VETERINARY OPHTHALMOLOGY. 17 



axis corresponds to the macula lutea, while the optic 

 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 

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

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

 formed on the upper and outer quadrant of the retina, 

 we refer it doxcmrard and imcard., from which direction 

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

 inverted 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 OQCWYty 2i much smaller 

 place upon the retina than the size of the jyujnl. 



Color is analagous 

 to pitch, violet corre- 

 sponding to the high, 

 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. lied 

 glass has the power of absorbing all the colors except 



