138 LABORATORY MANUAL 



funnel-shaped portion. Leading from this is a canal. 

 Across the inner end of this canal, or tube, is stretched 

 a thin membrane, known as the ear drum or tympanic 

 membrane. Examine the middle ear. What is its size? 

 How is it connected with the pharynx? What is the 

 name of this tube? What is its function? On the 

 inner surface of the cavity of the middle ear and 

 separating it from the inner ear are two small open- 

 ings covered with membrane. Across the cavity of the 

 middle ear is a chain of three smaH bones, called from 

 their shape the hammer (malleus), the anvil (incus), 

 and the stirrup (stapes) bones. How are they placed 

 with reference to each other? With reference to the 

 outer and inner ears? Can you suggest any functions 

 for them? The inner ear is formed by an irregular 

 cavity in the temporal bone, and is called the bony 

 labyrinth. It is lined with a membrane which secretes 

 a fluid. It is divided into three parts. The middle 

 part is the vestibule. The part back of this consists 

 of three tubes, the semi-circular canals. The part in 

 front of the vestibule is a single tube coiled like a 

 snail shell and called the cochlea. The branches of 

 the auditory nerve enter this bony labyrinth. Locate 

 the parts of the inner ear on the model. Draw a 

 diagram showing the relation of the parts in the ear. 



