426 QUESTIONS ON 



CHAPTER XVI. 



884. Where is the eye placed ? 



885. What is the aqueous humor ? What the vitreous ? The crys- 

 talline lens ? 



886. Describe the sclerotic coat ; the cornea. 



887. 8'88. Describe the choroid coat; the retina. 



889. What are the parts of the eye, beginning in front? Describe 

 the iris ; the pupil, and its action. 



890. Describe the lids. 



891. Describe the apparatus for the tears. 



892. What happens sometimes to the lachrymal canals ? 



893. What sympathies has the lachrymal apparatus ? 



894. What move the eye 1 



895. What is the cross-eye ? 



896. Describe the optic nerve. 



897. How is vision produced ? 



CHAPTER XVII. 



898. What is near-sightedness? How may it be avoided? 



899. What is the state of the lens ? What is the effect of concave 

 spectacles? How should they be worn? 



900. What is the effect of single eye-glasses ? 



901. What is far-sightedness? 



902. What are some of the diseases of the eye ? 



903. How should the eye be treated for cleansing ? 



904. How is the eye affected by air ? 



905. Who have weakened vision? 



906. How are the eyes sometimes injured? 



907.' What is the effect of protracted use of the eyes t 



CHAPTER XVIII. 



908. What does the organ of hearing include ? 



909. Describe the outer ear. 



910. What is the natural position of the ear? 



911. Should the ear be covered? 



912. Describe the external canal. 



913 Describe the membrane of the tympanum. 



914 Describe the internal cavity. The Eustachian tube. What 

 oflice does this tube fulfil ? 



915, 916. What are within the drum? 



917. What is the auditory nerve? 



918, 919. How is sound produced? What is necessary ? 



920. How do we know that air is necessary ? 



921. What is the effect of unsound ears ? 



922. What happens sometimes to the Eustachian tube? 



923. 924, 925. What causes deafness? 



