230 



ELEMENTS OF BIOLOGY 



The mammalian ear (Fig. 159) consists of an outer canal sur- 

 rounded by a more or less funnel-shaped structure of cartilage and 



ANTENNULE 



SAC 



SENSORY 

 END ORGANS 



SAND GRA/NS 

 Fig. 158. — The balancing organs of a lobster. 



integument. At the base of this canal is a membrane, the tympa- 

 num, stretched over a tympanic cavity that serves as a resonating 



EXTERNAL 

 CANAL 



MIDDLE 

 EAR BONES 

 I 

 SEMICIRCULAR 



AMPULLA 



If* 



^I^ AUDITORY 

 ^k NERVE 





TYMPANUM 

 TYMPANIC CAVITY- 



EUSTACHIAN TUBE 



PHARYNX 



Fig. 159. — Diagram of the human ear. (After Haggard: The Science of Health and 

 Disease, published by Harper and Brothers; original by Tscherniak.) 



