Veterinary anatomy, histology, physiology and comparative anatomy

Preface

Only those who, as students, are compelled to review at the close of the graded course, the first and second year studies can appreciate the difficulties encountered in wading through the standard textbooks on these subjects. Noticing the efforts of our best students toward relief by taking notes of lectures a,nd having them printed at a cost far above their actual value, I was induced to assemble in one volume the essentials of these allied branches. As this work is not intended to supplant any textbook, but only as a convenient reference in reviewing, all unnecessary details and illustrations have been omitted. In anatomy and comparative anatomy I have followed Strangeway, Chauveau and Grey. In histology, Bohm, Davidoff and Huber; and in physiology, Smith, Paton and Kirk.

J. HANSON.

ERRATA.

Page 5 Line 24 should follow line 3 9. 28 " 2 for striate, read striae. 31 " 24 " branchial, read brachial. 31 " 35 " flexor, read extensor. 51 " 13 " medium, read median.

PHYSIOLOGY, OOIVIPAKATIVE ANATOMY

CHAPTER I. ANATOMY OF THE SKELiETON

Bone tissue appears to the eye in two forms:

1. Compact; hard and dense, forming the external shell of all bones and the mass of the shaft of long bones.

2. Cancellated; spongy structure, forming the inner mass of all, except the shaft of long bones.

Bones are classed as long, flat or irregular.

1. T-iong; acting as pillars of support and levers of motion; in the limbs.

2. Flat; enclosing cavities and protecting important organs.

' 3. Irregular, where great strength is required, as the vertebrae, etc.

Covering: — The periosteum; a tough canvas-like membrane, forms the external covering of all bones; consisting of an external fibrous layer and an inner vascular, bone-forming layer, the osteogenetic membrane.

Marlving: — Eminences and depressions may be articular or non-articular.

1. Articular Eminences.

A head is a rounded prominence separated from the body by a constricted part, the neck.

A condyle is a ovoid prominence.

A trochlea is a condyle having a pulley-like surface.

A fa^^et is a small articular surface, may be a depression.

2. Non-articular eminences.

A spine is a pointed prominence.

A tubercle is a small blunt one.

A tuberosity is a larger blunt one.

A trochanter is a large, strong prominence.

A crest is a rough ridge, line or border.

3. Articular depressions.

A glenoid cavity is a shallow depression.

A cotyloid cavity is a deep depression.

4. Non-articular depressions.

A foramen, aqueduct, canal or meatus is a depression passing through all or part of a bone.

A notch, fissure, cleft or groove is a depression in the border or surface of a bone; two of which in contiguous bones may form a foramen, canal, etc.

A fossa is a depression, rough for attachment of muscles or ligaments.

A hiatus is a depression leading to two or more foramina.

Tlie Skeleton: — 1. Axial; in which we describe the skull, vertebral column, sternum and ribs. The skull, as the cranium, or that part enclosing the brain, and the remaining bones as the face.

Cranium: — 1. The occipital; supero-posteriorly is the crest from which the mastoid ridge descends on either side; below the crest the tuberosity, a^ depression on either side and the foramen magnum below. Externally the condyles, stylo-condyloid notches and styloid processes; in the notches the condyloid foramen The basilar process extends forward below the foramen magnum, on fts upper surface, the basilar fossa, on the lower surface the basilar fissure; the cupola is a depression on the inner surface below the crest.

2. Parietal, uniting in the median line, has on the inner surface a ridge, the crpst, which terminates posteriorly in the ossific tentorium, and in the crest is the longitudinal groove.

3. Frontal; forming the forehead, uniting in the frontal suture; also form-

VETEKINARY ANATOMY, HISTOIX)GY, ing part of the orbital and temporal fossae; the external orbital process extends outward to join the zygomatic arch, in its upper border the supraorbital foramen; the internal orbital process forms part of the orbital fossa, has a large notch for the orbital plate of the sphenoid, above which a depression lodges the lachrymal gland; and a small notch which helps to form the internal orbital foramen.

4. Temporal.

(a.) The squamosal portion; projecting upward and backward is the zygomatic spine; projecting forward the zygomatic process; on its under surface the glenoid cavity, in front of this the condyle, posterior to it the anterior mastoid process in the base of which is the mastoid foramen; on the inner surface is a groove which, with a like groove in the parietal, forms the parieto-temporal conduit.

(b.) The petrosal; lodges the essential part of the organ of hearing; on the inner surface is the internal auditory meatus, which leads to the aqueduct of Fallopius and the internal ear; near it is the aqueduct of the vestibule, a narrow slit. The mastoid ridge separates the posterior from the external surface; in front of it is the posterior mastoid process; crossing the ridge is the mastoid fissure. Externally is the external auditory meatus, below it the hyoid process, stylo-mastoid foramen and the mastoid protuberance. Projecting forward the styloid process; above which is the styloid foramen and below it the opening into the Eustacian tube.

5. The sphenoid has two center pieces which form the body, and two pairs of wings. On each side of the body is the pterygoid process, in the base of which is the pterygoid foramen; winding around the base is the Vidian fissure. In front of this process is the orbital hiatus and optic foramen; and in the body a notch which helps to form the internal orbital foramen. On the upper surface of the body is the pituitary fossa, in front of this the olivary process and optic hiatus; on each side of this surface two grooves, the inner is the cavernous, the outer the sphenoidal, fossa; terminating in the foramen lacerum orbitale and rotundum. On each side of the body anteriorly a cavity, the ethmoid fossa. The posterior border of the wing bounds the foramen lacerum basis cranii, has an inner notch, the carotid, and an outer, the inferior maxillary.

6. The ethmoid; separated from the nasal fossae by the cribriform plates, has a prominence posteriorly the crista galli process and laterally the ethmoid cells.

Tlie Face: — 1. Nasal, the smooth upper part of the inner surface is a gutter the superior nasal meatus, below this a ridge to which is attached the superior turbinal; the anterior extremities unite to form the nasal peak.

2. The superior maxilla; on the external surface the maxillary spine, above it the infraoirbital foramen; the palatine process forms the floor of the nasal fossae and the roof of the mouth; along the outer border of the roof is the palatine groove, posteriorly the palatine foramen; externally the molar alveoli, behind these the tuberosity, in front of them the diastema; in the posterior border the maxillary hiatus leading to the superior dental, spheno-palatine and palato-maxillary foramina.

3. The premaxilla; in the anterior border the incisor alveoli, in the inner border the incisive foramen, and projecting backward the palatine process.

4. The malar; forms the antero-inferior part of the orbit, passing backward externally the zygomatic process and ridge.

5. The lachrymal; in the supero-anterior part of the orbit, the upper border is the orbital ridge in the middle of which is the lachrymal tubercle; the posterior surface has the lachrymal fossa which lodges the lachrymal gland anfl leads to the lachrymal canal.

6. The palatine; placed beneath the posterior nares; in the middle is the spheno-palatine foramen; between the superior and nasal surfaces the crest; on the inferior surface which forms the arch, is the staphyline groove and a groove which helps to form the palatine foramen.

7. The pterygoid; on the inferior surface of the sphenoid, terminates anteriorly in a blunt process, the summit; the posterior extremity forming the Vidian canal.

8. The vomer; forming the postero-inferior part of the nasal septum, has a gfoove in its upper border lodging the cartilaginous part.

9. The turbinals; the upper attached to the nasal, the lower to the superior maxilla, divides the fossa into superior, middle and inferior meatuses.

10. The inferior maxilla; has on the posterior the condyle, in front of this the coronoid process, and between these the sigmoid notch. In the upper border the molar alveoli, the interdental space, and anteriorly the incisor alveoli; in the outer surface the mental foramen, in the inner surface the inferior dental, leading to the dental canal.

11. The hyoid series; the body has the spur process buried in the tongue; two heel processes articulating with the thyroid cartilages of the larynx; two cornicula rising from the body to the cornua; and the cornua which extend backward to articulate with the hyoid process of the petrosal bone.

The Veitebral Column. <7^3. Ijumbar7^ijr segrherits, by long transverse processes ; the fifth by one"! A vertebra is one segment, described as true or false vertebra.

1. A true vertebra has typical parts retained through life and does not unite with others by ossification in health. The typical parts of a true vertebra are: — Body, arch (pedicles and laminae) notches, and spinous, transverse and articular processes.

2. A false vertebra lacks some of these parts or becomes united to others by ossification.

Regions: — 1. Cervical, seven segments; known by greater size and length of body, and articular processes. Special segments:

First. By glenoid cavities and rudimentary body.

Second. By the odontoid process and prominent neural spine.

Sixth. By short body and three tuberosities on transverse processes.

Seventh. By absence of foramen in transverse process, and by facet for head of rib.

2. Dorsal, eighteen segments; by long neural spines and facets for ribs, articular facet on each transverse process; sixth, by two facets on each transverse process.

4. Sacral, five segments in the young, one in the adult; by union by ossification.

5. Coccygeal, thirteen to twenty; by rudimentary form. Thorax: — Enclosed by the dorsal vertebra, ribs and sternum.

1. The sternum; composed of six segments, united by cartilage in the young, by ossification in the adult; has on each side eight facets for articulation of the true ribs; prolonged anteriorly by the cariniform, posteriorly by the ensiform, cartilage.

2. The ribs; eighteen on each side, eight of which are attached to the sternum by their cartilages, forming true joints, and known as true ribs; the ten posterior ribs are attached to the sternum by their cartilages overlapping each other, and known as false ribs. On the proximal extremity is the head having two facets separated by a groove; below this the neck; posterior to the neck the tubercle with a facet for articulation with the transverse process of the vertebra; below the neck the angle; a groove in the posterior border for the blood vessels and nerves and a facet in the distal extremity for the costal cartilage. Pectoral Llnib.

1. Scapula; two surfaces, three borders, three angles; on the outer surface the spine, tubercle, antea and postea spinatus foss%; on the inner surface the subscapular fossa and nutrient foramen; on the anterior border the coracoid process, below it the neck and on the inferior angle the glenoid cavity; attached to the upper border the cartilage of prolongation.

2. Humerus; on the proximal extremity the head, neck, internal trochanter with three prominences, the external with two, and between the trochanters the bicipital groove. The distal extremity is divided by a groove which terminates in the coronoid fossa in front and the olecranon fossa posteriorly; on the inner side a condyle, on the outer a trochlea; extending upward posteriorly the epicondyle and epitrochlea. The shaft has four surfaces; in the outer the musculo-spiral groove, between this and the anterior is the deltoid ridge and external tuberosity, on the inner surface the internal tuberosity and nutrient foramen.

3. The radius; on the proximal extremity two glenoid cavities, bicipital tuberosity, external tuberosity and coronoid process; posteriorly two facets for the ulna. The distal extremity has three facets; on the anterior aspect two vertical and one oblique groove; laterally two prominences, the outer being marked by a vertical groove. The posterior surface has a rough triangular space for the ulna, above this a transverse groove assists in forming the radio-ulnar arch; and a ridge on the lower third of the internal border.

4. The ulna; attached by ossification to the posterior surface of the radius; above the attachment a transverse groove, above this two facets. The part above the radius is the olecranon process, which has two surfaces, two borders and a summit; the inner surface is smooth and forms the external boundary of the carpal arch; the anterior border has a concave articular surface and a prominent process above, the beak.

5. The carpus; eight bones arranged in two rows; the upper of which articulates with the radius, named from within outward, the scaphoid, lunar, cuneiform, and behind the last the trapezium; the lower row, articulating with the metacarpals, are the trapezoid, os magnum, unciform, and behind the first the pisiform.

6. The metacarpi magnum; on the proximal extremity three facets, and anteriorly a tubercle, posteriorly a rough prominence, and on each border two facets for the splint bones; the distal extremity has two condyles separated by a ridge, laterally two depressions; the postero-lateral borders have two rough spaces for the splint bones.

7. Splint bones (ossa metacarpi parva) : the outer has one facet superiorly, the inner, two; each having two facets on the inner surface of the head, and a rough space extending downward, terminating below in a small nodule.

8. The OS suffraginis; on the proximal end two glenoid cavities separated by a groove; laterally two prominences. The distal end has two condyles separated by a groove, and on each side a depression; the posterior surface has a rough triangular space base upward.

9. The OS coronae; on the upper surface two glenoid cavities separated by a ••idge, at each end of which is a slight eminence; the lower surface has two

PlfYSIOLOOY, COMPARATIVE ANATO»IY condyles separated by a groove; the posterior surface has a prominence covered by fibro-cartilage.

10. The OS pedis; the articular surface (upper) has two glenoid cavities separated by a ridge, and behind the cavities a narrow articular surface; the anterior surface (wall) is semi-circular, surmounting it the pyramidal process, on each side of which is a depression; the wall terminates posteriorly in the wings, which are divided by the pre-plantar fissure into a lower, retrossal, and an upper basilar process; the lower surface (sole) is semi-lunar, concave, and separated from the tendinous surface by the semilunar ridge; the tendinous surface is rough, triangular and has on each side the plantar groove which terminates in the plantar foramen.

11. The OS naviculare; the upper and lower surfaces each have two facets separated by a ridge; the anterior surface a narrow facet.

12. The sessamoid bones are two, of triangular shape, placed behind the fetlock joint, articulating with the metacarpi magnus, and forming a groove for the flexor tendons.

The Pelvic Arch and IJmib.

The arch formed by the os innominata; each of which is composed of three bones, the ilium, ischium and pubis. These with the sacrum enclose the pelvic cavity.

1. The ilium; the upper anterior part of the arch, is broad; the external surface concave, the internal convex and rough for articulation with the sacrum; the anterior spine is a strong prominence which forms the point of the hip; the posterior spine meets its fellow over the sacral spines; the inner border extends from the posterior spine to the acetabulum where it forms the sciatic spine; the crest extends from the anterior to the posterior spine; the posterior angle forms two-fifths of the acetabulum, in front of which are two depressions in the narrow three-sided part (shaft) of the bone.

2. The ischium; the posterior part of the arch, joins its fellow in the median line, the posterior borders forming the ischial arch, at the external angle of which is the tuberosity, and beneath it the inferior ischiatic spine; the ramus forms the inner, the body the posterior, and the shaft the outer boundary of the obturator foramen; the shaft at its anterior angle forms two-fifths of the acetabulum, and its upper border part of the sciatic (superior ischiatic) spine.

3. The pubis; the antero-inferior part of the arch, lodges the urinary bladder, extends to the cotyloid notch of the acetabulum, its lower surface grooved, its anterior border (crest) joining a ridge on the lower surface of the ilium, forming the ilio-pectineal line; the posterior border forms the anterior border of the obturator foramen.

The acetabulum (cotyloid cavity) receives the head of the femur, has a depression in the floor and a notch in its inner border. Pelvic Liimb.

1. The femur; on the proximal extremity is the head, neck, trochanter major with a summit and convexity; trochanteric fossa and ridge; on the distal extremity two condyles separated by the inter-condyloid groove, on the outer two depressions, on the inner a rough prominence; anterior to the groove a trochlea and between it and the external condyle a deep fossa. The posterior surface is marked by two rough spaces and a ridge superiorly, and the supracondyloid fossa and crest inferiorly; the external border a prominent ridge and on it the trochanter minor; the inner border the trochanter internus and a ridge from it to the head, another ridge extending downward.

2. The tibia; on the upper extremity two broad articular surfaces, a spine

8 VETERINARY ANATOMY, HlSTOIX)GY,

and a depression; anteriorly a tuberosity, externally a facet and between this and the tuberosity a deep groove; internally a tubercle. On the distal extremity two deep grooves separated by a ridge, bounded laterally by the prominent malleoli, the outer being grooved; the tibial ridge on the upper third of the anterior border joins the tuberosity above.

3. The fibula; rudimentary, has on the inner side of the head a facet; the space between this bone and the tibia is the tibio-fibular arch.

4. The tarsus; composed of six bones; the os calcis forming the point of the hock; the astragalus, with the tibia forming the true joint, rests on the cuneiform magnum, it on the medium, with the parvum internally and the cuboid externally, the last three articulating with the metatarsal bones.

5. The metatarsi magnum; on the upper extremity three facets and a fossa; the bone resembles the metacarpal, as do also the splint bones, and the digit.

6. The patella; a large sessamoid bone developed in the tendon of the extensor muscles articulates with the trochlea of the femur.

II. HISTOLOGY OF THE BONE.

Structure: — Bone is composed of earthy matter (principally lime salts) 67 per cent., and animal matter (collagen) 33 per cent., so intimately blended that either may be removed by heat or chemicals without changing the shape. To the eye bone appears in two forms; compact, a hard ivory-like substance forming the shaft of long bones and the external shell of all others; and cancellous, a spongy substance forming the inner mass of all except the shaft of long bones.

1. By the microscope compact bone is seen to contain channels, (Haversion canals) which anastomose, and are surrounded by concentric lamellae, the whole called a Haversion system. The spaces between these systems are filled bv interstlcial lamellae; a set of lamellae covers the bone externally, another lining the marrow cavity, called the outer and inner circumferential lamellae. Scattered between the lamellae are spaces (lacunae) communicating with each other, the Haversion canals, marrow cavities and subperiosteal tissue, by minute channels (canaliculi). Openings in the circumferential lamellae (Volkmann's canals) convey blood vessels to the Haversion canals, each of which contains an artery or vein or botli; the vessels are surrounded by perivascular spaces lined by endothelial cells resting on the outer coats of the vessels ana wans of the canals. These spaces communicate by means of the canaliculi, with the lacunae, and lymph spaces of the periosteum and marrow cavities; by this means a constant flow of lymph plasma passes through the lacunae, in each of which is lodged a bone cell, its processes extending into the canaliculi.

2. Cancellovis bone; forming the inner mass of all except the shaft of long bones, is a frame work of bone fibers in which is lodged red bone marrow, bloodvessels, nerves and lymphatics.

3. Covering of bone is a tough canvass-like membrane, having an external fibrous, and an inner vascular bone forming layer, the osteogenetic membrane.

4. Development. Bone is developed in two ways; in cartilage and in membrane.

a. Endochondral bone.

All the bones of the adult body, excepting those of the vault of the skull and the face, are in foetal life pre-formed in embryonic cartilage. This changes to hyaline, then the cells enlarge at the expense of the matrix and become arranged in rows; calcareous granules are deposited in the thinned walls of the matrix; the cells are thus cut off from nutrition and disappear, leaving spaces

PHYSIOLOGY, OOaiTAKATIVE ANATOMY 9

(primary narrow spaces) surrounded by walls of calcified cartilage matrix. While this change is taking place in the cartilage a thin layer of bone is deposited on its surface by the osteogenetic layer of the perichondrium (which now becomes .the periosteum) and through this bony shell the osteogenetic layer sends bud-like process into the cartilage; these buds consist of bone-destroying cells (osteoclasts) and bone-forming cells (osteoblasts). The osteoclasts absorb the calcareous partitions between the primary marrow spaces, forming secondary marrow spaces (Haversion spaces); into these spaces blood-vessels are pushed; osteoblasts now deposit layer after layer of bone (lamellae) on the inner wall of the spaces until a small channel (the Haversion canal) remains, the bloodvessels of the marrow spaces becoming the vessels of the Haversion systems. The large marrow cavity in the shaft of adult long bones is formed during development by the absorption of the embryonic bone (by osteoclasts), many of the lamellae first laid down by the periosteum are thus absorbed; as new layers from the outer surface increase the thickness of the wall the osteoclasts remove those first formed from the inner, until the permanent marrow cavity is formed. By this process the entire shaft of adult bone, which began as endochondral bone, is changed to bone formed in membrane (intramembranous). Ossification of cartilage and membrane begins at points called centers of ossification. The shaft of long bones (diaphysis) begins in the center, ossification extending toward the extremities, the ends of long bones begin at one or more centers, ossification extending in all directions. As the osseous tissue developed in the ends (epiphyses) approaches that in the diaphysis, there remains a zone of hyaline cartilage in which ossification is long delayed; at this point the perichondrium is thickened, projecting into the cartilage forming a depression (the ossification groove) the ridge filling it, the ossification ridge. This delay admits of the growth of bones in length, as bone tissue takes the place of cartilage at the ends of the zone new cartilage is formed by the perichondrium, the process continuing until the bone has reached full development.

b. Intramembranous bone.

As in the endochondral, this begins at a center of ossification, from which spicules of soft transparent substance (osteogen) shoot out in all directions, and are called osteogenetic fibers. On and around these calcareous granules are deposited until they become spicules of bone; this process extends until a thin lamella of bone is formed, the fibers interweaving (the intercrossing fibers of Sharpey). As new lamellae are added other fibers pierce the layers, binding them together (perforating fibers of Sharpey). The reticulated tissue of spongy bone is developed by osteoblasts becoming arranged about fibrous tissue bundles, forming large meshes of irregular osseous trabeculae enclosing marrow spaces in which the red bone marrow is lodged.

5. Bone marrow, red and yellow.

The buds which carry bone forming elements into the cartilage also carry marrow forming elements. The red marrow is first formed, consisting of cellular elements in a matrix of recticular tissue, surrounded by a fibrous membrane, the endosteum, and containing numerous vessels. The cells are:

1. Myelocytes (marrow cells).

2. Nucleated red blood cells, called erythroblasts, from which are developed normoblasts, also nucleated. While yet in the marrow or in its venous spaces the nuclei are extruded, the non-nucleated red blood cells resulting.

3. Cells with eosinophlle granules.

4. Cells with basophilic granules.

5. The various forms of leucocytes and lymphocytes found in blood and lymph.

6. Giant cells, or myeloplaxes.

Yellow marrow is derived from red marrow by a change of its cells to fat cells, is found principally in the shaft of long bones, and is not a blood forming organ.

III. PHYSIOLOGY OF BONE.

The bones of the extremities form pillars of support, and levers by which the body clianges position and moves from, place to place. Plat bones enclose and protect vital organs; while the bony skeleton forms the foundation on which the entire body is built. By the marrow it is also an important organ in the development and elaboration of the blood.

Chapter II. Articulations

Joints: — Two or more bones united to each other by fibrous or cartilaginous structures form a joint.

There are three classes of joints:

1. Immovable or synarthrodial.

a. Sutura I. S. Vera, the margins unite by interlocking processes. S. Vera, Dentata with tooth like processes.

S. Vera, Serrata with fine saw like processes.

S. Vera, Limbosa, the margins are dentated and bevelled.

2. S. Notha, the margins unite by plain rough surfaces. S. Notha Squamosa, the margins are bevelled and overlap.

S. Notha Harmonia, the margins unite with no irregularities.

b. Synchondrosis. Sutura united by cartilage instead of fibrous tissue.

c. Schindylesis. A plate of one bone is received in a slit of another.

d. Gomphosis. A process of one bone is set in a socket of another.

2. Movable or diarthrosis. True joints.

a. Arthrodia. Motion is slight and gliding.

b. Enarthrosis. Motion in all directions; ball and socket joint.

c. Ginglymus. Motion in one plane only; hinge joint.

d. Rotatory. Motion limited to rotation; pivot joint.

3. Amphiarthrosis. Mixed joint; this term refers to the structure, the bones being united by a pad of fibro-cartilage.

Motion:—!. Extension. The bones approach more nearly a straight line.

2. Flexion. The bones form a more acute ansle.

3. Abduction. The limb is moved from the central plane.

4. Adduction. The limb is moved toward the central plane.

5. Rotation. The limb or bone rotates on its own axis.

6. Gliding. One bone glides over another, always very limited.

7. Circumduction. The distal extremity of the limb describes a circle. LiS^aments:^ — Are binding structures of white fibrous tissue, in a few cases

of vellow elastic tissue.

1. Capsular ligaments surround and enclose joints, are lined by a serous membrane, and synovial glands.

2. Lateral ligaments are thickened portions of capsular, binding the bones of an articulation together.

3. Annular are thickened portions of capsular ligaments or fascia binding down tendons where they cross over joints.

PHYSIOLiOGY, COIVIPAIIATIVE ANATOMY 11

4. Check ligaments originate on bones and are attached to tendons of muscles, limiting their motion.

SjTiovial membranes (glands): — Are placed wherever lubrication of joints and tendons is necessary.

1. Capsular, within capsular ligaments.

2. Bursal, around points over which tendons move.

3. Vaginal, in sheaths through which tendons pass back and forth. Synovia: — Is a viscid lubricating fluid secreted by these glands. Cartilage: — Is a form of connective tissue, of various kinds.

1. Hyaline:

a. Articular, covering the articular surfaces of bones.

b. Costal, prolongations on distal extremities of ribs.

c. Membraniform, in plates or sheets as in the trachea.

2. Fibro-cartilage:

a. Interarticular (meniscus), a pad between bones of a true joint.

b. Connecting, the bond of union in mixed joints.

c. Stratiform (investing), covering points of bone over which tendons glide.

d. Curcumferential, deepens articular cavities.

Articulations of tlie skeleton: — The bones of the skull and face are united by immovable joints, the temporo-maxillary only being a true joint, with a meniscus, capsular, posterior and external lateral ligaments. ^

Hyoitl series: — The temporo-hyoid and proximal inter-hyoid and thyro-hyoid are mixed joints. The distal inter-hyoids are true joints.

Vertebral: — The occipito-atloid is a true joint with capsular," 2 lateral, (styloid) and superior and inferior suspensory ligaments. The atlo-axoid a true joint with capsular, superior and inferior odontoid. The 5th and 6th lumbar and last lumbar and sacrum form true joints by facets on their transverse processes, with capsular ligaments. The centra of the remaining vertebrae unite by mixed joints, the oblique processes by true joints with capsular ligaments. Ligaments of the vertebral column are superior and inferior common, supraspinous, inter-spinous, inter-transverse, ligaments of the arches, and ligamentum nuchae. The last two are yellow elastic tissue.

Thoracic: — Costo-vertebral; two true joints between head of rib and body of vertebra, one between tubercle of rib and transverse process, with three capsular, stellate, round, anterior and posterior transverse. The chondro-costal is a gomphosis. The costo-sternal a true joint with capsular, superior and inferior costo-sternal. The sternal segments unite by fibro-cartilage which ossifies in old age.

Pectoral Unib: — 1. Scapulo-humeral; capsular only; tendons passing over it acting as ligaments.

2. Humero-radio-ulnar; capsular, internal and external lateral.

3. Radia-ulnar; superior and inferior radiating and interosseous.

4. The carpus; special ligaments are:

a. Superior carpal (between bones of upper row) 3 anterior and 3 interosseous.

b. Inferior carpal (between bones of lower row) 2 anterior and 2 interosseous.

c. Radio-carpal (between radius and bones of upper row) oblique, superior trapezial, and a small one beneath it.

d. Inter-carpal (between the upper and lower rows) the inferior trapezial and two short ones under the posterior common ligament.

e. Carpo-metacarpal (between the lower row and the meta-carpal bones) 2 anterior, 2 posterior, and 2 interosseous.