XX. On the development of the ossicula auditus in the higher Mammalia

Abstract

Since the discovery by Meckel of the cartilage which bears his name and the subse­quent discovery by Rathke of the cartilaginous rods immediately succeeding it, anatomists and embryologists have not failed to be intensely interested in the elucida­tion of their history. Huschke was the first to limit the origin of the ossicula to the cartilages of the first two post-oral arches, but it is to Reichert that the first full and masterly description of these two cartilages is due. Looking at the wide­spread existence of these two rods in all classes of the Vertebrata, and the differentia­tion taking place at their proximal extremities, which may result either in the formation of a suspensory apparatus, or in one which, changing its function, is sub­ordinated to the organ of hearing, it can scarcely be wondered at that the opinions concerning the homology of the differentiated parts should be various and conflicting. Nor can it be otherwise, seeing that as yet there is no general agreement as to what parts are or are not derived from or connected with the upper extremities of these two cartilages in any one class of the Vertebrata. This portion of my work refers only to the Mammalia, but I hope soon to complete my observations upon the remaining classes of the Vertebrata. Before passing to the description of my own work I shall give a brief summary of the various views that have been advanced respecting the origin of the ossicula auditus.