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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![points, the first and the last are alwaj^s, or almost always, developed from a single point in their middle. The bodies of the vertebra? are most commonly formed from a single primitive nucleus : the same is the case u'ith the basilar portion of the occipital, the per- pendicular plate of the ethmoid, the vomer, and the spinous processes of the vertebrae. Instances of incomplete division of bones on the median line must not be adduced in proof of the existence of two primitive points of ossification. 2. Every eminence, according to M. Serres, is developed by a special point of ossifi- cation. This is true generally : but how many eminences are formed merely by the ex- tension of ossification from the piece which supports them ! Where, it may be asked, is the special point of ossification for the articular processes of the vertebra?, the coronoid process of the ulna, the external and internal protuberances of the occipital, Ac. 1 There are even double eminences developed from a single point, as the condyles of the femur. 3. Every cavity is formed by the union of at least two pieces of ossification ; so that, when a bone furnished with a cavity consists of several pieces, the place of junction of these pieces is at the cavity. Thus, the three pieces of the os innominatvun meet together at the cotyloid cavity. The same law, according to M. Serres, regulates the formation of the foramina and osseous canals of every kind, as the medullary cavity of the long bones, all the canals for vessels and nerves, as the carotid, vidian, i&c. : according to the same law, all the foramina in the bones of the scuU are formed originally of two halves. But the facts are opposed to this doctrine when apphed so universally. Progress of Ossification in the three Kinds of Bones.—1. In the long bones. Ossifica- tion commences in their middle part. A small cylinder of bone appears, narrow in the middle, expanded at the ends, tubular within, perforated already with the nutritious fo- ramen, which is very obvious, and receives very large vessels. This little cylinder grows gradually thicker and longer, extending towards the extremities of the bone, which it reaches about the time of birth; while at this period the ossification is so far advanced in the body of the long bones, their extremities are not yet osseous. It is only at later periods, varying in diflerent bones, that an osseous nucleus appears in the cartilaginous extremities, increasing and encroaching upon the portion of cartilage which separates it from the bony shaft, until that cartilaginous partition, gradually becoming thinner, is at last itself invaded by the ossification. AD the long bones have two essential or princi- pal epiphyses, to which complementary epiphyses are sometimes added. The phalan- ges* are an exception ; they have only one. It is this process which is named junction of the epiphyses. The time of its completion is not confined to any very definite limits, but it is over by twenty or twenty-five years. Throughout the whole time of development the growth in length takes place, chiefly by ossification of the intermediate cartilage, which separates' the epiphyses from the shaft, but partly, also, by longitudinal expansion of the ossified shaft itself The foimer mode of increase has been satisfactorily established by Hunter ; the latter is proved by the following experiment of Duhamel: Three needles being fixed in the shaft of a long bone of a bird, at measured distances, it is found that after a certain time they become farther separated, which proves that the osseous cylinder has undergone an elongation. 2. In the broad bones. 1. Among the broad bones, those which are symmetrical often commence by two points placed one on each side of the median line. 2. The asymmet- rical bones are developed sometimes from a single point of ossification, as the parietal; sometimes by several, as the temporal. One of the most remarkable circumstances in the development of broad bones is the sort of radiation by which the deposition of calcareous phosphate extends, which spreads from the centre where the first osseous point was deposited, and advances by divergent rays to all points of the circumference, forming bony stria? separated by intervals, which are soon filled up by new osseous rays. As these rays are of unequal length, and are separated at the circumference by intervals of greater or less extent, it follows that a broad bone in the process of ossification must have at its circumference a scalloped or jagged border, like the toothed edge of a comb. It is this form of ossification which gives rise to the serratures of the sutures. The broad bones are proportionally much thinner in the early periods of ossification than subsequently, because ai first the spongy texture is scarcely developed. At the time of birth, the primary pieces of ossification not having united except in very few places, and the ossification which spreads from the centre of the bones not having yet reached the limits of their circumference, it follows that the constituent parts of bones, and the edges of different bones which are destined in the end to meet together, are at this period separated by cartilaginous, and, in some measure, membranous intervals, which in the cranium constitute the fontanelles. After birth, ossification spreads more and more in the broad bones ; at the same time they increase in hardness and thickness, appearing as if to separate into two plates or tables, the interval between which be- comes filled with spongy tissue. The epiphysary or complementary points of ossification of some of the broad bones * [Also the clavicle, the metatarsal, and usually the metacarpal bones.] c .^](https://iiif.wellcomecollection.org/image/b21196801_0041.jp2/full/800%2C/0/default.jpg)
