An observation on the development of the mammalian vomer / by Robert J. Terry.
- Terry, Robert J. (Robert James), 1871-1966
- Date:
- 1909
Licence: In copyright
Credit: An observation on the development of the mammalian vomer / by Robert J. Terry. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![processes of tbe premaxillaries. These processes have been observed by Albrecht, Sutton and others to arise independently of, and subse- quently to fuse with, the tooth-hearing portions of the premaxillaries. In later years, Broom^ has contributed much to our Imowledge of the comparative anatomy of the vomer, and with evidence adduced from the investigations of Turner, W. R. Parker, Wilson and Sym- ington, he strongly supports the homology of the mammalian vomer and parasphenoid. As to the comparison of the paired vomers of the lower forms with the palatine processes of the premaxillaries, he does not agree entirely with Sutton. Broom has suggested the term ‘^prevomer” for the category of bones represented by the paired vomers (of other authors) in the lizard, and finds its homologues in the paired vomers of the Ichthyopsida. But in the great majority of the higher mammals the prevomer does not exist, its place being taken by invasion of the palatine processes of the premaxillaries. These are regarded as true portions of the premaxillaries and not inde- pendent elements which Sutton considered them to he. In the dumb- bell-shaped hone of Ornithorhynchus and in a median ossification in the nasal region of Miniopterus, Broom identifies the prevomer. These bones, although azygos in the adult, are both derived from a fusion of a pair of splints underlying the cartilages of the vomero- nasal organs. An objection to the comparison of the mammalian vomer and the non-mammalian parasphenoid lies in the fact that the latter presents in the series of animals a history of retrogression; in the lowest forms the parasphenoid reaches forward to the ethmoidal region, whereas in most reptiles and birds its anterior end is far back and away from this region. A more serious obstacle to the new homology is the circumstance, already mentioned, of the single vomer develop- ing from a pair of centers. The one instance in mammals might well be taken to be an exception to the rule of single origin, if ®Broom, R. On the Homology of the Palatine Process of the Mammalian Premaxillary. Proc. Linn. Soc. N. S. W., 1895, Vol. X. p. 477-485. On the OccniTence of an Ap]iarently Distinct Prevomer in Gomphogna- thns. .Tour. Anat. and Physiol., 1896, Vol. XXXI. On the Mammalian and Reptilian Vomerine Bones. Proc. Linn. Soc. N. S. W., 1902, Vol. XXVII, part 4, p. 545-560.](https://iiif.wellcomecollection.org/image/b22474067_0006.jp2/full/800%2C/0/default.jpg)
