On the modifications of the first and second visceral arches : with especial reference to the homologies of the auditory ossicles / by Hans Gadow.

  • Gadow, Hans Friedrich, 1855-1928.
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: On the modifications of the first and second visceral arches : with especial reference to the homologies of the auditory ossicles / by Hans Gadow. 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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    [ «1 ] XVII. On the Modifications of the First and Second Visceral Arches, with especial reference to the Homologies of the Auditory Ossicles. By Hans Gadow, Ph.D., M.A., Strickland Curator and Lecturer on the Advanced Morphology of Vertebrata in the University of Cambridge. Communicated by Professor M. Foster, Sec. R. S. * Received April 12,—Read April 26, 1888. [Plates 71-74.] An ample material of rare Elasmobranch forms, especially Heptanchus, Hexanchus, Centrophorus, Myliobates, and Trygon, which I had collected during the last summer on the South Coast of Portugal, and several fresh specimens of Hatteria, have induced me to submit the question of the modifications of the two first visceral arches to a reconsideration. The homologies of the auditory ossicles have not hitherto been settled beyond dispute, and only recently this question has again been taken up by Albrecht, Dollo, Bauer, and Gradenigo. The most important of these latest contributions has been made by Albrecht, who, chiefly for theoretical reasons, advocates that the whole of the auditory chain in all the Amphibia and Amniota is homologous with the hyomandibula of the Fishes. However, since one of his premisses is highly disputable (quadrate = processus tympanicus of the os squamosum), and considering that one of his principal conclusions leads to a complete and absolutely unjustified reversion of the views which are generally accepted regarding the morphology of the visceral arches, his conclusions as to the homologies of the auditory ossicles have never met with any favour. I trust, therefore, that my attempt to reconsider the whole question on the broadest basis will not be superfluous. Nearly all the preparations figured in this essay are in the Cambridge University Museum of Zoology and Comparative Anatomy. Heptanchus cinereus.—The second visceral, or hyoidean, arch consists of a hyoman- dibular bar, a hyoid bar, and the copula. The whole arch is very slender, especially at the level of the masticatory joint* and is almost completely hidden from a side view by the first visceral arch. MDCCCLXXXVIII.—B. 6.12.88