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.
Detail, illustrating his statements by the preparations he exhibited, the progress of ossification in the sternum of the fowl and of the duck, pointing out how it differed in each, and giving his interpretation of the differences.
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.
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.