"1%>.; xtT+r«: w<& /\ sn_j DUE TWO WEEKS FROM LAST DATE !.SEP ? $ 195. ^<% A SYSTEM OF ANATOMY / _. \ FOR THE USE OF ' /} . ■ STUDENTS OF MEDICINE. BY CASPAR W.I STAR, M.D., LATE PROFESSOR OF ANATOMY IN THE UNIVERSITY OF PENNSYLVANIA. WITH NOTES AND ADDITIONS, BY WILLIAM E. HORNER, M. D., PROFESSOR OF ANATOMY IN THE UNIVERSITY OF PENNSYLVANIA. ^ EIGHTH EDITION, ENTIRELY REMODELED, AND ILLUSTRATED BY MORE THAN TWO HUNDRED ENGRAVINGS. BY J. PAN COAST, M. D., PROFESSOR OP GENERAL DESCRIPTIVE AND SURGICAL ANATOMY IN JEFFERSON MEDICAL COLLEGE OF PHILADELPHIA, LECTURER ON CLINICAL SURGERY AT THE PHILADELPHIA HOSPITAL, FELLOW OF THE PHILADELPHIA' COLLEGE OF PHYSICIANS, ETC., ETC. IN TWO VOLUMES. V 0 L. I. ( ] *' Z> PHILADELPHIA: THOMAS, C 0 W P E R T H W AI T & C 0. 184 2. as Wills Entered, according to the Act of Congress, in the year 1812. by THOMAS, COWPERTHWAIT *& CO., in the Clerk's OfRce of the District Court of the Eastern District of Pennsylvania. Gihon, Fair-child f Purkinje ; 6 6, the first or primary stage of the bony structure, in which the osseous corpuscles arrange themselves somewhat into lines, and the bony fibres shoot in between them, and in the thickness of the corpuscles themselves saline particles are deposited, which renders them opaque ; c c, the new structure completely ossified. X These as shown p. 46, are now believed to be new bodies, bony corpuscles, which supplant the corpuscles (cartilaginous) of Purkinje. The above account is retained in order to show progressively the history of the discovery. NEW VIEWS OF THE GROWTH OF BONES. 45 lique in regard to the direction of the lamellae, and when the work of ossification has not commenced, appear to have no fixed arrangement, and are wedge-shaped, oval, oblong, or flattened, see Fig. 8. Of the nature of these corpuscles, little is posi- tively known. Neither vegetable or mineral acids have any effect upon them, except to render them a little more prominent on the surface of a section of cartilage. Alcohol, ether, or a cold solution of caustic potash does not change them; but if exposed to a hot caustic solution, or a long time macerated in water they become completely liquified. —The size of the corpuscles according to the measurements of Miescher, varied in length from the 0.0048 to the 0.0072 parts of a line, and in breadth from the 0.0017 to the 0.0030. The researches of this anatomist, of Muller, and other recent ob- servers, have shown that the formation of cartilage always precedes that of bone,* and that each ossescent or temporary cartilage, is an organic tissue, homogeneous, more or less pel- lucid, elastic, in its first state almost colourless, afterwards assuming a bluish cast, and having a great many peculiar minute corpuscles interspersed through its substance, as shown by the microscope. In the conversion of cartilage into bone, the change first commences in the cartilage that surrounds the corpuscles. —Weber, Beclard and others, believe that the calcareous mat- ter is deposited by the vessels, in the cartilaginous mould of the bone, as a foreign body, and that the cartilaginous particles are removed in proportion to make room for it; but this is a mere opinion which has not been proven. —Miescher, asserts that he was unable even with the micro- scope to ascertain in what manner, the calcareous particles were received into the cartilage, the strongest powers of the micro- * This which was admitted by Albinus, Haller, Scarpa, and others, has been de- nied by Howship and Beclard, in regard to the diaphysis of the long bones, and the bones of the cranium. In the bones of the rabbit, Miescher found a mould of carti- lage before a particle of ossific matter had been deposited, and between the pericrani- um and dura mater, a thin stratum of cartilage. An exception must be made how- ever in regard to certain flat bones of the human skull, as the parietal.—p. 46 NEW VIEWS OF THE GROWTH OF BONES. Fig. 8.* scope exhibiting no cells in which they were placed, nor any calcareous particles of the size of the dispersed corpuscles; all that appeared positively was that the cartilage seemed by degrees to assume the aspect of bone. The more recent researches of Gerber,+ have given if not a perfectly clear, at least a more satisfactory explanation of the manner in which the ossific cartilage is so modified, as to form bone. The primitive physical formation of all car- tilage is cellular, that is they grow from cell-germs, as is the case with the other tissues of the body. These cell-germs or cartilage corpuscles are seen at A. Fig. 8, magnified 250 diameters. Between these cells and filling up the vacant spaces between them, is an amorphous, hyaline or transparent intercellular substance; the cells themselves are filled with a softish granular matter. As the cartilage increases in growth, new cells are deve- loped in the hyaline substance by which the older ones are pushed farther and farther from each other. The original cells produce two or more young or se- condary cells by the developement of their granular nuclei: between these seconda- ry cells is also formed a secondary hya- line substance, and thus the original cells form each one a little group of cells enclosed within itself, and to each group the name * Fig. 8. Ascheme intended to represent cartilage in the progressive stages of ossifica- tion, magnified 250 diameters. A.Cartilage with the regularly disseminated corpuscles of Purkinje—cellular cartilage. B. The corpuscles when ossification has begun, are forced into groups, between which the hyaline cartilage is transformed into bone car- tilage. This bone cartilage has now undergone a change, so as to be chemically dif- t Elements of General and Minute Anatomy by T. Gerber. London, 1842. NEW VIEWS OF THE GROWTH OF BONES. 47 of cartilage corpuscle is still applied. This is the common em- bryonic constitution of cartilage. The fixed character of the cartilage depends upon the after changes which take place in it. If fibro-cartilage be formed, the intercellular or hyaline sub- stance is developed in the form of fibres and the cells disappear altogether. If elastic cartilage, fibres are developed around the cells forming a kind of network. If ossific cartilage, the hya- line substance takes on a stratified arrangement round the car- tilage cells, and in it a new set of corpuscles are developed, called the bone corpuscles, that are the nuclei of the bone cells, see Fig. 9, of which the microscope has shown in reality all bony structure to consist. As this process is commencing, the cluster of cartilage cells called cartilage corpuscles, become compressed together. The secondary hyaline substance be- comes dissolved, transudes through the walls of the parent cell, coagulates round it, and in this state of cytoblastema as it is called—thisbasis structure for the growth of other parts—it con- stitutes the proper ossific cartilage. In it arise the bone cor- puscles, called cytoblasts or germs, from which are formed the bone cells. These follow the same mode of developement, as the embryonic cartilage cells: that is new corpuscles are forming in the cytoblastema, while those recently produced are growing; the cartilage corpuscles ever more closely com- pressed together disappear; radiated points, nutrient vessels,etc. make their appearance, the nuclei of the bone cells, (corpuscles,) and thecellsthemselves when completely formed receive depos- its of calcareous salts, and the formation of bone is achieved. ferent from those cartilages which are to remain flexible during life. It does not on boiling yield gelatine like them, but a substance called chondrin, which differs from gelatine in not being precipitated by tannic acid, etc. C. The groups of cartilage corpus- cles are now seen completely inclosed by bone cartilage. D. The cartilage corpus- cles are here rendered less transparent by the process of resolution that is going on; the bone corpuscles are at the same time making their appearance in the bone car- tilage. E. The cartilage corpuscles are dissolved and partially removed. F. The cartilage corpuscles have disappeared ; have been absorbed. G. In spongy bones, the spaces occupied by the cartilage corpuscles remain as cells filled with globules of fat. In compact bones the cells are reduced to minute canals, by the growth of bony matter, or they disappear entirely. In Fig. 9, there is a representation of bone in its perfectly formed state, magnified 450 diameters, and representing the bone cells or corpuscles, with their calcareous canals. 48 FORMATION OF CALLUS. £3 It is according to this from a peculiar sub- stance, not ordinary cartilage, that bone is pro- duced, and we now know that the effused fluid of which the callus in fractures is formed, is in some respects different from the cartilagi- nous mould of bone, and that in fact bone is developed in many parts of the body, as in the human skull for instance, without the existence of any previous cartilaginous basis. Formation of Callus. —The most ancient opinion entertained in regard to the mode of union between broken bones, was, that it was owing to the con- cretion of a viscous fluid, or imaginary osseous juice poured out between the fragments. This was the opinion of Haller. Du- hamil demonstrated the fallacy of this belief, by numerous experiments, and instituted a theory of his own which is much nearer the truth. According to him the production of callus or new bony matter, is owing to the swelling, elongation, and subsequent adhesion between the periosteum and medullary membrane of one fragment with the corresponding parts of the other; and that from these membranes thus modified, bony matter was deposited in the form of a ring on the exterior of the bone and a plug in its medullary cavity, which held the fragments together by passing across the cavity of fracture, and sometimes by prolongations passing between them through the cavity. John Hunter believed that the re-union of fractured bones took place from the organization of the blood effused around the fracture and between the fragments; a doctrine which now has few supporters. —The credit of giving the most faithful account of the forma- * Fig. 9. Bone corpuscles, a, magnified 450 diameters, which have here been converted into bone cells. 6. Branches of the bony cells which by their inosculations form a net work. They are called by Miiller the canaliculi calicophori. It is not yet fully decided whether or not the cells and their branches are filled with cal- careous matter, or merely incrusted with it. The diameter of these calcigerous canals (canalic. calicoph.) is reckoned at their largest parts to be between one fourteen thousandth and the one twenty thousandth part of an inch. RESTORATION OF FRACTURED BONES. 49 tion of callus, is due to Dupuytren* and Sanson. According to these, the union of fragments of bone, is effected by the for- mation of two successive stages of callus. One which is pro- visional or temporary, is completed usually in the space of thirty or forty days, by the union and ossification of the perios- teum, cellular tissue, and even in some cases of the muscles, so as to constitute an external ring—and of the medullary mem- brane, so as to constitute an internal plug. The other, which he calls final or permanent, is formed by the reunion of the surfaces of the fracture, with a solidity so much superior to that of the bone in other parts, that it will break any where again, rather than at that point, and which is never fully com- pleted under eight, ten, or twelve months, by which time all the provisional callus has been removed, and the medullary canal is completely re-established. —Dupuytren divides the successive organic changes, which attend the formation of callus, intone periods. —The first period, extends from the time of the fracture to the eighth or tenth day, and is characterised by the following phenomena : the medullary membrane, the medulla, the peri- osteum, cellular tissue, and sometimes the muscles themselves, are torn at the time the fracture takes place ; blood escapes from the ruptured vessels, surrounds the fragments, spreads in the medullary canal and infiltrates in the surrounding tissue : the hemorrhage stops; a slight inflammation is developed in all these parts, which is the first step towards the production of the callus. The cellular tissue surrounding the bone, becomes very vascular, is thickened, loses its elasticity, and acquires a great degree of consistence ; it sends irregular processes into the neighbouring muscles, transforms them to a greater or less extent into an analogous tissue, and unites them in a common structure with the periosteum, which is also much thickened and very vascular. A nearly similar change takes place in the cavity of the bone in respect to the medulla and its membrane. Thecalibreof the medullary canal is contracted by the thickening of the membrane, which presents a fleshy appearance, in con- * Journal Univ. de Med. torn. 20. 5 50 RESTORATION OF FRACTURED BONES. sequence of a sort of gelatinous infiltration. The effused blood becomes absorbed, and a ropy, viscous, gelatinous fluid, is poured out between the ends of the fragments, which is essential to the production of the permanent callus. —The second period extends from the tenth or twelfth, to the twentieth or twenty-fifth day. During this period, the engorge- ment of the surrounding parts diminishes and the muscles are liberated : but the cellular tissue remains condensed and con- centrated round the fracture, presenting grooves or even canals to the tendons of the muscles if any pass in the vicinity of the fracture, in which they are able to play, though with little free- dom, in consequence of some existing induration of the cellular tissue. This constitutes the provisional callus, the external portion of which is thickest at the place of fracture, and insen- sibly terminates upon the fragments of bone. Its internal portion is formed by the periosteum, which is closely attached to the bone. Its structure is whitish, homogeneous, and of a cartilaginous or fibro-cartilaginous character. The medullary membrane forms a similar plug of provisional cartilaginous matter, which fills up the whole cavity of the bone, above and below the place of fracture. The viscous or gelatinous fluid interposed between the ends of the bones, isnow rose-coloured or red, presents sometimes a flocculent appearance, and is adherent by its margins to the external and internal callus. The limb may still be bent at the place of fracture, but no crepita- tion can be produced. —The third period extends from the twentieth or twenty-fifth day, to the thirtieth, fortieth or sixtieth, according to the age and health of the patient. —Ossification commences in the centre of the cartilage, and by degrees the whole tumour, internal and external, becomes os- seous. It is very vascular, and Howship* has succeeded in injecting the vessels. If at this period the bone be cut longitu- dinally, the provisional callus will be found presenting all the characters of spongy bone, while the fragments will be found * Microscop. Observ. TERMS USED IN THE DESCRIPTION OF BONES AND JOINTS. 51 movable upon each other, the substance poured out between them, not having apparently undergone much change. —'The fourth period extends from the fiftieth or sixtieth day, to the fifth or sixth month. During this period the callus has been changed from the state of spongy, to that of compact bone. —The substance intermediate to the fragments, which present- ed itself under the form of a line or septum between them, becomes more consistent, presents a whiter hue, and is ossified towards the end of this period ; and the permanent callus is now completed. —The fifth period extends from the fifth or sixth, to the eighth, tenth or twelfth month, during which time the whole of the provisional callus is entirely removed, the object of its formation having been effected, that of securely holding the bones together like splints till the fractured surfaces become firmly reunited. The periosteum resumes its usual thickness and polish, and the muscles and tendons their entire freedom of motion. —The internal plug of callus having been removed by absorp- tion, the central cavity of the bone, the medullary membrane and the marrow itself, present their usual appearance.— Of the Terms used in the Description of Bones and their Articulations. The study of this subject has been rendered more difficult by the unnecessary introduction of many hard words, but some of these words are so generally used, that they ought to be un- derstood by the student of anatomy. The word process signifies any protuberance or eminence arising from a bone. Particular processes receive names from their supposed re- semblance to certain objects; and their names are very often composed of two Greek words; thus the term coracoid, which is applied to a well-known process, is derived from the Greek words xoPa|„ a crow, and si<5os„ resemblance. 52 TERMS USED IN THE DESCRIPTION OF BONES AND JOINTS. If a process has a spherical form, it is called a head. If the head is flattened on the sides, it is denominated a condyle. A rough protuberance is called a tuberosity. A ridge on the surface of a bone is called a spine. The term apophysis, is nearly synonymous with process. It signifies a protuberance that has grown out of the bone, and.is used in opposition to the term epiphysis, which signifies a por- tion of bone growing upon another, but distinct and separable from it; as is the case in infancy with the extremities of the long bones. The cavities on the surfaces of bones are named in the same way, as will appear by a reference to the glossary at the end of this work. Words of this kind have been used most profusely in the descriptions of articulations, and here also their utility is doubt- ful. Therefore, for many terms used on this occasion, the reader is referred to the glossary; but the following are neces- sary to be understood. Symphysis does not merely imply the concretion of bones originally separate, as its derivation imports; but it is un- derstood also to mean the connexion of bones by intermediate substances. Thus, there are three species of symphysis, particularly noticed, viz. Synchondrosis, when bones are connected to each other by cartilage ; as the ribs and sternum. Synneurosis, when they are connected by ligaments, as in the movable articulations. Syssarcosis, when they are connected by muscle. The different articulations are of two kinds, viz. Synarthrosis and Diar- throsis. Synarthrosis is the name of that kind of articulation which does not admit of motion. There are three species of synar- throsis, viz. Suture, when the indented edges of the two bones are received into each other, as is the case with the bones of the cra- nium. TERMS USED IN THE DESCRIPTION OF BONES AND JOINTS. 53 Gomphosis, when one bone is fixed in another like a nail in a board, as the teeth in their sockets. Shindy lesis, when the thin edge of one bone is received into a narrow furrow of another, as the nasal plate of the ethmoid in the vomer. Diarthrosis is the name of that kind of articulation which admits of motion. Of these articulations there are three species, viz. Enarthrosis, when a large head is received in a deep cavity, as the head of the thigh bone in the acetabulum. Arthrodia, when the head is connected with a superficial cavity. Ginglimus, when the extremities of bones apply to each other so as to form a hinge. But most of the important joints have so many peculiarities that they cannot be understood without studying them sepa- rately. It may, therefore, be doubted whether the classification and arrangement of joints is any way necessary. —Some of the more common anatomical terms are explained in this place and in the glossary ; but they have now become too numerous, in consequence of the introduction of a multitude of new ones, some of which are of foreign origin, to be sepa- rately defined in this work. A medical dictionary will better serve the purposes of the student. That of Prof. Dunglison,* will be found the most comprehensive and useful. * Medical Lexicon—A new Diet, of Med. Science. 3d edit, by Robley Dunglison, M. D., Prof. Inst. Med., &c, in Jeff. Med. Coll. Lea & Blanchard. Phil. 1842. 5* 54 OF THE HEAD. CHAPTER II. Of the skeleton and its different parts, and the individual bones of which they are composed. The bones of an animal arranged and connected to each other in their natural order, separate from the soft parts, compose a skeleton. The skeleton is said to be natural when the bones are connected by their own ligaments, which have been allowed to remain for that purpose. It is called artificial when the bones are connected with wire, or any foreign substance. The artificial skeleton is best calculated for studying the motions of the different bones, because the dry and hard ligaments of the natural skeleton do not allow the bones to move; but the bones of young animals do not admit of the preparation necessary for an artificial skeleton, as their epiphyses would separate, and they are therefore formed into natural skeletons. The study of the skeleton and its mechanical properties, as a piece of machinery, is absolutely necessary to a perfect under- standing of many motions of the body, and of the action and co-operation of muscles; but any observations on this subject will be better understood after the individual bones and the muscles have been described. The skeleton is divided into the head, the trunk, the superior and the inferior extremities. Of the Head. The Head comprehends the Cranium, and Face. The cranium consists of eight distinct bones, which, when placed in their natural order, form a large spheroidal cavity for containing the brain, with many foramina or apertures that communicate with it. OF THE CRANIUM. 55 These bones are of a flattened form. They are composed of two lamina or plates called tables, with a cellular structure between them, called meditullium, or diploe. The external table is more firm and thick than the internal. The latter is comparatively very brittle, whence it is called the vitreous table. [Between the two tables which compose the flat bones of the cranium and running through the diploe are several sinuses, which are occupied by veins in the recent subject. They were discovered by M. Fleury about forty years ago, while he was Prosector at the School of Medicine in Paris, and engaged in some inquiries relative to the structure of the cranium at the instigation of M. Chaussier. The account which M. Chaussier gives of these veins is as follows : they-are situated in the middle of the diploe between the two tables of the skull, and like all other veins are intended to return the blood 1o the heart. They are furnished with small valves, have extremely thin and delicate parietes, and commence by capillary ramifications coming from the different points of the vascular membrane which lines the cells of the diploe. Their roots are at first extremely fine and numerous, form by their frequent anastomoses a kind of network, and produce by their successive junction, ramuscles, branches, and large trunks, which, becoming still more voluminous, are directed towards the base of the cranium. Some varieties exist in regard to the number, size, and disposition of these trunks, but generally one or two of them are found in each side of the frontal bone, two in the parietal bone, and one in each side of the occipital bone. Anastomoses exist between these several trunks, by which the veins in the parietal bone are joined to those in the frontal and in the occipital. Branches from the right side of the head also anastomose with some from the left side. Besides the branches already mentioned, one or two smaller than the others are directed towards the top of the head and terminate in the longitudinal sinus. The descending veins of the diploe communicate in their passage with the contiguous superficial veins, and empty into them the blood which they receive from the several points of 56 OF THE CRANIUM. the diploe. These communications are produced through small foramina which penetrate from the surface of the bone to the diploe. The trunks of such diploic veins as are continued to the base of the cranium, open partly into sinuses of the dura mater, and partly into the venous plexus at the base of the pterygoid apophyses, and form there the venous communica- tions called the emissaries of Santorini. Moreover, there are communications sent from the diploic veins through the porosi- ties of the internal table of the skull to the veins of the dura mater. This fact is rendered very evident by tearing off the skull cap, when the surface of the dura mater will be studded with dots of blood, and the internal face of the bone also, particularly in apoplectic subjects. It appears indeed that the arteries of the cranium are principally distributed on its exter- nal surface, and the veins on its internal surface and diploe. In the infant the diploic veins are small, straight, and have but few branches: in the adult they correspond with the description just given ; and in old age they are still more con- siderable, forming nodes and seeming varicose. In children, when the bones are diseased, they partake of the latter character. In order to see them fully, the external table of the skull must be removed with the chisel and mallet, both from its vaults and base.]* The periosteum, which is on their external surface, is called pericranium. Internally the dura mater, or membrane which covers the brain, supplies the place of periosteum. There are eight of these bones, which are thus denominated: Os Frontis, Ossa Parietalia, Ossa Temporum, Os Occipitis, Os Sphenoides, and Os Ethmoides. The two last are called common bones, to denote that they are connected with the bones of the face as well as with those of the cranium. The os frontis forms the whole fore part of the vault of the * The diploe, or meditullium, corresponds exactly in structure and situation with the spongy, or cellular tissue of the other bones of the body, though it has unneces- sarily received a distinct name. Neither are the diploic sinuses peculiar to the bones of the skull. They are found presenting exactly the same appearance in the bodies of the vertebrae, and appear in fact to be but a developement of the canaliculated tissue of the other bones. See Fig. 5, page 30.—p. THE SUTURES. 57 cranium: the two ossa parietalia form the upper and middle part of it; the ossa temporum compose the lower part of the sides ; the os occipitis makes the whole hinder part and some of the base; the os ethmoides is placed between the orbits of the eyes, and the sphenoides extends across the base of the cranium. The Sutures. The above bones are joined to each other by five sutures; the names of which are the Coronal, Lambdoidal, Sagittal, and two Squamous. The coronal suture is extended over the head, from within about an inch of the external angle of one eye, to the like dis- tance from the other; which being near the place where the ancients wore their garlands, this suture has hence got its name. Though the indentations of this suture are conspicuous in its upper part, yet an inch or more of its end on each side has none, but is squamous and smooth. The lambdoidal suture begins some way below, and further back than the vertex or crown of the head, whence its two legs are stretched obliquely downwards, and to each side, in form of the Greek letter A, and are now generally said to extend themselves to the base of the skull; but formerly, anatomists reckoned the proper lambdoidal suture to terminate at the squamous sutures: and the portion continued from them on each side, where the indentations are less conspicuous than in the upper part of the suture, they called additamentum suturse lambdoidis. This suture is sometimes very irregular, being made up of a great many small sutures, which surround a number of insulated bones, that are generally more conspicuous on the external surface of the skull than internally. These bones are commonly called triquetra or wormiana ; their formation is owing to a greater than ordinary number of points of ossification in the skull, or to the ordinary bones of the cranium not extending their ossification far enough or soon enough; in which case, the unossified interstice between such bones begins a separate 58 THE SUTURES. ossification, in one or more points; from which the ossification is extended to form as many distinct bones as there were points which are extended into the large ordinary bones, and into each other.* The sagittal suture is placed longitudinally, in the middle of the upper part of the skull, and commonly terminates at the middle of the coronal and of the lambdoidal sutures; between which it is said to be placed, as an arrow is between the string and the bow. This suture is sometimes continued through the middle of the os frontis down to the root of the nose. The squamous agglutinations, or false sutures, are one on each side, a little above the ear, of a semicircular figure, formed by the overlapping (like one scale upon another) of the upper part of the temporal bones on the lower part of the parietal, where, in both bones, there are a great many small risings, and furrows which are indented into each other: though these inequalities do not appear until the bones are separated. In some skulls, indeed, the indentations here are as conspicuous externally as in other sutures; and what is commonly called the posterior part of this squamous suture, always has the evident serrated form; and therefore is reckoned by some a distinct suture, under the name of additamentum posterius suturae squamosa?. The squamous suture is not confined to the conjunction of the temporal and parietal bones, but is made use of to join all the edges of the bones on which each temporal muscle is placed; for the two parts of the sphenoidal suture, which are continued from the anterior end of the common squamous suture just now described, one of which runs perpendicularly downwards, and the other horizontally forwards; and also the lower part of the coronal suture already taken notice of, may all be justly said to pertain to the squamous suture. * These ossa triquetra or wormiana are also frequently met with in the sagittal suture, and occasionally in all the different sutures of the cranium. As many as fifteen or twenty have been seen in a single head, though usually their number is much less. Where the cranium is of a globular form, few, and frequently none, are met with. They never begin to ossify till six months or a year after birth.—p. THE SUTURES. 59 This structure appears to depend upon the pressure of the temporal muscle externally, and the resistance of the brain within, which makes the bones so thin, that their edges opposed to each other are not sufficiently thick to stop the extension of their fibres in length, and thus to cause the common serrated appearances of sutures; but the narrow edge of the one bone slides over the other. The squamous form is also more con- venient here; because such thin edges of bones, when accurately applied one to another, have scarce any rough surface to obstructor hurt the muscle in its contraction; which is still farther provided for, by the manner of laying these edges on each other; for, in viewing their outside, we see the temporal bones covering the sphenoidal and parietal, and this last sup- porting^the sphenoidal, while both mount on the frontal; from which disposition it is evident, that while the temporal muscle is contracting, which is the only time it presses strongly in its motion on the bones, its fibres slide easily over the external edges. Another advantage of this structure is, that the whole part is made stronger by the bones thus supporting each other. The indentation of the sutures are not so strongly marked on the inside as on the outside of the cranium; and sometimes the bones seem to be joined by a straight line: in some skulls, the internal surface is found entire, while the sutures are manifest without. By this mechanism, there is no risk of the sharp points of the bones growing inwards, since the external serrae of each of the conjoined bones rest upon the internal smooth-edged table of the other. The advantages of the sutures are these : 1. The cranium is more easily formed and extended into a spherical figure, than if it had been one continued bone. 2. The bones which are at some distance from each other at birth, may then yield, and allow to the head a change of shape, accommodated to the passage it is engaged in. Whence, in difficult parturition, the bones of the cranium, instead of being only brought into contact, are sometimes made to mount one upon the other. [The sutures which unite the bones of the cranium, are 60 THE SUTURES. generally said to be made by the radii of ossification, from the opposite bones meeting and passing each other, so as to form a serrated edge. This explanation is however insufficient, for the following reasons: we always find the sutures m the same relative situation, and observing the same course in the cranium; if they, then, depended exclusively on so mechanical a process, as the shooting of the rays of bone across each other when they met, in ossification on one side of the head occurring sooner or faster than on the other, we ought to find the sagittal suture to one side of the middle line ; it should also, in many instances, be found crooked. Moreover, in all cases where bones arise from different points of ossification and meet, particubMfy in the flat bones, the serrated edges ought to be formed; this, however, is not the case. The os occipitis, which is formed originally from four points of ossification, and has therefore as many bones composing it in early life, never joins these bones together by the serrated edge; the acromion process of the scapula is never united to its spine by sutures; the three bones of the sternum never unite by suture, and the same observa- tion holds good in many other instances. Bichat, who rejects this mechanical doctrine, advances an opinion much better founded. The dura mater and the pericranium, before ossifi- cation commences, form one membrane, consisting of two lamina; it is generally known that the flat bones of the cranium are secreted between these two lamina; now the out- line of each bone, long before it has reached its utmost limits, is marked off by partitions passing between these two mem- branes. The peculiar shape of the bony junction, or the suture in adult life, will, therefore, depend upon the original shape of the partitions: when the latter are serrated, the points of ossification will fill up these serrse; but when they are simply oblique, the squamous suture will be formed. This also accounts for cases where the mode of junction is intermediate to the squamous and serrated suture; for the formation of the ossa triquetra, and why in some skulls they do not exist, whereas in others their extent and number are very considera- ble. The inference will also be drawn from this, that in all ossi- OS FRONTIS. 61 fications from different nuclei, where these original mem- braneous septa do not exist, a suture will not be formed ; but the bones will join each other, as in a case of callus between the broken extremities of bones. When these septa become weak or thin, either from original tendency, as in the case of the sagittal suture, which in early life is continued to the root of the nose frequently ; or from advanced age, as in the case of nearly all sutures, the bones of the opposite sides amalga- mate, and no appearance of suture is left. It is easy to make a preparation illustrative of these facts, and one now exists in the museum of the University of Pennsylvania, in which, bv removing the bone from between the membranes by means of an acid, and afterwards rendering the membranes transparent with oil of turpentine, the septa are seen sufficiently distinctly.] Os Frontis. The os frontis, as its name imports, forms the front part of the cranium, and the upper portion of the orbits of the eyes. Fig. 10.* The external surface of this bone is smooth at its upper convex part; but several pro- cesses and cavities are ob- servable below; for at the angles of each orbit, the bone projects to form four processes, two internal, and as many external; which are denominated angular. Be- tween the internal and exter- nal angular processes on each side, an arched ridge is ex- * The external surface of the os frontis. 1. Frontal protuberance or boss of the right side. 2. The superciliary ridge. 3. Supra-orbital ridge. 4. External angular process. 5. Internal angular process. 6. Supra-orbital notch for the transmission of the supra-orbital nerve and artery; it is occasionally converted into a foramen. 7. The nasal or superciliary boss; the swelling around this point denotes the situa- tion of the frontal sinuses. 8. The temporal ridge, commencing from the external angular process (4). The depression in which fig. 8 is situated is a part of the tem- poral fossa. 9. The nasal spine. 6 62 OS FRONTIS. tended, on which the eyebrows are placed. Very little above the internal end of each of these superciliary ridges, a protuberance may be remarked in most skulls, called the superciliary or nasal boss, where there are large cavities within the bone, called sinuses. Between the internal angular processes, and in front of the vacuity for the ethmoid bone, the edge of the os frontis is serrated for articulation with the ossa nasi, and the process of the upper maxillary bone ; and from the centre of this sur- face a small process arises, which is called the nasal spine. From the under part of the superciliary ridges, the frontal bone runs a great way backwards: these parts are called orbitar processes, which, contrary to the rest of this bone, are concave externally, for receiving the globes of the eyes, with their muscles, fat, &c. In each of the orbitar processes, at the upper and outer portion of the orbit, a considerable sinuosity is observed, where the glandula lachrymalis is lodged. Near each internal angular process a small pit may be remarked, where the cartilaginous pulley of the superior oblique muscle of the eye is fixed. Between the two orbitar processes, there is a large vacuity which the cribriform part of the os ethmoides occupies. The frontal bone has frequently little caverns formed in it where it is joined to the ethmoid bone.. The foramina, or holes, observable on the external surface of the frontal bone, are three in each side. On each supra-orbital ridge, 3 fig. 10, at the distance of one- third of its length from the nose, is a foramen, or a notch, through which pass a branch of the ophthalmic artery and a small nerve called the supra-orbital. In the internal edge of each orbitar process are two other foramina denominated anterior and posterior orbitar, or eth- moidal foramina, which lead to the nose: sometimes they are only notches or grooves which join with similar grooves in the bones below, and form foramina. They transmit the anterior and posterior ethmoidal arteries and veins, and the former trans- mits likewise the internal nasal branch of the ophthalmic nerve. The internal surface of the os frontis is concave, except at OS FRONTIS. 63 the orbitar processes, which Fig.ll* are convex, and support the anterior lobes of the brain. This surface is not so smooth as the externa]; for the larger branches of the arteries of the dura mater make some furrows in its sides and back parts, and its lower and fore parts are marked with the convolutions of the anterior lobes of the brain. In the middle of the concave inter- nal surface is a groove, which is small at its commencement, and gradually increases in dia- meter as it proceeds upwards. This is formed by the superior longitudinal sinus; at its commencement is a ridge to which the beginning of the falciform process of the dura mater is attached. At the root of this ridge is a small foramen, some- times formed jointly by this bone and the ethmoid; it is deno- minated foramen cozcum ; in it a small process of the falx is inserted, and here the longitudinal sinus begins. The frontal sinuses are formed by the separation of the two tables of this bone at the part above the nose and the internal extremities of the superciliary ridges. In the formation of these cavities, the external table commonly recedes most from the general direction of the bone. * The internal surface of the frontal bone; the bone is raised in such a manner as to show the orbito-nasal portion. 1. The grooved ridge for the lodgment of the superior longitudinal sinus and attachment of the falx. 2. The foramen csecum. 3. The superior or coronal border of the bone; the figure is situated near that part which is bevelled at the expense of the internal table. 4. The inferior border of the bone. 5. The orbital plate of the left side. 6. The cellular border of the ethmoidal fissure. The foramen cajcum (2) is seen through the ethmoidal fissure. 7. The anterior and posterior ethmoidal foramina; the anterior is seen leading into its canal. 8. The nasal spine. 9. The depression within the external angular process (12) for the lachrymal gland. 10. The depression for the pulley of the superior oblique muscle of the eye ; immediately to the left of this number is the supra-orbital notch, and to its right the internal angular process. 11. The opening leading into the frontal sinuses. 12. The same parts are seen upon the opposite side of the figure. 64 OSSA PARIETALIA. These cavities are divided by a perpendicular bony partition, which is sometimes perforated and admits a communication between them. Their capacities are often very different in different persons, and on the different sides of the same person. In some persons whose foreheads were very flat, they are said to have been wanting. They communicate with the nose by means of a canal in the cellular part of the os ethmoides. The os frontis is composed of two tables, and an interme- diate diploe, as the other bones of the cranium are: it is of a mean thickness between the os occipitisand the parietal bones; and is nearly equally dense throughout, except the orbitar pro- cesses, where, by the action of the eye on one side, and pres- sure of the lobes of the brain on the other, it is made extremely thin and diaphanous, and the diploe is entirely obliterated. In this place there is so weak a defence for the brain, that fencers esteem a push in the eye mortal. In such skulls as have the frontal bone divided by the sagittal suture, the partition separating these cavities is evidently com- posed of two plates, which easily separate. Each of the frontal sinuses opens into one of the uppermost cells in the anterior part of the ethmoid bone, and this cell communicates with the middle channel of the nose under the anterior end of the os turbinatum superius. This bone is united with the parietal, ethmoidal and sphe- noidal bones of the head; and with the nasal, maxillary, ungui- form and malar bones of the face. Ossa Parietalia. Each of the two ossa parietalia is an irregular square; its upper and front edges being longer than the one behind or below. The inferior edge is concave, the middle part receiving the upper round part of the temporal bone. The angle formed by the under and anterior edges is so extended as to have the appearance of a process. The external surface of each os parietale is convex. Upon it, somewhat below the middle height of the bone, there is a OSSA PARIETALIA. 65 transverse arched ridge, ge- nerally of a whiter colour than any other part of the bone: from which, in bones that have strong prints of muscles, we see a great many converging furrows, like so many radii drawn from a circumference towardsacen- tre. From this ridge of each bone the temporal muscle rises: and, by the pressure of its fibres, occasions the furrows just now mentioned. Below these we observe, near the semi- circular edges, a great many risings and depressions, which are joined to like inequalities on the inside of the temporal bone, and form the squamous suture. Near the upper edges of these bones, towards the hind part, is a small hole in each, through which a vein passes from the teguments of the head to the longitudinal sinus.t On the inner concave surface of the parietal bones we see a great many deep furrows, disposed somewhat like the branches of trees : the furrows are largest and deepest at the lower edge of each os parietale, especially near its anterior angle, where a complete canal is sometimes formed. [These furrows are made by the ramifications of the great middle artery of the dura mater: they have been commonly attributed to the pulsation of the artery causing the absorp- tion of the bone, but it is more probable that the deposition of the bone has been prevented where the artery beats, and fhus the bone becomes modelled over the artery in the same way that it is made to conform ^o the surface of the brain. If it * The external surface of the left parietal bone. 1. Superior or sagittal border. 2. Inferior or squamous border. 3. Anterior or coronal border. 4. Posterior or lambdoidal border. 5. The temporal ridge. The figure is situated immediately over the parietal protuberance. 6. The parietal foramen, unusually large. 7. The anterior inferior angle. 8. The posterior inferior angle. t It transmits, also, an artery from the integuments to the dura mater, and is called the parietal foramen.—?. 6* 66 OSSA TEMPORUM. were exclusively an absorption and not a deposition, we should scarcely find the artery occasionally surrounded perfectly by bone.] Fi"-. 13.* On the inside of the up- per edge of the ossa parie- talia there is a large sinuos- ity, frequently larger in the bone of one side than of the other, where the upper part of the falx is fastened, and the superior longitudinal sinus is lodged. Part of the late- ral sinuses generally makes a depression near the angle i formed by the lower and posterior edges of these bones; and the pits made by the convolutions of the brain are in no part of the skull more frequent or more conspicuous, than in the internal surface of these bones. The ossa parietalia are the most equal and smooth, and are among the thinnest bones of the cranium; but they enjoy the general structure of two tables and diploe most perfectly. These bones are joined at their foreside to the os frontis, at their long inferior angles, to the sphenoid bone ; at their lower edge, to the ossa temporum ; behind to the os occipitis, or ossa triquetra ; and above, to one another. Ossa TemporumA The ossa temporum are situated at the lateral and inferior * The internal surface of the left parietal bone. 1. The superior, or sagittal border. 2. The inferior, or squamous border. 3. The anterior, or coronal border. 4. The posterior, or lambdoidal border. 5. Part of the groove for the superior longitudinal sinus. 6. The internal termination of the parietal foramen. 7. The anterior inferior angle of the bone, on which is seen the groove for the trunk of the arteria meningea media. 8. The posterior inferior angle, upon which is seen a portion of the groove for the lateral sinus. t This bone has received the name of temporal, because at the region which it covers, the hair usually commences to turn gray, and thus in some measure indi- cates the different periods of life.—p. OSSA TEMPORUM. 67 parts of the cranium; each of them is divided into three portions, a superior or squamous, a posterior or mastoid, and a middle or petrous. The squamous portion is nearly semicircular in form, and very thin; its edge is sharp, and the inner table appears pared away to form the squamous suture with the corresponding edge of the parietal bone. Its external surface is covered by the temporal muscle. At the lower and anterior part of this surface, the zygomatic process arises, it proceeds forward to join the cheek bone, and form an arch under which the tem- poral muscle passes. At the base of the process is the glenoid cavity for the condyle of the lower jaw. Immediately before this cavity is a tubercle or protuberance, near the commencement of the zygoma and at its lower border, to which the external lateral ligament of the lower jaw is attached; continued horizontally inwards from the tubercle there is a rounded eminence, called the emi- nentia articularis, which forms part of the articular surface on which the condyle rises when the jaw is opened. In the pos- terior part of the cavity is a fissure—called the glenoid—in which part of the ligament of this articulation is fixed. In this fissure is an aperture—glenoid foramen—which communi- cates with the cavity of the tympanum of the ear, and is occu- pied by a small nerve called chorda tympani; and also by the anterior muscle of the malleus—one of the small bones of the ear. The internal surface of the squamous portion is concave ; it is marked by pits and small eminences, which correspond with the convoluted surface of the brain, and also by impressions of the arteries of the dura mater, see 4 fig. 13, as they go towards the parietal bone. The mastoid or occipital portion is the smallest of the three parts of the bone; it consists of an angular portion, which occupies a vacuity between the occipital and parietal bones; and of the mastoid process. The mastoid process has some resemblance to the nipple; it is composed internally of cells which communicate with the cavity of the tympanum. On 68 OSSA TEMPORUM. the internal side of its base is a deep groove in which the pos- terior belly of the digastric muscle is inserted. Behind this process is the mastoid hole, which transmits a vein, and some- times a small artery. On the internal surface of this portion is a large groove, which is formed by the lateral sinus. The mastoid hole above mentioned, opens into this groove . ■' The petrous portion, which is Fig. 14.* situated between the squa- mous and mastoid, resembles a triangular pyramid lying on one of its sides. When in its proper position it projects inward and forward. The two upper sides form a por- tion of the internal surface of the base of the cranium. The angle formed by these sur- faces is very prominent, and divides the fossa for the middle lobes of the brain, or rather the cavities for the cerebrum from those which contain the cerebellum. One of these sides of the petrous portion looks forward and outward, the other backward and inward. Each of them has eminences and depressions to correspond with the convolutions of the brain. Near the middle of the anterior side is a small furrow, leading to a foramen denominated Innominatum or Hiatus Fallopii, which transmits the vidian nerve to the aqueduct of Fallopius. * The external surface of the temporal bone of the left side. 1. The squamous portion. 2. The mastoid portion. 3. The extremity of the petrous portion. 4. The zygoma. 5. Indicates the tubercle of the zygoma, and at the same time its anterior root turning inwards to form the eminentia articularis. 6. The superior root of the zygoma, forming the posterior part of the temporal ridge. 7. The middle root of the zygoma terminating abruptly at the glenoid fissure. 8. The mastoid foramen. 9. The meatus auditorius externus, surrounded by the processus auditorius. 10. The digastric fossa, situated immediately to the inner side of (2) the mastoid process. 11. The styloid process. 12. The vaginal process. 13. The glenoid or Glaserian fissure ; the leading line from this number crosses the rough posterior portion of the glenoid fossa. 14. The opening and part of the groove for the Eustachian tube. OSSA TEMPORUM. 69 —There is another small oblique foramen immediately beneath this, whichjtransmits the nervous petrosus superficialis minor, a branch of Jacobson's nerve; near the apex of the petrous portion of the temporal bone there is seen a large foramen, the termination of the carotid canal. On this anterior face of the bone, especially in the young subject, is seen a rising or eminence running from base to apex, which is formed by the projection of the perpendicular semicircular canal. About the middle of the posterior side is the large aperture called meatus auditorius internus. The bottom of this cavity is perforated by several foramina : the largest and uppermost of which is the orifice of a winding canal, called improperly the aqueduct of Fallopius, which transmits the portio dura of the seventh pair of nerves. The other foramina transmit the fibres of the portio mollis of the same nerve. Posterior to the orifice of the meatus internus is an oblong depression, with a foramen in it, covered by a shell of bone, which is the orifice of a proper aqueduct or canal that passes from the vestibule of the ear.* —Neither of the so called aqueducts of the vestibule or cochlea, are deserving of the name which has nevertheless been continued to designate them, since we no longer believe with Cotugnius their discoverer, that they are a sort of passages, to admit of the overflow of the lymph, when it was secreted in superabundance in the labyrynth. They are both mere openings, for the transmission mainly of blood vessels. The aqueduct of the vestibule transmits a small artery and vein to the vestibule, and lodges a process of the dura mater.— The inferior side of the petrous portion forms a part of the external surface of the basis of the cranium. On the back part of it is the external orifice of the canal, through which the portio dura passes. It is called foramen stylo mastoideum. Before this foramen is a long and slender styloid process, which varies from one to two inches in length ; it projects * This orifice should not be confounded with one which is nearer to the meatus internus, and situated on the angle made by the two sides of the bone.—h. 70 OSSA TEMPORUM. almost perpendicularly from Fig. 15.* the basis of the cranium, and gives origin to a muscle of the tongue, of the os hyoides, and of the pharynx, and also to several ligaments. The base of this process is surrounded by a flat projection of bone, occasionally called the vaginal process. On the inside of this pro- cess, and rather before it, is the jugular fossa, which, when applied to a corresponding part of the occipital bone, makes the posterior foramen lacerum, through which the internal jugular vein, and the eighth pair of nerves pass out. A small spine called the jugular process often projects into this foramen from the temporal bone, and separates the nerve from the vein; the nerve being anterior. —Upon a ridge which is found at the root of this spine, and just behind the margin of the carotid foramen, there is a small opening leading into the canal which transmits Jacobson's tympanic branch of the glosso-pharyngeal nerve, which forms * The left temporal bone, seen from within. 1. The squamous portion. 2. The mastoid portion. The number is placed immediately above the inner opening of the mastoid foramen. 3. The petrous portion. 4. The groove for the posterior branch of the arteria meningea media. 5. The bevelled edge of the squamous border of the bone. 6. The zygoma. 7. The digastric fossa immediately internal to the mastoid process. 8. The occipital groove. 9. The groove for the lateral sinus. 10. The elevation upon the anterior surface of the petrous bone marking the situation of the perpendicular semicircular canal. 11. The opening or termination of the carotid canal. 12. The meatus auditorius internus. 13. A dotted line leads upwards from this number to the narrow fissure which lodges a process of the dura mater. Another line leads downwards to the sharp edge which conceals the opening of the aquaeductus cochleae, while the number itself is situated on the bony lamina which overlies the opening of the aquaeductus vestibuli. 14. The styloid process. 15. The stylo-mastoid foramen. 16. The carotid foramen. 17. The jugular process. The deep excavation to the left of this process forms part of the jugular fossa, and that to the right is the groove for the vein of the cochlea. 18. The notch for the fifth nerve upon the upper border of the petrous bone, near to its apex. 19. The extremity of the petrous bone which gives origin to the levator palati and tensor tympani muscles- OSSA TEMPORUM. 71 an important part of the nervous plexus of the tympanum.— Before this spine, or partition, is the orifice of the second aqueduct of the ear, the aqueduct of the cochlea, through which passes a vein from the cochlea to the internal jugular, and in which is lodged a process of the dura mater. This jugular fossa is at the termination of the groove, in the internal surface of the bone, made by the lateral sinus. At a small distance before the jugular fossa is the commencement of the carotid canal, which makes a curve almost semicircular, and then proceeds in a horizontal course to the anterior extremity of the bone : through this winding canal passes the carotid artery, and the filaments from the fifth and sixth pair of nerves, which are the beginning of the intercostal or sympathetic nerve. Between the carotid canal and the cavity for the condyle of the lower jaw, at the junction of the anteror part of the squamous portion with the petrous portion of this bone, is a very rough aperture, the bony margin of which appears broken; this is the orifice of the bony part of the Eustachian tube, or passage from the throat to the ear. This canal is divided lengthwise by a thin bony plate ; the upper passage contains the internal muscle of the malleus bone of the ear (tensor tympanij; the lower and largest canal is the bony part of the Eustachian tube. The external passage to the ear, called Meatus Auditorius Externus, is situated between the zygomatic and the mastoid processes. The orifice is large and smooth above, but rough below, and is surrounded by a rough lip called the auditory process. The direction of the canal is obliquely inward and forward. —Angles of the bone. The superior angle of the bone which separates the anterior and posterior faces, is sharp and gives attachment to the tentorium cerebelli. It is slightly grooved for the lodgement of the superior petrous sinus, and near its extremity is marked by a smooth notch, upon which rests the fifth or trigeminus nerve. The anterior angle which separates the anterior from the inferior or basilar surface of the bone, is grooved for the Eustachian tube, and forms the posterior 72 OS OCCIPITIS. boundary of the foramen lacerum anterius of the base of the cranium. The posterior angle separating the posterior from the basilar surface of the bone, is grooved for the inferior petrous sinus and excavated for the jugular fossa: it forms the anterior boundary of the foramen lacerum posterius.— The temporal is articulated with the parietal, occipital and sphenoidal bones, and by its zygomatic process with the malar bone. Os Occipitis. The occipital bone is situated at the posterior and inferior part of the cranium ; it is of a rhomboidal figure, with convex and concave surfaces. Fig. 16.* The upper part of the ex- ternal surface is smooth: at a small distance above the middle of the bone is the external occipital protuber- , ance, with a curved line on fy each side of it. Near the middle of the bone the tra- pezii muscles are attached to this line, and externally, on each side, the occipito fron- talis, and the sterno mas- toideus. Under this line is a depression, on each side, into which are inserted the complexus and the splenius capitis muscles. Below this is the inferior curved line, and still lower is a * The external surface of the occipital bone. 1. The superior curved line. 2. The external occipital protuberance. 3. The spine or vertical ridge. 4. The inferior curved line. 5. The foramen magnum. 6. The condvls of the right side. 7. The posterior condyloid fossa, in which the posterior condyloid foramen is found. 8. The antenor condyloid foramen, concealed by the margin of the condyle. 9. The jugular eminence or transverse process as it is sometimes called. 10. The notch in front of the jugular eminence, which forms part of the jugular foramen. 11. The basilar process. 12. The rough projections into which the moderator laments OS OCCIPITIS. 73 muscular depression to which the rectus minor posticus is attached on each side near the middle ; and the rectus major posticus, and obliquus superior, near the end. Below the protuberance is a spine which passes down the middle of the bone, and at the lower extremity of this spine is the great occipital foramen, which forms the communication between the cavities of the cranium, and the vertebral column. This great opening transmits the medulla spinalis with its membranes, the accessary nerves of Willis, and the vertebral arteries and veins. It is rather of an oval form, and the occipital condyles are situated anteriorly on its edges. These condyles are of an irregular oval figure; they are not parallel, but incline towards each other anteriorly. Their articulating surfaces are oblique, looking downward and outward; they are received into corresponding cavities of the atlas, or first cervical vertebra, and form with them the articulation of the head and neck. From the oblique position of their articulating surfaces, as well as the length of their ligaments and the inclination of their axes towards each other, it results, that their motion is confined to flexion and extension. On the internal sides of these condyles is a rough surface, to which are attached the strong ligaments that come from the processus dentatus of the second vertebra of the neck. Behind each condyle is a depression in which is situated the posterior condyloid foramen, for transmitting the cervical veins ; and at their anterior extremities are two large foramina, (anterior condyloid,) through which pass the ninth pair of nerves. On the internal surface of the os occipitis is the crucial ridge, to which are attached the falx cerebelli or vertical, and the tentorium or horizontal process of the dura mater. The groove made by the longitudinal sinus continues from the sagittal suture along the upper limb of this cross. Some- times it is on the side of the ridge, and sometimes the ridge is depressed, and it occupies its place; at the centre of the cross, where is lodged the torcular Herophili, formed by the 7 74 OS OCCIPITIS. common junction of the sinuses, the groove for the longitu- dinal sinus divides into two grooves for the lateral sinuses; Fig. 17.* these form the horizontal limbs of the cross, and pro- ceed towards the foramen lacerum where the lateral sinuses emerge from the cavity of the cranium. The lower limb of the cross is formed by a spine which pro- ceeds from the centre of the bone to the great occipital fora- men, and supports the falx of the cerebellum. The internal surface of the bone is divided by the cross into four por- tions, each of which is con- siderably depressed so as to form fossae; the two upper by the posterior lobes of the cerebrum, and the lower by those of the cerebellum. This circumstance occasions great inequalit3T in the thickness of the bone, as the depressed portions are extremely thin, while the ridge adds greatly to the thickness, especially at the centre of the cross, which is opposite to the great external protuber- ance. Before the great occipital foramen is the cuneiform process, which is thick and substantial; it terminates by a broad truncated extremity, that is articulated with the body of the sphenoid bone. The internal surface of the cuneiform process * The internal surface of the occipital bone. 1. The left cerebral fossa. 2. The left cerebellar fossa. 3. The groove for the posterior part of the superior longitudinal sinus. 4. The spine for the falx cerebelli, and groove for the occipital sinuses. 5. The groove for the left lateral sinus. 6. The internal occipital protuberance which lodges the torcular Herophili. 7. The foramen magnum. 8. The basilar process, grooved for the medulla oblongata. 9. The termination of the groove for the lateral sinus, bounded externally by the jugular eminence. 10. The jugular fossa; this fossa is completed by the petrous portion of the temporal bone. 11. The superior border. 12. The inferior border. 13. The border which articulates with the petrous portion of the temporal bone. 14. The anterior condyloid foramen. OS ETHMOIDES. 75 is somewhat excavated, and forms a large superficial groove for the medula oblongata; on each side of this groove is a small furrow for the inferior petrous sinuses. The two upper edges of the occipital bone are serrated, to articulate, with those of the parietal, and form the lambdoidal suture. The inferior edges are divided into two portions by a small prominence called the jugular eminence ; the upper and posterior portion is also serrated for articulation with the mastoid portion of the temporal; the inferior portion, which is not serrated, applies to the petrous portion of the temporal bone, and a notch in it contributes to the formation of the foramen lacerum. The upper angle of this bone is acute, the lateral angles are obtuse, and the inferior truncated. It is articulated with the parietal, the temporal, and the sphenoidal bones. Os Ethmoides. The os ethmoides is truly one of the most curious bones of the human body. It appears almost a cube, not of solid bone, but exceedingly light and spongy, and consisting of many con- voluted plates, which form a network like honey-comb. It is firmly enclosed in the os frontis, betwixt the orbitary processes of that bone. One horizontal plate receives the olfactory nerves, which perforate that plate with such a number of small holes, that it resembles a sieve ; whence the bone is named cribriform, or ethmoid. Other plates are so arranged that they form a cellular structure, on which the olfactory nerves are expanded by means of a particular membrane; while an additional plate, appropriated to the nose, descends into that cavity in a perpen- dicular direction, and forms a large proportion of the partitio n which divides it into two chambers. The cribriform plate is situated in the anterior part of the basis of the cranium. The cellular part occupies most of the space between the orbits of the eyes, and the perpendicular plate is to be found in the septum of the nose. The ethmoid bone, for the purposes of description, may be divided into three parts, viz. the cribriform plate, the nasal o r perpendicular lamella, and the cellular portions. 76 OS ETHMOIDES. The cribriform plate is oblong in shape, and firm in its structure; in the middle of the anterior extremity the crista galli projects from its upper surface, dividing it into two lateral portions, each of which is rather concave, and occupied by the bulbous extremity of the olfactory nerve; it is perforated by many foramina, which transmit the fibres of the aforesaid nerve. Near the crista galli, on each side, there is a small fis- sure, through which passes a nervous filament derived from the ophthalmic branch of the fifth pair. The crista galli varies in size in different subjects: the beginning of the falciform process of the dura mater is attached to it, and with the opposite part of the os frontis it forms the foramen caecum, already mentioned. It is very conspicuous in the basis of the cranium. The nasal plate of the ethmoid bone seems to be continued downwards from the crista galli through the cribriform plate. It is thin, but firm; it forms the upper portion of the septum of the nose, and, to complete the partition, it unites with the vomer and with a plate of cartilage before. It is very often inclined to one side, so that the nostrils are not of equal size. At a small distance from this perpendicular plate, on each side of it, the cellular portions originate from the lower surface of the cribriform plate; they extend from before backward, and are as long as the ethmoid bone ; their breadth between the eye and the cavity of the nose varies in different subjects, from half an inch to more; they extend downwards from the root of the nose or from the cribriform plate, more than half way to the roof of the mouth. Their external surface on each side forms a part of the surface of the orbit of the eye, and is called os planum; their internal surface forms part of the external lateral surface of each nostril. This surface extends the whole depth of the nostril, from before backward; but in many skeletons it is extremely imperfect, owing to the great brittleness of the bony plates of which it is composed. When the bone is perfect, the uppermost half part of this internal surface is uniformly flat, and rather rough; but below it, about the middle of the bone, a deep groove begins, which extends downwards and backwards, to the posterior extremity; this is OS ETHMOIDES. 77 the upper channel or meatus of the nose. The edge of the surface immediately above it projects in a small degree over this channel or groove ; having been described by Morgagni, it bears his name, and may be considered as one of the spongy or turbinated bones; from its situation, it should be called the first or superior. The groove is very deep, and most of the cells of the posterior part of the ethmoid bone communicate with it, through one or more foramina at its anterior extremity. The part of the surface of the ethmoid which is immediately below this groove, is convex; that which is before and below it, is rather flat; the convex part is the middle spongy or turbinated bone, as it has commonly been called; it projects obliquely into the cavity of the nose, and hangs over the middle channel or meatus, which is immediately below the ethmoid bone. The internal surface of this spongy bone, which is opposite the septum of the nose, is convex and rough or spongy; the external surface is concave. The anterior cells of the ethmoid, and particularly those which the frontal sinuses on each side communicate with, open into the middle channel or meatus, under the anterior end of this turbinated bone. This middle channel or meatus, is much larger than that above; it extends from the anterior to the posterior part of the nostrils, and slopes downwards and backwards. The cavity of the upper maxillary bone, or the antrum highmorianum, opens on each side into this meatus, and a thin plate of bone extends from the cellular part of the ethmoid so as to cover a part of it. The cellular portions of the ethmoid are composed of plates thinner than the shell of an egg; they are entirely hollow, and the cells are very various, in number, size, and shape. Some cells of the uppermost row communicate with those of the os frontis, formed by the separation of the plates of the orbitar process of that bone. From the posterior part of the cribriform plate, where it is in contact with the lesser wings of the sphenoidal bone, thin plates of bone pass down upon the anterior surface of the body of the os sphenoides, one on each side of the azygos process, and often diminish the opening into the sphenoidal cells. 7* 78 OS ETHMOIDES. These plates are sometimes triangular in form, the basis uniting with the cribriform plate. They have been described very differently by different authors, some considering them as belonging to the os ethmoides, and others to the sphenoid bone. To the perfect ethmoid bone there are attached two triangular pyramids, in place of the triangular bones; these pyramids are hollow, the azygos process of the os sphenoides is received between them; one side of each pyramid applies to each side of the azygos process, another side applies to the anterior surface of the body of the sphenoid bone, in place of the ossa triangularia, and the third side is the upper part of one of the posterior nares,* There are two apertures in each of these * This may be considered as an original observation of the lamented Wistar. The merit of it has been denied to him, more particularly by the anatomists of Paris, , under an impression that he had been anticipated in it by Berlin, who has written an excellent and minute treatise on osteology. The extent to which the claims of other anatomists interfere with his, he was fully aware of; and it will be seen by the fol- lowing communications to the American Philosophical Society, that these are placed in as important a light as they deserve, at the same time that he vindicates his own pretensions, to have first observed the " cornets sphenoidaux" in the form of trian- gular hollow pyramids, as constituting part of the perfect ethmoid bone.—h. Observations on those Processes of the Ethmoid Bone which originally form the Sphe- noid Sinuses. By C. Wistar, M. D., President of the Society, Professor oj Anatomy in the University of Pennsylvania.—Read, Nov. 4, 1814. "" It has been long believed that the sinuses, or cavities in the body of the os sphe- noides, were exclusively formed by that bone, when Winslow suggested that a small portion of the orbitar processes of the ossa palati contributed to their formation.* Many years after Winslow's publication, Monsieur Bertin described two bones which form the anterior sides of these sinuses, and contain the foramina by which they communicate with the nose.t These bones he denominates " Cornets Sphenoidaux," and states that they are most perfect and distinct between the ages of four years and twenty ; that they are not completely formed before this period, and that after it they appear like a part of the sphenoidal bone.—According to his account they are lamina of a triangular form, and are originally in contact with the anterior and inferior surface of the body of the os sphenoides, so that they form a portion of the surface of the cavity of the nose.— He believed, that as they increase in size, they become convex and concave, and present their concave surfaces to the body of the sphenoidal bone, which also becomes concave, and presents its concavity to those bones; thus forming the sinuses. * In his description of the Ossa Palati, printed in the Memoirs of the Academy of Sciences for 1720. ' t See Memoirs of the Academy of Sciences for 1774. OS SPHENOIDES. 79 pyramids ; one at the base opening directly into the nose, near the situation of the opening of the sphenoidal sinuses, in the bones of adults; and the other in each of the sides in contact with the azygos process. Os Sphenoides. The os sphenoides or pterygoideus, resembles a bat with its wings extended. It consists, This account of M. Bertin has been adopted by Sabatier, and also by Boyer, who has improved it by the additional observation, that these triangular bones are some- times united to the ethmoid, and remain attached to that bone when it is separated from the os sphenoides. Bichat and Fyfe have confirmed the description of Boyer. The specimens of ethmoid and sphenoid bones, herewith exhibited to the society, will demonstrate that in certain subjects, about two years of age, there are continued from the posterior part of the cribriform plate of the ethmoid, two Hollow Triangular Pyramids, which, when in their proper situations, receive between them the azygos process of the os sphenoides.—(See Plate X. Figures 1, 2, 3, with the explanation.) The internal side of each of these pyramids applies to the aforesaid azygos process ; the lower side of each forms part of the upper surface of the posterior nares; the external side at its basis is in contact with the orbitar process of the os palati. The base of each pyramid forms also a part of the surface of the posterior nares, and con- tains a foramen which is ultimately the opening into the sphenoidal sinus of that side. In the sphenoidal bones, which belong to such ethmoids as are above described, there are no cells or sinuses; for the pyramid of the ethmoid bones occupy their places. The azygos process, which is to become the future septum between the sinuses, is remarkably thick, but there are no cavities or sinuses in it. The sides of the pyramids, which are in contact with this process, are extremely thin, and sometimes have irregular foramina in them, as if their osseous substance had been partially absorbed.* That part of the external side of the pyramid which is in contact with the orbitar process of the os palati is also thin, and sometimes has an irregular foramen, which communicates with the cells of the aforesaid orbitar process. Upon comparing these perfect specimens of the ethmoid and sphenoidal bones of the subject about two years of age, with the os sphenoides of a young subject who was more advanced in years, it appears probable that the azygos process and the sides of the pyramid applied to it, are so changed, in their progress of life, that they simply constitute the septum between the sinuses; that the external side of the pyramid is also done away, and that the front side and the basis of the pyramid only remain ; constituting the Cornets Sphenoidauxt of M. Bertin. If this be really the case, the origin of the sphenoidal sinuses is very intelligible. * See e, Fig. 3. t " Cornet" is the word applied by several French anatomists to the Ossa Turbinati of the nose • they seem to have intended to express by it a convoluted lamina or plate of bone. The fine drawing of the Ethmoid Bone, for this plate was done by my friend M. Lesueur, whose talents are so conspicuous in the plates attached to Peron's " Voyage de Descouvertes aux Terres Australes." SO OS SPHENOIDES. 1st. Of a body with two processes arising from it, called the lesser wings, or apophyses of Ingrassias. 2dly. Of two large lateral processes, called the greater wings, or temporal processes; and, 3dly. Of two vertical portions, denominated pterygoid pro- cesses. The body is situated near the centre of the cranium, and in contact with the cuneiform process of the occipital bone ; the greater wings extend laterally between the frontal and temporal bones as high as the parietal; while the pterygoid processes pass downwards on each side of the posterior opening of the nose, as low as the roof of the mouth. It is, therefore, in contact with all the other bones of the cranium, and with many bones of the face. The body has a cubic figure; its upper surface forms a portion of the basis of the cranium; its lower and anterior surfaces form part of the cavity of the nose ; the posterior surface is articu- lated with the cuneiform process of the occipital bone; and Explanation of the Figures in the Plate referred to above. FIG. I. Represents the upper surface, or cribriform plate of the Ethmoid Bone. a. Crista Galli. bbbb. Cribriform plate. c. Surface denominated Os Planum. d d. Hollow Triangular Pyramids. e. Space between the Pyramids for receiving the Azygos Process of the Os Sphe- noides. FIG. II. A lateral View of the Bone. • a. Crista Galli. c. Os Planum. d. Triangular Pyramid. FIG. III. The Bone Inverted. a. The Nasal Plate of the Ethmoid Bone, which constitutes the upper portion of the Septum of the nose. f f ™°n TfT °f *e„Ethmoid which are called Superior Turbinated Bones. //. The Cellular Lateral Portions of the Bone. d d. The Triangular Pyramids. e. Space between the Pyramids for the Azygos Process of the Os Sphenoides- a foramen on the internal side of one of the Pyramids. r ■J OS SPHENOIDES. 81 laterally it is extended into the great wings, or temporal pro- cesses. On the upper surface of the body, the lesser wings or the apophyses of Ingrassias,* project from the lateral and anterior parts; these wings consist of two triangular plates, each of Fig. 18.t which is joined to the other by its base, and to the body of the os sphenoides by its un- der surface near the base, and terminates in a point; their direc- tion is forwards and outwards, and their flat surfaces are horizontal. Anteriorly they are connected by suture to the ethmoid and frontal bones ; their posterior edge is rounded, and detached from any other bone, forming the upper margin of the foramen lacerum of the orbit of the eye; this edge is thick and prominent at its internal extremity, and these prominences are called the anterior or clinoid processes; immediately before them are the optic foramina, which pass * A physician of Palermo, who died in 1580, aged 70.—h. t The superior or cerebral surface of the sphenoid bone. 1. The processus olivaris. 2. The ethmoidal spine. 3. The lesser wing of the left side. 4. The cerebral surface of the greater wing of the same side. 5. The spinous process. 6- The extremity of the pterygoid process of the same side, projecting downwards from the under surface of the body of the bone. 7. The foramen opticum. 8. The anterior clinoid process. 9. The groove by the side of the Sella Turcica, for lodging the internal carotid artery, cavernous plexus, cavernous sinus, and orbital nerves. 10. The Sella Turcica. 11. The'posterior boundary of the Sella Turcica; its projecting angles are the posterior clinoid processes. 12. The basilar portion of the bone. 13. Part of the sphenoidal fissure. 14. The foramen rotundum. 15. The foramen ovale. 16. The foramen spinosum. 17. The angular interval which receives the apex of the petrous portion of the temporal bone. The posterior extremity of the Vidian canal terminates at this angle. 18. The spine of the spinous process; it affords attachment to the internal lateral ligament of the lower jaw. 19. The border of the greater wing and spinous process which articulates with the anterior part of the squamous portion of the temporal bone. 20. The internal border of the spinous process, which assists in the formation of the foramen lacerum basis cranii. 21. That portion of the greater ala which articulates with the anterior inferior angle of the parietal bone. 22. The portion of the greater ala which articulates with the orbital process of the frontal bone. 82 OS SPHENOIDES. obliquely through the wings into the orbit of the eye, and transmit on each side the optic nerve and a small artery. Behind the optic foramen is a notch and sometimes a foramen, made by the carotid artery. When the notch is converted into a foramen, it is by a small bony pillar being extended from the anterior clinoid process, to the body of the sphenoid. A groove made by the optic nerves, is often seen extending across the body of the bone, from one of the optic foramina to the other. Behind it is a depression, which occupies the greatest part of this surface of the bone, in which the pituitary gland is lodged; the back part of this depression is bounded by a transverse emi- nence, called the posterior clinoid process. These three pro- cesses are called clinoid from their supposed resemblance to the supporters of a bed; and the depression for the pituitary gland is called sella turcica from its resemblance to the saddle used by the Turks. On each side of the posterior clinoid process is a groove in the body of the bone, made by the carotid artery as it passes from the foramen caroticum of the temporal bone. The posterior surface of the body of the sphenoides is rough,for articulation with the truncated end of the cuneiform process of the os occipitis. On the anterior and inferior surfaces is a spine, called the azygos process," or rostrum which is received into the base of the vomer, and extends forward until it meets the nasal plate of the ethmoid bone; on each side of this spine, in the anterior surface, are the orifices of the sphenoidal cells. Those orifices appear very differently in different bones; in some very perfect specimens, they are irregularly oval, being closed below and on their external sides, by the processes of the ossa palati, and above by the triangular plates, as they have been called, of the ethmoid bone. The cells or sinuses, to which these orifices lead, occupy the body of the sphenoidal bone; they are divided by a partition, and each of them has a communication with the cavity of the nose on its respective side, by the orifice above described. The sinuses do not exist during infancy; they increase in the progress of life, and are very large in old age. OS SPHENOIDES. 83 Laterally, the body of the sphenoides is extended into the portions called the great wings or temporal processes. These great wings compose the largest part of the bone, and their internal surface forms a portion of the middle fossa of the base of the cranium. Externally, the surface of each great wing is divided into two portions: one of which is lateral, and unites to the frontal, temporal, and malar bones, forming part of the smooth surface for the temporal muscle; the other portion forms part of the orbit of the eye, and is very regular and smooth. As the ethmoid bone forms part of the inside this portion of the great wing forms part of the outside of the orbit, and is termed the orbitary process of the sphenoid bone. The horizontal part of each wing terminates in an acute angle termed spinous process, which penetrates between the petrous portion and the articulating cavity of the temporal bone. In this angle is the foramen for the principal artery of the dura mater; near the point of the angle is a small process, which projects from the basis of the cranium, and is called styloid. Fig. 19.* The pterygoid pro- cesses pass downwards in a direction almost per- pendicular to the base of the skull. Each of them has two plates, and a middle fossa facing back- wards; to complete the comparison, they should be likened to the legs of the bat, but are inaccurately named pterygoid, or wing-like processes. The external plates are broadest, and the internal are longest. From each side of * The antero-inferior view of the sphenoid bone. 1. The ethmoid spine. 2. The rostrum. 3. The sphenoidal spongy bone, partly closing the left opening of the sphenoidal cells. 4. The lesser wing. 5. The foramen opticum piercing the base of the lesser wing. 6. The sphenoidal fissure. 7. The foramen rotundum. 8. The orbital surface of the greater wing. 9. Its temporal surface. 10. The pterygoid ridge. 11. The pterygopalatine canal. 12. The foramen of entrance to the Vidian canal. 13. The internal pterygoid plate. 14. The hamular process. 15. The external pterygoid plate. 16. The foramen spinosum. 17. The foramen ovale. 18. The extremity of the spinous process of the sphenoid. 84 FORAMINA OF THE SPHENOIDAL BONE. the external plates the pterygoid muscles take their rise. At the root of each internal plate, a small hollow may be remarked, where the musculus circumflexus palati rises, and part of the cartilaginous end of the Eustachian tube rests. At the lower end of the plate is a hook-like process {hamulus) round which the tendon of the last named muscle plays, as on a pulley. The ossa palati, on each side, rest upon these internal plates; and, therefore, the pterygoid processes seem to support the whole face. Foramina of the Sphenoidal Bone. Before these foramina are described, it is necessary to state, that the nerves of the brain are named numerically, beginning with the olfactory, which is foremost. It should also be observed, that each nerve of the fifth pair is divided, before it passes from the cavity of the cranium, into three large branches. The first foramina are the optic, which have been already described; they transmit the optic, or second pair of nerves, and a small artery, to the ball of the eye. The second foramen, on each side, is the foramen lacerum. It commences largely at the sella turcica, and extends laterally a considerable distance, until it is a mere fissure. The upper margin of this foramen is formed by the anterior clinoid processes, and the edges of the smaller wings of the sphenoid bone. This foramen transmits the third, fourth, and sixth pair of nerves, and the first branch of the fifth pair, to the muscles, and the other parts, subservient to the eye. The foramen rotundum, or third hole, is round ; as its name imports. It is situated immediately under the foramen lacerum, on each side, and transmits the second branch of the fifth pair of nerves to the upper maxillary bone. The foramen ovale is the fourth hole. It is larger than the foramen rotundum, and half an inch behind it. It transmits the third branch of the fifth pair of nerves to the lower jaw. The fifth hole is the foramen spindle. It is small and round, and placed in the point of the spinous process, behind the foramen ovale, to transmit the principal artery of the dura mater, which makes its impression upon the parietal bone. THE FACE. 85 The sixth foramen is under the basis of each pterygoid process, and is therefore called the pterygoid, or the Vidian* foramen. It is almost hidden by the point of the petrous portion of the temporal bone, and must be examined in the separated bone. It is nearly equal in size to the spinous hole. This foramen transmits a nerve that does not go out from the cavity of the skull, but returns into it. The second branch of the fifth pair, after passing out of the cranium, sends back, through this foramen, a branch called the Vidian, which upon its arrival in the cavity of the cranium, enters the temporal bone by the foramen innominatum. Of the Face. The face is the irregular pile of bones composing the front and under part of the head, and is divided into the upper and lower maxillae, or jaws. The upper jaw consists of six bones on each side, of one single bone placed in the middle, and of sixteen teeth. The thirteen bones are, two ossa maxillaria superiora, two ossa nasi, two ossa unguis, two ossa malarum, two ossa palati, two ossa spongiosa inferiora, and the vomer. The ossa maxillaria superiora form the principal part of the cavity of the nose, with the whole lower and forepart of the upper jaw, and a large proportion of the roof of the mouth. The ossa nasi are placed at the upper and front part of the nose. The ossa unguis are at the internal angles of the orbits of the eyes. The ossa palati in the back part of the palate, extending upwards to the orbits of the eyes. The ossa spongiosa in the lower part of the cavity of the nose; and The vomer in the partition which separates the two nostrils. * From its reputed discoverer, Vidius, a professor at Paris. 8 86 OSSA MAXILLARIA SUPERIORA. Ossa Maxillaria Superiora. The ossa maxillaria superiora, or upper jaw bones, may be considered as the basis or foundation of the face; as they form a large part of the mouth, the nose, and the orbit of the eye. The central part of each bone, which may be considered as its body, is hollow, and capable of containing, in the adult, near half an ounce of fluid. The plate which covers this cavity is the bottom of the orbit of the eye. The sockets of the large teeth are below it. The roof of the mouth projects laterally from the inside of it. A process for supporting the cheek bone is on the outside; and another process goes up before it, which forms the side of the nose. Fig. 20.* In each upper maxillary bone the fol- lowing parts are to be examined : The nasal process; the orbitar plate; the malar process; the alveolar process • the palatine process; the anterior and posterior surfaces; the great cavity; the internal ox nasal surface; and the three foramina. The nasal process, which extends upwards to form the side of the nose, is rather convex outwards, to give the nostril shape. Its sides above support the nasal bone; and a cartilage of the alas nasi is fixed to its edge below. The margin of the orbit of the eye is marked by a sharp ridge on the external surface of this process; and the part * The superior maxillary bone of the right side, as seen from the lateral aspect. 1. The external, or facial surface; the depression in which the figure is placed is the canine fossa. 2. The posterior, or zygomatic surface. 3. The superior, or orbital plate or surface. 4. The infra-orbital foramen: it is situated immediately below the number. 5. The infra-orbital canal, leading to the infra-orbital foramen. 6. The inferior border of the orbit. 7. The malar process. 8. The nasal process. 9. The concavity forming the lateral boundary of the anterior nares. 10. The nasal ?pine. 11. The incisive, or myrtiform fossa. 12. The alveolar process. 13. The internal border of the orbital surface, which articulates with the ethmoid and palate bones. 14. The concavity which articulates with the lachrymal bone, and forms ihe commencement of the nasal duct. 15. The palate process, i. The two incisor teeth, c. The canine, b. The two bicuspidati. m. The three molares. OSSA MAXILLARIA SUPERIORA. 87 posterior to this ridge is concave to accommodate the lachrymal sac. The orbitar plate, which covers the great cavity, and forms the bottom of the orbit, is rather triangular in form, and con- cave. In the posterior part is a groove or canal, which pene- trates the substance of the bone, as it advances forward, and terminates in the infra-orbitary foramen, below the orbit. At the place where this plate joins the nasal process above men- tioned, viz. at the inner angle of the orbit, is the commencement of the bony canal, which transmits the lachrymal duct into the cavity of the nose. The malar process projects from the external and anterior corner of the orbitar plate; it supports the malar bone, and is rough for the purpose of articulating with it. The alveolar processes compose the inferior and external margins of the upper maxillary bones. When these bones are applied to each other, they form more than a semicircle: their cavities contain the roots of the teeth, and correspond with them in size and form. They do not exist long before the formation of the teeth commences; they grow with the teeth; and when these bodies are removed, the alveoli disappear. The palate process is a plate of bone, which divides the nose from the mouth, constituting the roof of the palate, and the floor or bottom of the nostrils. It is thick where it first comes off from the alveolar process; it is thin in its middle; and it is again thick where it meets its fellow of the opposite side. At the place where the two upper jaw bones meet, the palate plate is turned upwards, so that the two bones are opposed to each other in the middle of the palate, by a broad flat surface, which cannot be seen but by separating the bones. This surface is so very rough, that the middle palate suture almost resembles the sutures of the skull; and the maxillary bones are neither easily separated, nor easily joined again. The meeting of the palate plates by a broad surface, makes a rising, or sharp ridge, towards the nostrils; so that the breadth of the surface by which these bones meet, serves a double purpose; it joins the 88 OSSA MAXILLARIA SUPERIORA. bones securely, and it forms a small ridge upon which the edge of the vomer, or partition of the nose, is planted. Thus we find the palate plates of the maxillary bones conjoined, forming almost the whole of the palate; while what properly belongs to the palate bones forms a very small share of the back part only. As these thinner bones of the face have no medulla, they are nourished by their periosteum only, and are of course perforated with many small holes. The anterior, external or facial surface of the upper maxil- lary bone is concave; the margin formed by the lower edge of the orbit, by the malar process, and by the alveolar processes, being more elevated than the central part, which consists of a depression called the fossa canina, which gives attachment to two muscles, the compressor nasi, and levator anguli oris. At a small distance below the orbit is the infra-orbitary foramen for transmitting a branch of the superior maxillary nerve. When these two bones are applied to each other, and the ossa nasi are in their places, they form the anterior orifice of the nasal cavity, which has a small resemblance to the inverted figure of the heart on cards.—The concave border of the open- ing of the nostrils, is projected forwards at its lower surface into a sharp process, -forming with a similar process at the opposite side the nasal spine. Beneath the nasal spine, and above the two superior incisor teeth, is a slight depression called the incisive or myrtiform fossa, which gives origin to the depressor labii superioris aleeque nasi muscle—. The posterior or zygomatic surface has been called a process or tuber. The tuberosity is pierced by a number of small foramina, giving passage to the posterior dental nerves, and branches of the superior dental artery. It expands to a consi- derable size, and is united internally and posteriorly to the ossa palati. The great cavity extends from the bottom of the orbit of the eye to the roof of the mouth, and from the anterior to the posterior surface of the bone; it opens in the cavity of the nose, and is called antrum maxillare, or Highmorianum.* There is but a small portion of bone between this cavity * After an anatomist who described it. OSSA NASI. 89 and the sockets of the teeth, particularly those of the second molar tooth; occasionally the fangs of the tooth enter the cavity. The internal or nasal surface of this bone forms a large part of the cavity of the nose, and is concave. At the root of the nasal process is a ridge, for supporting the anterior end of the lower turbinated bone. The nasal process seems continued into the cavity of the nose, and forms a portion of the orifice of the canal for the lachrymal duct, which is on the external side of this cavity, near its anterior opening, and under the lower turbinated bone. The orifice in this bone by which the antrum maxillare communicates with the nose, is very large ; but it is reduced to a small size, by a plate from the ethmoid bone, by a portion of the os palati, and of the lower spongy bone, each of which covers a part of it. The three foramina are, 1st. The infra-orbitary foramen already described. 2d. The foramen incisivum or anterior palatine hole, which passes through the palatine process, from the nose to the mouth. In the nose it forms generally two foramina, which unite and form but one in the mouth, imme- diately behind the middle incisor teeth. This foramen is closed by the soft parts during life, and transmits a branch of the spheno-palatine nerve from each side, which runs on the septum narium, and joining at the lower part of the canal with its fellow, they unite, and, according to M. Cloquet,* form a ganglion. 3d. The posterior palatine foramen, which is formed by this bone, and by the os palati, on each side, is situated in the suture which joins them to each other, and transmits to the palate a branch of the upper maxillary nerve. This bone is united to the frontal, nasal, unguiform, ethmoid and malar bones, above; to the ossa palati behind; to the corresponding bone, on the opposite side; and to the inferior spongy bone, in the cavity of the nose. Ossa Nasi. The ossa nasi are so named from their prominent situation * This ganglion, though it varies in size, is readily found. I always exhibit it in the course of my lectures.—p. 8* 90 OSSA UNGUIS. at the root of the nose. They are each of an irregular oblong figure, being broadest at their lower end, narrowest near the middle, and larger again at the top, where the edge is rough and thick, and their connexion with the os frontis is conse- quently very strong. They are convex externally, and concave within. The lower edges of these bones are thin and irregular. Their anterior edges are thick, and their connection with each other, by means of their edges, is firm; the suture between them, extending down the middle of the nose, forms a promi- nent line on the internal surface, by which they are united to the septum narium. The uppermost half of their posterior edges is covered by the edges of the nasal processes of the upper maxillary bones; the lower half laps over the edges of these bones; and by this structure they are enabled to resist pressure. [On the posterior surface of the os nasi is a groove occupied in the recent subject by a branch of the ophthalmic nerve called the nasal, which enters the nose through the fora- men orbitare internum anterius.] They are joined above to the os frontis; before, to each other; behind, to the upper maxillary bones; below, to the cartilages; and internally, to the septum of the nose. Ossa Unguis, or Ossa Lachrymalia. The ossa unguis are so named from their resemblance to a nail of the finger. They are situated on the internal side of the orbit of the eye, between the os planum of the ethmoid, and the nasal process of the upper maxillary bone. Their external surface is divided into two portions, by a middle ridge; the posterior portion forms part of the orbit; and the anterior, which is very concave, forms part of the fossa and canal, for containing the lachrymal sac and duct. This portion is perfo- rated by many small foramina; and the whole, being extremely thin and brittle, is therefore often destroyed by the preparation of the subject. The internal surface of this bone is generally in contact with the cells of the ethmoid; a small portion of the anterior parts is in the general cavity of the nose. Each os unguis is joined OSSA MALARUM. 91 above to the frontal bone; behind to the os planum; before and below to the maxillary bone. It sometimes is extended into the nose, as low as the upper edge of the inferior spongy bone. Ossa Ma I arum. The ossa malarum are the prominent square bones which form the cheek, on each side. Before, their surface is convex and smooth; backward, it is unequal and concave, for lodging part of the temporal muscles. The four angles of each of these bones have been reckoned as processes. The one at the external canthus of the orbit called the superior orbitar process, is the longest and thickest. The second terminates near the middle of the lower edge of the orbit in a sharp point, and is named the inferior orbitar process. The third, placed near the lower part of the cheek, and thence called maxillary, is the shortest and nearest to a right angle. The fourth, which is called zygomatic, because it is extended backwards to the zygoma of the temporal bone, ends in a point, and, has one side straight and the other sloping. Between the two orbitar angles there is a concave arch, which makes about a third of the external circumference of the orbit, from which a fifth process is extended backwards within the orbit, to form near one-sixth of that cavity; and hence it may be called the internal orbitar process. From the lower edge of each of the ossa malarum, which is between the maxillary and zygomatic processes, the masseter muscle takes its origin. On the external surface of each cheek bone, one or more small holes are commonly found for the transmission of small nerves or blood-vessels from, and sometimes, into the orbit. On the internal surface are the holes for the passage of the nutritious vessels of these bones. A notch, on the outside of the internal orbitar process of each of these bones, assists to form the great slit common to this bone, and to the sphenoid, maxillary, and palate bones. The substance of these bones is, in proportion to their bulk, thick, hard, and solid, with some cancelli. 92 OSSA PALATI. Each of the ossa malarum is joined, by its superior and internal orbitar processes, to the os frontis, and the orbitar process of the sphenoid bone ; by the edge between the internal and inferior orbitar processes, to the maxillary bone; by the side between the maxillary and inferior orbitar process, again to the maxillary bone; and by the zygomatic process to the os temporis. Ossa Palati. The ossa palati form the back part of the roof of the mouth, and extend from it along the external sides of the posterior openings of the nose, into the orbits of the eyes. Each bone may therefore be divided into four parts, the palate square bone, or palatine, or horizontal process, the pterygoid process or tuberosity, the nasal lamella or perpendicular plate, and the orbitar process. The square bone is irregularly concave, for enlarging both the mouth and cavity of the nose. The upper part of its internal edge rises in a spine, after the same manner as the palate plate of the maxillary bone does, to be joined with the vomer. Its anterior edge is unequally ragged, for its firmer connexion with the palate process of the os maxillare. The internal edge is thicker than the rest, and of an equal surface, for its conjunction with its fellow of the other side. Behind, this bone is somewhat in form of a crescent, and thick, for the firm connexion of the velum pendulum palati; the internal point being extended backwards, to afford origin to the palato- staphylinus or azygos muscle. This square bone is well dis- tinguished from the pterygoid process by a perpendicular fossa, which, applied to a similar one in the maxillary bone, forms a passage {pterygo-maxillary) for the palatine branch of the fifth pair of nerves; and by another small hole behind this, through which a twig of the same nerve passes. The pterygoid process is somewhat triangular, having a broad base, and ending smaller above. The back part of this process has three fossae formed in it; the two lateral receive the ends of the two pterygoid plates of the sphenoid bone; the OSSA PALATI. 93 Fig. 20.* middle fossa, which is very superficial, makes up a part of what is commonly called the fossa pterygoidea. The foreside of this pterygoid process is rough and irregular where it joins the back part of. the great tuberosity of the maxillary bone. Frequently several small holes may be observed in this triangular process, par- ticularly one near the mddle of its base, which a little above communicates with the common and proper holes of this bone already mentioned. The nasal lamella of this bone is extremely thin and brittle, and rises upwards from the upper side of the external edge of the square bone, and from the narrow extremity of the ptery- goid process; it is so weak, and, at the same time, so firmly fixed to the maxillary bone, as to be very liable to be broken in separating the bones. From the part where the plate rises, it runs up broad on the inside of the tuberosity of the maxillary bone, to form a considerable share of the sides of the maxillary sinus, and to close up the space between the sphenoid and the great bulge of the maxillary bone, where there would other- wise be a large slit opening into the nostrils. On the middle of the internal side of this thin plate, there is a transverse ridge, continued from one which is similar to it in the maxillary bone * A posterior view of the palate bone in its natural position; it is slightly turned to one side to obtain a view of the internal surface of the perpendicular plate (2). 1. The horizontal plate of the bone; its upper or nasal surface. 2. The perpendicular plate or nasal lamella, seen on its internal or nasal surface. 3, 10, 11. The pterygoid process or tuberosity. 4. The broad internal border of the horizontal or palatine process, which articulates with the similar process of the bone of the other side. 5. The ridge which with a similar elevation of the opposite bone forms the palate spine. 6. The horizontal ridge which gives attachment to the inferior turbinated bone ; the concavity below this ridge forms a part of the inferior meatus of the nose, and the concavity (2) above the ridge forms a part of the middle and superior meatus. 7. The spheno-palatine foramen. 8. The orbital process of the bone. 10. The middle facet of the pterygoid process or tuberosity which forms the middle of the pterygoid fossa. The fossae 11 and 3, articulate with the two pterygoid plates of the sphenoid bone ; 11 with the internal, and 3 with the external. 94 OSSA PALATI. for supporting the back part of the os spongiosum inferius. Along the outside of this plate, the perpendicular fossa made by the posterior palatine nerve is observable. At the upper and posterior edge of this nasal plate is a notch, which when applied to the sphenoid bone, forms the spheno- palatine foramen, through which a nerve, artery, and vein pass to the nostril; this notch forms two processes on the posterior part of the bone, the inferior of which is in contact with the internal plate of the pterygoid process of the sphenoidal bone, and has, therefore, been called by some French anatomists, the pterygoid apophysis of the os palati. The superior and anterior portion is the proper orbitar process of this bone, which is Fig. 21.* situated at the posterior part of the lower surface of the orbit, and forms a portion of it. This process of the os palati is hollow; and its cavity generally com- municates with the contiguous cell of the os ethmoides. It has several surfaces, one of which is to be found in the orbit, and another in the zygomatic fossa. The palate square part of the palate bone, and its pterygoid process, are firm and strong, with some cancelli; but the nasal plate, and orbitar processes, are very thin and brittle. The palate bones are joined to the maxillary, by the fore edges of the palate square bones; by their thin nasal plates, and part of their orbitary processes, to the same bones; by their pterygoid processes, and back part of the nasal plates, to * The perpendicular plate of the palate bone seen upon its external or spheno- maxillary surface. 1. The rough surface of this plate, which articulates with the superior maxillary bone. 2. The posterior palatine canal, completed by the tuber- osity of the superior maxillary bone. The rough surface to the left of the canal (2) articulates with the internal pterygoid plate. 3. The spheno-palatine or lateral nasal foramen. 4, 5, 6. The orbital portion of the perpendicular plate. 4. The pterygoid apophysis or spheno-maxillary facet of this portion. 5. Its orbital facet or process. 6. Its maxillary facet, to articulate with the superior maxillary bone. 7. The sphe- noidal portion of the perpendicular plate. 8. The pterygoid process or tuberosity of the bone. OSSA SPONGIOSA INFERIORA.--THE VOMER. 95 the pterygoid processes of the os sphenoides; by the transverse ridges of their nasal lamella? to the ossa turbinata inferiora, and by the spines of the square bones to the vomer. The Ossa Spongiosa, or Turbinata Inferiora. The ossa spongiosa, or turbinata inferiora, are so named to distinguish them from the upper spongy bones, which belong to the os ethmoides ; but these lower spongy bones are quite distinct, and connected in a very slight way with the upper jaw bones. They are rolled or convoluted, very spongy, and exceedingly light. Each of them is attached to the os maxil- lare superius, near the transverse ridge, by a hook-like process, and covers a part of the opening of the maxillary sinus. One end is turned towards the anterior opening of the nose, and covers the end of the lachrymal duct; the other end of the same bone points backwards towards the throat. The curling plate hangs down into the cavity of the nostril, with its convex side towards the septum. This spongy bone differs from the spongy processes of the ethmoid bone, in being less turbinated or complex, and in having no cells connected with it, The Vomer. The vomer is a thin flat bone, which forms the back part of the septum of the nose. Its posterior edge extends downwards from the body of the os sphenoides to the palatine processes of the ossa palati, separating the posterior nares from each other. The figure of this bone is an irregular rhomboid. Its sides are smooth; and its posterior edge appears in an oblique direction at the back part of the nostrils. The upper edge is firmly united to the base of the sphenoid bone, and to the nasal plate of the ethmoid. It is hollow for receiving the processus azygos of the sphenoid, and where it is articulated to the nasal plate of the ethmoid, it is composed of two lamina which receive this plate between them. The anterior edge has a long furrow in it, where the middle cartilage of the nose enters. The lower edge is firmly united to the nasal spines of the 96 MAXILLA INFERIOR. maxillary and palate bone. These edges of the bone are much thicker than its middle, which is as thin as paper; in consequence of which, and of the firm union or connexion this bone has above and below, it can very seldom be separated entire in adults; but in a child it is much more easily separated entire, and its structure is more distinctly seen. Its situation is not always perpendicular, but often inclined and bent to one side, as well as the nasal plate of the ethmoid bone. It is united above to the os sphenoides and the nasal plate of the ethmoid bone ; before to the middle cartilage of the nose; and below, to the ossa palati and ossa maxillaria superiora. Maxilla Inferior, or Lower Jaw. The form and situation of this bone are so generally known, that they do not require description. To acquire an accurate idea of the lower jaw, it is, however, necessary to examine attentively its different parts: viz. the chin, or mental protuber- ance, the sides, the angles, and the processes. In subjects where the bones are strongly marked, there is a prominent vertical ridge in the middle and most inferior part of the chin which becomes broad below so as to form a triangle, and on each side of this triangular prominence are transverse ridges; from these eminences the muscles of the lower lip originate. On each side of the jaw, commonly under the second of the bicuspides, or small molar teeth, is the anterior maxillary or mental foramen, through which pass out branches of the inferior maxillary nerve and blood-vessels. This foramen, has a direction upward and backward. At a small distance behind these foramina, on each side, is the commencement of a ridge which continues backward until it forms the edge of the anterior or coronoid process. The alveolar processes, which form the upper edge of the jaw, are on the inside of this ridge; the alveoli or sockets corresponding with the roots of the teeth, in number and form. The lower edge of the jaw, which is MAXILLA INFERIOR. 97 denominated the base, is round and firm, except at the angles, where it is thin. The angle is formed at the posterior extremity of the base : in children it is obtuse; but in adults whose teeth are perfect, it is nearly rectangular. The masseter muscle is. inserted into the lower jaw, at the angle ; and there are several inequalities on the surfaceanade by this muscle. Fig. 22.* The anterior or coronoid process, is rather higher than the posterior, and forms an obtuse point: into this process the temporal muscle is inserted. The anterior edge of the coro- noid process is sharp, and con- tinued into the ridge above mentioned ; from this edge the buccinator muscle arises. As the alveoli are on the inside of this edge and ridge, the jaw is very thick at this place. There is a semicircular or sigmoid notch between this coronoid process and the posterior or condyloid; and here the bone is very thin. The condyles are oblong, and are placed obliquely ; so that their longest axes, if extended until they intersect each other, would form an angle of more than one hundred and forty degrees. The neck of the process, or the part immediately below the condyle, is concave on the anterior, and convex on the posterior surface. On the inside of the jaw, in the middle of the chin, is a small protuberance, sometimes divided by a vertical fissure; to this are attached the fraenum linguae, and some muscles of the * The lower jaw. 1. The body. 2. The ramus. 3. The symphysis. 4. The fossa for the depressor labii inferioris muscle. 5. The mental foramen. 6. The external oblique ridge. 7. The groove for the facial artery. 8. The angle. 9. The extremity of the mylo-hyoidean ridge. 10. The coronoid process. 11. The condyle. 12. The sigmoid notch. 13. The inferior dental foramen. 14. The mylo-hyoidean groove. 15. The alveolar process, i. The middle and lateral incisor tooth of one side. c. 'Ihe canine tooth, b. The two bicuspides. m. The three molares. 9 98 MAXILLA INFERIOR. tongue and os hyoides. Farther back is a ridge called the mylo-hyoid, which extends backwards and upwards, until it approaches the alveoli of the last molar teeth; where it terminates in an oblong protuberance. To the anterior part of this line the mylo-hyoidei muscles are attached ; and to the posterior extremity, the superior constrictor of the pharynx. The surface of the bone above this ridge i$ smooth, and covered with the gums and lining membrane of the mouth. The surface below the posterior part of the line is rather concave, to accommodate the submaxillary gland. At a small distance behind the alveoli, and nearly on a line with them, midway between the roots of the two processes, is a large foramen, called the inferior dental, for transmitting the third, or inferior maxillary branch of the fifth pair of nerves, and the blood-vessels which accompany it; the canal which commences here, terminates at the anterior foramen, already described.* The surface of this canal is perforated by many foramina, through which blood-vessels and nerves pass to the different teeth, and to the cancelli of the bone. On the anterior side of the foramen is a sharp-pointed process, from which a ligament passes to the temporal bone. The nerve and vessels, before they enter into this foramen, make an impression on the bone; and there is generally a small super- ficial groove called the mylo-hyoid, which proceeds downwards from it, being made by a small nerve which supplies some of the parts under the tongue. At the angle of the jaw, on the inside, is a remarkable roughness, where the internal pterygoid muscle is inserted. The lower jaw moves like a hinge upon its condyles in the glenoid cavity, when the mouth opens and shuts in the ordinary way. When the mouth is opened very wide, the condyles move forward upon the tubercles before the cavities: if the effort to open the mouth is continued, the lower jaw is fixed in that situation, and the whole head is thrown back, which separates the upper jaw still farther from the lower. * A branch of this canal is costinued torwards to the symphysis by which the front teeth are supplied with vessels and nerves.—p. THE TEETH. 99 The lower jaw can be projected forward without opening the mouth, by the movement of both condyles, at the same time, on the tubercles. This bone can also rotate upon one condyle, as a centre, while the other moves out of the glenoid cavity, upon the tubercle : but these important motions can be better understood, after the muscles, and the articulation with the temporal bone, in its recent state, have been described. Fig. 23. Of the Teeth. In the adult, when the teeth are perfect, there are sixteen in each jaw, and those in corresponding situations, on the opposite sides, resemble each other exactly. They are of four kinds, viz. incisores, or the fore teeth; cuspidati, or the canine; bicuspides, or the small grinders ; and molares, or the large grinders. On each side of the jaw, supposing it divided in the middle there are two incisores, one cuspidatus, two bicuspides, and three molares. They occur in the order in which they have been named, beginning at the middle of the jaw, as in the above figure. Each tooth is divided into two parts, viz. the body, or that portion which is bare, and projects beyond the alveoli and 100 COMPOSITION OF THE TEETH. gums; and the root, which is lodged in the socket. The boundary between these parts, which is embraced by the gums, is called the neck of the tooth. The body and roots consist of a peculiar kind of bone (dentine) which is more firm and hard than the substance of the other bones; but. all the surface of the body, which projects beyond the gums, is covered with enamel, a substance very different from common bone. Every tooth in its natural condition has a cavity in it, which commences at the extremity of each root, and extends from it to the body of the tooth, where it enlarges considerably. This cavity is lined by a membrane, and contains a nerve, with an artery and vein, which originally entered the tooth, by a fora- men near the point of the root, as is evident during the growth of the teeth. These vessels, and the nerve, have been traced into the teeth; although in many subjects the foramina appear to be closed up. —A third substance has lately been discovered by Prof. Ret- zius of Stockholm as entering into the composition of the teeth of man, called the cortical substance or cementum. It com- mences at the lower edge of the enamel and surrounds com- pletely the fang. In many of the lower animals it is found also, on the faces of the compound teeth, filling up the spaces between the vertical ridges of enamel.— Composition of the Teeth. —The bone or ivory of the teeth, now called Dentine, (see Fig. 24,) constitutes the whole of the root, and a greater part of the body and neck. The cavity in the centre, for the lodge- ment of the pulp, (cavitas pulpij in whichever of the teeth it is examined, presents an exact similarity of shape to the bodies and fangs of the teeth, as though the latter had been moulded upon the pulp. The ivory is of a polished pearly whiteness, like that of a piece of white satin. It is composed chemically both of animal and earthy matter, but in different propor- tions from ordinary bone. If exposed for a considerable COMPOSITION OF THE TEETH. 101 time to the action of a weak acid solu- tion, the earthy matter is dissolved, and there is left a flexible, tenacious, dense, and homogeneous mass, much resembling cartilage, but more dense. If, on the contrary, it is exposed to the action of fire, the animal matter is first blackened, then consumed, and there is left a white, hard, friable residue of calcareous matter. —The enamel or vitreous substance, (see Fig. 24,) so named from its resemblance to vitrified minerals, has been with greater propriety called by Blake, the cortex striatum, from the lines which it presents upon its sides. It forms a covering nearly a line in thickness upon the crown of the teeth, and is thinned down at its termination upon the neck. Its texture is fibrous, or consists of particles piled one upon another, perpen- dicularly to the bony part, and so closely compressed together, as to leave no obvious interval between them. All the wear of the teeth takes place, therefore, at the end of these fibres and not upon their sides; and the enamel is rendered by this arrangement much less liable to fracture. —No vessels have been traced to this substance, nor has it ever been seen like the bony portion, coloured by madder in young animals fed on this substance during the developement of the teeth. But Mascagni, infatuated with his discoveries in the absorbent system, absurdly regarded this substance as entirely formed of absorbent vessels.* It is exceedingly hard and strikes fire, on collision with steel. While covering the bone, it presents a milky white appearance; removed from it, it is semi-transparent and opaline. —The enamel is thickest on those parts of the teeth most exposed to friction, as on the horizontal surfaces of the grinders, the edges of the incisors, and the points of the cuspi- dati. The position of the enamel and its arrangement into fibres is well seen in Fig. 24. Fig. 24. 9* * Vide Prodromo. 102 PURKINJE AND MULLER ON THE TEETH. —The enamel and ivory of the teeth are the most indestructible after death of all parts of the body. In opening tumuli or other ancient places of sepulchre, they are frequently found to have undergone scarcely any decomposition. —The cortical substance or cementum, see Fig. 24, consists of a thin osseous layer developed on the external part of the fangs, down to the orifices which lead to the cavity of the tooth. It is essentially of the same structure as true bone, con- taining the characteristic corpuscles, and calcigerous branching tubuli of that tissue. It is supposed to be formed by ossifica- tion of the capsule in contact with the fang, and is certainly the seat of the exostosis often met with on the roots of the teeth. In old age it makes its appearance in the cavity of the tooth, and is formed from the membrane of the pulp—the pulp shrinking and retiring in proportion as the cement accumu- lates. —The chemical composition of the two substances of the hu. man teeth, consists, according to Berzelius, in the hundred parts, of Enamel. Bone. Animal matter, - - 20.0 Phosphate of lime, with fluate of lime, 88.5 64.3 Carbonate of lime, ... - 8.0 5.3 Phosphate of magnesia, - - 1.5 1.0 Soda, with some chloride of soda, - 1.4 Free alkali and animal matter, - 2.0 100.0 100.0 —Purkinje and Muller, have recently, with the aid of the microscope, investigated very minutely, the structure of the teeth, and their discoveries have been confirmed by many other observers of high reputation. They describe the bony part of the tooth as consisting of fibres running parallel to each other from the external to the internal surface of the tooth, between which is placed a semi-transparent, homogeneous por- tion. These fibres they believe to be really tubular; for on PURKINJE AND MULLER ON THE TEETH. 103 bringing ink into contact with them, it was drawn into them, as if by capillary attraction. These tubes Muller believed to be filled, at least partially, with calcareous matter, which was the cause of the whiteness and opacity of the tooth. In the more transparent part of carious teeth, the white sub- stance in these tubes presented more of a granular, and less of a compact appearance, under the microscope, than in a sound tooth. —The white colour and opacity of these tubes were removed by the application of acids. On breaking a thin lamella of a tooth transversely in regard to the fibres, and examining the edge of the fracture, he perceived the tubes, stiff, straight, and inflexible, projecting here and there from the surfaces. If the lamella had previously been acted on by acid, the tubes were flexible, transparent, and often very long. Hence Muller inferred that the walls of the tubes have a basis of animal tissue, and that besides containing calcareous matter in their cavity, they have this tissue in the natural state impregnated with calcareous salts. The greater part of the earthy matter of the tooth is, however, contained in the transparent homogeneous portion between the fibres, in which it can be rendered visible in a granular state by boiling thin lamina of teeth in a ley of potash. —Purkinje, by the aid of high magnifying powers, discovered the corpuscles that characterise true bone, in layers taken from the external and internal surface of the root; he considers the great mass of the tooth, however, as destitute of organization.— —These fibres which have been still more fully proved by Retzius* to be true canals, having their own walls, are differ- ently arranged in the separate substances of the tooth, but are every where exceedingly minute. In the ivory they are about sisth of a line in diameter: they commence by open orifices at the cavity of the pulp, and extend in an undulating but nearly parallel direction to the surface, dividing and branching * Mikroskopiska Undersokningar ofver Tandernes sardeles Tandbenets, struk- tur: Stockholm, 1837. 104 OF THE ALVEOLI. in their course; the branches anastomosing together, and com- municating occasionally with very minute calcigerous cells, lodged in the transparent intertubular structure, which may be compared to the corpuscles of ordinary bone. The fibres ox filled tubes of the enamel are about ¥^th of a line in diameter, and are hexagonal. They are striated, arranged parallel to each other, and are applied by their internal extremities to corresponding depressions on the surface of the ivory. —The ordinary bony tubuli of the cement or cortical substance communicate here and there with the branching tubes of the ivory. —These minute but interesting details in regard to the structure of the teeth, which are found to vary in the different classes of animals, are important, not only as furnishing one of the best methods of their classification, but in exhibiting the striking analogy that exists, as to their structure, between teeth and bone. The tubes or canals of common bone are occupied by blood-vessels, the calcareous matters being lodged in the bony corpuscles and their reticular tubuli; while those of the teeth are vascular in the growing state, and become nearly all filled up as well as their corpuscles with earthy matter, to give that great degree of solidity requisite in biting and masti- cation.— The alveoli or sockets of the teeth, are formed upon the edge of the jaw: the bone, of which they consist, is less firm than any other part of the jaws : they correspond exactly with the roots of the teeth; and are lined with a vascular membrane, which serves as a periosteum to the roots, and assists in fixing them firmly. —They are developed pari passu, with the teeth, and solely for the purpose of giving them a lodgement; hence when the teeth are removed from the jaw, in the living subject, the sockets subsequently disappear by absorption, as being of no further use. There are two sets of alveoli, one for the deci- duous teeth of the child, and one for the permanent teeth of the adult. Their walls are formed of one plate on the external THE ALVEOLI. 105 side of the jaw, and one on the internal, with transverse bony laminse passing between them. On the side of the cavity which they form, their substance is loose and cellular; on their outer side, like other bones, they are smooth and compact. __The transverse processes, are rather more prominent than the lateral part of the parietes, corresponding in this respect inversely with the line of enamel on the teeth. __The enamel terminates on the neck of the teeth a little above the level of the sockets, leaving a small space on the bony part of the neck round which the gum is attached. —The alveoli, terminate in as many hollow processes, as there are fangs to the teeth which they lodge : and at the bottom of each of these processes there are one or more minute foramina, for the transmission of vessels and nerves to the internal mem- brane and pulp of the teeth. —The mode of articulation of the teeth in the sockets is called gomphosis; even in their perfect state, the teeth are slightly movable in the socket, of which dental surgeons, occasionally take advantage, in altering the direction of the teeth, by mechanical means. The firmness of the articulation, depends upon the adaptation in size and shape of the sockets to the fangs, on the gum which surrounds the neck, of the periosteum of the sockets which is continuous with that of the fangs, and of the vessels and nerves which enter into the foramina of the fangs. The teeth of different kinds differ greatly from each other, in form and size. The body of the incisores is broad, with two flat surfaces, one anterior and the other posterior; the anterior surface is rather convex and the posterior concave ; they meet in a sharp cutting edge. At this edge the tooth is thinnest and broadest; it gradually becomes thicker and narrower, as it is nearer the neck. The enamel continues farther down on the anterior and posterior surfaces than on the sides. The incisores of the upper jaw are broader than those of the lower; especially the two internal incisores. The cuspidati are longer than any other teeth, and are thicker 106 PERMANENT TEETH. than the incisors. Their edges are not broad, as those of the incisors, but pointed; this point is much worn away in the progress of life. The enamel covers more of the lateral part of these teeth than of the incisors. The bicuspides are next to the cuspidati, two on each side. They resemble each other strongly; but the first is smaller than the other, although it generally has a longer root. The bodies are flattened laterally, but incline to a roundish form. On the middle of the grinding surface are depressions which make the edges prominent. On the external edge there is generally one distinct point in each of the bicuspides. The internal edge is lower than the external in the first bicuspis, which gives it a resemblance to the cuspidatus. In the second bicuspis, the internal edge is more elevated, although the point is not so distinct as it is on the external edge. The bicuspides have generally but one root, which is often indented lengthwise, so as to resemble two roots united. The three molares or large grinders are placed behind the bicuspides, on each side. The first and second strongly resem- ble each other, but the third has several peculiarities. The body of the large grinders is rather square; the grinding surface has often five points, and three of these are on the external side. In the upper jaw these teeth have three roots, two situated externally, and one internally, which is very oblique in its direction ; they are all conical in their form. It seems probable that the roots of these teeth are arranged in this way to avoid the antrum maxillare. The molares of the lower jaw have but two roots, which are flat, and are placed one anterior and the other posterior; in each of these broad roots there are two canals, leading to the central cavity; whereas, in each root of the upper molares there is but one. The third grinder is called dens sapientia, from its late appearance. It is shorter and smaller than the others; its body is rather rounder, and its roots are not so regular and distinct; for they are sometimes com- pressed together, and sometimes there appears to have been but one root originally, when the whole tooth has a conical DECIDUOUS TEETH. 107 appearance. In some cases the dentes sapientiae take an irregular direction, and shoot against the adjoining teeth. Infants have a set of deciduous teeth, which differ in several respects from those of adults. They are but twenty in number; the five on each side of each jaw, consist of two incisores, one cuspidatus, and two molares or large grinders. The first of them generally protrudes through the gums between the fourth and eighth months of age; the last about the end of the second year. They commonly appear in pairs,* which succeed each other at irregular intervals. Those of the lower jaw are, in most cases, the first. The order of their appearance is this: the central incisors appear first, then the external incisors on each side ; after these the first molaris, then the cuspidatus, and finally the last molaris on each side. There are many deviations from this order of succession, but it takes place in a majority of cases. These deciduous teeth become loose, and are succeeded by those which are more permanent, nearly in the same order in which they appeared, but with a progress much more slow. The incisores generally become loose between the sixth and seventh year; the first molares about the ninth, the cuspidati and the second molares not until the tenth or twelfth, or even fourteenth year. The bicuspides take the places of the infant molares. The three permanent molares appear in the following order : the first of them protrudes a short time before the front teeth are shed; it is the first of the permanent teeth which appears, and is seen between the sixth and seventh year. The second molaris appears soon after the cuspidati and the second bicus- pides are seen. There is then a long interval; for the last molaris or dens sapientiae is seldom seen before the twentieth year, and sometimes not until the twenty-fifth. The teeth are formed upon pulpy substances, which are situated in the alveoli, and are contained in capsules. A shell of bone is first formed upon the surface of the pulp, which * The two teeth of a pair do not appear at the same precise time, but very near to each other. 108 DEVELOPEMENT OF THE TEETH. gradually increases, and the pulp diminishes within it. The body of the tooth is produced first, and the root is formed gradually afterwards; during its formation the root has a large opening at the extremity, which is gradually diminished to the small orifice before described. The roots, as well as the body, are formed upon the pulpy substance, which gradually diminishes, as they increase. After the external surface of the body of the tooth is formed, the enamel begins to appear upon it, and gradually increases, until it is completely invested. It is probable that the enamel is deposited upon the body of the tooth by the membranous capsule which contains it. This substance, which appears to be formed of radiated fibres, is harder and less destructible than bone. Like the substance of bone, it is composed of phosphate, with a small propor- tion of the carbonate of lime; but it is destitute of the car- tilaginous or membraneous structure which is demonstrable in bone. The pulpy substances, or rudiments of teeth, may be seen in the fcetus, when about four months old. At six months, ossification can be seen to have commenced on the pulps of the incisores. At the time of birth, the bodies of the infant teeth are distinctly formed. The alveoli, at first, have the appearance of grooves in the jaw, which afterwards are divided by transverse partitions; they enlarge, in conformity to the growth of the teeth, and appear to be altogether influ- enced by them. The permanent teeth are formed very early : the rudiments of the first permanent grinder on each side have commenced their ossification at birth. At the same time, the rudiments of the permanent incisors are to be perceived ; and their bodies will be found nearly ossified, by the time the infant incisors are protruded completely through the gums. About the age of six years, if none of the infant teeth are shed, there will be forty-eight teeth in the two jaws, viz: the twenty infantile, and twenty-eight permanent teeth, more or less completely formed. —From their mode of developement, apparent structure, and DEVELOPEMENT OF THE TEETH. 109 connexions with the rest of the economy, the teeth were prior to the microscopical researches above detailed considered analogous to the hair, nails, and feathers of mammiferae and birds, and to the shells of molluscae. It cannot be said that the teeth are absolutely inorganized, that they are mere con- cretions of an effused fluid, since there is no part appertaining to living beings, entirely destitute of life ; but in the hard structure of the teeth, no anatomist has yet demonstrated either vessels or nerves,though there are practical dentists, who assert that they have seen blood issue from the bony part of the teeth, in some of their operations.* * Hunter denies positively the existence of any vessels passing between the pulp and bone of the teeth, as he was not able to render them manifest by injection, as the colouring matter does not pass into them when animals are fed upon madder, except in the forming state, and as they do not share in the general softening of the bones, in rickets and malacosteum. Blake believed that these vessels did exist, but were difficult to demonstrate, like those that we know to pass in the eye from the capsule of the crystalline lens, to the lens itself; Beclard, that there were no vessels in the bone of the teeth, continuous with those of the pulp, but that the former received continually from the latter a nourishing liquid which penetrated it by imbi- bition, and that it was situated in regard to the pulp, as the hair and nails to the vascular part of the skin. But the morbid alterations which take place in the body of the teeth, the softening and exostosis seen frequently at their roots, and the fusion of the latter occasionally to the bottom of the alveoli, render their vascularity highly probable. The fang of a perfectly developed tooth, is covered closely by a membrane, called its periosteum, which is continuous with the periosteum of the socket, and is on all hands admitted to be vascular ; the internal cavity is also lined by a highly nervous and vascular membrane. Both of these are intimately connected with the bony structure of the tooth, and require a little force to separate them. This connexion Mr. T. Bell believes to be made by vessels and probably nerves, which pass between them and the bone. Though no artificial injection has been made of the teeth, this writer has seen them tinged with a bright yellow in a young woman who died of jaundice; and where death has taken place from hanging or drowning, when there is usually a congestion of the capillary system, " he has found the osseous part coloured with a dull deep red which could not possibly take place if they were devoid of a vascular system ; in both instances the enamel remained wholly free from discoloration." I have observed the same thing in the teeth of subjects who have died of cholera. The existence of nerves in the bony part of the teeth Bell considers manifested by the facts commonly observed by dentists; in filing the teeth no pain whatever is produced till the enamel is removed ; but the instant the file begins to act upon the bone, the sensation is exceedingly acute: and when the gums, alveoli and periosteal lining membrane, have receded from the teeth so as to leave the bony part bare, it is exquisitely sensitive when touched with any hard instrument. He admits likewise the existence of absorbents in the bony part of the teeth, for in 10 110 DEVELOPEMENT OF THE TEETH. —If the pulp which produces them be destroyed from any cause, they lose the little vitality that they may possess, become foreign bodies mechanically retained in the living parts, and sooner or later are thrown off. —The teeth are distinguished from the common bony tissue, by the absence of any demonstrable cellular or vascular paren- chyma in their composition, by their being in part exposed to the contact of the atmosphere, which no bone can be without losing its vitality, by the enamel which covers them externally, by their successive evolution and renovation at certain periods of life, and lastly by their wearing out, and being lost in old age, whilst the vital actions are still going on in the rest of the economy. —In many of the lower animals the teeth are evidently a production of the skin or dermoid tissue, which is reflected in at the commencement of the digestive passages, and many modern anatomists have for the reasons above mentioned, con- nected them with the description of the digestive organs. They have, however, again been restored for purposes of conve- nience to the student, to their proper connexion with the bones in which they are developed. Developement of the Teeth. —The teeth, as we have before observed, are developed on a principle different from that of other parts of the body, by germs or gemmules. If the jaws of a foetus are examined with care, even at the period of two months* after conception, an extremely soft, jelly-like substance is seen lying along the edge of each maxillary arch. At the third month it is more consistent, and two plates of bone have sprung up at its sides, which are the rudiments of the external and internal alveolar plates. Shortly after this period, the pulpy substance separates into distinct portions, and rudiments of the transverse plates of a tooth in which inflammation had existed for a considerable time, he found after its extraction an abscess in the very centre of the bony structure, communicating with the natural cavity and filled with pus.—p. * T. Bell.—Beclard. DEVELOPEMENT OF THE TEETH. Ill the alveoli are seen shooting across, from side to side. These distinct portions of the pulpy substance, are the germs or rudi- ments from which the teeth are formed; each is partially enclosed in a sac, and receive branches from the vessels and nerves which run along the bottom of the groove. At the fourth month, the enveloping sac is thick in its texture, and consists of two layers, which are easily separated after a short maceration. Both of these layers, Fox and T. Bell have proved, by their injections, to be vascular :* laying loosely within this double sac is the gelatinous vascular pulp itself, covered by an extremely thin, delicate vascular membrane, (to which it is closely united by vessels,) which secretes the bony part of the tooth, and is a sort of internal periosteum.t The pulp and its membrane receive their vascular and nervous filaments from the proper dental vessels and nerves, which run along the groove in the jaw. The double saccular membrane receives its vessels and nerves solely from the gums ; and the only attach- ment between this and the membrane of the pulp, is near the base of the latter, where the dental vessels enter it. The sac is closely united to the gum, hence if we tear away the gum that covers the jaws, we necessarily bring with it the entire structure of the germ. —If at this period, the fourth month, we open the germ, we find the pulp presenting exactly the size and shape of the body of the teeth first cut, (incisors) and that its membrane has already commenced the deposit of its bony tip. —At birth, ossification will be found to have commenced on all the pulps of the temporary teeth, (the body of the incisors being nearly completed,) and on each of those of the anterior permanent grinders. The commencement of ossification is by three points in the incisors, which form their serrated edges * Hunter declared, that the external is soft and spongy, without any vessels ; the other much firmer, " and extremely vascular." Blake on the contrary asserts, that the external is spongy and full of vessels, the internal one is more tender and delicate, and seems to contain no vessels capable of containing red blood. t This membrane is called by Bell the proper membrane of the pulp, and was con- jectured by Blake, with much probability, to be a "propagation of the periosteum of the jaw." Blake on the Teeth, p. 8.— 112 THE ENAMEL. as seen on their first developement, by a single point for the canine, two for the bicuspide, and three, four, or five on the large molar, according to the number of processes which they present. Continuous deposition of the bony matter from the membrane of the pulp, unites these points together, and by degrees at different epochs, all the bodies are formed; the pulp retiring as it were, as the deposition of bone goes on and encroaches upon its cavity, and elongates itself downward, into the shape of the fang. This is finally formed in the same manner as the bodies, and the pulp is completely enclosed in the bony case of the tooth, except at the foramina where the vessels and nerves enter. Where more than one fang exists to a tooth, the lower part of the pulp, is previously divided into an equal number of processes, by little bony partitions which shoot across from the sides of the alveoli. Of the Enamel. —When the devolopement of the bony shell has proceeded as far as the completion of the body and neck, the internal layer becomes thickened and more vascular, receives a greater amount of blood, becomes closely attached to the neck, and forms a loose capsule over the body. From the internal face of this membrane, is poured out a thickened whitish fluid, which Berzelius considers of the nature of lactic acid, which is speedily consolidated into a dark chalky substance, deposited first upon the tips of bone, and gradually extending down in layers till it covers the whole crown of the teeth. This is the enamel. It becomes gradually whiter and harder, as though by a more perfect crystallization, but (near to the period at which the teeth are cut,) it is still so soft, as to be frequently cut with the gum lancet.* * In man, the enamel is formed solely by the inner membrane of the sac. The external contributes nothing to the structure of the teeth. But in graminivorous animals, where the flinty covering of the food they feed on requires a more perfect grinding apparatus, it performs an important part, in adding another element to the structure of the molar teeth, called by Blake crusta petrosa. The cutting teeth are constructed as those of man. In these animals the enamel of the grinders does not form a continuous smooth layer as in man, but passes a little way into', the body of the teeth, and is arranged in the form of vertical layers, between which after the THE PERMANENT TEETH. 113 —Of the three membranes of the germ or follicle, one only may be considered as permanent, that of the pulp or internal, which secretes the bone of the tooth. —The two outer, or those of the sac, cover the crown of the tooth; and as this is pushed forwards by successive depositions of bony matter from within, they are pressed upon and wasted away by absorption, like the gum, in direct proportion with the advancement of the tooth, so that in perfectly natural den- tition, there is little tension or pressure felt. This is called cutting the teeth, a name which expresses the fact, sufficiently well, but literally conveys a wrong idea. —In cases of difficult dentition, the membranes of the sac re- tain their density and vascularity, and are probably thickened by inflammation, and the bony layers formed from the pulp, resisted in their advancement by these membranes, make compression upon the pulp and dental nerves; this, like continued pressure made in other parts of the body, becomes exquisitely painful, and gives rise to distressing sympathetic disturbances. The relief procured by cutting the gums and sac, will be more or less immediate, according to the degree of compression and inflammation of the pulp. —The periosteum covering the fangs of the tooth, is a reflected continuation of the periosteum lining the socket, and this again is continuous with that lining the jaw. Of the Permanent Teeth. —The adult or permanent teeth, are developed in a manner almost exactly analogous to the deciduous or infantile. The germs of many of them are distinctly perceptible in the gums of the infant at birth. They are placed at first deep in the jaw inner membrane of the sac has been removed by absorption, the outer one, accord- ing to Bell, deposits the pars petrosa, and fills up the intervening space. This is a substance harder than the bone, but softer than the enamel; and the advantage de- rived from it is, that it is worn off by trituration more readily than the enamel, so that the latter is constantly maintained in sharp prominent lines upon the surface of the teeth. The same object is here insensibly attained, as a natural consequence of the dif- ference in density of these parts, which the miller effects with much labour with hia pick-hammer, on the burr-stones of his mill.—f. 10* 114 THE PERMANENT TEETH. at the inner side of those of the deciduous teeth, to the sac of which they are attached at top by a neck-like process, as seen in Fig. 25. As the infantile teeth rise up and make their way Fig. 25. through the gum, this process becomes connected with the gum, and forms what is called by Hunter the gubernaculum dentis, from its influence in giving the permanent teeth their proper vertical direction, and preventing their making their way at random through the sides, as they do occasionally in cases where the gubernaculum has been destroyed. —Delabarre has given the gubernaculum the name of iter dentis, from an erroneous belief that it was tubular, like the duct of a sebaceous follicle, and gradually opened as the tooth progressed. —At the fifth month of foetal life, according to Bell, and the eighth and ninth, according to Blake and Fox, the germs of the first permanent molars, may be seen at the outside of the in- fantile row, and those of the permanent incisors behind the deciduous. Fig. 25—1, 2, shows the attachment of the incisor and molar germs of the two sets, just prior to the eruption of the first. The permanent germ is at first placed in the socket of the deciduous tooth, of which it appears, on first view, to be an offshoot or gemmipero-us production. Its vessels and nerves are believed to be mere branches of those of the deci- duous; set. By degrees a distinct socket is formed for it be- hind the latter, and its process or gubernaculum is elongated, as seen in Fig. 25—3. When the deciduous teeth have cut the gum, the two sockets are completely distinct, as seen in Fig. 26, and the gubernaculum is attached to the gum. -Ossification first commences in the permanent set on the anterior molares, and may be seen at birth; at the age of DEVELOPEMENT OF THE TEETH. 115 Fig. 26. twelve months, it has progressed to a considerable extent upon these as well as upon the incisors and the lower cuspi- /JMh data. At the sixth or seventh year of Will a&e tne wn°le of the permanent teeth are '•VPIl\ more or ^ess ossified, and the incisors are ^rl^lll s0 far completed as to be nearly ready to vff&y make their appearance through the gum. At this period there are no less than forty-eight teeth in the two jaws, the twenty deciduous and the twenty-eight permanent, which are in different degrees of developement. The last molars do not begin to ossify till the ninth year, and are the last of all to make their appearance through the gum, whence they have received the name of dentes sapientiae or wisdom teeth. —The permanent teeth, which are more in number and individually of larger size and form a larger arch than the temporary, are developed at successive intervals, so as to correspond exactly, with the increasing size of the jaws from the infantile to the adult state. Hence they cannot correspond in position with the deciduous teeth; the outer permanent incisor will rise up near the cuspidatus, and the permanent cuspidatus near the first molar of the deciduous set. —Exactly in proportion as the bodies of the permanent teeth are completed and approach the gum, the roots of the decidu- ous are removed by absorption, till finally the bodies of the latter only are left fixed mechanically in the gum, and are tumbled off at the slightest effort. The process of the removal of the fangs is not perfectly understood; it is not as was once supposed produced by the pressure of the subjacent tooth, for very frequently the commencement of absorption is at the neck, and not at the root of the tooth, where no pressure can come, and occasionally takes place even where the germ of the permanent tooth has been destroyed. It is more probably owing to the enlarged vessels of the growing permanent teeth, which come from the same branch with those of the deciduous, carrying off all its blood by derivation, which leads to the 116 DEVELOPEMENT OF THE TEETH. From 5 to 8 a 7 u 10 " 12 a 16 u 14 a 20 " 18 a 36 wasting of the latter set, a process of which we find the analogue in the developement of many parts of the foetus. —Below is a tabular view of the appearance of the temporary teeth, and also of the periods at which they are changed for the permanent. —It is to be taken, however, as a general rule liable to continual exceptions, not only in regard to the time, but also as to the regular order of appearance. As a general rule, the teeth of the lower jaw appear first, then the corresponding teeth of the upper. Deciduous Teeth. 8 months, the four central incisors, e four lateral incisors, ' four anterior molares, ' four cuspidati, 1 four posterior molares. Permanent Teeth. —The first permanent molares usually pierce the gum before the fall of the central incisors, and their appearance indicates the approaching change. —The following are about the medium periods at which they are cut, but there is a great degree of variation in this respect. Those of the lower are here indicated, and they most com- monly precede the upper by about two or three months. years, the anterior molares, " central incisors, " lateral incisors, " anterior bicuspides, posterior bicuspides, " cuspidati, " second molares, third molares or dentes sapientia. —Fig. 8 is a side view of a beautiful set of the permanent teeth of both jaws, fitted in their sockets, showing the exact manner in which the surfaces of each set are adjusted to each About 6 a 7 u 8 it 9 (( 10 11 to 12 12 " 13 17 " 19 ABERRATIONS OF DENTITION. 117 other, and the smaller dimensions of the fangs of the wisdom teeth, owing to the contracted space in which they are developed. These teeth decay early, are comparatively of little utility, and probably from the same cause; for in cases, where prior to their developement one of the molares in front of them have been removed, they take a more forward position, are developed with larger fangs, and become much more serviceable. —When the first teeth have made their appearance through the gum, they are not yet completed; the process of thickening the body by layers from within, and of lengthening the root below, is for a time still continued by the pulp. After their completion, the only physiological changes they undergo, is the wearing down of the bodies by friction, and the filling up of the top of their cavity within by the pulp, with a yellowish bony matter in old age, (cementu?n,) which prevents the exposure of the cavity, and protects the vasculo-nervous pulp, which is so exquisitely sensitive, as to be considered by some in the light of a nervous ganglion. This latter process unhap- pily is not universal, and is especially defective when the teeth decay early in life, apparently before the period nature has assigned them. Aberrations of Dentition. —Occasionally at birth teeth have been found developed on the surface of the gum, as in the cases of Louis XIV. of France and Richard III. of England: in such cases they are generally mere shells, and are quickly shed, and below exist the double series of germs, which are developed in the regular order. —In some rare cases, from the non-existence or disease of the germs, no teeth have ever been developed.* Borelli mentions a case of this sort occurring in a woman then seventy-two years old. —Sometimes the temporary teeth only exist, which fall at the regular period and are never replaced. Occasionally the set * Oudet. Consid. sur la Nature des Dents et leur Alterations ; Journal Univ. Des Sciences Med. torn. 43, 1826. 118 OS HYOIDES. of permanent teeth have consisted of double or molar teeth all round. Sometimes the appearance of the temporary teeth has been protracted to the sixth or seventh year, and even then followed at regular intervals by the permanent set. The number of the permanent teeth are sometimes less than usual, in consequence of the non-developement of the wisdom teeth, which remain locked up in the jaw, and occasionally produce pain, and even abscesses in the bony structure. —Sometimes there are supernumerary teeth. Haller has seen in an infant of fourteen years, seventy-two teeth, thirty-six in each jaw, which appeared to depend upon a greater number than usual of the dental germs. Some, fond of the marvellous, have described the eruption of a third set of teeth analogous to the two first: but according to Hudson and others, this appearance has probably been owing to the tardy removal of the deciduous set, and the late supplial of their place by the permanent teeth. —Sometimes the direction of the teeth is vicious, leading into the ramus of the jaw, or upon the outer or inner surface of the gums; or upon the roof of the mouth. Accidental develope- ments of teeth have likewise been met with in the orbit, the tongue, pharynx, stomach, and not unfrequently in the ovaries and uterus.— Os Hyoides. The os hyoides is a small insulated bone, supported between the lower jaw and the larynx, by muscles and ligaments, which proceed from the neighbouring parts in various directions. The figure of this bone, as its name imports, resembles the Greek letter u. In its natural situation, the central and convex part is anterior, and the lateral portions extend backwards. The central part is called the body, and the lateral portions the cornua. The body is broad and its upper edge bent inwards, so that the external surface is convex, vertically, as well as horizon- tally. On this surface is a horizontal ridge : the muscles which proceed from the lower jaw are generally inserted REGIONS OF THE SKULL. 119 above this ridge, and the muscles from the sternum and scapula below it. The internal or posterior surface of the body is very concave. The cornua, in young subjects, are distinct from the body of the bone, and joined to it by cartilages: near the body of the os hyoides they are flat; but their figure soon changes, and they terminate on each side in a small tubercle. Fig. 27.* 0Q tne uPPer eQ,ge °f the bone, where the cornua unite to the body, is a process, equal in size to a small grain of wheat, which has a direction upwards and backwards; this is called the appendix, or lesser cornu of the os hyoides: from it proceeds a ligament which is attached to the styloid process of the temporal bone, and is sometimes ossified. The basis of the tongue is attached to the os hyoides, and the motions of the bone have a particular reference to those of that organ; but they will be better understood when the parts with which it is connected have been described. Regions of the Skull. —The skull considered as a whole may be divided for the occasional purpose of defining the seats of injuries into four regions. —The superior region or vertex, is bounded anteriorly by the frontal eminences; on each side by the temporal ridges and parietal eminences, and behind by the superior curved line of the occipital bone and occipital protuberance. The anterior region ox face as seen in Fig. 28, is somewhat oval in contour, irregular in surface and excavated for the reception of two principal organs of sense, the eye and the nose. It is formed in part by the frontal bones and by the bones of the face. It is * The os hyoides seen from before. 1. The anterior convex side of the body. 2. The great cornu of the left side. 3. The lesser cornu of the same side. The cornua were ossified to the body of the bone in the specimen from which the figure was drawn. 120 ORBIT OF THE EYE. bounded above by the frontal protuberances, below by the chin, and on the sides by the malar bones.—If a per- Fig. 28.* pendicular line be drawn down the face from the inner third of the supraorbital ridge to the inner third of the body of the lower jaw, it will intersect three fora- mina, the supra-orbital, infra- orbital, and mental, each giving passage to one of the facial branches of the fifth nerve, the common seats of facial neu- ralgia. The lateral region or side of the head, comprises the tem- poral and zygomatic fossae and the mastoid portion of the tem- poral bone. —The inferior region or base of the skull, is very irregular and presents an internal or cerebral and an external or basilar surface. —From the importance of the vessels and nerves which traverse it, this region requires to be particularly studied.— An acquaintance with the individual bones which compose the head is principally useful, as it leads to a perfect understanding of the whole structure, of which each bone is but a small part. This structure comprises the cavities which contain the brain and the most important organs of sense, as well as the foramina subservient to them, which are of so much importance in the practice of medicine and surgery, and also in physiology, that the following descriptions are subjoined. Orbit of the Eye. The figure of this cavity is that of a quadrangular pyramid with its angles rounded; so it resembles a cone, the bottom being the apex and the orifice the base. * A front view of the skull. 1. The anterior portion of the frontal bone. 2. The nasal protuberance. 3. The supra-orbital ridge. 4. The optic foramen. 5. The sphenoidal fissure. 6. The spheno-maxillary fissure. 7. The lachrymal fossa in the lachrymal bones, the commencement of the nasal duct. The figures 4, 5, 6, 7. ORBIT OF THE EYE. 121 The diameter of the cavity passes obliquely outward from the apex behind. As the figure is irregular, the side next the nose does not partake of this general obliquity, but extends in a straight direction from behind forwards. The orbit is somewhat contracted at its orifice, and enlarged immediately within. The form of the orifice is rather oval, as the transverse diameter is longer than the vertical. Seven bones are concerned in the formation of this cavity; the os frontis and a portion of the lesser wing of the sphenoid bone above, the os planum of the ethmoid, the os unguis, and the nasal process of the upper maxillary bone,and the os palati below ; the os malae, and orbitar plate of the sphenoid bone, on the outside. On the upper surface is the depression for the lachrymal gland; and at the orifice is the notch or foramen for the supra- orbitary vessels, &c, which have already been mentioned. On the inner surface are two longitudinal sutures, which connect the os planum and the os unguis to the os frontis above, and the os maxillare below. In the upper suture are the two internal orbitary foramina mentioned in the description of the os frontis, the anterior of which transmits a fibre of the ophthalmic nerve, with an artery and vein ; the posterior transmits only an artery and vein. There are also two smaller vertical sutures on each side of the os unguis. On the anterior part of this inner surface is the ridge of the os unguis, and the grooves for accommodating the lachrymal sac, which passes into the canal of the same immediately below. On the lower surface is the aforesaid canal, formed by the nasal and orbitar process of the upper maxillary bone, and that part of the os unguis which is anterior to the ridge. On the posterior part of this surface is a groove which proceeds for- are within the orbit. 8. The opening of the anterior nares, divided into two parts by the vomer: the number is placed upon the latter. 9. The infra-orbital foramen. 10. The malar bone. 11. The symphysis of the lower jaw. 12. The mental foramen. 13. The ramus of the lower jaw. 14. The parietal bone. 15. The coronal suture. 16. The temporal bone. 17. The squamous suture. 18. The upper part of the great ala of the sphenoid bone. 19. The commencement of the temporal ridy:e. 20. The zygoma of the temporal bone, assisting to form the zygomatic arch. 21. Tlie mastoid process. 11 122 CAVITIES OF THE NOSE. wards, and penetrating into the bone, becomes a canal that terminates in the infra-orbitar foramen ; this groove in the bone is made a canal by the periosteum. The thin plate which forms this surface is the partition between the antrum maxillare and the orbit of the eye, and is more or less absorbed in those cases where polypi of the antrum maxillare occasion a protrusion of the eye. The external surface, formed by the malar bone and the orbitar plate of the sphenoid, is almost flat. In the posterior part of the orbit it is bounded by two large fissures, which are now to be described. In the posterior part of the orbit are three apertures. The optic foramen, the sphenoidal fissure, and the spheno-maxillary fissure. The optic foramen opens almost at the bottom of the orbit on the inside ; its direction is forwards and outwards. The sphenoidal fissure, formed principally by the lesser and greater wings of the sphenoidal bone, begins at the bottom of the orbit, and extends forward, upward, and outward. It is broad at the commencement, and gradually diminishes to a fissure. This fissure opens directly into the cavity of the cranium, and admits the passage of the third, fourth, sixth, and one branch ofthe fifth pair of nerves, and an artery, and a vein. The spheno-maxillary fissure commences also at the bottom of the orbit, and extends forward, outward, and downward, between the maxillary bone and the orbitar plate of the sphenoid, from the body of the sphenoid to the malar bone. This fissure opens from the orbit directly into the zygomatic fossa. In the recent subject it is closed, and only transmits the infra-orbitary nerve and vessels, and a small branch of the superior maxillary nerve. The Cavities of the Nose. These cavities, which are separated from each other by the septum narium, are contained between the cribriform plate of the ethmoid and the palatine processof the upper maxillary and palate bones, and between the anterior and posterior nares. CAVITIES OF THE NOSE. 123 They are, therefore, of considerable extent in these directions ; but the distance from the septum to the opposite side of the nose is so small, that each cavity is very narrow. The upper surface of each cavity consists of that portion of the cribriform plate ofthe ethmoid which is between the septum and the cellular portions. Anterior to this, each cavity is bounded by the internal surf ace of the os nasi of its respective side; and posterior to it, by the anterior surface ofthe body of the sphenoid bone. These anterior and posterior surfaces form obtuse angles with the upper surface of the nose, and are im- mediately above the openings called anterior and posterior nares. The anterior surface partakes of the figure of the os nasi; the upper surface has the perforations of the cribriform plate ; the posterior surface has an opening, equal in diameter to a small quill, that leads into the sphenoidal cell, and is also broader than the anterior or superior surface. The internal surface, formed by the septum of the nose, which is composed of the vomer, the nasal plate ofthe ethmoid, and the cartilaginous plate, is flat, but rather inclined to one side or the other, so as to make a difference in the size of the nasal cavities. The external surface is very irregular; it is formed by the cellular portions of the ethmoid; by a small portion of the os unguis; by the upper maxillary bone; the os turbinatum inferius; the os palati; and the internal pterygoid process of the os sphenoides. The upper part of this surface is formed by the internal surface of the cellular portions of the ethmoid, which have been described at page 76. It extends from the sphenoid bone, very near to the ossa nasi; and is uniformly flat and rough. About the middle of it begins a deep groove, which penetrates into the cellular structure of the ethmoides, and passes obliquely downwards and backwards. At the upper end of this groove is the foramen by which the posterior ethmoidal cells communicate with the nasal cavity. This is the upper channel or meatus of the nose. At the posterior end of it is a large foramen formed by the nasal 124 CAVITIES OF THE NOSE. plate of the os palati and the pterygoid process of the os sphe- noides, and therefore called pterygo or spheno-palatine fora- men. It opens externally, and transmits a nerve and an artery to the nose. Below the meatus is the upper spongy bone, which presents a convex surface ; its lower edge is rolled up and not connected with the parts about it. This spongy bone covers a foramen in the ethmoid bone, by which its anterior cells and the frontal sinuses communicate with the nose. Below this spongy bone is the middle channel, or meatus of the nose. The channel extends from the anterior to the posterior part of the cavity. It is very deep, as it penetrates to the maxillary bone. The cells of the ethmoid are above it; the inferior turbinated bone below it; and the upper spongy bone projects over it. In this channel is the opening of the great cavity of the upper maxillary bone. At the anterior extremity of it is a small portion of the os unguis, which inter- venes between the nasal process of the upper maxillary bone and the cells of the ethmoid, and continues down to the lower spongy bone. The lower spongy bone is nearly horizontal, and very conspi- cuous. It extends almost from one opening of the nose to the other. Under this bone is the third and largest channel ox infe- rior meatus of the nose. It is made large by an excavation of the upper maxillary bone, particularly at the anterior part. It affords a direct and very easy passage to the posterior opening of the nose and the throat. Near the anterior extremity of this meatus is the lower orifice of the lachrymal duct, which is so situated that a probe properly curved can be readily passed into it through the nostril. There are, then, four foramina on each side, which form communications between the cavities of the nose and the adja- cent cells, viz. One in the upper meatus, which leads to the posterior ethmoid cells. A second in the middle meatus, which leads to the anterior ethmoid cells and the frontal sinuses. THE INTERNAL BASIS OF THE CRANIUM. 125 A third in the same meatus, which opens into the maxillary sinus. A fourth in the anterior surface ofthe body of the sphenoidal bone, which opens into the sphenoidal sinus. To these must be added the opening of the lachrymal canal. It will be most useful to the student of anatomy, after placing three or four of the uppermost cervical vertebrae in their natural situation, to take a view of The Cavity between the spine and the posterior Nares, which is bounded above, by the cuneiform process, passing obliquely upward and forward; laterally,by soft parts not yet described; behind, by the bodies of the cervical vertebrae ; and before, by the posterior nares, each of which is oblong in form, rounded above, flat below, and separated from the other by a thin par- tition, the vomer. The Cavity of ihe Cranium. The upper concave surface of this cavity corresponds with the figure of the cranium. The ridge in it for supporting the falciform process of the dura mater, the groove made by the longitudinal sinus, the impressions of the arteries, and the pits made by the convolutions of the brain, are particularly to be noticed. The Internal Basis ofthe Cranium Is much more important. It is divided into three fossae on each side; the anterior of these are most superficial, and the posterior the deepest. The bottoms of the anterior fossa are formed by the orbitar processes of the os frontis, and conse- quently are convei; between them is the cribriform plate of the ethmoid, which is commonly sunk below the adjoining sur- face. The crista galli is very conspicuous; and the foramen coscum can almost always be seen. The crista galli is evidently the beginning of the prominent ridge, which continues on the os frontis, and supports the falx of the dura mater. The pos- terior margins of these fossae are formed by the lesser wings of the sphenoid bone. 11* 126 THE INTERNAL BASIS OF THE CRANIUM. The middle fossa axe formed by the great wings of the sphenoidal bone, and by the squamous and petrous portions of the temporal bone. They are lower than the anterior, and higher than the posterior fossae. The projection of the margin of the anterior fossae into these cavities, corresponds with the separation between the anterior and middle lobes of the brain. The suture be- tween the sphenoidal and tem- poral bones is evident in these fossae. The upper surface of the body ofthe sphenoid bone, or the sella turcica is between them ; and all the peculiarities of its surface are very conspi- cuous. The first five foramina of the sphenoidal bone can be easily ascertained, and also, the anterior foramen lacerum and termination of the foramen caroticum, with the impressions made by the carotid arteries on the sides of the sella turcica. The petrous portions of the temporal bones are the posterior boundaries of the middle fossae. Their oblique direction, inwards and forwards, is particularly remarkable; being formed * The cerebral surface of the base of the skull. 1. One side of the anterior fossa; the number is placed on the roof of the orbit, formed by the orbital plate of the frontal bone. 2. The lesser wing ofthe sphenoid. 3. The crista galli. 4. The foramen caecum. 5. The cribriform lamella of the ethmoid. 6. The processus olivaris. 7. The foramen opticum. 8. The anterior clinoid process. 9. The carotid groove uoon the side of the sella Turcica, for the internal carotid artery and cavern- ous sinus. 10, 11, 12. The middle fossa of the base of the skull. 10. Marks the great ala of the sphenoid. 11. The squamous portion of the temporal bone. 12. The petrous portion ofthe temporal. 13. The sella Turcica. 14. The basilar por- tion of the sphenoid bone, surmounted by the posterior clinoid processes. 15. The foramen rotundum. 16. The foramen ovale. 17. The foramen spinosum; the small irregular opening between 17 and 12 is the hiatus Fallopii. 18. The posterior fossa of the base of the skull. 19, 19. The groove for the lateral sinus. 20. The ridge upon the occipital bone, which gives attachment to the falx cerebelli. 21. The toramen magnum. 22. The meatus auditorius internus. 23. The jugular foramen. THE INTERNAL BASIS OF THE CRANIUM. 127 like triangular pyramids. Two of their sides are in the cavity ofthe cranium; one, which is anterior, forms a portion of the middle fossa ; and the other forms a part of the posterior fossa. The edge between them is very prominent, and has the tento- rium or horizontal process of the dura mater attached to it. On the anterior surface, in the middle fossa, may be traced the groove, and the foramen for the Vidian nerve. The posterior fossae are larger as well as deeper than the other two. Their boundaries are well defined by the edges of the petrous bones above mentioned, and by the grooves of the horizontal parts of the lateral sinuses. These fossae are nearly separated from the general cavity by the tentorium, which is attached to the edge of the petrous bone and also to the edge of the horizontal part of the groove for the lateral sinuses. On the tentorium lie the posterior lobes of the cerebrum; and under it, in these fossae, is the cerebellum. These fossae may be considered as one great cavity, which is circular behind, and somewhat angular before. The angular surfaces are formed by the posterior sides of the petrous portions. Between them, is the oblique surface of the cuneiform process of the occipital bone, which descends to the great foramen. On the surface of each petrous bone is the meatus auditorius internus, and the orifice of the aqueduct of the vestibule. Behind the petrous portion, the groove for the lateral sinus is very conspicuous; it terminates in the posterior foramen lacerum, which is evidently formed by the temporal and the occipital bones. At the anterior part of this foramen is most commonly a small bony process, which separates the eighth pair of nerves from the internal jugular vein, as they pass out here. The anterior condyloid foramen for the passage ofthe ninth pair of nerves, appears in the surface of the great occipital hole, immediately below the foramen lacerum. From the back part of this hole the spine, which forms the lower limb of the cross, passes up; and on each side of it are the great depressions which accommodate the two lobes of the cere- bellum. 128 . EXTERNAL BASIS OF THE SKULL. External Basis of the Skull. The external surface of the base of the skull is very irre- gular. When the head is inverted, we see the external protu- berances of the os occipitis, formerly described. The mastoid processes of the ossa temporum are on the same transverse line with the great foramen of the os occipitis ; but the foramen being larger extends farther forward. On the inside of the mastoid process, the fissure for the digastric muscle is very conspicuous, and also the suture between the mastoid process and the occipital bone. Fig. 30.* The oblique direction of the occipital condyles and the slanting position of their articulating surfaces are particularly striking. The posterior condyloid foramina for the cervical veins, and the anterior for the ninth pair of nerves, are also in view. The position of the cuneiform process of the os occipitis is by no means horizontal, but extends forwards and upwards. The petrous or pyramidal portion of the temporal bone commences between the mastoid process and the condyle of the lower jaw, and extends obliquely forwards and inwards, having the * The external or basilar surface of the base of the skull. 1, 1. The hard palate. The figures are placed upon the palate processes of the superior maxillary bones. 2. The incisive, or anterior palatine foramen. 3. The palate process of the palate bone. The large opening near the figure is the posterior palatine foramen. 4. The palate spine; the curved line upon which the number rests, is the transverse ridge. 5. The vomer, dividing the openings of the posterior nares. 6. The internal pterygoid process. 7. The scaphoid fossa. 8. The external pterygoid plate. The interval between 6 and 8 (left side of the figure), is the pterygoid process. 9. The zygomatic fossa. 10. The basilar process of the occipital bone. 11. The foramen BASIS OF THE SKULL. 129 occipital bone behind it, and the glenoid cavity or fossae and the os sphenoides before it. At the commencement, the surface of the petrous portion is not horizontal, but oblique, sloping into the glenoid cavity with a sharp edge downwards. This edge in some cases is curved so as to surround the basis of the styloid process, which arises in contact with it, and projects downwards, on each side of the vertebrae. Between the mastoid and styloid process, is the foramen stylo-mastoi- deum. On the inside of the styloid process, and rather anterior to it, is the foramen lacerum posterius, for the internal jugular vein, the eighth pair of nerves, &c. This foramen passes obliquely backwards and upwards, and is bounded behind by the jugular process of the os occipitis, which bone seems to contribute most to its formation. Very near to this hole on the inside is the anterior condyloid foramen; and rather anterior to it is the opening of the carotid canal, which forms a curve in the bone as it passes upwards, inwards, and forwards. From the foramen lacerum posterius, the suture between the cuneiform process of the occipital and the petrous portion ofthe temporal bone, extends to the foramen lacerum anterius of the base of the cranium; which is closed by cartilage in the recent subject, but is of an irregular and rather triangular form in the macerated head ; this hole is formed by the occipital, sphenoidal, and petrous bones. The suture or connexion between the petrous bone and the os sphenoides, is continued on the anterior side of the petrous bone, from the fissure of the glenoid cavity to the anterior foramen lacerum. The styloid process of the os sphenoides, which is seldom more than four lines in length, appears at the edge of this suture. On the inside of the glenoid cavity, and on the inside of this magnum. 12. The foramen ovale. 13. The foramen spinale. 14. The glenoid fossa. 15. The meatus auditorius externus. 16. The foramen lacerum basis cranii. 17. The carotid foramen of the left side. 18. The foramen lacerum posterius, or jugular foramen. 19. The styloid process. 20. The stylo-mastoid foramen. 21. The masioid process. 22. One of the condyles of the occipital bone. 23. The posterior condyloid foramen. 130 BASIS OF THE SKULL. process, in the suture formed between the petrous and sphenoid bones, is the bony orifice of the Eustachian tube. The foramen spinale, for the middle artery of the dura mater, is at a very small distance from the Eustachian tube, immediately anterior to it; and at a small distance on the inside and front of this foramen is the foramen ovale, for the inferior maxillary nerve, or the third branch of the fifth pair. —Proceeding from before backwards the base of the skull appertaining to the face is seen to be formed by the palate processes of the superior maxillary and palate bones; by the vomer; the pterygoid spinous processes, and part of the body of the sphenoid. —The roof of the mouth as seen at 1, 3, Fig. 30, is constituted by the palatine processes of the superior maxillary and palate bones. The transverse suture which separates them is well seen on the left side of the cut. In the longitudinal suture and directly behind the front incisor teeth, 2, is the incisive or anterior palatine foramen, the inferior opening of the naso- palatine canal, which lodges the ganglion of Cloquet (naso- palatine) and transmits the anterior palatine nerves. The posterior palatine foramina, are placed near the posterior angles of the hard palate, for the purpose of transmitting to the palate the blood-vessels and nerves of that name. The opening of the larger foramen is seen near 3, Fig. 30. On the inner side of this foramen is seen the transverse ridge upon which is inserted the expanded tendon of the tensor palati muscle. The rounded crescentic border, which terminates posteriorly each half of the hard palate, gives attachment to the velum pendu- lum palati; and in the middle line 4, is seen the palate spine from which is hung the azygos uvuloe muscle. The posterior nares is seen immediately above divided by the vomer, 5, and bounded externally by the internal pterygoid processes, 6. By the side of the shelving base of the vomer and partly formed by it are the pterygo-palatine canals, which transmit the pterygo-palatine arteries. The external pterygoid process is seen at 8, and between the two processes, is the pterygoid fossa, which is occupied by the internal pterygoid muscle. SIDE OF THE HEAD. 131 On the outer side of the external pterygoid process is the zygomatic fossa. The internal pterygoid process is long and narrow, having at its apex the hamulus, and at its base the scaphoid fossa from which arises the circumflexus or tensor palati muscle.— Side of ihe Head. Those portions of the side of the head which are formed by the frontal, parietal and occipital bones, and by the squamous part of the temporal, require no explanation here; but the region which is behind the malar and upper maxillary bone, and within \he* zygomatic processes of the temporal and malar bones, which comprises part of the temporal and zygomatic fossae of some anatomists, is both important and obscure. To obtain a view of this, the lower jaw should be removed, and the zygoma sawed away, in one preparation; and in another, the upper maxillary and palate bones of one side should be applied in their natural position, to the os sphenoides, without any of the other bones. The upper part of this region, formed by the sphenoidal, frontal and malar bones, is made concave by the form of the external angular part of the os frontis and of the os malas; which projects backwards so as to cover a large portion of it. The lower part is formed principally by the external surface of the pterygoid process of the sphenoid bone, and by the posterior surface of the upper maxillary. Between the lower end of the pterygoid process and the upper maxillary bone, a small portion of the os palati intervenes; but in many adult subjects it is not to be distinguished from the other bones. At this place, the pterygoid process and these bones appear to be in close contact; but as they pass upwards they recede from each other so as to form a considerable aperture, which continues the whole length of the pterygoid process. This fissure, which may be called pterygo-palatine or pterygo- maxillary, would open into the posterior part ofthe cavity of the nose, if the nasal plate of the os palati did not intervene ; 132 THE FORM OF THE CRANIUM. this plate forms a partition, which separates the nose from this fissure: and the spheno-palatine foramen, formed principally by it, transmits a nerve and blood-vessels to the nose. The fissure is vertical: at the back of the orbit, it unites with the spheno-maxillary fissure of the orbit, which is almost horizontal, and at the place of their junction, the sphenoidal, or upper fissure of the orbit, opens also. The foramen rotundum, which transmits the second branch of the fifth pair, or the upper maxillary nerve, is likewise situated near this place; and when the upper maxillary, the sphenoidal, and the palate bones are in their natural situation, the distribution of the branches of this important nerve can be easily understood : for the same view presents the course of its various branches; viz. to the nose, by the spheno-palatine fora- men ; to the cavity ofthe cranium, by the pterygoid foramen; to the orbit, and the inferior obitary canal, by the spheno-max- illary fissure; and to the roof of the mouth, by the palato-max- illary canal. The Form of the Cranium. The form of the cranium is that of an irregular oval. The greatest length of its cavity is between a part ofthe os frontis above the crista galli, and of the os occipitis above the centre of the crucial ridge. The greatest breadth is at about two-thirds of the distance from the first to the last of these positions. This transverse diameter touches the sides of the cranium near the posterior part of the basis of the petrous portion of the temporal bone. The difference between these longitudinal and transverse diameters varies greatly in different persons, as their craniums approach to the oval or round figures. The greatest depth of the cavity is between the posterior part of the cuneiform process of the occipital bone, and a part of the cranium which is nearly over it about the middle of the sagittal suture. The figure of the cranium is somewhat varied in different THE FORM OF THE CRANIUM. 133 races of men; and it has been much changed by the particular management of several savage nations. In North America, the Choctaw tribe of Indians were for- merly accustomed to make their foreheads perfectly flat, and sloping obliquely backwards. They have latterly disused this practice; but one of their nation, whose head had this form, was in Philadelphia about the year 1796. At this time a tribe who inhabit a district of country near the sources ofthe Missouri river, are in the practice of flatten- ing both the frontal and occipital regions of the head; so that a small part only, of the middle of it, remains of the natural form, between these flattened sloping surfaces. In the case of the Choctaw man above-mentioned, it did not appear that his health, or his intellectual operations, were any way affected by this form of his head. During infancy, the cranium sometimes increases to a pre- ternatural size, as disproportionate to the face as if it were affected by hydrocephalus. In many of these instances, that disease ultimately shows itself; but in other cases, the preter- natural increase of the cranium finally stops without the occurrence of disease; and the disproportion is lessened by the increase ofthe face in the ordinary progress of growth. In many cases where men have deviated from the ordinary stature, the head has preserved the common size. It is there- fore said to be small in giants, and large in dwarfs. —Many efforts have been made to determine rigorously the dimensions of the cavity of the cranium. This may be done with considerable accuracy from the exterior of the skull, by making allowances for the various degrees of developement in which the frontal sinuses are found in different individuals. The thickness of the diploe seldom varies in different skulls more than one or two lines in thickness. I have, however, several negro skulls in my possession the walls of which are nearly three-quarters of an inch in thickness, and so compact in their composition as to present very little of the diploic or cellular structure. When measured from the interior, a skull of ordinary capacity will be found in its 12 134 FACIAL AND OCCIPITAL ANGLES. longitudinal diameter, (between the frontal spine and longi- tudinal sulcus,) five inches and a half; in its transverse, (be- tween the bases of the petrous portions of the temporal bones,) four and a half; between the parietal fossas five inches, and between the lesser wings of the sphenoid bones, three inches and three-quarters; in the vertical, from the foramen magnum to the sagittal suture, four inches and a half. —Several plans have also been adopted, by the cranioscopists, to determine the relative developement of the cranium (which is filled with the brain) and that of the face. The best known of these are those of Camper, Daubenton and Cuvier. The facial angle of Camper, is taken by extending a horizontal line from the external auditory meatus, on a line with the floor of the nostrils, so as to follow nearly in the direction of the base of the cranium, and by dropping upon this a second from the most prominent part of the forehead to the extremity of the upper jaw. The area between them is the facial angle, and will be the more acute, in direct proportion as the face is de- veloped in front, and the forehead is sloped backwards. This angle is of course larger in man than in any other animal, and varies in size in the different races of men. In a well formed white or Caucasian, it is usually about 80°; in the Mongolian about 75°; in Negroes acout 70°; in the different species of monkeys it varies from 65° to 30°. As a test of the intellectual capacity of individuals, it is but little to be relied on. —The occipital angle of Daubenton, is formed by drawing two lines, one from the inferior border of the orbit, to the anterior margin of the occipital foramen, the other drawn from the anterior to the posterior border of the occipital foramen, and extended forwards. The angle between the two, is the occipital. As the direction of the occipital foramen depends upon the manner in which the head is articulated with the vertebral column, it will be the larger, the less favourably the animal is constructed for the upright posture. In a well-formed Caucasian skull, it is about 3°. In the ox it is about 70°. Daubenton has thus done for the posterior part of the head what Camper has done for the anterior. HEAD OF THE FCETUS. 135 —Cuvier's method consists in dividing the skull vertically, and establishing a comparison between the area of the cranium and that of the face. In a well-formed Caucasian he finds the area of the cranium, quadruple that of the face. In the Mongolian variety, he found the area of the face had increased over this proportion one-tenth, in the Negro, one-fifth; in monkeys, one- half. Tiedemann has adopted a plan of measuring the capacities of different crania, by filling them with seeds from the occipital foramen, and subsequently measuring their contents. This method as well as some others, has been employed for the same purpose by Prof. S. G. Morton of this city, in his elegant and interesting work on Crania Americana, and the results have been so carefully detailed by him, as to leave henceforth little to be wished upon a subject which has exerted much attention among physiologists. The whole capacity of the cranium is found on an average, greater in the Caucasian variety of the human race, than in any other. The Head of the Foetus. In the foetus, those bones, which form the vault of the cranium, originally consist of one plate only; which is com- posed of radiant fibres. At birth, the os frontis consists of two pieces, which join each other in the middle of the forehead. The parietal bones axe each in a single piece; but they are incomplete at their edges and their angles. The temporal bones have no appearance of mastoid or styloid processes. Instead of a meatus auditorius externus, there is a bony ring in which the membrana tympani is fixed. The squamous and petrous portions, and this ring, are originally formed separate ; but at the period of birth they often adhere to each other. The os occipitis is composed of four pieces: the first and largest, extends from the beginning or angle of the lambdoidal suture to the upper edge of the great occipital foramen. Each side of the foramen, and the condyle on it, is formed by a distinct piece. The front part is formed by the cuneiform 13G HEAD OF THE FffiTUS. process, which is separate from the other parts and forms the fourth piece. The sphenoidal bone may be separated by maceration into three pieces. The body and the little wings form one piece, Each of the great wings, with the pterygoid processes united to it, forms also a piece. The body of the bone is entirely solid. A large part of the ethmoid is in a cartilaginous state. It is divided into two portions by a partition of cartilage, which occupies the place ofthe nasal plate and the crista galli. In consequence of the imperfect formation ofthe bones which compose the vault of the cranium, there are several deficiencies in it. Thus the superior anterior angles of the parietal bones being incomplete, and also the upper angles of the pieces which compose the os frontis, a vacuity with four sides is occasioned, which is termed the Anterior fontanel. This opening may be distinguished by its form, as well as its greater size, from another vacuity which is produced in a similar way at the other end of the sagittal suture, and called the Posterior fontanel: but as there are only three bones con- cerned in its formation, viz. the two parietal and the occipital, this vacuity is triangular. Besides these, there are two other vacuities or fontanels on each side, at the two lower corners of each parietal bone: these, however, are much less than those first described. The smaller fontanels do not continue open long; but the anterior fontanel is seldom completely closed before the end of the third year. It is very obvious upon an examination ofthe cranium, that the centre ofthe base is better calculated to resist pressure than any other part; as the cuneiform process of the occipital bone, the petrous portion of the temporal, and the body of the sphenoidal bone, which compose a large part of it, are very firm and substantial. The face of the foetus differs very essentially from that ofthe adult. Although the orbits of the eyes are very large when THE SPINE. 137 compared with the size of the head, that portion of the face which is below them is very small, and has little depth. The upper maxillary bones have no sinuses in them ; and their orbitar plates are not much elevated above the cavities for containing the posterior teeth; in consequence, the depth of the face is very small, and its whole aspect is affected. The nose of the foetus differs greatly from that of the adult in respect to its sinuses; for not only are the maxillary cavities wanting, but those of the frontal and sphenoidal bones also. The lower jaw is formed in two pieces, which unite at the middle; and hence the term symphysis is used in describing the chin. The bone is not only less broad in proportion than that of the adult, but the angles are more obtuse, and the pro- cesses which arise from them are more sloping. The head of the foetus is much larger in proportion to the body than that of the adult. Ofthe Trunk. The Trunk consists of the Spine, Thorax, and Pelvis. The Spine. The spine is the long pile of bones extending from the condyles of the occiput to the end of the os coccygis. It some- what resembles two unequal pyramids joined in a common base. It is not, however, straight; for its upper part being drawn backwards by strong muscles, it gradually advances forwards to support the oesophagus, vessels of the head, &c. Then it turns backwards, to make room for the heart and lungs. It is next bent forwards to support the viscera ofthe abdomen. It afterwards turns backwards for the enlargement of the pelvis. And, lastly, it is reflected forwards, for sustaining the lowest great intestines. The spine is commonly divided into true and false vertebra; the former constituting the long] upper pyramid, which has its base below; while the false vertebrae make the shorter lower pyramid, whose base is above. 12* 138 THE VERTEBRA. True Vertebra. Fig. 31.* The true vertebra are the twenty-four upper bones ofthe spine, on which the several motions of the trunk of our bodies are per- formed. Their name is derived from the Latin verb vertere. Each of these vertebras is composed of its body and processes. The body is the thick spongy forepart, which is convex before, concave backwards, horizontal and flat in most of them above and below. Numerous small holes, especially on the fore and back part of their surface, giving passage to their vessels, and allow the ligaments to enter their substance. The edges of the body of each vertebrae are covered, especially at the forepart, with a ring of bone firmer and more solid than the substance of the body any where else. These rings seem to be joined to the vertebrae in the form of epiphysis. They are of great use in pre- venting the spongy bodies from being broken in the motions of the trunk. Between the bodies of each two adjoining vertebrae, a substance between the nature of ligament and cartilage is interposed; which seems to consist of concentrical curved fibres, when it is cut horizontally; but when it is divided perpendicularly, the fibres appear * The vertebral column—consisting of twenty-four true vertebrae; and two false, the sacrum and os coccygis, each made up by the consolidation of four bones which are sep- arate in the young subject.—It extends the whole length of the trunk.—It may be divided into four regions—the cervical comprising the seven vertebrae from a to b.—The dorsal, the twelve vertebrae from 6 to c.—The lumbar, the five vertrebrae from c to d.—The pelvic or sacro-coccygeal portion comprising the false vertebrae, the sacrum and coccyx from d to/—From e to/, are the four small bones forming the os coccygis. ion the two bones to which the interosseous membrane is attached. 8. The rounded head at the lower extremity of the ulna. 9. The styloid process. 10. The shaft of the radius. 11. Its head sur- rounded by the smooth border for articulation with the orbicular ligament. 12. The neck of the radius. 13. Its tuberosity. 14. The oblique line. 15. The lower extremity of the bone. 16. Its styloid process. THE ULNA. 187 that, we observe a smooth concavity, where the beginning of the flexor digitorum profundus sprouts out. The external angle ofthe triangular part ofthe ulna is very sharp, where the ligament that connects the two bones is fixed; the sides which make this angle are flat and rough, by the ac- tion and adhesion of the many muscles which are situated here. At the distance of one-third of the length of the ulna from the top, in its forepart, the passage of the medullary ves- sels may be seen slanting upwards. The internal side of the bone is smooth, somewhat convex, and the angles at each edge of it are blunted by the pressure ofthe muscles equally disposed about them. As this bone descends, it becomes gradually smaller; so that its lower end terminates in a little head, standing on a small neck: towards the inner and back part of which last, an oblique ridge runs, that gives rise to the pronator radii quadratus. The head is sometimes cylindrical, smooth, and covered with a car- tilage on its external side, to be received into the semilunar cavity of the radius; which a styloid process rises from its in- side, to which is fixed a strong ligament that is extended to the os cuneiforme and pisiforme of the wrist. At the root of the process, the end of the bone is smooth, and covered with a car- tilage. Between it and the bones of the wrist, a doubly con- cave movable cartilage is interposed; which is a continuation ofthe cartilage that covers the lower end of the radius, and is connected loosely to the root ofthe styloid process, and to the rough cavity there; in which mucilaginous glands* are lodged. The ulna is principally concerned in the articulation with the os humeri, and forms a hinge-like joint, which allows extension nearly to a straight line, and flexion to an acute angle. By the sloping of the pulley-like surface, the lower part of the arm is turned outwards in the extension, and inwards in the flexion ; which greatly facilitates the motion of the hand towards the head. * All these so called glands are mere masses of adipose matter, supposed, though wrongly by Havers to be the glands which secrete the synovia.—p. 188 RADIUS. Radius. Before the radius is described, it is necessary to observe that the lower end of this bone occasionally revolves half round the lower end of the ulna, and the hand with it. The relative situation of these parts is, therefore, different in different positions of the hand. In the following description, the palm of the hand is sup- posed to present forwards, and the thumb outwards; in which case, the two bones of the forearm will be parallel to each other. The radius is situated on the outside of the forearm, and is rather shorter than the ulna. Its extremities are the reverse of those of the ulna in their proportionate size; and the body is not triangular, although it approaches towards that form. Its upper end is formed into a cylindrical head, which is hollowed on the top for an articulation with the tubercle at the side of the pulley of the os humeri; and the half cylindrical circum- ference next to the ulna is smooth, and covered with a carti- lage, in order to be received into the semilunated cavity of that bone. Below the head,the radius is much smaller; and,therefore, this part is named its cervix. At the internal root of this neck is a fiat tubercle, into the inner part of which the biceps flexor cubiti is inserted. From this a ridge runs downwards and out- wards where the supinator radii brevis is inserted; and a little below, and behind this ridge, there is a rough scabrous surface, where the pronator radii teres is fixed. The body of the radius is not straight, but curved externally the greater part of its length. Its external surface is rounded; the anterior and posterior surfaces are flattened; and between them is a sharp spine, to which the strong ligament extended between the two bones of the forearm is fixed. On the ante- rior surface, at a distance from its head, nearly equal to one- third the length of the bone, is the orifice of the canal for the medullary vessels, which has a direction obliquely up- wards. Towards the lower end the radius becomes broader and flatter, especially on its forepart, where the pronator quadratus muscle is situated. Its back part, at this end, has a flat strong ridge in the middle, and fossae on each side. In a small groove, RADIUS. 189 immediately on the inside of the ridge, the tendon of the extensor of the last joint of the thumb plays. In a large one, inside of this, the tendons of the indicator, and of the common extensor muscles of the fingers pass. On the outside of the ridge there is a broad depression, which seems again subdivided, where the two tendons of the extensor carpi radialis are lodged. The external side of this end of the radius is also hollow- ed by the extensors of the first and second joints of the thumb. The ridges at the sides of the grooves, in which the tendons play, have an annular ligament fixed to them, by which the several sheaths for the tendons are formed. The forepart of this end of the radius is also depressed, where the flexors of the fingers and flexor carpi radialis pass. The internal side is formed into a semilunated smooth cavity, lined with a cartilage, for receiving the lower end of the ulna. The lowest part of the radius is formed into an oblong cavity; in the middle of which is a small transverse rising, gently hollowed, for lodging mucilaginous glands; while the rising itself is insinuated into the conjunction of the two bones of the wrist that are received into the cavity. The external side of this articulation is de- fended by a remarkable process of the radius, from which a ligament passes to the wrist; and this structure resembles that of the styloid process of the ulna with its ligament. The ends of both the bones of the forearm being thicker than the middle, and the radius being curved, there is a considerable distance between the bodies of these bones; in the larger part of which a strong, tendinous, but thin ligament, is extended, to give a sufficient surface for the origin of the numerous fibres of the muscles situated here, that are so much sunk between the bones as to be protected from injuries, to which they would otherwise be exposed. But this ligament is wanting near the upper end of the forearm, where the supinator radii brevis and flexor digitorum profundus, are immediately connected. As the head of the radius receives the tubercle of the os humeri, it is not only bended and extended along with the ulna, but may be moved almost half round its axis; and that this 190 THE HAND. motion round its axis may be sufficiently large, the ligament of the articulation is extended farther down than ordinary, on the neck of this bone, before it is connected to it; and it is very thin at its upper and lower part, but makes a firm ring in the middle. This bone is also joined to the ulna by a double articulation : for above, a tubercle of the radius plays in a socket of the ulna; whilst below, the radius gives the socket, and the ulna the tubercle. But then the motion performed at the two ends is very different: for, at the upper end, the radius does little more than turn round its axis; while, at the lower end, it moves nearly half round the cylindrical end of the ulna; and, as the hand is articulated and firmly connected here with the radius, they must move together. When the palm is turned uppermost, the radius is said to perform supination : when the back ofthe hand is above, it is said to be prone. But then the quickness and large extent of these two motions are assisted by the ulna, which, as was before observed, can move with a kind of small rotation on the sloping sides of the pulley. This rocking mo- tion, though very inconsiderable in the elbow joint itself, is conspicuous at the lower end of such a long bone; and the strong ligament connecting this lower end to the carpus, makes the hand more readily obey these motions. The Hand. The hand comprehends the whole structure, from the end of the radius to the points of the fingers. Its back part is convex, for greater firmness and strength; and it is concave before, for containing more surely and conveniently such bodies as we take hold of. One half of the hand has an obscure motion in comparison of what the other has; it serves as a base to the movable half, which can be extended back very little farther than to a straight line with the forearm, but can be considerably bent forwards. The hand consists of the carpus or wrist; metacarpus, or part adjoining the wrist; and the fingers, among which the thumb is reckoned. CARPUS. 191 Carpus. No part of the skeleton is more complex than the carpus. The following description will, therefore, be of little use to a young student, unless the bones are before him when he is reading it. Great advantage will be derived from examining two sets of carpal bones: each set belonging to the same side. In one of these sets the bones should be connected by their natural ligaments; but the two rows separated from each other. The bones of the other set should be accurately cleaned, so that their forms and surfaces may be examined. The carpus is composed of eight small bones, arranged in two rows; one of which rows is attached to the bones of the forearm, and the other to the body of the hand. These bones are named from their figure, and shall be mentioned in the order in which they occur, beginning with the row next to the forearm ; and with the external bone in each row. They are, Os Scaphoides, Lunare, Cuneiforme, Pisiforme, forming the upper row; Os Trapezium, Trapezoides, Mag- num, and Unciforme, forming the lower row. First Rotv. Os scaphoides is the largest of the eight, excepting one. It is convex above, concave and oblong below ; from which small resemblance to a boat, it has got its name. Its smooth convex surface is divided by a rough middle fossa, which runs obliquely across it. The upper largest division is articulated with the radius. The common ligament of the joint of the wrist is fixed into the fossa; and the lower division is joined to the trapezium and trapezoides. The concavity receives more than half of the round head of the os magnum. The internal side of this hollow is formed into a semilunar plane to be articulated with the following bone. The external, posterior, and anterior edges are rough, for fixing the ligaments that connect it to the sur- rounding bones. Os lunare has a smooth convex upper surface, by which it is articulated with the radius. The external side, which gives the name to the bone, is in the form of a crescent, and is joined with the scaphoid: the lower surface is hollow, for receiving part of the head of the os magnum. On the inside 192 CARPUS. Fig. 42.* of this cavity is another smooth, but narrow, oblong sinuosity, for receiving the upper end of the unciforme : and on the inside of this a small convexity is found, for its connexion with the os cuneiforme. Between the great convexity above, and the first deep inferior cavity, there is a rough fossa, in which the circular ligament of the joint of the wrist is fixed. Os cuneiforme is broader above and towards the back of the hand, than it is below and forwards; which gives it the resem- blance of a wedge. The superior slightly convex surface is included in the joint of the wrist, being opposed to the lower end of the ulna. Below this the cuneiforme bone has a rough fossa, wherein the ligament of the articulation of the wrist is fixed. On the external side of this bone, where it is contiguous to the os lunare, it is smooth, and slightly concave. Its lower surface, where it is contiguous to the os unciforme, is oblong, somewhat spiral, and concave. Near the middle of its anterior surface, a circular plane appears, where the os pisiforme is sustained. Os pisiforme is almost spherical, except one circular plane, or slightly hollowed surface, which is covered with cartilage for its motion on the cuneiforme bone, from which its whole * A diagram showing the dorsal surface of the bones of the carpus, with their articulations.—The right hand. R. The lower end of the radius. U. The lower extremity of the ulna. F. The inter-articular fibro-car'tilage attached to the styloid process of the ulna, and to the margin of the articular surface of the radius. S. The scaphoid bone: the numeral (5) indicates the number of bones with which it articu- lates. L. The semilunare articulating with five bones. C. The cuneiforme, artic- ulating with three bones. P. The pisiforme, articulating with the cuneiforme only. T. The first bone of the second row—the trapezium, articulating with four bones. T. The second bone—the trapezoides, articulating also with four bones. M. The os magnum, articulating with seven. U. The unciforme, articulating with five. The numerals, 1, 3, 1, 2, 1, on the metacarpal bones, refer to the number of their articulations with the carpal bones. J CARPUS. 193 rough body is prominent forwards into the palm; having the tendon of the flexor carpi ulnaris, and a ligament from the styloid process of the ulna fixed to its upper part; the trans- verse ligament of the wrist is connected to its external side: ligaments extended to the unciforme bone, and to the os metacarpi of the little finger, are attached to its lower part; the abductor minimi digiti has its origin from its forepart; and, at the external side of it, a small depression is formed for the passage of the ulnar nerve. Second Row. Os Trapezium has four unequal sides and angles in its back part, from which it has got its name. Above, its surface is smooth, slightly hollowed, and semicircular, for its conjunction with the os scaphoides. Its internal side is an oblong concave square, for receiving the following bone. The inferior surface is formed into a pulley, which faces obliquely outwards and downwards when the palm presents forward. On this pulley the first bone ofthe thumb is moved. At the internal side of the pulley, a small oblong smooth surface is formed by the os metacarpi indicis. The forepart ofthe trapezium is prominent in the palm, and near to the in- ternal side has a sinuosity in it, where the tendon of the flexor carpi radialis is lodged, on the ligamentous sheath of which the tendon of the flexor longus pollicis manus plays: near this the bone is scabrous, where the transverse ligament of the wrist is connected, the abductor and the flexor brevis pollicis have their origin, and ligaments go out to the first of the thumb. Os trapezoides, so called from the irregular quadrangular figure of its back part, is the smallest bone ofthe wrist, except the pisiforme. The figure of it is an irregular cube. It has a small hollow surface above, by which it joins the scaphoides; a long convex one externally, where it is contiguous to the trapezium; a small internal concavity, for its conjunction with the os magnum; and an inferior convex surface, the edges of which are, however, so raised before and behind, that 17 194 CARPUS. a sort of pully is formed, where it sustains the os metacarpi indicis. Os magnum, so called because it is the largest bone of the carpus, is oblong, having four quadrangular sides, with a round upper end, and a triangular plane one below. The round head is divided by a small rising, opposite to the connexion of the os scaphoides and lunare, which together form the cavity for receiving it. On the outside a short plane surface joins the os magnum to the trapezoides. On the inside is a long narrow concave surface where it is contiguous to the os unciforme. The lower end, which sustains the metacarpal bone of the middle finger, is triangular, slightly hollowed, and farther advanced on the external side than on the internal, having a considerable oblong depression made on the advanced outside by the metacarpal bone of the fore-finger; and generally there is a small mark of the os metacarpi digiti annularis on its in- ternal side. Os unciforme has got its name from a thin broad process that stands out from it forwards into the palm, and is hollow, for affording passage to the tendons of the flexors of the fingers. To this process, also, the transverse ligament is fixed that binds down, and defends these tendons ; and the flexor and abductor muscles of the little finger have part of their origin from it. The upper plane surface is small, convex, and joined with the os lunare : the external side is long and slightly convex, adapted to the contiguous os magnum. The internal surface is oblique, and irregularly convex, to be articulated with the cuneiforme bone. The lower end is divided into two concave surfaces; the internal is joined with the metacarpal bone of the little finger; and the external one is fitted to the metacarpal bone of the ring finger. The nature of the carpus will be best understood by studying the bones placed together, in their natural order, in the two rows. When thus placed, they compose a structure of an oblong form, whose greatest length extends across the wrist, and forms a concavity in front, while it is convex posteriorly. CARPUS. 195 Fig. 43.* Two bones of the first row, viz., the scaphoides and lunare, form an oblong convex surface, which has a transverse position with respect to the arm, and applies to the concave surface at the end of the radius. These surfaces are particularly calculated for flexion and extension, and also for a considerable motion to each side; and by a suc- cession of these flexures, in different directions, the hand performs a cir- cular motion, although it cannot perform at this joint a rotation, or revolution, on the axis of the car- pus. The under surface of the bones has a deep concavity, which is composed by the scaphoides, lunare and cuneiforme, and receives a prominence of the second row. It also presents a convex surface, formed by the scaphoides, which is received by the second row. The upper surface of the second row, which is concerned in this articulation, is very irregular ; it has a head formed by the magnum and unciforme, which penetrates deeply into the cavity of the first row. On the outside of this head the tra- pezium and trapezoides form a surface, which receives the projecting part of the scaphoides ; so that the first row receives, and is received by the second, and the two surfaces are well calculated for moving, to a certain extent, in the way of flexion and extension, upon each other. The lower surface ofthe second row, which is connected to * The hand viewed upon its anterior or palmer aspect. 1. The scaphoid bone. 2. The semilunare. 3. The cuneiforme. 4. The pisiforme. 5. The trapezium. 6. The groove in the trapezium that lodges the tendon of the flexor carpi radialis. 7. The trapezoides. 8. The os magnum. 9. The unciforme. 10, 10. The five metacarpal bones. 11, 11. The first row of phalanges. 12, 12. The second row. 13, 13. The third row, or ungual phalanges. 14. The first phalanx of the thumb. l.*>. The second and last phalanx ofthe thumb. 196 THE METACARPUS. the metacarpal bones, appears like the side of an arch, which is partly induced by the wedge-like form of the two bones in the centre; viz., the trapezoides, and the magnum. When the hand hangs by the side, and the palm is forward, all of this surface presents downwards, except that portion of it which is formed by the trapezium. This bone is placed obliquely between the two rows, and its surface for supporting the thumb presents obliquely downwards and outwards. The trapezoides supports the fore-finger, the magnum the middle finger. The scaphoides and the trapezium are very prominent at the external side of the anterior concave surface of the car- pus ; and the unciforme process, and the os pisiforme on the internal. The Metacarpus, Consists of four bones, which sustain the finger. Each bone is long and round, with its ends larger than its body. The upper end, which some call the base, is flat and oblong, in- clining somewhat to the wedge-like form, without any con- siderable head or cavity ; but it is, however, somewhat hollowed for the articulation with the carpus. It is made flat and smooth on the sides where these bones are contiguous to each other. Their bodies are flattened on the back part, particularly below the middle, by tendons of the extensors of the fingers. The anterior surface of these bodies is a little convex, especially in their middle ; along which a sharp ridge stands out, separating the musculi interossei placed on each side of these bones, which are there made flat and plain by these muscles. Their lower ends are raised into large oblong smooth heads, whose greatest extent is forwards from the axis of the bone. At the forepart of each side of the root of these heads, one or two tubercles stand out, for fixing the ligaments that go from one metacarpal bone to another, to preserve them from being drawn asunder. Around the heads a rough ring may be j THE METACARPUS. 197 remarked, for the capsular ligaments of the first joints of the fingers to be fixed to ; and both sides of these heads are flat, by pressing on each other. The substance ofthe metacarpal bones is the same with that of all long bones. The metacarpal bones are joined above to the bones of the carpus, and to each other by surfaces almost flat. These con- nexions do not admit of much motion. The articulation of the round heads, at their lower ends, with the cavities ofthe first bones ofthe fingers, will soon be described. The concavity on the forepart of the metacarpal bones, and the position of their bases on the arched carpus, cause them to form a hollow in the palm of the hand, which is often useful to us. The spaces between them lodge muscles, and their small motion makes them fit supporters for the fingers to play on. Though the ossa metacarpi so far agree, yet they may be distinguished from each other by the following marks : The metacarpal bone of the fore-finger is generally the longest. Its base, which is articulated with the os trapezoides, is hollow in the middle. The small ridge on the external side i of this oblong cavity is smaller than the one opposite to it, and is made flat on the side by the trapezium. The internal ridge is also smooth, and flat on its ulnar side, for its conjunction with the os magnum; immediately below which, a semicir- cular smooth flat surface shows the articulation of this to the second metacarpal bone. The back part of this base is flattened where the long head of the extensor carpi radialis is inserted, and its forepart is prominent where the tendon of the flexor carpi radialis is fixed. The tubercle at the internal root of its head is larger than the external. Its base is so firmly fixed to the bone it is connected with, that it has no motion. The metacarpal bone of the middle finger is generally the second in length ; but often it is as long as the former : some- times it is longer; and it frequently appears only to equal the first by the os magnum being farther projected downwards than any other bone of the wrist. Its base is a broad super- 17* 198 THE METACARPUS. ficial cavity, slanting inwards; the external posterior angle of which is so prominent, as to have the appearance of a process. The external side of this base is made plane in the same way as the external side of the former bone, while its internal side has two hollow circular surfaces, for joining the third meta- carpal bone ; and between these surfaces there is a rough fossa, for the adhesion of a ligament,and lodging mucilaginous glands. The extensor carpi radialis brevior is inserted into the back part of this base. The two sides of this bone are almost equally flattened; but the ridge on the forepart of the body inclines inwards. The tubercles at the forepart of the root of the head are equal. The motion of this bone is very little more than that of the former ; and therefore these two firmly resist bodies pressed against them by the thumb or fingers, or both. The metacarpal bone of the ring finger is shorter than the second metacarpal bone. Its base is semicircular and convex, for its conjunction with the os unciforme. On its external side are two smooth convexities, and a middle fossa, adapted to the second metacarpal bone. The internal side has a triangular smooth concave surface to join it with the fourth one. The anterior ridge of its body is situated more to the inside than to the outside. The tubercles near the head are equal. The motion of this third metacarpal bone is greater than the motion ofthe second. The metacarpal bone of the little finger is the smallest and sharpest. Its base is irregularly convex, and rises slanting inwards. Its external side is exactly adapted to the third metacarpal bone. The internal has no smooth surface,because it is not contiguous to any other bone; but it is prominent where the extensor carpi ulnaris is inserted. As this meta- carpal bone is furnished with a proper moving muscle, has the plainest articulation, is most loosely connected and least con- fined, it not only enjoys a much larger motion than any ofthe rest, but draws the third bone with it, when the palm of the hand is to be made hollow by its advancement forwards, and by the prominence of the thumb opposite to it. THUMB AND FINGERS. 199 Thumb and Fingers. The thumb and fore-fingers are each composed of three bones. The thumb is situated obliquely in respect to the fingers; neither opposite directly to them, nor in the same plane with them. All its bones are much thicker and stronger in proportion to their length, than the bones of the fingers are; which is extremely necessary, as the thumb counteracts all the fingers. The first bone of the thumb has its base adapted to the pecu- liar articulating surface of the trapezium: for, in viewing it from one side to the other, it appears convex in the middle; but, when viewed from behind forwards, it is concave there. The edge at the forepart of this base is extended farther than any other part; and round the back part of the base a rough fossa may be seen, for the connexion of the ligaments of this joint. The body and head of this bone are of the same shape as the ossa metacarpi; only that the body is shorter, the head flatter, and tubercles at the forepart of its root larger. The articulation of the upper end of this bone is remarkable; for, though it has protuberances and depressions adapted to the double pulley ofthe trapezium, yet it enjoys a circular motion, as the joints do where a round head of the one plays in the orbicular socket of another; it is, however, more confined, and less expeditious, but stronger and more secure than such joints generally are. The second bone of the thumb has a large base formed into an oblong cavity, whose greatest length is from one side to the other. Round it several tubercles may be remarked, for the insertion of ligaments. Its body is convex, or half round behind; but flat before, for lodging the tendon of the long flexor of the thumb, which is tied down by ligamentous sheaths, that are fixed on each side to the angle at the edge of this flat surface. The lower end of this second bone has two lateral round pro- tuberances, and a middle cavity, whose greatest extent of smooth surface is forwards and backwards. 200 FINGERS. The articulation of the upper end of this second bone would seem calculated for motion in all directions; yet, on account ofthe strength of its lateral ligaments, the oblong figure ofthe joint itself, and mobility of the first joint, it only allows flexion and extension; and these are generally much confined. The third bone ofthe thumb is the smallest, with a large base, whose greatest extent is from one side to the other. This base is formed into two cavities and a middle protuberance, to be adapted to the pulley of the former bone. This bone becomes gradually smaller, till near the lower end, where it is a little enlarged, and has an oval scabrous edge. Its body is rounded behind, but is flatter than in the former bone, for sustaining the nail. It is flat and rough before, by the insertion of the flexor longus pollicis. The motion of this third bone is confined to flexion and extension. The regular arrangement of the bones ofthe fingers in three rows, has obtained for them the name of the three phalanges. All of them have half round convex surfaces, covered with an aponeurosis, formed by the tendons of the extensors, lumbri- cales, and interossei, and placed directly backwards, for their greater strength; and their flat concave part is forwards, for taking hold more surely, and for lodging the tendons of the flexor muscles. The ligaments for keeping down these tendons are fixed to the angles that are between the convex and concave sides. The bones of the first phalanx of the fingers answer to the description of the second bone of the thumb; only that the cavity in their base is not so oblong; nor is their motion on the metacarpal bones so much confined; for they can move laterally or circularly, the fore-finger in particular, but have no rotation, or a very small degree of it, round their axis. The second bone of the fingers has its base formed into two lateral cavities, and a middle protuberance: while the lower end has two lateral protuberances, and a middle cavity: there- fore, it is joined at both ends in the same manner; which none of the bones of the thumb are. THE THIGH. 201 The third bone differs in nothing from the description ofthe third bone of the thumb, except in the general distinguishing marks; and, therefore, the second and third phalanx of the fingers enjoy only flexion and extension. All the difference of the phalanges of the several fingers consists in their magnitude. The bones of the middle finger being the longest and largest; those of the fore-finger come next to these in thickness, but not in length, for those of the ring finger are a little longer. The little finger has the smallest bones. This disposition is the best contrivance for holding the largest bodies; because the longest fingers are applied to the middle largest periphery of such substances as are of a spherical figure. The Inferior Extremities. The inferior extremities consist of the Thigh, Leg, and Foot. The Thigh Consists of one bone only; the os femoris, which is very strong, and larger than any other in the skeleton. It is nearly cylindrical in the middle, and slightly curved. The upper extremity is a spherical head, connected to the body ofthe bone by a neck. The lower extremity is much larger than the body, and is formed into two condyles. The upper end of this bone is not continued in a straight line with the body of it, but the axis of it inclines obliquely inwards and upwards, whereby the distance between these two bones, at their upper part, is considerably increased. The head is the greater portion of a sphere. Towards its lower internal part, a round, rough spongy pit is observable, where the strong ligament, commonly, but inaccurately, called the round one, is fixed, to be extended from thence to the lower internal part of the receiving cavity, where it is considerably broader than near to the head of the thigh bone. The neck of the os femoris has a great many large holes, into which the fibres of the strong 202 THE THIGH. ligament, continued from the capsular, enter, and are thereby firmly united to it; and round the root of the neck, where it rises from the bone, a rough ridge is found, where the capsular Fig. 44" ligament of the articulation itself is con- nected. Below this root, a large unequal protuberance, called trochanter major, stands out; the external convex part of which is distinguished into three different surfaces; whereof the one on the upper and front part is scabrous and rough, for the insertion ofthe glutaeus minimus; the supe- rior one is smooth, and has the glutaeus medius inserted into it; and the one behind is made flat and smooth, by the tendon of the glutaeus maximus passing over it. The upper edge of this process is sharp and pointed at its back part, where the glutaeus medius is fixed; but forwards it is more obtuse, and under it is a depression, into which some of the muscles, which rotate the thigh outwards, are fixed. From the posterior prominent part of this great tro- chanter, a rough ridge runs backwards and downwards, into which the quadratus is inserted. In the deep hollow, at the inter- nal upper side of this ridge, the obturator externus is implanted. More internally, a conical process, called trochanter minor, rises, for the insertion ofthe musculus psoas and iliacus internus; and the pectineus is implanted into a rough hollow, below its internal root. The muscles inserted into these processes being the principal instruments of the \M * The right femor, seen upon the anterior aspect. 1. The shaft. 2. The head. 3. The neck. 4. The great trochanter. 5. The anterior intertrochanteric line. 6. The lesser trochanter. 7. The external condyle. 8. The internal condyle. 9. The tuberosity for the attachment of the external lateral ligaments. 10. The groove for the tendon of origin of the popliteus muscle. 11. The tuberosity for the attachment of the internal lateral ligament. OS FEMORIS. 203 rotary motion of the thigh, have occasioned the name of tro- chanters to be given to these processes. The body of the os femoris is convex on the forepart and concave behind, which enables us to sit without leaning too much on the posterior muscles. On the posterior concave surface is a broad rough ridge called linea aspera, which commences near the great trochanter, and continues downwards, more than two-thirds of the length of the bone, when it divides into two ridges, which descend towards each condyle. The internal of these ridges is the most smooth, and the space between them is nearly flat. Near the end of each of these ridges, a small, smooth-protuberance may often be remarked, where the two heads of the external gas- trocnemius muscles take their rise; and from the forepart of the internal tubercle, a strong ligament is extended to the inside of the tibia. The lower end of the os femoris is larger than any other part of it, and is formed into two great protuberances, one on each side, which are called its condyles: between them a consider- able cavity is found, especially at the back part, in which the crural vessels and nerves lie. The internal condyle is longer than the external, which must happen from the oblique posi- tion of this bone, to give less obliquity to the leg. These pro- cesses are of an oblong form, and are placed obliquely with respect to each other; being in contact before and separated to a considerable distance behind. They form in front a smooth pulley-like surface, the external side of which is highest, on which the patella moves. Below, they are flat; and posteriorly, they are regularly convex. Between these convex portions is a rough cavity, from which the crucial ligament arises, to be attached to the tibia. Round the lower end ofthe thigh bone, large holes are found, into which the ligaments for the security of the joint are fixed, and blood-vessels pass to the internal substance of the bone. The thigh bone being articulated above with the acetabulum of the os innominatum, which affords its round head a secure and extensive play, can be moved to every side: but it is 204 THE LEG. restrained in its motion outwards by the high brims of the cavity, and by the round ligament; for otherwise the head of the bone would have been frequently thrust out at the breach of the brims on the inside, which allows the thigh to move con- siderably inwards. The body of this bone enjoys little or no rotary motion, though the head most commonly moves round its own axis; because the oblique direction of the neck and head from the bone, is such, that the rotary motion of the head can only bring the body ofthe bone forwards and backwards. Nor is the head, as in the arm, ever capable of being brought to a straight direction with its body; so far, however, as the head can move within the cavity backwards and forwards, the rest of the bone may have a partial rotation. From the oblique position of these bones it results, that there is a considerable distance between them above, while the knees are almost contiguous. Sufficient space is thereby left for the external parts of generation, for the two great outlets of urine and faeces, and for the large thick muscles that move the thigh inwards. At the same time this situation of the thigh bone renders our progression quicker, surer, straighter, and in less room : for, had the knees been at a greater distance from each other, we must have been obliged to describe some part of a circle with the trunk of our body in making a long step; and when one leg was raised from the ground, our centre of gravity would have been too far from the base of the other, and we should consequently have been in danger of falling; so that our steps would neither have been straight nor firm, nor would it have been possible to walk in a narrow path, had our thigh bones been otherwise placed. In consequence, however, of the weight of the body bearing so obliquely on the joint of the knee by this situation of the thigh bones, weak rickety children become knock-kneed. The Leg Is composed ofthe two bones, the tibia and fibula. The patella being evidently appropriated to the knee-joint, may be regarded as common both to the thigh and leg. THE TIBIA. 205 Fig. 45.* The Tibia Is the long thick triangular bone, situated at the internal part of the leg, and continued in almost a straight line from the thigh bone. The name is derived from its resem- blance to the ancient musical instrument. The upper end of the tibia is large, bul- bous, and spongy. It has a horizontal sur- face, divided into two cavities, by a rough, irregular protuberance, which is hollow at its most prominent part, as well as before and behind. The anterior of the two ligaments that compose the great crucial is inserted into the middle cavity; and the depression behind receives the posterior ligament. The two broad cavities at the sides of this pro- tuberance are not equal; for the internal is oblong and deep, to receive the internal condyle of the thigh bone ; while the exter- nal is more superficial and round, for the external condyle. In each of these two cavities of a recent subject, a semilunar cartilage is placed, which is thick at its convex edge, and becomes gradually thinner towards the con- cave or interior edge. The thick convex edge of each cartilage is connected to the capsular and other ligaments of the articu- lation ; but so near to their rise from the tibia, that the cartilages are not allowed to change their places ; while their narrow ends are fixed at the insertion of the strong cross ligament into the tibia, and seem to have their substance united with it; there- fore a circular hole is left between each cartilage and the ligament, in which the most prominent convex part of each * The tibia and fibula of the right leg, articulated and seen from the front. 1. The shaft of the tibia. 2. The inner tuberosity. 3. The outer tuberosity. 4. The spinous process. 5. The tubercle. 6. The internal or subcutaneous surface of the shaft. 7. The lower extremity of the tibia. 8. The internal malleolus. 9. The shaft of the fibula. 10. Its upper extremity. 11. Its lower extremity, the external malleolus. 18 206 TIBIA. condyle of the thigh bone moves. The circumference of these cavities is rough and unequal, for the firm connexion of the ligaments of the joint. Immediately below the edge, at its back part, two rough flattened protuberances stand out; into the internal, the tendon of the semimembranosus muscle is inserted; and a part of the cross ligament is fixed to the exter- nal. On the outside of this last tubercle, a smooth slightly hollowed surface is formed by the action of the popliteus muscle. Before the forepart of the upper end of the tibia, a large rough protuberance rises, to which the strong tendinous liga- ment of the patella is fixed. On the internal side of this, there is a broad scabrous slightly hollowed surface, to which the internal long ligament of the joint, the aponeurosis of the vastus internus, and the tendons of the semitendinous, gracilis, and sartorius, are fixed. Below the external edge of the upper end of the tibia, there is a flat circular surface, covered in a recent subject with cartilage, for the articulation of the fibula. The body of the tibia is triangular. The anterior angle is very sharp, and is commonly called the spine or shin. This ridge is not straight; but turns first inwards, then outwards, and lastly inwards again. The plane internal side is smooth and equal, being little subjected to the actions of muscle; but the external side is hollowed above by the tibialis anticus, and below by the extensor digitorum longus and extensor pollicis longus. The two angles behind these sides are rounded by the action of the muscles; the posterior side comprehended between them is not so broad as those already mentioned, but is more oblique and flattened by the action of the tibialis posticus and flexor digitorum longus. A little above the middle of the bone, the internal angle terminates, and the bone is made round by the pressure of the musculus soleus. Near to this, the passage of the medullary vessels is seen slanting obliquely downwards. The lower end of the tibia is hollowed, with a small protu- berance in the middle. The internal side of this cavity, which is smooth, and in a recent subject is covered with cartilage, is FIBULA. 207 extended into aconsiderableprocess,commonlynamedma//eo/ws internus ; the point of which is divided by a notch, and from it ligaments are sent out to the foot. The external side of this end of the tibia has a rough irregular cavity formed in it, for receiving the lower end of the fibula. The posterior side has two lateral grooves, and a small middle protuberance. In the internal depression, the tendons of the musculus tibialis posticis and flexor digitorum longus are lodged; and in the external, the tendon of the flexor longus pollicis plays. From the middle protuberance, ligamentous sheaths go out, for tying down these tendons. The Fibula Is the small bone, placed on the outside of the leg, opposite to the external angle of the tibia; the shape of it is irregular. The head of the fibula has a circular surface formed on its inside, which, in a recent subject is covered with a cartilage; and it is so closely connected to the tibia by ligaments, as to allow only a very small motion backwards and forwards. This head is protuberant and rough on its outside, where a strong round ligament and the musculus biceps are inserted, and, below the back part of its internal side, a tubercle may be re- marked, that gives rise to the strong tendinous part of the soleus muscle. The body of this bone is a little crooked inwards and back- wards : which figure is owing to the actions of the muscles. The sharpest angle of the fibula is forwards; on each side of which the bone is considerably, but unequally, depressed by the bellies of the several muscles that rise from or act upon it. The external surface of the fibula is depressed obliquely from above downwards and backwards, by the two peronsei. Its internal surface is unequally divided into two narrow longitudinal planes, by an oblique ridge extended from the upper part of the anterior angle. To this ridge the ligament stretched between the two bones of the leg is connected. The anterior of the two planes is very narrow above, where the extensor longus digitorum and extensor longus pollicis arise from it: but is 208 FIBULA. broader below, where it has the print of the peroneus tertius. The posterior plane is broad and hollow, giving origin to the larger share of the tibialis posticus. The internal angle of this bone has a tendinous membrane fixed to it, from which some fibres of the flexor digitorum longus take their rise. The posterior surface of the fibula is the plainest and smoothest; but is made flat above by the solseus, and is hollowed below by the flexor pollicis longus. In the middle of this surface, the canal for the medullary vessels may be seen slanting downwards. The lower end of the fibula is extended into a spongy oblong head: on the inside of which is a convex, irregular, and frequently a scabrous surface, that is received by the external hollow of the tibia, and so firmly joined to it by a very thin intermediate cartilage and strong ligaments, that it scarce can move. Below this the fibula is stretched out into a smooth coronoid process, covered with cartilage on its internal side, and is there contiguous to the outside of the first bone of the foot, the astragalus, to secure the articulation. This process, named malleolus externus, being situated farther back than is the internal malleolus, and in an oblique direction, obliges us, naturally, to turn the forepart of the foot outwards. At the lower internal part of this process, a spongy cavity for muci- laginous glands may be remarked; from its point, ligaments are extended to the bones of the foot, viz. the astragalus, os calcis, and os naviculare; and from its inside, short strong ones go out to the astragalus. On the back part of it a sinuosity is made by the tendons of the peronei muscles. When the ligament, extended over these tendons from the one side ofthe depression to the other, is broken, stretched too much, or made weak by the sprain, the tendons frequently start forwards to the outside of the fibula. The conjunction ofthe upper end of the fibula with the tibia is by plain surfaces tipped with cartilage; and at its lower end the cartilage seems to glue the two bones together; not, however, so firmly in young people, but that the motion at the other end is very observable. In old subjects, the two bones THE PATELLA OR ROTULA. 209 of the leg are sometimes united by anchylosis at their lower ends. The principal use of this bone is to afford origin and inser- tion to muscles; and to give a particular direction to their tendons. It likewise assists to make the articulation of the foot more secure and firm, and to complete the hinge-like joint at the ankle. The ends of the tibia and fibula being larger than their middle, a space is here left, which is filled up with a ligament similar to that which is extended between the bones of the forearm; and which is also discontinued at its upper part, where the tibialis anticus immediately adheres to the solaeus and tibialis posticus ; but every where else it gives origin to muscular fibres. The Patella or Rotula Is a small flat bone situated at the forepart of the joint of the knee. Its shape resembles the common figure of the heart with its point downwards. The anterior convex surface of the rotula is pierced by a great number of holes, into which are inserted the fibres of the strong ligament that is spread over it. Its posterior surface is smooth, covered with a cartilage, and divided by a middle convex ridge into two cavities, of which the external is largest; and both are exactly adapted to the pulley of the os femoris, on which they are placed in the most ordinary unstraining postures of the legs: but, when the leg is much bent, the patella descends far down on the condyles; and when the leg is fully extended, the patella rises higher in its upper part than the pulley of the thigh bone. The plane smooth surface is surrounded by a rough prominent edge, to which the capsular ligament adheres. Below, the point of the bone is scabrous, where the strong tendinous ligament from the tubercle of the tibia is fixed. The upper horizontal part of this bone is flattened and unequal where the tendons of the exten- sors of the leg are inserted. The substance of the patella is cellular, with very thin firm external plates ; but then these cells are so small and such a quantity of bone is employed in their formation, that scarce 18* 210 PATELLA. any bone of its bulk is so strong. But, notwithstanding this strength, it is sometimes broken by the violent straining effort of the muscles. The principal motions of the knee joint are flexion and extension. In the former of these, the leg may be brought to a very acute angle with the thigh, by the condyles of the thigh bones being round, and made smooth far backwards. In performing this, the patella is pulled down by the tibia. When the leg is to be extended, the patella is drawn upwards, conse- quently, the tibia forwards,by the extensor muscles; which,by means of the protuberent joint, and of this thick bone with its ligament, have the chord, with which they act, fixed to the tibia at a considerable angle, and act, on that account, with advantage ; but. they are restrained from pulling the leg farther than to a straight line with the thigh, by the posterior part of the cross ligament, that the body might be supported by a firm perpendicular column: for, at this time, the thigh and leg are as little movable in a rotary way, or to either side, as if they were one continued bone. But, when the joint is a little bent, the rotula is not tightly braced, and the posterior ligament is relaxed ; therefore, this bone may be moved a little to either side, or with a small rotation in the superficial cavities of the tibia; which is done by the motion of the external cavity backwards and forwards, the internal serving as a sort of axis. Seeing, then, one part of the cross ligament is situated perpen- dicularly, and the posterior part is stretched obliquely from the internal condyle of the thigh outwards, that posterior part of the cross ligament prevents the leg from being turned much inwards; but it could not hinder it from turning outwards almost round, were not that motion confined by the lateral ligaments of this joint, which can yield little. This rotation ofthe leg outwards is of great advantage to us in crossing our legs, and turning our feet outwards, on several necessary occasions; though it is necessary that this motion should not be very large, to prevent frequent luxations here. While all these motions are performing, the part of the tibia that moves immediately on the condyles is that which is within THE FOOT.--TARSUS. 211 the cartilaginous rings, which, by the thickness on their out- sides, make the cavities of the tibia more horizontal, by raising their external side where the surface of the tibia slants downwards. By these means the motions of this joint are more equal and steady than otherwise they would have been. The cartilages being capable of changing a little their situation, contribute to the different motions and postures of the limb, and, likewise, make the motions larger and quicker. The Foot. The foot is divided into the tarsus, metatarsus, and toes. The sole of the foot is necessarily described as the inferior part, and the side of the great toe as the internal. Tarsus. Fig. 46.* The tarsus consists of seven spongy bones; to wit, the astragalus, os calcis, naviculare, cuboides,cuneiforme externum, cuneiforme medium and cuneiforme inter- num. The astragalus is the uppermost of these bones. The os calcis is below the astragalus, and forms the heel. The os naviculare is in the middle of the internal sides of the tarsus. The os cuboides is the most external of the row of four bones,at its forepart. The os cuneiforme externum is placed at the inside of the cuboid. The cuneiforme medium is between the external and internal cuneiforme bones; and the internal cuneiforme is at the internal side of the foot. The upper part of the astragalus is formed * The dorsal surface of the left foot. 1. The astragalus; its superior quadrilateral articular surface. 2. The anterior extremity of the astragalus, which articulates with (4.) the scaphoid bone. 3. The os calcis. 4. The scaphoid bone. 5. The internal cuneiform bone. 6. The middle cuneiform bone. 7. The external cuneiform bone. 8. The cuboid bone. 9. The metatarsal bones of the first and second toes. 10. The first phalanx ofthe great toe. 11. The second phalanx ofthe great toe. 12. The first phalanx of the second toe. 13. Its second phalanx. 14. Its third phalanx. 212 ASTRAGALUS. into a large smooth head, which is slightly hollowed in the middle; and therefore resembles a superficial pulley, by which it is fitted to the lower end of the tibia. The internal side of this head is flat and smooth, to play on the inter- nal malleolus. The external side has also such a surface, but larger, for its articulation with the external malleolus. Round the base of this head there is a rough fossa; and immediately before the head, as also below its internal smooth surface, we find a considerable rough cavity. The lower surface of the astragalus is divided by an irregular deep rough fossa, which, at its internal end, is narrow, but gradually widens as it stretches obliquely outwards and forwards. The smooth surface, covered with cartilage, behind this fossa, is large, oblong, extended in the same oblique situa- tion with the fossa, and concave for its conjunction with the os calcis. The posterior edge of this cavity is formed by two sharp-pointed rough processes, between which is a depression made by the tendon of the flexor pollicis longus. The lower surface before the fossa is convex, and composed of three distinct smooth planes. The long one behind, and the exterior or shortest, are articulated with the heel bone ; while the internal, which is the most convex of the three, rests and moves upon a cartilaginous ligament, that is continued from the os calcis to the os naviculare, without which ligament the astra- galus could not be sustained, but would be pressed out of its place by the great weight it supports; and the other bones of the tarsus would be separated. Nor would a bone be fit here, because it must have been thicker than could conveniently be allowed; otherwise it would break, and would not prove such an easy bending base, to lessen the shock which is given to the body, in leaping, running, &c. The forepart of this bone is formed into a convex oblong smooth head, which is received by the os naviculare, and is placed obliquely; its longest axis inclining downwards and inwards. Round the root of this head, especially on the upper surface, a rough fossa may be remarked. The astragalus is articulated above to the tibia and fibula, which together form one cavity. In this articulation, flexion OS CALCIS. 213 and extension are the most considerable motions; the other motions being restrained by the malleoli, and by the strong ligaments which go out from the points of these processes, to the astragalus and os calcis. When the root is bent, as it commonly is when we stand, no lateral or rotary motion is allowed in this joint; for then the head of the astragalus is sunk deep between the malleoli, and the ligaments are tense : but when the foot is extended, the astragalus can move a little to either side, and with a small rotation. By this contrivance, the foot is firm, when the weight of the body is to be supported on it; and, when a foot is raised, we are at liberty to direct it more exactly to the place we intend next to step upon. The astragalus is joined below to the os calcis; and before to the os naviculare, in the manner to be explained when these bones are described. The os calcis is the largest bone of the seven. Behind, it is formed into a large knob, commonly called the heel, the poste- rior surface of which is rough below for the insertion of what is called the tendo-achillis, and oblique above to allow the heel to be depressed without pressing against the tendon. On the upper surface of the os calcis, there is an irregular oblong smooth convexity, adapted to the concavity at the back part of the astragalus ; and beyond this a narrow fossa is seen, which divides it from two small concave smooth surfaces, that are joined to the forepart of the astragalus. The posterior of these smooth surfaces, which is the largest, is the upper surface of a process which projects inwards: and under it is a small sinuosity for the tendon of the flexor digitorum longus. The external side of this bone is flat, with a superficial fossa running horizontally, in which the tendon of the musculus peroneus longus is lodged. The internal side of the heel bone is hollowed, for lodging the origin of the massa carnea,and for the safe passage of tendons, nerves, and arteries. Under the side of the internal smooth concavity, a particular groove is made by the tendon of the flexor pollicis longus; and from the thin protuberance of this internal side a cartilaginous ligament that supports the astragalus, goes out to the os naviculare; on 214 OS NAVICULARE. which ligament, and on the edge of this bone to which it is fixed, the groove is formed for the tendon of the flexor digito- rum profundus. The lower surface of this bone is flat at the back part, and immediately before this plane, there are two tubercles, from the internal of which the musculus abductor pollicis, flexor digitorum sublimis, as also part of the aponeurosis plantaris, and of the abductor minimi digiti, have their origin; and the other part of the abductor minimi digiti and aponeurosis plan- taris rises from the external. Before these protuberances, this bone is concave, for lodging the flexor muscles; and, at its forepart, we may observe a rough depression, from which, and a tubercle behind it, the ligament goes out that prevents this bone from being separated from the os cuboides. The forepart of the os calcis is formed into an oblong pulley- like smooth surface, which is circular at its upper external end, but is pointed below. The smooth surface is fitted to the os cuboides. Though the surfaces by which the astragalus and os calcis are articulated, seem fit enough for motion, yet the very strong ligaments, by which these bones are connected, prevent much motion, and give firmness to this principal part of our base, which rests on the ground. Os naviculare is somewhat oval. It is formed into an oblong concavity behind, for receiving the anterior head of the astragalus. The upper surface is convex. Below, the surface is very unequal and rough; but hollow for the safety of the muscles. Its internal extremity is very prominent. The abductor pollicis takes in part its origin from it, the tendon of the tibialis posticus is inserted into it, and to it two remarkable ligaments are fixed; the first is the strong one, formerly men- tioned, which supports the astragalus; the second is stretched from this bone obliquely across the foot, to the metatarsal bones of the middle toe, and of the toe next to the little one. On the outside of the os naviculare there is a semicircular smooth surface, where it is joined to the os cuboides. The forepart of this bone is covered with cartilage, and divided into three smooth planes, fitted to the three ossa cuneiformia. OS CUBOIDES.--OS CUNEIFORME EXTERNUM. 215 The os naviculare and astragalus are joined as a ball and socket; and the naviculare moves in several directions in turn- ing the toes inwards, or in raising or depressing either side of the foot, though the motions are greatly restrained by the liga- ments which connect this to the other bones of the tarsus. Os Cuboides is an irregular cube. Behind, it is formed into an oblong unequal cavity, adapted to the forepart of the os calcis. On its internal side, there is a small semicircular smooth cavity, to join the os naviculare. Immediately before which, an oblong smooth plane is made by the os cuneiforme exter- num ; below this the bone is hollow and rough. On the internal side of the lower surface, a round protuberance and fossa are found, where the musculus abductor pollicis has its origin. On the external side of this surface, there is a broad ridge running forwards and inwards, covered with cartilage; immediately before which a smooth fossa may be observed, in which the tendon of the peroneus primus runs obliquely across the foot. Before, the surface of the os cuboides is flat, smooth, and slightly divided into two planes, for sustaining the os metatarsi ofthe little toe, and ofthe toe next to it. The form of the back part of the os cuboides, and the liga- ments connecting the joint with the os calcis, both concur in allowing little motion in this part. Os cuneiforme externum is shaped like a wedge, being broad and flat above, with long sides running obliquely down- wards, and terminating in an edge. The upper surface of this bone is an oblong square. The one behind is nearly a triangle, but not complete at the inferior angle, and is joined to the os naviculare. The external side is an oblong square divided as it were by a diagonal; the upper half of it is smooth, for its conjunction with the os cuboides: the other is a scabrous hol- low, with a small smooth impression made by the os metatarsi ofthe toe next to the little one. The internal side of this bone is flattened before by the metatarsal bone of the toe next to the great one, and the back part is also flat and smooth where the os cuneiforme medium is contiguous to it. The forepart of this bone is triangular, for sustaining the os metatarsi of the middle toe. 216 OS CUNEIFORME. Os cuneiforme, or minimum, is still more exactly the shape of a wedge than the former. Its upper part is square; its in- ternal side has a flat smooth surface for its connexion with the adjoining bone; the external side is smooth and a little hol- lowed, where it is contiguous to the last described bone. Be- hind, this bone is triangular, where it is articulated with the os naviculare; and it is also triangular at its forepart, where it is contiguous to the os metatarsi of the toe next to the great one. The broad thick part of the os cuneiforme maximum, or in- ternum, is placed below, and the small thinner edge is above. The surface of the os cuneiforme behind, where it is joined to the os naviculare, is hollow, smooth, and of a circular figure below, but pointed above. The external side consists of two smooth and flat surfaces. With the posterior, that runs ob- liquely forwards and outwards, the os cuneiforme minimum is joined; and with the anterior, whose direction is longitudinal, the os metatarsi of the toe next to the great one is connected. The forepart of this bone is flat and smooth, for sustaining the os metatarsi of the great toe. The internal side is scabrous, with two remarkable tubercles below, from which the muscu- lus abductor pollicis rises, and the tibialis anticus is inserted into its upper part. The three cuneiforme bones are all so secured by ligaments, that very little motion is allowed in any of them. These seven bones of the tarsus, when joined, are convex above, and leave a concavity below, for lodging safely the several muscles, tendons, vessels, and nerves, that lie in the sole of the foot. In the recent subject, their upper and lower surfaces are covered with strong ligaments, which adhere firmly to them; and all the bones are so tightly connected by these and the other ligaments, which are fixed to the rough ridges and fossae, that notwithstanding the many surfaces covered with cartilage, some of which are of the form of the very movable articulations, no more motion is here allowed, than is necessary to prevent too great a shock of the fabric of the body in walking, leaping, &c, by falling on too solid a base. If the tarsus was one continued bone, it would likewise be METATARSUS. 217 much more liable to be broken, and the foot could not accom- modate itself to the surfaces we tread on by becoming more or less hollow, or by raising or depressing either of its sides. Metatarsus. The Metatarsus is composed of five bones, which agree, in their general characters, with the metacarpal bones; but may be distinguished from them by the following marks: 1. They are longer, thicker, and stronger. 2. Their anterior round ends are not so broad, and are less in proportion to their basis. 3. Their bodies are sharper above and flatter on their sides, with their inferior ridge inclined more to the outside. 4. The tubercles at the lower part of the round head are larger. Fig. 47.* The first or internal metatarsal bone is easily distinguished from the rest by its thickness. The one next to it is the longest, and with its sharp edge almost perpendicular. The others are shorter and more oblique, as their situation is more external. Which general remarks, with the description now to be given of each, may teach us to distinguish them from each other. Os metatarsi pollicis is by far the thickest and strongest, as having much the greatest weight to sustain. Its base is oblong, irregularly concave, and of a semilunar figure, to be adapted to the os cuneiforme maximum. The inferior edge of this base is a little prominent and rough, * The sole of the left foot. 1. The inner tuberosity of the os calcis. 2. The outer tuberosity. 3. The groove for the tendon of the flexor longus digitorum. 4. The rounded head of the astragalus. 5. The scaphoid bone. 6. Its tuberosity. 7. The internal cuneiform bone; its broad extremity. 8. The middle cuneiform bone. 9. The external cuneiform bone. 10,11. The cuboid bone. 11. Refers to the groove for the tendon of the peroneus longus. 12,12. The metatarsal bones. 13, 13. The first phalanges. 14, 14. The second phalanges of the four lesser toes. 15, 15. The third, or ungual phala'igos of the four lesser toes. 16. The last phalanx of the great toe. 19 218 METATARSUS. where the tendon of the peroneus primus muscle is inserted. On its outside, an oblique circular depression is made by the second metatarsal bone. Its round head has generally on its forepart a middle ridge, and two oblong cavities, for the ossa sesamoidea; and, on the external side, a depression is made by the following bone. Os metatarsi of the second toe is the longest of the five, with a triangular base supported by the os cuneiforme medium, and the external side produced into a process; the end of which is an oblique smooth plane, joined to the os cuneiforme externum. Near the internal edge of the base, this bone has two small depressions, made by the os cuneiforme maximum, between which is a rough cavity. Farther forwards we may observe a smooth protuberance, which is joined to a foregoing bone. On the outside of the base are two oblong smooth surfaces for its articulation with the following bone; the superior smooth surface being extended longitudinally, and the inferior perpen- dicularly, between which there is a rough fossa. Os metatarsi ofthe middle toe is the second in length. Its base, supported by the os cuneiforme externum, is triangular, but slanting outwards, where it ends in a sharp-pointed little process, and the angle below it is not completed. The internal side of this base is best adapted to the preceding bone; and the external side has also two smooth surfaces covered with cartilage, but of a different figure; for the upper one is concave, and being round behind, turns smaller as it advances forwards; and the lower surface is a little smooth, convex, and very near the edge of the base. Os metatarsi o£ the fourth toe is nearly as long as the former, with a triangular slanting base joined to the os cuboides, and made round at its external angle; having one hollow smooth surface on the outside, where it is pressed upon by the follow- ing bone; and two on the internal side, corresponding to the former bone, behind which is a long narrow surface impressed by the os cuneiforme externum. Os metatarsi of the little toe is the shortest, situated with its two flat sides above and below, and with the ridges laterally- STRUCTURE OF THE FOOT. 219 The base of it, part of which rests on the os cuboides, is very large, tuberous, and produced into a long-pointed process externally, where part of the abductor minimi digiti is fixed; and into its upper part the peroneus secundus is inserted. Its inside has a flat conoidal surface, where it is contiguous to the preceding bone. When we stand, the fore ends of these metatarsal bones, and the os calcis, are our only supporters, and, therefore, it is necessary that they should be strong, and should have a confined motion. The Toes. The bones of the toes are nearly similar to those of the thumb and fingers; particularly the two of the great toe, which are precisely formed as the two last of the thumb; but their position, as respects the other toes, is not oblique; and they are proportionally much stronger, because they are sub- jected to a greater force; for they sustain the impulse by which our bodies are pushed forwards by the foot behind at every step we make ; and on them principally the weight of the body is supported, when we are raised on our tip-toes. The three bones in each of the other four toes, compared with those of the fingers, differ from them in these particulars. They are less, and smaller in proportion to their lengths. Their basis are much larger than their anterior ends. The first pha- lanx is proportionally much longer than the bones of the second and third, which are very short. The toe next to the great one has the largest bones in all dimensions, and the bones of the other toes diminish according to the order of their position; those of the exterior being least. The General Structure ofthe Foot. The foot may be considered as an arch, of which the back part of the heel, and the anterior extremities of the metatarsal bones and the toes, are the abutments. The heel, or posterior abutment is not so broad as the anterior, and is placed on the outside and not in the middle ofthe extremity ofthe arch. The 220 STRUCTURE OF THE FOOT. process on the inside of the os calcis, which supports the astragalus, increases the breadth of the arch; and the os naviculare completes it. The arch, thus constructed, does not appear very firm, and this apparent want of strength seems increased by the position of the anterior portion of the astra- galus, a part of which is between the os calcis and os naviculare, and not supported by either. These bones, however, are firmly connected by ligaments, and one which passes from the os calcis to the os naviculare, under the forepart of the astrag- alus, gives effectual support to that bone. The outside of the foot, formed by the os calcis, os cuboides, and the lesser metatarsal bone, does not partake much of the nature of an arch; for it is almost flat. As the internal side forms a considerable arch, the foot is to be considered as possessing a double convexity, viz. transversely, as well as longitudinally. The great toe, from its internal situation, is the principal anterior abutment of the arch on the internal side of the foot; hence its great importance. The astragalus, which is the basis ofthe tibia, and of course pressed by half of the weight of the body when we stand, appears to be in a situation which is very oblique, and imper- fectly supported; and accordingly it has been completely forced tfrom its position, by accidents in which the leg has been twisted or turned inward, and the foot prevented from turning with it. It is probable that this misfortune would often take place if the fibula did not previously yield, as in some of the cases of fracture of that bone near the external ankle. One great object of this peculiar structure is, that the foot may yield in cases of violent and sudden pressure, as when we jump or fall upon the feet. The safety of the foot, and the facility of its ordinary movement, are not the only objects of its peculiar structure, but concussion of the whole body, and particularly of the brain, is thereby avoided to a certain de- gree. This may be inferred from the fact that many persons suffer SESAMOID BONES.—EXTREMITIES OF THE F03TUS. 221 violent concussions, in consequence of falling upon other parts of the body, who are free from these effects when they fall upon the feet.- The Sesamoid Bones Are seldom larger than half a pea. They are most commonly found at the second joint of the thumb, and of the great toe ; and are placed in pairs, especially at the great toe, between the tendons of the flexor muscles and the bones. In these situations they are convex externally, and on their internal surfaces they are concave and covered with cartilage. They are also sometimes found between the heads of the gastrocnemius muscle and the condyles of the os femoris. In the joints of the thumb and toe they appear to be very analogous to the patella. —Besides the four pair of sesamoid bones above described as belonging to the skeleton, viz. two upon the metacarpo-pha- langeal articulation of each thumb, and two upon the corres- ponding joint of each great toe, there is often found in addition, one upon the metacarpo-phalangeal joint of the little finger, and upon the corresponding joint in the foot. There is one also often met with in the tendon of the peroneus longus muscle, where it glides through the groove in the cuboid bone. Some- times they are found in the tendons that wind round the inner and outer malleolus and in the psoas and iliacus where they glide over the body ofthe os pubis.— The Extremities ofthe Foetus. In the upper extremity the clavicle is almost perfect at birth; but the acromion and coronoid processes of the scapula, as well as the head, are in a cartilaginous state. Both ends of the os humeri are cartilaginous. They after- wards ossify in the form of epiphyses, and are united to the body of the bone. The two bones of the forearm are in the same situation. There are no bones of the carpus; but in their situation is an equal number of cartilages, which resemble them exactly. 19* 222 EXTREMITIES OF THE FCETUS. These cartilages are separated from each other, by synovia membranes, as the bones afterwards are. Each of them ossifies from a single point, except the unciforme. The metacarpal bones, and the first bone of the thumb have cartilages at each extremity, which afterwards become epiphysis. The bones of the phalanges are likewise cartilaginous at each extremity. The extremities next to the hand are epiphyses; but it is probable that the other extremities ossify gradually from their centres.* In the lower extremity, the head and neck, and two tro- chanters of the os femoris are cartilaginous and form three epiphyses. The other end of this bone is also cartilaginous, and consti- tutes but one epiphysis, notwithstanding its size; the ossification commencing in the centre. At birth, the body of the os femoris is less curved than it becomes afterwards; and the angle formed by the neck of the bone is less obtuse than in the adult. The patella is entirely cartilaginous at birth. The two extremities of the tibia and fibula are also cartilag- inous, and become epiphyses. The astragalus and os calcis are somewhat ossified within, and have a large portion of cartilage exteriorly. In place of the other bones of the tarsus there are cartilages of their precise shape, which are as distinct from each other as the future bones are. The state of the metatarsal bones, and the phalanges of the toes, resembles that of the bones of the hand.t * See Nesbit's Osteology, page 126. t Volehn Koyter, a disciple of Fallopius, has given to the profession one of the best accounts of Osteogeny, according to Lassus.—h. PART II. SYNDBSMOLOGY. CHAPTER III. GENERAL ANATOMY OF THE LIGAMENTOUS, FIBROUS, OR DESMOID TISSUE. Of the ligaments and membranes which connect the different parts of the body to each other—Of the articular cartilage—Fibro-cartilages—Synovial capsules, and particular articulations. The tendons and the strong membranes connected with them called aponeuroses, the fascia which bind down some of the muscles and afford an origin to many of their fibres, and the membranes which confine the tendons, appear to be composed of the same substance. —Notwithstanding some slight shades of difference which exist in the physical and chemical composition of these different parts, they are all now included with the periosteum, perichon- drium, dura mater, sclerotic coat of the eye, &c, under the general head of ligamentous, fibrous, or desmoid tissue* This tissue is sometimes called, from the whiteness of its appearance, the albugineous tissue. It is spread very gene- rally throughout the body, and is found wherever extraordinary strength and resistance is required, without elasticity or muscu- lar contraction. It has been called ligamentous or desmoid, from its fastening together the bones and cartilages, as in the ligaments proper, and from binding down the muscles so as to preserve the symmetry of the limbs, in the form of fascia and * The term ligament is frequently, though not with exact propriety applied to the duplicatures of serous membranes, which are attached to and assist in supporting different viscera, as the liver, bladder, uterus, &c, since these doubtless do not belong to the fibrous or desmoid tissue.—p. 224 FIBROUS TISSUE. aponeurosis, and from fastening the tendons in their grooves in the form of their theca's or sheaths. The term fibrous was applied to it by Bichat, (though its elements are dissimilar to muscular fibre,) in consequence of its performing the office of bands or chords, and being composed essentially of firm in- elastic threads, or albuminous fibres. These fibres crossing each other in various directions and woven densely together, with some intervening cellular tissue, form the aponeuroses, fasciae, sheaths, articular capsules, periosteum, dura mater, and tunica albuginea ; arranged longitudinally, they form the tendons of the muscles and the straight ligaments of the joints. The tendons, by a little dissection, may be spread out into a membrane, and in some parts ofthe body we see them naturally unfolding themselves to form an aponeurosis. —Between all these different parts there is more or less con- nexion. The tendons are inserted upon the bones only through the intermedium of the periosteum, by which the bones are covered. The aponeuroses are connected with the periosteum by the fasciae which they send down between the muscles. The ligaments and periosteum are directly continuous, and the dura mater, as it sends out processes around the nerves, becomes continuous with the periosteum that lines the foramina of the bones, through which the nerves pass. Bichat, con- sidered the pesiosteum the source and centre of this system; Bonn, of Amsterdam, as well as Clarus, believed the aponeu- roses investing the limbs to be the centre;—an opinion more venerable than either of these, that of the Arabian anatomists, fixed it in the dura mater. But, in truth there is no proper centre. In many parts, there is a fibrous tissue isolated from the rest, as the investing coat of the spleen and kidneys, and the fibrous portion of the pericardium. —The fibrous tissue in all parts of the body is continuous, at its surfaces and margins, with the common cellular tissue, and in many parts we find it, especially in the aponeuroses and fasciae, degenerating insensibly into it. There appears in fact to be a close relationship between these two tissues; in its developement in the foetus, it first appears as a soft, flexible, PIBROUS TISSUE. 225 extensible, homogeneous tissue, resembling much the cellular, and presents no appearance of fibres, till near the period of birth. As life advances it becomes more hard, solid and yellow, and in extreme old age presents much rigidity, and is occasionally even converted into bone. When macerated in water, or imbued with fluids, as in scrofulous inflammation of the joints, it presents a pulpy, spongy appearance, in the cells of which the fluid is contained. If the maceration is carried only to a limited extent, the fibres will separate into filaments, as delicate as those ofthe silk worm; but by prolonged mace- ration these filaments themselves disappear in the cellular mass. Mascagni, believed these fibres were lymphatics en- closed in a vascular web. Beclard, that they were nothing but condensed cellular tissue. Isenflam, that it was cellular tissue, with the walls imbued and the cells filled with gluten and albumen, and more or less in the advance of life with earthy matter ; an opinion which seems to accord with the different phases which the tissue presents. Chaussier and Bichat, con- sidered the fibre as primitive and peculiar, and that maceration only brought into view the cellular tissue which connected the fibres together. —However this may be, and it is a question not yet decided, in the form in which it presents itself to study, it differs in many respects from cellular tissue. It is not elastic or yielding to the application of sudden force as the latter ; the fibres will break or tear up at their bony attachment, but cannot be stretched or strained in the proper sense of the word. But when the force is gradually applied, as by the accumulation of a fluid in a joint, they yield to receive it, by a sort of interstitial expansion or growth, and retract in the same gradual manner, when the distending power is removed. Fibrous tissue contains but little adipose matter, and is affected only to a slight extent in anasarca. —The labours ofthe microscopists have recently confirmed the opinion of Chaussier and Bichat. —They have shown fibrous tissue to consist of fine transparent undulating cylindrical filaments, from 30T00 to roooo of an 226 FIBROUS TISSUE. inch in diameter. They are generally collected in fasciculi, from 3TVo t0 7sVo °f an inch wide, the filaments of which are held together, by a firm structureless amorphous substance, which has received the name of cytoblastema. Under the microscope, the elementary structure of the cellular, fibrous and fibro-cellular tissues, appear to be the same. Their ana- tomical differences depending on the mode in which their elementary fibres are put together. In fibrous tissue the undu- lating primitive filaments are arranged side by side into fasci- culi, which differ from those of cellular tissue in being much larger, more dense and more opaque and in being straight instead of flexuous. Their whiteness and strength, depend upon the compact parallel disposition of the compound fila- ments ; and their slight amount of elasticity is owing to the absence of sinuosity in the arrangement of the compound fasciculi. According to the manner in which these fasciculi or fibres are arranged and combined, we have either the mem- branous or fascicular form of fibrous tissue as has heen above explained. Cellular membrane in a more or less condensed state, is found in general intermixed to a greater or less extent, with the fibrous fasciculi. The Ligaments ofthe Joints, —Are all divided into the capsular or bag-like, and into funic- ular, or cords. —The capsular, or fibrous bags, of greater or less thickness, open at both ends, into which the heads of the bones forming the respective joints are thrust, and round the necks of which it is closely inserted, where they are continuous with the peri- osteum of the bones. In very many of the joints the capsules are imperfect in some part of their periphery, and in others are represented only by a few scattered fibres. The hip and shoulder joint furnish the best specimen of a perfect capsule. —The funicular ligaments are cords, flat, round, or oval, intended to give a side support to the joints, and constitute the lateral ligaments. These are placed, some within, some FIBROUS TISSUE. 227 without, and some in the very thickness of the capsular liga- ment.— They consist of fibres which are flexible but extremely strong, and in general have but little elasticity ; their surfaces are smooth and polished; their colour is whitish and silver- like. The vessels which enter into their composition do not com- monly carry red blood; and although it seems certain that they must have nerves, many very expert anatomists have de- clared that no nerves could be traced into them. —A branch of the fourth cranial nerve, has however been found distributed in the dura mater. Blood vessels abound in the periosteum, but they merely divide in that membrane, so as to enter the bone at a great number of points, as has been before observed.— In a healthy state, they are entirely void of sensibility, and can be cut and punctured, or corroded with caustic appli- cations, without pain. When inflamed they are extremely painful. The ligaments which connect the different bones to each other, have a very strong resemblance to these tendinous parts, not only in their structure but in their qualities also. Many of them appear rather more firm in their texture and more vas- cular. Their vessels are also larger: their colour sometimes inclines to a dull white, and when examined chemically, they appear to differ, in some respects, from tendons. They agree, however, with the tendinous parts as to their insensibility in a sound state, and the extreme pain which occurs when they are inflamed. No nerves have been traced into their structure. Notwithstanding the ordinary insensibility of these parts, it was asserted by M. Bichat that several animals who seem to suffer no pain from cutting, puncturing, or corroding the liga- ments of their joints, appeared to be in great agony when these parts were violently stretched or twisted; and he de- clared this to be the case when all the nerves which passed over the ligaments, and could have been affected by the ^ 228 FIBROUS TISSUE. ' process, were cut away. He explained by this the pain which sometimes occurs instantaneously in sprains, in the reduction of luxations, and in other analogous processes. The ultimate structure of these parts is, perhaps, not perfectly understood. An anatomist of the highest authority, Haller, appears to have considered them as formed of membrane, while a late writer, who has paid great attention to the subject, and is also of high authority, M. Bichat, has satisfied himself that their structure is essentially fibrous. If a tendon, or portion of tendinous membrane, be spread out, or forcibly extended, in a direction which is transverse with respect to its fibres, it will seem to be converted into a fine membrane, and the fibres will disappear to the naked eye. The same circumstances will occur when a ligament is treated in a similar way; but much more force is required. Thus constructed, these parts are perfectly passive portions of the animal fabric, and have no more power of motion than the bones with which many of them are connected. But notwithstanding their ordinary insensibility, they often induce a general violent affection of the system when they are diseased. A high degree of fever, as well as severe pain, attends their acute inflammations ; and hectical symptoms, in their greatest extent, are often induced by their suppurations. There is another circumstance in their history which is very difficult to reconcile with their ordinary insensibility. They are the most common seats of gouty painful affections. In these cases, pain does not seem to be the simple effect of inflammation: it often occurs as the first symptom of the dis- ease ; it frequently exists with great violence for a short time and goes off without inflammation, and it is frequently vicarious with affections of the most sensible and irritable parts. Parts of a tendinous and ligamentous structure do not appear retentive of life, but lose their animation very readily, in con- sequence of the inflammation and other circumstances which attend wounds. When thus deprived of life, they retain their usual appear- YELLOW ELASTIC LIGAMENTOUS TISSUE. 229 ance and their texture a long time. The dead parts separate from the living in large portions, in a way which has a con- siderable analogy with the exfoliation of bones. The tendons and their expansions, and the various fasciae, have the same chemical composition. If boiled a long time, they dissolve completely, and form the substance called by chemists gelatine, or pure glue. The ligaments differ from them in some respects. When boiled they yield a portion of gelatine, and do not dissolve entirely; but are said to retain their form and even their strength, after a very long boiling. The composition of the part so insoluble in water, has not yet been ascertained. Of the Yellow Elastic Ligamentous Tissue. Fig. 48.* —This is a modification of the common ligamentous tis- sue, which though not usual- ly treated apart, differs from it in many essential particu- lars. It contains, according to the younger Girard, some fibrine in its composition; it is eminently elastic, and is placed to give resistance and support to parts, where in other animals, we meet with muscular fibres, for which it is in some sort a substitute. In some situations it is of a deep yellow colour, and rarely presents the silvery aspect of the common tissue. It forms the middle coat of the arteries, the ligaments between the bridges of the verte- brae, the ligamentum nucha? in quadrupeds with heavy pen- dant heads, the elastic involucrum of the corpus cavernosum and spongiosum penis in the male, of the clitoris in the female, * Reticulate elastic tissue from the ligamentum nuchae of the horse magnified to 200 diameters (from Gerber). a. Loosened elastic tissue with the meshes opened. 6. Elastic tissue in its natural condition, the meshes close; the fibres being disposed in lines and layers, parallel to one another. v 20 230 FIBRO-LIGAMENTOUS TISSUE. and the elastic covering of the spleen ; it is found in the rami- fications of the bronchia, in various parts of the eye ball, and in the ligaments of the larynx and os hyoides including the vocal chords; we might also add, the elastic membrane of the nose and ear, which are more allied to it, than to cartilage, though they are called membraniforrn cartilage. This yellow elastic tissue (tissue jaune) unlike other ligamentous tissue, yields no gelatine on boiling. It resists decomposition for a very long time, either by maceration,putrefaction,or digestion; it becomes brown and transparent on drying, but not brittle like cartilage. „. , ~ When examined with the mi- xes'. 49. croscope, it is found to bear in the arrangement of its fibres a strong resemblance to a net work of capillary vessels. Its fibres are rigid, prismatic in form and about the ^ part of a line in diameter, highly elastic and interlaced with each other at all angles; its embryonic cells are elon- gated and mixed with the fibres. If injured it is very imperfectly reproduced; a dense fibrous tissue being substi- tuted in its place. It is very sparingly supplied with blood- vessels. Ofthe Fibrocartilaginous or Ligamento-cartilaginous Tissue. —There is another variety of the desmoid tissue, which holds a middle station between ligament and cartilage, partakes partly of the nature of both, and has been treated of by Bichat as a distinct tissue under this compound name. Vesalius and * Elastic tissue from the middle fibrous coat of the aorta of the ox magnified 300 diameters. The intertangled fibres, and elongated cells are well shown (from Ger- ber). These fibres, according to Henle, are contractile, and resemble somewhat tb« muscular fibres of the stomach. FIBRO-LIGAMENTOUS TISSUE. 231 Morgagni, called them cartilaginous ligaments ; Haase, mixed ligaments. Like ligaments, they present a well marked fibrous appearance, and are strong and resisting. Like cartilages, they are white, very dense and elastic. Beclard divides them into the temporary and permanent* —The temporary, are those which pass regularly and at determined periods to the state of ossification, and are developed in the midst of the ligaments and tendons, as the patella and sesamoid bones. —The permanent are of several kinds. 1. Those which are free at both these surfaces, and are lined by the synovial mem- brane. These constitute the interarticular or meniscous carti- lages, (menisci,) and are attached at their outer surface to the inner face of the capsular ligament. They are found in the knee, maxillary, clavicular, and lower ulnar articulations. 2. Those which are adherent by one of their surfaces; these are found whenever the fibrous tissue is subjected to habitual friction by the tendons, as in the different grooves, through which they play, or upon the sides of the ligaments or carti- lages, against which they rub; the periosteum, or whatever fibrous membrane it may be, first becomes thickened and then converted into a semicartilage. It also exists in the fibrous rings, placed at the margin of the glenoid and cotyloid cavities for the purpose of deepening their sockets. 3. Those adherent by both surfaces. These are found between the bodies ofthe vertebrae and the pubic bones. —The accidental production of this tissue is by no means uncommon ; it is found occasionally in the cavities of fractures forming false joints, in the tubercular cavities of the lungs, in the uterus, ovaries, etc. * Bichat considered the elastic cartilaginous membranes of the nose, ear, and trachea, as belonging to this division of the tissues, but they certainly have a closer affinity to the yellow elastic fibrous tissue.—p. 232 OF ARTICULATIONS. CHAPTER IV. A GENERAL ACCOUNT OF ARTICULATIONS, AND OF BURS^ MUCOSAE. Of Articulations. Those surfaces of bones which form the movable articula- tions are covered with cartilaginous matter which has been already described.* —In many of the immobile articulations, as the sacro-iliac symphysis for instance, a thin lamen of cartilaginous matter, with all the other appurtenances of joints, are likewise met with. The connexion between the articular cartilage and the bones is strong, but its nature is not well known. None of the vessels of the bone pass into the cartilage, but terminate in its immediate neighbourhood. Gerdy, (page 29) considers it a secretion from these vessels, and that its formation is like that of the cuticle, from the vessels of the skin. This, however, is but a mere opinion, unsustained by proof. It presents the appearance of a couch of white wax spread over the end of the bones, though it is composed of vertical fibres like the frill of velvet, so crowded together as to leave no sensible interval between them, and presenting a free extremity to the cavity of the joint. The cartilages terminate insensibly at their circum- ference on the surface of the bone. On the heads of the bones they are thicker at the central part, than at their circumference; in the corresponding socket, the cartilaginous coating is thickest at the margin, and sometimes spreads out into a sort of carti- laginous rim.— —On the formation of the epiphysis of the long bones, and its covering cartilage.—In the foetus and young subject, there is no distinction between the cartilage that is to become the bone of the epiphysis and that which is to remain as articular carti- * See page 36. FORMATION OF THE EPIPHYSIS OF LONG BONE. 233 lage. In my preparations alluded to, page 236, a careful dis- section shows branches running from the zone of vessels across the head of the bone isolating the articular cartilage from the epiphysal. These branches have beds of bone formed round them, communicate freely with the vessels of the epiphysis, but appear to send no branches towards the free surface of the articular cartilage. The portion of the articular cartilage immediately overlaying them, is however more tough and periosteal in its character, than that on the free surface of the cartilage, and has been, though not with exact propriety, described by Mr. Liston, as cellular tissue connecting the carti- lage and epiphysis. It is well known that in young subjects, the articular cartilage is thick, and the compact layer of the epi- physis below it thin and fragile; while in old persons the com- pact layer of the epiphysis is thick and strong, and the cartilage covering it thin, rigid, and so firmly united to the bone below, as to be with difficulty removed from it by the ordinary process of cleaning. It would seem from this, that while the cartilage gets its nutritive fluids by imbibition from the epiphysal vessels and the marginal zone, some change is effected by their passage into its structure during the progress of life, by which the inner portions of the articular cartilage is converted into bone. Though in the healthy state no vessels can be injected in carti- lage, in some diseases of the joints blood-vessels and granula- tions may shoot up from the bone below into the place of the cartilage.—It has been most probably in cases of this de- scription, that the appearance of vascularity in the cartilages has been observed; that of Mr. Liston, detailed in a late num- ber of the medico-chirurgical transactions was from a diseased joint.— The bones are retained in their relative situations by liga- ments, such as have been lately mentioned, which are exterior to the cavities of the articulations, and placed in such situa- tions that they permit the motions the joints are calculated to perform, while they keep the respective bones in their proper places. 20* 234 SYNOVIAL CAPSULES. Ofthe Synovial Capsules. —The synovial capsules are formed of an extremely thin transparent, double reflected tissue, the vessels of which circu- late in the healthy state only the serous portions of the blood, and which, though erected into a distinct tissue or system by Bichat, under the name of synovial,is now generally considered as forming only a part of the general serous tissue, which it closely resembles in structure, and with which it intimately sympathises in disease. They are of three kinds : 1st. Those which line the inner surface of the ligaments of the joints, and are reflected over the surfaces of the articular cartilages. These are called the articular synovial cartilages. 2d. Those which are placed between the tendons of the muscles, and the bones and cartilages against which the tendons rub. These are called bursa mucosa. 3d. Those which are placed between the skin and the bones, tendons, or other hard parts, over which it per- forms frequent and extensive movements. These are called the subcutaneous synovial capsules.— Ofthe Articular Synovial Capsules. They are invested in a particular manner by a thin delicate membrane, which in some joints, as those of the hip and shoulder, seems to be the internal lamina of a stronger liga- ment called the capsular; and, in other joints, the knee, for example, appears to be independent of any other structure, In each case, this synovial membrane, as it has lately been called, forms a complete sac or bag which covers the articular surface of one bone, and is reflected from it to the correspond- ing 'surface of the other ; adhering firmly to each of the articulating surfaces, and extending loosely from the margin of one surface to that of the other. In the distribution it supplies the place of perichondrium to the cartilages, and of periosteum to those surfaces of bone with which it is connected. It seems greatly to resemble the membranes which line the abdomen and thorax, and invests the parts contained in these SYNOVIAL CAPSULES. 235 cavities; and like them it may be termed a reflected membrane. It is thin and very flexible, but dense and strong. It secretes, or effuses from its surface, a liquor, called synovia; which is particularly calculated to lubricate parts that move upon each other. The fluid is nearly transparent: it has the consistence of a thin syrup, and is very tenacious or ropy. It mixes with cold water, and, when heated, becomes milky, and deposits some pellicles without losing its viscidity. It appears to be composed of eighty parts in one hundred of water ; above eleven parts of fibrous matter; and between four and five parts of albumen. It also contains a small portion of soda, of muriate of soda, and of phosphate of lime. There are in many of the joints masses of fat which appear to project into the cavity, but are exterior to the synovial membrane, and covered by it; as the viscera in the abdomen are covered by the peritoneum. They are generally situated so as to be pressed gently, but not bruised, by the motions of the bones. In some joints, they appear like portions of the common adipose membrane ; in others, they appear more vascular, and have a number of blood-vessels spread upon them. Small processes often project from their side like fringe. These masses have been considered as synovial glands; but they do not appear like glands; and it is probable that the synovia is secreted by the whole internal surface of the mem- brane.* The synovial membrane, like the other parts of joints, is insensible in a sound state, but extremely painful when inflamed. The synovia, which is secreted, during the inflamation of this membrane, has a purulent appearance. —For the sake of facility in description it is common among anatomists, without admitting or denying the fact, to consider * Clopton Havers, ignorant that the synovia was derived by a sort of perspiration from the inner surface of this membrane, supposed it to be secreted by these masses of adipose matter, which are still known, in perpetuation of his mistake, as Havers1 glands.—p. 236 SYNOVIAL CAPSULES. the synovial membrane as passing over the face of the articular cartilages; it has however long been a question among anato- mists and surgeons, whether such be really the case. It can only be traced by the knife as far as the circumference of the cartilages, nor can vessels by any means in the healthy state be injected in it beyond this point. If it exist upon the carti- lages, it is certainly so modified as not to be recognisable. It is asserted by Mr. Toynbee* that it covers the cartilage as a vascular membrane only in the early periods of foetal life—and that towards the period of birth the sub-synovial vessels, gradu- ally recede from the surface of the articular cartilage and form a zone around its margin; a change somewhat like that which takes place in the membrana pupillaris. I have several minutely injected preparations of the joints taken from young subjects, which show this zone of vessels, arranged in loops somewhat like the mesenteric arches, around the beveled cir- cumference ofthe cartilage, which are strongly confirmatory of this opinion. But whether the synovial membrane recedes with these vessels, or becomes so altered in character as to form a smooth insensitive covering to the cartilage has not yet been determined. An amputation at the knee joint which I performed during the past winter at the Philadelphia Hospital, before the class of the Jefferson Medical College, gave me an opportunity of observing the changes daily, that are produced by morbid causes in the cartilages of the joints. From the diseased condition of the integuments of the leg, there was a scantiness of flap for covering the stump, which left the condyles partly exposed to view. —From round the margin of the cartilage and the place of attachment of the crucial ligaments, in front of which the synovial membrane passes, there was in the course of a fort- night inflammation, secretion and a vigorous growth of granu- lations. On the surface of the cartilage of the condyles there appeared to be up to this time the slightest change ; it preserved its polished shining, aspect and was totally insensible to the contact of an instrument. In the course of a few days more it * Memoir on the non vascular tissues, Phil. Trans. 1841. BURS.E MOCOS.E. 237 lost its polish, became soft and pulpy, like a joint exposed to maceration in a dissecting room,and melted off, flake after flake, till the compact layer of bone covering the cells of the epiphysis below was exposed to view. This layer was at first dark coloured, but soon became red and sensitive to the touch. Small firm whitish conical elevations, appeared over its surface; these grew by degrees into strong and healthy granulations, to which the inner face ofthe flaps, at the end of six weeks were firmly connected, leaving the patient a solid and serviceable stump, upon which she is able to bear her weight with the ordinary wooden support. The patient suffered none of the constitutional irritation common to synovial inflammation and it would be difficult to believe from the progress of this case, and analogous ones reported by other surgeons, either that the synovial membranes are spread over the cartilages of joints, or that the cartilages themselves are vascular. Of Bursa Mucosa. There are certain membranous cavities called bursas mucosae which are found between tendons and bones, near the joints, and in other places also, which have so strong a resemblance to the synovial membrane, and are so intimately connected with some of the articulations, that they ought now to be mentioned. They are formed of a thin dense membrane, and are attached to the surrounding parts by cellular substance; they contain a fluid like the synovia; and sometimes there are masses of fat, which, although exterior to them, appear to project into their cavities. There is, commonly, a thin cartilage, or tough membrane, between them and the bone on which they are placed. They often communicate with the cavities of joints, without inducing any change in the state of the part. As they are always situated between parts that move upon each other, there is the greatest reason to believe that they are intended to lessen friction.* *For further information respecting this subject, as well as joints in general, the reader is referred to a Description of the Bursae Mucosae of the Human Body, by Alexander Monro; to whom the world is so much indebted for the elucidation of many important points in anatomy and physiology. 238 SUBCUTANEOUS SYNOVIAL CAPSULES. These bursae mucosae are very numerous, as will appear from a subsequent account of them.. Several of them are very interesting on account of their con- nexion with very important joints. —These bursae form synovial sheaths to the tendons, where they run through grooves in the bones, or under their vaginal ligaments, or where they glide over each other, as in the palms of the hands and the soles of the feet: but they are especially met with, wherever a tendon changes its direction, and converts a bone, a cartilage, or ligament into a pulley; of which instances will be detailed hereafter. When a bursae, or tendinous sheath, invests a tendon about to subdivide, as the flexor tendons-of the fingers at the wrist, the sheath also subdivides so as to send a process along each parting tendon; a knowledge of which fact is of importance to the surgeon, as this membrane when injured, is much disposed to continuous inflammation. —The number of these bursae vary in different individuals. Ollivier reckons them at one hundred pairs. Subcutaneous Synovial Capsules. —These have been long observed about the wrist, ankle and knee, where they sometimes attain the size of walnuts, and are known to surgeons under the names of ganglions and hygroma, They were studied and described for the first time, however, by Beclard. They exist wherever the skin is strongly and frequently moved over a resisting part: as between the skin and the patella; between the olecranon and skin; over the trochanter; acromion ; thyroid cartilage ; at the metacarpal and metatarsal articulations, &c. &c. They are developed accidentally in different parts, when from any cause, as in curvature of the spine, the friction of the tendons is increased. When inflated,the cavities appear oblong and cellulated,contain some synovial fluid, and look like dilated cells of the cellular tissue, of which they are in all probability formed ; many of them, however, are visible in the foetus during the latter period of utero-gestation.— PARTICULAR ARTICULATIONS. 239 CHAPTER V. OF PARTICULAR ARTICULATIONS. The connexion of the Head with the Vertebra. The condyles of the occipital bone, and the corresponding cavities of the atlas, are covered with cartilage. The condyle and cavity on each side are invested with a synovial ligament, as described in the general account of articulations. Fig. 50.* An anterior ligament, (liga- mentum occipito-atloidal ante- rior,) descends from the front part of the great occipital fora- men, and is inserted into all the front part of the atlas, between its articulating processes. That portion of this ligament which is in the middle, and inserted into the tubercle of the atlas, appears stronger, and is distinct from the rest of it. A posterior ligament, (ligamentum occipito-atloidal pos- terior,) passes from the posterior margin of the occipital fora- men to the upper edge of the posterior arch of the atlas. From each side of the upper end of the tooth-like process of the vertebra dentata, a ligament (oblique, or moderator,) passes upwards and outwards, to be inserted into the internal side of the basis of each condyle of the occipital bone. There * A posterior view of the ligaments connecting the atlas, the axis, and the occipital bone. The posterior part ofthe occipital bone has been sawn away, and the arches of the atlas and axis removed. 1. The superior part of the occipito-axoid ligament, which has been cut away in order to show the ligaments beneath. 2. The trans- verse ligaments ofthe atlas. 3, 4. The ascending and descending slips ofthe trans- Verse ligament, which have obtained for it the title of cruciform ligament. 5. One of the odontoid or moderator ligaments. 6. One of the occipito-atloid capsular ligaments. 7. One of the atlo-axoid capsular ligaments. 240 ARTICULATIONS OF THE VERTEBRJS. is a small ligament, called the middle straight ligament (liga- mentum medium rectum,) which passes from the tip of the dentated process, to be inserted on the inner face of the occipital foramen between the insertion of the moderator liga- ments. From the anterior margin of the great occipital foramen, a ligament passes down on the inside of the vertebral cavity, over the tooth-like process, which is inserted in the body of the vertebra dentata, and the ligaments connected with it. This ligament is composed of a number of fibrous bands called by Caldani, lacerti ligamentosi. This must be dissected away before the moderator and transverse ligaments can be brought into view. See fig. 51. It is now more appropriately named the occipito-axoid ligament. Fig. 51.* There is also a ligament 7 which runs across from one side of the atlas to the other, to confine the tooth-like process in its anterior cavity, see fig. 50, page 239, (transverse liga- ment, ligamentum transver- sale atlantis.) This ligament adheres above to the occipital bone, and below to the body of the vertebra dentata. The anterior surface of the tooth-like process plays on the anterior arch of the atlas; the posterior surface plays on this ligament. A synovial capsule is placed on each surface of the tooth-like process. —From the middle of this transverse ligament a band of fibres extend downward to the vertebrae below, giving a cruciform arrangement to the ligament. See fig. 51. * The upper part of the vertebral canal, opened from behind in order to show the occipito-axoid ligament. 1. The basilar portion of the sphenoid bone. 2. Section of the occipital bone. 3. The atlas, its posterior arch removed. 4. The axis, the posterior arch also removed. 5. The occipito-axoid ligament, rendered prominent at its middle by the projection of the odontoid process. 6. Lateral and capsular ligament of the occipito-atloid articulation. 7. Capsular ligament between the arti- culating processes of the atlas and axis. ARTICULATIONS OF THE VERTEBRA. 241 The articulating surfaces of the oblique process of the atlas and vertebra dentata on each side, are invested by a synovial membrane. There are, also, additional ligaments placed before and behind these processes, that have an effect on their motions. The uses of these different ligaments are very obvious when they are dissected. The transverse ligament of the atlas, with the synovial membranes form an articu- lation for the tooth-like process, which is of a peculiar kind. The ligaments that pass from this process, to the bones of the condyles of the occipital bone, must have an effect in restraining the rotation of the head and atlas on this process, and there- fore have been called moderator ligaments. The Articulations ofthe Vertebrae with each other. To acquire a perfect idea of the construction of the Spine it is necessary to examine, at least, two preparations of it: in one of which the bodies of the vertebrae should be sawed off from the processes, so that the spinal canal may be laid open. The bodies of all the vertebrae, except the atlas, are connected' to each other by the intervertebral fibro-cartilaginous matter described in page 138, which unites them very firmly, at the same time that it allows of some motion, in consequence of its elasticity and compressibility. This connexion is strengthened by two ligaments, which extend the whole length ofthe spine, from the second cervical vertebra to the sacrum. The first of these, denominated the anterior vertebral ligament, covers a considerable part of the anterior sur- face of the bodies of the vertebrae; it is thickest in the middle, and varies in its breadth in different parts of the verte- bral column; it adheres very firmly to the intervertebral substance, and not so firmly to the bodies of the vertebrae. It has the shining silver-like appearance of tendon, and seems to consist entirely of longitudinal fibres. There are many fibres which appear to be connected with it, that do not extend the whole length of the spine. On the posterior surface of the bodies of the vertebrae, in the cavity which contains the spinal marrow, is the posterior or internal vertebral ligament, which, like the anterior, extends from the upper part of the spine to the sacrum. In its progress downwards it is broader where it is in contact 21 ^ 242 ARTICULATIONS OF THE VERTEBRiE. with the intervertebral matter, and narrower about the middle of each of the bodies of the vertebrae. It appears to consist of longitudinal tendinous fibres, which are similar to those of the anterior ligament. The fibres of which these ligaments are composed, are more closely connected by origin and insertion with the intervertebral matter, than with the bodies of the vertebrae. Some of the fibres are inserted into the next verte- brae or intervertebral substance below their place of origin, others into the second or third, and some into the fourth or fifth. The oblique processes of the vertebrae are covered with cartilage, and are invested with a synovial membrane, like the other movable articulations. In the neck and back these membranes are thin and delicate; but in the loins they are blended with ligamentous fibres which give them additional strength. Some of the most curious and interesting ligaments of the spine, or indeed of the body, are those which are attached to the bony plates or arches that extend from the oblique to the spinous processes of each vertebrae. These plates form a great portion of the posterior part of the vertebral canal and the vacant spaces between them are filled up by these ligaments, which extend from the plates of each upper vertebra of those of the next vertebra below. They are situated between the spinal process and the oblique processes on each side. They are, therefore, two distinct ligaments between the two vertebrae, one on each side of the spinal process; and as they extend only from the plates or arches of one vertebra to those of the other, they must necessarily be very short. They are much more conspicuous on the internal surface of the vertebral cavity than they are externally. They are thick and substantial, and very elastic; their colour resembles that of a yellowish adeps; and from that circumstance they are called the yellow or elastic ligaments. They complete the cavity for the spinal marrow. There are twenty-three pairs in all. As the plates or arches to which they are connected must ARTICULATIONS OF THE VERTEBRA. 243 recede from each other, when the spine is bent forwards, it seems that they should be elastic. Fig. 52.* There are also ligaments between the spinous processes, which extend from the under surface of one spinous process to the upper surface of the spinous process below it. These are composed of tendinous shining fibres, and are sufficiently loose to permit the anterior flexure of the vertebral column. From their situation they are denominated interspinal liga- ments. There is also a thin and narrow ligamentous band, which extends from the spinous process of the seventh cervical verte- bra to the spinous processes of the os sacrum, and adheres to the ends of the intermediate spinous processes. It is exterior to the tendinous origins of the trapezii and latissimi dorsi muscles. The upper portion is slightly connected to the trapezius, the lower part adheres more firmly to the latissimus dorsi. The ligamentum nucha, ligament of Diemerbrak, as it has been denominated, is a narrow but firm strip, which extends from the spinous process of the last cervical vertebra, to the occipital bone, at or near its protuberance. It is very strongly developed in all the larger quadrupeds, with pendant heads. That portion of the trapezius muscle which is between the occipital bone and the seventh cervical vertebra, originates from it, or is intimately connected with it; and a portion of the splenius muscle is also connected with it. From the internal surface of this ligament, a thin tendinous membrane arises, whose fibres run obliquely upwards and * A posterior view of a part of the thoracic portion of the vertebral column, showing the ligaments connecting the vertebra? with each other and the ribs with the vertebrae. 1. The supra-spinous ligament. 2, 2. The ligamenta subflava, or yellow elastic ligaments, connecting the lamina?. 3. The anterior costo-transverse ligament. 4. The posterior costo-transverse ligaments. ^ 244 ARTICULATION OF THE LOWER JAW. forwards, and are inserted into the spinous processes of each of the cervical vertebrae above the seventh, and also into the atlas and the os occipitis. Attached to the ligamentum nucha? and to the spine, this membrane seems like a partition between the muscles which lie on each side of the back of the neck. After inspecting the different ligaments of the spine, it will be obvious that the yellow ligaments are among the most important of them; in consequence of their position, their strength, and their elasticity. Articulation of the Lower Jaw, ( Temporo-maxillary.) The glenoid cavity of the temporal bone with the tubercle before it, and the condyle of the lower jaw, are covered with cartilages. A cartilage is placed between them called inter- articular, which being flexible, is accommodated to the con- vexity of the condyle and hollowness of the glenoid cavity, and also to the figure of the aforesaid tubercle to which it is extended. A synovial capsule, or bag, invests the glenoid cavity and the tubercle, and covers the upper surface of the cartilage. A second capsule of the same kind is attached to the condyle ofthe lower jaw, and the lower surface of the car- tilage. A few ligamentous fibres extend from the circumfer- ence of the cavity and tubercle of the temporal bone, over both synovial capsules and the cartilage between them,to the lower jaw below the condyle, and appear to be attached to the cartilage. These fibres are collected in such numbers, on the external and internal sides of the articulation, that they have been called the external and internal lateral ligaments. Another ligament called stylo-maxillary, is mentioned which arises from the styloid process of the temporal bone, and is in- serted into the lower jaw near its angle ; but this seems rather appropriated to the stylo-glossus muscle than to this articulation. In consequence of this structure, the condyle of the lower jaw moves out of the glenoid cavity upon the tubercle, when the mouth is opened widely. ARTICULATIONS OF THE SHOULDER. 245 Articulation ofthe Clavicle and Sternum, called Sternoclavicular. The connexion ofthe clavicle and sternum resembles strongly that of the lower jaw and temporal bone. A movable cartilage is placed between the articulating surfaces, with a distinct syno- vial capsule on each side of it, applied in the usual manner to the corresponding surface of the clavicle and of the sternum. Exterior to these capsules and the intervening cartilage, are many ligamentous fibres, which are most numerous on the anterior and posterior surfaces, but diverge from each other as they proceed from the clavicle to the sternum, and are, there- fore, called Radiated Ligaments. There is a strong ligament called the Interclavicular, which passes across the sternum internally, from one clavicle to the other. And another ligament, which arises from the inferior rough surface of the clavicle, near the sternum, which is inserted into the cartilage of the first rib. This is called the Rhomboid, or Costoclavicular ligament. Articulations of the Clavicle and Scapula, (Scapuloclavicular.) Fig. 53.* These are two in number; one which connects the acro- mion and external end of the clavicle called acromioclavicu- lar, and one which connects the lower surface of the outer part of the clavicle with the coracoid process of the scapula, called coraco-clavicular. Acromio-clavicular. The small surfaces of the clavicle and scapula, which are in contact with each other, are furnished * The ligaments of the sterno-clavicular and costo-sternal articulations. 1. The anterior sterno-clavicular ligament. 2. The inter-clavicular ligament. 3. The costo- clavicular or rhomboid ligament, seen on both sides. 4. The inter-articular fibro- cartilage, brought into view by the removal of the anterior and posterior ligaments. 5. The anterior costo-sternal ligaments ofthe first and second ribs. 21* 246 ARTICULATIONS OF THE SHOULDER. with the apparatus of a movable articulation. They are covered with cartilage, and are invested with a small synovial capsule. The upper and lower surfaces of the extremities of the clavicle and acromion are covered by a ligamentous mem- brane, which is called, from its situation, the superior and infe- rior ligament of this articulation. Coraco-clavicular, consisting of two portions, conoid and trape- zoid. But these bones are more firmly connected by the liga- ment which passes to the coracoid process of the scapula from the under side of the clavicle, and is very strong. Some ofthe fibres which compose this ligament are so arranged that they have the appearance of an inverted cone : the remaining fibres appear like another ligament, and therefore they have been called the trapezoid and conoid ligaments. —The base of the conoid ligament is upwards, and its apex or origin is at the root of the coracoid process. It is the stronger of the two. The trapezoid is at the outer side of the conoid. It is broad and thin, with its fibres separated by interstices. It rises from the root of the coracoid process, and is inserted on an oblique ridge, leading from the tubercle of the clavicle to its acromial end.— By their situation and strength they are enabled to retain the bones in their proper relative positions, at the same time that they permit a peculiar rotary motion. —There is a bifid ligament called ligamentum bicorne, arising from the root of the coracoid process, at the inner side of the conoid, which runs inwards in front of the subclavius muscle, to which it serves as a fascia, and bifurcates; one horn is attached to the under surface of the clavicle near the rhomboid ligament, and the other to the end of the first rib, under the tendon of the subclavius muscle.— Articulation ofthe Os Humeri and Scapula, (Scapulo-humeral) The spherical portion of the upper extremity ofthe os humeri is the part of that bone which is principally concerned in the articulation, and is covered with cartilage; as is also the gle- noid cavity ofthe scapula. ARTICULATIONS OF THE SHOULDER. 247 Fig. 54.* The glenoid cavity of the scapula, which is so small in the dried bone, when compared with the head of the os humeri, is enlarged by the long tendon of the biceps muscle, which is attached to the upper edge of its margin, and then divides and passes down on each side of the cavity, increasing the breadth of it considerably, thus forming what is called the glenoid ligament, deepen- ing the socket, and giving greater latitude of motion to the arm, from its elasticity, than if the socket had all been formed of bone. It appears to be blended with the cartilage that lines the cavity, and also with the capsular liga- ment which is exterior to it. The articulating surface, thus composed, is perfectly regular and uniform. The synovial ligament, in this articulation, is so blended with an external stronger ligament, that it cannot be separated in the recent subject; but, notwithstanding, it is applied to the articulating surfaces in the same way that it is applied to the other joints forming a capsule. The stronger exterior lamina is, of course, only applied to that part of the synovial capsule which proceeds from the margin of one cartilaginous articu- lating surface to the other: it appears to be most intimately connected with the periosteum, and is rendered more firm and thick in particular parts, by the addition of fibres from the ten- dons of the supra and infra-spinatus, and subscapularis muscles with which it is blended. It arises from the scapula at a small distance from the mar- * The ligaments of the scapula and shoulder joint. 1. The superior acromio-cla- vicular ligament. 2. The coraco-clavicular ligament; this aspect of the ligament is named trapezoid. 3. The coraco-acromial ligament. 4. Coracoid or transverse liga- ment as it is sometimes called. 5. Capsular ligament. 6. Coraco-humeral liga- ment. 7. The long tendons of the biceps issuing from the capsular ligament, and * entering the bicipital groove. 248 ARTICULATION OF THE ELBOW. gin or edge of the glenoid cavity, as formed by the tendon of the biceps, and is inserted into the os humeri at a small dis- tance from the edge of the cartilaginous articulating surface; and, if dissected away from the bones, would appear like a cylindrical bag with both extremities open.—The capsular ligament is thickened in front by a band of fibres, arising from the outer part of the back surface of the coracoid process, which proceeds beneath the triangular ligament to the upper part of the os humeri; it is closely blended with, and forms a part of the capsular ligament, and is denominated the coraco- humeral ligament, or ligamentum adscititium.— The long tendon of the biceps muscle, in the groove at the head of the os humeri, appears to penetrate this ligament; but it is^ not within the cavity of the synovial membrane; for this membrane sends down a process like the finger of a glove, which lines the groove, and is reflected from its surface upon the surface of the tendon, and covers it during its whole extent, being reflected from the tendon, at its upper termination, to the adjoining surface ; so that the tendon is in fact outside of the synovial capsule, which, therefore, confines the synovia com- pletely. This capsular ligament, which is one of the strongest, would not avail much in keeping the bones in their proper situations, if the muscles and their tendons were not disposed in such a manner, that when the muscles act, their power is excited to the same effect. In some cases of paralytic affection, where the muscles exert no influence, the weight of the arm, when it is allowed to hang without support, draws the head of the os humeri, below the glenoid cavity, notwithstanding the capsu- lar ligament. At the same time it ought to be observed, that this ligament must be lacerated in every case of complete luxa- tion of the os humeri; as it cannot possibly distend sufficiently to permit the separation of the bones to the extent which then takes place. The Articulation of the Elbow. Those surfaces of the os humeri, ulna, and radius, which move upon each other, are covered with cartilage. ARTICULATION OF THE WRIST. 249 Fig. 55.* The motion of the ulna and radius on the os humeri is that of the simple flexion and extension. The cylindrical head of the ra- dius performs a part of a revolution, nearly on its own axis, without moving from the depression in the side of the ulna, with which it is in contact. The synovial membrane adheres very firmly to the surface covered with cartilage on each of the bones, and is reflected from the margin of this surface, on one bone, to that of the others. As the principal motion performed is hinge-like, the principal liga- ments are on the sides. There is also a circular ligament, which arises from the ulna and invests the narrow part of the radius immediately below its cylindrical head like a loop, to confine the radius in contact with the ulna, and at the same time permit its motion. This ligament is so blended with the synovial membrane, that it sometimes cannot be separated from it. The lateral ligaments are denominated from their origin and insertion, Brachio-radial, and Brachio-cubital, or External and Internal. The external is a strong, narrow band, attached above to the external condyle of the humerus, and below to the orbicular ligament, and adjoining ridge of the ulna. The internal, is thick and triangular; its apex is attached to the internal condyle of the humerus, and its lower or broad part is inserted into the margin of the greater sigmoid fossa of the ulna extending from the coronoid process to the olecra- non.—Posterior to it runs the ulnar nerve. The ligament which invests the neck of the radius is called Coronary or Orbicular. * An internal view ofthe ligaments of the elbow joint. 1. The anterior ligament. 2. The internal lateral ligament. 3. The orbicular ligament. 4. The oblique liga- ment. 5. The interosseous ligament. 6. The internal condyle ofthe humerus, which conceals the posterior ligament. 250 ARTICULATION OF THE WRIST. —The orbicular ligament is a firm band Fig 56.* several lines in breadth, which surrounds the head of the radius, and is attached by each end to the extremities of the lesser sigmoid cavity. It is strongest behind where it receives the external lateral liga- ment.—On its inner surface it is lined by a process of synovial membrane from the elbow joint.—When this ligament is rup- tured, as often occurs in children, the head of the radius readily slips from its place.— There are also some ligamentous bands, which run upon the front and back parts of the joint to strengthen it, which are called Anterior and Posterior accessory liga- ments.-—They are broad thin membranous layers placed on the outer surface of the synovial membrane, and are both attached to the humerus above, and upon the sides to the lateral ligaments: below the poste- rior is attached to the olecranon ; the anterior to the coronoid process of the ulna and to the lateral ligament. Within the synovial membrane, in the upper margins of the depressions for the olecranon and coronoid processes of the ulna, are the adipose substances usually found in joints. Articulation of the Wrist. The structure ofthe wrist is particularly complex, because it consists of three articu- lations, which are contiguous to each other, viz. That of the ulna and radius; of the radius and first row of carpal bones, radio-carpal ; and of the first and second row of carpal bones with each other, middle carpal joint. An oblong convex head is formed by the upper surfaces of the scaphoides and lunare, and a portion of the upper surface * External view ofthe elbow joint. 1. Humerus. 2. Ulna. 3. Radius. 4. The external lateral ligament inserted below into the orbicular ligament. 6. The posterior extremity of the orbicular or coronary ligament, spreading out at its inser- tion into the ulna. 7. The anterior ligament, scarcely seen in this view of the arti- culation. 8. The posterior ligament, thrown into folds by the extension of the joint. ARTICULATION OF THE WRIST. 251 of the cuneiforme bone. This head is covered by one cartilage, which is so uniform that the different bones cannot be distin- guished from each other. The lower end of the radius is arti- culated with this head, but does not cover the whole of it; a portion of this head, therefore, is under the ulna, but not in contact with that bone : for the cartilage which lines the con- cavity of the radius, is continued beyond the radius, so as to cover the remainder of the head, formed by the carpal bones. Fig. 57.* —This cartilage which is extended from that covering the radius, is attached to a depression on the inner surface of the styloid process of the ulna. It is called the inter- articular or from its shape the triangular fibro-cartilage. The sy- novial membrane forming the joint between this cartilage and the end of the ulna is loose and is called the sacciform membrane, (see fig. 57,) The lower end of the ulna is in contact with the upper surface of this cartilage, and is articulated lat- erally with the semilunar cavity of the radius. This semilunar cavity * A careful dissection being made, the ligaments of the carpus will appear as seen in this and the following figures.— Dorsal surface, a. External lateral ligament. It runs from the styloid process of radius to os scaphoides. b. Internal lateral ligament which runs from the styloid process of the ulna and divides into two fasciculi, one of which is attached to the pisiform, the other to the cuneiforme bone. d. Posterior or dorsal ligament of the radio-carpal articulation. They are thin and weak and run from the radius to the first row of bones, g. Posterior radio ulnar ligament, i. A posterior or dorsal thin band of fibres, which connects the two rows of bones together. I. Dorsal liga- ments, which connect the metacarpal bones together at their base. n. Dorsal liga- ment connecting the anterior ends of these bones, o. A middle dorsal ligament stretched from the second metacarpal bone to the trapezoid, p. An external liga- ment running from this bone to the trapezium; another internal one running from this bone to the os magnum, is not here seen. r. An oblique ligament, running from the os unciforme to the third metacarpal bone. s. Capsular ligament of the metacarpo-carpal articulation of the thumb, t. A sort of capsular ligament ofthe metacarpo-carpal joint ofthe little finger, w. The place of dorsal ligament supplied in a great measure by extensor tendon, z. Lateral ligament. 252 ARTICULATION OF THE WRIST. is lined by a cartilaginous process, continued from the upper surface of the aforesaid cartilage; so that the extremity and the side of the ulna play upon the cartilage continued from the radius. This articulation of the ulna and radius is distinct from that of the radius and carpus. Fig. 58.* A synovial membrane covers the articulating head formed by the three bones of the carpus, and is reflected from the margin of their cartilaginous surface, to the carti- lage at the end of the radius. A plait or fold of this membrane passes from the head of the carpus, at the junction of the scaphoides and lunare, to the opposite part of the cartilage ofthe radius, and has been called the Mucous Ligament, (liga- mentum mucosum.) A strong ligament (internal lat- eral) is placed on the internal side of this articulation, which arises from the styloid process of the ulna, and is inserted into the anterior transverse ligament which confines the flexor tendons, and into the pisiforme and cuneiforme bones. * Anterior or palmar surface, a. External lateral ligament. 6. Internal lateral ligament, c. Three anterior or palmar ligaments belonging to the articulation ofthe first row of bones with the radius, or the radio-carpal articulation. They run from the radius to the bones of the carpus, e. Two very strong inferior ligaments which connect the pisiform and cuneiform bones together: besides these, four other liga- ments are discovered at this articulation, an external, an internal, and two lateral. So strong is this articulation, that the pisiform bone is rarely if ever dislocated. /. Anterior radio-lunar ligament. Articulation of the two bones together. I. An anterior or palmar ligament, running /rom the os magnum, and diverging to the three inner bones of the first row. m. Palmar ligaments which connect the meta- carpal bones at their base. There is another set of fibres called the interosseous, not seen here, which connect these bones at their base. n. Palmar or transverse ligament at the anterior end of these bones, s. Capsular ligament of the thumb. «. Ligamento-cartilaginous, thickens over the first joint of the fingers, v. Lateral ligaments, y. Palmar or glenoid ligaments, as they seem to deepen the articular surface for the phalanges. ARTICULATION OF THE WRIST. 253 Another ligament, (external lateral,) on the external side, arises from the styloid process of the radius, and is inserted into the scaphoides, some of its fibres being continued into the aforesaid transverse ligament, and the trapezium. There are two broad irregular ligamentous membranes: one of which arises from the anterior margin of the articulating surface of the radius; and the other from the posterior margin. One of them is inserted anteriorly, and the other posteriorly, into the margin of the corresponding surface ofthe scaphoides, lunare and cuneiforme. They adhere to the synovial membrane; but in some places this membrane appears through apertures The surfaces, by which the first and second rows of carpal bones are articulated with each other, are very irregular. The magnum and part of the unci- forme form a prominent oblong head ; on each side of which is a much lower surface, formed by the trapezium and trapezoides externally, and the remaining por- tion ofthe unciforme internally.t The scaphoides, lunare, and cuneiforme, form a cavity which corresponds with this head, and also with the lower surface * A diagram showing the disposition ofthe five synovial membranes ofthe wrist joint. 1. The sacciform membrane. 2. The second synovial membrane. 3, 3. The third, or large synovial membrane. 4. The synovial membrane between the pisiform bone and the cuneiforme. 5. The synovial membrane of the metacarpal articulation of the thumb. 6. The lower extremity of the radius. 7. The lower extremity of the ulna. 8. The interarticular fibro-cartilage. S. The scaphoid bone. L. The semilunare. C. The cuneiforme; the interosseous ligaments are seen passing between those three bones and separating the articulation of the wrist (2) from the articulation of the carpal bones (3). P. The pisiforme. T. The trapezium. 2T. The trapezoides. M. The os magnum. U. The unciforme; interosseous ligaments are seen connecting the os magnum with the trapezoides and unciforme. 9. The base ofthe metacarpal bone of the thumb. 10, 10. The bases of the other meta- carpal bones. t The palm of the hand is supposed to present forward. 22 which are in them. Fig. 59. 254 ARTICULATION OF THE CARPAL BONES. formed by the unciforme ; while another surface of the sca- phoides is articulated with the trapezium and trapezoides. These corresponding surfaces, formed by the two rows of carpal bones, irregular as they are, compose but one articulation, which is capable of a limited flexion and extension. It has a synovial membrane, with two lateral ligaments, and an anterior and posterior ligament; these last, however, are short, and can be best examined from within, by cutting open the articulation. The bones of each row move laterally upon each other. Their lateral surfaces, which are in contact, are covered with cartilage ; and the synovial sac which exists between the first and second row of bones, sends off processes between these surfaces, which are disposed like the ordinary synovial mem- branes in other articulations; adhering, as is supposed, to each of the cartilaginous surfaces, while they communicate with the larger cavity between the two rows. —Interosseous ligaments pass between the three outer bones of the upper row, and the three inner of the lower so as to intercept at these points the distribution of the synovial mem- branes between the individual bones of each row. By this means there is, as seen in fig. 59, including the sacciform mem- brane, five synovial membranes in the wrist joint. Articulation of the Carpal and Metacarpal Bones. The metacarpal bones are connected to the last row of the carpus by surfaces which are covered with cartilages, and supplied with synovial membranes, as the most movable articulations are ; but the ligaments which connect these bones do not permit much motion between them. The ligaments are all dorsal and palmar. The irregularity of the articulating surfaces of the metacarpal bones of the index and middle finger also contribute to restrain their motion; and these bones accord- ingly move less than the other two metacarpal bones, whose surfaces are better adapted for motion. ARTICULATION OF THE RIBS. 255 Articulation of the Fingers. The first joint of the fingers has a large synovial membrane, which invests the head of the metacarpal bone and the corres- ponding cavities of the bones of the first phalanx. On each side is a strong lateral ligament, which arise from the side of the head of the metacarpal bone, and is inserted into the side of the base of the first phalanx. Anteriorly there is also a ligament, which, although thick and strong, is very flexible. It is thickened by cartilaginous matter on its palmar face, which serves as a sort of pully to the tendons, and increases their power by removing them from their line of action. Posteriorly the expansion of the tendons ofthe extensor muscle, and the tendons ofthe interossei, have the effect of a ligament. The different phalanges are articulated with each other in a similar manner. The lateral ligaments are very strong: the tendon ofthe extensor covers the articulation posteriorly; and anteriorly, under the flexor tendons, there is a soft, but thick ligamentous substance. The metacarpal bone of the thumb differs greatly from the other metacarpal bones in its articulation with the wrist, as respects its motions. The articulating sur- faces are calculated for lateral motion as well as flexion and extension ; and there are no ligaments which prevent it. Its capsular ligament forms a complete sac. The first joint of the thumb resembles considerably that of the fingers ; and the. second joint resembles the last of the phalanges. Articulation of the Ribs. The ribs are connected to the bodies ofthe vertebrae and the intervertebral cartilages, by one articulation, and to the trans- verse processes of the vertebrse by another: these articulations have the ordinary apparatus for motion, with capsular liga- ments, which in one case pass from the heads of the ribs to the bodies of the vertebrse, and in the other from the tubercles to the transverse processes. These form what are called the costo-vertebral, and costo-transverse articulations. 256 ARTICULATION OF THE RIBS. —The capsular ligament of the costo-vertebralarticulation,is not complete. It is much thick- est in front and upon the sides, and radiates from its origin on the head of the ribs, whence it is usually called the anterior radiating or stellate ligament. —There is also a small inter-ar- ticulating ligament, in this arti- culation, which passes from a ridge on the head of the rib to a corresponding line on the intervertebral substance. It thus divides the joint into two halves, each of which has a separate synovial membrane. This ligament does not exist where the ribs are attached to a single vertebra, as the first, eleventh and twelfth. —The costo-transverse articulation, besides its feeble capsular ligament and synovial membrane connecting the tubercle ofthe rib with the facet of the transverse process, includes three other ligaments, the internal transverse, the external transverse, and the middle costo-transverse. —The internal transverse, arises from the inferior margin of the transverse process, and is inserted into the upper margin of the neck of the rib below. —The external transverse, arises from the extremity of the transverse process and is inserted into the corresponding rib, just beyond the tubercle. —The middle costo-transverse ligament is extended between the neck of the rib and the contiguous transverse process. To be well seen it is necessary to saw longitudinally through the neck of the rib and its transverse process. These ligaments permit the motions necessary for respira- tion, and restrain all others. * The anterior ligaments of the vertebra?, and ligaments of the ribs. 1. The anterior common ligament. 2. The anterior costo-vertebral or stellate ligament. 3. The anterior costo-transverse ligament. 4. The inter-articular ligament connecting the head of the rib to the intervertebral substance, and separating the two synovial membranes of this articulation. HIP JOINT. 257 Fig 61. The connexion of the ribs.anteriorly with their cartilages, is such as admits of no motion whatever between them; but the extremities of the cartilages are articulated with the sternum, at the pits on the edges of that bone. In many instances there is no appearance of synovia between the ends of the cartilages and the sternum; but this fluid is mostly to be found in the pits, on the lower extremity ofthe sternum. —In the articulations between the cartilages of the ribs and the sternum, there is a synovial membrane, and two ligaments, anterior and posterior. These radiate from the sternal end of the cartilage, one over the anterior, the other over the poste- rior face of the sternum, and are blended with its periosteum, see fig. 53, p. 245.— The Hip Joint. The acetabulum is lined with cartilage; and the brim or margin of it is much enlarged, and the cavity deepened, by the addition of fibro-carti- laginous matter, which forms a regular smooth edge. This cartilaginous ring is continued across the upper part of the notch in the acetabulum ; so that it completes the circular mar- gin ofthe cavity,but leaves the under part of the notch open. This forms what is called the cotyloid ligament. The head of the os femoris is covered with cartilage, but the depression in it is still visible. * The ligaments of the pelvis and hip-joint. 1. The lower part of the anterior common ligament of the vertebrae, extending downwards over the front of the sacrum. 2. The lumbo-sacral ligament. 3. The lumbo-iliac ligament. 4. The anterior sacro-iliac ligaments. 5. The obturator membrane. 6. Poupart's ligament. 7. Gimbernat's ligament. 8. The capsular ligament of the hip-joint. 9. The ilio- femoral or accessory ligament. 22* 258 HIP JOINT. From this depression a strong round ligament (ligamentum teres or rotundum) see fig. 70, p.270,arises, whichappearstopassinto the depression, near the centre of the. acetabulum ; but actually terminates in the lower edge ofthe cartilaginous ring or margin, where it crosses over the notch, and not in the bone. This ligament is in fact divided into two parts at its insertion; one passes out at the inferior part of the cotyloid notch and is inserted on the margin of the ischium ; the other runs to the superior end of the notch, and besides being blended with the cotyloid ligament, is attached to the margin of the acetabulum. The thin (synovial) membrane with which this ligament is invested extends to the centre of the acetabulum, and has given rise to the opinion that the ligament was inserted in the bottom ofthe acetabulum.* This ligament allows the head of the os femoris to rise out of the acetabulum, but it is probably torn in every luxation of the os femoris. The capsular ligament, which contains these articulating parts, is the strongest in the body. It arises around the aceta- bulum, near the basis ofthe cartilaginous brim, but it does not adhere to the cartilaginous edge; and it is inserted into the os femoris, near the roots of the trochanters, so that it includes a large portion of the neck of the bone. It is not every where of the same thickness and strength; for, in various places, there are additional ligamentous fibres. The largest portion of these additional fibres appears to arise from the inferior anterior spinous process of the ilium. The capsular ligament is thin- est at its internal and posterior part.—The additional fibres which arise from the anterior inferior spinous process of the ilium constitute the ilio-femoral, or accessory ligament. The synovial membrane forms the internal lamina of this ligament: it invests the articulating surfaces in the usual manner, and being reflected from the internal surface of the capsular ligament to the neck of the os femoris, it is in the place of periosteum to that part of the bone. It seems probable that this membrane is so reflected and * See motions of skeleton. ARTICULATION OF THE KNEE. 259 Fig. 62.* arranged, that the internal ligament is covered by it also, and of course, that this ligament is exterior to the synovial mem- brane. There is a considerable quantity of adipose matter near the termination of the aforesaid internal ligament, which is also exterior to the synovial membrane: some of this can be pressed out of the acetabulum, at the vacuity in the notch under the cartilaginous margin. Articulation of the Knee. The synovial membrane of the knee joint is, in some places, without the support of a proper capsular ligament, or external lamen, so that it is easier distinguished in this articulation than in many others. It adheres firmly to the cartilaginous sur- faces of the os femoris, tibia, and patella, and is reflected in the usual manner from one to the other of these surfaces. It arises closely from the edge of the cartilagi- nous surface at the top of the tibia; but on the anterior part of the os femoris, it is continued to some distance from the mar- gin of the pulley-like surface, and the edges of the condyles. On each of the portions of the cartilaginous surfaces of the tibia is a cartilage of a semilunar form, so placed that its convex edge rests on the margin of the cartilaginous surface, and its concave edge is internal. These cartilages are * The right knee joint laid open from the front, in order to show the internal liga- ments. 1. The cartilaginous surface of the lower extremity of the femur with its two condyles; the figure 5 rests upon the external; the figure 3 upon the internal condyle. 2. The anterior crucial ligament. 3. The posterior crucial ligament. 4. The transverse ligament. 5. The attachment of the ligamentum mucosum ; the rest has been removed. 6. The internal semi-lunar fibro-cartilage. 7. The external fibro-cartilage. 8. A part of the ligamentum patellae turned down. 9. The bursa, situated between the ligamentum patellae and the head of the tibia. It has been laid open. 10. The anterior superior tibio-fibular ligament. 11. The upper part of the interosseous membrane ; the opening above this membrane is for the passage of the anterior tibial artery. 260 ARTICULATION OF THE KNEE. thick at their external, and very thin at their internal edges; so that they form two superficial concavities on the top of the tibia. Their extremities are attached by ligaments to the central protuberance of the tibia, and their anterior extremities are also connected by a ligament to each other. The synovial membrane is so reflected as to cover the whole Fig. 63.* surface of these cartilages, except the exterior edge, which is connected with the external ligaments ofthe articulation. The use of these cartilages, is evidently to form concavities on the top of the tibia, for accomodating the condyles of the os femoris; and upon examination, they will not appear so anomalous as they do at first view, for there is a considerable analogy between them and the cartilagi- nous edges of the glenoid cavity and of the acetabulum. These are called the semi- lunar cartilages. The internal is but little more than a semicircle; the external is nearly circular in its shape. The patella appears to project into the cavity of the joint, * A longitudinal section of the left knee joint, showing the reflections of its syno- vial membrane. 1. The cancellous structure of the lower part of the femur. 2. The tendon of the extensor muscles of the leg. 3. The patella. 4. The ligamentum patellae. 5. The cancellous structure of the head of the tibia. 6. A bursa situated between the ligamentum patellae and the head of the tibia. 7. The mass of fat pro- jecting into the cavity of the joint below the patella. * * The synovial membrane, 8. The pouch of synovial membrane which ascends between the tendon of the extensor muscles of the leg, and the front of the lower extremity of the femur. 9. One of the alar ligaments; the other has been removed with the opposite section. 10. The ligamentum mucosum left entire; the section being made to its inner side. 11. The anterior or external crucial ligament. 12. The posterior ligament. The scheme ofthe synovial membrane which is here presented to the student, is divested of all unnecessary complications. It may be traced from the saeulus (at 8), along the inner surface of the patella; then over the adipose mass (7) from which it throws off the mucous ligament (10); then over the head ofthe tibia, forming a sheath to the crucial ligaments; then upwards along the posterior ligament and condyles of the femur, to the sacculus whence its examination commenced. KNEE JOINT. 261 and its internal surface is very prominent; around the margin of this surface, and especially at the under part of it, the adi- Fig. 64.* pose substance found in joints is very abun- dant. On each side of the adipose mass, under the patella, is a plait of the synovial membrane, called ligamentum alare minus, and majus; and a process of the mem- brane, called ligamentum mucosum passes from the neighbourhood of the adipose mass to the os femoris between the con- dyles. These processes retain the adipose sub- stance in its proper place, during the mo- tions of the joint. There are two very strong ligaments, called the anterior and posterior crucial, which arise from the middle protuberance of the tibia, one of which is inserted posteriorly into the corner face of the external condyle of the os femoris, and the other, into the outer face of the internal. These ligaments decussate each other partially, on which account the name crucial is applied to them. They are in a state of tension when the leg is extended, and prevent it from moving farther forward: when it is bended they are relaxed. They add greatly to the strength of the connexion between the os femoris and tibia. These ligaments are generally supposed to be in the cavity of the joint; but the synovial membrane is reflected round them in such a manner that they are exterior to it. In addition to the crucial ligaments, this articulation has the following external supports. When the leg is extended, these ligaments are tense, they therefore prevent rotation in the extended state: when the * Posterior view of the ligaments ofthe knee joint. 1. Posterior ligament of Winslow, connected by a tendinous expansion with 2, the tendon ofthe semi-mem- branous muscle ; the latter is cut short. 3. The processof the tendon, which spreads out in the fascia of the popliteus muscle. 4. A process which is sent inwards beneath the internal lateral ligament. 5. The posterior part of the internal lateral ligament. 6. The long external lateral ligament. 7. Short external lateral ligament. 8. Tendon of popliteus cut short. 9. The posterior superior tibio-fibular ligament. 262 KNEE JOINT. leg is bent, they ate relaxed, and, therefore, admit of that motion. 1. Two strong lateral ligaments, one on each side of the knee; the external of which arises from the tubercle above the external condyle of the os femoris, and is attached to the fibula a little below its head; and the internal, from the upper part and tubercle of the internal condyle, and is inserted into the upper and inner part of the tibia. 2. The posterior ligament, or ligament of Winslow, whose fibres run obliquely from the external condyle to the back part of the internal side of the head of the tibia. This ligament also prevents the leg from being drawn too far forwards. 3. The connexion ofthe tendons of the extensor muscles of the leg, with this articulation, has a great effect upon it. Their insertion into the patella places them in the situation of the upper part of the anterior ligament, of which the very strong ligament, that passes from the lower margin of the patella to the tubercle of the tibia, is only the lower portion; while the patella may be considered'as an inducted part of the ligament. Thejiendons ofthe ham-string muscles, also, serve to strengthen the articulation on the back and sides. —The fascia lata of the thigh as it passes down upon the leg, is thickened by a pro- cess of the extensor tendons, and forms a strong external in vestment'or involucrum to the knee joint. It constitutes in fact a sort of capsular ligament to the joint; it closely embraces the patella and its liga- ments, covers in and is partly blended with the lateral ligaments, and is firmly attached to the condyles. At the posterior part of the joint, it forms a thin membrane, and can scarcely be traced. Its place is there * The anterior view of the ligaments of the knee joint. 1. The tendon of the quadriceps extensor muscle of the leg. 2. The patella. -3. The anterior ligament, or ligamentum patellae, near its insertion. 4, 4. The synovial membrane. 5. The internal lateral ligament. 6. The long external lateral ligament. 7. The anterior superior tibio-fibular ligament. ARTICULATION OF THE TIBIA AND FIBULA. 263 supplied by the posterior ligament. On either side of the liga- ment of the patella its inner face is in contact with the synovial membrane of the joint.— Bursa Mucosa. There are two of these in connection with the ligamentum patellae; one of which is placed superficially between the ligament and the fascia lata. Thisis the seat of the enlargement by increase of secretion, known under the name of housemaid's knee. The other is placed between the tibia and the ligamentum patellae, as seen in fig. 65. Articulation of the Tibia and Fibula.—Superior Articulation. The surfaces of the upper extremities of the tibia and fibula, which are articulated with each other, are very small. When the bones are in their natural position, these surfaces are nearly horizontal, that of the tibia looking down, and that of the fibula looking up : they are covered with cartilages, and have a syno- vial membrane. This articulation is supported by some liga- mentous fibres, which have been called anterior superior, and posterior superior ligaments; it is strengthened also by the external lateral ligament of the knee, and by the tendon of the biceps muscle which is inserted into the upper end of the fibula. Inferior Articulation. At their lower extremities, the cartilaginous crust, which, on each of them, forms part of the articulating surface with the astragalous, is turned up on their lateral surfaces which are in contact with each other; so that a small portion (equal in breadth only to one sixth of an inch) of the contiguous surfaces, is covered with cartilage ; the other parts of these surfaces which are very considerable, are attached to each other by the intervention of fibrous or membranous matter, and there is very little motion of the bones on each other. There are very strong external ligaments, called the anterior 264 ANKLE JOINT. Fig. 66.* inferior, and posterior inferior, which connect the fibula to the tibia; and from the posterior surface of the end of the fibula, a ligament called the transverse, passes to the posterior part of the internal malleolus, which resembles the marginal ligament of the glenoid cavity and acetabulum; for it enlarges the articulation with the astragalus, while it serves as a liga- ment to the tibia and fibula. There are some short, strong fibres passing below and between the opposite surfaces of the tibia and fibia, called the inferior interosseous ligament. Articulation of the Leg, Foot, and Ankle Joint. It should be observed that the tibia and fibula are so firmly connected with each other below, that they may be considered as forming but one member of this articulation. Fig. 67.t The varied surfaces formed by the tibia and fibula and their two malleolar processes, and by the as- tragalus with its two lateral facets, where it is contiguous to them, are invested with the usual apparatus of articulation. The synovial fluid is generally observed to be very redun. dant in this joint. There are four ligaments which enter into this ar- ticulation. A triangular band of fibres called the internal lateral liga- * A posterior view of the ankle joint. 1. The lower part of the interosseoui membrane. 2. The posterior inferior ligament connecting the tibia and fibula. 3. The transverse ligament. 4. The internal lateral ligament. 5. The posterior fas- ciculus of the external lateral ligament. 6. The middle) fasciculus of the external lateral ligament. 7. The synovial membrane of the ankle joint. 8. The os calcis. t An internal view of the ankle joint. 1. The internal malleolus of the tibia. 2, 2. Part of the astragalus; the rest is concealed by the ligaments. 3. The os calcis. 4. The scaphoid bone. 5. The internal cuneiforme bone. 6. The internal lateral oi deltoid ligament. 7. The anterior ligament. 8. The tendo Achillis; a small bursa is seen interposed between'this tendon and the tuberosity of the os calcis. ARTICULATION OF THE ASTRAGALUS AND OS CALCIS. 265 ment passes downwards from the tibia at the internal malleolus, and is inserted into the inside of the astragalus, and also into the os calcis and naviculare. Some of the fibres are blended with those of the sheath for the tendon of the flexor communis • and some of them have a radiated arrangement, in consequence of which this has been called the deltoid ligament. From the fibula three ligaments arise, spoken of collectively as one ligament, external lateral, (ligamentum triquetrum.) The middle fasciculus, which is strong and thick, passes down- wards from the end of that bone, to be inserted into the outside ofthe os calcis. The anterior fasciculus passes forwards, and is attached to the astragalus. The posterior fasciculus passes backwards, and is attached to the posterior part ofthe astragalus. —The anterior ligament is a thin membranous layer, in contact with the synovial membrane, it passes from the anterior margin ofthe tibia and is inserted into the anterior portion of the astra- galus, near the articular surface. No well marked posterior liga- ment exists at this articulation. The transverse ligament sup- plies its place. Articulation of the Astragalus and Os Calcis. Fig. 68.* The astragalus is attached firmly to the os calcis by very strong and short ligamentous fibres, which arise from the fossa on its under surface, and are inserted into the fossa be- tween the upper articulating sur- faces of the os calcis. This is called the interosseous. This ligament separates the posterior articulations of the astragalus and os calcis from the anterior. The posterior articulation has a synovial mem- brane exclusively appropriated to it. The anterior articulation * An external view ofthe ankle joint. 1. The tibia. 2. External malleolus of the fibula. 3, 3. Astragalus. 4. Os calcis. 5. Cuboid bone. 6. The anterior fasciculus of the external lateral ligament attached to the astragalus. 7. Its middle fasciculus attached to the os calcis. 8. Its posterior fasciculus attached to the astragalus. 9. The anterior ligament of the ankle. 23 266 ARTICULATION OF THE TARSAL BONES. is supplied by an extension of the membrane which invests the articulating surfaces of the astragalus and naviculare. The connexion of the astragalus, with the os calcis is sup- ported by the lateral ligaments of the ankle joint, and also by many irregular ligamentous fibres. Articulation of the Astragalus with the Os JVaviculare. This articulation appears calculated for considerable motion, as well from the form of the two surfaces concerned in it, as the perfect state of their articulating investments. Their mo- tions are restrained to a certain degree, by ligaments, which are situated on the upper and internal surfaces of the foot. Fig. 69.* —On the upper surface of the foot, is a thin broad ligament formed of parallel and oblique fibres, stretched from the upper and inner face of the astragalus to the upper surface of the scaphoides or naviculare; some of the fibres extend even to the cunei- forme bones. —On the under surface of the foot, these bones are connected by two ligaments, cal- caneo-scaphoid internum, and externum. —The internal arises from the inner margin of the lesser apophysis of the os calcis, and runs obliquely forwards and inwards, to be inserted on the inner and under surface of the os naviculare. It is a strong ligament, and contributes much to the preservation of the arched form of the foot. On its under surface is a trochlea for the tendons of the flexor pollicis and * The ligaments of the sole of the foot. 1. The os calcis. 2. The astragalus. 3. The tuberosity of the scaphoid bone. 4. The long calcaneo-cuboid ligament. 5. Part of the short calcaneo-cuboid ligament. 6. The internal calcaneo-scaphoid ligament. 7. The plantar tarsal ligaments. 8, 8. The tendon of the peroneus lon- gus muscle. 9,9. Plantar tarso-metatarsal ligaments. 10. Plantar ligament of the metatarso-phalangeal articulation of the great toe ; the same ligament is seen upon the other toes. 11. Lateral ligaments ofthe metatarso-phalangeal articulation. 12. Transverse ligament. 13. The lateral ligaments of the phalanges ofthe great toe; the same ligaments are seen upon the other toes. ARTICULATION OF THE OS CALCIS AND CUBOIDES. 267 flexor longus digitorum. Below it is also in contact with the tendon of the tibialis posticus, and above with the head of the astragalus, which it in part supports. —The external is at the outer side of the last; it arises from the under surface of the greater apophysis of the os calcis, and is inserted upon the under internal surface of the os naviculare.— The ligaments which pass from the anterior internal extremity ofthe os calcis to the os naviculare, and support the head of the astragalus, ought to be observed with attention during the examination of this joint. Articulation ofthe Os Calcis and Cuboides. The articulating surfaces of this joint are arranged in the usual manner. There are two additional ligaments : one placed on the upper, and the other on the under surfaces of the bones. The upper ligament is thin ; but the under ligament is one of the strongest of the foot; and its fibres are blended with those which form the sheath for the tendon of the peroneus longus, as it passes along the groove in the cuboides. —These ligaments are called the superior and inferior calca- neo-cuboid. The latter is by some considered as consisting of two ligaments, the short and long. —The superior passes from the upper anterior surface of the os calcis to the adjoining surface ofthe os cuboides. —The inferior is the strongest ligament of the foot. It arises from the inferior back part Of the os calcis, and part of its fibres are inserted upon the oblique ridge or the tendon of the peroneus longus which traverses the under part of the os cu- boides. This part is sometimes called the short inferior calca- neo-cuboid ligament. The greater part of the fibres of this ligament, pass beyond the ridge, and are inserted in fasciculi upon the basis of the third and fourth metatarsal bones. These subtend the groove, in which passes the tendon of the peroneus longus muscle, and constitute the long inferior calcaneo-cuboid ligament. —The other bones ofthe foot are united in general by dorsal and plantar ligaments like the corresponding bones of the hand.— 268 PARTICULAR LIGAMENTS. CHAPTER VI. OF PARTICULAR LIGAMENTS, AND OF THE SITUATION OF THE INDIVIDUAL BURS.E MUCOSAE. Enumeration of the most important Ligaments, which have not been described. Ligaments proper to the Scapula. The triangular ligament (ligamentum coraco-acromialis) arises broad from the external surface of the coracoid process, and becomes narrower where it is fixed to the posterior margin of the acromion. It confines the tendon of the supra-spinatus, muscle, and assists in protecting the upper and inner part of the joint of the humerus. The posterior ligament of the scapula (coracoid) is some- times double, and is stretched across the semilunar notch of the scapula, forming that notch into one or two holes for the passage ofthe superior posterior scapujary vessels and nerves. It also gives rise to part of the omo-hyoideus muscle. The Interosseous Ligament of the Forearm, Extends between the sharp ridges of the radius and ulna, filling up the greater part of the space between these two bones, and is composed of small fasciculi, or fibrous slips, which run obliquely downwards and inwards. Two or three of these, however, go in the opposite direction, and one of them, termed oblique ligament and chorda transversalis cubiti, is stretched between the tubercle ofthe ulna and under part ofthe tubercle of the radius. In different parts of the ligament there are perforations for the passage of blood-vessels from the fore to the back part of the bone, and a large opening is found at the upper part of it which is filled up by muscles. It preventsthe radius from rolling too much outwards, and furnishes a com- modious attachment for muscles. J LIGAMENTS OF THE HAND. 269 Ligaments retaining the Tendons of the Muscles ofthe Hand and Fingers in their proper positions. The anterior annular ligament ofthe wrist is stretched across from the projecting points of the pisiform and unciform bones, to the os scaphoides and trapezium, and forms an arch which covers and preserves in their places the tendons of the flexor muscles ofthe fingers. The vaginal ligaments of the jlexor tendons are five mem- branes, connecting the tendons of the sublimis, first to each other, andthen to those of the profundus; forming, at the same time, bursae mucosae which surround the tendons. The vaginal or crucial ligaments of the phalanges arise from the ridges on the concave side ofthe phalanges, and run over the tendons of the flexor muscles of the fingers. Upon the body ofthe phalanges, they are thick and strong, to bind down the tendons, but over the joints they are thin, and have, in some parts, a crucial appearance, to allow the ready motion of the joints. The accessory ligaments of the jlexor tendons of the fingers are small tendinous frsena, arising from the first and second phalanges of the finger,. They run obliquely forwards within the vaginal ligaments, terminate in the tendons of the two flexor muscles ofthe fingers, and assist in keeping them in their places. The posterior annular ligament of the wrist is part of the aponeurosis of the forearm, extending across the back of the wrist, from the extremity of the ulna and os pisiforme to the extremity of the radius. It is connected with the small annular ligaments which tie down the tendons of the extensores ossis metacarpi et primi internodii pollicis, and the extensor carpi ulnaris. The vaginal ligaments adhere to the last mentioned, and serve as sheaths and bursae mucosae to the extensor tendons of the hand and fingers. The transverse ligaments, of the extensor tendons, are aponeurotic slips running between the tendons, near the heads ofthe metacarpal bones, and retaining them in their places. 23* 270 LIGAMENTS OF THE STERNUM. Ligaments on the Anterior part ofthe Thorax. The membrane proper to the sternum is a firm expansion, composed of tendinous fibres running in different directions, and covering the anterior and posterior surfaces of the bone, being confounded with the periosteum. The ligaments of the cartilago ensiformis axe part of the proper membrane of the sternum, divided into strong bands, which run obliquely from the under and forepart of the second bone of the sternum, and from the cartilages of the seventh pair of ribs, to be fixed to the cartilago ensiformis. The liga- ments covering the sternum serve considerably to strengthen that bone. There are also thin tendinous expansions which run over the intercostal muscles at the fore part ofthe thorax, and connect the cartilages of the ribs to each other. Ligaments of the Bones of the Pelvis. Articulations of the vertebral column with the pelvis. The lowermost lumbar vertebra is articulated with the sacrum in the same manner as the vertebrae are articulated with each other, viz., by the common anterior and posterior ligaments ofthe spinal column, intervertebral substance, yellow elastic liga- ments, capsular ligaments covering the oblique processes, and the interspinal ligaments. Two other ligaments connecting it with the bones ofthe pelvis, are denominated theilio lumbar or lumbo-iliac ligament, and the sacro-vertebral or lumbar sacral ligament. From their direction they are sometimes called the two transverse ligaments of the pelvis. The ilio-lumbar, (see fig. 61, p. 257,) arises from the point of the transverse process of the last lumbar vertebra, and from the oblique process below and is inserted for about two inches into the crest of the ileum just above its posterior superior spinous process. It sometimes from being blended with adipose substances presents the appearance of two distinct ligaments. The sacro-vertebral, arises from the under part of the trans- verse process of the last lumbar vertebra, and is inserted into j LIGAMENTS OF THE STERNUM. 271 the upper part of the base of the sacrum near the anterior liga- ment ofthe sacro-iliac articulation with which some of its fibres are blended. The proper ligaments of the pelvis, are as follows, viz. 1. Those which connect the ilium and sacrum. 2. Those between the sacrum and ischium. 3. Those between the sacrum and coccyx, and 4. Those which join the two pubic bones together. 1. Ligaments connecting the Rium and Sacrum. A long flat ligament called the sacro-spinous (lig. sacro- spinosum) arises from the posterior superior spinous process ofthe os ilium descends obliquely and is inserted into the third and fourth transverse processes of the sacrum. It sometimes presents the appearance of two separate ligaments. The ligaments which form the sacro-iliac junction are two in number, and are called anterior and posterior. —The anterior sacro-iliac ligament, consists of a thin plane of short, strong ligamentous fibres, passing from bone to bone on the anterior face of the joint. The posterior sacro-iliac-ligament, is the main stay of the articulation. It consists of many strong bundles of ligamentous fibres, which cross horizontally over the posterior part of the joint, and are attached by one extremity to the rough surface of the ilium immediately behind the joint, and by the other to two eminences on the lateral margin ofthe sacrum, as well as the rough surfaces of the bone between them. 2. Ligaments connecting the Sacrum and Ischium. The two sacro-ischiatic ligaments, see fig. 70, are situated in the under and back part of the pelvis. They arise nearly in common from the transverse processes of the os sacrum, from the under and lateral part of that bone, and from the upper part of the os coccygis. The first, called the external posterior or greater, descends obliquely, to be fixed to the tuberosity of the os ischium. The other, called the lesser, internal ox ante- rior sacro-sciatic or sacro-ischiatic ligament, runs transversely to be fixed to the spinous process of the os ischium. These 272 LIGAMENTS OF THE PELVIS. two ligaments assist in binding the bones of the pelvis, in sup- porting its contents, and in giving origin to part of its muscles. Fig. 70.* There are two membra- nous productions which are connected with the large sacro-ischiatic liga- ment, termed its superior and inferior appendices. The superior appendix, which is tendinous, arises from the back part of the os ilium, and is fixed along the outer edge of the liga- ment, which it increases in breadth. The inferior or falci- form appendix, situated within the cavity of the pelvis, the back part of which is connected with the middle of the large external ligament, and the rest of it is extended round the curvature of the os ischium. These two productions assist the large sacro-ischiatic liga- ment in furnishing a more commodious situation for, and insertion of, part of the gluteus maximus, and obturator internus muscles. The large holes upon the back part of the os sacrum are also surrounded with various ligamentous expansions, pro- jecting from one tubercle to another, and giving origin to mus- cular fibres, and protection to small vessels and nerves which creep under them. * Ligaments ofthe pelvis and hip-joint. The view is taken from the side. 1. The oblique sacro-iliac ligament. The other fasciculi of the posterior sacro-iliac ligaments are not seen in this view of the pelvis. 2. The posterior sacro-ischiatic ligament. 3. The anterior sacro-ischiatic ligament. 4. The great sacro-ischiatic foramen. 5. The lesser sacro-ischiatic foramen. 6. The cotyloid ligament of the acetabulum. 7. The ligamentum teres. 8. The cut edge of the capsular ligament, showing its extent posteriorly as compared with its anterior attachment. 9. The obturator membrane only partly seen. LIGAMENTS OF THE PELVIS. 273 3. Ligaments connecting the Sacrum and Os Coccygis. A general covering is sent down from the ligaments of the os sacrum, which spreads over and connects the different pieces of the os coccygis together, allowing considerable motion, as already mentioned, in the description of this bone. This forms what is called the anterior and posterior coccygeal lig- aments. The posterior longitudinal ligaments of the os coccygis descend from those upon the dorsum of the os sacrum, to be fixed to the back part of the os coccygis. The ligaments of this bone prevent it from being pulled too much forwards by the action of the coccygeus muscle, and they restore the bone to its natural situation, after the muscle has ceased to act. 4. Ligaments connecting the Ossa Pubis. A ligamentous fibro-cartilage, resembling in structure the intervertebral substance, unites the two ossa pubis so firmly together at their symphysis as to admit of no motion, excepting in me state of pregnancy, when it is frequently found to be so much softened as to yield a little in the time of delivery. —There are a few transverse ligamentous fibres on the front part of the symphysis pubis, called the anterior pubic liga- ment. These interlace in front ofthe symphysis. —There are also a few irregular fibres on the posterior face of the articulation crossing from bone to bone, called the pos- terior pubic ligament. —The sub, or interpubic ligament occupies the summit of the arch of the pubis. It is about half an inch in breadth, and passes from the crus of the pubis of one side to that of the other.— —A thick strong band of fibres is found crossing from bone to bone, on their superior face, and filling up the inequalities which exist there ; it is called the superior pubic ligament. The obturator membrane, ox ligament of the foramen thy- roideum, adheres to the margin of the foramen thyroideum, and fills the whole of that opening, excepting the oblique notch at 274 LIGAMENTS OF THE FOOT. its upper part for the passage of the obturator vessels and nerve. It assists in supporting the contents of the pelvis, and in giving origin to the obturator muscles. See fig. 61, p. 257. The interosseous ligament ofthe leg fills the space between the tibia and fibula like the interosseous ligament of the fore- arm, and is of a similar structure ; being formed of the oblique fibres, and perforated in various places for the passage of vessels and nerves. At the upper part of it there is a large opening, where the muscles of the opposite sides are in contact; and where vessels and nerves pass to the fore part of the leg. It serves chiefly for the origin of part of the muscles which belong to the foot. Ligaments retaining the Tendons of the Muscles ofthe Foot and Toes in their proper position. The annular ligament of the tarsus is a thickened part of the aponeurosis of the leg, splitting into superior and inferior portions, which bind down the tendons of the extensors of the toes upon the forepart of the ankle. The vaginal ligament ofthe tendons oftheperonei muscles, behind the ankle is common to both, but divides at the outer part of the foot, and becomes proper to each. They preserve the tendons in their places, and are the bursae of these tendons. The laciniated ligament arises from the inner ankle, and spreads in a radiated manner, to be fixed partly in the cellular substance and fat, and partly to the os calcis, at the inner side of the heel. It encloses the tibialis posticus and flexor digito- rum longus. The vaginal ligament of the tendon ofthe extensor pro- prius pollicis runs in a crucial direction. The vaginal ligament of the tendon of the flexor longus pollicis surrounds this tendon in the hollow of the os calcis. The vaginal and crucial ligaments ofthe tendons of the flexors ofthe toes inclose these tendons on the surfaces of the pha- langes, and form their bursae mucosas. The accessory ligaments of the jlexor tendons ofthe toes, as in BURS.E MUCOSAE. 275 the fingers, arise from the phalanges, and are included in the sheaths of the tendons in which they terminate. The transverse ligaments ofthe extensor tendons run between them, and preserve them in their places behind the roots of their toes. Enumeration of the most important Bursae Mucosae. Those about the articulation ofthe Shoulder are situated, 1. Under the clavicle, where it plays upon the coracoid pro- i cess. 2. Between the triangular ligament of the scapula and the i capsular ligament of the humerus. 3. Between the point of the coracoid process and capsular ligament of the humerus. 4. Between the tendon of the subscapulars muscle and cap- sular ligament of the humerus, frequently communicating with the cavity of that joint. 5. Between the origin of the coraco-brachialis and short head of the biceps muscles, and capsular ligament of the hu- merus. 6. Between the tendon of the teres major and the os humeri, and upper part of the tendon of the latissimus dorsi. 7. Between the tendon of the latissimus dorsi and os humeri. 8. Between the tendon of the long head of the biceps flexor cubiti and the humerus. The Bursae marked 3 and 5 are sometimes absent. Near ihe articulation of the Elbow there are, 1. With a peloton of fat, between the tendon of the biceps and tubercle of the radius. 2. Between the tendon common to the extensor carpi radialis brevior, extensor digitorum communis, and round head of the radius. 3. A small bursa, between the tendon of the triceps extensor cubiti and olecranon. 276 BURS.E MUCOSA OF THE UPPER EXTREMITY. On the Forearm and Hand are situated, 1. A very large bursa surrounding the tendon of the flexor pollicis longus. 2. Four long bursae lining the sheaths which enclose the tendons of the flexors upon the fingers. 3. Four short bursae on the forepart of the tendons of the flexor digitorum sublimis in the palm of the hand. 4. A large bursa between the tendons of the flexor pollicis longus, the forepart of the radius, and capsular ligament of the os trapezium. 5. A large bursa between the tendons ofthe flexor digitorum profundus, and the forepart of the end of the radius, and capsu- lar ligament of the wrist. These two last mentioned bursae arc sometimes found to communicate with each other. 7. A bursa between the tendon of the flexor carpi radialis and os trapezium. 8. Between the tendon of the flexor carpi ulnaris and os pisiforme. 9. Between the tendon of the extensor ossis metacarpi polli- cis and radius. 10. A large bursa common to the extensores carpi radiales, where they cross behind the extensor ossis metacarpi pollicis. 11. Another common to the entensores carpi radiales, where they cross behind the extensor secundi internodii pollicis. 12. A third, at the insertion of the tendon of the extensor carpi radialis brevior. 13. A bursa for the tendon of the extensor secundi internodii pollicis, which communicates with the second bursa common to the extensores carpi radiales. 14. Another bursa between the tendon ofthe extensor secun- di internodii pollicis and metacarpal bone of the thumb. 15. A bursa between the tendons of the extensor ofthe fore, middle, and ring fingers, and ligament of the wrist. 16. For the tendons ofthe extensor ofthe little finger. 17. Between the tendon of the extensor carpi ulnaris and ligament ofthe wrist. BURSJ2 MUCOSiE OP THE THIGH AND ANKLE. 277 Upon the Pelvis and upper part of the Thigh there are, 1. A very large bursa between the iliacus internus and psoas magnus muscles, and the capsular ligament of the thigh bone. 2. One between the tendon of the pectinalis muscle and the thigh bone. 3. Between the gluteus medius and trochanter major, and before the insertion of the tendon of the pyriformis. 4. Between the tendon of the gluteus minimis and trochanter major. 5. Between the gluteus maximus and vastus externus. 6. Between the gluteus medius and pyriformis. 7. Between the obturator internus and os ischium. 8. An oblong bursa continued a considerable way between the obturator internus, gemini, and capsular ligament of the thigh bone. 9. A small bursa at the head of the semimembranosus and biceps flexor cruris. 10. Between the origin of the semitendinosus and that of the two former muscles. 11. A large bursa between the tendon ofthe gluteus maximus and root of the trochanter major. 12. Two small bursas between the tendon of the gluteus maximus and thigh bone. About the Joint ofthe Knee are, 1. A large bursa behind the tendon of the extensors of the leg, frequently found to communicate with the cavity of the knee joint. 2. Behind the ligament which joins the patella to the tibia, in the upper part of the cavity of which a fatty substance pro- jects. 3. Between the tendons of the sartorius, gracilis, semiten- dinosus, and tibia. 4. Between the tendons of the semimembranosus and gemel- lus, and ligament of the knee. This bursa contains a small one within it, from which a passage leads into the cavity of the joint ofthe knee. 24 278 BURSJE MUCOS.33 OF THE ANKLE AND FOOT. 5. Between the tendon of the semimembranosus and the internal lateral ligament of the knee, from which also there is i a passage leading into the joint of the knee. 6. Under the popliteus muscle, likewise communicating with the cavity of the knee joint. About the Ankle there are, 1. A bursa between the tendon of the tibialis amicus, and under part of the tibia and ligament of the ankle. 2. Between the tendon of the extensor proprius pollicis pedis, and the tibia and capsular ligament of the ankle. 3. Between the tendons of the extensor digitorum longus, and ligament of the ankle. 4. Common to the tendons of the peronei muscles. 5. Proper to the tendon of the peroneus brevis. 6. Between the tendon achillis and os calcis, into the cavity of which a peloton or mass of fat projects. 7. Between the os calcis and flexor pollicis longus. 8. Between the flexor digitorum longus and the tibia and os calcis. 9. A bursa between the tendon of the tibialis posticus and the tibia and astragalus. On the Sole ofthe Foot are also, 1. A second bursa for the tendon of the peroneus longus, with an oblong peloton of fat within it. 2. One common to the tendon of the flexor pollicis longus, and that of the flexor digitorum profundus, at the upper end of which a fatty substance projects. 3. Another for the tendon of the tibialis posticus. 4. Several for the tendons ofthe flexors of the toes. PART III. MYOLOGY. CHAPTER VII, GENERAL ANATOMY OF MUSCLES.* That soft, fibrous, red-coloured substance, which constitutes so large a proportion of the volume of the more perfect ani- mals, is called Flesh or Muscle. By the contraction of this substance, the spontaneous mo- tions of animals are produced ; and, on this account the fibres which compose it have long been regarded with particular attention. Muscular fibres are not only arranged in those regular masses on the trunk and limbs of the body, which are so fami- liar to us by the name of muscles, but they also exist in some of the most important viscera, and produce the internal, as well as the external motions of animals. —Muscles have been divided in man, and the superior ani- mals, into two classes. The first class consists of those which produce the external motions of the body, and are placed exteriorly; these contract under the influence of the will, are the agents by which are executed the animal or voluntary func- tions which place the animal in relation with the exterior world, and are called the muscles of animal life, muscles of the life of relation, voluntary muscles, etc. These form by far the largest portion ofthe whole mass, and are attached in general, by one or both extremities to the skeleton. They are solid, * Muscles were first named according to their figure and situation, in 1587, by Jacques Dubois, surnamed Sylvius, a member of the Faculty of Medicine, in Paris.—h. 280 GENERAL ANATOMY OF MUSCLES. that is, have no cavity in their interior, and vary much in their size. The second class consists of those placed in the interior of the body, and which effect the movements requisite in the various processes of nutrition and generation. These are not under the control of the will, and are called the muscles of organic life, muscles ofthe life of nutrition, involuntary muscles, etc. They are generally membraniform, and assist in forming the hollow organs, as in the heart, digestive canal, uterus and bladder. With the exception of those of the heart, the fibres of this class of muscles are of a pale colour, and some entirely colourless. A few of the muscles of animal life, as those of the ears and some of those of the face, are likewise faintly coloured, and are considered by Isenflam,* as existing even in the adult in a state of rudimental developement, as their colour and func- tions are found much more fully manifested in some quadru- peds.t —The muscles in the inferior grades of animals appear to exist in a rudimental condition, and become more and more nume- rous, and of a colour more and more red generally, as we advance upwards from the zero point of the animal scale. In the developement of the human foetus they seem to undergo analogous changes. —They present themselves during the three first months of foetal life, as gelatinous or viscous masses, very slightly tinged with yellow, and with thin tendons, according to Isenflam, *Anatomisohe Untersuchungen, by H. F. Isenflam, Professors the University of Dorpat. t This physiological division of the muscles into two classes, after Bichat, is emi-' nently useful to the student, in enabling him to simplify and generalise his studies of the muscular system; one class is not, however, wholly separate from the other. Between, is interposed another subdivision of muscles, called the Respiratory of Sir C. Bell, which with the muscles of the pharynx and oesophagus, might be considered as a third or mixed class of muscles, as they execute certain motions involuntarily and unconsciously to the individual, and yet are under the influence of the will to per- form motions for other purposes or to execute the same motions more rapidly or more slowly. Thus, for instance, the muscles of respiration which carry on the process of breathing during sleep, produce involuntary sneezing, coughing and crying; and v, hen placed under the influence of the will are made to elicit the voice, etc.—r. GENERAL ANATOMY OF MUSCLES. 281 already apparent in the flexors and extensors of the fingers and loes. —At the end of the fourth or fifth month, the muscles present a reddish aspect, and at the period of birth, though they may be readily dissected from each other, they are very soft, and of a colour much less deep than those of the adult.— Muscular fibres are connected to each other by cellular mem- brane. This membrane surrounds each muscle; and its various lamina, gradually diminishing in thickness, pass be- tween the different bundles of fibres, and the different fibres of which each muscle is composed. The fibres of muscles, when examined with magnifying glasses, appear to be composed of fibrillae still smaller; and it has been supposed that this division of them extended beyond our powers of vision, even when assisted by microscopes : but so many errors have occurred in microscopical observations of very minute objects, and so much difference exists between the reports of different observers, that the subject at this time does not interest many persons; and very little attention is paid, by the anatomists and physiologists of the present day, to the opinions of those observers who supposed they had ascertained the structure of the ultimate fibrillae. —The cellular or reticular membrane investing the whole muscle, is called the muscular sheath. It is formed round every muscle of the body, but varies much in different places in regard to thickness and strength. Each of the many larger fasciculi, or bundles of fibres, (lacerti,) of which every muscle is obviously composed, is surrounded in like manner by pro- cesses sent inwards from the sheath, and is a perfect, though diminutive representative of the entire muscle. —This secondary sheath surrounding the fasciculi, sends pro- cesses likewise inwards, and invests and separates the indivi- dual fibres so called, or rather the primitive fasciculi, of which each larger fasciculus is formed. These fibres or primitive fasciculi themselves are again susceptible of subdivision into what are called the ultimate muscular filaments, between which, it is probable, though not susceptible of demonstration, 24* 282 STRUCTURE OF MUSCULAR FIBRES. the elementary particles of cellular tissue likewise pass. In the muscles of organic life, the cellular tissue is less abundant, but more dense than in those of animal life. In some parts, especially in the digestive canal it is so dense and resistant as to represent a sort of ligamentous tissue, and give attachment to muscular fibres. —This delicate sheath surrounding the primary fasciculus, has been designated by Mr. Bowman as the sarcolemma, or the primitive cellular investment of the muscular fibres.—The term myolemma has been applied to the same structure by Mr. Wil- son and Dr. Quain. —The entire muscle thus appears naturally susceptible of three subdivisions. 1st. Into fasciculi, or bundles of fibres. These are the minutest subdivisions which can be made with the naked eye, without resort to boiling or other mechanical means. These are themselves collected into bundles, by septa which pass in from the general sheath of the muscles, but which are easily unravelled by a little dissection ; so that what is at first sight mistaken by the student for a fasciculus, is in reality but a bundle of fasciculi. The size of each of these fasciculi, varies in the different muscles of the body, and occasionally in the same muscle, according to the number of fibres of which it is composed. 2d. Into fibres so called or the primitive fasciculi. These are rendered very apparent by boiling, as seen daily in culinary preparations, by which the muscular fibre is swoln, while the cellular envelope, at the same time softened and reduced to a gelatinous pulp, is readily burst. These fibres also vary in their thickness, some having a diameter three or four times as great as that of others, depending upon the num- ber of elementary filaments—usually amounting to several hun- dred—of which it is composed. 3d. Into the elementary, or ultimate muscular filaments. These are wholly microscopical, are not uniform in their diameter in all muscles, those of organic life being much smaller, and vary considerably in the numbers taken to constitute the muscular fibres of different size.* Each * Meckel, torn. i. p. 378. STRUCTURE OF MUSCULAR FIBRES. 283 ofthe muscular fibres, and also, each ofthe ultimate filaments, according to Prochaska and Rudolphi, extend the whole length of the fleshy part of the muscles, differing entirely in this respect from the ultimate structure of the bones. —Anatomists do not agree in regard to the diameter assigned the ultimate muscular filament, and from its microscopical diminutiveness any measurement can be considered as little more than an approximation. They have been examined by Hook, Lewenhoeck, Dehayde, Muys, and more recently still by Prochaska and others. According to Prochaska, they are generally straight and parallel with each other, flattened or prismatic, and of a diameter one-fifth of that of the red globules of blood. Autenreith supposed them equal to one-third of the diameter. Prevost and Dumas found them by their measure- ment, 7TVTth part of an inch in diameter, five or six times smaller than the red globules of the blood, and nearly equal, as Muller also has asserted, to the diameter of the chyle globules, or to the central nuclei of the red globules of blood, which may be considered the most minute compound constitu- ents of the economy. —Much of this discordance of opinion, is probably owing to the examinations not having always been practised upon single and well isolated filaments. From more recent observations by Bauer and Home, Beclard, Prevost, and Dumas, H. Cloquet, and H. M. Edwards, the ultimate filament may be considered as identical in its structure with the particles of blood deprived of their colouring matter, of which the central globules (nuclei) form the filaments by being articulated end to end, by a sort of delicate jelly or mucus, which is probably the elementary form of the cellular tissue. The more recent microscopical measure- ments of Henle, Lauth, Ficinis, Bruns and others, agree in giving to the ultimate or elementary muscular filament of animal life, a diameter of TiJ0oth part of an inch. The dia- meter of the primitive fasciculus, commonly called muscular fibre, which is cylindrical in shape, is considered upon an average about ^th Part °f an incn m diameter. Each one is marked by striae or streaks, which pass transversely round 284 STRUCTURE OF MUSCULAR FIBRES. them, in slightly curved or w^avy parallel lines from r-0ij5 to T2I0 otn °f an mcn apart. —The nature of these sjrite which belong solely to the mus- cles of animal life, are not well understood, whether they be delicate fibres wound round the primary fasciculi, mere wrinkles in its myolemma or sheath, or what seems more likely, depres- sions corresponding with the breaks between the globules or granules, which, appended end to end, constitute a primitive filament. —The primitive fasciculus, or muscular fibre of organic life, which is solely under the influence of the ganglionic nervous system, is paler and softer than those of animal life; is not so regularly arranged in a longitudinal and parallel direction; and is less easily divided into its primitive filaments. Though each fibre is round if singly examined, the bundles which they form are flattened, composing muscular membranes, often two or three layers deap, the bundles crossing each other at differ- ent angles, and forming networks and gratings. The most remarkable character of the organic muscular fibre, is the existence in it here and there of swellings somewhat larger than the diameter of the fibre, and produced by the nuclei of the original nucleated cells from which the fibre was devel- oped.*— These fibrillar have been represented as simple hollow tubes, as a series of globular vesicles, as continuations of arteries, as termination of nerves, as structures of rhomboidal bodies, and finally, as cellular.! It is supposed by one ofthe latest observers, who appears to be entitled to great attention,X that the muscular fibres are not thus minutely divided: that a single fibre, when separated from * For a more full and interesting account of these microscopical investigations, see Human Physiology, fourth edition, by R. Dunglison, M. D., Professor of the Institutes of Medicine and Medical Jurisprudence in Jefferson Medical College, &c. &c. Phila., 1841.—p. t A statement of these descriptions, with reference to the publications in which they are contained, may be seen in the Elementa Physiologiae of Haller, vol. iv. t Carlysle, in the Croonian Lecture, London Philosophical Transactions, 1805, Part I. STRUCTURE OF MUSCULAR FIBRES. 285 the adhering extraneous substances, and viewed in a powerful microscope, is a solid cylinder, formed of a pulpy substance, irregularly granulated, and covered by a portion ofthe reticular membrane. —The opinions of Sir A. Carlysle, are not at the present time, deemed of much weight in anatomy; subsequent researches having shown them to be full of empty and reckless speculation. Among those who believed the muscular fibre to be hollow, were Sink and Mascagni; the latter considered it as formed of little cylinders, the walls of which are composed of absorbent vessels and filled with a glutinous substance. More recently, Raspail (Chimie Organique) has adopted a view which appears a modification of, and no better founded than that of Mascagni. He considers each fibre formed of a bundle of cylinders, the cylinders made up of elongated vesicles, attached end to end, and having a spiral arrangement.— The connexion of these fibres with the blood-vessels and nerves, is an important circumstance in the structure of muscles. The arteries of muscles are very numerous; and they ramify minutely. They are accompanied by veins; and it appears, by the successful labours of Ruysch, that when these arteries are fully injected, they not only communicate with the veins, but also pour out some of their contents in a dew-like effusion in the muscle.* —With the exception of some ofthe viscera, as the lungs and kidneys, there are few organs that receive as much blood as the muscles. —The arteries that supply the muscles, enter them at all points. The larger trunks more generally enter at the middle of the muscle, and ramify towards each extremity, the branches being placed between the larger fasciculi or lacerti, so that the flow of blood, may be less impeded during muscular contraction ; minute branches only passing into the structure of the fasciculi. * See Ruysch's description of the 96th preparation in his Thesaurus Quartus; and of the 35th preparation in Thesaurus Decimus. 286 VASCULARITY OF MUSCLES. The veins which attend the arteries, are said by Bichat to have few valves. The free distribution of blood to the muscles, appears to be necessary to preserve them in a condition, healthy and capable of contraction. When the supply of blood is cut off by a ligature, the muscle gradually becomes paralysed, and does not regain its power, till it is again supplied by the anasto- mosing branches. —The colour ofthe muscle does not seem dependent wholly on the blood, but in part at least on their own peculiar structure, as seen in many animals, where the flesh is white and the blood red; and in the muscles of organic life in man, many of which are colourless, though more vascular than those of animal life. —The absorbent vessels exist no doubt in all the muscles, but they are traced with difficulty. They have been found in the muscles of the tongue, face and diaphragm.*— The blood-vessels must terminate, not in the cavities of the muscular fibres, but exterior to these fibres; otherwise the dew-like effusion, would not be apparent; and it is probable, that the red colour, which is so general in muscles, depends upon a portion of blood effused from these vessels, and not contained in them; for it has been observed by Bichat, that in drowned or strangled animals, black disoxygenated blood occupied all the vessels, while the florid colour of the muscles continued unchanged; which could not have been the case if the colour of the muscles was owing to the blood in the vessels. That the colour of the red muscles is owing to blood, is rendered certain by the fact that this colour may be completely washed away while the fibrous structure of the muscle remains unchanged. From this also it may be inferred that the blood is exterior to the muscular fibre, and to the vessels likewise. It is said by Sabatier, that the colour will likewise be completely removed, by injecting a large quantity of water through the arteries ; this does not invalidate the inferences drawn from the other facts; for the water effused from the * Vide Breschet, Sur le Systeme Absorbante. Paris, 1836. THE TENDONS. 287 extreme branches of the arteries must necessarily wash away the blood which was previously effused from the same branches. The water with which muscles have been washed, appears as if some blood had been mixed with it; it contains albumen and gelatine, with some fibrine, and a peculiar extractive substance, as well as the red colouring matter. The substance of the muscle, when thus separated from the above mentioned matter by washing, appears to be of the same nature with the fibrine of the blood : and after boiling some time in the water, it seems, like that substance, to consist of brown insoluble fibres which are brittle when dry. When the great function of muscles is under consideration, nerves appear of more importance than blood-vessels. The nerves appropriated to muscles of voluntary motion are more numerous than those appropriated to any other parts, except the organs of sense. They subdivide into very fine fibrillae; and it is the opinion of one of the latest observers, that these fibrillae become soft and transparent, and finally blended with reticular membrane which surrounds the muscular fibres. It ought to be noted that muscles are indued with great sensibility, and that the smallest puncture cannot be made in them without exciting pain. Ofthe Tendons. Thus arranged, the fibres of muscles are most generally attached to tendons, which are inserted into the bones these muscles are intended to move. They are also, in some cases, inserted into tendinous membranes, and other parts necessary to be moved ; but in all such instances these parts are perfectly passive; and the motion in which they are concerned is alto- gether produced by the contraction of the muscular fibres. —The tendons appear to be formed of a continuation of the cellular membrane which envelopes the fibres of the muscles. The ultimate construction of muscles was shown in page 283, to consist of a multitude of filaments each one composed of a linear series of the muscular molecules; each of the molecules 288 THE TENDONS. being contained in a series of cells of the cellular tissue, all of which are continuous with each other. The muscular matter is found in general only in the middle part ofthe cellular tissue; the latter part is continued on at each extremity of the muscle, where it is compacted into a solid mass, presents a ligamentous appearance, and constitutes the tendons, or cords by which the muscles are attached to the periosteum covering the bone. Hence the tendons are continuous with, and must obey to a certain extent the contraction of every muscular fibre. —The tendons exist under a great variety of forms: most generally round or cylindrical, sometimes flat, radiated, bifurcated, etc., but are always susceptible, by a little dissection, of being unfolded into a membrane. They have little vascu- larity, no sensation in a healthy state, no nerves having ever been traced into them, and are of a strength surpassing that of almost any other substance of equal size. They have a great affinity for phosphate of lime, especially in old persons, in whom it is not very unusual to find them ossified; and very frequently at all stages of life, we find developed in their substance sesamoid bones. —The muscles are often from inanition or want of use much wasted away, the red muscular matter disappearing from the cells in which its particles are contained. The cells however remaining, if the system regains its vigour, or the muscles are brought into use, they are filled anew with the muscular molecules, and the muscle is restored to its former size, and its contraction will take place again with its usual force. —From this mode of formation, it is evident that there must be an exact relation between the force of the muscle, and the strength of its tendons, even when the muscle is most fully de- veloped. The size and power ofthe muscle is much dependent upon its use. —The muscles of the legs in dancers, of the arms in black- smiths, of the shoulders and back in porters, all obtain an in- crease of bulk from use, which still better fits them for the duties they have to perform. This is strongly exemplified in birds; the breast bone and muscles attached to it being more PHENOMENA OF MUSCULAR MOTION. 289 strongly developed than those of the legs, in birds which are much upon the wing; the reverse taking place in the ostrich, cassowary and penguin, which employ the wings only as aids to the feet.— Notwithstanding the great attention that has been paid to this important operation of muscular fibres, the immediate cause is yet unknown. Muscular motion takes place under the following different circumstances:— 1st. When irritation or stimulus is applied directly to the muscular fibre. 2d. When irritation is applied to a nerve connected with the muscles. 3d. When it is induced by volition. There are several causes of muscular action which cannot be arranged under either of these heads, although it is probable they are not essentially different; such as the motions of coughing and sneezing, of yawning, &c. The immediate irritation of a muscle is effected by every mechanical process, which punctures, divides, lacerates or extends its fibres ; by acrid, and, perhaps, other chemical and peculiar qualities ofthe substance applied to the muscles; by a sudden change of temperature; and by electricity and gal- vanism. No satisfactory explanation has yet been made of the man- ner in which muscular contraction is excited, either by the above-mentioned agents, by irritation applied to a nerve, or by volition. When a muscular fibre begins to contract, there is often the appearance of a slight tremor in it. It becomes hard and rigid: its length diminishes, and its diameter increases. If a muscle makes an effort to contract, when the parts to which its ex- tremities are attached are prevented from moving towards each other, so that contraction cannot take place, the muscle will become hard and rigid notwithstanding. —This tremor of the fibres, is called fibrillary agitation, (agitationfibrillaire) and is heard when a stethoscope is applied 25 290 PHENOMENA OF MUSCULAR MOTION. over the belly of a muscle during its contraction, or when the end of the finger is introduced into the auditory meatus. During the contraction of a muscle there is no change in its colour, nor any increase in the amount of blood thrown into it by the arte- ries as was once supposed. Fig. 70.* a. --C --C —With the aid of the microscope it is easy to distinguish the manner in which the contraction of a muscle is effected. Fig. 70, exhibits a magnified view of the mus- cular fibres in a state of relaxation. When they contract they form suddenly a num- ber of zigzag flexions, or angular undula- tions, opposite each other, as seen in fig. 71, page 291, according to the observation of Edwards,t Prevost, and Dumas. By repeated experiments, these gentlemen have determined that the flexures of each fibre take place at certain determined points, and nowhere else. These points are precisely at the places where the nerve a, the trunk of which runs parallel with the muscular fasciculi, sends off its filaments to traverse the muscular fibres, at the spot where the angles of the undulations are formed. These nervous filaments after having continued their course for some time, are reflected in the form of loops, and return towards the brain, so as to constitute with that organ a continuous circle. —During the contraction of the muscle its extremities ap- proach, for though the absolute length of the fibre remains the same, the distance between its extremities is diminished by the undulations. The will transmitted through the nerves is the usual stimulus, which excites the voluntary muscles to con- traction. Galvanic electricity, or disease of nervous centres will produce the same result; that of the involuntary muscles, usually results from the impression made upon the organs, as * a, Nerve. 6 6, Fasciculi of muscular fibres which are straight and parallel, c, Nervous filament which separates from the nerve a, and crosses at right angles, and at regular distances, the muscular fasciculi. t Elements de Zoologie, etc., par M. H. Edwards. Paris, 1838. PHENOMENA OF MUSCULAR MOTION. 291 by food in the stomach, blood in the heart, urine in the blad- der, &c.— It has often been inquired whether the Fig. 71.* whole bulk of a muscle is diminished or 6 f increased by its contraction. It now seems generally agreed that the bulk is not in- creased; and, if there is any real diminution c ^; of the fibre itself, it is very small indeed. The irritability of the muscular fibre, or its power of contracting upon the applica- c">-" tion of stimulus, exists in a greater degree : in some muscular parts than others. It is suspended by the application of narcotic substances ; and it remains, in many cases, a short time after the vital functions have ceased. In a majority of cases a general contraction seems to take place in the last moments of life; and after death the body is stiff in consequence of it; all the movable parts being fixed in the precise situation in which they were when the vital motions ceased. The limbs being generally in a bended position at that time, if an attempt be made to extend them it will be very evident that the contracted state of the muscles impedes this extension. When this contraction is once overcome, the limbs continue perfectly flexible, and the muscles are ever after relaxed; but the force of contraction is sometimes so great that it will require a considerable exertion of strength to overcome it. This condition of the muscles, after death, although very common, is not universal: and some dead subjects are perfectly relaxed and flexible from the first cessation of the vital func- tions. The force with which muscles contract exceeds greatly their inanimate power of cohesion. Thus, a muscle deprived of life, would be completely lacerated by a weight suspended from it, which it could readily raise by its contraction during life. This l force of contraction is so great, that the tendo-achillis and the * The same muscle at the moment of contraction, and ab c, indicates the same, : as in Fig. 70. 292 PHENOMENA OF MUSCULAR MOTION. patella have been repeatedly broken by the mere power ofthe muscles, inserted into them. The rapidity with which the successive contractions of the same parts take place is extreme ; and as a striking proof of it, the motions of the tongue, in rapid speaking or reading, are referred to by physiologists. The extent or degree of muscular contraction, is in some cases, very great. In proof of this it was stated by the second Monro, that crude mercury, which passes so readily through the intestines, could not be carried along any parts of them whose position happened to be perpendicular, (as the colon on the right side when we stand,) unless the circular fibres of the intestine contract behind it to such a degree as to close com- pletely the cavity of that tube. An interesting question may be proposed here,—Whether the power of motion, as above described, is exclusively enjoyed by muscular fibres ; whether these fibres must be supposed to exist in all those parts of the body which occasionally perform contraction ? It has often been inferred, that parts were muscular because they were capable of contraction; but the question above ought to be decided affirmatively before such inferences can be properly made. The sac of the taenia hydatigena appears to be a membrane of a peculiar structure, very different from muscle ; yet it is as capable of contracting as if it were perfectly muscular.* The membrane of the urethra does not appear to be muscular in its structure; and yet it has been seen to protrude a bougie, which had passed near to the neck of the bladder, in a way that indicated regular successive contraction, throughout its whole extent. The question above stated, may, therefore, be considered as not yet decided affirmatively. Muscular fibres are situated very differently in different parts. They compose almost the whole substance of the heart, which * See the Croonian Lecture by Mr. Home ; London Philosophical Transactions for 1795, Part I. page 204. PHENOMENA OF MUSCULAR MOTION. 293 is therefore called a hollow muscle. They also form one of the coats of the stomach and intestines, and of the urinary bladder. In the muscles on the trunk and limbs, their arrangement is very various, being rectilinear, penniform, radiated, &c. There are a great many short fibres, with an oblique direc- tion, in some muscles of small volume, which have therefore great power and little motion, as in the semimembranosus. —Contraction, though the only power that muscles appear to exercise, is found likewise existing to some extent, in other tissues of the body, where some effort and resistance is required in the performance of their functions, without the necessity of that perfect antagonism of action which muscles usually establish. There appears, in fact, to be a regular gradation in the changes of the condition of the muscular fibre. The mus- cles of animal life in man are the most fully developed, most highly coloured, and enjoy to the fullest extent, the powers of contraction. Their only vital action is that of contraction, which has been before explained, (see page 291,) which causes their ends to approach each other, by moving one or the other of the bones, to which the two ends ofthe muscles are attached. One of the bones is usually more readily moved than the other, and that is the action of the muscle as usually set down in books. But the student will do well to impress upon his mind, that this is not the only movement which the muscle can effect and that if the part which it usually moves, becomes from some adventitious cause more solidly fixed than the other, as from a weight attached to it, or the opposing action of other muscles, the contraction of the muscle will produce a move- ment of the part, at which its other extremity is inserted. In this way the action of muscles is beautifully varied, and very complicated and useful movements are produced in the body, by what seems a very simple arrangement of the muscles. Thus the action of the great pectoral and latissimus dorsi mus- cles is usually to pull down the arms when they have been elevated by other muscles. But if the arms are thrown upwards, and the hands grasp some place above, as the limbs 25* 294 ANTAGONISM OF MUSCLES. of a tree, they then raise the body upwards towards the arms, and thus become the muscles used in climbing. —In violent dyspnoea, arising from spasmodic croup, asthma, or other causes, the arms are frequently drawn upwards so firmly by the muscles at the top of the shoulders, that the pectoralis major and latissimus dorsi cannot pull them down. When they contract, therefore, their extremities are made to approach by raising the ribs to which they are in part attached, and thus they become muscles of forced inspiration. —The muscles of animal life- are arranged, so that each one has its antagonist, or opposing muscle. Thus, there are flexors to bend the limbs, and extensors to straighten them, supinators and pronators, elevators and depressors. The muscles, which are very numerous, and like the bones are variously estimated, from 368 by Chaussier, to 400 or more by other writers, and producing by their single action a great variety of movements, are yet combined together in pairs or much larger numbers, so as to extend beyond computation the variety of movements they are capable of producing. Thus the two muscles already named, one of which, when acting separately, draws the arm usually downwards and forwards, the other downwards and backwards, when combined together draw it down in the dia- gonal or middle line. —The antagonism of the muscles is dependent upon their alter- nate contraction: the shortened or contracted muscle, is re- stored to its former length chiefly by the contraction of its an- tagonist, but partly also by the resiliency of the cellular tissue in its composition. They are also capable of acting to a certain extent in unison, and thus give firmness and steadiness to the limbs or other parts, and hold them in a fixed direction, as occurs habitually in walking or standing, or pointing with the arm. —The antagonising muscles do not appear to be equally balanced in regard to power; thus the most usual attitudes, in sleep, palsy or tetanus, where the muscles are uninfluenced by the will, is the extended position for the back, flexion to the arm in general, pronation to the fore arm, flexion to the lower MODE OF INSERTION. 295 extremities and adduction to the foot. This is not dependent upon a difference in length, as was supposed by Borelli, but, according to Beclard, chiefly upon a difference in size, and the relative advantages of insertion upon the bones. —Muscles have their tendons attached to the bones, in a man- ner to give them the least mechanical power, but to effect the greatest rapidity of motion; for, as has been observed by Archdeacon Paley, it is of far greater importance to man, to be able to carry his arm quickly to his head, than to raise several hundred weight more than he is now able to do : the two qualities could not well exist together. All that could be done to increase the power, without impairing the symmetry of the body, or diminishing the celerity of its movements, has been accomplished in endowing the muscles, with an extraordinary force of contraction, at least ten fold as great as the student would at first suppose it. The muscles are nearly all levers of the third order. —The force with which a muscle contracts, depends upon its volume and the energy ofthe will, as well as some other circum- stances. But the effect produced by the contraction will depend in a great measure upon the manner in which it is inserted upon the bone on which it acts. Fig. 72. & i —Thus, all things being the same, the effect of the contrac- tion will be the greater, in propor- tion as the muscle is less obliquely T connected with the bone. Thus if the muscle m, figure 72, the force of which we suppose equal to 10, is fixed perpendicularly to the bone I, the extremity of which a, is movable upon the fulcrum point r, it will have to overcome only the weight of the bone, and will carry it from the position a b, into the direc- tion of the line a c. But if this muscle acted obliquely upon the bone in the direction of the line n b, it would then tend to carry it in the direction of the line b n, and consequently to force it against the fixed articular surface r. This latter being 296 FORCE OF MUSCULAR CONTRACTION. a fixed surface, the bone can only turn upon the point r, as upon a pivot, and the contraction of the muscle n, having the same force as the muscle m, would only be able to carry the bone in the direction a d, and would require a force equal to 40, or four times that of m, to raise it in the direction of the line a c. —In the animal economy the muscles are inserted most usually, very obliquely, and consequently in a manner little favourable to the intensity of the result of their contraction. There is nevertheless a very happy contrivance, which tends to diminish the obliquity of their insertions, without marring the usefulness or symmetry of the limbs. It is the articular swellings at the extremities of the bones, which contribute also to the stability of the joints, the advantage of which is seen in fig. 73. —The tendon i of the muscle m, Fig. 73, is inserted as is the case in general immediately below the articula- tion, upon the mobile bone o, in a direc- Fig. 73. tion more approaching the perpendicular, thus making the head of the bone a sort of pulley over which it acts, by which the .. effect of the contraction is considerably increased. —A more striking instance is met with in the deltoid muscle. Baron Haller, has made an interesting calculation of the abso- lute force required to be exerted by the deltoid muscle, in order to raise a weight of 60 pounds at the elbow,reckoning the weight of the arm at five pounds of this. Its insertion is at an angle of 10 degrees upon the humerus, and at about one-third ofthe distance between the shoulder and elbow. The force requisite to raise a weight is exactly in the proportion of the distance, which the iveight from the fulcrum bears to that of the power from the fulcrum. Thus, from the disadvantage of insertion, the force requisite to be exercised there is three times as great as it would be if inserted at the elbow; therefore the actual weight lifted, as far as the muscle is concerned, is equal to 180 pounds. —But this is not all. The insertion of the muscle at an angle of 10 instead of 90 degrees, takes off the purchase in the MUSCLES OF ORGANIC LIFE. 297 proportion, as mathematicians have calculated, which 173 bears to 1000. The augmented weight, or what is the same thing, the increase of power necessary to raise it, amounts, therefore, to no less than 1058, instead ofthe original 60 pounds. There is yet another source of loss of effect in its contraction, which requires great additional power in the muscle to counteract it. The tendon of the muscle is never directly continuous with the muscular fibres, and the loss of power is exactly in proportion to the obliquity of their junction. The manner of this loss is evinced, when we attempt to draw a body to us, at one time with a crooked, and at another, with a straight bar or stick. From this cause there would be a further loss of power of 228 pounds, which would augment the muscular energy, required to raise the 60 pounds, up to 1284, according to this physiologist. —In the muscles of organic life, destined to act without the aid ofthe will, the system of antagonism, is much less perfectly developed. These muscles are hollow, and their fibres are arranged generally into layers, which cross each other at right angles, and contribute, to a certain extent, to produce this effect. The alternate contractions, of the auricles and ventricles of the heart, and of the uterus, though these organs have, properly speaking, no antagonist muscles, belong to this class. In sorrfe ofthe hollow organs, as the bladder, the contracted muscular fibres are expanded or antagonised, only by the matters which collect in their cavities. —The muscles of organic life, with the exception of the heart, are of a pale or grayish white colour. Some of them are so thin, and of so pale a colour, that it is impossible to draw the line of distinction between them and cellular or aponeurotic tissue. —There is a regular gradation between muscular and desmoid cellular tissue, now called contractile fibre or contractile tissue, and an occasional substitution of the one for the other, in parts that require elastic resistance, or firm support, that has been overlooked by anatomists. The yellow elastic ligamen- tous tissue, appears to be one medium between the muscular and ligamentous tissue. Comparative anatomy shows us that 298 CONTRACTILE TISSUE. parts formed in one animal of the elastic yellow tissue, are in others composed of muscular fibres. Thus, the suspensory ligaments of the sheath of the penis, are ligamentous in the horse, and muscular in the mule and bull. The middle coat of the arteries, which is composed of the elastic yellow tissue in man, is muscular in certain parts of the arterial system of the elephant. —The kindred nature of these two tissues, is likewise strongly manifested by chemical analysis. The yellow elastic tissue consists chemically of albumen, osmazome and fibrine.* The thick yellow elastic ligament which supports the weight ofthe abdominal viscera in the horse, and others of the solipediae, consists, in man, only of the fascia superficialis abdominis, and forms, as a late writer is disposed to think, the abdominal pouch, (poche musculaire,) of the didelphic animals, such as the opossum and kangaroo. —The parietes of the urethra, which, in man, is strongly elastic, in the horse and many other animals is endowed with a strong coat of palish muscular fibres. On close examination it will be found in man, that the fibres of the contractile tissue which constitute the dartos muscle, are also extended so as to cover the corpus cavernosum penis and the urethra; over this latter organ it is not improbable that they sometimes become the seat of stricture. They run more or less parallel, and near to one another, over the scrotum, where they are interwoven with transverse fibres and bundles of cellular substance—or they form plexuses, as on the penis, which resemble the terminal plexuses of nerves, with this difference, that the individual fibres interlace and amalgamate. —This same contractile fibre is found by the microscope to be interwoven in various places with the tissue of the skin, and that peculiar corrugation ofthe skin known under the name of goose flesh, is supposed to be produced by their agency. They act with such force upon the scrotum, as occasionally to make it hard as a ball, shrink it greatly in size, and force the testicles * Consid. sur les aponeuroses abdom. servant d'introduction a l'histoire des Hernies, dans les Monodactyles, par Girard, fils. CHEMICAL COMPOSITION. 299 up towards the inguinal rings. This contractile tissue enters as an element, into the constitution of the penis and clitoris and probably also into that of the blood vessels, and the excre- tory ducts of the glands. When viewed under the microscope, the contractile fibre is found different from the round fibres of the common fibrous tissue; they are larger, redder, and possess a peculiar kind of transparency. The muscular fibres on the inner face of the prostate glands, and the muscles of Wilson on the membranous part of the urethra? seem to be allied to this class of tissue. This opinion seems borne out by the de- velopement of the muscles in the foetus, as previously quoted from Isenflam. —Muscles are composed chemically, according to Berzelius, principally of fibrine; but they contain also albumen, gelatine, osmazome, phosphates of soda, ammonia and lime, carbonate of lime, and some free lactic acid. If the analysis is pushed farther—to the destruction ofthe flesh, there is developed a great quantity of nitrogen, hydrogen, oxygen and carbon, some iron, phosphorus, soda and lime. 300 INDIVIDUAL MUSCLES. CHAPTER VIII. OF THE INDIVIDUAL MUSCLES. Muscles ofthe Teguments ofthe Cranium. The skin that covers the cranium is moved by a single broad digastric muscle, and one small pair. 1. Occipito-Frontalis, Arises fleshy from the transverse protuberant ridge near the middle of the os occipitis laterally, where it joins with the tem- poral bone; and tendinous from the rest of that ridge back- wards, opposite to the lateral sinus; it rises after the same manner on the other side. From thence it comes straight forwards, by a broad thin tendon, which covers the upper part of thecranium at each side, as low down as the attollens auris, to which it is connected, as also to the zygoma, and covers a part of the aponeurosis ofthe temporal muscle; at the upper part of the forehead it becomes fleshy, and descends with straight fibres. Inserted into the orbicularis palpebrarum of each side, and into the skin of the eyebrows, sending down a fleshy slip be- tween them, as far as the compressor naris and levator labii superioris alaeque nasi. Use. Pulls the skin of the head backwards; raises the eye- brows upwards; and, at the same time, it draws up and wrin- kles the skin of the forehead. 2. Corrugator Supercilii. Arises fleshy from the internal angular process of the os frontis, above the joining of the os nasi and nasal process of the superior maxillary bone; from thence it runs outwards, and a little upwards. Inserted into the inner and inferior fleshy part of the occipito- frontalis muscle, where it joins with the orbicularis palpebrarum, MUSCLES OF THE EAR. 301 and extends outwards as far as the middle of the superciliary ridge. Use. To draw the eyebrow of that side towards the other, and make it project over the inner canthus of the eye. When both act, they pull down the skin ofthe forehead, and make it wrinkle particularly between the eyebrows. Muscles of the Ear. 1. Attollens Auris, Arises, thin, broad, and tendinous, from the tendon of the Fig. 74.* occipito-frontalis, from * Fig. 74.—g, Occipito-frontalis. m, Nasal slip of do. n, Compressor naris. k, Levator labii superioris alaeque nasi. 5, Masseter. q, Attollens auris. r, Retra- hentes auris, usually two in number, p, Platysma myoides. s, Sterno-cleido-mastoid. . «. Trapezius, v, Splenius capitis, i, Splenius colli, w, Deltoid. The rest of the muscles known by references to the cuts No. 75, 76, 77. 26 u L. 302 MUSCLES OF THE EYELIDS. 3. Retrahentes Auris, Arise, sometimes by three, but always by two distinct small muscles, from the external and posterior part of the root ofthe mastoid process, immediately above the insertion of the sterno- cleido-mastoid muscle. Inserted into that part of the back of the ear which is oppo- site to the septum that divides the scapha and concha. Use. To draw the ear back, and stretch the concha. Muscles of the Eyelids. The palpebral or eyelids, have one muscle common to both, and the upper eyelid one proper to itself. 1. Orbicularis Palpebrarum, Arises, by a number of fleshy fibres, from the outer edge of the orbitar process of the superior maxillary bone, and from a tendon near the inner angle of the eye ; these run a little down- wards, then outwards, over the upper part of the cheek, below the orbit covering the under eyelid, and surround the external angle, being loosely connected only to the skin and fat; run over the superciliary ridge of the os frontis, towards the inner canthus, where they intermix with those of the occipito-fron- talis and corrugator supercilii; then covering the upper eyelid, they descend to the inner angle opposite to the inferior origin of this muscle, firmly adhering to the internal angular process of the os frontis, and to the short round tendon which serves to fix the palpebral and muscular fibres arising from it. Inserted, by the short round tendon, into the nasal process of the superior maxillary bone, covering the anterior and upper part of the lachrymal sac; which tendon can be easily felt at the inner canthus ofthe eye. Use. To shut the eye, by drawing both lids close together, the fibres contracting from the outer angle towards the inner, press the eyeball, squeeze the lachrymal gland, and convey the tears towards the puncta lachrymalia. —When the muscle is in strong action, its upper fibres MUSCLES OF THE EYEBALL. 303 cause the skin of the forehead to descend, the lower ones elevate the integuments of the cheek. Like the other sphinc- ters, this is a mixed muscle. The fibres which are supposed to be the proper voluntary portion, are those which correspond to the margin of the orbit, and are of a red colour. The involun- tary fibres, form the thin portion which covers the lids, [musculus ciliaris of Albinus,) and are of a pale colour, like the muscles of organic life. They contract involuntarily while we are awake, in the action of winking, and during sleep in maintaining the lids closed.— The ciliaris of some authors is only a part of this muscle covering the cartilages of the eyelids, called cilia or tarsi. There is often a small fleshy strip, which runs down from the outer and inferior part of this muscle above the zygomati- cs minor, and joints with the levator labii superioris alaeque nasi. 2. Levator Palpebras Superioris, Arises from the upper part of the foramen opticum of the sphenoid bone, through which the optic nerve passes, above the levator oculi, near the trochlearis muscle. Inserted, by a broad thin tendon, into the cartilage that supports the upper eyelid, named tarsus. Use. To open the eye, by drawing the eyelid upwards; which it does completely, by being fixed to the tarsus, pulling it below the eyebrow, and within the orbit. * Muscles ofthe Eyeball. The muscles which move the globe of the eye are six, viz : four straight, and two oblique. The four straight muscles very much resemble each other: all Arising by a narrow beginning, a little tendinous and fleshy, from the bottom of the orbit around the foramen opticum of the sphenoid bone, where the optic nerve enters, so that they * There is no antagonist muscles provided especially to depress the lower lid. It i depression is effected, according to the suggestion of Sir C. Bell, by the protrusion o i o of the eyeball.—p. 304 MUSCLES OF THE EYE. may be taken out adhering to this nerve ; and all having strong fleshy bellies. Inserted at the forepart of the globe of the eye into the anterior part of the tunica sclerotica, and under the tunica adnata, at opposite sides, which indicates both their names and Use ; so that they scarcely require any farther description than to name them singly. The union of thin tendinous insertions forms the tunica albuginea. 1. Levator Oculi, (Rectus Superior,) Arises from the upper part of the foramen opticum of the sphenoid bone, below the levator palpebrae superioris, and runs forwards to be Inserted into the superior and forepart of the tunica sclero- tica, by a broad thin tendon. Use. To raise up the globe of the eye. 2. Depressor Oculi, (Rectus Inferior,) Arises from the inferior part of the foramen opticum. Inserted opposite to the former. Use. To pull the globe of the eye down. 3. Adductor Oculi, (Rectus Internus,) Fig. 75.* Arises, as the former, be- tween the obliquus superior and depressor, being from its situation, the shortest. Inserted opposite to the inner angle. Use. To turn the eye to- wards the nose. * The muscles of the eyeball; the view is taken from the outer side of the right orbit. 1. A small fragment of the sphenoid bone around the entrance of the optic nerve into the orbit. 2. The optic nerve. 3. The globe ofthe eye. 4. The levator palpebrae muscle. 5. The superior oblique muscle. 6. Its cartilaginous pulley. 7. Its reflected tendon. 8. The inferior oblique muscle, the small square knob at its com- mencement is a piece of its bony origin broken off. 9. The superior rectus. 10. The internal rectus almost concealed by the optic nerve. 11. Part of the external rectus, showing its two heads of origin. 12. The extremity of the external rectus at its inser- tion ; the intermediate portion of the muscle having been removed. 13. The in- ferior rectus. 14. The tunica albuginea, formed by the expansion of the tendons of the four recti. MUSCLES OP THE EYE. 305 4. Abductor Oculi, (Rectus Externus,) Arises from the bony partition between the foramen opticum and foramen lacerum, being the longest from its situation; and is Inserted into the globe opposite to the outer canthus. Use. To move the globe outwards. The oblique muscles are two: Obliquus Superior, seu Trochlearis, Arises, like the straight muscles, from the edge of the fora- men opticum at the bottom of the orbit, between the levator and abductor oculi; from thence, runs straight along the pars plana of the ethmoid bone to the upper part of the orbit, where a cartilaginous trochlea is fixed to the inside of the internal angular process of the os frontis, through which its tendon passes, and runs a little downwards and outwards, enclosed in a loose membranous sheath. Inserted by a broad thin tendon, into the tunica sclerotica, about half way between the insertion of the attollens oculi and optic nerve. Use. To roll the globe of the eye, and turn the pupil down- wards and outwards, so that the upper side of the globe is turned inwards, and the inferior part to the outside of the orbit, and the whole globe drawn forwards towards the inner canthus. 2. Obliquus Inferior, Arises, by a narrow beginning, from the outer edge of the orbitar process of the superior maxillary bone, near its juncture with the os unguis; and running obliquely outwards, is Inserted into the sclerotica, in the space between the abductor and optic nerve, by a broad and thin tendon. Use. To draw the globe of the eye forwards, inwards, and downwards; and, contrary to the superior, to turn the pupil upwards towards the inner extremity of the eyebrow; at the same time, that the external part of the globe is turned towards 26* 306 MUSCLES OF THE NOSE. the inferior side, and the internal rolls towards the upper part. The Muscle of the Nose. There is only one muscle on each side that can be called proper to the nose, though it is affected by several muscles of the face. Compressor Naris, ( Triangularis seu Transversalis Nasi,) Arises, by a narrow beginning, from the root of the ala nasi externally, where part of the levator labii superioris alaeque nasi is connected to it; it spreads into a number of thin separate fibres, which run up along the cartilage in an oblique manner towards the dorsum of the nose, where it joins with its fellow, and is Inserted slightly into the anterior extremity of the os nasi and nasal process of the superior maxillary bone, where it meets with some of the fibres descending from the occipito- frontalis muscle. * Use. To compress the ala towards the septum nasi, particu- larly when we want to smell acutely ; but, if the fibres of the frontal muscle, which adhere to it, act, the upper part of this thin muscle assists to pull the ala outwards. It also corrugates the skin of the nose, and assists in expressing certain passions. —It has been called by Columbus dilatans nasi, from a belief, in which, Bourgery coincides, that when it acts with its extrem- ity upon the nose as the fixed point, it dilates the nostril., When the other extremity of the muscle is the fixed point, it compresses it.— Muscles of the Mouth and Lips. The mouth has nine pair of muscles, which are inserted into the lips, and a common one formed by the termination of these; * The nasal slip of fibres descending from the occipito-frontalis, is sometimes spoken of as a distinct muscle, under the name of Pyramidalis nasi. MUSCLES OF THE MOUTH AND LIPS. 307 viz. three above, three below, three outwards, and the common muscle surrounds the mouth. The three above are, 1. Levator Anguli Oris, 2. Levator Labii Superioris Alaeque Nasi, Arises by two distinct origins: the first broad and fleshy, from the external part of the orbitar process of the superior maxillary bone which forms the lower part of the orbit, imme- *Fig. 76.—g-, Occipito-frontalis. Z, Levator labii superioris alaeque nasi. I, Levator anguli oris, n, Compressor naris. o, Orbicularis palpebrarum; the external palpebral ligament, seen on the right side, extending to the ear. 3 3, Zygomaticus major, and minor. 4, Orbicularis oris, with the slip to the lower part ofthe septum ofthe nose, called by Albinus, nasalis labii superioris. 5, Masseter. «, Depressor anguli oris, s s, Sternal and clavicular portions of the sterno-cleido-mastoid. u, Trapezius seen at its upper part. 6, Sterno-hyoid. 7, Sterno-thyroid. 8, Omo-hyoid. 9, Scalenus amicus. 10, Scalenus medius. L 308 MUSCLES OF THE FACE. diately above the foramen infra-orbitarium; the second portion arises from the nasal process of the superior maxillary bone, where it joins the os frontis at the inner canthus, descending along the edge of the groove for the lachrymal sac. The first and shortest portion is Inserted into the upper lip and orbicularis labiorum; the second and longest, into the upper lip and outer part ofthe ala nasi. Use. To raise the upper lip towards the orbit, and a little outwards ; the second portion serves to draw the skin of the nose upwards and outwards, by which the nostril is dilated. 3. Depressor Labii Superioris Alaeque Nasi, Arises, thin and fleshy, from the os maxillare superius, imme- diately above the joining ofthe gums with the two dentes inci- sores and the dens caninus; from thence it runs up under part of the levator labii superioris alaeque nasi. Inserted into the upper lip and root ofthe ala nasi. Use. To draw the upper lip and ala nasi downwards and backwards. The three below are, 1. Depressor Anguli Oris, Arises, broad and fleshy, from the lower edge of the maxilla inferior, at the side of the chin, being firmly connected to that part of the platysma myoides, which runs over the maxilla to the angle of the mouth, to the depressor labii inferioris within, and to the skin and fat without, gradually turning narrower; and is Inserted into the angle of the mouth, joining with the zygo- maticus major and levator anguli oris. Use, To pull down the corner of the mouth. 2. Depressor Labii Inferioris, Arises, broad and fleshy, intermixed with fat, from the infe- MUSCLES OF THE FACE. 309 rior part of the lower jaw next to the chin; runs obliquely upwards, and is Inserted into the edge of the under lip, extends along one half ofthe lid, and is lost in its red part. Use. To pull the under lip and the skin of the side of the chin downwards, and a little outwards. 3. Levator Labii Inferioris, Arises, from the lower jaw, at the roots of the alveoli of two dentes incisores and of the cani- nus; is Inserted into the under lip and skin ofthe chin. Use. To pull the parts, into which it is inserted, upwards. The three outward are, 1. Buccinator, Arises, tendinous and fleshy, from the lower jaw, as far back as the last dens molaris and forepart of the root of the coronoid process; fleshy from the upper jaw, between the last dens mo- laris and pterygoid process of the sphenoid bone; from the extremity of this process it arises tendinous, being continued between both jaws to the constrictor pharyngis superior, with which it joins; from thence, proceeding with straight fibres, and adhering close to the membrane that lines the mouth, it is Inserted into the angle of the mouth within the orbicularis oris. Use. To draw the angle of the mouth backwards and out- wards, and contract its cavity, by pressing the cheek inwards, by which the food is thrust between the teeth. —The bucci- *Fig. 18.*—a, Depressor labii inferioris. b, Buccinator, c, Levator anguli oris. e, Levator labii inferioris (levator menti;) this will be best seen in dissection by in- verting the Up and dissecting off the mucous membrane. /, Depressor anguli oris. 5, Masseter. g. Tendon ofthe superior or internal oblique muscle of the eye, after it passes its trochlea, h, Inferior oblique. 310 MUSCLES OF THE FACE. nator acts principally in front on the commissure of the lips, which it draws backwards horizontally, increasing transversely the aperture of the mouth, and throwing the cheek into the vertical folds, so conspicuous in old age. It thus antagonises the orbicularis oris. If both these muscles act together, the lips are extended and pressed against the teeth. When the cavity of the mouth is distended with air or liquids, the fibres of this muscle are protruded and curved. If the muscle now acts, the fibres become straightened, and the fluid is expelled from the mouth, suddenly or gradually, according to the resist- ance made by the orbicularis. —This muscle assists also in mastication and deglutition, by pressing the food from between the cheek and gums into the cavity of the mouth.— 2. Zygomaticus Major, Arises, fleshy, from the os males, near the zygomatic suture. Inserted into the angle of the mouth, appearing to be lost in the depressor anguli oris and orbicularis oris. Use. To draw the corner of the mouth and under lip towards the origin of the muscle, and make the cheek promi- nent, as in laughing. 2. Zygomaticus Minor, Arises from the upper prominent-part of the os malae, above the origin of the former muscle; and, descending obliquely downwards and forwards, is Inserted into the upper lip, near the corner of the mouth, along with the levator anguli oris. Use. To draw* the corner of the mouth obliquely outwards and upwards towards the external canthus of the eye. The common muscle is the Orbicularis Oris. This muscle is, in a great measure, formed by the muscles that move the lips; the fibres of the superior descending, those MUSCLES OF THE LOWER JAW. 311 ofthe inferior ascending, and decussating each other about the corner of the mouth, run along the lip to join those of the opposite side, so that the fleshy fibres appear to surround the mouth like a sphincter. Use. To shut the mouth, by contracting and drawing both lips together, and to counteract all the muscles that assist in forming it. There is another small muscle described by Albinus, which he calls Nasalis labii superioris ; but it seems to be only some fibres of the former connected to the septum nasi. —The orbicularis, possesses a very varied and extensive action, and may act as a whole or in parts. Its simplest action is to close the mouth by bringing the lips together. The upper or lower labial fibres may act separately, as well as those at the commissures of the lips, by which they are enabled in turn, to antagonise the different muscles which are attached around. By a very strong contraction of the labial and commissural fibres, the lips are thrown forwards in a circular projection, as in whistling. By the contraction of the inner labial fibres, they are drawn inwards upon the teeth.— Muscles of the Lower Jaw. The lower jaw has four pair of muscles for its elevation or lateral motions, namely, two, which are seen on the side of the face, and two concealed by the angle of the jaw. 1. Temporalis, Arises, fleshy, from a semicircular ridge of the lower and lateral part of the parietal bone, from all the pars squamosa of the temporal bone, from the external angular process of the os : frontis, from the temporal process of the sphenoid bone, and from an aponeurosis which covers it; from these different i origins the fibres descend like radii towards the jugum, under which they pass; and are, lnserted,by a strong tendon, into the upper part of the coro- i noid process of the lower jaw; in the duplicative of which ten- 312 MUSCLES OF THE LOWER JAW. don this process is enclosed as in a sheath, being continued down all its forepart to near the last dens molaris. Use. To pull the lower jaw upwards, and press it against the upper, at the same time drawing it a little backwards. N. B. This muscle is covered with a tendinous membrane, called its aponeurosis, which arises from the bones that give origin to the upper and semicircular part of the muscle; and descending over it, is inserted into all the jugum, and the adjoining part of the os frontis. The use of this membrane is to give room for the origin of a greater number of fleshy fibres, to fortify the muscle in its action, and to serve as a defence to it. 2. Masseter, Arises, by strong, tendinous, and fleshy fibres, which run in different directions, from the superiof maxillary bone, where it joins the os malse, and from the inferior and anterior part of the zygoma, its whole length, the external fibres slanting back- wards, and the internal forwards. Inserted into the angle of the lower jaw, and from that upwards to near the top of its coronoid process. Use. To pull the lower to the upper jaw, and by means of its oblique decussation, a little forwards and backwards. 3. Pterygoideus Internus, Arises, tendinous and fleshy, from the inner and upper part of the internal plate of the pterygoid process, filling all the space between the two plates; and from the pterygoid process of the os palati between these plates. Inserted into the angle of the lower jaw internally. Use. To draw the jaw upwards, and obliquely towards the opposite side. 4. Pterygoideus Externus, Arises from the outer side ofthe external plate ofthe ptery- goid process of the sphenoid bone, from part of the tuberosity of the os maxillare adjoining to it, and from the root of the tem- poral process ofthe sphenoid bone. MUSCLES OF THE NECK. 313 Fig. 78.* Inserted into the cavity in the neck of the condyloid process of the lower jaw; some of its fibres are inserted into the ligament that connects the movable carti- lage and that process to each other. Use. To pull the lower jaw forwards, and. to the opposite side; and to pull the ligament from the joint, that it may not be pinched during these motions : when both external ptery- goid muscles act, the fore teeth of the under jaw are pushed forwards beyond those of the upper jaw. The Muscles which appear about the anterior part of the Neck. On the side of the neck are two muscles, or layers. 1. Musculus Cutaneus,vulgo Platysma Myoides, (see fig. 74,) Arises, by a number of slender separate fleshy fibres, from the cellular substance that covers the upper part of the deltoid and pectoral muscles ; in their ascent they all unite to form a thin muscle, which runs obliquely upwards along the side of the neck, adhering to the skin. Inserted into the lower jaw, between its angle and the origin ofthe depressor anguli oris, to which it is firmly connected, and but slightly to the skin that covers the inferior part of the masseter muscle and parotid glands. Use. To assist the depressor anguli oris, in drawing the skin of the cheek downwards; and when the mouth is shut, it draws all that part of the skin, to which it is connected, below the lower jaw, upwards.—Some of its fibres are inserted into the angle of the mouth, and are connected with the muscles of * The two pterygoid muscles. The zygomatic arch and the greater part of the ramus of the lower jaw have been removed in order to bring these muscles into view. 1. The sphenoid origin of the external pterygoid muscle. 2. Its pterygoid origin. 3. The internal pterygoid muscle. 27 314 MUSCLES OF THE NECK. that region. They draw the corner of the mouth downwards, and constitute the musculus risorius of Santorini.— 2. Sterno-cleido-mastoideus, (see fig. 76.) Arises by two distinct origins: Fig 79.* the anterior tendinous and a little fleshy, from the top ofthe sternum near its junction with the clavicle ; the posterior* fleshy, from the upper and an- terior part of the clavicle ; both unite a little above the ante- rior articulation of the clav- icle, to form one muscle, which runs obliquely upwards and outwards, to be Inserted, by a thick strong tendon, into the mastoid pro- cess, which it surrounds; and, gradually turning thinner, is inserted as far back as the lambdoid suture. Use. To turn the head to one side, and bend it forwards. Muscles situated between the Lower Jaw and Os Hyoides. There are four layers before, and two muscles at the side. The four layers are, 1. Digastricus, (see fig. 7%,) fy Arises, by a fleshy belly, intermixed with tendinous fibres, from the fossa at the root of the mastoid process of the temporal bone, and soon becomes tendinous; runs downwards and for- wards : the tendon passes generally through the stylo-hyoideus muscle ; then it is fixed by a ligament to the os hyoides; and, having received from that bone an addition of tendinous and muscular fibres, runs obliquely forwards, turns fleshy again, and is *Fig. 79.-6, Buccinator, d, Depressor labii inferioris. k, Corrugator Supercilii. n, Compressor naris. s, Sterno-cleido-mastoid. t, Temporal, u, Trapezius. », Splenius capitis, v, Splenius colli, x, Digastricus. y, Mylo-hyoid. z, Stylohyoid. &,, Hyo-glossus. MUSCLES OF THE NECK. 315 Inserted, by its anterior belly, into a rough sinuosity at the inferior and anterior edge of that part of the lower jaw called the chin. Use. To open the mouth by pulling the lower jaw down- wards, and backwards; and when the jaws are shut, to raise the os hyoides, and, consequently, the pharynx, upwards, as in deglutition. 2. Mylo-Hyoideus, (See fig. "T7y) y~r , Arises, fleshy, from all the inside of the lower jaw, between, the. last dens molaris and the middle of the chin, where it joins with its fellow. Inserted into the lower edge of the basis of the os hyoides, and joins with its fellow. Use. To pull the os hyoides forwards, upwards, and to one side. 3. Genio-Hyoideus, Arises, tendinous, from a rough protuberance in the middle ofthe lower jaw internally, or on the inside of the chin. Inserted into the basis of the os hyoides. Use. To draw this bone forwards to the chin. 4. Genio-Hyo-Glossus. Arises, tendinous, from a rough protuberance in the inside of the middle of the lower jaw; its fibres run like a fan, for- wards, upwards, and backwards ; and are Inserted into the whole length of the tongue, and base of the os hyoides, near its cornu. Use. According to the direction of its fibres, to draw the tip of the tongue backwards into the mouth, the middle down- wards, and to render its dorsum concave; to draw its root and os hyoides forwards, and to thrust the tongue out of the mouth. The two muscles at the side are, 1. Hyo-Glossus, Arises, broad and fleshy, from the base, cornu, and appendix, of the os hyoides ; the fibres run upwards and outwards; to be 316 MUSCLES OF THE NECK. Inserted into the side of the tongue, near the stylo-glossus. Use. To pull the tongue inwards and downwards. 2. Lingualis, Arises from the root of the tongue laterally ; runs forwards between the hyo-glossus and genio-glossus, to be Inserted into the tip of the tongue, along with part of the stylo-glossus. Use. To contract the substance of the tongue, and bring it backwards, and to elevate the point of the tongue. Muscles situated between the Os Hyoides and Trunk. These may be divided into two layers. The first layer consists of two muscles, 1. Sterno-Hyoideus, Arises, thin and fleshy, from the cartilaginous extremity of the first rib, the upper and inner part of the sternum, and from the clavicle where it joins with the sternum. Inserted into the base of the os hyoides. Use. To pull the os hyoides downwards. 2. Omo-Hyoideus, Arises, broad, thin, and fleshy, from the superior costa of the scapula, near the semilunar notch, and from the ligament that runs across it; thence ascending obliquely,it becomes tendinous below the sterno-cleido-mastoid muscle; and, growing fleshy again, is Inserted into the base Of the os hyoides, between its cornu and the insertion of the sterno-hyoideus. Use. To pull the os hyoides obliquely downwards. The second layer consists of three muscles. 1. Sterno-Thyroideus, Arises, fleshy, from the whole edge of the uppermost bone of the sternum internally, opposite to the cartilage of the first rib, from which it receives a small part of its origin. MUSCLES BETWEEN THE JAW AND OS HYOIDES. 317 Inserted into the surface of the rough line at the external part of the inferior edge of the thyroid cartilage. Use. To draw the larynx downwards. 2. Thyro-Hyoideus, Arises from the rough line opposite to the insertion of the former muscle. Inserted into part of the basis, and almost all the cornu of the os hyoides. Use. To pull the os hyoides downwards, or the thyroid car- tilage upwards. 3. Crico-Thyroideus, Which will be described with the larynx: Chap. xiv. Muscles situated between the Lower Jaw and Os Hyoides laterally. They are five in number. They proceed three from the styloid process of the temporal bone, from which they have half of their names; and two from the pterygoid process of the sphe- noid bone. The three from the styloid process are, 1. Stylo-Glossus, Arises, tendinous and fleshy, from the styloid process, and from a ligament that connects that process to the angle of the lower jaw. Inserted into the root ofthe tongue, runs along its side, and is insensibly lost near its apex'. Use. To draw the tongue laterally and backwards. 2. Stylo-Hyoideus, Arises, by a round tendon, from the middle and inferior part of the styloid process. Inserted into the os hyoides at the junction of the base and cornu. Use. To pull the os hyoides to one side, and a little upwards. 27* 318 MUSCLES OF THE PALATE. N. B. Its fleshy belly is generally perforated by the tendon of the digastric muscle, on one or both sides. There is often another accompanying it, called stylo-hyoideus alter ; and has the same origin, insertion, and use. 3. Stylo-Pharyngeus, Arises, fleshy, from the root of the styloid process. Inserted into the side of the pharynx and back part of the thyroid cartilage. Use. To dilate the pharynx and raise it and the thyroid cartilage upwards. The two from the pterygoid process are, 1. Circumfiexus, or Tensor Palati, Arises from the spinous process of the sphenoid bone, behind the foramen ovale, which transmits the third branch of the fifth pair of nerves, from the Eustachian tube, not far from its osse- ous part; it then runs down along the pterygoideus internus, passes over the hook of the internal plate of the pterygoid process by a round tendon, which soon spreads into a broad membrane. Inserted into the velum pendulum palati, and the semilunar edge of the os palati, and extends as far as the suture which joins the two bones. Generally some of its posterior fibres join with the constrictor pharyngis superior, and palato-pharyngeus. Use. To stretch the velum, to draw it downwards, and to one side towards the hook. It has little effect upon the tube, being chiefly connected to its osseous part. 2. Levator Palati, Arises, tendinous and fleshy, from the extremity of the pars petrosa of the temporal bone, where it is perforated by the Eustachian tube, and also from the membranous part of the same tube. Inserted into the whole length of the velum pendulum palati, as far as the root of the uvula, and unites with its fellow. MUSCLES OF THE FAUCES. 319 Use. To draw the velum upwards and backwards, so as to shut the passage from the fauces into the mouth and nose. Muscles situated about the passage ofthe Fauces. There are two on each side, and a single one in the middle. The two on each side are, 1. Constrictor Isthmi Faucium, Arises, by a slender beginning, from the side of the tongue, near its root; thence running upwardswithin the anterior arch, before the amygdala, it is Inserted into the middle of the velum pendulum palati, at the root ofthe uvula anteriorly, being connected with its fellow, and with the beginning ofthe palato-pharyngeus. Use. Draws the velum towards the root of the tongue, which it raises at the same time, and with its fellow, contracts the passage between the two arches, by which it shuts the opening into the fauces. 2. Palato-Pharyngeus, Arises, by a broad beginning, from the middle of the velum palati, at the root of the uvula posteriorly, and from the ten- dinous expansion of the circumflexus palati. The fibres are collected within the posterior arch behind the amygdala, and run backwards to the top and lateral part of the pharynx, where the fibres are scattered, and mix with those of the stylo-pha- ryngeus. Inserted into the edge of the upper and back part of the thyroid cartilage; some of the fibres being lost between the membrane of the pharynx, and the two inferior constrictors. Use. Draws the uvula and velum downwards and back- wards ; and, at the same time, pulls the thyroid cartilage and pharynx upwards, and shortens it; with the constrictor supe- rior and tongue, it assists in shutting the passage into the nostrils ; and, in swallowing, it thrusts the foodYrom the fauces into the pharynx. 320 MUSCLES OF THE FAUCES. Salpingo-Pharyngenus, (from saXiriXI-,' trumpet,) Of Albinus, is composed of a few fibres of this muscle, which Arise from the anterior and lower part of the cartilaginous extremity ofthe Eustachian tube ; and are, Inserted into the inner part of the last-mentioned muscles. Use. To assist the former, and to dilate the mouth of the tube. The one in the middle is the Azygos Uvulae, Arises, fleshy, from the extremity of the suture which joins the palate bones, runs down the whole length of the velum and uvula, resembling a small earth-worm, and adhering to the tendons ofthe circumflexi. Two are frequently met with. Inserted into the apex of the uvula. Use. Raises the uvula upwards and forwards, and shortens it. Muscles situated on the posterior part of the Pharynx. Of these there are three pair : 1. Constrictor Paryngis Inferior, Arises, from the side of the thyroid cartilage, near the attach- ment of the thyroideus and thyro-hyoideus muscles; and from the cricoid cartilage, near the crieo-thyroideus. This muscle is the largest of the three ; and is Inserted into the white line, where it joins with its fellow; the superior fibres running obliquely upwards, covering nearly one half of the middle constrictor, and terminating in a point; the inferior fibres run more transversely and covers the begin- ning of the oesophagus. Use. To compress that part of the pharynx which it covers, and to raise it with the larynx a little upwards. 2. Constrictor Pharyngis Medius, Arises from the appendix of the os hyoides, from the cornu of that bone, and from the ligament which connects it to the thyroid cartilage; the fibres of the superior part running MUSCLES OP THE GLOTTIS. 321 obliquely upwards, and, covering a considerable part of the superior constrictor, terminate in a point. Inserted into the middle of the cuneiforme process of the os occipitis, before the foramen magnum, and joined to its fellow at a white line in the middle back part of the pharynx. The fibres at the middle part run more transversely than those above or below. Use. To compress that part of the pharynx which it covers, and to draw it and the os hyoides upwards. 3. Constrictor Pharyngis Superior, Arises, above, from the cuneiforme process of the os occi- pitis, before the foramen magnum, near the holes where the ninth pair of the nerves passes out: lower down, from the pterygoid process of the sphenoid bone ; from the upper and under jaw, near the roots of the last dentes molares; and between the jaws, it is continued with the buccinator muscle; and with some fibres from the root of the tongue, and from the palate. Inserted into a white line in the middle of the pharynx, where it joins with its fellow, and is covered by the constrictor medius. Use. To compress the upper part of the pharynx, and draw it forwards and upwards. See article, pharynx. Muscles situated about the Glottis. They consist generally of four pair of small muscles, and a single one. See Larynx, chapt. xiv. Muscles situated on the Anterior Part of the Neck, close to the Vertebrae. (Praevertebral Muscles.) These consist of one layer, formed by four muscles. 1. Longus Colli, Arises, tendinous and fleshy from the bodies of the three vertebrae ofthe back laterally; and from the transverse process of the third, fourth, fifth, and sixth vertebrae ofthe neck, near their roots. 322 MUSCLES OF THE SIDE OF THE NECK. Inserted into the forepart of the bodies of all the vertebra? of the neck, by as many small tendons, which are covered with flesh. Use. To bend the neck gradually forwards, and to one side. 2. Rectus Capitis Internus Major, Arises from the anterior points of the transverse process of the third, fourth, fifth, and sixth vertebrae of the neck, by four distinct beginnings. Inserted into the cuneiforme process of the os occipitis, a little before the condyloid process. Use. To bend the head forwards. 3. Rectus Capitis Internus Minor, Arises, fleshy, from the forepart of the body of the first ver- tebra of the neck opposite to the superior oblique process. * lS- 80.* Inserted near the root of the condyloid process of the os occipi- tis, under, and a little farther out- wards, than the former muscle. Use. To bend the head forwards. 4. Rectus Capitis Lateralis, Arises, fleshy, from the anterior part of the point of the transverse process of the first vertebra of the neck. Inserted into the os occipitis, opposite to the foramen stylo-mas- toideum of the temporal bone. Use. To] bend the head a little to one side. * The praevertebral group of muscles of the neck. 1. The rectus anticus major muscle. 2. The scalenus anticus. 3. The lower part of the longus colli of the right side; it is concealed superiorly by the rectus anticus major. 4. The rectus anticus minor. 5. The upper portion of the longus colli muscle. 6. Its lower portion; the figure rests upon the seventh cervical vertebra. 7. The scalenus posticus. 8. The rectus lateralis ofthe left side. 9. One ofthe intertransversales muscles. MUSCLES OF THE THORAX. 323 Muscles situated on the Anterior Part ofthe Thorax. These may be divided into two layers. The first layer con- sists of one muscle, named Pectoralis Major, Arises from the cartilaginous extremities of the fifth and sixth ribs, where it always intermixes with the external oblique muscle of the abdomen; from almost the whole length of the sternum : and from near half of the anterior part of the clavicle ; the fibres run towards the axilla in a folding manner. Inserted, by two broad tendons, which cross each other at the upper and inner part of the os humeri, above the insertion of the deltoid muscle, and outer side of the groove for lodging the tendon of the long head of the biceps. Use. To move the arm forwards, and obliquely upwards, towards the sternum. The second layer consists of three muscles. 1. Subclavius, Arises, tendinous, from the cartilage that joins the first rib to the sternum. Inserted, after becoming fleshy, into the inferior part of the clavicle, which it occupies from within an inch ofthe sternum, as far outwards as to its connexion, by ligament, with the coracoid process of the scapula. Use. To pull the clavicle downwards and forwards. 2. Pectoralis Minor, Arises, tendinous and fleshy, from the upper edge of the third, fourth, and fifth ribs, near where they join with their cartilages. Inserted, tendinous, into the coracoid process of the scapula: but soon grows fleshy and broad. Use. To bring the scapula forwards and downwards, or to raise the ribs upwards. 324 MUSCLES OF THE THORAX. 3. Serratus Magnus, Arises from the nine superior ribs, by an equal number of fleshy digitations, resembling the teeth of a saw. Inserted, fleshy, into the whole base of the scapula internally, between the insertion of the rhomboid and the origin of the subscapularis muscle, being folded about the two angles ofthe scapula. Use. To move the scapula forwards: and, when the scapula is forcibly raised, to draw upwards the ribs. Muscles situated between the Ribs, and within the Thorax. Between the ribs, on each side, there are eleven double rows of muscles, which are, therefore, named intercostals. These decussate each other like the strokes of the letter X. 1. Intercostales Externi, Arise from the inferior acute edge of each superior rib, and run obliquely forwards, the whole length from the spine to near the joining of the ribs with their cartilages; from which, to the sternum, there is only a thin membrane covering the internal intercostals. Inserted into the upper obtuse edge of each inferior rib, as far back as the spine, into which the posterior portion is fixed. 2. Intercostales Interni, Arise in the same manner as the external: but they begin at the sternum, and run obliquely backwards, as far as the angle of the rib; and from that to the spine they are wanting. Inserted in the same manner, as the external. Use. By means of these muscles, the ribs are equally raised upwards, during inspiration. Their fibres being oblique, give them a greater power of bringing the ribs near each other, than could be performed by straight ones. By the obliquity of the fibres, they are almost brought contiguous: and as the fixed points of the ribs are before and behind, if the external had been continued forwards to the sternum, and the internal ABDOMINAL MUSCLES. 325 backwards to the spine, it would have hindered their motion, which is greatest in the middle, though the obliquity of the ribs renders it less perceptible ; and, instead of raising the fibres fixed to the sternum and spine, would have depressed the ribs. N. B. The portions of the external intercostals, which arise from the transverse processes of the vertebrse where the ribs are fixed to them, and other portions that pass over one rib and terminate in the next below it, Albinus calls Levatores costarum longiores et breviores. The portions of the internal that pass over one rib, and are inserted into the next below it, are, by Douglas, called Costarum depressores proprii Cowperi. These portions of both rows assist in raising the ribs in the same manner as the rest of the intercostals. The muscles within the thorax form one pair, viz. Triangularis, or Sterno-Costalis, Arises, fleshy, and a little tendinous, from all the length of the cartilago-ensiformis laterally, and from the edge of the lower half of the middle bone of the sternum, from whence its fibres ascend obliquely upwards and outwards. Inserted, generally by three triangular terminations, into the lower edge of the cartilages of the third, fourth, and fifth ribs ; near where these join with the ribs. Use. To depress these cartilages, and the extremities of the ribs; and consequently to assist in contracting the cavity of the thorax. This muscle often varies; and is sometimes inserted into the cartilage of the second rib, sometimes into the cartilages of the sixth rib. Muscles situated on the anterior part of the Abdomen. They consist of three broad layers on each side of the belly and, of one layer in front. The three layers are : 2S 326 ABDOMINAL MUSCLES. 1. Obliquus Descendens Externus, Arises, by eight heads, from the lower edges of an equal num- ber of the inferior ribs, at a little distance from their cartilages: it always intermixes in a serrated manner, with portions of the Fig.-81.* * The muscles of the anterior aspect of the trunk; on the left side the superficial layer is seen, and on the right the deeper layer. 1. The pectoralis major muscle. 2. The deltoid; the interval between these muscles lodges the cephalic vein. 3. The anterior border of the latissimus dorsi. 4. The serrations of the serratus magnus. 5. The subclavius muscle of the right side. 6. The pectoralis minor. 7. Thecoraco- brachialis muscle. 8. The upper part of the biceps muscle, showing its two heads.. 9. The coracoid process ofthe scapula. 10. The serratus magnus ofthe right side. 11. The external intercostal muscle ofthe fifth intercostal space. 12. The external oblique muscle. 13. Its aponeurosis ; the median line to the right of this number is the linea alba; the flexuous line to its left is the linea semilunaris; and the transverse lines above and below the number, the lineae transversae, of which there were only ABDOMINAL MUSCLES. 327 serratus major anticus; and generally coheres to the pectoralis major, intercostals, and latissimus dorsi; which last covers the edge of a portion of it extended from the last rib to the spine of the ilium. —It interdigitates by its five upper heads with the serratus major anticus, and by the three lower with the latissimus dorsi, where the latter arises from the ribs; a slip from the pectoralis covers the first or upper head.— From these origins the fibres run obliquely downwards and forwards, and terminate in the anterior half of the spine of the ilium, and in a tendinous membrane, whose fibres are continued in the same direction until they meet the fibres of the cor- responding tendon of the other side, in a line which extends from the ensiform cartilage to the symphysis pubis. This line is called linea alba, from its white appearance, which is owing to the connexion of three tendons with each other, without the intervention of muscles, namely, those of the external and internal oblique, and the transversalis.* On each side of the line, two long narrow muscles, (the recti,) are situated between these tendons, and do away the white appearance; but exterior to these muscles, the tendons three in this subject. 14. Poupart's ligament. 15. The external abdominal ring; the margin above the ring is the superior or internal pillar; the margin below the ring, the inferior or external pillar; the curved intercolumnar fibres are seen pro- ceeding upwards from Poupart's ligament to strengthen the ring. The numbers 14 and 15 are situated upon the fascia lata ofthe thigh; the opening immediately to the right of 15 is the opening for the saphena vein. 16. The rectus muscle of the right side brought into view by the removal ofthe anterior segment of its sheath: * the posterior segment of its sheath with the divided edge of the anterior segment. 17. The pyrami- dalis muscle. 18. The internal oblique muscle. 19. The conjoined tendon of the internal oblique and transversalis descending behind Poupart's ligament to the pecti- neal line. 20. The arch formed between the lower curved border of the internal oblique muscle and Poupart's ligament; it is beneath this arch that the spermatic ord and hernia pass. * According to Meckel, the linea alba performs the same office in the abdomen as the sternum does in the thorax, with this only difference, that it is not formed of bone. The anterior tendons of the broad muscles are attached to it, in the same way that the cartilages of the ribs are articulated with the sternum, and the difference of tissue which exists between it and the sternum is attributable to the general differ- ence of structure between the abdominal and pectoral cavities, the latter being formed almost entirely of osseous parts, whilst the walls of the former are fleshy and ten- dinous.—r. 328 ABDOMINAL MUSCLES. are again united, and form a white line on each side, which is called linea semilunaris, from its curved shape. At the lower part of the tendon, near the os pubis, the fibres are so arranged, that they form two bands more firm and dense than the rest of the tendon, which are called columns: these columns are separated from each other; and the vacuity between them is the abdominal ring, or aperture, for the passage of the spermatic chord in males and the round ligament of the uterus in females. This vacuity or aperture has an oval form, which is occasioned by some additional tendinous fibres at the upper part of it, that have a transverse direction. The uppermost of the two columns is continued obliquely downwards, and is inserted into the os pubis of the opposite side, near the symphysis, decussating the fibres of the cor- responding column of that side. The lower edge of the tendon of the external oblique is attached to the superior anterior spinous process of the ilium, and is there blended with the tendinous fascia, which extends down the thigh. From this process the edge of the tendon is extended, like the chord of a bow, across the concavity formed by the os ilium and os pubis, and is inserted into the pubis near its sym- physis. As it proceeds from the spine ofthe ilium towards the pubis, the edge is folded inwards, so that the membrane is doubled. The portion which is turned inwards, (Gimbernat's ligament,) is very small at its commencement, and continues so for a great part of its extent; but becomes much broader within an inch of its termination. This broad extremity is inserted into the small process of the pubis near the sym- physis, and into a ridge which continues backward from the process to the brim of the pelvis, so that the tendinous mem- brane at this part is doubled ; the part which is turned back being about an inch broad at the place of its insertion into the pubis. This doubling forms a partial sheath near the pubis for con- taining the spermatic chord, and supports it for a short distance on the inside of the abdominal ring. ABDOMINAL MUSCLES. 329 The edge formed by the fold of the membrane is called Poupart's ligament, and is very firm and strong; owing to the membrane being thicker at that place. The real edge, or termination of the portion which is folded inwards, is arranged in the following manner : the part which is nearest to the spine of the ilium is continued into the cellular membrane, or the fascia, which is between the internal oblique and transversalis muscles, and the iliacus internus. But the edge of that part of Poupart's ligament which is inserted into the ridge of the pubis seems to form a portion of an oval opening, which is occupied in part, but not completely, by the crural vessels. —The femoral artery is found at the outer margin of this oval opening, see fig. 81. The femoral vein is placed on the inner side of the artery ; on the inner side of the vein again is left a roundish opening,the proper crural ring, occupied only by some loose fat, lymphatic vessels and a small gland, through which the viscera protrude in crural hernia.— —This edge of Poupart's ligament, inserted into the ridge or crest of the pubis is of a triangular shape, and is called Gim- bernat's ligament. It is one of the seats of stricture in crural hernia. The base of the triangle is towards the symphysis pubis.— A portion of the fascia lata of the thigh, which covers these vessels, passes under this portion of the tendon, and is also inserted into the ridge of the pubis; so that when the intestines protrude at this aperture, and are strangulated, this portion of the fascia of the thigh must also compress them. —This portion of the fascia lata femoris, is called the crescentic or falciform portion of the fascia lata. The sharp edge at its inner part, by which it is nearly continuous with Gimbernat's ligament, and which is directed downwards and backwards, is called Hey's ligament or the femoral ligament; it is directly above or in front of the crural ring—that space between the crural vein and Gimbernat's ligament, included in the sheath of the femoral vessels, and through which the viscera protrude in crural hernia.— 28* 330 ABDOMINAL MUSCLES. The fascia lata of the thigh is connected with the external or lower edge of Poupart's ligament,in its whole extent: this is called the sartorial portion. —The fascia lata may here be considered as divided into two layers: 1st, The sartorial. 2nd, The pectineal which contin- uous above and without, as seen in fig. 28, is reflected behind Fig. 82.* the sheath of the vessels, and over the anterior surface of the pectineus muscle up to the spine of the pubis. The sheath of the femoral vessels is formed by an extension downwards of the fascia transversalis and fascia iliacafor about an inch and a half between these layers of the fascia lata.—And there is * A section of the structures which pass beneath the femoral arch. 1. Poupart's ligament. 2, 2. The upper or sartorial portion of the'fascia lata, attached along the margin of the crest of the ilium, and along Poupart's ligament, as far as the spine ofthe os pubis (3). 4. The pubic or pectineal portion ofthe fascia lata, continuous at 3 with the iliac portion, and passing outwards behind the sheath of the femoral vessels to its outer border at 5, where it divides into two layers; one is continuous with the sheath of the psoas (6) and iliacus (7); the other (8) is lost upon the capsule ofthe hip-joint (9). 10. The femoral nerve, enclosed in the sheath ofthe psoas and iliacus. 11. Gimbernat's ligament. 12. The femoral ring, within the femoral sheath. 13. The femoral vein. 14. The femoral artery: the two vessels and the ring are surrounded by the femoral sheath, and thin septa are sent between the anterior and posterior wall ofthe sheath, dividing the artery from the vein, and the vein from the femoral ring. ABDOMINAL MUSCLES. 331 also a fascia (fascia superficialis abdominis) which covers the whole tendon of the external oblique muscle, and passes from it down upon the fascia of the thigh: which also connects the tendon of the external oblique ^to the fascia of the thigh, and serves to bind it down. From these connexions it is pro- bable that the tendon is in a very different situation before dissection, from what it is afterwards; as the division of these connexions, necessarily made by the dissection, renders it much more loose than it could have been while the parts were undi- vided. This structure has latterly been called the crural arch. The fascia which covers the tendon of the external oblique muscle, and descends upon the thigh, can be examined very easily in anasarcous subjects; as in them, the cellular mem brane, which is situated between this fascia and the tendon, is somewhat distended by the effused fluid. To prepare Poupart's ligament or the crural arch, for exam- ination, remove carefully the cellular membrane from the tendon of the external oblique, and also from the fascia of the thigh, taking care not to remove any part of the fascia which passes under the tendon to be inserted into the os pubis. Then make an incision in the tendon of the external oblique, about three inches above Poupart's ligament, parallel to it, and nearly of the same length ; make a second incision from the upper end of this, to the junction of the aforesaid ligament with the superior anterior spine of the ilium; and a third incision from the lower end to the abdominal ring. Dissect this flap carefully from the internal oblique, until the spermatic chord, the cremaster muscle, and the lower origin of the internal oblique, are perfectly uncovered. After examining the internal surface of the tendon and its insertion at the pubis, the fascia of the thigh may be dissected, so that its connexion with the folded edge of the tendon, and its insertion into the pubis, may also be examined. The external oblique muscles compress the abdomen, and therefore contribute to the evacuation of its contents: if the diaphragm is in a passive state, they force it upwards, by pressing the abdominal viscera against it; and thus assist in 332 ABDOMINAL MUSCLES. producing expiration and its various modifications of coughing, sneezing, &c. They bend the spine forwards, or approach the thorax to the pelvis. When one acts separately, it bends the trunk obliquely to the side on which it is situated. 3. Obliquus Ascendens Internus, Arises from the spine of the ilium the whole length between the posterior and superior anterior spinous process; from the os sacrum and the three undermost lumbar vertebra?, by a tendon, (fascia lumborum) common to it, to the serratus posticus inferior muscle, and to the latissimus dorsi; from Poupart's ligament, at the middle of which it sends off the beginning of the cremaster muscle; the spermatic chord in the male, or round ligament of the womb in the female, passes under its thin edge, with the exception of a few detached fibres. Inserted into the cartilago-ensiformis, into the cartilages of the seventh, and those of the false ribs; but, at the upper part, it is extremely thin, resembling a cellular membrane, and only becomes fleshy at the cartilage of the tenth rib. Here its tendon divides into two layers; the anterior layer, with a great portion of the inferior part of the posterior layer, joins the tendon of the external oblique, and runs over the rectus to be inserted into the whole length of the linea alba. The posterior layer joins the tendon of the transversalis muscle as low as half way between the umbilicus and os pubis; but, below this place, only a few fibres of the posterior layer are seen, and the rest of it passes before the rectus muscle, and is inserted into the linea alba; so that the whole tendon of the external oblique muscle, with the anterior layer of the internal oblique, passes before the rectus muscle; and the whole posterior layer of the internal oblique, together with the whole tendon of the transversalis muscle, excepting at the inferior part, passes behind the rectus, and is inserted into the linea alba. At its undermost part, it is inserted into the forepart of the os pubis. ABDOMINAL MUSCLES. 333 Use. To assist the former; but it bends the trunk in the reverse direction. % Fig. 83.* 3. Transversalis, Arises, tendinous, but soon becoming fleshy, from the inner or back part of the cartilages of the seven lower ribs, where some of its fibres are continued with those of the diaphragm and the intercostal muscles; by a broad thin tendon, connected to the transverse processes ofthe last vertebra ofthe back, and the four superior vertebrae of the loins; fleshy, from the whole spine of the os ilium internally, and from the tendon of the external oblique muscle where it intermixes with some fibres ofthe internal oblique. Inserted into the cartilago-ensiformis, and into the whole length of the linea alba, excepting its lowermost part. Use. To support and compress the abdominal viscera, and * Transverse section of abdomen.—a, Division ofthe tendon ofthe internal oblique into two layers, forming a sheath in which is contained the rectus muscle, b, External oblique, c, Internal oblique, d, Transversalis. e, Between the last rib and the crista of the ilia, the fibres of the transversalis, arise from a tendinous layer, which is trifoliate in its origin, according to Todd, f, The anterior division, arising from the roots of the transverse processes, and covering the quadratus lumborum muscle, h, g, The middle, which is weak, attached to the apices of the transverse processes. The posterior is the fascia lumborum. 334 ABDOMINAL MUSCLES. Fig. 84.* it is so particularly well adapted for the latter purpose, that it might be called the proper con- strictor of the abdomen. The long muscle in the middle is named Rectus Abdominis, Arises, by two heads, from the ligament of the cartilage which joins the two ossa pubis to each other; runs upwards the whole length of, and parallel to the linea alba, growing broader and thin- ner as it ascends. Inserted into the cartilages of the three inferior true ribs, and often intermixed with some fibres of the pectoral muscle. It is generally divided by three tendinous intersections : the first is at the umbilicus; the second, where it runs over the cartilage of the seventh rib; and the third in the middle between these; and there is commonly a half intersection below the umbilicus. These intersections (lineae transversa^) seldom penetrate through the whole thickness of the muscle : they adhere firmly to the * A lateral view of the trunk of the body, showing its muscles, and particularly the transversalis abdominis. 1. The costal origin of the lattissimus dorsi muscle. 2. The serratus magnus. 3. The upper part of the external oblique muscle divided in the direction best calculated to show the muscles beneath without interfering with its indigitations with the serratus magnus. 4. Two of the external intercostal mus- cles. 5. Two ofthe internal intercostals. 6. The transversalis muscle. 7. Its pos- terior aponeurosis. 8. Its anterior aponeurosis forming the most posterior layer of the sheath of the rectus. 9. The lower part of the left rectus with the aponeurosis of the transversalis passing in front. 10. The right rectus muscle. 11. The arched opening left between the lower border of the transversalis muscle and Pou- part's ligament, through which the spermatic cord and hernia pass. 12. The gluteus maximus, and medius, and tensor vaginae femoris muscles invested by fascia lata. ABDOMINAL MUSCLES. 335 anterior part of the sheath, but very slightly to the posterior layer.* Use. To compress the forepart, but more particularly the lower part ofthe belly; to bend the trunk forwards, or to raise the pelvis. By its tendinous intersection, it is enabled to con- tract at any of the intermediate spaces; and, by its connexion with the tendons of the other muscles, it is prevented from changing place, and from rising into a prominent form when in action. The short muscle in the middle is named Pyramidalis, Arises along with the rectus; and running upwards within the same sheath, is Inserted, by an acute termination, near half way between the os pubis and umbilicus, into the linea alba and inner edge of the rectus muscle. As it is frequently wanting in both sides without any incon- venience, its Use seems to be, to assist the inferior part of the rectus. Muscles about the male Organs of Generation. The testicles are said to have a thin muscle common to both, and one proper to each. The common muscle is called the Dartos. This consists of muscular fibres blended with the cellular membrane lining the scrotum; and therefore this portion of * To obtain an accurate idea of the arrangement of the tendons ofthe three large pair of abdominal muscles, it will be necessary to raise or separate the external oblique muscle and tendon from the internal oblique and its tendon, as far as the linea semi- lunaris, and to separate the internal oblique in the same manner from the transver- salis ; and then to make an incision in the tendon of the external oblique parallel to the linea alba, and about an inch and a half from it, so as to bring the whole of the rectus muscle into view. The structure of the sheath which contains the rectus can then be examined. 336 PERINEAL MUSCLES. skin is capable of being corrugated and relaxed in a greater degree than the skin in other places. The muscle proper to each testicle is the Cremaster. Arises from the internal oblique, where a few fibres of that muscle intermix with the transversalis, near the juncture ofthe os ilium and pubis, over which part it passes, after having pierced the ring of the externus obliquus; and then it descends upon the spermatic chord. Inserted into the tunica vaginalis ofthe testicle, upon which it spreads, and is insensibly lost.* Use. To suspend and draw up the testicle, and to compress it in the act of coition. The penis has three pairs of muscles: 1. Erector Penis. Arises, tendinous and fleshy, from the tuberosity of the os ischium, and runs upwards, embracing the whole crus of the penis Inserted into the strong tendinous membrane that covers the corpus cavernosum penis, nearly as far as the union of these bodies. Use. To compress the crura penis, by which the blood is * M. J. Cloquet says, that the scattered fasciculi of this muscle are collected after their distribution on the tunica vaginalis, and run up on the inner side ofthe chord, to be inserted into the spine of the pubis. He makes the inference from this, that the cremaster is a kind of muscular loop, drawn down by the descent ofthe testicle. I am satisfied that the muscle in robust subjects, frequently exists, more or less, after the manner in which he speaks of it: but, in the emaciated, it is very indistinct, as regards such an insertion. In the cases where I have seen this insertion into the spine of the pubis, the quantity of muscular fibre has been by no means so great there as at its origin. This observation of M. Cloquet's is ingenious and interesting, but it is well worthy of consideration,«that Mr. John Hunter's opinion, in his paper on the descent ofthe testicle, is opposed to it, and on the following grounds: in the young ram, and in several other animals, the cremaster muscle is formed before the testicle descends from the abdomen into the scrotum, being reflected along the gu- bernaculum testis upwards towards the loins. Mr. Hunter could not, it is true, verify the same observation on the human subject, but he is disposed, from analogy, to believe that something of the kind exists.—h. PERINEAL MUSCLES. 337 pushed from it into the forepart Fig. 85.* of the corpora cavernosa; and the penis is by that means more completely distended. The erec- tores seem, likewise, to keep the penis in its proper direction. 2. Accelerator Urinas seu Ejac- ulator Seminis. Arises, fleshy, from the sphinc- ter ani and membranous part of the urethra; and tendinous, from the crus, nearly as far forwards as the beginning of the corpus cavernosum penis: the inferior fibres run more transversely; and the superior descend in an oblique direction. Inserted into a line in the middle of the bulb where it joins with its fellow, by which the bulb is completely enclosed. Use. To drive the urine or semen forwards; and, by grasp- ing the bulb of the urethra, to push the blood towards the corpus cavernosum and the glans, by which these parts are distended. 3. Transversus Perinei, Arises from the tough fatty membrane that covers the tube- rosity of the os ischium; from thence it runs transversely inwards, and is Inserted into the accelerator urinse, and into that part of the * Cremaster, from Sir A. Cooper's work, a, Rectus muscle. 6, Descending portion of the fascia superficialis. c, The internal oblique, d, Conjoined tendons, e, The descending fibres of oblique. /, Point of insertion into the pubis, g, Ascending fibres, h, One of the reversed arches. The formation of the cremaster, appears to be effected by the testicle in its descent, (as Scarpa, Cloquet, Cooper, Velpeau, and Todd admit,) for before that takes place, the muscle does not exist, according to Cloquet. Prior to the descent, the gubernaculum testis occupies the inguinal canal, and is covered by the fibres ofthe internal oblique, which adhere to it. When the testis is drawn down by the guber- naculum, these fibres descend with it, forming a series of reversed arches. 29 [ 338 MUSCLES OF THE ANUS. sphincter ani which covers the bulb. The place of junction of these muscles is called the perineal point or centre. Use. To dilate the bulb, and draw the perineum and verge of the anus a little outwards and backwards. There is often a fourth muscle, named Transversus Perinei Alter, Arises behind the former, runs more obliquely forwards, and is Inserted into that part ofthe accelerator urinse which covers the anterior part ofthe bulb of the urethra. Use. To assist the former. In the Medico-Chirurgical Transactions, James Wilson, Esq. F. R. S. gives the following account of two small muscles of the membranous part of the urethra, viz: Each muscle has a tendon which, at first, is round, but soon becomes flattened as it descends. It is affixed to the back part of the symphysis pubis, about one-eighth of an inch above the lower edge of the cartilaginous arch of the pubes, and nearly at the same distance, below the attachment of the tendon of the bladder: to which, and to the tendon of the corresponding muscle, it is connected by very loose cellular membrane. The tendon descends at first in contact with, and parallel to, its fellow: it soon becomes broader, and sends off fleshy fibres, which also increase in breadth, and, when near the upper surface of the membranous part of the urethra, separate from those of the opposite side, spread themselves on the side of the membranous part of the urethra through its whole extent; then fold themselves under it, and meet in a middle tendinous line with similar fibres ofthe opposite side. Its action seems to be to draw up the membranous part of the urethra, and com- press it against the inside of the cartilaginous arch of the pubes; and also to contract the circle round the membranous portion, so as to diminish and even close up the passage of the urine.* It is known under the name of the muscle of Wilson. Muscles ofthe Anus. The anus has a single muscle, and one pair. The single muscle is Sphincter Ani. Arises from the skin and fat that surrounds the verge of the ' I have frequently dissected for this muscle, and in only two or three cases havs been able to satisfy myself of its having an existence distinct from that of the Leva- tor Ani. My friend, Mr. Shaw, who occupies a distinguished rank among the cul- tivators of anatomy in London, admits of this muscle, but says there is much difficulty in distinguishing it from the ligament of the urethra, meaning, I presume, its trian- gular ligament.—h. MUSCLES OF THE ANUS. 339 anus on both sides, nearly as far as the tuber of the os ischium; the fibres are gradually collected into an oval form, and surround the extremity ofthe rectum. Fig. 86.* Inserted, before, by a narrow point, into the perineum acceleratores urinse, and transversi perinei; behind, by an acute termination, into the extremity of the os coccygis. Use. Shuts the passage through the anus into the rectum; pulls down the bulb of the urethra, by which it assists in ejecting the urine and semen. —The sphincter ani is always in a contracted state, except at the time of the evacuation of the foeces. When the sphincter is in a healthy state, it may be made by an effort of the will to contract more strongly, but it cannot be made to relax. —The irritation induced by the accumulation of faeces in the rectum, causes it at first to contract more strongly, and the contraction continues till it is overcome, by the increasing * The muscles ofthe perineum. 1. The acceleratores urinae muscles; the figure rests upon the corpus spongiosum penis. 2. The corpus cavernosum of one side. 3. The erector penis of one side. 4. The transversus perinei of one side. 5. The triangular space through which the deep perineal fascia is seen. 6. The sphincter ani; its anterior extremity is cut off. 7. The levator ani of the left side; the deep space between the tuberosity ofthe ischium (8) and the anus, is the ischio-rectal fos- sa; the same fossa is seen upon the opposite side. 9. The spine of the ischium. 10. The left coccygeus muscle. The boundaries of the perineum are well seen in this engraving. 340 MUSCLES OF THE ANUS. effort of the muscular fibres of the rectum, and the action of the diaphragm and abdominal muscles. It acts also as an anta- gonist to the levator ani muscles.— N. B. The sphincter internus of Albinus and Douglas, is only that part ofthe cellular fibres of the muscular coat ofthe rectum which surrounds its extremity. Levator Ani, Arises from the os pubis within the pelvis, as far up as the upper edge of the foramen thyroideum, and joining of the os pubis with the os ischium; from the thin tendinous mem- brane that covers the obturator internus and coccygeus muscle, and from the spinous process of the os ischium: its fibres run down like rays from a circumference to a centre. Inserted into the sphincter ani, acceleratores urina3, and anterior part of the two last bones of the os coccygis; surrounds the extremity of the rectum, neck of the bladder, prostate gland, and part of the vesicula seminalis; so that its fibres behind and below the os coccygis joining it with its fellow, they together very much resemble the shape of a funnel. Use. To draw the rectum upwards after the evacuation of the faeces, and to assist in shutting it; to sustain the contents of the pelvis, and to help in ejecting the semen, urine, and con- tents of the rectum; and, perhaps by pressing upon the veins, to contribute greatly to the erection ofthe penis. —The muscular funnel, formed by the levator ani muscles of the two sides is antagonised by the action of the sphincter ani, which, by its connexion with the coccyx and perineal centre prevents its lower extremity from being drawn upwards. —When the sphincter is inflamed, and a fluid effused among its fibres, as is an occasional occurrence in the bowel complaint of children, the sphincter loses its power, and the levator ani muscles, unopposed, retract; and thus by everting the lower margin of the rectum, contribute mainly to the formation of prolapsus ani.— PERINEAL MUSCLES OF THE FEMALE. 341 Muscles ofthe Female Organs of Generation. The clitoris has one pair. Erector Clitoridis, Arises from the crus of the os ischium internally, and in its ascent covers the crus of the clitoris as far up as the os pubis. Inserted into the upper part of the crus and body of the clitoris. Use. Draws the clitoris downwards and backwards; and may serve to make the body of the clitoris more tense by squeezing the blood into it from its crus. The vagina has one pair. Sphincter Vaginae, Arises from the sphincter ani, and from the posterior side of the vagina, near the perineum; from thence it runs up the side of the vagina, near its external orifice, opposite to the nymphae and covers the corpus cavernosum vaginae. Inserted into the crus and body or union of the crura clitoridis. Use. Contracts the mouth of the vagina, and compresses its vascular plexus, called corpus'cavernosum, or rete mirabile. Transversus Perinei, Arises, as in the male,from the fatty cellular membrane which covers the tuberosity of the os ischium. Inserted into the upper part of the sphincter ani, and into a white hardish tough substance in the perineum, between the lower part ofthe pudendum and anus. Use. To sustain and keep the perineum in its proper place. The anus, as in the male, has a single muscle, and one pair. Sphincter Ani. Arises, as in the male, from the skin and fat surrounding the extremity ofthe rectum. Inserted, above, in the white tough substance ofthe perineum (perineal centre;) and below, into the point of the os coccygis. Use. To shut the passage into the rectum; and, by pulling 29* 342 MUSCLES OF THE ABDOMINAL CAVITY. down the perineum, to assist in contracting the mouth of the vagina. Levator Ani, Arises, as in the male, within the pelvis, and descends along the inferior part of the vagina and rectum. Inserted into the perineum, sphincter ani, extremity of the vagina and rectum. Use. To raise the extremity of the rectum upwards, to contract the inferior part of the rectum, and to assist in con- tracting and supporting the vagina; and, perhaps, by pressing on the veins, to contribute to the distention of the cells of the clitoris and corpus cavernosum of the vagina. Muscles situated within the Cavity ofthe Abdomen. Fig. 87/ C-. These consist of a single muscle, and four pair. Diaphragma. This broad thin muscle, which makes a complete septum between the tho- rax and abdomen, is con- cave below and convex above ; the middle of it on each side reaching as high within the thorax of the skeleton as the fourth rib: it is commonly divided into two portions. 1. The superior or, Greater Muscle of the Dia- phragm. Arises, by distinct fleshy * Thorax of a male.—On the left side the muscles are removed ; on tbe right they are left in situ, a, a, Cervical and lumbar parts of the spinal column, the dorsal portion is concealed by the sternum, b. c, c, The true ribs, c', The false ribs. ^_rrrirTrr^r^n p to its thickness, and transversely ffiK^ffiy#iSi4-f t0 the lines formed bY the z, papillae. In this, according to Gaultier, we see at a the lower surface of the derm, or cutis vera. 1, The prominences or as- perities of the derm, forming the papillae, each one with a slight depression upon the top. 2, Immediately above these and continuous with them we see a series of vascular fasci- culi surmounting these prominences, called bloody pim- * Gaultier, whose opinions have been adopted in the main by Beclard, Blandio, Cloquet and others, would, if he had lived, most probably done much towards sim- plifying and perfecting his views. Appointed army surgeon immediately after his graduation, he fell a victim to the disasters ofthe Russian campaign. The investi- gation has, however, been taken up by D utrochet who extended it to the skins of quadrupeds, by several ofthe German and Italian anatomists, and lastly by Breschet and Roussel de Vauzeme. The last have made it a subject of elaborate microsco- pical research, not only in man, but in the whale and many ofthe larger animals. The views of Gaultier thus modified and improved, are well deserving of study as the most satisfactory yet given, though, from the doubt which is always attached to microscopical observations, they must be looked upon rather as the probable than the proven structure.—p. ACCORDING TO GAULTIER. 421 pies, (bourgeons sanguins.) 3, The tunica albida profunda, covering these papillae upon their top and sides, and united to the upper surface of the derma, and composed entirely of white vessels, (serous capillaries.) 4, Gemmules; a sort of membrane so named from its undulations, excavated on its internal face, which coversi n the tunica albida profunda. This is the seat of the colouring matter of the skin, and each undulation receives two of the bifid tops of the papillae, called bourgeons sanguins. 5 Tunica albida superficialis, which covers over the gemmules, and is also formed entirely of white vessels. 6, The external face ofthe skin, which is only the dried surface of the tunica albida superficialis, or the proper epidermis. Gaultier considers four of these layers as belonging to the rete mucosum ; the perpen dicular vascular fasciculi (bourgeons sanguins,) the gemmules and the two white tunics. —The first and second of these Fig. 110.T ^ correspond with the two ^■^^l&MWmMM^^k^Wi vascular layers which Bichat as- -_. signs to the rete mucosum; and ] 1 the views of Gaultier differ from this writer's in his adding two more tunics, tun. albid. profun- da, and tun. albid. superficialis. But the vascular fasciculi, as Dutrochet and Beclard have asserted, belong to the cutis vera, and form a part of the proper papillary body ; and were probably the parts injected by Baynham and Cruikshank— thus leaving the rete mucosum formed of three layers. Thus modified, Gaultier's researches have been adopted by many writers. —But there were not wanting others who entertained different views. Gall believed the rete mucosum a nervous expansion * Fig. 109,—Is a representation of the skin, and the basis ofthe papillae, the latter surmounted' by the vascular villi or fasciculi, Qourgeons sanguins.) The space between these fasciculi is filled up, in the natural state of the parts, according to Gaultier, with the tunica albida profunda. ..... t Fig. 110,—Is a representation ofthe derm, or cutis vera, with a line of prominences on its upper'surface, constituting the basis of the papillae. 36 422 STRUCTURE OF THE SKIN for the reception of tactile impressions; an opinion purely hy- pothetical and erroneous; Chaussier, that the skin was com- posed of but two part.s, the dermis and epidermis, and that which had been called the -rete mucosum was probably a part of the dermis ; Blandin,* that the rete mucosum, consist- ing of three layers according to Dutrochet placed between the papillary bodies and the epidermis, had neither vessels or nerves, was a product of secretion from the papillae, like the epidermis, and formed in fact a second epidermis thicker and softer than the external, and that it had no more vitality than the hair and nails. —Breschet and Roiissel de Vauzeme,t have in this uncertain and imperfect state of our knowledge, endeavoured with the aid of the scalpel and the microscope, to determine positively its structure. Their researches have been extended not only to the skin of man, but to that of whales and others of the cetaceae. The discoveries which they allege to have made are surprising, and though their researches appear to have been made with much labour and ingenuity, their confirmation or overthrow must depend upon the investigation of others equally familiar with the same instruments. —But it must not be forgotten that such high magnifying powers as they have used, expose the most wary and honest observer to optical illusions. This cause led De la Torre, to assert that the globules of the blood were annular. —According to these writers, the skin consists of but two layers. The derm, or cutis vera, and an external layer, which they call indifferently epidermis, corneous matter, corneous tissue, or epidermic layers, that comprises the rete mucosum and epi- dermis of other writers, and which they consider composed of the same substance, mucus, in a greater or less state of desicca- tion. It is, however, composed of many distinct parts, not arranged in the form of layers. Fig. Ill, represents an imagi- nary scheme or plan, in which they have placed together the * See Anat. Generale of Bichat, Paris, 1831.— t Nouvelle recherches sur la structure de la peau, par G. H. Breschet and Roiissel de Vauzeme.—Paris, 1835.— ACCORDING TO BRESCHET AND ROUSSEL DE VAUZEME. 423 constituent parts of the skin, the existence of which they had proved separately under the microscope. —Thus, a is the derm, b, The corneous or horny epidermic matter, c, The vessels and nerves which go out from the der- mis, d, Space filled up by their capillary branches, e, Ner- Fig. 111.* vous or tactile papillae. The diapnogenous, or sudoriferous apparatus, composed of a glandular parenchyma,/, and of spi- ral sudoriferous canals, g. The glandular or secretory organ is inclosed in the substance of the skin, and the canals pass up between the papillae and open obliquely on the surface of the epidermis, constituting the microscopical orifices, from which we see the sweat exuding on the palms of the hand, and soles of the feet, h, The inhaling apparatus, or absorbent canals, which resemble in many respects the lymphatic vessels: they are situated in the corneous matter, or rete mucosum ; they are seen to commence under the most superficial layer of the corne- ous matter which forms the cuticle; no mouths or orifices are seen, and it is impossible to say, whether they commence in the form of a cul de sac or not. They pass down between the papil- lae, by the side of the sudoriferous canals, and communicate with 424 STRUCTURE OF THE SKIN a net-work of vessels, which they believe to be lymphatics mixed up with veins, spread upon the surface of the derm.* i, The organs which secrete the mucus, of which the rete mu- cosum and cuticle is formed, or blennogenous apparatus; this consists of a glandular parenchyma situated in the thickness of the derm, and of short excretory canals k, which deposit the mucous matter between the bases of the papillse. The chro- matogonous organs or glands, which secrete the colouring matter or scales, run parallel with, and immediately below the grooves on the surface, and between the papilli, which they are also placed a little below. The ends of them, marked by a collection of dots, can of course only be seen in the plan, in consequence of their running parallel with the grooves, and between the parallel ranges of papillae. —They consist of a glandular parenchyma, receiving an abun- dance of capillary vessels from the derm below, and possessing excretory canals above, that throw upon the surface of the derm, the colouring principle, which is mixed with the soft and diffluent corneous or mucous matter, secreted by the blennog- enous apparatus. From this mixture results the pretended rete mucosum of Malpighi, and the epidermis or cuticle. From this apparatus is also produced, they think, the horns, scales, spines, bristles, hair, wool, hoofs, nails, etc. of different animals. It is solidified in successive couches, to the right and left, as seen in the section across the grooves, /; but. in the longitudinal section m, these layers present a series of straight lines one above another like the leaves of a book. -—In consequence of this arrangement, the corneous matter, when macerated, throws off layer after layer. The superior face of the epidermis presents grooves, as represented at n, which correspond to the interpapillary grooves of the derm. o, Are the prominent ridges in the cuticle formed over the papillae, separated by transverse grooves, p, at the bottom of which are found the pores of the sudoriferous canals, e, Are * The existence of these inhalent vessels, from some observations I have made with a very powerful microscope, I should consider extremely doubtful.—p. ACCORDING TO BRESCHET AND ROUSSEL DE VAUZEME. 425 the vessels and nerves which enter into, or go out from the derm. d, An interval filled up by capillary filaments. Of the Derm. —The external surface of the derm, is lined by a very thin adherent membrane, which is reflected over the tops of the papillary bodies and forms their neurilema. The horny or epidermic matter is secreted in the grooves between the papillae, and is moulded around all the inequalities, the form of which is exactly impressed on all the layers of the epidermis. In serpents, the derm, has a singular arrangement; it is elevated in imbri- cated projections, covered by a thin layer of epidermis; these are called scales. In fishes, on the contrary, the surface of the derm is smooth, and the scales are formed only of the horny matter. The derm is a membrane, the fibres of which are solidly interlaced together, with interstices for the passage of vessels, nerves and canals, and in which are lodged many organs, as has been shown in the plan, page 423.* Of the Papillary Body, or Neurothelic Apparatus.} —This consists of a series of little prominences on the upper surface of the derm, the cleft at the top into two portions, each of which is composed of a bundle of nerves and vascular fila- ments—the bourgeons sanguins of Gaultier. The form of each papilla is that of a cone. The base is expanded in the upper surface of the derm, and its two prominences or villi, termi- nating in a rounded point, are received in the horny layers of the epidermis, like a sword in its sheath, (see page 426.) —The direction of the papilla is slightly oblique in the epider- * The method adopted by these writers for microscopical examination of the skin, was to take a piece of recent skin in which the vessels were distended by cadaveric accumulation of blood, or filled with injection. A portion from the heel is preferable. This is to be allowed partially to dry, and the thinnest possible transparent slice, cut off vertically. This is to be placed upon a piece of moistened glass and examined under the microscope with the use of a lamp and reflector. In this way they were able readily to see, and isolate with curved cataract needles, all the versels, nerves and glandular apparatus of the skin.—p. t From neuron, nerve, and thela, papilla.— 36* 426 STRUCTURE OF THE SKIN mic layers, as seen in fig. 112.* The nerves are here seen passing up into the papillae through the dermis; the vascular branches which accompany them are not here represented. The papilla first gets a neurilematic covering from the upper surface of the derm, and is there furnished with several layers of the epidermic horny matter, which cover it like a hood. This horny cov- ering is particularly thick at the heel, and serves to protect the papillae by the > deadening of shocks, and resisting the pressure of the weight of the body. The papillae are most numerous on the palms of the hands and soles of the feet, but are also scattered over other parts of the body.J Ofthe Sudoriferous or Diapnogenous Apparatus. —This consists of a gland, see fig. Ill, p. 423, placed in the substance of the dermis, near its inner surface, into which a great many capillary vessels run, and of a spiral duct which runs up through the horny layers and opens obliquely through the outer epidermic crust by a slight depression or pore, on the * According to these writers the nerves, as they pass up from the under surface of the skin, become soft, flexuous, and capillary, and as they enter the villi on the top ofthe papilli, lose their neurilema, and are expanded in the form of pulp. They look upon the changes which the nerve undergoes, and upon the derm, villi, and epidermic covering, as so many parts necessary to constitute the perfect organ of touch: thereby assimilating it to the more complicated organs of sight and hearing. —Loc. cit. p. 15, et seq.— t Fig. 112, represents the apparatus which constitutes the organ of touch in man. a, Nerve entering into the dermis, where it becomes capillary. 6, Its entry into the papilla, c, Neurilema furnished by the dermis. 1 d, Proper envelope of the nerve, e, Corneus layers more or less thick, which form the organ of protection to the nerve. The capillary blood-vessels which pass up with the nerves are not here shown. t From their observations upon the papillae of the whale, these anatomists are disposed to believe that the nervous fibrils terminate at the top of the villi, by loops with one another, as Prevost and Dumas have shown them to do in other parts of the body.— ACCORDING TO BRESCHET AND ROUSSEL DE VAUZEME. 427 back ofthe epidermic ridges, formed over the papillary bodies. These are the orifices from which the sweat exudes, and may be readily seen with a single lens of moderate magnifying power, on the palms ofthe hands, soles of the feet, nose, and other portions ofthe body. The obliquity of the orifice, gives it a valvular arrangement, like that of the ureters where they enter the bladder. In consequence of this the valve closes the orifice, when the epidermis is raised by cantharides, and the duct is broken off, so that the pores are not generally visible ; this has occasioned some anatomists, of great reputation, (J. F. Meckel, Cruikshank, Blumenbach, etc.)* to deny altogether the porosity of the epidermis, and to believe that the sweat passed by exudation or exosmosis directly through its sub- stance. In carefully elevating the cuticle from the subjacent coats, these ducts are visible as very fine transparent elastic filaments; the spiral being converted into straight tubes by the traction, and which W. Hunter, Bichat, and Chaussier, accor- ding to these writers, mistook for the exhalent and absorbent vessels.! Others supposed they were filaments of cellular tissue, uniting the epidermis to the subjacent layer.J The sudoriferous organs, which are exceedingly numerous, are probably the only exhaling organs of the skin. The Inhaling Apparatus. —This is properly an appendage of the absorbent system; and may be seen, according to these anatomists, with a lens of feeble magnifying power, or even with the naked eye, in rais- ing the epidermis with proper precaution. They have not, however, been enabled to make out their anatomy satisfactorily. * Beclard was disposed to consider these pores as the orifices of the sebaceous glands, though he expresses himself doubtingly upon the subject, and says that the rout by which the sweat traverses the epidermis is entirely unknown.—p. t The existence of exhalent vessels, was a mere presumption of Bichat, and has never been demonstrated.—p. t Eichhorn has also observed these sudoriferous canals, and his description of them corresponds in many respects with that of Breschet. (Memoire sur les exhala- tions que se font pour le peau, et sur la voies par lesquelles elles sontlieu ; par Ilcnri Eichhorn.) Arch, de Meckel—p. 428 STRUCTURE OF THE SKIN They describe them, see fig. Ill,as arising by isolated radicles from the under part of the grooves of the epidermis, and not opening to the surface ; the fluids which they take up getting into their cavities by previous imbibition through the outer cuticular covering. In passing downwards towards the derm, they are in company with the sudoriferous ducts, and in the substance of the derm, become continuous with the common absorbent vessels.* Fig. H3t. Blennogenous Apparatus, —Or organs that produce the mucous substance, which, in its first soft condition, forms the mucous body, heretofore known under the name of rete mucosum, and which, hardened upon the surface constitutes the horny matter ofthe epidermis. * The existence of these absorbent vessels immediately beneath the cuticle and on the upper surface ofthe dermis, has been demonstrated by Tiedemann, Fohman, and Lauth. Breschet asserts the discovery of an additional structure, in his inhaling apparatus, arising in the corneous tissue.—p. t Fig. 113.—a, Chromatogenous organ torn in two places, b and c, to show the escape of the scales, and the thread-like vessels of which this organ is composed, d, Its small excretory canals, torn in removing the corneous matter, e, Blennogenous or mucous gland, which throws its secretion above the chromatogenous organ. /, Fluid state of the corneous matter, that is to say, pigmentum or scales floating in the midst of mucus, (rete mucosum of Malpighi.) g, Layers of corneous or horny mat- ter stratified to the right and left, more and more condensed, the nearer they ap- proach the surface. Into the mucous gland is seen running a sanguineous vessel, and round it are placed a number of little whitish granules. ACCORDING TO BRESCHET AND ROUSSEL DE VAUZEME. 429 To see these well with the microscope, it is necessary to have a piece of fresh skin well injected with blood. There is then to be seen at the base of the derm, little reddish glands, irregu- lar on the surface and grooved by blood-vessels. They are enveloped in cellular membrane and surrounded by a multi- tude of minute adipose vesicles. From the top of each of these glands as seen in fig. 113, passes up a duct, which opens on the upper surface of the derm in the grooves between the pa- pillae. Many capillary vessels adhere to the tube and the gland, and a vessel of considerable size enters the base of the latter. The mucous matter thrown on the surface ofthe derm by these organs, quickly unites with a colouring matter, from which results the different tints of the corneous or epidermic substance, hair, nails, scales, feathers, etc. in man and other animals. This colouring is formed by the Cromatogenous* Apparatus, (see fig. 113,) —which is placed at right angles to the ducts of the mucous glands, at the upper surface of the derm, and at the bottom of the grooves. Its structure is parenchymatous or spongy. On its under surface, it receives a great number of minute capillary vessels, which is the outer limit of the vascular system, with the exception of the vessels which pass up into the villi. On its surface arises many short ducts, and which open in the grooves between the papillae, to convey up the colouring matter in the form of small granules to mix with the mucus.t When this tissue is torn, a great many small filaments are seen (a,) from which escape small scales or colourless corpuscles in great quantities, (b, c.) This reservoir of scales is found in no other part of the derm. —At/, is seen the fluid state of the corneous matter—that is to say, the pigment of the scales floating in the midst of the mucus. At g, couches of this matter, hardened and stratified, * From XF'*/"*' colour, and ytnttu, to create.—p. t The colouring matter as is very obvious in the black, is now found to be deposited in delicate hexahaedral cells which are called pigmentary cells. In the choroid coat of the eye the cells are arranged in several layers o,ver each other, so as to form a pigmentary membrane, the surface appearing perfectly black. 430 OF THE CUTICLE. to the right and left as they approach the surface, form the coverings of the papillae, and which are thus secreted and moulded around these organs. —The whole rof the corneous tissue of the skin, (included usually under the terms of rete mucosum and epidermis,) is formed according to these anatomists of the mingled products of these mucous and colouring glands.* The Cuticula or Epidermis, has been examined with the greatest care by several of the most successful anatomists; but notwithstanding their labours, the structure of this substance is by no means understood. It appears to have some resemblance to the matter of the nails, and of horn: but is rather more flexible, even after allowing for the difference in thickness. In those parts where it is thinnest it is semitransparent. It is insensible, and no vessels can be seen in it. t * In investigating this obscure and difficult part of anatomy, it has been usual with observers to select the skin ofthe palms ofthe hands and soles ofthe feet, as a type ofthe whole cutaneous system. There is, however, a difference to be observed. In the palms and soles resides pre-eminently the sense of touch. These parts are likewise destitute of hair, and the papillae which are there very numerous and visible to the naked eye, are very sparsely distributed and appear rudimental in other parts of the body. Much of the discrepancy among anatomists in regard to the structure of the skin, appears to be owing to whether they have made their researches mainly upon the palms and soles, or upon the skin of othef parts of the body. Chevalier* and Wallace,t have described, especially in the skin of the face, arms, and legs, a eystem of epidermoid glands, seated in the rete mucosum, and so minute that the latter counted one hundred of them in the one-twenty-fourth part of a square inch, and which gave issue to the sweat. These appear to me, to correspond with the diapnogenous apparatus of Breschet, as he represents them in the palms and soles. The opinion of Bichat, is therefore erroneous, that the sense of touch is only more perfect in the hands than other portions, in consequence ofthe shape ofthe parts, and the facility with which they may be applied round objects, and that the skin of the abdomen substituted for that of the fingers, would have constituted organs of touch.—p. t In the early part of the last century, an anatomist by the name of St. Andre' exhibited a preparation of the cuticle which appeared to be injected with mercury. Ruysh declared the thing impossible, and invited him to an investigation of the subject. This invitation was not accepted, and the affair has been generally consid- ered as a mistake or an imposition.—h. * Lectures on the general structure of the human body, and on the anatomy and functions of the skin, by J. Chevalier. t Lectures on the structure of the skin, by W. Wallace, London Lancet, 1837. OF THE CUTICLE. 431 It extends over the whole external surface of the body, except the parts covered by the nails, and is accommodated to the surface of the skin, by forming ridges or furrows, corres- ponding to it. It adheres most closely to the cutis; and when abraded by mechanical violence, the surface of the skin appears moistened by effusion. It is not certain that its mode of union with the skin is perfectly understood; the adhesion of these membranes to each other is as uniform as that of two smooth surfaces glued together, but it is generally said that the cuticle is attached to the cutis by very numerous and fine filaments. It has often been asserted that these filaments are the exhaling and absorbing vessels, which'pass through the cuticle, to and from the skin. This sentiment appears very reasonable, but no vessels that pass in this way can be injected. There are innumerable processes which pass from the cuticle to the skin. Many of these are the linings of the cavities which contain the roots of the hairs; but they are reported by micro- scopical observers to be like the fingers of a glove, closed at their extremities. There are also many processes which contain a sebaceous substance that may be pressed out of them in the form of worms; these are the ducts of sebaceous glands. Besides these, there is an immense number of whitish fila- ments, which are as fine as the most delicate thread of a spi- der's web. These filaments can be best seen while the cuticle is separating from the skin of the sole of the foot, as suggested by Dr. William Hunter.* They are supposed to be vascular, but they have never been injected. When the cuticle is in its natural situation, in union with the skin, there appears to be three species of foramina or pores, on its external surface: viz. 1. Those formed by the passage of the hairs; and 2. Those which are the orifices ofthe ducts of the sebaceous glands; each of which has been already men- * See the London Medical Observations and Inquiries, vol. ii— h. 432 OF THE CUTICLE. tioned. And 3. Such pores as exist on the ends of the fingers and the inside of the hands. It is said that these last are very visible, when magnified to twice or thrice their original bulk, and drawings of them have accordingly been made by Dr. Grew* and by Mr. Cruikshank.t Small specks of fluid can be seen with the naked eye, in the same situations, in warm weather, or when the ends of the fingers are made turgid by a ligature. It is probable that they are formed by the accumulation of fluid at these orifices. The above described pores are situated on the ridges at the ends of the fingers and not in the furrows; and it is probable that similar pores are distributed over the surface of the body. Notwithstanding the appearance of these foramina, when the cuticle is in its natural situation, several of the most suc- cessful investigators ofthe subject have declared that they could not discover any pores or foramina in the cuticle, when it was separated from the cutis. The late Professor Meckel of Berlin, who was one of this number, was induced to believe that the matter of exhalation, and of absorption, soaked through the cuticle, as the vapour of warm water passes through leather.^ In support of this doctrine he states that perspiration goes on through the cuticle on the palms of the hands and soles ofthe feet when it is Very thick ; and observes, that if it were trans- mitted by delicate vessels, the vessels in the feet must be torn by the weight ofthe body, in persons who walk; and those in the hands would experience the same fate, in labourers, who work with heavy hammers, &c. On the other hand, Mr. Cruikshank, who could likewise find no pores in the separated cuticle, contends strenuously for their existence notwithstanding ; and explains their non-appearance by the following facts, among others; viz. that no foramen will appear in the separated cuticle, although it has been punctured by a needle; and that when the cuticle has been peeled off, * In the Philosophical Transactions, vol. hi. Lowthrop's Abridgement. t See his Experiments on Insensible Perspiration. t See Memoirs ofthe Royal Academy of Sciences of Berlin, vol. xiii. for 1757. CAUSES WHICH PRODUCE VESICATION. 433 from portions of the cutis on which were hairs which must necessarily have perforated it, no foramina have appeared in it. M. Bichat took very different ground: he asserted that the pores of the separated cuticle were to be seen distinctly, in large numbers, by looking through it towards the light; he also believed that the course of the exhalent vessels, through the cuticle, might be seen in the same manner; and that they passed obliquely. That the cuticle is pervious, is proved incontestably by the functions of perspiration and sweating, as well as of absorption; but there are good reasons for believing that the perforations of the cuticle have a peculiar structure; and are not simple foramina. Thus, when a vesicle is formed by the operation of cantharides or any other process, if the cuticle is not lacerated, it will confine the effused fluid for a considerable time, without any appearance of its escape through these pores. This fact, which is strongly opposed to the hypothesis of Meckel, is explained by Cruikshank upon the supposition that the pores of the skin are lined by processes of the cuticle, and that when the cuticle is separated from the cutis, these pro- cesses go with it, and act like valves in confining the fluid. Bichat supposes the oblique vessels to produce the same effect upon analogous principles; and compares their situation to that of the ureters, which pass obliquely between the coats ofthe bladder. This peculiar quality of the cuticle, in admitting of perspira- tion and sweat, and also absorption, while it prevents evapo- ration from the parts which it encloses, is of immense impor- tance. If a portion of skin be deprived of cuticle a short time before death, by a blister for example, this portion will, in a few days, become perfectly dry and hard, like horn; while the other parts of the skin of the subject, covered by the cuticle, retain their moisture and flexibility. It may, therefore, be admitted, that the use' of the cuticle is to keep the skin soft and flexible, by confining its moisture, as 37 k. 434 SEPARATION OF THE CUTICLE. well as to defend it.* And it is probable that the sebaceous matter is secreted for the purpose of preserving the cuticle in a state of flexibility. As the cuticle is capable of confining fluid, and resisting the action of chemical agents, it is surprising that epispastics and rubefacients should act through it, upon the skin, with so much certainty as we find they do ; and that cantharides should pro- duce vesications, when applied dry. The thickness of the cuticle on every part of the body is much increased by long continued pressure, forming corns and excrescences of its own nature. By this cause also it is ren- dered very thick on the palms of the hands and soles of the feet; although it is originally thicker there than in other parts. It is said that, after long boiling, these thick portions of cuti- cle may be separated into distinct lamina. In the living subject, the cuticle, when immersed in warm water, seems to absorb some of that fluid; as is evinced by the hands when they have been long in that situation; and also by those parts of the skin to which poultices have been applied. Notwithstanding the uniform adhesion of the cuticle to the cutis, it is observed, in the living subject, to be separated, and formed into vesicles, by a variety of causes, viz. 1. Pinching of the skin, or violent mechanical irritation; such as labouring with hard instruments. 2. By the application of cantharides, and certain other sub- stances which produce vesications. Sometimes these sub- stances appear to inflame the skin; but on other occasions the vesication is produced while the skin appears unchanged in colour, and free from inflammation. The process appears dif- ferent from that of simple inflammation; for certain rubefa- cients often inflame the skin considerably without vesicating or blistering it. 3. Boiling heat will, very generally, produce vesication. 4. Certain diseased processes seem to occasion vesication in * This property of the cuticle is rendered very apparent in attempting to dry ana- tomical preparations with the skin on, in which the student will fail, unless the cuticle is previously removed by maceration.—p. CHEMICAL QUALITIES OF THE CUTICLE. 435 a manner which is not well understood, viz. erysipelas, zona, or shingles, pemphigus, and some other eruptions which have no name. In erysipelas there is an obvious inflammation of the skin; but in some ofthe other diseases the vesication takes place without the appearance of inflammation. 5. Vesications often appear when there is a tendency to gangrene. 6. They also occur in some cases of simple fracture, where there is considerable injury. In these cases the fluid effused is often tinged with blood. After death the cuticle is separated from the cutis: 1. By putrefaction; in which case large vesicles are some- times formed. 2. By long continued maceration. 3. By boiling, and 4. By violent dry heat. The cuticle appears to be least deranged when it is separated by putrefaction and maceration: in these cases the internal surface corresponds to the surface of the skin; and the pro- cesses which contain the hairs, as well as those which are the ducts of the sebaceous glands, are particularly obvious. The external surface ofthe cuticle varies in different places, according to the surface of the skin. In some places it appears scaly at times, and has therefore been supposed to consist entirely of scales; but in other parts, when examined atten- tively, it appears like a half transparent concreted substance, with a rough surface. When the skin has continued dry for a long time, bran-like scales can be rubbed off from it. These are probably com- posed of the residuum of the secretion deposited on the skin, and of a portion of the external surface of the cuticle. The same substance appears upon the first washing of the skin, after that process has been discontinued for any length of time. Many speculations have arisen respecting the manner in which the cuticle is originally formed, and reproduced ; but none of these are perfectly satisfactory. It is also a question whether the cuticle is endued with vitality, 436 CHEMICAL QUALITIES OF THE CUTICLE. or is merely an inanimate unorganized concrete. No decisive argument have been adduced in favour of its vitality ; and it has already been stated, that neither nerves nor vessels can be demonstrated in it. It appears particularly calculated for protecting the skin which it covers; for it is insoluble in water, and resists the action of several powerful chemical agents. Thus, it is not affected by immersion for a considerable time in the sulphuric and muriatic acids ; although the nitric acid acts upon it. It resists for a short time, but is at length dissolved, by the pure fixed alkalies, and by lime. It is supposed by the chemists to consist of albumen, in a peculiar state of modification. —Malpighi, was the first to discover, by the use of the microscope, an intervening substance between the cuticular covering, and the cutis vera, which he called the rete mucosum or corpus reticulare. This he considered the seat of coloration in the negro, and asserted the cuticle to be alike in all varieties of the human race—that is, colourless. For a long period his researches formed the basis of all the systematic treatises upon the skin, and it is only within a recent period, as has before been observed, that the study of the subject has been resumed. —The cuticle of the black is now generally admitted to be of an ashy colour.* And Flourenst has shown, that the reticular appearance of the rete mucosum is entirely an adventitious circumstance. Malpighi first discovered his rete mucosum on * Breschet has asserted that the colour of the skin in different animals is depend- ent upon the form of the scales of the epidermis, by which the light is reflected. Fig. 114. The larger cut represents, after this observer, the scales of the epidermic or corneous matter of a white man, diluted with water, and highly magnified, in which are seen fragments of the sudoriferous canals and inhalent vessels. The scales all have a trapezoidal or lozenge shape. The smaller cut, represents a single scale from the skin of a whale, highly magnified. It is black at its summit, and whitish at its pedicle of insertion. The skin ofthe whale is black, and these writers assert, that in all ani- mals with black skins, including negroes, the scales of the epidermis, appear under the microscope of this shape or spatulate.—p. tAnnales des sciences naturelles, 1837.— CHEMICAL QUALITIES OF THE CUTICLE. 437 the tongue of the ox, and subsequently under the epidermis of the human hand, from which he drew his description. By ebullition he softened the outer covering of the cutis vera, and then tearing off the epidermis, he saw a layer of soft substance with holes in it like the meshes of a net. This was owing to a laceration of the mucous layer: the part covering the apices of the villi going off with the cuticle, while that between the villi and the bases of the papillse adhered to the cutis vera. By maceration in water, which is the surest and most success- ful method of effecting a dissection in delicate parts, Flourens, found in the same organs the cuticle to come off, leaving the whole of the mucous body attached, which then presented none of the reticular appearance. The cuticle and mucous body were both continuous layers, covering the papillae and forming their sheaths. The sheaths formed by the latter body were broken in Malpighi's preparation. —The cuticular sheaths in the ox, were thin and delicate over the fungiform or smaller papillae, but formed thick horny layers over the larger which assist in the action of mastication. —Albinus, repeating the experiments of Malpighi, corrected his error, and in the beautiful designs of Ladmiral, has represented the mucous body as a continuous layer. Since then by Bichat and others, the use of the term rete mucosum, has been con- tinued, not exactly in the original signification of Malpighi, but under the belief that it contained a net-work of vessels. Its foliated structure has been well established by Cruikshank, Gaultier, and Flourens. It thus appears that the whole of the anatomy of the skin, requires to be constructed anew. Several of the German and French anatomists have applied themselves to the task, among whom may especially be men- tioned Weber* of Leipzig, and Breschet of Paris.t The views ofthe latter, on account of his having treated the subject more extensively than the rest, as well as from his high situation in the school of Paris, have already been given. The physiology * Arch, fur die Physiologic.— tNouvelles Recherches sur la Structure de la Peau, par G. W. Breschet et Roussel de Vauzeme. Paris, 1835.— 37* L 438 CHEMICAL QUALITIES OF THE CUTICLE. of cuticle has received an entirely new aspect, from recent observations, and especially from those of Henle.* He has shown that with very few exceptions, all the free surfaces of the body—not only the skin which has its culicular covering— but those of the serous cavities, the mucous passages,! the blood-vessels, and the ducts of the glands, are invested by a membrane, composed of one or more layers of primary cells, forming a delicate cuticle or epithelium. The epidermis, cuticle, or external covering of the skin, when examined with a powerful microscope, is seen to be composed of several layers of cells, which are the consequence of an uninterrupted process of exudation which has place upon the corion or true skin. This exudation, though unorganized, retains some vital properties, and is a cytoblastema; that is, a basis structure, or soil, from which new growths or developements take place. These new growths are cytoblasts, or cell germs; that is, cells or vesicles, at first globular, afterwards lenticular and opaque, (each one surrounding a central nucleus), which possess within themselves the inherent principles of growth.} The more recently produced cells, which of course are those in contact with the corion, are like all young cells, spherical in their figure; they become flattened as they develope themselves and approach the surface; so that when examined on a sec- tion, they are found to have undergone changes of form from that of a globular cell, provided with a nucleus, to that of a flat scale, in which no trace of a nucleus appears, and which lay, one over another, like so many layers of tiles or pavement. The innermost layers are soft and cellular; the outer ones become dried on the surface from exposure to the air, and fall off in squamae or scales.—§ * Allgem. Anat., p. 260. t Vide Gen. Anat. of Serous and Mucous Membr. Vol. 2. t The cell germs, here and in other parts of the body, bear a general relation to the size of the blood globules of the same individual. This is a remarkable fact, and somewhat in favour of the views of Dr. Barry, who states that it is the blood disks that are transformed into these cell germs.—Phil. Trans. Part 11. 1840. § Henle, makes three varieties of epithelium or cuticle, 1st. The pavemented squamous or tesselated epithelium, above described, found on the skin, serous mem- THE NAILS. 439 The Nails. The roots of the nails appear to originate in a fold of the cutis vera, from the epidermus which lines the fold; but the bodies of the nails adhere firmly to the cutis on which they lie, and appear to cover it, in the place of the cuticle. The papillae of those parts of the cutis which are covered by the nails are very conspicuous when the nails are removed. It has been supposed that there was no rete mucosum between the nails and cutis; but this opinion is probably erroneous, as the black pigment is perceptible under the nails of some negroes. The nails can be separated from the cutis by all those pro- cesses which separate the cuticle from it. When this is effected, they remain connected with the cuticle, which appears to be continued into them; and on this account, as well as their insensibility, and their resemblance to the horny excrescences of the cuticle, they are considered as appendages of it. The root is opaque, and appears white. The body is trans- parent, and in health shows the florid colour of the cutis which it covers; but the colour of this portion of the cutis depends upon the state of the circulation; and becomes livid when the blood is disoxygenated, or when the circulation ceases there; and this colour also appears through the nails. The nails are unquestionably organised, although their ultimate structure is not known. They appear to be composed of lamellae, and these lamellae of fibres. They grow rapidly, and when they are not pared or worn away, they sometimes acquire an immense size. As a remarkable instance of this, it is related, that a nail of the great toe was sent from Turin to the Academy of Sciences at Paris, which measured four inches and a half in length. The growth seems to take place altogether at the roots. The nails, when chemically examined, appear to consist of branes, the lining membrane ofthe mouth, pharynx, oesophagus, and the vagina and cervix uteri. 2d. The cylinder epithelium, found in the remainder of the alimen- tary canal, the ducts of the glands, and a great part of the genito-urinary apparatus of the male. 3. The ciliary epithelium, found in the respiratory organs, the lachrymal passages, Eustachian and Fallopian tubes, etc. Vide the account of these organs. 440 THE NAILS. a modification of albumen; and thus resemble cuticle and horn in their composition. —The growth of the nails, forwards, is entirely from a fold of the cutis vera, at its root, called, though not with exact pro- approaches the extremity, the deepest seated of which is the shortest. In this way the nail gets its thickness and strength, and occasionally, where the deposition of new matter, goes on more rapidly under the body of the nail than at the matrix, the body is thrown up into unsightly rugosities. Its developement is exactly similar to that of the horns and hoofs of animals. The striated appearances ofthe nail, is said to be owing to the papillary prominences below. The white semicircular line at the root, is called the lunula. —The nails are not exactlyanalogous in structure to the cuticle, in the ordinary acceptation of the term—to that part which is raised up under a blister. The proper cuticle is that thin coating which is scraped away and worn off near the root, and which otherwise would cover the surface. The nails consist of the proper cuticle, and tunica albuginea superficialis and gemmules of Gaultier—leaving interposed between them and the cutis vera, the tunica albuginea profunda which is insensible, and explains why it is that a splinter, or the blade of a small pair of scissors, in the operation for onychia, may be run along close on the under surface of the nail, without the production of much pain. According to Breschet, the nail is formed like the other parts of the horny coat exterior to the cutis vera, by the glands for the secretion of the mucous and colouring matter; the products of which would be mixed up together, colouring the substance of the nail, as we know is the case in regard to the horns and hoofs of animals.— THE HAIRS. 441 The Hairs Originate from bulbs which are situated at the bottom of pores or cavities in the skin. These pores appear to be lined by a production of the cuticle, and the extremities of the bulbs project beyond them into the cellular membrane. In some cases, where the cuticle is separated after putrefaction, it seems that these lining processes of the cuticle come away completely, and bring the hairs and roots with them ; but in other cases, the cuticle separates from the cutis, and leaves the hairs in their natural situation.* When viewed in a microscope, the bulb appears half trans- parent, and whitish; and of a softer consistence than the hair itself. The extremity of it is remarkably flexible, and some- times much darker than the rest of the bulb. The hair does not appear to extend completely to the end ofthe bulb. Neither blood-vessels nor nerves have been traced to these bulbs, although it is probable they extend there: for the operation of extracting hair by the roots is generally very painful; and blood sometimes appears in the pore from which the hair is extracted. The body of the hair appears to be composed of smaller fibres, enclosed in a membrane which often is imperfect at the extremity; in consequence of which the fibres often separate from each other, or split. Within the hair is diffused the substance upon which its colour depends: this does not appear to be essential to the structure, as in the advance of life the hair is so generally without it, while its structure continues unchanged, although it becomes less flexible. The colour of the hair appears to have some connexion with * Dr. Dom. Nardo, of Padua, asserts that he has succeeded frequently upon him- Belf, in transplanting a hair with its bulb, from one of the pores of the head into one ofthe pores of the chest; which is done by enlarging the latter pore with a needle, introducing the bulb into it with exactness, and exciting a slight inflammation around it by friction. The planted hair takes root, grows, and in process of time, undergoes the usual changes,—becomes gray, and is shed.—Giorn delV Ital— 442 BULBS OF THE HAIRS. the colour of the rete mucosum, as it is so generally black when the rete mucosum is dark coloured. The sudden change of colour in consequence of fright or grief, is a very rare occurrence indeed ; but Bichat relates an instance which came under his observation, in which the hair became perfectly white in one night, in consequence of grief. —The substance of the hair is of a corneous nature like the epidermis. Each hair consists of two parts, a bulb or follicle, and a stalk or hair proper. —The follicle is ovoidal, and consists of two membranes. The exterior is white, firm, and continuous with the cutis vera; the interior, which is thin, soft and reddish, appears to be con- tinuous with the rete mucosum. —The cavity of the follicle is filled up at the bottom with a conical papilla, into which, according to Beclard, the nerves and blood-vessels may be seen running below. Rudolphiand Andral, have traced nerves into the whiskers of the seal; Shaw has done the same, and discovered that they were branches of the fifth pair. The root of the hair possesses a coni- cal cavity, in ^hich is lodged the point of the papilla which appears to secrete the matter of the hair, and cause its growth, by the. continuous deposition of new matter at its root, as takes place in regard to the nails of man, and the horns of animals; this deposit of new matter in the fluid state, has been seen between the hair and papilla. It is sometimes secreted in pro- fusion, especially in the head ; and has appeared to me, by over- flowing from the follicles, and drying in the form of scales, to be the source of the dandriff. —The epidermis is reflected from the mouth of the follicle, and lost upon the surface of the hair. —The hair, when examined with the microscope, appears to be covered externally with small scales, and to be hollow internally. The latter, however, appears to be in the human hair, an optical illusion. The stalks of hairs have neither vessels nor nerves in their structure, and anatomists no longer admit STRUCTURE OF THE HAIRS. 443 a fluid in their interior described by Bichat and others as the marrow.* —Around the orifices ofthe follicle, and in the substance of its neck according to Gaultier, we find a number of minute sebaceous glands, that secrete an unctuous fluid, which imbues the hair and preserves its softness and pliability. The hairs are hygrometrical, and increase in length and thickness when exposed to humidity; and are shortened again by dry heat. —From the changes which take place in regard to the colour ofthe hair, there is reason to believe, that it is transversed by some fluid. This passes along the hair by imbibition, from the root upwards, in consequence of its hygrometrical nature, passing up through the spongy or cellular tissue of which the body of the hair appears to me to be formed. This fluid is derived from the surface of the skin forming the papilla, and is analogous to the fluid of the rete mucosum, and corresponds more or less in colour with that ofthe skin and iris. —The hairs vary much in size, but appear all to be constructed on the same plan. They have different names in different parts of the body, as beard, whiskers, eyelashes, &c. The minute hairs generally spread over the body, are Trailed down or duvette, and those which cover the scalp, in man, have particu- larly appropriated to them the term of hair. In the white or Caucasian variety of the human race, the hairs of the head are very numerous, fine, long, and vary in colour from white to black: in the Mongolian they are straight, black and short: in the Negro, black, fine, thick and crisped : in the Indian, black, straight, fine and thick: and in the Malay, thick and frizzled. —Their size and number vary in regard to their colour. Withoff, has calculated that in a quarter of an inch square of skin there are one hundred and forty-seven black hairs, one hundred and sixty-two chestnut, and one hundred and eighty- two, blond. —The hairs are composed chemically, agreeably to Vauquelin, * Note to Bichat, 4th edit. Paris.— 444 CHEMICAL COMPOSITION OF THE HAIRS. chiefly of animal matter, of some concrete white, and some black oily matter; iron, oxide of manganese, phosphate and carbonate of lime, silex and sulphur. The change of colour to gray, is said to be owing to a preponderance in the formation of the white oily substance, and the developement of some phosphate of magnesia.* The shape of the hairs vary in dif- ferent parts. —From the large size of the nerves which enter the papillae, to which the hairs are attached, they become in many animals delicate instruments of touch. The formation of the hair depends upon the follicle ; while this remains healthy, though the hair should be removed by its roots, it will again be repro- duced. —Boucheron in a recent work on the hair, says that in bald- ness the bulbs are often only partially atrophied, a circumstance which does not render hopeless the idea of their recovering their original functions, and re-secreting the horny matter which forms the hair, under the influence of certain stimuli. —Round the bulbs of the larger hairs, are found some smaller ones, which, as seen in extraction of the former in some cases of tinea capitis, are sometimes developed to an unusual extent. —It has also been frequently observed, that in many women the almost imperceptible down of the face presents, after the fortieth or fiftieth year of age, a great increase of develope- ment. The bulbs of the hairs are obliquely and confusedly implanted in the dermis—hence when one straggling white hair is extracted from the head, the neighbouring ones speedily whiten in their turn from the disturbance and injury which their bulbs have suffered. —There are many hairs, which are developed so feebly that they do not pass the epidermis, but roll and curve themselves under it. From accidental circumstances the energy of the bulbs of these hairs is sometimes so increased, that skin which had been previously smooth, becomes hairy. Boucheron, attri- butes the colour of the hair to a peculiar animal oil, secreted * C. P. Ollivier. CHEMICAL COMPOSITION OF THE HAIRS. 445 by the bulbs, and varying consequently in its properties in different individuals. It is to a change in the colour of this oily matter, arising from a variety of causes, which enfeeble the generalsystem, as grief, intense study, &c, that is attributed the whitening of the hair.—• The skin, constructed as above described, answers a fourfold purpose in the animal economy. It is the organ of touch. It covers and protects the whole structure. It is the outlet for a large proportion ofthe insensible perspiration, and it performs to a certain extent absorption. Many facts have been noticed by practitioners of medicine, which prove that it has a connexion with the lungs and stomach, which is not yet explained by an- atomy. As one of these, an effect of the urticaria or nettle-rash may be mentioned. This eruption sometimes relieves completely the spasmodic croup ; and in other cases, nausea and vomiting. Some children, when affected with this species of croup, are relieved by rubbing the skin with harsh woollen cloth. In some places, the urticaria and the affection of respiration are so much regarded as symptoms ofthe same disease, that the term hives is used as the name for each of them. 38 PART V. OF THE NOSE, THE MOUTH, AND THE THROAT. CHAPTER XII. OF THE NOSE. The prominent part of the face, to which the word nose is exclusively applied in ordinary language, is the anterior cover- ing of two cavities which contain the organ of smelling. These cavities are formed principally by the upper maxillary and palate bones; and, therefore, to acquire a complete idea of them, it is necessary to study these bones, as well as the os ethmoides, the vomer, and the ossa spongiosa inferiora, which are likewise concerned in their formation. In addition to the description of these bones, in the account of the bones of the head, it will be useful to study the descrip- tion of the cavities of the nose which follows it, (see page 122.) After thus acquiring a knowledge ofthe bony structure, the student will be prepared for a description of the softer parts. Of the External Nose, The superior part ofthe nose is formed by the ossa nasi, and the nasal processes of the upper maxillary bones, which have been already described, (see pages 86-89); but the inferior part, which is composed principally of cartilages, is much more complex in its structure. The orifice, formed by the upper maxillary and nasal bones, is divided by a cartilaginous plate, which is the anterior and inferior part of the septum, or partition between the two cavi- ties of the nose. The anterior edge of this plate projects beyond the orifice in the bones, and continues in the direction of the OF THE NOSE. 447 suture between the ossa nasi. This edge forms an angle with the lower edge of the same cartilage, which continues from it in a horizontal direction, until it reaches the lower part of the orifice of the nose, at the junction of the palatine processes of the upper maxillary bones; where a bony prominence is formed, to which it is firmly united. The upper part of the anterior edge of this cartilage, which is in contact with the ossa nasi, is flat, and is continued into two lateral portions that are extended from it one on each side, and form a part of the nose : these lateral portions are sometimes spoken of as distinct carti- lages, (superior lateral,) but they are really continuations of the middle portion or septum. Below the lower edge of these late- ral portions are situated the fibro carti- lages which form the orifices of the nose, or the nostrils. Of these, there is one of considerable size, (inferior late- ral,) and several small fragments, on each side of the septum. Each of the larger cartilages forms a portion of an oval ring, which is placed obliquely on the side of the septum : so that the extremity ofthe oval points downward and forward, while the middle part of the oval is directed upwards and back- wards. The sides of this cartilage are flat, and unequal in breadth. The narrowest side is internal, and projects lower down than the cartilaginous septum; so that it is applied to its fellow of the other nostril. The exter- nal side is broader, and continues backward and upward to a considerable distance. *Fig. 116.—a, b, Ossa nasi, which show above, the serrated surface by which they are united to the os frontis. c, d, Superior lateral cartilage, e, Vertical carti- laginous septum ofthe nose. /,/, Sesamoid cartilages, filling up part ofthe vacuity here, g, I, Oval or inferior lateral cartilages, or cartilages of the alae nasi; below they are thin and curved so as to form the arch of the anterior nares. h, i, k, -Small square cartilages appended to the alae nasi and circumscribing the outer and back part of the nostrils, m, n, o, Same parts of the right side. 448 OF THE NOSE. The upper and posterior part of this oval ring is deficient; but the remainder ofthe nostril consists of several small pieces of cartilage, (cartilages carres,) which are fixed in a ligamen- tous membrane that is connected by each of its extremities to the oval cartilage, and thus completes the orifice. The anterior parts of the oval cartilage form the point of the nose; and the ligamentous portions, the alae or lateral parts of the nostrils. When the external integuments and muscles are removed from the lower portion of the nose, so that the internal mem- brane and these cartilages only remain, the internal membrane will be found attached to the whole bony margin of each ori- fice, and to each side of the whole anterior edge of the middle cartilage, which projects beyond the bones. This membrane is afterwards continued so as to line the oval cartilages and the elastic membrane of the ala nasi, to the margin of the orifice of the nostril. The internal portions of the oval cartilages being situated without the septum, and applied to each other, they form the external edge of the partition between the nostrils, or the columna nasi; which is very movable upon the edge of the middle cartilage. The orifices of the nostrils, thus constructed, are dilated by that portion of the muscle, called Levator Labii Superioris Alaeque Nasi, which is inserted into the alae nasi. They are drawn down by the depressor labii superioris alaeque nasi. They are pressed against the septum and the nose by the muscle called Compressor Naris, which has how- ever an opposite effect when its upper extremity is drawn upwards by those fibres of the occipito frontalis, which descend upon the nose, and are in contact with it. The end of the nose is also occasionally drawn down, by some muscular fibres which descend from it, on the septum of the nose, to the orbicularis oris: they are considered as a por- tion of this muscle by many anatomists, but were described by Albinus as a separate muscle, and called Nasalis Labii Supe- rioris. OF THE CAVITIES OF THE NOSE. 449 When inspiration takes place with great force, the alee nasi would be pressed against the septum, if they were not drawn out and dilated by some of the muscles above mentioned. Of the Cavities of the Nose. To the description of the osseous parts of the nasal cavities in page 89, it ought now to be added, that the vacuity in the anterior part of the osseous septum is filled up by a cartilagi- nous plate, connected with the nasal lamella of the ethmoid bone above, and with the vomer below. This plate sends off those lateral portions already described, which form the carti- laginous part ofthe bridge ofthe nose. It should also be observed that at the back parts of these cavities are two orifices called the Posterior Nares, (see fig. 117, p. 456,) which are formed by the palate bones, the vomer, and the body of the sphenoidal bone, and are somewhat oval. The nasal cavities, thus constructed, are lined by a peculiar membrane, which is called pituitary from its secretion of mucus, or Schneiderian after the anatomist who described it with accuracy.* This membrane is very thick and strong, and abounds with so many blood-vessels, that in the living subject it is of a red colour. It adheres to the bones and septum of the nose like the periosteum, but separates from them more easily. The surface which adheres to the bones has some resemblance to periosteum, while the other surface is soft, spongy, and rather villous. Bichat seems to have considered this membrane as formed of two lamina, viz. periosteum, and the proper mucous membrane ; but he adds, that it is almost impossible to separate them. It has been supposed that many distinct glandular bodies were to be seen in the structure of this membrane by examin- ing the surface next to the bones ;t but this opinion is adopted * Conrad Schneider, a German professor, in a large work, " De Catarrhis," published about 1660. + See Winslow, Section X. No. 337. 3S* 450 SCHNEIDERIAN MEMBRANE. by very few of the anatomists of the present day. The texture of the membrane appears to be uniform ; and on its surface are a great number of follicles of various sizes, from which flows the mucus of the nose. These follicles appear like pits, made by pushing a pin obliquely into a surface which retains the form ofthe impression. They can be seen very distinctly with a common magnifying glass when the membrane is immersed in water, both on the septum and on the opposite surface. They are scattered over the membrane without order or regularity, except that in a few places they occur so as to form lines of various lengths, from half an inch to an inch. The largest of them are in the lower parts of the cavities. —The surface of this membrane when examined with the microscope, is found to be furnished with the ciliary epithe- lium, consisting of minute projections or columns, thickly set with fine cilia or fringes, which have a peculiar vibratile mo- tion of their own for carrying on fluids, not well understood.— It may be presumed that the secretion of mucus is effected here by vessels which are mere continuations of arteries spread upon a surface analogous to the exhalents, and not convoluted in circumscribed masses, as in the case of ordinary glands. The arteries of this membrane are derived from various sources: the most important of them is the nasal branch of the internal maxillary, which passes into the nose through the spheno-palatine foramen, and is therefore called the Spheno- palatine Artery. It divides into several twigs, which are spent upon the different parts of the surface of the nasal cavi- ties. Two of them are generally found on the septum of the nose: one, which is small, passes forwards near the middle; the other, which is much larger, is near the lower part of it. Two small arteries, called the anterior and posterior eth- moidals, which are branches of the ophthalmic, enter the nose by foramina of the cribriform plate of the ethmoidal bone. These arteries pass from the orbit to the cavity of the cranium, and then through the cribriform plate to the nose. In addition to these, there are some small arteries derived from the infra- OLFACTORY NERVES. 451 orbital, the alveolar and the palatine, which extend to the Schneiderian membrane; but they are not of much importance. The veins of the nose correspond with the arteries. Those which accompany the ethmoidal arteries open into the ocular vein of the orbit, which terminates in the cavernous sinuses of the head. The other veins ultimately terminate in the external jugulars. The nerves of the nose form an important part of the struc- ture ; they are derived from several sources ; but the most important branches are those of the olfactory. The olfactory nerves form oblong bulbs, which lie on each side of the crista gilli, on the depressed portions of the cribri- form plate ofthe ethmoid bone, within the dura mater. These bulbs are of a soft consistence, and resemble the cortical part of the brain mixed with streaks of medullary matter. They send off numerous filaments, which pass through the foramina of the ethmoid bone, and receive a coat from the dura mater as they pass through it. These filaments are so arranged that they form two rows, one running near to the septum, and the other to the surface of the cellular part of the ethmoid bone, and the os turbinatum: and in addition to these are some intermediate filaments. When the Schneiderian membrane is peeled from the bones to which it is attached, these nervous filaments are seen passing from the foramina of the ethmoid bone to the attached surfaces: one row passing upon that which covered the septum, and the other to that of the opposite side; while the intermediate fila- ments take an anterior direction, but unite to the membrane as soon as they come in contact with it. All of these can be traced down wards on the aforesaid surfaces of the membrane for a considerable distance, when they grad- ually sink into the substance of the membrane, and most pro- bably terminate on the internal villous surface; but they have not been traced to their ultimate termination. They ramify so that the branches form very acute angles with each other. On the septum the different branches are arranged so as to form 452 SPHENO-PALATINE AND OTHER NERVES OF THE NOSE. brushes, which lie in contact with each other. On the opposite sides, the different ramifications unite, so as to form a plexus. Dr. Soemmering has published some very elegant engravings of the nose, representing one of his dissections, which appears to have been uncommonly minute and successful.* These represent the ramifications as becoming more expanded and delicate in the progress towards their terminations, and as observing a tortuous course, with very short meandering flexures. It is to be observed that the ramifications of the olfactory nerve, thus arranged, do not extend to the bottom of the cavity. On the external side, they are not traced lower than the lower edge ofthe ethmoid, or of the superior spongy bone: and on the septum, they do not extend to the bottom, although they are lower than the opposite side. On the parts of the mem- brane not occupied by the branches of the olfactory nerves, several other nerves can be traced. The nasal twig of the ophthalmic branch ofthe fifth pair, after passing from the orbit into the cavity of the cranium, proceeds to the nasal cavity on each side by a foramen of the cribriform plate; and after send- ing off some fibrillae, descends upon the anterior part of the septum to the point of the nose. The spheno-palatine nerve, which is derived from the second branch of the fifth pair, and enters the nose by the spheno-palatine foramen, is spread upon the lower part of the septum and of the opposite side of the nose also, and transmits a branch through a canal in the fora- men incisivum to the mouth. Several small branches also pass to the nose from the palatine and other nerves; but those already mentioned are the most important. A question has been proposed, whether the olfactory nerve is exclusively concerned in the function of smelling, or whether the other nerves above mentioned are also concerned in it. It seems probable that this function is exclusively performed by the olfactory nerve, and that the other nerves are like the ophthalmic branch of the fifth pair, with respect to the optic * They are entitled, Icones Organorum Humanorum Olfactus. EXTENT OF THE SCHNEIDERIAN MEMBRANE. 453 nerve. In proof of this, it is asserted that the sense of smelling has entirely ceased in some cases, where the sensibility to mechanical irritation of every kind has remained unchanged. If the olfactory nerve alone is concerned in the function of smelling, it follows, that this function must be confined to the upper parts of the nasal cavities; but it ought to be remem- bered, that the structure of the Schneiderian membrane, in the lower parts of these cavities, appears exactly like that which is above. The surface of the nasal cavities and their septum, when covered with the Schneiderian membrane, correspond with the osseous surface formerly described. The membrane covers the bones and cartilage of the septum, so as to make one uniform regular surface. From the upper part of the septum, it is con- tinued to the under side ofthe cribriform plate ofthe ethmoid, and lines it; the filaments of the olfactory nerve passing through the foramina of that bone into the fibrous surface of the mem- brane. It is continued from the septum, and from the cribri- form plate, to the internal surface of the external nose, and lines it. It is also continued backwards to the anterior surface ofthe body of the sphenoidal bone; and, passing through the foramina or openings of the sphenoidal cells, it lines these cavities completely; but in these, as well as the other cavities, its structure appears somewhat changed; it becomes thinner and less vascular. At the above mentioned foramina, in some subjects, it forms a plate or fold, which diminishes the aperture considerably. From the upper surface of the nasal cavities, the membrane is continued downwards over the surface opposite to the sep- tum. On the upper flat surfaces of the cellular portions of the ethmoid, it forms a smooth uniform surface. Afterpassing over the first turbinated bone, or that called after Morgagni, it is reflected into the groove, or upper meatus immediately within and under it; the fold formed by the membrane, as it is reflect- ed into the meatus, is rather larger than the bone: and the edge of the fold therefore extends lower down than the edge of the bone, and partly covers the meatus like a flap, consisting 454 EXTENT OF THE SCHNEIDERIAN MEMBRANE. only of the double membrane. This fold generally continues backwards as far as the spheno-maxillary foramen, which it closes; the periosteum, exterior to the foramen, passing through it, and blending itself with the fibrous surface of the Schneide- Fig. 117.* * Fig. 117-^-is a vertical section, exhibiting a profile view from the inside of the cavities ofthe nostrils, mouth, and pharynx, a, The nose. 6, Upper lip, situated in front of the palatine arch, which runs horizontally backwards, and divides the cavity of the mouth from the nasal fossse. c, The tongue, the base of which is attached to the os hyoides d. e, The larynx, suspended from the os hyoides, by the thyreo-hoid ligaments which are seen intervening; it opens backwards towards the pharynx. /, Trachea, g, Cuneiform process of the occipital bone, united to the body ofthe sphenoid, and to which is chiefly suspended the pharynx h, which is laid open (in order to show its shape and position) by the removal of its right half, and is seen terminating below opposite the cricoid cartilage in the oesophagus, i, Com- mencement ofthe oesophagus, k, Section ofthe velum pendulum palatae, the lower point of which constitutes the uvula; above this is seen the opening of the posterior nares, 7, into the top part of the cavity of the pharynx; below this are seen the two half arches ofthe palate, o, Posterior half arch, r, Anterior half arch, the space or DISTRIBUTION OF THE SCHNEIDERIAN MEMBRANE. 455 rian membrane within. Here the spheno-palatine nerves and arteries join the membrane. Below this meatus, it extends over the middle, (formerly called the upper,) turbinated bone, and is reflected or folded inwards on the under side of this bone, and continued into the middle meatus below it. In the middle meatus, which is partly covered by the last mentioned turbina- ted bone, there are two foramina; one communicating with the maxillary sinus, and the other with the anterior cells rof the ethmoid and the frontal sinuses. The aperture into the maxil- lary sinuses is much less in the recent head, in which the Schneiderian membrane lines the nose, than it is in the bare bones. A portion of the aperture in the bones is closed by the Schneiderian membrane, which is extended over it: the re- mainder of the aperture is unclosed; and through this foramen, the membrane is reflected so as to line the whole cavity. As a portion of the foramen is covered by the membrane, and this portion, as well as the other parts of the cavity, is lined by the membrane, it is obvious that at the place where the membrane is extended over the foramen in the bone, it must be doubled; or, in other words, a part of the aperture of the maxillary sinus is closed by a fold of the Schneiderian membrane.* This aperture varies in size in different subjects, and is often equal in diameter to a common quill. It is situated in the cavity between these occupied by the tonsil gland or amygdala p. I, Sublingual gland, placed under the tongue, and communicating with the mouth by a small duct, (duc- tus Bartholinus:) many small ducts from this gland, open into the duct ofthe gland below, m, Sub-maxillary gland, situated below and behind the preceding gland. n, Thyroid gland, s, Vertical section of the border of the cervical vertebra, to which the pharynx is attached by cellular tissue, t, Spinal canal, u, Sec- tion of spinous processes and muscles of the neck, v, Left nostril, w, Bony palate, x, Trumpet-shaped orifice of the Eustachian tube, y, Inferior turbinated bone, covered by the Schneiderian membrane, z, Middle turbinated bone. 1 Su- perior turbinated bone, both covered with the same membrane. 2, Superior meatus. 3, Middle meatus. 4, Inferior meatus. 5, Place of opening of the ductus ad nasum. 6, Frontal sinuses. 7, The posterior nares. 8, Sphenoidal cell in the body of the Bphenoid bone, showing the orifice below, by which it communicates with the top of the pharynx ; above is seen the sella turcica of the sphenoid bone. * In the mucous membrane lining the cavities of the maxillary, sphenoid and ethmoid bones, no one has yet detected any mucous follicles. The pouch formed by the reflection of the membrane, seems itself to constitute a large follicle, from which mucus is abundantly secreted.—p. 456 OBSERVATIONS RESPECTING THE NOSE. middle of the meatus, and is covered by the middle turbinated bone immediately above it,—a prominence of the cellular structure of the ethmoid bone, which has a curved or semicir- cular figure. Near this prominence, in the same meatus, a groove terminates, which leads from the anterior ethmoid cells and the frontal sinuses. From the middle meatus, the membrane proceeds over the inferior turbinated bone, and is reflected round and under it into the lower meatus. It appears rather larger than the bone which it covers; and therefore the lower edge of the bone does not extend so low as the lower edge of the membrane, which of course is like a fold or plait. The membrane then continues and lines the lower meatus: here it appears less full than it is in the turbinated bone. In this meatus, near to its anterior end, is the lower orifice of the lachrymal duct; this is simply lined by the Schneiderian membrane, which is continued int< it, and forms no plaits or folds that effect the orifice. Orifice ofthe Eustachian Tube. Immediately behind each of the nasal cavities, on the exter- nal side, is the orifice of the Eustachian Tube. It has an oval form, and is large enough to admit a very large quill. Its posi- tion is oblique : the upper extremity being anterior to the other parts of the aperture, and on a line with the middle meatus, while the centre is behind the inferior turbinated bone. The lower part of the oval is deficient. This tube is formed poste- riorly by a cartilaginous plate. It is lined by the membrane continued from the nose. The cavities of the nose answer a twofold purpose in the animal economy; they afford a surface for the expansion of the olfactory nerves, and a passage for the external air to the windpipe, in respiration. The function of smelling appears to be dependent, to a certain degree, upon respira- tion. It has been asserted that unless the air passes in a stream through the nose, as in respiration, the perception of odour does not take place; that in persons who breathe through wounds and apertures in the windpipe, the function of smelling is not performed. It is rather in confirmation of this proposition, that most persons, when they wish to have an accurate perception of any odour, draw in air rapidly through the nose. Although the ultimate terminations of the olfactory nerves cannot be demonstrated like those of the optic and auditory nerves, it is probable, from the appearance of USES OF THE SINUSES OF THE NOSE. 457 the fibres, while they are distinguishable, that they are finally arranged with great delicacy. It is certain that the impressions from whence we derive the perceptions of many odours must be very slight, as some odorous bodies will impregnate the air of a large chamber for a great length of time, without losing any sensible weight. With respect to delicacy of structure and sensibility, it is probable that the nose holds a middle rank between the eye or ear, and the tongue : and on this account the mucus is necessary as a covering and defence of its surface. It has been ascertained, by the investigations of chemists, that this mucus contains the same ingredients as the tears already described, namely, animal mucus and water; and muriate of soda, and soda uncombined; phosphate of lime, and phos- phate of soda. The animal mucus, which is a most important ingredient in the composition, resem- bles the mucilage formed by some of the vegetable gums in several particulars; and differs from them in others. The mucus of the nose, if it remain there long after it is secreted, becomes much more viscid in consistence, and changes from a whitish colour to one which par- takes more or less of the yellow. It is probable than an incipient putrefaction may occasion these changes in it. The use of the frontal, maxillary and other sinuses, communicating with the nose, has been the subject of some inquiry. As there can be no stream of air through them, and as the membrane lining them is neither so thick, villous nor flexible as that lining the nose, it may be concluded, a priori, that they are not concerned in the function of smelling. This opinion is strengthened by the fact, that very young children, in whom these sinuses scarcely exist, enjoy the sense of smelling in per- fection. The following fact is also in support of it. The celebrated Desault attend- ed a patient, in whom one of the frontal sinuses was laid open by the destruction of the bone which covered it anteriorly. This patient was able to breathe a short time through the sinus when the mouth and nose were closed: at the request of Desault he breathed in this manner when a cup of some aromatic liquor was held near the opening ofthe sinus, and had not the least perception of odour. This ex- periment was repeated several times. Many physiologists believe that these sinuses have an effect in modulating the voice. 39 458 OF THE MOUTH. CHAPTER XIII. OF THE MOUTH. The general cavity of the mouth is formed anteriorly and laterally by the connexion of the lips and cheeks to the upper and lower jaws; so that the teeth and the alveoli of both jaws may be considered as within the cavity. Above, it is bounded principally by the palatine processes of the upper maxillary and palate bones, and the soft palate, which continues back- ward from them in the same direction. Below, the cavity is completed by several muscles, which proceed from almost the whole internal circumference of the lower jaw, and, by their connexions with each other, with the tongue and the os hyoides, form a floor or bottom to it. The tongue is particularly connected to this surface, and may be considered as resting upon and supported by it. To acquire an idea of the parietes of this cavity, after studying the upper and lower maxillary bones, the orbicularis oris and the muscles connected with it, especially the buccina- tor, ought to be examined; and also the diagastricus, the mylo-hyoideus, genio-hyoideus, and genio-hyoglossus. By this it will appear that the lips and cheeks, and the basis or floor of the mouth, are formed in a great measure by muscles. Upon the internal surface of these muscles, a portion of cellular and adipose substance is arranged, as well as glandular bodies of different sizes; and to these is attached the membrane which lines the inside of the mouth. This membrane passes from the skin of the face to the lips, and the inside of the mouth; and, although it is really a con- tinuation of the skin, there is so great a change of structure that it ought to be considered as a different membrane. At the orifice of the lips it is extremely thin, and so vascular, that it INTERNAL SURFACE OF THE MOUTH.--GUMS. 459 produces the fine florid colour which appears there in health. It is covered by a cuticle, called by some anatomists, Epithe- lium, which has a proportionate degree of delicacy, and can be separated like the cuticle in other parts. When this cuticle is separated, the lips and the membrane of the mouth appear to be covered with very fine villi, which are particularly apparent in some preparations of the lips after injection and maceration.* Under this membrane are many small glandular bodies of a roundish form, called glandulae labiales, whose excretory ducts pass through it to the inner surface of the mouth, for the pur- pose of lubrifying it with their secretion, which is mingled with the saliva. The membrane which lines the inside of the lips and cheeks, is somewhat different from that which forms the surface ofthe orifice ofthe mouth: it is not so florid; the blood-vessels in its texture are larger, and not so numerous. This change, however, takes place very gradually, in the progress of the membrane, from the orifice of the lips to the back part of the cheeks. Glandular bodies, like those of the lips, are situated immediately exterior to this membrane of the cheeks, between it and the muscles: their ducts open on its surface. These glands are called Buccales. This lining membrane is continued from the internal surface ofthe lips and cheeks to the alveolar portions ofthe upper and lower jaws, which are in the cavity of the mouth, and covers them, adhering firmly to the periosteum. The teeth appear to have passed through apertures in this membrane, and are surrounded by it closely at their respective necks. The portion of membrane, which thus invests the jaws, con- stitutes the gums ; which have now acquired a texture very different from that of the membrane from which they were continued. They are extremely firm and dense, and very vascular. It is probable that their ultimate structure is not perfectly understood. * Ruysch had a fine preparation of this structure. See Thesaurus VII. Tab. III. Fig. 5. 460 MEMBRANE LINING THE HARD OR BONY PALATE. In the disease called scurvy, they tumefy and lose the firm- ness of their texture: they acquire a livid colour, and are much disposed to hemorrhage. From the alveoli of the upper jaw, the lining membrane is continued upon the palatine processes of the upper maxillary and palate bones, or the roof of the mouth. The membrane of the palate is not quite so firm as that of the gums, and is also less florid: it adheres firmly to the peri- osteum, and thus is closely fixed to the bones. There is gen- erally a ridge on its surface, immediately under the suture between the two upper maxillary bones ; and some transverse ridges are also to be seen upon it. On the internal surface of this membrane, are small glandular bodies, whose ducts open on the surface of the palate. It is asserted, that this membrane has a limited degree of that sensibility which is essential to the functions of tasting; and that if certain sapid substances are carefully applied to it, their respective tastes will be perceived, although they have not been in contact with the tongue. The membrane is continued from the bones above mentioned to the soft palate, or velum pendulum palati, which is situated immediately behind them. This soft palate may be considered as a continuation of the partition between the nose and mouth ; it is attached to the posterior edge ofthe palatine pro- cesses of the ossa palati, and to the pterygoid processes of the sphenoidal bone. Its interior structure is muscular. The upper surface is covered by the membrane of the nose, the lower surface by the membrane which lines the mouth. The muscles, which contribute to the composition of this structure, are the circumflexi and the levatores palatii above, and the constrictores isthmi faucium and palato-pharyngei below. (See pages 318, 319.) Thus composed, the soft palate constitutes the back part of the partition between the nose and mouth. When viewed from before, with the mouth open, it presents towards the tongue an arched surface, which continues downwards on each side, until it comes nearly in contact with the edges of that organ. On each of the lateral parts of this SOFT PALATE.—UVULA. 461 arch, are two pillars, or rather prominent ridges, which project into the mouth. These ridges are at some distance from each other below, and approach much nearer above, so that they include a triangular space. They are called the lateral half arches of the palate, (see fig. 117, p. 455.) Each of them is formed by a plate or fold ofthe lining membrane ofthe mouth, and contains one of the two last mentioned muscles; the ante- rior, the constrictor isthmii faucium; the posterior, the palato- pharyngeus. These muscles, of course, draw the palate down toward the tongue when they contract. From the centre of the arch, near its posterior edge, is sus- pended the uvula, a conical body, which varies in length from less than half an inch, to rather more than one inch. It is connected by its basis to the palate ; but its apex is loose and pendulous. This body is covered by the lining membrane of the mouth. It contains many small glands, and a muscle also, the azygos uvulae, which arises from the posterior edge of the ossa palati, at the suture which connects them to each other, and, passing posteriorly upon the soft palate, extends from the basis to the apex of the uvula, into which it is inserted. By the action of this muscle, the length of the uvula can be very much diminished : and when its contraction ceases, that body is elongated.* The pendulous part of the uvula can also be moved, in cer- tain cases, to either side. It is commonly supposed, that the principal use of this little organ is to modulate the voice ; but there are good reasons for believing, that it has another object. It was remarked by Fallopius, (and the observation has been confirmed by many surgeons since his time,) that the uvula may be removed com- pletely without occasioning any alteration of the voice, or any difficulty of deglutition, if the soft palate be left entire. The soft palate is so flexible, that it yields to the actions of the levatores palati, which draw it up so as to close the poste- rior nares completely. * A careful dissection, shows two of these muscles.—p. 39* 462 THE TONGUE. It also yields to the circumflexi or tensores, which stretch it so as to do away its arched appearance. It is therefore very properly called the Palatum Molle, or soft palate. It is also frequently called the Velum Pendulum Palati, from the position which it assumes. The Tongue, which is a very important part of this structure, is retained in its position and connected with the parts adjoining it, by the following arrangements. The os hyoides, which, as its name imports, resembles the Greek letter u, or half an oval, is situated rather below the angles ofthe lower jaw, in the middle ofthe upper part ofthe neck. It is retained in its position by the sterno-hyoidei muscles, which connect it to the upper part of the sternum, by the coraco, or omo-hyoidei, which pass to it obliquely from the scapula; by the thyro-hyoidei, which pass to it directly upward from the thyroid cartilage, all of which connect it to parts below. To these should be added the stylo-hyoidei, which pass to it obliquely from behind and rather from above: the mylo-hyoidei, which come rather anteriorly from the lateral parts of the lower jaw ; and the genio-hyoidei, which arises from a situation directly anterior and superior to the chin. When these muscles are at rest, the situation of the os hyoides is, as above described, below the angles of the lower jaw : when those, in one particular direction act, while the others are passive, the bone may be moved upwards or downwards, backwards or forwards, or to either side. This bone may be considered as the basis of the tongue ; for the posterior extrem- ity of that organ is attached to it, and of course the move- ments of the bone must have an immediate effect upon those of the tongue. The tongue is a flat body of an oval figure, but subject to considerable changes of form. The posterior extremity, connected to the os hyoides, is commonly called its base ; the anterior extremity, which, when the tongue is quiescent, is rather more acute, is called its apex. The lower surface ofthe tongue is connected with a number STRUCTURE OF THE TONGUE. 463 of muscles, which are continued into its substance. This con- nexion is such, that the edges of the tongue are perfectly free and unconnected ; and so is the anterior extremity for a con- siderable distance from the apex towards the base. The substance of the tongue consists principally of muscu- lar fibres intermixed with a delicate adipose substance. It is connected to the os hyoides by the hyo-glossus muscle, and also by some other muscular fibres, as well as by a dense mem- branous substance, which appears to perform the part of a ligament. This connexion is also strengthened by the con- tinuance of the integuments from the tongue to the epiglottis cartilage, to be hereafter described ; for that cartilage is attached by ligaments to the os hyoides. The tongue is thin at its commencement at the os hyoides; but it soon increases in thickness. The muscular fibres in its composition have been considered as intrinsic, or belonging wholly to its internal structure ; and extrinsic, or existing in part outside of this structure. The lingualis muscles are intrinsic (see page 316): they are situated near the under sur- face ofthe tongue, one on each side, separated from each other by the genio-hyo-glossi muscles, and extending from the basis of the tongue to its apex. These muscles can be easily traced as above described: but there are also many fibres in the structure of the tongue, which seem to pass in every direction, and of course are different from those of the linguales muscles. To these two sets of fibres are owing many of the immensely varied motions ofthe different parts of the tongue. —According to Gerdy, (whose researches on this subject have been approved by Ribes and Breschet,) the structure of the tongue consists of the mucous membrane forming its outer coat, of a peculiar yellow lingual tissue which forms the liga- ment by which it is attached to the os hyoides and is extended along the middle line of the tongue to form a sort of raphe for the attachment of the transverse muscular fibres, and of the intrinsic and extrinsic muscles; it is mixed up with some delicate cellular and adipose tissue. The intrinsic muscles consist, 1st, of a superficial lingual muscle ; 2d, of two deep-seated, all of 464 STRUCTURE OF THE TONGUE. which are longitudinal; 3d, of transverse muscular fibres, reunited at the raphe, in the middle line of the tongue ; 4th, of some vertical fibres which are inserted on the lower surface of the mucous membrane. The ligament from the os hyoides extended along the middle line of the tongue, Blandin calls the lingual cartilage. The evidence in favour of its cartilaginous nature, is not very satisfactory in man. The epidermis of the tongue, which is much thicker than that of other portions of the mouth, forms, according to Blandin, a sheath open at top, round the sensitive papillae, which protects them when the tongue acts as an instrument of mastication, and through which the papillae protrude, to come fully in contact with the sapid sub- stance when tumefied or erected by the gustatory excitement.— In addition to these, are the extrinsic muscles, which origi- nate from the neighbouring parts, and are inserted and con- tinued into the substance ofthe tongue. See fig. 121. Among the most important of the muscles, are those which proceed from the chin, or the genio-hyo-glossi. They are in contact with each other; their fibres radiate from a central point on the inside of the chin, and are inserted into the middle of the lower surface of the tongue : the insertion commencing at a short distance from its apex, and continuing to its base. As the genio-hyo-glossi muscles have a considerable degree of thickness, they add much to the bulk of the tongue in the middle of the posterior parts of it. The hyo-glossi and the stylo-glossi, being continued into the posterior and lateral parts, contribute also to the bulk of these parts. The tongue, thus composed and connected, lies, when at rest, on the mylo-hyoidei muscles; and the space between it and these muscles is divided into two lateral parts by the above described genio-hyo-glossi. In the space above mentioned, is a small salivary gland, of an irregular oval form; the greatest diameter of which extends from before backwards, and its edges present outwards and inwards. It has several excretory ducts, the orifices of which form a line on each side of the tongue. This gland is very prominent under the tongue; and PAPILLJE OF THE TONGUE. 465 when the tongue is raised it is particularly conspicuous: it is called the Sublingual. The lining membrane of the mouth continues from the inside of the alveoli of the lower jaw, which it covers, over the sublin- gual glands to the lower surface of the tongue. In this situa- tion it is remarkably thin; but, as it proceeds to the upper surface of the tongue, its texture changes considerably, and on this surface it constitutes the organ of taste. The upper surface of the tongue, although it is continued from the thin membrane above described, is formed by a rough integument which consists, like the skin, of three lamina. The cuticle is very thin ; and under it, the rete mucosum* is thicker and softer than in other places. The true skin here abounds with eminences of various sizes and forms, all of which are denominated Papillae. The largest of these are situated on the posterior part of the tongue, and are so arranged that they form an angle rather acute, with its point backwards. They are commonly nine in number: they resemble an inverted cone, or are larger at their head than their basis. They are situated in pits or depressions, to the bottoms of which they are connected. In many of them there are follicles, or perforations, which have occasioned them to be regarded as glands. They are called Papillae Maximae, or Capitatas. The papillae, next in size, are denominated fungiform by some anatomists, and Mediae, or Semilenticulares by others. They are nearly cylindrical in form, with their upper extremi- ties regularly rounded. They are scattered over the upper surface of the tongue, in almost every part of it, at irregular distances from each other. The third class are called conoidal or villous. They are very numerous, and occupy the greatest part of the surface of the tongue. Although they are called conoidal, there is a great * M. Bichat appears to have had doubts whether the real rete mucosum existed here. He says that he could only perceive a decussation of vessels in the intervals ofthe papilla?, which, as he supposes, occasioned the florid colour ofthe tongue. 466 PAPILL2E OF THE TONGUE. difference in their form; many of them being kirregularly angular and serrated as well as conical. Soemmering and other German anatomists consider the smallest papillae as a fourth class, which they call the filiform: these lie between the others. It is probable that these papillae are essential parts of the organ of taste; and their structure is of course an interesting object of inquiry. The nerves of the tongue have been traced to the papillas, and have been compared by some anatomists to the stalk of the apple, while the papillae resembled the fruit; but their ultimate termination does not appear to have been ascer- tained.* —The papillae maximae or capitatae, are supplied, accor- ding to Cloquet, by filaments from the glosso-pharyngeal nerve, the fungiformes by filaments from the fifth. The papillae maximae appear to consist only of a collection of mucous follicles, which differ only from those of the soft palate and lips, by standing out more in relief. —The follicles of each papilla open occasionally upon the side; several open by a common orifice at the top of the papilla, which is often very visible to the naked eye, as a little reddish point. Weber succeeded in injecting this orifice with mercury, and found it led to a central cavity irregularly divided by septae into cells, visible to the naked eye, having some resemblance to, but much larger than those of the parotid. Other mucous follicles of a simpler kind are spread over the whole surface of the tongue between the smaller papillae. Some are mere small pouches, opening by simple orifices, without canals. Others are more complicated, and according to Weber, who filled them with mercury, have ducts three or four lines in length, which run down between the muscular fibres of the * In the explanation of the plates, referred to in the following sentence, Soemmer- ing observes, that when the fibrillae of the lingual nerve of the fifth pair are traced to the papillae of the second class, they swell out into a conical form; and these ner- vous cones are in such close contact with each other, that the point of the finest needle could not be insinuated into the papillae without touching a nerve. BLOOD-VESSELS OF THE TONGUE. 467 tongue, to terminate in little flattened sacs divided into several cells, and having sometimes, a diameter of three lines. —From all these follicles, comes that profusion of mucous secretion, which we see covering the tongue in diseases. —He describes the sebaceous glands of the skin as being analagous in structure to these follicles, as well as those of the trachea and of the inside of the lips and cheeks.— Soemmering has lately published some elegant engraved copies of drawings of these papillae, when they were magnified twenty-five times; from which it appears that a very large number of vessels, particularly of arteries, exist in them. These vessels are arranged in a serpentine direction, and are prominent on the surface; but they appear doubled, and the most prominent part is the doubled end.—This arrangement of vessels is perceptible on the sides of the tongue, as well as on the papillae.— Behind the large papillae is a foramen, first described by Morgagni, and called by him Foramen Ccecum. It is the orifice of a5 cavity which is not deep ; the excretory ducts of several mucous glands open into it. On the upper surface of the tongue, a groove is often to be seen, which is called the linea mediana, and divides it into two equal lateral parts.* Below, the lining membrane of the mouth, as it is continued from the lower jaw to the tongue, forms a plait, which acts as a ligament, and is called the fraenum lin- guae. It is attached to the middle of the tongue, at some dis- tance behind the apex. The tongue is well supplied with blood-vessels, which are derived from the lingual branch of the external carotid on each side. This artery passes from the external carotid, upwards, inwards, and forwards, to the body of the tongue. In this course it sends off several small arteries to the contig- uous parts, and one which is spent about the epiglottis and the adjoining parts, called the Dorsalis Linguae. About the anterior edge of the hyo-glossus muscle, it divides into two * This groove indicates the position of the middle raphe of Gerdy. 468 BLOOD-VESSELS OF THE TONGUE. large branches: one of which, called the Sublingual, passes under the tongue between the genio-hyo-glossus and the sub- lingual gland, and extends near to the symphysis of the upper jaw; sending branches to the sublingual gland, to the muscles under the tongue, to the skin, and the lower lip. The other is in the substance of the tongue, on the under side near the sur- face, and extends to the apex. The veins of this organ are not so regular as the arteries: they communicate with the external jugular, and some of them are always very conspicuous under the tongue: these are called ranular. It is to be observed, that the vessels on each side have but little connexion with each other; for those of one side may be injected while the others continue empty. The tongue is also well supplied with nerves, and derives them from three different sources on each side, namely, from the fifth, the eighth, and ninth pairs of the head. The lingual portion of the third branch of the fifth pair passing under the tongue, enters its substance about the middle, and forms many minute branches, which pass to the papillae of the forepart of the tongue. The glosso-pharyngeal portion of the eighth pair, sending off several branches in its course, passes to the tongue near its basis, and divides into many small branches, which are spent upon the sides and middle of the root of the tongue, and also upon the large papillae. The ninth pair of nerves are principally appropriated to the tongue. They pass on each side to the most fleshy part of it, and after sending one branch to the mylo-hyoideus, and another to communicate with the lingual branch of the fifth pair, they are spent principally upon the genio-glossi, and linguales muscles. The tongue answers a threefold purpose. It is the princi- pal organ of taste. It is a very important agent in the articu- lation of words, and it assists in those operations upon our food, which are performed in the mouth. PAROTID GLAND. 469 The Salivary Glands. The salivary glands have such an intimate connexion with the mouth that they may be described with it.* There are three principal glands on each side: the Parotid, Submaxillary, and the Sublingual. They are of a whitish or pale flesh colour, and are composed of many small united masses or lobuli, each of which sends a small excretory duct to join similar ducts from the other lobuli, and thereby form the great duct of the gland. The Parotid is much larger than the other glands. It occupies a large portion of the vacuity between the mastoid process and the posterior parts of the lower jaw. It extends from the ear and the mastoid process over a portion of the masseter muscle, and from the zygoma to the basis ofthe lower jaw. Its name is supposed to be derived from two Greek words which signify contiguity to the ear. It is of a firm con- sistence. It receives branches from the external carotid artery and from its facial branch. From the anterior edge of this gland, rather above the middle, the great duct proceeds anteriorly across the masseter muscle ; and, after it has passed over, it bends inward through the adipose matter ofthe cheek to the buccinator muscle, which it perforates obliquely, and opens on the inside of the cheek opposite to the interval between the second and third molar teeth of the upper jaw. The aperture of the duct is rather less than the general diameter of it, and this circumstance has the effect of a valve. When the duct leaves the parotid, several small glandular bodies called socise parotidis, are often attached to it, and their ducts communicate with it. The main duct is sometimes called ductus stenonianus, after Steno, who first described it. When the mouth is opened wide, as in gaping, there is often a jet of saliva from it into the mouth. The parotid gland furnishes the largest proportion of saliva. It covers the nerve called Portio Dura,aitex it has emerged from the foramen styto-mastoideum. * For a further account of glands, see General Anatomy of Glandular System. 40 470 ULTIMATUM STRUCTURE OF THE SALIVARY GLANDS. —This nerve after being covered a short distance by the gland, enters its substance, and forms there the plexus called pes anserinus, so as to leave a portion ofthe gland on the inner face of the nerve. The external carotid artery likewise traverses the gland and is situated rather more exteriorly than the nerve, so as to leave about one-third of the gland on its inner face. Branches from the artery are sent off in various direc- tions as it traverses the gland, to the face, and to the structure of the gland itself. —The duct of Steno, is very feebly attached to the surrounding parts, and is accompanied by many branches of the middle division of the facial nerves, and some small arteries which supply its walls ; it is covered only by the skin, some adipose tissue, by some fibres of the platysma myoides, and the zygomaticus major which crosses it obliquely. Its general diameter is about a line ; and it is very distensible. It will be found, according to the rule laid down by Dr. Physick, under a line drawn from the lobe of the ear, to the tip of the nose. Fig. 118. —The duct is composed of two coats, one, # external, white, fibrous, and resisting ; the other, internal, is a mucous membrane, con- tinuous with the lining membrane of the mouth, and appears to differ from it only in being paler. —Fig. 118, is a microscopical representation of the structure of a portion of the parotid gland of a young infant, after it had been minutely injected with mercury from the duct of Steno, by E. H. Weber, of Leipzic. The small figure, to the right, is the natural size of the piece magnified, in which the salivary ducts were filled with the fluid to their very terminations. A branch ofthe salivary duct, is seen on the right margin of this figure, ramifying like the branch of a tree. These ramifications never anastomose together, and are of much greater size than the capillary blood-vessels. Each ramification, at its termination, resolves itself into cells densely compacted together, like a THE SUBMAXILLARY GLAND. 471 bunch of grapes upon its stem, a, a, a. Some of the cells open by a minute excretory tube directly into the salivary duct. In other instances some of the ducts of the cells unite into a common tube, before entering the salivary duct. The cells are not round, and vary among themselves in regard to size. —The average diameter of these cells, measured by a micro- meter, were found by Weber, to be the T|„¥th part of an inch, which he finds to be three times greater than that of the most delicate sanguineous vessels. The cellular structure of the parotid, seems therefore to be very analogous to the cellular structure ofthe lungs discovered by Soemmering and Reisseis- sen, the cells of the lungs, however, being five or six times larger than those of the parotid. The elaborate researches of Weber and Muller, have shown also that this is the common mode of termination of the excretory ducts in the different glands of the body ; viz. that they terminate in closed cells, upon which ramify the delicate secretory capillary vessels.— The second gland is called the Submaxillary. It is much smaller than the parotid, and rather round in form. It is situated immediately within the angle of the lower jaw, between it on the outside, and the tendon of the digastric muscle and the ninth pair of nerves internally. Its posterior extremity is connected by cellular membrane to the parotid gland ; its anterior portion lies over a part of the mylo-hyoideus muscle; and from it proceeds the excretory duct, which is of considerable length, and passes between the mylo-hyoideus and genio-glossus muscles along the under and inner edge of the sublingual gland. In this course the duct is sometimes surrounded with small glandular bodies, which seem to be appendices to the sublingual gland. It terminates under the tongue, on the side of the frsenum linguae, by a small orifice which sometimes forms a papilla.* (See fig. 117, p. 454.) * Lassus informs us that Oribases, afterwards all the Arabians, and subsequently Guy De Chauliac, Lanfranc, Achillini, Berenger De Carpi, Charles Etienne, Cas- serius and several others have given the description of these salivary ducts; notwith- standing which, Wharton, a physician of London, attributed to himself the discovery of them on the bullock, in 1656.—h. 472 SUBLINGUAL GLAND. The orifice is often smaller than the duct; in consequence of which, obstruction frequently occurs here, and produces the disease called ranula. The Sublingual gland, which has already been mentioned, lies so that, when the tongue is turned up, it can be seen pro- truding into the cavity of the mouth, and covered by the lining membrane, which seems to keep it fixed in its place. It lies upon the mylo-hyoideus, by the side of the genio-hyoideus; and is rather oval in form, and flat. Its greatest length is from before backwards; its position is rather oblique, one edge being placed obliquely inwards and upwards, and the other outwards and downwards. It has many short excretory ducts, which open by orifices arranged in a line on each side : they are discovered with difficulty on account of their small size, and sometimes amount to eighteen or twenty in number. In some few instances, this gland sends off a single duct, which com- municates with the duct of the submaxillary gland. —The duct of the Submaxillary gland is called the duct of Wharton, (ductus Whartonionus) from an English anato- mist who first described it. It is accompanied in nearly the whole of its course by the lingual branch of the fifth pair of nerves. —The usual arrangement of the ducts of the sublingual gland is as follows: six or eight run from the upper part ofthe gland, to open by the side of the fraenum linguae. Five or six others proceed from its sides to open separately in the mucous membrane above the gland. Several open into the duct of Wharton which runs by the side of the gland; these most frequently unite to form a single duct, called the duct of Bar- tholinus, or duct of Rivinus. This I have frequently succeeded in distending with mercury from the duct of Wharton. —The structure and office of these salivary glands appear the same, and not unfrequently a slight continuation of structure is observed at the two extremities ofthe submaxillary gland.— The salivary fluid secreted by these glands is inodorous, insipid, and limpid, like water; but much more viscid, and of greater specific gravity. Water constitutes at least four-fifths OBSERVATIONS ON THE TONGUE. 473 of its bulk ; and animal mucus one half of its solid contents. It also contains some albumen; and several saline substances; as the muriate of soda, and the phosphates of lime, of soda, and of ammonia. It is probable that this fluid possesses a solvent power with respect to the articles of food. There are small glandular bodies, situated between the masseter and buccinator muscles, opposite to the last molar tooth ofthe upper jaw, whose nature is not well understood: they are called Glandulss molares. They are believed to be mere mucous glands, The motions of the tongue are very intelligible to a person who has a preparation of the lower jaw before him, with the tongue in its natural situation, and the mus- cles which influence it, properly dissected. Its complicated movements will ap- pear the necessary result of the action of those muscles upon it, and the os hyoides; and also upon the larynx, with which the os hyoides is connected. The muscular fibres of the tongue itself are also to be taken into this view, as they act a very important part. Although the tongue appears very necessary, in a mechanical point of view, to the articulation of many words, yet there are cases where it has been entirely deficient, in which the parties thus affected, have been able to speak very well in general, as well as to distinguish different tastes.* The tongue is also a very delicate organ of touch.—We can perceive the form ofthe teeth, and the state of the surface of the mouth, more accurately by the application ofthe tongue than of the fingers. On the three nerves which go to the tongue, it is generally supposed that the lingual portion of the third branch ofthe fifth pair is most immediately concerned in the function of tasting, as it passes to the front part ofthe surface ofthe tongue. The glosso-pharyngeal are probably concerned in the same function on the posterior part, while the ninth pair of nerves seems principally spent upon the muscular parts ofthe organ. It is obvious that the tongue is most copiously supplied with nerves. This probably accounts for the great facility of its motions, and the power of continuing them. * There is a very interesting paper on this subject, in the Memoirs of the Academy of Sciences for the year 1718, by Jussieu; in which he describes the case of a female fifteen years old, examined by himself, who was born without a tongue. In this paper he refers to another case, described by Rolland, a surgeon of Saumur, of a boy nine years old, whose tongue was destroyed by gangrene. In each of these cases the subject was able to articulate very well, with the exception of a few letters; and also enjoyed the sense of taste. 40* 474 OF THE THROAT. CHAPTER XIV. OF THE THROAT. To avoid circumlocution, the word throat is used as a general term to comprehend the structure which occurs behind the nose and mouth, and above the oesophagus and trachea. This structure consists, 1st. Ofthe parts immediately behind the mouth, which con- stitutes the Isthmus ofthe Fauces: 2d. Of the parts which form the orifice of the windpipe, or the Larynx ;—and 3d. Of the muscular bag, which forms the cavity behind the nose and mouth, that terminates in the oesophagus or the Pharynx. Of the Isthmus ofthe Fauces. In the back part of the mouth, on each side, are to be seen the two ridges or half arches, passing from the soft palate to the root of the tongue, (see fig. 117, p. 454,) formed by plaits of the mucous membrane, containing muscular fibres. The anterior plait, which contains the muscle called Constrictor Isthmi Faucium, passes directly from the side of the root of the tongue to the palate, and terminates near the commence- ment of the uvula. The posterior plait runs from the palate obliquely downwards and backwards, as it contains the palato- pharyngeus muscle, which passes from the palate to the upper and posterior part of the thyroid cartilage. In the triangular space between these ridges is situated a glandular body, called the Tonsil or Amygdala* This gland * It is named amygdala, from its resemblance in form and appearance to an al- mond covered by its shell. The exterior or adhering surface of the tonsil gland is connected by the means of cellular tissue to the superior constrictor muscle of the pharynx. The internal carotid artery is situated behind and to the outer side of the tonsil, and separated from it only by the constrictor muscle, and cellular tissue. It has been wounded in opening abscesses ofthe tonsils, when the cutting instru- ment has been inclined too much outwards and backwards.—p. TONSILS.—EPIGLOTTIS. 475 has an oval form, its longest diameter extending from above downwards. Its surface is rather convex, its natural colour is a pale red. On its surface are the large orifices of many cells of considerable size, which exist throughout the gland. These cells often communicate with each other, so that a probe can be passed in at one orifice and out at the other. Into these cells open many mucous ducts, which discharge in part the mucus of the throat, for the purpose of lubricating the surface, and facilitating the transmission of food. —In its healthy state, the free surface of the tonsil glands, are a little below the level of the two half arches of each side. —But when their cells are distended by inflammation, or effaced by granulations, as in tonsillitis, they sometimes project beyond the half arches so as nearly or quite to meet in the middle line.— The Epiglottis, or fifth cartilage ofthe larynx, is situated at the root of the tongue, in the middle, between the tonsils. The part which is in sight is partly oval in form, and of a whitish colour. Its position, as respects the tongue, is nearly perpen- dicular, and its anterior surface rather convex. The mucous membrane continued from the tongue over the epiglottis is so arranged that it forms a plait, which extends from the middle of the root of the tongue along the middle of the anterior surface of the epiglottis, from its base upwards. On each side of this plait or fraenum, at the junction of the surfaces of the tongue and of the epiglottis there is often a de- pression, in which small portions of food sometimes remain; and a small fraenum, similar to that above described, is some- times seen on the outside of each of these cavities. The epiglottis is situated immediately before the opening into the larynx. The above described parts can be well ascertained in the living subject, by a person who has a general knowledge ofthe structure. Thus, looking into the mouth, with the tongue de- pressed, the uvula and soft palate are in full view above, and the epiglottis is very perceptible below; while the two ridges 476 THE LARYNX. or lateral half arches can be seen on each side, with the tonsil between them. Of the Larynx. —The larynx is situated immediately below the os hyoides, and is continuous at its inferior part with the trachea, to which it is attached, like a capital upon a column. \t serves a double purpose; that of a tube for the introduction of air into the lungs; and that of a very complicated apparatus for the pro- duction of the voice. —It is composed of cartilages which form its frame-work, liga- ments and synovial capsules which unite the cartilages together, muscles to put them into motion, and an exquisitely sensitive mucous membrane, that lines the whole of its interior. It is larger and much more prominent in males than females, and undergoes a rapid and remarkable degree of developement, both in regard to size and energy of function at the period of puberty.— In this structure are five cartilages, upon which its form and strength depends, namely, the Cricoid, the Thyroid, the two Arytenoid, and the Epiglottis. These cartilages are articu- lated to each other, and are supplied with muscles by which certain limited motions are effected. The basis of the structure is a cartilaginous ring, called the cricoid cartilage, and which may be considered as the com- mencement of the windpipe. It may be described as an irregular section of a tube : its lower edge connected with the windpipe, being nearly hori- zontal when the body is erect; and the upper edge very oblique, sloping from before, backwards and upwards; in consequence of this, it has but little depth, before, but is eight or nine lines deep behind. —In front, and upon each side of the middle line there is a depression, in which arises the two crico-thyroid muscles. Upon each side, and near its upper and outer surface, there is a smooth convex facet, upon which is articulated, the corres- CRICOID CARTILAGE.—THYROID CARTILAGE. 477 ponding facet of the inferior cornua of the thyroid cartilage. Posteriorly are two slight vertical depressions, to which are attached the crico-arytenoidei postici muscles. Its internal face is covered by mucous membrane. Its superior border gives attachment in front to the crico-thyroid membrane, on the sides to the lateral crico-arytenoid muscles, and posteriorly presents a little notch, limited by two convex facets upon which are articulated the arytenoid cartilages.— The Thyroid cartilage is a single plate, bent in such manner that it forms an acute angle with two similar broad surfaces on each side of it. It is so applied to the cricoid cartilage, that the lower edge ofthe angular part is at a small distance above the front part of that cartilage, and connected to it by ligamen- tous membrane; while its broad sides are applied to it later- ally, and thus partially enclose it. The upper edge of the angular part of the thyroid cartilage forms a notch; and the natural position of the cartilage is such, that this part is very prominent in the neck; it is called the Pomum Adami. Both the upper and lower edges of the thyroid cartilage terminate posteriorly in processses, which are called Cornua. The two uppermost are longest: they are joined by ligaments to the extremities of the os hyoides. The lower and shorter processes are fixed to the cricoid cartilage. The thyroid car- tilage, therefore, partly rests upon the cricoid cartilage below, and is"attached to the os hyoides above. It is influenced by the muscles which act upon the os hyoides, and also by some mus- cles which are inserted into itself. It is moved obliquely downwards and forwards in a slight degree upon the cricoid cartilage, by a small muscle, the crieo-thyroideus, which arises from that cartilage and is inserted into it. —The external lateral surface of the thyroid cartilage is slightly concave, and across it, passes a small ridge obliquely from above downwards, and from behind forwards, which gives attachment above to the thyro-hyoid and below to the sterno-hyoid muscles. The posterior or inside face of the Pomum Adami presents an entering angle, where the two 478 ARYTENOID CARTILAGES. symmetrical sides of the cartilage meet, and in which is attached the thyro-arytenoid muscles, the pedicle of the epi- glottis and one end of the vocal ligaments. The upper margin of the cartilage presents a curved appearance like that of the italic long/; a similar curvature is also observable on its pos- terior margin.— Fig. 119.* The Arytenoid cartilages are two small 9 ^""^[llllBll"'--6 bodies of a triangular or pyramidal form ^""HHh and slightly curved backward. They are WiPf -a P^ace(i up°n tne upper and posterior edge viSra-"""'1' of the cricoid cartilage, near to each other; e """"■! I ° tnen* uPPer ena"s> taken together, resem- |!_jf ble the mouth of a pitcher or ewer; from Ja which circumstance their name is derived. Their bases are broad; and on their lower surfaces is a cavity, which corresponds with the convex edgeof the cricoid carti- lage, to which they are applied. At these places, a regular movable articulation is formed, by a capsular ligament between each of these cartilages and the cricoid, in consequence of which they can be inclined backward or forward, inward or outward. From the anterior part of each of these cartilages, near the base, a tendinous cord passes forward, in a direction which is horizontal when the body is erect, to the internal surface ofthe angle of the thyroid. These ligaments are not perfectly parallel to each other; they are nearer before than behind. The aperture between them is from two to five lines wide when the muscles are not in action ; and this aperturet is the orifice of the windpipe: for the exterior space, between these ligaments and the circumference of the thyroid, is closed up by mem- * Fig. 119. Vertical section ofthe larynx, h, Os hyoides. t, Thyroid cartilages. c c, Cricoid cartilage, a, Arytenoid cartilage, v, Ventricle of the larynx, bounded below by the ligamenta vocales, and above by the superior ligaments of the glottis. e, Epiglottis cartilage, g, Ligamentous attachment of the tongue to the os hyoides. b, Trachea cut off at the third ring. The lining membrane is left out in this section. t It forms also the rima glotlidis of the larynx. EPIGLOTTIS. 479 brane and muscle. At a small distance above these ligaments are two others, which also pass from the arytenoid to the thy- roid cartilages. They are not so tendinous and distinct as the first mentioned, and cannot be drawn so tense by the muscles of the arytenoid cartilages. They are also situated at a greater distance from each other, and thus form a large aperture. On the external side of the upper extremity of each of the arytenoid cartilages, and nearly in contact with it, is a small cartilaginous body, not so large as a grain of wheat, and nearly oval in form. These are connected firmly to the aryte- noid cartlages, and are called their Appendices* Being in the margin of the aperture of the larynx, they have an effect upon its form. The arytenoid cartilages are the posterior parts of the larynx. The Epiglottis, which has already been mentioned is the anterior. When this cartilage is divested of its membrane, it is oval in its upper extremity, and rather angular below, terminating in a long narrow process, which is like the stalk of a leaf. It is firmly attached to the internal surface of the angular part of the thyroid by this lower process; and, being placed in a perpendicular position, one of its broad surfaces is anterior— towards the tongue, and the other posterior—towards the open- ing of the windpipe. It is attached to the os hyoides by dense cellular texture or ligament, and to the tongue by those plaits of the membrane of the mouth which have been already described. It is elastic, but more flexible than the other cartilages; being somewhat different in its structure. Its surface is perforated by the orifices of many mucous ducts. There is a small space between the lower part of this carti- lage, and the upper part of the thyroid and the ligamentous membrane passing from it to the os hyoides. In this is a sub- stance, which appears to consist of glandular and of adipose * They are also called Cornicula Laryngis, Tubercles of Santorini.—r. 4S0 VENTRICLE OF GALEN OR MORGAGNI. matter, (see fig. 119.) It is supposed that some of the orifices on the lower part of the epiglottis communicate with this substance. —This substance is a collection of mucous glands, called glandulas epiglottidae; the ducts which arise from them are twenty or thirty in number, and perforate the epiglottis to throw their mucus on the side of the larynx.— In the erect position of the body, the epiglottis is situated rather higher up than the arytenoid cartilages, and at the dis- tance of ten or twelve lines from them. The mucous membrane which covers the epiglottis, is reflected backwards from the base of the tongue, and is extended from each side of it to the arytenoid cartilages, and being continued into the cavity of the larynx, as well as upon the general surface of the throat, it is necessarily doubled : this doubling forms the lateral margins of the orifice of the cavity of the larynx. In these folds of the membrane are seen some very delicate muscular fibres, forming the Aryteno-epi- glotlideus muscle. —The epiglottis maintains its vertical position, partly from its own elasticity of structure, and partly from the folds of mucous membrane, reflected to it from the tongue, which con- tain some yellow elastic ligamentous fibres.— The membrane continues down the cavity of the larynx, and, covering the upper ligaments, penetrates into the vacuity between them and the lower ligaments, so as to form a cavity on each side of the larynx, opening between the two ligaments, which is called the Ventricle of Morgagni. The shape of each cavity is oblong. Its greatest length extends from be- hind forward, on each side of the opening into the windpipe formed by the two lower or principal ligaments; so that when the larynx is removed from the subject, upon looking into it from above, you perceive three apertures: one in the middle, formed by the two lower ligaments ; and one on each side of it, between the lower and upper ligament, which is the orifice of the ventricle of Morgagni. —If a probe be passed into this ventricle of the larynx, or ven- VENTRICLE OF GALEN OR MORGAGNI--RIMA GLOTTIDIS. 481 tricle of Morgagni, it will be found to pass much above the supe- rior thyro-arytenoid ligament, into a prolongation of the cavity of Fig. 120.* the ventricle, which extends as high as the upper margin of the thyroid cartilage, and which has been called by Mr. Hilton, the .....t" Sacculus Laryngis. It was pointed out by Morgagni, and has been compared by '_"."•£ M. Cruvielhier, from its shape, to a Phry- gian casque.—It is apt to escape observation in the healthy state. When death has taken place, from pulmonary emphysema, or lar- yngeal phthisis, I have, on several occasions, found the sac so large as to project considerably above the thyroid cartilage. The ventricle and its sac, appear to be intended for the supply of a lubricating secretion to the vocal chords, which are kept in such constant action,during respiration and phonation. The sur- face ofthe cavity, is studded with sixty or seventy small follicu- lar glands, which are seated in the submucous tissue, and give to the mucous membrane, when dissected out, a rough appear- ance. The greater part of these follicles is placed in the sac, and the fluid which they form, is directed upon the rima glottidis, by two small folds of mucous membrane, at the entrance of the sacculus.— The aperture between the two lower ligaments is called the Rima Glottidis, or Chink of the Glottis; the upper aperture, formed by the fold of the membrane and extending from the epiglottis to the arytenoid cartilages, may be termed Glottis. —The folds of the membrane forming the upper margin of the glottis is loose and distensible, and is liable in laryngeal inflammation to become oedematous and bag out so as to im- pede respiration to a great extent, and even produce suffoca- tion.— If the windpipe is divided near the larynx, and the larynx inverted, so that the rima glottidis may be examined from below, the structure appears still more simple: it resembles a * Fi<*. 120. Front view of the larynx; plan of its interior cavity, represented by the lines aa,bb. Is, Superior ligaments of the glottis, li, Inferior ligaments. 41 482 GLOTTIS. septum fixed abruptly in the windpipe, with an aperture in it of the figure of the rima glottidis. The anterior surface of the two arytenoid cartilages is con- cave. This concavity is occupied in each by a glandular substance, which lies between the cartilage and the lining membrane; and extends itself horizontally, covered by the upper ligament of the glottis. The nature of these bodies is not perfectly understood; but they are supposed to secrete mucus.* The membrane which lines the cavity of the glottis being continued from the mouth and throat, resembles the membranes which invest those parts. In some places, where it is in close contact with the cartilages, it appears united with the perichon- drium, and acquires more firmness and density. The general motions of the larynx are very intelligible to those who are acquainted with the muscles which are con- nected with the thyroid cartilage, and which move the os hy- oides. They take place particularly in deglutition, and in some modifications ofthe voice; and also in vomiting.t The motions of the particular cartilages on each other can also be well understood, by attending to the origin and inser- tion of the various small muscles connected with them. The most important of these muscles are the crico-arytenoidei pos- tici and laterales, the thyreo-arytenoidei, the arytenoidei obli- qui, and the arytenoideus transversus. The effects of their actions appear to be the dilating or contracting the rima glotti- dis, and relaxing or extending the ligaments which form it. The arteries of the larynx are derived from two sources, namely, the superior thyroid, or laryngeal branch of the external carotid, and the thyroid branch of the subclavian. The nerves of the larynx also come to it in two very differ- ent directions on each side. It receives two branches from the par vagum; one which leaves that nerve high up in the neck, and is called the Superior Laryngeal branch; and another * They constitute the glandular arytenoidem.—p. t For an excellent exposition of the uses of the larynx, see Dunglison's Physiology, 4th edition.— VESSELS AND NERVES OF THE LARYNX. 483 which proceeds from it after it has passed into the cavity of the thorax, and is called from its direction the Recurrent. —According to M. Blandin, who has rather recently made some research upon this subject, the superior laryngeal nerve, is distributed chiefly to the mucous membrane and cryptse of the larynx; it likewise sends some filaments to the arytenoid and crico-thyroid muscles, and others which anastomose with the branches of the recurrent. The recurrent supplies all the muscles of the larynx, with the exception of the crico-thyroid. There is still among anatomists some difference of opinion in regard to the distribution of these nerves.— Muscles of the Larynx. These are divided into extrinsic and intrinsic. —The extrinsic muscles, which are attached by but one extre- mity to the larynx, have been already described. They consist of the sterno-hyoid, omo-hyoid, sterno-thyroid, and thyro- hyoid ; to which might indeed be added, all the muscles ofthe supra-hyoid region, and those of the pharynx, which are attached to the cricoid and thyroid cartilages. These, when they act upon the organ, move the entire larynx. —The intrinsic muscles, are attached by both extremities to different parts of the larynx, and produce various movements in the different pieces of which it is composed. There are ten, viz., five pairs, and one single muscle which are called the muscles of the chordae vocales, and rima glottidis. Those which exist in pairs are the crico-thyroid, the crico-arytenoidei postici, the crico-arytenoidei lateralis, the thyro-arytenoidei and the arytenoidei obliqui. The single muscle is the aryte- noideus transversus. The oblique and the transverse arytenoid muscles consist, but of a few thin fibres with difficulty distin- gushed from each other and are spoken of by many anato- mists, as a common muscle, called simply the arytenoid. __There are three other minute muscles, which are called the muscles of the epiglottis, viz. the thyro-epiglottideus, the aryteno-epiglottideus superior, and another muscle lately observed by Mr. Hilton, called, aryteno-epiglottideus inferior. 4S4 MUSCLES OF THE LARYNX. 1. Crico- Thyroideus, Fig. 121.* Arises from the side and forepart of the cricoid car- tilage, running obliquely up- J^;'■■.■;/ wards. Inserted by two portions : the first, into the lower part of the thyroid cartilage; the se- cond, into its inferior cornu. Use. To pull forwards and depress the thyroid, or to ele- vate and draw backwards the cricoid cartilage. 2. Crico-Arytasnoideus Pos- ticus, Arises, fleshy, from the back part of the cricoid cartilage ; and is Inserted into the posterior part of the base of the arytenoid cartilage. Use. To open the rima glottidis a little, and, by pulling back the arytenoid cartilage, to stretch the ligament so as to make it tense. 3. Crico-Arytaenoideus Lateralis, Arises, fleshy, from the cricoid cartilage, laterally, where it is covered by part ofthe thyroid, and is * The styloid muscles and the muscles ofthe tongue. 1. A portion of the tem- poral bone ofthe left side ofthe skull, including the styloid and mastoid processes, and the meatus auditorius externus. 2, 2. The right side of the lower jaw, divided at its symphysis; the left side having been removed. 3. The tongue. 4. The genio-hyoideus muscle. 5. The genio-hyo-glossus. 6. The hyo-glossus muscle; well seen at the base of the tongue. 7. Its portion connected with the os hyoides. 8. The anterior fibres of the lingualis issuing from between the hyo-glossus and genio-hyo-glossus. 9. The stylo-glossus muscle, with a small portion ofthe stylo- maxillary ligament. 10. The stylo-hyoid. 11. The stylo-pharyngeus muscle. 12. The os hyoides. 13. The thyro-hyoidean membrane. 14. The thyroid car- tilage. 15. The thyro-hyoideus muscle arising from the oblique line on the thyroid cartilage. 16. The cricoid cartilage. 17. The crico-thyroidean membrane, through which the operation of laryngotomy is performed. 18. The trachea. 19. The com- mencement of the oesophagus. MUSCLES OF THE LARYNX. 485 Inserted into the side of the base of the arytenoid cartilage near the former. Use. To open the rima glottidis, by pulling the ligaments from each other. 4. Thyreo-Arytaenoideus, Arises from the under and back part of the middle of the thyroid cartilage ; and, running backwards and a little upwards, along the side of the glottis, is Inserted into the arytenoid cartilage, higher up and farther forwards than the crico-arytsenoideus lateralis. Use. To pull the arytenoid cartilage forwards nearer the middle of the thyroid, and consequently to shorten and relax the ligament of the larynx or glottis vera. 5. Arytasnoideus Obliquus, Arises from the base of one arytenoid cartilage; and cros- sing its fellow, is Inserted near the tip of the other arytenoid cartilage. Use. When both act they pull the arytenoid cartilages to- wards each other. N. B. One of these is very often wanting. The single muscle is, the Arytasnoideus Transversus, Arises from the side of one arytenoid cartilage, from near its articulation with the cricoid to near its tip. The fibres run straight across, and are Inserted, in the same manner, into the other arytenoid car- tilage. * A posterior view ofthe larynx. 1. The thyroid cartilage. 2. One of its ascend- ing cornua. 3. One of the descending cornua. 4. 7. The cricoid cartilage. 5, 5. The arytenoid cartilages. 6. The arytenoideus muscle, consisting of oblique and trans- verse fasciculi. 7. the crico-arytenoidei postici muscles. 8. The epiglottis. 41* 486 MUSCLES OF THE LARYNX. Use. To shut the rima glottidis, by bringing these two carti- lages, with the ligaments, nearer one another. Ft" 123 * Besides these, there are a few separate muscular fibres on each side; which, from their general direction, are named 1. Thyro-Epiglottideus, Arises, by a few pale separated fibres, from the thyroid cartilage: and is Inserted into the epiglottis laterally. Use. To draw the epiglottis obliquely downwards, or, when both act, directly downwards; and at the same time, it ex- pands that soft cartilage. 2. Arytasno-Epiglottideus, superior. Arises, by a number of small fibres, from the lateral and upper part of the arytenoid cartilage; and, running along the outer side of the external rima, is Inserted into the epiglottis along with the former. Use. To pull that side of the epiglottis towards the external rima; or, when both act, to pull it close upon the glottis. It is counteracted by the elasticity ofthe epiglottis. 3. Aryteno-Epiglottideus, inferior. This muscle may be exposed by raising the mucous mem- brane immediately above the ventricle of the larynx. It arises by a narrow and fibrous origin from the arytenoid cartilage, just above the attachment of the chorda vocalis—and passing forwards and a little upwards, expands over the upper half or two-thirds of the sacculus laryngis, and is inserted by a broad attachment into the side of the epiglottis. Its action according * A side view ofthe larynx, one ala ofthe thyroid cartilage has been removed. 1. The remaining ala ofthe thyroid cartilage. 2. One ofthe arytenoid cartilages. 3. One of the cornicula laryngis. 4. The crycoid cartilage. 5. The crico-arytenoideus posticus muscle. 6. The crico-arytenoideus lateralis. 7. The thyro-arytenoideus. 8. The crico-thyroidean membrane. 9. One half of the epiglottis. 10. The upper part of the trachea. THE THYROID GLAND. 487 to Mr. Hilton, is to approximate the epiglottis and arytenoid cartilage, to compress the subjacent glands which open into the pouch of the larynx, to diminish the capacity of that cavity and to change its form. The extreme irritability of the glottis is unequivocally demonstrated by the cough, which is excited when a drop of water, or any other mild liquid, or a crumb of bread enters it. Notwithstanding this, a flexible tube, or catheter, has several times been passed into the windpipe through the rima glottidis, and been endured by the patient a considerable time. The cough, which occurs when these parts are irritated, does not appear to arise exclusively from the irritation of the membrane within the glottis; for, if it were so, mucilaginous substances, when swallowed slowly, could not suspend it. Their effect in relieving cough is universally known ; and as they are only applied to the surface exterior to the glottis, it is evident that the irritation of this surface must also produce coughing. Several curious experiments have been made to determine the effect of dividing the different nerves which go to the larynx; by which it appears that the recurrent branches supply parts which are essentially necessary to the formation of the voice ; whilst the laryngeal branches supply parts which merely influence its modulation, or tone. See Mr. Haigton's Essay on this subject: Memoirs ofthe Medical Society of London, vol. iii. The Thyroid Gland, (see fig. 117, p. 454 J May be described here, although a part of it is situated below the larynx. This body consists of two lobes, which are united at their lower extremities by a portion which extends across the anterior part of the windpipe. Each lobe generally rises upwards and backwards from the second cartilaginous ring of the windpipe over the cricoid cartilage and a portion of the thyroid. It lies behind the sterno-hyoidei, and sterno-thyroidei muscles. It is of a reddish-brown colour, and appears to consist of a granular substance; but its ultimate structure is not understood. It is plentifully supplied with blood, and receives two arteries on each side : one from the laryngeal branch* of the external carotid: and the other from the thyroid branch of the subclavian. Notwithstanding this large supply of blood, there is no * The main branch from the external carotid, is now more commonly called superior thyroid.—P. 488 THE THYROID GLAND. proof that it performs any secretion: for although, several respectable anatomists have supposed that they discovered excretory ducts passing to the windpipe, larynx, or tongue, it is now generally agreed that such excretory ducts are not to be found. Several instances, have, however, occurred, in which air has been forced, by violent straining, from the wind- pipe into the substance of this gland. [There are two membranous expansions in the neck which should be noticed in its dissection. The first, called Fascia Superficialis, lies immediately beneath the skin, may be considered as a continuation of the fascia superficialis abdomi- nis, and is strongly connected to the base of the lower jaw, being also spread over the parotid gland. It is not very distinct in all subjects. The second is called the Fascia Pro- funda Cervicis; it extends from the larynx and thyroid gland to the upper part ofthe sternum and first ribs; the great vessels, &c. of the superior mediastinum are placed immediately below it.] —The thyroid gland, gets a thin capsular investment, from two layers of the deep-seated cervical fascia, (fascia profunda cervicis) as seen in fig. 124. —The same fascia likewise gives off layers, that form cellular investments or tunics to the trachea, oesophagus, and to the blood-vessels of the neck. Other processes pass off from it which supply sheaths to the sterno-cleido mastoid and other muscles of the neck. Between the sheaths of the different muscles of the neck, dense processes of cellular tissue are con- tinued, so as to give them all the appearance of being formed as it were, from a common fascia. At the posterior part of the neck they are thus indirectly connected with the ligamentum nuchas. Though this for practical purposes is not considered the best way for studying the fascia of the neck, it serves to give an idea of the continuity of the cellular investments, which is so common throughout the body. The accompanying cut and explanation is taken from Wilson. —The two lobes of the thyroid gland, when extended and measured from side to side are together about three inches in THE THYROID GLAND. 489 diameter. The lobes extend upwards on the sides ofthe larynx and downwards on the oesophagus, and lie upon the inner face of, and partly covering the primitive carotid artery and internal jugular vein. That part of the gland which unites the lobes Fig. 124.* together, and is stretched across the trachea, covering the two or three usually and sometimes the seven upper rings of the trachea, is called the isthmus of the gland. From the upper surface of the isthmus a process of the gland is usually seen * A transverse section ofthe neck, showing the deep cervical fascia and its nume- rous prolongations, forming sheaths for the different muscles ofthe neck, the thyroid gland—trachea, oesophagus and blood-vessels. As the figure is symmetrical, the figures of reference are placed only on one side. 1. The platysma myoides. 2. The trapezius. 3. The ligamentum nuchae, from which the fascia may be traced forwards beneath the trapezius, enclosing the other muscles of the neck. 4. The point at which the fascia divides, to form a sheath for the sterno-mastoid muscle (5). 6. The point of reunion of the two layers of the sterno-mastoid sheath. 7. The point of union of the deep cervical fascia of opposite sides of the neck. 8. Section of the sterno-hyoid. 9. Omo-hyoid. 10. Sterno-thyroid. 11. The lateral lobe of the thyroid gland. 12. The trachea. 13. The oesophagus. 14. The sheath containing the common carotid artery, internal jugular vein, and pneumogastric nerve. 15. The longus colli. The nerve in front of the sheath of this muscle is the sympathetic. 16. The rectus anticus major. 17. Scalenus anticus. 18. Scalenus posticus. 19. The splenius capitis. 20. Splenius colli. 21. Levator anguli scapulae. 22. Complexus- 23. Trachelo-mastoid. 24. Transversalis colli. 25. Cervicalis ascendens. 26. The semi-spinalis colli. 27. The multifidus spinas. 28. A cervical vertebra. The transverse processes are seen to be traversed by the vertebral artery and vein. 490 THE PHARYNX. extending upwards, on the left side over the front surface of the larynx, to be attached by ligamentous fibres to the os hyoides. A small muscle called the levator glandulse thyroidese, has been described by Duverney, Soemmering and others, run- ding down from the os hyoides in front of the larynx to the upper part of the isthmus of the gland. According to Professor Horner, its existence is very rare, with which opinion my own more limited observation coincides. —The lobes of the gland are composed of smaller lobules, and the spongy structure of the latter, is filled with a yellowish and somewhat oily fluid. Ofthe uses of this gland nothing positively is known. Its importance in the system of the adult cannot be great, as its removal by extirpation, which has been many times practised, has not appeared to leave any functional lesion in the economy.— Of the Pharynx. The pharynx is a large muscular bag, which forms the great cavity behind the nose and mouth that terminates in the oesophagus. It has been compared to a funnel, of which the oesophagus is the pipe; but it differs from a funnel in this respect, that it is incomplete in front, at the part occupied by the nose and mouth and larynx. It is connected above, to the cuneiform process of the occipital bone, to the pterygoid processes of the sphenoidal, and to both the upper and lower maxillary bones. It is in contact with the cervical vertebrae behind; and, opposite to the cricoid cartilage, it terminates in the oesophagus. If the pharynx and oesophagus be carefully dissected and detached from the vertebrae, preserving the connexion of the pharynx with the head, and the head then be separated from the body, by dividing the articulation of the atlas and the os occipitis, and cutting through the soft parts below the larynx, the resemblance to a funnel will be very obvious. In this situation, if an incision be made from above down- wards through the whole extent of the posterior part of the STRUCTURE OF THE PHARYNX. 491 pharynx, the communication of the nose, mouth, and windpipe, with this cavity, will be seen from behind at one view. The openings into the nose, or the posterior nares, appear uppermost. Their figure is irregularly oval, or oblong; they are separated from each other by a thin partition, the vomer. Immediately behind, on the external side of each of these orifices, is the Eustachian tube. (See fig. 117, p. 454.) The soft palate will appear extending from the lower boundary of the posterior nares, obliquely backwards and downwards, so as nearly to close the passage into the mouth. The uvula hangs from it: and, on each side of the uvula, the edge of the palate is regularly concave. Below the palate, in the isthmus of the fauces, are the ridges or half arches, and the tonsils between them. The half arch which presents first, in this view, runs obliquely down- ward and backward, and not parallel to the other. Close to the root of the tongue is the epiglottis erect; and, immediately adjoining it, is an aperture large enough to admit the end of a middle-sized finger. This aperture is widest at the extremity next to the epiglottis, and rather narrower at the other extremity : it is the glottis or opening of the windpipe. When the larynx is elevated, the epiglottis can be readily depressed so as to cover it completely. The extremities of the arytenoid cartilages, and their appendices, may be recognised at the posterior edge of the glottis. At a short distance below this edge, the oesophagus begins. The Pharynx is composed of the membrane continued from the nose and mouth internally, and of a stratum of muscular fibres externally. The internal membrane is very soft and flexible and perforated by many muciferous ducts. The surface which it forms is rather rough, owing to the mucous glands which it covers. It has a red colour, but not so deep as that of some other parts. It is connected to the muscular stratum by a loose cellular membrane. The muscular coat consists of three different portions, which are considered as so many distinct muscles. They are called 492 CONSTRICTOR MUSCLES OF THE PHARYNX. the superior, middle, and inferior constrictor muscles of the pharynx. The fibres of each of these muscles originate on each side, and run in an oblique direction to meet in the middle, thus forming the posterior external surface of the dissected pharynx. The fibres of the tipper muscles originate from the cuneiform processes of the occipital bone, from the pterygoid processes of the os sphenoides, and from the upper and lower jaws, near the last dentes molares, on each side. They unite in a middle line in the back of the pharynx. The fibres of the middle muscles originate principally from the lateral parts of the os hyoides, and from the ligaments which connect that bone to the thyroid cartilage. The supe- rior fibres run obliquely upwards, so as to cover a part of the first mentioned muscle, and terminate in the cuneiform process of the occipital bone; while the other fibres unite with those of the opposite side in the middle line. The fibres of the lower muscles arise from the thyroid and the cricoid cartilages, and terminate also in the middle line: those which are superior, running obliquely upwards; the inferior, nearly in a transverse direction. It is obvious, from the origin and insertion of these fibres, that the pharynx must have the power of contracting its dimensions in every respect; and, particularly, that its diameter may be lessened at any place, and that the whole may be drawn upwards. PART VI. OF THE THOEAX. Before the thorax is described, it will be in order to con- sider the Mammae; Or those glandular bodies situated on the anterior part of it, which, in females, are destined to the secretion of milk. These glands lie between the skin and the pectoral muscles, and are attached to the surfaces of those muscles by cellular membrane. They are of a circular form; and consist of a whitish firm substance, divisible into small masses or lobesj which are com- posed of smaller portions or lobuli. Between these glandular portions, a great deal of adipose matter is so diffused, that it constitutes a considerable part of the bulk of the mammae. The gland, however, varies greatly in thickness in the same person at different periods of life. The mammae become much enlarged about the age of pu- berty. They are also very large during pregnancy and lacta- tion ; but after the period of child-bearing they diminish con- siderably. They are supplied with blood by the external and internal mammary arteries, the branches of which enter them irregularly in several different places. The veins correspond with the arteries. From the small glandular portions that compose the mamma, fine excretory tubes arise, which unite together and form the great lactiferous ducts of the gland. These ducts proceed in a 42 494 MAMMiE. radiated manner from the circumference to the centre, and terminate on the surface of the nipple.* They are commonly about fifteen in number, and vary con- siderably in size: the largest of them being more than one-sixth of an inch in diameter.t Fig. 1254 They can be very readily injected by the orifices ofthe nip- ple, from a pipe filled with mercury, in subjects who have died during lactation or pregnancy; but they are very small in sub- jects of a different description. It has been asserted by respectable anatomists, that these ducts communicate freely with each other; but they do not appear to do so; each duct seems to be connected with its pro- per branches only.§ Haller appears to have entertained the remarkable senti- * Described in the 10th century, by Charles Etienne, Vesalius and Posthius, but their uses were unknown.—h. t These ducts vary in number in different individuals, from fifteen to twenty.—P. t Fig. 125, is a vertical section of the mammary gland of a young female who died during lactation. The ducts were injected with wax, and two dissected out their full length to their origin in the lobules of the gland. 2,2, Base ofthe nipple. 3, 3,3, Lac tiferous ducts cut off at the base ofthe nipple. 4, 4, The top of the ducts ex- hibited their whole length. 5,5, Sinuses formed by these ducts at the base of the nipple. 6,6,>6, 6, Branches of these ducts running to the lobules. 7,7,7, 7, 7, The lobules separated from each other. 8, 8, The orifices of these ducts on the top of the nipple. $ See Edinburgh Medical Commentaries, vol. i. p. 31.—A paper by Meckel.—H. LACTIFEROUS DUCTS. 495 ment, that some of the ducts originate in the adipose matter about the gland, as well as in the glandular substance.* The papilla, or nipple, in which these ducts terminate, is in the centre of the mamma: it consists of a firm elastic sub- stance, and is nearly cylindrical in form. It is rendered tumid by irritation, and by certain emotions. —This power of erectibility ofthe nipple is due to the presence of some contractile tissue in its composition analogous to the dortus structure of the scrotum. There is now believed to be no erectile tissue in its composition.— The lactiferous ducts terminate upon its extremity. When it is elongated they can freely discharge their contents; but when it contracts, this discharge is impeded. The skin imme- diately around the nipple is of a bright red colour in virgins of mature age. In pregnant women it is sometimes almost black; and in women who have borne children it is often brownish. It abounds with sebaceous glands, which form small eminences on its surface. —During gestation these follicles or glands are much increased in size, so as to become in consequence of this enlargement, one of the most certain signs of pregnancy. During suckling they are still farther enlarged, so as to appear like small pim- ples projecting from the skin, and serve by the increased secre- tion they throw out, to defend the nipple and areola, from the excoriating action of the saliva of the child.— This gland exists in males, although it is very small. In boys, soon after birth, it has often been known to tumefy, and become very painful, in consequence ofthe secretion and accu- mulation of a whitish fluid, which can be discharged by pres- sure. It also sometimes swells and is painful, in males at the age of puberty. There have been some instances in which it has secreted * Elementa Physiologiae, Tom. 7, Pars II. page 7. —In the adipose matter about the gland, the lactiferous tubes {ducti galactophori) appear to communicate with the absorbent vessels. In injecting the gland with mercury, I have frequently found the metal to pass off from the ducts along the absorbent vessels.—p. 496 LACTIFEROUS DUCTS. milk in adult males ; and a few instances also in which it has been affected with cancer, in the same sex. The mamma is plentifully supplied with absorbent vessels, which pass from it to the lymphatic glands in the axilla. Its nerves are principally derived from the great plexus formed by the nerves of the arm. —The skin covering the mammary gland, is exceedingly thin, delicate and vascular, and that of the nipple and areola, more delicate and sensitive than any other portion. —Each lactiferous duct by its branching and convolutions, forms a distinct lobule of the gland, and terminates in a series of vascular granules* about the size of millet seed, which are readily distinguished from each other in individuals who have died during lactation. The lobules of the gland vary in size, which, in subjects where the subcutaneous matter is not abundant, gives a feeling of unevenness or roughness to the gland. —There are no valves in the lactiferous tubes.— * Histoire de la Generation, par Grimaud de Caux et Martin Saint-Ange, 4to. Paris, 1837.—p. CAVITY OF THE THORAX. 497 CHAPTER XV. OF THE GENERAL CAVITY OF THE THORAX. Ofthe Form ofthe Cavity ofthe Thorax. The osseous structure of the thorax is described in page 155. The cavity is completed by the intercostal muscles, which close the vacuities between the ribs ; and by the diaphragm, which fill up the whole space included within its lower margin. If we except the apertures of the diaphragm, which are completely occupied by the aorta, the vena cava, and the oeso- phagus, &c, the only outlet of this cavity is above : it is formed by the upper ribs, the first dorsal vertebra, and the sternum. The figure of this aperture is between that of the circle and the oval; but it is made irregular by the vertebrae, and by the upper edge of the sternum. When the superior extremities and the muscles appropriated to them are removed, the external figure ofthe thorax is coni- cal ; but the cavity formed by it is considerably influenced by the spine, which protrudes into it; while the ribs, as they pro- ceed from the spine, curve backwards, and thus increase the prominency of the cavity. The diaphragm has a great effect upon the figure of the cavity of the thorax. It protrudes into it from below, with a convexity of such form that it has been compared to an inver- ted bowl; so that although it arises from the lower margin of the thorax, the central parts of it are nearly as high as the fourth rib. The position of the diaphragm is also oblique. The anterior portion of its margin, being connected to the seventh and eighth ribs is much higher than the posterior portion, which is attach- ed to the eleventh and twelfth. In consequence of the figure and position of the diaphragm, 42* 498 PLEURA. the form of the cavity of the thorax resembles that of the hoof of the ox when its posterior part is presented forwards. Of the Arrangement of the Pleuros. The thorax contains the two lungs and the heart, as well as several very important parts of smaller size. The lungs occupy the greatest part of the cavity; and to each of them is appointed a complete sac, called Pleura, which is so arranged that it covers the surface of the lungs, and is continued from it to the contiguous surface of the thorax, which it lines. After covering the lung, it is extended from it to the spine posteriorly: so that in tracing the pleura in a circular direction, if you begin at the sternum, it proceeds on the inside of the ribs, to the spine; at the spine it leaves the surface of the thorax, and proceeds directly forwards towards the sternum. In its course from the spine to the sternum, it soon meets with the great branch of the windpipe and blood-vessels, which go to the lung: it continues on these vessels and round the lung until it arrives at the anterior side of the vessels, when it again proceeds forwards until it arrives at the sternum. Each sac being arranged in the same way, there is a part of each extended from the spine to the sternum. These two laminae form the great vertical septum of the thorax, called Medias- tinum. They are situated at some distance from each other; and the heart, with its investing membrane or pericardium, is placed between them. The pericardium is also a complete sac or bladder, which, after covering perfectly the surface of the heart, is extended from it so as to form a sac, which lies loose about it, and appears to contain it. This loose portion adheres to those parts of the laminae of the mediastinum, with which it is contiguous; and thus three chambers are formed within the cavity of the thorax: one for each lung, and one for the heart. The two laminoe of the pleura, which constitute the mediasti- num, are at different distances from each other, in different places. At the upper part of the thorax, they approach each other from the internal edges of the first ribs; and as these MEDIASTINUM. 499 include a space which is nearly circular, the vacuity between these laminae is necessarily of that form, at its commencement above. Here, therefore, is a space between them above, (Superior Mediastinum) which is occupied by the transverse vein that carries the blood of the left subclavian and the left internal jugular to the superior cava; by the trachea; by the oesopha- gus ; and by the subclavian and carotid arteries, as they rise from the curve ofthe aorta. This space is bounded below by the above mentioned curve of the aorta. The heart and pericardium are so placed that there is a small-distance between them and the sternum: in this space the two laminae of the mediastinum are very near to each other; and cellular substance intervenes between them. This portion of the mediastinum is called the Anterior Medias- tinum* Posteriorly, the heart and pericardium are also at a small distance from the spine; and here the lamina of the mediasti- num are at a greater distance from each other, and form a long narrow cavity which extends down the thorax in front of the vertebrae: this is called the Posterior Mediastinum. It > contains a considerable portion of the aorta as it descends from its curve, the oesophagus, the thoracic duct, and the vena azygos. The aorta is in contact with the left lamen, and can often be seen through it when the left lung is lifted up. —The posterior and anterior mediastina are separated from each other by the pericardium which encloses the heart. But as the serous layers of the anterior, are reflected one on each side of the pericardium, to meet the posterior mediastinum, it appears to me to render the study of this part more easy, to * This mediastinum, being placed in front of the longitudinal diameter of the pericardium is found at its lower part inclined to the left of the middle line. The cellular tissue between its layers, communicates indirectly with the cellular tissue on the outer side of the peritoneum, in the notch formed by the origin ofthe greater muscle of the diaphragm, under the xiphoid appendix of the sternum. By this channel, abscesses of the anterior mediastinum, may make their way externally upon the abdomen.—f. 500 PREPARATION OF THE THORAX. consider that embracing the pericardium as a middle medias- tinum. The oesophagus is in contact with the right lamen; in its progress downwards, it inclines to the left side and is advanced before the aorta. The vena azygos appears posterior to the oesophagus; it proceeds upwards until it is as high as the right branch of the windpipe: here it bends forward, round that branch, and opens into the superior cava, before that vein opens into the right auricle. The thoracic duct proceeds upwards from below, lying in the space between the aorta and the vena azygos, until the beginning of the curve of the aorta, when it inclines to the left, proceeding towards the place of its termination. —The anterior and posterior mediastinae are formed as is shown above, by the layers of the pleura, between the sternum and pericardium, and between the pericardium and spine. But the pericardium does not extend the whole length of the thoracic cavity; it terminates about two inches short of the top of the sternum, and at this part, there being nothing interposed to divide the layers into an anterior and posterior portion, they pass directly from the vertebras to the sternum, and constitute what is called the Superior Mediastinum. The two layers con- stituting this, continuous below with the anterior and superior mediastinae, and each lining the upper margin of the first rib, so as to form a conical pouch projecting a slight distance above the middle of the clavicle, constitute a triangular cavity, the base of which is upwards, and corresponds to the root of the neck. This cavity contains the thymus gland, the arteria innominata, the primitive carotid and subclavian of the left side, the superior vena cava, the trachea, oesophagus, and par vagum nerve. —The sympathetic nerve is not contained in this mediastinum; it passes a little to the outside of the posterior external angle • of it.— The formation of the mediastinum, and the arrangement of the pleura, as well as the connexion of these membranes with the parts contained in the thorax, may be PREPARATION OF THE THORAX. 501 studied advantageously, after the subject has been prepared in the manner [now to be described. Take away, from each side, the five ribs which are situated between the first and last true ribs, by separating their cartilages from the sternum, and their heads from the spine; so that the great cavities of the thorax may be laid open. The precise course of the mediastinum is thus rendered obvious; and the sternum may now be divided with a saw throughout its whole length in the same direction; so that the division of the bone may correspond with the space between the lamina ofthe mediastinum. Separate the portion of the sternum cautiously, so as to avoid lacerating the lamina of mediastinum; and to keep them separate, while the trachea is dissected from the neck into the cavity of the thorax; the great transverse Vein and the descending cava are dissected to the pericardium ; and the left carotid artery, with the right subclavian and carotid, are dissected to the curve of the aorta, taking care not to destroy the lamina of the mediastinum. After this preparation the upper space between the lamina of the mediastinum can be examined, and the relative situation of the trachea and the great vessels in it can be understood. The anterior mediastinum can also be studied : the root of each lung, or its connexion with the mediastinum, may be seen perfectly ; and the precise situation ofthe lung, in its proper cavity, may be well conceived. After this, while the portions of the sternum are separated, the pericardium may be opened, and the heart brought into view: the attachment of the pericardium, and to the mediastinum, and to the diaphragm, may be seen with advantage in this situation. The portions of the sternum may now be detached from the ribs, with which they remain connected; and further dissection may be performed to examine the posterior mediastinum and its contents, and the parts which constitute the roots of the lungs. 502 THE PERICARDIUM. CHAPTER XVI. OF THE HEART AND PERICARDIUM, AND THE GREAT VESSELS CONNECTED WITH THE HEART. Of the Pericardium. The heart is enclosed by a membranous sac, which, upon a superficial view, seems only connected with its great vessels. —The whole of the organ lays unattached in the cavity of the sac, except, by the arteries and veins connected with its base. The sac is in fact composed of two layers, one external and fibrous, and one internal and serous ; the latter of these not only lines the inner face of the outer membrane, but is reflected like other serous membranes, over the roots of the vessels placed in the pericardium, and over the whole of the outer sur- face of the heart itself. This internal serous lining is very thin and delicate, and can only be raised in small shreds, either from the outer layer of the pericardium, or from the heart; except at the base of the latter organ, where, in females, it is usually, and in males, frequently, separated from the muscular tissue, by some sub-serous fatty matter.— If it were dissected from the heart, without laceration or wounding, it would be an entire sac. The pericardium, thus arranged, is placed between the two lamina ofthe mediastinum, and adheres firmly to them where they are contiguous to it; it also adheres firmly to the dia- phragm below, and thus preserves the heart in its proper position. The figure of the pericardium, when it is distended, is some- what conical; the base being on the diaphragm. The cavity formed by it is larger than the heart after death, but it is probable, that the heart nearly fills it during life; for when this THE PERICARDIUM. 503 organ is distended by injection, it often occupies the whole cavity of the pericardium. —The attachment of the pericardium to the diaphragm, is exactly over the cordiform tendon of the latter. The French anatomists have erroneously considered the fibrous layer of the pericardium, as a mere reflection of the tendon upwards. By separating them with a knife, we find, they are united by a short cellular tissue, which is densest and strongest at the peri- phery of their junction. The sides of the pericardium are covered in part by the pleura, which gives the sac the appear- ance of being formed by three tunics. —Underneath the pleural lining, is found the phrenic nerve, and in fat subjects, a good deal of adipose matter.— The pericardium is composed of two lamina, the internal of which covers the heart, as has been already described ; while the external merely extends over the loose portion of the other, and blends itself with the mediastinum, where that membrane invests the great vessels. —Its principal attachment or termination above, is upon the arteries and veins entering the heart, (with the exception of the vena cava inferior,) over which it sends tubular prolongations, which gradually blend with their external coats. Between these prolongations on the inside of the sac, hollow pouches are necessarily left, which are called the cornua of the pericardium. —The fibrous layer of the pericardium resembles in structure and appearance, the dura mater ofthe brain. —The arteries of the pericardium are very small; they are de- rived from the phrenic, bronchial, oesophageal, internal mam- mary arteries, and from the aorta itself. Its veins terminate in the vena azygos. Its nerves are few and small, and originate from the cardiac plexus.— The internal surface of the pericardium is very smooth and pblished ; and in the living subject is constantly moistened with a fluid which is probably effused from the exhalent vessels on its surface. The quantity of this fluid does not commonly exceed two drachms • but in cases of disease it sometimes amounts to 504 THE HEART. many ounces.* It is naturally transparent, but slightly tinged with red in children, and yellow in old persons. It is often slightly tinged with red in persons who have died by violence. Of the Heart. The great organ of the circulation consists of muscular fibres, which are so arranged that they give it a conical form, and compose four distinct cavities within it. Two of these cavities, which are called Auricles, receive the contents of the veins; the other two communicate with the arteries, and are called Ventricles. The auricles form the basis of the cone; the ventricles the body and apex. The structure of the auricles is much less firm than that of the ventricles, and consists of a smaller proportion of muscular fibres. They appear like appendages of the heart, while the ventricles compose the body of the viscus. The ventricles are very thick, and are composed of muscular fibres closely compacted. The figure of the heart is not regularly conical; for a portion of it, extending from the apex to the base, is flattened; and in its natural position, this flat part of the surface is down- wards. It is placed obliquely in the body; so that its base presents backward and to the right, and its apex forward and to the left. Notwithstanding this obliquity, the terms right and left are applied to the different sides of the heart, and to the different auricles and ventricles; although they might, with equal pro- priety, be called anterior and posterior. The two great veins called Venae Cavae, which bring the blood from every part of the body, open into the right auricle from above and below ; the right auricle opens into the right * The pericardium has been so distended, by effusion in dropsy, that it has formed a tumour, protruding on the neck from under the sternum. This tumour had a strong pulsating motion. It disappeared completely when the other hydropic symp- toms were relieved. RIGHT AURICLE. 505 ventricle; and from this ventricle arises the artery denomi- nated Pulmonary, which passes to the lungs. The Pulmonary veins, which bring back the blood from the lungs, open into the left auricle ; this auricle opens into the left ventricle; and from this ventricle proceeds the Aorta, or great artery, which • carries blood to every part of the body. The heart is preserved in its position, 1st, by the venae cavae which are connected to all the parts with which they are con- tiguous in their course; 2d, by the vessels which pass between it and the lungs, which are retained in a particular position by the mediastinum; 3d, by the aorta, which is attached to the mediastinum in its course downwards, after making its great curve ; and 4th, by the pericardium, which is attached to the great vessels and to the mediastinum. By these different modes the basis of the heart is fixed, while its body and apex are perfectly free from attachment, and only contiguous to the pericardium. The external surface of the heart, being formed by the serous layer of the pericardium, is very smooth: under this surface] a large quantity of fat is often found. The two auricles are contigu- ous to each other at the base, and are separated by a partition which is common to both. The Right Auricle originates from the junction of the two venae cavas. These veins are united at some distance behind V *Fig 126.—Longitudinal section of the heart, showing its cavities, b,' Right ventricle, c, Septum ventriculorum. d,.Right auricle, e, Left auricle. /.Section of the mitral' valves, g, Section of tricuspid valves, h, Arch of aorta, h, descend- ing aorta i i, Vena cava superior and inferior, ft, ft, Right and left branches of the pulmonary'artery. I, I, Pulmonary veins. 43 506 RIGHT AURICLE. the right* ventricle, and are dilated anteriorly into a sac or pouch, which is called the Sinus, and extends to the right ven- tricle, to which it is united.! The upper part of this pouch, or sinus, forms a point with indented edges, which is detached from the ventricle, but lies loose on the right side of the aorta. This point has some resemblance to the ear of a dog, from which circumstance the whole cavity has been called auricle; but by many persons the cavity is considered as consisting of two portions: the Auricle, strictly speaking; and the Sinus Venosus, above described: they however form but one cavity. This portion of the heart,' or Right Auricle, is of an irregular oblong figure. In its posterior surface, it is indented; for the direction ofthe two cavae, at their junction, is not precisely the same; but they form an angle, which causes this indentation. The anterior portion of the auricle, or that which appears like a pouch between the ventricle and the veins, is different in its structure from the posterior part, which is strictly a portion of the veins. It consists simply of muscular fibres, which are arranged in fasciculi that cover the whole internal surface: this is also the case with the point, or that part which is strictly called auricle. These fasciculi are denominated Musculi Pectinati, from their resemblance to the teeth of a comb. That part of the internal surface, which is formed by the septum is smooth, and the whole is covered by a delicate mem- brane. On the surface of the septum, below the middle, is an oval depression, which has a thick edge or margin : this is called the Fossa Ovalis.\ In the foetal heart, it was the Foramen Ovale, or aperture which forms the communication between the two auricles. * In this description the heart is supposed to be in its natural position. t At the place of junction of these veins there is a projection, indistinctly seen in man, but very manifest in some of the larger mammalia, called tuherculum Loweri.—P. t The thick edge or margin is spoken of as the annulus ovalis.—p. RIGHT AURICLE. 507 Near this fossa is a large semilunar plait, or valve, with its points and concave edge uppermost, and convex edge down- wards. It was described by Eustachius, and therefore, is called the Valve of Eustachius. —It commences at the lower surface of the opening of the inferior vena cava, and runs forwards to terminate below the fossa ovalis. It served in the foetus to obstruct the passage of the venous blood from the right auricle into the right ven- tricle, and to direct it in a great measure through the foramen ovale.— Anterior to this valve, and near the union of the auricle and ventricle, is the orifice of the proper vein of the heart, or the coronary vein. This orifice is covered by another semilunar valve, which is sometimes reticulated.* The aperture, which forms the communication between the right auricle and right ventricle, is about an inch in diameter, and is called ostium venosum. From its whole margin arises a valvular ring, or duplicature of the membrane lining the surface : this circular valve is divided into three angular por- tions, which are called Valvulx Tricuspides. From their margins proceed a great mumber of fine tendinous threads, which are connected to a number of distinct portions of mus- cular substance, which arise from the ventricle. The Right Ventricle, when examined separately from the other parts ofthe heart, is rather triangular in its figure. It is composed entirely of muscular fibres closely compacted ; and is much thicker than the auricle, although not so thick as the other ventricle. Its internal surface is composed of bundles or columns of fleshy fibres, which are of various thickness and length. Some of these columns (columnae carneae) arise from the ventricle, and are connected with the tendinous threads, (chordae tendineae,) which are attached to the margin of the tricuspid valves: the direction of them is from the apex of the * The orifice is called the foramenThebesii, and the valve valvula Tliebesii, from the anatomist who first described them. There are several other orifices in the neighbourhood of the foramen of Thebesius^ by which some of the lesser coronary veins discharge into the right auricle.—p. 508 RIGHT VENTRICLE. heart towards the base. Others of the columns arise from one part ofthe surface ofthe ventricle, and are inserted into another part. A third species are attached to the ventricle throughout their whole length, forming ridges or eminences on it. The columns of the two last described species are very numerous. They present an elegant reticulated surface when the ventricle is laid open, and appear also to occupy a considerable portion of the cavity of the heart, which some of them run across in every direction near the apex. They are all covered by a membrane continued from the auricle and the tricuspid valves; but this membrane appears more delicate and transparent in the ventricle than it is in the auricle. —This is called the internal serous, or endo-cardial lining membrane of the heart. On the right side it is continuous with that of the veins and pulmonary artery, on the left with the aorta and pulmonary veins. It is extremely thin, smooth, and transparent, covers all the interior surface of the cavities ofthe heart, and by being thrown into folds, with some fibrous matter interposed between the layers to increase their strength, con- stitutes the valves.— A portion of the internal surface of the ventricle, which is to the left, is much smoother and less fasciculated than the rest: it leads to the orifice of the pulmonary artery, which arises from it near the basis of the ventricle. This artery is very conspicuous, externally, at the basis of the heart. It is very evident, upon the first inspection of the heart, that the valvulae tricuspides will permit the blood to flow from the auricle to the ventricle; but must rise and close the orifice, and thereby prevent its passage back again, when the ventricle contracts. The use of the tendinous threads, which connect the valves to the fleshy columns, is also very evident; the valve is sup- ported by this connexion, and prevented from yielding to the pressure and opening a passage into the auricle. The blood, therefore, upon the contraction of the ventricle, is necessarily forced into the pulmonary artery ; the passage to which is now perfectly free. In this artery the membrane lining the ventricle LEFT AURICLE. 509 seems continued; but immediately within the orifice of the artery, it is formed into three semicircular folds, each of which adheres to the surface of the artery by its circumference, while the edge constituting its diameter is loose. In the middle of this loose edge is a small firm tubercle, called Corpusculum Arantii* which adds to the strength of the valve. Each of these valves, by its connexion with the artery, forms a sac or pocket, the orifice of which opens forward towards the course of the artery, and the bottom of it presents towards the ventricle. Blood will, therefore, pass from the ventricle in the artery, and along it without filling these sacs ; and, on the contrary, in this course, will compress them and keep them empty. If it moves in the artery towards the heart, it will necessarily fill these sacs, and press the semicircular portions, from the sides of the artery, against each other; by this means a partition or sep- tum, consisting of three portions, will be formed between the artery and- the heart, which will always exist when the artery compresses, (or acts upon,) its contents. It is demon- strable, by injecting wax into the artery, in a retrogade direction, that these valves do not form a flat septum, but one which is convex towards the heart, and concave towards'the artery; and that this convexity is composed of three distinct parts, each of which is convex. At the place where these valves are fixed, the artery bulges out when extended by a retrogade injection. The enlargements thus produced are called the Sinuses of Valsalva, after the anatomist who first described them. The valves are called Semilunar—and, although they are formed by a very thin membrane, they are very strong. The Left Auricle is situated on the left side of the basis of the heart. It originates from the junction of the four pulmo- nary veins; two of which come from each side of the thorax, and appear to form a large part of it. It is nearly of a cubic form: but has also an angular portion, which constitutes the proper auricle, that proceeds from the upper and left part of * After Arantius, a professor at Bologna, who first described it. 43* 510 LEFT VENTRICLE. the cavity, and is situated on the left side of the pulmonary artery. This auricle is lined by a small membrane, from which the valves between it and the ventricle originate ; but it has no fleshy columns or musculi pectinati, except in the angular process properly called auricle. These valves and the orifice communicating with the ventricle, resemble those which have been already described between the right auricle and ventricle: but with this differ- ence, that the valvular ring is divided into two portions only, instead of three which are called Valvulae Mitrales* The tendinous threads, which are connected to the muscular columns, are also attached to these valves, as in the case of the right auricle. These valves admit the passage of blood from the auricle into the ventricle, but completely prevent its return when the ventricle contracts. One of them is so situated that it covers the mouth ofthe aorta while the blood is flowing into the ven- tricle, and leaves that orifice open when the ventricle contracts, and the passage to the auricle is closed. The Left Ventricle is situated posteriorly, and to the left of the Right Ventricle. Its figure is different, for it is rather conical, and it is also longer. The interna] surface of this ventricle resembles that of the right ventricle: but the columnae carneae are stronger and larger. On the right side of this ventricle is the mouth of the aorta. The surface of the ventricle near this opening is smooth and polished, to facilitate the passage of the blood. The mouth of the aorta is furnished with three semilunar valves, after the manner of the pulmonary artery, but the former are stronger; the corpuscula Arantii are better developed in them. Indeed, Mr. Hunter does not admit of their exist- ence in the pulmonary artery. The sinuses of Valsalva are about the same size in both arteries. * From a resemblance in shape to the mitre or bishop's cap.—p. FIBRES OF THE HEART. 511 The cavity of this ventricle is supposed to be smaller than that of the right: but the amount of the difference has not been accurately ascertained. This ventricle must have much more force than the right, as its parietes are so much thicker. Their thickness often exceeds half an inch. The difference in the strength ofthe two ventricles probably corresponds with the difference between the extent of the pul- monary artery and the aorta. The thickness of the septum between the ventricles is thicker than the sides of the parietes of the right ventricle, and less thick than those of the left. The muscular fibres of the heart are generally less florid than those of the voluntary muscles; they are also more closely compacted together. The direction of many of them is oblique or spiral; but this general arrangement is very intri- cate: it is such, however, that the cavities of the heart are lessened, and probably completely obliterated, by the contrac- tion of these fibres.* —The muscular fibres of the heart have been carefully stu- died by Wolf and Malpighi, and more recently still, by Mr. Searlet and M. Gerdy.J According to this latter anatomist, there is a fibrous zone or girdle formed around each auricle and arterial orifice of the heart, which zones are connected with each other and with the valves. From these zones origi- nate all the muscular fibres of the heart. Some which run upwards and turn in every direction round the auricles, and form loops, the extremities of which are inserted on the oppo- site sides of the zone. Others which run downwards and em- brace the ventricles, are also inserted on the opposite sides of the same zone, or that which surrounds the orifices of the aorta or pulmonary artery. The structure of the ventricular * Mr. Home has <*iven a precise description of the muscular fibres of the heart in his Croonian Lecture. London Philosophical Transactions for 1795, part I. page 215. t Cyclopedia of Anatomy and Physiology. London.—Article—Fibres ofthe heart, of which he has given a minute and lengthened description. t Journal Complementaire du Diet, des Scienc. Med. torn. ix. p. 97.— 512 CORONARY VESSELS. fibres is most complicated. They are first superficially placed, and as they make their spiral turns, sink deep into the sub- stance of the heart, somewhat like the contours of a leaf of paper rolled into the form of a cone. They consist of fibres proper to each ventricle, and fibres common to both. The former, after arising from the zone, turn spirally around the axis of the ventricle, so as to form many times the figure of 8, and coming upon the anterior face of the same side, terminate upon the zone surrounding the arterial orifice. The fibres common to the ventricles are of two kinds—superficial and deep-seated. The superficial are divided into anterior and posterior. The anterior arising from the anterior part ofthe arte- rial and auricular zones, run obliquely downwards and to the left, converging towards the apex of the heart; these are rolled around the axis of the left ventricle, and dip inwards to termi- nate in, or form the columnae carneae. The superficial part of this order of fibres, is common to both ventricles; the deep- seated part belongs to the left only. The posterior superficial fibres arise behind from the auricular zones only, and run downwards, so as to embrace the right border of the heart, come in front of the heart and opposite to the septum ventri- culorum, dip under the anterior superficial fibres, wind round the axis of the right ventricle and terminate in its columnae carneae. These also in part only, are common to both ven- tricles. —The deep-seated fibres form the internal part of the walls of the right ventricle. They arise from the fibrous zones of the right side. The anterior portion of these fibres runs obliquely downwards, and backwards to the septum; the posterior and internal, pass at once into the septum, roll themselves round the left ventricle and are lost amidst the other fibres. Thus it appears, that by removing the superficial layer ofthe common stratum, the heart may be divided into lateral halves, each consisting of two muscular sacs, an auricle and ventricle, adjoined to those of the opposite side in the middle line.— The external surface of the heart is covered by that portion of the pericardium which adheres to it. Adipose matter is often VESSELS AND NERVES OF THE HEART. 513 deposited between this membrane and the muscular surface ; being distributed irregularly in various places. This membrane is continued from the surface of the ventricles over that of the auricles. When it is dissected off from the place of their junction, these surfaces appear very distinct from each other. The proper blood-vessels of the heart appear to be arranged in conformity to the general laws of the circulation, and are very conspicuous on the surface. There are two arteries which arise from the aorta immediately after it leaves the heart, so that their orifices are covered by two of the semilunar valves. One of these passes from the aorta between the pulmo- nary artery and the right auricle, and continues in a circular course in the groove between the right auricle and the right ventricle, and sends off its principal branches to the right side of the heart. The other artery of the heart passes between the pulmonary artery and the left auricle. It divides into two branches; one, which is anterior, passes to a groove on the surface, corres- ponding to the septum between the two ventricles, and con- tinues on it to the apex of the heart, sending off branches in its course; another, which is posterior and circumflex, passes between the left auricle and ventricle. The great vein of the heart opens into the under side of the right auricle, as has been already mentioned : the main trunk of this vein passes for some distance between the left auricle and ventricle.* * It was asserted by Vicussens, at an early period in the last century, and soon afterwards by Thebesius, a German Professor, that there were a number of small orifices in the texture of the heart, which opened into the different cavities on both sides of it. This assertion of a fact so difficult to reconcile with the general principles of the circulation, was received with great hesitation: and although it was confirmed by some very respectable anatomists ofthe last century, it was denied by others. Some ofthe anatomists ofthe present day have denied the existence of these orifices, and some others have neglected them entirely. The subject was brought forward in the London Philosophical Transactions of 1798 Part I. by a very respectable anatomist, Mr. Abernethy, who states that he has often passed a coarse waxen injection from the proper arteries and veins of the 514 GREAT VESSELS OF THE HEART. From the course of these different vessels round the basis of the ventricles of the heart, they are generally called Coronary Vessels: the arteries are denominated, from their position, Right and Left Coronary. The nerves of the heart come from the cardiac plexus, which is composed of threads derived from the intercostal or great sympathetic nerves, and the nerves of the eighth pair. Of the Aorta, the Pulmonary Artery and Veins, and the Venae Cavae ; at their commencement. The two great arteries, which arise from the heart, com- mence abruptly, and appear to be extremely different in their composition and structure from the heart. They are composed of a substance, which has a whitish colour, and very dense texture, and is very elastic as well as firm and strong. When the pericardium is removed, these arteries appear to proceed together from the upper part of the basis of the heart: the pulmonary artery being placed to the left of the aorta with the left auricle on the left side of it, and the right auricle on the right side of the aorta. The pulmonary artery arises from the most anterior and left part of the basis of the right ven- tricle, and proceeds obliquely backwards and upwards; inclining gradually to the left side for about eighteen or twenty lines; when it divides into two branches which pass to the two lungs. The aorta arises from the left ventricle, under the origin of heart into all the cavities of that organ, and particularly into the Left Ventricle. Bui it was only in subjects with diseased lungs that this was practicable. The existence of this communication between the coronary vessels and the great cavities of the heart seems therefore to be proved. The easy demonstration of such subjects is ingeniously referred by Mr. Abernethy, to the obstruction of the circu- lation in the lungs ; and he regards the communication as a provision enabling the coronary vessels to unload themselves, when the coronary vein cannot discharge freely into the right auricle.* * This assertion of Mr. Abernethy's, has not been confirmed by subsequent investigations, except in cases where the tissue of the heart was softened, and its vessels had been ruptured by the force of the injection—P. GREAT VESSELS OF THE HEART. 515 the pulmonary artery, and immediately proceeds to the right, covered by that vessel, until it mounts up between it and the right auricle : it then forms a great curve, or arch, which turns backward and to the left, to a considerable distance beyond the pulmonary artery. In this course, it crosses the right branch of the pulmonary artery ; and, turning down in the angle between it and the left branch, takes a position on the left side of the spine. Fig. 127.* c cL b 7v a The course of this artery, from its commencement at the ven- tricle, to the end of the great curve or arch, is extremely varied. The uppermost part of the curve is in the bottom of the * Fig. 127.—-a, Left Ventricle, b, Right ventricle, c, Right auricle. The left auricle is seen above the left-ventricle of the same side, d, Vena cava inferior, e, Subclavian and jugular veins; those of the left side unite to form the vena transversa; those of the right, to form the vena innominata; the junction of these larger trunks, constitutes the vena cava superior or descendens. /, Left carotid, g, Left subclavian artery, arising from the arch of the aorta, h, Descending aorta, i, ft, Right subclavian, and right carotid, given off from the arteria innominata, which is seen arising from the arch of the aorta. I, Pulmonary artery, dividing into two branches, one for each lung—the left passing in front of the descending aorta, the right, behind the aorta, where it begins to form the curve, m, Vena cava superior, n, Aorta, o, Left pulmonary veins, entering auricle of same side. The right pulmonary veins, are seen on the opposite side, p, p, Lungs, t, Trachea.—p. 516 VENJE CAViE. chamber formed by the separation ofthe lamina of the medias- tinum when they join the first rib on each side. From this part of the curve three large branches go off, namely, one, which soon divides into the carotid and the sub- clavian arteries of the right side; a second, somewhat smaller, which is the left carotid; and a third, which is the left subclavian artery. When the heart and its great vessels are viewed from be- hind, (after they have all been filled with injection; and the pericardium, mediastinum, and windpipe have been removed,) the aorta appears first, descending behind the other vessels; the pulmonary artery then appears, dividing so as to form an obtuse angle with its two great branches, each of which divides again before it enters the lung to which it is destined. Under the main trunk of the pulmonary artery ^ is the left auricle: its posterior surface is nearly of a square form, and each of the pulmonary veins proceeds from one of its angles. These veins ramify in the substance of the lungs, at a very short distance from the auricle: the two uppermost of them are situated rather anterior to the branches of the pulmonary artery. In this posterior view, the pulmonary vessels of the right side cover a great part of the right auricle, as it is anterior to them. The lower portion of the auricle, with the termination of the inferior cava, is to be seen below them. Above them the superior cava appears; and in that part of it which is immediately above the right branch of the pulmonary artery, is the orifice of the vena azygos. In its natural situation in the thorax, the superior cava is connected by cellular membrane to the right lamen of the mediastinum, and is supported by it. At a small distance below the upper edge of the sternum, it receives the trunk formed by the left subclavian and internal jugular vein, which passes obliquely across the sternum below its inner edge, in the upper space between the lamina of the mediastinum. THE TRACHEA. 517 CHAPTER XVII. OF THE TRACHEA AND THE LUNGS. Although the principal part of the windpipe is situated in the neck above the cavity of the thorax, it is so intimately connected with the lungs, that it is necessary to describe them together. Ofthe Trachea. Trachea is the technical name for the windpipe, or the tube which passes from the larynx to the lungs. This tube begins at the lower edge of the cricoid cartilage, and passes down the neck in front of the oesophagus as low as the third dorsal vertebrae, when it divides into two branches called Bronchia, one of which goes to the right and the other to the left lung, in which they ramify very minutely. —The right bronchium is larger than the left, in proportion to the greater size of the right lung. It is also shorter and placed more anterior and more horizontal than the left, in consequence of the right lung being shorter in its vertical diameter, and longer in its antero-posterior than the lung of the left side. It enters near the centre of the root ofthe lung, opposite to the fourth dorsal vertebra. —The left bronchium terminates or enters the root of the left lung, opposite the fifth dorsal vertebrse. The right bronchium is embraced at its upper part by the vena azygos, the left by the arch of the aorta.— There is in the structure of each, a number of flat cartilaginous rings placed at small distances from each other, the edges of which are connected by membrane, so that they compose a tube. These cartilaginous rings are not complete, for they do not form more than three-fourths or four-fifths of a circle ; but their ends are connected by a membrane which forms the posterior part of the tube. 44 51S STRUCTURE OF THE TRACHEA AND BRONCHIA. They are not alike in their size or form ; some of them are rendered broader than others, by the union of two or three rings with each other, as the uppermost. The lowermost also is broad, and has a form which is accommodated to the bifurca- tion of the tube. Their number varies in different persons, from fifteen to twenty. These rings may be considered as forming a part of the first proper coat of the trachea, which is composed of them, and of an elastic membrane that occupies all the interstice between them; so that the cartilages may be regarded as fixed in this membrane. A similar arrangement of rings exists in the great branches of the bronchia; but after they ramify in the lungs, the carti- lages are no longer in the form of rings : they are irregular in their figures, and are so arranged in the membrane, that they keep the tube completely open. These portions of cartilage do not continue throughout the whole extent ofthe ramifications; for they become smaller, and finally disappear, while the mem- branous tube continues without them, ramifying minutely, and probably forming the air-cells of the lungs. —At the orifices of the bronchial ramifications, the existence of a semilunar cartilage has been pointed out by Prof. Horner, forming rather more than half of their circumference, and having its concave edge turned upwards. These cartilages appear to be intended to keep the orifices open.*— The membranous is very elastic : the lungs are very elastic also ; and it is probable that their elasticity is derived from this membrane. On the inside of this coat of the trachea is an arrangement of musclar fibres, which may be called a muscular coat. It is best seen by peeling off or removing the internal coat, to be next described. On the membranous part of the trachea, where the cartilagi- nous rings are deficient, these muscular fibres run evidently in a transverse direction : in the spaces between the cartilages * Special Anatomy, by W. E. Horner, M. D. Prof. Anat. Univers. Pennsylvania. STRUCTURE OF THE TRACHEA AND BRONCHIA. 519 their direction is longitudinal. There is some reason to doubt whether these longitudinal fibres are confined altogether to the spaces between the cartilaginous rings, and attached only to their edges, because there is a fleshy substance on the inter- nal surface of the rings, which appears to be continued from the spaces between them. The internal coat of the trachea is a thin and delicate mem- Fig. 128.* brane, perforated with an im- mense number of small foramina, which are the orifices of mucous ducts. On the surface of this mem- brane there is an appearance of longitudinal fibres which are not distributed uniformly over it, but run in fasciculi in some places, and appear to be deficient in others. These fasciculi are par- ticularly conspicuous in the rami- fications of the bronchia in the lungs. —Many of the German anato- mists have described these as longitudinal muscular fibres, the object of which is to shorten to some extent the air-passages during their contraction, and to assist in loosening the mucus and other matters which accumulate in their cavities. I have examined these carefully in the ox and elephant, where they are strongly marked; they appeared to me to consist only of longitudinal folds of mucous membrane, with a basis of the fibrous contractile tissue. The same arrangement of circular fibres, and these peculiar longitudinal fibres, can be traced with the microscope down the bronchia as far as * Fig. 128, represents the larynx, trachea, and bronchia; on the right side is seen the lung; on the left, the lung has been destroyed to show the ramification of the bronchia, a, Larynx, b, Trachea, dividing into right and left bronchium ; the left is the smaller, longer, and inclined most downwards, c, Larger divisions ofthe left bronchium; e, the more minute, d, Right lung.—p. 520 THE LUNGS. these can be distinctly opened. The contractibility ofthe pul- monary tissue under the influence of galvanism observed by Dr. C. J. B. Williams, seems to establish the muscularity ofthe circular fibres.— On the posterior membranous portion of the trachea, where the cartilages are deficient, a considerable number of small glandular bodies are placed, which are supposed to communicate with the mucous ducts that open on the internal surface. If these bodies are removed from the external surface of this portion, and the muscular fibres are also removed from the internal, a very thin membrane only remains, which is very different from that which is left between the rings, when the fleshy substance is removed from that situation. i The reason of the deficiency in the rings, at this posterior part, is not very obvious.* It continues in the bronchia until the form of their cartilages is changed in the lungs: if it were only to accommodate Lthe oesophagus, during the passage of food, there would be no occasion for its extension to the bronchia. At the bifurcation ofthe trachea, and on the bronchia, are a number of black coloured bodies, which resemble the lymphatic glands in form and texture. They continue on the ramifications of the bronchia some distance into the substance of the lungs. Their number is often very considerable; and they vary in size from three or four lines in diameter to eighteen or twenty. As lymphatic vessels have been traced to and from them during their course to the thoracic duct, they are considered as lym- phatic glands. Of the Lungs. There are two of these organs: each of which occupies one of the great cavities of the thorax. When placed together, in their natural position, they resem- ble the hoof of the ox, with its back part forward; but they are * Dr. Physick has advanced the opinion that it enables a person to expel the mucus ofthe lungs by contracting the size of the trachea, and consequently increas- ing the velocity or impetus ofthe air.—H. ROOT OF THE LUNGS. 521 at such a distance from each other, and of such a figure, that they allow the mediastinum and heart to intervene; and they cover every part of the heart anteriorly, except a small portion at the apex. Each lung fills completely the cavity in which it is placed, and every part of its external surface is in contact with some part of the internal surface of the cavity; but when in a natural and healthy state, it is not connected with any part except the lamina of the mediastinum. —The lower extremity or base of each lung, rests upon the pleural lining of the diaphragm, and fills up the angle between the diaphragm and the ribs; the superior projects upwards and backwards, along the first rib and above the level of the clavi- cle, so asto be separated from the scalenus anticus muscle only by the pleura. In laborious respiration, the elevation of the apex of the lung is increased, and the motion it produces becomes visible at the root of the neck. The external face of the lungs is convex, to suit the contour of the thoracic parietes. The internal, and especially that of the left, is concave to accommodate the heart and pericardium. The anterior edge is thin and sinuous, and presents on the left side a deep notch fitted to the shape of the heart, and a sort of lobular projection which in part covers that organ during deep inspiration.— One great branch of the trachea and of the pulmonary artery passes from the mediastinum to each lung, and enters it at a place which is rather nearer to the upper rib than to the diaphragm, and much nearer to the spine than the sternum: at this place also the pulmonary veins return from the lungs to the heart. These vessels are enclosed in a membrane, which is continued over them from the mediastinum, and extended from then to the lung. Thus covered they constitute what has been called the Root of the Lung. When their covering, derived from the mediastinum, is removed, the situation of these vessels appears to be such that the bronchia are posterior, the branches of the pulmonary 44* 522 COLOUR OF THE LUNGS. artery are rather above and before, and the veins below and before them. Each of these vessels ramifies before it enters into the substance of the lungs: the bronchia and the branches of the pulmonary artery send each a large branch downward to the inferior part of the lungs, from which the lower pulmonary veins pass in a direction nearly horizontal. In general, each of the smaller ramifications of the bronchia in the lungs is attended by an artery and a vein. Each lung is divided, by very deep fissures, into portions which are called Lobes. The right lung is composed of three of these lobes, and the left lung of two. (See fig. 127, page 515.) —Each of these lobes are subdivided into many smaller parts called lobules, which are marked out on the surface of the lungs, by various angular lines. Each bronchium divides into two principal branches for the lobes of the left lung, and into three for the right; after which, a still further subdivision takes place, so that a terminal bronchial branch is sent to each lobule.— The lungs are covered, as has been already stated, with the reflected portion of the pleura continued from the mediastinum, which is very delicate and almost transparent. They have, therefore, a very smooth surface, which is kept moist by exu- dation from the arteries of the membrane. The Colour of the Lungs is different in different subjects. In children they are of a light red colour; in adults they are often of a light gray, owing to the deposition of a black pig- ment in the substance immediately under the membranes which form their external surface. Their colour is often formed by a mixture of red and black. In this case they are more loaded with blood, and the vessels of the internal mem- branes being distended with it, the red colour is derived from them. The black pigment sometimes appears in round spots of three or four lines in diameter: under the external membrane it is often in much smaller portions, and sometimes is arranged in STRUCTURE OF THE LUNGS. 523 lines in the interstices of the lobuli, to be hereafter mentioned. It is also diffused in small quantities throughout the substance ofthe lungs. The sources of this substance, and the use of it, are unknown. The lungs are of a soft spongy texture ; and, in animals that have breathed, they have always a considerable quantity of air in them. They consist of cells, which communicate with the branches of the trachea that ramify through them in every part. These cells are extremely small, and the membranes which compose them are so thin and delicate, that if they are all filled by an injection of wax, thrown into the trachea, the whole cellular part of the lung will appear like a mass of wax. If a corroded preparation be made of a lung injected in this manner with force, the wax will appear like a concretion. These effects of injections prove that the membranes of which the cells are formed are very thin ; and, of course, that their volume is very small when compared with the capacity of the cells. In those corroded preparations, in which the ramifications of the bronchia are detached from the wax of the cells, these ramifications become extremely small indeed.—The cells above alluded to are in fact but the ultimate termination of the last branches of the bronchia in small dilated sacs, called the bron- chial or pulmonary cells.— If the lungs of the human subject, or of Janimals of similar construction, be examined when they are inflated, their cellu- lar structure will be very obvious, although their cells are so small that they cannot commonly be distinguished by the naked eye. Each of the extreme ramifications of the bronchia appears to be surrounded by a portion of this cellular sub- stance, which is gradually distended when air is blown into the ramification. This cellular substance is formed into small portions of various angular figures, which are denominated Lobuli: these can be separated to a considerable extent from each other. 524 STRUCTURE OF THE LUNGS. They are covered by the proper coat of the lungs, which is extremely delicate, and closely connected to the general cover- ing derived from the pleurae. Between the lobuli, where they are in contact with each other, there is a portion of common cellular substance, which is easily distinguished through the membrane covering the lungs. This is very distinct from the cellular structure which communicates with the^ramifications of the bronchia, and contains air; for it has no communica- tion with the air, unless the proper coat of the lungs be rup- tured. If a pipe be introduced by a puncture of the external coat of the lungs, and this interstitial cellular membrane be inflated, it will compress the lobuli. This cellular membrane is always free from adipose matter : it may be easily examined in the lungs of the bullock. Upon the membranes which compose the air-cells, the pul- monary artery and vein ramify most minutely; and it seems to have been proved by the united labours of chemists and physiologists, that the great object of respiration is to effect a chemical process between the atmospheric air, when taken into the air-cells, and the blood which circulates in these vessels. In addition to the blood-vessels which thus pass through the substance of the lungs, there are several smaller arteries deno- minated Bronchial, which arise either from the upper inter- costal, or from the aorta itself; they pass upon the bronchia, and are distributed to the substance of the lungs. The veins which correspond with these arteries terminate ultimately in the vena azygos. The nerves of the lungs are small in proportion to the bulk of these organs. They are derived principally from the par vagum and the intercostal nerves. —They form one plexus on the front, and another on the posterior surface of the bronchia, along which they are con- ducted to the minutest subdivision of the latter in the substance of the lungs.— The elasticity of the air-cells of the lungs and of the ramifi- cations ofthe bronchia which lead to them, is apparent in their STRUCTURE OF THE LUNGS. 525 rapid contraction after distention, and by the force with which they expel the air which is used to inflate them when taken out ofthe thorax. —The specific gravity of the lungs is not naturally greater than that of many other tissues. In a still-born child, sections of it sink in water like a piece of muscle. But when its cells have been once distended by air in respiration it becomes im- possible to extrude it completely (unless it is subjected to strong compression) and the lung floats upon the water and appears to have the least specific gravity of all the animal tissues. The lungs are endowed with a considerable degree of elasticity, that appears to be derived from the elastic tissue of the bronchia which is spread universally through the lungs. When distended they have a constant tendency either in or out ofthe body to return upon themselves and expel the air. —It will now be seen that the proper tissue of the lungs, the parenchyma, the areolar tissue, is very complicated. It consists of the cells of the bronchia for the reception of air, which are formed internally of mucous membrane and externally most probably of a thin expansion ofthe yellow elastic ligamentous layer of the bronchia ; of a branch of the pulmonary arteries and veins, which run over the outer surface of the cells, the former bringing the black blood, and the latter conveying it away after it has been changed by the action ofthe air through the walls of the cells ; of the bronchial arteries and veins for the purpose of nutrition ; of absorbent vessels to remove the molecules as they become effete; of filaments of the sympa- thetic and par vagum nerves, which preside over the function of hsemaetosis, and put the lungs in connexion with the brain; and lastly of cellular tissue which unites the whole together. The mucous membrane lining the trachea, bron- chia, and air cells, when examined with the microscope, have been found lined with a columnar epithelium, mounted with vibratile cilia, the same as has been described as covering the Schneiderian membrane. The use of the cilia in these organs, it is believed, is that of aiding in urging the secretions upwards towards the larynx. 526 THORAX OF THE FffiTUS. —Between the bronchial and pulmonary arteries and veins, there is an intimate anastomosis so that either system of ves- sels may be filled by the use of fine injecting fluid through the other. The cells of each lobule, according to Professor Horner, Cloquet, and some other anatomists of distinction, communi- cate laterally with each other. Reisseissen, Gerber, and other microscopists, figure each one as a perfect cul de sac; the developement of the lungs in the foetus resembling in its early stages very closely that of the compound glands. The diame- ter of these cells has been measured by Weber of Leipzig,* by the aid of a micrometer attached with extreme care and ingenuity to a microscope. According to him they are upon an average about ^-J „ part of an inch in diameter, which makes them five or six times larger than the cells of the parotid gland, and fifteen or twenty times larger than the finest capillary blood-vessels measured on a portion of skin which had been very perfectly injected by Dr. Pockels of Brunswick.— The Thorax of the Foetus. In the cavity between the lamina of the mediastinum, where they approach each other from the first ribs, is situated, a sub- stance which is denominated the Thymus Gland. This substance gradually diminishes after birth, so that in the adult it is often not to be found: and when it exists it is changed in its texture, being much firmer, as well as greatly diminished. In the foetus it is of a pale red colour; and during infancy it has a yellowish tinge. It generally extends from the thyroid gland, or a little below it, to the pericardium. From its supe- rior portion two lateral processes are extended upwards: below, it is formed into two lobes, which lie on the pericardium. If an incision be made into its substance, a fluid can be * Meckel's Archiv. fur Anat. and Physiol., 1830.— THORACIC FASCIA. 527 pressed out, which has a whitish colour, and coagulates upon the addition of alcohol. Although it is called a gland, no excretory duct has ever been found connected with it. —The thymus gland in the foetus at birth, extends from the fourth rib, as high up as the thyroid gland. It rests upon the pericardium below, and is separated from the arch of the aorta and the great vessels, by a fasciae, called by Sir A. Cooper, the thoracic, which is composed of a dense layer of fibro-cellular membrane, stretched between the concave margins of the first rib of each side horizontally across the upper opening of the Fig. 129.* thorax. It is connected below with the fibrous sac of the pericardium, with the arch of the aorta which it in a measure sustains, and the great vessels that come off from it. Above, it is connected with the sheath of the carotid, and the deep cervical and tracheal fasciae. This fascia has an opening in * A'section ofthe thymus gland at the eighth month, showing its anatomy. This figure is taken from one of Sir Astley Cooper's beamiful engravings. 1. The cer- vical portions of the gland; the independence of the two lateral glands is well marked. 2. Secretory cells seen upon the cut surface of the section; these are observed in all parts of the section. 3, 3. The pores or openings of the secretory cells and pouches; they are seen covering the whole internal surface of the great central cavity or reservoir. The continuity of the reservoir in the lower or thoracic portion ofthe gland, with the cervical portion, is seen in the figure. 528 INTIMATE STRUCTURE OF THE THYMUS GLAND. front, through which passes up the cervical portion of the thymus gland. —The gland consists of two halves, connected in the middle by cellular tissue only, which may properly be called a right and left lobe. According to Sir A. Cooper, who has published a beautiful monograph on the structure of this organ, the gland grows gradually with the increasing growth of the foetus, till the seventh month. During the ninth it is suddenly and greatly increased in size, and at birth weighs two hundred and forty grains. It continues to enlarge till the end of the first year after birth, when it begins to diminish in size, and by the period of puberty has almost entirely disappeared. Each right and left lobe, is composed of lobules disposed in a spiral form round a central cavity, which is called a reservoir. —The lobules are held together by dense cellular tissue, and, the whole gland is surrounded by a coarse cellular capsule. The lobules which make this a conglomerate gland are very numerous, and vary in size from that of the head of a pin to a common pea. In each lobule there is a small cavity or secre- tory cell. Several of these cells open into a small pouch, and this again into the central cavity or reservoir, which is lined by a vascular mucous membrane. —Each lobe of the gland may be carefully unravelled by removing the coarse cellular capsule and vessels, and dissecting away the firm cellular tissue that holds the lobules together; the reservoir then, which in its natural state is folded in a serpentine manner upon itself, may be drawn out into a length- ened tubular cord, around which the lobules are clustered in a spiral manner, and resemble knots upon a cord, or a string of beads. The reservoir, pouches, and cells, contain a white fluid like chyle or cream, with a small admixture of red globules. The use of this gland is not known. Sir A. Cooper, is disposed to believe, in common with several ofthe older writers, that the gland is designed to prepare a fluid from the blood of the mother, well fitted for the growth and nourishment of the foetus before its birth, and consequently, before chyle is formed by it from food; this process continuing for a short time after THORAX OF THE FQ3TUS. 529 Fig. 130. birth—the quantity of fluid secreted from the thymus, gradu- ally declining, as that of chylification becomes perfectly estab- lished.— The arteries of this body are de- rived from the thyroid branches of the subclavians, from the internal mammaries, and the vessels of the pericardium and mediastinum.—The veins terminate mainly in the left vena innominata. —The nerves are very minute, and are chiefly derived through the plexus about the internal mammary artery from the superior thoracic ganglion of the sympathetic. The lymphatics ter- minate at the common junction of the other vessels of the kind, at the union ofthe internal jugular and subclavian veins. Sir A. Cooper has injected them but once in the human foetus. In the calf he found two large lym- phatic ducts, see fig. 130, which com- mence at the upper extremities of the lobes, and pass downwards to termi- nate at the junction of the jugular and subclavian of each side. These ves- sels he considers the absorbent ducts the thymuc ducts which carry the fluid from the reservoir of the thymus into the veins.— of the glands The Heart, And the great arteries which proceed from it, have some very interesting peculiarities in the foetus. * The course and termination of the " absorbent ducts" ofthe thymus ofthe calf; from one of Sir Astley Cooper's preparations. 1. The'two internal jugular veins. 2 The superior vena cava. 3. The thoracic duct, dividing into two branches, which re-unite previously to their termination in the root of the left jugular vein. 4. The two thymic ducts ; that on the left side opens into the thoracic duct, and that on the right into the root of the right jugular vein. 45 530 THE THORAX OF THE FffiTUS. In the septum between the two auricles, is a foramen of suf- ficient size to permit the passage of a large quill, which inclines to the oval form, with its longest diameter vertical when the body is erect. On the left side of the septum, a valve, formed by the lining membranes, is connected to this foramen ; and allows a free passage to a fluid moving from the right auricle to the left; but prevents the passage of a fluid from the left to the right. This structure is evidently calculated to allow some ofthe blood which flows into the right auricle from the two venae cavae to pass into the left auricle of the heart, instead of going into the right ventricle. As the contents of the left auricle pass into the left ventricle, and from thence into the aorta, it is obvious that the blood which passes from the right auricle into the left through this foramen, must be transmitted from the system of the vena cava to the system of the aorta, without going through the lungs, as it must necessarily do in subjects who do not enjoy the foetal structure. —The valve, with which in the foetus the foramen ovale is provided, on the side of the left auricle, is of a semilunar shape and called the valve of Botal; it has a convex border, adherent, and turned downwards; and a concave border, free3 and turned upwards. The angles resulting from the union of these borders are at birth attached to each side of the fora- men about a quarter of an inch distant from each other. The valve makes its appearance in the foetus at the third month of intra-uterine existence, and gradually increases in size, so as to more than cover the foramen at the period of birth. When the child breathes and the lungs become filled with blood, the fluid, entering the left auricle by the pulmonary veins, throws down the valve against the septum auriculorum, to which its free border usually becomes firmly united. —Occasionally, however, the union of the parts is found so incomplete, even in old persons, as to allow a probe or even the handle of a scalpel to be passed obliquely through the opening : the obliquity of the orifice being such, as usually to enable it to act as a perfect valve. A communication of this sort, of greater or less magnitude between the auricles, exists TnE THORAX OF THE FffiTUS. 531 in adults, according to Biot, in the ratio of one to four. But judging from my own observations, this proportion of cases in which the opening exists is much too great. Sometimes the foramen is met with in adults so dilated as to be nearly an inch in diameter. I have met with two cases of this sort in the dissecting-room, both of which occurred in females between twenty and thirty years of age. The nutritive functions appeared to have been perfectly well performed in both these subjects, judging from the state of the body; the right auricle and ventricle were dilated and hypertrophied so as to present the same thickness of parietes as the corresponding parts of the left side. The tricuspid valves, and the semilunar valves of the pulmonary artery were thickened, and presented cartilaginous concretions on their edges, in which the work of ossification had just commenced. This thickening and ossification of the valves is almost wholly peculiar in the normal formation of the heart to the valves to the left side, and appears to be caused, as was first suggested by Cruveilhier, by the force with which the blood is dashed against the valves, in the forcible contrac- tions of the ventricle.— The Pulmonary Artery and the Aorta, Have a communication in the foetus, which is very analo- gous to the communication between the auricles of the heart. From the pulmonary artery, where it divides into the two great branches, another large branch continues in the direction ofthe main trunk, until it joins the aorta; with which vessel it communicates at a small distance below the origin ofthe left sub- clavian artery. In the young subject that has never respired, it appears as if the pulmonary artery was continued into the aorta and sent off in its course a branch on each side, much smaller than itself, to each lung. In subjects that have lived a few days, these branches to the lungs are' much larger; and then the main pulmonary artery appears to have divided into three branches: one to each lung, and one to the aorta; but that which continues to the aorta is larger than either of the others. 532 GENERAL OBSERVATIONS. In the course of time, however, this branch of the aorta is contracted, so that no fluid passes through it; and it has the appearance of a ligament, in which state it remains. The course ofthe blood from the right ventricle, through the pulmonary artery to the aorta below its curve, is more direct than that from the left ventricle to the same spot through the aorta at its commencement. The column of blood in the aorta below its curve is evidently propelled by the force of both ventricles: and this circumstance, although it seems to pro- ceed merely from the state of the foetal lungs, is particularly calculated for the very extensive circulation which the fcetus carries on, by means ofthe umbilical arteries and vein in the placenta. The Lungs of the Foetus Differ greatly from those of the adult. They appear solid, as if they were composed ofthe parenchymatous substance which constitutes the matter of glands, rather than the light spongy substance of the lungs of adults. They differ also in colour from the lungs of older subjects, being of a dull red. They have greater specific gravity than water ; but if air be once inspired, so much of it remains in them that they ever afterwards float in the former fluid. The nature of the process of respiration, and its effects upon the animal economy, particularly upon the action of the heart, appear to be much better understood at this time than they were before the discovery of the composition of the atmos- phere, by Dr. Priestley and Mr. Scheele. The publications upon this subject, which have appeared since that period, namely, 1774, are therefore much more interesting to the student of medicine than those which preceded them/- Two of these publications ought to be particularly noticed by him; namely, an essay, by Dr. Edward Goodwyn, entitled, "The Connexion of Life with Respiration;"- and the " Physiological Researches of M. Bichat upon Life and Death." Part Second.* The general doctrines respecting the oxygenation or decarbonization of the blood and the absolute necessity that it should take place to a certain degree in order to * Th!of!UfDt WiU derive much informati°n respecting the publications on this subject, prior to 1804, from Dr. Bostock's Essay on Respiration.-Since the publication of that essay several .nterestmg papers on respiration have appeared, namely, Two Memoirs by the late Abbe Spallan- zani; An Inquiry into the Changes induced on Atmospheric Air by the Germination of seeds," &c, by Ellis; two very important communications by Messrs. Allen and Pepys in the Transactions ofthe Royal Society of London for 1808 and 1809; and " Farther Inquiries into the Changes induced on Atmospheric Air," also by Ellis. CASES OF MALFORMATION. 533 preserve life, are confirmed by a number of cases of malformation of the heart or the great vessels, in which the structure was such that a considerable portion of venous blood passed from the right side of the heart to the aorta, without going through the lungs. In these different cases, notwithstanding the structure was somewhat varied, the symptoms produced were very much alike ; differing in the respective patients in degree only, and not in kind. The symptoms indicating this structure, are blue colour of the face, (such as gen- erally accompanies suffocation,) extending more or less over the whole body, and particularly apparent under the nails of the fingers and toes; anxiety about the region of the heart; palpitation; laborious respiration ; sensations of great debility, &c: all of which are greatly aggravated by muscular exertion. These effects have generally appeared to be proportioned to the quantity of venous blood admit- ted into the aortic system.* When these appearances take place immediately after birth, it is probable that they depend entirely upon malformation of the heart or great vessels; but when they commence at a subsequent period, they are commonly the effect of a diseased alteration in the lungs. They sometimes occur near the termination of fatal cases of pneumonia or catarrh; but a different cause, which has not latterly been sus- pected, appears to have produced them in the following case, related by Dr. Marcet, in the first volume of the Edinburgh Medical and Physical Journal. The blue colour occurred in a young woman, twenty-one years of age, in whom it had never been observed before. It came on during an affection of the breast, and was attended with great prostration of strength and difficulty of breathing, as well as cough, oedema of the hands and feet, and several other symptoms. About seven weeks after the commencement of these symptoms, she died; when it was ascertained by dissection, that there was no unnatural communication what- ever between the cavities of the heart, and that its valves were all in a perfect and natural state. The lungs were free from tubercles, or any other appearance of disease. Their substance seemed more compact than usual, especially the left lung, although it did not sink in water ; but they adhered every where to the inner surface of the thorax, to the diaphragm and to the pleura covering the pericardium. This case is the more remarkable, because numberless instances have occurred, in which very large portions of the external surface of the lungs have been found, upon dissection, to adhere to the internal surface of the thorax, without the oc- currence of such symptoms during life. It may be inferred, from a statement published by M. Dupuytren, in a volume of the Proceedings of the National Institute of France, that the oxygenation or decarbonation ofthe blood is much affected, in respiration, by an influence exercised bv the nerves which are appropriated to the lungs. From his account it appears, that although the complete division of the eighth pair of nerves produces death after some time; yet in the horse, whose nerves are thus divided, life continues, * Cases of this kind are related in several ofthe periodical publications on medical subjects. Two f th were described by Dr. William Hunter in the sixth volume of " Medical Observations .. • ies by a society of Physicians in London;" one quoted by Dr. Goodwyn, is in the Observa- A tomicae of Sandifort; and another by Dr. J. S. Dorsey, has been published in the fimnumber ofthe New England Journal of Medicine and Surgery. 45* 534 EFFECT OF VENOUS BLOOD ON THE HEART. and respiration goes on, from half an hour to ten hours ; but his arterial blood is in a state of great disoxygenation or carbonation during this time. This fact is more remarkable because venous blood, contained in a bladder exposed to the open air will become oxygenated or decarbonated. It is also asserted in another Memoir, read to the National Institute by Dr. J. M. Provencal; that animals, in whom the eighth pair of nerves has been divided, do not consume so much oxygen, or produce so much carbonic acid, by a considera- ble degree, as they did before the division of these nerves ; and that their temper- ature is considerably reduced.* The effect, that venous blood occasions death, when it is admitted into the left ventricle of the heart, and the aorta, is truly important. Dr. Goodwin explained it by suggesting that this blood was not sufficiently stimulating to produce the necessary excitement of the heart; but on this occasion one of his friends proposed to him the following question : Why does venous blood affect the left side of the heart in this injurious manner, when it appears to exert no noxious effects whatever on the right side of that organ ? His reply may be seen in a note at the 82d page of his Essay, in the first edition. Bichat has offered a solution which completely resolves this difficulty, viz. "The effect of venous blood upon the heart is produced by the presence of this blood in the proper, or coronary arteries of that organ, and not in its great cavities." For the animation of the heart, like that of the other parts of the body, depends upon the state of the blood in the arteries which penetrate its texture.t And while the heart acts, the blood of the coronary arteries will be the same with that of the left ventricle. See Bichat's Researches, P. II. art. 6, $ 2. The French anatomists at one time entertained some peculiar opinions respecting the course of the blood in the foetus, which have a particular relation to the subject last mentioned. Winslow, who paid great attention to the valve of Eustachius in the right auricle of the heart, was of opinion, that this valve was calculated for some important purpose in the foetal economy.t Although his hypothesis respecting its particular use has not been retained by his countrymen, many of them have adopted his general sentiment; and among others Sabatier. That learned anato- mist believed that this valve, in the foetal state, serves to direct the blood of the inferior cava, after its arrival in the right auricle through the foramen ovale into the left auricle; while the blood of the upper cava passes directly into the right ventricle. His opinion seems to be supported to a certain degree— 1. By the direction in which the two columns of blood enter the auricles from the two venae cavae. 2. By the position of the Eustachian valve. 3. By the foraman ovale, when its valve is complete ; as the passage through it from the right to the left, is at that time oblique, and from below upwards. The theory of Sabatier appears to be this:—the umbilical vein brings from the * These Memoirs were republished in the Eclectic Repertory of Philadelphia for April and October, 1811. t It is probable that the contents of the great cavitips of the heart have no more effect upon its animation than the contents ofthe stomach and bowels have upon the animation of those organs. X See Memoirs ofthe Academy of Sciences for 1717 and 1725. SENTIMENTS OF SABATIER, ETC. 535 placenta blood which has a quality essential to the animation of the fcetus. If there were no particular provision to the contrary, a large portion of this blood, after passing from the umbilical vein by the inferior cava into the right auricle of the heart, would proceed by the right ventricle through the pulmonary artery and arterial canal, into the aorta, below the origins of the carotid and subclavian arteries; and consequently none of it would pass to the head and upper extremities, but a considerable part would return again by the umbilical arteries to the placenta, without circulating through the body : while, on the other hand, the blood which passed by the carotid and subclavian arteries fo the head and upper extremities returning from them to the heart by the superior cava, might pass from the right auricle to the left auricle and ventricle and the aorta, and so to the head and upper extremities again, without passing through the placenta. But by means of this valve, the blood ofthe lower cava, and of course ofthe umbilical vein, is directed to the left auricle and ventricle and the aorta, by which a considerable portion of it will necessarily pass to the head and upper extremities; while the blood which returns from these parts by the superior cava, must consequently pass from the right auricle into the right ventricle and pulmonary artery; from whence a large portion of it will proceed through the arterial canal into the aorta beyond the caro- tids and subclavians, and of this portion a considerable part will go to the placenta by the umbilical arteries. Sabatier compares the course of the blood in the fcetus to the course of a fluid in a tube which has the form of the numeral character 8.* If this doctrine be true, the progress ofthe blood in the foetus and placenta is very analagous to that of the double circulation of the adult; the character 8 answering equally well in the description of either subject. According to Sabatier, the blood of the placenta takes this peculiar course through the heart, in order that some of it may be carried to the head and upper extremi- ties. But an additional reason may be suggested, which appears to be of great importance; namely, the supplying ofthe coronary or proper vessels ofthe heart, with some of the same blood. The heart of the adult, as has been before stated, cannot act without its proper or coronary arteries are supplied with arterial blood. The heart of the fcetus performs a more extensive circulation than that of the adult, and, therefore, is probably in greater need of such blood. But unless the blood of the placenta pass through the foramen ovale into the left auricle and ventricle, and so to the aorta, it cannot en- ter the coronary arteries which originate at the commencement of the aorta ; for the blood which flows from the right side ofthe heart through the arterial canal, passes into the aorta at so great a distance from the orifices of the coronary arteries, that it certainly cannot enter them. The whole of this doctrine seems to be supported by a fact very familiar to accouch- eurs, viz. the occurrence of death in the fcetus whenever the circulation through the umbilical cord is suspended during fifteen or twenty minutes; for as the pla- centa imparts to the foetal blood a quality essential to life, some arrangement seems necessary to provide for the equal distribution of the blood which comes from this organ and especially for carrying the requisite proportion of it to the substance of the heart. Life has existed for some time with a structure very different indeed from that which is natural. In the series of elegant engravings relating to morbid anatomy, * See Sabatier's Paper on this subject, in the Memoirs ofthe Academy of Sciences, for 1774. 536 USUAL CASES OF MALFORMATION. published by Dr. Baillie, is the representation of a heart, in which the venae cavae opened into the right auricle, and the pulmonary veins into the left auricle, in the usual manner; but the aorta arose entirely from the right ventricle, and the pul- monary artery as completely from the left. The canalis arteriosus, however, passed from the pulmonary artery to the aorta, and the foramen ovale existed. In this case, it is evident, that the pulmonary artery must have carried back to the lungs the arterial blood which came from them by the pulmonary veins, with a small quantity of venous blood that passed into the left auricle through the foramen ovale; and that the aorta must have returned to the body the venous blood, which just before had been brought from it by the venae cava3, with a small addition of arterial blood that passed through the ductus arteriosus. Yet with this structure the child lived two months after its birth. A case, which had a strong resemblance to the foregoing, occurred in Phila- delphia, and was examined by the author of this work. The venae cavae terminated regularly in the right auricle, and the pulmonary veins in the same regular manner in the left; but the pulmonary artery arose from the left ventricle, and the aorta from the right. There was no communication between these vessels by a canalis arteriosus ; but a large opening existed in the septum between the auricles. It is very evident, that, in this case also the pulmonary artery must have returned to the lungs the arterial blood as it came from them, and the aorta must have carried back to the general system the venous blood brought to the heart by the cavae ; excepting only those portions of the arterial and venous blood which must have flowed reciprocally from one auricle into the other, and thus changed their respective situations. The subject was about two years and a half old. The heart was nearly double the natural size, and the foramen, or opening in the septum between the auricles, was eight or nine lines in diameter. The pulmonary artery was larger in proportion than the aorta or the heart. With this organization, the child lived to the age above specified. His countenance was generally rather livid; and this colour was always much increased by the least irregularity of respiration. His nails were always livid. He sometimes appeared placid, but more frequently in distress. He never walked, and seldom, if ever, stood on his feet. When sitting on the floor, he would sometimes push himself about the room; but this muscular exertion always greatly affected his respiration. He attained the size common to children of his age, and had gene- rally a great appetite. For some weeks before death his legs and feet were swelled. It is probable that the protraction of life depended upon the mixture of the blood in the two auricles; and that they really were to be considered as one cavity, in this case. There seems reason to believe, that in adults of the common structure, there is no passage of blood from one auricle to the other, when the foramen ovale has re- mained open ; because in several persons in whom it was found by dissection to have remained open, there were no appearances during life, that indicated the presence of disoxygenated blood in the aortic system. It is probable, that the small size of the foramen ovale, the valvular structure which generally exists there, and the complete occupation of the left auricle by the blood flowing from the pul- monary veins, prevent the passage of blood from the right auricle to the left, in such persons; whereas in the case in question, the opening between the auricles was very large indeed, and there was no appearance of a valve about it. FORAMEN OVALE. 537 Although it be admitted, that in adults with the foramen ovale pervious, there is no transmission of blood from the right to the left auricle ; there is every reason to believe, that this transmission goes on steadily in the fcetus. To the arguments derived from the structure and the nature of the case, it may be added, that the pulmonary veins, in the foetal state, carry to the left auricle a quantity of blood, not sufficient to fill it; while the venae cavse carry to the right auricle, not only the whole blood of the body, but of the umbilical cord and placenta : some of which must flow into the unfilled left auricle, when the right auricle becomes fully distended. The question, how far the functions of the heart and lungs are dependent upon the brain, is very important, and has often been agitated with great zeal. In favor of the opinion that the motions of the heart are independent of the brain, may be stated the numerous cases in which the brain has been deficient in children, who have notwithstanding lived the full period of utero-gestation, and even a short time after birth, and have arrived at their full size, with every appearance of perfect vigour and action in the heart. In support ofthe doctrine, that the action ofthe heart is immediately dependent upon the brain, it may be observed, that no organ of the body appears to be so much influenced by passions and other mental affec- tions as the heart. These contradictory facts have occasioned this question to be considered as undecided, if not incapable of solution; although Cruikshank and Bichat* have stated circumstances very favourable to the opinion that the motions of the heart are independent of the brain. This question seems now to be settled by ,the experiments of Dr. Legallois, a phy- sician of Paris, which prove, that in animals who have suffered decapitation, the action of the heart does not cease as an immediate consequence of the removal of the head ; but its cessation is an indirect effect, induced by suspension of respira- ration. That respiration is immediately affected by decapitation, and depends upon the influence of the brain transmitted through the eighth pair of nerves. That the action of the heart will continue a long time after decapitation, if infla- tion of the lungs, or artificial respiration, be performed; but, on the contrary, if the spinal marrow be destroyed, the action ofthe heart ceases irrecoverably. The inference from these experiments seems very conclusive, that the Spinal Mar- row, and not the brain, is the source ofthe motions ofthe heart. It appears also by some of the experiments, that the power of motion in the trunk ofthe body, is derived from the spinal marrow; and that, when this organ is par- tially destroyed, the parts which receive nerves from the destroyed portion soon cease to live. By particular management of the spinal marrow, one part of the body can be preserved alive for some time after the other parts are dead. These experiments of Dr. Legallois, commenced in 1806, or 1807, were com- * See Cruikshank's Experiments on the Nerves and Spinal marrow of living Animals; London Philosophical Transactions for 1795. The eighth experiment has a particular relation to this subject. Bichat's researches, part 2, article 9. The Abbe Fontana has considered this subject in his Treatise on the Venom of the Viper, vol. ii. 194 English translation; and also in some of his other works. 538 HUMBOLDT AND OTHERS ON LEGALLOIS' PAPER. municated to the imperial Institute of France, in 1811. The committee of that body, to whom they were referred, namely, Messrs. Humboldt, Halle, and Percy, reported that the experiments had been repeated before them, at three different meetings of several hours each ; and that, to allow themselves sufficient time for reflection, they suffered an interval of a week to take place between the meetings. The committee believe these experiments to have proved, 1st. That the principle upon which all the movements of inspiration depend, has its seat about that part of the medulla oblongata from which the nerves of the eighth pair arise. 2nd. That the principle which animates each part of the trunk of the body, ia seated in that portion of the spinal marrow from which the nerves of the part arise. 3d. That the source of the life and strength of the heart is also in the spinal marrow; not in any distinct portion, but in the whole of it. 4th. That the great sympathetic nerve is to be considered as originating in the spinal marrow, and that the particular character of this nerve is to place each of the parts to which it is distributed under the immediate influence of the whole nervous power. The interesting memoir of Dr. Legallois is confirmed to a certain degree by a com- munication of B. C. Brodie to the Royal Society of London in 1810, in which are detailed many very interesting experiments, which induced the author to con- clude, That the influence of the brain is not directly necessary to the action of the heart; and That when the brain is injured or removed, the action of the heart ceases only because respiration is under its influence ; and if, under these circumstances, res- piration is artificially produced, the circulation will still continue. These various experiments apply particularly to the cases in which the brain is deficient. The effects of mental agitation on the heart are likewise reconcilable to the theory which arises out of them. But they throw no light on the question why the motions of the heart are so perfectly free from the influence of the will: and although they seem to prove incontestably that the motion of the heart is independent of the brain, it ought to be remembered that in certain diseased states of the brain, where that organ appears to be compressed, the action of the heart is often very irregular, and its contractions less frequent than usual. —For a later and more accurate account ofthe functions of respiration, the reader is referred to Dunglison's " Human Physiology, 4th Ed., Phila. 1841.— END OF VOL. I. NATIONAL LIBRARY OF MEDICINE NLM 03EQMA25 M NLM032048254