The Eustachian Tubes in the Crocodilia

THE eustachian tubes in the Crocodilia probably are unique because of the complexity of their development. This is a fact that is not very widely recognized among anatomists or herpetologists, although it has been noted in the literature by various authors during the past century. It was in 1850 that Owen first described the eustachian passages in the Crocodilia in the Philosophical Transactions of the Royal Society of London, with the characteristic thoroughness so indicative of his keen powers of observation and of his great skill as a comparative anatomist. Indeed, to the best of my knowledge, no subsequent description has been as complete or as well documented. Accompanying Owen's description are three plates, showing dissections of the skulls in certain crocodilians, but while these plates are accurate and well-executed, they fail to give an adequate picture of the complex courses and the branchings of the eustachian passages within the skull. This is perhaps the reason why the complex nature of the eustachian tubes in the Crocodilia has been overlooked by so many anatomists and herpetologists subsequent to Owen. In 1878 Miall described the eustachian tubes in the Crocodilia, with an accompanying figure that gives a reasonably clear idea as to the courses of these passages and their relationships to each other. Again, in 1890, a description of the crocodilian eustachian tubes was given in Bronn's Klassen und Ordnungen des Thier-Reichs, with an accompanying plate showing dissections of the skull. This work, like Owen's original description, fails in spite of its thorough description, to give an understandable picture of the eustachian tubes in these reptiles. Thus these publications have not added much to Owen's description. The present paper is written in an attempt to show more satisfactorily than has been done in the past the manner in which the eustachian tubes connect the tympanic cavity and the throat in the crocodilians. The reason that previous figures (with the exception of Miall's rather simple diagrammatic sketch) have failed to give an adequate impression of the eustachian