CHAPTEK VI. 



BINOCULAR VISION, ETC. 



Erect impressions produced by images inverted upon the retina Single vision 

 with both eyes Corresponding points The horopter Appreciation of dis- 

 tance and the form of objects Mechanism of the stereoscope Binocular 

 fusion of colors Duration of luminous impressions Irradiation Move- 

 ments of the eyeball Muscles of the eyeball Axes of rotation of the 

 globe for the diiferent sets of muscles Action of the recti muscles Action 

 of the oblique muscles Associated action of the different muscles of the 

 eyeball Parts for the protection of the eyeball Eyelids Muscles which 

 open and close the eyelids Conjunctival mucous membrane Lachrymal 

 apparatus Composition of the tears. 



IN beginning our study of the optical apparatus, it was 

 stated that we did not propose to treat of the subject ex- 

 haustively, and that we should omit the consideration of cer- 

 tain points, interesting in themselves, but not essential to a 

 comprehension of the physiology of vision. We have thus 

 far considered pretty fully the anatomy of the eye, a clear 

 idea of which is a necessary preparation for the study of its 

 physiology. We have also studied the action of the eye as 

 an optical instrument, with the mechanism of refraction, the 

 formation of images on the retina, the movements of the 

 iris, and the mechanism of accommodation. In this chapter, 

 we shall treat of binocular vision, the duration of luminous 

 impressions, irradiation, the movements of the eyeball, and 

 the parts for the protection of the eye. It does not seem 

 desirable to consider even these points with great elaborate- 

 ness. If we have become thoroughly acquainted with the 

 mechanism of the formation of images upon the retina and 

 the physiological action of the different parts of the optical 



