CORNELL UNIVERSITY THE JUotuer Upterittanj Hibranj FOUNDED BY ROSWELL P. FLOWER for the use of the N. Y. State Veterinary College 1897 Cornell University Library QM 101.H72 1887 Holden's human osteology comprising a de 3 1924 000 344 162 DATE DUE ^^£C U ~^U^ ^mK/c ? GAYLORD PRINTED IN U.S.A. H II Cornell University B kf Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://archive.org/details/cu31 9240003441 62 HOLDEN'S HUMAN OSTEOLOGY By the same Author, MANUAL of the DISSECTION of the HUMAN BODY. Edited by John Langton, Surgeon to, and Lecturer on Anatomy at, St. Bartholomew's Hospital. Fifth Edition, with 208 Engravings on Wood. 8vo. 20s. HOLDEN'S HUMAN OSTEOLOGY COMPRISING A DESCBIPTION OF THE BONES WITH DELINEATIONS OP THE ATTACHMENTS OF THE MUSCLES THE GENERAL AND MICROSCOPIC STRUCTURE OP BONE AND ITS DEVELOPMENT EDITED BY CHAELES STEWAET CONSERVATOR OF THE MUSEUM OP THE ROYAL COLLEGE OF SURGEONS OF ENGLAND ; HUNTERIAN PROFESSOR OF COMPARATIVE ANATOMY AND PHYSIOLOGY, ROYAL COLLEGE OF SURGEONS OF ENGLAND AND E. W. EEID, M.D., F.E.C.S. LECTURER ON ANATOMY, MEDICAL SCHOOL OF ST. THOMAS'S HOSPITAL; EXAMINER IN OSTEOLOGY, CONJOINED EXAMINING BOARD BY ROYAL COLLEGE OF PHYSICIANS OF LONDON AND ROYAL COLLEGE OF SURGEONS OF ENGLAND ; FORMERLY EXAMINER IN ANATOMY, UNIVERSITY OF ABERDEEN SEVENTH EDITION LONDON J. & A. CHUECHILL 11 NEW BURLINGTON STREET 1887 Iff*" 7 A a rl'T M £0 PBEFACE THE SEVENTH EDITION. It has been thought necessary in this Edition to endeavour to meet the requirements of the student, by giving a somewhat more detailed description of the Bones. This has been done by Mr. E. W. Eeid. A few alterations have also been made in the account of the minute structure and development of Bone. Some of the plates have been redrawn and several new ones added. As in former editions, the attachments of the muscles have been indicated by coloured lines, red being adopted for the origins or usually more fixed ends, and blue for the insertions or more movable ones. The descriptions of the larynx and soft parts of the ear have been omitted, as it was considered that they belonged rather to a work dealing with General Anatomy, than to one on Human Osteology. CONTENTS. Geneeal Observations on the Steuctuee op Bone 1 Miceoscopic Steuctuee op Bone Steuctuee op Caetilage Development of Bone . Bones op the Skull Occipital Bone . Parietal Bone . Frontal Bone . Temporal Bone . Sphenoid Bone . Ethmoid Bone . Wormian Bones Bones op the Face Superior Maxillary Bone Malar Bone Nasal Bone Lachrymal Bone Palate Bone Inferior Spongy or Turbinated Bone Vomer Inferior Maxillary Bone The Skull as a whole Sutures Skull-cap . Base of the Skull as seen from above Base of the Skull as seen from below Temporal, Zygomatic, and Spheno-maxil lary Fosssb The Orbits Nasal Fossae General Observations on the Skull . i. to IV. 13 22 23 36 36 . . v. 44 . . VI. 48 . . VII. 56 . . VIII., IX. 73 . . X., XI. 83 . . XI. 88 90 90 . . XII. 102 . . XIII. 105 . . XVI. 107 . . XIII. 108 . . XIII., XIV. 112 . . XV. 114 . . XVI. 116 . . XVII. 125 125 . . XVIII. 126 . . XVIII. 129 . . XIX. 132 . . XX., XXI. 138 . . XVI., XXII. 139 . . XXII. 141 . . XXIII., XXIV 144 Vlll CONTENTS PAGE FLA/EE Vebtebeal Column . 154 . . xxv. to XXVII. Saceum . 174 [. . XXVIII., XXIX. Coccyx 177 Bones of Lowee Extbemity . 180 Os innominatum . 180 ) Ilium . 181 Pubes . 183 K . xxx. to xxxii. Ischium . . 184 1 Pelvis in general 193 Femur 198 . . XXXIII., XXXIV Patella 213 Tibia 216 ■. . XXXV. Fibula 223, Bones op Foot 230 Astragalus 232\ Os Calcis or Calcaneum . 236 Scaphoid Bone 240 Cuboid Bone . 241 Cuneiform Bones 242 k . XXXVI. to XXXA Metatarsus 246 Phalanges 254 Sesamoid Bones 255/ Obseevations on the Foot as a whole 255 Inteeosseous Muscles of the Foot . 260 The Thoeax . 261 Sternum . 262) . 267)" Eibs . XXXIX. to XLI. Muscles of the Back . 275) Muscles of the back of the Neck . 277 [. . XLH. to XLVII Muscles in front of the Spine . . 278J Bones of the Uppee Exteemity . 280 Clavicle ..... . 280) Scapula ..... . 284 f ' . XLVIII., XLIX. Humerus .... . 295 . • L., LI. Badius . 303) . 3081" Ulna • LII., LIII. CONTENTS IX Bones of the Fingees . Sesamoid Bones ... Genebal Suevey of the Skeleton Os Hyoides Notes Index ...... PASS 317 Bones of the Hand . . . . • Carpus 317) Metacarpus *"'"' 327 J 334 337 338 343 347 351 LIV. xxxviii. HUMAN OSTEOLOGY. Importance and Interest of Osteology. — Whoever would become a good anatomist and a skilful surgeon must make him- self master of Human Osteology. It must be, not only his first, but his principal and constant study. He cannot understand his dissections without continually referring to the skeleton. Nor can he fail to be interested from the first in the science, if in studying each bone he will compare it with the corresponding bone in his own body, in order that he may become familiar with what he can feel of it in the living subject. He will thus see in osteology, not death, but life. In discovering and reducing the simplest dislocation, how important it is to have a competent knowledge of the feel of the bony parts and their relations to one another ! A little progress will convince him that, far from being dry, osteology is attractive, not only as conducive to professional success, but for its own sake. Undertaken in a right spirit, the study of it becomes, with many, a favourite pursuit, and creates a natural longing to know something of the skeleton of the lower animals, that we may the better judge of the advantageous construction of our own ; for it is only by comparison that we can judge. When the great truth unfolds itself, that our own structure appears to be but a modification of the ' one common pattern ' upon which all vertebrate animals are formed, we cannot but feel with the philosophic poet, that — 'Tis the sublime of man, Our noontide majesty, to know ourselves Parts and proportions of a wondrous whole. COLEKIDGE. r <£ COMPOSITION OF BONE Uses of the Bones.— The bones form the framework which supports the soft parts of the body. All the bones, either separately or in conjunction with others, form levers upon which the attached muscles act and give rise to our various movements. Take a few examples. If the biceps muscle contracts, the forearm becomes flexed ; this shows that the radius is a lever. It will likewise be seen that the other bones are levers, as the lower jaw in opening and shutting the mouth ; the skull as a whole in nodding the head; the vertebrae in balancing and flexing the trunk ; the pelvis as a whole (see fig. 27) ; the ribs when raised and depressed in respiration ; the clavicle in shrugging or depressing the shoulders ; the scapula and the humerus in raising the arm ; the ulna and the radius in flexing or extending the forearm ; the carpus and metacarpus as a whole in the move- ments of the wrist j oint ; the phalanges in the actions of the fingers. In like manner the bones of the lower extremities are levers, which, when acted upon by the various muscles attached to them, give rise to locomotion. The bones contribute to the formation of the joints, which admit of more or less movement, depending in direction and extent upon the shape of the articular surfaces and the attach- ments of the muscles and ligaments. Besides this, the bones of the head and trunk lodge and protect delicate organs ; thus, in the skull and spinal canal we find, respectively, the brain and spinal cord ; in the orbits are the eyes ; in the temporal bone are the internal parts of the ear ; and in the bony framework of the chest are the heart and lungs, which, as well as the upper abdominal viscera, it protects. The fact that the long bones are curved in their long axes increases their elasticity, gives them some amount of spring similar to that of a bow, and helps to diminish shocks. Composition of Bone. — Bone is composed of a basis of animal matter impregnated with earthy salts. If a bone be boiled in water for many hours it loses some of its elasticity and animal matter. The animal matter is found in solution in the water and is called jelly or ' gelatin.' The residual bone is white and brittle, and consists chiefly of earthy salts. A like result may COMPOSITION OF BONE be obtained by burning or calcining the bone : it first becomes black from the charring of the animal matter and then white, the animal matter having been completely burnt off and nothing left but the ' earthy salts.' If, on the other hand, a bone be soaked for a few days in a solution of hydrochloric acid (about one part of the dilute acid to six of distilled water), it loses its earthy salts, becomes soft, and may be bent in any direction. Bones are used in making soup for the gelatin they yield on boiling. Notwithstanding their antiquity, bones that have long been buried may still retain a considerable quantity of organic matter. Gimbernat made soup from the gelatin of the mastodon's tooth, as Dr. Buckland afterwards did from the fossil bones of the hyaena. The partial loss of organic matter renders bones more brittle and porous, so that when dry they readily absorb water, and by doing so they adhere when applied to the moistened lips. The latter feature is often used as a test of antiquity. Animal and Earthy matter. — From the above experi- ments bone is found to contain about one-third of animal matter, the rest being earthy salts, i.e. about 33 of animal matter and 67 of earthy salts in a hundred parts. Although bones yield gelatin on boiling, yet it is not this substance, but ossein, which exists in bone, the ossein becoming converted into gelatin by the process of extraction. The portion of the bony matrix forming the immediate walls of the lacunas and canaliculi is said to have elastin for its organic basis. Bones of children are softer, more elastic and less likely to be broken by slight injuries than those of the aged. This is due to the sponginess and great vascularity of children's bones, as well as to the fact that in them the shafts of the bones are united to the epiphyses by a layer of cartilage. Bone when pure, i.e. when entirely divested of fat or marrow and blood-vessels, probably does not differ much in composition, whether it be from a child or from an old person, but it varies in compactness and arrangement, and on these variations the differences in the strength and elasticity of bones depend. 1 The . following is a percentage analysis of adult human bone : 2 1 For this and other references see the end of the book. b 2 COMPOSITION OF BONE Animal matter Earthy salts Tribasic phosphate of calcium Carbonate of calcium, Ca C 3 Fluoride of calcium, Ca F 2 Phosphate of magnesium Soda and chloride of sodium . 33-30 51-04 11-30 2-00 1-16 1-20 100-00 Rickety Bones. — In the disease of early life called ' rickets,' in which the bones grow bent and distorted, from deficiency of earthy matter, the proportions of animal and earthy matter have been found to be : 3 Animal matter Earthy matter 79 - 75 per cent. 20-25 Of all animals, the bones of birds (especially of the predaceous kind) contain the largest proportion of earthy matter. The bones of mammalia come next ; then those of reptiles ; and last of all those of fishes. As in the birds of prey, so in the carnivora, the bones have a hard and compact structure. The tympanic bone of the whale is extremely hard ; but the skeleton most remarkable for hardness and weight is that of the manatee, which may be seen in the Osteological Series of the Eoyal College of Surgeons of England. When the late articulator to the College was taken to task for having charged the enormous sum of £15 (instead of about £5) for articulating the manatee, he pleaded, in justification, that the bones were so hard that it had taken him unusual labour to put them together, and had spoilt many of his tools. The truth of this assertion is at once clear to anyone who takes in his hand the weighty rib of a manatee. (See sections of ribs, No. 2741.*) Phosphate of lime s its Importance. — Of the earthy in- gredients of bone the phosphate of lime holds by far the first rank ; hence it is commonly called ' bone earth.' Adult bone con- * Throughout the work the numbers refer to specimens in the Osteological Series in the Museum of the Eoyal College of Surgeons of England, unless other- wise stated. PROPERTIES OF BONE 5 tains 51 per cent, of it, and about 11 per cent, of the carbonate of lime. Carbonate of lime is the principal ingredient in the harden- ing of shells. The phosphate of lime forms a harder compound with animal matter than the carbonate. What can be harder than the enamel of the teeth ? And this consists of a very large pro- portion of phosphate of lime combined with animal matter. There is only 2 per cent, of animal matter in the enamel, and of the remaining 98 parts, 88^ consist of phosphate of lime. Phosphate of lime enters not only as the principal earthy ingredient into the composition of bone, but is contained, more or less, in nearly all the tissues of the body. Of all inorganic materials it appears to be the most essential both for vegetable and animal life. Therefore it is not only a most important article of diet, but a necessary manure. ' Those parts of plants which ■experience has taught us to be the most nutritious, contain the largest proportion of the phosphates — such as bread-corn, peas, beans, and lentils.' 4 It has been ascertained by experiment, that if animals have their entire supply of phosphate of lime cut off, after some weeks of illness, they are attacked with diarrhoea, "which soon kills them. Their bones are found to be very soft ; and it is not unlikely that the phosphates are absorbed from their bones and supplied to other structures, such as the nerves and muscles. It is the quantity of phosphate of lime in the bones which makes them so valuable as manure. The bones are boiled to obtain the gelatin or glue and fat ; afterwards they are crushed in a mill, and, as ' bone dust,' form an extensive article of com- merce. Strength of Bone. — The strength of bone, contrasted with other substances, is remarkable. The following materials stand in point of strength to each other thus : Fine freestone, as . . 1-0 Lead . . . 6-5 Elm and ash . . 8-5 Box, yew, oak . 11-0 Bone .... . 22-0 6 CLASSIFICATION OF BONES Hence bone is twice as strong as oak. A cubic inch of bone will support 5,000 lbs. weight. 5 Besides this, we shall presently see that bone is so constructed that it gives great strength with but little expenditure of materials. The specific gravity of bone is from 1-87 to 1-97. Elasticity of Bone. — In consequence of the animal matter they contain, bones possess a certain amount of elasticity. If a skull be tbrown upon the ground, it will rebound. The degree of elasticity varies in different bones, according to their form and texture. The clavicle, for instance, owing to its curved form, is remarkably elastic — a property which enables it to break the shock of a fall upon the hand. If one end of a clavicle be placed at a right angle against a hard substance, and the other end struck smartly with a hammer, the bone will rebound to a dis- tance of nearly two feet. The ribs, too, are exceedingly elastic. The Arab children are said to make excellent bows with the ribs of camels. Perhaps the best instance of elasticity in bone is the united clavicles (merry-thought) of the bird. All the long bones are more or less curved, which gives them the benefit of elasticity. Classification of Bones. — Though the bones present every variety of form and size, yet, for convenience of description, anatomists divide them into three classes: 1. The long and round ; 2. The broad and flat ; 3. The short and cubical, or irregular. The long and round form the great levers of the limbs, and are moved by muscles. The broad and flat are found chiefly in the skull and pelvis, and protect the viscera. The short and irregular allow more limited motion combined with great strength, and serve to break shocks, as the bones of the spine, the carpal and tarsal bones. Nomenclature. — In describing the different parts of a bone, we use terms — Latin, Greek, or English — which denote either the form of the part, or its fancied resemblance to some natural object, or the purpose it serves. We soon become familiar with such terms as ' eminences,' ' depressions,' ' processes,' ' tubero- sities,' ' spines,' ' foramina,' ' notches,' ' canals,' ' sinus,' ' fossa,' 'trochanters,' 'condyles,' &c. Again, there are parts of bones named after some celebrated anatomist who first described them : PLATE I.' Drawn on From mature "by L.Holden. GENERAL STRUCTURE OF BONE / for instance, the ' aqueduct of Fallopius,' ' the antrum of High- more,' ' the fissure of Glaser,' the ' canal of Vidius.' These memorials of anatomists, though interesting to historians, are rather encumbering to anatomical nomenclature, and are there- fore very much to be deprecated. Structure of Bone : Naked Eye. — Let us examine, first, the structure of bone, as it can be seen with the naked eye ; afterwards, its minute structure with the microscope. Lastly, we will study the development and growth of bone. The best way to obtain a rough idea of the structure of bone is to make a vertical section through one of the long bones — say the femur — all the way down. (Plate I.) We then see that the outer part, or ' wall,' of the bone is compact, like ivory ; the interior is hollow, forming the ' medullary canal,' or cavity con- taining the marrow. The ends, which expand to form the joints, are composed of a beautiful network of plates and bars of bone, forming what is called ' cancellous or spongy tissue,' which in the recent state is also filled with marrow. Shaft of Bone hollow. — "What are the advantages of bones being hollow ? The amount of material being the same, a hollow cylinder is much stronger than a solid one. It is proved that the crushing pressures of two cylinders of equal weight and length, of which one is hollow and the other solid, are, re- spectively, as the diameters of their transverse sections ; pro- vided always that the diameter of the tube be within certain dimensions. Thus, let ab, c d (figs. 1 and 2) represent the sections of two cylinders ; then the strength of the tube c d is to that of the solid a b as the line d c is to the line a b. 6 In some animals which seldom or never leave the water, the bones have no medullary cavities, but are completely filled by cancellous tissue. This is the case in the penguins (Nos, 1138 to 1140), the whales, and amphibia, whose solid bones •appear to act as ballast. 8 GENEEAL STBUCTUKE OF BONE In the early part of the seventeenth century, Galileo observed in nature a variety of instances in which the strength of bodies was made very great consistently with lightness by the arrange- ment of their structure. This most profound philosopher, when accused of atheistical opinions, and interrogated before the Inqui- sition as to his belief in a Supreme Being, picked up a straw from the floor of his prison, and replied, ' If there were nothing else in nature to teach me the existence of a Deity, even this straw would be sufficient.' Air Cells in Bone. — Strength and lightness are thus com- bined in the economy of bones. This principle is carried to the extreme in certain bones of birds, which are filled with air instead of marrow. There is a communication between the lungs and the cavities in the bones of birds (Nos. 1107-8) ; and the air which fills the bones being warm, renders them still lighter. The great beak of the hornbill forms one large air-cell (No. 1492) ; even the thin columns of the cancellous tissue in the interior are hollow and filled with air. In this case as in that of other birds the air in the skull is derived from extensions of the cavity of the middle ear on each side. In this bird, as well as in the toucan, every bone of the skeleton, down to the little bones of the claws, is filled with air. In the little ' apteryx ' of New Zealand, which has no available wings, and in the penguin, which rarely leaves the water, no bones of the skeleton except those of the skull receive air. In the bones of the chick there are no medullary cavities ; as the bird grows its bones become hollowed out, and filled with marrow, which is subsequently, in the mature bird, removed and replaced by warm air. In mammalia there are no air-cells except in the bones of the head. There are large air-cells (sinuses) in the frontal, sphenoid, ethmoid, palate, maxillary and mastoid bones in man. Cancellous Tissue : Arrangement. — The cancellous tissue occupies the interior of bones, and chiefly the articular ends. It is formed by plates and fine bars of bone, which form a kind of lattice-work with a most delicate and elegant arrangement. The cancellous architecture of bones is arranged upon this prin- ciple: its columns always run along the lines of greatest pres- GENERAL STRUCTURE OF BONE 9 sure, or form arches, thus combining the greatest strength and elasticity with lightness. A beautiful example of this is seen in the section of the cancellous tissue of the thigh-bone (Plate I.). At the lower part, towards the knee, the layers run vertically — that is, in the direction of the axis of the shaft, this being the line of pressure when the body is erect. But in the neck of the thigh-bone the layers are arranged in decussating curves like Gothic arches, one within the other, and sustain with the greatest mechanical advantage the weight transmitted on to the heads of the thigh-bones. (Norm. Hum. Ost., Nos. 211 to 222.) Cancellous Tissue : Properties. — Though so light and spongy, the cancellous tissue is able to support a great weight without giving way. We may form some idea of its strength from the following experiment : 7 A cubic inch of cancellous texture was taken from the lower end of the femur, and placed with its principal layers upright. Four cwt. was then placed upon it, but it did not give way in the least. Six cwt. made it sink half an inch. Yet the cubic inch of bone itself did not weigh more than 54 grains. Not only is cancellous tissue strong as well as light, but it possesses another advantage — that of diminishing shocks. When a ball of ivory strikes another, as in the game of billiards, the whole force of the shock is trans- mitted from one to the other ; but let a ball made of the can- cellous tissue be interposed, and then see how the shock will be broken. This property of diminishing shocks is of course greater when the bone is in its natural state and filled with marrow. The spaces formed by the cancellous tissue vary in size and shape, but freely communicate with each other, and with the holes on the surface of the bones. This is easily proved by boring a hole at one end of a bone, and pouring mercury into it : we shall find that the mercury will run out freely through the natural holes at the other end. Marrow, Yellow.— The interior of the shaft of a long bone is filled with yellow marrow ; a substance composed almost en- tirely of fat (96 per cent.) ; that is, in bones that are healthy. 10 GENERAL STRUCTURE OF BONE Like all other fat, it is removed in cases of great emaciation —in general dropsy, for instance; and its place is supplied by an albuminous fluid. Hence the bones of a dropsical sub- ject are always the least greasy, and the best adapted for skeletons. marrow, Red The cancellous tissue of the articular ends of long bones, and of the bodies of the vertebrae, the sternum, the ribs, and the bones of the cranium, contain another kind of marrow of a red colour. This red marrow differs from the yellow, in that it contains little or no fat — not more than 1 per cent. It consists of 75 per cent, of water and 25 per cent, of solid matters, chiefly albumen. It is this kind of marrow which is found in all the bones of the foetus, and in infants. Hence it is sometimes called foetal marrow. Examined with a high magnifying power, it is found to contain a number of oval or irregular-shaped many-nucleated cells. (Plate IV. fig. 9.) Cells of this form are found in many rapidly growing tumours, and are called ' myeloid ' cells. They are especially abundant in the so-called myeloid tumours. 8 Small round cells, like white blood corpuscles, are also found in great numbers. Blood-supply of Bones. — At the articular ends of any long bone, or on the body of a vertebra, we observe a number of holes. Near the lower end of the thigh-bone we might soon count as many as 200 or more. What are these holes ? The smaller transmit the articular arteries which nourish the vascular can- cellous tissue. The larger contain veins which run by them- selves. These veins of the cancellous tissue are large and numerous. They traverse and ramify through this tissue in various directions in special canals with thin walls of bone. They are well seen in a section through the body of a vertebra (Plate XXV. fig. 7) , also in the cancellous tissue (termed ' diploe ' ) of the cranial bones. Prom a surgical point of view these ' diploic ' veins are interesting, on account of their liability to inflame after severe injuries of the head : such inflammation may lead to suppuration in the diploe, which is often fatal. The adjoining figure (3) shows the large venous canals hi the 'diploe' of the skull-cap. GENERAL STRUCTURE OF BONE 11 Fig. 3. VEINS IN THE DIPLOE OF THE SKULL. Again, on the outside of the shaft of a long hone there are a number of minute grooves, which run for the most part parallel to the shaft, and lodge blood-vessels. At the bottom of these grooves are still more minute holes, barely visible to the naked eye, but easily seen through a small pocket -lens. These holes transmit the blood-vessels from the ' periosteum,' or membrane covering the bone, to the compact tissue. Artery of the Marrow. — The marrow in the interior of the bone is supplied with blood by the ' medullary artery.' This artery reaches the marrow through a very distinct canal (canal for the nutrient artery of the medulla), which runs obliquely through the shaft, near its middle. In a long bone like the femur, there are generally two of these, situated at the back part. As soon as the artery reaches the medullary cavity, it divides into two branches, an ascending and a descending, which ramify in and supply the marrow and the greater portion of the thick- ness of the shaft, and finally communicate with the ' articular * arteries already described. Thus the several parts of a long bone are supplied with blood as follows : The outer compact wall of the shaft by blood-vessels from the periosteum ; the marrow in the interior and remainder of the shaft by a special medullary artery ; and the cancellous tissue of the ends by the articular arteries. The blood-vessels oi these several parts are not exclusive, but' communicate more or less with each other when the parts of the bone have united, with the shaft. Hence they readily reciprocate their morbid actions, and inflammation arising in the one part may spread to ihe other, although the extremities usually retain their life when 12 GBNEEAL STRUCTURE OF BONE Fia. 4. the shaft is killed by inflammation. Notwithstanding that these three orders of blood-vessels do communicate in the bone, yet we cannot be surprised to find that when a bone is broken below the canal for the nutrient artery of the marrow, the lower fragment, being deprived of part of its supply of blood, in some cases becomes atrophied and thinner. 9 Periosteum: its use.— A fibrous membrane, termed the periosteum, invests the bones everywhere except at the insertion of strong tendons, and where covered with cartilage. This periosteum consists of two layers, an external one, tough and fibrous, and an internal one (osteo- genetic), soft and cellular. The ad- joining figure shows the arrangement of the blood-vessels of the periosteum. The periosteum likewise provides each of the vessels entering the bone with a fibrous covering. It assists in the for- mation of bone, and afterwards in its nutrition. If, therefore, the periosteum be torn from the surface of a bone, there is a risk that a layer of the subjacent bone will lose its vitality, and be cast off. medullary membrane. — The medullary and Haversian canals and the cells (marrow spaces) of the cancellous tissue are lined by an extremely delicate membrane, termed the ' endosteum.' It is much more delicate than the periosteum ; nevertheless, it supports the marrow, and provides a stratum for the subdivisions of the medullary artery, before they penetrate the contiguous bone. Nerves in Bone. — Periosteum and bone unquestionably possess nerves. This is proved by absolute demonstration, and by disease. Nerves may be traced into some of the minute foramina on the shaft of a long bone, and into the articular ends. A nerve also enters the medullary canal with the nutrient artery of the medulla, and divides like the artery into an ascending and a descending branch. Of all the bones, the tibia presents the largest canal for the nutrient artery of the marrow ; in this bone BLOOD-VESSELS OF PERIOSTEUM. MICROSCOPIC STRUCTURE OF BONE 13 also it is easy to trace the entrance of the nerve with the artery. Though bone in health has but little feeling, when diseased it becomes highly sensitive. There is such a thing as ' neuralgia ' of bone. Every surgeon must have witnessed how sensitive are granulations from bone. Indeed, it is probable that the severe pain attendant on the ulceration of articular cartilage is occa- sioned by the pressure of the cartilage on the bone-granulations beneath it. Lymphatics of Bone. — The lymphatics of bone have been actually demonstrated by injecting the lymphatics of the body of a vertebra. 10 It has been recently proved by injections that the blood-vessels of Haversian canals are surrounded by peri- vascular lymphatic vessels. 11 Microscopic Structure of Bone. This is a most interesting and instructive study. It reveals to us that bones are as minutely provided with blood-vessels and nerves as the softer parts of the body. Being as fully organised as other parts, we cannot wonder that they are subject to like diseases. We have to investigate how the bones are formed in early life, how they grow to maturity, how their health is main- tained, how their injuries are repaired. Would anyone, looking at a solid bone, expect to find that even its hardest parts are tun- nelled out by a network of minute canals containing blood- vessels ; and that from these canals other tubes, infinitely more minute, and connected with a series of reservoirs, radiate in all directions and convey nutritious fluids ? General Idea : Haversian Canals. — Let us first get a general idea of the microscopic structure of bone, and go into de- tails afterwards. If a transverse section from the shaft of a long bone be ground extremely thin, and examined with a power of about 20 diameters (Plate II. fig. 5), we see a number of holes, with dark spots grouped around them, in a series of tolerably concentric circles. These holes are sections of the canals (termed ' Haversian ') 12 which transmit blood-vessels into the substance of the bone. The dark spots are minute reservoirs, called 14 MICEOSCOPIC STBUCTUBE OF BONE ' lacunae.' They look like solid bodies, but they are cavities and are occupied during life by soft 'bone corpuscles,' concerning which more will be said hereafter. Different parts of the section show that the' Haversian canals vary considerably in size and shape. They are generally round or oval. Those nearest to the circumference of the bone are very small; but towards the medullary cavity they are seen to be larger, and at last open out into the cells of the cancellous texture. Haversian Lamellae. — The same section examined with a higher power (Plate II. fig. 7) shows that the Haversian canals are surrounded by a series of concentric lines, resembling the transverse section of the branch of a tree. These lines are termed the ' lamellae.' They are so many layers or rings of bone that have been developed within the Haversian canal. Even the smallest Haversian canal was, when originally formed, a much wider space, and circumscribed by only a single layer of bone ; but in process of growth the canal becomes gradually contracted by the deposit of successive layers of bone. The dark spots, before alluded to as the ' lacunae,' are situated between the lamellae ; under a higher magnifying power (Plate II. fig. 6) they look like insects. The central part or the lacuna, repre- senting the body of the insect, is hollow, and the dark filaments which run out from it, representing the legs, are minute tubes termed ' canaliculi.' These are exceedingly numerous, and ra- diate from all parts of the ' lacuna,' through the lamellae. Now, since the canaliculi of one circle of lacunae communicate most freely with those of the next circle, and the canaliculi nearest to the Haversian canal open directly into it, it follows that by means of this system of radiating tubes a complete communica- tion is established between the Haversian canal in the centre, and the successive circles of bone which surround it. The nutrient material of the bone exudes from the blood-vessels in the central canal, and is transmitted through the canaliculi from one lacuna to another. Haversian System.— Every Haversian canal taken in con- junction with its concentric layers of bone, lacunae, and canali- [ culi, is termed an ' Haversian system.' (Plate II. fig. 7.) PLATE II. Ei.g.1. Fi<5.2 NotocWd of Lamprey Hyaline cartilage. 3iia? 383 cfca? Ti$. 3.. Transverse section. 333dta? *®5% r^i ^ ^ -V-i »" '',n'i. • - . — A. ■ i , .'fr-^4. ■ ■ lM%\;. frt> .^f/V' r4 ?¥$ : Q' ■ *V ' ' I! 'J -^ Ear op Mouse . Cellular cartilage. White Yellow. Fibro-oartilale. Longitudinal section. White -pibrous-tiss-ue . .Haversian canals 20 dia? Havuvsiari space Haversian canals. .Longitudinal section of Haversian canals Transverse section of Haversian canals . Bone. F*6 Osseous rfi-aiuilcs. Lacuna and CanalicuK higM/Tnagnifiecl Bg.7 100dia ? r rom nature bv Li.Hold.eri Drawn on Stone By T.GccUirt. Haversian systems. Printed l*y West.Newman & Co. MICROSCOPIC STRUCTURE OF BONE 15 Almost all the compact substance of bone is made up of a multitude of these ' Haversian systems.' Each system is, to a certain extent, independent of its neighbour, since the lacunae of one system communicate very sparingly with those of another. In consequence of this isolation, we sometimes find, in favourable sections, that each system is more or less circumscribed by a tolerably distinct white line, which is transparent bone with but few canaliculi. Haversian Interspaces. — As the Haversian systems in the transverse section are for the most part circular, it is clear they cannot touch each other in all parts of their circumference ; so that here and there triangular portions of bone fill up the gaps between them. Such portions are termed ' Haversian inter- spaces.' (Plate II. fig. 7.) They are either portions of Haver- sian systems, or the layer of investing periosteal bone which has elsewhere been encroached upon by other systems of more recent formation. These ' outlying ' portions of bone are also provided with lacunas and canaliculi, and they derive their nourishment from the surrounding Haversian systems, of which they are dependencies. The section we have hitherto been examining was a trans- verse one. We must now make an equally thin section in the longitudinal direction of the shaft, and we then have quite a different appearance. (Plate II. fig. 4.) We cut in the course of the Haversian canals, not across them ; and we find that, as a general rule, they run parallel to the surface of the bone (no matter whether long or flat), and that they communicate very frequently by transverse or more or less oblique canals. If the section be large enough to include the Haversian canals near the circumference, we find that some open on the outer surface and admit blood-vessels from the periosteum ; others, again, open into the medullary canal, and admit blood-vessels from the in- terior. In this way the Haversian canals permeate the compact substance of the bone, with occasional communications between the blood-vessels of the periosteum and those of the medulla. These canals may, in fact, be regarded as so many multiplica- tions of surface for the ramifications of blood-vessels, whereby 16 MICEOSCOPIC STKUCTUEB OF BONE every part of the bone-substance is brought within the range of nutrition. In this longitudinal section, the lamellae, instead of being arranged concentrically, are seen running in lines parallel with the longitudinal Haversian canals to which they belong. Bone Tissue.— At this stage of the investigation, a question naturally arises : Where is the earthy material, the phosphate and carbonate of lime ? To see this, the transverse section must be magnified about 1,200 diameters. (Plate II. fig. 6.) We then discover that the earthy ingredient consists of an infinite multitude of minute osseous granules, which are deposited in a ' matrix ' or bed of animal matter. This mixture of earthy granules and animal matter is called ' bone tissue.' It occupies all the space between the lacunas and their canaliculi. If the specimen were steeped for a time in dilute hydrochloric acid, the osseous granules would be dissolved out of it, and the little pits in the matrix in which the granules were embedded would become apparent. So far we have acquired a general notion of the minute structure of bone ; that is to say, of the ' Haversian canals,' the ' lacunae ' and their ' canaliculi,' the ' lamellae,' and the ' osseous granules.' We must now speak of these several parts a little more in detail ; and first, of the Haversian canals. Haversian Canals. — As said before, the Haversian canals are tunnels in the compact substance of the bone, which contain the blood-vessels. Observe, they form no part of the essential structure of bone. Wherever bone is so thin as to be able to derive its nutrition from the vascular membrane coverhig its surface, we do not find Haversian canals in it, nor does it re- quire any. For instance, the delicate plates of bone composing cancellous tissue, the paper-like bones in the interior of the nose, have no Haversian canals in them; but they have plenty of lacunas, which send out their canaliculi to open on the surface and imbibe the requisite nutriment. Bone so thin as to need no Haversian canals is called ' non-vascular ' bone. Such bone lives upon the blood which flows through the minute vessels of its periosteum. Bone has, therefore, like all other living structures,, MICROSCOPIC STRUCTURE OP BONE 17 a self-formative power, and draws from the blood the materials for its own nutrition. The Haversian canals vary in diameter from 10 * 00 to -^ of an inch, the average being about -gfo. The smallest are found near the outer surface, where the bone is the most compact ; but they gradually become larger towards the interior, where they open out into the cancellous tissue, or into the medullary cavity. All running in the long axis of the bone are surrounded by concentric lamellae of bone; but the number of the lamellae varies around different canals from 1 to 15 or more ; a smaller number in young bone, and a larger in old. All are lined by a very delicate membrane, continuous with the endosteum. The smallest canals contain only a single capillary blood-vessel ; the larger contain a network of vessels, while the largest, which gradually merge into the cancellous tissue, contain marrow as well as blood-vessels. Here it may be as well to mention a fact concerning the minute structure of bone, which should never be lost sight of. It is this : that everywhere the deepest part of the membrane in contact with the surface of bone, whether it be the periosteum covering the exterior, the lining of the Haversian canals, or the medullary mem- brane (endosteum) lining the cancelli, is formed by a delicate layer of soft connective tissue, with a multitude of small corpuscles in it, termed 'osteoblasts.' Now, it has been ascertained that these osteoblasts, and the soft tissue in which they are embedded, are alone concerned in the formation and the growth of the bone ; and that by the successive ossification of these tissues, the concentric layers of bone are produced within the Haversian canals. Haversian Spaces. — Irregular spaces not surrounded by any concentric lamellae may often be seen in transverse sections. (Plate II. fig. 5.) They are called Haversian spaces, and are formed mainly or entirely by cells named osteoclasts, which eat out and absorb the bone. The space having attained a certain size, the osteoclasts are replaced by osteoblasts, which then form layers of bone and build up an Haversian system. In bone under- going atrophy the spaces are naturally very large and numerous. c SEPABATION" OF LATEBS 18 MICROSCOPIC STRUCTURE OF BONE Haversian Canals dilated by Inflammation.— The know- ledge of the free circulation of blood through the substance of FlG _ 5 bone gives us the key to some of the effects produced by inflammation in it. For ex- ample, as inflammation in soft parts is attended by dilatation of the blood-vessels, so is it in the case of bone. When bone is actually inflamed, the blood-vessels in the Haversian canals become greatly enlarged, and cause the canals themselves to become by inflammation. larger by absorption of the bone tissue — so much so as to give the bone, sometimes, a reddish colour. In operations where the surgeon has to cut through inflamed bone, one may see the blood flowing from the cut surface of the bone, as it would from the soft parts. More than this, the distended blood-vessels may occasion not only a gradual enlargement of the Haversian canals, but their inflammatory deposit may, some think, cause even a general swelling of the compact substance of the bone and a natural separation of its component layers, so that it becomes light and spongy, as seen in the adjoining figure. 13 Haversian Canals obliterated by Inflammation. — On the other hand, in some cases, e.g. in chronic inflammation, we sometimes find that bones become harder and thicker than natural. They may become as hard as ivory, and can take a polish. Here the Haversian canals are nearly filled up by suc- cessive layers of bone. Indurated bone is therefore less vascular than healthy bone. A good example of ' eburnation ' of bone is occasionally seen as the result of chronic osteo-arthritis, where the articular ends of bone lose their cartilage and become hard and polished like ivory, owing to the blocking up of the Haversian canals by osseous tissue. Lacunae and their Contents. — The ' lacunas ' are the insect- like cavities which we find between the lamellae, arranged in concentric circles around the Haversian canals. They are charac- teristic of true bone, and distinguish it from ' calcifications,' some- times met with as products of disease. Formerly the lacunas and canaliculi, in consequence of their dark colour, were considered MICROSCOPIC STRUCTURE OF BONE 19 to be solid ; but later observations have proved them to be hollow spaces. Each lacuna in the living bone contains a soft nucleated substance termed a bone corpuscle, which sends its soft processes or ' outrunners ' along the canaliculi. The bodies in the lacunas and canaliculi circulate nutritious matter through the bone. The lacunse and canaliculi can be filled with Canada balsam. It is curious that in the bones of Egyptian mummies these minute cavities are filled with the bituminous material. Such a bone corpuscle, with its processes highly magnified, is shown in Plate III. fig. 5. As a rule, the lacunse are oval and flattened, so that one of their broad sides is turned towards the Haversian canal. The first ring of lacunse sends some of its canaliculi directly into the Haversian canal, while others communicate with the canaliculi of the second ring, and so on throughout the whole system. The nutrient fluid in the perivascular lymphatics in the Haversian canal enters the nearest canaliculi, and then the inhabitants of the nearest row of lacunse, and is gradually passed on to all the others in the Haversian system. One may say, then, that the inhabitants of the lacunae are parts of the machinery of the circulation and nutrition in the bone. Size and Shape. — In man, the lacunas measure about ^-jVo of an inch in their long diameter, and about -goVo in then- short. It has been shown that they vary in size and shape in the classes of vertebrata, so that by means of this test it can be ascertained with certainty whether a given fragment of bone be part of a mammal, a bird, a reptile, an amphibian, or a fish. As this test is equally applicable in the case of fossil bones, it has an important bearing upon the study of geology. Another interest- ing fact is, that the size of the lacunas bears very little relation to the size of the animals to which they belong. They are nearly is large in the bones of the little lizard as they are in those }f the enormous extinct lizard, the Iguanodon. But their size ioes bear an exact proportion to that of the blood corpuscles n the several classes of animals. Therefore, as amphibia lave the largest blood corpuscles, so have they the largest acunse. 14 c 2 20 MICROSCOPIC STRUCTURE OF BONE Canaliculi : Size and Office.— Eespecting the ' canaliculi ' (Plate II. fig. 6), observe how exceedingly minute they are; that they run off from all parts of the circumference of the lacuna? and communicate most freely with the canaliculi of the adjoining lacuna. Their diameters range from 1 4 \ of an inch to Tf | M of an inch; but there are some even smaller. Soft nucleated corpuscles, ' bone corpuscles,' lie in the lacunae, and have many delicate branching processes, by means of which they intercommunicate. These branching processes He in the cana- liculi. Lamella;. — The ' circumferential ' lamellae encircle the shaft of the bone (Plate II. fig. 5), and result from the bone growing in thickness by a deposit of new layers on the old shaft by the deep layers of the periosteum. The ' Haversian ' lamellae are the concentric tubes of bone enclosing the Haversian vessel. (Plate II. fig. 7.) These result from successive layers of bone being deposited around the Haver- sian vessel, the one within the other, encroaching more and more on the space in which the vessel lies. This process renders the bone more dense in structure. In transverse sections of fully formed Haversian systems there appear to be from one to fifteen concentric rings of bone, varying in thickness from 3-0V0 ^° 6 o'oo °f an hich. The ill-defined and interrupted layers apparent here and there in the spaces between Haversian systems are termed ' interstitial lamellae.' (Plate II. fig. 7.) Nails (Claviculi) of Gagliardi. — In carefully made pre- parations of bone, it may be seen that its constituent lamellae are connected by fibres which perforate them either at a right or an oblique angle, and thus ' bolt ' them together. These ' per- forating fibres ' or bolts appear to answer a mechanical purpose. They are best shown by separating the lamellae of a decalcified bone. Thus you see not only some of the bolts pulled out, but also the holes through which they passed.' 5 Osseous Granules.— The earthy salts are deposited in the animal matrix in the form of exceedingly minute granules. The Germans call them ' bone crumbs.' We cannot see them, MICROSCOPIC STRUCTURE OF BONE 21 however, without a magnifying power of 1,200 diameters. (Plate II. fig. 6.) They vary in size in different specimens of bone. In man their size ranges from ^-gVo to of an inch. They can be very distinctly seen in the skulls of small birds — the canary for instance — and also in the skull of the bat, where they are so much larger than in the human subject. After a section of bone has been steeped for some time in dilute hydrochloric acid, these sarthy particles will be dissolved out of the animal matrix, and the little cavities in which they are embedded can then be distinctly seen. Found in Pus from Dead Bone- — It is an interesting and valuable practical fact, that these earthy granules are gene- rally present in the pus which comes from dead bone. If a specimen of pus under such circumstances be examined with a power of 500 diameters, a number of earth granules may be detected among the pus cells, proving that there is dead bone somewhere. 16 In pus coming from diseased bone there is .as much as two and a half per cent, of phosphate of limp,. 17 Articular Bone. — By articular bone we understand a thin layer of hard tissue situated immediately under articular cartilage ; and since there is a peculiarity about the structure of it, we will allude to it here. If a sec- tion be made perpendicu- larly through the articular surface of any fresh bone with the cartilage attached, it will be observed (as seen in fig. 6) that the cartilage does not rest immediately upon the cancellous tissue of the bone, but upon a thin compact crust of •calcified cartilage resting on and partly penetrated by a layer of true bone. This, which we call ' articular bone,' varies in thickness, Fig. 6. Upper cartilage cells. Lower cartilage cells. Calcified Artieular cartilage, y , Bone. ] bone - Cancellous bone. STEUCTUBE OF AETICULAB BONE. 22 STRUCTURE OF CARTILAGE and is of a remarkably white colour. The blood-vessels of the can- cellous tissue run up only as high as its under surface, and then turn back in loops. This layer is much less porous than common bone, and in consequence of its closer texture is all the stronger, and supports the articular cartilage on a very unyielding surface. Although articular bone and adult articular cartilage have no blood-vessels in health, yet they both become vascular in some cases of disease of the cartilage. Blood-vessels, when well injected, may then be seen shooting up through the heretofore non-vascular layer of bone, into the cartilage on its surface. Structure and Varieties of Cartilage. Varieties of Cartilage. — Cartilage, commonly called ' gristle,' is tough, flexible, and more or less elastic. There are several kinds of it, which have functions varying with their posi- tion and structure. It consists of nucleated cells embedded in a matrix or intercellular substance. Cellular Cartilage. — Although all cartilages are cellular, this term is sometimes applied to cartilage or cartilage-like tissue in which the structureless matrix is so small in quantity that the cells are polygonal by mutual pressure. This variety is found in the external ear of many small animals, and in the notochord. (Plate II. fig. 1.) Hyaline Cartilage. — Where the matrix is translucent and structureless it is called hyaline cartilage. Nearly the entire skeleton of the fetus has this structure at some time or another as well as the cartilage covering the articular ends of bones. (Plate II. fig. 2.) White Fibro-Cartilage. — The intercellular substance may be white and fibrous, then it is called ' white fibro-cartilage.' This variety is but slightly elastic, but is stronger than the former, and the cells are small and scattered. (Plate II. fig. 1.) The intervertebral substance consists mainly of this variety as well as the interarticular fibro-cartilages. (Plate II. fig. 2.) Yellow Fibro-Cartilage.— The gristle of the ear, epiglottis, and the Eustachian tube is of a yellow colour, is very elastic, OSSIFICATION 23 and the hyaline intercellular substance is mixed with interlacing wavy fibres of elastin. It is therefore named 'yellow fibro- cartilage.' (Plate II. fig. 2.) Temporary Cartilage. — As early as the fourth week of foetal life, when the embryo is but f of an inch long, the principal part of the skeleton is mapped out by the formation of firm masses of tissue called ' temporary ' cartilage, which is only a variety of the hyaline. Cartilaginous Skeleton. — A week later the intercellular substance has more developed in this cartilage, converting it into ' hyaline ' cartilage of more ordinary character, and giving it greater solidity. Thus, the whole fetal skeleton, with the ex- ception of the skull-cap and the bones of the face, consists at one time of hyaline cartilage. At the fifth week bony substance begins to be formed in the middle of the clavicle ; at the sixth week in the lower jaw ; and by the seventh week, when the fetus is about an inch long (Norm. Hum. Ost. No. 1), a small deposit of bone has made its appearance in the middle of nearly every bone in the body. The points at which the formation of bone commences are called the ' centres of ossification.' It will therefore be understood that the formation of bone does not take place at the same time in all parts of the cartilage, but only about these ' centres of ossification.' meaning- of Centres of Ossification. — Every bone has a definite number of these centres, which always appear in the same place; and from these centres the ossification extends according to a regular plan. The number of centres varies in different bones. Some bones have only a single centre ; others two, three, five, seven, &c. ; and the bone called the ' sacrum ' has as many as thirty-three centres from which its ossification is completed. Observe, the centres of any given bone do not all appear at once ; some appear before birth, others after it, but all in regular succession, and at stated periods, according to the degree of im- portance of the bone, and the function which it has to perform ; e.g. the lower jaw and the ribs ossify early, because suction and 24 OSSIFICATION respiration are brought into play at birth. As a general rule, each centre appears first in the middle of the cartilage ; and thence the ossification extends towards the circumference in the flat bones, and towards the extremities in the long bones. Almost all the bones, then, in infancy and childhood are made up of so many distinct bony pieces united together by cartilage ; and these several pieces remain distinct until the stature of the individual is complete, after which they are all consolidated. Perichondrium. — All kinds of cartilage, with the exception of that which covers the ends of the bone (articular cartilage), are invested with a white fibrous membrane, termed ' perichondrium.' This, like the periosteum of the bones, contains plexuses of blood- vessels ramifying all over the cartilage. Cartilage usually contains few or no blood-vessels. But when rapidly growing or diseased, it has been proved by injection that blood-vessels do shoot into the cartilage from the adjacent parts. 18 Ossification of Femur — As an example of what can be seen of the process of ossification with the naked eye, let us follow out that of the thigh-bone. (Plate IV. figs. 1 to 6.) The future bone is at first sketched out in hyaline cartilage. About the seventh week after conception, the first centre of ossification appears in the middle of the shaft — as is the case in all the long bones (fig. 1). From this point ossification gradually extends up and down the shaft, which is all ossified before the other centres appear. About the last month of foetal life, a second centre appears in the lower end, which forms the knee (fig. 3). About the end of the first year after birth, a third centre appears at the upper end or head of the bone (fig. 4). In the course of the fourth year, a fourth centre appears, in the projection termed the 'trochanter major' (fig. 5). In the course of the fourteenth or fifteenth year a fifth and last centre appears in the ' trochanter minor ' (fig. 6) . ' Diaphysis ' and ' Epiphysis.'-— Thus, then, the thigh-bone has five centres of ossification. The shaft or body of the bone,;* which ossifies first, is called the ' diaphysis ; ' the other parts are termed ' epiphyses.' As these epiphyses, during the period of PLATE III. L|.2. p erl osteum- Periostialtone. L ve rsian c« JVfedullary cavity .^V - ' -. - " --S Transverse section of Lorn§ tone and its Periosteum shewing Blood vessels. Fig. 3. Lacunas and canaliculi. Fig. 5. Bone corpuscles and their processes. which, occupy the lacunae and canaliculi of Fig.4? Periosteum Osteoblast. .Trabecule, ofbone. .Bone c orpuscles Osteoblast becoming surrounded by bone t (Osteoclast eroding bone. Fi&I. Hyaline* f!artila^e J Cartilage celijs enlarged and arranged in. rows , seperatedby cAlcified main* / - % f *<* W $0 % %. Osteoplasts replace the cartilage cells, ^Formation of trifdullarj spaces ■ Trabecular 1 trcjrnams of cal Gt f i e d oavBl a-^e c oatecl with "thin layet of "bone Section of bone forming in fibrous tissue. Br-am nature hj C .Stewart . Drawn, on Siong by T ^oHnrl Vertical Sectioruof ossifying carbik^e at the Epiphysis. fcl- Fifc*. Diagrams showing the fprmationcf the Thighbone ■ «#M' 1^7 Parietal ~bor\£Or'a~Fcebus, Rfe.9. 6) ' • Epiphysis. i Bows of cartilage cells in calcified matrix. c Tubular spaces filled with osteoblastic tissue. d Circumferential crust of porous bone. * General medullary cavity. Periosteum. (The dark spots throughout the diagram represent osteoblasts.) DIAGRAM OF A LONGITUDINAL SECTION OF FCETAL LONG BONE. by the slender remains (trabecule) of the calcified matrix. These slender remains serve as the foundation upon which the true bone is laid, and by which its cancellous architecture is directed. For the more minute observation of the process of ossification in cartilage, it is best to take the ' line of ossification ' at the epiphysis of a long bone. The drawing (fig. 1, Plate III.) is intended to illustrate it. 32 OSSIFICATION Near the top of the drawing the cartilage cells are seen en- larged and arranged in rows (b). The calcified matrix, represented by a darker tint, lies not only between the rows, but, to a certain extent, between the cells, so that it makes transverse as well as vertical septa between them. A little lower, we see the tubular spaces, filled with the bone-building materials, namely, osteoblastic tissue and blood-vessels. The blood-vessels form loops along the line of ossification, where the osteoblasts, having absorbed the transverse septa of calcified matrix, are invading the cartilage cells which disappear. We see how the tubular spaces are formed by the vertical remains (trabecular) of the calcified matrix ; how these spaces communicate here and there with each other where their walls have been absorbed ; how the remains (trabecular) of the calcified matrix form a basis upon which the osteoblasts have formed bone. Experiments with madder. — That bones grow in thick- ness by additions to their surface, and not by interstitial de- posit, is proved from the interesting experiments made with madder. It was accidentally discovered by Mr. Belchier, that madder tinges the bones red. He gives the following account of the circumstances under which the discovery was made. 1 * He happened to be dining with a calico-printer on a leg of fresh pork, and was surprised to observe that the bones, instead of being white, as usual, were red. On making inquiry, he found that the pig had been fed on the refuse of the dyeing vats, which contained a large quantity of the colouring substance of madder. This fact naturally attracted the attention of physiologists. The red tinge was found to be communicated much more quickly to the bones of growing animals than to those full-grown. The bones of a young pigeon were tinged a rose colour in twenty-four hours. In the adult bird it took fifteen days to do it. The effect of madder upon bones depends upon this : The colouring principle of the madder (Eubia tinctorum) has a strong affinity for phosphate of lime. It appears, however, that the vegetable dye does not combine with the matrix already formed, but only with that which is actually forming. Therefore, since the dye tinges only the most recent de- posit of bone, it is possible to produce alternate rings of white a d^u °8 o% A'jnuq sgigqpia yao giq^s °s £<\ no pgoqs dT30-qm[S gq!} joi iroi^Tod v ngq& 'jq 'umg^sotrad Jieq^ o^ pa^oanuoo qi^s 8Jre : yex{\ Awe 9Aonigi o^ ^on yqSuo qm. 'guoq jo s^uotuS'B^ gsooj a:re 9iaq^ eieqM. 'am^u-n punodmoo jo es'eo 13 xij -s^ubo n'BiSJraA'Bjj ^ngo-BJqns qv^ ui sj9SS9A-poojq gq!). tnoxj !Uigmqsunon !)ugpinns eAuap A'bwl yt gsneogq 'gq> fyuvssaDdu yon qm !)j •SuiA'p jo qsii ^•B9a§ nn.i qm 9noq ijugo'BJqns gq!) jo ^"ed B '9uoq 13 jo goi3j.ms 9V$ raojjf as'Egsip 30 Ainfat A'q pgqo^gp eq 0!) uma!)SOi.igd jo noi^od "& gsoddng 'Tnng^BOijgd gq!) jo gnfBA gq!) ye 3[Ooq; •saydni'exg M.gj •e gAiS oj •mgq;) jo ^uani^gj^ ^noi^i '■ Grooves formin6 With the Ethmoid bone the internal orbital foramina., Drawn on Stone by T. Go dart. FrcEQ^aSjjre Vy L.Holden. Printed by WeatJIewmanit) Co. FKONTAL BONE 49 bella ' or ' nasion.' Just below the articular surface for the nasal bones, to be presently described, the mid-line juts forwards and downwards as a prominent projection termed the ' nasal spine.' This process is convex from side to side superiorly, also rough and articular for the nasal bones to rest upon. Inferiorly it is concave transversely, marked in the middle line by an antero- posterior groove for articulation with the vertical plate of the ethmoid, and on each side of this a smooth narrow surface help- ing to make the roof of the nasal cavities. Tracing the surface from below upwards on each side of the middle line, we notice first one half of the ' nasal notch.' This, with the other half, makes a rough serrated surface, arching in front of the roof of the nasal spine, and articulating internally with the nasal bones and externally with the nasal processes of the superior maxillaries. The outer extremity of the notch is termed the 'internal angular process,' for articulation with the lachrymal bone. Arching upwards and outwards from this pro- cess to terminate in a thicker projection externally — the ' external angular process,' for articulation with the malar bone — is the ' supra-orbital arch.' It is thick and rounded in the male, thin and clean cut in the female. Near the junction of the inner and middle thirds of the arch is the ' supra-orbital notch,' or it may be ' foramen,' for the transmission of the supra-orbital nerve, At the external angular process is the starting point of the ' temporal ridge.' This ridge is sharp and prominent inferiorly, arches forwards, upwards and then backwards, and becomes con- tinuous with the corresponding ridge on the parietal. It gives attachment to the temporal fascia, and below it is a small surface of bone which contributes to form the ' temporal fossa ' for the origin of the temporal muscle. Above the supra-orbital arch we notice a slight parallel depression, and above that an arched eminence termed the ' supraciliary ridge,' highest internally, where it is called the ' nasal eminence.' The supraciliary ridges and nasal eminences do not correspond to prominences of the brain, but are occasioned by air-cavities termed the ' frontal cells ' or ' sinuses,' situated between the two ' tables ' of the skull. And here it may be well to mention, that the cap of the skull consists 50 FRONTAL BONE ■ of two layers of compact bone, called, respectively, the outer and inner ' tables ' of the skull, and separated by an intermediate cancellous tissue termed the ' diploe.' We shall allude to the advantage of this structure hereafter (skull as a whole, fig. 20) ; meantime, observe that the frontal cells are formed by the separa- tion of these tables. To see the extent of the cells, one ought to make vertical sections as shown in Plate XXIII. • The Frontal Sinuses.— There are some points of interest, about the frontal sinuses. 1. They communicate freely with each nostril through a canal termed the ' infundibulum ' (fig. 2) ; therefore it is possible for foreign bodies to reach them from the exterior of the body. 2. As they are lined by a continuation of the same mucous membrane which lines all the other passages of the nose, we have a ready explanation of the aching pain in the forehead in cases of influenza, or a common head cold. 3. In cases of fracture of the base of the skull involving the walls of the cells, it is possible for fragments of the brain to escape from the nose. The author has seen a case of this kind where the patient recovered without any permanent ill-effects except partial loss of smell. 4. If the outer wall of the cells be injured by violence or disease, the air, in sneezing or coughing, is liable to escape under the skin of the forehead ; this condition is called '■ surgical emphysema.' 22 5. They not only contribute to the light- ness of the skull, but increase the resonance of the voice. They ■do not begin to be developed until about the second year, and. steadily increase in size afterwards. Even in Europeans then- size and extent vary exceedingly. A good idea may be formed of their size in some persons, by the fact that they may lodge a musket ball. A soldier was wounded at the battle of Talavera by a ball which struck him on the forehead and lodged in the frontal sinus. It was readily removed by enlarging the opening, and the man recovered. 23 The author has seen a case precisely similar, in a soldier who was wounded in the Crimea. The sinuses are commonly separated by a bony partition, often incomplete. The eminences or ' bumps ' are not prominent in children, because the tables of the skull do not begin to separate to any great extent before puberty. From an examination of more than.. FRONTAL BONE 51 100 skulls, it appears that the absence of the external pro- minence, even in middle age, does not necessarily imply the absence of the sinus itself, since it may be formed by a retro- cession of the inner table of the skull. In old persons, as a rule, when the sinuses enlarge, it is by the inner table encroaching on the brain-case. The skull wall follows the shrinking brain. The range of the sinuses may extend even more than halfway up the forehead, and backwards for an inch or more along the orbital plate of the bone. Sometimes one sinus is larger than the other, and consequently the ' bump ' on one side of the forehead may naturally be more prominent than that of the other. In the Nor. Hum. Ost. Ser. (Nos. 153 to 155) in the Museum of the Eoyal College of Surgeons, there is an instructive collection of horizontal sections through the frontal bone at the level of the sinuses. In a specimen from a man set. 32, it may be observed that though the sinuses are very extensive, there is no external protuberance. In another from a man set. 47, there are no sinuses, yet there is a great external protuberance. No doubt the supraciliary ridges, with overlying eyebrows, form a great protection for the delicate structures contained in the orbital cavities situated beneath them. They are better marked in the male than in the female. Above each supraciliary ridge we have a shallow groove, and above that an eminence called the ' frontal eminence.' This is the point from which each half of the bone was originally formed, and is therefore more prominent in a child's skull. Above the frontal eminence the anterior surface of the frontal bone is smooth and covered by the ' occipito- frontalis ' muscle. Posterior or Cerebral Surface (Plate VII. fig. 2). — The posterior surface of the vertical portion is concave, especially opposite the frontal eminences, when ,the surface presents what are called the ' frontal fossae.' It is marked by depressions for the convolutions of the brain, by tiny grooves for the anterior meningeal and, laterally, by larger grooves for branches of the middle meningeal arteries. In the middle line is a ' groove for the superior longitudinal sinus.' Trace the groove down, and seethat its margins gradually approximate and lead to a narrow I! 2 52 FEONTAL BONE notch made into a foramen by the apposition of the ethmoid bone. The foramen is termed the ' foramen cascum.' It sometimes leads into the frontal sinus, sometimes directly into the nose ; or it may open on the posterior or anterior surface of the nasal bones. Though called ' blind,' it generally transmits a small vein from the longitudinal sinus into the frontal cells ; sometimes it con- tains a small artery. Very often the margins of the groove for the longitudinal sinus coalesce, so as to form a small ridge — the ' crista frontis ' — before they reach the foramen caecum. They give attachment to a perpendicular sheet of the dura mater (termed, from its shape, the ' falx cerebri '), which separates the hemispheres of the cerebrum. Therefore, when we see a frontal bone with a well-marked ridge along the beginning of the longitu- dinal groove, it is but the ossification of part of this fibrous mem- brane. Pieces of bone occasionally occur in the falx cerebri, which remind us of the tentorium cerebelli in some Carnivora, as tigers, seals, and cats, in which the tentorium is for the most part bony instead of membranous (Nos. 4608 and 4483). On either side of the groove for the superior longitudinal sinus are numerous irregular pits for the reception of Pacchionian bodies. POSTBEIOB BOEDEE OF THE VEETICAL POETION. This border is thick, deeply serrated, and bevelled somewhat at the expense of the posterior surface superiorly ; thin, sharp, and bevelled at the expense of the anterior surface inferiorly. In its upper three- fourths it articulates with the parietal bones, thereby helping to form the ' coronal suture,' and in its lower fourth with the anterior margins of the greater wings of the sphenoid bone. Supeeioe Angle.— This angle of the vertical plate is situated at the ' bregma ' of the skull. It is an obtuse one, received into the retiring angle formed by the anterior borders of the two parietal bones. The point in the coronal suture where the temporal ridges of the frontal and parietal meet, we call the ' stephanion.' The point situated in the mid-line of the anterior surface of the vertical plate in the narrowest part of the forehead and in a cross line drawn between the parts of the temporal ridges, which approach nearest one another, we call the ' ophryon ' or ' supra-orbital point.' FRONTAL BONE 53 Between this point and the ' occipital point ' we measure both the length and the circumference of the cranium. By the occipital point, we mean a point in the mid-line of the occiput farthest away from the ophryon. The horizontal portion of the frontal we divide into a single mesial ' ethmoidal notch ' and two lateral ' orbital plates.' Ethmoidal Notch.— The orbital plates are separated by a wide gap, called the ' ethmoidal notch ,' because it receives the cribriform plate of the ethmoid bone, which here fits into the base of the skull. (Plate XIX.) On each side of the irregular margins of the notch, observe the incomplete cells with thin walls. These cells correspond with, and are closed in front by the lachrymal, and behind by the ethmoidal cells. (Plate XI. fig. 2.) The largest cell of all is in the front, and this, as seen in Plate VII. fig. 2, leads into the frontal sinus. All of them are filled with air, and lined by mucous membrane continuous with that of the nose. At the fore part of the ethmoidal notch we notice the under surface of the 'nasal spine,' and on each side of it, the 'nasal' and 'ethmoidal notches' are continuous with one another. Situated among the half-cells on each side of the ethmoidal notch we have two trans- verse and parallel grooves, converted into canals by the apposition of the ethmoid bone, and named respectively the ' anterior and posterior orbital ' or ' ethmoidal grooves.' The anterior transmits the nasal branch of the ophthalmic division of the fifth nerve and the anterior ethmoidal artery and vein ; the posterior, the pos- terior ethmoidal artery and vein. Orbital Plates. — Each ' orbital plate ' extends horizontally backwards, and forms a concave roof for the corresponding orbit, and a part of the anterior fossa of the cranium. Hold it to the light, and observe how thin it is. In extreme old age, when the diploe of the skull becomes absorbed, the orbital plates have some- times, though rarely, large holes in them. At any time of life their thinness renders them liable to be perforated by sharp instruments thrust into the orbit. Wounds of the brain from such accidents are sometimes met with. We may describe each plate as being triangular in shape, and as having an inferior or orbital surface, a superior or cerebral 54 FBONIAL BONE surface, an anterior, an inner and an outer border, an inner, an outer, and a posterior angle. Inferior or orbital surface. — The long axis of this surface is backwards and inwards. It is smooth and concave all over, especially externally, under cover of the outer angle, where it shows a smooth fossa called the ' lachrymal fossa,' for the lodgment of the lachrymal gland. We notice small grooves for arteries and a few small nutrient foramina. About midway between the supra-orbital notch and the internal angular pro- cess, and a little behind the orbital margin, is a small depression — in some bones, a slight eminence — for the attachment of the pulley of the ' superior oblique ' muscle. The superior or cerebral surface is arched upwards and marked by a number of smooth but prominent ridges fitting the sulci on the under sur- face of that part of the frontal lobe of the brain. The anterior border has already been described as the supra-orbital arch. The internal border forms the outer margin of the ethmoidal notch, and shows an irregular sharp articular outline, situated hi which is the commencement of the anterior and of the posterior eth- moidal groove. The external border is rough and serrated to arti- culate with the great wing of the sphenoid. The internal and external angles have been already described as the internal and external angular processes. The posterior angle, more a border than an angle, runs forwards and inwards, and is serrated for articulation with the anterior border of the lesser wing of the sphenoid bone. The frontal bone has attached to the inner parts of the supra- orbital arches the frontal bellies of the ' orbicularis palpebra- rum ; ' to the inner ends of the supracilkry ridges the ' corru- gator supercilii muscles ; ' and to the surface of bone below the temporal ridges, the ' temporal ' muscles. Connections.— The frontal is connected with twelve bones, of which two, the sphenoid and ethmoid, are single. It is united to the two parietal bones by the < fronto-parietal ' or ' coronal suture.' (Plate XVIII. fig. 2.) Concerning this suture, see how admirably it locks the bones together, and secures the arch of the skull. The margin of the frontal bone is bevelled at the expense FRONTAL BONE '55 of its inner table above, of its outer table below : and the parietal bone is adapted accordingly. The lower half of its temporal margin unites with the greater wing of the sphenoid. Its ex- ternal angular process is connected to the malar bone ; its internal angular process to the nasal bone and nasal process of the superior maxillary. Its orbital plate is connected to the sphenoid, ethmoid, and lachrymal bones. Look well into the orbits and see these several connections. They form a continuous suture from one external angular process to the other. This is called the ' transverse frontal suture.' Ossification. — The frontal bone is developed from two centres, which appear one on each side, in the situation of the frontal eminence, about the seventh week of foetal life. These lateral halves meet and form a vertical suture down the middle of the forehead, termed the ' frontal ' suture ; so that in children the two halves of the bone are easily separated. Usually this suture becomes obliterated during the second year ; but sometimes -traces of it persist, as seen in the skull Plate XVIII. ; hence the practical rule not to mistake it for a fracture. 24 Comparative Osteology. — In some animals, such as the Carnivora (see skull of tiger), the temporal muscle extends so far forwards that there is no room for articulation between the malar bone and the external angular process of the frontal. Thus, m these skulls the temporal fossa and the orbit are not separated by bone as in man. This character runs throughout the Carnivora, Eodentia, Edentata, and Pachyderrnata. In some animals the air-cells are very numerous and large.- Let anyone who, admir- ing the intelligence of the elephant, imagines him to have a huge brain, put his hand into the foramen magnum of the skull which stands on the pedestal in the Mus. Eoy. Coll. Surg, and explore the cranial cavity. He will find that this forms but a small portion of the size of the head. And now looking at the sections of the skulls in the case behind it, he will see that the larger part of the skull is formed by cells or air spaces between the tables of the frontal, parietal, and occipital bones, which often separate the inner and outer tables of the skull to the extent of a foot. These make a vast increase in the size of the skull— an 56 FBONTAL BONE increass of advantage, however, as it affords additional leverage for those muscles which are inserted into the back of the skull, and raise the massive head, including the trunk, tusks, and jaws. The place to aim at in this animal is just above the root of the trunk, where the case of the brain is not much thicker than a shilling. These sinuses are also well developed in the owl and the giraffe. In the great extinct sloths the upper, back, and side walls of the cranium were thus inflated with air ; so that in these instances the brain is protected by a double skull, with air between the two. This modification not only lightened the skull, but protected the brain from the falling trees uprooted for food by these animals. The horns of animals such as oxen, sheep, and antelopes, con- sist of a horny sheath supported upon a long mass of bone which grows from the surface of the frontal bone. These horns last the lifetime of the animal, excepting, indeed, in the case of the prong-horned antelope at the Zoological Gardens, which has twice shed its horns (No. 1419). The antlers of the deer consist entirely of bone, and grow from a projection on the frontal bone, and are shed annually : even the Wapiti deer sheds its huge antlers every year, and the extinct Irish elk formed no exception to this rule. Antlers are very vascular, and are covered by a vascular membrane, termed the ' velvet,' until the full growth, when they lose the ' velvet,' and are themselves ultimately shed. The horn of the rhinoceros is simply horny, and has no shaft of bone in its interior. TEMPORAL BONE. (Plate VIII.) This bone occupies the temples. It is a complicated bone, even on the surface ; much more so in its interior, because it includes the organ of hearing. It consists of three parts— a squamous portion, situated in the temple ; a mastoid, forming the little projection behind the ear ; and a petrous, which contains the organ of hearing, and projects like a wedge into the base of PLATE Vliv portion Mastoid foramen Scjuamous portion, Di^astricus Mastoid process Vaginal Process ■Zygoma., Tubercle of Zygoma.,! Eminentia. articvilari?. Glenoid cavity. Glenoid fissure, S^I^^H 'strous portion. .Meatus auditor ius externus. Styloid process, Middle meningeal artery Zygoma SujF Petrosal sinus Meatus auditoTius interaw ^ ■,.■■,-, --.^pr _ Mlfe! Carotid canal Acjuecliietus. cochlear A-queductus vestibuli SLylo-pha-ryngeus Drawn on Stone "by T. Godarfc. From nature "by L .Holden. Printed "by West, Newman &Co. TEMPORAL BONE 57 -the skull. This division is very convenient ; but the natural divi- sions of the bone are : (1) the squamo-zygomatic ; (2) theperiotic, comprising the petrous and mastoid ; and (3) the tympanic, or small ring of bone which surrounds the membrana tympani, and by its outward growth comes to form the greater part of the external auditory passage. These parts are separate in the human foetus, and permanently so in many of the lower animals. Squamous Portion. — The squamous portion, named from its scale-like appearance, forms part of the wall of the temple. It is very thin ; hence the danger of a blow here. We divide the ' squamous portion ' into an external and an internal surface, with a circumferential border. External Surface. — At the lower part of the surface there is an outgrowth of bone, termed the ' zygoma ' (£vya>/u,a, a bolt or bar). It projects horizontally forwards, and can be easily felt on the side of the face. It is connected by a strongly serrated suture, running from below and behind upwards and forwards, to a similar projection from the malar bone ; so that the two together form an arch, from whose under border and inner surface the ' masseter ' muscle arises, and beneath which the * temporal ' muscle plays. (Plate XV. fig. 2.) The base of the zygoma is very broad, and appears to spring by two roots inclosing the ' glenoid ' cavity, which cavity forms the socket for the lower jaw. At the point of junction of the two roots, there is a tubercle for the attachment of the external lateral ligament of the lower jaw joint. The anterior root is the main one. It is very broad and strong, and forms the front boundary of the glenoid cavity. It is called the 'eminentia articularis,' and near its inner extremity it gives off a rough ridge which passes horizontally forwards to become continuous with a similar rough ridge on the great wing of the sphenoid. The ' eminentia articularis ' is crusted with cartilage in the recent state, and forms an additional surface for the play of the lower jaw. Under ordinary circumstances -the condyle of the lower jaw is in the glenoid cavity ; but while the mouth is opening widely, the condyle can be felt sliding 80 far forward that the finger can be placed into the socket 58 teMpokal bone behind it. In fits of laughter or yawning, the condyles may be suddenly dragged in front of the articular eminences by the muscles, and then the jaw is dislocated into the zygomatic fossa. Under such circumstances the person presents a very ridiculous appearance, since the mouth remains wide open until the dis- location is reduced. The posterior root runs backwards in the same line as the zygoma, and forms the upper boundary of the glenoid cavity. It then divides into two branches : one, the ' supra-mastoid ridge,' passes over the meatus auditorius externus and then fades away, marking the line of separation between the squamous and mastoid divisions of the bone ; the other, short and thick, runs inwards and slightly backwards to terminate in front of the ' Glaserian fissure,' and in front of the ' tympanic plate ' of bone, which separates the glenoid cavity from the external auditory meatus. This branch shows a slight process, the ' post-glenoid process,' which affords support to the jaw, and guards against dislocation backwards. The post-glenoid process is generally well marked in African skulls, and always so in the gorilla, the animal which approaches man so nearly. In the negro race, the supramastoid ridge is strongly marked, and is characteristic of a degraded type of skull (see two Tasmanian skulls, Nor. Hum. Ost. Nos. 1096-1097). Arising by these roots the zygoma passes horizontally out- wards, and then twisting upon its axis passes horizontally forwards. The surfaces of the first part are upper and lower, and of the second inner and outer. The glenoid fossa is a deep oval depression, with its long axis directed forwards, outwards, and a little downwards. It is divided into an anterior and external articular portion, and a posterior and internal non-articular portion, by a fissure termed the ' Glaserian fissure,' running inwards and slightly forwards, and indicating the separation between the squamous and tympanic parts of the bone. The part in front of the fissure is the socket for the jaw, and notice that the bottom of this part is exceedingly thin : the part behind it is occupied by a lobe of the parotid salivary gland, and is formed by the < tympanic and vaginal plates of the temporal TEMPORAL BONE 59 bone. Pass a bristle up the fissure, to see that it leads to the tympanum of the ear. The Glaserian fissure contains the ' pro- cessus gracilis ' of the ' malleus,' the tympanic artery, and is usually said to transmit the ' chorda tympani ' nerve ; but this nerve, strictly speaking, runs through a little canal, opening from above and behind into the under aspect of the middle third of the fissure, and termed the ' canal of Huguier.' Above the zygoma the external surface of the squamous por- tion is smooth. It is marked by a few grooves for branches of the deep temporal arteries, helps to form the 'temporal fossa,' and gives origin to part of the temporal muscle. Internal Surface. — The internal surface of the squamous portion is marked by the convolutions of the brain, and by a narrow groove which sweeps, in a curved direction, from before backward, indicating the course of the posterior branch of the middle meningeal artery. (Plate VIII. fig. 2.) Circumferential Border. — The circumference behind, above, and slightly in front, is thin, sharp, serrated, and very much bevelled at the expense of the inner surface for articulation with the parietal. The greater part of the front is thick, serrated, and somewhat bevelled at the expense of the outer surface for articu- lation with the great wing of the sphenoid. Mastoid Portion. — The mastoid portion forms the promi- nence of bone which is felt behind the ear, and termed the ' mastoid process ' (paa-Tos, a nipple). It gives insertion and great lever- age to some of the muscles which move the head round. We shall describe it, as we did the squamous part, as having an external and an internal surface and a general circumference. External Surface. — This surface is rough all over, and is prolonged inferiorly into the conical projection called the ' mas- toid process.' At the upper and back part of the surface is a hole, called the 'mastoid foramen,' through which a vein runs from the lateral sinus to the outside of the head. This explains why leeches applied behind the ears may help to relieve congestion of the brain. Frequently this foramen is situated in the suture between the mastoid portion and the occipital, and sometimes it is absent altogether. The outer surface of the mastoid portion gives 60 TEMPOBAL BONE attachment above and in front to the ' sterno-cleido-mastoid,' below and behind it to the ' splenius capitis,' and below and behind the splenius to the ' trachelo-mastoid ' muscle. (Plate VIII. fig. 1.) As one would expect, the mastoid process is much more fully developed in the male than in the female. If a section be made through the process, it is found to contain large and freely communicating cells, termed ' mastoid,' which open into the back part of the middle ear, or tympanum. These cells, like the tympanum itself, contain warm air, which is admitted from the upper part of the pharynx through the ' Eustachian tube.' They not only make the bone light, but are useful to the sense of hearing, by allowing more space for the vibration of the air. They are not developed till the approach of puberty. The mastoid cells, as a whole, are sometimes termed the ' mastoid antrum.' Inteenal Subface. — The internal surface of the mastoid portion is divided into an upper, or intra- cranial, and a lower, or extra-cranial, portion by a narrow serrated surface for articulation with the occipital bone. The intra-cranial portion is smooth, presents posteriorly a slightly concave space for the cerebellum, with one or two small grooves on it for posterior meningeal arteries, and anteriorly a half-groove, made a whole one by the junction of a corresponding half- groove on the posterior surface of the petrous portion, for the lodgment of the lateral sinus. In this groove we notice the inner aspect of the mastoid foramen, if it be present. The extra-cranial portion is formed mostly by the inner surface of the ' mastoid process,' and presents from above downwards a shallow, smooth, narrow, anteroposterior groove' for the occipital artery, and below and outside that a deep, rough, broad antero-posterior one for the attachment of the posterior belly of the ' digastric ' muscle. Ciecumpeeence.— Superiorly the circumference runs pretty straight from before backwards, and is thick and serrated for articulation with the parietal bone. Posteriorly and inferiorly it runs downwards and forwards, and is slightly serrated for articu- lation with the occipital bone. Anteriorly and internally the mastoid portion is continuous with the petrous part. The point TEMPORAL BONE 61 of meeting of the superior-posterior angle of the mastoid portion with the lateral angle of the occipital and the posterior-inferior angle of the parietal we call the asterion. Petrous Portion.— The ' petrous portion ' derives its name from the hardness of its constituent bone (irsTpos, a rock). It projects from behind forwards, inwards, and slightly upwards into the base of the skull (Plate XIX.), and so carries far out of harm's way the delicate organ of hearing which it contains. Its shape is like a triangular pyramid with the apex inwards ; so that, for descriptive purposes, it may conveniently be divided into three surfaces — an anterior, a posterior, and an inferior : three borders — anterior, superior, and posterior : then there is a base and an apex. Our best plan is to examine each of these parts separately, that we may be able to answer the question, what is seen on the anterior, what on the posterior surface, and so forth. Take the base first. Base. — At the base of the petrous portion is the orifice of the passage to the ear, termed the ' meatus auditorius externus.' It is situated immediately behind the glenoid cavity, and its boun- daries are chiefly formed by a curved plate of bone, called the ' processus auditorus,' or ' tympanic plate.' Observe, first, that the edge of it is very jagged, for the attachment of the cartilage of the ear ; and then look carefully down the passage to see that this curved plate of bone forms its boundary wall all round, except at the uppermost part. This inspection will probably suggest that the whole plate is something superadded to the rest of the bone — a sort of after-growth ; which is precisely the case. In the foetus there is no meatus, but simply a ring of bone forming three-fourths of a circle, the deficiency being at the upper part. This ring is ossified independently about the third month, is quite distinct from the other parts, and to it is attached the membrane of the drum of the ear (membrana tympani) ; so fhat at this early period it might be rudely compared to a hoop with a membrane stretched across it. In many animals this remains permanently a distinct bone, under the name of the ' tympanic bone.' (Plate XVIII. fig. 5.) In process of time, however, the hoop begins to grow out on its external side, and .£2 TEMPORAL BONE thus becomes a. canal or meatus, which, as it grows longer, gradually coalesces with the other constituents of the bone, and runs forwards and inwards. Eespecting the shape of the passage, observe that it is oval, with the long diameter directed downwards and backwards; therefore all specula used for examining the ear ought to be of the like shape. The narrowest part of the passage, in the recent state, is about the middle ; hence if a foreign body, such as a pea, happen to get into the ear, it is generally pushed through the narrow part by clumsy efforts to extract it, and then the moisture of the ear causes it to swell, and makes its extraction most difficult and painful. In its course the external auditory canal is slightly arched upwards and backwards as it passes forwards and inwards. It is limited at its inner end by the ' membrana tympani,' which is attached to it in such a way that it strikes the anterior and inferior walls of the passage at an angle of 45° ; therefore the longest part of the external auditory canal is the line of junction between its anterior and inferior walls. Apex. — The apex of the petrous portion is cut obliquely, so as to articulate by a slightly serrated surface with the side of the basilar portion of the occipital bone, and to bound the ' foramen lacerum medium ' behind and outside. It presents the anterior opening of the ' carotid canal.' Anterior Surface. — The anterior surface (Plate IX. fig. 2) of the petrous portion forms part of the middle cerebral fossa, and bears cerebral impressions and small grooves for meningeal arteries. About the middle of it is a smooth eminence running forwards and outwards, indicating the position of the ' anterior semicircular canal' (a part of the internal ear). Anterior and internal to this is an elevation with a depression in front, corresponding to the roof of the middle ear or ' tympanum.' More forward is a small furrow leading backwards and outwards to an opening termed the ' hiatus Fallopii' for the passage of the 'great superficial petrosal' nerve. Immediately to the front and the outside of this is a smaller furrow and opening which give passage to the ' small superficial petrosal ' nerve. Near TEMPORAL BONE 63 tHe apex is a depression ' for the ' Gasserian ganglion,' and in front, and external to this, is the irregular upper opening of the 'carotid canal.' In most bones, at the line of union between this surface and the inner surface of the squamous portion, one sees the remains of the suture between the petrous and squamo-zygo- matic parts of the bone. '. Posterior Surface. — The posterior', surface of the petrous portion forms part of the posterior fossa of the base of the skull. It looks backwards, inwards, and upwards. (Plate XIX.) The most prominent object upon it is the ' meatus auditorus internus ' (Plate VIII. fig. 2), a large canal which runs nearly horizontally outwards and transmits the ' seventh ' nerve, which consists of the auditory nerve (portio mollis), and the motor nerve of the face (portio dura), with the pars intermedia of Wrisberg. It also transmits the auditory artery, a branch of the basilar. The meatus is much larger than the nerves which it transmits, the space between them and the bony canal being filled by a fluid (cerebro-spinal) , which surrounds and supports the brain. In fractures through the base of the skull involving the meatus, the fluid sometimes oozes out through the external ear : this, there- fore, is regarded as. a very grave symptom in cases of injuries to the head. A transverse section near the bottom of the meatus would show that it is divided by a small ridge of bone into two unequal parts, as seen in Plate LVIII. In the upper and smaller of the two is the commencement of a special canal (aqufeductus Pallopii) for the motor nerve of the face ; in the lower there are several minute apertures arranged in a spiral form. About a quarter of an inch behind the meatus is a slit-like opening which looks backwards, and is termed the ' aqumcluctus vestibuli.' This, though about a quarter of an inch long, soon contracts so much that it will barely admit a bristle. It leads to the vestibule of the internal ear. Between these two openings, and just under cover of the upper border, is a small hollow, with a little opening at the bottom, for the transmission of a process of dura mater and a small vein. Below the meatus auditorius internus we frequently see part of the ' aquseductus cochleae,' better, however, seen on the inferior surface, and 64 TEMPORAL BONE leading into the cochlear part of- the internal ear. Externally we notice a smooth half-groove, made into a whole one by the fusion of the corresponding half-groove upon the mastoid portion, for the transmission of the lateral sinus. Inferior Surface. — The inferior surface of the petrous portion presents an irregular aspect, and has many holes in it. (Plate IX. fig. 1.) Beginning near the base, notice, first, the ' auricular fissure ' separating the processus auditorius from the mastoid process, and transmitting a small blood-vessel ; next the ' styloid process,' so called from its resemblance to an ancient ' style ' or pen. It is, originally, distinct from the rest of the bone, but gradually has coalesced with it by the end of the third year. This long ' process ' descends with a slight inclination forwards, and gradually tapers to a sharp point. Its length varies in different skulls : generally it is about half an inch long. In old skulls it is sometimes longer : there is a skull in the museum of St. Bartholomew's Hospital which has a styloid process three inches long. It gives origin to three muscles and two ligaments. The muscles are for the movement of the tongue and pharynx ; they arise as follows ; the ' stylo-pharyngeus,' from the inner side of the base ; the ' stylo-hyoideus,' from the posterior side of the base ; and the ' stylo-glossus,' from the front of the process. (Plate VIII. fig. 1.) To the tip itself is attached the ' stylo-hyoid ligament,' which runs downward and forward to the lesser cornu of the os hyoides. The other ligament attached to the process is the ' stylo-maxillary,' which separates the sub- maxillary from the parotid gland. Lastly, the fore part of the root of the styloid process is surrounded by a kind of bony sheath, termed the ' vaginal process,' about which there is nothing to be remarked except that it is a continuation of the plate of bone which forms the hinder part of the glenoid cavity. Between the mastoid and the styloid processes is a hole termed the ' stylo-mastoid foramen.' (Plate IX. fig. 1.) It gives exit to the motor nerve of the face (portio dura), which entered the bone at the meatus auditorius internus. The stylo-mastoid artery, a branch of the posterior auricular, enters at the fora- men of the same name, and supplies the tympanum. If you intro- PLATE IX. Glenoid cavity. Glenoid fissure Mastoid process ...•Canal fbrTensor tympani. ■loo\ nere for ^r Processus Cochlear! fbrmis. ■■•.. '"Eustachian tube, Carotid canal. ,A_quecluctus cochlea. -Foramen tWJa^obson's nerve. Jugular Cossa. .Foramen f or /VrnoTol's nerve . . Stylomastoid foramen . .Groove For occipital arbery. Digastric fossa,. Mastoid foramen. TEMPORAL BONE. Groove for middle meningeal artery. Foramen for less Petrosal nerve Hiatus Kllop Depression. jasEerian. ^an^Tion. '.Eminence-oF Sup* Semicircular cana\ . SupT Petrosal smu Drecwn on Stone "by T. Go dart. From nature WL.Holden Printed ty West.Newman &Co. TEMPORAL BONE g5 duee a stiff bristle into the hole, you will probably succeed in passing it through the bony canal traversed by the nerve from its entrance to its exit. The canal is a complete tube of bone, called the ' aqueductus Fallopii ' 26 after the anatomist who first described it. (Plate LVIII.) The passage of this nerve through the tem- poral bone renders it liable to be injured in fractures of the base of the skull, or in disease of the ear ; and this explains the para- lysis of one side of the face which sometimes occurs under these •circumstances. On the inner side of the stylo-mastoid foramen is a four-sided, articular, and slightly serrated surface for articu- lation of the upper surface of the jugular process of the occipital bone, and called the 'jugular surface.' In front of this is a deep smooth depression, termed the ' jugular fossa.' This, with a corre- sponding part of the occipital bone, forms the ' foramen lacerum posterius.' (Plate XX.) Here the lateral sinus pours its blood into ihe commencement of the internal jugular vein, which forms a great bulge and fills the fossa. Here also the glossopharyngeal, pneumogastric, and spinal accessory nerves leave the skull (through a notch, it may be a foramen, in the front of the foramen lacerum; and here, one of the posterior meningeal arteries, a branch of the ascending pharyngeal (perhaps also a branch of the occipital) enters it, and the inferior petrosal sinus leaves it. On the outer wall of the jugular fossa, near the root of the styloid pro- cess, we find the minute foramen which transmits the auricular branch of the pneumogastric or Arnold's nerve. Anterior and internal to the jugular notch is the large circular commencement of the canal in the petrous bone, through which the carotid artery enters the skull ('carotid canal'). The canal mounts nearly perpendicularly for a short distance, and then, turning for- wards, upwards, and inwards, emerges at the apex of the bone. At the bend between the vertical and horizontal portions of the carotid canal, and situated on its upper wall, we see a small foramen for the smallest petrosal nerve. On the plate sepa- rating the jugular notch from the carotid canal is a minute hole, which transmits the tympanic branch of the glosso-pharyngeal (' Jacobson's nerve ') . Anterior and internal to the jugular notch, •and close to the posterior border of the petrous portion, is a F gg TEMPORAL BONE wide-mouthed foramen, sometimes partially seen on the pos- terior surface of the petrous bone, and which is the lower opening of the ' aqueductus cochlese,' a canal leading into the cochlear portion of the internal ear. Near the apex is a rough surface, which gives origin, close to the anterior border, to the 'tensor tympani,' and in the rest of its extent, to the ' levator palati.' Anterior Border.— This is partly free and partly attached. The attached part is continuous with the squamous portion, perhaps showing the remains of a suture indicating their original separation. The free portion runs forwards and inwards, is slightly serrated, and articulates with the great wing of the sphenoid bone. If we look at the angle between this free part and the adjacent serrated border of the squamous part, we shall observe two tubes running backwards and outwards parallel to each other, like a double-barrelled gun (except that they He one above the other) : they both lead to the tympanum. The upper of the two is the canal for the ' tensor tympani ' muscle ; the lower, which is by far the larger, is the ' Eustachian tube,' or the passage which conveys the air from the pharynx to the tym- panum. The thin partition which separates the two barrels is called the ' processus cochleariformis.' Just below the lower barrel is the anterior end of the Glaserian fissure. The Superior Border has a smooth narrow groove running along it for the superior petrosal sinus. The Posterior Border presents, from behind forwards, the lower end of the groove for the lateral sinus, next the posterior and internal border of the surface for articulation with the jugu- lar process of the occipital, next the similar part of the jugular notch, next, perhaps, part of the lower opening of the aqueductuB cochlese, next a smooth half-groove, made a whole one by the apposition of a corresponding one on the occipital bone, and lastly, parallel with the last, a rough serrated articular surface for articulation with the basilar portion of the occipital bone. In the recent state, the 'meatus auditorius externus' has its inner end closed by a membrane, ' membrana tympani,' on the inner side of which is a six-sided air chamber, called the ' tympanum.' It contains a series of ossicles, ' ossicula auditus,' TEMPORAL BONE 67 (Plate LVIIL), whose duty it is to convey the oscillations of the membrana tympani to the fluid lying in a complicated cavity, the ' bony labyrinth,' situated in the petrous portion of the temporal bone. Cavity of the Tympanum.— This is an irregular cube flattened from within outwards (narrowest below), and presenting, accordingly, external, anterior, posterior, superior, inferior, and internal walls or surfaces. The external surface is formed by the membrana tympani, and near its upper border in front are small openings for the chorda tympani nerve and the processus gracilis of the malleus. The anterior surface shows a large opening below, the ' Eusta- chian tube,' by which air can pass in and out from the pharynx ; and above, a thin-walled channel with an orifice at its extremity for the passage of the ' tensor tympani ' muscle. The posterior surface presents openings leading into the air- filled cells of the mastoid process. The superior surface is smooth — the bone forming it is very thin, and in cases of suppurative inflammation of the tympanum presents little impediment to the extension of the inflammation to the parts above. The inferior surface is the narrowest of all, and shows no- features of importance. The inner surface shows an upward extension of the tympanum separated by very thin bone from the cavity of the cranium. At the lower border of this extension is a thin layer of bone which divides the tympanic chamber from the ' aqueductus Pallopii.' Below this is an oval opening, the ' fenestra ovalis,' to the border of which the base of the stapes is attached by ligament. In front of this fenestra, and projecting outwards into the tympanum, is the canal in which the ' tensor tympani ' is lodged. Behind is a conical eminence, the ' pyramid,' in which arises the ' sta- pedius ' muscle, a small opening at the extremity of the emi- nence giving passage to its tendon. Below and a little behind the fenestra ovalis is the ' fenestra rotunda,' closed in the fresh state by membrane. It is partially concealed by the backward projection of an anterior lip of bone, which is continuous with a gg TEMPORAL BONE rounded projection in front, called the ' promontory.' The surface of the promontory is marked by grooves for the tympanic plexus of nerves. Osslcula Auditus. — Of these there are three, viz. Malleus, Incus, and Stapes. See Plate LVIII. Malleus.— This bone is attached by its two processes, ' pro- cessus brevis ' and ' longus,' to the membrana tympani. A slender process, ' processus gracilis,' projects downwards, inwards, and forwards, at right angles to the latter. It is lodged in the Glaserian fissure, but is commonly atrophied and lost in early life. Above these processes is the ' neck,' to the posterior surface of which, at its junction with the ' processus longus,' the ' tensor tympani' is attached. The neck expands above into a sub- globular head, directed upwards, and elongated from before backwards. The external and posterior sides of the head articu- late with two converging articular facets upon the anterior surface of the incus. Incus. — This bone presents a broad, backwardly directed pro- cess, the ' processus brevis,' which has a minute notch on its inner border near its posterior extremity. At right angles to the processus brevis the ' processus longus,' having a slightly sigmoid curve, passes downwards and inwards. Its inuer ex- tremity turns abruptly upwards, and is continuous with a small rounded nodule of bone, called the ' os orbiculare,' which small nodule is flattened from above downwards and articulates with the head of the stapes. Stapes. — This appropriately named bone consists of a ' head,' bearing a shallow concave articular surface inferiorly for articu- lation with the os orbiculare of the incus. On the posterior surface of the head a small bony process gives insertion to the ' stapedius ' muscle. From the head spring two ' crura,' hol- lowed out on their apposing surfaces, the ' anterior crus ' being slender, the ' posterior ' more robust, and showing a knee-like thickening at one point. The 'base' is borne by the upper extremities of the crura, and fits into the fenestra ovalis on the inner wall of the tympanum. It is oval in form, but its inner or inferior border is nearly straight. The anterior extremity of TEMPORAL BONE 69 the base is frequently more pointed than the posterior, and the surfaces are slightly concave in the centre, with an elevated and rounded circumferential border. Bony Labyrinth. — This highly complicated chamber lies concealed in the substance of the petrous portion of the temporal bone. At birth its walls are formed by a special thin layer of bone, having the vascular and foetal bone surrounding it. At this period, with care, the porous bone can be removed from the proper wall of the labyrinth, so that the form of the latter may be distinguished. (See Plate LVIII.) In adult life, the great density of the petrous bone renders this impossible. Its form is closely adapted to that of a membranous bag, the ' membranous labyrinth,' which is lodged in its interior, and is surrounded by fluid over the greater part of its surface. On certain parts of this bag the auditory nerve is distributed. If such a bony labyrinth be examined from its inner sur- face (Plate LVIII.), it will be seen to consist of three parts, viz. (1) a central irregular chamber, the ' vestibule? (2) three ' semi- circular canals ' and the ' common canal ' connected with the roof of the vestibule, (3) in front a snail-shell-like chamber, the cochlea. The vestibule shows on its inner surface in front two bulgings corresponding with depressions of its interior. The upper of these is the ' fovea hemi-elliptica,' and lodges the dilated anterior extremity of a part of the membranous labyrinth, the ' recessus utriculi ; ' the lower is the ' fovea hemispherica,' and is occupied by the * sacculus ' part of the same bag. A ridge of bone, ' crista vestibuli,' separates these two depressions. Above the vestibule are the three ' semicircular canals,' best named anterior, posterior, and horizontal. They lie in the three sides of a cube, and each has at one extremity a dilatation called the 'ampulla.' These bony canals contain portions of the membranous labyrinth, having similar names. The posterior extremity of the anterior canal and the anterior extremity of the posterior one open into a larger tube, spoken of as the ' common canal.' This common tube lodges a part of the membranous laby- rinth, best considered as the ' sinus superioris utriculi.' In the 70 TEMPORAL BONE inner wall of the common canal is a minute passage, the ' aque- ductus vestibuli,' opening below into the vestibule, and above into the cranial cavity. This aqueduct contains a blood-vessel and an exceedingly delicate tube, ' ductus endolymphaticus,' which terminates above in a blind and somewhat dilated ex- tremity, the ' saccus endolymphaticus,' and below divides into two branches, of which one opens into the ' sacculus,' and the other into the ' utriculus.' The ductus endolymphaticus is interesting, as it is the remains of the inpushing of the outer surface of the embryo, from which the epithelial lining of the membranous labyrinth is derived. The cochlea forms a spiral of two turns and a half round a hollow bony axis, the ' modiolus.' The axis is directed outwards, forwards, and slightly downwards in a plane parallel to that of the anterior semicircular canal. The commencement of the cochlea, as it bulges outwards into the tympanum, contributes to the formation of the promontory. A bony plate, the ' lamina spiralis ossea,' attached to the modiolus, partially divides the cavity of the cochlea into two passages, the division being com- pleted in the fresh state by a membrane, called the ' lamina spiralis membranacea vel membrana basilaris.' The posterior of these passages is the ' scala tympani,' which would open into the tympanic cavity, in the fresh state, at the fenestra rotunda, if that opening were not closed by membrane. The anterior pas- sage is divided by membrane, the ' membrane of Eeissner,' into two ; and of these the one nearest the modiolus is known as the ' scala vestibuli,' and opens into the vestibule ; the other, farthest from the modiolus, is called the ' scala media,' or ' ductus cochlea;.' The scala media terminates in a blind end at the top of the cochlea, whilst in the vestibule it is continuous with the sacculus by means of a fine tube, named the ' canalis reuniens.' At the apex of the cochlea the ' scala vestibuli ' and the ' scala tympani ' communicate by a small hole, the ' helicotrema,' and at the same place the osseous lamina terminates in a hook-like process, termed the ' hamulus,' these parts being concealed be- neath the dome-like apex or ' cupola.' Connections.— The temporal is connected with five bones. TEMPORAL BONE 7] The squamous portion is connected to the parietal bone and the great wing of the sphenoid by the ' temporo-parietal ' and ' temporo-sphenoidal ' sutures respectively, concerning which the following mechanism must be noticed ; namely, that the squamous part overlaps the parietal above, but is itself overlapped by the sphenoid below— an arrangement which greatly contributes to the security of the arch of the skull. The mastoid part is con- nected, above, to the posterior inferior angle of the parietal by the ' masto-parietal ' suture, and, behind, to the occipital by the ' masto-occipital ' suture. The petrous part is wedged into the base of the skull between the sphenoid and occipital bones. (Plate XIX.) The zygomatic process is connected to the malar bone by a strong suture, the ' zygomatic,' which slopes down- wards and backwards. Lastly, the glenoid cavity articulates with one of the condyles of the lower jaw. In the living sub- ject, an inter-articular fibro-cartilage, lined above and below by synovial membrane, separates the two articular surfaces, and protects this part of the skull from the effects of a blow under the lower jaw. Ossification. — The development of the temporal is somewhat complicated. It is divided into the following parts : a squamo- zygomatic, a tympanic, and a petro-mastoid. The squamo-zygo- matic starts from a nucleus of ossification which appears in membrane at the lower part of the squamous portion^' J»...X ^,. i e p„ TEMPORAL BONE 73. Notice the immense zygomatic arch in the skeleton of the manatee. (No. 2729.) In all the Mammalia, and in them alone, the lower jaw arti- culates directly with the temporal bone. By referring to No. 12 in the Nor. Hum. Ost. the tympanic bone and membrane in the foetus may be seen at the base of the skull. The fissura Glaseri is open widely, and the processus gracilis of the malleus lies in it. In all Mammalia the malleus remains very small and becomes cut off from the glenoid cavity by the outgrowth of the tympanic bone ; but in birds (see Sep. Ser.) the malleus becomes largely developed, projects between the squamous and tympanic bones, and, under the name of ' quadrate bone,' comes to support and form the articulation for the lower jaw. SPHENOID BONE. (Plates X. XI.) Constituent Parts. — The sphenoid bone is so called because it is wedged in at the base of the skull between all the other bones of the cranium (crrjv, a wedge, slSos, form). As it not only enters into the formation of the base of the skull, the orbits, the temples, and the nasal passages, but is connected with all the bones of the cranium, and many of those of the face, one cannot be surprised that it is a difficult bone ■ to understand. Fortunately, it bears a remarkable resemblance to a bat with ex- tended wings ; so that we can shape our description accordingly. It presents, then — 1. A body, or central part; 2. The two greater wings ; 3. The two lesser wings ; 4. The pterygoid pro- cesses, which make the two legs of the bat. Body : Six Surfaces. — Commencing with the body, we must examine its six surfaces — a 'superior' and an 'inferior,' an ' anterior' and a ' posterior,' and two ' lateral.' The Superior Surface of the body (Plate X. fig. 1) comprises wbat is seen of the body on the inside of the base of the skull. There is a deep depression in it, termed the ' pituitary fossa,' 74 SPHENOID BONE which lodges the ' pituitary ' body. 26 Another name given to it is the ' sella turcica,' from its resemblance to a Turkish saddle. In front of it is an eminence, termed the ' olivary process,' from its olive-like shape. This process supports the commissure of the optic nerve which makes a slight transverse groove (the ' optic groove ') upon it, leading on each side to the ' optic foramen ' through which the nerve enters the orbit. In front of the olivary process is a smooth and slightly concave surface, which supports the olfactory lobes, and terminates, in front, in the middle line in the ' ethmoidal spine,' which articulates with the ethmoid bone. Each side of the surface is more or less distinctly marked by a broad groove which winds upwards in a gentle curve, and lodges the internal carotid artery as it passes through the ' cavernous sinus, after entering the skull. In some bones a little tubercle, called the ' middle clinoid process,' rises from the side of the groove. In some skulls this tubercle is long enough to unite with the apex of the anterior clinoid process, so that the artery, in emerging from the groove, passes through a ring of bone. The anterior and posterior clinoid processes give attachment to the ' tentorium cerebelli.' The pituitary fossa is bounded behind by a square plate of bone, which, as it represents the back of the saddle, is termed the ' dorsum sellae.' The corners of the plate project and form what are called the ' posterior clinoid processes,' thus named from their fancied resemblance to bedposts. These are directly opposite to the 'anterior clinoid processes,' of which we shall speak presently. The posterior surface of the plate slopes very obliquely backwards, is continuous with the basilar process of the occipital bone, and forms an inclined plane which supports the ' pons varolii.' Lastly, in the side of the plate there is generally a notch which transmits the sixth nerve. The Posterioe Sueface of the body is connected with the basilar process of the occipital bone, in young subjects by carti- lage, in older ones by bone, so that after twenty-one or twenty- two it is impossible to separate the ' basilar suture ' without the saw. The section shows well the structure of this part of the base of the skull ; namely, two layers of compact tissue separated by about t V of an inch of cancellous, with a thin layer of com- SPHENOID BONE 75 pact bone forming the side walls. Thus the bone is light, and shocks transmitted to the base of the skull are broken. (Plate XI. fig. 1.) Anterior Surface. — The anterior surface of the body (Plate X. fig. 2) fits the posterior part of the ethmoid bone. It presents in the middle line a perpendicular ridge termed the ' sphenoidal ' or ' ethmoidal crest ' for articulation with the posterior border of the vertical plate of the ethmoid. It forms part of the bony sep- tum of the nose, and terminates below in the anterior end of the ' rostrum ' for articulation with the vomer, as may be seen hi Plate XXIII. fig. 1. On each side of this is a smooth surface help- ing to make the roof of the nasal fossa. In the upper part of each of these smooth surfaces is a rounded opening leading into the sphenoidal sinus, and external to each is an irregular serrated surface for articulation with the posterior surface of the lateral mass of the ethmoid and orbital process of the palate bone. The surface of bone we have described on each side of the eth- moidal crest is made by two plates, one on each side, termed the ' cornua sphenoidalia,' or ' sphenoidal turbinated bones.' Although apparently integral parts of the sphenoid, yet these little bones are formed each from a special centre of ossification, distinct in early life, and remain separable till adult age. The annexed drawing (fig. 10) shows the ' cornua sphenoidalia ' removed in a perfect state. The rostrum of the sphenoid would fit into the gap between them. Each cornu is triangular with the apex down- wards. Each completely walls in the sphenoidal cell of its own side, except at the upper part, where there is a round opening in the base of the cornu which admits air from the upper meatus of the nose. Pig. 11 represents one of the cornua seen from the surface towards the sphenoidal cell. It shows the thin scales of bone which project into the cell and assist in lining its walls. However, it is right to state that these cornua sphenoidalia are rarely met with perfect. In consequence of their coalescence with the Fig. 10. Fia. 11. CORNUA SPHENOIDALIA. >70 SPHENOID BONE sphenoid, ethmoid, and palate bones, they are generally broken in the process of separation, so that there appears in most sphe- noid bones a large irregular hole leading into the cell ; as shown on one side of Plate X. fig. 2. Next come the < sphenoidal cells ' or sinuses. These are large air-cavities in the body of the sphenoid, generally two in number, and separated by a more or less com- plete perpendicular partition. (Plate XXIII. figs. 1 and 2.) Like the other air-cells in the bones of the skull, they are not developed in young subjects ; but in the adult they gradually become large enough to excavate the whole body of the bone. The air is admitted freely into them from the upper meatus of the nose through an opening in the front wall of each sinus ; and they are lined with a prolongation from the nasal mucous membrane. This communication of the sphenoidal cells with the nasal cavities explains how bleeding from the nose may occur as a symptom of fracture through the base of the skull— that is, through the body of the sphenoid. Lastly, the sides of the anterior surface of the body are hollowed out into two or three small air-cells, one below the other. (Plate X. fig. 2.) Of these, the upper, one or more, are roofed by the posterior cells of the lateral mass of the ethmoid ; and the lower by the cell or cells in the orbital process of the palate bone. The Infeeiok Surface of the body (Plate XI. fig. 1) assists in forming the roof of the nasal fossa ; and the posterior part of the surface, continuous with the ' basilar surface ' of the occipital bone, looks towards the upper part of the pharynx, and may therefore be called the ' pharyngeal surface.' In the middle line we see the ' rostrum ' prominent anteriorly where it is continuous with the ethmoidal crest, but fading away posteriorly. Observe that it is expanded a little towards its base, and that it articulates with the upper border of the vomer. The mode of connection is rather singular. The rostrum fits into a deep cleft between the two plates or ' wings ' of the vomer, and thus serves as a foundation from which this bone passes forwards and forms the septum of the nose. But the chief thing to notice on this surface is a process or scale of bone which projects horizontally inwards, on each side, from the base of the internal pterygoid plate. These SPHENOID BONE 77 are termed the ' vaginal plates,* and their free edges rise enough to allow the alte or wings of the vomer to slide underneath them. Lastly, each of these plates is traversed by a small groove, made into a canal by the adjacent alee of the vomer and the sphenoidal processes of the palate, and termed the ' pterygo-palatine groove, ' and in the completed state ' canal,' for the passage of the pterygo- palatine vessels and nerve. Latebal Surfaces support at their anterior and superior angles the ' lesser wings,' each by two roots with the ' optic foramen ' between, and at their posterior and inferior angles the common roots of the ' greater wings ' and ' pterygoid processes.' Between the lesser and greater wings, on each lateral surface, we have the smooth base of the ' sphenoidal fissure,' and at the line of junction of the lateral surface with the upper surface of the body we have the groove for the cavernous sinus already described. Lesser Wing's. — The lesser wings (or orbito-sphenoids) pro- ject transversely from the upper part of each side of the body. (Plate X. fig. 1.) Their Uppee Surface is smooth and flat, and supports the frontal lobe of the brain ; their Lower Surface, also smooth, overhangs the sphenoidal fissure, and forms the back part of the roof of the orbit ; ' hence they are sometimes called the ' orbital wings.' Their Anterior borders are serrated, and articulate with the orbital plates of the frontal bone; their Posterior borders are free, and in life fit into the fissure of Sylvius. Their bases are traversed by the ' optic foramina,' through which pass the optic nerves and ophthalmic arteries into the orbit, and to the circumferences of which, anteriorly, muscles are attached as shown in' Plate X. fig. 3. The optic ' foramen ' should be described rather as a short ' canal ' directed outwards and forwards. Towards the ' sella turcica ' each wing projects, considerably, in the form of a blunt angle, termed the ' anterior clinoid process ; ' and between this and the body of the sphenoid there is either a deep notch or a complete ring for the internal carotid artery. Greater Wing's. — The greater wings, sometimes called the ' temporal wings ' or ' alisphenoids,' project from the ' lower and back part of each side of the body in common with the ' pterygoid 78 SPHENOID BONE processes.' Starting from the body, each great wing runs nearly horizontally outwards and then somewhat suddenly bends up- wards. It also extends back as a sharp projection called the ' spine of the sphenoid,' which fits into the retiring angle between the squamous and petrous portions of tbe temporal, and gives attachment inferiorly to the internal lateral ligament of the lower jaw, the ' tensor palati ' and ' tensor tympani ' muscles. Each wing presents three surfaces, viz. : Superior or Intra- cranial, Inferior or Extra-cranial, and Anterior or Orbital. The Superior or Intra-cranial Surface is concave in every direction, and presents a number of well-marked eminences with intervening depressions for the sulci and convolutions of the temporo-sphenoidal lobe of the brain. It is marked, also, by grooves for meningeal arteries, especially superiorly and inferiorly. We may sometimes see on the surface, in the neighbourhood of the sphenoidal fissure, and of the root of the wing, a few pits for Pacchionian bodies. Situated in a line, running forwards and inwards from the spinous process to the inner end of the sphenoidal fissure, are a number of foramina. Firstly, piercing the spinous process is the ' foramen spinosum ' for the passage of the ' middle meningeal artery.' This foramen will just admit the blunt end of an ordinary surgical probe. Secondly, we see the ' foramen ovale ' with the long axis of the oval directed for- wards and inwards, and measuring about a quarter of an inch in this axis. This hole transmits the third division of the fifth nerve, the small meningeal artery, and two or three emissary veins carrying blood from the cavernous sinus to the venous plexus situated outside the skull in this neighbourhood. Thirdly, we find usually one or more small holes, named the ' foramen ' or ' foramina of Vesalius,' opening inferiorly into the ' scaphoid ' or the ' pterygoid fossa ' or into both, and carrying emissary veins also. Lastly, we see the 'foramen rotundum,' more a canal than a foramen, running forwards and outwards to open into the spheno-maxillary fossa. This foramen transmits the second division of the fifth nerve, otherwise called the 'superior maxillary ' nerve. The Inferior or Extra-cranial Surface is divided into an SPHENOID BONE 79 upper or more or less vertical part, and a lower or more or less horizontal portion, by an antero-posterior ridge known as the ' infra-temporal crest,' ' pterygoid crest,' or ' horizontal ridge upon the great wing of the sphenoid.' The part above the crest is slightly concave in every direction, and helps to form the 'temporal fossa;' the part below is also slightly concave, and helps to form the 'zygomatic fossa,' and gives attachment to the ' external pterygoid ' muscle. Internally, the lower part of the extra-cranial surface shows the inferior aspects of the ' fora- men spinosum ' and ' foramen ovale.' The Anterior or Orbital Surface is a smooth, nearly flat, quadrilateral plate, looking forwards and inwards, and forming more than half of the outer wall of the orbit. (Plate XVI. fig. 2.) It shows a few smooth grooves for vessels, especially one near its inner side, which runs upwards and is continuous, over the upper border of the plate, with one of the deeper meningeal grooves, described as lying upon the upper part of the intra-cranial surface. Of the four borders of the plate, notice that the anterior or external slopes downwards and a little forwards, and is sharp and serrated for articulation with the orbital plate of the malar. The internal or posterior is continuous with the front of the common origin of the great wing and pterygoid process. The inferior is smooth, concave, and rather rounded, to make the upper margin of the ' spheno-maxillary fissure.' The superior is rough and serrated in its outer half for articulation with the frontal, and in its inner is smooth, sharp, and slopes downwards, backwards, and inwards to form the lower boundary of the ' sphenoidal fissure.' As the smooth part joins the rough part, this border shows the notch for the vessel already mentioned, and, about the middle of the smooth portion,, in well-marked bones, a slight projection for the outer head of the ' external rectus ' muscle is seen. As to the rest of the circumference of the greater wing : its upper part is thin, sharp, bevelled at the expense of the internal surface, and articulates with, or rather is applied to, the outer aspect of the anterior inferior angle of the parietal. Between the upper part and the spinous process the circum- §0 SPHENOID BONE ference is concave from above downwards, thin and bevelled at the expense of the outer surface above, thick and serrated and bevelled at the expense of the intra-cranial surface below, for articulation with the squamous portion of the temporal. Between the spinous process and the root of the wing the border runs nearly directly forwards and inwards; externally this part of the circumference is slightly serrated for articulation with the anterior border of the petrous portion of the temporal, while in- ternally it is non-articular and makes the front of the ' foramen lacerum medium.' Just as this part of the border joins the back of the root of the wing we notice that a process of bone projects backwards and outwards, for a variable distance, into the ' fora- men lacerum medium,' dividing it into a very much smaller outer part for the large superficial petrosal nerve, and a larger internal portion for the internal carotid artery. This process of bone is named the ' lingula sphenoidalis.' Immediately below the lingula we have the posterior end of the ' Vidian canal,' for the Vidian nerve. Sphenoidal Fissures. — Each greater wing is separated from the lesser one by a fissure, termed the ' sphenoidal fissure,' which has its long axis running upwards, outwards, and forwards, and is very much wider at its lower than at its upper end. The upper end is completed by a little piece of the frontal, and the fissure transmits nerves to the eye and its appendages. It gives passage to the third and fourth nerves, to the first or ophthalmic branch of the fifth, the sixth, a few filaments of the sympathetic nerve, and also to the ophthalmic vein. Pterygoid Processes — The ' pterygoid processes ' descend nearly perpendicularly from the under part of the bone, one on either side, and act as, buttresses which support the upper jaw bones. Each process consists of two parts, termed the ' internal ' and ' external pterygoid ' plates. These are united in front, but diverge from one another behind, forming a deep interval called the 'pterygoid fossa.' At its lower part the 'pterygoid fossa' presents a deep notch, which in the complete skull is filled up by the tuberosity of the palate bone. The external plate is broader than the internal, slopes outwards on its way backwards, and SPHENOID BONE 81 gives origin to the ' pterygoideus externus ' and the ' ptery- goideus internus ' muscles on its external and internal surfaces respectively. Its outer surface also forms part of the floor of the zygomatic fossa. Eespectirig the internal pterygoid plate, observe that it forms the lateral and part of the superior boundary of the posterior opening of the nose, and that it has a crescent-shaped margin above, leaving room for the cartilage of the Eustachian tube. At the root of the posterior border of this plate is a shallow groove called the ' scaphoid fossa,' which gives origin to the ' tensor palati ' muscle, the tendon of which plays round a notch on the ' hamular ' process projecting backwards and outwards from the lower end of the internal pterygoid plate. The hamular process gives attachment to the pterygo-maxillary ligament. Behind the last molar tooth we can distinctly feel this hamular process. Lastly, at the base of the internal pterygoid plate, we see the posterior end of the ' Vidian canal ' for the artery and nerve of the same name. The lower third of the posterior border of the internal pterygoid plate gives attachment to the ' superior constrictor of the pharynx.' Look now at the anterior aspect of the pterygoid process, and observe a plate of bone standing off like a side buttress connecting it with the greater wing. The plane of this plate nearly corre- sponds in direction with that of the orbital plate of the great wing. In their upper two-thirds the external and internal pterygoid plates are united anteriorly and form a smooth surface which constitutes the posterior wall of a deep fossa, termed the ' spheno-maxillary,' which, in the perfect skull, intervenes between the sphenoid and superior maxillary bones. At the upper extremity of this surface we see the anterior opening of the ' Vidian canal ' lying below and inside the anterior aspect of the 'foramen rotundum.' In the lower third the external and internal pterygoid plates diverge from one another; their anterior borders show serrated articular margins, convex from above downwards for articulation with correspondingly serrated grooves upon the ' tuberosity ' of the palate bone. Connections. — The sphenoid is connected with twelve bones, including all those of the cranium- and five of the face. The ' body ' g2 SPHENOID BONE is connected behind with the occipital bone by the basilar suture ; in front with the ethmoid bone, the two palate bones, and the vomer. The ' lesser wing ' is connected to the orbital plate of the frontal bone : the ' greater wing ' is connected to the orbital plate of the frontal by a rugged surface of considerable extent, to the anterior inferior angle of the parietal bone, to the squamous and petrous parts of the temporal bone; and to the malar bone. Lastly, the pterygoid processes are connected with the palate bones. 27 Ossification. — In the early foetus the sphenoid consists of several parts. Its centres of ossification appear in the base in the following way. (1) The presphenoid, consisting of the part of the body in front of the olivary eminence, and the lesser wings, is developed from two nuclei appearing outside the optic foramina and extending outwards so as to form the orbito- sphenoids or lesser wings. These nuclei appear about the eighth or ninth week, and join the basisphenoid or back part of the body about the seventh or eighth month. (2) The ali- sphenoids, consisting of the greater wings with the external pterygoid plates, are developed from nuclei which appear, one on each side, between the foramen rotundum and the foramen ovale about the eighth or ninth week, and join the body of the bone in the first year. (3) The basisphenoid or back part of the body is formed from two nuclei which appear, one on each side of the middle line, in the sella turcica about the eighth or ninth week, and which join one another about the fourth month, and the presphenoid part about the seventh or eighth month. (4) The hasitemporals or parts forming the linguls grow from two centres which appear just after the basisphenoids have joined one another, and which become connected with the basisphenoid part about the fifth month. (5) The internal pterygoid plates are developed from ossific nuclei deposited in membrane, appearing in the fourth month, and joining the external pterygoid plates in the fifth or sixth. The sphenoidal turbinated bones begin to be formed after birth, and join the body of the bone at puberty. Comparative Osteolog-y.— The top of the great wing of the- PLATE XI. Vidian canal. Scaphoid fossa . . Pterygoid fossa... Perpendicular plate AntTEthmo'idal cells. Post? Ethmoidal cells v Sujp T constrictor of Pharynx. .InFundibviVum. ...Crista, galll. .. Slit for theNasal Nerve. ..A'nif ethmoidal foramen . t?ose. ethmoidal foramen Hfc.2. Cribrifbrfn plate . ETHMOIDBONE PostTEthmoidal cells 5up^ Meatus Middle Meatus Unci form -process. ,.Sup? Sponbytone. .Middle Spongybone. Perpenolic ular plate . Drs From nature "by L.Holden. o. . 1 ■*ft*r f- Printed tyfcbt.Neww^i, Co. SPHENOID BONE 83 sphenoid, passing up between the frontal and temporal bones, articulates with the anterior inferior angle of the parietal bone. The union of these two bones separates the temporal from the frontal. In those types of men where the forehead slopes back- wards, these bones approximate, and in some cases actually articulate with each other. (Nor. Hum. Ost., Nos. 1159, 1160, 1161, and 1146.) The size and strength of the external pterygoid plate bear a direct relation to the development of the pterygoid muscles which cause the grinding movements of mastication ; consequently, it is highly developed in ruminants (see skulls of the deer and ox). In old skulls the sphenoidal cells often extend into part of the basilar process of the occipital bone. In the chimpanzee the sphenoidal cells extend far into the alisphenoid and pterygoid bones. THE ETHMOID BONE. (Plate XI. figs. 2 and 3.) Constituent Farts. — This remarkably light and spongy bone contains the organ of smell. It occupies the interval between the orbital plates of the frontal bone, and enters into the formation of the cranium, the orbit, and the nose. It appears, at first sight, complicated; but it is simple when one understands its plan. It consists of a 'horizontal plate,' which forms part of the base of the skull ; of a central ' perpendicular plate,' which forms part of the septum of the nose ; and of two ' lateral masses ' contain- ing the air-cells. Each of these must be examined separately. Horizontal or Cribriform Plate. — The horizontal plate fits into the ' notch ' between the orbital plates of the frontal bone, and completes the anterior fossa of the base of the skull. (Plate XIX.) It is called the 'cribriform plate' {cribrum, r)6fi6s, a sieve), because it is perforated by holes for the passage of the olfactory nerves. High above it rises a crest of bone, termed, from its resemblance to a cock's comb, the ' crista galli.' This, which is a continuation of the perpendicular plate, gradually rises G 2 84 ETHMOID BONE from behind, swells out as it proceeds, and, stopping suddenly short, presents two broken edges, with a groove between them, for articulation with the frontal bone. The groove contributes to form the ' foramen caecum.' The 'crista galli' serves for the attachment of the falx cerebri. It varies in size, and has often a slight lateral inclina- tion. Sometimes it contains an air-cell. On each side of the fore part of the crista galli is a long ' slit,' or rather a hole, for the passage of the nasal nerve (a branch of the first division of the fifth cranial nerve), which confers common sensation to the mucous membrane as well as the skin of the nose. The cribriform plate does not come up to the level of the lateral masses, but lies at the bottom of a deep groove (' olfactory groove '), which, being divided by the crista galli in the middle, forms in the perfect skull two recesses which lodge and support the olfactory bulbs of the brain. The foramina at the bottom are arranged on each side in two somewhat irregular rows — an inner and an outer. Pass bristles down these holes, and you will find that the inner lead into- olfactory grooves upon the upper part of the perpendicular plate, and the outer into grooves upon the inner surface of the superior and middle turbinated parts of the bone. By some anatomists a third set are situated midway between these two rows, simply passing through the cribriform plate and ramifying upon its under surface. These foramina and grooves lodge corresponding sets of olfactory nerves. Perpendicular Plate. — This plate descends from the cribri- form plate and assists in forming the septum of the nose. Notice the numerous grooves and perhaps minute canals in its upper third for the passage of the olfactory nerves. Its connections are well shown in Plate XXIII. fig. 1. Behind, it is connected along a sloping line with the ethmoidal crest of the sphenoid. Below, running downwards and forwards, it is very irregular for articulation with the vomer. In front it is divided into an upper and a lower part. The upper is the shorter, concave upwards and forwards, and shows a somewhat rough antero-posterior groove for articulation with the nasal spine of the frontal. The lower is the longer, slopes somewhat irregularly downwards and ETHMOID BONE 85 Fig. 12. backwards, and has two sharp edges with a rough intervening groove for the reception of the cartilage of the septum of the nose. Lateral Masses.— The lateral masses of the ethmoid (fig. 12) are made up of irregular air cells, surrounded by paper-like walls of bone, lined by mucous membrane continuous with that of the nose. Each lateral mass is suspended from the outer side of the horizontal plate, and when viewed as a whole forms a cubical figure with its concomitant six surfaces. The upper surface shows a number of incomplete cells roofed in by corresponding incomplete cells in the orbital plate of the frontal. The surface be- tween the cells is irregular and rough for articulation with the frontal, and in it we notice two parallel trans- verse grooves, one in front of the other, converted into canals in the united skull by the corresponding grooves on the orbital plate of the frontal, and thereby forming the ' anterior and posterior ethmoidal canals.' The an- terior transmits the nasal nerve and the anterior ethmoidal vessels ; the posterior gives passage to the posterior ethmoidal vessels. The anterior surface shows several half-cells completed mostly by the lachrymal, and slightly at the upper end by the nasal pro- cess of the superior maxillary. The posterior surface of the lateral mass is irregular and rough for articulation with the front of the body of the sphenoid and with the sphenoidal turbinated bone. It shows several irregular apertures leading into the posterior ethmoidal cells, communi- cating with the sphenoidal cells, and partly closed over by the sphenoidal turbinated bone. The inferior surface is very irregular, rough, and uneven, and TRANSVERSE SECTION, TO SHOW THE LATERAL AIR-CELLS OF THE ETHMOID BONE. 86 ETHMOID BONE articulates in front with the orbital plate of the superior maxil- lary, and behind with the orbital process of the palate bone. From the anterior part of the lower surface of the lateral mass an irregular plate of bone extends downwards and backwards, and terminates in a kind of hook ; hence it is called the ' unci- form process.' By referring to the inferior spongy bone it is seen that this process is connected with the inferior turbinated bone, and with the thin wall of the antrum of the superior maxillary bone ; it chiefly assists in narrowing the orifice of this great air-cavity. On the outer surface of each lateral mass the cells are closed by a smooth and four-sided plate of bone, termed the ' os planum,' belonging entirely to the ethmoid. This plate forms a large share of the inner wall of the orbit (Plate XXII.), where it is easy to learn its connections with the surrounding bones, by tracing the sutures between them. Its upper border articu- lates with the frontal, its lower with the superior maxillary and palate, its anterior with the lachrymal, and its posterior with the sphenoid. Lastly, notice the two notches on its upper border, which, with the frontal, form the ' anterior and posterior ethmoidal foramina,' leading into the canals of the same names. Turbinated Bones and Meatus. — On the inner aspect of the lateral mass we observe two thin plates of bone standing out, one below the other, and slightly curled, like a turbinated shell. These are the ' turbinated ' or ' spongy ' bones of the ethmoid (Plate XL fig. 3), and can be properly seen only in a divided skull. The ' superior ' is the smaller of the two, and does not reach so far forward as the other, which is called the ' middle,' because there is a third or ' inferior turbinated ' bone, still lower down in the nose ; but this does not belong to the ethmoid. The middle turbinated bone articulates with the ' superior turbinated crest ' of the superior maxillary. Now the spaces left between these turbinated bones and the lateral masses are called respec- tively the superior and middle ' meatus,' or passages of the nose. Each is distinct from the other, and leads to its own particular cavities, and to no other. The superior meatus being farther back than the middle, leads into the sphenoidal cells, and into the pos- ETHMOID BONE 87 terior ethmoidal cells. The middle meatus leads into the anterior ethmoidal cells, and also to the frontal sinus, along a funnel- shaped canal (' infundibulum ') which traverses the foremost of the ethmoidal. (Plate XXIII. fig. 2.) The middle turbinated bone articulates with the superior turbinated crest of the upper maxillary. Connections. — The ethmoid is connected with the following bones — namely, behind with the sphenoid (including the sphen- oidal turbinated bones) ; above with the frontal ; below with the two superior maxillary and two palate bones ; in front with the two lachrymal bones. The perpendicular plate is connected behind with the sphenoid, below with the vomer, and in front, with the nasal spine of the frontal. Lastly, the unciform process on each side is connected with the inferior spongy bone and the superior maxillary. Ossification. — Until the middle of foetal life the ethmoid is all cartilage. Ossification begins about the fourth or fifth month, from a centre for each of the lateral parts, and gradually extends into the two upper turbinated bones (ethmo-turbinals). Within a year after birth another centre appears for perpendicular and cribriform plates. In the foetus at birth there are no ethmoidal cells : these are not formed until the fifth year. Comparative Osteolog-y.— In man the rule is that there are three turbinated bones on each side ; sometimes there is a fourth, smaller than the rest, and higher up at the back part. This fourth bone is more frequently met with in some coloured races where the sense of smell is notoriously acute. The curled plates of the turbinated bones are covered by a very vascular membrane. The upper ones afford an extensive surface upon which the olfactory nerves are distributed after their passage through the cribriform plate. By the variation of the extent of surface o these bones it will be seen that the acuteness of the sense of smell and the capability of warming the air on its way through the nose to the lungs are regulated. The sense of smell is remarkably keen in the deer tribe anu carnivora, and their spongy bones are developed in proportion. ^ It is curious that they should both in a measure depend for a living 8g ETHMOID BONE upon the development of the same sense, the one to avoid its enemies, and the other to find its prey. The spongy bones on which the nerves of smell are distributed, and those which are only covered by a vascular membrane, are widely differentiated in their conformation in the lower animals. In the seal, for instance (Nos. 1064), which inhabits the arctic regions and necessarily breathes intensely cold air, the inferior spongy bones subdivide into a multitude of plates and afford a vast surface on which is distributed a profusion of blood-vessels which warm the air before entering the lungs. The surface of these bones has been estimated at about 120 square inches in each nostril ; a longitudinal section of such a nostril has the ap- pearance of being completely plugged by the convoluted warming plates of the lower spongy bone ; while those on which the olfac- tory nerves are distributed have a different form and are farther back and separated by a slight interval from the others. There is no ethmoid bone in serpents, but the olfactory filaments are spread out on a plicated mucous membrane. WORMIAN BONES. These are irregular pieces of bone, formed by separate centres of ossification and deposited frequently in the sutures between some of the cranial bones ; hence they are sometimes termed ' ossa suturarum.' We notice them as occurring most often in the lambdoidal and sagittal sutures. In the lambdoidal suture the superior angle of the occipital may be formed by one large or several small Wormian bones. Again, we may find several small ones lying in the lateral parts of the lambdoidal suture. The posterior inferior angle of the parietal may be formed by one, In the sagittal suture one, two, three, or more may occur. Occasionally one may be present in the anterior fontanelle forming the antero-superior angle of the parietal. Frequently a thin lamina termed the ' epiteric bone ' is present between the anteroinferior angle of the parietal and the great wing of the sphenoid. Earely we get a little one lying in the lesser wing of WORMIAN BONES 89 the sphenoid, and one or more very small ones in the suture "between the sphenoid and ethmoid bones. These are the chief seats of the ' ossa suturarum.' They may be found in the other sutures, although much less frequently. Ossification commences in these Wormian bones some time during the first year after birth. When we look at an adult skull and see such irregular pieces of bone, we must not ■conclude that these constitute the exact number which we might have observed had we been able to look at the same skull a year or so after birth, because some of these Wormian bones may appear and very soon afterwards form the bones of the skull they are nearest to, leaving no trace of the original separation in the fully formed state. To offer an explanation of the occur- rence of these ' suture bones ' is somewhat difficult. Professor Humphry says, in his work on ' The Human Skeleton : ' ' They are evidently stop-gaps developed in the membranous covering of the brain when the extension of the regular osseous nuclei is likely, for some reason, to be insufficient to cover-in the cranial cavity.' This explanation is borne out by what we see in certain diseased states of the skull, such as in Eickets and Hydro- cephalus. 90 SUPERIOR MAXILLARY BONE BONES OF THE FACE. There are fourteen bones of the face — namely, the two superior- maxillary, the two malar, the two nasal, the two lachrymal, the two inferior spongy, the two palate, the vomer, and the inferior- maxilla. SUPEEIOE MAXILLARY BONE. (Plate XII.) Constituent Parts.— This bone gives much character to the human face, and forms the greater part of its framework. It is exceedingly irregular in shape, and, besides forming sockets for the teeth, enters into the composition of the nose, the orbit, the cheek, and the palate. For convenience of description, we divide it into a 'body,' which is hollowed out into a large air-cavity, called the ' antrum of Highmore,' and four outstanding ' processes ' — namely, the ' alveolar,' which holds the teeth ; the ' palatine/ which forms part of the hard palate ; the ' nasal,' which assists hi forming the nose ; and the ' malar,' which helps to form the prominence of the cheek. Body. — Let us take the ' body ' first and learn its various relations well, for it is a part of great surgical interest, being liable to many diseases requiring surgical operations. The first thing to notice is that it is pyramidal in shape. The base of the pyramid looks inwards and helps to form the cavities of the nose and mouth. The apex of the pyramid is continuous with the malar process. The anterior surface looks towards the face ; the posterior looks towards the zygomatic fossa ; the superior looks towards the orbit. PLATE XII. SUPERIOR MA.XILLARY BONE. Lachrymal groove OVHciuus lTtfToculi. Orbital surface. pa-orbital canal — Malar iprooees-- Dental canals Tuberosity Nasal process. Tendo-oculi . Fig.l. Infra.-O'rbital fora-men. Compressor nstris. Depressor alae rif-xsi. Orloi>ju!;xri£ oris. Canine fbsea. Myrtiform fossa. Outer* Surface, B.tdbe'ftr middle sporty bone Lachrymal groove Bidj*far infr sp°nj>y bone Cells correspond! nfcto Ethmoid bone. T%2. Ant! 1 palatine canal Antf nasal spine Palate plate Posfc^paktinB c»nal . "Rou^lisurFate fcrPalate bone. Inner Surface. Drawn on Stone hy T. Godart. Printed hy 'West,Newma.Ti & Co. SUPEBIOB, MAXILLARY BONE 91 Base. — The base or inner surface of the body is partially divided into two unequal parts— an upper or nasal, and a lower or buccal — by the palatine process. The nasal and buccal portions- communicate with one another behind the palatine process. In the articulated skull they are separated from one another by the completion of the hard palate posteriorly by means of the palatine process of the palate bone. The first thing to notice on the nasal ■portion is the orifice of the antrum itself. (Plate XII. fig. 2.) In the separate bone this orifice is very irregular, and large enough to admit the end of a finger ; 28 but in the perfect skull (Plate XXII.) it is very much closed ha by thin plates from the ethmoid, the palate, and the inferior spongy bones. In the recent state the orifice, is generally so contracted by a fold of the mucous membrane of the nose, that it will only admit a crow-quill. The orifice is not near the bottom of the antrum, but very high up ; the consequence of this- is, that when fluid collects in the antrum it cannot run out until the antrum is nearly full, or until the head is inclined horizontally with the opposite cheek downwards. Above this orifice are a few half-cells completed by the lateral mass of the ethmoid, while running downwards and backwards from it below, to the outer end of the posterior border of the palatine process, is a fissure to- articulate with the 'maxillary process of the palate bone.' In front of and below the orifice of the antrum is a smooth surface, concave from above downwards, and slightly so from before backwards, helping to form the inferior meatus of the nose. Leading into this surface from above is the naso -lachrymal groove, and sepa- rating the surface from the inner surface of the nasal process is a rough ridge running forwards and downwards, for articulation with the inferior turbinated bone, and called the ' inferior tur- binated crest of the superior maxillary bone.' Behind and below the opening of the antrum the nasal surface is rough, for articu* lation with the vertical plate of the palate bone, and in this rough part is seen a smooth groove, called the ' posterior palatine groove,' and converted into a canal by the apposition of a cor- responding groove on the ' vertical plate ' of the palate, for the passage of the posterior palatine vessels and nerve. 92 SUPERIOR MAXILLARY BONE The buccal or oral portion, or the part below the palatine process, is rough, and marked by a large number of nutrient foramina. It is continuous inferiorly with the internal surface of the alveolar process, posteriorly and superiorly with the nasal portion, and anteriorly and superiorly with the inferior surface of the palatine process. At the line of junction between the palatine process and the buccal surface is a continuation of the posterior palatine groove already described. Apex. — The apex is continuous with the root of the malar process, to be presently described. Anterior Surface. — The anterior or facial surface is con- tinuous superiorly and anteriorly with the external surface of the nasal process ; inferiorly with the outer surface of the alveolar process ; posteriorly below the malar process with the zygomatic surface. It is divided into two fossas — an anterior or ' incisive ' or ' myrtiform,' and a posterior or ' canine ' — by a vertical ridge corresponding to the socket for the canine tooth, and called the ' canine ridge.' The incisive fossa gives attachment to the ' orbicularis oris,' the ' depressor alse nasi,' and the ' compressor naris.' The canine fossa lies behind the canine ridge, and is deeper in some skulls than in others. At its upper part, about a quarter of an inch below the margin of the orbit, and in the same vertical line as the upper second bicuspid tooth, is the ' infra-orbital foramen ' or termination of the ' infra-orbital canal,' which transmits the infra-orbital nerve and artery. Above this foramen we have the origin of the ' levator labii superioris,' and below it the origin of the ' levator anguli oris.' Posterior Surface. — The posterior or zygomatic surface bulges into the zygomatic fossa. 29 Above it is smooth, and below it is rough, and inferiorly may show a somewhat serrated surface for articulation with the tuberosity of the palate bone. On it we notice two or three foramina for the passage of superior dental nerves from the superior maxillary, descending palatine branches of Meckel's ganglion, and palatine branches of the internal maxillary artery. Superior Surface. — The superior or orbital surface looks up- wards and outwards, and enters into the formation of the floor SUPERIOR MAXILLARY BONE 9$ of the orbit. It is triangular in shape, with the base directed forwards. On the surface notice the ' infra-orbital canal,' for the passage of the superior maxillary nerve and infra-orbital artery. It commences behind as a groove, but soon becomes a canal, which terminates on the front wall of the antrum, just below the edge of the orbit. A little before its termination, the main canal gives off one or sometimes two smaller ones, termed the ' anterior dental canals.' These run down in the very sub- stance of the front wall of the antrum, and transmit blood-vessels and nerves to the two incisor and canine teeth, and send a branch inwards which carries a nerve to the fore part of the inferior meatus. Eunning down from the posterior end of the infra-orbital canal is another little channel in the posterior wall of the antrum, conveying the middle superior dental nerve to the bicuspid teeth. To see these canals it is necessary to intro- duce a bristle as a guide, and then to rasp away the external plate of the bone. Sometimes joining the anterior and posterior extremities of the infra-orbital canal is a suture extending along the orbital surface, and across the infra-orbital margin, indi- cating the imperfect closure of the roof of the infra-orbital canal. Close by the anterior internal corner of the orbital surface is a very slight depression (in some cases it may be a little eminence) for the origin of the ' inferior oblique ' muscle of the eyeball. Of the margins of the orbital surface, the anterior is smooth, non-articular, and somewhat sharp in its inner half, forming part of the infra-orbital margin, rough and serrated in its outer half, for articulation with the malar bone. The external is sharp and rough anteriorly for articulation with the ' orbital process ' of the malar, smooth and rounded posteriorly where it makes the lower margin of the ' spheno-maxillary fissure.' In the smooth part we notice the ' infra-orbital notch ' forming the commencement of the infra-orbital groovs. The internal margin presents, anteriorly, a smooth notch — the ' lachrymal notch ' — bounding the upper aperture of the naso-lachrymal canal externally ; behind that a serrated surface for articulation with the lower border of the lachrymal bone; behind that a longer serrated border, or rather a surface, with perhaps two or three half-cells in it, for g4 SUPERIOR MAXILLARY BONE articulation with the ethmoid ; and posterior to that a sloping oblique border, running downwards, outwards, and backwards, and bounding superiorly a rough concave surface for articulation with the orbital process of the palate bone. Antrum, Cavity of.— The ' maxillary sinus,' or ' antrum,' ™ is by far the largest of the air-cells in the bones of the head. It begins to be formed as a depression on the inner surface of the body about the fourth month. This depression gradually enlarges, so that at birth there is a very slight interval between the plates ■of bone forming the orbital and the other surfaces of the body. It is lined with mucous membrane, continuous with that of the nose, and is large enough to hold a musket-ball with ease. A ball has been known to lodge in the antrum for months, and •even for years, before it has been removed. 31 It varies in size and somewhat in shape in different persons ; but, as a rule, it has the form of a three-sided pyramid, with the base towards the nose, formed by the internal surface of the body, and the apex extending into the malar process. Its anterior wall supports the canine fossa, its posterior the zygomatic surface, and its superior the orbital surface of the body. Thin plates of bone often pro- ject into the antrum, making a kind of recess or pocket here and there ; 32 and the fangs of one or more of the molar teeth gene- rally project into it, either quite bare or covered by a thin scale of bone. Hence the practice, adopted by some surgeons, of drawing •one of these teeth (say the first or second molar) to let out matter from the antrum. Again, the fangs of decayed or otherwise injured molar teeth are liable to set up disease in the antrum ; and this is the explanation commonly given why morbid growths arise in the antrum more frequently than in any other of the air-cavities of the nose. The following case gives a good idea of the extent of the antrum : ' A lady suffering from toothache submitted to the extraction of the canine tooth of the upper jaw, with which a por- tion of the alveolar process was removed, making an aperture in the antrum, from which a watery fluid constantly issued. The patient, desirous of ascertaining the source of the discharge, took a pen, and, having stripped off the barbs from the feathered part, SUPERIOR MAXILLARY BONE 95 found that the whole of it, full six inches long, could be introduced into the cavity. At this she was greatly terrified, believing it must have gone into the brain. She consulted Highmore, who explained to her that the pen had turned spirally within the sinus, and he, be- sides, counselled her to submit with patience to the inconvenience of the discharge from the cavity,' 33 Alveolar Process and Teeth — The alveolar process is a thick and strong ridge of bone, curved so as to form with that of the other side the dental arch. It consists of two plates, an outer and an inner, connected by numerous septa which form the sockets (alveoli) of the teeth. The inner plate is the stronger ; therefore, in drawing a tooth, care should be taken to incline it a little outwards. The outer plate is marked by eminences corresponding to the fangs of the teeth, the eminence of the canine tooth being especially marked. In a child, from the end of the second to the end of the sixth year, the half of each jaw contains sockets for five teeth, i.e. for two incisors, one canine, and two molars. The formula for the ' milk dentition ' is therefore : .2 + 2 1 + 1 2 + 2 OA . ,, i. - , c , „ ■ m.- =20 m all. 2 + 2' 1 + 1 2 + 2 The half of each jaw contains, in the adult, sockets for eight teeth — namely, two ' incisors,' one ' canine,' two bicuspids (or ' prse-molars '), and three ' molars.' Thus the dental formula of the adult human skull is : .2 + 2 1 + 1 , 2 + 2 3 + 3 on ■ „ i. ^ , c. , b. or p.-^—, m. n - =32 in all. 2 + 2' 1 + 1' ^2 + 2' 3 + 3 The eruption of the second or permanent set of teeth commences about the end of the sixth year. The first to appear is the first permanent molar, which is therefore called the six-year-old tooth, and is the oldest tooth in the adult's head. Generally speaking, the twenty milk teeth are cut between the sixth and twenty-fourth months, and the thirty-two permanent teeth between the sixth and twenty-fourth years. 34 Sockets of Teeth.— The sockets correspond in number and size to the fangs of the teeth they receive. They vary in depth in 96 SUPERIOR MAXILLARY BOtfE different instances. The deepest of all is the socket of the canine tooth ; this is often -^ of an inch in depth in the dry bone. The first two molars of the upper jaw have three fangs each, and as many sockets. Of these fangs, two are external, and one inter- nal. In the last molar, or wisdom tooth, the fangs are generally consolidated into one. Irregularities in the shape and the direction of the fangs, whether diverging too much or converging, lead to unavoidable evils when it is necessary to extract them. Either a fang breaks, or part of the alveolus must be extracted with the fang. One cannot foresee this. At the bottom of each socket is a minute hole, through which the vessels and nerve come up and supply the pulp in the cavity of the tooth. There are also numerous holes in the bony partitions between the sockets, through which vessels supply the gums and the perio- steum. These are the sources of the bleeding after the extraction of a tooth. The teeth are fixed not only by the closely fitting socket, but also by the very vascular membrane, the periosteum, which lines the socket and adheres closely to the fang. This periosteum not only retains the teeth in their places, but helps to maintain their vitality, and, being elastic, breaks shocks which would otherwise be communicated to the jaws. When the dental periosteum inflames, the tooth is partly lifted out of its socket, and the teeth cannot be clenched without pain. If the inflamma- tion goes on to the formation of matter, the periosteum quits its hold of more or less of the fang, and abscess in the socket is the result. The matter then makes its way out by the side of the tooth, or through a small hole formed by ulceration in the alveolar wall — that is, a gumboil is the result. In the dry bones, most of the teeth fall out, because the periosteum shrinks, and thus the sockets become too large. The alveolar process gives origin (Plate XII. fig. 1) to the ' buccinator ' above the three molar teeth. Nasal Process — The nasal process ascends nearly per- pendicularly, in a line with the canine tooth, and abuts, by means of a very rough suture, upon the internal angular process of the frontal bone. It supports the nasal bone, and con- tributes to form the inner margin of the orbit. SUPERIOR MAXILLARY BONE 97 The process is flattened from within outwards, and is nar- tower from before backwards than from above downwards. It presents external and internal surfaces with superior, inferior, anterior, and posterior borders. The external surface is slightly concave in every direction, marked by a number of vascular foramina, and gives origin to the ' orbicularis palpebrarum ' and the ' levator labii superioris alseque nasi.' The internal surface enters into the formation of the nasal cavity and presents from above downwards, first, a smooth surface which, with the fore part of the lateral mass of the ethmoid, helps to form a few of the anterior ethmoidal cells, next a rough antero-posterior ridge, or it may be a surface, and termed the ' superior turbinated crest of the superior maxillary,' for articulation with the inferior tur- binated process of the ethmoid, or the middle turbinated bone of the nasal fossa. Below this is a smooth shallow antero-posterior groove, helping to form the middle meatus of the nose, and bounded below by the rough antero-posterior ' inferior turbinated crest ' for articulation with the inferior turbinated bone. The superior border of the nasal process is thick, deeply serrated, and articulates with the nasal notch of the frontal bone. The free part of the inferior border is thin, sharp, irregular, runs downwards, outwards, and backwards, helping to form the side of the anterior opening of the nose. The attached part is continuous with the body of the bone. The anterior border runs downwards, outwards, and forwards, and is thick and bevelled at the expense of the outer surface above, thin and bevelled at the expense of the inner surface below, for articulation with the outer border of the nasal bone. The posterior border is more a surface than a border, and presents a groove running downwards, outwards, and backwards, called the ' lachrymal groove,' lodging the ' naso-lachrymal sac ' and the ' naso-lachrymal duct.' The anterior lip of the groove is smooth and rounded above, sharper and more prominent below, is continuous with the anterior margin of the orbital surface of the body, and helps to make the inner margin of the orbit. The posterior Up is smooth and flattened at its upper end where it helps to complete the anterior ethmoidal cells, sharp and rough in the rest of its extent for articulation with the anterior border of 98 SUPERIOR MAXILLARt ; BONE the lachrymal bone. The ' lachrymal ' groove is converted into a canal in the lower half-inch of its course by the lachrymal and inferior turbinated bones, and is about the size of a very small goose-quill. When, from inflammation or other cause — such as a tumour — the canal becomes obstructed, the tears necessarily flow over and run down the cheek. To obviate this, it is often requisite to slit up one of the lachrymal canaliculi and introduce a probe into the naso-lachrymal duct. : Therefore one must know well the direction of the lachrymal canal. It runs from above downwards, and slightly backwards, and outwards. The anterior lip of the groove gives attachment to fibres of the 'orbicularis palpebrarum,' with the 'tendo oculi,' or 'palpebrarum,' between them. Palatine Process. — The palatine process extends horizontally inwards, and forms the anterior two-thirds of one half of the hard palate and floor of the nose, the posterior third being com- pleted by the palate bone. It is slightly arched from before backwards, and is thicker in front near the alveolus than behind^ The process is four-sided, with an upper or nasal and a lower or palatine surface. The upper surface is smooth, concave from side to side, slightly so from before backwards, and helps to make the floor of the nasal fossa. Near the anterior part of its inner side we see a large foramen, the 'incisor foramen,' or 'foramen of Stenson,' leading downwards and slightly forwards into a deep groove, seen in the inner border of the palatine process, and termed the ' anterior palatine groove ' (in the articulated skull, the anterior palatine canal). The incisor foramen transmits blood-vessels, and is the remains of a communication between the nose and mouth — a condition well seen in the skulls of carnivora. In young superior maxillary bones, and sometimes in adult ones, we see a faint line running towards the front of the socket for the canine tooth, and named the ' incisor fissure,' or ' incisive suture.' The lower surface of the palatine process is very rough and marked by a number of vascular foramina. Ex- ternally it helps to form the ' posterior palatine groove ' with the inner surface of the body of the bone. At the fore part of the surface, and situated on the inner border j is the ' anterior palatine SUPEBIOR .MAXILLARY BONB -99 groove,' with the incisor foramen opening into its. upper end, and at the anterior and posterior extremities of the itipper end. of the groove two little notches formed by little grooves— the 'grooves of Scarpa' — on the inner .border- of the process.- Always in young bones, and sometimes remaining persistent in fully formed skulls — never, however, extending across the alveolar border — is the lower aspect of the incisive suture, already, seen on the upper surface and limiting the so-called ' premaxillary bone ' posteri- orly. The anterior border of the palatine process- is smooth, concave from side to side, and usually grooved in the same direction, and forms one-half of the lower margin of the anterior opening of the nose.. It is continuous with the upper border of the incisive fossa of the body of the bone. The posterior border is thin, sharp, serrated, beyelled at the expense of the upper sur- Fig. 13. e is° rs ' jrf lPs<£~r^\ ( Foramina of Scarpa J^ 1 ' -\r^ \\ 1/ )/*V sx"' j for Naso-palatine f \ y^jX\-JJ-""y^''^ Nerves. . . . ~-V^-— fK3*^-2L-- J Foramina of Stenson ■^^■~^> X r^'~1y^Y\ " "' for Blood-vessels. Incisive Suture. UNDER- VIEW OF FORE PABI OF HARD PALATE. face, and articulates with the horizontal plate of the- : palate bone. The internal border shows a number of parallel vertical rough sharp ridges, with corresponding grooves between, for arti- culation with the opposite bone. Above, the border rises towards the nose in a half-crest, made a whole one by the apposition of the opposite bone, to articulate with the vomer- and form the base of the bony septum of the nose. (Plate XXIII. fig. 1.) This half-crest projects fowards, and, by joining with the correspond- ing part of the opposite bone, makes the ' anterior nasal spine,' to which is attached the cartilaginous part of the nasal septum. The root of the anterior nasal spine is called the ' subnasal point ' by craniologists. On the inner border we see, too, the .' anterior and posterior grooves of Scarpa' (converted into -canals- by the 100 SUPERIOR MAXILLARY BONE apposition of the vomer and the corresponding parts of the opposite bone), leading into the anterior palatine groove. The anterior is usually the larger of the two grooves of Scarpa, and transmits the left naso-palatine nerve ; the posterior is usually the smaller, and transmits the right naso-palatine nerve. This ar- rangement of the nerves may, however, be reversed. The external border of the process is continuous with the body of the bone. Malar Process. — The malar process stands off from the outer side of the antrum. It is remarkably thick and strong, and is connected, by a very rugged triangular surface, with the malar bone. The malar process is situated just over the first and second molar teeth, and is therefore well calculated to resist pressure in mastication. It forms the apex of the pyramidal body of the bone. It3 superior surface is continuous with the orbital surface of the body ; its anterior with the canine fossa, and gives origin to the ' levator labii superioris proprius ; ' its posterior surface with the zygomatic surface ; its apex is rough for articulation with the malar bone ; its base is continuous with the body of the bone. Connections. — The superior maxilla is connected with nine bones, as follows : With the malar, the frontal, the nasal, the lachrymal, the vomer, the inferior spongy, the palate bone, its fellow, and, lastly, the ethmoid. Ossification. — The ossification of the upper jaw begins about the seventh week of foetal life, and proceeds so quickly that the number of its independent centres has not yet been accurately determined. Itappears to have five distinct centres : one for the alveolus behind the incisors, one for the palatine process, one for the floor of the orbit and malar process, a fourth for the portion in front of the antrum with the nasal process, and, lastly, a very dis- tinct centre, 35 which includes the sockets of the two incisor teeth. In most human skulls, if not very old, one can trace the remains of the ' pre-maxillary ' suture. (Plate XX.) It runs outwards from the anterior palatine canal, and then through the alveolar border of the jaw, invariably between the second incisor and the canine tooth ; and here we lose all trace of it. This is interesting surgically. In cases of double hare-lip, where the fissure is not confined to the lips, the pre-maxillary bones on each side fail to SUPERIOR MAXILLARY BONE . 101 unite with the rest of the upper jaw, and often project in a hideous manner through the fissure of the lip. When removed by opera- tion, these bones are always found to contain the capsules of the four incisor teeth. 36 Comparative Osteology — The teeth which grow from the pre-maxillary bones are called incisors. On a close inspection of the narwhal hanging in the Mus. Eoy. Coll. Surg, the sharp spiral tusk will be found to spring from the left pre-maxillary bone. It is therefore the left incisor tooth. The right one usually remains undeveloped ; but there is a specimen in the Cambridge Museum where both are of full length. Evidence of the narwhal's power of offence or defence is given by the tusks having been found buried to a depth of ten or twelve inches in the timbers of ships. The female narwhal has no such extra- ordinary growth of the incisor tooth. It is interesting to notice in the skull of the elephant that the suture between the superior maxillary and pre-maxillary bones is visible, and that his tusks grow from the pre-maxillary bones, and are therefore also incisor teeth. The tusks of the walrus have their origin externally to the pre-maxillary bone, and are therefore canine teeth, and this animal belongs to the carnivora. (No. 999.) Examine the bull, and it will be seen that there are no in- cisors in the upper jaw.- This is the case in all the Euminants, excepting the camel, which loses the central incisors early in life. In the bull, deer, and other Euminants also notice that the so- called canines in the lower jaw are in a regular series with the six incisors, and much resemble them. They seize their food between this even row of teeth and the prehensile upper lip, and then chew it with the molars. In the order Monotremata, the one member, Echidna, has no teeth, and the other, Ornithorhynchus paradoxus, has but horny plates to represent them. (See Sep. Ser.) In many of the lower animals teeth are not confined to the alveolar margins of the jaw, but are found scattered about the upper part of the alimentary canal. Thus, in the Labroid fishes (No. 96), large teeth maybe seen developed upon the palate. In the perch there are teeth in the pharynx. (No. 197.) In the 102 SUPBEIOE MAXILLAEY BONE lobster there are horny teeth in the stomach, where the food is ground. In birds the superior maxillary, with the inter-maxillary bones, are prolonged forwards, and when covered with the appropriate horny material, constitute the beak ; the lower jaw also projecting forms the'lower half of the beak. (Nos. 1678, 1678A.) The upper jaw is movable in parrots (No. 1438), and has a broad transverse articulation with the frontal. It consists of the coalesced nasal, maxillary, and pre-maxillary bones. In Primates there are never more than four incisors above, and the same number below. In the -Rodents the incisors continue to grow throughout life, and are long" and curved. See the Canadian beaver (No. 3118). , In Cetacea the pre-maxillse, which are small in proportion to the maxillae, are prolonged far in advance of the nasal aperture, as may be seen in the skeleton of the great sperm whale in the; Mus. Eoy. Coll. Surg. ; Examine the poison-fang in a serpent from New Holland (No. 650). It is situated in the upper jaw, and has a bristle passed through it, showing that it is tubular. This tube is continuous with the duct of the poison-gland. Look at the "plates of whalebone hanging from the upper jaw of the whalebone whale. It is by means of these plates that he entangles the small molluscs, &c, on which he feeds. MALAB BONE. (Plate XIII. fig. 3.) The malarbone forms the prominence of the cheek, a part of the margin and wall of the orbit, and the greater portion of the; zygomatic arch. It is remarkably thick and strong, and resists injury, to which the face, in this situation, is so exposed. We divide it into a ' body ' and an ' orbital process.'" ' Body.— The ■* body' is diamond -shaped, with external and internal surfaces; 1 superior, inferior, anterior, and posterior MALAR BONE 103 angles ; anterior-superior, anterior-inferior, posterior-superior, posterior-inferior borders. Suefaces. — The external or facial surface is subcutaneous, marked by a number of small vascular foramina, and one large foramen, known as the ' external opening of the malar canal,' for the transmission of a malar nerve. Sometimes there may be more than one large opening. From the outer surface arise the ' zygomaticus major ' and ' minor ' muscles, and close to the posterior-inferior border fibres of the ' masseter.' In most skulls we see a distinct elevation where the zygomaticus major is attached. This elevation is termed the 'malar point' by cranio- logists. The internal surface presents a rough, triangular, deeply dentated surface to articulate with the malar process of the superior maxillary, and a smooth concave surface entering into the formation of the zygomatic fossa. The surface is marked by a few small elevations near the lower border, where it gives origin to the ' masseter ' muscle, also to one or two ' temporal foramina ' or openings of malar foramina leading into the zygomatic >fossa and occupied by temporal branches of the temporo-malar nerve. Angles. — The superior angle is dentated to articulate with the external angle of the frontal bone. The inferior angle is nearly a right angle, and articulates with the malar process of the superior maxillary. The anterior angle is very acute. • It articulates with the superior maxillary bone at the infra-orbital margin above the infra-orbital foramen. The posterior angle is cut obliquely from above downwards and backwards, and is ser- rated for articulation with the zygomatic process of the temporal. Boedees. — The anterior-superior border is smooth and rounded, and forms the outer and part of the lower margin of .the orbit. The anterior-inferior border is somewhat sinuous and serrated. It forms the anterior limit of the triangular serrated surface for articulation with the malar process of the superior .maxillary. The posterior-superior border is curved like an italic s. It is rather sharp and rough for the attachment of the' temporal fascia. The posterior-inferior border runs backwards and slightly upwards, and is rough for the attachment of the 'masseter ' muscle. j •^04 MALAE BONE The Orbital Process is continuous externally with the upper half or so of the anterior-superior border of the body of the bone. It is a four-sided plate of bone, forming part of the outer wall of the orbit and looking forwards and inwards. Subfacbs.— The antero-internal or orbital is smooth, slightly concave both from above downwards and from before backwards. It shows the internal openings of one or two of the malar canals. The postero-external or zygomatic is convex from above down- wards and concave from before backwards, and helps to form the zygomatic fossa. Borders.— The superior is serrated for articulation with the frontal bone. The inferior is shorter than the superior, and articulates with the anterior end of the external border of the orbital surface of the superior maxillary bone. The postero-internal in its upper four-fifths or so is rough and sharp for articulation with the outer border of the orbital surface of the great wing of the sphenoid. In its lower fifth it forms a smooth notch bounding the ' spheno-maxillary fissure' externally. In some cases this border is articular throughout, in which case the malar bone will not form the outer end of the spheno-maxillary fissure, and the sphenoid will articulate with the superior maxillary. In some rare cases a little Wormian bone forms the outer end of the spheno-maxillary fissure. The antero-external border is continuous with the body of the bone. ' The malar canal ' (more fully the ' temporo-malar canals ') starts by one or two openings on the orbital surface of the orbital process. They run outwards into the body of the bone, some appearing externally on the facial surface of the body as the ' malar foramina,' and others on the zygomatic surface of the body as the ' temporal foramina.' The primary canal (or canals), starting in the orbital process, lodge temporo-malar nerves ; the branches contain malar and temporal divisions respectively. - Connections. — The malar bone is connected with four bones, namely, by a broad and very roughly serrated surface, with the superior maxillary ; by suture, with the external angle of the frontal, the orbital plate of the sphenoid, and the zygomatic pro- cess of the temporal. These several connections are so strong MALAR BONE 105 that the bone cannot be driven inwards towards the orbit, and fractures of it are very rare. Ossification. — The malar is developed from a single centre of ossification, which appears about the eighth week. According to some anatomists, it is developed from three centres, which join one another by the fourth month. The non-union of one of these centres explains why we sometimes see the body of the bone divided by a suture into an upper or larger and a lower or smaller portion. This condition is well seen in the skull of a Japanese recently added to the collection of human skeletons in the Museum of the Eoyal College of Surgeons. Comparative Osteology. — The upper process of the malar bone does not articulate with the frontal in the carnivora (Nos. 363, 365, 4562). In the Great Kangaroo and Wombat the zygomatic process of the malar bone extends backwards so far that it forms part of the glenoid cavity and articulates with the lower jaw. NASAL BONE. (Plate XVI. fig. 3.) The nasal bones, situated one on either side, occupy the space between the nasal processes of the superior maxillary bones, and, together, complete the bridge of the nose. Their length, breadth, and degree of inclination, determine the shape of the nose. We have to examine their anterior and posterior surfaces, and their four borders. Surfaces. — The anterior surfaces are subcutaneous, convex, and present the orifices of one or more canals, which transmit blood-vessels. The posterior surfaces are concave, form part of the roof of the nose, and each is marked by a groove for the passage of the external branch of the nasal division of the fifth nerve. Borders.— The upper borders are broad, serrated, and firmly articulated with the frontal bone. The lower borders 106 NASAL BONE are thin and free in the "dry bone, but connected in the recent subject with the lateral cartilages of the nose. Each has gene- rally a little notch in it, through which the external branch of the nasal nerve comes and supplies the skin at the tip of the nose. Their outer borders are serrated, slightly sloped, and rest upon the nasal processes of the superior maxillary bones. Their inner borders articulate with each other, in the middle line, along the ' nasal suture.' From the under surface of this suture a high ' crest ' of bone projects. By putting the bones together, it is seen how their crests' form the beginning of the bony septum of the nose, and how they articulate with the nasal spine of the frontal bone, and if that does not extend far enough forwards, with the perpendicular' plate of the ethmoid. (Plate XXIII. tig. 1.) Hence, with a depressed fracture of the nasal bones there must be a fracture of the perpendicular plate of the ethmoid, either directly or indirectly, through the nasal spine of the frontal. In some rare instances, the injury extends through the perpendi- cular plate of the ethmoid to the base of the brain. Observing the great strength of the nasal-bones and the massive arch they form, how the sides of the arch are supported by the nasal pro- cesses of the superior maxillary, while the centre is propped up by the nasal spine of the frontal and the perpendicular plate of the ethmoid (Plate XXIV. fig. 2), one can readily understand what makes the arch so strong, and why the bones are so seldom broken. Connections. — The nasal bone articulates with four others, namely its fellow, the superior maxillary, the frontal, and the per- pendicular plate "of the ethmoid should the nasal spine of the^ frontal not extend so far forwards as to completely separate them.. Ossification.— Each : nasal bone is developed from a single centre of ossification, which appears about the eighth week of foetal life. Comparative Osteology.— The only difference between the skulls of a tiger and a lion is that in the lion the upper ends of the nasal bones and the nasal processes of the superior maxillary bones are on the same level, whereas in the tiger the nasal bones- run up considerably beyond the nasal processes. LACmiYlVIAL BONE 107 LACHEYMAL BONE. (Plate XIII. fig. 4.) The lachrymal bpnes are situated, one on each side, on the inner wall of the orbit. They are exceedingly thin and delicate, and shaped somewhat like a finger-nail, hence the name ' os unguis.' In old skulls they are often as thin as silver paper, and sometimes perforated. One surface is directed towards the orbit; the other towards the nose. One of these bones is seen in situ in Plate XVI. fig. 2. The bone is four-sided, with external and internal surfaces, superior, anterior, inferior, and posterior borders. Suefacbs. — The external or orbital surface has a smooth vertical ridge upon it, which terminates below in a small hook- like process or tongue, termed- hamulus,' running forwards and outwards, then forwards and inwards, to articulate with the so- called ' lachrymal tubercle ' of the superior maxillary, and thereby complete the upper opening of the naso-lachrymal canal ex- ternally. (Plate XXII.) In front of this is a vertical groove ('lachrymal groove'), which, together with the groove on the nasal process of the superior maxilla, lodges the naso-lacbrymal sac or the upper dilated end of the duct for the passage of the tears into the nose. The ridge itself gives origin to the ' tensor tarsi ' muscle. The bone behind the ridge is smooth, slightly concave, and forms part of the inner wall of the orbit. Tbe internal or nasal surface presents a slight groove, corresponding to the external ridge. The surface in front of this forms part of the middle meatus of the nose ; that behind it covers the anterior cells of the ethmoid -bone, and sometimes a small cell or two in the frontal bone. Bobdees. — The superior border is thin, straight, dentated, and articulates "with "the internal angular process- of the frontal bone. Sometimes we notice a half-cell in it, completed by the frontal. The anterior border is the strongest border. It is slightly arched forwards, and is sharp and articular to join the 108 LACHRYMAL BONE inner lip of the posterior border of the nasal process of the superior maxilla. The inferior border posteriorly is thin and rough to articulate with the orbital process of the superior maxillary, and anteriorly is prolonged downwards as a process, termed the ' angle of the lachrymal,' which forms the inner wall of the naso-lachrymal canal, and articulates with the ' lachrymal process ' of the inferior turbinated bone. The pos- terior border is thin and uneven, and articulates with the anterior border of the os planum of the ethmoid. Connections. — The lachrymal bone articulates with four bones, viz. the frontal, superior maxillary, ethmoid, and inferior turbinated. Sometimes the ' hamular process ' is developed as a separate piece of bone, and called the ' lesser lachrymal bone.' Ossification. — It has one centre of ossification, which appears about the eighth week of fcetal life. PALATE BONE. (Plateb XIII. and XIV.) Each 'palate bone' is wedged in between the pterygoid process of the sphenoid and the superior maxillary bone. Each forms part of the nasal fossa, of the orbit, and of the palate. As the palate bone somewhat resembles the letter L in shape, we can divide it, for convenience of description, into a * horizontal ' and a 'vertical plate,' with an 'orbital' and a 'sphenoidal process ' rising from the upper border of the latter plate. Horizontal Plate.— The horizontal plate completes the bony palate by fitting on to the palate plate of the superior maxillary bone. It is quadrilateral in shape, with inferior and superior surfaces, inclosed by anterior, posterior, internal, and external borders. Surfaces.— The inferior surface (Plate XIV. fig. 2) presents a transverse ridge for the attachment of the aponeurosis of the 'tensor palati.' The rest of the surface is smooth, different therefore from the under surface of the palatine process of the PLATE XIII. Fifcl. gpKenoid surface 4K_ ~i»— -EtWioid surFace ■Rid^efer middle spenkjbone N Tlidbr for inferior spon&y bone Klpii* Tuberosity Plate projecting over oriPicBof Antrum. INTERNAL VIEW OF PALATE BONE. Maxillary. Exter-nal aspect . A B Zygomatic Fi|.2. Anterior aspect. Ethmoidal Sphenoidal . Nasal . Pos terior aspect. Sphenoidal. Internal aspect. Diagram of surfaces of Orbital (A)ScSpherioidal IBjprocesses of Palate "bone. %3, Malar canals Orbital surface. n of Tensor tarsi ic^rymal brovvel i -Ria^ Hamulus for articulation with lachrymal tuoercle of Superior maxillary. LACHRYMAL BONE. MALAR BONEL. Drawn on Stone "by T. Godart. Frcgaaature WL.Holden. Printed by Wes^Newman &, Co. PLATE XIV Orbital surface. Zygomatic surface Spheno-palatme foramen Tuberosity Groove completing pterygoid fossa Sphenoidal surface. Jlv.... Sphenoidal process- Posterior palatine ca-nal -M-A Pid&efbr inferior spon^ybone ■ ..Jlor'izontal plate. Posterior view. PALATE BONE, T?i§2. of- posterior palatine oaniL. P^e for Tensor palati . ^f^^ p^t, ne CEUW l a TJ-nckr surface.. Ethmoidal surface ^Tasal surface of Sphenoidal -process.-' Median crest .Orbital surface MatUWy surface. TSg.3. ..Tuberosity- rYutertor view Drawn on Stone "by T Go dart From nature. T-v.r T, TMJ« Printed VyVfeetjNewmn* & Co PALATE BONE 109 superior maxillary bone, which, we remember, was very rough. The superior surface is smooth and slightly concave, thus form- ing part of the floor of the nose. Bokdbes. — The anterior border of the plate is serrated. and cut obliquely, so as to articulate with, and be supported by, the palate plate of the superior maxillary. The internal border firmly articulates with its fellow, and by means of a half-crest, made a whole one by the apposition of the half-crest of the opposite bone, precisely like the corresponding parts in the superior maxillary bone (Plate XXIII. fig. 1), supports the vomer, and forms a basis for the septum of the nose. Behind, it terminates in a pointed process, which articulates with a similar one on the opposite bone, and the two together form the ' posterior nasal spine ' (Plate XX.) giving origin to the ' azygos uvulffi ' muscle. The external border is continuous with the perpendicular plate, and, when viewed on its inferior aspect, shows anteriorly a smooth notch, or, it may be, a complete foramen, the lower end of the 'posterior palatine groove,' for the passage of the descend- ing palatine vessels and the large palatine nerve from the spheno-palatine ganglion. Vertical Plate. — The vertical plate of the palate bone con- tributes to form the outer boundary of the nasal fossa. It is a four-sided plate, elongated vertically and resting against the posterior part of the inner surface of the body of the superior maxillary bone. Surfaces. — The internal (Plate XIII. fig. 1) presents from above downwards, first, an antero-posterior ridge, close to the upper border of the plate, and termed the ' superior turbinated crest,' to the fore part of which the inferior turbinated process of the ethmoid or the middle turbinated bone of the articulated skull is joined ; next, a smooth antero-posterior groove, helping to form the middle meatus ; next, a rough ridge, the ' inferior turbinated crest,' running from behind upwards and forwards, for articulation with the inferior turbinated bone; and lastly, a smooth antero-posterior groove helping to form the inferior meatus of the nose. The external presents a smooth groove run- ning downwards and slightly forwards to terminate at the notch 5.10 PALATE £ONE already described, upon the outer border of the horizontal' plate. The groove is termed the ' posterior palatine groove,' and is con- verted into a canal by a corresponding groove upon the inner surface of the superior maxillary bone. In some bones the lower •end of the canal is formed entirely by the palate bone. The upper end of the groove widens and makes a little triangular surface which forms the inner wall of the spheno-maxillary fossa. The posterior palatine groove lodges the descending palatine blood-vessels and the large palatine nerve. The rest of the ex- ternal surface is rough and articulates with the superior maxillary bone. Borders.— The superior supports the * orbital ' and the ' sphe- noidal process' at its anterior and posterior extremity respec- tively. Between the two processes it forms a smooth notch, the ' spheno-palatine notch ' (Plate XIV.) forming the lower part of the ' spheno-palatine foramen ' of the united skull, and giving passage to nasal and naso-palatine branches of Meckel's ganglion -with corresponding arteries. The inferior is continuous with the horizontal plate. The anterior is sharp and irregular. It helps to close the opening of the antrum posteriorly, and, below the level of the inferior turbinated crest, is prolonged forward into a triangular process with a sharp serrated anterior inferior edge which is received into the fissure already described on the inner surface of the superior maxillary bone. The process is termed the ' maxillary process,' and by its upper part it helps to close the opening of the maxillary sinus inferiorly. The posterior is sharp and rough superiorly where it articulates with the front of the pterygoid process of the sphenoid. Inferiorly it swells out into what is called the ' tuberosity of the palate bone.' This is the thickest and strongest part of the whole bone, and it fits into and fills up the ' notch ' which is seen between the pterygoid plates of the sphenoid. Notice also that its posterior aspect presents a groove which completes the pterygoid fossa, and, gives origin to a part of the ' pterygoideus internus.' The groove is bounded by two rough grooves, which diverge from each other like the letter -V reversed. (Plate X. fig. 2.) The inner groove is the deeper and more vertical, and articulates with the anterior border of the PALATE BONE 1U internal pterygoid plate ; the outer is the shallower and more oblique, articulating with the" anterior border of the external pterygoid plate. The anterior aspect of the tuberosity looks out- wards as well as forwards, and presents a very rugged surface, which articulates with the tuberosity of the superior maxillary bone. Behind this rugged surface is a smooth portion continuous with the outer surface of the ' external pterygoid ' plate ; this smooth part gives origin to some of the fibres of the ' external pterygoid ' muscle. The inferior aspect has nothing remarkable on it, except the orifices of one or two canals large enough to admit a pin. They are the. ' accessory palatine canals,' and "transmit the external and the small palatine nerves to the soft palate. Turn now your attention to the upper part of the palate bone, and. observe that at the top of the vertical plate there are two processes separated by a deep notch, which forms the greater part of the ' spheno-palatine foramen.' One of these processes is called.the ' orbital,' because it fills up a little corner at the back part of the orbit ; the other is called the ' sphenoidal,' because it fits under the body of the sphenoid bone. Orbital Process. — The ' orbital process ' springs from the top of the bone by a narrow ' neck,' and is hollow, so that it forms a cell. The cell contains air, admitted through one of the pos- terior ethmoidal cells. This little process has five surfaces, un- equal in extent, and looking, in different directions. If you hold the bone before you, precisely as it is in your own person, and re- member that it is interposed between the maxillary in front and the sphenoid behind, you will have no difficulty in recognising the direction of the surfaces to be as follows (see Plate XIII. fig. 2) : the superior, smooth, looks upwards and outwards, and contributes to form the. floor of. the orbit ; the antero-external is rough, looks downwards, forwards, and outwards, and articulates with the superior maxillary bone ; the postero-external is smooth, and con- tributes to form the bottom of the zygomatic fossa ; the antero- internal is rather eoncave and rough for articulation with the ethmoid, presenting a large irregular opening through which the cavity is continuous with the posterior ethmoidal cells ; the 112 PALATE BONE postero-internal looks backwards, upwards, and slightly inwards, occasionally shows a second opening of the cell contained by the process, and articulates with the body of the sphenoid. Sphenoidal Process This is a somewhat thin plate of bone, which arches hiwards beneath the body of the sphenoid, and forms part of the outer wall of the nasal fossa. As it is generally broken in the separate bone, one can see it best in the perfect skull. (Plate XX.) The arch which it forms has four surfaces : the superior or sphenoidal, articulating with the body of the sphenoid and closing in the pterygo-palatine canal ; the internal or nasal, smooth, and forming part of the upper meatus of the nose ; the antero-extemal or zygomatic, helping to form the bottom of the zygomatic fossa ; the postero-external, looking upwards and outwards, and articulating with the body of the sphenoid. Spheno-palatine Notch. — Eespecting the spheno-palatine notch, we need, for the present, merely observe, that it is converted into a foramen by the body of the sphenoid above ; and that the opening so made leads from the spheno-maxillary fossa, that is the bottom of the zygomatic fossa, into the cavity of the nose, and transmits, as already said, the nasal and naso-palatine nerves with their corresponding arteries. (Plate XXII.) Connections.— The palate bone articulates with six bones — namely, its fellow, the sphenoid, the ethmoid, the inferior spongy bone, the vomer, and the superior maxilla. Ossification. — It is developed from a single centre of ossi- fication, which appears at the angle of the horizontal and vertical portions, about the seventh or eighth week of festal life. INFERIOR SPONGY OR TURBINATED BONE. (Plate XV. figs. 1 and 3.) In each nasal cavity there are three spongy or turbinated bones— an upper, a middle, and a lower. The upper and middle form part of the ethmoid bone, and have been already described. We have now to examine the lower one. PLATE XV Lachrymal process InPenorSponigy"bone, inner surface. LacWy mil's -Lachryma.1 "process E-fhTnoidal process Maxillary process Inferior Sponby bone , outer surface. T?i*.3. Drawn, on Stone "by T. Godart. From nature "by L.HoUen. £riEieiivWe s t. Newman fcCo. INFERIOR SPONGY OR TURBINATED BONE 113 Its Position and Use.. — This thin plate of bone- is well called 'spongy,' from its structure, and 'turbinated,' from its curved form. By referring to Plate XXIII. fig. 2, you see it in situ, and observe how much longer it is than either of the others. Surfaces. — Its internal surface, forming the convex part of the roll, looks towards the septum of the nose ; its external surface forms the concave part, and bounds the inferior meatus of the nose. Both surfaces are covered with little ridges and furrows, and more or less horizontal canals, which lodge numerous plexuses of arteries, but chiefly of veins. This quite accords with the function served by the bone, namely, of affording an additional extent of surface which warms the air on its passage to the lungs. It has nothing to do with the sense of smell. The olfactory nerves have not ' been traced lower than the middle spongy bone. Borders. — Its swperior border is arched upwards and is divi- sible into thirds, of which the anterior is the shortest.. This third is sharp and rough, and slopes downwards and forwards, articulating with the inferior turbinated crest of the superior maxillary bone. Its posterior third is also sharp and slopes downwards and backwards to articulate with the inferior turbi- nated crest of the palate bone. Its middle third is nearly hori- zontal, and gives attachment to three processes — one attached to the anterior extremity and running upwards and slightly for- wards for articulation with the angle of the lachrymal, helping to close the naso-lachrymal canal inferior ly, and termed the ' lachyrmal process ; ' one attached to the posterior extremity, projecting upwards and slightly forwards to meet the uncinate process of the ethmoid, and hence called the ' ethmoidal process ; ' and another attached to the whole length of the middle third, tri- angular in shape, turning down like a dog's ear, helping to narrow the lower part of the orifice of the antrum, and termed the ' maxillary process.' Notwithstanding these numerous connec- tions, the bone is by no means strongly fixed in its position : in the dry skull it often falls out ; and in the operation of extracting a polypus from the nose, it is quite possible to pull out part of the bone or even the entire bone with the polypus. Its inferior i 114 INFERIOR SPONGY OR TURBINATED BONE border is free, rough, thickened, perhaps containing a cell or two, and stretching nearly horizontally from before backwards with a slight sweep downwards. It is situated about half an inch above the floor of the nose, so that there is just room enough to introduce the tube of a stomach-pump through the nasal cavity. Ossification The bone has one centre of ossification, which appears in cartilage about the fifth month of foetal life. Comparative Osteology — See the remarks at the end of ' The Ethmoid Bone.' THE VOMER. (Plate XVI. fig. 1.) The ' vomer ' is so named from its resemblance to a plough- share. It is a thin and delicate plate, situated perpendicularly in the middle line, and, together with the perpendicular plate of the ethmoid bone, forms the greater part of the bony septum of the nose. (Plate XXIII. fig. 1.) When looked at from the side the vomer is four-sided with a very sharp anterior inferior angle. Surfaces. — Both its lateral surfaces are smooth and marked by grooves for blood-vessels and nerves. The only groove deserv- ing special notice is one which descends from behind and above, downwards and forwards to terminate in the corresponding fora- men of Scarpa, already described in connection with the superior maxillary bone. The groove may be a complete canal in some places, and may be better marked on one side than on the other. Borders.— The superior border expands into two ' alee.' The outer margins of these ' wings ' articulate with and are overlapped by the vaginal plates of the sphenoid, and the smooth groove included by the wings rests against the rostrum of the sphenoid, fibrous tissue containing blood-vessels intervening between the two. The inferior border in its posterior three-fourths or so runs nearly straight from before backwards, and is rough to articulate with the crest formed by the palate and superior maxillary bones. In its anterior fourth it presents a deep concavity directed down- PLATE XVI Groove for Na.50-pala.tin Fto.l. VOMER .iiSiSfi^jS^S^S? Temporal fossa. - ^Zygomatic fossa..-. Sphenoid boTie. Malar bone. Sphenoidal fissure.' Palate bone. 'EtTimoidboneXLachryrnalborie. Crest: Groove for r,asajr MASAL BONE %3 Posterior vie* Anterior vievv", . „ —^ m - LcaiBQmi Stone by T Godart. E'-'pynatUre byL.HoldenT^ Erintedby"West,NewmsiifcCo. THE VOMBK 115 ■wards and forwards to articulate with the particularly high part of the vomerine crest formed by the superior maxillary bones. The posterior half or so of the lower border is thin and sharp, and is received by the crest formed by the palate and superior maxil- lary bones. In the anterior half the lower border usually spreads out into two little wings, which receive from below the crest formed by the superior maxillae. The anterior border slopes from behind downwards and forwards. It is usually grooved in its upper half to articulate with the vertical plate of the ethmoid, and very frequently so in its lower half to join with the septal cartilage of the nose. The posterior border is sharp and smooth, branches somewhat above, and is slightly concave downwards and back- wards as it runs from above downwards and forwards. It forms the boundary between the posterior openings of the nasal cavities. Connections. — The vomer is connected with six bones. Below, it articulates with the crest of the maxillary and palate bones ; above, with the lower edge of the rostrum of the sphe- noid ; in front, with the perpendicular plate of the ethmoid. It is necessary to know that the direction of the vomer is not, in all persons, perpendicular. In 100 skulls the vomer was found to be perpendicular only in 24. There are instances in which it projects into one side of the nose to such an unusual extent, that when covered by its vascular and swollen mucous membrane, the projection might easily be mistaken for a polypus. Such mis- takes are alluded to in surgical works. 37 Ossification The vomer is developed from one centre of ossification, which appears at the lower and back part of the sep- tum of the nose about the eighth month of fcetal life, and which gradually rises up as two plates, one on each side of the middle line, embracing the septal cartilage. As they grow upwards these plates fuse with one another from below upwards and from behind forwards. At the age of puberty we find the bone con- solidated into one piece with the exception of the groove between the alee and the smaller one usually situated on the anterior border. Very frequently we notice that the ossification is incom- plete in the upper and anterior half of the bone, and that the bone in that region consequently presents a rough, open, cellular I 2 116 THE VOMER appearance. Indeed, in some cases we may find that it is com- pletely perforated, so that the nasal fossse of opposite sides communicate with one another in the bony state. INFEBIOE MAXILLAEY BONE. (Plate XVII.) For convenience of description we divide the lower jaw into the arched part in front, the ' body ' or ' horizontal ramus,' and two ascending parts behind, the ' ascending ' or ' vertical rami.' At the top of each vertical ramus are the ' condyle ' or articular surface, the ' coronoid process ' for the insertion of the temporal muscle, and the ' sigmoid notch.' Body or Horizontal Ramus. — Surfaces. — The anterior or convex surface of the body presents, in the middle line, a slight ridge, the ' symphysis,' which is the strongest part of the bone and indicates where the two halves of the bone have grown to- gether. Its direction is vertical or even projects forwards : this is one of the characteristics of man, who alone has a chin. The * symphysis ' terminates, below, in the triarjgular ' mental pro- cess.' On each side of the symphysis is a slight depression, the 'mental fossa,' which gives origin to the ' levator menti.' More externally, and generally in a line with the second bicuspid tooth, is the ' mental foramen,' which transmits the ' mental branches ' of the inferior dental nerve and artery, and forms the lower opening of the ' dental canal.' Prom the base of the mental process we trace the ' external oblique line ' running upwards and backwards to become continuous with the anterior border of the vertical ramus. From it we find the ' depressor anguli oris ' arising ; above it, the ' depressor labii inferioris ; ' and below it, the inser- tion of the 'platysma myoides.' Along the alveolar border adjacent to the three molar teeth is one of the origins of the ' buccinator,' and outside the mental fossa, on the ridge corre- sponding to the socket of the canine tooth, a few of the deep fibres of the ' orbicularis oris ' take their attachment. The posterior surface of the body is concave from side to side. PLATE XVII. Bucoina-to External oblique line Fife.? Mylo-nyoid ridbe Situation for Sublingual gland, Situation oF submaxillary gland. Tubercle for (renio-hyo-blossus. Tubercle for Genio-hyoiclens. Dental foramen. Mylo-hyoid groove. Drawn an Stone try T. Godart. From nature kyL.Holden. Printed tyWest.Wewman&Co. INFERIOR MAXILLARY BONE 117 In the middle line in front it shows a narrow vertical groove with a nutrient foramen or two in it inferiorly, and a plane surface superiorly, indicating the symphysis menti. Placed on each side of the lower half of the middle line we have two rough tubercles, one above the other, and close by the lower border of the bone an oval, rough, shallow depression. The tubercles are named the ' superior ' and ' inferior genial tubercles ' for the attachment of the ' genio-hyoglossus ' and ' genio-hyoid ' muscles respectively — the shallow rough depres- sion the ' digastric fossa ' for the attachment of the digastric muscle. Very frequently the four genial tubercles are confluent and appear as one irregular vertical ridge on the posterior aspect of the symphysis. Leading obliquely upwards and back- wards from the lower genial tubercle, to become continuous with the inner lip of the anterior border of the vertical ramus, is the 'internal oblique line' or 'mylo-hyoid ridge,' for the attachment of the ' mylo-hyoid ' muscle, and quite at its posterior extremity the ' superior constrictor ' of the pharynx. The part of the surface below the ridge is rather concave and smooth, and, because it lodges the submaxillary gland, it is named the ' sub- maxillary fossa.' In it we notice a few small nutrient foramina, directed towards the symphysis. Above the ridge is the place for the sublingual gland, hence termed the ' sublingual fossa.' It is not so well marked as the submaxillary fossa. These ' oblique ' ' lines ' or ' ridges ' on the two surfaces of the body are something more than mere muscular impressions. They indicate the limit between the ' alveolar ' part which contains the teeth, and the lower or ' basilar ' part of the jaw. These distinctions are made because these parts come and go at different periods of life. In infancy there is only the alveolar part ; towards puberty the basilar part slowly grows to perfection : in old age when the teeth fall out, and their sockets are absorbed, the basilar part alone remains, and the chin gradually approximates the nose. The absorption of the sockets (alveoli) , which is natural in old persons, often occurs prematurely. It is apt to arise from long salivation, scurvy, or purpura, and is frequently hereditary. Borders. — The inferior border of the body forms, in front, the 118 INFEEI0R MAXILLARY BONE base of the mental process. Laterally it is rounded and rough for the attachment of the ' platysma ' muscles. As the posterior extremity of the border, on each side, becomes continuous with the corresponding lower margin of the vertical ramus, it forms the anterior half of the groove of the passage of the facial artery on to the face. The upper border is narrower in front than behind and is marked by sockets for the teeth. Teeth. — The teeth in the lower jaw correspond in number (eight on each side) with those in the upper, but differ from them in these particulars : 1. The first two lower molars have only two fangs, an anterior and posterior, while the upper molars have three. In the third molar or wisdom tooth the fangs are often consolidated into one ; 2. When the mouth is closed the teeth of the lower jaw shut within those of the upper jaw, which form a larger arch ; 3. The external tubercles or cusps of the teeth of the lower jaw fit into the hollows between the external and in- ternal cusps of the teeth of the upper jaw ; by which arrange- ment we are enabled to use the entire surface of the opposing teeth in grinding the food. When the jaws are closed, each tooth in one jaw is opposed by two in the opposite jaw; one good result of this is, that when we lose a tooth, the corresponding tooth in the other jaw, being still more or less opposed, is still of service in mastication. Vertical Ramus. — The vertical ramus of the jaw mounts up from each of the posterior ends of the body at nearly a right angle in adult age, when the upper and lower jaws are kept well apart behind by the molar teeth. In infancy, before the development of the molars, and in age, when they are lost, the ' angle ' between horizontal and vertical rami becomes obtuse. Excluding the outstanding processes, the vertical ramus is quad- rilateral. Surfaces. — The outer surface is smooth above and rough below and behind. It gives insertion, in almost the whole of its ex- tent, to the ' masseter ' muscle (fig. 1). Its posterior and inferior angle is always turned more or less outwards. The internal surface (fig. 2) is concave from before backwards and very slightly so from above downwards and forwards. A little above the middle, INFERIOR MAXILLARY BONE 119 is the large ' dental foramen,' or the upper aperture of the in- ferior dental canal for the transmission of the inferior dental nerve and artery. Leading from above and behind downwards and forwards to this foramen is a broad shallow groove for the passage of the same nerve and artery, and running from the fora- men downwards and forwards, to lose itself in the submaxillary fossa of the body, is a small narrow groove for the passage of the mylo-hyoid nerve and artery, and termed the ' mylo-hyoidean groove.' Below the dental foramen and these two grooves, the surface is rough for the insertion of the ' internal pterygoid ' muscle ; above them the surface is smooth, excepting in the im- mediate neighbourhood of the superior and anterior borders, where it is rough for the insertion of the ' temporal ' muscle. The anterior and internal lip of the dental foramen rises up into a sharp projection called the ' dental spine ' for the attachment of the internal lateral ligament of the jaw. Borders. — The anterior border presents, in its upper half which is free, the appearance of a vertical groove with an outer and an inner lip. The outer lip is the more prominent and is con- tinuous superiorly with the anterior border of the coronoid pro- cess and interiorly with the external oblique line of the body. The inner lip is the rounder and flatter of the two ; it is continuous interiorly with the internal oblique line of the body and superiorly gradually fades off on the inner surface of the coronoid process. Both lips of the groove between give attachment to the temporal muscle, excepting interiorly just behind the last molar tooth, where we find, in muscular jaws, a little vertical crest rising up, to which the ' buccinator ' is attached, and which is named the ' buccinator crest.' The lower half or so of the anterior border is continuous with the body of the bone. The posterior border is smooth and rounded superiorly, rough and narrow interiorly. The inner aspect of the border, just below the root of the condyloid process, shows a smooth groove continuous with the one described upon the inner surface, and lodging the internal maxillary artery. The narrow rough part of the border affords insertion to the ' masseter ' externally and to the ' internal ptery- goid ' internally. The inferior border is continuous with the lower 120 INFERIOR MAXILLARY BONE border of the body, and is rough behind for the attachment of the two last named muscles. Anteriorly it presents a smooth shallow half-groove, made a whole one by the opposition of the corresponding half on the lower border of the body, for the passage of the facial artery. The superior border supports the neck of the condyle posteriorly, the root of the coronoid proeess anteriorly, and makes the bottom of the sigmoid notch between these processes. The angle of the lower jaw is formed by the meeting of the posterior with the inferior border of the vertical ramus. In the adult jaw it is rather more than a right angle. In infancy and in old age it becomes much more obtuse, for reasons we have previously mentioned. Condyloid Process. — This process projects from the posterior and superior angle of the vertical ramus to form the joint of the jaw, and fits into the glenoid cavity of the temporal bone, a pad of fibro-cartilage intervening between the two in the recent state. The upper part of the process is the ' condyle,' and the con- tracted part supporting it is called the ' neck of the jaw ' or the ' neck of the condyloid process.' The condyle is oblong in form, and convex both from without inwards and from before back- wards. The long axis is directed from without backwards, inwards, and slightly upwards. In some jaws the long axis is horizontal, and in a still fewer number the outer end of the condyle is a little higher than the inner. The outer extremity of the condyle is termed the ' tubercle ' for the attachment of the: external lateral ligament. The neck is flattened in the same direction as the condyle, and is slightly excavated in front, form- ing the 'pterygoid fossa' for the insertion of the ' pterygoideu's externus ' muscle. The oblique direction of the condyles of the jaw renders easy the rotatory movement necessary in mastication. In masticat- ing we can readily feel that one condyle advances towards the anterior margin of its glenoid cavity, while the other recedes to- the posterior. Coronoid Process. — The coronoid process is a triangular, lofty plate of bone which rises upwards and slightly outwards. INFERIOR MAXILLARY BONE 121 from the anterior superior angle of the vertical ramus beneath the zygomatic arch and increases the leverage of the ' temporal ' muscle. Its external surface is smooth, and is occupied by the ' masseter ' muscle, except close to the anterior and posterior margins, where a few fibres of the temporal are attached. The internal surface is rougher, shows the gradual fading off from below upwards of the inner lip of the anterior border of the vertical ramus, and gives insertion to the ' temporal ' muscle. Its anterior border is sharp and continuous with the outer lip of the anterior border of the vertical ramus ; its posterior is also sharp and forms the anterior part of the sigmoid notch. Both these borders and the apex between them afford attachment to the temporal muscle. Its base or inferior border is continuous with the rest of the bone. Sigmoid Notch. — This is a semilunar space left by the rising up of the coronoid and condyloid processes anteriorly and pos- teriorly, and transmits the small masseteric vessels and nerve. Structure. — The walls of the lower jaw, particularly at the basilar part, are exceedingly compact and tough. In operations for removal of this part of the bone, it is necessary to use the saw freely, before the bone-forceps can be of any service. The interior assumes the form of ' diploe,' and is traversed by the ' inferior dental canal,' which carries the vessels and nerves to the teeth (Nor. Hum. Ost. No. 234). This canal begins on each side on the inner side of the ramus, curves forwards, beneath the sockets of the teeth, and opposite the interval between the first. and second bicuspid tooth curves backwards, upwards, and out- wards to terminate on the anterior surface of the body as the mental foramen. From the convexity of the curve a small canal runs towards the symphysis menti, giving off smaller canals leading upwards to the sockets of the two incisors, canine, and first bicuspid teeth. Ossification.— Each lateral half of the lower jaw is repre- sented in the early fetus by what is called the ' first visceral arch,' or ' cartilage of Meckel.' In the process of development the proximal part of this cartilage is converted into the ' malleus ' bone of the middle ear. The distal part, mostly by the growth 122 INFEBIOB, MAXILLAEY BONE of bone round the cartilage, but slightly by a direct ossification of the cartilage itself, is converted into one half of the lower jaw. The part between these two end portions becomes the ' internal lateral ligament' of the temporo-maxillary articulation. The bony lower jaw begins to be formed, with perhaps the exception of the clavicle, earlier than any other bone in the body. For each of the lateral halves of the bone, we find that several osseous nuclei appear about the sixth week of fcetal life in the membrane which invests Meckel's cartilage. These nuclei speedily join one another and form a large plate outside, and a smaller one inside Meckel's cartilage. The smaller plate forms the inferior dental canal and the inner wall of the sockets for the teeth. The symphysis end of each half of the body is formed by a direct ossification of the corresponding part of Meckel's cartilage. The condyle and part of the vertical ramus are formed by ossification of cartilage not connected with Meckel's, and the junction of the two lateral halves of the body at the symphysis does not take place till the first year after birth. In infancy the body is swollen and larger in proportion to the vertical ramus than it is in the adult. The alveolar portion is broad and thick, on account of its containing the growing teeth, the mental foramen being thereby thrown nearer the lower than the upper border of the body. The vertical ramus is thin as compared with the body, and the angle obtuse. In old age the whole bone is attenuated. The alveolar portion disappears almost entirely by its absorption, consequent on the falling out of the teeth. The mental foramen, consequently, is situated nearer the upper than the lower borders of the body, and the ' angle ' becomes obtuse. In the adult jaw, as we have already described, the mental foramen is situated about midway between the upper and the lower borders of the body, and the angle is very little more than a right angle. Connections. — The lower jaw articulates with the glenoid fossa of the temporal bones, and has lodged in it, in the fully formed state, four incisor, two canine, four bicuspid, and six molar teeth. Comparative Osteology — In the order Monotremata, ob- INFERIOR MAXILLARY BONK 123 serve that there is scarcely any bend or inflexion in the lower jaw (No. 3964). The jaw of the anteater is also straight, thus greatly resembling that of the pelican (see Sep. Ser.) In snakes (Ophidia) the two halves of the lower jaw are not united by bone, but held together by an elastic ligament, which permits the two halves of the jaw to be separated from each other sideways to a considerable extent. This is one of the many arrangements by which the boa is enabled to swallow its prey though larger than its own body. This is shown in the specimen of the tiger-boa (No. 602). In the lower animals the two halves of the jaw generally remain separate throughout life. In all mammalia each half of the lower jaw consists of a single piece which articulates with the squamosal bone of the skull. In all below the mammals it articu- lates with a modified malleus called the quadrate bone. This is well seen in the skull of the ostrich and other birds in the Separate Series. [For some interesting points as to the relation between the size of the coronoid process and the temporal fossa the student should read the Comparative Osteology paragraph at the end of the chapter on ' The Skull as a Whole.'] It has been said that man is the only creature which has a chin. It is most distinct in the Caucasian race, becomes faintly marked in the Negro, and does not exist in the Apes. Eodentia have never more than two incisors in the lower jaw ; and usually only two, but sometimes four, in the upper. When there are four incisors in the upper jaw, as in hares and rabbits, there are two small ones behind the two large ones (No.. 3285). These incisors have a persistent pulp, and continue to grow in adult life. They have no canines. Carnivora have milk and permanent teeth, which are enamelled, and always consist of incisors, canines, and molars. In elephants the teeth consist of tusk-like incisors, growing from persistent pulps, and molars. Look at the lower jaw of the crocodile (No. 717 "D) and see how greatly the angle projects backwards. This projection is for 124 INFERIOR MAXILLARY BONE the insertion of the digastricus, the muscle which opens the mouth, and which acts upon the jaw as a lever of the first order. In man it acts as a lever of the second order, as it is inserted near the symphysis. To appreciate the mechanism of the lower jaw, look at the form of the joint in animals. In them it varies according to the Fro. 14. structure of their teeth and the food they eat. There are three principal types of it : the car- nivorous, the ruminant, and the rodent. The carnivorous type is a simple transverse hinge : this form is well seen in the badger (No. 751), where the condyle of the jaw is mechanically locked in its socket. It is shown in fig. 14, where G represents the shape of the glenoid cavity, and C the shape of the condyle which fits into it. The ruminant type presents a socket and a condyle nearly flat, so as to admit of the lateral movement necessary for grinding the food. This form is see i in fig. 15, which is taken from the sheep (No. 1250). 15 _ In the rodent type there is a longitudinal groove in the temporal bone in which the condyle plays from before backwards like a plane. Fig. 16 shows the corresponding surfaces of the glenoid cavity (G), and the condyle (C), in the capybara (No. 3276). f *^ Tb. e joint of the lower jaw in man partakes e somewhat of the nature of these three types : we can move our jaw in the vertical direction, from side to side, and from before backwards. The teeth of man are likewise inter- Fia. 16. mediate in structure between those of carnivorous and those of ruminant animals. Man is adapted, by his dentition, to eat animal or vegetable food, and is said to be omnivorous. But the presence of grinding, tearing", and cutting teeth, equally de- veloped, in the jaws of any animal, is no proof that he is omnivorous. Monkeys have large canines, yet live on vegetables ; all bats possess well-formed in- cisors, canines, and molars, yet some are purely frugivorous, whilst the British species live entirely on insects. PLATE XVIII. %2. life.*. Kg. 3. Fife. I. Anterior fontanelle . Posterior fontanelle , Fatal skull fiill term. Tympanic bone. Foetal s"kull full term. Drawn on Stone "by T. Godant. 125 THE SKULL AS A WHOLE. The examination of the Skull as a whole is easy and intelligible, provided the individual bones have been carefully studied. Course of Sutures. — A knowledge of the course of the sutures is of practical value — 1, because it enables us to say with precision in what direction the head of the child is presenting during labour ; 2, because in injuries of the skull we must not commit the error of mistaking a suture for a fracture. 38 Cobonal Suture. — The ' coronal suture ' (Plate XVIII.) (fronto- parietal) connects the frontal with the parietal bones. It extends transversely across the top of the skull, from the great wing of the sphenoid on one side to the other. In the middle the frontal overlaps the parietal bones, but at the sides the parietals overlap the frontal, by which arrangement the bones are locked together. Sagittal Suture. — The 'sagittal suture ' (inter-parietal) con- nects the two parietal bones. It runs backwards, in the middle line, from the frontal to the occipital bone. This suture is much serrated, except near the parietal foramina, where it is always much straighter than elsewhere. 39 Frontal Suture. — The ' frontal suture ' is formed by the union of the two halves of the frontal bone. It runs down the middle of the forehead, from the sagittal suture to the root of the nose. It always exists in infancy and childhood, but is generally obliterated in the adult (Plate XVIII.) Lambdoid Suture. — The ' lambdoid suture ' (Greek letter A) (occipito-parietal) unites the two parietals to the occipital bone. Occipito-Mastoid Suture. — The ' occipito-maBtoid suture,' 40 126 THE SKULL AS A WHOLE apparently a continuation of the lambdoid, connects the occipital with the mastoid portion of the temporal bone. Masto-Parietal Suture. — The mastoid part of the temporal is connected to the posterior inferior angle of the parietal bone by the ' masto-parietal suture.' Squamous Suture. — The squamous part of the temporal is connected to the parietal bone by the ' squamous suture ' (squamo- parietal) ; and to the great wing of the sphenoid by the ' squamo- sphenoidal ' suture. The squamous bone so overlaps the parietal as to strengthen the arch of the skull at the sides, and prevent the lateral expansion of the buttresses. Transverse Frontal Suture. — Of the sutures which connect the bones of the cranium with the face, the chief one is the ' transverse frontal suture.' It extends from the external angular process of the frontal bone, from one side to the other, across both orbits and the root of the nose (Plate XVI.) It connects the frontal with the malar, sphenoid, ethmoid, lachrymal, supe- rior maxillary, and nasal bones. Other short sutures, such as the ' spheno-malar,' ' spheno-parietal,' ' zygomatic,' &c, speak for themselves. A knowledge of the sutures is of practical value in midwifery. Thus when we feel the meeting of the three sutures at the top of the occipital bone, we know that the back of the head presents ; if, again, we feel the ' anterior fontanelle,' or lozenge-shaped space where four sutures meet (Plate XVIII.) , we know it is a fore- head presentation. THE SKULL-CAP. Skull-Cap : Outer Surface. — The skull-cap forms an oval dome which protects the brain with its greatest breadth about the parietal protuberances. In a well-formed European head, if we look at the skull-cap from above (the beginning of the sagittal suture being in the centre of the perspective plane), we see scarcely anything but the smooth expanded vault of the cranium. But in the Negro and the Australian, the narrowness of the temples allows the zygomata to come into view, and, in the most THE SKULL-CAP 127 ' prognathous ' 41 examples, the incisor teeth appear in front of the frontal sinuses. Foramina. — On the outer surface of the skull-cap are a mul- titude of small foramina, which transmit blood-vessels from the pericranium into the substance of the bone. Hence, if this mem- brane be torn off during life, the bone bleeds through minute pores. On each side of the sagittal suture is the ' parietal fora- men,' which transmits a vein from the superior longitudinal sinus to the outside of the skull ; sometimes a small artery runs with it, and communicates with a branch of the middle meningeal. Temporal Eidge. — Along the side of the skull-cap is a curved line, the temporal ridge (Plate XV.) (or ridges, as described in connection with the temporal bone), which indicates the attach- ment of the temporal aponeurosis to the frontal and parietal bones, and the limit of the attachment of the ' temporal ' muscle to the fossa of the same name. Temporal Fossa. — The ridge circumscribes the ' temporal fossa,' which is formed by the frontal, parietal, temporal, sphenoid, and malar bones. The fossa gives origin to the temporal muscle, of which the tendinous rays, converging beneath the zygoma, are inserted into the coronoid process of the lower jaw. The size of the temporal fossa in all animals depends upon the size of the temporal muscle. Hence it is largest in the carnivora. Skull-Cap : Inner Surface. — On the inner surface of the skull-cap we observe — 1, the groove in the middle line, which gradually becomes broader as we trace it backwards, for the superior longitudinal sinus ; 2, on either side of this, especially in old skulls, are a number of irregular excavations, occasioned by the ' Pacchionian bodies ; ' 42 3, grooves for the ramifications of the middle meningeal artery. The main groove, at first some- times a complete canal, is seen at the anterior-inferior angle of the parietal bone ; from thence it spreads widely over the frontal and parietal bones, one branch of considerable size traversing the posterior-inferior angle of the parietal above the groove for the lateral sinus. In fractures of the skull, the arteries running in these grooves are liable to be injured, and thus occasion an effusion of blood, producing compression of the brain. 128 THE SKULL-CAP Thickness of the Skull-Cap. — The skull-cap differs in thick- ness in different parts. This is easily ascertained by holding it to the light. As a rule, it is thicker in parts which were the centres of ossification — as at the frontal and parietal eminences. It is thinnest in the temporal region. The ordinary thickness of an adult skull is about one-fifth of an inch, though it varies very much at different periods of life. Skulls vary in thickness, even in persons of the same age, and this without any obvious reason. Old age causes general thinning of the skull, as it does all bones in the body, by a process of absorption ; while certain diseased states occasion either general or partial thickening or thinning of the skull. Cerebral Impressions. — The inner surface of the skull-cap is marked by the cerebral convolutions, so that it takes, to a certain extent, an impression of the brain. But it cannot be said that a particular impression on the • inner surface has a corresponding bump outside. A glance at any skull-cap is sufficient to prove this. The depressions occasioned by the convolutions take place at the expense of the diploe ; and the external bumps are often caused by a mere thickening of the outer table. On the other hand, it holds good, as a general rule, that the external form and dimensions of the cra- nium may be taken as a general expression of the corresponding lobe of the brain, whether in the frontal, the pa- rietal, or the occipital region. The general characters of the brain, then, may be ascer- tained by external examination, but not the individual details. Veins of the Diploe.— The diploe of the skull-cap is tra- versed by numerous venous canals. These (fig. 17) are of considerable size, and are best displayed by filing off the outer Fio. 17. VENOUS CANALS IN THE DIPLOE. PLATE XIX "Foramen caecum .Groove for aritr meningeal artery. ..Crista. ^>aTK. . Slit for nasal nerve . ..01fa.efcory canals in nSe Olfactory groove . Sphenoidal fissure . Foramen opticum. .01 ivary process . Ant? cl i noi 6\ proces s . Pituitary-fog Sa. Tro rajneii rotuno^rrn • •PostTcli-noid process. . Crroovefor Caro+idartery ."Foramen ovate. Eoramen laeerurn medium. .Foramen, gpinosutn, ffiatusFaHopii.. «.. ..Inf r petrasal. groove. TVCea.tus aud'tonus interims , .■_,•■;'.■. EoTamenlaceruirf posterms Aquecluctus vest'ibuli. .Ant 1 * condyloid ftjratnrn. .Post 1 ? condyloid foramer. ..pupTpetroaal groove. Mastoid -foramen.. . . G roove for posterior roerucrtje&l artery. Groove for lateral sinus. Internal occipital prcAuberarsj Drawn on. Stoae by T. Godart . From nature byL.Holclen. Printed tyWest,Nevrniaii&vO' THE SKULL-CAP 129 table. Their course is by no means so regular as they are commonly drawn ; but, in a general way, we may speak of the frontal, anterior and posterior temporal, and occipital ' diploic ' veins on each side of the skull. The frontal discharges its blood at the supra-orbital notch into the supra-orbital vein; the anterior temporal opens externally into the deep temporal vein and internally into the spheno-parietal sinus ; the posterior tem- poral opens internally into the lateral sinus ; the occipital pours its blood either externally into the occipital veins or internally into the lateral sinus. After injuries of the head, these veins are liable to inflammation, which may give rise to pus in the diploe and pyaemia. Hence the occasional occurrence of visceral ab- scesses, especially hepatic, after injuries of the head — a circum- stance which had not escaped the notice of the old surgeons. BASE OP THE SKULL AS SEEN FROM ABOVE. By referring to Plate XIX. it is seen that the base of the skull presents, on each side, three fossae, — an anterior, a middle, and a posterior, — respectively lodging the frontal and temporo- sphenoidal lobes of the cerebrum, and the cerebellum. The occipital lobe of the cerebrum rests upon the ' tentorium cere- belli,' and not upon bone. The anterior and middle fossae are marked by the cerebral convolutions just as much as the skull- cap, especially the anterior. Anterior Fossa of the Cranium. — The anterior fossa of the cranium is formed by the orbital plates of the frontal, the cribriform plate of the ethmoid, with the front part of the body and the lesser wings of the sphenoid. The points to be noticed in this fossa are as follows : 1. The ' foramen caecum,' which is usually pervious, and transmits a vein from the superior longi- tudinal sinus into the nose. 2. The grooves for the ' anterior meningeal arteries,' branches of the anterior and posterior eth- moidal of the ophthalmics. 3. The ' crista galli,' which gives attachment to the falx cerebri. 4. The slits for the 'nasal 130 BASE OF THE SKULL AS SEEN FEOM ABOVE nerves,' branches of the first divisions of the fifth nerves. 5. The ' olfactory grooves,' perforated by foramina, which give passage to the filaments of the olfactory lobes. 6. The ' anterior ethmoidal foramina ' on the outer side of the olfactory grooves for the transmission of the nasal nerves and anterior ethmoidal vessels. 7. The ' posterior ethmoidal foramina,' at the hinder extremities of the olfactory grooves, for the passage of the pos- terior ethmoidal vessels. middle Fossa of the Cranium. — The middle fossa of the cranium supports the temporo-sphenoidal lobes of the cerebrum, and is formed by the body and the great wings of the sphenoid, squamous and petrous portions of the temporal bones, and a little bit of the anterior inferior angle of the parietals. It is narrow in the middle and wide at the sides. The fossa is separated from the anterior one by the anterior edge of the optic groove, the upper margin of the optic foramina, the ' anterior clinoid processes ' to which the ' tentorium ' is attached, and the posterior borders of the lesser wings of the sphenoid. The basilar suture, if present, and the upper margins of the petrous portions of the temporal bones separate it from the posterior fossa. In each lateral half of the fossa the chief points to be noticed are : 1. ' The sphe- noidal fissure ' between the wings of the sphenoid, leading to the orbit, and transmitting the 3rd, the 4th, the first division of the 5th, and the 6th nerves, also filaments of the sympathetic nerve and the ophthalmic vein. 2. The ' foramen rotundum ' giving passage to the superior maxillary, or second division of the 5th nerve, and behind it one or two ' foramina of Vesalius.' 3. The ' foramen ovale ' giving passage to the inferior maxillary, or third division of the 5th nerve, and to the arteria meningea parva, and sometimes to the lesser petrosal nerve. 4. The ' foramen spinosum ' giving passage to the arteria meningea media and its two veins— the main trunk of this artery grooving the squamous part of the temporal and the anterior-inferior angle of the parietal bone. 5. The ' foramen lacerum medium ' blocked up, in the recent state, by fibro-cartilage — the Vidian (great petrosal) nerve running through the cartilage. The internal carotid artery also passes through it. 6. At the apex of the petrous portion of the BASE OF THE SKULL AS SEEN FROM ABOVE 131 temporal bone the termination of the ' carotid canal,' through which the carotid artery enters the skull : the artery then winds along the groove on the side of the body of the sphenoid. 7. On the front surface of the petrous portion of the temporal bone the 'hiatus Fallopii,' which transmits the great petrosal nerve, and external to it is the opening of the canal for the lesser petrosal nerve. Further back, on the same surface, we may ob- serve the eminence for the anterior (superior) semicircular canal. In the middle line we see the — 8. ' Groove for the optic nerve,' terminating at each end in the ' optic foramen.' 9. The ' olivary eminence,' which supports the commissure of the optic nerves, and perhaps on each side of it the ' middle clinoid process.' 10. The ' pituitary fossa,' or ' sella turcica,' for the reception of the pituitary body, with the ' groove for the cavernous ' sinus on each side of it. 11. The broad ' dorsum sellse,' with the 'posterior clinoid process ' formed by its free superior-external angles, and giving attachment to the tentorium cerebelli, and, under cover of each of these processes, a notch for the passage of the third nerve. In the lateral part of the fossa we notice a fairly deep groove for the passage of the middle meningeal artery. Posterior Fossa of the Cranium. — The posterior fossa is the largest and deepest of the cranial fossae, and is formed by the occipital bone, with the petrous and mastoid parts of the temporal bone. It supports the cerebellum and does not show eminences and depressions for the brain as the anterior and the middle fossae do. Proceeding from before backwards, we observe, in the middle line : 1. The ' basilar groove,' which supports the medulla oblongata and the pons Varolii. 2. On each side of this is the groove for the ' inferior petrosal sinus.' 3. Along the top of each petrous bone is the groove for the ' superior petrosal sinus.' 4. Both these sinuses terminate in the corresponding great 'lateral sinus,' which grooves successively the occipital, posterior- inferior angle of the parietal, mastoid part of the temporal, and, last of all, the jugular process of the occipital bone. A line drawn on the outside of the head, from the occipital protuberance to the front border of the mastoid process, corresponds with the lateral sinus of the corresponding side. On the posterior aspect x 2 132 BASE OF THE SKTJLTi AS SEEN FEOM ABOVE of the petrous part of the temporal bone is — 5. The ' meatus auditorius interims,' for the facial, auditorypars intermedia nerves and the little auditory artery. 6. Some distance behind, and external to the meatus, is the ' aqueductus vestibuli,' somewhat concealed by an overhanging ridge of bone. This so-called ' aque- duct ' transmits, if anything, a small vein from the vestibule of the ear. Behind the basilar process is — 7. The ' foramen magnum,' which transmits the spinal cord and its membranes, the vertebral arteries, and the spinal part of the spinal accessory nerves. 8. On each side of the foramen magnum are the ' condyloid foramina,' of which the ' anterior ' transmits the hypoglossal or 9th nerve (motor nerve of the tongue) ; the ' posterior,' a vein from the lateral sinus to the outside of the skull. 9. The ' mastoid foramen ' transmitting a vein from the lateral sinus to the outside of the skull. 10. Lastly, the 'foramen lacerum posterius 'transmitting tbe three divisions of the 8th nerve, the inferior petrosal sinus, and also the blood from the lateral sinus into the internal jugular vein. The nerves pass through the anterior part of the foramen, which part is separated from the posterior by a bony ridge ; one or two small ' posterior meningeal ' arteries also lie in the foramen. 11. In the mid-line, between the 'foramen magnum' and the ' internal occipital protuberance,' is the ' internal occipital crest,' with the ' groove for the occipital sinus.' 12. On the right side of the internal occipital protuberance, sometimes on the left, is the 'torcular Herophili,' forming the dilated beginning of the right lateral sinus. BASE OF THE SKULL, WITHOUT THE LOWEE JAW, AS SEEN PEOM BELOW. (Plates XX., XXI.) When viewed from below the base of the skull, the lower jaw having been removed, presents an oval figure, bounded upon each side in front by the incisor, canine, bicuspid, first molar teeth and the lower border of the malar process of the superior PLATE XX. Ant^patatine canal fi Palatine groove. Posterior palatine canal, Rid^e of palate bone. . Aece sso ry pakti n e canals . ,Ebst T nasal spine. .Hatnular process . . Sphenoidal process of palate tone. . Pterygopalatine canal. mma Scaphoid fossa. .Tjbrarrten ovale. . Eor am e nlace rum "medium. . .Eoramen spLnogum, .Canal 'fbr Eustachian tube. ..CaroticTi ca.T\a\. ..Ant^condlyloii foramen. .foramen for Jaosbsorte Tierve .Aqueductus cochleae. ..Foramen laeerurri posterius . .Foramen fbr- Arnolds nerve .. Stylomastoid foramen . . Post r eon3yloi6l foramen External Occipital protuberir.ee.; Drawn on. Stone "by T. Godart. From, nature by L.Holden. Printed ToyWest,Hewman&. Co. BASE 0E THE SKULL AS SEEN FROM BELOW 133 maxillary bones ; laterally, by the lower border of the zygomatic arch, the posterior root of the zygomatic process of the temporal, its upper branch, an imaginary line connecting the posterior root with the outer end of the superior curved line across the base of the mastoid process ; posteriorly, on each side, the superior curved line terminating internally in the external occipital pro- tuberance. The principal points to be noticed are the : — Arch of the Palate. — In front is the arch of the ' hard palate,' formed by the superior maxillary and palate bones : its ' middle ' and ' transverse ' sutures cross each other at right angles. A pin introduced at the point of crossing would touch five bones, the 5th being the vomer. Generally speaking, when the palate presents a fine arch, free from contraction in any direction, the voice is clear and sonorous. The best singers have always well- formed palates. Its surface is rugged, excepting that part formed by the palate processes of the palate bones, for the lodgment of the palatine glands, and it is riddled with minute holes for the passage of blood-vessels. Behind the incisor teeth is the ' anterior palatine canal ; ' a single orifice below, but showing, a little way up, the antero-pdsteriorly placed foramina of Scarpa and the two laterally situated foramina of Stenson. The antero- posterior foramina transmit the naso-palatine nerves, the lateral ones the anterior palatine blood-vessels. Near the last molar "tooth, of each side, is the orifice of the ' posterior palatine canal,' formed conjointly by the palate and superior maxillary bones : and from this we trace forwards the ' palatine groove ' for the lodgment of the descending palatine vessels and the large pala- tine nerve. Lastly, there is the ' ridge ' on the palate bone for the attachment of the ' tensor palati,' and the 'posterior nasal spine,' to which is attached the ' azygos uvulae.' Bounding the palatine arch anteriorly and laterally is the horseshoe- shaped alveolar border, with sockets corresponding to the fangs of the teeth. Posterior Opening's of Nose. — Behind the palate are the posterior openings of the nasal fossa, separated by the sharp edge of the vomer. Each opening is somewhat oval, about one 134 BASE OF THE SKULL AS SEEN FROM BELOW inch in the long diameter and half an inch in the transverse. We should remember this in plugging the nostril. It is bounded,; above, by the alae of the vomer and the vaginal processes of the sphenoid ; below by the horizontal plate of the palate ; outside, by the internal pterygoid plate of the sphenoid ; and inside, by the vomer. In the upper boundary of each is the posterior opening of the ' pterygo-palatine canal ' for the transmission of a branch of the internal maxillary artery and a nerve from the spheno-palatine ganglion to the top of the pharynx. Pterygoid Reg-ion. — On each side of the nasal openings are the ' pterygoid processes ' of the sphenoid. These pterygoid pro-' cesses bound the posterior openings of the nose ; act as buttresses to support the upper jaw-bones behind ; and serve for the origin of the powerful pterygoid muscles which grind the food. From the pterygoid fossa, or, more strictly, from the inner surface of the external' pterygoid plate and the back of the tuberosity of the palate bone which fits into the gap between the pterygoid pro- cesses, arises the ' pterygoideus internus ; ' while the outer surface of the same plate and the adjacent outer aspect of the tuberosity of the palate bone give origin to the ' pterygoideus externus.' At the base of the internal plate is the scaphoid fossa, for the origin of the ' tensor palati,' and into which, as also into the bottom of the pterygoid fossa, open the ' foramina of Vesalius;' and at the apex is a pulley, termed the ' hamular process,' around which the tendon of this muscle plays. Besides this, the hamular process gives origin to part of the ' superior constrictor ' of the pharynx. Immediately above the ' scaphoid fossa,' and really not seen when viewing the skull from below, is the posterior orifice of the Vidian canal. Proceeding backwards from the base of the pterygoid pro- cesses, we come next upon the great foramina at the base of the skull, most of which have already been seen in the examination of the base from above. In the great wing of the sphenoid there is the ' foramen ovale.' The ' foramen rotundum ' cannot be seen on the inferior aspect of the base of the skull : look for it at the back of the orbit. Behind the foramen ovale is the ' foramen spino- sum ; ' and still farther back is the apex of the wing, termed the PLATE XXI. Aponeurosis or Tensor pajati Asy^os uvulse Suj^constrictorofPhary Aponeurosis of Pharynx Reetois capitis amicus rrnn Drawn on Stone Vy T. Go dart. Printed loyWest,Newmaii& Co. BASE OF THE SKULL AS SEEN FROM BELOW 135 ' spinous process,' which is wedged between the squamous and petrous bones, and gives attachment to the internal lateral liga- ment of the lower jaw. From the spinous process we trace out- wards the glenoid fissure,' which runs across the ' glenoid cavity ' Fig. 18. DIAGBAM Or THE RELATIVE POSITIONS OF THE HOKE ISHPOETANT PAKTS AT THE EASE OF THE SKULL. The dotted arrow shows that the mastoid process, the stylo-mastoid foramen, styloid process, and the spinous process of the sphenoid (represented by stars), and the Eustachian tube are pretty nearly in a line. Outside the arrow are : 1. Scaphoid fossa. 2. Foramen ovale. 3. Foramen spinosum. 4. Spinous process. 5. Glaserian fissure. 6. Meatus auditorius externus. Inside the arrow are : 7. Pterygo-palatine canal. 8. Foramen laeerum medium. 9. Carotid canal. 10. Foramen jugulare. 11. Notch for 8th nerve. 12. Anterior condyloid foramen. with the ' eminentia articularis ' in front of it. Between the sphenoid and petrous bones are the canals for the ' Eustachian tube ' and the ' tensor tympani ' muscle. Petrous Region. — The petrous portion of the temporal bone 136 BASE OF THE SKULL AS SEEN FEOM BELOW is wedged in between the sphenoid and the basilar process of the occipital. Observe that the apex of the wedge is cut short, so that an irregular opening, termed the ' foramen lacerum medium,' remains between the three bones. In the recent skull this space is filled with cartilage, in which lie the internal carotid artery surrounded with filaments of the sympathetic nerve, and the Vidian nerve. The apex of the petrous bone gives origin to the ' tensor tympani ' and ' levator palati.' In the middle of the petrous bone is the wide orifice of the carotid canal which trans- mits the carotid artery. Trace this canal, and you will find that it does not enter the cranial cavity directly, but that it ascends for a short distance, and then runs horizontally forwards and inwards through the petrous bone, till it opens at the apex into the foramen lacerum. Thus the carotid artery makes two curves, like the letter S, before it enters the cranium — the first curve in the bony canal, and the second in the cartilage which fills up the foramen lacerum. This disposition of the great arteries at the base checks the force of the blood on its passage to the brain. Behind the carotid canal is the ' foramen lacerum posterius,' or ' foramen jugulare,' another opening left between the petrous and occipital bones. The size and shape of it are subject to great variety. The right jugular foramen is usually larger than the left. It is generally divided by a projecting tongue of bone into an interior part, which transmits the eighth nerve, and a posterior, which is by far the larger, for the passage of the blood from the lateral sinus into the commencement of the internal jugular vein. The posterior meningeal arteries (from the .occipital and ascending pharyngeal branches of the external carotid) and the inferior petrosal sinus pass through this aperture. Outside the foramen lacerum posterius is the ' styloid process,' projecting, more or less, beyond the ' vaginal process ' at its root. Behind this is the ' stylo-mastoid foramen, through which the facial nerve emerges from, and the stylo-mastoid artery enters, the skull. Still farther back is the ' mastoid process,' and the ' digastric fossa ' for the origin of the digastric muscle. Internal BASE OF THE SKULL AS SEEN FEOM BELOW 137 to this fossa may be generally seen a groove for the occipital artery. Basilar Process. — The basilar process of the occipital bone projects into the base of the skull, and joins the body of the sphenoid. It affords insertion to the ' rectus capitis anticus major ' and ' minor,' and (by means of a little tubercle) to the aponeurosis of the pharynx. Behind the basilar process is the ' foramen magnum.' On each side of this are the ' condyles ' of the occiput, with the ' anterior ' and ' posterior condyloid ' fora- mina ; and on the outside of each condyle is the ' jugular emi- nence,' which gives insertion to the ' rectus capitis lateralis.' Occipital Foramen. — In a well- formed European skull, the plane of the occipital foramen looks downwards with a slight in- clination forwards when the body is erect, and its anterior ex- tremity is about half-way between the tuberosity of the occipital bone and the incisors of the upper jaw. This central position of the occipital foramen and the condyles is one of the great pecu- liarities of man, who stands erect. His head, therefore, is almost equally balanced on the top of the spine. In monkeys, who hold a middle rank between man and quadrupeds, the foramen mag- num is placed farther back : in the orang-outan, it is about twice as far from the foramina incisiva as from the back of the head. Consequently, although monkeys can stand erect for a time, they cannot do so long. In quadrupeds, again, the foramen magnum is still nearer to the back of the head, and its plane forms a considerable angle with the horizon. The weight of the head in quadrupeds is sustained, not only by the spine, but by an elastic ligament of great strength (ligamentum nuchas), which arises from the lofty spines of the dorsal vertebrae, and is fixed to the crest of the occiput. Stretching from the posterior ex- tremity of the foramen magnum to the ' external occipital pro- tuberance ' is the ' external occipital crest ' for the attachment of the ' ligamentum nuchas.' Extending from each side of the middle of this crest to the lateral angle of the occipital bone is the 'inferior curved line.' In the occipito-mastoid suture, or situated entirely in the mastoid portion of the temporal bone, is the ' mastoid foramen ' for the passage of a vein, and usually a 138 BASE OF THE SKULL AS SEEN FROM BELOW small artery. Between the foramen magnum and superior curved lines muscles are attached as shown in Plate XXI. TEMPORAL, ZYGOMATIC, AND SPHENO-MAXILLARY FOSSAE. The temporal fossa (see p. 127) leads into the zygomatic fossa, the boundary between them being the crest of the sphenoid bone. Zygomatic Fossa. — The ' zygomatic fossa ' is bounded ex- ternally by the zygomatic arch, which serves as a strong buttress to support the bones of the face, and gives origin to the powerful ' masseter ' muscle which closes the mouth. In front of the fossa there is the back part of the superior maxilla, and at the bottom of it, the outer pterygoid plate of the sphenoid, which gives origin to the external pterygoid muscle. At the deepest part of the fossa are two wide fissures at right angles to each other : one, nearly horizontal, leads into the orbit, and is called the ' spheno- maxillary fissure,' through which the superior maxillary nerve and the infra-orbital artery enter the infra-orbital groove on the floor of the orbit. Spheno-maxillary Fossa. — The other fissure, nearly ver- tical, leads to the ' spheno-maxillary fossa,' in which the third part of the internal maxillary artery breaks up into terminal branches. This fossa is bounded in front by the back of the superior maxilla ; behind, by a smooth surface at the base of the pterygoid process ; internally, it is separated from the nasal fossaB by the perpendicular plate of the palate bone. There are five openings into the spheno-maxillary fossa (see Plate XXII.), as follows : Five Openings into Spheno-maxillary Fossa. , . ., . , | Internal or nasal branches of spheno- f transmits into ... ,. r 1. Sphenopalatine foramen the nasaK „ pal , atme &*&«*■ . ( . JN asal or spheno-palatine branch ot { internal maxillary artery. 2. Posterior-palatine canal \ tr « wmitB *° , Descending palatine artery and large i the palate I palatine nerve. o -c j ., (Superior maxillary nerve, or secon 3. Foramen rotundum . transmits . \ f . . . * »„, . I division of fifth pair. PLATE XXII. Lachrymal tone. /Groove fomasalduct, .Art 7 " ethmoidal foramen PostTethmoiia 1 foramen. Ethmoid bone Bool/ of Sphenoid bone. Pala.be "bone, Foramen rotun.clum.... Pfcery^o- palati ne catial . Vidian canal Sphenopalatine ■foramen at tVietobtom of tlie Sphenomaxillary fossa. ■ PostTpalatine canal , Maxillary process of infr Spongy bone.--'' 'Unciform process oF Ethmoid bone Diagram of. the Bone? and ForaTrun.a. on the inner wall op the Orbits the five openings into the Spheno-maxillary fossa. , the Antrum and bones contracting its orifice. TEMPORAL, ZYGOMATIC, AND SPHENO-MAXILLARY FOSSJE 139 4. Vidian canal . . . transmits . Vidian artery and nerve. Pterygopalatine branch of internal 5. Pterygo-palatine canal . transmits maxillary artery, and pharyngeal nerve from Meckel's ganglion. THE OEBITS. The orbits, or sockets for the eyes, are like crypts excavated beneath the cranium. (Plate XVIII.) To use the words of Sir Charles Bell, ' these under arches are groined ; ' that is to say, they are provided with strong ribs of bone, so that there is no need of thick bone in the interstices of the groinings. The plate between the eye and the brain is as thin as parchment : but look bow strong- is the arch forming the orbital margin, and what a strong ridge of bone runs up from the zygoma, like a buttress to support the side of the arch. When the eye is threatened, the margin of the orbit is more than strong enough to protect it from the effects of violence. ■ Each orbit is pyramidal, with the apex behind. Their axes, if prolonged, would pass through the optic foramina, and meet behind the pituitary fossa of the sphenoid. This divergence gives a greater range of vision. The anterior opening of the orbit is quadrilateral and consists of an upper, a lower, an inner, and an outer margin. In the higher types of man these openings are more rounded. Upper Wall of Orbit. — The upper wall of the orbit is slightly arched, and formed by the frontal bone and lesser wing of the sphenoid. On this wall are — 1, the optic foramen; 2, the fossa beneath the external angular process for the lachrymal gland ; 3, the little depression for the pulley of the ' superior oblique ' muscle ; 4, the supra-orbital foramen or notch, situated at the junction of the inner with the middle third of the orbital margin. Lower Wall or Floor of Orbit. — The lower wall of the orbit slopes downwards and outwards, and is formed by the orbital plate of the superior maxilla, by part of the malar bone, and behind by the orbital plate of the palate bone. On this wall is the groove for the infra-orbital nerve. 140 THE ORBITS Inner Wall op Orbit. — The inner wall (Plate XXII.) is formed by the nasal process of the superior maxilla, by the lachrymal, the os planum of the ethmoid, and the side of the body of the sphenoid bone. Here we observe the groove for the nasal duct, formed conjointly by the nasal process of the superior maxilla, the lachry- mal, and the inferior spongy bone. Its direction is downwards, backwards, and a little outwards, and it leads into the inferior meatus of the nose. Besides this, there are the ' anterior and posterior ethmoidal foramina.' Outer Wall of Orbit. — The outer wall of the orbit is formed by the malar bone and the orbital plate of the great wing of the sphenoid. Here there are one or two small foramina (malar canals), which transmit small nerves from the orbit to the skin of the cheek and temple. (See p. 104.) The outer wall of the orbit recedes more than the other parts of its circumference, giving so great a range of vision externally, that by rotating the head on each side of the spine, we can see all round. Bones Composing- Orbit. — Look into the orbit and examine two four-sided plates, one on the inner side belonging to the ethmoid, and one on the outer belonging to the great wing of the sphenoid. The four-sided plate of the ethmoid articulates above with the frontal ; below with the superior maxillary bone, in front with the lachrymal and behind with the sphenoid. Besides these the orbital process of the palate bone here comes up between the sphenoid and superior maxilla (articulating with both of them) and joins the posterior in- ferior angle of this plate. The four-sided plate of the sphenoid articulates likewise with the frontal bone above, the frontal bone arching over from the top of the aforesaid plate of the ethmoid ; below, its edge is separated from the superior, maxillary bone by the spheno-maxillary fissure ; in front, it articulates with the malar bone, and behind, its edge is separated from the rest of the sphenoid, by the sphenoidal fissure. These articulations should be traced on the bones and thoroughly mastered. Thus, seven bones enter into the composition of each orbit : namely— the frontal, ethmoid, and sphenoid, the superior maxilla, the malar, the lachrymal, and the palate ; but there are only eleven PLATE H Nasal spine of ErontaA bone ... Crest of Nasal "bone Per pendieular •plate of ■E"thfTioiatoone Crest of sup^Maxillarybone Frontal sinus. Crista. 6aTVi . Rostrum or {3pnenoicl bone Crest of Palate W, View of tVie Septum of tbeNose Probe/passed from Frontal pinus into Middle meatus Middle 5pon6y bone.^ Superior "Meatus., Superior Spongy bone, Pterygopalatine canal 5 pheno -palatine foramen Middle meatuss.. Inferior Tneatu 5 . ....NasaTbone ..Lachrymal,- bone. .Unciform ^eomss Orifice of Antrum. Inf!" Spongy bone. ; Groove of Scarpa, A.nt?Palafcii>ecai*L View of the tWee" Meatus" of -fheTSSoae. Drawn on Stone by T. Godart. From nature by L.Holden * illied llj ^J^JsIewrriaii &, Co- THE OEBITS 141 bones in the two orbits, since the first three bones are common to both. Sphenoidal and Spheno-maxillary Fissures. — At the back of the orbit are two wide fissures for the admission of blood- vessels and nerves. The upper one is the ' sphenoidal fissure,' formed between the greater and lesser wings of the sphenoid bone, It leads into the cranium, and transmits the third and fourth nerves, the ophthalmic branch of the fifth, the sixth nerve, some filaments of the sympathetic nerve, and the ophthalmic vein. The lower one, the ' spheno-maxillary fissure,' leads into the zygomatic fossa. The borders of this fissure are formed antero-internally by the superior maxillary and palate bones, postero-externally by the sphenoid. It is completed in front and outside by the malar. 43 Through this fissure the infra-orbital artery and the superior maxillary nerve enter the groove along the floor of the orbit. NASAL FOSSA (Plate XXIII.) These cavities open widely in front, and admit the air through the nostrils, and behind into the top of the pharynx. To study them properly it is indispensable to have a skull divided lon- gitudinally on one side of the septum, so that we can examine the roof, the floor, the outer and inner surfaces of the cavities. Boundaries of Nasal Fossae. — The 'roof of each of the nasal fossae is formed by the nasal bones, by the nasal spine of the frontal, the cribriform plate of the ethmoid, and the body of the sphenoid, with the alaa of the vomer and the vaginal plates resting upon it. It does not form a horizontal plane from before backwards. It is only the cribriform plate which is horizonta ; from this, the roof slopes downwards and forwards towards the nose, and downwards and backwards towards the pharynx : there- fore the vertical depth is much greater in the middle than else- where. Notice the greater thinness of the cribriform plate, and 142 NASAL FOSSAE how easily an instrument might be thrust through this part of the roof into the brain. The 'floor ' is nearly horizontal, and is formed by the palate plates of the superior maxillary and palate bones. In the dry bones can be seen, on each side of the septum, the foramina of Scarpa and Stenson. The outer wall of the nasal fossa is made irregular by the ' meatus ' or passages in the nose, and the numerous openings leading to the air-cells, in the neighbouring bones. It is formed by the ethmoid (including its two turbinated bones), the nasal, the superior maxillary, the lachrymal, the inferior turbinated, the palate, and the internal pterygoid plate of the sphenoid. It is important to observe the position of the turbinated bones and the three ' meatus ' or passages of the nose. (Plates XXIII. and XXIV.) Superior Meatus. — Beneath the superior turbinated bone lies the ' superior meatus,' into which open the posterior eth- moidal cells and the sphenoidal cells. At the back parts of this meatus is the spheno-palatine foramen, which leads into the spheno-maxillary fossa. Middle Meatus. — Below the middle turbinated bone is the ' middle meatus.' Into this open — 1, towards the front, the frontal sinus (or cell), along a passage termed the ' infundibulum ; ' 2, the anterior ethmoidal cells (distinct from the posterior) ; 3, the antrum or maxillary sinus. The orifice of the antrum is large and irregular in the dry bones ; but in the recent state it is so narrowed by mucous membrane that it will just admit a crow-quill. Inferior Meatus. — Below the inferior turbinated bone is the ' inferior meatus.' No air-cells open into this meatus : there is only the termination of the nasal duct or channel which con- veys the tears into the nose : this cannot be seen without re- moving part of the turbinated bone. The openings into the several ' meatus ' of the nose may be thus tabulated : Into the Superior Meatus . open J The s P henoidal cells - I. The posterior ethmoidal cells. %1. Section showing the Meatus of the Nose. %?• ..Nasal bone. .JMapal process op the upper Jaw. Nasal sp ine oFtheT?rontal bone Perpendicular plate oPEthmoiiibone. section, sho w m£ theNapal arch . „jn — r I mi —tyjiP-^J 311 iS-t-ons by T.Godart. From\ :i 4t-ure by L. Holder, . . Printed VWe s t,Newman & Co. NASAL FOSSAE 143 (The anterior ethmoidal cells. Into the Middle .... open J The frontal cells. [The antrum. Into the Inferior . . . opens The nasal duct. The two upper turbinated bones (belonging to the ethmoid) are delicately channelled for the lodgment of the olfactory nerves. The lower or third turbinated bone has nothing to do with the sense of smell, and is coarser in its texture. It is traversed by several canals and grooves, which run from before backwards, and in the recent state contain large veins. The turbinated bones do not extend throughout the whole length of the outer wall. All the surface in front of a perpendicular line let fall from the nasal spine of the frontal bone is smooth, as is also all the surface be- hind a perpendicular line from the spheno-palatine foramen. Inner Wall of Nose. — The bony septum of the nose, one of the principal supports of the nasal arch (Plate XXIII.) , is formed chiefly by the perpendicular plate of the ethmoid and the vomer. (Plate XXIV. fig. 2.) The formation of the septum is assisted by the nasal spine of the frontal, the crests of the nasal, superior maxillary, and palate bones ; also by the rostrum or crest of the sphenoid, making ten bones in all. The triangular interval left in the septum in the dry skull is filled up in the perfect one by the middle cartilage of the nose, which fits into a fissure in the bone. The posterior openings of the nasal fossa have been already described in the ' base of the skull ' (p. 133). The anterior open- ing is heart-shaped, with the broad part below. It is bounded on either side by the nasal bone, and by the nasal process of the superior maxilla. Below it is bounded by the palatine processes of the superior maxillary bones, which terminate in front in a sharp projection, termed the ' anterior nasal spine,' the promin- ence of which is a marked feature in the higher races of mankind. This projection is very diminutive in some of the lower races, and absent in monkeys. 144 GENEEAL OBSERVATIONS ON THE SKULL General Observations on the Skull. Skull a Lever of the rirst Order. — The entire skull repre- sents a lever of the first order. The fulcrum or point of support Fig. 19. F (see fig. 19) is at the occipito-atlantoid articu- lation ; the resistance is the weight of the head W ; the power P is the mass of muscle attached to the occiput. The skull is nearly balanced on the spine, and the muscles moving it have but small leverage. Contrast this, however, with that of the elephant (see p. 44), the massive appendages of whose head have proportionally strong muscles and ligaments for their movements and support. Three Layers or Tables of the Skull. — The cranial bones consist of three layers — an outer, an inner, and an intermediate ' diploe.' The outer is formed of compact and tough bone ; the inner is harder, but more brittle (hence called ' tabula vitrea ') ; while the diploe is softer and spongy, and diminishes the effects of shocks. Altogether, then, this structure may be coarsely com- pared to a case composed of wood outside, porcelain inside, and soft leather between the two. The different structure of these three layers or ' tables ' of the skull is interesting practically. In blows on the head, the inner table, in consequence of its great brittleness, is likely to be broken more extensively than the outer. Locking of the Bones.- — The bones are mechanically locked Fig- 20. together by the sutures; and in the recent state there is a thin layer of fibrous tissue between their edges, which diminishes the effects of blows. Most of the bones mutually support each other, by having their edges bevelled alternately on opposite sides, as in the' frontal suture ; or by one overlapping the other; as in the squamous suture, where the temporal prevents the ' starting ' of the parietal bone (see fig. 20). The GENERAL OBSERVATIONS ON THE SKULL 145 effect of this is, that no single bone can be taken out of the cranium without, separating the whole fabric. (Nor. Hum. Oat., No. 175.) Groins along- the Sinuses. — Notice how the interior of the dome is strengthened by' ribs ' or ' groins ' of bone, which run in the line of the principal sinuses. One rib extends from the centre of the frontal bone to the foramen magnum, and spans from before backwards the whole arch of the cranium. Another crosses transversely the back part of the occipital bone ; the point of intersection of these two ribs being at the occipital protuberance, which is the thickest and strongest part of the skull. Buttresses of the Skull. — Like all other arches, the cra- nium transmits shocks towards its buttresses ; these are firmly wedged into the base, and all meet at the centre, that is, at the body of the sphenoid. The frontal part of the arch is supported by the wings of the sphenoid and the malar bones, the parietal part by the temporal bones, and the occipital part supports itself by running, wedge-like, into the base, and abutting on the sphenoid. A knowledge of the buttresses which support the respective parts of the skull-cap affords an explanation of the direction which fractures generally take along the base of the skull, according as the injury has been received on the frontal, the parietal, or the occipital region of the cranium. Power of resisting' Shocks. — The older French school generally advocates the doctrine that the cranium resists shocks after the manner of other spheres, namely, that a blow struck on one side is transmitted to the opposite one ; as when a glass tumbler, struck smartly with the finger-nail, is made to crack on the opposite side. This they call fracture by ' contre-coup.' But the modern school contends that the cranium resists shocks like all architectural arches ; and that vibrations, instead of going round to the base direct, are lost upon the supporting pillars. The frontal pillars are the malar and sphenoid bones — the parietal pillars are the temporal bones — the occipital pillars are the ribs of the occipital bone itself. When the head is struck, the parietal region is most often the seat of injury. The bone breaks at the part struck, and the fracture runs on through the temporal bone, L 146 GENERAL OBSERVATIONS ON THE SKULL and most frequently through the tympanum — the weakest part. There are many excavations in the hone which weaken it about this part : 1, there is the ' meatus auditorius externus ' — 2, the cavity of the tympanum itself — 3, the jugular fossa — 4, the carotid canal — 5, the Eustachian tube. This accounts for the frequency of haemorrhage from the ear in cases of fracture of the base of the skull. Buttresses of the Upper Jaw. — In the bones of the face there are two points to be noticed — 1st, the great strength of the nasal arch (Plate XXIV.) ; 2nd, the extreme firmness of the upper jaw, fixed by its three buttresses on each side — namely, the nasal, the zygomatic, and the pterygoid. The nasal buttresses rest against the internal angles of the frontal bone, and between them is the heart-shaped opening of the nose. The zygomatic but- tresses are exceedingly strong ; they are supported by the external angles of the frontal bone and the zygomatic processes of the tem- poral, and correspond to the molar teeth, which have to sustain the greatest pressure. The pterygoid buttresses descend perpendicu- larly from the base of the skull, and support the upper jaw behind. male and Female Crania. — The capacity of the cranial cavity varies, as a general rule, with the intelligence of the indi- vidual or of the race. It has been shown that in almost all races the capacity of the cranial cavities of the women is to that of the men as 9 is to 10. The mastoid and the other processes for the attachment of muscles are less pronounced in women than in men. The orbital margins, and especially the external angular processes, are thinner and sharper in females' skulls. In women's skulls the glabella and frontal sinuses are but slightly developed. The digastric groove is better marked in males than in females. The masticatory apparatus is more massive in the males' skulls. The development of the frontal, parietal, and occipital regions may be taken as a general expression of the development of the corre- sponding lobes of the brain. Upon this is founded the study of Craniology. 44 Craniolog'y.— The accompanying diagram (fig. 21) and table of terms, introduced chiefly by Broca, are given here, as it is thought that some guide to the most important measurements of GENERAL OBSERVATIONS ON THE SKULL 147 the skull may be of use to those who, without a special know- ledge of anthropology, may take an interest in that science, and have opportunities for adding to our information in some par- ticulars. The most important points for mensuration and descriptive purposes situated in the middle line of the cranium, taken in order, are : 1. Alveolar point (A). The centre of the anterior margin of the upper alveolar arch. 2. Subnasal point or Spinal point (S). The middle of the SIDE VIEW OF SKDLL OF MALE AUSTEAIiIAN. A. Alveolar point. S. Subnasal point. N. Nasion. G. Glabella. Op. Ophryon, the centre of supraorbital line {Op I). Bg. Bregma. L. Lambda. 0. Occipital point, or most distant part of occiput from Op. B. Basion. St. Stephanion. Ft. Pterion. As. Asterion. O. Length of cranium. B Bg. Height of cranium. B N. Basinasal length. B A. Basialveolar length. N S. Nasal height. inferior border of the anterior nasal aperture, at the base of the nasal spine. 3. Nasion, or Nasal point (N). The middle of the naso- frontal suture at the root of the nose. 4. Ophryon (Op). A point situated immediately above the glabella, or, more exactly, the centre of the supraorbital L 2 148 GENERAL OBSERVATIONS ON THE SKULL line, which, drawn across the narrowest part of the fore- head, separates the face from the cranium. 5. Bregma (Bg). The point of junction of the coronal and sagittal sutures. 6. Lambda (L). The point of junction of the sagittal and lambdoidal sutures. 7. Opisthion. The middle of the posterior margin of the foramen magnum. 8. Basion (B). The middle of the anterior margin of the foramen magnum. On the lateral surface of the cranium are : 9. Pterion (Pt). The region, near the anterior part of the temporal fossa, where the great wing of the sphenoid, the squamosal, the parietal, and the frontal bones come near to each other in a varying manner in different individuals. 10. Stephanion (St). The point where the temporal ridge crosses the coronal suture. 11. Asterion (As). The point, behind the mastoid process, where the parietal, occipital, and temporal bones meet. The measurements of crania, except the circumference and capacity, are best taken with one instrument, a sliding caliper, which combines the purposes of the French compas d'epaisseur Fm. 22. CRANIOMETER : ONE-FIFTH THE ACTUAL SIZE. and compas-glissihr. It has been found so convenient for all cranial as well as other osteological measurements that a sketch of it is subjoined (fig. 22). The larger dimensions of the cranium GENERAL OBSERVATIONS ON THE SKULL 149 are taken with the curved arms, the smaller ones, as those of the nose and orhit, with the shorter pointed arms. C. Horizontal circumference. This is taken with the tape in the usual way, passing in front round the supraorbital line (above the glabella) and behind across the most prominent part of the occiput (fig. 21, Op 0). It gives a general idea of the size of the exterior of the cranium. L. Length. Unfortunately craniometrists are not yet in accord as to the best measure for taking this important measurement, which affects considerably the two follow- ing indices. It is in the Osteological Catalogue of the Eoy. Coll. of Surgeons always taken by placing one arm of the craniometer on the opbryon, and the other on the most distant part of the occiput (fig. 21, Op 0). The glabella, which is properly a part of the face, and which may vary much in development without any alteration in the essential form of the cranium, is thus excluded. The more usual continental method is given in fig. 21. B. Breadth, is the greatest parietal breadth. Bi. Index of Breadth. Latitudinal index or cephalic index. B x 100 L ' H. Height. Of the various methods of estimating the height, the one here used is that generally adopted by the French anthropologists — that is, the distance between the basion and the bregma (fig. 21, B Bg). Hi. Index of height, or altitudinal index. = . BN. Basinasal length. Basion to nasion. BA. Basialveolar length. Basion to alveolar point, or the most distant part of the anterior margin of the alveolar arch. Ai. Alveolar index. B ^* 100 . This affords the readiest BN method of estimating the amount of forward projection of the jaw. It is not always perfectly accurate, as it is affected by any abnormal position of the basion, 150 GENERAL OBSERVATIONS ON THE SKULL independently of the real relation of the face to the' cranium ; but these cases are comparatively rare, and scarcely affect large averages. Unfortunately, in crania in which the incisor teeth have been lost during life and the alveolar margin absorbed, the basialveolar length, and consequently the alveolar index, cannot be obtained, As will be seen in the sequel, this index forms one of the most important characteristics of race. Nh. Nasal height. A vertical line between the nasion and the lower border of the nasal aperture. Nw. The greatest width of the nasal aperture. to- at i • a NwxlOO m. Nasal index. — =-= . Nh Ow. Orbital width. The inner point of measurement is the spot where the ridge which forms the posterior boundary of the lachrymal groove meets the fronto-lachrymal suture. This is rather behind the dacryon of Broca, (point of junction of the frontal, ascending process of maxilla, and lachrymal), and completely excludes the lachrymal groove from the measurement. The outer point is the most distant part from this on the outer edge of the outer border of the orbit. Oh. Orbital height. The distance between the upper and lower margins of the orbit at the middle. The right orbit, unless injured or of abnormal form, is that usually measured. Oi. Orbital index. 0h ^ x 10 °. Ow Ca. Capacity in cubic centimetres. This is one of the most important and difficult measurements. The material used is shot or sometimes mustard seed, with which the cranium is filled to its maximum. The measurement of the shot or seed is then taken with the choremometer designed and constructed by Mr. Busk. 45 Comparative Osteology. — A student may, with careful observation, discover slight points of difference between opposite sides of the same skull. For instance, the posterior condyloid GENERAL OBSERVATIONS ON THE .'SKULL 151 foramen of one side may be wanting, the mastoid process of one side may be larger than that of the other, or the digastric fossse may be of unequal size ; one nasal passage may be larger than the other ; the lateral sinus may be much deeper on the one side than on the other, or there may be a middle clinoid process on one side Only. Asymmetry may occur in men highly gifted, as in the celebrated French anatomist Bichat. This is no more than one might expect, seeing the difference often exist- ing between features of the two sides of the same face. Such want of symmetry is greatly exaggerated in many of the lower animals, as may be seen in the Cetacea, in the head of the great • sperm-whale or in that of the narwhal (Mus. Eoy. Coll. Surg.), : for the details of which see the comparative osteology of. the superior maxillary bone. But the most striking example of asymmetry is seen in those flat fish which lie usually on their left sides, viz. soles and plaice (Pleuronectids, Nos. 179-190). For in them both eyes are on the right or upper side of the skull, and one orbit only is completed, the eyes being directed away from the ground on which they lie. The teeth are chiefly developed on the left side of their jaws — away from the side on which their eyes are — that is, on the white side. It is interesting to note that in these fish, when very young, the skulls are sym- metrical. When the turbot is just hatched, it has an eye on each side of the head, and it is only by subsequent development that the asymmetry occurs. The turbot, unlike soles and plaice, lies on its right side. Different habits develop different muscles ; and these muscles give rise to modifications in the form of the bones as well as of the bodily configuration. It will therefore be extremely interesting to contrast the skulls of the Carnivora with those of the Ungulata, or hoofed animals. Take, for example, a tiger's skull and that of a deer. The skull of the tiger is in perfect adaptation to his enormous temporal muscle. It has a high median ridge, to which the muscles are attached, great arches of the zygoma, under which they pass, and broad and lofty coronoid processes, into which they are inserted. But his masseters are comparatively small, therefore the zygomata and the angles of the. jaw are not specially strong 1 . 152 GENBKAL OBSERVATIONS ON THE SKULL Now, the sole action of this temporal muscle is to clench the teeth together as on a hinge ; so we find that his jaw articulation is hinge- like, and allows no other motion. This mechanism is admirably fitted for cutting purposes, but is quite unfit for grinding ; so his teeth are cutters. He has no grinders. Exactly the converse of all that is true of the deer : his temporals are small, he has no median ridge, the passage under the zygoma is small, and his coronoid process is delicate and scarcely deserves notice. On the other hand, his masseters and pterygoid muscles are very large, his zygomata broad, the external pterygoid plates greatly expanded, the angles of the jaw massive and extensive. The masseters acting with the internal pterygoids cause the grinding action ; so here the articulation of the jaw is nearly flat, allowing of a free grind- ing movement ; and in accordance with this, we find the teeth are flattened on the surface, and good grinders. It will be seen how clearly this, conformation is in keeping with the habits and nature of each animal. From what has been said of the temporal muscles of the tiger, as well as from what will be said of the pectoral muscles of the flying birds (Carinatae) , it appears that those sets of muscles by which an animal gets its living are the most largely developed, and that their bony attachments are large in proportion. Thus the history of the animal is always written on its bones clearly enough for any careful student to read. He who learns to love osteology will soon feel that it is far from dry, and that beauty finds indelible expression even in the bones ; for. he will see that low degraded types have skeletons which cannot be mistaken, while the. healthy, intelligent, and upright carry their characters in their skeletons as much as they do in their faces. In the ant-eater, which has no teeth, the zygomatic arch is incomplete (No. 3543). In reptiles the cranial cavity is remarkably small. In a Nilotic crocodile (No. 717 D) nearly fifteen and a half feet long, the cranial cavity is only just large enough to admit the thumb. Some heads are long, some are broad, and others round. These different forms are determined by the varying extent of GENERAL OBSERVATIONS ON THE SKULL 153 growth of bone either in the transverse or the longitudinal sutures, or by the early union of one or other of them, as may be readily understood by a reference to the Gen. Ost. Ser. (Nos. 126, 127), ■where, the parietal bones uniting early, the skull was unable to accommodate the growing brain by increasing in breadth, and therefore could only increase in length by growing at the fronto- parietal and the occipito-parietal sutures, thus giving rise to these extraordinarily long skulls. The great and heavy skull of the crocodile contains large nasal passages and air-cavities which float it, so that its body can lie under water while its eyes and nostrils alone appear just above the surface (No. 712). One of the hrstfruits of the study of comparative anatomy was the discovery of the law, ' That an invariable co-relation exists not only between the different parts of an animal's body, but like- wise between the parts of his body and his mode of life.' The discovery was made by Cuvier, and would of itself have been sufficient to immortalise his name. He was led to the detection of this law by the study of a number of fossil bones which were found in quarries in the neighbourhood of Paris. The following is his own account : 46 ' I found myself in the position of a man who had received a confused heap of the mutilated and incomplete remains of some hundreds of skeletons belonging to a score of different kinds of animals ; each bone had to search for those with which it should articulate — it seemed almost a resurrection in miniature. I had not at my command the all-powerful trumpet, but the im- mutable laws prescribed to living beings answered its purpose, for at the voice of comparative anatomy every bone, every fragment of bone, resumed its natural position. I am at a loss for words to describe my delight when so soon as I discovered any characteristic feature, I saw all the sequences of this character, more or less foreseen, develop themselves in succession. I found the teeth conformed to what the feet had foretold, and the feet to what the teeth foretold, and all the bones between the feet and the teeth conformed as could be judged beforehand ; in a word, •each of these species sprang up again out of one of its elements. 154 GENERAL OBSERVATIONS ON THE SKULL Those who will have the patience to follow me will be able to form an idea of the sensations I experienced in thus restoring by degrees these antique monuments of fearful revolutions. Sub- sequent discoveries of fossils have hardly ever contradicted my earlier conclusions.' THE VEBTEBB A.L COLUMN. (Plates XXV.— XXIX.) The vertebral column, or spine (Plate XXVI.), consists of a series of bones articulated together so as to describe three slight and graceful curves, the bend being forward in the loins, backward in the chest, and again forward in the neck. These bones are called ' vertebras,' because they permit the bending and rotation of the body (verto, I turn). They are 33 in number : of which 7 con- stitute the cervical region, 12 the dorsal, and 5 the lumbar. Below the lumbar vertebras, the spine is supported upon a bone termed the ' os sacrum,' which consists of five vertebrae firmly coalesced into a single bone. Below the sacrum is the little bone termed the ' coccyx,' from its resemblance to the beak of a cuckoo (icoKKvg). This also contains the rudiments of four, sometimes only three, vertebrae. The vertebral formula of man, therefore, ia — 7 cervical, 12 dorsal, 5 lumbar, 5 sacral, and 4 coccygeal, or caudal : that is, 33 in all. Constituent Farts of a Vertebra. — The vertebrae have certain general characters which are common to all. These are modified in the different regions of the spine, according to the functions they perform. (See separate series, Mus. Eoy. Coll, Surg.) Therefore, first obtain a general knowledge of a vertebra, and of the names given to its several parts ; afterwards examine the characteristics of the vertebrae in each region. Taking the first lumbar vertebra as a pattern (Plate XXV.), it is seen to consist of a ' body,' or ' centrum,' which forms the columnar part, and supports the weight of the spine. The body is convex in front from side to side, but slightly concave behind, where it assists in the formation of the ' vertebral foramen,' PLATE XXV. Ant r Tubercle rfcieukr surface for] Odontoid process. .Transverse -process. ,Sup^ articular process. Su/tuberck £—kZ\M M - 'orarnen for Vertebral Artery. - Groove for Vertebral Artery. Spinous process. First Cervical Vertebra or Atlas. Articular surface forAtl F%6. Transverse process Inf Particular surFace Contend poramen for Vertebral Artery. .arnTTia. \ \ Spinous p-rocess. Lamina . Spinous process Second Cervical Vertebra or Axis. Fio.l Inf r notch. Inf r tubercle' ^. In P Particular process. Lumbar Vertebra. :V:-.:\::v?i' i, :/- ; :> «PI#5 .Transverse process Sup r articular process. Section showing Venous canals Kfe-7. Lumbar Vertebra. Articulation for Rib Sup T articular process Fi$*. ATro.cess. Articulation for "Rib ransverse process. Articulation for Rib Inferior articular process Spinous process . Cervical Vertebra. Dorsal Vertebra. Drawn on Stone "by T. Godart. From nature ty L.Holden. Prmtedtjy'WeiSt^Newrnan &Co. THE VERTEBRAL COLUMN 155 ■which transmits and protects the spinal cord. The upper and lower surfaces of the body present a disc Of solid bone at the circumference (Plate XXV. fig. 2), and a slight cup in the centre which lodges the elastic ' intervertebral fibro-cartilage,' found in the recent subject, and acting as a ' buffer ' between the vertebra. These discs or rings of compact bone deserve notice, not only because they strengthen the spongy bodies, but because they have separate centres of ossification, and remain until about the 25th year, as ' epiphyses.' A section through the body of a vertebra shows it to be composed of cancellous tissue, which • makes it light compared to its bulk. (Nor. Hum. Ost., Nos. 175-185.) This tissue is traversed by large ' venous canals,' of which the orifices are observable on the surface, but chiefly on the back part of the body, towards which the larger canals converge (Plate XXV. fig. 7) . Behind the body is the ' vertebral foramen.' Now this foramen is formed by two thick processes of bone, which proceed, one from each side of the posterior part of the body, and gradually converging, unite and form an arch (vertebral or neural arch). The spring of the arch, where it joins the body, is called the ' pedicle ; ' the converging plates are termed the ' laminse.' The arch sends off seven ' processes.' Of these, three — namely, the ' spinous ' and the two * trans- verse ' — give attachment to muscles. The ' spinous process ' arises from the top of the arch ; the two ' transverse processes ' pass off, nearly horizontally, one from each side of it, near the junction of the ' pedicle ' with the ' lamina.' The remaining four are termed ' articular processes '—two superior articulating with corresponding processes of the vertebra above and two inferior articulating with corresponding processes of the vertebra below ; they are situated on the point of union of the pedicles with the laminse. Their articular surfaces are covered with cartilage in the fresh state, and project beyond the bodies, so that the joints are on a level with the intervertebral fibro- cartilages. Lastly, on the pedicles, we observe two ' notches ' on either side— an upper and a lower, the lower being always the larger. When the vertebras are together, these notches make what are called the 'intervertebral foramina,' in which the spinal 156 THE VERTEBRAL COLUMN nerves lie. (Plate XXVII.) The ' pedicle,' or the part of the arch between the notches, is the weakest part of a vertebra, and consequently it is the principal seat of torsion in curvatures of the spine. Such, then, are the constituent parts of a vertebra : namely, a body, an arch, a vertebral foramen : seven outstanding processes, of which four are articular, and three give attachment to muscles ; lastly, the notches which transmit the spinal nerves. In examining a single vertebra it is necessary first to ascertain to which region it belongs, and then which vertebra it is of that region. We will therefore describe first the distinctive characters of the region, and then the peculiar characters of the individual vertebrae, as far as they can with certainty be distinguished. Cervical VertebrsB — Distinctive Character. — All the cer- vical vertebrae, and they alone, have a foramen in the base of each transverse process, which (excepting that in the 7th) transmits the vertebral vessels and a plexus of sympathetic nerves. General Characters of the Cervical Vertebrae. — There are seven cervical vertebrae. The ' bodies," excepting the first and second, are broader from side to side than from before back- wards, and a lateral ridge projects from each side of their upper borders, and fits into a corresponding depression on the sides of the vertebra above (Plate XXV. fig. 4). Each 'body' slopes a little forward, and overlaps the one below. (Plate XXVII.) By all this interlocking, lateral displacement is prevented; this mechanism compensating for the apparently insecure connec- tions of the articular processes. Their ' spinous processes ' are horizontal, and give attachment to the ligamentum nuchas as well as to the muscles which maintain the head erect. But the spinous processes of the third, fourth, and fifth are especially short, and permit the free extension of the neck, and are very distinctly bifurcated ; they overlap each other a little in extension, as any- one may see in the dry bones by moving them backwards over each other. There is a groove on the upper surface of each trans- verse process in which lodges the spinal nerve ; and this groove bifurcates the summit, so that there are two ' tubercles ' formed, an anterior and a posterior (in the lower five), both for the THE YBETEBEAL COLUMN 157 attachment of muscles. Observe especially the large size of the anterior tubercle of the sixth cervical vertebra. It is called the carotid tubercle, being a guide to the carotid artery. Strictly speaking, we ought to say that the transverse process of a cervical vertebra arises by two roots or bars, an anterior and a posterior, which subsequently join, and so form the foramen which transmits the vertebral artery, vein, and a plexus of nerves : the anterior root springs from the side of the body : the posterior springs from the arch. Their ' articular processes ' are flat, oblique, and in- clined, so that their planes make an angle of about 45° with the horizon. The upper processes look backward and upward, the lower forward and downward. They are placed nearly in the same transverse plane and the obliquity of their direction permits flexion and extension, and a motion round an oblique axis. In this oblique motion the articular process of one side glides', downward and backward upon the corresponding articular surface below, and that of the other side rises upwards and. forwards upon the corresponding one above. In this way a. combination of rotation and lateral flexion may occur between two contiguous cervical vertebrae. 1st and 2nd Cervical Vertebrae — The 1st and 2nd cervical vertebrae differ most remarkably from the rest, as they respec- tively permit the nodding and the rotation of the head. 1st Cervical Vertebra : Atlas — The 1st cervical vertebra (Plate XXV. fig. 5) is called the ' atlas,' because it supports the head. This is the only vertebra which has no body. The odontoid process of the axis (the 2nd cervical vertebra) is the body of the atlas, and is thus transferred and fixed to the second vertebra, forming a pivot or axis upon which the atlas rotates. It seems, at first sight, rather far-fetched to say that the atlas rotates round its own body (detached); but it is nevertheless true, and borne out by the facts of philosophical anatomy. The 'spinous process' is a mere tubercle (the posterior tubercle) to which the ' rectus capitis posticus minor ' is attached. A large spine here would interfere with the free backward movement of the head. This vertebra is like a ring, wider behind than in front, and thickened on each side, forming the ' lateral masses ' 158 THE VEBTEBRAL COLUMN and the articular surfaces. In front there is a small ' anterior tubercle,' into which is inserted a portion of the 'longus colli.' Now the form of the atlas is adapted to the rotatory move- ment of the head. In the first place there is a little articular surface, the odontoid articulation, on the back of the anterior part of the ring of the atlas. The ' transfer se processes ' are thick and strong, and project far beyond those of the other cervical vertebra, and give great leverage to the inferior oblique muscles which assist in rotating the head from side to side. Its ' inferior articular ' processes look downwards and slightly in- wards ; they are nearly horizontal, flat and circular, like the upper ones on the axis on which they slide, in the movement of rotation of the head. The ' superior articular surfaces ' are con- cave, and articulate with the convex condyles of the occipital bone, and are similarly oval, converge anteriorly, and lie near the front of the foramen. The outer edges being the highest, they form two little cups looking upwards and inwards, which receive the occipital condyles, sustain the whole weight of the head, and permit its nodding movement. On the inner side of each articular process is a tubercle which gives attachment to the strong ' transverse ' ligament, which confines the odontoid process in its position. The ' arch ' formed by the laminse is wider than in other vertebrae, and leaves such ample space that lateral displacement of the atlas has occurred without compres- sion of the spinal cord. 47 On the upper surface of each .lamina is a groove (sometimes a complete bony canal) for the vertebral artery and suboccipital nerve ; this corresponds to the superior notch in the other vertebrae. Lastly, the ' notches ' for the nerves are placed behind the articular processes, while in all the other vertebrae (except the upper notch in the axis) they are in front of them. The ' vertebral foramen ' is large, presenting the appearance in outline of a small uterus. It is occupied in front by the odontoid process with the transverse ligament, and behind by the spinal cord with its vessels and membranes. 2nd Cervical Vertebra : Axis. — The 2nd cervical vertebra or ' vertebra dentata ' (Plate XXV. fig. 6) is called the ' axis,' because it is the axis upon which the atlas (with the head) THE VERTEBRAL COLUMN 159 rotates. The pivot, termed the ' odontoid process ' from its re- semblance to a tooth, rises vertically from the ' body ' of the axis, and fits into a ring formed in front by the atlas, and behind by "the strong ' transverse ' ligament which passes between the lateral masses of the atlas, and divides the vertebral foramen of that bone into two parts, an anterior for the reception of the odontoid process, and a posterior for the passage of the spinal cord. It is a mechanism resembling a tenon and mortise. 48 The odontoid process has a smooth surface in front, which articulates with the atlas ; another behind, on which plays the ligament. There is a distinct synovial membrane and a layer of cartilage on each surface, so that they possess all the apparatus of a joint. More- over, it is slightly constricted at its lower part (forming what is called the 'neck'), which the 'transverse' ligament clasps securely. Lastly, its summit or ' head ' is rough and sloped laterally. From these lateral slopes proceed the ' check ' or * odontoid ' ligaments, which fasten the odontoid process to the occipital bone. Considering the importance of the odontoid process, we are not surprised that its internal structure is much more compact than that of the body of the axis. The upper * articular processes ' are placed, partly on the body and partly on the root of each transverse process ; they are neatly flat and circular, and slope a little downward and outward. Like those of the first vertebra, they have a very strong base, and transmit to the ' body ' the weight of the head. The ' notch ' is behind them. The lower ' articular processes ' are oblique, and placed considerably behind the upper, and correspond with the line of the articular processes of the succeeding vertebras which they resemble. The intervertebral ' notch ' is in front of them, as in all the vertebra below. The ' transverse processes ' are com- paratively small, and not grooved or bifurcated ; but the hole at their base is inclined obliquely outwards, corresponding to the curve of the vertebral artery. The ' laminae ' of the arch are remarkably strong. The ' spinous process ' stands well out, and bifurcates widely, giving great leverage to the inferior oblique muscles which rotate the head. The great size and projection of this spinous process is one of the distinguishing characters of the 160 THE VEBTEBRAL COLUMN axis ; and with this we should associate the large size of the transverse processes of the atlas, these being the respective attach- ments of the inferior oblique muscles. 3rd, 4th, and 5th Cervical Vertebrae. — The 3rd, 4th, and 5th cervical vertebras can be easily distinguished from the rest, although not from one another, by the following points : Their spinous processes are spread out horizontally, and are thin, bifid, and short (Plate XXV. fig. 4) , thus allowing the neck to be bent backwards very considerably before the spines come into contact. 6th Cervical Vertebra. — The spine of the 6th is short, it is not bifid (or rarely so), and runs nearly horizontally backwards, but is not spread out like the 3rd, 4th, and 5th. The foramen in the transverse process is the largest of all the series. 7th Cervical Vertebra. — The 7th cervical is caUed the ' ver- tebra prominens ' on account of its long horizontal and prominent spine, which can be easily felt at the back of the neck. It slopes a little downwards, and thus somewhat resembles those in the dorsal region, and gives attachment to the ' ligamentum nuchas.' The foramen in the transverse process is never traversed by the vertebral vessels, and is small and irregular in shape. More- over, the transverse processes, though so long and broad as to suggest a rudimentary rib, are but slightly grooved, and have no distinct tubercles. This vertebra in some rare instances has two little (cervical) ribs attached to it, one on either side, in form and situation resembling the cervical ribs of animals. A cervical rib may be mistaken for a bony tumour if the surgeon does not bear in mind that such an anomaly may exist in the skeleton. It is sometimes united with the first rib. Dorsal Vertebrae : Distinctive Character. — All the dorsal vertebras, and they alone, have facets on the sides of their bodies with which the heads of the ribs articulate. Dorsal Vertebras : General Characters. — The general cha- racters of the twelve dorsal vertebrae are as follows : Their ' bodies ' are heart-shaped, and smaller than those of the lumbar, and they have less weight to bear. Their vertical depth is less in front than behind, especially near the middle of the back, in adapta- tion to the dorsal curve. They are slightly wider from side to THE VERTEBRAL COLUMN 161 side than from before backwards. Tbey have two little cup-like facets on each side for the articulation of the heads of the ribs, the lower cups being the larger. By referring to the spine (Plate XXVI.), we observe that the socket for the bead of the rib is formed by the' articular facets of two ' vertebra with the intervening fibro-cartilage. These 'rib facets' distinguish a dorsal vertebra from a vertebra of any other region of the spine. Their ' spinous processes ' are long, clubbed at the end, and slant downwards, so that they overlap each other, especially near the middle of the back, and prevent extension of the spine in this region. Their ' transverse processes ' are thick and strong, and each has in front, near its end, an articular surface for the tubercle of a rib, which it supports like a buttress. Observe that the transverse processes of the seven upper dorsal vertebrae are very thick and strong, and support the seven true ribs, whilst the five lower gradually diminish in size ; those of the eleventh and twelfth are the smallest of all, and they do not support ribs ; these lower ones present three tubercles, of which more will be said hereafter. The ' pedicles ' are compressed from side to side, short, and start from the body nearer the upper than the lower surface. The ' laminas ' are broad and flat, and slope one over the other. Of the ' articular processes ' the upper look backward and outward, the lower forward and inward, and the planes of both are so nearly vertical that it is manifest there can be but little movement between any two dorsal vertebras. Any that does occur consists of very slight flexion and extension, and very limited rotation. The ' vertebral foramen ' is nearly round. The lower ' intervertebral notches ' are larger than the upper. 1st, 9th, 10th, 11th, and 12th Dorsal Vertebrae.— The first dorsal vertebra has on the side of its ' body ' an articular surface for the whole of the head of the first rib, and a smaller one at the lower border for half of that of the second rib. Again, the upper surface of its body has lateral ridges like the cervical vertebras. The ninth dorsal has usually only half a facet on the upper part of the body. The tenth dorsal has generally an entire facet for the tenth rib. The eleventh and twelfth dorsal have each a single articular facet for the eleventh and M 162 THE VERTEBKAL COLUMN twelfth ribs respectively, and their ' transverse processes,' much reduced in size, do not articulate with the ribs. Moreover, they are smaller than in the upper dorsal region, and they resolve themselves into three tubercles (seen in fig. 23). The twelfth dorsal may be distinguished from the eleventh by the fact that its lower articular processes look outward, like the corresponding processes in the lumbar vertebra. Its spinous process is short and square, and more like those of the lumbar vertebras. The Fig. 23. ■d. Superior articular process, d ■a. Superior or mammillary a tubercle. b. External tubercle (rudi- b mentary trans. P.) ■c. Inferior or acccessory tu- c bercle. e. Inferior articular process. TWELFTH DORSAL VERTEBRA, SHOWING THE THREE TUBERCLES ON THE TRANSVERSE PROCESSES. tubercles of its transverse process are always well marked. (Plate XLV. fig. 2.) It must be remarked, however, that the above description of the special characters distinguishing the so-called 'peculiar dorsal vertebra ' apply only to vertebrae which are typi- cally normal. In many instances these appearances do not show themselves in the respective vertebras ; for example, the twelfth may have its inferior articular processes directed fonvards as an ordinary one, or forwards and outwards, or, again, the first one may have only one whole facet upon the side of its body. Con- sequently before making up one's mind as to the exact number THE VERTEBRAL COLUMN 163 of any given peculiar dorsal vertebra, one should have regard to the general features of the whole bone as well as to the so-called * distinctive characters ' ascribed to it. Lumbar Vertebrae : Distinctive Characters. — The lumbar vertebrae have neither holes in their transverse processes nor articulations for ribs. General Characters of the Lumbar VertebraB. — The general characters of the five lumbar vertebras are as follows : The ' bodies ' are large, with their broad diameters transverse, and firmly support the trunk. The vertical measurement of the bodies is greater in front than behind, in adaptation to the lumbar curve. Their sides are slightly excavated, which econo- mises weight and bulk. Their ' spinous processes ' are broad, in their vertical measurement, thickest at the lower border, and give good leverage to the extensor muscles of the spine : they stand out horizontally, and so do not interfere which the exten- sion of the back. Their ' transverse processes ' are thin and long, and appear like stunted ribs, but are not true ribs. Their ' articular processes ' are vertical, and very strong : the upper, slightly concave, look towards each other ; the lower, slightly convex, are nearer together, and fit in between the upper ones of the succeeding vertebra. Thus, these articulations are so shaped that they admit, not only of extension and flexion of the loins, but of a certain amount of bending of the spine to one side ('lateral flexion'), which is useful in progression. The ' vertebral foramen ' is triangular, with the angles rounded. The lower intervertebral notches are larger than the upper ones. Characters of the last Lumbar Vertebra. — The last lumbar vertebra is distinguished (1) by the slope on the lower surface of its body, in adaptation to the slope of the sacrum ; (2) by the transverse processes being short and very thick, and arising from the sides of the body, as well as the pedicle. In some cases the lower border of the transverse process may be prolonged downward and form a rough articular surface, meeting a corre- sponding upward projection of the back of the ala of the sacrum, as is well seen in a specimen in the anatomical collection at St. Thomas's Hospital ; (3) by its lower articulating processes being M 2 164 THE VERTEBEAL COLUMN placed so widely apart ; and (4) by its spinous process being somewhat reduced in size, thereby leaving room for the free extension in this part of the back. The Fourth Lumbar Vertebra. — This vertebra has very frequently its inferior articular processes as far apart as its upper ones, and so appear like the fifth. We may distinguish it, how- ever, by its slender transverse processes arising from the junction of the pedicles and laminae, and not from the body, as in the fifth. The Third lumbar Vertebra. — If we are shown the whole lumbar series we can distinguish this vertebra by the great length of its transverse processes. Tubercles on the Lower Dorsal and Lumbar Vertebrae. — An observant eye looking at the back of a well-marked spinal column will find that the transverse processes of the lower dorsal vertebrae have a tendency to resolve themselves into three bony prominences at their extremities. The twelfth (often the eleventh) transverse process actually terminates in three such prominences or tubercles ; one being superior, a second inferior, and a third external (see fig. 23). The ' superior or mammillary tubercle' is close behind the superior articular process. The 'inferior or accessory tubercle ' is in a straight line immediately below the superior ; the ' external ' projects in front of the other two tuber- cles, and is seen to be in a line with that part of the transverse processes of the upper dorsal vertebrae which bears the ribs. Now the superior and inferior tubercles gradually fade away in the lumbar vertebrae ; but the external tubercle increases in size, and forms the transverse process of the lumbar region. Hence the transverse process of a human lumbar vertebra is homologous to that part of the transverse process of a typical dorsal vertebra which articulates with the tubercle of a rib. The tubercles are shown in Plate XLV. fig. 2. In the human subject these ' tubercles ' 49 serve only as attachments for muscles ; but in some animals they attain extra- ordinary size, and have other functions. For instance : in the armadillo (No. 2335 B), the superior tubercle is as long as the spinous process itself, and helps to support the armour. In the THE VERTEBRAL COLUMN 165 Carnivora the inferior tubercles gain a conspicuous development in the lower dorsal and upper lumbar regions, and contribute to the lateral security of the spine. Table contrasting the Important Parts of the Vertebra in the Different Begions. We have shown how the vertebrae of the different regions of the spinal column may be distinguished, within certain limits, by the examination of any one of their constituent parts. These important parts are contrasted in the annexed table. Cervical. — Always broadest transversely. Lateral ridges on upper surface. Dorsal. — Greatest transverse measurement greater than antero- posterior. Facets or parts of facets on sides for heads of ribs. Lumbar. — Always broadest transversely, somewhat kidney-shaped, no ridges, no facets. / Cervical. — Long, thin, and flattened. I Dorsal. — Short, very broad vertically. (Lumbar. — Very short and stout. ( Cervical. — Bifurcated, grooved underneath. \ Dorsal. — Long, very oblique, tubercle at summit. { Lumbar. — Broad and square. Cervical. — Bifurcated, grooved on upper surface. Foramina for vertebral artery. Dorsal. — Large and strong ; facets for tubercles of ribs, except eleventh and twelfth. \Lumbar. — Thin, long and narrow. Cervical. — Surfaces plane, inclined at angle of 45°, look backward and upward. Dorsal. — Surfaces plane, almost vertical, look backward and out- ward. \Lumbar. — Surfaces concave, vertical, look backward and inward. Vertebral Column as a Whole. — The spine is a most wonderful piece of mechanism, and has excited the admiration of anatomists in all ages, from the various and apparently incom- patible offices it serves (Plate XXVI.) It forms a column, at once strong and firm, which supports the body in the erect posi-, tion ; it is flexible, and so admits the bending of the trunk in various degrees ; it is elastic, diminishing concussion of the head, Bodies oe Centra. Laminae. Spines. Transverse Processes. Superior Articular Processes. 166 THE VERTEBRAL COLUMN It forms a continuous canal at the back of the column, which contains and protects the spinal cord, a basis for the origin of the muscles which spread over the trunk, and a lever for the muscles which keep the body erect. Strength of the Spine. — The main strength of the spine depends upon this : that it consists of a chain of bones so locked together "that the degree of motion between any two is limited, though the sum of the whole is extensive. Another reason of the strength of the spine is its arrangement in alternate curves. The largest primary curve is situated in. the dorsal region, with its concavity directed forwards to make room for the large thoracic viscera; the small counter-curves are situated above and below in the cervical and lumbar regions respectively. Mathematicians have calculated that it is many times stronger, and more adapted to resist vertical pressure, than if it were straight, the force being decomposed by the curves. 50 Look at the enormous weight which a man can carry with ease and safety on his head. Moreover, the curves convert the spine into so many elastic springs, which prevent the jarring of the brain. Besides this, the curves are admirably disposed for the lodgment of the internal organs, and the transmission of the weight of the head and trunk in the line of gravity. They are so regular and gentle withal, that the spinal cord runs no risk of compression ; and lastly, they give the body that graceful form which has been the ' line of beauty ' in every age. In infancy the spine above the sacrum is almost wanting in curves, forming a nearly straight column, giving the characteristic upright appearance observable in the backs of very young children. The weakest part of the spine is about the last dorsal vertebra : firstly, because it is the narrowest part of the column ; secondly, because it is not supported by the ribs like the higher dorsal vertebrae ; thirdly, because it is the centre of the spine and the centre of motion in the back, and therefore exposed to the power- ful leverage of the spine above and below it. Again, at the arti- culation between the last dorsal and the first lumbar vertebra, the pliable lumbar part of the spine suddenly joins the compara- tively rigid dorsal region. PLATE XXVI 1" Cervical Or Alius 2nd " or Axis. Vertebra prominent... I Dorsal. sHss* A - ■',.■;«, 10 \Z 1- Lumtiar '". -:<: YY 1- i^P Sc '. .Auricular Surface of ScLCc-utn . &Tptf >*m " a %'4i^ Drawn on Stone "by T. Godart. From nature by LHolAen. Printed by West.Newman & Co. THE VERTEBRAL COLUMN 167 Curves of the Spine. — The curves of the spine are produced partly by the relative thickness of the bodies of the vertebrae in the different regions, but chiefly by the relative thickness of the intervertebral fibro-cartilages and the tension and elasticity of the ' ligamenta subflava ' which connect the laminai. Extent of motion in Different Reg-ions. — The movements of the spine are fourfold — (1) flexion and extension ; (2) lateral inclination ; (3) rotation ; (4) circumduction. Flexion and exten- sion are freest in the cervical, less free in the lumbar, and least free in the dorsal region. The greatest extension is permitted in the cervical region and the greatest flexion in the lumbar, especially between the fourth and fifth vertebrae. This is chiefly brought about by the different thickness of the intervertebral cartilages in the different regions. The other movements are regulated by the articular surfaces. In the cervical region the articular pro- cesses are set obliquely and nearly in the same transverse plane ; consequently pure rotation or pure lateral inclination cannot occur, but a gliding motion round an oblique axis takes, place, the vertebras gliding upwards and forwards on one side and downwards and backwards on the other, or vice versa. In this way a mixture of lateral flexion and rotation is gained. In the dorsal region, the articular processes lying in the circumference of a circle, whose centre is between the bodies of the vertebrae, a slight degree of rotation is allowed. In the lumbar region the articular processes lie in the circumference of a circle whose centre is behind the vertebra, and hence no rotation can occur ; the articular processes allow of a certain amount of lateral inclination, which, mixed with flexion and extension, forms a slight degree of circumduction. Intervertebral Fibro-Cartilag-e. — The intervertebral fibro- cartilage provides for the elasticity as well as the flexibility of the spine. The solidity of this substance gradually diminishes from the circumference towards the centre, where it forms a soft and almost incompressible pulp, permitting, to a limited extent, the motions of a ball-and-socket joint; namely, a gentle bend in every direction. Its great elasticity breaks the force of jars by gradually yielding, and always tends to restore the column to 168: THE VEKTEBBAL COLUMN. its erect form. Long-continued pressure during the day will, indeed, make the intervertebral substances yield, so that a man loses in height perhaps ^ or even ^ an inch ; but this is recovered after a night's rest. At the same time it should be remembered that a habit of leaning too much on one side will make the yielding of the intervertebral substance permanent. Even the bones themselves, while they are growing, will yield under such circumstances. There may be considerable distortion without actual disease. Shape of the Column from the Front. — As to the form of the column in front, we observe that it is pyramidal, and that the bodies of the vertebrae gradually increase in size from above, and form a broader and broader base of support as the weight to be supported by each one in succession becomes greater. The atlas, in consequence of the great projection of its transverse processes, necessary for the rotation of the head, tops the pillar like a ' capital.' It is, however, necessary to remark, that there is a partial enlargement of the column about the lower part of the cervical region, which gives a broader base to the neck; and again a slight decrease in its breadth, about the third and fourth dorsal vertebras, which allows more room for the lungs. Moreover, we commonly observe a very gentle lateral curve in the dorsal region, particularly about the third, fourth, and fifth vertebras, with the concavity, towards the left side. The cause of this curve has been much discussed. Some anatomists attri- bute it to the more frequent use of the right arm ; others to the presence of the aorta. The solution of the question is of no prac- tical value ; all we need remember is, that the curve is natural. Back of the Column. — At the back of the column, we observe the long row of spinous processes forming the vertical interrupted crest which gives the name to the ' spine.' The spines of the vertebras should be examined on the living subject when the head is bent forwards and the arms folded. At the risk of repetition we will again direct attention : 1. To the sup- pression of the spine in the atlas, which permits the free exten- sion of the head. 2. To the great projection and bifurcation of the spine of the axis which gives attachment to the inferior. THE YBETBBEAIi COLUMN 169 oblique muscles which rotate the head and atlas. 3. To the shortness and horizontal position of the spines of the third, fourth, and fifth, which allow of free extension. 4. To the spine of the ' vertebra prominens,' where the ligamentum nucha is attached. 5. To the overlapping of the long spines of the dorsal vertebrae which limits movement in the region of the heart and lungs. These organs could not resist stretching or compression like the abdominal viscera. 6. To the square lumbar spines, the planes of which are vertical. Vertebral Groove. — On either side of the spine is a deep furrow, termed the 'vertebral groove,' and formed by the lamina. It is bounded in the neck and back by the transverse processes, in the loins by the articular processes. The groove is narrowest about the junction between the last dorsal and first lumbar vertebra (the weakest part of the back), and widest at the sacrum. The groove is occupied by the strong muscles of the back. The crest, being all that we can either see or feel of the spine during life, is the part we immediately examine in cases of injury or disease. In making this examination, we ought to be aware that the spines of the several vertebrae do not always succeed each other in a precisely straight line, but that one, here and there, may deviate to the right or the left, even in persons of the strongest frame. Throughout the spine the intervertebral notches, excepting those of the atlas and the upper ones of the axis, are in front- of the articular processes. But it is worth observing that the transverse processes vary in position. In the cervical region they lie between the foramina and are grooved by nerves. In the dorsal region they lie farther back between the articular processes in accommodation to the ribs which lie between the foramina. In the lumbar region the transverse processes lie between the articular processes and the intervertebral foramina. Vertebral Canal. — Eespecting the vertebral canal (shown throughout in Plate XXVII.), remark how well it is protected from injury by the breadth of the arches of the vertebral. The arches overlap each other, so that it would be difficult for a cutting instrument to penetrate anywhere, except perhaps in the lumbar 170 THE VERTEBRAL COLUMN region, and, again, between the arch of the atlas and the occiput, where animals are usually ' pithed.' The area of the canal is larger in the lower cervical and in the lumbar region than else- where, for the reason that the spinal cord itself presents corre- sponding enlargements in those parts where the great nerves of the limbs proceed from it. Observe well the relative size and mode of formation of the intervertebral foramina by the notches (Nor. Hum. Ost., No. 73). Ossification. — As a rule, each vertebra is ossified in cartilage from eight centres, of which three are ' principal ' — namely, one for the body and one on each side for the arch and its processes (Nor. Hum. Ost., No. 35) : the remaining five are ' epiphyses,* and appear, soon after the age of puberty, as follows : one in the cartilaginous end of the spinous process, one in the cartilaginous end of each of the transverse processes, and one for each of the discs which form the articular surfaces of the body. The five epiphyses appear from the sixteenth to the twentieth year and become united to the vertebra by bone about the twenty-fifth year. Ossification usually commences at the sides of the arch just before it begins in the body of the vertebra — viz. about the seventh week after conception. The sides of the arch unite first at the base of the spinous process, so that the ossification of the arch is complete in the first year after birth. During the third year the bases of the arch unite with the independently ossified ' centre ' or ' body.' It must be borne in mind that the posterior parts of the sides of the bodies are ossified from the arches ; the line of junction is the ' neuro-central suture ' of scientific anatomists. The mam- millary processes are developed from separate centres of ossifica- tion, and occasionally the transverse processes of the first lumbar are formed from nuclei belonging to themselves. The anterior parts of the transverse processes of the seventh cervical generally present separate centres of ossification, and small nuclei have been seen in the second, fifth, and sixth. It ought to be mentioned that some anatomists consider that the body of a vertebra is developed from two nuclei placed on either side of the middle line — a notion which is borne out by the fact THE VERTEBRAL COLUMN 171 that we occasionally find a deficiency of a half of one or more vertebrae. A specimen in the museum of St. Thomas's Hospital shows the half of a dorsal interposed in a wedge-shaped way between the two contiguous vertebrae, and Sir William Turner has lately described the body of the tenth dorsal vertebra of a Maori skeleton as consisting of two distinct lateral wedge-shaped portions, separated by a mesial cleft. Exceptions to the General Rule. — Where vertebrae under- go great modifications of form, we meet with exceptions to the above rule. Thus the atlas has one or two centres of ossification for the anterior arch, which appear in the first year. The posterior arch and lateral masses are formed from two lateral centres, appearing about the seventh week. These lateral centres join behind in the third year, and unite with the anterior arch in the fifth or sixth year. Frequently there is a separate centre for the rudimentary spinous process at the back of the posterior arch. The development of the axis, as far as its neural arch and pro- cesses are concerned, is the same as in an ordinary vertebra. The body is developed from one or two centres which are common to it and the root of the odontoid process, and which appear about the fourth month. The rest of the odontoid process is formed by two lateral centres, appearing a little later than the centre for the body, and joining it in the third year, and a centre situated at the apex of the process appearing in the second year. The separate centres of ossification for the odontoid process help to justify the opinion that the odontoid process is really the body of the atlas. Comparative Osteology. — In all known mammalia there are seven cervical vertebrae, with the following exceptions : Hoff- mann's two-toed sloth— Cholcepus Hoffmannii (No. 3439)— has six ; the Three-toed sloth— Bradypus Tridactylus (No. 3422)— has nine. In Bradypus, however, the ninth, and sometimes the eighth, bears a pair of short movable ribs ; the manatee, again — Manatus Americanus (No. 2729) — has only six cervical vertebrae. The number of cervical vertebrae bears in no case any relation to the length of the neck. The short neck of the whale and the 172 THE VEKTEBEAL COLUMN long neck of the giraffe (No. 1437) contain each seven cervical vertebrae. The Greenland fin-whale in the Mus. Boy. Coll. Surg, appears to have but one cervical vertebra. An inspection of the transverse processes, however, shows that it has seven, and that they have become anchylosed. The lesser fin-whale, next to it, has the seven vertebral bodies perfectly distinct. The bifurcation of the spines of the cervical vertebrae is almost peculiar to the human skeleton. It affords more room for the insertion of the powerful muscles which maintain the neck, and therefore the head, erect. In the gorilla, the spines of the five lower cervical vertebras (No. 20) are longer in proportion than those of any other known animal. They measure from three to four inches in length, and form one of the most striking features of difference between this skeleton and that of man. The whale (Cetacea) has no odontoid process, and thus differs from the manatee (Sirenia), which has a well-marked one. See Series of Separate Bones, Mus. Boy. Coll. Surg. In the chameleon each of the two lower cervical vertebrse bears a pair of cervical ribs (Nos. 664 a, 665 a) ; and in the snakes all the vertebras, excepting those of the tail, carry mov- able ribs. Cervical ribs may also be seen in crocodiles (see Nilotic Crocodile, No. 717 D). When mammalian vertebrse are very numerous, the great number is made up of caudal vertebras ; but when a bird's vertebrse are numerous, the number is made up of cervical. There are nine in the neck of the sparrow, and twenty-three in that of the swan. In the wading birds (Grallatores), whose long legs raise the body some two feet or more above the water in which they wade, the neck is long enough to enable their beaks to reach the ground. Thus their necks are in proportion to the length of their legs. See the flamingo. In swimming birds, as ducks and swans, the length of the neck is in no relation to the length of their short legs, but is in proportion to the depth to which they have to reach for food. In man the upper and lower surfaces of the bodies of the vertebrae are slightly cup-shaped, and receive in their depressions THE VERTEBRAL COLUMN 173 the convex surfaces of the discs of fibro-cartilage, which are placed between the bodies of the vertebrae, and give the spinal column its elasticity. In most fishes the bodies are so deeply cupped above and below, that there is a perforation in the centre through which the intervertebral substances are continuous (Nos. 433-437). In man the soft central part of this intervertebral substance is the remains of the chorda dorsalis, which persists in fishes, and is con- tinuous through the central perforations. See the central cavities for the chorda dorsalis in the blue shark, No. 413 ; also No. 13. In the mud fish (Dipnoi) all the notochord is persistent, and there are no centra to the vertebras whatever. This may also be seen in the lamprey, amphioxus, &c. The epiphyses on the anterior and posterior surfaces of the bodies of the vertebrae should be especially examined in the whale (Separate Series). They form complete plates of great size, and being separable from the bodies of the vertebras in many of these animals, are very abundant on the sea-shore in northern climates. It is interesting that when H.M.S. 'Hecla' was wrecked, the crew used these discs as plates. In serpents (Ophidia) the body of each vertebra is cup-shaped in front, and receives the rounded head of the one in front of it (Nos. 604-609), and this is the same in many of those of the crocodiles, in which the upper surfaces of the bodies are cup- shaped, and each receives the convex projection from the lower surface of the vertebra above. In many flying birds, the dorsal vertebras are fixed to one another by fusion of the spines, and often of the transverse pro- cesses and bodies. In birds that do not fly, such as the cassowary and the ostrich, they retain their mobility (Nos. 1633, 1633 A-B, and 1634). The vertebras, which vary in number so widely throughout the animal kingdom, attain in the tiger-boa (Python tigris, No. 602) the enormous number. of 291 in all. In tortoises (Chelonia) the dorsal vertebras are immovably connected, and have no transverse processes. The proximal ends of the ribs unite directly with the vertebras, and are also immovable. 174 THE SACRUM THE SACEUM. (Plates XXVIII, XXIX.) Situation and Inclination. — The ' sacrum ' 51 is situated at the back of the pelvis, and wedged in between the two inno- minate bones. It forms the ' keystone ' of the arch which supports the spine, and transmits the weight of it to the lower limbs. Observe that it inclines backwards, and forms, with the last lumbar vertebra, a rounded angle, termed the ' promontory ' of the sacrum. This inclination answers a double purpose : it not only makes the pelvis capacious, but breaks the force of shocks transmitted from the pelvis to the spine. Composed of Five Vertebrae. — Its general shape is tri- angular. It plainly consists of five vertebrae, 52 with their bodies and processes all consolidated into a single bone. Examine its anterior and posterior surfaces, its sides, its base, and its apex. Anterior Surface. — Its anterior surface is concave from above downwards, and from side to side, in adaptation to the pelvic cavity. The curvature of the bone forwards, inferiorly, not only assists in supporting the pelvic viscera, but permits us to sit, which we could not have done had the bone projected like a tail. In the middle, are the anchylosed bodies of the five sacral vertebrae, decreasing in size from above downwards, and the four transverse ridges indicating their union. On each side of the ridges are the four anterior sacral foramina, with grooves leading from them for the passage of the anterior branches of the sacral nerves. The bone exterior to the foramina, on each side, is made up of parts which in the three upper sacral vertebrae are homologous to ribs. These are united to the bodies, to each other, and to the transverse processes behind, so as to form a solid lateral mass. Here the ' pyriformis ' arises. (Plate XL VII.) Posterior Surface. — The posterior surface of the sacrum is ■convex, and presents, in the middle line, the spines of the four upper sacral vertebrae, usually coalesced into a vertical crest. PLATE XXVIII. SACRUM. promontory. Coeqyqeus interior view, Art'icuW process Term'mat'ipnoP Yer ■fbrfift^ sacral nerve. Posterior view. ..Cornu %3. coccy x . Drawn on Stone "by T. Godart. PVam nature tvL.Hold.eii. rIm y THE SACRUM 175 for the origin of the ' erector spinae.' The last sacral vertebra, and sometimes the last two, have no spines, and even their arches are more or less deficient, so that the termination of the vertebral canal is here left unprotected in the dry bone ; and in the recent state it is covered only by a fibrous membrane. This explains the serious effects that are apt to follow an injury to this part. Sloughs from bed-sores are sometimes deep enough to expose the vertebral canal. On each side of the crest is the vertebral groove ; and here are the faint traces of the anchylosed articular processes of the sacral vertebra. The most conspicuous of these processes are those of the last vertebra : they project like two knobs of bone, and are called the ' cornua ' of the sacrum : they correspond with the cornua of the coccyx, with which they are connected by ligaments. Next to the articular processes are the four foramina which transmit the posterior sacral nerves. These posterior foramina are directly opposite the anterior, and are smaller in size. Beclard, in his lectures, relates the case of a sharp instrument running through both into the pelvic cavity. The fifth sacral nerve emerges through the little ' notch ' beneath the sacral cornu. Still more externally are the ' tubercles,' in- dicating the anchylosed transverse processes. The posterior sur- face of the sacrum gives origin to the erector spinse, multifidus spinse, and gluteus maximus, as shown in Plate XLIII. Base of Sacrum. — The base or upper end of the sacrum presents the oval surface of the body of the first sacral vertebra, which articulates with the last lumbar, a thick fibro-cartilage intervening. "When the bone is in its proper position, this upper surface slants downwards and forwards, forming, with the lumbar vertebra, the sacro-vertebral angle, or 'promontory.' On each side of the body are its thick and strong lateral masses, expanded like wings, which transmit the weight of the trunk to the iliac bones. Each wing has a rounded edge in front, which forms part of the brim of the true pelvis. Behind the body is the triangular opening of the vertebral canal formed by the vertebral arches. Lastly, on each side of the canal are the articular processes for the last lumbar vertebra. They are set very wide apart, giving a broad base of support to the spine, 176 THE SACRUM and look backwards and inwards, being slightly concave from side to side. In front of each articular process is the indication of the notch for the passage of the last lumbar nerve. Apex. — The apex of the sacrum is formed by the diminutive body of the last sacral vertebra, and has an oval articular surface for the coccyx. At the sides of the sacrum, notice the surface which is con- nected to the ilium, forming what is called the ' sacro-iliac ' sym- physis. Three sacral vertebras concur to form it. The connec- tion is effected partly by cartilage, partly by ligament. The cartilaginous part is in front, and is mapped out on the dry bone in the shape of a little ear, hence it is called the ' auricular ' surface of the sacrum. We may divide the auricular surface into an anterior or vertical and a posterior or horizontal portion. The surface is irregular and concave from before backwards, and from above downwards in both portions. Behind this is a very rough surface, denoting the attachment of the posterior sacro-iliac liga- ments. Lastly, the side of the sacrum below the auricular part gives origin to some of the fibres of the ' gluteus maximus.' Ossification. — The sacral vertebras are ossified like the others, with the addition of an independent centre on each side of the first three for the formation of the lateral mass, and appearing from the sixth to the eighth month. Now, since every vertebra has three primary centres (one for the body and two for the laminae, or arches), and two secondary centres for the body (the discs on the upper and lower surface appearing after puberty), the number of centres for the five sacral vertebras stands thus : 3 x 5 = 15 centres for the bodies. 2 x 5 = 10 centres for the arches. 2 x 3-= 6 additional centres for the lateral masses of the — first three vertebras, that is 81. To these add four epiphysial plates, two on each side, the upper for the auricular surface, the lower for the outer margin of the sacrum beneath that surface, and appearing from the eighteenth to the twentieth year— making in all 35 centres. THE SACRUM 177 The component parts of each vertebra unite tbgether first. Thus complete, the vertebrae remain separate until about the fifteenth year, when they begin to unite ; not all at once, but in regular succession from below upwards. The lateral masses unite before the bodies. The whole bone is not consolidated before the twenty-fifth year, or thereabouts. However, even in advanced age, one sometimes finds the bodies of the upper sacral vertebrae still united in the centre by cartilage only. Comparative Osteology. —Animals with well- developed hind-legs, which articulate with a pelvis, have a more or less de- veloped sacrum, formed by one or more vertebrae. Supple animals, such as the tiger, will be seen to have a very rudimentary sacrum ; the component parts are not welded together into a confused mass like that of man. Snakes (Ophidia) have no sacrum, although there are rudi- mentary hind limbs in Typhlops, Python, and Tortrix. In the dugong and manatee (No. 2647, Sirenia) the sacrum is wanting as well as the hind limbs. There is no sacrum in the whales (Cetacea) . The simplest form of sacrum is seen in the frog. It consists of one vertebra only, the transverse processes of which are ex- panded to articulate with the ilia. THE COCCYX. (Plates XXVIII., XXIX.) Constitution and Shape. — The coccyx derives its name from a fancied resemblance to the beak of a cuckoo (kokkv%). It consists of four or sometimes five rudimentary vertebrae, articu- lated (or anchylosed) together, and successively decreasing in size, the last being a mere nodule of bone. As a whole, it is tri- angular. The body of the first coccygeal vertebra articulates by an oval surface with that of the last sacral : and it has two little articular processes termed ' cornua ' which are connected with N 178 THE COCCYX the ' cornua ' of the sacrum, either by fibrous tissue or cartilage. The first vertebra has also two rudimentary transverse processes, and two ' notches ' (one beneath each cornu) for the last sacral nerves. The first coccygeal vertebra articulates with the lower end of the sacrum by an intervening fibro-cartilage, and the succeeding ones are also separated by a fibro-cartilage. Thus the coccyx admits of being bent backwards and forwards, which is of great advantage in parturition, and gives as much as one inch more space in the antero-posterior diameter of the outlet of the pelvis. About the age of 45 or 50, and indeed sometimes earlier, these little bones become anchylosed to each other and often to the sacrum. This condition is one of the causes of difficult labour, and is gene- rally met with in women bearing a first child late in life, and in those who have been accustomed to sit during the greater part of the day, as in the case of milliners. 53 Under these circumstances, the bone will sometimes break in labour. The coccyx gives attachment to the ' coccygeus ' and ' sphincter ani externus ' muscles. Ossification. — Each bone of the coccyx is ossified from a single centre. The first begins to ossify soon after birth; the second from the fifth to the tenth year ; the third about puberty ; and the fourth about the fifteenth or twentieth year. Comparative Osteology. — The coccyx in man corresponds to the tail of other animals. It now and then happens that the end of the coccyx projects somewhat, and is enclosed in a tube of integument ; the man is then said to have a tail, and is looked upon by the vulgar with great suspicion. In Mammalia the number of caudal (or coccygeal) vertebra mostly far exceed those of any other region. This maybe seen in the tail of the great ant-eater, which has forty, and that of the long-tailed Manis, which has forty-five. The Barbary ape (No. 170) has but three caudal vertebras. The gibbon (No. 65) has two. The vampire bat (No. 3419) is the only mammalian animal which has no coccyx. In all birds, except the extinct Archseopteryx, the caudal region of the spine is shorter than the body, and numbers only PLATE XXIX. Articular process -forLumbar Vertebra . Vertebral canal. Articular surface for the Ilium . Tubercles or Trans verse processes Gluteus .-*' Erector on™ of Sacrum . OT-nu of Coeoyx . Sphincter an Posterior surface of Sacrum . witVi muscles at7fca.cT1e.cl, From -nntiirp rn T T ■ W" 1 '- 5 "-, -Dc gwn on .Stone "by T. Godart Printed by West, Newman h Co. THE COCCYX 179 eight or nine at most. In nearly all birds the terminal vertebrae will be seen to be anchylosed into a ploughshare-shaped bone, as in the ostrich and the vulture (No. 1674). In No. 70 A (the sheat-fish and the halibut) the last caudal vertebra is triangular and flat, and to the posterior edge of it articulate the rays form- ing the tail. N 2 180 BONES OF THE LOWER EXTREMITY. Constituent Bones. — The bones of the lower extremity con- sist of the ' femur,' the ' patella,' the two bones of the leg, namely, the 'tibia' and ' fibula,' the bones of the 'tarsus,' the ' metatarsus,' and the ' phalanges ' of the toes. The femur articulates with the pelvis. The pelvis consists of the ' os sacrum,' the coccyx, and the two ' ossa innominata.' These bones form an arch, of which the sacrum is the keystone, and the innominate bones are the pillars. (Plate XXXII.) The weight of the spine is supported on the top of the sacrum, and the pressure is communicated down the pillars of the arch to the thigh bones which articulate with the innominate bones. It is in this way that the weight of the body is supported by the lower extremities. OS INNOMINATUM. (Plate XXX.) General Description. — The ' os innominatum,' so by Galen, is made up of three bones, distinct in childhood, but united in the adult, and termed the ' ilium,' ' ischium,' and 'pubes.' Thus its constituents have received appropriate names, but the bone, consolidated, remains ' nameless.' The ' ilium ' is the expanded part which supports the flank (ilia) : the 'ischium' supports the body in the sitting posture (layia, the buttocks) ; the 'pubes' is the front part — so called from its being covered with hair. All three contribute to form the ' acetabulum,' or socket for the head of the femur, and in the following proportions PLATE XXX. OS INNOMINATUM. OS INNOMINATUM. ^^Lysisiij «.* <* ^^--Uiwfn. dratus lurrVborum. B *V2 Posterior Su^ spine Posterior infr spine. Spine of Ischium X.esser tsehiatic nofccVi Tuberosity of Ischium VTransversalts perinei . Outer s u-rfaoe Inner surface. From, nature l3yL.H0ld.en. Drawn on Stone ty T. Godart. Printed- hj West, Newman &, Co. OS INNOMINATUM 181 (Plate XXX. fig. 3) : the ischium contributes rather more than two-fifths, the ilium rather less than two-fifths, and the pubes about one-fifth. Until the age of puberty they are separated at the bottom of the acetabulum by a piece of cartilage shaped like the letter Y ; in the adult, however, little trace is left of the original division, so that, for practical purposes, it is better to consider the bone as one. Looking at the bone generally, we notice that it is constricted in the middle, so as to assume somewhat of an hour-glass shape. The constricted portion we call the ' isthmus ' of the innominate bone. At this isthmus the bone is twisted in such a way that a surface which looks upwards, inwards, and forwards above looks inwards, backwards, and slightly upwards below. As the ilium, pubes, and ischium merge into one another at the isthmus, without any line of demarcation between them in the fully formed bone, it is more convenient to consider the os innominatum as a whole, and as having a general circumference, enclosing an external and an internal surface. In studying the relative bearings of the several parts of the bone, it is well to hold it as it lies in the erect position of the body. This position is obtained by placing the bone in such a way that the notch in the margin of the acetabulum directly faces the ground, or that the anterior superior iliac spine and the spine of the pubes are in the same vertical plane. Circumference. — This may be divided into an upper part, looking more or less upwards ; an anterior part, looking for- wards and slightly upwards ; a, lower part, looking downwards and slightly forwards ; and a posterior part, looking backwards and somewhat inwards. The upper part, or border, presents more the appearance of a surface than of a border. It is called the ' crest of the ilium.' When looked at from side to side it is pretty uniformly convex upwards, with the highest point of the curve just behind the middle. When viewed from above downwards it is curved so as to present from before backwards externally, first a slight concavity, next a larger convexity, next a still larger concavity, and lastly 182 OS INNOMINATUM a smaller convexity. It commences in front in a small rounded projection, called the ' anterior superior iliac spine,' -which lies quite under cover of the adjacent overhanging upper border and gives attachment to the outer end of Poupart's ligament. It terminates behind in a similar projection named the ' posterior superior iliac spine,' also under cover of the overhanging upper border, and whose position in the living body is indicated by a dimple in the skin. We divide the crest of the ilium into an outer and an inner lip with an intervening rough surface. The outer lip is the more prominent of the two lips and gives attach- ment in its anterior half to the ' external oblique ' and in its posterior half to the ' latissimus dorsi.' The inner lip is not so prominent as the outer one. It is more rounded and uniform in outline and not so rough, and gives origin in its anterior two- thirds to the ' transversalis abdominis,' and in its posterior third to the ' erector spinse ' and ' multifidus spinse ' muscles. The ' quadratus lumborum ' arises also from about an inch and a half of the inner lip in front of the ' erector spinse ' (Plate XXX.) The intervening surface is rough and convex transversely. It is specially broad in its anterior and posterior small thirds and narrow in its large middle third. It gives origin in its anterior two-thirds to fibres of the ' internal oblique ' and in its posterior third to parts of the ' erector ' and ' multifidus spines ' muscles. The anterior border commences above at the anterior superior iliac spinous process and terminates below at the ' angle of the pubes,' i.e. the meeting of this border with the inferior one, and situated at the upper end of the surface for articulation with the bone of the opposite side. Looked at as a whole it is con- cave from above downwards and is directed forwards and slightly upwards. It presents immediately below the anterior superior spine a notch, called the ' anterior superior spinous notch,' rough and giving origin in its upper half to the ' sartorius ' and in its lower half to part of the straight head of the ' rectus femoris ; ' next a rounded elevation, the ' anterior inferior iliac spine,' for the attachment of the rest of the straight head of the ' rectus femoris,' and below it a rough sharp edge forming part of OS INNOMINAXUM 188 the circumference of the articular surface for the femur, and usually showing a notch indicating the point of junction of the iliac and pubic portions of the bone in this region. Eunning downwards and forwards from this is a crest, the ' obturator crest,' flattened in its outer third, where it gives attachment to a strong part of the capsular ligament of the hip joint, smooth, prominent, looking downwards and backwards and forming the upper edge of a groove situated immediately underneath it, in its inner two-thirds. At the inner end of this obturator crest the border is elevated into the ' spine of the pubes,' for the attach- ment of the inner end of Poupart's ligament. Surgically the spine of the pubes is of great importance. It can be readily felt through the skin and forms a guide to the external abdominal and the femoral rings. Starting from the spine, and running inwards and slightly downwards for about three-quarters of an inch, is a rough flattened ridge, called the ' crest of the pubes,' giving origin anteriorly to the ' pyramidalis ' and posteriorly to the ' rectus abdominis ' muscles. Inferior border : Looked at as a whole, this border runs downwards, backwards, and outwards. It presents a general convexity facing downwards, forwards, and inwards, and when looked at in its long axis it appears sinuous, so as to present at the junction of its inner third with its outer two-thirds a slight convexity pointing upwards, inwards, and backwards, and in its outer two-thirds a larger convexitypointing downwards, outwards, and forwards. The border may be conveniently divided into an inner third or articular portion and an outer two-thirds or non- articular part. The articular portion is called the ' symphysis pubis,' united to the corresponding surface of the opposite bone by fibro-cartilage of at least three-eighths of an inch in thick- ness in front, which is elastic, completing the pelvic arch below and serving to obviate the effects of concussion. The ' symphysis pubis ' is a flattened oval surface joining the inner end of the ' crest ' at what we have already called the ' angle of the pubes.' Its long axis runs downwards, backwards, and slightly outwards, and measures about an inch and a half in the male and rather less in the female. In a well-marked bone it shows a series of 184 OS. INNOMINATUM antero-posteriorly directed and parallel rows of rough tubercles for the firm attachment of the fibro-cartilage, excepting in a small elongated space which is flat but rough and which is placed rather above and behind the middle of the whole articular sur- face. The posterior edge of the symphysis is the more pro- minent. The non-articular part of the lower border forms one half of the so-called ' pubic arch ' of the articulated pelvis. It forms a rough everted margin (more everted in the female bone than in the male one), and gradually increasing in thickness as it passes backwards. About the junction of its anterior third with its posterior third we frequently see a notch indicating the point of junction of the pubic and ischial parts of the border. Ex- ternally the border gives origin to fibres of the ' adductor magnus,' anteriorly to fibres of the ' gracilis,' internally, where the border is slightly grooved, to the ' crus penis ' or ' crus clitoridis ' and to fibres of origin of the ' erector penis ' (Plates XXX. and XXXI.) The posterior border begins superiorly at the posterior supe- rior iliac spine and terminates below by joining the posterior end of the inferior border. Tracing it from above downwards, we notice first a small rough notch, called the ' posterior superior iliac spinous notch,' for the attachment of ligaments, next a sharp rounded prominence forming the posterior extremity of an arti- cular surface seen on the inner surface of the bone, and called the ' posterior inferior spinous process.' Next we come on a large smooth excavation — the ' great ischiatic notch.' This notch is converted into a foramen by the greater and lesser ischiatic ligaments (fig. 24), and transmits the great vessels and nerves from the pelvis to the buttock, back of the thigh, and fore part of the pubic arch, viz. Gluteal vessels and nerve. Pyriformis muscle. Greater and lesser ischiatic nerves. Ischiatic vessels. Pudic vessels and nerve (out of pelvis). Nerve to obturator internus (out of pelvis). The upper two-thirds of the notch belongs to the ilium, the lower third to the ischium. The lower end of the great sciatic OS INNOMINATUM 185 notch is prolonged into a flat, triangular projection, with a blunt apex, and called the spine of the ischium. It projects more in- wards in the male than in the female bone, and in the latter is a very important bony prominence helping to regulate the passage of the foetal head in parturition. It gives attachment by its apex to the lesser ischiatic ligament, anteriorly to fibres of the ' coccygeus ' and ' levator ani,' and posteriorly it gives origin to the ' superior gemellus.' Below this spine we come upon a smooth smaller notch — the ' lesser ischiatic notch ' — covered in Fig. 24. ^ Sacro-isohiatic Greater 1 Li g*™ent. the recent state by cartilage and lined by synovial membrane for the play of the tendon of the ' obturator internus ' muscle. This lesser ischiatic notch is converted into a foramen by liga- ments (fig. 24), and gives passage to Tendon of the obturator internus, Nerve to obturator internus (into pelvis). Pudie vessels and nerve (into pelvis). Below the lesser sciatic notch the posterior border merges into the posterior end of the inferior one and forms a prominent rough ledge in the adult bone, looking inwards and affording attachment to the falciform process of the great sciatic ligament. The ligaments converting the notches into foramina answer three important purposes : 1. They mainly contribute to the fixation of the sacrum, which is the keystone of the pelvic arch. 186 OS INNOMINATUM 2. They afford an extensive surface for the origin of the great muscle of the buttock (gluteus maxim us). 3. They help to form the floor of the pelvis, and support the pelvic viscera, without adding much to the weight of the cavity. External Surface. — This surface is twisted at the isthmus in such a way that the broad upper expanded portion, formed by the ilium, looks backwards and outwards, and the lower smaller portion, formed by the pubes, looks forwards, downwards, and somewhat outwards. Above the isthmus the external surface forms a fan-shaped space — the ' dorsum ilii.' The base of the fan is formed by the outer lip of the iliac crest, and the blunt apex of the fan is continuous with the rest of the bone along the top of the articular surface for the femur. It is a sinuously curved space, following the sinuosities of the crest, already described, and presenting a ' superior,' ' middle,' and an ' inferior curved line,' limiting the attachments of the three great rotator muscles of the hip joint, viz. the ' gluteus maximus,' ' medius,' and 'minimus.' The 'superior curved line 'begins above at the outer lip of the iliac crest, about an inch and a half in front of the posterior superior iliac spine, runs downwards with its convexity directed backwards, to terminate at the top of the great sciatic notch, a little way in front of the posterior inferior iliac spine. Above this line is a rough surface for the origin of the ' gluteus maximus.' The ' middle curved line ' begins above at the iliac crest, about an inch and a half behind the anterior superior iliac spine, sweeps upwards and backwards, and then downwards and backwards to terminate at the upper part of the great sciatic notch. The rough surface between it and the superior curved line gives origin to the ' gluteus medius,' and close to the line, and situated about two inches or so from its lower end, are usually found one or two large nutrient foramina. The ' inferior curved line ' is commonly not so well marked as the other two. It begins in front at the anterior inferior spinous process, or the lower part of the anterior superior spinous notch, and runs nearly straight backwards, curving slightly upwards in its course, to terminate at the fore part of the great sciatic notch. The surface of bone between it and the middle curved line gives OS INNOMINATUM 187 origin to the ' gluteus minimus,' and in the fore part of the sur- face are situated a number of large nutrient foramina. Under the inferior curved line we come upon a rough, swollen surface, continuous anteriorly with the upper part of the rim of the acetabulum, and posteriorly merging into the part of the external surface of the bone formed by the body of the ischium, in some ossa innominata the line of junction being indicated by a shallow groove leading from the fore part of the sciatic notch to the margin of the acetabulum. Above the acetabulum this part of the surface is rough for the origin of the ' reflected head of the rectus muscle ' and a strong part of the capsular ligament of the hip joint. Posteriorly it is smooth for the play of the overlying ' pyriformis ' muscle, and all over it, especially in front, we notice a number of large nutrient foramina. Passing downwards we come upon the articular surface for the femur, called the ' aceta- bulum ' or ' cotyloid cavity.' It is a hemispherical excavation, wanting below, looking downwards, outwards, and somewhat for- wards, and formed, as already said, by the ischium, ilium, and pubes in the respective proportions of f, a large £, and a small £. The margin of the cavity is sharp, rough, and uneven, and forms about three-fifths of the circumference of a circle. The cotyloid ligament, attached to it, fills up its inequalities and converts it into an even uniform margin. This ligament also, under the name of the transverse ligament, completes the circle, inferiorly, by bridging over the part of the cotyloid cavity which is wanting below. The cavity itself we divide into a circum- ferential or horseshoe-shaped articular portion and a central or inferior non-articular part. The horseshoe-shaped articular portion is slightly broader at its posterior than at its anterior end, but broadest of all superiorly, as it has there to support the greatest weight. Traced from the circumference towards the centre of the cavity, the articular surface is uniformly concave, and in some bones shows by shallow grooves the lines of junction between the iliac portion above and the pubic and ischial por- tions, situated respectively in front and behind, below (fig. 25). The groove is commonly best seen at the line of junction of the iliac and pubic portions. The non-articular part occupies the 188 OS INNOMINATUM bottom of the cavity and communicates with the exterior by means of a large notch, lying between the ' heels ' of the ' horse- shoe ' formed by the articular portion, and known as the ' coty- loid notch.' The non-articular part is depressed below the adjacent articular surface, and is formed by an exceedingly thin plate of bone. It is covered by a pad of fat, known as the pad of Havers, and is marked by a number of large nutrient fora- mina, especially superiorly. The 'cotyloid notch' is smooth. Its lower margin forms part of the circumference of the ' obtu- rator foramen,' to be presently described. Its anterior and posterior extremities give attachment to corresponding branches Fig. 26. Ischium Internal Aspect. External Aspect. DIAGRAM OF FORMATION OF ACETABULUM BY ILIUM, ISCHIUM, AND PUBES (modified from Henle). of the ' ligamentum teres,' and on it rest articular vessels and nerves for the ligamentum teres and the Haversian pad of fat. Below and in front of the acetabulum is the obturator foramen, or foramen ovale. This is a wide opening of an oval form in the male, but triangular, with rounded angles, in the female. It is closed in the recent state by the ' obturator membrane,' everywhere excepting above and in front, where there is a broad groove leading downwards and forwards for the passage of the obturator vessels and nerve into the thigh. The anterior lip of the groove is rounded and formed by the ' obturator crest.' It runs from the spine of the pubes upwards, backwards, and outwards, arches PLATE XXX|, Rfcl. Horizontal ramus of Pifbes. Pyramidailis, Gracilis. Descending ramus of Pubes . cendiiTib ramus of Ischium .

' **,'■ '•-•H Eostf inte External tuberosity. ■ J^^^^m&Mii lit 5 !!* Psoas magnus anc\ iHacusinternus "j6-*i rectineu Adduc-tortrev(s 7 / / / .,||.. .Vastus exte- nus. . MeohaUsLry fora-men . PH factor tubercle. IiiTier Viead of Gastrocnemius^ I .,-Planta.ris. _Outer lieao\ of Gastrocnemius. *M Y! 'MS IP K»Mf ^fLlnternal tuberosity Jffl ft v >W ? r* ;•« «A',i External Co '•.'■ ^SmSmSm ndyle V- ' Anterior surPace. -Internal condyle. *if\... posterior lip of the digital fossa, and is continuous with the ' posterior intertrochanteric line.' The inferior border is a rough, ridge separating the outer surface of the trochanter from the* outer surface of the shaft and giving attachment to fibres of the ' vastus externus.' The superior border is broad in front,. ( where it is marked by two facets, the anterior one for the insertion of the ' obturator internus ' and ' gemelli,' and the posterior one for the insertion of the ' pyriformis ' (Plate XXXIV.) Behind, the superior border is narrow, and at its junction with the posterior" border it forms a sharp angle for the attachment of the most posterior fibres of the ' gluteus medius.' The external surface is free, and looks outwards and backwards. It is divided into an anterior and a posterior smooth part by the ' diagonal ' or ' oblique line ' of the great trochanter — more- an irregularly oval surface than a line, running from the pos- terior superior angle to the anterior inferior angle. The diagonaL- line gives attachment to the ' gluteus medius.' The smooth part below the line is for the play of the tendon of the ' gluteus maximus,' a large bursa being interposed. The smooth part above the line is for the play of the ' gluteus medius,' a smaller bursa being interposed there too; The internal surface, anteriorly and inferiorly, is continuous with the upper extremity of the shaft ; posteriorly and superiorly, it is free and forms a deep excavation called the ' digital fossa ' (Plate XXXIII.) The pit is very rough, and very often shows short spicules of bone rising. ; PLATE XXXIV. Pbburabor mbernus &. Getnelli. JPyriformis. Surface over which plays the tendon of the Gluteus maximus Plantari Fi^.l Rfc.2. ,. Outer "he5.3 oE GastrocneTri-ius., Attachment of external lateral ligament .Pbpliteus. External condyle. fitmio try T. Godart. Prmtsd. ty "West.TSTewiriaii & Co. THE FEMUR 20$ from the bottom and running into the tendon of the ' obturator externus,' which is inserted here. Trochanter Minor. — The trochanter minor projects from the inner and back part of the shaft, just below the base of the neck. It is a flattened, truncated cone, rising by three roots ; viz. a superior one continuous with the lower border of the neck, a posterior one continuous with the ' posterior intertrochanteric line,' and an inferior one continuous with the middle of the upward branches of the linea aspera. Its top is flattened and rough for the insertion of the 'psoas ' part of the ' ilio-psoas.' The posterior surface is smooth and covered by the adjacent borders of the ' quadratus femoris ' and the ' adductor magnus.' The superior and anterior surfaces are also smooth, and the lower root gives insertion to the iliac part of the ' ilio-psoas.' (Plate XXXIII.) Observe that the trochanter minor is directed backwards and that the muscles inserted into it turn the thigh outwards at the same time that they raise it. These are the muscles which, in fracture of the upper third of the shaft, it is often difficult to- prevent from tilting up the upper fragment. Intertrochanteric Eidges. — The ' anterior intertrochan- teric ridge ' commences above in an eminence situated on the anterior aspect of the bone at the upper part of the base of the neck and internal to the anterior border of the great trochanter, and called the ' tubercle ' of the femur. It runs obliquely down- wards and inwards as a flattened rough ridge, separating the anterior surface of the neck from the corresponding surface of the shaft, as far as the level of the small trochanter ; it then divides into two branches, a short upper and rough one about an inch long, stretching upwards and inwards above and outside the small trochanter, about half an inch distant from it, and fading off in the lower border of the neck. The lower branch is a continuation of the main ridge, and runs downwards, inwards, and backwards in front of, and then below the level of, the small trochanter, to terminate in the upper end of the inner lip of the linea aspera. This branch is not well marked above, but gets better marked below, and limits the attachment of the 204 THE FEMUB * vastus interims.' The main ridge and its upward branch afford attachment to the ilio-femoral and pubo-femoral parts of the •capsular ligament of the hip joint. The main ridge and the lower branch are ordinarily called the ' spiral line.' The ' posterior intertrochanteric ' ridge is a very short rounded ridge connecting the posterior inferior angle of the great with the posterior root of the small trochanter. It forms the lower limit of the neck below and behind. Shaft. — The shaft of the femur presents both antero-posterior and lateral curves. The antero-posterior curves are two — one, a very distinct one, pointing forwards and occupying almost the whole of the shaft, and the other, a very much less one, pointing hackwards with the greatest projection at the level of the small trochanter. The highest point of the curve forwards is situated about the middle of the shaft, and at this point too the shaft is narrowest and weakest ; consequently we find it more often hroken here than elsewhere. The lateral curves are not so well marked ; one is situated in the upper third, with the convexity directed outwards, and the other in the lower third, with the convexity pointing inwards. Besides presenting these curvatures the whole shaft is twisted in such a way that the anterior surface looks forwards and slightly outwards at the upper extremity and straight forwards at the lower. By means of these cur- vatures and twisting a double advantage is gained : first, it is rendered more springy than if it were straight; secondly, more room is gained for the flexor muscles behind and the adductor muscles inside, and more power for the extensor muscles in front. In cross section the shaft at the upper end forms a four- sided figure with rounded angles, and flattened from before backwards. In the middle it is triangular with the prominent apex of the triangle pointing backwards, while at the lower end it forms a triangle with rounded angles and the blunt apex of the triangle looking inwards. For convenience of description we consider the whole shaft as prismatic; and describe it as possess- ing internal, external, and posterior borders, separating anterior, internal, and external surfaces. The internal border commences above at the spiral line, where THE FEMUE 205 that line divides into its two branches, and terminates in the front of the internal condyle. It is smooth and rounded in its whole extent, and by its upper two-thirds gives origin to fibres of the ' crureus.' The external border is very indistinct. It commences at the anterior inferior angle of the trochanter major, and terminates at the front of the external condyle, separating the anterior from the external surface. Its upper two-thirds or so give attachment to the ' crureus.' The posterior border forms a rough, strong buttress to the middle third of the shaft, termed the ' linea aspera.' At first sight it appears as a single ridge, but look carefully and you will find traces of two borders, termed its external and internal 'lips,' separated by a rough interval. About the lower third of the shaft these lips diverge from each other, and may be traced to the ' tuberosities ' of the condyles. Of the two the external is the more prominent. The internal is interrupted at its upper end by a smooth space for the passage of the femoral artery to the back of the thigh and inferiorly it terminates in a prominence on the inner tuberosity, termed the ' adductor tubercle,' for the attachment of a strongly tendinous part of the ' adductor magnus.' The triangular interval between the divergence of these lips is termed the ' popliteal surface of the femur,' and upon it the popliteal artery rests in its passage through the ham. It is a flat space showing numerous large nutrient foramina at its lower end and giving attachment inferiorly and internally to the inner head of the ' gastrocnemius.' At the junction of the upper and middle thirds of the shaft the linea aspera divides into three branches — an external one, forming a low rough ridge termi- nating at the posterior inferior angle of the great trochanter, and affording attachment to the ' gluteus maximus ; ' a middle one, not so well marked, terminating at the lower border of the small trochanter and affording attachment to the 'pectineus' and 'adductor brevis ; ' and an internal one, already described as part of the spiral line limiting the attachment of the 'vastus internus.' Between the middle and outer branches are attached the upper fibres of the 'adductor brevis ' and ' magnus ' muscles. 206 THE FEMUR Commencing in the middle of the posterior intertrochanteric line, and running vertically down the bone for about an inch and a half, is an indistinct line — more an elevated surface than a line, and best marked above — termed the ' linea quadrati,' for the insertion of the ' quadratus femoris ' muscle. What has been said of the linea aspera and its lower bifurca- tions or ' condyloid ridges ' will help us towards understanding the muscles attached to it. Take the outer lip. To its whole length, and to the upper two-thirds or so of the outer condyloid ridge, is attached the ' short head of the biceps.' To the same ridge, and immediately above the condyle, arise the ' plantaris ' and the upper fibres of the outer head of the ' gastrocnemius.' The inner lip gives attachment above to a few fibres of the ' adductor brevis,' in its lower third to fibres of the ' adductor magnus,' and in the rest of its extent to the closely connected fibres of the ' adductor longus ' and ' vastus internus.' The interval between the two lips in the upper two-thirds is occupied by the ' adductor magnus.' Excepting in the smooth part above, the internal supra-condyloid line gives attachment to the closely incorporated fibres of the ' adductor magnus ' and ' vastus in- ternus.' Usually at the upper and at the lower end of the linea aspera is a large foramen leading to a canal, directed upwards, which conveys a nutrient blood-vessel to the marrow. The anterior surface lies between the inner and outer borders. It looks forwards and outwards above and forwards below. It is convex from above downwards, excepting at its upper end, where it is slightly concave. It is convex also from side to side, excepting at its lower end, where it is slightly concave. It is broader above and below than in the middle, and gives origin in its upper three-fourths to fibres of the ' crureus,' and in its lower fourth to a few slips which constitute the ' sub-crureus.' At its lower end we notice a number of large nutrient foramina. The external surface is smooth and convex from before back- wards, affording attachment to the * vastus externus ' and ' crureus.' (Plate XXXIII.) The internal surface, also smooth and convex from before THE FEMUR 207 backwards, lies between the internal and posterior borders. It is continuous above with the lower border of the neck, imme- diately below which it shows part of the spiral line. Interiorly it looks forwards and inwards, and is continuous with the inner surface of the internal condyle. Just below the spiral line, and •close by the posterior border, it gives origin to the ' vastus in- ternus.' In the rest of its extent it gives origin to no muscular fibres ; here the bone is simply covered by the fibres of the ' vastus internus.' (Plate XXXIII.) Condyles. — The lower end of the femur gradually expands io form the ' external and internal condyle,' separated by the * intercondyloid notch.' Of the two condyles the external is the broader, both antero-posteriorly and laterally. It also projects more forwards and is placed more in the direction of the long axis of the shaft than the internal one. The direction of its long axis is straight from before backwards, while that of the internal one is obliquely backwards and inwards. The inner condyle projects much more downwards, and is fully half an inch lower than the outer when the bone is placed perpendicularly, but when the bone slants, as it naturally does, both condyles are on the same level. This must needs be, as the plane of the knee joint is horizontal, in adaptation to the erect posture. Looking at the condyles individually we notice that the ' ex- ternal condyle ' presents upon its anterior, inferior, and posterior aspects a smooth articular surface, the anterior part of the surface being for articulation with the patella and the rest for the tibia and interposed nbro-cartilages. The patellar part is broad, four-sided, convex transversely as well as antero-posteriorly. It is limited above by a convex lip, the convexity being directed upwards, and behind by a faintly marked groove parallel with that lip and visible on the fore part of the inferior aspect of the bone. Internally it is continuous with the corresponding surface on the internal condyle, and. externally its margin separates the external surface of the condyle from the anterior and fore part of the inferior surface of the condyle. Behind the curved line, limiting the patellar surface, We have the condyloid surface _proper, for articulation with the upper surface of the external 208 THE FEMUR tuberosity of the tibia. Looking at this surface as it lies on the inferior aspect of the condyle, we notice that it is convex from side to side and very slightly so from before backwards. As seen on the posterior aspect of the condyle, it is convex from side to side, but very much more so when traced from above- downwards. The ' condyloid surface proper ' forms part of the circumference of a circle of which a roughness on the external surface of the condyle, for the attachment of the external lateral ligament, is the centre. Above the articular surface, pos- teriorly, the condyle is rather concave in every direction, marked by several nutrient foramina, and gives origin in the immediate neighbourhood of the supra-condyloid line to the ' plantaris ' and a few fibres of the outer head of the ' gastro- cnemius.' The external surface of the condyle, while traced from before backwards, gradually rises up into a rough eminence called the ' external tuberosity.' The highest point of this tuberosity is situated at the junction of the posterior third with the anterior two-thirds of the surface, and is continuous with the lower end of the external supra-condyloid line. The posterior side of the summit shows a rough impression for the origin of the external head of the gastrocnemius, while the anterior side, in the immediate neighbourhood of the apex, shows a somewhat flattened space for the attachment of the external lateral ligament. Below and behind the tuberosity is a deep groove, narrower and deeper below and in "front than above and behind. It is called the ' popliteal groove,' and gives attachment at its anterior and inferior end to the popliteal tendon. The upper two-thirds of the groove and of the corresponding lower lip are smooth and covered in the recent " state by cartilage, to allow of free play of the tendon. The surface in front of the tuberosity is slightly rough and marked by a number of large nutrient foramina. The internal surface of the condyle is continuous anteriorly and superiorly with the rest of the bone, while posteriorly and in? feriorly it is free and forms the external wall of the ' intercon- dyloid notch.' The ' internal condyle ' is narrower than the external condyle.' Its long axis runs obliquely backwards and inwards, and it THE FEMUR 209 projects from the lower end of the bone to a greater extent, both laterally and inferiorly, than the external one. Its anterior surface presents above a rough concave part marked by nutrient foramina. Next is seen the surface for articulation with the patella — patellar surface. This is a less extensive surface than the corresponding one on the external condyle, and with which it is continuous. It is quadrilateral, with its inner border much smaller than its outer one. In some femora the inner border does not exist at all, causing the surface to be triangular in shape with the apex pointing inwards. The inferior and posterior aspects of the condyle are occupied by the condyloid surface proper. Looking at this surface we notice that it presents a much more uniform curve from before backwards than the external one. If we look more closely, however, we see that its anterior part is occupied by a triangular space which does not belong to the circumference of the same circle as that belonging to the rest of the condyloid surface. The base of the triangle is formed by the inner edge of the condyloid surface. The anterior and posterior sides are formed by two smooth and curved lips with their convexities directed forwards, and converging from the ends of the base to the fore part of the intercondyloid notch. The anterior side separates the patellar surface from the condy- loid surface. The triangular space is called the ' oblique surface,' and on it the tibia slides outwards in the last act of extension of the knee joint. At the apex of the triangle in well-marked femora we notice a facet for articulation with the patella in com- plete flexion. The rest of the ' condyloid surface proper ' is not so flat inferiorly as the external one is. When traced from before backwards it forms part of the circumference of a circle of which an impression for the attachment of the internal lateral ligament, situated behind the middle of the internal surface of the condyle, is the centre. The internal margin of the condyloid surface is bevelled off inferiorly for articulation with the spine of the tibia. The internal surface of the condyle gradually rises up from before backwards into the 'internal tuberosity.' The summit of this eminence is situated behind the middle of the surface, and is continuous above with a prominent tubercle formed by the end 210 THE FEMUR of the internal condyloid line, and called the ' adductor tubercle,' for the attachment of the lowest fibres of the ' adductor magnus.' This tubercle is sometimes very large and so interferes with the gripping of the knee in riding. It is an important landmark too, as it is situated immediately below the line of junction of the lower epiphysis with the shaft, and can be readily felt underneath the skin. Behind the summit of the internal tuberosity we notice a flattened, rough space for the attachment of the internal lateral ligament. The posterior surface of the condyle, above the articular surface, is marked by nutrient foramina, and is rough, especially internally, for the origin of the inner head of the gas- trocnemius. The free part of the external surface of the condyle forms the internal wall of the intercondyloid notch. (Plate XXXIV. fig. 3.) The tuberosities being situated nearer the back than the front of the condyles increases the strength of the knee joint, for the reason that the ligaments attached to them are fixed behind the centre of motion, so that they become stretched when the joint is extended. Trochlea for Patella. — The patellar articular surfaces of the condyles unite to form the pulley (' femoral trochlea') over which the patella plays. It is four-sided, but very much narrower on its inner than on its outer side, so that in some bones we may describe it as triangular, with the apex pointing inwards. On its anterior, internal, and external borders we find a prominent lip separating it from the adjacent rough surfaces of the lower extremity of the bone. Posteriorly it is separated from the condyloid surfaces proper by the curved lines already de- scribed, and which lead from notches in the lateral edges of the articular surfaces of the corresponding condyles to the front of the intercondyloid notch. The larger share of the pulley is formed by the external condyle, and it mounts not only higher, but projects more, and is more convex transversely, than the inner, preventing the natural tendency of the patella to be drawn outwards by the quadriceps extensor muscle. Intercondyloid Notch. — This space lies between the free parts of the condyles. Its greatest .breadth is nearly equal to that THE FEMUR 211 Fig. 33. Fiq. 34. of the tibial articular surface on either condyle. It is seen on the lower, posterior, and upper aspects of the lower extremity of the bone. Its long axis looks from above downwards and back- wards. Its outer side is made by the free part of the inner surface of external condyle and shows a rough depression for the> attachment of the anterior crucial ligament. The inner side is formed by the free part of the external surface of the internal condyle, and is also rough, especially in front, for the attachment of the posterior crucial ligament. It is separated posteriorly from the popliteal space of the femur by a smooth transverse non- arti- cular ridge. It is wider behind than it is in front and is marked by one or two large nutrient foramina at its deepest part. The two woodcuts (33 and 34) show very well the attachments and the direction of the crucial ligaments a b, a c. Being attached to the condyles behind the centre, they necessarily limit extension beyond the straight line. But they do more : by crossing like braces they prevent lateral displacement ■ of the tibia. In the erect attitude the natter parts of the ' condyloid surfaces ' rest on the shallow excavation of the tibia, and all the ligaments are on the stretch ; but when the knee is bent the more convex parts of the condy- loid surfaces rest on the tibia, and admit of a certain amount of rotation, all the ligaments being loose. Mechanism and Structure. — Pages might be written about the wonderful mechanical structure of this bone. The chief points, however, which strike one are : 1. The oblique position of the head and the acetabulum, with which it articulates. This allows of greater freedom of antero-posterior motion than a simple ball-and-socket joint, placed vertically, would admit of. 2. The obliquity of the neck. This permits more of the head to rest in the acetabulum, by converting flexion and extension into rotation. It allows, too, more room for the adductors, and gives increased power to the great rotators by throwing their inser- p 2 CEUCIAL LIGAMENTS *0]? THE KNEE. 212 THE FEMUR tions away from the head. 3. The obliquity, curves, and twisting of the shaft give elasticity to the bone, and so break shocks trans- mitted to the bone from below. 4. The obliquity of the lower end. This, we have seen, is apparent, not real ; the plane of the articu- lar surface for the tibia is horizontal, the internal condyle pro- jecting downwards to allow for the divergence of the upper end of the bone caused by the breadth of the pelvis. The internal structure of the bone exhibits in a wonderful way the arrangement of the compact and cancellous tissue, so as to give the greatest strength, elasticity, and lightness to the bone. The fibres of the cancellous tissue at the upper extremity are Fig. 35. arranged in a beautiful way to support the articular surface of the head, as seen in fig. 35. The me- dullary cavity is well developed, and is interrupted at irregular intervals by thin transverse septa of cancellous tissue. The lower end is enlarged by cancellous tissue whose fibres follow the ordinary law in being arranged so as to strike the plane of pressure at right angles. Ossification. — The femur is ossified from three primary centres (one for the shaft and neck, and one for each articular end), and two secondary centres, one for each trochanter. (See Plate IV.) The centre for the shaft appears about the seventh week of fcetal life. The centre of the lower epiphysis does not appear until within the last fifteen days of the full term of gestation. Hence the existence of this centre enables us to pronounce with something like certainty as to the age of a fetus. 58 It is the only epiphysis in which ossification commences before birth. As this is the first of all the epiphyses to ossify, so, in accordance with the general law, it remains the THE FEMUR 218 longest a separate piece. The epiphysis at the upper end of the femur includes only the head of the bone, and begins to ossify about one year after birth. The great trochanter begins to ossify about the third or fourth year ; the lesser about the four- teenth. All the pieces have united about the age of twenty-one. Comparative Osteology. — In the horse, the rhinoceros, and the tapir (Perissodactyla) the gluteal ridge is so largely developed that it has received the name of a ' third trochanter.' The lower end of the femur in most mammals presents three separate articular surfaces, viz. the patellar articulation and two condyles. In man these three are blended into one, although there can be seen a trace of the separation along the lower border of the surface for the patella. The actual separation in man does exist in the foetus, but becomes obliterated, the three articulations merging into one. The ligamenta alaria and the ligamentum mucosum are the only remains of the originally separate synovial membranes of the knee joint. In elephants (Proboscidia) when standing, the bones of the leg and thigh are vertical, as in man. If you examine the femurs of birds you will find they have but one trochanter, viz. that corresponding to our trochanter major. In two or three serpents, e.g. Python tigris (No. 602), Python regius (No. 629), there are rudimentary hind limbs ending in hook-like claws sheathed in horn. These claws are put in action by certain muscles,- and, serving as antagonists to the tail, give it greater prehensile power. The ventral fins of fish correspond to the hind limbs of other animals. THE PATELLA. (Plate XXXV.) This is a flat triangular bone gliding on the trochlear surface of the femur, and with its apex pointing downwards. It presents anterior, posterior, and superior surfaces, and inner and outer borders. Its anterior surface is convex, and marked by longitudinal. 214 THE PATELLA streaks, indicating the insertion of the fibres of the ' quadriceps ex- tensor cruris ' tendon, and also by a number of vascular foramina. Its posterior swrface is divisible into a smaller lower non-arti- cular part and a larger upper articular portion. The non-articular part lies under cover of the apex of the bone. It is triangular in shape and is rough, and shows several large nutrient foramina. It attaches, by its inner and outer margin and its apex, fibres of the ligamentum patellae, and in the rest of its extent is covered by fat underlying the synovial membrane of the knee joint. The upper, articular portion is for articulation with the trochlea, It is large and quadrilateral, rises higher up externally than Fig. 36. AETIOULAB SUBFACE OF THE EIGHT PATELLA. a, b, in contact with femur in complete flexion. b, c „ „ rectangular flexion. d, e „ „ semi-extension. /, g „ „ complete extension. internally, and is unequally divided into two parts by a smooth vertical ridge. The outer part is the larger. It is concave from side to side and is further subdivided into three facets, upper, middle, and lower, by smooth and faintly marked transverse ridges for articulation with the outer part of the trochlea in certain positions of the knee joint. The inner part is again sub- divided into two unequal portions by a smooth vertical ridge. The smaller is the inner portion. It lies close to the inner edge of the bone, and articulates with the facet situated at the inner angle of the ' oblique surface ' of the femur in extreme flexion THE PATELLA 215 ■of the knee joint. The larger external portion is further sub- divided into three facets by two faintly marked elevations of the articular surface, viz. an upper, middle, and lower for articulation with the femur in certain positions of the knee joint. (See fig. 36.) The upper surface or base of the bone is triangular in shape and looks upward and forward. It gives attachment in front to fibres of the ' quadriceps extensor ' tendon. The inner and outer borders are convex and rough, and give attachment each to its own ' lateral patellar ligament.' The apex is pointed,' and gives attachment to the ligamentum patellar. Structure and Mechanism. — In structure the patella con- sists of a mass of cancellous tissue covered by a thin layer of compact bone, forming the longitudinal ridges with the interven- ing grooves for the attachment of the tendon of the quadriceps extensor cruris muscle. It is the largest and best example of a sesamoid bone. It is developed in the extensor tendon of the knee, where it protects the knee joint and increases the power of the extensor muscles by enabling them to act at a greater angle. It is a principle in mechanics that the efficiency of a force which acts upon a lever is greatest when its direction is at right angles to the lever, and that the force decreases as the obliquity of its direction is increased. The patella, thus serving a mechanical purpose in the sub- stance of the extensor tendon, is liable to be broken by a sudden and violent action of the extensor muscles, as in making a strong effort to regain the balance of the body in danger of fall- ing backwards. In this position — that is, when the knee is half-bent — the upper part of the patella is not supported by its trochlea : there is a hollow under it, and here the patella snaps transversely, like a stick broken across the knee. The broken ends separate widely, and therefore in these transverse fractures it is very difficult to obtain osseous, and not ligamentous reunion. ; But even when the knee is extended, violent muscular con- traction is able to snap the patella. Desault speaks of both patellae being broken by convulsions in a patient after he had .been cut for the stone. 216 THE PATELLA Ossification. — The patella is developed from a single centre, which appears about the third year. It is not fully ossified until the age of fourteen or fifteen. THE TIBIA. (Plate XXXV.) Situation and Direction. — The tibia is the larger of the two bones of the leg, and is placed on the inner side. It entirely supports the condyles of the femur, and transmits the weight of the body to the foot. Its direction is not oblique like the femur, but vertical ; so that in well-formed legs the two tibiae should be parallel. Let us examine in succession the upper end, the shaft, and the lower end. Head. — The upper end is called the ' head ' of the tibia. It is very broad in the transverse direction for the support of the condyles of the femur : this great breadth is another peculiarity of the human skeleton. The two articular surfaces for the con- dyles are very shallow in the dry bone, but slightly deepened in the recent state by discs of fibro-cartilage (termed the ' semilunar cartilages '). These cartilages convert the shallow articular sur- faces of the tibia into variable sockets ; that is, sockets which adapt themselves to the varying forms of the condyles in' flexion and extension of the knee. The outer articular surface is more or less round, slightly concave from before backwards and from within outwards. It appears as a gradual rising up of the bone from the margin of the articular surface to the top of the ' spine ' — an eminence which lies between the two articular surfaces. The inner is oval, with the long diameter from before backwards. It is more concave, especially internally, and narrower than the outer one. Its inner part rises up abruptly, to be continuous with the inner surface of the ' spine.' Both articular surfaces show flattened crescentic spaces at their margins, upon which rest the semilunar fibro-cartilages. The crescentic space is usually best seen upon the internal surface. The condyloid surfaces of the femur will therefore touch only the internal and external parts PLATE XXXV. TIBIA. TIBIA. Groove -for -bention of Tibialis "posticus . Spin* Outer surface. ^^ Posterior view. II f §f| If 1 Groove for* tendons ~§ top PeroneMston&uaariel * il>r FIBULA External "tuberosity Inner facette Ihnerfacefcfce I la-, anterior view Fig. 3. s "**s s>sL Interns! tu berosity. Tubercle External malleolus _. Internal maileolu roiTL nature tyL-KaLien. Drawn on Stone hy T. Go dart. Anterior view. Printed. ~by-"West,lSfo wmstn & Lio . THE TIBIA 217 of the external and internal condyles respectively. Between the articular surfaces is the projection termed the ' spine.' It lies in the intercondyloid notch, acting like the flange of a wheel and preventing lateral displacement of the tibia from the femur at the knee joint. Its inner and outer sides are articular and con- tinuous with the corresponding articular surfaces on the head of the bone. The front of the spine is rough and gives attachment internally to the anterior crucial ligament and externally to the anterior end of the external semilunar fibro-cartilage. The pos- terior surface of the spine is also rough and gives attachment to the posterior end of the external semilunar fibro-cartilage and slightly to that of the internal. In front of the spine is a triangular, rough surface, looking upwards, and marked by a number of nutrient foramina for blood- vessels derived from the adjacent ' infra-patellar synovial pad.' On it rests too the transverse ligament connecting the anterior ends of the semilunar fibro-cartilages. It gives attachment likewise to the anterior extremity of the internal and to some fibres of the external semilunar fibro-cartilage and of the anterior crucial ligament. Behind the spine is another rough space, not so exten- sive as the one in front. It is rough and looks backwards as well as upwards. It gives attachment to the posterior end of the internal semilunar fibro-cartilage, the lower end of the posterior crucial ligament, and anteriorly to fibres belonging to the posterior extremity of the external semilunar fibro-cartilage. Tuberosities, External and Internal. — The lateral masses which support the articular surfaces are called the ' tuberosities ' of the tibia. The external tuberosity has at its back part a small nearly circular articular surface for the head of the fibula : this articular surface is on a kind of bony ledge, and its direction is obliquely downwards, backwards, and outwards. The internal tuberosity is much larger, and projects more than the external. It has a horizontal groove behind for the insertion of the ' semi- membranosus.' About one inch and a half below the head of the tibia, and in front of it, is the ' tubercle ' for the insertion of the common extensor tendon of the leg (ligamentum patellae) . In a few tibiae we notice that the lower part of the tubercle 218 THE TIBIA is rough for insertion of the ligament, and the upper part smooth to allow the easy play of the tendon (a bursa being interposed between the ligament and the bone). Starting from the superior internal and superior external angles of the ' tubercle ' are two ridges which run upwards and then diverge to be lost on the inner and outer surfaces of the corresponding tuberosities about half an inch below the articular margin. Of the two the outer is the most prominent and gives attachment to the lateral patellar ligament, and limits superiorly the origin of the 'ex- tensor longus digitorum ' and the ' tibialis anticus.' The inner one affords attachment to the inner patellar ligament and fibres of the internal ligament of the knee joint. Both ridges are con- tinuous with the inner and outer borders of the tubercle, and indicate the line of junction of the upper epiphysis with shaft in that region (fig. 39). The tuberosities are separated behind by a notch, continuous with the posterior triangular rough surface on the upper end, and called the ' popliteal notch,' for the attachment of the posterior crucial ligament. The outer surface of the external tuberosity is rough and gives origin to the tibial head of the ' extensor longus digitorum ' and the upper fibres of the ' tibialis anticus,' also to the ' fibrous expansion of the vastus externus.' The inner surface of the internal tuberosity is rough, shows posteriorly the fore part of the groove for the ' semimembranosus,' and gives attach- ment to the ■ fibrous expansion ' of the ' vastus internus ' and ' crureus ' and to the internal lateral ligament of the knee joint. About half an inch below the upper articular surfaces we notice horizontal ridges on the inner and outer and posterior surfaces of the tuberosities continuous with the divergent ridges on the anterior surfaces already described, and indicating the line of junction of the epiphysis with the shaft. Shaft. — The shaft of the tibia is triangular on section. It is a little twisted outwards, determining the obliquity of the foot; conse- quently the inner malleolus advances a little more than the outer. This disposition corresponds with the obliquity of the neck of the femur, the position of its trochanters, and the oblique direction of the muscles ; the result of all being to give a natural inclination THE TIBIA 219 outwards to the lower extremity. The narrowest part of the shaft is about the junction of the lower fourth with the upper three- fourths. This is the part most frequently broken. It presents internal, external, and •posterior surfaces, separated by anterior, external, and internal borders. The internal surface is subcutaneous. Notice on it, below the internal tuberosity, the insertions of the ' sartorius,' the 'gracilis,' and the ' semitendinosus.' Behind these is a slightly rough surface ior the attachment of the internal lateral ligament of the knee. The external surface is slightly hollowed in its upper half for the origin and lodgment of the ' tibialis anticus : ' its lower part is turned forwards, presenting a smooth surface for the play -of the tendons which run oyer the front of the ankle joint. The posterior surface presents in its upper third a rough line (' soleal ridge'), slanting from the outer towards the inner side, and running from the articular surface for the fibula down- wards and inwards to join the internal border at the junction of its upper with its middle thirds. It is ordinarily called the ' oblique line of the tibia,' and it marks part of the tibial origin of the ' soleus ; ' the remainder of this origin runs down the inner edge of the shaft to the extent of about three inches. This origin is important, since it concerns the operation of tying the ^posterior tibial artery. Above the ' oblique line ' is a triangular surface, indicating the insertion of the ' popliteus.' The surface of the bone below the ridge is occupied, internally, by the origin of the ' flexor longus digitorum ; ' externally, by part of the origin ■of the ' tibialis posticus.' Just below the line is the canal for the medullary artery. It is the largest of all the like canals in the long bones, runs very obliquely from above downwards, and when divided in amputations sometimes occasions troublesome hemor- rhage. A nerve has often been traced through this canal with the artery into the medullary cavity. With regard to the borders of the tibia, the anterior, called the ' crest,' or ' shin,' is very sharp, and readily felt beneath the skin, but only along the upper two-thirds of the shaft : in the lower third the front of the bone is flattened, for the passage of the extensor tendons and the anterior tibial vessels and nerve. 220 THE TIBIA Fig. 37. It begins above at the tubercle, runs a sigmoid course downwards, and terminates in front of the internal malleolus. It is convex inwards in its upper and convex outwards in its lower half. The external border looks towards the fibula, and gives attach- ment to the interosseous membrane (represented by the dotted line in fig. 37) which connects the two bones. It begins above about half an inch in front of the articular facet for the fibula, runs downwards, and bifurcates below into two branches which enclose a rough space for the attachment of strong ligamentous fibres between the tibia and the fibula. The internal border runs from the hinder part of the head of the tibia down to the inner malleolus. It gives attach- ment to fibres of the ' popliteus,' ' soleus,' and ' flexor longus digitorum ' muscles (Plate XXXV.) If the direction of the force in run- ning, leaping, or walking be considered, it will be seen that the chief strain on the tibia is at the crest or anterior border — the shin. This, therefore, is by far the strongest and densest part of the bone. Lower End. — The lower end of the tibia is expanded transversely to form a hinge joint with the astragalus. Its articular surface is concave from before backwards ; but the transverse plane of the joint is horizontal (as seen in fig. 38), like that of the knee, for the better support of the weight of the body. The joint is secured on the inner side by the projection termed the 'malleolus in- ternus.' ., The anterior surface of the lower end SECTION TO SHOW THAT THE J plane of the ankle joint is is smooth and slightly convex from side to side, for the transmission of the ex- tensor tendons. Immediately above the anterior margin of the SECTION THROUGH THE TIBIA T, AND FIBULAF, TO SHOW THE THICKNESS OF THEIK WALLS. Fig. 38. Astragalus. Tunnel. Os Calcis. THE TIBIA 221 terminal articular surface it shows a transverse rough groove for the attachment of the anterior ligament of the ankle joint. The posterior surface is marked from within outwards by a deep oblique half-groove, made a whole one by the addition of the corresponding half on the back of the internal malleolus, and serving for the transmission of the ' tibialis posticus ' tendon. Next the surface presents a slightly convex space, on which is sometimes placed a shallow oblique groove, parallel with the large orje for the ' tibialis posticus,' situated about the middle of the space, and transmitting the ' flexor longus pollicis ' tendon. The edge of the surface which separates it from the articular surface on the inferior aspect of the bone is rounded and rough for the attachment of the transverse ligament of the inferior tibio-fibular joint. The external surface presents a rough triangular excavation for the reception of the fibula, the anterior side of the triangle being more prominent than the posterior one. There is no sen- sible movement between the bones, but enough to give a slight amount of elasticity, thereby breaking the shock striking the leg from the foot below. The security of the ankle requires that the bones of the leg be firmly riveted together by a strong inter- osseous ligament ; and their contiguous surfaces are found to be rough, marking the attachment of such a ligament. The inner surface is smooth and subcutaneous, and is pro- longed downwards into a transversely flattened and four- sided process, the ' malleolus internus.' The inner surface of the pro- cess is smooth, subcutaneous, and continuous with the inner sur- face of the lower extremity of the bone. The external surface is smooth and articular, broader in front than behind, and con- tinuous with the articular surface on the inferior aspect of the bone. The anterior border of the process is rounded and rough, for the attachment of fibres of the anterior ligament of the ankle joint. The posterior surface forms the inner half of the oblique groove, already described, for the ' tibialis anticus.' We notice too that the internal lip of the groove projects more than the outer. The lower border of the malleolus is rough, and extends lower down in front than behind. It is bevelled at the expense 222 THE TIBIA of the internal surface in front and the external surface behind. It is important to notice that the lowest point of the internal malleolus is situated in a plane anterior to the lowest point of the external malleolus. The inferior or terminal articular surface of the lower extremity is four-sided, broader in front than behind, and outside than inside. It is concave from before backwards, and concavo-convex when traced from side to side, a smooth antero-posterior eleva- tion rising up about the middle of the surface. It is continuous with the articular surface upon the internal aspect of the inner malleolus, and articulates with the astragalus. The ankle joint is such a perfect hinge that in any position of the joint no lateral movement whatever is permitted. Structure and Mechanism. — In structure the tibia follows the ordinary laws with reference to the arrangement of the fibres of the cancellous tissue. Its compact wall is especially developed at the most slender part of the shaft, to form the anterior border or crest. The weakest part of the bone is situated about the junction of the upper three-fourths with the lower fourth of the shaft, so that if a person fall from a great height upon the foot the bone usually breaks there. Eickets, too, usually shows itself early, by an increase of the natural curve of the bone in this situation. The shaft is sigmoid in its long axis and twisted outwards below. Elasticity and strength are thereby gained, and the foot at the same time turned outwards. The anterior border strengthens the bone very much. It terminates above in the tubercle, and is more in the line of the external tuberosity than of the internal. The weight of the body, which is mostly trans- mitted to the leg through the external condyle of the femur, strikes, therefore, the strongest part of the shaft, viz. the outer and anterior part. The outer tuberosity overhangs the fibula, 1 thereby transmitting a certain amount of weight to it. It receives, too, directly all shocks coming to it from below through the fibula. The medullary canal is specially large to transmit the vessel for the chief supply of the marrow : the compact tissue of the shaft is so dense that few other nutrient blood-vessels penetrate it. THE TIBIA 223 Ossification. — The tibia is ossified from three centres : one for the shaft, and one for each end. The centre for the shaft appears at the seventh week of foetal life. The one Fb. 39. for the upper end, which (see fig. 39) includes the tubercle, appears just before or just after birth, nearly as early as the lower epiphysis of the femur. The centre of the lower end appears about the second year. The tubercle is occasion- ally formed from a separate centre. The upper epiphysis joins the shaft in the twenty-first or twenty-second year, while the lower one joins in the eighteenth or nineteenth year. The tibia has been found congenitally absent, as in a case recorded by Billroth. Comparative Osteology. — The tubercle of the tibia is very largely developed in the rhinoceros, but in the elephant there is no trace of it. The high and expanded crest in the pig, camel, and tapir are remarkable. In the higher quadrumana, as the gorilla, chimpanzee, and ourang outan, the tubercle and crest are flat- tened. (For all these specimens see the Separate Series.) EPIPHYSES OF THE TIBIA. THE FIBULA. (Plate XXXV.) Relations of Tibia to Fibula. — The ' fibula ' (a clasp) is the outer of the two bones of the leg. Though quite as long as the tibia, it is a slender bone, and sustains hardly any of the weight of the body. The upper end is placed on a lower level than the knee joint, and forms no part of it ; but the lower end projects considerably below the tibia, and constitutes the outer ankle. The bone not only secures the ankle externally, but gives additional extent of origin to the powerful muscles of progression. Look well at the relative position of the two bones of the leg in an articulated skeleton. The fibula articulates with the outer and 224 THE FIBULA ■back part of the head of the tibia, and the shaft of the fibula arches backwards, while that of the tibia arches forwards : the result of this is, that the fibula lies very much in the background, except at its lower part, where it advances to form the malleolus externus. A knowledge of this relative bearing of tbe two bones is important in the adjustment of fractures, but more especially in the per- Fia. 40. formance of flap amputations ; and for this reason : that the knife, introduced from the tibial side, is apt, unless properly directed, to pass between the two bones, instead of behind them : and this is the more likely since the plane of the posterior surface of the tibia slants considerably in front of the fibula. The relative position of the two bones, as well as their relative thickness, is shown by a transverse section (fig. 40). The dotted line represents the interosseous membrane. Head The upper end of the fibula is called its ' head,' and can be felt plainly beneath the skin. On its upper surface is a small oval facet looking forward, upward, and inward to arti- culate with the tibia. Its anterior surface is rough, giving attach- ment above to fibres of the anterior tibio-fibular ligament, and below to fibres of the ' extensor longus digitorum ' muscle. The external surface is much bulged outwards by an antero-posterior ridge. Above the ridge we have the ' biceps ' tendon and the long external lateral ligament of the knee joint attached, and below the ridge the highest up fibres of the ' peroneus longus ' muscle. The posterior surface is rough and flattened. Its superior and external angle rises into a short projection termed the ' styloid process,' for the attachment of the short external lateral liga- ment of the knee joint. The surface gives origin to fibres of the ' soleus ' and internally to the posterior tibio-fibular ligament. The internal surface is rough, slightly hollowed, and lodges the superior interosseous ligament. Shaft. — As we have mentioned before, the shaft, excepting at its lower end, lies in a plane posterior to that of the tibia. In its long axis it is curved backwards and outwards in its upper half THE FIBULA 225 and backwards and inwards in its ' lower. The space between the two bones is widest about the junction of its upper and middle thirds. The surfaces and borders follow a spiral course along the bone in such a way that a surface which looks out- wards above looks as near as possible backwards below. The shaft too is irregularly prismatic in its upper three-fourths and gets flattened from within outwards in its lower fourth, the most slender part being situated at the meeting of these two parts. We describe anterior, internal, and external borders, separating internal, external, and posterior surfaces, corresponding to those of the tibia. The anterior border commences superiorly at the junction of the anterior" and external surfaces of the head. It is rounded and indistinct above, but is well marked in the rest of its extent. Tracing it down the bone, it gradually turns outwards, and, about three inches from the lower end, it bifurcates into branches which run to the front and back of the lower end of the bone and enclose a flattened triangular subcutaneous space facing outwards. In this space we feel for fractures of the lower part of the fibula. The internal border begins above at the inside of the posterior surface of the head and terminates about an inch and a half above the lower end of the bone by dividing into an anterior and a posterior branch, enclosing a rough triangular space. This space is rough in its upper two-thirds for the attachment of strong interosseous fibres, and presents below a somewhat flattened and smooth crescentic surface for articulation with the external surface of the lower end of the tibia. In most fibulae the border is very well marked in its upper three-fourths. It takes an oblique or spiral course down the shaft, looking in- wards and slightly backwards at its upper end, inwards and slightly forwards at its lower. Its upper three-fifths is ordinarily called the ' oblique line of the fibula.' It gives origin in the upper part of the middle third and lower part of the upper third to fibres of the'' tibialis posticus,' and in the rest of its extent attaches the fibrous septum which separates the ' soleus ' and ' flexor longus pollicis ' on the one side from the ' tibialis posticus ' on the other. 226 THE FIBULA The external border begins above at the root of the styloid process, runs down the shaft, gradually inclining towards the back, and terminates below by joining the posterior branch of the internal border at the lower end of the shaft. In some fibulae it is sharp and distinct throughout. In others it is rounded in the upper and lower thirds, and well marked in the middle. It separates the external from the posterior surface, and gives attachment to the fibrous septum between the ' peronei ' muscles on the one side from the ' soleus ' and ' flexor longus pollicis ' on the other. The surfaces we have named internal, external, and posterior. The internal faces the external surface of the tibia. It looks forwards and inwards above, forwards below. It is unequally divided into a smaller anterior part and a larger posterior part by a vertical ridge. This ridge is called the ' interosseous ridge* of the fibula, affording attachment to the interosseous membrane, which stretches between it and the external border of the tibia, and which separates the muscles on the front from the deep muscles on the back of the leg. In well-marked bones the ridge commences above at the inside of the head and somewhat nearer the anterior than the internal border, runs downwards, inclining backwards as it 'descends, and blends with the internal border at a point about an inch to two inches above its lower bifurcation. In slender fibulae the interosseous ridge may blend with the anterior border of the shaft for a good way below its upper end. The anterior part of the internal surface is therefore broader below than above and more hollowed from side to side. It affords origin anteriorly in its upper three-fourths to the ' extensor longus digitorum ' and in its lower fourth to the ' peroneus tertius,' and posteriorly in its middle two-fourths to the ' extensor proprius pollicis.' The posterior part of the internal surface is broader above than below, concave from side to side, and gives origin to the fibular fibres of the ' tibialis posticus.' The external surface lies between the anterior and external borders. It looks forwards and outwards, but towards the lower end of the shaft it inclines backwards. It gives origin to the ' peroneus longus ' above and the ' peroneus brevis ' below. (Plate XXX?. 1 ) THE FIBULA 227 The posterior surface lies between the external and internal borders. It looks backwards above and inwards below, and gives origin in its upper third to the ' soleus ' and in its lower two-thirds to the ' flexor longus pollieis.' Near the internal border, situated somewhere in the middle third of the surface, is the medullary foramen, leading downwards. In a few rare specimens we may see, in this surface, an additional foramen directed upwards. Lower End. — The lower end of the fibula descends below that of the tibia, and forms the 'malleolus externus.' This process we may describe as a pyramid flattened laterally, whose base is continuous with the shaft of the bone, and whose apex is free, points downwards, and is situated in a plane posterior and inferior to that of the corresponding part of the malleolus in- terims. The external surface of the pyramid is smooth, sub- cutaneous, and continuous with the triangular subcutaneous surface already described as formed by the bifurcating anterior border of the shaft. The anterior surface is narrow, slightly rough, slopes downwards and backwards, and affords attachment to fibres of the anterior inferior tibio-fibular ligament and an- terior ligament of the ankle joint, and anterior fasciculus of the external ligament of the ankle joint. It is more a border than a surface. The posterior surface presents a smooth longitudinal groove, running downwards and outwards, for the passage of the 'peronei' tendons. The inner lip of the groove is rough, and attaches fibres of the posterior inferior tibio-fibular ligament and posterior fasciculus of the external ligament of the ankle joint. The internal surface is divisible into a larger anterior superior part, triangular in shape, somewhat convex from above down- wards and concave from before backwards, for articulation with the astragalus, and a smaller posterior and inferior part, rough and deeply depressed, for the attachment of the middle fas- ciculus of the external ligament of the ankle joint. The apex is rounded and rough, and has attached to it anteriorly, posteriorly, and internally the anterior, posterior, and middle fasciculi of the external ligament of the ankle joint. Structure and mechanism. — In its structural formation the fibula presents the ordinary characters of a long bone. Its Q 2 228 THE FIBULA function is very slight as regards helping the tibia to supporl the weight of the body. The outer tuberosity does overhang the head of the fibula, but the plane of the articulation between the two is very oblique, and the fibula can therefore act as a very weak prop to that part of the tibia. Its chief office is to give increased breadth to the leg for muscular attachment, and to support the ankle joint. We notice, also, the general bendings backwards of the shaft, throwing it into a plane which is pos- terior to that of the tibia. We observe too, that the shaft is farthest away from the tibia above, so as to give greater breadth to the interosseous membrane as the muscles of the leg arise from the upper part and not the lower part of the tibia. There is a certain amount of movement between the tibia and fibula, just enough to help to break shocks transmitted to the bones of the leg from below. The fact that the fibula is embedded in muscles in the greater part of its extent makes the diagnosis of fractures of its shaft somewhat difficult : hence the rule to test its natural resistance by pressing it against the tibia, and notice whether there is a slight natural rebound after having done so. The external malleolus supports the ankle joint on the outer side, The two malleoli with the terminal articular surface of the astra- galus form an arch for articulation with the astragalus. The external one projects farther down and farther back than the internal one. The result of this is that the foot may receive, in the best possible way, shocks transmitted to it from above. In the ordinary act of walking, when the foot is thrown forwards and the leg gradually raised over it, the weight of the body strikes the astragalus, from above and behind, downwards^ forwards, and inwards; hence the external malleolus and the facet for it on the outside of the astragalus are placed as far back as possible, to transmit and receive their share of the shock- On the contrary, when the leg is behind the body, with the toes touching the ground and throwing the body forward, the shock is transmitted to the astragalus from above and in front down- wards, backwards, and outwards ; hence the internal malleolus and corresponding facet upon the astragalus are placed as far forward as possible. The relative position of the two malleoli is THE FIBULA 229 important in relation to Syme's amputation at the ankle joint. The weakest part of the shaft is situated about 2£ inches from the lower end ; hence we find that fractures of the bone most commonly occur here. Ossification. — The fibula has three centres of ossification : one for the shaft, and one for each end. The centre for the shaft appears about the seventh week of foetal life. The lower end begins to ossify about the second year ; the upper about the third or fourth. It is interesting to note that the lower end, the early solidity of which is so necessary, is the first to unite to the shaft, and is thus contrary to the rule laid down on p. 25. The lower epiphysis joins the shaft about the twenty-first year, the upper about the twenty-fourth. The fibula is sometimes — rarely, however — congenitally ab- sent. It is more common to find absence of a part of it than of the whole bone. In some cases the shaft may be represented by thickening of the interosseous membrane connecting the upper and lower ends of the bone. In other cases the upper part, and in others the lower part of the bone may be wanting. Complete or partial absence of the fibula is usually associated with an im- perfect development of the bones of the tarsus a,nd an absence of one or more of the four outer toes. Comparative Osteology. — It is interesting to notice the. gradual disappearance of the fibula in reviewing the vertebrata. In the horse it is reduced to a mere splint at the upper part of the tibia. In the Ornithorynchus (No. 3964) there will be seen a broad flat process, projecting high upwards at the back of the fibula, which gives origin to enormous extensor and flexor muscles, which work the paddle-like foot (see Phys. Ser. Mus. Eoy. Coll. Surg., No. 255 C). A similar process exists on the fibula of the Echidna (No. 3952 C). The fibula of the Armadillo (No. 3580), attains a great size, and is anchylosed above and below to the tibia and enters into the formation of the knee joint. 230 THE BONES OF THE FOOT. (Plates XXXVI., XXXVII.) Number and Shape of Bones. — There are twenty- six bones in the foot (excluding the two sesamoid bones of the great toe, and two others in connection with tendons. We divide them into three sets, viz. a posterior set or ' tarsus,' a middle set or 'metatarsus,' and an anterior set or 'phalanges,' corresponding to similar sets described in the hand as ' carpus,' ' metacarpus,' and ' phalanges.' The ' tarsus ' consists of seven more or less cubical bones arranged in an inner and an outer row. The inner row consists of five bones named the ' astragalus,' ' scaphoid,' and 'inner,' 'middle,' and 'outer cuneiform,' supporting the three inner toes ; the outer row consists of two, viz. the ' os calcis ' or ' calcaneum,' and the ' cuboid,' for the support of the two outer toes. From a mechanical point of view this is the best division of the tarsus, although surgically the tarsus is conveniently divided into a posterior row, consisting of the ' astragalus ' and ' os calcis,' and an anterior row made up of the rest. The line of junction between these rows is called the ' medio-tarsal joint,' and through it Chopart's amputation is performed. The ' metatarsus ' consists of five long bones named first, second, third, fourth, and fifth, counting from the inside of the foof. The posterior end of the metatarsus is firmly dovetailed into the front of the tarsus, while the anterior end supports the ' phalanges.' The ' phalanges ' consist of fourteen long bones, three for each toe excepting the first one, which has only two. They are more diminutive than those of the hand, and are named THE BONES OF THE FOOT 231 metatarsal, proximal or first, middle, and ungual, distal, or third for the four outer toes ; proximal, metatarsal or first, and distal, or third for the first or great toe. Advantage of many Bones. — The advantage of so many bones entering into the formation of the foot is the same for the foot as for the hand. With a larger number of joints motion and elasticity are increased, while the chances of fracture or disloca- tion are lessened. Arches of the Foot. — The bones of the foot form two arches : one, ' longitudinal,' extends in the long axis of the foot ; the other, transverse, is most marked at the instep. The longitudinal arch is supported, behind, by the os calcis, and in front by the heads of the metatarsal bones. Its height and span are greatest on the inner side of the foot, and gradually decrease towards the outer side. The marks made by wet feet show how much more the outer border of the foot comes in contact with the ground than the inner. The weight of the body falls perpendicularly on the astragalus, which is the key-stone or crown of the arch. Con- cerning the astragalus, two points must be borne in mind : 1. A part (the head) of it is supported below by a remarkably strong and slightly elastic ligament (calcaneo-scaphoid), which admits of its rising and falling like a spring ; 2. It is articulated with the os calcis and the scaphoid in such a way as to allow the lateral motions of the foot (adduction and abduction). Flexion and extension of the foot are performed at the ankle joint. Further, all the bones of the foot are more or less movable on each other, thus breaking shocks and increasing elasticity ; and yet their mutual connection is so well secured that dislocation of any one bone is extremely rare. Tarso-BXetatarsal Articulations. — The secondrow of tarsal bones consists of four: namely, the three cuneiform and the cuboid. These articulate with the metatarsal bones as follows : The internal cuneiform with two, those of the great and second toes ; the middle cuneiform with one, that of the second toe ; the external cuneiform with three, those of the middle, the second, and fourth toes ; and the cuboid with two, those of the fourth and fifth toes. See how this exactly corresponds with the articu- 232 THE BONES OF THE FOOT lations of the second row of carpal bones with the metacarpals; Starting from the great toe, or thumb side, these bones articu* late with 2, 1, 3, and 2 metatarsal and metacarpal bones- respectively. THE ASTRAGALUS. (Plate XXXVI.) The Key-Stone : its Six Aspects. — The astragalus (currpa*. !iyo-gIo Rg.I. ^Tid.constr oP Fharynx. Hyo-c5lossus. S"tylo-hyoid Orno-hyoid. Mylohyoid S"terno-l l yoia. Genio-Viyoid . Os-Kyoides Scaphoid- - JiSk M Trapezium -^SslS^CjiiPi™' WMmmm ant r annular lidannent. Areh of the Carpus. Sea.pVion3 Calcaneo-scapWid ligament Sustentaculum tali , Drawn on Stone by T.Godart. m nature Ly L^j^gn^ __ Printed ty Weat.Newman ft, Co 261 THE THORAX. (Plates XXXIX.-XLII.) General Description. — The thorax is the framework which contains the heart and lungs. The ribs, with their cartilages, describe a series of arcs, successively increasing in length as far as the seventh, and form, with the spine and sternum, a barrel of a somewhat conical shape, much broader from side to side than from before backwards. The lower aperture or base of the cavity is open in the skeleton, but closed in the recent subject by a thin flat muscle, called the ' diaphragm,' which separates the chest from the abdomen, and has openings for the passage of the alimentary canal and the great blood-vessels. This muscular partition is not flat, but arched, so that it forms a vaulted floor for the chest. By alternately falling and rising, it increases and diminishes the capacity of the chest. The spaces between the ribs are filled by the intercostal muscles. Such, in outline, is the framework of the chest. Its walls are made up of different structures — bones, cartilages, and muscles — which by their union answer two apparently incompatible pur- poses. By their solidity and elasticity they protect the important organs contained in the chest ; and by alternately dilating and contracting, serve as the mechanical agents of respiration. They enlarge the cavity of the chest in three directions : in height, by the descent of the diaphragm ; in luidth, by the turning outwards of the ribs ; in depth, by the raising of the sternum. 262 • THE STERNUM THE STEBNUM. (Plate XXXIX.) Position. — The sternum {arspvov, the breast) is a long flat bone, situated in front of the chest, and supports the ribs and the clavicles. In the' adult male, it is from six to seven inches long : rather less in the female. Observe that its direction is not perpendicular, but that it slants forwards, and thus makes more room for the heart and lungs. It is much broader and thicker at the upper end (manubrium) , wher,e it supports the clavicles. The middle of its upper border is on a level with the under edge of the second dorsal vertebra, while the corresponding part of its lower edge is somewhere opposite the tenth dorsal vertebra. The sternum was compared by the ancients to a sword ; the broad part was called ' manubrium,' the middle part ' mucro,' or gla- diolus, and the cartilage at the end the ' xiphoid ' or ' ensiform ' cartilage. Manubrium, or Presternum. — This part of the sternum presents an anterior surface which is somewhat convex from side to side and concave from above downwards. The surface is marked by a number of good-sized nutrient foramina, and gives . attachment above to the ' sterno-mastoid ' and below those to the 'pectoralis major ' muscles. The posterior surface is smooth, slightly concave in every direction, marked by a number of large nutrient foramina, and in the neighbourhood of its lateral borders gives origin to the ' sterno-hyoid ' and ' sterno-thyroid ' muscles. The superior border is divisible into thirds : a middle one, smooth and rounded, called the ' suprasternal ' or ' intra-clavicular notch,' and giving attachment to a ligament of the same name ; two lateral ones, broad from before backwards and looking up- wards and outwards. Each of the lateral ones is oval in shape, concave from above downwards and outwards, and slightly so from before backwards (in some bones it is rather convex in this direction), and articular for articulation with the sternal ex- :the stbknum 263 tremity of the clavicle. These ' clavicular facets " of the' sternum present the . above appearances in a much more marked degree ■when they are covered by their articular cartilage, and they thereby permit the clavicles to rotate upon them nearly as freely asthe thumb does upon the trapezium. The end of the "clavicle is much larger than- the' surface on which it rotates ; yet disloca- tion of it is exceedingly rare, owing, to the great strength of the ligaments. To break the clavicle is much easier than ' to dislo- cate it. The inferior border is not so broad as the superior one. It presents an oval, rough surface for articulation by the interven- tion of a plate of cartilage: with the upper border of the meso- sternum. Its anterior : and posterior edges are somewhat pro- minent for the attachment .oi anterior and posterior ligamentous fibres. Frequently in old age the. intervening cartilage gets -ossified at its circumference, the central part remaining soft and flexible. ", Each lateral border, thicker above than below, presents, in its upper half, an elongated, triangular, rough, concave facet for the junction of the cartilage of the first rib, and in its lower half, from above downwards, first a smooth rounded notch, forming an inner end of the first intercostal space and next a slightly con- cave, somewhat triangular facet, which, with a corresponding one oh the mesosternum, articulates with the cartilage of the second rib. - Gladiolus, or Mesosternum. — This presents a flattened, oval figure, with the broadest part of the oval at the level of the fifth costal cartilages. It is bent forwards, so as to present its greatest convexity in that direction at the level of the third or fourth costal cartilages or in the interval between these. Ante- rior surface : This surface is broadest at the line of junction of - the fifth costal cartilages. It is marked by three transverse ridges, indicating the original formation of the gladiolus by four primary pieces, and situated opposite the junction of the third, fourth, and fifth costal cartilages. The upper ridge is usually the best marked, and the lowest one may be Very indis- tinct. The intervening. spaces between these ridges are slightly 264 THE STEBNUM concave both from side to side and from above downwards; They afford attachment, on each side of the middle line, to fibres of the ' pectoralis major ' muscles. The posterior surface is smoother than the anterior ; it shows indications of the transverse ridges and is concave from above downwards and slightly so from side to side. Close to the lower half of each of its lateral margins it gives origin to part of the ' triangularis sterni.' In a few rare cases the gladiolus presents an aperture, called the ' sternal foramen,' at the junction of its third and fourth pieces, and leading from the anterior to the posterior surface of the bone. It is filled up by membrane in the recent state. In a still fewer number of cases the fourth piece and lower part of the third are split by a fissure which runs through the metasternum. This latter appearance gives rise to the term ' cleft sternum.' The lateral borders are each marked by six blunt teeth sup- porting concave notches for the reception of the lower half of the articular extremity of the second costal cartilage, the whole of the articular extremities of the third, fourth, fifth, sixth, and the upper half of the seventh. The intervals between the costal- cartilage notches form smooth concavities, looking outwards and forming the inner ends of the ' intercostal spaces.' They decrease in size from above downwards, and in many cases the interval between the sixth and seventh cartilage facets is wanting. The notches for the third, fourth, and fifth rib-cartilages are situated where the original pieces of the gladiolus unite ; the notches for the whole of the sixth and upper half of the seventh rest on the side of its fourth or last piece. The superior border forms a rough oval surface, corresponding to a similar one on the lower edge of the manubrium, and to which it is united by cartilage and ligaments. The articulation between the manubrium and gladiolus forms a somewhat pro- minent transverse ridge on the front of the sternum, readily felt in the living person, and situated on the level of the body of the fourth dorsal vertebra. The inferior border is short and irregular, and joined to the metasternum by cartilage and fibrous tissue. THE STERNUM 265 Ensiform Cartilag-e, Xiphi-sternum, Xiphoid Cartilage, or Metasternum, generally remains unossiiied even at a great age. Its length and shape vary much in different persons. Sometimes it is bent forwards, or it may be backwards, and this ■especially in workmen who hold tools against the pit of their stomach. Occasionally it is forked at the lower end. It gives attachment to the ' linea alba,' a narrow aponeurotic band, which descends along the middle line of the abdomen to the symphysis pubis, and is the fibrous continuation of the sternum. To its anterior surface is attached the ' rectus abdominis,' and to its posterior the ' diaphragm ' and ' transversalis abdominis ' muscles. Ossification. — The presternum has usually a single centre, appearing about the sixth month of foetal life. Sometimes there are two, and rarely several. In the mesosternum we find a centre for the first segment appearing at the seventh month, a centre for each of the second and third segments at the eighth or beginning of the ninth month, and a centre for the fourth seg- ment appearing in the first year. In the metasternum ossifica- tion begins in the sixth year, or it may be much later. The second, third, and fourth pieces of the mesosternum unite about puberty. The first part joins the second about the twenty-fifth year. The metasternum joins the mesosternum about middle age and the mesosternum rarely unites with the presternum. If it does, it is only in advanced age, and even then, there is only a thin layer of bone externally, the cartilage in the centre still remaining. The above is the ordinary mode of ossification of the sternum, but sometimes we find each of the second, third, and fourth pieces of the mesosternum and the single piece of the metasternum developed from two centres placed on either side of the middle line of each segment. Should these centres not join one another across the middle line, a ' cleft sternum ' will remain. Should each of the lower segments of the mesosternum possess two lateral centres of ossification, and those not join across the middle line, the" sternal foramen ' shall then be formed. Two little pieces of bone, ossa supersternalia, axe, in a very rare number of cases, situated on each side of the suprasternal 266 THE .STEENUM notch. If present they are joined to the presternum by liga- mentous fibres. They are probably remains of the episternal bone of monotremata. Comparative Osteology. — Contrast the broad chest of man with that of the oiirang utan (No. 37) and that of the chim- panzee (Nos. 1-2). In the adult gorilla the parts of the sternum^ which in us are united, are seen to remain separate. In the Separate Series, as well as in the two complete skeleton"?, in the Normal Human Osteological Series, examine the sternum of the Bushman, and you will' see that the manubrium sterni is firmly united to the gladiolus, and there is little or no trace of the original separations between the pieces of which the sternum, is composed. Most flying animals support themselves in the air by the action of their pectoralis major muscle on the upper extremity, and therefore this muscle is large in proportion with the flying capability. The surface of origin in such animals is increased, by the development of a great keel down the middle of the sternum, which may be seen in nearly all of the flying birds (Garinatce) — for instance, in the great bustard (No. 1349) — as well as in the extinct flying lizards (Pterosauria, No. A 119, Pal. Ser. Mus. Eoy. Coll. Surg.) This keel is absent in the non-flying birds, such as the ostrich (No. 1362), the extinct dinornis (No. 1588 A, Pal. Ser. Eoy. Coll. Mus. Surg.), the apteryx (Nos. 1355 and 1355 E), showing that this keel exists for the function of flight, or where the pectoral muscles are from any reason large, and not as a class character of aves. Among the variations which the sternum undergoes perhaps the most curious is that in the male wild swan and guinea fowl (see Nos. 1248 B, 1249 A, B, C), where it will be seen to'be tun- nelled extensively, and to contain a long tortuous trachea as well as the inferior larynx. In snakes (Ophidia) there is neither a sternum nor a pectoral arch (No. 629), and there is no trace of a fore limb. There is no sternum either in ichthyosauria or plesiosauria (Nos. 172 and 222 Paheontological Series, Mus. Roy. Coll. Surg.) Sterno-njastoid., Fibi PLATE XXXIX. Scalenus rnedius Scalenus anticus Scalenus posticus Subclavius __ 2" d 3ysenra.ti o n of Serratus magnus Tubercle ArticHla-tion of clavicle do ferJf'Costa.1 cartii** Si erno thyroid. Sternol-iyoid . Fh>.2 Sternum . From, nature "by L.HolcLen. Drawn on Stone "by T. Godsrt. Printed "by "West , Newman & Co. THE RIBS 267 THE EIBS. Plate XXXIX.) Number and Division. — There are twelve ribs on each side ; the upper seven, the ' sternal,' or ' true ribs,' increase in length from the first, and are fixed to the sternum by their cartilages, and hence may be called ' vertebrosternal ' ribs. The lower five, or ' false ribs,' decrease in length, from above down- wards, and their cartilages fall short of the sternum. The eighth, ninth, and tenth ribs are connected behind with the spine and in front with the costal cartilages, and may therefore be called ' vertebro-chondral ' ribs. The eleventh and twelfth are free at their anterior ends, and are therefore called ' floating r or ' vertebral ribs.' One sometimes, though rarely, meets with skeletons with thirteen ribs, the thirteenth being a cervical or a lumbar rib. This is a retrocession. The chimpanzee has- thirteen ribs, but the same number of vertebrae as man. General Characters of a Rib. — As an example of the general characters of a rib, take the fifth or sixth. In the first place, observe that the curve is not uniform. It is more curved towards the vertebral end than elsewhere. Besides which, if laid on a table, the vertebral end will rise. The rib is twisted, too, in its long axis in such a way that a surface which looks- backwards and inwards at the posterior end of the bone looks forwards, outwards, and slightly upwards at the anterior end. It- is plain in the skeleton that the vertebral ends of the ribs are higher than the sternal ends. If both ends had been on the same level, the sternum could not have been raised forwards in inspiration. Vertebral End.— The vertebral end or ' head ' (Plate XXXIX. fig. 3) has two oblique, slightly concave surfaces (with an interven- ing ridge, to which the interarticular ligament is attached), which articulate with the sides of the bodies of two contiguous vertebras. The lower of these two surfaces is always the larger. The head of the rib is the' fulcrum upon which the rib moves. It is wedged 268 THE kibs in between two vertebrae, and is less liable to be dislocated than if supported by one only ; and, moreover, it has the benefit of the elasticity of the intervening fibro-cartilage. Neck. — Next to the head comes the ' neck ' of the rib. This is flattened from before backwards. It is smooth in front, where p ia . 56. it is covered by pleura, but rough behind, where is attached a ligament (middle costo-transverse) connecting it to the transverse process by which the rib is supported, as seen in the adjoining figure ; again, the neck has a ridge along its upper surface to dobsal vebtebba with eib3 which is attached a second ligament (superior costo-transverse) ; this con- nects it to the transverse process above it. Tubercle. — External to the neck is the ' tubercle.' It has a little facet which looks downwards, backwards, and inwards, and articulates with the transverse process supporting the rib ; out- side and above the facet is the rougher part of the tubercle which gives attachment to a third ligament connecting the rib to the transverse process (posterior costo-transverse). Angle. — External to the tubercle, the rib makes a curve for- wards and downwards, forming the ' angle.' Here there is a prominent line — ' the oblique line ' — which runs downwards and forwards, and indicates the attachment of muscles, which form the outer border of the ' erector spines.' Observe that the distance between the angle and the tubercle increases as we trace the ribs downwards, and makes room for the great muscle of the spine (erector spinse) . It is near the angle that the rib breaks when the chest is compressed — for instance, in a crowd. In this kind of fracture — i.e. by indirect violence — the broken ends project outwards, and are therefore less liable to injure the pleura. But in direct violence — e.g. a kick by a horse — the rib breaks where it is struck, the broken ends are driven inwards, and con- sequently are more liable to injure the pleura. Shaft. — The part of the rib arching forwards from the angle ajlong the side of the chest is called the ' shaft.' It is flattened THE BIBS 269 both, from above downwards, and from without inwards, like a- bow. Its outer surface is smooth and gives attachment to muscles, and near the anterior end presents, in some bones, a slightly marked oblique line, called the ' anterior angle.' On its inner surface, near the lower border, is a deep groove, called the ' sub- costal groove,' for the intercostal vessels and nerve. Observe, the groove does not extend the whole length of the rib ; it begins inside the angle, and is gradually lost about the junction of the anterior third with the posterior two-thirds of the shaft. The vessels and nerves are safe where they lie in the groove ; but between the angle of the rib and the spine, and again in front of the chest, they are liable to be injured through the intercostal spaces. In consequence of this groove, the lower edge of the rib is much thinner than the upper, which is thick and rounded. The upper edge of the subcostal groove gives attachment to the 'internal intercostal' and the lower to the external inter- costal muscle. In the ' groove itself are the orifices of the numerous canals, mostly directed towards the vertebral end, and which transmit blood-vessels into the interior of the rib. The ribs are the most vascular bones in the body : hence the rapidity with which they unite after a fracture. Anterior End. — Eespecting the anterior end, remark that it is rough, and a little excavated to receive the costal car- tilage. Peculiarities of certain Ribs. — The first, second, tenth, eleventh, and twelfth ribs have peculiarities requiring separate notice. First Rib. — The plane of the first rib is nearly horizontal. It is the shortest, the most curved, the flattest and broadest of all. Its head has a single articular surface which rests on the first dorsal vertebra. It has the largest tubercle, and this is well supported by the strong transverse process of the first dorsal vertebra. There is no angle. On its upper surface we may see in a well-marked bone two slight transverse grooves about the breadth of a finger ; the subclavian artery lies in the posterior groove as it crosses the rib, the vein passes along the anterior. Against this surface the subclavian artery may be effectually ■270 THE RIBS compressed. The grooves are separated on the inner border of the rib by a. ' tubercle ' denoting the insertion of the ' scalenus anticus.' Behind this are the rough surfaces for the insertion of the ' scalenus medius,' and, near the outer border, for the attach- ments of the first digitation of the ' serratus "magnus ' and the first ; levator costse ' muscle. Lastly, there is no groove for the intercostal artery. It is an interesting fact, that the compact tissue forming the concave margin of the first rib is very much thicker than that on the convex side. The first rib is the strongest of all : it has to support the manubrium sterni and the clavicles, and to protect all the important parts at the base of the neck. The first rib is very rarely fractured, being so well, protected by the clavicle; but when it does happen it is a most serious accident, because it is the starting point of all the other ribs in respiration, and because there are so many important vessels and nerves in rela- tion with.it. Second Rib.— The second rib has little or no angle, no twist on its axis, and has, near the middle of its outer surface, a rough eminence for the origin of the second and third digitations of the serratus magnus. It has a short groove for the intercostal artery. Tenth Rib.— The tenth rib has a single 'facet ' on the head, for the tenth dorsal vertebra. Eleventh and Twelfth Ribs. — The eleventh and twelfth ribs being shorter and less perfectly developed, are chiefly distin- guished by their negative characters. Each articulates with only one vertebra, so that the head has only one facet, does not touch the transverse process, and has no tubercle. Each is tipped with cartilage. The eleventh has a trace of an angle and a groove. In the twelfth, angle and groove are imperceptible. Ossification — Ossification in the ribs begins about the eighth week of foetal life. There is one ' primary ' centre for the body, an epiphysis for the head, and another for the tubercle. There is no epiphysis for the tubercle in the eleventh and twelfth ribs. The epiphyses appear from the fifteenth to the eighteenth year, and unite with the rest of the bone about the age of maturity. PLATE XL. ^^^^ Drawn on Stone by T. Go dart. Frasm aiat\S-e¥r"^SS||£ Printed by We3t,Newman & Co . PLATE XLI. 1- j_.ximbar yer-tebra Drawn on Stone by T Godart. From nature by L.Holden Printed "by West/Newman & Co. THE BIBS 271 Costal Cartilages.— Kespecting the costal cartilages, re- member that the first seven are connected with the sternum. •The first cartilage is united directly with the manubrium. The others, from the second to the seventh inclusive,- are articulated to the sternum with the intervention of 'synovial membranes. The cartilages of the eighth, ninth, and tenth ribs' are gradually bevelled, off, and each joins the costal-, cartilage; immediately above it. Moreover, synovial "membranes; exist between these last-mentioned ribs. The last two costal cartilages do not join those above, 'but merely cap the eleventh and twelfth ribs. These ■numerous little .articulations, connected with .the cartilages, much facilitate. the. respiratory movements of the thorax. The costal cartilages increase in length' and decrease in breadth from the first to the seventh ;. below, that they decrease in length, .as. well as' in breadth from above downwards. The first descends a little on its way to the" sternum, the second is nearly horizontal, the third ascends a little, while the re- mainder, excepting, the eleventh and twelfth, which are short and free, follow- the direction of the ribs they belong to for a little way, and then ascend obliquely upwards and inwards. Their upper and lower borders are smooth and rounded, completing ■the intercostal spaces in front; and, as the sixth, seventh, eighth, and sometimes the ninth and tenth, are in .contact with one another,. they present small oval articular facets. The sternal extremity, of the first is /joined directly to the. presternum without the intervention of a synovial cavity. The same extre- mities x>f the second, third, fourth, fifth, sixth, and seventh are slightly, enlarged and are jointed by ligaments, enclosing synovial cavities, to the facets already described as existing upon the pre- sternum, mesosternum, and metasternum. . The" anterior extre- mities of the eighth, ninth, and tenth gradually taper to a point as they join their corresponding cartilages above, while those of •the eleventh and twelfth are free and pointed.. The rib ends of all the cartilages are. received into, the sockets,, supported by >the anterior extremities of the shafts 'of the ribs. It is quite common to find the costal cartilages more or less •covered by a sheath of true bony substance and calcified cartilage. 272 THE EIBS This process may be found commencing in comparatively young persons and is not confined to old age. It begins at the rib ends of the cartilages and spreads inwards towards the sternal extre- mities. However far the process advances no fusion ever occurs between the sheath of bone and calcified cartilage and the ster- num. Even in the case of the first cartilage this holds true. The great elasticity of the costal cartilages answers two pur- poses. 1. They act as mechanical agents of expiration by depress- ing the ribs after they have been raised by muscular action. 2. A blow on the sternum is distributed over fourteen elastic arches ! One can understand, then, why the chest is able to bear such tre- mendous blows with impunity; more especially during a full inspiration. During expiration the bones are less able to resist injury, because the muscles are not acting. Notwithstanding these beautiful provisions, the sternum is sometimes broken, especially when the cartilages of the ribs are ossified. Thorax as a whole. — In addition to what has been said of the thorax at p. 261, attention should be directed to one or two points which might otherwise be overlooked. 1. The great narrow- ness of the upper opening of the chest. In an adult of average size, it measures about 2 inches from before backwards, and 3j inches transversely. Yet in this seemingly narrow space there • is room for the trachea, the oesophagus, the great blood-vessels and nerves at the root of the neck, besides the apex of each lung, and three muscles on each side. 2. Notice how much the ribs slope in subserviency to the mechanism of respiration. Their sternal and vertebral ends are not in the same horizontal plane ; for instance, the sternal end of the third rib is not on a level with the third dorsal vertebra, but, roughly speaking, with the sixth. 3. Notice how much additional space is gained poste- riorly (for the lungs) by the backward projection of the ribs. 4. Notice that the lower margin of the thorax is represented by a> line sloping from the end of the sternum downwards and back- wards to the last rib. 5. Notice that the intercostal spaces are widest where the ribs unite to their cartilages, and narrowest where the ribs join the spine. Comparative Osteology. — It is curious that the gorilla and. THE RIBS 273 chimpanzee have each 13 pairs of ribs. So that man in his descent from his pretended ancestors must have lost a rib, for he (like the man of the woods, orang utan) has only 12. In mammalia the number of ribs on each side ranges from 9 in the bottle-nosed whale (Hyperoodon, No. 2892) to 24 in the two-toed sloth (No. 3434). The horse and tapir have 18 pairs each, and the elephant 19. The ribs of the manatee (No. 2729) are extraordinarily thick, broad, and massive. In whales some of the posterior ribs are attached only to the transverse processes of the vertebras. Commonly in mammalia about 6 ribs articulate with the sternum by carti- lage or bone, but in whales the number so attached is much smaller, in the whalebone whale there being only one pair of true ribs. This freedom of action allows the great play of the respiratory apparatus in cetacea. Some animals have the costal cartilages ossified, forming sternal ribs, as in the giraffe, crocodile, ox, porpoise, and dol- phin; in many there is an intermediate rib, or shaft of bone, set in between the sternal and vertebral ribs (see Nilotic crocodile, No. 717 D, and monotremata, No. 3964). The ribs mostly serve in respiratory movements and protec- tion of thoracic viscera throughout the animal kingdom. In addition to this the snakes use the tips of them to walk upon, and the flying lizard (Draco volans, No. 673) has the 5 pos- terior ribs so recurvated and elongated as to form the bony skeleton of the membranous sail by which he supports himself in his flight from tree to tree. The middle part of the ribs in birds (see griffin vulture, No. 1674) presents a long flat process which projects backwards and rests on the rib below. These are called uncinate processes. There are no processes in mammalia corresponding to the uncinate processes in birds. They are, however, seen in alliga- tors and sphenodon, &c. (No. 760 A). Sharks and rays have no ribs. What appear to be ribs in the Porbeagle shark (No. 419 A) are simply the supports of the 274 THE BIBS gills, as may be understood by a reference to the skeleton of the cod-fish (No. 147 A), which has 17 pairs of ribs. Examine the great Nilotic crocodile (No. 717 D), and you will see that an anterior and a posterior bar forming the transverse processes of the cervical vertebras correspond to the two processes which in the dorsal vertebras support respectively the head and the tubercle of the rib. In its middle and posterior dorsal regions the end of a transverse process supports both the head and the tubercle of the rib. There will be seen also what are called intermediate ribs, i.e. a piece of bone between the end of the rib and the costal cartilage or sternal rib. Some of the ribs are furnished with uncinate processes, as in birds ; but this is better seen in the alligator (No. 760 A). Seven pairs of false ribs are developed as superficial ossifications of the lineee trans- versa in the abdominal wall (see also No. 711 A). The extinct flying lizards, Pterosauria (No. 119 A), had splint- like sternal, as well as abdominal, ribs. In Ophidia (No. 630) the ribs articulate only with the ends of transverse processes. PLATE XLU From nature "by THol&en, Drawn, on Stone Ly T. Go dart. Printedty West ' NemnB1 275 ATTACHMENTS OF THE MUSCLES OF THE BACK. (Plates XLII.-XLVII.) In the description of the attachments of the muscles of the back the more superficial muscles, connected with the arm, will be first considered. These removed, the great muscles of the spine, which fill up the vertebral grooves, and keep the body erect, are exposed. Lastly, there is the mass of muscles at the back of the neck attached to the occipital bone. THE SUPERFICIAL MUSCLES OP THE BACK. These are shown in Plate XLII. The most superficial is the 'trapezius,' a triangular muscle of which the limits are defined by the continuous dark line. The other wide-spreading superficial muscle is the ' latissimus dorsi.' Under the trapezius we have the 'rhomboidei' and the ' levator anguli scapula, ' shown in Plate XLIV. ' O. Occiput ; ligamentum nucha : spines of all the „, . dorsal vertebra. Trapezius . . . .-/_„. „ . . .,.,.. I. Spine of scapula ; acromion, acromial third of clavicle. ,0. Crest of the ilium. Spines of all the lumbar, I sacral, and six lower dorsal vertebras, crest Latissimus dorsi . . . -j of ilium, and by digitations from the three I or four lower ribs. Vl. Bottom of bicipital groove of humerus. 0. Spines of last cervical and five upper dorsal vertebras. 1. Vertebral border of scapula. (0. Transverse processes (posterior tubercles) of Levator anguli scapulas . . -i four upper cervical vertebras. [ I. Upper angle of scapula. When the preceding muscles are removed, there still remain the ' serratus posticus superior ' and ' inferior.' These belong not to the arm, but to the ribs. T 2 Bhomboideus (major and minor) 276 THE SUPEBFICIAL MUSCLES OF THE BACK 53 S § £ I o *• g> -Sis "| So * 3 *. ^ H3 2 ^ b£S« ° k " m ■^ ^ 3 o 33 % .ss.^ .S gC 8 p< o sa £ " I * g a -I ss^-s sgcogj CO CD 2 13 5 " ' ri . S * V. 33 ^ 32 cf o •a 5 g s a eh "8 8 » § 'I '& t .3 « I 8 - i »1 11 s'l | | *3 - |g lll-g I 1* al "J S«5 go ■§ d • ™ * S *o ^^^.2^a,^o |a- ii ^ n ° a | § .-a s * 4 sill j g.gfis -♦■= .— _-. """*-' l __J fll ,— i >S. _. _l_H & r-| _ >M rft JJ ' «a £ y>»^2 .3 a £ £ ^ . | |^ = SS ^8|-s| ^Z* EP CD b■ ft 5 u 4^c3tg O Jdqjn^gfl,_,H-^mcS-MS a 3 CD a c5 O a i— t CO • i— I CQ CO a o • i— ( is rd ^3 -U o •4-t of 64-1 c3 O » O -4-J CO CD c3 CO .3 a "§) •Td & a a 1=1 QQ 8 cS S -^' -h d Slav's ! i— I -4—i ~ ^ ^ > OJ QJ » i— — I sl-i H' K \4 i— < — CJ r~. -a a - 3. a i 5 d &- _ S-3.C*' 3 CQ M • e3 ft PLATE E-recto soi nse Drawn, cm. Stone byT.Godart. From nature by L HolcLen. Printed by "West,Newmaaii.Go. PLATE XLIV. 1 # 1 ~v 1 3 I ftj ' « ! o 1 "* 1 '-— 7 J i a ; ^ ' .' a I i ctf I / ^ / ! o , -t> i ft ' ,' i ' Co. J THE HUMERUS 295 THE HUMEEUS. (Plates L., LI.) The humerus is the longest and strongest of the bones of the Upper extremity. It is a lever of the third order, the fulcrum being at the shoulder joint, and the power at the insertions of the several muscles which move the bone. It articulates with the scapula above, and the radius and ulna below. Like all the long bones, it has a ' body ' or ' shaft,' and an ' upper ' or a ' lower extremity.' Upper Extremity. — Head and Neck. — At the upper end is the smooth eminence termed the ' head.' It forms about one- third of a sphere, and articulates with the glenoid cavity of the scapula. The head of the humerus is much larger than the socket in which it plays. This arrangement, together with the shallow- ness and direction (p. 285) of the socket, explains the great range of motion which the shoulder joint enjoys. It is the freest of all the joints, and resembles what mechanics call a ' universal ' joint : there is no part of the body which cannot be touched by one hand or the other. The head springs from the shaft by a slightly con- stricted base, called the ' anatomical neck,' to the outer margin of which the capsular ligament of the joint is attached, and which is marked by a number of large nutrient foramina in front, below, and behind. Although this part of the bone is so short and thick as hardly to deserve the name of neck, yet it serves the important purpose of removing the head a little away from the axis of the shaft. In consequence of this, the axis of the head and neck forms an obtuse angle with that of the shaft. When the arm hangs quietly by the side, with the thumb in front, the precise direction of the axis of the head and neck of the humerus is upwards, in- wards, and a little backwards from the shaft— a direction- which facilitates rotation inwards. In the axis of the neck of the femur, where rotation outwards is more required than rotation inwards, this direction is reversed. Baise the arm of the skeleton to a right angle, and you observe 296 THE HTJMEKUS that much of the lower part of the head of the humerus is out of the socket. This is one of the reasons why the humerus is so liable to be dislocated when the arm is extended ; the head of the bone in this position being chiefly supported, below, by the fibrous capsule of the joint. Again, when the arm is raised to a right angle, there is another point worthy of notice : that the humerus alone cannot be raised higher, for the reason that the articular surface of the head of the bone does not admit of elevation beyond a right angle. When we do raise the arm beyond a right angle, the additional elevation is accomplished by the movement of the scapula upon the chest, an effect chiefly due to the action of the trapezius and serratus magnus muscles. Tuberosities. — At the root of the neck, or rather at the top of the shaft, are two projections, termed the ' tuberosities,' which give greater leverage to the muscles moving the bone. They are separated by a perpendicular groove which runs about three inches down the shaft, and is called the ' bicipital groove,' be- cause the tendon of the long head of the biceps plays in it. Of these tuberosities the ' greater ' is the more external. It presents an external surface, which is free, somewhat streaked vertically by slight grooves and ridges, and presents a few rather large nutrient foramina. Its upper border is marked by three flat- tened impressions, of which the middle one is the largest, for the insertion from before backwards of the ' supra-spinatus,' ' infra- spinatus,' and ' teres minor ' respectively. Its anterior border is prominent, continuous with the anterior border of the shaft, and makes the upper part of the outer lip of the bicipital groove* Its posterior border is flattened and rough and gives attachment to the ' teres minor.' In a thin person it can be plainly felt immediately below the acromion, and the centre of its outer sur- face is in the same vertical line as the ' external condyle ' at the inferior extremity. It is useful to know this in determining the nature of injuries about the shoulder. The ' lesser -tuberosity' is the more internal, and points straight forwards. It is a rough conical eminence and gives insertion to the ' subscapularis.' Shaft. — The first thing to be observed in the shaft is, that its lower part is twisted inwards, and that it is slightly curved PLATE LI. Internal condyle UrcateT tuberosity Groove "for trmsculo-spiral nerve. 01e.era.Tion losaa.* External condyle. Humerus, posterior view. _ rirninri. I|u Qmiluby T. Go dart. ^^JyirMSMen. Printed 'by "West,Newman &Co. THE HUMERUS 297 forwards. This twist and curve make the axis of motion at the elbow such, that the forearm naturally bends towards the front of the body. The upper half of the shaft is more or less cylin- drical ; the lower half is prismatic, although somewhat flattened from before backwards below. Immediately below the tuberosities is the ' surgical neck ' of the humerus ; so called in contradis- tinction to the anatomical neck already described. Fracture of the surgical neck is common ; of the anatomical neck rare. The muscles play an important part in causing displacement in frac- ture when it occurs through the surgical neck. There is often a double displacement : i.e. the upper fragment is drawn outwards by the muscles inserted into the tuberosities, and the lower frag- ment is drawn upwards and inwards by the muscles which go from the trunk to the arm. The shaft presents three borders, anterior, internal, and ex- ternal ; and three surfaces, internal, external, and posterior. The anterior border begins above as a continuation of the anterior border of the greater tuberosity, and runs down the front of the bone to terminate at the lower end by dividing into branches to enclose depressions in that situation, viz. the coro- noid fossa, and the radial depression. In its upper third the border forms the outer lip of the bicipital groove and is rough for the insertion of the ' pectoralis major.' The upper part of its middle third is also rough, and forms the anterior edge of the eminence for the insertion of the ' deltoid.' In its lower third, and in the lower part of its middle third, it is smooth and rounded and gives attachment to the ' brachialis anticus.' The internal border reaches from the lesser tuberosity to the internal condyle. Its upper fourth forms the inner lip of the bicipital groove for the insertion of the ' teres major.' About the middle, the border is rough for the insertion of the ' coraco- brachialis,' and below that it becomes very prominent and dis- tinct, and is called the 'internal condyloid ridge,' for the attach- ment of the 'internal inter-muscular septum.' Immediately above the condyle the ' pronator radii teres ' arises. The external border runs from the posterior border of the greater tuberosity to the external condyle. It is - indistinctly ^98 THE HUMERUS marked above, where it gives attachment to the ' teres minor ' and ' external head of the triceps.' In the middle it is hollowed by the commencing ' musculo-spiral groove,' and below it is very prominent, forming the external condyloid ridge, for the attach- ment of the ' external intermuscular septum,' « supinator longus,' and ' extensor carpi radialis longior.' The internal surface lies between the anterior and internal borders. It looks forwards at its upper end and forwards and inwards below. Its upper fourth forms about the lower two- thirds of the bicipital groove, for the passage of the long tendon of the ' biceps.' The surface here is rough for the attachment of the ' latissimus dorsi.' Towards the lower and back part of the middle third we notice an elongated roughness for the insertion of the ' coraco-brachialis ' and immediately below that the medul- lary foramen, directed downwards. In the lower third the bone is smooth and gives origin to the brachialis anticus. The external surface looks backwards and outwards above, forwards and outwards below. Its upper third is smooth and rounded. Its middle third shows in its upper part a large tri- angular rough eminence — the deltoidal eminence — for the inser- tion of the 'deltoid.' The base of the triangle is above, and its superior angles in well-marked bones are usually prolonged for a short distance up the bone. The lower part of the middle third presents the musculo- spiral groove, smooth and running down- wards and forwards for the transmission of the musculo-spiral nerve and vessels. The lower third of the surface is more or less smooth and gives attachment to the ' brachialis anticus.' It is generally below the insertion of the deltoid that ununited fractures of the humerus are met with, partly on account of the injury to the nutrient artery, and partly on account of the action of the deltoid in causing a displacement of the upper fragment over the lower. The posterior surface, in its upper third, is rounded trans- versely and gives attachment quite at its upper end to the teres minor and in the rest of its extent to the ' external head of the triceps.' In its middle third it shows the commencement of the musculo-spiral groove. The remainder of the surface is some- THE HUMERUS 299 -what flattened, and even concave transversely below, for the attachment of the ' internal head of the triceps.' Lower Extremity. — The lower end of the humerus curves slightly forwards, and is much flattened from before backwards, and widened from side to side. It presents, on either side, a condyle with articular surfaces between, suited to the flexion and extension, as well as the rotatory movement of the forearm. On the outer side, we observe the ' lesser head ' (capitellum) , which corresponds with the shallow cavity at the end of the radius. The chief point about this head is, that it projects directly forwards, so that when the forearm is bent there is a smooth surface ready for the rotation of the radius. On the inner side is the ' trochlea ' or pulley for the ulna. This admits of flexion and extension only. The direction of this pulley is oblique ; that is, it slants from behind forwards, and from without inwards, so that the forearm, in the act of bending, comes naturally in front of the chest. Observe that the inner border of the trochlea descends much lower than the outer, thus protecting the ulna from dislocation inwards. The downward projection of the inner edge of the trochlea allows also for the divergence of the upper end of the humerus, and enables the bones at the elbow joint to fall inwards and adapt themselves to the contour of the trunk in that neighbourhood. Above the trochlea there is a deep cavity in front (coronoid fossa) which re- ceives the coronoid process of the ulna in flexion ; and a similar but deeper one behind (olecranon fossa) receiving the ' olecranon,' ■or the point of the elbow, in extension of the forearm. External to the coronoid fossa, immediately above the lesser head, is a shallow depression (radial depression) for the head of the radius in extreme flexion. Between the ' olecranon and coronoid fossae ' the bone is translucent, as is well seen in fig. 58, which exhibits a section through the joint. In consequence of this thinness, a transverse fracture through the humerus in this situation is not uncommon. Prom the displacement produced so close to the elbow joint this accident is very liable to be mistaken for a dislocation of the radius and ulna backwards. However, the bearing of the condyles with respect to the olecranon enables us 300 THE HUMERUS in most cases to determine the diagnosis. If the olecranon be higher than the condyles, there is dislocation of the elbow; if Fm 5g not higher, the ulna is in its proper place. The internal condyle projects more than the external, and gives origin to the powerful pronator and flexors of the hand and fingers, namely, to the ' pro- nator radii teres,' ' flexor carpi radialis,' section to show the TRo- ' palmaris longus,' ' flexor sublimis digi- chlea oe the humeecs. toruHi,' and ' flexor carpi uinaris.' The o. Olecranon internal lateral ligament of the elbow c. Coronoid process. . , ,, , -, , ., is also attached to it. The external condyle is not so prominent as the internal. It is flattened, and gives origin, in front, to the common tendon of the extensor muscles ; namely, the ' extensor carpi radialis bre- vior,' ' extensor digitorum communis,' ' extensor minimi digiti,' and ' extensor carpi uinaris : ' behind, it gives origin to the ' anconeus.' Lastly, the external lateral ligament of the elbow is attached to it. Connections. — The head of the humerus articulates with the glenoid cavity of the scapula at the shoulder. At the lower end on its outer side is a round convex surface which articulates with the cup on the top of the radius ; while the trochlea is adapted to the form of the sigmoid cavity of the ulna. Ossification. — -The humerus has seven centres of ossifica- tion. There is one for the shaft, which appears about the seventh week of foetal life, when the foetus is about an inch long. About the second year after birth the centre of the head appears ; and about the third year, the centre of the great tuberosity. The centre for the lesser tuberosity appears about the fifth year,, or it may be produced by an extension of the ossification of the great one. About the end of the fifth year the centres for the head and tuberosities have coalesced, and form a large epiphysis, which joins the top of the shaft about the twentieth year. It is necessary to remember that this epiphysis includes the tubero- sities (see fig. 59). On the inner side, the line of junction runs THE HUMERUS 301 EPIPHYSIS OF THE HEAD Or THE HUMERUS, SHOWING THAT IT INCLUDES TUBEROSITIES. close to the cartilage on the head of the bone : therefore, in the event of separation, the shoulder joint would certainly be impli- cated. About the beginning of the third year, ossifica- tion of the lower end commences by a fourth centre in the lesser head. About the fifth year, a fifth centre appears in the internal condyle. About the twelfth year, a sixth centre appears in the great sweep of the trochlea ; and, lastly, about the thirteenth year, the seventh centre appears in the external condyle. The centres for the external condyle, capi- tellum, and trochlea coalesce and form an epiphysis which joins the shaft in the sixteenth or seventeenth year. The epiphysis formed by the internal condyle does not join the shaft till the eighteenth year. Therefore there may be a separation of the upper epiphysis from the shaft by violence as late as about the twentieth, but of those at the lower end not later than about the sixteenth, seventeenth, or eighteenth year Nor. Hum. Ost. No. 54.) It is interesting to remark, that the epiphysis of the upper end, though the first to ossify, yet remains separate from the shaft about two or three years longer than those of the lower end. This is in accordance with the rule, that, of the epiphyses of a long bone, those towards which the nutrient artery of the marrow runs, are always the first to unite with the shaft. Ee- member, that the nutrient arteries of the marrow of the bones of the upper extremity run towards the elbow. In the bones of the lower extremity, they run from the knee. Structure and Mechanism.— The cancellous tissue follows the ordinary law, viz. that its spicules run at right angles to the plane of pressure. There is a well-developed ' medullary cavity.' Extensive movement at the upper end of the bone is obtained by the large size of the articular surface of the head and the small size and shallowness of the ' glenoid cavity.' The tuberosities are applied close to the fulcrum ; therefore great play is gained at the far end of the lever. The upper end is protected by over- (See 302 THE HUMEBUS hanging bony processes. The lower end is oblique, for the reasons- we stated in its description (p. 289), and the motion taking place there too is limited in extent. The whole bone is twisted and curved, thereby gaining elasticity. Comparative Osteology. — In man the legs are longer than the arms, and grow faster than the rest of the body after birth. In apes and monkeys the converse of this is true, and, after birth, the arms grow faster than the rest of the body. In most giants the great proportion of the height is due to the length of the lower extremity. It is curious that the right humerus of the gorilla (No. 20) is of the same length as that of the Irish giant O'Brien (Hum. Ost. Ser. No, 223), who stood about eight feet, while the height of the gorilla is only four feet four inches. The left humerus of O'Brien is 20 mm. shorter than the right, and there exists a similar difference in the two humeri of the gorilla. It may be well to mention that the corresponding bones of oppo- site sides commonly differ a little in length, without giving rise to any obvious deformity. The olecranon and coronoid fossae occasionally communicate by a small hole in man. This seems to be pretty constantly the case in the Bushman, gorilla, tapir, and dogs. (See Separate Series, Mus. Boy. Coll. Surg., as well as in the articulated skeletons.) Above the inner condyle in many carnivora is a foramen (supra-condyloid) which transmits the median nerve and the- brachial artery. (See Separate Series, Mus. Boy. Coll. Surg. : tiger, lion, and leopard.) A trace of this foramen occurs now and then in man by the ossification of a part of the fibrous band which passes over the median nerve and from which the pronator teres arises. 03 The deltoid ridge is especially prominent in the Carnivora (see that of the seal) . It is extensive in the rhinoceros, the tapir r and the horse, which have heavy limbs to raise. The tuberosities are very large in the heavy-limbed rhino- ceros and the heavy-boned dugong. Notice how extensive the supinator ridge is in the aye aye and the beaver. In moles the clavicle articulates with the humerus (No. 3329). THE HUMERUS 303 There is no complete articulation between the humerus and forearm in Cetecea, nor between their carpus, forearm or digits ; the upper extremity forming a nipper which has free movement only at the shoulder joint. (See the Cachalot Whale.) In flying birds, notice the large foramen, at which the air enters the cavity in the bone immediately below the head, and feel the great lightness of their bones. The humerus of the adjutant (No. 1306) is a mere shell. A bone of this bird, thirteen inches long, weighed only half an ounce, while a corresponding one seventeen inches long of an ostrich weighed half a pound, that is, it was sixteen times as heavy. In snakes there is no trace of fore limb, and consequently no humerus (No. 629). Near the end of the humerus of the turtle there is a line which may appear to denote an epiphysis, but it simply marks the limit to which the cartilaginous cap extended in the recent bone (see No. 1016). These animals have no epiphyses. THE BADIUS. (Plates LII., LIII.) The radius is the external of the two bones of the forearm, and is so called from its resemblance to the spoke of a wheel. In learning this bone, keep in mind that both its ends move upon the ulna, and admit of the pronation and supination of the hand. It is a long bone with its inferior extremity much expanded for the support of the wrist, and its upper end small, entering but slightly into the formation of the elbow joint. Upper Extremity. — The upper extremity of the radius pre- sents the 'head,' 'neck,' and 'tubercle' for description. The 'head' has a shallow circular cup above, which articulates (when the forearm is bent) with the lesser head of the humerus, and in the recent state is held in its place by the strong ' orbicular ' ligament which encircles it. ' The head ' is surrounded by an articular surface narrower below than above to articulate with '304 THE RADIUS the lesser cavity of the ulna. The ' broadest part of the surface (measuring vertically) rests in the lesser sigmoid cavity, when the bones are parallel. The narrowest part is situated on the opposite side of the head. The rotation of the radius can be distinctly felt in one's own person below the external condyle of the humerus ; a fact of great value in determining the existence of fracture or dislocation. Below the head is the constricted part termed the ' neck,' which may be described as a truncated cone with its base upwards. It is surrounded by a continuation downwards of the orbicular ligament. The conical shape of the neck prevents the bone slipping down from its bony and liga- mentous socket. Below this is the ' tubercle' which gives inser- tion to the tendon of the ' biceps.' The tubercle projects on the inner side of the bone, so that the biceps can supinate, as well as bend, the forearm. The posterior half of the tubercle is rough for the insertion of the tendon ; the anterior half is smooth, and is the seat of a bursa which facilitates the play of the tendon. Shaft. — The outer side of the shaft is thick and rounded ; and from it the anterior and posterior surfaces gradually converge to a sharp edge, which faces a cor- responding edge of the ulna (see ( "%Ng- ^y \ ^8- 60) , and gives attachment to the \ wO?""~ < \T^^® ) interosseous membrane represented ^-^ ^\T/ by ^he dotted line. The shaft is slightly arched outwards, by which arrangement it increases the breadth of the forearm, and gives more power to the ' pronator teres.' 64 The shafts of the radius and ulna are farthest apart when the hand is placed vertically with the thumb uppermost : hence, fractures of the forearm are put up with the hand vertical, that there may be less risk of the opposite bones uniting. The shaft increases in size, too, towards its lower end, for the support of the hand. Looking at the bone more carefully, we notice that the shaft presents an anterior, posterior, and internal border, separating anterior, posterior, and external surfaces. The anterior border is continuous above with the front of the, PLATE Lll. Olecranon Greater sigmoid eavi-ty Lesser sigmoid eavity Surface Tor posterior Interosseous nerve." Supinator radii lonfeus Styloid p 'Radius Ulna Anterior view. moid -process . 2 "^ origin oP Flexor Sublimts dijiitPrutn. 2?? W When the arm is bent to a right angle, the olecranon is an inch and, a half from the condyle and. below it. By this, test dislocation 312 THE ULNA of the ulna backwards and fracture through the lower end of the humerus can be distinguished. Shaft.— The shaft of the ulna is triangular in cross section, and tapers gradually from the upper towards the lower end. The lower extremity inclines a little outwards towards the radius and terminates in the little ' head ' round which the radius rolls. A Fig. 63. transverse section, seen in fig. 63, %s~\ shows the shape of the radius and ^-_, c-^^^^ i uma a ^out the middle. We observe X^JSP J ^at their sharp edges are turned to- wards each other, and that to these is attached the interosseous membrane (represented by the dotted line) which connects the bones. Together, they form a shallow concavity in front and behind, wherein the muscles of the fore- arm are lodged. We notice too that the shaft is somewhat sigmoid from side to side when looked at in its long axis, pre- senting a convexity looking outwards in its upper third and a con- vexity in the opposite direction in its lower third. When viewed laterally it is pretty uniformly bowed backwards. The body or shaft of the bone presents an external, anterior, and posterior border, bounding an anterior, internal, and posterior surface. The external border begins above by two branches running to the front and back of the lesser sigmoid cavity, and enclosing a rough, hollowed, and triangular surface for the ulnar origin of the ' supinator brevis.' In its middle two-fourths it is very sharp and prominent, giving attachment to the interosseous membrane, and in the lower fourth it is rounded, approaches the anterior aspect of the bone, and terminates at the middle of the articular surface on the side of the lower extremity. The lower fourth affords attachment to fibres of the ' pronator quadratus ' and to the interosseous membrane, which is thinned in this part of its extent. The anterior border stretches between the ' tubercle of the ulna ' superiorly, and the front of the root of the ' styloid, pro- cess' inferiorly. It is smooth and rounded in its upper three- fourths, where it gives origin to the ' flexor profundus digitorum.' THE ULNA 313 It is rough below, -where it gradually twists towards the pos- terior aspect of the bone and gives attachment to fibres of the ^ pronator quadratus.' The posterior border gives attachment to a strong aponeurosis, -which covers the muscles on the inner side of the forearm, and affords additional surface for the origin of the ' flexor carpi ulnaris,' the ' flexor profundus digitorum,' and the ' extensor ■carpi ulnaris.' The posterior edge (or ridge of the ulna, as it is generally called) deserves the more notice, because being sub- cutaneous it can be traced from the olecranon to the styloid process, and is therefore an important guide in cases of doubtful fracture. Before reaching the elbow the ridge becomes continuous -with the posterior surface of the olecranon, which is also subcu- taneous : here we feel for fractures of the olecranon. The anterior surface lies between the external and anterior bor- ders. It is concave from above downwards in its upper three- fourths, where it looks forwards and gives attachment to the 4 flexor profundus digitorum. ' Its lower fourth is somewhat convex from side to side, is directed inwards at its lower end, and gives origin to the 'pronator quadratus.' The lower fourth is marked off from the rest of the surface in well-developed bones by an oblique ridge running from the external border downwards, in- wards, and backwards, to join the anterior border about an inch above the root of the styloid process. At the junction of the upper and middle thirds of the surface we notice the medullary foramen entering the bone obliquely upwards. The internal surface lies between the anterior and posterior borders. It is continuous above with the inner surface of the olecranon process, looks backwards as well as inwards, and is somewhat flattened. It gets more and more convex, both from side to side and in its long axis as it is traced downwards, and gradually gains a direction so as to look nearly straight backwards at its lower end. It is smooth all over, and gives origin in its upper three-fourths to the ' flexor profundus digitorum.' The posterior surface looks backwards and slightly outwards above, where it is continuous with the external surface of the olecranon process, but very slightly backwards and very much 314 THE ULNA outwards below, as it joins the lower extremity of the bone. It- is divided into two very unequal parts by the ' oblique line of the ulna.' This is a ridge which runs obliquely from the pos- terior inferior angle of the lesser sigmoid cavity downwards and backwards to join the posterior border about the junction of its. upper and middle thirds. The part of the surface above the- line is continuous with the external surface of the olecranon, and is marked by a few low elevations, and has the ' anconeus ' inserted into it. The part below the line is subdivided into two- unequal parts by a vertical line or ridge, which commences in the- oblique line, rather above its middle. It runs down the posterior surface hi a slightly wavy manner, keeping nearly parallel to the posterior border of the bone, and gradually disappears about the junction of the lower fourth with the upper three-fourths of th& posterior surface. The part of the posterior surface which is internal to this line is the broader. It is slightly hollowed from side to side in its upper part, somewhat rounded from side to- side below. On it, without being attached to it, lies the ' extensor carpi ulnaris.' The part of the posterior surface external to the vertical line is somewhat broader above than below, slightly concave transversely, and rough in its upper three-fourths, and rounded and smooth in its lower fourth. The upper three-fourths is divided into three nearly equal impressions, which overlap one another from below and are marked off from one another by two- oblique ridges running from the vertical line downwards and out- wards to the external border of the bone. The impressions give attachment respectively, from below upwards, to the ' extensor indicis,' 'extensor secundi internodii pollicis,' and the ulnar origin of the ' extensor ossis metacarpi pollicis.' Lower End. — The lower end of the ulna -presents a rounded prominence of bone, plainly to be felt on the back of the insidfr of the wrist when the hand is pronated— the 'head' of the ulna- and a short blunt process projecting from the inner and posterior side of the lower extremity — the ' styloid process.' The ' head ' is slightly rough in front for ligamentous attach- ment, concave from side to side behind, and smooth for the passage of the ' extensor carpi ulnaris ' tendon. Externally it is- THE ULNA 3 15 convex from before backwards, and slightly so from above down- wards, smooth and articular, the upper edge overhanging the lower. The articular surface forms rather more than half a circle from before backwards, and on it the radius glides in pronation and supination of the forearm. The inferior surface of the head presents, externally, a semilunar, flattened, articular facet, con- tinuous with the one on the outside of the head and articular for the triangular fibro-cartilage which separates it from the cunei- form bone of the carpus. Internally, where the lower surface joins the styloid process there is a rough depression for the attachment of the apex of the triangular fibro-cartilage. The styloid process projects from the inner and back part of the lower end of the ulna, and thus does not interfere with the rotation of the radius ; it gives attachment to the internal lateral ligament of the wrist. Between the process and the head there is a groove on the posterior aspect of the bone for the passage of the tendon of the ' extensor carpi ulnaris ' (Plate LVI.) ; and externally the process is separated from the head by the depres- sion for the attachment of the triangular fibro-cartilage of the wrist, already described. The styloid processes of the radius and ulna can be readily felt beneath the skin, and are important guides in the determina- tion of injuries of the wrist, whether fracture of the radius or dislocation. The relative position of the styloid processes with regard to the axis of motion at the wrist will settle the question. Connections. — The ulna articulates, above, with the trochlea of the humerus: and with the head of the radius ; below, it arti- culates with the sigmoid notch of the radius, but is prevented from articulating with the cuneiform bone of the wrist, by the intervention of ;an interarticular fibro-cartilage. Ossification. — The ulna has three centres of ossification — one for the shaft and coronoid process, one for the lower end,, and a third for the olecranon. The lower end begins to ossify about the fifth year, and unites to the shaft about the twentieth. The top of the 'olecranon remains cartilaginous until the age of eight, about which time it begins to ossify :• it coalesces with the base about puberty. (Nor. Hum. Ost. No. 54.) 316 THE ULNA Structure and mechanism of Radius and Ulna. — Struc- turally the radius and ulna are typical examples of long bones. The ulna is longer than the radius by the olecranon process, and articulates to a greater extent with the humerus for steadiness. The radius is thick below and articulates to a greater extent than the ulna with the carpus. Shocks from the hand are therefore received directly by the radius, and transmitted to the ulna partly by the head of the ulna overhanging the sigmoid cavity of the radius, but chiefly by the interosseous membrane stretch- ing between the shafts of the bones ; the direction of the fibres of the membrane from the radius downwards and inwards to the ulna favours this transmission. In the act of pronation and supination the radius articulates with the ulna in a conical way. The centre of the head of the radius is the apex of the cone. The pit at the root of the styloid process is the centre of the . base of the cone ; that is to say, the centre of the base of the Fig. 64. cone is the centre of a circle of which the sigmoid cavity of the radius is part of the circumference. The axis of the cone therefore runs through the centre of the head and neck of the radius, leaves the shaft just below the tuberosity, crosses obliquely the interosseous space, and enters the ulna a little above its lower end and terminates at the pit at the root of its styloid process. Pure rota- tion consequently takes place at the superior radio-ulnar joint, and a gliding, circumductory, forward and backward motion at the inferior radio-ulnar joint. With pronation there is slight flexion of the elbow and with supination slight extension. Comparative Osteology. — The ulna in many birds will be seen to be very long, like the radius, forming the largest part of the length of the wing, and to be dotted by a line of small tubercles along its outer surface where the winged feathers are attached. See the length of the ulna in the Frigate bird (No. 1188 A) and the prominent feather-tubercles in the Adjutant (No. 1306). Contrast the great length of the ulna and radius in the swift-flying birds, as the Frigate (No. 1188 A) and Albatross (No. 1189), with the shortness of those which do not fly, as the Great Auk (No. 1118), the Ostrich (No. 1362),, and the Cassowary (No. 1357 A). PLATK LIV. GrooveforFlexor carpi rad'iaHs Abductor pollvcis Opponens pollicis .Extensor ossis rnatacarpt pollicis .Flexor carpi ulnaris Abductor miw'midiAiti, TWor brevis ■minimi cl^rti, Opponensdi'foti minimi. l«or carpi ulnar is Abducto po11ic\s. plexor brcMis -pott ic is Palmar surface. Drawn on Stone "by T. Go dart. From nature "byL.Holden. Printed 'by-Weet,!NewmanfcCo. 317 BONES OF THE HAND. (Plates LIV., LV., LVI.) The skeleton of the hand consists of twenty-seven bones. The first eight are the little bones of the carpus ; the five succeeding bones constitute the metacarpus : these support the bones of the fingers. Each finger has three bones, termed, in order from the wrist, the first, or proximal or metacarpal, the second, or middle, and the third, or distal or ungual phalanges. The thumb has only two phalanges. THE CABPTJS. (Plate LVI.) Number and Names. — The carpus consists of eight little bones, arranged in two transverse rows of four bones each, thus forming a broad base for the support of the hand. What is the advantage of so many bones in the wrist ? It confers strength and elasticity and permits some motion. The contiguous surfaces are crusted with cartilage and form synovial joints. Suppose there had been a single bone instead of the eight carpal bones, bow much more liable it would have been to fracture and dislo- cation. As it is, dislocation of one or more bones of the carpal range is a rare occurrence ; but it does happen sometimes. Sir C. Bell tells us that ' the boy that played the dragon in a panto- mime at Covent Garden, fell upon his hands, owing to the breaking of the wire that suspended him, and he suffered dislo- cation of some of the carpal bones in both hands.' 318 THE CAEPUS The bones of the carpus are named as follow, beginning from the radial side : First or Proximal Eow . 'Scaphoid,' 'semilunar,' 'Cuneiform,' 'pisiform.- Second or Distal Eow . ' Trapezium,' ' trapezoid,' ' os magnum,' ' unciform.' The student will obtain a better idea of the general shape and arrangement of these bones by examining them, at first, collectively. For this purpose it is very desirable that he should have before him an articulated hand, as well as the separate bones. Carpal Arch. — The outline of the carpus as a. whole is oblong, with the broad diameter in the transverse direction. Its Toones are wedged together, and so form an arch with the con- cavity towards the palm, which gives passage to the flexor tendons of the fingers. Fig. 3 in Plate XXXVIII. shows that the piers of the arch are formed on one side by projections from the scaphoid and trapezium ; on the other, by the pisiform and the hook of the unciform. The arch is converted into a complete tunnel by the anterior annular ligament. Radio-carpal Joint. — To begin with the bones of the first row. Excluding the pisiform, which is only an outstanding * sesamoid ' bone, it will be seen that the scaphoid, semilunar and cuneiform bones form a convex articular surface, which, with the lower end of the, bones of the forearm, forms the radio-carpal joint. This joint admits not only of the movements of flexion and extension, but also of the horizontal movements of the wrist (abduction and adduction). The upper articular surfaces of the first row of bones are prolonged farther down their dorsal than their palmar aspect : hence the free movement of extension at the wrist. The articular surfaces of the scaphoid and semilunar bones fit into the radius ; while that of the cuneiform, which is the least extensive of the three, would articulate with the ulna, but for the intervention of the triangular fibro-cartilage attached, in the recent state, to the lower end of the ulna. The bones of the first row articulate with each other by plane surfaces crusted with cartilage, but they are so firmly connected by ligaments that there is very little movement between them. THE CARPUS 319 Intercarpal Joint. — Collectively, the lower ends of the first tow form, with the bones of the second row, an important movable joint, which we call the ' intercarpal.' It is very different in form from the first joint (radio-carpal) of the wrist, since its outline is alternately convex and concave. By means of this second joint we get a great range of flexion and extension at the wrist. If there had been only a single joint for this amount of motion, it would have been comparatively insecure, and very liable to dislocation, whereas dislocation of the wrist happens very rarely indeed. By reference to Plate LVI. it is seen that the lower part of the scaphoid has a convex articular surface which corresponds with the trapezium and trapezoid, and also a concave one, which, with a concavity in the semilunar and cunei- form bones, forms a deep socket for the reception of the head of the os magnum and the unciform. Articulations of First Row. — The ' scaphoid ' articulates with five bones, viz. the ' trapezium,' ' trapezoid,' ' semilunar,' 'os magnum,' and ' radius ; ' the ' semilunar ' with five, viz. the 'scaphoid,' 'cuneiform,' 'os magnum,' 'unciform,' and 'radius;' the < cuneiform ' with three, viz. the ' semilunar,' ' unciform,' and ' pisiform ; ' and the ' pisiform ' with one, namely, the ' cuneiform.' In consequence of the flexors and extensors of the wrist being inserted below the second row of carpal bones, they necessarily act on the ' intercarpal joint ' as well as on the radio-carpal. 'Thus a greater amount of motion is provided at the wrist than it •otherwise could have possessed with safety. If such free motion had been given to one joint, the angle of flexion must have been great and the ligaments looser than would have been consistent with the security of the joint. Bones of the Second Row. — The trapezium and trapezoid form a shallow socket for part of the scaphoid, while the os magnum and unciform form a convexity, which fits into the deep socket formed by the scaphoid, semilunar, and cuneiform in the first row. Below, the second row articulates with the metacarpal bones, as follows : The trapezium with two, that of the thumb ■by a concavo-convex surface, and partly with that of the index 320 THE CARPUS finger ; the trapezoid with one, that of the forefinger ; the os magnum with three, that of the middle finger, and besides this with those of the index and ring fingers ; and the unciform with two, those of the ring and little fingers. Thus the trapezium supports the metacarpal bone of the thumb ; the trapezoid that of the index finger ; the os magnum that of the middle finger ; and the cuneiform those of the ring and little fingers. The con- sequence is, that the metacarpal bones present different degrees, of mobility — that of the thumb being the most movable, those of the fore and middle fingers the least so. Articulations of Second Row. — Like the bones of the first row, those of the second articulate with each other by plane surfaces firmly connected by ligaments. The trapezium articu- lates with four bones ; the trapezoid with four ; the os magnum with seven ; the unciform with five. Description of Individual Bones. — Thus far we have ex- amined the bones of the carpus collectively ; let us now look at them individually. Each bone of the carpus is more or less cubical in shape. Hence we describe six surfaces upon it — ■ superior, inferior, external, internal, anterior, and posterior. In all except the ' scaphoid ' and ' semilunar ' the posterior or dorsal surface is larger than the anterior or palmar. Both these surfaces likewise, except in one bone, the ' cuneiform,' are rough all over for the attachment of ligaments. Scaphoid Bone. — This bone is so named from its boat- shaped socket (cncddyto ossify. The ' os centrale,' lying in the typical carpus jtween the bones of the first and second row, is present in man s a small cartilage, situated between the ' trapezium,' ' trapezoid,' ndgnum ' and ' scaphoid ' at the second month, and disappears bout the fourth month of fcetal life. In rare cases it persists as separate bone in the adult. Again, a part of the ' scaphoid,' jrresponding to its tuberosity, may remain separate, and repre- snts the ' radial sesamoid ' of Gegenbaur. Comparative Osteology. — In many of the Carnivora, as the sal, walrus, tiger, and dog, the scaphoid and lunar are anchy- ised into one mass. In the bat, the scaphoid, lunar, and cunei- )rm form only one bone. In the dugong, all the carpal bones are nchylosed into three bones, the distal row being in one piece. In birds, as in other animals, they are diminished in number ccording to the disappearance of the digits which each usually iipports. The carpus of the orang utan, baboon, several other monkeys nd reptiles, contains one more bone than that of man, which sems due to the division of the scaphoid into two parts : it is nown as the os centrale. (See Separate Series, Mus. Eoy. Coll. lurg.) THE METACAKPUS. (Plates LIV., LV. The metacarpus consists of the five bones which support the halanges of the thumb and fingers. They are described as the rst, second, third, fourth, and fifth, counting from that of the humb, or as metacarpal bones of the thumb, index, middle, ing, and little fingers ; and, regarding them as ' long bones,' finch they much resemble in their general structure, we speak l their shafts and their two ends ; the upper end being termed 328 THE METACAKPUS the ' base ' ' or proximal end,' the lower the ' head '. or ' distal end ' of the bone. S HAFTS . — The ' shafts ' are slightly concave towards the palm, forming the hollow of the hand. They are made somewhat triangular on section by the impressions of the ' interosseous ' muscles, which occupy the ' interosseous spaces.' The apex of the triangle is on the palmar surface, the base on the dorsal sur- face forming the support of the extensor tendons of the fingers. We consequently describe anterior, internal, and external borders separating internal, external, and posterior surfaces. The ■ anterior border is curved backwards in its long axis. It begins behind by two branches enclosing a rough space on the palmar surface of the base, is sharp, prominent in the middle of the shaft, and terminates anteriorly by two branches running each to its own condyle at the distal end of the bone. The internal and external borders begin behind on either side of the base of the bone, and are rather rounded posteriorly, sharp and prominent anteriorly, where they terminate in the tubercles of the distal end. The internal and external surfaces are both seen when look- ing at the bone in its palmar aspect. They are somewhat con- cave antero-posteriorly and convex from side to side. They are smooth, and give attachment to the interosseous muscles. The ' medullary foramina ' of the second, third, fourth, and fifth meta- carpal bones are usually situated about the middle of the external surfaces, close to the external borders, and directed obliquely to- wards the base. In the metacarpal bone of the thumb the ' me- dullary foramen ' is generally seen on the internal surface near the ' internal border,' and directed obliquely towards the distal end. The posterior surface, enclosed by the inner and outer borders, is bowed backwards in its long axis. It is divided into three parts by three lines. A vertical line, which begins in the middle of the posterior surface of the bone, runs vertically down the middle of the posterior surface in its posterior third, and then divides into two branches which terminate in the tubercles of the distal end. Three surfaces are thus marked off — two pos- teriorly, which are hollowed from back to front and give origin to interosseous muscles ; and one anterior, which is large, tri- THE METACARPUS 329 ngular, flattened, and covered by the tendon of the ' extensor ommunis digitorum ' muscle. The posterior surfaces of the Irst and fifth metacarpal bones are not thus mapped out, as we hall see in their description. Bases.— The ' bases ' are cubical in shape with their ante- ior surfaces less than their posterior ones, and both rough for igamentous attachment. They articulate not only with the lones of the carpus by their superior surfaces, but, by articular acets on their inner and outer surfaces with each other : that if the thumb, however, stands out alone, so as to oppose all the ithers. It is one of the great characteristics of the hand of nan, that the point of the thumb can touch with perfect ease he tips of all the fingers. Heads. — The lower ends or ' heads ' are rounded for articu- ation with the first phalanges of the fingers. The articular urfaces of the heads extend chiefly towards the palm, and are iroader on that aspect than on the dorsal side. They run back, oo, upon the palmar surfaces of the heads as lateral projections ermed the 'condyles,' which are grooved antero -posteriorly for esamoid bones where such bones exist. They allow the fingers lot only to be flexed and extended, but to be moved laterally, he latter motion being especially well seen when the metacarpo- ihalangeal joint is extended. On each side of the heads are a ubercle and a deep pit for the attachment of the thick and trong lateral ligaments. Let us now look at the features peculiar to the individual aetacarpal bones. Metacarpal Bone of the Thumb. — Viewed generally it is he shortest, stoutest, and broadest of all the metacarpal bones. ts base presents, superiorly, a saddle-shaped surface much pointed orwards, and broader externally than internally, for articulation pith the trapezium. It shows no articular facets on the sides of ts base, but externally there is a rough, oval depression for the nsertion of the ' extensor ossis metacarpi pollicis.' Its distal end is much flattened from before backwards, and hows well-marked condyles, with an antero-posterior groove on ach, for articulation with the sesamoid bones which are developed 330 THE METACAEPUS EASE OF FIEST EIGHT HETA- in connection with the tendons crossing the front of the metacarpo- phalangeal articulation of the thumb. The shaft too is much flattened, so that its anterior border is ill marked. To its outer surface we have attached the ' opponena pollicis,' and to its inner the first ' dorsal inter- osseous ' or ' abductor indicis ' muscle. There are no less than nine muscles to work the thumb. Its great mobility in all directions, so essential to the power and perfection of the human hand, depends upon this saddle-shaped joint at its base ; and its power of antagonising the fingers is owing to its base being set off on a plane anterior to them. caepal, outee But for a little buttress of bone which projects from SIDE - the inner and front part of the trapezium, the thumb would fall into the same line as the fingers, and would not pos- sess that power of opposing them which makes the human hand such a wonderful instrument. 68 Metacarpal of Pore-fing-er. — The metacarpal bone of the fore-finger is the longest of all the metacarpal bones. Its base- Fig. 66. presents superiorly an antero-posterior groove, wider ii- behind than in front and inclining inwards posteriorly, for articulation with the ' trapezoid.' The outer lip of this groove is the lower, and is marked by a facet looking forwards and upwards for articulation with the ' tra- pezium.' The inner lip projects upwards and is ar- ticular along its edge, for the ' external angular facet ' of the ' os magnum.' The anterior surface is rough for the insertion of the tendon of the ' flexor carpi radialis.' The posterior surface is also rough and metacaepal, presents externally a flattened, rough mark for the innee side, insertion of the ' extensor carpi radialis longior,' and internally a smaller rough space, looking towards the third metacarpal bone, for the insertion of part of the tendon of the ' extensor carpi radialis brevior.' Externally the base presents- no facet for articulation with the first metacarpal, but internally it has a well-marked articular surface, notched below, for the third metacarpal. BASE OB- SECOND EIGHT PLATE LVI. Ultia. Radius, Extensor mdicis | E»t!"min'im\di^iti ... Extfcarpi ultiar'is Supinator radi i lon^us . ExtTossis metacarpi pollicis £x£pnmi lnternoSii pollicis. ..ExtTcarpi raolialis" lon^ior et brevior . _| ...ExP"secunc|i inbernoSii pollicis. View of "the intercarpal joint Drawn on Stone "by T. Godart . Irom nerture WLHnU" Printed by-Weat,Newmstfi4,Co. THE METACARPUS 331 The shaft and distal end present the characters 1 common to all metacarpal bones. The external surface of the shaft gives origin to the first ' dorsal interosseous,' and the internal surface, to the second ' dorsal ' and first ' palmar interosseous ' muscles (figs. 73, 74). Metacarpal of middle Finger. — The metacarpal bone of the middle finger is second in length of all the metacarpal bones. Its base presents superiorly a four-sided, FlG> 67 PlG 68 somewhat sinuous surface for articulation m . m . with the 'os magnum,' while its posterior and external angle rises up into a blunt projection, overlapping the posterior surface of the ' os magnum ' from below, and called the ' tuberosity ' or ' peak ' of the third metacarpal bone. Anteriorly the base is rough and bulged forwards for the insertion of a few fibres of the tendon of the < flexor INNEB SIDE " 0CIEE SIDE - carpi radialis ' and the origin of part of the EiSE 0E THE THIED EIGHT , . HETACAEPAL. ' flexor brevis polhcis muscle, rosteriorly the base is rough and shows externally a depressed rough surface, running upon the back of the ' peak ' for the insertion of the extensor ' carpi radialis brevior.' The sides of the base present the appearances shown in figs. 67 and 68. There is nothing peculiar to notice on the distal end and shaft of the bone. The outer and inner surfaces of the shaft give origin to the second andthird 'dorsal interosseous' respectively (figs. 73, 74). The anterior border gives origin in its upper fourth to the 'flexor brevis polhcis,' and in its lower three-fourths to the ' adductor polhcis.' Metacarpal of Ring Finger. — The metacarpal bone of the ring finger presents on the superior surface of its base a four- sided flattened .surface, for articulation with the 'unciform.' Outside this facet is a deep, rough, antero-posterior groove, and, external to it, are the upper edges of the facets upon the exter- nal surface of the base. The upper edge of the posterior facet is cut off obliquely, so as to present a small flat facet, looking back- wards, upwards, and outwards for articulation with the ' os 332 THE METACARPUS INNBE SIDE. OUTEE SIDE. BASE Or FOUETH EIGHT METACAEPAL. magnum.' The outer surface of the base shows two oval flattened facets separated from one another by a deep vertical groove con- tinuous with the horizontal one on the superior surface of the base. These isolated facets are for articulation with the third metacarpal. The inner surface presents a single large facet rather hollowed in every direction for articulation with the outside of the base of the fifth meta- carpal. The rest of the base, the shaft, and distal extremity offer nothing peculiar for description. The outer surface of the shaft gives attachment to the second ' palmar ' and the third ' dorsal inter- osseous,' the inner to the fourth ' dorsal interosseous ' (figs. 65, 66, 69, 70). metacarpal of Little Finger. — The metacarpal bone of the little finger has upon the superior surface of its base a saddle- Pig. 72. shaped surface with the convexity running from before backwards and inwards for arti- culation with the ' unciform ' bone. Exter- nally the base has a single oblong, flattened facet for articulation with the fourth meta- carpal. Internally it projects into a rough low ridge for the attachment of the 'ex- tensor carpi ulnaris.' The only other pecu- liar feature noticed on the fifth metacarpal bone is that the posterior surface shows a single oblique line running from above down- wards and outwards ; the surface outside the line giving attach- ment to the fourth ' dorsal ' and third ' palmar interosseous ' muscles (figs. 69, 70). In well-marked bones there is a second •oblique line running from near the upper end of the ' oblique line ' downwards and inwards, and marking off a space internal to it for the insertion of the ' opponens minimi digiti.' Ossification. — Each metacarpal bone has a centre of ossifi- cation for the shaft and proximal end, which appears near the OUTEB SIDE. INNEE SIDE. BASE OF FIFTH EIGHT METACAEPAL. THE METACAEPUS 333 distal end about the eighth week of foetal life. Each also has an epiphysis at its distal end, of which the nucleus appears about the third to the fifth year. The metacarpal bone of the thumb, however, has its epiphysis at the proximal end, like the phalanges of the fingers. All unite to the shafts about the twentieth year. 6 * (Nor. Hum. Ost. No. 54.) Very often there is a distal epiphysis appearing in the metacarpal bone of the thumb about the eighth Fia. 73. Fia. 74. TOTJE DOKSAIi LNTEBOSSEI DBAWING FKOM THE MIDDLE LINE. THBEE PALMAR INTEBOSSEI DEAWING TOWARDS THE MIDDLE LINE. year, and an epiphysis at the proximal end of the second metacar- pal about the same time. Comparative Osteology. — In all birds excepting the extinct archaeopteryx the metacarpal bones are anchylosed together. (See the Separate Series in the Mus. Eoy. Coll. Surg.) Contrast the short metacarpal bones of the elephant with the enormously long ones of the horse or giraffe. 334 THE BONES OF THE FINGERS. (Plate LIV.) General Description. — Each finger consists of three bones, successively decreasing in size, and termed respectively the first, or proximal, the second, and the last, or third or ungual ' pha- langes.' The thumb has only two phalanges. A general description will suffice for all. The structure of each phalanx is precisely like that of the great long bones, and a longitudinal section through one of them would display the great thickness of the compact wall of the shaft. Considering the phalanges as ' long ' bones, we speak of then- shafts and their articular ends. The shafts are convex on the dorsal surface, and flat on the palmar ; on each side of this flat surface is a ridge for the attachment of the fibrous sheath (theca), which keeps the tendons in their places. First Phalanges. — The first phalanges are distinguished by their greater length, and by the shape of their metacarpal ends, which do not form strictly hinge-joints, but have concave oval surfaces, with the long diameters transverse, adapted for lateral movement as well as flexion on the heads of the metacarpal bones. In accordance with this lateral movement, we observe, on each side, a tubercle for the insertion of the interosseous muscles which produce it. The articular surfaces of the distal ends encroach more upon the palmar than on the dorsal surface, and are divided by a shallow groove into two condyles. On each side of the distal ends are tubercles and depressions for the attachment of lateral ligaments. The base of the metacarpal phalanx of the thumb is rough externally for the insertion of the THE BONES OF THE FINGERS 335 'abductor indicis ' and outer head of the ' flexor brevis pollicis,' and internally for the insertion of the ' adductor indicis ' and inner head of the ' flexor brevis pollicis.' Posteriorly the base shows a rough triangular depression for the insertion of the tendon of the ' extensor primi internodii pollicis.' Second Phalanges. — The second phalanges are shorter than the first, and are recognised by the shape of their proximal ends, each of which has two little concave surfaces, with an intervening ridge, encroaching more on the palmar than on the dorsal sur- faces, and so forming hinges, with the little condyles of the first phalanges. On each side of the palmar surfaces, close to the lateral borders and placed rather behind the middle of the shafts, are rough ridges for the insertions of the tendons of the ' flexor sublimis digitorum.' The first phalanges have only one articular surface at their proximal ends, and are thus distinguished from the second. The posterior surfaces of the second, third, fourth, and fifth present, close to the proximal articular surfaces, trans- verse ridges for the attachment of the ' extensor communis digit- orum ' tendons — that on the index finger attaching the ' extensor indicis ' tendon as well. Third Phalanges. — The last or ungual phalanges are the shortest. Each of their distal ends expands into a horse-shoe shape, smooth on one surface for the support of the nails, and rough on the other for the support of the pulp of the fingers. Anteriorly their bases are rough for the attachment, on the four outer fingers, of the ' flexor profundus digitorum,' and posteriorly the ' extensor communis digitorum,' with the ' extensor indicis ' on the index finger. The base of the last phalanx of the thumb presents anteriorly a large rough depression for the insertion of the 'flexor longus pollicis,' and posteriorly a rough transverse ridge for the insertion of the ' extensor secundi internodii pollicis.' Unequal Length of Fingers. — It has been asked, What are the advantages of the fingers being of unequal length ? Close them upon the palm, and then see whether or not they correspond. This difference in the length of the fingers serves a thousand purposes, to which the works of human art and industry bear ample testimony. 336 THE BONES OF THE FINGERS Ossification. — Each phalanx has two centres of ossification : one for the shaft and distal end, appearing about the eighth week ; the other for the proximal end, appearing from the third to the fifth year, and remaining an epiphysis till about the twentieth year. 70 (Nor. Hum. Ost. No. 54.) Comparative Osteology. — In the Separate Series in the Mus. Eoy. Coll. Surg, it will be seen that the elephant has five digits ; the elk four, viz. the 2nd, 3rd, 4th, and 5th ; the ox two, the 3rd and 4th ; the rhinoceros three, the 2nd, 3rd, and 4th ; the tapir four, the 2nd, 3rd, 4th, and 5th; the zebra and horse one, the 3rd. The flipper of the whale, which corresponds to the front limb, has no nails ; some of the digits have more than three phalanges. (See the round-headed whale, No. 2988 B, and the lesser fin- whale.) Bats (Cheiroptera) have their four ulnar digits very much elongated, forming the framework for the wing. At least three of these digits bear no nails. The hook at the top of the bat's wing is the thumb-nail. (See Sep. Ser. Mus. Boy. Coll. Surg., as well as Nos. 3383, 3419.) In the digitigrade Carnivora, as the tiger and cat, the sharp claws are firmly fixed into the ungual phalanges, and these are under ordinary circumstances bent backwards on to the back and outer side of each corresponding second phalanx by an elastic ligament, and are thus held out of the way as long as the flexor profundus digitorum remains at rest. When a cat pats you in play she only uses the flexor sublimis digitorum ; but when she claws you in anger she uses her flexor profundus digitorum, which flexes the ungual phalanx and brings down the claw. That which is commonly called the knee in the horse, is really the wrist. From this joint down to the foot extends the greatly elongated third metacarpal bone. In birds these fingers can be traced as forming the extremity of the wing. (See Sep. Ser. Mus. Boy. Coll. Surg.) The phalanges were very numerous in the Ichthyosauria. (Pal. Ser. No. 222, Mus. Boy. Coll. Surg.) SESAMOID BONES 337 SESAMOID BONES. (Plate LIV.) Position and Use. — These little bones are so called from their resemblance in size and shape to the grain ' sesamwm.' They are met with in the substance of tendons in the neighbour- hood of joints — the ' patella,' or ' knee-pan,' being the best ex- ample. Their use is to increase the leverage of the tendons. The thumb has two of these bones beneath its metacarpal joint, which increase the leverage of the ' flexor brevis pollicis.' We rarely find any in the fingers. Comparative Osteology. — Of all animals, the mole has the most remarkable apparatus of ' sesamoid ' bones. Its prodigiously strong digging feet are provided with many of them, which in- crease the leverage of the brachial muscles, and^enable the animal almost to swim through the earth. 338 GENERAL SURVEY OF THE SKELETON. A general survey of the human skeleton shows how admirably it is adapted to the erect attitude. Adaptation of the Skeleton to the Erect Position. — 1. When a man stands erect, an imaginary vertical plane (a b) supposed to fall through the top of the head would pass through the occipito-atlantoid, lumbo-sacral, sacro-iliac, hip, knee, and ankle joints ; in a word, through all the joints which transmit Fig. 75. the weight to the ground. This explains why a man can carry a weight on the top of his head easier than in any other way. Position of Foramen Magnum and Con- dyles. — 2. The foramen magnum and the condyles of the occiput are nearly horizontal (when the head is held upright) , and they are advanced almost to the middle of the base of the skull, and thus the head is nearly balanced on the cups of the atlas. The head has a slight tendency to drop forwards, but this is limited by the ligamentum nuchae. Contrast the position of the condyles in the human skull with that of the orang utan, in which the condyles are not only placed near to the back of the head, but obliquely, making an angle of 40° with the horizon. The lower we go in the scale, the greater is the contrast. In the horse, for ^J^^z instance, the plane of the condyles and foramen l» magnum is vertical. In this, and all other her- bivorous quadrupeds, the weight of the head is sustained by an enormously strong and elastic ligament (ligamentum nuchse, or GENERAL SURVEY OP THE SKELETON 339 •pack-wax), the strength of which is in proportion to the weight of the head and its tendency to drop. It extends from the lofty spines (withers) of the anterior dorsal vertebrae to the crest of the occiput. Direction of the Face. — 3. The face is placed perpendicularly under the cranium, so that the planes of the face and forehead are parallel, and this characteristic of the human face is well adapted for the erect attitude. If man went on all- fours, he would habitually see and smell nothing but the ground. As it is, the direction of the orbits is horizontal, and therefore gives the greatest range of vision ; and the direction of the nose gives the greatest range of smell. We are reminded here of the beautiful lines — Pronaque dum spectent animalia csetera terrain, Os homini sublime dedit, coelumque tueri Jussit, et ereotos ad sidera tollere vultus. Ovid, Metam. I. 84-86. Breadth of the Thorax. — 4. The thorax is much broader in the transverse than in the antero-posterior diameter. This great breadth of the chest is peculiar to man and the highest species of ape ; it throws the arms farther apart, and gives them a more extensive range ; besides which, it diminishes the tendency there would otherwise be in the trunk to fall forwards. Contrast this with the chest of quadrupeds, compressed laterally, and deep from sternum to spine, so that the fore legs come nearer together, and fall perpendicularly under the trunk. Curves of the Spine. — 5. The vertebral column gradually increases in size towards the base. It is curved, which makes it all the stronger, and better adapted to break and diffuse shocks : and these curves, waving alternately, distribute the weight in the line of gravity. This line passes through all the curves, and falls exactly on the centre of the base. Observe, moreover, the length and size of the spinous processes in the lumbar region for the origin of the ' erector spinas.' Sbape and Inclination of the Pelvis. — 6. The weight of the vertebral column is supported on a sacrum broader in pro- portion than in any other animal. The iliac bones are widely z 2 340 GENERAL SURVEY OF THE SKELETON expanded and concave internally ; they support the viscera and give powerful leverage to the muscles which balance the trunk. The whole pelvis is remarkably broad, and thus the base of support is widened ; and the plane of its arch so inclines as to transmit the weight from the sacrum (or crown of the arch) vertically on to the heads of the thigh bones : lastly, the deepest and strongest part of the socket for the thigh bone is in the line of weight : consequently, the joint is never more secure than in the erect position. With the broad and capacious pelvis of man, contrast the long and narrow pelvis of animals, which, instead of forming an angle with the spine, is almost in the same line with it. lower Limbs. — 7. In proportion to the trunk, the lower limbs of man are longer than in any other mammal, the kangaroo not excepted. Their great length prevents their being adapted ; for locomotion in any but the erect attitude. The femur has a long neck, set on to the shaft at a very open angle, so that the base of support is rendered still wider. The long shaft of the femur inclines inwards, bringing the weight well under the pelvis, which is obviously of great advantage in progression : and when the leg is extended, the femur can be brought into the same line with the tibia; thus the weight is transmitted ver- tically on to the horizontal plane of the knee joint, while the articular surfaces of the bones are expanded and give adequate extent of support. Contrast our long lower limbs with the short and bowed legs of the gorilla, chimpanzee, and orang utan. Watch attentively one of these three apes (the highest of the mammalia below man) in the act of walking ; you will find that he supports himself alternately on the right and left knuckles as well as on his feet. Feet. — 8. The foot of man is broader, stronger, and larger in proportion to the size of the body than in any other animal ; so that man can stand on one leg, which no other mammal can do. Its strong component bones form a double arch of exceeding elasticity, which touches the ground at both ends, and receives the superincumbent weight vertically on its ' crown.' The great bulk and backward prolongation of the os calcis at right angles GENERAL SURVEY OP THE SKELETON 341 to the tibia support the arch behind, and form a powerful lever for the great muscles of the calf, which raise the body in pro- gression, while the bones of the great toe are proportionately strong, and form the chief support upon which the body may be raised. Upper Limbs. — 9. We see, then, that the whole fabric of the skeleton is so adjusted as to exempt the upper limbs from taking any part in its support. These are kept wide apart by the clavicles, and their component joints admit of the freest range of motion. The twenty-seven bones at the extremity of each constitute those instruments of consummate perfection the 'hands, of which, even if a formal dissertation 71 had not been written, one might well forbear to speak, since they have such eloquence of their own. ' Nam ceeterse partes loquentum adjuvant, hse, prope est ut dicam, ipsse loquuntur : his poscimus, pollicemur, vocamus, dimittimus, minamur, supplicamus, abomi- namur, timemus ; gaudium, tristitiam, dubitationem, confes- sionem, pcenitentiam, modum, copiam, numerum, tempus, OBtendimus.' u Comparative Osteology- — Some of the vertebrata have bones which do not exist in man as such and are only represented in him by fibrous or cartilaginous tissue. Thus there is the bone of the heart, 'os cordis,' in the bullock— bos taurus— (No. 4), an example of the visceral system of bones or splanchno-skeleton. Another instance is the bony sclerotic of many fishes and some birds. This is well seen in a specimen from the sun-fish (No. 5). There was a ring of bone in the sclerotic of the extinct flying lizards (Pterosauria) , as well as in that of the Ichthyo3auria, the life-size models of which animals are seen at the Crystal Palace, a similar ring being present in modern lizards and chelonia. In the Phocidse, Trichechus, the walrus, and in many dogs, is found the ' os penis ' (Nos. 3906, 3907, 3908, 3909, and 3910, the last showing a fracture which has been repaired). Another is the ' interclavicula ' found in Eeptilia. It is often, too, present in birds, though it is in them confluent with the clavicles. In many of the Lacertilia a partially ossified or cartilaginous rod runs up from the symphysis of the ischia, and supports the front 342 GENBBAL SURVEY OF THE SKELETON wall of the cloaca, and is called the ' os cloacae.' In all pouched animals (Marsupialia), as in the kangaroo (Macropus major, Ost. Ser. Coll. Surg. Mus. 3699), and in the Monotremata (that is, in Echidna and Ornithorhynchus, Ost. Ser. Coll. Surg. Mus. 3952, 3964), are found the marsupial bones : ossifications, or often only chondrifications, of the internal pillars of the external abdominal rings. 343 OS HYOIDES. (Pi-ate XXXVIII.) Position and Use. — The os hyoides, so called from its re- semblance to the Greek letter upsilon, is situated between the larynx and the root of the tongue. It is suspended from the styloid processes of the temporal bones by the stylo-hyoid liga- ments, often partly ossified in man, and generally distinct bones in animals. When the neck is in its natural position the bone can be felt just below the lower border of the body of the lower jaw, and about an inch inside and behind the arch formed by that part of the bone. It supports the tongue, and gives attach- ment to the most powerful extrinsic muscles which move that organ. It is divided, for the sake of description, into the body, or front part, and a greater and a lesser cornu on each side. Body. — The ' body ' (basi-hyal part) is the thickest and strongest part of the bone. In the easy position of the head and neck it is on the same level as the ' intervertebral ' substance between the fourth and fifth cervical vertebrae. It is flattened from before backwards, and from above downwards, so as to pre- sent an anterior and a posterior surface, with superior, inferior, and two lateral borders. The anterior surface presents a general convexity forwards and upwards, and shows a prominent rough transverse ridge, situated nearer the upper than the lower borders. Crossing this at right angles in the middle line is a less prominent vertical ridge, and often at the point of junction there is a little projection, which is interesting as being a rudiment of the process to which is attached the lingual bone of animals, which runs into the sub- 344 OS HYOIDES stance of the tongue. The spaces enclosed by these ridges • are hollowed, rough, marked by a number of nutrient foramina, and give attachment to muscles, as shown in Plate XXXVIII. The posterior surface looks downwards and backwards, is concave in every direction, marked by small nutrient foramina, and separated from the epiglottis (one of the cartilages of the larynx) by fatty fibrous tissue and the thyro-hyoid membrane. A bursa is usually situated in the fibrous tissue immediately behind the ' body.' The superior border is rough, uneven, somewhat rounded, and gives attachment anteriorly to muscles (see plate) and posteriorly to the thyro-hyoid membrane. The inferior border is slightly concave downwards, and forms the lower limit of the muscular attachments on the anterior surface. The lateral borders show, in their upper two-thirds, oval and slightly rough depressions, to which the greater cornua are united by fibrous tissue. This fibrous tissue usually gets ossified after middle life. Frequently the oval surface is covered, in the adult state, by smooth articular cartilages and distinct synovial cavities, existing between the body and greater horns. The lower thirds of the lateral borders are sharp and rough for muscular attach- ment. At the angles between the superior and lateral borders are little smooth articular half-facets, looking upwards and out- wards, and which, with corresponding half- facets upon the upper borders of the greater cornua, form whole facets, covered in the recent state by cartilage and articulating by distinct synovial cavities with the lesser cornua. Greater Cornua. — The greater cornu ('thyro-hyal' part) projects backwards about an inch and a quarter, not quite hori- zontally, but with a slight inclination upwards, and terminates in a smooth, blunt, enlarged end. The horn presents an external surface looking forwards, outwards, and slightly upwards pos- teriorly, upwards, forwards, and outwards anteriorly. It shows a smooth groove running from its lower border posteriorly, forwards, and slightly downwards, to become continuous with the upper part of the anterior surface of the body. The surface gives attachment to muscles (see plate) , and the tendon of the ' digastric ' with the ' stylo-hyoid muscle ' lies against the groove in the easy position OS hyoides 345 of the head and neck. The inner surface is smooth, presents & sinuosity corresponding to the twist of the external surface, and is covered by the thyro-hyoid membrane. The upper border is sharp and attaches the thyro-hyoid membrane. The lower border is sharp posteriorly, broad and rough anteriorly, lies in a plane external to the upper border, and gives attach- ment to a muscle. The posterior extremity is rounded, swollen and smooth, and gives attachment to the lateral thyro-hyoid ligament. The anterior extremity shows a small half-facet above, for articulation with the lesser horn, and a large oval facet below for union with the similar facet already described as existing upon the lateral border of the body. Lesser Cornua. — The lesser cornu (' cerato-hyal ' part) is not much larger than a barley-corn, and projects upwards and back- wards from the upper end of the junction of the body with the greater horn. It varies in size in different persons and in the same bone on opposite sides. Its apex gives attachment to the stylo- hyoid ligament, and its base articulates, by a complete synovial joint, with the body and greater horn, and is freely movable. It gives attachment to muscles as shown in the plate. Ossification.— The bone is ossified from five centres — one for the body and one for each of the four cornua. The body and greater cornua begin to ossify in the last month of foetal life, the lesser cornua in the first year after birth. The greater cornua are usually ossified to the body after middle age, and the lesser ones sometimes in advanced age. Comparative Osteology. — The posterior surface of the hyoid bone is concave from side to side and from above downwards. This concavity is characteristic of the higher mammalia. In the gorilla it will lodge the tip of the finger, while in the howling monkey, Mycetes laniger, it develops into a sac large enough to hold a pigeon's egg. Notice a remarkable anterior projection from the front of the body of the hyoid bone of the horse, seen also more or less in many other animals and especially in birds. (Sep. Ser. Mus. Boy. Coll. Surg.) PLATE LVII. Malleus... Incus MeWbrana iympani Kfrl. deiTcular canals tube. Diagram of the Ear. H ,0pe n i n§ into Mastoid cell 3 . Jerestra rotunda. ^^P ; *&^? ^^&»L. ' fenestra, ovabs. JHHkSJMrs .Ca.na.1 forTJenso'-r. tympani Eustachian tiibe Groove for ICembran a tympani ioramen chordae...'' Pyramid ■f o ■ Stapedius. Preparation to shew inner wall of tympanum. Fr, '°m nature. Drawn on Stone "by T. Godart Printed tyWestjNe-wmaiii. Co. PLATE LVIH, Horizo-ntal canal Fi|.2. Pyramid. Fenestra ovalis. Canal for tensor tympani m. Fenestra rotunda- Promontory. Aq.Fallopii for facial nerve. Fjiramin a for n erves to utri culu s & ant.ampull ce. F.fornerves to sacculus. F. for blood-vessels. F.for nerve to post. ampulla. F.foT nerves to cochlea-. Grooves for tympanic plexus. Outer wall of meatus aud.int. x 2 cham . Inner wall of tympanum, x 2oliam. Fig. 3. <■■ ^Processus gracilis. 1 \ Pr.lorevis. v. Art. surfaces. « I V Mairubrium . Capitulwm . Malleus.ant.surfae, %3> Bones in their natural relation to one another. O.ssicula auclitus. x 4 diam. Fig.5 Pr.longus Os oroiculane. InCUS, ant. surface. \Z": 1' ^J^J-Head. \W$ : ' (_£«U/ Insfofstap 3 \/ Post.crus. Base, Stapes. Fi|.*. Ant. semicircular canal. / Common canal. Post. s. canal. / tk X Bony labyrinth. X 2d.»m. C.Stewart olel.ajiriat. RIGHT EAR. West, Newman &Co.lith. NOTES. 1. Dr. Stark, 'Edin. Med. and Surg. Jour.,' April 1845 ; Nekton, 'Ele- ments de Pathologie,' vol. i. p. 636. 2. Berzelius's ' Analysis of Bone.' 3. Dr. Bostock's ' Analysis of Eickety Bones.' 4. Liebig's ' Letters on Chemistry,' p. 522. 5. Gregory's ' Mechanics,' vol. i. c. 5. 6. Bishop ' On Deformities,' 1852, p. 14. 7. ' Outlines of Osteology,' p. 368. T. Ward. 8. ' Lectures on Surgical Pathology.' Sir J. Paget, F.R.S. 9. Curling, ' Medico-Chir. Trans.' vol. xx. 10. Cruikshank, ' Anatomy of the Absorbent Vessels,' 1790, p. 198. 11. Budge, ' Archiv f. Microsc. Anatomie,' bd. 13. 12. Dr. Clopton Havers, an English physician of the seventeenth century, was the first to describe these canals. 13. From a preparation in the museum at St. Bartholomew's Hospital. 14. Discovered by Mr. Queckett. 15. First described by Domenico Gagliardi, Professor of Medicine at Eome in the seventeenth century. Anatomie Ossium novis inventis illustrata. Boms, 1689, in 8vo. 16. Mr. Queckett. 17. Mr. Bransby Cooper. 18. See ' Catalogue of Historical Series,' Mus. Boy. Coll. Surg., vol. i. plate viii. fig. 11. 19. 'Philosoph. Trans.' for 1736, vol. xxxix. 20. Stanley, ' Diseases of the Bones,' p. 108. 21. ' Callus ' is the term applied by the old surgeons to the materials by which fractures are repaired. 22. Hyrtl, ' Topog. Anatomie.' 23. Guthrie, ' Commentaries on Surgery,' 6th edition, p. 374. 24. Dr. Leach and others, who have examined the immense collection of crania in the Catacombs at Paris, have remarked that the number of adult skulls in which the frontal suture remained unobliterated was about one in eleven. 25. Fallopius was a distinguished Italian anatomist, born 1523, died 1563. 26. This name was given to it by Galen, who thought that it secreted the 'pituita,' or mucus, and that this passed down into the throat through the small foramina which are often found at the bottom of the fossa (' De usu partium,' lib. ix. cap. 1). Its functions are not even yet understood ; it is gene- 348 NOTES rally classed as a ' ductless ' or 'vascular gland,' along with the spleen and thyroid body. 27. In some skulls, in which the malar bone does not enter into the com- position of the spheno -maxillary fissure, the sphenoid meets the superior max- illary bone. In such exceptional skulls the sphenoid would be connected with seven bones of the face. 28. Sometimes there are two openings, separated by the thin plate (unci- form process) which descends from the ethmoid bone. 29. Blandin (' Anat. Topog.' p. 44) relates a case in which a tumour, originating in the antrum, made its way into the zygomatic fossa, and caused a swelling in the temple. 30. Nathaniel Highmore was an English anatomist, born 1613, died 1684, who wrote much about the diseases of the antrum. He did not discover the antrum, for it was known to Galen as the ' sinus maxillaris.' 81. ' Commentaries,' p. 528. Guthrie. 32. See a curious case by Catlin, ' Trans. Odontolog. Soc' vol. ii. 1857. 33. Drake's ' System of Anatomy,' 8vo. 1707. 34. ' Dental Anatomy,' p. 179. Tomes, 1876. 35. This part, in man, was first pointed out by the poet Goethe. 36. For the most recent investigations concerning the ' Formation and Early Growth of the Bones of the Human Face,' see a very interesting and elaborate paper by Mr. G. W. Callender in the ' Philosoph. Trans.' for 1869. 37. Jarjavay, ' Anatomie Chir.' t. ii. p. 61. 38. Skilful as he was, Hippocrates once mistook a natural suture of the skull for a fracture, and was afterwards so ingenuous as to leave his mistake on record. On this, Celsus observes : ' A suturis se deceptum esse Hippocrates memoriae prodidit, more scilicet magnorum virorum, et fiduciam magnarum rerum habentium. Nam levia ingenia, quia nihil habent, nihil sibi detrahunt : magno ingenio, multaque nihilominus habituro, convenit etiam simplex veri erroris confessio ; preecipueque in eo ministerio quod utilitatis causa posteris •traditur, ne qui decipiantur eadem ratione, qua quis ante deceptus est.' (Liber viii. cap. iv.) 39. Broca, ' Ost^ologie du Crane,' 1875. 40. The old anatomists call this the ' additamentum suturse lambdoidalis.' This old name as well as others mentioned in the text, e.g. ' coronal,' ' sagittal,' and ' lambdoid,' are gradually falling into disuse, and giving place to more appropriate terms, derived from the bones connected, as ' inter-parietal,' ' fronto-parietal,' etc. 41. ' Prognathous ' signifies ' with prominent jaws.' 42. These bodies are developed from the ' arachnoid ' or serous membrane investing the brain, beneath the ' dura mater,' which they perforate, and thus come to press immediately on the bony vault of the skull. Vide Quain's ' Anatomy,' vol. ii. p. 379, 9th edition. 43. Except in cases where the sphenoid and superior maxillary come into contact and exclude the malar. (See note, 27.) 44. Craniology is nothing new. An Italian poet in the age of Dante writes : — NOTES g^g Nel Capo son tre cells, Et io dir6 di quelle, Davanti e lo intelletto E la forza d' apprendere ; In mezzo e la ragione E la discrezione, Che scerne bnono e male. Indietro sta con gloria La valente memoria, etc. etc. 45. The above is taken, with but slight alteration, from the Osteological Catalogue, Part I., of the Museum of the Royal College of Surgeons, by kind permission of the Council. 46. Cuvier, ' Eecherches sur les ossemens fossiles,' 1822, vol. ii. p. 231. . 47. See a case of this kind, with a drawing, in ' Med.-Chir. Trans.' vol. xxxi., by Sir James Paget. 48. 'Natural Theology.' Paley. 49. The inferior tubercles are alluded to by Monro, ' Anatomy of the Human Bones,' 1726 ; also by Soemmering, ' De Corp. Human. Fabrica,' 8vo. 1794. The superior as well as the inferior tubercles are developed as little epiphyses with distinct centres of ossification, and unite to the rest of the vertebrae about the twenty-fifth year. 50. Bolli n and Magendie make it sixteen times -stronger. 51. It is not easy to say why this was called the ' sacred bone ' (Upbv ocrreov). The reason generally assigned is, that it was the part used in sacri- fices. The following is another : — It appears the Jewish Eabbis entertained a notion that this part of the skeleton, which they call the ' luz,' would resist decay, and become the germ from which the body would be raised. Hence Butler has it — ' The learned Babbins of the Jews, Write there's a bone, which they call " Luz," I' the rump of man of such a virtue No force in Nature can do hurt to : Therefore at the last great day All th' other members shall, they say, Spring out of this, as from a seed All sorts of vegetals proceed ; From whence the learned sons of art " Os sacrum " justly call that part.' Htjdibras, part hi. cant. ii. 52. It is not uncommon to meet with six sacral vertebrae. Sometimes there are but four. The first sacral may be detached from the lower sacral vertebras. Again, the last lumbar may be anchylosed to the sacrum by its body, or to the ilium by one or both of its transverse processes. This last condition is frequent among the higher monkeys. 53. Dr. Ramsbotham's ' Principles and Practice of Obstetric Medicine and Surgery,' 5th edition, p. 9. 54. Some authors state the reverse. But Albinus (' De Sceleto ') says 350 NOTES truly: 'Sacrum feminis latius, per longitudinem rectius, infra non seque inourvatum in priora.' 55. In his lectures ' On the Comparative Anatomy of Man,' 1877, Professor Flower gives 61° as the mean subpubic angle in men, 80° in women. 56. The brothers Weber, ' Mechanik der mensch. Gehwerk.,' Gott. 1836. 57. See ' Medical and Surgical Landmarks,' by the Author, 3rd edition, 1881. 58. Concerning the bearing of Osteogeny on forensic medicine, see ' MSde- cine legale,' by M. Orfila. 59. We are indebted for this outline to Mr. Keetely, late Assistant-Demon- strator of Anatomy at St. Bartholemew's Hospital. 60. For further 'practical remarks on this subject, see ' Anatomy and Surgery of the Human Foot,' by J. Hancock, 1873. 61. Professor Flower, F.B.S., ' Fashion in Deformity,' p. 67 ; also Pro- fessor Marshall, F.E.S., ' Anatomy for Artists,' p. 45. 62. The nucleus at the margin of the glenoid cavity is not to be regarded as an epiphysis, but only an occasionally present scale, like those sometimes found on the coracoid and having no morphological bearing, and scarcely worthy of notice. Professor Humphrey, F.K.S. 63. On the supra-condyloid foramen read Hyrtl, ' Topog. Anat.' vol. ii. p. 283 ; also Gruber, ' Canalis supra Condyloideus humeri,' Mem. de l'Aead. Imp. de St. PStersbourg, 1859, p. 57 ; and Professor Struthers, ' Edin. Med. Jour.' 1848. 64. The radius of the skeleton of the gorilla in the Museum of the College of Surgeons is extremely arched. The power of his arms is enormous. 65. So called from its fancied resemblance to the letter Sigma, which the Greeks originally used in the form of the English C. 66. Very often the coronoid process gives origin to a second head of the flexor longus pollicis. 67. Mr. Liston, ' Practical Surgery.' 68. Mr. Lockwood, Demonstrator of Anatomy at St. Bartholomew's Hospital. 69. To the rule stated there are certainly exceptions. I have seen pre- parations clearly showing separate epiphyses at the bases of the metacarpal bones of the fore and middle fingers. I have also seen a separate epiphysis at the head of the metacarpal bone of the thumb. Whether these additional epiphyses be normal or exceptional, they always unite the first to the shaft, in accordance with the direction of the artery of the marrow, which in the metacarpal of the thumb runs towards the head, in those of the fingers towards the base. 70. The centre of ossification in the shaft of every long bone appears in its middle, excepting in the case of the ungual phalanges, which commence to ossify at their distal ends. 71. ' The Hand, its Mechanism and Vital Endowments, as evincing Design.' London, 1834, by Sir Charles Bell, F.E.S. 72. Quintilian. INDEX. ACE PAGE ACETABULUM 188 ■fi Acromion 290 Air-cells in bone 8 Alveolar process 95 Ampullse 69 Analysis of bones 4 Anatomical neck of humerus 295 Animal matter of bone 3 Anterior clinoid process 74 Antlers 56 Antrum of Highmore 94 Aquseductus cochleae 66 Fallopii 65 vestibuli 63 Arch, carpal 318 of foot 231 Arches of foot 257 Articular arteries 10 Astragalus 232 Atlas 157 Axis 158 "DASILAE process 38, 137 -" Bicipital groove of humerus... 298 Blood-supply of bones 10 Bones, air-cells in 8 classification of 6 composition of 2 elasticity of 6 hollow shaft of 7 microscopic structure of 13 naked-eye structure of 7 ■ nomenclature of 3 CEL PAGE Bones, properties of 5 strength of 5 uses of 2 OALCANEUM 236 Callus 35 Callus provisional 35 Canal, anterior dental ;.- 93 anterior palatine 88,133 carotid 65 infra-orbital 93 of Huguier 59 posterior palatine 91, 11 pterygopalatine 134 malar 103 semicircular 69 „ membranous 69 vertebral 169 Vidian 81 Canaliculi of bone 20 Canals, accessory palatine Ill Cancellous tissue 9 Canine fossa 92 Carotid canal 62 Carpal arch 318 Carpus 317 Cartilages, costal 271 Cavity, sigmoid, of radius 306 „ of ulna 309 Cells, ethmoidal 83 frontal 49 mastoid 60 maxillary 94 352 INDEX CBL PAGE Cells, palatine Ill sphenoidal 76 Clavicle... 280 curves of 280 Coccyx 177 Cochlea 70 membranous 70 Condyloid ridge of humerus, external 298 „ „ „ internal 297 Coraeoid process 291 Cornua sphenoidalia 75 Coronoid fossa 299 process of lower jaw 120 ulna 309 Costal cartilages 271 Cranial fossae 129 Cribriform plate 83 Cristigalli 83 vestibuli 96 Cuboid bone 241 Cuneiform bone of carpus 322 bones of tarsus 242 Cupola 70 Cuvier on fossil bones 153 DENTAL foramen 119 Digital fossa 202 Diploe 11, 106 Diploic veins 106 TAAB, anatomy of 69 -L' Earthy matter of bones 3 Endosteum 12 Ensiform cartilage 265 Epipteric bone 72 Ethmoid bone 83 Ethmoidal foramen, anterior 85 „ „ posterior 85 notch 53 Eustachian tube 66 T^ACE, bones of 90 -*- Falx cerebri 84 Femur 198 Fenestra ovalis 67 rotunda 67 FEA PAGE Fibula 22S- First rib 269 Fissura Glaseri 58 Fissure, sphenoidal 80, 141 spheno-maxillary 141 Floating ribs 270 Fontanelles 47 Foot, arches of 257 as a whole 255 bones of 230 mechanism in walking 258 Foramen csscum 52 condyloid, anterior 137 „ posterior 137 ethmoidal, anterior 85 „ posterior 85 infra-orbital 92 magnum 38 mentale 121 obturatum 188- occipital 137 opticum 77 • ovale 188 parietal 127 rotundum 78- spheno-palatine 110- spinosum 78 stylo-mastoid 64 supra-orbital 49 Vesalii 78. Fossa, canine 92 coronoid 299 digastric 60 digital 202 iliac 190 jugular 65 mental 116 olecranon 299 pituitary 73. pterygoid 80 scaphoid 81 spheno-maxillary 138 temporal 127 zygomatic 138 Fossa?, nasal 141 of skull 129 Fovea hemielliptica 69 hemispherica 69- Fractures, repair of 35 INDEX 353 FEO Frontal bone 48 sinus 49 GLASERIAN fissure 58 Glenoid cavity 57, 285 Glenoid fissure 58 Groove, bicipital, of humerus 296 optie 74 Growth in length of bones 33 Gumboil 96 HAMULAK process 81 Hamulus of cochlea 70 Hamulus of lachrymal bone 108 Hand, bones of 317 Haversian canals 13, 16 interspaces 15 lamella? 14 system 14 Helicotrema 70 Hiatus Fallopii 62 Highmore, antrum of 94 Hollow shaft of bone 7 Horns 56 Huguier, canal of 59 Humerus 295 Hunter's experiments with shots... 33 Hyoidbone 343 TNCUS 68 -^ Inferior maxillary bone 116 Inferior spongy bone 112 turbinated bone 112 Infra-orbital canal 92 foramen 92 Infundibulum 50, 87 Iliac fossa 190 Ilium 180 Innominate bone 180 Intervertebral fibro-cartilage 167 Ischium 180 TAW, buttresses of upper 145 " Jaw, joint of 124 MYB PAGE Jaw-bone, lower H6 upper 90 Jugular foramen 136 f °ssa 65 T ABYBINTH, membranous 69 J -' Lachrymal bone 107 Lachrymal fossa 54 groove 97, 107 process 113 sac 97 Laeume of bone 14 Lamina, spiralis ossea 70 Levers, bones act as 2 Linea aspera 205 Lower extremity, bones of 180 Lymphatics of bone 13 MADDEB, experiments with 32 Malar bone 102 Malar canals 103 Malleolus externus 227 internus 220 Malleus 68 Manubrium 262 Marrow, artery of 11 red 10 yellow 9 Mastoid process 59 Maxillary sinus 94 Meatus auditorius externus 61 internus 63 of nose 86, 142 Median crest of palate bone 109 MeduUary artery 11 membrane 12 Membrana tympani 62 Metacarpus 327 Metatarsus 246 Microscopic structure of bone 13 Milk dentition 95 Modiolus 70 Muscles in front of the spine 278 of back 275 „ superficial 275 of the back of the neck 277 Myeloid cells 10 A A 354 INDEX NAS PAGE NASAL bone 105 Nasal duct 97 Nasal fossae 141 process of sup. maxillary bone 96 slit 8.1 spine, anterior 99 ,,. posterior 109 suture 106 Neck of humerus, anatomical 295 „ surgical 297 Necrosis 34 Nerves in bone 12 Neuralgia of bone 13 Nose, meatus of 142 posterior openings of 133 septum of 143 Notch of acetabulum 188 intercondyloid 207 ischiatic, greater 184 „ lesser 185 sigmoid 309 Notches in sternum 264 Nutrient artery of bone 11 OCCIPITAL bone 36 Olecranon 308 Olecranon fossa 299 Optic foramen 77 groove 74 Orbital wings of sphenoid 77 Orbits 139 Os calcis 236 Os hyoides 343 Os innominatum 180 Os magnum 324 Os orbiculare 68 Os planum 86 Os unguis 107 Ossification 23 Osteoblasts 27 Osteology, interest of 1 PACCHIONIAN bodies 46, 127 J- Palate bone 108 Parietal bone 44 Paroceipital process 40 Patella 213 EEP PAGE Pelvis, arch of 194 axes of 195 brim of the 193 diameters of 196 lever of first order 193 obliquity of 195 sexual differences of 197 Periosteum 12 blood-vessels of 12 value of 33 Perivascular lymphatics 13 Phalanges of fingers 334 of toes 254 Phosphate of lime 4 Pisiform bone 322 Pituitary fossa 73 Pre-maxillary bones 99 suture 99 Process, acromion 290 alveolar 95 basilar 137 clinoid 74 coracoid 291 coronoid, of lower jaw 120 „ of ulna 309 hamular 81 lachrymal 113 malar 100 mastoid 59 nasal 96 palatine 98 post-glenoid 58 pterygoid 80 sphenoidal 112 styloid 64 „ of radius 306 ,, of ulna 314 unciform 86 vaginal > 77 Promontory of tympanum 68 Pterygoid process 80 Pterygo-palatine canal 77 Pubes 180 Pyramid 67 DADIUS 303 -" Radius, rotation of 316 Eepair of f raotures 35 INDEX 355 EIB PAGE Eibs, general characters of 267 Rickety bones 4 Bidge, deltoid 298 Mdges, intertrochanteric 203 condyloid of humerus 297 Bostrum of sphenoid 76 SABKE-cuts 34 Saccule 69 Sacro-iliae symphysis 176 Sacrum 174 Scalatympani 70 vestibuh" 70 Scaphoid bone of carpus 320 „ of tarsus 240 fossa 81 Scapula 284 spine of 288 Sella Turcica 74 Semicircular canals 69 „ membranous ... 69 Semilunar bone 321 Septum of nose 143 Sesamoid bones of hand 337 „ of foot 255 Sigmoid cavity of radius 306 Sinus, frontal 50 inferior petrosal 131 lateral 131 superior petrosal 131 Skeleton, general survey of 338 Skull as a whole 125 base of 132 bones of 36 buttresses of 145 -cap 126 general observations on 144 lever of first order 144 locking of bones of 144 power of resisting shocks 145 sexual differences 146 tables of 144 Sphenoid bone 73 lesser wings of 77 rostrum of 76 Sphenoidal fissure 141 process 112 TOE PAGE Spheno-maxillary fossa 138 fissure m Spheno-palatine foramen 112 s P ine 154 curves of 157 ethmoidal 74 extent of motion of 167 of pubes 183 of scapula 289 Spines of ilium, anterior and post'. 182 Spongy bones 86 Squamosal bone 57 Stapes 68 Stature of individual 33 Sternum 262 Styloid process of radius 306 „ of ulna 314 Superciliary ridge ' 49 Superior maxillary bone 90 Surgical neck of humerus 297 Suture, basilar 74 coronal 54 zygomatic 71 Sutures of skull 125 Symphysis of lower jaw 116 pubis 183 sacro-iliac 176 TABLES of skull 144 Tarsus, bones of 230 Tarsus, tunnel of 234 Teeth 95 fangs of 96 milk 95 of lower jaw , 118 of upper jaw 95 permanent 95 sockets of 95 Temporal bone 56 „ mastoid portion of... 59 „ petrous portion of... 61 „ squamous portion of 57 Tendo oculi 98 Thorax as a whole 2 72 general description of 261 Tibia 216 Toes, relative length of 259 356 INDEX PAGE' Torcular Herophili 41 Trapezium 323 Trochanters, major and minor 201 Tubercle of radius 304 Tubercles of dorsal and lumbar ver- tebra? 164 Tuberosities of femur 208 of humerus, greater 296 „ lesser 296 of tibia 217 Tuberosity of ischium 190 Tunnel of tarsus 234 Turbinated bones 86 bone, sphenoidal 75 Tympanum 67 TTLNA 308 'J Unciform bone 325 Unciform process 86 Upper extremity, bones of 280 Utricle 69 ZYG PAGE VAGINAL processes 77 Vertebra, constituent parts of 154 Vertebrae, cervical 156 coccygeal 177 dorsal 160 lumbar 163 sacral 174 Vertebral canal 169 column 154 „ shape of 168 „ strength of 166 groove 169 Vestibule '. 69 Vidian canal 81 Vomer 114 WALKIN G, mechanism of foot in 258 "Wormian bones 88 I ZYGOMA 57 Zygomatic fossa 138 PRINTED BY SP0TTISW0OKE AND CO., NEW.STBEET SQUARE LONDON No. 3. 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