Licence: Public Domain Mark
Credit: The anatomy of the human body / By J. Cruveilhier. Source: Wellcome Collection.
Provider: This material has been provided by the University of Massachusetts Medical School, Lamar Soutter Library, through the Medical Heritage Library. The original may be consulted at the Lamar Soutter Library at the University of Massachusetts Medical School.
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![Development of Bones, or Osteogeny. From the time of their first appearance in the foetus, to the period of their complete development, the bones pass through a series of changes, which constitute one of the most important circumstances in their history. The investigation of these changes, or of the successive periods of development, is the object o( osteogeny. The development of the bones, considered generally, presents three phases or periods, designated by the name mucous, cartilaginous, and osseous stage. 1. The mucous stage. The mucous condition, the cellular of some authors, has not been vrell defined. Some apply the term to that period of formation in which the bones and the other organs of the body form but one homogeneous mass of a mucous aspect: others use the term to signify a more advanced stage, in which the bones, acquiring a greater consistence than the surrounding parts, begin to show their development through these more transparent tissues. In the latter sense, the mucous stage is obviously no- thing but the commencement of the cartilaginous, and therefore the first acceptation is the only one to be retained. 2. The cartilaginous stage succeeds the mucous, though the time of the transition from the one to the other has not been precisely ascertained. Several anatomists are of opin- ion, with Mr. Howship, that the cartilaginous state does not necessarily intervene be- tween the mucous and osseous conditions ; that its occurrence is only satisfactorily de- monstrated in such bones as are late in ossifying, and that it constitutes a sort of provis- ional condition, in which the cartilage is employed to perform the office of bone. But when we take into consideration, in the first place, the rapid transition from the cartila- ginous to the osseous stage in certain bones, and, secondly, the translucency of newly- formed cartilage when of inconsiderable thickness, as in the cranium, where the carti- lage is scarcely to be distinguished from the two membranes between which it is placed, we can conceive that the cartilaginous stage may easily have been overlooked. On the other hand, the constant result of my observations proves that, in the natural process of ossification, every bone passes through the state of cartilage. When the different pieces of the skeleton assume the cartilaginous condition, the change occurs throughout their whole substance at once. The notion of central points of cartilaginification, corresponding with the points of ossification, is purely hypotheti- cal : a bone becomes cartilaginous in all parts simultaneously, and never by insulated points. The cartilage has the same figure as the future bone. Bones which are to be permanently united by intermediate cartilage, are formed from one primitive piece of cartilage, as those of the cranium and face : those, on the other hand, which are connected together only by ligaments, are distinct and separable while in the cartilaginous state. 3. The osseous stage. The cartilaginous condition of the skeleton is completed by the end of the second month ;* but ossification commences in several places long before this period. The first point of ossification appears after the fourth week in the clavicle ; the second, in the lower jaw. From the thirty-fifth to the fortieth day points of ossifica- tion appear sometimes successively, in other cases simultaneously, in the thigh-bone, the humerus, the tibia, and upper jaw-bone. From the fortieth to the fifty-fifth day, points of ossification appear at short intervals in the annular portion of the uppermost vertebrae, in the bodies of the dorsal vertebrae, in the ribs, the tabular bones of the scull, the fibula, the scapula, the ilium, the nasal, palatine, and metacarpal bones, the phalan- ges of the fingers and toes, the metatarsus, &,c. Once commenced, the ossification pro- ceeds with more or less rapidity in the different bones during the remainder of intra- uterine life. In the child at birth, the shafts of the long, as well as the broad bones, are far advan- ced in development. As to the short bones, the vertebrae are scarcely less early in their evolution than the long and broad bones ; the calcaneum, cuboid, and sometimes the as- tragalus, have points of ossification, but only commencing. The extremities of the long bones, with a single exception, the lower end of the femur, are as yet without ossifying points. The remaining short bones and extremities of long bones ossify subsequently. Of the tarsal bones, the scaphoid is the last to ossify; the pisiform is the latest among the carpal bones ; the patella is ossified at the age of three years. In regard to the process of ossification, a question of the highest interest presents it- self, viz., 7s the successive appearance of the centres of ossification governed by any general law? The order of commencement of the points of ossification is in no way dependant on the size of the bones. It is true that the smaller bones, excepting the ossicles of the ear, are later in appearing; but, at the same time, it is not the largest bones that are the earliest; thus, the bones of the pelvis appear long after the clavicle. * [The relative time of ossification of the diiTerent bones, or, at least, the order in which it commences in them, is easily determined ; but owing to the uncertainty respecting the age of the embryo in its early stages, the absolute time of fcetal life at which each bone begins to ossify is very uncertain, and, accordingly, the statements of many anatomists differ from that given in the text: thus the seventh week is assigned by soma as the period when ossification commences in the clavicle. The age fised by the author appears too early.]](https://iiif.wellcomecollection.org/image/b21196801_0039.jp2/full/800%2C/0/default.jpg)
