some of them pass obliquely through this muscle and join the anterior thoracic branches in the pecto- ralis major. The Branches given off below the Clavicle. The Axillary or Circumflex Nerve. — This is no less remarkable for its great size, which has led some anatomists to regard it as a terminal branch of the brachial plexus, than for its reflected course : it comes off from the back of the plexus, behind the musculo- spiral nerve, or, rather, the circumflex and musculo-spiral nerves (e and f, fig. 286) ap- pear to be the two divisions of a trunk formed by filaments from the five branches of the brachial plexus. Immediately after its origin, the circumflex nerve passes downward and outward (g, fig. 288) in front of the sub-scapularis, which separates it from the shoulder-joint, turns obliquely round the lower border of that muscle, round the back part of the articulation, and, lastly, round the surgical neck of the humerus, is then reflected upward, so as to de- scribe a curve with the concavity turned in the same direction, and terminates by ram- ifying in the deltoid. During this curved course, the circumflex nerve, accompanied by the posterior cir- cumflex vessels, passes at first between the sub-scapularis and the teres major, then be- low the teres minor, on the outer side of the long head of the triceps (z. e., next to the bone), and then lies in contact with the deep surface of the deltoid, against which it is held by a very dense layer of fascia. The relation of the circumflex nerve to the articulation explains the possible occur- rence of laceration of this nerve in luxations of the humerus downward. The collateral branches of the circumflex nerve are three in number. One branch almost always goes to the sub-scapularis. I have already said that the sub-scapular nerves might be regarded as branches of the circumflex. As it turns round the lower border of the sub-scapularis, the circumflex gives off a branch for the teres minor and the cutaneous branch of the shoulder. The nerve for the teres minor enters that muscle by its lower border ; it almost always arises by a common trunk with a deltoid branch, which runs upward and backward to supply the back part of the deltoid muscle. The cutaneous nerve of the shoulder frequently arises by a common trunk with the two preceding, and, in this case, the circumflex nerve appears to bifurcate ; it passes under the posterior border of the deltoid, then lies in contact with the skin covering the back part of the top of the shoulder, and divides into diverging branches, some ascending, oth- ers descending, and others running horizontally. A second, and sometimes a third cu- taneous branch perforates the fleshy fibres of the dehoid, and is distributed to the corre- sponding skin. The terminal or deltoid branches of the circumflex nerve are given off as that nerve is turn- ing round the neck of the humerus, in which situation it divides into several diverging branches, the superior of which ascends, and appears like the continuation of the nerve, while the others descend, and may be traced as far as the insertion of the muscle into the humerus. * The anterior thoracic nerves of those who name the nerve for the serratua majnus the posterior thoracic. 784 JtEUlOLOGT. sszieraiv lesj^nT'tc as i tc : S'jLO-ic&p^izr Senrex. — ^Tlie aerte for ti£ littinrwKms iam is the laigesi of the " as the ni-acmmdmr; it eaaeaaSat aBaotte aagjtefimathe -= i-i i^?r^-'r - — :?all^iiithe Bsiist of the eefiolartissae - -jttoB macBTFT. posafid to Ae eztenal __;__. iod diFECtiaK as well as ih it? leii ?th : it sb^a : :;-:_: :::;- :Ti:i;i I'ls ocier border, izi — i \-. ::;ri i;-^n of the 5 3J: a very acute an^ fraai : i55es to the sai>-seapdads, r^ :" le :eres m^orliT' a grea: --rr j»j-r- 15 •^TTnirTTth thr rTinmiflrr nr-rr ax: :riT"e Sh- the toes n^or. ^^liare-rr : : . E entas giT^Q aS&an the bc^ : :i:6rs the saioe miBek The Internal Cut2r.ici2.f .^Vr^« and iu ^iccesscry. iuLerifid ^0C]i^i past of 8&e anr: THE MUSCULO-CUTANEOUS NEEVE. 785 Frequently, before reaching the epitroclilea, this branch has already given off a twig which anastomoses with the same nerve. Sumniary. — The internal cutaneous nerve, then, is exclusively intended for the skin. It only gives one small branch to the arm : its other divisions are intended for the forearm. One of them belongs to the dorsal, and the other to the internal aspect. The Accessory Nerve of the Internal Cuta?ieous. — I have applied this term to a small branch (cutaneus minor internus, Wrisberg), which it is difficult to discover, and which would be more properly classed among the collateral than the terminal branches of the brachial plexus : it arises above and sometimes below the clavicle, from the back part of the nervous cord formed by the junction of the eighth cervical and first dorsal nerves : it passes downward upon the sides of the thorax, and divides into two branches, an ex- ternal and an internal. The external branch (a', fig. '29>1), which is the smaller one, passes vertically downward, and crosses the conjoined tendons of the teres major and latissimus dorsi at right an- gles ; it lies in contact with the skin covering the inner and back part of the arm, and may be traced as low as the elbow. The internal branch (c) anastomoses with the second intercostal nerve, descends ver- tically, crossing the conjoined tendons of the latissimus dorsi and teres major, becomes applied to the skin, and divides into several very slender filaments, which correspond to the internal, anterior, and posterior regions of the arm, and may be traced as far as the region of the elbow ; one of these lilaments anastomoses with the internal cutaneous.* The Musculo-cutaneous JVerve. The musculo-cutaiieous nerve {b, fig. 286), the most external of the terminal branches of the brachial plexus, and, with the exception of the internal cutaneous, the smallest, arises by a common trunk with the external root of the median nerve (c), passes down- ward and outward, in front of the humeral insertion of the sub-scapularis, and on the inner side of the coraco-brachialis, which is perforated by it, and is therefore called the perforated muscle of Casserius.j After emerging from the muscle, through which it passes very obliquely,^ the musculo-cutaneous nerve {h,fig. 288) is situated between the biceps and the brachialis anticus, continues its oblique course, escapes from beneath the outer border of the tendon of the biceps, and then becomes sub-cutaneous. During its course along the arm it gives off the following branches The branches for the coraco-brachialis are two in number ; one superior, which enters the upper part of this muscle, and is then lost in the short head of the biceps ; the other in- ferior, which, in some subjects, after having furnished a certain number of filaments to the coraco-brachialis, becomes applied to the trunk of the musculo-cutaneous nerve itself The branches for the biceps are very numerous : not uncommonly they arise by a com- mon trunk, which then appears to result from the bifurcation of the musculo-cutaneous. One of these branches perforates the biceps, and passes transversely outward to reach the elbow-joint, to which it is distributed. The branches for the brachiulis ayiticus almost always arise by a large common trunk which appears to result from a farther bifurcation of the nerve, already diminished one half, after it has supplied the branches for the biceps. While these last-namod branches enter the posterior surface of the corresponding muscle, the branches for the brachialis anticus penetrate that muscle by its anterior surface. After having given off all these muscular branches, the musculo-cutaneous nerve, re- duced to a fourth or a fifth of its original size, is distributed entirely to tlie skin ; it passes vertically downward in front of the elbow-joint, behind the median cephalic vein {a, fig. 287), and divides into two terminal branches, of which the internal (h) runs along the inner, and the external along the outer side of the radial vein. These two branches, during their course along the forearm, lie between the fascia of the forearm and the superficial fascia ; they gradually diminish in size as they give off their filaments to the skm, and terminate in the following manner : The external branch passes to the dorsal surface of the forearm, and may be traced as far as the skin which covers the carpus. The internal branch has a more extensive distribution ; it anastomoses with a branch of the radial nerve at the lower part of the forearm, and gives off a deep or articular branch, which divides into several twigs that surround the radial artery. One of these twigs expands into a number of filaments which enter the fore part of the radio-carpal articulation ; the others accompany the radial artery in its oblique course upon the outer side of the carpus, and then spread out to terminate on the back part of the synovial membrane of the wrist-jomt. After having given off this very remarkable articular branch, ij the internal terminal division of the musculo-cutaneous nerve passes in front * [And -with the internal cutaneous branch of the musculo-spiral nerve.] t [The nerve is also called perforans Casserii.] X Not unfrequently the nerve does not perforate the coraco-brachialis. [It sometimes has an anastomosis with the medi.in nerve after emerging from the coraco-brachialis.] i In one subject, the articular filaments had some gangliform enlargements on their sides precisely similar 5 G 786 NEUROLOGY. of the tendons of the extensor brevis pollicis and abductor longus polhcis, in front of and more superficially than the corresponding branch of the radial nerve, and then divides into several twigs, vi^hich are intended for the skin of the thenar eminence. One of these branches, which runs along the outer side of that eminence, may be traced into the skin upon the first phalanx of the thumb. Summary. — The musculo-cutaneous nerve, then, supplies certain muscular branches, which belong exclusively to the coraco-brachialis, the biceps, and the brachialis anticus ; the section of this nerve would, therefore, destroy the power of flexing the forearm : certain cutaneous branches to the skin on the outer side of the forearm and hand ; and, lastly, some articular branches to the elbow and to the wrist. The Median JsTerve. The median nerve (c, fig. 286), one of the terminal branches of the brachial plexus, arises from the plexus by two very distinct roots between the musculo-cutaneous (b) on the outer side, and the ulnar nerve {d) on the inner.* The internal root arises from a nervous cord which is common to it, to the ulnar, and to the internal cutaneous (^)- The external root arises from a cord common to it and to the musculo-cutaneous. The axillary artery passes between these two roots. The trunk resulting from the union of these two roots is situated on the inner side of the axillary artery ; it is at first grooved to receive the inner half of tho artery, but it soon forms a rounded cord, proceeds vertically downward (c, fig. 288), gains the middle and fore part of the elbow-joint, dips between the muscles on the anterior region of the forearm (rf), and passes behind the annular ligament to enter the palm of the hand (r), where it terminates by dividing into six branches. We shall examine it in the arm, the forearm, and the hand. Fis- 288. In the Arm. The median nerve (c), which is straight and vertical, and the satellite nerve of the brachial artery, passes some- what obliquely downward, forward, and outward, to the middle and fore part of the elbow -joint. Relations. — On the inner side it is sub-aponeurotic, so that when the arm is held away from the side, and the forearm is extended upon the arm, it projects below the skin like a tense cord, which is very distinctly seen in emaciated subjects. On the outside, it corresponds at first to the brachialis anticus, and is then received in the sort of groove formed between the inner border of the biceps and the brachialis anticus. \n front, it is covered by the inner border of the biceps, excepting in emaciated subjects. Behind, it is in relation with the ulnar nerve (/), and then with the brachialis anticus. Its relations with the brachial artery are of the greatest importance, in reference to the application of a ligature to that vessel. The nerve is at first situated to the outer or radial side of the axillary artery, but soon passes in front of the vessel, and then it crosses over slightly, so that at the bend of the elbow it is situated about two lines to the inner or ulnar side of the artery. This last relation is not con- stant : I have seen the nerve on the outer side of the artery at t\ie bend of the elbow. The following are its relations with the other nerves : the internal cutaneous nerve runs along its inner side, at first immediately in contact with it, and then separated from it by the fascia of the arm. The ulnar nerve runs behind it in the upper third of the arm, and is then separated from it, so that the two nerves bound the sides of a triangular interval, the base of which is below and the apex above. The median nerve does not give any branch in the arm.t to those which are met with on the cutaneous nerves in the palm of the hand ; the articular filaments, moreover, have almost always the grayish aspect of the nerves of org^anic life. * These two roots of the median nerve, when united to the musculo-cu- taneous and the ulnar, represent very nearly a capital M. Not unfre- quently there is a third internal root for the median nerve. t [Except, occasionally, an anastomotic branch to the musculo-cutane- ous, after the latter has emerged from the coraco-brachialis.] THE MEDIAN NERVE IN THE FOREARM AND HAND. 787 In the Forearm. The median nerve, like the brachial artery, to the inner side of which it is generally situated, passes beneath the tendinous expansion of the biceps, and is separated from the elbow-joint by the brachialis anticus. It almost always perforates the pronator teres in such a manner as to leave only a very small tongue of fleshy fibres behind it;* it then passes {d, fig. 288) between the flexor sublimis and flexor profundus digitorum, opposite the cellular interval between the latter muscle and the flexor longus pollicis ; at the lower part of the forearm it runs along the outer border of the flexor sublimis, where it might be easily exposed between the tendon of the palmaris longus on the inside, and of the flexor carpi radialis on the outside. I have seen this nerve perforate the upper part of the flexor sublimis, which formed a sheath for it. Branches. — These are muscular, excepting the palmar cutaneous, which arises at the lower part of the forearm : they supply all the muscles of the anterior region of the fore- arm except a part of the flexor profundus, and the whole of the flexor carpi ulnaris, which receive branches from the ulnar nerve. Lastly, with the exception of the palmar cutaneous, the branches arise near the bend of the elbow. The branch for the pronator teres comes off from the anterior part of the median nerve, a little above the elbow-joint, and passes downward to enter the substance of the mus- cle. It gives off several articular filaments, which dip from before backward, around the termination of the brachial artery and the commencement of the radial and ulnar arter- ies, form loops with their concavities turned upward in the angle of bifurcation of the brachial, and then enter the articulation. The other collateral branches of the median in the forearm arise from its posterior aspect : they are the branch for the superficial layer of muscles, which arises opposite the elbow-joint, and then divides successively into several others, which enter the pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor sublimis. The filaments for the flexor sublimis are remarkably slender, and are reflected upward below the epi- trochlea : they belong to the upper part only of this muscle, which is also supplied by two or three other branches, given off in succession from the median, a little below the bend of the elbow. The branch for the deep layer of muscles is a large trunk, which soon divides into sev- eral branches, viz., one external, for the flexor longus pollicis, the upper extremity of which it enters ; two internal, which enter the flexor profundus, but only supply its inner half, the other half receiving its nerves from the ulnar ;t and a middle branch, the inter- osseous nerve (c), which requires a particular description. It passes vertically downward, in front of the interosseous ligament, between the flexor profundus and the flexor lon- gus pollicis, to both of which it gives several filaments ; having reached the upper bor- ders of the pronator quadratus, it passes behind that muscle and divides into a great number of filaments, some of which penetrate the muscle from behind, while others de- scend to gain the lower part of the muscle. I have seen the interosseous nerve per- forate the interosseous ligament, run a very short distance upon its posterior surface, then pass through it again, and ramify in the pronator muscle. The palmar cutaneous branch {i, fig. 287) comes off from the median nerve opposite the junction of the three upper fourths with the lower fourth of the forearm, runs along the median nerve, and divides into two branches, which perforate the fascia of the forearm immediately above the annular ligament. The external branch is the smaller, and cross- es obliquely over the tendon of the flexor carpi radialis, and terminates in the skin upon the ball of the thumb ;t the internal branch, which is larger, descends vertically in front of the annular ligament and beneath the skin, from which it is separated by a layer of adipose tissue, and is lost in the pahn of the hand, much sooner than might be expected from its size ;$ it can scarcely be traced as far as the middle of the palm. In the Hand. The median nerve, while passing behind the annular ligament of the carpus, becomes considerably wider and flattened ; it might even be said to increase gradua/ly in size. Immediately after it has passed below the ligament, still flattened out, it dji'ides (r) into two branches, one internal, the other external, which are themselves subdivided ; the in- ternal into two, and the external into four branches, so that in all there are six terminal branches. * In one case, in which the humeral attachments of the pronator teres were as high as those of the supina- tor long^us, the median nerve passed throug-h the highest attachments of the pronator teres, and was situated between the brachialis anticus and that muscle, which also covered it at the i)end of the elbow ; in this same case, the brachial artery divided into the radial and ulnar at the middle of the arm ; and the ulnar artery ap- plied against the nerve had the same relations as the brachial artery in ordinary cases. t All the deep branches may be traced as far as the periosteum of the bones of the forearm. [Some of them have been seen to comraunicate with filaments of the ulnar nerve.] t CThis branch anastomoses with the terminal cutaneous division of the musculo-spir.il or radial nerve.] I) This sudden mode of termination is common to all nerves of sensation, which are often lost almost imme- diately in the skin ; the nerves of motion, on the other hand, run a very long course as filaments before they terminate in the muscles. 788 NEUROLOGY. Tlie terminal branches of the median nerve. Of these one only is muscular, and be- longs to the muscles of the ball of the thumb ; the other five are intended for the integ- uments of the fingers, of which they form the palmar collateral nerves. The branch for the muscles of the ball of the thumb is a recurrent nerve ; it arises from the front of the median, passes upward and outward, forming a horizontal curve with the concavity turned upward, perforates the superficial layers of the flexor brevis, im- mediately gives off a descending branch to that muscle, and, continuing to ascend itself, is divided almost equally between the abductor brevis and the opponens pollicis. The External Collateral Branch of the Thumb* — This nerve passes obliquely down- ward and outward, on the inner side of the tendon of the flexor longus pollicis, crosses the metacarpo-phalangal articulation, to gain the external border of the anterior surface of the thumb, and, running along the outer side of the tendon of the long flexor, arrives at the ungual phalanx. On this phalanx, it divides into two branches, a dorsal or ungual, properly so called, which turns round the side of the phalanx, anastomoses with the dor- sal collateral branches of the radial nerve, and is distributed to the dermis beneath the nail ; and a palmar, which is lost in the skin covering the pulp of the thumb. Some of these latter filaments turn round the tip of the phalanx, and are distributed to the skin beneath the nail. None of the filaments of the external collateral branch anastomose with those of the internal collateral. The internal collateral branch for the thumb is less oblique in its course and larger than the preceding ; it runs along the first interosseous space in front of the adductor pollicis, and reaches the inner side of the anterior surface of the thumb, along the tendon of the long flexor, and terminates like the preceding branch. This branch gives off a twig to the adductor pollicis. The external collateral branch for the index finger sometimes arises by a common trunk with the preceding ; it runs along the first interosseous space in front of the adductor pollicis, on the outer border of the first lumbricalis muscle, to which it gives a filament, and then divides into two branches, a dorsal and a palmar : the dorsal branch, which is the smaller, passes backward and downward, along the outer border of the first phalanx, unites with the dorsal collateral branch derived from the radial nerve, gains the poste- rior surface of the second phalanx, and terminates upon the third, near the nail. The palmar branch, which forms the true continuation of the trunk of the nerve, is arranged like the corresponding nerve of the thumb, and does not anastomose with the internal collateral branch. The common trunk of the internal collateral branch of the index finger, and external collat- eral branch of the middle finger, passes vertically downward, in front of the second inter- osseous space, at the middle of which it divides into two branches, one of which forms the internal collateral branch of the index finger, and the other the external collateral branch of the middle finger. These collateral nerves, like the preceding, divide into a dorsal and a palmar branch, the latter of which again subdivides into a sub-ungual branch and a branch for the pulp of the finger. The common trunk of these two collateral nerves, before bifurcating, gives off a twig to the second lumbricalis. The common trunk of the internal collateral branch of the middle finger, and external col- lateral branch of the ring finger, passes somewhat obliquely inward, in front of the third interosseous space, and is distributed in the same way as the preceding branches ; be- fore bifurcating, it sometimes gives a twig to the third lumbricalis ; it receives an anas- tomotic filament from the ulnar nerve. The bifurcation of this sixth branch takes place a little below the metacarpo-phalangal articulations. Relations. — The following are the relations of the palmar and digital portions of the median nerve : Behind the anterior annular ligament of the carpus, the median nerve is situated on the outer side of the tendons of the flexor sublimis and in front of those of the flexor pro- fundus : like the tendons among which it is placed, it is at first covered by the synovial membrane in front and behind. In the pulm of the hand, the median nerve is covered by the palmar fascia, and is situ- ated in front of all the flexor tendons. The superficial palmar arch lies in front of it, and crosses at light angles over its three internal branches. The collateral nerves of the fingers accompany the collateral vessels, and pass with them from the palm of the hand opposite the intervals between the metacarpo-phalangal ar- ticulations. Like the vessels which run along their outer side, these nerves occupy the borders of the palmar aspect of the fingers, one on each side of the tendinous groove. Summary. — From what has been stated, it follows, then, that the median nerve gives off no branch in the arm ;t that, in the forearai, it gives no nerve to the skin, but sup- plies all the muscles of the anterior region, excepting the flexor carpi ulnaris and the inner half of the flexor profundus, which we shall see are supplied by the ulnar ; and, lastly, that, in the hand, it supplies the cutaneous nerves of the palm, the external and * I have seen it arise after the third branch, and upon a plane anterior to that branch, the origin of which It then crossed. t See note, p. 766. THE ULNAR NERVE IN THE ARM AND FOREARM. 789 internal collateral nerves of the thumb, index finger, and middle fingers, and the exter- nal collateral nerve of the ring finger, and also the muscular nerves of the ball of the thumb and the nerves of the tvpo outer lumbricales, and sometimes that of the third lumbricalis. The Ulnar J^erve. The ulnar nerve {i, fig. 286), a little smaller than the preceding, behind which it is situated, arises by a trunk which is common to it, to the internal root of the median nerve (c), and to the internal cutaneous nerve {g) ; it passes vertically downward be- hind, and at first in contact with the median, but soon leaves that nerve, and runs some- what backward (/, fig. 288), while the median is directed forward and outward ; it per- forates the upper fibres of the internal head of the triceps, and enters the sheath of that muscle, behind the internal inter-muscular septum. It thus gains the groove between the inner condyle of the humerus and the olecranon, passes between the two origins of the flexor carpi ulnaris, and is reflected from behind forward in this groove, and then upon the inner side of the coronoid process : having thus reached the anterior aspect of the forearm, it passes vertically downward (/) between the flexor carpi ulnaris and the flexor profundus, and gains the palm of the hand (s), where it divides into its terminal branches. As with the median nerve, we shall examine the ulnar in succession in the arm, the forearm, and the hand. In the Arm. The most important relation of this nerve (/) in the arm is that at its upper part with the median nerve and brachial artery. It runs along the inner side of the artery, while the median nerve is situated in front of the vessel, or, rather, the artery is situated be- tween the median and ulnar nerves, so that it may be exposed immediately below the axilla, by separating these two nerves. The ulnar nerve gives off no branch in the arm ; the error of those who have stated the contrary has arisen from the fact that the branch given from the musculo-spiral nerve to the internal portion of the triceps lies in contact with the ulnar nerve for a great part of its extent, so that it would seem at first sight to come off from it. The Forearm. The ulnar nerve in the forearm (/) is at first covered by the fleshy belly of the flexor carpi ulnaris, which separates it from the skin ; it becomes sub-aponeurotic below, where the fleshy fibres of that muscle cease, and is found between the tendon of the flexor carpi ulnaris on its inner side, and those of the flexor sublimis on its outer side. Its relation with the ulnar artery is remarkable. This vessel describes a curve so as to reach the outer or radial side of the nerve ; but the nerve and artery are in contact in the lower third only of the forearm. The branches of this nerve in the forearm are somewhat numerous. Between the in- ternal condyle and the olecranon, the ulnar nerve gives several very delicate articular filaments, which pass into the elbow-joint ; it also gives off branches for the flexor carpi ulnaris ; one of which is very large, and may be traced as far as the lower part of the fleshy belly of the muscle. After its reflection, the ulnar nerve gives a branch to the flexor profundus digitorum, subdivides, and enters the substance of that muscle. Its divisions run upon the anterior surface of the muscle before penetrating it. This branch is intended for the two inner portions of the flexor profundus, the two outer portions receiving their filaments from the median nerve.* At the middle of the forearm, a small, long, and slender branch is given off from the anterior part of the ulnar nerve, and divides into two filaments, one of which follows the ulnar artery {filament of the ulnar artery), while the other perforates the fascia of the fore- arm, and anastomoses with the internal cutaneous nerve {anastomotic filament). The internal dorsal nerve of the hand {x) is the largest of the branches of the ulnar nerve, so that it might be regarded as a terminal branch of that nerve ; it is exclusively intended for the skin of the dorsal region of the hand. It comes off opposite the junc- tion of the two upper thirds with the lower third of the forearm, passes obliquely down- ward, backward, and inward between the ulna, over which it crosses, and the flexor car- pi ulnaris, and emerges {x, fig. 289) from below the tendon of that muscle, a very short distance above the lower end of the ulna. It then descends vertically between the skin and that part of the bone, runs along the inner side of the carpus, and divides into two dorsal branches, an internal and an external. The internal dorsal branch is the smaller; it runs along the ulnar border of the fifth metacarpal bone, and along the internal or ulnar side of the dorsal region of the little finger, of which it forms the internal collateral dorsal nerve. The external dorsal branch is much larger ; it first gives off a small anastomotic twig, which crosses obliquely over the metacarpal bone, and anastomoses with a correspond- * [The ulnar may communicate in this position with filaments of the anterior interosseous.] 790 NEUROLOGY. ingly oblique branch from the radial nerve, opposite the lower part of the second interos- seous space. It then descends vertically along the fourth interosseous space, and di- vides into two secondary branches, which again subdivide to form the dorsal collateral nerves, in the following manner : one forms the external collateral nerve of the little finger, and the internal collateral nerve of the ring finger ; and the other the external collaieral nerve of the ring finger, and the internal collaieral nerve of the middle finger.* In the Hand. The ulnar nerve enters the palm of the hand {s,fig. 288), not by passing behind the an- terior annular ligament, but in a special sheath, which is common to it and to the ulnar artery, is situated on the inner side of the annular ligament, and has the pisiform bone to its inner side, and unciform bone to its outer side. This sheath is completed behind by the ligament which extends from the pisiform to the unciform bone, and in front by a sort of annular ligament. The nerve is covered by a synovial membrane during its passage through this sheath. As soon as it leaves this sheath, the ulnar nerve divides into two terminal branches, the one superficial, and the other deep. The superficial terminal branch, or trunk of the palmar collateral nerves of the fingers, im- mediately gives off a branch which passes beneath the flexor brevis digiti minimi, pene- trates the deep surface of that muscle, and immediately divides into two other branches, an internal and an external. The internal is the smaller branch ; it crosses over the muscles of the ball of the little finger, beneath the palmaris brevis, when it exists, gains the inner side of the anterior surface of the httle finger, and forms its internal palmar col- lateral nerve. i The external is larger ; it sends a communicating twig to the median nerve, and bifurcates to form the external palmar collateral nerve of the little finger, and the internal palmar collateral nerve of the ring finger. The deep terminal or muscular branch is somewhat larger than the superficial branch. Immediately after its origin, it is reflected outward below the unciform bone, perforates the flexor brevis digiti minimi, and passes deeply into the palm of the hand, so that it cannot be exposed without dividing all the tendons of the palmar region. This branch describes a transverse curve or arch with the concavity directed upward, in front of the metacarpal bones, corresponding to and situated within the curve de- scribed by the deep palmar arterial arch, which crosses it at an acute angle. No branch arises from the concavity of this nerve, but from its convexity a great num- ber are given off, in the following order : During the passage of the nerve between the pisiform and unciform bones, three branch- es for the three muscles of the hypothenar eminence. Two very remarkable descending filaments, which supply the palmar interossei of the third and fourth spaces, and end in the third and fourth lumbricales. The first and sec- ond lumbricales, and frequently the third also, are supplied by the median nerve. Three perforating branches pass backward between the upper ends of the metacarpal bones, give some branches to the palmar interossei, proceed along the cellular interval between the palmar and dorsal interossei, supply the last-mentioned muscles, and termi- nate by anastomosing with the dorsal collateral branches of the ulnar and radial nerves. We may regard as terminal divisions of the deep branch, two branches, which are given to the two portions of the adductor pollicis,t and a branch for the first dorsal inter- osseous muscle, from which a filament is given off that enters the adductor poUicis near its lower border. Summary. — From what has been stated, it appears that the ulnar nerve gives ofl^ no branch in the arm ; that in the forearm it supplies some articular branches to the elbow- joint, certain muscular branches for the flexor carpi ulnaris, and the inner half of the flexor profundus, and a cutaneous filament which anastomoses with the internal cu- taneous nerve ; that it gives off to the hand a dorsal cutaneous branch, from which the dorsal collateral nerves of the little and ring fingers, and the internal dorsal collateral of the middle finger, proceed ; a palmar cutaneous division, which supplies the palmar collateral nerves of the little finger, and the internal palmar collateral nerve of the ring finger ; and a muscular division, which is distributed to the three muscles of the hypothenar emi- nence, to all the interossei, among which we may include the adductor polliciSjiSi and to the two internal lumbricales. * [This latter branch often anastomoses with the dorsal cutaneous branch of the radial nerve.] t I have observed that it supplies the palmaris brevis, when that muscle exists. i The reader must here be reminded, that I have regarded all that portion of the flexor brevis pollicis (of authors) which is situated to the inner side of the tendon of the flexor longus pollicis, or, in other words, all that portion which is attached to the internal sesamoid bone, as belonging to the adductor pollicis. (See Myology, p. 190.) The distribution of the nerves favours this view ; for the flexor brevis is supplied by the median nerve, while the two portions of the adductor receive their nerves from the ulnar. [This general statement is not quite correct ; the outer portion of the adductor (the inner head of the flexor brevis of au- thors generally) also receives a small branch from the median nerve (see p. 787 ; also Swan and Ellis).] () It is perfectly rational to consider the adductor pollicis as the first palmar interosseous muscle, which, for the sake of increased power of adduction, is attached to the third metacarpal bone. MUSCULO-SPIRAL NERVE. 791 Musculo-spiral J^ferve. The musculo-spiral or radial nerve, which is the largest of the terminal divisions of the brachial plexus, is intended for the triceps extensor cubiti, for the muscles of the pos- terior and external region of the forearm, and for the skin of the arm, the forearm, and dorsal region of the hand. It arises {f^fig. 286) from all the live nerves of which the brachial plexus is composed, by a trunk which is common to it and to the circumflex nerve, and it issues from the plexus behind the ulnar nerve, to which it is closely applied. Immediately after its ori- gin, it passes downward, backward, and outward {b, fig. 288), in front of the conjoined tendons of the latissimus dorsi and teres major, to gain the groove of torsion or spiral groove of the humerus, into which it enters, passing between the long head of the tri- ceps and the bone, then between the external head and the bone ; it traverses the whole extent of this groove, and is in relation with the profunda humeri artery and vein. Leaving this groove, opposite the junction of the two upper thirds with the lower third of the humerus, it hes on the external and anterior aspect of the arm, descends vertical- ly between the supinator longus and brachialis anticus, and next between the brachialis anticus and extensor carpi radialis longior, crosses the elbow-joint (at b), passing in front of the outer condyle of the humerus and the upper extremity of the radius, and then di- vides into two terminal branches. Collateral Branches of the Musculo-spiral Nerve. During its winding and spiral course along the arm, this nerve gives off a great num- ber of collateral branches in the following order : Branches given off hy the Musculo-spiral Nerve before it enters the Spiral Groove. — The first is the internal cutaneous branch {f, fig. 287) of the musculo-spiral, which is sub- aponeurotic at its commencement, but perforates the fascia, becomes applied to the skin, and divides into two filaments, which pass obliquely backward, and may be traced as far as the olecranon.* There are several considerable branches to the long head of the triceps ; the highest of which is recurrent, and may be traced as far as the scapular attachments of the muscle. A very large descending branch may be traced to the olecranon. There is a branch for the internal head of the triceps, one division of which is rather large, and runs along the inner border of the humerus in front of the muscle, which it does not enter until it approaches the elbow. Branches given off by the Musculo-spiral after leaving the Spiral Groove. — These are the external cutaneous bra/ich of the musculo-spiral, a very large branch which perforates the muscular fibres of the triceps and the brachial aponeurosis, then lies in immediate con- tact with the skin of the external region of the arm, passes obliquely backward, and di- vides into a great number of filaments, which supply the skin of the posterior region of the forearm, and may be traced down to the carpus. The branch for the external head of the triceps and for the anconeus, which is remarkable for its length, descends vertically between the external and long heads of the triceps, supplies the former of these, enters the anconeus, and may be traced as far as the lower part of that muscle. All these branches are remarkable for 6eing given off at nearly the same height ; that is to say, near the shoulder-joint, and for accompanying the trunk of the musculo-spiral nerve. Branches given off by the Musculo-spiral Nerve in the Forearm. — These are the branches for the supinator longus, and those for the extensor carpi radialis longior, which enter the inner surface of the upper part of those muscles. Terminal Branches of the Musculo-spiral Nerve. Reduced to one half, or less, of its original size, by the successive emission of the pre- ceding branches, the musculo-spiral or radial nerve divides in front of the elbow {b,fig. 288) into two unequal branches, the one deep or muscular, the other superficial or digital. The deep or muscular division of the musculo-spiral nerve, or the posterior interosseous, is larger than the superficial division ; it immediately gives off a branch which passes "vertically in front of the extensor carpi radialis brevier, and soon dips into that muscle ; the nerve then becomes flattened, perforates the supinator brevis, and pursues a very oblique and spiral course around the radius and within that muscle, to which it gives branches (branches for the supinator brevis) : it then emerges from the posterior aspect of this muscle, and immediately divides into a great number of diverging branches, some of which are intended for the superficial, and the others for the deep layer of muscles on the posterior region of the forearm. The branches given to the superficial layer are, those for the extensor communis digi- torum, which are very numerous and diverging, the superior being also recurrent ; the Iranch for the extensor proprius digiti minimi ; and the branch for the extensor carpi ul- * [Anastomosing with the accessorv of the internal cutaneous.] 792 NEUROLOGY. rmris : all these branches arise by a common trunk, and enter the deep surface of the muscles. The branches for the deep laijer also arise by a common trunk {i, Jig. 289), which may be Fig. 289. regarded as the continuation of the muscular division of the mus- culo-spiral, considerably diminished in size. This common trunk passes vertically downward between the superficial and deep lay- ers of muscles, gives off a branch, which enters the superficial as- pect of the extensor longus pollicis, then passes between the adduc- tor longus and extensor brevis pollicis on the one hand, and the extensor longus pollicis on the other, runs in contact with the inter- /■/. osseous ligament, and gives off a first branch to the extensor lon- gus pollicis, a second which enters the deep surface of the same muscle, and a small branch which enters the outer border of the entensor proprius indicis. Reduced at length to a very small branch, the muscular division of the musculo-spiral nerve enters the groove (at s) for the tendons of the extensor communis digitorum, lying beneath them, in con- tact with the periosteum ; it runs over the carpus, and expands into a number of articular filaments, which enter the radio-carpal, carpal, and carpo-metacarpal articulations ; in this latter portion of its course, the nerve is of a gra3dsh colour, swollen, and, as it were, knotted ; a condition which is observed in all articular nerves. The superficial, eutaneous, or digital division of the musculo-spiral nerve, or the rad-ial nerve properly scT called, forms the external dor- sal nerve of the hand, and is about half the size of the muscular di- vision. It passes vertically downward, between the supinator lon- gus and the extensor carpi radialis longior, along the outer side of the radial artery : having reached the middle of the forearm, it es- capes from beneath the tendon of the supinator longus, and runs along the outer border of that tendon. Situated at first beneath the fascia, it soon perforates it, becomes sub-cutaneous, runs vertically downward, and, about an inch and a half above the styloid process of the radius, divides into an external and an internal branch. The external branch (o, figs. 288, 289), which is the smaller, runs along the outer side of the styloid process of the radius, and then along the outer border of the carpus,* of the first metacarpal bone, and of the first and second phalanges of the thumb, and termi- nates in the skin beneath the nail ; it is the external dorsal collateral branch of the thumb. The internal branch {e, fig- 289), which is much larger, passes obliquely behind the ra- dius, crosses the tendons of the adductor longus and extensor brevis pollicis, and divides into 'three secondary branches, namely, counting from without inward, the internal dor- sal collateral nerve of the thumb, and the external and internal dorsal collateral nerves of the index finffcr.'t Summary The musculo-spiral nerve gives off, in the arm, two cutaneous branches, one internal, the other external, the latter of which is much the larger, and may be tra- ced as far as the carpus ; and also muscular branches to the three portions of the triceps and to the anconeus : to the forearm, it supplies muscular branches to all the muscles of the deep and superficial layers of the posterior and external regions ; and to the hand, certain cutaneous branches, namely, the dorsal collateral nerves of the thumb and index finger. General Summary of the Distribution of the.JSTerves of the Brachial Plexus. The preceding description shows that the brachial plexus supplies the skin, the mus- cles, and the articulations of the upper extremity, including the shoulder. We shall briefly recapitulate, first the muscular and then the cutaneous branches. The Muscular Brandies.— By its collateral branches, the brachial plexus supplies the scaleni and all the muscles which move the shoulder, excepting the trapezius, which receives its nerves from the brachial plexus and from the spinal accessory nerve of Wil- lis ; by its terminal branches it supplies all the muscles of the arm, the forearm, and the hand. ^ . j ^i. Each of the muscles which move the shoulder receive a special nerve ; thus, besides the nervous filaments for the scaleni, there is the nerve for the sub-clavius ; the nerve for the levator anguli scapulae ; the nerves for the rhomboideus ; the nerve for the serratus magnus, which is better known as the external thoracic nerve ; the nerve for the latis- simus dorsi, which is generally described as a branch of the sub-scapular ; and the nerves for the pectoralis major and minor. The muscles which move the arm upon the shoulder also receive their nerves from the * [Wliere it sends an anastomotic filament to the palmar cutaneous branch of the median.] t [It also supplies the external dorsal collateral of the middle fing-er, and oftpn unites with the ulnar cuta- neous, to form the dorsal collaterals for the contiguous sides of the middle and ring fingers.] THE NERVES OF THE BRACHIAL PLEXUS. 793 brachial plexus ; sometimes there is a separate nerve for each muscle, sometimes the same nerve supplies two muscles. The nerve for the deltoid, or the circumflex nerve, also supplies the teres minor. The supra-spinatus and infra-spinatus receive their fila- ments from the same branch, viz., the supra-scapulum nerve. The teres major receives a branch from the sub-scapular nerve.* Of the muscles which move the forearm upon the arm. Those of the anterior region, or the flexors, viz., the biceps, coraco-brachialis, and brachialis anticus, receive their fila- ments from the musculo-cutaneous nerve ; the muscle of the posterior region, the tri- ceps, is supplied entirely by the musculo-spiral nerve. The ulnar nerve gives no branch in the arm. The muscles which move the radius upon the ulna, and those which move the hand and the fingers, are thus supplied. The interosseous division of the musculo-spiral nerve sup- plies the muscles of the posterior region of the forearm, viz. , in the superficial layer, the common extensor, the extensor proprius digiti minimi, and the extensor carpi ulnaris ; in the deep layer, the supinator brevis, the adductor longus, extensor brevis, and extensor longus pollicis, and the extensor proprius indicis. The muscles of the exterior region of the forearm, namely, the two supinators, and the two radial extensors of the carpus, also receive their branches from the musculo-spiral nerve. The muscles of the anterior region of the forearm receive their filaments from the median nerve, excepting the flexor carpi ulnaris and the internal half of the flexor profundus, which are supplied by the ulnar nerve. The flexor profundus, then, hf a peculiarity which not unfrequently occurs in regard to compound muscles, receives its nerves from two different sources. The intrinsic muscles of the hand are supplied in the following manner : Those of the ball of the thumb by the median nerve ; those of the ball of the little finger by the ulnar nerve ; the two external lumbricales by the median nerve ; the two internal lumbricales by the ulnar nerve ; all the interossei, including the adductor polhcis, by the ulnar nerve. The Cutaneous Branches A — The skin which covers the shoulder on the outer side re- ceives its nerves from the cervical plexus. The skin of the external surface of the arrn receives its nerves from the cutaneous branches of the circumflex nerve, and from the external cutaneous branch of the mus- culo-spiral. The skin of the anterior and internal regions of the arm receives its nerves from the internal cutaneous branch of the musculo-spiral, from the accessory nerve of the internal cutaneous, which anastomoses with the second intercostal, from a small branch of the internal cutaneous, and from the humeral branch of the third intercostal. The skin of the forearm receives its filaments from the internal cutaneous, which anastomoses with the cutaneous filaments of the musculo-spiral, ulnar, and musculo-cu- taneous nerves. The skin of the dorsal region of the hand and of the fingers receives its filaments from the dorsal branches of the radial nerve, in the two external thirds of that region, and from the dorsal branch of the ulnar nerve in the internal third. The skin of the palmar region of the hand and fingers receives its filaments from the median nerve in the two external thirds, and from the ulnar in the internal third, or, to speak more precisely, the median nerve supplies the external and internal collateral branches of the thumb, the index, and the middle fingers, and the external collateral nerve of the ring finger ; the ulnar nerve supplies the external and internal collateral nerves of the little finger, and the internal collateral branch of the ring finger. Some of the terminal branches of the median nerve, and the terminal divisions of the internal cutaneous and musculo-cutaneous, are lost in the skin of the upper part of the palm of the band. The palmar collateral nerves of the fingers offer the following peculiarities : the branches which they give to the skin are placed either opposite to each other, or alter- nately ; each of these branches terminates separately in a pencil of filaments ; the twigs from the internal branches do not anastomose with those from the external ; lastly, the terminal extremities of the external and internal collateral branches do not anastomose with each other in the pulp of the finger, but expand separately, and are distributed to the skin of the pulp and to the skin under the nail. The branches which supply the palmar aspect of the fingers present a very remark- able condition, t consisting in the presence of small, grayish, gangliform bodies, always of a crescentic form. These bodies are very numerous ; they are sometimes separate, * The teres minor and the infra-spinatus are, therefore, supplied by two different branches, which would induce us to describe these muscles separately, did we not see that compound, and sometimes even simple, muscles receive two or more distinct nerves. t A beautiful preparation of the cutaneous nerves of the upper extremity may be made by removing the skin, either by turning it inside out, in the same way as an eel is skinned, or by making a longitudinal incision along the outer side of the limb. In both cases the fascia should be removed with the skm. In the first meth- od, by which a very fine preparation may be made, the everted skin represents a kind of glove, the inner sur- face of which IS formed by tlie epidermis, and the outer by the deep surface of the skin. X This was pointed out in one of the last concours of the assistants (aides) of the Faculty, by MiVI, Andral, Camus, and Lacroix, who had to dissect the cutaneous nerves of the hand. 5H . 794 NEUROLOGY. and sometimes arranged in groups ; they do not essentially belong to the nerves, but are applied to them, and may be separated from them by slight force. They are, therefore, not ganglia. If we consider that these gangliform bodies occupy the palmar region only, and are never found in the dorsal region, that they exist in the sole of the foot as well as in the palm of the hand, that they have been found upon the nerves which surround the artic- ulations, and, consequently, upon nerves which are subject to constant pressure, that I have even found them upon an intercostal nerve which was reflected over the side of the sternum, and, lastly, that they do not exist in the infant at birth, and are more numer- ous in proportion as the palm of the hand is more callous we shall be warranted in con- cluding that they are the result of external pressure. THE ANTERIOR BRANCHES OF THE DORSAL NERVES, OR THE INTER- COSTAL NERVES. Dissection. — Enumeration. — Common Characters. — Characters proper to each. Dissection. — Search carefully for the cutaneous branches, some of which are to be found opposite the sides of the sternum, and others about the middle of the intercostal spaces. Saw through the sternum in the median line, and open the abdomen through the linea alba. Sacrifice one half of the thorax, or, rather, break the ribs through the middle, so as»to trace the nerves from within outward. The anterior branches of the dorsal nerves, twelve in number, are intended for the parietes of the thorax and abdomen.* These branches offer at once a great uniformity, and a great simplicity in their distri- bution. I shall first explain their common characters, and shall then notice the pecu- liarities nresented by each. Common Characters. The anterior branches of the dorsal nerves, or the intercostal nerves, separated from the posterior branches by the superior costo-transverse ligament, appear like flattened cords, which pass to the middle of the corresponding intercostal space {see fig. 268) ; there they are situated between the pleura and the aponeurosis, which is continuous with the in- ternal intercostal muscle. After proceeding for a certain distance, they pass between the external and internal intercostal muscles, and approach the groove of the rib above, but they are not lodged in it, for they always lie below the intercostal vessels. At about the same situation in each space, that is to say, about halfway between the vertebral column and the sternum, the intercostal nerves divide into two branches, the one intercostal, and the other perforating or cutaneous. The iyitercostal branch is the continuation of the trunk of the nerve, and is distinguish- ed from it only by its smaller size. It runs along the lower border of the rib above, and then that of the corresponding costal cartilage ; it is sometimes situated on the internal surface of the cartilage, and having reached the forepart of the intercostal space, it per- forates this space from behind forward, runs along the sternum, is inclined somewhat inward over that bone, and is then reflected outward, between the pectorahs major and the skin, to which latter it is distributed. These small filaments may be called the an- terior perforating filaments. During its course, the intercostal nerve and its continua- tion give off a great number of nervous filaments. Not unfrequently the intercostal nerve gives off, in the back part of the space, a small branch, which reaches the upper border of the rib below. When this branch does not exist, its place is supplied by sev- eral twigs which have a similar distribution, some of which even pass to the intercostal space below, crossing obliquely over the internal surface of the rib. In like manner, we sometimes find some small twigs proceeding from the upper side of the nerve over the internal surface of the rib above, and reaching the next intercostal space. Lastly, from the lower side of the intercostal nerve and its continuation a series of twigs are given off, which divide into filaments that curve towards each other so as to form arches or loops, from which the terminal filaments proceed. In no part of the body are there found longer or more delicate nervous filaments ; some of them run through half the length of an intercostal space without diminishing in size, and several evidently belong to the periosteum. The perforating or cutaneous branches are often larger than the intercostal branches ; they pass very obliquely through the external intercostal muscles, and after running for a certain distance between those muscles and the serratus magnus, each of them divides into two smaller branches, the one anterior, and the other posterior or reflected : the an- terior branches run horizontally forward, become sub-cutaneous by escaping between the digitations of the serratus magnus in the eight superior intercostal spaces, and between the digitations of the obliquus externus abdominis in the four lower spaces, and then, * Haller only admits eleven dorsal nerves, because he considers, and not without reason, the twelfth as a lumbar nerve. ANTERIOR BRANCHES OF THE DORSAL NERVES. 795 becoming applied to the skin, spread into a nunaber of filaments, which almost always anastomose with the adjacent filaments of the nerves above and below. The posterior or reflected branches immediately perforate the serratus magnus and the obliquus externus abdominis, are reflected upon themselves, pass backward between the latissimus dorsi and the skin, and after running horizontally lor a distance of one or two inches, are again reflected forward, and are then lost in the skin. Proper Characters of each of the interior Branches of the Dorsal JVerves. The First Dorsal Nerve. — This nerve belongs to the brachial plexus, into which it en- ters immediately after its escape from the inter- vertebral foramen, crossing over the neck of the first rib at an acute angle. From its size, it resembles the lower cervical nerves, and differs widely from the remaining dorsal nerves. It becomes intercostal only by giving off a small intercostal twig at its exit from the inter- vertebral foramen. This in- tercostal branch is applied to the under surface of the first rib, which it crosses obliquely from behind forward, so that it does not reach the first intercostal space until opposite the junction of the rib with its cartilage ; it gains the middle of this space near the ster- num, at which point it passes forward through the space, like the other intercostal nerves, and ramifies in the muscles and the skin. The Second Dorsal Nerve. — This nerve crosses obliquely over the second rib, on the outer side of its neck, to reach the first intercostal space, and then recrosses the same rib, about its middle, to gain the second intercostal space, where it divides into two branches : the intercostal, which follows the lower border of the second rib, and presents nothing remarkable ; and the perforating or cutaneous branch, which requires a special description. The perforating or cutaneous branch, which is destined exclusively for the skin of the arm, is much larger than the other branches of the same kind. It emerges from the thorax at the middle of the second intercostal space, immediately below the second rib, passes directly through that space, is reflected at right angles over an aponeurotic arch, runs outward, and immediately subdivides into two branches of equal size, the one ex- ternal and the other internal. The external or intercosto-humeral branch (to the left of d, fig. 287) traverses the axilla, receives an anastomotic twig from the accessory nerve (c) of the internal cutaneous of the arm, reaches and crosses over the outer border of the latissimus dorsi, and divides into two cutaneous filaments, one of which is distributed to the skin of the posterior re- gion of the arm, while the other lies in contact with the skin of the internal region of the arm, runs parallel to the accessory nerve of the internal cutaneous, and may be traced as low down as the elbow. The internal branch crosses the outer border of the latissimus dorsi, lower down than the preceding branch, becomes applied to the skin, and divides into internal and posterior filaments, which are lost in the skin of the arm. The perforating branch, therefore, of the second dorsal nerve completes the system of cutaneous nerves of the arm. The third dorsal nerve is precisely similar to the others, excepting in its perforating, cutaneous, or intercosto-humeral branch, which is distributed to the integuments both of the thorax and arm. It is much smaller than the preceding ; it emerges {d,fig. 287) from between the digitations of the serratus magnus, is reflected backward upon itself, gives a small branch to the mamma, crosses the outer border of the latissimus dorsi, below the perforating branch of the preceding nerve, and having reached the upper part of the shoulder, is reflected upon itself, describing a curve with the concavity turned upward, and terminates in the skin of the inner and upper part of the arm. T\ie fourth, fifth, sixth, and seventh dorsal nerves agree exactly with the general descrip- tion. The intercostal muscles, the triangularis sterni, the serratus magnus, the obli- quus externus abdominis, the upper part of the recti abdominis, and the integuments of the thorax, are supplied with nerves from these branches, in the order and manner al- ready pointed out. I would direct attention to the considerable number of filaments dis- tributed to the skin of the mamma in the female. The perforating branches of the fourth and fifth dorsal nerves each give a branch to the mamma, and a posterior branch, which crosses the latissimus dorsi, and is distributed to the skin over the scapula ; the skin of the mamma receives nerves from the third, fourth, and fifth dorsal nerves. The eighth, ninth, tenth, and eleventh dorsal nerves belong to the intercostal spaces form- ed by the false ribs : they leave those spaces at the point where the costal cartilages change their direction to bend upward ; they perforate the costal attachments of the di- aphragm, without giving that muscle any filaments, continue their oblique course in the substance of the parietes of the abdomen, for which they are destined, and are distribu- ted to these parts, in the same way as the nerves in the intercostal spaces, with some slight modifications. Thus, the perforating branches perforate the external intercostals and the obliquus externus abdominis in the same line as the perforating branches of the preceding nerves ; the intercostal branches, properly so called, having thus become ab- dominal, run between the external and internal oblique muscles, jus-t as, in the upper spa- 796 NEUROLOGY. ces, they ran between the external and internal intercostals. Having reached the rec- tus abdominis, they give ofT a cutaneojis or perforating branch, and then enter the sheath of that muscle, through certain openings at its outer border, and proceed between the muscle and the posterior layer of the sheath : at the junction of the two external thirds with the internal third of the rectus, these branches pass through it very obhquely to- wards the middle line, and divide into muscular filaments, which are lost in the muscle, and the lowest of which pass vertically downward, and cutaneous filaments, which per- forate the anterior layer of the sheath of the rectus, on each side of the linea alba, but not always at the same distance from it, and are reflected horizontally outward in the sub-cutaneous cellular tissue lying immediately in contact with the skin. The tioelfth dorsal nerve {d, fig. 290) might, according to the opinion of Haller, be re- garded as the first lumbar nerve. It is larger than the other dorsal nerves ; it emerges from the vertebral canal between the last rib and the first lumbar vertebra, passes in front of the costal attachments of the quadratus lumborum, runs along the lower border of the twelfth rib, proceeds very obhquely downward, like that rib, perforates the apo- neurosis of the transversalis muscle, and, like the preceding nerves, divides almost im- mediately into two branches. The abdominal branch, which corresponds to the inter- costal branch of the other nerves, passes horizontally forward between the transversalis and obliquus intenius, supplying those muscles, and almost always gives off, below, an anastomotic branch to the abdominal or ilio-inguinal branch of the lumbar plexus, and then penetrates the sheath of the rectus, where it is arranged like the preceding nerves. The perforating or cutaneous branch is remarkable for being larger than the abdominal branch, and for its distribution ; it perforates very obliquely, and at the same time gives branches to the external and internal oblique muscles, becomes sub-cutaneous, passes vertically downward, crosses at right angles over the crest of the ilium, and divides into anterior, posterior, and middle branches, which are distributed to the skin of the gluteal region. Not unfrequently this gluteal cutaneous branch is given off by the first lumbar nerve, and then the cutaneous branch of the twelfth dorsal nerve is arranged like those of the preceding nerves, and ramifies in the skin between the last rib and the crest of the ili- um. There is a mutual relationship between the twelfth dorsal and the first lumbar nerves, so that they are often inversely developed ; they always communicate with each other by a branch called the dorsi-lumbar, but the mode and place of communication are subject to many varieties : thus, it is sometimes effected by a winding branch which runs along the outer border of the quadratus lumborum, at other times it takes place in the substance of the abdominal muscles.* Summary of the Dorsal or Intercostal J^erves. These nerves are distributed to the parietes both of the thorax and the abdomen, which in all respects may be regarded as constituting a single cavity, the thoracico-abdominal. The muscular and cutaneous thoracic branches from the brachial plexus, some small branches derived from the lumbar plexus, and the posterior spinal branches of the dorsal nerves, complete the nervous system of the thoracic and abdominal parietes. The dorsal nerves are divided into muscular nerves, for the muscles of the thoracico- abdominal parietes, and for the muscles which lie upon them, and into cutaneous nerves. To obtain a good idea of the latter, they should all be displayed in the same preparation. Several rows of parallel cutaneous filaments will then be seen, in the following order, proceeding from before backward. The ajiterior perforating or cutaneous nerves, which are extremely small, emerge at the sides of the sternum and of the linea alba, and are reflected forward. The perforating or cutaneous nerves, which might be called middle, divide into one set of branches, which run parallel to each other forward, towards the sternum, and another set, also parallel, which run backward, towards the vertebral column. We have elsewhere stated that other posterior cutaneous branches are given off from the posterior branches of the dorsal nerves. They are parallel, and run outward, and may be traced as far as on a level with the axilla. THE ANTERIOR BRANCHES OF THE LUMBAR NERVES. Enumeration. — The Lumbar Plexus — Collateral Branches, Abdominal and Inguinal. — Ter- minal Branches — the Obturator Nerve — the Crural Nerve and its Branches, viz., the Mus- culo-cutaneous — the Accessory of the Internal Saphenous — the Branch to the Sheath of the Vessels — the Muscular Branches — the Internal Saphenous. Dissection. — In order to see these nerves at their exit from the inter- vertebral forami- na, and also to obtain a view of the lumbar plexus, it is necessary carefully to divide the * In a subject which had a thirteenth or lumbar rib, there was a thirteenth dorsal nerve, of large size, which crossed the supernumerary rib, and which corresponded in its distribution with both the twelfth dorsal and the first lumbar nerves ; it only communicated with the first lumbar ner\-e by a ver>- small filament ; it gave off a deep perforating or cutaneous branch to the gluteal region, and also an ilio-scrolal branch. In this subject there were only four lumbar nerves. THE LUMBAR PLEXUS. 797 psoas muscle, in which they are situated ; the branches which emerge from the plexus must be dissected with the greatest care as they are passing under the femoral arch, and then to their final distribution. The anterior branches of the lumbar nerves (21 to 25, fig. 268) are five in number, and are distinguished as the first, second, third, fourth, and fifth : they gradually increase in size from the first to the fifth, and form a continuation of the series of anterior branches of the dorsal nerves : after having given off one or two branches to the lumbar ganglia (m) of the sympathetic, and some branches to the psoas muscle, they end by anastomo- sing so as to form the lumbar plexus (Z). The anterior branch of the first lumbar nerve (1 I, fig. 290) is the smallest of all, and is almost equal in size to the anterior branch of the K^. 290. twelfth dorsal nerve ; immediately after emerging from the inter-vertebral foramen, it divides into three unequal branches ; two of these (a and above b) are external and oblique, and constitute the ab- dominal branches {ilio-scrotal nerves of some authors) ; the third is internal, vertical, and often very small ; it is the anastomotic branch which joins the second nerve. The anterior branch of the second lumbar nerve is at least twice as large as the preceding ; it passes al- most vertically downward, and gives off an anterior branch, the internal inguinal {genito-crural of Bichat, b), and an external branch, the external inguinal (in- guino-cutaneous of Chaussier, c). It is scarcely di- minished in size by giving off these nerves, but be- comes flattened, plexiform, and riband-shaped, fur- nishes some large branches to the psoas, and anas- tomoses with the third nerve. The anterior branch of the third lumbar nerve is twice as large as the preceding, passes obliquely downward and outward, and is joined by the branch from the second nerve, which greatly increases its size. The large trunk thus formed, after a short course divides into two unequal branch- es, which diverge at a very acute angle, and anastomose with two branches derived from the fourth nerve, to constitute the crural (g) and the obturator (h) nerves. The anterior branch of the fourth lumbar nerve is a little larger than the third ; it divides after a short course into three branches : an external, which unites with the external bifurcation of the third to form the crural nerve ; 3 middle, which unites with the internal bifurcation of the same nerve to form the obturator nerve ; and an internal, vertical, an- astomotic branch, which joins the fifth nerve. The anterior branch of the fifth lumbar nerve (5 I) is somewhat larger than the fourth ; it receives the internal branch of that nerve, and with it forms a large trunk, which enters the sacral plexus, and was named by Bichat the lumbosacral nerve (?)• The Lumbar Plexus. The lumbar plexus {fig. 290) (lumbo-abdominal, Bichat) is a rather complicated inter- lacement, formed by the anastomoses of the anterior branches of the lumbar nerves. It is narrov.- above, where it consists of the sometimes slender communicating cord be- tween the first and second lumbar nerves, and it becomes wider towards its lower part, so as to have a triangular form ; it is situated upon the sides of the lumbar vertebrae, be- tween the transverse processes and the fasciculi of the psoas muscle. The branches which emanate from the lumbar plexus are divided into terminal branch- es, namely, the crural (g), obturator {h), and lumbosacral nerves (i) ■ and collateral branches, improperly named musculo-cutaneous ; these are four in number ; they run between the psoas and iliacus and the peritoneum, and reach the femoral arch. I shall divide these collateral branches into two sets : an abdominal set, subdivided into the great (a) and small (above b) ; and an inguinal set, subdivided into the internal {b) and external (c).* Of these collateral branches, the abdominal only run in the sub-peritoneal adipose tis- sue, the inguinal branches being covered by a layer of fascia, which keeps them in con- tact with the psoas iliac muscle. Collateral Branches of the Lumbar Plexus. Abdominal Branches. The abdominal branches of the lumbar plexus are intended for the parietes of the abdo- * A change in the nomenclature of the collateral branches of the lumbar plexus appeared to me to be ne- cessary. Bichat, who first distinguished them by special names, divides them into external or musculo-cuta- neous branches, and an internal or genito-crural branch. Of the three external branches, Chaussier named the external the ilio-scrotnh and the internal the inguino-culaneous ; the intermediate one, to which he gave no particular name, reiai..iag its old appellation of the middle branch. 798 NEUROLOGY. men, and form a continuous series with the dorsal nerves, to which they are very anal- ogous as regards their distribution.* The great abdominal nerve {a, fig. 270) is the most external, or, rather, the highest of the branches which come from the lumbar plexus (it is the superior musculo-cutaneous nerve of Bichat) ; the terms ilio-inguinal and ilio-scrotal, which are generally applied to it, are derived from the fact of its giving a small cutaneous branch to the pubic region.f It arises from the first lumbar nerve, of which it may be regarded as a continuation ; it immediately perforates the psoas, becomes sub-peritoneal, runs in front of the quad- ratus lumborum obliquely downward and outward, through the sub-peritoneal adipose tissue, parallel to the twelfth dorsal nerve, and thus reaches the crest of the ilium to the outer side of the quadratus lamborum. It next passes obliquely through the aponeu- rotic attachments of the transversalis, runs along the crest of the ilium between that muscle and the obliquus internus, and divides into two branches, the abdominal branch, properly so called, and the pubic branch. The abdominal branch, properly so called, runs inward between the transversalis and the internal oblique, parallel to the abdominal branch of the twelfth dorsal nerve, with which it almost always anastomoses, and soon divides, hke the lower intercostal nerves, into two filaments, one of which perforates the rectus, while the other, after having en- tered the sheath of that muscle, perforates it and ramifies upon the skin. The pjibic branch {a, fig. 292) continues in the original course of the nerve : opposite the anterior superior spinous process of the ilium, and often much beyond that point, it receives an anastomotic twig from the small abdominal nerve {b'), and sometimes even the whole of that nerve, runs parallel to the femoral arch, at a variable distance above it, meets with the spermatic cord in the male, and the round ligament in the female, emerges from the anterior orifice of the inguinal canal {a, fig. 291), is reflected outward upon the superior angle of that orifice, and then expands into internal or pubic filaments, which are distributed to the skin of the pubes, and external filaments, which supply the skin of the fold of the groin ; this pubic branch sometimes divides behind the femoral arch into two filaments, which escape separately from the inguinal ring. At the point where the great abdominal nerve reaches the crest of the ilium, it very frequently divides into two branches, a gluteal cutaneous, which crosses obliquely over the crest of the ilium, and an abdominal, properly so called, which is distributed in the manner just described ; in this case, the great abdominal nerve has an analogous distri- bution to that of the dorsal nerves. The small abdominal or small musculo-cutaneous nerve (above b, fig. 290), the second branch derived from the lumbar plexus, counting from without inward (the middle muscu- lo-cutaneous of Bichat), is merely an accessory of the great abdominal nerve, sometimes arising from it, often applied to it, and always anastomosing with it. It crosses oblique- ly over the anterior surface of the quadratus lumborum, and then over the iliacus, and is sometimes directed obliquely outward towards the anterior superior spine of the ilium, to join the pubic branch of the great abdominal nerve, with which it is blended ; it some- times runs alone between the transversalis and internal oblique : having reached the middle of the femoral arch, it anastomoses {b',fig. 291) by a single twig with the pubic branch of the great abdominal nerve, runs along the femoral arch below and parallel to that branch, and terminates in the same manner, that is to say, in the skin of the pubes and groin. I have seen it give off a small branch to the lower part of the rectus ab- dominis. The small abdominal nerve deserves the name of ilio-scrotal as much as the great abdominal. If this denomination is to be preserved, it might be called the small ilio-scrotal. The Inguinal Branches. The external inguinal, or external cutaneous nerve (c, fig. 290), the third branch of the lumbar plexus, counting from without inward (inguino-cutaneous, Chauss. ; inferior mus- culo-cutaneous, Bichat), is intended exclusively for the integuments of the external and posterior regions of the thigh. It generally comes off from the second lujnbar nerve : I have seen it arise by a common trunk from the second and third lumbar nerves, and I have also seen it come off from the outer side of the crural nerve. It arises by one and often by two cords, which unite as they emerge from the psoas, or within the substance of that muscle. In either case, the nerve passes obliquely through the back part of the psoas, crosses the iliacus, being bound down by a layer of fascia, and then gains the an- terior superior spinous process of the ilium, below which it emerges {cfig. 291) from the abdomen, passing behind the femoral arch, and apparently increasing in size during its passage. Below the femoral arch the nerve is sub-aponeurotic, or, rather, is situated in a sheath * The varieties which they present as to their number, origin, and divisions, render their description diffi- cult ; I shall point out the most important varieties as we pripceed. t I have frequently found the great abdominal branch divided into two distinct branches, which anastomosed upon the crest of the ilium, and then had a common distribution. I have seen the uppermost division lying so close to the twelfth dorsal nerve that it might have been taken for a branch of that nerve. THE INGUINAL BRANCHES, ETC. 799 formed by the deepest layers of the fascia lata, and divides into two cutaneous branches (c c,fig. 292), di posterior or gluteal * and an anterior ox femoral. The posterior or gluteal branch turns very obliquely outward, downward, and backward, crosses the tensor vaginae femoris, and is distributed to the skin of the posterior region of the thigh. It is sometimes derived from the internal inguinal nerve, and then emerges from the abdomen on the outer side of the external inguinal nerve, crossing obliquely in front of it. When the great abdominal nerve (iho-scrotal of authors) gives off a cuta- neous gluteal branch, there is only a trace of this posterior branch of the external ingui- nal nerve. The anterior or cutaneous branch divides into two others, which diverge at an acute angle : one is external, the other internal ; the external branch gives off a series of fila- ments, which pass backward and downward, forming loops with their concavities turned upward, and is then lost towards the lower third of the thigh ; its place is then supplied by the internal branch, which had at first descended vertically, but now turns outward and backward, and is distributed over the outer and fore part of the knee. These several divisions of the external inguinal nerve lie in contact with the femoral fascia, and their ultimate filaments are applied to the skin. The internal inguinal nerve (branche genito-crurale, Bichat ; rameau sous-pubien, Chauss., b, Jig. 290) arises from the second lumbar nerve, passes directly forward through the psoas, from which it emerges at the side of the bodies of the lumbar verte- brae, runs vertically downward upon the anterior surface of the muscle covered by a very thin layer of fascia, and having arrived within a greater or less distance from the femo- ral arch, divides into two branches, an internal or scrotal, and an external or femoral cuta- neous branch (e). Not unfrequently this division takes place as the nerve emerges from the psoas. Sometimes, indeed, the genito-crural nerve is double, but this arises merely from its early subdivision. During its course, the "internal inguinal nerve is crossed by the ureter and covered by the spermatic vessels.! The internal or scrotal branch (e. Jig. 290) crosses over the front of the femoral artery, gains the internal orifice of the inguinal canal, crosses the epigastric artery, and, before entering the inguinal canal, gives off several filaments, which are reflected upward, and dip into the substance of the internal oblique and transversalis ; the scrotal branch is placed below the spermatic cord, from which it is perfectly distinct, runs with it through the whole length of the inguinal canal {b,fig. 291), rests upon the reflected portion of the femoral arch or Gimbernat's ligament, and emerges from the external orifice of the in- guinal canal, opposite the lower end of the external pillar : at this point it is reflected, passes vertically downward behind the cord, and ramifies in the skin of the scrotum of the male, and of the labia majora in the female. The femoral cutaneous branch gains the crural ring ; but before entering the ring, it gives off a great number of very delicate filaments, which are reflected upward behind the arch, to be distributed to the lower part of the psoas-iliac and transverse muscles : it then passes through the crural ring, in contact with its outer angle, and crosses the circumflex ilii artery at its origin, just as we have shown that the scrotal nerve crosses the epigastric artery ; after leaving the crural ring (e. Jigs. 291, 292), it lies beneath the fascia, but soon becomes sub-cutaneous, anastomoses with a cutaneous branch of the crural nerve, and may be traced beyond the middle of the thigh, t I have already stated, in describing the external inguinal nerve, that the posterior or gluteal cutaneous branch of the external inguinal nerve is often given off by the internal inguinal nerve. In that case, this branch runs outward, crosses the external nerve at a very acute angle under the femoral arch, and escapes from below the arch on the outer side of that nerve to turn round the tensor vaginae femoris. Not unfrequently the fila- ments for the lower part of the internal oblique and transverse muscles arise by one or more distinct branches. Thk Tkrminal Branches of the Lumbar Plexus. These are three in number, viz., the obturator nerve, the crural nerve, and the great communicating branch between the lumbar and sacral plexus, called the lumbosacral trunk or nerve, which I regard as a dependance of the sacral plexus. The Obturator Jferve. The obturator nerve {h, Jig. 290), which is distributed exclusively to the external obtu- * Not unfrequently the external inguinal nerve gives off a third and very small internal branch, wliich lies immediately in contact with the skin of the anterior reg-ioii of the thigh, and may be traced as far as the lower third of that region. This branch always anastomoses with a cutaneous branch of the crural nerve. t Sometimes a small filament comes off from the genito-crural nerve while it is still within the substance of the psoas, descends vertically on the inner side of this nerve, gives off a filament which is lost upon the ex- ternal iliac artery, and then again becomes united with the nerve from which it had been given off. t In order to assist the memory, by connecting these nerves with important parts, I am in the habit of call- ing the femoral cutaneous branch of the internal inguinal nerve the branch of the crural ring, and the scrotal branch, the branch of the inguinal canal. The scrotal briinch may be cut, in relieving the stricture in inguinal hernia, by the division of Gimbernat's ligament ; and the femoral cutaneous branch may be wounded when the eilemal angle of the crural ring is divided for the relief of femoral hernia. 800 NEUROLOGY. rator muscle, to the three adductors of the thigh, and to the gracilis, is the smallest of Fig. 391. the terminal branches of the lumbar plexus ; it arises from the third and fourth lumbar nerves by two equal branches, which unite at an acute angle ; it perforates the psoas, passes under the angle of bifurcation of the common iliac artery and vein, runs along the inner surface of the psoas, crosses very obhquely over the sides of the brim of the pelvis, and is then placed below ^^Ov2\':\ the external iliac vessels, with which it forms an acute angle, y,\^ and above the obturator artery : throughout the whole of this %\ course, it is enveloped in the sub-peritoneal cellular tissue of that ^^ region, and, thus flattened and enlarged, reaches the internal ori- /^7*\) fice of the obturator or sub-pubic canal, on emerging from which ';i ,';J it expands into diverging branches (A, fig. 291) for the adductors and the gracilis muscle of the thigh. Collateral Branch. — The obturator nerve gives off no branch in the pelvis : during its passage through the obturator or sub-pubic canal, it gives two filaments to the obturator externus ; one of these penetrates the upper border of the muscle, and the other enters at its anterior surface.* The obturator internus receives no fila- ment from the obturator nerve. Terminal Branches. — These are four in number ;t three of them, constituting a superficial set, pass under the pectineus, and are dis- tributed as follows : the internal to the gracilis, the external to the adductor longus, and the middle to the adductor brevis ; the fourth, which is more deeply seated, belongs to the adductor magnus. The branch for the gracilis expands, as it enters the muscle, into several filaments, the largest of which {r,fig. 291) runs for some distance upon the internal surface of the muscle before termi- nating in it. The branch for the adductor longus enters the upper border and deep surface of the muscle : a rather large division {q) of this branch, taking a different course, passes sometimes in front of and sometimes behind the muscle, which is crossed by the nerve in the first case, and perforated by it in the second ; the nerve then divides into several filaments, some of which anastomose with the accessory branch (atm) of the internal saphenous nerve, while another anastomoses with the saphenous nerve itself, and a third terminates in the synovial membrane of the knee-joint : this is an articular nerve ; it may unite with the articular branch of the nerve for the vastus internus. The anastomotic division of the branch for the adductor longus is sometimes as large as the muscular branch itself J The branch for the adductor brevis crosses the upper border of that muscle, expands upon it, but does not enter it until it reaches the middle ; there is almost always an anastomotic twig, which joins the internal saphenous branch of the crural nerve. ij The fourth branch, or branch for the adductor magnus, is the deep- est ; it passes between the adductor brevis and magnus, and ram- ifies in the last-mentioned muscle. II * [It also gives off, in this situation, articular filaments to the hip-joint ; these are small or absent when the articular branches of the accessory to the obturator are large.] t [Before dividing into its terminal branches, the obturator is joined by its ac- cessory nei-ve (see notes, infra) ; it supplies a separate branch to the pectineus when that from the accessory neiTe is wanting.] t See note, infra. ^ In a great number of subjects I have found a small nervous cord, which sometimes came off from the third lumbar nerve, sometimes from the obturator itself, and which may be called the accessor!/ of the obturator nerve or the nerve of the coxo-femoral articulation ; it perforates the psoas to reach its inner surface, runs par- allel to and above the obturator nerve, gains the pubes, which it crosses on the inner side of the ilio- pectineal eminence, with which it is in contact, dips beneath the pectineus, and anastomoses with the internal saphenous nerve, passing into the angle of bifurcation of the femoral artery, where it gives off the profunda. Opiiosite the pubes it gives off several branches, which perforate the fibrous capsule of the coxo-femoral articulation, and are distributed to the synovial membranes. [This small accessory nerve was first described by Schmidt. As it passes under the pectineus it partially supplies that muscle : its anastomotic branch is described as uni- ting with the obturator nerve beneath the pectineus, and not with the internal saphenous (see also notes, p. infra et 803). The articular branch was believed by Schmidt to end in the fat near the acetabulum. When the acces'sury nerve is small, the articular filaments and the brunch to the pectineus are replaced by others from the trunk of the obturator itself. In the pelvis the nerve has been seen to give filaments to the levator am.— (Schmidt, De Nervis Lumbahbus curumque Plexu, 1794 ; Dr. Alex. Thomson, Lond. Med. and Surg. Journal, T^os. ^5, ha ; hhs, Demonslrations of Anatomy).-i , , , , ^ II [In the dissections of Schmidt, Thomson, and Ellis, the branches of the obturator nerve were found to have a much more extensive distribution than that described in the text. According to their observations, one of the superficial branches, which is named the long cutaneous nerve (.q,fis- 291), and which corresponds THE CRURAL NERVE. 801 The Crural J^erve. The crural nerve {g,fig. 290) is the external tenniual brancli of the lumbar plexus; the third and fourth lumbar nerves are almost entirely devoted to ttie formation of this large branch, which supplies all the muscles of the anterior region of the thigh, and the integuments of the anterior regions of the thigh, leg, and foot. After emerging from the psoas, the crural nerve is lodged in the groove betw^een the psoas and iliacus ; it escapes from the pelvis with this muscle, in the sheath of which it is contained : having arrived below the femoral arch {g,fig. 291), it turns slightly out- ward, becomes flattened and widened, and immediately divides into a great number of diverging branches. The nerve sometimes bifurcates, and then gives off these different branches. Relations. — In the iliac fossa, the crural nerve is covered by the iliac fascia, and is separated by the psoas from the external iliac artery and vein. Opposite the femoral arch it always occupies the groove between the psoas and iliacus, and is situated on the outer side of the femoral artery, being separated from the vessel by the psoas, which is very narrow at that point. It is of importance to remark, that the crural nerve is not contained in the sheath of the femoral vessels, but is separated from them by the iliac fascia (see _^^. 136). Collateral Branches. — In the pelvis, the crural nerve gives off from its outer side a great number of small branches {iliac branches), which enter separately into the iliacus muscle, after having run for some distance obliquely downward and outward upon the surface of that muscle. Only one branch enters the psoas. One of the branches for the iliacus is very long, and descends vertically in front of that muscle, into which it enters, after having turned round its outer border. I have already said that the external ingui- nal nerve {inguino-cutancous of authors) not unfrequently arises from the crural nerve. Of the terminal branches of the crural nerve there are two which arise in fro7it of the Others : these are, the musculo-cutaneous nerve, and the small nerve for the sheath of the femoral vessels.* The other branches are, proceeding from without inward, the branch for the rectus, the branches for the vastus externus, the branches for the vastus internus, and the cutaneous branch, called the internal saphenous nerve. The Musculo-cutaneous Crural Nerve. This nerve passes obliquely downward and outward between the sartorius and the psoas and iliacus, and immediately expands into muscular branches, distributed exclu- sively to the sartorius, and cutaneous branches. The muscular branches may be divided into the short, which enter the upper part of the sartorius, and the loiig, which run for some distance upon the deep surface of that mus- cle, before passing into it. The cutaneous branches are three in number ; two of them perforate the sartorius at different points, and may be called perforating branches. I shall call the third the acces- sory branch of the internal saphenous nerve. The superior perforating cutaneous or middle cutaneous nerve (ffg- 291) passes, very obliquely, through the upper part of the sartorius, and often, as it emerges from that muscle, anastomoses with a branch from the internal inguinal (genito-crural) nerve ; it then passes vertically downward, parallel to and on the inner side of the external ingui- nal (external cutaneous) nerve ; it lies in contact with the femoral fascia (ffig. 292), or, rather, is contained in a proper fibrous sheath. During its course, the superior per- forating cutaneous nerve gives off internal and external cutaneous filaments, and bifur- cates, opposite the middle of the thigh, into two branches of equal size, which run par- allel to each other, gradually diminishing in size, and may be traced down to the skin over the patella. to the anastomotic division of the branch for the adductor longus, gives off cutaneous branches {q,fig. 292) which perforate the fascia to the inner side of the sartorius muscle, and supply the skin on the inner part of the thigh ; it also gives anastomotic branches to the plexus {m,Jig. 291; formed m the middle of the thigh, and sometimes an articular filament to the knee (these anastomotic and articular branches are described in the text, p. 800) ; it then ends in a descending cutaneous branch, which perforates the fascia near the knee (r, J?". 292), communicates with the internal cutaneous and internal saphenous nerves, and is distributed to the skin on the inner and back part of the two upper thirds of the leg. The deep branch of the obturator gives off ■within the upper part of the adductor niagnus an articular filament destined for the knee-joint ; this filament descends in the substance of the adductor near the linea aspera, and enters the popliteal space, either by per- forating the tendinous insertion of the muscle about its lower third, or by coming forward on the front of that insertion, and then passing backward through the opening for the femoral artery : havin" reached the popli- teal space, It surrounds the artery with small filaments, and enters the back part of the knee-joint. The cutaneous branches just stated to be given off by the superficial part of the obturator to the thigh and leg, and the articular filament given by the deep branch of the obturator to the knee-joint, correspond, in their distnbution, with the three collateral branches described by M. Cruveilhier (p. 803) as arising from the in- ternal saphenous nerve after it has received a remarkable branch of origin from the obturator nerve, opposite to the commencement of the profunda artery : these collateral branches of the internal saphenous were never met with in Mr. Ellis's dissections. In some cases, then, it seems that part of the obturator joins the internal saphenous, which afterward gives off cutaneous branches to the thigh and leg, and an articular filament to the knee ; in other cases, again, the obturator does not join the internal saphenous, the above-mentioned branches arise directly from the obturator, and the internal saphenous gives no collateral branches.] * iTue crural nerve also gives some small branches (s,/g-. 292), which pass inward behind the femoral vessels, enter the pectineus muscle, and sometimes the psoas also.] 5 1 802 NEUROLOGY. The inferior perforating cutaneous or internal cutaneous nerve {I, fig. 291) run along the inner border of the sartorius, enclosed in its sheath, passes obliquely through the muscle at the middle of the thigh, but perforates the femoral fascia much lower down (/, jig. S92) ; it descends vertically, in contact with that fascia, and having arrived opposite the internal condyle of the femur, is reflected forward upon itself, describing a loop with the concavity turned upward ; it thus gains the patella, runs between the skin and the sub-cutaneous bursa, and expands into a number of diverging filaments, which anasto- mose with the reflected branch (/ /) of the internal saphenous nerve on the inner side of the patella. A small filament often remains in the sheath of the sartorius, anastomoses upon that muscle with a branch from the accessory of the internal saphenous nerve, per- forates the sheath of the sartorius opposite the knee, and anastomoses, on the inner side of the joint, with the reflected branch of the internal saphenous. The accessory cutaneous branch of the internal saphenous nerve arises from the musculo- cutaneous nerve on the inner side of the perforating branches, descends vertically, and divides into two branches. The smaller of these is superficial («, fig. 291) ; it enters the sheath of the sartorius, runs along the inner border of the muscle, escapes from the sheath below the middle of the thigh, crosses the adductor and the gracilis, and is in contact with the internal saphenous vein until it reaches the inner side of the knee, where it anastomoses with the internal saphenous nerve. The other branch, the satel- lite nerve of the femoral artery, crosses obliquely over the nerve for the vastus internus and the internal saphenous nerve, and is situated in front of the latter, runs along the femoral artery, covering the lower fourth of that vessel, and crosses very obliquely over it, then passes over the tendon of the adductor magnus, and, having reached the fibrous ring through which the femoral artery passes, it expands into a great number of fila- ments, of which one anastomoses with the preceding branch (n), another joins the obtu- rator nerve (at m), and a third unites with the internal saphenous nerve ; a sort of plex- us is thus formed which gives origin to several nerves that cross obliquely over the gra- cilis, to be distributed to the skin upon the posterior region of the leg. The Small Nerve for the Sheath of the Femwal Vessels. This branch, which often comes off separately from the lumbar plexus, is situated, like the musculo-cutaneous, in front of the other branches of the crural nerve ; it then expands into a great number of very slender filaments, which surround the femoral ar- tery and vein. Two of these filaments, of which one passes in front of and the other behind the femoral artery, unite to form a small nerve {p, figs. 291, 292), that escapes by the opening {p) for the internal saphenous vein, and accompanies the vein for a great part of its course. Not unfrequently, the filaments which have passed between the ar- tery and vein perforate a lymphatic ganglion. Two other filaments are distributed to the adductor brevis and adductor longus ; several of them turn round the deep femoral artery and vein, to become sub-cutaneous, and anastomose with other accompanying branches of the femoral vessels, and more particularly with the internal saphenous nerve. This small branch presents many varieties. 1 have seen it arise separately from the fourth lumbar nerve, and it then runs along the anterior surface of the crural nerve. The Nerve for the Rectus Femoris. The nerve for the rectus femoris arises on the inner side of the preceding, enters the upper part of the deep surface of the muscle, and divides into a superior or short branch, which passes horizontally outward in the substance of the muscle, and an inferior or long branch, which lies in contact with its inner border, and enters the muscle at the middle of the thigh. The Nerve for the Vastus Externus. The nerve for the vastus externus sometimes arises by a common trunk with the pre- ceding, passes obliquely downward and outward beneath the rectus, to which it gives a filament, and then divides into two branches : one of these immediately enters the upper part of the vastus externus, and gives off, before penetrating it, a cutaneous branch, which perforates the fascia lata and lies in contact with the skin of the external region of the thigh : the other is longer, dips between the vastus externus and internus, and enters the middle of the former muscle. This last branch almost always gives off a small twig to the vastus internus. The Nerves for the Vastxis Internus.* These are two in number ; the one is external, and descending vertically, enters that portion of the vastus internus which corresponds to the anterior surface of the femur (the crureus of authors), and may be traced as far as the lower part of the muscle : this nerve furnishes several periosteal and articular filaments ; the other is internal, and much larger ; it often arises by a common trunk with the internal saphenous nerve, runs ver- tically downward in front of the vastus internus, parallel to and on the outer side of the * It will be remembered that, according' to my views, the portion of the triceps which is called the mtreua is not distinct from the vastus internus (see Myology). THE INTERNAL SAPHENOUS NERVE. 803 femoral artery, being in contact with that vessel above, but separated from it belovr, where it enters the vastus internus. Before penetrating it, it gives off a very remark- able eL-rticular and periosteal branch, which runs along the surface of the muscle, to the aponeurosis of which it is applied :* opposite to the knee-joint it is reflected forward, perforates the thick fibrous layer which invests the inner side of the joint, and divides into two filaments, of which one, the articular, is lost behind the ligamentum patellaj in the quantity of adipose tissue which is found there ; while the other, or the periosteal, gains the anterior surface of the patella, and is lost in the periosteum. This last filament is re-enforced upon the inner border of the patella by another which passes out from the substance of the vastus internus. Fig. 292. ../t ^y. The Internal Saphenous Nerve. The internal saphenous nerve {t t',fig. 291), the satellite nerve of the femoral artery in the thigh, and of the internal saphenous vein in the leg, is at first situated on the outer side of the ar- tery, but soon passes in front of that vessel, and is contained in the same fibrous sheath ; when the artery passes through the tendon of the adductor magnus to enter the popliteal space, the nerve continues its vertical course in front of that tendon, and crossing it very obliquely from before backward, gains the back of the internal condyle of the femur, situated in front of the ten- don of the gracilis, and separated from the skin by the sartorius ; it then divides into two terminal branches (u, t',figs. 291, 292). This division often takes place as the nerve is crossing the ten- don of the adductor magnus. Collateral Branches. — At its upper part, the internal saphenous nerve receives from the obturator nerve a remarkable branch of origin, which passes from behind forward in the angle formed by the femoral artery and the profunda.! It then gives off from its inner side, at the middle of the thigh, a cutaneous femoral branch, which passes between the sartorius and the gracilis, runs back- ward and downward, and is distributed to the skin of the poste- rior and internal region of the thigh. Several filaments continue their course to the inner and back part of the knee, anastomose with some branches given off from the saphenous nerve in the leg, and are distributed to the skin of the internal and posterior region of the leg. At the point where the femoral artery perforates the adduc- tor magnus, the internal saphenous nerve gives off a second or tibial cutaneous branch, which passes between the sartorius and gracilis, turns round the inner border of the latter muscle, pass- es vertically downward parallel to the saphenous nerve, and di- vides into several filaments, some of which anastomose with that nerve, while the others are distributed to the skin upon the internal and posterior region of the leg. In the sheath of the adductor magnus the saphenous nerve gives off an articular filament, which passes vertically downward in the substance of the internal inter-muscular septum, gains the knee-joint, perforates the fibrous layer, and may be traced into the synovial adipose tissue. J Terminal Branches. — The anterior, reflected, or patellar branch (m, figs. 291, 292) perforates the sartorius^ opposite to the back of the internal condyle, is reflected forward and downward in a flattened form upon the inner side of the knee-joint, parallel to and above the tendon of the sartorius, and expands widely into ascending filaments, which pass in front of the ligamentum patellae, and turn round the lower and then the outer borders of the patella ; into descending filaments, which cross obliquely over the crest of the tibia, and ramify in the skin which covers the external region of the leg ; and into middle filaments, which oc- cupy the space between the two preceding sets ; they are all dis- tributed to the skin, and several of them anastomose with the cu- taneous filaments upon the external region of the patella. * [In this situation it sometimes receives the articular filament of the anasto- ■ motic or long cutaneous branch of the obturator nerve.] "^-■v.'' t [This junction of part of the obturator with the internal saphenous nerve was never seen in the dissec- tions of IWr. Elhs, nor did the saphenous give any collateral branch in the thigh ; but branches correspond- ing in their distribution to the three collateral branches described in the text arose from the obturator itself (see also note, p. 800.)] ^ See note, p. 800. ^ The sartorius is, therefore, perforated in succession by three cutaneous branches, namely, two perfora-- ting branches from the musculo-cutaneous nerve, and one from the internal saphenous. 804 iNEtTROLOGY. The posterior or straight branch {t') is larger than the preceding, and continues in the original course of the nerve ; it almost always receives an anastomotic branch from the obturator nerve, passes in front of the tendon of the gracilis, then between the sartorius and that tendon,' which it crosses very obliquely, to meet the internal saphenous vein («), whose direction it then follows : having arrived opposite the junction of the three upper fourths with the lower fourth of the leg, it divides into two branches : the one, jiosterim- and smaller, passes vertically downward in front of the internal malleolus, upon which it ramifies, some of the filaments reaching as far as the skin upon the inner side of the sole of the foot ; the other branch, which is anterior and larger, runs along the internal saphenous vein, like it, is situated in front of the internal surface of the tibia, then in front of the internal malleolus, and expands into articular branches, which enter the tib- io-tarsal articulation, and into cutaneous filaments, which ramify in the skin upon the inner side of the tarsus. The following are the relations of the saphenous nerve with the internal saphenous vein : the nerve is at first placed in front of the vein, then crosses obliquely under it to get behind it, and, lastly, it again returns to its position in front of the vessel. During its course along the leg, the posterior branch of the saphenous nerve gives off some internal and some external branches : the internal branches are very small ; the up- per ones anastomose with the tibial cutaneous branch of the trunk of the internal saphenous nerve, and concur with it in supplying filaments to the skin of the back of the leg. The external branches, three or four in number, are large, and, in this respect, diminish from above downward ; their direction is obliquely downward and outward, in front of the tibia, which they cross ; their course is a long one, and they are distributed extensively to dif- ferent portions of the skin of the leg. All these divisions are parallel to each other, and to the anterior reflected or patellar branch of the saphenous nerve. THE ANTERIOR BRANCHES OF THE SACRAL NERVE. Dissection. — Enumeration. — The Sacral Plexus. — Collateral Branches, viz., the Visceral Nerves — the Muscular Nerves — t?ie Inferior Hemorrhoidal — the hiternal Pudic and its Branches — the Superior Gluteal Nerve — the Inferior Gluteal, or Lesser Sciatic Nerve — the Nerves for the Pyramidalis, Quadratus Femoris, and Gemelli. — Terminal Branch of the Sacral Plexus, or the Great Sciatic: Nerve.— ^The External Popliteal and its Branches — the Peroneaf Saphenous, Cutaneous, and Muscular Branches — the Miisculo-cutanemis — the Anterior Tibial. — The Internal Popliteal and its Branches — the Tibial or External Saphenous — Muscular and Articular Branches — the Internal Plantar — the External Plan- tar.— Summary of the Nerves of the Lower Extremity. — Comparison of the Nerves of the Upper with those of the Lower Extremity. Dissection. — Make an antero-poSterior section of the pelvis, as in dissecting the inter- nal iliac artery. The anterior branches of the sacral nerves (26 to 31, j^^. 268), which are six in number, communicate with the sacral gangha of the sympathetic, after they have emerged from the sacral foramina, and present the following arrangement : The first nerve {I, fig- 290), which is very large, passes obliquely downward and out- ward, in front of the pyriformis, and is joined at a very acute angle by the lumbo-sacral nerve (i), to assist in the formation of the sacral plexus. The second nerve, which is as large as the preceding, passes much more obhquely downward and outward, and immediately enters the sacral plexus. The third nerve (3), which is scarcely one fourth as large as the second, passes more horizontally outward to enter the sacral plexus. A considerable interval, in which is a large part of the pyriformis, separates it from the second nerve. A filament stretched in front of this muscle passes from the second to the third sacral nerve. The fourth nerve (4), which is only one third the size of the third, is divided and dis- tributed in the following manner : One of its divisions assists in forming the sacral plexus ; it gives off several visceral branches, which enter the hypogastric plexus ; it communicates with the fifth sacral nerve by another division ; it gives off one or two branches to the coccygeus muscle ; and, lastly, it gives a cutaneous coccygeal branch, which runs along the border of the sacrum, penetrates the great sacro-sciatic ligament, crosses that ligament very obliquely, and turns round its lower edge, perforates the coc- cygeal attachments of the glutaeus maximus, passes very obliquely through the muscle, gives branches to it, and then ends in the integuments. The fifth and sixth nerves, which have no connexion with the sacral plexus, are ex- tremely small ; the fifth is not more than half the size of the fourth ; the sixth is so very slender a filament, that it has often escaped the notice of anatomists, and hence the in- correct but prevalent opinion that there frequently exist only five sacral nerves. The fifth nerve, at its exit from the anterior sacral foramen, divides into an ascending branch, which communicates with the fourth, and a descending branch, which passes di- COLLATERAL BRANCHES OF THE SACRAL PLEXUS. 805 rectly downward'to anastomose with the sixth, of which it appears to form the ascend- ing branch. The sixth nerve consists of a mere filament, which divides, while still contained within the sacral foramen, into an ascending or anastomotic branch, which is merely the de- scending branch of the fifth ; a descending or hiferior coccygeal branch, which passes ver- tically downward along the coccyx in the substance of the sacro-sciatic ligament, and is distributed to the skin ; and certain external branches, which perfpra^te the sacro-sciatjic ligament, and terminate in the glutseus maximus. The Sacral Plexus. The sacral plexus (fig. 290) is formed by the four upper sacral nerves (1 to 4) and the lumbo-sacral nerve (z) from the lumbar plexus ; the three superior sacral nerves pass entirely into this plexus ; the fourth nerve only sends one of its divisions to it. The lumbo-sacral trunk or nerve, which emanates from the lumbar plexus, is formed by the whole of the fifth lumbar nerve added to a branch from the fourth. This great nervous trunk establishes a free connexion between the lumbar and sacral plexuses, which, in fact, constitute only one plexus, which may be called the lumbo-sacral. I would here recall to mind' that there is a precisely similar arrangement with regard to the cervical and brachial plexuses, to which the lumbar and sacral plexuses have an undoubted an- alogy. The sacral plexus is distinguished by its simplicity from most other plexuses, which are always more or less complicated. It is formed by the convergence of five cords to- wards the sciatic notch. As the lumbo-sacral cord is vertical, and the third and fourth sacral nerves are horizontal, it follows that the form of the sacral plexus resembles a triangle, the base of which measures the entire length of the sacrum, while its apex corresponds to that portion of the sciatic notch which is situated above the spine of the ischium. The great sciatic nerve {*) is the continuation of this plexus, which, as Bichat judiciously remarked, is merely the sciatic nerve itself flattened from before backward, the intricacy of arrangement so evident in the plexus representing that which exists in all nervous cords. The following are the relations of the sacral plexus : It rests behind upon the pyri- formis, and it corresponds in front to the internal iliac vessels, from which it is separa- ted by a layer of fascia : these vessels also separate the plexus from the rectum and peritoneum. Of the collateral branches, some are anterior, namely, the visceral nerves, which enter the hypogastric plexus ; the nerve for the levator ani ; the nerve for the obturator inter- nus ; the internal pudic nerve : the other collateral branches are posterior, namely, the superior gluteal nerve ; the inferior gluteal or lesser sciatic nerve ; the nerve for the pyriformis ; the nerve for the gemelli ; and the nerve for the quadratus femoris. The great sciatic nerve is the only terminal branch of the sacral plexus. The Collateral Branches of the Sacral Plexus. The Visceral JVerves. Dissection. — After having made a section of the pelvis at one side of the symphysis, turn the bladder and the rectum over to the same side ; carefully detach the peritoneum, which is reflected from the pelvis upon these viscera ; lacerate the cellular tissue to reach the branches given off from the fourth nerve ; and then trace the rectal and vis- ceral nerves, following the annexed description. It is advantageous to empty the large veins of the pelvis, and to soak it in water for some time previously to dissecting these nerves. The visceral nerves do not, properly speaking, come from the sacral plexus, but rather directly from the fourth and fifth sacral nerves ; they are three or four in number, and pass upward upon the sides of the rectum and bladder in the male, and of the rectum vagina, and bladder in the female ; some of them are distributed directly to those origans,' but the greater number (y, fig. 302) enter the hypogastric plexus (m), which will be de- scribed with the sympathetic system. The JSTervesfor the Levator Ani. Besides several rectal and vesical filaments which go to the levator ani, this muscle receives two filaments directly from the fourth sacral nerve (4, fig. 290) : the larger of these filaments enters the middle of the muscle ; the other, which is smaller, passes upon the sides of the prostate in the male, and of the vagina in the female, and iexm- nates in the anterior portion of the muscle. The Kerve for the Obturator Internus. It arises from the anterior part of the sacral plexus, and more particularly from that portion which belongs to the lumbo-sacral cord and the first sacral nerve ; it passes im- mediately behind the spine of the ischium, is reflected forward through the small sciatic 806 NEUROLOGY. notch, and expands into three diverging branches, which are distributed within the mns- cle. In order to expose this nerve, the lesser sacro-sciatic hgament may be divided. The Inferior Hemorrhoidal Jferve. This nerve, which is intended for the sphincter ani and the adjacent skin, arises (from A:, fig. 290) on the inner side of the internal pudic nerve, of which it is sometimes a branch, passes, lilce that nerve, behind the spine of the ischium, and then between the two sacro-sciatic ligaments, reaches the front of that portion of the glutaeus maximus which projects below the great sacro-sciatic ligament, communicates with the superfi- cial nerve of the perineum, gains the side of the rectum, and opposite the upper border of the sphincter expands into a great number of branches ; of these, some are anterior, and often anastomose with one of the divisions of the superficial perineal nerve ; others are median, and pass upon the sides of the sphincter ani as far as the skin, in which they terminate ; lastly, others are posterior, and proceed to the back part of the sphincter. The hemorrhoidal or anal nerve is sometimes distributed exclusively to the skin round the anus ; it may then be named the ayial cutaneous nerve. The Internal Pudic Jferve. Dissection. — It is convenient to commence the dissection of this nerve from within outward, by dividing the lesser sacro-sciatic ligament, and separating the obturator fas- cia from the obturator internus muscle. The superior branch of the nerve upon the dor- sum of the penis may then be traced without taking it away. The perineal branches must then be very carefully dissected, and the continuity of these branches with those already dissected within the pelvis should be made out. The internal pudic nerve {d, fig. 293) arises from the lower border of the flattened band formed by the nerves of the sacral plexus opposite to their junction ; it passes be- hind the spine of the ischium, and then enters the ischio-rectal fossa through the lesser sciatic notch, that is, between the two sacro sciatic ligaments, on the inner side of the internal pudic artery, and divides into two branches {i, fig. 290), the inferior branch, or perineal nerve, and the superior or deep branch, or the dorsal nerve of the penis. The Perineal Nerve. The inferior branch or perineal nerve con-esponds to the trunk of the internal pudic ar- tery, and to all its divisions, excepting the dorsal artery of the penis. It is the true con- tinuation of the nerve, and accompanies the trunk of the internal pudic artery, being sit- uated below that vessel ; it runs forward and then upward between the obturator inter- nus and the obturator fascia, describes a curve having its concavity directed upward, and placed on the inner side of the tuberosity of the ischium, perforates the obturator fascia, opposite to the junction of the tuberosity with the ascending ramus of the ischium, and immediately divides into two branches : an inferior or anterior superficial perineal, which corresponds to the superficial artery of the perineum ; and a superior, which corresponds to the artery of the bulb, but which has a much more extensive distribution ; I shall call it the bulbo-urethral nerve. The Collateral Branches of the Perineal Nerve. — During its course,, the perineal nerve gives off a branch which might be called the external perineal ( posterior superficial perin- eal) ; this branch perforates the great sacro-sciatic ligament, passes by the internal sur- face of the tuberosity of the ischium, turns inward and downward, and then beneath the tuberosity, runs along the crus of the corpus cavernosum, and is lost in the dartos and scrotum in the male, and in the substance of the labia majora in the female. I have seen this nerve give a branch to the coccygeus, and two branches to the sphincter. This external perineal branch, moreover, presents many varieties. In some cases it terminates by anastomosing with the superficial branch of the perineum. In one case, in which the external perineal branch was very small, it was re-enforced by a branch from the inferior gluteal or lesser sciatic nerve, which crossed the outer side of the tuberosity of the ischium, and united, in front of that tuberosity, with the external perineal branch. The Terminal Branches of the Perineal Nerve. — The superficial {anterior superficial) pe- rineal nerve follows the superficial artery of the perineum, passes, like it, obliquely in- ward and forward, through the cellular interval between the ischio-cavernosus, and bulbo-cavernosus, receives a rather large filament from the external perineal branch, and almost always divides into several remarkably long filaments, which pass through the dartos, some reaching the bottom of the scrotum, while others, running along the lower surface of the penis, are distributed to the skin of that organ, and may be traced as far as the prepuce. The bulbo-urethral nerve, the second terminal branch of the perineal nerve, passes above and sometimes through the fibres of the transversus perinei muscle, supplies some small branches to the anterior part of the compressor urethra? and the posterior part of the bulbo-cavernosus, furnishes a bulbar branch which dips into the substance of the bulb, and then expands into very delicate filaments on the corpus spongiosum.. DEEP BRANCH OF THE INTERNAL PUDIC, ETC. 807 The Ikcp Branch of the Internal Pudic, or the Dorsal Nerve of the Penis. This is the highest of the terminal divisions of the internal pudic nerve, and corre- sponds to the deep branch of the internal pudic artery. It is at first applied, together with that vessel, against the internal surface of the tuberosity of the ischium, and pass- ing upward between the levator ani and obturator internus, gains the arch of the pubes ; it then runs forward among the sub-pubic veins through the several ligamentous struc- tures below the arch, and reaches the dorsum of the penis, where it is situated at the side of the suspensory ligament. Having now become the dorsal nerve of the penis, it runs along that organ in the median line, like the dorsal artery, but superficially to that vessel, and divides into an internal and an external branch. The internal branch, or branch for the glans penis, continues in the original course of the nerve upon one side of the median line, becomes more deeply seated as it runs for- vi^ard, but without entering the corpus cavernosum, and thus arrives at the corona glan- dis ; at this point it expands and passes deeply between the base of the glans and the corpus cavernosum, gives no filament to the latter, but is entirely distributed to the glans, penetrating that part by extremely delicate filaments, which traverse the spongy tissue, and may be traced, at least in a great measure, to the papillae on the surface of the glans. The external or cutaneous branch, which is more superficial, comes off from the prece- ding at a very acute angle, passes obliquely upon the sides of the penis, and expands into a number of very long and slender filaments, some of which lie in contact with the corpus cavernosum, and supply it with very slender filaments, while others run into the sub-cutaneous cellular tissue, and are distributed to the skin of the penis ; a considera- ble number terminate in the prepuce. The external branch of the dorsal nerve of the penis supplies the skin upon the three upper fourths of the circumference of the penis. The perineal branches supply that of the lower fourth. I have not found any branch of the internal pudic nerve corresponding to the artery of the corpus cavernosum. In the female, when this nerve reaches the clitoris, it becomes very small ; it passes under the arch of the pubes, between it and the crus of the clitoris ; it runs along that cms, becomes curved like the clitoris itself, upon the side of which it expands into fila- ments, and then ramifies in the substance of that organ ; several of the filaments run forward to the skin of the anterior part of the labia majora. The superficial perineal branch passes between the constrictor muscle and the bulb of the vagina, and then terminates in these parts. The internal pudic nerve in the female does not appear to me to be half the size of the internal pudic nerve of the male. In one case I found that it consisted only of the branch for the clitoris, the superficial branch being supplied by the inferior gluteal nerve. The Superior Gluteal J^erve. The superior gluteal nerve, which is intended for the glutaeus medius and minimus, and the tensor vaginae femoris, arises from the back of the lumbo-sacral trunk, before its junction with the first sacral nerve. I have seen it arising by two roots, of which one came from the lumbo-sacral nerve and the other from the posterior surface of the plex- us : it emerges from the pelvis {a, fig. 293) by the upper and fore part of the great sci- atic notch, in front of the pyriformis, is reflected upon this notch to pass between the glutaeus medius and minimus, and divides into two branches ; the one ascending, which en- circles the origin of the glutaeus minimus, like the corresponding branch of the gluteal ar- tery ; and the other descending, which passes obUquely downward and outward, between the glutaeus medius and minimus, to which it gives off numerous filaments, and thus, grad- ually diminished in size, it embraces, as it were, the posterior surface of the gluteeus min- imus, and having reached the external border of that muscle, it passes downward, and enters the sheath of the tensor vaginae femoris, in which it terminates. Before entering the sheath of the tensor vaginae it gives off a remarkable branch, which turns round the anterior border of the glutaeus minimus, and ramifies in that muscle. The J^ervefor the Pyriformis. This little nerve arises separately from the posterior surface of the sacral plexus, and more particularly from the third sacral nerve ; it divides into two branches, which im- mediately enter the anterior surface of the muscle. The Inferior Gluteal Kerve. The inferior gluteal nerve (Bichat), or the lesser sciatic nerve {Boyer), is intended for the glutaeus maximus, the integuments of the posterior region of the thigh, and for a part of the skin of the leg. It arises from the back of the sacral plexus, sometimes by one cord, sometimes by several very distinct cords. It emerges from the pelvis (near c,fig. 293), below the pyriformis, together with and on the inner side of the great sciatic nerve, to which it may be regarded as an accessory ; it passes behind that nerve, and divides into two sets of branches, viz., muscular and cutaneous. The muscular branches (c) are numerous, although exclusively intended for the glutaeus maximus ; they divide into ascending and external branches, which run along the ante- 808 NEUROLOGY. rior surface of the muscle, spread out upon it, and may be traced as far as its upper bor- der, and descending and internal branches, which pass between the tuberosity of the is- chium and the muscle, and then enter the latter. The cutaneous branch (b) continues in the original course of the nerve, behind the great sciatic, and in front of the glutaeus maximus ; it crosses obliquely, downward and in- ward, over the tuberosity of the ischium and the origins of the biceps and semi-tendi- nosus muscles ; considerably reduced in size, from having given off several branches, it assumes the name of lesser sciatic (/), runs vertically downward, becomiog smaller and smaller, and may be traced down to the posterior region of the leg. The cutaneous branch, as it emerges from the glutaeus maximus, gives off!" a consid- erable recurrent branch («), which might be regarded as a terminal branch of the nerve. This branch is reflected upward so as to describe a curve having its concavity turned upward, and subdivides into two secondary branches, an internal and an external : the external branch is the larger, and ramifies in the skin of the gluteal region ; the internal or scrotal branch (pudendalis longus inferior, Scemmerinff) is a very remarkable one ; it is reflected forward upon the under surface of the tuberosity of the ischium, runs along at some distance from the ascending ramus of the ischium and the descending ramus of the OS pubis, anastomoses with the superficial perineal nerve, reaches the scrotum above the testis, and divides into two branches — an external, which passes on the outer side, and an internal, which runs on the inner side of the testis ; having embraced this organ, they are distributed to the skin of the anterior part of the scrotum and the lower part of the penis. In the female, this branch belongs to the labia majora. All along the thigh, the cutaneous branch of the inferior gluteal nerve gives oii'some very small external branches, and some larger internal branches, which are reflected forward, describing curves having the concavity turned upward, and supply the skin of the internal region of the thigh. In the popliteal space, the cutaneous branch divides into two filaments, one sub-cuta- neous, which may be traced, notwithstanding its extreme tenuity, as far as the middle of the posterior region of the leg ; and the other sub-aponeurotic, which perforates the fas- cia of the leg, runs along the external saphenous vein, and anostomoses with the exter- nal saphenous nerve. The JVerves for the Quadratus Femoris and the Gemelli. The superior gemellus receives a special nerve from the anterior part of the sacral plexus. The nerve for the inferior gemellus is a branch of the nerve for the quadratus femoris. The nerve for the quadratus femoris is remarkable. It arises from the front of the sa- cral plexus, or, rather, from the hmit between this plexus and the great sciatic nerve, passes vertically downward in front of the gemelli and obturator internus, by which it is separated from the great sciatic nerve, and it is placed in contact with the os innomi- natum, to the outer side of the tuberosity of the ischium. It gives off some external pe- riosteal and osseous branches, which enter the foramina in the tuberosity of the ischium ; some internal or articular branches, which perforate the fibrous capsule of the hip-joint ; a branch for the inferior gemellus ; and then terminates in the quadratus femoris, which it enters by its anterior surface. The Terminal Br-^nch of the Sacral Plexus, or the Great Sciatic Nerve. The great sciatic nerve (grand femoro-poplite, Chauss.) is intended for the muscles of the posterior region of the thigh, and for the muscles and integuments of the leg and foot : it is the termination (s, fi.g. 290) of the sacral plexus, or, rather, it is the sacral plexus itself condensed into a nervous cord. The fifth lumbar nerve, a branch of the fourth lumbar, the three superior sacral nerves, and a branch from the fourth, form the Origins of this great nerve, which is the largest in the body. It emerges from the pelvis, through the great sciatic notch, below the pyriformis im- mediately above the spine of the ischium, passes vertically downward {s, fig. 293) be- tween the tuberosity of the ischium and the great trochanter, both of which project so as to separate it from the skin, or, more exactly, it runs along the outer side of the tu- berosity of the ischium, in a very deep groove between that process and the margin of the cotyloid cavity. At its exit from the pelvis, it is a flat, riband-shaped nerve, six lines in breadth, but it soon becomes rounded, runs vertically downward along the back of the thigh, sloping, however, a little outward ; having arrived about three or four fin- gers' breadth above the knee-joint, it divides into two branches, which are called the ea>ternal popliteal sciatic or the peroneal nerve (i), and the internal popliteal sciatic or tibial nerxe (A). The sciatic nerve sometimes divides at its exit from the pelvis, but it may do so at any lOther point between that and the popliteal space. This premature division is of no importance ; in fact, it always exists ; for when there is apparently only one trunk, the two branches of the bifurcation are perfectly distinct through the whole length of the thigh, and are merely in contact with each other.* * When the great sciatic nerve divides vf ithin the pelvis, the upper division perforates the pyriformis, while -tha lower emerges from below that muscle. THE GREAT SCIATIC NERVE, ETC. 800 Relations. — Behind, the great sciatic nerve is covered by the Fig^ ! glutaeus maximus, and then by the long head of the biceps and the semi-tendinosus ; lower down it occupies the cellular inter- val between these two last-named muscles, and when they sep- arate from each other to form the borders of the popliteal space, it becomes sub-aponeurotic. ^>^ In front, it corresponds to the gemelH and obturator internus, ^^^^ by which it is separated from the os coxa;;, to the quadratus feme- V '' ris and the adductor magnus. During its course it is surround- Iv ^ ed by a large quantity of adipose cellular tissue, but has no ac- VV// companying vessel.* Collateral Branches of the Great Sciatic.^The great sciatic nerve gives off in the thigh five muscular and three articular branches ; they sometimes arise separately, sometimes by a common trunk. They are the following : The nerve for the long head of the biceps, which divides into two ascending branches for the origin of that muscle from the ischium, and descending branches, which run for a long time in front of the muscle, and then enter it by a series of filaments. The nerve for the semi-tendinosus, which runs upon the anterior surface of the muscle, and does not enter it until it reaches the lower third of the thigh. The nerves for the semi-membranosus are two in number ; they almost always anastomose and enter the internal surface of the muscle at two different points. A nerve for the adductor magnus, which runs forward and then inward, and enters near the inner border of the muscle. We have seen that the adductor magnus receives most of its nerves from the obturator nerve. All the preceding branches arise from the upper part of the sciatic nerve, opposite to the quadratus femo- ris, and often by a common trunk. A nerve for the short head of the biceps sometimes arises at the same height as the preceding, but is most commonly given off from the sciatic nerve at the middle of the thigh. When the sci- atic nerve divides prematurely, the branch we are now descri- bing comes from the external popliteal. This nerve enters the upper extremity of the muscle, expanding into diverging fila- ments. An articular nerve of the knee, which often arises by a common trunk with the preceding, and is not unfrequently given off from the external popliteal ; it passes vertically downward in front of the great sciatic nerve, through some adipose tissue, to gain the outer side of the joint ; having arrived above the external con- dyle, it turns and divides into several filaments, which perforate the fibrous tissue of the joint, and are distributed to the articular adipose tissue, where they are scattered, some above, others be- low, and others on the outer side of the patella, t The External Popliteal Sciatic or Peroneal Jferve. The external popliteal sciatic, external popliteal, or peroneal nerve (i, fig. 293), the external terminal branch of the great sciatic, is intended for all the muscles of the anterior and external region of the leg, and for the skin on the leg and on the dorsum of the foot. It is scarcely half the size of the internal popliteal ; it runs obliquely downward and out- ward, behind the external condyle of the femur through the popliteal space, and is pla- ced nearer to the surface than the internal popliteal nerve, which is lodged in the inter- condyloid fossa ; it then crosses obliquely over the origin of the outer head of tbe gas- trocnemius, passes behind the head of the fibula, from which it is separated by the ori- gin of the soleus, turns horizontally upon the neck of that bone (at v), between it and the peroneus longus, and expands into four branches, two superior or recurrent, for the tib- ialis anticus, and two inferior and larger, which form the true terminations of the nerve. Collateral Branches. During this course, the external popliteal nerve gives off two superficial collateral * In three instances I have found the great sciatic accompanied by a larg-e vein, which was continuous vsrith the popliteal vein, ani perforated the upper part of the adductor magnus, like the profunda artery. In two of these ca-ses the sciatio nerve dirided at its exit from the pelvis. I did not note the arrangement of the nerve in the third case. It was a remarlcable circumstance that there was another popliteal vein accompanying the ■artery : in one of the cases the vein was in front instead of behind the artery. t See note, p. 812. 5K 810 NEUROLOGY. nerves : a saphenous nerve, which we shall call the peroneal saphenous, to distinguish it from the tibial saphenous, and the peroneal cutaneous branch. The Peroneal Saphenous Nerve. The peroneal saphenous nerve (n) presents many varieties in different subjects, both in regard to its size and origin. It is generally smaller than the tibial saphenous (/), of which it may be regarded as an accessory ; it arises in the popliteal space, descends vertically beneath the fascia, between the external and internal popliteal nerves, perfo- rates the fascia opposite the middle of the leg, to join the external saphenous vein, with which it runs along the tendo Achillis, and terminates upon the outer side of the OS calcis. During this course, it gives off several cutaneous filaments and a communi- cating branch to the tibial saphenous nerve : this branch is of considerable size, and comes off while the nerve is still beneath the fascia. Having become very slender after giving these branches, the peroneal saphenous nerve subdivides opposite the lower part of the tendo Achillis, and upon the outer side of the os calcis, into several calcaneal branches, one of which turns obliquely round the posterior surface of the os calcis, while the others descend vertically, are reflected upon the under surface of that bone, and are distributed to the skin of the heel. Not unfrequently the peroneal saphenous nerve gives off a malleolar branch, which passes between the external malleolus and the skin, and anastomoses in front of the ankle-joint {y,fig. 291) with a twig from the musculo-cuta- neous nerve. This malleolar branch, which often comes from the last-mentioned nerve, is, moreover, remarkable, like all nerves which are subjected to strong pressure, for its thickness, its grayish colour, and, lastly, for its knotted, and, as it were, gauglionated appearance. The peroneal saphenous nerve is often very small, and is lost in the skin upon the middle of the leg : its place is then supplied in the lower two thirds of the leg by the tib- ial saphenous nerve, the size of which is always in an inverse ratio to that of the pero- neal saphenous. No nerve presents more varieties than the peroneal saphenous ; they relate to its size and to the point at which it anastomoses with the tibial saphenous. One of the most remarkable varieties is that in which the peroneal and tibial saphenous nerves, those call- ed communicating sapheiious branches {communicans fibulae, n ; communicans tibicz, I) unite in the popliteal space into a single trunk, the external saphenous (p), the distribution of which corresponds to the ordinary distribution of the two nerves. The Peroneal Cutaneous Branch. This comes off from the external popliteal nerve, behind the outer condyle of the fe- mur, passes vertically downward along the fibula, in contact with the skin, and divides into ascending and descending branches, the latter of which may be traced as far as the lower part of the leg. The Terminal Branches of the External Popliteal Jferve. The Branches for the Tibialis Anticus. The two superior or recurrent branches, resulting from the subdivision of the external popliteal, pass horizontally inward, behind the extensor communis digitorum, and are distributed to the tibiahs anticus ; one of these branches supplies the peroneo-tibial ar- ticulation. The Musculo-cutaneous Branch, or External Peroneal Nerve The musculo-cutaneous branch {x,fig. 291), the lowest of the terminal branches of the external popliteal, is intended for the muscles of the external region of the leg, and for the skin upon the dorsum of the foot (pretibio-digital, Chauss. ; peroneus externus, Samm..). It passes at first obliquely, then vertically downward in the substance of the peroneus longus, turns forward to enter between the extensor longus digitorum and the peroneus longus and brevis, and perforates the fascia of the leg, above the ankle-joint : having thus become sub-cutaneous, it passes obliquely downward and inward, following the di- rection of the extensor longus digitorum, becomes flattened and widened, and divides a little below the tibio-tarsal articulation into an internal and an external branch ; the lat- ter subdivides into three other branches, so that there are in all four terminal branches, which form the dorsal collateral nerves of the toes. Not unfrequently the musculo-cutaneous nerve bifurcates as it escapes from beneath the fascia of the leg, and its two branches reunite opposite to the tibio-tarsal articula- tion, so as to describe an elongated ellipse. Collateral Branches. — There are two branches for the peroneus lon^^is, of which one comes off from the nerve immediately after its origin, while the other arises lower down, and runs a very long course in the substance of the muscle ; there is also a branch for the peroneus brevis, which often arises by a common trunk with the preceding. In Its sub-cutaneous portion, the musculo-cutaneous nerve supplies several filaments to the skin, among which we should distinguish an external malleolar filament, which passes between the external malleolus and the skin, increases considerably in size, and becomes THE ANTEUIOR TIBIAL NERVE, ETC. 811 grayish and knotted, like all nerves subjected to pressure. This filament often anastomo- ses with the malleolar branch of the peroneal saphenous nerve, and sometimes suppUes the place of that malleolar branch. Terminal Branches. — There are four terminal branches of the musculo-cutaneous nerve, distinguished numerically as the first, second, third, and fourth {see Jig. 291). The first or internal branch passes very obliquely forward and inward, to form the internal dorsal collateral nerve of the great toe ; this nerve, like all nerves subjected to pressure, increas- es in size and becomes grayish, and, as it were, knotted opposite the metatarso-phalan- gal articulation. The second branch, vv^hich often arises by a common trunk with the first, supplies the external dorsal collateral nerve of the great toe, and the internal collateral nerve of the second toe. The third branch supplies the external collateral nerve of the sec- ond, and the internal collateral nerve of the third toe. These two large branches are often replaced by one (v) from the anterior tibial nerve, with which they anastomose. The fourth terminal branch or internal branch supplies the external dorsal collateral nerve of the third, and the iyiternal dorsal collateral nerve of the fourth toe. All the filaments from these branches are distributed to the skin upon the dorsal re- gion of the foot and digital phalanges. In a great number of subjects, the tibial or external saphenous nerve supplies the in- ternal collateral nerve of the little toe, and the external collateral nerve of the fourth toe : but in others, these nerves are furnished by an additional terminal branch of the musculo-cutaneous nerve ; in all cases the nerves anastomose with each other. The Anterior Tibial, or Interosseous Nerve. The anterior tibial or interosseous nerve (« v,fig. 291), intended for the muscles on the anterior region of the leg, for the extensor brevis digitorum, and for the interosseous muscles in the foot, is as large as the musculo-cutaneous nerve just described ; it runs to the inner side of that nerve, beneath the extensor communis digitorum, and passes along the interosseous ligament, together with the anterior tibial artery lying in front of that vessel. It is placed, like the artery, between the tibialis anticus and the extensor communis digitorum, from which it is separated below by the extensor proprius pollicis pedis ; it supplies a great number of filaments to all these muscles, passes with the ar- tery under the annular ligament of the tarsus, in the sheath of the extensor proprius pol- licis, and divides into two branches : The interrial deep branch of the dorsum of the foot (v), which is the true continuation of the nerve, passes horizontally forward, under the arteria dorsalis pedis, over the first in- terosseous space, gives off a small twig to the muscles of that space, and divides into two branches, which form the deep external dorsal collateral nerve of the great toe, and the internal dorsal collateral nerve of the second toe. These branches communicate with the superficial dorsal branches of the musculo-cutaneous nerve, and sometimes supply their place. The external and deep nerve of the dorsum of the foot runs outward between the tarsus and the extensor brevis digitorum, in which it terminates ; it gives off in front, opposite the interosseous spaces, a series of very delicate filaments, which enter the posterior extremities of those spaces. The filaments for the fourth and fifth spaces often arise by a common trunk. They are extremely delicate, and are closely applied to the tarsus. The Internal Popliteal Sciatic, or Tibial Jferve. The internal popliteal sciatic, internal popliteal, or tibial nerve (h, fig. 293), is intended for all the muscles of the back of the leg, and for the skin of the sole of the foot ; both in direction and size it appears to be the continuation of the great sciatic nerve. It pass- es vertically downward in the inter-condyloid fossa of the femur ; it is at first placed be- tween the heads of the gastrocnemius, it then passes under that muscle and under the arch formed by the soleus, descends, under the name of the posterior tibial nerve (k), be- tween the soleus and the deep layer of muscles, inclines a little inward, and, having reached the termination of the fleshy belly of the soleus, gains the inner side of the ten- do Achillis ; lower down, it passes behind the internal malleolus, against which it is flat- tened and widened, and divides into the internal and external plantar nerves {a, b, and c, fig. 294). In the popliteal space it is sub-aponeurotic, in the fleshy portion of the leg it is sep- arated from the fascia by the double layer formed by the gastrocnemius and the soleus, and it again becomes sub-aponeurotic along the tendo Achillis. It is in relation, ia front, with the popliteal and posterior tibial vessels, which separate it, above, from the knee-joint and popliteus muscle, and lower down, from the deep layer of muscles in the leg.* Behind the internal malleolus, and under the groove upon the os calcis, it is en- closed in a common fibrous sheath with the posterior tibial vessels, which are placed in front of it ; this sheath is behind that for the tendons of the tibialis posticus and flexor communis digitorum. * [The nerre is at first at a short distance to the outer side of the artery ; lower down it lies immediately behind the vessel, and still lower crosses to the inner bide of the artery, and is separated from it by the vein.] 812 NEUROLOGY. Its collateral branches are very numerous. I shall divide them into those given off op- posite the knee-joint, and those supplied along the leg. The Collateral Branches of the Internal Popliteal Merve, behind the Knee- Joint. These are six in number, namely, two anterior, which are very small, one for the plantaris longus, and one for the knee-joint ; two internal, namely, the tibial saphenous nerve, and the nerve for the inner head of the gastrocnemius ; two external, namely, the nerve for the outer head of the gastrocnemius, and the nerve for the soleus. The Tibial Saphenous Nerve. This is generally known as the external saphenous. It is much larger than the pero- neal saphenous, which -always anastomoses with it. I have already said that the mode and situation of this anastomosis present many varieties. The tibial saphenous nerve {communicans tibia, I, Jig. 293) arises in the popliteal space, passes vertically downward between the two heads of the gastrocnemius, and then upon their posterior surface, along their fibrous septum, between them ; it is here situated in a small fibrous canal common to it and to a small artery and vein ; it receives, at a variable height in the leg, a more or less considerable filament from the peroneal saphenous nerve (or communicans fibula, n) ; it then becomes sub-cutaneous, forming the external saphenous nerve (p), runs along the outer side of the tendo Achillis, just as the posterior tibial runs along its inner side ; it now accompanies the external saphenous vein, which is accompanied above this point by the peroneal saphenous nerve ; it is reflected behind the external malleolus, in the same manner as the tibial nerve is reflected upon the internal malleolus, then runs forward and downward (y, fig. 291) upon the outer side of the os calcis, where it gives off several very large external calcaneal nerves, and terminates diflerently in va- rious subjects. In some it terminates by forming the dorsal collateral nerve of the fifth toe ; in others it is larger, and divides into two branches, of which the external forms the external collateral nerve of the fifth toe, while the internal, which receives an anasto- motic branch from the musculo-cutaneous nerve (x), passes horizontally forward, crosses the extensor brevis digitorum, and the tendons of the long extensors, and divides into two secondary branches, of which one constitutes the internal dorsal collateral nerve of the little toe, and the other the external dorsal collateral nerve of the fourth toe. I may point out the thickening, the gray colour, and the knotted, and, as it were, ganglionated structure of the external collateral nerve of the little toe opposite to the articulations. The external calcaneal nerves, which may be regarded as forming the termination of the tibial saphenous, are very remarkable ; they pass vertically along the outer side of the OS calcis, expand into several filaments, which are reflected upon the ridge which separates the external from the inferior surface of that bone, and are distributed to the skin upon the heel. During its course along the leg, the tibial saphenous gives off scarcely a single fila- ment, but along the outer border of the foot it supplies a great number, which run down- ward and forward, and terminate in the skin covering the external plantar region. The size of the tibial saphenous nerve is inversely proportioned to that of the pero- neal saphenous and musculo-cutaneous nerves. Thus, when the peroneal saphenous nerve is large, it furnishes most of the external calcaneal branches ; and when the mus- culo-cutaneous nerve is large, it supplies, besides the external calcaneal, the internal dorsal collateral nerve of the little toe, and the external dorsal collateral nerve of the fourth toe. The Nerves for the two Heads of the Gastrocnemius and for the Soleus. The nerve for the inner head of the gastrocnemius often arises by a common trunk with the tibial saphenous ; again, the nerves for the outer head of the gastrocnemius and for the soleus often arise by a common trunk : the nerves for the gastrocnemius en- ter the anterior surface of the head of that muscle, and immediately ramify. The nerve for the soleus is the largest, and enters the muscle at its upper arch ; all these nerves ramify as soon as they enter the muscles which they supply. The Articular Nerve and Nerve for the Plantaris Longus. The posterior articular nerve of the knee runs forward to enter the posterior ligamgnt of the articulation : one of its filaments follows the direction of the internal articular ar- tery, and is lost in the popliteus.* * [From the dissections of Mr. Ellis, it appears that there is an articular nerve to the knee-joint with each articular artery. The superior external articular nerve is the one described at p. 809; it mosit commonly arises from the external popliteal. The inferior external articular also arises from the e.\ternal popliteal, and sometimes from the sciatic nerve ; it is a long branch vi-hich descends towards the external condyle, passes be- low it on the outer side of the joint, and perforates the capsule. The superior internal articular is very small, and is not constant ; it arises from the internal popliteal nerve, and passes on the outer side, and then in front of (i. e., deeper than) the popliteal vessels, and reaches with its artery the inner side of the joint. The infe- rior internal articular is the largest of all : it arises from the internal popliteal above the joint, descends on the outer side, and then in front of the popliteal vessels, is applied to th» corresponding- artery upon the popliteus muscle, passes beneath the internal lateral ligament, and enters the inner side of the joint. The posterior ar- ticular, or azygos, is given off opposite the joint from the internal popliteal, or from the inferior internal ar- ticular i it perforates the posterior ligament.— (£Hw'f Demonstrations of Anatomy, p. 675, 676.J j THE INTERNAL PLANTAR NERVE. 813 Tlie nerve for the plantaris longus always arises separately from the posterior tibial nerve, and immediately dips into the substance of the muscle. Collateral Branches of the Internal Popliteal JVerve in the Leg. There are three sets of collateral branches given off by the posterior tibial nerve in the leg: namely, the nerve for the popliteus ; the nerves for the deep layer of muscles-, the internal calcaneal nerve. Lastly, several very small filaments come off from the nerve, run along the posterior tibial artery, and, after a course of variable length, perfo- rate the aponeurosis and ramify in the skin. The nerve for the popliteus arises opposite the knee-joint, runs forward on the outer side of the popliteal vessels to gain the lower border of the muscle, around which it turns ; before entering the muscle, the nerve expands into several branches, all pf which pass horizontally forward opposite to the interosseous ligament, which they ap- pear to perforate. But with a little care it is seen that almost all of these filaments are lost in the muscle. I have, however, seen one of them perforate the interosseous liga- ment together with the anterior tibial artery, and then, leaving that vessel, return through the substance of the ligament, and terminate in the tibialis posticus ; several filaments of the popliteal nerve are also evidently distributed to the peroneo-tibial artic- ulation, and to the periosteum of the tibia and fibula. The 7terves for the deep layer of muscles of the leg consist of two sets. The nerve for the tibialis posticus almost always arises by a common trunk with the preceding, runs down- ward and forward, is applied to the posterior surface of the muscle, to which it gives a series of filaments from its anterior aspect ; the continuation of the nerve enters the muscle about its middle, and may be traced in it as far as its lower part. The nerves for the flexor longus pollicis and for the flexor communis arise by a common trunk a little be- low the preceding ; the nerve for the flexor longus pollicis, which is larger than those for the flexor communis and tibialis posticus, accompanies the peroneal artery as far as the lower part of the leg. The Internal Calcaneal Nerve. — This is a large branch whicli comes off from the inner side of the posterior tibial nerve, and which, in cases of premature bifurcation of that nerve into the internal and external plantar, comes from the external plantar ; it passes vertically downward, on the inner side of the os calcis, and divides into two diverging branches, which are applied to the inner side of the bone, are reflected upon its lower surface, and are distributed to the skin of the heel, one in front, and the other behind. The Terminal Branches of the Internal Popliteal JVerve. The Internal Plantar Nerve. The internal plantar nerve, which is intended for the muscles and skin of the sole ot the foot, is larger than the external plantar ; at its origin it is situated behind the inter- nal malleolus, in front of the posterior tibial vessels, which cross it at an acute angle, and occupies a groove which is common to it and to those vessels, and which is quite distinct from and lies behind the groove for the tendons. It is reflected beneath the in- ternal malleolus, becomes horizontal, reaches the calcaneal groove, perforates the pos- terior extremity of the flexor brevis digitorum, and during this passage through the groove is protected by a fibrous canal, which is subjacent to the grooves for the tendons. At its exit from this fibrous canal, the internal plantar nerve is situated upon the boundary, between the internal and middle plantar regions, between the flexor brevis pollicis on the inside, and the flexor brevis digi- torum on the outside ; having given off a considerable branch (a, Jig. 294), which becomes the internal plantar collateral nerve of the great toe, it perforates the aponeurosis of the flexor brevis digitorum to enter the same sheath as that muscle, and runs {h) along its in- ner border. Having reached the posterior extremity of the meta- tarsal bones, it divides into three branches, which form the collateral nerves of the toes. Sometimes there is a fourth branch (d), which passes outward, to anastomose with the external plantar nerve. The collateral branches are very numerous. Some of them are cutaneous, and perforate the plantar fascia to ramify in the skin. The most remarkable are, a small calcaneal cutaiieous nerve, which crosses the posterior tibial vessels, to supply the skin upon the in- ner side of the os calcis ; and a plantar cutaneous nerve, which emerges between the flexor brevis pollicis and the flexor brevis digitorum, and divides into two small cutaneous branches, one of which pro- ceeds forward, while the other runs backward, like a recurrent nerve. There are also some muscular collateral branches, namely, for the flexor brevis pollicis, the abductor pollicis, and the flexor brevis digitorum. Lastly, the ijiternal plantar collateral nerve of the great toe (a), which is so large that it might be regarded as a terminal branch of the internal plantar nerve ; it comes off from the last- Fig. 294. 814 NEUROLOGY. named nerve, at its exit from the covered canal formed for it by the flexor brevis pollicis, passes forward along the outer side of the tendon of the flexor longus poUicis, below, i. c, superficial to the inner portion of the adductor pollicis (oblique adducteur, Cmvcilhier), and gains the inner and under surface of the metatarso-phalangal articulation of the great toe ; in this place it is situated in the furrow between the internal and external sesamoid bones of that articulation ; it runs forward below the inner border of the former, and then of the second phalanx of the great toe, and, having arrived below that bone, it divides, like the collateral nerves of the fingers, into two branches, the one dorsal or un- gual, and the other plantar. The terminal branches of the internal plantar nerve are three in number, and are distin- guished as the first, second, and third, counting from within outward. The^r*^ terminal branch, which is the largest, runs along the outer side of the tendon of the flexor longus pollicis, gives filaments to that muscle, passes between the meta- tarso-phalangal articulations of the first and second toes, under an arch which is com- mon to it and the corresponding vessels, and divides into two secondary branches, which form the external collateral nerve of the great toe, and the internal collateral nerve of the second toe. Not unfrequently this branch gives an anastomotic filament to the internal collateral nerve of the great toe, which passes beneath the metatarso-phalangal articu- lation of that toe. The first terminal branch of the internal plantar nerve gives off the filament for the first lumbricalis ; it then supplies several articular twigs to the metatarso-phalangal artic- ulation of the great toe, and a very numerous series of cutaneous filaments. The second terminal branch, much smaller than the preceding, passes somewhat out- ward, crossing below, i. e., superficial to the flexor tendon of the second toe, and then forward, and bifurcates opposite the metatarso-phalangal articulations, to constitute the external plantar collateral nerve of the second toe, and the internal plantar collateral nerve of the third. During its course, this branch supplies filaments to the second lumbricalis, to the meta- tarso-phalangal articulation of the second toe, and also to the integuments. The third terminal branch passes very obliquely outward, crosses below the flexor tendon of the third toe, and bifurcates to form the external collateral nerve of the third and the internal collateral nerve of the fourth toe. This branch supplies the metatarso-phalangal articulations of the third and fourth toes, and the corresponding integuments. Summary. — The internal plantar nerve, therefore, supplies branches to the skin on the inner part of the sole of the foot, also the plantar collateral nerves of the first, second, and third toes, and the internal collateral nerve of the fourth toe, all of which are cu- taneous branches. It gives muscular branches to the flexor brevis pollicis, the abductor pollicis, the flexor brevis digitorum, and to the two internal lumbricales. Lastly, it gives off a great number of articular filaments to the tarsal, tarso-metatarsal, metatarso-phalangal, and phalangal articulations. The External Plantar Nerve. The external plantar nerve (c, fig. 294), which is smaller than the internal, is placed with it in the groove of the os calcis, and perforates the flexor brevis, under an arch dis- tinct from that for the internal plantar, and which is common to it and the external plantar vessels ; it then runs downward and outward, between the flexor brevis and flexor accessorius, is reflected forward, and divides into two branches, a superficial and a deep. Collateral Branches. — During its course, the external plantar nerve gives off, immedi- ately after its origin, one large branch, which runs horizontally outward, in front of the tuberosities of the os calcis, passes under the flexor accessorius, and is reflected for- ward to enter the abductor minimi digiti. At the point of its reflection, it gives off a transverse branch, which is lost in the posterior attachment of the muscle. The exter- nal plantar also supplies the nerve or nerves for the flexor accessorius. Terminal Branches. — The superficial terminal branch (c, fig. 294), which is the continu- ation of the trunk of the nerve, divides into two others, one external, the other internal. The external branch passes very obliquely outward, below the flexor brevis digiti min- imi, crosses the tendon of the abductor brevis obliquely, then runs along the outer side of the fifth metatarso-phalangal articulation, and forms the external collateral nerve of the little toe. It supplies a great number of cutaneous nerves, also the nerves for the flexor brevis digiti minimi, those for the interosseous muscles of the fourth space, and, lastly, some articular filaments. The internal branch passes forward, below the flexor tendon, following the original di- rection of the superficial branch of the external plantar, and, after a rather long course, bifurcates to form the internal collateral nerve of the little toe, and the external collateral nerve of the fourth toe; like the external branch, it also gives off some cutaneous and ar- ticular nerves. The deep terminal branch of the external plantar passes above, ;. e., deeper than the THE EXTERNAL PLANTAR NERVE. 815 flexor accessorius, changes its direction, so as to describe an arch, having its concavity turned inward and backward, and the convexity outward and forward, enters, together with the external plantar artery, above which it is situated, between the adductor polli- cis and the interossei, and is lost in the former muscle. Before reaching the adductor pollicis it gives off some articular filame^its to the meta- tarsal and tarso-metatarsal articulations, and also a filament for the fourth lumbricalis. Beyond the adductor pollicis the nerve gives offthe filament for the third lumbricalis ; this filament, which is remarkable for the length of its course, passes horizontally forward, opposite to the third interosseous space, and passes through the fibres of the transversus pedis, to reach its destination ; it then gives off the filaments for the transversus, and those for the interosseous muscles of the third, second, and first spaces. Summary of the External Plantar Nerve. — The external plantar nerve, therefore, sup- plies cutaneous filaments to the outer side of the sole of the foot, to the fifth toe, of which it forms both collateral nerves, and to the fourth toe, of which it forms the external col- lateral nerve. It also gives ofCmuscular nerves to the flexor accessorius, the flexor bre- vis, and abductor digiti minimi, to the adductor pollicis, and transversus pedis, to all the interossei, and to the two external lumbricales. Lastly, it furnishes some articular filameiits. Summary of the Nerves of the Lower Extremity. — The lower extremity is supplied with nerves from the lumbar and sacral plexuses. The Lumbar Plexus. — The lumbar plexus gives almost all its branches to the lower extremity, viz., the external and internal inguinal nerves, the obturator nerve, and the crural nerve ; the lumbo-sacral cord is also distributed to the lower extremity through the medium of the sacral plexus. The external and internal inguinal nerves are the principal cutaneous nerves of the anterior and external regions of the thigh ; the obturator nerve is a muscular nerve in- tended for the obturator externus, the three adductors, and the gracilis.* The crural nerve is a musculo-cutaneous nerve which supplies the following parts : its cutaneous portion is distributed to the skin upon the anterior region of the thigh, upon the internal region of the leg, and internal dorsal region of the foot ; its muscular portion supplies all the muscles of the anterior region of the thigh ;! it also gives several articular nerves to the hip and knee joints. The Sacral Plexus. — The sacral plexus is entirely distributed to the lower extremity, excepting the internal pudic nerve and certain rectal and vesico-prostatic branches in the male, and rectal, vaginal, and uterine branches in the female. The obturator internus, the pyriformis, the gemelli, and the quadratus femoris, are each provided with a special nerve from the sacral plexus ; the glutaeus medius and min- imus, and the tensor vaginae femoris, are especially supplied by the superior gluteal nerve, and the glutaeus maximus by the inferior gluteal or lesser sciatic nerve. The last-named nerve also furnishes the cutaneous nerves of the posterior region of the thigh. The great sciatic is the nerve of the posterior region of the thigh, and of the entire leg and foot. It supplies all the muscles of the posterior region of the thigh ; thus, its external popliteal or peroneal division supplies the muscles of the external region of the leg by its musculo-cutaneous branch, and the muscles of the anterior region by its in- terosseous branch ; it also supplies the external region of the leg, and the dorsal region of the foot. Its internal popliteal or tibial division supplies all the muscles of the posterior region of the leg, the skin upon the internal and external calcaneal regions, and that upon the external dorsal region of the foot. Of its terminal branches, the internal plantar nerve is distributed to the muscles of the internal plantar region of the foot, to the flexor brevis digitorum, to the two internal lumbricales, and to the skin of the internal plantar region ; lastly, it gives off the col- lateral branches of the toes, excepting the two for the fifth toe, and the external collat- eral branch of the fourth. The external plantar nerve is distributed to the muscles of the external plantar region, to the flexor accessorius, to all the interossei, to the two external lumbricales, to the adductor pollicis and transversus pedis, and to the skin of the external plantar region : it also gives the internal and external collateral nerves of the fifth toe, and the external collateral nerve of the fourth. Comparison of the Nerves of the Upper and Lower Extremities. The lumbo-sacral plexus, which supplies the whole of the lower extremity, precisely corresponds to the cervico-brachial, which supplies the upper extremity. The lumbar corresponds to the cervical, and the sacral to the brachial plexus. The connexion, or sort of fusion of the cervical with the brachial plexus, and of the lumbar with the sacral plexus, explains why it is found, on comparing the nerves of the upper and lower extrem- * [The obturator also supplies part of the pectineus, and sometimes gives cutaneous branches to the thigh and leg, and an articular filament to thp knee (see note II, p. 800).] [And also a few filaments to the ili»ciis, psoas, and pectineus.] 816 NEUROLOGY. ity, that several of the nerves arising from the brachial plexus are represented by nerves from the sacral plexus, and that several of those from the cervical plexus have their lepresentatives in nerves derived from the lumbar plexus. It will be seen, moreover, that this analogy ought not to be carried too far, and that it is necessary, in making the comparison, to exclude all nerves vi^hich belong to peculiar organs in both regions. Thus, the phrenic, occipital, and auricular nerves, branches of the cervical plexus, have no representatives in the lower extremity, nor is there any nerve in the upper extremity corresponding to the internal pudic. . On the other hand, there is no objection to admitting that the external and internal inguinal nerves in the lower extremity are represented by the clavicular nerves in the upper extremity. The crural nerve, a branch of the lumbar plexus, has no corresponding branch in those of the cervical plexus, but its muscular branches are represented by the brachial portion of the musculo-spiral nerve, and its cutaneous branches by the internal brachial cutane- ous. The crural nerve, in fact, supplies the muscles which extend the leg upon the thigh, in the same way that the musculo-spiral nerve supplies the muscles which ex- tend the forearm upon the arm ; the internal saphenous nerve supplies the skin of the leg, just as the internal brachial cutaneous is distributed to the skin of the forearm. The obturator nerve, which supplies the adductors of the thigh, is represented by the thoracic nerves and the nerve for the latissimus dorsi, which supply the pectoraUs ma- jor and latissimus dorsi, the adductor muscles of the arm. The gluteal nerves are analogous to the supra-scapular and circumflex nerves. The superior gluteal, which is distributed to the glutaeus medius and minimus, corresponds to the supra-scapular, which belongs to the supra- and infra-spinatus ; and the inferior gluteal or lesser sciatic nerve, which supplies the glutaeus maximus and the skin of the thigh, corresponds to the circumflex nerve, which is distributed to the deltoid, and the skin of the arm. The trunk of the great sciatic nerve represents by itself the musculo-cutaneous, the ulnar, and the median nerves, and the musculo-spiral in the forearm. The muscles of the anterior region of the arm, that is to say, the muscles that flex the forearm upon the arm, receive their branches from the musculo-cutaneous nerve, just as the muscles of the posterior region of the thigh, or the flexors of the leg upon the thigh, receive theirs from the great sciatic. The external popliteal nerve represents the musculo-spiral in the forearm : the former supplies the muscles of the anterior and external regions of the leg, while the latter is distributed to the muscles of the posterior and external regions of the forearm ; the for- mer gives off the dorsal cutaneous nerves of the foot, and the latter furnishes the dorsal cutaneous nerves of the hand. The internal popliteal nerve represents the median and ulnar nerves together. The muscles of the posterior region of the leg are supplied by the internal popliteal, as the muscles of the anterior region of the forearm are supplied by the median and the ulnar. The internal popliteal nerve completes the series of dorsal cutaneous nerves of the foot, just as the ulnar nerve completes the dorsal nerves of the hand. Lastly, the internal plantar nerve gives off" all the plantar collateral nerves of the toes, excepting those for the little toe, and the external plantar collateral of the fourth toe ; it therefore represents the palmar portion of the median nerve ; and so the external plan- tar represents the palmar portion of the ulnar nerve, and completes the series of plantar collateral nerves. THE CRANIAL NERVES. Definition and Classification. — The Central E.itremities of the Cranial Nerves — vjz., of the Olfactory — of the Optic — of the Common Motor Oculi — of the Pathetic — of the Tu- geminal — of the External Motor Oculi — of the Portio Dura and Portio Mollis of the Sev- enth— of the Glosso-pharynffcal, Pneumo-gastric, and Spinal Accessory Divisions of the Eighth — and of the Ninth Nerves. The cranial nerves are those which pass through the foramina in the base of the cra- nium, not those which arise from the brain, as the rather generally adopted terms cere- bral nerves and encephalic nerves would seem to indicate. "We shall follow Willis and the majority of anatomists in admitting nine pairs of cra- nial nerves, which are almost indifferently named, either numerically, from the order of their origin, counting from before backward, or they are named from their distribution and uses. The following exhibits their nomenclature upon both principles : First pair, or olfactory nerves. Second pair, or optic nerves. Third pair, or common motor nerves of the eyes. Fourth pair, or pathetic nerves, nervi trochleares. Fifth pair, or trifacial nerves, nervi trigemini. CENTRAL EXTREMITY OF THE OLFACTORY NERVE. 817 Sixth pair, or external motor nerves of the eyes, nervi abducentes. c ^, ■ J- J J ■ . ( portio mollis, or auditory nerve, Seventh pair, divided into j ^^^^-^ ^^^^^ ^^ ^^^-^^ ^^^^^ ^ pneumogastric nerve, or par vagum, Eighth pair, divided into < glosso-pharyngeal nerve, ( spinal accessory nerve of Willis. Ninth pair, or hypoglossal nerve. Soemmering has introduced the following modification of this nomenclature. He has divided the seventh pair into two, viz., the facial nerves, which form his seventh pair, and the auditory nerves, which he calls the eighth ; and then he has divided the eighth pair into three others, namely, a ninth pair formed by the glosso-pharyngeal nerves, a tenth formed by the pneumogastric nerves, an eleventh by the spinal accessory nerves ; the hypoglossal nerves, therefore, constitute his twelfth pair. This modification is founded on the separation of nerves so completely distinct as the facial and the auditory, which have only been described together because they enter the same canal in the base of the cranium, namely, the internal auditory meatus. Still, this modification is a useless one, and it has the greater inconvenience of render- ing the language employed obscure, from giving a double acceptation to the same terms. It would be more philosophical to name and describe the cranial nerves from behind forward, so that the hypoglossal nerves would constitute the first pair, and the olfactory the last. The indisputable analogy which exists between the posterior cranial and the spinal nerves, and, moreover, the example of J. F. Meckel, would fully warrant this innovation. Nevertheless, I think it right to retain the old usage, and to proceed from before back- ward, in the enumeration as well as in the description of the nerves. As the origins or central extremities of all the cranial nerves and their course within the cranium can be studied upon the same brain, I have thought it right to describe, in one article, all these origins or central extremities, which will mutually illustrate each other by their differences and their analogies : the experience of the dissecting-room proves, moreover, that, from want of a sufficient number of brains to study the origin of each nerve in particular, this part of anatomy is generally neglected. The Central Extremities of the Cranial Nerves. ' Dissection. — Two preparations are required, namely, a brain removed from the crani- um, together with the origins of the nerves perfectly preserved ; and the base of a crani- um, together with those parts of the brain which are near the origin of the nerves. The first will serve for the examination of the central extremities of the nerves ; and the sec- ond for tracing their course within the cranium. While the origin of all the spinal nerves is uniform and regular, that of the cranial nerves appears to be subject to no rule ; so that the cranial nerves differ as much from each other in regard to their origin as they differ collectively from the spinal nerves in the same particular. We shall see presently, however, that the origins of all but the special nerves of the head may, to a certain extent, be referred to the same law of double roots (one of which is ganglionic) which presides over the origin of the spinal nerves. The Central Extremity of the Olfactory JVerve. The olfactory nerves, or the first pair of cranial nerves (nerfs ethmoidaux, Chauss., 1, Jig. 276) are two bands, composed of white and gray substance, which arise from the hindermost convolution of the anterior lobe of the brain, run forward in the anfractuosity already described as the anfractuosity of the olfactory nerves, and expand in the ethmoidal groove into a sort of ganglion or bulb, from which filaments are given off to be distribu- ted to the pituitary membrane. In regard to their central extremity and their course within the cavity of the cranium, the olfactory nerves are singular, and their peculiarities justify the uncertainty which has for a long time prevailed, and still prevails, concerning their true character. The old anatomists did not regard them as nerves, but as prolongations of the brain, named by them carunculce or processus maxillares, and believed to be intended to drain off the mucosity of that organ : it was Massa, according to Sprengel, and Zerbi, according to Haller, who first connected them with the other cranial nerves as the first pair. Com- parative anatomy, which probably suggested to the older anatomists the opinion which they held concerning these nerves, has now caused some doubts as to the propriety of considering them as nerves, and has given rise to the opinion that they are the repre- sentatives of the olfactory lobes of the lower animals.* Without entering here into dis- cussions which belong to philosophical anatomy, let us examine the most remarkable circumstances connected with the origin and cranial course of this nerve. Apparent Origin. — The olfactory nerves arise from the cerebrum, and this is a char- * When speaking- of the comparative anatomy of the brain, it was mentioned that in a great number of ani- mals there existed, in front of the cerebral lobes or hemispheres, a pair of lobes (olfactory lobes), which were continuous with the nerves distributed to the pituitary membrane, and the development of which corresponded to the size of those nerves, and to the relative state of perfection of the sense of smell. 5L 818 XEUROLOGY. acter which belongs exclusively to them ; they are the only cerebral nerves, properly so called. They arise from the hindermost convolution of the anterior lobe, in front of the ante- rior locus perforatus (h.fig. 276), which is situated behind that convolution. This origin consists of a mammilla or pyTamidal enlargement, gray pyramid, which is regarded as the gray root of the nerve. This grayish enlargement, which can be ver\- well seen by re- flecting the nerve backward, is prolonged as a linear tract of gray substance upon the upper surface of the nerve. Besides this gray enlargement or origin, which was so well described by Scarpa^ there are two or three white roots, or, rather, certain white striae, verv" accurately represent- ed by Vicq d"Azyr ; these are the external or long root, which is concealed in the fissure of Sylvius, and appears to me to arise from the posterior lobe [middle lobe] of the cere- brum, or, more exactly, from the posterior lip of the fissure of Sylvius -, and the internal or short root, which arises from the innermost convolution of the anterior lobe and joins the long root at an acute angle ; between these roots we often see one, two, or even three striae, which come from the back part of the anterior lobe. It would be both use- less and tedious to describe all the varieties of this origin. Real Origin. — Anatomists have not confined themselves to the investigation of the apparent origin of the olfactorj' nerves, but have also endeavoured to ascertain their deep or real origin. WUIis described them as arising from the medulla oblongata, Rid- ley from the corpus callosum, Vieussens, Winslow, and Monro from the corpora striata.* If, after the example of Scarpa, a transverse perpendicular section of the brain be made opposite the junction of the gray and white roots of the olfactorj^ nerves, or if a stream of water be directed upon the pvTamidal mammilla above described, or, lastly, if Herbert Mayo"s method be adopted, and the origin of this nerve be examined in a brain hardened in alcohol, it will be seen that, besides the white superficial striEe, there are a great number of deep and diverging white roots, which appear to me to come from the anterior commissure, and not from the corpus striatimi.t It would follow, therefore, that the olfactory nerves arise by a commissttre like the optic nerves. • Cranial Course. — Having arisen in this manner by a sort of bulb or gray enlargement {enlargement or bulb of origin), the olfactory nerve immediately tapers, and is received into the antero-posterior sulcus intended for it, which conducts it as far as the ethmoidal groove or fossa (1, Jig. 296), where it forms an enlargement or bulb, named the ethmoidal bulb, which is analogous in many respects to its bulb of origin. "When seen from below, the olfactory ner^-ejias the appearance of a soft, smooth band, grooved longitudinally along the middle.! But, on reflecting the nerve backward, it is found to be prismatic and triangular, that its two lateral surfaces are concave and correspond to the convolutions which bound the antero-posterior sulcus for the nerve, and that its upper ridge is formed by a hnear tract of gray matter which connects the gray substance of its bulb of origin with that of the ethmoidal bulb. The arachnoid has a peculiar arrangement in relation to this nerve : instead of im- mediately forming a sheath for it, the arachnoid passes below it, and maintains it in contact with its protecting sulcus ; while the pia mater passes above it, and lines the sulcus. The nerve is not entirely separated from the brain until about a few lines from the ethmoidal bulb. In the human subject the olfactor}- nerve is not hollow in its centre, as in the mam- malia ; when hardened by alcohol, it may be decomposed into wliite parallel fibres, ex- actly similar to the fibres of the white substance of the brain. The Ethmoidal Bulb or Enlargements. — The olfactory nerves, converging towards each other, reach the ethmoidal fossae, where each immediately expands into an olive-shaped, ash-coloured, and extremely soft bulb (the ethmoidal bulb, \,fig. 276), to which Mala- carne first applied the term ganglion, and which is formed in the following manner : The white filaments of which the olfactorj^ band or prism is composed spread out like a palm branch as they are about to enter the bulb, and dip into the gray or ash-coloured substance, which occupies the inter^^als between them : this substance is precisely anal- ogous to the gray matter of the brain, but is less consistent ; it also resembles the sub- stance of the nervous ganglia, so that Scarpa does not hesitate to regard the ethmoid bulb as a ganglion. From this enlargement are given off the olfactorj" nerves properly so called, which seem as if they were pressed through the foramina of the cribriform * Chaussicr, who adopted the latter opinion, called the corpora striata the olfactory lobes, in contradistinc- tion to the optic thalami, which he terms the optic lobes. But comparative anatomy shows that there is no relation in point of development between the corpora striata and the olfactory nerves. t Scarpa says that the deep roots come from a white cord placed in front and below the corpora striata. Herbert Mayo, in his beautiful plates, has represented these roots as coming- from the corpora striata. X Willis and Santorini have noticed this groove. Scarpa has obsen-ed three groove.^, which he regards as corresponding to as many lines of gray substance. M. Hippolyte Cloquet ( Anat. Descript., t. ii., p. 88) goes still farther than Scarpa, and describes seven longitudinal strise, three of which are gray, and four wliite. Scarpa has very jastlv remarked, that the proportion of ash-coloured or gray substance is much more consid- erable in the foetus, that it diminishes in the adult, and that it scarcely, if at all, exists in the old subject. CENTRAL EXTREMITY OF THE OPTIC NERVE. 819 plate of the ethmoid bone. It is said that the gray matter sends prolongations through these foramina, but this has not been demonstrated. The Central Extremity of the Optic Nerve. The x>ft{<, nerves, or seeond pair (2, fig. 276), present certain peculiarities in their tex- ture, and in their cranial course, which distinguish them from all other nerves. They have this peculiar character, that they arise by a commissure (the optic com- missure), or, rather, the two optic nerves unite before they pass to their respective des- tinations. On turning the cerebellum for^vard, it is seen that the optic tracts (2, fig. 295) are continuous with the corpora geniculata externa {b), and, consequently, take their origin from the optic thalami (a), of which these bodies are a dependance. In some cases, the white riband-like band, or optic tract, which constitutes the origin of the optic nerve, is also continuous with the corpus geniculatum internum (c). In the human subject, the optic nerves never arise, either entirely or in part, from the anterior tubercula quadri- gemina (nates) ; it is only by induction that this mode of origin has been admitted in the human subject.* The optic tract (2, fig. 272), having arisen from the corpus geniculatum externum (above i), with which it is continuous, without any other line of demarcation excepting the difference of colour, assumes the appearance of a thin and broad riband, which turns round the cerebral peduncle (c), parallel to and on the inner side of the great transverse fissure of the brain. During this course, it lies in contact with the peduncle of the cere- brum, from which it may be separated without laceration, excepting at its outer border, by which it adheres so intimately that the peduncle has been supposed to supply it with several roots. As soon as it gets beyond the peduncle, the optic tract (s, fig. 276) is condensed into a flat cord, which leaves the peduncle, passes inward and forward, and unites with its fellow of the opposite side to form the chia^ma (square space of Zinn, t), or, rather, to form, with the optic tract of the opposite side, a commissure which is convex in front and concave behind. On leaving the commissure, it completely changes its direction (2), passing forward and outward, to enter almost immediately into the optic foramen (2, fig. 296). During its course in front of the peduncle of the cerebrum, it is in relation with the following parts : behind, with the tuber cinereum (»), from the interior of which some white fibres arise, and pass to the chiasma ; in front, with the membrane which forms the anterior portion of the floor of the third ventricle, and which is prolonged upon the upper surface of the chiasma. An important question here presents itself, viz., Is there a complete or'partial decus- sation of the optic nerves in the commissure \ Do these two nerves interlace without decussating, or, rather, is there an intimate mixture of their fibres ] Are the nerves placed in simple juxtaposition and united by a transverse band ! Lastly, does the chi- asma constitute a commissure in which the two optic tracts terminate, or, rather, which serves as a point of origin for the optic nerves ^ AU these opinions have found sup- porters, and facts have been quoted in favour of each ; a circumstance which proves, not that there are anatomical varieties in the structure of the chiasma, but that its struc- ture is of a complex nature. Comparative anatomy proves that the optic nerves decussate in the commissure : in fishes, the two nerves cross without uniting : it is also proved by pathological facts ; in a great number of cases of atrophy of one eye, atrophy of the nerve extended, beyond the commissure, to the opposite optic tract. On the other hand, in an equally large number of cases of atrophy of one eye, the dis- ease affected the optic tract of the same side, so that this would seem to show that there was no decussation. Lastly, in all cases of atrophy of one eye, the disease aflects one of the optic nerves in particular, but the other has always appeared to me to be evidently reduced in size. On attempting to determine the point, either by the dissection of optic nerves harden- ed in alcohol, or unravelled by means of a stream of water, it is seen that these nerves present the following threefold arrangement at the commissure : The external fibres of * The origin of the optic nen-es varies in the different classes of animals. In birds, in which these nerves are at their maximum development, they arise entirely from the tubercula quadrigemina, which are the optic lobes in these animals, and are transposed from the side to the base of the brain. The optic thalami do not tissist in forming the.se nen-es. In rodentia, a small number of tibres from the optic thalami join the mass of those which are derived from the nates. In camivora, the number of filaments from the tubercula quadri- gemina and from the optic thalami are almost equal. Moreover, if it be remembered that the tubercula quad- rigemina, the corpora geniculata externa and interna, and the optic thalami themselves, belong to the same system of organs, and form a continuation of the re-enforcing fasciculi ( faisceux innomines) of the medulla ob- longata ; and if other facts confirmatory of the preceding also be taken into consideration, namely, that a white band proceeds on each side from the natis to the corpus geniculatum externum, and another from the testis to the corpus geniculatum internum, it will be easy- to account for these varieties of origin, which can all be re- duced to the same type. It is of some importance in regard to this question, that in a great number of cases of atrophy of the optic nerve, which I have had occasion to examine in the human subject, the corpus genicu- latum was affected, and not the natis. '^^;620 NEUROLOGY. the commissure do not decussate ; the internal fibres (and these are the most numerous) do decussate ; and the posterior fibres are continued from one side to the other like a commissure. Structure. — The optic nerve has a peculiar structure. It does not commence by fila- ments of origin or distinct cords, like the other nerves, but the optic tracts and the optic commissure are composed of two medullary bands, the fibres of which are parallel and in immediate contact with each other, precisely as in the olfactory nerves, and in the cerebral substance ;* after leaving the commissure, the optic nerves are enveloped in a neurilemmatic sheath, from the internal surface of which certain prolongations or septa are given off, which divide the interior of the nerve into longitudinal canals, in which the medullary substance is contained. I'he optic nerve, therefore, does not consist, like other nerves, of a plexiform group of nervous filaments or cords, but of a collection of canals closely applied to each other, so that it has the appearance of the pith of the rush ; hence, doubtless, the opinion of Eustachius and some other authors who conceived that the optic nerve was traversed by canals ; and hence, also, the error of Red, who, having taken the structure of the op- tic nerve as the type of that of all nerves, regarded each nervous cord as containing a central canal, t The Central Extremity of the Common Motor Jferve of the Eye. The apparent origin of the motor nerves of the eyes (3, fig. 276), motores oculorum, com- mon oculo-muscular nerve, or third pair, have a penicillate character ; these origins con- sist of a linear series of very delicate filaments proceeding from the fasciculi found be- tween the peduncles of the cerebrum, in the depression between the pons Varolii and the corpora albicantia. Some filaments converge from the cerebral peduncles them- selves.$ This origin extends about a line and a half, in a direction obliquely inward and forward. The internal filaments of origin reach the middle line, so that Varolius and Vieussens believed that the nerves of the right and left sides are continuous, and explained the simultaneous action of the two eyes by this anatomical arrangement. Real Origin. — In a brain hardened by alcohol, or, stiU better, in the brain of a foetus, Fie-. 295. ^^^ filaments of origin of the nerve (3, fig. 295) can be easily traced into the substance of the median fasciculi (d) found between the peduncles of the cerebrum, and which have already been shown to be prolongations of the fasciculi of re-enforcement {faisceaux innomines) of the meduUa oblongata. The filaments of the nerves traverse these fasciculi in a diverging manner, and descend to a level with the pons, beyond which I have not been able to trace them, on account of their slenderness and divergence. I have never observed any of them running towards the corpora albican- tia, and reaching the walls of the third ventricle or the anterior commissure, as has been stated by some. Nor have I found that they are re-enforced, as Gall believed, in the blackish substance {locus niger) which separates the peduncles of the cerebrum, prop- erly so called, from the prolongations of the re-enforcing fasciculi of the medulla oblongata. Cranial Course. — Having arisen in this manner, the fibres of the motor oculi nerve converge into a flat bundle, which passes be- tween the posterior cerebral and the superior cerebellar arteries, upon which latter it is reflected : on emerging from the interval between these two vessels it becomes rounded, and then passing upward, outward, and forward, enters the reticular sub-arachnoid cellular tissue at the base of the brain, and gains the side of the sella turcica {3, fig. 296), where it enters a proper sheath formed for it by the dura mater. The Central Extremity of the Pathetic JVerve. The nervi pathetici (4, fig. 276), nerves of the superior oblique muscle of the eyes, nervi trochleares, the internal and superior oculo-muscular nerves, or the fourth pair, as they are variously called, are the smallest of the cranial nerves, and are as remarkable for being * See note, p. 767. t In most fishes, whose faculty of vision is exercised in a less transparent medium than air, the optic nerve is formed by a membrane folded upon itself. In birds of prey, the membrane is sometimes folded like a fan, sometimes like the leaves of a book. These folds are intended to increase the extent of surface, and to aug- ment the power of vision. Malpighi first made this observation upoa the optic nerve of some fishes. Des- moulins, who has studied the point more carefully, has shown that it is in relation with the perfection of the sense of sight. The same thing is also observed in the retina : thus, in the eagle, the retina presents two, three, or four superimposed folds, so that each luminous ray acts upon sixteen surfaces instead of upon two. t In fact, the external filaments often anse from the inner border, and even from the lower surface of the cerebral peduncle, at a certain distance from the inner border ; in this case, they do not arise from the pedun- cles, but merely pass through them. The same is doubtless the case w^ith the filaments of origin which Rid- ley and Molinelli state that they have seen coming from the pons. I have never met with this origin from the pons, nor with that accessory nerve which Malacame has described as proceeding from the upper part of the peduncle of the cerebellum, turning round the border of the pons, and joinini the motor oculi nerve. CENTRAL EXTREMITY OF THE TRIGEMINAL NERVE. 821 exclusively distributed to the superior oblique muscle of the eyes, as for their origin and for the length of their course within the cranium. The term patheticus is derived from the opinion that the superior oblique muscle is especially concerned in the expression of love and of compassion. According to Bell, this nerve is the respiratory nerve of the eye. The apparent origin of this (4, Jig. 280) nerve is below the tubercula quadrigemina, on each side of the valve of Vieussens, sometimes by one, sometimes by two, and even by three or four roots. Occasionally there are several roots on one side, and only a single root on the other. The nerves of the two sides are often united by some white streaks, which form a transverse commissure ; at other times they do not arise at the same level. Real Origin. — It has been supposed that some fibres come from the testes, others from the cerebellum, and that others coimnence much lower down than the apparent origin : all that can be seen is, that these nerves {4:,Jig. 295) arise from the valve of Vieussens, to which they adhere so slightly that the least force is sufficient to detach them. Cranial Course. — Immediately after its origin, the pathetic nerve turns forward and downward, around the isthmus of the encephalon, in front of the anterior border of the cerebellum, and thus reaches the base of the cranium (4, fig. 276), accompanied by the superior cerebellar artery, between the fifth and third cranial nerve, but much nearer to the fifth ; it then passes directly forward upon the side of the sella turcica (4, ^o^. 296), and perforates the dura mater, considerably below the third nerve. During its whole course, it is situated between the arachnoid and the pia mater, in the reticular cellular tis- sue found in this region. Wrisberg says that the right pathetic nerve is larger than the left. Ruysch states that he found this nerve double, which it is difficult to believe, unless he meant to say that it bifurcated at its origin. Vesalius regarded this nerve as a root of the third cra- nial nerve ; other anatomists have considered it as a dependance of the fifth. The Central Extremity of the Trigeminal JVerve. Apparent Origin. — The trigeminal or trifacial, nerves (5, fig. 276), the middle sympathet- ic, or the fifth pair, are the largest of the cranial nerves, exceptmg the optic : they arise at the sides of the pons Varolii, at the point where the pons becomes continuous with the corresponding peduncles of the cerebellum, and exactly where the middle fibres of the pons cross in front of the inferior, to form that peduncle, so that the fasciculi of ori- gin appear to converge from a narrow slit in the pons itself This origin (5, fig. 295) consists of two roots, the large and the small root, which have a small prominence be- tween them. The large or ganglionic root is a thick, fasciculated mass, which is, as it were, constricted at its point of emergence, but immediately expands into a thick, flat bundle, in which w^e may count about 100 fibres. On tearing off this bundle, all the fibres do not give way opposite the same place, and a sort of mammillary prominence is left, which Bichat regarded as belonging to the pons, as intended for the nerve to arise from, and as having the effect of multiplying the surfaces of origin, in consequence of its con- vexity. The small root, which is non-ganglionic, is composed of small and very distinct bun- dles, which arise from the pons, above and behind the great root, by several cords ; it emerges from the pons through a fissure distinct from that for the great root, and gains the upper border of that root. It win hereafter be seen that the small root has no share in the formation of the gan- gliform plexus known by the name of the semilunar or Gasserian ganglion, and that it goes exclusively to assist in forming the inferior maxillary division of the fifth nerve. Real Origin. — Until modern times, the origin of the fifth nerve had not been traced be- yond the point of its emergence. Late authors have described its real origin with so much detail that little remains to be desired. Gall, while examining the fifth nerve, first in mammalia and then in the human subject, saw that in many the origin of the nerve is concealed by certain transverse fibres of the pons which do not exist in the lower ani- mals. Having traced the nerve by clearing off the fibres of the pons, he thought he ob- served that the great root divided into three principal fascicuh, which he conceived arose in succession from the gray matter of the pons, and which he succeeded in tracing as far as to the outer side of the olivary body.* Rolando, by successive sections made through the pons towards the medulla oblongata, has clearly shown that the great root of the fifth nerve consists of only one fasciculus, which runs downward and backward, under the form of a thick cord (see_^^. 295), in the substance of the pons, or, rather, at the boundary between the pons and the middle ped- uncle of the cerebellum, parallel to the fasciculi of the anterior pyramid, and that it pro- gressively diminishes in size, until it disappears opposite to the inferior angle of the fourth ventricle. The examination of this origin in a brain hardened by alcohol, or, still better, in the foetal brain, confirms Rolando's observations, and proves that the great root of the * In the human subject, the origin of the fifth nerve is extremely deep-seated ; it is not so deep in the car- nivora, and still more superficial in ruminantia. In oviparous animals, which have neither a pons Varolii, nor lateral lobes of the cerebellum, nor pyramids, nor olivary bodies, the origin of the fifth pair is seen without any dissection. 822 NEUROLOGY. Pig- 296. fifth nerve comes from the back part of the medulla ob- longata, from the interior of its fasciculi of re-enforce- ment {faisceaux innomines).* As to the small root, it cannot be traced beyond the surface of the pons.f Cranial Course. — After emerging from the pons, the fifth nerve passes upvi'ard, outward, and forward, under the form of a flattened bundle, gains the upper border of the petrous portion of the temporal bone {5, Jig- 296), on which there is a depression that is converted into a canal for the nerve by a fold of the dura mater ; the nerve is reflected upon this border, and proceeds as will presently be described. The Central Extremity of the External Motor Jferve of the Eye. The external motor jierves of the eye (6, figs. 276, 295), external oculo-muscular nerves, nervi abducentes, or the sixth pair, which are distributed exclusively to the external rectus or abductor muscle of each eye, and which are so re- markable for their communications with the sympathetic system, are smaller than aU the cranial nerves, excepting the pathetic. Apparent Origin. — The statements of authors regarding the apparent origin of this nerve have been singularly various : some, with Morgagni, describe it as arising both from the pons and the anterior pyramids ; others, with Vieussens, from the pons alone ; and others, with Lieutaud, from the anterior pyramids only. Winslow states that it arises between the pons Varohi and the olivary body, and Haller, that it proceeds from the furrow be- tween the anterior pyramid and the pons. The fact is that this nerve, among some varieties of origin, presents two very distinct roots (see fig. 276) : one internal and smaller, which arises from the pons, either at or near its lower border ; the other external and larger, which appears to emerge on the outer side of the upper part of the anterior pyramid. These two roots are fasciculated : not unfrequently some fibres are seen arising from the olivary body, or from the furrow between the two pyramids. Real Origin. — This is more easily seen in mammalia generally than in man. In the former. Gall has traced it along the side of the pyramids. Mayo believes that the fibres traverse the pons, and pass to the back part of the medulla oblongata. From the tenu- ity and whiteness of the fibres of this nerve, I have not been able to trace their course in the substance of the medulla. Cranial Course. — This nerve runs upward and a little outward, on the side of the basi- lar groove, and perforates the dura mater (6, fig. 296) opposite to and above the apex of the petrous portion of the temporal bone, to enter the cavernous sinus : the two roots of the nerve often unite before perforating the dura mater, but they usually pass separately through it and unite within the sinus. The Central Extremity of the Seventh Merve. The central extremity of the facial nerve, or port.io dura of the seventh nerve {7, fig. 270, 276). The facial nerve (on the inner side of 7) arises in the deep depression between the middle peduncle of the cerebellum and the pons in front of the auditory nerve (on the outer side of 7) : it emerges from the front of the restiform body, under the form of a fasciculated band, some fibres of which are at first situated at a distance from the gen- eral mass, but soon join it ; it then turns round the lower borders of the peduncle of the cerebellum, against which it is closely applied, and then becoming free, passes outward and upward. It has no neurilemma up to the point .where it becomes free. The real origin of this nerve (7, fig. 295) is much deeper ; it may be traced through the restiform body into the fasciculus of re-enforcement, near the median furrow of the calamus scriptorius. The Central Extremity of the Auditory Nerve. — The auditory nerve, or portio mollis of the seventh (on the outer side of 7, fig. 275), is riband- shaped, and non-fasciculated at its origin ; it arises {7', fig. 295) in the same depression as the facial nerve, but behind that nerve, and opposite to the restiform body : it presents two very distinct roots : an anterior, which is arranged like the facial nerve ; and a posterior, which turns horizontally round the back part of the restiform body, appears upon the posterior surface of the medulla ob- longata (see fig. 271), and separates into fibres, which may be traced as far as the me- * Vicq d'Azyr says that, the roots of this nerve extend as far as the cerebellum, but this assertion has not been verified. The same anatomist declares that he has often seen the fifth nerve of the right side larger than that of the left. t According to Dr. Alcoclt, there is a slight enlargement at the origin of the large root of the fifth nerve, in the lower-part of the floor of the fourth ventricle ; he has also traced the small root to this enlargement, from which he states that two cords descend, one to the anterior, the other to the posterior column of the cord. — {Cyclop, of Anat. and Phys., art. Fifth Paik of Nerves.) CENTRAL EXTREMITY OF THE EIGHTH NERVE. 823 dian furrow of the calamus scriptorius, and which represent some of the barbs of the quill. It is very generally admitted that the auditory nerves have a tranverse commis- sure, but this does not appear to me to be clearly demonstrated. The portio dura and the portio mollis of the seventh nerve, which arise so near to each other, follow the same cranial course : they arise at the same height from the medulla oblongata, pass outward and upward in front of the pneumogastric or sub-peduncular lobule of the cerebellum, and enter the internal auditory meatus (7, Jig. 296). During this course, the portio dura always lies in front of the portio mollis. The auditory nerve is the softest of all the cranial nerves ; the difference between it and the facial nerve, in this respect, has led, in a great measure, to the subdivision of the nerves into the soft or sensory, and the hard or motor. The Central Extremity of the Eighth J^erve. Of the three nerves on each side which together constitute the eighth nerve {8, Jigs. 270, 276, 295), the glosso-pharyngeal is the highest, the ^pneumogastric is the next, and the spinal accessory is the lowest. The Coitral Extremity of the Glosso-pharyngeal and Pneumogastric Nerves. — The glosso- pharyngeal and pneumogastric nerves have a common origin. They arise, like the spinal nerves, by a linear series of funiculi (see_^D-. 270), which come off, not from the furrows between the olivary and restiform bodies, but from the restiform body itself, on a line with the auditory nerves. Soemmering states that he has seen some of these funiculi arise from the anterior wall of the fourth ventricle. Moreover, as in the spinal nerves, each funiculus of origin is formed by the union of two or three converging filaments ; the funiculi of the glosso-pharyngeal nerve, which are the highest, and which come off immediately below the auditory nerve, are not dis- tinct at their origin from those of the pneumogastric ; nor, as will presently be stated, are the funiculi of origin of the pneumogastric distinct from those of the spinal acces- sory. The division into the three nerves cannot be made until after the funiculi are finally grouped. It has been stated, but without proof, that the fibres of the glosso-pharyngeal and pneumogastric nerves might be traced through the restiform body as far as the back of the medulla oblongata. The funiculi of origin of these nerves, which are enveloped by the neurilemma at the point where they emerge from the medulla, are so small that, when torn off, scarcely any trace of their points of attachment can be detected even by the aid of a lens. The Central Extremity of the Spinal Accessory Nerve of Willis. — The origin of the spinal accessory nerve {s, Jig. 295) is quite peculiar, and has obtained much notice from modern anatomists. It arises from the sides of the cervical region of the spinal cord, between the anterior and posterior roots of the cervical nerves, and behind the ligamentum denticulatum. Sir C. Bell, who classes it among the respiratory nerves, strongly insists upon its ori- gin from that column of the cord which is situated between the anterior and posterior columns, in a line with the pneumogastric and facial nerves, which column (the respira- tory tract) he assumes to give origin solely to the respiratory nerves. The funiculi of origin of the spinal accessory vary much both in number and size, and are widely separ- ated from each other ; the lowest as well as the highest funiculi appear to me to be con- tinuous with the posterior roots of the spinal nerves ; and, again, the -highest are con- tinuous above with those of the pneumogastric nerve, and appear to me to establish a transition between the origin of that nerve and the posterior roots of the spinal nerves. The lowest funiculus of the spinal accessory is generally situated not lower than the fifth cervical nerve ; it has been seen to arise opposite the sixth, and even the seventh cervical nerve ; the latter is the normal condition in the ox. It is of importance to remark the connexion which exists between the spinal acces- sory nerve and the first cervical or sub-occipital nerve. Almost always one or two, and frequently all of the posterior funiculi of the sub-occipital, join the spinal accessory. Not unfrequently a small funiculus joins the spinal accessory from the second cervical nerve. Opposite its connexion with the sub-occipital nerve, the spinal accessory sometimes pre- sents a gangliform enlargement, which was well described by Huber {in ganglion vix hordeaceum iniumescit nervus accessorius). In some cases a filament proceeds from this ganglion and joins the anterior roots of the sub-occipital nerve. Winslow believed that the funiculi of origin of the spinal accessory communicated with the hypoglossal : this is an error. The greater number and even the whole of the funiculi of the sub-occipital nerve have been seen to join the spinal accessory, in which case, filaments from the latter nerve always supply the place of those which are usually furnished by the first cervical.* The Cranial Course of the Glosso-pharyjigeal and Pneumogastric Nerves. — They pass horizontally outward, in contact with the lateral fibrous layer of the fourth ventricle, forming two groups having a very small interval between them. The two, three, or four small bundles which constitute the glosso-pharyngeal nerve pass through a special * Lobstejn, De Nervo Spinali. Vide Scriptor. Neurol., Minor de Ludwig-., t. ii. 824 NEUROLOGY. opening in the upper part of the foramen lacerum posterius (8, fig. 296). The bundles which form the pneumogastric nerve are collected together and pass through the same foramen, but by a distinct opening from the preceding one. The cranial, or, rather, the vertebral course of the spinal accessory nerve of Willis, is re- markable. This nerve, which is very small below, where it is formed by one or two funiculi, ascends vertically upon the side of the cervical region of the spinal cord, to which it is closely applied below, just behind the ligamentum denticulatum, and from which it is separated above, where it is immediately in front of the posterior roots of the cervical nerves ; it goes on increasing in size as it receives additional funiculi, which are blended with it ; having arrived a few lines below the posterior lacerated foramen, it passes upward and outward to enter the same opening as the pneumogastric, being situ- ated below that nerve, and emerging with it from the cranium. The Central Extremity of the Hypoglossal Jferve, The hypoglossal nerves {9, figs. 276, 295), or ni7ith pair, arise on each side, from the fur- row between the olivary and pyramidal bodies, in the same manner as the spinal nerves, i. e., by a linear series of funiculi placed one above the other. The furrow from which the funiculi of the ninth nerve arise is continuous with the line formed by the origins of the anterior roots of the spinal nerves ; no funiculus arises from the line formed by the posterior roots.* The relation of the origin of the ninth nerve with the vertebral artery in front, and the vascular ramifications which surround the funiculi of this origin, require to be mentioned. The real origin of the ninth nerve cannot be traced beyond its apparent origin. It is certain that no fibres come from the pyramids ; it has appeared to me that the fibres en- tered the substance of the olivary bodies, in which they could not be traced to any depth. Cranial Course. — All the funiculi of origin of the hypoglossal nerve commence by two or three filaments, which are immediately covered by the neurilemma ; they are then grouped into two or three bundles, which pass horizontally outward to the anterior con- dyloid foramen, through which (9, fig. 296) they almost always pass separately. Thus the dura mater forms two and sometimes three distinct canals for the hypoglossal nerve. DISTRIBUTION OF THE CRANIAL NERVES. The First Pair or Olfactory Nerves. — The Second or Optic Nerves. — The Third or Common Motor Nerves. — The Fourth or Pathetic Nerves. — The Fifth or Trigeminal Nerves — the Ophthalmic Division of the Fifth, and its Lachrymal, Frontal, and Nasal Branches — the Ophthalmic Ganglion — the Superior Maxillary Division of the Fifth, aiid its Orbital Branch — the Sphcno-palatine Ganglion, and its Palatine, Spheno-palatine, and Vidian Branches — the Posterior and Anterior Dental, and the Terminal Braiiches of the Superior Maxillary Nerve — the Inferior Maxillary Division of the Fifth — its Collateral Branches, viz., the Deep Temporal, the Masseteric, Buccal, and Interiial Pterygoid, and Awriculo-temporal — its Terminal Branches, viz., the Lingual and Inferior Dental — the Otic Ganglion. — The Sixth Pair or External Motor Nerves. — The Seventh Pair — the Portio Dura or the Facial Nerve — its Collateral Branches — its Terminal Branches viz., the Temporo-facial and Cervico-fascial — the Portio Mollis or Auditory Nerve. — The Eighth Pair — its First Por- tion of the Glosso-pharyngeal Nerve — its Second Portion or the Pneumogastric Nerve, di- vided into a Cranial, Cervical Thoracic, and Abdominal Part — its Third Portion, or the Spinal Accessory Nerve. — The Ninth Pair or the Hypoglossal Nerves. — General View of the Craiiial Nerves. The First Pair, or the Olfactory Nerves. Dissection. — Harden the nerve in dilute nitric acid. Examine the pituitaiy membrane, not from its free surface, but from the surface which adheres to the periosteum. The nerve ramifies between the periosteum and the pituitary membrane. Before the time of Scarpa, the olfactory pedicles or bands and the ethmoidal bulb were the only parts well known ; the passage of the olfactory nerves through the foramina of the cribriform plate, and their distribution in the pituitary membrane, were scarcely noticed. Passage of the Olfactoy Nerves through the Cribriform Plate. — I must here remind the student that the cribriform plate of the ethmoid bone is perforated by foramina, or, rather, by different sets of canals which ramify in its substance ; that some of these canals ter- minate directly upon the roof or upper wall of the nasal fossae, and that the others are divided into an internal set, which pass along the septum and end by becoming grooves, and an external set, which descend on the superior and middle turbinated bones, and on the rough quadrilateral surface in front of them. The olfactory nerves arise from the ethmoidal bulb {l,figs. 296, 297) by a considera- ♦ [Tn the ox and dog Mayer discovered a small posterior root with a ganglion for this nerve ; and he states that he once found a small posterior root on one side in the human subject.] THE OPTIC NERVES. 825 Fig. 297. ^^^ number of white bundles, which immediately pass through the cribriform plate, and divide and ramify {d, fig. 297) in the same way as the bony canals themselves ; the dura mater forms a sheath for each of the subdivisions of the nerve, and supports their soft substance. All these nervous filaments are distributed upon the septum (d) and upon all the external wall (a, fig: 299) of each nasal fossa ; the anterior run forward, the middle vertically downward, and the posterior backward. Some of them only in- terlace as they leave the cribriform plate. They all expand into very delicate pencils. They are situated between the periosteum and the pituitary membrane, and none of them reach either the inferior turbinated bone, or the maxillary, sphenoidal, or ethmoidal sinuses ; on the inner wall of each fossa they do not pass lower than the middle of the septum ; and on the outer wall they do not descend below the middle turbinated bone.* With regard to the ultimate termination of the fibres of the olfactory nerve, there has been a difference of opinion ; some believe that they terminate in papillae like those of the skin ; and others imagine that they expand into a membrane, like the optic nerve in the retina and the auditory nerve in the membranous labyrinth. I have never seen them terminate otherwise than by pencils of extremely delicate filaments very closely applied to each other. Function. — The olfactory nerves are the essential organs of smell. Their distribution proves that the sense of smell resides essentially and exclusively in the roof of the nasal fossae and the immediately adjacent parts. The Second Pair, or the Optic Nerves. The optic nerves have already been described from their origin to the optic commis- sure, and from the commissure to the optic foramina (2, fig. 296) ; they pass through these foramina together with the ophthalmic arteries which are below them ; they are also accompanied by a sheath formed by the dura mater and by a prolongation of the arachnoid, the latter being immediately reflected from them. The optic nerve, which is flattened up to this point, becomes rounded on emerging from the optic foramen, and is received in a fibrous ring formed by the origins of the muscles of the eye ; it here, also, changes its direction slightly, for, instead of passing obliquely forward and outward, it runs almost directly forward to the globe of the eye, which it enters behind, and somewhat below, and to the inner side (see o, figs. 237, 238, 240). There is a very evident circular constriction at the point where the optic nerve enters the eye.t During its course in the orbit, the optic nerve is surrounded by a great quantity of adipose tissue, which separates it from the muscles and nerves. The ophthalmic gan- glion and the ciliary nerves and vessels are in immediate contact with it. It is accom- panied, as far as the sclerotic, by a fibrous sheath given off from the dura mater, so that this nerve differs from all others, in being provided with two protecting sheaths, name- ly, a proper neurilemma, and a sheath formed by the dura mater. A section of the optie nerve also presents throughout its course that pecuhar appearance resembling the pith of the rush, which we have already described as commencing at the commissure (see Centr.\l Extremity of the Optic Nerve). As it enters the ball of the eye the nerve loses its two sheaths, which appear to be- come continuous with the sclerotic, and is thus reduced to its pulp, which spreads out to form the retina. In some subjects the retina presents a distinctly radiated appear- ance around the abrupt termination of the nerve (see Globe of the Eye — Retina). Function. — The optic nerves are the nerves of vision ; their continuity vrith the retina leaves no doubt of this being their function. The Third Pair, or the Common Motor Nerves of the Eyes. Dissection. — All the nerves of the orbit should be studied together. The frontal and lachrymal branches of the ophthalmic nerve and the fourth nerve may be first examined ; then the orbital portion of the nasal branch of the ophthalmic, which will afterward be traced into the nasal fossae ; next, the common and external motor nerves ; and, lastly, the ophthalmic ganglion and the optic nerve. The common motor nerve has already been traced (3, figs. 298, 301) from its origin with- in the peduncles of the cerebrum to the side of the quadrilateral plate of the sphenoid bone, below and to the outer side of the posterior clinoid process ; in this situation (3, fig. 296) it is received into a groove formed for it by. the dura mater ; it then perforates that membrane, enters the cavernous sinus, passes through it from behind forward and * In mammalia, and particularly in the horse, a cord arises from the olfactory nerve, runs downward and forward along the septum, parallel to and in front of the naso-palatine nerve, and terminates in the small in- cisory cavity which exists in the arch of the palate in the lower animals, and is thought by M. Jacobson to be the seat of a sixth sense. t M. Arnold, in his beautiful plates of the nerves of the head, has represented two very delicate filaments as establishing a communicatii^n between the sunerior maxillary and the optic nerves. 5M 826 NEUROLOGY. a little outward, and before entering the orbit divides into two branches of unequal size, of which one is superior and the other inferior. The following are its relations in the cavernous sinus : it is situated in the substance of the external wall of the sinus, to the outer side of the internal carotid artery, above the external motor nerve, and to the inner side of the fourth nerve and of the ophthalmic branch of the fifth ; it enters the orbit at the innermost, and, consequently, the widest part of the sphenoidal fissure. It has no immediate relations with the other nerves that pass through the cavernous sinus, until it is about to enter the orbit ; at this point it receives some very delicate fil- aments from the cavernous plexus of the sympathetic, and an equally small filament from the ophthalmic branch of the fifth nerve ; after which, the external motor nerve* becomes situated below the common motor, while the frontal and pathetic nerves cross above it ; the nasal branch of the ophthalmic is in contact with its outer side, and then passes between its two divisions. As the common motor nerve passes through the sphenoidal fissure, the tendon of the external rectus forms a fibrous ring around it, which is quite distinct from the ring be- longing to the optic nerve ; this fibrous ring also surrounds the external motor nerve and the nasal branch of the ophthalmic. The superior terminal division of the third nerve is much smaller than the inferior ; it passes below the superior rectus of the eye, and immediately expands into a great num- ber of filaments, one of which is very large, and runs along the outer border of that mus- cle. Almost all these filaments are intended for the superior rectus, which they enter by its under surface. Several of them are very small, and run along the inner border of the superior rectus, to be distributed to the levator palpebrae superioris. The fila- ments for this last muscle are proportionally much smaller and less numerous than those for the superior rectus. The inferior terminal division is the true continuation of the nerve both as regards its size and direction ; it runs between the optic nerve and the external motor nerve, which is in contact with it, and which lies between it and the external rectus muscle, and al- most immediately subdivides into three branches : an internal, which, passing beneath the optic nerve, gains the internal surface of the internal rectus, and ramifies in that muscle ; a median, which penetrates the inferior rectus ; and an external branch, which is the smallest, and runs along the outer side of the inferior rectus as far as the inferior oblique, and enters that muscle at its posterior border, and almost at right angles. The short, thick filament which enters the ophthalmic ganglion proceeds from the branch for the inferior oblique muscle. This filament for the ganglion sometimes arises separately, and appears to be a fourth branch of the inferior division of the third nerve. t Function. — The common motor nerve supplies all the muscles of the eye, excepting the superior oblique and the external rectus. It is remarkably large, and is proportion- ed to the activity and frequency of contraction in these muscles. That the muscular nerves do not terminate in loops or arches may be well seen in these muscles. The Fourth Pair, or the Pathetic Nerves. The pathetic nerve (A:, figs. 298, 301) is remarkable for its extreme slenderness, for its origin upon the side of the valve of Vieussens, for the length of its cranial portion, and for its winding course around the peduncle of the cerebrum ; it enters (4, fig. 296) an opening in the dura mater upon the anterior extremity of the inner or concave border of the tentorium cerebelli, on the outer side of the common motor nerve ; it runs in the sub- stance of the external wall of the cavernous sinus, to the outer side and a little below the level of the common motor nerve (3), and directly above the ophthalmic division {a) of the fifth, to which it sends off a filament, and then, running along the upper surface of that nerve, communicates with it by several twigs ; it then enters the orbit together with the frontal nerve, the principal branch of the ophthalmic, through the widest part of the sphenoidal fissure, passes inward and forward, leaves the frontal nerve, crosses obliquely over the superior branch of the common motor nerve and the back part of the levator palpebrae superioris and superior rectus of the eye, to reach the superior oblique, and, having previously ramified, enters the upper border of that muscle. During its course in the orbit, this nerve, like the frontal branch of the ophthalmic, is in contact with the periosteum. The union of the ophthalmic branch and the pathetic nerve is so intimate that it has been imagined that the lachrymal nerve is always derived entirely from the pathetic, and not from the ophthalmic itself But a careful dissection shows that this is generally in- correct. However, I have found the pathetic nerve in several subjects giving offa branch, * It appears to me that there is a communication between tlie common and external motor nerves in the cavernous sinus. t I have seen the hranch for the inferior rectus arise by two roots, one from the branch for the internal rectus, and the other from the branch for the inferior oblique. I have seen the branch for the inferior oblique give off a supernumerary branch to the inferior rectus. Lastly, sometimes the branches for the inferior oblique and inferior rectus are united, so that the inferior division of the third nerve was subdivided into two branches only. THE TRIGEMINAL NERVES. 827 which united with another from the ophthalmic nerve to constitute the lachrymal nerve. This anastomosis took place at the bottom of the orbit. Another and well-founded view re- gards the pathetic nerve and the ophthalmic branch of Willis as forming a single nerve ; in fact, in certain subjects they interlace so intimately that it is impossible to separate them. The Branch for the Tentorium Ccrebelli. — The pathetic nerve, while still contained in the substance of the external wall of the cavernous sinus, gives off a branch which runs backward in the substance of the tentorium cerebelli, and may be traced as far as the lateral sinus, near which it divides into two or three filaments. In several subjects I found that the branch for the tentorium was formed by a twig which arose from the oph- thalmic nerve, became applied to the pathetic nerve, then diverged from it, and passed backward in the substance of the tentorium. It appears, then, that the nerve of the ten- torium has a retrograde course.* Function. — The fourth pair of nerves is intended for the superior oblique muscle only of the eye. It has been supposed that this muscle has a special nerve to enable it to ex- press certain mental emotions, and especially love and pity ; but, as Soemmering remarks, it exists in all mammalia, in birds, and even in fishes. Camper states that the vital functions of the pathetic survive those of the other nerves, and that this circumstance influences the direction of the eyes in dying persons. According to Sir C. Bell, the pathetic is the respiratory nerve of the eye. Its origin is situated at the highest part of the respiratory tract. According to the same physi- ologist, it is the nerve of expression ; it associates the muscles of the eye, and estab- lishes certain relations between the eye and the respiratory system. The Fifth P.iiE, or the Trigeminal Nerves. The nervus trigeminus (trifacial, Chauss., 5, fig. 296), which, as already stated, arises from the side of the pons Varolii by two distinct roots, gains the upper border of the pe- trous portion of the temporal bone, over which it is reflected, and near the apex of which there is a depression for the reception of the nerve : a bridge-like fold of the dura ma- ter converts this depression into a canal. The nerve, which increases in width as it passes over the upper border of the petrous bone, continues to get wider while upon the upper surface of the same bone, and runs downward, forward, and outward ; its fibres immediately spread out and interlace to enter the concave surface of a grayish semilu- nar enlargement called the semilunar or Gasserian ganglion. All the fibres of origin of the fifth nerve do not assist in the formation of this ganglion ; for, on reflecting the nerve from within outward, a flat cord {b,fig. 299) is seen below the ganglion, and giving no fibre to it ; and, on tracing this cord upon the side of the pons Varohi, it is found to con- sist of the small root of the fifth nerve, which is at first placed on the inner side of this nerve, and then turns round it to gain its under surface. This very remarkable disposition establishes a complete analogy between the fifth cra- nial nerve and the spinal nerves, which, as we have seen, have ganghonic roots (the posterior roots) and non-ganglionic roots (the anterior). The Gasserian ganglion (behind a b c, fig. 298 ; c, fig. 299) is lodged in a special de- pression in the petrous portion of the temporal bone {fig. 296), and it adheres so closely to the dura mater that it is impossible to separate the ganglion without tearing it. From its convex surface, which is directed forward and outward, proceed three plexiform ner- vous trunks, which diverge like the toes of a bird ; these are, proceeding from before backward, the ophthalmic nerve of Willis {a, figs. 296, 298, &c), the superior maxillary nerve (i), and the inferior maxillary nerve (c) : the non-ganglionic root {h, fig. 299) of the fifth nerve goes directly to the inferior maxillary division (c) of the nerve : t1ie ophthalmic and the superior maxillary divisions often arise by a common trunk. Several scattered fila- ments are given off from the three divisions of the nerve, but soon join them again. Communicating filaments are sometimes seen between the superi- or and inferior maxillary divisions as these latter enter their respective foramina. The ganglionic nature of the Gasserian gangli- on cannot be doubted ; for, like all ganglia, it con- sists of a grayish, pulpy matter, in which the ner- vous fibres are spread out, and, as it were, entan- gled, to enter into new combinations. The Gasserian gangliont gives off several fila- ments for the dura mater, which may be traced into the substance of the tentorium cerebelli : a certain number of filaments appear to be destined * Arnold has described the branch (f,fig. 296) for the ten- torium cerebeUi, which is derived from the fifth nerve, and not that which comes from the pathetic. t The Gasserian ganglion might serve as a type for demon- strating the structure of all ganglia, so easy is the separation of the gray matter and white fibres. Fig. 298. 828 NEUROLOGY. for that part of the dura mater which covers the petrous portion of the temporal bone and the sphenoid bone. In order to demonstrate these twigs, the dura mater must be previously rendered transparent by maceration in diluted nitric acid. The Ophthalmic Division of the Fifth JVerve. The ophthalmic nerve of Willis, or ophthalmic division of the fifth nerve (nerf orbitaire, Wmslow; orbito-frontal, Chauss., a, fig. 296, &c.), is the highest and smallest of the three divisions : it passes forward, outward, and upward, in the substance of the exter- nal wall of the cavernous sinus, in which situation it has a plexiform structure. It is there divided into an external branch, called the lachrymal nerve (e, fig. 296), a middle branch, the frontal nerve (continuation of a), and an internal branch, or the nasal nerve ; these three branches enter the orbit through different parts of the sphenoidal fissure. Before this division, the ophthalmic nerve gives off a retrograde filament (nervus recur- rens inter laminas tentorii, Arnold, f,fig. 296), which passes backward, closely applied to the twig furnished by the pathetic nerve to the tentorium cerebeUi, and running paral- lel to that twig, enters the tentorium. The Lachrymal or Lachrymo-palpebral Nerve. Dissection. — First expose the nerve in the orbit, and then trace it backward to its ori- gin. This dissection is difl^cult, unless the parts have been macerated in diluted nitric acid. The nerve is then to be traced into the substance of the upper eyelid. The lachrymal nerve {e,fig. 296), the smallest of the three branches of the ophthalmic, comes off from the outer side of that nerve, in the substance of the external wall of the cavernous sinus, where it is difficult to discover its origin and course, on account of its intimate adhesion to the dura mater ; it enters the orbit through the narrowest part of the sphenoidal fissure, runs along (below s,fig. 300) the upper border of the external rec- tus, passes through the lachrymal gland, to which it gives several filaments, pierces the fibrous layer of the upper eyelid, descends vertically within that eyelid, between its fibrous layer and the orbicularis muscle, and divides into two principal cutaneous fila- ments : a palpebral, which runs along the lower border of the tarsal cartilage ; and an as- cending temporal, which is lost in the integuments upon the anterior temporal region. During its course, the lachrymal nerve gives off a maiar branch, which may be regarded as resulting from a bifurcation of the nerve. This branch perforates the malar bone, and anastomoses with the facial nerve upon the cheek.* The lachrymal branches, properly so called, are extremely small. The real termination of the lachrymal nerve is in the upper eyelid, and hence the term lachrymo-palpebral has been given it. I have already said that the lachrymal nerve not unfrequently arises by two filaments, one of which is derived from the ophthalmic of the fifth, and the other from the pathetic nerve (Mr. Swan describes this as the usual condition). In a specimen which I have now before me, there are two lachrymal nerves, one of which arises in the ordinary manner, that is to say, from the ophthalmic division of the fifth, while the other, which is external and smaller, arises both from the pathetic and the frontal nerve. These two lachrymal nerves anastomose with each other. The Frontal Nerve. The frontal nerve (fronto-palpebral, Chauss.)xm.y be regarded as the continuation of the ophthalmic {a, fig. 296) both in size and direction ; it enters the orbit at the highest and broadest part of the sphenoidal fissure, together with the pathetic nerve, t It passes horizontally forward, between the periosteum and the levator palpebree su- perioris, crossing that muscle at an acute angle, and divides at the bottom of the orbit into two unequal branches, which do not diverge until they reach the front of that cavity ; these are the internal frontal and the external frontal. X The External Frontal or Supra-orbital Nerve {r,figs. 296, &c.). — This is larger than the internal branch ; it passes out of the orbit through the supra-orbital foramen, and ex- pands into ascending or frontal, and descending or palpebral branches. The palpebral branches are very numerous, and descend vertically in the substance of the upper eye- * Authors speak of a filament from the lachrymal nerve which anastomoses with the superior maxillary nerve near the anterior extremity of the infra-orbital fissure. I have never seen this filament. [Before reaching the lachrymal gland, the lachrymal nerve may give olf one or two communicating filaments, to join the temporal filaments of the orbital branch {t,fig. 300) of the superior maxillary nerve, before these latter perforate the outer wall of the orbit.] t The orbital nerves which enter the sphenoidal fissure are divided into two sets : those which pass through the fibrous ring of the external rectus, namely, the common motor nerve, the nasal branch of the ophthalmic, and the external motor nerve ; and those which pass above and to the outer side of the preceding, immediately below the lesser ring of the sphenoid bone, between the periosteum and the superior rectus, namely, the fron- tal branch of the ophthalmic, the pathetic, and the lachrymal branch of the oplithalmic ; the latter nerve pass- es separately through the sphenoidal fissure. % Not unfrequently a third branch arises from the inner side of the frontal nerve ; this might be called the fronto-nasal ; it passes obliquely inward and fonvard, crosses over the superior oblique, anastomoses with the external nasal nerve, emerges from the orbit below the pulley for the tendon of the superior oblique, and ter- minates with the external nasal nerve in the upper eyelid. [This fronto-nasal branch may arise from the in- ternal frontal nerve. J THE NASAL NERVE. 829 lid ; one of these branches runs horizontally outward under the orbicularis palpebrarum, to anastomose u-ith the branches of the facial nerve. The frontal branches are generally two in number, an external and an internal. They form the true continuation of the ex- ternal frontal nerve, which almost always bifurcates as it passes through the supra-orbi- tal foramen ; they are reflected upward ; the external, which is the larger, passes between the frontal muscle and the periosteum ; the internal {h, fig. 285) lies between the muscle and the skin ; they both run somewhat obliquely upward and outward, spread out into ramifications, which diverge from each other at acute angles, and may be traced as far as the lambdoidal suture. Almost all these ramifications are distributed to the skin. Some of them are periosteal, and these require for their proper demonstration that the parts should be macerated in diluted nitric acid : it is doubtful whether any of them ter- minate in the frontal portion of the occipito-frontalis muscle. In some subjects there is a very remarkable osseous frontal branch, which enters an opening in the supra-orbital fo- ramen, and passes along a canal formed in the substance of the frontal bone ; it as- cends vertically like the canal, gives off a succession of small periosteal filaments, and at length, emerging from the canal opposite to the frontal eminence, becomes sub-cutaneous. The Internal Frontal or Supra-trochlear Nerve {s,figs. 296, 301). — This is almost always smaller, but is sometimes as large as the external frontal ; its size appears to me to be inversely proportioned to that of the external nasal and external frontal nerves togeth- er ; it is often divided into two branches ; it passes out of the orbit between the supra- orbital foramen and the pulley of the superior oblique (hence it is called the supra-troch- lear nerve), and divides into ascending or frontal filaments, which ramify in all that portion of the integuments of the forehead which lies between the branches of the right and left external frontal nerves, and into descending or palpebral and nasal filaments, which de- scend vertically ; the former set in the upper eyelid, and the latter upon the dorsum of the nose, where they anastomose with the branches of the nasal nerve.* When there are two internal frontal nerves, the inner one of them enters a fibrous ring formed in the upper part of the puUey for the superior oblique, and divides into pal- pebral and nasal twigs, while the outer one supplies the frontal filaments. This outer nerve sometimes perforates the orbital arch from behind forward in a special canal : I have seen it pass from without inward to enter the frontal sinus, then run along the an- terior wall of the sinus, and finally emerge through a special foramen at the side of the nasal eminence. This nerve gave no branch in the sinus, although it was situated be- tween its anterior wall and the lining membrane. I have seen the frontal nerve divided, from its entrance into the orbit, into four branch- es, of which the two outer ones corresponded to the external frontal, and the two inner ones to the internal frontal nerve. The Nasal Nerve. Dissection. — The orbital portion of this nerve is easily exposed between the optic nerve and the superior rectus. The external nasal branch can also be easily traced upon the frontal region. In order to see the internal nasal branch in the corresponding nasal fos- sa, an antero-posterior vertical section of the head must be made on one side of the sep- tum nasi ; this section will also serve for the demonstration of all the deep nerves of the face. The nasal nerve (above t,fig. 301), which is intermediate in size between the other two branches of the ophthalmic, viz., the frontal and lachrymal nerves, arises from the inner side of the ophthalmic, sometimes even as that nerve is entering the cavernous si- nus ; it is at first applied to the inner side of the ophthalmic nerve, and then to the outer side of the common motor nerve, together with which it enters the orbit, passing be- tween the superior and inferior branches of that nerve. It then runs inward and for- ward, crosses obliquely over the optic nerve, passes below the superior rectus, then be- low the superior oblique, gains the internal wall of the orbit, and divides, near the upper border of the internal rectus, into two branches, named the internal and the external na- sal nerve. Before its entrance into the orbit, the nasal nerve gives off a long and slender filament (sometimes two), which enters the ophthalmic ganglion ; it also furnishes one or more ciliary nerves, which run on the inner side of the optic nerve, and are distributed like the ciliary nerves derived from the ophthalmic ganglion. The external nasal nerve (palpebral, Chauss.). This branch {t,figs. 296, 301) runs for- ward, following the original direction of the nerve below the superior oblique, and emer- ges from the orbit by passing under the cartilaginous pulley for the tendon of that mus- cle (infra-troclilearis nerve, Arnold) ; it is sometimes joined by that division of the fron- tal nerve which 1 have named the fronto-nasal (note, p. 828),t and divides into the fol- lowing branches : palpebral filaments, which run downward and outward in the orbicu- laris palpebrarum, and form anastomotic arches at the free margin of the upper eyelid ; a great number of nasal twigs, which pass upon the dorsum of the nose, and anastomose * [The supra-trochlear nerve supplies filaments to the corrugator supercilii, and to the orbicularis.] t I have seen the external nasal nerve give off a branch which ran inward, anastomosed with the fronto-na- sal, perforated the roof of the orbit, ran for about an inch beneath the dura mater, perforated the frontal bone above and to the outer side of the frontal sinus, and was distributed to the skin upon the forehead. 880 . . NEUROLOGY. with the filaments of the facial nerve, which accompany the angular vein ; and frontal twigs, which anastomose with those of the internal frontal nerve.* The Internal Nasal or Ethmoidal Nerve (u, Jig. 296). — The course of this nerve is very remarkable. It enters the anterior internal orbital canal, which conducts it into the eth- moidal groove, on the internal surface of the basis oranii ;t it is then reflected forward upon the side of liie crista galJi, passes through the ethmoidal fissure into the corre- sponding nasal fossa, becomes sensibly increased in size, and divides into two filaments, an internal, or nerve for the septum, and an external, or naso-lobar nerve. The internal filament, or anterior nerve of the septum nasi {a, fig. 297), enters the fibro- mucous membrane upon the anterior part of the septum, and divides into several very slender filaments, which may be traced below the middle of the septum. The external filament, or nerve of the external wall of the iiasal fossa (w, fig. 299), runs along the anterior border of the septum, and divides into two terminal filaments, one of which passes upon the fore part of the external wall of the nasal fossa, and ramifies upon the turbinated bones ; while the other and larger filament (e, naso-lobaire, Chauss.) fol- lows the original course of the nerve, and passes behind the nasal bone, which is mark- ed with a groove, and frequently even by a canal for the reception of the nerve ; from this latter filament several twigs proceed, which perforate the nasal bone more or less obliquely, and are distributed to the skin of the nose ; having reached the lower border of the nasal bone, it passes forward, increasing in size, through the fibrous tissue which unites the bone to the lateral cartilage of the nose, and then ramifies in the skin cover- ing the ala and lobe of the nose, where I have seen it anastomose with the facial nerve. While within the cavity of the cranium, the internal nasal nerve lies beneath the dura mater, and is perfectly distinct from the olfactory nerve, with which it never anastomoses. The Ophthalmic Ganglion and its Branches.X Dissection. — The ophthalmic ganglion may be exposed in several ways : for example, either in dissecting the branch given by the common motor nerve to the inferior oblique muscle, or directly by removing the adipose tissue between the external rectus and the optic nerve. The long branch from the nasal nerve to the ophthalmic ganglion and the ciliary nerves can also be exposed with the greatest ease. The ophthalmic or ciliary ganglion (behind i, fig. 298) is a small, grayish, and flattened enlargement, of a lenticular form (the lenticular ganglion), applied to the outer side of the optic nerve, and situated about two or three lines from the optic foramen, in the midst of a great quantity of adipose tissue, which renders its dissection difficult. It varies much in size, and sometimes consists of a simple miliary enlargement, which forms a point of origin and termination for a certain number of nerves. For the convenience of description, this ganglion is said to have four angles, two posterior and two anterior ; by its posterior and superior angle it receives a long slender branch {its long root), given off from the nasal nerve while still contained within the cavernous sinus. Not unfre- quently a second long, but extremely slender root, is furnished by the nasal nerve to the ophthalmic ganglion. By its posterior and inferior angle it receives a short, thick branch, which comes from the inferior division of the common motor nerve {its short root). From its two anterior angles it gives off two small bundles of nerves, named the ciliary nerves {i, fig. 298 ; X, fig. 301). Lastly, the ophthalmic ganglion has a ganglionic or soft root, or, rather, a communicating filament, between this ganglion and the superior cervical gan- glion of the sympathetic ; this soft root arises from the cavernous plexus, and passes sometimes to the long or nasal root of the ophthalmic ganglion, and sometimes to the ophthalmic ganglion itself The ciliary nerves are remarkable for their tortuous course, in which respect they re- semble the ciliary arteries ; and also for being collected into two bundles, the one supe- rior, which is generally composed of four filaments, and the other inferior, composed of five or six. The ciliary nerves do not anastomose before they reach the globe of the eye, with the exception, however, of the ciliary nerve, which is derived directly from the nasal nerve, and which anastomoses with an inferior cihary nerve from the ophthal- mic ganglion. Having reached the sclerotic, the ciliary nerves perforate the coat more or less obliquely, around the entrance of the optic nerve, excepting two or three, which enter the globe of the eye near the attachment of the muscle ; after having perforated the sclerotic, they become flattened or riband-shaped, and run forward {a, fig. 242) par- allel to each other, between the sclerotic and the choroid coats, slightly adhering to the former of these membranes, on which grooves exist for their reception ; on approaching the ciliary circle or ligament {b), they bifurcate, and divide into filaments, which anasto- mose with the neighbouring filaments, and appear to be lost in the ciliary circle, which * [It also supplies branches to the lachrymal sac and caruncula, and to the parts of the inner canthus.] t Not unfrequently the internal nasal nerve, while within the ethmoidal groove, gives off a recurrent ner- vous twig, which enters the orbit by a small canal, in front of the anterior internal orbital canal, and anasto- moses wUh the external na-ial or infra-trochlear nerve. I have seen this small nerve anastomose with the fronto-nasal branch, whic^h I have already described (note, p. 828) as an unusual branch of the frontal nerve. i The connexions of the ophthalmic ganglion with the nasal nerve, as well as with the common motor nerve, have induced me to describe it here. SUPERIOR MAXILLARY DIVISION OF THE FIFTH NERVE. . 831 has been, and not without some reason, considered by modern anatomists as a nervous ganglion, ganglion annulare (annulus gangliformis seu ganghon annulare, Sczmmcring). I have seen some of these ciliary nerves pass through the ciliary circle and enter the iris ; they are not distinctly seen to enter the ciliary processes.* The Superior Maxillary Division of the Fifth Merve. Dissection. — Saw through the zygomatic arch, turn down the masseteric muscle, and remove the roof of the orbit ; first dissect tJie lachrymal, malar, and temporal twigs of Jthe orbital branch of the nerve ; then clean out the orbital cavity, remove the upper wall of the zygomatic fossa to reach the spheno-maxillary fossa by means of two cuts joined at an acute angle in the foramen rotundum. Detach the origins of the pterygoid mus- cles ; lastly, trace the nerve into the infra-orbital canal and on the face. The superior maxillary nerve {b,figs. 298, 300, 301), the second or middle division of the fifth nerve, both in position and size, runs forward to enter, after a very short course, the foramen rotundum, by which it is conducted into the spheno-maxillary fossa ; from thence it passes into and traverses the whole length of the infra-orbital canal, where it is named the infra-orbital nerve (/) ; having reached the fore part of that canal, it bends downward, and ramifies in the cheek. It is plexiform at its origin and in the foramen rotundum, but is fasciculated throughout the rest of its course. Its collateral branches, taken in the order of their origin, are the orbital nerve ; certain nerves which are given off from the enlargement called Meckel's ganglion, namely, the palatine, spheno-palatine, and vidian or pterygoid nerves ; the posterior dental nerves, and the anterior dental nerve ; lastly, several small filaments come off either from the ganglion of Meckel or from the superior maxillary nerve itself, and, surrounding the in- ternal maxillary artery, assist in the formation of its plexus. The Orbital Nerve. This branch {t,fig. 300) comes off immediately in front of the foramen rotundum, from the upper side of the superior maxillary nerve, passes through the spheno-maxillary fis- sure, along which it proceeds to enter the orbit ; it then runs along the floor of the orbit, and divides into two branches : the one ascending, the lachrymal branch of the orbital nerve, which enters the lower surface of the lachrymal gland, anastomoses with the lachrymal branch (s) of the ophthalmic nerve (a), and sends off some branches to the upper eyelid, near its external angle ; the other branch is the temporo-malar, which pass- es horizontaOy forward, enters a small canal in the malar bone, and subdivides into a malar filament, which perforates the bone, and is distributed to the skin upon the malar region,! and a temporal filament, which perforates the orbital portion of the malar bone, and dips into the anterior part of the temporal muscle, in which it anastomoses with the anterior deep temporal nerve, a branch of the inferior maxillary. I have sometimes seen two temporal filaments pass through the malar bone at two different points. J The Spheno-palatine Ganglion and its Branches. After having given off the orbital nerve, and while it is still contained in the spheno- maxillary fossa, the superior maxillary nerve gives off from its lower side a thick branch, frequently two, and occasionally several branches, from which a great number of diver- ging nerves immediately proceed ; these are the three palatine nerves, the spheno-pala- tine nerves, and the vidian nerve ; at the point where these nerves diverge is found an enlargement which the elder Meckel,^ whose name is connected with the description of the fifth pair, regarded as a ganglion, and which is, therefore, called Meckel's ganglion, or the spheno-palatine ganglion (situated before s,fig. 299 ; below b,fig. 301). In a certain number of cases, I have sought in vain for the ganglionic structure in this enlargement, i. e., for gray matter with white filaments scattered through it. It appear- ed then to be nothing more than the common trunk or starting-point of a great number of nerves ; in the majority of cases, however, a quantity of gray matter certainly exists, but is so arranged that the nerves may generally be traced quite through the enlarge- ment, so that they clearly are not given off from the ganglion itself, but come directly from the superior maxillary nerve. II * Tiedemann, from the results of observations in comparative anatomy, believes that the arteries which ram- ify in the retina are accompanied by very delicate nervous filaments, derived from the ophthalmic gang-lion and the ciliary nerves : he has seen a nen-ous filament penetrate the optic nerve with the arteria centralis retinie ; and he states that the ciliary arteries are accompanied by very delicate nervous filaments, which he has tra- ced into the retina as far as the zone of Zinn. Tiedemann also says that he has seen, only once, it is true, a rather large nervous filament proceed from Meckel's g-ang-lion, aiid join the thick and short branch which is given off from the third pair to assist m the formation of the ophthalmic g-ano-lion. t It IS said that this twig- anastomoses with the facial nerve in the malar region ; I have never been fortu- nate enough to discover this anastomosis. t [Both of these temporal filaments maybe joined by communicating twigs from the lachrymal nerve within the orbit ; one of them anastomoses with the anterior deep temporal nerve, as al)ove mentioned ; the other, having entered the temporal fossa through the malar bone, ascends on the temporal surface of that bone, turns outward, perforates the temporal fascia about an inch above the zygoma, anastomoses with filaments of the facial nerve, and of the auriculo-temporal brunch of the inferior maxillary nerve, and is lost in the skin on the temple.] "iti! the canine fossa with a filament from the anterior dental nerve. The posterior and inferior dental nerve, which is larger than the preceding, runs in a curved direction below the malar eminence, the concavity of the curve being directed upward, and anastomoses with the posterior and superior dental nerve, on a level with the canine fossa. No filament is given off from the upper side of these nerves, but they give off a great number of filaments downward, which anastomose, and form a series of very remarkable meshes or areolae ; these meshes, and the dental nerve which come from them, are situated within the substance of the bone, but are much nearer to the sinus than to the outer surface of the bone. It is from these meshes that the extremely delicate filaments arise which form the dental nerves of the molars and bicuspids ; their number corresponds to that of the fangs of these teeth.* Some filaments evidently terminate in the substance of the superior maxillary bone ; no other bone in the body has so large a number of proper filaments. The Anterior Dental Nerve. The anterior dental or alveolo-dental nerve {j,fig. 298) is the only branch given off by the superior maxillary nerve wViile within the infra-orbital canal ;t it arises about five or six lines from the anterior orifice of that passage. It is so large that it may be regarded as resulting from the bifurcation of tiie infra-orbital nerve. It soon enters a special ca- nal formed for it in the superior maxillary bone, gives off on the outer side a small branch which anastomoses with the posterior and superior dental nerve, passes at first horizontally inward, and then vertically dowmvard, turning round the margin of the an- terior opening of the corresponding nasal fossa, and is reflected upon the floor of that fossa ; during the whole of this course, it is situated within the substance of the superiw maxillary bone ; its horizontal portion is superficial, and ns vertical portion is deep- seated, having merely a thin bony lamella between it and the pituitary membrane. Having arrived on a level with the floor of the nasal fossa, about two lines from its an- terior opening, it expands into a great number of ascending and descending filaments; the ascending filaments are reflected upward within the anterior nasal spine, where they ter- minate. They appear to me to send off a small ramification to the pituitary membrane. The descending filaments terminate by supplying the dental nerves for the incisor, canine, and first bicuspid teeth. A great number of filaments are also lost in the substance of the bone. I have never seen any filaments from the dental nerves entering the membrane of the maxillary sinus. The Terminal Branches of the Superior Maxillary Nerve. Having reached the anterior orifice of the infra-orbital canal, the superior maxillary nerve, the component bundles of which had been merely in juxtaposition, immediately expands {i,fig- 301) into a pencil of diverging filaments beneath the levator labii supe- Tioris. These filaments (i, fig. 285) may be divided into ascending or palpebral, which pass upward and outward beneath the orbicularis palpebrarum, and are distributed to the skin and conjunctiva of the lower eyelid ; a great number of internal or nasal filaments, which run upon the side of the nose, and are distributed to the skin of that organ ; one of them runs along beneath the septum ; and, lastly, into descending or labial filaments, which are the most numerous, and which enter the substance of the upper lip, and are distributed to the skin and the mucous membrane : all these filaments, and especially the labial, interlace and anastomose with the facial nerve, so as to form a plexus, named the infra-orbital, to which we shah return in describing the facial nerve. I have seen the nasal and the palpebral filaments arise together from the superior max- illary nerve, before it had given off the anterior dental, enter a special canal situated on the inner side of the infra-orbital canal, emerge opposite the line of demarcation between the cheek and the nose, and then expand into their nasal and palpebral divisions ; while the labial filaments had their usual arrangement. The Inferior Maxillary Division of the Fifth JVerve. Dissection. — As this nerve must be examined both upon its internal and its external aspect, it must be dissected in both directions. An antero-posterior section of the head in the median line will enable us to see, on the internal surface of the nerve, the chorda tympani, the otic ganglion, and the origins of all the other branches which come from the inner side of the inferior maxillary nerve, viz., the nerve of the internal pterygoid, the lingual nerve, and the dental nerve. In order to see the distribution of the deep temporal, the masseteric, the buccal, the internal pterygoid, and the auriculo-teniporal nerves, the inferior maxillary nerve must be exposed from its outer side, by breaking down the zygomatic arch, reflecting down the masseter, which is to be detached as far * In those molar teeth whirh have two or three roots, the nervous filaments subdivide and anastomose with each other in the substance of the dental pulp. t Sometimes, however, I have seen the posterior and superior dental nen-e arise within the infra-orbital canal. THE DEE? TEMPORAL NEUVE, ETC. 835 back as the sigmoid notch, hy sawing through the base of the coronoid process, and turning the temporal muscle upward, and then by carefully dividing the external ptery- goid muscle, through which the buccal nerve passes. The inferior maxillary nerve {c,Jigs. 296, &c.), the most posterior and the largest di- vision of the fifth nerve, passes outward and a little forward, and, after a very short course within the cranium, escapes through the foramen ovale into. the zygomatic fossa, where it divides successively into seven branches. The non-ganglionic root {b, Jig. 299) of the fifth nerve is connected exclusively with the inferior maxillary division (c) of its other root, beneath which it lies, from which it can be distinguished by not having a plexiform structure, with which it is not blended until it emerges from the foramen ovale. Of the seven branches of the inferior maxillary nerve, three are external, namely, the an- terior and posterior deep temporal, the masseteric, and the buccal ; one is posterior, name- ly, the auriculo-temporal ; one is internal, the internal pterygoid ; and two are inferior, the lingual or gustatory, and the inferior dental. These nerves may also be divided into col- lateral branches, including the first five, and the terminal branches, namely, the lingual and the inferior dental ; the otic ganglion, described by Arnold, is connected with this nerve.* The Collateral Branches of the Inferior Maxillary Nerve. The Deep Temporal Nerve. The first external branch, or the deep temporal nerve, arises from the outer side of the inferior maxillary nerve, passes horizontally outward and forward between the roof of the zygomatic fossa, with which it is in contact, and the eternal pterygoid muscle. Having arrived at the ridge which separates the temporal from the zygomatic fossa, it anasto- moses with several temporal branches derived from the buccal and masseteric nerves, and forms a sort of plexus with them. The branches which emerge from this plexus ascend vertically in the deep layers of the temporal muscle, in which most of them ter- minate. Some twigs anastomose with the temporal filaments derived from the lachrymal branch of the ophthalmic nerve, and from the orbital branch of the superior maxillary nerve. t One and sometimes two filaments perforate the temporal fascia, about a finger's breadth above the zygomatic arch, and then ascend beneath the skin, to anastomose with the auriculo-temporal and the facial nerves. t The Masseteric Nerve. The second external branch, or the masseteric nerve, arises from the same point as the last nerve, and greatly exceeds it in size ; it comes off at an acute angle, passes horizon- tally backward and outward in contact with the roof of the zygomatic fossa, between it and the external pterygoid muscle ; it is then reflected downward over the upper part of that muscle to gain the sigmoid notch of the lower jaw, upon which it is again reflected, and then descends vertically, between the ramus of the jaw and the masseter, or, rather, in the substance of the deep layersof that muscle, down to the insertion of which it may be traced. During its course along the upper wall of the zygomatic fossa, the masse- teric nerve gives off a small, deep temporal branch, which runs along the periosteum, passes into the temporal fossa, and sends off an articular branch to the temporo-max- illary articulation. The Buccal or Bucco-labial Nerve. The^-hird external branch {g, Jig. 300), the buccal, or, rather, the bucco-labial nerve {Chauss.}, is very remarkable on account of its size and the extent of its distribution, which gives it some resemblance to the corresponding portion of the facial nerve. It arises from the outer side of the inferior maxillary nerve, by one, two, and sometimes three roots, which perforate the external pterygoid, and join together as they emerge from that muscle ; from thence it runs downward between the coronoid process of the lower jaw and the tuberosity of the upper jaw, gives several twigs to the external pterygoid muscle, and also some branches to the temporal muscle, of which one ascends and an- astomoses with the deep temporal nerve, while another descends and is distributed to the same muscle, near its insertion into the coronoid process ; the buccal nerve itself sometimes perforates the lowest part of the insertion of the temporal muscle, and having reached the back part of the buccinator, it expands into a great number of diverging branches, like the facial nerve. The ascending branches are distributed to the skin of the malar and buccal regions ; one of them forms an anastomic arch with the facial nerve behind the duct of Steno. This anastomosis is very remarkable. The middle branches pass horizontally forward on a level with the commissure of the lips, and terminate in the skin ; several o.*" them form a sort of plexus around the inferior coronary artery of the lip. The lowest of the descending branches pass vertically downward, and even a little backward, unon the outer surface of the buccinator, also beneath the deep surface and upon the outer surface of * We sometimes find a communicating: filament between the superior and inferior maxillary nerves imme- diately before they enter their respective foramina. t [There is hence a communication between the branches of the three divisions of the fifth nerve.] % [This cutaneous filament is one of the temporal filaments of the orbital branch of the superior maxillary nerve, — (.Ellis's Demonstrations ; see note, p. 831.)] 836 NEUROLOGY. the triangularis oris, and are entirely lost either in the skin or in the mucous membrane. It is doubtful whether the buccal nerve partially terminates in the orbicularis oris, the triangularis oris, and the zygomaticus major. All the filaments which enter these mus- cles, and which appear at first sight to terminate in their substance, pass through them to supply the mucous membrane ; their branches anastomose with the mental nerve be- neath the triangularis oris ; several filaments are lost in the buccinator. The Internal Pterygoid Nerve. The internal collateral branch {t, fig. 299), or nerve for the internal pterygoid muscle, which is very slender, comes off from the inner side of the inferior maxillary nerve in contact with a grayish body, named the otic ganglion, runs downward and inward along the inner surface of the internal pterygoid muscle, and ramifies in it. The Auriculo-temporal Nerve. The posterior collateral branch, or the auriculo-temporal nerve (the auricular or superfir cial temporal nerve of authors), is very large, flattened, and plexiform at its origin (be- hind c, fig. 298 ; r, fig. 299) ; it sometimes arises by a great number of distinct roots ; it passes backward and a little downward behind the neck of the condyle of the lower jaw, and divides into two branches, a superior or ascending, and an inferior or dcscendiitg branch. The superior or ascending branch, the superficial temporal nerve, turns round the back of the neck of the condyle, and ascends vertically between the articulation and the ex- ternal auditory meatus ; having become sub-cutaneous, it divides into several filaments (r, fig 285), which may be traced up to the highest part of the temporal fassa. During its course this nerve gives off a very remarkable anastomotic branch, which arises behind the neck of the condyle, and is reflected upon it so as to run forward be- neath the facial nerve, with which it is blended opposite to the posterior border of the masseter. This anastomotic branch is sometimes double. It may be regarded as one of the origins of the facial nerve, which increases considerably in size after having re- ceived it. This branch is one of the principal communications between the facial nerve and the fifth nerve, and modern physiologists have justly attached great importance to it. The ascending branch also gives off some plexiform branches to the temporo-max- illary articulation, and several filaments to the auditory meatus and the auricle. In the temporal region it anastomoses with a very small filament, which is derived from the deep temporal nerve, and which perforates the temporal fascia.* It accompanies the temporal artery, for which it forms a sort of plexus, and then di- vides into cutaneous filaments, which reach the crown of the head. The inferior, descending, or auricular branch is as large as the preceding ; it forms a plexus around the internal maxillary artery, behind the condyle, and sometimes presents small ganglia ; it divides into several branches, some of which pass through the parotid gland and are distributed to the lobe of the ear, while the others anastomose with some filaments of the auricularis magnus nerve derived from the cervical plexus. One of these branches joins the dental nerve, before that nerve enters the dental canal ; an- other branch terminates in the temporo- maxillary articulation. The Terminal Branches of the Inferior Maxillary Nerve. The Lingual Nerve. The lingual or gustatory nerve {7i,figs. 298, 300; n n', fig. 301) passes downward and Fig. 300. forward : it is at first situated between the exter- nal pterygoid muscle and the pharynx, but it soon passes between the two pterygoids {fig. 300), then between the internal pterygoid and the ramus of the lower jaw {fig. 298), and then runs forward along the upper border of the sub-maxillary gland, between it and the buccal mucous membrane, and above the mylo-hyoid muscle ; it then passes be- neath the sub-lingual gland, which it crosses, to pass to its inner side, and, accompanied by the Warthonian duct, which lies to its inner side and crosses it at a very acute angle, it gains the corre- sponding border of the tongue, and ramifies in the substance of that organ. During its passage between the two pterygoids the hngual nerve is joined by that branch of the fa- cial nerve which is known as the chorda tympani {x, fig. 298), and which unites to it behind, forming a very acute angle opening upward ; this branch of the facial, which may be regarded as one of the roots * tThis perforating cutaneous filament is one of tKe temporal filaments of the orbital branch of the superior maxillary nerve (see notes, p. 831,835).] THE INFERIOR DENTAL NERVE, ETC. 837 of the lingual, remains in contact with that nerve for some time, and is at last blended with it. The lingual nerve also receives, sometimes before, and sometimes after being joined by the chorda tympani, a very considerable anastomotic branch from the inferior dental : this branch is rarely wanting. After receiving these two branches, the lingual nerve becomes considerably increased in size, and during its course gives off several filaments to the tonsils, the mucous mem- brane of the cheeks and the gums. Opposite the sub-maxillary gland, the lingual nerve presents a very remarkable gan- glion, generally described as the sub-maxillary ganglion (situated behind x, fig. 300) ; the trunk of the nerve does not enter into its formation, but it appears to be formed only by its inferior filaments. It has been gratuitously supposed that this ganglion is formed exclusively by the chorda tympani, which, according to such a view, after running in mere contact with the lingual nerve, becomes detached from it (opposite n) to enter the ganglion (z) : we have stated that there was equally little reason to suppose that the chorda tympani was the continuation of the cranial branch of the vidian. The sub-max- illary ganglion, the size of which is very variable, gives off a great number of filaments, most of which are distributed to the sub-maxillary gland ; one of these filaments accom- panies the Warthonian duct. Having reached the sub-hngual gland, the lingual nerve supplies that gland with a great number of filaments, which dip into it and form a plexus of very delicate meshes. In the tongue, the lingual nerve is situated at the lateral border of that organ, and on a plane above that of the hypoglossal nerve, with which it communicates by an anasto- motic branch, forming a loop. It becomes gradually diminished in size by giving off a very numerous series of filaments {n',fig. 301), which turn round the border of the tongue, pass forward and upward, perforate the muscles of that organ, and spread out into pen- cils, the filaments of which may be traced into the papillae of the mucous membrane. The nerve, reduced to a single filament, terminates at the point of the tongue The Inferior Dental Nerve. The inferior dental nerve (m, fig. 298), larger* than the lingual, descends with it, at first between the two pterygoid muscles, and then between the internal pterygoid and the ra- mus of the lower jaw : in this situation it is kept in contact with the bone by a layer of fibrous tissue, which is improperly called the internal ligament of the temporo-maxiliary articulation, and which separates the nerve from the lingual nerve and the internal pter- ygoid muscle ; it soon enters the dental canal, which it traverses (m) throughout its entire extent, accompanied by the inferior dental artery, and protected by a fibrous ca- nal ; during its course it supplies the molar and the bicuspid teeth, giving a twig to each prong, and having reached the mental foramen, divides into a mental and an incisor branch. The Myloid Branch. — As it enters the inferior dental canal, the nerve gives offa small branch, the myloid branch {z, fig. 300), which arises from its posterior border, opposite the corresponding artery, is received into a furrow upon the inner surface of the ramus of the jaw, against which it is retained by a layer of fibrous tissue, and then, emerging from this furrow, passes upon the upper surface of the mylo-hyoid muscle, in which it ramifies. A great number of filaments from the myloid nerve enter the anterior belly of the digastric muscle. t The mental branch {t, fig. 285), the continuation of the inferior dental nerve, as far as size is concerned, passes through the mental foramen, and expands into diverging fila- ments, which are distributed, in reference to the lower lip, in the same way as the infra- orbital branch is to the upper lip. These filaments interlace with the facial nerve, and form with it a sort of mental plexus ; they are intended for the skin and the mucous membrane of the lower lip : most of them pass to the free border of that lip. The incisor dental branch, which is extremely small, continues in the original course of the inferior dental nerve, and subdivides to supply the canine and two corresponding incisor teeth. The inferior dental nerve represents in the lower jaw the infra-orbital portion of the superior maxillary nerve in the upper jaw. The Otic Ganglion. I cannot terminate the description of the inferior maxillary nerve without noticing a ganglion recently described by Arnold, under the name of the otic ganglion, which he compares to the ophthalmic ganglion, and which has served him as the basis of an inge- nious theory respecting the nerves of the head. The following is the position of the ganglion, as indicated by Arnold : "The otic ganglion is situated (behind I, fig. 299) im- mediately below the foramen ovale, on the inner side of the third or inferior maxillary * I have observed that this nerve v^as much smaller in old than in young- subjects. t [Filaments are also given to the sub-maxillary gland ; according to Ellis, some branches pass through the mylo-hyoid muscle and enter the genio-hyoid ; and it is stated by Alcock that a branch reaches the de- pressor labii inferioris.] 838 NEUROLOGY. division (c) of the fifth nerve, a httle above the origin of the superficial temporal or au- ricular nerve (auriculo-temporal), at the spot where the inferior maxillary nerve gives off from its external surface the deep temporal and buccal nerves, and where the small root of the fifth unites intimately with the large root. On the inner side, this ganglion is covered by the cartilaginous portion of the Eustachian tube, and by the origin of the ex- ternal peristaphyline {circumflexus palati) muscle ; behind, it is in contact with the mid- dle meningeal artery. Its external surface rests upon the inner side of the inferior max- illary nerve." There can be no doubt that in the situation indicated by Arnold, there is a thin and not very well-defined layer of reddish, pulpy tissue, placed upon the inner side of the in- ternal pterygoid nerve, and which presents the chief characters of ganglionic tissue ; for it is traversed by nervous filaments, which proceed from it as from a centre, and run in various directions. Its connexions with the inferior maxillary nerve are effected by its direct adhesion to that nerve, which adhesion, according to Arnold, takes place by means of several very short, nervous filaments {short root), which appear to come from the small root of the fifth pair, and also by its adhesion to the internal pterygoid nerve ; so that, at first sight, the ganglion would appear to originate from that nerve, or the nerve from the ganglion. The otic ganglion is also connected with the glosso-pharyngeal by means of a filament, which Arnold describes under the name of the small superficial petrosal nerve, to distin- guish it from the great superficial petrosal, or cranial branch of the vidian. This fila- ment, which proceeds from the nerve of Jacobson, or tympanic branch of the glosso-pha- ryngeal, is compared by Arnold to the long root of the ophthalmic ganglion : it passes out of the cavity of the tympanum by a special canal, in front of the hiatus Fallopii, runs forward and outward (from 7 towards c, fig. 296), emerges from the cranium through a special foramen, between the petrous portion of the temporal bone and the spinous pro- cess of the sphenoid, and proceeds (above I, fig. 300) to enter the otic ganglion.* Ar- nold admits a third root for the otic ganglion, namely, a soft root, which he traces from the nervous plexus that surrounds the middle meningeal artery, and is derived from the great sympathetic. The preceding filaments may be regarded as the filaments of origin of the otic gan- glion.! The Branches which proceed from the Otic Ganglion. — The principal filament from the otic ganglion runs backward and upward towards the canal v/hich contains the internal muscle of the malleus, and is lost in that muscle. This twig must be carefully distin- guished from the small superficial petrosal nerve, which is placed above it. Some other filaments join the auriculo-temporal nerve, which generally arises by two roots. Lastly, the otic ganglion sends off a twig to the circumflexus palati muscle. The Sixth Pair, or External Motor Nerves of the Eyes. The very simple distribution of the external motor nerve of the eye, or sixth crania! nerve, contrasts strongly with that of the fifth nerve ; it arises from the furrow between the pons Varolii and the medulla oblongata, immediately forms two fasciculi or roots, a large and a small, which unite in the cavernous sinus ; they pass vertically upward, per- forate the dura mater (6, fig. 296) at the side of the basilar groove by one or two open- ings, to the inner side of and below the fifth nerve, gain the apex of the petrous portion of the temporal bone, over which they turn, and then pass horizontally forward to enter the cavernous sinus. During the course of the nerve through that sinus, it rests upon its lower wall, crosses (above G,fig. 301) on the outer side of the vertical portion of the internal carotid artery, around which it turns, and then runs along its horizontal portion. The sixth nerve forms a most important anastomosis, on account of which it was for a long time regarded as the origin of the great sympathetic. As it crosses the internal carotid in the cavernous sinus, it communicates by one or two filaments with the supe- rior cervical ganglion. It also communicates, at the same point, with the ophthalmic division of the fifth nerve. Lastly, it enters the orbit through the widest part of the sphenoidal fissure, passes through the fibrous ring which is common to it and to the inferior division of the com- mon motor nerve, crosses, at an acute angle, beneath the ophthalmic nerve, and gains the inner surface of the external rectus, and penetrates that muscle, after having ex- panded into a pencil of very delicate filaments. We shall again advert to the communication between this nerve and the superior cer- vical ganglion. * This small superficial petrosal nerve is very distinct from the great superficial petrosal nerve, being- situ- ated in front of and parallel to that nerve. In a saliject which I dissected in 182fi, 1 found this small nerve presenting the following peculiarity : it had a well-marked nodule or ganglion, which g;ive off a filament to the midd'e meningeal artery, and some small twigs, which appeared to me to be lust in the substance of the sphenoid bone ; but I did not discover the connexions of this nerve. t Arnold admits an indirect communication between the otic ganglion and the acoustic ner%'e through the intervention of the facial nerve. The existence of this communication appears to me very doubtful, as well as the communication of the otic ganglion with the great sympathetic, by means of Lhe twigs on the middls meningeal artery. THE FACIAL KERVE. 839 The Seventh Pair of Nerves The Portio Dura, or the Facial J^erve. We have already traced the facial nerve, or the portio dura of the seventh, from its ori- gin to the internal auditory meatus, which it enters together with the auditory nerve (7, Jig. 296), which nerve lies below and behind the facial, and forms a groove for its recep- tion. Having reached the bottom of the internal auditory meatus, this nerve follows the long course of the facial canal,* or aqueduct of Fallopius, a winding passage which is formed in the petrous portion of the temporal bone, and which opens by one end into the internal auditory meatus, and, by the other, upon the lower surface of the pars petrosa at the stylo-mastoid foramen. The facial nerve traverses this canal, which is exclusively appropriated to it ; it is at first directed outward '{n,fig. 296), and, after proceeding for about a line, bends sudden- ly, and runs backward, in the substance of the internal wall of the cavity of the tympa- num, above the fenestra ovalis. Having reached the back of the tympanum, it forms another bend, and passes vertically downward (o, figs. 298, 300) to the stylo-mastoid fo- ramen. It follows, therefore, that the facial nerve describes two curves, like the aque- duct of Fallopius, and is horizontal in its first two portions and vertical in the third. On emerging from the stylo-mastoid foramen, the facial nerve runs forward in the substance of the parotid gland, and, after a course of about five or six lines, divides into two terminal branches, the temporo-facial [g, fig. 285) and the'cervico-facial (/), which expand into a great number of diverging filaments, and cover the temples, the whole of the face, and the upper part of the neck, with their radiations and anastomoses. The facial nerve gives off and receives certain collateral branches before and others after its exit from the stylo-mastoid foramen. The Collateral Branches of the Facial Nerve, before its Exit from the Stylo-mastoid Foramen. In the internal auditory meatus the facial nerve receives some twigs from the auditory, a remarkable anastomosis, which deserves the attention of physiologists. Opposite to the hiatus Fallopii, i. e., at the first bend formed by the Fallopian aque- duct, the facial nerve is joined by the cranial branch of the vidian, or the great super- ficial petrosal nerve {v, figs. 296, 300). According to MM. Ribes, Hippolyte Cloquet, and Hirzel, this branch is applied to the facial nerve, but does not anastomose with it, and is detached from it lower down to constitute the chorda tympani nerve ; and as the cranial branch of the vidian arises from the spheno-palatine ganglion, and the chorda tympani is supposed to enter the sub-maxillary ganglion, it is seen that, according to this view, the cranial branch of the vidian and the chorda tympani, which is regarded as its prolongation, would establish a communication between the spheno-palatine and sub-maxillary gangha. It is by no means proved, however, that the chorda tympani en- ters the sub-maxillary ganglion ; and, again, the supposed connexion between the cra- nial branch of the vidian and the chorda tympani is opposed to facts. The cranial branch of the vidian and the facial nerves, indeed, are not in mere juxtaposition, but anastomose and are blended with each other, and the chorda tympani has no sort of re- lation to the former of these nerves. This independence of the branch of the vidian nerve and the chorda tympani can be most clearly seen when the parts have been ma- cerated in diluted nitric acid.t If an explanation must be given of this remarkable anastomosis between the vidian and facial nerves, I would say that the cranial branch of the vidian may be regarded as a remote origin or a re-enforcing branch of the facial nerve. The facial nerve, according to Soemmering and those who have followed him, gives off a twig to the internal muscle of the malleus, and another to the small muscle of the stapes ; but, in the first place, the existence of a stapedius muscle is doubtful, and, con- sequently, the existence of a corresponding nervous twig must also be so, and, in the second place, the internal muscle of the malleus is not supplied from the facial nerve, but from the inferior maxillary division of the fifth nerve, and more especially from that pulpy, reddish tissue, named by Arnold the otic ganglion. Before leaving the aqueduct of Fallopius, the facial nerve {n,fig. 296) gives a remark- able filament, named the chorda tympani, which pursues a recurrent course (y) from be- low upward in a peculiar canal, parallel to the aqueduct of Fallopius, enters the cavity of the tympanum through an opening to the inner side of and behind the attachment of the membrana tympani, passes downward and forward through the cavity of the tym- * For what purpose is this long; coarse within the petrous portion of the temporal bone ? Those physiolo- gists who believe the facial nerve to be of a mixed nature, that is, both sensory and motor, have laid great stress upon this point, which they conceive to be favourable to their views ; but there is not the slightest shadow of a proof that the facial nerve possesses these two properties. t Arnold has pointed out, at the junction of the cranial branch of the vidian with the facial nerve, a gangli- form swelling, vvhich he regards as a transition between a gangliform enlargement and a true ganglion ; from this swelling, which he compares to the ganglia of the posterior roots of the spinal nerves, he says a filament is given off to anastomose with the auditory nerve at the bottom of the internal auditory meatus. I have not been fortunate enough to discover this filament ; nor have I ever seen any gangliform appearance at the junc- tion of the vidian and facial nerves. 840 NEUROLOGY. panum, between the handle of the malleus and the vertical ramus of the incus, and emerging from that cavity {x, fig. 298), not through the Glasserian fissure, but through a special opening already described ^see Organ of Hearing — Cavity of the Tympanum), is applied to the lingual nerve (m), of which it may be regarded as a late origin, or re-enfor- cing branch. The facial branch also receives, in the aqueduct of Fallopius, opposite to where it gives off the chorda tympani, a very remarkable branch from the pneumogastric nerve, which Arnold has named the auricular branch of the pneumogastric. The Collateral Branches of the Facial Nerve, after its Exit from the Stylo-mastoid Foramen. Before its terminal division, the facial nerve gives off two branches, the posterior auricular and the styloid. I have never seen any parotid branch, properly so called. The posterior auricular, which would be better named the auriculo-occipital, comes off from the nerve within the stylo-mastoid foramen, and is immediately applied against the: mastoid process, turning round over its anterior and then its outer surface ;* as it lies ia front of the mastoid process, it anastomoses with a remarkable twig from the deep auric- ular branch of the auricularis magnus from the cervical plexus ;t after this, it divides into two branches : an ascending or auricular branch (m, fig. 299), properly so called, which, having first supplied, then perforates the posterior auricular muscle, turns round the auricle, and terminates in the superior auricular muscle ; and a horizontal or occipital branch (», fig. 285), which is larger, and forms the continuation of the nerve ; it passes immediately beneath the posterior auricular muscle, to which it gives some filaments, then runs exactly along the superior semicircular line of the occipital bone, and termi- nates by giving off from its upper side a series of small filaments, which are lost in the occipital portion of the occipito-frontalis : they can be traced as far as the median line, but none of them are distributed to the skin. The styloid branch arises from the back of the facial nerve, at its exit from the stylo- mastoid foramen, and enters the stylo-hyoid muscle, after having run along its upper border. The posterior mastoid or digastric branch often arises by a common trunk with the pre- ceding, -enters the posterior belly of the digastric muscle, and sends off an anastomotic twig to the glosso-pharyngeal nerve. The Terminal Branches of the Facial Nerve. The Temporo-facial Nerve. The temporofacial nerve {g, fig. 285) passes upward and forward in the substance of the parotid, forming, with the trunk of the facial nerve, an arch having its concavity turned upward ; it crosses the neck of the condyle of the lower jaw, and receives in this situation, by its deep surface, one, or sometimes two branches from the auriculo-tempo- ral nerve, a branch of the inferior maxillary. This anastomotic branch establishes a very important connexion between the fifth and facial nerves. The temporo-facial nerve, which is flattened and plexiform where it is joined by the branch from the fifth, afterward expands into a number of filaments, which anastomose with each other, so as to form arches, from the convexity of which a number of diverging filaments of unequal size proceed like rays, and cover the whole space comprised be- tween a vertical line drawn in front of the ear, and a horizontal line corresponding to the base of the nose. All these branches, which anastomose several times with each other, and form a suc- cession of arches somewhat resembling those of the mesenteric arteries, may be divided into the temporal, the orbital, and the infra-orbital or buccal branches. The temporal branches ascend, cross over the zygomatic arch at right angles, and cov- er with their ramifications the whole of the temporal and frontal regions, anastomosing with filaments from the frontal branch of the first [from the orbital branch of the second], and from the auriculo-temporal branch of the third division of the fifth nerve. All these branches lie between the skin and the temporal aponeuroses : some of them supply the skin, but the majority are distributed to the frontal portion of the occipito- frontalis muscle, below which they are situated, and may be traced as far as the median line. The orbital branches may be divided into the superior palpebral, which are remarkably long, and pass beneath the orbicularis palpebrarum, to ramify in that muscle and the corrugator supercilii. Several of these anastomose with twigs from the supra-orbital nerve : the middle palpebral branches, which gain the outer angle of the eyelids, and are distributed between the upper and lower eyelids, and the superior palpebral branches^ which are generally named the malar branches ; they pass horizontally forward, opposite to the lower part of the orbicularis palpebrarum, and are reflected upward, to enter the * This little nerve is lodged in the furrow between the mastoid and vaginal processes (see Osteology, p. 43). t [It is also joined, according to Arnold, by a filament from the auricular branch of the pneumogastric (see note, p. 844). THE CERVICO-FACIAL NERVE. 841 substance of the lower eyelid, between tlie palpebral aponeurosis and the palpebral por- tion of the orbicularis, in which they terminate. They may be traced as far as the free border of the tarsal cartilage, where they anas- tomose with each other. The infra-orbital or buccal branches of the temporo-facial are given off from one or two large branches which accompany the Stenonian duct ; they expand into a great number of filaments, which may be divided into a superficial and a deep set : the superficial, branch- es run beneath the skin, and above the orbicularis oris, the two zygomatic, and the le- vator labii superioris, all of which they supply ; there can be no doubt that they also give cutaneous filaments ; these are very small, and very long, and may be followed as far as the hair follicles in the upper lip ; some of these superficial branches reach the lower eyelid, several accompany the facial and angular veins, anastomose with twigs- from the infra-trochlear branch of the nasal nerve, and ascend as far as the pyramidally nasi, in which they terminate. The deep branches pass beneath the levator labii superioris, send off numerous fila- ments to that and the levator anguli oris, and form, together with the terminal divisions of the infra-orbital branch of the superior maxillary, a very remarkable plexus, which may be called the infra-orbital. This plexus is formed by the interlacement of the radiating branches of the facial nerve with those of the infra-orbital branch of the superior maxillary division of the fifth nerve. Now, as the facial nerve radiates from without inward, and the infra-orbital from above downward, it follows that the branches of these two nerves meet each other at right angles. This arrangement can be rendered more evident by pulling the two sets of nerves in the direction of their length. Most of these branches interlace with- out anastomosing, and proceed directly to their destination. The destination of the facial nerve is evidently rather to the muscles than to the skin ; that of the infra-orbital branch of the fifth nerve is rather to the skin and mucous membrane than to the mus- cles ; nevertheless, it cannot be doubted that the facial nerve supplies some cutaneous filaments, and that the fifth nerve gives some twigs to the muscles. Besides, there are some undoubted anastomoses between these two nerves. The facial also communicates very freely with the buccal nerve, a branch of the inferior maxillary. The infra-orbital branches of the temporo-facial nerve supply the two zygomatics, the levator labii superioris, the levator labii superioris alaeque nasi, the depressor ala? nasi, the transversalis nasi, the levator anguli oris, and the orbicularis oris. I would also point out a very remarkable branch, which enters the substance of the ala of the nose, and appears to be intended for that sort of sphincter muscle found in the cutaneous fold of the alae. This branch anastomoses with the naso-lobar branch of the internal nasal nerve. The infra-orbital branches of the fifth nerve are distinguished from the infra-orbital branches of the facial nerve, by their direction ; by being more deeply seated ; by being much larger ; and by being arranged in successive layers, which are three in number : a sub-cutaneous, a sub-mucous, and a muscular ; this last set perforates the orbicularis oris, in which some filaments appear to terminate. Among the infra-orbital branches of the fifth nerve, there is one which may be called the nerve of the sub-septum, which runs on the side of the median line, as far as the tip of the nose, where it terminates. Lastly, the infra-orbital branches of the fifth give a dorsal branch for the nose, and two ascending palpebral branches, which can be easily distinguished from the palpebral branches of the facial nerve. The Cervico- facial Nerve. The cervico-facial nerve (/, fig. 285), which is smaller than the temporo-facial, follows the original course of the facial nerve, and, like it, runs downward and forward in the parotid gland ; opposite to the angle of the lower jaw it divides into three or four branch- es, which subdivide into secondary branches, which may be arranged into the buccal, men- tal, and cervical sets. The buccal branches run horizontally forward in front of the masseter, to which they give off some small filaments, and then anastomose with each other and with the infra- orbital branches of the temporo-facial nerve. A very beautiful anastomosis is found be- tween the buccal branch of the inferior maxillary and one of these buccal branches of the cervico-facial nerve : we have already pointed out a similar anastomosis between an infra-orbital branch of the temporo-facial and this same buccal branch of the inferior maxillary. The mental branches are intended for the lower lip. They are reflected upward, so as to describe an arch having its concavity directed upward ; they are at first situated be- neath the platysma myoides, then pass beneath the triangularis oris, and form, with the mental branch of the infeVior maxillary division of the fifth nerve, an interlacement or mental plexus, which has a close analogy with the interlacement of the infra-orbital branches of the facial with those of the superior maxillaiy division of the fifth nerve, but is less comnlicated. 50 842 NEUROLOGY. Thus, the mental branches of the facial nerve are more superficial than those of the fifth, and their filaments are smaller ; the radiating branches of the facial nerve run at first forward and then upward, while those of the fifth nerve run directly upward. The mental branches of the facial nerve perforate the quadratus menti and the orbicularis oris, to which muscles they are almost entirely distributed ; they also send several long and slender filaments to the point of the chin, some of which are cutaneous. The men- tal branches of the fifth nerve are chiefly situated between the muscles and the mucous membrane, to which latter they are distributed, more especially to the free borders of the lower lip. The cervical branches of the cervico-facial run forward in the supra-hyoid region, be- neath the platysma, and, describing arches with their concavities turned upward, they pass upward and forward to terminate near the chin. Among these branches, there is one which passes vertically downward to anastomose with the superficial cervical nerve of the cervical plexus. The cervical branches of the facial nerve are separated from the cervical branches of the cervical plexus by the platysma, and they are all distributed to that muscle and the levator labii superioris. Summary. — The facial nerve supplies all the cutaneous muscles of the cranium and of the face, and, therefore, section and compression of this nerve cause complete paral- ysis of these muscles : it is the nerve of expression, or the respiratory nerve of the face {Bell) ; it also evidently gives off some cutaneous filaments, especially near the commissure of the lips, and this may explain the numbness which I have known to oc- cur in individuals affected w"ith hemiplegia of the face ; lastly, it furnishes a great num- ber of anastomotic filaments (whence it has been called the small sympathetic) ; these are given to the branches of the cervical plexus, to the auditory nerve, to the pneumo- gastric, and more especially to the fifth nerve. The anastomoses of the facial with the fifth nerve merit special notice ; they are ef- fected with the frontal and nasal nerves of the ophthalmic or first division of the fifth ; with the superior maxillary or second division by means of the infra-orbital nerves and the cranial branch of the vidian, which latter I even regard as one of the origins of the facial nerve ; and with the inferior maxillary or third division of the fifth by means of the mental nerve, the buccal nerve, and more especially the auriculo-temporal nerve. The branch given by the auriculo-temporal to the facial nerve may be regarded as one of the origins of the last-mentioned nerve. Notwithstanding these numerous anastomoses, the facial nerve and the fifth nerve cannot supply the place of each other. Anatomy shows no difference in the structure of these nerves, but a great difference in their distribution ; the facial nerve being in- tended for the muscles, while the fifth is distributed to the integuments and the organs of the senses. Function. — The facial is a nerve of motion. This fact may be deduced from its ana- tomical description no less than from physiological experiments and the effects of disease. The Portio Mollis^ or the Auditory Jferve. The auditory nerve (7, figs. 296, 301), which we have already traced as far as the in- ternal auditory meatus, enters that canal with the facial nerve, for which it forms a groove, and divides into two cords, which remain distinct throughout the whole extent of the passage, but continue in contact with each other, and at length pass through the foramina in the cribriform plate already described as existing at the bottom of the meatus (see Osteology). In order to understand the farther distribution of the auditory nerve, the cribriform plate of the auditory meatus must be examined with the same attention as was devoted by Scarpa to the cribriform plate of the ethmoid, with which it has so many analogies. As the cribriform plate of the ethmoid presents a particular fissure for the passage of the ethmoidal branch of the ophthalmic nerve, so the cribriform plate of the internal auditory meatus presents a special opening for the passage of the facial nerve ; and again, the auditory, like the olfactory nerve, seems as if it were pressed through the foramina of the cribriform plate to enter the internal ear. Of the two terminal branches of the auditory nerve, the anterior is intended for the cochlea, the posterior for the vestibule and semicircular canals. The cochlear branch turns spirally, like that part of the bottom of the auditory meatus to which it belongs, and which is called the tractus spiralis. It then turns upon itself, as observed by Valsalva, and presents somewhat of a ganglionic appearance. From this sort of enlargement the cochlear filaments proceed ; those which belong to the first turn of the cochlea run along the surface of the modiolus ; the others enter the canals of the modiolus, and are distributed on the second, and the succeeding half turn at the summit of the cochlea. I have already described the very regular manner in which these fila- ments spread upon the spiral septum, the subdivision of each of them into two or three filaments, which anastomose with each other like the ciliary nerves, and the gradual dim- inution in the length of these filaments from the base to the apex of the cochlea ; so that, THE GLOSSO-PHARYNGEAL NERVE. 843 if we suppose the spiral septum spread out, it might be compared to a harpsichord, the longest strings of which would he represented by the filaments at the base of the trian- gle formed by the septum, and the shortest by those at its apex (see Internal Ear, p. 681). The vestibular branch divides into three parts, the largest of which enters the utricle and the ampullcz of the superior vertical and horizontal membranous canals, the middle- sized branch passes to the sacculus, and the smallest branch to the ampulla of the pos- terior or inferior vertical semicircular canal. Function. — The auditory nerve is exclusively the nerve of hearing. The Eighth Pair op Nerves. The First Portion, or Glosso-P /laryngeal JSTerve. Dissection. — Remove, by a triangular section, the posterior half of the border of the foramen lacerum posterius ; carefully detach the jugular vein, in front of which the nerves are situated, examine the connexions of the glosso-pharyngeal with the pneumo- gastric and spinal accessory nerves. The glosso-pharyngeal nerve {pharyngo-glossal), the anterior portion of the eighth nerve (8, Jigs. 296, 301), the ninth nerve of some authors, is intended for the pharynx and the tongue. Having arisen from the restiform body, above and on a line with the pneumogastric,* by a series of roots which are continuous with the roots of that nerve, the glosso-pharyn- geal emerges from the foramen lacerum posterius through a fibrous canal which is prop- er to it, and which is situated in front of the canal that is common to the pneumogastric and spinal accessory nerves ; it is placed to the inner side of the internal jugular vein, from which it is separated by a cartilaginous and sometimes osseous lamina. During its passage through this canal it presents a ganglionic enlargement, which was described by Andersh under the name of ganglion petrosum, and is now more generally known as the ganglion of Andersh. This ganglion is situated in a depression on the petrous portion of the temporal bone {receptaculum ganglii petrosi) ; from it the nerve pro- ^ ceeds as a rounded cord, which descends vertically {I, fig. 301) behind the styloid muscle in front of the internal carotid, then between the stylo-pharyngeus and the stylo-glossus, and passing forward so as to describe a curve with its concavity turned upward, runs in front of the posterior pillar of the fauces and behind the tonsil, and then passing beneath the hyo- glossus muscle {z), ramifies, to enter the base of the tongue and supply the mucous membrane. During this course it gives off the nerve of Jacob- son, and an anastomotic twig to the facial nerve ; it communicates with the spinal accessory and the pneumogastric ; it gives off a muscular branch to the digastricus and stylo-pharyngeus, and it supplies some carotid filaments, and some pharyngeal and tonsillar branches. The Nerve of Jacobson. — In order to facilitate the study of the course of this nerve, I shall first de- scribe the canals through which it passes : Upon the ridge which separates the jugular fossa from the carotid canal, to the outer side of the aqueduct of the cochlea, is found an open- ing, which is the inferior orifice of the canal of Jacobson. This canal runs backward and upward into the substance of the internal wall of the cavity of the tympanum, in front of the fenestra rotunda ; there it branches into three canals : one descending, which opens into the carotid canal ; and two ascending canals, an anterior, which runs" forward and upward, and opens into the groove for the great superficial petrosal or cranial branch of the vidian nerve, and a posterior, which at first ascends vertically behind the fenestra ovalis, then curves suddenly and becomes horizontal, and opens upon the upper surface of the pars petrosa in a groove parallel to and on the outer side of the groove for the cranial branch of the vidian nerve. The nerve of Jacobson, which comes off from the petrosal ganglion, or ganglion of An- dersh, enters this canal. In one subject I found it to consist of two filaments, one from the pneumogastric, and the other from the glosso-pharyngeal. t This nerve soon divides into three filaments corresponding to the three branches of the * Several modern physiologists, believing the glosso-pharyngeal to be a mixed nerve, sensory in its lingual portion, and motor in its pharyngeal, have, therefore, supposed it to have two distinct roots : a larger, which is near the par vagum, and a smaller, which lies near the facial nerve ; and, from analogy, they regard the former as the sensory, and the latter as the motor root. t In another subject it was formed by the anastomoses of a twig from the auricular branch of the pneumo- gastrio with a twig from the glosso-pharyngeal. 844 NEUROLOGY. canal ; the descending filament joins the carotid plexus ; of the two ascending filaments, one anastomoses with the cranial branch of the vidian, or the great superficial petrosal nerve {v, fig. 300), while the other constitutes the smaD superficial petrosal nerve, which reaches the upper surface of the pars petrosa in front of the preceding, and terminates in the reddish tissue known as the otic ganglion.* It follows, therefore, that the nerve of Jacobson connects the glosso-pharyngeal nerve with the superior maxillary division of the fifth nerve (especially with the spheno-pal- atine ganghon through the intervention of the vidian nerve), with the otic ganglion of the inferior maxillary division, and with the superior cervical ganglion of the sympathetic. The anastomotic branch to the facial nerve arises from the ganglion of Andersh imme- diately below the nerve of Jacobson ; it runs downward and outward behind the styloid process, is then reflected upward, so as to describe a loop with its concavity turned up- ward, and anastomoses with the facial immediately after the exit of that nerve from the stylo-mastoid foramen. This branch appears to me to be the remaining trace of a con- siderable branch of the facial nerve, which I have seen partially supplying the place of the glosso-pharyngeal (see the Tongue, p. 646). The Anastomosis of the Glosso-pharyngeal with the Spinal Accessory and Pneumogastric Nerves. — Most commonly the glosso-pharyngeal runs along the pneumogastric, or, more correctly, along the anastomotic branch of the spinal accessory. Sometimes it is com- pletely separated from these nerves, and merely communicates with them by means of its pharyngeal branches. The Branch for the Digastricus and Stylo-hyoideus. — This branch comes ofTfrom the outer side of the nerve, and bifurcates ; one of its divisions enters the posterior belly of the digas- tricus, and the other supplies the stylo-pharyngeus and stylo-hyoideus. It has already been stated that this branch anastomoses with the facial nerve in the digastric muscle. The Carotid Filaments. — These are very numerous ; they descend along the internal carotid artery, and, having reached the point of bifurcation of the common carotid, anas- tomose with the carotid filaments of the superior cervical ganglion, and assist in form- ing the arterial plexus. I have not been able to trace them below the bifurcation of the common carotid. Some of these filaments are described as joining the cardiac nerves. The Pharyngeal Branches. — These are two or three in number ; they anastomose with the pharyngeal branches of the pneumogastric, to constitute the pharyngeal plexus. These branches evidently supply the middle and superior constrictors. The filaments for the latter muscles are reflected upward upon the posterior surface of the pharynx. The tonsillar branches are very numerous, and form a sort of plexus. The Lingual Branches. — After having given off the different branches above mentioned, the glosso-pharyngeal, reduced to half its original size, enters the base of the tongue, and then ramifies ; some of its lingual branches lie close beneath the mucous membrane ; others traverse the upper layers of the muscular substance of the tongue to proceed to the mucous membrane in front of the preceding branches ; they are all intended for the mucous membrane ; the internal branches proceed from without inward at the side of the median line, while the external runs along the border of the tongue ; I have never seen any filament terminating in the muscular fibres. Function. — From its distribution, this nerve must be regarded as a motor nerve for the pharynx, and a sensory nerve for the base of the tongue. The Second Portion of the Eighth JVerve, or the Pneumogastric JVerve. Dissection. — Lay open the back part of the foramen lacerum posterius, and afterward examine the nerve in the different parts of its course successively. The pneumogastric nerve, called also the vagus nerve, the par vagum, and the teiith cra- nial nerve of some modern authors, is the principal branch of the eighth nerve {8, fig. 301), and is one of the most remarkable nerves in the body, both on account of the extent of its distribution, and of the importance of the organs supplied by it. It supplies branches, on the one hand, to the larynx, the lungs, and the heart ; and, on the other, to the pharynx, the oesophagus, the stomach, and the solar plexus. It has already been stated that this nerve arises from the upper part of the medulla ob- longata, upon the restiform bodies, and in a line with the posterior roots of the spinal nerves ; that its filaments of origin converge, and then unite at first into seven or eight fasciculi, and then into a single cord, which passes towards the foramen lacerum poste- rius, through which it emerges from the cranium. The pneumogastric nerve then runs vertically {p,fig. 301) in the neck along the vertebral column, enters the thorax, runs along the oesophagus, with which it passes through the diaphragm, and terminates on the stomach and in the solar plexus We shall now proceed to examine this nerve while it is within the foramen lacerum * Arnold admits six filaments for the nerve of Jacobson, and, consequently, six small ducts as branches of the canal of Jacobson ; these six filaments consist of the three described in the text above, and of a twig for the fenestra rotunda, one for the fenestra ovalis, and one for the Eustachian tube. I have distinctly seen the twig for the fenestra ovalis, that is to say, a twig which reaches the margin of the fenestra ovalis, but cannot be traced any farther. I have also seen the twig which passes to the Eustachian tube ; but I have not yet been able to find the twig for the fenestra rotunda. THE PNEUMOGASTRIC NERVE. 845 posterius ; as it is emerging from that foramen ; and as it descends in the neck, in the thorax, and in the abdomen. The Pneumogastric Nerve within the Foramen Lacerum Posterius. At the foramen lacerum posterius, the pneumogastric nerve passes through the same opening as the spinal accessory, which lies in contact with it ; a fibrous, cartilaginous, or bony septum separates it from the glosso-pharyngeal, which lies in front of it ; and an- other cartilaginous and often bony septum separates it from the internal jugular vein. As it is passing through the foramen it presents a well-marked ganglionic structure ; I would say, rather, a gray substance containing white nervous filaments, but without any observable swelling : hence most anatomists have denied the existence of a ganghon at this spot. To this ganglion, the ganglion of the pneumogastric, which may be compared to the Gasserian ganglion and to the inter-vertebral ganglia, the spinal accessory nerve is ap- plied, and is connected with it by several very delicate filaments. I have aheady sta- ted that, not unfrequently, the highest roots of the spinal accessory nerve join the pneu- mogastric directly. This ganglion gives off an anastomotic twig, which enters the petrosal ganglion of the glosso-pharyngeal : I have not always found this filament ; it also gives an anastomotic branch to the facial nerve, viz., the auricular branch of the ■pneumogastric of Arnold. This branch might be called, the branch of the jugular fossa ; it can be very well seen through the coats of the jugular vein when that vessel is laid open. It runs along the anterior part of the jugular fossa, between it and the internal jugular vein, gives off an anasto- motic twig to the nerve of Jacobson, enters the temporal bone through an opening in the jugular fossa, near the styloid process, and traverses a very short canal, which conducts it directly into the Fallopian aqueduct, in which it anastomoses with the facial nerve.* The PncumogoMric Nerve, at its Exit from the Foramen Lacerum Posterius. At its exit from the foramen lacerum posterius, the pneumogastric nerve presents the appearance of a plexiform cord, which is often accompanied by the gray matter of the ganglion for the space of about six lines or an inch. This plexiform cord has certain important connexions with the spinal accessory, the ninth or hypo-glossal nerve, the glos- so-pharyngeal nerve, and the superior cervical ganghon. It is joined by one of the branches of bifurcation of the spinal accessory, which we shall name the internal or anastomotic branch of the spinal accessory nerve ; it becomes apphed to the pneumogastric nerve, and may be distinguished from it for a considerable distance. It also anastomoses with the hypo-glossal, at the point where it is crossed by that nerve, and at other times above that point. This anastomosis, moreover, is subject to great variety ; sometimes it takes place by a very small filament, at other times by two or three twigs, which form a sort of plexus. It also anastomoses with the glosso-pharyngeal. The examination of this anastomo- sis, after the parts had been macerated in diluted nitric acid, enabled me to see that it is not, properly speaking, effected with the pneumogastric nerve, but with the anasto- motic branch of the spinal accessory. Nothing can be more variable than these anasto- moses, which are sometimes wanting on one side, and which are rather frequently ef- fected through the intervention of the pharyngeal branches. Lastly, the pneumogastric nerve communicates with the great sympathetic by one or two branches in man and some mammalia ;t in the other classes of animals the con- nexion is so intimate that it is altogether impossible to separate the pneumogastric from the superior cervical ganglion. The connexions of the pneumogastric with the spinal accessory and superior cervical ganglion are two very important points in its anatomy. J The Pneumogastric Nerve in the Neck. In the cervical region, the pneumogastric nerve {p,figs. 298, 300, 301) is situated in front of the vertebral column, the praevertebral muscles intervening between them, upon the side of the pharynx and oesophagus, and between the internal and then the common carotid, which are on its inner side, and the jugular vein, which is on its outer side ; it is placed behind these vessels. It is closely applied to the carotid artery, being in the same * I have seen this branch, immediately after its origin, enter the sheath of the glosso-pharyngeal nerve, run along its ganglion, and then curve backward to enter the jugular fossa. Arnold, who first described this anas- tomotic branch, represents it as divided into three filaments : an ascending, which anastomoses with the trunk of the facial ner\'e ; a descending, which anastomoses with the posterior auricular branch of the same nerve ; and a middle (u,fig. 299), which ramifies upon the external auditory meatus. t I have seen the pneumogastric nerve communicate with the great sympathetic, by filaments which come off at different heights from the cervical ganglion ; two proceeded from the upper part of the superior cervical ganglion, and then ascended ; and two came from the lower part of the ganglion, and descended to unite with the pneumogastric. I have met with a case in which the superior cervical ganglion was applied in its whole extent so closely to the pneumogastric that it was impossible to separate them. t [The pneumogastric also receives a filament from the anastomotic loop of the first and second cervical nerves (see p. 777).] 846 NEUROLOGY. sheath : it is separated from the cervical portion of the great sympathetic (/;), which lies behind and to the outer side of it, by a great quantity of cellular tissue. During this course it supplies the pharyngeal branch, the superior laryngeal nerve, and the cardiac filaments. The Pharyngeal Branch, or Small Pharyngeal Nerve. — This is often double, and is then distinguishable into a superior and an inferior ; it comes off at a little distance from the foramen lacerum posterius, but its real origin is variable. In some cases it arises ex- clusively from the pneumogastric ; at other times exclusively from the anastomotic branch of the spinal accessory, which, as already stated, does not become immediately blended with the pneumogastric ; and it often arises both from the pneumogastric and the spinal accessory : lastly, the glosso-pharyngeal sometimes gives it a filament. It passes behind the internal carotid, gives off some carotid filaments, which join the more numerous twigs from the glosso-pharyngeal, and then anastomoses with the ramifica- tions of the glosso-pharyngeal, and with several large branches from the superior cervi- cal ganglion, to form the ■pharyngeal plexus, which is one of the most remarkable plex- uses in the body, and to which the varied and frequent nervous phenomena observed in that region must be referred. I shall recur to this plexus when describing the great sympathetic. The Superior Laryngeal Nerve {x',jig. 301). — This is larger than the pharyngeal branch ; it comes off from the inner side of the pneumogastric* as a rounded cord, which may be traced as high as the ganglion of the nerve ; it passes downward and inward upon the side of the pharynx, behind the internal and external carotid arteries, which it crosses obliquely : it then turns forward and inward to gain the thyro-hyoid membrane, passing above the upper margin of the inferior constrictor of the pharynx ; it runs for some time between the thyro-hyoid muscle and the thyro-hyoid membrane, perforates the lat- ter at the side of the median line, and then enters the substance of the aryteno-epiglot- tid fold of mucous membrane, where it terminates by dividing into a great number of fil- aments. During its course, it gives off a branch which is called the external laryngeal (y), and which I have seen arise directly from ihe pneumogastric itself; this branch communi- cates with the superior cervical ganglion by one or tv/o filaments, and passes inward and downward upon the side of the larynx. It gives off one or two filaments, which anasto- mose with the superior cardiac nerve, behind the common carotid ; Haller calls this communication between the external laryngeal and the great sympathetic the laryn- geal plexus.f The external laryngeal nerve also gives off several branches to the infe- rior constrictor of the pharynx, some to join the pharyngeal plexus, and some twigs to the thyroid gland ; it then passes downward and forward between the inferior constric- tor and the thyroid cartilage, and terminates by ramifying in the crico-thyroid muscle. The terminal expansion of the superior laryngeal nerve is remarkable for its radiated arrangement ; it is preceded by a flattening and thickening of the nerve. These ex- panded branches are all sub-mucous, and may be arranged into the anterior or epiglotlid, and the posterior. The anterior or epiglottid branches are numerous and small ; they run upon the margin, and on the fore part of the epiglottis ; some of them reach its free extremity, otliers run between the fibro-cartilage of the epiglottis and the adipose tissue, called the epiglottid gland ; some of them perforate the epiglottis, and ramify upon its posterior surface. Among these anterior terminal filaments of the superior laryngeal nerve there is at least one which runs forward under the mucous membrane covering the base of the tongue, and may be traced as far as the two rows of glands, which are arranged like the letter V. These filaments of the superior laryngeal nerve to the tongue are placed be- tween the lingual branches of the right and left glosso-pharyngeal nerves, with which they have probably been confounded. The posterior or laryngeal filaments contained in the aryteno-epiglottid fold are more numerous than the anterior branches ; they are divided into the mucous filaments, the arytenoid filament, and the anastomotic or descending filament. The mucous filaments are very numerous, and run upward in the aryteno-epiglottid fold ; some of them lie beneath the external, and others beneath the internal layer of mucous membrane of this fold. They are intended for these two layers, and they ter- minate, for the most part, at the superior orifice of the larynx : their number explains the exquisite sensibility of this opening. Some of these mucous filaments may be traced into the substance of the arytenoid glands. The filament for the arytenoid muscle is very liable to be confounded with the mucous * It arises, therefore, nn the opposite side to the anastomotic branch of the spinal accessory, which has not appeared to me to assist in its formation. I have seen the superior laryngeal arise by two roots, the larger of which carae from the pneumogastric, while the other, whicli was very small, came from the glosso- pharyn- geal. It appears to loe that M. Uischoff's remarks concerning the origin of the su|)erior laryngeal nen-e on a level with the spinal accessory, would apply to the pharyngeal branch of the pneumogasfric. t The superior laryngeal nerve {x',fg. 301) forms a loop behind the carotids, like that funned by the hypo- glossal {d) in front ot them, but lower down in the neck ; that portion of the nerve which runs between the thyro-hyoid membrane and the thyru-hyoid muscle is evceedingly tortuous in some positions of the laryni. THE PNEUMOGASTRIO NERVE IN THE THORAX, ETC. 847 filaments ; it perforates the muscle from behind forward, and is partly distributed to it and partly to the lining membrane of the larynx. The descending or anastomotic filament, which is small, but of variable size, descends vertically, between the mucous membrane on the one hand, and the thyro- and crico- arytenoid muscles on the other, gains the posterior surface of the cricoid cartilage, and anastomoses upon it with the recurrent laryngeal nerve. This remarkable anastomosis was known to Galen.* Thus, the superior laryngeal nerve chiefly belongs to the mucous membrane of the larynx ; but it gives branches to the arytenoid and crico-thyroid muscles : the branch for the latter comes from the external laryngeal division of this nerve. The Cardiac Branches of the Piieumogastric Nerve of the Neck. — These vary both in number and size in different subjects, and even upon the two sides of the same body : they come off at ditferent heights from the trunk of the pneumogastric ; some of them, after a course of variable extent, join the superior cardiac nerves, either in the neck or in the thorax ; the others pass directly to the cardiac plexus. The most remarkable of the cervical cardiac branches of the pneumogastric is that which comes olTat the lower part of the neck, a little above the first rib ; on the right side, it descends in front of the common carotid, and then in front of the brachio-cephalic artery, below which it anasto- moses with the superior cardiac nerve. On the left side, it passes in front of the arch of the aorta, and anastomoses below that vessel with the superior cardiac nerve of that side. This branch sometimes goes directly to the cardiac plexus : it is sometimes double. The Pneumogastric Nerve in the Thorax. The thoracic portion of the pneumogastric nerve presents this peculiarity, that it differs remarkably on the right and left sides. On the right side, the nerve {p, fig. 302) enters the thorax between the sub-clavian vein and artery : lower down, it passes behind the brachio-cephalic vein and the supe- rior cava, and behind the phrenic nerve, at the side of the trachea, or, rather, in the groove between the trachea and oesophagus : it then passes behind the root of the lung, where it becomes flattened and enlarged, gives off a great number of branches, and ap- pears to expand, in order to unite in a different arrangement. Below the root of the lung the right pneumogastric is always divided into two flattened branches, which run along the right side of the cesophagus, join together at a short distance from the dia- phragm, and pass behind the cesophagus, with which canal the common trunk enters the abdomen. On the left side, the pneumogastric enters the thorax between the common carotid and the sub-clavian artery, in the triangular interval between those vessels, internal to and then behind the phrenic nerve, behind the brachio-cephalic vein, and to the left of the arch of the aorta ;t it then passes behind the left bronchus, upon which it ramifies, and unites again into one or two branches, which pass in front of the oesophagus, and enter the abdomen with it. In the thorax the pneumogastric gives off the recurrent or inferior laryngeal nerve, a cardiac branch, some tracheal and (esophageal branches, and branches to the anterior and posterior pulmonary plexuses. The Recurrent or Inferior Laryngeal Nerve.t This nerve (r, fig. 302), so called on account of its reflected course, arises in front of the arch of the aorta on the left side, and of the sub-clavian artery on the right side : it is sometimes so large that it may be regarded as resulting from the bifurcation of the pneumogastric : it is reflected below and then behind the arch of the aorta on the left side, and the sub-clavian artery on the right, so as to form a loop or arch, which has its concavity turned upward, and which embraces the corresponding vessel. Having thus changed its course from a descending to an ascending one, the recurrent nerve enters the groove {q,fig- 301) between the trachea and the cesophagus, and continues to ascend as high as the lower border of the inferior constrictor muscle of the pharynx ; it the-n passes beneath that muscle, gives some filaments to it, runs behind the lesser cornu of the thyroid cartilage and the crico-thyroid articulation, along the outer border of the posterior crico-arytenoid muscle, and terminates by ramifying in the muscles of the larynx. During its course, the recurrent nerve gives off the following collateral branches : at the point of its reflection, it gives several cardiac filaments, which unite with the cardiac branches of the pneumogastric and great sympathetic. It is important to remark the intimate connexion which exists between the recurrent and the cardiac nerves : some very considerable anastomoses are almost always found between the superior and infe- * See note, p. 848. t The relation of the pneumogastric with the arch of the aorta explains the stretching and atrophy of this nerve in aneurisms of that portion of the vessel. 4 Those anatomists who regard the superior laryngeal nerve as a dependance of the spinal accessory be- lieve that the inferior or recurrent laryngeal has a similar origin. I may repeat, and with still more reason, in reference to this nerve, what I have already stated in regard to the superior laryngeal, that it is impossible to demonstrate this continuity by dissecticm. 848 NEUROLOGY. dor cardiac nerves and the recurrent nerve : sometimes, indeed, the recurrent nerve forms the point at which the superior and middle cardiac nerves meet, and from which the inferior cardiac nerve is given off; the anastomoses between the recurrent and car- diac nerves sometimes form a true plexus. The recurrent also gives esophageal branches, which are much more numerous on the left than on the right side, so that the left recurrent nerve is much smaller in the larynx than the right nerve. It also gives tracheal branches, which chiefly supply the posterior or membranous por- tion of that canal. And, lastly, some pharyngeal filaments^ all of which are destined for the inferior con- strictor. Excepting an anastomotic branch* for the superior laryngeal nerve, all of the terminal branches of the recurrent nerve are intended for the muscles of the larynx, and are thus distributed : The branch for the posterior crico-arytenmd simply enters that muscle. The branch for the arytenoid runs between the cricoid cartilage and the posterior crico- arytenoid muscle, and then ramifies in the arytenoid. It has already been stated that the last-named muscle is also supplied by the superior laryngeal nerve. The branch for the lateral crico-arytenoid and thyro-arytenoid muscles is the true termina- tion of the nerve ; it passes on the outer side of these two muscular bundles, which, as formerly stated, constitute a single muscle in the human subject, and then enters them by very delicate filaments. I have distinctly seen a very delicate filament entering the crico-thyroid articulation. After the pneumogastric has given off the recurrent nerve, and often before doing so, it furnishes certain cardiac branches {thoracic cardial) ; these are subdivided into the pericardial, which run upon the outer surface of the pericardium, and are lost in it and in the cellular tissue which replaces the thymus ; and into the cardiac branches, properly so called, which assist in the formation of the cardiac plexus. The pneumogastric also gives off certain anterior pidmonary branches, which run in front of the bronchus and of the pulmonary arteries and veins, cross obliquely over them, and then enter the substance of the lung, following the ramifications of the air-tubes and bloodvessels ; these pulmonary branches form what is called the anterior pidmonary plex- us. I have seen several of them extend some considerable distance beneath the serous membrane, covering the inner surface of the lungs, before they entered the substance of those organs. Behind the bronchus, and along the cesophagus, the pneumogastric nerve gives off posterior branches, consisting of a great number of oesophageal branches ; of some tracheal branches, which principally supply the back or membranous portion of the trachea ; and, lastly, of posterior pulmonary or bronchial branches, which form the posterior pulmonary plexus. The posterior pulmonary plexus is one of the most remarkable in the body ; in it the pneumogastric nerve appears to be decomposed and expanded ; there is a right and a left pulmonary plexus. The left is much larger than the right. The two plexuses are not independent of each other, but are connected by free anastomoses : this remarkable disposition establishes a community of function between the two nerves, and explains how one of them may supply the place of the other. The pulmonary plexuses, which are completed by filaments from the great sympathetic, are situated behind the root of each lung, or, to speak more exactly, behind the bronchi (whence the name of bronchial plexuses). A few of the twigs emerging from them follow the pulmonary arteries, and appear to be lost in their coats ; the others accompany the bronchi, some of them passing behind these canals, and others, being reflected forward in the angles formed by their bifurcation, run along their anterior aspect, and terminate in their parietes. They may be traced as far as the ultimate ramifications of the air- tubes. In large animals they can be easily seen entering the circular muscular fibres which surround the bronchial tubes. t Below the pulmonary plexus, the pneumogastric merely gives off certain oesophageal branches, which surround the oesophagus in very great numbers. The right and left pneumogastric nerves anastomose with each other ; but the communicating arches do not constitute those circular anastomoses, which have been so decidedly said to explain the pain caused by swallowing too large a morsel of food. The Pneumogastric Nerve in the Abdomen. The two pneumogastrics enter the abdomen with the oesophagus, the left nerve being in front and the right nerve behind that canal, and are distributed in the following manner : * [This anastomotic branch is superficial, and joins the descending- filament from the superior laryngeal nerve, beneath the mucous membrane on the back of the larynx, and sometimes sends filaments into the ary- tenoid muscle ; there is, generally, a second anastomosis between the superior and inferior laryngeal nerves on the side of the larynx, between the thyroid cartilage and the thyro-arytenoid muscle.] t I have seen a nerve from the pulmonary plexus pass through some of the fibres of the oesophagus and ram- ify in the aorta. SPINAL ACCESSORY NERVE OF WILLIS. 849 The left nerve {q, fig. 302), which is situated in front of the cardia, expands into a very great number of diverging filaments, some of which extend over the great cul-de-sac, and others over the anterior surface of the stomach ; but the greater number gain the lesser curvature, and divide into two sets or groups ; one of these leaves the lesser cur- vature, enters the gastro-hepatic omentum, is conducted by it to the transverse fissure of the liver, and enters that gland. The other group continues in the lesser curvature, and may be traced as far as the duodenum. The right pneumogastric {p'), situated behind the cardia, gives a much smaller number of branches to the stomach than the left, and joins the solar plexus (x), of which it may be regarded as one of the principal origins. Summary of the Distribution of the Pneumogastric Nerve. — This nerve, it will be seen, has an extremely complicated distribution. Within the foramen laccrum posterius, it anastomoses with the spinal accessory ; with the facial nerve by means of the auricular branch of Arnold, or the branch of the jugular fossa ; and with the nerve of Jacobson, and, therefore, with the glosso-pharyngeal nerve, by a twig from the same auricular branch. At its exit from the foramen lacerum posterius, it anastomoses with a large branch of the spinal accessory ; with the hypo-glossal ; with the glosso-phyrangeal ; and with the su- perior cervical ganglion. In the neck, it gives off the pharyngeal branch or small pharyngeal nerve, the superior laryngeal nerve, and the superior cardiac branches of the pneumogastric. In the thorax, it gives off the recun-ent or inferior laryngeal nerve, which supplies some cardiac, cssophageal, pliaryngeal, tracheal, and laryngeal branches ; the inferior cardiac branches ; and the pulmonary or bronchial branches. In regard to its structure, the pneumogastric differs essentially from the other cerebro- spinal nerves, by the tenuity of its filaments and by their plexiform arrangement ; and in both of these particulars, as well as in its distribution, it rather resembles the nerves of organic than those of animal life. In the description of the sympathetic it will be seen how intimate are its relations with the pneumogastric nerve. Functions of the Pneumogastric. — From the manner in which the pneumogastric is dis- tributed, it follows that it is a nerve both of sensation and ot motion ; for it supplies both the lining membrane of the respiratory and digestive passages, and the muscles and muscular coats of the same canals. Anatomy does not confirm the ingenious idea of Bischoff, that the pneumogastric is essentially a nerve of sensation, and that the por- tion which appears to be motor really belongs to the spinal accessory. Physiologists have studied the influence of the pneumogastric upon the larynx, the lungs, the heart, and the stomach in an infinite variety of ways ; it appears, from some experiments which I made upon this subject, that animals in which both pneumogastrics are sunul- taneously cut die almost immediately, when they are permitted to eat as much as they please ; for, the contractility of the stomach and oesophagus being destroyed, the food, after having filled the stomach, distends the oesophagus, and passes from it into the larynx. The Third Portion of the Eighth Jferve, or the Spinal Accessory Merve of Willis. We have already described the very remarkable origin of the spmal accessory nerve at the side of the cervical portion of the spinal cord, between the anterior and posterior roots of the spinal nerves, or, rather, immediately in front of the posterior roots, of which it appears to be a dependance : we particularly alluded to the arrangement of its highest filaments of origin, which come from the restiforrti bodies, and are continuous above with the roots of the pneumogastric, so that they sometimes even join that nerve, and below with the posterior roots of the spinal nerves. Lastly, we have pointed out the varieties of its origin, its connexions with the first pair of cervical nerves, of which it almost always forms the posterior roots, its ascend- ing course to the foramen magnum, through which it enters the cranium, and its exit from the scull by the foramen lacerum posterius. It emerges from the foramen lacerum posterius by an opening quite distinct from that for the glosso-pharyngeal, but common to itself and the pneumogastric nerve, behind which it is situated {ii,fig. 301). While passing through the foramen lacerum poste- rius, it lies in contact with the ganglionic enlargement of the pneumogastric, and is con- nected with the ganglion by very delicate filaments, but it neither assists in the forma- tion of that enlargement, nor is blended with it : at its exit from the foramen it divides into two branches of equal size ; an internal or anastomotic, which remains in contact with the pneumogastric, and is distributed with it, and a muscular branch* (cut off in fig. 301). The Anastomotic Branch. — So intimately are the spinal accessory and pneumogastric nerves connected, or, as it were, fused together, that, up to the time of Willis, they were * It is well to observe, that as they are passing through the foramen lacerum posterius, the pneumogastric and spinal accessory nerves adhere to the dura mater, in the same manner as the Gasserian ganglion. 5P 850 NEUROLOGY. regarded as a single ner%'e. Willis first described the former, perhaps erroneously, as a separate nerve, under the name of nercus ajtcessorius ad par vagTim. sive nercus spinalis. In an excellent thesis, published in 1822,* M. Bischoff endeavoured to prove that the pnetunogastric or par vagum and spinal accessor)' form but a single nerve, analogous to the spinal nerves in every respect ; the spinal accessory being the nerve of motion, and the par vagum the nerve of sensation : " Nervus accessorius WilHsii est nervus moto- rius, atque eandern habet rationem ad nervum vagum quam antica radix nervi spinalis ad posticam. Omnis motio cui vagus praeesse videtur, ab ilia portione accessorii quae ad vagum accidit, efficitur. Itaque vox quoque, sive musculorum laryngis et glottidis motus, ab accessorio pendet, et eo nomine accessorius nervus vocalis vocari potest." To this view there are serious objections : in the first place, it is opposed to the law that the anterior roots preside over motion and the posterior over sensation ; for the filaments of origin of the spinal accessory evidently form part of the posterior roots. Again, how can it be supposed that two nerves, which, like the spinal accessory and piTeumogastric, arise so distinctly from the same line, that it is oft«n difficult to separate them, can have such opposite functions ! Must we suppose that the law which regulates the anterior and posterior roots of the spinal nerves ceases to operate at the medulla oblongata ' or must we admit, with Ar- nold, that there is not orJy a decussation of fibres from side to side in the medulla ob- longata, but also from before backward, so that the posterior columns of the medulla ob- longata become the motor and the anterior the sensory ] Still, even with this hypothe- sis, it must be remembered that the spinal accessory arises in part below the point where this antero-posterior decussation is supposed to exist. There evidently is an antero- posterior decussation opposite to the two anterior pyramids, as I have elsewhere stated (see Medclla Obloxgata). but the other columns of the spinal cord are not concerned in it. However this may be, the anastomotic branch of the spinal accessory may be traced, after maceration in dilute nitric acid, along the outer side of the pneumogastric. In a great number of cases, it evidently gives off the small pharyngeal nerre, which sometimes arises exclusively from the pneumoga-stric, and sometimes from both the pnetmiogastric and the spinal accessory. Scarpa declares the last arrangement to be constant and normal, and has represented it in several figures. In some subjects, the spinal accessory appears to have no share in the pharyngeal nerve, but then its anastomotic branch be- comes applied to the pneumogastric below the origin of the pharyngeal nerve. The anastomotic branch appears to me to have no share in the formation of the supe- rior laryngeal nerve ; and the same is the case with regard to the recurrent nerve. It appears to me anatomically impossible to prove the continuity of the spinal accessoiy and the superior and recurrent laryngeal nerves ; I cannot, therefore, admit that the spi- nal accessory supplies the intrinsic muscles of the larynx. The spinal accessory generally gives off a number of twigs, which unite in front of the reddish, and, as it w-ere.' ganghonlc trunk of the pnexunoga-stric nerve, to form a smaU plexus, which adheres to^hat nerve, and ends in the hypo-glossal nerve. Lastlv, there are so many varieties in the mode of communication between the pneu- mogastric and spinal accessory nerves, that it is extremely difficult to refer them to any general law. Thf. Muscular Branch. — This nerve descends vertically between the internal jugular vein and the occipital arter\', beneath the digastric and stylo-hyoid muscles ; it runs back- ward and outward {t, fivs. 285, 298), beneath the sterno-mastoid, generally perforating that muscle, but sometimes merely running along its deep surface, passes obliquely .across the supra-clavicular triangle, and terminates in the deep surface of the traipezius. While perforating the sterno-mastoid, the spinal accessory nerve gives several branches to that muscle, which anastomose with others from the third cervical nerve, and form a sort of plexus within the muscle. On emerging, somewhat reduced in size, from the sterno-mastoid, it receives a branch [v, fig. 298) from the anastomosis, between the second and third cervical nerves, by which its size is greatly increa.sed : it assists in the formation of the cervical plexus, and some- times of the posterior auricular nerve. Having reached the anterior surface of the trapezius, it receives two considerable branches, derived from the third, fourth, and fifth cenical nerves, which appear to me to re-enforce it. It gives off ascending filaments to the occipital portion of the muscle ; and descending filaments, which continue in the original course of the nerve in front of the muscle, approach its scapular attachments, and may be traced down to its inferior angle. The muscular branch of the spinal accessory belongs exclusively to the sterno- mastoid and trapezius muscles. It has been incorrectly stated that it supplies other mus- cles, such as the rhomboidei, the levator anguli scapiilec, the complexus, the splenius, and the sub-scapularis, and that it is also distributed to the skin. In front of or, rather, in the substance of the trapezius, the spinal accessory anasto- moses with the posterior branches of the spinal nerves. * Nerri Axxessarii WiUisii Anatomia et Pbysiologia. Bischoff. Dannstadii, THE HYPO-GLOSSAL NERVE. 851 Summaiy. — The spinal accessory gives branches to the stemo-mastoid, the trapezius, and the pharynx ; it is believed also to send some to the larynx by means of its anasto- motic branch with the pneumogastric. It communicates with the second, third, fourth, and fifth cervical nerves. Functioiu — In reference to its muscular branch, Sir C. Bell has classed the spinal ac- cessory among the respiratory nerves, under the name of the superior respiratory nerve of the trunk; for, according to that anatomist, it arises from the lateral column of the cord, between the anterior and pos1;erior columns. With regard to the anastomotic branch of this nerve, which becomes blended with the par vagum, M. Bischofflays down the following proposition (page 95) : "Ner\'um acces- sorium nimirum nervum motorium esse, ideoque in partes vagi adscisci, ut motus, qui- bus hie qui sensificus tantummodo nervus est, prseesse videatur. ipse perficiat : eundem ergo praeesse motibus quoque musculorum laryngis, indeque nervum esse vocalem." This idea, which was suggested to him by theory, he endeavoured to confirm by experi- ment. The section of all the roots of the spinal accessory proved to be very "difficult ; but, after many fruitless attempts, he at length succeeded in dividing them on both sides. The hoarseness produced by section of all the roots of the right side gradually increased as he divided those of the left side, and when all had been cut, the natural voice of the animal was changed to a very hoarse sound, which could not be called the voice. I have already said that anatomy affords no proof that the laryngeal nerves are derived from the spinal accessory ; nor does it show that the muscular fibres of the bronchi, tesophagus, and stomach, receive their filaments from it. The Nixtk Pair, or Hypo-glossal Nerves. The hypo-glossal, or great hypo-glossal nerve, the ninth cranial, or the twelfth nerve of some modern authors, arises on each side from the furrow between the olivary and pyramidal bodies, by a row of filaments collected into two very distinct fasciculi, which proceed to the anterior condyloid foramen iq,Jig. 296), perforate the dura mater separ- ately, and join together so as to emerge from the canal in the form of a rounded cord.* After leaving the anterior condyloid canal, the hypo-glossal nerve {d, Jig. 301) descends vertically between the internal carotid, which is on its inner side, and the internal jugu- lar on its outer side. At first it lies behind the pneumogastric (8 to p) ; it then crosses very obliquely over the outer side, and lower down it gets in front of that nerve, around which, therefore, it describes a semi-spiral. Having arrived below the posterior belly of the digastric muscle, the hypo-glossal changes its direction and rims forward and downward {d, fig. 300), crossing in front of the internal and external carotids [and hooking beneath the occipital artery] ; it is then reflected upward to reach the under surface of the tongue {d, near x), and thus describes a loop having the concavity turned upward, parallel to and below the digastricus, and almost ten lines above the os hyoides. Relations. — It is situated deeply in its vertical portion, where it runs along the verte- bral column, becomes superficial in its middle portion {d, fig. 298), where it is merely separated from the skin by the platysma and the prominence of the sterno-mastoid, and again becomes deep-seated anteriorly, where it rests on the hyo-glossus muscle, and is covered by the anterior beUy of the digastricus and by the stylo-hyoideus, and then by the sub-maxillary gland and the mylo-hyoideus, after which it enters the genio-glossus, and is lost in the substance of the tongue. The relations of the hypo-glossal nerve and the lingual artery are worthy of remark. The nerve is at first parallel to and above the artery, is soon separated from it by the hyo-glossus, and then rejoins it in front of that muscle. In the substance of the tongue, the artery lies to the outer side of the genio-glossus, while the nerve runs forward through the fibres of the muscle. The Collateral Branches of the Hypo-glossal Nerve. Some of these are anastomotic. Thus, as it crosses the three divisions of the eighth nerve, the hypo-glossal lies in contact with the pneumogastric nerve, with which it sometimes communicates by very delicate filaments. Most commonly the anastomosis between these two nerves forms a true plexus, t This communication is sometimes effected with the anastomotic branch of the spinal accessory, sometimes with the pneu- mogastric itself The hypo-glossal is also connected by a very small anastomotic twig to the superior cervical ganglion. It also receives three filaments frorn the nervous loop formed by the union of the first and second cervical nerves, namely, two from the first nerve and one from the second. The superior filament from the first nerve ascends, an arrangement which it is difficult to uirderstand, for it passes in a direction towards the roots of the hypo-glossal ; if it be * The v»rtebral artery is situated in front -^f the filaments of the hypo-glossal. t [In connexion with this fact, it may be observed that the descendens noni (a branch of the hypo-glossal nervej sometimes arises in part or entirely from the pneumogastric, lower down iu the neck.] 852 NEUROLOGY. supposed that this filament is derived from the hypo-glossal, then it is directed towards the roots of the first cervical nerve. Opposite to the anterior border of the hyo-glossus it gives off a very remarkable anas- tomotic branch, which forms an arch with the lingual nerve. The other collateral branches which it gives off are the descending branch ; a small muscular infra-hyoid branch; and the branches for the hyo-glossus and stylo- glossus. The descending branch {ramus descendens noni, h,figs. 298, 300, 301). This is the most remarkable branch of the hypo-glossal nerve.* It comes off at the point where the nerve changes its direction, descends vertically in front of the internal carotid and then of the common carotid, curves outward, and anastomoses upon the internal jugular vein with the descending branch of the cervical plexus {^,fig. 298), so as to form a loop, hav- ing its concavity turned upward. From the convexity of this loop two branches proceed, of which one is distributed to the omo-hyoid, while the other {g) divides into two twigs, one of which enters the outer border of the sterno-hyoid, while the other penetrates the deep surface of the sterno-thyi-oid muscle. I have seen one of these branches come di- rectly from the hypo-glossal, t It is equally important to study both the mode of origin and anastomosis of the de- scending branch of the ninth nerve. t The origin of this branch is, in fact, almost en- tirely from the anastomotic branches of the first and second cervical nerves, which, after having been in contact with the hypo-glossal, are given off from it to constitute the de- scending branch. This arrangement is especially evident in preparations that have been macerated in diluted nitric acid. I should state, however, that it is not equally evident in all subjects ; and that some filaments, derived from the hypo-glossal itself, always join those from the cervical nerves. It has appeared to me that the most internal of the fila- ments derived from the hypo-glossal nerve itself followed a retrograde course ; that is to say, that it ran from below upward, as if it arose at the terminal extremity of the hypo- glossal, and then left that nerve to join the descendens noni at the point where that branch is given off. The branches from the first and second cervical nerves to the hypo-glossal should be regarded as late origins of that nerve, which is sensibly increased in size after being joined by them. I have seen the third and even the fourth cervical nerve assist in the formation of the descendens noni ; the branch from the fourth nerve arose partly from the phrenic. The mode of anastomosis of the descendens noni with the descending branch of the cervical plexus, or, rather, of the third cranial nerve, is subject to much variety. The following is the most frequent arrangement : All the filaments composing these two descending branches unite together, with the exception of the uppermost filament, which describes a loop having its concavity turned upward, and resembling a vascular anastomosis : so that, if we suppose it to be derived from the loop of the hypo-glossal, it would be directed towards the origin of the cervical nerves ; and if, on the contrary, we suppose it to arise from the cervical nerves, it would be directed towards the origin of the hypo-glossal. This arrangement, which I have had the opportunity of observing in many parts of the nervous system, appears to me to con- stitute a mode of anastomosis well worthy the attention of physiologists. I am induced to regard it as intended to establish connexions between the different points of the spinal cord.ij * See note, last page. t [Another branch is described and figured by Arnold as descending- in front of the vessels, and joining the cardiac nerves in the thorax.] X There are certain cases in which the descendens noni is analyzed by nature ; namely, when the branch from the second cervical nerve is not applied to the hypo-glossal, but remains at a distance from it. In this case, the filaments derived from the hypo-glossal join themselves to this branch ; one of them ascends towards the origin of the second cervical nerve, and the others proceed towards its termination. In one case, the hypo- glossal gave a very small twig to the first cervical nerve, before receiving its accustomed branch from that nerve ; the descending branch from the cervical plexus was replaced by three branches derived from the first, second, third, and fourth cervical nerves, which formed, together with the descendens noni and its branches, a succession of loops, in front of the external and common carotids. In another case, the three superior cervical nerves assisted in forming the descendens noni. The following is a detailed description of that case, which throws considerable light upon the connexions between the hypo-glossal and cervical nerves. One large branch proceeded from the anastomotic arch of the first and second cervical nerves ; this large branch, as soon as it reacted the hypo-glossal nerve, divided into three filaments of unequal size : an ascending, which was directed towara= the origin of the hypo-glossal nerve ; a middle, which became blended with that nen-e ; and a descend- ing, which was the largest, and which merely ran along in contact with the same nerve. At the point where this last-named filament left the hypo-glossal to form the descendens noni, it evidently received a twig from the hypo-glossal itself, which came from the lower part of that nerve, and was reflected upon the descendens noni in a retrograde manner, so that this twig, derived from the hypo-glossal, liad one end at the terminal ex- tremity of that nerve, i. e., in the muscles of the tongue, and the other end in the muscles of the infra-hyoid region. In this sanio case, the descending branch of the second cervical nerve divided into three filaments, one of which joined the hypo-glossal nen-e, another formed an anastomotic arch with the third cervical nerve, ■while the third filament jrassed downward to assist in forming the descending branch of the cervical plexus. Lastly, the third cervical nervs in this case gave off an ascending branch, which anastomosed with the secimd, and a descending branch, which assisted in forming the descending branch of the cervical plexus ; there were therefore two loops or arches, one internal and the other external ; they were situated opposite to the bifurca- tion of the common carotid artery. 4 This mode of anastomosis may, perhaps, have some relation to that reflex action of the spinal cord, which GENERAL VIEW OF THE CRANIAL NERVES. 853 The Small Muscular Branch of the Infra-hyoid Region. — This nerve comes off at the posterior border of the hyo-glossus, and ramifies in the upper part of the muscles of the infra-hyoid region ; a small transverse filament runs along the hyoid attachments of these muscles. This small nerve may be regarded as an accessory to the descendens noni. The Branches for the Hyo-glossus and Stylo-glossus. — As the hypo-glossal nerve comes into contact vs'ith the hyo-glossus, it becomes flattened and widened, and gives off sev- eral ascending branches, most of vs'hich ramify in the hyo-glossus, though several end in the stylo-glossus. The Terminal Branches of the Hypo-glossal Nerve. Opposite to the anterior border of the hyo-glossus the hypo-glossal nerve gives ofT some twigs to the under surface of the genio-hyoideus ; it then enters the genio-hyo- glossus, and expands (rf, near x,fig. 300) into a great number of filaments, which run for- ward, perforate that muscle at successive points, and are lost in the substance of the tongue. It is impossible to follow these filaments to the papillary membrane of the tongue. Some of them anastomose with the lingual («) nerve, a branch of the inferior maxillary division of the fifth ; several accompany the lingual artery. The relations of the lingual portions of the hypo-glossal nerve with the lingual of the fifth are worthy of attention. The lingual nerve occupies the under part of the border of the tongue, runs along the stylo-glossus, and may be traced as far as the apex of the organ : it is sub-mucous in the whole of its extent. The hypo-glossal nerve is situated on a much lower plane, and occupies the under surface of the tongue, on each side of the median line. Function. — The hypo-glossal is a muscular nerve : it regulates the movements of the tongue, while the lingual of the fifth and the glosso-pharyngeal confer sensibility upon it. This fact is most clearly established by anatomical, physiological, and pathological ob- servations. Like all nerves having a simple distribution, the hypo-glossal has not a plexiform structure. General View op the Cranial Nerves. All the spinal nerves present the greatest regularity in arising from two series of roots, in having a ganglionic enlargement on their posterior roots, and even in their course and termination, the differences or modifications of which depend on the different struc- ture of the parts to which they are distributed ; hut the greatest irregularity appears to prevail in reference to the origin, the course, and the termination of the cranial nerves. From the comparison which has been made between the scull and the vertebrae, and from the possibility of resolving the bones of the cranium into a certain number of cra- nial vertebra;, anatomists have entertained the idea of drawing a parallel between the cranial and the spinal nerves. It has been conceived that the number of cranial nerves ought to be regulated by the number of cranial vertebra; admitted by different anato- mists ; and, moreover, that in order to draw a fair comparison between these two sets of nerves, the special nerves of the face, namely, the olfactory, the optic, and the auditory nerves, should be entirely disregarded. Now we have already shown (see Osteology) that there are three cranial vertebrae, between which there are two inter- vertebral foramina ; that the anterior inter-vertebral foramen is represented by the sphenoidal fissure, to which we must annex the foramen rotundum and the foramen ovale ; and that the posterior inter-vertebral foramen is rep- resented by the foramen lacerum posterius, together with the anterior condyloid foramen. This being premised, we shall admit two pairs of cranial nerves, an anterior and a posterior. The posterior cranial pair consists on each side of 'the eighth and ninth nerves, namely, of the pneumogastric, glosso-pharyngeal, spinal accessory, and hypo-glossal nerves. The pneumogastric and the glosso-pharyngeal, each of which has a ganglion analogous to the inter- vertebral ganglia, represent the posterior roots of a spinal nerve, while the spi- nal accessory and the hypo-glossal, which have no ganglion, represent the anterior root. The two last-named nerves are exclusively motor, while the pneumogastric and the glosso-pharyngeal appear to me to be mixed nerves, that is, both sensory and motor. The anterior cranial pair is composed on each side of the fifth nerve, the ganglion of which is quite analogous to the inter- vertebral ganglia, and the large portion of the root of which accurately represents the posterior root of a spinal nerve ; and of the third or common motor nerve of the eye, of the fourth or pathetic nerve, of the sixth or exter- nal motor nerve of the eye, of the portio dura of the seventh, and, lastly, of the non- ganglionic portion of the fifth. All these last-named nerves are the nerves of motion ; while the ganglionic portion of the fifth is the nerve of sensation. Moreover, as the spinal nerves communicate with the ganglia of the great sympa- thetic, it is of importance, for the completion of our comparison, to determine the com- munications of the two cranial pairs of nerves with the same system of ganglia. Now Dr. Marshall Hall believes to be the cause of certain instinctive motion.s. (" On the Reflex Functions of the Medulla Oblongata and Medulla Spinalis."— PAti. Trans., 1833.) 854 NEUROLOGY. I regard the superior cervical ganglion of the great sympathetic as common to the two supposed cranial pairs and to the three superior cervical pairs ; in fact, the superior cer- vical ganglion communicates with all the branches of the posterior cranial pair, except- ing the spinal accessory, viz., with the pneumogastric, the glosso-pharyngeal, and the hypo-glossal ; and it also communicates with the anterior cranial pair, and more partic- ularly with the fifth and sixth nerves. As to the ophthalmic, spheno-palatine, otic, and sub-maxillary ganglia, which Arnold regards as annexed to the organs of the senses, viz., the ophthalmic to the eye, the spheno-palatine to the nose, the otic to the ear, and the sub-maxillary to the organ of taste, and which Bichat described as the cephalic portion of the great sympathetic, I am of opinion that they are mere local ganglia, which do not form part of the general sym- pathetic system : besides, the ophthalmic and the otic ganglion only can be shown to be connected with the organs of any sense : it is impossible to show that the spheno-pala- tine ganglion, the very existence of which as a ganghon is often doubtful, has any con- nexions with the organ of smell, or that the sub-maxillary ganglion, which is much more closely connected with the sub-lingual gland, has any relations with the organ of taste. THE SYMPATHETIC SYSTEM OF NERVES. General Remarks. — The Cervical Portion of the Sympathetic. — The Superior Cervical Gan- glion— its Superior Branch, Carotid Plexus, and Cavernous Plexus — its Anterior, Exter- nal, Inferior, and Internal Branches. — The Middle Cervical Ganglion. — The Inferior Cer- vical Ganglion. — The Vertebral Plexus. — The Cardiac Nerves : Right, Superior, Middle, and Inferior, Left. — The Cardiac Ganglion and Plexuses. — The Thoracic Portion of the Sympathetic. — The External arid Internal Branches. — The Splanchnic Nerves, Great and Small. — The Visceral Ganglia and Plexuses in the Abdomen, viz., the Solar Plexus and Semilunar Ganglia. — The Diaphragmatic and Supra-renal ; the Caliac, the Superior Mesenteric, the Inferior Mesenteric, and the Renal, Spermatic, and Ovarian Plexuses. — The Lumbar Portion of the Sympathetic. — The Communicating, External, and Internal Branches. — The Lumbar Splanchnic Nerves and Visceral Plexuses in the Pelvis. — The Sacral Portion of the Sympathetic. — General View of the Sympathetic System. We have seen that the nerves arising from the cerebro-spinal axis are distributed to the organs of the senses, to the skin, to the muscles, in short., to all the organs of ani- mal life. The pneumogastric nerve alone is distributed to the organs of respiration, and the upper part of the alimentary canal, viz., the pharynx, the oesophagus, and the stom- ach. We shall now see that all the internal organs, which are beyond the influence of volition and consciousness, are provided with a special nervous apparatus, which is call- ed the great sympathetic, the sympathetic system, the ganglionic system, or the nervous sys- tem of organic or nutritive life. The sympathetic system consists of two long, knotted cords (/to v,flg. 268, in which figure these cords are represented as if drawn outward away from their natural position) extended one on each side of the vertebral column, from the first cervical to the last sacral vertebra ; these cords are enlarged opposite each vertebra, to form a series of ganglia, which communicate with all the spinal and cranial nerves on the one hand, and give off all the visceral branches on the other. The sympathetic system consists es- sentially of two distinct parts : of a central portion, formed by the two cords ; and of a visceral, median, or pravertebral portion, consisting of certain plexuses and ganglia, which communicate with the central cords, surround the arteries as if in sheaths, penetrate the viscera with them, and establish a communication between the sympathetic cords of the right and left sides. We cannot pay too much attention to the connexion be- tween the ganglionic nerves and the arteries, which always serve as a support for these nerves, and for which, according to some anatomists, the nerves are exclusively des- tined. Each half of the sympathetic system may be described in two ways : either as a con- tinuous cord, having ganglia at intervals upon it, or as a series of ganglia or centres, which may first be examined independently of each other, and around which all the fila- ments that enter or emerge from them may then be arranged. The first method, which is the more natural one, was adopted by the older anato- mists, who described the sympathetic in the same way as other nerves ; according to the second method, which is the one adopted by Bichat, all the ganglia, whatever situa- tion they may occupy, are included in the sympathetic system ; the ophthalmic, the spheno-palatine, and other cranial ganglia would, according to this view, be comprised in the sympathetic system. I believe that the better mode of description is one which associates the idea of a centre with that of a cord. In fact, as the sympathetic system consists of a double line, it is natural to describe it as a nervous cord, having two extremities, one cephalic, the other pelvic ; and as each ganglion forms the point of termination or of origin to a great THE SUPERIOR CERVICAL GANGLION. 855 number of nervous filaments, these bodies may very properly be regarded as central points. The visceral portion of the sympathetic nerves will be described with the gan- glia to which they are connected. I shall describe in succession the cervical, the thoracic, the abdominal, and the pelvic portion of the sympathetic. I have already said that I do not recognise any proper ce- phalic portion of this system of nerves, for the ophthalmic and the other cranial ganglia seem to me to belong to a totally different class. The Cervical Portion of the Sympathetic System. The cervica^ portion of the sympathetic {ft, fig- 302) has this peculiarity, that, instead of being composed of as many ganglia as there are jrj„. 302. vertebrae, it has only two or three. This may be explained by supposing that the superior cervical ganglion represents by itself the ganglia which are wanting. It will hereafter be seen that the lumbar ganglia are rather frequently fused in a similar man- ner. The cervical portion of the sympathetic is situated on the anterior region of the vertebral col- umn, behind the internal and common carotid ar- teries, the internal jugular vein, and the pneumo- gastric nerve {p). It is connected to all these parts, and to the praevertebral muscles, by some very loose cellular tissue, a layer of fascia intervening between them ; it commences by a large fusiform ganglion, the superior cervical ganglion (/) ; this is succeeded by a nervous cord of variable size, which terminates in the middle cervical ganglion (a) when that exists, but when it is absent in the inferior cer- vical ganglion (i), which is continuous with the first thoracic ganglion, either directly or through the medium of two or three very remarkable nervous loops, or frequently by both methods of connexion. We shall proceed to examine the three cervical ganglia. The Superior Cervical Ganglion. Dissection. — Remove the corresponding ramus of the lower jaw ; separate the ganglion very careful- ly from the pneumogastric, giosso-pharyngeal, and hypo-glossal nerves, behind which it is placed. In order to trace the superior or carotid branch, make an antero-posterior median section of the head ; open the foramen lacerum posterius from behind, in the manner indicated for exposing the pneumo- gastric, and then examine the ganglion and its su- perior branch from the inner side. The superior cervical ganglion (/) is olive-shaped or fusiform : it is situated in front of the second and third cervical vertebrae, from which it is sep- arated by the rectus capitis anticus ; it is behind the internal carotid artery, and the glosso-pharyn- geal, pneumogastric, and hypo-glossal nerves ; its upper extremity is about ten or twelve lines distant from the lower orifice of the carotid canal ; it is said to have been found two inches from it. It is larger than the other cervical ganglia {gan- glion cervicale magnum), but it varies much both in its length and its other dimensions ; thus, its low- er extremity has been seen to reach the fourth, fifth, and even the sixth cervical vertebra. Its col- our is grayish, and its surface smooth : not unfre- quently it is bifurcated at its lower extremity ; it is rather often double. Lobstein has figured a case of this kind ; and there were also two superior cervical ganglia, one placed above the other, in a case of hypertrophy of these ganglia, examined and represented by myself — (ATiat. Path., liv. i., pi. 3.) These cases of a double superior cervical ganglion evidently depend on subdivision of the single ganglion usually existing. The branches which end in or emerge from the superior cervical ganglion may be di- vided into superior, inferior, external, internal, and anterior. I shall divide them into these 856 NEUROLOGY. which communicate with the cranial and cervical nerves, those which communicate with the other cervical ganglia, and into arterial and visceral branches. The superior cervical ganglion also gives ofT several twigs to the muscles of the praevertebral region. The superior cervical ganglion communicates with the cranial nerves by means of its superior or carotid branch and its anterior branches. It communicates with the cervical nerves by its external branches. It communicates with the other cervical ganglia by its inferior branch. Its visceral and arterial branches are the pharyngeal, the cardiac, and the branches for the external carotid. The Superior or Carotid Branch from the Inferior Cervical Ganglion. The superior or carotid branch, or the branch of communication with the nerves Avhich constitute the anterior cranial pair, has been for a long time regarded as the origin of the sympathetic nerve ; and as, previously to the time of Meckel, the anastomosis of this carotid branch with the sixth cranial nerve, or external motor of the eye, was the only one known, it was supposed that the sympathetic arose from the sixth nerve ; the discovery of the vidian nerve by the elder Meckel has led to the admission of two ori- gins or roots of the sympathetic, namely, one from the fifth and another from the sixth cranial nerve. Since the researches of modern anatomists, the study of the superior or carotid branch of the superior cervical ganglion has become one of the most complicated points in the anatomy of the nervous system. This carotid branch appears to be a prolongation of the superior cervical ganglion ; it tapers as it approaches the carotid canal, into which it enters, after having divided into two branches, one of which runs on the inner side and the other on the outer side of the artery. These branches communicate with each other, subdivide, and unite to form the carotid plexus, and having reached the cavernous sinus, form a plexus, named the cavernous plexus, which gives olf the communicating branches to the sixth and fifth nerves, and also the small plexuses which surround the internal carotid and its branches.* Laumonier, and after him Lobstein and several others, described a ganghon, named the carotid ganglion, in the first turn of the carotid canal ; but it is in vain to search for it, unless some slight enlargements on the external and internal branches, wherever they give off or receive twigs, are to be regarded as ganglionic, t During their course in the carotid canal, the external and internal divisions of the ca- rotid portion of the sympathetic give off the following branches : An Anastomotic Twig to the Nerve of Jacohson. — This comes off from the external branch, and is very small ; it perforates the external wall of the carotid canal, enters the cavity of the tympanum, and anastomoses with the nerve of Jacobson, a branch of the glosso-pharyngeal. An Anastomotic Twig to the Spheno-palatine, or MeckeVs Ganglion. — This, like the pre- ceding, comes from the external division of the carotid branch of the sympathetic, and passes to the vidian or pterygoid branch of the superior maxillary nerve. We have al- ready spoken of this twig, under the name of the carotid or deep branch of the vidian nerve. Anatomists differ as to whether it should be regarded as passing from the fifth nerve to the superior cervical ganglion, or from the superior cervical ganglion to the fifth nerve. Arnold, on account of its grayish colour and slight consistence, regards it as coming from the superior cervical ganglion, while he believes the great superficial petrosal nerve, i. e., the cranial branch of the vidian, also from its colour and consist- ence, to belong to the cerebro-spinal system of nerves, and to be a branch of the fifth nerve. I have already said that I have never found sufficient difference between the superior petrosal and carotid branches of the vidian to warrant this distinction. These two nerves are, moreover, perfectly distinct from each other as far as the spheno-pala- tine ganglion, in which they terminate. It is important to observe that the two branches of the vidian nerve terminate in the enlargement called the spheno-palatine, or Meckel's ganglion : the connexion of this ganglion with the superior cervical ganglion has not been overlooked by those anato- mists who regard the spheno-palatine enlargement as a ganglion, and who consider the cranial ganglia as forming part of the sympathetic system. Anastomotic Branches to the Sixth Nerve. — Several branches, generally three, turn round the convex side of the second curve of the internal carotid, reach the outer side of that artery, and anastomose, either separately, or, after having united together, with the sixth or external motor oculi nerve. The nerves join at an acute angle opening backward, within the cavernous sinus, and at the point where the sixth nerve crosses the carotid : as this nerve becomes flattened and widened opposite to the artery, it has been imagined that it was really enlarged, and that this augmentation was due to the addition of fila- ments from the sympathetic nerve ; but the enlargement is only apparent, and, notwith- standing the difference in colour, I should be inclined to admit that the communicating * The carotid branch is sometimes single, and turns spirally around the artery, being- placed at first behind, then on the outer side, next on the inner, and again on the outer side of the vessel. t Arnold, whose authority upon such a subject is of great weight, has never seen this ganglion ; he very properly remarks, that even those anatomists who admit the existence of it are not agreed as to its situation THE CAVERNOUS PLEXUS, ETC. 857 filaments between the sixth nerve and the carotid branches of the sympathetic are fur- nished by the sixth nerve, and have a reflected course. I have seen the three commu- nicating filaments between the upper part of the sympathetic and the sixth nerve form a gangliform enlargement as they were about to join the latter; and it was this gangli- form enlargement which gave origin to the plexus surrounding the internal carotid ar- tery and its branches. The Cavernous Plexus. The cavernous plexus, in which the two divisions of the carotid branch of the superior cervical ganglion at length terminate, is situated on the inner side of the carotid artery, at the point where that vessel enters the cavernous sinus. From this grayish plexus, which is intermixed with small vessels (plexus nervoso-arteriosus, Walter), a consider- able number of filaments proceed, some of which establish a communication between it and the fifth nerve, while others surround the internal carotid, and accompany all its ramifications. The following very numerous branches emerge from the cavernous plexus : Some communicating Filaments to the Third Nerve or External Motor Oculi, before the Di- vision of that Nerve. — These filaments pass above the sixth nerve, to which they appear to be applied.* A Filament of Communication ivith the Ophthalmic Ganglion. — This arises from the an- terior part of the cavernous plexus, enters the orbit between the third nerve and the oph- thalmic division of the fifth, and unites sometimes with the long root of the ophthalmic ganglion, which we have stated to be derived from the nasal branch of the ophthalmic, and sometimes with the ophthalmic ganglion itself This root had been described and figured by Lecat, before Bock, Ribes, and Arnold recalled the attention of anatomists to it. It follows, from the arrangement just described, that the ophthalmic ganglion has three roots, two cerebro-spinal and one ganglionic. Communicating Filaments of the Fifth Nerve. — Some of these pass to the Gasserian gan- glion, and others to the ophthalmic division of the fifth, t The Filaments which accompany the Internal Carotid Artery and its Branches. — These are extremely delicate, but they are beautifully distinct in some subjects. They may be followed even upon the branches of the internal carotid. Anatomists admit the existence of a plexus for the ophthalmic artery, and for each of its subdivisions. It is even supposed that there is one for the arteria centralis retinae. t Several authors have described a certain number of filaments proceeding from the cavernous plexus to the pituitary body (filets sus-sphenoidaux, Chaussier). I have nev- er been fortunate enough to discover them, nor yet the ganglion (the ganglion of Ribes) which is said to exist upon the anterior communicating artery of the brain, and which is found at the point of junction of the right and left trunks of the sympathetic. It follows, from what has been stated, that the superior cervical ganglion, by means of its upper or carotid branch, communicates with most of the nerves of the anterior cra- nial pair ; namely, with the fifth nerve, by means of the Gasserian ganglion, of the oph- thalmic division of the fifth, and of the ophthalmic ganglion, either directly or indirectly ; also by means of the superior maxillary division of this nerve, through the intervention of the spheno-palatine ganglion ; secondly, with the third nerve ; and, lastly, with the sixth. The Anterior Branches from the Superior Cervical Ganglion. The anterior branches of the superior cervical ganglion establish a communication with the different nerves of the posterior cranial pair, excepting the spinal accessory nerve, which does not appear to have any direct communication with it. The glosso-pharyngeal and pneumogastric nerves communicate with the superior cervical ganglion at two different points, viz., at their ganglia, and by their branches. The communication of the superior cervical ganglion with the ganglia of the glosso-pha- ryngeal and pneumogastric nerves has been pointed out by Arnold ; it is difficult to dem- onstrate it through the dense tissue which surrounds these ganglia. On the contrary, it is extremely easy to demonstrate the communications of the glos- so-pharyngeal nerve and the plexiform cord of the pneumogastric with the superior cer- vical gangUon. I have already said (see Pneumogastric Nerve) that in one case I found the pneumogastric so closely applied to the whole length of the superior cervical gangli- on, that it was impossible to separate them. The communication of the superior cervi- cal ganglion with the hypo-glossal is quite as evident as the preceding. The filaments of communication with the nerves forming the posterior cranial pair do not always proceed from the superior cervical ganglion itself, but sometimes from its ca- rotid branch. * I have never seen the communication between the superior cervical gang-lion and the facial nerve noticed by some anatomists. t I may here again notice, that in two subjects I have seen a twig from the spheno-palatine ganglion join the communicating branches between the sixth nerve and the sympathetic, t i\l. Ribes, Memoires de la Societe M6dicale d'Emulation, t. vii. 5Q 858 NEUROLOGY. The External Branch from the Superior Cervical Ganglion. The external branches of the superior cervical ganghon establish a communication be- tween it and the first, second, and third cervical nerves ; they are large, have a gray colour, and a ganglionic structure ; we may regard them as true prolongations of the superior cervical ganglion ; the principal of them enter the angle of bifurcation of the second cer- vical nerve, into its ascending and descending branches ; the others, which are very small, join the first cervical nerve. They constitute a true ganglionic plexus, and often form two distinct groups. Frequently the superior cervical ganglion communicates only with the first and sec- ond cervical nerves. At other times it also communicates with the third and fourth nerves by means of a long and very oblique branch. In one case it communicated di- rectly with the phrenic nerve. The Inferior Branch from the Superior Cervical Ganglion. The inferior branch from the superior cervical ganglion, or the branch of communica- tion with the middle cervical ganglion, is a white cord, resembling a spinal nerve, ex- cepting in a few cases, in which it appears to be a prolongation of the tissue of the ganglion itself: when the lower extremity of the superior cervical ganglion is divided into two parts, its inferior branch arises from the external division. It varies much in size in different subjects : it descends vertically in front of the spinal column, behind the com- mon carotid, the internal jugular vein, and the pneumogastric nerve, to which it is uni- ted by a very loose cellular tissue. Having reached the inferior thyroid artery, the cord of the sympathetic passes behind that vessel, and enters the middle cervical ganglion, when that exists ; but when it is ab- sent, the cord continues on to join the inferior cervical ganglion. As it descends, it most commonly receives some twigs from the third and fourth cervical nerves, which twigs we have already said occasionally enter the superior cervical ganglion. At its origin, it gives off on the inner side two filaments, which join the superior cardiac nerve, and in- crease its size ; and an anastomotic twig to the external laryngeal nerve, a branch of the superior laryngeal. Not unfrequently the superior cardiac nerve arises entirely from the communicating branch between the superior and middle cervical ganglia, that branch appearing to bifurcate. The communication between the superior and middle cervical ganglia is subject to much variety. I have seen a small ganglion upon it opposite to the inferior thyroid ar- tery ; from this ganglion, which rested upon the artery, and which might be regarded as the vestige of a middle cervical ganglion, two cords proceeded, an anterior, which join- ed the cardiac nerve, and a posterior, which ended in the inferior cervical ganglion : both of these had a gangliform structure. The cord of the sympathetic is not uncom- monly found enlarged at intervals into ganglionic nodules. The Internal Branches, or Carotid and Visceral Branches. The internal branches from the superior cervical ganglion are divided into those which accompany the external carotid and its ramifications, and those which are distributed to the viscera. The Carotid Branches. — It has been stated that from the upper extremity of the supe- rior cervical ganglion certain branches are given off, which surround the internal carot- id, and are prolonged upon its ramifications. From the inner border of the same ganglion other branches proceed, which embrace the external carotid and the ramifications of that vessel. These nerves are of a gray colour (subrufi), of a soft texture (nervi moUes et pene mu- eosi, Scarpa), and of a knotted and gangliform structure (rami gangliformes, Neubauer) ; they come off from the ganglion opposite to the origin of the facial artery ; they pass in- ward behind the external and internal carotids, and form a sort of gray plexus, which ex- tends as far as the origin of the internal and external carotid ;* they turn like a loop around the former of these vessels, and anastomose with the carotid filaments from the glosso-pharyngeal, and from the pharyngeal and superior laryngeal branches of the pneu- mogastric. None of the branches from this plexus are prolonged upon the common ca- rotid ; they all pass upon the external carotid and its different ramifications, forming as many plexuses as there are vessels, and are distributed with those vessels to the neck and the face. Thus, there is a thyroid plexus, which surrounds the superior thyroid ar- tery, and may be traced into the thyroid body ; a lingual plexus, which enters the sub- stance of the tongue, and is supposed to anastomose with the lingual branch of the infe- rior maxillary division of the fifth, and even with the hypo-glossal nerve ; and a facial plexus, which is supposed to anastomose with the facial nerve. Anatomists have par- ticularly directed their attention to the branches which enter the sub-maxillary gland ; some imagining, and others regarding it as certain, that these branches communicate with the sub-maxillary ganglion. I have never been fortunate enough to discover this communication. * At this division there is frequently a gangliform enlargement, which Arnold proposes to call the inter-ca- rotid ganglion . THE MIDDLE AND INFERIOR CERVICAL GANGLIA. 859 There is, moreover, a pharyngeal •plexus, an occipital plexus, and an auricular plexus : the elder Meckel* has even described an anastomosis between the facial nerve and the sympathetic filament which accompanies the posterior auricular artery. Lastly, the temporal artery, and the internal maxillary artery and its divisions, are also surrounded (hederae ad modum, Scarpa) by small nervous plexuses ; these plexuses are sometunes so well developed, that the elder Meckel states that the arteries of the face have larger nervous plexuses than any others in the body. These plexuses appear to me to be pe- culiarly remarkable for containing a mixture of white fibres and nervi moUes, which proves their double origin. All these plexuses present gangliform enlargements at various points, as is shown in the splendid plate in Scarpa's work.t This author has figured, after Andersh, a gangli- on which he believes to be constant at the division of the external carotid and temporal arteries. A twig from the facial nerve terminates in this ganglion. t The Visceral Branches. — All these come off from the inner side of the ganglion, and divide into pharyngeal, laryngeal, and cardiac branches. The pharyngeal branches are certain thick ganglionic cords which arise from the upper and inner part of the superior cervical ganglion, pass transversely inward, and combine with the pharyngeal branches of the glosso-pharyngeal and pneumogastric nerves to form one of the most remarkable plexuses in the body, which is distributed to the pha- rynx. To this plexus must be referred all those highly important nervous phenomena which are manifested in connexion with the pharynx, more particularly the sensation of thirst. The laryngeal branches unite with the superior laryngeal nerve and its divisions. In a case in which the external laryngeal nerve arose separately from the pneumogastric and not from the superior laryngeal, it had as many filaments of origin from the superior cervical ganglion as from the pneumogastric itself. The cardiac branches form the superior cardiac nerve, to which I shall recur after hav- ing described the middle and inferior cervical ganglia. The Middle Cervical Ganglion. The middle cervical ganglion {a, fig. 302) is wanting in a great number of subjects, and then the branches usually given off from and received by it are given off and received by the cords which connect the superior and inferior cervical ganglia, or by the inferior cervical ganglion itself The middle cervical ganglion is sometimes double ; at other times it is in quite a rudimentary state. It is situated on a level with the fifth or sixth cervical vertebra, in front of the inferior thyroid artery, opposite to the first curve of that vessel, and sometimes behind it ; its relation to this artery, which is very nearly constant, induced Haller to name it the thy- roid ganglion : however, I have frequently seen it eight lines above that artery. Its form and size are extremely variable, not only in different subjects, but even upon oppo- site sides of the same subject. Sometimes it is a simple gangliform enlargement. Scarpa has figured a middle cervical ganglion almost as large as the superior, and, like it, olive-shaped. I have never seen it as large as this.ij The middle cervical ganglion, when it exists, receives, Above, the cord which communicates with the superior cervical ganglion ; belmv, the cord of communication, often multiple, with the inferior cervical ganglion ; on the out- side, three branches, derived from the third, fourth, and fifth cervical nerves : not un- frequently the communicating branch from the fourth cervical nerve belongs to the phrenic ; on the inside, the middle cardiac nerve, or great cardiac of Scarpa, which I shall presently describe. The size of the middle cervical ganglion has always appeared to me to be proportioned to that of its filaments of communication with the cervical nerves. The Inferior Cervical Ganghon. Neubauer has given an excellent description of the inferior cervical ganglion, under the name of the first thoracic ganglion, rather an appropriate title for it, because it is fre- quently continuous with the first thoracic ganglion (as at ?', fig. 302) ; and, secondly, be- cause it is situated in front of the transverse process of the seventh cervical vertebra and of the head of the first rib. This ganglion is constant ; it is deeply seated behind the origin of the vertebral artery, by which it is completely concealed, ii * Memoires de I'Acad, de Berlin, 1752. t Tahulie Neurolog-ics, tab. iii., 1794. f Arnold has described and figured a twig from the plexus which surrounds the middle mening-eal or spheno- Bpinous artery, and which, according to this laborious inquirer, terminates in the otic ganglion ; he also de- scribes some nervous twigs passing from the plexus of the ascending palatine artery to the sub-ma.\illary ganglion. In this way he establishes a connexion between the sympathetic system and these two cranial gan- plia. I have devoted great care to this subject, but have never been able to make out these communicating filaments, even though all the difficult dissections have been made upon specimens previously macerated in diluted nitric acid. ij I believe that it is incorrect to regard as a middle cervical ganglion those ganglionic nodules, without either aflferent or efferent filaments, which are rather frequently found at various points on the trunk of the sympathetic. H It is not ram to see the inferior cervical ganglion describe around the vertebral artery a half ring, which is completed in front by a gray cord extended from one end of the ganglion to the other. 860 NEUROLOGY. It is of a semilunar shape, its concave border being turned upward and its convex one downward ; at its internal extremity it receives the trunk of the sympathetic ; at its ex- ternal extremity it receives a large nerve which accompanies the vertebral artery, and which may be called the vertebral nerve ; at the same extremity it also receives some communicating branches from the fifth, sixth, and seventh cervical nerves, and often from the first dorsal. Several branches proceed from its convex border, which is turned downward ; some pass in front of and others behind the sub-clavian artery, which they embrace like loops. Most of these inferior branches are the communicating branches between the inferior cervical and the superior thoracic ganglion, and they exist even when the two ganglia are directly continuous with each other. One of the branches sometimes joins the recurrent laryngeal branch of the pneumogastric ; the most remark- able of the inferior branches constitutes the inferior cardiac nerve, which is rather fre- quently derived from the superior thoracic ganglion. To complete the description of the cervical portion of the sympathetic, we have now only to speak of the vertebral nerve and of the cardiac nerves. The Vertebral Plexus. The vertebral plexus or vertebral nerve occupies the canal which is formed for the verte- bral artery in the transverse processes. It is generally said that this nerve arises from the inferior cervical ganglion ; that it traverses the entire length of the canal formed for the vertebral artery, enters the cranium with that vessel, and then unites with its fel- low of the opposite side to form the basilar plexus, which divides and subdivides around the terminal ramifications of the basilar artery, like the plexuses which are formed around the internal carotid ; but such is not a correct description of the nerve. It ap- pears to me to be formed by the junction of filaments derived from the third, fourth, and fifth cervical nerves, gradually to increase in size from above downward as it receives new filaments, then to pass behind the artery, to emerge from the canal also behind the vessel, and, finally, to enter the inferior cervical ganglion. I conceive that this branch is intended to establish a communication between the third, fourth, and fifth cervical nerves and the inferior cervical ganglion. I have never found upon these branches the swellings or gangh which, according to M. Blainville's ingenious idea, might be intend- ed to supply the place of the cervical sympathetic ganglia, and to destroy the appear- ance of irregularity which exists in the cervical region in this respect. The Cardiac JVerves. Dissection. — This comprises the dissection of the cardiac nerves, from their origin to the point where the aorta and pulmonary artery cross each other ; and from that point to the extreme divisions of the nerves. For this purpose, after having previously ex- posed the cervical ganglia and the cardiac nerves, the preparation should be macerated in diluted nitric acid ; all the internal nerves which proceed from the ganglion should then be carefully dissected, so as to preserve their relations with the cardiac branches of the pneumogastric and recurrent nerves ; we must then examine the nerves which pass in front of the aorta, those which run between that vessel and the pulmonary ar- tery and trachea, and, lastly, those which pass behind the pulmonary artery ; we should study, at the same time, their relations with the anterior and posterior cardiac plexuses. The cardiac nerves, or nerves of the heart, which are distinguished into the right and the left,* arise essentially from the cervical ganglia. These ganglionic nerves are then joined by several branches from the pneumogastric ; they all converge upon the origin of the aorta and pulmonary artery to form the cardiac plexuses, which give off the right and left coronary plexuses ; these latter plexuses surround the coronary arteries, and their branches are scattered over the surface of the heart, but do not enter its substance un- til they have advanced a considerable distance beneath the serous membrane by which the heart is covered. Such is the most general idea that can be given of the cardiac nerves and plexuses, which afford one example of the most remarkable of the median anastomoses. Scarpa first described and figured them correctly in his plates, which will always be models for anatomical drawings. No nerves present so many varieties, in number, size, and ori- gin, as the cardiac nerves ; and on this subject especially, the want of a work upon ana- tomical varieties is especially felt. For my part, I declare that I have never found the cardiac nerves in my dissections as they are represented in Scarpa's magnificent plates, * The history of the nerves of the heart is singular. The ancient philosophers, with Aristotle, influenced by certain preconceived ideas, stated that the heart vfas the source of all the nerves in the body. Galen re- futed this opinion, and admitted that the heart had but one very small nerve, which descended from the brain. Vesalius considered that this slender nerve came from the recurrent, and represented it in a figure. Fallo- pius first described the nerves of the heart, and says that he showed his audience " insignem nervorum plexum a quo abundans copia nervosa: materia: totam cordis basim comp/exatur, perque ipsam plures propagines parvo- rum nervorum dispergit." Behrends, in 1792, defended a thesis in which he endeavoured to demonstrate that the heart has no nerves, cor nervis carere. Such was the amount of knowledge on this subject when, in 1794, Scarpa published his splendid work, and settled the state of science on this point.— {Tabula: Neurological ad Illustrandam Anatomiam Cardiacorum Nervorum, Noni Nervorum Cerebri, Glosso-pharynga:i et Pharyngai es Octavo Cerebri.) THE RIGHT CARDIAC NERVES. 861 ■which have served as the type for all descriptions. I have minutely described the cardiac nerves in eight different subjects ; these eight descriptions present very great differen- ces, at least, until one arrives at the account of the cardiac plexuses ; the ultimate dis- tribution of the nerves of the heart appeared to be the same in all these subjects. All the cardiac nerves are gray, but they are not all soft, as declared by Scarpa, who called them nervi molles. Sometimes the right, and sometimes the left cardiac nerves, are the larger ; the nerves of the two sides are inversely proportioned to each other in this respect, and there is evidently a mutual dependance between them. In one case, in which the middle and inferior cardiac nerves of the right side were wanting, and the superior cardiac nerve very small, their places were supphed by some large branches from the right recurrent nerve, and by the left cardiac nerves, which were largely de- veloped. Anatomists follow Scarpa in describing three cardiac nerves on each side : a superior, named by him the superficial cardiac nerve, which is derived from the superior cervical ganglion ; a middle, called by him the great or deep cardiac nerve, which arises from the middle cervical ganglion ; and an inferior, or small cardiac nerve, proceeding from the inferior cervical ganglion. Although this is the usual arrangement, it is often impossible to distinguish three nerves, in consequence of the anatomical varieties which I have al- ready mentioned. There is frequently no middle cardiac nerve properly so called ; at other times there is no inferior cardiac nerve, or, rather, they are both in a rudimentary state ; lastly, the superior cardiac nerve, if not entirely wanting, may be extremely small, and may join the middle cardiac nerve. Sometimes all the cardiac nerves of one side unite into a single trunk, or else into a plexus situated behind the sub-clavian artery, upon the side of the trachea ; the recurrent nerve assists in forming this plexus, from which three, four, or more branches are given off to be distributed to the heart in the usual manner. One of the most important points in the history of the cardiac nerves is their sort of fusion with the pneumogastric, which is so intimate that the cardiac branch- es of the pneumogastric, and those which come from the ganglia, fonn a single system. There is a similar fusion between the superior, middle, and inferior cardiac nerves of each side, and between the nerves of the two sides. The recurrent nerve, in particular, appears sometimes to be distributed equally to the larynx and the heart, so large and numerous are the cardiac branches given off from it ; it will hereafter be seen that there is an equally intimate connexion between the pneu- mogastric nerve and the solar plexus. I shall first describe in detail the right cardiac nerves, and shall then briefly point out the differences between them and the left cardiac nerves. The Right Cardiac Nerves. The Superior Cardiac Nerve. — Its origin is very variable. Most commonly, it arises from the internal division of the bifurcated lower extremity of the superior cervical gan- glion, the cord of communication between the superior and the next cervical ganglion forming the external division. At other times it arises from the communicating cord. In a great number of cases it has several origins, being formed by two or three very small filaments, which come from the inner side of the superior cervical ganglion ; by a branch, often a large one, from the cord of communication ; and by two filaments from the pneumogastric nerve. In one of these latter cases the cardiac branch from the cord of communication presented a very distinct ganglion. "Whatever may be its origin, the superior cardiac nerve passes obliquely downward and inward, behind the common carotid, from which it is separated by a very thin layer of fascia, so that it is almost impossible to include it iu applying a ligature to that artery ; it runs along the trachea, very often receives a branch from the trunk of the sympathet- ic, and crosses in front of the inferior thyroid artery, or sometimes divides into two branch- es, one of which, the anterior, passes in front of the artery, while the posterior joins the recurrent nerve.* At the lower part of the neck the superior cardiac nerve runs along the recurrent laryngeal nerve, with which it may be confounded ; it enters the thorax, passing behind and sometimes in front of the sub-clavian artery,t runs along the brachio- cephalic trunk, gains the back of the arch of the aorta, gives off a certain number of fila- ments, which pass in front of that part of the vessel, then runs obliquely downward and to the left between the arch of the aorta and the trachea, anastomoses very frequently with the middle and inferior cardiac nerves and with the branches of the recurrent, and divides into two sets of filaments ; some of these pass between the aorta and the pul- monary artery, and others between the right pulmonary trunk and the trachea ; they both * The trunk of the sympathetic, having reached the inferior thyroid artery, sometimes divides into two branches, one of which passes in front of that artery, to join the superior cardiac nerve, while the other passes behind it to the inferior cervical ganglion ; not unfrequently the superior cardiac nerve presents a ganglionic enlargement, which occupies the whole or a part of the thickness of the nerve. t The superior cardiac nerve often bifurcates so as to embrace the sub-clavian artery in a complete ring. At other times the superior cardiac nerve passes behind the sub-clavian artery, and the cardiac branch of the pneumogastric in front of it, so as to form beneath the sub-clavian an anastomotic loop, which lies to the inner side of the one formed by the recurrent nerve. IVIost commonly the cardiac branch of the pneumogastric anas- tomoses with the superior cardiac nerve, between the arch of the aorta and the trachea. 662 NEUROLOGY. anastomose with the left cardiac nerves, and are arranged as we shall soon describe. In some rare cases, the right superior cardiac nerve goes directly to the cardiac plexus, Vi-ithout anastomosing with the middle and inferior cardiac nerves. During its course along the neck, the right superior cardiac nerve receives the small superior cardiac branches of the pneumogastric, and gives ofT several filaments, some to the pharynx, others to the trachea and the thyroid body, while several assist in forming the plexus of the inferior thyroid artery ; it often gives off three or four branches which anastomose with the recurrent nerve. In the thorax, the superior cardiac nerve is joined by the cardiac branch given off by the pneumogastric in the lower part of the neck, and which is sometimes of very consid- erable size, and evidently re-enforces the cardiac nerve ; this branch of the pneumogas- tric sometimes terminates directly in the cardiac plexus. The Middle Cardiac Nerve. — This nerve arises from the middle cervical ganglion, or, when that is absent, from the trunk of the sympathetic, at a variable distance from the inferior cervical ganglion. It is rather frequently the largest of the cardiac nerves, and has, therefore, been called by Scarpa the great cardiac nerve {magnus, profundus). At other times it is in a rudimentary state, and is replaced either by the superior or the in- ferior cardiac nerve, or by branches from the recurrent : it frequently divides into sev- eral twigs, between which the sub-clavian passes ; it almost always anastomoses with the superior and inferior cardiac nerves of the same side, runs along the recurrent nerve, for which it might be mistaken, and with which it is always connected, and then terminates in the cardiac plexus. TTie Inferior Cardiac Nerve. — This is generally smaller (cardiacus minor) than the pre- ceding nerve, though it is sometimes larger ; it usually arises from the inferior cervical ganglion, but rather fequently from the first thoracic ; it accompanies the middle cardi- ac nerve, anastomoses with that nerve, and, hke it, descends vertically in front of the trachea, and terminates in the cardiac plexus. The connexion of the middle and inferior cardiac nerves with the recurrent nerve de- mands especial attention. Sometimes the recurrent sends off certain large branches which join the cardiac nerves, and form their principal origin. I have seen the middle and inferior, cardiac nerves united together, crossing over the recurrent nerve at right angles, and adhering intimately to it without presenting that admixture of filaments which constitutes an anastomosis.* The Left Cardiac Nerves. The peculiarities of the left cardiac nerves may be stated in a few words :t in the neck, they are situated in front of the oesophagus, on account of the position of that canal. The connexions between the cardiac nerves and the recurrent on the left side appear to me more numerous than those on the right. In one case, the superior and inferior car- diac nerves gave off a series of four rather large filaments, which ran along the recur- rent, left that nerve opposite to its point of reflection, and then terminated in the usual manner. I ascertained that, in this case, the two nerves were merely in contact, and did not anastomose. In the thorax, the superior and middle cardiac nerves of the left Side descend between the carotid and sub-clavian, and then run upon the concavity of the arch of the aorta ; the inferior cardiac nerve, which is the largest of all the cardiac nerves in a subject which I have now before me, passes to the left of the trunk of the pulmonary artery, turns round its back part, and embraces it in a loop, so as to enter that portion of the cardiac plexus which is situated between the aorta and the right division of the pulmo- nary artery. Lastly, on the left s;de, more commonly than on the right, the anterior nulmonary plexus sends off some flaments to this same part of the cardiac plexus. The Cardiac Ganglion and Plexuses. We have seen that the cardiac nerves of the same side anastomose with eacn other on the sides or in front of the trachea. Besides this, the right cardiac nerves anasto- mose with the left upon the concavity of the arch of the aorta ; also in front of the tra- chea, above the right pulmonary artery ; and, lastly, in the anterior and posterior coro- nary plexuses. Wrisberg was the first to describe a ganglion in the situation of the first-named anas- tomosis, that is to say, upon the concavity of the arch of the aorta, between that vessel and the pulmonary artery, to the right of the remains of the ductus arteriosus. This ganglion, which is by no means constant, is named the cardiac ganglion ; it is joined [so as to form the superficial cardiac plexus] by the superior cardiac nerve of the right side, * It is especially in these anastomoses between the cardiac and recurrent nen'es that I have been able, from the ditferent aspect of the filaments of each, to ascertain that the anastomoses of nerves are often mere- ly apparent, and consist of a simple juxtaposition of two nerves without any communication of their component fasciculi, which can lie traced uninterruptedly from their entrance to their emergence. The same observa- tion applies also to some of the anastomoses between nerves of the same kind. t In one subject, three filaments arose from the left superior cervical ganglion, and united in a small gan- glionic nodule, which also received a twig from the laryngeal nerve. This ganglionic nodule gave off several pharyngeal twigs, and also the superior cardiac nerve. THORACIC PORTION OP THE SYMPATHETIC SYSTEM. 863 by the same nerve of the left side, and sometimes also by the right and left cardiac branches given off from the pneumogastric nerves in the lower part of the neck. The second anastomosis, or that which takes place in front of the trachea, above the right pulmonary artery, and behind the arch of the aorta, has been known, since the time of Haller, as the great cardiac plexus (magnus, profundus plexus cardiacus, Scarpa). A ganglionic enlargement is not unfrequently found at the junction of the principal branch- es. This great cardiac plexus is chiefly formed by the middle and inferior cardiac nerves of both sides : [it also receives part of the right superficial nerves.] Lastly, all the car- diac nerves end in the third set of anastomoses, namely, those upon the anterior and posterior coronary arteries around the root of the aorta. Great as the variety may be in the course and size of the cardiac nerves up to the origin of the great vessels from the heart, there is as constant a uniformity in their ar- rangement around those vessels, and in their ultimate distribution to the heart. Upon the origin of the great vessels, the cardiac nerves are arranged in three layers or sets. The superficial layer of nerves is the smallest ; it occupies the anterior surface of the arch of the aorta, and especially its right side ; the nerves are visible without any dis- section through tiie transparent pericardium ; they all pass (y) to the anterior coronary artery, to the right side of the infundibulum of the right ventricle. In this superficial layer, the superficial cardiac plexus, may be included the ganglion of Wrisberg, when it exists, and its several branches, which in a great measure assist in forming the anterior coronary plexus. The middle layer of nerves is composed of two very distinct parts, viz., of the great or deep cardiac plexus of Haller, which is situated between the trachea and the arch of the aorta, above the right pulmonary artery ; and of a much smaller part, situated below the great cardiac plexus, from which it is derived, and between the right pulmonary artery and the arch of the aorta. In order to obtain a good view of this layer, the arch of the aorta must be cut through. The deep layer of iierves is situated between the right pulmonary artery and the bifur- cation of the trachea. The trunk of the pulmonary artery must be divided in order to expose it. The Anterior and Posterior Coronary Plexuses. — The whole of the superficial cardiac plexus or superficial layer of nerves ends in the anterior coronary plexus {v) which sur- rounds the right coronary artery. The middle and posterior layers unite below the right pulmonary artery, in front of the auricles, to form a plexus, which might more properly be named the great or deep cardiac plexus than the interlacement so called by Haller. From this plexus, into which the left inferior cardiac nerve enters directly, the follow- ing branches proceed ; anterior auricular branches, which are very numerous ; certain branches which pass between the aorta and the pulmonary artery to gain the right side of the infundibulum, and join the anterior coronary plexus, which, as we have seen al- ready, is derived from the superficial cardiac plexus ; lastly, the branches for the poste- rior coronary plexus, which surrounds the origin of the left coronary artery, and divides, like that vessel, into two secondary plexuses, one of which runs round the left auriculo- ventricular furrow, while the other {v') enters the anterior ventricular furrow. The nervous filaments from these plexuses soon leave the ramifications of the arter- ies ; they proceed separately ; they are all equally small, and can be seen without any dissection, like white lines, extending from the base towards the apex of the heart. They all belong to the ventricular portion of the heart ; a few of them, however, ascend on the posterior surface of the auricles, which are much more abundantly supplied upon their anterior surface. The cardiac nerves are not entirely distributed to the heart ; several of them are lost in the coats of the aorta, some join the anterior pulmonary plexus, and some ramify in the pericardium. The Thoracic Portion of the Sympathetic System. In the thorax, the trunk of the sympathetic (*' t,fig. 302) consists, on each side, of a grayish cord, having as many nodules or ganglia upon it as there are vertebra;. This cord is situated, not in front of the dorsal vertebrae, but in front of the heads of the ribs, to which the ganglia for the most part correspond : the two superior thoracic ganglia are the largest, and are almost always united ; the succeeding ganglia are almost of equal size, the twelfth being next in size to the first and second. The ganglionic struc- ture is observed throughout the whole extent of this part of the sympatlietic, so that the cords of communication between the ganglia may be said to be merely prolongations of the ganglia. In some subjects the ganglia cannot be distinguished from the portions of the sympathetic trunk above and below them, except by the branches which enter and converge from those points ; it would, therefore, be a serious anatomical error to regard the portions of the trunk between the ganglia as mere filaments of communica- tion. In some subjects the cords between the ganglia are divided into two or three fila- ments. The varieties observed in the number of the thoracic ganglia are rather appa- 864 NEUROLOGY. rent than real : they depend, some upon fusion of the first thoracic ganghon with the inferior cervical ganglion, or of the first and second thoracic ganglia ; others upon fusion of two central ganglia, or upon that, which is more common, of the last thoracic with the first lumbar ganglion ; upon a transposition of the last thoracic ganglion, which is then found upon the first lumbar vertebra ; and, lastly, upon the two inferior thoracic ganglia being situated in the last intercostal space. Besides this, the three lowest tho- racic ganglia are subject to much variety, both in situation and in shape ; and the same may be said of the mode of connexion between the twelfth thoracic and the first lumbar ganglion. The thoracic portion of the sympathetic lies beneath the pleura and the very thin fibrous layer by which that membrane is strengthened. It can be distinctly seen with- out any dissection, in consequence of the transparency of these layers. The intercos- tal arteries and veins pass behind it ; on the right side, the vena azygos runs along it. The thoracic portion of tlie sympathetic gives off external hranches, or branches of communication with the dorsal nerves ; and the internal branches, which are intended for the aorta and the abdominal viscera. The Ezterjial or Spinal Branches. There are at least two spinal branches from each ganglion, one superficial and larger, which is connected to the outer angle of the ganglion ; the other deep and smaller, which is attached to its posterior surface : there is sometimes a third filament of com- munication. Not unfirequently these branches unite into a single trunk, before reaching the ganglion. I regard these anastomotic branches (e e), between the spinal nerves and the ganglia of the sympathetic, not as branches furnished by the ganglia to the spinal nerves, nor simply as means of communication between one and the other, but rather as branches of origin of the sympathetic : this, indeed, is clearly demonstrated by the arrangement of these spinal branches of the sympathetic, which are always proportioned to the size of the ganglia from which they arise. In general, each ganglion communicates only with the corresponding spinal nerve ; not unfrequently, however, a ganglion receives a twig from the intercostal nerve immediately below it.* The branches of communication from the dorsal nerves to the thoracic ganglia of the sympathetic are horizontal, or, rather, they are inclined obliquely downward and inward, excepting those which ascend to the first thoracic ganglion, and those which descend to join the last thoracic ganglion. These branches are white, like the nerves of the cere- bro-spinal system, and not gray, like the ganglionic nerves. On examining their ulti- mate distribution in the sympathetic ganglia, and their connexions with the dorsal and intercostal nerves, after the parts have been macerated, first in diluted nitric acid and then in water, it is seen that these branches are evidently reflected funiculi of the spi- nal nerves ; and that the nerves, immediately after having given off these branches, are proportionally diminished in size ; that, having reached the ganglia, the communicating branches divide into filaments, of which some ascend, and may be traced upon the trunk of the sympathetic above the ganglion, and appear to be continuous with the descending filaments derived from the spinal nerve above, while the others descend to pass upon the portion of the sympathetic trunk below the ganglion ; and, lastly, that these white fila- ments run upon the surface of the sympathetic, and contrast with the gray colour of the central portion of that nerve. The Internal, or Aortic and Splanchnic Branches. The internal branches of the first jive or six thoracic ga7igiia are exclusively intended for the aorta ; some of them appear to enter the pulmonary plexus. Some of the internal branches of the last six thoracic ganglia are intended for the aorta, and the remainder, which are the principal, unite to form the splanchnic nerves or nerves of the abdominal viscera. I have never seen any of them pass to the oesophagus. The Aortic Branches. — The aortic hranches consist of very small filaments, of which two or .three proceed from each ganglion. They accompany the intercostal arteries, around which they form small plexuses. These filaments are much longer on the right than on the left side, on account of the position of the aorta ; they pass, some in front and others behind that vessel, upon which it soon becomes impossible to follow them. The aortic branch from the fourth thoracic ganglion is the only one of any considerable size ; it appears to be shared between the aorta and the pulmonary plexus. A number of these aortic filaments sometimes converge towards certain small knots or ganglia, which are arranged in front or along the sides of the aorta, and give off a number of fil- aments. The first thoracic ganglion sends some twigs to the cardiac plexuses ; and not unfre- * In one subject I found a very remarkable disposition of tbe branches for the four inferior thoracic ganglia. Some small twigs from these four ganglia terminated in a minute gangliform structure, which gave off the branches to the spinal nerves. It will be seen that the same arrangement frequently occurs in the lumbar region. THE SPLANCHNIC NERVES. 865 quently the inferior cardiac nerve proceeds from this ganglion. Some filaments from the same ganglion are distributed to the lower part of the longus colli muscle. Lobstein {Dc Nervo Magna Sympathetico, p 19) describes a very delicate filament from this ganglion, which perforates the anterior common vertebral ligament, and enters the substance of one of the vertebrae. A similar filament appears to me to be given off by all the cervical, thoracic, lumbar, and sacral sympathetic ganglia. The vertebrae, like the other bones, are provided with nerves, which are overlooked in a hasty examination, from their excessive tenuity. The Splanchnic Branches. — These constitute the splanchnic nerves, which require a separate description. The Splanchnic Jferves. The splanchnic nerves are divided into the great splanchnic and the small splanchnic, or renal. The Great Splanchnic Nerve. — The great splanchnic is a white nerve, and has no re- semblance to the ganglionic nerves. It is formed in the following manner : a thick branch derived from the sixth and seventh thoracic ganglia, sometimes also from the fifth, and even from the fourth ganglion (see fig. 302), passes downward and inward upon the side of the dorsal vertebrae : this branch is joined by a series of three or four smaller branches given off not only from the succeeding thoracic ganglia, but also from the com- municating cords between them ; these branches {g g) are parallel to each other, and pass obliquely downward and inward. The eleventh and twelfth thoracic ganglia never assist in the formation of the great splanchnic nerve. The branches just mentioned unite on each side to constitute the great splanchnic nerves, which have the same relation to the thoracic ganglia that the cardiac nerves have to the cervical ganglia: it is important to remark that the ganglionic nerves of the thoracic viscera are derived from the cervical ganglia of the sympathetic, and that the ganglionic nerves of the abdominal viscera are given off from the thoracic ganglia. In general, the great splanchnic nerve arises by four roots ; but not unfrequently it arises only by two, which then represent the four origins. If, after having macerated the parts in diluted nitric acid, an attempt be made to de- termine exactly the highest point from which the great splanchnic nerve originates, it will be seen that the white filaments of which this nerve is composed are already dis- tinct opposite the third thoracic ganglion, and, moreover, that they are merely in contact with the trunk of the sympathetic and with the ganglia, and are continuous with the communicating branches from the spinal nerves. Anatomy, therefore, most clearly proves that the splanchnic nerve is continuous with the spinal nerves. Thus formed and completed opposite to the eleventh rib, the great splanchnic nerve passes downward and inward in front of the vertebral column : it becomes flattened and widened, perforates the diaphragm, the fibres of which separate to allow it to pass through, and immediately terminates in the semilunar ganglion {x). An ohve-shaped ganglion is not unfrequently found upon the great splanchnic, at a short distance before the nerve passes through the diaphragm.* The Small Splanchnic, or Renal Nerves. — I think it proper to include in the same de- scription the lesser splanchnic nerve of authors, and the posterior renal nerves of Walter, the distinction between these nerves appearing to me to be quite arbitrary. They are two, and sometimes three in number. The highest is named the small splanchnic (h) ; it arises from the eleventh thoracic ganglion, and sometimes from both the tenth and the eleventh. The lowest, which is the renal neroe of authors, is larger than the preceding, and is derived from tlie twelfth thoracic ganglion {t) : it often gives off a small filament to the first lumbar ganglion, and in a great number of cases this is the only means of communication between the thoracic and the lumbar ganglia of the sympathetic. In such a case, the series of ganglia is said to be interrupted ; but a complete interruption never exists. The small splanchnic or renal nerves exactly resemble the separate or single origins of the great splanchnic, with which they form a continuous series. They arise in the same manner, from the two or tliree inferior thoracic ganglia. They pass inward and downward, parallel to and on the outer side of the great splanchnic, perforate the crus of the diaphragm either to the outer side of or at the same point as the great nerve, and enter the renal and aortic plexuses ; they are often shared between these two plexuses and the great splanchnic nerve. The highest of the small splanchnic nerves rather fre- quently anastomoses with the great splanchnic, or even becomes entirely blended with it.f * Lobstein has recorded a case (p. 2) in which this unusual ganglion on the great splanchnic was of a serai- lunar shape, and gave off, from its convex side, seven or eight slender filaments, which accompanied the aorta and were all lost in the diaphragm ; he has also mentioned another case, in which three filaments arose from this ganglion, two going to the solar plexus, and the third to the mesenteric pleius. t Among the numerous varieties which I have observed in the formation of the small splanchnic nerves, I would especially notice the following : a twig from the eleventh thoracic ganglion, and one frOm the great splanchnic nerve, terminated in a small ganglion ; from this ganglion were given off several filaments that were lost upon the aorta, and also a small cord which joined with a twig from the twelfth. thoracic ganglion, and was distributed in the ordinary manner. 5R 866 NJEUROLOG^. 7%e Visceral Ganglia and Plexuses in the Ahdomen, As the semilunar ganglia and the visceral plexuses in the abdomen form the continuation of the splanchnic nerves, it is not only theoretically, but practically convenient to enter upon their description now. The central point of all these ganglia and plexuses is situated at the epigastrium, and is formed by a ganglionic plexus, named the solar or epigastric plexus. The Solar or Epigastric Plexus. The solar plexus (opposite x, fig. 302) is formed by an uninterrupted series of ganglia, extending from the great splanchnic nerve of the one side to its fellow of the opposite side. From this point as from a centre proceed a great number of branches, which have been compared to the rays of the sun, and hence the term solar plexus. This solar plexus, which is regarded by physiologists as the centre of the nervous sys- tem of nutritive life, is deeply seated in the epigastric region, and might therefore be called the epigastric nervous centre; it is situated in the median line, in front of the aorta, around the cceliac axis, and above the pancreas ; it is bounded on each side by the supra- renal capsules, and is of too irregular a shape to be clearly defined. The ganglia of which it is composed, the solar ganglia, are as irregular and variable as the plexus it- self. They consist of thick and swollen cords, or ganglionic arches or circles, arranged in a network, in the meshes of which are found somei lymphatic glands easily distin- guishable from the nervous ganglia and cords. Anatomists, in general, describe only the two extreme ganglia of the solar plexus, in which the great splanchnic nerves terminate ; these are the semilunar ganglia (x), so called from their shape, but which are subject to much variety both in form and size. Their convex border, which is turned downward, is divided into several teeth, from each of which a pencil of nerves is given off; a great number of filaments are also given off from their concave border, which is directed up- ward. These ganglia are situated close to the supra-renal capsules ; they are often without any regular form, and, as it were, divided into fragments. A single glance at the solar plexus will suffice to convince us of the impossibility of extirpating it, as some experimenters pretend to have done, in living animals. The great splanchnic nerve of each side (g), a part of the small splanchnic nerves (h), and the right pneumogastric nerve {p'), end in tlie solar plexus. I have also seen the right phrenic enter this plexus. From it, as from a centre, plexuses are given off for all the arteries arising from the fore part of the aorta, and also for the renal and spermatic arteries. The plexuses for the renal arteries and the inferior mesenteric artery are completed by the visceral nerves derived directly from the lumbar ganglia. There are two diaphragmatic plexuses, a cceliac plexus, a superior and an inferior mesenteric plexus, renal plexuses, spermatic or ova^ rian plexuses, and supra-renal plexuses. All the nerves given off from the solar ganglia are g^ray, and very small ; they are al- ways plexiform, and are generally strong on account of the thickness of their neurilemma. The Diaphragmatic and Supra^renal Plexuses. "The diaphragmatic or phrenic plexuses are small ; they are given off from the upper part (0f the solar plexus, and reach the phrenic arteries, with which they enter the diaphragm ;; sthey at first lie beneath the peritoneum, but afterward dip into the substance of the fleshy fibres of the muscle., and do not exactly follow the course of the vessels- In some cases I have been able to ascertain that they anastomose with tlie filaments of the phrenic nerve : they always run in nearly the same direction. The diaphragmatic plexus of the right side is larger than that of the left. I have seen two ganglia, upon the right crus of the diaphragm, which formed the origin of the right diaphragmatic plexus and of some hepatic nerves. I arrange the plexuses of the supra-renal bodies with the preceding, because they have so many relations with them. They arise directly from the semilunar ganglia, by two very delicate pencils of nerves, which reach the back of the supra-i-enal arteries, and are lost in the substance of the supra-renal bodies. Several filaments from the diaphrag- matic plexuses join them, passing in front of the arteries. The supra-renal plexuses are large in proportion to the size of the organs they supply. The Caeliac Plexus. The cceliac plexus is one of the principal divisions of the solar plexus, of which it is the immediate prolongation, so that it is almost impossible to distinguish one from the other ; it surrounds the cceliac axis, and immediately divides, like it, into three plexuses, the coronary of the stomach, the hepatic, and the splenic. The Coronary Plexus of the Stomach. — This is given off from the upper part of the solar plexus; it receives some filaments from the right pneumogastric, before that nerve joins the solar plexus ; of these filaments, some ramify upon the cardia, while the remainder follovsr the coronary artery along the lesser curvature of the stomach, and anastomose •Avith the pyloric filaments of the hepatic plexus. It follows, therefore, that the stomach THE SUPERIOR MESENTERIC PLEXUS. 867 is principally supplied by the pneumogastric nerve.. The filaments from the coronary plexus of the stomach, as well as those of the pneumogastric nerve, after having run for some distance beneath the peritoneum, perforate the muscular coat of the stomach, and appear to be partly lost in it and partly in the mucous membrane. The hepatic plexus is of very considerable size, and might be divided, after the example of Lobstein, into an anterior and a posterior plexus. The anterior accompanies the hepat ic artery, and is formed by some twigs from the right pneumogastric, and by seven or eight large gray, cylindrical filaments from the left semilunar ganglion, which are joined by two or three branches from the right semilunar ganglion. The posterior hepatic plexus accompanies the vena porta;, and is derived almost entirely from the right semilunar ganglion ; it is also composed of grayish, thick, cylindrical cords. I would especially notice one cord, which is remarkable both from its size and its course ; it arises directly from the solar ganglion of the right side, passes in a horizontal and curved direction to reach the gastro-hepatic omentum, and continues horizontally be- tween the layers of that omentum, in front of the lobulus Spigelii ; it then ascends to the transverse fissure of the liver, becomes situated beneath the vena port», and may be traced along that vein into the interior of the liver. I have seen this great he- patic branch come directly from two ganglia situated upon the right crus of the dia- phragm. Before reaching the liver, the hepatic plexus gives off a secondary plexus of consider- able size, around the right gastro-epiploic artery, the right gastro-epvplmc plexus ; it is considerably augmented by filaments which are derived immediately from the solar plexus, and perforate the pancreas. The hepatic plexus also furnishes branches to the pylorus and the lesser curvature of the stomach, to the pancreas, to the great curvature of the stomach, and to the great omentum. The pylorus, therefore, and the great curvature of the stomach, are supplied almost exclusively by the hepatic plexus.* The hepatic plexus likewise gives off a small ci/stic plexus, which is easily seen beneath the peritoneum, surrounding the cystic artery as far as the gall-bladder. Diminished in size, from having given off a series of branches and plexuses, the he- patic plexus gains the transverse fissure of the liver, divides like the hepatic artery and vena portae, and may he traced for some distance in the capsule of Glisson. All the nerves of the liver are gray, but very strong. The Splenic and Pancreatic Plexuses. — The splenic plexus is not so remarkable for the number as for the size of the filaments of which it is composed ; it surrounds the splenic artery, furnishes some twigs to the pancreas, and it also gives off the left gastro-epiploic plexus, which is smaller than the right, is situated upon the great curvature of the stom- ach, and supplies that organ and the great omentum. The splenic plexus also gives off nervous filaments to the great cul-de-sac of the stomach, and being thus very much di- minished in size, reaches the hilus of the spleen, within which organ it can be easily tra- ced in man, and still more easily in the larger animals, along the ramifications of the bloodvessels. These nerves are gray, and very strong. The numerous filaments which pass to the pancreas, and form a plexus around its arteries, constitute the pancreatic plexus, which may be regarded as a dependance of the splenic plexus. The Superior Mesenteric Plexus. ' . . The superior mesenteric plexus, which may be regarded as the lower division of the bi- furcation of the epigastric plexus, is the largest of all the abdominal plexuses ; it sur- rounds the superior mesenteric artery, forming an extremely thick plexiform sheath for it ; it passes below the pancreas, enters the substance of the mesentery (w) with the artery, and divides, like that vessel, into a great number of secondary plexuses, which are distributed to all the parts supplied by the artery, namely, to the whole of the small intestine, excepting the duodenum, and to the right portion of the great intestine. Without entering into tedious and useless details, I shall content myself with a few remarks upon the general distribution of these nerves. The mesenteric nerves are remarkable for their length, their number, and their strength. I am certain that their neurilemmatic sheath is proportionally much thicker than that of other nerves. They are placed at variable distances from the vessels, and proceed in a straight line in the substance of the mesentery towards the intestine, with- out giving off any filaments : at a short distance from the concave border of the intes- tine, they either pass directly to the bowel, or else they anastomose at an angle or in an arch ; from the convexity of these anastomotic arches the filaments for the intestine are given off. There is never more than one series of anastomotic nervous arches in the mesentery, whatever may be the number of rows of vascular arches ; the single nervous arch al- * The cardia and the lesser curvature of the stomach are the parts which are the most abundantly provided ■with nerves. The pylorus, to which we attribute such great s-ensibility, has incomparably fewer. 868 NEUROLOGY. ways corresponds to the vascular arch nearest to the intestine : the filaments which proceed from it are exceedingly minute.* The nervous filaments penetrate the intestine by its adherent border, run for some time between the serous and muscular coats, perforate the latter, to which they give some twigs, then spread out in the fibrous coat, and finally terminate in the mucous mem- brane The Inferior Mesenteric Plexus. The inferior mesenteric -plexus {n) is formed by some twigs from the epigastric plexus, or, rather, from the superior mesenteric plexus, with which it is continuous on the front of'the abdominal aorta ; and, secondly, by some branches from the lumbar sympathetic ganglia, which, as hereafter stated, constitute the lumbo-aortic plexus. The nieshes of the inferior mesenteric plexus are by no means so close as those of the superior mesen- teric plexus. The inferior mesenteric plexus, like the artery by which it is supported, supplies the left half of the transverse arch of the colon, the descending colon, the sigmoid flexure, and the rectum : of its filaments, those which accompany the left colic arteries are re- markable for their tenuity, their length, and for giving no branches in their course to the intestine. I would particularly notice the twig which accompanies the left superior colic artery. It is not uninteresting to remark, that these nerves are more numerous in the iliac meso-colon, which supports the sigmoid flexure, than at any other point. The inferior mesenteric plexus, thus diminished by having given off other smaller plexuses, terminates, like the inferior mesenteric artery, by bifurcating ; the two divis- ions of this bifurcation are called the hemorrhoidal plexuses ; they surround the two divis- ions of the artery, viz., the superior hemorrhoidal arteries, and tenninate partly in the hypo-gastric plexus and partly in the rectum. The Renal and Spermatic, or Ovarian Plexuses. The renal plexuses are extremely complicated : they are formed by branches from the solar plexus, and by the two or three small splanchnic or renal nerves, and terminate almost exclusively by surrounding the renal artery. The two spermatic plexuses in the male, and ovarian plexuses in the female, are derived principally from the renal plexuses. The spermatic plexuses are destined exclusively for the testicles ; the ovarian plexuses, like the arteries of the same name, are distributed both to the ovaries and the uterus. The intimate connexions between the nerves of the kidneys and testicles in the male, and those of the kidneys, ovaries, and uterus in the female, deserve the most particular attention of anatomists. The Lumbar Portion of the Sympathetic System. The lumbar portion of the trunk of the sympathetic {I I, fig. 302) is situated in front of the vertebral column, along the inner border of the psoas muscle. The ganglia of this re- gion are therefore nearer the median line than the thoracic gangha ; but the inferior lum- bar ganglia not unfrequently deviate from their ordinary position, and approach the lum- bar nerves as these emerge from the spinal canal : in this case, they are concealed by the psoas muscle. The lumbar ganglia of the sympathetic vary much in size ; some of them are so small that they would escape notice, if their grayish colour did not distinguish them from the rest of the trunk of the sympathetic. The number of these ganglia is also variable ; there are rarely more than four. Two or three ganglia are often blended into a gangliform cord ; this fusion may be easily recognised by the arrangement of the communicating filaments between it and the lum- bar spinal nerves. In one-subject, the twelfth thoracic ganglion on the right side was blended with the first lumbar ganglion : a small filament, corresponding in length to the thickness of two vertebrae, established a communication between this ganglion and a large gangliform cord, which represented by itself the four inferior lumbar ganglia. On the left side, the second and third lumbar ganglia were united, and the fifth was blended with the first sacral. This fusion of the lumbar ganglia almost constantly exists, and it establishes a close analogy between the lumbar portion of the sympathetic and the cervical portion, which, as we have already seen, has only three, and frequently only two ganglia. It proves that the superior cervical ganglion may be regarded as representing five superior cervical gangha and the ganglia corresponding to the two sets of cranial nerves, and that the inferior cervical ganglion may be viewed as the representative of two lower cer- vical gangha, when the middle ganglion is wanting. Moreover, the trunk of the sympathetic is not unfrequently interrupted either between the twelfth thoracic and the first lumbar ganglion, or between the last lumbar and the * In one case I found a very remarkable anastomosis. Four filaments, proceeding from four opposite points, converged towards a common centre ; but, as they were about to cross, they diverged from one another so as to intercept a lozenge-shaped space. Two of these might be regarded as filaments of origin, and the other two as terminating filaments LUMBAR PORTION OP THE SYMPATHETIC SYSTEM. 869 first sacral ganglion : this interruption is, however, more apparent than real, for. as I have already stated, the continuity between the twelfth thoracic and the first lumbar ganglion is always established by means of a small twig from the renal nerve. The branches of the lumbar ganglia may be divided into the branches of communi- cation between the ganglia ; the external branches, and the internal branches : besides these, there are some small and very delicate filaments, which enter the bodies of the vertebrae. The Communicating Branches between the Ganglia. These communicating branches consist of one or more white cords extending between every two ganglia ; they scarcely ever have the gray appearance and ganglionic struc- ture usually found in similar branches of communication : the communicating filament between the fourth and fifth lumbar ganglion is often wanting. The External Branches. These are the branches (at d) which communicate with the lumbar nerves. I con- ceive that they are furnished by the lumbar spinal nerves to the lumbar ganglia of the sympathetic. There are generally two, but sometimes three for each ganglion ; they arise from the anterior branches of the several lumbar nerves, as they emerge from the inter-vertebral foramina;* they accompany the lumbar arteries, along the grooves upon the bodies of the lumbar vertebrae, and terminate in the corresponding ganglia ; they are usually directed obliquely downward. In general, each ganglion receives branches not only from the corresponding lumbar nerve, but also from the nerve next above it. Thus, two branches end in the second lumbar ganglion, one from the first, and another from the second lumbar nerve ; the third ganglion receives filaments from the second and third lumbar nerves ; when one ganglion is wanting, its place is supplied by the next, which receives its own proper branches, and also those belonging to the absent ganglion. One ganglion not unfrequent- ly communicates with three lumbar nerves. When several ganglia are united into one, it is easy to conceive that this single gan- glion must receive all the filaments corresponding to those ganglia. It is also easy to understand that these filaments must be directed more or less obliquely either upward or downward, and that they will correspond in length to the distance between the lum- bar nerves and the single ganglion, the superior filaments being directed downward, and the inferior filaments upward. A very remarkable condition of the branches of communication between the lumbar nerves and the sympathetic ganglia consists in the existence of certain ganglia or swell- ings upon them ; and the almost indefinite anomalies observed in this particular are no less remarkable. I have found as many as three ganglionic nodules upon the same communicating branch : sometimes, when the two or three communicating branches reach the side of a vertebra, they unite in a ganglion, from which two or thi-ee other branches are given off to the proper sympathetic ganglion.! Moreover, these ganglia, like all the irregular ganglia, rarely present that peculiar character which is common to the regular ganglia, namely, that of forming a centre in which a certain number of filaments end, and from which others are given off. The Internal, or Aortic and Splanchnic Branches. The internal branches from the lumbar ganglia are the aortic and the lumbar splanchnic branches, and form a continuous and uninterrupted series with the aortic and splanchnic branches from the thoracic ganglia ; so that the internal branches from the first (/) and sometimes from the second lumbar ganglion join the branches from the eleventh and twelfth thoracic ganglia, to form a small splanchnic nerve, which is shared between the solar and the renal plexus. Some small gangliform nodules are occasionally found upon the course of these branches, among which are some very delicate filaments, which evi- dently pass into the bodies of the lumbar vertebrae. All these internal branches assist in the formation of the lumbar splanchnic, or pelvic visceral nerves. The Lumbar Splanchnic Jferves and the Visceral Plexuses in the Pelvis. The lumbar splanchnic nerves (at h) pass inward in front of the aorta, below the su- perior mesenteric artery, and anastomose with each other and with those of the opposite side to form a very complicated plexus, which is completed by a very considerable pro- longation from the superior mesenteric plexus. This plexus {n), which may be called the lumbo-aortic plexus, surrounds all that por- tion of the aorta which is included between the superior and inferior mesenteric arteries ; in the intervals between the nervous filaments are found lymphatic glands, which should be carefully distinguished from some nervous ganglia which form part of the plexus. The lumbo-aortic plexus is bifurcated below ; one portion of it passes upon the infe- * These communicating- branches frequently arise in the substance of the psoas muscle from twigs derived from the lumbar plexus. t This disposition is well seen in the beautiful plate of the sympathetic published by M. Manec. 870 NEUROLOGY. rior mesenteric artery te constitute the greater part of the inferior mesenteric plexus (below n) ; while the other portion descends upon the aorta, and even a little below the bifurcation of that vessel, and ends between the common iliac arteries, in front of the sacro-vertebral angle, from which it is separated by the common iliac veins. Some fila- ments are prolonged around the common iliac and the external and internal iliac arter- ies and their branches. The aortic portion of the lumbo-aortic plexus bifurcates below into two secondary plex- iform cords, one right and the other left, which pass downward upon the sides of the rec- tum and bladder, and enter the right and left hypogastric plexuses, which are aknost entirely formed by these cords. The Hypogastric Plexuses. The hypogastric plexuses (m) are among the great plexuses of the body ; they supply the rectum and the bladder in both sexes, and also the prostate and testicle in the male, and the vagina, uterus, and Fallopian tubes in the female. There are two hypogastric plexuses, one on the right, the other on the left side. They are situated upon the lateral and inferior surfaces of the rectum and bladder in the male, and of the rectum, vagina, and bladder in the female ; they are distinct from each other, and are connected not by median anastomoses, which I have never been able to detect, but through the lumbo-aortic plexus, by the bifurcation and spreading out of which they may be said to be formed. The hypogastric plexuses, from the enlargement and areolar disposition of their component cords, very closely resemble the solar plexus. Each plexus is formed essentially by one of the two divisions of the lumbo-aortie plexus ; it is also joined by some filaments from the inferior mesenteric plexus, by some very small twigs from the sacral ganglia, among which those derived from the third sa- cral ganglion are especially remarkable ; and, lastly, by some twigs from the anterior branches of the sacral nerves (see Sacral Nerves). Formed by a combination of filaments from these different sources, each hypogastric plexus gives off a hemorrhoidal, a vescical, a vaginal, a uterine, and a spermatic or ova- rian plexus ; all of these plexuses, like the hypogastric plexus itself, are found on each side of the body. The inferior hemorrhoidal plexuses are blended with the superior hemorrhoidal plex- uses, which, as already stated, are the terminations of the inferior mesenteric plexus ; they pass behind and in front of the rectum. The filaments belonging to the anterior branches of the sacral nerves may be distinguished from those belonging to the sympa- thetic system by the difference in the colour of the two kinds of nerves. The vesical plexuses are composed of a great number of exceedingly small filaments. They are situated upon the sides of the posterior fundus (bas-fond) of the bladder, on the outer side of the ureters, and are divided into two sets, viz., ascending vesical nerves,, which pass upward upon the sides of the bladder, embrace the outer and inner surfaces of the ureters, and ramify upon the anterior and posterior surfaces of the bladder; and horizontal vesical nerves, which run forward upon the sides of the fundus of the bladder,, externally to the large plexus of veins found in that situation, and spread out into ex- tremely delicate filaments, of which some enter the substance of the bladder, especially at its neck, while the others, in considerable numbers, turn round the prostate gland, and are distributed within it ; one of the prostatic filaments may be traced into the mem- branous portion of the urethra. The Plexuses for the VcsiculcB Seminales, and Vasa Deferentia, and Testicles. — Some of the filaments situated on the inner side of the ureters surround the vesiculee seminales, and are lost in them ; these are very small ; two or three remarkably large filaments run upward along each vas deferens ; having reached the inguinal ring, they unite with the corresponding spermatic plexus, which is a production of the renal plexus, and descend to the testicle. The branches for the prostate, vesiculae seminales, vasa deferentia, and testicles, are represented in the female by the utero-vaginal, ovarian, and tubal nerves. The Uterine Nerves. — Notwithstanding the figures of the sympathetic published by Walter, in which the nerves of the uterus are well represented, and notwithstanding the still more explicit description given of them by Hunter, most anatomists continue to en- tertain doubts regarding the existence of the uterine nerves. Lobstein, in his work on the Sympathetic, published in 1822, even denied them altogether ; but Tiedemann, in the same year, published two beautiful figures, representing the nerves of the gravid uterus.* The uterine nerves are derived from several sources. I have already stated that the plexuses surrounding the ovarian arteries, which are productions of the renal plexuses, are distributed, like the vessels by which they are supported, both to the uterus and the ovaries. It appears to me that the ovarian nerves and vessels have a similar arrangement, that is to say, that the uterine branches derived from the ovarian plexuses are larger than the ovarian nerves properly so called. * Tabulae Nervorum Uteri, Heidelberg, 1822, folio. ^ GENERAL VIEW OF TUi: SYMPATHETIC SYSTEM. 871 The tubal nerves are also derived from tne ovarian plexuses. The uterine nerves derived from the hypogastric plexuses are divided into ascending branches, which run upward along the lateral borders of the uterus, pass forward and backward upon the surfaces of that organ, and terminate in its substance ; and into de- scending branches, which run along the sides of the vagina, and terminate in it. These vaginal nerves appear to be inseparably blended with the vesical and hemorrhoidal nerves.* Such are the divisions of the hypogastric plexuses ; analogy, rather than direct obser- vation, has led to the admission of the existence of gluteal, ischiatic, and internal pudic plexuses ; in fact, of plexuses around all the branches of the internal iliac arteries. The Sackal Portion of the Sympathetic System^ The sacral portion of the sympathetic (s s,Jig. 302) is formed on each side by a cord en- larged at intervals, and situated on the inner side of, and along the anterior sacral fo- ramina. It forms a continuation of the lumbar portion of the sympathetic ; but sometimes there appears to be an interruption in the ganglionic chain, between the fifth lumbar ganf^lion and the first sacral. This interruption is merely apparent ; it is never complete. The sacral trunks of the sympathetic of the right and left sides gradually approach each other as they descend, corresponding in this respect to the anterior sacral foramina. The sacral ganglia, which are rarely five, more Commonly four, and sometimes three in number, are occasionally collected into a small gangliform enlargement, situated be- tween the first and second anterior sacral foramen ; the first sacral ganglion is some- times double, and at other times it rather resembles a gangliform cord than a true gan- glion. The mode of connexion between the first sacral and the last lumbar ganglion is sub- ject to much variety.t The manner in which the sacral portion of the sympathetic ter- minates is also somewhat variable. The following is the arrangement most generally admitted : a filament proceeds from the last sacral ganglion, which is usually the fourth, and forms an anastomotic arch with its fellow of the opposite side, in front of the base of the coccyx. At their point of junction is often found a small ganglion {ganglion im- par, c), from which certain terminal filaments are given off. Sometimes there is neither a coccygeal ganglion nor any anastomosis, properly so called, but the terminal filaments are distributed in the usual way. I have not been able to trace these filaments beyond the periosteum of the coccyx and the sacro- sciatic ligaments. Like the other ganglia of the sympathetic, the sacral ganglia present communicating branches with each other ; rather large external brayiches derived from the corresponding sacral nerves ; internal branches, which anastomose with those of the opposite side, in front of the sacrum, and surround the middle sacral artery. Some of these filaments I have distinctly seen entering the substance of the sacrum ; and, lastly, very small ante- rior branches (y), some of which join the hypogastric plexuses, while the others termi- nate directly upon the rectum. General View of the Sympathetic System. The following dissection is necessary, in order to present a correct general idea of the sympathetic system. Take a spinal column which has been macerated in diluted nitric acid, remove the bodies of the vertebrae, leaving, if it be wished, the inter-vertebral substances ; be very careful to preserve the branches of communication between the sympathetic aad the cra- nial and spinal nerves. It is then clearly seen that the two gangliated trunks of the sympathetic are connect-, ed with the cerebro-spinal axis by as many roots, or small groups of roots, t as there are cranial and spinal nerves ; it is, moreover, no less evident that the^ communicating branches between the ganglionic chain and the spinal nerves do not pi'oceed from the ganglia, but from the spinal nerves ; so that it may be stated as a demonstrated ana- tomical fact, that the sympathetic system has its origin in the cerebrospinal system.^ * [Dr. Lee has recently examined minutely the distribution of the nerves of the unirapr^gnated and gravid; uterus. He has described {Anatomy of the Nerves of the Uterus, with plates, 1841, and Proceedings of the Royal Society, No. 49) several large uterine plexuses ; also, several "large ganglia on the uterine nerves, and! on those of the vagina and bladder ;" and, farther, " two great ganglia situated on the sides of the neck of the. uterus."] t In one case, the continuation of the lumbar portion of the sympathetic deviated outward, and joineditfts fifth lumbar nerve ; a very small filament only formed the communication between the last lumbar gangliiis' ^ and the first sacral. In another case, these two filaments proceeded from the last lumbar ganglion of the-ij^ jj. side, the inner of which joined the first sacral ganglion of the opposite side, crossing over the sacro-veJitRif j^j angle. i It must be remembered that there are always two, and sometimes three communicating branches; biW ween the sympathetic and each of the spinal nerves. (l These facts in human anatomy are in perfect accordance with the observatioiis in comparative^ a „jf made by Meckel and Weber, namely, that the development of the sympathetic system is- in direct ua'tio with- that of the cerebro-spinal system ; that the former is more developed in maa than in.any. othet aioiaaal and is proportionally larger in the foetus than in the adult, 872 NEUROLOGY. The sympathetic trunks of the right and left side generally anastomose below in front of the coccyx ; it has been somewhat hastily affirmed that they anastomose above, either upon the pituitary body, or upon the anterior communicating artery of the brain ; the true anastomoses of the two halves of the sympathetic system are in the central and median plexuses. If, after having acquired this general idea of the trunks of the sympathetic, its neuri- lemma be removed by continued maceration in water, the connexions of the branches given from the spinal nerves to the ganglia, with the branches given from the ganglia to the viscera, may then be ascertained : it then becomes evident, that the greater number of the branches from the spinal nerves do not penetrate to the centre of the ganglia, but expand, as it were, upon their surface, and divide into two sets of filaments ; of these, some are applied to tlie surface of a ganglion, and proceed directly to form the internal or visceral branches ;* while the others assist in forming the cords of communication between one ganglion and another, and divide into ascending and descending filaments, of which the latter are the more numerous. They all run along the outer side of the cords of communication, and afterward become visceral branches themselves ; it is doubtful whether any filament arises in the interior of a ganglion ; the continuity of them all can be traced completely through these bodies. It follows, therefore, that it is anatomically shown that the visceral nerves given off from the sympathetic are connected or belong to a very great number of spinal nerves at once, and always to spinal nerves much higher than that portion of the sympathetic from which the visceral branches are immediately given off; and again, that the vis- ceral or splanchnic nerves, the actual origins of which we have seen to be so complica- ted and so remote from their apparent origins, always run a very long course before reaching their destination. Thus, the splanchnic nerves of the thorax or the cardiac nerves are derived from the cervical ganglia ; the splanchnic nerves of the abdomen are given off, for the most part, by the thoracic ganglia ; and most of the splanchnic nerves of the pelvis proceed from the lumbar ganglia. Nevertheless, the proper ganglia of each splanchnic cavity complete the visceral nerves belonging to that cavity. Thus, the first thoracic ganglion assists in the formation of the cardiac nerves ; the superior lumbar ganglia in that of the visceral nerves of the abdomen ; and the sacral ganglia in that of the pelvic nerves. The visceral nerves sometimes pass directly to the viscera from the ganglia of the sympathetic, and sometimes indirectly, after being mingled and combined in plexuses. There is no relation between the branches which enter and those which pass out of the several visceral plexuses, so that the branches which proceed from the ganglia and trunk of the sympathetic to those plexuses must be regarded, not as branches of forma- tion, but as branches of communication. The visceral plexuses are also formed in a very peculiar manner, not only by inter- laced nerves, but by nerves and ganglia, and these nerves themselves pi'esent a gangli- onic structure altogether different from the fasciculated and plexiform structure of other nerves. There are four great visceral plexuses : the pharyngeal plexus, the cardiac plexus, the solar plexus, and the hypogastric plexus ; the largest of all these is the solar plexus, which, both in an anatomical and in a physiological point of view, deserves the title of the abdominal brain, which was given to it by Wrisberg. These four great plexuses may also be very properly regarded as nervous centres, to which all the physiological and pathological phenomena of the nutritive system are singly or collectively referred. These visceral plexuses differ as much from the ganglionic chain formed by the two trunks of the sympathetic as these trunks differ from the spinal cord itself : in these plexuses a sort of fusion is effected between the cerebro-spinal and the sympathetic sys- tems, and also between the trunks of the sympathetic belonging to the two sides of the body. The pneumogastric assists in the formation of three of these plexuses ; namely, the pharyngeal, the cardiac, and the solar plexus. In man there is a tendency to fusion of the pneumogastric with the sympathetic, and in the lower animals this fusion is still more complete ; it is in those animals in which the sympathetic is the least developed that the par vagum acquires its greatest development, and supplies the place of the for- mer in reference to the intestinal canal. The glosso-pharyngeal nerve also assists in the formation of the pharjmgeal plexus, and the sacral nerves contribute to that of the hypogastric plexus. The visceral plexuses differ essentially from those formed by the cerebro-spinal nerves. In the latter, the branches vviiich emerge from the plexus are precisely the same branch- • es that entered it, only combined in a different manner. However inextricable they may be, the plexuses of the spinal nerves are merely points in which a number of affe- rent branches converge and combine together. In the visceral plexuses, on the contra- ry, there is no relation, either in size or structure, between the afferent branches and -the plexuses themselves. * Some filaments from the spinal nerves are seen to cro.^s at right a".gles over the anterior surface of the ganglia, and then to join the visceral nerves directly. .GENERAL VIEW OF THE SYMPATHETIC SYSTEM. 873 The nerves derived from the sympathetic system differ also in their mode of distribu- tion from the nerves of the cerebro-spinal system. In general, they form a plexiform sheath around the vessels, and enter with them into the substance of organs. This ar- rangement has induced some anatomists to believe that the sympathetic nerves belong essentially and exclusively to the vascular system, and are lost upon the coats of the arteries ; others hold an opposite opinion, and deny altogether that the sympathetic nerves enter the coats of those vessels. From some researches which I have made on this subject, I believe that there are proper filaments for the coats of the vessels, but that these are very few in number, and that by far the larger number of the nervous fila- ments are intended for the several organs. It is not uninteresting to remark, that the sympathetic nerves always accompany the arteries, and never the veins ; the trunk of the vena portae forming the only exception to this rule. A gray colour and a soft texture are not, as is generally stated, the peculiar character- istics of the nerves of the sympathetic system ; the gray colour is observed only in a portion of this system ; and the softness, which only very rarely accompanies the gray colour, is confined to a very minute portion of it indeed. There are gray cords, which are nothing more than prolonged ganglia, and are not nerves, properly so called ; when examined they present no nervous structure, that is to say, they contain no white funiculi which can be decomposed into primitive filaments as fine as the silk fibre. Almost all the sympathetic nerves are of a white colour, which is sometimes concealed by an unusually thick neurilemma. The structure of the white nerves of the sjmipathetic system does not differ from that of the cerebro-spinal nerves ; except that the funiculi of the former are smaller, and their arrangement is more deci- dedly plexiform.* Lastly, there are some mixed nerves, partly gray and partly white, which partake of the structural characters of both the gray and the white nerves, t * See note, p. 840. t I am much indebted to M. C. Bonamy, my private prosector, for the zeal and ability with which he has assisted me in the numerous dissections required for the compilation of this work. SOURCES FROM WHICH THE ILLUSTRATIVE ENGRAVINGS HAVE BEEN TAKEN. Figs. 1 to 7, 8t, 9 to 20, 24, 25, 28 to 30, 33, 34, 36, 38, 41 to 45, 47, 48t, 49 to 53, 57 {Sue). Figs. 21 to 23, 37 (Gordon). Figs. 26, 27, 35, 58t to 60t, 61 to 70, 71t, 72 to 84, 106 to 110, lilt, 112, 113, 114+, 115, 116+ to 123t, 124 to 126, 127t, 128 to 133, 141t, 147+, 155, 161, 163t, 169t, 170, 171t, 191t. 192, 194, 195 {Bourgerij). Figs. 39, 40, 46+, 54 to 56 (Cheselden). Figs. 85 to 94 {Hunter). Fig. 95 (d.) {Retzius). Fig. 97 (d.) {Goodsir). Fig. 98 {Serves). Figs. 99, 101, 102 {Blahe). Fig. 100 (T. Bell). Figs. 103 (d.) to 105 (d.), 286 {Cloquet). Figs. 136+, 138, 181 (Morton). Fig. 140t {Watts). Figs. 142, 173 to 175, 178, 231, 233, 234, 257 (Swm- mering). Figs. 145, 160, 182, 187, 189,220, 221, 223i {Weber). Figs. 152, 153 {Boyd). Figs. 154t, 198 to 206, 208 to 218 {Tiedemann). Fig. 156 (No. 2) {Krause). Fig. 156 (No. 3) {Vallinger). Figs. 157 to 159, 162 (Boehm). Fig. 172 {Reisseissen). Fig. 180 (d.) (Wagner). Fig. 183 (A. Cooper). Fig. 185 (Haller). Figs. 207, 232t, 235 to 240, 242 to 246, 248, 249, 251 1, 252 to 256, 258 to 265, 266, 269 to 275, 284, 285, 296tto 301t (Arnold). Fig. 219t (Walter). Fig. 222t (Caldani). Fig. 226 (Harvey). Figs. 227, 228 (Gurlt) Fig. 2.50 (Brewster). Fig. 268 (Cruveilhier). Figs. 281t, 283, 295 (Mayo). Figs. 289t, 290t (Swan). Fig. 302+ (Manec). Figs. 143 (d.), 144 (d.), 164* (d.), 179 (d.), 193t, 197, 241 (d.), 276 to 280, 262 (Models, Casts, and Di- agrams in the Museum of Anatomy, University College). Figs. 31, 32, 96, 98* (d.), 134 (d.), 135 (d.), 137 (d.), 139 (d.), 146 (d.), 148 (d.), 149 (d.) to 151 (d.), 156 (No. 1, d.), 164, 176 (d.) to 178 (d.), 184 (d.), !86 (d.), 190 (d.),196 (a.),218* (d.),224 (d.),225 (d.), 229 (d.), 230 (d.), 247 (d.), 267 (d.), 287 (d.), 288 (d.l, 291 (d.) to 293 (d.) (Original). Figs. 165 to 168 (Kiernan). The mark (+), affixed to the number of a figure, indicates that such figure differs in some respects from the original. The letter (d.), similarly affixed, signifies that the figure is intended as a diagram or jilan. The asterisk (*), used occasionally, serves to distinguish between two figures bearing the same number. 5 S INDEX. Abdomen, aponeurosis of, anterior, 300. ■ piisierior, 305. — superficial, 297. . regions of, 352. Abducens, nerve. See .Yeri'e, Motor OcuL Abductor muscles. See Muscles. Accessory ligaments. See Ligaments. nerves. See Serves. Acetabulum. SS. Acini of glands. See those glands. Acromion process, 76. Adductor muscles. See Muscles. Adipose tissue, 173. Alee of sphenoid bone, lesser, 37. . greater, 37. Tespertilionis, 475. Alimentary canal, 322. . appendages of, 3&4. coats of, 322. direction and situation of, 323. di\"isions of. 322. dimeiLsions of, 323. form of, 323. membriiues ol". 323. muscular fibres of, 323. • structure of, 323. Alveoli, 53, 58. Amphiarthroses, 113. • characters, ligaments, and motions, 113. Ampulla of semicircular canals, 677. Amygdala. 333. See Tonsils. Amygdaloid fossa, 331. Anastomoses of arteries, 496. lymphatics. 614. nerves, 762> .^ . veins, 574. Anastomotic artery, brachial, 544. femoral, 565. Anatomy, objects and divisions of, 1, 2. •^-^ descriptive, 1. .^—^— — general, 1, 2. Anfractuosities. See Cerebrum. Angeiology, 479. Angle, sacro-vertebral, 26. of the femur, 93. • facial, of Camper, 45. ■ occipital, of Daubenton, 45. of the jaw, 5S. changes during groivtli, 59. Aponeuroses, cerrical, superficial, 299. cephalo-pharv-ngeal. 346. costo-cla\icalar, 137, of the cranium. 299. cremasteric, 3U2. cribriform, 309. deltoid, 315. dorsal of the foot, 314. metacarpus, 318. • interosseous, of foot, 314. ■ hand, 318. ■ epicranial, 295. ■ external oblique, 301. • of the eyelids, 647. face, 299. • femoral, 309. septa of, 310. sheath for vessels, 310. muscles, 311. ■ of the fore-arm, 316. • gluteal, 311. ■ hypothenar, 319. • iliac, 306. ■ infra-spinous, 315. ■ intercostal, 360. ■ inter-muscular of thigh, 310. ■ of internal oblique, 304. •of the leg, 312. lower extremity, 309. superficial, 297. lumbar, or posterior abdominal, 306, lumbo-iliac, 306. masseteric. 29S. of the neck, 299. obturator, 309. occipito-frontal. 293. occipito-pharj-ngeal, 346. palmar, 319. parotid, 298. pedal, 314. pelvic lateral, 308. superior, 308, of the pelvis, 306. — proper, 307. ■ of the pubes, 89. Angles of bone&. 9. Ankle joint, 168. ligaments of, 169. Ankle. See Tarsus. ^nnu?ar ligaments. See Ligaments. Anti-helix, and its fossa, 666, tragus, 666. Antrum Highmori, 52. pylori, 355. Anus, 3S0. muscles of, 380. structure of, 380. Aorta. See Arteries. Aponeurology, 294. Aponeuroses in general, 294. classification of, 294. ■ containing, 294. ■ definition of, 294. functions of, 296. insertion of. 294. structure of. 296. ■ tensor muscles of, 295. Aponeuroses in particular, 297. • abdominal anterior, 300. layers of, 301. posterior, 305. superficial, 297. brachial, 316. buccinator, 29S. buccinato-pharyngeal, 235. cerrical, deep, 299^ ■ perinsal. deep, 307 superficial. 306. ■ petro-pharv-ngeal. 346. ■ of the pharynx. 346. ■ plantar, external, 314. internal, 314. interosseous, 315. middle, 314. - prjevertebral, 299. - of the quadratus lumbortim, 306. - recto-vesical, 308. - of the serratus posticus, 300.. shoulder. 315. spermatic cord, 304. - sub-peritoneal, 305. - sub-scapular, 315. - superficial, 297. of abdomen, 297. - supra-clavicular, 299. - supra-spinous, 315. - temporal, 298. - thenar, 319. ■ of the thorax. 300. ■ of transversalis, 305. • of the upper extremity, 316. superficial, 297. • of velum palati, 346. • Tertebral. 205. — vesical, 309. Aponeurotic sheaths for muscles, 296 tendons, 296. — vessels, 296. Apparatus, hyoid, 109. Apparatuses of human l)ody, general view of, 3, 4, Appendices epiploicae, 372. Appendix, ensifonn, or xiphoid, 65. venniformis, 373 876 INDEX. Appendix, vermiformis, development of, 384. structure of, 373. Aqueductus Fallopii, 43, 839. vestibuli, 44. — cochle33, 44. Sylvii, 719, 742. Aqueous humour, 65.'5. membrane of, 655. Arachnoid, 6S7. canal (of Bichat), 687. cranial portion of, 687. internal, 691. loose, 690. membrane of eye, 656 (note). spinal portion of, 690. uses of, 692. Arbor vitas uterina, 465. Arch, aortic, 502. of colon, 374. crural, 302. femoral, 302. gluteal, 311. orbital, 36. palatine, 329. pubic, 89. sub-pubic, 307. zygomatic, 61. Arches, alveolar, 174. dental, 174. zygomatic, 61. Arm, bone of, 78. , , . , , t^', compared with thigh bone, lU/. Arteries in general, 496. anastomoses of, 496. branches of, 497. coat of, external or cellular, 498. internal, 498. . middle, proper, or elastic, 498 course or direction of, 496. . definition of, 496 division of, 496. form of, 496. nerves of, 497. nomenclature of, 495. origin of, 496. preparation of, 497. relations vv'ith other parts, 497. retia mirabilia of, 496. satellite muscles of, 497. sheaths for, 499. structure of, 499. termination of, 498. varieties of, 496. Tasa vasoruni of, 499. venie comites of, 497. - vessels of, 499. • , auricular, anterior, 521. posterior, 519. . axillary, 531, 542. axis, cosliac, 507. thyroid, 535. . azygos, or middle articular of knee 565. ■ basilar, 534. ■ brachial, 543. brachio-cephalic, 531. ■ bronchial, 505. - distribution of, 421. buccal, 524. of bulb, 558. calcaneal, external, 570. inferior, 571. capsular, inferior, 513. middle, 513. superior, 513 cardiac, 503. carotid, common, left and right, 514. general distribution of, 530. - external or facial, 515. - internal, 525. - superficial, 515. carpal, radial, anterior, 546. posterior dorsal, 546. ulnar, anterior, 549. - posterior dorsal, 549. central of retina, 527, 665 cerebellar, inferior, anterior, 534. • posterior, 534 ■ superior, 535. cerebral, anterior. 529. communicating anterior, 529. • posterior, 529. middle, 530. — posterior, 537 cervical, ascendmg, 538. deep, 540. princeps, 519. superficial, 539. Artery or Arteries in particular, 497. of particular organs or tissues. gans, &c. acromial, descending, 542. . supra-scapular, 538. transverse, 542. acromio-thoracic, 542. of ala nasi, 518. . alar thoracic, 542. . alveolar, 524. . anastomotic, brachial, 544. - great, of thigh, 564 See those or- angular, of face, 517,529, aorta, 501. abdominal, 503. arch of, 502. ascending, 503. branches of 503 descending, 502. sinuses of, 501. thoracic, 503. valves of, 486. arising from abdominal aorta, 506. . arch of aorta, 513. varieties of, 513. .^ origin of aorta, 504. termination of aorta, 552. thoracic aorta, 505. cervico-spinal, 538 choroid, anterior, 530. posterior, 536, ciliary, anterior, 527. middle, or long, 528. Bsterior, or short, 528, 665. circle of Willis, 536. circumflex, femoral, external, 564. internal, 563. iliac, 560. humeral, anterior, 543. posterior, 543. ■ of clitoris, 558. ■ coccygeal, 552. • cceliac (axis), 507. ■ colic, left, 511. right, 510. ■ collateral, of fingers, radial, 547. ulnar, 549. ■ humeral, external, 543. internal, 543. ■ of knee. See Articular. ■ of toes, from external plantar, 5*'?. ■ internal plantar, 572. comites. See Satellite. communicating, cerebral, anterior, 529. posterior, 529, 535, ■ palmar, 548. ■ plantar, 572. of Willis, 529. coronary of heart, left or anterior, 504. ■ right or posterior, 504. - lips, inferior, 51' superior, 518. ■ stomach, 507. ■ of corpus callosum, 529. • cavemosum, 558. ■ articular, of hip, 564. knee, inferior, 565. middle, or azyges, 565. superior, 565. - ascending cervical, 538. " pharyngeal, 520. cremasteric, 560. crural, 560. ■ cystic, 508. • deep, brachial or humeral, 544. cervical, 540. femoral, 563. temporal, 522. - deferential, 452. - dental, anterior, 524. inferior, 523. ■ superior, 524. diaphragmatic, inferior, 506. INDEX. 877 Artery, diaphragmatic, superior, 539. digital, collateral, radial, 547 ulnar, 549. of foot, 572. \ Artery, mixgna pollicis, of hand, 547. malar cutaneous, 521. I malleolar, external, 567. ■ internal, 567. dorsal, carpal, radial, 547. ■ ulnar, 549. - of foot, 568. — index finger, 548. ■ metacarpal, radial, 547. ulnar, 549. — metatarsal, 569. — of nose, 529. — penis, 558. — scapula, 538. — tarsus, 572. — thumb, 548. _ — toe, great, 572. tongue, 518. - dorsi-spinal, of inferior intercostals, 507. superior intercostals, 540 emulgent, 512. epigastric, 559. superficial, 562. - epiploic, 510. - ethmoidal, anterior, 528. ■ posterior, 528 ■ facial, 517. ■ femoral, 559. - deep, 563. - of fissure of Sylvius, 529. - of frisnum linguae, 519. - frontal, 523. of temporal, 520. - gastric, inferior, 509. ■ superior, 509. - gastro-duodenal, 508. epiploic, left, 509. right, 508. hepatic, 508. -gluteal, inferior, 556. superior, 556. -hemorrhoidal, 557. inferior, 557. middle, 554. superior, 511. • helicine, 456. - hepatic, 508. ■ in the liver, 391, 392. ■ mammary, e.Kteiiinl, 542. internal, 539. — masseteric, 521, 523. — mastoid, 520. posterior, 519. — maxillary, external, 517. internal, 522. - general distribution of, 525. — of median nerve, 549. — mediastinal, 540. — medullary, 506. — meningeal, anterior, 528. middle or great, 522. of ascending pharyngeal, 520. posterior, 519, 5'i4. - small, 523. — mental, 523. -- mesenteric, inferior, 511. ■ superior, 510. — metacarpal, radial, 546. ulnar, 549. — metatarsal, 569. — muscular, of orbit, 528. thigh, 562. — niusculo-phrenic, 540. — for mylo-liyoideus, 523. — nasal, 528. dorsal, 529. lateral, 518. of pterygo-palatine, 524. of septum, 518. nutritious, of femur, 542. fibula, 570. ■ humerus, 545 -■ tibia, 569. • humeral, 543. deep, inferior, 544. ■ deep, superior, 544. -hyoid, of lingual, 518. ■ superior thyroid, 515 (note). hypogastric, 553. iliac, common, 552. external, 559. internal, 553. general distribution of, 558. - ileo-colic, 511. - ilio-lumbar, 555. - incisory, inferior, 523. superior, 524. - infra-orbital, 524. - or sub-scapular, 542 — spinous, 542. • innominate, 531. ■ intercostals, anterior, 540. aortic or inferior, 505. ■ superior, 540. ■ interlobular, of liver, 391 ■ interosseous, dorsal, of foot, 569. — hand, 547 of forearm, anterior, 548. posterior, 549. ■ obturator, 554. ■ occipital, 519. ■ oesophageal, 505. • omphalo-mesenteric, 511 ■ ophthalmic, 525. - orbital, of temporal, 521. - ovarian, 512. - palatine, inferior, 517. — superior, 524. palmar, deep, 546. palmar, interosseous, 548. superficial, 547. recurrent, 547. • palpebral, inferior, 528. - superior, 528. • pancreatic, great (from splenic), 509. small (from mesenteric), 510. ■ pancreatico-duodenal, 508. ■parietal, 519, 521. ■ parotid, 520. ' - of penis, 558. dorsal, 558. - perforating, of forearm, 549 palmar, 548. peroneal, 570. plantar, anterior and posterior, 569, 572. ■ of thigh, 564. - pericardiac, 495. ■ perinaeal, superficial, 557. • transverse, 557. • palmar, 547. plantar, 572. recurrent, of forearm, 549. - of the intestines, great, 511. small, 510. intra-spinal, 534. ischiatic, 556. of labia pudendi, 558. labial, inferior, 517. superior, 517. lachrymal, 526. laryngeal, inferior, 516. superior, 5 1 6. lingual, 518. lumbar, 506. magna pollicis, of foot, 572. • peroneal, 570. anterior, 570. - perforating, 570. pharyngeal, ascending or inferior, 520. pharyngo-meningeal, 520. phrenic, inferior, 507. superior, 539. for phrenic nerve, 539. plantar, external, 571. internal, 571. popliteal, 564 prievertebral, 520. princeps cervicis, 519. pollicis, 547. profunda cervicis, 549. femoris, 563. humeri, inferior, 545. luperior, 544. pterygoid, of facial, 517. internal maxillary, 623. 878 INDEX. Artery., pterygo-palatine, 524. ■ pudic, external Uiferior, 562. ■' superior, 562. — internal, 557. ' in the female, 558. ■ — pulmonary, 500. •^ left branch of, 501 . '^^ right branch of, 501. distribution of, 421. ■^ pyloric, inferior, 508. • superiol', 508. ' radial, 546. ■ ■ — ■ collateral of fingera, 547. • • recurrent, 540. ■ radialis indicis, .548. radio-cubital, 549. " palmar, 547. • ranine, 518. '^ of receptaculum, 525. ■"■ recurrent interosseous, of forearm, 549. ■ palmar, 517 Artery, thoracic humeral, or deltoid, of acromio-thora- cic, 542. ■ inferior, 542. ong-, 542. radial, 546. '" tibial, anterior, 568. internal, 569. ulnar, anterior, 549. •—^ posterior, 549, renal, 512. ■ — distribution of, 439. — ' of retina, central, 527. ■ — ' sacral, lateral inferior, 556. — — superior, 556. — ' ■ middle or anterior, 552. ■ satellite of median nerve, 549- •^ phrenic, 540, sciatic, 556. — ' ulnar, 548. scapular, inferior, 542, posterior, 538. superior, 538, - — "^ — sciatic, 556. ' for sciatic nerve, 556. . scrotal, 557. — "' of septum of nose, 518. ^- ventricles of heart, 504. short, of stomach, 511. - thymic, 540. - thyroid axis, 537. — inferior, 537, — middle, 515. of Neubauer, 537. ~" superior, 516. ■ tibial, anterior, 567. posterior, 570. ■ — recurrent, 567. • tibio-peroneal, 569. • tonsillar, 521. ■ transverse, of perineum, 556. neck, 539. face, 521. ■ shoulder, 538. — tympanic, 522. — ulnar, 548. collateral, 543. ■ ^ of fingers, 549. recurrent, anterior, 549. posterior, 549. — umbilical, 553. — uterine, 554. — vaginal, 554. of liver, 392, — vasa brevia, of stomach, 509. -- for vertebrse, 604. — vertebral, 533. — vesical, 553. vidian, 524. Arthrodia, 114. characters, ligaments, and motions, 113 Arthrology, 1] 1. Articular surfaces, in general. 111. — of particular articulations, those articulations. See ' sigmoid, 511. spermatic, 511. ■ spheno-palatine, 524. spinous, 522. -'■— spinal, 534, 609. anterior, 531. '— ' general distribution of, 609. posterior, 534. re-enforcing, cervical, 534. ■^ lumbar, 504. thoracic, 504. ■ borders, 112. structure of, 177. ■ cartilages. 111. -^ — structure of, 177. ■ cavities, 10. supplementary, 128. processes, or eminences, 10- of vertebrie, 20, 22. — union of, 116. Articular a.nenes. See Arteries, nerves. See Nerves ' of spinal cord, 504, 534. — splenic, 509. in spleen, 405. for sterno-mastoid, 516, 519. — ■" stylo-mastoid, 519. — " sub-clavian, left and right, 531. — sub-diaphragmatic, 504. — ' sub-lingual, 518. — •- for sub-maxillary gland, 517. sub-mental, 517. —^—■- — sub-scapular, 542. — "-= — - superciliary, 527. — superficial, of neck, 546. palm, 547. perineum, 556. . superficialis volie, 547. . — -■ supra-orbital, 527. ■ — renal, inferior, 512, middle, 512. superior, 512. . ' scapular, 538. spinous, 538. . sural, 565. . tarsal, dorsal, or external, 568. ■ internal, 568. temporal, 521. ■ deep anterior, 524. . ■ middle, 521. • posterior, 523. superficial, 521. testicular, 511, • distribution of, 536. thoracic acromial, 542. — alar, 542 (note). Articulations in general, 111-116. — ' amphiarthroses, 113. — arthrodia, 114. classification of, 113. ■ ■ — condylarthrosis, 114, — = definition of, HI, diarthroses, 113. enarthrosis, 114. ' ginglymus, 114. -= goinphosis, 114. ' harmonia, 114. ' immovable, 113. — meningoses, 113 — mixed, 113. — movable, 113. — movements of, 113. — by mutual reception, 113. — schindylesis, 114. — sutures, 114. — symphyses, 114. — synarthroses, 114. — synchondroses, 113, — syneuroses, 113. — syssarcoses, 113. — trochlear, 114. — trochoid, 114. Articulations in particular, 113. acromio-clavicular, 135. mechanism of, 136. ■of ankle. See Tibio-tarsal. ■ astragalo-scaphoid, 171. ■ of astragalus with os calcis, 170. ■ movements of, 153. atlanto-axoid, 117. mechanism of, 124. — odontoid, 117. ' of atlas and axis, 117. — — ■ articular processen of, 118. mr»EX. 879 ■Arii! lations, calcaneo-cuboid, 173. ■ carpal, in g-pneral, 147. m^'chanism of, 148. — '"each ro%\, .147. - - A two rows together, 147. — pisiform and cuneiform, 147. carpo- metacarpal, in general, 149. ■ — mrchaniam o.'', 150. . first, 149. mechanism of, 150. ._^ fifth, 150. mechanism of, 150. second, third, & fourth, 150. carpo-metacarpal, of the thumb, 150. mechanism of, 150 chondro-costal, 132. sternal, in general, 131. in particular, 131. movements of, 133. ■ coccygeal, 120. ■ condyloid, of occiput and atlas, 116. ■ coraco-clavicular, 135. mechanism of, 136. of the costal cartilages, 132 • movements of, 132 costo-clavicular, 138. mechanism of, 138. — costo-ttansverse, 131. -■ vertebral, 131. in general, 131. in particular, 131. movements of, 131. proper, 131. of first rib, 131. of eleventh and twelfth ribs, 131. • coxo-femoral, 159. ■ movements of, 161. ■ cranial, 124. ■ mechanism of, 125. ■ cranio-vertebral, 120. ^^ mechanism of, 123. crico-arytenoid, 426. thyroid 426. ■ of the elbow, 143. of the extremities, upper, 135. lower, 153. ■ of the face, 126. of the fingers, in general, 151. --- of the head, with vertebral column. Cranio-vertebral. — of the hip. See Coxo-femoral. — humero-cubital, 141. — movements of, 142. See of jaw, lower. See Temporo-mwnllary, — upper, 126. — with cranium, 126. of the knee, 162. mechanism of, 166. ■ of larynx, 425. ■ of metacarpal bones. Carpal ends of, 148. • digital ends of, 149. ' with carpus, 149. metacarpo-phalangal, 151. movements of, 152. of metacarpus in general, 148. of metatarsal bones, tarsal ends of, 175. • — digital ends of, 175. ■ mechanism of, 175. — metatal'so-phalangal, 175. movements of, 1* — - occipito-atlantoid, 116. -■ mechanism of, 122i axoid, 117 peroneo-tibial, inferior, 167. ' ■ middle, 168. superior, 168. ■' ^ mechanism of, 168, of the pelvis, 154. mechanism of, 156. phalangal, of fingers, 153. — movements of, 153. toes, 177 movements of, 17 Articulations, radio-cubital, mechanism of, 144. inferior, 142, sacro-coccygeal, 120. iliac, 154. sciatic, 155. vertebral, 120. movements of, 144. -- middle, 143. movements of, 143. — superior, 142. — movements of, 144. scapulo-humeral, 138. movements of, 139. of the shoulder, 135. — - sterno-clavicular, 136. : — mechanism of, 137. syndesmo-odontoid, 117. tarsal, in general, 170. mechanism of, 173. • of first row, 171. ■ of second row, 171. ■ movements of, 173. of two rows together, 172. movements of, 173. tarso-metatarsal, in general, 174. • movements of, 173. -in particular, 173. - temporo-maxillary, 128. mechanism of, 129. of the thorax, 130. mechanism of, 132, movements of, 134, thyro-hyoid, 425. tiljio-tarsal, 168. — - mechanism of, 169, 170. tracheo-cricoid, 426. of the vertebral column, 115. mechanism 121-123. ' • "^ movements 122. — of the vertebrse with each other, 115. — • bodies of, 115. . articular processes of, 116. laminte of, 116. spinous processes of, 116. ' peculiar, 1 16. •" of the wrist, 145. See Radio-carpal, Astragalus, 100. Atlas, 23. Auditory process, 44. meatus, internal, 44. ■ =- external, 44. — nerve. See Nerve, portio mollis. Auricle or auricula of ear, 666. See Ear, Auricles of heart. See Heart. Auricular surface of os coxas, 91. Axis (vertebra), 24. Basilar process, 34. groove, 35. Bicipital groove, 78. tuberosity, 81. Bi-parietal suture, 46. Biventer cervicis, 205. maxillae inferioris, 245. Bladder, 440, bas-fond of, 442, coats of, 442. development of, 443. functions of, 444. fundus, inferior, 442. • superior, or summit. 442. igaments of, anterior, 441. posterior, 441. — sacculated and fasciculated, 444. — sphincter of, 443. '- structure of, 443. — trigone of, 443. — uvula of, 443. vessels and nerves, 444. pubic, 155. radio-carpal, 145. movements of, 145 Bones in general, 5-18. — arteries of, three kinds, 14, 15. — asymmetrical, 8. broad or flat, 9. diploe of, 13. ossification of, 17. ■ structure, internal, 13. tables of, 13. — — — — — ■ vitreous, 35. 880 Bones, cavities of, 9, 10. articular, 10. _^ ^^ alveolar, 10, - cotyloid, 10. glenoid, 10. trochleae, 10. INDEX. non-articular, 10, canals or conduits, 10. . foSSiB, 10. furrows, grooves, or chan- nels, 10. ■ notches, 10. sinuses or cells, 10. Bones, coronal, 35, — costs. See Ribs. — of cranium, 33. — cubital, 79. — cuboid, 101. — cuneiform, carpal, 83. tarsal, external, 102. — internal, 102. middle, 102. ■ ossification of, 17. changes in, after maturity, 18. chemical composition of, 14. . description of, mode of, 11. development of, 15. . = cajtilaginous stage, 15. mucous stage, 15. . osseous stage, 16. symmetry of, 17. direction of, absolute and relative, 7. eminences of, 9. — articular, 9. condyles, 9. heads and necks, 9. -non-articular, 9. apophyses, 9. epiphyses, 9. -marginal, 18 - of ear, 673. - epactal, 50. - ethmoid, 40. -development of, 41. ■ of face, 51. ■ femur, 93. development of, 95 ■ fibula, 98. development of, 99. - of fingers. See Phalanges. of foot, 99. — of forearm, 79, 80. — frontal, 35. development of, 36. -ossification of, 16. lines and crests, 9. mammillary process- es, 9. processes, 10. prominences, 9. spines or spinous pro- cesses, 9. tuberosities, 9. -of hand, 82. ■ of haunch, 89. - humerus, 78. development of, 79. -hyoid, 109. development of. 111. ilium, 89. incus, 674. ischium, 89. of jaw, lower, 57. upper, 51. — jugal, 54. — lachrymal, 56. development of, 56. — foramina of, 11. — growth, mode of, 18. — long, 8. extremities and shafts of, 9. marrow or medulla of, 10. medullary canal of, 10. membrane of, 13. - structure of, internal, 10. -ossification of, 16. nerves of, 14. nomenclature of, 6. number of, 6. — — — nutrition of, 18. ossific points of, 16. ossification of, 16, 17. eminences and cavities of, 17. - — three kinds of, 17. regions of, 9. shape and symmetry of, 8. short, 9. ossification of, 18. structure, internal, of, 13. '■- situation of, general, 6. size, weight, and density of, 7. structure of, internal, 13. -microscopic, 11. - of leg, 96. - lenticular, 674. - malar, 54. -development of, 55. malleus, 673. maxillary, inferior, 57. development of, 58. superior, 51. development of, 53. of metacarpus, 84. development of, 85. - first, 85 second, third, and fourth, 85. fifth, 85. of metatarsus, 103 development of, 104. - first, 103 second, third, and fourth, 103. fifth, 103. - nasal, 55. development of, 56. -navicular, of carpus, 83. - tarsus, 101. occipital, 33. development of, 34. - substance of, areolar, 11. cancellated, or spongy, 11. compact, 11. reticulated, 11, 13. surfaces, angles, and borders of, 8. syiiiiiietrical, 8. torsion of, 99. veins and lymphatics of, 14. Bones in particular, 18-111. of arm, 78. astragalus, 100. — '■ — atlas, 23. development of, 31. axis, 24. -development of, 31. — calcaneum, 100. — of carpus or wrist, 82. development of, 84. first row of, 83. ■ second row of, 83. ■ clavicle, 74. -- development of. — orbicular, 674 OS calcis, 100. — carince, 33. hyoides, 110. innoininatum, 89. development of, 90. magnum, 83. planum, 40. prorte, and os puppis, 33. — - quadratum, 53. unguis, 55. ossa triquetra, or Wormiana, 50 ossicula auditus, 673. palate, 53. ■ development of, 54. ■ parietal, 41. development of, 42. • patella, 95. development of, 96. - of pelvis, 87. - perone. See Fibula. - phalanges of fingers, 86. development of, 87. ■ toes, 104. development of, 104. ■ coccyx, 20. development of, 31. INDEX 881 Bones, radius, development of, 82. ribs, 67. development of, 68. false and true, 67. rotuta, 95. sacrum, 26. - development of, 32. — scaphoid of carpus, 83. tarsus, 101. scapula, 75. development of, 75. ■ semilunar, 83. sesamoid, 96. of foot, 176. of g-astrocuemius, 165. of hand, 152. of knee or patella, 96. of shoulder, 73. sphenoid, 36. development of, 38. ■ spheno-occipital, 36. ■ spongy. See Turbinated. ■ sternum, 64. development of, 65. styloid, 43. of tarsus, 99. development of, 102. first row of, 100. second row of, 101. temporal, 42. development of, 44. mastoid portion of, 43. petrous portion of, 43. squamous portion of, 43. of thigh, 93. of thorax, 64. tibia, 96. — — development of, 98- of toes. See Phalanges. trapezium, S3. trapezoid, 83. turbinated, ethmoidal, 41. inferior, 56. • development of, 56. middle, 41. sphenoidal, 37. superior, 41. tympanic, 45. ulna, 79. development of, 81. unciform, 83. of vertebral column. See Vertebra, Vertehrm, and Vertebral Column. vomer or ploughshare, 57. ■ development of, 57. Wormian, 50. zygomatic, 54. Borsa appiattita, 706. Brain. See Cerebrum, Cerebellum, Isthmus, and Me- dulla Oblongata. Bronchi^ ill. structure of, 420. Bronchia or bronchial tubes, 418. relations of, with lobules, 418. structure of, 420. Bronchial arteries, 420. ultimate distribution, 420 glands (lymphatic), 420. tubes, 418. veins, 420. - ■ ultimate distribution, 420 mucous membrane, 342. — characters of, 342. Bwcco-lal)ial furrow, 326. Bulbs of forni.x, or corpora albicantia, 728. Bulbus arteriosus, 494. Bursa synovial of tendo Achillis, 283. — of ligamentum patellae, 164. over patella, 311. Bursa: mucosae (so called). 175. synovial, 175. around eyeball, 649. near shoulder joint, 142. hip joint, 161. j knee joint, 164. Canal, for anterior muscle of malleus, 672. arachnoid, of Bichat, 978. carotid, 43. for chorda tympani, 672. crural. 310. dental, inferior, 59 of Fontana, 656. godronne, (561. hyaloid, 661. incisive, 52. infra-orbital, 51. inguinal, 306. for internal muscle of malleus, 43, 672. of Jacobson, 671. maxillary, superior, 51. inferior, 60. medullary of long bones, 13. nasal, 653. of Nuck, 465. palatine, anterior, 52. posterior, 54. of Petit, 661. pterygo-palatine, 38. pterygoid, 38. sacral, 27. for tensor tympani muscle, 43, 671. tympanic, 673. vertebral, 30. vidian, 38. of Wirsung, 401. zygomatic, 55. Canals of bones, 12. dental, superior, 51. lachrymal, 652. palatine, accessory, 54. semicircular, 576. See Semicircular Canals. Canine fossa, 51. Canthi of eyelids, 647. Capitula laryngis, 426. Capitulum costa;, 68. ligaments. See Ligament Capsule of Glisson, 478. lens, 663. Capsules, synovial, 114. of particular joints. See those joints. supra-renal, 445. See Supra-renal Capsules. atrabiliary, 445. Caput ccEcum coli, 371. gallinaginis, 464. Cardia, 442. See Nerves. ^ Carotid arteries. See Arteries. See Nerves. Carpal arteries. See Arteries. Carpus, bones of, 82. bones of first row of, 63. • compared with first row of tarsus, 108. second row of, 83. compared with secondrow of tarsus, 108. compared with tarsus, 107. sheaths for tendons on, 316. Cartilage, chemical composition of, 174. — cricoid, 423. of ear, 666. ensiform, 65. — ■ structure of, 174. thyroid, 423. xiphoid, 65. Cartilages, articular. 111. - characters of. 111. - structure of, 174. - chemical composition of, 174; sub-cutaneous, 630. Calamus scriptorius, 703. Calcaneum, 100. Calcar, T3fi. Canal, alimentary. See Alimentary Canal. 5T • arytenoid, 424. • costal, 69. articulations of, 133. ■ falciform, of knee, 162. ■ inter-articular, 112. structure of, 174. temporo-maxillary, 128. acromio-clavicular, 136. sterno-clavicular, 137. of wrist, 143. of knee joint, 162. ■ inter-osseous, 112. structure of, 174. of larynx, 423. ossification of, 435. of nose. See Nose. 882 INDEX. Cartilages, semilunar, of knee, 1^62. tarsal, of eyelids, 647. Caruncula lachrymalis, 647, CarunculcE myrtiformes, 468. Cauda equina, 770. Caudal extremity of helix and antihelis, 667. Cavernous body. See Corpus Cavernosum. Cavity, coronoid, 80. cotyloid, 88. digital or ancyroid, 947. glenoid, of scapula, 76. temporal bone, 43. — olecranoid, 80. — of omentum, 478. — sigmoid, great and lesser, 81- -- supplementary, of temporo-maxillary articula- tion, 128. of shoulder joint, 139. — trochanteric, 95. Cerebrum, anfractuosities, uses of, 735l arbor vitie of, 750. base of, 727. lateral regions, 731 . median excavation of, 727. commissures, 753. See Commissure- comparative anatomy of, 757, convolutions or gyri, 732. ' ' of digital cavity, 733. ■ inft-rioT surface, 733. superior surface, 734, ■■ internal surface, 733. ' structure of, 755. Cavities, articular, 10. supplementary, 128. orbital, 62. glenoid, of tibia, 97. non-articular, 11. Cells of bone?, 11. ethmoidal, 42. - frontal, 36. sphenoidal, 39. Cellular tissue, 298. lymphatics of, 613. Central foramen of retina, 661. Centrum ovale minus, 736. of Vieussens, 736, 752. semicirculare geminum, 746. Cerebellar arteries. See Arteries. veins. See Veins. Cerebellum, 715, . arbor vitie, lateral and median, 721. commissures of, 723. . comparative anatomy. 724. corpus callosum of, 711. _ dentatum or rhomboideum, 721. development of, 724. falx of, 684. fasciculi, converging and diverging, 724. fibres of, formative and uniting, 724. fissure of, median, 717. furrows of, 717. Gall's views of, 724. ganglia of, 721. general view of, 724, internal structure of, 718. examined by hardening, 722. sections, 721. water, 722. . laminte and lamellas of, 717. uses of, 734. Gall's views of, 754. — crura of, 723. — development of, 756. — falx of, 684. — fibres of, formati-ve or diverging, 752. radiating, 754. uniting or converging, 752. - general idea of, 754. ■ fissure, longitudinal, 726. Sylvian, 727. transverse, great, 727. • ganglia of, 752. hemispheres of, 726. • nucleus of, 749. internal structure of, 735. examined by hardening, 750 sections of, 736. •water, 750 Foville's views of, 755. Gall's views of, 751. general idea of, 753. Mayo's views of, 754. Rolando's views of, 755. 1 (note), 735. • lobes of, ■ medullary centres of, 737. peduncles of, 710. transverse fibres of, 711. course of, in brain, 753. structure of, 713. ■ structure of, 722 (note). lobe, sub-peduncular, 718. lobes, lateral and median, 717. lobule of circumference, 718. medulla oblongata, 718. pneumogastric nerve, 718. lobules or segments, 717. • medullary centre of, 722. ■ peduncles of inferior, 704, 722. middle, 710, 722. superior, 711, 722. sections of, 720. horizontal, 722. — vertical, 721. size and weight of, 716. substances, gray, white, and yellow, 721. surface, upper, 716. lower, 717. ■ section, vertical median, 748. Willis's, 750. __ ■ sections of horizontal, 736. vertical, transverse, 750. general remarks on, 751. • size and weight, 725. — compared to that of cere- bellum, 725. - substance, gray or cortical, 702 (note). white or medullary, 702 (note). - surface, inferior, or base, 727 superior, or convex, 727. •unfolding of, by Gall, 753. ventricles of, 753. See Ventricle. Cervical arteries. See Arteries — ganglia. See Ganglion. — nerves. See Nerves. plexuses. See Plexuses. vertebra. See Vertebra and Vertebra!. Cervix uteri, 465. Cheeks, 328. development of, 328. muscles of, 328. structure of, 328. essels of, 328. tentorium of, 684. ventricle of. See Ventricle, fourth. Cerebral arteries. See Arteries. nerves. See Nerves, cranial. peduncles, substance, &c. See Cerebrum. veins. See Veins. CereJro-spinal axis, 681. divisions of, 682. membranes of, 682. See Arachnoid, Dura Mater, and Pia Mater. Cerebrum, 725. anfractuosities or sulci, 732. of digital cavity, 733. ■ inferior surface, 733. ■ internal surface, 734. superior surface, 734. Chemical composition of tissues, &c. See those tis* sues, &c. Chiasma, optic, 728, 819. Chorda tympani nerve, 836. canal for, 672. Chordce tendineoe, 483. vocales, 426. inferior or true, 427. superior or false, 427. Chorion, 631. Choroid coat of eye. 657. structure of, 657 ■ pigment, 659. ■ plexuses, 747. See Plexuses. ■ veins of brain, 586. ■ eye, 657. \Ciliary body, crown, or disc, 656. canal, 656. I circle, ligament, or ring, 656. ' processes of the choroid coat, 656. zone of Ziiin, 657. INDEX. 883 CircJe of Willis, 727. Circular sinus of Hidley, 587. Circuiriflex arteries. See Arteries. veins. See Feins. Clavicle, 74. Clitoris, 471. ^— artery of, S.'^S. crura, glans and prepuce of, 471. ligaments and muscles of, 471. — nerve of, 807. Cochlea, 677. ■ aqueduct of, 679. axis, columella, or modiolus of, 678. lamina gyrorum, or tube of, 678. ■ spiralis of, membranous and osseous, 678. nei-ves of, 681. scalaj of, tympanic and vestibular, 677- Cochleariform process, 44. Coccygeal vertebrse, 18, 27. Coccyx, 27. Ccecal appendix, 373. Caecum, 371. • appendix veiTniformis of, 373. development of, 383. • internal surface, 373. ■ structure, 378. Collateral arteries. See Arteries. nerves. See Nerves. Colon, 373. arch of, 374. ascending, 374. descending, 374. development of, 384- flexures of, iliac and sigmoid, 371. internal surface of, 376. longitudinal bands of, 374. lumbar, left and right, 374. structure of, 378. transverse, 375. Columella of cochlea, 708. • valve of Vieussens, 712. ColumntE carneae, 483. of rectum, 377. Columns, fronto-nasal, 127. zygomato-jugal, 127. jugal, 127. pterygoid, 127. efface, 127. of vagina, 469. of spinal cord. See Spinal Cord. Comites, arteriie. See Arteries, satellite. nervi. See Nerves, satellite. vense, 572, Commissura mollis, 740. * • Commissure, anterior, of brain, 741. antero-posterior, 753, e.xternal and internal, of eyelids, 647. . ■ — great transverse, of brain, 735. of lips, 326. longitudinal, of brain, or fornix, 737. optic, 729. of pineal body, 742. ■ posterior, of brain, 742, soft or gray, 741. — — ■ of spinal cord, anterior, 698. ■ gray and white, 699. at Sylvian fissure, 746. Commissures of brain, 742. See Commissure. Common mass of posterior spinal muscles, 201. Communicating arteries. See Arteries. nerves. See Nerves, Comparison of arm-bone with thigh-bone, 105. aiteries of upper and lower extremities, 572. bones of upper and lower extremities, 105. carpus and tarsus, 107. development of upper and lower extrem- ities, 109. — ■■— ■ enamel and ivory of teeth, 183. first rows of carpus and tarsus, 108. hand and foot, 107. leg with forearm, 105, — lower parts of radius and tibia, 107. metacarpus and metatarsus, 108. nerves of upper and lower extremities, 815. permanent and temporary teeth, 187. phalanges of fingers and toes, 109. Comparison of second rows of cai-pus and tarsus, 108. shoulder with pelvis, 105. — — ■ teeth and bones, 177. epidermoid appendages, 177 upper ai d lower molar teeth, 181. upper parts of ulna and tibia, 107, Compressor muscles. See Muscles Conarium, 742. Concha of ear, 666. tragic fossa of, 668. ■ nose, inferior, 56. middle, 41. . superior, 41. Concha, ethmoidal, 41. Condylarthrosis, characters, &c,, J14. Condyle, 10. humeral, 78. Condyles, occipital, 34, of lovver Jaw, 58. femur, 95. tibia, 97. Condyloid foramen, anterior, 34, posterior, 34. ■ — — fossas, 34. Confluences of the sinuses, 588. Coni vasculosi testis, 452. Conjunctiva, 648. Constrictor muscles. See Muscles, Conus arteriosus, 481. Convolutions of brain. See Cerebrwm. small intestines, 364, Coracoid process, 76. Cordiform tendon of diaphragm, 2i2. Cornea, opaque, 655. transparent, 655. Cornicula laryngis, 424, Cornu Ammonis, 745. Cornua of hyoid bone, 109, lateral ventricle. See Ventrish. styloid, !09. thyroid cartilage, 424. Corona ciliaris, 656. radians of Reil, 755, of glans penis, 461, Coronal bone, 35. Coronary arteries. See Arteries, ligaments. See Ligaments. veins. See Veins. Coronoid cavity, 80. process of lo^er jaw, 58, ulna, 80. Corpora albicantia, 728. structure of, 738, Arantii, 486. bigemina, 712. lutea, 462. mammillaria, 728. olivaria, or ovata, 706. quadrigemina, 712. restiformia, 707, Corpus bulbosum, 461, artery of, 558, nerve of, 806. callosum, artery of, 529. bourrelet or cushion of, 731. of cerebellum, 711. extremity, anterior, 737. posterior, 731. genu or knee, 737. peduncles of, 730. reflected portion, anterior, 7; rostrum or beak, 737. ■ — convolution of, 733. ventricle of, 737. ' longitudinal tracts of, 737. fibres of, 753. cavernosum penis, 455. ■ crura of, 455. — nerves, 456. structure, 455. - vessels, 456. dentatura cerebelli, 721. medulla, 705. fimbriatum, 739. uteri, 464. geniculatum externum, 728. internum, 712. Highmori, 450. ■ luteum, 462. ■ muoasum of skin, 635- 884 Corpus papillare of skin, 632. ■ psalloides, 738. reticulare of skin, 635. spongiosum urethrse, 460. striatum, 744. . . fibres of, 753. lobule of, 731» vein of, 745. Costal cartilages, 69. Costa, 67. See Rihs. of scapula, 76. Cotyloid cavity, 88. _ cavities in general, II. Crania, national, 44. Cranial nerves, in general. See Nerves. in particular. See Nerves. ganglia. See Ganglia. arachnoid. See Arachnoid. dura mater. See Dura Mater. Cranium, aponeuroses of, 299. area of, 45. articulations of, 125. base of, exterior of, 45, — • interior of, 46. bones of, 34. . circulation of, arterial, 531. venous, 562. INDEX. Dorsal ligaments. See I/I.gaments. nerves. See Nerves. veins. See Veins. vertebree. See Vertebra and Vertebral. Dorsum ilii, or external iliac fossa, 88. linguae, 337. manus, 82. nasi, 641. pedis, ' Duct, common biliary, 398. . internal surface, 399. structure, 399. development of, 50. external surface of, 45. lymphatic system of, 627. in general, 45. internal surface of, 46. mechanism of, 126. — ^— regions of, 45. -. sutures of, in general, 154. ■ particular. See Sutures. — cystic, 397- structure, 399. — ejaculatory, 452. — hepatic, 395. internal surface, 399. structure, 399. lymphatic, riglit, 619. nasal, 653. pancreatic, 402. parotid, 341. Stenonian, 341. thoracic, 618. right, 619. Warthonian, 342. Ducts, biliary, 390. lactiferous or galactophorous, 4T3. prostatic, 458. of Rivinus, 342. Ductus arteriosus, 500. communis choledochus, 398. ejaculatorius, 452. venosus, 600. Duodenum, 361. curvatures of, 362. varieties of, 45. vault of, 45. Crest of iliam, 89. pubes, 89. tibia, 97. urethra, 459. Crests, occipital, 35. Cribriform plate of ethmoid bone, 40- Cnsia g.ilh, 40. ilii, 89. vestibuli, 676. Crura of clitoris, 471. — corpus cavernosum, 455. diaphragm, 212. cerebri, 711. Crural arch, 309. ring, 310. septum, 310. Crust of cerebral peduncles, 713 (note). Crusta petrosa, 182. Crypts of Lieberkuhn, 369. Cuneiform bone of carpus, 83. Cutaneous nerves. See Nerves- Cuticle, 633. Cutis, or cutis vera, 631, anserina, 630. Cystic duct, 397. Cystis fellea, 396. Dartns, 446. tissue of, 446 (note). Deltoid impression, 78. Dental arteries. See Arteries. canal, inferior, 57. canals, superior, 51. nerves. See Nerves, veins. See Veins. Dentata (vertebra), 24. Denies. See Teeth, Depressor muscles. See Muscles. Development of particular bones, organs, or parts body. See those bones, organs, &c. Diaphragm, 212. Diarthroscs, 1 14. Digastric fossa, 43. groove, 43. Digestive apparatus, general view of, 3. Digital arteries. See Arteries. nerves. See Nerves. Diploe, 14. Diploic canals, 591. veins, 585, 591. Dissection of different parts. See those parts. Qorsal arteries. See Arteries. glands of, 370. lymphatic glands of, 625. structure of. See Small Intestine. Dura mater, 682. cranial portion of, 683. cranial nerves of, 686. sinuses of, 584. structure of, 685. uses of, 686. vessels of, f dissection of, 682, — spinal portioii of, 686. — vessels of, 687. Ear, auricle of, 666. cartilage of, 666. ligaments of, 667. muscles of, extrinsic. See MuscleSj auricular. intrinsic, 668. ■ skin of, 668. ■ vessels and nerves, 668. drum of. See Tympanum. external. See auricle and meatus of. general view of, 666. internal, or laliyrinth of See Labyrinth. meatus of external, 668. - cartilaginous and fibrous portion of, - glands of, 669. •- osseous portion of, 44. -- skin of, 6. -- internal, 44. bottom of, 680. middle. See Tympanum. ossicula of, 673. movements of, 674. muscles belonging to, 674. j tympanum of. See Tympanum. ' vessels of, 680. Eighth cranial nerve. See Nerves, glosso-pharyngeaS, pneumoga^tric, and spinal accessory. Ejaculatory duct, 452. Elastic tissue, structure of, 174. chemical composition of, 174. — ligaments, general characters of. 112. : of vertebra, 115. EWioic-joint, 143. Eminence, jugular, 34. nasal, 35. frontal, 35. ilio-pectineal, 89. hypothenar, 261. thenar, 260. unciform of lateiul ventricle, 730. INDEX. 885 Sminentia coUateralis, 746, EminenlicB natifonnes, 712. testiformes, 712. Enamel of teeth. See Teeth. Enarthroses, 114. Encephalic nerves. See Nerves, cranial. Encephalon, arteries of, in general, 535. isthmus of. See Isthmus. £rt(fo-cardium, 488. lymph, 680. Ensiform process, cartilage or appendix, 65. Epactal boiies. 50. Epicondyle, 79. Epidermis, 633. Epididymis, 451. — g-lobus major, 451. ■ • minor, 451. . structure, 451. Epigastric region, 352. Epiglottis, 425. Epiploon, 478. See Omentum. Epithelium ciliated, 323. columnar, 323. squamous, 323. of particular membranes. branes. Epitrochlea, 80. Erectores muscles. See Muscles. Ergot, 736. Ethmoid bone, 40. Ethmoidal balb, 818. cells or sinuses, 40. See those mem- — fossa, 48. — groove, 40. labyrinth, 40. Eustachian tube, or trumpet, 672. cartilaginous and fibrous portion, 672. mucous membrane, 673 (note). osseous portion, 44, 672. Extensores muscles. See Muscles. Extremities, lower, aponeuroses of, 306. articulations of, 153. arteries vif, .557. bouBs of, 87. development of, 104. lymphatic system of, 619. nerves of, 797. veins of, 603. upper, aponeuroses of, 315. arteries of, 531. articulations of, 135. liones of, 74. ■ development of, 87. • lymphatic system of, 628. nerves of, 781. ■ veins of, 593. upper and \o-vier, arteries of, compared, 572. — ^— ^— — — — ^— bones of, compared, 105. development of, compa- red, 109. nerves of, compared, 815. Eye, 645. appendages of, 646. brows, 646. chamber of, anterior, 658. posterior, 658. globe of, 654. humours of, aqueous, 6G4. crystalline, 662. ■ vitreous, 661. - lashes, 646. - lids, 646. cartilages of, 647. commissures or canthi, 647. glands, 648. mucous membrane, 647. muscles of. 647. uses of, 647. vessels and nerves, 648. - membranes of, 654. of aqueous humour, 655. arachnoid of, 656 (note). ■ • — capsule of lens, 662. choroid coat, 656. ■ cornea, 655. hyaloid, 661. iris, 657. Jacob's, 661. pupillary, 659. retina, 660. Eye, membrane, Ruyscli's, 659. sclerotic coat, 654. of vitreous humour, 661. muscles of, oblique, 651. recti, or straight, 651. action of, 651. nerve of. See Nerve, optic. pigment of, 660. vessels of, 665. Face, area of, 46. bones of, 51. cavities of, 62. circulation of, arterial, 530. venous, 593. development of, general, 63. regions of, 63, 64. in general, 60. lymphatic system of, 626. movements of, 238. muscles of, 231. regions of, €0. Facial angle of Camper, 45. nerve. See Nerve, portio dura. Fallopian aqueduct, 43. hiatus, 44. ligament, 302. tubes, 463. — fimbriae of, 463. structure and uses of, 463. Falx of umbilical vein, 475. eerebelli, 684. cerebri, 684. Fascia. See Aponeurosis. cervical, 209. cremasteric, .102. cribriform, 309, 621, dentata, 476. ■ iliac, 302. — infundibuliform, of cord, 302. — intercolumnar, of inguinal ring, 301. lata, 309. iliac portion, 310. pubic portion, 311. -structure, 311. obturator, 308. propria (sub-peritoneal fascia), 303-305. recto- vesical, 308. spermatic, 304. superficial, 297, 630. tensor muscles of, 294. transversal is, 305. Fasciculi, muscular, 193. of medulla. See MeduUa. Fauces, arches of, 330. isthmus of, 330. pillars of, 330. Femur, 93. Fenestra ovalis, 670. rotunda, and its fossa, 671. Fibres, muscular, involuntary, 324. voluntary, 193. nervous, 767. Fibrous tissue, 298. Fiiro-cartilage of epiglottis, 423. cartilages, 177. of particular joints. Fibula, 98. Fifth cranial nerve. See Nerve, tri/aciai. Filaments, muscular, 193. nervous, 767. See those joints. Fillet, 712. Fimbria; of Fallopian tubes, 463. Fingers, 86. phalanges of, 86. — — and toes, phalanges of, compared, 120. First cranial nerve. See Nerve, olfactory. Fissure, Glasserian, 43. glenoidal, 43. incisive, 53. orbital, 53. pterygo-maxillary, 55. spheno-maxillary, 39, 52, 55. sphenoidal, 39. Sylvian, 730. Fissures of brain, liver, &c. See those organs. Flexor muscles. See Muscles. Flocculus, 718. Fluid, ventricular, 744. - of Scarpa, 680. 886 INDEX. Fluid, sub-arachnoid, 144. Folds, aryteno-epiglottid, 433. glosso-epiglottid, 336. phar/ngeo-epigluttid, 426. Follicles, dental, 184. of Goodsir, 183. intestinrJ. See Intestines. — Lieberkuhn"s, 379. sebaceous, 635. — solitary, 3T0. of stomach, 360. tubular, 360. uterine, 471. Fontanelles of scull, 49. Foot, bones of, 99. compared with hand, 106. Foramen, of Bichat, 688. ofBotal, 486. centrale of retina, 660. caecum of frontal bone, 36. Morgagni (in tongue), 333. medulla oblongata, 703. condyloid, anterior, 34. posterior, 34. infra-orbitary, 59. lacerum superius, 39. posterius, 44, 47, 49^ anterius, 47. magnum, 34. mastoid, 43. mental, 57. of Monro, 740. nutritious of humerus, 78. ulna, 79. radius, 81. femur, 93. tibia, 96. fibula, 99. obturator, 88. occipital, S4. optic, 37. orbital, internal anterior, 36. posterior, 36. ovale of heart, 487. sphenoid bone, 38. parietal, 42. rotundum, 38. spheno-palatine, 54. spheno-spinosum or spinosuiD, 38. stylo-mastoid, 43. superciliary, 36. supra-orhitary, 36. vertebral, 20, 21. of Winslow, 476. Foramina Thebesii, 488. malar, 54. of bones, ] 1 . inter-vertebral, 20, 30. posterior, 775 (note). sacral, 27. Forearm, bones of, 79. compared with leg, 105. Fornix, 739. ■ bulbs of, 740. pillars of anterior, 739. posterior, 740. Fossa, amygdaloid, 331. canine, 51. digastric, 43. ethmoidal, 48. iliac, external, 88. internal, 88. infra-spinous, 76. ischio-rectal, 309. jugular, 43. lachrymal, 36. mental, 58. myrtiform, 49. navicalaris of urethra, 461. vulva, 470. • ear, 670. ■ ovalis of heart, 488. ■ parietal, 43. • perineal, 309. ■ pituitary, 37, 48, • pterygoid, 38. ■ scaphoid. See Navicvlaris. ■ spheno-maxillary, 60. ■ sub-lingual, 57, 60. ■ sub-maxiUary, 57, 60. Fossa, sub-pyramidal, 671. sub-scapular, 75. supra-sjihenoidal, 37. supra-spinons, 76. temporal, 47. zygomatic, 60. Fossa of bones, 1 1 . condyloid, 34. frontal, 36. internal iliac, 91. nasal, 62. middle lateral, or spheno-temporal, 48. occipital, 35. Fovrchette of sternum, 65. vulva, 470. Fourth cranial nerve. See Nerve, pathetic. Fovea heniispherica, 676. semi-elliptica, 676. Frcenum labii, 324. linguifi, 336. praeputii, 455. Frontal bone, 35. cells or sinuses, 37. eminence, 35. fossse, 36. Fronto-iuga\ suture, 48. maxillary suture, 59. nasal suture, 59. columns, 127. parietal suture, 45, 47. sphenoidal suture, 48. Fundus of stomach, bladder, &c. Furrow, mylo-hyoidean, 57. mento-labial, 326. bucco-labial, 326. Furrows of heart and spina] coid. See those organs. Galactophorous ducts, 473. Galea capitis, 208. GoZZ-bladder, 396. structure of, 397. use of, 400. Ganglia, lymphatic. See Lymphatic Glands. Ganglia, nervous, in general. See Nerves, ganglia of. Ganglia, nervous, in particular, 765. abdominal, 865. of brain, 753. cervical, syTapathetic. See GaTtglion. cranial, 765. ;ympathetic, 854. See those orgaas. -intercostal, 765. - lumbar, sympathetic, ■spinal or rachidian, 765. ■ splanchnic, 765. - sympathetic, 765. connexions of, 766. structure of, 768. external and inteiBal branches of, 869. - thoracic, 864. external branches, 864. ■ internal branches, 864. -vertebral, 761. Ganglion of Andersh, 843. annulare (of eye), 831. cardiac, 862. carotid, 856. of cerebellum, 722. cervical, inferior, 859. middle, 859. superior, 855. branches of, anterior, 857. external, 858. inferior, 8.58. internal, 858. superior, 856. ciliary, 830. Gasserian, 827. of glosso-pharyngeal, 843. impar, 871. inter-carotid, 858. lenticular, 830. Meckel's, 831. naso-palatine, 831. ophthalmic, and branches, 830. otic, and branches, 837. petrosal, 843. of pneumotfastric, 845. of Ribes, 85'. of root of hypoglossal, 823 (note). INDEX. 887 Ganglion of root of spinal accessory, 823. semilunar abdominal, 806. of fifth nerve, 827. solar, 866. spheuo-palatiue, and branches, 831. sub-raaxillary, 837. thoracic, first, 8591. thyroid, 859. Gasserian ganglion, 827. Genial processes, 58. v Ginglymus, angular and lateral, 114. Glabella, 35. ^land, accessory, of parotid, 341. epiglottid (so called), 430. lachrymal, 652. • parotid, 340. See Parotid Gland. pineal. See Pineal Gland. pituitary, 729. prostate, 459. structure, 459. suL)-hnguaI. See Sub-lingual Glana. sub-niaxiUary, 342. See Sub-maxillary Gland. thymus, 415. ■ thyroid, 433. Glands, agmiuated, 370. arytenoid, 433. Bruuner's, 370. buccal, 329. ceruminous, 669. conglobate (lymphatic), 614. Cowper's, 460. duodenal, 37i). epiglottid, 430. of Havers, 113. in knee, 163. intestinal. See Intestines, labial, 328. laryngeal, 432. lingual, 337. lymphatic, in general, 616. particular. Glands. mammary, 472. See Lymphatic. — Meibomian, 648. ( — molar, 329. — odoriferous, of prepuce, 453. — oesophageal, 352. — of PacchionL, 585, 685. — palatine, 329. — Peyer's, 370. — salivary, 340. See Salivary Glands. — solitary, 370. — sudoriferous, 633. — synovial (so called), 113. — of trachea, 410. — tubular, 360, 370. — Tyson's, 454. — of uterus, 467. of Vesalius (bronchial), 625. Glandula socia parotidis, 341 Glans clitoridis, 471. penis, 460. corona of, 460. structure of, 461. Glasserian fissure, 43. Globuli Arantii, 486. Globus major, 451. minor, 451. Glomeruli, 437. GZosso-epiglottid folds or ligaments, 430. pharyngeal nerve. See Nerve. Glenoid cavities in general, 11. ligaments. See Ligaments. Glottis, 430. differences in size of, 435. Gomphosis, 114. Groove, basilar, 34. bicipital, 78. cuboid, 100. dental primitive, 184. secondary, 184. digastric, 43, 47. ethmoidal, 40. inferior petrosal, 49. lachrymo-nasal, 51. longitudinal, of cranium, 47. mylo-hyoidean, 50. obturator, 88. optic, 37. sub-pubic, 88. Groove, superior petrosal, 44. of torsion, of humerus, 78. Grooves of bones, 12. calcaneal, 100. carotid, 37. cavernous, 37. for lateral sinuses, 34. — on back of radius, 81. — sacral, 92. — of spinal cord. See Spinal Cord. ■ vertebral, 29. Gubernaculum dentis, 189. testis, 446, Gula, 344. Gulf of the internal jugular, 583. Gums, 329. Habence of pineal body, 742. Hamular process of sphenoid bone, 37. cochlea, 678. Hand, bones of, 82. compared with foot, 107. Hairs, description of, general, 638. follicles of, 638. structure and growth, 638 (note). Harmonia, 114. Harmonic sutures, 114. Haunch bone, 89. Heads of bones, 9. particular. See those bones. Heart, 479. auricles of, external surface, 482. — — interior of, 486. muscular fibres of, 490. musculi pectinati, 4tM. orifices of, 484. ■ auriculte of, 482. ■ interior of, 487 ■ bone in, 489. ■ cellular tissue, 493. • chordiE tendineae, 483, ■ columnae carneae, 483. ■ conformation of, external, 480. internal, 482. • development of, 492. ■ fibrous framework of, 488. ■ foramen of Botal, 486. ovale, 486, remains of, 486. foramina Thebesii, 487. • fossa ovalis, 486. • function, 492. ■ furrow, auriculo-ventricular, 481. inter-auricular, 482. ventricular, anterior and poste- rior, 481. ■ muscular fibres of, 488. structure of, 488. ■ nerves of, 492, • separation of, into right and left hearts, 490. ■ septum, inter-auricular, 482. ventricular, 481. serous coat, external, 487. internal, 487. sounds of, 493, • structure of, 487. ■ tubercle of Lower, 486. ■ valve. Eustachian, 486. mitral, 484. of Thebesius, 486, tricuspid or triglochin, 484. ■ valves of, auriculo-ventricular left, 484. right, 485. semilunar. See Sigmoid, ■ sigmoid, aortic, 484. pulmonary, 484. ventricles of, external surface, 480. interior of, 483. — muscular fibres of, 488. musculi papillares, 484. orifices of, 483. vessels of, 491. zones, fibrous, of, 488. Heel, bone of, 100. Helicotrema, 679. Helix, and its furrow or groove, 666. - cartilaginous process of, 667. Hemorrhoidal arteries. See Arteries. nerves. See Nerves. Hepatic artery, in the liver, 394, 395. 888 INDEX. Hepatic duct, 395. in the liver, 394, 3S5. Hiatus Fallopii, 44. Hilus of spleen, &c. See those organs. JJip-joint, 159. ligaments of, 160. Horizontal plate of palate bone, 53. Human body, general view of, 1-4. Humerus, 78. Humours of eye. See Eye. Hymen, 469. Hyoid bone or apparatus, 109. JHyyo-glossal nerve. See Nerve. ZZeo-coecal valve, 372. development of, 384. structure of, 373. uses of, 373. colic valve, 372. Ileum, 362. structure of. See Intestine.^ smaU. Iliac arteries. See Arteries.. flexure, 371. fossa, external, 88. internal, 88. region, 352. veins. See Veins. JZio-pectineal eminence, 89. Ilium, 89. Impression, deltoid, 78. Incisive canal, 52. fissure, 53. Incisura tragica, 666. Incus, 674. Indented sutures, 115'. in/ra-orbital canal, 51. foramen,. 59. nerves. See Nerves. spinous fossa, 76. Infundibula of kidneys, 439. Infundihulum of base of brain, 729. cochlea, 078. nasal fossa, 41, 62. right ventricle of heart, 481. Inguinal canal, 304. ring, 303. Insula of Reil, 745. Integumentum, 713 (not*). /nier-articular cartilages. See Cartilages. auricular furrow, 482. septum, 482. columnar fascia, 301. condyloid notch, 95. — ^— costal arteries. See Arteries. nerves. See Nerves. spaces, 71. lobular fissures, spaces, and vessels of liver, i of lungs, 414. osseous arteries. See Arteries. cartilages, 112. ligaments. See Ligaments, muscles. See Muscles. nerves. See Nerves. spaces of hand, 84. . foot, 106. • peduncular space, 711, 728. ■ spinous ligaments, 119. ■ trochanteric line, 94. • ventricular furrow, 480. — septum, 480. ■ vertebral foramina, 20, 30. substance or disc, ligaments, 115. 115. Intestine, large, 370. ' coats of, 378, 379. development of, 383. divisions of, 371. ■ follicles of, 379. functions of, 382. lymphatic glands and vessels, 379. structure of, 378. tubuli of, 379. vessels and nerves of, 379. Intestine, small, 361. coats of, 366. Intestine, small, follicles of, Lieberkuhn's, 370. solitary, 369. . functions of, 370. glands of, 366. lymphatic glands of, 624. lymphatics of, 624. papiUiE of, 367. properly so called, 363. structure of, 365. tubuli of, 370. valves of, 366. vessels and nerves of, 370, villi of, 367. Intestines in general, 361. - development of, 383. /nira-lobular veins of liver, 395 (note). spinal veins. See Veins. Iris, 657. layers of, 659. muscular fibres of, 658 (note). structure, 658. uses of, 659. vessels and nerves of, 659. Ischiadic notch, 89. Ischio rectal fosste, 308. Ischium, 89. Island of Reil, 745. Isthmus faucium, 325. ovalis (heart), 486. of the encephalon, 710. comparative anatomy, 715. development of, 715. divisions of, 710. fasciculus of, triangular, 710-712. furrow, lateral, of, 710. internal structure of, 713. lower stratum, 713. middle stratum, 713. upper stratum, 713. Iter dentis, 16 Ivory of teeth. ■ sections of, 713. i8. See Teeth. Jacob's membrane, 660. structure of, 06]. Jaw, lower, 57. articulations of, 128. upper, bones of, 51. — articulations of, 126. Jejunum, 362. structure of. See Small Intestine. Joints. See Articulations. Jugal columns, 127. bone, 54. Jugular eminence, 34. fossa, 43. veins. See Veins. internal, sinus of, 583. Kidneys, 436. acini, 438. adipose capsule of, 437 calyces of, 439. coat of, 437. cortical substance of, 438. development of, 440. -- functions of, 440. — glomeruli, 437. — hilus or fissure, 436. — papilUe, 437. — pelvis of, 440. — pyramids of, Ferrein's, 437. -Malpighi's, 437. ■ tubes of, convoluted, 437 straight, 437. tubular portion, 438. — structure of, 438. convolutions of, 364. crypts of, 370. development of, 383. divisions of, 361. follicles of, agminated, 369. vessels and nerves, 438. Knee-joi-at, arteries, ligaments, and nerves. See those parts. Labia pudendi, 470. ILabyrmth, ethmoidal, 40. fluids of. 679. lining membrane of, 680. membranous, 679. osseous,j 675. See Cochlea, Semi-circular Canals, and Vestibule. Lacerated, foramen anterior, 47. posterior, 44. INDEX. 889 Lacerated, foramen superior, 39. Lacerti teretes of heart, 483. Lachrymal bone, 56. canals, 651. caruncula, 647. gland, 651. groove, or fossa, 36, 651. papillfe, or tubercles, 645. passages, 65!. raucous coat of, 654. puncta, 652. sac, 653. iacArymo-nasal groove. 51. canal, 652. Lacteals, 611. of intestines, 612. Lactiferous ducts, 473. Lacuna magna, 460 (note). Lacuna: of urethra, 460. Lacus lachrymalis, 647. Lambdoidal suture, 46. Lamina cinerea, 730. of cornea, 745. cribrosa of ethmoid, 40. of internal auditory meatus, 678, 680. gyrorum, 677. papyracea, 41. spiralis, membranous and osseous, 677. Laryngeal ner\'es. See Nerves. Larynx, 422. articulations of, 426. cartilages of, 423. ossification of, 435. development of, 435 functions of, 435. glottis, 430. in general, 429. ligaments of, 425. mucous membrane and glands of, 475. muscles of, 427. sinus of, 434. surface, external, 429. internal, 430. ventricle of, 427. vessels and nerves, 435. Leg, articulatiims of, 168. bones of, 96. compared svith forearm, 105. fascia of, 311. Lemniscus, 711. Lens. See Crystalline Lens. Levator muscles. See Muscles. Levers, three orders of, in body, 199. Ligament aAata of uterus, 475. subflava, general characters, 112. — . of vertebral column, 115. Ligaments in general, 112. articular, 112. capsular, 112. . interosseous, 112. membranous, 112. structure of, 174. yellow or elastic, 112. Ligaments in particular, 113. accessory, of shoulder-joint, 139. hip-joint, 160. knee-joint, 165. Weitbrecht, 144. alar, of axis (or odontoid), 119. ■ of knee, 165. of ankle-jomt, lateral, anterior external, 169. external proper, 169. internal, 169. — posterior, 169. Ligaments of auricle, intrinsic, 667. of bladder, anterior, 308, 440. posterior, 440, 475. broad, of liver, 386. uterus, 465. calcaneo-cuboid, inferior, 173. internal, 173. superior, 172. • scaphoid, inferior, 172. superior, 172. of canthus, external, 647. capsular, acmmio-clavicular, 135. atlanto-axoid, 119. carpo-niPtacarpal of thumb, 150. ■ of little finger, 150. hip-joint, 160. — knee-joint, \t — occipito-atlantoid, 119. axoid, 119. — scapulo-humeral, 137. sterno-elavicular, 136. annular, of radius, 142. -atlas, 117. carpus, anterior, 318. dorsal, 318. tarsus, dorsal and lateral, 313. — aryteno-epiglottid, 426. — astragalo-calcaneal, interosseous, 171. external, 171. — posterior, 171. of each row of carpal bones, 147. two rows of carpal bones, 147. carpo-metacarpal, dorsal, 150. palmar, 150. interosseous, with os mag'- num, 150. of little finger, 150. • thumb, 150. — - cervical, posterior, of quadrupeds, 117. check, of axis (or odontoid), 119. chondro-sternal, anterior, 131. interosseous, 131. posterior, 131. superior and inferior, 131. xiphoid, 131. ciliary, 656. conoid, 135. coraco-aoromial, 140. — ■ ■ clavicular, anterior, or trapezoid, 136 posterior, or conoid, 136 coraco-humeral, 139. coracoid, 139. costo-clavicular, 138. coracoid, 139. ■ transverse, interosseous, 131. posterior, 131. superior, 131. -vertebral, anterior, 131. inferior, 131. interosseous, 131. stellate, 131. superior, 131. cotyloid, of hip-joint, 159. erico-arytenoid, 426. thyroid, middle and lateral, 426 crucial, of atlas, 117 knee-joint, 1C4. of cuneiform bones of tarsus, 170. and scaphoid, 17j • third and cuboid, 171. deltoid, 169. dorsal, annular, of carpus, 318. tarsus, 313. carpo-metacarpal, 149. of carpus, 149. ■ metacarpus, 149. metatarsus, 175. tarso-metatarsal, 175. of tarsus, 171. elbow-joint, external lateral, 141. internal lateral, 141. anterior, 141. ■ posterior, 142. scaphoid, superior, 172. — atlanto-axoid, anterior, 117. posterior, 117. capsular, 117. odontoid, transverse or annular, 117. crucial, 1 1 of auricle, anterior and posterior, 667. falciform, 303. Fallopius's, 302 of Ferrein, 427. Gimbernat's, 303. glenoid, carpal anterior, 148. posterior, 148. metacarpo-phalangal, 152. metatarso-phalan§ral, 175. phalangal, of fingers, 153. ■ toes, 176. scapulo-humeral, 138. 5U — glosso-epiglottid, 425. — of hip-joint, anterior superior, 160. accessory, 160. — - cotyloid,' 160. inter-articular, 161. INDEX. Ligaments of hip-joint, round. 161. capsular, 160. of huraero-cubital, 141. hyo-epiglottid, 425. ilio-lujnbar, 156. • inter-articular, acromio-clavicular, 135. • of hip-joint, 160- of siioulder-joint, 137. sterna-clavicular, 136. temporo- maxillary, 128. of wrist, 143. osseous, astragalo-calcaneal, 171. of carpal bones, 147. carpo-metacarpal, 149. costo-transverse, 131. vertebral, 131. — of forearm. 144. knee-joint, 164. leg, 169. OS maffnum and metacar- pus, 149. • metacarpal, 149. ■ metatarsal, 175. • peroneo-tibial, 168. pubic, 156. radio-cubital, 143. sacrn-iliac, 155. tarsal, of first row, 171. ■ second row, 171. tarso-metatarsal, 175. vertebral, 115. clavicular, 137. spinous, 116. -— — vertebral, 1 15. of knee-joint, 163. accessory, 166. adipose (so called), 166. alar, 166. ■ — ■ anterior, 163. capsular, 163. crucial anterior, 164. ■ posterior, 163. ■ inter-articular, 163. osseous, 164. lateral, external, 163. internal, 163. ■ mucous (so called), 166. • posterior, 163. - transverse, 163. of larynx, 425. — malleus, 673. metacarpo-phalangal, glenoid, 152. lateral, 152. ■ of thumb, 152. of metacarpus, 148. metatarso-phalangal, glenoid, 176. — lateral, 176. of metatarsus, 175. occipito-atlantal anterior, superficial, 116. — deep, 116. capsular, 117. lateral, 117. posterior, 116. ■ axoid, lateral, 120. middle, 120. odontoid, lateral, 120. middle, 120. orbicular, of acromio-clavicular articula- tion, 137. of hip-joint, 158. scapulo-humeral, 139. sterno-clavicular, 137. palmar of carpo-metacarpal joints, 149. carpus, 147. - metacarpus, 148. of patella, 164. perinsal, 307. peroneo-tarsal, anterior external, 170. ■ external, 170. — posterior, 170. of peroneo-tibiaJ articulations, 167, 168. perpendicular, 170. phalangal of fingers, glenoid, 153. lateral, 153. toes, glenoid, 177. lateral, 177. of pisiform and cuneiform bones, 147. plantar inferior, 174. of metatarsus, 176. ■ tarso-metatarsal, 176. Ligaments, plantar of tarsus, 172. Poupart's, 302. proper, of scapula, anterior, 140. posterior, 140. pterygo-maxillary, 235. pubic anterior, 155. ■ inferior, 155. interosseous, 155. posterior, 155. superior, 155. triangular, 155. radiated chondro-sternal, 133. of radio-carpal articulation, 145. cubital articulations, 144. ' recto-uterine, 467 ■ round, of forearm, 144. hip-joint, 161. ■ uterus, 466. • sacro-coccygeal, anterior, 120. posterior, 120. - ihac, anterior, 154. interosseous, 154. posterior vertical, 155. superior, 154. sciatic, great, 155. -— small, 155. vertebral, 120. ■ scaphoid and cuboid, 172. ■ of shoulder-joint, 136. • spheno-maxillary, 129. • stellate, costo-vertebral, 130. ■ or radiated, chondro-sternal, 13L • stylo-maxillary, 129. niylo-hyoid, 129. • sub-pubic, or inferior pubic, 156. • supra-spinous, 119. ■ suspensory of clitoris, 471. — • penis, 456. • liver, 3S6, 475. ■ of first row of tarsal bones, 171. second row of tarsal bones, 171. tarso-metatarsal, dorsal, 174. interosseous, 174. oblique of fifth toe, 175. plantar, 174. ■ of temporo-maxiliary articulation, lateral external, 128. - internal, 129. - thy ro- arytenoid, or chorda vocales, 427. epiglotlid, 425. hyoid, middle and lateral, 425. - tibio-tarsal, anterior, 169. internal, 169. posterior, 169. • of tragus, 667. - transverse of atlas, 117. knee, 163. metacarpus, 149. ■ trapezoid, 136. ' ■ triangular of perinffium, 307. penis, 455. symphysis pubis, 156. urethra, 307. vrist, 143. ■ of two rows of tarsal bones, 171. ■ vertebral, anterior common, 116. interosseous, 116. posterior, 116. yellow elastic, 117. ■ vesico-uterine, 467. ■ of Weitbrecht, 144. — Winslow, 164. — wrist-joint, external anterior, 146. internal anterior, 146. middle anterior, 146. external lateral, 146. internal lateral, 146. posterior, 146. • of Zinn, 650. Ligamentum arcuatum of diaphragm, 213 denticulatum, 694. fibulae anterius, 170. medium, 170. perpendiculare, 170. posterius, 170. gastro-phrenicum, 354. latum pulmonis, 413. longum plantae, 173. mucosum of knee-joint, 164. nuchae, 202. INDEX. 891 LigamentuTrfpateWs, 164. phrenico-lienale, 403. propnuiii antenus scapuljE, 140. ■ posterius scapals, 140. • teres of forearm, 144. hip-joint, 161. Limbs. See Extremities. Limbus luteus, 66U. Line, iuter-trochanteric, 94. mylo-hyoidedn, 57. nasd-labial, 327- Lines, semicircular of occipital bone, 33. OS coxiE, 88. Linea alba, 301. cervical, 300. aspera, 94. Lips, 325. -— development of, 326. movements of, 238. muscles of, 326. structure of, 326. uses of, 327. vessels of, 327. LiJ^uor Cotunni, 680. Morgag-ni, 663. ■■ of Scarpa, 680. Liver, 385. acini of, 390. circumference of, 389. coats of, 390. colour and frag-ility, 369. development of, 399. ducts of, 391 (notes). excretory apparatus of, 395. figure, 386. fissures, 387. functions, 400. groove for vena cava, 389. hilusof, 388. — — ligament, broad or suspensory, 386. coronary, 390. falciform, 386. triangular, left and right, 390. ■ lobes. 387. -^^— lobules or granules, 388. ■■ arrangement of, 391. structure of, 394 (note). - lymphatics of, 393. -nerves of, 393. -porta of, 388. -proper tissue, 390 (note). • situation, 385. ■ size, 385. - structure of, 390. -surface, inferior or plane, 386. -- superior, 386. vessels of, 392. arrangement of, 393. Lohes and lobules of organs. See those organs. Lobule of ear, 666. Lobulus caudatus, 389. quadrat us, 389. Spigelii, 389. Locus niger, 751. perforatus anterior, 731. middle or posterior, 727. Longissimus dorsi. See Muscles. Longitudinal fissures of liver, &c. See those organs. vein of spine. See Veins. Luetic of bladder, 459. Lumbar nerves. See Nerves. • region of abdomen, 352. veins. See Veins. vertebne. See Vertebra and Vertebrce. Lungs, 409. air-cells of, 415. air- tubes of, 416. cellular tissue of, inter-lobular, 415. development of, 421. external conformation of, 411. fissures of, inter-lobular, 411. fostal, 421. functions, 422. lobes of, 411. . lobules of, 415. structure of, 419. lymphatic system of, 421. root of, 412. size of, 409. structure of, 413. Lungs, vessels and nerves of, 421. weight of, absolute and specific, 410. Lymphatic duct, right, 619. glands in general, 616. preparation of, 617. structure of, 617. in particular, 619. axillary, 628. bronchial, 625. cervical, deep, 628. superficial, 627. ■ of craui um, 626. • duodenal, 624. ■ of face, 626. - ileo-culir, 624. ■ iliac, external, 622. internal, 622. - inguinal, 619. - intercostal, 625. ■ of intestine, great, 624. smaU, 624. - of liver, 623. - of lower extremity, 620. - lumbar, B2I. ■ mammary, 625. - mediastinal, 625. ■ mesenteric, 625. - meso-colic, 624. - of pancreas, 624. - parotid, 627. ■of pelvis, 621. ■ popliteal, 619. ■ pulmonary, 625. - sacral, 621. of spleen, 624. - of stomach, 624. ■sub-maxillarv, 627. ■ sub-steni:il, 625. • tibial anterior, 619. ■ tracheal, 627. ■ of upper extremity, 628. part of trunk, 6 hearts of lower animals, 61" networks, superficial and deep, 612. plexuses, 612. system, 611. vessels in general. 611. afferent, 614. anastomoses of, 614. branches of, 614. coat of external, 616. — internal, 616. — course and direction, 614. — deep and superficial sets of, 612. — ett'ereut, 614. — origin of, m difl^erent tissues, 612. — preparation of, 617. — structure of, 616. — terminations of, 614. — valves of, 617. — vessels of, 616. — in particular, 618. — of bones, 16. — of brain, 628. — of cellular tissue, 612. — cervical, 628. posterior, 629. — of cranium, 627. — dors:\l, 629. — of dura mater, 627. — epigastric, 622. — of external genitals, male and fe- male, 620. — of face, 627. — gluteal, 620. — of heart, 626. — ilio-lumbar, 622. — intercostal, 626. — of intestines, great, 635. smaU, 625. — of kidneys, 622. — of lining membrane of bloodvessels, 613. — of liver, deep, 623. superficial, 633. of lower extremity, deep and super- ficial, 619. lumbar, lateral, 622. ■ superficial, 620. of lungs, deep and superficial, i 892 INDEX. Lymphatic vessels, mammary, internal, 626. meningeal, 627. of mucous membranes, 612. occipital, 627. of pelvis, 621. pericardiac, 626. perinceal, 620. peroneal, 620. of serous and synovial tissues, 613. of skin, 613. . of spleen, 624. • of stomach, 624. sub-sternal, 626 supra-renal, 622. temporal, 626. of testicles, 622. thorax, 625. thymic, 626. thyroid, 627. — — tibial, anterior and posterior, 620. of upper extremity, 628. ■ part of trunk, 628. Medulla oblongata, foramen caecum of, 703. furrow of median, anterit^, 703. posterior, 704. internal structure of, 705. examined by hardening-, 706. sections, 705. water, 706. uterine 622. neck of, 702. sections of, 705. -^— of long bones, 12. spinalis. See Spinal Cord. Medullary canal of long bones, 13. — membrane, 14. Meibomian glands, 648. Membrana nictitans, 648. pupillaris, 659. Ruyschiana, 657. sacciformis, 143. tympani, 669. secundaria, 670. Lyra, 738. Macula cribrosa, 676i Malar foramina, 54. process, 51, bone, 54. Malleolus, external, 97. internal, 98. Malleus, and ligament of, 673. muscles of, 673. Mamma, 471. adipose tissue of, 473. development of, 474. fibrous tissue of, 473. glandular tissue of, 473. lactiferous ducts of, 473. of the male, 473. vessels and nerves of, 474. Mammary gland. See Mamma. Mammilla. See Nipples. Mammillary enlargements of posterior median columns of spinal cord, 704. — ■ of inferior vermis, 716, 718. tubercles, 426. Manubrium of malleus, 673. of sternum, 65. Marrow of bones, 12. Massa carnea Jacobi Sylvii, 291. Mastoid foramen, 43. portion of temporal bone, 43. process, 43. Maxillary arteries. See Arteries. bone, inferior, 57. • superior, 51. uvea, 659. Membrane, hyaloid, 661. obturator, or sub-pubic, 155. Membranes of cerebro-spinal axis. See Arachnoid, Dura Mater, and Pia Mater. of eye. See Eye. fibro-mucous See Fibro-mucous Mem- branes, fibro-serous. See Fibro-serous Membranes. mucous. See Mucous Membranes. serous. See Serous Membranes. ' synovial. See Synovial Membranes. Membranous labyrinth, 679. part of urethra, 458. Meningeal arteries. See Arteries. Meninges, 681. Meningoses, 113. Meniscus, 113. Mental fossa, 57. foramen, 57. process, 56. Mesentery, 364, 477. left layer, 475. right layer, 475. il/eio-coecum, 471. -colon, iliac, 475. left and right, 475. transverse, 375. layer, inferior, 476. superior, 477. canal, superior, 51. inferior, 58. ■ nerves. See Nerves. See Ear. See Ear. tuberosity, 51. ilfarg-o-dentatus, 660. Meatus of nose, inferior, 54. middle, 41. superior, 41. auditorius externus, 44. . internus, 44. urinarius, fem;ile, 471. male, 461. Mechanism of particular joints. See those joints. Mediastinum, anterior, 414. posterior, 413. Medulla oblongata, 702. comparative anatomy of, 709. . development of, 708. external conformation of, 702. . anterior surface, 703. — lateral surfaces, 704. posterior surface, 704. faisceaux innomines of, 706. at base of brain, 706. '. ■ in isthmus, 715. fasciculi graciles, 708 (note). ^ olivary, 708 (note). re-enforcing, 708. . teretes, 708 (note). — pyramidal, 702, 704, 7 fibres of, antero-posterior, 707. arched, 704. decussation of, 706. — gastrium, 478. — — rectum, 475. Metacarpus, bones of, 84. differential characters, 85. general characters, 85. ■ compared with metatarsus, 109. Metatarsus, bones of, 103. — characters, general, 103. differential, 102. compared with metacarpus, 109. Milk teeth. See Teeth. Modiolus of cochlea, 678. Mons Veneris, 470. Morsus diaboli, and fimbria; of Fallopian tube, 463. Molores oculi nerves. See Nerves. Mouth, component parts of, 422. situation, dimensions, &c., 422. Movements of joints. See Articulations. in general, 148. lips and face, 238. Mucous bursa (so called), 175. membranes, in general. 421. chemical composition, 421. epithelium, 421. of particular organs. Sei organs. structure, 421. Mucro, 65. MuUifidus spina;. See Muscles. Muscles in general, 190. action of, 194. angle of incidence on bones, 195. antagonist, 196. aponeuroses of, 193. arrangement, physiological, of, 291. — ■ — attachments of, 192. fixed, 193. movable, 193. broad, 190. congener"! 107 INDEX. 893 Muscles, direction of, 191. - figure of, 191. insertion of, into other parts, 192. long, 191. momentum of, 195. nerves-of, 763. nomenclature of, 190. number of, 190. order of description of, 197. origin and termination of, 193. preparation of, 197. relations of, to other parts, 191 satellite, 192. sheaths for, 296. short, 191. structure of, 193. — tendons of, l93. . uses of, 194. volume of, 190. in particular, 196-291. of particular organs, parts, or regions. those organs, parts, or regions. abductor brevis pollieis, 260. digiti minimi, 262. pedis, 289. See • indicis, 264. ■ longus pollieis, 258. ■ oculi, 650. • pollieis, 287. - pedis, 277. ■ accelerator urinje, 456. • aocessorious pedis, 280. ad sacro-lumbalem, 277. Juctor brevis feinoris, 276. digiti minimi (opponens), 281. longus femoris, 276. magnus femoris, 276. oculi, 650. pollieis manfls, 288. pedis, 288. - anconeus, 258. • anterior auriculs, 230. • antitragicus, 667. ■ articulo-spinalis, 201. • arytenoideus, 429. — obliquus, 429. transversus, 430. aryteno-epiglottideus, 430. attollens auriculam, 231. oculum, 650. attrahens auriculam, 231. auricularis anterior, 231. posterior, 231. superior, 231. azygos uvuliE, 332. basio-glossus, 338. biceps cruris vel femoris, flexor cubiti, 245. — biventer cervicis, 201. — brachialis anticus, 246. — buccinator, 235. — bulbo-cavernosus, 456. — caninus, 236. — cerato-glossus, 338. — chondro-glossus, 338. — ciliaris, 232. — circumflexus palati, 332. — coccygeus. 381. — complexus, 205. minor, 205. ■ compressor narium, 233. urethrse, 460. in the female, 470. — venEe dorsalis penis, 460. constrictor inferior, 346. medius, 347. superior, 347. vaginas, 469. coraco-brachialis. 246. corrugator supercilii, 232. cremaster, 210, 450. crico-arytenoideus lateralis, 428. posticus, 428. oEsophageus, 352. thyroideus, 421. crotaphyte, 240. crureus, 2T3. cutanei, 294. — deltoideus, 241. — depresssor alue nasi, 234. Muscles, Ae'pressor anguli oris, 237. labii inferioris, 237. superioris alaeque nasi, 234. oculi, 650. urethrae (Santorini), 460, ■ in the female, 470. diaphragma, 212. digastricus, 228. elevatores urethrs (Santorini), 460. erector clitoridis, 471. — ■ penis, 450. spiniE, 202. extensor brevis disitorum pedis, 286. -- pollieis, 259. carpi radialis brevior, 255. longior, 255. ulnaris, 258. — communis digitorum, 256, -- digiti minimi, 257. — indicis, 259. — longus digitorum pedis, 278. • pollieis, 259. — ossis metacarpi pollieis, 258. — primi internodii poUic-is, 258. — proprius auricularis, 256. indicis, 259. ■ pollieis pedis, 279, secundi internodii pollieis, 258. flexor accessorius, 290. brevis digiti minimi, 262. — minimi pedis, 289. digitorum pedis, 289 pollieis, 262. ■ pedis, 287. carpi radialis, 250. ulnaris, 250. longus digitorum pedis, 235. — ■ pollieis, 253. pedis, 285. perforans, 251. pedis, 285. perforatus, 252. • pedis, 290. profundus digitorum, 252. sublimis digitorum 251. ~ frontalis, 230. — gastrocnemius, 281. — gemellus inferior, 267. " superior, 267. — genio-hyoglossus, 338. hyoideus, 229. glosso-staphyliiius, 332. glutiEus maxinius, 264. medius, 265. minimus, 266. gracilis, 2iD. helicis major, 667. minor, 667. Homer's, 653. Houston's, 457. hyo-glossus, 338. iliacus, 215. indicator, 260. infra-costales, 222. spinatus, 243. inter-costales externi, 222. interiii,222. - ossei mands, 262. dorsales, 264. palmares, 264. pedis dorsales, 290. plantares, 290. • spinales colli, 286. ■ transversales colli, 217. lumborum, 218. ischio-bulbosus, 457. in the female, 470. cavernosus, 456. ■ in the female, 471. coccygeus, 380. — latissimus dorsi, 198. — laxator tympani, 675. — levator anguli oris, 236. scapuliE, 201 380. am, laliii inferioris, 237. superioris, 936. alajque nasi, 233. menti, 237. oculi, 649. INDEX. Muscles, levator palati, 332. „„„ . palpebrie supenons, 233, t , prostatEB, 382. . uTulte, 337. ..^__ levatores rostarum breviores, 222. - longiores, 222. Muscles, rectus oculi superior, 649. retraheris auriculam, 230. rhomboideus major, 200. minor, 200. . 1U115.WIX.0, — — lingualis (Albiniis aiid Douglas), 337. inferior, 337. superficialis, 337. lonffissimus dorsi in the loins, 202. . ! neck, 203. • thorax, 203. longus colli, 218. lumbricales nian6s, 253. ■ pedis, 290. accessory fibres to, 203, 204. mallei externus magnus, 673. parvus, 673. intemus, 674. -masseter, 239. -multifidus spinie in the loins, 202, (note). - — back, 203. — neck, 204. -mylo-hyoideus, 229. - rayrtiformis, 234. -nasn-labialis, 234. -obliquus abdominis externus, 208. • internus, 209. capitis inferior, 206. superior, 206. oculi inferior, 651. superior, 651. -risorius Santorini, 284. -sacro-lumbalis, in the loins, 203. in the thorax, 204. on the chest, 204. -salpingo-pharyngeus, 338. — sartorius, 272. — scalenus anticus, 217. posticus, 218. - scalptor ani, 275. scapulo-hyoideuE, 226. semi-spinalis colH, 204 (note), dorsi, 204 (note). ■ membranosus, 270. • tendinosus, 270. -serratus anticus, 223. - parvus, 223. magnus, 221. —posticus inferior, 201. superior, 201. - soleus, 282. - spheno-pharyngeus, 338. - sphincter ani externus, 380. • internus, 380. • (Esophagi, 350. ■ vaginse, 470. — vesicee, 442. - obturator externus, 268. . intemus, 267. occipitalis, 230. . occipito-frontalis, 230. - pharyngeus, 338. omo-hyoideus, 226. opponens digiti minimi, 262. pollicis, 260. - orbicularis oris, 235. palpebrarum, 231. - palato-glossus, 332. ■ pharyngeus, 332. staphylinus, 332. palmaris brevis, 261. longus, 250. — palpebralis, 231. — patheticus, 651. pectineus, 275. — pectoralis major, 220. minor, 221. perforatus Casserii, 253. peri-staphylinus externus, 332. internus, 332. peroneus brevis, 230. longus, 280. tertius, vel anticus, 279. petro-pharyngeus, 348. pharyngo-staphylinus, 332. plantaris, 282. platysma myoides, 224. popliteus, 283. pronator quadratus, 253. radii teres, 249. rotundus, 249. psoas-iliacus, 214. magnus, 215. parvus, 216. . pterygoideus externus, 241 - internus, 240. -spinales posteriores, 201. action of, 203. general view of, 203. in the loins, 201. . neck, 204. - spinalis dorsi, 204. cervicis, 204. - splenius capitis, 202. -colli. 202. — thorax, 204. - stapedius, 671. - sterno-cleido-mastoideus, 224. hyoideus, 226. thyruideus, 227. -stylo-glossus, 337. hyoideus, 229. alter, 230. ■ pharyngeus, 346. — sub-clavius, 221. - scapularis, 244. -super-ciliaris, 232. -supinator radii brei-is, 256. ■ longus, 254. - supra-costales, 221. — spinatus, 243. suralis, 281. temporalis, 239. tensor palati, 332. tarsi, or Homer's, 653. tympani, 671. vagina; femoris, 271. pterygo-pharyngeus, 347. pubio-urethralis, 457. pyramidalis abdominis, 212. nasi, 233. pyriformis, 266. quadratus femoris, 268. . lumborum, 216. ■ menti, 237 -rectus abdominis, 210. capitis anticus major, 218. ■ minor, 218- - lateralis, 217. - posticus major, 206. minor, 206. - femoris, 270. • intemus, 272. -tensors of fascise, 296. -teres major, 198. — minor, 243. - thyro-arytenoideus, 428. epiglottidens. 428. hyoideus, 227. - tibialis anticus, 278. - posticus, 284. - trachelo-mastoideus, 204. - tragicus, 667. - transversalis abdominis, 210. cervicis, 205. -colli, 204. nasi, 234. transverso-spinalis, 202. in the loins, 202. _ in the neck, 204. in the thorax, 204. transversus auriculse, 667. nasi, 234. pedis, 290. ■ perinaei, 381. — alter, 457. pollicis pedis, 290. • oculi externus, 650. internus, 650. inferior, 650. -trapezius, U -triangularis nasi, 234. oris, 237. ■ sterni, 223. -triceps adductor femoris, 274. INDEX. 895 Muscles, triceps extensor cruris, 272. cubiti, 247. ■feiuoralis, 272. femoris (auctor), 872. ■ suralis, 281. ■ trochlenris, 651. ■ of the ureters, 445. vastus extcrnus, 273. iiiternus, 273. - Wilson's, 457. - which move the arm upon the shoulder, 292. fingers, 293. foot upon the leg, 293. forearm upon the arm, 293. hand upon the forearm, 293. ■ leg- upon the thigh, 292. lower jaw, 292. — OS hyoides, 292. pelvis, 392. — radius upon the ulna, 293. ribs, 292. shoulder. 292. skin, 293. thigh upon the pelvis, 292. toes, 293. vertebro-cranial column, 292, walls of thorax and abdomen. 292. Nerves, sensory, romnion, 759, 762. — ' special, 762. spinal, 750. structure of, 766. ^ — symmetrical, 760. sympathetic, 762, 764. structure of, 767. termination of, 764. in particular, 769. abdominal, great, 798. small, 799. abducens oculi. See Mo/ or Oculi, external. accessory, of internal cutaneous, 7S5. saphenous, 601. obturator, SOI (note). spinal, distribution of, 849. function of, 851. ganglion of, 624. origin of, 823. vertebral course, 824. • zygomaticus major, 236. -minor, 236. Muscular fibres, filaments, and fasciculi, 198 (note). fibres of particular organs. See those organs. sheaths, 296. tissue, involuntary, 198. • structure, 322. — voluntary, 198. — — — chemical composition, 199. structure, 198. acromial, ' alveolo-dental, anterior, 834. posterior, 834. anal cutaneous, 806. aortic, sympathetic, 863. articular of ankle, 812. of elbow, 785, 786. hip-joint, 800. of knee, anterior, 602. external, 808. internal, 812. from obturator, 801. recurrent, 609. posterior, or azygos, 812. of wrist, 765. Musculi pectinati, 486. papillares, 464. 3/«scu/o-cutaneou3 nerves. See Nerves. Myology, 190. Nails, 636. lunule of, 636. — m.atrix, 636. structure and growth of, 637. Nares, anterior, 60. posterior, 60. Nasal arteries. See Arteries. bone. 55. • — cartilages. See Nose. duct and canal, 653. . eminence, 35. — fossae, 62. meatuses, 41. nerves. See Nerves. process, 51. spine, anterior and posterior, 52, 54. Nates (of brain), 712. Navicular fossie. See Fossa. Nechs of bones, 10. particular. See those bones. Nerves in general, 759. anastomoses of, 762. i of animal life, 761, central extremity of, 760. classification of, 759, course of, 762. cranial, 759. different kinds of, 761. direction of, 763. division of into sets, 769. fibres and filaments of, 767. ganglia of, 765. • connexions of, 765. different kinds of, 765. structure ol", 768. ganglionic, 764. mode of division of, 764. ■ motor, 759. neurilemma of, 766. of organic life, 761. origin of, apparent and real, 758. — — plexuses of, 762. See Plexuses preparation of, 769. ■ relations of, 763. respiratory, 760, 762. roots of, anterior or mctor, 762. ■ posl;_'r!i;r or sciisji-y, 7l!2. auditor)'. See Portio Mollis. auricular, anterior, 836. great, 778. of pneumogastric, 845. posterior, 840. auriculo-occipital, 840. temporal, 636. axillary, or circtimflex. 783. azygos, of knee-joint, 813. buccal, 635. of facial, 641. bucco-labial, 835. bulbo-urethral, 806. calcaneal, external, 612. internal, 813. cardiac, great, 861. inferior, left, 861. right, 861. — ■ lesser, 861. middle, left. 862. - right, 861. of pneumogastric, in neck, 847. in thorax, 837. of recurrent laryngeal, 837 — siiperfici.ll, 861. — superior, left, 861. — Tight, 800. of sympathetic, 860. carotid branch of vidian, 833. of sympathetic, 765. cerebral. See Cranial. cervical, bninches of, anterior, 776, 781. posterior, 773. number of, 771. roots of, 771. cervical, first, anterior branch of, 776. posterior branch of, 773. second, anterior branch, 776. -poMtcrior branch, 774. — third, anterior branch, posterior br.uu'h, 7T4. — fourth, anterior branch, 777. posterior brancli. 774. — fifth to eighth, anterior branches, 781. posterior branches, 774, -of facial. 841. — internal descending, 780. — superficial, 778. cervieo-facial, 639. 841. chorda tyni|iaui, 836. canal for, 672. ciliarv, 659, 830. nasal, 830. ophihaliriic, I INDEX. Nerves, clavicular, 78_3. of clituris, 607. • for cochlea, 842. collateral dorsal of fingers, 790. . of thumb, 792. of toes, 811. palmar of fingers, 788, 790. ■ thumb, 783. coniniunioatiiig fibular, 811. tibial, 811. - for complexus, 773 - for coxo-femoral articulation, 800 (note). ~ cranial, in general, 816. central, extremities of, 817. classification of, 816. — distribution of, 832. general view of, 853. • nomenclature of, 817. - cranial, in particular, 832. first. See Olfactory. second. See Optic. third. See Motor Oculi, common. fourth. See Pathetic. . — ■ fifth. See Trifacial. sixth. See Motor Oculi, external seventh. See Portio Dura and Portio Mollis eighth. See Pneumogastric, Glosso- pharyngeal, and Spinal Accessory. ninth. See Hypo-glossal. - crural, 801. - for crureus, 802. - cutaneous, accessory of saphenous, 801. . anal, 806. external, of arm, 785. . of musculo-spiral, 791. of thi?h, 799. Nerves, frontal, external, 829. — internal, 829. — osseous, 829. fronto-nasal, 829 (note). for gastrocnemius, 812. for gernelli, 808. genito-crural, 799. glosso-pharyngeal, distribution of. 843. function of, 845. ganglion of, 844. origin and cranial course, 823. — gluteal, inferior, 807. - superior, 807. — gustatory, 836. — hemorrhoidal, inferior, 806. — to hip-joint, 800 'note). — hypo-glossal, distribution, 851. • function, 853. ganglion, 823. origin and cranial course, 824 ■ ilio inguinal, 798. scrotal, 798. — small, 79 — incisor, 837. — infra-hyoid, of hypo-glossal, 852. orbital, 831,841. ■ of facial, 841. trochlear, 830. ■ inguinal, external, 797. - internal, 797. ■ of intercostal, 794. • internal, of arm, 784. accessory of, 78S. of musculo-spiral, 791. of thigh, 801. J ■ of Wrisberg, 785. — lonft, of obturator, 801 (note), --middle, of thigh, 801. — of musculo-culaneous of arm, 785. — palmar, 787. — perforating, of intercostal, 794. - of thigh, 802. - inguino-cutaneous, 797. - intercostal, 794. muscular, 794. perforating, 794. ■ summary of, 796. — costo-hurneral, 795. — osseous, anterior, of forearm, 795. • ischiadic, 802 lesser, 802 -of leg, 811. posterior, of forearm, 790. — of Jacobson, 838. — lachrymal, 828. — of orbital, 831. lachrymo-palpebral, 828. laryngeal, anastomotic, 847 ixternal, 846 — plantar, 613. — radial, 792. — of shoulder, 784. — of Soemmering, 807. ~ tibial. 803. • ulnar, dorsal, 769. deep palmar, 789 plantar, 814. temporal, 835. dental, anterior, 834. inferior, 837. posterior, 833. descendens noni, 853 descending cervical. internal, 777. — diaphragmatic, 780. — digastric, 840. — digital, of median, 788 of radial, 792. of ulnar, 789. — dorsal, branches of, anterior, 794. posterior, 775. number of, 771. roots of, 772. collateral of fingers, 790, 792. toes, 811. of foot, deep external, 811. — . internal, 811. of hand, external, 792. internal, 790. intercostal. Sec Intercostal. — of penis, 806. ■ dorsi-lumbar, 796. - to dura mater, 835. ■ encephalic. See Cranial. ■ ethmoidal, 830. - facial. See Portio Dura. branches, collateral, 839. summary of, 842. - to femoral artery, 802. frontal, 828. inferior, or recurrent, 847. superior, 646. of sympathetic, 859. ■ to latissimus dorsi, 784. - levator anguli .scapulie, 782. ani, 805. - lingual, 836. — of glosso-pharyngeal, 844. - longitudinal, of Lancisi, 737. - lumbar, branches of, anterior, 796. posterior, 776. — number of, 772. — roots of, 772. ■ lumbo-sacral, 797. -malar, 831. of facial, 840 - masseteric, 835. - mastoid, great, 779. - small, 780. - maxillary, inferior, 834. superior, 831. terminal brandies of, 834. - median, 786. in arm, 7S6. in forearm, 787 • in hand, 787. - mental, 83. . of facial, 841. motor oculi, common, distribution of, 825. function of, 826. — origin and cranial course, 820. external, distribution, 838. origin and cranial course, 822. • musculo-cutaneous, brachial, 766. crural, 801. dorsal, 775. of leg, 810. . lumbar, inferior, 798. middle, 798. superior, 798. INDEX. 897 Nerves, musculo-spiral. 766, 791. myloid, 837. nasal, 829. external, 829. internal, 830. — posterior, 832. ■ superior, 833. — of nasal fossa, external, 830. — naso-lobar, 830. palatine, 832. — obturator, 799. accessory of, 800 (note). — articular of, to hip, 800. — knee, 801 (note). long- cutaneous, 801 (note). ■ to obturator internus, 805. ■ occipital, external, 779. great, 777. small, 780. • oculo-muscular. See Motor Oculi and Pathetic. ■ oesophageal, 847. • olfactory, bulb of, 817. distribution of, 824. function of, 825. origin and cranial course, 818. structure of, 818. ■ ophthalmic, 827. • optic, chiasma or commissure of, 819. distribution of, 825. function, 825. origin and cranial course, 819. roots of, gray, 608. structure, 820. terminations of, 671. — - tracts of, 819. •orbital, 831. ■ of facial, 840. ■ palatine, anterior, 832. middle, 832. — posterior, 832. palmar collateral, 769, 790. cutaneous, 768. palpebral, inferior, 840. superior, 840. of particular organs, parts, or tissues. those organs, &c. par vagum. See Pneumogastric, pathetic, distribution, 826. function, 826. origin and cranial course, 820. to pectineus, 801 (note), 802 (note). pectoralis major, 783. minor, 783. perforans Casserii, 786. perforating, of hand, 790. cutaneous, of inter-costals, thigh, 802. ■ perineal, 806. superficial, anterior, 806. posterior, 806. ■ peroneal, 808. cutaneous, 810. external, 810. saphenous, 810. petrosal, superficial, great, 833. small, 838. pharyngeal, of glosso-pharyngeal, 844. pneumogastric, 846. small, 846, 850. -1 of spheno-palatiue, 833 (note). sympathetic, 859. • phrenic, 780. • plantar, collateral, 813, 814. external, 814. • deep, 814. — internal, 813. ■ for plantaris longus, 812. ■ pneumogastric, in abdomen, 848. anastomoses of, 845. cranial course, 823. fibrous layers of, 719. in foramen lacerum, 845. functions of, 849. ganglion of, 845. in neck, 845. origin of, 823. summary of, 849. in thorax, 847. popliteal, external, 808. internal, 812. Nerves, popliteal, sciatic, external, 808. internal, 811. portio dura, distribution, 839. function, 843. origin and cranial course, 822. mollis, distril)Ution, 681, 842. function, 842. origin and cranial course, 822. structure, 768. pterygoid, 833. internal, 836. pudendal, long, 808. pudic, internal, 806. in female, 807, - pulmonary, anterior and posterior, 848. - to pyriformis, 807. - for quadratus femoris, 808. - radial, or musculo-spiral, 790. proper, 791. to rectus femoris, 802. - recurrent, of knee, 810. laryngeal, 848. lesser sciatic, 808. • renal, 865. ■ respiratory, external, 782. of eye, 821. superior, of trunk, 850. ■ to rhomboideus, 782. ■ sacral, branches of, anterior, 804. posterior, 777. — number of, 772. roots of, 772. ■ saphenous, external, 812. internal, 803. accessory, of, 802. peroneal, 810. satellite, of femoral artery, 802. ■ ulnar artery, 790. ■ sciatic, great, lesser, 801. ■ of septum nasi, anterior, 830. posterior, 832. ■ to serratus, 782. • of sheath of femoral vessels, 805 • soft (nervi molles), 845. ■ spheno-palatine, external, 833. internal, 832. spinal, 770. accessory of Willis. See Accessory. branches of, in general, 771. anterior, 771. ganglionic, 771. posterior, 773. classification of, 770. — numl)er of, 770. — origin of, apparent, real, 772. 70. plexuses of, ' roots of, anterior, or non-ganglionic, 771. roots of, posterior, or ganglionic, 771. splanchnic, great, 865. lesser, 865. lumbar, 869. 780. ■ splenic, 867. ■ to splenius, 843. ■ sternal cutaneous, ' ■ styloid, 840. ■ to sub-clavius, 782. ■ sub-occipital, anterior branch, 778. posterior, 776. scapular, inferior, 784. — superior, 783. of sub-septum, 841. superficial cardiac, 862. cervical, 776. petrosal, great, 833. lesser, 837. — temporal, 835. supra-clavicular, 779. orbital, 828. scapular, 782. • trochlear, 829. to supra and infra-spinati, 782. sympathetic, in general, 761. characters of, 871. structure of, 766. in particular, 854, ■ abdominal, 851. 5X — cervical, 855. -- lumbar, 848. / 898 INDEX. Nerves, sympathetic, sacral, 8" I. thoracic, 868 temporal, deep, 835. of facial, 839. — superficial, 836. • temporo-facial, 839. malar, 831. - to tensor tympani, 837. ■-- vaginae fenioris, 807. tentorium cerebelli, 827. teres major, 874. minor, 783. thoracic, 783. anterior, 783. — posterior,782. ■tibial, 811. anterior, 811. cutaneous, 802. posterior, 811- saphenous, 812. ' to trapezius, 781. ■ trifacial, distribution of. 827. divisiims of, 827. ganglion of, 821. origin and cranial course, 821. root of, large, 821. small, 821. • trigeminal. See Trifacial. ■ trochlear. See Pathetic. • tympanic, of Jacobson, 838. ■ ulnar, 789. in the arm and forearm, 789. hand, 790. • for ulnar artery, 790. - uterine, 870. ■ vagina), 870. - for vasti fernoris, 802. - vertebral (sympathetic), 860. - vesical, 870. ■ vestibular, 843. ■ vidian, 833. ■ visceral, abdominal, 866. ceiTical, 845. pelvic, 869 ■ sacral, 805 Nervi molles, 845. Nervous system, central portion, 681. peripheral portion, 759. Nervus impar, 698. Neurilemma of nerves, 766. spinal cord, 697. Neurology, 629. Ninth nerve. See Nerve, hypoglossal. Nipples, 472. glands and papillae of, 473. Noduli Arantii, 479. Nodulus of cerebellum, 716 (note). Nodus encephali (Scemmering), 844. NcEud de I'encephale, 844. Nose, general description, 641. bones of, 53, 641. cartilages of, 641. mucous membrane of, 642. muscles of, 643. septum of, 56, 642. skin of, 643. Nostrils, 641. • cartilages of, 641. Notch, inler-condyloid, 91. ischiatic, 89. . sacro-sciatic, 89. ■ great, 155. small, 155. sciatic, 89. ■ sigmoid, 57. Notches, vertebral, 20, 21. Nutritious arteries. See Arteries. foramina of bones. See Foramen, NymphiB, 471. Oblique muscles. See Muscles. ■Obturator foramen and groove, 88, nerve. See Nerves. Occipital angle of Daubenton, 45. bone, 33. — — ^ condyles, 33. crests, 34. foramen, 34. fossae, 34. nerves. See Nerves. Occipital protuberances, 34. veins. See Veins. Occipito-atiantoid articulations, 118. ligaments, 118. - axoid articulations, 119. ligaments, 120. Ocu?o-muscular nerves. See Nerves, Motor OciUi and Pathetic. Odontoid process, 26. Odontogeny, 184. Odontology, 177. (Esophagus, 350. glands of, 352. mucous membrane, 352. muscular coat, 351. structure of, 351. uses, 352. vessels and nerves, 352. — parietal suture, 46. Olecranoid cavity, 80. Olecranon process, 80. Olfactory nerve. See Nerve. lobes, 758. Olivary process, 37. bodies, 703. corpus dentatum of, 704. sections of, 704. structure of, 705. fasciculi, 705. Omentum, colic, 478 (note), gastro-colic, 478. hepatic, 476. splenic, 403. ■ great, 476. layers of, anterior, 476. posterior, 476. ■ eac of. 477. vessels and nerves of, 478. lesser, 476. layer of, anterior, 476. ■ posterior, 476. Operculum laryngis, 426. Ophthalmic nerve, 828. Optic thalami, 727, 745. fibres of, 746. -tracts, 820. Orbicular ligaments of joints. See Ldgaments. Orbital arch, 36. cavities, 6 fissure, 53. foramina, internal, 36. process of palate bone, 55. processes of frontal bone, 36. plate, 36. Orbits, 62. Organ of hearing, 665. See Ear. sight, 645. See Eye. smell, 641. See Nose, ani. Pituitary Membrane. taste, 639. See Tongue. touch, 629. See Skin. the voice, 422. See Larynx. Organs, anatomical elements of, 320. colour and consistence of, 321. — development of, 321. — of digestion, 322. — direction and relations of, 321. — dissection of, 322. — functions of, 322. — of generation, female, 461. • male, 446. genito-urinary, 435. nomenclature, 320. number, 320. ■ of respiration, 409. ■ of the senses, 629. ■ situation, 320. • size and figure, 321. structure of, 321. urinary, 435. Os, bone. See Bone, os. tincfe, 465. uteri, 465. Ossa pisiformia, or lingualia, 111. triquetra, or Wormiana, 50. Ossicula auditus, 669. movements of, 675. muscles belonging to, 674. Ossification of bones. See those bones. Osteology, 5. Osteogeny, 16. INDEX. Ostia of Fallopian tube, 463. Ostium internum of uterus, 465. Otoconia and otolithes, H43. Ova of Nabolh, 4()6. Ovarian vesicles, 463. Ovaries, 461. ligaments of, 461. structure, 462. Ovum, 462. Palate, bone, 53. hard, 330. development, 330. ■ structure, 330. uses, 330. ■ soft, 330. ————— aponeurosis of, 331. - development of, 333. — glands of, 333. — mucous membrane of, 333. — muscles of, 331. — pillars of, 331. —- structure of, 331 — uses of, 331. — vessels, &c., of, 333. Palatine aponeurosis, 331. arch, 329. ■ canals, 52, 54. ■ accessory, 52, 54. ■ glands, 330. ■ process, 52. Palm of hand, 83. Palmar arteries. See Arteries. ligaments. See Ligaments. • nerves. See Nerves. Pancreas, 400. development of, 402. • duct of, 402. ■ function of, 402. lesser, 402. • structure of, 401. vessels and nerves of, 402. Panniculus adiposus, 629. carnosus, 629. Papillm, conjunctival, 648. • dental, 181. (Goodsir), 183. • of kidney. 437. • lachrymal, 646. of skin, 630. of small intestine, 367. • of stomach, 361. • of tongue, 333. Par vagum. See Nerve, pneumogastric Parietal bone, 41. foramen, 41. • fossa, 41. • protuberance, 41. Parotid duct, 341. gland, 340. development of, 340 (note). structure of, 340. Pars niastoidea of temporal bone, 43. petrosa of temporal bone, 43. squamosa of temporal bone, 43. Patella, 95. ligament of, 97. Pathetic nerve. See Nerves, Patte d'oie, 270, 271. Peduncles of cerebellum and cerebrum. See those or- gans. Pelvis, aponeuroses of, 306. ■ articulations of, 154. ■ axes of, 90. • circumferences of, 92. • compared with shoulder, 105. ■ development of, general, 93. in general, 90. • great or false, 90. of the kidney, 439. — structure of, 439. little or true, 90. brim of, 92. ' strait, superior, 92. inferior, 92. mechanism of, 158-159. recrions of, 90. varieties of, sexual, 90. ■ excavation or cavity of, 122. ■ outlet of, 92. Penis, 454. corpus cavernosum of, 455. glans of, 461. ligament, suspensory or triangular, 454 muscles of, 457. Perforated spot, anterior, 734. posterior, 730. Perforating arteries. See Arteries. nerves. See Nerves. Peri-cardium, 494. structure, 494. vessels, 495. ■ glottis, 640. lymph, 679. osteuin, 296. alveolo-dental, S38. Peritoneum, 474. folds of, 478. general description of, 478. portion of, parietal, 478. sub-umbilical, 474. supra-umbilical, 475, visceral, 477. structure of. 479. Permanent teeth. See Teeth. Perone, 98. Peroneal arteries. See Arteries. See Nerves. Pes accessorius, 746. hippocampi, 745. Petrosal nerves. See Nerves. Petrous portion of temporal bone, 43. process, 43. Pharyngeal nerves. See Nerves. Pharynx, 344. aponeuroses of, 346. development of, 349. mucous membrane of, 349. muscles of, 346. extrinsic, 346. ' • intrinsic, 346. supernumerary, 346. uses, 349. vessels and nerves, 349. Pia mater, 692. • cerebral, 692. spinal, or rachidian, 697. Pigmentum of skin, 632 (note). eye, 659. Pillar of valve of Vieussens, 712. Pillars of diaphragm, 212. fauces, or palate, 331. fornix, 740. Pineal gland or body, 742. - commissure and peduncles of, 743. - concretions, 743. function of, 744. Pisiform bone, 83. Piluila, 749. Pituitary body or gland, 729. fossa, 37. membrane, 643. follicles of, 645. nei ,'es of, 645. • structure, 644. ■ vessels of, 645. Plantar ligaments. See Ligaments. nerves. See Nerves. Plaques gaufr6es, 366. Plate, cribrifor.m, of ethmoid bone, 40. horizontal, of palate bone, 53. orbital, 35. perpendicular, of ethmoid bone, 41. Pleura, costal, diaphragmatic, mediastinal, and pulmo- nary, 413. structure and uses of, 413. Pleura:, 413. Plexuses of lymphatics, 614. of nerve, 762, et infra. auricular, 858. brachial, 781. - general vievi^ of nerves of, 792. bronchial, 848. cardiac, deep, 860. great, 863. ■ superficial, 862. ■ carotid, 856. ■ cavernous, 856. ■ cervical, 777. deep, 777. 900 plexuses, cervical, posterior, 774. -superficial, 777. INDEX. cervico-brachial, 776. coeliac, 866. . coronary, of heart, anterior and posterior, ood, of stomach, 866. . diaphragmatic, 866. . epigastric, 866. ■ facial (sympathetic), 858. - eastro-epiploic, left, 868. - right, 867. - hemorrhoidal, inferior, superior, — hepatic, 867 — hypogastric, 870. — infra-orbital, 841. — laryngeal, 846. — lingual, 858. — lymphatic, 612. — lumbar, 797. — lumbo-aortic, 868, 869. sacral, 776. • mental, 837. • mesenteric, inferior, 868. superior, 867. — nervous, 762. — occipital, 859. — ovarian, 868. — pharyngeal, 846, 859. — phrenic, 866. — pulmonary, anterior and posterior, 848. — renal, 868. — sacral, 805. solar, 866. — spermatic, 868. — splenic, 867. — supra-renal, 866. — thyroid, 858. — tympanic, 843. — uterine, 870. • vertebral, 860, vesical, 870, visceral of abdomen, 866. - pelvis, 805, 869. of veins, 575, et infra. alveolar, 589. choroid, of brain, 747. fourth ventricle, 720. third ventricle, 741. reflected portion of, 746. — . hemorrhoidal, 601 — intra-spinal, 609. — lingual, 590. — masseteric, 590. — pampiniform, 598. — phai'yngeal, 591. — pterygoid, 590. spermatic, 598. — - spinal, deep, 609. longitudinal, 609. - transverse, 609. - tonsillar, 333. - uterine, 602. - vaginal, 602. - vesico-prostatic, 601. - urethral, 602. Plica semilunaris, 648. Pneumo-gastric nerve. See Nerve, Pomum Adami, 424. PoTis Varolii, or cerebelli, 710. internal structure of, 713 . Porta, 388. Portio dura nerve. See Nerve. mollis nerve. See Nerve. Prepuce, 454. of clitoris, 471. froenum of, 454. Process, acromion, 76. auditory, 44. basilar, 34. cochleariforra, 44, 672. coracoid, 76. coronoid, of lower jaw, 58. of ulna, 80. ensiform, 65. of fifth metatarsal bone, 104. genial, 58. gracilis of Raw, 673. hamular, of sphenoid bone, 37. ■I of cochlea, 678. Process, of helix, 667. - malar, 51. - mastoid, 43. - mental, 58. - nasal, 51. - odontoid, 26. - olecranon, 80. ■- olivary, 37. - orbital, external, 36. internal, 36. of palate bone, 54 - palatine, 52. - petrous, 43. - pyramidal, 54. - scaphoid, 101. - styloid, of temporal bone, 43 ulna, 80. radius, 81. fibula, 99. vaginal, of temporal bone, 44. vermiform, inferior, 716. superior, 716, zygomatic, of temporal bone, 42, of malar bone, 55. Processes of bones, 9. ciliary, of choroid coat, 656. vitreous humour, 661. - calcaneal, 101. . cUnoid, 37. • pterygoid, 37. ■ spinous, of ilium, spinous, of vertebrae, 21. Processus a cerebello ad meduUam, 704. pontem, 721. testes, 711. a cerebro ad raeduUam, 710. arciformes, 703. gracilis of Raw, 673. Profunda artery. See Arteries. - vein. See Veins. Promontory of sacrum, 26, tympanum, 671. Pronator muscles. See Muscles. Protuberances, occipital, 34. parietal, 42. Psalterium, 738 Pterygoid canal, 37. columns, 126. fossa, 37. processes, 37. P/ery^o-maxillary fissure, 52. - palatine canal, 38, 52. Pubes, 90. Pubic arch, 89. Pudic arteries. See Arteries. Pulmonary arteries. See Arteries. veins. See Veins. Puncta lachrymalia, 647. Pupil of eye, 657. Pupillary membrane, 659. Pyloric valve, 355. Pylorus, 354. antrum of, 354. Pyramid of cerebellum, or of Malacarne, 717. of tympanum, and its canal, 671. Pyramids, anterior, 703. decussation of, 706. sections of, 706. - of kidney, 437. - posterior, 704. sections of, 706. Quadrati muscles. See Muscles. Rachis. See Vertebral Column. Rachidian bulb, proper. See Medulla Oblongata, bulbs, 697. veins. See Veins, spirtdl. Radial nerve. See Nerve. Radiating crown of Reil, 744. Radius, 81. and tibia, lower parts of, compared, 107, Rami of lower jaw, 57. Ramus of pubes, 90. ischium, 91. Receptaculi arteris, 525. Receplaculum chyli, 618. ganglii petrosi, 843. Recess of tympanum, 672. Recessus sulciforrais, 676. INDEX. 901 Recti miiscles. See Muscles. Rectum, 376. columnse of, 377. curves of, 377. internal surface, 378. muscular coat of, 377. structure of, 377. Recurrent arteries. See Arteries. nerves. See Nerves. Renes. See Kidneys. succenturiati. See Supra-renal Capsules. Respiratory apparatus, 409. nerves, in particiilar. See Nerves. Restiform bodies, 704. Rete of Malpighi, 640. —— mucosum, 640. of tongue, 646. vasculosum testis, 451. Retia mirabilia, 496. Retina, 660. artery of, 660. folds of, 660. foramen centrale, and limbtis luteus of, 660. margo dentatus, 660. structure of, 660 (note). termination of, 660 (note). Ribs, angles of, 68. characters of, general, 67. special, 68. false, 67. movements of, 134. supernumerary, 32. true, 67. torsion of, 67. tubercle of, 68. Rima glottidis, 434. palpebrarum, 646. Ring, crural, 310. inguinal, 310. umbilical, 308. Rostrum of cochlea, 678. of corpus callosum, 737. Rotula, 95. Rugce, vaginal, 468. Sac, lachrymal, 652. Sacculus vestibuli, 680. or sinus laryngis, 434. Sacral arteries. See Arteries- canal, 27. foramina, 27. nerves. See Nerves. vertebrce. See Vertebra and Vertebrte. Sacro-coccygeal vertebra, 26. sciatic notch, 92. vertebral angle, or promontory, 26. Sacrum, 26. promontory of, 26. small cornua of, 27. Saliva, 396. Salivary glands, 340. Saphenous nerves. See Nerves. Satellite arteries. See Arteries. nerves. See Nerves. Scaphoid hone of csirpus, 83. . of tarsus, 101. process, 101. Scapula, 75. Scapular arteries. See Arteries. Schindylesis, 114. Sciatic notch, 89. spine, 89. Scrobiculis cordis, 354, 482. Scrotum, Ail. Second cranial nerve. See Nerve, optic. Sella turcica, 37. Semen, 453. Semi-circular canals, and their ampullae, 677. membranous, 680. Sc;)i«m, inter-ventricular (of brain), 518. - (of heart), 481. ■ lucidum, 738. layers of, 738. ■ ventricle of, 738. nasal, artery of, 518. cartilaginous, 642. • osseous, 56, 62. - pectiniforme, 454. Serrati muscles. See Muscles. Sesamoid bones, 96. of hand, 153. of foot, 177. of gastrocnemius, 164. Seventh cranial nerve. See Nerve, Portia Dura, and Portio Mollis. Sheath of brachial vessels, 316. femoral vessels, 310. for muscles, 296. — of arm, 316. thigh, 311. ■ synovial, 178. ■ for tendons, 397. around carpus, 319. tarsus, 314. Shoulder, aponeuroses of, 315. bones of, 73. compared with pelvis, 105. development of, general, 77. in general, 77. Sigmoid cavities, great and small, 80. flexure, 371. notch, 57. valves, 484. • for vessels, 396. ■ structure of, 397. Sinus, or sinuses, aortic, 498. — basilar, 587. — of bones, 11. — of bulb of urethra, 459. — cavernous, 587. — circular, of Ridley, 588. — common, of vestibule, 680. — confluences of, 588. ' — coronary, of heart. 577. - of Ridley, 587. — of dura mater, 583. — ethmoidal, 43. — frontal, 36. — of internal jugular, 583L lateral, or transverse, 584. — of larynx, or sinus of Morgagni, 584> — longitudinal, inferior, 586. superior, 584. - lines of occipital bone, 33. OS coxae, lunar bone, 83. ganglion, of fifth nerve, 843. Seminiferous tubes, 454 Septa, inter-muscular, 294. of arm, 315. of thigh, 306. Septum crurale, 303. of dartos, 446. inter-auncular, 482. — maxillary, 52. — of Morgagni, 461. — occipital, anterior, 587. posterior, 587. ■ ophthalmic, 587. petrosal, inferior, 586. superior, 586. prostatic, 459. sphenoidal, 40. straight, 585. transverse, or lateral, 584. of urethra, 459. uterine, 602. of Valsalva, 498. of veins, 575. of vena portte, 599. venosus (heart), 492. Sixth cranial nerve. See Nerve. Skeleton, general view of, 5. natural, 5. artificial, 5. Skin, 629. appendages of, 635. characters, external, 629. Spine, cutis or dermis of, 630. epidermis of, 632 (note). follicles, sebaceous, 627. functions of, 627. glands, sudoriferous, 632. lymphatics of, 631- papillae of, 639. pigmentum of, 631, 632 (note). pores of, 632. rete mucosum, 633 (note). structure of, 630-634. true, 630. 902 INDEX. Skull, 33. See Cranium and Face, Socia parotidis, 341. Sole of foot, 102. Solitary glands. See Glands.^ Space, inter-peduncular, 711, 728. Spaces, inter-cnstal, 71. osseous, hand, 84. foot, 106. ■ sub-arachnoid, 688. Sphenoidal cells, or sinuses, 39. fissure, 39. Sphenoid bone, 37. iSpAeno-frontal suture, 47. jugal suture, 47. maxillary fissure, 39, 55. fossa, 60. occipital bone, 36. — suture, 47, palatine foramen, 54. parietal suture, 47. spinous foramen, 39. temporal fossas, 48. — suture, 47. Sphincter muscles. See Muscles. Spinal accessory nerve. See Nerve, accessory. arteries. See Arteries. cord, 693. arachnoid of, 690. enlargements of, cervical, lumbar, and oc- cipital, 697. enveloped in its proper membrane, 697. extent and situation of, 694 form, direction, and relations of, 696. furrows or grooves, 698. . membrane proper, or neurilemma of, 097. pia mater of, 697. I sections of, 700. structure of, internal, 700. examined by hardening, 702, sections, 700. water, 701. substance, gray and white, 702. minute structure, 702 (note). Stomach, follicles of, 360. function, 361. • ventricles of, 702. muscles, posterior. See Muscles. nerves. See Nerves. veins and plexuses. See Veins. Spine, nasal, anterior, 52. posterior, 54- of ischium, 89. of pubes, 89. of scapula, 75. • sciatic, 89. or spinal column, 18. See Vertebral Column. of tibia, 97. Spinous foramen of sphenoid, 39. processes of ilium, 89. of vertebra;, 19, 21. Splanchnic nerves. See Nerves. Splanchnology, 320. Spleen, 403. cells of, 405. coats of, 405. corpuscules of, 407. development of, 407. • fissure, or hilus, 405. functions, 408. lymphatics of, 407. size of, differences in, 403. structure of, 405. vessels and nerves, 405, 408. Spleens, supernumerary, 403. Splenic artery, 406. • omentum, 405. veins, 406. Spongy bones. See Bones. Stapes, 674. Stenonian duct, 341. Sternum, 64. Stomach, 352. alveoli of, 361. coat of, cellular or fibrous, 357. mucous, 356. muscular, 356. nervous (so called), 356. serous, or peritoneal, 357. - cu!s-de-sac of, 354. ■ curvatures of, 354. ■ development of, 361. - extremities of, 354. glands of, 360. granular appearance of, 357. lymphatic system of, 360. orifices of, 355. papilliE or villi, 359. structure of, 356. surface of, external, 353. internal, 355. — tuberosity of, 355. tubuli of, 360. vessels and nerves of, 360. Structure of tissues and organs. See those organs and tissues. Styloid bone, 43. process of temporal bone, 43. fibula, 99. radius, 81. ulna, 80. SuJ-arachnoid fluid, 690. uses of, 692. • space, cranial, anterior, 688. • posterior, 688. spinal, 689 (note). — lingual fossa, 58. gland, 343. ducts of, 343. ■ maxillary fossa. 58. gland, 342. - duct of, 342. synovial adipose tissue, 113 .S'u/ci. See Cerebrum, anfractuosities of. Super-ciliary foramen, 36. — ridge, 35. Superficial petrosal nerves. See Nerves. Supplementary cavity of shoulder-joint, 139. of temporo-raaxillary joint, 128. Supra-oihitary foramen, 36, 59. renal capsules, development of, 445. tructure, 446. — sphenoidal fossa, 37. — spinous fossa, 76. Sustentaculum tali, 101. Suture, coronal, or fronto-parietal, 45, 47. ethnioido-frontal, 48. ethmo-sphenoidal, 48. fronto-jugal, 48, 59. maxillary, 59. nasal, 59. — sphenoidal, 48. ■ lambdoidal, or occipito-parietal, 46. . maxillary, 59. • palatine, 60. -petro-occipital, 47. sphenoidal, 48. - sagittal or hi-parietal, 46. • sphenofrontal, 47. jugal, 47. parietal, 47. temporal, 48. - squamous, 47. - temporo-parietal, 47. ■ transverse or spheno-occipital, 46, 49. Sutures, 114. indented, squamous, and harmonic, 114. cranial, in general, 154. Sympathetic ganglia in particular. See Ganglia. nerves. See Nerves. plexuses, in particular. See Plexuses. system, in particular. See Ganglia and Nerves. Symphyses, characters of, 114. Symphysis menti, 57. pubis, 89, 155. sacro-iliac, 155. Synarthroses, 114. characters, bgaments, and motions, Hi. Synchondroses, 113. Syndesmology, 111. Syneuroses, 113. Synovia, 112. Synovial huis?e, 178. capsules, 112. of particular joints. See those jointa. fringes, 112. in the knee, 164. •glands (so-called), 112. membranes, articular, general characters of, 112. INDEX. 903 Synovial membranes, bursal, 178, 298. -— minute structure of, 178. vaginal, 178, 299. sheaths for tendons, 178, 298. Si/ssarcoses, 114. Taniu hippocampi, 746. semicircularis, 740, 745. Tarsus, bones of, 99. first row of, 100. compared with first row of carpus, 107. second row of, 101. compared with second row of carpus, 107. ■ compared with carpus, 108. sheaths for tendons on, 313. Teeth, 177. arteries of, 182. • bicuspid, 179. bulbs of, 181. canine, 180. cement of, 182. changes in, after eruption, 190. characters of, general, 179. differential, 179. ■ classification of, 178. ■ compared with bones, 183 (note). epidermoid appendages, I' • compound, 182. • conformation of, external, 179. internal, 181. ■ cortical portion of, 181. — — substance of, proper, 182. ■ crowns of, 179. ■ erusta petrosa of, 182, and note, ■ cuspid, 179. ■ development of, 183. different stages of, 184. ■ distinguished from bones, 177. - enamel of, 182. chemical composition of, 182. development of, 186. structure of, 183 (note). fangs of, 178. • formation of, 186. ■ follicles of, 185. (Goodsir). 183 (note). general idea of, 190. ■ incisor, 179. ■ ivory of, 183. - chemical composition of, 182. development of, 165. structure of, 182 (no*e). ■ milk. See Temporary. ■ molar, 180. great and small, 180. upper and lower compared, 181. • multi-cuspid, 181. • nerves of, 181. • number of, 177. • permanent, 177. decadence of, 190. development of, 190. differences of, from temporary, 190 eruption of, 189. follicular stage of, 184. origin of pulps and sacs of, 184. papillary stage of, 184. • saccular stage of, 185. Teeth, wisdom, 181. uses of, 189. two sets of, provisional. See Temporary. pulps of, 181. ■ origin of, 184. quadri-cuspid, 181. ■ sacs of, 186. origin of, 184. ' simple, 183. ■ structure, general, 181. — minute, 183. ■ supernumerary, 187. tartar of, 183. ■ temporary, 177. development of, 183. differences of, from permanent, 190, eruption of, 183. follicular stage of, 180. origin of pulps and sacs of, 184. papillary stage of, 184. saccular stage of, 184. shedding of, 188. Tela choroidea, 731. Temporal a-rteries. See Arteries. ——- bone, 42. fossa, 47. nerves. See Nerves. Temporo-panelaX suture, 47. Tendo AchiUis, 283. Tendon of Zinn, 650. straight of orbicularis palpebrarum, 653. Tendons of muscles, 193. structure of, 299. Tensor muscles. See Muscles. Tentorium cerebelli, 0s4. Testes (of brain), 712. Testicles, 446. coverings of, 446. excretory duct of, 452. proper coat ot, 449. structure of, 449. tubuli of, 450. tunica albuginea, 449. erythroides, 447, propria, 449. - vaginalis, 447 -vessels and nerves of, 451. Testis, coni vasculusi of, 452. mediastinum, 450. rete vasculosum, 451. tubuli, 450. Testicular artery, 451. Thalumi optic, 742. — structure of, 744. Thigh bone, 93. compared with arm bone, 105 Third cranial nerve. See Nerve. Tiwracic arteries. See Arteries. Thorax, aponeuroses of, 300. — articulations of, 130. — bones of, 64. — development of, general, 72. — general description of, 70. — mechanism of, 132. — movements of, in general, 134. one rib of, 132 TAyro-aryteuoid ligaments. See Chorda Vocales. Thyroid arteries. See Arteries. veins. See Veins. Tibia, 96. — and ulna, upper parts of, compared, 107. radius, lower parts of, compared, 107. Tibial arteries. See Arteries. nerves. See Nerves. Tissue, adipose, 175. bony, 12, 13. cartilaginous, 174. cellular, 298. elastic, 174. fibro-cartilaginous, 174. ■- cellular, 298. fibrous, 298. ligamentous, 174. muscular, 198. nervous, 757. tendinous, 289. Toes, articulations of, 174. bones of, 104. phalanges of, 104. Tongue, 332. bone of, 333. developia&t of, 336. dorsum ff, 332. frEEnum of, 333. lymphatics of, 646. median cartilage of, 333. mucous membrane of, 646. muscles of, 333. extrinsic, 334. intrinsic, 334. nerves of, 646- — papillae of, 333. rete mucosum of, 646. structure of, 334. uses of, 339. — vessels, 339. Ton.iils, 333. of cerebellum, 718. Torcular Herophili, 588. 904 Trabecule of corpus cavernosura, 455. spleen, 405. Trachea, 416. cervical portion, 416. glands of, 416. structure of, 416. thoracic portion, 416. vessels and nerves, 416. Tracius spiralis foraminulentus, 678. Tragic fossa, 668. Tragus, 666. ligament of, 666. Transversales muscles. See Muscles. Transverse arteries. See Arteries. muscles. See Muscles. suture, 46, 47. veins. See Veins. Trtmsverso-spinaXis muscle. See Muscle. Trapezium, 83. Trapezoid bone, 83. — — ligament, 136. Triangulares muscles. See Muscles. Triceps muscles. See Muscles. Trifacial, or trigeminal nerve. See Nerve. Trochanteric cavity, or fossa, 95. Trochanters of femur, 95. of humerus, 79. Trochlea, femoral, 95. humeral, 79. of orbit, 651. Trochlear articulations, characters of, &c., 114. nerve. See Nerve, pathetic- Trochoid articulations, characters of, &c., 114. Tube, Eustachian. See Eustachian Tube. Fallopian, 463. Tuber annulare. See Pons Varolii. cinereum, 729. Tubercle, ash-coloured, of Rolando, 703. lachrymal, 645. laminated, 717. of Lower, 488. Tubercles of Santorini, in larjTix, 424. in nose, 640- Tubercula quadrigemina, or bigeroina, 712. structure of, 714. Tuberosities, calcaneal, 102. of femur, 95. of humerus, 79. of tibia, 97. Tuberosity, bicipital, 81. of ischium, 89. maxillary, 51. ruJf^ of Bellini, 437. TuJuZi of intestine. See Intestine. recti, of kidney, 437. of testicle, 452. seminiferi, 452. of stomach, 361. uriniferi, convoluted, 437. straight, 437. Tubulus centralis modioli, 679. Tunica adnata, 648. albuginea testis, 449. conjunctiva, 648. erythroides, 448. propria testis, 449. Ruyschiana, 657. sclerotica, 654. vaginalis testis, 448. vasculosa testis, 449 (note). Tunics of eye. See Eye. Turbinated bone, inferior, 56. middle, 41, superior, or ethmoidal, 41. sphenoidal, 38. Tympanic bone, circle, or ring, 45. Tympanum, bones in, 674. — circumference of, 672. — — lining membrane of, 670. membrane of, 675. -- secondary, 671. ■ orifice of, cochlear, 671. vestibular, 670. • recess of, 672. ■ wall of, external, 669. internal, 670. Unciform bone, 83. eminence, 730. Unguis, 730. Urachus, 443. Ureter, 440. structure of, 441. orifices of, 444. muscles of, 445. valve of, 444. Urethra, female, 469. - muscles of, 470. male, 457. bulb of, 459. dilatations, or sinuses, 459. internal surface, 459. lacunae, 460. membranous portion, 459. muscles of, 457. prostatic portion of, 457. spongy portion of, 459. structure of, 460. Urinary apparatus, 435. Uterine veins, 467. Uterus, 464. cavity and mouth of, 465. cervix or neck of, 465. coat, mucous, 467. serous, 467. — development, 468. — follicles of, 466. — functions of, 468. — fundus of, 466. — glands, tubular, of, 468 (note). — gravid, fibres of, 467. sinuses of, 467. vessels and nerves of, 464. — ligaments of, broad, 466. - — round, 466. nerves of, 468. structure of, 466. vessels of, 468. Ulriculus vestibuU, 681. Uvea, 670. Uvula, 332. vesicE, 459. cerebelli, 715 (note). Vagina, 468. bulb of, 469. columns and rugas of, 468. development of, 469. mucous membrane of, 469. muscles of, 469. r- structure of, 468. Vaginal process of temporal bone, 44. Valve of Bauhin, 372. Eustachian, 486. ileo-coscal, 372. colic, 372. mitral, 484. pyloric, 352. of Thebesius, 486. tricuspid, 484. of Vieussens, 711. columella of, 712. Valves of Kerkringius, 365. of heart. See Heart. of intestines. See Intestine. of lymphatics, 617. semilunar, or sigmoid, 484. of Tarin, 720. of veins, 575. Valvula conniventes, 365. Vas aberrans, 452. deferens, 452. structure, 452. Vasa afferentia, lymphatic, 614. brevia, arterial, 509. venous, 599. ■ efferentia of epididj'mis, 451. ■ lymphatic, 614. Ulna, 79. and tibia, upper parts of, compared, 107 Umbilicus, 308. — sudatoria, 634. -- vasorum of arteries, 520. of veins, 576. — vorticosa, 587, 665. Veins, in general, 573. — anastomoses of, 574. — braiiriies of, 575. — cnuts of, 576. — course of, 574. IIVDEX. 905 Veins, deep, 574. method of description of, 577. nerves of, 576. origin of, 574. plexuses of, 574. preparation of, 576. relations of, with arteries, 575. satellite, 574. sinuses of, 575. structure of, 576. sub-cutaneous, 574. superficial, 574. termination of, 575. valves of, 575. varieties of, 575. vasa vasorum of, 575. — vessels of, 575. in particular, 577. abdominal sub-cutaneoiis, 604. of ala of nose, 588. alveolar, 589. angular, 588. of the arm, superficial, 594. articular, of knee, 603. ascending cervical, 580. lumbar, 606. auricular anterior, 590. ■ posterior, 590. axillary, 593. azygos, general remarks on, 607. great, 605. lesser, 606. lumbar, 607. — basilic, 595. — brachial, 597. — brachio-cephalic, left and right, 579. — bronchial, left, 420. right, 420, 606. ■ distribution of, 421. — buccal, 589. — calcaneal, internal, 604. — capsular, inferior and middle, 597. — cardiac, great, 578. small, 578. — cava, ascending or inferior, 596. ■ descending or superior, 578. cephalic, 595. ■of thumb, 594. ■ cerebral, inferior, anterior, 587. lateral, 584. median, 586. internal, 565. superior, 585. ■ median, 58C. cerebellar, anterior lateral, 586. inferior lateral, 584. ■ cervical, ascending, 580. deep, 580. • choroid, 586. of eye, 658. • ciliary, 587. circumflex, brachial, 598. ■ femoral, 603. - iliac, 603. colic, left and right, 599. . coronary of the heart, anterior, 578. great, 578. lips, inferior, 589. - superior, 589. stomach, 362. of the corpus cavemosum, 601. striatum, 586. deep cervical, 580. — femoral, 603. ■ dental, anterior, 589 inferior, 590. superior, 589 ■ diaphragmatic, 601. • diploic, 585, 591. • dorsal of the foot, deep, 602. external, 603. internal, 603. • nose, 588. ■ penis, 601. — dorsi-spinal, 608. — of the dura mater, 583. — at the elbovir, 595. — emulgent, 598. — epigastric, deep, 603. superficial, 603. Veins, facial, 588. posterior, 589. of the falx cerebri, 586. femoral, 603. deep, 603. frontal, 587. ■ of Galen in brain, 584. heart, 577. ■ gastro-epiploic, 361. ■ gluteal, 601. ■ of hand, superficial, 594. ■ hemorrhoidal, inferior, 601. middle, 601. •superior, 601. — head, general remarks on, 592. — hepatic, 600. in the liver, 391, 392. — hypo-gastric, 601. — iliac, common, 600. external, 603. -- internal, 601. — ilio-lumbar, 607 — infra-orbital, 589. — innominate of Meckel, 579. • of Vieussens, 578. inter-costal, 607. superior, left, 606. right, 606. lobular, of liver, 391 (note). of intestines, 599. intra-lobular, of liver, 393 (note). spinal, 609. anterior, longitudinal, 609. ■ transverse, 609. ■ lateral, 010. posterior, longitudinal, 610. transverse, 610. compared with cranial, 610. ■ jugular, 581. anterior, 582. external, 581. internal, or deep, 583. posterior, 607. laryngeal, inferior, 580. -— superior, 582. lingual, 590. longitudinal of scull, inferior, 586. spine. See Intraspinal. ■ of lower extremity, deep, 602. superficial, 603. lumbar, or vertebro-lumbar, 597. ascending, 606. — azygos, 607. -- mammary, internal, 580. — masseteric, anterior, 589. ■ posterior, 590. ■ mastoid, 584, 590. ■ maxillary, external, 588. internal, 589. ■ median of the arm, 595. basilic, 595. • cephalic, 595. mediastiiml, 580, 606. ■ medullary, 610. ■ meningeal, 591. ■ middle, 590. ■ mesaraic, 599. ■ mesenteric, inferior or small, 599. superior or great, 599. ■ nasal, 588. obturator, 601. occipital, deep, 590. superficial, 589. ■ (Esophageal, 606. ■ omphalo-mesenteric, 599. ■ ophthalmic; 587. ■ orbital, external, 589. ■ ovarian, 598. • palatine, inferior, 589. superior, 589. ■ palmar, 593. ■ palpebral, external, 589. — inferior, 588. pancreatic, 402. ■ parotid, 590. • of particular organs or tissues, gans or tissues. • of pelvis, in female, 602. male, 601. See those ot- 5 Y of penis, 601. 906 INDEX. Veins, pericardiac, 580. peroneal, 602. pharyiig-eal, 591. phrenic, inferior, 598. superior, 5b0. plantar, 602. popliteal, 602. portal, or vena portse, 597, 599. branches of origin of, 598. in the liver, 390. sinus of, 599. profunda cervicis, 580. fenioris, 603. — pterygoid, 590. — pudic, external, 604. internal. 601. — pulmonary, 577. distribution of, 421. — ruchidian. See Spinal. — radial cutaneous, 595. deep, 594. — ranine, 590. — renal, 597. — sacral, lateral, 607. middle, 607. — salvatella, 594. — of Santorini, 585. — saphenous, external, 605. ■ internal, 603. ■ second, 604. — satellite, of lingual nerve, 590. — scapular, superior, 582. posterior, 582. — sciatic, 601. — scrotal, 601. — semi-azygos, 606. — short, of stomach, 599. — spermatic, left and right, 598. — spheno-palatine, 589, 591. — spinal, 605. • deep. See Intraspinal. — general remarks on, 611. — posterior, deep. See Intra- spinal. ■ superficial, 608. ■ superficial, 605. in neck, 608. — posterior, 608. — of spinal cord, 610. — splenic, 599. — distribution of, 406. — stylo-mastoid, 590. — sub-clavian, left and right, 593. mental, 589. — supra-orbital, 588. renal, inferior and middle, 598. scapular, 581. — sural, 603. — temporal, 589. deep, 590. middle, 589. superficial, 589. — temporo-maxillary, 589. — of Thebesius, 578. — thymic, 580. — thyroid, inferior, 580. middle, 591. • superior, 591. Veins, vertebro-lumbar. 607. vesical, female, 602. male, 601. vidian, 589. Velum interpositum, 731, 740. meduUare, anterior, 713. ■ posterior, 718 (note). palati, 331. See Palate, soft. pendulum palati, 331. Vena cava inferior, or ascending, 596. superior, or descending, 578. Vence comites, 572. minimae, 508. Venous plexuses. See Plexuses. system generally, 572. Venter ilii, or internal iliac fossa, 88. Ventricle of Arantiu.s, 704. of corpus callosum, 737. fifth, 738. fourth, 718. choroid plexuses of, 720. fibrous layers of, 719. fossette of, 704. laminated tubercle of, 717. orifice, inferior, 719. semilunar fold of, 719. valves of base of, 719. of larynx, 424. lateral, 744. body of, 744. cornu anterior, 744. descending, 744. posterior, 744. of septum lucidum, 738. third, 729, 741. choroid plexuses of, 741. commissure of, anterior, 742. posterior, 742. ■ soft or gray, 729, 741. floor of, anterior part of, 729. middle and posterior part of, 729. ■ openings of, 742. Ventricles, cerebral, fluid of, 744. lining membrane of, 747. Gall's views regarding, 750. of heart. See Heart. of spinal cord, 701. • tibial, anterior, 602. posterior, 602. • tibio-peroneal, 602. ■ tonsillar, 333. ■ transverse, cervical, 582. facial, 590. humeral, 582. ■ ulnar cutaneous, anterior, 595. posterior, 595. ■ deep, 592. ■ umbilical, 600. • of upper extremity, deep, 592. superficial, 593. ■ uterine, 467, 601, 602. • vaginal, 602. • vasa brevia, 599. vorticosa, 587. ventricular, cerebral, 586. — of vertebra, 610. vertebral, 581. vertebro-costal, inferior, 606. superior, left, 606. — — ■ ~ right, 605. Ventriculus, 352. succenturiatus, 362. Vermiform appendix, 373. process, inferior, 716. superior, 716. Vertebra, cervical, first, 23. second, 24. seventh, 25. dentata, 24. dorsal, first, 25. eleventh and twelfth, 25. general description of, 19. lumbar, fifth, 26. prominens, 25. Vertebra;, articular processes of, in different regions, ! articulations of. See Articulations. bodies of, in different regions, 20. cervical, 19. characters of, general, 19. distinctive, 20. proper, 22. — coccygeal, 19. — development of, 31. — dorsal, 19. — false, 19. — foramen of, in different regions, 19. — internal structure of, 31. — laminae of, in different regions, 20. — ligaments of. See Ligaments. — lumbar, 19. — notches of, in different regions, 20. -- number of, 19. — sacral, 19. -► sacro-coccygeal, 26. union of, 32. spinous processes of, in different regions, 22. transverse processes of, in different regions, 23. true, 19. Vertebral canal, 30. colunui, 19. articulations of, 115-123. INDEX. 907 Vertebral column, curvatures of, 28. development of, 32. > dimensions of, 28. figure and aspects of, 29. movements of entire, 121-123. grooves, 29. ligaments. See Ligaments. Vertebro-costal veins. See VetJis. Verumontanum, 461. Vesica fellea, 394. urinaria, 440. Vesicles, Graafian, 461. Vesiculce seminales, 453. efferent duct of, 454. structure, 454. Vestibule of ear, 676. aqueduct of, 676. calcareous matter of, 681. crista of, 676. ■ fovea and recessus stJcifonnis, 676. membranous, 680. openings into, 676. sacculus of, 680. sinus, common, or utricle of, 680. Visceral nerves. See Nerves. Vitreous table of cranial bones, 35. j Vocal cords, 426. Vomer, 57. Vulva, 470. ! development of, 471. I fourchette, 470. mucous membrane, 471. I parts of, 470. Wings of sphenoid bone, lesser, 37. great, 38. Ingrassius, 37. See Uterus. Womb Wormian bones, 50. ' ' Wrist. See Carpus. Xiphoid cartilage, or appendix, 65. Zinn, zone of, 655. Zonula Zinni, 655. Zygoma, 61. Zygomatic arch, 61. bone, 54. canal, 55. ■ fossa, 61. process of temporal bone, 42. malar bone, 55. THE END. c/ 0 e'-f^t-^^d^^y^^ t *k w r: s.^