Animal Morphology. 131 



Serous Membrane. The fibro-cartilages of the nose, and 



the cartilaginous rings of the trachea. 

 Muscular Membrane. Levator palati, tensor palati, tensor 



tarsi, and the muscles comprising the external nasal 



group. 



III. 



THE SENSE OF HEARING. 



This sense, and that of sight, appear to have two tripartite 

 membranes an essential, and a supplementary 

 tripartite membrane. 

 Essential Tripartite Membrane, or Inner Ear. 



Mucous Membrane. Cochlea, with its modiolus and the 

 semi-circular canals. 



Serous Membrane. Lining membrane of cochlea and semi- 

 circular canals and otolithes. 



Muscular Membrane. Arytaenoid muscles displaced to 



regulate the voice. 

 Supplementary Tripartite Membrane, or External Appendages. 



'Mucous Membrane. The small bones of the Tympanum, with 

 the membrane round the fenestra ovalis, and mem- 

 brana tympani, being a species of basement 

 membrane.* 



Serous Membrane or Differentiation. The cartilage of the 

 concha as far as to the membrana tympani, and the 

 elastic tissue of the Eustachian tube. 



Muscular Membrane. The muscle moving the small bones 

 of the ear and concha. 



* Of course, in fishes, where the small bones of the ear are 

 differentiated into large lateral bones of the head, their associations with 

 hearing are nil, and the impressions are chiefly given to the sense of 

 force ; but these bones really belong to the outer protecting department 

 of the skull more than to any particular function of the ear direct, for 

 this sense in fishes is feebly developed. 



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