APPARATUS OF MOTION. 



of the glottis, which is between them, can be narrowed or enlarged. 

 Under ordinary circumstances, the air expelled from the lungs, 

 passes freely through the larynx, and produces no sound ; but 

 when the opening of the glottis is narrowed, by the contraction of 

 the muscles of this organ, and the passage of the air, becomes 

 more rapid, the voice is heard. 



45. Words are produced by the modifications which the column 

 of air receives in the interior of the mouth, by the combined 

 action of the palate, the cheeks, the tongue, and lips. 



LESSON X. 



FUNCTIONS OF RELATION. Apparatus of motion The skele- 

 ton Structure of hones; their composition Enumeration of the 

 bones Articulations Muscles Attitudes Locomotion. 



MOTION. 



1. The organs of motion are divided into two classes: 1st. 

 Those which act and produce the motive force: 2nd. Those to 

 which the action is communicated ; or, in other words, they are 

 divided into the active and passive organs of locomotion. 



2. The first are the muscles ; the second are the bones or those 

 parts which hold their place. 



OF THE OSSEOUS SYSTEM. 



3. Man, and all the other mammalia, as well as birds, reptiles 

 and fishes, have in their structure, solid parts which are called 

 hones, and the union of these bones, one with the other, consti- 

 tutes the Skeleton. ( page 97, fig. 37.) 



4. The skeleton is a kind of frame which gives firmness to the 

 body, in a considerable degree, determines its dimensions and its 

 form, serves to protect the organs which are most important to 

 life, and furnishes the passive instruments of motion to the 

 function of locomotion. 



OF THE COMPOSITION OF BONES. 



5. The bones are formed of a species of cartilage, composed of 

 gelatine, (the substance which constitutes strong glue,) all the 



45. How are words produced ? 



1. How are the organs of motion divided ? 



2. Which are the active organs of motion ? Which are the 

 organs of motion? 



3. What are bones? What do they constitute? 



4. What is the skeleton ? What are its uses ? 



5. Of what are the bones composed? 



8 



