2l6 ELEMENTARY PHYSIOLOGY 



QUESTIONS ON LESSON XXXV. 



1. What structures form the orbit of the eye? What does the orbit contain? 



2. How is the ball of the eye protected from injury ? 



3. How are the eyelids moved ? 



4. Describe the arrangement of the muscles which move the eyeball. De- 



scribe also the action of each muscle. 



5. Where do the tears come from ? Why do the tears roll over the cheeks 



when people cry ? 



6. Are tears produced at all times ? If so, what becomes of them ? 



7. Describe the structure of the ball of the eye. 



8. Where is the cornea 1 What is its use ? 



9. What is the iris ? Where is it placed ? What is its use? How does it 



act? 



10. What is the pupitt How and why does it change in size ? 



11. What is the retinal Where is it situated ? Which portion of the retina 



is most sensitive, and which portion is quite unaffected by light ? 



12. Through what parts of the eye must light pass before it reaches the retina ? 



13. What is meant by ' long-sight ' and ' short-sight ' ? What is the cause of 



each, and how may each be remedied ? 



14. Sometimes, as in cases of cataract, the crystalline lens has to be removed. 



What difference does its removal make in the power of seeing 



1 5. Why is the eyeball black inside ? 



1 6. Describe an experiment by which you would illustrate the formation of 



images in the eye. 



17. What change takes place in the form of the crystalline lens when we 



direct the attention from a near to a distant object? 



1 8. Compare the eye with a photographer's camera. 



19. Why does a rapidly revolving spark look like a circle of fire ? 



20. What do you notice when you look at a sheet of white paper after gazing 



intently on a bright green object? Explain the cause. 



LESSON XXXVI. 



THE EAR. 



THE ear consists of three parts : the external ear, the middle ear 

 or tympanum, and the internal ear or labyrinth. The last of these 

 divisions is the essential part of the organ of hearing, the other two 

 being concerned merely in the collection and transmission of 

 sound vibrations. 



The outer ear consists of the pinna (Lat. a wing), that part 

 which projects from the side of the head, and the auditory canal. 



The pinna, being concave, is especially adapted for the collection of sound 

 waves which are reflected by it into the canal. It consists of a cartilaginous 

 framework, surrounded by a certain amount of fatty tissue and a few small 

 muscles, the whole being covered with integument. The pinna is thrown 

 into several elevations and depressions, the names of which may be learnt 

 from the accompanying illustration. 



