568 MR. J. B. SUTTON ON THE CRANIAL ARCADE. [DeC. 2, 



(vomer) stops short at, and does not pass be3'ond, 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 suffi- 

 ciently protects the ethmoid ref^ion, 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 ? 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 ou 

 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, wiio 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 tiie order of their ap- 

 pearance ; but this affects the general result so little that the descrip- 

 tion 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 boundarj' of the anterior 

 palatine canal. Superiorly it has a vertical portion, which forms 

 the lower and outer boundary of the anterior nares, and in well- 

 marked cases it sends up a spiculum to articulate with the nasal bone. 

 Dr. Paul Albrecht recently communicated to the Societe d'An- 

 thropologie de Bruxelles' a paper to the effect that the premaxillary 

 bone is, as a matter of fact, developed fiomtwo centres, and supports 

 his view by reference to cases of cleft-palate and hare-lip. I have 



^ October 1882. 



