2O2 



ELEMENTARY PHYSIOLOGY 



7. How would you prove that the sense of smell is intimately associated with 



that of taste ? 



8. Describe the general structure of the walls of the nasal cavities. How 



are these cavities separated from the mouth, the brain, and from each 

 other ? 



9. What is the course taken by the air when we breathe (i) with the mouth 



open and (2) with the mouth shut ? 



10. By what part of the nose do we smell ? How does sniffing assist the sense 

 of smell ? 



LESSON XXXV. 

 THE EYE AND VISION. 



THE organ of vision consists of the eyeball, which, with its 

 muscles, blood-vessels, nerves, fatty tissue and other protecting 

 structures, completely fill the orbit or eye-socket. 



Fig. 185. Section through the Orbit and its Contents. 



i, frontal bone ; b, superior maxillary bone ; c, eyebrow ; d, eyelids ; e, conjunctiva ; f, the 

 muscle which raises the upper lid ; g and f, recti muscles ; h, inferior oblique muscle cut 

 across ; i, optic nerve ; 2, cornea ; 2', sclerotic ; 3, aqueous chamber ; 4, crystalline lens ; 

 5, vitreous chamber. 



In front the ball of the eye is protected by movable folds of 

 the skin or integument called the eyelids. The inner surfaces of 

 the lids are lined by a mucous membrane called the conjunctiva, 

 which is also reflected over the front of the ball. The upper 

 eyelid is larger and more movable than the lower one, and it is 



