Parietal bone

“ We may now return to the skull of our chimpanzee. In considering the nature of the divisions in the parietal bones of this skull, we can at once and absolutely discard the idea of the divisions being due to fractures, or being boundaries of Wormian or fontanel bones, and thus really extra-parietal in their nature. There is nothing about the sutures, or the divided pieces, or the neighboring bones, that would even suggest such an explanation; and in our records on Wormian and fontanel bones we find no analogies either in man, or apes, or lower animals, to the conditions here observed. ”

“ A positive strain represents stretching, whilst compression is represented by a negative figure. Direct experimental measurements in a human showed that the strain levels in the parietal bone of the skull are 10 fold lower compared with the tibia [4] . ”

“ Ranke [10] opposes both Gruber's and Putnam's opinion, and presents instead a theory somewhat vague and not satisfactorily demonstrated, by which he accounts for the origin of oblique sutures from partial horizontal sutures in the parietal bone through "half-pathological processes." In his words, "the oblique parietal suture is allied to the half-pathological conditions of the skull; it is wholly unjustifiable to speak, as W. Gruber has done, of a separate Parietale secundarium posterius, severed by the suture, as of a typical, in a certain sense normal, formation. ”

“ The division consisted invariably of a longer or shorter remnant of a horizontal "parietal suture," ending in the coronal suture at the top of the bend above referred to. A similar anterior remnant of an abnormal parietal suture was found by Ranke in a young chimpanzee skull; but the author questions the word "chimpanzee," which evidently means that the identity of the skull is somewhat doubtful.
In consequence of his finds, Ranke believes both complete and incomplete divisions in the parietal bone to be much more [Pg 282] frequent in the orang than in man. ”

“ A straight course, ending with one extremity in or near the middle of the anterior or posterior border of the parietal, a complex serration, no continuity of the division on the neighboring bones, and particularly a co-existence of an allied or similar division on the opposite parietal,—all favor the conclusion that the division under consideration is a real congenital suture, and not the result of a fracture. ”

“ It can be well explained, though there may at times be other factors present, by a difference in the blood-supply to the two centres. This of course may occur not only in different skulls, but also on the two sides of the same cranium.
Footnotes
[1] Die überzähligen Hautknochen des menschlichen Schädeldachs, Abh. d. k. bayer. Akad. d. ”

“ The periosteum strips off readily, and under this is a thin shell of compact bone, which appears somewhat ridged on the side towards the periosteum. The rest of the tumor consists of cancellous bone. The whole swelling cuts readily with bone forceps and consists of quite soft bone. On making microscopical preparations there were signs of ossification in membrane proceeding under the periosteum, and the rest appeared like ordinary wide-meshed cancellous bone. The whole process appeared to be that of a slow “osteoplastic periostitis.” ”

“ The flat bones often show well-marked periostitis, but the great thickening sometimes seen in certain of the bones of the head appears to be the result of a special osteo-periostitis. It is quite certain that the disease is due to something more than a mere want of mineral constituents in the bone, and poverty in this respect certainly does not explain the hypertrophic changes. The nutrition of the bones as a whole is disturbed, resulting in alterations both in the ossein and in the mineral salts, the whole process being accompanied by symptoms of osteo-periostitis. ”

“ Lining the medullary and cancellous cavities is a delicate connective tissue lining, the endosteum, which contains many bone-forming cells, while on the outside of the bone, except at the articular ends, is the periosteum with its outer protective layer and its inner vascular layer containing osteoblasts or bone-forming cells. The periosteum is essential for the growth of new bone where the old bone has died, and if the periosteum is removed from healthy bone the part beneath is liable to die, as it is by the constant growth of the osteoblasts that the bone grows and is renewed. ”

“ We find on all the non-articular cartilages a membrane exactly analogous to the periosteum, and which is called perichondrium. The larynx, the ribs, &c. exhibit it in a very evident manner; it is delicate, with fibres interlaced in all directions, less closely united to the organs it covers, than the periosteum is to the bones, because the cartilages having on their surface less numerous foramina, it does not send to them as many fibrous elongations; hence a less intimate relation between the life of the perichondrium and that of the cartilage, than between that of the bone and its periosteum. ”

“ A long-continued and chronic irritation of the periosteum, sufficient to cause a proliferation of the osteogenetic cells of the periosteum, is common in a great many diseases. A chronic thickening of the periosteum with a new formation of bone, is seen frequently after traumatism, blows or contusions; sometimes after the occurrence of superficial abscess of the soft tissues in the immediate vicinity of the shaft of the long bone, described as chronic ulcer of the surface of the tibia ”

“ If the periosteum has been extensively destroyed, new bone may only be formed in patches, or not at all. The dead bone is separated from the living by the agency of granulation tissue with its usual complements of phagocytes and osteoclasts, so that the sequestrum presents along its margins and on its deep surface a pitted, grooved, and worm-eaten appearance, except on the periosteal aspect, which is unaltered. Ultimately the dead bone becomes loose and lies in a cavity a little larger than itself; the wall of the cavity is formed by the new case, lined with granulation tissue. ”

“ The periosteum becomes inflamed; a widespread suppurative periostitis is the result; necrosis of the bone from insufficient nutrition follows, while mechanical pressure on the pus aids in its absorption. The medulla frequently takes on suppurative inflammation, and here the surgeon fails to receive prompt warning of danger; slowly the suppuration progresses, without pain or other symptoms unless the disease has extended to the other tissues; the medullary cavity at the fractured end of the bone may be completely or partially occluded by a new osseous formation ”

“ On the dorsal side of the cartilage there is a projecting ridge composed mainly of a bone known as the pterotic, sometimes erroneously [Pg 596] called the squamosal, and continued in front by the sphenotic. The pterotic, or the cartilaginous region corresponding to it, always supplies the articular surface for the hyomandibular.
In the floor of the skull, in the region of the pituitary body, there is formed a basisphenoid; while in the lateral parts of the wall of this part of the cranium, there is a bone known as the alisphenoid. ”

“ The head of the os femoris, situated where it is usually found in luxations outward and upward, was surrounded by a cartilage equally tumefied.
5. Here the cause of the displacement of the os femoris was evident. The cartilages becoming tumefied, in consequence of the contusion and violence done to them, had by degrees, filled up the acetabulum, forcing out in the same gradual manner the head of the bone. Hence arose the original lengthening of the limb. ”

“ On longitudinal section of a long bone during the active stage of the disease, the marrow is seen to be replaced by a vascular young connective tissue which encroaches on the surrounding spongy bone, reducing it to the slenderest proportions; the formation of bone from the periosteum does not keep pace with the absorption and replacement going on in the interior, and the cortex may be reduced to a thin shell of imperfectly calcified bone which can be cut with a knife. The young connective tissue which replaces the marrow is not unlike that seen in osteomalacia ”

“ They exhibit a rough symmetry; they rarely attain any size; and they usually cease growing when the skeleton attains maturity—the conversion of cartilage into bone being then completed. While they originate from the ossifying junctions of the long bones, they tend, as the shaft increases in length, to project from the surface of the bone at some distance from the ossifying junction and to “point” away from it. They may cause symptoms by “locking” the adjacent joint or by pressing upon nerve-trunks or blood vessels. ”

“ The most common is an osteomyelitis commencing in the marrow exposed in a wound infected with pyogenic organisms. In amputation stumps, fungating granulations protrude from the sawn end of the bone, and if necrosis takes place, the sequestrum is annular, affecting the cross-section of the bone at the saw-line; or tubular, extending up the shaft, and tapering off above. The periosteum is more easily detached, is thicker than normal, and is actively engaged in forming bone. ”

“ The disorder of growth is confined to those elements of the skeleton where a core of bone formed in cartilage comes to be encased in a sheath of bone formed beneath the periosteum. To indicate this abnormality the name _diaphysial aclasis_ has been employed by Arthur Keith at the suggestion of Morley Roberts.
Bones formed entirely in cartilage are exempt, namely, the tarsal and carpal bones, the epiphyses of the long bones, the sternum, and the bodies of the vertebrae. Bones formed entirely in membrane, that is, those of the face and of the cranial vault, are also exempt. ”

“ In a work of this limited size the sensibility of the various tissues cannot be fully treated but it should be borne in mind that the integument and the subcutaneous tissue, fat and muscles as well as the tendons, their sheaths, the muscles and periosteum and perichondrium covering the bones and cartilages throughout the body, are all highly sensitive to pain. It is also equally true that the bone substance, the bone marrow, and the cartilages are devoid of any of the four modalities of sensation. ”

“ The external investment—the periosteum—is thick and vascular during the period of growth, but becomes thin and less vascular when the skeleton has attained maturity. Except where muscles are attached it is easily separated from the bone; at the extremities it is intimately connected with the epiphysial cartilage and with the epiphysis, and at the margin of the latter it becomes continuous with the capsule of the adjacent joint. ”

“ Very commonly the child ceases to move one of his lower limbs--pseudo-paralysis--and screams if it is touched; a swelling is found over one of the bones, usually the femur, accompanied by exquisite tenderness; the skin is tense and shiny, and there may be some oedema. These symptoms are due to a sub-periosteal haemorrhage, and associated with this there may be crepitus from separation of an epiphysis, rarely from fracture of the shaft of the bone. X-ray photographs show enlargement of the bone, the periosteum being raised from the shaft and new bone formed in relation to it. ”

“ If death was not too soon the consequence of the puncture of the head of hydrocephalic patients, I am persuaded that we should see the bones gradually contract, and restore the cavity of the cranium to its natural dimensions. When we remove the dead piece from a long bone in necrosis, the new bone, formed on the exterior by means of the periosteum contracts in an evident manner. In paralysis of the optic nerve, its foramen becomes narrower. The orbit contracts when a cancerous eye has been extirpated. ”

“ From the closeness and intimacy of the connection existing between the two principal elements of the bony structure while in health, it frequently becomes exceedingly difficult, when a state of disease has supervened, to discriminate accurately as to the part primarily affected and to determine positively whether the periosteum or the body of the bone is originally implicated. ”

“ The periosteum is exquisitely sensible, and is the safe-guard to the substance of the bone, which is delicately tender notwithstanding it is not so sensible as the skin that covers it; insomuch that it will become carious on the least exposure to the air, or the attack of any foreign body of matter whatever; whence in wounds and fractures in general, great attention should be paid to the substance of the bone, being very subject to become carious and to exfoliation, which is of the greatest consequence ”

“ The cranial part is in contact with the inner table of the skull, and is adherent along the lines of the sutures and to the margins of the foramina, which transmit the nerves, more especially to the foramen magnum. It forms, therefore, for these bones an internal periosteum, and the meningeal arteries which ramify in it are the nutrient arteries of the inner table. As the growth of bone is more active in infancy and youth than in the adult, the adhesion between the dura mater and the cranial bones is greater in early life than at maturity. ”

“ Finally, this red zone was covered with a fairly thick layer of 42 white bone: this was the layer formed after the madder had been left off.... We shall have no further difficulty in understanding whence transudes the osseous juice that was thought necessary for the formation of callus and the filling-up of the wounds of the bones, now we see that it is the periosteum that fills up the wounds, or is made thick round the fractures, and afterward becomes of the consistence of cartilage, and at last acquires the hardness of bones. ”