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.
Fig. 102.—Frontal Section of Left Femur of Ox, Front View.
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.
Fig. 104.—Skeleton of Distal Part of Left Hind Limb of Ox, Internal View. 24, Tuber calcis; 25, large metatarsal bone; 30, first phalanx; 31, second phalanx; 32, third phalanx. (After Ellenberger-Baum, Anat. für Künstler.)
The small metatarsal bone is a quadrilateral disc a little less than an inch in width and height. Its anterior face bears a facet for articulation with the large metatarsal bone.
The large metatarsal bone is usually regarded as consisting of the fused third and fourth metatarsal bones. The medullary cavity is subdivided like that of the large metacarpal bone. Some anatomists, however, consider that the ridges at the upper end of each border represent the second and fifth metatarsals (Rosenberg and Retterer). On this basis the small bone would be the first metatarsal.
The phalanges and sesamoids resemble those of the thoracic limb so closely as to render separate description unnecessary.
SKELETON OF THE PIG
VERTEBRAL COLUMN
The vertebral formula is C7T14–15L6–7S4Cy20–23.
Fig. 105.—Skeleton of Pig, Lateral View.
a, Cranium; b, upper jaw; c, lower jaw; 1H.-7H., cervical vertebræ; 1R.w., first thoracic vertebra; 13 R.w., thirteenth thoracic vertebra (next to last); 1L., first lumbar vertebra; 6L., sixth lumbar vertebra (next to last usually); K., sacrum; S., coccygeal vertebra; 1R., first rib; 14R., last rib; R.kn., costal cartilages; St., sternum; d, supraspinous fossa of scapula; d′, infraspinous fossa; 1, spine of scapula; 2, neck of scapula; e, humerus; 3, head of humerus; 4, tuberosities of humerus; 5, deltoid tuberosity; 6, external epicondyle of humerus; f, radius; g, ulna; 7, olecranon; h, carpus; 18–25, carpal bones; i-i⁗, metacarpus; k-k⁗, proximal phalanges; l-l⁗, middle phalanges; m-m⁗, distal phalanges; n, o, sesamoids; p, ilium; 8, external angle of ilium (tuber coxæ); 9, internal angle of ilium (tuber sacrale); 10, superior ischiatic spine; q, ischium; 11, tuber ischii; r, pubis; 12, acetabulum; s, femur; 13, trochanter major; 14, trochanter minor; 15, external epicondyle; t, patella; u, tibia; 16, crest of tibia; 17, external condyle of tibia; v, fibula; w, tarsus; 26–31, tarsal bones; 26′, tuber calcis. (After Ellenberger, in Leisering’s Atlas.)
The cervical vertebræ are short and wide. The bodies are elliptical in cross-section, the long diameter being transverse. The anterior articular surfaces are slightly convex from side to side and concave dorso-ventrally; the posterior ones are slightly concave. A ventral crest is not present. The arches are wide from side to side, but the laminæ are narrow, so that a considerable interval (Spatium interarcuale) separates adjacent arches dorsally. The pedicles are perforated by a foramen on either side in addition to the usual intervertebral foramina. The transverse processes divide into two branches, both of which increase in size from the third to the sixth. The upper branch projects outward and backward; it is short and is thickened at its free end. The lower branch is a quadrilateral plate directed ventrally; each overlaps the succeeding one to a small extent, and the series forms the lateral boundary of a deep and wide groove beneath the bodies. The spines increase in height from the third to the last; the anterior ones are inclined backward, the posterior ones forward. The last cervical is recognized by the great length of its spine (ca. 10 cm. in the adult), the absence of the ventral plate of the transverse process, and the flatness of the body, which bears a pair of small facets on its posterior margin for the heads of the first ribs. It has foramina transversaria, and usually two foramina in either side of the arch.
The dorsal arch of the atlas bears a large tuberosity. The ventral tubercle is long, compressed laterally, and projects back under the axis. The wing is flattened and bears a posterior tuberosity. The foramen transversarium passes through the posterior border of the wing to the fossa under the latter, and is not visible dorsally; it is sometimes very small or absent. The sides of the vertebral foramen bear two lateral projections which partially divide it into a ventral narrow part, which receives the odontoid process, and a dorsal larger part for the spinal cord. In the fresh state the division is completed by the transverse ligament, which is attached to the projections.
The axis has a large spinous process, which is directed upward and backward. The odontoid process is a thick cylindrical rod. The transverse process is very small and the foramen transversarium is often incomplete.
Fig. 106.—Atlas of Pig, Dorsal View.
a, Wing; b, ventral tubercle; c, foramen transversarium; d, alar foramen; e, intervertebral foramen; f, dorsal tuberosity; g, articular surface corresponding to that of posterior articular process of typical vertebra; h, facet on ventral arch for odontoid process. (Ellenberger-Baum, Anat. d. Haustiere.)
Fig. 107.—Axis of Pig, Left Lateral View.
a, Odontoid process (dens); b, spinous process; c, anterior articular process; d, posterior articular processes; e, transverse process; f, foramen transversarium; g, bar of bone which bounds h, intervertebral foramen; i, vertebral foramen. (Ellenberger-Baum, Anat. d. Haustiere.)
The thoracic vertebræ are often fifteen in number. Their bodies are relatively long, constricted in the middle, and without ventral crests. Their extremities are elliptical, depressed in the middle and prominent at the periphery. The arch is perforated by a foramen on either side, and in most of the series there is also a foramen in the posterior part of the root of the transverse process which communicates with the former or with the posterior intervertebral foramen. Sometimes there is a foramen in the anterior part of the process also. There are mammillary processes except on the first two; in the posterior five or six vertebræ they project from the anterior articular processes. The facet for the tubercle of the rib is absent or fused with that for the head in the last five or six. The last transverse process is lumbar in character, plate-like, and about an inch (2 cm.) long. Small accessory processes occur in the posterior part of the region. The first spinous process is broad, very high, and inclined a little forward. The others diminish very gradually in length to the tenth, beyond which they are about equal. The second to the ninth are inclined backward, the tenth is vertical (anticlinal), and the rest incline forward. The width decreases decidedly from the fourth to the tenth, beyond which there is a gradual increase. The summits are slightly enlarged and lie almost in a straight line.
The occurrence of fifteen thoracic vertebræ appears to be quite common, and some observers have recorded the existence of sixteen and even seventeen; a reduction to thirteen is rare.
The lumbar vertebræ are six or seven in number. The bodies are longer than in the thoracic region and bear a ventral crest. They become wider and flatter in the posterior part of the series. The arches are deeply notched, and are separated by an increasing space dorsally. The mammillary processes project outward and backward. The transverse processes are bent downward and incline a little forward. Their length increases to the fifth and is much diminished in the last. They form no articulation with each other or with the sacrum. The posterior edge of the root of the process is marked by a notch in the anterior part of the series, a foramen in the posterior part. The spines are broad and incline forward, with the exception of the last, which is narrow and vertical.
Lesbre states that six and seven lumbar vertebræ occur with almost equal frequency. The number may be reduced to five, and the number of presacral vertebræ varies from twenty-six to twenty-nine.
The sacrum consists usually of four vertebræ, which fuse later and less completely than in the other domesticated animals. It is less curved than in the ox. The spines are absent, excepting small rudiments on the last two segments. The middle of the dorsal surface is flattened and smooth, and presents openings into the sacral canal between adjacent arches (Spatia interarcualia). On either side are the superior sacral foramina, and tubercles which indicate the fused articular processes. The wings resemble those of the ox. The anterior articular processes are very large. The pelvic surface resembles that of the ox, but is not so strongly curved, and the transverse lines are very distinct.
Fig. 108.—Sacrum of Pig, Dorsal View.
a, Wing; b, dorsal sacral foramina; c, articular process; 1–4, segments or sacral vertebræ. (Ellenberger-Baum, Anat. d. Haustiere.)
The coccygeal vertebræ are specially characterized by the presence of functional articular processes on the first four or five, beyond which these processes become non-articular and smaller. The arches of the first five or six are complete. The transverse processes are broad and plate-like in the anterior part of the series and diminish very gradually.
The numerical variation here is twenty to twenty-six according to the observation of several anatomists. Lesbre states that he has found twenty-three most frequently.
Curves.—The cervical region is practically straight. The thoracic and lumbar regions form a gentle curve, concave ventrally, the highest point of which is at the junction of the two regions. The sacral promontory is not so pronounced as in the ox, and the sacral curve is flatter.
The Ribs
The ribs number fourteen or fifteen pairs, of which seven are sternal and seven or eight asternal usually. They are in general strongly curved in the improved breeds, so that there is a fairly distinct angle, except toward the end of the series. The backward slope of the posterior ribs is slight. The first rib is prismatic, has a large sternal end, and a very short cartilage. The width is greatest in the third to the sixth, and the length in the sixth and seventh usually. The tuberosity fuses with the head on the last five or six. The second to the fifth form diarthrodial joints with their cartilages, which are wide and plate-like.
THE STERNUM
The sternum consists of six segments and resembles that of the ox in general form. The first segment (Manubrium) is long, flattened laterally, and bears a blunt-pointed cartilage on its anterior end; its posterior end forms a diarthrodial joint with the body. The latter is flattened, wide in its middle, narrow at either end. The widest segments are formed of two lateral parts, which are not completely fused in the adult. The last segment has a long narrow part which bears the xiphoid cartilage.
The thorax is long and is more barrel-shaped than in the horse or ox, since the ribs are more strongly curved and differ less in relative length.
Fig. 109.—Skull of Pig, Lateral View without Mandible.
1, Occipital condyle; 2, paramastoid or styloid process; 3, bulla ossea; 4, external auditory meatus, 5, zygomatic process of temporal bone; 6, sphenoid bone; 7, orbital opening of supraorbital canal; 8, malar bone; 9, pterygoid bone; 10, pterygoid process of sphenoid; 11, pterygoid process of palate bone; I1–3, incisor teeth; C, canine tooth; P1–4, premolars; M1–3, molars.
BONES OF THE SKULL
Cranium
The occipital bone has an extensive squamous part or supraoccipital, which forms a very broad and prominent crest. The latter is concave, and is thick and rough above, where it forms the highest part of the skull; laterally it becomes thinner, turns downward, and is continuous with the temporal crest. Two divergent ridges pass upward from the foramen magnum, and the surface between them is concave and smooth. The greater part of the inner (or anterior) surface of the supraoccipital is united with the parietal bones, but a lower concave area faces into the cranial cavity. The foramen magnum is almost triangular, and is narrow above, where it is flanked by two small tuberosities. The paramastoid processes are extremely long and project almost straight downward. The hypoglossal foramen is at the inner side of the root of the process. The basilar part is short and wide; its lower surface bears a thin median ridge and two lateral imprints or tubercles which converge at the junction with the sphenoid bone.
Fig. 110.—Skull of Pig, Dorsal View.
The interparietal fuses before birth with the occipital. The tentorium osseum is absent.
The parietal is overlapped by the occipital bone behind and concurs in the formation of the occipital crest. Its external surface is divided by the parietal crest into two parts. The inner part (Planum parietale) faces upward and forward, and is flattened and smooth. Its inner border is short and straight and unites early with the opposite bone. Its anterior border is concave and joins the frontal bone. The outer part (Planum temporale) faces outward and is more extensive; it is concave, forms a large part of the temporal fossa, and is overlapped below by the squamous temporal. The parietal crest extends in a curve from the occipital crest forward and outward to the supraorbital process. The internal surface is concave and is marked by digital impressions. The lower border projects into the cranial cavity and forms a crest which separates the cerebral and cerebellar compartments laterally. The interior forms part of the frontal sinus in the adult. There is no parieto-temporal canal.
The frontal bone is long. The frontal surface slopes downward and forward, the inclination varying in different subjects. The anterior part is concave and is marked by the supraorbital foramen and the groove leading forward from the foramen to the nasal bone. The supraorbital canal opens into the orbit at the upper part of the inner wall of the latter. The supraorbital process is short and blunt-pointed, and is not connected with the zygomatic arch. The gap in the orbital margin is closed by the orbital ligament in the fresh state. The orbital part is extensive and forms the greater part of the inner wall of the orbit. Its upper part is perforated by the orbital orifice of the supraorbital canal, in front of which is the distinct fovea trochlearis. The ethmoidal or internal orbital foramen is situated in the lower part near the junction with the orbital wing of the sphenoid. The temporal part is very narrow and is separated from the orbital plate by a ridge which joins the pterygoid crest below. The interior of the bone is excavated by the frontal sinus in practically its entire extent in the adult. In the young subject the cavity is confined to the anterior part and the rest of the bone is thick.
The temporal bone has a general resemblance to that of the ox. The zygomatic process is short and stout and is bent at a right angle. The upper border of the process is thin; traced from before backward it curves sharply upward and forms a high prominence in front of the external auditory meatus; beyond this it drops rather abruptly and is then continued upward to the occipital crest. The anterior part of the lower border joins the zygomatic process of the malar, which is deeply notched. The condyle is concave in the transverse direction. The postglenoid process is absent, but the articular surface is bounded behind and internally by a crest. There is no parieto-temporal canal. The external auditory canal is very long and is directed upward and outward. The bulla ossea is large, compressed laterally, and bears a pointed muscular process in front. A narrow space intervenes between the bulla and the basilar part of the occipital bone, so that the foramen lacerum resembles that of the horse. The small hyoid process is situated in a deep depression in front of the root of the paramastoid process, and the stylo-mastoid foramen is immediately external to it. The petrous part presents no important differential features. The squamous part (including the root of the zygomatic process) contains an air-cavity, which is continuous with the sphenoidal sinus.
Fig. 111.—Basal Surface of Skull of Young Pig, without the Mandible.
Sq.o., Supraoccipital; E.o., exoccipital; B.o., basioccipital; B.s., body of sphenoid; Sq., squamous temporal bone; V, vomer; Mx., maxilla; Pa., horizontal part of palate bone; P.p., palate process of maxilla; Z, malar bone; J, premaxilla; D.c., canine tooth; J1–3, incisor teeth; O, temporal fossa; 1, occipital crest; 2, for. magnum; 3, occipital condyle; 4, paramastoid (styloid) process; 5, bulla ossea; 6, for. lacerum basis cranii; 7, pterygoid process of sphenoid; 8, posterior nares; 9, anterior palatine foramen; 10, palatine cleft. (Struska, Anat. d. Haustiere.)
The sphenoid bone is short and resembles that of the ox in general. The body is narrow. The pituitary fossa is very deep, and is limited behind by a prominent dorsum sellæ; the dorsum bears lateral projections, the posterior clinoid processes. The foramen ovale is absent, being included in the foramen lacerum anterius. The other foramina are like those of the ox. The pterygoid process is broad and twisted. Its base is not perforated and its free edge is thin and sharp. It concurs with the pterygoid and palate bones in the formation of the pterygoid fossa, which opens backward and is not present in the horse or ox. The sphenoidal sinus is very large and occupies the body, the temporal wings, and a great part of the pterygoid processes in the adult; it is continued into the temporal bone as mentioned above.
The ethmoid bone has a relatively long perpendicular plate, which is marked by ridges corresponding to the ethmoidal meatuses. The cribriform plate is extensive and very oblique, so that it and the crista galli are almost in line with the basi-cranial axis. A linear series of relatively large foramina is found on either side of the crista. The lateral mass consists of five endoturbinals and eighteen ectoturbinals (Paulli). The lamina papyracea concurs in the formation of the pterygo-palatine fossa.
Face
The maxilla is extensive. Its external surface forms a longitudinal groove, which is continued upon the premaxilla in front and the facial parts of the lacrimal and malar behind. The infraorbital foramen—sometimes double—is large and is situated above the third or fourth cheek tooth. The alveolus for the canine tooth produces a ridge at the anterior end which is very pronounced in the boar. The facial crest extends forward from the root of the zygomatic process and fades out behind the infraorbital foramen; in some specimens it is prominent and thin-edged, in others it is rounded and projects little. The zygomatic process is short but stout and buttress-like; it is overlapped externally by the malar. The maxillary tuberosity forms in the young subject a long bulla, which occupies most of the pterygo-palatine fossa and contains the developing permanent molars; after the eruption of the teeth the tuberosity flattens and joins the vertical part of the palate bone. The palatine process is very long and is marked in its anterior part by transverse ridges corresponding with those of the mucous membrane of the palate. The anterior palatine foramen is near the junction with the palate bone; from it the palatine groove can be traced distinctly along the entire length of the process. The alveolar border presents a large alveolus for the canine tooth at its anterior end; behind this are seven alveoli for the cheek teeth, which increase in size from first to last. The maxillary foramen and infraorbital canal are very large. The maxillary sinus is small.
The body of the premaxilla is narrow and prismatic. It presents three alveoli for the incisor teeth, which are separated by short intervals and diminish in size from before backward. As in the ox, a narrow space separates the right and left bones and takes the place of the foramen incisivum. The palatine process is long and narrow. The nasal process is very extensive and is somewhat rhomboid in outline. Its upper border forms a very long suture with the nasal bone, and the lower articulates to about the same extent with the maxilla. The palatine fissure is relatively wide.
The horizontal part of the palate bone forms a fourth to a fifth of the length of the palate; its palatine surface is triangular, the apex being anterior; its nasal surface is deeply grooved and smooth. A pterygoid process (processus pyramidalis of man) projects backward and downward, and its thick rounded end is received between the pterygoid process of the sphenoid and the pterygoid bone. The perpendicular part is largely overlapped externally by the maxilla and concurs in forming part of the palatine canal. Superiorly the two plates separate and inclose an air-cavity which opens into an ethmoidal meatus. The inner plate curves inward and unites with the vomer and ethmoid to form a horizontal plate (Lamina transversalis), which divides the posterior part of the nasal cavity into an upper olfactory part and a lower respiratory part.
The pterygoid bone is nearly vertical in direction, and is narrow in its middle, wide at each end. The external surface is free below and forms the inner wall of the pterygoid fossa. The lower end is notched and forms a distinct hamulus.
The nasal bone is very long and its width is almost uniform, except at the anterior end, which is pointed and reaches almost as far forward as the premaxilla. The facial surface is flattened from side to side. In profile it is nearly straight in some subjects, variably concave in others. The external border is free to a small extent in front only; otherwise it is firmly connected with the premaxilla and maxilla. In the adult the frontal sinus extends into the posterior part of the bone.
The lacrimal bone is very sharply bent. Its facial surface presents a deep depression, surmounted by a ridge or tubercle. On or close to the orbital margin are two lacrimal foramina which lead to the lacrimal canals. The orbital surface presents a fossa in which the inferior oblique muscle of the eyeball arises, and its lower part bears a crest, which is crossed obliquely by a vascular furrow. The upper border articulates with the frontal only. The bone concurs in the formation of the maxillary sinus.
The malar bone is strongly compressed from side to side. Its facial surface is small and presents a fossa which is continuous with the depressions of the maxilla and lacrimal. The orbital surface is still smaller and is smooth and deeply grooved. The zygomatic process is very extensive, especially in the vertical direction. Its external surface is convex and free, and bears a rough eminence in its middle. Its internal surface is concave; it is overlapped in front by the maxilla, and in the remainder of its extent is free and smooth. The upper border is thick and rounded in front, where it forms the lower part of the orbital margin; behind this it forms an extensive notch which receives the zygomatic process of the temporal. (It might be regarded as dividing into frontal and temporal branches.) The lower border is convex and becomes thinner behind.
The turbinal bones resemble those of the ox. The superior turbinal is, however, relatively longer, less fragile, and more firmly attached to the nasal bone. There is no middle turbinal.
The vomer is very long. The anterior extremity reaches to the body of the premaxilla or very close to it. The lower border is received into a groove formed by the nasal crest of the maxillæ and palate bones and in front by the palatine processes of the premaxillæ. The posterior border is concave, thin, and sharp.
The os rostri (or prenasal bone) is situated in the snout between the nostrils. It has the form of a short three-sided prism. The upper surface is convex and is notched at each end. The lateral surfaces are concave, smooth, and converge below, forming a grooved lower border. The posterior surface is triangular, notched centrally, and rough laterally. The anterior surface is deeply pitted and is surrounded by an irregular sharp border.
The mandible is very strong, and differs very much from that of the horse or ox. The body narrows decidedly in front; the lingual surface is deeply concave; the mental surface is strongly convex, slopes downward and backward, and forms a distinct prominence at the point of divergence of the rami. Above this prominence is a pair of foramina. The alveolar border presents six alveoli for the incisor teeth, and a little further back two large cavities for the canine teeth. There are two pairs of mental foramina of considerable size and a variable number of smaller ones. The rami diverge more than in the horse or ox, and the upper part is somewhat incurved. The horizontal part is very thick and strong. Its outer surface is strongly convex from above downward. The inner surface is prominent over the roots of the molar teeth and overhangs the concave lower part. The alveolar border is thin in front and widens behind; it does not follow the axis of the ramus, but runs nearly straight and produces the marked overhang noted above. There are seven alveoli for the lower cheek teeth, which increase in size from before backward. The first is small, not always present in the adult, and is separated by short spaces from the second and the canine alveolus. The vertical part is relatively wide above. The condyle is convex in both directions, wide in front, narrow and declivitous behind. The very small and thin-edged coronoid process is not quite so high as the condyle, from which it is separated by a very wide notch. The mandibular foramen is large. The two halves of the bone unite soon after birth in the improved breeds.
The body of the hyoid bone is broad from before backward, short transversely, and bears on its ventral aspect a very short pointed lingual process. The thyroid cornua are wide and curved, concave and grooved dorsally; their ends are attached to the thyroid cartilage of the larynx by rather long bars of cartilage. The small cornua are short, wide, and flattened dorso-ventrally; they are attached to short bars which project from the junction of the body and thyroid cornua. The middle cornu is a little longer than the small cornu, but is relatively slender; it is largely cartilaginous in the young subject and does not ossify at either end. The great cornu is a very slender rod, slightly enlarged at either end; the upper extremity is attached to the hyoid process of the temporal by a rather long and wide bar of cartilage.
Fig. 112.—Mandible of Pig.
a, Body of mandible; b, horizontal part of ramus; f, vertical part of ramus; c, interalveolar border; c′, interval between canine and corner incisor; c″, interval between first and second premolars; d, mental foramina; e, vascular impression; g, coronoid process; h, condyle; i, sigmoid notch; k, mandibular foramen; 1–7, cheek teeth, 8, canine tooth; 9, 10, 11, incisors. (Ellenberger-Baum, Anat d. Haustiere.)
THE SKULL AS A WHOLE
The length and the profile contour vary greatly in different subjects. Primitively the skull is long—especially in its facial part—and the frontal profile is almost straight. The condition is very pronounced in wild or semi-feral pigs, and exists also in the improved breeds during extreme youth. Most of the latter are decidedly brachycephalic when fully developed; the face is “dished” in a pronounced fashion. The frontal region slopes sharply upward, and the nasal region is shortened, and in some specimens even distinctly concave in profile. The supraorbital foramina are about midway between the orbital margin and the frontal suture. The supraorbital grooves extend forward from the foramina to the nasal region and turn outward and downward toward the infraorbital foramina over the ridges which separate the nasal and lateral regions.
The lateral surface is triangular when the mandible is included. The temporal fossa is entirely lateral and its long axis is almost vertical. It is bounded above by the occipital crest, behind by the temporal crest, in front by the parietal crest, and is marked off from the orbital cavity by the supraorbital process and a curved crest which extends from it to the root of the pterygoid process. The zygomatic arch is strong, high, and flattened from side to side. Its root is notched above and bears a projection below. It curves sharply upward behind and forms a pointed recurved projection above and in front of the external auditory meatus. The orbit is small. Its margin is deficient behind in the dry skull, thick and rounded in front and below. The cavity is limited below by a ridge on the frontal and lacrimal bones, and is separated by a crest from the temporal fossa. The inner wall is perforated above by the orbital opening of the supraorbital canal, and below by the optic and ethmoidal foramina; on its antero-inferior part is the fossa in which the inferior oblique muscle of the eye takes origin. Two lacrimal foramina are found on or close to the anterior margin. The pterygo-palatine fossa is well defined; its upper part forms a deep groove which leads from the large foramen in the sphenoid (like that of the ox) to the very large maxillary foramen. The preorbital region is deeply grooved in its length and is clearly marked off by a ridge from the nasal and frontal regions. The facial crest is short, usually thin-edged, and lies above the fifth and sixth cheek teeth. A little (ca. 2 cm.) in front of it is the infraorbital foramen. There is a ridged prominence over the canine alveolus. In some skulls the anterior part of the upper jaw is inclined upward.
The most striking features of the basal surface are as follows: The paramastoid processes are extremely long, less flattened than in the horse and ox, and nearly vertical. At the inner side of the root of each is the hypoglossal foramen, and in front of it are the stylo-mastoid foramen and a deep cavity in which the hyoid process is concealed. The bulla ossea is long, compressed laterally, and bears a sharp, short, muscular process. The basioccipital is wide and flattened; it bears a median crest and two lateral tubercles. The posterior nares are small and are wider below than above. On either side of them is the tuberosity of the palate bone, and above this is the pterygoid fossa. The palate is remarkably long and is relatively narrow. It constitutes about two-thirds of the entire length of the skull. It is widest between the canines and premolars and narrow at each end. It is marked by a crest medially and by the palatine foramen and groove laterally. The anterior part bears transverse ridges. It is moderately arched from side to side. In some specimens it is nearly straight or slightly concave in its length; in others it curves upward to a variable degree in front. The posterior end always slopes upward more or less.
The posterior or nuchal surface is remarkable for its height and the breadth of the occipital crest. The central part above the foramen magnum is smooth and concave from side to side, and is bounded laterally by ridges, which converge below and end on two tubercles at the upper margin of the foramen magnum. The surface is separated from the temporal fossæ by the temporal crests, which curve downward and outward and blend with the external auditory canals. The mastoid process has the form of a plate which overlaps the root of the paramastoid process and bears a crest on its anterior part.
The cranial cavity is small, in spite of the great size of the cranium; the discrepancy is due to the enormous development of the frontal sinuses in the adult. It is relatively longer, but much lower than that of the ox. Its width is greatly diminished between the orbits. The olfactory fossæ are extensive and very oblique. The floor resembles that of the ox, but the foramen ovale is absent, the dorsum sellæ is more developed, and the foramen lacerum basis cranii is like that of the horse. Two oblique lateral crests clearly mark the limit between the cerebral and cerebellar compartments. The tentorium osseum and the parieto-temporal canals are absent.
The nasal cavity is very long. Its posterior part is divided by a horizontal plate into olfactory and respiratory parts. The olfactory part or fundus is above, and contains the ethmoturbinals and ethmoidal meatuses. The lower part is continuous with the inferior meatus and leads to the pharyngeal orifice; hence it is sometimes called the naso-pharyngeal meatus. The bony roof is almost complete in front on account of the great length of the nasal bones.
The frontal sinus is a vast excavation in the adult animal. It involves all of the roof and almost all of the sides of the cranium, and extends forward into the roof of the nasal cavity a variable distance—sometimes as far as a transverse plane through the infraorbital foramina. The septum between the right and left sinuses is usually deflected in an irregular manner in its middle part, but is practically median at either end. Each sinus is subdivided by numerous septa, some of which are complete. Thus the sinus is divided into compartments, each of which communicates with an ethmoidal meatus.
In the young pig the sinus is small and is confined to the anterior part of the frontal bone. Later it extends backward, outward, and to a less extent forward. In the old subject it penetrates laterally into the supraorbital process and the root of the zygomatic process of the temporal bone, and behind almost down to the foramen magnum and the occipital condyles. It then consists of six to eight compartments usually.
The maxillary sinus is relatively small. Its anterior end is a little less than an inch (ca. 2 cm.) behind the infraorbital foramen, and it extends upward into the lacrimal and backward into the malar bone. The infraorbital canal passes along its floor, and the roots of the molar teeth do not project up into it. It does not communicate with the frontal and sphenoidal sinuses, but with the posterior part of the middle meatus by means of a considerable orifice.
The sphenoidal sinus is very large. It involves the body, pterygoid processes, and temporal wings of the sphenoid bone, and extends into the squamous temporal. It communicates with the ventral ethmoidal meatus.
There is a small sinus in the perpendicular part of the palate bone which communicates with an ethmoidal meatus.
BONES OF THE THORACIC LIMB
The scapula is very wide, the index being about 1 ∶ 0.7. The spine is triangular and is very wide in its middle, which curves backward over the infraspinous fossa and bears a large tuberosity. Its lower part bears a small projection (rudimentary acromion). The anterior border is strongly convex in profile, sinuous when viewed from the front, and thick and rough in its middle. The posterior border is wide, slightly concave, and bears an outer rough lip. The vertebral border is convex, and the cartilage is not so extensive as in the horse and ox. The cervical angle is thin and bent inward a little. The dorsal angle is thick and is about a right angle. The neck is well defined. The rim of the glenoid cavity is rounded and not notched. The tuberosity is just above the antero-internal part of the glenoid cavity and bears no distinct coracoid process.
The humerus has an appearance in profile somewhat like an italic f minus the cross-bar; this is due to the marked backward and forward inclination of the proximal and distal ends respectively. The shaft is decidedly compressed from side to side. The internal surface is extensive and flattened; it is separated from the anterior surface by a distinct border, and bears no teres tubercle. The musculo-spiral groove is shallow. The deltoid tuberosity is small, and there is a larger rounded eminence midway between it and the external tuberosity. The nutrient foramen is on the posterior surface below its middle. The head is more strongly curved and the neck better marked than in the horse or ox. The external tuberosity is very large and extends upon the front of the extremity. It is divided into two high prominences by a wide deep groove. There is a third eminence below and externally for the attachment of the supraspinatus muscle. The bicipital groove is at the front of the inner side; it is undivided and is almost converted into a canal. The outer groove on the distal articular surface is so shallow as to give the appearance of two condyles of similar size. The olecranon fossa is very deep, and the plate of bone which separates it from the coronoid fossa is thin and sometimes perforated. The proximal end unites with the shaft at three and a half years, the distal at one year.
The radius is short and narrow, but thick. The shaft increases in size from above downward. The greater part of the posterior surface is in apposition with the ulna; this part is marked by a vascular furrow which runs downward from the upper interosseous space, and has the nutrient foramen at its proximal end. The bicipital tuberosity is represented by a rough area. The distal end is relatively large. Its carpal surface consists of concavo-convex facets for the radial and intermediate carpal bones. There is a wide shallow groove on the middle of the front. The proximal end fuses with the shaft at one year, the distal at three and a half years.
The ulna is massive. It is much longer and considerably heavier than the radius. The shaft is curved. The anterior surface is convex and most of it is rough and attached to the radius by the interosseous ligament. There is a smooth area on the upper third, which concurs with the radius in forming the upper interosseous space, and is marked in its upper part by the nutrient foramen. From this space a vascular furrow passes downward to the lower part of the shaft, where there is often a distal interosseous space for the passage of vessels. The internal surface is extensive, concave, and smooth. The external surface is slightly convex, and its upper part is marked by an oblique rough line or ridge. The proximal extremity is large and is bent inward somewhat; its length is more than one-third of that of the entire bone. The distal extremity is relatively small; it articulates with the ulnar and accessory carpal bones, and is notched in front to accommodate the ridge on the radius. The bone contains a considerable medullary canal. The bone is consolidated at three to three and a half years.
The carpus comprises eight bones, four in each row. The bones of the proximal row resemble those of the ox, with the exception of the accessory, which is more like that of the horse, but has no external groove. The first carpal is small, elongated from before backward, rounded, and articulates in front with the second carpal. The latter is high and narrow, and articulates with the second and third metacarpal bones below. The third carpal articulates with the radial and intermediate above, the third metacarpal bone below. The fourth is the largest bone of the row; it articulates with the intermediate and ulnar above, the fourth and fifth metacarpals below, and bears a tuberosity on its volar aspect.