VETEKINAEY OPHTHALMOLOGY. 17 



axis corresponds to the macula lutea, while the optio 

 axis extends from pole to pole. 



We are not aware of an image being on the retina, 

 nor of its position there, but only of the stimulus pro- 

 duced on the perceptive nerve elements of the retina. 

 So, understand, we do not see the image, but the object 

 irora which the rays emanate, and we refer the sensa- 

 tions in their direction. For instance, if an image is 

 formed on fh-Q upper and outer quadrant of the r-etina, 

 we refer it downward and inward, from which direction 

 the rays must have come. At this point a word on 

 inve,rted images: — The great advantage of inverted 

 images is, that for a given-size pupil a much larger 

 picture can be formed on the retina than would be the 

 case if no inversion took place, for in the latter 

 case all images must necessarily occupy a much smaller- 

 •place upon, the retina than the size of the pupil. 



Color is analagous 

 to pitch, violet corre- 

 sponding to the highi, 

 and red to the low 

 tones. Intensity of 

 color, as of sound, 

 depends upon the 

 ^•*'' amplitude of the 



vibrations. When a body absorbs all the colors of the 

 spectrum except blue, we call it a blue body. Red 

 glass has the power of absorbing all the colors except 



