Scapula

“ Bones of the Extremities. The Scapula in its double spine, the osseous arch formed by the confluence of the acromion with the coracoid process, and the substitution of a distinct foramen for the suprascapular notch, agrees with that of the Megatherium: but the span of the acromial arch is relatively wider, and the surface for the articulation of the clavicle is better marked. This articular surface, which is distinctly shewn upon the acromion of both the scapulæ in Pl. XX. is the more interesting, as being the only evidence of the clavicle of the Scelidothere which we at present possess ”

“ The scapula is of nearly the same length as the coracoid, but is much less stout. It is a thin, spatulate bone, slightly expanded at the distal extremity, where the margin is rounded, and without the characteristic oblique articular facet. It has no supra-glenoid expansion or process on the posterior proximal border, but has its margin nearly straight or gently concave from the articulation to its extremity. The space included between the bones of the two sides as they lie is a nearly regular, oval one, measuring ninety-five millimeters in its greater, forty-five in its lesser diameter. ”

“ A soldier was struck September 27, near Berry au Bac, by a shell fragment in the right scapular region and was thrown, according to his story, 15 meters. Upon entrance at Val-de-Grâce, October 13, the shoulder-girdle was found intact. There was a very painful point in the spinous process of the scapula, suggesting a fracture; but the bone was proved intact on X-ray. The scapula was very mobile, as if unslung from the thorax. The arm was paralyzed. On raising the arm the scapula followed its movements and detached itself completely from the thorax, dislocating upwards with lively pain. ”

“ It seems quite legitimate to regard the muscular union between the thorax and forelimb as a joint. There are no bones resting on each other, no synovia; but where the scapula has its largest range of movement there is a remarkable amount of areolar tissue, which renders movement easy. The whole central area beneath the scapula and humerus not occupied by muscular attachment, is filled with this easy-moving, apparently gaseously distended, crepitant, areolar tissue over which the fore legs glide on the chest wall as freely as if the parts were a large, well lubricated joint. ”

“ A right scapula, a right ulna, five anterior-middle dorsal vertebrae (D1 and D4–D7) preserved in series, and some dorsal ribs occur together in a small region. They are disarticulated, but appear to be in association. Similar to the condition seen in the right maxilla, jugal and dentary, the right scapula has a derived feature that is typical of hadrosaurids, namely the arcuate dorsal edge of the scapular blade. In addition, the neural spines of the anterior dorsals, which are nearly complete in D1 and D5, are more elongate than those in G. mongoliensis. ”

“ The free use of the hand, and the square form of the chest, are alike greatly owing to the clavicle, or collar-bone, which runs across from the breast-bone to the top of the shoulders. The scapula, or shoulder-blade, which is flat and triangular, lies on the ribs, is cushioned with muscles, shifts and revolves in its place with every movement of the arm, and has the power of moving upward and downward, backward and forward, so that when these motions succeed rapidly, the arm is rotated. ”

“ To sum up, if we fancy the human being in the position of the quadruped, the scapula will have its surfaces almost parallel to the ground (Fig. 10) ; while in quadrupeds, the surfaces are situated in a plane which is almost perpendicular to the ground (Fig. 11) . This position of the scapula in an almost vertical plane is designed to give the necessary point of support to the osseous columns that form the skeleton of the other portions of the anterior limbs. ”

“ The patient experiences great relief from the limb being put up in this manner and maintained so; and inflammatory action, with much of the swelling, is averted.
The inferior angle of the Scapula occasionally escapes from under the border of the latissimus dorsi, usually with some laceration of the muscular fibres. The displacement is occasioned by raising the arm above the head to an unusual extent. The angle of the bone projects considerably, and the muscle is felt playing beneath it distinctly during motion of the parts; the movements of the limb are limited and painful. ”

“ The muscle 1 draws the arm by the side, and across the chest, and likewise draws the scapula forward. The muscle 2 elevates the arm. The muscle 6 elevates the ribs when the scapula is fixed, or draws the scapula forward and downward when the ribs are fixed. The muscles 12, 16, 18, bend the body forward or elevate the hips when the muscles of both sides act. They likewise depress the rib in expiration. When the muscles on only one side act, the body is twisted to the same side. ”

“ Ossification of the Tibia.
clavicle are also largely developed; the scapula too is more bird- like in shape than mammalian. In the higher mammals the scapula develops a spine and usually an acromial process, and has a triangular outline.^ As long as the forelimb is used for support, the vertebral border is the shortest of the three, and the long axis of the bone runs from this border to the glenoid cavity ”

“ Primitively, that is, in all the old reptiles, the girdle is composed of scapula, coracoid, metacoracoid, clavicles, and interclavicle, while in some of the very oldest there is yet another bone, more or less of a vestige, derived from the ancestral amphibians and called the cleithrum or supraclavicle. The scapula is more or less elongated in crawling and climbing reptiles; more slender and bird-like in those which walked erect after the manner of birds and mammals; shorter and more fan-shaped in the swimming reptiles, as we shall see. ”

“ Insertion by a short tendon (1 millimeter long) into the vertebral border of the scapula, the line of insertion passing gradually from the inner (Fig. 78, e) to the outer (Fig. 76, i) surface; and by fleshy fibres into the outer surface of the glenovertebral angle of the scapula (Fig. 76, i) in close connection with the origin of the teres major (j) . ”

“ There are present, distinctly preserved in the type specimen, the scapulæ, the clavicles, and the interclavicle, with the possibility of the coracoid. The peculiar element referred to by Cope as resembling a "lacertilian pubis" is without doubt the left scapula of the animal (plate 16, fig. 1) . Its form compares very favorably with that of Ceraterpeton as figured by Woodward (630) . The coracoid may be represented by the fragment which lies close to the scapula. The sculptured element lying next to the supratemporal horn of the skull is the right clavicle preserved bottom side up. ”

“ The upper arm consists of a single bone, the head of which is hemispherical; standing obliquely backward from the bone, and received into a cavity with which the scapula is provided, it forms a ball and socket-joint. In this arrangement there is a provision for the rotating of the arm-bone on the scapula: thus the guards are made in fencing, and various similar movements are performed. In others the wrist has a finer and easier rolling, but this is from the motion of the radius and the ulna. ”

“ The scapula is very large, the coracoid small, and there is no precoracoid, or T-shaped interclavicle. Clavicles are only known in a few cases. In the pelvis the ilium is elongated both in front of, and behind, the acetabulum, sometimes the pre-pubis, sometimes the post-pubis is the better developed. The anterior limbs are shorter than the posterior, and the long bones are sometimes solid, sometimes hollow. ”

“ In most other Vertebrates the pectoral girdle has shifted backwards along the vertebral column, by a "metastasis" (Geoffroy) similar to that by which the pelvic fins in many fish have shifted up close to the pectoral girdle. The scapula (with supra-scapula) is the pleurapophysis, the coracoid the hæmapophysis, of the occipital vertebra. The clavicle is homologised with the slender bone in fish now known as the post-clavicle, which shows a connection with the first or atlas vertebra of the vertebral column, forming, according to Owen, the hæmapophysis of the atlas. ”

“ It is known to human anatomists as the coracoid process of the scapula. It has been found, however, by Professor Howes [19] and others, that this process really consists of two separate centres of ossification, forming two separate bonelets, which in the adult become firmly ankylosed to each other and to the scapula. These two separate bones have been met with in the embryo of Lepus, Sciurus, and the young of various other mammals belonging to very diverse orders, such as Edentates and Primates. The separation even occasionally persists in the adult. ”

“ From near its ventral end the scapula sends off a long process, which converges transversely with its fellow. This process, the clavicle (!) or the precoracoid of many authors, is the acromial process, the Plesiosauri giving the clue as to how an acromion can assume such an abnormal position. The coracoid, with a suture between it and the scapula, is very long and extends horizontally backwards, not meeting that of the other side. ”

“ An osseous scapula is usually present, resembling the scapula of modern salamanders, in that it was largely embedded in cartilage. The position of the pectoral girdle is largely a matter of doubt, especially for the American species. After death and before fossilization the girdle was always moved by post-mortem shifting, so that its exact relation to the ribs and vertebral column is still in doubt. Credner (186) has restored the pectoral girdle close behind the head, which would cause an amount of rigidity in the body which probably did not exist. ”

“ The same shortness of the spines of the dorsal vertebrae prevails in this group as in the other Amblypoda, though it is perhaps hardly so marked. The scapula has not the peculiar acuminate form that exists in Coryphodon, but is triangular and broad above. The limbs are elephantine, in that the angle between the humerus and the femur respectively, and the bones which follow, is not marked. ”

“ The surface may be uniform or bossed, the consistence varies at different parts, and the swelling gradually tapers off along the shaft. On firm pressure, fine crepitation may be felt from crushing of the delicate framework of new bone.
[Illustration: FIG. 148.--Chondro-Sarcoma of Scapula in a man aet. 63; removal of the scapula was followed two years later by metastases and death.]
In _central sarcoma_ pain is the first symptom, and it is usually constant, dull, and aching; is not obviously increased by use of the limb, but is often worse at night. ”

“ Post-temporal more or less distinctly forked, more or less firmly ankylosed to the skull; scapula and coracoid well developed, in contact with each other or separated by cartilage; pectoral rays inserted {695}on the scapula and on 3 or 4 large, hour-glass or anvil-shaped pterygials, two of which are in contact with the coracoid. Ventral fins close together, with 1 spine and 3 to 5 soft rays. Spinous dorsal strong, usually longer than the soft, sometimes extending on the head; anal usually with 3 spines. Body covered with scales or naked. ”