xii CONTENTS. 



CHAPTER IV. 



HEARING. 



SECTION I. 



ON THE GENERAL STRUCTURE OF THE EAR AND ON THE STRUCTURE 

 AND FUNCTIONS OF THE SUBSIDIARY AUDITORY APPARATUS. 



PAGE 



808. The embryonic history of the Ear. The otic vesicle . . . 1314 

 809. The general relations of the parts of the Ear ; vestibule and cochlea, 

 membranous and bony labyrinth, tympanum, auditory ossicles, 



membrana tympani and external meatus 1315 



810. The general use of the several parts 1318 



The Conducting Apparatus of the Tympanum. 



811. The auditory ossicles 1319 



812. The tympanum ; its structure and relations ..... 1320 



813. The membrana tympani 1323 



814. The joints, ligaments, and positions of the auditory ossicles . . 1325 



815. The chain of ossicles as a lever 1327 



The Conduction of Sound through the Tympanum. 



816. Longitudinal and transversal sonorous vibrations. The vibrations 



of the tympanic membrane 1328 



817. The conduction of vibrations through the chain of ossicles . . 1330 



818. The conduction of vibrations through the bones of the skull . . 1331 



819. The action of the tensor tympani and stapedius muscles . . . 1332 



820. The Eustachian tube 1334 



SECTION II. 

 THE STRUCTURE OF THE LABYRINTH. 



821. The parts of the vestibule ; utricle, saccule and semicircular canals 1336 



822. The perilymph cavity of the vestibule ...... 1338 



823. The auditory nerve ; the maculaa and cristaa acusticae . . . 1339 



824. The general structure of the Cochlea . . . . . . 1340 



The Vestibular Labyrinth. 



The minute structure of the parts free from nerve endings . .. . . . 1344 



The structure of the cristae acusticaa . . .- ., I 1344 



