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Show 568 MR. J. B. SUTTON ON THE CRANIAL ARCADE. [Dec. 2, (vomer) stops short at, and does not pass beyond, the girdle-bone. In this case it is interesting to note that the anterior portion of the skull is in no need of extraneous support, for the girdle-bone sufficiently protects the ethmoid region, whereas the region between the occipital and girdle-bones is still only cartilaginous at the base, and requires support from the dagger-like parasphenoid (vomer). The question then arises, If the parasphenoid of the Pike and the vomer of Man are homologous, to what do the bones marked vomers in the skull of fishes and batrachians correspond 1 This is a broad question, and involves a consideration of several facial bones. It is to me very obvious that no small amount of confusion with regard to the morphology of the bones of the anterior region of the fish's skull has arisen from the fact, that most anatomists, who have attempted to compare the skulls of the two extremes of vertebrate organization, have not taken sufficiently into account the mode of ossification of the superior maxillae in mammals. This is necessarily of fundamental importance in its bearing on the question ; and after the excellent results Professor Huxley obtained by applying this method of research in elucidating the morphology of the various parts of the temporal bone, I was induced to work out in the same way the facial region. To attempt to give even a resume of all that has been written on the subject of the ossification of the superior maxillary would be a labour in itself; therefore I shall content myself by saying that from the time of Portal onwards anatomists of eminence, who have devoted any attention to the matter, have maintained that this bone arises from more than one centre. The bones are of membranous origin throughout. The various centres are deposited so nearly at one time, and grow so rapidly, that it is an exceedingly difficult matter to determine the order of their appearance ; but this affects the general result so little that the description will be commenced by a consideration of the premaxillary portion. It is certainly very remarkable that any anatomist should be so incredulous as to doubt the origin of this interesting element from an independent centre ; but such is the fact, simply because the maxillo-premaxillary suture, so evident on the palatal aspect of skulls up to end of the first dentition, is obliterated very early on the facial surface of the bone, due to a deposition of osseous material from the periosteum. The segment may be thus described : - It comprises that portion of the superior maxilla which lodges the two incisor teeth; from its mesial surface a horizontal piece projects backwards to form the inner boundary of the anterior palatine canal. Superiorly it has a vertical portion, which forms the lower and outer boundary of the anterior nares, aud in well-marked cases it sends up a spiculum to articulate with the nasal bone. Dr. Paul Albrecht recently communicated to the Societe d'Anthropologic de Bruxelles1 a paper to the effect that the premaxillary bone is, as a matter of fact, developed from two centres, and supports his view by reference to cases of cleft-palate and hare-lip. I have 1 October 1882. |