Part 14

The =maxillary sinus= is excavated chiefly in the maxilla, lacrimal, and malar, and is not divided by a septum as in the horse. It extends forward as far as the facial tuberosity, or a little further in old animals. Its upper limit is indicated approximately by a line drawn from the infraorbital foramen to the upper margin of the orbit. It is continued directly backward into the lacrimal bulla to a point nearly opposite to the bifurcation of the zygomatic process of the malar. It also extends upward and backward through a large opening into a cavity formed by the lacrimal, frontal, ethmoid, and turbinal bones, at the inner side of the orbit.[26] The floor of the cavity is irregular and the roots of the last three or four cheek teeth project up into it, covered by a plate of bone. The sinus communicates with the palatine sinus freely over the infraorbital canal through an oval opening about two to three inches (ca. 5 to 7.5 cm.) long. Above this it communicates by a shorter and much narrower opening with the middle meatus nasi.

The =palatine sinus= is excavated in the hard palate, and is separated from that of the opposite side by a median septum. It extends from the posterior border of the palate to a plane an inch or more (2.5 to 3 cm.) in front of the first cheek tooth. As mentioned above, there is a large communication with the maxillary sinus over the infraorbital canal, so that the cavity is sometimes regarded as a part of that sinus. The large defect in the bony roof of the sinus is closed by two layers of mucous membrane in the fresh state. The palatine canal passes obliquely through the posterior part of the sinus.

The =sphenoidal sinus= is almost entirely in the sphenoid bone and does not communicate with the palatine and maxillary sinus. It has one or two openings into the ventral ethmoidal meatuses. There is no cavity in the perpendicular part of the palate bone.

There are several small air-cavities between the lateral mass of the ethmoid and the anterior part of the frontal sinus, which communicate separately with ethmoidal meatuses.

BONES OF THE THORACIC LIMB

The =scapula= is more regularly triangular than in the horse, relatively wider at the vertebral end and narrower at the lower end. The scapular index is about 1 ∶ 0.6. The spine is more prominent and is placed further forward, so that the supraspinous fossa is narrow and does not extend to the lower part of the bone. The spine is sinuous, bent backward in its middle, forward below. Its free border is somewhat thickened in its middle, but bears no distinct tubercle. Instead of subsiding below as in the horse the spine becomes a little more prominent, and is prolonged by a pointed projection, the =acromion=, from which part of the deltoid muscle arises. The subscapular fossa is shallow. The areas for the attachment of the serratus muscle are not very distinct. The nutrient foramen is usually in the lower third of the posterior border. The glenoid cavity is almost circular and without any distinct notch. The tuberosity is small and close to the glenoid cavity. The coracoid process is short and rounded. The cartilage resembles that of the horse.

The =humerus= has a shallow musculo-spiral groove. The deltoid tuberosity is less prominent than in the horse, and the curved line running from it to the neck bears a well-marked tubercle on its upper part. The nutrient foramen is usually in the lower third of the posterior surface. The external tuberosity is very large, and rises an inch or more (ca. 3 cm.) above the level of the head. Its anterior part curves inward over the bicipital groove, and below it externally there is a prominent circular rough area for the insertion of the tendon of the supraspinatus. The anterior part of the internal tuberosity has a small projection which curves over the groove. The groove is undivided. The distal articular surface is decidedly oblique, and the grooves and ridge are very well marked. The coronoid and olecranon fossæ are deep and wide. The external condyloid crest is represented by a rough raised area. The proximal end unites with the shaft at three and one-half to four years, and the distal at about one and one-half years.

The =radius= is short and relatively broad. It is somewhat oblique, the lower end being nearer the median plane than the upper. The curvature is more pronounced below than above. The shaft is prismatic in its middle part and has anterior, external, and posterior faces. There is a marked increase in width and thickness below. The proximal articular surface presents a synovial fossa which extends inward from the deep groove between the two glenoid cavities. The bicipital tuberosity is represented by a slightly elevated rough area. The posterior facets for the ulna are larger than in the horse. The two bones commonly fuse above the proximal interosseous space and always fuse below it, except near the distal end, where there is a small distal interosseous space. A groove connects the two spaces externally. The distal extremity is large, and is thickest internally. Its articular surface is oblique in two directions, _i. e._, from within upward and backward. The grooves for the extensor tendons are shallow. The proximal end unites with the shaft at one to one and one-half years, and the distal at three and one-half to four years.

The approximation of the lower ends of the forearms and the carpi gives the “knock-kneed” appearance in cattle. The obliquity of the joint surfaces produces lateral deviation of the lower part of the limb in flexion. The facets for the radial and intermediate carpals are narrower than in the horse and run obliquely forward and outward. The surface for the ulnar carpal is extensive and saddle-shaped; its outer part is furnished by the ulna.

[Illustration:

FIG. 99.—SKELETON OF LEFT FORE LIMB OF OX, FROM SHOULDER DOWNWARD, ANTERIOR VIEW. (After Ellenberger-Baum, Anat. für Künstler.) ]

The =ulna= is more fully developed than in the horse. The shaft is complete, three-sided, and strongly curved. It is fused with the radius in the adult, except at the two interosseous spaces mentioned above. Its upper part contains a medullary canal which extends somewhat into the proximal end. The olecranon is large and bears a rounded tuberosity above. The distal end is fused with the radius; it projects below the level of the latter, forming the =styloid process= (Processus styloideus ulnæ), which furnishes part of the facet for the ulnar carpal. The proximal and distal ends unite with the shaft at three and one-half to four years.

[Illustration:

FIG. 100.—SKELETON OF LEFT FORE LIMB OF OX, FROM ELBOW DOWNWARD, EXTERNAL VIEW. (After Ellenberger-Baum, Anat. für Künstler.) ]

The =carpus= consists of six bones, four in the upper row, and two in the lower. The upper row is oblique in conformity with the carpal articular surface of the radius. The radial and intermediate resemble in general those of the horse, but are less regular in shape, and their long axes are directed obliquely backward and inward. The radial is narrower than in the horse and curves upward behind. The intermediate is constricted in its middle, and wider behind than in front. The ulnar is large and very irregular. Its proximal surface is extensive and sinuous and articulates with both radius and ulna. Behind is a large oval facet for articulation with the accessory carpal. The accessory is short, thick, and rounded; it articulates with the ulnar carpal only. The first carpal is absent. The second and third carpals are fused to form a large quadrilateral bone. The fourth carpal is a smaller quadrilateral bone.

The =metacarpus= consists of a large metacarpal and an external small metacarpal bone. The large metacarpal bone (Mc. 3 + 4) results from the fusion of the third and fourth bones of the fœtus, and bears evidences of its double origin even in the adult state. The shaft is shorter than in the horse, and is relatively wider and flatter. The anterior surface is rounded, and is marked by a vertical vascular groove connecting two canals which traverse the ends of the shaft from before backward. The posterior surface is flat and presents a similar but much fainter groove. The borders are rough in the upper third. The proximal end bears two slightly concave facets for articulation with the bones of the lower row of the carpus; the inner area is the larger, and they are separated by a ridge in front and a notch behind. The outer angle has a facet behind for the small metacarpal bone. The inner part of the extremity has anterior and posterior tuberosities. The distal end is divided into two parts by a sagittal notch. Each division bears an articular surface similar to that in the horse, but much smaller. The =medullary canal= is divided into two parts by a =vertical septum= which is usually incomplete in the adult.

The =small metacarpal= bone (Mc. 5) is a rounded rod about an inch and a half (ca. 3.5 to 4 cm.) in length, which lies against the upper part of the outer border of the large bone. Its upper end articulates with the latter, but not with the carpus. The lower end is pointed.

Four cartilaginous metacarpals are present in the early fœtal state, viz., the second, third, fourth, and fifth. The second commonly either disappears or unites with the third; sometimes it develops as a small rod of bone. The third and fourth gradually unite, but can be cut apart at birth. Each has three centers of ossification; the proximal epiphysis fuses with the shaft before birth, the distal at two to two and one-half years.

Four =digits= are present in the ox. Of these, two—the third and fourth—are fully developed and have three phalanges and three sesamoids each. The second and fifth are vestiges and are placed behind the fetlock; each contains one or two small bones which do not articulate with the rest of the skeleton.

The =first phalanges= are shorter and narrower than in the horse and are three-sided. The interdigital surface is flattened and its posterior part bears a prominence for the attachment of the interdigital ligaments. The proximal extremity is relatively large, and is somewhat compressed from side to side. The articular surface is concave from before backward and is divided by a sagittal groove into two areas, of which the abaxial one is the larger and higher. Behind these are two facets for articulation with the sesamoid bones. The posterior surface bears two tuberosities separated by a deep depression. The distal extremity is smaller than the proximal, especially in the antero-posterior direction. Its articular surface is divided by a sagittal groove into two convex facets, of which the abaxial one is decidedly the larger. There are depressions on either side for ligamentous attachment. The bone consists at birth of two pieces—the distal end and the fused shaft and upper extremity. Union occurs at one and one-half to two years.

The =second phalanges= are about two-thirds of the length of the first and are distinctly three-sided. The proximal articular surface is divided by a sagittal ridge into two glenoid cavities, of which the abaxial one is much the larger. There is a central prominence in front and two lateral tubercles behind. The distal extremity is smaller than the proximal. Its articular surface encroaches considerably on the anterior and posterior surfaces, and is divided into two lateral parts by a groove. There is a deep depression for ligamentous attachment on the interdigital side. The bone contains a small medullary canal. The distal end unites with the rest of the bone about the middle of the second year.

The =third phalanges= resemble in a general way one-half of the bone of the horse. Each has four surfaces. The dorsal or wall surface is marked in its lower part by a shallow groove, along which there are several foramina of considerable size; the posterior one of the series is the largest, and conducts to a canal in the interior of the bone. Below the groove the surface is prominent, rough, and porous. Near and on the extensor process are several relatively large foramina. The slope of the surface is very steep posteriorly, but in front it forms an angle of 25 to 30 degrees with the ground plane. The articular surface is narrow from side to side, and slopes downward and backward. It is also oblique transversely, the interdigital side being the lower. It is adapted to the distal surface of the second phalanx, with the exception of a facet behind for the distal sesamoid. The extensor process is very rough. The volar or sole surface is narrow and slightly concave, and presents two or three foramina of considerable size. It is separated from the wall surface by a border which is sharp in front, rounded behind. There is no semilunar crest, since the deep flexor tendon is attached to the thick posterior border of the sole surface. The interdigital surface is smooth and grooved below, rough and porous above. At the upper angle it is perforated by a large foramen, which is equivalent to the volar foramen of the horse and leads to a cavity in the middle of the bone. The surface is separated by a rounded border from the wall surface, and by a sharp edge from the sole surface. The wing or angle is very short and blunt, and there is no lateral cartilage.

Four =proximal sesamoids= are present, two for each digit. They are much smaller than in the horse. The bones of each pair articulate with the corresponding part of the distal end of the large metacarpal bone by their anterior surfaces, with each other and with the first phalanx by small facets.

The two =distal sesamoids= are short and their ends are but little narrower than the middle.

BONES OF THE PELVIC LIMB

The =ilia= are almost parallel to each other and are also less oblique with regard to the horizontal plane than in the horse. They are relatively small. The gluteal line is prominent and is nearly parallel to the external border; it joins the superior ischiatic spine. A rounded ridge separates the two parts of the ventral surface. The surface for articulation with the sacrum is triangular. The internal angle is truncated, does not extend as high as the vertebral spines, and is separated from the opposite angle by a wider interval than in the horse. The external angle is relatively large and prominent; it is not so oblique as in the horse, and is wide in the middle, smaller at either end. The shaft is short and compressed from side to side.

The =ischium= is large. Its long axis is directed obliquely upward and backward, forming an angle of about 45 to 50 degrees with the horizontal plane. The transverse axis is oblique downward and inward at a similar angle, so that this part of the pelvic floor is deeply concave from side to side. The middle of the ventral surface bears a rough ridge or imprint for muscular attachment. The superior ischiatic spine is high and thin, and bears a series of almost vertical rough lines externally. The tuber ischii is large and three-sided, bearing upper, lower, and external tuberosities. The ischial arch is narrow and deep. The symphysis bears a ventral ridge, which fades out near the ischial arch.

The acetabular branch of the =pubis= is narrow, and is directed outward and a little forward. The anterior border is marked by a transverse groove which ends below the rough ilio-pectineal eminence. The longitudinal branch is wide and thin.

The =acetabulum= is smaller than in the horse. The rim is rounded and is usually marked by two notches. One of these is postero-internal and is narrow and deep; it leads to the deep acetabular fossa and is commonly almost converted into a foramen by a bar of bone. The other notch is antero-internal, small, and sometimes replaced by a foramen or absent.

The =obturator foramen= is large and elliptical. Its inner border is thin and sharp.

[Illustration:

FIG. 101.—SKELETON OF LEFT HIND LIMB OF OX, FROM MIDDLE OF THIGH DOWNWARD, POSTERIOR VIEW. _21_, Tibia; _24_, tuber calcis; _25_, large metatarsal bone. (After Ellenberger-Baum, Anat. für Künstler.) ]

The =pelvic inlet= is elliptical and is more oblique than in the horse. In a cow of medium size the =conjugate diameter= is about nine and a half inches (ca. 23 to 24 cm.), and the transverse about seven inches (ca. 18 cm.). The anterior end of the symphysis lies in a transverse plane through the junction of the third and fourth sacral segments. The roof is concave in both directions. The =floor= is deeply concave, particularly in the transverse direction. The =cavity= is narrower and its =axis= is inclined strongly upward in the posterior part. The distance between the acetabulum and the external angle of the ilium is only a little (ca. 3 to 4 cm.) more than the distance between the former and the tuber ischii.

[Illustration:

FIG. 102.—FRONTAL SECTION OF LEFT FEMUR OF OX, FRONT VIEW. ]

[Illustration:

FIG. 103.—FRONTAL SECTION OF LEFT TIBIA OF OX, ANTERIOR VIEW.

These figures show the internal architecture of these bones, and especially the great extent of the medullary cavity as compared with those of the horse (Figs. 67 and 72). ]

The =femur= has a relatively small shaft, which is cylindrical in its middle, prismatic below. The trochanter minor has the form of a rough tuberosity, and is situated higher up than in the horse and encroaches on the posterior surface. The trochanteric ridge (Crista intertrochanterica posterior) connects it with the trochanter major. The third trochanter is absent. The supracondyloid (plantar) fossa is shallow. The proximal extremity is very wide. The head is smaller than in the horse and the articular surface extends considerably on the upper surface of the neck. Instead of the notch there is a small depression on the middle of the head for the attachment of the round ligament. The neck is well defined except above. The trochanter major is very massive and is undivided; its external surface is very rough. The trochanteric fossa is deep, but does not extend so far downward as in the horse. The distal end presents no very striking differential features, but the lips of the trochlea are less oblique than in the horse, and converge very slightly below. The proximal extremity unites with the shaft at about three and one-half years, the distal at three and one-half to four years.

The =tibia= resembles that of the horse rather closely, but is somewhat shorter. The shaft is distinctly curved, so that the inner side is convex. The posterior surface is not divided into two areas, and the lineæ musculares are fewer and extend up higher than in the horse. The articular grooves and ridge of the distal end are almost sagittal in direction, and present an extensive but shallow synovial fossa. The external groove is separated by a sharp ridge from an outer area which is for articulation with the external malleolus. The anterior part of the internal malleolus is prolonged downward and has a pointed end. The groove behind it is broad and well defined. Externally there is a deep narrow groove which separates two prominences. The proximal extremity fuses with the shaft at three and one-half to four years, the distal at two to two and one-half years.

The =fibula= usually consists of the two extremities only. The head is fused with the external condyle of the tibia and bears a small blunt-pointed prolongation below. The distal end remains separate and forms the external malleolus (sometimes called the os malleolare). It is quadrilateral in outline and compressed from side to side. The proximal surface articulates with the distal end of the tibia, and bears a small spine which fits into the groove on that bone. The distal surface rests on the fibular tarsal, and the inner articulates with the external ridge of the tibial tarsal bone. The outer surface is rough and irregular.

The early cartilaginous fibula is complete, but later the shaft is reduced and is usually represented by a fibrous cord which connects the two ends. In some cases, however, the upper part undergoes partial ossification, forming a slender rod which is usually united with the outer border of the tibia and is joined to the head by fibrous tissue.

The =patella= is long, narrow, and very thick. The anterior surface is strongly convex and very rough and irregular. The articular surface is convex from side to side and nearly straight in the vertical direction. The large prominence on the inner side for the attachment of the accessory cartilage allows prompt determination of the side to which the bone belongs. The apex is more pointed than in the horse.

The =tarsus= consists of five pieces; the central and fourth, and the second and third tarsal bones are fused.

The =tibial tarsal= bone is relatively long and narrow, and is somewhat flattened from before backward. It bears a trochlea at either end. The groove and ridges of the proximal trochlea are not spiral, but almost sagittal; the outer ridge is the wider, and articulates with both tibia and fibula. The distal trochlea consists of two condyles divided by a groove, and articulates with the combined central and fourth tarsals. The posterior surface bears a large oval facet for articulation with the fibular tarsal; this occupies most of the surface, and is convex and grooved from above downward. The outer surface presents two facets for articulation with the fibular tarsal, and is excavated and rough elsewhere. The inner surface bears a tuberosity at its upper part, and is flattened below.

The =fibular tarsal= bone is longer and more slender than in the horse. The distal part of the body is compressed laterally, and bears a projection in front which articulates with the external malleolus. The tuber calcis is marked posteriorly by a wide shallow groove, which is coated with cartilage in the fresh state.

The =central= and =fourth tarsals= are fused to form a large bone (Os centrotarsale quartum, scapho-cuboid), which extends across the entire width of the tarsus and articulates with all of the other bones. The greater part of the upper surface is molded on the distal trochlea of the tibial tarsal, and its inner part rises high above the rest posteriorly. Externally there is a narrow undulating surface for articulation with the distal end of the fibular tarsal bone. The posterior surface bears two tuberosities, of which the outer one is rounded, the inner more prominent and narrower.

The =first tarsal= bone is quadrilateral and small. It articulates with the central above, the metatarsus below, and the second tarsal in front.

The =second= and =third tarsals= are fused to form a rhomboid piece. The proximal surface is concavo-convex, and articulates with the central component. The distal surface is undulating and rests on the metatarsus. The external surface bears a small facet in front for the fourth tarsal component, and the posterior surface a very small one for the first tarsal bone.

The =large metatarsal= bone is about one-seventh (ca. 3 cm.) longer than the corresponding metacarpal. Its shaft is compressed laterally and is distinctly four-sided. The groove on the anterior surface is deep and wide. The posterior surface is marked by variable grooves. The upper foramen on this surface does not perforate the shaft, but passes obliquely through the extremity, opening on the posterior part of its proximal surface. The postero-internal angle of the proximal end bears a facet for articulation with the small metatarsal bone.

[Illustration: