310 



DETAILED SYNTHESIS. 



202. 851. THE MEATUS is CON- 



STRUCTED of a frame partly 

 gristly and partly bony,lined 

 with skin, in which there are 

 numerous glands secreting 

 the ear-wax. The meatus 

 is about an inch in length, 

 inclining a little downward 

 fl and forward, and closed by 

 the skin lining the meatus 

 stretching across. 



Fig. 202, 1, mouth of; 2, meatus 

 extending to 3, bony ring ; 4, ham- 

 mer attached to membrana stretched 

 upon 3 ; 5, 6, 7, labyrinth ; the anvil closes the ovale near 5. 



852. THE BOTTOM OR END OF THE MEATUS is CALLED 

 the membrane of the drum (membrana tympani). It is 

 not parallel with the external openings, nor is it stretched 

 directly across, but is slightly concave or funnel-shaped 

 externally. 



853. THE^USE OF THE EXTERNAL EAR is to conduct the 

 vibrations of the air down to the membrane of the drum, 

 which is thereby thrown into corresponding vibrations. 



854. THE MIDDLE EAR is CONSTRUCTED of the drum 

 (tympanum), Mastoid cells, and Eustachian tube. 



855. THE DRUM is a cavity about as large as a kid- 

 ney-bean, placed flatwise toward the external ear. It 

 is excavated in the temporal bone. In the outside of the 

 drum is the membrane previously mentioned. In its op- 

 posite or inside bony walls are two openings, called the 

 round and oval windows (fenestra rotundum and ovale), 

 the former covered by the lining of the drum, and the 

 latter closed by the stirrup-bone and its ligament. 



856. A CHAIN OF BONES, the smallest in the body, 

 stretches across the drum. The hammer is attached by 



851. How is ? Describe Fig. 202. 852. what? 858. What is *? 854. How 

 is _y 855. flmt is ? 856. Describe the . 



