Ossification Sentence Examples
It had hitherto been generally believed that the mode of ossification in the fowl was that which obtained in all birds - the ostrich and its allies (as L'Herminier, we have seen, had already shown) excepted.
Geoffroy here maintained that the five centres of ossification existed in the duck just as in the fowl, and that the real difference of the process lay in the period at which they made their appearance, a circumstance which, though virtually proved by the preparations Cuvier had used, had been by him overlooked or misinterpreted.
In their case the sternum begins to ossify from three very distinct points - one of which is the centre of ossification of Nitzsch's grouping.
These conditions are quite distinct from the normal process of ossification as is seen in bone.
Uncomplicated, normal, progressive ossification of the sound horse's collateral cartilages causes no clinical problems and requires no treatment.Advertisement
There is no evidence, so far as we can see, of his having been aware of Merrem's views; but like that anatomist he without hesitation divided the class into, two great " coupes," to which he gave, however, no other names than " Oiseaux normaux " and" Oiseaux anomaux "-exactly corresponding with his predecessor's Carinatae and Ratitae-and, moreover, he had a great advantage in founding these groups, since he had discovered, apparently from his own investigations, that the mode of ossification in each was distinct; for hitherto the statement of there being five centres of ossification in every bird's sternum seems to have been accepted as a general truth, without contradiction, whereas in the ostrich and the rhea, at any rate, L'Herminier found that there were but two such primitive points, 3 and from analogy 1 Their value was, however, understood by Gloger, who in 1834, as will presently be seen, expressed his regret at not being able to use them.
Less commonly, the body may develop calcium deposits at the injury site in a process called heterotopic ossification.
Many scientists believe it is the result of a defect in the ossification (bone formation) in the bones of the skull.
Ossification (the process whereby tissue becomes bone) of most bony nuclei of the long bones and round bones does not complete until after birth.
Flat bones develop by intramembranous ossification, where bone develops within sheets of connective tissue.Advertisement
At birth, long bones have more than one ossification center (regions from which bone growth starts).
The age at appearance of individual ossification centers then becomes a useful measure of skeletal development and especially in the form of "bone age" assessments of the hand, foot, or knee.
The sequence of ossification of the bones also differs significantly from child to child, and the different sequences are controlled by genetics.
Thus, poorly nourished boys and girls may be delayed in linear bone growth, diminished in all bone widths, later in the appearance of ossification centers, and delayed in epiphyseal union (completion of long-bone growth).
Prefrontal bones are absent; post-frontals are possibly indicated by a frequently occurring separate centre of ossification in the postorbital process, to which the frontals always contribute.Advertisement
In many birds the spaces between the metasternum and the posterior processes and again the spaces between this and the oblique process are filled up by proceeding ossification and either remain as notches, or as fenestrae, or they are completely abolished so that the breastbone is turned into one solid more or less oblong plate.
Another cartilage or ossification, the posterior sclerotic ring, occurs within the walls of the posterior portion of the cup, and surrounds, especially in the Pici and in the Passeres, the entrance of the optic nerve.
Moreover, the author goes on to remark that in adult birds trace of the origin of the sternum from five centres of ossification is always more or less indicated by sutures, and that, though these sutures had been generally regarded as ridges for the attachment of the sternal muscles, they indeed mark the extreme points of the five primary bony pieces of the sternum.
But it was now made to appear that the struthious birds in this respect resembled, not only the duck, but a great many other groups - waders, birds-of-prey, pigeons, passerines and perhaps all birds not gallinaceous - so that, according to Cuvier's view, the five points of ossification observed in the Gallinae, instead of exhibiting the normal process, exhibited one quite exceptional, and that in all other birds, so far as he had been enabled to investigate the matter, ossification of the sternum began at two points only, situated near the anterior upper margin of the side of the sternum, and gradually crept towards the keel, into which it presently extended; and, though he allowed the appearance of detached portions of calcareous matter at the base of the still cartilaginous keel in ducks at a certain age, he seemed to consider this an individual peculiarity.
Then, it is true, two lateral points of ossification appear at the margin, but subsequently the remaining three are developed, and when once formed they grow with much greater rapidity than in the fowl, so that by the time the young duck is quite independent of its parents, and can shift for itself, the whole sternum is completely bony.Advertisement
As regards the struthious birds, they could not be likened to the duck, for in them at no age was there any indication of a single median centre of ossification, as Geoffroy had satisfied himself by his own observations made in Egypt many years before.
Cuvier seems to have acquiesced in the corrections of his views made by Geoffroy, and attempted no rejoinder; but the attentive and impartial student of the discussion will see that a good deal was really wanting to make the latter's reply effective, though, as events have shown, the former was hasty in the conclusions at which he arrived, having trusted too much to the first appearance of centres of ossification, for, had his observations in regard to other birds been carried on with the same attention to detail as in regard to the fowl, he would certainly have reached some very different results.
L'Herminier arrived at the conclusion that, so far from there being only two or three different modes by which the process of ossification in the sternum is carried out, the number of different modes is very considerable - almost each natural group of birds having its own.
The principal theory which he hence conceived himself justified in propounding was that instead of five being (as had been stated) the maximum number of centres of ossification in the sternum, there are no fewer than nine entering into the composition of the perfect sternum of birds in general, though in every species some of these nine are wanting, whatever be the condition of development at the time of examination.
In the Gallinae the five well-known pieces or centres of ossification are said to consist of the two side-pieces of the second or middle series, and the three of the posterior.Advertisement
As regards the ducks, L'Herminier agreed with Cuvier that there are commonly only two centres of ossification - the side-pieces of the middle series; but as these grow to meet one another a distinct median " noyau," also of the same series, sometimes appears, which soon forms a connexion with each of them.
In the ostrich and its allies no trace of this median centre of ossification ever occurs; but with these exceptions its existence is invariable in all other birds.
The maxillo-palatals are bound together (whence the name of the " Suborder ") across the middle line, either directly or by the ossification of the nasal septum.
Both as regards structure and habits, the leopard may be reckoned as one of the more typical representatives of the genus Felis, belonging to that section in which the hyoid bone is loosely connected with the skull, owing to imperfect ossification of its anterior arch, and the pupil of the eye when contracted under the influence of light is circular, not linear as in the smaller cats.
From the fact that the bony horn-core of the hollow-horned ruminants first develops as a separate ossification, as do the horns of the giraffe, while the pedicle of the antlers of the deer grow direct from the frontal bone, it has been proposed to place the hollow-horned ruminants (inclusive of the prongbuck) and the giraffes in one group and the deer in another.
In the Aglossa, which are remarkable for the large size and complexity of the larynx, the thyro-hyal bones are incorporated into the laryngeal apparatus, whilst the recently discovered Hymenochirus is further remarkable for the large size and ossification of the hyoidean cornua (ceratohyals), a feature tt; which, though not un 3 E /L?_ n.s.c s4.
Long, short, and irregular bones develop by endochondral ossification, where cartilage is replaced by bone.