Vvft,::,\.<..-,\. ■ ',■/. ^'.V'.-'.V. '*,:'- Vv> .>.*..~!' '* ' ".*J>f:iVt..'.'t:f(C Hi'! tcijiVi::,-/cY-!",'t , ■ , !.-j: ■y-.-v.'.y^lr;./,.'.-;:^!;-,. „■. .■• •. ;."..1(U.i;:K-.Pi ;'::.■!':.'^l,i ■:"•'■. \ ' .', it,-{ .;.;=■: ,,!.::;.!,;-!■,,,;-,. ■-. »»V>:,., ;■ . ■ •,. iti^.i■;.»:(.*!>'••;>• :n.v<.;;; j. ■,•;•-.'. :. ..•..... •'Vi > »??? -if/Vo/, y^ y o? The following Valuable Medical Works are constantly for sale by J. Grigg, No. 9, N. Fourth Street. MEDICAL, CHEMICAL, BOTANICAL, &c. Averil's Surgery. Abernethy's Surgical works, com- plete. Armstrong on Typhus Fever. Barton's Botany and Flora. Bostock's Physiology. Bell on the Nerves. Buchan's Domestic Medicine. Bell on the Muscles, col'd plates. Bichat's Anatomy, 4 vols. Bell's Surgery. Brown's Elements. Bateman's Synopsis. Bell on Wounds. Bell's Dissection. Burns on Inflammation. Bell on the "Venereal. Blumenbach's Physiology. Bichat's Treatise on the Mem- branes in general. Beyer's Surgery, 2 vols. Blackall on Dropsies. 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GRIGG Has in Press and will speedily publish, A MANUAL OF PRACTICAL OBSTETRICS: Arranged so as to afford a Concise and Accurate Descrip- tion of the Management of Preternatural Labours; PRECEDED BY AN ACCOUNT OF THE MECHANISM OF NATURAL LABOUR. FROM THE FRENCH OF JULES HATIN, Doctor of Medicine of the Faculty of Paris, Professor of Obstetrics and of the Diseases of Women and Children, &c. &c. &c. BY S. D. GROSS, M. D. MANUAL yyb'7 GENERAL ANATOMY, CONTAINING A CONCISE DESCRIPTION OF THE ELEMENTARY TISSUES HUMAN BODY. FBOM THE FRENCH OF A. L. J. BAYLE and H. HOLLARD. S. D. GROSS, M. D. \ \ .'91'91/^^ PlrftADELPHIA: JOHN GRIGG, NO. 9, NORTH FOURTH STREET, 1828, LIBRARY SUIPiSHFRftl'SflffH!' JANS 1912. Eastern District of Pennsylvania, to wit; BE IT REMEMBERED, that on the twenty-seventh day of Septem- ber, in the fifty-third year of the Independence of the United States of America, A. fa. 1828, J. Grigg of the said district hath deposited in this office the title of a book, the right whereof he claims as proprietor in the words following, to wit: "A Manual of General Anatomy, Containing a Concise Description of the Elementary Tissues of the Human Body. From the French of A. L. J. Bayle and H. Hollard. By S. D. Gross, M. D." In conformity to the act of the Congress of the United States, entitled " An act for the encouragement of learning, by securing the copies of maps, charts, and books to the authors and proprietors of such copies during the times therein mentioned;"—And also to the act entitled " An act supplementary to an act entitled 'An act for the encourage- ment of learning by securing the copies of maps, charts, and books to the authors and proprietors of such copies during the times therein mentioned,' and extending the benefits thereof to the arts of designing, engraving:, and etching historical and other prints." 55 D.CALDWELL. Clerk of the Eastern District of Pennsylvania. ,» TO GEO. M'C1«EL.L.AN, M. D. PROFESSOR OF ANATOMY AND SURGERY IN THE JEFFERSON MEDICAL COLLEGE, Whose great skill and extensive knowledge in the va- rious departments of the Medical Sciences, add lustre to the profession, and whose integrity of principle and pri- vate virtues are not less distinguished than his professional attainments, the following pages are inscribed as a testi- mony of the esteem, the gratitude and respectful attach- ment of his friend and pupil, S. D. GROSS. Philadelphia, August, 1828. The Reader is requested to correct the following ERRATA. Page. Line. 2, 30, for lymph, read chyle. 9, 1, for spungy, read spongy. 17, 5, for anasarca and oedema, read cedema and anasarca. 19, 10, for recrementitial, read excrementitial. 31, 7, for carachus, read urachus. 84, 10, for consists, read consist. 86, 11, for desication, read desiccation. 120, 24, for vertebra, read vertebrae. 163, 28, for on dividing of the ganglia, read on division o* the ganglia. PREFACE. General Anatomy is a science of comparatively modern date; and like every other great and important improve- ment, it has gradually arrived at its present degree of per- fection. To Bichat, no doubt, is due the honour of having first established this branch of anatomy into a science, and the work which he has left us upon this subject, is at once an imperishable monument of his great talents and of his ingenious and profound researches. Notwithstanding the importance of a thorough know- ledge of General Anatomy, it is a fact, that it has received less attention in this country, than perhaps in any other part of the globe to which medical science has hitherto found its way. For the truth of this assertion, we appeal to the candid and high minded student, whether during the course of his attendance upon lectures, he has heard his anatomical professor enter into any minute details on this important branch of his professional studies, or whether he has not merely glanced at it,.or perhaps said nothing upon the subject. We shall not stop to inquire into the cause of this neglect; but we fondly anticipate the day when this evil shall be remedied; and ardently hope that the science of general anatomy may soon receive that share of attention from the physicians of this country, which it so justly merits, and which it at present receives in the medical schools of Europe, and particularly in those of France and Germany. VI PREFACE. We have been aware that a work on general anatomy is much wanted in this country; and with these impressions we have undertaken the translation of the Manual of MM. Bayle and Hollard; in doing which we have not scrupled to make a few alterations, but the deviations from the original are trifling. If, however, we have failed in some instances, in doing justice to the original, we ask only the indulgence of those who have the liberality and can- dour to receive with impartiality whatever is intended to facilitate the progress of their studies, while we neither ask nor care for the indulgence or liberality of sentiment of those of an opposite character. S. D. GROSS. INDEX. Dedication, Preface, Introduction, CHAPTER I. Cellular System, .... Section 1. Cellular tissue, properly so called, Pathological Anatomy, Bibliography, - Section 2. Adipose tissue, Pathological Anatomy, Bibliography, - - CHAPTER II. Vascular System, - Section 1. General Observations, - Pathological Anatomy, Section 2. Of the Arteries, Pathological Anatomy, Section 3. Of the Capillary vessels, Pathological Anatomy, Section 4. Of the Veins, - Pathological Anatomy, Section 5. Of the Lymphatic System, 1. Of the Lymphatic vessels, - 2. Of the Lymphatic Ganglia, - Pathological Anatomy, Bibliography of the Vascular System, Page. 9 ib. 16 19 20 24 25 26 ib. 31 32 38 42 47 49 55 57 ib. 63 64 65 V1U INDEX. CHAPTER IH. 68 ib. 71 74 77 ib. 81 82 84 Or the Serous System, Section 1. General Observations, - Pathological Anatomy, Section 2. Of the Sero-splanchnic Membranes, - Pathological Anatomy, Section 3. Of the Synovial Membranes, - Pathological Anatomy, Bibliography of the Serous System, - CHAPTER IV. Of the Fibrous System, - - - - First Division. Of the Fibrous System, properly so called, - ib. Section 1. General Observations, - -to. Pathological Anatomy, - - - 87 Section 2. Of the organs composing the Fibrous System, properly so called, - Article 1. Of the Fibrous Ligamentous organs, - ib. §1. Of the Ligaments, - - - ib. §2. Of the Tendons, - - - 90 Article 2. Of the Fibrous Envelopes, - - 92 § 1. Aponeurotic Envelopes, - - ib. § 2. Of the Tendinous Sheaths, - - 93 §3. Of the Periosteum, - - - 94 Pathological Anatomy, _ - - - 95 § 4. Perichondrium, - - - 96 § 5. Of the Fibrous Envelopes of the brain, the Spinal Marrow, and some other organs, - § 6. Of the Fibro-serous, and the Fibro- mucous Membranes, - - 97 Second Division. Yellow elastic Fibrous System, - 98 Pathological Anatomy, - - - 99- Third Division. Fibro-cartilaginous System, - - - ib. Pathological Anatomy, - - - 101 Bibliography of the Fibrous System, - - 102 ib. INDEX. IX CHAPTER V. Cartilaginous System, - - 103 Section 1. General Observations, - - - - ib. Pathological Anatomy, - - - 105 Section 2. Articular Cartilages, - - - - 106 Pathological Anatomy, - - - 108 Section 3. Perichondroidal Cartilages, - - 109 Pathological Anatomy, - . - - 110 Bibliography of the Cartilaginous system, - 111 CHAPTER VI. Of the Osseous System, ------ 112 Section 1. Of the Bones, ----- ib. Article 1. General Observations, - - - ib. Article 2. Of the long, broad, short, and mixed bones, in particular, - 122 §1. Of the long Bones, - - - ib. §2. Of the broad or flat Bones, - - 125 §3. Of the short Bones, - T - 127 §4. Of the mixed Bones, - - 128 Pathological Anatomy, - - - ib. Section 2. Of the Articulations of the Bones, - - 136 Pathological Anatomy, - - - 140 Bibliography of the Osseous System. - - 142 CHAPTER VII. Of the Nervous System, ------ 144 Section 1. General Observations, - - - - ib. Section 2. Of the Nervous Centres, - - - 154 Article 1. Of the Cerebro-spinal Centre, - - ib. Pathological Anatomy, - - - 160 Article 2. Of the Nervous Ganglia, - - - 162 Section 3. Of the Nerves, ----- 167 Article 1. Of the Cerebro-Spinal nerves, - - ib. Pathological Anatomy, - - - 173 Article 2. Of the Ganglionic Nerves, -, - 175 Pathological Anatomy, - - - 179 Bibliography of the Nervous System, - ib. CHAPTER VIII. 1 ioumentary System, 182 INDEX. Section 1. General observations, - - ib. Section 2. Of the Skin, - - - - 188 Pathological Anatomy, - - - 198 Section 3. Of the Mucous Membranes, - - - 205 Pathological Anatomy, - - - 213 Section 4. Ofthe appendages oftheTegumentary System, 217 Article 1. Ofthe Hairs, ... - ib. Pathological Anatomy, - - - 221 Article 2. Ofthe Nails, - - - - 222 Pathological Anatomy, - - 225 Article 3. Of the Teeth, .... ib. Pathological Anatomy, - - - 230 Bibliography ofthe Tegumentary System, 231 CHAPTER EX. Glandular System, ...... 235 Pathological Anatomy, - - - 240 Bibliography, .... 241 CHAPTER "X. Muscular System, ---... 242 Section 1. General observations, - - . ib. Pathological Anatomy, - - - 253 Section 2. Of the Exterior Muscles, - - . 255 Section 3. Ofthe Interior Muscles, - - - 259 Bibliography ofthe Muscular System, - 263 APPENDIX, containing an account of the Accidental Tissues, - 264 Article 1. Of Tubercles, .... 266 Article 2. Of Schirrus, .... 268 Article 3. Of Encephaloid or Cerebriform Cancer, 269 Article 4. Of Melanosis, - 270 Bibliography of Pathological Anatomy, - 271 INTRODUCTION. Life is the phenomenon which results from the actions of an assemblage of organs, which are more or less inti- mately connected together according to the ultimate func- tions which they are destined to perform. Duringa long time the study ofthe organs in relation to their form, their struc- ture and physical characters, and the study ofthe same parts in relation to their functions, were always combined, and were made the special object of the science of physiology. But in consequence ofthe progress of our knowledge of organi- zation, theseparation of these two kinds of study hasbecome essentially necessary. Anatomy is the science which treats of the conformation, the situation and structure of the or- gans, while physiology regards in a more especial manner, the functions ofthe animal economy. Anatomy is divided into two branches; into special and general anatomy. The former has for its object the par- ticular study of each individual organ enjoying an action peculiar to itself; it describes the physical properties, the form and relative situation, and shows the mutual arrange- ment of the elementary tissues which contribute to its formation. The latter, of which this work is intended to present a summary, treats ofthe elementary tissues and or- ganic systems, considered in a general point of view, and abstractedly ofthe organs which they contribute to form. The term tissue is applied to every species ofthe ani- mal solids having peculiar and distinctive characters. The tissues are the constituent parts of our organs, or in other 2 2 INTRODUCTION. words, their elements. Each tissue, regarded as a whole, is called system, in whatever part of the body it is found. The human body is composed of solids and fluids, the latter of which, form by far the most considerable share. Before we enter upon the examination of the organic sys- tems, it is necessary to say something of those materials which perform a general and important character in the animal economy-*-a character, which, after having engag- ed for ages the exclusive attention and study of physicians, was lost sight of by the moderns, who uniformly sought in the solids the seat of every morbid derangement. Ofthe Fluids. It is impossible to determine with any degree of pre- cision, the relative quantity of the solids and fluids: some believe that the latter are to the solids as six to one; others that their relative proportion is as nine to one. The fluids are contained within the solids, which are more or less penetrated, according' to the kind of organ that is examined. Their fluidity is owing more to the vi- tal influence than to the quantity of caloric which they contain. When drawn from the vessels of a living ani- mal, and removed from the heat to which they have been exposed, most of them coagulate. The animal fluids consist, first, of the fluids which are converted into blood; secondly, ofthe blood itself, which is the source and reservoir of all the other humours; and, thirdly, ofthe fluids which are derived from the blood. Of the Fluids which are converted into blood. The fluids which are converted into blood are the lymph and the chyle. The lymph is the milk-like fluid which results from the changes which the chymous pulp under- goes in the duodenum. Examined a short time after it has been absorbed by the chyliferous vessels of the intestines, it is slightly coagulable, of a saltish taste, and of a whitish INTRODUCTION. 3 appearance. In the glands of the mesentery, its charac- ters are sensibly modified; it becomes more coagulable, and presents a reddish tint, which, upon the arrival of the chyle in the thoracic duct, is changed to a beautiful red colour. Examined with the microscope, the chyle is found to con- sist of a great number of globules and corpuscles which are precisely analogous to those of the blood, with the excep- tion of their colour, which is much fainter. Lymph is a transparent, viscid and albuminous fluid, whose quantity is much smaller than is commonly sup- posed. It is contained in the lymphatic vessels, and is mixed with the chyle in the thoracic duct. Ofthe Blood. The blood of a healthy person, is a fluid of abeautful red colour, contained in the cavity of the heart, and blood- vessels, and varying in quantity from ten to twenty-five pounds. When flowing from its vessels in the living ani- mal, it is an unctuous liquid of a peculiar odour and saline taste, ofthe temperature of 9S° of Farenheit's thermome- ter, and ofthe specific gravity of 1050. The microscopic observations of Hewson, Beclard, Pre- vost and Dumas, tend to prove that the blood, while cir- culatingin its vessels, is nothing else than the serum, hold- ing in suspension small, regular, and insoluble corpuscles. These are uniformly composed of a central, colourless spheroid, and of a red, semi-transparent envelope. When the blood has ceased to be under the vital influ- ence, it gradually loses its heat, disengages a considerable quantity of carbonic acid gas, and coagulates. A short time after coagulation, the clot separates into two elements; the solid part is called the crassamentum, the fluid part, the serum of the blood. When the coagulum of the blood is carefully and repeatedly washed in a small stream of water, the colouring matter is gradually disengaged, and a glutinous and fibrous mass remains, which has been termed 4 INTRODUCTION. fibrin or coagulable lymph. This substance is of a grayish colour, of a firm consistence, and has all the properties of the muscular fibre. The serum ofthe blood is of a greenish-yellow colour, and of the average specific gravity of 1030. It is alkaline, and when exposed to a temparature of 160°, it is converted into a white coherent mass, from which a fluid, termed the serosity, may be obtained by pressure. According to the analysis of Dr. Marcet, the serum conists ofthe following ingredients:— Water, .... 900.00 Albumen, .... . 86.80 Muriate of potash and soda, . 6.60 Muco extractive matter, . 4.00 Sub-carbonate of soda, 1.65 Sulphate of potash, 0.35 Earthy phosphates, . 0.60 1000.00 The colouring matter of the blood results from a mix- ture of the disengaged red matter and the serum. It is insoluble in water, and its chemical properties show that it is a peculiar animal principle united with a per-oxide of iron.* Besides these, the blood contains an unctuous substance, and a halitus which is seen to rise from the surface of blood recently drawn, upon the same principle that a sensi- ble evaporation takes place from the surface of other li- quids whose temperature had been considerably elevated. * According to the analyses of Berzelius, the colouring matter of the blood, after being incinerated, affords the following residue:—Oxide of iron, 50.0; sub-phosphate of iron, 7.5; phosphate of lime with a very small proportion of magnesia, 6.0; pure lime, 20.0; carbonic acid gas and loss, 16.5.—100.0. (c)—S. D. § 3. Of the Periosteum. Definition.—The periosteum is the fibrous envelope of the bones. Form and arrangement.—This membrane represents the form of the bones which it surrounds and covers. It is wanting on the cartilaginous surfaces of the moveable OF THE FIBROUS SYSTEM. 95 joints where its continuity is of course interrupted; in the immoveable articulations it passes without interruption from one bone to the other.—In infancy it is thick, and can be easily separated from the bones; while in the adult it is more firm and compact, and is intimately connected with the short bones and the extremities of the long ones, and, in short, every where, where they present a spongy texture. The periosteum gives off numerous prolonga- tions which accompany the vessels that enter every where the spongy substance of the bones. Texture.—The direction of the fibres of the periosteum is analogous to that of the long and the short bones; but its arrangement is different in the flat bones. It receives a great number of blood-vessels, and some lymphatics; and when subjected to continued pressure, it is converted into a fibro-cartilaginous substance. Differences according to age.—In the foetus, the perios- teum is soft and spongy, moistened by a gelatinous fluid, and possessed of but little vascularity. As we advance in years, its fibres become more distinct, and the membrane increases in firmness, consistence, and vascularity; in old age, it has extreme tenacity, and even becomes ossified on its internal surface. Functions.—The periosteum defends the bones which it covers from the impression of the organs that move upon its surface, and strengthens the parietes of their vessels. In infancy, it unites the epiphyses to the bodies of the bones, and serves for the insertion of the ligaments and tendons, which subsequently and in consequence of the os- sification of this membrane at their points of attachment, adhere to the bone itself. Pathological Anatomy. Wounds of the periosteum are followed by a cicatrix which resembles it in texture, and when a small portion of it has been raised or detached, it is generally reproduced. 96 OF THE FIBROUS SYSTEM. Inflammation of this membrane seldom terminates in gan- grene, but most frequently in suppuration, which detaches it from the bone, and has a tendency to produce periostosis, osssification, soft cancer, and the development of fungous growths, § 4. Perichondrium. The perichondrium is the fibrous membrane which covers the non-articular cartilages; it is less intimately connected to them, than the periosteum is to the bones, and does not send to them as many fibrous elongations. It contains fewer blood-vessels than the periosteum, has less vitality, and differs from it also in some of the characters which we have just pointed out. § 5. Of the fibrous envelopes of the brain, the spinal marrow, and some other organs. These membranes are, 1st. The dura mater, (meninx of Chaussier), a very dense, and vascular membrane, composed of tendinous-like fibres, running in various di- rections, and situated within the cranium and the ver- tebral canal, to the former of which it forms an internal peri-cranium. It is intimately united with the tunica arachnoides, covers the brain and spinal marrow, and sends elongations in the form of sheaths upon the nerves which pass out at the base of the cranium, and through the verte- bral holes. This membrane forms a number of folds or duplicatures within the cavity ofthe cranium, which may be distinguished into those which separate the different parts of the brain, as the falx major, the tentorium cerebelli, and the falx minor; and into the sinuses of the dura mater, or those which perform the offices of veins, and are lined by a continuation of the internal membrane of the veins. 2d. The sclerotica, an opake, white, elastic, fibrous membrane, of unequal thickness, possessed of little vascu- OF THE FIBROUS SYSTEM. 97 larity, and serving as a covering to the eye, determining its shape and supporting and defending the more delicate and useful parts within it. 3d. The tunica albuginea, a strong, dense, in-elastic membrane, varying in thickness, possessed of but little vascularity, and serving to surround and defend the testes. —Under this head may also be included the fibrous en- velopes of the ovaries. 4th, and lastly, the fibrous capsules of the kidneys, which surround them, and send prolongations into the interior of their substance. It remains to be remarked, that none ofthe organs which are surrounded by coverings of the non-elastic fibrous tis- sue, are destined to undergo any temporary changes of Volume, as are those which are surrounded and enveloped by the elastic fibrous tissue. § 6. Of the fibro-serous and the fibro-mucous mem- branes. Every where, where the fibrous membranes are found in relation with the serous or the mucous, they are so firm- ly united to them, that it is impossible to separate them by dissection; so that they appear to form a single membrane, fibrous on its external, and mucous or serous on its inter- nal surface. The pericardium and the tunica vaginalis, are, in a part of their extent, true fibrb-serous membranes; the union ofthe dura-mater and the arachnoides is also very intimate every where, where these envelopes are applied, the one upon the other. We see examples of the fibro- mucous membranes in the trachea, where the fibrous tunic is inseparably united with the mucous; in the periosteum and perichondrium, wherever the internal teguments lie immediately upon them, as in the nasal fossa?, the meatus auditorius externus, the larynx, &c. 14 98 OF THE FIBROUS SYSTEM. SECOND DIVISION. Yellow elastic fibrous System. Definition.—This system comprehends a great number of membranous, ligamentous parts, &c, formed of a tissue analogous to the preceding in texture, but differing from it by its great elasticity. Situation.—This tissue is found in every part of the body, where it is necessary that there should be a continu- al or intermittent resistance to the impression of weight, to the action of the muscles, &c. In the human subject, the principal organs in which this tissue occurs, are, the yellow ligaments of the vertebrae, the proper coats of the vessels, especially those of the arteries, the excretory and aereal ducts, the covering ofthe spleen, and ofthe corpora cavernosa. * Conformation.—The fibrous elastic tissue is found un- der three forms; 1st, under that of fasciculi, as in the yel- low ligaments; 2d, under that of tubes, as in the vessels and excretory ducts; and 3d, under that of membranous capsules, with interior reticular elongations, as in the cov- erings of the spleen, and the corpora cavernosa. Structure.—This tissue is formed of fibrous fasciculi, parallel with each other, or nearly so, but never interlac- ed, and easily separable; it contains little cellular substance and but few vessels. Characters, physical and chemical properties.—In the living subject, the elastic fibrous tissue is firm and opake, and of a white yellowish colour, which becomes more dis- tinct after death; it has less tenacity, and more extensibili- ty than the other fibrous tissue, is more tenacious than the * In quadrupeds, this tissue constitutes the ligamentum nuchx, or the posterior cervical ligament, and the ligament which is inserted into the claws of some of the feline species. OF THE FIBROUS SYSTEM. 99 muscular, in the dead than the living subject, and bears a greater resemblance to it, than the preceding tissue. It contains a great quantity of water, upon which depends its most remarkable physical property—elasticity—by vir- tue of which, it immediately recovers its original state, when it has been distended or compressed. When this tis- sue is dried, it loses half its weight, and assumes a cor- neous appearance, but a few days maceration is sufficient to recover its elasticity and original characters. The yellow fibrous tissue resists for a long time the ac- tion of boiling water, the acids and alkalies; and macera- tion scarcely produces any alterations.—It is composed prin- cipally of albumen and fibrin. Vital properties.—This tissue appears to have neither sensibility nor contractility. Functions.—The yellow fibrous tissue serves the pur- pose of ligaments or envelopes to certain organs, yields by its extensibility to their changes of volume or situation, and recovers its natural form as soon as the cause, which in- duces these changes, has ceased to act. Pathological Anatomy.—The anatomical history ofthe diseases of this tissue, having been included under that of the fibrous tissue, properly so called, we shall only remark here, that this tissue very seldom ossifies, and that it has a tendency to lose its elasticity from too frequent, excessive, or continued distention. THIRD DIVISION. Fibro-cartilaginous System. Definition.—This system comprehends those organs, which, by their texture and tenacity, participate in the cha- racters of the fibrous tissue, and by their density and whiteness in those ofthe cartilages.* * Bichat has placed in this system the membraniform cartilages whicli 100 OF THE FIBROUS SYSTEM. Division.—The fibro-cartilaginous organs are distin- guished; 1st, into the inter-articular, or those which are free on both surfaces; 2d, into those which have one sur- face free and the other adherent; these are the fibro-carti- lages of the tendinous sheaths and of the circumference of the articular cavities; 3d, into those, which adhere by their two surfaces to the bones to which they serve as a bond of union. Situation, conformation, and arrangement.—1. The inter-articular fibro-cartilages, are situated 'in the articula- tions of the knee, the inferior maxilla?, and the clavicle. They are lamelliform, free on their surfaces, connected by their borders to the synovial capsules or the articular car- tilages, and sufficiently moveable to adapt themselves to the motions of the joints in which they are placed; 2, The fibro- cartilages, adhering by one of their surfaces, consist, 1st, of those of the tendinous sheaths, which facilitate the glid- ing of the tendons, and protect them from the impression ofthe bones; and 2d, of those which surround the glenoid and cotyloid cavities; 3, The fibro-cartilages which are ad- herent by their two faces, are placed between the surfaces ofthe bones, to which they serve as bonds of union: these vary in form, being circular in those which connect the bodies of the vertebras, almost quadrilateral between the symphysis pubis, &c. Structure.—The fibrous and cartilaginous tissues are not combined in the same proportion, nor disposed in the same manner in every part of the fibro-cartilaginous sys- tem, nor every where in the same fibro-cartilage. Thus, the fibrous substance predominates in the inter-vertebral ligaments, where it forms concentric layers; it is less abun- dant, and consists of circular fibres where it surrounds the are regarded by Meckel, Beclard and other anatomists, as true cartilages. We shall see in the following chapter, that this manner of observing the membraniform cartilages is preferable to that of Bichat. OF THE FIBROUS SYSTEM. 101 glenoid and cotyloid cavities; still less abundant in the in- ter-articular fibro cartilages, and often scarcely distinguish- able in the sheaths of the tendons, where it is formed at the expense of the periosteum, which is almost entirely converted into cartilage. In general, the fibrous substance is more apparent in proportion as the fibro-cartilage is ex- amined near its external surface; and the cartilaginous, in proportion as we approach nearer to the centre of an organ where the fibres disappear. In some instances there is alternately a layer ofthe fibrous tissue and one ofthe car- tilaginous. The fibro-cartilaginous system, like the two of which it is composed, has but little vascularity. Characters, physical and chemical properties.—The fibro-cartilages are of a whitish appearance, and unite to the tenacity ofthe fibrous system, the elasticity ofthe car- tilages. It has been observed, that during pregnancy, the fibro-cartilages which unite the bones of the pelvis are sen- sibly softened, and become more humid. The fibro-carti- lages resist, for a considerable time, the action of boiling water, but dissolve at last into gelatine. Vital properties.—In the healthy state, the fibro-carti- lages appear to have neither sensibility nor contractility. Differences according to age.—In infancy, the fibro-car- tilages are soft, and appear to be composed principally of ahomogeneoussubstance,and as their consistency increases, their fibres become distinct, and more fully developed. They seldom ossify in old age. Functions.—The fibro-cartilaginous organs differ in their uses in the different parts of the body: some facilitate the motions of the tendons, giving them a point of attach- ment at once solid and elastic; others favour the mobility of the articular surfaces between which they are situated, either as a kind of cushion, or as elastic ligaments. Pathological Anatomy. In consequence of their small degree of vitality, the 102 BIBLIOGRAFHY OF THE FIBROUS SYSTEM. fibro-cartilages are seldom subject to diseases; when wounded, they inflame, and after a considerable time they cicatrize and heal. Inflammation of these organs is slow in its progress and is characterized by redness, which is either uniform or striated, and often passes to a brown colour; it often terminates in the effusion of a kind of ichorous matter, which is either deposited in their substance, or exhaled upon their external surface. They seldom ulc'erate, though this has been observed to take place. In many ricketty sub- jects, and in some of those who suffer from mal-conforma- tion of the vertebral column, the inter-vertebral fibro-car- tilages tumify, and become softened and engorged with fluids. Amongst the preternatural fibro-cartilaginous pro- ductions, we may cite those which are developed in the fibrous tissue in consequence of accidental friction, and those which occur in some cysts, or in certain tumours, and cicatrices, as in tubercles of the lungs, and in many other fibrous bodies. Bibliography of the fibrous System, Besides the works already cited, the reader is referred particularly to the excellent articles by Beclard in his ad- ditions to the Anatomie Generale de Bichat, and to those in his own work, Chap. VII. (vas. sys.) p. 323, et seq. For an account of the pathological anatomy of the fibrous and fibro-cartilaginous systems, see l'Histoire Anatomique des Inflammations de M. le docteur Gendrin, p. 322, et seq., and the articles by Laennec, in Dictionnaire des Sciences Medicales; tome XV. CARTILAGINOUS SYSTEM. 103 CHAPTER V. CARTILAGINOUS SYSTEM. SECTION 1. General Observations. Definition. —The cartilages, or the organs which com- pose this system, consist of hard whitish substances, some- what flexible and elastic, having apparently neither texture nor organization, independent of each other, and generally in connexion with the osseous system. Division.—The cartilages are divided into two great classes; into those which are temporary and those which are permanent. These last are again subdivided into two classes; the first comprehends the articular cartilages, or those which are not covered by the perichondrium; in the second are included all those which receive a covering from this membrane, viz. the membraniform cartilages, the cartilages of the ribs, the larynx, &c. Conformation and relations.—The cartilaginous or- gans present a great variety of form; some are long and narrow, others thin and broad and spread out like a kind of membrane; all are more or less flattened. We shall enter more into detail with regard to their form in the following sections. The articular cartilages are firmly united to the articular extremity of the bones, either by their two sur- faces, as in the synarthrodia! joints, or by one only, as in the moveable articulations. Those of the second subdivi- 104 CARTILAGINOUS SYSTEM. sion adhere to the bones, as those of the ribs, the ear, the nose, &c. or they are in relation with the soft parts, as those of the larynx, &c. Texture.—At first sight, the cartilaginous tissue appears to be composed of a homogeneous substance, but upon a more minute examination, small fibres may be discovered, whose direction varies in the two subdivisions of the per- manent cartilages, as we shall see when treating of each of them separately. When macerated for a long time in water, this tissue exhibits the appearance of a cellular net- work: no nerves can be traced into it; nor does it appear to have any blood-vessels, unless we consider as such the reddish or striated appearance which it sometimes ex- hibits. The cartilages are, nevertheless, penetrated by the fluids ofthe system; this fact, which the nutrition of these organs supposes, is rendered evident by the yellow colour with which they are tinged in some cases of jaundice. Characters, physical and chemical properties.—The cartilages are of a pearly white colour, very elastic and smooth, and when divided into thin layers, they present the semi-transparency of horn; they are divisible by the scalpel, and are the only substances which are exceeded by the bones in hardness and density. The cartilages may be greatly distended without rupture of their tissue; they con- tain a great quantity of water; when dried, they assume a transparent, yellowish colour; but upon exposing them to water for a short time, they recover their former aspect: a long time is required for their maceration, and when ex- posed to putrefaction, they yield to its action less readily than many other animal substances. When boiled, they become brittle and indented, and the articular ones are alone dissolved and converted into a kind of gelatine; while the others remain insoluble and afford no gela- tine. Chemical analysis has hitherto afforded us no posi- tive data with regard to the composition of the cartilages of the human subject. According to the experiments of CARTILAGINOUS SYSTEM. 105 Hatchett and Davy, they are composed of albumen and phosphate of lime, and according to Mr. Allen, of albumen and a small proportion of carbonate of lime. Mr. Gendrin regards the gelatinous substance, obtained by boiling arti- cular cartilages, as a compound of albumen, animal mucus and phosphate of lime; according to this author, the carti- lages of the larynx contain gelatine, formed in great mea- sure of fibrin in combination with water. Vital properties.—The cartilages have little sensibility in their healthy state, and their vital action is very ob- scure: they are slowly developed, except at the period of puberty, when those of the larynx suddenly increase, and form one of the most remarkable characteristics of that age. Differences according to age.—The cartilages have at first the appearance and consistence of thick mucilage; but they gradually increase in density, until they at length ac- quire their proper degree of solidity. In adult life, they are more elastic than at any other period; in old age, they become more dry, increase in colour and opacity; and sometimes, in consequence of the greater proportion of calcareous substance, they become hard and ossified either in part, or entirely. The cartilages of the diarthrodial joints are the only ones which are not subject to this trans- formation, which sometimes affects the others at a very early age. Functions.—The use of the cartilages is to facilitate the motions of the bones, to connect them together, and to form the basis of certain parts, either in part or entirely. Pathological Anatomy. When the cartilages are divided without loss of sub- stance, the surfaces of the solution of continuity remain in juxta-position, but do not contract adhesions, and the peri- chondrium alone, when it exists, cicatrizes and forms an osseous callus which closes up the wound. When detached from the surrounding tissues, they do not unite with them. 15 106 CARTILAGINOUS SYSTEM. Inflammation of these organs, though not well characteriz- ed, sometimes terminates in ulceration, tumefaction, and softening, and the development of lardaceous productions, especially in some of the diseases of the joints. We shall speak more in detail concerning these alterations, when treating ofthe different kinds of cartilages. In some instances, cartilages are accidentally developed in the animal economy: Mr. Laennec has divided them into perfect and imperfect—a division which has been re- jected by Meckel, who made his observations at different periods of the development of similar productions. The accidental cartilages occur under the form of layers in the thickness ofthe parietes of the arteries, the subserous tis- sue ofthe spleen, the lungs, the testicles, &c; in irregular masses in the substance of some organs, as the thyroid glands, the ovaries, &c, and finally, in some schirrous and lardaceous tumours under the form of small, flattened bodies, which are either attached or free on the exterior or in the interior of the synovial membranes, but seldom in the se- rous. The ureters, the vagina, and the prepuce, are all sometimes the seat of a cartilaginous transformation; and sometimes, though very seldom, even the bones them- selves. section 2. Articular Cartilages. Definition.—The articular cartilages are those which cover the articular surfaces of the bones. Division.—The articular cartilages are divided into the diarthrodial and synarthrodial, or into those of the movea- ble and immoveable articulations. Conformation and arrangement.—(a) The diarthro- dial cartilages are in the form of flattened lamellae, which are more thin at the circumference than at the centre CARTILAGINOUS system. 107 ofthe convex articular surfaces; more thick, on the contra- ry, at their borders than at their centre on the concave ar- ticular extremities, spread upon the osseous diarthrodial surfaces, which they cover in every part of their extent, and to which they are firmly united by one of their sur- faces, while the other is lined by the synovial capsule which separates it from the corresponding surface of the opposite articular cartilage, (b) In the immoveable joints, the articular cartilages are lamelliform, and adhere to the bones by their two surfaces, and to the periosteum by their borders.* Texture.—By long maceration, the action of ebullition, &c, it can be satisfactorily shown that the tissue of the articular cartilages is of a homogeneous nature, and com- posed of fibres. These fibres are small, and are disposed perpendicularly on the osseous surface which they cover, and to which they are very intimately united; those of the diarthrodial cartilages appear to become soft at their free extremity, where the cellular tissue which enters into their composition is modified, so as to perform the office of the synovial capsule which lines the cartilage. The blood- vessels, nerves, and lymphatic vessels of the articular car- tilages are so small as to elude observation, but there can be no doubt of their existence, as is clearly shown by the phenomena of disease. Chemical characters.—The articular cartilages are the only ones that can be reduced into gelatine by the action of ebullition. Differences according to age.—To what we have al- ready said upon this subject in the preceding section, we may add that the diarthrodial cartilages become very sen- sibly thinner in old age, and that they ossify less readily * The synarthrodial cartilages of the bones of the cranium are more thick on its convex surface than on its concave; so that the sutures are less distinguishable on the interior than on the exterior of that osseoue vault. 108 CARTILAGINOUS SYSTEM. and more seldom than any other; and that, on the contrary, those of the immoveable articulations belong rather to the class of temporary cartilages than to that of permanent. Functions.—The articular cartilages counteract, by vir- tue of their elasticity, the efforts of compression and the shocks which are experienced by the articular surfaces; they facilitate, also, by virtue of the same property, the motions ofthe diarthrodial joints. Pathological Anatomy. In the phlegmasia? of the joints, the articular cartilages are sometimes swollen and softened, so that their fibres be- come apparent on their interior as well as on their free sur- face, which assumes a velvety appearance. These cartilages, especially those of the diarthrodial articulations, are seldom subject to inflammation; sometimes, however, it takes place, and terminates in suppuration, in ulceration, and the destruction of the cartilage.* In some instances, the articular cartilages are replaced by a hard, ivory substance, which, according to Meckel, consists ofthe urate of soda. It sometimes happens that the diarthrodial cartilages be- come thinner than natural—a phenomenon which Mr.Laen- nec has attributed to the incomplete reproduction of a part of a cartilage that has been destroyed by ulceration. The cartilaginous or osseous incrustations which are sometimes found in the articular cartilages, are new productions which enter the joint by traversing the synovial membrane, and are lodged in depressions of the cartilaginous layer. In the false articulations which are found between the two fragments of a broken bone, there is generally a tissue which is more or less analogous to that of the diarthrodial cartilages, but which ought to be considered merely as an imperfect callus. • This destruction is followed by the union of the denuded surfaces of the bones which are then brought in contact, and constitute true anchy- losis. (V. Path. Anat. ofthe Oss. Sys. p. 167.) CARTILAGINOUS SYSTEM. 109 SECTION. 3. Perichondro'idal Cartilages. Definition.—The perichondro'idal cartilages are those which constitute the basis of certain organs, either in part or in whole; are covered by the perichondrium, and may be reduced into gelatine by the action of ebullition. These cartilages, are those of the ribs, the larynx, the auricular canal, the septum nasi; and those of the alas nasi, the eye- lids, the pavilion of the ear, the tongue, the epiglottis, the trachea and bronchia, which Bichat has improperly ar- ranged under the head of fibro-cartilages. Form and connexions.—The perichondro'idal cartilages vary in form; some, as the thyroid, &c, are membraniform; others, as those of the ribs, are in the form of thick nar- row bands, while others again, as those ofthe trachea and bronchia, represent incomplete rings. In some instances they adhere to the bones by their borders, or their extremi- ties are intimately united to them like the articular car- tilages, as the cartilages of the ribs, the septum nasi, &c, while others are in relation only with the soft parts, as those of the eye-lids, the larynx, and the trachea. Some of these cartilages, as those of the larynx, form true articula- tions, and are united together by ligamentous capsules.— For a more minute account of the form and connexions of these organs, the reader must consult the works on de- scriptive anatomy. Texture.—(a) The costal cartilages consist of elliptical plates, united together by transverse fibres: according to Herissant, they have a spiral arrangement. Whatever it may be, it is certain that they can be decomposed into fibres, and reduced finally to cellular tissue; but to analyze the tex- ture of these cartilages, it is necessary to macerate them for a long time in water, followed by their desiccation or 110 CARTILAGINOUS SYSTEM. the action of the acids. By maceration and ebullition, the other cartilages of this class may at first be reduced to short and very delicate fibres, and afterwards to cellular tissue. Those of the eye-lids, of the ear, and all the membraniform fibro-cartilages of Bichat are less dense, and offer less re- sistance to maceration, &c, than the other cartilages. They are covered by a thick perichondrium, which sends fibrous elongations into the interior of their substance, while the fibrous envelope of the preceding cartilages is united to them merely by cellular tissue. Physical properties.—The perichondro'idal cartilages, especially the membraniform, are more or less flexible, and very elastic; they contain more earthy matter than the diar- throdial, and can not be resolved into gelatine by the ac- tion of boiling. Differences according to age.—Some of the perichon- dro'idal cartilages, and especially those of the ribs, the larynx and the trachea, after they are fully developed, be- come hard, and ossified either in part, or in whole, and ac- quire a soft and spongy texture in their centre. In the cos- tal cartilages, this normal transformation is accelerated by phthisis pulmonalis,and in the larygeal, by phthisis laryn- gitis. Functions.—The cartilages, of which we are treating, constitute, either alone or in conjunction with the bones, the basis of certain parts of the body, determine their form, and perform the offices of bones wherever the movements of dilatation and contraction, &c, require an elastic and more or less flexible structure. Pathological Anatomy. The form of the perichondro'idal cartilages is sometimes altered by the action of mechanical agents; thus tumours of the neck, such as goitre, &c, give the tracheal and bronchial arches a flattened or triangular form by the com- pression which they exert upon them. CARTILAGINOUS SYSTEM. Ill The solutions of continuity of these cartilages are not followed by their cicatrization; but the perichondrium forms a cartilaginous or osseous ring, which surrounds the fragments and maintains them in contact. This ring is smaller in proportion as the corresponding extremities of the fragments are maintained in apposition. If ossification of the cartilage has already taken place, it forms a true cal- lus between the fractured extremities. (V. Path. Anat. of the Oss. Syst.)—Inflammation of these cartilages ordinarily terminates in ossification. The cases of caries and necrosis that occur in the cartila- ginous organs, particularly in the larynx, affect only those parts which are"subject to osseous transformations. Amongst the small number of congenital anoftialies that have hitherto been observed in these cartilages, we may notice the absence of some of them, and particularly those of the ribs. Bibliography ofthe Cartilaginous System. Besides the works already cited: Hirissant. Sur la structure des cartilages des cotes de l'homme et du cheval; dans Mem. de Paris, 1748, page 355. Delassone. Sur l'organization des os; dans Mem. de Paris, 1752, page 253—258.—In this memoir are contained some very interesting details on the texture of the ar- ticular cartilages. J. G. Haase. De fabrica cartiligium, Leipsig, 1767. Doerner. De gravioribus quibusdam cartiliginum muta- tionibus, Tubing. 1798. Cruveilhier. Observations sur les cartilages diarthrodiaux et les maladies des articulations diarthrodiales; dans Arch, gtntr. de. Med., fevr. 1814, pag. 161. Gendrin. Hist, anatom. des inflammations, tom. I, pag. 322 et seq. * 112 OF THE OSSEOUS SYSTEM. CHAPTER VI. OF THE OSSEOUS SYSTEM. SECTION 1. OF THE BONES. • ARTICLE 1. General Observations. Definition.—The osseous system is composed of an as- semblage of hard organic pieces, which are united together in various ways and in such a manner as to form a kind of frame, which serves as the basis upon which the whole fabric is built; determines the general configuration of the body, the motions of its several members, and regulates its attitudes. Situation.—The bones are always situated in the cen- tre of the soft parts, under the teguments and the muscles that cover them. Division.—Accordingly as one or two of their dimensions predominate, or as all three are nearly equal, the bones are divided into long, broad and short: when they have the dimensions of any two of the preceding kinds, they are called mixed. These varieties differ not only with regard to their dimensions, but also in some other characters, as we shall see when speaking of each in particular. Conformation.—As the^osseous system presents in its whole the general configuration of the body, it is evident that that ofthe individual bones themselves presents many OF THE OSSEOUS SYSTEM. 113 varieties in the different regions in which they are situa- ted—a fact which indicates the division which we have just established: we shall revert to this subject in the history of the different kinds of bone; while we speak here of the protuberances and depressions which are presented on the surfaces of all the bones, and which modify their confor- mation. 1. Of the eminences.—The eminenoes are either arti- cular or non-articular: the first are in crusted with cartilage, and enter into the formation of the joints; the second are destitute of cartilage, are more or less rough, and are des- tined for the most part to give insertion to muscles, &c. The varieties of form, which are presented by these emi- nences, have induced anatomists to distinguish them into several species, known under the generic names of apo- physes, processes, and rami, when they are long and very salient; by those of protuberances and tuberosities, when they are short, rough and unequal; by those of crests, when they are very salient, narrow, and extended; of spines, when they are small, thin and acute; of lines, when they are long and slightly projecting. 2. Of the depressions.—The depressions, or cavities, are also distinguished into articular and non-articular: the first only, like the corresponding eminences, are incrusted with cartilage. (See History of the Articul.) The second, which will alone occupy our attention on the present occa- sion, are either external or internal. The external cavi- ties are generally mere depressions, but sometimes they constitute true cavities: both present many varieties of form; thus, when the depressions have a large and wide cavity, they are termed fossae, or digital impressions. When the cavities are deeper, narrow at their origin, and wide in the rest of their extent, they are termed cells or sinuses, according to their number and capacity, which are in an inverse ratio; the former being predominant in the cells; the latter in the sinuses: thev are lined by a mu- 16 114 OF THE OSSEOUS SYSTEM. cous membrane, and contain atmospheric air. The third class comprehends, under the names of furrows, grooves, &c, the depressions which are more or less narrow and elongated, and which generally receive blood-vessels and nerves; in the fourth class are included the foramina, fis- sures and canals, which pierce through the substance ofthe bones, and are more especially destined to give passage to vessels and nerves. The osseous eminences and cavities are formed either by a single bone, or, as is most frequently the case, by the union of two or more of these organs. Many of the bones, also, present rough, uneven surfaces, which serve for the attachment of muscles, ligaments, &c. Besides the cavities which communicate on the exterior of the bones, there are some which are completely internal, and which modify in a considerable degree, the interior conformation of these organs. On the internal surface there are small cavities which are single, and in the form of ca- nals in the bodies of the long bones, and under the form of cells, varying in number, size and figure, in all the other parts of the osseous system. These cavities, which result immediately from the texture of these organs, are always more developed in the centre of the bones than at their extremities: they sustain the marrow and prevent one part of it from compressing another. Texture.—The bones are composed of a fibro-lamellated tissue, very compact at their exterior, more spongy at their interior; this difference of texture has induced anato- mists to distinguish in them a compact, a reticular, and spongy tissue. In the first, which serves always as a co- vering to the others, the fibres and lamellae are applied upon each other in such a manner as to give the bone a fibrous appearance. The fibres being very irregular, and in juxta-position, leave mere microscopic interstices be- tween them of the form of small canals, being composed of lamellated layers, united together by transverse or ob- OF THE OSSEOUS SYSTEM. 115 lique fibrillar. The reticular tissue is less compact and con- stitutes the most internal layers of the bone. In the spongy tissue, the fibres and lamellae leave small spaces or cells between them, which resemble those of sponge or of inflated cellular tissue, and form the second kind of the small osse- ous cavities to which we have just alluded. Modern re- searches have ascertained that the osseous texture is nothing but cellular tissue, hardened by its combination with a ge- latino-calcareous substance, but which preserves the inte- rior form of its primitive state until the fat is deposited into its cells. Besides the osseous tissue, there are other parts that en- ter into the composition of bones, and these are: 1st, a fi- brous membrane which serves as an external envelope, and which has already been described under the name of peri- osteum (v. page 94); 2d, the marrow, or the adipose tis- sue of the bones, which is lodged in the cells of the spongy and reticular substance, and even in the compact tissue, as well as in the large interior canal of the long bones, where it is contained in a cellulo-vascular membrane peculiar to that canal. The fat of bones consists, if not every where, at least in the most spacious lacunae, of small spheroids fill- ed with an oily substance, more fluid and of a more yel- lowish colour than that of the general adipose tissue; 3d, blood-vessels, which have been distinguished by anatomists into three orders: the first comprehends the small arterial branches, which are derived from the vascular net-work of the periosteum, and which enter the microscopic orifices, and are distributed to the compact substance. The second order consists of the vessels which penetrate into the spongy substance by the foramina, which are observable upon the surfaces of the short and at the extremities of the long bones: in the third order are included the vessels known more particularly under the name of nutritient, which tra- verse, without ramifying, the hollow canals in the compact substance, and are distributed to the membrana medullaris. 116 OF THE OSSEOUS SYSTEM. The corresponding veins of the first two orders do not pass out at the orifices which receive the arteries, while the ar- teries ofthe third order are generally accompanied by veins which exactly correspond to them in number and volume. The parietes of the veins of the compact and spongy tis- sues are formed merely of the internal membrane of the venous system; they present a cellular arrangement, which establishes an analogy between them and those which con- stitute the erectile tissue of the corpora cavernosa, &c, being formed, like them, merely of the internal mem- brane of the venous system—a character which belongs also to the small venous ramifications of the compact sub- stance. As yet, no lymphatic vessels have been traced into the substance of the bones; and the nerves, which accompany the vessels of the medullary membranes of the long bones, can not be discovered in the osseous tissue itself. Characters, physical and chemical properties.—The bones are of a white, yellowish colour, very hard, compact and resisting, possessed of a very small degree of flexibili- ty and elasticity, and susceptible of slow extension, follow- ed, when the cause of extension is removed, by the return of these organs to their primitive dimensions; (as in some of the osseous cavities, such as the nasal fossa?, the orbit, &c. which are sometimes temporally enlarged by the pre- sence of tumours, and which regain their original capacity as soon as these tumours are removed). The solidity of the bones depends upon their chemical composition, which, according to the analysis of Berzelius, consists of the fol- lowing ingredients:—Animal substance reducible into ge- latine, 32.17; insoluble animal substance, 1.13; carbonate of lime, 11.3; phosphate of lime, 51.4; flu ate of lime, 2.00; phosphate of magnesia, 1.16; soda, and phosphate of soda, 1.20. The analysis of Fourcroy and Vauquelin differs somewhat from the preceding; for, besides the ingredients already enumerated, these chemists have detected the pre- OF THE OSSEOUS SYSTEM. 117 sence of a small quantity of iron and silica. The composi- tion of the bones varies also according to the age of the individual, the state of health or disease, and the kind of bone that is examined. The gelatinous parts of bone are extracted slowly by boiling water, and the saline part is readily decomposed by some of the acids. Vital properties.—The bones, in their healthy state, possess but a small share of sensibility; they are destitute of contractility, and the slowness with which they are formed and repaired, sufficiently proves that they are en- dowed with but a small degree of vitality. Mode of development, and differences according to age.—The bones, which are at first liquid like all the other parts of the body, become gradually gelatinous, and pass suc- cessively (at least the majority of them,) into the cartilagin- ous and fibro-cartilaginous states, and from these into the osseous. At the commencement of embryotic life, the os- seous system is merely of the consistence of mucus, and forms an uninterrupted whole, which is soon after divided into a great number of parts. Ossification begins about a month after the time of conception, and is not fully com- pleted before the twelfth, and in some accessory parts, not until the eighteenth year of age. Ossification does not appear to result uniformly from the change of cartilage into bone. According to Howship, some parts of the os- seous system, such as the bodies ofthe long bones and the broad bones of the cranium, pass immediately from the mucous to the osseous state. The formation of bone is accompanied by some very remarkable and curious pheno- mena: in the centre of the temporary cartilage, which is formed about two months after conception, and which has already the configuration of the bone, may be observ- ed small canals, and vessels which are lined by a vascular membrane, filled at first with a viscous, and subsequently with a sanguineous fluid: the appearance of this fluid is 118 OF THE OSSEOUS SYSTEM. soon followed by that ofthe first osseous point.* The car- tilage, being injected with red around the' transformed part, presents a homogeneous aspect in proportion as it is examined near its circumference. Ossification thus ex- tends gradually from within outwards, and finally termi- nates by the complete removal of the cartilage. The canals to which we have just alluded, being large at the com- mencement of ossification, diminish progressively, and in proportion as the process of ossification is completed: and instead of the homogeneous substance of the temporary cartilage, there is a complete bone, having distinct fibres and blood-vessels. Though numerous hypotheses have been advanced in explanation of the conversion of the cartilaginous into the osseous tissue, our information of the nature of this nutri- tive phenomenon is still involved in doubt and uncertainty like that of every other part of the animal economy; and all the knowledge we possess upon this subject is, that the formation of bone results from a change of nutrition ofthe cellular net-work, in consequence of the afflux of blood to the cartilage, and by virtue of which, the albuminous, ho- mogeneous substance is converted into a lamellated tissue, composed of gelatino-calcareous fibres. In many of the bones, ossification takes place in several points; thus, in some instances, the two symmetrical halves of the azygos bones are developed separately, coalesce from the opposite sides, and are confounded with each other on the mesian line, as in the frontal and inferior * Every normal or accidental ossification is preceded by the develop- ment of a small, red, vascular apparatus, in the point of the cartilage or fibro-cartilage which is about to be changed into bone. From the moment that ossification takes place (always in the centre of this appa- ratus,) the formation of vessels, or at least their development and colo- ration, continue to increase, and in such a manner that the ossified part is always separated from the surrounding parts by another portion in- jected with red. OF THE OSSEOUS SYSTEM. 119 maxillary bones; while, in some ofthe other symmetrical bones, as in the sphenoid, the vertebras, &c., ossification commences by lateral and mesian points. The symmetri- cal bones differ from each other, both with regard to their number, and the respective arrangement of their primitive osseous points. The trace of union of some parts of the same bone, originally distinct, sometimes remains during the whole period of life, as in the bones of the sacrum. Many ofthe articular and non-articular eminences are form- ed by distinct points of ossification, which appear at very different periods, from the fifteenth day after birth to the fifteenth and sixteenth year of age. These osseous points are termed epiphyses, and are separated from the bone, by cartilage: when this cartilage is converted into bone, the epiphyses are changed into apophyses. We shall endeavour to express, in a general manner, the order in which ossifi- cation takes place in the different bones of the skeleton, though these rules do not always obtain. The two follow- ing are those which present the least exceptions; 1st, in % the human subject, the bones are developed by degrees, and run through the same stages of organization as may be observed in the animal scale; 2d, The long bones are form- ed before the flat, and these before the short.* * The following being the order in which the different parts ofthe skele- ton ossify, we shall perceive how difficult it is, after having read trapse details, to establish general rules with regard to this point. Ossification begins at the end of the first month in the clavicle, and successively in the inferior maxilla, femur, tibia, humerus, inferior maxilla, and in the bones of the fore-arm, where it commences about the thirty- fifth day. Ossification begins about the fortieth day in the fibula, scapu- la, palate, and subsequently in the central portions ofthe occipital and frontal bones, the arches ofthe first vertebrae, the ribs, the great wing of the sphenoid bone, the zygomatic apophysis, the phalanges ofthe fingers, the bodies ofthe middle vertebrae, the nasal and zygomatic bones, the ilium, metacarpal bones; the phalanges ofthe toes, the occipital condyles, and then in its basilar portion, the squamous part ofthe temporal; the pa- V 120 OF THE OSSEOUS SYSTEM. The formation of bone then takes place, as we have al- ready said, from within outwards, by the deposition of new osseous substance around the primitive nucleus: besides, the periosteum being more vascular at the period of ossifica- tion than at any other time, secretes and deposits upon its internal surface, osseous layers, which are united to the bone and add to its thickness.* It is then by a kind of juxta- rietal and the vomer: in all these bones ossification commences about the middle ofthe seventh week. In the course ofthe same week, it begins in the orbitar process of the sphenoid, and finally, in the metatarsal bones and phalanges of the toes, and in the last joints of the fingers. During the ten succeeding days, ossification commences in the body ofthe sphe- noid, in those of the first sacral vertebrae, and in the circle of the tym- panum. About two months and a half after conception, it is manifested in the costiform appendix of the seventh vertebra; before the end of the third month, in the labyrinth, and about the end ofthe third month in the ischium, and internal pterygoid apophysis; about the middle of the fourth month, in the small bones ofthe tympanum; at half the term of uterine life in the pubis, os calcis, the last joints of the toes, in the lateral portions ofthe ethmoid, and in the spongy bones of the nose; and somewhat later in the first pieces of the sternum; about the sixth month, the body and processus dentatus of the second cervical verte- bra, and the anterior and internal masses ofthe pelvic or sacral verte- bra, and subsequently, the astragalus begin to ossify. About the sev- enth month, the ethmoidal pyramids ossify, then the crista galli; and at the period of birth, the first coccygeal vertebra, the os cuboides and the anterior arch of the altas. About the twelfth month, the coracoid process, os magnum and unciforme ofthe carpus are solid; about the third year, the first cuneiform bone, the patella and the triquetral bones are ossified; at the fourth year, the second and third cuneiform; about the fifth, the scaphoid ofthe tarsus, the trapezium and lunare; at eight, the scaphoid ofthe carpus ossifies; at nine, the trapezoides, and finally the pisiforme, about the twelfth year of age. Beclard, Anat. Generale, p. 496. * The depressions and cavities of the bones are determined at the mo- ment of ossification, either by the presence of some organ upon which the bone is modelled, or by active pressure, which is opposed to the de- velopment of the parti, where ossification takes place; there being no OF THE OSSEOUS SYSTEM. 121 position that the first development of the bones is effect- ed; but, when once formed, they increase by an interstitial nutrition, which becomes gradually less active, until at a certain age, (about the time when all the epiphyses are completely ossified and are united to their respective bones,) it is no more than sufficient to nourish the bone and keep up its preservation.* In the adult, the nutritive process continues to become more slow; the number and volume ofthe vessels diminish, and the bones, being less pervaded with blood, become more dry and calcareous, lose their elasticity, and diminish in thickness; hence the remarkable enlargement of their interior cavities and their brittleness in old age. In the female, the bones retain a much longer hollows in the osseous tissue as we might be led at first sight to suppose; the bones ofthe cranium are moulded upon the brain, the articular sur- faces upon the eminences which receive them, &c. &c. * The knowledge ofthe property of madder in colouring the bones of animals that have been fed with it for a long time, has led several learn- ed physiologists to experiment with this plant, with the view to deter- mine the mode of nutrition and growth of the bones. As those of Du Hamel are the most interesting, we shall sum up his principal results. The bones of young animals that have been fed with madder, soon be- come red, while those of old animals, on the contrary, scarcely undergo any sensible change, even after protracted feeding. If a young animal be fed with madder for some time, and then on ordinary food, the bones become red and white in alternate layers, which indicates a juxta-position, and not an interstitial nutrition. This does, probably, not take place after the epiphyses are fully united to the bones. Du Ilamel does not, however, admit this juxta-position, but is of opinion, that the bones in- crease in length and breadth, merely by extension. To refute this theory, J. Hunter performed the following experiment: having perforated the two extremities ofthe body of one ofthe long bones of a young animal, it was killed some time after, and upon examination it was found that the distance which separated the two foramina, was the same as at the time ofthe operation. From the results, therefore, of this experiment, which was several times repeated, Mr. Hunter concluded that the bones are not subject to elongation. 17 122 OF THE OSSEOUS SYSTEM. time than in man, the characters which they possessed in youth. Functions.—The bones form an essential part of the or- gans of locomotion, performing the office of levers for the action of the muscles and their tendons, which arise and are inserted into them; they also protect from external in- jury the brain, heart, lungs, and other organs on which life more immediately depends; as well as the larger and more important blood-vessels and nerves. article 2. Ofthe long, broad, short, and mixed bones in particular. § 1. Of the long Bones. Definition.—By the long bones we understand those elongated, osseous pieces, which contain a medullary canal.* They comprehend the humerus, the ulna, and radius; the femur, the tibia and peroneus; the metacarpal and metatar- sal bones, and the phalanges of the fingers and the toes. Situation.—All the long bones are situated in the ex- tremities, which they occupy throughout their whole ex- tent, with the exception of the carpus and the tarsus. Conformation and arrangement.—Thick and volumi- nous at their extremities, where we observe apophyses of insertion, eminences and articular cavities, the bones gra- dually diminish and form imperfect cylinders: this inter- mediate part to the extremities is termed their body or dia- physis. On the body of the bone are ridges for the attach- ment of muscles, generally three in number, directed ob- liquely, and in such a manner as to give the bone a twisted - * It is from this character alone that we ought to draw the generic name of the bones of which we are treating; the other denomination be- ing too general and equally applicable to the bones without a medullary canal, as for instance, those of the ribs. OF THE OSSEOUS SYSTEM. 123 appearance. The long bones of each extremity, taken as a whole, represent a broken column, whose pieces, being ar- ticulated in various ways, as we shall hereafter see, dimin- ish in volume, and increase in number in proportion as they recede from the trunk. Structure.—There is a great difference with regard to their interior form, between the body and the extremities of the long bones. The first is composed of compact sub- stance, which is somewhat rarefied, and becomes reticular towards the centre of the bone; hence there is a canal which is lined by a cellulo-vascular membrane, which sends numerous prolongations into its interior, supported in some instances by others that are derived from the os- seous substance, and forming, by their mutual interlace- ment, a great number of cells, which are destined to receive the adipose vesicles which are deposited in their interior, or the marrow properly so called.* The medullary mem- brane appears to result from a net-work of the blood-ves- sels, lymphatics and nerves, which are derived from the ramifications of those which enter the canal through the nutritient foramina; and are strengthened and defended from injury by cellular tissue. This membrane is com- monly considered as the internal periosteum of the long bones: the quantity and consistence of the fat which it con- tains are in relative proportion to the exterior state of the individual: it is small in quantity, and almost entirely aqueous in emaciated persons, while in those who enjoy an ordinary degree of embonpoint, its proportion- is more considerable. Towards the extremities of the bone, the compact substance greatly diminishes,and is finally reduced to a mere plate which covers the spongy substance of which the extremities are composed. The medullary canal is not continued into the extremities; and, although there is some- * In birds, the medullary canal is filled with air which comes directly from the lungs. 124 OF THE OSSEOUS SYSTEM. times a small quantity of marrow in the cells of the spongy substance, there is never any distinct membrane. Characters and physical properties.—The long bones unite to the physical characters, which they possess in com- mon with the rest of the osseous system, the property of resisting, in a very great degree, such forces as have a ten- dency to break them, by virtue of the compact texture of their bodies, and of the medullary canal which occupies their centre: indeed, in consequence of this arrangement, the bones have a greater diameter, without increase of sub- stance, and consequently of weight. Vital properties.—The osseous part of the long bones affords nothing peculiar with regard to its vitality; but the medullary membrane which lines their interior canal is endowed with true sensibility: for when this membrane is irritated after the bone has been divided, the animal im- mediately evinces symptoms of pain. It is also endowed with a small share of contractility, analogous to that of the cellular tissue. Mode of development and differences according to age.—The long bones are developed by three points of os- sification; one for the body and two for the extremities. The former appears before the other two, about two months after conception, without passing to the cartilaginous state; there being already a hollow which is occupied by the principal nutritient artery. The temporary cartilages hav- ing already the form of the extremities of the bone, are united to the ends of this cylinder, and at the period of birth, ossification begins in the centre of these terminal parts; from this mode of ossification result the epiphyses which, as we have already seen, remain several years se- parated from the body of the bone by means of cartilage. The bones gradually increase in length by the addition of new osseous substance to the extremities of the diaphysis, and by the union of this with the epiphyses. The medul- lary canal, which is at first nothing but a mere narrow ca- OF THE OSSEOUS SYSTEM. 125 nal filled by the nutritient artery, gradually enlarges, and becomes filled with a soft viscid substance; as the canal in- creases in size, the cellulo-vascular membrane becomes apparent, which, in the foetus and new-born infant, contains nothing but a very aqueous fluid, which by degrees acquires the properties of marrow. The medullary canal continues to enlarge with the age ofthe individual, without encroaching upon the parietes of the bones, which themselves increase on their external sur- face; but in proportion as these cease to grow, their parietes become progressively thinner; so that in old age they form but a small share of the diameter ofthe body ofthe bone. In proportion also as the medullary canal enlarges, the quantity of marrow increases. Functions.—The long bones constitute essential parts in the articulations of the extremities, and form solid, though flexible columns, capable of being moved in various directions, by the muscles and tendons which are attached to them. § 2. Of the broad or flat Bones. Definition.—The class of bones which we are about to describe comprehends those pieces which vary in thick- ness, but are nearly equal in their length and breadth; as the frontal and parietal bones, the scapula and os ilium. Situation.—The broad bones form, in part, the parietes of the cranium, the thorax and pelvis. Conformation.—They are lamelliform, quadrilateral, semicircular, &c, more or less curved, or contorted in va- rious directions, so that the same side may be entirely con- vex or concave, or alternately the one and the other; while the opposite sides are concave and convex. The flat bones are thicker at their circumference than in the centre, hav- ing inequalities of different kinds, which are more promi- nent upon their articular borders than upon those which give attachment to muscles. 126 OF THE OSSEOUS SYSTEM. Structure.—The flat bones are uniformly composed of two laminae or tables of solid and compact substance: in the flat bones of the cranium the internal layer is thinner and more dense than the external, and is hence called ta- bula vitrea. In some instances these tables are in contact with each other, especially in the centre of the bone, and in others they are separated by a layer of intermediate spongy substance called the diploe. This is exceedingly vascular, having a great number of veins, and containing a small quantity of marrow without any distinct membrane. Mode of development, and differences according to age.—The broad bones are developed by two or more points of ossification, which become manifest in the mu- cous substance at the end of the second month of pregnan- cy, between the periosteum and the dura mater for the bones of the cranium, and between the two laminae of the periosteum for the other flat bones. The osseous fibres issue in rays from the centre towards the circumference, and finally form laminae with radiated fibres, which are still separated by the mucous substance. It has been observed by Bichat, that we ought to refer the origin of the su- tures, which unite some of the flat bones with each other, to the interspaces which are left at this period between the fibres of these bones. Soon after the laminae of which the flat bones are composed, are united, their substance be- comes more conspicuous, and the tables, which were at first confounded, become more distinct in proportion as they increase in density; leaving between them, as they sepa- rate, an intermediate spongy substance formed at the ex- pense of the internal fibres of their contiguous surfaces. In old age this substance is absorbed, the two tables are again brought in contact, and the bone becomes sensibly thinner and weaker: to this circumstance ought to be at- tributed the sinking ofthe parietal protuberances observa- ble on the skulls of old people. Functions.—The flat bones serve to defend from exter- OF THE OSSEOUS SYSTEM. 127 nal injury the organs which are contained in the cavities which they contribute to form, and participate in the func- tions of locomotion, either by furnishing immoveable ful- cra for the action of the muscles, or in performing the mo- tions which these organs impress upon them. § 3. Of the Short Bones. Definition.—Under this class are comprehended all the bones whose length, and breadth, and thickness, are nearly ofthe same dimensions. Situation.—The short bones are generally collected in groups, and are situated in the hand and foot, &c, and in the vertebral column, which is formed exclusively by them. Conformation.—The short bones present too many ir- regularities to enable us to point them out in a general de- scription. Their form is generally determined by the parts around and between which they are situated: they are globular, tretroidal, cuneiform, cuboidal, &c.: all of them are furnished with eminences and depressions, either for their articulation or for the attachment of the soft parts. Structure.—The internal substance of the short bones consists of a soft, spongy, and areolar texture, which is covered and defended exteriorly by a layer of firm com- pact substance: they are supplied with blood-vessels, and contain a small quantity of marrow without any distinct membrane, like all the bones that have no medullary canal. Mode of development, and differences according to age.—The short bones ossify slowly, and pass from the mucous to the cartilaginous state; and the temporary carti- lages in which they are formed have the shape and volume ofthe bone long before it is completed: ossification of the short bones also takes place from the centre towards the circumference, and is attended with the same phenomena as the ossification of the other bones. Some of the short bones are developed in the thickness or in the continuity of some of the tendons or ligaments, and pass successively 128 OF THE OSSEOUS SYSTEM. from the fibrous to the fibro-cartilaginous state, and finally to the osseous. The patella and the sesamoid bones are formed in this way; so that they do not appear to be es- sential parts of the skeleton, and are considered by some as accidental bones. Functions.—Nature has placed the short bones in every place, where it is necessary to combine a great degree of solidity with that of mobility. To attain this double pur- pose, it was necessary that they should be small and ar- ranged in groups. Indeed, we know, that an instrument, formed of several pieces which are firmly united together, is more solid than one that is composed of a single piece, because such efforts as have a tendency to break it are lost at their point of union, and that the principal motion of a series of organs occupying a given extent, is also much greater in proportion as these organs are more numerous, and consequently smaller. The short bones of the verte- bral column, moreover, form a kind of bony case for the spinal marrow, which is thus defended from external in- jury. § 4. Of the Mixed Bones. Definition.—The mixed bones are those which combine the form and characters of the preceding classes, and ap- pear to result from the union of the bones of two or even three of them; as in the sphenoid, the ethmoid, the tem- poral, the occipital, the ribs and the sternum. Situation.—Most of them belong to the head and the thorax. Conformation.—Their form is very variable, and re- sults most frequently from the union of a broad, a short, and a thick part. Structure.—The mixed bones present the same struc- ture as the bones with which they are connected. It is in this class that is comprehended the hardest and most com- OF THE OSSEOUS SYSTEM. 129 pact osseous part of the skeleton, viz. the petrous portion of the temporal bone. Mode of development.—These bones are formed by several points of ossification, and possess in each of their respective parts the mode of development of the kind of bone with which they are connected. Functions.—The mixed bones perform different func- tions in the animal economy; they contribute to form the cranium and the thoracic cavity, surround and defend the organs which they contain, the encephalic nerves and some parts of the organs of sense, and give attachment to muscles. Pathological Anatomy. The bones are often subject to mal-formations, which are either congenital or accidental. The first are frequently observed on the vault of the cranium, less often on the pa- rietes of the thorax and abdomen, and seldom in the ex- tremities. They consist either in a defect, or in an excess of development of the osseous parts where they are found, and are most frequently accompanied by congenital ano- malies ofthe viscera which they surround. The mal-for- mations which are consequent upon the development of the bones, depend sometimes upon accidental hypertrophy or atrophy, as may be observed in some of the chronic dis- eases. Sometimes also they result from inflammation and swelling of the periosteum, accompanied by the secretion of osseous matter, which is deposited upon the internal surface of that membrane, and which, uniting with the bone, constitutes what is called external exostosis: this morbid development is presented either under the form of a circumscribed nodosity, and is then termed node, or under that of a tumour, varying in extent, and composed of large and superadded layers. When treating of inflammation of the bones, we shall have occassion to point out some ofthe 130 OF THE OSSEOUS SYSTEM. various alterations which it is capable of producing in the osseous system. The solutions of continuity or fractures of the bones, de- serve our particular attention in relation to their mode of healing. In the following exposition ofthe different the- ories of the formation of callus (cicatrix,) that have been hitherto advanced, we shall see the great discrepancy in the opinions of some of the most learned and experienced physiologists, with regard to this highly interesting and important subject. The ancients were of opinion, that the extremities ofthe fragments of a broken bone secreted a kind of osseous fluid or coagulable lymph, which gradually acquired con- sistency, and glued the extremities together. Haller af- terwards extended this theory, and asserted that the fluid, exhaled by the extremities ot the fragments and the mar- row, was effused around them, and became successively mucous, then cartilaginous, and finally osseous; passing thus through all the different stages of the original ossifi- cation. According to Haller the periosteum is entirely passive in the formation of callus. By Mr. John Hunter the formation of callus is referred to the organization and ossification ofthe blood which is extravasated around the broken fragments. In the present day, Mr. Howship, embracing the ideas of M. Dupuytren, has added addi- tional proof to the theory of Hunter, and asserts that the periosteum becomes cartilaginous at the extremities of the fragments; that the matter of callus is deposited successively upon the surface of the bone, the circum- ference of the extremity, and in the medullary cavity; —in a word, that the fragments are firmly re-united at their exterior parts before they are cicatrized at their extremities. The theory of Du Hamel, published before the time of HallerTs, tends to prove, that the periosteum and the medullary membrane, and sometimes the first only, are elongated and united to those of the opposite frag- OF THE OSSEOUS SYSTEM. 131 merits, and ossified in such a manner as to surround the fracture by a kind of osseous ring. This re-union, in which, according to Du Hamel, the extremities of the fractured bone themselves did not participate, was regarded by him as definite. According to the opinions of Bordenave, Bi- chat and Richerand, fractures, that are attended by lacera- tion of the soft parts, have their contiguous extremities re-united by the development of fleshy granulations. Not- withstanding the theories already stated, little was known with regard to the phenomena of osseous cicatrization, un- til the researches of Dupuytren, Breschet- and Villerme, threw new light upon this subject, and gave us more cor- rect and satisfactory information. We shall find in the ideas of these gentlemen some of those of Du Hamel, of Haller, and of Howship. According to the new theory, there are three distinct stages for the formation of callus. In the first stage, the small quantity of blood, that escapes and is effused between the fragments at the moment the frac- ture occurs, is soon followed by the exhalation of a viscid serum; the blood gradually loses its colour, and the peri- osteum, the medullary membrane, and the divided soft parts are re-united. The second stage is characterized by inflammation and swelling, accompanied by the secretion of coagulating lymph in the thickness of the periosteum, and between it and the bone: this matter is gradually ossi- fied, as well as the medullary membrane: externally, the ossification extends to the surrounding cellular tissue, and even to the muscles. Finally, a provisional callus is form- ed, a kind of osseous incrustation on the surface of the contiguous extremities, which may be compared to the osseous rings (virole,) observable in a great number of bones, and which, in the long ones, is completed by the formation of a kind of osseous pin (cheville) in the me- dullary cavity, in consequence of the ossification of the medullary membrane. The provisional callus is nothing more than a kind of solid, retentive apparatus, which serves to maintain the fragments in contact. As soon as 132 OF THE OSSEOUS SYSTEM. this is formed, commences the third stage—that of the permanent callus. Until now the bone itself has experi- enced no sensible changes; but at this period the substance that was effused between the fragments acquires consist- ency and firmness; vessels are developed which communi- cate with those ofthe bone and the periosteum, and finally ossification is effected, and the two extremities are thus firmly re-united. When this consolidation is perfect, the provisional retentive apparatus is gradually absorbed, and the medullary canal is re-established. When the fragments, however, can not be maintained in their natural relations, after they have been brought in contact, the medullary canal remains obliterated, and the exterior callus, instead of being merely provisional, becomes permanent. When the fragments are not properly reduced, and maintained perfectly in contact, they are re-united by a kind of fibrous cicatrix, which generally happens in fractures of the patella and cervix femoris, on account of the difficulty of pre- venting the separation ol the fragments. Sometimes the extremities of the fragments are rounded, becoming firm and compact, and even incrusted with car- tilage, and covered by synovial membrane: hence the ano- malous articulations which either prevent or greatly im- pede the motions of the injured parts. It sometimes happens that the epiphyses are separated from the bones by mechanical causes, or morbid changes, such as inflammation; and in these cases re-union is effect- ed in the same manner as in fractures. In cases of com- minuted fractures, the disorganized parts are re-united by callus. Wounds of the bones, with loss of substance, are generally followed by mortification, and exfoliation of the external laminae, and subsequently, by fleshy granulations and the restoration of the exfoliated substance.* In "-ene. * When the periosteum alone has been injured, and the soft parts are immediately brought in contact, re-union often takes place without pre- vious exfoliation. OF THE OSSEOUS SYSTEM. 133 ral, wounds of the bones are rapidly repaired, and show the great recuperative power ofthe osseous tissue. The bones are often rendered thin by the pulsations of aneurismal tu- mours, and are even sometimes perforated, especially when they are thin and soft and in contact with the tumour. After amputations, the extremity of the osseous frag- ment ofthe stump inflames, unites with the surrounding soft parts, and is rounded and covered with a compact osseous plate, which closes up the mouth of the medullary canal. If there be lesion of the bone or the periosteum, beyond the extremity of the fragment, slight exfoliation takes place, but the cure is afterwards effected as in ordinary cases. Primary inflammation of the bones is a very rare disease; but it is often propagated to them by the surrounding parts, and always in consequence of mechanical injuries; and un- der these circumstances it is that we can best observe in them the anatomical characters of this morbid state. When the osseous tissue inflames, it swells, becomes more spongy and rarified than in its normal state, and its vessels are highly injected with blood. These phenomena are accom- panied by the secretion of a gelatinous or red serous fluid, which is deposited into its cells; the calcareous salts are gradually absorbed, and the gelatinous substance itself is evi- dently altered; the medullary canal disappears in the neigh- bourhood of the affected part; and the membrana medul- lars, whose interior elongations are red and thickened, is filled in its interstices with a fibrous substance. Inflam- mation of the bones often terminates in mortification or necrosis: their compact portions are more especially subject to these morbid derangements, on account of their small degree of vascularity. The necrosed part is uneven and of a reddish brown colour; and sometimes, when mortification succeeds to gangrenous inflammation, the es- char is brown and spongy, and emits the smell that charac- terizes gangrene of the soft parts: most frequently the gelatinous substance of the bones disappears, and even 134 OF THE OSSEOUS SYSTEM. sometimes, the calcareous salts themselves are decomposed. The hospital gangrene also extends to the osseous tissue, and reduces it to a soft, grayish, foetid, and pultacious sub- stance. In necrosis of the long bones there are some interesting peculiarities, which are important to be understood by the surgeon, and which afford another example of the recu- parative powers of the tissue of which we have been treat- ing. When the body of one ofthe long bones is mortifi- ed, either in part or in whole, nature sets up her restorative efforts, and forms around it another osseous portion equal to the original, and pierced by several apertures, by tra- versing which by means of a stylet, we may perceive the dead bone, and readily distinguish it in the interior ofthe new, by its mobility.* The sequestrum or dead part is discharged, either by the efforts of nature, or those of sur- gery, through the apertures to which we have just alluded: after the removal ofthe sequestrum, the openings gradual- ly close; and the new bone, assuming the form of the origi- nal, unites with its terminal portions, and, finally exceeds it in density:—it is furnished with a medullary canal and membrane. In cases where the entire thickness of the body of the bone is necrosed, the restoration is effected by the periosteum: in some instances, the internal laminae alone are mortified, and then the reproduction consists merely in an increase of the external plates, accompanied, as in all other cases of new formation, by the phenomena which are necessary for the removal ofthe sequestrum: in necrosis ofthe flat and short bones, and in the extremities of the long ones, restoration is less frequently effected than in the bodies ofthe long bones. Caries, or softening and ulceration of the bones, is another * The probe penetrates as far as the sequestrum b)' traversing the fis- tulous openings, which nature has established in the soft parts, to favour its elimination. OF THE OSSEOUS SYSTEM. 135 effect of inflammation: it is characterized by a softening of the osseous tissue, accompanied by a great degree of fria- bility, and a fetid ichorous discharge; when the quantity of this fluid is small and inconsiderable, the disease is term- ed dry caries—a variety which seldom occurs but in the flat bones and in old people. This ulcerative inflammation attacks more particularly the spongy bones, so that the short bones are more liable to be affected by it, than the others. When the inflammation has continued for some time, the oseous tissue becomes swollen and assumes a lamella- ted appearance; its fibres separate, and contain in their in- terstices a thick reddish matter, of the intermediate con- sistence of indurated cellular tissue and tubercles: this mat- ter is often converted into fibro-cartilage, and finally into an osseous substance constituting a kind of exostosis, charac- terized by a simultaneous swelling and increase in the densi- ty of the bone. In the exostoses, which are derived from the bone itself, there are all the characters, that are presented in the sub-inflamed osseous tissue—facts which amply prove that these tumours are the result of phlegmasiae. It is in- deed, to inflammation that we ought to look for the cause of spina-ventosa, and of osteo-steatoma, in which the swell- ing: ofthe organ is combined with the condensation of its tissue and the alteration of its chemical composition. The bones often experience tuberculous, schirrous and cerebri- form degenerations, &c.: they are also subject to a re- markable softening, which arises from an absorption ofthe earthy part of the osseous system, while the animal matter remains. When this disease arises during the growth of the individual, it constitutes what is termed rickets. The bones of ricketty subjects are of a reddish appearance, spongy, and easily cut with the bistoury; and those which are naturally spongy, become more rarefied and volumi- nous than the others; as in the extremities of the long bones, whose size induces the vulgar to say that the subject is 136 OF THE OSSEOUS SYSTEM. ricketty. This state is generally only temporary; but as they acquire their natural density and solidity, the bones retain the deviations and curvatures which the pressure of the body and the action of the muscles produced dur- ing the disease. The mollities ossium is a disease aris- ing from a softening of the bones, and is generally attended by a greater degree of absorption of the earthy salts, than in the disease called rickets: it often supervenes after the formation and growth of the bones are complete; when it is accompanied by a softening and fleshy appear- ance ofthe osseous tissue, it is called osteo-sarcoma. In some instances, the bones are soft and brittle, at the same time that they retain their cellular texture. All the tissues, whether normal or adventitious, are sub- ject to accidental osseous productions: in the first, they result ordinarily from the effects of old age, and are sel- dom perfectly similar to the osseous tissue. Sometimes, these productions consist in mere incrustations, having a greater quantity of calcareous matter than bone, as in the arteries; at others, they consist of a soft, friable, chalk-like substance, composed of animal matter, and earthy salts, as well as a kind of ebony-like substance, as is sometimes found to occur in the cartilages ofthe diarthrodial joints. Ossification of the cartilages and fibro-cartilages presents all the characters of the osseous tissue. section 2. Of the Articulations of the Bones. The bones are connected together through the medium of other substances, and in such a manner as to form an en- tire whole called the skeleton, which determines the ge- neral configuration of the body, and constitutes the basis upon which the whole fabric is built. The bones are all so admirably arranged, that the extremity of every one is OF THE OSSEOUS SYSTEM. 137 perfectly adapted to the end of the bone with which it is connected; and this connexion is termed their articula- tion. Every articulation has its articular osseous parts and the media by which they are united. The articular surfaces, generally, present inequalities, which determine the different kinds of joints, as well as the extent of mo- tion of the moveable articulations. The long bones are ar- ticulated by their extremities, the broad ones by their bor- ders, and the short ones by different points of their surfaces. All the bones are united through the media of cartilages, fibro-cartilages, or, fibrous ligaments. In consequence of the varietjr of form of the articular parts; of the differences of their mode of union, and their immobility or mobility, anatomists distinguish three kinds of articulation; the first is called synarthrosis, the second amphiarthrosis, and the third diarthrosis. 1. Synarthrodial Articulation.—All the bones ofthe head, except the inferior maxilla, are connected by the synarthrodial articulation, and are immoveable with regard to each other. The articulator}' parts present many varie- ties as regards their form and relations, but they are all united by an intermediate cartilage which adheres firmly to them, and by the periosteum which covers it in its pas- sage from one bone to the other. In old age, the synarthrodial articulation is often oblite- rated by the immediate continuity ofthe two bones which it connects, in consequence ofthe ossification of the synar- throdial cartilage. Synarthrosis is divided into several varieties: 1st. The true suture is that kind of articulation which ex- ists between the bones ofthe cranium, where the articular surfaces present a great number of indentations, which cor- respond to an equal number of proportionate depressions, into which they are received. Owing to the trifling dif- ferences which exist in the form of the indentations, this 19 138 OF THE OSSEOUS SYSTEM. suture has been divided into three varieties, viz., the den- tata, serrata, and limbosa. 2d. The false or harmonic suture, in which the bones are connected together by means of rough margins; in this manner the bones of the nose are connected together. 3d. The scaly suture, when the corresponding bones overlap each other, by the separation of their borders, which are sharp and unequal, as in the temporo-pari- etal articulation. The scaly suture is said to be double or reciprocal when the bones do not correspond by the same surfaces throughout their whole extent: the spheno- frontal articulation is an example of this variety. 4th. Schindylesis, when a thin lamella of bone is re- ceived into the narrow furrow of another, as in the articu- lation of the vomer with the ethmoid and sphenoid. 5th. Gomphosis.—This term is expressive ofthe mode of articulation of the teeth with the alveolar cavities, if the first be considered as bones. 2. Amphiarthrosis.—Amphiarthrosis is nothing but a mixed or synarthrodial articulation, with large, smooth, ar- ticular surfaces connected together by^n intermediate fibro-cartilaginous substance, which adheres firmly to them, and has sufficient suppleness and elasticity to admit of an obscure motion. Thus the bodies ofthe vertebrae are unit- ed, and move upon each other by turning upon their axes, or in bending forwards. The fibrous ligaments which are situated around the amphiarthrodial articulations also add to their solidity; though, they are subject at the different periods of life to the changes dependant upon those that are experienced by the intervertebral fibro-cartilages. (See Fibro-Cart. Syst.) 3. Diarthrosis.—Diarthrosis or moveable articulation/re- sults from the contiguity of osseous surfaces which are in- crusted with cartilageand lined by synovial membrane. This kind of connection takes place between the bones of the extremities and the trunk; between the os occipitis and the OF THE OSSEOUS SYSTEM. 139 vertebra dentata, and between the ribs and the vertebral column, &c. &c. The diarthrodial surfaces are sometimes plain, more frequently convex or concave, or both at the same time; but their configuration is always such that they adapt themselves readily to their corresponding parts. When the convex eminences stand out in a roundish ball and constitute the entire articular surface, they are termed heads; when they are rounded, elongated and flattened, they obtain the appellation of condyles. When the heads and condyles rise narrow, and then become larger, the nar- row or small part is termed cervix or neck, as in those of the femur and humerus.—When the depressions are deep, are more or less concave, and constitute the entire ar- ticular surface, they are denominated cotyloid and gle- noid cavities: sometimes they are designated by the names of pulleys or trochlea. The diarthrodial articulations are connected by means of fibrous ligaments, which are gene- rally attached around their circumference, and sometimes to their centre, and always in such a manner as to admit or prevent different kinds of motion. The firmness of the diarthrodial joints is less than in the other classes of articu- lations, and is generally in an inverse ratio to their mo- bility. Diarthrosis is sub-divided into several species, which differ from each other by the form of their articular sur- faces, their means of union and their quantity of motion. 1st. Planiform Diarthrosis* is the articulation where the articular surfaces are nearly plain: are connected by strong and firm ligaments, and are susceptible of vague, but obscure motions, as in the junction of the ossa cunei- formia with the os naviculare; of the articular processes of the vertebrae, &c. 2d. Arthrodia.—When the articular surfaces are more round, less firmly united, and susceptible of more extensive motions than in the preceding. * The amphiarthrosis of Meckel and some other anatomists. 140 OF THE OSSEOUS SYSTEM. 3d. Enarthrosis, when a large head is received into a deep cavity, and is maintained there by a capsular liga- ment: this species of union admits of motion to all sides. 4th. Lateral ginglymus.—When the articular surfaces are convex in the one and concave in the other, and have a part of their circumference formed by an osseous cylinder, and the other by a ligament; as in the articulation of the radius with the ulna. 5th. Angular ginglymus, or ginglymus, properly so called.—In this articulation the surfaces present eminences and depressions, by means of which they move the one upon the other; and where, by the arrangement of these projections and the ligaments which connect the joint, the motions are confined to flexion and extension, as in the ar- ticulations of the elbow and the knee. Pathological Anatomy. The diarthrodial articular surfaces are often displaced in consequence of such efforts as have a tendency to extend or rupture the ligaments which connect them: these dis- placements are termed luxations; and, when they super- vene in consequence of organic alterations of the ligaments, they receive the appellation of spontaneous. The articu- lations are more subject to these displacements in propor- tion as they are more moveable, and their articular surfaces are smaller, and less intimately connected. Besides the accidental articulations which are sometimes established, as we have already seen between the two frag- ments of a broken bone, there are others, which are termed supplementary, and which are consequent upon irreduci- ble luxations: thus, when the articular head of a bone is removed from its cavity, it is applied against another bone, and produces a depression whose circumference is strength- ened by a fibro-cartilaginous or osseous border, while its bottom is lined by a substance analogous to fibro-cartilage: —in fact, we generally find these kinds of articulation pos- OF THE OSSEOUS SYSTEM. 141 sessed of fibrous and capsular ligaments, &c, and of syno- vial membranes. The natural cavity becomes obliterat- ed, and assumes the form which it would have receiv- ed originally from the free development of all its os- seous points: it is in this manner that the cotyloid cavity, which is developed by three points of ossification, becomes triangular after the complete displacement of the head of the os femoris. In some instances the synarthrodial articulations become swollen and relaxed: it is in this manner that the symphy- sis pubis is separated during the last stages of pregnancy, in consequence of the swelling and softening of the inter- mediate fibro-cartilage. * In some cases this separation of the articular surfaces amounts to a considerable extent, as is observed in some of those cases which result from hy- drocephalus and the effects of external injury. The bones are sometimes firmly articulated together, either in consequence of acquired stiffness and rigidity, and the ossification ofthe connecting ligaments; or in con- sequence of adhesions between the contiguous parts of the synovial membrane; or in consequence of the synovial membrane, and cartilages of the articulation having been destroyed by inflammation or some other cause, the spongy extremities of the bones are brought in contact, and are united with each other: in the last case, which constitutes what surgeons have called true anchylosis, the motion of the joint is completely destroyed, while, in the preceding, * This separation of the pubes being of very rare occurrence in the human subject, should by no means be regarded as a provision of nature intended to facilitate the delivery of the female; but as purely accidental, and as a consequence of some morbid derangement of the intermediate fibro-cartilage. In some animals, however, as the Guinea pig, this separation of the bones ofthe pelvis during the latter stages of pregnancy, does actually take place, and seems to be an operation of nature intended to facilitate the parturient efforts.—S. D. G. 142 OF THE OSSEOUS SYSTEM. which constitute false anchylosis, the motion is always less than in the natural state, and is also, sometimes, totally destroyed. The articulations of the elbow and the knee are more frequently affected with anchylosis than any other joints in the body. The diseases known under the name of white-swelling, depend most frequently upon chronic inflammation, and affect, either alone or simultaneously, both the soft as well as the hard parts of the articulations. Bibliography of the Osseous System. Besides the works already quoted: Malpighi. De ossium structura in op. posthum. B. S. Albinus. De constructione ossium, in annotat. Acad., Lib. VII, cap. 17. Delasone. Memoire sur l'organ. des os; dans les Me- moires de l'Acad. royale des sciences. Paris, 1751. J. G. Courtial, J. L. Petit et Limery. Description ex- acte des os, comprise en trois traites. A. Scarpa. De Penitiori ossium structura commentarius. Lips., 1795, Paris, 1804. V. Malacarne. Auctuarium obs. et icon, ad osteol. et os- teopath. Lugduwigii et Scarpae; Patav. 1801. On Osteogeny consult the following: H. Eysson. De oss. infant., cui tractatui annexus est V. Coiter ossium infantis historia. Groning., 1659. Th. Ker firing. Osteogeniae foetus. Lugd.-Bat., 1717. Albi- nus. Annot. Acad., lib. VI, VII.—Id. Icones oss. foetus hum. accedit osteogeniae brevis historia. Lugd.-Batav. 1737.—Duhamel, Mem. de l'Acad. royale des sciences, ann. 1739—41—43—46.—Haller, experimenta de oss. formatione, in op. min.II.—HSrissant, Mem. de l'Acad. royale des Sciences; 1768.—Biclard, Mem. sur l'osteose, dans le Nouv. Journ. de med., vol. IV, 1S19.—Serres, Des lois de l'Osteogenie; analyse des travaux de l'Acad. royale des Sciences, ann. 1819.—Dutrochet, observa- OF THE OSSEOUS SYSTEM. 143 tions sur l'Ost6ogenie, dans le Journ. de physique, sept. 1822. On the history of Callus, consult, Duhamel. Memoires de l'Acad. royale des Sciences; Paris, 1741.—P. Camper, Observat, circa callum ossium frac- tor.; in Essay, and obs. phys. and litter., vol. III. Edimb., 1771.—Bonn, de ossium Callo, etc.; Amstel. 1783.— Macdonald. De Necrosi et Callo; Edimb. 1799.—Bres- chet, quelques recherches historiques et experimentales sur le cal; Paris, 1819.—J. Sanson, Expose de la doc- trine de M. Dupuytren sur le cal; dans le Journal univ. des Sciences medic, tome XX, p. 131. On the pathological anatomy ofthe bones, consult: Tenon. Trois memoires sur l'exfol. des os, in Mem. et ob- serv. sur l'anatomie, la pathologie et la chirurgie, etc. Paris, 1816. J. L. Bracket. Mem. de Physiol, pathol., sur ce que devi- ent le fragment de l'os apres une amputation; in Bull, de la Soc. m6dic. d'emul. de Paris, 1822. Chopart et Robert. De Necrosi ossium theses anat.-ehir.; Paris, 1765.—Troja, de nov. oss. Paris, 1775.—Char- meil, de la Regeneration des os. Metz. 1821. Reichel. De Epiphysium ab ossium diaphysi diductione. Lips., 1769. A. Bonn. Descriptio thesauri ossium morbosorum Hoviani. Amstel. 1783.—Sandifort, de ossibus diverso modo a solita conformatione abludentibus; in obs. anat. path., lib. Ill et IV. Lugd.-Batav., 1777—81. The following works on accidental ossification may be consulted with much advantage: J. H. Van Heckern. De Osteogeni praeternaturali; Lugdu- ni-Batav., 1797.—P. Rayer, Mem. sur l'ossification morbide; dans les Arch. gen. de medec, tome I; Paris, 1823. !44 OF THE NERVOUS SYSTEM. CHAPTER VII. OF THE NERVOUS SYSTEM. SECTION 1. General Observations. Definition.—The nervous system is an assemblage of organs which are continuous with each other, are formed by one of the secondary elements of the animal organiza- tion—the nervous substance; and are composed, first, of masses or ganglia of different sizes, and secondly of fasciculi and cords; some of which establish communications between the different masses, while others extend from them to the different parts of the body. Division.—From remote ages to the present day, anato- mists have regarded the nervous system as composed: 1st, of a central unique part—the spinal marrow, according to Praxagoras and Bartholine, and the brain according to Ga- len and most of his successors; and 2d, of prolongations, by which they understood the nerves and all the other parts ofthe nervous system. Bichat, in unfolding the theories of Winslow and Reil, established the distinction of two nervous systems: the one, which he called the nervous sys- tem of animal life, consists of the spinal marrow, the brain and the nerves which are given off by them; the other, termed the nervous system of organic life, com- prehends the ganglia and the nerves which form the great sympathetic or trisplanchnic nerve. With regard to the OF THE NERVOUS SYSTEM. 145 latter, Bichat has proved that it does not consist of a sin- gle system, but of a combination of small distinct sys- tems, communicating together^ and with the great cerebro- spinal system. Thus, Mr. Gall asserts, that the encepha- lon and spinal marrow are an assemblage of ganglia or in- dependent nervous systems, united by filaments of commu- nication, and susceptible of being brought under three groups. The first comprehends the nervous apparatus ofthe voluntary motions and of the tactile sensations, or those which form the spinal marrow; the second consists ofthe nervous apparatus of sense, comprehended under the name of medulla oblongata, and the third, of the cerebrum and cerebellum, or those of the faculties of the mind. A fourth group, composed of the ganglia and the trisplanchnic nerves, completes the grand nervous apparatus. The plurality ofthe nervous system is generally admit- ted at the present day; but many anatomists, in adopting this capital doctrine, have modified its application, and especially M. de Blainville, who, founding his opinion up- on profound study of comparative anatomy, has defined the nervous system, considered with regard to the whole scale of animal beings, to be " a number of ganglia of differ- ent sizes, each of which sending off nerves, some to.be dis- tributed to the organ which it is to animate and endow with its appropriate life, and others to communicate with the other ganglia and the central ganglion (when it exists) to establish its general life." The central ganglion exists only in the higher classes of animals, and establishes, in the most complete manner, the individuality of being. M. de Blainville, in applying these ideas to the nervous sys- tem of man, represents it as being composed of a central part—the spinal marrow—at the extremities and upon the sides of which are placed ganglia that perform entirely dif- ferent functions. At its superior extremity and on the me- sian line, there are seven ganglia composing the encephalic mass, and being subservient, some to the intellectual facul- 20 146 OF THE NERVOUS SYSTEM. ties; others to the senses, the partial motions of the head, and to the functions of respiration and digestion. On each side of the spinal marrow is another set of ganglia which give origin to the spinal nerves:—finally, in the splanch- nic cavities are the ganglia which are subservient to the functions of nutrition, and are situated near the organs to which they distribute their nerves; these ganglia are, the cardiac ganglion in the thorax, and the semi-lunar plexus in the abdomen. The trisplanchnic holds the same cha- racter here as was assigned to it before the time of Bichat, being an intermediate nerve to all these apparatus, and des- tined to establish communications between them, and in a word, to be a true sympathetic nerve. We repeat here, that the doctrine ofthe plurality ofthe nervous system is generally admitted in the present day, and that authors differ only in regard to the application of this capital idea. The manner in which M. de Blainville regards the grand apparatus of which we are treating, is undoubtedly that which is the most expressive of the ge- neral laws of organization. Although the ideas of this anatomist are not as yet generally adopted, it becomes us, in a work of this kind, to adopt the division of the nervous system into the cerebrospinal and the trisplanchnic, a di- vision, which will at once facilitate the description of this system, and enable us to give an account of the different opinions of the physiologists that have written upon this subject. Situation.—The nervous system is spread throughout every region of the body: its central parts are situated in- teriorly, while its large cords are more superficial, and ap- proach nearer towards the periphery in proportion as they ramify: we shall have occasion to see, however, in a sub- sequent part of this work, that there are some important differences with regard to the situation of the two divisions of the nervous system. Form and general arrangement.—The nervous sys- OF THE NERVOUS SYSTEM. 147 tern may be represented as a grand net-work, whose fila- ments, being interrupted by the small ganglia in the dif- ferent regions of the body, and united together by fre- quent communications, extend from the periphery of the body to the brain and spinal marrow, diminishing in num- ber, and acquiring, generally, a larger volume, and a more completely symmetrical arrangement in the two lateral halves ofthe body: this arrangement is more perfect in the brain and spinal marrow than in any other part ofthe ner- vous system. Texture.—The nervous system is far from having the same organization in every part, notwithstanding in this respect it presents the same common characters. Every part is formed of a peculiar substance called the nervous fibre, which has been regarded by M. de Blainville as a secondary element, resulting from the modification of the primary or cellular element of our bodies. This nervous substance is presented under two principal aspects, which has led to the distinction into the white and gray sub- stance. We shall presently see that this distinction does not merely rest upon the difference of colour indicated by these denominations. 1. White substance.—The white substance ofthe ner- vous system forms a continuous whole, and is generally surrounded by the gray substance; but this is not the case everywhere, as the term medullary, which is also some- times used to designate it, would appear to indicate. If its consistence be increased by immersing it in alkohol, or in weak solutions of the nitric or muriatic acids, upon di- viding it, it will exhibit a very remarkable fibrous struc- ture, apparent in some parts, as in the nerves without pre- vious preparation. The fibres are disposed in parallel or oblique fasciculi, which can be readily separated into capilli- form fibrillae; but the mechanical division can not be carri- ed so far as to enable us to say whether these filaments, which are very intimately united together, are themselves 148 OF THE NERVOUS SYSTEM. composed of other still more minute fibrillae. The white substance is plentifully supplied with blood-vessels, but not so much so as the gray. 2. Gray substance.—The gray substance is generally situated externally to the white; so that it is often called cortical—a term which is by no means always applicable, as we shall see in the next section. It does not, like the white substance, form a continuous whole; but is always found in insulated portions. This substance occurs at the central extremities or points of origin of the nerves, and is there more abundant in proportion as the nerves are larger and more numerous, as in the superior part ofthe brachial plexus: it is found, also, everywhere where the white sub- stance is most abundant and more fully developed. From this disposition, many physiologists have inferred that the gray substance produces the other, and is the matrix of all the nerves. If this were true, the appearance of the first would necessarily precede that of the second, which is not the case, as we shall presently see. The fibrous texture of the gray substance being difficult to be distinguished, even when prepared as we shall hereafter direct, is not admitted by all anatomists, though its exist- ence does not appear to be doubted at the present day, at least not in the encephalo-rachidian mass. The gray sub- stance is generally very vascular; but variously in the dif- ferent parts of the system. Examined with the microscope, the nervous substance appears to be composed of small, semi-transparent globules, connected together by a viscid substance, irregularly dis- posed according to some, (as in the brain;) and according to others, in linear orders, (as in the nerves,) so as to form extremely delicate fibres. Anatomists are not perfectly agreed as regards the volume of these globules; some assert that they differ in the different parts of the nervous system, and agree to locate the largest in the encephalon; while others, equally positive, affirm that their diameter is every- OF THE NERVOUS SYSTEM. 149 where the same. According to the late researches of M. H. M. Edwards, their diameter is equivalent to 1-3000 part of an inch. As to the nature of the globules, the Wenzells, who have made a great number of observations, regard them as vesicles containing a white or grayish substance, accord- ing to the parts in which they are situated; but all our knowledge upon this subject is still involved in doubts and hypotheses. The globules appear to be connected together by extremely delicate cellular tissue, which also connects, and in a very intimate manner, the small delicate fibres which result from their linear disposition. The cellular tissue, which is more compact on the surface than in the interior of the nervous organs, forms a thin membranous layer, having different names, and varying in different parts, as we shall have occasion to point out in the following sec- tions. This membrane is exceedingly vascular, and the vessels which are distributed upon it, penetrate the nerv- ous substance, and are, as we have already said, more nu- merous in the gray than in the white substance. The nervous system appears to be destitute of lymphatic ves- sels. Characters, physical and chemical properties. —The nervous organs are very excellent conductors of the elec- tric fluid. The two substances do not everywhere pre- sent the same shades of their respective colours; the grayish substance, especially, varies so much, that in some places it is yellowish, ash-coloured, and even black; these differ- ences of colour, however, depend uniformly upon the de- gree of vascularity of the part. The consistence of the medullary substance is by no means the same in every part of the nervous system; but it is always in relative pro- portion to that of the cortical: both, but especially the medullary substance, are slightly elastic, retractile, and more resisting in the direction of their fibres than in. any other. When macerated, the nervous substance resists for a long time the action of water, and its first effect is a 150 OF THE NERVOUS SYSTEM. softening and slight discoloration ofthe cortical substance. The effects of the dilute acids and of alkohol, upon the cortical and medullary substances, have been already pointed out. By desiccation the former is rendered brit- tle and pulverizable, and both are rendered hard by solutions of the bi-chloride of mercury. According to the analysis of M. Vauquelin, the nervous substance is composed ofthe following ingredients:—a white fat, 4.53; a reddish brown liquid fat, called cerebrin,* by M. Chev- reul, 0.7; water, 80; albumen, 7.0; osmazome, 1.12; phos- phorus, 1.5; phosphate of potash, muriate of soda, phos- phate of lime, and phosphate of magnesia, 5.15. The quantity of albumen is in an inverse ratio to that of the fatty matter, which is most abundant in the spinal marrow, less in the brain, and quite small in the nerves: the phos- phorus appears to exist only in the medullary substance. The analysis of Vauquelin has no reference to the grayish substance of the ganglia of the great sympathetic. Order of development and differences according to age.—We have no positive knowledge with regard to the time in which the nervous system begins to be perceptible, nor of the state in which it is at its origin. It appears, however, to be one of the first of the systems that are de- veloped. Its different parts are not formed simultaneous- ly, but in a gradual and successive manner;t and though authors are not agreed upon the order of this succession, it would appear sufficiently evident that the nerves and their ganglia appear first; then the medulla spinalis, and finally, the different parts of the encephalon. This general order, and that which we shall point out hereafter, when speaking of each part of the central masses in particular, correspond to that in which the nervous system is pro- * According to M. Chevreul, this substance also exists in the blood. \ This progress of the development of the nervous organs is not, as the ancients thought, the result of a vegetative elongation of the pri- mary parts of this system. OF THE NERVOUS SYSTEM. 151 gressively complicated in the animal scale, in ascending from the inferior to the higher classes. This fact consti- tutes the principal anatomical proof ofthe plurality ofthe nervous system. Mr. Gall is of opinion that the grayish substance is formed previously to the medullary; but ac- cording to M. Serres, this is true only with regard to the encephalon. According to the researches of Tiedemann, and other anatomists, the medullary substance appears al- ways before the cortical; and this opinion appears to have the most probabilities in its favour.* Be this as it may, it is certain that the nervous substance passes through all the intermediate gradations between fluids and solids, being soft in infancy, and acquiring consistency by degrees. The growth of the nervous organs is effected by interstitial nu- trition, and by the deposition of layers upon their surfaces, which are, apparently, secreted by the cellulo-vascularmem- brane by which they are covered. This growth, which is extremely rapid during foetal life, becomes gradually slow- er after birth, until it is finally converted into a simple nutritive process, which itself diminishes, so that at length in old age the organs of which we are treating, have sensi- bly lost a share of the volume which they had acquired in adult age. Vital properties and functions.—The nervous system is essentially sensible, but in such degrees and conditions as vary according to the different parts of which it is com- posed. It is to its presence in the other organic systems that are owing the phenomena of the sensibility which they enjoy. This sensibility of the organic systems is nothing but a modification of a property belonging exclusively to the nervous system—a property, which physicians have designated by the names of vital energy, nervous power, * The circumstance which has led physiologists into error as regards this subject is, that in the foetus, the medullary substance is slightly co- loured, which is owing to its being more penetrated by the fluids dur- ing pregnancy than at any other period. 152 OF THE NERVOUS SYSTEM. and by virtue of which, it animates the whole animal economy, and performs the most important functions. Physiologists have at all times endeavoured to ascertain the nature of this property: how far they have succeeded will appear from the statement ofthe principal hypotheses, after we shall have described, in a general manner, the ac- tions which depend upon it. The nervous system is the apparatus of innervation, a multiple function, at least as to its results, by which it ani- mates all our organs, presides over all their vital actions, both voluntary and involuntary, transmits and receives the sensorial and affective impressions, and is the agent ofthe operations of intelligence. Every part of the nervous system has its determinate function. In the inferior animals, the small apparatus which compose this system, are independent of each other, and their actions are less rigidly specified; but in ascend- ing the scale to the higher classes, we find the functions are multiplied in proportion as the nervous system becomes more complicated; at the same time that these functions, though always distinct, become less and less independent, and are placed, moreover, under the influence of a centre of action, whose integrity is necessary to their perform- ance and regularity. This physiological centre of action, to which we have just alluded, is the encephalon. and par- ticularly the medulla oblongata, upon which depend all the other parts ofthe nervous system, as well as the functions which they perform, in proportion as they have less for their object the nutrition ofthe individual. The grayish substance of the nervous tissue, as has been demonstrated by Mr. Tiedemann, increases the activity of the medullary, by concentrating a greater quantity of blood towards the parts where this activity is more essen- tially necessary: thus the substance of which we are speak- ing is very abundant in the medulla spinalis, at the origin OF THE NERVOUS SYSTEM. 153 of the nerves, and more so in proportion as these are larger. Physiologists have not been contented with merely re- ferring the faculty of the senses and innervation to a peculiar property of the nervous system, but they have also endea- voured to ascertain the nature of these functions. The hy- potheses that have been advanced upon this subject, may be reduced to two principal ones, both very old. Accord- ing to the first, which has had the smallest number of sup- porters, the nerves perform their functions by the centri- petal and centrifugal transmission of vibrations, excited in the one case by external agents, and in the other by the brain, the point of egress of innervation and volition. In- dependently of the fact that this hypothesis is founded upon no direct experiment, it would be entirely inadmis- sible from the circumstance, that the nerves are too soft to perform the office of vibrating cords. The second suppo- sition has had by far the greatest number of partizans, and ranks amongst its number, the most celebrated physicians of both ancient and modern times, and amongst others, the immortal Galen, Baglivi, Boerhaave, Haller, &c. This hypothesis consists in the admission of a subtile fluid which is secreted by the brain, and is designated by the names of nervous fluid, animal spirit, and pervades the nerves with the greatest rapidity, from their cerebral to their periphe- ral extremity, and vici versa; transmitting to the centre of the nervous system the impressions which are received by the sentient extremities of the nerves, and carrying to the organs, the volitions and the nervous influx emanating from the brain. Some have even gone so far as to imagine there are two fluids, destined, each to one of these motions, and so subtile, that they might traverse the same nervous cords, in an inverse direction at the same instant; while other physiologists, to explain the differences ofthe sensa- tions in the brain, and of the volitions, &c, which are de- rived from it, have combined the two hypotheses, and have 21 154 OF THE NERVOUS SYSTEM. attributed the first to vibrations, and the second to animal spirits. Finally, this association of hypotheses, has been inverted, and the hypothesis of animal spirits has been modified in various ways. No sooner was this admitted, than physiologists, anxious to ascertain its nature, advanc- ed the most absurd and ill founded propositions; so that the only one, which is at all plausible and worthy of our attention, is that which compares the nervous agent to the electric fluid. In the present day, physiologists are contented with ob- serving the laws of innervation, and, if they go beyond this, it is with the view of drawing conclusions from the remarkable analogy which exists between certain effects of electricity upon the animal organization, either dead or liv- ing, and the vital phenomena, which allow us to presume the existence of an imponderable agent, which presides over, and regulates the functions of the nervous system. section 2. Of the Nervous Centres. ARTICLE 1. Of the Cerebro-Spinal Centre- Definition.—By the term cerebro-spinal, we under- stand, with most modern authors, the mass of nervous sub- stance which is contained within the cavities of the cra- nium and the vertebral column.* • We must recollect that this mass comprehends, according to Messrs. Gall and de Blainville, a series of ganglia, so many centres of small sys- tems or nervous apparatus, and having, according to the latter physiolo- gist, a common centre—the spinal marrow: these divisions, however various they may be, are not in contradiction with the ancient denomina- tion of cerebro-spinal centre,—a collective denomination which is applied to every division of this continuous mass. OF THE NERVOUS SYSTEM. 155 Division.—The cerebro-spinal centre is composed (a) of the medulla spinalis; and (b) of the encephalon, which comprehends the medulla oblongata, the cerebrum and cerebellum. Situation.—(a) The medulla spinalis is situated within the vertebral canal which is formed by the vertebrae of the neck, the back, the loins, and the sacrum; but in the hu- man subject, it extends only from the superior part of this canal to a level with the second lumbar vertebra. (b) The encephalon is situated at the superior part of the medulla spinalis, with which it is continuous, and fills com- pletely the cavity of the cranium. Form and arrangement.—(a) The spinal marrow is a ' large nervous fasciculus, irregularly cylindroid, divided into two lateral symmetrical halves, by two fissures which ex- tend throughout the whole length of its anterior and pos- terior surfaces. Each lateral half comprehends two fasci- culi, an anterior and a posterior, whose line of demarcation is marked out by the insertion ofthe ligamentum denticu- latum. The spinal marrow is more voluminous superiorly than inferiorly, but its decrease is by no means uniform: it enlarges where it gives off the nerves, and this in propor- tion to the size of the nerves which are separated sym- metrically from its lateral parts, to the amount of thirty pairs. Superiorly, the spinal marrow enlarges considera- bly in entering the cranium, where it begins the encephalon under the name ofthe medulla oblongata. Here it presents three pairs of lateral and symmetrical fasciculi: the anterior, which is disposed on the sides of the mesian fissure, con- stitutes the pyramidal fasciculi, which, after having inter- changed fibres, form the peduncles and hemispheres ofthe cerebrum;* the second pair comprehends the middle fasciculi, * We ought not to understand by the word " to form," a real vegeta- tive growth; it is merely expressive ofthe order of development and of the connexion ofthe different parts of the encephalon. 156 OF THE NERVOUS SYSTEM. which are situated on the outside of the preceding, and which, being reinforced by the corpora olivaria, terminate in the tubercula quadrigemina; the third pair or the pos- terior fasciculi, are strengthened by the corpora restiformia, and form the cerebellum and tuber annulare, which em- braces the base of the medulla oblongata. All these fasci- culi give rise to smaller ones which communicate with, and establish relations between, every part of the encephalon. —The encephalon, regarded as a whole, constitutes a lo- bulated mass, irregularly hemispherical, composed of sym- metrical portions, presenting depressions and correspond- ing eminences, and, in short, a very complicated struc- ture, for a minute description of which, we must refer to descriptive anatomy. The medulla oblongata is the only part of the encephalon that gives origin to nerves.-—The encephalo-rachidian mass is surrounded and protected by three kinds of membranes; the external belongs to the fibrous system and is termed the dura mater; the middle is a kind of serous membrane, and is called the tunica arach- noides; the internal is the pia mater, a very delicate cellulo- vascular net-work, applied immediately upon the nervous masses, lining all the sinuosities upon the surface of the encephalon, and dipping into the anterior and posterior furrows of the spinal marrow. We must recollect that Mr. Gall considers the medulla spinalis and the encephalon as a series of ganglia connected together by intermediate fasciculi, and that M. de Blainville professes a nearly simi- lar opinion, with the exception that he regards the spinal marrow as a single ganglion—the centre of all the others; and reduces the encephalic ganglia to seven pairs, as we have already seen in the preceding section. Texture.—It is only in the cerebro-spinal mass that we observe the two kinds of nervous substance, the white and the grayish. Their relations of situation and quantity vary in the different parts of this mass; thus, in the spinal marrow, the grayish substance is interiorly and surround- OF THE NERVOUS SYSTEM. 157 ed by the white, which is disposed around it in the form of a layer:—the grayish substance is most abundant at the points where the large nerves are given off. In the ence- phalon, on the contrary, the grayish substance forms the exterior and cortical layer of the hemispheres of the cere- brum and cerebellum, while the white, which is surround- ed by it, composes the whole interior of these parts. Be- sides, in the medulla oblongata, the peduncles of the cere- brum and cerebellum, &c, we meet with masses of the grayish substance, which are enveloped by white fibres, (origin of the encephalic nerves), and alternate layers of both substances, &c. In this variety of arrangement, there is but one general law—that of the continuity of the white substance throughout the whole encephalo-rachidian mass, and the insulation of the different parts of the grayish. The fibres of the medullary substance, the only ones that are at all conspicuous, are much less apparent in the cere- bro-spinal mass, than in the nerves; they are parallel in the two fasciculi of the spinal marrow, which are connected together by transverse fibres, and not, as some anatomists have asserted, by a decussation of their filaments. There is nearly the same arrangement with regard to those of the medulla oblongata, with the exception that they are more divergent, and that those of the two anterior or pyramidal fasciculi are interlaced upon the mesian line. The fibres of the peduncles of the cerebrum and the cerebellum proceed in radii to form the hemispheres of these organs, and, if we may credit Mr. Gall, these diverging fibres, after hav- ing reached the grayish substance that forms the cortical layer of the hemispheres, are reflected upon the mesian line, under the name of the converging fibres, to form the corpus callosum and the commissures. This manner of observing has been disputed by Mr. Tiedemann, who re- gards the cerebral commissures and the corpus callosum as being derived from the cerebral peduncles. The cortical substance of the cerebrum and the cerebellum is so abun- 1 58 OF THE NERVOUS SYSTEM. dantly supplied with blood-vessels, that, when well inject- ed, it appears to be almost entirely composed of them. To judge of the vascularity of both the white and the cor- tical substances, it will be sufficient merely to tear them; we shall then observe that they are covered with small reddish points, which are more or less conspicuous, and are more numerous in the grayish than in the medullary sub- stance: these points are the extremities ofthe small blood vessels that have been ruptured. Characters, physical and chemical properties.—To what we have already said upon this subject in the gene- ral observations of the nervous system, we have only to add, that the consistence of the encephalo-rachidian mass is much less than that ofthe nerves. Order of development, and differences according to age.—The spinal marrow is developed before the ence- phalon, and amongst its different parts, the medulla ob- longata is the first that comes into existence; this, which is nothing but the superior portion ofthe spinal marrow, has added to its fasciculi in a gradual and successive manner, the cerebellum, the tubercula quadrigemina, and the cere- brum. The cerebellum and the cerebrum are much larger, com- pared with the spinal marrow, in proportion as the subject is farther advanced in age; while the tubercles are much larger compared with the brain, as the foetus is younger, and are bigeminous before they are converted into the quadrigemena. The hemispheres of the cerebellum are at first equal to the middle lobe (vermiform process), but as they increase, they greatly exceed it in size. The cere- bral hemispheres form by far the larger portion of the en- cephalon, and project farther backwards in proportion as the nervous system is more perfectly developed. All that we have just observed with regard to the human foetus is equally applicable to the different classes of vertebral ani- mals. OF THE NERVOUS SYSTEM. 159 The encephalo-rachidian mass is at first nothing but a semi-fluid substance, which subsequently and by degrees, assumes the characters of the white nervous substance, and finally unites with the grayish substance which is se- creted by the pia mater. In old age the spinal marrow and the encephalon become more dense, and there is a very sensible diminution of volume. Vital properties and functions. —Although the ence- phalon and the spinal marrow enjoy the highest degree of nervous energy, there are not wanting some who have en- deavoured to deny the sensibility of the brain. This error would not have been committed, if physiologists had been aware of the fact that, though there are some organs which can not be rendered painful by external irritants, they may be all excited by internal causes, whether physiological or .pathological. We have already seen, that modern anatomists, in ad- mitting the plurality of the nervous system, recognize an assemblage of distinct masses or ganglia in the cerebro-spi- nal centre, and attribute to each of them a determinate function, which it exercises in virtue of its nervous energy, and which is placed under the influence of a common cen- tre. By those (Magendie) who do not consider with M. de Blainville, that the spinal marrow is the central part of the nervous system, it is regarded as the seat of general sensibility. The posterior part of the spinal marrow, some parts of the medulla oblongata, and according to some, the cerebellum, appear destined especially to the external sen- sations. The anterior portion of the spinal marrow, that of the medulla oblongata which gives rise to the motor nerves of the face, and, according to Magendie, the cere- bellum and some parts of the base ofthe cerebrum, preside over the voluntary motions. Finally, the cerebrum is the seat of the internal or affective sensations and of the intel- lectual faculties. The spinal marrow is really nothing but an organ of transmission; perceptions and determinations 160 OF THE NERVOUS SYSTEM. belong to the encephalon. The portion of the medulla ob- longata from which originate the peduncles of the cerebrum and the cerebellum, appears to be the physiological centre ofthe encephalo-rachidian mass, and consequently, ofthe whole system. Nevertheless, physiologists have come to very different conclusions with regard to the parts of this mass which correspond to the different functions of inner- vation. Pathological Anatomy. There are observations which would induce us to believe that the brain is susceptible of undergoing a diminution of volume before old age, but it does not appear that it is ever subject to hypertrophia. The conformation of the cerebro-spinal masses, is sometimes altered by the pres- sure of tumours situated in their neighbourhood. The spinal marrow is often compressed by curvatures of the spine, and altered in its form, though most frequently without creating any disturbance in its functions. The solutions of continuity of the encephalon and the spinal marrow, when they do not terminate fatally, heal, like those of the other organs, either by immediate re-union, or by the formation of a brain-like substance, which is depo- sited upon the points that have been left open from the loss of substance, or by the simple separation of the lips of the wound. In cases of apoplexy and in certain cerebral dis- turbances, where there is an effusion of blood or serum into the nervous tissue, if the subject be young, the fluid is soon surrounded by a cyst, and is gradually absorbed;* and its parietes approximate and form adhesions so as to com- pletely obliterate its cavity. The organs of which we are treating are very frequent- ly subject to sanguineous congestions, which can be readi- ' In this case, the blood is decomposed into its two elements, the clot and the serum, and becomes really a foreign body. OF THE NERVOUS SYSTEM. 161 ly explained by the great quantity of blood which they receive, and by the facility with which it exalts their ac- tivity. Inflammation of these organs is by no means a rare disease, and is generally accompanied by that of the meninges. Inflammation of the encephalon and medulla spinalis is characterized by the redness and softening of their substance, and sometimes, by suppuration, ulceration, and even gangrene. The sub-inflammatory state of the nervous central masses may also give rise to the secretion of purulent matter, which is sometimes collected in a sin- gle abscess, in the substance of the organ, and excites the formation of a cyst in which it remains for a variable time; at other times, the secretion is nothing but serum, which is collected either in the ventricles of the brain, or in the nervous substance itself, or between the organ and its en- velopes: when this is the case, it constitutes what physicians call acute hydrocephalus, a disease which differs from chro- nic hydrocephalus, inasmuch as the latter, which is most generally congenital, is not accompanied by any inflamma- tory process. When this affection attacks the spinal mar- row and its coverings, it is termed hydro-rachitis, of which the disease termed spina-bifida is a remarkable variety. In consequence of the chronic phlegmasiae, the cerebro-spinal centre is also sometimes affected with tuberculous, schir- rous and carcinomatous degenerations, fungous growths, and fibrous, fibro-cartilaginous, and osseous transforma- tions. Hydatids are also found in some instances in the ventricles of the brain, and even in the substanee of the encephalon and the spinal marrow. These organs are often subject to considerable softening, attended with a very va- riable change of colour; in many cases this alteration is evidently the result of chronic inflammation. Induration of the eticephalo-rachidian mass is another disease which exists either by itself, or in union with the preceding. The indurated substance, sometimes perfectly homogeneous, and, in appearance, inorganic, resembles coagulated albu- 22 162 OF THE NERVOUS SYSTEM. men; at others, however, it is more evidently fibrous. This alteration appears to be more peculiar to the white sub- stance. The brains of idiots, epileptics, &c. are frequently indurated and softened to a greater or less extent. The encephalon and spinal marrow are by no means ex- empt from mal-conformations: the entire absence of these organs, especially of the encephalon or some of its parts, is not an unfrequent occurrence. From the existence of the rest of the nervous system, under these circumstances, it is evident, that every part of it is independent as regards its development and origin. In the early age of the foetus, the spinal marrow presents a longitudinal groove on its posterior surface, and subsequently a central canal; some- times we observe the one or the other of these arrange- ments at birth; at others, this organ is entirely wanting, and in its stead, the pia mater forms a canal which is filled with a fluid, and gives insertion, as it naturally does, to the roots of the spinal nerves. Amongst the defects of symmetry which are sometimes, though rarely observed, between the different parts of the nervous central masses, we may notice the disproportions which occur between the lobes of the cerebrum. article 2. Of the Nervous Ganglia. Definition.—The nervous ganglia are small masses, ir- regularly rounded, and situated on the course of the nerves.4* * We have seen that Gall and De Blainville have also applied the term ganglion to the divisions of the cerebo-spinal masses; this generali- zation, a natural consequence of their manner of regarding the nervous system, gives tlvis expression an exclusively physiological sense: but it should not be used when we consider the ganglia in a less exclusive point of view—under that of their structure. OF THE NERVOUS SYSTEM. 163 Division.—The ganglia are divided into two classes; the first comprehends those which belong to the cerebro- spinal nerves, and the second those which occur in the course ofthe trisplanchnic nerve: the latter may again be subdivided into those which form a double series upon the sides of the vertebral column, and into those which are more immediately upon the mesian line. Situation.—The nervous ganglia are found exclusively in the head, the neck, and in the cavities of the thorax and abdomen; there being none in the extremities. The ganglia of the first class occur near the central extremity, or origin of some of the encephalic, and at the posterior roots of all the spinal nerves. Amongst the ganglia of the second class or of the trisplanchnic nerve, some are lateral, and placed in a double series upon the sides of the anteri- or part of the vertebral column, and are designated by the names ofthe cervical, the thoracic, the lumbar and the sacral ganglia; in this enumeration ought to be included the small coccygean ganglion, which, though it is single and situated upon the mesian line, belongs to this series. The other ganglia ofthe second class are more immediately upon the mesian line, and are termed the cardiac and semi-lunar. Form and volume.—All the spinal ganglia are of an oval form; amongst the others, some are oblong, others ir- regularly globular, and, in a word, of a very different form. Their volume varies from that of a lentil to that of an al- mond. Structure.—On dividing of the ganglia, their tissue appears at first sight to be homogeneous; but after they have been subjected to maceration for some time, we find that there are two substances, that contribute to their composi- tion: the one is white or medullary, and is disposed in fila- ments in the same manner as in the nerves; the other is of a grayish red, somewhat pulpy, different from the grayish substance of the encephalo-rachidian mass, deposited in cells, and firmly adherent to the medullary filaments, and 164 OF THE NERVOUS SYSTEM, more consistent in the ganglia of the trisplanchnic than in those of the medulla spinalis. The medullary filaments are evidently the continuation of those which constitute the nerves upon whose course the ganglia occur. In entering the ganglia, the cords are deprived of their neurilema, and are divided into filaments, which, after having plunged into the grayish substance with which they are intimately connected, especially in the ganglia of the trisplanchnic, are separated from each other to re-unite and anastomose in such a manner as to present a very complicated arrangement in the ganglia of the second class, and sufficiently simple in those of the first. The medullary filaments, being again united with the cord, issue from the cerebro-spinal ganglia by the ex- tremity opposite to that by which they entered, while, in the ganglia of the trisplanchnic, the points of entrance and of egress of these filaments are in very different rela- tions of situation. All the nervous ganglia are enveloped by a more or less dense membrane which, in the spinal, has the solidity of fibrous tissue, while in the other ganglia it is merely a membraniform layer of cellular tissue. The blood vessels of the ganglia are exceedingly numerous, and most of them send branches to their envelopes before they enter the ganglia themselves.* Characters, physical and chemical properties.—The ganglia are of a grayish red colour, which is most conspi- cuous in those of the trisplanchnic, which are also harder than the others. When exposed to the action of the acids and of boiling water, they are at first hardened and final- * In comparing these details upon the structure of the ganglia with what we shall hereafter say with regard to the nervous plexus, we shall see whether the relations which exist between them will justify the opinion of Scarpa, and other authors who regard the terms ganglia and plexus as synonymous. The texture ofthe first is evidently more com- plicated than that of the second, and their uses, moreover, do not appear to authorize this approximation. OF THE NERVOUS SYSTEM. 165 ly softened; they are slowly dissolved by the alkalies. They resist for a long time the putrefactive process; and, according to Lobstein, are converted into a kind of adipose substance after long continued maceration.—The reddish substance of the ganglia does not consist of fat, as has been asserted by some who have adopted the opinion of Scarpa upon this subject. According to the chemical researches of Wutzer and Las- saigne upon the composition of the ganglia, they contain less adipose substance than the nerves, and much less than the brain, but on the contrary more albumen and gelatine. Development and differences according to age. The spinal ganglia come into existence before any ofthe others, and even before the rest of the nervous system, with the exception of the nerves which belong to them. The gan- glia ofthe trisplanchnic are not perceptible before the third month of uterine life: they are all from the beginning of nearly the same consistence which they present during the course of life. In old age and decrepitude they become smaller, harder, and of a fainter colour. Vital properties and functions.—All the ganglia, both of the cerebro-spinal and of the trisplanchnic order, are desti- titute of contractility, and the nervous energy appears to be distributed to them in the same manner as to the other por- tions of the nervous system; though it seems to be more energetic in the spinal ganglia than in those of the second class, at least, if we may judge from the severe pain which accompanies their mechanical or chemical irritation; while those of the trisplanchnic are entirely free from pain when they are the seat of irritation brought on by some internal cause. The history ofthe functions of the ganglia is still involv- ed in the greatest obscurity. According to some, such as Meckel and Scarpa, they are destined to collect and blend the nerves or the nervous filaments; others, such as Vieus- sens, Winslow, Reil, Bichat, and others, regard them as fo- cal centres ofthe nervous action, presiding over those func- 166 OF THE NERVOUS SYSTEM. tions of innervation which are independent rjf volition, that is, over the actions of vegetative life. This opinion, which does not concern the ganglia of the trisplanchnic, is that which is most generally adopted at the present day. Many suppose, also, that the ganglia arrest, to a cer- tain degree, the impression which they receive from the nerves which traverse them; that they concentrate for dis- tribution, the nervous energy emanating from the medulla spinalis, and that in this manner the trisplanchnic sys- tem is rendered independent of the cerebro-rachidian masses: we ought not, however, as the authors to whom we have just alluded, exaggerate this independence, which is merely relative. As yet we are entirely ignorant of the functions ofthe encephalic and spinal ganglia; M. de Blainville considers them as the centres of the nerves to which they belong. Alterations.—This part ofthe history of the ganglia is still involved in the mists of obscurity. Several authors, and amongst others Mr. Lobstein, have observed inflamma- tion of these organs in several diseases, such as tetanus, pertussis, and in some of the abdominal neuroses. Bichat once found the semi-lunar ganglion more dense, and in another instance more voluminous than natural: this last anomaly was accompanied by the presence of a cartilaginous substance in the centre of the small organ: the subject that presented it had died in consequence of a periodical ma- nia. Anatomists have also observed cases of hypertrophia and atrophia of the ganglia of the trisplanchnic; and, indeed, it would appear probable that most of the abdominal neu- croses depend upon an alteration of these organs. OF THE NERVOUS SYSTEM. 167 SECTION. 3. Of the Nerves. ARTICLE 1. Of the Cerebro-Spinal Nerves. Definition.—The cerebro-spinal nerves are the white cords, which are connected by their central extremities to the substance of the encephalon or the spinal marrow, and terminate, after successive ramifications, in certain organs which are more or less near the periphery of the body. Division.—We may divide the nerves, according to the seat of their central extremity, into encephalic and rachi- dian; according to the manner in which they are detached from this extremity, into nerves with a double, and into those with a single root; and, finally, according to their functions, into the sensitive, motor, and mixed. Each of these last divisions is again subdivided before it comes un- der the last term of specification: this subdivision can not be pointed out on the present occasion without anticipating some of the subjects of this article. Situation.—The central extremity of the nerves of which we are treating, is situated within the cavities ofthe cranium and the vertebral column; and the other approaches the periphery of the body in proportion as the nerves ramify. Conformation.—In consequence of their numerous anas- tomoses, the cerebro-spinal nerves, considered as a whole, represent the form of a grand net-work, which is much more symmetrical in its two lateral halves, in proportion as it approaches the nervous centres. Their particular in- dividual form is generally cylindrical; some of them, how- ever, are flattened and ribband-like. Examined with a 168 OF THE NERVOUS SYSTEM. magnifying glass, their surface presents small spiral folds, which belong, however, merely to the neurilema. Central extremity, improperly called the origin of the nerves.—All the encephalo-rachidian nerves communicate by their central extremity with the spinal marrow, or the medulla oblongata; there being none detached either from the cerebellum or from the brain properly so called. The nerves are always implanted in the grayish substance of the spinal marrow, and the medulla oblongata, and may be traced farther than the point where they are separated. They do not intercharge filaments at their origin, as has been supposed by those who have endeavoured to explain ^jjg* in this manner the symptoms of paralysis, and partial con- vulsions in the lateral half of the body opposite to that in which the lesion occurred.* By the root of a nerVe we understand its central extremity, and, according as it is single or bifurcated, we say that the nerve has one or two roots. All the encephalic nerves belong to the first class, with the exception of the trigeminus, which, together with all the spinal and the sub-occipital nerves, is comprehended in the second.—The nerves with double roots are attached by the one, to the anterior fasciculi, and by the other, to the posterior fasciculi of the spinal marrow. It is to the pos- terior roots alone that the spinal ganglia belong—the ante- rior roots being simply appended to them. Course.—In receding from their central extremity, the nerves are successively divided into branches, smaller branches and filaments, by the simple separation ofthe fasci culi and the cords, by the union of which their trunk is com- posed. In their course, the nerves form connexions either between themselves, or with the neighbouring nerves, by simple anastomoses, or by a kind of complicated interlace- ment, termed plexus. The anastomoses take place by the * The optic are the only nerves which decussate, and this only in a partial manner, and after their separation from the encephalon.—In fishes this decussation is complete. OF THE NERVOUS SYSTEM. 169 junction of two nerves, which are very intimately united by the continuity of substance, and are finally confounded with each other. The plexuses are anastomotic unions be- tween several nerves which converge towards one com- mon point: these anastomotic junctions are formed in such a manner, that the nerves which issue from the plexus con- sist of filaments which are derived from all the nerves that enter into the formation of the plexus. The cervical, lum- bar, sacral, and sciatic plexuses are the principal of the cerebro-spinal system. The nerves generally retain the same volume from their origin to the place where they are divided; and the aggregate of their divisions presents a greater volume than that of the trunk from which they are derived. Peripheral extremity, or termination.—After repeated and numerous ramifications, the cerebro-spinal nerves ter- minate in the integuments, in the organs of the special senses, in the exterior muscles, in the arteries of the parts which are subject to the influence of volition, &c. When they have arrived at their termination, the nervous filaments are deprived of their neurilema, and become sensibly en- larged: and this is all that we know positively upon this subject. Amongst the anatomists that have endeavoured to penetrate farther, some have supposed, but have never de- monstrated3 the existence of a kind of fusion ofthe nerve in the substance of the organ in which it terminates; others have said, that the nervous filaments, after they have ar- rived at their termination, are reflected upon themselves, and return to the branch from which they have been derived. Structure.—At first sight, the nerves seem to be compos- ed of a certain number of cords which are divisible into fila- ments of great tenuity: these are composed, 1st, of a white nervous substance, disposed in parallel fibres;* and 2d, of a * According to the recent observations of Prevost and Dumas, the nerves are composed of a very greatnumber of parallel filaments which are of equal size, and are flat and continuous throughout the whole length of 23 170 OF THE NERVOUS SYSTEM. membranous sheath or envelope termed neurilema. All the filaments which enter into the composition of the nervous cords, have, besides their proper neurilema, a common one; and in the same manner all the cords which enter into the composition of the nerves have a general neurilema. The nervous cords are placed upon each other, give off filaments of communication, and present a plexiform union: the same arrangement is found between the filaments, which, by their union, constitute the cord; so that neither the one nor the other retain the same situation throughout the whole extent of the nerve. Towards the central extremity of the nerves, the neu- rilema leaves first the filaments, then the cords, and where the nerve is continuous with the pia mater, the gene- ral neurilema alone remains. It results from this arrange- ment, that when a nerve is torn from the central mass, its interior part will break before those which are strengthen- ed by the general neurilema, and leave a projection, which is believed by some to be destined for the insertion of the nerve. We have already seen that the neurilema leaves the nerve entirely at its peripheral extremity. The nerves are surrounded by a layer of cellular tissue, which penetrates between their cords and filaments, so as to unite them mutually together. The neurilema itself is nothing but a condensed cellulo-vascular tissue, which some anatomists have placed in the fibrous system. No lym- the nerve. Each filament consists of four elementary fibres; two external, and well marked, and two middle and less distinct. These fibres are form- ed each of a series of globules, like those of every part of the nervous system. Bogros asserts that he has demonstrated by minute injections, which do honour to his skill, that the nervous pulp is hollow in the cen- tre ofthe nerves.- His experiments have been repeated by other anato- mists, but not uniformly with the same results. We are therefore at present unable to decide, whether the canal admitted by Bogros, does really exist before the injections which render it obvious, or whether it is merely the result of these injections, OF THE NERVOUS SYSTEM. 171 phatics can be traced into the substance of the nerves; but their blood vessels are very numerous and penetrate the neurilema as far as the nervous filaments. Characters, physical and chemical properties.—The cerebro-spinal nerves possess but a slight degree of elasticity, are of a faint rose colour, and owe to their neurilema the slight degree of tenacity which they enjoy. The dilute acids, especially the nitric, dissolve the neurilema, and expose the nervous pulp, while the alkaline solutions destroy it and leave the neurilema untouched: it is this knowledge ofthe modus operandi of the acids and alkalies upon the nerves, that has furnished Reil with the means of analysing and detecting the anatomical elements which contribute to their structure. The medullary substance of the nerves yields a greater quantity of albumen, but less of the fatty sub- stance, than the encephalo-rachidian masses. Development.—The cerebro-spinal nerves, are the first parts of the nervous system ofthe embryo that are brought into existence. In the foetus, they are proportionably more vascular than they are subsequently, but their struc- ture is indistinct, and their neurilemic part appears to ex- ceed the medullary, which is nothing but a mere liquid. The volume ofthe nerves is much greater in proportion to that of the encephalo-rachidian centre, as they are exam- ined near the period of conception. In old age, they are smaller, more dry and firm, than'in adult life, at the same time that their vitality is less energetic. Vital properties and functions.—The nervous energy of the organs of which we are treating, is rendered evident by the violent pains and the muscular contractions which are occasioned by their artificial or morbid irritation. This power is inherent in the nerves, and is merely called into action by that ofthe medulla spinalis, and the encephalon; for, when we irritate a motor nerve, that has been sepa- rated from these centres by the knife or ligature, the mus- cles to which it is distributed are agitated with convulsive 172 OF THE NERVOUS SYSTEM. motions. Anatomists have hitherto been unable to trace the least sign of vital contractility in the cerebro-spinal nerves. The nerves are the organs which transmit to the centre of perception, the impressions which they receive in the or- gans to which they are distributed, and carry to every part of the body the nervous power upon which depends the muscular contractility. They are thus conductors of sen- sibility and of motion by a double action, from the centre to the circumference, and from the circumference to the centre, during which they manifest neither the vibrations nor the oscillations that have been admitted by some au- thors to explain the mechanism of the functions of trans- mission. The rapidity with which they are performed has induced many to believe, that there is an imponderable fluid, analogous to that which produces the phenomena of electricity, and of which the nerves are the mere conduc- tors. Several physiological experiments give support to this hypothesis. Be this as it may, however, we ought to distinguish, amongst the encephalo-rachidian nerves, those which are exclusively devoted to the transmission of mo- tion, or the motor nerves; those which belong merely to the functions of the external sensations, or the sensitive nerves; and those which are at once conductors of sensi- bility and of motion, or the mixed nerves. The first two classes comprehend all the nerves ofthe head, with the exception of the fifth pair, which, together with all the spinal nerves is included under the class of mixed nerves. Magendie, however, has satisfactorily demonstrated, that even in the spinal nerves, the two orders of functions have, to a certain degree, their distinct seat; that the anterior root is destined to motion, and the posterior to sensibility.* * Mr. Charles Bell has lately performed a great number of experiments with the view of specifying the functions ofthe nerves, and has obtained very important results to physiology. He divides the nerves into regu- lar and irregular: the first, which are common to all the vertebral ani- OF THE NERVOUS SYSTEM. 173 Pathological Anatomy. The nerves sometimes increase in volume, in conse- quence of serous, gelatinous, or fatty infiltrations of their tissue; they are often compressed, flattened, or displaced, from the development of tumours in the surrounding parts, and their atrophy, which sometimes depends upon the same cause, may also be the result of the cessation of their func- tions, (paralysis.) When a nerve has been divided, the two extremities, if they have been separated but a small distance, are re-united by a nervous cicatrix, and the mo- tions ofthe nerve, at first interrupted between the solution of continuity and the peripheral extremity, are perfectly re-established. The manner in which this re-union is ef- fected, may be comprised under the following observations. The superior extremity of the divided nerve, in conse- mals, preside over the general sensibility and voluntary motions, and comprise the spinal nerves, (including the sub-occipital,) the trifacial, or fifth encephalic pair, and all the nerves with a double root; the second are the nerves with a single root, and being connected with the preceding, in proportion as the organism is complicated, are distributed to the organs which are amply provided with the former, and preside over the special functions. Mr. Bell, having divided the branches of the facial nerve of an ass, (the portio-duro ofthe seventh pair of Willis) which are distributed to the nostrils, paralysed the muscles ofthe parts, but those only which are subservient to respiration, and the expression ofthe face: on the contrary, when he divided the superior maxillary branch ofthe fifth pair, the skin ofthe face was deprived of sensibility, and the subjacent muscles lost their contractility, with the exception of those which perform the motions of respiration and expression, whose nerves were left undivided. From these facts, and others of a similar nature, Mr. Bell concludes that the presence of several nerves in a part coming from different origins, has not for its object the accumulation of a great quantity ofthe nervous influence, but the performance of seve- ral distinct and peculiar functions. From these researches, we perceive also how favourable are the results to the doctrine ofthe plurality ofthe nervous system. 174 OF THE NERVOUS SYSTEM. quence of the afflux of blood becoming the seat of the ex- halation of coagulating lymph, begins to swell in a short time after the division, and forms a kind of firm, elongat- ed, grayish nodule; the inferior extremity presents, in its turn, the same phenomena as the preceding; and as the tu- mefaction increases, the extremities approximate, and are finally agglutinated together, by means ofthe plastic sub- stance which they exhaled. The enlargement which re- sults from the junction of the two nodules remains some time; but it gradually diminishes and finally disappears. The re-union is perfectly re-established in about six weeks or two months. In this process, there appears to be a re- production ofthe medullary part ofthe nerve, and several anatomists have asserted that they have even traced the medullary filaments into the interior of the cicatrix. What proves this fact is, that the cicatrix acquires the conduct- ing power of the organs of which we are treating, and that when submitted to the action of nitric acid, far from being decomposed, it assumes more consistence, as is the case under similar circumstances with the nervous substance. The restoration of the functions of a divided nerve does not take place, if the separation ofthe extremities be too consid- erable, and where the re-union is effected merely by means of cellular substance. If, on the contrary, the separation is so inconsiderable as scarcely to be perceived, the action of transmission may take place, to a certain degree, from one part of the nerve to the other, from the moment the divi- sion has been effected. Inflammation ofthe nerves (neuritis) appears to be a more common disease than is generally be- lieved; it is often observed in oases of neuralgia—a disease which, however, frequently presents no appreciable alter- ation of the nervous tissue. It is in part to a sub-inflam- matory state of these organs that we must attribute their softening, and the tuberculous and schirrous tumours, de- signated collectively by the name of neuroma. To the same cause may also be referred the cartilaginous and osse- OF THE NERVOUS SYSTEM. 175 ous metamorphoses of the nerves—a kind of alteration, which is sometimes, though rarely observed, and is confin- ed to some insulated points of these organs. article 2. Of the Ganglionic Nerves. Definition.—The ganglionic nerves are those which constitute, with the ganglia of the second class, the system ofthe great sympathetic or trisplanchnic nerve,—those, in other words, which being situated exclusively within the trunk, form with the ganglia just mentioned, a particular order of nervous apparatus, communicating with each other and with the spinal nerves by intermediate branches, and distributing numerous ramifications to the arteries and the organs of vegetative life: hence, the distinction of the nerv- ous system of organic life, given by Bichat to the assem- blage of this apparatus. Division.—The ganglionic nerves are distinguished into three varieties: the first comprehends those which form the communications between the ganglia, the second, those which are intermediate between the ganglia and the cere- bro-spinal nerves, and the third, those which are ramified within the organs. Situation.—The intermediate ganglionic nerves are mostly situated upon the sides of the vertebral column, parallel with its axis, and between the double series ofthe lateral ganglia, which extend from the head to the os coc- cygis. The others extend from the lateral to the mesian ganglia. The ramifications of the second variety are placed, most of them, transversely upon the sides of the vertebral column, between each lateral ganglion and the corresponding spinal nerve. The situation of the ramifi- cations varies in each organ to which they are distribut- 17G OF THE NERVOUS SYSTEM. ed; but, like the preceding, they belong exclusively to the trunk. Conformation.—Considered as a whole, the ganglionic nerves by no means exhibit the symmetry of those which issue from the encephalo-rachidian masses. Beclard has justly compared the system of the great sympathetic " to a subterraneous stem or articulated root (rhizome,) which, upon one side of each bulb presents small roots, and upon the other, small branches, all of which are separated at right angles, or nearly so." As to their peculiar form, the ganglionic nerves are not all alike: those of the second variety are rounded, and re- semble, in this respect, the spinal nerves: those of the other varieties are flattened, and, besides, those of the third present this peculiar character, that instead of diminishing in vo- lume in proportion as \hey ramify, they augment or dimin- ish in different ways. All are larger in the neighbourhood of the ganglia than in the rest of their extent. Origin.—Many anatomists have disputed whether the ganglionic nerves arise from those of the cerebro-spinal system, with which, as we have already seen, they com- municate, or whether the ganglia ought to be regarded as their centres of origin. Neither of these propositions, however, is properly admissible, for the development of the ganglionic nerves is perfectly independent of that of the other parts ofthe nervous system; but in applying, as we have already done, to the term origin, the signification of central extremity, wc ought to place it in the ganglia of the great sympathetic, and consider the nerves which pass from them to the organs, as forming with the first so many small nervous apparatus, which communicate with each otherand with the encephalo-rachidian nerves. Atthis central extremity, the medullary filaments ofthe ganglion are continued with those of the nerve, and moreover, the envelope of the first being extended upon it, adds firmness to their mutual adhesion, and, by covering the second to a OF THE NERVOUS SYSTEM. 177 small extent, gives it the appearance of a part of the gan- glion, elongated in the form of a cord. Course.—The ganglionic nerves of the first variety pass directly, and without presenting any thing peculiar, to the cerebro-spinal nerves. The same arrangement obtains with regard to the cords which form the communications between the ganglia, and especially with those, which, be- ing placed at each side of the vertebral column, form with these what is called the trunk of the great sympathetic nerve. As to the nerves which pass from the ganglia to the arteries, and to the different organs of the head and neck, and to those ofthe chest and the abdomen, they are ramified in their course and form more or less intricate plexuses, either before they have reached their destination, as in the cardiac and-solar plexuses, or after they have ar- rived upon the parietes where they decussate with the fila- ments coming directly from the ganglia. In their course, as well as in the plexuses, these nervous filaments are con- nected with the ramifications of the encephalic nerves, and particularly with those ofthe pneumo-gastric. Organic extremity or termination.—The ganglionic nerves (and we speak here only of those of the third varie- ty,) terminate in the parietes of the arteries of the trunk, in the heart, the digestive canal and its appendages, and in the urinary and genital organs. Structure.—The ganglionic nerves of the first variety, and even those ofthe second, are formed of small medullary fibres, and of a neurilemic envelope, which is more dense at their extremities, where it is sometimes continuous with the envelope of the ganglia, more thin and delicate at their middle part, and more intimately connected with the small fibrillEe than that of the cerebro-spinal nerves. These last are very difficult to be separated from each other, and are, moreover, plunged into the peculiar grayish red substance, which we have already described as belonging to the gan- glia. Notwithstanding the differences which we have just 24 178 OF THE NERVOUS SYSTEM. pointed out between these nerves and those of the cerebro- spinal system, both resemble each other with regard to form, colour and structure: the branches which connect the ganglia with the spinal nerves, resemble these in par- ticular, and much more in proportion as they approach them. As to the nerves of the third variety, we can not distinguish in them any fibrillse, and they appear to be entirely formed of a soft reddish pulp, around which we can not demonstrate the existence of a neurilema. Characters and physical properties.—The nervous cords which pass from the ganglia to the cerebro-spinal nerves have a whitish appearance, are less firm and resist- ing than these, and appear to be destitute of elasticity. Those which connect the ganglia together are of a grayish colour, have more ofthe bulbous substance, and are some- what less tenacious and consistent than the preceding. The ganglionic nerves which are distributed to the organs are, with some very few exceptions, of a reddish colour, very soft and brittle. Vital properties and functions.—The nervous energy of the ganglionic nerves appears to be less active than that ofthe cerebro-spinal nerves, and this in proportion as they are more frequently intersected by the ganglia. In their healthy state, this nervous power of the ganglionic nerves is not manifested, either by sensibility or contractility; but in certain diseases, they are the seat of a peculiarly painful affection. The ganglionic nerves serve to transmit the nervous in- fluence to the organs ofthe involuntary functions, but they do not convey to the centre of perception the impressions which are received by these organs; these being, under or- dinary circumstances and unless the action of the nerves be stimulated by disease, arrested by the ganglia. All the ganglionic nerves, at least those of the first two varieties, contribute to the phenomena of sympathy, by establishing communications between the ganglionic and the cerebro- OF THE NERVOUS SYSTEM. 179 spinal system; but it is doubtful whether they are, as was asserted before the time of Bichat, the essential organs of the sympathies. All the nerves are, by reason of their con- tinuity, susceptible of producing these phenomena. The action ofthe nerves of which we are treating, though more independent than that of the cerebro-spinal nerves, is, how- ever, subordinate to them, inasmuch as it ceases as soon as these nerves are separated from the cerebro-spinal. The nervous influence, which is transmitted to the ganglionic nerves by the centres above mentioned, arrives in the organs only after it has been, probably, diminished, divided and modified by the ganglia, which distribute it. It is, therefore, to this character which we attribute to the ganglia that ought to be referred the independence of the portion of the nervous system to which they appertain. Pathological Anatomy.—Few anatomists have paid attention to the study of the pathological anatomy of the ganglionic nerves. They have been known to be inflam- ed in cases of neuroses of the abdominal organs, and in subjects who have died from pertussis: they are also some- times affected with atrophia and hypertrophia, especially when the organs to which they are distributed present the same pathological conditions. Bibliography of the Nervous System. Vicq-d'Azyr. Recherches sur la structure du cerveau, etc., dans les Mem. de l'Acad. des Sciences, 1781-83. -------Traite d'Anatomie et de Physiologie, gr. in fob, avec pi. Paris, 1786. Gall et Spurzheim. Anat. et Physiologie du systeme ner- veux en general, et du cerveau en particulier. Paris, 1810-19. Fr. Tiedemann. Anatomie du cerveau, trad, de l'allem. par Jour dan. Paris, 1823. Serres. Anatom. comparee du cerveau dans les quatre 180 OF THE NERVOUS SYSTEM. classes des animaux vert6bres, 2 vol. in So. avec atlas. Paris, 1824 et 1826. Desmoulins. Anatomie des systemes nerveux des animaux a vertebres, etc. Paris, 1825". Rolando. De la v6ritable structure du cerveau de I'homme et des animaux, et des fonctions du systeme nerveux; trad, de l'italien et insere dans le Journal Physiol, ex- perim. tom. III. J. et Ch. Wenzell. De penitiori structura cerebri. Tubing. 1812. H. M. Edwards. Mem. sur la struct. 616m. des principaux tissus organiques des animaux vertebres. Paris, 1823. Proschaska. De structura nervorum anat. in opera minora. Reil. Exercitationes anatomical de structurS nervorum. Halle, 1797. Privost et Dumas. Mem. sur les phenomenes qui accom- pagent la contraction musculaire. (Journal de physiol. experim., tom. III.) In this memoir are contained some very interesting de- tails upon the structure of the nerves, a concise account of which will be found in a note in the third section of this chapter. Bogros. Note sur la structure des nerfs (dans la Revue medec, mai 1825, p. 237.) Haase. De gangliis nervorum. Leipsic, 1772. Scarpa. De nervor. gangliis et plexubus. Modene, 1779. Lobstein. De nervi sympathetici humani frabrica, usu et morbis. Paris, 1823, in 4o. avec pi. Bracket. Memoire sur les fonctions du Systeme nerveux ganglionnaire. Lyon, 1825. Ch. Bell. Recherches anat. et physiol. sur le systeme ner- veux (Journal de physiol. experimentale, tom. I. et II.) Bell on the Nerves. Legallois. Exp6rienccs sur le principe de la vie. Paris, 1812. OF THE NERVOUS SYSTEM. 181 Georget. De la physiologie du systeme nerveux. Paris, 1821. % Breschet. Art. Ac6phale, et Anencephale du Dictionn. de Medecine en 18 vol. Geoffroy-St. Hilaire. Philosoph. anatom., tom. II. Pinel fits. Recherches sur l'endurcissement du systeme nerveux. Paris, 1822. Lallemand. Recherches anatomico-pathologiques sur l'en- cephale et ses dependences: quatre lettres. Paris, 1820, 1823. Rostan. Recherches sur le ramollissement du cerveux, 2e. edit. Paris, 1823. Ollivier (d'Angers). Trait6 de la moelle epiniere et de ses maladies. Paris, 1823. Rochoux. Recherches sur l'apoplexie. L. G. Descot. Dissertation sur les affections locales des nerfs. Paris, 1822. Magendie. Exper. sur les racines des nerfs qui naissent de la moelle epiniere (Journal de Physiologie exp6rimen- tale, tom. II.) Breschet, M. Edwards et Levasseur. De I'influence du systeme nerveux sur la digestion stomacale (Arch. g6ner. deMed.,aout 1823.) Wilson Philipp. De I'influence du galvanisme sur la di- gestion, la respiration, etc. (Arch, gener. de M6d., mai 1823.) Humboldt. Resultat d'experiences sur les actions galva- niques, etc. (Arch, gener. de Med., octobre 1823.) Flourens. Recherches experimentales sur les fonctions et les proprietes du systeme nerveux dans les animaux ver- t6bres. Paris, 1824. 1812 TEGUMENTARY SYSTEM. CHAPTER VIII. TEGUMENTARY SYSTEM. SECTION 1. General Observations. Definition.—The tegumentary system is composed of a large membrane which covers the entire surface of the body, and enters it so as to line all the cavities which com- municate with the exterior world. Division.—The tegumentary system is divided into two secondary systems, the cutaneous and the mucous. Situation.—The teguments are placed upon the surfaces of the animal which communicate more or less directly with exterior objects: thus, after having covered the whole exterior surface of the body, it lines the mouth, the oeso- phagus, the stomach, the intestines, and all the excretory ducts that empty into them, the aerial passages, the nasal fossae and all their sinuses, and the urinary and genital or- gans. General conformation.—The tegumentary system, re- presents, by its situation, all the other organs ofthe body, and its general form may be compared with that which re- sults from the union of two hollow cylinders, which are continuous by their extremities and are separated at their contiguous surfaces by an intermediate substance. This comparison is applicable only to the skin and to the mu- cous membrane which extends from the mouth to the anus; TEGUMENTARY SYSTEM. 183 it will include, however, all the teguments, if we add to the cylinders which we have just mentioned, certain pro- longations or appendages, which are plunged in different points of the intermediate substance, and line the aerial passages, the excretory ducts of the glands, the genito- urinary organs, &c. Surfaces.—The tegumentary membrane presents two surfaces, one of which is free, the other adherent: the first, which is external to the skin, and internal to the mucous membrane, is in relation in a continuous or interrupted manner with the substances that are actually foreign to the organization. The free surface presents small granular eminences, porous depressions, and horny or calcare- ous productions, either situated together, or scattered in different points: the adherent surface, which is internal to the skin, and external to the mucous teguments, corres- ponds immediately with the layer of cellular tissue, which we described in the first chapter, and, through the medi- um of which, this surface is connected with the subjacent organs. The adherent surface has small eminences, which are more or less prominent and correspond to the depres- sions on the free surface. Structure.—In the organization of the teguments, we are to consider: 1st, the different layers of which they are composed and upon which their form depends, and 2d, their small secretory organs. The layers which form the tegumentary membrane are five in number: they vary in a very sensible manner, in the different parts of this organ, and especially, in its two grand divisions: we shall enumerate them in pointing out their most general characters. 1st. The dermis or chorion constitutes the basis of the teguments, is the thickest of the layers of which we are treating, and is situated underneath them: it is formed of compact cellular tissue, which permits numerous blood ves- sels and nerves to ramify between its fibres. 184 TEGUMENTARY SYSTEM. 2d. The vascular retiform layer, which is placed upon the dermis, is extremely thin and delicate, and results from the interlacement ofthe small arteries, veins and lympha- tics which traverse it. 3d. The small papillae, axe formed by the peripheral extremities of the nerves which traverse the preceding laminae. It is probable, that the nerves of these small nerv- ous papilla?, which are situated upon the surface of the teguments, belong, like most of the others, to the dermis itself; and are only invested by the extremities of the nerves which traverse it with the vessels, and terminate upon its surface. These last two lamina? are not well marked, and ought to be regarded rather as the most superficial parts of the first. 4th. The rete mucosum of Malpighi consists of a layer of semi-organized mucus which contains the pigment or colouring matter of the skin, and is situated between the epidermis and the superficial laminae ofthe chorion. The existence ofthe rete muscosum, first described by Malpighi, and since by many anatomists, has been denied by Bichat and M. Chaussier; while some, and amongst others, M. Gaultier, founding their opinion upon observations on the skin of the negro, assert that it consists even of several layers. 5th. The epidermis or scarf-skin, is the most superfi- cial of the tegumentary lamina?, and is by no means dis- tinct in every part of the system of which we are treating. The epidermis, considered by some as formed of several lamina?, endowed with a certain degree of vitality, which diminishes progressively from the most internal to the most superficial, and by others, as having a squamous structure, is a whitish, semi-transparent, membraniform substance, which is moulded upon the prominences ofthe chorion, and is generally regarded in the present day as destitute of life, and as deposited upon the surface of the teguments by an excretory process. TEGUMENTARY SYSTEM. 185 The small secretory organs that are observed in the tegu- mentary system are known under the names offolliculi, cryptse, &c. and consist of a species of very small, oblong or rounded cyst, terminated by a more narrow part,—a kind of neck, which performs the office of excretory duct, and opens upon the free surface of the teguments: hence, the small porous depressions which are observed upon this surface. The follicles appear to result from a simple de- pression ofthe tegumentary membrane, and are formed of the same anatomical elements, that is, of a dense capsule similar to the chorion, surrounded and pervaded by nume- rous vessels; of a vascular nervous net-work spread upon the concave surface of the dermis, and of excretory parts which vary according to the kinds of follicles, and which sometimes contain a pigment or colouring matter, as that which is observed in the hairs, &c. The follicles may be divided, according to the nature of their secretions, into two kinds: the first comprehends those which secrete a more or less fluid substance, and carry it to the surface of the tegu* ments: these are the crypta? or the follicles properly so called, whose secretions vary accordingly as they belong to the skin, or to the mucous membranes. They occur in every part of the teguments; but they are not every where equally numerous. We find them sometimes in- sulated, sometimes in groups, and sometimes again in regu- lar orders. The second is composed of the follicles which are designated more particularly under the name of bulbs, and which M. de Blainville has called phaneres*, because their secretions, being always solid, remain apparent on the surface ofthe animal: these productions are, the hairs, the nails and the teeth. The bulbs occur only in certain parts of the tegumentary tissue, and are almost always col- lected in groups. Characters, physical and chemical properties.—The * From